Plasticity mechanisms in HfN at elevated and room temperature.

PubMed

Vinson, Katherine; Yu, Xiao-Xiang; De Leon, Nicholas; Weinberger, Christopher R; Thompson, Gregory B

2016-10-06

HfN specimens deformed via four-point bend tests at room temperature and at 2300 °C (~0.7 T m ) showed increased plasticity response with temperature. Dynamic diffraction via transmission electron microscopy (TEM) revealed ⟨110⟩{111} as the primary slip system in both temperature regimes and ⟨110⟩{110} to be a secondary slip system activated at elevated temperature. Dislocation line lengths changed from a primarily linear to a curved morphology with increasing temperature suggestive of increased dislocation mobility being responsible for the brittle to ductile temperature transition. First principle generalized stacking fault energy calculations revealed an intrinsic stacking fault (ISF) along ⟨112⟩{111}, which is the partial dislocation direction for slip on these close packed planes. Though B1 structures, such as NaCl and HfC predominately slip on ⟨110⟩{110}, the ISF here is believed to facilitate slip on the {111} planes for this B1 HfN phase.

INDUCED SEISMICITY. Seismicity triggered by fluid injection-induced aseismic slip.

PubMed

Guglielmi, Yves; Cappa, Frédéric; Avouac, Jean-Philippe; Henry, Pierre; Elsworth, Derek

2015-06-12

Anthropogenic fluid injections are known to induce earthquakes. The mechanisms involved are poorly understood, and our ability to assess the seismic hazard associated with geothermal energy or unconventional hydrocarbon production remains limited. We directly measure fault slip and seismicity induced by fluid injection into a natural fault. We observe highly dilatant and slow [~4 micrometers per second (μm/s)] aseismic slip associated with a 20-fold increase of permeability, which transitions to faster slip (~10 μm/s) associated with reduced dilatancy and micro-earthquakes. Most aseismic slip occurs within the fluid-pressurized zone and obeys a rate-strengthening friction law μ = 0.67 + 0.045ln(v/v₀) with v₀ = 0.1 μm/s. Fluid injection primarily triggers aseismic slip in this experiment, with micro-earthquakes being an indirect effect mediated by aseismic creep. Copyright © 2015, American Association for the Advancement of Science.

Inferring Fault Frictional and Reservoir Hydraulic Properties From Injection-Induced Seismicity

NASA Astrophysics Data System (ADS)

Jagalur-Mohan, Jayanth; Jha, Birendra; Wang, Zheng; Juanes, Ruben; Marzouk, Youssef

2018-02-01

Characterizing the rheological properties of faults and the evolution of fault friction during seismic slip are fundamental problems in geology and seismology. Recent increases in the frequency of induced earthquakes have intensified the need for robust methods to estimate fault properties. Here we present a novel approach for estimation of aquifer and fault properties, which combines coupled multiphysics simulation of injection-induced seismicity with adaptive surrogate-based Bayesian inversion. In a synthetic 2-D model, we use aquifer pressure, ground displacements, and fault slip measurements during fluid injection to estimate the dynamic fault friction, the critical slip distance, and the aquifer permeability. Our forward model allows us to observe nonmonotonic evolutions of shear traction and slip on the fault resulting from the interplay of several physical mechanisms, including injection-induced aquifer expansion, stress transfer along the fault, and slip-induced stress relaxation. This interplay provides the basis for a successful joint inversion of induced seismicity, yielding well-informed Bayesian posterior distributions of dynamic friction and critical slip. We uncover an inverse relationship between dynamic friction and critical slip distance, which is in agreement with the small dynamic friction and large critical slip reported during seismicity on mature faults.

Stacking with stochastic cooling

NASA Astrophysics Data System (ADS)

Caspers, Fritz; Möhl, Dieter

2004-10-01

Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105 the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some considerations to the 'azimuthal' schemes.

Anode protection system for shutdown of solid oxide fuel cell system

DOEpatents

Li, Bob X; Grieves, Malcolm J; Kelly, Sean M

2014-12-30

An Anode Protection Systems for a SOFC system, having a Reductant Supply and safety subsystem, a SOFC anode protection subsystem, and a Post Combustion and slip stream control subsystem. The Reductant Supply and safety subsystem includes means for generating a reducing gas or vapor to prevent re-oxidation of the Ni in the anode layer during the course of shut down of the SOFC stack. The underlying ammonia or hydrogen based material used to generate a reducing gas or vapor to prevent the re-oxidation of the Ni can be in either a solid or liquid stored inside a portable container. The SOFC anode protection subsystem provides an internal pressure of 0.2 to 10 kPa to prevent air from entering into the SOFC system. The Post Combustion and slip stream control subsystem provides a catalyst converter configured to treat any residual reducing gas in the slip stream gas exiting from SOFC stack.

Transformation of fault slip modes in laboratory experiments

NASA Astrophysics Data System (ADS)

Martynov, Vasilii; Alexey, Ostapchuk; Markov, Vadim

2017-04-01

Slip mode of crust fault can vary because of many reasons. It's well known that fault structure, material of fault gouge, pore fluid et al. in many ways determines slip modes from creep and slow slip events to mega-earthquakes [1-3]. Therefore, the possibility of fault slip transformation due to external action is urgent question. There is popular and developing approach of fluid injection into central part of fault. The phenomenon of earthquakes induced due to pumping of water was investigated on small and large scales [4, 5]. In this work the laboratory experiments were conducted to study the evolution of the experimental fault slip when changing the properties of the interstitial fluid. The scheme of experiments is the classical slider-model set-up, in which the block under the shear force slips along the interface. In our experiments the plexiglas block 8x8x3 cm3 in size was put on the plexiglas base. The contact of the blocks was filled with a thin layer (about 3 mm thick) of a granular material. The normal load varied from 31 to 156 kPa. The shear load was applied through a spring with stiffness 60 kN/m, and the rate of spring deformation was 20 or 5 mcm/s. Two parameters were recorded during experiments: the shear force acting on the upper block (with an accuracy of 1 N) and its displacement relatively the base (with an accuracy of 0.1 μm). The gouge was composed of quartz sand (97.5%) and clay (2.5%). As a moisturizer were used different fluids with viscosity varying from 1 to 103 mPa x s. Different slip modes were simulated during slider-experiments. In our experiments slip mode is the act of instability manifested in an increase of slip velocity and a drop of shear stress acting on a movable block. The amplitude of a shear stress drop and the peak velocity of the upper block were chosen as the characteristics of the slip mode. In the laboratory experiments, slip events of one type can be achieved either as regularly recurring (regular mode) or as random stochastic (irregular mode). To investigate regularities of transformation and get statistically correct results we simulated only regular mode. During the experiments, after the establishment of a regular mode, we injected fluid into central part of interblock contact. Varying injecting fluid we were able both to decrease and increase amplitude of events. For example, after injection of 1 mPa x s fluid (water) in gouge, moisturized with 100 mPa x s fluid (ethylene glycol), peak velocity rose by almost an order. But after injection of an aqueous solution of starch (big viscosity and dilatant rheology) amplitude decreased 1.5 times and then slip almost completely stabilized. It's probably connected with the viscosity of solution, which increases with quick shift. Time of injection also has the significant impact on the possibility of transformation and its efficiency. Thus, it is well known that if the time of injection is in the vicinity of loss of strength moment, any external influence only initiates slip events. Preliminary results of our laboratory experiments show that the fluid injection can both reduce the part of deformation energy going seismic wave radiation, and to increase it. The most effective action observed in experinemts with injection of dilatant fluid. Findings demonstrate the prospectivity of further research in this direction. The work was supported by the Russian Science Foundation (Grant No. 16-17-00095) [1] Fagereng A., Sibson R.H. 2010. Melange rheology and seismic style. Geology. Vol.38, p.751-754. [2] Kocharyan G.G., et al. 2017. A study of different fault slip modes governed by the gouge material composition in laboratory experiments. Geophys. J. Int. Vol.208, p. 521-528. [3] Yamashita T. 2013. Generation of slow slip coupled with tremor due to fluid flow along a fault. Geophys. J. Int. Vol.193, p.375-393. [4] Guglielmi Y., et. al. 2015. Seismicity triggered by fluid injection-induced aseismic slip. Science. Vol.348, p.1224-1226. [5] Wei S., et al. 2015. The 2012 Brawley swarm triggered by injection-induced aseismic slip. EPSL. Vol. 422, p.115-122.

Cooler and particulate separator for an off-gas stack

DOEpatents

Wright, George T.

1992-01-01

An off-gas stack for a melter comprising an air conduit leading to two sets of holes, one set injecting air into the off-gas stack near the melter plenum and the second set injecting air downstream of the first set. The first set injects air at a compound angle, having both downward and tangential components, to create a reverse vortex flow, counter to the direction of flow of gas through the stack and also along the periphery of the stack interior surface. Air from the first set of holes pervents recirculation zones from forming and the attendant accumulation of particulate deposits on the wall of the stack and will also return to the plenum any particulate swept up in the gas entering the stack. The second set of holes injects air in the same direction as the gas in the stack to compensate for the pressure drop and to prevent the concentration of condensate in the stack. A set of sprayers, receiving water from a second conduit, is located downstream of the second set of holes and sprays water into the gas to further cool it.

Modelling induced seismicity due to fluid injection

NASA Astrophysics Data System (ADS)

Murphy, S.; O'Brien, G. S.; Bean, C. J.; McCloskey, J.; Nalbant, S. S.

2011-12-01

Injection of fluid into the subsurface alters the stress in the crust and can induce earthquakes. The science of assessing the risk of induced seismicity from such ventures is still in its infancy despite public concern. We plan to use a fault network model in which stress perturbations due to fluid injection induce earthquakes. We will use this model to investigate the role different operational and geological factors play in increasing seismicity in a fault system due to fluid injection. The model is based on a quasi-dynamic relationship between stress and slip coupled with a rate and state fiction law. This allows us to model slip on fault interfaces over long periods of time (i.e. years to 100's years). With the use of the rate and state friction law the nature of stress release during slipping can be altered through variation of the frictional parameters. Both seismic and aseismic slip can therefore be simulated. In order to add heterogeneity along the fault plane a fractal variation in the frictional parameters is used. Fluid injection is simulated using the lattice Boltzmann method whereby pore pressure diffuses throughout a permeable layer from the point of injection. The stress perturbation this causes on the surrounding fault system is calculated using a quasi-static solution for slip dislocation in an elastic half space. From this model we can generate slip histories and seismicity catalogues covering 100's of years for predefined fault networks near fluid injection sites. Given that rupture is a highly non-linear process, comparison between models with different input parameters (e.g. fault network statistics and injection rates) will be based on system wide features (such as the Gutenberg-Richter b-values), rather than specific seismic events. Our ultimate aim is that our model produces seismic catalogues similar to those observed over real injection sites. Such validation would pave the way to probabilistic estimation of reactivation risk for injection sites using such models. Preliminary results from this model will be presented.

Cooler and particulate separator for an off-gas stack

DOEpatents

Wright, G.T.

1991-04-08

This report describes an off-gas stack for a melter, furnace or reaction vessel comprising an air conduit leading to two sets of holes, one set injecting air into the off-gas stack near the melter plenum and the second set injecting air downstream of the first set. The first set injects air at a compound angle, having both downward and tangential components, to create a reverse vortex flow, counter to the direction of flow of gas through the stack and also along the periphery of the stack interior surface. Air from the first set of holes prevents recirculation zones from forming and the attendant accumulation of particulate deposits on the wall of the stack and will also return to the plenum any particulate swept up in the gas entering the stack. The second set of holes injects air in the same direction as the gas in the stack to compensate for the pressure drop and to prevent the concentration of condensate in the stack. A set of sprayers, receiving water from a second conduit, is located downstream of the second set of holes and sprays water into the gas to further cool it.

Atomistically determined phase-field modeling of dislocation dissociation, stacking fault formation, dislocation slip, and reactions in fcc systems

NASA Astrophysics Data System (ADS)

Rezaei Mianroodi, Jaber; Svendsen, Bob

2015-04-01

The purpose of the current work is the development of a phase field model for dislocation dissociation, slip and stacking fault formation in single crystals amenable to determination via atomistic or ab initio methods in the spirit of computational material design. The current approach is based in particular on periodic microelasticity (Wang and Jin, 2001; Bulatov and Cai, 2006; Wang and Li, 2010) to model the strongly non-local elastic interaction of dislocation lines via their (residual) strain fields. These strain fields depend in turn on phase fields which are used to parameterize the energy stored in dislocation lines and stacking faults. This energy storage is modeled here with the help of the "interface" energy concept and model of Cahn and Hilliard (1958) (see also Allen and Cahn, 1979; Wang and Li, 2010). In particular, the "homogeneous" part of this energy is related to the "rigid" (i.e., purely translational) part of the displacement of atoms across the slip plane, while the "gradient" part accounts for energy storage in those regions near the slip plane where atomic displacements deviate from being rigid, e.g., in the dislocation core. Via the attendant global energy scaling, the interface energy model facilitates an atomistic determination of the entire phase field energy as an optimal approximation of the (exact) atomistic energy; no adjustable parameters remain. For simplicity, an interatomic potential and molecular statics are employed for this purpose here; alternatively, ab initio (i.e., DFT-based) methods can be used. To illustrate the current approach, it is applied to determine the phase field free energy for fcc aluminum and copper. The identified models are then applied to modeling of dislocation dissociation, stacking fault formation, glide and dislocation reactions in these materials. As well, the tensile loading of a dislocation loop is considered. In the process, the current thermodynamic picture is compared with the classical mechanical one as based on the Peach-Köhler force.

Shear response of Fe-bearing MgSiO3 post-perovskite at lower mantle pressures

PubMed Central

METSUE, Arnaud; TSUCHIYA, Taku

2013-01-01

We investigate the shear response of possible slip systems activated in pure and Fe-bearing MgSiO3 post-perovskite (PPv) through ab initio generalized stacking fault (GSF) energy calculations. Here we show that the [100](001) slip system has the easiest response to plastic shear among ten possible slip systems investigated. Incorporation of Fe2+ decreases the strength of all slip systems but does not change the plastic anisotropy style. Therefore, pure and Fe-bearing MgSiO3 PPv should demonstrate similar LPO patterns with a strong signature of the [100](001) slip system. An aggregate with this deformation texture is expected to produce a VSH > VSV type polarization anisotropy, being consistent with seismological observations. PMID:23318681

Data-driven fault mechanics: Inferring fault hydro-mechanical properties from in situ observations of injection-induced aseismic slip

NASA Astrophysics Data System (ADS)

Bhattacharya, P.; Viesca, R. C.

2017-12-01

In the absence of in situ field-scale observations of quantities such as fault slip, shear stress and pore pressure, observational constraints on models of fault slip have mostly been limited to laboratory and/or remote observations. Recent controlled fluid-injection experiments on well-instrumented faults fill this gap by simultaneously monitoring fault slip and pore pressure evolution in situ [Gugleilmi et al., 2015]. Such experiments can reveal interesting fault behavior, e.g., Gugleilmi et al. report fluid-activated aseismic slip followed only subsequently by the onset of micro-seismicity. We show that the Gugleilmi et al. dataset can be used to constrain the hydro-mechanical model parameters of a fluid-activated expanding shear rupture within a Bayesian framework. We assume that (1) pore-pressure diffuses radially outward (from the injection well) within a permeable pathway along the fault bounded by a narrow damage zone about the principal slip surface; (2) pore-pressure increase ativates slip on a pre-stressed planar fault due to reduction in frictional strength (expressed as a constant friction coefficient times the effective normal stress). Owing to efficient, parallel, numerical solutions to the axisymmetric fluid-diffusion and crack problems (under the imposed history of injection), we are able to jointly fit the observed history of pore-pressure and slip using an adaptive Monte Carlo technique. Our hydrological model provides an excellent fit to the pore-pressure data without requiring any statistically significant permeability enhancement due to the onset of slip. Further, for realistic elastic properties of the fault, the crack model fits both the onset of slip and its early time evolution reasonably well. However, our model requires unrealistic fault properties to fit the marked acceleration of slip observed later in the experiment (coinciding with the triggering of microseismicity). Therefore, besides producing meaningful and internally consistent bounds on in-situ fault properties like permeability, storage coefficient, resolved stresses, friction and the shear modulus, our results also show that fitting the complete observed time history of slip requires alternative model considerations, such as variations in fault mechanical properties or friction coefficient with slip.

Effects of Cobalt Concentration on the Relative Resistance to Octahedral and Cube Slip in Nickel-Base Superalloys

NASA Technical Reports Server (NTRS)

Bobeck, Gene E.; Miner, R. V.

1988-01-01

Compression yielding tests were performed at 760 C on crystals of the Ni base superalloys Rene 150 and a modified MAR-M247, both having two different Co concentrations. For both alloy bases, increasing Co concentration was shown to decrease the critical resolved shear stress for octahedral slip, but to have little effect on that for cube slip. The results suggest that decreasing complex stacking fault energy in the gamma-prime with increasing Co could account for the observed effects.

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation.

PubMed

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-05-22

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures.

Elastic stress transfer as a diffusive process due to aseismic fault slip in response to fluid injection

NASA Astrophysics Data System (ADS)

Viesca, R. C.

2015-12-01

Subsurface fluid injection is often followed by observations of an enlarging cloud of microseismicity. The cloud's diffusive growth is thought to be a direct response to the diffusion of elevated pore fluid pressure reaching pre-stressed faults, triggering small instabilities; the observed high rates of this growth are interpreted to reflect a relatively high permeability of a fractured subsurface [e.g., Shapiro, GJI 1997]. We investigate an alternative mechanism for growing a microseismic cloud: the elastic transfer of stress due to slow, aseismic slip on a subset of the pre-existing faults in this damaged subsurface. We show that the growth of the slipping region of the fault may be self-similar in a diffusive manner. While this slip is driven by fluid injection, we show that, for critically stressed faults, the apparent diffusion of this slow slip may quickly exceed the poroelastically driven diffusion of the elevated pore fluid pressure. Under these conditions, microseismicity can be first triggered by the off-fault stress perturbation due to the expanding region of slip on principal faults. This provides an alternative interpretation of diffusive growth rates in terms of the subsurface stress state rather than an enhanced hydraulic diffusivity. That such aseismic slip may occur, outpace fluid diffusion, and in turn trigger microseismic events, is also suggested by on- and near-fault observations in past and recently reported fluid injection experiments [e.g., Cornet et al., PAGEOPH 1997; Guglielmi et al., Science 2015]. The model of injection-induced slip assumes elastic off-fault behavior and a fault strength determined by the product of a constant friction coefficient and the local effective normal stress. The sliding region is enlarged by the pore pressure increase resolved on the fault plane. Remarkably, the rate of self-similar expansion may be determined by a single parameter reflecting both the initial stress state and the magnitude of the pore pressure increase.

First-principles calculations on slip system activation in the rock salt structure: electronic origin of ductility in silver chloride

NASA Astrophysics Data System (ADS)

Nakamura, Atsutomo; Ukita, Masaya; Shimoda, Naofumi; Furushima, Yuho; Toyoura, Kazuaki; Matsunaga, Katsuyuki

2017-06-01

First principles calculations were performed to understand an electronic origin of high ductility in silver chloride (AgCl) with the rock salt structure. From calculations of generalised stacking fault energies for different slip systems, it was found that only the {1 1 0}? slip system is favourably activated in sodium chloride (NaCl) with the same rock salt structure, whereas AgCl shows three kinds of possible slip systems along the ? direction on the {0 0 1}, {1 1 0}, and {1 1 1} planes, which is in excellent agreement with experiment. Detailed analyses of the electronic structures across slip planes showed that the more covalent character of bonding of Ag-Cl than Na-Cl tends to make the slip motion energetically favourable. It was also surprising to find out that strong Ag-Ag covalent bonds across the slip plane are formed in the {0 0 1}〈1 1 0〉 slip system in AgCl, which makes it possible to activate the multiple slip systems in AgCl.

Early Beam Injection Scheme for the Fermilab Booster: A Path for Intensity Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhat, C. M.

Over the past decade, Fermilab has focused efforts on the intensity frontier physics and is committed to increase the average beam power delivered to the neutrino and muon programs substantially. Many upgrades to the existing injector accelerators, namely, the current 400 MeV LINAC and the Booster, are in progress under the Proton Improvement Plan (PIP). Proton Improvement Plan-II (PIP-II) proposes to replace the existing 400 MeV LINAC by a new 800 MeV LINAC, as an injector to the Booster which will increase Booster output power by nearly a factor of two from the PIP design value by the end ofmore » its completion. In any case, the Fermilab Booster is going to play a very significant role for nearly next two decades. In this context, I have developed and investigated a new beam injection scheme called "early injection scheme" (EIS) for the Booster with the goal to significantly increase the beam intensity output from the Booster thereby increasing the beam power to the HEP experiments even before PIP-II era. The scheme, if implemented, will also help improve the slip-stacking efficiency in the MI/RR. Here I present results from recent simulations, beam studies, current status and future plans for the new scheme.« less

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation

PubMed Central

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-01-01

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures. PMID:25998415

Acupuncture injection for field amplified sample stacking and glass microchip-based capillary gel electrophoresis.

PubMed

Ha, Ji Won; Hahn, Jong Hoon

2017-02-01

Acupuncture sample injection is a simple method to deliver well-defined nanoliter-scale sample plugs in PDMS microfluidic channels. This acupuncture injection method in microchip CE has several advantages, including minimization of sample consumption, the capability of serial injections of different sample solutions into the same microchannel, and the capability of injecting sample plugs into any desired position of a microchannel. Herein, we demonstrate that the simple and cost-effective acupuncture sample injection method can be used for PDMS microchip-based field amplified sample stacking in the most simplified straight channel by applying a single potential. We achieved the increase in electropherogram signals for the case of sample stacking. Furthermore, we present that microchip CGE of ΦX174 DNA-HaeⅢ digest can be performed with the acupuncture injection method on a glass microchip while minimizing sample loss and voltage control hardware. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wall-slip of highly filled powder injection molding compounds: Effect of flow channel geometry and roughness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hausnerova, Berenika; Sanetrnik, Daniel; Paravanova, Gordana

2014-05-15

The paper deals with the rheological behavior of highly filled compounds proceeded via powder injection molding (PIM) and applied in many sectors of industry (automotive, medicine, electronic or military). Online rheometer equipped with slit dies varying in surface roughness and dimensions was applied to investigate the wall-slip as a rheological phenomenon, which can be considered as a parameter indicating the separation of compound components (polymer binder and metallic powder) during high shear rates when injection molded.

Wall-slip of highly filled powder injection molding compounds: Effect of flow channel geometry and roughness

NASA Astrophysics Data System (ADS)

Hausnerova, Berenika; Sanetrnik, Daniel; Paravanova, Gordana

2014-05-01

The paper deals with the rheological behavior of highly filled compounds proceeded via powder injection molding (PIM) and applied in many sectors of industry (automotive, medicine, electronic or military). Online rheometer equipped with slit dies varying in surface roughness and dimensions was applied to investigate the wall-slip as a rheological phenomenon, which can be considered as a parameter indicating the separation of compound components (polymer binder and metallic powder) during high shear rates when injection molded.

Shear-induced mechanical failure of β -G a2O3 from quantum mechanics simulations

NASA Astrophysics Data System (ADS)

An, Qi; Li, Guodong

2017-10-01

Monoclinic gallium oxide (β -G a2O3 ) has important applications in power devices and deep UV optoelectronic devices because of such novel properties as a wide band gap, high breakdown electric field, and a wide range of n -type doping conductivity. However, the intrinsic failure mechanisms of β -G a2O3 remain unknown, which limits the fabrication and packaging of β -G a2O3 -based electronic devices. Here we used density-functional theory at the Perdew-Burke-Ernzerhof level to examine the shear-induced failure mechanisms of β -G a2O3 along various plausible slip systems. We found that the (001 )/〈010 〉 slip system has the lowest ideal shear strength of 3.8 GPa among five plausible slip systems, suggesting that (001 )/〈010 〉 is the most plausible activated slip system. This slip leads to an intrinsic failure mechanism arising from breaking the longest Ga-O bond between octahedral Ga and fourfold-coordinated O. Then we identified the same failure mechanism of β -G a2O3 under biaxial shear deformation that mimics indentation stress conditions. Finally, the general stacking fault energy (SFE) surface is calculated for the (001) surface from which we concluded that there is no intrinsic stacking fault structure for β -G a2O3 . The deformation modes and SFE calculations are essential to understand the intrinsic mechanical processes of this semiconductor material, which provides insightful guidance for designing high-performance semiconductor devices.

Deterministic estimate of hypocentral pore fluid pressure of the M5.8 Pawnee, Oklahoma earthquake: Lower pre-injection pressure requires lower resultant pressure for slip

NASA Astrophysics Data System (ADS)

Levandowski, W. B.; Walsh, F. R. R.; Yeck, W.

2016-12-01

Quantifying the increase in pore-fluid pressure necessary to cause slip on specific fault planes can provide actionable information for stakeholders to potentially mitigate hazard. Although the M5.8 Pawnee earthquake occurred on a previously unmapped fault, we can retrospectively estimate the pore-pressure perturbation responsible for this event. We first estimate the normalized local stress tensor by inverting focal mechanisms surrounding the Pawnee Fault. Faults are generally well oriented for slip, with instabilities averaging 96% of maximum. Next, with an estimate of the weight of local overburden we solve for the pore pressure needed at the hypocenters. Specific to the Pawnee fault, we find that hypocentral pressure 43-104% of hydrostatic (accounting for uncertainties in all relevant parameters) would have been sufficient to cause slip. The dominant source of uncertainty is the pressure on the fault prior to fluid injection. Importantly, we find that lower pre-injection pressure requires lower resultant pressure to cause slip, decreasing from a regional average of 30% above hydrostatic pressure if the hypocenters begin at hydrostatic pressure to 6% above hydrostatic pressure with no pre-injection fluid. This finding suggests that underpressured regions such as northern Oklahoma are predisposed to injection-induced earthquakes. Although retrospective and forensic, similar analyses of other potentially induced events and comparisons to natural earthquakes will provide insight into the relative importance of fault orientation, the magnitude of the local stress field, and fluid-pressure migration in intraplate seismicity.

Self-assemblies, helical ribbons and gelation tuned by solvent-gelator interaction in a bi-1,3,4-oxadiazole gelator

NASA Astrophysics Data System (ADS)

Zhao, Chengxiao; Bai, Binglian; Wang, Haitao; Qu, Songnan; Xiao, Guanjun; Tian, Taiji; Li, Min

2013-04-01

A bi-1,3,4-oxadiazole derivative (BOXDH-T12) showed intramolecular charge transition at concentrations lower than 1 × 10-5 mol/L. The self-assembling behaviors of BOXDH-T12 depended on solvents that it self-assembled into H-aggregates in alcohols and slipped packing aggregates in DMSO. FTIR, 1H NMR and TGA results revealed that strong gelator-gelator hydrogen bonding interaction induced H-aggregation of BOXDH-T12 in alcohols and the interactions between DMSO and BOXDH-T12 molecules caused a slipped stacking. BOXDH-T12 can gel the mixtures of DMSO and ethanol through a cooperative effect of the hydrogen bonding, van der Waals interaction and π-π stacking forces, furthermore, helical ribbons could be observed in DMSO/ethanol due to DMSO molecule interacting. In alcohols, solvophobic/solvophilic effect plays a critical role in gelation behaviors.

On the effective stress law for rock-on-rock frictional sliding, and fault slip triggered by means of fluid injection.

PubMed

Rutter, Ernest; Hackston, Abigail

2017-09-28

Fluid injection into rocks is increasingly used for energy extraction and for fluid wastes disposal, and can trigger/induce small- to medium-scale seismicity. Fluctuations in pore fluid pressure may also be associated with natural seismicity. The energy release in anthropogenically induced seismicity is sensitive to amount and pressure of fluid injected, through the way that seismic moment release is related to slipped area, and is strongly affected by the hydraulic conductance of the faulted rock mass. Bearing in mind the scaling issues that apply, fluid injection-driven fault motion can be studied on laboratory-sized samples. Here, we investigate both stable and unstable induced fault slip on pre-cut planar surfaces in Darley Dale and Pennant sandstones, with or without granular gouge. They display contrasting permeabilities, differing by a factor of 10 5 , but mineralogies are broadly comparable. In permeable Darley Dale sandstone, fluid can access the fault plane through the rock matrix and the effective stress law is followed closely. Pore pressure change shifts the whole Mohr circle laterally. In tight Pennant sandstone, fluid only injects into the fault plane itself; stress state in the rock matrix is unaffected. Sudden access by overpressured fluid to the fault plane via hydrofracture causes seismogenic fault slips.This article is part of the themed issue 'Faulting, friction and weakening: from slow to fast motion'. © 2017 The Authors.

On the effective stress law for rock-on-rock frictional sliding, and fault slip triggered by means of fluid injection

NASA Astrophysics Data System (ADS)

Rutter, Ernest; Hackston, Abigail

2017-08-01

Fluid injection into rocks is increasingly used for energy extraction and for fluid wastes disposal, and can trigger/induce small- to medium-scale seismicity. Fluctuations in pore fluid pressure may also be associated with natural seismicity. The energy release in anthropogenically induced seismicity is sensitive to amount and pressure of fluid injected, through the way that seismic moment release is related to slipped area, and is strongly affected by the hydraulic conductance of the faulted rock mass. Bearing in mind the scaling issues that apply, fluid injection-driven fault motion can be studied on laboratory-sized samples. Here, we investigate both stable and unstable induced fault slip on pre-cut planar surfaces in Darley Dale and Pennant sandstones, with or without granular gouge. They display contrasting permeabilities, differing by a factor of 105, but mineralogies are broadly comparable. In permeable Darley Dale sandstone, fluid can access the fault plane through the rock matrix and the effective stress law is followed closely. Pore pressure change shifts the whole Mohr circle laterally. In tight Pennant sandstone, fluid only injects into the fault plane itself; stress state in the rock matrix is unaffected. Sudden access by overpressured fluid to the fault plane via hydrofracture causes seismogenic fault slips. This article is part of the themed issue 'Faulting, friction and weakening: from slow to fast motion'.

On the effective stress law for rock-on-rock frictional sliding, and fault slip triggered by means of fluid injection

PubMed Central

Hackston, Abigail

2017-01-01

Fluid injection into rocks is increasingly used for energy extraction and for fluid wastes disposal, and can trigger/induce small- to medium-scale seismicity. Fluctuations in pore fluid pressure may also be associated with natural seismicity. The energy release in anthropogenically induced seismicity is sensitive to amount and pressure of fluid injected, through the way that seismic moment release is related to slipped area, and is strongly affected by the hydraulic conductance of the faulted rock mass. Bearing in mind the scaling issues that apply, fluid injection-driven fault motion can be studied on laboratory-sized samples. Here, we investigate both stable and unstable induced fault slip on pre-cut planar surfaces in Darley Dale and Pennant sandstones, with or without granular gouge. They display contrasting permeabilities, differing by a factor of 105, but mineralogies are broadly comparable. In permeable Darley Dale sandstone, fluid can access the fault plane through the rock matrix and the effective stress law is followed closely. Pore pressure change shifts the whole Mohr circle laterally. In tight Pennant sandstone, fluid only injects into the fault plane itself; stress state in the rock matrix is unaffected. Sudden access by overpressured fluid to the fault plane via hydrofracture causes seismogenic fault slips. This article is part of the themed issue ‘Faulting, friction and weakening: from slow to fast motion’. PMID:28827423

Frictional stability and earthquake triggering during fluid pressure stimulation of an experimental fault

NASA Astrophysics Data System (ADS)

Scuderi, M. M.; Collettini, C.; Marone, C.

2017-11-01

It is widely recognized that the significant increase of M > 3.0 earthquakes in Western Canada and the Central United States is related to underground fluid injection. Following injection, fluid overpressure lubricates the fault and reduces the effective normal stress that holds the fault in place, promoting slip. Although, this basic physical mechanism for earthquake triggering and fault slip is well understood, there are many open questions related to induced seismicity. Models of earthquake nucleation based on rate- and state-friction predict that fluid overpressure should stabilize fault slip rather than trigger earthquakes. To address this controversy, we conducted laboratory creep experiments to monitor fault slip evolution at constant shear stress while the effective normal stress was systematically reduced via increasing fluid pressure. We sheared layers of carbonate-bearing fault gouge in a double direct shear configuration within a true-triaxial pressure vessel. We show that fault slip evolution is controlled by the stress state acting on the fault and that fluid pressurization can trigger dynamic instability even in cases of rate strengthening friction, which should favor aseismic creep. During fluid pressurization, when shear and effective normal stresses reach the failure condition, accelerated creep occurs in association with fault dilation; further pressurization leads to an exponential acceleration with fault compaction and slip localization. Our work indicates that fault weakening induced by fluid pressurization can overcome rate strengthening friction resulting in fast acceleration and earthquake slip. Our work points to modifications of the standard model for earthquake nucleation to account for the effect of fluid overpressure and to accurately predict the seismic risk associated with fluid injection.

Limiting the Magnitude of Potential Injection-Induced Seismicity Associated With Waste-Water Disposal, Hydraulic Fracturing and CO2 Sequestration

NASA Astrophysics Data System (ADS)

Zoback, Mark

2017-04-01

In this talk, I will address the likelihood for fault slip to occur in response to fluid injection and the likely magnitude of potentially induced earthquakes. First, I will review a methodology that applies Quantitative Risk Assessment to calculate the probability of a fault exceeding Mohr-Coulomb slip criteria. The methodology utilizes information about the local state of stress, fault strike and dip and the estimated pore pressure perturbation to predict the probability of the fault slip as a function of time. Uncertainties in the input parameters are utilized to assess the probability of slip on known faults due to the predictable pore pressure perturbations. Application to known faults in Oklahoma has been presented by Walsh and Zoback (Geology, 2016). This has been updated with application to the previously unknown faults associated with M >5 earthquakes in the state. Second, I will discuss two geologic factors that limit the magnitudes of earthquakes (either natural or induced) in sedimentary sequences. Fundamentally, the layered nature of sedimentary rocks means that seismogenic fault slip will be limited by i) the velocity strengthening frictional properties of clay- and carbonate-rich rock sequences (Kohli and Zoback, JGR, 2013; in prep) and ii) viscoplastic stress relaxation in rocks with similar composition (Sone and Zoback, Geophysics, 2013a, b; IJRM, 2014; Rassouli and Zoback, in prep). In the former case, if fault slip is triggered in these types of rocks, it would likely be aseismic due the velocity strengthening behavior of faults. In the latter case, the stress relaxation could result in rupture termination in viscoplastic formations. In both cases, the stratified nature of sedimentary rock sequences could limit the magnitude of potentially induced earthquakes. Moreover, even when injection into sedimentary rocks initiates fault slip, earthquakes large enough to cause damage will usually require slip on faults sufficiently large that they extend into basement. This suggests that an important criterion for large-scale CO2 sequestration projects is that the injection zone is isolated from crystalline basement rocks by viscoplastic shales to prevent rupture propagation from extending down into basement.

Characterizing the Potential for Injection-Induced Fault Reactivation Through Subsurface Structural Mapping and Stress Field Analysis, Wellington Field, Sumner County, Kansas

NASA Astrophysics Data System (ADS)

Schwab, Drew R.; Bidgoli, Tandis S.; Taylor, Michael H.

2017-12-01

Kansas, like other parts of the central U.S., has experienced a recent increase in seismicity. Correlation of these events with brine disposal operations suggests pore fluid pressure increases are reactivating preexisting faults, but rigorous evaluation at injection sites is lacking. Here we determine the suitability of CO2 injection into the Cambrian-Ordovician Arbuckle Group for long-term storage and into a Mississippian reservoir for enhanced oil recovery in Wellington Field, Sumner County, Kansas. To determine the potential for injection-induced earthquakes, we map subsurface faults and estimate in situ stresses, perform slip and dilation tendency analyses to identify well-oriented faults relative to the estimated stress field, and determine the pressure changes required to induce slip at reservoir and basement depths. Three-dimensional seismic reflection data reveal 12 near-vertical faults, mostly striking NNE, consistent with nodal planes from moment tensor solutions from recent earthquakes in the region. Most of the faults cut both reservoirs and several clearly penetrate the Precambrian basement. Drilling-induced fractures (N = 40) identified from image logs and inversion of earthquake moment tensor solutions (N = 65) indicate that the maximum horizontal stress is approximately EW. Slip tendency analysis indicates that faults striking <020° are stable under current reservoir conditions, whereas faults striking 020°-049° may be prone to reactivation with increasing pore fluid pressure. Although the proposed injection volume (40,000 t) is unlikely to reactive faults at reservoir depths, high-rate injection operations could reach pressures beyond the critical threshold for slip within the basement, as demonstrated by the large number of injection-induced earthquakes west of the study area.

Seismic and aseismic fault slip in response to fluid injection observed during field experiments at meter scale

NASA Astrophysics Data System (ADS)

Cappa, F.; Guglielmi, Y.; De Barros, L.; Wynants-Morel, N.; Duboeuf, L.

2017-12-01

During fluid injection, the observations of an enlarging cloud of seismicity are generally explained by a direct response to the pore pressure diffusion in a permeable fractured rock. However, fluid injection can also induce large aseismic deformations which provide an alternative mechanism for triggering and driving seismicity. Despite the importance of these two mechanisms during fluid injection, there are few studies on the effects of fluid pressure on the partitioning between seismic and aseismic motions under controlled field experiments. Here, we describe in-situ meter-scale experiments measuring synchronously the fluid pressure, the fault motions and the seismicity directly in a fault zone stimulated by controlled fluid injection at 280 m depth in carbonate rocks. The experiments were conducted in a gallery of an underground laboratory in south of France (LSBB, http://lsbb.eu). Thanks to the proximal monitoring at high-frequency, our data show that the fluid overpressure mainly induces a dilatant aseismic slip (several tens of microns up to a millimeter) at the injection. A sparse seismicity (-4 < Mw < -3) is observed several meters away from the injection, in a part of the fault zone where the fluid overpressure is null or very low. Using hydromechanical modeling with friction laws, we simulated an experiment and investigated the relative contribution of the fluid pressure diffusion and stress transfer on the seismic and aseismic fault behavior. The model reproduces the hydromechanical data measured at injection, and show that the aseismic slip induced by fluid injection propagates outside the pressurized zone where accumulated shear stress develops, and potentially triggers seismicity. Our models also show that the permeability enhancement and friction evolution are essential to explain the fault slip behavior. Our experimental results are consistent with large-scale observations of fault motions at geothermal sites (Wei et al., 2015; Cornet, 2016), and suggest that controlled field experiments at meter-scale are important for better assessing the role of fluid pressure in natural and human-induced earthquakes.

First-principles study of crystallographic slip modes in ω-Zr.

PubMed

Kumar, Anil; Kumar, M Arul; Beyerlein, Irene J

2017-08-21

We use first-principles density functional theory to study the preferred modes of slip in the high-pressure ω phase of Zr. The generalized stacking fault energy surfaces associated with shearing on nine distinct crystallographic slip modes in the hexagonal ω-Zr crystal are calculated, from which characteristics such as ideal shear stress, the dislocation Burgers vector, and possible accompanying atomic shuffles, are extracted. Comparison of energy barriers and ideal shear stresses suggests that the favorable modes are prismatic 〈c〉, prismatic-II [Formula: see text] and pyramidal-II 〈c + a〉, which are distinct from the ground state hexagonal close packed α phase of Zr. Operation of these three modes can accommodate any deformation state. The relative preferences among the identified slip modes are examined using a mean-field crystal plasticity model and comparing the calculated deformation texture with the measurement. Knowledge of the basic crystallographic modes of slip is critical to understanding and analyzing the plastic deformation behavior of ω-Zr or mixed α-ω phase-Zr.

Fault Creep along the Southern San Andreas from Interferometric Synthetic Aperture Radar, Permanent Scatterers, and Stacking

NASA Technical Reports Server (NTRS)

Lyons, Suzanne; Sandwell, David

2003-01-01

Interferometric synthetic aperture radar (InSAR) provides a practical means of mapping creep along major strike-slip faults. The small amplitude of the creep signal (less than 10 mm/yr), combined with its short wavelength, makes it difficult to extract from long time span interferograms, especially in agricultural or heavily vegetated areas. We utilize two approaches to extract the fault creep signal from 37 ERS SAR images along the southem San Andreas Fault. First, amplitude stacking is utilized to identify permanent scatterers, which are then used to weight the interferogram prior to spatial filtering. This weighting improves correlation and also provides a mask for poorly correlated areas. Second, the unwrapped phase is stacked to reduce tropospheric and other short-wavelength noise. This combined processing enables us to recover the near-field (approximately 200 m) slip signal across the fault due to shallow creep. Displacement maps fiom 60 interferograms reveal a diffuse secular strain buildup, punctuated by localized interseismic creep of 4-6 mm/yr line of sight (LOS, 12-18 mm/yr horizontal). With the exception of Durmid Hill, this entire segment of the southern San Andreas experienced right-lateral triggered slip of up to 10 cm during the 3.5-year period spanning the 1992 Landers earthquake. The deformation change following the 1999 Hector Mine earthquake was much smaller (4 cm) and broader than for the Landers event. Profiles across the fault during the interseismic phase show peak-to-trough amplitude ranging from 15 to 25 mm/yr (horizontal component) and the minimum misfit models show a range of creeping/locking depth values that fit the data.

Cross-slip in face-centered cubic metals: a general Escaig stress-dependent activation energy line tension model

NASA Astrophysics Data System (ADS)

Malka-Markovitz, Alon; Mordehai, Dan

2018-02-01

Cross-slip is a dislocation mechanism by which screw dislocations can change their glide plane. This thermally activated mechanism is an important mechanism in plasticity and understanding the energy barrier for cross-slip is essential to construct reliable cross-slip rules in dislocation models. In this work, we employ a line tension model for cross-slip of screw dislocations in face-centred cubic (FCC) metals in order to calculate the energy barrier under Escaig stresses. The analysis shows that the activation energy is proportional to the stacking fault energy, the unstressed dissociation width and a typical length for cross-slip along the dislocation line. Linearisation of the interaction forces between the partial dislocations yields that this typical length is related to the dislocation length that bows towards constriction during cross-slip. We show that the application of Escaig stresses on both the primary and the cross-slip planes varies the typical length for cross-slip and we propose a stress-dependent closed form expression for the activation energy for cross-slip in a large range of stresses. This analysis results in a stress-dependent activation volume, corresponding to the typical volume surrounding the stressed dislocation at constriction. The expression proposed here is shown to be in agreement with previous models, and to capture qualitatively the essentials found in atomistic simulations. The activation energy function can be easily implemented in dislocation dynamics simulations, owing to its simplicity and universality.

Ductilizing bulk metallic glass composite by tailoring stacking fault energy.

PubMed

Wu, Y; Zhou, D Q; Song, W L; Wang, H; Zhang, Z Y; Ma, D; Wang, X L; Lu, Z P

2012-12-14

Martensitic transformation was successfully introduced to bulk metallic glasses as the reinforcement micromechanism. In this Letter, it was found that the twinning property of the reinforcing crystals can be dramatically improved by reducing the stacking fault energy through microalloying, which effectively alters the electron charge density redistribution on the slipping plane. The enhanced twinning propensity promotes the martensitic transformation of the reinforcing austenite and, consequently, improves plastic stability and the macroscopic tensile ductility. In addition, a general rule to identify effective microalloying elements based on their electronegativity and atomic size was proposed.

Optimization research on the concentration field of NO in selective catalytic reduction flue gas denitration system

NASA Astrophysics Data System (ADS)

Zheng, Qingyu; Zhang, Guoqiang; Che, Kai; Shao, Shikuan; Li, Yanfei

2017-08-01

Taking 660 MW generator unit denitration system as a study object, an optimization and adjustment method shall be designed to control ammonia slip, i.e. adjust ammonia injection system based on NO concentration distribution at inlet/outlet of the denitration system to make the injected ammonia distribute evenly. The results shows that, this method can effectively improve NO concentration distribution at outlet of the denitration system and decrease ammonia injection amount and ammonia slip concentration. Reduce adverse impact of SCR denitration process on the air preheater to realize safe production by guaranteeing that NO discharge shall reach the standard.

First-Principles Quantum Dynamics of Singlet Fission: Coherent versus Thermally Activated Mechanisms Governed by Molecular π Stacking

NASA Astrophysics Data System (ADS)

Tamura, Hiroyuki; Huix-Rotllant, Miquel; Burghardt, Irene; Olivier, Yoann; Beljonne, David

2015-09-01

Singlet excitons in π -stacked molecular crystals can split into two triplet excitons in a process called singlet fission that opens a route to carrier multiplication in photovoltaics. To resolve controversies about the mechanism of singlet fission, we have developed a first principles nonadiabatic quantum dynamical model that reveals the critical role of molecular stacking symmetry and provides a unified picture of coherent versus thermally activated singlet fission mechanisms in different acenes. The slip-stacked equilibrium packing structure of pentacene derivatives is found to enhance ultrafast singlet fission mediated by a coherent superexchange mechanism via higher-lying charge transfer states. By contrast, the electronic couplings for singlet fission strictly vanish at the C2 h symmetric equilibrium π stacking of rubrene. In this case, singlet fission is driven by excitations of symmetry-breaking intermolecular vibrations, rationalizing the experimentally observed temperature dependence. Design rules for optimal singlet fission materials therefore need to account for the interplay of molecular π -stacking symmetry and phonon-induced coherent or thermally activated mechanisms.

First-principles study of crystallographic slip modes in ω-Zr

DOE PAGES

Kumar, Anil; Kumar, M. Arul; Beyerlein, Irene Jane

2017-08-21

We use first-principles density functional theory to study the preferred modes of slip in the high-pressure ω phase of Zr. The generalized stacking fault energy surfaces associated with shearing on nine distinct crystallographic slip modes in the hexagonal ω-Zr crystal are calculated, from which characteristics such as ideal shear stress, the dislocation Burgers vector, and possible accompanying atomic shuffles, are extracted. Comparison of energy barriers and ideal shear stresses suggests that the favorable modes are prismatic < c >, prismatic-II <101¯0> and pyramidal-II < c+a >, which are distinct from the ground state hexagonal close packed α phase of Zr.more » Operation of these three modes can accommodate any deformation state. The relative preferences among the identified slip modes are examined using a mean-field crystal plasticity model and comparing the calculated deformation texture with the measurement. In conclusion, knowledge of the basic crystallographic modes of slip is critical to understanding and analyzing the plastic deformation behavior of ω-Zr or mixed α-ω phase-Zr.« less

Kinematic evolution of Internal Getic nappes (Serbian Carpathians, eastern Serbia)

NASA Astrophysics Data System (ADS)

Krstekanic, Nemanja; Stojadinovic, Uros; Toljic, Marinko; Matenco, Liviu

2017-04-01

The tectonic evolution of the Carpatho - Balkanides Mountains is less understood in the critical segment of the Serbian Carpathians due to lack of available kinematic data. We have performed a field kinematic analysis combined with existing information from previous local and regional studies by focusing on the internal part of this orogenic segment, where the three highest most units of the nappe stack are exposed and separated by large offsets thrusts, i.e. the Supragetic, Upper Getic and Lower Getic. These units expose their metamorphic basement and Permo-Mesozoic cover penetrated by syn- and post-kinematic plutons and overlain or otherwise in structural contact with the Neogene fill of intramontane basins and the one of the Morava river corridor located in the prolongation of the much larger Pannonian basin. The kinematic analysis demonstrates seven superposed tectonic events of variable magnitudes and effects. Available superposition criteria and the correlation with the regional evolution demonstrate that four events are major tectonic episodes, while three others have a more limited influence or are local effects of strain partitioning and rotations. The first deformation event observed is the late Early Cretaceous cataclastic to brittle thrusting and shearing associated with the emplacement of the Supragetic nappe over the Getic unit. The observed paleostress NW-SE to SW-NE compressional directions were affected by the subsequent Cenozoic oroclinal bending of the Carpathians nappe stack. The first event was followed by Late Cretaceous E-W compression associated with significant strike-slip and transpression, the paleostress orientation being affected by the same subsequent rotations. The Paleogene - Early Miocene activation of the Cerna - Jiu and Timok faults system that cumulates an observed offset of 100 km is associated with large strikes-slip deformation with presently observed NNE-SSW oriented compressional directions in the study area. The formation of the Pannonian Basin and its prolongation in the Morava river corridor was associated at first with Early-Middle Miocene orogen-perpendicular extension, which was followed by orogen-parallel extension and strike-slip that started in the late Middle Miocene and lasted possibly until Pliocene times. This was followed by the Pliocene-Quaternary reactivation and thrusting of the Upper Getic thrust and strike slip with NNE-SSW to NNW-SSE oriented compression. All these deformations demonstrate a complex poly-phase history characterized at first by Cretaceous nappe stacking and transpressional deformations. This nappe stacking was followed by Cenozoic oroclinal bending associated with large-offset strike slip faults during the translation and rotation associated with the gradual closure of the Carpathians embayment, which interacted in the Serbian Carpathians with the back-arc extension of the Pannonian basin. This was followed by the regional inversion of the larger Pannonian Basin often reactivating inherited major structures or nappe contacts. This complex interplay was associated with significant strain partitioning that resulted in local rotations and changes of the paleostress directions.

Growth of Fault-Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

NASA Astrophysics Data System (ADS)

Johnson, Kaj M.

2018-03-01

Fault-related folds develop due to a combination of slip on the associated fault and distributed deformation off the fault. Under conditions that are sufficient for sedimentary layering to act as a stack of mechanical layers with contact slip, buckling can dramatically amplify the folding process. We develop boundary element models of fault-related folding of viscoelastic layers embedded with a reverse fault to examine the influence of such layering on fold growth. The strength of bedding contacts, the thickness and stiffness of layering, and fault geometry all contribute significantly to the resulting fold form. Frictional contact strength between layers controls the degree of localization of slip within fold limbs; high contact friction in relatively thin bedding tends to localize bedding slip within narrow kink bands on fold limbs, and low contact friction tends to produce widespread bedding slip and concentric fold form. Straight ramp faults tend to produce symmetric folds, whereas listric faults tend to produce asymmetric folds with short forelimbs and longer backlimbs. Fault-related buckle folds grow exponentially with time under steady loading rates. At early stages of folding, fold growth is largely attributed to slip on the fault, but as the fold increases amplitude, a larger portion of the fold growth is attributed to distributed slip across bedding contacts on the limbs of the fold. An important implication for geologic and earthquake studies is that not all surface deformation associated with blind reverse faults may be attributed to slip on the fault during earthquakes.

SIMULATIONS OF TRANSVERSE STACKING IN THE NSLS-II BOOSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fliller III, R.; Shaftan, T.

2011-03-28

The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme.more » We show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The injectors must provide 7.5nC in bunch trains 80-150 bunches long every minute for top off operation of the storage ring. Top off then requires that the linac deliver 15nC of charge once losses in the injector chain are taken into consideration. This is a very stringent requirement that has not been demonstrated at an operating light source. For this reason we have developed a method to transversely stack two bunch trains in the booster while maintaining the charge transport efficiency. This stacking scheme has been discussed previously. In this paper we show the simulations of the booster ramp with a single bunch train in the booster. Then we give a brief overview of the stacking scheme. Following, we show the results of stacking two bunch trains in the booster with varying beam emittances and train separations. The behavior of the beam through the ramp is examined showing that it is possible to stack two bunch trains in the booster.« less

Distinct Element Method modelling of fold-related fractures in a multilayer sequence

NASA Astrophysics Data System (ADS)

Kaserer, Klemens; Schöpfer, Martin P. J.; Grasemann, Bernhard

2017-04-01

Natural fractures have a significant impact on the performance of hydrocarbon systems/reservoirs. In a multilayer sequence, both the fracture density within the individual layers and the type of fracture intersection with bedding contacts are key parameters controlling fluid pathways. In the present study the influence of layer stacking and interlayer friction on fracture density and connectivity within a folded sequence is systematically investigated using 2D Distinct Element Method modelling. Our numerical approach permits forward modelling of both fracture nucleation/propagation/arrest and (contemporaneous) frictional slip along bedding planes in a robust and mechanically sound manner. Folding of the multilayer sequence is achieved by enforcing constant curvature folding by means of a velocity boundary condition at the model base, while a constant overburden pressure is maintained at the model top. The modelling reveals that with high bedding plane friction the multilayer stack behaves mechanically as a single layer so that the neutral surface develops in centre of the sequence and fracture spacing is controlled by the total thickness of the folded sequence. In contrast, low bedding plane friction leads to decoupling of the individual layers (flexural slip folding) so that a neutral surface develops in the centre of each layer and fracture spacing is controlled by the thickness of the individual layers. The low interfacial friction models illustrate that stepping of fractures across bedding planes is a common process, which can however have two contrasting origins: The mechanical properties of the interface cause fracture stepping during fracture propagation. Originally through-going fractures are later offset by interfacial slip during folding. A combination of these two different origins may lead to (apparently) inconsistent fracture offsets across bedding planes within a flexural slip fold.

A computational study of bulk porous two-dimensional polymers related to graphyne.

PubMed

Sánchez-González, A; Dobado, J A; Torneiro, M

2016-08-03

Over the last twelve years there has been an explosion in the area of reticular chemistry with several classes of carbonaceous or carbon-rich reticular compounds coming into the scene and/or suffering an exponential growth in the number of related studies. Examples are MOFs, COFs, graphene and 2D polymers. π-Conjugated reticular compounds in particular are of great interest due to their optoelectronic properties. In this study we use density functional theory methods with periodic boundary conditions to investigate the stacking arrangements of bulk 2D polymer multilayer porous graphyne A, the related carbon allotrope multilayer graphyne B, and the analog bulk 2D polymer C in which the triple bonds of A are substituted by double bonds. The results show that for the three materials the eclipsed stacking arrangements are considerably less stable than staggered and slipped arrangements, with the more stable structures being slipped, staggered and off-centered-staggered arrangements for A, B and C, respectively. To shed light on the π-π interactions responsible for the geometry and relative energies of the different stacking modes we analyze the topology of the electron density using the electron localization function. In addition, simulated patterns for powder X-ray diffraction have been obtained from the optimized systems, which can be used for identification of the bulk 2D reticular compounds in future syntheses.

Injected carrier concentration dependence of the expansion of single Shockley-type stacking faults in 4H-SiC PiN diodes

NASA Astrophysics Data System (ADS)

Tawara, T.; Matsunaga, S.; Fujimoto, T.; Ryo, M.; Miyazato, M.; Miyazawa, T.; Takenaka, K.; Miyajima, M.; Otsuki, A.; Yonezawa, Y.; Kato, T.; Okumura, H.; Kimoto, T.; Tsuchida, H.

2018-01-01

We investigated the relationship between the dislocation velocity and the injected carrier concentration on the expansion of single Shockley-type stacking faults by monitoring the electroluminescence from 4H-SiC PiN diodes with various anode Al concentrations. The injected carrier concentration was calculated using a device simulation that took into account the measured accumulated charge in the drift layer during diode turn-off. The dislocation velocity was strongly dependent on the injected hole concentration, which represents the excess carrier concentration. The activation energy of the dislocation velocity was quite small (below 0.001 eV between 310 and 386 K) over a fixed range of hole concentrations. The average threshold hole concentration required for the expansion of bar-shaped single Shockley-type stacking faults at the interface between the buffer layer and the substrate was determined to be 1.6-2.5 × 1016 cm-3 for diodes with a p-type epitaxial anode with various Al concentrations.

Anisotropy of high temperature strength in precipitation-hardened nickel-base superalloy single crystals

NASA Technical Reports Server (NTRS)

Nakagawa, Y. G.; Terashima, H.; Yoshizawa, H.; Ohta, Y.; Murakami, K.

1986-01-01

The anisotropy of high temperature strength of nickel-base superalloy, Alloy 454, in service for advanced jet engine turbine blades and vanes, was investigated. Crystallographic orientation dependence of tensile yield strength, creep and creep rupture strength was found to be marked at about 760C. In comparison with other single crystal data, a larger allowance in high strength off-axial orientation from the 001 axis, and relatively poor strength at near the -111 axis were noted. From transmission electron microscopy the anisotropic characteristics of this alloy were explained in terms of available slip systems and stacking geometries of gamma-prime precipitate cuboids which are well hardened by a large tantalum content. 100 cube slip was considered to be primarily responsible for the poor strength of the -111 axis orientation replacing the conventional 111 plane slip systems.

Resolving the Detailed Spatiotemporal Slip Evolution of Deep Tremor in Western Japan

NASA Astrophysics Data System (ADS)

Ohta, Kazuaki; Ide, Satoshi

2017-12-01

We study the detailed spatiotemporal behavior of deep tremor in western Japan through the development and application of a new slip inversion method. Although many studies now recognize tremor as shear slip along the plate interface manifested in low-frequency earthquake (LFE) swarms, a conventional slip inversion analysis is not available for tremor due to insufficient knowledge of source locations and Green's functions. Here we introduce synthetic template waveforms, which are typical tremor waveforms obtained by stacking LFE seismograms at arranged points along the plate interface. Using these synthetic template waveforms as substitutes for Green's functions, we invert the continuous tremor waveforms using an iterative deconvolution approach with Bayesian constraints. We apply this method to two tremor burst episodes in western and central Shikoku, Japan. The estimated slip distribution from a 12 day tremor burst episode in western Shikoku is heterogeneous, with several patchy areas of slip along the plate interface where rapid moment releases with durations of <100 s regularly occur. We attribute these heterogeneous spatiotemporal slip patterns to heterogeneous material properties along the plate interface. For central Shikoku, where we focus on a tremor burst episode that occurred coincidentally with a very low frequency earthquake (VLF), we observe that the source size of the VLF is much larger than that estimated from tremor activity in western Shikoku. These differences in the size of the slip region may dictate the visibility of VLF signals in observed seismograms, which has implications for the mechanics of slow earthquakes and subduction zone processes.

Generalized stacking fault energies, cleavage energies, ionicity and brittleness of Cu(Al/Ga/In)Se2 and CuGa(S/Se/Te)2

NASA Astrophysics Data System (ADS)

Xue, H. T.; Tang, F. L.; Gruhn, T.; Lu, W. J.; Wan, F. C.; Rui, Z. Y.; Feng, Y. D.

2014-04-01

We calculate the generalized stacking fault (GSF) energies and cleavage energies γcl of the chalcopyrite compounds CuAlSe2, CuGaSe2, CuInSe2, CuGaS2 and CuGaTe2 using first principles. From the GSF energies, we obtain the unstable stacking fault energies γus and intrinsic stacking fault energies γisf. By analyzing γus and γisf, we find that the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) direction is the easiest slip direction for these five compounds. Also, for CuInSe2, it is most possible to undergo a dislocation-nucleation-induced plastic deformation along the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) slip direction. We show that the (1 1 2) plane is the preferable plane for fracture in the five compounds by comparing γcl of the (0 0 1) and (1 1 2) planes. It is also found that both γus and γcl decrease as the cationic or anionic radius increases in these chalcopyrites, i.e. along the sequences CuAlSe2 → CuGaSe2 → CuInSe2 and CuGaS2 → CuGaSe2 → CuGaTe2. Based on the values of the ratio γcl/γus, we discuss the brittle-ductile properties of these compounds. All of the compounds can be considered as brittle materials. In addition, a strong relationship between γcl/γus and the total proportion of ionic bonding in these compounds is found.

Dislocation mechanism based model for stage II fatigue crack propagation rate

NASA Technical Reports Server (NTRS)

Mazumdar, P. K.

1986-01-01

Repeated plastic deformation, which of course depends on dislocation mechanism, at or near the crack tip leads to the fatigue crack propagation. By involving the theory of thermally activated flow and the cumulative plastic strain criterion, an effort is made here to model the stage II fatigue crack propagation rate in terms of the dislocation mechanism. The model, therefore, provides capability to ascertain: (1) the dislocation mechanism (and hence the near crack tip microstructures) assisting the crack growth, (2) the relative resistance of dislocation mechanisms to the crack growth, and (3) the fracture surface characteristics and its interpretation in terms of the dislocation mechanism. The local microstructure predicted for the room temperature crack growth in copper by this model is in good agreement with the experimental results taken from the literature. With regard to the relative stability of such dislocation mechanisms as the cross-slip and the dislocation intersection, the model suggests an enhancement of crack growth rate with an ease of cross-slip which in general promotes dislocation cell formation and is common in material which has high stacking fault energy (produces wavy slips). Cross-slip apparently enhances crack growth rate by promoting slip irreversibility and fracture surface brittleness to a greater degree.

Heat Transfer Analysis for Stationary Boundary Layer Slip Flow of a Power-Law Fluid in a Darcy Porous Medium with Plate Suction/Injection

PubMed Central

Aziz, Asim; Ali, Yasir; Aziz, Taha; Siddique, J. I.

2015-01-01

In this paper, we investigate the slip effects on the boundary layer flow and heat transfer characteristics of a power-law fluid past a porous flat plate embedded in the Darcy type porous medium. The nonlinear coupled system of partial differential equations governing the flow and heat transfer of a power-law fluid is transformed into a system of nonlinear coupled ordinary differential equations by applying a suitable similarity transformation. The resulting system of ordinary differential equations is solved numerically using Matlab bvp4c solver. Numerical results are presented in the form of graphs and the effects of the power-law index, velocity and thermal slip parameters, permeability parameter, suction/injection parameter on the velocity and temperature profiles are examined. PMID:26407162

A Viscoplastic Stress Relaxation Model for Predicting Variations of the Least Principal Stress With Depth in Unconventional Reservoirs

NASA Astrophysics Data System (ADS)

Zoback, M. D.; Xu, S.; Rassouli, F.; Ma, X.

2016-12-01

In this paper we extend the viscoplastic stress relaxation model of Sone and Zoback (Jour. Petrol. Sci. and Eng., 2014) for predicting variations of least principal stress with stress and its impact on the vertical propagation of hydraulic fractures. Viscoplastic stress relaxation in clay-rich (or diagenetically immature) sedimentary rocks makes the stress field more isotropic. In normal faulting and strike-slip faulting environments, this causes the least principal stress to increase making such formations likely barriers to vertical hydraulic fracture growth. In order to predict the magnitude of viscoplastic stress relaxation in different unconventional formations, we generalize a constitutive law developed from a wide range of creep experiments in our lab over the past several years and apply it to areas of stacked pay in Oklahoma and Texas. Using frac gradients were measured from minifrac and DFIT (Diagnostic Fracture Injection Test) experiments. The viscoplastic model does a good job of explaining vertical hydraulic fracture propagation, as indicated by the distribution of microseismic events recorded during stimulation.

Slip behaviour of experimental faults subjected to fluid pressure stimulation: carbonates vs. shales

NASA Astrophysics Data System (ADS)

Collettini, C.; Scuderi, M. M.; Marone, C.

2017-12-01

Fluid overpressure is one of the primary mechanisms for triggering tectonic fault slip and human-induced seismicity. This mechanism has been invoked to explain the dramatic increase in seismicity associated with waste water disposal in intra-plate setting, and it is appealing because fluids lubricate the fault and reduce the effective normal stress that holds the fault in place. Although, this basic physical mechanism is well understood, several fundamental questions remain including the apparent delay between fluid injection and seismicity, the role of fault zone rheology, and the relationship between injection volume and earthquake size. Moreover, models of earthquake nucleation predict that a reduction in normal stress, as expected for fluid overpressure, should stabilize fault slip. Here, we address these questions using laboratory experiments, conducted in the double direct shear configuration in a true-triaxial machine on carbonates and shale fault gouges. In particular, we: 1) evaluate frictional strength and permeability, 2) characterize the rate- and state- friction parameters and 3) study fault slip evolution during fluid pressure stimulations. With increasing fluid pressure, when shear and effective normal stresses reach the failure condition, in calcite gouges, characterized by slightly velocity strengthening behaviour, we observe an acceleration of slip that spontaneously evolves into dynamic failure. For shale gouges, with a strong rate-strengthening behaviour, we document complex fault slip behavior characterized by periodic accelerations and decelerations with slip velocity that remains slow (i.e. v 200 µm/s), never approaching dynamic slip rates. Our data indicate that fault rheology and fault stability is controlled by the coupling between fluid pressure and rate- and state- friction parameters suggesting that their comprehensive characterization is fundamental for assessing the role of fluid pressure in natural and human induced earthquakes.

Geomorphology, kinematic history, and earthquake behavior of the active Kuwana wedge thrust anticline, central Japan

NASA Astrophysics Data System (ADS)

Ishiyama, Tatsuya; Mueller, Karl; Togo, Masami; Okada, Atsumasa; Takemura, Keiji

2004-12-01

We combine surface mapping of fault and fold scarps that deform late Quaternary alluvial strata with interpretation of a high-resolution seismic reflection profile to develop a kinematic model and determine fault slip rates for an active blind wedge thrust system that underlies Kuwana anticline in central Japan. Surface fold scarps on Kuwana anticline are closely correlated with narrow fold limbs and angular hinges on the seismic profile that suggest at least ˜1.3 km of fault slip completely consumed by folding in the upper 4 km of the crust. The close coincidence and kinematic link between folded terraces and the underlying thrust geometry indicate that Kuwana anticline has accommodated slip at an average rate of 2.2 ± 0.5 mm/yr on a 27°, west dipping thrust fault since early-middle Pleistocene time. In contrast to classical fault bend folds the fault slip budget in the stacked wedge thrusts also indicates that (1) the fault tip propagated upward at a low rate relative to the accrual of fault slip and (2) fault slip is partly absorbed by numerous bedding plane flexural-slip faults above the tips of wedge thrusts. An historic earthquake that occurred on the Kuwana blind thrust system possibly in A.D. 1586 is shown to have produced coseismic surface deformation above the doubly vergent wedge tip. Structural analyses of Kuwana anticline coupled with tectonic geomorphology at 103-105 years timescales illustrate the significance of active folds as indicators of slip on underlying blind thrust faults and thus their otherwise inaccessible seismic hazards.

Mechanism and energetics of dislocation cross-slip in hcp metals

NASA Astrophysics Data System (ADS)

Wu, Zhaoxuan; Curtin, W. A.

2016-10-01

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

Exploration of the role of permeability and effective stress transfer effects on Earthquakes Migration in a Fault Zone induced by a Fluid Injection in the nearby host rock: Experimental and Numerical Result.

NASA Astrophysics Data System (ADS)

Tsopela, A.; Guglielmi, Y.; Donze, F. V.; De Barros, L.; Henry, P.; Castilla, R.; Gout, C.

2016-12-01

Although it has long been known that anthropogenic fluid injections can induce earthquakes, the mechanisms involved are still poorly understood and our ability to assess the seismic hazard associated to the production of geothermal energy or unconventional hydrocarbon remains limited. Here we present a field injection experiment conducted in the host rock 4m away from a fault affecting Toarcian shales (Tournemire massif, France). A dense network of sensors recorded fluid pressure, flow-rate, deformation and seismic activity. Injections followed an extended leak-off test protocol. Failure in the host rock was observed for a pressure of 4.4 MPa associated to a strike-slip-to-reverse reactivation of a pre-existing fracture. Magnitude -4.2 to -3.8 seismic events were located in the fault zone 3.5-to->10m away from the injection showing focal mechanisms in reasonable agreement with a strike-slip reactivation of the fault structures. We first used fully coupled hydro-mechanical numerical modeling to quantify the injection source parameters (state of stress, size of the rupture patch and size of the pressurized patch). We applied an injection loading protocol characterized by an imposed flow rate-vs-time history according to the volume of fluid injected in-situ, to match calculated and measured pressure and displacement variations at the injection source. We then used a larger model including the fault zone to discuss how predominant the effects of stress transfer mechanisms causing a purely mechanical fault activation can be compared to the effects of effective stress variations associated to fluid propagation in the fault structures. Preliminary results are that calculated slipping patches are much higher than the one estimated from seismicity, respectively 0.3m and <10-6m, and that the dimensions of the pressurized zone hardly matches with the distance of the earthquakes.

Distribution of aseismic slip rate on the Hayward fault inferred from seismic and geodetic data

USGS Publications Warehouse

Schmidt, D.A.; Burgmann, R.; Nadeau, R.M.; d'Alessio, M.

2005-01-01

We solve for the slip rate distribution on the Hayward fault by performing a least squares inversion,of geodetic and seismic data sets. Our analysis focuses on the northern 60 km of the fault. Interferometric synthetic aperture radar (InSAR) data from 13 independent ERS interferograms are stacked to obtain range change rates from 1992 to 2000. Horizontal surface displacement rates at 141 bench marks are measured using GPS from 1994 to 2003. Surface creep observations and estimates of deep slip rates determined from characteristic repeating earthquake sequences are also incorporated in the inversion. The fault is discretized into 283 triangular dislocation elements that approximate the nonplanar attributes of the fault surface. South of the city of Hayward, a steeply, east dipping fault geometry accommodates the divergence of the surface trace and the microseismicity at depth. The inferred slip rate distribution is consistent with a fault that creeps aseismically at a rate of ???5 mm/yr to a depth of 4-6 km. The interferometric synthetic aperture radar (InSAR) data require an aseismic slip rate that approaches the geologic slip rate on the northernmost fault segment beneath Point Pinole, although the InSAR data might be complicated by a small dip-slip component at this location. A low slip rate patch of <1 mm/yr is inferred beneath San Leandro consistent with the source location of the 1868 earthquake. We calculate that the entire fault is accumulating a slip rate deficit equivalent to a Mw = 6.77 ?? 0.05 per century. However, this estimate of potential coseismic moment represents an upper bound because we do not know how much of the accumulated strain will be released through aseismic processes such as afterslip. Copyright 2005 by the American Geophysical Union.

Major and micro seismo-volcanic crises in the Asal Rift, Djibouti

NASA Astrophysics Data System (ADS)

Peltzer, G.; Doubre, C.; Tomic, J.

2009-05-01

The Asal-Ghoubbet Rift is located on the eastern branch of the Afar triple junction between the Arabia, Somalia, and Nubia tectonic plates. The last major seismo-volcanic crisis on this segment occurred in November 1978, involving two earthquakes of mb=5+, a basaltic fissure eruption, the development of many open fissures across the rift and up to 80 cm of vertical slip on the bordering faults. Geodetic leveling revealed ~2 m of horizontal opening of the rift accompanied by ~70 cm of subsidence of the inner-floor, consistent with models of the elastic deformation produced by the injection of magma in a system of two dykes. InSAR data acquired at 24-day intervals during the last 12 years by the Canadian Radarsat satellite over the Asal Rift show that the two main faults activated in 1978 continue to slip with periods of steady creep at rates of 0.3-1.3 mm/yr, interrupted by sudden slip events of a few millimeters, in 2000 and 2003. Slip events are coincident with bursts of micro earthquakes distributed around and over the Fieale volcanic center in the eastern part of the Asal Rift. In both cases (the 1978 crisis and micro-slip events), the observed geodetic moment released by fault slip exceeds by a few orders of magnitude the total seismic moment released by earthquakes over the same period. Aseismic fault slip is likely to be the faults response to a changing stress field associated with a volcanic process and not due to dry friction on faults. Sustained injection of magma (1978 crisis) and/or crustal fluids (micro-slip events) in dykes and fissures is a plausible mechanism to control fluid pressure in the basal parts of faults and trigger aseismic slip. In this respect, the micro-events observed by InSAR during a 12-year period of low activity in the rift and the 1978 seismo-volcanic episode are of same nature.

Steady boundary layer slip flow along with heat and mass transfer over a flat porous plate embedded in a porous medium.

PubMed

Aziz, Asim; Siddique, J I; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile.

Steady Boundary Layer Slip Flow along with Heat and Mass Transfer over a Flat Porous Plate Embedded in a Porous Medium

PubMed Central

Aziz, Asim; Siddique, J. I.; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile. PMID:25531301

An experimental study of the influence of stress history on fault slip during injection of supercritical CO2

NASA Astrophysics Data System (ADS)

Cuss, Robert J.; Wiseall, Andrew C.; Tamayo-Mas, Elena; Harrington, Jon F.

2018-04-01

The injection of super-critical CO2 into a depleted reservoir will alter the pore pressure of the basin, which if sufficiently perturbed could result in fault slip. Therefore, knowledge of the acceptable pressure limits is required in order to maintain fault stability. A two-part laboratory study was conducted on fully saturated kaolinite fault gouge to investigate this issue. Previously, we showed that fault slip occurred once pore-pressure within the gouge was sufficient to overcome the normal stress acting on the fault. For kaolinite, this behaviour occurred at a pressure similar to the yield stress. The current study shows that following a slow-reduction in the maximum principal stress, as would be expected through changes in effective stress, the reactivation pressure shows a stress memory. Consequently, the pressure necessary to initiate fault slip is similar to that required at the maximum stress encountered. Therefore, fault slip is at least partially controlled by the previous maximum stress and not the current stress state. During the slow reduction in normal stress, the flow characteristics of the fault remain unchanged until pore-pressure exceeds shear stress and does not increase significantly until it exceeds normal stress. This results in fault slip, which slows the rate of flow increase as shear is an effective self-sealing mechanism. These observations lead to the conclusion that stress history is a vital parameter when considering fault stability.

Temperature-dependent stability of stacking faults in Al, Cu and Ni: first-principles analysis.

PubMed

Bhogra, Meha; Ramamurty, U; Waghmare, Umesh V

2014-09-24

We present comparative analysis of microscopic mechanisms relevant to plastic deformation of the face-centered cubic (FCC) metals Al, Cu, and Ni, through determination of the temperature-dependent free energies of intrinsic and unstable stacking faults along [1 1̄ 0] and [1 2̄ 1] on the (1 1 1) plane using first-principles density-functional-theory-based calculations. We show that vibrational contribution results in significant decrease in the free energy of barriers and intrinsic stacking faults (ISFs) of Al, Cu, and Ni with temperature, confirming an important role of thermal fluctuations in the stability of stacking faults (SFs) and deformation at elevated temperatures. In contrast to Al and Ni, the vibrational spectrum of the unstable stacking fault (USF[1 2̄ 1]) in Cu reveals structural instabilities, indicating that the energy barrier (γusf) along the (1 1 1)[1 2̄ 1] slip system in Cu, determined by typical first-principles calculations, is an overestimate, and its commonly used interpretation as the energy release rate needed for dislocation nucleation, as proposed by Rice (1992 J. Mech. Phys. Solids 40 239), should be taken with caution.

CHARACTERIZATION OF POLED SINGLE-LAYER PZT FOR PIEZO STACK IN FUEL INJECTION SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hong; Matsunaga, Tadashi; Lin, Hua-Tay

2010-01-01

Poled single-layer PZT has been characterized in as-extracted and as-received states. PZT plate specimens in the former were extracted from a stack. Flexure strength of PZT was evaluated by using ball-on-ring and 4-point bend tests. Fractography showed that intergranular fractures dominated the fracture surface and that volume pores were the primary strength-limiting flaws. The electric field effect was investigated by testing the PZT in open circuit and coercive field levels. An asymmetrical response on the biaxial flexure strength with respect to the electric field direction was observed. These experimental results will assist reliability design of the piezo stack that ismore » being considered in fuel injection system.« less

REDUCTION OF COAL-BASED METAL EMISSIONS BY FURNACE SORBENT INJECTION

EPA Science Inventory

The ability of sorbent injection technology to reduce the potential for trace metal emissions from coal combustion was researched. Pilot scale tests of high-temperature furnace sorbent injection were accompanied by stack sampling for coal-based, metallic air toxics. Tested sorben...

Post-Injection Induced Seismicity in EGS: Triggering Mechanisms and Mitigation.

NASA Astrophysics Data System (ADS)

De Simone, S.; Carrera, J.; Vilarrasa, V.

2017-12-01

Induced microseismicity is a controversial issue related to Enhanced Geothermal Systems (EGS) and in general with fluid injection into deep geological formations. The occurring of felt earthquakes after stopping injection especially generates concern, because the correlation between injection and seismic activity is unclear. The aim of this work is to advance in the understanding of the processes that may induce or trigger co- and post-injection seismicity. To this end we investigate the thermo-hydro-mechanical coupling by means of numerical simulations of hydraulic stimulation of deep geothermal systems. We find that preferential flow through conductive fractures or fault zones provokes pressure and temperature perturbations that result in not only heterogeneous variation of the stress field, but also highly anisotropic variations of the local stress tensor. Anisotropic variations tend to stabilize some fractures, but destabilize others. Moreover, activation of shear slip causes a significant variation of the stress field that enlarges the range of critical fracture orientations. We find that post-injection seismicity may occur on non-critically oriented faults that were originally stable. During injection, such faults become destabilized by thermal and shear slip stress changes, but remain static by the superposition of the stabilizing effect of pressure forces. However, these fractures become unstable and fail when the pressure forcing dissipates shortly after injection stops abruptly, which suggests that a slow reduction in injection rate may mitigate post-injection seismicity.

A 3-Dimensional Numerical Modelling Study on the Effects of Different Stress Regimes on the Magnitude of Induced Seismic Events

NASA Astrophysics Data System (ADS)

Amini, A.; Eberhardt, E.

2016-12-01

Producing oil and gas from shale reservoirs requires permeability enhancement treatments. This is achieved by injecting fluid under pressure to either propagate cracks through the rock (hydraulic fracture) or to stimulate slip across pre-existing fractures (hydroshear), which allows gas or oil to flow more readily into the well bore. After treatment is performed, the fluid is disposed of by injecting it back into the ground. The injection of these fluids, whether related to permeability enhancement or waste water disposal , into deep formations serves to create localized increases in pore pressures and reductions in the effective normal stresses acting on critically stressed faults, resulting in induced earthquakes. There have been numerous reports of anomalous seismic events with high magnitudes felt on surface that have given rise to public concerns. However, it must be recognized that different producing fields in Canada and the U.S. are situated in different tectonic regimes that favour different fault slip mechanisms. This study will explore the importance of stress regime, comparing the generation of induced seismicity under thrust versus strike slip conditions, with focus on their respective magnitudes distributions. To do so, we will first study empirical data pertaining to recorded seismicity related to hydraulic fracture operations with respect to source mechanisms and magnitude distributions. These will be analyzed in parallel with a series of advanced 3-dimensional numerical models using the distinct element code 3DEC to simulate fault slip under different stress regimes.

Origin analysis of expanded stacking faults by applying forward current to 4H-SiC p-i-n diodes

NASA Astrophysics Data System (ADS)

Hayashi, Shohei; Naijo, Takanori; Yamashita, Tamotsu; Miyazato, Masaki; Ryo, Mina; Fujisawa, Hiroyuki; Miyajima, Masaaki; Senzaki, Junji; Kato, Tomohisa; Yonezawa, Yoshiyuki; Kojima, Kazutoshi; Okumura, Hajime

2017-08-01

Stacking faults expanded by the application of forward current to 4H-SiC p-i-n diodes were observed using a transmission electron microscope to investigate the expansion origin. It was experimentally confirmed that long-zonal-shaped stacking faults expanded from basal-plane dislocations converted into threading edge dislocations. In addition, stacking fault expansion clearly penetrated into the substrate to a greater depth than the dislocation conversion point. This downward expansion of stacking faults strongly depends on the degree of high-density minority carrier injection.

Aseismic and seismic slip induced by fluid injection from poroelastic and rate-state friction modeling

NASA Astrophysics Data System (ADS)

Liu, Y.; Deng, K.; Harrington, R. M.; Clerc, F.

2016-12-01

Solid matrix stress change and pore pressure diffusion caused by fluid injection has been postulated as key factors for inducing earthquakes and aseismic slip on pre-existing faults. In this study, we have developed a numerical model that simulates aseismic and seismic slip in a rate-and-state friction framework with poroelastic stress perturbations from multi-stage hydraulic fracturing scenarios. We apply the physics-based model to the 2013-2015 earthquake sequences near Fox Creek, Alberta, Canada, where three magnitude 4.5 earthquakes were potentially induced by nearby hydraulic fracturing activity. In particular, we use the relocated December 2013 seismicity sequence to approximate the fault orientation, and find the seismicity migration spatiotemporally correlate with the positive Coulomb stress changes calculated from the poroelastic model. When the poroelastic stress changes are introduced to the rate-state friction model, we find that slip on the fault evolves from aseismic to seismic in a manner similar to the onset of seismicity. For a 15-stage hydraulic fracturing that lasted for 10 days, modeled fault slip rate starts to accelerate after 3 days of fracking, and rapidly develops into a seismic event, which also temporally coincides with the onset of induced seismicity. The poroelastic stress perturbation and consequently fault slip rate continue to evolve and remain high for several weeks after hydraulic fracturing has stopped, which may explain the continued seismicity after shut-in. In a comparison numerical experiment, fault slip rate quickly decreases to the interseismic level when stress perturbations are instantaneously returned to zero at shut-in. Furthermore, when stress perturbations are removed just a few hours after the fault slip rate starts to accelerate (that is, hydraulic fracturing is shut down prematurely), only aseismic slip is observed in the model. Our preliminary results thus suggest the design of fracturing duration and flow-back strategy, either allowing stress perturbations to passively dissipate in the medium or actively dropping to the pre-perturbation level, is essential to inducing seismic versus aseismic slip on pre-existing faults.

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals.

PubMed

Wu, Zhaoxuan; Curtin, W A

2016-10-04

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated [Formula: see text] dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of [Formula: see text] dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal [Formula: see text] dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

Mechanism and energetics of 〈c + a〉 dislocation cross-slip in hcp metals

PubMed Central

Wu, Zhaoxuan; Curtin, W. A.

2016-01-01

Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated 〈c+a〉 dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of 〈c+a〉 dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal 〈c+a〉 dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension–compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals. PMID:27647908

Resolving the detailed spatiotemporal slip evolution of deep tremor in western Japan

NASA Astrophysics Data System (ADS)

Ohta, K.; Ide, S.

2017-12-01

A quantitative evaluation of the slip evolution of tremor is essential to understand the generation mechanism of slow earthquakes. The recent studies have revealed the most part of tremor signals can be expressed as the superposition of low frequency earthquakes (LFE). However, it is still challenging to explain the entire waveforms of tremor, because a conventional slip inversion analysis is not available for tremor due to insufficient knowledge of source locations and Green's functions. Here we investigate the detailed spatiotemporal behavior of deep tremor in western Japan through the development and application of a new slip inversion method. We introduce synthetic template waveforms, which are typical tremor waveforms obtained by stacking LFE seismograms at arranged points along the plate interface. Using these synthetic template waveforms as substitutes for Green's functions, we invert the continuous tremor waveforms using an iterative deconvolution approach with Bayesian constraints. We apply this method to two tremor burst episodes in western and central Shikoku, Japan. The estimated slip distribution from a 12-day tremor burst episode in western Shikoku is heterogeneous, with several patchy areas of slip along the plate interface where rapid moment releases with durations of <100 s regularly occur. We attribute these heterogeneous spatiotemporal slip patterns to heterogeneous material properties along the plate interface. For central Shikoku, where we focus on a tremor burst episode that occurred coincidentally with a very low frequency earthquake (VLF), we observe that the source size of the VLF is much larger than that estimated from tremor activity in western Shikoku. These differences in the size of the slip region may dictate the visibility of VLF signals in observed seismograms, which has implications for the mechanics of slow earthquakes and subduction zone processes.

Comparative study on sample stacking by moving reaction boundary formed with weak acid and weak or strong base in capillary electrophoresis: II. Experiments.

PubMed

Zhang, Wei; Fan, Liuyin; Shao, Jing; Li, Si; Li, Shan; Cao, Chengxi

2011-04-15

To demonstrate the theoretic method on the stacking of zwitterion with moving reaction boundary (MRB) in the accompanying paper, the relevant experiments were performed. The experimental results quantitatively show that (1) MRB velocity, including the comparisons between MRB and zwitterionic velocities, possesses key importance to the design of MRB stacking; (2) a much long front alkaline plug without sample should be injected before the sample injection for a complete stacking of zwitterion if sample buffer is prepared with strong base, conversely no such plug is needed if using a weak base as the sample buffer with proper concentration and pH value; (3) the presence of salt in MRB system holds dramatic effect on the MRB stacking if sample solution is a strong base, but has no effect if a weak alkali is used as sample solution; (4) all of the experiments of this paper, including the previous work, quantitatively manifest the theory and predictions shown in the accompanying paper. In addition, the so-called derivative MRB-induced re-stacking and transient FASI-induced re-stacking were also observed during the experiments, and the relevant mechanisms were briefly demonstrated with the results. The theory and its calculation procedures developed in the accompanying paper can be well used for the predictions to the MRB stacking of zwitterion in CE. Copyright © 2011 Elsevier B.V. All rights reserved.

Deformation modeling and constitutive modeling for anisotropic superalloys

NASA Technical Reports Server (NTRS)

Milligan, Walter W.; Antolovich, Stephen D.

1989-01-01

A study of deformation mechanisms in the single crystal superalloy PWA 1480 was conducted. Monotonic and cyclic tests were conducted from 20 to 1093 C. Both (001) and near-(123) crystals were tested, at strain rates of 0.5 and 50 percent/minute. The deformation behavior could be grouped into two temperature regimes: low temperatures, below 760 C; and high temperatures, above 820 to 950 C depending on the strain rate. At low temperatures, the mechanical behavior was very anisotropic. An orientation dependent CRSS, a tension-compression asymmetry, and anisotropic strain hardening were all observed. The material was deformed by planar octahedral slip. The anisotropic properties were correlated with the ease of cube cross-slip, as well as the number of active slip systems. At high temperatures, the material was isotropic, and deformed by homogeneous gamma by-pass. It was found that the temperature dependence of the formation of superlattice-intrinsic stacking faults was responsible for the local minimum in the CRSS of this alloy at 400 C. It was proposed that the cube cross-slip process must be reversible. This was used to explain the reversible tension-compression asymmetry, and was used to study models of cross-slip. As a result, the cross-slip model proposed by Paidar, Pope and Vitek was found to be consistent with the proposed slip reversibility. The results were related to anisotropic viscoplastic constitutive models. The model proposed by Walter and Jordan was found to be capable of modeling all aspects of the material anisotropy. Temperature and strain rate boundaries for the model were proposed, and guidelines for numerical experiments were proposed.

Wastewater injection and slip triggering: Results from a 3D coupled reservoir/rate-and-state model

NASA Astrophysics Data System (ADS)

Babazadeh, M.; Olson, J. E.; Schultz, R.

2017-12-01

Seismicity induced by fluid injection is controlled by parameters related to injection conditions, reservoir properties, and fault frictional behavior. We present results from a combined model that brings together injection physics, reservoir dynamics, and fault physics to better explain the primary controls on induced seismicity. We created a 3D fluid flow simulator using the embedded discrete fracture technique and then coupled it with a 3D displacement discontinuity model that uses rate and state friction to model slip events. The model is composed of three layers, including the top-seal, the injection reservoir, and the basement. Permeability is anisotropic (vertical vs horizontal) and along with porosity varies by layer. Injection control can be either rate or pressure. Fault properties include size, 2D permeability, and frictional properties. Several suites of simulations were run to evaluate the relative importance of each of the factors from all three parameter groups. We find that the injection parameters interact with the reservoir parameters in the context of the fault physics and these relations change for different reservoir and fault characteristics, leading to the need to examine the injection parameters only within the context of a particular faulted reservoir. For a reservoir with no flow boundaries, low permeability (5 md), and a fault with high fault-parallel permeability and critical stress, injection rate exerts the strongest control on magnitude and frequency of earthquakes. However, for a higher permeability reservoir (80 md), injection volume becomes the more important factor. Fault permeability structure is a key factor in inducing earthquakes in basement rocks below the injection reservoir. The initial failure state of the fault, which is challenging to assess, can have a big effect on the size and timing of events. For a fault 2 MPa below critical state, we were able to induce a slip event, but it occurred late in the injection history and was limited to a subset of the fault extent. A case starting at critical stress resulted in a rupture that propagated throughout the entire physical extent of the fault generated a larger magnitude earthquake. This physics-based model can contribute to assessing the risk associated with injection activities and providing guidelines for hazard mitigation.

Study on ammonia slip detection in the harsh combustion environments using diode laser spectroscopy

NASA Astrophysics Data System (ADS)

You, Kun; Zhang, Yu-jun; Li, Hong-bin; He, Yin; Gao, Yan-wei; Wang, Li-ming; Liu, Wen-qing

2016-10-01

The emissions of NOX from Cement plant or Coal-fired power plant have serious pollution to the environment. In recent years, Selective Catalytic Reduction (SCR) is an effective means of reducing the emissions of NOX by injecting ammonia into the combustion flue gas, which ideally reacts with the NOX to produce harmless components (H2O and N2). The efficiency of SCR is determined by monitoring the ammonia slip of the flue exhaust outlet, excess ammonia injection can cause ammonia slip, which not only destroy the plant, but also increase the operating costs. In addition, ammonia is also pollution gases as NOX. The flue gas at the measurement point is high temperature, vibrate and high particle density processes in Cement plant primarily, such harsh conditions coupled with the highly reactive nature of ammonia, so it is difficult to reliable extractive low level analysis. The paper describes an in-situ Tunable Diode Laser analyzer for measuring ammonia slip in the combustion flue gas after SCR in Cement Plant or Coal-fired power plant. A correlation filtering algorithm is developed to select high-quality spectral absorption signal, which improve the accuracy of concentration inversion of analyzer. The paper also includes field test data on an actual Cement plant all day, and we compare the ammonia slip and NOX emissions of flue gas during actual production process, the results indicate that the measured values of the ammonia slip and NOX emissions present a good correlation and comply with the principle of SCR.

Efficient barrier for charge injection in polyethylene by silver nanoparticles/plasma polymer stack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milliere, L.; Makasheva, K., E-mail: kremena.makasheva@laplace.univ-tlse.fr; Laurent, C.

2014-09-22

Charge injection from a metal/insulator contact is a process promoting the formation of space charge in polymeric insulation largely used in thick layers in high voltage equipment. The internal charge perturbs the field distribution and can lead to catastrophic failure either through its electrostatic effects or through energetic processes initiated under charge recombination and/or hot electrons effects. Injection is still ill-described in polymeric insulation due to the complexity of the contact between the polymer chains and the electrodes. Barrier heights derived from the metal work function and the polymer electronic affinity do not provide a good description of the measurementsmore » [Taleb et al., IEEE Trans. Dielectr. Electr. Insul. 20, 311–320 (2013)]. Considering the difficulty to describe the contact properties and the need to prevent charge injection in polymers for high voltage applications, we developed an alternative approach by tailoring the interface properties by the silver nanoparticles (AgNPs)/plasma polymer stack, deposited on the polymer film. Due to their small size, the AgNPs, covered by a very thin film of plasma polymer, act as deep traps for the injected charges thereby stabilizing the interface from the point of view of charge injection. After a quick description of the method for elaborating the nanostructured layer near the contact, it is demonstrated how the AgNPs/plasma polymer stack effectively prevents, in a spectacular way, the formation of bulk space charge.« less

Multi-color γ-rays from comb-like electron beams driven by incoherent stacks of laser pulses

NASA Astrophysics Data System (ADS)

Kalmykov, S. Y.; Davoine, X.; Ghebregziabher, I.; Shadwick, B. A.

2017-03-01

Trains of fs-length, GeV-scale electron bunches with controlled energy spacing and a 5-D brightness up to 1017 A/m2 may be produced in a mm-scale uniform plasma. The main element of the scheme is an incoherent stack of 10-TW-scale laser pulses of different colors, with mismatched focal spots, with the highest-frequency pulse advanced in time. While driving an electron density bubble, this stack remains almost proof against nonlinear red-shift and self-compression. As a consequence, the unwanted continuous injection of background electrons is minimized. Weak focusing of the trailing (lower-frequency) component of the stack enforces expansions and contractions of the bubble, inducing controlled periodic injection. The resulting train of electron bunches maintains exceptional quality while being accelerated beyond the energy limits predicted by accepted scalings. Inverse Thomson scattering from this comb-like beam generates a sequence of quasi-monochromatic, fs-length γ-ray beams, an asset for nuclear forensics and pump-probe experiments in dense plasmas.

Orientation Dependence of the Deformation Microstructure of Ta-4%W after Cold-Rolling

NASA Astrophysics Data System (ADS)

Zhang, J.; Ma, G. Q.; Godfrey, A.; Shu, D. Y.; Chen, Q.; Wu, G. L.

2017-07-01

One of the common features of deformed face-centered cubic metals with medium to high stacking fault energy is the formation of geometrically necessary dislocation boundaries. The dislocation boundary arrangements in refractory metals with body-centered cubic crystal structure are, however, less well known. To address this issue a Ta-4%W alloy was cold rolled up to 70% in thickness in the present work. The resulting deformation microstructures were characterized by electron back-scattering diffraction and the dislocation boundary arrangements in each grain were revealed using sample-frame misorientation axis maps calculated using an in-house code. The maps were used to analyze the slip pattern of individual grains after rolling, revealing an orientation dependence of the slip pattern.

Hydraulic Fracture Induced Seismicity During A Multi-Stage Pad Completion in Western Canada: Evidence of Activation of Multiple, Parallel Faults

NASA Astrophysics Data System (ADS)

Maxwell, S.; Garrett, D.; Huang, J.; Usher, P.; Mamer, P.

2017-12-01

Following reports of injection induced seismicity in the Western Canadian Sedimentary Basin, regulators have imposed seismic monitoring and traffic light protocols for fracturing operations in specific areas. Here we describe a case study in one of these reservoirs, the Montney Shale in NE British Columbia, where induced seismicity was monitored with a local array during multi-stage hydraulic fracture stimulations on several wells from a single drilling pad. Seismicity primarily occurred during the injection time periods, and correlated with periods of high injection rates and wellhead pressures above fracturing pressures. Sequential hydraulic fracture stages were found to progressively activate several parallel, critically-stressed faults, as illuminated by multiple linear hypocenter patterns in the range between Mw 1 and 3. Moment tensor inversion of larger events indicated a double-couple mechanism consistent with the regional strike-slip stress state and the hypocenter lineations. The critically-stressed faults obliquely cross the well paths which were purposely drilled parallel to the minimum principal stress direction. Seismicity on specific faults started and stopped when fracture initiation points of individual injection stages were proximal to the intersection of the fault and well. The distance ranges when the seismicity occurs is consistent with expected hydraulic fracture dimensions, suggesting that the induced fault slip only occurs when a hydraulic fracture grows directly into the fault and the faults are temporarily exposed to significantly elevated fracture pressures during the injection. Some faults crossed multiple wells and the seismicity was found to restart during injection of proximal stages on adjacent wells, progressively expanding the seismogenic zone of the fault. Progressive fault slip is therefore inferred from the seismicity migrating further along the faults during successive injection stages. An accelerometer was also deployed close to the pad operations providing information about the local ground motion at near offsets, although no ground motion was recorded that exceeds the minimum levels requiring mandatory reporting to the regulator.

40 CFR Table 6 to Subpart Jjjjjj... - Establishing Operating Limits

Code of Federal Regulations, 2014 CFR

2014-07-01

... Dry sorbent or activated carbon injection rate operating parameters Establish a site-specific minimum sorbent or activated carbon injection rate operating limit according to § 63.11211(b) Data from the sorbent or activated carbon injection rate monitors and the mercury performance stack tests (a) You must...

40 CFR Table 6 to Subpart Jjjjjj... - Establishing Operating Limits

Code of Federal Regulations, 2013 CFR

2013-07-01

... Dry sorbent or activated carbon injection rate operating parameters Establish a site-specific minimum sorbent or activated carbon injection rate operating limit according to § 63.11211(b) Data from the sorbent or activated carbon injection rate monitors and the mercury performance stack tests (a) You must...

Microstructural characterization of high-manganese austenitic steels with different stacking fault energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Shigeo, E-mail: s.sato@imr.tohoku.ac.jp; Kwon, Eui-Pyo; Imafuku, Muneyuki

Microstructures of tensile-deformed high-manganese austenitic steels exhibiting twinning-induced plasticity were analyzed by electron backscatter diffraction pattern observation and X-ray diffraction measurement to examine the influence of differences in their stacking fault energies on twinning activity during deformation. The steel specimen with the low stacking fault energy of 15 mJ/m{sup 2} had a microstructure with a high population of mechanical twins than the steel specimen with the high stacking fault energy (25 mJ/m{sup 2}). The <111> and <100> fibers developed along the tensile axis, and mechanical twinning occurred preferentially in the <111> fiber. The Schmid factors for slip and twinning deformationsmore » can explain the origin of higher twinning activity in the <111> fiber. However, the high stacking fault energy suppresses the twinning activity even in the <111> fiber. A line profile analysis based on the X-ray diffraction data revealed the relationship between the characteristics of the deformed microstructures and the stacking fault energies of the steel specimens. Although the variation in dislocation density with the tensile deformation is not affected by the stacking fault energies, the effect of the stacking fault energies on the crystallite size refinement becomes significant with a decrease in the stacking fault energies. Moreover, the stacking fault probability, which was estimated from a peak-shift analysis of the 111 and 200 diffractions, was high for the specimen with low stacking fault energy. Regardless of the difference in the stacking fault energies of the steel specimens, the refined crystallite size has a certain correlation with the stacking fault probability, indicating that whether the deformation-induced crystallite-size refinement occurs depends directly on the stacking fault probability rather than on the stacking fault energies in the present steel specimens. - Highlights: {yields} We studied effects of stacking fault energies on deformed microstructures of steels. {yields} Correlations between texture and occurrence of mechanical twinning are discussed. {yields} Evolutions of dislocations and crystallite are analyzed by line profile analysis.« less

AN ELECTROCHEMICAL SYSTEM FOR REMOVING AND RECOVERING ELEMENTAL MERCURY FROM FLUE-STACK GASES

EPA Science Inventory

the impending EPA regulations on the control of mercury emissions from the flue stacks of coal-burning electric utilities has resulted in heightened interest in the development of advanced mercury control technologies such as sorbent injection and in-situ mercury oxidation. Altho...

Optimization of throughput in semipreparative chiral liquid chromatography using stacked injection.

PubMed

Taheri, Mohammadreza; Fotovati, Mohsen; Hosseini, Seyed-Kiumars; Ghassempour, Alireza

2017-10-01

An interesting mode of chromatography for preparation of pure enantiomers from pure samples is the method of stacked injection as a pseudocontinuous procedure. Maximum throughput and minimal production costs can be achieved by the use of total chiral column length in this mode of chromatography. To maximize sample loading, often touching bands of the two enantiomers is automatically achieved. Conventional equations show direct correlation between touching-band loadability and the selectivity factor of two enantiomers. The important question for one who wants to obtain the highest throughput is "How to optimize different factors including selectivity, resolution, run time, and loading of the sample in order to save time without missing the touching-band resolution?" To answer this question, tramadol and propranolol were separated on cellulose 3,5-dimethyl phenyl carbamate, as two pure racemic mixtures with low and high solubilities in mobile phase, respectively. The mobile phase composition consisted of n-hexane solvent with alcohol modifier and diethylamine as the additive. A response surface methodology based on central composite design was used to optimize separation factors against the main responses. According to the stacked injection properties, two processes were investigated for maximizing throughput: one with a poorly soluble and another with a highly soluble racemic mixture. For each case, different optimization possibilities were inspected. It was revealed that resolution is a crucial response for separations of this kind. Peak area and run time are two critical parameters in optimization of stacked injection for binary mixtures which have low solubility in the mobile phase. © 2017 Wiley Periodicals, Inc.

Air-stable n-channel organic thin-film transistors with high field-effect mobility based on N ,N'-bis(heptafluorobutyl)-3,4:9,10-perylene diimide

NASA Astrophysics Data System (ADS)

Oh, Joon Hak; Liu, Shuhong; Bao, Zhenan; Schmidt, Rüdiger; Würthner, Frank

2007-11-01

The thin-film transistor characteristics of n-channel organic semiconductor, N ,N'-bis(2,2,3,3,4,4,4-heptafluorobutyl)-perylene tetracarboxylic diimide, are described. The slip-stacked face-to-face molecular packing allows a very dense parallel arrangement of the molecules, leading to field-effect mobility as high as 0.72cm2V-1s-1. The mobility only slightly decreased after exposure to air and remained stable for more than 50days. Our results reveal that molecular packing effects such as close stacking of perylene diimide units and segregation effects imparted by the fluorinated side chains are crucial for the air stability.

Particle beam injection system

DOEpatents

Jassby, Daniel L.; Kulsrud, Russell M.

1977-01-01

This invention provides a poloidal divertor for stacking counterstreaming ion beams to provide high intensity colliding beams. To this end, method and apparatus are provided that inject high energy, high velocity, ordered, atomic deuterium and tritium beams into a lower energy, toroidal, thermal equilibrium, neutral, target plasma column that is magnetically confined along an endless magnetic axis in a strong restoring force magnetic field having helical field lines to produce counterstreaming deuteron and triton beams that are received bent, stacked and transported along the endless axis, while a poloidal divertor removes thermal ions and electrons all along the axis to increase the density of the counterstreaming ion beams and the reaction products resulting therefrom. By balancing the stacking and removal, colliding, strong focused particle beams, reaction products and reactions are produced that convert one form of energy into another form of energy.

Robust real-time fault tracking for the 2011 Mw 9.0 Tohoku earthquake based on the phased-array-interference principle

NASA Astrophysics Data System (ADS)

Zhang, Yong; Wang, Rongjiang; Parolai, Stefano; Zschau, Jochen

2013-04-01

Based on the principle of the phased array interference, we have developed an Iterative Deconvolution Stacking (IDS) method for real-time kinematic source inversion using near-field strong-motion and GPS networks. In this method, the seismic and GPS stations work like an array radar. The whole potential fault area is scanned patch by patch by stacking the apparent source time functions, which are obtained through deconvolution between the recorded seismograms and synthetic Green's functions. Once some significant source signals are detected any when and where, their signatures are removed from the observed seismograms. The procedure is repeated until the accumulative seismic moment being found converges and the residual seismograms are reduced below the noise level. The new approach does not need any artificial constraint used in the source parameterization such as, for example, fixing the hypocentre, restricting the rupture velocity and rise time, etc. Thus, it can be used for automatic real-time source inversion. In the application to the 2011 Tohoku earthquake, the IDS method is proved to be robust and reliable on the fast estimation of moment magnitude, fault area, rupture direction, and maximum slip, etc. About at 100 s after the rupture initiation, we can get the information that the rupture mainly propagates along the up-dip direction and causes a maximum slip of 17 m, which is enough to release a tsunami early warning. About two minutes after the earthquake occurrence, the maximum slip is found to be 31 m, and the moment magnitude reaches Mw8.9 which is very close to the final moment magnitude (Mw9.0) of this earthquake.

Lamination cooling system formation method

DOEpatents

Rippel, Wally E [Altadena, CA; Kobayashi, Daryl M [Monrovia, CA

2012-06-19

An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Lamination cooling system formation method

DOEpatents

Rippel, Wally E [Altadena, CA; Kobayashi, Daryl M [Monrovia, CA

2009-05-12

An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Stability of fault submitted to fluid injections

NASA Astrophysics Data System (ADS)

Brantut, N.; Passelegue, F. X.; Mitchell, T. M.

2017-12-01

Elevated pore pressure can lead to slip reactivation on pre-existing fractures and faults when the coulomb failure point is reached. From a static point of view, the reactivation of fault submitted to a background stress (τ0) is a function of the peak strength of the fault, i.e. the quasi-static effective friction coefficient (µeff). However, this theory is valid only when the entire fault is affected by fluid pressure, which is not the case in nature, and during human induced-seismicity. In this study, we present new results about the influence of the injection rate on the stability of faults. Experiments were conducted on a saw-cut sample of westerly granite. The experimental fault was 8 cm length. Injections were conducted through a 2 mm diameter hole reaching the fault surface. Experiments were conducted at four different order magnitudes fluid pressure injection rates (from 1 MPa/minute to 1 GPa/minute), in a fault system submitted to 50 and 100 MPa confining pressure. Our results show that the peak fluid pressure leading to slip depends on injection rate. The faster the injection rate, the larger the peak fluid pressure leading to instability. Wave velocity surveys across the fault highlighted that decreasing the injection-rate leads to an increase of size of the fluid pressure perturbation. Our result demonstrate that the stability of the fault is not only a function of the fluid pressure requires to reach the failure criterion, but is mainly a function of the ratio between the length of the fault affected by fluid pressure and the total fault length. In addition, we show that the slip rate increases with the background effective stress and with the intensity of the fluid pressure pertubation, i.e. with the excess shear stress acting on the part of the fault pertubated by fluid injection. Our results suggest that crustal fault can be reactivated by local high fluid overpressures. These results could explain the "large" magnitude human-induced earthquakes recently observed in Oklahoma (Mw 5.6, 2016).

The effect of aluminium on mechanical properties and deformation mechanisms of hadfield steel single crystals

NASA Astrophysics Data System (ADS)

Zakharova, E. G.; Kireeva, I. V.; Chumlyakov, Y. I.; Shul'Mina, A. A.; Sehitoglu, H.; Karaman, I.

2004-06-01

On single crystals of Hadfield steel (Fe-13Mn-1.3C, Fe-13Mn-2.7Al-1.3C, wt.%) the systematical investigations of deformation mechanisms - slip and twinning, stages of plastic flow, strain hardening coefficient depending on orientation of tensile axis have been carried out by methods of optical and electron microscopy, x-ray analysis. Is has been shown that the combination of low stacking fault energy (γ{SF}=0.03J/m^2) with high concentration of carbon atoms in aluminium-free steel results in development of the mechanical twinning at room temperature in all crystal orientations. The new type of twinning with formation of extrinsic stacking fault has been found out in [001] single crystals. Experimentally it has been established that alloying with aluminium leads to increase of stacking fault energy of Hadfield steel and suppresses twinning in all orientations of crystals at preservation of high values of strain-hardening coefficients θ.

Cretaceous and Paleogene granitoid suites of the Sikhote-Alin area (Far East Russia): Geochemistry and tectonic implications

NASA Astrophysics Data System (ADS)

Grebennikov, Andrei V.; Khanchuk, Alexander I.; Gonevchuk, Valeriy G.; Kovalenko, Sergey V.

2016-09-01

The Mesozoic and Cenozoic geological history of NE Asia comprises alternating episodes of subduction or transform strike-slip movement of the oceanic plate along the continental margin of Eurasia. This sequence resulted in the regular generation of granitoid suites that are characterized by different ages, compositions, and tectonic settings. The Hauterivian-Aptian orogenic stage of the Sikhote-Alin, associated with the strike-slip displacement of the early Paleozoic continental blocks, the successive deformation of the Jurassic and Early Cretaceous terranes, and the injection of the earliest S-type granitoids. During late Albian, the area underwent syn-strike-slip compression caused by collision with the Aptian island arc and resulted in the injection of voluminous magmas of calc-alkaline magnesian (S- and I-type) and alkali-calcic ferroan (A-type) granitoids into syn-faulting compressional and extensional basins, respectively. Northwestward to westward movement of the Izanagi Plate resulted in the initiation of frontal subduction of the Paleo-Pacific Plate during the Cenomanian-Maastrichtian. In turn, this resulted in the generation of plateau-forming ignimbrites and their intrusive analogs formed from metaluminous I-type felsic magmas. Paleocene-Eocene magmatism in the Sikhote-Alin area commenced after the termination of subduction in a rifting regime related to strike-slip movement of the oceanic plate relative to the continent. The break-off of the subducted plate and the injection of oceanic asthenospheric material into the subcontinental lithosphere resulted in the eruption of lamproites and fayalite rhyolites, and coeval intrusions of gabbro and alkali feldspar granites (A-type). The A-type granitic-rocks and coeval gabbro-monzonites are considered to be reliable indicators of the transform continental margin geodynamic settings.

Megathrust Earthquake Swarms Contemporaneous to Slow Slip and Non-Volcanic Tremor in Southern Mexico, Detected and Analyzed through a Template Matching Approach

NASA Astrophysics Data System (ADS)

Holtkamp, S.; Brudzinski, M. R.; Cabral-Cano, E.; Arciniega-Ceballos, A.

2012-12-01

An outstanding question in geophysics is the degree to which the newly discovered types of slow fault slip are related to their destructive cousin - the earthquake. Here, we utilize a local network along the Oaxacan segment of the Middle American subduction zone to investigate the potential relationship between slow slip, non-volcanic tremor (NVT), and earthquakes along the subduction megathrust. We have developed a multi-station "template matching" waveform cross correlation technique which is able to detect and locate events several orders of magnitude smaller than would be possible using more traditional techniques. Also, our template matching procedure is capable of consistently locate events which occur during periods of increased background activity (e.g., during productive NVT, loud cultural noise, or after larger earthquakes) because the multi-station detector is finely tuned to events with similar hypocentral location and focal mechanism. The local network in the Oaxaca region allows us to focus on documented megathrust earthquake swarms, which we focus on because slow slip is hypothesized to be the cause for earthquake swarms in some tectonic environments. We identify a productive earthquake swarm in July 2006 (~600 similar earthquakes detected), which occurred during a week-long episode of productive tremor and slow slip. Families of events in this sequence were also active during larger and longer slow slip events, which provides a potential link between slow slip in the transition zone and earthquakes at the downdip end of the seismogenic portion of the megathrust. Because template matching techniques only detect similar signals, detected waveforms can be stacked together to produce higher signal to noise ratios or cross correlated against each other to produce precise relative phase arrival times. We are using the refined signals to look for evidence of expansion or propagation of hypocenters during these earthquake swarms, which could be used as a test for determining their underlying processes (e.g., fluid diffusion or slow slip).

Slip and Twinning in the [ 1 ¯ $ /line{mathbf{1}} $ 49]-Oriented Single Crystals of a High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Kireeva, I. V.; Chumlyakov, Yu. I.; Pobedennaya, Z. V.; Platonova, Yu. N.; Kuksgauzen, I. V.; Kuksgauzen, D. A.; Poklonov, V. V.; Karaman, I.; Sehitoglu, H.

2016-12-01

Using [ overline{1} 49] - oriented single crystals of an FCC Fe20Ni20Mn20Cr20Co20 (at.%) high-entropy alloy subjected to tensile deformation, the temperature dependence of critical resolved shear stresses τcr(T) and the deformation mechanism of slip and twinning are investigated in the early stages of deformation at ɛ ≤ 5% within the temperature interval T = 77-573 K. It is shown that τcr increases with decreasing the testing temperature and the τcr(T) temperature dependence is controlled by the slip of perfect dislocations a/2<110>. The early deformation stages ɛ ≤ 5% are associated with the development of planar slip by pileups of perfect dislocations a/2<110>, stacking faults and mechanical twins, which is observed in the temperature interval from 77 to 423 K. A comparison of the temperature dependence τcr(T) and the development of mechanical twinning is performed between the [ overline{1} 49] -oriented single crystals of the Fe20Ni20Mn20Cr20Co20 high-entropy alloy, the single crystals of the austenitic stainless steel, Fe - 18% Cr - 12% Ni - 2Mo (wt.%) without nitrogen atoms (Steel 316) and Hadfield steel, Fe - 13% Mn - (1-1.3)% C (wt.%).

Finite-fault slip model of the 2011 Mw 5.6 Prague, Oklahoma earthquake from regional waveforms

USGS Publications Warehouse

Sun, Xiaodan; Hartzell, Stephen

2014-01-01

The slip model for the 2011 Mw 5.6 Prague, Oklahoma, earthquake is inferred using a linear least squares methodology. Waveforms of six aftershocks recorded at 21 regional stations are used as empirical Green's functions (EGFs). The solution indicates two large slip patches: one located around the hypocenter with a depth range of 3–5.5 km; the other located to the southwest of the epicenter with a depth range from 7.5 to 9.5 km. The total moment of the solution is estimated at 3.37 × 1024 dyne cm (Mw 5.65). The peak slip and average stress drop for the source at the hypocenter are 70 cm and 90 bars, respectively, approximately one half the values for the Mw 5.8 2011 Mineral, Virginia, earthquake. The stress drop averaged over all areas of slip is 16 bars. The relatively low peak slip and stress drop may indicate an induced component in the origin of the Prague earthquake from deep fluid injection.

Phase Modulator with Terahertz Optical Bandwidth Formed by Multi-Layered Dielectric Stack

NASA Technical Reports Server (NTRS)

Keys, Andrew S. (Inventor); Fork, Richard L. (Inventor)

2005-01-01

An optical phase modulator includes a bandpass multilayer stack, formed by a plurality of dielectric layers, preferably of GaAs and AlAs, and having a transmission function related to the refractive index of the layers of the stack, for receiving an optical input signal to be phase modulated. A phase modulator device produces a nonmechanical change in the refractive index of each layer of the stack by, e.g., the injection of free carrier, to provide shifting of the transmission function so as to produce phase modulation of the optical input signal and to thereby produce a phase modulated output signal.

Dependences of contraction/expansion of stacking faults on temperature and current density in 4H-SiC p–i–n diodes

NASA Astrophysics Data System (ADS)

Okada, Aoi; Nishio, Johji; Iijima, Ryosuke; Ota, Chiharu; Goryu, Akihiro; Miyazato, Masaki; Ryo, Mina; Shinohe, Takashi; Miyajima, Masaaki; Kato, Tomohisa; Yonezawa, Yoshiyuki; Okumura, Hajime

2018-06-01

To investigate the mechanism of contraction/expansion behavior of Shockley stacking faults (SSFs) in 4H-SiC p–i–n diodes, the dependences of the SSF behavior on temperature and injection current density were investigated by electroluminescence image observation. We investigated the dependences of both triangle- and bar-shaped SSFs on the injection current density at four temperature levels. All SSFs in this study show similar temperature and injection current density dependences. We found that the expansion of SSFs at a high current density was converted to contraction at a certain value as the current decreased and that the value is temperature-dependent. It has been confirmed that SSF behavior, which was considered complex or peculiar, might be explained mainly by the energy change caused by SSFs.

Real-time Microseismic Processing for Induced Seismicity Hazard Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzel, Eric M.

Induced seismicity is inherently associated with underground fluid injections. If fluids are injected in proximity to a pre-existing fault or fracture system, the resulting elevated pressures can trigger dynamic earthquake slip, which could both damage surface structures and create new migration pathways. The goal of this research is to develop a fundamentally better approach to geological site characterization and early hazard detection. We combine innovative techniques for analyzing microseismic data with a physics-based inversion model to forecast microseismic cloud evolution. The key challenge is that faults at risk of slipping are often too small to detect during the site characterizationmore » phase. Our objective is to devise fast-running methodologies that will allow field operators to respond quickly to changing subsurface conditions.« less

Laboratory scale micro-seismic monitoring of rock faulting and injection-induced fault reactivation

NASA Astrophysics Data System (ADS)

Sarout, J.; Dautriat, J.; Esteban, L.; Lumley, D. E.; King, A.

2017-12-01

The South West Hub CCS project in Western Australia aims to evaluate the feasibility and impact of geosequestration of CO2 in the Lesueur sandstone formation. Part of this evaluation focuses on the feasibility and design of a robust passive seismic monitoring array. Micro-seismicity monitoring can be used to image the injected CO2plume, or any geomechanical fracture/fault activity; and thus serve as an early warning system by measuring low-level (unfelt) seismicity that may precede potentially larger (felt) earthquakes. This paper describes laboratory deformation experiments replicating typical field scenarios of fluid injection in faulted reservoirs. Two pairs of cylindrical core specimens were recovered from the Harvey-1 well at depths of 1924 m and 2508 m. In each specimen a fault is first generated at the in situ stress, pore pressure and temperature by increasing the vertical stress beyond the peak in a triaxial stress vessel at CSIRO's Geomechanics & Geophysics Lab. The faulted specimen is then stabilized by decreasing the vertical stress. The freshly formed fault is subsequently reactivated by brine injection and increase of the pore pressure until slip occurs again. This second slip event is then controlled in displacement and allowed to develop for a few millimeters. The micro-seismic (MS) response of the rock during the initial fracturing and subsequent reactivation is monitored using an array of 16 ultrasonic sensors attached to the specimen's surface. The recorded MS events are relocated in space and time, and correlate well with the 3D X-ray CT images of the specimen obtained post-mortem. The time evolution of the structural changes induced within the triaxial stress vessel is therefore reliably inferred. The recorded MS activity shows that, as expected, the increase of the vertical stress beyond the peak led to an inclined shear fault. The injection of fluid and the resulting increase in pore pressure led first to a reactivation of the pre-existing fault. However, with increasing slip, a second conjugate fault progressively appeared, which ultimately accommodated all of the imposed vertical displacement. The inferred structural changes resemble fault branching and dynamic slip transfer processes seen in large-scale geology. This project was funded by the ANLEC R&D in partnership with the WA Government.

Analyses of sulfonamide antibiotics by a successive anion- and cation-selective injection coupled to microemulsion electrokinetic chromatography.

PubMed

Lin, Yun-Ta; Liu, Yu-Wei; Cheng, Yi-Jie; Huang, Hsi-Ya

2010-07-01

In this study, an MEEKC was used to detect and analyze nine sulfonamide antibiotics. Owing to an insufficient sensitivity of on-column UV detection, a field-amplified sample injection, successive anion- and cation-selective injection, was used for the on-line concentration of the nine antibiotics. In the successive anion- and cation-selective injection mode, a leading water plug was introduced prior to anion injection, and then an acidic plug followed by a terminal water plug had to be used before subsequent cation injection. The results indicated some sulfonamides (sulfamonomethoxine, sulfamethazine, sulfamerazine and sulfadiazine) were determined as split signals in pairs, and this was likely due to the use of a longer acid plug (360 s) which caused the sulfonamide anions and cations to be stacked in two distinct zones of the leading water and acid plugs. Meanwhile, all the sulfonamides that were introduced either by anion or cation injection were stacked within the leading water plug when a shorter acid plug (210 s) was used. As a result, the nine sulfonamides were determined as single and symmetrical peaks with low LODs (0.9-4.2 microg/L). Furthermore, the MEEKC method was successfully applied for the detection of trace sulfonamide residues in several food and water samples.

Singlet Fission and Excimer Formation in Disordered Solids of Alkyl-Substituted 1,3-Diphenylisobenzofurans

DOE PAGES

Dron, Paul I.; Michl, Josef; Johnson, Justin C.

2017-10-16

Here, we describe the preparation and excited state dynamics of three alkyl derivatives of 1,3-diphenylisobenzofuran (1) in both solutions and thin films. The substitutions are intended to disrupt the slip-stacked packing observed in crystals of 1 while maintaining the favorable energies of singlet and triplet for singlet fission (SF). All substitutions result in films that are largely amorphous as judged by the absence of strong X-ray diffraction peaks.

Phase stability tuning in the NbxZr1-xN thin-film system for large stacking fault density and enhanced mechanical strength

NASA Astrophysics Data System (ADS)

Joelsson, T.; Hultman, L.; Hugosson, H. W.; Molina-Aldareguia, J. M.

2005-03-01

The phase stability of hexagonal WC-structure and cubic NaCl-structure 4d transition metal nitrides was calculated using first-principles density functional theory. It is predicted that there is a multiphase or polytypic region for the 4d transition metal nitrides with a valence electron concentration around 9.5 to 9.7 per formula unit. For verification, epitaxial NbxZr1-xN (0⩽x⩽1) was grown by reactive magnetron sputter deposition on MgO(001) substrates and analyzed with transmission electron microscopy (TEM) and x-ray diffraction. The defects observed in the films were threading dislocations due to nucleation and growth on the lattice-mismatched substrate and planar defects (stacking faults) parallel to the substrate surface. The highest defect density was found at the x =0.5 composition. The nanoindentation hardness of the films varied between 21GPa for the binary nitrides, and 26GPa for Nb0.5Zr0.5N. Unlike the cubic binary nitrides, no slip on the preferred ⟨11¯0⟩{110} slip system was observed. The increase in hardness is attributed to the increase in defect density at x =0.5, as the defects act as obstacles for dislocation glide during deformation. The findings present routes for the design of wear-resistant nitride coatings by phase stability tuning.

The core structure and recombination energy of a copper screw dislocation: a Peierls study

NASA Astrophysics Data System (ADS)

Szajewski, B. A.; Hunter, A.; Beyerlein, I. J.

2017-09-01

The recombination process of dislocations is central to cross-slip, and transmission through ?3 grain boundaries among other fundamental plastic deformation processes. Despite its importance, a detailed mechanistic understanding remains lacking. We apply a continuous dislocation model, inspired by Peierls and Nabarro, complete with an ab-initio computed ?-surface and continuous units of infinitesimal dislocation slip, towards computing the stress-dependent recombination path of both an isotropic and anisotropic Cu screw dislocation. Under no applied stress, our model reproduces the stacking fault width between Shockley partial dislocations as predicted by discrete linear elasticity. Upon application of a compressive Escaig stress, the two partial dislocations coalesce to a separation of ??. Upon increased loading the edge components of each partial dislocation recede, leaving behind a spread Peierls screw dislocation, indicating the recombined state. We demonstrate that the critical stress required to achieve the recombined state is independent of the shear modulus. Rather the critical recombination stress depends on an energy difference between an unstable fault energy (?) and the intrinsic stacking fault energy (?-?). We report recombination energies of ?W = 0.168 eV/Å and ?W = 0.084 eV/Å, respectively, for the Cu screw dislocation within isotropic and anisotropic media. We develop an analytic model which provides insight into our simulation results which compare favourably with other (similar) models.

Biluminescence via Fluorescence and Persistent Phosphorescence in Amorphous Organic Donor(D4)-Acceptor(A) Conjugates, and Application in Data Security Protection.

PubMed

Bhatia, Harsh; Bhattacharjee, Indranil; Ray, Debdas

2018-06-25

Purely organic biluminescent materials are of great interest due to the involvement of both singlet and long-lived triplet emissions, which have been used in bio-imaging and organic light-emitting diodes. We show two molecules 3,4,5,6-tetraphenyloxy-phthlonitrile (POP) and 3,4,5,6-tetrakis-p-tolyloxy-phthalonitrile (TOP), in which POP was found to exhibit fluorescence and persistent room-temperature green phosphorescence (pRTGP) in the amorphous and crystal states. Both POP and TOP show aggregation induced emission in tetrahydrofuran-water mixture. We found in single crystal X-ray analysis that intra-and inter molecular lp(O)•••π interactions along with (π(C=C)•••π(C≡N), hydrogen bond (H-B), and C-H•••π interactions induce head-to-tail slipped-stacked arrangement in POP. In addition, X-ray structure of TOP with slipped-stack arrangement induced by only (π(C=C)•••π(C≡N) and H-B interactions, shows dim afterglow only in crystals. These indicate that more number of non-covalent interactions may reinforce relatively efficient inter system crossing that leads to pRTGP even in the amorphous state of POP. Given the unique green afterglow feature in amorphous state of POP, document security protection application is achievable.

System for adding sulfur to a fuel cell stack system for improved fuel cell stability

DOEpatents

Mukerjee, Subhasish; Haltiner, Jr., Karl J; Weissman, Jeffrey G

2013-08-13

A system for adding sulfur to a reformate stream feeding a fuel cell stack, having a sulfur source for providing sulfur to the reformate stream and a metering device in fluid connection with the sulfur source and the reformate stream. The metering device injects sulfur from the sulfur source to the reformate stream at a predetermined rate, thereby providing a conditioned reformate stream to the fuel cell stack. The system provides a conditioned reformate stream having a predetermined sulfur concentration that gives an acceptable balance of minimal drop in initial power with the desired maximum stability of operation over prolonged periods for the fuel cell stack.

Epidural Steroid Injections

MedlinePlus

... slipped vertebrae’, also known as spondylolisthesis). The epidural space is a fat filled ‘sleeve’ that surrounds the ... spinal cord. Steroids (‘cortisone’) placed into the epidural space have a very potent anti-inflammatory action that ...

Constraints and inferences of conditions of seismic slip from analyses of exhumed faults

NASA Astrophysics Data System (ADS)

Evans, J. P.

2008-12-01

The study of exhumed faults, where constrained by geochemical or geochronologic evidence for depth of deformation, has provided abundant insights into the processes by which the upper crust accommodates strain. What remains elusive in these studies are: a] what evidence do we have for diagnosing [paleo] seismic slip, b ] how do we extrapolate the textures and composition of formerly active faults to constraining the conditions at depth, c] determining the conditions that promote seismic vs. aseismic slip, and d] to what degree do interseismic [healing] and post-slip processes exhumation affect what we see at the surface. Field evidence for the conditions that promote or are of diagnostic seismic vs. aseismic slip, is elusive, as there are few ways to determine seismic rates of slip in faults other than the presence of pseudotachylytes. Recent work on these rocks in a variety of settings and the increase in recognition of the presence of fault- related melts document the relationships between pseudotachylytes and cataclastically deformed rocks in what is thought to be the frictional regime, or with ductily deformed rocks at the base of a fault. Conditions that appear to promote seismic slip are alteration of granitic host rock to lower melting temperature phases and the presence of geometric complexities that may act as stress risers in the faults. Drilling into portions of faults where earthquakes occur at the top of the seismogenic zone have sampled fault-related rocks that have striking similarities to exhumed faults, exhibiting narrow slip surfaces, foliated cataclasites, injected gouge textures, polished slip surfaces, and thermally altered rocks along slip surfaces. We review the recent work from a wide range of studies to suggest that relatively small changes in conditions may initiate seismic slip, and suggest further avenues of investigation.

Measurement and characterization of slippage and slip-law using a rigorous analysis in dynamics of oscillating rheometer: Newtonian fluid

NASA Astrophysics Data System (ADS)

Azese, Martin Ndi

2018-02-01

This article presents a rigorous calculation involving velocity slip of Newtonian fluid where we analyze and solve the unsteady Navier-Stokes equation with emphasis on its rheological implication. The goal of which is to model a simple yet effective non-invasive way of quantifying and characterizing slippage. Indeed this contrasts with previous techniques that exhibit inherent limitations whereby injecting foreign objects usually alter the flow. This problem is built on the Couette rheological flow system such that μ-Newton force and μ-stress are captured and processed to obtain wall slip. Our model leads to a linear partial differential equation and upon enforcing linear-Navier slip boundary conditions (BC) yields inhomogeneous and unsteady "Robin-type" BC. A dimensional analysis reveals salient dimensionless parameters: Roshko, Strouhal, and Reynolds while highlighting slip-numbers from BC. We also solve the slip-free case to corroborate and validate our results. Several graphs are generated showing slip effects, particularly, studying how slip-numbers, a key input, differentiate themselves to the outputs. We also confirm this in a graphical fashion by presenting the flow profile across channel width, velocity, and stress at both walls. A perturbation scheme is introduced to calculate long-time behavior when the system seats for long. More importantly, in the end, we justify the existence of a reverse mechanism, where an inverse transformation like Fourier transform uses the output data to retrieve slip-numbers and slip law, thus quantifying and characterizing slip. Therefore, we not only substantiate our analysis, but we also justify our claim, measurement and characterization, and theorize realizability of our proposition.

Morphology of single Shockley-type stacking faults generated by recombination enhanced dislocation glide in 4H-SiC

NASA Astrophysics Data System (ADS)

Matsuhata, Hirofumi; Sekiguchi, Takashi

2018-04-01

Morphology of single Shockley-type stacking faults (SFs) generated by recombination enhanced dislocation glide (REDG) in 4H-SiC are discussed and analysed. A complete set of the 12 different dissociated states of basal-plane dislocation loops is obtained using the crystallographic space group operations. From this set, six different double rhombic-shaped SFs are derived. These tables indicate the rules that connect shapes of SFs with the locations of partial dislocations having different core structures, the positions of slip planes in a unit cell, and the Burgers vectors of partial dislocations. We applied these tables for the analysis of SFs generated by the REDG effect reported in the past articles. Shapes, growing process of SFs and perfect dislocations for origins of SFs were well analysed systematically.

The use of Stress Tensor Discriminator Faults in separating heterogeneous fault-slip data with best-fit stress inversion methods. II. Compressional stress regimes

NASA Astrophysics Data System (ADS)

Tranos, Markos D.

2018-02-01

Synthetic heterogeneous fault-slip data as driven by Andersonian compressional stress tensors were used to examine the efficiency of best-fit stress inversion methods in separating them. Heterogeneous fault-slip data are separated only if (a) they have been driven by stress tensors defining 'hybrid' compression (R < 0.375), and their σ1 axes differ in trend more than 30° (R = 0) or 50° (R = 0.25). Separation is not feasible if they have been driven by (b) 'real' (R ≥ 0.375) and 'hybrid' compressional tensors having their σ1 axes in similar trend, or (c) 'real' compressional tensors. In case (a), the Stress Tensor Discriminator Faults (STDF) exist in more than 50% of the activated fault slip data while in cases (b) and (c), they exist in percentages of much less than 50% or not at all. They constitute a necessary discriminatory tool for the establishment and comparison of two compressional stress tensors determined by a best-fit stress inversion method. The best-fit stress inversion methods are not able to determine more than one 'real' compressional stress tensor, as far as the thrust stacking in an orogeny is concerned. They can only possibly discern stress differences in the late-orogenic faulting processes, but not between the main- and late-orogenic stages.

Aseismic Slip of a Thin Slab Due to a Fluid Source

NASA Astrophysics Data System (ADS)

Aubin, P. W.; Viesca, R. C.

2017-12-01

We explore the effects of an increase of pore pressure on the frictional interface along the base of a thin slab. The thin slab approximation corresponds to a layer overriding a substrate in which variations along the layer's length occur over distances much greater than the layer thickness. We consider deformation that may be in-plane or anti-plane, but approximately uniform in depth, such that spatial variations of displacement (and hence, slip) occur only along one direction parallel to the interface. Such a thin-sheet model may well represent the deformation of landslides and glacial ice streams, and also serves as a first-pass for fault systems, which, while better represented by elastic half-spaces in frictional contact, nonetheless show qualitatively similar behavior. We consider that the friction coefficient at the layer's interface remains (approximately) constant, and that aseismic slip is initiated by a (line) source of fluid at constant pressure, with one-dimensional diffusion parallel to the interface. As posed, the problem yields a self-similar expansion of slip, whose extent grows proportionally to (α * t)^(1/2) (where α is the hydraulic diffusivity) and can either lag behind or outpace the fluid diffusion front. The problem is controlled by a single parameter, accounting for the friction coefficient and the initial (pre-injection) states of stress and pore pressure. The problem solution consists of the self-similar slip profile and the coefficient of proportionality for the crack-front motion. Within the problem parameter range, two end-member scenarios result: one in which the initial level of shear stress on the interface is close to the value of the pre-injection strength (critically stressed) or another in which fluid pressure is just enough to induce slip (marginally pressurized). For the critically stressed and marginally pressurized cases, the aseismic slip front lies far ahead or far behind, respectively, the fluid diffusion front. We find closed-form solutions for both end-members, and in the former case, via matched asymptotics. These solutions provide a basis to solve the general problem, which we also solve numerically for comparison. The solutions also provide a starting point for examining the progression of slip and locking following the shutoff of the fluid source.

A geodetic matched filter search for slow slip with application to the Mexico subduction zone

NASA Astrophysics Data System (ADS)

Rousset, B.; Campillo, M.; Lasserre, C.; Frank, W. B.; Cotte, N.; Walpersdorf, A.; Socquet, A.; Kostoglodov, V.

2017-12-01

Since the discovery of slow slip events, many methods have been successfully applied to model obvious transient events in geodetic time series, such as the widely used network strain filter. Independent seismological observations of tremors or low-frequency earthquakes and repeating earthquakes provide evidence of low-amplitude slow deformation but do not always coincide with clear occurrences of transient signals in geodetic time series. Here we aim to extract the signal corresponding to slow slips hidden in the noise of GPS time series, without using information from independent data sets. We first build a library of synthetic slow slip event templates by assembling a source function with Green's functions for a discretized fault. We then correlate the templates with postprocessed GPS time series. Once the events have been detected in time, we estimate their duration T and magnitude Mw by modeling a weighted stack of GPS time series. An analysis of synthetic time series shows that this method is able to resolve the correct timing, location, T, and Mw of events larger than Mw 6 in the context of the Mexico subduction zone. Applied on a real data set of 29 GPS time series in the Guerrero area from 2005 to 2014, this technique allows us to detect 28 transient events from Mw 6.3 to 7.2 with durations that range from 3 to 39 days. These events have a dominant recurrence time of 40 days and are mainly located at the downdip edges of the Mw>7.5 slow slip events.

Atomistic Simulations of Surface Cross-Slip Nucleation in Face-Centered Cubic Nickel and Copper (Postprint)

DTIC Science & Technology

2013-02-15

molecular dynamics code, LAMMPS [9], developed at Sandia National Laboratory. The simulation cell is a rectangular parallelepiped, with the z-axis...with assigned energies within LAMMPs of greater than 4.42 eV (Ni) or 3.52 eV (Cu) (the energy of atoms in the stacking fault region), the partial...molecular dynamics code LAMMPS , which was developed at Sandia National Laboratory by Dr. Steve Plimpton and co-workers. This work was supported by the

An improved low-frequency earthquakes catalogue in the vicinity of the late-interseismic central Alpine Fault, Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Baratin, Laura-May; Chamberlain, Calum J.; Townend, John; Savage, Martha K.

2017-04-01

Characterising the seismicity associated with slow deformation in the vicinity of the Alpine Fault may provide constraints on the state of stress of this major transpressive margin prior to a large (≥M8) earthquake. Here, we use recently detected tectonic tremor and low-frequency earthquakes (LFEs) to examine how slow tectonic deformation is loading the Alpine Fault toward an anticipated large rupture. We initially work with a continous seismic dataset collected between 2009 and 2012 from an array of short-period seismometers, the Southern Alps Microearthquake Borehole Array. Fourteen primary LFE templates, found through visual inspection within previously identified tectonic tremor, are used in an iterative matched-filter and stacking routine. This method allows the detection of similar signals and establishes LFE families with common locations. We thus generate a 36 month catalogue of 10718 LFEs. The detections are then combined for each LFE family using phase-weighted stacking to yield a signal with the highest possible signal to noise ratio. We found phase-weighted stacking to be successful in increasing the number of LFE detections by roughly 20%. Phase-weighted stacking also provides cleaner phase arrivals of apparently impulsive nature allowing more precise phase picks. We then compute non-linear earthquake locations using a 3D velocity model and find LFEs to occur below the seismogenic zone at depths of 18-34 km, locating on or near the proposed deep extent of the Alpine Fault. To gain insight into deep fault slip behaviour, a detailed study of the spatial-temporal evolution of LFEs is required. We thus generate a more extensive catalogue of LFEs spanning the years 2009 to 2016 using a different technique to detect LFEs more efficiently. This time 638 synthetic waveforms are used as primary templates in the match-filter routine. Of those, 38 templates yield no detections over our 7-yr study period. The remaining 600 templates end up detecting between 370 and 730 events each totalling ˜310 000 detections. We then focus on only keeping the detections that robustly stack (i.e. representing real LFEs) for each synthetic template hence creating new LFE templates. From there, we rerun the match-filter routine with our new LFE templates. Finally, each LFE template and its subsequent detections form a LFE family, itself associated with a single source. Initial testing shows that this technique paired up with phase-weighted stacking increases the number of LFE families and overall detected events roughly thirtyfold. Our next step is to study in detail the spatial and temporal activity of our LFEs. This new catalogue should provide new insight into the deep central Alpine Fault structure and its slip behaviour.

Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO2 injection site Ketzin (Germany)

NASA Astrophysics Data System (ADS)

Bergmann, Peter; Yang, Can; Lüth, Stefan; Juhlin, Christopher; Cosma, Calin

2011-09-01

The Ketzin project provides an experimental pilot test site for the geological storage of CO2. Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO2 had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO2, and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon. Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey. Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO2 related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO2 signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO2, as expected, but shows signs of a pressure response in the repeat data.

Development of a dynamic coupled hydro-geomechanical code and its application to induced seismicity

NASA Astrophysics Data System (ADS)

Miah, Md Mamun

This research describes the importance of a hydro-geomechanical coupling in the geologic sub-surface environment from fluid injection at geothermal plants, large-scale geological CO2 sequestration for climate mitigation, enhanced oil recovery, and hydraulic fracturing during wells construction in the oil and gas industries. A sequential computational code is developed to capture the multiphysics interaction behavior by linking a flow simulation code TOUGH2 and a geomechanics modeling code PyLith. Numerical formulation of each code is discussed to demonstrate their modeling capabilities. The computational framework involves sequential coupling, and solution of two sub-problems- fluid flow through fractured and porous media and reservoir geomechanics. For each time step of flow calculation, pressure field is passed to the geomechanics code to compute effective stress field and fault slips. A simplified permeability model is implemented in the code that accounts for the permeability of porous and saturated rocks subject to confining stresses. The accuracy of the TOUGH-PyLith coupled simulator is tested by simulating Terzaghi's 1D consolidation problem. The modeling capability of coupled poroelasticity is validated by benchmarking it against Mandel's problem. The code is used to simulate both quasi-static and dynamic earthquake nucleation and slip distribution on a fault from the combined effect of far field tectonic loading and fluid injection by using an appropriate fault constitutive friction model. Results from the quasi-static induced earthquake simulations show a delayed response in earthquake nucleation. This is attributed to the increased total stress in the domain and not accounting for pressure on the fault. However, this issue is resolved in the final chapter in simulating a single event earthquake dynamic rupture. Simulation results show that fluid pressure has a positive effect on slip nucleation and subsequent crack propagation. This is confirmed by running a sensitivity analysis that shows an increase in injection well distance results in delayed slip nucleation and rupture propagation on the fault.

Slip Potential of Faults in the Fort Worth Basin

NASA Astrophysics Data System (ADS)

Hennings, P.; Osmond, J.; Lund Snee, J. E.; Zoback, M. D.

2017-12-01

Similar to other areas of the southcentral United States, the Fort Worth Basin of NE Texas has experienced an increase in the rate of seismicity which has been attributed to injection of waste water in deep saline aquifers. To assess the hazard of induced seismicity in the basin we have integrated new data on location and character of previously known and unknown faults, stress state, and pore pressure to produce an assessment of fault slip potential which can be used to investigate prior and ongoing earthquake sequences and for development of mitigation strategies. We have assembled data on faults in the basin from published sources, 2D and 3D seismic data, and interpretations provided from petroleum operators to yield a 3D fault model with 292 faults ranging in strike-length from 116 to 0.4 km. The faults have mostly normal geometries, all cut the disposal intervals, and most are presumed to cut into the underlying crystalline and metamorphic basement. Analysis of outcrops along the SW flank of the basin assist with geometric characterization of the fault systems. The interpretation of stress state comes from integration of wellbore image and sonic data, reservoir stimulation data, and earthquake focal mechanisms. The orientation of SHmax is generally uniform across the basin but stress style changes from being more strike-slip in the NE part of the basin to normal faulting in the SW part. Estimates of pore pressure come from a basin-scale hydrogeologic model as history-matched to injection test data. With these deterministic inputs and appropriate ranges of uncertainty we assess the conditional probability that faults in our 3D model might slip via Mohr-Coulomb reactivation in response to increases in injected-related pore pressure. A key component of the analysis is constraining the uncertainties associated with each of the principal parameters. Many of the faults in the model are interpreted to be critically-stressed within reasonable ranges of uncertainty.

Optimal Terminal Descent Guidance Logic to Achieve a Soft Lunar Touchdown

NASA Technical Reports Server (NTRS)

Lee, Allan Y.

2011-01-01

Altair Lunar Lander is the linchpin in the Constellation Program for human return to the Moon. In the 2010design reference mission, Altair is to be delivered to low Earth orbit by the Ares V heavy lift launch vehicle, and after subsequent docking with Orion in LEO, the Altair/Orion stack is delivered through trans-lunar injection (TLI). The Altair/Orion stack separates from the Ares V Earth departure stage shortly after TLI and continues the flight to the Moon as a single stack. Fig. 1 depicts one version of the Altair lunar lander.

Focal mechanisms and inter-event times of low-frequency earthquakes reveal quasi-continuous deformation and triggered slow slip on the deep Alpine Fault

NASA Astrophysics Data System (ADS)

Baratin, Laura-May; Chamberlain, Calum J.; Townend, John; Savage, Martha K.

2018-02-01

Characterising the seismicity associated with slow deformation in the vicinity of the Alpine Fault may provide constraints on the stresses acting on a major transpressive margin prior to an anticipated great (≥M8) earthquake. Here, we use recently detected tremor and low-frequency earthquakes (LFEs) to examine how slow tectonic deformation is loading the Alpine Fault late in its typical ∼300-yr seismic cycle. We analyse a continuous seismic dataset recorded between 2009 and 2016 using a network of 10-13 short-period seismometers, the Southern Alps Microearthquake Borehole Array. Fourteen primary LFE templates are used in an iterative matched-filter and stacking routine, allowing the detection of similar signals corresponding to LFE families sharing common locations. This yields an 8-yr catalogue containing 10,000 LFEs that are combined for each of the 14 LFE families using phase-weighted stacking to produce signals with the highest possible signal-to-noise ratios. We show that LFEs occur almost continuously during the 8-yr study period and highlight two types of LFE distributions: (1) discrete behaviour with an inter-event time exceeding 2 min; (2) burst-like behaviour with an inter-event time below 2 min. We interpret the discrete events as small-scale frequent deformation on the deep extent of the Alpine Fault and LFE bursts (corresponding in most cases to known episodes of tremor or large regional earthquakes) as brief periods of increased slip activity indicative of slow slip. We compute improved non-linear earthquake locations using a 3-D velocity model. LFEs occur below the seismogenic zone at depths of 17-42 km, on or near the hypothesised deep extent of the Alpine Fault. The first estimates of LFE focal mechanisms associated with continental faulting, in conjunction with recurrence intervals, are consistent with quasi-continuous shear faulting on the deep extent of the Alpine Fault.

Observations of fault zone heterogeneity effects on stress alteration and slip nucleation during a fault reactivation experiment in the Mont Terri rock laboratory, Switzerland

NASA Astrophysics Data System (ADS)

Nussbaum, C.; Guglielmi, Y.

2016-12-01

The FS experiment at the Mont Terri underground research laboratory consists of a series of controlled field stimulation tests conducted in a fault zone intersecting a shale formation. The Main Fault is a secondary order reverse fault that formed during the creation of the Jura fold-and-thrust belt, associated to a large décollement. The fault zone is up to 6 m wide, with micron-thick shear zones, calcite veins, scaly clay and clay gouge. We conducted fluid injection tests in 4 packed-off borehole intervals across the Main Fault using mHPP probes that allow to monitor 3D displacement between two points anchored to the borehole walls at the same time as fluid pressure and flow rate. While pressurizing the intervals above injection pressures of 3.9 to 5.3 MPa, there is an irreversible change in the displacements magnitude and orientation associated to the hydraulic opening of natural shear planes oriented N59 to N69 and dipping 39 to 58°. Displacements of 0.01 mm to larger than 0.1 mm were captured, the highest value being observed at the interface between the low permeable fault core and the damage zone. Contrasted fault movements were observed, mainly dilatant in the fault core, highly dilatant-normal slip at the fault core-damage zone interface and low dilatant-strike-slip-reverse in the damage-to-intact zones. First using a slip-tendency approach based on Coulomb reactivation potential of fault planes, we computed a stress tensor orientation for each test. The input parameters are the measured displacement vectors above the hydraulic opening pressure and the detailed fault geometry of each intervals. All measurements from the damage zone can be explained by a stress tensor in strike-slip regime. Fault movements measured at the core-damage zone interface and within the fault core are in agreement with the same stress orientations but changed as normal faulting, explaining the significant dilatant movements. We then conducted dynamic hydromechanical simulations of the Coulomb stress variations on discrete fault planes, considering the injection pressure variations with time in the packed-off sections as the source parameters. Results suggest that the fault architecture and heterogeneity play an important role on the local stress variation at the core-damage zone interface, favouring slip activation below sigma 3.

Slip behaviour of carbonate-bearing faults subjected to fluid pressure stimulations

NASA Astrophysics Data System (ADS)

Collettini, Cristiano; Scuderi, Marco; Marone, Chris

2017-04-01

Earthquakes caused by fluid injection within reservoir have become an important topic of political and social discussion as new drilling and improved technologies enable the extraction of oil and gas from previously unproductive formations. During reservoir stimulation, the coupled interactions of frictional and fluid flow properties together with the stress state control both the onset of fault slip and fault slip behaviour. However, currently, there are no studies under controlled, laboratory conditions for which the effect of fluid pressure on fault slip behaviour can be deduced. To cover this gap, we have developed laboratory experiments where we monitor fault slip evolution at constant shear stress but with increasing fluid pressure, i.e. reducing the effective normal stress. Experiments have been conducted in the double direct shear configuration within a pressure vessel on carbonate fault gouge, characterized by a slightly velocity strengthening friction that is indicative of stable aseismic creep. In our experiments fault slip history can be divided in three main stages: 1) for high effective normal stress the fault is locked and undergoes compaction; 2) when the shear and effective normal stress reach the failure condition, accelerated creep is associated to fault dilation; 3) further pressurization leads to an exponential acceleration during fault compaction and slip localization. Our results indicate that fault weakening induced by fluid pressurization overcomes the velocity strengthening behaviour of calcite gouge, resulting in fast acceleration and earthquake slip. As applied to tectonic faults our results suggest that a larger number of crustal faults, including those slightly velocity strengthening, can experience earthquake slip due to fluid pressurization.

Slip-additive migration, surface morphology, and performance on injection moulded high-density polyethylene closures.

PubMed

Dulal, Nabeen; Shanks, Robert; Gengenbach, Thomas; Gill, Harsharn; Chalmers, David; Adhikari, Benu; Pardo Martinez, Isaac

2017-11-01

The amount and distribution of slip agents, erucamide, and behenamide, on the surface of high-density polyethene, is determined by integral characteristics of slip agent structure and polymer morphology. A suite of surface analysis techniques was applied to correlate physicochemical properties with slip-additive migration behaviour and their surface morphology. The migration, surface morphology and physicochemical properties of the slip additives, crystallinity and orientation of polyethene spherulites and interaction between slip additives and high-density polyethene influence the surface characteristics. The high-density polyethene closures were produced with erucamide and behenamide separately and stored until they produced required torque. Surface composition was determined employing spectroscopy and gas chromatography. The distribution of additives was observed under optical, scanning electron and atomic force microscopes. The surface energy, crystallinity and application torque were measured using contact angle, differential scanning calorimeter and a torque force tester respectively. Each slip additive produced a characteristic amide peak at 1645cm -1 in infrared spectroscopy and peaks of oxygen and nitrogen in X-ray photoelectron spectroscopy, suggesting their presence on the surface. The erucamide produced placoid scale-like structures and behenamide formed denticulate structures. The surface erucamide and behenamide responsible for reducing the torque was found to be 15.7µg/cm 2 and 1.7µg/cm 2 . Copyright © 2017 Elsevier Inc. All rights reserved.

Optically controlled laser-plasma electron accelerator for compact gamma-ray sources

NASA Astrophysics Data System (ADS)

Kalmykov, S. Y.; Davoine, X.; Ghebregziabher, I.; Shadwick, B. A.

2018-02-01

Generating quasi-monochromatic, femtosecond γ-ray pulses via Thomson scattering (TS) demands exceptional electron beam (e-beam) quality, such as percent-scale energy spread and five-dimensional brightness over 1016 A m-2. We show that near-GeV e-beams with these metrics can be accelerated in a cavity of electron density, driven with an incoherent stack of Joule-scale laser pulses through a mm-size, dense plasma (n 0 ˜ 1019 cm-3). Changing the time delay, frequency difference, and energy ratio of the stack components controls the e-beam phase space on the femtosecond scale, while the modest energy of the optical driver helps afford kHz-scale repetition rate at manageable average power. Blue-shifting one stack component by a considerable fraction of the carrier frequency makes the stack immune to self-compression. This, in turn, minimizes uncontrolled variation in the cavity shape, suppressing continuous injection of ambient plasma electrons, preserving a single, ultra-bright electron bunch. In addition, weak focusing of the trailing component of the stack induces periodic injection, generating, in a single shot, a train of bunches with controllable energy spacing and femtosecond synchronization. These designer e-beams, inaccessible to conventional acceleration methods, generate, via TS, gigawatt γ-ray pulses (or multi-color pulse trains) with the mean energy in the range of interest for nuclear photonics (4-16 MeV), containing over 106 photons within a microsteradian-scale observation cone.

Sample stacking of fast-moving anions in capillary zone electrophoresis with pH-suppressed electroosmotic flow.

PubMed

Quirino, J P; Terabe, S

1999-07-30

On-line sample concentration of fast moving inorganic anions by large volume sample stacking (LVSS) and field enhanced sample injection (FESI) with a water plug under acidic conditions is presented. Detection sensitivity enhancements were around 100 and 1000-fold for LVSS and FESI, respectively. However, reproducibility and linearity of response in the LVSS approach is superior compared to the FESI approach.

Device for equalizing molten electrolyte content in a fuel cell stack

DOEpatents

Smith, J.L.

1985-12-23

A device for equalizing the molten electrolyte content throughout the height of a fuel cell stack is disclosed. The device includes a passageway for electrolyte return with electrolyte wettable wicking material in the opposite end portions of the passageway. One end portion is disposed near the upper, negative end of the stack where electrolyte flooding occurs. The second end portion is placed near the lower, positive end of the stack where electrolyte is depleted. Heating means are provided at the upper portion of the passageway to increase electrolyte vapor pressure in the upper wicking material. The vapor is condensed in the lower passageway portion and conducted as molten electrolyte in the lower wick to the positive end face of the stack. An inlet is provided to inject a modifying gas into the passageway and thereby control the rate of electrolyte return.

Device for equalizing molten electrolyte content in a fuel cell stack

DOEpatents

Smith, James L.

1987-01-01

A device for equalizing the molten electrolyte content throughout the height of a fuel cell stack is disclosed. The device includes a passageway for electrolyte return with electrolyte wettable wicking material in the opposite end portions of the passageway. One end portion is disposed near the upper, negative end of the stack where electrolyte flooding occurs. The second end portion is placed near the lower, positive end of the stack where electrolyte is depleted. Heating means are provided at the upper portion of the passageway to increase electrolyte vapor pressure in the upper wicking material. The vapor is condensed in the lower passageway portion and conducted as molten electrolyte in the lower wick to the positive end face of the stack. An inlet is provided to inject a modifying gas into the passageway and thereby control the rate of electrolyte return.

Structural modeling of HTS tapes and cables

NASA Astrophysics Data System (ADS)

Allen, N. C.; Chiesa, L.; Takayasu, M.

2016-12-01

Structural finite element analysis (FEA) has been used as an insightful tool to investigate the electromechanical behavior of HTS REBCO tapes and twisted stacked-tape cables under tension, torsion, bending and combined loads. A novel technique was developed for modeling the layered composite structure of the 2G tapes with structural solid-shell elements in ANSYS®. The FEA models produced detailed strain information for the REBCO superconducting layer which was then paired with an analytical model to predict the critical current performance of the 2G HTS tapes under various loads. Two commercially available HTS tapes (SuperPower and SuNAM) under tension, torsion and combined tension-torsion were first analyzed with FEA and compared with available experimental results at 77 K. A sharp critical current degradation was experienced at the yield strength of the tapes under tension and below a 100 mm twist-pitch under torsion. Combined tension-torsion loads had a more gradual degradation of critical current for twist-pitches of 115 mm or shorter but had a negligible difference compared to pure tension for longer twist-pitches. Using the structural solid-shell technique for modeling 2G tapes in ANSYS®, an FEA methodology for simulating full scale three-dimensional HTS stacked-tape cables under pure bending was created. A model of a Twisted-Stacked Tape Cable (TSTC), a configuration first proposed at MIT, was initially developed and then adapted to the slotted-core HTS Cable-In-Conduit Conductor produced by the ENEA laboratory in Italy. The numerical axial strain of the HTS REBCO tapes within the cables as calculated by FEA were found to agree with an analytical model for two cases: perfect-slip (frictionless) and no-slip (bonded). The ENEA CICC model was also compared with recent experimental critical current data at 77 K and was found to match best using a low friction coefficient of 0.02 indicating that the tapes within the cable freely slide with respect to each other helping to reduce the axial strain during bending.

Correlation of Coseismic Velocity and Static Volumetric Strain Changes Induced by the 2010 Mw6.3 Jiasian Earthquake under the Southern Taiwan Orogenic Belt

NASA Astrophysics Data System (ADS)

Wu, S. M.; Hung, S. H.

2015-12-01

Earthquake-induced temporal changes in seismic velocity of the earth's crust have been demonstrated to be monitored effectively by the time-lapse shifts of coda waves recently. Velocity drop during the coseismic rupture has been explicitly observed in proximity to the epicenters of large earthquakes with different styles of faulting. The origin of such sudden perturbation in crustal properties is closely related to the damage and/or volumetric strain change influenced by seismic slip distribution. In this study, we apply a coda wave interferometry method to investigate potential velocity change in both space and time related to the moderate-sized (Mw6.3) 2010 Jiasian earthquake, which nucleated deeply in the crust (~23 km), ruptured and terminated around the depth of 10 km along a previously unidentified blind thrust fault near the lithotectonic boundary of the southern Taiwan orogenic belt. To decipher the surface and crustal response to this relatively deep rupture, we first measure relative time-lapse changes of coda between different short-term time frames spanning one year covering the pre- and post-seismic stages by using the Moving Window Cross Spectral Method. Rather than determining temporal velocity variations based on a long-term reference stack, we conduct a Bayesian least-squares inversion to obtain the optimal estimates by minimizing the inconsistency between the relative time-lapse shifts of individual short-term stacks. The results show the statistically significant velocity reduction immediately after the mainshock, which is most pronounced at the pairs with the interstation paths traversing through the hanging-wall block of the ruptured fault. The sensitivity of surface wave coda arrivals mainly in the periods of 3-5 s to shear wave speed perturbation is confined within the depth of 10 km, where the crust mostly experienced extensional strain changes induced by the slip distribution from the finite-fault model. Compared with coseismic slip distribution from GPS data and finite-fault inversion, peak ground velocity, and static volumetric strain field following the earthquake, the velocity decrease observed in the hanging wall side of the shallow crust is most likely attributed to pervasive dilatational strain changes induced by the slip rupture on the underlying blind thrust.

Analysis of anabolic androgenic steroids in urine by full-capillary sample injection combined with a sweeping CE stacking method.

PubMed

Wang, Chun-Chi; Cheng, Shu-Fang; Cheng, Hui-Ling; Chen, Yen-Ling

2013-02-01

This study describes an on-line stacking CE approach by sweeping with whole capillary sample filling for analyzing five anabolic androgenic steroids in urine samples. The five anabolic steroids for detection were androstenedione, testosterone, epitestosterone, boldenone, and clostebol. Anabolic androgenic steroids are abused in sport doping because they can promote muscle growth. Therefore, a sensitive detection method is imperatively required for monitoring the urine samples of athletes. In this research, an interesting and reliable stacking capillary electrophoresis method was established for analysis of anabolic steroids in urine. After liquid-liquid extraction by n-hexane, the supernatant was dried and reconstituted with 30 mM phosphate buffer (pH 5.00) and loaded into the capillary by hydrodynamic injection (10 psi, 99.9 s). The stacking and separation were simultaneously accomplished at -20 kV in phosphate buffer (30 mM, pH 5.0) containing 100 mM sodium dodecyl sulfate and 40 % methanol. During the method validation, calibration curves were linear (r≥0.990) over a range of 50-1,000 ng/mL for the five analytes. In the evaluation of precision and accuracy for this method, the absolute values of the RSD and the RE in the intra-day (n=3) and inter-day (n=5) analyses were all less than 6.6 %. The limit of detection for the five analytes was 30 ng/mL (S/N=5, sampling 99.9 s at 10 psi). Compared with simple MECK, this stacking method possessed a 108- to 175-fold increase in sensitivity. This simple and sensitive stacking method could be used as a powerful tool for monitoring the illegal use of doping.

Replace with abstract title

NASA Astrophysics Data System (ADS)

Coho, Aleksander; Kioussis, Nicholas

2003-03-01

We use the semidiscrete variational generelized Peierls-Nabarro model to study the effect of Cu alloying on the dislocation properties of Al. First-principles density functional theory (DFT) is used to calculate the generalized-stacking-fault (GSF) energy surface when a <111> plane, on which one in four Al atoms has been replaced with a Cu atom, slips over a pure Al <111> plane. Various dislocation core properties (core width, energy, Peierls stress, dissociation tendency) are investigated and compared with the pure Al case. Cu alloying lowers the intrinsic stacking fault (ISF) energy, which makes dislocations more likely to dissociate into partials. We also try to understand the lowering of ISF energy in terms of Al-Cu and Al-Al bond formation and braking during shearing along the <112> direction. From the above we draw conclusions about the effects of Cu alloying on the mechanical properties of Al.

Sprayable superhydrophobic nano-chains coating with continuous self-jumping of dew and melting frost

PubMed Central

Wang, Shanlin; Zhang, Wenwen; Yu, Xinquan; Liang, Caihua; Zhang, Youfa

2017-01-01

Spontaneous movement of condensed matter provides a new insight to efficiently improve condensation heat transfer on superhydrophobic surface. However, very few reports have shown the jumping behaviors on the sprayable superhydrophobic coatings. Here, we developed a sprayable silica nano-porous coating assembled by fluorinated nano-chains to survey the condensates’ dynamics. The dewdrops were continuously removed by self- and/or trigger-propelling motion due to abundant nano-pores from random multilayer stacking of nano-chains. In comparison, the dewdrops just could be slipped under the gravity effect on lack of nano-pores coatings stacked by silica nano-spheres and nano-aggregates. More interestingly, the spontaneous jumping effect also occurred on micro-scale frost crystals under the defrosting process on nano-chains coating surfaces. Different from self-jumping of dewdrops motion, the propelling force of frost crystals were provided by a sudden increase of the pressure under the frost crystal. PMID:28074938

Automated Detection and Modeling of Slow Slip: Case Study of the Cascadia Subduction Zone

NASA Astrophysics Data System (ADS)

Crowell, B. W.; Bock, Y.; Liu, Z.

2012-12-01

The discovery of transient slow slip events over the past decade has changed our understanding of tectonic hazards and the earthquake cycle. Proper geodetic characterization of transient deformation is necessary for studies of regional interseismic, coseismic and postseismic tectonics, and miscalculations can affect our understanding of the regional stress field. We utilize two different methods to create a complete record of slow slip from continuous GPS stations in the Cascadia subduction zone between 1996 and 2012: spatiotemporal principal component analysis (PCA) and the relative strength index (RSI). The PCA is performed on 100 day windows of nearby stations to locate signals that exist across many stations in the network by looking at the ratio of the first two eigenvalues. The RSI is a financial momentum oscillator that looks for changes in individual time series with respect to previous epochs to locate rapid changes, indicative of transient deformation. Using both methods, we create a complete history of slow slip across the Cascadia subduction zone, fully characterizing the timing, progression, and magnitude of events. We inject the results from the automated transient detection into a time-dependent slip inversion and apply a Kalman filter based network inversion method to image the spatiotemporal variation of slip transients along the Cascadia margin.

The core structure and recombination energy of a copper screw dislocation: a Peierls study

DOE PAGES

Szajewski, B. A.; Hunter, A.; Beyerlein, I. J.

2017-05-19

The recombination process of dislocations is central to cross-slip, and transmission through Σ3 grain boundaries among other fundamental plastic deformation processes. Despite its importance, a detailed mechanistic understanding remains lacking. In this paper, we apply a continuous dislocation model, inspired by Peierls and Nabarro, complete with an ab-initio computed -surface and continuous units of infinitesimal dislocation slip, towards computing the stress-dependent recombination path of both an isotropic and anisotropic Cu screw dislocation. Under no applied stress, our model reproduces the stacking fault width between Shockley partial dislocations as predicted by discrete linear elasticity. Upon application of a compressive Escaig stress,more » the two partial dislocations coalesce to a separation of ~|b|. Upon increased loading the edge components of each partial dislocation recede, leaving behind a spread Peierls screw dislocation, indicating the recombined state. We demonstrate that the critical stress required to achieve the recombined state is independent of the shear modulus. Rather the critical recombination stress depends on an energy difference between an unstable fault energy (γτ) and the intrinsic stacking fault energy (γτ-γisf). We report recombination energies of ΔW = 0.168 eV/Å and ΔW = 0.084 eV/Å, respectively, for the Cu screw dislocation within isotropic and anisotropic media. Finally, we develop an analytic model which provides insight into our simulation results which compare favourably with other (similar) models.« less

The core structure and recombination energy of a copper screw dislocation: a Peierls study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szajewski, B. A.; Hunter, A.; Beyerlein, I. J.

The recombination process of dislocations is central to cross-slip, and transmission through Σ3 grain boundaries among other fundamental plastic deformation processes. Despite its importance, a detailed mechanistic understanding remains lacking. In this paper, we apply a continuous dislocation model, inspired by Peierls and Nabarro, complete with an ab-initio computed -surface and continuous units of infinitesimal dislocation slip, towards computing the stress-dependent recombination path of both an isotropic and anisotropic Cu screw dislocation. Under no applied stress, our model reproduces the stacking fault width between Shockley partial dislocations as predicted by discrete linear elasticity. Upon application of a compressive Escaig stress,more » the two partial dislocations coalesce to a separation of ~|b|. Upon increased loading the edge components of each partial dislocation recede, leaving behind a spread Peierls screw dislocation, indicating the recombined state. We demonstrate that the critical stress required to achieve the recombined state is independent of the shear modulus. Rather the critical recombination stress depends on an energy difference between an unstable fault energy (γτ) and the intrinsic stacking fault energy (γτ-γisf). We report recombination energies of ΔW = 0.168 eV/Å and ΔW = 0.084 eV/Å, respectively, for the Cu screw dislocation within isotropic and anisotropic media. Finally, we develop an analytic model which provides insight into our simulation results which compare favourably with other (similar) models.« less

Numerical analysis of ammonia homogenization for selective catalytic reduction application.

PubMed

Baleta, Jakov; Martinjak, Matija; Vujanović, Milan; Pachler, Klaus; Wang, Jin; Duić, Neven

2017-12-01

Selective catalytic reduction based on urea water solution as ammonia precursor is a promising method for the NO x abatement form exhaust gasses of mobile diesel engine units. It consists of injecting the urea-water solution in the hot flue gas stream and reaction of its products with the NO x over the catalyst surface. During this process flue gas enthalpy is used for the urea-water droplet heating and for the evaporation of water content. After water evaporates, thermolysis of urea occurs, during which ammonia, a known NO x reductant, and isocyanic acid are generated. The uniformity of the ammonia before the catalyst as well as ammonia slip to the environment are important counteracting design requirements, optimization of which is crucial for development of efficient deNO x systems. The aim of this paper is to show capabilities of the developed mathematical framework implemented in the commercial CFD code AVL FIRE ® , to simulate physical processes of all relevant phenomena occurring during the SCR process including chemical reactions taking part in the catalyst. First, mathematical models for description of SCR process are presented and afterwards, models are used on the 3D geometry of a real SCR reactor in order to predict ammonia generation, NO x reduction and resulting ammonia slip. Influence of the injection direction and droplet sizes was also investigated on the same geometry. The performed study indicates importance of droplet sizes on the SCR process and shows that counterflow injection is beneficial, especially in terms of minimizing harmful ammonia slip to environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.

This paper applies a multiscale hydro-geochemical-mechanical approach to analyze faulted CO 2 reservoirs using the STOMP-CO 2-R code that is coupled to the ABAQUS® finite element package. STOMP-CO 2-R models the reactive transport of CO 2 causing mineral volume fraction changes that are captured by an Eshelby-Mori-Tanka model implemented in ABAQUS®. A three-dimensional (3D) STOMP-CO 2-R model for a reservoir containing an inclined fault was built to analyze a formation containing a reaction network with 5 minerals: albite, anorthite, calcite, kaolinite and quartz. A 3D finite element mesh that exactly maps the STOMP-CO 2-R grid is developed for coupled hydro-geochemical-mechanicalmore » analyses. The model contains alternating sandstone and shale layers. The impact of reactive transport of CO 2 on the geomechanical properties of reservoir rocks and seals are studied in terms of mineral composition changes that affect their geomechanical responses. Simulations assuming extensional and compressional stress regimes with and without coupled geochemistry are performed to study the stress regime effect on the risk of hydraulic fracture. The tendency for the fault to slip is examined in terms of stress regime, geomechanical and geochemical-mechanical effects as well as fault inclination. The results show that mineralogical changes due to long-term injection of CO 2 reduce the permeability and elastic modulus of the reservoir, leading to increased risk of hydraulic fracture in the injection location and at the caprock seal immediately above the injection zone. Fault slip is not predicted to occur. However, fault inclination and stress regime have an important impact on the slip tendency factor.« less

Splay Fault Branching from the Hikurangi Subduction Shear Zone: Implications for Slow Slip and Fluid Flow

NASA Astrophysics Data System (ADS)

Henrys, S. A.; Plaza-Faverola, A. A.; Pecher, I. A.; Klaeschen, D.; Wallace, L.

2016-12-01

Seismic reflection data along the East Coast of the New Zealand North Island are used to map the offshore character and geometry of the central Hikurangi subduction thrust and outer wedge in a region of short term ( 2-3 weeks duration) geodetically determined slow-slip events (SSEs). Pre-stack depth migration of line 05CM-38 was used to derive subducting slab geometry and upper crustal structure together with a Vp image of the crust that is resolved to 14 km depth. The subduction interface is a shallow dipping thrust at < 7 km deep near the trench and steps down to 14 km depth along an approximately 18 km long ramp, beneath Porangahau Ridge. This bend in the subducted plate is associated with splay fault branching and coincides with the zone of maximum slip (90 mm) inferred on the subduction interface during slow slip events in June and July 2011. We infer that the step down in the décollement transfers slip on the plate interface from the top of subducting sediments to the oceanic crust and drives underplating beneath the inner margin of central Hikurangi margin. Low-velocity subducting sediments (LVZ) beneath the plate interface, updip of the plate interface ramp, are interpreted as being capped with a low permeability condensed layer of chalk and interbedded mudstones. We interpret this LVZ as fluid-rich overpressured sediments that have been displaced and later imbricated by splay faults in a region that may mark the up-dip transition from seismic to aseismic behavior. Further, we hypothesize that fluids derived from the overpressured sediment are channeled along splay faults to the shallow sub-seafloor near Porangahau Ridge where seafloor seepage and an upwarping of the gas hydrate Bottom-Simulating Reflector have been documented.

Surface slip during large Owens Valley earthquakes

NASA Astrophysics Data System (ADS)

Haddon, E. K.; Amos, C. B.; Zielke, O.; Jayko, A. S.; Bürgmann, R.

2016-06-01

The 1872 Owens Valley earthquake is the third largest known historical earthquake in California. Relatively sparse field data and a complex rupture trace, however, inhibited attempts to fully resolve the slip distribution and reconcile the total moment release. We present a new, comprehensive record of surface slip based on lidar and field investigation, documenting 162 new measurements of laterally and vertically displaced landforms for 1872 and prehistoric Owens Valley earthquakes. Our lidar analysis uses a newly developed analytical tool to measure fault slip based on cross-correlation of sublinear topographic features and to produce a uniquely shaped probability density function (PDF) for each measurement. Stacking PDFs along strike to form cumulative offset probability distribution plots (COPDs) highlights common values corresponding to single and multiple-event displacements. Lateral offsets for 1872 vary systematically from ˜1.0 to 6.0 m and average 3.3 ± 1.1 m (2σ). Vertical offsets are predominantly east-down between ˜0.1 and 2.4 m, with a mean of 0.8 ± 0.5 m. The average lateral-to-vertical ratio compiled at specific sites is ˜6:1. Summing displacements across subparallel, overlapping rupture traces implies a maximum of 7-11 m and net average of 4.4 ± 1.5 m, corresponding to a geologic Mw ˜7.5 for the 1872 event. We attribute progressively higher-offset lateral COPD peaks at 7.1 ± 2.0 m, 12.8 ± 1.5 m, and 16.6 ± 1.4 m to three earlier large surface ruptures. Evaluating cumulative displacements in context with previously dated landforms in Owens Valley suggests relatively modest rates of fault slip, averaging between ˜0.6 and 1.6 mm/yr (1σ) over the late Quaternary.

Synthesis and crystal structure of a new aluminum-silicon-nitride phosphor containing boron, Ba5B2Al4Si32N52:Eu

NASA Astrophysics Data System (ADS)

Yoshimura, Fumitaka; Yamane, Hisanori; Nagasako, Makoto

2017-07-01

Single crystals of Ba5B2Al4Si32N52:Eu were grown on the wall of a boron nitride crucible by heating a starting mixture of binary nitrides at 2050 °C and a N2 pressure of 0.85 MPa. The fundamental reflections of X-ray diffraction (XRD) for the crystals were indexed with triclinic cell parameters, a=9.7879(11) Å, b=9.7920(11) Å, c=12.7226(15) Å, α=96.074(4)°, β=112.330(3)°, and γ=94.080(4)°. Streak lines were observed between the fundamental reflections in the direction of the c* axis in the oscillation XRD images and selected area electron diffraction (SAED) patterns, indicating stacking faults in the structure. The atomic images of stacking faults with a slip system of (0 0 1)[-1 1 0]/3, and displacement of a Ba atom layer with (0 0 1)[-1 -1 0]/6 were observed with a scanning transmission electron microscope (STEM). The models of the basic (normal-stacking) structure with space group P1 and local structures of the stacking faults are herein presented. The single crystals emitted blue light with a peak wavelength of 472 nm and a full width at half maximum of 78 nm under 365 nm excitation.

Thermal and capillary effects on the caprock mechanical stability at In Salah, Algeria

DOE PAGES

Vilarrasa, Víctor; Rutqvist, Jonny; Rinaldi, Antonio Pio

2015-04-20

Thermo-mechanical effects are important in geologic carbon storage because CO 2 will generally reach the storage formation colder than the rock, inducing thermal stresses. Capillary functions, i.e., retention and relative permeability curves, control the CO 2 plume shape, which may affect overpressure and thus, caprock stability. To analyze these thermal and capillary effects, we numerically solve non-isothermal injection of CO 2 in deformable porous media considering the In Salah, Algeria, CO 2 storage site. Here, we find that changes in the capillary functions have a negligible effect on overpressure and thus, caprock stability is not affected by capillary effects. But,more » we show that for the strike slip stress regime prevalent at In Salah, stability decreases in the lowest parts of the caprock during injection due to cooling-induced thermal stresses. Simulations show that shear slip along pre-existing fractures may take place in the cooled region, whereas tensile failure is less likely to occur. Indeed, only the injection zone and the lowest tens of meters of the 900-m-thick caprock at In Salah might be affected by cooling effects, which would thus not jeopardize the overall sealing capacity of the caprock. Furthermore, faults are likely to remain stable far away from the injection well because outside the cooled region the injection-induced stress changes are not sufficient to exceed the anticipated shear strength of minor faults. Nonetheless, we recommend that thermal effects should be considered in the site characterization and injection design of future CO 2 injection sites to assess caprock stability and guarantee a permanent CO 2 storage.« less

Injection method of barrier bucket supported by off-aligned electron cooling for CRing of HIAF

NASA Astrophysics Data System (ADS)

Shen, Guo-Dong; Yang, Jian-Cheng; Xia, Jia-Wen; Mao, Li-Jun; Yin, Da-Yu; Chai, Wei-Ping; Shi, Jian; Sheng, Li-Na; Smirnov, A.; Wu, Bo; Zhao, He

2016-08-01

A new accelerator complex, HIAF (the High Intensity Heavy Ion Accelerator Facility), has been approved in China. It is designed to provide intense primary and radioactive ion beams for research in high energy density physics, nuclear physics, atomic physics as well as other applications. In order to achieve a high intensity of up to 5×1011 ppp 238U34+, the Compression Ring (CRing) needs to stack more than 5 bunches transferred from the Booster Ring (BRing). However, the normal bucket to bucket injection scheme can only achieve an intensity gain of 2, so an injection method, fixed barrier bucket (BB) supported by electron cooling, is proposed. To suppress the severe space charge effect during the stacking process, off-alignment is adopted in the cooler to control the transverse emittance. In this paper, simulation and optimization with the BETACOOL program are presented. Supported by New Interdisciplinary and Advanced Pilot Fund of Chinese Academy of Sciences

Automated identification and modeling aseismic slip events on Kilauea Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Desmarais, E. K.; Segall, P.; Miklius, A.

2006-12-01

Several aseismic slip events have been observed on the south flank of Kilauea volcano, Hawaii (Cervelli et al., Nature, 2002; Brooks et al., EPSL, 2006; Segall et al., Nature, 2006). These events are identified as spatially coherent offsets in GPS time series. We have interpreted the events as slip on a sub-horizontal surface at depths consistent with a decollement under Kilauea's south flank. In order to determine whether smaller slow slip events are present in the time series, we developed an algorithm that searches for coherent displacement patterns similar to the known slow slip events. We compute candidate displacements by taking a running difference of the mean position 6 days before and after a window of 6 days centered on the candidate time step. The candidate displacements are placed in a 3N dimensional data vector, where N is the number of stations. We then compute the angle, in the 3N dimensional data space, between the candidate displacement and a reference vector at each time step. The reference vector is a stack of displacements due to the four largest known slow slip events. Small angles indicate similar displacement patterns, regardless of amplitude. The algorithm strongly identifies four events (September 20, 1998, November 9, 2000, December 16, 2002, and January 26, 2005), each separated by approximately 2.11 years. The algorithm also identified one smaller event (March 3, 1998) that preceeded the September 1998 event by ~ 200 days, and another event (July 4, 2003) that followed the December 2002 event by ~ 200 days. These smaller, 'paired' events appear to alternate rupturing of the eastern and western parts of the south flank. Each of the slow slip events is correlated with an increase, sometimes slight, in microseismicity on the south flank of Kilauea. The temporal evolution of the microseismicity for the 2005 event is well explained by increased stress due to the slow slip (Segall et al., Nature, 2006). The microearthquakes, at depths of 6.5 - 8.5 km, thus constrain the depth of the slow earthquakes to comparable depths. The triggering of microearthquakes implies that there is finite probability that a larger earthquake could be triggered, given appropriate stress conditions. In order to better constrain the locations of the slow slip events based solely on geodetic observations, we expand on the simple uniform slip models by adding the effects of distributed slip, layered elastic structure, and topography. There are many difficulties in observing slow slip events on Kilauea volcano. The GPS network only provides displacements on land, which is primarily to the north of the largest slip. The vertical displacement field is essential to understanding the northward extent of the slip, however, the GPS observations of slow slip events are primarily observed in the horizontal component, which have smaller noise levels (~ 3 mm). The maximum vertical deformation from the largest event (2005) was very small (± 9 mm), about the same size as the typical vertical noise. We are exploring the possibility that tiltmeters will allow sufficiently accurate measurements to help identify the northern extent of the slip surface.

Stacked white OLED having separate red, green and blue sub-elements

DOEpatents

Forrest, Stephen; Qi, Xiangfei; Slootsky, Michael

2014-07-01

The present invention relates to efficient organic light emitting devices (OLEDs). The devices employ three emissive sub-elements, typically emitting red, green and blue, to sufficiently cover the visible spectrum. Thus, the devices may be white-emitting OLEDs, or WOLEDs. Each sub-element comprises at least one organic layer which is an emissive layer--i.e., the layer is capable of emitting light when a voltage is applied across the stacked device. The sub-elements are vertically stacked and are separated by charge generating layers. The charge-generating layers are layers that inject charge carriers into the adjacent layer(s) but do not have a direct external connection.

Using quantum dot photoluminescence for load detection

NASA Astrophysics Data System (ADS)

Moebius, M.; Martin, J.; Hartwig, M.; Baumann, R. R.; Otto, T.; Gessner, T.

2016-08-01

We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL) of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N',N'-Tetrakis(3-methylphenyl)-3,3'-dimethylbenzidine (HMTPD) and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

g-Jitter Mixed Convective Slip Flow of Nanofluid past a Permeable Stretching Sheet Embedded in a Darcian Porous Media with Variable Viscosity

PubMed Central

Uddin, Mohammed J.; Khan, Waqar A.; Amin, Norsarahaida S.

2014-01-01

The unsteady two-dimensional laminar g-Jitter mixed convective boundary layer flow of Cu-water and Al2O3-water nanofluids past a permeable stretching sheet in a Darcian porous is studied by using an implicit finite difference numerical method with quasi-linearization technique. It is assumed that the plate is subjected to velocity and thermal slip boundary conditions. We have considered temperature dependent viscosity. The governing boundary layer equations are converted into non-similar equations using suitable transformations, before being solved numerically. The transport equations have been shown to be controlled by a number of parameters including viscosity parameter, Darcy number, nanoparticle volume fraction, Prandtl number, velocity slip, thermal slip, suction/injection and mixed convection parameters. The dimensionless velocity and temperature profiles as well as friction factor and heat transfer rates are presented graphically and discussed. It is found that the velocity reduces with velocity slip parameter for both nanofluids for fluid with both constant and variable properties. It is further found that the skin friction decreases with both Darcy number and momentum slip parameter while it increases with viscosity variation parameter. The surface temperature increases as the dimensionless time increases for both nanofluids. Nusselt numbers increase with mixed convection parameter and Darcy numbers and decreases with the momentum slip. Excellent agreement is found between the numerical results of the present paper with published results. PMID:24927277

Magnetohydrodynamic peristaltic motion of a Newtonian fluid through porous walls through suction and injection

NASA Astrophysics Data System (ADS)

Sivaiah, R.; Hemadri Reddy, R.

2017-11-01

In this paper, we investigate the peristaltic transport of a conducting Newtonian fluid bounded by permeable walls with suction and injection moving with constant velocity of the wave in the wave frame of reference under the consideration of long wavelength and low Reynolds number. The analytical solution for the velocity field, pressure gradient and the frictional force are obtained. The effect of suction/injection parameter, amplitude ratio and the permeability parameter including slip on the flow quantities are discussed graphically. It is found that the greater the suction/injection parameter, the smaller the pressure rise against the pump works. Further, the pressure rise increases with increasing Magnetic parameter.

Unsteady Heat and Mass Transfer of Chemically Reacting Micropolar Fluid in a Porous Channel with Hall and Ion Slip Currents

PubMed Central

2014-01-01

This paper presents an incompressible two-dimensional heat and mass transfer of an electrically conducting micropolar fluid flow in a porous medium between two parallel plates with chemical reaction, Hall and ion slip effects. Let there be periodic injection or suction at the lower and upper plates and the nonuniform temperature and concentration at the plates are varying periodically with time. The flow field equations are reduced to nonlinear ordinary differential equations using similarity transformations and then solved numerically by quasilinearization technique. The profiles of velocity components, microrotation, temperature distribution and concentration are studied for different values of fluid and geometric parameters such as Hartmann number, Hall and ion slip parameters, inverse Darcy parameter, Prandtl number, Schmidt number, and chemical reaction rate and shown in the form of graphs. PMID:27419211

Slip reactivation model for the 2011 Mw9 Tohoku earthquake: Dynamic rupture, sea floor displacements and tsunami simulations.

NASA Astrophysics Data System (ADS)

Galvez, P.; Dalguer, L. A.; Rahnema, K.; Bader, M.

2014-12-01

The 2011 Mw9 Tohoku earthquake has been recorded with a vast GPS and seismic network given unprecedented chance to seismologists to unveil complex rupture processes in a mega-thrust event. In fact more than one thousand near field strong-motion stations across Japan (K-Net and Kik-Net) revealed complex ground motion patterns attributed to the source effects, allowing to capture detailed information of the rupture process. The seismic stations surrounding the Miyagi regions (MYGH013) show two clear distinct waveforms separated by 40 seconds. This observation is consistent with the kinematic source model obtained from the inversion of strong motion data performed by Lee's et al (2011). In this model two rupture fronts separated by 40 seconds emanate close to the hypocenter and propagate towards the trench. This feature is clearly observed by stacking the slip-rate snapshots on fault points aligned in the EW direction passing through the hypocenter (Gabriel et al, 2012), suggesting slip reactivation during the main event. A repeating slip on large earthquakes may occur due to frictional melting and thermal fluid pressurization effects. Kanamori & Heaton (2002) argued that during faulting of large earthquakes the temperature rises high enough creating melting and further reduction of friction coefficient. We created a 3D dynamic rupture model to reproduce this slip reactivation pattern using SPECFEM3D (Galvez et al, 2014) based on a slip-weakening friction with sudden two sequential stress drops . Our model starts like a M7-8 earthquake breaking dimly the trench, then after 40 seconds a second rupture emerges close to the trench producing additional slip capable to fully break the trench and transforming the earthquake into a megathrust event. The resulting sea floor displacements are in agreement with 1Hz GPS displacements (GEONET). The seismograms agree roughly with seismic records along the coast of Japan.The simulated sea floor displacement reaches 8-10 meters of up-lift close to the trench, which may be the cause of such a devastating tsunami followed by the Tohoku earthquake. To investigate the impact of such a huge up-lift, we ran tsunami simulations with the slip reactivation model using sam(oa)2 (O. Meister et al., 2012), a state-of-the-art Finite-Volume framework to simulate the resulting tsunami waves.

Lightweight bipolar storage battery

NASA Technical Reports Server (NTRS)

Rowlette, John J. (Inventor)

1992-01-01

An apparatus [10] is disclosed for a lightweight bipolar battery of the end-plate cell stack design. Current flow through a bipolar cell stack [12] is collected by a pair of copper end-plates [16a,16b] and transferred edgewise out of the battery by a pair of lightweight, low resistance copper terminals [28a,28b]. The copper terminals parallel the surface of a corresponding copper end-plate [16a,16b] to maximize battery throughput. The bipolar cell stack [12], copper end-plates [16a,16b] and copper terminals [28a,28b] are rigidly sandwiched between a pair of nonconductive rigid end-plates [20] having a lightweight fiber honeycomb core which eliminates distortion of individual plates within the bipolar cell stack due to internal pressures. Insulating foam [30] is injected into the fiber honeycomb core to reduce heat transfer into and out of the bipolar cell stack and to maintain uniform cell performance. A sealed battery enclosure [ 22] exposes a pair of terminal ends [26a,26b] for connection with an external circuit.

Slipping and friction at the interface between two-dimensional materials

NASA Astrophysics Data System (ADS)

Sreenivas, Vijayashree Parsi; Nicholl, Ryan; Bolotin, Kirill

Friction at the macroscopic scale is primarily due to the surface roughness while at the atomic scale it is governed by commensurability and environmental conditions. Here, we investigate slipping and friction at the interface between two dissimilar two-dimensional materials, such as graphene and monolayer molybdenum disulfide. Such a system provides a powerful platform to study frictional forces at the atomic scale as chemical nature of the interface and commensurability between the layers can be varied with ease. To carry out such a study, a monolayer of e.g. graphene is exfoliated onto a flexible substrate material - polypropylene - and clamped down by evaporating titanium to avoid slippage. A monolayer of e.g. MoS2 is then transferred on top of graphene and the entire stack is strained using a four point bending apparatus. By measuring strain vs. bending via Raman spectroscopy, we detect slippage at graphene/MoS2 interface and characterize frictional forces as a function of interface parameters.

Resolving plate structure across the seismogenic zone in Cascadia from onshore-offshore receiver function imaging

NASA Astrophysics Data System (ADS)

Audet, P.; Schaeffer, A. J.

2017-12-01

Studies of the forearc structure in the Cascadia subduction zone using teleseismic P-wave receiver function have resolved structures associated with deep fluid cycling, such as the basalt-to-eclogite reaction and fluid overpressure within the subducting oceanic crust, as well as the serpentinization of the forearc mantle wedge. Unfortunately, the updip extent of the over-pressured zone, and therefore the possible control on the transition from episodic slow slip to seismic slip, occurs offshore and is not resolved in those studies. The Cascadia Initiative (CI) has provided an opportunity to extend this work to the locked zone using teleseismic receiver functions from the deployment of a dense line of ocean-bottom seismograph stations offshore of Washington State, from the trench to the coastline. Here we calculate P-wave receiver functions using data from offshore (CI) and onshore (CAFE) broadband seismic stations. These data clearly show the various scattered phases associated with a dipping low-velocity layer that was identified in previous studies as the downgoing oceanic crust. These signals are difficult to untangle offshore because they arrive at similar times. We process receiver functions using a modified common-conversion point (CCP) stacking technique that uses a coherency filter to optimally stack images obtained from the three main scattered phases. The resulting image shows along-dip variations in the character of the seismic discontinuities associated with the top and bottom of the low-velocity layer. Combined with focal depth information of regular and low-frequency earthquakes, these variations may reflect changes in the material properties of the megathrust across the seismogenic zone in Cascadia.

Processing of sintered alpha SiC

NASA Technical Reports Server (NTRS)

Storm, R. S.

1984-01-01

Processing methods of sintered alpha SiC for engine applications are developed in a cost effective manner, using a submicron sized powder blended with sintering aids (boron and carbon). The processes for forming a green powder compact, such as dry pressing, cold isostatic pressing and green machining, slip casting, aqueous extrusion, plastic extrusion, and injection molding, are described. Dry pressing is the simplest route to component fabrication, and is carried out at approximately 10,000 psi pressure, while in the cold isostatic method the pressure could go as high as 20,000 psi. Surfactants are added to control settling rates and casting characteristics in the slip casting. The aqueous extrusion process is accomplished by a hydraulic ram forcing the aqueous mixture through a die. The plastic forming processes of extrusion and injection molding offer the potential of greater diversity in shape capacity. The physical properties of sintered alpha SiC (hardness, Young's modulus, shear modulus, and thermal diffusivity) are extensively tested. Corrosion resistance test results of silicon carbide are included.

Interchange Slip-Running Reconnection and Sweeping SEP-Beams

NASA Technical Reports Server (NTRS)

Masson, S.; Aulanier, G.; Pariat, E.; Klein, K.-L.

2011-01-01

We present a new model to explain how particles, accelerated at a reconnection site that is not magnetically connected to the Earth, could eventually propagate along the well-connected open flux tube. Our model is based on the results of a low-beta resistive magnetohydrodynamics simulation of a three-dimensional line-tied and initially current-free bipole, that is embedded in a non-uniform open potential field. The topology of this configuration is that of an asymmetric coronal null-point, with a closed fan surface and an open outer spine. When driven by slow photospheric shearing motions, field lines, initially fully anchored below the fan dome, reconnect at the null point, and jump to the open magnetic domain. This is the standard interchange mode as sketched and calculated in 2D. The key result in 3D is that, reconnected open field lines located in the vicinity of the outer spine, keep reconnecting continuously, across an open quasi-separatrix layer, as previously identified for non-open-null-point reconnection. The apparent slipping motion of these field lines leads to form an extended narrow magnetic flux tube at high altitude. Because of the slip-running reconnection, we conjecture that if energetic particles would be travelling through, or be accelerated inside, the diffusion region, they would be successively injected along continuously reconnecting field lines that are connected farther and farther from the spine. At the scale of the full Sun, owing to the super-radial expansion of field lines below 3 solar radius, such energetic particles could easily be injected in field lines slipping over significant distances, and could eventually reach the distant flux tube that is well-connected to the Earth.

Temperature-dependent ideal strength and stacking fault energy of fcc Ni: a first-principles study of shear deformation.

PubMed

Shang, S L; Wang, W Y; Wang, Y; Du, Y; Zhang, J X; Patel, A D; Liu, Z K

2012-04-18

Variations of energy, stress, and magnetic moment of fcc Ni as a response to shear deformation and the associated ideal shear strength (τ(IS)), intrinsic (γ(SF)) and unstable (γ(US)) stacking fault energies have been studied in terms of first-principles calculations under both the alias and affine shear regimes within the {111} slip plane along the <112> and <110> directions. It is found that (i) the intrinsic stacking fault energy γ(SF) is nearly independent of the shear deformation regimes used, albeit a slightly smaller value is predicted by pure shear (with relaxation) compared to the one from simple shear (without relaxation); (ii) the minimum ideal shear strength τ(IS) is obtained by pure alias shear of {111}<112>; and (iii) the dissociation of the 1/2[110] dislocation into two partial Shockley dislocations (1/6[211] + 1/6[121]) is observed under pure alias shear of {111}<110>. Based on the quasiharmonic approach from first-principles phonon calculations, the predicted γ(SF) has been extended to finite temperatures. In particular, using a proposed quasistatic approach on the basis of the predicted volume versus temperature relation, the temperature dependence of τ(IS) is also obtained. Both the γ(SF) and the τ(IS) of fcc Ni decrease with increasing temperature. The computed ideal shear strengths as well as the intrinsic and unstable stacking fault energies are in favorable accord with experiments and other predictions in the literature.

Surface dislocation nucleation controlled deformation of Au nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roos, B.; Kapelle, B.; Volkert, C. A., E-mail: volkert@ump.gwdg.de

2014-11-17

We investigate deformation in high quality Au nanowires under both tension and bending using in-situ transmission electron microscopy. Defect evolution is investigated during: (1) tensile deformation of 〈110〉 oriented, initially defect-free, single crystal nanowires with cross-sectional widths between 30 and 300 nm, (2) bending deformation of the same wires, and (3) tensile deformation of wires containing coherent twin boundaries along their lengths. We observe the formation of twins and stacking faults in the single crystal wires under tension, and storage of full dislocations after bending of single crystal wires and after tension of twinned wires. The stress state dependence of themore » deformation morphology and the formation of stacking faults and twins are not features of bulk Au, where deformation is controlled by dislocation interactions. Instead, we attribute the deformation morphologies to the surface nucleation of either leading or trailing partial dislocations, depending on the Schmid factors, which move through and exit the wires producing stacking faults or full dislocation slip. The presence of obstacles such as neutral planes or twin boundaries hinder the egress of the freshly nucleated dislocations and allow trailing and leading partial dislocations to combine and to be stored as full dislocations in the wires. We infer that the twins and stacking faults often observed in nanoscale Au specimens are not a direct size effect but the result of a size and obstacle dependent transition from dislocation interaction controlled to dislocation nucleation controlled deformation.« less

A geodetic matched-filter search for slow slip with application to the Mexico subduction zone

NASA Astrophysics Data System (ADS)

Rousset, B.; Campillo, M.; Lasserre, C.; Frank, W.; Cotte, N.; Walpersdorf, A.; Socquet, A.; Kostoglodov, V.

2017-12-01

Since the discovery of slow slip events, many methods have been successfully applied to model obvious transient events in geodetic time series, such as the widely used network strain filter. Independent seismological observations of tremors or low frequency earthquakes and repeating earthquakes provide evidence of low amplitude slow deformation but do not always coincide with clear occurrences of transient signals in geodetic time series. Here, we aim to extract the signal corresponding to slow slips hidden in the noise of GPS time series, without using information from independent datasets. We first build a library of synthetic slow slip event templates by assembling a source function with Green's functions for a discretized fault. We then correlate the templates with post-processed GPS time series. Once the events have been detected in time, we estimate their duration T and magnitude Mw by modelling a weighted stack of GPS time series. An analysis of synthetic time series shows that this method is able to resolve the correct timing, location, T and Mw of events larger than Mw 6.0 in the context of the Mexico subduction zone. Applied on a real data set of 29 GPS time series in the Guerrero area from 2005 to 2014, this technique allows us to detect 28 transient events from Mw 6.3 to 7.2 with durations that range from 3 to 39 days. These events have a dominant recurrence time of 40 days and are mainly located at the down dip edges of the Mw > 7.5 SSEs.

Sliding history and energy budget recorded in a frozen mantle earthquake

NASA Astrophysics Data System (ADS)

Ferrand, Thomas P.; Labrousse, Loïc; Hilairet, Nadège; Schubnel, Alexandre

2017-04-01

In the Balmuccia massif (NW Italy), pseudotachylytes (PST) are found within a spinel lherzolite. Coming from the solidification of the melt generated during seismic rupture, these rocks constitute a geological record of fossilized earthquakes. Here, combining field observations, Raman spectrometry and Electron Back-Scattered Diffraction (EBSD), we decipher the sliding history of an ancient Mw >6 earthquake. The earthquake fault displays a 1-1.2 m strike-slip component. The average width of the principal fault plane is about 5 mm. A dense network of thin (20-200 µm) faults and injection veins decorates this principal slip surface. Ultramylonitic faults, filled with olivine (0.2-2 µm), pyroxenes and Al-spinel exhibit strong olivine fabric, with (010) planes parallel to the sliding of the fault and [100] direction parallel to the slip direction. The EBSD pole figure for the [100] direction shows an angle of about 40° with respect to Z-axis, indicating a non-negligible dip-slip component of 1.2-1.5 m, i.e. a probable total relative displacement of 1.6-1.9 m. The olivine fabric is consistent with partial melting and/or high temperature (> 1250 °C) diffusion-accommodated grain boundary sliding, which proves: 1) that the ultramylonite originates from a recrystallized melt; 2) that the earthquake occurred at a depth greater than 35 km (stable Al-spinel, no plagioclase). Raman spectrometry in micrometric injectites reveals amorphous material, with water content of 1-2 wt%, structurally bounded. Assuming a peak temperature of 1600-1800°C during sliding, the melt viscosity was < 1 Pa s. Fracture surface energy and thermally dissipated energy are estimated from fracture density and melt volume (including injected volume) around 50 kJ/m2 and 50 MJ/m2 respectively. Considering a metric displacement, an average melting width of 1 cm and high normal stress, > 1 GPa, this yields a dynamic friction coefficient << 0.1, which demonstrates that complete fault lubrication occurred during co-seismic sliding. We argue however, that lubrication is transient, as the melt could rapidly flow (2-10 m/s) into tensile fractures. Melt injection within the fracture led to rapid cooling and may have promoted strength recovery and sliding arrest. Post-seismic slip is nevertheless recorded in the main PST axes, which are mylonitized, contrary to the thin fault network. Finally, the finding of water fossilized in a frozen mantle earthquake strongly suggests that fluid and/or hydrous minerals were present and emphasizes the need for a better understanding of their role in the mechanics of earthquakes.

A rapid sample screening method for authenticity control of whiskey using capillary electrophoresis with online preconcentration.

PubMed

Heller, Melina; Vitali, Luciano; Oliveira, Marcone Augusto Leal; Costa, Ana Carolina O; Micke, Gustavo Amadeu

2011-07-13

The present study aimed to develop a methodology using capillary electrophoresis for the determination of sinapaldehyde, syringaldehyde, coniferaldehyde, and vanillin in whiskey samples. The main objective was to obtain a screening method to differentiate authentic samples from seized samples suspected of being false using the phenolic aldehydes as chemical markers. The optimized background electrolyte was composed of 20 mmol L(-1) sodium tetraborate with 10% MeOH at pH 9.3. The study examined two kinds of sample stacking, using a long-end injection mode: normal sample stacking (NSM) and sample stacking with matrix removal (SWMR). In SWMR, the optimized injection time of the samples was 42 s (SWMR42); at this time, no matrix effects were observed. Values of r were >0.99 for the both methods. The LOD and LOQ were better than 100 and 330 mg mL(-1) for NSM and better than 22 and 73 mg L(-1) for SWMR. The CE-UV reliability in the aldehyde analysis in the real sample was compared statistically with LC-MS/MS methodology, and no significant differences were found, with a 95% confidence interval between the methodologies.

Slip Zone versus Damage Zone Micromechanics, Arima-Takasuki Tectonic Line, Japan

NASA Astrophysics Data System (ADS)

White, J. C.; Lin, A.

2017-12-01

The Arima-Takasuki Tectonic Line (ATTL) of southern Honshu, Japan is defined by historically active faults and multiple splays producing M7 earthquakes. The damage zone of the ATTL comprises a broad zone of crushed, comminuted and pulverized granite/rhyolite1,2containing cm-scale slip zones and highly comminuted injection veins. In this presentation, prior work on the ATTL fault rocks is extending to include microstructural characterization by transmission electron microscopy (TEM) from recent trenching of the primary slip zone, as well as secondary slip zones. This is necessary to adequately characterize the extremely fine-grained material (typically less than 1mm) in both damage and core zones. Damage zone material exhibits generally random textures3 whereas slip zones are macroscopically foliated, and compositionally layered, notwithstanding a fairly homogeneous protolith. The latter reflects fluid-rock interaction during both coseismic and interseismic periods. The slip zones are microstructurally heterogeneous at all scales, comprising not only cataclasites and phyllosilicate (clay)-rich gouge zones, but Fe/Mn pellets or clasts that are contained within gouge. These structures appear to have rolled and would suggest rapid recrystallization and/or growth. A central question related to earthquake recurrence along existing faults is the nature of the gouge. In both near-surface exposures and ongoing drilling at depth, "plastic" or "viscous" gouge zones comprise ultra-fine-grained clay-siliciclastic particles that would not necessarily respond in a simple frictional manner. Depending on whether the plastic nature of these slip zones develops during or after slip, subsequent focusing of slip within them could be complicated. 1 Mitchell, T.A., Ben-Zion, Y., Shimamoto, T., 2011. Ear. Planet. Sci. Lett. 308, 284-297. 2 Lin, A., Yamashita, K, Tanaka, M. J., 2013. Struc. Geol. 48, 3-13. 3 White, J.C., Lin, A. 2016. Proc. AGU Fall Mtg., T42-02 San Francisco.

The effects of intrinsic properties and defect structures on the indentation size effect in metals

NASA Astrophysics Data System (ADS)

Maughan, Michael R.; Leonard, Ariel A.; Stauffer, Douglas D.; Bahr, David F.

2017-08-01

The indentation size effect has been linked to the generation of geometrically necessary dislocations that may be impacted by intrinsic materials properties, such as stacking fault energy, and extrinsic defects, such as statistically stored dislocations. Nanoindentation was carried out at room temperature and elevated temperatures on four different metals in a variety of microstructural conditions. A size effect parameter was determined for each material set combining the effects of temperature and existing dislocation structure. Extrinsic defects, particularly dislocation density, dominate the size effect parameter over those due to intrinsic properties such as stacking fault energy. A multi-mechanism description using a series of mechanisms, rather than a single mechanism, is presented as a phenomenological explanation for the observed size effect in these materials. In this description, the size effect begins with a volume scale dominated by sparse sources, next is controlled by the ability of dislocations to cross-slip and multiply, and then finally at larger length scales work hardening and recovery dominate the effect.

N-[4-(9-Chloro­quino[3,2-b]benzo[1,4]thia­zin-6-yl)but­yl]acetamide1

PubMed Central

Jeleń, Małgorzata; Suwińska, Kinga; Pluta, Krystian; Morak-Młodawska, Beata

2012-01-01

In the title mol­ecule, C21H20ClN3OS, the tetra­cyclic system is close to planar [r.m.s. deviation = 0.110 (4) Å]. The dihedral angle between the quinoline ring system and the benzene ring is 178.3 (1)° and the angle between two (S—C=C—N) halves of the thia­zine ring is 173.4 (1)°. In the crystal, mol­ecules are arranged via π–π inter­actions [centroid–centroid distances = 3.603 (2)–3.739 (2) Å] into slipped stacks extending along [010]. Inter­molecular N—H⋯O hydrogen bonds link the amide groups of neighbouring mol­ecules along the stack, generating a C(4) motif. The title compound shows promising anti­proliferative and anti­cancer activity. PMID:23476166

Design of a Minimum Surface-Effect Tendon-Based Microactuator for Micromanipulation

NASA Technical Reports Server (NTRS)

Goldfarb, Michael; Lipsey, James H.

1997-01-01

A piezoelectric (PZT) stack-based actuator was developed to provide a means of actuation with dynamic characteristics appropriate for small-scale manipulation. In particular, the design incorporates a highly nonlinear, large-ratio transmission that provides approximately two orders of magnitude motion amplification from the PZT stack. In addition to motion amplification, the nonlinear transmission was designed via optimization methods to distort the highly non-uniform properties of a piezoelectric actuator so that the achievable actuation force is nearly constant throughout the actuator workspace. The package also includes sensors that independently measure actuator output force and displacement, so that a manipulator structure need not incorporate sensors nor the associated wires. Specifically, the actuator was designed to output a maximum force of at least one Newton through a stroke of at least one millimeter. For purposes of small-scale precision position and/or force control, the actuator/sensor package was designed to eliminate stick-slip friction and backlash. The overall dimensions of the actuator/sensor package are approximately 40 x 65 x 25 mm.

Energy investigation of effects of O on mechanical properties of NiAl intermetallics.

PubMed

Hu, Xue-Lan; Liu, Li-Hua; Zhang, Ying; Lu, Guang-Hong; Wang, Tianmin

2011-01-19

We have investigated effects of O on mechanical properties of NiAl by calculating the cleavage energy (γ(C)) and the unstable stacking fault energy (γ(us)) using a first-principles method. O is shown to reduce γ(C)/γ(us) for the [001](110) and [100](001) slip systems, indicating that the presence of O should be associated with the ductility reduction of NiAl. Further, γ(C)/γ(us) of the NiAl-O system can be increased by Cr, suggesting the possibility to suppress the negative effect of O via alloying elements.

Potency backprojection

NASA Astrophysics Data System (ADS)

Okuwaki, R.; Kasahara, A.; Yagi, Y.

2017-12-01

The backprojection (BP) method has been one of the powerful tools of tracking seismic-wave sources of the large/mega earthquakes. The BP method projects waveforms onto a possible source point by stacking them with the theoretical-travel-time shifts between the source point and the stations. Following the BP method, the hybrid backprojection (HBP) method was developed to enhance depth-resolution of projected images and mitigate the dummy imaging of the depth phases, which are shortcomings of the BP method, by stacking cross-correlation functions of the observed waveforms and theoretically calculated Green's functions (GFs). The signal-intensity of the BP/HBP image at a source point is related to how much of observed waveforms was radiated from that point. Since the amplitude of the GF associated with the slip-rate increases with depth as the rigidity increases with depth, the intensity of the BP/HBP image inherently has depth dependence. To make a direct comparison of the BP/HBP image with the corresponding slip distribution inferred from a waveform inversion, and discuss the rupture properties along the fault drawn from the waveforms in high- and low-frequencies with the BP/HBP methods and the waveform inversion, respectively, it is desirable to have the variants of BP/HBP methods that directly image the potency-rate-density distribution. Here we propose new formulations of the BP/HBP methods, which image the distribution of the potency-rate density by introducing alternative normalizing factors in the conventional formulations. For the BP method, the observed waveform is normalized with the maximum amplitude of P-phase of the corresponding GF. For the HBP method, we normalize the cross-correlation function with the squared-sum of the GF. The normalized waveforms or the cross-correlation functions are then stacked for all the stations to enhance the signal to noise ratio. We will present performance-tests of the new formulations by using synthetic waveforms and the real data of the Mw 8.3 2015 Illapel Chile earthquake, and further discuss the limitations of the new BP/HBP methods proposed in this study when they are used for exploring the rupture properties of the earthquakes.

Highly efficient solution-processed phosphorescent organic light-emitting devices with double-stacked hole injection layers

NASA Astrophysics Data System (ADS)

Chen, Yuehua; Hao, Lin; Zhang, Xinwen; Zhang, Xiaolin; Liu, Mengjiao; Zhang, Mengke; Wang, Jiong; Lai, Wen-Yong; Huang, Wei

2017-08-01

In this paper, solution-processed nickel oxide (NiOx) is used as hole-injection layers (HILs) in solution-processed phosphorescent organic light-emitting diodes (PhOLEDs). Serious exciton quenching is verified at the NiOx/emitting layer (EML) interface, resulting in worse device performance. The device performance is significantly improved by inserting a layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) between the EML and NiOx. The solution-processed blue PhOLED with the double-stacked NiOx/PEDOT:PSS HILs shows a maximum current efficiency of 30.5 cd/A, which is 75% and 30% higher than those of the devices with a single NiOx HIL and a PEDOT:PSS HIL, respectively. Improvement of device efficiency can be attributed to reducing exciton quenching of the PEDOT:PSS layer as well as the electron blocking effect of the NiOx layer.

Interfacial Cation-Defect Charge Dipoles in Stacked TiO2/Al2O3 Gate Dielectrics.

PubMed

Zhang, Liangliang; Janotti, Anderson; Meng, Andrew C; Tang, Kechao; Van de Walle, Chris G; McIntyre, Paul C

2018-02-14

Layered atomic-layer-deposited and forming-gas-annealed TiO 2 /Al 2 O 3 dielectric stacks, with the Al 2 O 3 layer interposed between the TiO 2 and a p-type germanium substrate, are found to exhibit a significant interface charge dipole that causes a ∼-0.2 V shift of the flat-band voltage and suppresses the leakage current density for gate injection of electrons. These effects can be eliminated by the formation of a trilayer dielectric stack, consistent with the cancellation of one TiO 2 /Al 2 O 3 interface dipole by the addition of another dipole of opposite sign. Density functional theory calculations indicate that the observed interface-dependent properties of TiO 2 /Al 2 O 3 dielectric stacks are consistent in sign and magnitude with the predicted behavior of Al Ti and Ti Al point-defect dipoles produced by local intermixing of the Al 2 O 3 /TiO 2 layers across the interface. Evidence for such intermixing is found in both electrical and physical characterization of the gate stacks.

Stacking multiple connecting functional materials in tandem organic light-emitting diodes

PubMed Central

Zhang, Tao; Wang, Deng-Ke; Jiang, Nan; Lu, Zheng-Hong

2017-01-01

Tandem device is an important architecture in fabricating high performance organic light-emitting diodes and organic photovoltaic cells. The key element in making a high performance tandem device is the connecting materials stack, which plays an important role in electric field distribution, charge generation and charge injection. For a tandem organic light-emitting diode (OLED) with a simple Liq/Al/MoO3 stack, we discovered that there is a significant current lateral spreading causing light emission over an extremely large area outside the OLED pixel when the Al thickness exceeds 2 nm. This spread light emission, caused by an inductive electric field over one of the device unit, limits one’s ability to fabricate high performance tandem devices. To resolve this issue, a new connecting materials stack with a C60 fullerene buffer layer is reported. This new structure permits optimization of the Al metal layer in the connecting stack and thus enables us to fabricate an efficient tandem OLED having a high 155.6 cd/A current efficiency and a low roll-off (or droop) in current efficiency. PMID:28225028

Stacking multiple connecting functional materials in tandem organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Zhang, Tao; Wang, Deng-Ke; Jiang, Nan; Lu, Zheng-Hong

2017-02-01

Tandem device is an important architecture in fabricating high performance organic light-emitting diodes and organic photovoltaic cells. The key element in making a high performance tandem device is the connecting materials stack, which plays an important role in electric field distribution, charge generation and charge injection. For a tandem organic light-emitting diode (OLED) with a simple Liq/Al/MoO3 stack, we discovered that there is a significant current lateral spreading causing light emission over an extremely large area outside the OLED pixel when the Al thickness exceeds 2 nm. This spread light emission, caused by an inductive electric field over one of the device unit, limits one’s ability to fabricate high performance tandem devices. To resolve this issue, a new connecting materials stack with a C60 fullerene buffer layer is reported. This new structure permits optimization of the Al metal layer in the connecting stack and thus enables us to fabricate an efficient tandem OLED having a high 155.6 cd/A current efficiency and a low roll-off (or droop) in current efficiency.

Surface slip during large Owens Valley earthquakes

USGS Publications Warehouse

Haddon, E.K.; Amos, C.B.; Zielke, O.; Jayko, Angela S.; Burgmann, R.

2016-01-01

The 1872 Owens Valley earthquake is the third largest known historical earthquake in California. Relatively sparse field data and a complex rupture trace, however, inhibited attempts to fully resolve the slip distribution and reconcile the total moment release. We present a new, comprehensive record of surface slip based on lidar and field investigation, documenting 162 new measurements of laterally and vertically displaced landforms for 1872 and prehistoric Owens Valley earthquakes. Our lidar analysis uses a newly developed analytical tool to measure fault slip based on cross-correlation of sublinear topographic features and to produce a uniquely shaped probability density function (PDF) for each measurement. Stacking PDFs along strike to form cumulative offset probability distribution plots (COPDs) highlights common values corresponding to single and multiple-event displacements. Lateral offsets for 1872 vary systematically from ∼1.0 to 6.0 m and average 3.3 ± 1.1 m (2σ). Vertical offsets are predominantly east-down between ∼0.1 and 2.4 m, with a mean of 0.8 ± 0.5 m. The average lateral-to-vertical ratio compiled at specific sites is ∼6:1. Summing displacements across subparallel, overlapping rupture traces implies a maximum of 7–11 m and net average of 4.4 ± 1.5 m, corresponding to a geologic Mw ∼7.5 for the 1872 event. We attribute progressively higher-offset lateral COPD peaks at 7.1 ± 2.0 m, 12.8 ± 1.5 m, and 16.6 ± 1.4 m to three earlier large surface ruptures. Evaluating cumulative displacements in context with previously dated landforms in Owens Valley suggests relatively modest rates of fault slip, averaging between ∼0.6 and 1.6 mm/yr (1σ) over the late Quaternary.

Lubrication of dislocation glide in MgO by hydrous defects

NASA Astrophysics Data System (ADS)

Skelton, Richard; Walker, Andrew M.

2018-02-01

Water-related defects, principally in the form of protonated cation vacancies, are potentially able to weaken minerals under high-stress or low-temperature conditions by reducing the Peierls stress required to initiate dislocation glide. In this study, we use the Peierls-Nabarro (PN) model to determine the effect of protonated Mg vacancies on the 1/2<110>{110} and 1/2<110>{100} slip systems in MgO. This PN model is parameterized using generalized stacking fault energies calculated using plane-wave density functional theory, with and without protonated Mg vacancies present at the glide plane. It found that these defects increase dislocation core widths and reduce the Peierls stress over the entire pressure range 0-125 GPa. Furthermore, 1/2<110>{110} slip is found to be more sensitive to the presence of protonated vacancies which increases in the pressure at which {100} becomes the easy glide plane for 1/2<110> screw dislocations. These results demonstrate, for a simple mineral system, that water-related defects can alter the deformation behavior of minerals in the glide-creep regime by reducing the stress required to move dislocations by glide. (Mg, Fe)O is the most anisotropic mineral in the Earth's lower mantle, so the differential sensitivity of the major slip systems in MgO to hydrous defects has potential implications for the interpretation of the seismic anisotropy in this region.

Direct visualization and in-depth physical study of metal filament formation in percolated high-κ dielectrics

NASA Astrophysics Data System (ADS)

Li, X.; Pey, K. L.; Bosman, M.; Liu, W. H.; Kauerauf, T.

2010-01-01

The migration of Ta atoms from a transistor gate electrode into the percolated high-κ (HK) gate dielectrics is directly shown using transmission electron microscopy analysis. A nanoscale metal filament that formed under high current injection is identified to be the physical defect responsible for the ultrafast transient breakdown (BD) of the metal-gate/high-κ (MG/HK) gate stacks. This highly conductive metal filament poses reliability concerns for MG/HK gate stacks as it significantly reduces the post-BD reliability margin of a transistor.

40 CFR 60.1820 - How do I monitor the injection rate of activated carbon?

Code of Federal Regulations, 2010 CFR

2010-07-01

... activated carbon? If your municipal waste combustion unit uses activated carbon to control dioxins/furans or... dioxins/furans and mercury stack test, determine the average carbon feed rate in kilograms (or pounds) per...

40 CFR 62.15275 - How do I monitor the injection rate of activated carbon?

Code of Federal Regulations, 2010 CFR

2010-07-01

... carbon? If your municipal waste combustion unit uses activated carbon to control dioxins/furans or... dioxins/furans and mercury stack test, determine the average carbon feed rate in kilograms (or pounds) per...

40 CFR 60.1330 - How do I monitor the injection rate of activated carbon?

Code of Federal Regulations, 2010 CFR

2010-07-01

... combustion unit uses activated carbon to control dioxins/furans or mercury emissions, you must meet three... feed rate (for example, screw feeder speed). (b) During each dioxins/furans and mercury stack test...

Structural and Depositional Evolution of the Stevenson Basin, a Gulf of Alaska Forearc Basin: Insights from Legacy Seismic and Borehole Data

NASA Astrophysics Data System (ADS)

Bhattacharya, R.; Liberty, L. M.; Almeida, R. V.; Hubbard, J.

2016-12-01

We explore the structural and depositional evolution of the Stevenson Basin, Gulf of Alaska from a dense network of 2-D marine seismic profiles that span the Gulf of Alaska continental margin. The grid of 71 seismic profiles was acquired as part of a 1975 Mineral Management Services (MMS) exploration project to assess basin architecture along the Alaska continental shelf. We obtained unmigrated and stacked seismic profiles in TIFF format. We converted the data to SEGY format and migrated each profile. Within the Stevenson Basin, we identify key seismic horizons, including the regional Eocene-Miocene unconformity, that provide insights into its depositional and structural history. Using these observations combined with stacking velocities, sonic logs from wells, and refraction velocities from the Edge profile of Ye et al. (1997), we develop a local 3D velocity model that we use to depth-convert the seismic reflection profiles. By using ties to >2.5 km deep exploration wells, we note the Stevenson Basin is one of many Eocene and younger depocenters that span the forearc between Kodiak and Prince William Sound. Well logs and seismic data suggest basal strata consist of Eocene sediments than are unconformably overlain by Neogene and younger strata. Faults that breach the sea floor suggest active deformation within and at the bounds of this basin, including on new faults that do not follow any pre-existing structural trends. This assessment is consistent with slip models that place tsunamigenic faults that ruptured during the 1964 Great Alaska earthquake in the vicinity of the basin. The catalog of faults, their slip history and the depositional evolution of the Stevenson Basin, all suggest that the basin evolution may be controlled by heterogeneities along the incoming plate.

Solution-Processable Transparent Conductive Hole Injection Electrode for OLED SSL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pschenitzka, Florian; Mathai, Mathew; Torke, Terri

2012-07-15

An interconnected network of silver nanowires has been used as transparent anode in OLED devices. This layer was deposited by spin-coating and slot-die coating from an aqueous nanowire suspension. The sheet resistance of the film was 10ohms/sq with a transmission (including the glass substrate) of higher than 85%. The first phase of the project focused on the implementation of this nanowire layer with a hole-injection-layer (HIL) which has been developed at Plextronics and has been shown to provide good stability and efficiency in conventional OLED devices. We modified the HIL solution such that it coated reasonably well with suitable surfacemore » morphology so that actual devices can be manufactured. During the second phase we investigated the hole-injection and stability of hole-onlydevices. We determined that the use of the nanowire network as anode does not introduce an additional degradation mechanism since the observed device characteristics did not differ from those made with ITO anode. We then proceeded to make actual OLED devices with this nanowire / HIL stack and achieved device characteristics similar state-of-the-art OLED devices with a single junction. In order to gain traction with potential OLED manufacturers, we decided to contract Novaled to prepare large-area demonstrators for us. For these devices, we used an allevaporated stack, i.e. we did use Novaled's HIL material instead of Plextronics. We successfully fabricated demonstrators with an area of 25cm2 with a double or triple junction stack. Minor stack optimizations were necessary to achieve efficacies and lifetime equivalent with ITO devices made with the same devices stack. Due to the reduced microcavity effect, the color of the emitted light is significantly more stable with respect to the viewing angle compared to ITO devices. This fact in conjunction with the promise of lower production cost due to the elimination of the ITO sputtering process and the direct patterning of the anode layer are the obvious advantages of this technology. The project has shown that this nanowire technology is a viable option to achieve OLED devices with good lifetime and efficiency and we are currently working with manufacturers to utilize this technology in a production setting.« less

A theoretical and experimental study of turbulent nonevaporating sprays

NASA Technical Reports Server (NTRS)

Solomon, A. S. P.; Shuen, J. S.; Zhang, Q. F.; Faeth, G. M.

1984-01-01

Measurements and analysis limited to the dilute portions of turbulent nonevaporating sprays injected into a still air environment were completed. Mean and fluctuating velocities and Reynolds stress were measured in the continuous phase. Liquid phase measurements included liquid mass fluxes, drop sizes and drop size and velocity correlation. Initial conditions needed for model evaluation were measured at a location as close to the injector exit as possible. The test sprays showed significant effects of slip and turbulent dispersion of the discrete phase. The measurements were used to evaluate three typical models of these processes: (1) a locally homogenous flow (LHF) model, where slip between the phases were neglected; (2) a deterministic separated flow (DSF) model, where slip was considered but effects of drop dispersion by turbulence were ignored; and (3) a stochastic separated flow (SSF) model, where effects of interphase slip and turbulent dispersion were considered using random-walk computations for drop motion. The LHF and DSF models did not provide very satisfactory predictions for the present measurements. In contrast, the SSF model performed reasonably well with no modifications in the prescription of eddy properties from its original calibration. Some effects of drops on turbulence properties were observed near the dense regions of the sprays.

Tectonic contraction across Los Angeles after removal of groundwater pumping effects

USGS Publications Warehouse

Bawden, G.W.; Thatcher, W.; Stein, R.S.; Hudnut, K.W.; Peltzer, G.

2001-01-01

After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan Los Angeles, a network of 250 continuously recording global positioning system (GPS) stations was deployed to monitor displacements associated with deep slip on both blind and surface faults. Here we augment this GPS data with interferometric synthetic aperture radar imagery to take into account the deformation associated with groundwater pumping and strike-slip faulting. After removing these non-tectonic signals, we are left with 4.4 mm yr-1 of uniaxial contraction across the Los Angeles basin, oriented N 36??E (perpendicular to the major strike-slip faults in the area). This indicates that the contraction is primarily accommodated on thrust faults rather than on the northeast-trending strike-slip faults. We have found that widespread groundwater and oil pumping obscures and in some cases mimics the tectonic signals expected from the blind thrust faults. In the 40-km-long Santa Ana basin, groundwater withdrawal and re-injection produces 12 mm yr-1 of long-term subsidence, accompanied by an unprecedented seasonal oscillation of 55 mm in the vertical direction and 7 mm horizontally.

The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe 40.4Ni 11.3Mn 34.8Al 7.5Cr 6 high entropy alloys

DOE PAGES

Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; ...

2016-09-01

A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe 40.4Ni 11.3Mn 34.8Al 7.5Cr 6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures,more » as determined by a TEM, show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

The metallic state in neutral radical conductors: dimensionality, pressure and multiple orbital effects.

PubMed

Tian, Di; Winter, Stephen M; Mailman, Aaron; Wong, Joanne W L; Yong, Wenjun; Yamaguchi, Hiroshi; Jia, Yating; Tse, John S; Desgreniers, Serge; Secco, Richard A; Julian, Stephen R; Jin, Changqing; Mito, Masaki; Ohishi, Yasuo; Oakley, Richard T

2015-11-11

Pressure-induced changes in the solid-state structures and transport properties of three oxobenzene-bridged bisdithiazolyl radicals 2 (R = H, F, Ph) over the range 0-15 GPa are described. All three materials experience compression of their π-stacked architecture, be it (i) 1D ABABAB π-stack (R = Ph), (ii) quasi-1D slipped π-stack (R = H), or (iii) 2D brick-wall π-stack (R = F). While R = H undergoes two structural phase transitions, neither of R = F, Ph display any phase change. All three radicals order as spin-canted antiferromagnets, but spin-canted ordering is lost at pressures <1.5 GPa. At room temperature, their electrical conductivity increases rapidly with pressure, and the thermal activation energy for conduction Eact is eliminated at pressures ranging from ∼3 GPa for R = F to ∼12 GPa for R = Ph, heralding formation of a highly correlated (or bad) metallic state. For R = F, H the pressure-induced Mott insulator to metal conversion has been tracked by measurements of optical conductivity at ambient temperature and electrical resistivity at low temperature. For R = F compression to 6.2 GPa leads to a quasiquadratic temperature dependence of the resistivity over the range 5-300 K, consistent with formation of a 2D Fermi liquid state. DFT band structure calculations suggest that the ease of metallization of these radicals can be ascribed to their multiorbital character. Mixing and overlap of SOMO- and LUMO-based bands affords an increased kinetic energy stabilization of the metallic state relative to a single SOMO-based band system.

Permeability evolution associated to creep and episodic slow slip of a fault affecting clay formations: Results from the FS fault activation experiment in Mt Terri (Switzerland).

NASA Astrophysics Data System (ADS)

Guglielmi, Y.; Nussbaum, C.; Birkholzer, J. T.; De Barros, L.; Cappa, F.

2017-12-01

There is a large spectrum of fault slow rupture processes such as stable creep and slow slip that radiate no or little seismic energy, and which relationships to normal earthquakes and fault permeability variations are enigmatic. Here we present measurements of a fault slow rupture, permeability variation and seismicity induced by fluid-injection in a fault affecting the Opalinus clay (Mt Terri URL, Switzerland) at a depth of 300 m. We observe multiple dilatant slow slip events ( 0.1-to-30 microm/s) associated with factor-of-1000 increase of permeability, and terminated by a magnitude -2.5 main seismic event associated with a swarm of very small magnitude ones. Using fully coupled numerical modeling, we calculate that the short term velocity strengthening behavior observed experimentally at laboratory scale is overcome by longer slip weakening that may be favored by slip induced dilation. Two monitoring points set across the fault allow estimating that, at the onset of the seismicity, the radius of the fault patch invaded by pressurized fluid is 9-to-11m which is in good accordance with a fault instability triggering when the dimensions of the critical slip distance are overcome. We then observe that the long term slip weakening is associated to an exponential permeability increase caused by a cumulated effective normal stress drop of about 3.4MPa which controls the successive slip activation of multiple fracture planes inducing a 0.1MPa shear stress drop in the fault zone. Therefore, our data suggest that the induced earthquake that terminated the rupture sequence may have represented enough dynamic stress release to arrest the fault permeability increase, suggesting the high sensitivity of the slow rupture processes to the structural heterogeneity of the fault zone hydromechanical properties.

The probable source of certain spurious frequencies found in the output of a variable speed generating system using slip recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlin, P W

1989-06-01

As part of US Department of Energy-sponsored research on wind energy, a Mod-O wind turbine was used to drive a variable-speed, wound-rotor, induction generator. Energy resulting from the slip frequency voltage in the generator rotor was rectified to dc, inverted back to utility frequency ac, and injected into the power line. Spurious changing frequencies displayed in the generator output by a spectrum analyzer are caused by ripple on the dc link. No resonances of any of these moving frequencies were seen in spite of the presence of a bank of power factor correcting capacitors. 5 figs.

Real-time on-line ultrasonic monitoring for bubbles in ceramic 'slip' in pottery pipelines.

PubMed

Yim, Geun Tae; Leighton, Timothy G

2010-01-01

When casting ceramic items in potteries, liquid 'slip' is passed from a settling tank, through overhead pipelines, before being pumped manually into the moulds. It is not uncommon for bubbles to be introduced into the slip as it passes through the complex piping network, and indeed the presence of bubbles is a major source of financial loss to the ceramics industry worldwide. This is because the bubbles almost always remain undetected until after the ceramic items have been fired in a kiln, during which process bubbles expand and create unwanted holes in the pottery. Since there it is usually an interval of several hours between the injection of the slip into the moulds, and the inspection of the items after firing, such bubble generation goes undetected on the production line during the manufacture of hundreds or even thousands of ceramic units. Not only does this mean hours of wasted staff time, power consumption and production line time: the raw material which makes up these faulty items cannot even be recycled, as fired ceramic cannot be converted back into slip. Currently, the state-of-the-art method for detecting bubbles in the opaque ceramic slip is slow and invasive, can only be used off-line, and requires expertise which is rarely available. This paper describes the invention, engineering and in-factory testing across Europe of an ultrasonic system for real-time monitoring for the presence of bubbles in casting slip. It interprets changes in the scattering statistics accompanying the presence of the bubbles, the latter being detected through perturbations in the received signal when a narrow-band ultrasonic probing wave is transmitted through the slip. The device can be bolted onto the outside of the pipeline, or used in-line. It is automated, and requires no special expertise. The acoustic problems which had to be solved were severe, and included making the system capable of monitoring the slip regardless of the material of pipe (plastic, steel, etc.) and nature of the slip (which can be very variable). It must also be capable of detecting bubbles amongst the myriad solid particles and other species present in the flowing slip. The completed prototype was tested around several factories in Europe, and proved not only to be more versatile, but also more sensitive, than the state-of-the-art method.

Lamination cooling system

DOEpatents

Rippel, Wally E.; Kobayashi, Daryl M.

2005-10-11

An electric motor, transformer or inductor having a lamination cooling system including a stack of laminations, each defining a plurality of apertures at least partially coincident with apertures of adjacent laminations. The apertures define a plurality of cooling-fluid passageways through the lamination stack, and gaps between the adjacent laminations are sealed to prevent a liquid cooling fluid in the passageways from escaping between the laminations. The gaps are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. The apertures of each lamination can be coincident with the same-sized apertures of adjacent laminations to form straight passageways, or they can vary in size, shape and/or position to form non-axial passageways, angled passageways, bidirectional passageways, and manifold sections of passageways that connect a plurality of different passageway sections. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Micellar electrokinetic chromatography and capillary electrochromatography of nitroaromatic explosives in seawater.

PubMed

Giordano, Braden C; Copper, Christine L; Collins, Greg E

2006-02-01

The ability to separate nitroaromatic and nitramine explosives in seawater sample matrices is demonstrated using both MEKC and CEC. While several capillary-based separations exist for explosives, none address direct sampling from seawater, a sample matrix of particular interest in the detection of undersea mines. Direct comparisons are made between MEKC and CEC in terms of sensitivity and separation efficiency for the analysis of 14 explosives and explosive degradation products in seawater and diluted seawater. The use of high-salt stacking with MEKC results, on average, in a three-fold increase in the number of theoretical plates, and nearly double resolution for samples prepared in 25% seawater. By taking advantage of long injection times in conjunction with stacking, detection limits down to sub mg/L levels are attainable; however, resolution is sacrificed. CEC of explosive mixtures using sol-gels prepared from methyltrimethoxysilane does not perform as well as MEKC in terms of resolving power, but does permit extended injection times for concentrating analyte onto the head of the separation column with little or no subsequent loss in resolution. Electrokinetic injections of 8 min at high voltage allow for detection limits of explosives below 100 microg/L.

[Analysis of phthalate esters in plastic-packaging bags on-line sample stacking-microemulsion electrokinetic chromatography].

PubMed

Xiao, Jia; Huang, Ying; Wang, Minyi; Chen, Guonan

2012-09-01

Two convenient, effective, and reproducible methods using microemulsion electrokinetic chromatography (MEEKC)-normal stacking mode (NSM) and reversed electrode polarity stacking mode (REPSM) were developed for the on-line sample stacking of phthalate esters (PAEs). REPSM coupled with MEEKC increased the sensitivity of 937.5 to 7,143 times for four PAEs compared to the conventional MEEKC. The separating conditions in the MEEKC method were studied, and many factors influencing the two sample stacking processes were investigated in detail. The optimum sample matrices for the two stacking methods were as follows: 30 mmol/L sodium cholate (SC) and 30.0 mmol/L borate (pH 8.5). Additionally, sample injections as large as 3.45 kPa x 40 s and 3.45 kPa x 90 s were applied for NSM-MEEKC and REPSM-MEEKC, respectively. The linear relationship and reproducibility were also examined. Under the optimum conditions, the detection limits (S/N = 3) of the PAEs were in the ranges of 0.021 - 0.33 mg/L and 0.7 - 4 microg/L for NSM-MEEKC and REPSM-MEEKC, respectively. The proposed REPSM-MEEKC has been successfully applied to determine PAEs in plastic-packaging bags, and the spiked recoveries were in the range of 89.1% - 105.6% with satisfactory results.

Multi-scale Investigation on Microstructure, Mechanical Properties, and Deformation Mechanisms in Mg Alloys

NASA Astrophysics Data System (ADS)

Zhang, Dalong

Mg and its alloys are promising candidates for light-weight structural applications, e.g., aircraft, automobile, electronic, etc. However, the inherent hexagonal close packed crystal structure makes the deformation of Mg anisotropic, namely deformation only occurs predominantly by dislocation slip in the close-packed (0001) plane (i.e., basal plane), or by deformation twinning in {101¯2} planes. Both basal slip and twinning cause the crystal to re-orient. Consequently, polycrystalline Mg alloys that have undergone thermomechanical processing usually contain strong texture, i.e., preferred crystallographic orientation in grains. The texture in turn leads to anisotropic deformation in wrought Mg alloys. For example, in extruded Mg alloys, the compressive yield strength is usually much lower than the tensile yield strength (so-called yield asymmetry and strength differential). It is the anisotropy that hinders the broader application of Mg alloys. Recent modeling studies on Mg predict that certain alloying elements, particularly rare-earth elements (e.g., Y, Ce, Nd, Gd, etc.), could alter the active deformation modes and enhance homogeneous deformation and overall mechanical properties in Mg. Therefore, the objective of this dissertation research is to investigate experimentally the effects of alloying element Y in reducing the intrinsic and extrinsic anisotropy, modifying texture, and enhancing the overall strength and ductility for Mg. In addition, the research also uncovered some unexpected "side effects" of Y and these phenomena were studied and explained from a fundamental perspective. The methodology used in this work is described as follows. Ultrafine grained Mg 2.5 at.% Y alloy (UFG Mg-2.5Y) was prepared by powder metallurgy method, including gas atomization for producing Mg-2.5Y powder, degassing and hot isostatic pressing (HIP), and hot extrusion. Both the as-HIPed and the as-extruded materials were characterized by electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), and/or atom probe tomography (APT). It is noted that different configurations of stacking faults (all in basal plane, i.e., basal stacking faults, BSFs for short) were observed in the as-extruded Mg-2.5Y, whereas no BSFs were documented in the as-HIPed alloy. Feasible models to explain the formation of BSFs were proposed based on the activity of different dislocations. Tension and compression tests were carried out along the extrusion direction (ED) for UFG Mg-2.5Y. Unlike common Mg alloys exhibiting yield asymmetry, the UFG Mg-2.5Y exhibits yield "symmetry" and significantly reduced strength differential. Namely, the deformation is more isotropic. In addition to post-mortem TEM characterization for deformed UFG Mg-2.5Y, in-situ TEM was also performed, in an effort to understand the fundamental deformation mechanisms in UFG Mg-Y that lead to reduced anisotropy. In-situ TEM for single-crystal Mg-Y nano-pillars reveals that deformation twinning is replaced by dislocation slip in non-basal planes (i.e., prismatic planes), which diametrically differs from any other Mg alloys. However, it is noted that deformation twinning still occurs in the polycrystalline UFG Mg-2.5Y occasionally, and a new type of stacking faults (i.e., prismatic stacking faults, PSFs for short) may be present in the vicinity of twins. Feasible mechanisms explaining the formation of PSFs are proposed.

Maine Pseudotachylyte Localities and the Role of Host Rock Anisotropy in Fault Zone Development and Frictional Melting

NASA Astrophysics Data System (ADS)

Swanson, M. T.

2004-12-01

Three brittle strike-slip fault localities in coastal Maine have developed pseudotachylyte fault veins, injection veins and other reservoir structures in a variety of host rocks where the pre-existing layering can serve as a controlling fabric for brittle strike-slip reactivation. Host rocks with a poorly-oriented planar anisotropy at high angles to the shear direction will favor the development of R-shears in initial en echelon arrays as seen in the Two Lights and Richmond Island Fault Zones of Cape Elizabeth that cut gently-dipping phyllitic quartzites. These en echelon R-shears grow to through-going faults with the development of P-shear linkages across the dominantly contractional stepovers in the initial arrays. Pseudotachylyte on these faults is very localized, typically up to 1-2 mm in thickness and is restricted to through-going fault segments, P-shear linkages and some sidewall ripouts. Overall melt production is limited by the complex geometry of the multi-fault array. Host rocks with a favorably-oriented planar anisotropy for reactivation in brittle shear, however, preferentially develop a multitude of longer, non-coplanar layer-parallel fault segments. Pseudotachylyte in the newly-discovered Harbor Island Fault Zone in Muscongus Bay is developed within vertical bedding on regional upright folds with over 50 individual layer-parallel single-slip fault veins, some of which can be traced for over 40 meters along strike. Many faults show clear crosscuts of pre-existing quartz veins that indicate a range of coseismic displacements of 0.23-0.53 meters yielding fault vein widths of a few mm and dilatant reservoirs up to 2 cm thick. Both vertical and rare horizontal lateral injection veins can be found in the adjoining wall rock up to 0.7 cm thick and 80 cm in length. The structure of these faults is simple with minor development of splay faults, sidewall ripouts and strike-slip duplexes. The prominent vertical flow layering within the mylonite gneisses of Gerrish Island serves as host to the complex Fort Foster Brittle Zone where it localizes brittle fault slip and contributes to a maximum area of contact between the sliding surfaces which, in turn, yields fault vein thicknesses of 1-2 mm and locally up to 2 cm. The reactivation of this planar anisotropy in brittle shear produces long overlapping geometries that develop linking structures in both extensional and contractional stepovers may reflect the development of sidewall ripouts due to adhesive wear. The prominent development of closely-spaced individual single-slip fault veins suggests frictional welding as an effective strain hardening mechanism for repeated stick-slip.

Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

NASA Astrophysics Data System (ADS)

Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

2015-04-01

Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar conditions. The ultra-fine grains and extreme slip localization in these experiments are generally similar to ultra-cataclasites found in exhumed faults-zones, and the intensely pulverized gouge found in drilling across active faults.

Fault activation by hydraulic fracturing in western Canada.

PubMed

Bao, Xuewei; Eaton, David W

2016-12-16

Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (M W ) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months. Copyright © 2016, American Association for the Advancement of Science.

Characterizing the potential for fault reactivation related to CO2 injection through subsurface structural mapping and stress field analysis, Wellington Field, Sumner County, KS

NASA Astrophysics Data System (ADS)

Schwab, D.; Bidgoli, T.; Taylor, M. H.

2015-12-01

South-central Kansas has experienced an unprecedented increase in seismic activity since 2013. The spatial and temporal relationship of the seismicity with brine disposal operations has renewed interest in the role of fluids in fault reactivation. This study focuses on determining the suitability of CO2 injection into a Cambro-Ordovician reservoir for long-term storage and a Mississippian reservoir for enhanced oil recovery in Wellington Field, Sumner County, Kansas. Our approach for determining the potential for induced seismicity has been to (1) map subsurface faults and estimate in-situ stresses, (2) perform slip and dilation tendency analysis to identify optimally-oriented faults relative to the estimated stress field, and (3) monitor surface deformation through cGPS data and InSAR imaging. Through the use of 3D seismic reflection data, 60 near vertical, NNE-striking faults have been identified. The faults range in length from 140-410 m and have vertical separations of 3-32m. A number of faults appear to be restricted to shallow intervals, while others clearly cut the top basement reflector. Drilling-induced tensile fractures (N=78) identified from image logs and inversion of earthquake focal mechanism solutions (N=54) are consistent with the maximum horizontal stress (SHmax) oriented ~E-W. Both strike-slip and normal-slip fault plane solutions for earthquakes near the study area suggest that SHmax and Sv may be similar in magnitude. Estimates of stress magnitudes using step rate tests (Shmin = 2666 psi), density logs (Sv = 5308 psi), and calculations from wells with drilling induced tensile fractures (SHmax = 4547-6655 psi) are determined at the gauge depth of 4869ft. Preliminary slip and dilation tendency analysis indicates that faults striking 0°-20° are stable, whereas faults striking 26°-44° may have a moderate risk for reactivation with increasing pore-fluid pressure.

CO2 Push-Pull Single Fault Injection Simulations

DOE Data Explorer

Borgia, Andrea; Oldenburg, Curtis (ORCID:0000000201326016); Zhang, Rui; Pan, Lehua; Daley, Thomas M.; Finsterle, Stefan; Ramakrishnan, T.S.; Doughty, Christine; Jung, Yoojin; Lee, Kyung Jae; Altundas, Bilgin; Chugunov, Nikita

2017-09-21

ASCII text files containing grid-block name, X-Y-Z location, and multiple parameters from TOUGH2 simulation output of CO2 injection into an idealized single fault representing a dipping normal fault at the Desert Peak geothermal field (readable by GMS). The fault is composed of a damage zone, a fault gouge and a slip plane. The runs are described in detail in the following: Borgia A., Oldenburg C.M., Zhang R., Jung Y., Lee K.J., Doughty C., Daley T.M., Chugunov N., Altundas B, Ramakrishnan T.S., 2017. Carbon Dioxide Injection for Enhanced Characterization of Faults and Fractures in Geothermal Systems. Proceedings of the 42st Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 13-17.

SiO2/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistors

NASA Astrophysics Data System (ADS)

Watanabe, Kenta; Terashima, Daiki; Nozaki, Mikito; Yamada, Takahiro; Nakazawa, Satoshi; Ishida, Masahiro; Anda, Yoshiharu; Ueda, Tetsuzo; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2018-06-01

Stacked gate dielectrics consisting of wide bandgap SiO2 insulators and thin aluminum oxynitride (AlON) interlayers were systematically investigated in order to improve the performance and reliability of AlGaN/GaN metal–oxide–semiconductor (MOS) devices. A significantly reduced gate leakage current compared with that in a single AlON layer was achieved with these structures, while maintaining the superior thermal stability and electrical properties of the oxynitride/AlGaN interface. Consequently, distinct advantages in terms of the reliability of the gate dielectrics, such as an improved immunity against electron injection and an increased dielectric breakdown field, were demonstrated for AlGaN/GaN MOS capacitors with optimized stacked structures having a 3.3-nm-thick AlON interlayer.

Formation mechanism of fivefold deformation twins in a face-centered cubic alloy.

PubMed

Zhang, Zhenyu; Huang, Siling; Chen, Leilei; Zhu, Zhanwei; Guo, Dongming

2017-03-28

The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. In this study, fivefold deformation twins are observed in a single crystal of face-centered cubic (fcc) alloy. A new formation mechanism is proposed for fivefold deformation twins in a single crystal. A partial dislocation is emitted from the incoherent twin boundaries (ITBs) with high energy, generating a stacking fault along {111} plane, and resulting in the nucleating and growing of a twin by the successive emission of partials. A node is fixed at the intersecting center of the four different slip {111} planes. With increasing stress under the indentation, ITBs come into being close to the node, leading to the emission of a partial from the node. This generates a stacking fault along a {111} plane, nucleating and growing a twin by the continuous emission of the partials. This process repeats until the formation of fivefold deformation twins.

Formation mechanism of fivefold deformation twins in a face-centered cubic alloy

NASA Astrophysics Data System (ADS)

Zhang, Zhenyu; Huang, Siling; Chen, Leilei; Zhu, Zhanwei; Guo, Dongming

2017-03-01

The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. In this study, fivefold deformation twins are observed in a single crystal of face-centered cubic (fcc) alloy. A new formation mechanism is proposed for fivefold deformation twins in a single crystal. A partial dislocation is emitted from the incoherent twin boundaries (ITBs) with high energy, generating a stacking fault along {111} plane, and resulting in the nucleating and growing of a twin by the successive emission of partials. A node is fixed at the intersecting center of the four different slip {111} planes. With increasing stress under the indentation, ITBs come into being close to the node, leading to the emission of a partial from the node. This generates a stacking fault along a {111} plane, nucleating and growing a twin by the continuous emission of the partials. This process repeats until the formation of fivefold deformation twins.

Modeling of fluid injection and withdrawal induced fault activation using discrete element based hydro-mechanical and dynamic coupled simulator

NASA Astrophysics Data System (ADS)

Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove

2016-04-01

Operation of fluid injection into and withdrawal from the subsurface for various purposes has been known to induce earthquakes. Such operations include hydraulic fracturing for shale gas extraction, hydraulic stimulation for Enhanced Geothermal System development and waste water disposal. Among these, several damaging earthquakes have been reported in the USA in particular in the areas of high-rate massive amount of wastewater injection [1] mostly with natural fault systems. Oil and gas production have been known to induce earthquake where pore fluid pressure decreases in some cases by several tens of Mega Pascal. One recent seismic event occurred in November 2013 near Azle, Texas where a series of earthquakes began along a mapped ancient fault system [2]. It was studied that a combination of brine production and waste water injection near the fault generated subsurface pressures sufficient to induced earthquakes on near-critically stressed faults. This numerical study aims at investigating the occurrence mechanisms of such earthquakes induced by fluid injection [3] and withdrawal by using hydro-geomechanical coupled dynamic simulator (Itasca's Particle Flow Code 2D). Generic models are setup to investigate the sensitivity of several parameters which include fault orientation, frictional properties, distance from the injection well to the fault, amount of fluid withdrawal around the injection well, to the response of the fault systems and the activation magnitude. Fault slip movement over time in relation to the diffusion of pore pressure is analyzed in detail. Moreover, correlations between the spatial distribution of pore pressure change and the locations of induced seismic events and fault slip rate are investigated. References [1] Keranen KM, Weingarten M, Albers GA, Bekins BA, Ge S, 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection, Science 345, 448, DOI: 10.1126/science.1255802. [2] Hornbach MJ, DeShon HR, Ellsworth WL, Stump BW, Hayward C, Frohlich C, Oldham HR, Olson JE, Magnani MB, Brokaw C, Luetgert JH, 2015, Causal factors for seismicity near Azle, Texas, nature communications 6:6728, DOI: 10.1038/ncomms7728 [3] Yoon JS, Zimmermann G, Zang A, Stephansson O, 2015, Discrete element modeling of fluid injection-induced seismicity and activation of nearby fault, Can Geotech J 52: 1457-1465, DOI: 10.1139/cgj-2014-0435.

Decaying two-dimensional turbulence in a circular container.

PubMed

Schneider, Kai; Farge, Marie

2005-12-09

We present direct numerical simulations of two-dimensional decaying turbulence at initial Reynolds number 5 x 10(4) in a circular container with no-slip boundary conditions. Starting with random initial conditions the flow rapidly exhibits self-organization into coherent vortices. We study their formation and the role of the viscous boundary layer on the production and decay of integral quantities. The no-slip wall produces vortices which are injected into the bulk flow and tend to compensate the enstrophy dissipation. The self-organization of the flow is reflected by the transition of the initially Gaussian vorticity probability density function (PDF) towards a distribution with exponential tails. Because of the presence of coherent vortices the pressure PDF become strongly skewed with exponential tails for negative values.

A theoretical and experimental study of turbulent evaporating sprays

NASA Technical Reports Server (NTRS)

Solomon, A. S. P.; Shuen, J. S.; Zhang, Q. F.; Faeth, G. M.

1984-01-01

Measurements and analysis limited to the dilute portions of turbulent evaporating sprays, injected into a still air environment were completed. Mean and fluctuating velocities and Reynolds stress were measured in the continuous phase. Liquid phase measurements included liquid mass fluxes, drop sizes and drop size and velocity correlation. Initial conditions needed for model evaluation were measured at a location as close to the injector exit as possible. The test sprays showed significant effects of slip and turbulent dispersion of the discrete phase. The measurements were used to evaluate three typical models of these processes: (1) a locally homogeneous flow (LHF) model, where slip between the phases were neglected; (2) a deterministic separated flow (DSF) model, where slip was considered but effects of drop dispersion by turbulence were ignored; and (3) a stochastic separated flow (SSF) model, where effects of interphase slip and turbulent dispersion were considered using random-walk computations for drop motion. For all three models, a k-epsilon model as used to find the properties of the continuous phase. The LHF and DSF models did not provide very satisfactory predictions for the present measurements. In contrast, the SSF model performed reasonably well--with no modifications in the prescription of eddy properties from its original calibration.

Exact Analytical Solution of the Peristaltic Nanofluids Flow in an Asymmetric Channel with Flexible Walls and Slip Condition: Application to the Cancer Treatment

PubMed Central

Ebaid, Abdelhalim; Aly, Emad H.

2013-01-01

In the cancer treatment, magnetic nanoparticles are injected into the blood vessel nearest to the cancer's tissues. The dynamic of these nanoparticles occurs under the action of the peristaltic waves generated on the flexible walls of the blood vessel. Studying such nanofluid flow under this action is therefore useful in treating tissues of the cancer. In this paper, the mathematical model describing the slip peristaltic flow of nanofluid was analytically investigated. Exact expressions were deduced for the temperature distribution and nano-particle concentration. In addition, the effects of the slip, thermophoresis, and Brownian motion parameters on the temperature and nano-particle concentration profiles were discussed and further compared with other approximate results in the literatures. In particular, these results have been obtained at the same values of the physical examined parameters that was considered in Akbar et al., “Peristaltic flow of a nanofluid with slip effects,” 2012. The results reveal that remarkable differences are detected between the exact current results and those approximately obtained in the literatures for behaviour of the temperature profile and nano-particles concentration. Accordingly, the current analysis and results are considered as optimal and therefore may be taken as a base for any future comparisons. PMID:24151526

Laser patterning of platinum electrodes for safe neurostimulation

NASA Astrophysics Data System (ADS)

Green, R. A.; Matteucci, P. B.; Dodds, C. W. D.; Palmer, J.; Dueck, W. F.; Hassarati, R. T.; Byrnes-Preston, P. J.; Lovell, N. H.; Suaning, G. J.

2014-10-01

Objective. Laser surface modification of platinum (Pt) electrodes was investigated for use in neuroprosthetics. Surface modification was applied to increase the surface area of the electrode and improve its ability to transfer charge within safe electrochemical stimulation limits. Approach. Electrode arrays were laser micromachined to produce Pt electrodes with smooth surfaces, which were then modified with four laser patterning techniques to produce surface structures which were nanosecond patterned, square profile, triangular profile and roughened on the micron scale through structured laser interference patterning (SLIP). Improvements in charge transfer were shown through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and biphasic stimulation at clinically relevant levels. A new method was investigated and validated which enabled the assessment of in vivo electrochemically safe charge injection limits. Main results. All of the modified surfaces provided electrical advantage over the smooth Pt. The SLIP surface provided the greatest benefit both in vitro and in vivo, and this surface was the only type which had injection limits above the threshold for neural stimulation, at a level shown to produce a response in the feline visual cortex when using an electrode array implanted in the suprachoroidal space of the eye. This surface was found to be stable when stimulated with more than 150 million clinically relevant pulses in physiological saline. Significance. Critical to the assessment of implant devices is accurate determination of safe usage limits in an in vivo environment. Laser patterning, in particular SLIP, is a superior technique for improving the performance of implant electrodes without altering the interfacial electrode chemistry through coating. Future work will require chronic in vivo assessment of these electrode patterns.

Atomistic simulations of deformation mechanisms in ultralight weight Mg-Li alloys

NASA Astrophysics Data System (ADS)

Karewar, Shivraj

Mg alloys have spurred a renewed academic and industrial interest because of their ultra-light-weight and high specific strength properties. Hexagonal close packed Mg has low deformability and a high plastic anisotropy between basal and non-basal slip systems at room temperature. Alloying with Li and other elements is believed to counter this deficiency by activating non-basal slip by reducing their nucleation stress. In this work I study how Li addition affects deformation mechanisms in Mg using atomistic simulations. In the first part, I create a reliable and transferable concentration dependent embedded atom method (CD-EAM) potential for my molecular dynamics study of deformation. This potential describes the Mg-Li phase diagram, which accurately describes the phase stability as a function of Li concentration and temperature. Also, it reproduces the heat of mixing, lattice parameters, and bulk moduli of the alloy as a function of Li concentration. Most importantly, our CD-EAM potential reproduces the variation of stacking fault energy for basal, prismatic, and pyramidal slip systems that in uences the deformation mechanisms as a function of Li concentration. This success of CD-EAM Mg-Li potential in reproducing different properties, as compared to literature data, shows its reliability and transferability. Next, I use this newly created potential to study the effect of Li addition on deformation mechanisms in Mg-Li nanocrystalline (NC) alloys. Mg-Li NC alloys show basal slip, pyramidal type-I slip, tension twinning, and two-compression twinning deformation modes. Li addition reduces the plastic anisotropy between basal and non-basal slip systems by modifying the energetics of Mg-Li alloys. This causes the solid solution softening. The inverse relationship between strength and ductility therefore suggests a concomitant increase in alloy ductility. A comparison of the NC results with single crystal deformation results helps to understand the qualitative and quantitative effect of Li addition in Mg on nucleation stress and fault energies of each deformation mode. The nucleation stress and fault energies of basal dislocations and compression twins in single crystal Mg-Li alloy increase while those for pyramidal dislocations and tension twinning decrease. This variation in respective values explains the reduction in plastic anisotropy and increase in ductility for Mg-Li alloys.

USPIO-enhanced 3D-cine self-gated cardiac MRI based on a stack-of-stars golden angle short echo time sequence: Application on mice with acute myocardial infarction.

PubMed

Trotier, Aurélien J; Castets, Charles R; Lefrançois, William; Ribot, Emeline J; Franconi, Jean-Michel; Thiaudière, Eric; Miraux, Sylvain

2016-08-01

To develop and assess a 3D-cine self-gated method for cardiac imaging of murine models. A 3D stack-of-stars (SOS) short echo time (STE) sequence with a navigator echo was performed at 7T on healthy mice (n = 4) and mice with acute myocardial infarction (MI) (n = 4) injected with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles. In all, 402 spokes were acquired per stack with the incremental or the golden angle method using an angle increment of (360/402)° or 222.48°, respectively. A cylindrical k-space was filled and repeated with a maximum number of repetitions (NR) of 10. 3D cine cardiac images at 156 μm resolution were reconstructed retrospectively and compared for the two methods in terms of contrast-to-noise ratio (CNR). The golden angle images were also reconstructed with NR = 10, 6, and 3, to assess cardiac functional parameters (ejection fraction, EF) on both animal models. The combination of 3D SOS-STE and USPIO injection allowed us to optimize the identification of cardiac peaks on navigator signal and generate high CNR between blood and myocardium (15.3 ± 1.0). The golden angle method resulted in a more homogeneous distribution of the spokes inside a stack (P < 0.05), enabling reducing the acquisition time to 15 minutes. EF was significantly different between healthy and MI mice (P < 0.05). The method proposed here showed that 3D-cine images could be obtained without electrocardiogram or respiratory gating in mice. It allows precise measurement of cardiac functional parameters even on MI mice. J. Magn. Reson. Imaging 2016;44:355-365. © 2016 Wiley Periodicals, Inc.

Quality evaluation of six bioactive constituents in goji berry based on capillary electrophoresis field amplified sample stacking.

PubMed

Wang, Wei-Feng; Yang, Jun-Li; Shi, Yan-Ping

2018-04-27

Goji berry, fruits of the plant Lycium barbarum L., has long been used as traditional medicine and functional food in China. In this work, a simple and easy-operation on-line concentration capillary electrophoresis (CE) for detection flavonoids in goji berry was developed by coupling of field amplified sample stacking (FASS) with an electroosmotic (EOF) pump driving water removal process. Due to the EOF pump and electrokinetic injection showing different influence on the concentration, the analytes injection condition should be systemically studied. Thereafter, the verification of the analytes injection conditions was achieved using response surface experimental design. Under the optimum conditions, 86-271 folds sensitivity enhancement upon normal capillary zone electrophoresis (CZE, 50 mbar × 5 s) were achieved for six flavonoids, and the detection limits ranged from 0.35 to 1.82 ng/mL; the LOQ ranged from 1.20 to 6.01 ng/mL. Eventually, the proposed method was applied to detect flavonoids in 30 goji berry samples from different habitats of China; and the results indicated that the flavonoids were rich in the eluent of 30-60% methanol, which provided a reference for extraction of goji berry flavonoids. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Possible silica gel in the Olive Fault, Naukluft Nappe Complex, Namibia: A geologic record of dynamic weakening in faults during continental orogenesis

NASA Astrophysics Data System (ADS)

Faber, C.; Rowe, C. D.; Miller, J. A.; Backeberg, N.; Sylvester, F.

2009-12-01

The apparently low frictional strength of faults during earthquake slip is not sufficiently well explained. Dynamic weakening has been observed in recent laboratory experiments at seismic slip rates, even if materials are strong at slow slip rates. Di Toro et al. (2004) performed experiments on crystalline rocks at slip rates of 1m/s and observed frictional strength drops to near zero. Examination of the slip surface revealed an amorophous silica had formed during fast slip and interpreted this as a solidified silica gel. If similar silica gel forms during earthquakes, and solidifies to amorphous silica, it would be expected to slowly crystallize over time. Ujiie et al (2007) reported a microcrystalline silica fault vein from the Shimanto Complex (Japan) which contains colloidal microspheres of silica, consistent with its origin as a silica gel. This vein may have been created during seismic slip, although other explanations are possible. No other natural examples of this potentially important coseismic weakening mechanism have been reported. To investigate whether silica gel actually forms during seismic slip, it will be necessary to discover and fully characterize additional natural examples. The Naukluft Nappe Complex in central Namibia is a foreland thrust stack at the distal southern margin of the Pan-African Damara Orogen (active at ~ 550Ma). A fault vein of microcrystalline silica has been found in an intra-nappe thrust fault . The vein occurs as a mostly continuous, planar, 0.1-1.0cm-thick fault vein within dolomite breccias of the Olive Fault. There are no other veins of silica associated with the fault. The hanging wall and footwall are dolomite and calcareous shales, respectively. The layer is petrographically similar to the microcrystalline silica described by Ujiie et al. (2007). The silica layer is purple-blue to white in color cathodoluminescence, in contrast to the bright turquoise typical of quartz. Although X-ray diffraction spectra show only silica and minor dolomite in the fault vein, SEM revealed the presence of small grains of Ti-oxides which have not been observed in the host rock. The cathodoluminescence has also revealed primary textures in the dolomite breccias which are overprinted by recrystallization and invisible in transmitted light . Transmission Electron Microscopy will be used to determine whether colloidal silica particles are present. The possible finding of the solidified silica gel in the Olive Fault is significant because it may represent a new way to identify fault surfaces which have slipped seismically in the past. In particular, the presence of this unusual silica vein in a carbonate-dominated environment is consistent with the experiments of Di Toro et al (2004) who suggested that quartz need not be present in the source rocks in order to form silica gel. Di Toro, G. et al. (2004) Friction falls towards zero in quartz rock as slip velocity approaches seismic rates. Nature, 427, 436-439 Ujie, K. et al. (2007) Fluidization of granular material in a subduction thrust at seismogenic depths. EPSL, 259, 307-318

Induced seismicity constraints on subsurface geological structure, Paradox Valley, Colorado

NASA Astrophysics Data System (ADS)

Block, Lisa V.; Wood, Christopher K.; Yeck, William L.; King, Vanessa M.

2015-02-01

Precise relative hypocentres of seismic events induced by long-term fluid injection at the Paradox Valley Unit (PVU) brine disposal well provide constraints on the subsurface geological structure and compliment information available from deep seismic reflection and well data. We use the 3-D spatial distribution of the hypocentres to refine the locations, strikes, and throws of subsurface faults interpre­ted previously from geophysical surveys and to infer the existence of previously unidentified subsurface faults. From distinct epicentre lineations and focal mechanism trends, we identify a set of conjugate fracture orientations consistent with shear-slip reactivation of late-Palaeozoic fractures over a widespread area, as well as an additional fracture orientation present only near the injection well. We propose simple Mohr-Coulomb fracture models to explain these observations. The observation that induced seismicity preferentially occurs along one of the identified conjugate fracture orientations can be explained by a rotation in the direction of the regional maximum compressive stress from the time when the fractures were formed to the present. Shear slip along the third fracture orientation observed near the injection well is inconsistent with the current regional stress field and suggests a local rotation of the horizontal stresses. The detailed subsurface model produced by this analysis provides important insights for anticipating spatial patterns of future induced seismicity and for evaluation of possible additional injection well sites that are likely to be seismically and hydrologically isolated from the current well. In addition, the interpreted fault patterns provide constraints for estimating the maximum magnitude earthquake that may be induced, and for building geomechanical models to simulate pore pressure diffusion, stress changes and earthquake triggering.

Geomorphology and Kinematics of the Nobi-Ise Active Fault Zone, Central Japan: Implications for the kinematic growth of tectonic landforms within an active thrust belt

NASA Astrophysics Data System (ADS)

Ishiyama, T.; Mueller, K. J.; Togo, M.; Takemura, K.; Okada, A.

2002-12-01

We present structural models constrained by tectonic geomorphology, surface geologic mapping and high-resolution seismic reflection profiles to define the kinematic evolution and geometry of active fault-related folds along the Nobi-Ise active fault zone (NAFZ). The NAFZ is an active intraplate fault system in central Japan, and consists of a 110-km-long array of active, east-verging reverse faults. We focus on the northern half of the NAFZ, where we use the kinematic evolution of active fault-related folds to constrain rates of slip on underlying blind thrusts and the rate of contraction across the belt since early Quaternary time. Fluvial terraces folded across the east-dipping forelimb, and west-dipping backlimb of the frontal Kuwana anticline suggest that it grows above a stacked sequence of thin-skinned wedge thrusts. Numerous secondary, bedding-parallel thrusts also deform the terraces and are interpreted to form by flexural slip folding that acts to consume slip on the primary blind thrusts across synclinal axial surfaces. Late Holocene fold scarps formed in the floodplain of the Ibi River east of Kuwana anticline coincide with the projected surface trace of the east-vergent wedge thrust tip and indicate the structure has accommodated coseismic (?) kink-band migration of a fault-bend fold during a historic blind thrust earthquake in 1586. A topographic cross-section based on a detailed photogrammetric map suggests 111 m of uplift of ca. 50-80 ka fluvial terraces deposited across the forelimb. For a 35° thrust, this yields the minimum slip rate of 2.7-4.8 mm/yr on the deepest wedge thrust beneath Kuwana anticline. Kinematic analysis for the much larger thrust defined to the west (the Fumotomura fault) suggests that folding of fluvial terraces occurred by trishear fault-propagation folding above a more steeply-dipping (54°), basement-involved blind thrust that propagated upward from the base of the seismogenic crust (about 12 km). Pleistocene growth strata defined by tephra (ca. 1.6 Ma) suggest the Fumotomura fault slips at a rate of 0.7-0.9 mm/yr.

Gas-Driven Fracturing of Saturated Granular Media

NASA Astrophysics Data System (ADS)

Campbell, James M.; Ozturk, Deren; Sandnes, Bjørnar

2017-12-01

Multiphase flows in deformable porous materials are important in numerous geological and geotechnical applications; however, the complex flow behavior makes subsurface transport processes difficult to control—or even characterize. Here, we study gas-driven (pneumatic) fracturing of a wet unconsolidated granular packing confined in a Hele-Shaw cell, and we present an in-depth analysis of both pore-scale phenomena and large-scale pattern formation. The process is governed by a complex interplay among pressure, capillary, frictional, and viscous forces. At low gas-injection rates, fractures grow in a stick-slip fashion and branch out to form a simply connected network. We observe the emergence of a characteristic length scale—the separation distance between fracture branches—creating an apparent uniform spatial fracture density. We conclude that the well-defined separation distance is the result of local compaction fronts surrounding fractures and keeping them apart. A scaling argument is presented that predicts fracture density as a function of granular friction, grain size, and capillary interactions. We study the influence of the gas-injection rate and find that the system undergoes a fluidization transition above a critical injection rate, resulting in directional growth of the fractures, and a fracture density that increases with an increasing rate. A dimensionless fluidization number F is defined as the ratio of viscous to frictional forces, and our experiments reveal a frictional regime for F <1 characterized by stick-slip, rate-independent growth, with a transition to a viscous regime (F >1 ) characterized by continuous growth in several fracture branches simultaneously.

A Controllable Earthquake Rupture Experiment on the Homestake Fault

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Murdoch, L. C.; Garagash, D.; Reches, Z.; Martel, S. J.; Gwaba, D.; Elsworth, D.; Lowell, R. P.; Onstott, T. C.

2010-12-01

Fault-slip is typically simulated in the laboratory at the cm-to-dm scale. Laboratory results are then up-scaled by orders of magnitude to understand faulting and earthquakes processes. We suggest an experimental approach to reactivate faults in-situ at scales ~10-100 m using thermal techniques and fluid injection to modify in situ stresses and the fault strength to the point where the rock fails. Mines where the modified in-situ stresses are sufficient to drive faulting, present an opportunity to conduct such experiments. During our recent field work in the former Homestake gold mine in the northern Black Hills, South Dakota, we found a large fault present on multiple mine levels. The fault is subparallel to the local foliation in the Poorman formation, a Proterozoic metamorphic rock deformed into regional-scale folds with axes plunging ~40° to the SSE. The fault extends at least 1.5 km along strike and dip, with a center ~1.5 km deep. It strikes ~320-340° N, dips ~45-70° NE, and is recognized by a ~0.3-0.5 m thick distinct gouge that contains crushed host rock and black material that appears to be graphite. Although we could not find clear evidence for fault displacement, secondary features suggest that it is a normal fault. The size and distinct structure of this fault make it a promising target for in-situ experimentation of fault strength, hydrological properties, and slip nucleation processes. Most earthquakes are thought to be the result of unstable slip on existing faults, Activation of the Homestake fault in response to the controlled fluid injection and thermally changing background stresses is likely to be localized on a crack-like patch. Slow patch propagation, moderated by the injection rate and the rate of change of the background stresses, may become unstable, leading to the nucleation of a small earthquake (dynamic) rupture. This controlled instability is intimately related to the dependence of the fault strength on the slip process and has been analyzed for the Homestake fault conditions. Scale analyses indicate that this transition occurs for the nucleation patch size ~1 m. This represents a fundamental limitation for laboratory experiments, where the induced dynamic patch could be tractable, and necessitates larger scale field tests ~10-100 m. The ongoing dewatering is expected to affect displacements in the fault vicinity. This poroelastic effect can be used to better characterize the fault. Nucleation, propagation, and arrest of dynamic fault slip is governed by fluid overpressure source, diffusion, and the magnitude of the background loading in relation to the peak and residual strength in the fault zone at the ambient pore pressure level. More information on in-situ stresses than currently available is required to evaluate the fault state. Yet, initial modeling suggests that a suitable place for such an experiment is where the Homestake fault intersects the 4850-ft mine level or at greater depths.

Hair analysis for abused drugs by capillary zone electrophoresis with field-amplified sample stacking.

PubMed

Tagliaro, F; Manetto, G; Crivellente, F; Scarcella, D; Marigo, M

1998-04-05

The present paper describes the methodological optimisation and validation of a capillary zone electrophoresis method for the determination of morphine, cocaine and 3,4-methylenedioxymethamphetamine (MDMA) in hair, with injection based on field-amplified sample stacking. Diode array UV absorption detection was used to improve analytical selectivity and identification power. Analytical conditions: running buffer 100 mM potassium phosphate adjusted to pH 2.5 with phosphoric acid, applied potential 10 kV, temperature 20 degrees C, injection by electromigration at 10 kV for 10 s, detection by UV absorption at the fixed wavelength of 200 nm or by recording the full spectrum between 190 and 400 nm. Injection conditions: the dried hair extracts were reconstituted with a low-conductivity solvent (0.1 mM formic acid), the injection end of the capillary was dipped in water for 5 s without applying pressure (external rinse step), then a plug of 0.1 mM phosphoric acid was loaded by applying 0.5 psi for 10 s and, finally, the sample was injected electrokinetically at 10 kV for 10 s. Under the described conditions, the limit of detection was 2 ng/ml for MDMA, 8 ng/ml for cocaine and 6 ng/ml for morphine (with a signal-to-noise ratio of 5). The lowest concentration suitable for recording interpretable spectra was about 10-20-times the limit of detection of each analyte. The intraday and day-to-day reproducibility of migration times (n = 6), with internal standardisation, was characterised by R.S.D. values < or = 0.6%; peak area R.S.D.s were better than 10% in intraday and than 15% in day-to-day experiments. Analytical linearity was good with R2 better than 0.9990 for all the analytes.

Transition Crossing in the Main Injector for PIP-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ainsworth, R.; Chaurize, S.; Kourbanis, I.

2017-05-01

Proton Improvement Plan-II (PIP-II) [1] is Fermilab’s plan for providing powerful, high-intensity proton beams to the laboratory’s experiments. PIP II will include upgrades to the Booster, Recycler and Main Injector which will be required to accelerate 50% more beam as well as increasing the Booster repetition rate from 15 to 20 Hz. To accommodate the faster rate, the momentum separation of the slip stacking beams in the Recycler must increase which will result in in larger longitudinal emittance bunches in MI. In order to cross transition without losses, it is expected a gamma-t jump will be needed. Gamma-t jump schemesmore » for the MI are investigated.« less

An Overview of the Effects of Alloying Elements on the Properties of Lightweight Fe-(15-35) Mn-(5-12) Al-(0.3-1.2) C Steel

NASA Astrophysics Data System (ADS)

Xing, Jia; Wei, Yinghui; Hou, Lifeng

2018-06-01

In this review, the influences of alloying elements on the phase constitution, density, and stacking fault energy of Fe-(15-35) Mn-(5-12) Al-(0.3-1.2) C lightweight steel are discussed. The mechanical properties of austenite single-phase and austenite-ferrite dual-phase Fe-Mn-Al-C steels processed by different procedures are also statistically analyzed. The austenite single-phase steel was found to possess superior strength and plasticity. Three reasonable explanations for the mechanism of plastic deformation are presented, namely, shear band-induced plasticity, microband-induced plasticity, and slip band refinement-induced plasticity.

Solution softening in magnesium alloys: the effect of solid solutions on the dislocation core structure and nonbasal slip.

PubMed

Tsuru, T; Udagawa, Y; Yamaguchi, M; Itakura, M; Kaburaki, H; Kaji, Y

2013-01-16

There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete variational Peierls-Nabarro model. Yttrium was found to have an anomalous influence on the solution softening owing to a reduction in the GSF energy gradient.

Transition Crossing in the Main Injector for PIP-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ainsworth, R.; Chaurize, S.; Kourbanis, I.

2017-01-01

Proton Improvement Plan-II (PIP-II) is Fermilab’s plan for providing powerful, high-intensity proton beams to the laboratory’s experiments. PIP II will include upgrades to the Booster, Recycler and Main Injector which will be required to accelerate 50% more beam as well as increasing the Booster repetition rate from 15 to 20 Hz. To accommodate the faster rate, the momentum separation of the slip stacking beams in the Recycler must increase which will result in in larger longitudinal emittance bunches in MI. In order to cross transition without losses, it is expected a gammat jump will be needed. Gamma-t jump schemes formore » the MI are investigated« less

An Overview of the Effects of Alloying Elements on the Properties of Lightweight Fe-(15-35) Mn-(5-12) Al-(0.3-1.2) C Steel

NASA Astrophysics Data System (ADS)

Xing, Jia; Wei, Yinghui; Hou, Lifeng

2018-04-01

In this review, the influences of alloying elements on the phase constitution, density, and stacking fault energy of Fe-(15-35) Mn-(5-12) Al-(0.3-1.2) C lightweight steel are discussed. The mechanical properties of austenite single-phase and austenite-ferrite dual-phase Fe-Mn-Al-C steels processed by different procedures are also statistically analyzed. The austenite single-phase steel was found to possess superior strength and plasticity. Three reasonable explanations for the mechanism of plastic deformation are presented, namely, shear band-induced plasticity, microband-induced plasticity, and slip band refinement-induced plasticity.

Coseismic Origin of Foliated Cataclasites and Preservation Potential During the Seismic Cycle

NASA Astrophysics Data System (ADS)

Demurtas, M.; Smith, S. A. F.; Spagnuolo, E.; Fondriest, M.; Di Toro, G.

2016-12-01

Foliated gouges and cataclasites are most commonly interpreted as the result of aseismic faulting in the brittle upper crust. However, the occurrence of foliated cataclasites associated with possible indicators of earthquake ruptures (mirror-like slip surfaces with truncated clasts, in-situ pulverized rocks, etc.) suggests that some examples may have a coseismic origin. Here we present the results of friction experiments and microstructural analysis performed on mixtures (50/50wt%) of calcite-dolomite gouges to ascertain the conditions of foliation formation. The gouges were sheared for 40 cm in a rotary shear apparatus (SHIVA, INGV-Rome) under constant normal stress of 17.5 MPa and slip rates of 30 µm/s to 1 m/s. In room-humidity conditions, a striking foliated fabric was formed only at V = 1 m/s, associated with strain localization and evidence of thermal decomposition and crystal-plastic deformation in a slipping zone less than a few micrometres-thick. Instead, in water-dampened conditions, no foliation was formed at any slip rate and strain localized within an ultrafine (grain size << 1 µm) fluidized layer whose thickness decreased with increasing velocity. To investigate the preservation potential of these microstructures during the seismic cycle, we also conducted experiments that stepped from slow (30 µm/s for 10 cm slip) to high (1 m/s for 30 cm slip) velocity and vice-versa. In the 30 µm/s to 1 m/s experiment, in room-humidity conditions, characteristic microstructures of both slip velocities were preserved and the overall fabric strongly resembles that found in natural foliated cataclasites from the active Vado di Corno Fault Zone, Italian Central Apennines. In the 1 m/s to 30 µm/s experiment, performed under water-dampened conditions, evenly spaced gouge injection veins departing from the localized slip surface formed during the 30 µm/s slip event. Our experiments suggest that foliations defined by compositional banding and/or grain size variations in gouge and cataclasite can form during coseismic sliding (V ≥ 1 m/s) in dry conditions and that foliation is likely to be preserved during the seismic cycle. Recognition of such foliated cataclasites in the geological record would provide a marker of seismic rupture and also a window in to the mechanics of strain localization in brittle fault rocks.

Strain Hardening of Hadfield Manganese Steel

NASA Astrophysics Data System (ADS)

Adler, P. H.; Olson, G. B.; Owen, W. S.

1986-10-01

The plastic flow behavior of Hadfield manganese steel in uniaxial tension and compression is shown to be greatly influenced by transformation plasticity phenomena. Changes in the stress-strain (σ-ɛ) curves with temperature correlate with the observed extent of deformation twinning, consistent with a softening effect of twinning as a deformation mechanism and a hardening effect of the twinned microstructure. The combined effects give upward curvature to the σ-ɛ curve over extensive ranges of plastic strain. A higher strain hardening in compression compared with tension appears to be consistent with the observed texture development. The composition dependence of stacking fault energy computed using a thermodynamic model suggests that the Hadfield composition is optimum for a maximum rate of deformation twinning. Comparisons of the Hadfield steel with a Co-33Ni alloy exhibiting similar twinning kinetics, and an Fe-21Ni-lC alloy deforming by slip indicate no unusual strain hardening at low strains where deformation is controlled by slip, but an unusual amount of structural hardening associated with the twin formation in the Hadfield steel. A possible mechanism of anomalous twin hardening is discussed in terms of modified twinning behavior (pseudotwinning) in nonrandom solid solutions.

Performance Testing of Tracer Gas and Tracer Aerosol Detectors for use in Radionuclide NESHAP Compliance Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuehne, David Patrick; Lattin, Rebecca Renee

The Rad-NESHAP program, part of the Air Quality Compliance team of LANL’s Compliance Programs group (EPC-CP), and the Radiation Instrumentation & Calibration team, part of the Radiation Protection Services group (RP-SVS), frequently partner on issues relating to characterizing air flow streams. This memo documents the most recent example of this partnership, involving performance testing of sulfur hexafluoride detectors for use in stack gas mixing tests. Additionally, members of the Rad-NESHAP program performed a functional trending test on a pair of optical particle counters, comparing results from a non-calibrated instrument to a calibrated instrument. Prior to commissioning a new stack samplingmore » system, the ANSI Standard for stack sampling requires that the stack sample location must meet several criteria, including uniformity of tracer gas and aerosol mixing in the air stream. For these mix tests, tracer media (sulfur hexafluoride gas or liquid oil aerosol particles) are injected into the stack air stream and the resulting air concentrations are measured across the plane of the stack at the proposed sampling location. The coefficient of variation of these media concentrations must be under 20% when evaluated over the central 2/3 area of the stack or duct. The instruments which measure these air concentrations must be tested prior to the stack tests in order to ensure their linear response to varying air concentrations of either tracer gas or tracer aerosol. The instruments used in tracer gas and aerosol mix testing cannot be calibrated by the LANL Standards and Calibration Laboratory, so they would normally be sent off-site for factory calibration by the vendor. Operational requirements can prevent formal factory calibration of some instruments after they have been used in hazardous settings, e.g., within a radiological facility with potential airborne contamination. The performance tests described in this document are intended to demonstrate the reliable performance of the test instruments for the specific tests used in stack flow characterization.« less

The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe 40.4 Ni 11.3 Mn 34.8 Al 7.5 Cr 6 high entropy alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhangwei; Baker, Ian; Cai, Zhonghou

2016-11-01

A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. The consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Fault reactivation and seismicity risk from CO2 sequestration in the Chinshui gas field, NW Taiwan

NASA Astrophysics Data System (ADS)

Sung, Chia-Yu; Hung, Jih-Hao

2015-04-01

The Chinshui gas field located in the fold-thrust belt of western Taiwan was a depleted reservoir. Recently, CO2 sequestration has been planned at shallower depths of this structure. CO2 injection into reservoir will generate high fluid pressure and trigger slip on reservoir-bounding faults. We present detailed in-situ stresses from deep wells in the Chinshui gas field and evaluated the risk of fault reactivation for underground CO2 injection. The magnitudes of vertical stress (Sv), formation pore pressure (Pf) and minimum horizontal stress (Shmin) were obtained from formation density logs, repeat formation tests, sonic logs, mud weight, and hydraulic fracturing including leak-off tests and hydraulic fracturing. The magnitude of maximum horizontal stress (SHmax) was constrained by frictional limit of critically stressed faults. Results show that vertical stress gradient is about 23.02 MPa/km (1.02 psi/ft), and minimum horizontal stress gradient is 18.05 MPa/km (0.80 psi/ft). Formation pore pressures were hydrostatic at depths 2 km, and increase with a gradient of 16.62 MPa/km (0.73 psi/ft). The ratio of fluid pressure and overburden pressure (λp) is 0.65. The upper bound of maximum horizontal stress constrained by strike-slip fault stress regime (SHmax>Sv>Shmin) and coefficient of friction (μ=0.6) is about 18.55 MPa/km (0.82 psi/ft). The orientation of maximum horizontal stresses was calculated from four-arm caliper tools through the methodology suggested by World Stress Map (WMS). The mean azimuth of preferred orientation of borehole breakouts are in ~65。N. Consequently, the maximum horizontal stress axis trends in 155。N and sub-parallel to the far-field plate-convergence direction. Geomechanical analyses of the reactivation of pre-existing faults was assessed using 3DStress and Traptester software. Under current in-situ stress, the middle block fault has higher slip tendency, but still less than frictional coefficient of 0.6 a common threshold value for motion on incohesive faults. The results also indicate that CO2 injection in the Chinshui gas field will not compromise the stability of faults.

Wavelets solution of MHD 3-D fluid flow in the presence of slip and thermal radiation effects

NASA Astrophysics Data System (ADS)

Usman, M.; Zubair, T.; Hamid, M.; Haq, Rizwan Ul; Wang, Wei

2018-02-01

This article is devoted to analyze the magnetic field, slip, and thermal radiations effects on generalized three-dimensional flow, heat, and mass transfer in a channel of lower stretching wall. We supposed two various lateral direction rates for the lower stretching surface of the wall while the upper wall of the channel is subjected to constant injection. Moreover, influence of thermal slip on the temperature profile beside the viscous dissipation and Joule heating is also taken into account. The governing set of partial differential equations of the heat transfer and flow are transformed to nonlinear set of ordinary differential equations (ODEs) by using the compatible similarity transformations. The obtained nonlinear ODE set tackled by means of a new wavelet algorithm. The outcomes obtained via modified Chebyshev wavelet method are compared with Runge-Kutta (order-4). The worthy comparison, error, and convergence analysis shows an excellent agreement. Additionally, the graphical representation for various physical parameters including the skin friction coefficient, velocity, the temperature gradient, and the temperature profiles are plotted and discussed. It is observed that for a fixed value of velocity slip parameter a suitable selection of stretching ratio parameter can be helpful in hastening the heat transfer rate and in reducing the viscous drag over the stretching sheet. Finally, the convergence analysis is performed which endorsing that this proposed method is well efficient.

Applications of optical measurement technology in pollution gas monitoring at thermal power plants

NASA Astrophysics Data System (ADS)

Wang, Jian; Yu, Dahai; Ye, Huajun; Yang, Jianhu; Ke, Liang; Han, Shuanglai; Gu, Haitao; Chen, Yingbin

2011-11-01

This paper presents the work of using advanced optical measurement techniques to implement stack gas emission monitoring and process control. A system is designed to conduct online measurement of SO2/NOX and mercury emission from stacks and slipping NH3 of de-nitrification process. The system is consisted of SO2/NOX monitoring subsystem, mercury monitoring subsystem, and NH3 monitoring subsystem. The SO2/NOX monitoring subsystem is developed based on the ultraviolet differential optical absorption spectroscopy (UV-DOAS) technique. By using this technique, a linearity error less than +/-1% F.S. is achieved, and the measurement errors resulting from optical path contamination and light fluctuation are removed. Moreover, this subsystem employs in situ extraction and hot-wet line sampling technique to significantly reduce SO2 loss due to condensation and protect gas pipeline from corrosion. The mercury monitoring subsystem is used to measure the concentration of element mercury (Hg0), oxidized mercury (Hg2+), and total gaseous mercury (HgT) in the flue gas exhaust. The measurement of Hg with a low detection limit (0.1μg/m3) and a high sensitivity is realized by using cold vapor atom fluorescence spectroscopy (CVAFS) technique. This subsystem is also equipped with an inertial separation type sampling technique to prevent gas pipeline from being clogged and to reduce speciation mercury measurement error. The NH3 monitoring subsystem is developed to measure the concentration of slipping NH3 and then to help improving the efficiency of de-nitrification. The NH3 concentration as low as 0.1ppm is able to be measured by using the off-axis integrated cavity output spectroscopy (ICOS) and the tunable diode laser absorption spectroscopy (TDLAS) techniques. The problem of trace NH3 sampling loss is solved by applying heating the gas pipelines when the measurement is running.

Development of a repetitive compact torus injector

NASA Astrophysics Data System (ADS)

Onchi, Takumi; McColl, David; Dreval, Mykola; Rohollahi, Akbar; Xiao, Chijin; Hirose, Akira; Zushi, Hideki

2013-10-01

A system for Repetitive Compact Torus Injection (RCTI) has been developed at the University of Saskatchewan. CTI is a promising fuelling technology to directly fuel the core region of tokamak reactors. In addition to fuelling, CTI has also the potential for (a) optimization of density profile and thus bootstrap current and (b) momentum injection. For steady-state reactor operation, RCTI is necessary. The approach to RCTI is to charge a storage capacitor bank with a large capacitance and quickly charge the CT capacitor bank through a stack of integrated-gate bipolar transistors (IGBTs). When the CT bank is fully charged, the IGBT stack will be turned off to isolate banks, and CT formation/acceleration sequence will start. After formation of each CT, the fast bank will be replenished and a new CT will be formed and accelerated. Circuits for the formation and the acceleration in University of Saskatchewan CT Injector (USCTI) have been modified. Three CT shots at 10 Hz or eight shots at 1.7 Hz have been achieved. This work has been sponsored by the CRC and NSERC, Canada.

The shear instability energy: a new parameter for materials design?

NASA Astrophysics Data System (ADS)

Kanani, M.; Hartmaier, A.; Janisch, R.

2017-10-01

Reliable and predictive relationships between fundamental microstructural material properties and observable macroscopic mechanical behaviour are needed for the successful design of new materials. In this study we establish a link between physical properties that are defined on the atomic level and the deformation mechanisms of slip planes and interfaces that govern the mechanical behaviour of a metallic material. To accomplish this, the shear instability energy Γ is introduced, which can be determined via quantum mechanical ab initio calculations or other atomistic methods. The concept is based on a multilayer generalised stacking fault energy calculation and can be applied to distinguish the different shear deformation mechanisms occurring at TiAl interfaces during finite-temperature molecular dynamics simulations. We use the new parameter Γ to construct a deformation mechanism map for different interfaces occurring in this intermetallic. Furthermore, Γ can be used to convert the results of ab initio density functional theory calculations into those obtained with an embedded atom method type potential for TiAl. We propose to include this new physical parameter into material databases to apply it for the design of materials and microstructures, which so far mainly relies on single-crystal values for the unstable and stable stacking fault energy.

Fast stack activation procedure and effective long-term storage for high-performance polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Yang, Seung Yong; Seo, Dong-Jun; Kim, Myeong-Ri; Seo, Min Ho; Hwang, Sun-Mi; Jung, Yong-Min; Kim, Beom-Jun; Yoon, Young-Gi; Han, Byungchan; Kim, Tae-Young

2016-10-01

Time-saving stack activation and effective long-term storage are one of most important issues that must be resolved for the commercialization of polymer electrolyte membrane fuel cell (PEMFC). Herein, we developed the cost-effective stack activation method to finish the whole activation within 30 min and the long-term storage method by using humidified N2 without any significant decrease in cell's performance for 30 days. Specifically, the pre-activation step with the direct injection of DI water into the stack and storage at 65 or 80 °C for 2 h increases the distinctive phase separation between the hydrophobic and hydrophilic regions in Nafion membrane, which significantly reduces the total activation time within 30 min. Additionally, the long-term storage with humidified N2 has no effect on the Pt oxidation and drying of Nafion membrane for 30 days due to its exergonic reaction in the cell. As a result, the high water content in Nafion membrane and the decrease of Pt oxidation are the critical factors that have a strong influence on the activation and long-term storage for high-performance PEMFC.

Techno-Economic Analysis of Scalable Coal-Based Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuang, Steven S. C.

Researchers at The University of Akron (UA) have demonstrated the technical feasibility of a laboratory coal fuel cell that can economically convert high sulfur coal into electricity with near zero negative environmental impact. Scaling up this coal fuel cell technology to the megawatt scale for the nation’s electric power supply requires two key elements: (i) developing the manufacturing technology for the components of the coal-based fuel cell, and (ii) long term testing of a kW scale fuel cell pilot plant. This project was expected to develop a scalable coal fuel cell manufacturing process through testing, demonstrating the feasibility of buildingmore » a large-scale coal fuel cell power plant. We have developed a reproducible tape casting technique for the mass production of the planner fuel cells. Low cost interconnect and cathode current collector material was identified and current collection was improved. In addition, this study has demonstrated that electrochemical oxidation of carbon can take place on the Ni anode surface and the CO and CO 2 product produced can further react with carbon to initiate the secondary reactions. One important secondary reaction is the reaction of carbon with CO 2 to produce CO. We found CO and carbon can be electrochemically oxidized simultaneously inside of the anode porous structure and on the surface of anode for producing electricity. Since CH 4 produced from coal during high temperature injection of coal into the anode chamber can cause severe deactivation of Ni-anode, we have studied how CH 4 can interact with CO 2 to produce in the anode chamber. CO produced was found able to inhibit coking and allow the rate of anode deactivation to be decreased. An injection system was developed to inject the solid carbon and coal fuels without bringing air into the anode chamber. Five planner fuel cells connected in a series configuration and tested. Extensive studies on the planner fuels and stack revealed that the planner fuel cell stack is not suitable for operation with carbon and coal fuels due to lack of mechanical strength and difficulty in sealing. We have developed scalable processes for manufacturing of process for planner and tubular cells. Our studies suggested that tubular cell stack could be the only option for scaling up the coal-based fuel cell. Although the direct feeding of coal into fuel cell can significantly simplify the fuel cell system, the durability of the fuel cell needs to be further improved before scaling up. We are developing a tubular fuel cell stack with a coal injection and a CO 2 recycling unit.« less

Monitoring CO 2 Storage at Cranfield, Mississippi with Time-Lapse Offset VSP – Using Integration and Modeling to Reduce Uncertainty

DOE PAGES

Daley, Thomas M.; Hendrickson, Joel; Queen, John H.

2014-12-31

A time-lapse Offset Vertical Seismic Profile (OVSP) data set was acquired as part of a subsurface monitoring program for geologic sequestration of CO 2. The storage site at Cranfield, near Natchez, Mississippi, is part of a detailed area study (DAS) site for geologic carbon sequestration operated by the U.S. Dept. of Energy’s Southeast Regional Carbon Sequestration Partnership (SECARB). The DAS site includes three boreholes, an injection well and two monitoring wells. The project team selected the DAS site to examine CO 2 sequestration multiphase fluid flow and pressure at the interwell scale in a brine reservoir. The time-lapse (TL) OVSPmore » was part of an integrated monitoring program that included well logs, crosswell seismic, electrical resistance tomography and 4D surface seismic. The goals of the OVSP were to detect the CO 2 induced change in seismic response, give information about the spatial distribution of CO 2 near the injection well and to help tie the high-resolution borehole monitoring to the 4D surface data. The VSP data were acquired in well CFU 31-F1, which is the ~3200 m deep CO 2 injection well at the DAS site. A preinjection survey was recorded in late 2009 with injection beginning in December 2009, and a post injection survey was conducted in Nov 2010 following injection of about 250 kT of CO 2. The sensor array for both surveys was a 50-level, 3-component, Sercel MaxiWave system with 15 m (49 ft) spacing between levels. The source for both surveys was an accelerated weight drop, with different source trucks used for the two surveys. Consistent time-lapse processing was applied to both data sets. Time-lapse processing generated difference corridor stacks to investigate CO 2 induced reflection amplitude changes from each source point. Corridor stacks were used for amplitude analysis to maximize the signal-to-noise ratio (S/N) for each shot point. Spatial variation in reflectivity (used to ‘map’ the plume) was similar in magnitude to the corridor stacks but, due to relatively lower S/N, the results were less consistent and more sensitive to processing and therefore are not presented. We examined the overall time-lapse repeatability of the OVSP data using three methods, the NRMS and Predictability (Pred) measures of Kragh and Christie (2002) and the signal-to-distortion ratio (SDR) method of Cantillo (2011). Because time-lapse noise was comparable to the observed change, multiple methods were used to analyze data reliability. The reflections from the top and base reservoir were identified on the corridor stacks by correlation with a synthetic response generated from the well logs. A consistent change in the corridor stack amplitudes from pre- to post-CO 2 injection was found for both the top and base reservoir reflections on all ten shot locations analyzed. In addition to the well-log synthetic response, a finite-difference elastic wave propagation model was built based on rock/fluid properties obtained from well logs, with CO 2 induced changes guided by time-lapse crosswell seismic tomography (Ajo-Franklin, et al., 2013) acquired at the DAS site. Time-lapse seismic tomography indicated that two reservoir zones were affected by the flood. The modeling established that interpretation of the VSP trough and peak event amplitudes as reflectivity from the top and bottom of reservoir is appropriate even with possible tuning effects. Importantly, this top/base change gives confidence in an interpretation that these changes arise from within the reservoir, not from bounding lithology. The modeled time-lapse change and the observed field data change from 10 shotpoints are in agreement for both magnitude and polarity of amplitude change for top and base of reservoir. Therefore, we conclude the stored CO 2 has been successfully detected and, furthermore, the observed seismic reflection change can be applied to Cranfield’s 4D surface seismic for spatially delineating the CO 2/brine interface.« less

Fluid-injection and the mechanics of frictional stability of shale-bearing faults

NASA Astrophysics Data System (ADS)

Scuderi, Marco Maria; Collettini, Cristiano; Marone, Chris

2017-04-01

Fluid overpressure is one of the primary mechanisms for triggering tectonic fault slip and human-induced seismicity. This mechanism is appealing because fluids lubricate the fault and reduce the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction, imply that stable sliding is favored by the increase of pore fluid pressure. Despite this apparent dilemma, there are a few studies on the role of fluid pressure in frictional stability under controlled, laboratory conditions. Here, we describe laboratory experiments on shale fault gouge, conducted in the double direct shear configuration in a true-triaxial machine. To characterize frictional stability and hydrological properties we performed three types of experiments: 1) stable sliding shear experiment to determine the material failure envelope resulting in fault strength of µ=0.28 and fault zone permeability (k 10-19m2); 2) velocity step experiments to determine the rate- and state- frictional properties, characterized by a velocity strengthening behavior with a negative rate parameter b, indicative of stable aseismic creep; 3) creep experiment to study fault slip evolution with increasing pore-fluid pressure. In these creep experiments fault slip history can be divided in three main stages: a) for low fluid pressure the fault is locked and undergoes compaction; b) with increasing fluid pressurization, we observe aseismic creep (i.e. v=0.0001 µm/s) associated with fault dilation, with maintained low permeability; c) As fluid pressure is further increased and we approach the failure criteria fault begins to accelerate, the dilation rate increases causing an increase in permeability. Following the first acceleration we document complex fault slip behavior characterized by periodic accelerations and decelerations with slip velocity that remains slow (i.e. v 200 µm/s), never approaching dynamic slip rates. Surprisingly, this complex slip behavior is associated with fault zone compaction and permeability increase as opposite to the dilation hardening mechanism that is usually invoked to quench the instability. We relate this complex fault slip behaviour to the interplay between fault weakening induced by fluid pressurization and the strong rate-strengthening behaviour of shales. Our data show that fault rheology and fault stability is controlled by the coupling between fluid pressure and rate- and state- friction parameters suggesting that their comprehensive characterization is fundamental for assessing the role of fluid pressure in natural and human induced earthquakes.

PBO Borehole Strainmeters and Pore Pressure Sensors: Recording Hydrological Strain Signals

NASA Astrophysics Data System (ADS)

Gottlieb, M. H.; Hodgkinson, K. M.; Mencin, D.; Henderson, D. B.; Johnson, W.; Van Boskirk, E.; Pyatt, C.; Mattioli, G. S.

2017-12-01

UNAVCO operates a network of 75 borehole strainmeters along the west coast of the United States and Vancouver Island, Canada as part of the Plate Boundary Observatory (PBO), the geodetic component of the NSF-funded Earthscope program. Borehole strainmeters are designed to detect variations in the strain field at the nanostrain level and can easily detect transient strains caused by aseismic creep events, Episodic Tremor and Slip (ETS) events and seismically induced co- and post-seimic signals. In 2016, one strainmeter was installed in an Oklahoma oil field to characterize in-situ deformation during CO2 injection. Twenty-three strainmeter sites also have pore pressure sensors to measure fluctuations in groundwater pressure. Both the strainmeter network and the pore pressure sensors provide unique data against which those using water-level measurements, GPS time-series or InSAR data can compare possible subsidence signals caused by groundwater withdrawal or fluid re-injection. Operating for 12 years, the PBO strainmeter and pore pressure network provides a long-term, continuous, 1-sps record of deformation. PBO deploys GTSM21 tensor strainmeters from GTSM Technologies, which consist of four horizontal strain gauges stacked vertically, at different orientations, within a single 2 m-long instrument. The strainmeters are typically installed at depths of 200 to 250 m and grouted into the bottom of 15 cm diameter boreholes. The pore pressure sensors are Digiquartz Depth Sensors from Paros Scientific. These sensors are installed in 2" PVC, sampling groundwater through a screened section 15 m above the co-located strainmeter. These sensors are also recording at 1-sps with a resolution in the hundredths of hPa. High-rate local barometric pressure data and low-rate rainfall data also available at all locations. PBO Strainmeter and pore pressure data are available in SEED, SAC-ASCII and time-stamped ASCII format from the IRIS Data Managements Center. Strainmeter data are available at 2-hour latency while the pore pressure data are available in real-time. Links for data access, instrument and borehole information and station histories are available from UNAVCO's Borehole Data web page (https://www.unavco.org/data/strain-seismic/bsm-data/bsm-data.html ).

EVALUATION OF IODINE BASED IMPINGER SOLUTIONS FOR THE EFFICIENT CAPTURE OF HG USING DIRECT INJECTION NEBULIZATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (DIN-ICP/MS) ANALYSIS

EPA Science Inventory

Currently there are no EPA reference sampling methods that have been promulgated for measuring stack emissions of Hg from coal combustion sources, however, EPA Method 29 is most commonly applied. The draft ASTM Ontario Hydro Method for measuring oxidized, elemental, particulate-b...

Electrokinetic sample preconcentration and hydrodynamic sample injection for microchip electrophoresis using a pneumatic microvalve.

PubMed

Cong, Yongzheng; Katipamula, Shanta; Geng, Tao; Prost, Spencer A; Tang, Keqi; Kelly, Ryan T

2016-02-01

A microfluidic platform was developed to perform online electrokinetic sample preconcentration and rapid hydrodynamic sample injection for zone electrophoresis using a single microvalve. The polydimethylsiloxane microchip comprises a separation channel, a side channel for sample introduction, and a control channel which is used as a pneumatic microvalve aligned at the intersection of the two flow channels. The closed microvalve, created by multilayer soft lithography, serves as a nanochannel preconcentrator under an applied electric potential, enabling current to pass through while preventing bulk flow. Once analytes are concentrated, the valve is briefly opened and the stacked sample is pressure injected into the separation channel for electrophoretic separation. Fluorescently labeled peptides were enriched by a factor of ∼450 in 230 s. This method enables both rapid analyte concentration and controlled injection volume for high sensitivity, high-resolution CE. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrokinetic Sample Preconcentration and Hydrodynamic Sample Injection for Microchip Electrophoresis Using a Pneumatic Microvalve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Yongzheng; Katipamula, Shanta; Geng, Tao

2016-02-01

A microfluidic platform was developed to perform online electrokinetic sample preconcentration and rapid hydrodynamic sample injection for electrophoresis using a single microvalve. The PDMS microchip consists of a separation channel, a side channel for sample introduction, and a control channel which is used as a pneumatic microvalve aligned at the intersection of the two flow channels. The closed microvalve, created by multilayer soft lithography, can serve as a preconcentrator under an applied electric potential, enabling current to pass through while blocking bulk flow. Once analytes are concentrated, the valve is briefly opened and the stacked sample is pressure injected intomore » the separation channel for electrophoretic separation. Fluorescently labeled peptides were enriched by a factor of ~450 in 230 s. The performance of the platform was validated by the online preconcentration, injection and electrophoretic separation of fluorescently labeled peptides. This method enables both rapid analyte concentration and controlled injection volume for high sensitivity, high resolution capillary electrophoresis.« less

Interseismic secular deformation in Southern California from InSAR-derived maps over the time period between 1992 and 2006

NASA Astrophysics Data System (ADS)

Rivet, D. N.; Fialko, Y.

2007-12-01

We analyzed secular deformation in Southern California using an extensive catalog of InSAR data that spans 15 years between 1992 and 2006. We generated a map of the satellite line-of-sight displacements based on a stack of ~300 interferograms from 6 adjacent tracks of the ERS-1 and ERS-2 satellites covering Southern California. The main limitation to the accuracy of InSAR measurements of tectonic deformation is the atmospheric phase delay. We introduce a new method aimed to improve the signal-to-noise ratio in the InSAR- derived maps of secular deformation. The method involves identifying SAR acquisitions that are highly affected by atmospheric noise, and an optimal choice of interferometric pairs for stacking. We begin by generating a set of all possible interferometric pairs having baselines and time spans within prescribed limits. We then select interferograms with sufficiently high correlation. Subsequently, we identify noisy SAR acquisitions by means of calculating RMS of the phase signal. Finally, we generate a stack of interferograms by following a "connectivity tree" that minimizes contributions of noisy scenes. Using this method we obtained a continuous velocity field characterizing surface deformation in Southern California over the last 15 years. We identify interseismic deformation on a number of major faults, including those of the southern San Andreas system, and the Eastern California Shear Zone (ECSZ). We study the time dependency from 1992 to 2006 of those deformation patterns. Variations in the line-of- sight velocity across the Eastern California Shear Zone are non-monotonic, with the maximum along the strike of the Hector Mine fault of ~4 mm/yr, and total LOS velocity between the eastern and western boundaries of the shear zone of less than 2 mm/yr. We observe increases in the radar range to the east of ECSZ. This signal most likely results from subsidence east of the Death Valley-Mule Springs fault system, either due to hydrologic effects, or dip-slip tectonics. No resolvable interseismic deformation is detected across the Garlock fault. The Blackwater fault is associated with line-of-sight velocity of 2 mm/yr. By combining data from the ascending and descending satellite orbits, we infer that most of that strain is associated with the differential vertical motion across the fault (east side up), so that the accelerated strike-slip motion on the deep extension of the Blackwater fault is not required.

Shockwave-Induced Plasticity Via Large-Scale Nonequilibrium Molecular Dynamics

NASA Astrophysics Data System (ADS)

Holian, Brad Lee

1997-07-01

In nonequilibrium molecular-dynamics (MD) simulations of shock waves in single crystals, carried out in 1979 at Los Alamos,(B.L. Holian and G.K. Straub, Phys. Rev. Lett. 43), 1598 (1979). we discovered that, above a threshold strength, strongly shocked crystals deform in a very simple way. Rather than experiencing massive deformation, a simple slippage occurs at the shock front, relieving the peak shear stress, and leaving behind a stacking fault. We realized, of course, that real materials could yield at much lower thresholds, and speculated then that pre-existing defects could nucleate plastic flow at lower shock strengths than those characteristic of pure single crystals. (Historical note: at about the same time as our earliest dynamical shockwave simulations, Mogilevsky, working independently in the Soviet Union, carried out relaxation MD calculations under uniaxial strain, and observed spontaneous production of dislocations.(M.A. Mogilevsky, in Shock Waves and High Strain Rate Phenomena in Metals) (Plenum, New York, 1981), p.531.) Further Los Alamos calculations, carried out nearly a decade later in five-times larger systems (up to 10,000 atoms), confirmed this observation and quantified the threshold strength, namely the yield strength of the perfect crystal.(B.L. Holian, Phys. Rev. A 37), 2562 (1988); for a review, see B.L. Holian, Shock Waves 5, 149 (1995). Subsequently, Zaretskii and co-workers,(E.B. Zaretskii, G.I. Kanel, P.A. Mogilevskii, and V.E. Fortov, Sov. Phys. Dokl. 36), 76 (1991). using x-ray diffraction of shocked single crystals, confirmed our MD observations of stacking faults produced by shockwave passage. With the advent of massively parallel computers, we have recently studied systems with over six-times larger cross-sectional area and four-times longer distance of run to the steady state (approximately 270,000 atoms). We have seen that the increased cross-section allows the system to slip along both available forward slip systems, in different places along the now non-planar shock front, though only one stacking fault survives. This leads us to attempt simulations with even larger cross-sectional areas, and with pre-existing defects embedded in the sample, such as those we will report on here (36-times larger cross-sectional area: 10 million atoms). We report on shock waves in fcc copper, where the atoms interact via an EAM (embedded-atom-method) many-body potential, as well as pair-potential materials.(B.L. Holian, P.S. Lomdahl, S.J. Zhou, D.M. Beazley, and A.F. Voter, (1997, unpublished).)

Witnessing a Large-scale Slipping Magnetic Reconnection along a Dimming Channel during a Solar Flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Ju; Lee, Jeongwoo; Xu, Yan

We report the intriguing large-scale dynamic phenomena associated with the M6.5 flare (SOL2015-06-22T18:23) in NOAA active region 12371, observed by RHESSI , Fermi , and the Atmospheric Image Assembly (AIA) and Magnetic Imager (HMI) on the Solar Dynamics Observatory ( SDO ). The most interesting feature of this event is a third ribbon (R3) arising in the decay phase, propagating along a dimming channel (seen in EUV passbands) toward a neighboring sunspot. The propagation of R3 occurs in the presence of hard X-ray footpoint emission and is broadly visible at temperatures from 0.6 MK to over 10 MK through themore » differential emission measure analysis. The coronal loops then undergo an apparent slipping motion following the same path of R3, after a ∼80 minute delay. To understand the underlying physics, we investigate the magnetic configuration and the thermal structure of the flaring region. Our results are in favor of a slipping-type reconnection followed by the thermodynamic evolution of coronal loops. In comparison with those previously reported slipping reconnection events, this one proceeds across a particularly long distance (∼60 Mm) over a long period of time (∼50 minutes) and shows two clearly distinguished phases: the propagation of the footpoint brightening driven by nonthermal particle injection and the apparent slippage of loops governed by plasma heating and subsequent cooling.« less

Analysis of acrylamide in food products by in-line preconcentration capillary zone electrophoresis.

PubMed

Bermudo, Elisabet; Núñez, Oscar; Puignou, Luis; Galceran, Maria Teresa

2006-09-29

Two in-line preconcentration capillary zone electrophoresis (CZE) methods (field amplified sample injection (FASI) and stacking with sample matrix removal (LVSS)) have been evaluated for the analysis of acrylamide (AA) in foodstuffs. To allow the determination of AA by CZE, it was derivatized using 2-mercaptobenzoic acid. For FASI, the optimum conditions were water at pH > or = 10 adjusted with NH3 as sample solvent, 35 s hydrodynamic injection (0.5 psi) of a water plug, 35 s of electrokinetic injection (-10 kV) of the sample, and 6s hydrodynamic injection (0.5 psi) of another water plug to prevent AA removal by EOF. In stacking with sample matrix removal, the reversal time was found to be around 3.3 min. A 40 mM phosphate buffer (pH 8.5) was used as carrier electrolyte for CZE separation in both cases. For both FASI and LVSS methods, linear calibration curves over the range studied (10-1000 microg L(-1) and 25-1000 microg L(-1), respectively), limit of detection (LOD) on standards (1 microg L(-1) for FASI and 7 microg L(-1) for LVSS), limit of detection on samples (3 ng g(-1) for FASI and 20 ng g(-1) for LVSS) and both run-to-run (up to 14% for concentration and 0.8% for time values) and day-to-day precisions (up to 16% and 5% for concentration and time values, respectively) were established. Due to the lower detection limits obtained with the FASI-CZE this method was applied to the analysis of AA in different foodstuffs such as biscuits, cereals, crisp bread, snacks and coffee, and the results were compared with those obtained by LC-MS/MS.

CFD simulation of MSW combustion and SNCR in a commercial incinerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Zihong; Li, Jian; Wu, Tingting

Highlights: • Presented a CFD scheme for modeling MSW incinerator including SNCR process. • Performed a sensitivity analysis of SNCR operating conditions. • Non-uniform distributions of gas velocity, temperature and NO{sub x} in the incinerator. • The injection position of reagent was critical for a desirable performance of SNCR. • A NSR 1.5 was recommended as a compromise of NO{sub x} reduction rates and NH{sub 3} slip. - Abstract: A CFD scheme was presented for modeling municipal solid waste (MSW) combustion in a moving-grate incinerator, including the in-bed burning of solid wastes, the out-of-bed burnout of gaseous volatiles, and themore » selective non-catalytic reduction (SNCR) process between urea (CO(NH{sub 2}){sub 2}) and NO{sub x}. The in-bed calculations provided 2-D profiles of the gas–solid temperatures and the gas species concentrations along the bed length, which were then used as inlet conditions for the out-of-bed computations. The over-bed simulations provided the profiles of incident radiation heat flux on the top of bed. A 3-dimensional benchmark simulation was conducted with a 750 t/day commercial incinerator using the present coupling scheme incorporating with a reduced SNCR reduction mechanism. Numerical tests were performed to investigate the effects of operating parameters such as injection position, injection speed and the normalized stoichiometric ratio (NSR) on the SNCR performance. The simulation results showed that the distributions of gas velocity, temperature and NO{sub x} concentration were highly non-uniform, which made the injection position one of the most sensitive operating parameters influencing the SNCR performance of moving grate incinerators. The simulation results also showed that multi-layer injections were needed to meet the EU2000 standard, and a NSR 1.5 was suggested as a compromise of a satisfactory NO{sub x} reduction and reasonable NH{sub 3} slip rates. This work provided useful guides to the design and operation of SNCR process in moving-grate incinerators.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Bao; Liu, Wen-Jun; Wei, Lei

Excellent voltage linearity of metal-insulator-metal (MIM) capacitors is highly required for next generation radio frequency integration circuits. In this work, employing atomic layer deposition technique, we demonstrated how the voltage linearity of MIM capacitors was modulated by adding different thickness of SiO{sub 2} layer to the nano-stack of Al{sub 2}O{sub 3}/ZrO{sub 2}. It was found that the quadratic voltage coefficient of capacitance (α) can be effectively reduced from 1279 to −75 ppm/V{sup 2} with increasing the thickness of SiO{sub 2} from zero to 4 nm, which is more powerful than increasing the thickness of ZrO{sub 2} in the Al{sub 2}O{sub 3}/ZrO{sub 2}more » stack. This is attributed to counteraction between the positive α for Al{sub 2}O{sub 3}/ZrO{sub 2} and the negative one for SiO{sub 2} in the MIM capacitors with Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} stacks. Interestingly, voltage-polarity dependent conduction behaviors in the MIM capacitors were observed. For electron bottom-injection, the addition of SiO{sub 2} obviously suppressed the leakage current; however, it abnormally increased the leakage current for electron top-injection. These are ascribed to the co-existence of shallow and deep traps in ZrO{sub 2}, and the former is in favor of the field-assisted tunnelling conduction and the latter contributes to the trap-assisted tunnelling process. The above findings will be beneficial to device design and process optimization for high performance MIM capacitors.« less

Control of Structure in Turbulent Flows: Bifurcating and Blooming Jets.

DTIC Science & Technology

1987-10-10

injected through computational boundaries. (2) to satisfy no- slip boundary conditions or (3) during ’ grid " refinement when one element may be split...use of fast Poisson solvers on a mesh of M grid points, the operation count for this step can approach 0(M log M). Additional required steps are (1...consider s- three-dimensionai perturbations to the uart vortices. The linear stability calculations ot Pierrehumbert & Widnadl [101 are available for

The tectonographic development of Patagonia and its relevance to hydrocarbon exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Light, M.P.R.; Urien, C.M.; Maslanyj, M.P.

1993-02-01

Patagonia accreted successively from the southwest onto the southern margin of the Proterozoic Plata Craton and Brazilian Guapore Shield between the Late Proterozoic and Early Devonian. The thrust-like stacking of terranes onto the southern termination of the Pelotas Terrane is considered to have developed a pervasive northwest to north-trending fabric. During the Permo-Triassic the northwest to north-trending fabric of the Patagonian Plate was re-activated by dextral strike-slip movement causing extension. The deformation was caused by oblique subduction and accretion of the madre Dos Dios to Pichidangui Terranes along its western margin. To the northeast the more competent shield underwent compressionmore » (Ventania-Gond-wanide Folding) and extension occurred parallel to the axis of the embryo South Atlantic, where a shallow sea transgressed. Ridge on its western side, now preserved on the facing shelf margins of Argentina and Namibia. In the Late Triassic-Lower Jurassic, the Malvinas and Microplate was situated south of the Transkei (South Africa) and an intracratonic basin separated it from two sutures formed at the margin of the Argentine Shelf and along the axis of the West Malvinas Basin. Subduction/arc activity on the west flank of this intracratonic basin, in association with trench pull is believed to have initiated Late Triassic-Early Jurassic strike slip extension and volcanicity in Patagonia. This exploited the pervasive northwest and north-trending Paleozoic fabric. By the Mid-Jurassic the Malvinas Microplate had docked with the eastern margin of the Patagonian Shelf and was undergoing clockwise rotation between the Malvinas-Agulhas and Burwood Bank-Scotia Ridge dextral strike-slip systems. Rifting had now progressed southwestwards to the Pacific and north eastwards to the Colorado and Outeniqua Basins.« less

Effects of Processing Parameters on the Forming Quality of C-Shaped Thermosetting Composite Laminates in Hot Diaphragm Forming Process

NASA Astrophysics Data System (ADS)

Bian, X. X.; Gu, Y. Z.; Sun, J.; Li, M.; Liu, W. P.; Zhang, Z. G.

2013-10-01

In this study, the effects of processing temperature and vacuum applying rate on the forming quality of C-shaped carbon fiber reinforced epoxy resin matrix composite laminates during hot diaphragm forming process were investigated. C-shaped prepreg preforms were produced using a home-made hot diaphragm forming equipment. The thickness variations of the preforms and the manufacturing defects after diaphragm forming process, including fiber wrinkling and voids, were evaluated to understand the forming mechanism. Furthermore, both interlaminar slipping friction and compaction behavior of the prepreg stacks were experimentally analyzed for showing the importance of the processing parameters. In addition, autoclave processing was used to cure the C-shaped preforms to investigate the changes of the defects before and after cure process. The results show that the C-shaped prepreg preforms with good forming quality can be achieved through increasing processing temperature and reducing vacuum applying rate, which obviously promote prepreg interlaminar slipping process. The process temperature and forming rate in hot diaphragm forming process strongly influence prepreg interply frictional force, and the maximum interlaminar frictional force can be taken as a key parameter for processing parameter optimization. Autoclave process is effective in eliminating voids in the preforms and can alleviate fiber wrinkles to a certain extent.

Geomechanical simulation of the stress tensor rotation caused by injection of cold water in a deep geothermal reservoir

DOE PAGES

Jeanne, Pierre; Rutqvist, Jonny; Dobson, Patrick F.; ...

2015-11-12

We present a three-dimensional thermohydromechanical numerical study of the evolution and distribution of the stress tensor within the northwest part of The Geysers geothermal reservoir (in California), including a detailed study of the region around one injection well from 2003 to 2012. Initially, after imposing a normal faulting stress regime, we calculated local changes in the stress regime around injection wells. Our results were compared with previously published studies in which the stress state was inferred from inverting the focal plane mechanism of seismic events. Our main finding is that changes in stress tensor orientation are caused by injection-induced progressivemore » cooling of the reservoir, as well as by the seasonal variations in injection rate. Because of the gravity flow and cooling around a liquid zone formed by the injection, the vertical stress reduction is larger and propagates far below the injection well. At the same time, the horizontal stress increases, mostly because of stress redistribution below and above the cooling area. These two phenomena cause the rotation of the stress tensor and the appearance of a strike-slip regime above, inside, and below the cooling area. The cooling and the associated rotation of the stress regime can play a significant role in the observed long-term deepening of the microseismicity below active injection wells.« less

Diffraction of a shock wave by a compression corner; regular and single Mach reflection

NASA Technical Reports Server (NTRS)

Vijayashankar, V. S.; Kutler, P.; Anderson, D.

1976-01-01

The two dimensional, time dependent Euler equations which govern the flow field resulting from the injection of a planar shock with a compression corner are solved with initial conditions that result in either regular reflection or single Mach reflection of the incident planar shock. The Euler equations which are hyperbolic are transformed to include the self similarity of the problem. A normalization procedure is employed to align the reflected shock and the Mach stem as computational boundaries to implement the shock fitting procedure. A special floating fitting scheme is developed in conjunction with the method of characteristics to fit the slip surface. The reflected shock, the Mach stem, and the slip surface are all treated as harp discontinuities, thus, resulting in a more accurate description of the inviscid flow field. The resulting numerical solutions are compared with available experimental data and existing first-order, shock-capturing numerical solutions.

Anionic microemulsion to solvent stacking for on-line sample concentration of cationic analytes in capillary electrophoresis.

PubMed

Kukusamude, Chunyapuk; Srijaranai, Supalax; Quirino, Joselito P

2014-05-01

The common SDS microemulsion (i.e. 3.3% SDS, 0.8% octane, and 6.6% butanol) and organic solvents were investigated for the stacking of cationic drugs in capillary zone electrophoresis using a low pH separation electrolyte. The sample was prepared in the acidic microemulsion and a high percentage of organic solvent was included in the electrolyte at anodic end of capillary. The stacking mechanism was similar to micelle to solvent stacking where the micelles were replaced by the microemulsion for the transport of analytes to the organic solvent rich boundary. This boundary is found between the microemulsion and anodic electrolyte. The effective electrophoretic mobility of the cations reversed from the direction of the anode in the microemulsion to the cathode in the boundary. Microemulsion to solvent stacking was successfully achieved with 40% ACN in the anodic electrolyte and hydrodynamic sample injection of 21 s at 1000 mbar (equivalent to 30% of the effective length). The sensitivity enhancement factors in terms of peak height and corrected peak area were 15 to 35 and 21 to 47, respectively. The linearity R(2) in terms of corrected peak area were >0.999. Interday precisions (%RSD, n = 6) were 3.3-4.0% for corrected peak area and 2.0-3.0% for migration time. Application to spiked real sample is also presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Human Mars Mission: Transportation Assessment

NASA Technical Reports Server (NTRS)

Kos, Larry

1998-01-01

If funding is available, and for NASA planning purposes, the Human Mars Mission (HMM) is baselined to take place during the 2011 and 2013/2014 Mars opportunities. Two cargo flights will leave for Mars during the first opportunity, one to Mars orbit and the second to the surface, in preparation for the crew during the following opportunity. Each trans-Mars injection (TMI) stack will consist of a cargo / payload portion (currently coming in at between 65 and 78 mt) and a nuclear thermal propulsion (NTP) stage (currently coming in at between 69 and 77 mt loaded with propellant) for performing the departure (Delta)Vs to get on to the appropriate Mars trajectories. Three 66,700 N thrust NTP engines comprise the TMI stage for each stack and perform a (Delta)V ringing from 3580 to 3890 m/s is required by the trajectory (with gravity losses and various performance margins to this for the total TMI (Delta)V performed). This paper will discuss the current application of this NTP stage to a Human Mars mission, and project what implications a nuclear trans-Earth injection (TEI) stage as well as a bi-modal NTP stage could mean to a human visit to Mars.

Rapid and direct determination of glyphosate, glufosinate, and aminophosphonic acid by online preconcentration CE with contactless conductivity detection.

PubMed

See, Hong Heng; Hauser, Peter C; Ibrahim, Wan Aini Wan; Sanagi, Mohd Marsin

2010-01-01

Rapid and direct online preconcentration followed by CE with capacitively coupled contactless conductivity detection (CE-C(4)D) is evaluated as a new approach for the determination of glyphosate, glufosinate (GLUF), and aminophosphonic acid (AMPA) in drinking water. Two online preconcentration techniques, namely large volume sample stacking without polarity switching and field-enhanced sample injection, coupled with CE-C(4)D were successfully developed and optimized. Under optimized conditions, LODs in the range of 0.01-0.1 microM (1.7-11.1 microg/L) and sensitivity enhancements of 48- to 53-fold were achieved with the large volume sample stacking-CE-C(4)D method. By performing the field-enhanced sample injection-CE-C(4)D procedure, excellent LODs down to 0.0005-0.02 microM (0.1-2.2 microg/L) as well as sensitivity enhancements of up to 245- to 1002-fold were obtained. Both techniques showed satisfactory reproducibility with RSDs of peak height of better than 10%. The newly established approaches were successfully applied to the analysis of glyphosate, glufosinate, and aminophosphonic acid in spiked tap drinking water.

Graphene-on-GaN Hot Electron Transistor

NASA Astrophysics Data System (ADS)

Zubair, Ahmad; Nourbakhsh, Amirhasan; Hong, Jin-Yong; Song, Yi; Qi, Meng; Jena, Debdeep; Kong, Jing; Dresselhaus, Mildred S.; Palacios, Tomas

Hot electron transistors (HETs) are promising devices for potential high-frequency operation that currently CMOS cannot provide. In an HET, carrier transport is due to the injection of hot electrons from an emitter to a collector which is modulated by a base electrode. Therefore, ultra-thin base electrodes are needed to facilitate ultra-short transit time and high performance for THz operation range. In this regard, graphene, the thinnest conductive membrane in nature, is considered the best candidate for the base material in HETs. The existing HETs with SiO2/Si as emitter stack suffer from low current gain and output current density. In this work, we use the two-dimensional electron gas (2-DEG) in a GaN-based heterostructure as emitter and monolayer graphene as the base electrode. The transport study of the proof-of-concept device shows high output current density (>50 A/cm2) , current gain (>3) and ballistic injection efficiency of 75%. These results indicate that performance parameters can be further improved by engineering the band offset of the graphene/collector stack and improved interface between graphene and GaN. Army Research Office (ARO) (Grant Nos. W911NF-14-2-0071, 6930265, and 6930861).

Overview and First Results of an In-situ Stimulation Experiment in Switzerland

NASA Astrophysics Data System (ADS)

Amann, F.; Gischig, V.; Doetsch, J.; Jalali, M.; Valley, B.; Evans, K. F.; Krietsch, H.; Dutler, N.; Villiger, L.

2017-12-01

A decameter-scale in-situ stimulation and circulation (ISC) experiment is currently being conducted at the Grimsel Test Site in Switzerland with the objective of improving our understanding of key seismo-hydro-mechanical coupled processes associated with high pressure fluid injections in a moderately fractured crystalline rock mass. The ISC experiment activities aim to support the development of EGS technology by 1) advancing the understanding of fundamental processes that occur within the rock mass in response to relatively large-volume fluid injections at high pressures, 2) improving the ability to estimate and model induced seismic hazard and risks, 3) assessing the potential of different injection protocols to keep seismic event magnitudes below an acceptable threshold, 4) developing novel monitoring and imaging techniques for pressure, temperature, stress, strain and displacement as well as geophysical methods such as ground penetration radar, passive and active seismic and 5) generating a high-quality benchmark datasets that facilitates the development and validation of numerical modelling tools. The ISC experiment includes six fault slip and five hydraulic fracturing experiments at an intermediate scale (i.e. 20*20*20m) at 480m depth, which allows high resolution monitoring of the evolution of pore pressure in the stimulated fault zone and the surrounding rock matrix, fault dislocations including shear and dilation, and micro-seismicity in an exceptionally well characterized structural setting. In February 2017 we performed the fault-slip experiments on interconnected faults. Subsequently an intense phase of post-stimulation hydraulic characterization was performed. In Mai 2017 we performed hydraulic fracturing tests within test intervals that were free of natural fractures. In this contribution we give an overview and show first results of the above mentioned stimulation tests.

Seismicity rate surge on faults after shut-in: poroelastic response to fluid injection

NASA Astrophysics Data System (ADS)

Chang, K. W.; Yoon, H.; Martinez, M. J.

2017-12-01

Subsurface energy activities such as geological CO2 storage and wastewater injection require injecting large amounts of fluid into the subsurface, which will alter the states of pore pressure and stress in the storage formation. One of the main issues for injection-induced seismicity is the post shut-in increases in the seismicity rate, often observed in the fluid-injection operation sites. The rate surge can be driven by the following mechanisms: (1) pore-pressure propagation into distant faults after shut-in and (2) poroelastic stressing caused by well operations, depending on fault geometry, hydraulic and mechanical properties of the formation, and injection history. We simulate the aerial view of the target reservoir intersected by strike-slip faults, in which injection-induced pressure buildup encounters the faults directly. We examine the poroelastic response of the faults to fluid injection and perform a series of sensitivity tests considering: (1) permeability of the fault zone, (2) locations and the number of faults with respect to the injection point, and (3) well operations with varying the injection rate. Our analysis of the Coulomb stress change suggests that the sealing fault confines pressure diffusion which stabilizes or weakens the nearby conductive fault depending on the injection location. We perform the sensitivity test by changing injection scenarios (time-dependent rates), while keeping the total amount of injected fluids. Sensitivity analysis shows that gradual reduction of the injection rate minimizes the Coulomb stress change and the least seismicity rates are predicted. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

Experimental study on the particulate matter and nitrogenous compounds from diesel engine retrofitted with DOC+CDPF+SCR

NASA Astrophysics Data System (ADS)

Zhang, Yunhua; Lou, Diming; Tan, Piqiang; Hu, Zhiyuan

2018-03-01

The increasingly stringent emission regulations will mandate the retrofit of after-treatment devices for in-use diesel vehicles, in order to reduce their substantial particulate matter and nitrogen oxides (NOX) emissions. In this paper, a combination of DOC (diesel oxidation catalyst), CDPF (catalytic diesel particulate filter) and SCR (selective catalytic reduction) retrofit for a heavy-duty diesel engine was employed to perform experiment on the engine test bench to evaluate the effects on the particulate matter emissions including particle number (PN), particle mass (PM), particle size distributions and nitrogenous compounds emissions including NOX, nitrogen dioxide (NO2)/NOX, nitrous oxide (N2O) and ammonia (NH3) slip. In addition, the urea injection was also of our concern. The results showed that the DOC+CDPF+SCR retrofit almost had no adverse effect on the engine power and fuel consumption. Under the test loads, the upstream DOC and CDPF reduced the PN and PM by an average of 91.6% and 90.9%, respectively. While the downstream SCR brought about an average decrease of 85% NOX. Both PM and NOX emission factors based on this retrofit were lower than China-Ⅳ limits (ESC), and even lower than China-Ⅴ limits (ESC) at medium and high loads. The DOC and CDPF changed the particle size distributions, leading to the increase in the proportion of accumulation mode particles and the decrease in the percentage of nuclear mode particles. This indicates that the effect of DOC and CDPF on nuclear mode particles was better than that of accumulation mode ones. The upstream DOC could increase the NO2/NOX ratio to 40%, higher NO2/NOX ratio improved the efficiency of CDPF and SCR. Besides, the N2O emission increased by an average of 2.58 times after the retrofit and NH3 slip occurred with the average of 26.7 ppm. The rate of urea injection was roughly equal to 8% of the fuel consumption rate. The DOC+CDPF+SCR retrofit was proved a feasible and effective measurement in terms of reducing particulate emissions and NOX simultaneously for in-use engine. However, it also resulted in higher N2O emission, NH3 slip as well as urea injecting strategy problem which should be of further concern.

Oklahoma experiences largest earthquake during ongoing regional wastewater injection hazard mitigation efforts

USGS Publications Warehouse

Yeck, William; Hayes, Gavin; McNamara, Daniel E.; Rubinstein, Justin L.; Barnhart, William; Earle, Paul; Benz, Harley M.

2017-01-01

The 3 September 2016, Mw 5.8 Pawnee earthquake was the largest recorded earthquake in the state of Oklahoma. Seismic and geodetic observations of the Pawnee sequence, including precise hypocenter locations and moment tensor modeling, shows that the Pawnee earthquake occurred on a previously unknown left-lateral strike-slip basement fault that intersects the mapped right-lateral Labette fault zone. The Pawnee earthquake is part of an unprecedented increase in the earthquake rate in Oklahoma that is largely considered the result of the deep injection of waste fluids from oil and gas production. If this is, indeed, the case for the M5.8 Pawnee earthquake, then this would be the largest event to have been induced by fluid injection. Since 2015, Oklahoma has undergone wide-scale mitigation efforts primarily aimed at reducing injection volumes. Thus far in 2016, the rate of M3 and greater earthquakes has decreased as compared to 2015, while the cumulative moment—or energy released from earthquakes—has increased. This highlights the difficulty in earthquake hazard mitigation efforts given the poorly understood long-term diffusive effects of wastewater injection and their connection to seismicity.

Hexa-μ-chlorido-hexa­chlorido(η6-hexa­methyl­benzene)trialuminium(III)lanthanum(III) benzene solvate

PubMed Central

Filatov, Alexander S.; Gifford, Sarah N.; Kumar, D. Krishna; Petrukhina, Marina A.

2009-01-01

In the title compound, [Al3LaCl12(C12H18)]·C6H6, all mol­ecules are located on a mirror plane. Three chloridoaluminate groups and a hexa­methyl­benzene mol­ecule are bound to the central lanthanum(III) ion, forming a distorted penta­gonal bipyramid with the η6-coordinated arene located at the apical position. The hexa­methyl­benzene ligand disordered between two orientations in a 1:1 ratio is also involved in parallel-slipped π–π stacking inter­molecular inter­actions with a benzene solvent mol­ecule [centroid–centroid distance 3.612 (4) Å]. PMID:21582071

Stacking and determination of phenazine-1-carboxylic acid with low pKa in soil via moving reaction boundary formed by alkaline and double acidic buffers in capillary electrophoresis.

PubMed

Sun, Chong; Yang, Xiao-Di; Fan, Liu-Yin; Zhang, Wei; Xu, Yu-Quan; Cao, Cheng-Xi

2011-04-01

As shown herein, a normal moving reaction boundary (MRB) formed by an alkaline buffer and a single acidic buffer had poor stacking to the new important plant growth promoter of phenazine-1-carboxylic acid (PCA) in soil due to the leak induced by its low pK(a). To stack the PCA with low pK(a) efficiently, a novel stacking system of MRB was developed, which was formed by an alkaline buffer and double acidic buffers (viz., acidic sample and blank buffers). With the novel system, the PCA leaking into the blank buffer from the sample buffer could be well stacked by the prolonged MRB formed between the alkaline buffer and blank buffer. The relevant mechanism of stacking was discussed briefly. The stacking system, coupled with sample pretreatment, could achieve a 214-fold increase of PCA sensitivity under the optimal conditions (15 mM (pH 11.5) Gly-NaOH as the alkaline buffer, 15 mM (pH 3.0) Gly-HCl-acetonitrile (20%, v/v) as the acidic sample buffer, 15 mM (pH 3.0) Gly-HCl as the blank buffer, 3 min 13 mbar injection of double acidic buffers, benzoic acid as the internal standard, 75 μm i.d. × 53 cm (44 cm effective length) capillary, 25 kV and 248 nm). The limit of detection of PCA in soil was decreased to 17 ng/g, the intra-day and inter-day precision values (expressed as relative standard deviations) were 3.17-4.24% and 4.17-4.87%, respectively, and the recoveries of PCA at three concentration levels changed from 52.20% to 102.61%. The developed method could be used for the detection of PCA in soil at trace level.

Spectral element modelling of fault-plane reflections arising from fluid pressure distributions

USGS Publications Warehouse

Haney, M.; Snieder, R.; Ampuero, J.-P.; Hofmann, R.

2007-01-01

The presence of fault-plane reflections in seismic images, besides indicating the locations of faults, offers a possible source of information on the properties of these poorly understood zones. To better understand the physical mechanism giving rise to fault-plane reflections in compacting sedimentary basins, we numerically model the full elastic wavefield via the spectral element method (SEM) for several different fault models. Using well log data from the South Eugene Island field, offshore Louisiana, we derive empirical relationships between the elastic parameters (e.g. P-wave velocity and density) and the effective-stress along both normal compaction and unloading paths. These empirical relationships guide the numerical modelling and allow the investigation of how differences in fluid pressure modify the elastic wavefield. We choose to simulate the elastic wave equation via SEM since irregular model geometries can be accommodated and slip boundary conditions at an interface, such as a fault or fracture, are implemented naturally. The method we employ for including a slip interface retains the desirable qualities of SEM in that it is explicit in time and, therefore, does not require the inversion of a large matrix. We performa complete numerical study by forward modelling seismic shot gathers over a faulted earth model using SEM followed by seismic processing of the simulated data. With this procedure, we construct post-stack time-migrated images of the kind that are routinely interpreted in the seismic exploration industry. We dip filter the seismic images to highlight the fault-plane reflections prior to making amplitude maps along the fault plane. With these amplitude maps, we compare the reflectivity from the different fault models to diagnose which physical mechanism contributes most to observed fault reflectivity. To lend physical meaning to the properties of a locally weak fault zone characterized as a slip interface, we propose an equivalent-layer model under the assumption of weak scattering. This allows us to use the empirical relationships between density, velocity and effective stress from the South Eugene Island field to relate a slip interface to an amount of excess pore-pressure in a fault zone. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

Frictional Properties of Main Fault Gouge of Mont Terri, Switzerland

NASA Astrophysics Data System (ADS)

Aoki, K.; Seshimo, K.; Guglielmi, Y.; Nussbaum, C.; Shimamoto, T.; Ma, S.; Yao, L.; Kametaka, M.; Sakai, T.

2016-12-01

JAEA participated in the Fault Slip Experiment of Mont Terri Project which aims at understanding (i) the conditions for slip activation and stability of clay faults, and (ii) the evolution of the coupling between fault slip, pore pressure and fluids migration. The experiment uses SIMFIP probe to estimate (i) the hydraulic and elastic properties of fault zone elements, (ii) the state of stresses across the fault zone and (iii) the fault zone apparent strength properties (friction coefficient and cohesion). To elaborate on the Fault Slip Experiment, JAEA performed friction experiment of borehole cores of depths 47.2m and 37.3m using a rotary-shear low to high-velocity friction apparatus at Institute of Geology, China Earthquake Administration. Friction experiments were performed either dry with room humidity or with 30wt% of H2O, at a normal stress of 1.38 MPa and at low to intermediate slip rates ranging 0.21 microns/s to 2.1mm/s. Sample from a depth of 37.3 m is a fault rock with scaly fabric with calcite veins, whereas that from 47.2 m in depth is a pelitic rock that disaggregates easily with water. Main experimental results are summarized as follows. (1) Gouge samples from both depths exhibit slight velocity-strengthening at V below 0.021 mm/s and notable velocity strengthening at V above approximately 0.021 mm/s. Frictional regimes can be classified into low-velocity and intermediate-velocity regimes, characterized by slight and clear velocity-strengthening behaviors, respectively. (2) Wet gouge from a depth of 47.2 m has mss of 0.12 0.2 at low V and 0.11 0.24 at intermediate V, while dry gouge from the same depth has mss two to three times as high as that for the wet gouge from the same depth. (3) In contrast, both dry and wet gouges from a depth of 37.3 m has mss of around 0.4 to 0.74 at low V and from around 0.45 to 0.75 at intermediate V. There are almost no differences between the dry and wet gouges from this depth (4) The wet gouge from 47.2 m depths has clear slip zone at the gouge-moving piston interface, but clear slip zones are missing in wet gouge from 37.3 m depth. (5) It is hoped that the frictional strength from the present experiments would give some insight on the initiation conditions of fault slip during fluid injection. Results of four other depths will be discussed at the session.

Progress in net shape fabrication of alpha SiC turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.; Naum, R. G.

1983-01-01

The development status of component technology in an automotive gas turbine Ceramic Applications in Turbine Engines program is discussed, with attention to such materials and processes having a low cost, net shape fabrication potential as sintered alpha-SiC that has been fashioned by means of injection molding, slip casting, and isostatic pressing. The gas turbine elements produced include a gasifier turbine rotor, a turbine wheel, a connecting duct, a combustor baffle, and a transition duct.

Maturity of nearby faults influences seismic hazard from hydraulic fracturing.

PubMed

Kozłowska, Maria; Brudzinski, Michael R; Friberg, Paul; Skoumal, Robert J; Baxter, Nicholas D; Currie, Brian S

2018-02-20

Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: ( i ) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values < 1, and many post-shut-in earthquakes, versus ( ii ) shallower earthquakes in Paleozoic rocks ∼400 m below HF, with smaller magnitudes (M < 1), b-values > 1.5, and few post-shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ∼1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

Maturity of nearby faults influences seismic hazard from hydraulic fracturing

NASA Astrophysics Data System (ADS)

Kozłowska, Maria; Brudzinski, Michael R.; Friberg, Paul; Skoumal, Robert J.; Baxter, Nicholas D.; Currie, Brian S.

2018-02-01

Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: (i) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values < 1, and many post–shut-in earthquakes, versus (ii) shallower earthquakes in Paleozoic rocks ˜400 m below HF, with smaller magnitudes (M < 1), b-values > 1.5, and few post–shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ˜1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

Earthquake Nucleation and Fault Slip: Possible Experiments on a Natural Fault

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Murdoch, L. C.; Garagash, D.; Reches, Z.; Martel, S. J.; Johnston, M. J.; Ebenhack, J.; Gwaba, D.

2011-12-01

High-resolution deformation and seismic observations are usually made only near the Earths' surface, kilometers away from where earthquake nucleate on active faults and are limited by inverse-cube-distance attenuation and ground noise. We have developed an experimental approach that aims at reactivating faults in-situ using thermal techniques and fluid injection, which modify in-situ stresses and the fault strength until the fault slips. Mines where in-situ stresses are sufficient to drive faulting present an opportunity to conduct such experiments. The former Homestake gold mine in South Dakota is a good example. During our recent field work in the Homestake mine, we found a large fault that intersects multiple mine levels. The size and distinct structure of this fault make it a promising target for in-situ reactivation, which would likely to be localized on a crack-like patch. Slow patch propagation, moderated by the injection rate and the rate of change of the background stresses, may become unstable, leading to the nucleation of a dynamic earthquake rupture. Our analyses for the Homestake fault conditions indicate that this transition occurs for a patch size ~1 m. This represents a fundamental limitation for laboratory experiments and necessitates larger-scale field tests ~10-100 m. The opportunity to observe earthquake nucleation on the Homestake Fault is feasible because slip could be initiated at a pre-defined location and time with instrumentation placed as close as a few meters from the nucleation site. Designing the experiment requires a detailed assessment of the state-of-stress in the vicinity of the fault. This is being conducted by simulating changes in pore pressure and effective stresses accompanying dewatering of the mine, and by evaluating in-situ stress measurements in light of a regional stress field modified by local perturbations caused by the mine workings.

Effect of Pore Pressure on Slip Failure of an Impermeable Fault: A Coupled Micro Hydro-Geomechanical Model

NASA Astrophysics Data System (ADS)

Yang, Z.; Juanes, R.

2015-12-01

The geomechanical processes associated with subsurface fluid injection/extraction is of central importance for many industrial operations related to energy and water resources. However, the mechanisms controlling the stability and slip motion of a preexisting geologic fault remain poorly understood and are critical for the assessment of seismic risk. In this work, we develop a coupled hydro-geomechanical model to investigate the effect of fluid injection induced pressure perturbation on the slip behavior of a sealing fault. The model couples single-phase flow in the pores and mechanics of the solid phase. Granular packs (see example in Fig. 1a) are numerically generated where the grains can be either bonded or not, depending on the degree of cementation. A pore network is extracted for each granular pack with pore body volumes and pore throat conductivities calculated rigorously based on geometry of the local pore space. The pore fluid pressure is solved via an explicit scheme, taking into account the effect of deformation of the solid matrix. The mechanics part of the model is solved using the discrete element method (DEM). We first test the validity of the model with regard to the classical one-dimensional consolidation problem where an analytical solution exists. We then demonstrate the ability of the coupled model to reproduce rock deformation behavior measured in triaxial laboratory tests under the influence of pore pressure. We proceed to study the fault stability in presence of a pressure discontinuity across the impermeable fault which is implemented as a plane with its intersected pore throats being deactivated and thus obstructing fluid flow (Fig. 1b, c). We focus on the onset of shear failure along preexisting faults. We discuss the fault stability criterion in light of the numerical results obtained from the DEM simulations coupled with pore fluid flow. The implication on how should faults be treated in a large-scale continuum model is also presented.

Inversion of inherited thrusts by wastewater injection induced seismicity at the Val d’Agri oilfield (Italy)

NASA Astrophysics Data System (ADS)

Buttinelli, M.; Improta, L.; Bagh, S.; Chiarabba, C.

2016-11-01

Since 2006 wastewater has been injected below the Val d’Agri Quaternary basin, the largest on-land oilfield in Europe, inducing micro-seismicity in the proximity of a high-rate injection well. In this study, we have the rare opportunity to revise a massive set of 2D/3D seismic and deep borehole data in order to investigate the relationship between the active faults that bound the basin and the induced earthquakes. Below the injection site we identify a Pliocene thrusts and back-thrusts system inherited by the Apennines compression, with no relation with faults bounding the basin. The induced seismicity is mostly confined within the injection reservoir, and aligns coherently with a NE-dipping back-thrust favorably oriented within the current extensional stress field. Earthquakes spread upwards from the back-thrust deep portion activating a 2.5-km wide patch. Focal mechanisms show a predominant extensional kinematic testifying to an on-going inversion of the back-thrust, while a minor strike-slip compound suggests a control exerted by a high angle inherited transverse fault developed within the compressional system, possibly at the intersection between the two fault sets. We stress that where wastewater injection is active, understanding the complex interaction between injection-linked seismicity and pre-existing faults is a strong requisite for safe oilfield exploitation.

Organic doping of rotated double layer graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, Lijin; Jaiswal, Manu, E-mail: manu.jaiswal@iitm.ac.in

2016-05-06

Charge transfer techniques have been extensively used as knobs to tune electronic properties of two- dimensional systems, such as, for the modulation of conductivity \\ mobility of single layer graphene and for opening the bandgap in bilayer graphene. The charge injected into the graphene layer shifts the Fermi level away from the minimum density of states point (Dirac point). In this work, we study charge transfer in rotated double-layer graphene achieved by the use of organic dopant, Tetracyanoquinodimethane. Naturally occurring bilayer graphene has a well-defined A-B stacking whereas in rotated double-layer the two graphene layers are randomly stacked with differentmore » rotational angles. This rotation is expected to significantly alter the interlayer interaction. Double-layer samples are prepared using layer-by-layer assembly of chemical vapor deposited single-layer graphene and they are identified by characteristic resonance in the Raman spectrum. The charge transfer and distribution of charges between the two graphene layers is studied using Raman spectroscopy and the results are compared with that for single-layer and A-B stacked bilayer graphene doped under identical conditions.« less

THE DETERMINATION OF MERCURY SPECIES AND MULTIPLE METALS IN COAL COMBUSTION EMISSIONS USING IODINE-BASED IMPINGERS AND DIRECT INJECTION NEBULIZATION - INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY ANALYSIS

EPA Science Inventory

Mercury (Hg) emissions from coal utilities are difficult to control. Hg eludes capture by most air pollution control devices (APCDs). To determine the gaseous Hg species in stack gases, U.S. EPA Method 5 type sampling is used. In this type of sampling a hole is drilled into th...

New families of low frequency earthquakes beneath the Olympic Peninsula, Washington

NASA Astrophysics Data System (ADS)

Chestler, S.; Creager, K. C.; Sweet, J. R.

2013-12-01

Using data from the Array of Arrays (AofA) and Cascadia Arrays for Earthscope (CAFÉ) experiments we search for new families of low frequency earthquakes (LFEs) beneath the Olympic Peninsula, Washington. LFE families are clusters of repeating LFEs that occur in approximately the same location. Following methodology similar to Bostock et al. [2012, G3], we cross correlate 6-second long windows within an hour of data during the 2010 and 2011 ETS events. We apply this to 99 hours of tremor data. For each hour, we stack the autocorrelation functions from a set of 7 3-component base stations chosen for their high signal-to-noise ratios (SNRs). We extract a maximum of 10 windows per hour with correlation coefficients higher than 9 times the median absolute deviation (MAD). These time windows contain our preliminary LFE detections. We then cross correlate these data and group them using a hierarchical clustering algorithm. We produce template waveforms by stacking the waveforms corresponding to a given cluster. To strengthen the templates we scan them through on day of tremor and stack all waveforms that correlate with the original template. Our efforts have yielded dozens of new families scattered beneath the AofA stations. These additional LFE families add to the 9 known families beneath the Olympic Peninsula [Sweet et al., AGU fall meeting, 2012]. The detection of more LFE families will allow us to (1) interpolate the pattern of stress transfer through the transition zone [Wech et al., Nature Geoscie., 2011], (2) gain insight into the distribution of asperities, or sticky spots, on the plate interface [Ghosh et al., JGR, 2012], and (3) track slow slip rupture propagation with unprecedented spatial and temporal accuracy.

Array observations and analyses of Cascadia deep tremor

NASA Astrophysics Data System (ADS)

McCausland, W. A.; Malone, S.; Creager, K.; Crosson, R.; La Rocca, M.; Saccoretti, G.

2004-12-01

The July 8-24, 2004 Cascadia Episodic Tremor and Slip (ETS) event was observed using three small aperture seismic arrays located near Sooke, BC, Sequim, WA, and on Lopez Island, WA. Initial tremor burst epicenters located in the Strait of Juan de Fuca and were calculated using the relative arrivals of band-passed, rectified regional network signals. Most subsequent epicenters migrated to the northwest along Vancouver Island and a few occurred in the central to southern Puget Sound. Tremor bursts lasting on the order of a few seconds can be identified across the stations of any of the three arrays. Individual bursts from distinct back-azimuths often occur within five seconds of each other, indicating the presence of spatially distributed but near simultaneous tremor. None of this was visible at such a fine scale using Pacific Northwest Seismograph Network (PNSN). Several array processing techniques, including beam-forming, zero-lag cross correlation and multiple signal classification (MUSIC), are being investigated to determine the optimal technique for exploring the temporal and spatial evolution of the tremor signals during the whole ETS. The back-azimuth and slowness of consecutive time windows for a one half-hour period of strong tremor were calculated using beam-forming with a linear stack, with an nth-root stack, and using zero-lag cross-correlation. Results for each array and each method yield consistent estimates of back azimuth and slowness. Beam-forming with a nonlinear stack produces results similar to the linear case but with larger uncertainty. Among the arrays, the back-azimuths give a reasonable estimate of the tremor epicenter that is consistent with the network determined epicentral locations.

Seismic Reservoir Characterization for Assessment of CO2 EOR at the Mississippian Reservoir in South-Central Kansas

NASA Astrophysics Data System (ADS)

Tsoflias, G. P.; Graham, B.; Haga, L.; Watney, L.

2017-12-01

The Mississippian in Kansas and Oklahoma is a highly heterogeneous, fractured, oil producing reservoir with thickness typically below seismic resolution. At Wellington field in south-central Kansas CO2 was injected in the Mississippian reservoir for enhanced oil recovery. This study examines the utility of active source surface seismic for characterization of Mississippian reservoir properties and monitoring CO2. Analysis of post-stack 3D seismic data showed the expected response of a gradational transition (ramp velocity) where thicker reservoir units corresponded with lower reflection amplitudes, lower frequency and a 90o phase change. Reflection amplitude could be correlated to reservoir thickness. Pre-stack gather analysis showed that porosity zones of the Mississippian reservoir exhibit characteristic AVO response. Simultaneous AVO inversion estimated P- and S-Impedances, which along with formation porosity logs and post-stack seismic data attributes were incorporated in multi-attribute linear-regression analysis and predicted reservoir porosity with an overall correlation of 0.90 to well data. The 3D survey gather azimuthal anisotropy analysis (AVAZ) provided information on the fault and fracture network and showed good agreement to the regional stress field and well data. Mississippian reservoir porosity and fracture predictions agreed well with the observed mobility of the CO2 in monitoring wells. Fluid substitution modeling predicted acoustic impedance reduction in the Mississippian carbonate reservoir introduced by the presence of CO2. Future work includes the assessment of time-lapse seismic, acquired after the injection of CO2. This work demonstrates that advanced seismic interpretation methods can be used successfully for characterization of the Mississippian reservoir and monitoring of CO2.

Determination of nitrite and nitrate in water samples by an automated hydrodynamic sequential injection method.

PubMed

Somnam, Sarawut; Jakmunee, Jaroon; Grudpan, Kate; Lenghor, Narong; Motomizu, Shoji

2008-12-01

An automated hydrodynamic sequential injection (HSI) system with spectrophotometric detection was developed. Thanks to the hydrodynamic injection principle, simple devices can be used for introducing reproducible microliter volumes of both sample and reagent into the flow channel to form stacked zones in a similar fashion to those in a sequential injection system. The zones were then pushed to the detector and a peak profile was recorded. The determination of nitrite and nitrate in water samples by employing the Griess reaction was chosen as a model. Calibration graphs with linearity in the range of 0.7 - 40 muM were obtained for both nitrite and nitrate. Detection limits were found to be 0.3 muM NO(2)(-) and 0.4 muM NO(3)(-), respectively, with a sample throughput of 20 h(-1) for consecutive determination of both the species. The developed system was successfully applied to the analysis of water samples, employing simple and cost-effective instrumentation and offering higher degrees of automation and low chemical consumption.

Lacustrine Paleoseismology Reveals Earthquake Segmentation of the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Howarth, J. D.; Fitzsimons, S.; Norris, R.; Langridge, R. M.

2013-12-01

Transform plate boundary faults accommodate high rates of strain and are capable of producing large (Mw>7.0) to great (Mw>8.0) earthquakes that pose significant seismic hazard. The Alpine Fault in New Zealand is one of the longest, straightest and fastest slipping plate boundary transform faults on Earth and produces earthquakes at quasi-periodic intervals. Theoretically, the fault's linearity, isolation from other faults and quasi-periodicity should promote the generation of earthquakes that have similar magnitudes over multiple seismic cycles. We test the hypothesis that the Alpine Fault produces quasi-regular earthquakes that contiguously rupture the southern and central fault segments, using a novel lacustrine paleoseismic proxy to reconstruct spatial and temporal patterns of fault rupture over the last 2000 years. In three lakes located close to the Alpine Fault the last nine earthquakes are recorded as megaturbidites formed by co-seismic subaqueous slope failures, which occur when shaking exceeds Modified Mercalli (MM) VII. When the fault ruptures adjacent to a lake the co-seismic megaturbidites are overlain by stacks of turbidites produced by enhanced fluvial sediment fluxes from earthquake-induced landslides. The turbidite stacks record shaking intensities of MM>IX in the lake catchments and can be used to map the spatial location of fault rupture. The lake records can be dated precisely, facilitating meaningful along strike correlations, and the continuous records allow earthquakes closely spaced in time on adjacent fault segments to be distinguished. The results show that while multi-segment ruptures of the Alpine Fault occurred during most seismic cycles, sequential earthquakes on adjacent segments and single segment ruptures have also occurred. The complexity of the fault rupture pattern suggests that the subtle variations in fault geometry, sense of motion and slip rate that have been used to distinguish the central and southern segments of the Alpine Fault can inhibit rupture propagation, producing a soft earthquake segment boundary. The study demonstrates the utility of lakes as paleoseismometers that can be used to reconstruct the spatial and temporal patterns of earthquakes on a fault.

High-resolution numerical modeling of tectonic underplating in circum-Pacific subduction zones: toward a better understanding of deformation in the episodic tremor and slip region?

NASA Astrophysics Data System (ADS)

Menant, A.; Angiboust, S.; Gerya, T.; Lacassin, R.; Simoes, M.; Grandin, R.

2017-12-01

Study of now-exhumed ancient subduction systems have evidenced km-scale tectonic units of marine sediments and oceanic crust that have been tectonically underplated (i.e. basally accreted) from the downgoing plate to the overriding plate at more than 30-km depth. Such huge mass transfers must have a major impact, both in term of long-term topographic variations and seismic/aseismic deformation in subduction zones. However, the quantification of such responses to the underplating process remains poorly constrained. Using high-resolution visco-elasto-plastic thermo-mechanical models, we present with unprecedented details the dynamics of formation and destruction of underplated complexes in subductions zones. Initial conditions in our experiments are defined in order to fit different subduction systems of the circum-Pacific region where underplating process is strongly suspected (e.g. the Cascadia, SW-Japan, New Zealand, and Chilean subduction zones). It appears that whatever the subduction system considered, underplating of sediments and oceanic crust always occur episodically forming a coherent nappe stacking at depths comprised between 10 and 50 km. At higher depth, a tectonic mélange with a serpentinized mantle wedge matrix developed along the plates interface. The size of these underplated complexes changes according to the subduction system considered. For instance, a 15-km thick nappe stacking is obtained for the N-Chilean subduction zone after a series of underplating events. Such an episodic event lasts 4-5 Myrs and can be responsible of a 2-km high uplift in the forearc region. Subsequent basal erosion of these underplated complexes results in their only partial preservation at crustal and mantle depth, suggesting that, after exhumation, only a tiny section of the overall underplated material can be observed nowadays in ancient subduction systems. Finally, tectonic underplating in our numerical models is systematically associated with (1) an increasing thickness of the high-strained subduction channel and (2) an accumulation of fluid-rich materials that serve as an environment for episodic tremor and slip events assisted by tectonic shearing and fluid release and percolation.

Dislocation imaging for orthopyroxene using an atom-resolved scanning transmission electron microscopy.

PubMed

Kumamoto, Akihito; Kogure, Toshihiro; Raimbourg, Hugues; Ikuhara, Yuichi

2014-11-01

Dislocations, one-dimensional lattice defects, appear as a microscopic phenomenon while they are formed in silicate minerals by macroscopic dynamics of the earth crust such as shear stress. To understand ductile deformation mechanisms of silicates, atomic structures of the dislocations have been examined using transmission electron microscopy (TEM). Among them, it has been proposed that {100}<001> primary slip system of orthopyroxene (Opx) is dissociated into partial dislocations, and a stacking fault with the clinopyroxene (Cpx) structure is formed between the dislocations. This model, however, has not been determined completely due to the complex structures of silicates. Scanning transmission electron microscopy (STEM) has a potential to determine the structure of dislocations with single-atomic column sensitivity, particularly by using high-angle annular dark field (HAADF) and annular bright field (ABF) imaging with a probing aberration corrector.[1] Furthermore, successive analyses from light microscopy to atom-resolved STEM have been achieved by focused ion beam (FIB) sampling techniques.[2] In this study, we examined dislocation arrays at a low-angle grain boundary of ∼1° rotation about the b-axis in natural deformed Opx using a simultaneous acquisition of HAADF/ABF (JEM-ARM200F, JEOL) equipped with 100 mm2 silicon drift detector (SDD) for energy dispersive X-ray spectroscopy (EDS). Figure 1 shows averaged STEM images viewed along the b- axis of Opx extracted from repeating units. HAADF provides the cation-site arrangement, and ABF distinguishes the difference of slightly rotated SiO4 tetrahedron around the a- axis. This is useful to distinguish the change of stacking sequence between the partial dislocations. Two types of stacking faults with Cpx and protopyroxene (Ppx) structures were identified between three partial dislocations. Furthermore, Ca accumulation in M2 (Fe) site around the stacking faults was detected by STEM-EDS. Interestingly, Ca is distributed not only in these stacking faults but also Opx matrix around the faults. jmicro;63/suppl_1/i17/DFU063F1F1DFU063F1Fig. 1. (a) HAADF and (b) ABF of Opx view of [010] direction with inset simulation images and models of its unit cell (a = 0.52, c = 1.83 nm). © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Microseismic techniques for avoiding induced seismicity during fluid injection

DOE PAGES

Matzel, Eric; White, Joshua; Templeton, Dennise; ...

2014-01-01

The goal of this research is to develop a fundamentally better approach to geological site characterization and early hazard detection. We combine innovative techniques for analyzing microseismic data with a physics-based inversion model to forecast microseismic cloud evolution. The key challenge is that faults at risk of slipping are often too small to detect during the site characterization phase. Our objective is to devise fast-running methodologies that will allow field operators to respond quickly to changing subsurface conditions.

[Matrix effect and application of field-amplified sample injection in the analysis of four tetracyclines in waters by capillary electrohoresis].

PubMed

2014-08-01

The system abilities of two chromatographic techniques, capillary electrophoresis (CE) and high performance liquid chromatography (HPLC), were compared for the analysis of four tetracyclines (tetracycline, chlorotetracycline, oxytetracycline and doxycycline). The pH, concentration of background electrolyte (BGE) were optimized for the analysis of the standard mixture sample, meanwhile, the effects of separation voltage and water matrix (pH value and hardness) effects were investigated. In hydrodynamic injection (HDI) mode, a good quantitative linearity and baseline separation within 9. 0 min were obtained for the four tetracyclines at the optimal conditions; the analytical time was about half of that of HPLC. The limits of detection (LODs) were in the range of 0. 28 - 0. 62 mg/L, and the relative standard deviations (RSDs) (n= 6) of migration time and peak area were 0. 42% - 0. 56% and 2. 24% - 2. 95%, respectively. The obtained recoveries spiked in tap water and fishpond water were at the ranges of 96. 3% - 107. 2% and 87. 1% - 105. 2%, respectively. In addition, the stacking method, field-amplified sample injection (FASI), was employed to improve the sensitivity, and the LOD was down to the range of 17.8-35.5 μg/L. With FASI stacking, the RSDs (n=6) of migration time and peak area were 0. 85%-0. 95% and 1. 69%-3.43%, respectively. Due to the advantages of simple sample pretreatment and fast speed, CE is promising in the analysis of the antibiotics in environmental water.

Predictions of the shear response of (Mg,Fe)SiO3 post-perovskite

NASA Astrophysics Data System (ADS)

Metsue, A.; Tsuchiya, T.

2011-12-01

Observation of seismic data put in forth evidence of a spatial anisotropy in the seismic wave velocities in the D'' layer, the lowermost part of the mantle. (Mg,Fe)SiO3 post-perovskite (PPv) is thought to be the most abundant phase in this part of the mantle, and this mineral exhibits a strong elastic anisotropy and may contribute significantly to the seismic anisotropy in the D'' layer. However, the seismic anisotropy cannot be expressed at the rock scale if the orientations of the grains are distributed randomly. Consequently, the formation of lattice preferred orientations with an anisotropic mechanism of plasticity, such as dislocation creep, can cause the seismic anisotropy in the D'' layer. Some experiments have been done on the plasticity of pure and Fe-bearing MgSiO3 post-perovskite and lead to textures of deformation dominated by the (100) and (110) slip planes (Merkel et al., 2007) and by the (001) slip plane (Miyagi et al., 2010). On the other hand, theoretical calculations on the dislocations mobility on pure MgSiO3 (Carrez et al., 2007; Metsue et al., 2009) suggested a texture dominated by the (010) slip plane. A first step to understanding the mechanisms of plasticity and, therefore, the shear wave splitting occurring in the deep Earth is to test the response of the PPv phase to a plastic shear in a geophysical relevant composition. In this study, we present new results from first-principles calculations on the shear response of pure and ferrous iron-bearing MgSiO3 PPv. The originality of this work is the use of internally consistent LSDA+U formalism to accurately describe the local interactions between the d-states of iron. About 8% of iron is incorporated in the high spin state as a Mg substitution defect, since several studies suggest that iron is in the high spin in the D'' layer pressure range (Stackhouse et al., 2006; Metsue and Tsuchiya, 2011). We also performed the calculations for incorporated iron in the low spin state if an eventual spin transition of Fe occurs. The response of the PPv to a plastic shear is investigated at 120 GPa through the calculations of the Generalized Stacking Faults (GSF) energy in pure and iron-bearing systems for ten potential {hkl} slip systems, since these latter are not well constrained for the PPv phase. The GSF energies are obtained by shearing homogeneously half of an infinite crystal over the other half for every slip plane and give the value of the ideal shear stress (ISS), which can be defined as the theoretical elastic limit of the crystal. The [100](001) slip system in pure and iron-bearing phases exhibits the lowest ISS and may play an important role in the plastic deformation of the PPv phase. The activation of this slip system is compatible with the observed shear wave splitting VSH>VSV. We show that incorporation of iron decreases the GSF energy and the ISS of all slip systems. We discuss the plastic anisotropy of pure and iron-bearing phases from the values of the ISS and the orientation of applied tensile stress. Our results suggest that the incorporation of ferrous iron in the PPv phase has a limited effect on its plastic anisotropy.

Pattern palette for complex fluid flows

NASA Astrophysics Data System (ADS)

Sandnes, B.

2012-04-01

From landslides to oil and gas recovery to the squeeze of a toothpaste tube, flowing complex fluids are everywhere around us in nature and engineering. That is not to say, though, that they are always well understood. The dissipative interactions, through friction and inelastic collisions, often give rise to nonlinear dynamics and complexity manifested in pattern formation on large scales. The images displayed on this poster illustrate the diverse morphologies found in multiphase flows involving wet granular material: Air is injected into a generic mixture of granular material and fluid contained in a 500 µm gap between two parallel glass plates. At low injection rates, friction between the grains - glass beads averaging 100 µm in diameter - dominates the rheology, producing "stick-slip bubbles" and labyrinthine frictional fingering. A transition to various other morphologies, including "corals" and viscous fingers, emerges for increasing injection rate. At sufficiently high granular packing fractions, the material behaves like a deformable, porous solid, and the air rips through in sudden fractures.

Source Complexity of an Injection Induced Event: The 2016 Mw 5.1 Fairview, Oklahoma Earthquake

NASA Astrophysics Data System (ADS)

López-Comino, J. A.; Cesca, S.

2018-05-01

Complex rupture processes are occasionally resolved for weak earthquakes and can reveal a dominant direction of the rupture propagation and the presence and geometry of main slip patches. Finding and characterizing such properties could be important for understanding the nucleation and growth of induced earthquakes. One of the largest earthquakes linked to wastewater injection, the 2016 Mw 5.1 Fairview, Oklahoma earthquake, is analyzed using empirical Green's function techniques to reveal its source complexity. Two subevents are clearly identified and located using a new approach based on relative hypocenter-centroid location. The first subevent has a magnitude of Mw 5.0 and shows the main rupture propagated toward the NE, in the direction of higher pore pressure perturbations due to wastewater injection. The second subevent appears as an early aftershock with lower magnitude, Mw 4.7. It is located SW of the mainshock in a region of increased Coulomb stress, where most aftershocks relocated.

Charge generation layers for solution processed tandem organic light emitting diodes with regular device architecture.

PubMed

Höfle, Stefan; Bernhard, Christoph; Bruns, Michael; Kübel, Christian; Scherer, Torsten; Lemmer, Uli; Colsmann, Alexander

2015-04-22

Tandem organic light emitting diodes (OLEDs) utilizing fluorescent polymers in both sub-OLEDs and a regular device architecture were fabricated from solution, and their structure and performance characterized. The charge carrier generation layer comprised a zinc oxide layer, modified by a polyethylenimine interface dipole, for electron injection and either MoO3, WO3, or VOx for hole injection into the adjacent sub-OLEDs. ToF-SIMS investigations and STEM-EDX mapping verified the distinct functional layers throughout the layer stack. At a given device current density, the current efficiencies of both sub-OLEDs add up to a maximum of 25 cd/A, indicating a properly working tandem OLED.

Swarms of repeating stick-slip glacierquakes triggered by snow loading at Mount Rainier volcano

NASA Astrophysics Data System (ADS)

Allstadt, K.; Malone, S. D.; Shean, D. E.; Fahnestock, M. A.; Vidale, J. E.

2013-12-01

We have detected over 150,000 low-frequency (~1-5 Hz) repeating earthquakes over the past decade at Mount Rainier volcano by scanning continuous seismic data from the permanent seismic network. Most of these were previously undetected due to their small size (M<1), shallow locations, and emergent waveforms. The earthquakes are located high (>3000 m) on the glacier-covered part of the edifice. They occur primarily in week- to month-long swarms of activity that strongly correlate with precipitation, namely snowfall, with a lag of about 1-2 days. Furthermore, there is a linear relationship between inter-event repeat time and the size of the subsequent event - consistent with slip-predictable stick-slip behavior. This pattern suggests that the additional load imparted by the sudden added weight of snow during winter storms triggers a temporary change from smooth aseismic sliding to seismic stick-slip basal sliding in locations where basal conditions are close to frictional instability. This sensitivity is analogous to the triggering of repeating earthquakes due to tiny overall stress changes in more traditional tectonic environments (e.g., tremor modulated by tides, dynamic triggering of repeating earthquakes). Using codawave interferometry on stacks of the repeating waveforms of the families with the most events, we found that the sources move at speeds of ~1 m/day. Using a GAMMA ground based radar interferometer, we collected spatially continuous line-of-sight velocities of several glaciers at Mount Rainier in both summer and late fall. We found that the faster parts of the glaciers also move at ~1 m/day or faster, even in late fall. Movement of the sources of these repeating earthquakes at glacial speeds indicates that the asperities are dirty patches that move with the ice rather than stationary bedrock bumps. The reappearance of some event families up to several years apart suggests that certain areas at the base of certain glaciers are prodigious producers of conditions favorable to this behavior. Stick-slip basal sliding of glaciers is supported over other potential moving shallow source mechanisms such as crevassing, unsteady fluid flow, and calving because the source must be non-destructive, highly repeatable at regular intervals, large enough to be detected on multiple stations, lack strong spectral peaks, and have a potential physical tie to the effects of winter precipitation. Identification of the source of these frequent signals offers a view of basal glacier processes, discriminates against alarming volcanic noises, and documents effects of weather on the cryosphere.

Diverse Functionalities of Vertically Stacked Graphene/Single layer n-MoS2/SiO2/p-GaN Heterostructures.

PubMed

Perumal, Packiyaraj; Karuppiah, Chelladurai; Liao, Wei-Cheng; Liou, Yi-Rou; Liao, Yu-Ming; Chen, Yang-Fang

2017-08-30

Integrating different dimentional materials on vertically stacked p-n hetero-junctions have facinated a considerable scrunity and can open up excellent feasibility with various functionalities in opto-electronic devices. Here, we demonstrate that vertically stacked p-GaN/SiO 2 /n-MoS 2 /Graphene heterostructures enable to exhibit prominent dual opto-electronic characteristics, including efficient photo-detection and light emission, which represents the emergence of a new class of devices. The photoresponsivity was found to achieve as high as ~10.4 AW -1 and the detectivity and external quantum efficiency were estimated to be 1.1 × 10 10 Jones and ~30%, respectively. These values are superier than most reported hererojunction devices. In addition, this device exhibits as a self-powered photodetector, showing a high responsivity and fast response speed. Moreover, the device demonstrates the light emission with low turn-on voltage (~1.0 V) which can be realized by electron injection from graphene electrode and holes from GaN film into monolayer MoS 2 layer. These results indicate that with a suitable choice of band alignment, the vertical stacking of materials with different dimentionalities could be significant potential for integration of highly efficient heterostructures and open up feasible pathways towards integrated nanoscale multi-functional optoelectronic devices for a variety of applications.

An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid.

PubMed

van Staden, J F; Mashamba, Mulalo G; Stefan, Raluca I

2002-09-01

An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid is proposed. A solution of 0.1 mol L(-1) sodium chloride is used as carrier. Titration is achieved by aspirating acetic acid samples between two strong base-zone volumes into a holding coil and by channelling the stack of well-defined zones with flow reversal through a reaction coil to a potentiometric sensor where the peak widths were measured. A linear relationship between peak width and logarithm of the acid concentration was obtained in the range 1-9 g/100 mL. Vinegar samples were analysed without any sample pre-treatment. The method has a relative standard deviation of 0.4% with a sample frequency of 28 samples per hour. The results revealed good agreement between the proposed sequential injection and an automated batch titration method.

Reviews on factors affecting fatigue behavior of high-Mn steels

NASA Astrophysics Data System (ADS)

Kim, Sangshik; Jeong, Daeho; Sung, Hyokyung

2018-01-01

A variety of factors affect the fatigue behavior of high-Mn steels, which include both extrinsic (i.e., loading type, R ratio, specimen type, surface condition, temperature, and environment) and intrinsic (i.e., chemical composition, grain size, microstructure, stacking fault energy) factors. Very often, the influence of extrinsic factors on the fatigue behavior is even greater than that of intrinsic factors, misleading the interpretation of fatigue data. The metallurgical factors influence the initiation and propagation behaviors of fatigue by altering the characteristics of slip that is prerequisite for fatigue damage accumulation. It is however not easy to separate the effect of each factor since they affect the fatigue behavior of high-Mn steels in complex and synergistic way. In this review, the fatigue data of high-Mn steels are summarized and the factors complicating the interpretation are discussed.

Elastic Organic Crystals of a Fluorescent π-Conjugated Molecule.

PubMed

Hayashi, Shotaro; Koizumi, Toshio

2016-02-18

An elastic organic crystal of a π-conjugated molecule has been fabricated. A large fluorescent single crystal of 1,4-bis[2-(4-methylthienyl)]-2,3,5,6-tetrafluorobenzene (over 1 cm long) exhibited a fibril lamella morphology based on slip-stacked molecular wires, and it was found to be a remarkably elastic crystalline material. The straight crystal was capable of bending more than 180° under applied stress and then quickly reverted to its original shape upon relaxation. In addition, the fluorescence quantum yield of the crystal was about twice that of the compound in THF solution. Mechanical bending-relaxation resulted in reversible change of the morphology and fluorescence. This research offers a more general approach to flexible crystals as a promising new family of organic semiconducting materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced characterization of faults and fractures at EGS sites by CO2 injection coupled with active seismic monitoring, pressure-transient testing, and well logging

NASA Astrophysics Data System (ADS)

Oldenburg, C. M.; Daley, T. M.; Borgia, A.; Zhang, R.; Doughty, C.; Jung, Y.; Altundas, B.; Chugunov, N.; Ramakrishnan, T. S.

2016-12-01

Faults and fractures in geothermal systems are difficult to image and characterize because they are nearly indistinguishable from host rock using traditional seismic and well-logging tools. We are investigating the use of CO2 injection and production (push-pull) in faults and fractures for contrast enhancement for better characterization by active seismic, well logging, and push-pull pressure transient analysis. Our approach consists of numerical simulation and feasibility assessment using conceptual models of potential enhanced geothermal system (EGS) sites such as Brady's Hot Spring and others. Faults in the deep subsurface typically have associated damage and gouge zones that provide a larger volume for uptake of CO2 than the slip plane alone. CO2 injected for push-pull well testing has a preference for flowing in the fault and fractures because CO2 is non-wetting relative to water and the permeability of open fractures and fault gouge is much higher than matrix. We are carrying out numerical simulations of injection and withdrawal of CO2 using TOUGH2/ECO2N. Simulations show that CO2 flows into the slip plane and gouge and damage zones and is driven upward by buoyancy during the push cycle over day-long time scales. Recovery of CO2 during the pull cycle is limited because of buoyancy effects. We then use the CO2 saturation field simulated by TOUGH2 in our anisotropic finite difference code from SPICE-with modifications for fracture compliance-that we use to model elastic wave propagation. Results show time-lapse differences in seismic response using a surface source. Results suggest that CO2 can be best imaged using time-lapse differencing of the P-wave and P-to-S-wave scattering in a vertical seismic profile (VSP) configuration. Wireline well-logging tools that measure electrical conductivity show promise as another means to detect and image the CO2-filled fracture near the injection well and potential monitoring well(s), especially if a saline-water pre-flush is carried out to enhance conductivity contrast. Pressure-transient analysis is also carried out to further constrain fault zone characteristics. These multiple complementary characterization approaches are being used to develop working models of fault and fracture zone characteristics relevant to EGS energy recovery.

Low driving voltage simplified tandem organic light-emitting devices by using exciplex-forming hosts

NASA Astrophysics Data System (ADS)

Zhou, Dong-Ying; Cui, Lin-Song; Zhang, Ying-Jie; Liao, Liang-Sheng; Aziz, Hany

2014-10-01

Tandem organic light-emitting devices (OLEDs), i.e., OLEDs containing multiple electroluminescence (EL) units that are vertically stacked, are attracting significant interest because of their ability to realize high current efficiency and long operational lifetime. However, stacking multiple EL units in tandem OLEDs increases driving voltage and complicates fabrication process relative to their standard single unit counterparts. In this paper, we demonstrate low driving voltage tandem OLEDs via utilizing exciplex-forming hosts in the EL units instead of conventional host materials. The use of exciplex-forming hosts reduces the charge injection barriers and the trapping of charges on guest molecules, resulting in the lower driving voltage. The use of exciplex-forming hosts also allows using fewer layers, hence simpler EL configuration which is beneficial for reducing the fabrication complexity of tandem OLEDs.

Hot Dry Rock Induced Seismicity - Latest results from Basel, Switzerland

NASA Astrophysics Data System (ADS)

Deichmann, N.; Kraft, T.; Husen, S.

2009-12-01

The Deep Heat Mining project in Basel, Switzerland, was one of the first purely commercially oriented Enhanced Geothermal System (EGS) projects. Beginning on 2 December 2006, water was injected into a 5 km deep well with increasing flow rates. Because of strongly increased seismic activity, which included a ML2.7 event, injection had already been stopped a few hours prior to a ML3.4 event that occurred on 8 December 2006. This earthquake rattled the local population and received international media attention. Slight nonstructural damage has been claimed by many homeowners, with a damage sum of US$7 million. Bleed-off of the injection well was initiated about 1 hour after the ML3.4 event, and hydrostatic down-hole pressure was reached within 4 days. Since then, the seismicity slowly decayed. Three additional earthquakes with ML > 3 were felt 1-2 months after bleed-off. More than 2 years later, sporadic seismicity inside the stimulated rock volume is still being detected by the down-hole instruments. At present, the EGS project is on hold and awaits the completion of an independent risk analysis study. Here, we report on latest results of the analysis of the induced earthquake sequence which is one of the most densely monitored deep fluid-injections in the world. The seismic monitoring system consisted of six borehole seismometers near the injection well and of up to 30 seismic surface stations in the Basel area. The network is to a large part operational until today. Considerable improvement of the hypocenter locations was achieved by refinement of arrival-time picks and subsequent relocation. First, highly similar events where grouped by a cluster analysis based on broad-banded waveform cross-correlation. In a second step, we improve the P and S arrival-time picks in a semi-automatic procedure by taking advantage of the waveform similarity within the clusters and the improvement of the signal-to-noise ratio by stacking. Finally, we relocate the strongest event of each cluster using the double-difference technique and apply a master-event technique to relocate the individual cluster members with respect to these events. The results indicate an improvement of the location accuracy by a factor of 10 and a reduction in the geometric complexity of the earthquake cloud. Based on P-onset polarities, focal mechanisms of the 28 strongest events where derived. Based on relative hypocenter locations, the Ml3.4 mainshock was identified as dextral strike-slip motion on a steeply dipping WNW-ESE striking fault. Overall, the observed focal mechanisms agree with what would be expected from both the in-situ stress observations and the stress field derived from the previously known natural seismicity. Although some of the focal mechanisms show signs of non-double-couple components with a volume change, overall the results are compatible with shear failure on pre-existing faults. To extend the moment tensor analysis to events that have only been recorded on the down-hole instruments, we have started to include relative amplitudes of P and S-onsets into the inversion. First results will be presented in this paper.

CO 2 storage and potential fault instability in the St. Lawrence Lowlands sedimentary basin (Quebec, Canada): Insights from coupled reservoir-geomechanical modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konstantinovskaya, E.; Rutqvist, J.; Malo, M.

2014-01-21

In this paper, coupled reservoir-geomechanical (TOUGH-FLAC) modeling is applied for the first time to the St. Lawrence Lowlands region to evaluate the potential for shear failure along pre-existing high-angle normal faults, as well as the potential for tensile failure in the caprock units (Utica Shale and Lorraine Group). This activity is part of a general assessment of the potential for safe CO 2 injection into a sandstone reservoir (the Covey Hill Formation) within an Early Paleozoic sedimentary basin. Field and subsurface data are used to estimate the sealing properties of two reservoir-bounding faults (Yamaska and Champlain faults). The spatial variationsmore » in fluid pressure, effective minimum horizontal stress, and shear strain are calculated for different injection rates, using a simplified 2D geological model of the Becancour area, located ~110 km southwest of Quebec City. The simulation results show that initial fault permeability affects the timing, localization, rate, and length of fault shear slip. Contrary to the conventional view, our results suggest that shear failure may start earlier for a permeable fault than for a sealing fault, depending on the site-specific geologic setting. In simulations of a permeable fault, shear slip is nucleated along a 60 m long fault segment in a thin and brittle caprock unit (Utica Shale) trapped below a thicker and more ductile caprock unit (Lorraine Group) – and then subsequently progresses up to the surface. In the case of a sealing fault, shear failure occurs later in time and is localized along a fault segment (300 m) below the caprock units. The presence of the inclined low-permeable Yamaska Fault close to the injection well causes asymmetric fluid-pressure buildup and lateral migration of the CO 2 plume away from the fault, reducing the overall risk of CO 2 leakage along faults. Finally, fluid-pressure-induced tensile fracturing occurs only under extremely high injection rates and is localized below the caprock units, which remain intact, preventing upward CO 2 migration.« less

Source Mechanisms of Low Frequency Seismicity in a Hydraulic Fracturing Context

NASA Astrophysics Data System (ADS)

Zecevic, M.; Daniel, G.; Hubans, F.; Gouedard, P.

2014-12-01

In recent years, long-period long-duration (LPLD) events have been observed during hydraulic fracturing of hydrocarbon reservoirs (Das & Zoback, 2013). LPLDs are low-amplitude signals lasting from tens of seconds to minutes. Their source mechanisms are not fully understood. However, as they are remarkably similar in character to tectonic tremors it has been suggested that they may also have comparable source models. Current models suggest that a tectonic tremor consists of numerous slow-slip earthquakes superposed on each other to form continuous waveforms (Shelley et al., 2007). These slow-slip earthquakes are thought to be a result of shear slip on faults close to failure with low confining pressure, most likely due to the presence of fluid with pore pressures close to lithostatic pressures (Peng & Gomberg, 2010). This study aims to further understand the source mechanism of LPLDs. A hydraulic fracturing dataset containing thousands of located microseismic earthquakes (MEQs) and numerous LPLDs is presented. The MEQs are located around the injection stages whereas the LPLDs are clustered in a limited region within the reservoir. This clustering suggests that LPLDs can only be generated where the conditions in the reservoir are favorable. These results correspond with the possibility that LPLDs are manifestations of slow-slip, with the source locations confined by variations in the mechanical properties of the reservoir. To test this hypothesis a further understanding of the mechanisms of LPLDs and the stress field in which they occur is needed. However, calculating focal mechanisms for LPLDs is difficult due to their emergent onset and lack of clear phases. Consequently, LPLDs must be put into context with the observed MEQs. We will present the spatial distribution of the focal mechanisms of the MEQs and analyze our findings with respect to the occurrence of the LPLD events.

Material flow data for numerical simulation of powder injection molding

NASA Astrophysics Data System (ADS)

Duretek, I.; Holzer, C.

2017-01-01

The powder injection molding (PIM) process is a cost efficient and important net-shape manufacturing process that is not completely understood. For the application of simulation programs for the powder injection molding process, apart from suitable physical models, exact material data and in particular knowledge of the flow behavior are essential in order to get precise numerical results. The flow processes of highly filled polymers are complex. Occurring effects are very hard to separate, like shear flow with yield stress, wall slip, elastic effects, etc. Furthermore, the occurrence of phase separation due to the multi-phase composition of compounds is quite probable. In this work, the flow behavior of a 316L stainless steel feedstock for powder injection molding was investigated. Additionally, the influence of pre-shearing on the flow behavior of PIM-feedstocks under practical conditions was examined and evaluated by a special PIM injection molding machine rheometer. In order to have a better understanding of key factors of PIM during the injection step, 3D non-isothermal numerical simulations were conducted with a commercial injection molding simulation software using experimental feedstock properties. The simulation results were compared with the experimental results. The mold filling studies amply illustrate the effect of mold temperature on the filling behavior during the mold filling stage. Moreover, the rheological measurements showed that at low shear rates no zero shear viscosity was observed, but instead the viscosity further increased strongly. This flow behavior could be described with the Cross-WLF approach with Herschel-Bulkley extension very well.

A Computational Model of Coupled Multiphase Flow and Geomechanics to Study Fault Slip and Induced Seismicity

NASA Astrophysics Data System (ADS)

Juanes, R.; Jha, B.

2014-12-01

The coupling between subsurface flow and geomechanical deformation is critical in the assessment of the environmental impacts of groundwater use, underground liquid waste disposal, geologic storage of carbon dioxide, and exploitation of shale gas reserves. In particular, seismicity induced by fluid injection and withdrawal has emerged as a central element of the scientific discussion around subsurface technologies that tap into water and energy resources. Here we present a new computational approach to model coupled multiphase flow and geomechanics of faulted reservoirs. We represent faults as surfaces embedded in a three-dimensional medium by using zero-thickness interface elements to accurately model fault slip under dynamically evolving fluid pressure and fault strength. We incorporate the effect of fluid pressures from multiphase flow in the mechanical stability of faults and employ a rigorous formulation of nonlinear multiphase geomechanics that is capable of handling strong capillary effects. We develop a numerical simulation tool by coupling a multiphase flow simulator with a mechanics simulator, using the unconditionally stable fixed-stress scheme for the sequential solution of two-way coupling between flow and geomechanics. We validate our modeling approach using several synthetic, but realistic, test cases that illustrate the onset and evolution of earthquakes from fluid injection and withdrawal. We also present the application of the coupled flow-geomechanics simulation technology to the post mortem analysis of the Mw=5.1, May 2011 Lorca earthquake in south-east Spain, and assess the potential that the earthquake was induced by groundwater extraction.

Analysis of Geologic CO2 Sequestration at Farnham Dome, Utah, USA

NASA Astrophysics Data System (ADS)

Lee, S.; Han, W.; Morgan, C.; Lu, C.; Esser, R.; Thorne, D.; McPherson, B.

2008-12-01

The Farnham Dome in east-central Utah is an elongated, Laramide-age anticline along the northern plunge of the San Rafael uplift and the western edge of the Uinta Basin. We are helping design a proposed field demonstration of commercial-scale geologic CO2 sequestration, including injection of 2.9 million tons of CO2 over four years time. The Farnham Dome pilot site stratigraphy includes a stacked system of saline formations alternating with low-permeability units. Facilitating the potential sequestration demonstration is a natural CO2 reservoir at depth, the Jurassic-age Navajo formation, which contains an estimated 50 million tons of natural CO2. The sequestration test design includes two deep formations suitable for supercritical CO2 injection, the Jurassic-age Wingate sandstone and the Permian-age White Rim sandstone. We developed a site-specific geologic model based on available geophysical well logs and formation tops data for use with numerical simulation. The current geologic model is limited to an area of approximately 6.5x4.5 km2 and 2.5 km thick, which contains 12 stacked formations starting with the White Rim formation at the bottom (>5000 feet bgl) and extending to the Jurassic Curtis formation at the top of the model grid. With the detail of the geologic model, we are able to estimate the Farnham Dome CO2 capacity at approximately 36.5 million tones within a 5 mile radius of a single injection well. Numerical simulation of multiphase, non- isothermal CO2 injection and flow suggest that the injected CO2 plume will not intersect nearby fault zones mapped in previous geologic studies. Our simulations also examine and compare competing roles of different trapping mechanisms, including hydrostratigraphic, residual gas, solubility, and mineralization trapping. Previous studies of soil gas flux at the surface of the fault zones yield no significant evidence of CO2 leakage from the natural reservoir at Farnham Dome, and thus we use these simulations to evaluate what factors make this natural reservoir so effective for CO2 storage. Our characterization and simulation efforts are producing a CO2 sequestration framework that incorporates production and capacity estimation, area-of-review, injectivity, and trapping mechanisms. Likewise, mitigation and monitoring strategies have been formulated from the site characterization and modeling results.

Towards efficient next generation light sources: combined solution processed and evaporated layers for OLEDs

NASA Astrophysics Data System (ADS)

Hartmann, D.; Sarfert, W.; Meier, S.; Bolink, H.; García Santamaría, S.; Wecker, J.

2010-05-01

Typically high efficient OLED device structures are based on a multitude of stacked thin organic layers prepared by thermal evaporation. For lighting applications these efficient device stacks have to be up-scaled to large areas which is clearly challenging in terms of high through-put processing at low-cost. One promising approach to meet cost-efficiency, high through-put and high light output is the combination of solution and evaporation processing. Moreover, the objective is to substitute as many thermally evaporated layers as possible by solution processing without sacrificing the device performance. Hence, starting from the anode side, evaporated layers of an efficient white light emitting OLED stack are stepwise replaced by solution processable polymer and small molecule layers. In doing so different solutionprocessable hole injection layers (= polymer HILs) are integrated into small molecule devices and evaluated with regard to their electro-optical performance as well as to their planarizing properties, meaning the ability to cover ITO spikes, defects and dust particles. Thereby two approaches are followed whereas in case of the "single HIL" approach only one polymer HIL is coated and in case of the "combined HIL" concept the coated polymer HIL is combined with a thin evaporated HIL. These HIL architectures are studied in unipolar as well as bipolar devices. As a result the combined HIL approach facilitates a better control over the hole current, an improved device stability as well as an improved current and power efficiency compared to a single HIL as well as pure small molecule based OLED stacks. Furthermore, emitting layers based on guest/host small molecules are fabricated from solution and integrated into a white hybrid stack (WHS). Up to three evaporated layers were successfully replaced by solution-processing showing comparable white light emission spectra like an evaporated small molecule reference stack and lifetime values of several 100 h.

Episodic Tremor and Slip (ETS) as a chaotic multiphysics spring

NASA Astrophysics Data System (ADS)

Veveakis, E.; Alevizos, S.; Poulet, T.

2017-03-01

Episodic Tremor and Slip (ETS) events display a rich behaviour of slow and accelerated slip with simple oscillatory to complicated chaotic time series. It is commonly believed that the fast events appearing as non volcanic tremors are signatures of deep fluid injection. The fluid source is suggested to be related to the breakdown of hydrous phyllosilicates, mainly the serpentinite group minerals such as antigorite or lizardite that are widespread in the top of the slab in subduction environments. Similar ETS sequences are recorded in different lithologies in exhumed crustal carbonate-rich thrusts where the fluid source is suggested to be the more vigorous carbonate decomposition reaction. If indeed both types of events can be understood and modelled by the same generic fluid release reaction AB(solid) ⇌A(solid) +B(fluid) , the data from ETS sequences in subduction zones reveal a geophysically tractable temporal evolution with no access to the fault zone. This work reviews recent advances in modelling ETS events considering the multiphysics instabilities triggered by the fluid release reaction and develops a thermal-hydraulic-mechanical-chemical oscillator (THMC spring) model for such mineral reactions (like dehydration and decomposition) in Megathrusts. We describe advanced computational methods for THMC instabilities and discuss spectral element and finite element solutions. We apply the presented numerical methods to field examples of this important mechanism and reproduce the temporal signature of the Cascadia and Hikurangi trench with a serpentinite oscillator.

A universal piezo-driven ultrasonic cell microinjection system.

PubMed

Huang, Haibo; Mills, James K; Lu, Cong; Sun, Dong

2011-08-01

Over the past decade, the rapid development of biotechnologies such as gene injection, in-vitro fertilization, intracytoplasmic sperm injection (ICSI) and drug development have led to great demand for highly automated, high precision equipment for microinjection. Recently a new cell injection technology using piezo-driven pipettes with a very small mercury column was proposed and successfully applied in ICSI to a variety of mammal species. Although this technique significantly improves the survival rates of the ICSI process, shortcomings due to the toxicity of mercury and damage to the cell membrane due to large lateral tip oscillations of the injector pipette may limit its application. In this paper, a new cell injection system for automatic batch injection of suspended cells is developed. A new design of the piezo-driven cell injector is proposed for automated suspended cell injection. This new piezo-driven cell injector design relocates the piezo oscillation actuator to the injector pipette which eliminates the vibration effect on other parts of the micromanipulator. A small piezo stack is sufficient to perform the cell injection process. Harmful lateral tip oscillations of the injector pipette are reduced substantially without the use of a mercury column. Furthermore, ultrasonic vibration micro-dissection (UVM) theory is utilized to analyze the piezo-driven cell injection process, and the source of the lateral oscillations of the injector pipette is investigated. From preliminary experiments of cell injection of a large number of zebrafish embryos (n = 200), the injector pipette can easily pierce through the cell membrane at a low injection speed and almost no deformation of the cell wall, and with a high success rate(96%) and survival rate(80.7%) This new injection approach shows good potential for precision injection with less damage to the injected cells.

Combination Space Station Handrail Clamp and Pointing Device

NASA Technical Reports Server (NTRS)

Hughes, Stephen J. (Inventor)

1999-01-01

A device for attaching an experiment carrier to a space station handrail is provided. The device has two major components, a clamping mechanism for attachment to a space station handrail, and a pointing carrier on which an experiment package can be mounted and oriented. The handrail clamp uses an overcenter mechanism and the carrier mechanism uses an adjustable preload ball and socket for carrier positioning. The handrail clamp uses a stack of disk springs to provide a spring loaded button. This configuration provides consistent clamping force over a range of possible handrail thicknesses. Three load points are incorporated in the clamping mechanism thereby spreading the clamping load onto three separate points on the handrail. A four bar linkage is used to provide for a single actuation lever for all three load points. For additional safety, a secondary lock consisting of a capture plate and push lock keeps the clamp attached to the handrail in the event of main clamp failure. For the carrier positioning mechanism, a ball in a spring loaded socket uses friction to provide locking torque; however. the ball and socket are torque limited so that the ball ran slip under kick loads (125 pounds or greater). A lead screw attached to disk spring stacks is used to provide an adjustable spring force on the socket. A locking knob is attached to the lead screw to allow for hand manipulation of the lead screw.

Wilson Prize Talk

NASA Astrophysics Data System (ADS)

Symon, Keith R.

2005-04-01

In the late 1950's and the 1960's the MURA (Midwestern Universities Research Association) working group developed fixed field alternating gradient (FFAG) particle accelerators. FFAG accelerators are a natural corollary of the invention of alternating gradient focusing. The fixed guide field accommodates all orbits from the injection to the final energy. For this reason, the transverse motion in the guide field is nearly decoupled from the longitudinal acceleration. This allows a wide variety of acceleration schemes, using betatron or rf accelerating fields, beam stacking, bucket lifts, phase displacement, etc. It also simplifies theoretical and experimental studies of accelerators. Theoretical studies included an extensive analysis of rf acceleration processes, nonlinear orbit dynamics, and collective instabilities. Two FFAG designs, radial sector and spiral sector, were invented. The MURA team built small electron models of each type, and used them to study orbit dynamics, acceleration processes, orbit instabilities, and space charge limits. A practical result of these studies was the invention of the spiral sector cyclotron. Another was beam stacking, which led to the first practical way of achieving colliding beams. A 50 MeV two-way radial sector model was built in which it proved possible to stack a beam of over 10 amperes of electrons.

Combination of micelle collapse and field-amplified sample stacking in capillary electrophoresis for determination of trimethoprim and sulfamethoxazole in animal-originated foodstuffs.

PubMed

Liu, Lihong; Wan, Qian; Xu, Xiaoying; Duan, Shunshan; Yang, Chunli

2017-03-15

An on-line preconcentration method combining micelle to solvent stacking (MSS) with field-amplified sample stacking (FASS) was employed for the analysis of trimethoprim (TMP) and sulfamethoxazole (SMZ) by capillary zone electrophoresis (CZE). The optimized experimental conditions were as followings: (1) sample matrix, 10.0mM SDS-5% (v/v) methanol; (2) trapping solution (TS), 35mM H 3 PO 4 -60% acetonitrile (CH 3 CN); (3) running buffer, 30mM Na 2 HPO 4 (pH=7.3); (4) sample solution volume, 168nL; TS volume, 168nL; and (5) 9kV voltage, 214nm UV detection. Under the optimized conditions, the limits of detection (LODs) for SMZ and TMP were 7.7 and 8.5ng/mL, and they were 301 and 329 times better compared to a typical injection, respectively. The contents of TMP and SMZ in animal foodstuffs such as dairy products, eggs and honey were analyzed, too. Recoveries of 80-104% were acquired with relative standard deviations of 0.5-5.4%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Portable DMFC system with methanol sensor-less control

NASA Astrophysics Data System (ADS)

Chen, C. Y.; Liu, D. H.; Huang, C. L.; Chang, C. L.

This work develops a prototype 20 W portable DMFC by system integration of stack, condenser, methanol sensor-less control and start-up characteristics. The effects of these key components and control schemes on the performance are also discussed. To expedite the use of portable DMFC in electronic applications, the system utilizes a novel methanol sensor-less control method, providing improved fuel efficiency, durability, miniaturization and cost reduction. The operating characteristics of the DMFC stack are applied to control the fuel ejection time and period, enabling the system to continue operating even when the MEAs of the stack are deteriorated. The portable system is also designed with several features including water balance and quick start-up (in 5 min). Notably, the proposed system using methanol sensor-less control with injection of pure methanol can power the DVD player and notebook PC. The system specific energy and energy density following three days of operation are 362 Wh kg -1 and 335 Wh L -1, respectively, which are better than those of lithium batteries (∼150 Wh kg -1 and ∼250 Wh L -). This good energy storage feature demonstrates that the portable DMFC is likely to be valuable in computer, communication and consumer electronic (3C) markets.

Greenschist-Facies Pseudotachylytes and Gouge: a Microstructural Study of the Deformation Propagation at the Boundary Between Hp-Metabasite and Calcite Bearing Metasediments

NASA Astrophysics Data System (ADS)

Crispini, L.; Scambelluri, M.; Capponi, G.

2013-12-01

Recent friction experiments on calcite-bearing systems reproduce pseudotachylyte structures, that are diagnostic of dinamic calcite recrystallization related to seismic slip in the shallow crust. Here we provide the study of a pseudotachylyte (PT) bearing low angle oblique-slip fault. The fault is linked to the exhumation of Alpine HP-ophiolites and it is syn- to post-metamorphic with respect to retrograde greenschist facies metamorphism. The observed microstructures developed at the brittle-ductile transition and suggest that seismic and interseismic slip was enhanced by interaction with fluids. The fault zone is in-between high-pressure eclogite-facies metabasites (hangingwall) and calcite bearing metasediments (footwall). The mafic rocks largely consist of upper greenschist facies hornblende, albite, chlorite, epidote with relict eclogitic garnet, Na-pyroxene and rutile; metasediments correspond to calcschist and micaschist with quartz, phengite, zoisite, chlorite, calcite and relics of garnet. Key features of the oucrop are: the thickness and geometry of the PT and gouge; the multiple production of PT characterized by overprinting plastic and brittle deformation; the occurrence in footwall metasediments of mm-thick bands of finely recrystallized calcite coeval with PT development in the hangingwall. The damage zone is ca. 2 m-thick and is characterized by two black, ultra-finegrained straight and sharp Principal Slip Zones (PSZ) marked by PT. The damage zone shows a variety of fault rocks (cataclasite and ultracataclasite, gouge and PT) with multiple crosscutting relationships. Within the two main PSZ, PT occurs in 10-20 cm thick layer, in small scale injection veins and in microfractures. In the mafic hanging wall, the PT is recrystallized and does not preserve glass: it shows flow structures with subrounded, embayed and rebsorbed quartz in a fine grained matrix composed of isotropic albite + chlorite + quartz + epidote + titanite, suggesting recrystallization at ca. 270-300°C, 8-10 km of the original glass. PT show plastic deformations overprinted by shear bands and fracturing. The matrix of cataclastic layers has the same mineral assemblage as PT and clasts of recrystallised PT, to indicate polyphase PSZ formation. In the metasedimentary footwall, the original foliation is deflected parallel to the PSZ and is cut by cm-spaced shear bands parallel to PSZ. Deformation propagates in the footwall through mm-thick injections veins, shear bans, P-shears and veins. Pockets of recrystallized PT occur along the pre-existing mylonitic foliation of metasediments. Worthnote is the presence of mm-thick deformation bands (CDB) that are post-mylonitic foliation and mainly composed of fine grained calcite bounded by dissolution seams or ribbon grains of deformed calcite. CDB are characterised by subrounded embayed and rebsorbed quartz grains rimmed by new Ca-Mg amphibole, K-feldspar (90-93%K), in a dinamic recrystallized calcite 2-10 micron in size and slightly elongated. The features of the CDB suggest that these structures can be considered as diagnostic of localised deformation during coesismic slip in metasedimentary rocks.

Combined effects of suction/injection and wall surface curvature on natural convection flow in a vertical micro-porous annulus

NASA Astrophysics Data System (ADS)

Jha, B. K.; Aina, B.; Muhammad, S. A.

2015-03-01

This study investigates analytically the hydrodynamic and thermal behaviour of a fully developed natural convection flow in a vertical micro-porous-annulus (MPA) taking into account the velocity slip and temperature jump at the outer surface of inner porous cylinder and inner surface of outer porous cylinder. A closed — form solution is presented for velocity, temperature, volume flow rate, skin friction and rate of heat transfer expressed as a Nusselt number. The influence of each governing parameter on hydrodynamic and thermal behaviour is discussed with the aid of graphs. During the course of investigation, it is found that as suction/injection on the cylinder walls increases, the fluid velocity and temperature is enhanced. In addition, it is observed that wall surface curvature has a significant effect on flow and thermal characteristics.

Frictional Heat Generation and Slip Duration Estimated From Micro-fault in an Exhumed Accretionary Complex and Their Relations to the Scaling Law for Slow Earthquakes

NASA Astrophysics Data System (ADS)

Hashimoto, Y.; Morita, K.; Okubo, M.; Hamada, Y.; Lin, W.; Hirose, T.; Kitamura, M.

2015-12-01

Fault motion has been estimated by diffusion pattern of frictional heating recorded in geology (e.g., Fulton et al., 2012). The same record in deeper subduction plate interface can be observed from micro-faults in an exhumed accretionary complex. In this study, we focused on a micro-fault within the Cretaceous Shimanto Belt, SW Japan to estimate fault motion from the frictional heating diffusion pattern. A carbonaceous material concentrated layer (CMCL) with ~2m of thickness is observed in study area. Some micro-faults cut the CMCL. Thickness of a fault is about 3.7mm. Injection veins and dilatant fractures were observed in thin sections, suggesting that the high fluid pressure was existed. Samples with 10cm long were collected to measure distribution of vitrinite reflectance (Ro) as a function of distance from the center of micro-fault. Ro of host rock was ~1.0%. Diffusion pattern was detected decreasing in Ro from ~1.2%-~1.1%. Characteristic diffusion distance is ~4-~9cm. We conducted grid search to find the optimal frictional heat generation per unit area (Q, the product of friction coefficient, normal stress and slip velocity) and slip duration (t) to fit the diffusion pattern. Thermal diffusivity (0.98*10-8m2/s) and thermal conductivity (2.0 W/mK) were measured. In the result, 2000-2500J/m2 of Q and 63000-126000s of t were estimated. Moment magnitudes (M0) of slow earthquakes (slow EQs) follow a scaling law with slip duration and its dimension is different from that for normal earthquakes (normal EQ) (Ide et al., 2007). The slip duration estimated in this study (~104-~105s) consistent with 4-5 of M0, never fit to the scaling law for normal EQ. Heat generation can be inverted from 4-5 of M0, corresponding with ~108-~1011J, which is consistent with rupture area of 105-108m2 in this study. The comparisons in heat generation and slip duration between geological measurements and geophysical remote observations give us the estimation of rupture area, M0, and earthquake style, for non-active geological records.

Shallow Repeating Seismic Events Under an Alpine Glacier at Mount Rainier, Washington

NASA Astrophysics Data System (ADS)

Allstadt, K.; Thelen, W. A.; Malone, S. D.; Vidale, J. E.; de Angelis, S.; Moran, S. C.

2010-12-01

We observed a swarm of repeating sequences of seismic events during three weeks in May and June 2010 near the summit of Mount Rainier, Washington. These sequences likely marked stick-slip motion at the base of alpine glaciers. The dominant set of nearly identical earthquakes repeated more than 4000 times and had no diurnal variation in recurrence interval nor amplitude. A second set of earthquakes recurred about 500 times with a strong diurnal pattern. We also detected 14 other minor sets of repeating earthquakes of less than 20 occurrences during this time. Due to the low amplitudes of these events, we were able to locate only the dominant sequence by stacking 4000 signals. This event was located about 1km north of the crater, near the top of Winthrop glacier. Both volcanoes and glaciers groan and pop frequently, with great variability and energy. The low-frequency radiation and periodic recurrence of these events mimic more ominous volcano grumbles, but the shallow location, correspondence with weather, and sometimes diurnal patterns indicate ice-related sources. The most likely scenario is that a rapid influx of spring meltwater to the lower portions of these glaciers after several days of warm temperatures overwhelmed underdeveloped subglacial conduits, driving water into basal cavities and till. This decreases effective pressure at the base of the glacier, thus temporarily increasing basal slip rates. The earthquakes we observed may be generated by repeated stick-slip motion over bedrock bumps or other asperities under these glaciers near the summit as they were pulled along by down-glacier acceleration. The low frequency nature of these earthquakes is a path effect due to wave propagation through the glacial ice and surficial rock layers of the volcano. These sequences underline the difficulties in differentiating glacial noise from signs of magmatic unrest while monitoring volcanoes.

Brittle-viscous deformation of vein quartz under fluid-rich lower greenschist facies conditions

NASA Astrophysics Data System (ADS)

Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

2015-06-01

We studied by Electron BackScatter Diffraction (EBSD) and optical microscopy a coarse-grained (ca. 0.5-6 mm) quartz vein embedded in a phyllonitic matrix to gain insights into the recrystallization mechanisms and the processes of strain localization in quartz deformed under lower greenschist facies conditions, broadly coincident with the brittle-viscous transition. The vein deformed during faulting along a phyllonitic thrust of Caledonian age within the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The phyllonite hosting the vein formed at the expense of a metabasaltic protolith through feldspar breakdown to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the quartz vein acted as a relatively rigid body. Viscous deformation in the vein was initially accommodated by quartz basal slip. Under the prevailing deformation conditions, however, dislocation glide- and possibly creep-accommodated deformation of quartz was inefficient, and this resulted in localized strain hardening. In response to the (1) hardening, (2) progressive and cyclic increase of the fluid pressure, and (3) increasing competence contrast between the vein and the weakly foliated host phyllonite, vein quartz crystals began to deform by brittle processes along specific, suitably oriented lattice planes, creating microgouges along microfractures. Nucleated new grains rapidly sealed these fractures as fluids penetrated the actively deforming system. The grains grew initially by solution precipitation and later by grain boundary migration. We suggest that the different initial orientation of the vein crystals led to strain accommodation by different mechanisms in the individual crystals, generating remarkably different microstructures. Crystals suitably oriented for basal slip, for example, accommodated strain mainly viscously and experienced only minor fracturing. Instead, crystals misoriented for basal slip hardened and deformed predominantly by domainal fracturing. This study indicates the importance of considering shear zones as dynamic systems wherein the activated deformation mechanisms may vary through time in response to the complex temporal and spatial evolution of the shear zone, often in a cyclic fashion.

Late Palaeozoic to Triassic evolution of the Turan and Scythian platforms: The pre-history of the Palaeo-Tethyan closure

NASA Astrophysics Data System (ADS)

Natal'in, Boris A.; Şengör, A. M. Celâl

2005-08-01

A number of en échelon-arranged, southwest-facing arc fragments of Palaeozoic to Jurassic ages, sandwiched between two fairly straight east-northeast trending boundaries, constitute the basement of the Scythian and the Turan platforms located between the Laurasian and Tethyside units. They have until now largely escaped detection owing to extensive Jurassic and younger cover and the inaccessibility of the subsurface data to the international geological community. These units are separated from one another by linear/gently-curved faults of great length and steep dip. Those that are exposed show evidence of strike-slip motion. The arc units originally constituted parts of a single "Silk Road Arc" located somewhere south of the present-day central Asia for much of the Palaeozoic, although by the late Carboniferous they had been united into a continental margin arc south of the Tarim basin and equivalent units to the west and east. They were stacked into their present places in northern Afghanistan, Turkmenistan, Caucasus and the northern Black Sea by large-scale, right-lateral strike-slip coastwise transport along arc-slicing and arc-shaving strike-slip faults in the Triassic and medial Jurassic simultaneously with the subductive elimination of Palaeo-Tethys. This gigantic dextral zone ("the Silk Road transpression") was a trans-Eurasian structure and was active simultaneously with another, similar system, the Gornostaev keirogen and greatly distorted Eurasia. The late Palaeozoic to Jurassic internal deformation of the Dniepr-Donets aulacogen was also a part of the dextral strain in southern Europe. When the emplacement of the Scythian and Turan units was completed, the elimination of Palaeo-Tethys had also ended and Neo-Tethyan arcs were constructed atop their ruins, mostly across their southern parts. The western end of the great dextral zone that emplaced the Turan and Scythian units horsetails just east of north Dobrudja and a small component goes along the Tornquist-Teisseyre lineament.

Evaluation of nitrous oxide as a substitute for sulfur hexafluoride to reduce global warming impacts of ANSI/HPS N13.1 gaseous uniformity testing

NASA Astrophysics Data System (ADS)

Yu, Xiao-Ying; Barnett, J. Matthew; Amidan, Brett G.; Recknagle, Kurtis P.; Flaherty, Julia E.; Antonio, Ernest J.; Glissmeyer, John A.

2018-03-01

The ANSI/HPS N13.1-2011 standard requires gaseous tracer uniformity testing for sampling associated with stacks used in radioactive air emissions. Sulfur hexafluoride (SF6), a greenhouse gas with a high global warming potential, has long been the gas tracer used in such testing. To reduce the impact of gas tracer tests on the environment, nitrous oxide (N2O) was evaluated as a potential replacement to SF6. The physical evaluation included the development of a test plan to record percent coefficient of variance and the percent maximum deviation between the two gases while considering variables such as fan configuration, injection position, and flow rate. Statistical power was calculated to determine how many sample sets were needed, and computational fluid dynamic modeling was utilized to estimate overall mixing in stacks. Results show there are no significant differences between the behaviors of the two gases, and SF6 modeling corroborated N2O test results. Although, in principle, all tracer gases should behave in an identical manner for measuring mixing within a stack, the series of physical tests guided by statistics was performed to demonstrate the equivalence of N2O testing to SF6 testing in the context of stack qualification tests. The results demonstrate that N2O is a viable choice leading to a four times reduction in global warming impacts for future similar compliance driven testing.

A comparison of forming technologies for ceramic gas-turbine engine components

NASA Technical Reports Server (NTRS)

Hengst, R. R.; Heichel, D. N.; Holowczak, J. E.; Taglialavore, A. P.; Mcentire, B. J.

1990-01-01

For over ten years, injection molding and slip casting have been actively developed as forming techniques for ceramic gas turbine components. Co-development of these two processes has continued within the U.S. DOE-sponsored Advanced Turbine Technology Application Project (ATTAP). Progress within ATTAP with respect to these two techniques is summarized. A critique and comparison of the two processes are given. Critical aspects of both processes with respect to size, dimensional control, material properties, quality, cost, and potential for manufacturing scale-up are discussed.

Is the Local Seismicity in Haiti Capable of Imaging the Northern Caribbean Subduction?

NASA Astrophysics Data System (ADS)

Corbeau, J.; Clouard, V.; Rolandone, F.; Leroy, S. D.; de Lepinay, B. M.

2017-12-01

The boundary between the Caribbean (CA) and North American (NAM) plates in the Hispaniola region is the western prolongation of the NAM plate subduction evolving from a frontal subduction in the Lesser Antilles to an oblique collision against the Bahamas platform in Cuba. We analyze P-waveforms arriving at 27 broadband seismic temporary stations deployed along a 200 km-long N-S transect across Haiti, during the Trans-Haiti project. We compute teleseismic receiver functions using the ETMTRF method, and determine crustal thickness and bulk composition (Vp/Vs) using the H-k stacking method. Three distinctive crustal domains are imaged. We relate these domains to crustal terranes that have been accreted along the plate boundary during the northeastwards displacement of the CA plate. We propose a N-S crustal profile across Haiti accounting for the surface geology, shallow structural history and these new seismological constraints. Local seismicity recorded by the temporary network from April 2013 to June 2014 is used to relocate the seismicity. A total of 593 events were identified with magnitudes ranging from 1.6 to 4.5. This local seismicity, predominantly shallow (< 20 km) and situated in the southern part of Haiti along the major Enriquillo-Plantain-Garden strike-slip fault zone (EPGFZ) and offshore in Gonâve Bay, helps us to image deep active structures. Moment tensors for earthquakes with magnitudes between 3 and 4 were calculated by full waveform inversion using the ISOLA software. The analysis of the new moment tensors for the Haiti upper lithosphere indicates that normal, thrust and strike-slip faulting are equitably distributed. We found strike-slip events along the EPGFZ, near the location of the January 12th, 2010 earthquake. Most of the normal events are located in the area of Enriquillo and Azuei lakes, while the thrust events are located on both sides of the southern Peninsula of Haiti. The preliminary seismic data of our Haitian network, even noisy, tend to confirm that the North American slab in western Hispaniola is disappearing and that the scarcity of the seismic events could not be only the effect of the lack of a seismic network. Due to the geometry of the plate boundary, the deformation is predominantly strike-slip and there is no accommodation of an important part of convergence in this area.

Barrier inhomogeneities at vertically stacked graphene-based heterostructures.

PubMed

Lin, Yen-Fu; Li, Wenwu; Li, Song-Lin; Xu, Yong; Aparecido-Ferreira, Alex; Komatsu, Katsuyoshi; Sun, Huabin; Nakaharai, Shu; Tsukagoshi, Kazuhito

2014-01-21

The integration of graphene and other atomically flat, two-dimensional materials has attracted much interest and been materialized very recently. An in-depth understanding of transport mechanisms in such heterostructures is essential. In this study, vertically stacked graphene-based heterostructure transistors were manufactured to elucidate the mechanism of electron injection at the interface. The temperature dependence of the electrical characteristics was investigated from 300 to 90 K. In a careful analysis of current-voltage characteristics, an unusual decrease in the effective Schottky barrier height and increase in the ideality factor were observed with decreasing temperature. A model of thermionic emission with a Gaussian distribution of barriers was able to precisely interpret the conduction mechanism. Furthermore, mapping of the effective Schottky barrier height is unmasked as a function of temperature and gate voltage. The results offer significant insight for the development of future layer-integration technology based on graphene-based heterostructures.

Two types of seismicity accompanying hydraulic fracturing in Harrison County, Ohio - implications for seismic hazard and seismogenic mechanism

NASA Astrophysics Data System (ADS)

Kozlowska, M.; Brudzinski, M.; Friberg, P. A.; Skoumal, R.; Baxter, N. D.; Currie, B.

2017-12-01

While induced seismicity in the United States has mainly been attributed to wastewater disposal, Eastern Ohio has provided cases of seismicity induced by both hydraulic fracturing (HF) and wastewater disposal. In this study, we investigate five cases of seismicity associated with HF in Harrison County, OH. Because of their temporal and spatial isolation from other injection activities, this provide an ideal setting for studying the relationships between high pressure injection and earthquakes. Our analysis reveals two distinct groups of seismicity. Deeper earthquakes occur in the Precambrian crystalline basement, reach larger magnitudes (M>2), have lower b-values (<1), and continue for weeks following stimulation shut down. Shallower earthquakes, on the other hand, occur in Paleozoic sedimentary rocks 400 m below HF, are limited to smaller magnitudes (M<1), have higher b-values (>1.5), and lack post-stimulation activity. We seek the physical explanation of observed difference in earthquakes character and hypothesize that the maturity of faults is the main factor determining sequences b-values. Based on published results of laboratory experiments and fault modeling, we interpret the deep seismicity as slip on more mature faults in the older crystalline rocks and the shallow seismicity as slip on immature faults in the younger, lower viscosity sedimentary rocks. This suggests that HF inducing seismicity on deeper, more mature faults poses higher seismic hazards. The analysis of water and gas production data from these wells suggests that wells inducing deeper seismicity produced more water than wells with shallow seismicity. This indicates more extensive hydrologic connections outside the target reservoir, which may explain why gas production drops more quickly for wells with deeper seismicity. Despite these indications that hydraulic pressure fluctuations induce seismicity, we also find only 2-3 hours between onset of stimulation of HF wells and seismicity that is too short for typical fluid pressure diffusion rates across distances of 1 km. We conclude that a combination of pore fluid pressure changes and poroelastic stress changes are responsible for inducing shear slip during HF.

Singlet Fission and Excimer Formation in Disordered Solids of Alkyl-Substituted 1,3-Diphenylisobenzofurans.

PubMed

Dron, Paul I; Michl, Josef; Johnson, Justin C

2017-11-16

We describe the preparation and excited state dynamics of three alkyl derivatives of 1,3-diphenylisobenzofuran (1) in both solutions and thin films. The substitutions are intended to disrupt the slip-stacked packing observed in crystals of 1 while maintaining the favorable energies of singlet and triplet for singlet fission (SF). All substitutions result in films that are largely amorphous as judged by the absence of strong X-ray diffraction peaks. The films of 1 carrying a methyl in the para position of one phenyl ring undergo SF relatively efficiently (≥75% triplet yield, Φ T ) but more slowly than thin films of 1. When the methyl is replaced with a t-butyl, kinetic competition in the excited state favors excimer formation rather than SF (Φ T = 55%). When t-Bu groups are placed in both meta positions of the phenyl substituent, SF is slowed further and Φ T = 35%.

Pressure Dependence of the Peierls Stress in Aluminum

NASA Astrophysics Data System (ADS)

Dang, Khanh; Spearot, Douglas

2018-03-01

The effect of pressure applied normal to the {111} slip plane on the Peierls stress in Al is studied via atomistic simulations. Edge, screw, 30°, and 60° straight dislocations are created using the Volterra displacement fields for isotropic elasticity. For each dislocation character angle, the Peierls stress is calculated based on the change in the internal energy, which is an invariant measure of the dislocation driving force. It is found that the Peierls stress for dislocations under zero pressure is in general agreement with previous results. For screw and 60° dislocations, the Peierls stress versus pressure relationship has maximum values associated with stacking fault widths that are multiples of the Peierls period. For the edge dislocation, the Peierls stress decreases with increasing pressure from tension to compression. Compared with the Mendelev potential, the Peierls stress calculated from the Mishin potential is more sensitive to changes in pressure.

Deformation and erosion of f.c.c. metals and alloys under cavitation attack

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1984-01-01

Experimental investigations have been conducted to determine the early stages of cavitation attack on 6061-T6 aluminum alloy, electrolytic tough pitch copper, brass, and bronze, all having polycrystalline fcc matrices. The surface profiles and scanning electron micrographs show that the pits are initially formed at the grain boundaries, while the grain surfaces are progressively roughened by multiple slip and twinning. The initial erosion is noted to have occurred from the material in the grain boundaries, as well as by fragmentation of part of the grains. Further erosion occurred by shearing and necking of the surface undulations caused by plastic deformation. The mean penetration depth, computed on the basis of mass loss, was lowest on the bronze and greatest on the copper. Attention is given to the relation of cavitation attack to grain size, glide stress and stacking fault energy.

Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing.

PubMed

McAdam, C John; Hanton, Lyall R; Moratti, Stephen C; Simpson, Jim

2015-12-01

The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure.

Instabilities in wormlike micelle systems. From shear-banding to elastic turbulence.

PubMed

Fardin, M-A; Lerouge, S

2012-09-01

Shear-banding is ubiquitous in complex fluids. It is related to the organization of the flow into macroscopic bands bearing different viscosities and local shear rates and stacked along the velocity gradient direction. This flow-induced transition towards a heterogeneous flow state has been reported in a variety of systems, including wormlike micellar solutions, telechelic polymers, emulsions, clay suspensions, colloidal gels, star polymers, granular materials, or foams. In the past twenty years, shear-banding flows have been probed by various techniques, such as rheometry, velocimetry and flow birefringence. In wormlike micelle solutions, many of the data collected exhibit unexplained spatio-temporal fluctuations. Different candidates have been identified, the main ones being wall slip, interfacial instability between bands or bulk instability of one of the bands. In this review, we present experimental evidence for a purely elastic instability of the high shear rate band as the main origin for fluctuating shear-banding flows.

Precise tremor source locations and amplitude variations along the lower-crustal central San Andreas Fault

USGS Publications Warehouse

Shelly, David R.; Hardebeck, Jeanne L.

2010-01-01

We precisely locate 88 tremor families along the central San Andreas Fault using a 3D velocity model and numerous P and S wave arrival times estimated from seismogram stacks of up to 400 events per tremor family. Maximum tremor amplitudes vary along the fault by at least a factor of 7, with by far the strongest sources along a 25 km section of the fault southeast of Parkfield. We also identify many weaker tremor families, which have largely escaped prior detection. Together, these sources extend 150 km along the fault, beneath creeping, transitional, and locked sections of the upper crustal fault. Depths are mostly between 18 and 28 km, in the lower crust. Epicenters are concentrated within 3 km of the surface trace, implying a nearly vertical fault. A prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6.0 Parkfield earthquake.

The ABCD matrix for parabolic reflectors and its application to astigmatism free four-mirror cavities

NASA Astrophysics Data System (ADS)

Dupraz, K.; Cassou, K.; Martens, A.; Zomer, F.

2015-10-01

The ABCD matrix for parabolic reflectors is derived for any incident angles. It is used in numerical studies of four-mirror cavities composed of two flat and two parabolic mirrors. Constraints related to laser beam injection efficiency, optical stability, cavity-mode, beam-waist size and high stacking power are satisfied. A dedicated alignment procedure leading to stigmatic cavity-modes is employed to overcome issues related to the optical alignment of parabolic reflectors.

Ultra-sensitive speciation analysis of mercury by CE-ICP-MS together with field-amplified sample stacking injection and dispersive solid-phase extraction.

PubMed

Chen, YiQuan; Cheng, Xian; Mo, Fan; Huang, LiMei; Wu, Zujian; Wu, Yongning; Xu, LiangJun; Fu, FengFu

2016-04-01

A simple dispersive solid-phase extraction (DSPE) used to extract and preconcentrate ultra-trace MeHg, EtHg and Hg(2+) from water sample, and a sensitive method for the simultaneous analysis of MeHg, EtHg and Hg(2+) by using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) with field-amplified sample stacking injection (FASI) were first reported in this study. The DSPE used thiol cotton particles as adsorbent, and is simple and effective. It can be used to extract and preconcentrate ultra-trace mercury compounds in water samples within 30 min with a satisfied recovery and no mercury species alteration during the process. The FASI enhanced the sensitivity of CE-ICP-MS with 25-fold, 29-fold and 27-fold for MeHg, EtHg and Hg(2+) , respectively. Using FASI-CE-ICP-MS together with DSPE, we have successfully determined ultra-trace MeHg, EtHg and Hg(2+) in tap water with a limits of quantification (LOQs) of 0.26-0.45 pg/mL, an RSD (n = 3) < 6% and a recovery of 92-108%. Ultra-high sensitivity, as well as much less sample and reagent consumption and low operating cost, make our method a valuable technique to the speciation analysis of ultra-trace mercury. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of deferasirox in human plasma by short-end injection and sweeping with a field-amplified sample stacking and micellar electrokinetic chromatography.

PubMed

Lin, Hung-Ju; Hsieh, Kun-Pin; Chiou, Shyh-Shin; Kou, Hwang-Shang; Wu, Shou-Mei

2016-11-30

A field-amplified sample stacking-sweeping micellar electrokinetic chromatography with short-end injection was established for determination of deferasirox (DFX) in plasma. DFX was extracted from plasma and reconstituted with deionized water (lower conductivity solution). Capillary (effective length, 10cm) was filled with background electrolyte (40mM phosphate buffer, pH 4.5, containing 20% methanol). After sample loading from outlet end at 5psi for 15s, separation was carried out by applying high voltage at 15kV for 10min. Sodium dodecyl sulfate (SDS) was used to sweep DFX for enhancing sensitivity. The optimal CE separation conditions were 40mM phosphate buffer at pH 4.5 containing 100mM SDS and 20% methanol. The analysis time was about 3.5min for DFX. The calibration curve of DFX was ranged from 1 to 20μg/ml. The linearity (r) was more than 0.998. RSD and RE in intra- and inter-day assays were all below 12.14%. The limit of detection (LOD, S/N=3) for DFX was 0.3μg/ml. The sensitivity enhancement factor between sweeping-FASS MEKC and capillary zone electrophoresis is 3.3. Finally, the method was applied for determination of DFX in β-thalassemia patients. Copyright © 2016 Elsevier B.V. All rights reserved.

The Rock Record of Seismic Nucleation: examples from pseudotachylites beneath the Whipple Detachment Fault, eastern California

NASA Astrophysics Data System (ADS)

Ortega-Arroyo, D.; Behr, W. M.; Gentry, E.

2017-12-01

The mechanisms that lead to nucleation and dynamic weakening in the middle crust are not well understood. Proposed mechanisms include flash heating of asperities, thermal pressurization of pore fluids, dynamic instabilities, and fracture interactions. We investigate this issue in the rock record using exhumed mid-crustal rocks exposed beneath the Whipple Detachment fault (WDF) in eastern CA. Analysis of pseudotachylites (PS) beneath the WDF, representing paleo-earthquakes, reveal two types: Type 1 PS exhibit little to no precursory cataclasis and are concentrated along shear bands at the margins of feldspar-rich lenses embedded in more quartz-rich domains. These appear synkinematic with S-C fabrics in the surrounding mylonites and they exhibit finely dynamically recrystallized grains in quartz at their margins, suggesting coeval ductile deformation. By contrast, Type 2 PS occur along the principal slip surface of a brittle shear zone and show evidence for precursory cataclasis, brecciation, and fracturing. Some cataclasites inject into the host rock, forming eddies along the boundary with the PS. Slip appears to localize progressively into a 2 cm thick fault core, with PS concentrated primarily in the interior- the presence of solidified melt and fluidized cataclasite as clasts within the fault core suggests multiple slip events are preserved. We interpret the two types of pseudotachylites to represent different conditions and mechanisms of earthquake nucleation near the brittle-ductile transition (BDT). Type 1 PS are interpreted to represent nucleation in deeper sections of the BDT by failure along mineralogically-controlled stress concentrations hosted within an otherwise viscously deforming mylonite. Our data suggest that these do not develop into large-magnitude EQ's because seismic slip is dampened into the surrounding quartz-rich viscous matrix; instead they may represent deep microseismicity and/or seismic tremor. By contrast, Type 2 PS are interpreted to nucleate when thermally pressurized pore fluids are able to escape into the permeable damage zone, causing a recovery in the fault's effective friction, and promoting melting. Type 2 PS appear to experience greater weakening, accumulate larger slip, and may represent larger-magnitude seismicity at the base of the seismogenic zone.

Diffusion of chemically reactive species in MHD oscillatory flow with thermal radiation in the presence of constant suction and injection

NASA Astrophysics Data System (ADS)

Sasikumar, J.; Bhuvaneshwari, S.; Govindarajan, A.

2018-04-01

In this project, it is proposed to investigate the effect of suction/injection on the unsteady oscillatory flow of an incompressible viscous electrically conducting fluid through a channel filled with porous medium and non-uniform wall temperature. The fluid is subjected to a uniform magnetic field normal to the channel and the velocity slip at the cold plate is taken into consideration. With the assumption of magnetic Reynolds number to be very small, the induced magnetic field is neglected. Assuming pressure gradient to be oscillatory across the ends of the channel, resulting flow as unsteady oscillatory flow. Under the usual Bousinessq approximation, a mathematical model representing this fluid flow consisting of governing equations with boundary conditions will be developed. Closed form solutions of the dimensionless governing equations of the fluid flow, namely momentum equation, energy equation and species concentration can be obtained . The effects of heat radiation and chemical reaction with suction and injection on temperature, velocity and species concentration profiles will be analysed with tables and graphs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutqvist, Jonny; Cappa, Frederic; Rinaldi, Antonio P.

We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about M w = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzedmore » the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic M w = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO 2 leakage, but would certainly be felt by the local population.« less

Modes of orogen-parallel stretching and extensional exhumation in response to microplate indentation and roll-back subduction (Tauern Window, Eastern Alps)

NASA Astrophysics Data System (ADS)

Scharf, A.; Handy, M. R.; Favaro, S.; Schmid, S. M.; Bertrand, A.

2013-09-01

The Tauern Window exposes a Paleogene nappe stack consisting of highly metamorphosed oceanic (Alpine Tethys) and continental (distal European margin) thrust sheets. In the eastern part of this window, this nappe stack (Eastern Tauern Subdome, ETD) is bounded by a Neogene system of shear (the Katschberg Shear Zone System, KSZS) that accommodated orogen-parallel stretching, orogen-normal shortening, and exhumation with respect to the structurally overlying Austroalpine units (Adriatic margin). The KSZS comprises a ≤5-km-thick belt of retrograde mylonite, the central segment of which is a southeast-dipping, low-angle extensional shear zone with a brittle overprint (Katschberg Normal Fault, KNF). At the northern and southern ends of this central segment, the KSZS loses its brittle overprint and swings around both corners of the ETD to become subvertical, dextral, and sinistral strike-slip faults. The latter represent stretching faults whose displacements decrease westward to near zero. The kinematic continuity of top-east to top-southeast ductile shearing along the central, low-angle extensional part of the KSZS with strike-slip shearing along its steep ends, combined with maximum tectonic omission of nappes of the ETD in the footwall of the KNF, indicates that north-south shortening, orogen-parallel stretching, and normal faulting were coeval. Stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the KSZS to have begun at 23-21 Ma, leading to rapid cooling between 21 and 16 Ma. This exhumation involved a combination of tectonic unroofing by extensional shearing, upright folding, and erosional denudation. The contribution of tectonic unroofing is greatest along the central segment of the KSZS and decreases westward to the central part of the Tauern Window. The KSZS formed in response to the indentation of wedge-shaped blocks of semi-rigid Austroalpine basement located in front of the South-Alpine indenter that was part of the Adriatic microplate. Northward motion of this indenter along the sinistral Giudicarie Belt offsets the Periadriatic Fault and triggered rapid exhumation of orogenic crust within the entire Tauern Window. Exhumation involved strike-slip and normal faulting that accommodated about 100 km of orogen-parallel extension and was contemporaneous with about 30 km of orogen-perpendicular, north-south shortening of the ETD. Extension of the Pannonian Basin related to roll-back subduction in the Carpathians began at 20 Ma, but did not affect the Eastern Alps before about 17 Ma. The effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the Tauern Window area. Therefore, we propose that roll-back subduction temporarily enhanced rather than triggered exhumation and orogen-parallel motion in the Eastern Alps. Lateral extrusion and orogen-parallel extension in the Eastern Alps have continued from 12 to 10 Ma to the present and are driven by northward push of Adria.

Source parameters of microearthquakes on an interplate asperity off Kamaishi, NE Japan over two earthquake cycles

USGS Publications Warehouse

Uchida, Naoki; Matsuzawa, Toru; Ellsworth, William L.; Imanishi, Kazutoshi; Shimamura, Kouhei; Hasegawa, Akira

2012-01-01

We have estimated the source parameters of interplate earthquakes in an earthquake cluster off Kamaishi, NE Japan over two cycles of M~ 4.9 repeating earthquakes. The M~ 4.9 earthquake sequence is composed of nine events that occurred since 1957 which have a strong periodicity (5.5 ± 0.7 yr) and constant size (M4.9 ± 0.2), probably due to stable sliding around the source area (asperity). Using P- and S-wave traveltime differentials estimated from waveform cross-spectra, three M~ 4.9 main shocks and 50 accompanying microearthquakes (M1.5–3.6) from 1995 to 2008 were precisely relocated. The source sizes, stress drops and slip amounts for earthquakes of M2.4 or larger were also estimated from corner frequencies and seismic moments using simultaneous inversion of stacked spectral ratios. Relocation using the double-difference method shows that the slip area of the 2008 M~ 4.9 main shock is co-located with those of the 1995 and 2001 M~ 4.9 main shocks. Four groups of microearthquake clusters are located in and around the mainshock slip areas. Of these, two clusters are located at the deeper and shallower edge of the slip areas and most of these microearthquakes occurred repeatedly in the interseismic period. Two other clusters located near the centre of the mainshock source areas are not as active as the clusters near the edge. The occurrence of these earthquakes is limited to the latter half of the earthquake cycles of the M~ 4.9 main shock. Similar spatial and temporal features of microearthquake occurrence were seen for two other cycles before the 1995 M5.0 and 1990 M5.0 main shocks based on group identification by waveform similarities. Stress drops of microearthquakes are 3–11 MPa and are relatively constant within each group during the two earthquake cycles. The 2001 and 2008 M~ 4.9 earthquakes have larger stress drops of 41 and 27 MPa, respectively. These results show that the stress drop is probably determined by the fault properties and does not change much for earthquakes rupturing in the same area. The occurrence of microearthquakes in the interseismic period suggests the intrusion of aseismic slip, causing a loading of these patches. We also found that some earthquakes near the centre of the mainshock source area occurred just after the earthquakes at the deeper edge of the mainshock source area. These seismic activities probably indicate episodic aseismic slip migrating from the deeper regions in the mainshock asperity to its centre during interseismic periods. Comparison of the source parameters for the 2001 and 2008 main shocks shows that the seismic moments (1.04 x 1016 Nm and 1.12 x 1016 Nm for the 2008 and 2001 earthquakes, respectively) and source sizes (radius = 570 m and 540 m for the 2008 and 2001 earthquakes, respectively) are comparable. Based on careful phase identification and hypocentre relocation by constraining the hypocentres of other small earthquakes to their precisely located centroids, we found that the hypocentres of the 2001 and 2008 M~ 4.9 events are located in the southeastern part of the mainshock source area. This location does not correspond to either episodic slip area or hypocentres of small earthquakes that occurred during the earthquake cycle.

Peierls-Nabarro modeling of dislocations in UO2

NASA Astrophysics Data System (ADS)

Skelton, Richard; Walker, Andrew M.

2017-11-01

Under conditions of high stress or low temperature, glide of dislocations plays an important role in the deformation of UO2. In this paper, the Peierls-Nabarro model is used to calculate the core widths and Peierls stresses of ½<110> edge and screw dislocations gliding on {100}, {110}, and {111}. The energy of the inelastic displacement field in the dislocation core is parameterized using generalized stacking fault energies, which are calculated atomistically using interatomic potentials. We use seven different interatomic potential models, representing the variety of different models available for UO2. The different models broadly agree on the relative order of the strengths of the different slip systems, with the 1/2<110>{100} edge dislocation predicted to be the weakest slip system and 1/2<110>{110} the strongest. However, the calculated Peierls stresses depend strongly on the interatomic potential used, with values ranging between 2.7 and 12.9 GPa for glide of 1/2<110>{100} edge dislocations, 16.4-32.3 GPa for 1/2<110>{110} edge dislocations, and 6.8-13.6 GPa for 1/2<110>{111} edge dislocations. The glide of 1/2<110> screw dislocations in UO2 is also found to depend on the interatomic potential used, with some models predicting similar Peierls stresses for glide on {100} and {111}, while others predict a unique easy glide direction. Comparison with previous fully atomistic calculations show that the Peierls-Nabarro model can accurately predict dislocation properties in UO2.

Atomistic Simulation of the Rate-Dependent Ductile-to-Brittle Failure Transition in Bicrystalline Metal Nanowires.

PubMed

Tao, Weiwei; Cao, Penghui; Park, Harold S

2018-02-14

The mechanical properties and plastic deformation mechanisms of metal nanowires have been studied intensely for many years. One of the important yet unresolved challenges in this field is to bridge the gap in properties and deformation mechanisms reported for slow strain rate experiments (∼10 -2 s -1 ), and high strain rate molecular dynamics (MD) simulations (∼10 8 s -1 ) such that a complete understanding of strain rate effects on mechanical deformation and plasticity can be obtained. In this work, we use long time scale atomistic modeling based on potential energy surface exploration to elucidate the atomistic mechanisms governing a strain-rate-dependent incipient plasticity and yielding transition for face centered cubic (FCC) copper and silver nanowires. The transition occurs for both metals with both pristine and rough surfaces for all computationally accessible diameters (<10 nm). We find that the yield transition is induced by a transition in the incipient plastic event from Shockley partials nucleated on primary slip systems at MD strain rates to the nucleation of planar defects on non-Schmid slip planes at experimental strain rates, where multiple twin boundaries and planar stacking faults appear in copper and silver, respectively. Finally, we demonstrate that, at experimental strain rates, a ductile-to-brittle transition in failure mode similar to previous experimental studies on bicrystalline silver nanowires is observed, which is driven by differences in dislocation activity and grain boundary mobility as compared to the high strain rate case.

Low-frequency earthquakes reveal punctuated slow slip on the deep extent of the Alpine Fault, New Zealand

USGS Publications Warehouse

Chamberlain, Calum J.; Shelly, David R.; Townend, John; Stern, T.A.

2014-01-01

We present the first evidence of low-frequency earthquakes (LFEs) associated with the deep extension of the transpressional Alpine Fault beneath the central Southern Alps of New Zealand. Our database comprises a temporally continuous 36 month-long catalog of 8760 LFEs within 14 families. To generate this catalog, we first identify 14 primary template LFEs within known periods of seismic tremor and use these templates to detect similar events in an iterative stacking and cross-correlation routine. The hypocentres of 12 of the 14 LFE families lie within 10 km of the inferred location of the Alpine Fault at depths of approximately 20–30 km, in a zone of high P-wave attenuation, low P-wave speeds, and high seismic reflectivity. The LFE catalog consists of persistent, discrete events punctuated by swarm-like bursts of activity associated with previously and newly identified tremor periods. The magnitudes of the LFEs range between ML – 0.8 and ML 1.8, with an average of ML 0.5. We find that the frequency-magnitude distribution of the LFE catalog both as a whole and within individual families is not consistent with a power law, but that individual families' frequency-amplitude distributions approximate an exponential relationship, suggestive of a characteristic length-scale of failure. We interpret this LFE activity to represent quasi-continuous slip on the deep extent of the Alpine Fault, with LFEs highlighting asperities within an otherwise steadily creeping region of the fault.

Fast and sensitive method to determine parabens by capillary electrophoresis using automatic reverse electrode polarity stacking mode: application to hair samples.

PubMed

Sako, Alysson V F; Dolzan, Maressa D; Micke, Gustavo Amadeu

2015-09-01

This paper describes a fast and sensitive method for the determination of methyl, ethyl, propyl, and butylparaben in hair samples by capillary electrophoresis using automatic reverse electrode polarity stacking mode. In the proposed method, solutions are injected using the flush command of the analysis software (940 mbar) and the polarity switching is carried out automatically immediately after the sample injection. The advantages compared with conventional stacking methods are the increased analytical frequency, repeatability, and inter-day precision. All analyses were performed in a fused silica capillary (50 cm, 41.5 cm in effective length, 50 μm i.d.), and the background electrolyte was composed of 20 mmol L(-1) sodium tetraborate in 10 % of methanol, pH 9.3. For the reverse polarity, -25 kV/35 s was applied followed by application of +30 kV for the electrophoretic run. Temperature was set at 20 °C, and all analytes were monitored at 297 nm. The method showed acceptable linearity (r (2) > 0.997) in the studied range of 0.1-5.0 mg L(-1), limits of detection below 0.017 mg L(-1), and inter-day, intra-day, and instrumental precision better than 6.2, 3.6, and 4.6 %, respectively. Considering parabens is widely used as a preservative in many products and the reported possibility of damage to the hair and also to human health caused by these compounds, the proposed method was applied to evaluate the adsorption of parabens in hair samples. The results indicate that there is a greater adsorption of methylparaben compared to the other parabens tested and also dyed hairs had a greater adsorption capacity for parabens than natural hairs.

Illuminating the Intricate Details of Tremor and Slow Slip Using an Array of Arrays

NASA Astrophysics Data System (ADS)

Creager, K. C.; Vidale, J. E.; Sweet, J. R.; Chestler, S.; Ghosh, A.

2014-12-01

Our Array of Arrays experiment consisted of eight 1-km aperture arrays, each containing 10-20 three-component continuously recording stations. One of these arrays ran continuously for five years and the others for more than one year. We applied frequency-domain beam forming to each array, and a multi-beam back projection method to detect and locate tremor on the Cascadia subduction plate interface every minute. We have also used the arrays to detect and locate over 10,000 tiny repeating Low-Frequency Earthquakes (LFEs) in dozens of distinct families. Repeating events are detected by autocorrelating every 6-s window with every other one during many 1-hour periods and stacking them across several stations to find repeating events. Clean templates are built for each family by iteratively scanning for new repeats and stacking them into the previous template. LFE catalogs are obtained by scanning templates through years of continuous data. Waveform similarities across LFEs and across stations within arrays are used to estimate seismic moment, double-difference event locations and source spectra. These methods have revealed fascinating space-time patterns in both tremor and LFEs that shed light on the propagation modes of slow slip earthquakes on the subduction plate interface including tremor streaks that propagate 100 km/hour parallel to relative plate motion, Rapid Tremor Reversals that propagate at 10 km/hour, and up to 4 times variations in the 0.4 km/hour along-strike propagation speed of the main rupture front that indicates sticky spots on the plate interface. Rather than following a standard Gutenberg-Richter power-law relation, the distributions of seismic moment of LFEs within each family follow an exponential law, allowing estimates of characteristic size. LFEs for a given family cluster in time. Going up dip, time between LFE bursts vary systematically from about a week to a year, durations from an hour to several days, and characteristic moment magnitudes from 1.25 to 1.85. The characteristic moment for up dip LFEs is thus 8 times bigger than their down-dip counter parts. Double-difference locations indicate that many of the families occur on patches that are elongated in the direction of relative plate motion, perhaps related to structural features on the plate interface.

Botulinum toxin treatment for slipping rib syndrome: a case report.

PubMed

Pirali, Caterina; Santus, Gianna; Faletti, Sofia; De Grandis, Domenico

2013-10-01

Slipping rib syndrome (SRS) is a musculoskeletal cause of severe and recurrent thoracic or abdominal pain. The etiology of SRS is unknown, it seems to arise from costal hypermobility with a tendency of one of the ribs (usually from 8th to 10th but also 11th and 12th have been described) to slip under the superior adjacent rib. Its prevalence is underestimated because SRS is mainly a clinical diagnosis, frequently missed. The critical aspect of the diagnosis is knowledge of the condition itself, which, when lacking, often results in the patient being referred to many different specialists and exposed to unnecessary and costly investigations. The management of the condition includes conservative techniques such as manipulation, localized anesthetic, and steroid or anesthetic nerve block. However, where conservative therapy fails, surgical treatment, with excision of the rib, may be performed. In this paper we describe the case of a patient with persistent and debilitating flank pain who, after many investigations, was diagnosed with SRS. The usual conservative treatment failed, after which we treated the patient with injections of incobotulinumtoxin A into muscles inserting on the inferior side of the rib cage (quadratus lumborum muscle, muscle transversus abdomini, abdominal external oblique muscle, and recto abdomini) achieving a complete relief from pain. To our knowledge botulinum toxin has never been proposed before for the treatment of SRS. We believe that it should be considered as a therapeutic option, especially where other medical treatments have failed or as an intermediate step before surgical intervention.

Induced Seismicity at the UK "Hot Dry Rock" Test Site for Geothermal Energy Production

NASA Astrophysics Data System (ADS)

Li, Xun; Main, Ian; Jupe, Andrew

2018-03-01

In enhanced geothermal systems (EGS), fluid is injected at high pressure in order to stimulate fracturing and/or fluid flow through otherwise relatively impermeable underlying hot rocks to generate power and/or heat. The stimulation induces micro-earthquakes whose precise triggering mechanism and relationship to new and pre-existing fracture networks are still the subject of some debate. Here we analyse the dataset for induced micro-earthquakes at the UK "hot dry rock" experimental geothermal site (Rosemanowes, Cornwall). We quantify the evolution of several metrics used to characterise induced seismicity, including the seismic strain partition factor and the "seismogenic index". The results show a low strain partition factor of 0.01% and a low seismogenenic index indicating that aseismic processes dominate. We also analyse the spatio-temporal distribution of hypocentres, using simple models for the evolution of hydraulic diffusivity by (a) isotropic and (b) anisotropic pore-pressure relaxation. The principal axes of the diffusivity or permeability tensor inferred from the spatial distribution of earthquake foci are aligned parallel to the present-day stress field, although the maximum permeability is vertical, whereas the maximum principal stress is horizontal. Our results are consistent with a triggering mechanism that involves (a) seismic shear slip along optimally-oriented pre-existing fractures, (b) a large component of aseismic slip with creep (c) activation of tensile fractures as hydraulic conduits created by both the present-day stress field and by the induced shear slip, both exploiting pre-existing joint sets exposed in borehole data.

Mathematical modeling of sample stacking methods in microfluidic systems

NASA Astrophysics Data System (ADS)

Horek, Jon

Gradient focusing methods are a general class of experimental techniques used to simultaneously separate and increase the cross-sectionally averaged concentration of charged particle mixtures. In comparison, Field Amplified Sample Stacking (FASS) techniques first concentrate the collection of molecules before separating them. Together, we denote gradient focusing and FASS methods "sample stacking" and study the dynamics of a specific method, Temperature Gradient Focusing (TGF), in which an axial temperature gradient is applied along a channel filled with weak buffer. Gradients in electroosmotic fluid flow and electrophoretic species velocity create the simultaneous separating and concentrating mechanism mentioned above. In this thesis, we begin with the observation that very little has been done to model the dynamics of gradient focusing, and proceed to solve the fundamental equations of fluid mechanics and scalar transport, assuming the existence of slow axial variations and the Taylor-Aris dispersion coefficient. In doing so, asymptotic methods reduce the equations from 3D to 1D, and we arrive at a simple 1D model which can be used to predict the transient evolution of the cross-sectionally averaged analyte concentration. In the second half of this thesis, we run several numerical focusing experiments with a 3D finite volume code. Comparison of the 1D theory and 3D simulations illustrates not only that the asymptotic theory converges as a certain parameter tends to zero, but also that fairly large axial slip velocity gradients lead to quite small errors in predicted steady variance. Additionally, we observe that the axial asymmetry of the electrophoretic velocity model leads to asymmetric peak shapes, a violation of the symmetric Gaussians predicted by the 1D theory. We conclude with some observations on the effect of Peclet number and gradient strength on the performance of focusing experiments, and describe a method for experimental optimization. Such knowledge is useful for design of lab-on-a-chip devices.

Structural and Magnetic Properties of M(mnt)(2) Salts (M = Ni, Pt, Cu) with a Ferrocene-Based Cation, [FcCH(2)N(CH(3))(3)](+). Interplay between M.M and M.S Intermolecular Interactions.

PubMed

Pullen, Anthony E.; Faulmann, Christophe; Pokhodnya, Konstantin I.; Cassoux, Patrick; Tokumoto, Madoka

1998-12-28

A series of metal bis-mnt complexes (mnt = 1,2-dithiolatomaleonitrile) with the trimethylammonium methylferrocene cation have been synthesized and characterized using X-ray diffraction, magnetic susceptibility, and differential scanning calorimetry measurements. The complexes have the formulas (FcCH(2)NMe(3))[Ni(mnt)(2)] (2), (FcCH(2)NMe(3))[Pt(mnt)(2)] (3), and (FcCH(2)NMe(3))(2)[Cu(mnt)(2)] (4) (where Fc = ferrocene). At 300 K, the crystal structures of 1:1 complexes 2 and 3 are very similar. They consist of pairs of [M(mnt)(2)](-) in a slipped configuration packed in stacks. Each [M(mnt)(2)](-) stack is separated from adjacent stacks by two columns of cations. Within the pairs, the [M(mnt)(2)](-) anions interact via short M.S contacts, while there are no short contacts between the pairs. Complex 4, which has a 2:1 stoichiometry, exhibits a markedly different packing arrangement of the anionic units. Due to the special position of the Cu atom in the asymmetric unit cell, [Cu(mnt)(2)](2)(-) dianions are completely isolated from each other. The magnetic susceptibility behavior of the nickel complex is consistent with the presence of magnetically isolated, antiferromagnetically (AF) coupled [Ni(mnt)(2)](-) pairs with the AF exchange parameter, J = -840 cm(-)(1). The platinum complex undergoes an endothermic structural phase transition (T(p)) at 247 K. Below T(p) its structure is characterized by the formation of magnetically isolated [Pt(mnt)(2)](2)(2)(-) dimers in an eclipsed configuration with short Pt.Pt and S.S contacts between monomers. In the magnetic properties, the structural changes reveal themselves as an abrupt susceptibility drop implying a substantial increase of the AF exchange parameter. A mechanism of the phase transition in the platinum compound is proposed. For compound 4, paramagnetic behavior is observed.

Modeling of coulpled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cappa, F.; Rutqvist, J.

2010-06-01

The interaction between mechanical deformation and fluid flow in fault zones gives rise to a host of coupled hydromechanical processes fundamental to fault instability, induced seismicity, and associated fluid migration. In this paper, we discuss these coupled processes in general and describe three modeling approaches that have been considered to analyze fluid flow and stress coupling in fault-instability processes. First, fault hydromechanical models were tested to investigate fault behavior using different mechanical modeling approaches, including slip interface and finite-thickness elements with isotropic or anisotropic elasto-plastic constitutive models. The results of this investigation showed that fault hydromechanical behavior can be appropriatelymore » represented with the least complex alternative, using a finite-thickness element and isotropic plasticity. We utilized this pragmatic approach coupled with a strain-permeability model to study hydromechanical effects on fault instability during deep underground injection of CO{sub 2}. We demonstrated how such a modeling approach can be applied to determine the likelihood of fault reactivation and to estimate the associated loss of CO{sub 2} from the injection zone. It is shown that shear-enhanced permeability initiated where the fault intersects the injection zone plays an important role in propagating fault instability and permeability enhancement through the overlying caprock.« less

Dynamic modeling of injection-induced fault reactivation and ground motion and impact on surface structures and human perception

DOE PAGES

Rutqvist, Jonny; Cappa, Frederic; Rinaldi, Antonio P.; ...

2014-12-31

We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about M w = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzedmore » the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic M w = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO 2 leakage, but would certainly be felt by the local population.« less

Vacuum MOCVD fabrication of high efficience cells

NASA Technical Reports Server (NTRS)

Partain, L. D.; Fraas, L. M.; Mcleod, P. S.; Cape, J. A.

1985-01-01

Vacuum metal-organic-chemical-vapor-deposition (MOCVD) is a new fabrication process with improved safety and easier scalability due to its metal rather than glass construction and its uniform multiport gas injection system. It uses source materials more efficiently than other methods because the vacuum molecular flow conditions allow the high sticking coefficient reactants to reach the substrates as undeflected molecular beams and the hot chamber walls cause the low sticking coefficient reactants to bounce off the walls and interact with the substrates many times. This high source utilization reduces the materials costs power device and substantially decreases the amounts of toxic materials that must be handled as process effluents. The molecular beams allow precise growth control. With improved source purifications, vacuum MOCVD has provided p GaAs layers with 10-micron minority carrier diffusion lengths and GaAs and GaAsSb solar cells with 20% AMO efficiencies at 59X and 99X sunlight concentration ratios. Mechanical stacking has been identified as the quickest, most direct and logical path to stacked multiple-junction solar cells that perform better than the best single-junction devices. The mechanical stack is configured for immediate use in solar arrays and allows interconnections that improve the system end-of-life performance in space.

Room-temperature lasing operation of a quantum-dot vertical-cavity surface-emitting laser

NASA Astrophysics Data System (ADS)

Saito, Hideaki; Nishi, Kenichi; Ogura, Ichiro; Sugou, Shigeo; Sugimoto, Yoshimasa

1996-11-01

Self-assembled growth of quantum dots by molecular-beam epitaxy is used to form the active region of a vertical-cavity surface-emitting laser (VCSEL). Ten layers of InGaAs quantum dots are stacked in order to increase the gain. This quantum-dot VCSEL has a continuous-wave operating current of 32 mA at room temperature. Emission spectra at various current injections demonstrate that the lasing action is associated with a higher-order transition in the quantum dots.

Evaluation of nitrous oxide as a substitute for sulfur hexafluoride to reduce global warming impacts of ANSI/HPS N13.1 gaseous uniformity testing

DOE PAGES

Yu, Xiao-Ying; Barnett, J. Matthew; Amidan, Brett G.; ...

2017-12-12

The ANSI/HPS N13.1–2011 standard requires gaseous tracer uniformity testing for sampling associated with stacks used in radioactive air emissions. Sulfur hexafluoride (SF 6), a greenhouse gas with a high global warming potential, has long been the gas tracer used in such testing. To reduce the impact of gas tracer tests on the environment, nitrous oxide (N 2O) was evaluated as a potential replacement to SF 6. The physical evaluation included the development of a test plan to record percent coefficient of variance and the percent maximum deviation between the two gases while considering variables such as fan configuration, injection position,more » and flow rate. Statistical power was calculated to determine how many sample sets were needed, and computational fluid dynamic modeling was utilized to estimate overall mixing in stacks. Results show there are no significant differences between the behaviors of the two gases, and SF 6 modeling corroborated N 2O test results. Although, in principle, all tracer gases should behave in an identical manner for measuring mixing within a stack, the series of physical tests guided by statistics was performed to demonstrate the equivalence of N 2O testing to SF 6 testing in the context of stack qualification tests. In conclusion, the results demonstrate that N 2O is a viable choice leading to a four times reduction in global warming impacts for future similar compliance driven testing.« less

Evaluation of nitrous oxide as a substitute for sulfur hexafluoride to reduce global warming impacts of ANSI/HPS N13.1 gaseous uniformity testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Xiao-Ying; Barnett, J. Matthew; Amidan, Brett G.

The ANSI/HPS N13.1–2011 standard requires gaseous tracer uniformity testing for sampling associated with stacks used in radioactive air emissions. Sulfur hexafluoride (SF 6), a greenhouse gas with a high global warming potential, has long been the gas tracer used in such testing. To reduce the impact of gas tracer tests on the environment, nitrous oxide (N 2O) was evaluated as a potential replacement to SF 6. The physical evaluation included the development of a test plan to record percent coefficient of variance and the percent maximum deviation between the two gases while considering variables such as fan configuration, injection position,more » and flow rate. Statistical power was calculated to determine how many sample sets were needed, and computational fluid dynamic modeling was utilized to estimate overall mixing in stacks. Results show there are no significant differences between the behaviors of the two gases, and SF 6 modeling corroborated N 2O test results. Although, in principle, all tracer gases should behave in an identical manner for measuring mixing within a stack, the series of physical tests guided by statistics was performed to demonstrate the equivalence of N 2O testing to SF 6 testing in the context of stack qualification tests. In conclusion, the results demonstrate that N 2O is a viable choice leading to a four times reduction in global warming impacts for future similar compliance driven testing.« less

Determination of finasteride and its metabolite in urine by dispersive liquid-liquid microextraction combined with field-enhanced sample stacking and sweeping.

PubMed

Chen, Chun-Hsien; Chao, Yu-Ying; Lin, Yi-Hui; Chen, Yen-Ling

2018-04-27

The on-line preconcentration technique of field-enhanced sample stacking and sweeping (FESS-sweeping) are combined with dispersive liquid-liquid microextraction (DLLME) to monitor the concentrations of finasteride, which is used in the treatment of androgenetic alopecia, and its metabolite, finasteride carboxylic acid (M3), in urine samples. DLLME is used to concentrate and eliminate the interferences of urine samples and uses chloroform as an extracting solvent and acetonitrile as a disperser solvent. A high conductivity buffer (HCB) was introduced into capillary and then sample plug (90.7% capillary length) was injected into capillary. After applying voltage, the sodium dodecyl sulfate (SDS) swept the analytes from the low conductivity sample solution into HCB. The analytes were concentrated on the field-enhanced sample stacking boundary. The limit of detection for the analytes is 20 ng mL -1 . The sensitivity enrichment of finasteride and M3 are 362-fold and 480-fold, respectively, compared with the conventional MEKC method. The on-line preconcentration technique of field-enhanced sample stacking and sweeping possess good selectivity because the endogenous steroid did not interfere the detection of finasteride and M3. The analytical technique is applied to investigate the concentrations in urine samples from patients who have been administered finasteride for the treatment of androgenetic alopecia; the amount of M3 detected in 12 h was 72.69 ± 4.18 μg. Copyright © 2018 Elsevier B.V. All rights reserved.

Winding Pack Height Management During Fabrication of the ITER CS Module

NASA Astrophysics Data System (ADS)

Martovetsky, Nicolai N.; Irick, David K.; Reed, Richard P.; Haefelfinger, Rolf; Salazar, Erica

The Central Solenoid (CS) stack consists of six modules, 2.1 m tall each [1]. In order to verify good impregnation, we performed a vacuum pressure impregnation (VPI) test of a full cross section of the CS module (CSM), 40 conductors tall and 14 conductors wide [2]. It was discovered that after preparation of the full cross section stack until completion of the VPI, the stack shrunk in height by 20-25 mm. Our study of the literature and discussions with the leading experts in VPI did not reveal obvious reasons for this change of height, so we launched a study to address this issue. We assembled two 12x1 (tall by wide) arrays and several 7x1 arrays in order to study characteristics of the dry winding pack under compressive force and effects of different fabrication steps. Then we impregnated these arrays in different conditions under compressive force and studied change of height as a result of compression, impregnation, gelling and curing of the stack of insulated conductors. We showed that by controlling the application of the compressive force, before closing the mold and during impregnation, one can reduce the height uncertainty. Most of the height reduction takes place while the glass is dry under the dead weight and the applied compressive force. Reduction of height during injection of the resin and during gelling, curing and cooling of the coil is noticeable, reproducible and relatively small. The paper presents results of our studies and recommendations for assembly and VPI of tall windings.

TEM studies of plasma nitrided austenitic stainless steel.

PubMed

Stróz, D; Psoda, M

2010-03-01

Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

Inter-comb synchronization by mode-to-mode locking

NASA Astrophysics Data System (ADS)

Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo

2016-08-01

Two combs of fiber femtosecond lasers are synchronized through the optical frequency reference created by injection-locking of a diode laser to a single comb mode. Maintaining a mHz-level narrow linewidth, the optical frequency reference permits two combs to be stabilized by mode-to-mode locking with a relative stability of 1.52  ×  10-16 at 10 s with a frequency slip of 2.46 mHz. This inter-comb synchronization can be utilized for applications such as dual-comb spectroscopy or ultra-short pulse synthesis without extra narrow-linewidth lasers.

Dynamics of Rifting in two Active Rift Segments in Afar - Geodetic and Structural Studies - DoRA Project

NASA Astrophysics Data System (ADS)

Doubre, C.; Socquet, A.; Masson, F.; Jacques, E.; Grandin, R.; Nercessian, A.; Kassim, M.; Vergne, J.; Diament, M.; Hinderer, J.; Ayele, A.; Lewi, E.; Calais, E.; Peltzer, G.; Toussaint, R.; de Chaballier, J.; Ballu, V. S.; Luck, B.; King, G. C.; Vigny, C.; Cattin, R.; Tiberi, C.; Kidane, T.; Jalludin, M.; Maggi, A.; Dorbath, C.; Manatschal, G.; Schmittbuhl, J.; Le Moigne, N.; Deroussi, S.

2009-12-01

The DoRA project aims to conduct complementary studies in two volcano-tectonic rifts in the Afar Depression. In Northern Afar, the Wal’is Dabbahu Rift (WD, Ethiopia) is currently undergoing a major rifting episode. This event started in September 2005 with a significant seismic activity. InSAR data revealed the injection of a 65 km-long mega-dyke that opened by up to 8 m, the slip of numerous normal faults and opening of fissures, and a rhyolitic eruption. Similarly, the Asal-Ghoubbet Rift (AG, Djibouti) was affected in 1978 by a smaller episode of rifting associated with the intrusion of a 2 m wide dyke into the crust. Since then, a large catalog of geodetic data that includes recent InSAR time series reveals the importance of non-steady deformation controlling the rift dynamics. Our goal is to gain an understanding of such volcano-tectonic segments on several time scales, including the dyking period itself and the post-event period. The study of the behavior of the AG Rift during its whole post-rifting period offers an image at t+30 years of the WD segment, while keeping in mind important structural and scale differences. First, we propose to build a complete and accurate set of geodetic data (InSAR, cGPS, GPS), covering the period under study. With a narrow temporal sample window, we will precisely describe the aseismic slip affecting the normal faults of these rifts, the periods of sudden slip and/or slip acceleration but also measure the deformation associated with probable future dyke intrusion. Second, we aim to constrain the origin of these displacements and their relation with mass transfers within the crust. Series of gravity measurements will be pursue or initiated in both rifts. Third, the recording of seismic activity is essential to constrain the relative importance of seismic and aseismic deformation. This will also help to evaluate the thickness of the seismogenic layer. Together with structural data collected during a seismic survey in the AG Rift, these results will offer crucial constraints on modeling the rifting dynamics in order to test the relative influences of the rheology, the fault/dyke geometry and fluids on the rupture mechanics, the viscous relaxation, dyke intrusion/inflation and aseismic slip and their interactions. Our multidisciplinary approach should provide important new constraints on the dynamics of rifting along divergent plate boundaries, and ultimately, in other geodynamical contexts affected by aseismic fault slip transients.

Interpretation of Microseismicity Observed From Surface and Borehole Seismic Arrays During Hydraulic Fracturing in Shale - Bedding Plane Slip Model

NASA Astrophysics Data System (ADS)

Stanek, F.; Jechumtalova, Z.; Eisner, L.

2017-12-01

We present a geomechanical model explaining microseismicity induced by hydraulic fracturing in shales developed from many datasets acquired with two most common types of seismic monitoring arrays, surface and dual-borehole arrays. The geomechanical model explains the observed source mechanisms and locations of induced events from two stimulated shale reservoirs. We observe shear dip-slip source mechanisms with nodal planes aligned with location trends. We show that such seismicity can be explained as a shearing along bedding planes caused by aseismic opening of vertical hydraulic fractures. The source mechanism inversion was applied only to selected high-quality events with sufficient signal-to-noise ratio. We inverted P- and P- and S-wave arrival amplitudes to full-moment tensor and decomposed it to shear, volumetric and compensated linear vector dipole components. We also tested an effect of noise presented in the data to evaluate reliability of non-shear components. The observed seismicity from both surface and downhole monitoring of shale stimulations is very similar. The locations of induced microseismic events are limited to narrow depth intervals and propagate along distinct trend(s) showing fracture propagation in direction of maximum horizontal stress from injection well(s). The source mechanisms have a small non-shear component which can be partly explained as an effect of noise in the data, i.e. events represent shearing on faults. We observe predominantly dip-slip events with a strike of the steeper (almost vertical) nodal plane parallel to the fracture propagation. Therefore the other possible nodal plane is almost horizontal. The rake angles of the observed mechanisms divide these dip-slips into two groups with opposite polarities. It means that we observe opposite movements on the nearly identically oriented faults. Realizing a typical structural weakness of shale in horizontal planes, we interpret observed microseismicity as a result of shearing along bedding planes caused by seismically silent (aseismic) vertical fracture opening.

Pore fluid pressure and the seismic cycle

NASA Astrophysics Data System (ADS)

French, M. E.; Zhu, W.; Hirth, G.; Belzer, B.

2017-12-01

In the brittle crust, the critical shear stress required for fault slip decreases with increasing pore fluid pressures according to the effective stress criterion. As a result, higher pore fluid pressures are thought to promote fault slip and seismogenesis, consistent with observations that increasing fluid pressure as a result of wastewater injection is correlated with increased seismicity. On the other hand, elevated pore fluid pressure is also proposed to promote slow stable failure rather than seismicity along some fault zones, including during slow slip in subduction zones. Here we review recent experimental evidence for the roles that pore fluid pressure and the effective stress play in controlling fault slip behavior. Using two sets of experiments on serpentine fault gouge, we show that increasing fluid pressure does decrease the shear stress for reactivation under brittle conditions. However, under semi-brittle conditions as expected near the base of the seismogenic zone, high pore fluid pressures are much less effective at reducing the shear stress of reactivation even though deformation is localized and frictional. We use an additional study on serpentinite to show that cohesive fault rocks, potentially the product of healing and cementation, experience an increase in fracture energy during faulting as fluid pressures approach lithostatic, which can lead to more stable failure. Structural observations show that the increased fracture energy is associated with a greater intensity of transgranular fracturing and delocalization of deformation. Experiments on several lithologies indicate that the stabilizing effect of fluid pressure occurs independent of rock composition and hydraulic properties. Thus, high pore fluid pressures have the potential to either enhance seismicity or promote stable faulting depending on pressure, temperature, and fluid pressure conditions. Together, the results of these studies indicate that pore fluid pressure promotes seismogenesis in the brittle shallow crust where fluid pressures are elevated but sub-lithostatic and promote slow, stable failure near seismic to aseismic transitions and under near-lithostatic fluid pressures.

Development of a 5 kW Prototype Coal-Based Fuel Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuang, Steven S.C.; Mirzababaei, Jelvehnaz; Rismanchian, Azadeh

2014-01-20

The University of Akron Fuel Cell Laboratory pioneered the development of a laboratory scale coal-based fuel cell, which allows the direct use of high sulfur content coal as fuel. The initial research and coal fuel cell technology development (“Coal-based Fuel Cell,” S. S. C. Chuang, PCT Int. Appl. 2006, i.e., European Patent Application, 35 pp. CODEN: PIXXD2 WO 2006028502 A2 20060316) have demonstrated that it is feasible to electrochemically oxidize carbon to CO2, producing electricity. The key innovative concept of this coal-based fuel cell technology is that carbon in coal can be converted through an electrochemical oxidation reaction into manageablemore » carbon dioxide, efficiently generating electricity without involving coal gasification, reforming, and water-gas shift reaction. This study has demonstrated that electrochemical oxidation of carbon can take place on the Ni anode surface and the CO and CO 2 product produced can further react with carbon to initiate the secondary reaction. A carbon injection system was developed to inject the solid fuel without bringing air into the anode chamber; a fuel cell stack was developed and tested to demonstrate the feasibility of the fuel cell stack. Further improvement of anode catalyst activity and durability is needed to bring this novel coal fuel cell to a highly efficient, super clean, multi-use electric generation technology, which promises to provide low cost electricity by expanding the utilization of U.S. coal supplies and relieving our dependence on foreign oil.« less

The Pawnee Sequence: Poroelastic Effects from Injection in Osage County, Oklahoma

NASA Astrophysics Data System (ADS)

Barbour, A. J.; Rubinstein, J. L.

2016-12-01

Aggregate multi-year records of wastewater injection in Oklahoma show that the strongest change in injection within 20 km of the 2016 M5.8 Pawnee strike-slip earthquake was in Osage County, where injection rates increased rapidly in late-2012 by nearly a factor of three above previous levels. After this increase, rates there declined steadily over two years to an average rate characteristic of all other injection wells in Pawnee and Noble Counties, remaining relatively constant until the beginning of the earthquake sequence. Here we test if poroelastic effects associated with this injection-rate transient can help explain the relative timing between peak injection rates and the beginning of the Pawnee sequence. Although the alternative hypothesis that regional-scale faults and fractures in critically stressed rock serve as fast-pathways for fluid diffusion cannot be ruled out, it appears to be difficult to reconcile based solely on injection data and space-time patterns for this seismic sequence. We simulate the cylindrically symmetric, transient strain and pore pressure fields for an injection-source time function emulating the injection history in a layered half-space in accordance with linear poroelasticity. In the simulation domain, injection occurs at depths of 1300 - 1900 m, into a homogeneous basal sedimentary reservoir representing the Arbuckle Group, overlying a semi-infinite layer representing granitic basement; we determined the hydraulic, elastic, and poroelastic properties of these layers from published literature. At the mainshock hypocenter, this numerical model predicts a delay between peak injection rates and pore pressure increase that is strongly dependent on hydraulic diffusivity; however, the duration is also controlled by the bulk elastic properties and the undrained Skempton's coefficient of the rock. Furthermore, because of fluid-strain coupling, pore pressures in the basement rock decrease during this delay period, which would tend to stabilize temporarily a critically stressed fault. Even though pore pressure diffusion is the dominant mechanism at play, poroelastic effects do affect the relative timing assuming a reasonable set of material parameters, even though strain rates in the basement are relatively low compared to rates in the Arbuckle layer (and above).

Reduced electron back-injection in Al2O3/AlOx/Al2O3/graphene charge-trap memory devices

NASA Astrophysics Data System (ADS)

Lee, Sejoon; Song, Emil B.; Min Kim, Sung; Lee, Youngmin; Seo, David H.; Seo, Sunae; Wang, Kang L.

2012-12-01

A graphene charge-trap memory is devised using a single-layer graphene channel with an Al2O3/AlOx/Al2O3 oxide stack, where the ion-bombarded AlOx layer is intentionally added to create an abundance of charge-trap sites. The low dielectric constant of AlOx compared to Al2O3 reduces the potential drop in the control oxide Al2O3 and suppresses the electron back-injection from the gate to the charge-storage layer, allowing the memory window of the device to be further extended. This shows that the usage of a lower dielectric constant in the charge-storage layer compared to that of the control oxide layer improves the memory performance for graphene charge-trap memories.

Dual-Wavelength InGaAsSb/AlGaAsSb Quantum-Well Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Nguyen, Tien Dai; Hwang, Jehwan; Kim, Yeongho; Kim, Eui-Tae; Kim, Jun Oh; Lee, Sang Jun

2018-05-01

We have investigated the structural characteristics and the device performance of three-stack InGaAsSb/AlGaAsSb quantum-well (QW) light-emitting diodes (LEDs) grown by using molecular beam epitaxy. The QW LED structure with an 8-nm well thickness had a single peak emission wavelength of 2.06 μm at an injection current of 0.3 A at room temperature. However, the QWLEDs with three different well thicknesses of 5-, 10-, and 15-nm had double peak emission wavelengths of 1.97 and 2.1 μm at an injection current of 1.1 A, which were associated with the radiative recombination in the QW with a 5-nm well thickness and the overlapped emission from the QWs with 10- and 15-nm well thicknesses, respectively.

Weak Bond-Based Injectable and Stimuli Responsive Hydrogels for Biomedical Applications

PubMed Central

Ding, Xiaochu; Wang, Yadong

2017-01-01

Here we define hydrogels crosslinked by weak bonds as physical hydrogels. They possess unique features including reversible bonding, shear thinning and stimuli-responsiveness. Unlike covalently crosslinked hydrogels, physical hydrogels do not require triggers to initiate chemical reactions for in situ gelation. The drug can be fully loaded in a pre-formed hydrogel for delivery with minimal cargo leakage during injection. These benefits make physical hydrogels useful as delivery vehicles for applications in biomedical engineering. This review focuses on recent advances of physical hydrogels crosslinked by weak bonds: hydrogen bonds, ionic interactions, host-guest chemistry, hydrophobic interactions, coordination bonds and π-π stacking interactions. Understanding the principles and the state of the art of gels with these dynamic bonds may give rise to breakthroughs in many biomedical research areas including drug delivery and tissue engineering. PMID:29062484

Modified electrokinetic sample injection method in chromatography and electrophoresis analysis

DOEpatents

Davidson, J. Courtney; Balch, Joseph W.

2001-01-01

A sample injection method for horizontal configured multiple chromatography or electrophoresis units, each containing a number of separation/analysis channels, that enables efficient introduction of analyte samples. This method for loading when taken in conjunction with horizontal microchannels allows much reduced sample volumes and a means of sample stacking to greatly reduce the concentration of the sample. This reduction in the amount of sample can lead to great cost savings in sample preparation, particularly in massively parallel applications such as DNA sequencing. The essence of this method is in preparation of the input of the separation channel, the physical sample introduction, and subsequent removal of excess material. By this method, sample volumes of 100 nanoliter to 2 microliters have been used successfully, compared to the typical 5 microliters of sample required by the prior separation/analysis method.

Tying the spectral ends of the M9.0 Tohoku-Oki earthquake sequence: High-frequency radiators and early quasi-static afterslip

NASA Astrophysics Data System (ADS)

Inbal, A.; Ampuero, J. P.; Avouac, J.; Lengliné, O.; Helmberger, D. V.

2012-12-01

The March 11, 2011 M9.0 Tohoku-Oki earthquake was recorded by dense seismological and geodetical networks deployed in Japan, as well as by a vast number of seismic stations worldwide. These observations allow us to study the properties of the subduction interface with unprecedented accuracy and resolution. Here we examine the spectral tails of the co- and post-seismic stages using local geodetic and seismological recordings. First, we study the details of high-frequency (HF) energy radiation during the rupture by using strong-motion recordings. Second, we jointly invert 1Hz GPS, ocean-bottom GPS and aftershock data for the spatio-temporal distribution of early afterslip. In order to constrain the spatial distribution of HF radiators we model waveform envelopes recorded by Kik-net borehole accelerometers located in northeastern Japan. We compute theoretical envelopes for waves traveling in a heterogeneous scattering medium, and invert for the location and amplitude of energy radiators for frequencies ranging from 1 to 16 Hz. Because the inversion is extremely sensitive to the response of individual sites, we adopt an empirical approach and iteratively separate the source and site terms from the stacked spectra of numerous events recorded by the network. The output response functions for each site are used to stabilize the inversion. Preliminary results are consistent with far-field observations and suggest that the HF energy emitted during the M9.0 event originated at the down-dip limit of the rupture zone. We apply waveform cross-correlation to identify repeating events within the aftershock sequence, and locate them by match-filtering their waveforms with known templates. Many of these events occur on seismic asperities loaded by the surrounding creep. We jointly invert the slip histories on these fault patches and the available GPS data for the spatio-temporal distribution of afterslip during the first few hours following the mainshock. We use the Principal Component Analysis Inversion Method to determine the time history of slip on the megathrust during seismic slip and aseismic afterslip. The eigenfunctions are constrained in an iterative process that incorporates the slip histories of seismic asperities. This approach allows documenting the seismic and aseismic phases in a self-consistent manner. The GPS-only inversion places most of the early afterslip east of the hypocenter up to the trench, an area that seemed to have undergone dynamic overshoot.

New-Generation BeiDou (BDS-3) Experimental Satellite Precise Orbit Determination with an Improved Cycle-Slip Detection and Repair Algorithm

PubMed Central

Hu, Chao; Wang, Qianxin; Wang, Zhongyuan; Hernández Moraleda, Alberto

2018-01-01

Currently, five new-generation BeiDou (BDS-3) experimental satellites are working in orbit and broadcast B1I, B3I, and other new signals. Precise satellite orbit determination of the BDS-3 is essential for the future global services of the BeiDou system. However, BDS-3 experimental satellites are mainly tracked by the international GNSS Monitoring and Assessment Service (iGMAS) network. Under the current constraints of the limited data sources and poor data quality of iGMAS, this study proposes an improved cycle-slip detection and repair algorithm, which is based on a polynomial prediction of ionospheric delays. The improved algorithm takes the correlation of ionospheric delays into consideration to accurately estimate and repair cycle slips in the iGMAS data. Moreover, two methods of BDS-3 experimental satellite orbit determination, namely, normal equation stacking (NES) and step-by-step (SS), are designed to strengthen orbit estimations and to make full use of the BeiDou observations in different tracking networks. In addition, a method to improve computational efficiency based on a matrix eigenvalue decomposition algorithm is derived in the NES. Then, one-year of BDS-3 experimental satellite precise orbit determinations were conducted based on iGMAS and Multi-GNSS Experiment (MGEX) networks. Furthermore, the orbit accuracies were analyzed from the discrepancy of overlapping arcs and satellite laser range (SLR) residuals. The results showed that the average three-dimensional root-mean-square error (3D RMS) of one-day overlapping arcs for BDS-3 experimental satellites (C31, C32, C33, and C34) acquired by NES and SS are 31.0, 36.0, 40.3, and 50.1 cm, and 34.6, 39.4, 43.4, and 55.5 cm, respectively; the RMS of SLR residuals are 55.1, 49.6, 61.5, and 70.9 cm and 60.5, 53.6, 65.8, and 73.9 cm, respectively. Finally, one month of observations were used in four schemes of BDS-3 experimental satellite orbit determination to further investigate the reliability and advantages of the improved methods. It was suggested that the scheme with improved cycle-slip detection and repair algorithm based on NES was optimal, which improved the accuracy of BDS-3 experimental satellite orbits by 34.07%, 41.05%, 72.29%, and 74.33%, respectively, compared with the widely-used strategy. Therefore, improved methods for the BDS-3 experimental satellites proposed in this study are very beneficial for the determination of new-generation BeiDou satellite precise orbits. PMID:29724062

Fluid thermodynamics control thermal weakening during earthquake rupture.

NASA Astrophysics Data System (ADS)

Acosta, M.; Passelegue, F. X.; Schubnel, A.; Violay, M.

2017-12-01

Although fluids are pervasive among tectonic faults, thermo-hydro-mechanical couplings during earthquake slip remain unclear. We report full dynamic records of stick-slip events, performed on saw cut Westerly Granite samples loaded under triaxial conditions at stresses representative of the upper continental crust (σ3' 70 MPa) Three fluid pressure conditions were tested, dry, low , and high pressure (i.e. Pf=0, 1, and 25 MPa). Friction (μ) evolution recorded at 10 MHz sampling frequency showed that, for a single event, μ initially increased from its static pre-stress level, μ0 to a peak value μ p it then abruptly dropped to a minimum dynamic value μd before recovering to its residual value μr, where the fault reloaded elastically. Under dry and low fluid pressure conditions, dynamic friction (μd) was extremely low ( 0.2) and co-seismic slip (δ) was large ( 250 and 200 μm respectively) due to flash heating (FH) and melting of asperities as supported by microstructures. Conversely, at pf=25 MPa, μd was higher ( 0.45), δ was smaller ( 80 μm), and frictional melting was not found. We calculated flash temperatures at asperity contacts including heat buffering by on-fault fluid. Considering the isobaric evolution of water's thermodynamic properties with rising temperature showed that pressurized water controlled fault heating and weakening, through sharp variations of specific heat (cpw) and density (ρw) at water's phase transitions. Injecting the computed flash temperatures into slip-on-a-plane model for thermal pressurization (TP) showed that: (i) if pf was low enough so that frictional heating induced liquid/vapour phase transition, FH operated, allowing very low μd during earthquakes. (ii) Conversely, if pf was high enough that shear heating induced a sharp phase transition directly from liquid to supercritical state, an extraordinary rise in water's specific heat acted as a major energy sink inhibiting FH and limiting TP, allowing higher dynamic fault strengths. Further extrapolation of this simplified model to mid- and low- crustal depths shows that, large cpw rise during phase transitions makes TP the dominant weakening mechanism up to 5 km depth. Increasing depth allows somewhat larger shear stress and reduced cpw rise, and so substantial shear heating at low slip rates, favouring FH for fault weakening.

Fossil rocks of slow earthquake detected by thermal diffusion length

NASA Astrophysics Data System (ADS)

Hashimoto, Yoshitaka; Morita, Kiyohiko; Okubo, Makoto; Hamada, Yohei; Lin, Weiren; Hirose, Takehiro; Kitamura, Manami

2016-04-01

Fault motion has been estimated by diffusion pattern of frictional heating recorded in geology (e.g., Fulton et al., 2012). The same record in deeper subduction plate interface can be observed from micro-faults in an exhumed accretionary complex. In this study, we focused on a micro-fault within the Cretaceous Shimanto Belt, SW Japan to estimate fault motion from the frictional heating diffusion pattern. A carbonaceous material concentrated layer (CMCL) with ~2m of thickness is observed in study area. Some micro-faults cut the CMCL. Thickness of a fault is about 3.7mm. Injection veins and dilatant fractures were observed in thin sections, suggesting that the high fluid pressure was existed. Samples with 10cm long were collected to measure distribution of vitrinite reflectance (Ro) as a function of distance from the center of micro-fault. Ro of host rock was ~1.0%. Diffusion pattern was detected decreasing in Ro from ~1.2%-~1.1%. Characteristic diffusion distance is ~4-~9cm. We conducted grid search to find the optimal frictional heat generation per unit area per second (Q (J/m^2/s), the product of friction coefficient, normal stress and slip velocity) and slip duration (t(s)) to fit the diffusion pattern. Thermal diffusivity (0.98*10^8m^2/s) and thermal conductivity (2.0 w/mK) were measured. In the result, 2000-2500J/m^2/s of Q and 63000-126000s of t were estimated. Moment magnitudes (M0) of slow earthquakes (slow EQs) follow a scaling law with slip duration and its dimension is different from that for normal earthquakes (normal EQ) (Ide et al., 2007). The slip duration estimated in this study (~10^4-~10^5s) consistent with 4-5 of M0, never fit to the scaling law for normal EQ. Heat generation can be inverted from 4-5 of M0, corresponding with ~10^8-~10^11J, which is consistent with rupture area of 10^5-10^8m2 in this study. The comparisons in heat generation and slip duration between geological measurements and geophysical remote observations give us the estimation of rupture area, M0, and earthquake style, for geological records.

Paper 58714 - Exploring activated faults hydromechanical processes from semi-controled field injection experiments

NASA Astrophysics Data System (ADS)

Guglielmi, Y.; Cappa, F.; Nussbaum, C.

2015-12-01

The appreciation of the sensitivity of fractures and fault zones to fluid-induced-deformations in the subsurface is a key question in predicting the reservoir/caprock system integrity around fluid manipulations with applications to reservoir leakage and induced seismicity. It is also a question of interest in understanding earthquakes source, and recently the hydraulic behavior of clay faults under a potential reactivation around nuclear underground depository sites. Fault and fractures dynamics studies face two key problems (1) the up-scaling of laboratory determined properties and constitutive laws to the reservoir scale which is not straightforward when considering faults and fractures heterogeneities, (2) the difficulties to control both the induced seismicity and the stimulated zone geometry when a fault is reactivated. Using instruments dedicated to measuring coupled pore pressures and deformations downhole, we conducted field academic experiments to characterize fractures and fault zones hydromechanical properties as a function of their multi-scale architecture, and to monitor their dynamic behavior during the earthquake nucleation process. We show experiments on reservoir or cover rocks analogues in underground research laboratories where experimental conditions can be optimized. Key result of these experiments is to highlight how important the aseismic fault activation is compared to the induced seismicity. We show that about 80% of the fault kinematic moment is aseismic and discuss the complex associated fault friction coefficient variations. We identify that the slip stability and the slip velocity are mainly controlled by the rate of the permeability/porosity increase, and discuss the conditions for slip nucleation leading to seismic instability.

Variable modes of rifting in the eastern Basin and Range, USA from on-fault geological evidence

NASA Astrophysics Data System (ADS)

Stahl, T.; Niemi, N. A.

2017-12-01

Continental rifts are often divided along their axes into magmatic (or magma-assisted) and amagmatic (or magma-poor) segments. Less is known about magmatic versus non-magmatic extension across `wide' continental rift margins like the Basin and Range province of the USA. Paleoseismic trench investigations, Quaternary geochronology (10Be and 3He exposure-age, luminescence, and 40Ar/39Ar dating), and high-resolution topographic surveys (terrestrial laser scanning and UAV photogrammetry) were used to assess the timing and spatial variability of faulting at the Basin and Range-Colorado Plateau transition zone in central Utah. Results show that while the majority of strain is accommodated by a single, range- and province-bounding fault (the Wasatch fault zone, WFZ, slip rate of c. 3-4 mm yr-1), a transition to magma-assisted rifting occurs near the WFZ southern termination marked by a diffuse zone of faults associated with Pliocene to Holocene volcanism. Paleoseismic analysis of faults within and adjacent to this zone reveal recent (<18 ka) surface-ruptures on these faults. A single event displacement of 10-15 m for the Tabernacle fault at c. 15-18 ka (3He exposure-age) and large fault displacement gradients imply that slip was coeval with lava emplacement and that the faults in this region are linked, at least in part, to dike injection in the uppermost crust rather than slip at seismogenic depths. These results have implications for the controversial nature of regional seismic hazard and the structural evolution of the eastern Basin and Range.

Induced seismicity at the UK `hot dry rock' test site for geothermal energy production

NASA Astrophysics Data System (ADS)

Li, Xun; Main, Ian; Jupe, Andrew

2018-07-01

In enhanced geothermal systems (EGS), fluid is injected at high pressure in order to stimulate fracturing and/or fluid flow through otherwise relatively impermeable underlying hot rocks to generate power and/or heat. The stimulation induces microearthquakes whose precise triggering mechanism and relationship to new and pre-existing fracture networks are still the subject of some debate. Here, we analyse the data set for induced microearthquakes at the UK `hot dry rock' experimental geothermal site (Rosemanowes, Cornwall). We quantify the evolution of several metrics used to characterise induced seismicity, including the seismic strain partition factor and the `seismogenic index'. The results show a low strain partition factor of 0.01 per cent and a low seismogenic index indicating that aseismic processes dominate. We also analyse the spatio-temporal distribution of hypocentres, using simple models for the evolution of hydraulic diffusivity by (1) isotropic and (2) anisotropic pore-pressure relaxation. The principal axes of the diffusivity or permeability tensor inferred from the spatial distribution of earthquake foci are aligned parallel to the present-day stress field, although the maximum permeability is vertical, whereas the maximum principal stress is horizontal. Our results are consistent with a triggering mechanism that involves (1) seismic shear slip along optimally oriented pre-existing fractures, (2) a large component of aseismic slip with creep and (3) activation of tensile fractures as hydraulic conduits created by both the present-day stress field and by the induced shear slip, both exploiting pre-existing joint sets exposed in borehole data.

Brittle-viscous deformation of vein quartz under fluid-rich low greenschist facies conditions

NASA Astrophysics Data System (ADS)

Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

2015-01-01

A coarse grained, statically crystallized quartz vein, embedded in a phyllonitic matrix, was studied by EBSD and optical microscopy to gain insights into the processes of strain localization in quartz deformed under low-grade conditions, broadly coincident with the frictional-viscous transition. The vein is from a high strain zone at the front of the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The vein was deformed under lower greenschist facies conditions during deformation along a large out-of-sequence phyllonitic thrust of Caledonian age. The host phyllonite formed at the expense of metabasalt wherein feldspar broke down to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the studied quartz vein acted as a relatively rigid body deforming mainly by coaxial strain. Viscous deformation was initially accommodated by basal ⟨a⟩ slip of quartz during the development of a mesoscopic pervasive extensional crenulation cleavage. Under the prevailing boundary conditions, however, dislocation glide-accommodated deformation of quartz resulted inefficient and led to dislocation tangling and strain hardening of the vein. In response to hardening, to the progressive increase of fluid pressure and the increasing competence contrast between the vein and the weak foliated host phyllonite, quartz crystals began to deform frictionally along specific, optimally oriented lattice planes, creating microgouges along microfractures. These were, however, rapidly sealed by nucleation of new grains as transiently over pressured fluids penetrated the deforming system. The new nucleated grains grew initially by solution-precipitation and later by grain boundary migration. Due to the random initial orientation of the vein crystals, strain was accommodated differently in the individual crystals, leading to the development of remarkably different microstructures. Crystals oriented optimally for basal slip accommodated strain mainly viscously and experienced only minor fracturing. Instead, the crystals misoriented for basal slip hardened and deformed by pervasive domainal fracturing. This study indicates the importance of considering shear zones as dynamic systems wherein the activated deformation mechanisms vary transiently in response to the complex temporal and spatial evolution of the shear zone, often in a cyclic fashion.

Role Of Impurities On Deformation Of HCP Crystal: A Multi-Scale Approach

NASA Astrophysics Data System (ADS)

Bhatia, Mehul Anoopkumar

Commercially pure (CP) and extra low interstitial (ELI) grade Ti-alloys present excellent corrosion resistance, lightweight, and formability making them attractive materials for expanded use in transportation and medical applications. However, the strength and toughness of CP titanium are affected by relatively small variations in their impurity/solute content (IC), e.g., O, Al, and V. This increase in strength is due to the fact that the solute either increases the critical stress required for the prismatic slip systems ({10- 10}) or activates another slip system ((0001), {10-11}). In particular, solute additions such as O can effectively strengthen the alloy but with an attendant loss in ductility by changing the behavior from wavy (cross slip) to planar nature. In order to understand the underlying behavior of strengthening by solutes, it is important to understand the atomic scale mechanism. This dissertation aims to address this knowledge gap through a synergistic combination of density functional theory (DFT) and molecular dynamics. Further, due to the long-range strain fields of the dislocations and the periodicity of the DFT simulation cells, it is difficult to apply ab initio simulations to study the dislocation core structure. To alleviate this issue we developed a multiscale quantum mechanics/molecular mechanics approach (QM/MM) to study the dislocation core. We use the developed QM/MM method to study the pipe diffusion along a prismatic edge dislocation core. Complementary to the atomistic simulations, the Semi-discrete Variational Peierls-Nabarro model (SVPN) was also used to analyze the dislocation core structure and mobility. The chemical interaction between the solute/impurity and the dislocation core is captured by the so-called generalized stacking fault energy (GSFE) surface which was determined from DFT-VASP calculations. By taking the chemical interaction into consideration the SVPN model can predict the dislocation core structure and mobility in the presence and absence of the solute/impurity and thus reveal the effect of impurity/solute on the softening/hardening behavior in alpha-Ti. Finally, to study the interaction of the dislocation core with other planar defects such as grain boundaries (GB), we develop an automated method to theoretically generate GBs in HCP type materials.

Exploiting broadband seismograms and the mechanism of deep-focus earthquakes

NASA Astrophysics Data System (ADS)

Jiao, Wenjie

1997-09-01

Modern broadband seismic instrumentation has provided enormous opportunities to retrieve the information in almost any frequency band of seismic interest. In this thesis, we have investigated the long period responses of the broadband seismometers and the problem of recovering actual groundmotion. For the first time, we recovered the static offset for an earthquake from dynamic seismograms. The very long period waves of near- and intermediate-field term from 1994 large Bolivian deep earthquake (depth = 630km, Msb{W}=8.2) and 1997 large Argentina deep earthquake (depth = 285km, Msb{W}=7.1) are successfully recovered from the portable broadband recordings by BANJO and APVC networks. These waves provide another dynamic window into the seismic source process and may provide unique information to help constrain the source dynamics of deep earthquakes in the future. We have developed a new method to locate global explosion events based on broadband waveform stacking and simulated annealing. This method utilizes the information provided by the full broadband waveforms. Instead of "picking times", the character of the wavelet is used for locating events. The application of this methodology to a Lop Nor nuclear explosion is very successful, and suggests a procedure for automatic monitoring. We have discussed the problem of deep earthquakes from the viewpoint of rock mechanics and seismology. The rupture propagation of deep earthquakes requires a slip-weakening process unlike that for shallow events. However, this process is not necessarily the same as the process which triggers the rupture. Partial melting due to stress release is developed to account for the slip-weakening process in the deep earthquake rupture. The energy required for partial melting in this model is on the same order of the maximum energy required for the slip-weakening process in the shallow earthquake rupture. However, the verification of this model requires experimental work on the thermodynamic properties of rocks under non-hydrostatic stress. The solution of the deep earthquake problem will require an interdisciplinary study of seismology, high pressure rock mechanics, and mineralogy.

Maule MW 8.8 Gravity and Deformation Signature in GRACE Range Data

NASA Astrophysics Data System (ADS)

Ivins, E. R.; Tanaka, Y.; Byun, S. H.; Watkins, M.; Yuan, D.; Klemann, V.

2011-12-01

Shortly after the Feb. 27, 2010 Maule, Chile subduction zone mega-thrust earthquake of energy scale magnitude 8.8, we began to use a data stacking method to examine the effects of the change in gravity field on the GRACE A-B intersatellite range accelerations. The initial discovery of the robust influence of the in co-seismic + afterslip deformational changes could be seen very clearly in the monthly JPL global mascon solution. Detection was, quite independently, reported by Han, Sauber and Luthcke. They also employed the raw ranging data (GRL, Dec., 9, 2010). The detection is important to advancing concepts for both the science and technical capabilities for potential earthquake studies in future space gravimetry experiments. The slip distribution and surface vertical displacements for the Maule quake are fairly well-constrained using terrestrial GPS, InSAR and broadband seismic wave analyses. Pollitz et al. (GRL, May 6, 2011) used a spherical self-gravitating layered earth model to provide a comprehensive simulation of the co-seismic deformation character of the event, noting that the slip distribution was roughly 8 meters over an area of about 1.2 x 105 km2. Much of the slip is projected to areas in the crust/lithosphere that are submarine. GPS recorded as much as 14.2 cm of negative vertical motion at the northern coastline of the rupture field (Delouis et al., GRL, Sept, 10, 2010), while other measurements suggest positive motions on off shore island which emerged by as much as 240 cm. Here we reexamine some of the detection and resolution issues of the gravitational signature, modeling both solid earth and ocean responses and sea-level equation using a layered compressible spherical self-gravitating model as described by Tanaka et al. (2009,2010). Such research helps determine the necessary spatio-temporal density of space and terrestrial gravity observations that are required for improving our understanding of the deformation in the off-shore subduction-zone environment where GPS and InSAR observations cannot be made.

Frequency-dependent moment release of very low frequency earthquakes in the Cascadia subduction zone

NASA Astrophysics Data System (ADS)

Takeo, A.; Houston, H.

2014-12-01

Episodic tremor and slip (ETS) has been observed in Cascadia subduction zone at two different time scales: tremor at a high-frequency range of 2-8 Hz and slow slip events at a geodetic time-scale of days-months. The intermediate time scale is needed to understand the source spectrum of slow earthquakes. Ghosh et al. (2014, IRIS abs) recently reported the presence of very low frequency earthquakes (VLFEs) in Cascadia. In southwest Japan, VLFEs are usually observed at a period range around 20-50 s, and coincide with tremors (e.g., Ito et al. 2007). In this study, we analyzed VLFEs in and around the Olympic Peninsula to confirm their presence and estimate their moment release. We first detected VLFE events by using broadband seismograms with a band-pass filter of 20-50 s. The preliminary result shows that there are at least 16 VLFE events with moment magnitudes of 3.2-3.7 during the M6.8 2010 ETS. The focal mechanisms are consistent with the thrust earthquakes at the subducting plate interface. To detect signals of VLFEs below noise level, we further stacked long-period waveforms at the peak timings of tremor amplitudes for tremors within a 10-15 km radius by using tremor catalogs in 2006-2010, and estimated the focal mechanisms for each tremor source region as done in southwest Japan (Takeo et al. 2010 GRL). As a result, VLFEs could be detected for almost the entire tremor source region at a period range of 20-50 s with average moment magnitudes in each 5-min tremor window of 2.4-2.8. Although the region is limited, we could also detect VLFEs at a period range of 50-100 s with average moment magnitudes of 3.0-3.2. The moment release at 50-100 s is 4-8 times larger than that at 20-50 s, roughly consistent with an omega-squared spectral model. Further study including tremor, slow slip events and characteristic activities, such as rapid tremor reversal and tremor streaks, will reveal the source spectrum of slow earthquakes in a broader time scale from 0.1 s to days.

Fault zone architecture of a major oblique-slip fault in the Rawil depression, Western Helvetic nappes, Switzerland

NASA Astrophysics Data System (ADS)

Gasser, D.; Mancktelow, N. S.

2009-04-01

The Helvetic nappes in the Swiss Alps form a classic fold-and-thrust belt related to overall NNW-directed transport. In western Switzerland, the plunge of nappe fold axes and the regional distribution of units define a broad depression, the Rawil depression, between the culminations of Aiguilles Rouge massif to the SW and Aar massif to the NE. A compilation of data from the literature establishes that, in addition to thrusts related to nappe stacking, the Rawil depression is cross-cut by four sets of brittle faults: (1) SW-NE striking normal faults that strike parallel to the regional fold axis trend, (2) NW-SE striking normal faults and joints that strike perpendicular to the regional fold axis trend, and (3) WNW-ESE striking normal plus dextral oblique-slip faults as well as (4) WSW-ENE striking normal plus dextral oblique-slip faults that both strike oblique to the regional fold axis trend. We studied in detail a beautifully exposed fault from set 3, the Rezli fault zone (RFZ) in the central Wildhorn nappe. The RFZ is a shallow to moderately-dipping (ca. 30-60˚) fault zone with an oblique-slip displacement vector, combining both dextral and normal components. It must have formed in approximately this orientation, because the local orientation of fold axes corresponds to the regional one, as does the generally vertical orientation of extensional joints and veins associated with the regional fault set 2. The fault zone crosscuts four different lithologies: limestone, intercalated marl and limestone, marl and sandstone, and it has a maximum horizontal dextral offset component of ~300 m and a maximum vertical normal offset component of ~200 m. Its internal architecture strongly depends on the lithology in which it developed. In the limestone, it consists of veins, stylolites, cataclasites and cemented gouge, in the intercalated marls and limestones of anastomosing shear zones, brittle fractures, veins and folds, in the marls of anastomosing shear zones, pressure solution seams and veins and in the sandstones of coarse breccia and veins. Later, straight, sharp fault planes cross-cut all these features. In all lithologies, common veins and calcite-cemented fault rocks indicate the strong involvement of fluids during faulting. Today, the southern Rawil depression and the Rhone Valley belong to one of the seismically most active regions in Switzerland. Seismogenic faults interpreted from earthquake focal mechanisms strike ENE-WSW to WNW-ESE, with dominant dextral strike-slip and minor normal components and epicentres at depths of < 15 km. All three Neogene fault sets (2-4) could have been active under the current stress field inferred from the current seismicity. This implies that the same mechanisms that formed these fault zones in the past may still persist at depth. The Rezli fault zone allows the detailed study of a fossil fault zone that can act as a model for processes still occurring at deeper levels in this seismically active region.

Simplified efficient phosphorescent organic light-emitting diodes by organic vapor phase deposition

NASA Astrophysics Data System (ADS)

Pfeiffer, P.; Beckmann, C.; Stümmler, D.; Sanders, S.; Simkus, G.; Heuken, M.; Vescan, A.; Kalisch, H.

2017-12-01

The most efficient phosphorescent organic light-emitting diodes (OLEDs) are comprised of complex stacks with numerous organic layers. State-of-the-art phosphorescent OLEDs make use of blocking layers to confine charge carriers and excitons. On the other hand, simplified OLEDs consisting of only three organic materials have shown unexpectedly high efficiency when first introduced. This was attributed to superior energy level matching and suppressed external quantum efficiency (EQE) roll-off. In this work, we study simplified OLED stacks, manufactured by organic vapor phase deposition, with a focus on charge balance, turn-on voltage (Von), and efficiency. To prevent electrons from leaking through the device, we implemented a compositionally graded emission layer. By grading the emitter with the hole transport material, charge confinement is enabled without additional blocking layers. Our best performing organic stack is composed of only three organic materials in two layers including the emitter Ir(ppy)3 and yields a Von of 2.5 V (>1 cd/m2) and an EQE of 13% at 3000 cd/m2 without the use of any additional light extraction techniques. Changes in the charge balance, due to barrier tuning or adjustments in the grading parameters and layer thicknesses, are clearly visible in the current density-voltage-luminance (J-V-L) measurements. As charge injection at the electrodes and organic interfaces is of great interest but difficult to investigate in complex device structures, we believe that our simplified organic stack is not only a potent alternative to complex state-of-the-art OLEDs but also a well suited test vehicle for experimental studies focusing on the modification of the electrode-organic semiconductor interface.

Two stacked tandem white organic light-emitting diodes employing WO3 as a charge generation layer

NASA Astrophysics Data System (ADS)

Bin, Jong-Kwan; Lee, Na Yeon; Lee, SeungJae; Seo, Bomin; Yang, JoongHwan; Kim, Jinook; Yoon, Soo Young; Kang, InByeong

2016-09-01

Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO3) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL'/B-EML/ETL/N-CGL/P-CGL (WO3 or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO3 as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm2, respectively. This performance with inserting WO3 as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

Trapped charge densities in Al{sub 2}O{sub 3}-based silicon surface passivation layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Paul M., E-mail: Paul.Jordan@namlab.com; Simon, Daniel K.; Dirnstorfer, Ingo

2016-06-07

In Al{sub 2}O{sub 3}-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al{sub 2}O{sub 3} layers are grown by atomic layer deposition with very thin (∼1 nm) SiO{sub 2} or HfO{sub 2} interlayers or interface layers. In SiO{sub 2}/Al{sub 2}O{sub 3} and HfO{sub 2}/Al{sub 2}O{sub 3} stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured inmore » pure Al{sub 2}O{sub 3}. In Al{sub 2}O{sub 3}/SiO{sub 2}/Al{sub 2}O{sub 3} or Al{sub 2}O{sub 3}/HfO{sub 2}/Al{sub 2}O{sub 3} stacks, very high total charge densities of up to 9 × 10{sup 12} cm{sup −2} are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al{sub 2}O{sub 3} layer thickness between silicon and the HfO{sub 2} or the SiO{sub 2} interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al{sub 2}O{sub 3} layers opens the possibility to engineer the field-effect passivation in the solar cells.« less

The Pawnee earthquake as a result of the interplay among injection, faults and foreshocks.

PubMed

Chen, Xiaowei; Nakata, Nori; Pennington, Colin; Haffener, Jackson; Chang, Jefferson C; He, Xiaohui; Zhan, Zhongwen; Ni, Sidao; Walter, Jacob I

2017-07-10

The Pawnee M5.8 earthquake is the largest event in Oklahoma instrument recorded history. It occurred near the edge of active seismic zones, similar to other M5+ earthquakes since 2011. It ruptured a previously unmapped fault and triggered aftershocks along a complex conjugate fault system. With a high-resolution earthquake catalog, we observe propagating foreshocks leading to the mainshock within 0.5 km distance, suggesting existence of precursory aseismic slip. At approximately 100 days before the mainshock, two M ≥ 3.5 earthquakes occurred along a mapped fault that is conjugate to the mainshock fault. At about 40 days before, two earthquakes clusters started, with one M3 earthquake occurred two days before the mainshock. The three M ≥ 3 foreshocks all produced positive Coulomb stress at the mainshock hypocenter. These foreshock activities within the conjugate fault system are near-instantaneously responding to variations in injection rates at 95% confidence. The short time delay between injection and seismicity differs from both the hypothetical expected time scale of diffusion process and the long time delay observed in this region prior to 2016, suggesting a possible role of elastic stress transfer and critical stress state of the fault. Our results suggest that the Pawnee earthquake is a result of interplay among injection, tectonic faults, and foreshocks.

Pressurized capillary electrochromatographic analysis of water-soluble vitamins by combining with on-line concentration technique.

PubMed

Jia, Li; Liu, Yaling; Du, Yanyan; Xing, Da

2007-06-22

A pressurized capillary electrochromatography (pCEC) system was developed for the separation of water-soluble vitamins, in which UV absorbance was used as the detection method and a monolithic silica-ODS column as the separation column. The parameters (type and content of organic solvent in the mobile phase, type and concentration of electrolyte, pH of the electrolyte buffer, applied voltage and flow rate) affecting the separation resolution were evaluated. The combination of two on-line concentration techniques, namely, solvent gradient zone sharpening effect and field-enhanced sample stacking, was utilized to improve detection sensitivity, which proved to be beneficial to enhance the detection sensitivity by enabling the injection of large volumes of samples. Coupling electrokinetic injection with the on-line concentration techniques was much more beneficial for the concentration of positively charged vitamins. Comparing with the conventional injection mode, the enhancement in the detection sensitivities of water-soluble vitamins using the on-line concentration technique is in the range of 3 to 35-fold. The developed pCEC method was applied to evaluate water-soluble vitamins in corns.

Microinjector for blasocysts

DOEpatents

Remenyik, Carl J.; Woychik, Richard P.; Patek, David R.; Hawk, James A.; Turner, John C.

1999-01-01

An electromechanical device for driving the tip of a microinjection cannula, or needle, through the outer barrier of a blastocyst, cell, or cell nucleus for the injection of cells or other bioactive materials. Either a flexible frame or a ram moving within a base member is employed. Cannula motion is achieved by means of a piezoelectric stack and spring return system. The thrust motion over a predetermined microscopic distance is achieved without cannula setback prior to the thrust movement. Instead of specially prepared beveled and tipped needles, standard unimproved cannulas or needles can be used.

Microinjector for blasocysts

DOEpatents

Remenyik, C.J.; Woychik, R.P.; Patek, D.R.; Hawk, J.A.; Turner, J.C.

1999-03-02

An electromechanical device is disclosed for driving the tip of a microinjection cannula, or needle, through the outer barrier of a blastocyst, cell, or cell nucleus for the injection of cells or other bioactive materials. Either a flexible frame or a ram moving within a base member is employed. Cannula motion is achieved by means of a piezoelectric stack and spring return system. The thrust motion over a predetermined microscopic distance is achieved without cannula setback prior to the thrust movement. Instead of specially prepared beveled and tipped needles, standard unimproved cannulas or needles can be used. 6 figs.

High-efficiency non-blocking phosphorescent organic light emitting diode with ultrathin emission layer

NASA Astrophysics Data System (ADS)

Qiu, Jacky; Helander, Michael G.; Wang, Zhibin; Chang, Yi-Lu; Lu, ZhengHong

2012-09-01

Non-blocking Phosphorescent Organic Light Emitting Diode (NB-PHOLED) is a highly simplified device structure that has achieved record high device performance on chlorinated ITO[1], flexible substrates[2], also with Pt based phosphorescent dopants[3] and NB-PHOLED has significantly reduced efficiency roll-off[4]. The principle novel features of NB-PHOLED is the absence of blocking layer in the OLED stack, as well as the absence of organic hole injection layer, this allows for reduction of carrier accumulation in between organic layers and result in higher efficiencies.

Planar array stack design aided by rapid prototyping in development of air-breathing PEMFC

NASA Astrophysics Data System (ADS)

Chen, Chen-Yu; Lai, Wei-Hsiang; Weng, Biing-Jyh; Chuang, Huey-Jan; Hsieh, Ching-Yuan; Kung, Chien-Chih

The polymer electrolyte membrane fuel cell (PEMFC) is one of the most important research topics in the new and clean energy area. The middle or high power PEMFCs can be applied to the transportation or the distributed power system. But for the small power application, it is needed to match the power requirement of the product generally. On the other hand, the direct methanol fuel cell (DMFC) is one of the most common type that researchers are interested in, but recently the miniature or the micro-PEMFCs attract more attention due to their advantages of high open circuit voltage and high power density. The objective of this study is to develop a new air-breathing planar array fuel cell stacked from 10 cells made by rapid prototyping technology which has potential for fast commercial design, low cost manufacturing, and even without converters/inverters for the system. In this paper, the main material of flow field plates is acrylonitrile-butadiene-styrene (ABS) which allows the fuel cell be mass-manufactured by plastic injection molding technology. The rapid prototyping technology is applied to construct the prototype and verify the practicability of the proposed stack design. A 10-cell air-breathing miniature PEMFC stack with a volume of 6 cm × 6 cm × 0.9 cm is developed and tested. Its segmented membrane electrode assembly (MEA) is designed with the active surface area of 1.3 cm × 1.3 cm in each individual MEA. The platinum loading at anode and cathode are 0.2 mg cm -2 and 0.4 mg cm -2, respectively. Results show that the peak power densities of the parallel connected and serial connected stack are 99 mW cm -2 at 0.425 V and 92 mW cm -2 at 4.25 V, respectively under the conditions of 70 °C relative saturated humidity (i.e., dew point temperature), ambient temperature and free convection air. Besides, the stack performance is increased under forced convection. If the cell surface air is blown by an electric fan, the peak power densities of parallel connected and serial connected stack are improved to 123 mW cm -2 at 0.425 V and 105 mW cm -2 at 5.25 V, respectively. The forced convection air can not only increases the oxygen diffusion rate at the air-breathing surface, but also enhance the uniformity of output voltage distribution. The performance obtained in this work reaches to the state-of-the-air of air-breathing planar PEMFC stack comparing to recent literatures. In this study, the different behavior of output performance at water-rich region and water-lean region is also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zijiao; Sheng, Hongwei; Wang, Zhangjie

Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dualmore » function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness.« less

Shock compression of [001] single crystal silicon

DOE PAGES

Zhao, S.; Remington, B.; Hahn, E. N.; ...

2016-03-14

Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent withmore » dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.« less

Shock compression of [001] single crystal silicon

NASA Astrophysics Data System (ADS)

Zhao, S.; Hahn, E. N.; Kad, B.; Remington, B. A.; Bringa, E. M.; Meyers, M. A.

2016-05-01

Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

Seismic rupture and ground accelerations induced by CO 2 injection in the shallow crust

DOE PAGES

Cappa, Frédéric; Rutqvist, Jonny

2012-09-01

We present that because of the critically stressed nature of the upper crust, the injection of large volumes of carbon dioxide (CO 2) into shallow geological reservoirs can trigger seismicity and induce ground deformations when the injection increases the fluid pressure in the vicinity of potentially seismic faults. The increased fluid pressure reduces the strength against fault slip, allowing the stored elastic energy to be released in seismic events that can produce felt ground accelerations. Here, we seek to explore the likelihood ground motions induced by a CO 2 injection using hydromechanical modelling with multiphase fluid flow and dynamic rupture,more » including fault-frictional weakening. We extend the previous work of Cappa and Rutqvist, in which activation of a normal fault at critical stress may be possible for fast rupture nucleating by localized increase in fluid pressure and large decrease in fault friction. In this paper, we include seismic wave propagation generated by the rupture. For our assumed system and injection rate, simulations show that after a few days of injection, a dynamic fault rupture of few centimetres nucleates at the base of the CO 2 reservoir and grows bilaterally, both toward the top of the reservoir and outside. The rupture is asymmetric and affects a larger zone below the reservoir where the rupture is self-propagating (without any further pressure increase) as a result of fault-strength weakening. The acceleration and deceleration of the rupture generate waves and result in ground accelerations (~0.1–0.6 g) consistent with observed ground motion records. Finally, the maximum ground acceleration is obtained near the fault, and horizontal accelerations are generally markedly higher than vertical accelerations.« less

Fragmentation of wall rock garnets during deep crustal earthquakes

PubMed Central

Austrheim, Håkon; Dunkel, Kristina G.; Plümper, Oliver; Ildefonse, Benoit; Liu, Yang; Jamtveit, Bjørn

2017-01-01

Fractures and faults riddle the Earth’s crust on all scales, and the deformation associated with them is presumed to have had significant effects on its petrological and structural evolution. However, despite the abundance of directly observable earthquake activity, unequivocal evidence for seismic slip rates along ancient faults is rare and usually related to frictional melting and the formation of pseudotachylites. We report novel microstructures from garnet crystals in the immediate vicinity of seismic slip planes that transected lower crustal granulites during intermediate-depth earthquakes in the Bergen Arcs area, western Norway, some 420 million years ago. Seismic loading caused massive dislocation formations and fragmentation of wall rock garnets. Microfracturing and the injection of sulfide melts occurred during an early stage of loading. Subsequent dilation caused pervasive transport of fluids into the garnets along a network of microfractures, dislocations, and subgrain and grain boundaries, leading to the growth of abundant mineral inclusions inside the fragmented garnets. Recrystallization by grain boundary migration closed most of the pores and fractures generated by the seismic event. This wall rock alteration represents the initial stages of an earthquake-triggered metamorphic transformation process that ultimately led to reworking of the lower crust on a regional scale. PMID:28261660

Preface to the focus section on injection-induced seismicity

USGS Publications Warehouse

Eaton, David; Rubinstein, Justin L.

2015-01-01

The ongoing, dramatic increase in seismicity in the central United States that began in 2009 is believed to be the result of injection‐induced seismicity (Ellsworth, 2013). Although the basic mechanism for activation of slip on a fault by subsurface fluid injection is well established (Healy et al., 1968; Raleighet al., 1976; Nicholson and Wesson, 1992; McGarr et al., 2002; Ellsworth, 2013), the occurrence of damaging M≥5 earthquakes and the dramatic increase in seismicity in the central United States has brought heightened attention to this issue. The elevated seismicity is confined to a limited number of areas, and accumulating evidence indicates that the seismicity in these locations is directly linked to nearby industrial operations. This Seismological Research Letters (SRL) focus section presents a selected set of seven technical papers that cover various aspects of this topic, including basic seismological and ground‐motion observations, case studies, numerical simulation of fault activation, and risk mitigation.

GENERALIZATION OF TREADMILL-SLIP TRAINING TO PREVENT A FALL FOLLLOWING A SUDDEN (NOVEL) SLIP IN OVER-GROUND WALKING

PubMed Central

Yang, Feng; Bhatt, Tanvi; Pai, Yi-Chung

2012-01-01

The purposes of the study were to determine 1) whether treadmill-slip training could reduce the likelihood of falls during a novel slip in over-ground walking, and 2) to what extent such (indirect) training would be comparable to (direct) over-ground-slip training. A treadmill-slip training group (Group A, n=17) initially experienced repeated perturbations on treadmill intended to simulate forward-slip in over-ground walking. Perturbation continued and its intensity reduced when necessary to ensure subjects’ successful adaptation (i.e., when they could land their trailing foot ahead of the slipping foot in at least 3 of 5 consecutive trials). They then experienced a novel slip during over-ground walking. Another 17 young adults in Group B experienced an identical novel slip that served as the controls. They then underwent more slip trials during over-ground walking. Their 16th slip trial was analyzed to represent the over-ground-slip training effect. Eight subjects (47%) in Group A fell upon their first treadmill slip, while all adapted successfully after a minimum of 15 slip trials. Upon the novel slip during over-ground walking, none of them fell in comparison to four subjects (23.5%) fell in Group B upon the same trial (p<0.05). Group A’s control of stability, both proactive and reactive, was significantly better than that of Group B’s on their first over-ground slip, while the level of improvement derived from indirect treadmill training was not as strong as that from direct over-ground-slip training, as demonstrated in Group B’s 16th slip trial (p<0.001). These results clearly demonstrated the feasibility of fall reduction through treadmill-slip training. PMID:23141636

In-situ analysis of the slip activity during tensile deformation of cast and extruded Mg-10Gd-3Y-0.5Zr (wt.%) at 250 °C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, H.; The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240; Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824

The slip activity and slip interaction in tensile deformation of peak-aged cast and extruded Mg-10Gd-3Y-0.5Zr (wt.%) at 250 °C was investigated using in-situ scanning electron microscopy. Basal slip was the most likely system to be activated during the tensile deformation, while prismatic < a > and pyramidal < c + a > slip also contributed to the deformation. No twinning was observed. The number of non-basal slip systems accounted for ~ 36% of the total active slip systems for the cast alloy, while non-basal slip accounted for 12–17% of the total deformation observations in the extruded alloy. Multiple-slip was observedmore » within grains, and the basal/prismatic pairing type dominated the multiple-slip observations. Slip transfer occurred across grain boundaries and most of the slip transfer observations showed basal-basal type. The involved slip systems of slip transfer pairs were always associated with the same < a > direction. The slip transfer occurred more easily at low angle boundaries (LABs) and boundaries with misorientations greater than 75°. - Highlights: • Slip deformation of a Mg-RE alloy at 250 °C was investigated using in-situ SEM. • The extruded-T5 GW103 alloy did not exhibit a high anisotropic behavior. • Multiple-slip was observed within grains, and basal/prismatic type dominated. • Slip transfer occurred and most of the observations showed basal-basal type. • Slip transfer occurred more easily at LABs and boundaries with misorientations > 75°.« less

Combination of intracellular staining of retrogradely labeled neurons and anterograde fluorescent tracing: use of the confocal laser scanning microscope.

PubMed

Shi, C; Cassell, M D

1993-04-01

This report describes a combined retrograde tracing, intracellular injection and anterograde fluorescence labeling method using the application of confocal laser scanning microscopy. By simultaneously viewing the morphology of identified projection neurons and the distribution of anterogradely labeled fibers and terminals, this approach allows accurate characterization of the anatomical relationships between these two elements. To demonstrate this approach, the retrograde tracer Fast Blue was injected into the bed nucleus of stria terminalis (BNST) and the anterograde tracer tetramethylrhodamine-conjugated dextran was injected into the insular cortex in adult rats. After one week survival time, the brains were fixed and sectioned on a vibratome. Individual BNST projecting neurons identified in the amygdaloid complex on 120 microns thick sections were intracellularly injected with Lucifer Yellow under visual control and analyzed with confocal laser scanning microscopy. The results demonstrate that images from very thin optical sections can clearly show potential synaptic contacts between anterograde labeling and intracellularly labeled projecting neurons. Stacked images from optical sections show, in very great detail, the morphology of projection neurons in three-dimensions. Compared to other methodological combinations, the present method provides a more simple and efficient means to trace three successive components of a putative neuron chain.

Semiquinone-bridged bisdithiazolyl radicals as neutral radical conductors.

PubMed

Yu, Xin; Mailman, Aaron; Lekin, Kristina; Assoud, Abdeljalil; Robertson, Craig M; Noll, Bruce C; Campana, Charles F; Howard, Judith A K; Dube, Paul A; Oakley, Richard T

2012-02-01

Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna2(1), revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-temperature conductivity measurements on 3a and 3a·MeCN indicated high values of σ(300 K) (>10(-3) S cm(-1)) with correspondingly low thermal activation energies E(act), reaching 0.11 eV in the case of 3a·MeCN. Overall, the strong performance of these materials as f = ½ conductors is attributed to a combination of low U and large W. Variable-temperature magnetic susceptibility measurements were performed on both 3a and 3a·MeCN. The unsolvated material 3a orders as a spin-canted antiferromagnet at 8 K, with a canting angle φ = 0.14° and a coercive field H(c) = 80 Oe at 2 K. © 2012 American Chemical Society

Lunar lander conceptual design

NASA Technical Reports Server (NTRS)

Stecklein, J. M.; Petro, A. J.; Stump, W. R.; Adorjan, A. S.; Chambers, T. V.; Donofrio, M.; Hirasaki, J. K.; Morris, O. G.; Nudd, G.; Rawlings, R. P.

1992-01-01

This paper is a first look at the problems of building a lunar lander to support a small lunar surface base. A series of trade studies was performed to define the lander. The initial trades concerned choosing number of stages, payload mass, parking orbit altitude, and propellant type. Other important trades and issues included plane change capability, propellant loading and maintenance location, and reusability considerations. Given a rough baseline, the systems were then reviewed. A conceptual design was then produced. The process was carried through only one iteration. Many more iterations are needed. A transportation system using reusable, aerobraked orbital transfer vehicles (OTV's) is assumed. These OTV's are assumed to be based and maintained at a low Earth orbit (LEO) space station, optimized for transportation functions. Single- and two-stage OTV stacks are considered. The OTV's make the translunar injection (TLI), lunar orbit insertion (LOI), and trans-Earth injection (TEI) burns, as well as midcourse and perigee raise maneuvers.

Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

PubMed Central

Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

2016-01-01

The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics. PMID:27507171

Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

NASA Astrophysics Data System (ADS)

Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

2016-08-01

The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics.

Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

NASA Astrophysics Data System (ADS)

Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

2003-11-01

We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

USGS Publications Warehouse

Barnhart, William; Briggs, Richard; Reitman, Nadine G.; Gold, Ryan D.; Hayes, Gavin

2015-01-01

Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip – normal, reverse, or strike-slip – until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200+ km 200+km"> 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

Factors associated with use of slip-resistant shoes in US limited-service restaurant workers.

PubMed

Verma, Santosh K; Courtney, Theodore K; Corns, Helen L; Huang, Yueng-Hsiang; Lombardi, David A; Chang, Wen-Ruey; Brennan, Melanye J; Perry, Melissa J

2012-06-01

Slips and falls are a leading cause of injury at work. Several studies have indicated that slip-resistant shoes can reduce the risk of occupational slips and falls. Few studies, however, have examined the determinants of slip-resistant shoe use. This study examined the individual and workplace factors associated with slip-resistant shoe use. 475 workers from 36 limited-service restaurants in the USA participated in a study of workplace slipping. Demographic and job characteristic information about each participant was collected. Restaurant managers provided information on whether slip-resistant shoes were provided and paid for by the employer and whether any guidance was given regarding slip-resistant shoe use when they were not provided. Kitchen floor coefficient of friction was measured. Slip-resistant status of the shoes was determined by noting the presence of a 'slip-resistant' marking on the sole. Poisson regression with robust SE was used to calculate prevalence ratios. 320 participants wore slip-resistant shoes (67%). In the multivariate analysis, the prevalence of slip-resistant shoe use was lowest in 15-19-year age group. Women were more likely to wear slip-resistant shoes (prevalence ratio 1.18, 95% CI 1.07 to 1.31). The prevalence of slip-resistant shoe use was lower when no guidance regarding slip-resistant shoes was given as compared to when they were provided by the employer (prevalence ratio 0.66, 95% CI 0.55 to 0.79). Education level, job tenure and the mean coefficient of friction had no significant effects on the use of slip-resistant shoes. Provision of slip-resistant shoes was the strongest predictor of their use. Given their effectiveness and low cost, employers should consider providing slip-resistant shoes at work.

Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

NASA Astrophysics Data System (ADS)

Barnhart, W. D.; Briggs, R. W.; Reitman, N. G.; Gold, R. D.; Hayes, G. P.

2015-06-01

Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip - normal, reverse, or strike-slip - until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200 + km 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

Sensitive determination of four tetracycline antibiotics in pig plasma by field-amplified sample stacking open-tubular capillary electrochromatography with dimethylethanolamine aminated polychloromethyl styrene nano-latex coated capillary column.

PubMed

Guo, Yaxiao; Meng, Lei; Zhang, Yanhao; Tang, Wei; Zhang, Wenfen; Xia, Yan; Ban, Fuguo; Wu, Ningpeng; Zhang, Shusheng

2013-12-30

This paper described the preparation and application of a new dimethylethanolamine aminated polychloromethyl styrene nano-latex (DMEAPL) coated capillary column (ccc-DMEAPL) in the determination of four tetracycline antibiotics (TCA) including tetracycline (TC), oxytetracycline (OTC), doxycycline (DC) and chlorotetracycline (CTC) in pig plasma. The ccc-DMEAPL column was characterized with steady EOF values of ca. 1.5-5.2×10(-5)cm(2)/Vs at pH 1.8-6.3. The optimized conditions for field-amplified sample stacking open-tubular capillary electrochromatography (FASS-OT-CEC) were as following: background electrolyte, 10mmol/L Na2HPO4+15mmol/L citric acid (pH 3.2); ccc-DMEAPL, 50μm i.d.×50cm (effective length 41.5cm), separation voltage, 18kV; column temperature, 25°C; UV detection wavelength, 270nm; water-plug injection: 30mbar×10s; sample electrokinetic injection, 10kV×20s. The four TCA were extracted with the solution of 10mmol/L Na2HPO4+15mmol/L citric acid+4g/L EDTA-2Na (pH 3.2). The FASS-OT-CEC method was validated in terms of linearity, sensitivity, selectivity, precision and accuracy. The LODs ranged from 3 to 7ng/mL, the recoveries for the four TCA were all more than 80%. The developed method was successfully applied for the determination of TCs in the actual pig plasma samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Structure of the Sumatra wedge affected by the 26th December 2004 :Effects of the lower plate volcanic ridges.

NASA Astrophysics Data System (ADS)

Rangin, C.; Sibuet, J. C.; Lin, J. Y.; Le Pichon, X.

2009-04-01

Detailed swath-bathymetry, coupled with echo-sounder data were collected offshore the northern tip of Sumatra over the rupture area of the 26th December 2004 Mw=9.2 earthquake during the Sumatra aftershock cruise. 20 ocean bottom seismometers were also deployed in the northern Sumatra area., and more than 1000 events were identified during the 12 days recording period. We mapped recently active steeply dipping thrust fault zone within the western termination of the Sunda accreted wedge. Main N10°W trending out of sequence thrust fault zones with a discrete westward vergency and some component of dextral strike-slip motion were continuously mapped within the wedge, on the basis of bathymetry and low frequency sounder profiles. The interplate boundary does not appear to extend into the frontal part of the wedge but most probably merges in its central part along these major faults, the Lower and Upper Splay Faults. After relocation, the seismicity shows different pattern in each side of this Upper Splay Fault. East of this boundary, beneath the Aceh basin, the earthquake depths ranged from 30 to 60 km allow us to illustrate the subducted plate. In the western part, the aftershock distribution is strongly influenced by the N-S orientated oceanic fracture zones. Two clusters of earthquakes between 10 and 50 km in depth trending along N-S direction are observed in the lower wedge that we interpret to be reactive fracture zones. The lower wedge is interpreted as the northern prolongation below the wedge of the lower plate NS oceanic fracture zone ridges affected by NS trending left lateral strike-slip faults. This wedge outer ridge is in the process of being transferred to the upper plate. On the other hand the central ridge is interpreted as possible stacked volcanic ridge slivers already incorporated into the upper plate along the subduction buttress (the inner ridge of the wedge). We propose that the tectonic interaction of the volcanic Indian Ocean fracture ridges of the subducted plate with the leading edge of the upper Sunda plate subduction zone is an active tectonic transfer process of oceanic material to the upper plate. The proposed emergence of the interplate boundary into the middle part of the wedge along the Lower Splay Fault, could have favoured the formation of the giant Sumatra tsunami at moderate water depth. This docking and temporary stacking of these volcanic ridges before their subduction at depth, is favoured by the strong oblique convergence that prevails up to the Bengal basin into the north.

Immediate and Latent Interlimb Transfer of Gait Stability Adaptation Following Repeated Exposure to Slips

PubMed Central

Bhatt, T.; Pai, Y.-C.

2008-01-01

The authors trained 21 participants by using blocked-and-mixed exposure to right-side slips and then caused them to slip unexpectedly on the untrained left side. Authors retested participants with a right slip and a left slip at 1 week, 2 weeks, 1 month, and 4 months. The authors found that preslip stability on the first untrained left slip improved and was significantly greater than that on the first right slip, which probably contributed to the reduction in incidence of falls from ∼30% to ∼10%. Postslip stability and base of support (BOS) slip velocity were similar to those on the first right slip and much lower than those on the last right slip. Increases in pre- and postslip stabilities and BOS slip velocity during the left slip led to reductions in backward balance loss (BLOB) from ∼95% on initial left slip to ∼60% and to ∼25% on the 1st and 3rd retest sessions, respectively. In contrast, BLOB remained at a constant ∼40% level on the right slip of the same retest sessions. The results indicate a partial immediate transfer and a possible latent transfer. PMID:18782713

Slip in the 2015 Mw 7.9 Gorkha and Mw 7.3 Kodari, Nepal, earthquakes revealed by seismic and geodetic data: Delayed slip in the Gorkha and slip deficit between the two earthquakes

NASA Astrophysics Data System (ADS)

Zhang, G.; Hetland, E.; Shan, X.

2017-12-01

We investigate the rupture process of the April 25, 2015 Gorkha, Nepal Mw7.9 earthquake, and its biggest aftershock on May 12, 2015, based on joint inversion of teleseismic body waves, InSAR and GPS measurements. The Gorkha earthquake propagated unilaterally to the southeast along the MFT, with coseismic slip separating into patches up-dip and down-dip of the hypocenter. Slip in the up-dip patch initially surrounded a region on the fault that did not slip. About 15 seconds after being surrounded, this region of no slip then slipped, filling in the slip deficit. The delayed slip accounts for about 20% of the moment release in the Gorkha earthquake. The inferred coseismic slip in the Kodari earthquake is localized to one patch, extending to the south and southeast from the hypocenter, and 20-30 km to the northeast of the main slip patch in the Ghorka earthquake. The maximum coseismic slip in both the Gorkha and Kodari earthquakes is about 4.5 meters.

Binary ionic porphyrin nanosheets: electronic and light-harvesting properties regulated by crystal structure

NASA Astrophysics Data System (ADS)

Tian, Yongming; M. Beavers, Christine; Busani, Tito; Martin, Kathleen E.; Jacobsen, John L.; Mercado, Brandon Q.; Swartzentruber, Brian S.; van Swol, Frank; Medforth, Craig J.; Shelnutt, John A.

2012-02-01

Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS4- (an electron donor) and three half molecules of dihydroxy-SnTNMePyP4+ (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS4- (an electron donor) and three half molecules of dihydroxy-SnTNMePyP4+ (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers. Electronic supplementary information (ESI) available: Details of the crystallographic refinement, tables of refinement parameters and bond distances and NSD analysis, and figures showing SEM images of Zn/Sn nanosheets and clovers, the solid grown at different porphyrin concentrations, SEM images of nanosheets at high and low magnification, an ORTEP image showing the five crystallographically distinct porphyrin molecules and the water molecules, and a view of the crystal structure down the b axis are given in the ESI. CCDC reference number 833006. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr11826b

The influence of footwear sole hardness on slip characteristics and slip-induced falls in young adults.

PubMed

Tsai, Yi-Ju; Powers, Christopher M

2013-01-01

Theoretically, a shoe that provides less friction could result in a greater slip distance and foot slipping velocity, thereby increasing the likelihood of falling. The purpose of this study was to investigate the effects of sole hardness on the probability of slip-induced falls. Forty young adults were randomized into a hard or a soft sole shoe group, and tested under both nonslippery and slippery floor conditions using a motion analysis system. The proportions of fall events in the hard- and soft-soled shoe groups were not statistically different. No differences were observed between shoe groups for average slip distance, peak and average heel velocity, and center of mass slipping velocity. A strong association was found between slip distance and the fall probability. Our results demonstrate that the probability of a slip-induced fall was not influenced by shoe hardness. Once a slip is induced, slip distance was the primary predictor of a slip-induced fall. © 2012 American Academy of Forensic Sciences.

Slip speed feedback for grip force control.

PubMed

Damian, D D; Arita, A H; Martinez, H; Pfeifer, R

2012-08-01

Grasp stability in the human hand has been resolved by means of an intricate network of mechanoreceptors integrating numerous cues about mechanical events, through an ontogenetic grasp practice. An engineered prosthetic interface introduces considerable perturbation risks in grasping, calling for feedback modalities that address the underlying slip phenomenon. In this study, we propose an enhanced slip feedback modality, with potential for myoelectric-based prosthetic applications, that relays information regarding slip events, particularly slip occurrence and slip speed. The proposed feedback modality, implemented using electrotactile stimulation, was evaluated in psychophysical studies of slip control in a simplified setup. The obtained results were compared with vision and a binary slip feedback that transmits on-off information about slip detection. The slip control efficiency of the slip speed display is comparable to that obtained with vision feedback, and it clearly outperforms the efficiency of the on-off slip modality in such tasks. These results suggest that the proposed tactile feedback is a promising sensory method for the restoration of stable grasp in prosthetic applications.

Consistent lattice Boltzmann modeling of low-speed isothermal flows at finite Knudsen numbers in slip-flow regime: Application to plane boundaries

NASA Astrophysics Data System (ADS)

Silva, Goncalo; Semiao, Viriato

2017-07-01

The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over distinct wall slippage conditions, namely, no-slip, first-order slip, and second-order slip. The modeling of channel walls is discussed at both lattice-aligned and non-mesh-aligned configurations: the first case illustrates the numerical slip due to the incorrect modeling of slippage coefficients, whereas the second case adds the effect of spurious boundary layers created by the deficient accommodation of bulk solution. Finally, the slip-flow solutions predicted by LBM schemes are further evaluated for the Knudsen's paradox problem. As conclusion, this work establishes the parabolic accuracy of slip velocity schemes as the necessary condition for the consistent LBM modeling of the slip-flow regime.

Consistent lattice Boltzmann modeling of low-speed isothermal flows at finite Knudsen numbers in slip-flow regime: Application to plane boundaries.

PubMed

Silva, Goncalo; Semiao, Viriato

2017-07-01

The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over distinct wall slippage conditions, namely, no-slip, first-order slip, and second-order slip. The modeling of channel walls is discussed at both lattice-aligned and non-mesh-aligned configurations: the first case illustrates the numerical slip due to the incorrect modeling of slippage coefficients, whereas the second case adds the effect of spurious boundary layers created by the deficient accommodation of bulk solution. Finally, the slip-flow solutions predicted by LBM schemes are further evaluated for the Knudsen's paradox problem. As conclusion, this work establishes the parabolic accuracy of slip velocity schemes as the necessary condition for the consistent LBM modeling of the slip-flow regime.

Structure of the Red Dog District, western Brooks Range, Alaska

USGS Publications Warehouse

de Vera, Jean-Pierre P.; McClay, K. R.

2004-01-01

The Red Dog district of the western Brooks Range of northern Alaska, which includes the sediment-hosted Zn-Pb-Ag ± Ba deposits at Red Dog, Su-Lik, and Anarraaq, contains one of the world's largest reserves of zinc. This paper presents a new model for the structural development of the area and shows that understanding the structure is crucial for future exploration efforts and new mineral discoveries in the district. In the Red Dog district, a telescoped Late Devonian through Jurassic continental passive margin is exposed in a series of subhorizontally stacked, internally imbricated, and regionally folded thrust sheets. These sheets were emplaced during the Middle Jurassic to Late Cretaceous Brookian orogeny and subsequently were uplifted by late tectonic activity in the Tertiary. The thrust sheet stack comprises seven tectonostratigraphically distinct allochthonous sheets, three of which have been subject to regional and detailed structural analysis. The lowermost of these is the Endicott Mountains allochthon, which is overlain by the structurally higher Picnic Creek and Kelly River allochthons. Each individual allochthon is itself internally imbricated into a series of tectonostratigraphically coherent and distinct thrust plates and subplates. This structural style gives rise to duplex development and imbrication at a range of scales, from a few meters to tens of kilometers. The variable mechanical properties of the lithologic units of the ancient passive margin resulted in changes in structural styles and scales of structures across allochthon boundaries. Structural mapping and analysis of the district indicate a dominant northwest to west-northwest direction of regional tectonic transport. Local north to north-northeast transport of thrust sheets is interpreted to reflect the influence of underlying lateral and/or oblique ramps, which may have been controlled by inherited basin margin structures. Some thrust-sheet stacking patterns suggest out-of-sequence thrusting. The west-northwest-east-southeast-trending Wrench Creek and Sivukat Mountain faults were previously interpreted to be strike-slip faults, but this study shows that they are Tertiary (Eocene?) late extensional faults with little or no lateral displacement.

Resonant slow fault slip in subduction zones forced by climatic load stress.

PubMed

Lowry, Anthony R

2006-08-17

Global Positioning System (GPS) measurements at subduction plate boundaries often record fault movements similar to earthquakes but much slower, occurring over timescales of approximately 1 week to approximately 1 year. These 'slow slip events' have been observed in Japan, Cascadia, Mexico, Alaska and New Zealand. The phenomenon is poorly understood, but several observations hint at the processes underlying slow slip. Although slip itself is silent, seismic instruments often record coincident low-amplitude tremor in a narrow (1-5 cycles per second) frequency range. Also, modelling of GPS data and estimates of tremor location indicate that slip focuses near the transition from unstable ('stick-slip') to stable friction at the deep limit of the earthquake-producing seismogenic zone. Perhaps most intriguingly, slow slip is periodic at several locations, with recurrence varying from 6 to 18 months depending on which subduction zone (or even segment) is examined. Here I show that such periodic slow fault slip may be a resonant response to climate-driven stress perturbations. Fault slip resonance helps to explain why slip events are periodic, why periods differ from place to place, and why slip focuses near the base of the seismogenic zone. Resonant slip should initiate within the rupture zone of future great earthquakes, suggesting that slow slip may illuminate fault properties that control earthquake slip.

Slow slip events and seismic tremor at circum-Pacific subduction zones

NASA Astrophysics Data System (ADS)

Schwartz, Susan Y.; Rokosky, Juliana M.

2007-09-01

It has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements. However, only recently has a fuller spectrum of strain release processes, including normal, slow, and silent earthquakes (or slow slip events) and continuous and episodic slip, been observed and generated by numerical simulations of the earthquake cycle. Despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive. The concurrence of seismic tremor with slow slip episodes in Cascadia and southwestern Japan provides insight into the process of slow slip. A perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface. Alternatively, evidence is accumulating to support the notion that tremor results from shear failure during slow slip. Global observations of the location, spatial extent, magnitude, duration, slip rate, and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation. Most slow slip events occur just downdip of the seismogenic zone, consistent with rate- and state-dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation. At a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation. Slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault, bringing it closer to or farther from earthquake failure, respectively. This paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide, with a focus on circum-Pacific subduction zones. Trends in global observations of slow slip events suggest that (1) slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it, (2) different frictional properties likely control fast versus slow slip, (3) the depth range of slow slip may be related to the thermal properties of the plate interface, and (4) the equivalent seismic moment of slow slip events is proportional to their duration (Moατ), different from the Moατ3 scaling observed for earthquakes.

Are Geotehrmal Reservoirs Stressed Out?

NASA Astrophysics Data System (ADS)

Davatzes, N. C.; Laboso, R. C.; Layland-Bachmann, C. E.; Feigl, K. L.; Foxall, W.; Tabrez, A. R.; Mellors, R. J.; Templeton, D. C.; Akerley, J.

2017-12-01

Crustal permeability can be strongly influenced by developing connected networks of open fractures. However, the detailed evolution of a fracture network, its extent, and the persistence of fracture porosity are difficult to analyze. Even in fault-hosted geothermal systems, where heat is brought to the surface from depth along a fault, hydrothermal flow is heterogeneously distributed. This is presumably due to variations in fracture density, connectivity, and attitude, as well as variations in fracture permeability caused by sealing of fractures by precipitated cements or compaction. At the Brady Geothermal field in Nevada, we test the relationship between the modeled local stress state perturbed by dislocations representing fault slip or volume changes in the geothermal reservoir inferred from surface deformation measured by InSAR and the location of successful geothermal wells, hydrothermal activity, and seismicity. We postulate that permeability is favored in volumes that experience positive Coulomb stress changes and reduced compression, which together promote high densities of dilatant fractures. Conversely, permeability can be inhibited in locations where Coulomb stress is reduced, compression promotes compaction, or where the faults are poorly oriented in the stress field and consequently slip infrequently. Over geologic time scales spanning the development of the fault system, these local stress states are strongly influenced by the geometry of the fault network relative to the remote stress driving slip. At shorter time scales, changes in fluid pressure within the fracture network constituting the reservoir cause elastic dilations and contractions. We integrate: (1) direct observations of stress state and fractures in boreholes and the mapped geometry of the fault network; (2) evidence of permeability from surface hydrothermal features, production/injection wells and surface deformations related to pumping history; and (3) seismicity to test the correlation between the reservoir geometry and models of the local stress state.

Paleomagnetic and structural evidence for oblique slip in a fault-related fold, Grayback monocline, Colorado

USGS Publications Warehouse

Tetreault, J.; Jones, C.H.; Erslev, E.; Larson, S.; Hudson, M.; Holdaway, S.

2008-01-01

Significant fold-axis-parallel slip is accommodated in the folded strata of the Grayback monocline, northeastern Front Range, Colorado, without visible large strike-slip displacement on the fold surface. In many cases, oblique-slip deformation is partitioned; fold-axis-normal slip is accommodated within folds, and fold-axis-parallel slip is resolved onto adjacent strike-slip faults. Unlike partitioning strike-parallel slip onto adjacent strike-slip faults, fold-axis-parallel slip has deformed the forelimb of the Grayback monocline. Mean compressive paleostress orientations in the forelimb are deflected 15??-37?? clockwise from the regional paleostress orientation of the northeastern Front Range. Paleomagnetic directions from the Permian Ingleside Formation in the forelimb are rotated 16??-42?? clockwise about a bedding-normal axis relative to the North American Permian reference direction. The paleostress and paleomagnetic rotations increase with the bedding dip angle and decrease along strike toward the fold tip. These measurements allow for 50-120 m of fold-axis-parallel slip within the forelimb, depending on the kinematics of strike-slip shear. This resolved horizontal slip is nearly equal in magnitude to the ???180 m vertical throw across the fold. For 200 m of oblique-slip displacement (120 m of strike slip and 180 m of reverse slip), the true shortening direction across the fold is N90??E, indistinguishable from the regionally inferred direction of N90??E and quite different from the S53??E fold-normal direction. Recognition of this deformational style means that significant amounts of strike slip can be accommodated within folds without axis-parallel surficial faulting. ?? 2008 Geological Society of America.

Systematic deficiency of aftershocks in areas of high coseismic slip for large subduction zone earthquakes

PubMed Central

Wetzler, Nadav; Lay, Thorne; Brodsky, Emily E.; Kanamori, Hiroo

2018-01-01

Fault slip during plate boundary earthquakes releases a portion of the shear stress accumulated due to frictional resistance to relative plate motions. Investigation of 101 large [moment magnitude (Mw) ≥ 7] subduction zone plate boundary mainshocks with consistently determined coseismic slip distributions establishes that 15 to 55% of all master event–relocated aftershocks with Mw ≥ 5.2 are located within the slip regions of the mainshock ruptures and few are located in peak slip regions, allowing for uncertainty in the slip models. For the preferred models, cumulative deficiency of aftershocks within the central three-quarters of the scaled slip regions ranges from 15 to 45%, increasing with the total number of observed aftershocks. The spatial gradients of the mainshock coseismic slip concentrate residual shear stress near the slip zone margins and increase stress outside the slip zone, driving both interplate and intraplate aftershock occurrence near the periphery of the mainshock slip. The shear stress reduction in large-slip regions during the mainshock is generally sufficient to preclude further significant rupture during the aftershock sequence, consistent with large-slip areas relocking and not rupturing again for a substantial time. PMID:29487902

Slow slip generated by dehydration reaction coupled with slip-induced dilatancy and thermal pressurization

NASA Astrophysics Data System (ADS)

Yamashita, Teruo; Schubnel, Alexandre

2016-10-01

Sustained slow slip, which is a distinctive feature of slow slip events (SSEs), is investigated theoretically, assuming a fault embedded within a fluid-saturated 1D thermo-poro-elastic medium. The object of study is specifically SSEs occurring at the down-dip edge of seismogenic zone in hot subduction zones, where mineral dehydrations (antigorite, lawsonite, chlorite, and glaucophane) are expected to occur near locations where deep slow slip events are observed. In the modeling, we introduce dehydration reactions, coupled with slip-induced dilatancy and thermal pressurization, and slip evolution is assumed to interact with fluid pressure change through Coulomb's frictional stress. Our calculations show that sustained slow slip events occur when the dehydration reaction is coupled with slip-induced dilatancy. Specifically, slow slip is favored by a low initial stress drop, an initial temperature of the medium close to that of the dehydration reaction equilibrium temperature, a low permeability, and overall negative volume change associated with the reaction (i.e., void space created by the reaction larger than the space occupied by the fluid released). Importantly, if we do not assume slip-induced dilatancy, slip is accelerated with time soon after the slip onset even if the dehydration reaction is assumed. This suggests that slow slip is sustained for a long time at hot subduction zones because dehydration reaction is coupled with slip-induced dilatancy. Such slip-induced dilatancy may occur at the down-dip edge of seismogenic zone at hot subduction zones because of repetitive occurrence of dehydration reaction there.

Triggered surface slips in the Salton Trough associated with the 1999 Hector Mine, California, earthquake

USGS Publications Warehouse

Rymer, M.J.; Boatwright, J.; Seekins, L.C.; Yule, J.D.; Liu, J.

2002-01-01

Surface fracturing occurred along the southern San Andreas, Superstition Hills, and Imperial faults in association with the 16 October 1999 (Mw 7.1) Hector Mine earthquake, making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the Salton Trough. Fractures associated with the event formed discontinuous breaks over a 39-km-long stretch of the San Andreas fault, from the Mecca Hills southeastward to Salt Creek and Durmid Hill, a distance from the epicenter of 107 to 139 km. Sense of slip was right lateral; only locally was there a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 13 mm. Maximum slip values in 1999 and earlier triggered slips are most common in the central Mecca Hills. Field evidence indicates a transient opening as the Hector Mine seismic waves passed the southern San Andreas fault. Comparison of nearby strong-motion records indicates several periods of relative opening with passage of the Hector Mine seismic wave-a similar process may have contributed to the field evidence of a transient opening. Slip on the Superstition Hills fault extended at least 9 km, at a distance from the Hector Mine epicenter of about 188 to 196 km. This length of slip is a minimum value, because we saw fresh surface breakage extending farther northwest than our measurement sites. Sense of slip was right lateral; locally there was a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 18 mm, with the largest amounts found distributed (or skewed) away from the Hector Mine earthquake source. Slip triggered on the Superstition Hills fault commonly is skewed away from the earthquake source, most notably in 1968, 1979, and 1999. Surface slip on the Imperial fault and within the Imperial Valley extended about 22 km, representing a distance from the Hector Mine epicenter of about 204 to 226 km. Sense of slip dominantly was right lateral; the right-lateral component of slip ranged from 1 to 19 mm. Locally there was a minor (~1-2 mm) vertical component of slip; larger proportions of vertical slip (up to 10 mm) occurred in Mesquite basin, where scarps indicate long-term oblique-slip motion for this part of the Imperial fault. Slip triggered on the Imperial fault appears randomly distributed relative to location along the fault and source direction. Multiple surface slips, both primary and triggered slip, indicate that slip repeatedly is small at locations of structural complexity.

Coupled Mechanical and Thermal Modeling of Frictional Melt Injection to Constrain Physical Conditions of the Earthquake Source Region

NASA Astrophysics Data System (ADS)

Sawyer, W.; Resor, P. G.

2016-12-01

Pseudotachylyte, a fault rock formed through coseismic frictional melting, provides an important record of coseismic mechanics. In particular, injection veins formed at a high angle to the fault surface have been used to estimate rupture directivity, velocity, pulse length, stress and strength drop, as well as slip weakening distance and wall rock stiffness. These studies, however, have generally treated injection vein formation as a purely elastic process and have assumed that processes of melt generation, transport, and solidification have little influence on the final vein geometry. Using a modified analytical approximation of injection vein formation based on a dike intrusion model we find that the timescales of quenching and flow propagation are similar for a composite set of injection veins compiled from the Asbestos Mountain Fault, USA (Rowe et al., 2012), Gole Larghe Fault Zone, Italy (Griffith et al., 2012) and the Fort Foster Brittle Zone. This indicates a complex, dynamic process whose behavior is not fully captured by the current approach. To assess the applicability of the simplifying assumptions of the dike model when applied to injection veins we employ a finite-element time-dependent model of injection vein formation. This model couples elastic deformation of the wall rock with the fluid dynamics and heat transfer of the frictional melt. The final geometry of many injection veins is unaffected by the inclusion of these processes. However, some injection veins are found to be flow limited, with a final geometry reflecting cooling of the vein before it reaches an elastic equilibrium with the wall rock. In these cases, numerical results are significantly different from the dike model, and two basic assumptions of the dike model, self-similar growth and a uniform pressure gradient, are shown to be false. Additionally, we apply the finite-element model to provide two new constraints on the Fort Foster coseismic environment: a lower limit on the initial melt temperature of 1400 *C, and either significant coseismic wall rock softening or high transient tensile stress.

Discrimination and Assessment of Induced Seismicity in Active Tectonic Zones: A Case Study from Southern California

NASA Astrophysics Data System (ADS)

Bachmann, C. E.; Lindsey, N.; Foxall, W.; Robertson, M.

2014-12-01

Earthquakes induced by human activity have become a matter of heightened public concern during recent years. Of particular concern is seismicity associated with wastewater injection, which has included events having magnitudes greater than 5. The causes of the induced events are primarily changes in pore-pressure, fluid volume and perhaps temperature due to injection. Recent research in the US has focused on mid-continental regions having low rates of naturally-occurring seismicity, where induced events can be identified by relatively straightforward spatial and temporal correlation of seismicity with high-volume injection activities. Recent examples include events correlated with injection of wastewater in Oklahoma, Arkansas, Texas and Ohio, and long-term brine injection in the Paradox Valley in Colorado. Even in some of the cases where there appears at first sight to be a clear spatial correlation between seismicity and injection, it has been difficult to establish causality definitively. Here, we discuss methods to identify induced seismicity in active tectonic regions. We concentrate our study on Southern California, where large numbers of wastewater injection wells are located in oil-producing basins that experience moderate to high rates of naturally-occurring seismicity. Using the catalog of high-precision CISN relocations produced by Hauksson et al. (BSSA, 2012), we aim to discriminate induced from natural events based on spatio-temporal patterns of seismicity occurrence characteristics and their relationships to injection activities, known active faults and other faults favorably oriented for slip under the tectonic stress field. Since the vast majority of induced earthquakes are very small, it is crucial to include all events above the detection threshold of the CISN in each area studied. In addition to exploring the correlation of seismicity to injection activities in time and space, we analyze variations in frequency-magnitude distributions, which can be related to differences between the physical conditions at the sources of fluid-induced and natural earthquakes. While induced seismicity often does not show different mechanisms than tectonic earthquakes, an abundance of induced microseismicity causes the slope of the frequency-magnitude distribution to increase locally.

Investigation into nanoscratching mechanical response of AlCrCuFeNi high-entropy alloys using atomic simulations

NASA Astrophysics Data System (ADS)

Wang, Zining; Li, Jia; Fang, QiHong; Liu, Bin; Zhang, Liangchi

2017-09-01

The mechanical behaviors and deformation mechanisms of scratched AlCrCuFeNi high entropy alloys (HEAs) have been studied by molecular dynamics (MD) simulations, in terms of the scratching forces, atomic strain, atomic displacement, microstructural evolution and dislocation density. The results show that the larger tangential and normal forces and higher friction coefficient take place in AlCrCuFeNi HEA due to its outstanding strength and hardness, and high adhesion and fracture toughness over the pure metal materials. Moreover, the stacking fault energy (SFE) in HEA increases the probability to initiate dislocation and twinning, which is conducive to the formation of complex deformation modes. Compared to the single element metal workpieces, the segregation potency of solutes into twinning boundary (TB) is raised due to the decreasing segregation energy of TB, resulting in the stronger solute effects on improving twinning properties for HEA workpiece. The higher dislocation density and the more activated slipping planes lead to the outstanding plasticity of AlCrCuFeNi HEA. The solute atoms as barriers to hinder the motion of dislocation and the severe lattice distortion to suppress the free slipping of dislocation are significantly stronger obstacles to strengthen HEA. The excellent comprehensive scratching properties of the bulk AlCrCuFeNi HEAs are associated with the combined effects of multiple strengthening mechanisms, such as dislocation strengthening, deformation twinning strengthening as well as solute strengthening. This work provides a basis for further understanding and tailoring SFE in mechanical properties and deformation mechanism of HEAs, which maybe facilitate the design and preparation of new HEAs with high performance.

Subsurface architecture of a strike-slip collapse structure: insights from Ilopango caldera, El Salvador

NASA Astrophysics Data System (ADS)

Saxby, Jennifer; Gottsmann, Joachim; Cashman, Katherine; Gutierrez, Eduardo

2016-04-01

While most calderas are created by roof collapse along ring-like faults into an emptying magma reservoir during a large and violent explosive eruption, an additional condition for caldera formation may be tectonically induced extensional stresses. Here we provide geophysical insights into the shallow sub-volcanic plumbing system of a collapse caldera in a major strike-slip tectonic setting by inverting Bouguer gravity data from the Ilopango caldera in El Salvador. Despite a long history of catastrophic eruptions with the most recent in 500 A.D., the internal architecture of the caldera has not been investigated, although studies of the most recent eruption have not identified the ring faults commonly associated with caldera collapse. The gravity data show that low-density material aligned along the principal stress orientations of the El Salvador Fault Zone (ESFZ) forms a pronounced gravity low beneath the caldera. Extending to around 6 km depth, the low density structure likely maps a complex stacked shallow plumbing system composed of magmatic and fractured hydrothermal reservoirs. A substantial volume of the plumbing system must be composed of a vapour phase to explain the modeled negative density contrasts. We use these constraints to map the possible multi-phase parameter space contributing to the subsurface architecture of the caldera and propose that the local extension along the complex ESFZ controls accumulation, ascent and eruption of magma at Ilopango. The data further suggest that future eruptions at Ilopango could be facilitated by rapid rise of magma along conjugate fault damage zones through a mechanically weak crust under tension. This may explain the absence of clear ring fault structures at the caldera.

Very low frequency earthquakes (VLFEs) detected during episodic tremor and slip (ETS) events in Cascadia using a match filter method indicate repeating events

NASA Astrophysics Data System (ADS)

Hutchison, A. A.; Ghosh, A.

2016-12-01

Very low frequency earthquakes (VLFEs) occur in transitional zones of faults, releasing seismic energy in the 0.02-0.05 Hz frequency band over a 90 s duration and typically have magntitudes within the range of Mw 3.0-4.0. VLFEs can occur down-dip of the seismogenic zone, where they can transfer stress up-dip potentially bringing the locked zone closer to a critical failure stress. VLFEs also occur up-dip of the seismogenic zone in a region along the plate interface that can rupture coseismically during large megathrust events, such as the 2011 Tohoku-Oki earthquake [Ide et al., 2011]. VLFEs were first detected in Cascadia during the 2011 episodic tremor and slip (ETS) event, occurring coincidentally with tremor [Ghosh et al., 2015]. However, during the 2014 ETS event, VLFEs were spatially and temporally asynchronous with tremor activity [Hutchison and Ghosh, 2016]. Such contrasting behaviors remind us that the mechanics behind such events remain elusive, yet they are responsible for the largest portion of the moment release during an ETS event. Here, we apply a match filter method using known VLFEs as template events to detect additional VLFEs. Using a grid-search centroid moment tensor inversion method, we invert stacks of the resulting match filter detections to ensure moment tensor solutions are similar to that of the respective template events. Our ability to successfully employ a match filter method to VLFE detection in Cascadia intrinsically indicates that these events can be repeating, implying that the same asperities are likely responsible for generating multiple VLFEs.

Deformation Behavior of Ultra-Strong and Ductile Mg-Gd-Y-Zn-Zr Alloy with Bimodal Microstructure

NASA Astrophysics Data System (ADS)

Xu, C.; Fan, G. H.; Nakata, T.; Liang, X.; Chi, Y. Q.; Qiao, X. G.; Cao, G. J.; Zhang, T. T.; Huang, M.; Miao, K. S.; Zheng, M. Y.; Kamado, S.; Xie, H. L.

2018-02-01

An ultra-strong and ductile Mg-8.2Gd-3.8Y-1Zn-0.4Zr (wt pct) alloy was developed by using hot extrusion to modify the microstructure via forced-air cooling and an artificial aging treatment. A superior strength-ductility balance was obtained that had a tensile yield strength of 466 MPa and an elongation to failure of 14.5 pct. The local strain evolution during the in situ testing of the ultra-strong and ductile alloy was quantitatively analyzed with high-resolution electron backscattered diffraction and digital image correlation. The fracture behavior during the tensile test was characterized by synchrotron X-ray tomography along with SEM and STEM observations. The alloy showed a bimodal microstructure, consisting of dynamically recrystallized (DRXed) grains with random orientations and elongated hot-worked grains with < { 10{\\bar{1}}0} > parallel to the extrusion direction. The DRXed grains were deformed by the basal <;a> slip and the hot-worked grains were deformed by the prismatic slip dominantly. The strain evolution analysis indicated that the multilayered structure relaxed the strain localization via strain transfer from the DRXed to the hot-worked regions, which led to the high ductility of the alloy. Precipitation of the γ' on basal planes and the β' phases on the prismatic planes of the α-Mg generated closed volumes, which enhanced the strength by pinning dislocations effectively, and contributed to the high ductility by impeding the propagation of micro-cracks inside the grains. The deformation incompatibility between the hot-worked grains and the arched block-shaped long-period stacking ordered (LPSO) phases induced the crack initiation and propagation, which fractured the alloy.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, J.R.

1997-03-18

An apparatus is described for treating water in a circulating water system that has a cooling water basin which includes a slip stream conduit in flow communication with the circulating water system, a source of acid solution in flow communication with the slip stream conduit, and a decarbonator in flow communication with the slip stream conduit and the cooling water basin. In use, a slip stream of circulating water is drawn from the circulating water system into the slip stream conduit of the apparatus. The slip stream pH is lowered by contact with an acid solution provided from the source thereof. The slip stream is then passed through a decarbonator to form a treated slip stream, and the treated slip stream is returned to the cooling water basin. 4 figs.

Native and sodium dodecyl sulfate-capillary gel electrophoresis of proteins on a single microchip.

PubMed

Tsai, Shuo-Wen; Loughran, Michael; Suzuki, Hiroaki; Karube, Isao

2004-02-01

Simultaneous electrophoresis of both native and Sodium dodecyl sulfate (SDS) proteins was observed on a single microchip within 20 min. The capillary array prevented lateral diffusion of SDS components and avoided cross contamination of native protein samples. The planar sputtered electrode format provided a more uniform distribution of separation voltage into each of the 36 parallel microchannel capillaries than platinum wire electrodes commonly used in conventional electrophoresis. The customized geometry of the stacking capillary machined into the cover plate of the microchip facilitated reproducible sample injection without the requirement for stacking gel. Polyimide served as a mask and facilitated insulation of the anode and cathode to prevent electrode lift off and deterioration during continuous electrophoresis, even at a constant current of 8 mA. Improved protein separation was observed during capillary electrophoresis at lower currents. Ferguson plot analysis confirmed the electrophoretic mobility of native globular proteins in accordance with their charge and size. Corresponding Ferguson plot analysis of SDS-associated proteins on the same chip confirmed separation of marker proteins according to their molecular weight.

Demonstration of 1024x1024 pixel dual-band QWIP focal plane array

NASA Astrophysics Data System (ADS)

Gunapala, S. D.; Bandara, S. V.; Liu, J. K.; Mumolo, J. M.; Ting, D. Z.; Hill, C. J.; Nguyen, J.; Rafol, S. B.

2010-04-01

QWIPs are well known for their stability, high pixel-pixel uniformity and high pixel operability which are quintessential parameters for large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). The dual-band QWIP device was developed by stacking two multi-quantum-well stacks tuned to absorb two different infrared wavelengths. The full width at half maximum (FWHM) of the mid-wave infrared (MWIR) band extends from 4.4 - 5.1 μm and FWHM of the long-wave infrared (LWIR) band extends from 7.8 - 8.8 μm. Dual-band QWIP detector arrays were hybridized with direct injection 30 μm pixel pitch megapixel dual-band simultaneously readable CMOS read out integrated circuits using the indium bump hybridization technique. The initial dual-band megapixel QWIP FPAs were cooled to 68K operating temperature. The preliminary data taken from the first megapixel QWIP FPA has shown system NE▵T of 27 and 40 mK for MWIR and LWIR bands respectively.

Analysis of pesticides in soy milk combining solid-phase extraction and capillary electrophoresis-mass spectrometry.

PubMed

Hernández-Borges, Javier; Rodriguez-Delgado, Miguel Angel; García-Montelongo, Francisco J; Cifuentes, Alejandro

2005-06-01

In this work, the determination of a group of triazolopyrimidine sulfoanilide herbicides (cloransulam-methyl, metosulam, flumetsulam, florasulam, and diclosulam) in soy milk by capillary electrophoresis-mass spectrometry (CE-MS) is presented. The main electrospray interface (ESI) parameters (nebulizer pressure, dry gas flow rate, dry gas temperature, and composition of the sheath liquid) are optimized using a central composite design. To increase the sensitivity of the CE-MS method, an off-line sample preconcentration procedure based on solid-phase extraction (SPE) is combined with an on-line stacking procedure (i.e. normal stacking mode, NSM). Samples could be injected for up to 100 s, providing limits of detection (LODs) down to 74 microg/L, i.e., at the low ppb level, with relative standard deviation values (RSD,%) between 3.8% and 6.4% for peak areas on the same day, and between 6.5% and 8.1% on three different days. The usefulness of the optimized SPE-NSM-CE-MS procedure is demonstrated through the sensitive quantification of the selected pesticides in soy milk samples.

Lifetime improvement mechanism in organic light-emitting diodes with mixed materials at a heterojunction interface

NASA Astrophysics Data System (ADS)

Minagawa, Masahiro; Takahashi, Noriko

2016-02-01

To investigate the lifetime improvement mechanism caused by mixing at the heterojunction interface, organic light-emitting diodes (OLEDs) with stacked and mixed 4,4‧-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPD)/tris(8-hydroxyquinoline)aluminum (Alq3) interfaces were fabricated, and changes in their displacement current due to continuous operation were measured. A decrease in accumulated holes at the α-NPD/Alq3 interface was observed in the stacked configuration devices over longer operations. These results indicate that the injected hole density was reduced during continuous operation, implying that the carrier balance became uneven in the emission region. However, few accumulated holes and changes in the displacement current due to continuous operation were observed in the devices having the mixed layer. Therefore, it was deduced that the number of holes concentrated between the α-NPD and Alq3 layers was decreased by mixing at the heterojunction interface, and that the change in the number of holes was smaller during continuous operation, resulting in less degradation.

All-printed diode operating at 1.6 GHz

PubMed Central

Sani, Negar; Robertsson, Mats; Cooper, Philip; Wang, Xin; Svensson, Magnus; Andersson Ersman, Peter; Norberg, Petronella; Nilsson, Marie; Nilsson, David; Liu, Xianjie; Hesselbom, Hjalmar; Akesso, Laurent; Fahlman, Mats; Crispin, Xavier; Engquist, Isak; Berggren, Magnus; Gustafsson, Göran

2014-01-01

Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (IoT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within IoT applications. PMID:25002504

A prospective study of floor surface, shoes, floor cleaning and slipping in US limited-service restaurant workers.

PubMed

Verma, Santosh K; Chang, Wen Ruey; Courtney, Theodore K; Lombardi, David A; Huang, Yueng-Hsiang; Brennan, Melanye J; Mittleman, Murray A; Ware, James H; Perry, Melissa J

2011-04-01

Slips and falls are a leading cause of injury at work. Few studies, however, have systematically examined risk factors of slipping outside the laboratory environment. This study examined the association between floor surface characteristics, slip-resistant shoes, floor cleaning frequency and the risk of slipping in limited-service restaurant workers. 475 workers from 36 limited-service restaurants from three major chains in six states in the USA were recruited to participate in a prospective cohort study of workplace slipping. Kitchen floor surface roughness and coefficient of friction (COF) were measured in eight working areas and then averaged within each restaurant. The use of slip-resistant shoes was determined by examining the participant's shoes and noting the presence of a 'slip-resistant' marking on the sole. Restaurant managers reported the frequency of daily kitchen floor cleaning. Participants reported their slip experience and work hours weekly for up to 12 weeks. The survey materials were made available in three languages: English, Spanish and Portuguese. The associations between rate of slipping and risk factors were assessed using a multivariable negative binomial generalised estimating equation model. The mean of individual slipping rate varied among the restaurants from 0.02 to 2.49 slips per 40 work hours. After adjusting for age, gender, BMI, education, primary language, job tenure and restaurant chain, the use of slip-resistant shoes was associated with a 54% reduction in the reported rate of slipping (95% CI 37% to 64%), and the rate of slipping decreased by 21% (95% CI 5% to 34%) for each 0.1 increase in the mean kitchen COF. Increasing floor cleaning frequency was significantly associated with a decreasing rate of slipping when considered in isolation but not after statistical adjustment for other factors. These results provide support for the use of slip-resistant shoes and measures to increase COF as preventive interventions to reduce slips, falls and injuries.

Integrated dry NO{sub x}/SO{sub 2} emissions control system performance summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunt, T.; Muzio, L.J.; Smith, R.

1997-12-31

The Integrated Dry NO{sub x}/SO{sub 2} Emissions Control System was installed at Public Service Company of Colorado`s Arapahoe 4 generating station in 1992 in cooperation with the US Department of Energy (DOE) and the Electric Power Research Institute (EPRI). This full-scale 100 MWe demonstration combines low-NO{sub x} burners, overfire, air, and selective non-catalytic reduction (SNCR) for NO{sub x} control and dry sorbent injection (DSI) with or without humidification for SO{sub 2} control. Operation and testing of the Integrated Dry NO{sub x}/SO{sub 2} Emissions Control System began in August 1992 and will continue through 1996. Results of the NO{sub x} controlmore » technologies show that the original system goal of 70% NO{sub x} removal has been easily met and the combustion and SNCR systems can achieve NO{sub x} removals of up to 80% at full load. Duct injection of commercial calcium hydroxide has achieved a maximum SO{sub 2} removal of nearly 40% while humidifying the flue gas to a 20 F approach to saturation. Sodium-based dry sorbent injection has provided SO{sub 2} removal of over 70% without the occurrence of a visible NO{sub 2} plume. Recent test work has improved SNCR performance at low loads and has demonstrated that combined dry sodium injection and SNCR yields both lower NO{sub 2} levels and NH{sub 3} slip than either technology alone.« less

Interplate coupling and seismic-aseismic slip patterns

NASA Astrophysics Data System (ADS)

Senatorski, Piotr

2017-04-01

Numerical simulations were carried out to explain the seismic and aseismic slip paradox. Recent observations of megathrust faults show that stable and unstable slip movements can occur at the same locations. This contradicts the previous view based on frictional sliding theories. In the present work, an asperity fault model with the slip-dependent friction and stress dependent healing is used to show that the character of slip can change, even if friction parameters, such as strength and slip-weakening distance, are fixed. The reason is that the slow versus fast slip interplay is more than just about the friction law problem. The character of slip depends both on the local friction and on the system stiffness. The stiffness is related to the slipping area size and distribution of slips, so it changes from one event to another. It is also shown that the high strength interplate patches, such as subducted seamounts, can both promote and restrain large earthquakes, depending on the slip-weakening distance lengths.

Viscous Moment, Mechanism of Slow Slip, and Subduction Megathrust Viscosity

NASA Astrophysics Data System (ADS)

Fagereng, A.

2015-12-01

Slow slip events (SSEs) represent transient slip velocities slower than earthquakes but faster than steady, average plate motion. SSEs repeating at the same location have characteristic slip magnitude and duration. Contrary to earthquakes, however, average slip relates to neither duration nor area. Variations in duration, slip, and slip rate can instead be tied to variations in effective viscosity, calculated from a viscous definition of moment. In this paradigm, the observation that deep slow slip events are slower and longer, implies a higher effective viscosity than in shallower, colder SSEs. Observed variations in effective viscosity and slip rate can be interpreted in terms of differences in driving stress and shear zone width, and likely arise in anastomosing shear zones containing a heterogeneous mixture of materials.

Spatial and Temporal Variations in Slip Partitioning During Oblique Convergence Experiments

NASA Astrophysics Data System (ADS)

Beyer, J. L.; Cooke, M. L.; Toeneboehn, K.

2017-12-01

Physical experiments of oblique convergence in wet kaolin demonstrate the development of slip partitioning, where two faults accommodate strain via different slip vectors. In these experiments, the second fault forms after the development of the first fault. As one strain component is relieved by one fault, the local stress field then favors the development of a second fault with different slip sense. A suite of physical experiments reveals three styles of slip partitioning development controlled by the convergence angle and presence of a pre-existing fault. In experiments with low convergence angles, strike-slip faults grow prior to reverse faults (Type 1) regardless of whether the fault is precut or not. In experiments with moderate convergence angles, slip partitioning is dominantly controlled by the presence of a pre-existing fault. In all experiments, the primarily reverse fault forms first. Slip partitioning then develops with the initiation of strike-slip along the precut fault (Type 2) or growth of a secondary reverse fault where the first fault is steepest. Subsequently, the slip on the first fault transitions to primarily strike-slip (Type 3). Slip rates and rakes along the slip partitioned faults for both precut and uncut experiments vary temporally, suggesting that faults in these slip-partitioned systems are constantly adapting to the conditions produced by slip along nearby faults in the system. While physical experiments show the evolution of slip partitioning, numerical simulations of the experiments provide information about both the stress and strain fields, which can be used to compute the full work budget, providing insight into the mechanisms that drive slip partitioning. Preliminary simulations of precut experiments show that strain energy density (internal work) can be used to predict fault growth, highlighting where fault growth can reduce off-fault deformation in the physical experiments. In numerical simulations of uncut experiments with a first non-planar oblique slip fault, strain energy density is greatest where the first fault is steepest, as less convergence is accommodated along this portion of the fault. The addition of a second slip-partitioning fault to the system decreases external work indicating that these faults increase the mechanical efficiency of the system.

Slow Earthquakes and The Mechanics of Slow Frictional Stick-Slip

NASA Astrophysics Data System (ADS)

Marone, Chris; Scuderi, Marco; Leeman, John; Saffer, Demian; Collettini, Cristiano; Johnson, Paul

2015-04-01

Slow earthquakes represent one mode of the spectrum of fault slip behaviors ranging from steady aseismic slip to normal earthquakes. Like normal earthquakes, slow earthquakes can occur repetitively, such that a fault fails in a form of stick-slip failure defined by interseismic strain accumulation and slow, quasidynamic slip. The mechanics of frictional stick-slip and seismogenic faulting appear to apply to slow earthquakes, however, the mechanisms that limit dynamic slip velocity, rupture propagation speed, and the scaling between moment and duration of slow earthquakes are poorly understood. Here, we describe laboratory experiments that explore the mechanics of repetitive, slow frictional stick-slip failure. We document the role of loading stiffness and friction constitutive behavior in dictating the properties of repetitive, frictional stick-slip. Our results show that a spectrum of dynamic and quasidynamic slip velocities can occur in stick-slip events depending on the relation between loading stiffness k and the rheologic critical stiffness kc given, in the context of rate and state friction, by the ratio of the friction rate parameter (b-a) divided by the critical friction distance Dc. Slow slip is favored by conditions for which k is ~ equal to kc, whereas normal, fast stick slip occurs when k/kc < 1. We explore the role of elastic coupling and spatially extended slip propagation by comparing slow slip results for shear in a layer driven by forcing blocks of varying stiffness. We evaluate our data in the framework of rate and state friction laws and focus on the frictional mechanics of slow stick-slip failure with special attention paid to the connections between quasidynamic failure and mechanisms of the brittle-ductile transition in fault rocks.

An integrated perspective of the continuum between earthquakes and slow-slip phenomena

USGS Publications Warehouse

Peng, Zhigang; Gomberg, Joan

2010-01-01

The discovery of slow-slip phenomena has revolutionized our understanding of how faults accommodate relative plate motions. Faults were previously thought to relieve stress either through continuous aseismic sliding, or as earthquakes resulting from instantaneous failure of locked faults. In contrast, slow-slip events proceed so slowly that slip is limited and only low-frequency (or no) seismic waves radiate. We find that slow-slip phenomena are not unique to the depths (tens of kilometres) of subduction zone plate interfaces. They occur on faults in many settings, at numerous scales and owing to various loading processes, including landslides and glaciers. Taken together, the observations indicate that slowly slipping fault surfaces relax most of the accrued stresses through aseismic slip. Aseismic motion can trigger more rapid slip elsewhere on the fault that is sufficiently fast to generate seismic waves. The resulting radiation has characteristics ranging from those indicative of slow but seismic slip, to those typical of earthquakes. The mode of seismic slip depends on the inherent characteristics of the fault, such as the frictional properties. Slow-slip events have previously been classified as a distinct mode of fault slip compared with that seen in earthquakes. We conclude that instead, slip modes span a continuum and are of common occurrence.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, Joe R.

1997-01-01

An apparatus (10) for treating water in a circulating water system (12) t has a cooling water basin (14) includes a slip stream conduit (16) in flow communication with the circulating water system (12), a source (36) of acid solution in flow communication with the slip stream conduit (16), and a decarbonator (58) in flow communication with the slip stream conduit (16) and the cooling water basin (14). In use, a slip stream of circulating water is drawn from the circulating water system (12) into the slip stream conduit (16) of the apparatus (10). The slip stream pH is lowered by contact with an acid solution provided from the source (36) thereof. The slip stream is then passed through a decarbonator (58) to form a treated slip stream, and the treated slip stream is returned to the cooling water basin (14).

Slip and frictional heating of extruded polyethylene melts

NASA Astrophysics Data System (ADS)

Pérez-González, José; Marín-Santibáñez, Benjamín M.; Zamora-López, Héctor S.; Rodríguez-González, Francisco

2017-05-01

Extrusion of polymer melts with slip at the die generates frictional heating. The relationship between slip flow and frictional heating during the continuous extrusion of a non-slipping linear low-density (LLDPE) and a slipping high-density polyethylene (HDPE), respectively, both pure as well as blended with a fluoropolymer processing aid (PA), was investigated in this work by Rheo-particle image velocimetry and thermal imaging. Significant rises in temperature were measured under slip and no slip conditions, being these much higher than the values predicted by the adiabatic flow assumption. Clear difference was made between viscous and frictional heating before the stick-slip regime for the LLDPE, even though they could not be distinguished from one another at higher stresses. Such a difference, however, could not be made for the slipping HDPE, since overall in the presence of slip, frictional and viscous heating act synergistically to increase the melt temperature.

Evidence for Seismic and Aseismic Slip along a Foreland Thrust Fault, Southern Appalachians

NASA Astrophysics Data System (ADS)

Newman, J.; Wells, R. K.; Holyoke, C. W.; Wojtal, S. F.

2013-12-01

Studies of deformation along ancient thrust faults form the basis for much of our fundamental understanding of fault and shear zone processes. These classic studies interpreted meso- and microstructures as formed during aseismic creep. Recent experimental studies, and studies of naturally deformed rocks in seismically active regions, reveal similar microstructures to those observed locally in a carbonate foreland thrust from the southern Appalachians, suggesting that this thrust fault preserves evidence of both seismic and aseismic deformation. The Copper Creek thrust, TN, accommodated 15-20 km displacement, at depths of 4-6 km, as estimated from balanced cross-sections. At the Diggs Gap exposure of the Copper Creek thrust, an approximately 2 cm thick, vein-like shear zone separates shale layers in the hanging wall and footwall. The shear zone is composed of anastomosing layers of ultrafine-grained calcite and/or shale as well as aggregate clasts of ultrafine-grained calcite or shale. The boundary between the shear zone and the hanging wall is sharp, with slickensides along the boundary, parallel to the shear zone movement direction. A 350 μm-thick layer of ultrafine-grained calcite separates the shear zone and the footwall. Fault parallel and perpendicular calcite veins are common in the footwall and increase in density towards the shear zone. Microstructures within the vein-like shear zone that are similar to those observed in experimental studies of unstable slip include: ultrafine-grained calcite (~0.34 μm), nano-aggregate clasts (100-300 nm), injection structures, and vein-wrapped and matrix-wrapped clasts. Not all structures within the shear zone and ultrafine-grained calcite layer suggest seismic slip. Within the footwall veins and calcite aggregate clasts within the shear zone, pores at twin-twin intersections suggest plasticity-induced fracturing as the main mechanism for grain size reduction. Interpenetrating grain boundaries in ultrafine-grained calcite and a lack of a lattice preferred orientation suggest ultrafine-grained calcite deformed by diffusion creep accommodated grain boundary sliding. These structures suggest a strain-rate between 10-15 - 10-11 s-1, using calcite flow laws at temperatures 150-250 °C. Microstructures suggest both seismic and aseismic slip along this ancient fault zone. During periods of aseismic slip, deformation is accommodated by plasticity-induced fracturing and diffusion creep. Calcite veins suggest an increase in pore-fluid pressure, contributing to fluidized and unstable flow, but also providing the calcite that deformed by diffusion creep during aseismic creep.

Surface slip associated with the 2004 Parkfield, California, earthquake measured on alinement arrays

USGS Publications Warehouse

Lienkaemper, J.J.; Baker, B.; McFarland, F.S.

2006-01-01

Although still continuing, surface slip from the 2004 Parkfield earth-quake as measured on alinement arrays appears to be approaching about 30-35 cm between Parkfield and Gold Hill. This includes slip along the main trace and the Southwest Fracture Zone (SWFZ). Slip here was higher in 1966 at about 40 cm. The distribution of 2004 slip appears to have a shape similar to that of the 1966 event, but final slip is expected to be lower in 2004 by about 3-15 cm, even when continuing slip is accounted for. Proportionately, this difference is most notable at the south end at Highway 46, where the 1966 event slip was 13 cm compared to the 2004 slip of 4 cm. Continuous Global Positioning System and creepmeters suggest that significant surface coseismic slip apparently occurred mainly on the SWFZ and perhaps on Middle Mountain (the latter possibly caused by shaking) (Langbein et al., 2005). Creepmeters indicate only minor (<0.2 cm) surface coseismic slip occurred on the main trace between Parkfield and Gold Hill. We infer that 3-6 cm slip accumulated across our arrays in the first 24 hr. At Highway 46, slip appears complete, whereas the remaining sites are expected to take 2-6 years to reach their background creep rates. Following the 1966 event, afterslip at one site persisted as much as 5-10 years. The much longer recurrence intervals between the past two Parkfield earthquakes and the decreasing slip per event may suggest that larger slip deficits are now growing along the Parkfield segment.

Evaluation of ceramics for stator application: Gas turbine engine report

NASA Technical Reports Server (NTRS)

Trela, W.; Havstad, P. H.

1978-01-01

Current ceramic materials, component fabrication processes, and reliability prediction capability for ceramic stators in an automotive gas turbine engine environment are assessed. Simulated engine duty cycle testing of stators conducted at temperatures up to 1093 C is discussed. Materials evaluated are SiC and Si3N4 fabricated from two near-net-shape processes: slip casting and injection molding. Stators for durability cycle evaluation and test specimens for material property characterization, and reliability prediction model prepared to predict stator performance in the simulated engine environment are considered. The status and description of the work performed for the reliability prediction modeling, stator fabrication, material property characterization, and ceramic stator evaluation efforts are reported.

Ceramic technology for solar thermal receivers

NASA Technical Reports Server (NTRS)

Kudirka, A. A.; Smoak, R. H.

1981-01-01

The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

Effective slip identities for viscous flow over arbitrary patterned surfaces

NASA Astrophysics Data System (ADS)

Kamrin, Ken; Six, Pierre

2012-11-01

For a variety of applications, most recently microfluidics, the ability to control fluid motions using surface texturing has been an area of ongoing interest. In this talk, we will develop several identities relating to the construction of effective slip boundary conditions for patterned surfaces. The effective slip measures the apparent slip of a fluid layer flowing over a patterned surface when viewing the flow far from the surface. In specific, shear flows of tall fluid layers over periodic surfaces (surfaces perturbed from a planar no-slip boundary by height and/or hydrophobicity fluctuations) are governed by an effective slip matrix that relates the vector of far-field shear stress (applied to the top of the fluid layer) to the effective slip velocity vector that emerges from the flow. Of particular note, we will demonstrate several general rules that describe the effective slip matrix: (1) that the effective slip matrix is always symmetric, (2) that the effective slip over any hydrophobically striped surface implies a family of related results for slip over other striped surfaces, and (3) that when height or hydrophobicity fluctuations are small, the slip matrix can be approximated directly using a simple formula derived from the surface pattern.

Refining the shallow slip deficit

NASA Astrophysics Data System (ADS)

Xu, Xiaohua; Tong, Xiaopeng; Sandwell, David T.; Milliner, Christopher W. D.; Dolan, James F.; Hollingsworth, James; Leprince, Sebastien; Ayoub, Francois

2016-03-01

Geodetic slip inversions for three major (Mw > 7) strike-slip earthquakes (1992 Landers, 1999 Hector Mine and 2010 El Mayor-Cucapah) show a 15-60 per cent reduction in slip near the surface (depth < 2 km) relative to the slip at deeper depths (4-6 km). This significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated. In this study, we improve the static coseismic slip inversion for these three earthquakes, especially at shallow depths, by: (1) including data capturing the near-fault deformation from optical imagery and SAR azimuth offsets; (2) refining the interferometric synthetic aperture radar processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU (Statistical Non-linear Approach for Phase Unwrapping) assuming a maximum discontinuity and an on-fault correlation mask; (3) using more detailed, geologically constrained fault geometries and (4) incorporating additional campaign global positioning system (GPS) data. The refined slip models result in much smaller SSDs of 3-19 per cent. We suspect that the remaining minor SSD for these earthquakes likely reflects a combination of our elastic model's inability to fully account for near-surface deformation, which will render our estimates of shallow slip minima, and potentially small amounts of interseismic fault creep or triggered slip, which could `make up' a small percentages of the coseismic SSD during the interseismic period. Our results indicate that it is imperative that slip inversions include accurate measurements of near-fault surface deformation to reliably constrain spatial patterns of slip during major strike-slip earthquakes.

A Model for Low-Frequency Earthquake Slip in Cascadia

NASA Astrophysics Data System (ADS)

Chestler, S.; Creager, K.

2017-12-01

Low-Frequency Earthquakes (LFEs) are commonly used to identify when and where slow slip occurred, especially for slow slip events that are too small to be observed geodetically. Yet, an understanding of how slip occurs within an LFE family patch, or patch on the plate interface where LFEs repeat, is limited. How much slip occurs per LFE and over what area? Do all LFEs within an LFE family rupture the exact same spot? To answer these questions, we implement a catalog of 39,966 LFEs, sorted into 45 LFE families, beneath the Olympic Peninsula, WA. LFEs were detected and located using data from approximately 100 3-component stations from the Array of Arrays experiment. We compare the LFE family patch area to the area within the LFE family patch that slips through LFEs during Cascadia Episodic Tremor and Slip (ETS) events. Patch area is calculated from relative LFE locations, solved for using the double difference method. Slip area is calculated from the characteristic moment (mean of the exponential moment-frequency distribution) and number LFEs for each family and geodetically measured ETS slip. We find that 0.5-5% of the area within an LFE family patch slips through LFEs. The rest must deform in some other manner (e.g., ductile deformation). We also explore LFE slip patterns throughout the entire slow slip zone. Is LFE slip uniform? Does LFE slip account for all geodetically observed slow slip? Double difference relocations reveal that LFE families are 2 km patches where LFE are clustered close together. Additionally, there are clusters of LFE families with diameters of 4-15 km. There are gaps with no observable, repeating LFEs between LFE families in clusters and between clusters of LFE families. Based on this observation, we present a model where LFE slip is heterogeneous on multiple spatial scales. Clusters of LFE families may represent patches with higher strength than the surrounding areas. Finally, we find that LFE slip only accounts for a small fraction ( 0.1%) of the slip that occurs during an ETS event.

Geothermal induced seismicity: What links source mechanics and event magnitudes to faulting regime and injection rates?

NASA Astrophysics Data System (ADS)

Martinez-Garzon, Patricia; Kwiatek, Grzegorz; Bohnhoff, Marco; Dresen, Georg

2017-04-01

Improving estimates of seismic hazard associated to reservoir stimulation requires advanced understanding of the physical processes governing induced seismicity, which can be better achieved by carefully processing large datasets. To this end, we investigate source-type processes (shear/tensile/compaction) and rupture geometries with respect to the local stress field using seismicity from The Geysers (TG) and Salton Sea geothermal reservoirs, California. Analysis of 869 well-constrained full moment tensors (MW 0.8-3.5) at TG reveals significant non-double-couple (NDC) components (>25%) for 65% of the events and remarkably diversity in the faulting mechanisms. Volumetric deformation is clearly governed by injection rates with larger NDC components observed near injection wells and during high injection periods. The overall volumetric deformation from the moment tensors increases with time, possibly reflecting a reservoir pore pressure increase after several years of fluid injection with no significant production nearby. The obtained source mechanisms and fault orientations are magnitude-dependent and vary significantly between faulting regimes. Normal faulting events (MW < 2) reveal substantial NDC components indicating dilatancy, and they occur on varying fault orientations. In contrast, strike-slip events dominantly reveal a double-couple source, larger magnitudes (MW > 2) and mostly occur on optimally oriented faults with respect to the local stress field. NDC components indicating closure of cracks and pore spaces in the source region are found for reverse faulting events with MW > 2.5. Our findings from TG are generally consistent with preliminary source-type results from a reduced subset of well-recorded seismicity at the Salton Sea geothermal reservoir. Combined results imply that source processes and magnitudes of geothermal-induced seismicity are strongly affected by and systematically related to the hydraulic operations and the local stress state.

Modeling of rock friction 2. Simulation of preseismic slip

USGS Publications Warehouse

Dieterich, J.H.

1979-01-01

The constitutive relations developed in the companion paper are used to model detailed observations of preseismic slip and the onset of unstable slip in biaxial laboratory experiments. The simulations employ a deterministic plane strain finite element model to represent the interactions both within the sliding blocks and between the blocks and the loading apparatus. Both experiments and simulations show that preseismic slip is controlled by initial inhomogeneity of shear stress along the sliding surface relative to the frictional strength. As a consequence of the inhomogeneity, stable slip begins at a point on the surface and the area of slip slowly expands as the external loading increases. A previously proposed correlation between accelerating rates of stable slip and growth of the area of slip is supported by the simulations. In the simulations and in the experiments, unstable slip occurs shortly after a propagating slip event traverses the sliding surface and breaks out at the ends of the sample. In the model the breakout of stable slip causes a sudden acceleration of slip rates. Because of velocity dependency of the constitutive relationship for friction, the rapid acceleration of slip causes a decrease in frictional strength. Instability occurs when the frictional strength decreases with displacement at a rate that exceeds the intrinsic unloading characteristics of the sample and test machine. A simple slider-spring model that does not consider preseismic slip appears to approximate the transition adequately from stable sliding to unstable slip as a function of normal stress, machine stiffness, and surface roughness for small samples. However, for large samples and for natural faults the simulations suggest that the simple model may be inaccurate because it does not take into account potentially large preseismic displacements that will alter the friction parameters prior to instability. Copyright ?? 1979 by the American Geophysical Union.

Fixed recurrence and slip models better predict earthquake behavior than the time- and slip-predictable models 1: repeating earthquakes

USGS Publications Warehouse

Rubinstein, Justin L.; Ellsworth, William L.; Chen, Kate Huihsuan; Uchida, Naoki

2012-01-01

The behavior of individual events in repeating earthquake sequences in California, Taiwan and Japan is better predicted by a model with fixed inter-event time or fixed slip than it is by the time- and slip-predictable models for earthquake occurrence. Given that repeating earthquakes are highly regular in both inter-event time and seismic moment, the time- and slip-predictable models seem ideally suited to explain their behavior. Taken together with evidence from the companion manuscript that shows similar results for laboratory experiments we conclude that the short-term predictions of the time- and slip-predictable models should be rejected in favor of earthquake models that assume either fixed slip or fixed recurrence interval. This implies that the elastic rebound model underlying the time- and slip-predictable models offers no additional value in describing earthquake behavior in an event-to-event sense, but its value in a long-term sense cannot be determined. These models likely fail because they rely on assumptions that oversimplify the earthquake cycle. We note that the time and slip of these events is predicted quite well by fixed slip and fixed recurrence models, so in some sense they are time- and slip-predictable. While fixed recurrence and slip models better predict repeating earthquake behavior than the time- and slip-predictable models, we observe a correlation between slip and the preceding recurrence time for many repeating earthquake sequences in Parkfield, California. This correlation is not found in other regions, and the sequences with the correlative slip-predictable behavior are not distinguishable from nearby earthquake sequences that do not exhibit this behavior.

Stick-slip as a monitor of rates, states and frictional properties along thrusts in sand wedges

NASA Astrophysics Data System (ADS)

Rosenau, Matthias; Santimano, Tasca; Ritter, Malte; Oncken, Onno

2014-05-01

We developed a sandbox setup which allows monitoring the push of the moving backwall indenting a layer of sand. Depending on the ratio between indenter compliancy versus strain weakening of the granular material, wedge deformation shows unstable slip marked by force drops of various sizes and at multiple temporal scales. Basically we observe long-period slip instabilities related to strain localization during the formation of new thrusts, intermediate-period slip instabilities related to reactivation of existing thrusts and short-period slip instabilities related to the stick-slip mechanism of slip accumulation along "seismic" faults. Observed stick-slip is characterized by highly correlated size and frequency ("regular stick-slip") and is sensitive to integrated normal load, slip rate and frictional properties along the active thrust(s). By independently constraining the frictional properties using a ring-shear tester, we infer the integrated normal loads on the active faults from the stick-slip events and benchmark the results against a model calculating the normal loads from the wedge geometry. This way we are able to monitor rates, states and frictional properties along thrusts in sand wedges at unprecedented detail. As an example of application, a kinematic analysis of the stick slip events in the sandbox demonstrates how slip rates along thrusts vary systematically within accretion cycles although the kinematic boundary condition is stationary. Accordingly transient fault slip rates may accelerate up to twice the long-term convergence rate during formation of new thrusts and decelerate in the post-thrust formation stage in a non-linear way. Applied to nature this suggests that fault slip rate variations at the thousand-year time scale might be attributable to the elasticity of plates and material weakening rather than changes in plate velocities.

Earthquake scaling laws for rupture geometry and slip heterogeneity

NASA Astrophysics Data System (ADS)

Thingbaijam, Kiran K. S.; Mai, P. Martin; Goda, Katsuichiro

2016-04-01

We analyze an extensive compilation of finite-fault rupture models to investigate earthquake scaling of source geometry and slip heterogeneity to derive new relationships for seismic and tsunami hazard assessment. Our dataset comprises 158 earthquakes with a total of 316 rupture models selected from the SRCMOD database (http://equake-rc.info/srcmod). We find that fault-length does not saturate with earthquake magnitude, while fault-width reveals inhibited growth due to the finite seismogenic thickness. For strike-slip earthquakes, fault-length grows more rapidly with increasing magnitude compared to events of other faulting types. Interestingly, our derived relationship falls between the L-model and W-model end-members. In contrast, both reverse and normal dip-slip events are more consistent with self-similar scaling of fault-length. However, fault-width scaling relationships for large strike-slip and normal dip-slip events, occurring on steeply dipping faults (δ~90° for strike-slip faults, and δ~60° for normal faults), deviate from self-similarity. Although reverse dip-slip events in general show self-similar scaling, the restricted growth of down-dip fault extent (with upper limit of ~200 km) can be seen for mega-thrust subduction events (M~9.0). Despite this fact, for a given earthquake magnitude, subduction reverse dip-slip events occupy relatively larger rupture area, compared to shallow crustal events. In addition, we characterize slip heterogeneity in terms of its probability distribution and spatial correlation structure to develop a complete stochastic random-field characterization of earthquake slip. We find that truncated exponential law best describes the probability distribution of slip, with observable scale parameters determined by the average and maximum slip. Applying Box-Cox transformation to slip distributions (to create quasi-normal distributed data) supports cube-root transformation, which also implies distinctive non-Gaussian slip distributions. To further characterize the spatial correlations of slip heterogeneity, we analyze the power spectral decay of slip applying the 2-D von Karman auto-correlation function (parameterized by the Hurst exponent, H, and correlation lengths along strike and down-slip). The Hurst exponent is scale invariant, H = 0.83 (± 0.12), while the correlation lengths scale with source dimensions (seismic moment), thus implying characteristic physical scales of earthquake ruptures. Our self-consistent scaling relationships allow constraining the generation of slip-heterogeneity scenarios for physics-based ground-motion and tsunami simulations.

Spontaneous Imbibition Process in Micro-Nano Fractal Capillaries Considering Slip Flow

NASA Astrophysics Data System (ADS)

Shen, Yinghao; Li, Caoxiong; Ge, Hongkui; Guo, Xuejing; Wang, Shaojun

An imbibition process of water into a matrix is required to investigate the influences of large-volume fracturing fluids on gas production of unconventional formations. Slip flow has been recognized by recent studies as a major mechanism of fluid transport in nanotubes. For nanopores in shale, a slip boundary is nonnegligible in the imbibition process. In this study, we established an analytic equation of spontaneous imbibition considering slip effects in capillaries. A spontaneous imbibition model that couples the analytic equation considering the slip effect was constructed based on fractal theory. We then used a model for various conditions, such as slip boundary, pore structure, and fractal dimension of pore tortuosity, to capture the imbibition characteristics considering the slip effect. A dynamic contact angle was integrated into the modeling. Results of our study verify that the slip boundary influences water imbibition significantly. The imbibition speed is significantly improved when slip length reaches the equivalent diameter of a tube. Therefore, disregarding the slip effect will underestimate the imbibition speed in shale samples.

Reconsidering earthquake scaling

USGS Publications Warehouse

Gomberg, Joan S.; Wech, Aaron G.; Creager, Kenneth; Obara, K.; Agnew, Duncan

2016-01-01

The relationship (scaling) between scalar moment, M0, and duration, T, potentially provides key constraints on the physics governing fault slip. The prevailing interpretation of M0-T observations proposes different scaling for fast (earthquakes) and slow (mostly aseismic) slip populations and thus fundamentally different driving mechanisms. We show that a single model of slip events within bounded slip zones may explain nearly all fast and slow slip M0-T observations, and both slip populations have a change in scaling, where the slip area growth changes from 2-D when too small to sense the boundaries to 1-D when large enough to be bounded. We present new fast and slow slip M0-T observations that sample the change in scaling in each population, which are consistent with our interpretation. We suggest that a continuous but bimodal distribution of slip modes exists and M0-T observations alone may not imply a fundamental difference between fast and slow slip.

The impact of a pressurized regional sea or global ocean on stresses on Enceladus

NASA Astrophysics Data System (ADS)

Johnston, Stephanie A.; Montési, Laurent G. J.

2017-06-01

Liquid water is likely present in the interior of Enceladus, but it is still debated whether this water forms a global ocean or a regional sea and whether the present-day situation is stable. As the heat flux of Enceladus exceeds most heat source estimates, the liquid water is likely cooling and crystallizing, which results in expansion and pressurization of the sea or ocean. We determine, using an axisymmetric Finite Element Model, the tectonic patterns that pressurization of a regional sea or global ocean might produce at the surface of Enceladus. Tension is always predicted above where the ice is thinnest and generates cracks that might be at the origin of the Tiger Stripes. Tectonic activity is also expected in an annulus around the sea if the ice shell is in contact with but slips freely along the rocky core of the satellite. Cracks at the north pole are expected if the shell slips along the core or if there is a global ocean with thin ice at the pole. Water is likely injected along the base of the ice when the shell is grounded, which may lead to cycles of tectonic activity with the shell alternating between floating and grounded states and midlatitude faulting occurring at the transition from a grounded to a floating state.

Fluid Pressures at the Shoe-Floor-Contaminant Interface During Slips: Effects of Tread & Implications on Slip Severity

PubMed Central

Beschorner, Kurt E.; Albert, Devon L.; Chambers, April J.; Redfern, Mark S.

2018-01-01

Previous research on slip and fall accidents has suggested that pressurized fluid between the shoe and floor is responsible for initiating slips yet this effect has not been verified experimentally. This study aimed to 1) measure hydrodynamic pressures during slipping for treaded and untreaded conditions; 2) determine the effects of fluid pressure on slip severity; and 3) quantify how fluid pressures vary with instantaneous resultant slipping speed, position on the shoe surface, and throughout the progression of the slip. Eighteen subjects walked on known dry and unexpected slippery floors, while wearing treaded and untreaded shoes. Fluid pressure sensors, embedded in the floor, recorded hydrodynamic pressures during slipping. The maximum fluid pressures (mean+/−standard deviation) were significantly higher for the untreaded conditions (124 +/−75 kPa) than the treaded conditions (1.1 +/−0.29 kPa). Maximum fluid pressures were positively correlated with peak slipping speed (r = 0.87), suggesting that higher fluid pressures, which are associated with untreaded conditions, resulted in more severe slips. Instantaneous resultant slipping speed and position of sensor relative to the shoe sole and walking direction explained 41% of the fluid pressure variability. Fluid pressures were primarily observed for untreaded conditions. This study confirms that fluid pressures are relevant to slipping events, consistent with fluid dynamics theory (i.e. the Reynolds equation), and can be modified with shoe tread design. The results suggest that the occurrence and severity of unexpected slips can be reduced by designing shoes/floors that reduce underfoot fluid pressures. PMID:24267270

Volcanotectonic earthquakes induced by propagating dikes

NASA Astrophysics Data System (ADS)

Gudmundsson, Agust

2016-04-01

Volcanotectonic earthquakes are of high frequency and mostly generated by slip on faults. During chamber expansion/contraction earthquakes are distribution in the chamber roof. Following magma-chamber rupture and dike injection, however, earthquakes tend to concentrate around the dike and follow its propagation path, resulting in an earthquake swarm characterised by a number of earthquakes of similar magnitudes. I distinguish between two basic processes by which propagating dikes induce earthquakes. One is due to stress concentration in the process zone at the tip of the dike, the other relates to stresses induced in the walls and surrounding rocks on either side of the dike. As to the first process, some earthquakes generated at the dike tip are related to pure extension fracturing as the tip advances and the dike-path forms. Formation of pure extension fractures normally induces non-double couple earthquakes. There is also shear fracturing in the process zone, however, particularly normal faulting, which produces double-couple earthquakes. The second process relates primarily to slip on existing fractures in the host rock induced by the driving pressure of the propagating dike. Such pressures easily reach 5-20 MPa and induce compressive and shear stresses in the adjacent host rock, which already contains numerous fractures (mainly joints) of different attitudes. In piles of lava flows or sedimentary beds the original joints are primarily vertical and horizontal. Similarly, the contacts between the layers/beds are originally horizontal. As the layers/beds become buried, the joints and contacts become gradually tilted so that the joints and contacts become oblique to the horizontal compressive stress induced by a driving pressure of the (vertical) dike. Also, most of the hexagonal (or pentagonal) columnar joints in the lava flows are, from the beginning, oblique to an intrusive sheet of any attitude. Consequently, the joints and contacts function as potential shear fractures many of which, when loaded by the dike driving pressure, slip and generate double-couple earthquakes. All types of faulting occur, but strike-slip and reverse faulting are particularly common. Dike-induced faulting is one reason why (mostly small) reverse and strike-slip faults are so commonly observed in palaeorift-zones. Here I present field examples of dike-induced extension fractures and fault slips. I also present numerical and analytical models to explain the effects of mechanical layering and heterogeneity on the likely dike paths and the associated variations in the type and location of the dike-induced earthquakes. Becerril, L., Galindo, I., Gudmundsson, A., Morales, J.M., 2013. Depth of origin of magma in eruptions. Sci. Reports (Nature Publishing), 3, 2762, doi: 10.1038/srep02762. Gudmundsson, A., Lecoeur, N., Mohajeri, N., Thordarson, T., 2014. Dike emplacement at Bardarbunga, Iceland, induces unusual stress changes, caldera deformation, and earthquakes. Bull. Volcanol., 76, 869, doi: 10.1007/s00445-014-0869-8.

The Mechanics of Transient Fault Slip and Slow Earthquakes

NASA Astrophysics Data System (ADS)

Marone, C.; Leeman, J.; Scuderi, M.; Saffer, D. M.; Collettini, C.

2015-12-01

Earthquakes are understood as frictional stick-slip instabilities in which stored elastic energy is released suddenly, driving catastrophic failure. In normal (fast) earthquakes the rupture zone expands at a rate dictated by elastic wave speeds, a few km/s, and fault slip rates reach 1-10 m/s. However, tectonic faults also fail in slow earthquakes with rupture durations of months and fault slip speeds of ~100 micron/s or less. We know very little about the mechanics of slow earthquakes. What determines the rupture propagation velocity in slow earthquakes and in other forms of quasi-dynamic rupture? What processes limit stress drop and fault slip speed in slow earthquakes? Existing lab studies provide some help via observations of complex forms of stick-slip, creep-slip, or, in a few cases, slow slip. However, these are mainly anecdotal and rarely include examples of repetitive slow slip or systematic measurements that could be used to isolate the underlying mechanisms. Numerical studies based on rate and state friction also shed light on transiently accelerating slip, showing that slow slip can occur if: 1) fault rheology involves a change in friction rate dependence (a-b) with velocity or unusually large values of the frictional weakening distance Dc, or 2) fault zone elastic stiffness equals the critical frictional weakening rate kc = (b-a)/Dc. Recent laboratory work shows that the latter can occur much more commonly that previously thought. We document the complete spectrum of stick-slip behaviors from transient slow slip to fast stick-slip for a narrow range of conditions around k/kc = 1.0. Slow slip occurs near the threshold between stable and unstable failure, controlled by the interplay of fault zone frictional properties, normal stress, and elastic stiffness of the surrounding rock. Our results provide a generic mechanism for slow earthquakes, consistent with the wide range of conditions for which slow slip has been observed.

Surface fault slip associated with the 2004 Parkfield, California, earthquake

USGS Publications Warehouse

Rymer, M.J.; Tinsley, J. C.; Treiman, J.A.; Arrowsmith, J.R.; Ciahan, K.B.; Rosinski, A.M.; Bryant, W.A.; Snyder, H.A.; Fuis, G.S.; Toke, N.A.; Bawden, G.W.

2006-01-01

Surface fracturing occurred along the San Andreas fault, the subparallel Southwest Fracture Zone, and six secondary faults in association with the 28 September 2004 (M 6.0) Parkfield earthquake. Fractures formed discontinuous breaks along a 32-km-long stretch of the San Andreas fault. Sense of slip was right lateral; only locally was there a minor (1-11 mm) vertical component of slip. Right-lateral slip in the first few weeks after the event, early in its afterslip period, ranged from 1 to 44 mm. Our observations in the weeks following the earthquake indicated that the highest slip values are in the Middle Mountain area, northwest of the mainshock epicenter (creepmeter measurements indicate a similar distribution of slip). Surface slip along the San Andreas fault developed soon after the mainshock; field checks in the area near Parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event. Slip along the Southwest Fracture Zone developed coseismically and extended about 8 km. Sense of slip was right lateral; locally there was a minor to moderate (1-29 mm) vertical component of slip. Right-lateral slip ranged from 1 to 41 mm. Surface slip along secondary faults was right lateral; the right-lateral component of slip ranged from 3 to 5 mm. Surface slip in the 1966 and 2004 events occurred along both the San Andreas fault and the Southwest Fracture Zone. In 1966 the length of ground breakage along the San Andreas fault extended 5 km longer than that mapped in 2004. In contrast, the length of ground breakage along the Southwest Fracture Zone was the same in both events, yet the surface fractures were more continuous in 2004. Surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the San Andreas fault and the Southwest Fracture Zone, further revealing aspects of the structural setting and fault interactions in the Parkfield area.

Comparison of GPS and Quaternary slip rates: Insights from a new Quaternary fault database for Central Asia

NASA Astrophysics Data System (ADS)

Mohadjer, Solmaz; Ehlers, Todd; Bendick, Rebecca; Mutz, Sebastian

2016-04-01

Previous studies related to the kinematics of deformation within the India-Asia collision zone have relied on slip rate data for major active faults to test kinematic models that explain the deformation of the region. The slip rate data, however, are generally disputed for many of the first-order faults in the region (e.g., Altyn Tagh and Karakorum faults). Several studies have also challenged the common assumption that geodetic slip rates are representative of Quaternary slip rates. What has received little attention is the degree to which geodetic slip rates relate to Quaternary slip rates for active faults in the India-Asia collision zone. In this study, we utilize slip rate data from a new Quaternary fault database for Central Asia to determine the overall relationship between Quaternary and GPS-derived slip rates for 18 faults. The preliminary analysis investigating this relationship uses weighted least squares and a re-sampling analysis to test the sensitivity of this relationship to different data point attributes (e.g., faults associated with data points and dating methods used for estimating Quaternary slip rates). The resulting sample subsets of data points yield a maximum possible Pearson correlation coefficient of ~0.6, suggesting moderate correlation between Quaternary and GPS-derived slip rates for some faults (e.g., Kunlun and Longmen Shan faults). Faults with poorly correlated Quaternary and GPS-derived slip rates were identified and dating methods used for the Quaternary slip rates were examined. Results indicate that a poor correlation between Quaternary and GPS-derived slip rates exist for the Karakorum and Chaman faults. Large differences between Quaternary and GPS slip rates for these faults appear to be connected to qualitative dating of landforms used in the estimation of the Quaternary slip rates and errors in the geomorphic and structural reconstruction of offset landforms (e.g., offset terrace riser reconstructions for Altyn Tagh fault). Other factors such as a low density in the GPS network (e.g., GPS rate based on data from a single station for the Karakorum fault) appear to also contribute to the mismatch observed between the slip rates. Taken together, these results suggest that GPS-derived slip rates are often (but not always) representative of Quaternary slip rates and that the dating methods and sampling approaches used to identify transients in a fault slip rate history should be heavily scrutinized before interpreting the seismic hazards for a region.

Micelle to solvent stacking of organic cations in micellar electrokinetic chromatography with sodium dodecyl sulfate.

PubMed

Quirino, Joselito P; Aranas, Agnes T

2011-10-14

The on-line sample concentration technique, micelle to solvent stacking (MSS), was studied for small organic cations (quaternary ammonium herbicides, β-blocker drugs, and tricyclic antidepressant drugs) in reversed migration micellar electrokinetic chromatography. Electrokinetic chromatography was carried out in fused silica capillaries with a background solution of sodium dodecyl sulfate (SDS) in a low pH phosphate buffer. MSS was performed using anionic SDS micelles in the sample solution for analyte transport and methanol or acetonitrile as organic solvent in the background solution for analyte effective electrophoretic mobility reversal. The solvent also allowed for the separation of the analyte test mixtures. A model for focusing and separation was developed and the mobility reversal that involved micelle collapse was experimentally verified. The effect of analyte retention factor was observed by changing the % organic solvent in the background solution or the concentration of SDS in the sample matrix. With an injection length of 31.9 cm (77% of effective capillary length) for the 7 test drugs, the LODs (S/N=3) of 5-14 ng/mL were 101-346-fold better when compared to typical injection. The linearity (R(2), range=0.025-0.8 μg/mL), intraday and interday repeatability (%RSD, n=10) were ≥0.988, <6.0% and <8.5%, respectively. In addition, analysis of spiked urine samples after 10-fold dilution with the sample matrix yielded LODs=0.02-0.10 μg/mL. These LODs are comparable to published electrophoretic methods that required off-line sample concentration. However, the practicality of the technique for more complex samples will rely on dedicated sample preparation schemes. Copyright © 2011 Elsevier B.V. All rights reserved.

Time-lapse seismic waveform modelling and attribute analysis using hydromechanical models for a deep reservoir undergoing depletion

NASA Astrophysics Data System (ADS)

He, Y.-X.; Angus, D. A.; Blanchard, T. D.; Wang, G.-L.; Yuan, S.-Y.; Garcia, A.

2016-04-01

Extraction of fluids from subsurface reservoirs induces changes in pore pressure, leading not only to geomechanical changes, but also perturbations in seismic velocities and hence observable seismic attributes. Time-lapse seismic analysis can be used to estimate changes in subsurface hydromechanical properties and thus act as a monitoring tool for geological reservoirs. The ability to observe and quantify changes in fluid, stress and strain using seismic techniques has important implications for monitoring risk not only for petroleum applications but also for geological storage of CO2 and nuclear waste scenarios. In this paper, we integrate hydromechanical simulation results with rock physics models and full-waveform seismic modelling to assess time-lapse seismic attribute resolution for dynamic reservoir characterization and hydromechanical model calibration. The time-lapse seismic simulations use a dynamic elastic reservoir model based on a North Sea deep reservoir undergoing large pressure changes. The time-lapse seismic traveltime shifts and time strains calculated from the modelled and processed synthetic data sets (i.e. pre-stack and post-stack data) are in a reasonable agreement with the true earth models, indicating the feasibility of using 1-D strain rock physics transform and time-lapse seismic processing methodology. Estimated vertical traveltime shifts for the overburden and the majority of the reservoir are within ±1 ms of the true earth model values, indicating that the time-lapse technique is sufficiently accurate for predicting overburden velocity changes and hence geomechanical effects. Characterization of deeper structure below the overburden becomes less accurate, where more advanced time-lapse seismic processing and migration is needed to handle the complex geometry and strong lateral induced velocity changes. Nevertheless, both migrated full-offset pre-stack and near-offset post-stack data image the general features of both the overburden and reservoir units. More importantly, the results from this study indicate that integrated seismic and hydromechanical modelling can help constrain time-lapse uncertainty and hence reduce risk due to fluid extraction and injection.

A novel micro-Raman technique to detect and characterize 4H-SiC stacking faults

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piluso, N., E-mail: nicolo.piluso@imm.cnr.it; Camarda, M.; La Via, F.

A novel Micro-Raman technique was designed and used to detect extended defects in 4H-SiC homoepitaxy. The technique uses above band-gap high-power laser densities to induce a local increase of free carriers in undoped epitaxies (n < 10{sup 16} at/cm{sup −3}), creating an electronic plasma that couples with the longitudinal optical (LO) Raman mode. The Raman shift of the LO phonon-plasmon-coupled mode (LOPC) increases as the free carrier density increases. Crystallographic defects lead to scattering or recombination of the free carriers which results in a loss of coupling with the LOPC, and in a reduction of the Raman shift. Given that the LOmore » phonon-plasmon coupling is obtained thanks to the free carriers generated by the high injection level induced by the laser, we named this technique induced-LOPC (i-LOPC). This technique allows the simultaneous determination of both the carrier lifetime and carrier mobility. Taking advantage of the modifications on the carrier lifetime induced by extended defects, we were able to determine the spatial morphology of stacking faults; the obtained morphologies were found to be in excellent agreement with those provided by standard photoluminescence techniques. The results show that the detection of defects via i-LOPC spectroscopy is totally independent from the stacking fault photoluminescence signals that cover a large energy range up to 0.7 eV, thus allowing for a single-scan simultaneous determination of any kind of stacking fault. Combining the i-LOPC method with the analysis of the transverse optical mode, the micro-Raman characterization can determine the most important properties of unintentionally doped film, including the stress status of the wafer, lattice impurities (point defects, polytype inclusions) and a detailed analysis of crystallographic defects, with a high spectral and spatial resolution.« less

Slip resistance of industrial floor surfaces: development of an elastomer suited to in-situ measurement.

PubMed

Leclercq, S; Saulnier, H

2001-01-01

Slips contribute to 12% of occupational accidents. A slip resistant floor is a mean to prevent slipping accidents occurring in workshops. Floor slip resistance is often evaluated by measuring a friction index, proportional to the force opposing slipping of a reference elastomer on the floor surface under test. When implementing a portable appliance, slip resistance measurements carried out on lubricated floors were not stabilized. The authors advanced the hypothesis of oil impregnating the elastomer. A new elastomer suited to in-situ measurement has been developed to achieve stable measuring conditions. This study highlights the fact that the nature and characteristics of a reference elastomer must be specified when slip resistance measurements are carried out.

Development of compact slip detection sensor using dielectric elastomer

NASA Astrophysics Data System (ADS)

Choi, Jae-young; Hwang, Do-Yeon; Kim, Baek-chul; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, Ja Choon

2015-04-01

In this paper, we developed a resistance tactile sensor that can detect a slip on the surface of sensor structure. The presented sensor device has fingerprint-like structures that are similar with the role of the humans finger print. The resistance slip sensor that the novel developed uses acrylo-nitrile butadiene rubber (NBR) as a dielectric substrate and graphene as an electrode material. We can measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To manufacture our sensor, we developed a new imprint process. By using this process, we can produce sensor with micro unit structure. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip is successfully detected. We will discuss the slip detection properties.

Permeability Evolution of Slowly Slipping Faults in Shale Reservoirs

NASA Astrophysics Data System (ADS)

Wu, Wei; Reece, Julia S.; Gensterblum, Yves; Zoback, Mark D.

2017-11-01

Slow slip on preexisting faults during hydraulic fracturing is a process that significantly influences shale gas production in extremely low permeability "shale" (unconventional) reservoirs. We experimentally examined the impacts of mineralogy, surface roughness, and effective stress on permeability evolution of slowly slipping faults in Eagle Ford shale samples. Our results show that fault permeability decreases with slip at higher effective stress but increases with slip at lower effective stress. The permeabilities of saw cut faults fully recover after cycling effective stress from 2.5 to 17.5 to 2.5 MPa and increase with slip at constant effective stress due to asperity damage and dilation associated with slip. However, the permeabilities of natural faults only partially recover after cycling effective stress returns to 2.5 MPa and decrease with slip due to produced gouge blocking fluid flow pathways. Our results suggest that slowly slipping faults have the potential to enhance reservoir stimulation in extremely low permeability reservoirs.

Slip rate and tremor genesis in Cascadia

USGS Publications Warehouse

Wech, Aaron G.; Bartlow, Noel M.

2014-01-01

At many plate boundaries, conditions in the transition zone between seismogenic and stable slip produce slow earthquakes. In the Cascadia subduction zone, these events are consistently observed as slow, aseismic slip on the plate interface accompanied by persistent tectonic tremor. However, not all slow slip at other plate boundaries coincides spatially and temporally with tremor, leaving the physics of tremor genesis poorly understood. Here we analyze seismic, geodetic, and strainmeter data in Cascadia to observe for the first time a large, tremor-generating slow earthquake change from tremor-genic to silent and back again. The tremor falls silent at reduced slip speeds when the migrating slip front pauses as it loads the stronger adjacent fault segment to failure. The finding suggests that rheology and slip-speed-regulated stressing rate control tremor genesis, and the same section of fault can slip both with and without detectable tremor, limiting tremor's use as a proxy for slip.

Development of microsized slip sensors using dielectric elastomer for incipient slippage

NASA Astrophysics Data System (ADS)

Hwang, Do-Yeon; Kim, Baek-chul; Cho, Han-Jeong; Li, Zhengyuan; Lee, Youngkwan; Nam, Jae-Do; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, J. C.

2014-04-01

A humanoid robot hand has received significant attention in various fields of study. In terms of dexterous robot hand, slip detecting tactile sensor is essential to grasping objects safely. Moreover, slip sensor is useful in robotics and prosthetics to improve precise control during manipulation tasks. In this paper, sensor based-human biomimetic structure is fabricated. We reported a resistance tactile sensor that enables to detect a slip on the surface of sensor structure. The resistance slip sensor that the novel developed uses acrylonitrile-butadiene rubber (NBR) as a dielectric substrate and carbon particle as an electrode material. The presented sensor device in this paper has fingerprint-like structures that are similar with the role of the human's finger print. It is possible to measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip was successfully detected. In this paper, we will discuss the slip detection properties so four sensor and detection principle.

Laws of evolution of slip trace pattern and its parameters with deformation in [1.8.12] – single crystals of Ni{sub 3}Fe alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teplyakova, Ludmila, E-mail: lat168@mail.ru; Koneva, Nina, E-mail: koneva@mail.ru; Kunitsyna, Tatyana, E-mail: kma11061990@mail.ru

2016-01-15

The slip trace pattern of Ni{sub 3}Fe alloy single crystals with the short range order oriented for a single slip were investigated on replica at different stages of deformation using the transmission diffraction electron microscopy method. The connection of staging with the formation of slip trace pattern and the change of its parameters were established. The number of local areas where two or more slip systems work is increased with the change of stages. In these conditions the character of slip localization in the primary slip system is changed from the packets to the homogeneous distribution. The distributions of themore » distances between slip traces and the shear power in slip traces were plotted. The correlation between the average value of the shear power in the primary slip traces and the average distance between them was revealed in this work. It was established that the rates of the average value growth of the relative local shear and the shear power in the slip traces reach the largest values at the transition stage.« less

Spontaneous Aseismic and Seismic Slip Transients on Evolving Faults Simulated in a Continuum-Mechanics Framework

NASA Astrophysics Data System (ADS)

Herrendoerfer, R.; Gerya, T.; van Dinther, Y.

2016-12-01

The convergent plate motion in subduction zones is accommodated by different slip modes: potentially dangerous seismic slip and imperceptible, but instrumentally detectable slow slip transients or steady slip. Despite an increasing number of observations and insights from laboratory experiments, it remains enigmatic which local on- and off-fault conditions favour slip modes of different source characteristics (i.e., slip velocity, duration, seismic moment). Therefore, we are working towards a numerical model that is able to simulate different slip modes in a consistent way with the long-term evolution of the fault system. We extended our 2D, continuum mechanics-based, visco-elasto-plastic seismo-thermo-mechanical (STM) model, which simulated cycles of earthquake-like ruptures, albeit only at plate tectonic slip rates (van Dinther et al, JGR, 2013). To model a wider slip spectrum including seismic slip rates, we, besides improving the general numerical approach, implemented an invariant reformulation of the conventional rate-and state dependent friction (RSF) and an adaptive time-stepping scheme (Lapusta and Rice, JGR, 2001). In a simple setup with predominantly elastic plates that are juxtaposed along a predefined fault of certain width, we vary the characteristic slip distance, the mean normal stress and the size of the rate-weakening zone. We show that the resulting stability transitions from decaying oscillations, periodic slow slip, complex periodic to seismic slip agree with those of conventional RSF seismic cycle simulations (e.g. Liu and Rice, JGR, 2007). Additionally, we will present results of the investigation concerning the effect of the fault width and geometry on the generation of different slip modes. Ultimately, instead of predefining a fault, we simulate the spatio-temporal evolution of a complex fault system that is consistent with the plate motions and rheology. For simplicity, we parametrize the fault development through linear slip-weakening of cohesion and apply RSF friction only in cohesionless material. We report preliminary results of the interaction between slip modes and the fault growth during different fault evolution stages.

Is the co-seismic slip distribution fractal?

NASA Astrophysics Data System (ADS)

Milliner, Christopher; Sammis, Charles; Allam, Amir; Dolan, James

2015-04-01

Co-seismic along-strike slip heterogeneity is widely observed for many surface-rupturing earthquakes as revealed by field and high-resolution geodetic methods. However, this co-seismic slip variability is currently a poorly understood phenomenon. Key unanswered questions include: What are the characteristics and underlying causes of along-strike slip variability? Do the properties of slip variability change from fault-to-fault, along-strike or at different scales? We cross-correlate optical, pre- and post-event air photos using the program COSI-Corr to measure the near-field, surface deformation pattern of the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes in high-resolution. We produce the co-seismic slip profiles of both events from over 1,000 displacement measurements and observe consistent along-strike slip variability. Although the observed slip heterogeneity seems apparently complex and disordered, a spectral analysis reveals that the slip distributions are indeed self-affine fractal i.e., slip exhibits a consistent degree of irregularity at all observable length scales, with a 'short-memory' and is not random. We find a fractal dimension of 1.58 and 1.75 for the Landers and Hector Mine earthquakes, respectively, indicating that slip is more heterogeneous for the Hector Mine event. Fractal slip is consistent with both dynamic and quasi-static numerical simulations that use non-planar faults, which in turn causes heterogeneous along-strike stress, and we attribute the observed fractal slip to fault surfaces of fractal roughness. As fault surfaces are known to smooth over geologic time due to abrasional wear and fracturing, we also test whether the fractal properties of slip distributions alters between earthquakes from immature to mature fault systems. We will present results that test this hypothesis by using the optical image correlation technique to measure historic, co-seismic slip distributions of earthquakes from structurally mature, large cumulative displacement faults and compare these slip distributions to those from immature fault systems. Our results have fundamental implications for an understanding of slip heterogeneity and the behavior of the rupture process.

Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

USGS Publications Warehouse

Beeler, N.M.; Tullis, T.E.

1996-01-01

Seismological observations of short slip duration on faults (short rise time on seismograms) during earthquakes are not consistent with conventional crack models of dynamic rupture and fault slip. In these models, the leading edge of rupture stops only when a strong region is encountered, and slip at an interior point ceases only when waves from the stopped edge of slip propagate back to that point. In contrast, some seismological evidence suggests that the duration of slip is too short for waves to propagate from the nearest edge of the ruptured surface, perhaps even if the distance used is an asperity size instead of the entire rupture dimension. What controls slip duration, if not dimensions of the fault or of asperities? In this study, dynamic earthquake rupture and slip are represented by a propagating shear crack. For all propagating shear cracks, slip velocity is highest near the rupture front, and at a small distance behind the rupture front, the slip velocity decreases. As pointed out by Heaton (1990), if the crack obeys a negative slip-rate-dependent strength relation, the lower slip velocity behind the rupture front will lead to strengthening that further reduces the velocity, and under certain circumstances, healing of slip can occur. The boundary element method of Hamano (1974) is used in a program adapted from Andrews (1985) for numerical simulations of mode II rupture with two different velocity-dependent strength functions. For the first function, after a slip-weakening displacement, the crack follows an exponential velocity-weakening relation. The characteristic velocity V0 of the exponential determines the magnitude of the velocity-dependence at dynamic velocities. The velocity-dependence at high velocity is essentially zero when V0 is small and the resulting slip velocity distribution is similar to slip weakening. If V0 is larger, rupture propagation initially resembles slip-weakening, but spontaneous healing occurs behind the rupture front. The rise time and rupture propagation velocity depend on the choice of constitutive parameters. The second strength function is a natural log velocity-dependent form similar to constitutive laws that fit experimental rock friction data at lower velocities. Slip pulses also arise with this function. For a reasonable choice of constitutive parameters, slip pulses with this function do not propagate at speeds greater than the Raleighwave velocity. The calculated slip pulses are similar in many aspects to seismic observations of short rise time. In all cases of self-healing slip pulses, the residual stress increases with distance behind the trailing edge of the pulse so that the final stress drop is much less than the dynamic stress drop, in agreement with the model of Brune (1976) and some recent seismological observations of rupture.

Quantitative Assessment of Potentially Active Faults in Oklahoma Utilizing Detailed Information on In Situ Stress Orientation and Relative Magnitude

NASA Astrophysics Data System (ADS)

Walsh, R.; Zoback, M. D.

2015-12-01

Over the past six years, the earthquake rate in the central and eastern U.S. has increased markedly, and is related to fluid injection. Nowhere has seismicity increased more than in Oklahoma, where large volumes of saline pore water are co-produced with oil and gas, then injected into deeper sedimentary formations. These deeper formations appear to be in hydraulic communication with potentially active faults in crystalline basement, where nearly all the earthquakes are occurring. Although the majority of the recent earthquakes have posed little danger to the public, the possibility of triggering damaging earthquakes on potentially active basement faults cannot be discounted. To understand probability of slip on a given fault, we invert for stresses from the hundreds of M4+ events in Oklahoma for which moment tensors have been made. We then resolve these stresses, while incorporating uncertainties, on the faults from the preliminary Oklahoma fault map. The result is a probabilistic understanding of which faults are most likely active and best avoided.

Extended-release naltrexone (XR-NTX) attenuates brain responses to alcohol cues in alcohol-dependent volunteers: a bold FMRI study.

PubMed

Lukas, Scott E; Lowen, Steven B; Lindsey, Kimberly P; Conn, Nina; Tartarini, Wendy; Rodolico, John; Mallya, Gopi; Palmer, Christopher; Penetar, David M

2013-09-01

Oral naltrexone reduces heavy drinking, but is less consistent as an abstinence promoter, whereas once-monthly extended-release naltrexone (XR-NTX) also maintains abstinence. The present study sought to determine if alcohol cue reactivity is attenuated by XR-NTX. Twenty-eight detoxified alcohol-dependent adult male and female volunteers received a single i.m. injection of either XR-NTX or placebo under double-blind conditions. An fMRI/cue reactivity procedure was conducted immediately before and two weeks after injection. At baseline, alcohol-related visual and olfactory cues elicited significant increases in orbital and cingulate gyri, inferior frontal and middle frontal gyri. Subsequently, brain activation was significantly altered in XR-NTX-treated individuals. These affected brain regions are associated with the integration of emotion, cognition, reward, punishment, and learning/memory, suggesting that XR-NTX attenuates the salience of alcohol-related cues. Such an effect on brain function may interrupt the processes associated with "slips" and relapse, which may account for XR-NTX's ability to maintain abstinence. Copyright © 2013 Elsevier Inc. All rights reserved.

Repeatability of high-speed migration of tremor along the Nankai subduction zone, Japan

NASA Astrophysics Data System (ADS)

Kato, A.; Tsuruoka, H.; Nakagawa, S.; Hirata, N.

2015-12-01

Tectonic tremors have been considered to be a swarm or superimposed pulses of low-frequency earthquakes (LFEs). To systematically analyze the high-speed migration of tremor [e.g., Shelly et al., 2007], we here focus on an intensive cluster hosting many low-frequency earthquakes located at the western part of Shikoku Island. We relocated ~770 hypocenters of LFEs identified by the JMA, which took place from Jan. 2008 to Dec. 2013, applying double differential relocation algorithm [e.g., Waldhauser and Ellsworth, 2000] to arrival times picked by the JMA and those obtained by waveform cross correlation measurements. The epicentral distributions show a clear alignment parallel to the subduction of the Philippine Sea plate, as like a slip-parallel streaking. Then, we applied a matched-filter technique to continuous seismograms recorded near the source region using relocated template LFEs during 6 years (between Jan. 2008 and Dec. 2013). We newly detected about 60 times the number of template events, which is fairly larger than ones obtained by conventional envelope cross correlation method. Interestingly, we identified many repeated sequences of tremor migrations along the slip-parallel streaking (~350 sequences). Front of each or stacked migration of tremors can be modeled by a parabolic envelope, indicating a diffusion process. The diffusivity of parabolic envelope is estimated to be around 105 m2/s, which is categorized as high-speed migration feature (~100 km/hour). Most of the rapid migrations took place during occurrences of short-term slow slip events (SSEs), and seems to be triggered by ocean and solid Earth tides. The most plausible explanation of the high-speed propagation is a diffusion process of stress pulse concentrated within a cluster of strong brittle patches on the ductile shear zone [Ando et al., 2012]. The viscosity of the ductile shear zone within the streaking is at least one order magnitude smaller than that of the slow-speed migration. This discrepancy of viscosity indicates that the streaking has different rheology compared with background main tremor/SSE belt. In addition, the diffusivity did not show any significant change before and after the Tohoku-Oki M9.0 Earthquake, suggesting that the high-speed propagation of tremors seems to be stable against external stress perturbations.

The evolution of slip surface roughness during earthquake propagation in carbonate faults

NASA Astrophysics Data System (ADS)

Zhu, B.; De Paola, N.; Llewellin, E. W.; Holdsworth, R.

2014-12-01

Slip surface roughness is understood to control the dynamics of earthquake propagation. Quantifying the micro- and nano-scale roughness of slip surfaces can give insight into the grain-scale processes controlling the strength of faults during earthquake propagation. Friction experiments were performed on fine-grained calcite gouges, at speed 1 ms-1, normal stress 18 MPa, displacements 0.009-1.46 m, and room temperature and humidity. Results show a two stage-evolution (S1-2) of the fault strength, with an initial increase up to peak value 0.82 (S1), followed by a sudden decrease to a low, steady-state value 0.18 (S2). Samples retrieved at the end of S1 show the development of a cohesive slip zone (SZ), made of micron-scale, angular clasts formed by brittle fracturing and cataclasis. The SZ of samples deformed up to S2, is composed of nanograin aggregates which exhibit polygonal grain boundaries indicating high temperature grain boundary sliding creep deformation. In both cases, the SZ is bounded by a sharply defined slip surface. The 3-D geometry of seven experimental slip surfaces (40μm×40μm) has been reconstructed by digital processing of sets of 1800 images of SZ cross sections acquired at 20 nm intervals perpendicular to the slip direction, using a slicing (Focussed Ion Beam) and viewing (Field Emission Scanning Electron Microscope) technique. Spectrum power density analyses show that nano- and micron-scale slip surface roughness is anisotropic for both S1 and S2 slip surfaces. At the nano- and micron-scale, root mean square values decrease with length for S1 slip surfaces, but only slightly for S2 surfaces, and are anisotropic in the slip-normal and slip-parallel directions. The anisotropy is reduced at the nano-scale, although S2 slip surfaces are still smoother parallel to slip than normal to slip. Hurst exponents vary through scales, and are anisotropic in the directions parallel and normal to slip. Variable Hurst exponents indicate that slip surface roughness is scale-dependent with anisotropic, not self-affine behaviour at the micro/nano-scale, in contrast to the self-affine behaviour inferred at the mm to km scales. Dynamic weakening and creep deformation, observed during S2, coincide with an evolution towards less anisotropic and scale-dependent slip surface roughness at the nanoscale.

Gait adaptations to awareness and experience of a slip when walking on a cross-slope.

PubMed

Lawrence, Daniel; Domone, Sarah; Heller, Ben; Hendra, Timothy; Mawson, Susan; Wheat, Jon

2015-10-01

Falls that occur as a result of a slip are one of the leading causes of injuries, particularly in the elderly population. Previous studies have focused on slips that occur on a flat surface. Slips on a laterally sloping surface are important and may be related to different mechanisms of balance recovery. This type of slip might result in different gait adaptations to those previously described on a flat surface, but these adaptations have not been investigated. The aim of this study was to assess whether, when walking on a cross-slope, young adults adapted their gait when made aware of a potential slip, and having experienced a slip. Gait parameters were compared for three conditions--(1) Normal walking; (2) Walking after being made aware of a potential slip (participants were told that a slip may occur); (3) Walking after experiencing a slip (Participants had already experienced at least one slip induced using a soapy contaminant). Gait parameters were only analysed for trials in which there was no slippery contaminant present on the walkway. Stride length and walking velocity were significantly reduced, and stance duration was significantly greater in the awareness and experience conditions compared to normal walking, with no significant differences in any gait parameters between the awareness and experience conditions. In addition, 46.7% of the slip trials resulted in a fall. This is higher than reported for slips induced on a flat surface, suggesting slips on a cross-slope are more hazardous. This would help explain the more cautious gait patterns observed in both the awareness and experience conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Estimators of wheel slip for electric vehicles using torque and encoder measurements

NASA Astrophysics Data System (ADS)

Boisvert, M.; Micheau, P.

2016-08-01

For the purpose of regenerative braking control in hybrid and electrical vehicles, recent studies have suggested controlling the slip ratio of the electric-powered wheel. A slip tracking controller requires an accurate slip estimation in the overall range of the slip ratio (from 0 to 1), contrary to the conventional slip limiter (ABS) which calls for an accurate slip estimation in the critical slip area, estimated at around 0.15 in several applications. Considering that it is not possible to directly measure the slip ratio of a wheel, the problem is to estimate the latter from available online data. To estimate the slip of a wheel, both wheel speed and vehicle speed must be known. Several studies provide algorithms that allow obtaining a good estimation of vehicle speed. On the other hand, there is no proposed algorithm for the conditioning of the wheel speed measurement. Indeed, the noise included in the wheel speed measurement reduces the accuracy of the slip estimation, a disturbance increasingly significant at low speed and low torque. Herein, two different extended Kalman observers of slip ratio were developed. The first calculates the slip ratio with data provided by an observer of vehicle speed and of propeller wheel speed. The second observer uses an original nonlinear model of the slip ratio as a function of the electric motor. A sinus tracking algorithm is included in the two observers, in order to reject harmonic disturbances of wheel speed measurement. Moreover, mass and road uncertainties can be compensated with a coefficient adapted online by an RLS. The algorithms were implemented and tested with a three-wheel recreational hybrid vehicle. Experimental results show the efficiency of both methods.

Coseismic slip distribution of the 1923 Kanto earthquake, Japan

USGS Publications Warehouse

Pollitz, F.F.; Nyst, M.; Nishimura, T.; Thatcher, W.

2005-01-01

The slip distribution associated with the 1923 M = 7.9 Kanto, Japan, earthquake is reexamined in light of new data and modeling. We utilize a combination of first-order triangulation, second-order triangulation, and leveling data in order to constrain the coseismic deformation. The second-order triangulation data, which have not been utilized in previous studies of 1923 coseismic deformation, are associated with only slightly smaller errors than the first-order triangulation data and expand the available triangulation data set by about a factor of 10. Interpretation of these data in terms of uniform-slip models in a companion study by Nyst et al. shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies, even one which involved distributed slip. Using the geometry of the Nyst et al. two-plane slip model, we perform inversions of the same geodetic data set for distributed slip. Our preferred model of distributed slip on the Philippine Sea plate interface has a moment magnitude of 7.86. We find slip maxima of ???8-9 m beneath Odawara and ???7-8 m beneath the Miura peninsula, with a roughly 2:1 ratio of strike-slip to dip-slip motion, in agreement with a previous study. However, the Miura slip maximum is imaged as a more broadly extended feature in our study, with the high-slip region continuing from the Miura peninsula to the southern Boso peninsula region. The second-order triangulation data provide good evidence for ???3 m right-lateral strike slip on a 35-km-long splay structure occupying the volume between the upper surface of the descending Philippine Sea plate and the southern Boso peninsula. Copyright 2005 by the American Geophysical Union.

Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy

DOE PAGES

Zhang, Zijiao; Sheng, Hongwei; Wang, Zhangjie; ...

2017-02-20

Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dualmore » function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness.« less

Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy

PubMed Central

Zhang, Zijiao; Sheng, Hongwei; Wang, Zhangjie; Gludovatz, Bernd; Zhang, Ze; George, Easo P.; Yu, Qian; Mao, Scott X.; Ritchie, Robert O.

2017-01-01

Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dual function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness. PMID:28218267

Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy.

PubMed

Zhang, Zijiao; Sheng, Hongwei; Wang, Zhangjie; Gludovatz, Bernd; Zhang, Ze; George, Easo P; Yu, Qian; Mao, Scott X; Ritchie, Robert O

2017-02-20

Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dual function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness.

Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

DOE PAGES

Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; ...

2015-12-09

Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening andmore » ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.« less

Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

PubMed Central

Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

2015-01-01

Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

Crystal induced phosphorescence from Benz(a)anthracene microcrystals at room temperature

NASA Astrophysics Data System (ADS)

Maity, Samir; Mazumdar, Prativa; Shyamal, Milan; Sahoo, Gobinda Prasad; Misra, Ajay

2016-03-01

Pure organic compounds that are also phosphorescent at room temperature are very rare in literature. Here, we report efficient phosphorescence emission from aggregated hydrosol of Benz(a)anthracene (BaA) at room temperature. Aggregated hydrosol of BaA has been synthesized by re-precipitation method and SDS is used as morphology directing agent. Morphology of the particles is characterized using optical and scanning electronic microcopy (SEM). Photophysical properties of the aggregated hydrosol are carried out using UV-vis, steady state and time resolved fluorescence study. The large stoke shifted structured emission from aggregated hydrosol of BaA has been explained due to phosphorescence emission of BaA at room temperature. In the crystalline state, the restricted intermolecular motions (RIM) such as rotations and vibrations are activated by crystal lattice. This rigidification effect makes the chromophore phosphorescent at room temperature. The possible stacking arrangement of the neighboring BaA within the aggregates has been substantiated by computing second order Fukui parameter as local reactivity descriptors. Computational study also reveals that the neighboring BaA molecules are present in parallel slipped conformation in its aggregated crystalline form.

γ-Herringbone Polymorph of 6,13-Bis(trimethylsilylethynyl)pentacene: A Potential Material for Enhanced Hole Mobility.

PubMed

Bhat, Vinayak; Gopan, Gopika; Nair, Nanditha G; Hariharan, Mahesh

2018-04-06

The introduction of the trialkylsilylethynyl group to the acene core is known to predominantly transform the herringbone structure of pentacene to a slip-stacked packing. However, herein, the occurrence of an unforeseen polymorph of 6,13-bis(trimethylsilylethynyl)pentacene (TMS-pentacene), with an atypical γ-herringbone packing arrangement, is reported. Intermolecular noncovalent interactions in the γ-herringbone polymorph are determined from Hirshfeld surface and quantum theory of atoms-in-molecules (QTAIM) analyses. Furthermore, a comparative truncated symmetry-adapted perturbation theory (SAPT(0)) energy decomposition analysis discloses the role of exchange repulsions that govern molecular packing in the γ-herringbone polymorph. Moreover, the computationally predicted electronic coupling and anisotropic mobility reveal the possibility of enhanced hole transport (μ h =3.7 cm 2  V -1  s -1 ) in the γ-herringbone polymorph, in contrast to the reported polymorph with a hole mobility of μ h =0.1 cm 2  V -1  s -1 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observations that Constrain the Scaling of Apparent Stress

NASA Astrophysics Data System (ADS)

McGarr, A.; Fletcher, J. B.

2002-12-01

Slip models developed for major earthquakes are composed of distributions of fault slip, rupture time, and slip velocity time function over the rupture surface, as divided into many smaller subfaults. Using a recently-developed technique, the seismic energy radiated from each subfault can be estimated from the time history of slip there and the average rupture velocity. Total seismic energies, calculated by summing contributions from all of the subfaults, agree reasonably well with independent estimates based on seismic energy flux in the far-field at regional or teleseismic distances. Two recent examples are the 1999 Izmit, Turkey and the 1999 Hector Mine, California earthquakes for which the NEIS teleseismic measurements of radiated energy agree fairly closely with seismic energy estimates from several different slip models, developed by others, for each of these events. Similar remarks apply to the 1989 Loma Prieta, 1992 Landers, and 1995 Kobe earthquakes. Apparent stresses calculated from these energy and moment results do not indicate any moment or magnitude dependence. The distributions of both fault slip and seismic energy radiation over the rupture surfaces of earthquakes are highly inhomogeneous. These results from slip models, combined with underground and seismic observations of slip for much smaller mining-induced earthquakes, can provide stronger constraint on the possible scaling of apparent stress with moment magnitude M or seismic moment. Slip models for major earthquakes in the range M6.2 to M7.4 show maximum slips ranging from 1.6 to 8 m. Mining-induced earthquakes at depths near 2000 m in South Africa are associated with peak slips of 0.2 to 0.37 m for events of M4.4 to M4.6. These maximum slips, whether derived from a slip model or directly observed underground in a deep gold mine, scale quite definitively as the cube root of the seismic moment. In contrast, peak slip rates (maximum subfault slip/rise time) appear to be scale invariant. A 1.25 m/s slip rate for one of the mining-induced earthquakes was estimated by dividing the corresponding slip observed at depth by the duration of the seismically-recorded slip pulse. Peak slip rates determined from the slip models for the major earthquakes are similar, ranging from about 0.8 to 4.8 m/s. Thus, for earthquakes in the moment magnitude range 4.4 to 7.4, the peak slip rate shows no dependence on M. Whatever variation there is in slip rate is probably due to factors related to the strength of the seismogenic rock mass such as depth. These observations support the idea that apparent stress does not vary systematically with seismic moment inasmuch as the apparent stress is determined by slip rate. Indeed, our finding that fault behavior of M4.4 earthquakes can be scaled readily to events of M greater than 7 with slips up to about 8 m suggests, quite persuasively, that the source physics for crustal earthquakes is much the same over this magnitude range. Interestingly, the mining-induced earthquakes involved brittle failure across very old pre-existing faults for which the cohesive strength is high and the pore pressure is zero, due to mining operations.

Mirror-like slip surfaces in dolostone: natural and experimental constraints on a potential seismic marker

NASA Astrophysics Data System (ADS)

Fondriest, M.; Smith, S. A.; Di Toro, G.; Nielsen, S. B.

2012-12-01

The lack of clear geological markers of seismic faulting represents a major limitation in our current comprehension of earthquake physics. At present pseudotachylytes (i.e. friction-induced melts) are the only unambiguously identified indicator of ancient seismicity in exhumed fault zones, but pseudotachylytes are not found in many rock types, including carbonates. We report the occurrence of small-displacement, mirror-like slip surfaces from a fault zone cutting dolostones. A combination of field observations and rotary shear friction experiments suggests that such slip surfaces: 1) are formed only at seismic slip rates, and 2) could potentially be used to estimate power dissipation during individual slip events. The Foiana Line (FL) is a major NNE-SSW-trending sinistral transpressive fault in the Italian Southern Alps. The outcropping fault zone consists of a <300 m wide zone of heavily fractured ("pulverized") dolostones cut by a network of mirror-like slip surfaces. The slip surfaces have displacements ranging between 0.04 m and 0.5 m and their mirror-like appearance indicates that the wavelength of surface roughness is <1 μm. The slip surfaces have mainly dip-slip reverse kinematics and were exhumed from ~2 km depth. Resolved normal stress on the slip surfaces is estimated in the range 30-50 MPa. To understand how the mirror-like slip surfaces may have developed, slow- to high-velocity rotary-shear experiments using SHIVA (INGV, Rome) were performed on 3 mm thick layers of dolomite gouge (grain size <250 μm) collected from the FL. Tests were conducted using a purpose-built gouge sample holder at slip rates of 0.0001-1.13 m/s, normal stresses up to 26 MPa and displacements in the range 0.02-3.5 m. At seismic slip rates of 1.13 m/s the dolomite gouge shows a dramatic reduction of the friction coefficient (μ) from a peak value of ~0.7 to a steady-state value of ~0.25. The gouge starts to weaken above a threshold velocity in the range 0.19-0.49 m/s following a transient phase of strengthening. During the tests the instantaneous power density (shear stress*slip rate) dissipated on the sample reaches values of 6-10 MW/m2 over distances of 0.02-1 m, comparable to those of natural earthquakes. At 26 MPa normal stress a mirror-like slip surface is formed after only 0.03 m of slip. At intermediate slip rates (0.113 m/s) only moderate reductions in μ are observed. Instantaneous power density is ~1 MW/m2 and the mirror-like slip surface starts to develop after 0.1 m of slip. At sub-seismic slip rates (0.0001-0.0013 m/s) μ remains ~0.7, instantaneous power density is ~0.02 MW/m2, and no mirror-like slip surface develops. Microstructural observations suggest that the natural and experimental slip zones are comparable: both have a compacted layer up to 20 μm thick immediately below the mirror-like slip surface in which deformation is strongly localized. The layer consists of partially-welded dolomite clasts 0.1-10 μm in size. In the experimental samples, chemical analyses recognized small (<100 μm long), discontinuous patches of periclase and Mg-calcite nanoparticles formed by dolomite decomposition. Field, experimental and microstructural data suggest that mirror-like slip surfaces in dolostone develop at seismic conditions, when instantaneous power density is of the order of 1-10 MW/m2.

The 2016 Mw5.1 Fairview, Oklahoma earthquakes: Evidence for long-range poroelastic triggering at >40 km from fluid disposal wells

DOE PAGES

Goebel, T. H. W.; Weingarten, M.; Chen, X.; ...

2017-05-30

Wastewater disposal in the central U.S. is likely responsible for an unprecedented surge in earthquake activity. Much of this activity is thought to be driven by induced pore pressure changes and slip on pre-stressed faults, which requires a hydraulic connection between faults and injection wells. However, direct pressure effects and hydraulic connectivity are questionable for earthquakes located at large distances and depths from the injectors. Here, we examine triggering mechanisms of induced earthquakes, which occurred at more than 40 km from wastewater disposal wells in the greater Fairview region, northwest Oklahoma, employing numerical and semi-analytical poroelastic models. The region exhibitedmore » few earthquakes before 2013, when background seismicity started to accelerate rapidly, culminating in the Mw5.1 Fairview earthquake in February 2016. Injection rates in the ~2–2.5km deep Arbuckle formation started to increase rapidly in 2012, about two years before the start of seismicity-increase. Most of the injection activity was concentrated toward the northeast of the study region, generating a relatively cohesive zone of pressure perturbations between 0.1 and 1MPa. Much of the near-injection seismicity was likely triggered by pressure effects and fault-assisted pressure diffusion to seismogenic depth. Outside of the high-pressure zone, we observed two remarkably detached, linear seismicity clusters, which occurred at 20 to 50 km distance from the initial seismicity and 10 to 40 km from the nearest, high-rate injector. Semi-analytical models reveal that poroelastically-induced Coulomb-stress-changes surpass pore pressure changes at these distances, providing a plausible triggering mechanism in the far-field of injection wells. These results indicate that both pore-pressures and poroelastic stresses can play a significant role in triggering deep and distant earthquakes by fluid injection and should be considered for seismic hazard assessment beyond the targeted reservoir.« less

The 2016 Mw5.1 Fairview, Oklahoma earthquakes: Evidence for long-range poroelastic triggering at >40 km from fluid disposal wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goebel, T. H. W.; Weingarten, M.; Chen, X.

Wastewater disposal in the central U.S. is likely responsible for an unprecedented surge in earthquake activity. Much of this activity is thought to be driven by induced pore pressure changes and slip on pre-stressed faults, which requires a hydraulic connection between faults and injection wells. However, direct pressure effects and hydraulic connectivity are questionable for earthquakes located at large distances and depths from the injectors. Here, we examine triggering mechanisms of induced earthquakes, which occurred at more than 40 km from wastewater disposal wells in the greater Fairview region, northwest Oklahoma, employing numerical and semi-analytical poroelastic models. The region exhibitedmore » few earthquakes before 2013, when background seismicity started to accelerate rapidly, culminating in the Mw5.1 Fairview earthquake in February 2016. Injection rates in the ~2–2.5km deep Arbuckle formation started to increase rapidly in 2012, about two years before the start of seismicity-increase. Most of the injection activity was concentrated toward the northeast of the study region, generating a relatively cohesive zone of pressure perturbations between 0.1 and 1MPa. Much of the near-injection seismicity was likely triggered by pressure effects and fault-assisted pressure diffusion to seismogenic depth. Outside of the high-pressure zone, we observed two remarkably detached, linear seismicity clusters, which occurred at 20 to 50 km distance from the initial seismicity and 10 to 40 km from the nearest, high-rate injector. Semi-analytical models reveal that poroelastically-induced Coulomb-stress-changes surpass pore pressure changes at these distances, providing a plausible triggering mechanism in the far-field of injection wells. These results indicate that both pore-pressures and poroelastic stresses can play a significant role in triggering deep and distant earthquakes by fluid injection and should be considered for seismic hazard assessment beyond the targeted reservoir.« less

The 2016 Mw5.1 Fairview, Oklahoma earthquakes: Evidence for long-range poroelastic triggering at >40 km from fluid disposal wells

NASA Astrophysics Data System (ADS)

Goebel, T. H. W.; Weingarten, M.; Chen, X.; Haffener, J.; Brodsky, E. E.

2017-08-01

Wastewater disposal in the central U.S. is likely responsible for an unprecedented surge in earthquake activity. Much of this activity is thought to be driven by induced pore pressure changes and slip on pre-stressed faults, which requires a hydraulic connection between faults and injection wells. However, direct pressure effects and hydraulic connectivity are questionable for earthquakes located at large distances and depths from the injectors. Here, we examine triggering mechanisms of induced earthquakes, which occurred at more than 40 km from wastewater disposal wells in the greater Fairview region, northwest Oklahoma, employing numerical and semi-analytical poroelastic models. The region exhibited few earthquakes before 2013, when background seismicity started to accelerate rapidly, culminating in the Mw5.1 Fairview earthquake in February 2016. Injection rates in the ∼2-2.5 km deep Arbuckle formation started to increase rapidly in 2012, about two years before the start of seismicity-increase. Most of the injection activity was concentrated toward the northeast of the study region, generating a relatively cohesive zone of pressure perturbations between 0.1 and 1 MPa. Much of the near-injection seismicity was likely triggered by pressure effects and fault-assisted pressure diffusion to seismogenic depth. Outside of the high-pressure zone, we observed two remarkably detached, linear seismicity clusters, which occurred at 20 to 50 km distance from the initial seismicity and 10 to 40 km from the nearest, high-rate injector. Semi-analytical models reveal that poroelastically-induced Coulomb-stress-changes surpass pore pressure changes at these distances, providing a plausible triggering mechanism in the far-field of injection wells. These results indicate that both pore-pressures and poroelastic stresses can play a significant role in triggering deep and distant earthquakes by fluid injection and should be considered for seismic hazard assessment beyond the targeted reservoir.

Episodic tremor and slip on the Cascadia subduction zone: the chatter of silent slip.

PubMed

Rogers, Garry; Dragert, Herb

2003-06-20

We found that repeated slow slip events observed on the deeper interface of the northern Cascadia subduction zone, which were at first thought to be silent, have unique nonearthquake seismic signatures. Tremorlike seismic signals were found to correlate temporally and spatially with slip events identified from crustal motion data spanning the past 6 years. During the period between slips, tremor activity is minor or nonexistent. We call this associated tremor and slip phenomenon episodic tremor and slip (ETS) and propose that ETS activity can be used as a real-time indicator of stress loading of the Cascadia megathrust earthquake zone.

Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Sehitoglu, H.; Alkan, S.

2018-03-01

This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non- Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

Fault Slip Partitioning in the Eastern California Shear Zone-Walker Lane Belt: Pliocene to Late Pleistocene Contraction Across the Mina Deflection

NASA Astrophysics Data System (ADS)

Lee, J.; Stockli, D.; Gosse, J.

2007-12-01

Two different mechanisms have been proposed for fault slip transfer between the subparallel NW-striking dextral- slip faults that dominant the Eastern California Shear Zone (ECSZ)-Walker Lane Belt (WLB). In the northern WLB, domains of sinistral-slip along NE-striking faults and clockwise block rotation within a zone of distributed deformation accommodated NW-dextral shear. A somewhat modified version of this mechanism was also proposed for the Mina deflection, southern WLB, whereby NE-striking sinistral faults formed as conjugate faults to the primary zone of NW-dextral shear; clockwise rotation of the blocks bounding the sinistral faults accommodated dextral slip. In contrast, in the northern ECSZ and Mina deflection, domains of NE-striking pure dip-slip normal faults, bounded by NW-striking dextral-slip faults, exhibited no rotation; the proposed mechanism of slip transfer was one of right-stepping, high angle normal faults in which the magnitude of extension was proportional to the amount of strike-slip motion transferred. New geologic mapping, tectonic geomorphologic, and geochronologic data from the Queen Valley area, southern Mina deflection constrain Pliocene to late Quaternary fault geometries, slip orientations, slip magnitudes, and slip rates that bear on the mechanism of fault slip transfer from the relatively narrow northern ECSZ to the broad deformation zone that defines the Mina deflection. Four different fault types and orientations cut across the Queen Valley area: (1) The NE-striking normal-slip Queen Valley fault; (2) NE-striking sinistral faults; (3) the NW-striking dextral Coyote Springs fault, which merges into (4) a set of EW-striking thrust faults. (U-Th)/He apatite and cosmogenic radionuclide data, combined with magnitude of fault offset measurements, indicate a Pliocene to late Pleistocene horizontal extension rate of 0.2-0.3 mm/yr across the Queen Valley fault. Our results, combined with published slip rates for the dextral White Mountain fault zone (0.3-0.8 mm/yr) and the eastern sinistral Coaldale fault (0.4 mm/yr) suggest that transfer of dextral slip from the narrow White Mountains fault zone is explained best by a simple shear couple whereby slip is partitioned into three different components: horizontal extension along the Queen Valley fault, dominantly dextral slip along the Coyote Springs fault, and dominantly sinistral slip along the Coaldale fault. A velocity vector diagram illustrating fault slip partitioning predicts contraction rates of <0.1 to 0.5 mm/yr across the Coyote Springs and western Coaldale faults. The predicted long-term contraction across the Mina deflection is consistent with present-day GPS data.

Coseismic slip on the southern Cascadia megathrust implied by tsunami deposits in an Oregon lake and earthquake-triggered marine turbidites

NASA Astrophysics Data System (ADS)

Witter, Robert C.; Zhang, Yinglong; Wang, Kelin; Goldfinger, Chris; Priest, George R.; Allan, Jonathan C.

2012-10-01

We test hypothetical tsunami scenarios against a 4,600-year record of sandy deposits in a southern Oregon coastal lake that offer minimum inundation limits for prehistoric Cascadia tsunamis. Tsunami simulations constrain coseismic slip estimates for the southern Cascadia megathrust and contrast with slip deficits implied by earthquake recurrence intervals from turbidite paleoseismology. We model the tsunamigenic seafloor deformation using a three-dimensional elastic dislocation model and test three Cascadia earthquake rupture scenarios: slip partitioned to a splay fault; slip distributed symmetrically on the megathrust; and slip skewed seaward. Numerical tsunami simulations use the hydrodynamic finite element model, SELFE, that solves nonlinear shallow-water wave equations on unstructured grids. Our simulations of the 1700 Cascadia tsunami require >12-13 m of peak slip on the southern Cascadia megathrust offshore southern Oregon. The simulations account for tidal and shoreline variability and must crest the ˜6-m-high lake outlet to satisfy geological evidence of inundation. Accumulating this slip deficit requires ≥360-400 years at the plate convergence rate, exceeding the 330-year span of two earthquake cycles preceding 1700. Predecessors of the 1700 earthquake likely involved >8-9 m of coseismic slip accrued over >260 years. Simple slip budgets constrained by tsunami simulations allow an average of 5.2 m of slip per event for 11 additional earthquakes inferred from the southern Cascadia turbidite record. By comparison, slip deficits inferred from time intervals separating earthquake-triggered turbidites are poor predictors of coseismic slip because they meet geological constraints for only 4 out of 12 (˜33%) Cascadia tsunamis.

Implications of basal micro-earthquakes and tremor for ice stream mechanics: Stick-slip basal sliding and till erosion

NASA Astrophysics Data System (ADS)

Barcheck, C. Grace; Tulaczyk, Slawek; Schwartz, Susan Y.; Walter, Jacob I.; Winberry, J. Paul

2018-03-01

The Whillans Ice Plain (WIP) is unique among Antarctic ice streams because it moves by stick-slip. The conditions allowing stick-slip and its importance in controlling ice dynamics remain uncertain. Local basal seismicity previously observed during unstable slip is a clue to the mechanism of ice stream stick-slip and a window into current basal conditions, but the spatial extent and importance of this basal seismicity are unknown. We analyze data from a 2010-2011 ice-plain-wide seismic and GPS network to show that basal micro-seismicity correlates with large-scale patterns in ice stream slip behavior: Basal seismicity is common where the ice moves the least between unstable slip events, with small discrete basal micro-earthquakes happening within 10s of km of the central stick-slip nucleation area and emergent basal tremor occurring downstream of this area. Basal seismicity is largely absent in surrounding areas, where inter-slip creep rates are high. The large seismically active area suggests that a frictional sliding law that can accommodate stick-slip may be appropriate for ice stream beds on regional scales. Variability in seismic behavior over inter-station distances of 1-10 km indicates heterogeneity in local bed conditions and frictional complexity. WIP unstable slips may nucleate when stick-slip basal earthquake patches fail over a large area. We present a conceptual model in which basal seismicity results from slip-weakening frictional failure of over-consolidated till as it is eroded and mobilized into deforming till.

An experimental investigation of the effect of temperature and space velocity on the performance of a cu-zeolite flow-through SCR and a SCR catalyst on a DPF with and without PM loading

NASA Astrophysics Data System (ADS)

Kadam, Vaibhav

The heavy-duty diesel (HDD) engines use the diesel oxidation catalyst (DOC), catalyzed particulate filter (CPF) and urea injection based selective catalytic reduction (SCR) systems in sequential combination, to meet the US EPA 2010 PM and NOx emission standards. The SCR along with a NH 3 slip control catalyst (AMOX) offer NOx reduction >90 % with NH3 slip <20 ppm. However, there is a strong desire to further improve the NOx reduction performance of such systems, to meet the California Optional Low NOx Standard implemented since 2015. Integrating SCR functionality into a diesel particulate filter (DPF), by coating the SCR catalyst on the DPF, offers potential to reduce the system cost and packaging weight/ volume. It also provides opportunity to increases the SCR volume without affecting the overall packaging, to achieve NO x reduction efficiencies >95 %. In this research, the NOx reduction and NH3 storage performance of a Cu-zeolite SCR and Cu-zeolite SCR catalyst on DPF (SCRFRTM) were experimentally investigated based on the engine experimental data at steady state conditions. The experimental data for the production-2013-SCR and the SCRFRTM were collected (with and without PM loading in the SCRFRTM) on a Cummins ISB 2013 engine, at varying inlet temperatures, space velocities, inlet NOx concentrations and NO2/NOx ratios, to evaluate the NOx reduction, NH3 storage and NH 3 slip characteristics of the SCR catalyst. The SCRFRTM was loaded with 2 and 4 g/L of PM prior to the NOx reduction tests to study the effect of PM loading on the NOx reduction and NH3 storage performance of the SCRFRTM. The experimental setup and test procedures for evaluation of NOx reduction performance of the SCRFRTM, with and without PM loading in the SCRFRTM are described. The 1-D SCR model developed at MTU was calibrated to the engine experimental data obtained from the seven NOx reduction tests conducted with the production-2013-SCR. The performance of the 1-D SCR model was validated by comparing the simulation and experimental data for NO, NO2 and NH3 concentrations at the outlet of the SCR. The NO and NO 2 concentrations were calibrated to +/-20 ppm and NH3 was calibrated to +/-20 ppm. The experimental results for the production-2013-SCR indicate that the NOx reduction of 80 - 85% can be achieved for the inlet temperatures below 250°C and above 450°C and NO x reduction of 90 - 95% can be achieved for the inlet temperatures between 300 - 350°C, at ammonia to NO2 ratio (ANR) 1.0, while the NH3 slip out of the SCR was <75 ppm. Conversely, the SCRFRTM showed 90 - 95 % NOx reduction at ANR of 1.0, while the NH3 slip out of the SCRFRTM was >50 ppm, with and without PM loading in the SCRFRTM, for the inlet temperature range of 200 - 450 °C, space velocity in the range of 13 to 48 k/hr and inlet NO 2/NOx in the range of 0.2 to 0.5. The NOx reduction in the SCRFRTM increases to >98 % at ANR 1.2. However, the NH3 slip out of the SCRFRTM increases significantly at ANR 1.2. The effect of PM loading at 2 and 4 g/L on the NOx reduction performance of the SCRFRTM was negligible below 300 °C. However, with PM loading in the SCRFRTM, the NO2 reduction decreased by 3 - 5% when compared to the clean SCRFRTM, for inlet temperature >350 °C. Experimental data were also collected by reference [1] to investigate the NO2 assisted PM oxidation in the SCRFRTM for the inlet temperature range of 260 - 370 °C, with and without urea injection and thermal oxidation of PM in the SCRFRTM for the inlet temperature range of 500 - 600 °C, without urea injection by reference [1]. The experimental data obtained from this study and [1] will be used to develop and calibrate the SCR-F model at Michigan Tech. The NH3 storage for the production-2013-SCR and the SCRFRTM (with and without PM loading) were determined from the steady state engine experimental data. The NH3 storage for the production-2013-SCR and the SCRFRTM (without PM loading) were within +/-5 gmol/m 3 of the substrate, with maximum NH3 storage of 75 - 80 gmol/m3 of the substrate, at the SCR/SCRFRTM inlet temperature of 200°C. The NH3 storage in the SCRFRTM, with 2 g/L PM loading, decreased by 30%, when compared to the NH3 storage in the SCRFRTM, without PM loading. The further increase in the PM loading in the SCRFRTM, from 2 to 4 g/L, had negligible effect on NH 3 storage.