Brady 1D seismic velocity model ambient noise prelim
Mellors, Robert J.
2013-10-25
Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.
Minimum 1D P- and S- Velocity Models for Montenegro and Vicinity
NASA Astrophysics Data System (ADS)
Vucic, Ljiljana; Kissling, Edi; Spakman, Wim; Glavatovic, Branislav
2015-04-01
The territory of Montenegro and its vicinity are characterized by high-seismicity rate and very complex tectonics. Namely, southern Adria microplate subducts beneath Eurasia, forming the Dinarides fold-and-thrust belt which spreads through whole Montenegro and the western Balkans. Present-day lithosphere structure of the Adria-Dinarides collision zone in general is not constrained very well and, consequently, there is a lack of three-dimensional (3D) velocity models in this region. For these reasons, high resolution 3D tomography modeling of this area is considered to be of great importance. As part of preparatory phase for conducting a 3D local earthquake tomography study, a substantial amount of waveform data was collected, from all surroundings national seismic networks including 130 seismic stations from 11 countries. The data set comprises waveforms from 1452 earthquakes in the region recorded during time period 1990 - 2014. The collected data were obtained in different formats and the data base was harmonized by converting and integrating all data to miniseed format. The potential resolution of collected data for seismic tomography purpose was analyzed by ray density testing, using specially developed software for this specific purpose. The result is expressed as the number of rays between selected group of earthquake hypocenters and seismic stations, penetrating through the 3D model of the Earth crust and it documents the great potential of the data set for 3D seismic tomography. As a prerequisite to 3D tomography and for consistent high-precision earthquake locations, a minimum 1D velocity model has been calculated. The data set of around 400 earthquakes was selected from the main database and consistent wave onsets picking was performed, including seismic phase interpretation and its quality assessment. This highly consistent travel time data set is used for calculation of 1D velocity models for the region under study. The minimum 1D models were derived through the iterative inversion procedure using VELEST software. Comparison of the results between previous routinely processed seismic data at the studied area and the earthquake relocation results by applying the new 1D models, shows a significant improvement in quality of hypocenter parameters of all earthquakes used in the experiment. Since a minimum 1D model represents a solution to the coupled hypocenter-velocity problem, the resulting velocity information will be used as a suitable velocity model for further routine earthquake location in the region, and also as the appropriate initial reference model for 3D tomography modeling, applying the full seismic database. Keywords: minimum 1D model, seismic tomography, Velest, Montenegro
NASA Astrophysics Data System (ADS)
Akbar, Akhmad Fanani; Nugraha, Andri Dian; Sule, Rachmat; Juanda, Aditya Abdurrahman
2013-09-01
Hypocenter determination of micro-earthquakes of Mount "X-1" geothermal field has been conducted using simulated annealing and guided error search method using a 1D seismic velocity model. In order to speed up the hypocenter determination process a three-circle intersection method has been used to guide the simulated annealing and guided error search process. We used P and S arrival time's microseismic data. In the simulated annealing and guided error search processes, the minimum travel time from a source to a receiver has been calculated by employing ray tracing with shooting method. The resulting hypocenters from the above process occurred at depths of 3-4 km below mean sea level. These hypocenter distributions are correlated with previous study which was concluded that the most active microseismic area in which the site of many fractures and also vertical circulation place. Later on, resulting hypocenters location was used as input to determine 1-D seismic velocity using joint hypocenter determination method. The results of VELEST indicate show low Vp/Vs ratio value at depths of 3-4 km. Our interpretation is this anomaly may be related to a rock layer which is saturated by vapor (gas or steam). Another feature is high Vp/Vs ratio value at depths of 1-3 km that may related to a rock layer which is saturated by fluid or partial melting. We also analyze the focal mechanism of microseismic using ISOLA method to determine the source characteristic of this event.
A 1D P wave velocity model under the pacific region using multiply reflected P waves
NASA Astrophysics Data System (ADS)
Foundotos, M.; Nolet, G.
2012-12-01
In order to constrain the shallow structure of the Earth in global tomography, Love and Rayleigh waves are often used. However these waves are mostly sensitive to the S wave velocity structure. P-wave energy is either evanescent, or leaking away at every surface reflection that generates an S wave which travels much deeper into the mantle. For that reason, to study the shallow P velocity structure of the Earth, we need to study P-waves at regional distances if a good seismic station coverage is available. Otherwise we can use multiply reflected P waves at teleseismic distance when regional data are not available (as in the oceans for instance). We used 203 events of magnitude Mw > 6.0 recorded from the dense network of US ARRAY, which allows us to make a very large number of group arrival and slowness measurements of multiply reflected P waves . Our study shows that two times reflected PPP and three times reflected PPPP waves are very well observed despite the ray- theoretical prediction that at certain distances almost all of their compressional energy is converted to shear waves. We also observed Four times reflected 5P and five times reflected 6P which show a strong interference for epicentral distances larger than 80 degree. These observations of multiply reflected P waves allow us to inferred a 1D P wave model for the shallow structure under the pacific region.
Sabtaji, Agung E-mail: agung.sabtaji@bmkg.go.id; Nugraha, Andri Dian
2015-04-24
West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.
NASA Astrophysics Data System (ADS)
Kim, Seongryong; Rhie, Junkee; Kim, Geunyoung
2011-04-01
We propose a full-grid search procedure for broad-band waveform modelling to determine a 1-D crustal velocity model. The velocity model can be more constrained because of the use of broad-band waveforms instead of traveltimes for the crustal phases, although only a small number of event-station pairs were employed. Despite the time-consuming nature of the full-grid search method to search the whole model parameter space, the use of an empirical relationship between the P- and S-wave velocities can significantly reduce computation time. The proposed method was applied to a case in the southern Korean Peninsula. Broad-band waveforms obtained from two inland earthquakes that occurred on 2007 January 20 (Mw 4.6) and 2004 April 26 (Mw 3.6) were used to test the method. The three-layers over half-space crustal velocity model of the P- and S-wave velocities was estimated. Comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes. In addition, 1-D velocity models were determined for three distinct tectonic regions, namely, the Gyonggi Massif, the Okcheon Belt and the Gyeongsang Basin, which are all located inside the study area. A comparison between the three models demonstrates that the crustal thickness of the southern Korean Peninsula increases from NW to SE and that the lower crustal composition of the Okcheon belt differs from that of the other tectonic regions.
NASA Astrophysics Data System (ADS)
Graves, R. W.
2012-12-01
I have performed low frequency (f < 1 Hz) ground motion simulations for the 2008 Mw 5.23 Mt. Carmel, Illinois and 2011 Mw 5.74 Mineral, Virginia earthquakes to calibrate a rock-site 1D crustal velocity and Q structure model for central and eastern US (CEUS). For each earthquake, the observed ground motions were simulated at sites extending out to about 900 km from the epicenter. Sites within the Mississippi embayment are not included in the modeling. The initial 1D velocity model was developed by averaging profiles extracted from the CUS V1.3 3D velocity model (Ramirez-Guzman et al, 2012) at each of the recording sites, with the surface shear wave velocity set at 2200 m/s. The Mt. Carmel earthquake is represented as a point double couple (strike=25, dip=90, rake=-175) at a depth of 14 km and a slip-rate function having a Brune corner frequency of 0.89 Hz (Hartzell and Mendoza, 2011). The Mineral earthquake is represented as a point double couple (strike=26, dip=55, rake=108) at a depth of 6 km and a slip-rate function having a corner frequency of 0.50 Hz. Full waveform Green's functions were computed using the FK method of Zhu and Rivera (2002). The initial model does well at reproducing the median level of observed response spectral acceleration (Sa) for most sites out to 300 km at periods of 2 to 5 sec, including the observed flattening in distance attenuation between 70 and 150 km. However, this model under predicts the motions beyond about 400 km distance. Increasing Q in the mid- and lower crust from the original value of 700 to 5000 removes this under prediction of the larger distance motions. Modified Mercalli Intensity (MMI) estimates have been computed from the simulations using the ground motion-intensity conversion equations of Atkinson and Kaka (2007; AK2007) and Dangkua and Cramer (2011; DC2011-ENA) for comparison against the observed "Did You Feel It" intensity estimates. Given the bandwidth limitations of the simulations, I use the conversion relations for 2 sec Sa. For both earthquakes, the MMI values obtained from DC2011-ENA are systematical higher than the AK2007 values for all distances and over predict the median level of the observed values by roughly 1 MMI unit, whereas the AK2007 values provide a close match to the observed median levels.bserved and simulated spectral acceleration levels at 2 second period (left) and MMI (right) for the Mt. Carmel earthquake.
NASA Astrophysics Data System (ADS)
Jechumtálová, Zuzana; Bulant, Petr
2014-07-01
Retrieving the parameters of a seismic source from seismograms involves deconvolving the response of the medium from seismic records. Thus, in general, source parameters are determined from both seismograms and the Green functions describing the properties of the medium in which the earthquake focus is buried. The quality of each of these two datasets is equally significant for the successful determination of source characteristics. As a rule, both sets are subject to contamination by effects that decrease the resolution of the source parameters. Seismic records are generally contaminated by noise that appears as a spurious signal unrelated to the source. Since an improper model of the medium is quite often employed, due to poor knowledge of the seismic velocity of the area under study, and since the hypocentre may be mislocated, the Green functions are not without fault. Thus, structures not modelled by Green functions are assigned to the source, distorting the source mechanism. To demonstrate these effects, we performed a synthetic case study by simulating seismic observations in the Dobrá Voda area of the Little Carpathians region of Slovakia. Simplified 1-D and 3-D laterally inhomogeneous structural models were constructed, and synthetic data were calculated using the 3-D model. Both models were employed during a moment tensor inversion. The synthetic data were contaminated by random noise up to 10 and 20 % of the maximum signal amplitude. We compared the influence of these two effects on retrieving moment tensors, and determined that a poor structural model can be compensated for by high-quality data; and that, in a similar manner, a lack of data can be compensated for by a detailed model of the medium. For examples, five local events from the Dobrá Voda area were processed.
A 1-D model of sinking particles
NASA Astrophysics Data System (ADS)
Jokulsdottir, T.; Archer, D.
2006-12-01
Acidification of the surface ocean due to increased atmospheric CO2 levels is altering its saturation state with respect to calcium carbonate (Orr et al., 2005) and the ability of calcifying phytoplankton to calcify (Riebesell et al., 2000). Sequestration of atmospheric carbon dioxide into the deep ocean is affected by this, because calcite is the key component in ballasting sinking particles (Klaas and Archer, 2001). The settling velocity of particles is not explicitly modeled but often represented as a constant in climate models. That is clearly inaccurate as the composition of particles changes with depth as bacteria and dissolution processes act on its different components, changing their ratio with depth. An idealized, mechanistic model of particles has been developed where settling velocity is calculated from first principles. The model is forced 100m below the surface with export ratios (organic carbon/calcium carbonate) corresponding to different CO2 levels according to Riebesell et al. The resulting flux is compared to the flux generated by the same model where the settling velocity is held constant. The model produces a relatively constant rain ratio regardless of the amount of calcite available to ballast the particle, which is what data suggests (Conte et al., 2001), whereas a constant velocity model does not. Comparing the flux of particulate organic carbon to the seafloor with increasing CO2 levels, the outcome of the constant velocity model is an increase whereas when the velocity is calculated a decrease results. If so, the change in export ratio with an increase in CO2 concentrations acts as a positive feedback: as increased atmospheric CO2 levels lead to the ocean pH being lowered, reduced calcification of marine organisms results and a decrease in particulate organic carbon flux to the deep ocean, which again raises CO2 concentrations. Conte, M.,, N. Ralph, E. Ross, Seasonal and interannual variability in deep ocean particle fluxes at the Oceanic Flux Program (OFP)/Bermuda Atlantic Time Series (BATS) site in the western Sargasso Sea near Bermuda, Deep-Sea Research II 48 1471-1505, 2001 Klaas, C., and D.E. Archer, Association of sinking organic matter with various types of mineral ballast in the deep sea: Implications for the rain ratio, Global Biogeochemical Cycles, 16, 2002. Orr, J. C. and et. al. Anthropogenic ocean acidification over calcifying organisms. Nature, 437(29):681 686, 2005. U. Riebesell, I. Zondervan, B. Rost, P.D. Tortell, R.E. Zeebe, and F.M.M.Morel. Reduced calcification of marine plankton in response to increased atmospheric CO2. Nature, 407:364 368, 2000.
A 1-D morphodynamic model for rill erosion
NASA Astrophysics Data System (ADS)
Papanicolaou, Athanasios N.; Sanford, John T.; Dermisis, Dimitrios C.; Mancilla, Gabriel A.
2010-09-01
The key objective of this paper is to develop a 1-D hydrodynamic and sediment transport model, namely, RILL1D, that handles transcritical flows over abrupt changes (e.g., formation of pool crests and width change) in a single rill and also predicts changes in rill bed elevation. Replication of rill conditions in terms of flow and bed evolution changes necessitated the use of an enhanced TVD-MacCormack scheme with implementation of Tseng's surface gradient method, to provide an oscillation free solution over formed pool crests. The model at the end of each time step calculates the flow depth, velocity, and bed shear stress and provides changes in bed elevation and grain size distribution within a cell. The hydrodynamic performance of RILL1D is evaluated by comparing its results with either analytical solutions or experimental observations from various benchmark tests with rigid bed conditions that include (1) formation of a hydraulic jump in a rectangular channel, (2) steady subcritical and transcritical flow (without a shock) over a hump, (3) formation of a hydraulic jump in a converging-diverging frictionless channel, and (4) flows over step-pools. It is shown that the enhanced TVD-MacCormack scheme adequately simulates transcritical flows by preserving the mass conservation and reducing the artificial numerical error. The scheme also approximates satisfactorily depth and velocity for a single rill, with a fixed bed consisting of steps and pools, except near the pool headwalls where a backroller forms with negative velocities. The sediment component of RILL1D is evaluated by two field investigations of single rills with mobile beds. With the field data the code is tested for its ability to reproduce measured values of sediment transport rates. A sensitivity analysis is performed to assess the effects of cell size and critical erosional strength in the predictive ability of the model. RILL1D performs reasonably well in these simulations in terms of sediment prediction rates and fared adequately in terms of replicating rill bed morphology.
NASA Astrophysics Data System (ADS)
Mulligan, Brian W.; Wheeler, J. C.
2014-01-01
Observations of Type Ia supernovae (SN Ia) have shown the presence of Ca, Si, and Fe features with velocities of 8,000-14,000 km/s higher than that associated with the photosphere of the supernova ejecta. Some studies have suggested the high velocity lines could be explained by interaction of the ejecta with a circumstellar medium (CSM). Using FLASH, we perform 1-D hydrodynamic simulation of interaction between the ejecta and a 210^{-2} M_? circumstellar shell of solar abundance. We use the Sobolev approximation to estimate the line optical depths as a function of time and position. The results of our simulation show two line generating regions: within the ejecta, and within the fast moving shell. The velocity separation between the line generating regions are consistent with the values observed in actual SN Ia, lending credence to the CSM shell model.
Modeling an electric motor in 1-D
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1991-01-01
Quite often the dynamicist will be faced with having an electric drive motor as a link in the elastic path of a structure such that the motor's characteristics must be taken into account to properly represent the dynamics of the primary structure. He does not want to model it so accurately that he could get detailed stress and displacements in the motor proper, but just sufficiently to represent its inertia loading and elastic behavior from its mounting bolts to its drive coupling. Described here is how the rotor and stator of such a motor can be adequately modeled as a colinear pair of beams.
Lifting the Seismic Lid Beneath Cameroon Volcanic Line Using 1D Shear Wave Velocities
NASA Astrophysics Data System (ADS)
Tokam Kamga, Alain; Durrheim, Ray; Tabod, Charles; Nyblade, Andrew; Nguiya, Severin
2014-05-01
The composition of the lithosphere beneath Cameroon and the origin of the Cameroon Volcanic Line (CVL) is a matter of debate. Although many studies based on regional or global observations provide models for the setting of the CVL, none of them are strong enough to be considered as definitive. We used the joint inversion of Rayleigh wave group velocities and Rayleigh wave group velocities to derive shear wave velocity profiles of the lithosphere beneath Cameroon andshow that lithosphere is, on average, faster beneath the Congo Craton than beneath the Pan-African age crust. Using recently published dispersion curves, we extend the depth of investigation from 60 to 200 km. The calculated velocity-depth profiles do not show any sharp discontinuity that could be interpreted as the lithosphere-asthenosphere transition. Furthermore, there is no clear evidence of the existence of a low velocity zone beneath any geologic province within Cameroon. The smooth velocity variations observed on the velocity models are believed to be influenced by lateral mantle heterogeneities rather than vertical ones. The shear wave velocities for the uppermost mantle are in general greater than 4.3 km/s at all stations. This is higher than the values obtained in the Main Ethiopian Rift, and suggest that the perturbation of the by thermal anomalies does not extend as far as the CVL. This suggests that the source of volcanism along the CVL is from small scale convection in the asthenosphere and controlled by lithospheric fractures that are probably driven by the cold (and fast) edge of the Congo Craton.
GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL
KALYANAPU, ALFRED; MCPHERSON, TIMOTHY N.; BURIAN, STEVEN J.
2007-01-17
This paper presents a GIS-based 1-d distributed overland flow model and summarizes an application to simulate a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the 1-d diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. Simulated runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.
Ion velocity distribution at the termination shock: 1-D PIC simulation
Lu Quanming; Yang Zhongwei; Lembege, Bertrand
2012-11-20
The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.
ERIC Educational Resources Information Center
Brand, Neal; Quintanilla, John A.
2013-01-01
Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…
ERIC Educational Resources Information Center
Brand, Neal; Quintanilla, John A.
2013-01-01
Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their
Non-cooperative Brownian donkeys: A solvable 1D model
NASA Astrophysics Data System (ADS)
Jiménez de Cisneros, B.; Reimann, P.; Parrondo, J. M. R.
2003-12-01
A paradigmatic 1D model for Brownian motion in a spatially symmetric, periodic system is tackled analytically. Upon application of an external static force F the system's response is an average current which is positive for F < 0 and negative for F > 0 (absolute negative mobility). Under suitable conditions, the system approaches 100% efficiency when working against the external force F.
NASA Astrophysics Data System (ADS)
Qian, Hui; Mechie, James; Li, Haibing; Xue, Guangqi; Su, Heping; Cui, Xiang
2016-01-01
Earthquake location is essential when defining fault systems and other geological structures. Many methods have been developed to locate hypocenters within a 1D velocity model. In this study, a new approach, named MatLoc, has been developed which can simultaneously invert for the locations and origin times of the hypocenters and the velocity structure, from the arrival times of local earthquakes. Moreover, it can invert for layer boundary depths, such as Moho depths, which can be well constrained by the Pm and Pn phases. For this purpose, the package was developed to take into account reflected phases, e.g., the Pm phase. The speed of the inversion is acceptable due to the use of optimized matrix calculations. The package has been used to re-locate the Lushan earthquake series which occurred in Sichuan, China, from April 20 to April 22, 2013. The results obtained with the package show that the Lushan earthquake series defines the dip of the Guankou fault, on which most of the series occurred, to be 39° toward the NW. Further, the surface projection of the Lushan earthquake series is consistent with the regional tectonic strike which is about N45° E.
Nonlocal Order Parameters for the 1D Hubbard Model
NASA Astrophysics Data System (ADS)
Montorsi, Arianna; Roncaglia, Marco
2012-12-01
We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.
A simple quasi-1D model of Fibonacci anyons
NASA Astrophysics Data System (ADS)
Aasen, David; Mong, Roger; Clarke, David; Alicea, Jason; Fendley, Paul
2015-03-01
There exists various ways of understanding the topological properties of Ising anyons--from simple free-fermion toy models to formal topological quantum field theory. For other types of anyons simple toy models rarely exist; their properties have to be obtained using formal self-consistency relations. We explore a family of gapped 1D local bosonic models that in a certain limit become trivial to solve and provide an intuitive picture for Fibonacci anyons. One can interpret this model as a quasi-1D wire that forms the building block of a 2D topological phase with Fibonacci anyons. With this interpretation all topological properties of the Fibonacci anyons become manifest including ground state degeneracy and braid relations. We conjecture that the structure of the model is protected by an emergent symmetry analogous to fermion parity. 1) NSF Grant DMR-1341822 2) Institute for Quantum Information and Matter, an NSF physics frontier center with support from the Moore Foundation. 3) NSERC-PGSD.
A 1-D morphodynamic model of postglacial valley incision
NASA Astrophysics Data System (ADS)
Tunnicliffe, Jon F.; Church, Michael
2015-11-01
Chilliwack River is typical of many Cordilleran valley river systems that have undergone dramatic Holocene degradation of valley fills that built up over the course of Pleistocene glaciation. Downstream controls on base level, mainly blockage of valleys by glaciers, led to aggradation of significant glaciofluvial and glaciolacustrine valley fills and fan deposits, subsequently incised by fluvial action. Models of such large-scale, long-term degradation present a number of important challenges since the evolution of model parameters, such as the rate of bedload transport and grain size characteristics, are governed by the nature of the deposit. Sediment sampling in the Chilliwack Valley reveals a complex sequence of very coarse to fine textural modes. We present a 1-D numerical morphodynamic model for the river-floodplain system tailored to conditions in the valley. The model is adapted to dynamically adjust channel width to optimize sediment transporting capacity and to integrate relict valley fill material as the channel incises through valley deposits. Sensitivity to model parameters is studied using four principal criteria: profile concavity, rate of downstream grain size fining, bed surface sand content, and the timescale to equilibrium. Model results indicate that rates of abrasion and coarsening of the grain size distributions exert the strongest controls on all of the interrelated model performance criteria. While there are a number of difficulties in satisfying all model criteria simultaneously, results indicate that 1-D models of valley bottom sedimentary systems can provide a suitable framework for integrating results from sediment budget studies and chronologies of sediment evacuation established from dating.
A scattering model of 1D quantum wire regular polygons
NASA Astrophysics Data System (ADS)
Estarellas, Cristian; Serra, Llorenç
2015-07-01
We calculate the quantum states of regular polygons made of 1D quantum wires treating each polygon vertex as a scatterer. The vertex scattering matrix is analytically obtained from the model of a circular bend of a given angle of a 2D nanowire. In the single mode limit the spectrum is classified in doublets of vanishing circulation, twofold split by the small vertex reflection, and singlets with circulation degeneracy. Simple analytic expressions of the energy eigenvalues are given. It is shown how each polygon is characterized by a specific spectrum.
Constitutive modeling and control of 1D smart composite structures
NASA Astrophysics Data System (ADS)
Briggs, Jonathan P.; Ostrowski, James P.; Ponte-Castaneda, Pedro
1998-07-01
Homogenization techniques for determining effective properties of composite materials may provide advantages for control of stiffness and strain in systems using hysteretic smart actuators embedded in a soft matrix. In this paper, a homogenized model of a 1D composite structure comprised of shape memory alloys and a rubber-like matrix is presented. With proportional and proportional/integral feedback, using current as the input state and global strain as an error state, implementation scenarios include the use of tractions on the boundaries and a nonlinear constitutive law for the matrix. The result is a simple model which captures the nonlinear behavior of the smart composite material system and is amenable to experiments with various control paradigms. The success of this approach in the context of the 1D model suggests that the homogenization method may prove useful in investigating control of more general smart structures. Applications of such materials could include active rehabilitation aids, e.g. wrist braces, as well as swimming/undulating robots, or adaptive molds for manufacturing processes.
Data Analysis of cGPS stations in central Greece: station velocities and 1-D strain estimates
NASA Astrophysics Data System (ADS)
Ganas, Athanassios; Chousianitis, Konstantinos; Gianniou, Michalis
2013-04-01
We processed 30-s GPS data from permanent GNSS stations in central Greece, available at NOA since 2006. We obtained position time series along with horizontal and vertical velocities using the Kalman filtering approach and accounting for time-correlated noise content. The station distribution allowed us to draw velocity profiles and to calculate rates of baseline length change (1-D strain). In central Greece, the coherent picture of the velocity pattern for Attica and north-eastern Peloponnese (Corinth) stations (effectively a velocity "plateau" at 30 mm/yr) indicates that these areas belong to the same crustal block, although some internal strain is present within Attica's crust as well as across the Saronic Gulf. Our 1-D strain estimates are in general agreement with geological data (fault slip rates) in central Greece, implying accommodation of this crustal extension along E-W striking active normal faults. Some NE-SW directed shortening is mapped in the wider area to the west of the termination of the North Anatolian Fault (Sporades islands).
Examination of 1D Solar Cell Model Limitations Using 3D SPICE Modeling: Preprint
McMahon, W. E.; Olson, J. M.; Geisz, J. F.; Friedman, D. J.
2012-06-01
To examine the limitations of one-dimensional (1D) solar cell modeling, 3D SPICE-based modeling is used to examine in detail the validity of the 1D assumptions as a function of sheet resistance for a model cell. The internal voltages and current densities produced by this modeling give additional insight into the differences between the 1D and 3D models.
Flooding flows in city crossroads: experiments and 1-D modelling.
Rivière, N; Perkins, R J; Chocat, B; Lecus, A
2006-01-01
This study focuses on the discharge distribution in an intersection of four channels, similar to a city crossroad. The channels and the intersection are all horizontal. Flow enters through two of the channels, and leaves through the other two. The flow is subcritical everywhere, and flow depths are controlled by vertical weirs at the exits of the outlet channels. The main variables that are measured are the flow rates in the four channels. When the weir heights in the outlet channels are the same, the ratio of flow rates in the outlet channels depends only on the ratio of flow rates in the inlet channels; if the outlet conditions are different, other parameters, such as the total flow rate also become important. The flow has also been simulated numerically using a solution of the 1-D Saint Venant equations, with a simple model to predict flow distribution in the intersection. A comparison with the experimental data shows that this model works well for the limited range of experimental conditions studied here. However, further work is needed on a wider range of conditions, closer to real conditions, before the model can be considered valid for practical applications. PMID:17120636
On the mixture model of two-phase proppant transport in 1D fracturing flows
NASA Astrophysics Data System (ADS)
Li, Weiming
2012-11-01
A mixture model of two-phase fluid flow is derived for proppant transport in 1D hydraulic fracturing. The governing equations of the model consists of the mass balance equations for the mixture and the proppant phase, the momentum equation for the mixture and the constitutive equation between proppant average velocity and fluid average velocity. Mass loss and momentum loss due to proppant settling are considered. One dimensional numerical simulations based on discontinuous Galerkin finite element method in space are performed. Both steady cases and transient cases are compared with available analytical solutions or manufactured solutions. Predicted numerical results agree well with exact solutions. This one dimensional two-phase model captures necessary proppant flow phenomena in hydraulic fracturing and also provides numerical efficiency and accuracy.
A 1D model of the arterial circulation in mice.
Aslanidou, Lydia; Trachet, Bram; Reymond, Philippe; Fraga-Silva, Rodrigo A; Segers, Patrick; Stergiopulos, Nikolaos
2016-01-01
At a time of growing concern over the ethics of animal experimentation, mouse models are still an indispensable source of insight into the cardiovascular system and its most frequent pathologies. Nevertheless, reference data on the murine cardiovascular anatomy and physiology are lacking. In this work, we developed and validated an in silico, one dimensional model of the murine systemic arterial tree consisting of 85 arterial segments. Detailed aortic dimensions were obtained in vivo from contrast-enhanced micro-computed tomography in 3 male, C57BL/6J anesthetized mice and 3 male ApoE-/- mice, all 12-weeks old. Physiological input data were gathered from a wide range of literature data. The integrated form of the Navier-Stokes equations was solved numerically to yield pressures and flows throughout the arterial network. The resulting model predictions have been validated against invasive pressure waveforms and non-invasive velocity and diameter waveforms that were measured in vivo on an independent set of 47 mice. In conclusion, we present a validated one-dimensional model of the anesthetized murine cardiovascular system that can serve as a versatile tool in the field of preclinical cardiovascular research. PMID:26555250
3-D velocity model beneath Taal Volcano, Luzon Island Philippines
NASA Astrophysics Data System (ADS)
You, S.; Konstantinou, K. I.; Gung, Y.; Lin, C.
2011-12-01
We derive a three dimensional velocity model of seismic waves beneath Taal Volcano, Philippines, from about 2300 local earthquakes recorded by the Taal Volcano seismic network during the time period from March 2008 to March 2010. In the early data processing stage, with the cross-correlation functions of continuous record of station pairs, unexpected linear drifting of clock time was clearly identified. The drifting rates of each problematic station were determined and the errors were corrected before further processing. With the corrected data, we first determined initial locations by using the program HYPO71 and the reference 1-D global model ak135. 749 well-located events with 3381 P-wave and 2896 S-wave arrivals were used to derive the 'minimum 1-D velocity model' with the program VELEST developed by Kissling to further improve the 1-D velocity model and event locations. With the robust 1-D velocity model and improved event locations, we inverted a high-resolution 3-D velocity model by using the program LOTOS-10 developed by Koulakov. We present the derived 3-D model and discuss its tectonic implications.
Numerical Modeling of Imploding Plasma liners Using the 1D Radiation-Hydrodynamics Code HELIOS
NASA Astrophysics Data System (ADS)
Davis, J. S.; Hanna, D. S.; Awe, T. J.; Hsu, S. C.; Stanic, M.; Cassibry, J. T.; Macfarlane, J. J.
2010-11-01
The Plasma Liner Experiment (PLX) is attempting to form imploding plasma liners to reach 0.1 Mbar upon stagnation, via 30--60 spherically convergent plasma jets. PLX is partly motivated by the desire to develop a standoff driver for magneto-inertial fusion. The liner density, atomic makeup, and implosion velocity will help determine the maximum pressure that can be achieved. This work focuses on exploring the effects of atomic physics and radiation on the 1D liner implosion and stagnation dynamics. For this reason, we are using Prism Computational Science's 1D Lagrangian rad-hydro code HELIOS, which has both equation of state (EOS) table-lookup and detailed configuration accounting (DCA) atomic physics modeling. By comparing a series of PLX-relevant cases proceeding from ideal gas, to EOS tables, to DCA treatments, we aim to identify how and when atomic physics effects are important for determining the peak achievable stagnation pressures. In addition, we present verification test results as well as brief comparisons to results obtained with RAVEN (1D radiation-MHD) and SPHC (smoothed particle hydrodynamics).
Survey of Multi-Material Closure Models in 1D Lagrangian Hydrodynamics
Maeng, Jungyeoul Brad; Hyde, David Andrew Bulloch
2015-07-28
Accurately treating the coupled sub-cell thermodynamics of computational cells containing multiple materials is an inevitable problem in hydrodynamics simulations, whether due to initial configurations or evolutions of the materials and computational mesh. When solving the hydrodynamics equations within a multi-material cell, we make the assumption of a single velocity field for the entire computational domain, which necessitates the addition of a closure model to attempt to resolve the behavior of the multi-material cells’ constituents. In conjunction with a 1D Lagrangian hydrodynamics code, we present a variety of both the popular as well as more recently proposed multi-material closure models and survey their performances across a spectrum of examples. We consider standard verification tests as well as practical examples using combinations of fluid, solid, and composite constituents within multi-material mixtures. Our survey provides insights into the advantages and disadvantages of various multi-material closure models in different problem configurations.
Bechtel, S.E.; Forest, M.G.; Holm, D.D.; Lin, K.J.
1988-01-01
In this paper we derive one space dimensional, reduced systems of equations (1-D closure models) for viscoelastic free jets. We begin with the three-dimensional system of conservation laws and a Maxwell-Jeffreys constitutive law for an incompressible viscoelastic fluid. First, we exhibit exact truncations to a finite, closed system of 1-D equations based on classical velocity assumptions of von Karman. Next, we demonstrate that the 3-D free surface boundary conditions overconstrain these truncated systems, so that only a very limited class of solutions exist. We then proceed to derive approximate 1-D closure theories through a slender jet asymptotic scaling, combined with appropriate definitions of velocity, pressure and stress unknowns. Our nonaxisymmetric 1-D slender jet models incorporate the physical effects of inertia, viscoelasticity (viscosity, relaxation and retardation), gravity, surface tension, and properties of the ambient fluid, and include shear stresses and time dependence. Previous special 1-D slender jet models correspond to the lowest order equations in the present asymptotic theory by an a posteriori suppression to leading order of some of these effects, and a reduction to axisymmetry. Solutions of the lowest order system of equations in this asymptotic analysis are presented: For the special cases of elliptical inviscid and Newtonian free jets, subject to the effects of surface tension and gravity, our model predicts oscillation of the major axis of the free surface elliptical cross section between perpendicular directions with distance down the jet, and drawdown of the cross section, in agreement with observed behavior. 15 refs.
A One-Dimensional (1-D) Three-Region Model for a Bubbling Fluidized-Bed Adsorber
Lee, Andrew; Miller, David C.
2012-01-01
A general one-dimensional (1-D), three-region model for a bubbling fluidized-bed adsorber with internal heat exchangers has been developed. The model can predict the hydrodynamics of the bed and provides axial profiles for all temperatures, concentrations, and velocities. The model is computationally fast and flexible and allows for any system of adsorption and desorption reactions to be modeled, making the model applicable to any adsorption process. The model has been implemented in both gPROMS and Aspen Custom Modeler, and the behavior of the model has been verified.
Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.
2008-01-01
Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.
Uniform Contractivity in Wasserstein Metric for the Original 1D Kac's Model
NASA Astrophysics Data System (ADS)
Hauray, Maxime
2016-03-01
We study here a very popular 1D jump model introduced by Kac: it consists of N velocities encountering random binary collisions at which they randomly exchange energy. We show the uniform (in N) exponential contractivity of the dynamics in a non-standard Monge-Kantorovich-Wasserstein: precisely the MKW metric of order 2 on the energy. The result is optimal in the sense that for each N, the contractivity constant is equal to the L^2 spectral gap of the generator associated to Kac's dynamic. As a corollary, we get an uniform but non optimal contractivity in the MKW metric of order 4. We use a simple coupling that works better that the parallel one. The estimates are simple and new (to the best of our knowledge).
Quasi 1D Modeling of Mixed Compression Supersonic Inlets
NASA Technical Reports Server (NTRS)
Kopasakis, George; Connolly, Joseph W.; Paxson, Daniel E.; Woolwine, Kyle J.
2012-01-01
The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.
Validation of 1-D transport and sawtooth models for ITER
Connor, J.W.; Turner, M.F.; Attenberger, S.E.; Houlberg, W.A.
1996-12-31
In this paper the authors describe progress on validating a number of local transport models by comparing their predictions with relevant experimental data from a range of tokamaks in the ITER profile database. This database, the testing procedure and results are discussed. In addition a model for sawtooth oscillations is used to investigate their effect in an ITER plasma with alpha-particles.
Analyzing and modeling /1+1d markets
NASA Astrophysics Data System (ADS)
Challet, Damien; Stinchcombe, Robin
2001-11-01
We report on a statistical analysis of the Island ECN (NASDAQ) order book. We determine the static and dynamic properties of this system, and then analyze them from a physicist's viewpoint using an equivalent particle system obtained by treating orders as massive particles and price as position. We identify the fundamental dynamical processes, test existing particles models of such markets against our findings, and introduce a new model of limit order markets.
Potential and limitations of 1D modelling of urban flooding
NASA Astrophysics Data System (ADS)
Mark, Ole; Weesakul, Sutat; Apirumanekul, Chusit; Aroonnet, Surajate Boonya; Djordjevi?, Slobodan
2004-12-01
Urban flooding is an inevitable problem for many cities around the world. In the present paper, modelling approaches and principles for analyses of urban flooding are outlined. The paper shows how urban flooding can be simulated by one-dimensional hydrodynamic modelling incorporating the interaction between (i) the buried pipe system, (ii) the streets (with open channel flow) and (iii) the areas flooded with stagnant water. The modelling approach is generic in the sense that it handles both urban flooding with and without flood water entry into houses. In order to visualize flood extent and impact, the modelling results are presented in the form of flood inundation maps produced in GIS. In this paper, only flooding from local rainfall is considered together with the impact in terms of flood extent, flood depth and flood duration. Finally, the paper discusses the data requirement for verification of urban flood models together with an outline of a simple cost function for estimation of the cost of the flood damages.
Kinetic and Stochastic Models of 1D yeast ``prions"
NASA Astrophysics Data System (ADS)
Kunes, Kay
2005-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeasts have proteins, which can undergo similar reconformation and aggregation processes to PrP; yeast ``prions" are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein (1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics along with our own stochastic approach (2). Both models assume reconformation only upon aggregation, and include aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates.
Kinetic Model for 1D aggregation of yeast ``prions''
NASA Astrophysics Data System (ADS)
Kunes, Kay; Cox, Daniel; Singh, Rajiv
2004-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeast have proteins which can undergo similar reconformation and aggregation processes to PrP; yeast forms are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein(1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics(2). The model assumes reconformation only upon aggregation, and includes aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates. We will compare to a more realistic stochastic kinetics model and present prelimary attempts to describe recent experiments on SUP35 strains. *-Supported by U.S. Army Congressionally Mandated Research Fund. 1) P. Chien and J.S. Weissman, Nature 410, 223 (2001); http://online.kitp.ucsb.edu/online/bionet03/collins/. 2) J. Masel, V.A.> Jansen, M.A. Nowak, Biophys. Chem. 77, 139 (1999).
1D internal structure models of the Moon: the best way to the core?
NASA Astrophysics Data System (ADS)
Garcia, R. F.; Urvoy, M.; Gagnepain-Beyneix, J.; Chevrot, S.; Lognonne, P.; Mimoun, D.
2011-12-01
Despite recent attempts, the size, state and internal structure of the lunar core remains poorly constrained. The most successful approach to constraint the deep interior structure of the planets is to fit both geodetic and seismic data with consistent 1D internal structure models including seismic velocities and density. We demonstrate that for such models, global geodetic parameters, such as mass, moment of inertia and love numbers, constrain poorly the core size and state. Moreover, the mass and moment of inertia budgets create correlations betwen crust and core density structures. Another source of information comes from the deviations from cassini spin state and the magnetic induction of the lunar core that provides independent constraints on the lunar core size and state. However, seismology remains the best tool to constrain the deep internal structure of the planets. In a previous study, Birch law and adiabaticity physical constraints were used to construct internal structure models of the lunar mantle linking seismic velocities to density. The detection of core reflected seismic phases allowed to obtain a reference model (VPREMOON) including the core. An updated version of this model is presented, in which the P and S propagation times have been more precisely measured, and latest versions of the average crust/mantle density models has been included. Synthetic waveforms of Apollo records are compared to real ones, suggesting that additional core reflected phases may be detected for some deep moonquake events. An analysis of these additional core reflected phases allows to reduce the error bars on the deep internal structure of the Moon. However, the data set is limited by its size, space sampling and frequency bandwidth. Such that, only additional deployments of broad band seismic sensors, through space missions similar to SELENE2 (JAXA) or GEMS (NASA), will precise the deep internal structure at a level allowing unambiguous geochemical interpretations.
1D numerical model of muddy subaqueous and subaerial debris flows
Imran, J.; Parker, G.; Locat, J.; Lee, H.
2001-01-01
A 1D numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows is presented. The model incorporates the Herschel-Bulkley and bilinear rheologies of viscoplastic fluid. The more familiar Bingham model is integrated into the Herschel-Bulkley rheological model. The conservation equations of mass and momentum of single-phase laminar debris flow are layer-integrated using the slender flow approximation. They are then expressed in a Lagrangian framework and solved numerically using an explicit finite difference scheme. Starting from a given initial shape, a debris flow is allowed to collapse and propagate over a specified topography. Comparison between the model predictions and laboratory experiments shows reasonable agreement. The model is used to study the effect of the ambient fluid density, initial shape of the failed mass, and rheological model on the simulated propagation of the front and runout characteristics of muddy debris flows. It is found that initial failure shape influence the front velocity but has little bearing on the final deposit shape. In the Bingham model, the excess of shear stress above the yield strength is proportional to the strain rate to the first power. This exponent is free to vary in the Herschel-Bulkley model. When it is set at a value lower than unity, the resulting final deposits are thicker and shorter than in the case of the Bingham rheology. The final deposit resulting from the bilinear model is longer and thinner than that from the Bingham model due to the fact that the debris flow is allowed to act as a Newtonian fluid at low shear rate in the bilinear model.
GaAs solar cell photoresponse modeling using PC-1D V2.1
NASA Technical Reports Server (NTRS)
Huber, D. A.; Olsen, L. C.; Dunham, G.; Addis, F. W.
1991-01-01
Photoresponse data of high efficiency GaAs solar cells were analyzed using PC-1D V2.1. The approach required to use PC-1D for photoresponse data analysis, and the physical insights gained from performing the analysis are discussed. In particular, the effect of Al(x)Ga(1-x)As heteroface quality was modeled. Photoresponse or spectral quantum efficiency is an important tool in characterizing material quality and predicting cell performance. The strength of the photoresponse measurement lies in the ability to precisely fit the experimental data with a physical model. PC-1D provides a flexible platform for calculations based on these physical models.
Potent neutralizing anti-CD1d antibody reduces lung cytokine release in primate asthma model
Nambiar, Jonathan; Clarke, Adam W; Shim, Doris; Mabon, David; Tian, Chen; Windloch, Karolina; Buhmann, Chris; Corazon, Beau; Lindgren, Matilda; Pollard, Matthew; Domagala, Teresa; Poulton, Lynn; Doyle, Anthony G
2015-01-01
CD1d is a receptor on antigen-presenting cells involved in triggering cell populations, particularly natural killer T (NKT) cells, to release high levels of cytokines. NKT cells are implicated in asthma pathology and blockade of the CD1d/NKT cell pathway may have therapeutic potential. We developed a potent anti-human CD1d antibody (NIB.2) that possesses high affinity for human and cynomolgus macaque CD1d (KD ?100 pM) and strong neutralizing activity in human primary cell-based assays (IC50 typically <100 pM). By epitope mapping experiments, we showed that NIB.2 binds to CD1d in close proximity to the interface of CD1d and the Type 1 NKT cell receptor ?-chain. Together with data showing that NIB.2 inhibited stimulation via CD1d loaded with different glycolipids, this supports a mechanism whereby NIB.2 inhibits NKT cell activation by inhibiting Type 1 NKT cell receptor ?-chain interactions with CD1d, independent of the lipid antigen in the CD1d antigen-binding cleft. The strong in vitro potency of NIB.2 was reflected in vivo in an Ascaris suum cynomolgus macaque asthma model. Compared with vehicle control, NIB.2 treatment significantly reduced bronchoalveolar lavage (BAL) levels of Ascaris-induced cytokines IL-5, IL-8 and IL-1 receptor antagonist, and significantly reduced baseline levels of GM-CSF, IL-6, IL-15, IL-12/23p40, MIP-1?, MIP-1?, and VEGF. At a cellular population level NIB.2 also reduced numbers of BAL lymphocytes and macrophages, and blood eosinophils and basophils. We demonstrate that anti-CD1d antibody blockade of the CD1d/NKT pathway modulates inflammatory parameters in vivo in a primate inflammation model, with therapeutic potential for diseases where the local cytokine milieu is critical. PMID:25751125
Wave propagation modelling in 1D structures using spectral finite elements
NASA Astrophysics Data System (ADS)
Kudela, P.; Krawczuk, M.; Ostachowicz, W.
2007-02-01
The application of spectral finite elements (SFE) to one-dimensional (1D) elastic wave propagation problems is presented. Travelling waves in an isotropic rod and Timoshenko beam have been investigated. The rod has been modelled using 1D SFEs while the beam has been modelled using 1D and 2D SFEs. Numerical results have been compared to those obtained from the classical finite element approach. This comparison highlighted the efficiency of the SFE method. The numerical results have been also verified experimentally. A high degree of accuracy has been observed.
Deconvolution of Complex 1D NMR Spectra Using Objective Model Selection
Hughes, Travis S.; Wilson, Henry D.; de Vera, Ian Mitchelle S.; Kojetin, Douglas J.
2015-01-01
Fluorine (19F) NMR has emerged as a useful tool for characterization of slow dynamics in 19F-labeled proteins. One-dimensional (1D) 19F NMR spectra of proteins can be broad, irregular and complex, due to exchange of probe nuclei between distinct electrostatic environments; and therefore cannot be deconvoluted and analyzed in an objective way using currently available software. We have developed a Python-based deconvolution program, decon1d, which uses Bayesian information criteria (BIC) to objectively determine which model (number of peaks) would most likely produce the experimentally obtained data. The method also allows for fitting of intermediate exchange spectra, which is not supported by current software in the absence of a specific kinetic model. In current methods, determination of the deconvolution model best supported by the data is done manually through comparison of residual error values, which can be time consuming and requires model selection by the user. In contrast, the BIC method used by decond1d provides a quantitative method for model comparison that penalizes for model complexity helping to prevent over-fitting of the data and allows identification of the most parsimonious model. The decon1d program is freely available as a downloadable Python script at the project website (https://github.com/hughests/decon1d/). PMID:26241959
Modelling turbulent vertical mixing sensitivity using a 1-D version of NEMO
NASA Astrophysics Data System (ADS)
Reffray, G.; Bourdalle-Badie, R.; Calone, C.
2014-08-01
Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k + l from Blanke and Delecluse, 1993 and two equation models: Generic Lengh Scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a one-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between -2 and 2 C during the stratified period (June to October). However the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 C during the stratified period and from 0.03 to 0.15 C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (1D_PAPA">http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D_PAPA). This package is a good starting point for further investigation of vertical processes.
Modelling turbulent vertical mixing sensitivity using a 1-D version of NEMO
NASA Astrophysics Data System (ADS)
Reffray, G.; Bourdalle-Badie, R.; Calone, C.
2015-01-01
Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k+l from Blanke and Delecluse, 1993, and two equation models: generic length scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a 1-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between -2 and 2 C during the stratified period (June to October). However, the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 C during the stratified period and from 0.03 to 0.15 C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (1D_PAPA">http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D_PAPA). This package is a good starting point for further investigation of vertical processes.
NASA Astrophysics Data System (ADS)
Kabe, Yoshiro; Hasunuma, Ryu; Yamabe, Kikuo
2014-03-01
We investigated the oxidation of silicon by O(1D2) and O(3P2) radicals in a microwave plasma at 673 K in an Ar/O2 atmosphere containing a small amount of hydrogen. O(1D2) radical oxidation with hydrogen gave a much higher growth rate than wet thermal oxidation at 1223 K. The activation energies for the parabolic rate constant owing to O(1D2) and O(3P2) radical oxidations were respectively 0.18 and 0.40 eV, which are much lower than that (0.71 eV) by thermal oxidation. In time-dependent dielectric breakdown tests, despite SiO2 films formed by radicals having a higher degradation rate than those produced by thermal oxidation, SiO2 films formed by O(1D2) radicals had longer lifetimes. Our dielectric breakdown model indicates this is due to the flat SiO2 surface and interface suppressing two-dimensional local breakdown. A stress-relaxation oxidation model for O(1D2) radicals is proposed that well explains the formation of flat SiO2 surfaces and interfaces.
The (2 + 1)-d U(1) quantum link model masquerading as deconfined criticality
NASA Astrophysics Data System (ADS)
Banerjee, D.; Jiang, F.-J.; Widmer, P.; Wiese, U.-J.
2013-12-01
The (2 + 1)-d U(1) quantum link model is a gauge theory, amenable to quantum simulation, with a spontaneously broken SO(2) symmetry emerging at a quantum phase transition. Its low-energy physics is described by a (2 + 1)-d RP(1) effective field theory, perturbed by an SO(2) breaking operator, which prevents the interpretation of the emergent pseudo-Goldstone boson as a dual photon. At the quantum phase transition, the model mimics some features of deconfined quantum criticality, but remains linearly confining. Deconfinement only sets in at high temperature. Dedicated to the memory of Bernard B Beard (1957-2012).
3D Versus 1D Radiative Transfer Modeling of Planetary Nebulae
NASA Astrophysics Data System (ADS)
Pantoja, Blake M.; Ladjal, Djazia
2015-01-01
Planetary nebulae are the products of the fast stellar wind from the end of the AGB star phase. To date, there are many one-dimensional radiative transfer codes, and a few fully 3D codes that can model the ionization of the planetary nebulae. Some limitations on 1D codes are that they can only make spherical or parallel plane models, while 3D codes take much computing power and memory to run. A pseudo-3D code such as pyCloudy can model a planetary nebula in 3D by making multiple runs of a 1D code such as Cloudy in different angles from the center of the nebula. We compared the 1D models with pseudo-3D models to determine if the 1D models give good approximations for the observed parameters of the planetary nebulae. We find that one-dimensional codes can actually give good estimates for electron temperature and density in a bipolar planetary nebula.
Newberry EGS Seismic Velocity Model
Templeton, Dennise
2013-10-01
We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.
HYDRUS-1D Modeling of an Irrigated Agricultural Plot with Application to Aquifer Recharge Estimation
Technology Transfer Automated Retrieval System (TEKTRAN)
A variety of methods are available for estimating aquifer recharge in semi-arid regions, each with advantages and disadvantages. We are investigating a procedure for estimating recharge in an irrigated basin. The method involves computing irrigation return flows based on HYDRUS-1D modeling of root z...
Review of Zero-D and 1-D Models of Blood Flow in the Cardiovascular System
2011-01-01
Background Zero-dimensional (lumped parameter) and one dimensional models, based on simplified representations of the components of the cardiovascular system, can contribute strongly to our understanding of circulatory physiology. Zero-D models provide a concise way to evaluate the haemodynamic interactions among the cardiovascular organs, whilst one-D (distributed parameter) models add the facility to represent efficiently the effects of pulse wave transmission in the arterial network at greatly reduced computational expense compared to higher dimensional computational fluid dynamics studies. There is extensive literature on both types of models. Method and Results The purpose of this review article is to summarise published 0D and 1D models of the cardiovascular system, to explore their limitations and range of application, and to provide an indication of the physiological phenomena that can be included in these representations. The review on 0D models collects together in one place a description of the range of models that have been used to describe the various characteristics of cardiovascular response, together with the factors that influence it. Such models generally feature the major components of the system, such as the heart, the heart valves and the vasculature. The models are categorised in terms of the features of the system that they are able to represent, their complexity and range of application: representations of effects including pressure-dependent vessel properties, interaction between the heart chambers, neuro-regulation and auto-regulation are explored. The examination on 1D models covers various methods for the assembly, discretisation and solution of the governing equations, in conjunction with a report of the definition and treatment of boundary conditions. Increasingly, 0D and 1D models are used in multi-scale models, in which their primary role is to provide boundary conditions for sophisticate, and often patient-specific, 2D and 3D models, and this application is also addressed. As an example of 0D cardiovascular modelling, a small selection of simple models have been represented in the CellML mark-up language and uploaded to the CellML model repository http://models.cellml.org/. They are freely available to the research and education communities. Conclusion Each published cardiovascular model has merit for particular applications. This review categorises 0D and 1D models, highlights their advantages and disadvantages, and thus provides guidance on the selection of models to assist various cardiovascular modelling studies. It also identifies directions for further development, as well as current challenges in the wider use of these models including service to represent boundary conditions for local 3D models and translation to clinical application. PMID:21521508
Behavioral Responses in Animal Model of Congenital Muscular Dystrophy 1D.
Comim, Clarissa M; Schactae, Aryadnne L; Soares, Jaime A; Ventura, Letcia; Freiberger, Viviane; Mina, Francielle; Dominguini, Diogo; Vainzof, Mariz; Quevedo, Joo
2016-01-01
Congenital muscular dystrophies 1D (CMD1D) present a mutation on the LARGE gene and are characterized by an abnormal glycosylation of ?-dystroglycan (?-DG), strongly implicated as having a causative role in the development of central nervous system abnormalities such as cognitive impairment seen in patients. However, in the animal model of CMD1D, the brain involvement remains unclear. Therefore, the objective of this study is to evaluate the cognitive involvement in the Large(myd) mice. To this aim, we used adult homozygous, heterozygous, and wild-type mice. The mice underwent six behavioral tasks: habituation to an open field, step-down inhibitory avoidance, continuous multiple trials step-down inhibitory avoidance task, object recognition, elevated plus-maze, and forced swimming test. It was observed that Large(myd) individuals presented deficits on the habituation to the open field, step down inhibitory avoidance, continuous multiple-trials step-down inhibitory avoidance, object recognition, and forced swimming. This study shows the first evidence that abnormal glycosylation of ?-DG may be affecting memory storage and restoring process in an animal model of CMD1D. PMID:25465243
Constraint on the 1D earth model near core-mantle boundary by free core nutation
NASA Astrophysics Data System (ADS)
Huang, Chengli; Zhang, Mian
2015-04-01
Free core nutation (FCN) is a normal mode of the rotating earth with fluid outer core (FOC). Its period depends on the physics of the mantle and FOC, especially the parameters near core-mantle boundary (CMB), like the density and elastic (Lame) parameters. FCN period can be determined very accurately by VLBI and superconductive tidal gravimetry, but the theoretical calculation results of FCN period from traditional approaches and 1D earth model (like PREM) deviate significantly from the accurate observation. Meanwhile, the influence of the uncertainty of a given earth model on nutation has never been studied before. In this work, a numerical experiment is presented to check this problem, and we want to see whether FCN can provide a constraint on the construction of a 1D earth model, especially on the gradient of material density near CMB.
Zero finite-temperature charge stiffness within the half-filled 1D Hubbard model
Carmelo, J.M.P.; Beijing Computational Science Research Center, Beijing 100084; Institut fr Theoretische Physik III, Universitt Stuttgart, D-70550 Stuttgart ; Gu, Shi-Jian; Department of Physics and ITP, Chinese University of Hong Kong, Hong Kong ; Sacramento, P.D.; Beijing Computational Science Research Center, Beijing 100084
2013-12-15
Even though the one-dimensional (1D) Hubbard model is solvable by the Bethe ansatz, at half-filling its finite-temperature T>0 transport properties remain poorly understood. In this paper we combine that solution with symmetry to show that within that prominent T=0 1D insulator the charge stiffness D(T) vanishes for T>0 and finite values of the on-site repulsion U in the thermodynamic limit. This result is exact and clarifies a long-standing open problem. It rules out that at half-filling the model is an ideal conductor in the thermodynamic limit. Whether at finite T and U>0 it is an ideal insulator or a normal resistor remains an open question. That at half-filling the charge stiffness is finite at U=0 and vanishes for U>0 is found to result from a general transition from a conductor to an insulator or resistor occurring at U=U{sub c}=0 for all finite temperatures T>0. (At T=0 such a transition is the quantum metal to MottHubbard-insulator transition.) The interplay of the ?-spin SU(2) symmetry with the hidden U(1) symmetry beyond SO(4) is found to play a central role in the unusual finite-temperature charge transport properties of the 1D half-filled Hubbard model. -- Highlights: The charge stiffness of the half-filled 1D Hubbard model is evaluated. Its value is controlled by the model symmetry operator algebras. We find that there is no charge ballistic transport at finite temperatures T>0. The hidden U(1) symmetry controls the U=0 phase transition for T>0.
SILVA: EDF two-phase 1D annular model of a CFB boiler furnace
Montat, D.; Fauquet, P.; Lafanechere, L.; Bursi, J.M.
1997-12-31
Aiming to improve its knowledge of CFB boilers, EDF has initiated a R and D program including: laboratory work on mock-ups, numerical modelling and on-site tests in CFB power plants. One of the objectives of this program is the development of a comprehensive steady-state 1D model of the solid circulation loop, named SILVA, for plant operation and design evaluation purposes. This paper describes its mathematical and physical modelling. Promising validation of the model on cold mock-up and industrial CFB is presented.
Assessment of improved root growth representation in a 1-D, field scale crop model
NASA Astrophysics Data System (ADS)
Miltin Mboh, Cho; Gaiser, Thomas; Ewert, Frank
2015-04-01
Many 1-D, field scale crop models over-simplify root growth. The over-simplification of this "hidden half" of the crop may have significant consequences on simulated root water and nutrient uptake with a corresponding reflection on the simulated crop yields. Poor representation of root growth in crop models may therefore constitute a major source of uncertainty propagation. In this study we assess the effect of an improved representation of root growth in a model solution of the model framework SIMPLACE (Scientific Impact assessment and Modeling PLatform for Advanced Crop and Ecosystem management) compared to conventional 1-D approaches. The LINTUL5 crop growth model is coupled to the Hillflow soil water balance model within the SIMPLACE modeling framework (Gaiser et al, 2013). Root water uptake scenarios in the soil hydrological simulator Hillflow (Bronstert, 1995) together with an improved representation of root growth is compared to scenarios for which root growth is simplified. The improvement of root growth is achieved by integrating root growth solutions from R-SWMS (Javaux et al., 2008) into the SIMPLACE model solution. R-SWMS is a three dimensional model for simultaneous modeling of root growth, soil water fluxes and solute transport and uptake. These scenarios are tested by comparing how well the simulated water contents match with the observed soil water dynamics. The impacts of the scenarios on above ground biomass and wheat grain are assessed
NASA Astrophysics Data System (ADS)
Altarejos-Garca, L.; Martnez-Chenoll, M. L.; Escuder-Bueno, I.; Serrano-Lombillo, A.
2012-07-01
This paper addresses the use of reliability techniques such as Rosenblueth's Point-Estimate Method (PEM) as a practical alternative to more precise Monte Carlo approaches to get estimates of the mean and variance of uncertain flood parameters water depth and velocity. These parameters define the flood severity, which is a concept used for decision-making in the context of flood risk assessment. The method proposed is particularly useful when the degree of complexity of the hydraulic models makes Monte Carlo inapplicable in terms of computing time, but when a measure of the variability of these parameters is still needed. The capacity of PEM, which is a special case of numerical quadrature based on orthogonal polynomials, to evaluate the first two moments of performance functions such as the water depth and velocity is demonstrated in the case of a single river reach using a 1-D HEC-RAS model. It is shown that in some cases, using a simple variable transformation, statistical distributions of both water depth and velocity approximate the lognormal. As this distribution is fully defined by its mean and variance, PEM can be used to define the full probability distribution function of these flood parameters and so allowing for probability estimations of flood severity. Then, an application of the method to the same river reach using a 2-D Shallow Water Equations (SWE) model is performed. Flood maps of mean and standard deviation of water depth and velocity are obtained, and uncertainty in the extension of flooded areas with different severity levels is assessed. It is recognized, though, that whenever application of Monte Carlo method is practically feasible, it is a preferred approach.
NASA Astrophysics Data System (ADS)
Altarejos-Garca, L.; Martnez-Chenoll, M. L.; Escuder-Bueno, I.; Serrano-Lombillo, A.
2012-01-01
This paper addresses the use of reliability techniques such as Rosenblueth's Point-Estimate Method (PEM) as a practical alternative to more precise Monte Carlo approaches to get estimates of the mean and variance of uncertain flood parameters water depth and velocity. These parameters define the flood severity, which is a concept used for decision-making in the context of flood risk assessment. The method proposed is particularly useful when the degree of complexity of the hydraulic models makes Monte Carlo inapplicable in terms of computing time, but when a measure of the variability of these parameters is still needed. The capacity of PEM, which is a special case of numerical quadrature based on orthogonal polynomials, to evaluate the first two moments of performance functions such as the water depth and velocity is demonstrated in the case of a single river reach using a 1-D HEC-RAS model. It is shown that in some cases, using a simple variable transformation, statistical distributions of both water depth and velocity approximate the lognormal. As this distribution is fully defined by its mean and variance, PEM can be used to define the full probability distribution function of these flood parameters and so allowing for probability estimations of flood severity. Then, an application of the method to the same river reach using a 2-D Shallow Water Equations (SWE) model is performed. Flood maps of mean and standard deviation of water depth and velocity are obtained, and uncertainty in the extension of flooded areas with different severity levels is assessed. It is recognized, though, that whenever application of Monte Carlo method is practically feasible, it is a preferred approach.
A preliminary one-dimensional crustal velocity model for Himachal Pradesh, India
NASA Astrophysics Data System (ADS)
Parija, Mahesh Prasad; Kumar, Sushil; Biswal, Shubhasmita; Kumar, Narendra; Mishra, Saurabh Kumar
2015-10-01
A preliminary one-dimensional (1D) velocity model for Himachal Pradesh, India has been developed by utilising the P and S wave travel time data. A very steady and narrow velocity model was obtained with travel time inversion, and a range of velocity models were tested with earthquake locations to derive the best-fit velocity model. The 1D velocity model proposed for the study region has seven uniform layers with interfaces at depths of 0, 5, 10, 15, 20, 25 and 30 km with P wave velocity of 5.219, 5.314, 5.391, 5.392, 5.964, 6.071 and 6.073 km/s and S wave velocity of 2.998, 3.015, 3.134, 3.135, 3.441, 3.482 and 3.647 km/s, respectively. According to the proposed model, the Moho in this part of the Himalaya lies at 60 km depth on an average. For P and S waves, the station correction ranges from -0.88 to 1.50 and -0.58 to 3.59 s, respectively. This low variation in station residuals indicates small lateral velocity changes that confirm the accuracy and stability of the proposed 1D velocity model. Using the new derived 1D velocity model, the earthquake epicentres were relocated and we observe a shallow seismic activity in the region at <30 km depth that clearly describes the ongoing convergence of the India-Eurasia plates in the study region. This study also infers a new, highly active seismic window in the latitude range of 31.8 N to 32.8 N and longitude range of 76.8 E to 78.8 E in the study region across the Kaurik-Chango fault, a causative fault for the 1975 Kinnaur earthquake.
A preliminary one-dimensional crustal velocity model for Himachal Pradesh, India
NASA Astrophysics Data System (ADS)
Parija, Mahesh Prasad; Kumar, Sushil; Biswal, Shubhasmita; Kumar, Narendra; Mishra, Saurabh Kumar
2016-01-01
A preliminary one-dimensional (1D) velocity model for Himachal Pradesh, India has been developed by utilising the P and S wave travel time data. A very steady and narrow velocity model was obtained with travel time inversion, and a range of velocity models were tested with earthquake locations to derive the best-fit velocity model. The 1D velocity model proposed for the study region has seven uniform layers with interfaces at depths of 0, 5, 10, 15, 20, 25 and 30 km with P wave velocity of 5.219, 5.314, 5.391, 5.392, 5.964, 6.071 and 6.073 km/s and S wave velocity of 2.998, 3.015, 3.134, 3.135, 3.441, 3.482 and 3.647 km/s, respectively. According to the proposed model, the Moho in this part of the Himalaya lies at 60 km depth on an average. For P and S waves, the station correction ranges from -0.88 to 1.50 and -0.58 to 3.59 s, respectively. This low variation in station residuals indicates small lateral velocity changes that confirm the accuracy and stability of the proposed 1D velocity model. Using the new derived 1D velocity model, the earthquake epicentres were relocated and we observe a shallow seismic activity in the region at <30 km depth that clearly describes the ongoing convergence of the India-Eurasia plates in the study region. This study also infers a new, highly active seismic window in the latitude range of 31.8 °N to 32.8 °N and longitude range of 76.8 °E to 78.8 °E in the study region across the Kaurik-Chango fault, a causative fault for the 1975 Kinnaur earthquake.
Short-time dynamics in the 1D long-range Potts model
NASA Astrophysics Data System (ADS)
Uzelac, K.; Glumac, Z.; Barii?, O. S.
2008-05-01
We present numerical investigations of the short-time dynamics at criticality in the 1D Potts model with power-law decaying interactions of the form 1/r1+?. The scaling properties of the magnetization, autocorrelation function and time correlations of the magnetization are studied. The dynamical critical exponents ?' and z are derived in the cases q=2 and q=3 for several values of the parameter ? belonging to the nontrivial critical regime.
Box model and 1D longitudinal model of flow and transport in Bosten Lake, China
NASA Astrophysics Data System (ADS)
Li, Ning; Kinzelbach, Wolfgang; Li, WenPeng; Dong, XinGuang
2015-05-01
Bosten Lake in the southeast of Yanqi Catchment, China, supports the downstream agricultural and natural environments. Over the last few decades the intensive agricultural activities in Yanqi Catchment resulted in decreased lake levels and deteriorated lake water quality. A two-box model is constructed to understand the evolution of lake level and salinity between 1958 and 2008. The two-box model of the lake indicates that the evaporation does have the same trend as the observed lake area and the annual average evaporation agrees with the value obtained from the Penman-Monteith approach. To achieve a correct salt balance, the ratio of outflow concentration and average lake concentration has to be around 0.7. This is due to the incomplete mixing of the lake caused by short-circuiting between tributary inflow and the main outflow via the pump stations abstracting water from the lake. This short-circuiting is investigated in more detail by a 1D numerical flow and transport model of the lake calibrated with observations of lake level and lake concentrations. The distributed model reproduces the correct time-varying outflow concentration. It is used for the assessment of two basic management options: increasing river discharge (by water saving irrigation, reduction of phreatic evaporation or reduction of agricultural area) and diverting saline drainage water to the desert. Increasing river discharge to the lake by 20% reduces the east basin salt concentration by 0.55 kg/m3, while capturing all the drainage water and discharging it to depressions instead of the lake reduces the east basin salt concentration by 0.63 kg/m3. A combination of increasing river inflow and decreasing drainage salt flux is sufficient to bring future lake TDS below the required 1 kg/m3, to keep a lake level that sustains the lake ecosystem, and to supply more water for downstream development and ecosystem rehabilitation.
Comparing plasma fluid models of different order for 1D streamer ionization fronts
NASA Astrophysics Data System (ADS)
Markosyan, Aram H.; Teunissen, Jannis; Dujko, Saa; Ebert, Ute
2015-12-01
We evaluate the performance of three plasma fluid models: the first order reaction-drift-diffusion model based on the local field approximation; the second order reaction-drift-diffusion model based on the local energy approximation and a recently developed high order fluid model by Dujko et al (2013 J. Phys. D 46 475202) We first review the fluid models: we briefly discuss their derivation, their underlying assumptions and the type of transport data they require. Then we compare these models to a particle-in-cell/Monte Carlo (PIC/MC) code, using a 1D test problem. The tests are performed in neon and nitrogen at standard temperature and pressure, over a wide range of reduced electric fields. For the fluid models, transport data generated by a multi-term Boltzmann solver are used. We analyze the observed differences in the model predictions and address some of the practical aspects when using these plasma fluid models.
Velocity-jump models with crowding effects
NASA Astrophysics Data System (ADS)
Treloar, Katrina K.; Simpson, Matthew J.; McCue, Scott W.
2011-12-01
Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.
MAST-1D, a Model to Route Sediment and Tracers in Channel-Floodplain Complexes
NASA Astrophysics Data System (ADS)
Viparelli, E.; Lauer, J. W.; Belmont, P.
2014-12-01
Sediment exchange between the channel and floodplain can occur via meander migration, overbank deposition or erosion, and channel widening or narrowing. Depending on channel and floodplain history, floodplains can act either as sources or sinks of bed material and/or wash load. The Morphodynamics And Sediment Tracers in 1D program (MAST-1D) is a numerical model built to describe grain size specific transport of sediment and tracers and the long-term - i.e. decadal and longer - evolution of channel floodplain complexes. MAST-1D differs from other 1D numerical models because it allows for 1) uneven exchange of sediment and tracers between the river channel and the floodplain, 2) temporal changes in channel geometry, bed elevation and floodplain thickness, which result in changes in the channel hydraulic capacity, and 3) temporal changes of size distribution and tracer content in the floodplain, in the load and in the underlying substrate. Under conditions of constant base level, water and sediment supply, the main assumptions in the model result in the system evolving asymptotically toward a steady state wherein channel bed erosion is balanced by channel bed deposition. When at this condition, the amount of sediment deposited on the floodplain through point bar deposition and overbank sedimentation is balanced by the erosion of sediment from the floodplain through lateral migration. However, imbalances in floodplain storage can persist for many years even when the channel bed elevation and size distribution are near steady state. The MAST-1D program is applied to study the long term response of a sand bed river, an 80 km long reach of the Minnesota River between Mankato and Jordan, Minnesota, to changes in flow regime and the sediment load due to the development of intensive agriculture in the watershed. The simulations are performed in successive phases, the model is first set up so that under the best estimates available for pre-agriculture conditions, channel floodplain exchange is even. Changes in flow regime, sediment load, and grain size of sediment load are then applied to represent agricultural development of the basin. The model is first validated against field data. It is then applied to investigate how the channel-floodplain response changes for different grain size distributions of the sediment load.
Emergent 1d Ising Behavior in AN Elementary Cellular Automaton Model
NASA Astrophysics Data System (ADS)
Kassebaum, Paul G.; Iannacchione, Germano S.
The fundamental nature of an evolving one-dimensional (1D) Ising model is investigated with an elementary cellular automaton (CA) simulation. The emergent CA simulation employs an ensemble of cells in one spatial dimension, each cell capable of two microstates interacting with simple nearest-neighbor rules and incorporating an external field. The behavior of the CA model provides insight into the dynamics of coupled two-state systems not expressible by exact analytical solutions. For instance, state progression graphs show the causal dynamics of a system through time in relation to the system's entropy. Unique graphical analysis techniques are introduced through difference patterns, diffusion patterns, and state progression graphs of the 1D ensemble visualizing the evolution. All analyses are consistent with the known behavior of the 1D Ising system. The CA simulation and new pattern recognition techniques are scalable (in both dimension, complexity, and size) and have many potential applications such as complex design of materials, control of agent systems, and evolutionary mechanism design.
The Hubbard model and optics: reflectivity of 1D and 2D systems
NASA Astrophysics Data System (ADS)
Celebonovic, Vladan
2012-12-01
The Hubbard model (HM) was proposed around the middle of the last century as a model of the behavior of correlated electrons. It has so far been solved only in the 1D case. The HM is used in condensed matter physics in work on high Tc superconductors, organic conductors, graphene,... It is known that reflectivity is related to the electrical conductivity, and both quantities can be measured. This paper is divided into several sections. It begins with a brief introduction to the HM, and the links between the reflectivity and conductivity of a material with its parameters. In the second and third parts, the explicit calculations of the reflectivity of a 1D and 2D square rectangular lattices will be presented. Expressions for the reflectivity thus obtained are tied to the material parameters via previous results of the author on the conductivity of a 1D lattice. We attempt to find a set of material parameters in both cases of lattices, for which the reflectivity becomes close to zero, or equal to an arbitrary constant. If such a set of material parameters could be found, it could have interesting applications in material science such as invisibility.
NASA Astrophysics Data System (ADS)
Kaystrenko, Victor; Pelinovsky, Efim
2013-04-01
1-D linear inverse problem for initial sea level disturbance in the tsunami source ?0(x) using sea level record f(t) near the shore was investigated. Sea bottom can be considered as the slopping plane and water depthh(x) = k x. Let the function ?(x,t) describing sea level oscillations depending from time t and space coordinate xis satisfying the linear shallow water equation (gkx??x)x = ?tt If initial velocities in the source zone are equal to zero (?t(x,0)=0) than initial sea level disturbance in the tsunami source ?0(x) = ?(x,0) and sea level record (marigram) on the shore f(t) = ?(0,t) are tied by the integral equation of Abel type which has an unique analytical solution. Situation looks different if initial wave field in the tsunami source is related to sea level disturbance and current velocities not equal to zero. In this case specially constructed initial wave field with ?0(x) = ?(x,0) and ?1(x) = ?t(x,0) tied by the integral equation ?0(Z) = -2 ? zZK(° ---- (Z-)2 - 1) z) ? ?1(z)zdz where K is the full elliptic integral and z = 2° -- xkg- = ?2gxh-, gives the tsunami non observed near the shore: ?(0,t)=0. The work was supported by grant 11-05-01054 of the Russian foundation for basic research.
Nested 1D-2D approach for urban surface flood modeling
NASA Astrophysics Data System (ADS)
Murla, Damian; Willems, Patrick
2015-04-01
Floods in urban areas as a consequence of sewer capacity exceedance receive increased attention because of trends in urbanization (increased population density and impermeability of the surface) and climate change. Despite the strong recent developments in numerical modeling of water systems, urban surface flood modeling is still a major challenge. Whereas very advanced and accurate flood modeling systems are in place and operation by many river authorities in support of flood management along rivers, this is not yet the case in urban water management. Reasons include the small scale of the urban inundation processes, the need to have very high resolution topographical information available, and the huge computational demands. Urban drainage related inundation modeling requires a 1D full hydrodynamic model of the sewer network to be coupled with a 2D surface flood model. To reduce the computational times, 0D (flood cones), 1D/quasi-2D surface flood modeling approaches have been developed and applied in some case studies. In this research, a nested 1D/2D hydraulic model has been developed for an urban catchment at the city of Gent (Belgium), linking the underground sewer (minor system) with the overland surface (major system). For the overland surface flood modelling, comparison was made of 0D, 1D/quasi-2D and full 2D approaches. The approaches are advanced by considering nested 1D-2D approaches, including infiltration in the green city areas, and allowing the effects of surface storm water storage to be simulated. An optimal nested combination of three different mesh resolutions was identified; based on a compromise between precision and simulation time for further real-time flood forecasting, warning and control applications. Main streets as mesh zones together with buildings as void regions constitute one of these mesh resolution (3.75m2 - 15m2); they have been included since they channel most of the flood water from the manholes and they improve the accuracy of interactions within the 1D sewer network. Other areas that recorded flooding outside the main streets have been also included with the second mesh resolution for an accurate determination of flood maps (12.5m2 - 50m2). Permeable areas have been identified and used as infiltration zones using the Horton infiltration model. A mesh sensitivity analysis has been performed for the low flood risk areas for a proper model optimization. As outcome of that analysis, the third mesh resolution has been chosen (75m2 - 300m2). Performance tests have been applied for several synthetic design storms as well as historical storm events displaying satisfactory results upon comparing the flood mapping outcomes produced by the different approaches. Accounting for the infiltration in the green city spaces reduces the flood extents in the range 39% - 68%, while the average reduction in flood volume equals 86%. Acknowledgement: Funding for this research was provided by the Interreg IVB NWE programme (project RainGain) and the Belgian Science Policy Office (project PLURISK). The high resolution topographical information data were obtained from the geographical information service AGIV; the original full hydrodynamic sewer network model from the service company Farys, and the InfoWorks licence from Innovyze.
Evaluation of 2 1-D cloud models for the analysis of VAS soundings
NASA Technical Reports Server (NTRS)
Emmitt, G. D.
1984-01-01
Evaluation of the satellite Visual Infrared Spin Scan Radiometer Atmospheric Sounder (VISSR) has begun to document several of its critical shortcomings as far as numerical cloud models are concerned: excessive smoothing of thermal inversions; imprecise measurement of boundary layer moisture; and tendency to exaggerate atmospheric stability. The sensitivity of 1-D cloud models to their required inputs is stressed with special attention to those parameters obtained from atmospheric soundings taken by the VAS or rawinsonde. In addition to performing model experiments using temperature and moisture profiles having the general characteristics of VAS soundings, standard input sensitivity tests were made and 1-D model performance was compared with observations and the results of a 2-D model experiment using AVE/VAS data (Atmospheric Variability Experiment). Although very encouraging, the results are not sufficient to make any specific conclusions. In general, the VAS soundings are likely to be inadequate to provide the cloud base (and subcloud layer) information needed for inputs to current cumulus models. Above cloud base, the tendency to exaggerate the stability of the atmosphere requires solution before meaningful model experiments are run.
Testing a 1-D Analytical Salt Intrusion Model and the Predictive Equation in Malaysian Estuaries
NASA Astrophysics Data System (ADS)
Gisen, Jacqueline Isabella; Savenije, Hubert H. G.
2013-04-01
Little is known about the salt intrusion behaviour in Malaysian estuaries. Study on this topic sometimes requires large amounts of data especially if a 2-D or 3-D numerical models are used for analysis. In poor data environments, 1-D analytical models are more appropriate. For this reason, a fully analytical 1-D salt intrusion model, based on the theory of Savenije in 2005, was tested in three Malaysian estuaries (Bernam, Selangor and Muar) because it is simple and requires minimal data. In order to achieve that, site surveys were conducted in these estuaries during the dry season (June-August) at spring tide by moving boat technique. Data of cross-sections, water levels and salinity were collected, and then analysed with the salt intrusion model. This paper demonstrates a good fit between the simulated and observed salinity distribution for all three estuaries. Additionally, the calibrated Van der Burgh's coefficient K, Dispersion coefficient D0, and salt intrusion length L, for the estuaries also displayed a reasonable correlations with those calculated from the predictive equations. This indicates that not only is the salt intrusion model valid for the case studies in Malaysia but also the predictive model. Furthermore, the results from this study describe the current state of the estuaries with which the Malaysian water authority in Malaysia can make decisions on limiting water abstraction or dredging. Keywords: salt intrusion, Malaysian estuaries, discharge, predictive model, dispersion
Hillslope Hydrographs Analyzed Using 1D and 2D Numerical Models
NASA Astrophysics Data System (ADS)
Dusek, J.; Vogel, T. N.; Dohnal, M.; Sanda, M.
2014-12-01
Stable isotopes of water naturally occurring in rainwater have the potential to reveal principal transport mechanisms at multiple scales - from soil profile to hillslope and catchment scale. In this contribution, we study transport processes at the hillslope scale by combining field observations of hillslope discharge and the associated oxygen-18 contents with detailed process-based numerical modeling. In the one-dimensional (1D) approach, 1D dual-continuum vertical flow and transport model (based on Richards and advection-dispersion equations) is coupled with 1D single-continuum lateral flow and transport model (based on diffusion wave equation for saturated subsurface flow and advection-dispersion equation for isotope transport). In the two-dimensional (2D) approach, the movement of water in a variably saturated hillslope segment is modeled as vertical planar flow (i.e., the vertical and lateral flow components are fully integrated into one flow system). Both modeling approaches, taking into account flow and transport through the soil matrix and the system of preferential pathways, were used to simulate the subsurface processes during observed rainfall-runoff episodes. The observed subsurface runoff and its oxygen-18 composition were compared with the model predictions. In addition, contributions of pre-event and event water to hillslope runoff during major rainfall-runoff episodes were evaluated by means of numerical experiments involving synthetic oxygen-18 rainfall signatures. The simulated hillslope responses showed a reasonable agreement with the experimental data in terms of subsurface runoff and oxygen-18 transport dynamics. Pre-event water was found to be the significant runoff component in most major rainfall-runoff events, though preferential flow played an important role in the hillslope runoff formation.
A simple 1-D PC-based plasma edge engineering model for divertor design calculations
Baehre, M.D.; Steiner, D.; Embrechts, M.J.
1989-03-01
A simple, but comprehensive, PC-based 1D axial divertor model has been developed for divertor design and pumping calculations. In the course of successfully benchmarking the model several interesting observations emerged which impact the engineering approaches generally considered to alleviate excessive heat loads and sputtering. The major conclusion is that first attention must be paid to the total heat flux being exhausted to each divertor. Other approaches (such as adjusting the recycling regime, inclining the plate, or injecting impurities) can be used to finetune divertor operation for optimal results. These other approaches all have limited utility or costs associated with their use which may degrade divertor performance.
A world-line framework for 1D topological conformal ?-models
NASA Astrophysics Data System (ADS)
Baulieu, L.; Holanda, N. L.; Toppan, F.
2015-11-01
We use world-line methods for pseudo-supersymmetry to construct sl(2|1)-invariant actions for the (2, 2, 0) chiral and (1, 2, 1) real supermultiplets of the twisted D-module representations of the sl(2|1) superalgebra. The derived one-dimensional topological conformal ?-models are invariant under nilpotent operators. The actions are constructed for both parabolic and hyperbolic/trigonometric realizations (with extra potential terms in the latter case). The scaling dimension ? of the supermultiplets defines a coupling constant, 2? + 1, the free theories being recovered at ? = - /1 2 . We also present, generalizing previous works, the D-module representations of one-dimensional superconformal algebras induced by N = ( p , q ) pseudo-supersymmetry acting on (k, n, n - k) supermultiplets. Besides sl(2|1), we obtain the superalgebras A(1, 1), D(2, 1; ?), D(3, 1), D(4, 1), A(2, 1) from (p, q) = (1, 1), (2, 2), (3, 3), (4, 4), (5, 1), at given k, n and critical values of ?.
Assessing the impact of different sources of topographic data on 1-D hydraulic modelling of floods
NASA Astrophysics Data System (ADS)
Ali, A. Md; Solomatine, D. P.; Di Baldassarre, G.
2015-01-01
Topographic data, such as digital elevation models (DEMs), are essential input in flood inundation modelling. DEMs can be derived from several sources either through remote sensing techniques (spaceborne or airborne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the light detection and ranging (lidar), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30 to 90 m). On the other hand, the lidar technique is able to produce high-resolution DEMs (at around 1 m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of 1-D hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. To test model selection, the outcomes of the 1-D models were also compared, in terms of flood water levels, to the results of 2-D models (LISFLOOD-FP). The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicate that the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. lidar 1 m) to lower resolution is much less than the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the 1-D hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.
Turbulent combustion modeling using explicit convolution of 1-D laminar flame
NASA Astrophysics Data System (ADS)
Mukhopadhyay, S.; Bastiaans, R. J. M.; van Oijen, J. A.; de Goey, L. P. H.
2013-11-01
Increasing computational power is enabling highly resolved Large Eddy Simulation (LES) of turbulent reacting flows. However resolving chemical scales in a practical combustor even with tabulated chemistry methods, still remains unaffordable and requires a model. DNS of a premixed slot flame is performed and a priori analysis indicates that laminar flame filtered at suitable scale can represent the chemical state in a turbulent reacting flow. But to represent all the chemical states, multiple filter widths will be required. This work explores a new modeling approach, Filtered Flamelet Generated Manifold (FFGM) based on explicit convolution of 1-D laminar flame solutions with spatial filter kernel of varying widths. To test the validity of the model a posteriori analysis, using tabulated chemistry constructed by convoluting a premixed laminar flame with top hat kernel of multiple widths is performed for the DNS configuration. The results indicate good performance of the model compared to DNS at a fraction of computational cost.
Velocity model of the shallow lunar crust
NASA Technical Reports Server (NTRS)
Gangi, A. F.
1980-01-01
The travel times of the seismic waves obtained for the Apollo-14 and -16 active seismic experiments and the Apollo-16 grenade launches are shown to be consistent with a powder-layer model of the shallow lunar crust. The velocity variation with depth determined from these data is: V(z) = approximately 110 z to the 1/6 power m/sec for z less than 10 meters and V(z) is nearly = to 250 m/sec for z greater than 10 meters. The velocity values found for the 10 meter depth are similar to those found by Kovach, et al. (1972). The z to the 1/6 power depth dependence for the velocity of the topmost layer is that predicted on the basis of a powder layer (Gangi, 1972). The Amplitude variation of the direct waves as a function of source-to-receiver separation, x, is A(x) = A(o)x to the -n power exp(-ax) where 1.5 n 2.2 and a is nearly = to 0.047 neper/m. Velocity-spectra analyses of the direct, surface-reflected, bottom-reflected and refracted waves give results that are consistent with the velocity model inferred from the traveltime data.
Optimal modeling of 1D azimuth correlations in the context of Bayesian inference
NASA Astrophysics Data System (ADS)
De Kock, Michiel B.; Eggers, Hans C.; Trainor, Thomas A.
2015-09-01
Analysis and interpretation of spectrum and correlation data from high-energy nuclear collisions is currently controversial because two opposing physics narratives derive contradictory implications from the same data, one narrative claiming collision dynamics is dominated by dijet production and projectile-nucleon fragmentation, the other claiming collision dynamics is dominated by a dense, flowing QCD medium. Opposing interpretations seem to be supported by alternative data models, and current model-comparison schemes are unable to distinguish between them. There is clearly need for a convincing new methodology to break the deadlock. In this study we introduce Bayesian inference (BI) methods applied to angular correlation data as a basis to evaluate competing data models. For simplicity the data considered are projections of two-dimensional (2D) angular correlations onto a 1D azimuth from three centrality classes of 200-GeV Au-Au collisions. We consider several data models typical of current model choices, including Fourier series (FS) and a Gaussian plus various combinations of individual cosine components. We evaluate model performance with BI methods and with power-spectrum analysis. We find that FS-only models are rejected in all cases by Bayesian analysis, which always prefers a Gaussian. A cylindrical quadrupole cos(2 ϕ ) is required in some cases but rejected for 0%-5%-central Au-Au collisions. Given a Gaussian centered at the azimuth origin, "higher harmonics" cos(m ϕ ) for m >2 are rejected. A model consisting of Gaussian +dipole cos(ϕ )+quadrupole cos(2 ϕ ) provides good 1D data descriptions in all cases.
Microscopic approach to a class of 1D quantum critical models
NASA Astrophysics Data System (ADS)
Kozlowski, Karol K.; Maillet, Jean Michel
2015-12-01
Starting from the finite volume form factors of local operators, we show how and under which hypothesis the c = 1 free boson conformal field theory in two-dimensions emerges as an effective theory governing the large-distance regime of multi-point correlation functions for a large class of one-dimensional massless quantum Hamiltonians. In our approach, in the large-distance critical regime, the local operators of the initial model are represented by well suited vertex operators associated to the free boson model. This provides an effective field theoretic description of the large distance behaviour of correlation functions in 1D quantum critical models. We develop this description starting from the first principles and directly at the microscopic level, namely in terms of the properties of the finite volume matrix elements of local operators.
Stochastic patterns in a 1D Rock-Paper-Scissors model with mutation
NASA Astrophysics Data System (ADS)
Cianci, Claudia; Carletti, Timoteo
2014-09-01
In the framework of a 1D cyclic competition model, the Rock-Paper-Scissors model, where three kinds of generic agents are allowed to mutate, to interact and to move in space, we study the formation of stochastic patterns, where all the agents do coexist. We modelled the problem using an individual-based setting and we used the system size van Kampen expansion to deal with the Master Equation. We have hence been able to characterise the spatio-temporal patterns using the power spectrum of the fluctuations. We proved that such patterns are robust against the intrinsic noise and they can be found for parameter values beyond the ones fixed by the deterministic approach (mean field approximation). We complement such analytical results with numerical simulations based on the Gillespie algorithm.
NASA Astrophysics Data System (ADS)
Dearden, C.
2009-04-01
This work describes the method by which the performance of a suite of microphysics schemes of varying levels of complexity can be compared in isolation. Bulk schemes using both single-moment and dual-moment treatments of liquid water will be considered, and also an explicit bin-resolving scheme will be used which determines droplet activation from Kohler theory. The purpose is to establish the level of microphysical sophistication required for the successful simulation of liquid clouds in operational models, paying particular attention to the required level of coupling with aerosols. It is important to capture liquid phase processes accurately, not just because they determine the structure of warm clouds, but also because liquid droplets can exist at temperatures below 0degC in the form of supercooled water, which plays a role in ice formation through homogeneous and heterogeneous freezing mechanisms. Each scheme will be implemented within the same 1-D dynamical framework for consistency, and a range of idealised single column cloud simulations will be conducted to explore the parameter space of key variables such as cloud base vertical velocity, aerosol concentration and type. Once the comparison of the microphysical schemes has been conducted in the 1-D framework, a series of warm and mixed-phase cloud case studies will be performed in a mesoscale model framework, to qualitatively demonstrate whether the use of a dual-moment bulk microphysical treatment can lead to improvements in the representation of cloud relative to a single-moment scheme. The simulations will be assessed through quantities such as cloud reflectivity structure, precipitation rate and phase. Ultimately the work will aim to advance our understanding of the key microphysical processes that need to be parameterised in NWP and climate models, and on this basis will seek to quantify the strengths and weaknesses of each scheme.
This technical report describes the new one-dimensional (1D) hydrodynamic and sediment transport model EFDC1D. This model that can be applied to stream networks. The model code and two sample data sets are included on the distribution CD. EFDC1D can simulate bi-directional unstea...
NASA Astrophysics Data System (ADS)
Bellerive, Andre; Tang, Justin; Radulescu, Matei
2013-11-01
1-D Asymptotic analysis on Fickett's model for reactive compressible flow, i.e Burgers' equation with an added reactive term. The model's simplicity is useful to identify the mechanisms that control the detonation stability. An induction-reaction, two-step, chain-branching reaction model is used. We assume a slowed time evolution based on the particle transit through the induction zone. The equation is derived for a high activation energy and a larger exothermic reaction layer than induction layer. The evolution equation is second order in time in the shock front velocity perturbation. The equation yields both stable and unstable solutions, the unstable solutions lead to high amplitude limit-cycles. The results show the stability boundary to be the activation energy times the ratio of induction time to reaction time, ? < CST , at high activation energies. For larger reaction time to induction time the stability is only dependent on the activation energy, ? < CST . The stability boundary and unstable solutions agree with numerical simulation and are consistent with previous reactive Euler models.
Evaluation of a Revised Interplanetary Shock Prediction Model: 1D CESE-HD-2 Solar-Wind Model
NASA Astrophysics Data System (ADS)
Zhang, Y.; Du, A. M.; Du, D.; Sun, W.
2014-08-01
We modified the one-dimensional conservation element and solution element (CESE) hydrodynamic (HD) model into a new version [ 1D CESE-HD-2], by considering the direction of the shock propagation. The real-time performance of the 1D CESE-HD-2 model during Solar Cycle 23 (February 1997 - December 2006) is investigated and compared with those of the Shock Time of Arrival Model ( STOA), the Interplanetary-Shock-Propagation Model ( ISPM), and the Hakamada-Akasofu-Fry version 2 ( HAFv.2). Of the total of 584 flare events, 173 occurred during the rising phase, 166 events during the maximum phase, and 245 events during the declining phase. The statistical results show that the success rates of the predictions by the 1D CESE-HD-2 model for the rising, maximum, declining, and composite periods are 64 %, 62 %, 57 %, and 61 %, respectively, with a hit window of 24 hours. The results demonstrate that the 1D CESE-HD-2 model shows the highest success rates when the background solar-wind speed is relatively fast. Thus, when the background solar-wind speed at the time of shock initiation is enhanced, the forecasts will provide potential values to the customers. A high value (27.08) of ? 2 and low p-value (< 0.0001) for the 1D CESE-HD-2 model give considerable confidence for real-time forecasts by using this new model. Furthermore, the effects of various shock characteristics (initial speed, shock duration, background solar wind, longitude, etc.) and background solar wind on the forecast are also investigated statistically.
1-D and 2-D modeling of U-Ti alloy response in impact experiments
NASA Astrophysics Data System (ADS)
Hermann, B.; Favorsky, V.; Landau, A.; Shvarts, D.; Zaretsky, E. B.
2003-09-01
Dynamie response of a U-0.75wt%Ti alloy bas been studied in planar (disk-on-disk), reverse (disk-on-rod) and symmetric (rod-on-rod) ballistic impact experiments performed with a 25 mm light-gas gun. The impact velocities ranged between 100 and 500 m/see and the samples were softly recovered for further examination, revealing different degrees of spall fracture (planar impact) and of adiabatic shear bands (ballistic experiments). The back (planar experiments) and the lateral (ballistic experiments) surface velocities were continuously monitored by VISAR. The velocity profiles and the damage maps were simulated using a 2-D AUTODYN^TM Lagrangian finite differences code. Simulations of the planar experiments were performed with special attention to the compressive path of the loading cycle in order to calibrate a modified Steinberg-Cochran-Guinan (SCG) constitutive model. The Bauschinger effect and a single-parameter spall model were added to describe the unloading and tensile paths. The calibrated SCG model was then employed to simulate the ballistic experiments. An erosion AUTODYN built-in subroutine with a threshold value of plastic strain was chosen to describe the failure in the ballistic impact experiments. The results of the suggested experimental-numerical technique can be taken into account in estimating the different contributions to the shock-induced plastic deformation and failure.
Fluid friction and wall viscosity of the 1D blood flow model.
Wang, Xiao-Fei; Nishi, Shohei; Matsukawa, Mami; Ghigo, Arthur; Lagrée, Pierre-Yves; Fullana, Jose-Maria
2016-02-29
We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity. PMID:26862041
Prototype oscillator development and 1-D MHD modeling for Oscillating Field Current Drive in an RFP
NASA Astrophysics Data System (ADS)
Blair, A. P.; Lovell, T. W.; Nonn, P. D.; Prager, S. C.; Sarff, J. S.; Wright, J. C.
1999-11-01
Oscillating Field Current Drive (OFCD) is a proposed method of steady state current sustainment in a plasma by application of two oscillating voltages, 90^o out of phase, to the toroidal & poloidal circuits. A novel, low cost sine-wave multivibrator based on ignitron switches has been designed for generating these voltages. A low power (<350 kW) prototype has been built and tested on the Madison Symmetric Torus. Efforts, to date, have focussed on eliminating voltage and/or current limits associated with ignitron turn-off characteristics. In a complementary theoretical effort, a 1-D model of the penetration of oscillating electromagnetic fields into a resistive MHD plasma is explored in a slab geometry. An equilibrium RFP-like magnetic field configuration is imposed in the model and the oscillating field boundary conditions serve to perturb the linearized solution. Effects studied include field penetration and mean current generation in the absence of plasma turbulence.
Calibration and Validation of 1-d and 2-d Flood Flow Models
NASA Astrophysics Data System (ADS)
Horritt, M.; Bates, P.
The complexity of model required to predict inundation extent at reach lengths of ~10km is unknown. Recent advances in remote sensing have enabled maps of flood extent to be used to assess model predictions, and therefore flood flow models can now be rigorously validated in terms of inundated area. Three flood flow models (HEC- RAS, LISFLOOD-FP and TELEMAC-2D) are tested on a 60km reach of the river Severn, UK, for two flood events for which SAR imagery has been acquired. The use of two events enable one to be used for calibration of model friction parameters and the other for independent validation data. Point discharge measurements can also be used for calibration and validation. When calibrating on one flood event and validating on the other, the results indicated that the 1-D model is capable of predicting flood extent well with only discharge calibration data, whereas the 2-D approaches require inundated area data to be calibrated adequately. All 3 models give similar levels of performance in terms of inundated area.
Quantum cosmological relational model of shape and scale in 1D
NASA Astrophysics Data System (ADS)
Anderson, Edward
2011-03-01
Relational particle models are useful toy models for quantum cosmology and the problem of time in quantum general relativity. This paper shows how to extend existing work on concrete examples of relational particle models in 1D to include a notion of scale. This is useful as regards forming a tight analogy with quantum cosmology and the emergent semiclassical time and hidden time approaches to the problem of time. This paper shows furthermore that the correspondence between relational particle models and classical and quantum cosmology can be strengthened using judicious choices of the mechanical potential. This gives relational particle mechanics models with analogues of spatial curvature, cosmological constant, dust and radiation terms. A number of these models are then tractable at the quantum level. These models can be used to study important issues (1) in canonical quantum gravity: the problem of time, the semiclassical approach to it and timeless approaches to it (such as the naive Schrdinger interpretation and records theory) and (2) in quantum cosmology, such as in the investigation of uniform states, robustness and the qualitative understanding of the origin of structure formation.
NASA Astrophysics Data System (ADS)
Bernardie, S.; Desramaut, N.; Russo, G.; Grandjean, G.
2012-04-01
Predicting landslide surface displacements is a challenge for scientists, as it may help save human lives and protect individual housing or transport, energetic facilities. One of the main challenges in active landslide monitoring concerns the prediction of slope's movements in the near future. This study focuses on an innovative methodology to predict landslide surface accelerations, based on a black box tool coupled to a 1D mechanical model. These models are able to predict the evolution of the daily displacements according to the variations of precipitation. More specifically, the impulse response model allows predicting the changes in the landslide movements by computing the transfer function between the input signal (precipitation in this case) and the output signal (the displacements). The second model is based on a simple 1D mechanical assumption, with considering a viscoplastic behavior of the landslide's material, and with taking into account the evolution of the pore water pressure in time. These methods have been applied to the Super-Sauze landslide, located in the Southern French Alps, mountainous region. This site is controlled by complex hydrologic processes leading to active movements within black marls, with velocities ranging between 0.002 and 0.4 m per day. After preliminary tests, results show that the snowmelt has to be taken into account in the models, since the phenomena of freezing /thawing has an influence on the water refills, leading to movement changes. Different approaches to integrate rainfall and/or snow-melting inputs are compared and their complementarity is demonstrated. Finally, a validated methodology for predicting movement changes within landslide based on criteria of comparison between the observed and calculated velocities can be proposed. The results suggest that the impulse response model reproduces the observed data with very good accuracy, whereas the mechanical model seems to be more adapted to predict the movements within 10 days. Moreover, the RMSE criterion permits to highlight the occurrence of the flow, with considering all models, 11 days before the flow itself.
Exploring triggers for polar tropospheric ODEs, using a 1-D snow photochemistry model (MISTRA-SNOW).
NASA Astrophysics Data System (ADS)
Buys, Z.; Jones, A. E.; von Glasow, R.
2012-04-01
Tropospheric Ozone Depletion Events (ODEs) have been known to occur in polar regions for over 20 years. During such events, ozone concentrations can fall from background amounts to below instrumental detection limits within a few minutes and remain suppressed for on the order of hours to days. The chemical destruction of ozone is driven by halogens (especially bromine radicals) that have a source associated with the sea ice zone. Although our knowledge of ODEs has increased greatly since their discovery, some of the key processes involved are not yet fully understood. We now know that heterogeneous reactions lead to the activation of Br2 and BrCI, via uptake of HOBr onto aqueous salt solutions /aerosol/ surface snowpack (Fickert et al., 1999), and it is widely accepted that bromine catalytic reaction cycles (the 'bromine explosion') in the gas phase are responsible for surface ozone destruction (Simpson et al., 2007). There is still much debate over the source of bromine in the atmosphere that drives ODEs, but there is strong evidence to suggest a source associated with the sea ice zone. A 1D Marine Boundary Layer (MBL) chemistry model (MISTRA; von Glasow et al., 2002) has been modified to be representative of Antarctic conditions. The chemistry module includes chemical reactions in the gas phase, in and on aerosol particles and takes into account transfer between the gas and aqueous phase. A new snow-photochemistry module has been developed which includes chemistry which takes place in the quasi-liquid layer on aerosol (Thomas et al., 2011), which is of great importance to our understanding of the chemistry which initiates a bromine explosion. Here we use this newly developed 1-D snow photochemistry model (MISTRA-SNOW) to look at some of the suggested triggers for, and the different meteorological conditions required to produce, tropospheric ODEs in polar regions.
Dynamic and steady state 1-D model of mediated electron transfer in a porous enzymatic electrode.
Do, T Q N; Varni?i?, M; Flassig, R J; Vidakovi?-Koch, T; Sundmacher, K
2015-12-01
A 1-D mathematical model of a porous enzymatic electrode exhibiting the mediated electron transfer (MET) mechanism has been developed. As a model system, glucose oxidation catalyzed by immobilized glucose oxidase (GOx) in the presence of a co-immobilized tetrathiafulvalene (TTF) mediator in the porous electrode matrix has been selected. The balance equations for potential fields in the electron- and ion-conducting phases as well as concentration field have been formulated, solved numerically and validated experimentally under steady state conditions. The relevant kinetic parameters of the lumped reaction kinetics have been obtained by global optimization. The confidence intervals (CIs) of each parameter have been extracted from the respective likelihood. The parameter study has shown that the parameters related to mediator consumption/regeneration steps can be responsible for the shift of the reaction onset potential. Additionally, the model has shown that diffusion of the oxidized mediator out of the catalyst layer (CL) plays a significant role only at more positive potentials and low glucose concentrations. Only concentration profiles in different layers influence the electrode performance while other state fields like potential distributions in different phases have no impact on the performance. The concentration profiles reveal that all electrodes work through; the observed limiting currents are diffusion-reaction limiting. The normalized electrode activity decreases with an increase of enzyme loading. According to the model, the reason for this observation is glucose depletion along the CL at higher enzyme loadings. Comparison with experiments advices a decrease of enzyme utilization at higher enzyme loadings. PMID:26257008
Martian Mesospheric CO2 Ice Clouds in a 1D-Model
NASA Astrophysics Data System (ADS)
Listowski, C.; Mttnen, A.; Spiga, A.; Montmessin, F.; Lefvre, F.
2013-09-01
Since the first probable observation of a CO2 mesospheric cloud on Mars [1] their formation - out of the main component of the atmosphere (95%) - has not been fully addressed yet by studies dealing with CO2 ice cloud modeling in general (e.g [2][15]). Their formation process may be constrained by various recent observations from which effective sizes of crystals have been derived ([8][10][11][14]). Moreover, temperatures far below the CO2 condensation point have been revealed by the SPICAM instrument in the mesosphere, suggesting a strong potential for triggering CO2 ice condensation in extremely supersaturated environment ([3][10]). Mesoscale modeling has shown that locations where gravity waves are able to propagate through the martian atmosphere up to the mesosphere are strongly correlated with locations of CO2 ice cloud observations [13]. These elements strongly suggest an interesting way to model the formation of CO2 mesospheric clouds within a 1D-model, by creating highly supersatured cold pockets with the help of gravity waves.
A 1-D evolutionary model for icy satellites, applied to Enceladus
NASA Astrophysics Data System (ADS)
Prialnik, Dina; Malamud, Uri
2015-11-01
A 1-D long-term evolution code for icy satellites is presented, which couples multiple processes: water migration, geochemical reactions, water and silicate phase transitions, crystallization, compaction by self-gravity, and ablation. The code takes into account various energy sources: tidal heating, radiogenic heating, geochemical energy released by serpentinization or absorbed by mineral dehydration, gravitational energy, and insolation. It includes heat transport by conduction, convection, and advection.The code is applied to Enceladus, by guessing the initial conditions that would render a structure compatible with present-day observations, and adopting a homogeneous initial structure. Assuming that the satellite has been losing water continually along its evolution, it follows that it was formed as a more massive, more ice-rich and more porous object, and gradually transformed into its present day state, due to sustained tidal heating. Several initial compositions and evolution scenarios are considered, and the evolution is simulated for the age of the Solar System. The results corresponding to the present configuration are confronted with the available observational constraints. The present configuration is shown to be differentiated into a pure icy mantle, several tens of km thick, overlying a rocky core, composed of dehydrated rock in the central part and hydrated rock in the outer part. Such a differentiated structure is obtained not only for Enceladus, but for other medium size ice-rich bodies as well.Predictions for Enceladus are a higher rock/ice mass ratio than previously assumed, and a thinner ice mantle, compatible with recent estimates based on gravity field measurements. Although, obviously, the 1-D model cannot be used to explain local phenomena, it sheds light on the internal structure invoked in explanations of localized features and activities.
Testing the accuracy of a 1-D volcanic plume model in estimating mass eruption rate
Mastin, Larry G.
2014-01-01
During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historical eruptions where plume height Hobs was well observed and mass eruption rate Mobs could be calculated from mapped deposit mass and observed duration. The simulations considered wind, temperature, and phase changes of water. Atmospheric conditions were obtained from the National Center for Atmospheric Research Reanalysis 2.5 model. Simulations calculate the minimum, maximum, and average values (Mmin, Mmax, and Mavg) that fit the plume height. Eruption rates were also estimated from the empirical formula Mempir?=?140Hobs4.14 (Mempir is in kilogram per second, Hobs is in kilometer). For these eruptions, the standard error of the residual in log space is about 0.53 for Mavg and 0.50 for Mempir. Thus, for this data set, the model is slightly less accurate at predicting Mobs than the empirical curve. The inability of this model to improve eruption rate estimates may lie in the limited accuracy of even well-observed plume heights, inaccurate model formulation, or the fact that most eruptions examined were not highly influenced by wind. For the low, wind-blown plume of 1418 April 2010 at Eyjafjallajkull, where an accurate plume height time series is available, modeled rates do agree better with Mobs than Mempir.
A 1-D evolutionary model for icy satellites, applied to Enceladus
NASA Astrophysics Data System (ADS)
Malamud, Uri; Prialnik, Dina
2016-04-01
We develop a long-term 1-D evolution model for icy satellites that couples multiple processes: water migration and differentiation, geochemical reactions and silicate phase transitions, compaction by self-gravity, and ablation. The model further considers the following energy sources and sinks: tidal heating, radiogenic heating, geochemical energy released by serpentinization or absorbed by mineral dehydration, gravitational energy and insolation, and heat transport by conduction, convection, and advection. We apply the model to Enceladus, by guessing the initial conditions that would render a structure compatible with present-day observations, assuming the initial structure to have been homogeneous. Assuming the satellite has been losing water continually along its evolution, we postulate that it was formed as a more massive, more icy and more porous satellite, and gradually transformed into its present day state due to sustained long-term tidal heating. We consider several initial compositions and evolution scenarios and follow the evolution for the age of the Solar System, testing the present day model results against the available observational constraints. Our model shows the present configuration to be differentiated into a pure icy mantle, several tens of km thick, overlying a rocky core, composed of dehydrated rock at the center and hydrated rock in the outer part. For Enceladus, it predicts a higher rock/ice mass ratio than previously assumed and a thinner ice mantle, compatible with recent estimates based on gravity field measurements. Although, obviously, the model cannot be used to explain local phenomena, it sheds light on the internal structure invoked in explanations of localized features and activities.
1D Tight-Binding Models Render Quantum First Passage Time "Speakable"
NASA Astrophysics Data System (ADS)
Ranjith, V.; Kumar, N.
2015-12-01
The calculation of First Passage Time (moreover, even its probability density in time) has so far been generally viewed as an ill-posed problem in the domain of quantum mechanics. The reasons can be summarily seen in the fact that the quantum probabilities in general do not satisfy the Kolmogorov sum rule: the probabilities for entering and non-entering of Feynman paths into a given region of space-time do not in general add up to unity, much owing to the interference of alternative paths. In the present work, it is pointed out that a special case exists (within quantum framework), in which, by design, there exists one and only one available path (i.e., door-way) to mediate the (first) passage -no alternative path to interfere with. Further, it is identified that a popular family of quantum systems - namely the 1d tight binding Hamiltonian systems - falls under this special category. For these model quantum systems, the first passage time distributions are obtained analytically by suitably applying a method originally devised for classical (stochastic) mechanics (by Schroedinger in 1915). This result is interesting especially given the fact that the tight binding models are extensively used in describing everyday phenomena in condense matter physics.
1D-3D hybrid modeling—from multi-compartment models to full resolution models in space and time
Grein, Stephan; Stepniewski, Martin; Reiter, Sebastian; Knodel, Markus M.; Queisser, Gillian
2014-01-01
Investigation of cellular and network dynamics in the brain by means of modeling and simulation has evolved into a highly interdisciplinary field, that uses sophisticated modeling and simulation approaches to understand distinct areas of brain function. Depending on the underlying complexity, these models vary in their level of detail, in order to cope with the attached computational cost. Hence for large network simulations, single neurons are typically reduced to time-dependent signal processors, dismissing the spatial aspect of each cell. For single cell or networks with relatively small numbers of neurons, general purpose simulators allow for space and time-dependent simulations of electrical signal processing, based on the cable equation theory. An emerging field in Computational Neuroscience encompasses a new level of detail by incorporating the full three-dimensional morphology of cells and organelles into three-dimensional, space and time-dependent, simulations. While every approach has its advantages and limitations, such as computational cost, integrated and methods-spanning simulation approaches, depending on the network size could establish new ways to investigate the brain. In this paper we present a hybrid simulation approach, that makes use of reduced 1D-models using e.g., the NEURON simulator—which couples to fully resolved models for simulating cellular and sub-cellular dynamics, including the detailed three-dimensional morphology of neurons and organelles. In order to couple 1D- and 3D-simulations, we present a geometry-, membrane potential- and intracellular concentration mapping framework, with which graph- based morphologies, e.g., in the swc- or hoc-format, are mapped to full surface and volume representations of the neuron and computational data from 1D-simulations can be used as boundary conditions for full 3D simulations and vice versa. Thus, established models and data, based on general purpose 1D-simulators, can be directly coupled to the emerging field of fully resolved, highly detailed 3D-modeling approaches. We present the developed general framework for 1D/3D hybrid modeling and apply it to investigate electrically active neurons and their intracellular spatio-temporal calcium dynamics. PMID:25120463
1D-coupled photochemical model of neutrals, cations and anions in the atmosphere of Titan
NASA Astrophysics Data System (ADS)
Dobrijevic, M.; Loison, J. C.; Hickson, K. M.; Gronoff, G.
2016-04-01
Many models with different characteristics have been published so far to study the chemical processes at work in Titan's atmosphere. Some models focus on neutral species in the stratosphere or ionic species in the ionosphere, but few of them couple all the species throughout the whole atmosphere. Very few of these emphasize the importance of uncertainties in the chemical scheme and study their propagation in the model. We have developed a new 1D-photochemical model of Titan's atmosphere coupling neutral species with positive and negative ions from the lower atmosphere up to the ionosphere and have compared our results with observations to have a comprehensive view of the chemical processes driving the composition of the stratosphere and ionosphere of Titan. We have updated the neutral, positive ion and negative ion chemistry and have improved the description of N2 photodissociation by introducing high resolution N2 absorption cross sections. We performed for the first time an uncertainty propagation study in a fully coupled ion-neutral model. We determine how uncertainties on rate constants on both neutral and ionic reactions influence the model results and pinpoint the key reactions responsible for this behavior. We find very good agreement between our model results and observations in both the stratosphere and in the ionosphere for most neutral compounds. Our results are also in good agreement with an average INMS mass spectrum and specific flybys in the dayside suggesting that our chemical model (for both neutral and ions) provides a good approximation of Titan's atmospheric chemistry as a whole. Our uncertainty propagation study highlights the difficulty to interpret the INMS mass spectra for masses 14, 31, 41 and we identified the key reactions responsible for these ambiguities. Despite an overall improvement in the chemical model, disagreement for some specific compounds (HC3N, C2H5CN, C2H4) highlights the role that certain physical processes could play (meridional dynamics or sticking on aerosols). We find that some critical key reactions are important for many compounds including both neutrals and ions and should be studied in priority to lower the remaining model uncertainties. Extensive studies for some specific processes (including photolyses) are required.
Deriving snow hardness from density and its application to the 1-D snow cover model SNOWPACK
NASA Astrophysics Data System (ADS)
Monti, F.; Schweizer, J.
2012-04-01
Estimating snow density (?s) based on snow hardness and grain type is often exploited in snow science. In snow hydrology snow water equivalent (SWE) that strongly depends on ?s needs to be determined; in avalanche forecasting an appropriate calculation of ?s is crucial to assess the load on a possible weak layer. However, collecting ?s is time consuming and difficult to do for very thin layers, and thus a parameterisation of ?son hand hardness is useful. On the other hand, the 1D snow cover model SNOWPACK derives snow hardness on simulated snow density. Recently, a new snow settling parameterization was introduced in the model which affects the simulation of density so that a new calibration is needed. We established a relation between ?sand hand hardness which is representative for various climatic regions of the European Alps. Two data sets including 14'455 dry-snow layers with measured density, grain type and hand hardness were used to relate density to hand hardness for the major grain types. The data were collected in the surroundings of Davos (Switzerland) and in the Veneto region (Italy), and cover different climatic regions and elevations. We applied least square and robust regressions to explore the data. The regression equations for both data sets were generally in reasonable agreement. The data collected in the Veneto region showed a higher variance than those of Davos; nevertheless the Veneto data was normally distributed and the mean values of ?s and hand hardness were highly correlated (R2? 0.9). Only for the grain type melt forms the correlation was lower. The linear relations were then used for the model calibration of SNOWPACK. First hardness simulations obtained with the different settings of the model are promising as simulated hardness is in fair agreement with observed values
A Zonal Climate Model for the 1-D Mars Evolution Code: Explaining Meridiani Planum.
NASA Astrophysics Data System (ADS)
Manning, C. V.; McKay, C. P.; Zahnle, K. J.
2005-12-01
Recent MER Opportunity observations suggest there existed an extensive body of shallow water in the present Meridiani Planum during the late Noachian [1]. Observations of roughly contemporaneous valley networks show little net erosion [2]. Hypsometric analysis [3] finds that martian drainage basins are similar to terrestrial drainage basins in very arid regions. The immaturity of martian drainage basins suggests they were formed by infrequent fluvial action. If similar fluvial discharges are responsible for the laminations in the salt-bearing outcrops of Meridiani Planum, their explanation may require a climate model based on surface thermal equilibrium with diurnally averaged temperatures greater than freezing. In the context of Mars' chaotic obliquity, invoking a moderately thick atmosphere with seasonal insolation patterns may uncover the conditions under which the outcrops formed. We compounded a 1-D model of the evolution of Mars' inventories of CO2 over its lifetime called the Mars Evolution Code (MEC) [4]. We are assembling a zonal climate model that includes meridional heat transport, heat conduction to/from the regolith, latent heat deposition, and an albedo distribution based on the depositional patterns of ices. Since water vapor is an important greenhouse gas, and whose ice affects the albedo, we must install a full hydrological cycle. This requires a thermal model of the regolith to model diffusion of water vapor to/from a permafrost layer. Our model carries obliquity and eccentricity distributions consistent with Laskar et al. [5], so we will be able to model the movement of the ice cap with changes in obliquity. The climate model will be used to investigate the conditions under which ponded water could have occurred in the late Noachian, thus supplying a constraint on the free inventory of CO2 at that time. Our evolution code can then investigate Hesperian and Amazonian climates. The model could also be used to understand evidence of recent climate change, and the specifics of the layering of the northern polar cap. References [1] Hynek, B. M. (2004) Nature 431, 156. [2] Irwin, R. et al. (2004) LPI Conf. 35, 1991. [3] Stepinski, T. F., (2004) JGR E18, 2005 [4] Manning, C. V., et al. (2005Icarus submitted [5] Laskar, J. et al. (2004) Icarus, 170, 343.
Results and limits in the 1-D analytical modeling for the asymmetric DG SOI MOSFET
NASA Astrophysics Data System (ADS)
Cobianu, O.; Glesner, M.
2008-05-01
This paper presents the results and the limits of 1-D analytical modeling of electrostatic potential in the low-doped p type silicon body of the asymmetric n-channel DG SOI MOSFET, where the contribution to the asymmetry comes only from p- and n-type doping of polysilicon used as the gate electrodes. Solving Poisson's equation with boundary conditions based on the continuity of normal electrical displacement at interfaces and the presence of a minimum electrostatic potential by using the Matlab code we have obtained a minimum potential with a slow variation in the central zone of silicon with the value pinned around 0.46 V, where the applied VGS voltage varies from 0.45 V to 0.95 V. The paper states clearly the validity domain of the analytical solution and the important effect of the localization of the minimum electrostatic potential value on the potential variation at interfaces as a function of the applied VGS voltage.
Modelling hydrology of a single bioretention system with HYDRUS-1D.
Meng, Yingying; Wang, Huixiao; Chen, Jiangang; Zhang, Shuhan
2014-01-01
A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems. PMID:25133240
Open boundary conditions for the Diffuse Interface Model in 1-D
NASA Astrophysics Data System (ADS)
Desmarais, J. L.; Kuerten, J. G. M.
2014-04-01
New techniques are developed for solving multi-phase flows in unbounded domains using the Diffuse Interface Model in 1-D. They extend two open boundary conditions originally designed for the Navier-Stokes equations. The non-dimensional formulation of the DIM generalizes the approach to any fluid. The equations support a steady state whose analytical approximation close to the critical point depends only on temperature. This feature enables the use of detectors at the boundaries switching between conventional boundary conditions in bulk phases and a multi-phase strategy in interfacial regions. Moreover, the latter takes advantage of the steady state approximation to minimize the interface-boundary interactions. The techniques are applied to fluids experiencing a phase transition and where the interface between the phases travels through one of the boundaries. When the interface crossing the boundary is fully developed, the technique greatly improves results relative to cases where conventional boundary conditions can be used. Limitations appear when the interface crossing the boundary is not a stable equilibrium between the two phases: the terms responsible for creating the true balance between the phases perturb the interior solution. Both boundary conditions present good numerical stability properties: the error remains bounded when the initial conditions or the far field values are perturbed. For the PML, the influence of its main parameters on the global error is investigated to make a compromise between computational costs and maximum error. The approach can be extended to multiple spatial dimensions.
Modelling Hydrology of a Single Bioretention System with HYDRUS-1D
Meng, Yingying; Wang, Huixiao; Chen, Jiangang; Zhang, Shuhan
2014-01-01
A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems. PMID:25133240
Simulating Helium abundances in the Martian upper atmosphere using 1-D and 3-D models
NASA Astrophysics Data System (ADS)
Bell, Jared M.; Bougher, S. W.; Mahaffy, Paul; Elrod, Meredith
2015-11-01
Chemically inert species, such as Helium, serve as an excellent tracer for the interplay between turbulent eddy diffusive processes and molecular diffusive processes. Using species such as Helium, we can effectively constrain the altitude of the homopause—or the transition from the well-mixed lower atmosphere to the mass-separation characteristic of the upper atmosphere. In this study, we will use the Mars Global Ionosphere-Thermosphere Model (M-GITM) to examine the impacts of altering the turbulent diffusion coefficient (eddy diffusion coefficient) on the simulated abundances of Helium. Using data obtained by the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile Evolution (MAVEN) mission as a benchmark, we can examine what possible values for eddy diffusion in the thermosphere are most likely present in Mars’s upper atmosphere—in other words, we can assess where the mean homopause altitude is most likely located during the MAVEN mission. Furthermore, we will compare and contrast the results obtained when using a strictly classical, 1-D treatment of the problem with a more complete coupled, global 3-D treatment of the Martian atmosphere.
Evaluating alternative river management options in the tidal Ouse using the QUESTS1D model.
Wang, Tao; Cresser, Malcolm S
2007-02-01
The tidal Ouse forms a significant part of the Humber river system in Eastern England, which provides the largest UK fresh water source to the North Sea and a valuable habitat for fish. However it suffers from dissolved oxygen (DO) sag in summer, exacerbated by the industrial effluent discharged at Selby. A one-dimensional water quality model, QUESTS1D, as utilized by the Environment Agency (EA) has been used to evaluate the effectiveness of management options based on exploiting spatial distribution of the assimilative capacity of the river as an alternative to implementing more stringent effluent consents. Significant improvements in water quality of the tidal Ouse are predicted compared to the effects of tightening effluent consents. A system of water quality functions is derived in this paper for quicker and more direct predictions of water quality, which will be useful in future research when combined with other analyses. Taking account the assimilative capacity in policy making, this paper suggests that a combined water management framework should be applied to ensure the required water quality. PMID:17188337
1D and 2D urban dam-break flood modelling in Istanbul, Turkey
NASA Astrophysics Data System (ADS)
Ozdemir, Hasan; Neal, Jeffrey; Bates, Paul; Döker, Fatih
2014-05-01
Urban flood events are increasing in frequency and severity as a consequence of several factors such as reduced infiltration capacities due to continued watershed development, increased construction in flood prone areas due to population growth, the possible amplification of rainfall intensity due to climate change, sea level rise which threatens coastal development, and poorly engineered flood control infrastructure (Gallegos et al., 2009). These factors will contribute to increased urban flood risk in the future, and as a result improved modelling of urban flooding according to different causative factor has been identified as a research priority (Gallegos et al., 2009; Ozdemir et al. 2013). The flooding disaster caused by dam failures is always a threat against lives and properties especially in urban environments. Therefore, the prediction of dynamics of dam-break flows plays a vital role in the forecast and evaluation of flooding disasters, and is of long-standing interest for researchers. Flooding occurred on the Ayamama River (Istanbul-Turkey) due to high intensity rainfall and dam-breaching of Ata Pond in 9th September 2009. The settlements, industrial areas and transportation system on the floodplain of the Ayamama River were inundated. Therefore, 32 people were dead and millions of Euros economic loses were occurred. The aim of this study is 1 and 2-Dimensional flood modelling of the Ata Pond breaching using HEC-RAS and LISFLOOD-Roe models and comparison of the model results using the real flood extent. The HEC-RAS model solves the full 1-D Saint Venant equations for unsteady open channel flow whereas LISFLOOD-Roe is the 2-D shallow water model which calculates the flow according to the complete Saint Venant formulation (Villanueva and Wright, 2006; Neal et al., 2011). The model consists a shock capturing Godunov-type scheme based on the Roe Riemann solver (Roe, 1981). 3 m high resolution Digital Surface Model (DSM), natural characteristics of the pond and its breaching such as depth, wide, length, volume and breaching shape and daily total rainfall data were used in the models. The simulated flooding in the both models were compared with the real flood extent which gathered from photos taken after the flood event, high satellite images acquired after 20 days from the flood event, and field works. The results show that LISFLOOD-Roe hydraulic model gives more than 80% fit to the extent of real flood event. Also both modelling results show that the embankment breaching of the Ata Pond directly affected the flood magnitude and intensity on the area. This study reveals that modelling of the probable flooding in urban areas is necessary and very important in urban planning. References Gallegos, H. A., Schubert, J. E., and Sanders, B. F.: Two dimensional, high-resolution modeling of urban dam-break flooding: A case study of Baldwin Hills California, Adv. Water Resour., 32, 1323-1335, 2009. Neal, J., Villanueva, I., Wright, N., Willis, T., Fewtrell, T. and Bates, P.: How mush physical complexity is needed to model flood inundation? Hydrological Processes, DOI: 10.1002/hyp.8339. Ozdemir H., Sampson C., De Almeida G., Bates P.D.: Evaluating scale and roughness effects in urban flood modelling using terrestrial LiDAR data, Hydrology and Earth System Sciences, vol.17, pp.4015-4030, 2013. Roe P.: Approximate Riemann solvers, parameter vectors, and difference-schemes. Journal of Computational Physics 43(2): 357-372, 1981. Villanueva I, Wright NG.: Linking Riemann and storage cell models for flood prediction. Proceedings of the Institution of Civil Engineers, Journal of Water Management 159: 27-33, 2006.
1-D/3-D geologic model of the Western Canada Sedimentary Basin
Higley, D.K.; Henry, M.; Roberts, L.N.R.; Steinshouer, D.W.
2005-01-01
The 3-D geologic model of the Western Canada Sedimentary Basin comprises 18 stacked intervals from the base of the Devonian Woodbend Group and age equivalent formations to ground surface; it includes an estimated thickness of eroded sediments based on 1-D burial history reconstructions for 33 wells across the study area. Each interval for the construction of the 3-D model was chosen on the basis of whether it is primarily composed of petroleum system elements of reservoir, hydrocarbon source, seal, overburden, or underburden strata, as well as the quality and areal distribution of well and other data. Preliminary results of the modeling support the following interpretations. Long-distance migration of hydrocarbons east of the Rocky Mountains is indicated by oil and gas accumulations in areas within which source rocks are thermally immature for oil and (or) gas. Petroleum systems in the basin are segmented by the northeast-trending Sweetgrass Arch; hydrocarbons west of the arch were from source rocks lying near or beneath the Rocky Mountains, whereas oil and gas east of the arch were sourced from the Williston Basin. Hydrocarbon generation and migration are primarily due to increased burial associated with the Laramide Orogeny. Hydrocarbon sources and migration were also influenced by the Lower Cretaceous sub-Mannville unconformity. In the Peace River Arch area of northern Alberta, Jurassic and older formations exhibit high-angle truncations against the unconformity. Potential Paleozoic though Mesozoic hydrocarbon source rocks are in contact with overlying Mannville Group reservoir facies. In contrast, in Saskatchewan and southern Alberta the contacts are parallel to sub-parallel, with the result that hydrocarbon source rocks are separated from the Mannville Group by seal-forming strata within the Jurassic. Vertical and lateral movement of hydrocarbons along the faults in the Rocky Mountains deformed belt probably also resulted in mixing of oil and gas from numerous source rocks in Alberta.
Predicting plate velocities with mantle circulation models
NASA Astrophysics Data System (ADS)
Becker, Thorsten W.; O'Connell, Richard J.
2001-12-01
We predict plate motions from a comprehensive inversion of theoretical estimates of tectonic forces in order to evaluate the relative importance of these and the uncertainties of such models. Plate-driving forces from the mantle are calculated using global flow models that are driven by tomography and subduction-derived density fields. Observed and predicted plate velocities agree well for a variety of models, leading to varied conclusions about the relative importance of forces. The dominance of the subduction related density pattern in the mantle is confirmed; it appears that P wave models do not satisfactorily image all of the slab-associated anomalies in the upper mantle. Furthermore, lower mantle structure always improves the plate motion fit with respect to models that are based on upper mantle anomalies and lithospheric thickening only. We show that the average torques from the lower mantle scale with the radial flow through the 660-km phase transition; the amplitude of the lower mantle torques will be significant for a range of models if there is mass flux through 660 km. We also evaluate parameterized edge forces and find that the additional inclusion of such torques does not significantly improve the model fit. The main reason for the nonuniqueness of the inversions is plate boundary geometry since all plate motions are dominated by the trench-ridge system, and plates move from ridges to trenches.
Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao
2014-10-01
Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.
A 1-D radiative conductive model to study the SOIR/VEx thermal profiles
NASA Astrophysics Data System (ADS)
Mahieux, Arnaud; Erwin, Justin T.; Chamberlain, Sarah; Robert, Sverine; Carine Vandaele, Ann; Wilquet, Valrie; Thomas, Ian; Yelle, Roger V.; Bertaux, Jean-Loup
2015-04-01
SOIR is an infrared spectrometer on board Venus Express that probes the Venus terminator region since 2006. The measurements are taken on the morning and evening sides of the terminator, covering all latitudes from the North Pole to the South Pole. Its wavelength range - 2.2 to 4.3 ?m - allows a detailed chemical inventory of the Venus atmosphere [1-5], such as CO2, CO, H2O, HCl, HF, SO2 and aerosols. CO2 is detected from 70 km up to 165 km, CO from 70 km to 140 km, and the minor species typically below 110 km down to 70 km. Number density profiles of these species are computed from the measured spectra. Temperature profiles are obtained while computing the spectral inversion of the CO2 spectra combined with the hydrostatic law [6]. These temperature measurements show a striking permanent temperature minimum (at 125 km) and a weaker temperature maximum (over 100-115 km). The time variability of the CO2 density profiles spans over two orders of magnitude, and a clear trend is seen with latitude. The temperature variations are also important, of the order of 35 K for a given pressure level, but the latitude variation are small. Miss-RT, a 1D radiative transfer model has been developed to reproduce the SOIR terminator profiles, derived from the Mars thermosphere code presented in [7]. This model has been expanded to better account for the CO2, CO, and O non-LTE radiative heating and cooling processes which have to be considered in the dense atmosphere of Venus. Radiative cooling by minor species detected by SOIR (e.g. HCl, SO2, and H2O) are found to be small in comparison to the 15 ?m CO2 cooling. Aerosol cooling in the 60-90km altitude range may be important to the thermal balance. There is a good agreement between the 1D model temperature profile and the mean SOIR temperature profile. Further we can suggest parameters that can be adjusted to improve the agreement between the model and measurements. The remaining differences can be attributed to the atmosphere dynamics at the terminator. 1. Bertaux, J.L., et al., A warm layer in Venus' cryosphere and high altitude measurements of HF, HCl, H2O and HDO. Nature, 2007. 450(29 November): p. 646-649, doi:10.1038/nature05974. 2. Vandaele, A.C., et al., Carbon monoxide short term variability observed on Venus with SOIR/VEX. Planet. Space Sci., 2014. (in press). 3. Mahieux, A., et al., Venus mesospheric sulfur dioxide measurement retrieved from SOIR on board Venus Express. Planet. Space Sci., 2014. (in press). 4. Mahieux, A., et al., Hydrogen Halides measurements in the Venus upper atmosphere retrieved from SOIR on board Venus Express. Planet. Space Sci., 2014. (in press). 5. Wilquet, V., et al., Optical extinction due to aerosols in the upper haze of Venus: Four years of SOIR/VEX observations from 2006 to 2010. Icarus, 2012. 217(2): p. 875-881. 6. Mahieux, A., et al., Update of the Venus density and temperature profiles at high altitude measured by SOIR on board Venus Express. Planet. Space Sci., 2014. (submitted). 7. Yelle, R., et al., Perturbation of the Mars Atmosphere by the Near-Collision with Comet C/2013 A1 (Siding Spring). Icarus, 2014. 237: p. 202-210.
Epstein, Sally; Willemet, Marie; Chowienczyk, Phil J; Alastruey, Jordi
2015-07-01
Patient-specific one-dimensional (1D) blood flow modeling requires estimating model parameters from available clinical data, ideally acquired noninvasively. The larger the number of arterial segments in a distributed 1D model, the greater the number of input parameters that need to be estimated. We investigated the effect of a reduction in the number of arterial segments in a given distributed 1D model on the shape of the simulated pressure and flow waveforms. This is achieved by systematically lumping peripheral 1D model branches into windkessel models that preserve the net resistance and total compliance of the original model. We applied our methodology to a model of the 55 larger systemic arteries in the human and to an extended 67-artery model that contains the digital arteries that perfuse the fingers. Results show good agreement in the shape of the aortic and digital waveforms between the original 55-artery (67-artery) and reduced 21-artery (37-artery) models. Reducing the number of segments also enables us to investigate the effect of arterial network topology (and hence reflection sites) on the shape of waveforms. Results show that wave reflections in the thoracic aorta and renal arteries play an important role in shaping the aortic pressure and flow waves and in generating the second peak of the digital pressure and flow waves. Our novel methodology is important to simplify the computational domain while maintaining the precision of the numerical predictions and to assess the effect of wave reflections. PMID:25888513
Epstein, Sally; Willemet, Marie; Chowienczyk, Phil J.
2015-01-01
Patient-specific one-dimensional (1D) blood flow modeling requires estimating model parameters from available clinical data, ideally acquired noninvasively. The larger the number of arterial segments in a distributed 1D model, the greater the number of input parameters that need to be estimated. We investigated the effect of a reduction in the number of arterial segments in a given distributed 1D model on the shape of the simulated pressure and flow waveforms. This is achieved by systematically lumping peripheral 1D model branches into windkessel models that preserve the net resistance and total compliance of the original model. We applied our methodology to a model of the 55 larger systemic arteries in the human and to an extended 67-artery model that contains the digital arteries that perfuse the fingers. Results show good agreement in the shape of the aortic and digital waveforms between the original 55-artery (67-artery) and reduced 21-artery (37-artery) models. Reducing the number of segments also enables us to investigate the effect of arterial network topology (and hence reflection sites) on the shape of waveforms. Results show that wave reflections in the thoracic aorta and renal arteries play an important role in shaping the aortic pressure and flow waves and in generating the second peak of the digital pressure and flow waves. Our novel methodology is important to simplify the computational domain while maintaining the precision of the numerical predictions and to assess the effect of wave reflections. PMID:25888513
Locating earthquakes in west Texas oil fields using 3-D anisotropic velocity models
Hua, Fa; Doser, D.; Baker, M. . Dept. of Geological Sciences)
1993-02-01
Earthquakes within the War-Wink gas field, Ward County, Texas, that have been located with a 1-D velocity model occur near the edges and top of a naturally occurring overpressured zone. Because the War-Wink field is a structurally controlled anticline with significant velocity anisotropy associated with the overpressured zone and finely layered evaporites, the authors have attempted to re-locate earthquakes using a 3-D anisotropic velocity model. Preliminary results with this model give the unsatisfactory result that many earthquakes previously located at the top of the overpressured zone (3-3.5 km) moved into the evaporites (1-1.5 km) above the field. They believe that this result could be caused by: (1) aliasing the velocity model; or (2) problems in determining the correct location minima when several minima exist. They are currently attempting to determine which of these causes is more likely for the unsatisfactory result observed.
NASA Astrophysics Data System (ADS)
Carmelo, J. M. P.; Čadež, T.
2016-03-01
A modified version of the metallic-phase pseudofermion dynamical theory (PDT) of the 1D Hubbard model is introduced for the spin dynamical correlation functions of the half-filled 1D Hubbard model Mott-Hubbard phase. The Mott-Hubbard insulator phase PDT is applied to the study of the model longitudinal and transverse spin dynamical structure factors at finite magnetic field h, focusing in particular on the singularities at excitation energies in the vicinity of the lower thresholds. The relation of our theoretical results to both condensed-matter and ultra-cold atom systems is discussed.
Development of a 1D canopy module to couple mesoscale meteorogical model with building energy model
NASA Astrophysics Data System (ADS)
Mauree, Dasaraden; Kohler, Manon; Blond, Nadge; Clappier, Alain
2013-04-01
The actual global warming, highlighted by the scientific community, is due to the greenhouse gases emissions resulting from our energy consumption. This energy is mainly produced in cities (about 70% of the total energy use). Around 36% of this energy are used in buildings (residential/tertiary) and this accounts for about 20% of the greenhouse gases emissions. Moreover, the world population is more and more concentrated in urban areas, 50% of the actual world population already lives in cities and this ratio is expected to reach 70% by 2050. With the obviously increasing responsibility of cities in climate change in the future, it is of great importance to go toward more sustainable cities that would reduce the energy consumption in urban areas. The energy use inside buildings is driven by two factors: (1) the level of comfort wished by the inhabitants and (2) the urban climate. On the other hand, the urban climate is influenced by the presence of buildings. Indeed, artificial surfaces of urban areas modify the energy budget of the Earth's surface and furthermore, heat is released into the atmosphere due to the energy used by buildings. Modifications at the building scale (micro-scale) can thus have an influence on the climate of the urban areas and surroundings (meso-scale), and vice and versa. During the last decades, meso-scale models have been developed to simulate the atmospheric conditions for domain of 100-1000km wide with a resolution of few kilometers. Due to their low resolution, the effects of small obstacles (such as buildings, trees, ...) near the ground are not reproduced properly and parameterizations have been developed to represent such effects in meso-scale models. On the other side, micro-scale models have a higher resolution (around 1 meter) and consequently can better simulate the impact of obstacles on the atmospheric heat flux exchanges with the earth surface. However, only a smaller domain (less than 1km) can be simulated for the same computational time. To simulate the processes at the micro-scale (building) as well as at the meso-scale (city and surroundings), it is necessary to connect these two types of models. It is proposed here to develop a canopy module able to act as an interface between these two scales. The meso-scale model provides the meteorological parameters to the micro-scale model via the canopy module. The micro-scale model then calculates the influence of the different type of surfaces on the variables and gives its back through the module to the meso-scale model. By simulating in a better way the interactions between the atmosphere and the urban surfaces, the model will enhance the estimation of the energy use by building. The tool produced by this research could be coupled in the future with an urban dynamics model to optimize urban planning in order to improve the sustainability of cities.
Diesel Engine performance improvement in a 1-D engine model using Particle Swarm Optimization
NASA Astrophysics Data System (ADS)
Karra, Prashanth
2015-12-01
A particle swarm optimization (PSO) technique was implemented to improve the engine development and optimization process to simultaneously reduce emissions and improve the fuel efficiency. The optimization was performed on a 4-stroke 4-cylinder GT-Power based 1-D diesel engine model. To achieve the multi-objective optimization, a merit function was defined which included the parameters to be optimized: Nitrogen Oxides (NOx), Nonmethyl hydro carbons (NMHC), Carbon Monoxide (CO), Brake Specific Fuel Consumption (BSFC). EPA Tier 3 emissions standards for non-road diesel engines between 37 and 75 kW of output were chosen as targets for the optimization. The combustion parameters analyzed in this study include: Start of main Injection, Start of Pilot Injection, Pilot fuel quantity, Swirl, and Tumble. The PSO was found to be very effective in quickly arriving at a solution that met the target criteria as defined in the merit function. The optimization took around 40-50 runs to find the most favourable engine operating condition under the constraints specified in the optimization. In a favourable case with a high merit function values, the NOx+NMHC and CO values were reduced to as low as 2.9 and 0.014 g/kWh, respectively. The operating conditions at this point were: 10 ATDC Main SOI, -25 ATDC Pilot SOI, 0.25 mg of pilot fuel, 0.45 Swirl and 0.85 tumble. These results indicate that late main injections preceded by a close, small pilot injection are most favourable conditions at the operating condition tested.
Testing the early Mars H2-CO2 greenhouse hypothesis with a 1-D photochemical model
NASA Astrophysics Data System (ADS)
Batalha, Natasha; Domagal-Goldman, Shawn D.; Ramirez, Ramses; Kasting, James F.
2015-09-01
A recent study by Ramirez et al. (Ramirez, R.M. et al. [2014]. Nat. Geosci. 7(1), 59-63.) demonstrated that an atmosphere with 1.3-4 bar of CO2 and H2O, in addition to 5-20% H2, could have raised the mean annual and global surface temperature of early Mars above the freezing point of water. Such warm temperatures appear necessary to generate the rainfall (or snowfall) amounts required to carve the ancient martian valleys. Here, we use our best estimates for early martian outgassing rates, along with a 1-D photochemical model, to assess the conversion efficiency of CO, CH4, and H2S to CO2, SO2, and H2. Our outgassing estimates assume that Mars was actively recycling volatiles between its crust and interior, as Earth does today. H2 production from serpentinization and deposition of banded iron-formations is also considered. Under these assumptions, maintaining an H2 concentration of ˜1-2% by volume is achievable, but reaching 5% H2 requires additional H2 sources or a slowing of the hydrogen escape rate below the diffusion limit. If the early martian atmosphere was indeed H2-rich, we might be able to see evidence of this in the rock record. The hypothesis proposed here is consistent with new data from the Curiosity Rover, which show evidence for a long-lived lake in Gale Crater near Mt. Sharp. It is also consistent with measured oxygen fugacities of martian meteorites, which show evidence for progressive mantle oxidation over time.
NASA Astrophysics Data System (ADS)
Whitten, Daniel; Hartl, Darren
2014-03-01
Shape memory alloy constitutive models have been shown to accurately predict 1-D and 3-D material response under general thermomechanical loading. As with any constitutive model, however, the degree to which simulation results match experimental data is dependent on the accurate calibration of model parameters. This work presents a general framework for the identi cation of SMA material parameters using numerical optimization methods and experimental results that include both 1-D data (i.e., stress-strain and strain-temperature line plots) as well as 2-D digital image correlation (DIC) strain eld data. The optimization framework is verified using 1-D and 3-D nite-element-based simulated results as pseudo-experimental data. The study shows that the proposed optimization methods can identify SMA parameters in an automated fashion using data taken from multiple types of experiment, identifying parameters that t very closely to the pseudo-experimental data.
Crosswell born inversion for heterogeneous velocity models
Hegge, R.F.; Herman, G.C.; Sevink, A.G.J.
1994-12-31
The application of high-frequency asymptotic Born inverse scattering methods to cross-well imaging is discussed and illustrated with a number of model studies for synthetic data. In particular, attention is given to imaging problems that are associated with typical cross-well geometries. A severe problem is the existence of multiple travel paths between sources and receivers that are particularly apparent if low-velocity layers are present. When this occurs, the high-frequency asymptotic imaging method is no longer valid and large artifacts in the images can result. However, it is concluded that, even in the case of multiple travel paths, good images can be obtained by omitting the singularities in the imaging formula and by combining the results for different source locations.
Comparison of 1D and 2D CSR Models with Application to the FERMI@ELETTRA Bunch Compressors
Bassi, G.; Ellison, J.A.; Heinemann, K.
2011-03-28
We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces [1]. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. As an application, we present numerical results for the Fermi{at}Elettra first bunch compressor with the configuration described in [1].
Revisiting the capture velocity of a cesium magneto-optical trap: model, simulation and experiment
NASA Astrophysics Data System (ADS)
Anwar, Muhammad; Magalhes, Daniel V.; Mller, Stella T.; Faisal, Muhammad; Nawaz, Muhammad; Ahmed, Mushtaq
2014-12-01
In this work, we have explored ab initio the capture process in a magneto-optical trap by theory, simulation and experiment. We measured the capture velocity vc of a cesium vapor cell magneto-optical trap (VCMOT) from its capture rate R and developed an exact model for the capture rate of a VCMOT in terms of its capture velocity, background density and trap laser beam diameter. We measured the capture velocity of a cesium VCMOT for various trap laser intensities and magnetic field gradients. We observed that the capture velocity is a damping force as well as a restoring force phenomenon. We supported our findings by performing simulations for single atom trajectories in a 1D cesium MOT. Finally, we concluded that two MOTs can have the same capture velocities but very different capture rates, thereby revealing that these are two fundamentally different characteristics of the MOT.
ABSTRACTION OF INFORMATION FROM 2- AND 3-DIMENSIONAL PORFLOW MODELS INTO A 1-D GOLDSIM MODEL - 11404
Taylor, G.; Hiergesell, R.
2010-11-16
The Savannah River National Laboratory has developed a 'hybrid' approach to Performance Assessment modeling which has been used for a number of Performance Assessments. This hybrid approach uses a multi-dimensional modeling platform (PorFlow) to develop deterministic flow fields and perform contaminant transport. The GoldSim modeling platform is used to develop the Sensitivity and Uncertainty analyses. Because these codes are performing complementary tasks, it is incumbent upon them that for the deterministic cases they produce very similar results. This paper discusses two very different waste forms, one with no engineered barriers and one with engineered barriers, each of which present different challenges to the abstraction of data. The hybrid approach to Performance Assessment modeling used at the SRNL uses a 2-D unsaturated zone (UZ) and a 3-D saturated zone (SZ) model in the PorFlow modeling platform. The UZ model consists of the waste zone and the unsaturated zoned between the waste zone and the water table. The SZ model consists of source cells beneath the waste form to the points of interest. Both models contain 'buffer' cells so that modeling domain boundaries do not adversely affect the calculation. The information pipeline between the two models is the contaminant flux. The domain contaminant flux, typically in units of moles (or Curies) per year from the UZ model is used as a boundary condition for the source cells in the SZ. The GoldSim modeling component of the hybrid approach is an integrated UZ-SZ model. The model is a 1-D representation of the SZ, typically 1-D in the UZ, but as discussed below, depending on the waste form being analyzed may contain pseudo-2-D elements. A waste form at the Savannah River Site (SRS) which has no engineered barriers is commonly referred to as a slit trench. A slit trench, as its name implies, is an unlined trench, typically 6 m deep, 6 m wide, and 200 m long. Low level waste consisting of soil, debris, rubble, wood, etc. is disposed within the trench which is then covered with soil and a cap. The filled trench resembles the surrounding soil, albeit with a higher porosity. As a result, the flow field through the trench is essentially 1-dimensional. This dimensionality makes the abstraction of information from this waste form fairly simple. Engineered waste forms present challenges not seen in the slit trench because of their higher dimensionality. Flow fields must conform to the barriers and are therefore subject to changes in direction. This paper will examine one case and show how this multidimensional flow field can be abstracted into a 1-dimensional flow field while retaining characteristics important to the transport of radioactive contaminants. One complication not addressed by the two preceding examples is that of multiple sources. This presents quite a challenge to the benchmarking exercise, but a fairly robust method has been developed to deal with it. While the PorFlow analyses can treat all sources as independent in space, this is not possible with a 1-D model. This problem has been addressed by constructing multiple 1-D models of the waste forms and using plume overlaps at the assessment points to address the multiple sources which can contribute to a distinct assessment point.
A 1-D modelling of climatic and chemical effects of greenhouse gases
NASA Astrophysics Data System (ADS)
Vupputuri, R. K. R.; Higuchi, K.; Hengeveld, H. G.
1995-09-01
A coupled 1-D time-dependent radiative-convective-photochemical diffusion model which extends from the surface to 60 km is used to investigate the potential impact of greenhouse trace gas emissions on long-term changes in global climate, atmospheric ozone and surface UV-B radiation, taking into accoont the influence of aerosol loading into the atmosphere from major volcanic eruptions, of thermal inertia of the upper mixed layer of the ocean and of other radiativephotochemical feedback mechanisms. Experiments are carried out under global and annual average insolation and cloudiness conditions. The transient calculations are made for three different growth scenarios for increase in trace gas concentrations. Scenario 1, which begins in 1850, uses the best estimate values for future trace gas concentrations of CO2, CH4, N2O, CFC-11, CFC-12 and tropospheric O3, based on current observational trends. Scenarios 2 and 3, which begin in 1990, assume lower and upper ranges, respectively, of observed growth rates to estimate future concentrations. The transient response of the model for Scenario 1 suggests that surface warming of the ocean mixed layer of about 1 K should have taken place between 1850 and 1990 due to a combined increase of atmospheric CO2 and other trace gases. For the three scenarios considered in this study, the cumulative surface warming induced by all major trace gases for the period 1850 to 2080 ranges from 2.7 K to 8.2 K with the best estimate value of 5 K. The results indicate that the direct and the indirect chemistry-climate interactions of non-CO2 trace gases contribute significantly to the cumulative surface warming (up to 65% by the year 2080). The thermal inertia of a mixed layer of the ocean is shown to have the effect of delaying equilibrium surface warming by almost three decades with an e-folding time of about 5 years. The volcanic aerosols which would result from major volcanic eruptions play a significant role by interrupting the long-term greenhouse surface warming trend and replacing it by a temporary cooling on a time scale of a decade or less. Furthermore, depending on the scenario used, a reduction in the net ozone column could result in an increase in the solar UV-B radiation at the surface by as much as 300% towards the end of 21st century.
MODELLING TRANSIENT VARIABLY SATURATED FLOW IN SILT LOAM SOILS USING HYDRUS-1D
Technology Transfer Automated Retrieval System (TEKTRAN)
The Hydrus-1D software package (Simunek et al., 1998), based on the Richards equation, was used to study variably saturated flow and deep drainage in an old abandoned terraced area under grass. The field site was located in the Vallcebre research catchment of the Eastern Pyrenees in North-Eastern Sp...
NASA Astrophysics Data System (ADS)
Subin, Z. M.; Riley, W. J.
2009-12-01
Compared to solid ground, lakes tend to have decreased albedo, increased ground heat conductance, and increased effective ground heat capacity. These features alter local surface fluxes compared to nearby vegetation, which in turn alter the climate of the nearby atmosphere and surrounding land areas. Interest in feedbacks between lake behavior and climate change provides motivation for including lakes in global climate models, as does the desire to do effective regional downscaling of climate model predictions over regions with large lake area fraction, like the Great Lakes region. Finally, the initiation, warming, and expansion of Arctic thermokarst lakes could provide an important geophysical and biogeochemical feedback to climate warming. The Community Land Model (CLM) 3.5 currently uses a 1D Hostetler lake scheme. We have updated this model to improve the characterization of surface fluxes, eddy diffusivity, and convective mixing. We also link the lake model with the full snow physics found over other land surface types (including 5 snow layers, aerosol deposition, partial transparency of snow layers, and snow aging), add phase change & ice physics to the lake model, and include soil layers beneath lakes. These soil layers will be an important component of future thermokarst lake modeling, as thermokarst lakes tend to form regions of unfrozen soil (talik) beneath them that become active sites for anaerobic decomposition of pre-modern peat. We have also integrated the updated lake model into a modified version of the Weather Research and Forecasting (WRF) Model 3.0. We will present comparisons between predicted and observed thermal conditions, snow and ice depths, and surface energy fluxes at several lake sites, using local meteorological forcing or integrated regional atmospheric coupling. The thermal predictions are generally reasonable and show a marked improvement from runs performed with the baseline CLM 3.5 version of the lake model. Over Sparkling Lake, the lake model simulates the hourly lake water temperatures from 2002-2005 in very good agreement (<3 K error) with observations at all depths when the model is forced with the observed climatology. Over other relatively shallow (2 m - 50 m) lakes, thermal depth profiles are generally well reproduced, with maximum summer surface temperatures generally within ~3 K of the observations and mixing depths accurate to about 20% of lake depth. Snow depths, ice depths, and freezing duration are evaluated. Over very deep lakes like Lake Geneva, the model predicts insufficient mixing below about 30 m depth, which is a known deficiency of the Hostetler Lake Model, although the surface temperature is well replicated. We conclude that the model is suitable for inclusion into regional and global climate models for evaluating climate feedbacks, particularly for shallow thermokarst lakes. Finally, we present a comparison of the simulated historical surface climatology to observations for the Great Lakes region in WRF, both with and without the new lake model.
Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.
Ekama, G A; Marais, P
2004-01-01
The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1 m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST, In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs--for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the appropriate flux rating is applied to the 1DFT estimate of the surface area. PMID:15553476
1D Runoff-runon stochastic model in the light of queueing theory : heterogeneity and connectivity
NASA Astrophysics Data System (ADS)
Harel, M.-A.; Mouche, E.; Ledoux, E.
2012-04-01
Runoff production on a hillslope during a rainfall event may be simplified as follows. Given a soil of constant infiltrability I, which is the maximum amount of water that the soil can infiltrate, and a constant rainfall intensity R, runoff is observed where R is greater than I. The infiltration rate equals the infiltrability when runoff is produced, R otherwise. When ponding time, topography, and overall spatial and temporal variations of physical parameters, such as R and I, are neglected, the runoff equation remains simple. In this study, we consider soils of spatially variable infiltrability. As runoff can re-infiltrate on down-slope areas of higher infiltrabilities (runon), the resulting process is highly non-linear. The stationary runoff equation is: Qn+1 = max(Qn + (R - In)*Δx , 0) where Qn is the runoff arriving on pixel n of size Δx [L2/T], R and In the rainfall intensity and infiltrability on that same pixel [L/T]. The non-linearity is due to the dependence of infiltration on R and Qn, that is runon. This re-infiltration process generates patterns of runoff along the slope, patterns that organise and connect to each other differently depending on the rainfall intensity and the nature of the soil heterogeneity. The runoff connectivity, assessed using the connectivity function of Allard (1993), affects greatly the dynamics of the runoff hillslope. Our aim is to assess, in a stochastic framework, the runoff organization on 1D slopes with random infiltrabilities (log-normal, exponential, bimodal and uniform distributions) by means of theoretical developments and numerical simulations. This means linking the nature of soil heterogeneity with the resulting runoff organisation. In term of connectivity, we investigate the relations between structural (infiltrability) and functional (runoff) connectivity. A theoretical framework based on the queueing theory is developed. We implement the idea of Jones et al. (2009), who remarked that the above formulation is identical to the waiting time equation in a single server queue. Thanks to this theory, it is possible to accurately describe some outputs of our numerical model, notably the runoff repartition over the slope for uncorrelated exponential infiltrability distributions. Alternative formulations for the connectivity function of Allard (which cannot be predicted theoretically to our knowledge) are discussed with regard to predictability, efficiency in computation and qualification of the "near-connectedness" state of the system.
NASA Astrophysics Data System (ADS)
Ponsar, Stephanie; Luyten, Patrick; Ozer, Jose
2011-11-01
The combined estimation of model state and parameters is investigated by using an ensemble Kalman filter in a 1-D numerical study of the temperature profile at a North Sea station located at 5530' North and 055' East. This simplified model implementation allows to test many configurations for the sampling of the model error for the model state as well as for the parameters. Temperature profiles from thermistor data are assimilated. The influence of a vertically or non-vertically correlated model error is examined through the computation of correlation coefficients, root mean square errors, and model bias. As the CS station is located in the North Sea region stratified in summer, vertically non-correlated model error terms have a slight positive impact on the assimilative runs. The benefit of the combined estimation of the model state and parameters is examined by comparison of a simulation where the model parameters are not adjusted to simulations with the combined estimation of the model state either with one parameter or with a set of parameters related to the surface heat exchange. The optical attenuation coefficient, the sensible, and latent heat exchange coefficients are considered. The best results are obtained when a set of parameters are simultaneously adjusted.
A crustal seismic velocity model for the UK, Ireland and surrounding seas
Kelly, A.; England, R.W.; Maguire, Peter K.H.
2007-01-01
A regional model of the 3-D variation in seismic P-wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity-depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 ?? 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data. ?? 2007 The Authors Journal compilation ?? 2007 RAS.
Bengoechea, Rocio; Pittman, Sara K; Tuck, Elizabeth P; True, Heather L; Weihl, Conrad C
2015-12-01
Limb-girdle muscular dystrophy type 1D (LGMD1D) is caused by dominantly inherited missense mutations in DNAJB6, an Hsp40 co-chaperone. LGMD1D muscle has rimmed vacuoles and inclusion bodies containing DNAJB6, Z-disc proteins and TDP-43. DNAJB6 is expressed as two isoforms; DNAJB6a and DNAJB6b. Both isoforms contain LGMD1D mutant residues and are expressed in human muscle. To identify which mutant isoform confers disease pathogenesis and generate a mouse model of LGMD1D, we evaluated DNAJB6 expression and localization in skeletal muscle as well as generating DNAJB6 isoform specific expressing transgenic mice. DNAJB6a localized to myonuclei while DNAJB6b was sarcoplasmic. LGMD1D mutations in DNAJB6a or DNAJB6b did not alter this localization in mouse muscle. Transgenic mice expressing the LGMD1D mutant, F93L, in DNAJB6b under a muscle-specific promoter became weak, had early lethality and developed muscle pathology consistent with myopathy after 2 months; whereas mice expressing the same F93L mutation in DNAJB6a or overexpressing DNAJB6a or DNAJB6b wild-type transgenes remained unaffected after 1 year. DNAJB6b localized to the Z-disc and DNAJB6b-F93L expressing mouse muscle had myofibrillar disorganization and desmin inclusions. Consistent with DNAJB6 dysfunction, keratin 8/18, a DNAJB6 client also accumulated in DNAJB6b-F93L expressing mouse muscle. The RNA-binding proteins hnRNPA1 and hnRNPA2/B1 accumulated and co-localized with DNAJB6 at sarcoplasmic stress granules suggesting that these proteins maybe novel DNAJB6b clients. Similarly, hnRNPA1 and hnRNPA2/B1 formed sarcoplasmic aggregates in patients with LGMD1D. Our data support that LGMD1D mutations in DNAJB6 disrupt its sarcoplasmic function suggesting a role for DNAJB6b in Z-disc organization and stress granule kinetics. PMID:26362252
Multi-objective optimisation of cost-benefit of urban flood management using a 1D2D coupled model.
Delelegn, S W; Pathirana, A; Gersonius, B; Adeogun, A G; Vairavamoorthy, K
2011-01-01
This paper presents a multi-objective optimisation (MOO) tool for urban drainage management that is based on a 1D2D coupled model of SWMM5 (1D sub-surface flow model) and BreZo (2D surface flow model). This coupled model is linked with NSGA-II, which is an Evolutionary Algorithm-based optimiser. Previously the combination of a surface/sub-surface flow model and evolutionary optimisation has been considered to be infeasible due to the computational demands. The 1D2D coupled model used here shows a computational efficiency that is acceptable for optimisation. This technological advance is the result of the application of a triangular irregular discretisation process and an explicit finite volume solver in the 2D surface flow model. Besides that, OpenMP based parallelisation was employed at optimiser level to further improve the computational speed of the MOO tool. The MOO tool has been applied to an existing sewer network in West Garforth, UK. This application demonstrates the advantages of using multi-objective optimisation by providing an easy-to-comprehend Pareto-optimal front (relating investment cost to expected flood damage) that could be used for decision making processes, without repeatedly going through the modelling-optimisation stage. PMID:21411958
Marin-Valencia, Isaac; Good, Levi B.; Ma, Qian; Duarte, Joao; Bottiglieri, Teodoro; Sinton, Christopher M.; Heilig, Charles W.; Pascual, Juan M.
2012-01-01
Brain glucose supplies most of the carbon required for acetyl-coenzyme A (acetyl-CoA) generation (an important step for myelin synthesis) and for neurotransmitter production via further metabolism of acetyl-CoA in the tricarboxylic acid (TCA) cycle. However, it is not known whether reduced brain glucose transporter type I (GLUT-1) activity, the hallmark of the GLUT-1 deficiency (G1D) syndrome, leads to acetyl-CoA, TCA or neurotransmitter depletion. This question is relevant because, in its most common form in man, G1D is associated with cerebral hypomyelination (manifested as microcephaly) and epilepsy, suggestive of acetyl-CoA depletion and neurotransmitter dysfunction, respectively. Yet, brain metabolism in G1D remains underexplored both theoretically and experimentally, partly because computational models of limited brain glucose transport are subordinate to metabolic assumptions and partly because current hemizygous G1D mouse models manifest a mild phenotype not easily amenable to investigation. In contrast, adult antisense G1D mice replicate the human phenotype of spontaneous epilepsy associated with robust thalamocortical electrical oscillations. Additionally, and in consonance with human metabolic imaging observations, thalamus and cerebral cortex display the lowest GLUT-1 expression and glucose uptake in the mutant mouse. This depletion of brain glucose is associated with diminished plasma fatty acids and elevated ketone body levels, and with decreased brain acetyl-CoA and fatty acid contents, consistent with brain ketone body consumption and with stimulation of brain beta-oxidation and/or diminished cerebral lipid synthesis. In contrast with other epilepsies, astrocyte glutamine synthetase expression, cerebral TCA cycle intermediates, amino acid and amine neurotransmitter contents are also intact in G1D. The data suggest that the TCA cycle is preserved in G1D because reduced glycolysis and acetyl-CoA formation can be balanced by enhanced ketone body utilization. These results are incompatible with global cerebral energy failure or with neurotransmitter depletion as responsible for epilepsy in G1D and point to an unknown mechanism by which glycolysis critically regulates cortical excitability. PMID:22683290
Marin-Valencia, Isaac; Good, Levi B; Ma, Qian; Duarte, Joao; Bottiglieri, Teodoro; Sinton, Christopher M; Heilig, Charles W; Pascual, Juan M
2012-10-01
Brain glucose supplies most of the carbon required for acetyl-coenzyme A (acetyl-CoA) generation (an important step for myelin synthesis) and for neurotransmitter production via further metabolism of acetyl-CoA in the tricarboxylic acid (TCA) cycle. However, it is not known whether reduced brain glucose transporter type I (GLUT-1) activity, the hallmark of the GLUT-1 deficiency (G1D) syndrome, leads to acetyl-CoA, TCA or neurotransmitter depletion. This question is relevant because, in its most common form in man, G1D is associated with cerebral hypomyelination (manifested as microcephaly) and epilepsy, suggestive of acetyl-CoA depletion and neurotransmitter dysfunction, respectively. Yet, brain metabolism in G1D remains underexplored both theoretically and experimentally, partly because computational models of limited brain glucose transport are subordinate to metabolic assumptions and partly because current hemizygous G1D mouse models manifest a mild phenotype not easily amenable to investigation. In contrast, adult antisense G1D mice replicate the human phenotype of spontaneous epilepsy associated with robust thalamocortical electrical oscillations. Additionally, and in consonance with human metabolic imaging observations, thalamus and cerebral cortex display the lowest GLUT-1 expression and glucose uptake in the mutant mouse. This depletion of brain glucose is associated with diminished plasma fatty acids and elevated ketone body levels, and with decreased brain acetyl-CoA and fatty acid contents, consistent with brain ketone body consumption and with stimulation of brain beta-oxidation and/or diminished cerebral lipid synthesis. In contrast with other epilepsies, astrocyte glutamine synthetase expression, cerebral TCA cycle intermediates, amino acid and amine neurotransmitter contents are also intact in G1D. The data suggest that the TCA cycle is preserved in G1D because reduced glycolysis and acetyl-CoA formation can be balanced by enhanced ketone body utilization. These results are incompatible with global cerebral energy failure or with neurotransmitter depletion as responsible for epilepsy in G1D and point to an unknown mechanism by which glycolysis critically regulates cortical excitability. PMID:22683290
NASA Astrophysics Data System (ADS)
Sinha, Sumit; Rode, Michael; Borchardt, Dietrich
2014-05-01
The Bode River catchment in the Harz Mountain area of central Germany is heavily influenced by anthropogenic factors. 70% of the catchment is dominated by agriculture, 23 % by forest and the rest 7% is urban in nature. The area of the catchment is approximately 3300 km2 and is characterized by sharp gradients in temperature, precipitation and land use. In order to acquire better understanding of the hydrological nature of the catchment and biogeochemical characteristics of the Bode River various monitoring stations have been deployed as a part of the larger earth observation network initiative named Terrestrial Environmental Observatories. One of the major issues with the catchment is the problem of eutrophication due to solute inputs from agriculture. The research presented here evaluated the application and development of 1D and 2D hydrodynamic and water quality models in the downstream area of the Bode River. A stretch of 30 kms between Hadmersleeben and Stassfurt in the downstream area of the Bode River was modeled using 1D model HEC-RAS, the focus of the water quality modeling was transport and uptake of nitrate in the aforementioned modeled stretch. Flood events of varying peak magnitude at different times of the year were modeled. As regards to 2D modeling, TELEMAC-2D model was applied for the same reach. The hydrodynamic simulation results were validated with the help of free surface elevation at Athensleben, 8 kms upstream from the downstream end at Stassfurt. Water quality modeling, focusing on the Nitrate removal for the aforementioned stretch, is applied and developed for both 1D and 2D modeling framework. Results from hydrodynamic and water quality modeling were validated with RMSE (Root Mean Square Error) value of 0.074 and 0.36 for the modeled state variables across various events simulated. For the nutrient-rich reach modeled in this research it was found that the nutrient removal capacity of the stream is directly proportional to the incoming nitrate concentration.
NASA Astrophysics Data System (ADS)
Corliss, Jason B.; Harris, Walt M.; Mierkiewicz, Edwin J.; Roesler, Frederick L.
2015-11-01
Thorough analysis of narrow bandpass high spectral resolution (R ?100,000) observations of [O 1 D] 630nm emission from comet 9P/Tempel 1 taken over a ~1 FOV both before and after the Deep Impact event provides evidence for a long-lived high velocity jet-like feature. The observations were obtained with an all-reflective spatial heterodyne spectrometer (SHS) coupled to the McMath-Pierce Main telescope. Several spectra centered on Tempel 1 were acquired during the period of 07/04/2005-07/06/2005 UT. We report here on the presence and evolution of a cometary emission feature that appears consistently and exclusively in the post-impact narrow-band spectra centered near the telluric [O 1 D] 630nm emission line. This cometary emission feature shows substantial and distinct Doppler shifts over consecutive post-impact observational nights and if the feature is the anticipated [O 1 D], the corresponding line of sight velocities are -13.4 to -6.5 km/s, relative to the comets rest frame.
Velocity statistics of the Nagel-Schreckenberg model
NASA Astrophysics Data System (ADS)
Bain, Nicolas; Emig, Thorsten; Ulm, Franz-Josef; Schreckenberg, Michael
2016-02-01
The statistics of velocities in the cellular automaton model of Nagel and Schreckenberg for traffic are studied. From numerical simulations, we obtain the probability distribution function (PDF) for vehicle velocities and the velocity-velocity (vv) covariance function. We identify the probability to find a standing vehicle as a potential order parameter that signals nicely the transition between free congested flow for a sufficiently large number of velocity states. Our results for the vv covariance function resemble features of a second-order phase transition. We develop a 3-body approximation that allows us to relate the PDFs for velocities and headways. Using this relation, an approximation to the velocity PDF is obtained from the headway PDF observed in simulations. We find a remarkable agreement between this approximation and the velocity PDF obtained from simulations.
A 1D Model For Describing Ion Cyclotron Resonance Heating At Arbitrary Cyclotron Harmonics
NASA Astrophysics Data System (ADS)
Van Eester, Dirk; Lerche, Ernesto
2011-12-01
Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ICRF heating scenario's creating high energy tails. The present paper discusses an extension of the 1D TOMCAT wave equation solver [1] to arbitrary harmonics and arbitrary wavelengths. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response that is suitable for numerical application. This choice of variable yields symmetric and intuitive expressions, and guarantees that a positive definite power absorption is obtained for any of the wave modes in the plasma. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integro-differential approach is proposed. To keep the required computation time for this generalized description reasonable tabulation of integrals is intensively used. An example is provided to illustrate the potential of the new wave code.
Sidorov, K. A.; Ovchinnikov, S. G.; Tikhonov, N. V.
2013-02-15
It is shown that the canonical partition function in the 1D Hubbard model with U = {infinity} in the nearest neighbor approximation is determined by the product of canonical partition functions of spinons and holons. In this approximation, the concentration and temperature dependences of the free and internal energies, as well as of the chemical potential, entropy, and heat capacity, are calculated for electron concentrations of 0 {<=} n{sub e} < 1.
REACTIVE TRANSPORT MODELLING IN THE VADOSE ZONE WITH COUPLED PHREEQC-HYDRUS 1D CODE
Technology Transfer Automated Retrieval System (TEKTRAN)
To model multicomponent transport during transient variably-saturated flow in the vadose zone, complex models are needed. Ideally such models should incorporate simultaneous solutions for the water flow equation, solute transport and equilibrium or kinetically homogeneous and heterogeneous geochemic...
Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling
NASA Astrophysics Data System (ADS)
Zhang, Pengjie; Zheng, Yi; Jing, Yipeng
2015-02-01
Cosmology based on large scale peculiar velocity prefers volume weighted velocity statistics. However, measuring the volume weighted velocity statistics from inhomogeneously distributed galaxies (simulation particles/halos) suffers from an inevitable and significant sampling artifact. We study this sampling artifact in the velocity power spectrum measured by the nearest particle velocity assignment method by Zheng et al., [Phys. Rev. D 88, 103510 (2013).]. We derive the analytical expression of leading and higher order terms. We find that the sampling artifact suppresses the z =0 E -mode velocity power spectrum by 10 % at k =0.1 h /Mpc , for samples with number density 10-3 (Mpc /h )-3 . This suppression becomes larger for larger k and for sparser samples. We argue that this source of systematic errors in peculiar velocity cosmology, albeit severe, can be self-calibrated in the framework of our theoretical modelling. We also work out the sampling artifact in the density-velocity cross power spectrum measurement. A more robust evaluation of related statistics through simulations will be presented in a companion paper by Zheng et al., [Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modelling, arXiv:1409.6809.]. We also argue that similar sampling artifact exists in other velocity assignment methods and hence must be carefully corrected to avoid systematic bias in peculiar velocity cosmology.
NASA Astrophysics Data System (ADS)
Zhang, MingLiang; Xu, YuanYuan; Hao, ZiNing; Qiao, Yang
2014-04-01
The purpose of this study is to set up a dynamically linked 1D and 2D hydrodynamic and sediment transport models for dam break flow. The 1D-2D coupling model solves the generalized shallow water equations, the non-equilibrium sediment transport and bed change equations in a coupled fashion using an explicit finite volume method. It considers interactions among transient flow, strong sediment transport and rapid bed change by including bed change and variable flow density in the flow continuity and momentum equations. An unstructured Quadtree rectangular grid with local refinement is used in the 2D model. The intercell flux is computed by the HLL approximate Riemann solver with shock captured capability for computing the dry-to-wet interface for all models. The effects of pressure and gravity are included in source term in this coupling model which can simplify the computation and eliminate numerical imbalance between source and flux terms. The developed model has been tested against experimental and real-life case of dam-break flow over fix bed and movable bed. The results are compared with analytical solution and measured data with good agreement. The simulation results demonstrate that the coupling model is capable of calculating the flow, erosion and deposition for dam break flows in complicated natural domains.
Construction of an initial velocity model for migration velocity analysis from gravimetric inversion
NASA Astrophysics Data System (ADS)
Santos, H. B.; Macedo, D. L.; Santos, E. B.; Schleicher, J.; Novais, M.
2013-12-01
The construction of the best possible image in depth from the acquired data is a major challenge in both seismic exploration and seismological investigations. Migration is one of the main methods of seismic imaging, and prior knowledge of a subsurface velocity model is needed for its application. On the other hand, migration itself gives clues about the quality of the used velocity model. This property gives rise to iterative migration velocity analysis (MVA) methods. MVA is an important seismic processing step in prestack time and depth imaging, which basically exploits the redundancy of seismic data to improve an a-priori velocity model. For fast convergence and reliable results, MVA requires good starting models. We present a new 3D velocity model building algorithm based on geometry information acquired from a recently introduced efficient gravity gradiometry inversion method. This gravity inversion method is useful to estimate a 3D density-contrast distribution on a grid of prisms. It is highly efficient because it does not require the solution of a large equation system. Instead, the solution grows systematically around prismatic elements called "seeds". This allow to test different density contrasts for different bodies. Here, we propose the use of the estimated density-contrast distribution (i.e., the skeleton of the body) as a first guess for the velocity model. The basic idea is to replace the density value contained in each prism by a velocity consistent with the presumed geology. The result of MVA can then, in turn, be used to improve on the geometry for the gravity inversion. This joint processing and interpretation can be considered as an alternative way to improve the knowledge of complex structures. For example, the image quality of salt structures and sub-salt sediments obtained by reflection seismic is almost always limited by the effects of wavefield transmission, scattering and absorption. We tested whether the geometry of complex structures such as salt structures obtained by gravity inversion is sufficiently well approximated to build a seismic velocity model. For this purpose, we performed an inversion of several 3D bodies with different geometries and different densities. To demonstrate the capability of the technique, we extracted 2D profiles from the inverted solution in various directions, and replaced the density value by a consistent and convenient velocity. Thereafter, we performing 2D depth- and time-migration for seismic data previously modeled with the real geometry using the velocity model of each extracted profile. Our results indicate the usefulness of the discussed velocity model building algorithm to generate initial velocity models for MVA, even for complex geologic structures. To corroborate our point, we will compare our velocity models and migrated sections with results from other methods commonly used in MVA.
Comparing 1D, 2D and 3D models for predicting root water uptake at the plant scale
NASA Astrophysics Data System (ADS)
de Willigen, Peter; van Dam, Jos; Heinen, Marius; Javaux, Mathieu
2010-05-01
Numerous modeling approaches exist to simulate soil water extraction by plant roots. They mainly differ in terms of dimensionality (from 1-D to 3-D) and in the degree of detail involved in the root geometry. One dimensional models consider 1-D root length density profiles and assume uniform horizontal soil water distribution and are very efficient regarding computation time. On the opposite, very detailed 3-D approaches, which consider explicitly the root architecture and the root water flow, may need more computation power and time. In between these two extreme cases, other approaches exist, which may be more accurate and less computationally demanding. Our objective is to compare different modeling approaches and check how their implicit or explicit simplifications or assumptions affect the root water uptake (RWU) predictions. Four models were subject to our comparison, all based on Richards equation. The first is a 1-D model solving Richards equation (SWAP) with the Feddes (1978) approach for RWU. The second one is also based on SWAP but with the root water uptake defined by a microscopic approach developed by de Jong van Lier (2008). The third one, FUSSIM, solves the Richards equation in 2-D based on a 2-D distribution of root length density (RLD). The fourth one is R-SWMS, a 3-D model simulating the water flow in the soil and in the roots, based on the complete root architecture description. A 45-day maize root was generated in 3-D and simplified in 2-D or 1-D RLD distributions. We simulated a constant uptake rate for 30 days with a 1-day rainfall at day 15 in three different soil types. We compared relative water uptake versus relative root length density profiles, and actual transpiration time series. On the one hand, the general trends of cumulative transpiration with time for the three soils were relatively similar for all models. On the other hand, some features like hydraulic lift are simulated by both FUSSIM and RSWMS models while other models do not explicitly estimate the water potential in the plant and roots.
UCVM: Open Source Software for Understanding and Delivering 3D Velocity Models
NASA Astrophysics Data System (ADS)
Gill, D.; Small, P.; Maechling, P. J.; Jordan, T. H.; Shaw, J. H.; Plesch, A.; Chen, P.; Lee, E. J.; Taborda, R.; Olsen, K. B.; Callaghan, S.
2014-12-01
Physics-based ground motion simulations can calculate the propagation of earthquake waves through 3D velocity models of the Earth. The Southern California Earthquake Center (SCEC) has developed the Unified Community Velocity Model (UCVM) framework to help researchers build structured or unstructured velocity meshes from 3D velocity models for use in wave propagation simulations. The UCVM software framework makes it easy to extract P and S wave propagation speeds and other material properties from 3D velocity models by providing a common interface through which researchers can query earth models for a given location and depth. Currently, the platform supports multiple California models, including SCEC CVM-S4 and CVM-H 11.9.1, and has been designed to support models from any region on earth. UCVM is currently being use to generate velocity meshes for many SCEC wave propagation codes, including AWP-ODC-SGT and Hercules. In this presentation, we describe improvements to the UCVM software. The current version, UCVM 14.3.0, released in March of 2014, supports the newest Southern California velocity model, CVM-S4.26, which was derived from 26 full-3D tomographic iterations using CVM-S4 as the starting model (Lee et al., this meeting), and the Broadband 1D velocity model used in the CyberShake 14.2 study. We have ported UCVM to multiple Linux distributions and OS X. Also included in this release is the ability to add small-scale stochastic heterogeneities to extract Cartesian meshes for use in high-frequency ground motion simulations. This tool was built using the C language open-source FFT library, FFTW. The stochastic parameters (Hurst exponent, correlation length, and the horizontal/vertical aspect ratio) can be customized by the user. UCVM v14.3.0 also provides visualization scripts for constructing cross-sections, horizontal slices, basin depths, and Vs30 maps. The interface allows researchers to visually review velocity models . Also, UCVM v14.3.0 can extract isosurfaces of shear-wave velocities equal to 1 km/s (Z1.0) and 2.5 km/s (Z2.5) for any of the registered velocity models. We have also improved our open source distribution by including a user's guide, an advanced user's guide, and a developer's guide so that users of all levels can get started using and extending the UCVM platform.
NASA Astrophysics Data System (ADS)
Dobrynina, Anna; Sankov, Vladimir; Chechelnitsky, Vladimir
2014-05-01
The deep profiles of quality factor were obtained using coda-waves of local strong and moderate earthquakes (epicentral distances up to 50 km) occurred within north-eastern flanc of the Baikal rift system during 2002-2009. We used two methods: 1 - the coda envelope method [Experimental.., 1981; Kopnichev, 1991] and 2 - the sliding window method (lapse time window 10-15 sec with a step of 5 sec). Depth of coda-wave penetration was determined according to Pulli's formulae [1984], the velocity of coda-wave is 3.55 km/s (equal to shear wave velocity). For analysis we used the Q values at frequency 1 Hz since for this frequency the attenuation field heterogeneity is most evident [Aptikaeva and Kopnichev, 1991]. In result Q-profiles for eleven local areas were obtained. The Q-values vary from 50 to 170 for different profiles and depths. Herewith quality factor changes nonuniformly - the alternation of layers with high and low Q-values is observed. This phenomenon can be explained by existing velocity discontinuity. In particular for all profiles this alternation is confined to the depth about 100 km. Analysis VP-anomalies obtained in result of 2D teleseismic tomography along Baikal rift system [Mordvinova, 2009] shows the existence discontinuity on depth about 100 km under most of Baikal rift system structures. Analysis of 1D profiles of shear wave velocities in the crust and upper mantle after inversion of receiver functions [Anan'in et al., 2009] also shows presence of these discontinuity dividing high and low velocity layers. The comparison of Q-values and shear wave velocities [Anan'in et al., 2009] shown that in high velocity layers quality factor is higher too and vice versa. Multilayer quality factor model for the lithosphere in north-eastern flanc of the Baikal rift system with the alternation of layers with high and low attenuation determined by us together with analogous data obtained by Yu.F. Kopnichev [1992] for south-western flanc of the rift system can be one of inferential evidences of passive rifting mechanism in studied area. The reported study was supported by RFBR (research project N12-05-31038-mol_a) and by grant of President of Russian Federation (research project N MK-1171.2014.5).
Uncertainty assessment of 3D instantaneous velocity model from stack velocities
NASA Astrophysics Data System (ADS)
Emanuele Maesano, Francesco; D'Ambrogi, Chiara
2015-04-01
3D modelling is a powerful tool that is experiencing increasing applications in data analysis and dissemination. At the same time the need of quantitative uncertainty evaluation is strongly requested in many aspects of the geological sciences and by the stakeholders. In many cases the starting point for 3D model building is the interpretation of seismic profiles that provide indirect information about the geology of the subsurface in the domain of time. The most problematic step in the 3D modelling construction is the conversion of the horizons and faults interpreted in time domain to the depth domain. In this step the dominant variable that could lead to significantly different results is the velocity. The knowledge of the subsurface velocities is related mainly to punctual data (sonic logs) that are often sparsely distributed in the areas covered by the seismic interpretation. The extrapolation of velocity information to wide extended horizons is thus a critical step to obtain a 3D model in depth that can be used for predictive purpose. In the EU-funded GeoMol Project, the availability of a dense network of seismic lines (confidentially provided by ENI S.p.A.) in the Central Po Plain, is paired with the presence of 136 well logs, but few of them have sonic logs and in some portion of the area the wells are very widely spaced. The depth conversion of the 3D model in time domain has been performed testing different strategies for the use and the interpolation of velocity data. The final model has been obtained using a 4 layer cake 3D instantaneous velocity model that considers both the initial velocity (v0) in every reference horizon and the gradient of velocity variation with depth (k). Using this method it is possible to consider the geological constraint given by the geometries of the horizons and the geo-statistical approach to the interpolation of velocities and gradient. Here we present an experiment based on the use of set of pseudo-wells obtained from the stack velocities available inside the area, interpolated using the kriging geo-statistical method. The stack velocities are intersected with the position of the horizons in time domain and from this information we build a pseudo-well to calculate the initial velocity and the gradient of increase (or decrease) of velocity with depth inside the considered rock volume. The experiment is aimed to obtain estimation and a representation of the uncertainty related to the geo-statistical interpolation of velocity data in a 3D model and to have an independent control of the final results using the well markers available inside the test area as constraints. The project GeoMol is co-funded by the Alpine Space Program as part of the European Territorial Cooperation 2007-2013. The project integrates partners from Austria, France, Germany, Italy, Slovenia and Switzerland and runs from September 2012 to June 2015. Further information on www.geomol.eu
Detailed analysis of the continuum limit of a supersymmetric lattice model in 1D
NASA Astrophysics Data System (ADS)
Huijse, L.
2011-04-01
We present a full identification of lattice model properties with their field theoretical counterparts in the continuum limit for a supersymmetric model for itinerant spinless fermions on a one-dimensional chain. The continuum limit of this model is described by an {N}=(2,2) superconformal field theory (SCFT) with central charge c = 1. We identify states and operators in the lattice model with fields in the SCFT and we relate boundary conditions on the lattice to sectors in the field theory. We use the dictionary we develop in this paper to give a pedagogical explanation of a powerful tool to study supersymmetric models based on spectral flow (Huijse 2008 Phys. Rev. Lett. 101 146406). Finally, we employ the developed machinery to explain numerically observed properties of the particle density on the open chain presented in Beccaria and De Angelis (2005 Phys. Rev. Lett. 94 100401).
NASA Astrophysics Data System (ADS)
Pek?en, Ertan; Yas, Trker; K?yak, Alper
2014-09-01
We examine the one-dimensional direct current method in anisotropic earth formation. We derive an analytic expression of a simple, two-layered anisotropic earth model. Further, we also consider a horizontally layered anisotropic earth response with respect to the digital filter method, which yields a quasi-analytic solution over anisotropic media. These analytic and quasi-analytic solutions are useful tests for numerical codes. A two-dimensional finite difference earth model in anisotropic media is presented in order to generate a synthetic data set for a simple one-dimensional earth. Further, we propose a particle swarm optimization method for estimating the model parameters of a layered anisotropic earth model such as horizontal and vertical resistivities, and thickness. The particle swarm optimization is a naturally inspired meta-heuristic algorithm. The proposed method finds model parameters quite successfully based on synthetic and field data. However, adding 5 % Gaussian noise to the synthetic data increases the ambiguity of the value of the model parameters. For this reason, the results should be controlled by a number of statistical tests. In this study, we use probability density function within 95 % confidence interval, parameter variation of each iteration and frequency distribution of the model parameters to reduce the ambiguity. The result is promising and the proposed method can be used for evaluating one-dimensional direct current data in anisotropic media.
The 1D Ising model and the topological phase of the Kitaev chain
Greiter, Martin Schnells, Vera Thomale, Ronny
2014-12-15
It has been noted that the Kitaev chain, a p-wave superconductor with nearest-neighbor pairing amplitude equal to the hopping term ?=t, and chemical potential ?=0, can be mapped into a nearest neighbor Ising model via a JordanWigner transformation. Starting from the explicit eigenstates of the open Kitaev chain in terms of the original fermion operators, we elaborate that despite this formal equivalence the models are physically inequivalent, and show how the topological phase in the Kitaev chain maps into conventional order in the Ising model.
An Extended Global Sensitivity Analysis Implemented on a 1D Land Biosphere Model
NASA Astrophysics Data System (ADS)
Ioannou-Katidis, Pavlos; Petropoulos, George; Griffiths, Hywel; Bevan, Rhodri
2014-05-01
The implementation of sophisticated mathematical models is undoubtedly becoming increasingly widely used in a variety of fields in geosciences. SimSphere belongs to a special category of land biosphere models called Soil Vegetation Atmosphere Transfer (SVAT) models. Those provide representations, in a vertical profile, of the physical mechanisms controlling the physical interactions occurring in the soil/vegetation/atmosphere continuum at a temporal resolution that is in good agreement with the dynamic timescale of the atmospheric and surface processes. This study builds on previous works conducted by the authors and aims at extending our understanding of this model structure and further establishing its coherence. Herein we present the results from a thorough sensitivity analysis (SA) performed on SimSphere using a cutting edge and robust Global Sensitivity Analysis (GSA) approach, based on the use of the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) tool. In particular, the sensitivity of selected key variables characterising land surface interactions simulated by SimSphere were evaluated at different times of model output. All model inputs were assumed to be normally distributed with their probability distribution functions (PDFs) defined using mean and variance taken from the entire theoretical range that these inputs can take in SimSphere. The sensitivity of the following SimSphere outputs was evaluated: Daily Average Net Radiation, Daily Average Latent Heat flux, Daily Average Sensible Heat flux, Daily Average Air Temperature , Daily Average Radiometric Temperature, Daily Average Surface Moisture Availability, Daily Average Evaporative Fraction and Daily Average Non-Evaporative Fraction. Our results showed largely comparable trends in terms of identifying the most sensitive model inputs in respect to the model outputs examined. In addition, a high percentage of first order interactions between the model inputs were reported, suggesting strong model coherence between inputs and outputs. Among the most sensitive model inputs for the outputs examined were the Fractional Vegetation Cover, Soil Moisture and topographically-related parameters (i.e. slope, aspect). Our study represents a significant step forward in the global efforts towards SimSphere verification given that its use is progressively expanding including present efforts to explore its synergy with Earth Observation for operationally deriving key land surface parameters at a global scale from space. KEYWORDS: Global Sensitivity Analysis, BACCO method, GEM-SA
NASA Astrophysics Data System (ADS)
Hooshyar, M.; Hagen, S. C.; Wang, D.
2014-12-01
Hydrodynamic models are widely applied to coastal areas in order to predict water levels and flood inundation and typically involve solving a form of the Shallow Water Equations (SWE). The SWE are routinely discretized by applying numerical methods, such as the finite element method. Like other numerical models, hydrodynamic models include uncertainty. Uncertainties are generated due to errors in the discrete approximation of coastal geometry, bathymetry, bottom friction and forcing functions such as tides and wind fields. Methods to counteract these uncertainties should always begin with improvements to physical characterization of: the geometric description through increased resolution, parameters that describe land cover variations in the natural and urban environment, parameters that enhance transfer of surface forcings to the water surface, open boundary forcings, and the wetting/drying brought upon by flood and ebb cycles. When the best possible physical representation is achieved, we are left with calibration and data assimilation to reduce model uncertainty. Data assimilation has been applied to coastal hydrodynamic models to better estimate system states and/or system parameters by incorporating observed data into the model. Kalman Filter is one of the most studied data assimilation methods that minimizes the mean square errors between model state estimations and the observed data in linear systems (Kalman , 1960). For nonlinear systems, as with hydrodynamic models, a variation of Kalman filter called Ensemble Kalman Filter (EnKF), is applied to update the system state according to error statistics in the context of Monte Carlo simulations (Evensen , 2003) & (Hitoshi et. al, 2014). In this research, Kalman Filter is incorporated to simultaneously estimate an influential parameter used in the shallow water equations, bottom roughness, and to adjust the physical feature of bathymetry. Starting from an initial estimate of bottom roughness and bathymetry, and applying EnKF, more accurate bottom roughness and bathymetry are obtained by utilizing measurements available in a limited number of gages. The procedure is examined along five typical near shore transects located in Gulf of Mexico.
NASA Astrophysics Data System (ADS)
Zhang, Lianxin; Zhang, Xuefeng; Han, Guijun; Wu, Xinrong; Cui, Xiaojian; Shao, Caixia; Sun, Chunjian; Zhang, Xiaoshuang; Wang, Xidong; Fu, Hongli
2015-09-01
At the interface between the lower atmosphere and sea surface, sea spray might significantly influence air-sea heat fluxes and subsequently, modulate upper ocean temperature during a typhoon passage. The effects of sea spray were introduced into the parameterization of sea surface roughness in a 1-D turbulent model, to investigate the effects of sea spray on upper ocean temperature in the Kuroshio Extension area, for the cases of two real typhoons from 2006, Yagi and Soulik. Model output was compared with data from the Kuroshio Extension Observatory (KEO), and Reynolds and AMSRE satellite remote sensing sea surface temperatures. The results indicate drag coefficients that include the spray effect are closer to observations than those without, and that sea spray can enhance the heat fluxes (especially latent heat flux) considerably during a typhoon passage. Consequently, the model results with heat fluxes enhanced by sea spray simulate better the cooling process of the SST and upper-layer temperature profiles. Additionally, results from the simulation of the passage of typhoon Soulik (that passed KEO quickly), which included the sea spray effect, were better than for the simulated passage of typhoon Yagi (that crossed KEO slowly). These promising 1-D results could provide insight into the application of sea spray in general circulation models for typhoon studies.
NASA Astrophysics Data System (ADS)
Ingeman-Nielsen, Thomas; Baumgartner, Franois
2006-11-01
We have constructed a forward modelling code in Matlab, capable of handling several commonly used electrical and electromagnetic methods in a 1D environment. We review the implemented electromagnetic field equations for grounded wires, frequency and transient soundings and present new solutions in the case of a non-magnetic first layer. The CR1Dmod code evaluates the Hankel transforms occurring in the field equations using either the Fast Hankel Transform based on digital filter theory, or a numerical integration scheme applied between the zeros of the Bessel function. A graphical user interface allows easy construction of 1D models and control of the parameters. Modelling results are in agreement with other authors, but the time of computation is less efficient than other available codes. Nevertheless, the CR1Dmod routine handles complex resistivities and offers solutions based on the full EM-equations as well as the quasi-static approximation. Thus, modelling of effects based on changes in the magnetic permeability and the permittivity is also possible.
Space-based Observational Constraints for 1-D Plume Rise Models
NASA Technical Reports Server (NTRS)
Martin, Maria Val; Kahn, Ralph A.; Logan, Jennifer A.; Paguam, Ronan; Wooster, Martin; Ichoku, Charles
2012-01-01
We use a space-based plume height climatology derived from observations made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the NASA Terra satellite to evaluate the ability of a plume-rise model currently embedded in several atmospheric chemical transport models (CTMs) to produce accurate smoke injection heights. We initialize the plume-rise model with assimilated meteorological fields from the NASA Goddard Earth Observing System and estimated fuel moisture content at the location and time of the MISR measurements. Fire properties that drive the plume-rise model are difficult to estimate and we test the model with four estimates for active fire area and four for total heat flux, obtained using empirical data and Moderate Resolution Imaging Spectroradiometer (MODIS) re radiative power (FRP) thermal anomalies available for each MISR plume. We show that the model is not able to reproduce the plume heights observed by MISR over the range of conditions studied (maximum r2 obtained in all configurations is 0.3). The model also fails to determine which plumes are in the free troposphere (according to MISR), key information needed for atmospheric models to simulate properly smoke dispersion. We conclude that embedding a plume-rise model using currently available re constraints in large-scale atmospheric studies remains a difficult proposition. However, we demonstrate the degree to which the fire dynamical heat flux (related to active fire area and sensible heat flux), and atmospheric stability structure influence plume rise, although other factors less well constrained (e.g., entrainment) may also be significant. Using atmospheric stability conditions, MODIS FRP, and MISR plume heights, we offer some constraints on the main physical factors that drive smoke plume rise. We find that smoke plumes reaching high altitudes are characterized by higher FRP and weaker atmospheric stability conditions than those at low altitude, which tend to remain confined below the BL, consistent with earlier results. We propose two simplified parameterizations for computing injection heights for fires in CTMs and discuss current challenges to representing plume injection heights in large scale atmospheric models.
Assessing the impact of different sources of topographic data on 1-D hydraulic modelling of floods
NASA Astrophysics Data System (ADS)
Ali, A. Md; Solomatine, D. P.; Di Baldassarre, G.
2014-07-01
Topographic data, such as digital elevation models (DEMs), are essential input in flood inundation modelling. DEMs can be derived from several sources either through remote sensing techniques (space-borne or air-borne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the Light Detection and Ranging (LiDAR), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30-90 m). On the other hand, LiDAR technique is able to produce a high resolution DEMs (around 1m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicates the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. LiDAR 1 m) to lower resolution are much less compared to the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.
2D MHD and 1D HD Models of a Solar Flarea Comprehensive Comparison of the Results
NASA Astrophysics Data System (ADS)
Falewicz, R.; Rudawy, P.; Murawski, K.; Srivastava, A. K.
2015-11-01
Without any doubt, solar flaring loops possess a multithread internal structure that is poorly resolved, and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modeling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of one-dimensional (1D) hydrodynamic and two-dimensional (2D) magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters of the modeled loop are set according to the progenitor M1.8 flare recorded in AR 10126 on 2002 September 20 between 09:21 UT and 09:50 UT. The nonideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy-loss mechanisms, while the nonideal 2D models take into account viscosity and thermal conduction as energy-loss mechanisms only. The 2D models have a continuous distribution of the parameters of the plasma across the loop and are powered by varying in time and space along and across the loop heating flux. We show that such 2D models are an extreme borderline case of a multithread internal structure of the flaring loop, with a filling factor equal to 1. Nevertheless, these simple models ensure the general correctness of the obtained results and can be adopted as a correct approximation of the real flaring structures.
NASA Astrophysics Data System (ADS)
Ching, Yu-Tai; Liu, Yu-Hsian; Chang, Chwen-Liang; Chen, James S. J.
2001-05-01
Echocardiography is the most convenient means for both physicians and patients for heart disease diagnosis. The 3D + 1D echocardiogram provides important information for evaluation of the 3D heart function such as the ejection fraction or wall motion. The most basic task to evaluate such functions of a heart is to segment left ventricles and reconstruct the 3D geometric model of left ventricle from a set of echocardiographic images. Since there are many images involved, the method should not need too many user assists. In this work, we design a method for reconstructing the left ventricles with very few user assists.
The stability and dynamics of a spike in the 1D Keller-Segel model
NASA Astrophysics Data System (ADS)
Kang, K.; Kolokolnikov, T.; Ward, M. J.
2007-04-01
In the limit of a large mass M >> 1 and on a finite interval of length 2L, an equilibrium spike solution to the classical Keller-Segel chemotaxis model with a linear chemotactic function is constructed asymptotically. By calculating an asymptotic formula for the translational eigenvalue for M >> 1, it is shown that the equilibrium spike solution is unstable to translations of the spike profile. If in addition L >> 1, the equilibrium spike is shown to be metastable as a result of an asymptotically exponentially small eigenvalue. For M >> 1 and L >> 1, an asymptotic ordinary differential equation for the metastable spike motion is derived that shows that the spike drifts exponentially slowly towards one of the boundaries of the domain. For a certain reduced Keller-Segel model, corresponding to a domain of small length, a solution with a spike at each of the two boundaries is constructedE This solution is found to be metastable, and it is shown that there is an exponentially slow exchange of mass between the two spikes that occurs over very long timescales. For arbitrary initial conditions, energy methods are used to show the global existence of solutions. The relationship between this reduced Keller-Segel model and a Burgers-type equation modelling the upward propagation of a flame front in a finite channel is emphasized. Full numerical computations are used to confirm the asymptotic results.
Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment.
Vanpoucke, Danny E P
2014-04-01
Atomic scale nanowires attract enormous interest in a wide range of fields. On the one hand, due to their quasi-one-dimensional nature, they can act as an experimental testbed for exotic physics: Peierls instability, charge density waves, and Luttinger liquid behavior. On the other hand, due to their small size, they are of interest not only for future device applications in the micro-electronics industry, but also for applications regarding molecular electronics. This versatile nature makes them interesting systems to produce and study, but their size and growth conditions push both experimental production and theoretical modeling to their limits. In this review, modeling of atomic scale nanowires on semiconductor surfaces is discussed, focusing on the interplay between theory and experiment. The current state of modeling efforts on Pt- and Au-induced nanowires on Ge(001) is presented, indicating their similarities and differences. Recently discovered nanowire systems (Ir, Co, Sr) on the Ge(001) surface are also touched upon. The importance of scanning tunneling microscopy as a tool for direct comparison of theoretical and experimental data is shown, as is the power of density functional theory as an atomistic simulation approach. It becomes clear that complementary strengths of theoretical and experimental investigations are required for successful modeling of the atomistic nanowires, due to their complexity. PMID:24599293
A 1-D Model of the 4 Bed Molecular Sieve of the Carbon Dioxide Removal Assembly
NASA Technical Reports Server (NTRS)
Coker, Robert; Knox, Jim
2015-01-01
Developments to improve system efficiency and reliability for water and carbon dioxide separation systems on crewed vehicles combine sub-scale systems testing and multi-physics simulations. This paper describes the development of COMSOL simulations in support of the Life Support Systems (LSS) project within NASA's Advanced Exploration Systems (AES) program. Specifically, we model the 4 Bed Molecular Sieve (4BMS) of the Carbon Dioxide Removal Assembly (CDRA) operating on the International Space Station (ISS).
A Simplified 1-D Model for Calculating CO2 Leakage through Conduits
Zhang, Y.; Oldenburg, C.M.
2011-02-15
In geological CO{sub 2} storage projects, a cap rock is generally needed to prevent CO{sub 2} from leaking out of the storage formation. However, the injected CO{sub 2} may still encounter some discrete flow paths such as a conductive well or fault (here referred to as conduits) through the cap rock allowing escape of CO{sub 2} from the storage formation. As CO{sub 2} migrates upward, it may migrate into the surrounding formations. The amount of mass that is lost to the formation is called attenuation. This report describes a simplified model to calculate the CO{sub 2} mass flux at different locations of the conduit and the amount of attenuation to the surrounding formations. From the comparison among the three model results, we can conclude that the steady-state conduit model (SSCM) provides a more accurate solution than the PMC at a given discretization. When there is not a large difference between the permeability of the surrounding formation and the permeability of the conduits, and there is leak-off at the bottom formation (the formation immediately above the CO{sub 2} plume), a fine discretization is needed for an accurate solution. Based on this comparison, we propose to use the SSCM in the rapid prototype for now given it does not produce spurious oscillations, and is already in FORTRAN and therefore can be easily made into a dll for use in GoldSim.
Tuning a physically-based model of the air-sea gas transfer velocity
NASA Astrophysics Data System (ADS)
Jeffery, C. D.; Robinson, I. S.; Woolf, D. K.
Air-sea gas transfer velocities are estimated for one year using a 1-D upper-ocean model (GOTM) and a modified version of the NOAA-COARE transfer velocity parameterization. Tuning parameters are evaluated with the aim of bringing the physically based NOAA-COARE parameterization in line with current estimates, based on simple wind-speed dependent models derived from bomb-radiocarbon inventories and deliberate tracer release experiments. We suggest that A = 1.3 and B = 1.0, for the sub-layer scaling parameter and the bubble mediated exchange, respectively, are consistent with the global average CO 2 transfer velocity k. Using these parameters and a simple 2nd order polynomial approximation, with respect to wind speed, we estimate a global annual average k for CO 2 of 16.4 5.6 cm h -1 when using global mean winds of 6.89 m s -1 from the NCEP/NCAR Reanalysis 1 1954-2000. The tuned model can be used to predict the transfer velocity of any gas, with appropriate treatment of the dependence on molecular properties including the strong solubility dependence of bubble-mediated transfer. For example, an initial estimate of the global average transfer velocity of DMS (a relatively soluble gas) is only 11.9 cm h -1 whilst for less soluble methane the estimate is 18.0 cm h -1.
Modeling Low Velocity Impacts: Predicting Crater Depth on Pluto
NASA Astrophysics Data System (ADS)
Bray, V. J.; Schenk, P.
2014-12-01
The New Horizons mission is due to fly-by the Pluto system in Summer 2015 and provides the first opportunity to image the Pluto surface in detail, allowing both the appearance and number of its crater population to be studied for the first time. Bray and Schenk (2014) combined previous cratering studies and numerical modeling of the impact process to predict crater morphology on Pluto based on current understanding of Pluto's composition, structure and surrounding impactor population. Predictions of how the low mean impact velocity (~2km/s) of the Pluto system will influence crater formation is a complex issue. Observations of secondary cratering (low velocity, high angle) and laboratory experiments of impact at low velocity are at odds regarding how velocity controls depth-diameter ratios: Observations of secondary craters show that these low velocity craters are shallower than would be expected for a hyper-velocity primary. Conversely, gas gun work has shown that relative crater depth increases as impact velocity decreases. We have investigated the influence of impact velocity further with iSALE hydrocode modeling of comet impact into Pluto. With increasing impact velocity, a projectile will produce wider and deeper craters. The depth-diameter ratio (d/D) however has a more complex progression with increasing impact velocity: impacts faster than 2km/s lead to smaller d/D ratios as impact velocity increases, in agreement with gas-gun studies. However, decreasing impact velocity from 2km/s to 300 m/s produced smaller d/D as impact velocity was decreased. This suggests that on Pluto the deepest craters would be produced by ~ 2km/s impacts, with shallower craters produced by velocities either side of this critical point. Further simulations to investigate whether this effect is connected to the sound speed of the target material are ongoing. The complex relationship between impact velocity and crater depth for impacts occurring between 300m/s and 10 km/s suggests that there might be a larger range of 'pristine' crater depths on Pluto than on bodies with higher mean impact velocity. This might affect our ability to define a pristine crater depth as a starting point for crater infill and relaxation studies.
Constraining the temporal evolution of a deep hypersaline anoxic basin by 1D geochemical modelling
NASA Astrophysics Data System (ADS)
Goldhammer, Tobias; Aiello, Ivano; Zabel, Matthias
2014-05-01
Deep hypersaline anoxic basins (DHABs) are seafloor features of the accretionary prism of the Mediterranean Ridge. They have formed by the dissolution of exhumed shallow Messinian evaporites and subsequent concentration of the ultra-saline solutions in depressions on the seafloor. As an example, the horseshoe-shaped Urania basin is a DHAB south of the Peloponnese peninsula contains one of the most saline (about six times higher than Mediterranean seawater) and sulfidic (up to 15mM) water bodies of the Earth. Furthermore, its deepest part is underlain by a mud volcano that is responsible for the injection of fluid mud beneath the brine lake, with exceptionally sharp chemoclines between water column, brine, and mud layer. We here present a model approach to reconstruct the temporal aspects of the formation, dynamics and persistence of the brine-mud-system in the deep pit of the Urania Basin. Based on data from a sampling campaign with RV Meteor (Cruise M84/1 in February 2011), we set up a one-dimensional geochemical model that integrates diffusion, reaction and advective transport and mixing. Using a set of model preconditions, we aimed to answer (1) which processes are required to maintain the current situation of steep chemical gradients of the brine-mud-system, (2) how fast the current situation could have developed under different scenarios, and (3) how long such extraordinary conditions could have persisted through Earth's history. We further discuss the consequences of the temporal framework for the evolution of prokaryotic life in this extreme habitat.
Constraining Quantum Critical Dynamics: (2 +1 )D Ising Model and Beyond
NASA Astrophysics Data System (ADS)
Witczak-Krempa, William
2015-05-01
Quantum critical (QC) phase transitions generally lead to the absence of quasiparticles. The resulting correlated quantum fluid, when thermally excited, displays rich universal dynamics. We establish nonperturbative constraints on the linear-response dynamics of conformal QC systems at finite temperature, in spatial dimensions above 1. Specifically, we analyze the large frequency or momentum asymptotics of observables, which we use to derive powerful sum rules and inequalities. The general results are applied to the O (N ) Wilson-Fisher fixed point, describing the QC Ising model when N =1 . We focus on the order parameter and scalar susceptibilities, and the dynamical shear viscosity. Connections to simulations, experiments, and gauge theories are made.
Dynamical signature of the edge state in the 1D Aubry-Andr model
NASA Astrophysics Data System (ADS)
Shen, H. Z.; Yi, X. X.; Oh, C. H.
2014-04-01
Topological features have become an intensively studied subject in many fields of physics. As a witness of topological phase, the edge states are topologically protected and may be helpful in quantum information processing. In this paper, we define a measure to quantify the dynamical localization of the system and simulate the localization in the one-dimensional Aubry-Andr model. We find an interesting connection between the edge states and the dynamical localization of the system, this connection may be used as a signature of the edge state and topological phase.
Dynamical correlation functions of the 1D Bose gas (Lieb Liniger model)
NASA Astrophysics Data System (ADS)
Caux, Jean-Sebastien; Calabrese, Pasquale
2007-03-01
The momentum- and frequency-dependent correlation functions (one-body and density-density) of the one-dimensional interacting Bose gas (Lieb-Liniger model) are obtained for any value (repulsive or attractive) of the interaction parameter. In the repulsive regime, we use the Algebraic Bethe Ansatz and the ABACUS method to reconstruct the correlators to high accuracy for systems with finite but large numbers of particles. For attractive interactions, the correlations are computed analytically. Our results are discussed, with particular emphasis on their applications to quasi-one-dimensional atomic gases.
NASA Astrophysics Data System (ADS)
Lauer, Wesley; Viparelli, Enrica; Piegay, Herve
2014-05-01
Sedimentary deposits adjacent to rivers can represent important sources and sinks for bed material sediment, particularly on decadal and longer timescales. The Morphodynamics and Sediment Tracers in 1-D model (MAST-1D) is a size-specific sediment transport model that allows for active exchange between channel and floodplain sediment on river reaches of tens to hundreds of kilometers in length. The model is intended to provide a mechanism for performing a first-order assessment of the likely importance of off-channel sediment exchange in controlling decadal-scale geomorphic trends, thereby helping plan and/or prioritize field data collection and higher resolution modeling work. The model develops a sediment budget for short segments of an alluvial valley. Each segment encompasses several active river bends. In each segment, a sediment transport capacity computation is performed to determine the downstream flux of bed material sediment, following the approach of most other 1-D sediment transport models. However, the model differs from most other bed evolution models in that sediment can be exchanged with the floodplain in each segment, and mass conservation is applied to both the active layer and floodplain sediment storage reservoirs. The potential for net imbalances in overall exchange as well as the size specific nature of the computations allows the model to simulate reach-scale aggradation/degradation and/or changes in bed texture. The inclusion of fine sediment in the model allows it to track geochemical tracer material and also provides a mechanism to simulate, to first order, the effects of changes in the supply of silt and clay on overall channel hydraulic capacity. The model is applied to a ~40 km reach of the Ain River, a tributary of the Rhne River in eastern France that has experienced a significant sediment deficit as a result of the construction of several dams between 1920 and 1970. MAST-1D simulations result in both incision and the formation of a bed armor near the upstream end of the study reach, where sediment load has been disrupted. The inclusion of active exchange with the floodplain allows the floodplain evolve into a net source of bed material sediment as the channel incises. This effect prevents the sediment deficit from reaching the confluence with the Rhone for several simulated decades. When spatially variable migration rates similar to those measured from aerial photography are used to drive sediment exchange, the model shows complex interaction between bed and bank sediment, with the relatively fine-grained bank sediment supply mobilizing the coarser fraction of the active layer within rapidly shifting portions of the channel. This increases overall transport rates and leads to additional channel incision relative to what is simulated without bank sediment supply in these rapidly shifting reaches. The model is also helpful for evaluating the potential reach-scale effects of gravel augmentation downstream of the dams.
Hiergesell, R.; Taylor, G.
2010-11-17
An investigation was conducted to compare and evaluate contaminant transport results of two model codes, GoldSim and Porflow, using a simple 1-D string of elements in each code. Model domains were constructed to be identical with respect to cell numbers and dimensions, matrix material, flow boundary and saturation conditions. One of the codes, GoldSim, does not simulate advective movement of water; therefore the water flux term was specified as a boundary condition. In the other code, Porflow, a steady-state flow field was computed and contaminant transport was simulated within that flow-field. The comparisons were made solely in terms of the ability of each code to perform contaminant transport. The purpose of the investigation was to establish a basis for, and to validate follow-on work that was conducted in which a 1-D GoldSim model developed by abstracting information from Porflow 2-D and 3-D unsaturated and saturated zone models and then benchmarked to produce equivalent contaminant transport results. A handful of contaminants were selected for the code-to-code comparison simulations, including a non-sorbing tracer and several long- and short-lived radionuclides exhibiting both non-sorbing to strongly-sorbing characteristics with respect to the matrix material, including several requiring the simulation of in-growth of daughter radionuclides. The same diffusion and partitioning coefficients associated with each contaminant and the half-lives associated with each radionuclide were incorporated into each model. A string of 10-elements, having identical spatial dimensions and properties, were constructed within each code. GoldSim's basic contaminant transport elements, Mixing cells, were utilized in this construction. Sand was established as the matrix material and was assigned identical properties (e.g. bulk density, porosity, saturated hydraulic conductivity) in both codes. Boundary conditions applied included an influx of water at the rate of 40 cm/yr at one end of the string and no-flow lateral flow boundaries. A unit quantity of each contaminant was introduced at the influx boundaries and the rate of outflux at the opposite end of the 10-element string was recorded to make the comparisons. Saturated conditions were assumed in this evaluation. Under these carefully controlled conditions the two codes produced essentially identical results, demonstrating that both codes appear to be accurately implementing the contaminant transport mechanisms. The conclusion is that a satisfactory basis was established to justify the exercise in which 1-D GoldSim model was benchmarked against the 2-D unsaturated zone and 3-D saturated zone Porflow models used at the Savannah River Site (SRS).
NASA Astrophysics Data System (ADS)
Jahromi, Amir E.; Miller, Franklin K.
2016-03-01
A sub Kelvin Active Magnetic Regenerative Refrigerator (AMRR) is being developed at the University of Wisconsin - Madison. This AMRR consists of two circulators, two regenerators, one superleak, one cold heat exchanger, and two warm heat exchangers. The circulators are novel non-moving part pumps that reciprocate a superfluid mixture of 4He-3He in the system. Heat from the mixture is removed within the two regenerators of this tandem system. An accurate model of the regenerators in this AMRR is necessary in order to predict the performance of these components, which in turn helps predicting the overall performance of the AMRR system. This work presents modeling methodology along with results from a 1-D transient numerical model of the regenerators of an AMRR capable of removing 2.5 mW at 850 mK at cyclic steady state.
Comprehensive 1D Modelling of Reactive Chemical Transport in Unsaturated Soil
NASA Astrophysics Data System (ADS)
Wissmeier, L.; Barry, D. A.
2007-12-01
Computer models for simulating environmental processes of water flow, solute transport and geochemical reactions have greatly advanced during recent years. However, there is still demand for the development of programs that a capable of simulating the numerous interactions between physical transport processes and biogeochemical reactions in natural soils. We present a new tool for simulating transient vadose zone flow and solute transport according to the moisture- based form of Richards' equation within the widely used geochemical software PHREEQC. The direct implementation into the geochemical framework provides access to comprehensive geochemical models, giving capabilities beyond existing software for coupled unsaturated flow and reaction. Possible reactions include complex aqueous speciation, cation exchange, equilibrium phase dissolution and precipitation, formation of solid solutions, redox reactions, gas phase exchange, surface adsorption considering electrostatics and kinetic reactions with user-defined rate equations, among others. As a result of the close coupling procedure, the influence of geochemical reactions on water content, e.g., through dissolution or precipitation of water-containing phases, can be investigated. For the solution of the partial differential equations of flow and transport, an explicit finite-difference formulation with a second-order space discretization and first-order time discretization was employed. The use of integrated diffusivities transforms Richards' equation into a simple advection-diffusion equation. Changes in water content and solute concentration were conceptualized as local kinetic reactions of individual elements where changes in moisture content result from fluxes of oxygen and hydrogen across cell boundaries. Reactions and chemical element transport are coupled via sequential two-step operator splitting. The scheme was implemented into PHREEQC without any source code modification such that it can be applied by an experienced user within the existing freely available software. In this presentation, we show results from extensive code verification and demonstrate the unique capabilities of the model for simulating surface sorption to variable charge surface sites including the development of a diffuse double layer as well as dissolution reactions with effects on soil moisture.
Constraining quantum critical dynamics: (2+1)D Ising model and beyond.
Witczak-Krempa, William
2015-05-01
Quantum critical (QC) phase transitions generally lead to the absence of quasiparticles. The resulting correlated quantum fluid, when thermally excited, displays rich universal dynamics. We establish nonperturbative constraints on the linear-response dynamics of conformal QC systems at finite temperature, in spatial dimensions above 1. Specifically, we analyze the large frequency or momentum asymptotics of observables, which we use to derive powerful sum rules and inequalities. The general results are applied to the O(N) Wilson-Fisher fixed point, describing the QC Ising model when N=1. We focus on the order parameter and scalar susceptibilities, and the dynamical shear viscosity. Connections to simulations, experiments, and gauge theories are made. PMID:25978256
Modeling of the Plasma Electrode Bias in the Negative Ion Sources with 1D PIC Method
Matsushita, D.; Kuppel, S.; Hatayama, A.; Fukano, A.; Bacal, M.
2009-03-12
The effect of the plasma electrode bias voltage in the negative ion sources is modeled and investigated with one-dimensional plasma simulation. A particle-in-cell (PIC) method is applied to simulate the motion of charged particles in their self-consistent electric field. In the simulation, the electron current density is fixed to produce the bias voltage. The tendency of current-voltage characteristics obtained in the simulation show agreement with the one obtained from a simple probe theory. In addition, the H{sup -} ion density peak appears at the bias voltage close to the plasma potential as observed in the experiment. The physical mechanism of this peak H{sup -} ion density is discussed.
Hyperbolic reformulation of a 1D viscoelastic blood flow model and ADER finite volume schemes
Montecinos, Gino I.; Mller, Lucas O.; Toro, Eleuterio F.
2014-06-01
The applicability of ADER finite volume methods to solve hyperbolic balance laws with stiff source terms in the context of well-balanced and non-conservative schemes is extended to solve a one-dimensional blood flow model for viscoelastic vessels, reformulated as a hyperbolic system, via a relaxation time. A criterion for selecting relaxation times is found and an empirical convergence rate assessment is carried out to support this result. The proposed methodology is validated by applying it to a network of viscoelastic vessels for which experimental and numerical results are available. The agreement between the results obtained in the present paper and those available in the literature is satisfactory. Key features of the present formulation and numerical methodologies, such as accuracy, efficiency and robustness, are fully discussed in the paper.
Vlasov dynamics of 1D models with long-range interactions
NASA Astrophysics Data System (ADS)
Druken, Kelsey A.
Subduction zones, mid-ocean spreading centers and mantle plumes are three of the largest sources for volcanism on Earth. With subduction as the driving tectonic force, these systems are responsible for the evolution of both the crust and mantle and as a result are important processes in our understanding of the solid Earth. Mantle plume processes, however, are still strongly debated within the community, particularly when occurring near subduction zones. Using both laboratory (i.e. analog) and numerical modeling techniques, we examine the dynamic interaction between subduction-driven and plume-driven flow. Results highlight the weak nature of buoyant plumes in comparison to the dominant slab-induced circulation. As a consequence of the subduction-induced flow, surface expressions differ significantly from traditional plume expectations. Variations in slab sinking style and plume position lead to a range in plume head and conduit melting signatures, as well as migrating hotspots. Motivated by the debated origin of recent (< 20 Ma) volcanism in the Northwest U.S., we also report results of the evolution of finite strain within rollback-induced as well as plume-driven flow fields. If the patterns differ between background subduction and plume structures, seismic anisotropy observations could help distinguish the plume and non plume models that are suggested for the region. We find rollback-induced horizontal shear causes predominantly trench-normal strain alignment in the backarc mantle wedge in contrast to longitudinal subduction which, despite the simple flow field, results in complex and variable orientations from the lack of strong horizontal shear. Splitting observations from the High Lava Plains region with the Northwest U.S. are in good agreement with the trench-normal laboratory predictions of strain alignment. Alignment within plume heads are found to exhibit striking tangential patterns that are perpendicular to the plume-driven flow. While we show that alignment does not reflect the direction of plume-driven flow, the study does show strong patterns of alignment that can be used as new guidelines for seismic interpretations.
A 1D pulse wave propagation model of the hemodynamics of calf muscle pump function.
Keijsers, J M T; Leguy, C A D; Huberts, W; Narracott, A J; Rittweger, J; van de Vosse, F N
2015-07-01
The calf muscle pump is a mechanism which increases venous return and thereby compensates for the fluid shift towards the lower body during standing. During a muscle contraction, the embedded deep veins collapse and venous return increases. In the subsequent relaxation phase, muscle perfusion increases due to increased perfusion pressure, as the proximal venous valves temporarily reduce the distal venous pressure (shielding). The superficial and deep veins are connected via perforators, which contain valves allowing flow in the superficial-to-deep direction. The aim of this study is to investigate and quantify the physiological mechanisms of the calf muscle pump, including the effect of venous valves, hydrostatic pressure, and the superficial venous system. Using a one-dimensional pulse wave propagation model, a muscle contraction is simulated by increasing the extravascular pressure in the deep venous segments. The hemodynamics are studied in three different configurations: a single artery-vein configuration with and without valves and a more detailed configuration including a superficial vein. Proximal venous valves increase effective venous return by 53% by preventing reflux. Furthermore, the proximal valves shielding function increases perfusion following contraction. Finally, the superficial system aids in maintaining the perfusion during the contraction phase and reduces the refilling time by 37%. PMID:25766693
A 1D pulse wave propagation model of the hemodynamics of calf muscle pump function
Keijsers, J M T; Leguy, C A D; Huberts, W; Narracott, A J; Rittweger, J; van de Vosse, F N
2015-01-01
The calf muscle pump is a mechanism which increases venous return and thereby compensates for the fluid shift towards the lower body during standing. During a muscle contraction, the embedded deep veins collapse and venous return increases. In the subsequent relaxation phase, muscle perfusion increases due to increased perfusion pressure, as the proximal venous valves temporarily reduce the distal venous pressure (shielding). The superficial and deep veins are connected via perforators, which contain valves allowing flow in the superficial-to-deep direction. The aim of this study is to investigate and quantify the physiological mechanisms of the calf muscle pump, including the effect of venous valves, hydrostatic pressure, and the superficial venous system. Using a one-dimensional pulse wave propagation model, a muscle contraction is simulated by increasing the extravascular pressure in the deep venous segments. The hemodynamics are studied in three different configurations: a single artery–vein configuration with and without valves and a more detailed configuration including a superficial vein. Proximal venous valves increase effective venous return by 53% by preventing reflux. Furthermore, the proximal valves shielding function increases perfusion following contraction. Finally, the superficial system aids in maintaining the perfusion during the contraction phase and reduces the refilling time by 37%. © 2015 The Authors. International Journal for Numerical Methods in Biomedical Engineering published by John Wiley & Sons Ltd. PMID:25766693
NASA Astrophysics Data System (ADS)
Cheviron, B.; Moussa, R.
2015-09-01
This review paper investigates the determinants of modelling choices, for numerous applications of 1-D free-surface flow and erosion equations, across multiple spatiotemporal scales. We aim to characterize each case study by its signature composed of model refinement (Navier-Stokes: NS, Reynolds-Averaged Navier-Stokes: RANS, Saint-Venant: SV or Approximations of Saint-Venant: ASV), spatiotemporal scales (domain length: L from 1 cm to 1000 km; temporal scale: T from 1 second to 1 year; flow depth: H from 1 mm to 10 m), flow typology (Overland: O, High gradient: Hg, Bedforms: B, Fluvial: F) and dimensionless numbers (Dimensionless time period T*, Reynolds number Re, Froude number Fr, Slope S, Inundation ratio Λz, Shields number θ). The determinants of modelling choices are therefore sought in the interplay between flow characteristics, cross-scale and scale-independent views. The influence of spatiotemporal scales on modelling choices is first quantified through the expected correlation between increasing scales and decreasing model refinements, identifying then flow typology a secondary but mattering determinant in the choice of model refinement. This finding is confirmed by the discriminating values of several dimensionless numbers, that prove preferential associations between model refinements and flow typologies. This review is intended to help each modeller positioning his (her) choices with respect to the most frequent practices, within a generic, normative procedure possibly enriched by the community for a larger, comprehensive and updated image of modelling strategies.
Modeling non-Fickian dispersion by use of the velocity PDF on the pore scale
NASA Astrophysics Data System (ADS)
Kooshapur, Sheema; Manhart, Michael
2015-04-01
For obtaining a description of reactive flows in porous media, apart from the geometrical complications of resolving the velocities and scalar values, one has to deal with the additional reactive term in the transport equation. An accurate description of the interface of the reacting fluids - which is strongly influenced by dispersion- is essential for resolving this term. In REV-based simulations the reactive term needs to be modeled taking sub-REV fluctuations and possibly non-Fickian dispersion into account. Non-Fickian dispersion has been observed in strongly heterogeneous domains and in early phases of transport. A fully resolved solution of the Navier-Stokes and transport equations which yields a detailed description of the flow properties, dispersion, interfaces of fluids, etc. however, is not practical for domains containing more than a few thousand grains, due to the huge computational effort required. Through Probability Density Function (PDF) based methods, the velocity distribution in the pore space can facilitate the understanding and modelling of non-Fickian dispersion [1,2]. Our aim is to model the transition between non-Fickian and Fickian dispersion in a random sphere pack within the framework of a PDF based transport model proposed by Meyer and Tchelepi [1,3]. They proposed a stochastic transport model where velocity components of tracer particles are represented by a continuous Markovian stochastic process. In addition to [3], we consider the effects of pore scale diffusion and formulate a different stochastic equation for the increments in velocity space from first principles. To assess the terms in this equation, we performed Direct Numerical Simulations (DNS) for solving the Navier-Stokes equation on a random sphere pack. We extracted the PDFs and statistical moments (up to the 4th moment) of the stream-wise velocity, u, and first and second order velocity derivatives both independent and conditioned on velocity. By using this data and combining the Taylor expansion of velocity increments, du, and the Langevin equation for point particles we obtained the components of velocity fluxes which point to a drift and diffusion behavior in the velocity space. Thus a partial differential equation for the velocity PDF has been formulated that constitutes an advection-diffusion equation in velocity space (a Fokker-Planck equation) in which the drift and diffusion coefficients are obtained using the velocity conditioned statistics of the derivatives of the pore scale velocity field. This has been solved by both a Random Walk (RW) model and a Finite Volume method. We conclude that both, these methods are able to simulate the velocity PDF obtained by DNS. References [1] D. W. Meyer, P. Jenny, H.A.Tschelepi, A joint velocity-concentration PDF method for traqcer flow in heterogeneous porous media, Water Resour.Res., 46, W12522, (2010). [2] Nowak, W., R. L. Schwede, O. A. Cirpka, and I. Neuweiler, Probability density functions of hydraulic head and velocity in three-dimensional heterogeneous porous media, Water Resour.Res., 44, W08452, (2008) [3] D. W. Meyer, H. A. Tchelepi, Particle-based transport model with Markovian velocity processes for tracer dispersion in highly heterogeneous porous media, Water Resour. Res., 46, W11552, (2010)
NASA Astrophysics Data System (ADS)
Mahieux, A.; Erwin, J. T.; Chamberlain, S.; Robert, S.; Thomas, I.; Vandaele, A. C.; Trompet, L.; Wilquet, V.; Yelle, R. V.
2015-10-01
The SOIR instrument on board Venus Express routinely measures the CO2 number density profiles in the mesosphere and thermosphere region at the Venus terminator using the solar occultation technique. Assuming the hydrostatic equilibrium, we derive temperature profiles, which show a permanent cold layer at 125 km, surrounded by two warmer layers at 100 km and 140 km. We developed a 1D conductive radiative transfer model to study the mean SOIR thermal profile, considering the main species, and carefully modelling the radiative terms. In order to correctly reproduce the thermal profile, aerosols cooling and heating terms are added. We describe how aerosols number density profiles can be calculated to have a good match of the thermal profiles.
The galaxy velocity field and CDM models
NASA Technical Reports Server (NTRS)
Tormen, Giuseppe; Moscardini, Lauro; Lucchin, Francesco; Matarrese, Sabino
1993-01-01
It is generally accepted that some kind of non-baryonic dark matter accounts for most of the mass density of the universe. Considering such a component has become, in the last decade, a key ingredient in current theories of structure formation. In particular, the Cold Dark Matter (CDM) scenario has proven to be quite successful in explaining most of the observed properties of galaxies and of their large-scale distribution. The standard CDM model is characterized by a primordial Zel'dovich spectrum, of random-phase adiabatic perturbations in a universe with density parameter omega sub 0 = 1 and vanishing cosmological constant. This poster paper presents an analysis of observational data on peculiar motion of optical galaxies in comparison to the predictions of CDM models where the assumptions of the standard scenario: omega sub 0 = 1, n = 1, and bias parameter b = 1 are relaxed. In particular, CDM models with 0 less than n less than 1 and 0.4 less than omega sub 0 less than 1 are considered.
Adhikari, K; Pal, S; Chakraborty, B; Mukherjee, S N; Gangopadhyay, A
2014-10-01
The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4-12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11-0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (KS ?=?5.25??10(-4) cm/s). The soil containing 47 % silt, 11 % clay, and 1.54% organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R(2)?=?0.977, RMSE?=?1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42-49%. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion point was reached within 12 days of elapsed time. This clearly demonstrated poor attenuation capacity of the soil to retard migration of phenol to the groundwater from the surface outfall site. Suitable liner, based on these data, may be designed to inhibit subsurface transport of phenol and thereby to protect precious groundwater from contamination. PMID:24929358
Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E
2009-07-06
In this project, we are developing models of lithospheric structure for a wide variety of tectonic regions throughout Eurasia and the Middle East by regionalizing 1D velocity models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities. We expect the regionalized velocity models will improve our ability to predict travel-times for local and regional phases, such as Pg, Pn, Sn and Lg, as well as travel-times for body-waves at upper mantle triplication distances in both seismic and aseismic regions of Eurasia and the Middle East. We anticipate the models will help inform and strengthen ongoing and future efforts within the NNSA labs to develop 3D velocity models for Eurasia and the Middle East, and will assist in obtaining model-based predictions where no empirical data are available and for improving locations from sparse networks using kriging. The codes needed to conduct the joint inversion of P-wave receiver functions (PRFs), S-wave receiver functions (SRFs), and dispersion velocities have already been assembled as part of ongoing research on lithospheric structure in Africa. The methodology has been tested with synthetic 'data' and case studies have been investigated with data collected at an open broadband stations in South Africa. PRFs constrain the size and S-P travel-time of seismic discontinuities in the crust and uppermost mantle, SRFs constrain the size and P-S travel-time of the lithosphere-asthenosphere boundary, and dispersion velocities constrain average S-wave velocity within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D velocity models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background velocity model constrained by the dispersion velocities. In our first year of this project we will (i) generate 1D velocity models for open broadband seismic stations in the western half of the study area (Eurasia and the Middle East) and (ii) identify well located seismic events with event-station paths isolated to individual tectonic provinces within the study area and collect broadband waveforms and source parameters for the selected events. The 1D models obtained from the joint inversion will then be combined with published geologic terrain maps to produce regionalized models for distinctive tectonic areas within the study area, and the models will be validated through full waveform modeling of well-located seismic events recorded at local and regional distances.
NASA Astrophysics Data System (ADS)
Minrik, Stanislav
2015-08-01
In this paper, we propose theoretical basis for investigation of dynamics of acoustic phonons in a thin layers containing nano-scale structural inhomogeneities. One-dimensional (1D) model of a crystal lattice was considered to reveal specific features of the processes arising in such system of phonons in equilibrium state. Standard quantization of energy of 1D ionic chain vibrating by acoustic frequencies was carried out while the presence of foreign ions in this chain was taken into account. Since only two dimensions are dominant in thin layers, only longitudinal vibrations of the chain in the plane of the layer were considered. Results showed that foreign ions affect the energy quantization. Phonon-phonon interaction between two phonon`s modes can be expected if the mass of foreign ions implanted by ion-beam differs from the mass of ions in the initial layer. We believe that the obtained results will help to understand the character of phonon systems in nanostructured thin layers prepared by ion-bem technology, and will allow better explain some thermal and electrical phenomena associated with lattice dynamics in such layers.
NASA Astrophysics Data System (ADS)
Raybaud, V.; Nival, P.; Prieur, L.
2011-01-01
Modelling was used as a tool to better understand the physical and biological processes observed during the multidisciplinary cruise DYNAPROC 2 (DYNAmic of rapid PROCesses in the water column), which took place in the Ligurian Sea in September-October 2004. The aim of the cruise was to study the short time-scale physical and biological processes that occur when the ecosystem switches from summer oligotrophy to autumnal mesotrophy. In this study, we have tested two 1D physical-biological coupled models. The first was a classical model in which surface layer dynamics were obtained using the turbulent kinetic energy model of Gaspar [Gaspar et al., 1990]. The simulated food-web took into account ten state variables: three nutrients, three classes of phytoplankton, two classes of zooplankton and two types of detritus. The second model (called IDA, Isopycnals Depth Adjustment) was based on the initial one but it took into account the measured variations of isopycnals depths. The results showed that the IDA model most efficiently reproduced the observed ecosystem dynamics. We have therefore used the IDA model to show that physical processes observed during the cruise had a major effect on biological compartment, mainly on nano- and picophytoplankton.
Asymmetric optimal-velocity car-following model
NASA Astrophysics Data System (ADS)
Xu, Xihua; Pang, John; Monterola, Christopher
2015-10-01
Taking the asymmetric characteristic of the velocity differences of vehicles into account, we present an asymmetric optimal velocity model for a car-following theory. The asymmetry between the acceleration and the deceleration is represented by the exponential function with an asymmetrical factor, which agrees with the published experiment. This model avoids the disadvantage of the unrealistically high acceleration appearing in previous models when the velocity difference becomes large. This model is simple and only has two independent parameters. The linear stability condition is derived and the phase transition of the traffic flow appears beyond the critical density. The strength of interaction between clusters is shown to increase with the asymmetry factor in our model.
Cosmological model with variable light velocity
Petit, J.P.
1988-12-01
The model with variable c,G,h is extended to electromagnetism. The entropy is found to vary like log t and, in a space-entropy representation, the metric is conformally flat. A new gauge relations is suggested, based on geometrical considerations, which corresponds to a Rydberg constant varying like R. The Hubble's law still applies. The age of the universe is unchanged while its span is found to be half of the Mattig's value. The complete decoding of the red shift can be done. The distances of the sources are very similar. The large volumic power densities of distant quasars could have been greatly overestimated, while the increase of their absolute magnitude, as derived from the classical theory, could be due to the secular variation of absolute magnitude, as derived from the classical theory, could be due to the secular variation of c. Assuming the electron-proton mass ratio to vary like R, the authors get a fine structure constant ..cap alpha.., a Bohr radius and a ratio of electromagnetic force to gravitational force which behave like absolute constants.
Data assimilation with the EnKF in a 1-D numerical model of a North Sea station
NASA Astrophysics Data System (ADS)
Ponsar, Stphanie; Luyten, Patrick
2009-12-01
A series of numerical experiments for data assimilation with the Ensemble Kalman Filter (EnKF) in a shallow water model are reported. Temperature profiles measured at a North Sea location, 5530? North and 055? East (referred to as the CS station of the NERC North Sea project), are assimilated in 1-D simulations. Comparison of simulations without assimilation to model results obtained when assimilating data with the EnKF allows us to assess the filter performance in reproducing features of the observations not accounted for by the model. The quality of the model error sampling is tested as well as the validity of the Gaussian hypothesis underlying the analysis scheme of the EnKF. The influence of the model error parameters and the frequency of the data assimilation are investigated and discussed. From these experiments, a set of optimal parameters for the model error sampling are deduced and used to test the behavior of the EnKF when propagating surface information into the water column.
Velocity-density twin transforms in the thin disc model
NASA Astrophysics Data System (ADS)
Bratek, Łukasz; Sikora, Szymon; Jałocha, Joanna; Kutschera, Marek
2015-08-01
Ring mass density and the corresponding circular velocity in thin disc model are known to be integral transforms of one another. But it may be less familiar that the transforms can be reduced to one-fold integrals with identical weight functions. It may be of practical value that the integral for the surface density does not involve the velocity derivative, unlike the equivalent and widely known Toomre's formula.
Bautista, Debra L; Morris, Deanna H; Stein, Lauren; Asher, Wesley; Hammitt, Timothy
2006-01-01
In this study, we have developed a two receptor model system to describe the R and R states of G-protein coupled receptors, specifically the alpha(1D) adrenergic receptor. The two models interact with agonist (epinephrine) and antagonist (BMY7378) differently. The active model has increased interactions with epinephrine. The inactive model has increased interactions with BMY7378. We also explored the protonation state of the ligands. When the most basic amine was protonated, we found increased hydrogen bonding and increased aromatic interactions. Protonated epinephrine hydrogen bonds with Asp176 and has aromatic residues Trp172, Trp235, Trp361, and Phe388 within 3 Angstroms. Protonated BMY7378 hydrogen bonds with Trp172 and Lys236 and has aromatic residues Trp172, Trp254, Phe364, Phe384, and Phe388 within 3 Angstroms. We conclude that the two model system is required to represent the two states of the receptor and that protonation of the ligand is also critical. PMID:16426068
An analytical 1-D model for vertical momentum and energy flux through a fully developed wind farm
NASA Astrophysics Data System (ADS)
Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando
2014-05-01
Wind farms capture momentum from the atmospheric boundary layer (ABL) both at the leading edge and from the atmosphere above. Momentum is advected into the wind farm and wake turbulence draws excess momentum in from between turbines until momentum is only available from above the wind farm. This distance can be described by the so-called drag development length scale, which arises from the canopy drag force term in the momentum equation. At this point the flow can be considered fully developed. The horizontally-averaged velocity profile for a fully developed wind farm flow exhibits a characteristic inflection point near the top of the wind farm, similar to that of sparse canopy-type flows (Markfort et al., JoT, 2012). The inflected vertical velocity profile is associated with the presence of a dominant characteristic turbulence scale, which may be responsible for a significant portion of the vertical momentum flux. We evaluate an analytical canopy-type flow model for wind farm-atmosphere interaction by testing it against wind-tunnel experimental data of flow through a model wind farm. The model is adapted to predict the mean flow, vertical momentum flux, and the mean kinetic energy flux as well as kinetic energy dissipation within the wind farm. This model is particularly useful for wind farm configuration optimization, considering wind turbine spacing and surface roughness and can also be useful to represent wind farms in regional scale atmospheric simulations.
A 3-mode, Variable Velocity Jet Model for HH 34
NASA Technical Reports Server (NTRS)
Raga, A.; Noriega-Crespo, A.
1998-01-01
Variable ejection velocity jet models can qualitatively explain the appearance of successive working surfaces in Herbig-Haro (HH) jets. This paper presents an attempt to explore which features of the HH 34 jet can indeed be reproduced by such a model.
SCEC CVM-Toolkit (CVM-T) -- High Performance Meshing Tools for SCEC Community Velocity Models
NASA Astrophysics Data System (ADS)
Small, P.; Maechling, P. J.; Ely, G. P.; Olsen, K. B.; Withers, K.; Graves, R. W.; Jordan, T. H.; Plesch, A.; Shaw, J. H.
2010-12-01
The SCEC Community Velocity Model Toolkit (CVM-T) enables earthquake modelers to quickly build, visualize, and validate large-scale 3D velocity meshes using SCEC CVM-H or CVM-4. CVM-T is comprised of three main components: (1) a current SCEC community velocity model for Southern California, (2) tools for extracting meshes from this model and visualizing them, and (3) an automated test framework for evaluating new releases of CVMs using SCECs AWP-ODC forward wave propagation software and one, or more, ground motion goodness of fit (GoF) algorithms. CVM-T is designed to help SCEC modelers build large-scale velocity meshes by extracting material properties from the most current version of Community Velocity Model H (CVM-H) and to provide a consistent interface as new CVM-H versions are developed. The CVM-T software provides a highly-scalable interface to CVM-H 6.2 (and later) voxets. Along with an improved interface to CVM-H material properties, the CVM-T software adds a geotechnical layer (GTL) to CVM-H 6.2+ based on Elys Vs30-derived GTL. The initial release of CVM-T also extends the coverage region for CVM-H 6.2 with a Hadley-Kanamori 1D background. Smoothing is performed within the transition boundary between the core model and the 1D background. The user interface now includes a C API that allows applications to query the model either by elevation or depth. The Extraction and Visualization Tools (EVT) include a parallelized 3D mesh generator which can quickly generate meshes (consisting of Vp, Vs, and density) from either CVM-H or CVM-4 with over 100 billion points. Python plotting scripts can be employed to plot horizontal or profile slices from existing meshes or directly from either CVM. The Automated Test Framework (ATF) is a system for quantitatively evaluating new versions of CVM-H and ensuring that the model improves against prior versions. The ATF employs the CruiseControl build and test framework to run an AWP-ODC simulation for the 2008 Chino Hills event (Mw = 5.39) and perform a goodness of fit statistics calculation on the generated synthetic and recorded observed seismograms using the GoF algorithm, based on comparison of synthetic peak amplitudes to observed peak amplitudes, used in the SCEC Broadband platform. CVM-T produced plots include comparisons of synthetic and observed seismograms, plots of bias versus period, and spatial plots of the pseudo-AA bias over the entire region.
NASA Astrophysics Data System (ADS)
Ashworth, K.; Chung, S. H.; Griffin, R. J.; Chen, J.; Forkel, R.; Bryan, A. M.; Steiner, A. L.
2015-11-01
Biosphere-atmosphere interactions play a critical role in governing atmospheric composition, mediating the concentrations of key species such as ozone and aerosol, thereby influencing air quality and climate. The exchange of reactive trace gases and their oxidation products (both gas and particle phase) is of particular importance in this process. The FORCAsT (FORest Canopy Atmosphere Transfer) 1-D model is developed to study the emission, deposition, chemistry and transport of volatile organic compounds (VOCs) and their oxidation products in the atmosphere within and above the forest canopy. We include an equilibrium partitioning scheme, making FORCAsT one of the few canopy models currently capable of simulating the formation of secondary organic aerosols (SOAs) from VOC oxidation in a forest environment. We evaluate the capability of FORCAsT to reproduce observed concentrations of key gas-phase species and report modeled SOA concentrations within and above a mixed forest at the University of Michigan Biological Station (UMBS) during the Community Atmosphere-Biosphere Interactions Experiment (CABINEX) field campaign in the summer of 2009. We examine the impact of two different gas-phase chemical mechanisms on modelled concentrations of short-lived primary emissions, such as isoprene and monoterpenes, and their oxidation products. While the two chemistry schemes perform similarly under high-NOx conditions, they diverge at the low levels of NOx at UMBS. We identify peroxy radical and alkyl nitrate chemistry as the key causes of the differences, highlighting the importance of this chemistry in understanding the fate of biogenic VOCs (bVOCs) for both the modelling and measurement communities.
NASA Astrophysics Data System (ADS)
Daehne, A.; van Asch, Th. W. J.; Corsini, A.; Spickerman, A.; Bgueria-Portugus, S.
2010-05-01
Understanding the behavior of landslides often starts with a numerical simulation that accurately accounts for observed physical processes. This research proposes a method for the implementation of the dynamic SLOWMOVE model to a high-mobility, moderate velocity earth flow located in the northern Apennines. The Valoria landslide is 3.5 km long earth slide- earth flow that resumed activity in 2001. Landslide materials comprised of disaggregated Flysch, Marl and Claystones are mainly transported as earth slides in the upper slope, and as earth flows in the main track. Repeated acceleration events lasting several weeks occur seasonally since 2001 reactivation. During events it can reach velocities of about 10 m per hour with a cumulative displacement of hundreds of meters. Through this intermittent activity, more than ten million cubic meters have been transferred down-slope since 2001, changing significantly and several times the morphology of the slope. The SLOWMOVE model postulates that landslide materials can be represented as a homogeneous material with rheological properties and constant density. The approach is based on the Navier-Stokes equations. Under the assumptions that the inertia of the moving mass can be neglected, the behavior of the landslide depends solely on the balance between driving forces and resisting forces which contain a Coulomb-viscous component. Excess pore pressure due to undrained loading and lateral force form the main parameters that control the acceleration. The effects of lateral force and excess pore pressure allow a numerical simulation of landslide reactivation by coupling of two landslide bodies. A numerical scheme based on a finite difference solution (2D Eulerian space with Cartesian coordinates) was implemented in Microsoft Excel and used to compute propagation of the mass in 1D. The model allows coupling between mass movements having different geotechnical characteristic. In practice, it allows simulating the reactivation of dormant landslide parts as an effect of undrained loading and changed pressure conditions caused by active movements approaching from upslope. A representative landslide cross-section of the Valoria landslide, stretching from the main track zone down to the toe zone, was analyzed in SLOWMOVE. A large set of surface displacement data obtained since March 2008 through continuous total-station monitoring allowed for evaluation and calibration of the numerical implementations in terms of velocity. Multi-temporal Lidar surveys allowed for calibration of the model in terms of event-induced morphological changes along the selected cross section. Model parameters were defined, on such basis, via a trial and error approach starting from laboratory and literature data. The model was able to reproduce realistic velocities and morphological changes. The specific function of coupling between interacting portion of the mass movement, allowed for simulation of landslide toe reactivation, that was observed during major acceleration events as a result of the domino effect caused by active flows in the main flow track. Further development is needed in order to integrate in the model transient pore pressure conditions. Nevertheless, results are promising, as they point to a possible application of the model in quantitative hazard and risk assessment.
NASA Astrophysics Data System (ADS)
Yang, Aijun; Wang, Xiaohua; Rong, Mingzhe; Liu, Dingxin; Iza, Felipe; Kong, Michael G.
2011-11-01
In this paper atmospheric-pressure rf He+O2 cold plasmas are studied by means of a 1-D fluid model. 17 species and 60 key reactions selected from a study of 250+ reactions are incorporated in the model. O2+, O3-, and O are the dominant positive ion, negative ion, and reactive oxygen species, respectively. Ground state O is mainly generated by electron induced reactions and quenching of atomic and molecular oxygen metastables, while three-body reactions leading to the formation of O2 and O3 are the main mechanisms responsible for O destruction. The fraction of input power dissipated by ions is 20%. For the conditions considered in the study 6% of the input power is coupled to ions in the bulk and this amount will increase with increasing electronegativity. Radial and electrode losses of neutral species are in most cases negligible when compared to gas phase processes as these losses are diffusion limited due to the large collisionality of the plasma. The electrode loss rate of neutral species is found to be nearly independent of the surface adsorption probability p for p > 0.001 and therefore plasma dosage can be quantified even if p is not known precisely.
NASA Astrophysics Data System (ADS)
Pradel, J.-L.; David, C.; Quinebche, S.; Blondel, P.
2014-05-01
Industrial scale-up (or scale down) in Compounding and Reactive Extrusion processes is one of the most critical R&D challenges. Indeed, most of High Performances Polymers are obtained within a reactive compounding involving chemistry: free radical grafting, in situ compatibilization, rheology control... but also side reactions: oxidation, branching, chain scission... As described by basic Arrhenius and kinetics laws, the competition between all chemical reactions depends on residence time distribution and temperature. Then, to ensure the best possible scale up methodology, we need tools to match thermal history of the formulation along the screws from a lab scale twin screw extruder to an industrial one. This paper proposes a comparison between standard scale-up laws and the use of Computer modeling Software such as Ludovic applied and compared to experimental data. Scaling data from a compounding line to another one, applying general rules (for example at constant specific mechanical energy), shows differences between experimental and computed data, and error depends on the screw speed range. For more accurate prediction, 1D-Computer Modeling could be used to optimize the process conditions to ensure the best scale-up product, especially in temperature sensitive reactive extrusion processes. When the product temperature along the screws is the key, Ludovic software could help to compute the temperature profile along the screws and extrapolate conditions, even screw profile, on industrial extruders.
NASA Astrophysics Data System (ADS)
Joyce, Michael; Sicard, Franois
2011-05-01
Studies of a class of infinite 1D self-gravitating systems have highlighted that, on one hand, the spatial clustering which develops may have scale-invariant (fractal) properties and, on the other hand, they display self-similar properties in their temporal evolution. The relevance of these results to 3D cosmological simulations has remained unclear. We show here that the measured exponents characterizing the scale-invariant non-linear clustering are in excellent agreement with those derived from an appropriately generalized stable-clustering hypothesis. Further an analysis in terms of haloes selected with a friend-of-friend algorithm reveals that such structures are, statistically, virialized across the range of scales corresponding to scale invariance. Thus the strongly non-linear clustering in these models is accurately described as a virialized fractal structure, very much in line with the clustering hierarchy which Peebles originally envisaged qualitatively as associated with stable clustering. If transposed to 3Ds these results would imply, notably, that cold dark matter haloes (or even subhaloes) are (1) not well modelled as smooth objects and (2) that the supposed universality of their profiles is, like apparent smoothness, an artefact of poor numerical resolution.
NASA Astrophysics Data System (ADS)
Gallovic, F.; Pacor, F.; Zahradnik, J.; Luzi, L.; Puglia, R.
2013-12-01
We perform an extended study of the largest aftershock of the 2009 L'Aquila, Italy, Mw 6.3 earthquake, based on low-frequency inversion and broadband simulation of strong-motion data. The M 5.6 aftershock occurred on April 7 and was recorded by ~30 permanent and temporal accelerometric stations located within 50km from the epicenter. Using ISOLA software we perform a CMT inversion, finding the centroid at 15km depth in agreement with previous studies. Distribution of relocated small aftershocks by Valoroso et al. (2013) suggests that the event ruptured a normal fault dipping NE at 60 degrees, antithetic to the major L'Aquila fault. Considering a finite-extent source model with homogenous slip and radial propagation at constant speed we further constrain the model, inverting strong-motion data in the frequency range 0.1-0.5 Hz. We estimate fault dimension of 6x6km, static stress drop of 1 MPa (relatively low with respect to other studies), and find a weak indication of bilateral rupture propagation. These properties are used to setup a broadband (0-10Hz) composite source model with fractal number-size distribution of overlapping subsources. The Green's functions are calculated in 1D layered medium in the full frequency range, assuming shallow site-specific structure, wherever available, and a generic soil profile for rock stations; no stochastic Green's functions are used. At stations with not very strong site effects, the fit between synthetic and observed waveforms is generally good both in frequency and time domains (velocities and accelerations). Only at some stations we observe a peculiar mismatch of ground motion polarization at high frequencies. Careful analysis suggests that the (predominantly) linear S-wave polarization correctly modeled at low frequencies (up to ~2Hz) remains linear even at higher frequencies but at different, frequency dependent, angle.
Three-dimensional seismic velocity model of the West Bohemia/Vogtland seismoactive region
NASA Astrophysics Data System (ADS)
R?ek, Bohuslav; Horlek, Josef
2013-11-01
In this paper, we present a smooth 3-D seismic model WB2012 for the West Bohemia/Vogtland earthquake swarm region derived by means of seismic tomography. Inverted data were represented by a set of 2920 P-wave traveltimes from controlled shots fired in a framework of different experiments and a set of 11339 P- and S-wave arrival times from 661 local earthquakes between 1991 December and 2010 March. We used a standard tomographic approach for independent calculation of P- and S-wave velocity fields in a rectangular grid whose size was 1 km in all coordinates. The traveltimes and rays were calculated by a numerical solution of the eiconal equation. While locating seismic events, our new WB2012 model yielded arrival time residuals on average by 13 per cent lower and hypocentre depths by 0.95 km shallower compared to the locations of the foci in the standard 1-D vertically inhomogeneous isotropic velocity model of the West Bohemia swarm region WB2005. Further, we converted the P- and S-wave velocities to the bulk modulus K and Poisson's ratio ?. The bulk modulus (40-70 GPa) correlates acceptably with the tectonic and geological structure of the area. The anomalously low values of the Poisson's ratio (0.15) are typical for the most active focal zones of Nov Kostel and Lazy in West Bohemia.
A new settling velocity model to describe secondary sedimentation.
Ramin, Elham; Wgner, Dorottya S; Yde, Lars; Binning, Philip J; Rasmussen, Michael R; Mikkelsen, Peter Steen; Plsz, Benedek Gy
2014-12-01
Secondary settling tanks (SSTs) are the most hydraulically sensitive unit operations in biological wastewater treatment plants. The maximum permissible inflow to the plant depends on the efficiency of SSTs in separating and thickening the activated sludge. The flow conditions and solids distribution in SSTs can be predicted using computational fluid dynamics (CFD) tools. Despite extensive studies on the compression settling behaviour of activated sludge and the development of advanced settling velocity models for use in SST simulations, these models are not often used, due to the challenges associated with their calibration. In this study, we developed a new settling velocity model, including hindered, transient and compression settling, and showed that it can be calibrated to data from a simple, novel settling column experimental set-up using the Bayesian optimization method DREAM(ZS). In addition, correlations between the Herschel-Bulkley rheological model parameters and sludge concentration were identified with data from batch rheological experiments. A 2-D axisymmetric CFD model of a circular SST containing the new settling velocity and rheological model was validated with full-scale measurements. Finally, it was shown that the representation of compression settling in the CFD model can significantly influence the prediction of sludge distribution in the SSTs under dry- and wet-weather flow conditions. PMID:25243657
Novel phase-space Monte-Carlo method for quench dynamics in 1D and 2D spin models
NASA Astrophysics Data System (ADS)
Pikovski, Alexander; Schachenmayer, Johannes; Rey, Ana Maria
2015-05-01
An important outstanding problem is the effcient numerical computation of quench dynamics in large spin systems. We propose a semiclassical method to study many-body spin dynamics in generic spin lattice models. The method, named DTWA, is based on a novel type of discrete Monte-Carlo sampling in phase-space. We demonstare the power of the technique by comparisons with analytical and numerically exact calculations. It is shown that DTWA captures the dynamics of one- and two-point correlations 1D systems. We also use DTWA to study the dynamics of correlations in 2D systems with many spins and different types of long-range couplings, in regimes where other numerical methods are generally unreliable. Computing spatial and time-dependent correlations, we find a sharp change in the speed of propagation of correlations at a critical range of interactions determined by the system dimension. The investigations are relevant for a broad range of systems including solids, atom-photon systems and ultracold gases of polar molecules, trapped ions, Rydberg, and magnetic atoms. This work has been financially supported by JILA-NSF-PFC-1125844, NSF-PIF-1211914, ARO, AFOSR, AFOSR-MURI.
Thermal characterization of large size lithium-ion pouch cell based on 1d electro-thermal model
NASA Astrophysics Data System (ADS)
Vertiz, G.; Oyarbide, M.; Macicior, H.; Miguel, O.; Cantero, I.; Fernandez de Arroiabe, P.; Ulacia, I.
2014-12-01
Thermal management is one of the key factors to keep lithium-ion cells in optimum electrical performance, under safe working conditions and into a reasonably low ageing process. This issue is becoming particularly relevant due to the heterogeneous heat generation along the cell. Cell working temperature is determined by ambient temperature, heat generation and evacuation capacity. Therefore, thermal management is established by: i) the intrinsic thermal properties (heat capacity & thermal conductivity) and ii) the heat generation electro-thermal parameters (internal resistance, open circuit voltage & entropic factor). In this research, different methods - calculated and experimental - are used to characterize the main heat properties of a 14Ah -LiFePO4/graphite-commercial large sizes pouch cell. In order to evaluate the accuracy of methods, two comparisons were performed. First, Newman heat generation estimations were compared with experimental heat measurements. Secondly, empirical thermal cell behaviour was match with 1D electro-thermal model response. Finally, considering the results, the most adequate methodology to evaluate the key thermal parameters of a large size Lithium-ion pouch cell are proposed to be: i) pulse method for internal resistance, ii)heat loss method for entropic factor; and iii)experimental measurement (ARC calorimeter and C-177-97 standard method) for heat capacity and thermal conductivity.
NASA Astrophysics Data System (ADS)
Rhie, J.; Kim, S.; Lee, S.
2012-12-01
We construct a preliminary 3D seismic velocity model for the crust beneath the southern part of the Korean Peninsula. Broadband waveforms obtained from seismic network in and around the study area are used. First, a quasi-3D S-wave model is estimated from Rayleigh wave tomography using ambient seismic noise. During the depth-inversion of dispersion curve for each inversion node, a Bayesian approach is used to introduce sharp boundaries and to provide a statistical assessment of inverted 1D Vsv models. Crustal thickness and average Vp/Vs ratio are constrained from the result of previous receiver function (RF) study. Then, Love wave dispersions are inverted for 1D Vsh models by allowing small velocity perturbations with respect to the previously defined 1D Vsv-wave models. Lastly, a series of forward 3D waveform modeling are performed based on the anisotropic S-wave model. The starting P-wave velocity model is determined by using Vp/Vs ratio from the RF study and an average model between Vsv and Vsh models. Values of Vp/Vs ratio, Vsv, Vsh, and crustal thickness are systematically varied during the forward modeling to fit observed three-component broadband (~0.05-0.3 Hz) waveforms. By doing this, we develop a preliminary 3D velocity model for the southern Korean Peninsula. Our model is a starting model of the realistic 3D model, which takes into account more data such as surface geological feature, high-frequency body wave travel times, and gravity. The final model will be used to predict strong g round motion of potential large scenario earthquakes after correcting site effects.
NASA Astrophysics Data System (ADS)
Maman, M. J.; Borzotta, E.; Venencia, J. E.; Maidana, A.; Moyano, C. E.; Castiglione, B.
2000-05-01
Four magnetotelluric soundings were carried out in 1993 in the region of the Copahue active volcano located at the border between Chile and Argentina (3745'S, 7118'W). Three soundings were located inside the caldera of the ancient stratovolcano (east of Copahue) and the fourth outside it. The soundings inside the caldera were situated at about 6, 11, and 14 km from the volcano. Digital data were obtained covering the range of periods from 1 sec to 10,000 sec using induction coils and a flux-gate magnetometer to obtain the magnetic data and Cu-SO 4Cu electrodes for electric field measurements. The apparent resistivity curves corresponding to principal directions were analyzed in conjunction with the geological background in order to eliminate distortion which is very important in this hot volcanic region. Then, 1D modellings were performed using the "normal" curves i.e., curves without distortions. Using the apparent resistivity curves with distortions, 2D modelling was also performed along a profile perpendicular to the regional tectonic trend suggested by MT soundings into the caldera. Results show low resistivity values of about 3-15 ?m between 9 km to 20 km depth in the crust, suggesting high temperatures, with minimum values of about 700C with partially melted zones in the upper crust between 9 km to 20 km depth under the caldera. The presence of a possible sulphide-carbonaceous layer (SC layer) in the upper basement could play an important role in lowering the electrical resistivities because of its high electronic conductivity.
NASA Astrophysics Data System (ADS)
Reynolds, Dylan; Wood, Stephen E.; Bapst, Jonathan; Mehlhaff, Joshua; Griffiths, Stephen G.
2014-11-01
We have applied a self-consistent 1-D model for heat diffusion, vapor diffusion, and ice condensation/sublimation, and surface energy balance to investigate our hypothesis for the source of the recently observed water vapor around Ceres [1]. As described in a companion presentation [2], we find that the estimated global flux of 6 kg/s can be produced by steady-state sublimation of subsurface ice driven by the geothermal temperature gradient for a heat flux of 1 mW/m2 - the value estimated for a chondritic abundance of heat-producing elements [3,4]. We will present a detailed description of our Ceres cryothermal diffusion model and comparisons with previous models. One key difference is the use of a new physics-based analytic model (MaxRTCM) for calculating the thermal conductivity (Kth) of planetary regolith [5] that has been validated by comparisons to a wide range of laboratory data [6]. MaxRTCM predicts much lower Kth values in the upper regolith than those in previous work [3]. It also accounts for a process first modeled in a study of unstable equatorial ground ice on Mars [7,8], where vapor diffusing up from a receding ice table toward the surface can recondense at shallower depths - eventually forming a steady-state profile of pore ice volume fraction that increases with depth and maintains a constant flux of vapor at all depths [7]. Using MaxRTCM we calculate the corresponding Kth(z) profiles and will present predictions and implications of the resulting temperature profile in the upper few kilometers of Ceres megaregolith.References: [1] Kppers et al. (2014), Nature, 505(7484), 525-527. [2] Wood et al., 2014, this meeting. [3] Fanale & Salvail (1989) Icarus 82, 97-110. [4] McCord and Sotin (2005) JGR 110, E05009. [5] Wood (2013) LPSC Abs. 44, 3077. [6] Wood (2014), Icarus, in revision. [7] Mellon et al. (1997), JGR, 102, 19357-69. [8] Clifford (1993), JGR, 98, 10973-11016.
Mg line formation in late-type stellar atmospheres. II. Calculations in a grid of 1D models
NASA Astrophysics Data System (ADS)
Osorio, Y.; Barklem, P. S.
2016-02-01
Context. Mg is the α element of choice for Galactic population and chemical evolution studies because it is easily detectable in all late-type stars. Such studies require precise elemental abundances, and thus departures from local thermodynamic equilibrium (LTE) need to be accounted for. Aims: Our goal is to provide reliable departure coefficients and equivalent widths in non-LTE, and for reference in LTE, for diagnostic lines of Mg studied in late-type stars. These can be used, for example, to correct LTE spectra and abundances. Methods: Using the model atom built and tested in the preceding paper in this series, we performed non-LTE radiative transfer calculations in a grid of 3945 stellar 1D atmospheric models. We used a sub-grid of 86 models to explore the propagation of errors in the recent atomic collision calculations to the radiative transfer results. Results: We obtained departure coefficients for all the levels and equivalent widths (in LTE and non-LTE) for all the radiative transitions included in the "final" model atom presented in Paper I. Here we present and describe our results and show some examples of applications of the data. The errors that result from uncertainties in the collisional data are investigated and tabulated. The results for equivalent widths and departure coefficients are made freely available. Conclusions: Giants tend to have negative abundance corrections while dwarfs have positive, though small, corrections. Error analysis results show that uncertainties related to the atomic collision data are typically on the order of 0.01 dex or less, although for few stellar models in specific lines uncertainties can be as large as 0.03 dex. As these errors are less than or on the same order as typical corrections, we expect that we can use these results to extract Mg abundances from high-quality spectra more reliably than from classical LTE analysis. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/586/A120
http://The same data is accessible via the INSPECT project http://inspect.coolstars19.com
NASA Astrophysics Data System (ADS)
Manful, D. Y.; Kaule, G.; Wieprecht, S.; Rees, J.; Hu, W.
2009-12-01
Hydroelectric Power (HEP) is proving to be a good alternative to carbon based energy. In the past hydropower especially large scale hydro attracted significant criticism as a result of its impact on the environment. A new breed of hydroelectric dam is in the offing. The aim is to have as little a footprint as possible on the environment in both pre and post construction phases and thus minimize impact on biodiversity whilst producing clean renewable energy. The Bui dam is 400 MW scheme currently under development on the Black Volta River in the Bui national park in Ghana. The reservoir created by the Bui barrage is expected to impact (through inundation) the habitat of two species of hippos know to exist in the park, the Hippopotamus amphibius and the Choeropsis liberiensis. Computer-based models present a unique opportunity to assess quantitatively the impact of the new reservoir on the habitat of the target species in this case the H. amphibious. Until this undertaking, there were very few studies documenting the habitat of the H. amphibious let alone model it. The work and subsequent presentation will show the development of a habitat model for the Hippopotamus amphibius. The Habitat Information retrieval Program based on Streamflow Analysis, in short HIPStrA, is a one dimensional (1D) in-stream, spatially explicit hybrid construct that combines physico-chemical evidence and expert knowledge to forecast river habitat suitability (Hs) for the Hippopotamus amphibius. The version of the model presented is specifically developed to assess the impact of a reservoir created by a hydroelectric dam on potential dwelling areas in the Bui gorge for hippos. Accordingly, this version of HIPStrA simulates a special reservoir suitability index (Rsi), a metric that captures the”hippo friendliness” of any lake or reservoir. The impact of measured and simulated flood events as well as low flows, representing extreme events is also assessed. Recommendations are made for the operating rules of the reservoir in the post-construction phase of the dam. A great deal of work has been done on the effects of stream flow changes on fish especially salmonids. Very little work however has been done assessing the impact of hydropower schemes on aquatic mammals especially in Africa. HIPStrA is the first attempt at developing a computer-based habitat model for a large aquatic megaherbivore. The need for energy for development, the availability of large rivers and a rich biodiversity base in Africa makes a case for careful and ecological smart exploitation. The overarching aim of the study is the sustainable development of hydroelectric power through the use of methodologies and tools to rigorously assess changes in instream conditions that impact aquatic mammals.
Intraglottal velocity and pressure measurements in a hemilarynx model.
Oren, Liran; Gutmark, Ephraim; Khosla, Sid
2015-02-01
Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model. PMID:25698025
1D-Var multilayer assimilation of X-band SAR data into a detailed snowpack model
NASA Astrophysics Data System (ADS)
Phan, X. V.; Ferro-Famil, L.; Gay, M.; Durand, Y.; Dumont, M.; Morin, S.; Allain, S.; D'Urso, G.; Girard, A.
2014-10-01
The structure and physical properties of a snowpack and their temporal evolution may be simulated using meteorological data and a snow metamorphism model. Such an approach may meet limitations related to potential divergences and accumulated errors, to a limited spatial resolution, to wind or topography-induced local modulations of the physical properties of a snow cover, etc. Exogenous data are then required in order to constrain the simulator and improve its performance over time. Synthetic-aperture radars (SARs) and, in particular, recent sensors provide reflectivity maps of snow-covered environments with high temporal and spatial resolutions. The radiometric properties of a snowpack measured at sufficiently high carrier frequencies are known to be tightly related to some of its main physical parameters, like its depth, snow grain size and density. SAR acquisitions may then be used, together with an electromagnetic backscattering model (EBM) able to simulate the reflectivity of a snowpack from a set of physical descriptors, in order to constrain a physical snowpack model. In this study, we introduce a variational data assimilation scheme coupling TerraSAR-X radiometric data into the snowpack evolution model Crocus. The physical properties of a snowpack, such as snow density and optical diameter of each layer, are simulated by Crocus, fed by the local reanalysis of meteorological data (SAFRAN) at a French Alpine location. These snowpack properties are used as inputs of an EBM based on dense media radiative transfer (DMRT) theory, which simulates the total backscattering coefficient of a dry snow medium at X and higher frequency bands. After evaluating the sensitivity of the EBM to snowpack parameters, a 1D-Var data assimilation scheme is implemented in order to minimize the discrepancies between EBM simulations and observations obtained from TerraSAR-X acquisitions by modifying the physical parameters of the Crocus-simulated snowpack. The algorithm then re-initializes Crocus with the modified snowpack physical parameters, allowing it to continue the simulation of snowpack evolution, with adjustments based on remote sensing information. This method is evaluated using multi-temporal TerraSAR-X images acquired over the specific site of the Argentire glacier (Mont-Blanc massif, French Alps) to constrain the evolution of Crocus. Results indicate that X-band SAR data can be taken into account to modify the evolution of snowpack simulated by Crocus.
Analytic solutions for seismic travel time and ray path geometry through simple velocity models.
Ballard, Sanford
2007-12-01
The geometry of ray paths through realistic Earth models can be extremely complex due to the vertical and lateral heterogeneity of the velocity distribution within the models. Calculation of high fidelity ray paths and travel times through these models generally involves sophisticated algorithms that require significant assumptions and approximations. To test such algorithms it is desirable to have available analytic solutions for the geometry and travel time of rays through simpler velocity distributions against which the more complex algorithms can be compared. Also, in situations where computational performance requirements prohibit implementation of full 3D algorithms, it may be necessary to accept the accuracy limitations of analytic solutions in order to compute solutions that satisfy those requirements. Analytic solutions are described for the geometry and travel time of infinite frequency rays through radially symmetric 1D Earth models characterized by an inner sphere where the velocity distribution is given by the function V (r) = A-Br{sup 2}, optionally surrounded by some number of spherical shells of constant velocity. The mathematical basis of the calculations is described, sample calculations are presented, and results are compared to the Taup Toolkit of Crotwell et al. (1999). These solutions are useful for evaluating the fidelity of sophisticated 3D travel time calculators and in situations where performance requirements preclude the use of more computationally intensive calculators. It should be noted that most of the solutions presented are only quasi-analytic. Exact, closed form equations are derived but computation of solutions to specific problems generally require application of numerical integration or root finding techniques, which, while approximations, can be calculated to very high accuracy. Tolerances are set in the numerical algorithms such that computed travel time accuracies are better than 1 microsecond.
A Comparison of Different-Mode Fields Generated from Grounded-Wire Source Based on the 1D Model
NASA Astrophysics Data System (ADS)
Zhou, Nan-Nan; Xue, Guo-qiang; Li, Hai; Younis, M.; Hou, Dong-yang; Zhong, Hua-sen; Chen, Wei-ying; Cui, Jiang-wei
2016-02-01
Traditional TEM study mainly focuses on the generation and application of the TE field using a loop or grounded-wire source; but in recent decades, lots of efforts have been made for implementation of the TM field and even the integration of the TE field with the TM one into anomaly detection in the subsurface. However, no applicable principles have been proposed for selecting the optimal electromagnetic field for various subsurface targets. The transient electromagnetic (TEM) fields generated from grounded-wire source consist of the TE-mode response (current-carrying wire), the TE-TM mode response (grounding ends) and the combined TEM-mode response (current-carrying wire and grounding ends). This study performs a comparison of TE/TE-TM/TEM fields by generating them from grounded-wire source and testing their distribution characteristics, detection depth, and sensitivity to anomalies, using both synthetic 1D model and two field surveys in China. The comparisons demonstrate that, the detection depth of the TE-TM field is smaller than those of both the TE and combined TEM fields. Meanwhile, for electric field, the TE-TM response provides a better detection than the TEM one, but with an uneven distribution. Therefore, the TE-TM electric field requires well-designed arrangements of receiving positions when applied to real projects. For the magnetic field, the TEM response has the best detection capability compared to the TE and TE-TM ones, but is least sensitive to layer thickness and resistivity, especially for an embedded layer with low resistivity.
Differential cell proliferation in the cortex of the APPswePS1dE9 Alzheimer's disease mouse model.
Kamphuis, Willem; Orre, Marie; Kooijman, Lieneke; Dahmen, Maurice; Hol, Elly M
2012-04-01
Plaque deposition in Alzheimer's disease (AD) is known to decrease proliferation in neurogenic niches in AD mouse models, but the effects on cell proliferation and differentiation in other brain areas have not been studied in detail. We analyzed cell proliferation in the cortex of wild type (WT) and APPswePS1dE9 transgenic (AD) mice at different ages. Mice were studied shortly after the last BrdU injection (BrdU[ST]). In AD mice, the number of proliferating cells increased fourfold, coinciding with plaque appearance and its associated reactive gliosis and activation of microglia. An increase in the number of BrdU[ST]-cells expressing markers for activated microglia is underlying the enhanced proliferation. Cortical reactive astrocytes did not become proliferative since BrdU[ST]-cells were negative for different astrocyte-specific markers. The number of Olig2-positive oligodendrocyte precursor cells was unchanged. Four weeks after the last BrdU application, the number of BrdU[LT]-cells with an activated microglia signature was still enhanced in AD mice. None of the newborn cells had differentiated into oligodendrocytes, astrocytes, or neurons. On the basis of these observations, we conclude that amyloid plaque deposition increases proliferation of microglia around plaques but does not affect the proliferation of cortical oligodendrocyte precursor cells. No evidence was found for damage-induced proliferation of reactive astrocytes or for a redirected neurogenesis from the subventricular zone. The proliferation of microglia contributes to the rapid accumulation of microglia around plaques and may play a role in limitating plaque expansion. PMID:22262260
Floodplain mapping via 1D and quasi-2D numerical models in the valley of Thessaly, Greece
NASA Astrophysics Data System (ADS)
Oikonomou, Athanasios; Dimitriadis, Panayiotis; Koukouvinos, Antonis; Tegos, Aristoteles; Pagana, Vasiliki; Panagopoulos, Panayiotis-Dionisios; Mamassis, Nikolaos; Koutsoyiannis, Demetris
2013-04-01
The European Union Floods Directive defines a flood as 'a covering by water of land not normally covered by water'. Human activities, such as agriculture, urban development, industry and tourism, contribute to an increase in the likelihood and adverse impacts of flood events. The study of the hydraulic behaviour of a river is important in flood risk management. Here, we investigate the behaviour of three hydraulic models, with different theoretical frameworks, in a real case scenario. The area is located in the Penios river basin, in the plain of Thessaly (Greece). The three models used are the one-dimensional HEC-RAS and the quasi two-dimensional LISFLOOD-FP and FLO-2D which are compared to each other, in terms of simulated maximum water depth as well as maximum flow velocity, and to a real flood event. Moreover, a sensitivity analysis is performed to determine how each simulation is affected by the river and floodplain roughness coefficient, in terms of flood inundation.
NASA Astrophysics Data System (ADS)
Augustins, L.; Billardon, R.; Hild, F.
2015-06-01
One of the critical points of the thermomechanical fatigue design process is the correct description of the cyclic behavior of the material. This work focuses on the material of automotive brake discs, namely flake graphite cast iron. The specificity of this material is its asymmetric behavior under tensile and compressive loadings, which is due to the shape of graphite that acts as small cracks. Multiscale models inspired from the literature are first presented. They lead to a good description of the material behavior under cyclic loadings. An elastoviscoplastic constitutive model is then proposed in a one-dimensional setting in order to accurately describe cyclic tests from room temperature up to 600 C.
The USGS 3D Seismic Velocity Model for Northern California
NASA Astrophysics Data System (ADS)
Brocher, T. M.; Aagaard, B.; Simpson, R. W.; Jachens, R. C.
2006-12-01
We present a new regional 3D seismic velocity model for Northern California for use in strong motion simulations of the 1906 San Francisco and other earthquakes. The model includes compressional-wave velocity (Vp), shear-wave velocity (Vs), density, and intrinsic attenuation (Qp, Qs). These properties were assigned for each rock type in a 3D geologic model derived from surface outcrops, boreholes, gravity and magnetic data, and seismic reflection, refraction, and tomography studies. A detailed description of the model, USGS Bay Area Velocity Model 05.1.0, is available online [http://www.sf06simulation.org/geology/velocitymodel]. For ground motion simulations Vs and Qs are more important parameters than Vp and Qp because the strongest ground motions are generated chiefly by shear and surface wave arrivals. Because Vp data are more common than Vs data, however, we first developed Vp versus depth relations for each rock type and then converted these to Vs versus depth relations. For the most important rock types in Northern California we compiled measurements of Vp versus depth using borehole logs, laboratory measurements on hand samples, seismic refraction profiles, and tomography models. These rock types include Salinian and Sierran granitic rocks, metagraywackes and greenstones of the Franciscan Complex, Tertiary and Mesozoic sedimentary and volcanic rocks, and Quaternary and Holocene deposits (Brocher, USGS OFR 05-1317, 2005). Vp versus depth curves were converted to Vs versus depth curves using new empirical nonlinear relations between Vs and Vp (Brocher, BSSA, 2005). These relations, showing that Poisson's ratio is a nonlinear function of Vp, were similarly based on compilations of diverse Vs and Vp measurements on a large suite of rock types, mainly from California and the Pacific Northwest. The model is distributed in a discretized form with routines to query the model using C++, C, and Fortran 77 programming languages. The geologic model was discretized at higher resolution near the surface (100m horizontal and 25m vertical) compared with depth (800m horizontal and 200m vertical). The model contains material properties at nearly 190 million locations and is stored as an Etree database (Tu et al., 2003). The query routines provide a simple interface to the database, returning the material properties for a given latitude, longitude, and elevation or depth.
Code package MAG c user tool for numerical modeling of 1D shock wave and dynamic processes in solids
NASA Astrophysics Data System (ADS)
Rudenko, Vladimir; Shaburov, Michail
1999-06-01
Design and theoretical and numerical preparation of shock wave experiments require, as a rule, conduction of a large amount of calculations. Usually preparation of a problem for numerical solution, calculation and processing of the results is done be programmers c mathematicians. The appearance of powerful personal computers and interface tools allows to develop such user-oriented programs that a researcher can handle them without the help of a mathematician, even if he does not have special programming background. Code package MAG for numerical solution of 1D system of equations of hydrodynamics, elastoplastics, heat conduction and magnetic hydrodynamic. A number of modern models of elastoplastics and kinetics of power materials is implemented in it. The package includes libraries of equations of state, thermal physical and electromagnetic properties of substances. The code package is an interactive visual medium providing a user with the following capabilities: ? Input and edit initial data for a problem; ? Calculate separate problems, as well as series of problems with a possibility of automatic variation of parameters; ? View the modeled phenomena dynamically using the means of visualization; ? Control the process of calculation: terminate the calculation, change parameters, make express-processing of the results, continue the calculation etc.; ? Process the numerical results producing final plots and tables; ? Record and store numerical results in databases, including the formats supported by Microsoft Word, Acces, Exel; ? Make dynamic visual comparison of the results of several simultaneous calculations; ? Carry out automatic numerical optimization of a selected experimental scheme. The package is easy in use, allows prompt input and convenient information processing. The validity of numerical results obtained with the package MAG has been proved by numerous hydrodynamic experiments and comparisons with numerical results from similar programs. The package was developed using the means of the integrated medium of visual development of applications Delphi-4 and contains about 50000 lines of initial code in Object Pascal programming language. An executable file runs on IBM-compatible personal computers under operation systems Windows-NT, Windows-95,-98.The code package MAG is under constant improvement and development. A tutorial package on physics of solids for high institutions and scientific research centers is developed on its basis. The package may be adjusted and improved in collaboration with interested users.
NASA Astrophysics Data System (ADS)
Daskalakis, Nikos; Krol, Maarten; Kanakidou, Maria
2014-05-01
Hydroxyl radical (OH) is one of the main oxidants in the troposphere. It drives photochemistry and thus cleaning the troposphere from ubiquitous reactive compounds that impact on the environment and the ecosystems. Due to the high reactivity of OH, both its atmospheric measurements and the simulations of its concentrations remain challenging. Recent measurements have shown significant mismatch with atmospheric simulations based on current knowledge of organic atmospheric chemistry. New degradations pathways in the oxidation chemistry of isoprene, initiated by OH radical, have been proposed based on chamber experiments and theoretical calculations. These pathways regenerate OH and are actually missing from global chemistry and transport models (CTMs) that show an underestimation of OH when compared to the limited number of observations. In this study we use the 1-dimensional model Wageningen University Single Column Model (WUSCM) to investigate, evaluate and reduce for use in global CTMs, isoprene oxidation pathways that are leading to OH regeneration and were recently proposed in literature applied on the PEGASOS 2012 campaign over Cabauw, Netherlands. The WUSCM simulates boundary layer meteorology (radiation, land-atmosphere interaction and mixing) and can support different chemistry schemes coupled with the KPP solver. The chemistry scheme used in the TM4-ECPL global model chemical scheme is the basis for the development and testing of the new pathways of isoprene chemistry.
NASA Astrophysics Data System (ADS)
Mackenzie, G. D.; Maguire, P. K. H.; Denton, P.; Morgan, J.; Warner, M.
2001-08-01
A 20 element seismic array was deployed onshore across the 65 Ma. Chicxulub impact crater, Yucatan, Mexico as part of an integrated onshore-offshore seismic experiment. Fundamental and higher mode group velocity dispersion curves have been calculated through the application of multiple filter and phase match techniques to high frequency (0.2-5 Hz) Rayleigh waves recorded on the array and originating from local quarry blasts. Several 1-D shear wave velocity-depth models across the crater have been produced through the optimisation of these dispersion curves using a genetic algorithm. These models are resolved to a depth of circa 3.5 km and provide information on the velocity structure of the upper crater sequences and post-impact sedimentation, placing constraints on crater morphology and post impact sedimentation patterns. Shear wave velocities of 0.8-2.2 km s -1 are modelled within the interpreted Tertiary sedimentary sequence. An inverted velocity gradient is observed over the upper 300 m of the sediments with the exception of a circular region across the crater centre, suggesting the crater influenced sedimentation throughout the Tertiary. The base of the Tertiary sequence is modelled at circa 1-1.5 km depth where a thin layer with velocities up to 30% higher than the overlying sediments is observed. Immediately below this high velocity layer a circa 200 m thick low velocity zone with velocities of 1.0-2.3 km s -1 is interpreted as a layer of suevitic impact breccia. A shallowing to the base of this layer to circa 1.3 km depth between 30 and 40 km radius from the crater centre would be consistent with the existence of a peak ring occurring as a topographic high above the crater floor.
Sleipner CCS site: velocity and attenuation model from seismic tomography
NASA Astrophysics Data System (ADS)
Rossi, G.; Chadwick, R. A.; Williams, G. A.
2012-04-01
The results of the travel-time and frequency shift tomographic inversion of the seismic data from one of the high-resolution lines acquired in 2006 on the Sleipner CO2 geological storage site are here presented. The work has been performed within the European project CO2ReMoVe, to produce an accurate model in-depth, of both seismic velocities and attenuation, to constrain better the quantification studies of the project's partners. Tomographic techniques have the advantage of not assuming horizontal layering or uniform lateral velocities, and of enabling an easy comparison of models, even if resulting from seismic data acquired with different geometries, unavoidable in a time-lapse data set. Through an iterative process, the differences in travel-times between observed direct, reflected or refracted arrivals and the same, calculated on a discrete model, with a ray-tracing based on the Fermat's principle, are minimized. Other minimization procedures provide the reflector/refractor geometries in -depth. Analogously, in attenuation tomography, the minimization process takes into account the observed and calculated spectral-centroid frequency-shift, due to the loss of the highest frequency of the seismic wave, while crossing an attenuating medium. The result is a seismic quality factor (Q) model in-depth, and hence of the attenuation that is known to be more sensitive to subtle changes in physical properties than seismic velocity. The model is across the center of the CO2 plume, on the in-line 1838, and is constituted by nine layers, four resulting by a preliminary analysis of the pre-injection 1994 data set, i.e. seabed, a strong reflection in the overburden and the top and bottom of the Utsira Sand, plus additional five horizons, four of which within Utsira Sands, and one just above the top of it. The layers within the reservoir are very close to each other and in some cases they merge together laterally. The accumulation of CO2 in the uppermost layer of the reservoir, observed by other analyses, is confirmed by our analysis, whereas within the plume, lateral variations of both seismic velocity and Q values are observed. The presence of fine shale lenses, and their impact on the CO2 distribution within the plume may be the reason for these lateral variations. The seismic velocity and Q tomographic values have been compared with the theoretical curves from petrophysics studies, so to give to the results an interpretation in terms of effective variations in CO2 saturation and heterogeneity within the plume.
Santos-Villalobos, Hector J; Gregor, Jens; Bingham, Philip R
2014-01-01
At the present, neutron sources cannot be fabricated small and powerful enough in order to achieve high resolution radiography while maintaining an adequate flux. One solution is to employ computational imaging techniques such as a Magnified Coded Source Imaging (CSI) system. A coded-mask is placed between the neutron source and the object. The system resolution is increased by reducing the size of the mask holes and the flux is increased by increasing the size of the coded-mask and/or the number of holes. One limitation of such system is that the resolution of current state-of-the-art scintillator-based detectors caps around 50um. To overcome this challenge, the coded-mask and object are magnified by making the distance from the coded-mask to the object much smaller than the distance from object to detector. In previous work, we have shown via synthetic experiments that our least squares method outperforms other methods in image quality and reconstruction precision because of the modeling of the CSI system components. However, the validation experiments were limited to simplistic neutron sources. In this work, we aim to model the flux distribution of a real neutron source and incorporate such a model in our least squares computational system. We provide a full description of the methodology used to characterize the neutron source and validate the method with synthetic experiments.
NASA Astrophysics Data System (ADS)
Zulkoffli, Zuliani; Abu Bakar, Elmi
2016-02-01
This paper present pose estimation relation of CAD model object and Projection Real Object (PRI). Image sequence of PRI and CAD model rotate on z axis at 10 degree interval in simulation and real scene used in this experiment. All this image is go through preprocessing stage to rescale object size and image size and transform all the image into silhouette. Correlation of CAD and PRI image is going through in this stage. Magnitude spectrum shows a reliable value in range 0.99 to 1.00 and Phase spectrum correlation shows a fluctuate graph in range 0.56 - 0.97. Euclidean distance correlation graph for CAD and PRI shows 2 zone of similar value due to almost symmetrical object shape. Processing stage of retrieval inspected PRI image in CAD database was carried out using range phase spectrum and maximum magnitude spectrum value within ±10% tolerance. Additional processing stage of retrieval inspected PRI image using Euclidean distance within ±5% tolerance also carried out. Euclidean matching shows a reliable result compared to range phase spectrum and maximum magnitude spectrum value by sacrificing more than 5 times processing time.
NASA Astrophysics Data System (ADS)
Liu, Gang; Kojima, Keitaro; Yoshimura, Kei; Oka, Akira
2014-11-01
The oxygen isotopic ratio in the seawater (?18Osw) recorded in ?18O of coral skeleton for several centuries in tropical regions is an important variable for reconstructing the past climate. However, the relationship between ?18Osw and hydrological balance has not been clearly uncovered yet. In this study, a one-dimensional ocean budget model forced by the global quasi-reanalysis isotope data, which is the output of an isotope-incorporated global spectral model, is employed to simulate ?18Osw. The results from the simulations are compared with 31 coral records in tropical oceanic regions. The 1-D model successfully reproduces ?18Osw in 21 coral records, indicating these corals have the potential to reconstruct the local hydrological budget. The results also confirm that the reproducibility of the 1-D model generally increases with the annual precipitation variability. However, in the regions where the precipitation variability is less, it is more difficult to reconstruct climatic information from the ?18Osw, since the nonlocal physical processes unaccounted for in the 1-D model may affect ?18Osw. The sensitivity analysis of the 1-D model shows that in tropical oceanic regions, the large-scale precipitation is the dominant factor for ?18Osw, confirming that ?18Osw recorded in the coral records is a proxy for the precipitation anomaly. This study implies that ?18Osw is more closely associated with precipitation and local water isotope budget in tropical oceanic regions than elsewhere, and that the 1-D model is a useful approach for the proxy interpretation in tropical oceanic regions.
NASA Astrophysics Data System (ADS)
Kirkby, A.; Heinson, G.; Holford, S.; Thiel, S.
2015-06-01
We present 1D anisotropic inversion of magnetotelluric (MT) data as a potential tool for mapping structural permeability in sedimentary basins. Using 1D inversions of a 171 site, broadband MT data set from the Koroit region of the Otway Basin, Victoria, Australia, we have delineated an electrically anisotropic layer at approximately 2.5 to 3.5 km depth. The anisotropy strike is consistent between stations at approximately 160° east of north. The depth of anisotropy corresponds to the top depth of the Lower Cretaceous Crayfish Group, and the anisotropy factor increases from west to east. We interpret the anisotropy as resulting from north-northwest oriented, fluid-filled fractures resulting in enhanced electrical and hydraulic conductivity. This interpretation is consistent with permeability data from well formation tests. It is also consistent with the orientation of mapped faults in the area, which are optimally oriented for reactivation in the current stress field.
NASA Astrophysics Data System (ADS)
Molin, P.; Pazzaglia, F. J.; Dramis, F.
In active tectonic regions, topography is the result of the interactions of tectonics that deform and move rocks and surface processes that erode rocks. So first-order topo- graphic features including relief, drainage patterns, and stream gradient slope repre- sent ways to quantitatively characterize the interaction between tectonics and geomor- phology, providing a basis for modelling landscape evolution. We characterize tectonic processes through geomorphic investigations in the Sila Massif (Calabria, Italy). Here the Apennines are a narrow and rugged chain, composed of relatively uniform rock- type (crystalline Paleozoic plutonic and metamorphic rocks), that appears to have been affected by extensional tectonics since the early Pliocene and that were rapidly raised above sea level in the Pleistocene. Our study examines the tectonic geomorphology of the northern portion of the Sila Massif focusing on the general topographic met- rics, drainage patterns, and river longitudinal profiles. Our goal is to develop a general picture of the influence of extensional tectonics in the landscape evolution of the Sila Massif in the context of the recent and rapid uplift (0.6-1 mm/yr in the last 700.000 yrs) of the entire Italian peninsula. Our main data base is composed of map and DEM- based topographic analyses, supplemented with field investigations. These data are consistent with a landscape dominated by intra-chain extensional tectonics including block tilting and footwall flexure, superimposed on a regional rock and surface uplift. In particular the flexure of the extensional fault that surround the Sila Massif could have generated the bowl-shape plateau presently located on the Sila top. We develop a simple, flexural,1-D geodynamic model (Turcott and Schubert, 1982) to explain the uplift of the Sila Massif flank. The topographic imprint of the long-wavelength Qua- ternary uplift of the massif is removed by filtering the topography with a low pass filter. The flexural analysis is then performed on the residual topography which nor- malizes the elevation of the plateau flank to sea level. The model generates a plate elastic thickness between 3500-4000 m. This value is consistent with the ones found in the Basin and Range and in Tibet (Masek et al., 1994), confirming a possible flexu- ral isostatic origin of the Sila plateau rim. The uplifted plateau flank fixes the drainage divide and hinders the drainages from integrating into the plateau interior and fully dissecting the rolling upland surface. As a result, the clear geomorphic expression of active normal faulting is well evident around Sila, but is masked within the massif it- 1 self allowing the general perception that it is a vertically uplifted plateau. Furthermore, the marine terrace data on the Ionian coast that suggest an uplift rate of 0.6 mm/yr in the last 350.000 years confirm the broad uplift of the area. These results support the notion of a old landscape less rugged than the modern one that is coincident with a slow uplift related to syn- and late-orogenic exhumation, the eastward migration of the arc, and roll-back in the subducting slab. This old landscape have been preserved by the footwall flexure of the extensional faults surrounding the Sila Massif and uplifted in the Pleistocene as the wavelength of deformation broadened. References Masek J.G., Isacks B.L., and Fielding E.J. (1994) U Rift flank uplift in Tibet: evidence for a viscous lower crust, Tectonics, 13, 659-667. Turcotte D. L. and Schubert G. (1982) U Geodynamics U Applications of continuum physics to ge- ological problems, John Wiley and Sons, pp.450 2
NASA Astrophysics Data System (ADS)
Udodov, Vladimir; Katanov Khakas State Univ Team
2014-03-01
Symmetry breaking transitions. The phenomenological (L.D.Landau, USSR, 1937) way to describe phase transitions (PT's). Order parameter and loss of the symmetry. The second derivative of the free energy changes jump wise at the transition, i.e. we have a mathematical singularity and second order PT (TC>0). Extremes of free energy. A point of loss of stability of the symmetrical phase. The eigenfrequency of PT and soft mode behavior. The conditions of applicability of the Landau theory (A.Levanyuk, 1959, V.Ginzburg, 1960). 1D Ising model and exact solution by a transfer matrix method. Critical exponents in the L.Landau PT's theory and for 1D Ising model. Scaling hypothesis (1965) for 1D Ising model with zero critical temperature. The order of PT in 1D Ising model in the framework of the R.Baxter approach. The anthropic principle and the dimension of the space. Why do we have a three-dimensional space? Big bang, the cosmic vacuum, inflation and PT's. Higgs boson and symmetry breaking transitions. Author acknowledges the support of Katanov Khakas State University.
Stochastic optimal velocity model and its long-lived metastability.
Kanai, Masahiro; Nishinari, Katsuhiro; Tokihiro, Tetsuji
2005-09-01
In this paper, we propose a stochastic cellular automaton model of traffic flow extending two exactly solvable stochastic models, i.e., the asymmetric simple exclusion process and the zero range process. Moreover, it is regarded as a stochastic extension of the optimal velocity model. In the fundamental diagram (flux-density diagram), our model exhibits several regions of density where more than one stable state coexists at the same density in spite of the stochastic nature of its dynamical rule. Moreover, we observe that two long-lived metastable states appear for a transitional period, and that the dynamical phase transition from a metastable state to another metastable/stable state occurs sharply and spontaneously. PMID:16241502
Comment on "Analysis of optimal velocity model with explicit delay".
Davis, L C
2002-09-01
The effect of including an explicit delay time (due to driver reaction) on the optimal velocity model is studied. For a platoon of vehicles to avoid collisions, many-vehicle simulations demonstrate that delay times must be well below the critical delay time determined by a linear analysis for the response of a single vehicle. Safe platoons require rather small delay times, substantially smaller than typical reaction times of drivers. The present results do not support the conclusion of Bando et al. [M. Bando, K. Hasebe, K. Nakanishi, and A. Nakayama, Phys. Rev. E 58, 5429 (1998)] that explicit delay plays no essential role. PMID:12366309
Traveling waves in an optimal velocity model of freeway traffic.
Berg, P; Woods, A
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137]. PMID:11308709
Traveling waves in an optimal velocity model of freeway traffic
NASA Astrophysics Data System (ADS)
Berg, Peter; Woods, Andrew
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].
NASA Astrophysics Data System (ADS)
Gems, B.; Achleitner, S.; Plrer, M.; Schberl, F.; Huttenlau, M.; Aufleger, M.
2012-12-01
Sediment transport in mountain rivers and torrents is a substantial process within the assessment of flood related hazard potential and vulnerability in alpine catchments. Focusing on fluvial transport processes, river bed erosion and deposition considerably affects the extent of inundation. The present work deals with scenario-specific bed-load transport modelling in a large alpine valley in the Austrian Alps. A routing scheme founding on empirical equations for the calculation of transport capacities, incipient motion conditions and drag forces is set up and applied to the case study area for two historic flood events. The required hydraulic data result from a distributed hydrological-1-D-hydraulic model. Hydraulics and bed-load transport are simulated sequentially providing a technically well-founded and feasible methodology for the estimation of bed-load transport rates during flood events.
Liu, Yanying; Hettinger, Casey L; Zhang, Dong; Rezvani, Khosrow; Wang, Xuejun; Wang, Hongmin
2014-04-01
Alzheimer's disease (AD), the most common cause of dementia, is neuropathologically characterized by accumulation of insoluble fibrous inclusions in the brain in the form of intracellular neurofibrillary tangles and extracellular senile plaques. Perturbation of the ubiquitin-proteasome system (UPS) has long been considered an attractive hypothesis to explain the pathogenesis of AD. However, studies on UPS functionality with various methods and AD models have achieved non-conclusive results. To get further insight into UPS functionality in AD, we have crossed a well-documented APPswe/PS1dE9 AD mouse model with a UPS functionality reporter, GFPu, mouse expressing green fluorescence protein (GFP) fused to a constitutive degradation signal (CL-1) that facilitates its rapid turnover in conditions of a normal UPS. Our western blot results indicate that GFPu reporter protein was accumulated in the cortex and hippocampus, but not striatum in the APPswe/PS1dE9 AD mouse model at 4 weeks of age, which is confirmed by fluorescence microscopy and elevated levels of p53, an endogenous UPS substrate. In accordance with this, the levels of ubiquitinated proteins were elevated in the AD mouse model. These results suggest that UPS is either impaired or functionally insufficient in specific brain regions in the APPswe/PS1dE9 AD mouse model at a very young age, long before senile plaque formation and the onset of memory loss. These observations may shed new light on the pathogenesis of AD. PMID:24363091
NASA Astrophysics Data System (ADS)
Maher Abourabia, Aly; Hassan, Kawsar Mohammad; Abo-Elghar, Eman Mohammad
2015-02-01
We investigate a bio-system composed of a shape memory alloy (SMA) immersed and subjected to heat convection in a blood vessel, affected by heart beats that create a wave motion of long wavelength. The tackled model in (2+1)-D is based on the continuity and momentum equations for the fluid phase, besides; the state of the SMA are described via previous works in the form of statistical distributions of energy for both Martensite and Austenite phases. The solution based on the reductive perturbation technique gives a thermal diffusion-like equation as a key for expressing the temperature and velocity components of the blood. In terms of two cases concerning the difference between the wave numbers in the perpendicular directions, it is found that the system's temperature increases nonlinearly from a minimum initial temperature 293 K (20 C) up to a maximum value about 316.68 K (43.68 C), then tends to decrease along the blood flow (anisotropy of K and L) direction. In both cases it is observed that the SMA acquires most of this temperature raising not the blood because of its conventional biological limits (37-40 C). The range of the heart beats wave numbers characteristic for each person plays an important role in realizing phase changes in the anisotropic case leading to the formation of the hysteresis loops Martensite-Austenite-Martensite or vice versa, according to the energy variation. The entropy generation ? is investigated for the system (Blood + SMA), it predicts that along the flow direction the system gains energy convectively up to a maximum value, then reverses his tendency to gradually loosing energy passing by the equilibrium state, then the system looses energy to the surroundings by the same amount which was gained beforehand. The loss diminishes but stops before arriving to equilibrium again. For certain differences in wave numbers the system starts to store energy again after it passes by the state of equilibrium for the second time. In the curves of ? the common points of intersections can be looked for as the positions where the phase changes take place. It is observed that the effect of heat transfer is dominated over the viscous dissipation substantially; this is illustrated by the irreversibility distribution ratio ? and the Bejan number. On the other hand this is assured by the smallness of the ratio between the initial effect of shear viscosity to the initial thermal effect in the alloy (? ? 10-8). Furthermore, this allows the SMA to reveal the properties of phase change in order, for instance, to prevent the passage of large clots from reaching the lungs.
Velocity response curves demonstrate the complexity of modeling entrainable clocks.
Taylor, Stephanie R; Cheever, Allyson; Harmon, Sarah M
2014-12-21
Circadian clocks are biological oscillators that regulate daily behaviors in organisms across the kingdoms of life. Their rhythms are generated by complex systems, generally involving interlocked regulatory feedback loops. These rhythms are entrained by the daily light/dark cycle, ensuring that the internal clock time is coordinated with the environment. Mathematical models play an important role in understanding how the components work together to function as a clock which can be entrained by light. For a clock to entrain, it must be possible for it to be sped up or slowed down at appropriate times. To understand how biophysical processes affect the speed of the clock, one can compute velocity response curves (VRCs). Here, in a case study involving the fruit fly clock, we demonstrate that VRC analysis provides insight into a clock׳s response to light. We also show that biochemical mechanisms and parameters together determine a model׳s ability to respond realistically to light. The implication is that, if one is developing a model and its current form has an unrealistic response to light, then one must reexamine one׳s model structure, because searching for better parameter values is unlikely to lead to a realistic response to light. PMID:25193284
NASA Astrophysics Data System (ADS)
Wittkowski, M.; Chiavassa, A.; Freytag, B.; Scholz, M.; Höfner, S.; Karovicova, I.; Whitelock, P. A.
2016-03-01
Aims: We aim at comparing spectro-interferometric observations of Mira variable asymptotic giant branch (AGB) stars with the latest 1D dynamic model atmospheres based on self-excited pulsation models (CODEX models) and with 3D dynamic model atmospheres including pulsation and convection (CO5BOLD models) to better understand the processes that extend the molecular atmosphere to radii where dust can form. Methods: We obtained a total of 20 near-infrared K-band spectro-interferometric snapshot observations of the Mira variables o Cet, R Leo, R Aqr, X Hya, W Vel, and R Cnc with a spectral resolution of about 1500. We compared observed flux and visibility spectra with predictions by CODEX 1D dynamic model atmospheres and with azimuthally averaged intensities based on CO5BOLD 3D dynamic model atmospheres. Results: Our visibility data confirm the presence of spatially extended molecular atmospheres located above the continuum radii with large-scale inhomogeneities or clumps that contribute a few percent of the total flux. The detailed structure of the inhomogeneities or clumps show a variability on time scales of 3 months and above. Both modeling attempts provided satisfactory fits to our data. In particular, they are both consistent with the observed decrease in the visibility function at molecular bands of water vapor and CO, indicating a spatially extended molecular atmosphere. Observational variability phases are mostly consistent with those of the best-fit CODEX models, except for near-maximum phases, where data are better described by near-minimum models. Rosseland angular diameters derived from the model fits are broadly consistent between those based on the 1D and the 3D models and with earlier observations. We derived fundamental parameters including absolute radii, effective temperatures, and luminosities for our sources. Conclusions: Our results provide a first observational support for theoretical results that shocks induced by convection and pulsation in the 3D CO5BOLD models of AGB stars are roughly spherically expanding and of similar nature to those of self-excited pulsations in 1D CODEX models. Unlike for red supergiants, the pulsation- and shock-induced dynamics can levitate the molecular atmospheres of Mira variables to extensions that are consistent with observations. Based on observations made with the VLT Interferometer (VLTI) at Paranal Observatory under program IDs 082.D-0723, 084.D-0839, 088.D-0160, 090.D-0817, and 091.D-0765.
Unsteady velocity measurements in a realistic intracranial aneurysm model
NASA Astrophysics Data System (ADS)
Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György
2012-01-01
The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.
Modeling the velocity field during Haines jumps in porous media
NASA Astrophysics Data System (ADS)
Armstrong, Ryan T.; Evseev, Nikolay; Koroteev, Dmitry; Berg, Steffen
2015-03-01
When nonwetting fluid displaces wetting fluid in a porous rock many rapid pore-scale displacement events occur. These events are often referred to as Haines jumps and any drainage process in porous media is an ensemble of such events. However, the relevance of Haines jumps for larger scale models is often questioned. A common counter argument is that the high fluid velocities caused by a Haines jump would average-out when a bulk representative volume is considered. In this work, we examine this counter argument in detail and investigate the transient dynamics that occur during a Haines jump. In order to obtain fluid-fluid displacement data in a porous geometry, we use a micromodel system equipped with a high speed camera and couple the results to a pore-scale modeling tool called the Direct HydroDynamic (DHD) simulator. We measure the duration of a Haines jump and the distance over which fluid velocities are influenced because this sets characteristic time and length scales for fluid-fluid displacement. The simulation results are validated against experimental data and then used to explore the influence of interfacial tension and nonwetting phase viscosity on the speed of a Haines jump. We find that the speed decreases with increasing nonwetting phase viscosity or decreasing interfacial tension; however, for the same capillary number the reduction in speed can differ by an order of magnitude or more depending on whether viscosity is increased or interfacial tension is reduced. Therefore, the results suggest that capillary number alone cannot explain pore-scale displacement. One reason for this is that the interfacial and viscous forces associated with fluid-fluid displacement act over different length scales, which are not accounted for in the pore-scale definition of capillary number. We also find by analyzing different pore morphologies that the characteristic time scale of a Haines jump is dependent on the spatial configuration of fluid prior to an event. Simulation results are then used to measure the velocity field surrounding a Haines jump and thus, measure the zone of influence, which extends over a distance greater than a single pore. Overall, we find that the time and length scales of a Haines jump are inversely proportional, which is important to consider when calculating the spatial and temporal averages of pore-scale parameters during fluid-fluid displacement.
NASA Astrophysics Data System (ADS)
Pancha, A.; Pullammanappallil, S.; Louie, J. N.; DePolo, C. M.
2012-12-01
Estimation of shallow and deep shear velocity is a key element in the assessment of sites for potential earthquake ground shaking, damage, and the calibration of recorded ground motions. We assess shear-wave velocities across the deepest portion of the Reno-area basin as defined by gravity, as well as at twelve seismic stations in the near-field region of the 26 April 2008 Mw 5.0 Mogul, Nevada earthquake 12 km west of Downtown Reno. To date, no permanent seismic instrumentation is located over this thickest portion of the Reno-area basin and little structural and velocity data is available. Existing velocity models for the region are limited in resolution to intervals of 1 km to 3 km. As a result, 3D basin details are currently insufficient for scenario modeling and ShakeZoning, essential components of seismic hazard evaluation. These efforts contribute towards development of the Western Basin and Range Community Velocity Model and the Reno-Carson urban hazard map. As part of a NEHRP-IMW grant, we measured shear velocities to depths of 500 m using refraction-microtremor (ReMi) arrays across this portion of the basin with 50 m depth resolution. This was achieved through the deployment of 30 stand alone wireless instruments in arrays 2.9 to 5.8 km long, to record ambient urban noise. Data were obtained along two parallel east-west arrays and one shorter north-south array. The ReMi technique was employed to obtain 1D velocity profiles as a function of depth across each array from these noise records. To further characterize and map lateral velocity heterogeneity beneath the arrays, subsets of instruments were used to obtain a series of 1D soundings that were then interpolated to obtain a 2D structural representation of shear-wave velocities. The 1D and 2D velocity soundings along each array are combined produce a 3D shear-velocity volume delineating the deep velocity structure of the basin. Observed lateral velocity variations were identified and correlated with the locations of hypothesized faults in an attempt to constrain their locality. The 26 April 2008 Mw 5.0 Mogul, Nevada earthquake, located at a shallow depth of 3.1 km, was the largest event during a shallow earthquake swarm that began in February 2008 and persisted for several months. The largest peak acceleration vector during this mainshock was recorded at station MOGL (1.19g; 1164 cm/s2), which is among the 25 largest recorded earthquake accelerations worldwide. Strong ground motions were observed at the four closest stations installed at the time of the mainshock, which exceed accelerations of 300 cm/s2 and velocities of 14 cm/s. Both shear-wave (ReMi) and P-wave (refraction) techniques were used to characterize and map lateral velocity heterogeneity beneath the twelve near-field seismic sites. 2D shear-velocity sections together with 2D P-wave refraction tomography sections show complex site conditions beneath these stations. Some of these sites may be crossed by local faults, and the velocity sections reflect this possibility. These resultant site condition assessments at these near-filed sites will contribute towards quantification of local site response and calibration of the high peak ground motions recorded during both the mainshock event and the foreshock/aftershock swarm events.
Authentication Based on Pole-zero Models of Signature Velocity.
Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad
2013-10-01
With the increase of communication and financial transaction through internet, on-line signature verification is an accepted biometric technology for access control and plays a significant role in authenticity and authorization in modernized society. Therefore, fast and precise algorithms for the signature verification are very attractive. The goal of this paper is modeling of velocity signal that pattern and properties is stable for persons. With using pole-zero models based on discrete cosine transform, precise method is proposed for modeling and then features is founded from strokes. With using linear, parzen window and support vector machine classifiers, the signature verification technique was tested with a large number of authentic and forgery signatures and has demonstrated the good potential of this technique. The signatures are collected from three different database include a proprietary database, the SVC2004 and the Sabanci University signature database benchmark databases. Experimental results based on Persian, SVC2004 and SUSIG databases show that our method achieves an equal error rate of 5.91%, 5.62% and 3.91% in the skilled forgeries, respectively. PMID:24696797
Modelling nonstationary Doppler noise in exoplanetary radial velocity data
NASA Astrophysics Data System (ADS)
Baluev, Roman V.
2015-08-01
We construct a new class of analytic nonstationary noise models for exoplanetary Doppler data. The observable correlated noise is represented as a convolution of a parent activity process with a given memory function. The model honours the casuality principle, meaning that only past values of the activity may affect the observable value. This model does not approximate detailedly any real stellar activity phenomena, but it becomes mathematically simple, simultaneously satisfying the basic natural principles of physical sensibility and self-consistency.Additionally, we develop a new type of periodograms that can be used to detect periodic modulations in the Doppler noise characteristics, rather than in the observed radial velocity curve itself. We present first results of applying this technique to public Doppler time series available for a set of planet-hosting stars.This work was supported by the Russian Foundation for Basic Research (project No. 14-02-92615 KO_a), the UK Royal Society International Exchange grant IE140055, by the President of Russia grant for young scientists (No. MK-733.2014.2), by the programme of the Presidium of Russian Academy of Sciences P21, and by the Saint Petersburg State University research grant 6.37.341.2015.
Modeling Normal Shock Velocity Curvature Relation for Heterogeneous Explosives
NASA Astrophysics Data System (ADS)
Yoo, Sunhee; Crochet, Michael; Pemberton, Steve
2015-06-01
The normal shock velocity and curvature, Dn(?) , relation on a detonation shock surface has been an important functional quantity to measure to understand the shock strength exerted against the material interface between a main explosive charge and the case of an explosive munition. The Dn(?) relation is considered an intrinsic property of an explosive, and can be experimentally deduced by rate stick tests at various charge diameters. However, experimental measurements of the Dn(?) relation for heterogeneous explosives such as PBXN-111 are challenging due to the non-smoothness and asymmetry usually observed in the experimental streak records of explosion fronts. Out of the many possibilities, the asymmetric character may be attributed to the heterogeneity of the explosives, a hypothesis which begs two questions: (1) is there any simple hydrodynamic model that can explain such an asymmetric shock evolution, and (2) what statistics can be derived for the asymmetry using simulations with defined structural heterogeneity in the unreacted explosive? Saenz, Taylor and Stewart studied constitutive models for derivation of the Dn(?) relation on porous `homogeneous' explosives and carried out simulations in a spherical coordinate frame. In this paper, we extend their model to account for `heterogeneity' and present shock evolutions in heterogeneous explosives using 2-D hydrodynamic simulations with some statistical examination. (96TW-2015-0004)
Authentication Based on Pole-zero Models of Signature Velocity
Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad
2013-01-01
With the increase of communication and financial transaction through internet, on-line signature verification is an accepted biometric technology for access control and plays a significant role in authenticity and authorization in modernized society. Therefore, fast and precise algorithms for the signature verification are very attractive. The goal of this paper is modeling of velocity signal that pattern and properties is stable for persons. With using pole-zero models based on discrete cosine transform, precise method is proposed for modeling and then features is founded from strokes. With using linear, parzen window and support vector machine classifiers, the signature verification technique was tested with a large number of authentic and forgery signatures and has demonstrated the good potential of this technique. The signatures are collected from three different database include a proprietary database, the SVC2004 and the Sabanci University signature database benchmark databases. Experimental results based on Persian, SVC2004 and SUSIG databases show that our method achieves an equal error rate of 5.91%, 5.62% and 3.91% in the skilled forgeries, respectively. PMID:24696797
A transport model of the turbulent scalar-velocity
NASA Technical Reports Server (NTRS)
Amano, R. S.; Goel, P.; Chai, J. C.
1987-01-01
Performance tests of the third-order turbulence closure for predictions of separating and recirculating flows in backward-facing steps were studied. Computations of the momentum and temperature fields in the flow domain being considered entail the solution of time-averaged transport equations containing the second-order turbulent fluctuating products. The triple products, which are responsible for the diffusive transport of the second-order products, attain greater significance in separating and reattaching flows. The computations are compared with several algebraic models and with the experimental data. The prediction was improved considerably, particularly in the separated shear layer. Computations are further made for the temperature-velocity double products and triple products. Finally, several advantages were observed in the usage of the transport equations for the evaluation of the turbulence triple products; one of the most important features is that the transport model can always take the effects of convection and diffusion into account in strong convective shear flows such as reattaching separated layers while conventional algebraic models cannot account for these effects in the evaluation of turbulence variables.
NASA Astrophysics Data System (ADS)
Oc?o?, Pawe?; ?opata, Stanis?aw; Nowak, Marzena
2015-04-01
This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.
NASA Astrophysics Data System (ADS)
Oc?o?, Pawe?; ?opata, Stanis?aw; Nowak, Marzena
2014-09-01
This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.
NASA Astrophysics Data System (ADS)
Kirkegaard, Casper; Foged, Nikolaj; Auken, Esben; Christiansen, Anders Vest; Srensen, Kurt
2012-09-01
Helicopter borne time domain EM systems historically measure only the Z-component of the secondary field, whereas fixed wing systems often measure all field components. For the latter systems the X-component is often used to map discrete conductors, whereas it finds little use in the mapping of layered settings. Measuring the horizontal X-component with an offset loop helicopter system probes the earth with a complementary sensitivity function that is very different from that of the Z-component, and could potentially be used for improving resolution of layered structures in one dimensional modeling. This area is largely unexplored in terms of quantitative results in the literature, since measuring and inverting X-component data from a helicopter system is not straightforward: The signal strength is low, the noise level is high, the signal is very sensitive to the instrument pitch and the sensitivity function also has a complex lateral behavior. The basis of our study is a state of the art inversion scheme, using a local 1D forward model description, in combination with experiences gathered from extending the SkyTEM system to measure the X component. By means of a 1D sensitivity analysis we motivate that in principle resolution of layered structures can be improved by including an X-component signal in a 1D inversion, given the prerequisite that a low-pass filter of suitably low cut-off frequency can be employed. In presenting our practical experiences with modifying the SkyTEM system we discuss why this prerequisite unfortunately can be very difficult to fulfill in practice. Having discussed instrumental limitations we show what can be obtained in practice using actual field data. Here, we demonstrate how the issue of high sensitivity towards instrument pitch can be overcome by including the pitch angle as an inversion parameter and how joint inversion of the Z- and X-components produces virtually the same model result as for the Z-component alone. We conclude that adding helicopter system X-component to a 1D inversion can be used to facilitate higher confidence in the layered result, as the requirements for fitting the data into a 1D model envelope becomes more stringent and the model result thus less prone to misinterpretation.
NASA Astrophysics Data System (ADS)
Ji, Rubao; Chen, Changsheng; Franks, Peter J. S.; Townsend, David W.; Durbin, Edward G.; Beardsley, Robert C.; Gregory Lough, R.; Houghton, Robert W.
2006-11-01
A coupled biological-physical model was developed and tested in one-dimensional (1-D, vertical) and two-dimensional (2-D, cross-sectional) domains to examine the spring phytoplankton bloom and associated lower trophic level food web dynamics on Georges Bank (GB). The biological model consists of nine compartments: dissolved inorganic nutrients (nitrate, ammonium and silicate), phytoplankton (large and small size classes), zooplankton (large and small size classes), and detrital organic nitrogen and biogenic silica. The 1-D model results showed that in the shallow central bank, the timing and duration of spring blooms are closely linked to the light intensity and its downward penetration, while the intensity of blooms is regulated by initial nutrient concentrations and zooplankton grazing pressure. In the deeper flank area, the bloom dynamics is directly controlled by the seasonal development of stratification. The interactions between the shallow and deep regions of the bank were examined by a 2-D model, which showed that the cross-sectional gradients of biological quantities were caused mainly by the shallow-deep topographic transition and tidal mixing. Between the shallow and deep regions, a possible phytoplankton maximum concentration area was seen in the model at the time before the formation of the tidal-mixing front. Once the tidal-mixing front was established during late spring, the model showed a relatively high concentration of phytoplankton near the front as the result of the tidally driven up-front nutrient flux. Both the 1-D and 2-D models captured the basic seasonal cycles of the nutrients and phytoplankton in the central bank, but failed to reproduce those patterns in the deep flank regions, where horizontal advection might play a significant role.
NASA Astrophysics Data System (ADS)
Ramos, Catalina; Mechie, James
2015-04-01
Using active and passive seismology data from project TIPTEQ (from The Incoming Plate to mega-Thrust EarthQuake processes) we derive a shear (S) wave velocity and a Poisson's ratio (?) model across the Chilean convergent margin along 3815'S, where the Mw 9.5 Valdivia earthquake is believed to have occurred. The obtained S-wave velocity model consists of three different tomographic images that were merged together. In the upper part (0 - 5 km depth), controlled source data from explosions were used to obtain a S-wave travel-time tomography. In the middle part (5 - 20 km depth) a dispersion analysis and then a noise tomography were carried out in two different ways: one used the dispersion curves to obtain a 3D S-wave velocity model in one step and the other used the dispersion curves to obtain surface-wave velocity tomographic images for different periods and then used the surface-wave velocity values every 10 km along the profile to obtain 1D S-wave velocity profiles every 10 km that were then interpolated to obtain a 2D S-wave tomography. Both methods produce similar S-wave travel-times. In the lower part (20 - 75 km depth, depending on the longitude) an already existent S-wave velocity model from local earthquake tomography was merged with the other two sections. The final S-wave velocity model and already existent compressional (P) wave velocity models along the same transect allowed us to obtain a Poisson's ratio model. The results show that the velocities and Poisson's ratios in this part of the Chilean convergent margin can all be explained in terms of normal rock types. There is no requirement to call on the existence of significant amounts of present-day fluids in the continental lithosphere above the plate interface in this part of the Chilean convergent margin, to explain the derived velocities and Poisson's ratios.
NASA Astrophysics Data System (ADS)
Van Eester, Dirk; Lerche, Ernesto
2013-05-01
Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenario's creating high energy tails. This paper discusses an extension TOMCAT-U of the 1D TOMCAT tokamak plasma wave equation solver (Van Eester and Koch 1998 Plasma Phys. Control. Fusion 40 1949) to arbitrary harmonics and arbitrary wavelengths while only keeping leading order terms in equilibrium variation terms. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response that is suitable for numerical application. This choice of independent variable yields intuitive expressions involving the Kennel-Engelmann operator which can directly be linked to the corresponding expressions in the RF diffusion operator appearing in the Fokker-Planck equation. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integrodifferential approach that retains all finite Larmor radius effects is proposed. To keep the required computation time for this generalized description reasonable, tabulation of integrals is intensively used. Although the accent is on the presentation of the upgraded formalism as well as the adopted recursions and tabulations, a few examples are provided to illustrate the potential of the new wave code that relies on these tabulations.
Comparison of CME radial velocities from a flux rope model and an ice cream cone model
NASA Astrophysics Data System (ADS)
Kim, T.; Moon, Y.; Na, H.
2011-12-01
Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.
NASA Astrophysics Data System (ADS)
Mastin, L. G.; Sherrod, D. R.; Vallance, J. W.; Thornber, C. T.; Ewert, J. W.
2005-12-01
The dome-building eruption at Mount St. Helens has occurred through glacial ice and snow that would be expected to substantially affect the character of the eruption. Nevertheless, the role of water in the eruption to date has not always been clear. For example, on March 8, 2005, a half-hour-long tephra blast sent a plume to a maximum of ~9 km above the vent (based on pilot reports); seismicity and plume heights were greatest during the first ~10 minutes, then persisted for another ~15 minutes at a lower level before the eruption stopped. Tephra volume within 5 km2 downwind of the vent was ~5x104 m3 DRE, but trace amounts were reported at least to Ellensburg, WA (150 km NE), suggesting a total areal coverage >5,000 km2 and total volume >1x105 m3. Assuming that most of this material was expelled in the first ten minutes and had a density of 2500 kg/m3, the mass flow rate (M) during the vigorous phase was >~4x105 kg/s. The tephra, composed primarily of non-pumiceous broken and decrepitated dome rock, could have been expelled either by groundwater and steam at relatively modest (boiling-point) temperatures, or by magmatic gas at much higher temperatures. The high plume, however, suggested significant buoyancy, perhaps driven by temperatures closer to magmatic. To assess the effect of magmatic heat on plume height, we employ a 1-D steady volcanic plume model that uses specified vent diameter, exit velocity, eruption temperature, mass fractions of gas and added external water, and profiles of atmospheric temperature and humidity, to calculate plume height and plume properties as a function of elevation. The model considers the enthalpy of equilibrium water condensation and of ice formation. Model results show that, under atmospheric temperature and humidity profiles measured near Mount St. Helens on the afternoon of March 8, 2005, a plume height (h) of 7-9 km could have developed with eruption temperatures (T) as low as 100° C, provided the mass fraction of water vapor in the plume (n) exceeded ~0.25 (mixtures containing less gas at this temperature would collapse before reaching 7-9 km height). At T=100° C and n=0.25, however, a mass flux of 0.6-1x105 kg/s will generate the observed 7-9km plume height, whereas a mass flow rate >~4x105 kg/s, in line with observations, results in h>~11 km. Under more typical magmatic temperatures (900° C) and gas mass fractions (0.02-0.03), plume heights of 7-9 km require M=4-6x105 kg/s -- nearly an order of magnitude greater than the vapor-rich, boiling point mixture, but more in line with the estimated mass flow rate of this eruption. These results, though not definitive, suggest that magmatic heat may have been important in driving the March 8 eruption. Relationships between mass flow rate and plume height may be useful in assessing the roles of magmatic and phreatic sources during other small eruptions.
Verley, Jason C.; Axness, Carl L.; Hembree, Charles Edward; Keiter, Eric Richard; Kerr, Bert
2012-04-01
Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools such as SPICE [1] can be used to analyze these threats, and typically rely on compact models for individual electrical components such as transistors and diodes. Compact models consist of a handful of differential and/or algebraic equations, and are derived by making simplifying assumptions to any of the many semiconductor transport equations. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of qualitative approximation, rather than mathematically correct solutions to the ambipolar diffusion equation. A practical consequence of this inaccuracy is that a given model calibration is trustworthy over only a narrow range of operating conditions. This report describes work to produce improved compact models for photocurrent. Specifically, an analytic model is developed for epitaxial diode structures that have a highly doped subcollector. The analytic model is compared with both numerical TCAD calculations, as well as the compact model described in reference [2]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the compact model from reference [2].
Korrodi-Gregrio, Lus; Margarida Lopes, Ana; Esteves, Sara L C; Afonso, Sandra; Lemos de Matos, Ana; Lissovsky, Andrey A; da Cruz e Silva, Odete A B; da Cruz e Silva, Edgar F; Esteves, Pedro Jos; Fardilha, Margarida
2013-01-01
T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4) contains the canonical phosphoprotein phosphatase 1 (PPP1) binding motif, composed by the amino acid sequence RVSF. We identified and validated the binding of TCTEX1D4 to PPP1 and demonstrated that indeed this protein is a novel PPP1 interacting protein. Analyses of twenty-one mammalian species available in public databases and seven Lagomorpha sequences obtained in this work showed that the PPP1 binding motif 90RVSF93 is present in all of them and is flanked by a palindromic sequence, PLGS, except in three species of pikas (Ochotona princeps, O. dauurica and O. pusilla). Furthermore, for the Ochotona species an extra glycosylation site, motif 96NLS98, and the loss of the palindromic sequence were observed. Comparison with other lagomorphs suggests that this event happened before the Ochotona radiation. The dN/dS for the sequence region comprising the PPP1 binding motif and the flanking palindrome highly supports the hypothesis that for Ochotona species this region has been evolving under positive selection. In addition, mutational screening shows that the ability of pikas TCTEX1D4 to bind to PPP1 is maintained, although the PPP1 binding motif is disrupted, and the N- and C-terminal surrounding residues are also abrogated. These observations suggest pika as an ideal model to study novel PPP1 complexes regulatory mechanisms. PMID:24130861
Korrodi-Gregório, Luís; Margarida Lopes, Ana; Esteves, Sara L. C.; Afonso, Sandra; Lemos de Matos, Ana; Lissovsky, Andrey A.; da Cruz e Silva, Odete A. B.; Esteves, Pedro José; Fardilha, Margarida
2013-01-01
T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4) contains the canonical phosphoprotein phosphatase 1 (PPP1) binding motif, composed by the amino acid sequence RVSF. We identified and validated the binding of TCTEX1D4 to PPP1 and demonstrated that indeed this protein is a novel PPP1 interacting protein. Analyses of twenty-one mammalian species available in public databases and seven Lagomorpha sequences obtained in this work showed that the PPP1 binding motif 90RVSF93 is present in all of them and is flanked by a palindromic sequence, PLGS, except in three species of pikas (Ochotona princeps, O. dauurica and O. pusilla). Furthermore, for the Ochotona species an extra glycosylation site, motif 96NLS98, and the loss of the palindromic sequence were observed. Comparison with other lagomorphs suggests that this event happened before the Ochotona radiation. The dN/dS for the sequence region comprising the PPP1 binding motif and the flanking palindrome highly supports the hypothesis that for Ochotona species this region has been evolving under positive selection. In addition, mutational screening shows that the ability of pikas TCTEX1D4 to bind to PPP1 is maintained, although the PPP1 binding motif is disrupted, and the N- and C-terminal surrounding residues are also abrogated. These observations suggest pika as an ideal model to study novel PPP1 complexes regulatory mechanisms. PMID:24130861
Technology Transfer Automated Retrieval System (TEKTRAN)
Watershed modeling is a key component of watershed management that involves the simulation of hydrological and fluvial processes for predicting flow and sediment transport within a watershed. For practical purposes, most numerical models have been developed to simulate either runoff and soil erosion...
Fujita, Miki; Himmelspach, Regina; Ward, Juliet; Whittington, Angela; Hasenbein, Nortrud; Liu, Christine; Truong, Thy T.; Galway, Moira E.; Mansfield, Shawn D.; Hocart, Charles H.; Wasteneys, Geoffrey O.
2013-01-01
Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function. The dwarf mutants have reduced anisotropic growth of roots, aerial organs, and trichomes. Interestingly, cellulose microfibrils were disordered only in the epidermal cells of the any1 inflorescence stem, whereas they were transverse to the growth axis in other tissues of the stem and in all elongated cell types of roots and dark-grown hypocotyls. Overall cellulose content was not altered but both cell wall crystallinity and the velocity of cellulose synthase complexes were reduced in any1. We crossed any1 with the temperature-sensitive radial swelling1-1 (rsw1-1) CesA1 mutant and observed partial complementation of the any1 phenotype in the transheterozygotes at rsw1-1s permissive temperature (21C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29C). In rsw1-1 homozygotes at restrictive temperature, a striking dissociation of cellulose synthase complexes from the plasma membrane was accompanied by greatly diminished motility of intracellular cellulose synthase-containing compartments. Neither phenomenon was observed in the any1 rsw1-1 transheterozygotes, suggesting that the proteins encoded by the any1 allele replace those encoded by rsw1-1 at restrictive temperature. PMID:23532584
The Candy Wrapper Velocity Model for the Earth's Inner Core
NASA Astrophysics Data System (ADS)
Mattesini, M.
2014-12-01
Recent global expansion of seismic data motivated a number of seismological studies of the Earth's inner core that proposed the existence of increasingly complex structure and anisotropy. In the meantime, new hypotheses of dynamic mechanisms have been put forward to interpret seismological results. Here, the nature of hemispherical dichotomy and anisotropy is re-investigated by bridging the observations of PKP(bc-df) differential travel-times with the iron bcc/hcp elastic properties computed from first-principles methods.The Candy Wrapper velocity model introduced here accounts for a dynamic picture of the inner core (i.e., the eastward drift of material), where different iron crystal shapes can be stabilized at the two hemispheres. We show that seismological data are best explained by a rather complicated, mosaic-like, structure of the inner core, where well-separated patches of different iron crystals compose the anisotropic western hemispherical region, and a conglomerate of almost indistinguishable iron phases builds-up the weakly anisotropic eastern side.
NASA Astrophysics Data System (ADS)
Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.
2013-12-01
An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal regime well. Detailed temperature comparison suggests that the 1-D thermal diffusion model results closely approximate the measured temperature at all depths with the average square root of the mean squared error (SRMSE) of 0.15oC; a linear correlation between modeled and measured temperatures yields an average R2 value of 0.9997. Prominent seasonal temperature variations diminish with depth, and it equilibrates to mean annual temperature at about 21.5 m depth. The amount of heat generated/consumed by ice condensation/sublimation is insufficient to significantly impact the thermal regime.
NASA Astrophysics Data System (ADS)
Anderson, Laurence A.
2009-08-01
The objective of this study was to fit a simple ecosystem model to climatological nitrogen cycle data in the Gulf of Maine, in order to calibrate the biological model for use in future 3-D modelling studies. First depth-dependent monthly climatologies of nitrate, ammonium, chlorophyll, zooplankton, detritus and primary production data from Wilkinson Basin, Gulf of Maine, were created. A 6-box nitrogen-based ecosystem model was objectively fitted to the data through parameter optimization. Optimization was based on weighted least squares with model-data misfits nondimensionalized by assigned uncertainties in the monthly climatological estimates. These uncertainties were estimated as the standard deviations of the raw data from the 6-meter and monthly bin averages. On average the model fits the monthly means almost within their assigned uncertainties. Several statistics are examined to assess model-data misfit. Pattern statistics such as the correlation coefficient lack practical significance when data errors are large relative to the signal, as in this application. Thus Taylor diagrams were not found to be useful. The RMSE and model bias normalized by the data error were found to be the most useful skill metrics as they indicate whether the model fits the data within its estimated error. The optimal simulated nitrogen cycle budgets are presented, as an estimate of the seasonal nitrogen cycle in Wilkinson Basin, and discussed in context of the available data. Wilkinson Basin has spring and fall phytoplankton blooms, and strong summer stratification with a deep chlorophyll maximum near 21 m, just above the nitracline. The mean euphotic zone depth is estimated to be 25 m, relatively constant with season. The model estimates annual primary production as 176 g C m - 2 yr - 1 , annual new production as 71 g C m - 2 yr - 1 and sinking PON fluxes of 9.7 and 4.7 g N m - 2 yr - 1 at 24 and 198 m respectively. Areas for improvement in the biological model, the model optimization method, and significant data gaps are identified.
An extension of the Savage-Hutter gravity driven granular flow model on arbitrary topography in 1D
NASA Astrophysics Data System (ADS)
Fellin, Wolfgang; Ostermann, Alexander; Staggl, Gregor
2015-04-01
In an implementation of the Savage-Hutter model in a GIS (geographic information system, e.g. GRASS GIS) curvature terms must be accounted for. We extend the work of Bouchut et al. (2003) to include friction between flowing mass and bed, as well as the active/passive earth pressure coefficient to model the behavior of the granular flow according to the original Savage-Hutter idea. Conservation of mass and momentum in curvilinear coordinates are integrated over the flow height yielding a shallow water model. This work is part of the project avaflow: http://www.avaflow.org/ References: F. Bouchut, A. Mangeney-Castelnau, B. Perthame, J.-P. Vilotte, A new model of Saint Venant and Savage-Hutter type for gravity driven shallow water flows, C.R. Acad. Sci. Paris, srie I 336 (2003), 531-536.
Grant, K.E.; Taylor, K.E.; Ellis, J.S.; Wuebbles, D.J.
1987-07-01
The authors have implemented a series of state of the art radiation transport submodels in previously developed one dimensional and two dimensional chemical transport models of the troposphere and stratosphere. These submodels provide the capability of calculating accurate solar and infrared heating rates. They are a firm basis for further radiation submodel development as well as for studying interactions between radiation and model dynamics under varying conditions of clear sky, clouds, and aerosols. 37 refs., 3 figs.
Smith, R; Taha, T; Cui, Z F
2005-01-01
Tubular membrane ultrafiltration and microfiltration are important industrial separation and concentration processes. Process optimisation requires reduction of membrane build-up. Gas slug introduction has been shown to be a useful approach for flux enhancement. However, process quantification is required for design and optimisation. In this work we employ a non-porous wall CFD model to quantify hydrodynamics in the two-phase slug flow process. Mass transfer is subsequently quantified from wall shear stress, which was determined from the CFD. The mass transfer model is an improved one-dimensional boundary layer model, which empirically incorporates effects of wall suction and analytically includes edge effects for circular conduits. Predicted shear stress profiles are in agreement with experimental results and flux estimates prove more reliable than that from previous models. Previous models ignored suction effects and employed less rigorous fluid property inclusion, which ultimately led to under-predictive flux estimates. The presented model offers reliable process design and optimisation criteria for gas-sparged tubular membrane ultrafiltration. PMID:16003963
Invariant methods for indexing and relative reconstruction of 3D models using 1D HRR and 2D SAR
NASA Astrophysics Data System (ADS)
Payton, Paul M.; Barrett, Eamon B.; Kober, Wolfgang; Thomas, John K.; Johnson, Steven E.
1998-10-01
We describe a geometric model of high-resolution radar (HRR), where objects being imaged by the sensor are assumed to consists of a collection of isotropic scattering centers distributed in three dimensions. Three, four, five and six point pure HRR invariant quantities for non-coplanar reflecting centers are presented. New work showing invariants combining HRR and SAR measurements are then presented. All these techniques require matching corresponding features in multiple HRR and/or SAR views. These features are represented using analytic scattering models. Multiple features within the same HRR resolution cell can be individually detected and separated using interference-suppression filters. These features can then be individually tracked to maintain correspondence as the object poise changes. We validate our HRR/SAR invariants using the XPATCH simulation system. Finally, a view-based method for 3D model reconstruction is developed and demonstrated.
NASA Astrophysics Data System (ADS)
Ireland, Gareth; Petropoulos, George P.; Carlson, Toby N.; Purdy, Sarah
2015-04-01
Sensitivity analysis (SA) consists of an integral and important validatory check of a computer simulation model before it is used to perform any kind of analysis. In the present work, we present the results from a SA performed on the SimSphere Soil Vegetation Atmosphere Transfer (SVAT) model utilising a cutting edge and robust Global Sensitivity Analysis (GSA) approach, based on the use of the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) tool. The sensitivity of the following model outputs was evaluated: the ambient CO2 concentration and the rate of CO2 uptake by the plant, the ambient O3 concentration, the flux of O3 from the air to the plant/soil boundary, and the flux of O3 taken up by the plant alone. The most sensitive model inputs for the majority of model outputs were related to the structural properties of vegetation, namely, the Leaf Area Index, Fractional Vegetation Cover, Cuticle Resistance and Vegetation Height. External CO2 in the leaf and the O3 concentration in the air input parameters also exhibited significant influence on model outputs. This work presents a very important step towards an all-inclusive evaluation of SimSphere. Indeed, results from this study contribute decisively towards establishing its capability as a useful teaching and research tool in modelling Earth's land surface interactions. This is of considerable importance in the light of the rapidly expanding use of this model worldwide, which also includes research conducted by various Space Agencies examining its synergistic use with Earth Observation data towards the development of operational products at a global scale. This research was supported by the European Commission Marie Curie Re-Integration Grant "TRANSFORM-EO". SimSphere is currently maintained and freely distributed by the Department of Geography and Earth Sciences at Aberystwyth University (http://www.aber.ac.uk/simsphere). Keywords: CO2 flux, ambient CO2, O3 flux, SimSphere, Gaussian process emulators, BACCO GEM-SA, TRANSFORM-EO.
NASA Technical Reports Server (NTRS)
Schmitt, G. A.; Abreu, V. J.; Hays, P. B.
1981-01-01
Thermal and nonthermal O(1D) number density profiles are calculated. The two populations are assumed to be coupled by a thermalization cross-section which determines the loss and production in the nonthermal and thermal populations, respectively. The sources, sinks and transport of the two populations are used to model volume emission rate profiles at 6300 A. The 6300 A brightness measured by the Visible Airglow Experiment is then used to establish the presence of the nonthermal population and to determine the thermalization cross-section.
Combining flow routing modelling and direct velocity measurement for optimal discharge estimation
NASA Astrophysics Data System (ADS)
Corato, G.; Moramarco, T.; Tucciarelli, T.
2011-03-01
A new procedure is proposed for estimating river discharge hydrographs during flood events, using only water level data measured at a gauged site, as well as 1-D shallow water modelling and sporadic maximum surface flow velocity measurements. During flood, the piezometric level is surmised constant in the vertical plane of the river section, where the top of the banks is always above the river level, and is well represented by the recorded stage hydrograph. The river is modelled along the reach directly located downstream the upstream gauged section, where discharge hydrograph is sought after. For the stability with respect to the topographic error, as well as for the simplicity of the data required to satisfy the boundary conditions, a diffusive hydraulic model is adopted for flow routing. Assigned boundary conditions are: (1) the recorded stage hydrograph at the upstream river site and (2) the zero diffusion condition at the downstream end of the reach. The MAST algorithm is used for the numerical solution of the flow routing problem, which is embedded in the Brent algorithm used for the computation of the optimum Manning coefficient. Based on synthetic tests concerning a broad prismatic channel, the optimal reach length is chosen so that the approximated downstream boundary condition effects on discharge hydrograph assessment at upstream end are negligible. The roughness Manning coefficient is calibrated by using sporadic instantaneous surface velocity measurements during the rising limb of flood that are turned into instantaneous discharges through the solid of velocity estimated by a two-dimensional entropic model. Several historical events, occurring in three gauged sites along the upper Tiber River wherein a reliable rating curve is available, have been used for the validation. The analysis outcomes can be so summarized: (1) criteria adopted for selecting the optimal channel length and based on synthetic tests have been proved reliable by using field data of three gauged river sites. Indeed, for each of them a downstream reach, long not more than 500 m, is turned out fair for achieving good performances of the diffusive hydraulic model, thus allowing to drastically reducing the topographical data of river cross-sections; (2) the procedure for Manning's coefficient calibration allowed to get high performance of the hydraulic model just considering the observed water levels and sporadic measurements of maximum surface flow velocity during the rising limb of flood. Indeed, in terms of errors in magnitude on peak discharge, for the optimal calibration, they were found, in average, not exceeding 5% for all events observed in the three investigated gauged sections, while the Nash-Sutcliff efficiency was, in average, greater than 0.95. Therefore, the proposed procedure, apart from to have turned out reliable for the rating curve assessment at ungauged sites, can be applied in realtime for whatever flood conditions and this is of great interest for the practice hydrology seeing that, looking at new monitoring technologies, it will be possible to carry out velocity measurements by hand-held radar sensors in different river sites and for the same flood.
NASA Astrophysics Data System (ADS)
Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos
2014-05-01
Soil develops as a result of interacting processes, many of which have been described in more or less detailed models. A key challenge in developing predictive models of soil function is to integrate processes that operate across a wide range of temporal and spatial scales. Many soil functions could be classified as "emergent", since they result from the interaction of subsystems. For example, soil organic matter (SOM) dynamics are commonly considered in relation to carbon storage, but can have profound effects on soil hydraulic properties that are conventionally considered to be static. Carbon fixed by plants enters the soil as litterfall, root turnover or via mycorrhizae. Plants need water and nutrients to grow, and an expanding root system provides access to a larger volume of soil for uptake of water and nutrients. Roots also provide organic exudates, such as oxalate, which increase nutrient availability. Carbon inputs are transformed at various rates into soil biota, CO2, and more persistent forms of organic matter. The SOM is partly taken up into soil aggregates of variable sizes, which slows down degradation. Water availability is an important factor as both plant growth and SOM degradation can be limited by shortage of water. Water flow is the main driver for transport of nutrients and other solutes. The flow of water in turn is influenced by the presence of SOM as this influences soil water retention and hydraulic conductivity. Towards the top of the unsaturated zone, bioturbation by the soil fauna transports both solid material and solutes. Weathering rates of minerals determine the availability of many nutrients and are in turn dependent on parameters such as pH, water content, CO2 pressure and oxalate concentration. Chemical reactions between solutes, dissolution and precipitation, and exchange on adsorption sites further influence solute concentrations. Within the FP7 SoilTrEC project, we developed a model that incorporates all of these processes, to explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.
Study of fog characteristics by using the 1-D COBEL model at the airport of Thessaloniki, Greece
NASA Astrophysics Data System (ADS)
Stolaki, S.; Pytharoulis, I.; Karacostas, T.
2010-07-01
An attempt is made to couple the one dimensional COBEL - ISBA (COuche Brouillard Eau Liquide - Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting) numerical weather prediction model. This accomplishment will improve the accuracy on the short-term forecasting of fog events, which is of paramount importance -mainly to the airway companies, the airports functioning and the community as well- and will provide the means for the implementation of extensive studies of fog events formed at the "Macedonia" airport of Thessaloniki. Numerical experiments have been performed to study in depth the thermodynamic structure and the microphysical characteristics of the fog event that was formed on 06/01/2010. Moreover, the meteorological conditions -under the influence of which- the fog event was formed are also investigated. Sensitivity tests with respect to the initial conditions of temperature, relative humidity and geostrophic wind speed profiles have been performed to illustrate the models performance. Dew deposition rates have also been examined in order to test the importance of it on controlling the fog formation. The numerical results have been compared with actual measurements and the findings have been evaluated and discussed.
NASA Astrophysics Data System (ADS)
Ashworth, K.; Chung, S. H.; Griffin, R. J.; Chen, J.; Forkel, R.; Bryan, A. M.; Steiner, A. L.
2015-07-01
Biosphere-atmosphere interactions play a critical role in governing atmospheric composition, mediating the concentration of key species such as ozone and aerosol, thereby influencing air quality and climate. The exchange of reactive trace gases and their oxidation products (both gas and particle phase) is of particular importance in this process. The FORCAsT (FORest Canopy AtmoSphere Transfer) one-dimensional model is developed to study the emission, deposition, chemistry and transport of volatile organic compounds (VOCs) and their oxidation products in the atmosphere within and above the forest canopy. We include an equilibrium partitioning scheme, making FORCAsT one of the few canopy models currently capable of simulating the formation of secondary organic aerosols (SOA) from VOC oxidation in a forest environment. We evaluate the capability of FORCAsT to reproduce observed concentrations of key gas-phase species and report modeled SOA concentrations within and above a mixed forest at the University of Michigan Biological Station (UMBS) during the Community Atmosphere-Biosphere Interactions Experiment (CABINEX) field campaign in summer 2009. We examine the impact of two different gas-phase chemical mechanisms on modelled concentrations of short-lived primary emissions, such as isoprene and monoterpenes, and their oxidation products. While the two chemistry schemes perform similarly under high-NOx conditions, they diverge at the low levels of NOx at UMBS. We identify peroxy radical and alkyl nitrate chemistry as the key causes of the differences, highlighting the importance of this chemistry in understanding the fate of biogenic VOCs (bVOCs) for both the modelling and measurement communities.
NASA Astrophysics Data System (ADS)
Riel, Nicolas; Mercier, Jonathan
2014-05-01
It is now widely accepted that the formation and the evolution of high elevation plateaus such as the Tibet and the Altiplano-Puna are strongly linked to mantel magma underplating at crustal root level and partial melting of the lower crust. Understanding the rheological behavior of the deep continental crust during these episodes is therefore crucial to constrain the evolution of such plateau. In this study we present results obtained from pressure-temperature estimates and thermal modeling of gabbro underplating at crustal root level (25km) in the El Oro Metamorphic Complex (Ecuador). The aim of this study is: (1) to complete previously published P-Tmax estimates in the northern part of the migmatitic unit, close to the magmatic contact with the gabbroic unit, to obtain better constraints on the metamorphic gradient during partial melting, (2) to characterize the effects of melt extraction, latent heat capture and release and a temperature-dependent thermal diffusivity on the thermal evolution of the system using a specifically developed numerical model, and (3) in the light of the thermal modeling results, to discuss the geological processes involved during partial melting of the metasedimentary crust. Our modeling results show that the estimate metamorphic gradient cannot be reproduced when solely taking into account latent heat, melt extraction and thermal-dependent diffusivity. In the light of geological, geochemical and modeling evidence we show that the lower migmatitic unit, controlled by biotite-dehydration melting reactions was subject to convective motion that contributed to lower the metamorphic gradient and rapidly transfer heat upward. For a biotite-rich rock (~20%) containing 15-20% of melt, we estimate the maximum viscosity of the rock that allows convection at ~7.5e17 Pa.s. Our results also suggest that convection can be maintained as long as heat is provided and that temperature lies in the stability field of biotite-dehydration melting (750-900C).
Study of the mixed layer depth variations within the north Indian Ocean using a 1-D model
NASA Astrophysics Data System (ADS)
Babu, K. N.; Sharma, Rashmi; Agarwal, Neeraj; Agarwal, Vijay K.; Weller, R. A.
2004-08-01
Mixed layer depth (MLD) over the north Indian Ocean (30S to 30N and 40E to 110E) is computed using the simple one-dimensional model of [1986] forced by satellite-derived parameters (winds and chlorophyll). Seasonal chlorophyll observations obtained from the Coastal Zone Color Scanner allow us to examine how biology interacts with physics in the upper ocean by changing the absorption of light and thus the heating by penetrative solar radiation, an effect we refer to as biological heating. Our analysis focus mainly on two aspects: the importance of varying biology in the model simulations relative to runs with constant biology and secondly, the contribution of biology to the seasonal variability of the MLD. The model results are compared with observations from a surface mooring deployed for 1 year (October 1994 to October 1995) in the central Arabian Sea and also with available conductivity-temperature-depth (CTD) observations from the Arabian Sea during the period 1994-1995. The effect of biological heating on the upper ocean thermal structure in central Arabian Sea is found to be greatest in August. In other months it is either the wind, which is the controlling factor in mixed layer variations, or the density variations due to winter cooling and internal dynamics. A large number of CTD observations collected under the Joint Global Ocean Flux study and World Ocean Circulation Experiment have been used to validate model results. We find an overall improvement by approximately 2-3 m in root-mean-square error in MLD estimates when seasonally varying chlorophyll observations are used in the model.
Solid-liquid interdiffusion (SLID) bonding in the Au–In system: experimental study and 1D modelling
NASA Astrophysics Data System (ADS)
Deillon, Léa; Hessler-Wyser, Aïcha; Hessler, Thierry; Rappaz, Michel
2015-12-01
Au–In bonds with a nominal composition of about 60 at.% In were fabricated for use in wafer-level packaging of MEMS. The microstructure of the bonds was studied by scanning electron microscopy. The bond hermeticity was then assessed using oxidation of Cu thin discs predeposited within the sealed packages. The three intermetallic compounds AuIn2, AuIn and Au7In3 were observed. Their thickness evolution during bonding and after subsequent heat treatment was successfully modelled using a finite difference model of diffusion, thermodynamic data and diffusion coefficients calibrated from isothermal diffusion couples. 17% of the packages were hermetic and, although the origin of the leaks could not be clearly identified, it appeared that hermeticity was correlated with the unevenness of the metallisation and/or wafer and the fact that the bonds shrink due to density differences as the relative fractions of the various phases gradually evolve.
Creating Flood Inundation Maps Using 1D Hydrologic Model and GIS for Lower Meric River Basin, Turkey
NASA Astrophysics Data System (ADS)
Sonmez, O.; Dogan, E.; Demir, I.
2012-12-01
In Turkey, one of the areas facing the danger of flooding is Lower Meric River basin, the part between Edirne and Enos, Turkey. Despite being in the flood zone, the region is used widely as an agricultural and settlement land. The State Hydraulic Works (DSI) has built levees to prevent flood damages on the Lower Evros River Basin. However, having floods in the region reaching areas behind levees, clearly showed the need for reviewing and updating the cross-sections of the critical areas in the river bed. In this study, determination of floodplains for various stream-flow values in any cross sections of the river is aimed. The study area is divided into two sections (Study Area 1 & Study Area 2). Available stream flow gauging station data, which is located in study areas, are used in model. Model created using HEC-RAS, is calibrated with 2006 flood which occurred in the study area. After calibration, floodplain maps are created for 1000 m3/s flows from 1000 to6000 m3/s flows for Study Area1. For Study Area 2, floodplain maps are created for 2, 5, 10, 50, 100 years return periods. The models can illustrate the extent of flooding under different conditions allowing residents in the area to see how predicted flood levels could affect their property, and help them make informed decisions.
NASA Astrophysics Data System (ADS)
Zhou, Jun; Liu, Hongyi; Han, Ting; Chen, Yijian
2015-03-01
In this paper, a stitch database is built from various identified stitching structures in an open-cell layout library. The corresponding stitching yield models are developed for the hybrid optical and self-aligned multiple patterning (hybrid SAMP). Based on the concept of probability-of-success (POS) function, we first develop a single-stitching yield model to quantify the effects of overlay errors and cut-hole CD variations. The overhang distance designed in a stitching process (or its mean value μ) is found to be critical to the stitching yield performance and can be optimized using this yield model. We also investigate the physical significance of several process parameters such as half pitch (HP), standard deviation (σ) of the random overhang distribution, and cut-hole CD (CL). Our study shows that certain types of stitching yield are sensitive to σ and HP, while in general high yield can be achieved for a large number of stitching types we examined. To improve the yield of certain challenging stitching structures, various layout modification strategies are proposed and discussed.
NASA Astrophysics Data System (ADS)
Petropoulos, George P.; Carlson, Toby N.
2013-04-01
Earth Observation (EO) has played an imperative role in extending our abilities for obtaining information on the spatio-temporal distribution of surface soil moisture (SSM). A wide range of techniques have been proposed for this purpose, utilising spectral information acquired from remote sensing instruments operating in different regions of the electromagnetic spectrum. Some of these methods have been based on the integration of satellite-derived estimates of Fractional Vegetation Cover (Fr) and Land Surface Temperature (Ts) in the form of a scatterplot domain, often combining simulations from land surface process model. In this work we present results from the evaluation of one such technique implemented using ENVISAT's Advanced Along Track Scanning Radiometer (AATSR) medium resolution sensor imagery and SimSphere land surface model. Validation of the derived SMC maps was undertaken in different sites in Europe representing a variety of climatic, topographic and environmental conditions, for which validated in-situ observations from diverse operational ground observational networks were available. Our results indicated a generally close agreement between the inverted SMC maps and the in-situ observations, with accuracies often comparable to previous studies implemented using different types of EO data. Comparisons of the derived SMC maps regionally against other satellite-derived products also showed largely an explainable distribution of SMC in relation to surface heterogeneity. The present work was conducted in the framework of the PROgRESSIon (Prototyping the Retrievals of Energy Fluxes and Soil Moisture Content) project, funded by the European Space Agency (ESA) Support to Science Element (STSE). The project aims at exploring the development of a series of prototype products for the estimation of turbulent heat fluxes and SMC derived from the synergy of SimSphere land surface model with EO observations from advanced technologically designed medium resolution ESA-funded or co-funded instruments. KEYWORDS: surface soil moisture, remote sensing, triangle, SimSphere, AATSR.
An empirical model to forecast solar wind velocity through statistical modeling
NASA Astrophysics Data System (ADS)
Gao, Y.; Ridley, A. J.
2013-12-01
The accurate prediction of the solar wind velocity has been a major challenge in the space weather community. Previous studies proposed many empirical and semi-empirical models to forecast the solar wind velocity based on either the historical observations, e.g. the persistence model, or the instantaneous observations of the sun, e.g. the Wang-Sheeley-Arge model. In this study, we use the one-minute WIND data from January 1995 to August 2012 to investigate and compare the performances of 4 models often used in literature, here referred to as the null model, the persistence model, the one-solar-rotation-ago model, and the Wang-Sheeley-Arge model. It is found that, measured by root mean square error, the persistence model gives the most accurate predictions within two days. Beyond two days, the Wang-Sheeley-Arge model serves as the best model, though it only slightly outperforms the null model and the one-solar-rotation-ago model. Finally, we apply the least-square regression to linearly combine the null model, the persistence model, and the one-solar-rotation-ago model to propose a 'general persistence model'. By comparing its performance against the 4 aforementioned models, it is found that the accuracy of the general persistence model outperforms the other 4 models within five days. Due to its great simplicity and superb performance, we believe that the general persistence model can serve as a benchmark in the forecast of solar wind velocity and has the potential to be modified to arrive at better models.
Monte Carlo solution of the Boltzmann equation via a discrete velocity model
NASA Astrophysics Data System (ADS)
Morris, A. B.; Varghese, P. L.; Goldstein, D. B.
2011-02-01
A new discrete velocity scheme for solving the Boltzmann equation is described. Directly solving the Boltzmann equation is computationally expensive because, in addition to working in physical space, the nonlinear collision integral must also be evaluated in a velocity space. Collisions between each point in velocity space with all other points in velocity space must be considered in order to compute the collision integral most accurately, but this is expensive. The computational costs in the present method are reduced by randomly sampling a set of collision partners for each point in velocity space analogous to the Direct Simulation Monte Carlo (DSMC) method. The present method has been applied to a traveling 1D shock wave. The jump conditions across the shock wave match the Rankine-Hugoniot jump conditions. The internal shock wave structure was compared to DSMC solutions, and good agreement was found for Mach numbers ranging from 1.2 to 10. Since a coarse velocity discretization is required for efficient calculation, the effects of different velocity grid resolutions are examined. Additionally, the new scheme's performance is compared to DSMC and it was found that upstream of the shock wave the new scheme performed nearly an order of magnitude faster than DSMC for the same upstream noise. The noise levels are comparable for the same computational effort downstream of the shock wave.
NASA Astrophysics Data System (ADS)
Harel, Marie-Alice; Mouche, Emmanuel
2015-04-01
Despite the recent research focused on runoff pattern connectivity in hydrology, there is a surprising lack of theoretical knowledge regarding hillslope runoff generation and dynamics during a rainfall event. The transient problem is especially unaddressed. In this paper we propose a model based on queueing theory formalism for the infiltration-excess overland flow generation on soils with random infiltration properties. The influence of rainfall intensity and duration on runoff dynamics and connectivity is studied thanks to this model, numerical simulation and available steady-state results. We limit our study to a rainfall intensity that is a rectangular function of time. Exact solutions for the case of spatially random exponential distributions of soil infiltrability and rainfall intensity are developed. Simulations validate these analytical results and allow for the study the rising and recession limbs of the hydrograph for different rainfall characteristics. The case of a deterministic uniform rainfall rate and different infiltrability distributions is also discussed in light of runoff connectivity. We show that the connectivity framework contributes to a better understanding and prediction of runoff pattern formation and evolution with time. A fragmented overland flow is shown to have shorter charge and discharge periods after the onset and offset of rainfall compared to well connected runoff fields. These results demonstrate that the transient regime characteristics are linked with connectivity parameters, rainstorm properties and scale issues.
NASA Technical Reports Server (NTRS)
Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.
2007-01-01
The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.
Santini, E.; Steinheimer, J.; Bleicher, M.; Schramm, S.
2011-07-15
We analyze dilepton emission from hot and dense matter using a hybrid approach based on the ultrarelativistic quantum molecular dynamics (UrQMD) transport model with an intermediate hydrodynamic stage for the description of heavy-ion collisions at relativistic energies. During the hydrodynamic stage, the production of lepton pairs is described by radiation rates for a strongly interacting medium in thermal equilibrium. In the low-mass region, hadronic thermal emission is evaluated by assuming vector meson dominance including in-medium modifications of the {rho} meson spectral function through scattering from nucleons and pions in the heat bath. In the intermediate-mass region, the hadronic rate is essentially determined by multipion annihilation processes. Emission from quark-antiquark annihilation in the quark gluon plasma (QGP) is taken into account as well. When the system is sufficiently dilute, the hydrodynamic description breaks down and a transition to a final cascade stage is performed. In this stage dimuon emission is evaluated as commonly done in transport models. By focusing on the enhancement with respect to the contribution from long-lived hadron decays after freezeout observed at the SPS in the low-mass region of the dilepton spectra, the relative importance of the different thermal contributions and of the two dynamical stages is investigated. We find that three separated regions can be identified in the invariant mass spectra. Whereas the very low and the intermediate-mass regions mostly receive contribution from the thermal dilepton emission, the region around the vector meson peak is dominated by the cascade emission. Above the {rho}-peak region the spectrum is driven by QGP radiation. Analysis of the dimuon transverse mass spectra reveals that the thermal hadronic emission shows an evident mass ordering not present in the emission from the QGP. A comparison of our calculation to recent acceptance-corrected NA60 data on invariant as well as transverse mass spectra is performed.
NASA Astrophysics Data System (ADS)
Santini, E.; Steinheimer, J.; Bleicher, M.; Schramm, S.
2011-07-01
We analyze dilepton emission from hot and dense matter using a hybrid approach based on the ultrarelativistic quantum molecular dynamics (UrQMD) transport model with an intermediate hydrodynamic stage for the description of heavy-ion collisions at relativistic energies. During the hydrodynamic stage, the production of lepton pairs is described by radiation rates for a strongly interacting medium in thermal equilibrium. In the low-mass region, hadronic thermal emission is evaluated by assuming vector meson dominance including in-medium modifications of the ? meson spectral function through scattering from nucleons and pions in the heat bath. In the intermediate-mass region, the hadronic rate is essentially determined by multipion annihilation processes. Emission from quark-antiquark annihilation in the quark gluon plasma (QGP) is taken into account as well. When the system is sufficiently dilute, the hydrodynamic description breaks down and a transition to a final cascade stage is performed. In this stage dimuon emission is evaluated as commonly done in transport models. By focusing on the enhancement with respect to the contribution from long-lived hadron decays after freezeout observed at the SPS in the low-mass region of the dilepton spectra, the relative importance of the different thermal contributions and of the two dynamical stages is investigated. We find that three separated regions can be identified in the invariant mass spectra. Whereas the very low and the intermediate-mass regions mostly receive contribution from the thermal dilepton emission, the region around the vector meson peak is dominated by the cascade emission. Above the ?-peak region the spectrum is driven by QGP radiation. Analysis of the dimuon transverse mass spectra reveals that the thermal hadronic emission shows an evident mass ordering not present in the emission from the QGP. A comparison of our calculation to recent acceptance-corrected NA60 data on invariant as well as transverse mass spectra is performed.
NASA Astrophysics Data System (ADS)
Linders, J.; Bjrk, G.
2009-04-01
To investigate the impact of ocean stratifications on the ice cover, a one-dimensional numerical model (Bjrk, 1989) is used to compute oceanic heat flux and ice thickness development, during the ice growth season. The Arctic Ocean is divided into six regions according to their stratification of the upper layer. Observed salinity and temperature profiles, from several stations within each region, are used as initial conditions in the model. Observed data come from the NODC data base. Resent observations, from ice tethered profilers (IT?s) deployed during the IPY period, is also used to increase the spatial coverage. The computations show that the central regions have a largest ice growth, more than 0.7 m, over one growth season, using an initial ice thickness of 2 m. The large ice growth is due to the present cold halocline layer preventing upward mixing of heat from below. The weak stratification in the Nansen Basin enables deeper mixing into the warm Atlantic layer, which reduces the ice growth to a minimum of 0.25 m at some locations. In the Canada Basin the inflow of warm Pacific summer water generates a temperature maximum at 50 m. This heat reservoir is large enough to reduce the ice growth to about 0.55 m, in spite of the strong salinity stratification in the region. The regions with the largest ice growth have correspondingly the lowest annual mean oceanic heat fluxes, around 0.5 W m-2. However some locations in the Nansen and Canada Basins have heat fluxes larger than 1 W m-2. In our investigation we found a net melting over a full year only for one station, located close to the Bering Strait.
NASA Astrophysics Data System (ADS)
Laginha Silva, Patricia; Martins, Flvio A.; Boski, Tomsz; Sampath, Dissanayake M. R.
2010-05-01
Fluvial sediment transport creates great challenges for river scientists and engineers. The interaction between the fluid (water) and the solid (dispersed sediment particles) phases is crucial in morphodynamics. The process of sediment transport and the resulting morphological evolution of rivers get more complex with the exposure of the fluvial systems to the natural and variable environment (climatic, geological, ecological and social, etc.). The earlier efforts in mathematical river modelling were almost exclusively built on traditional fluvial hydraulics. The last half century has seen more and more developments and applications of mathematical models for fluvial flow, sediment transport and morphological evolution. The first attempts for a quantitative description and simulation of basin filling in geological time scales started in the late 60s of the last century (eg. Schwarzacher, 1966; Briggs & Pollack, 1967). However, the quality of this modelling practice has emerged as a crucial issue for concern, which is widely viewed as the key that could unlock the full potential of computational fluvial hydraulics. Most of the models presently used to study fluvial basin filling are of the "diffusion type" (Flemmings and Jordan, 1989). It must be noted that this type of models do not assume that the sediment transport is performed by a physical diffusive process. Rather they are synthetic models based on mass conservation. In the "synthesist" viewpoint (Tipper, 1992; Goldenfeld & Kadanoff, 1999; Werner, 1999 in Paola, 2000) the dynamics of complex systems may occur on many levels (time or space scales) and the dynamics of higher levels may be more or less independent of that at lower levels. In this type of models the low frequency dynamics is controlled by only a few important processes and the high frequency processes are not included. In opposition to this is the "reductionist" viewpoint that states that there is no objective reason to discard high frequency processes. In this viewpoint the system is broken down into its fundamental components and processes and the model is build up by selecting the important processes regardless of its time and space scale. This viewpoint was only possible to pursue in the recent years due to improvement in system knowledge and computer power (Paola, 2000). The primary aim of this paper is to demonstrate that it is possible to simulate the evolution of the sediment river bed, traditionally studied with synthetic models, with a process-based hydrodynamic, sediment transport and morphodynamic model, solving explicitly the mass and momentum conservation equations. With this objective, a comparison between two mathematical models for alluvial rivers is made to simulate the evolution of the sediment river bed of a conceptual 1D embayment for periods in the order of a thousand years: the traditional synthetic basin infilling aggregate diffusive type model based on the diffusion equation (Paola, 2000), used in the "synthesist" viewpoint and the process-based model MOHID (Miranda et al., 2000). The simulation of the sediment river bed evolution achieved by the process-based model MOHID is very similar to those obtained by the diffusive type model, but more complete due to the complexity of the process-based model. In the MOHID results it is possible to observe a more comprehensive and realistic results because this type of model include processes that is impossible to a synthetic model to describe. At last the combined effect of tide, sea level rise and river discharges was investigated in the process based model. These effects cannot be simulated using the diffusive type model. The results demonstrate the feasibility of using process based models to perform studies in scales of 10000 years. This is an advance relative to the use of synthetic models, enabling the use of variable forcing. REFERENCES Briggs, L.I. and Pollack, H.N., 1967. Digital model of evaporate sedimentation. Science, 155, 453-456. Flemmings, P.B. and Jordan, T.E., 1989. A synthetic stratigraphic model of foreland basin development. J. Geophys. Res., 94, 3851-3866. Miranda, R., Braunschweig, F., Leito, P., Neves, R., Martins, F. & Santos A., 2000. MOHID 2000 - A coastal integrated object oriented model. Proc. Hydraulic Engineering Software VIII, Lisbon, 2000, 393-401, Ed. W.R. Blain & C.A. Brebbia, WITpress. Paola, C., 2000. Quantitative models of sedimentary basin filing. Sedimentology, 47, 121-178. Schwarzacher, W., 1966. Sedimentation in a subsiding basin. Nature, 5043, 1349-1350. ACKNOWLEDGMENTS This work was supported by the EVEDUS PTDC/CLI/68488/2006 Research Project
Key elements of regional seismic velocity models for long period ground motion simulations
Brocher, T.M.
2008-01-01
Regional 3-D seismic velocity models used for broadband strong motion simulations must include compressional-wave velocity (Vp), shear-wave velocity (Vs), intrinsic attenuation (Qp, Qs), and density. Vs and Qs are the most important of these parameters because the strongest ground motions are generated chiefly by shear- and surface-wave arrivals. Because Vp data are more common than Vs data, many researchers first develop a Vp model and convert it to a Vs model. I describe recent empirical relations between Vs, Vp, Qs, Qp, and density that allow velocity models to be rapidly and accurately calculated. ?? Springer Science+Business Media B.V. 2007.
Shuttle data book: SRM fragment velocity model. Presented to the SRB Fragment Model Review Panel
NASA Technical Reports Server (NTRS)
1989-01-01
This study was undertaken to determine the velocity of fragments generated by the range safety destruction (RSD) or random failure of a Space Transportation System (STS) Solid Rocket Motor (SRM). The specific requirement was to provide a fragment model for use in those Galileo and Ulysses RTG safety analyses concerned with possible fragment impact on the spacecraft radioisotope thermoelectric generators (RTGS). Good agreement was obtained between predictions and observations for fragment velocity, velocity distributions, azimuths, and rotation rates. Based on this agreement with the entire data base, the model was used to predict the probable fragment environments which would occur in the event of an STS-SRM RSD or randon failure at 10, 74, 84 and 110 seconds. The results of these predictions are the basis of the fragment environments presented in the Shuttle Data Book (NSTS-08116). The information presented here is in viewgraph form.
Boukazouha, F; Poulin-Vittrant, G; Tran-Huu-Hue, L P; Bavencoffe, M; Boubenider, F; Rguiti, M; Lethiecq, M
2015-07-01
This article is dedicated to the study of Piezoelectric Transformers (PTs), which offer promising solutions to the increasing need for integrated power electronics modules within autonomous systems. The advantages offered by such transformers include: immunity to electromagnetic disturbances; ease of miniaturisation for example, using conventional micro fabrication processes; and enhanced performance in terms of voltage gain and power efficiency. Central to the adequate description of such transformers is the need for complex analytical modeling tools, especially if one is attempting to include combined contributions due to (i) mechanical phenomena owing to the different propagation modes which differ at the primary and secondary sides of the PT; and (ii) electrical phenomena such as the voltage gain and power efficiency, which depend on the electrical load. The present work demonstrates an original one-dimensional (1D) analytical model, dedicated to a Rosen-type PT and simulation results are successively compared against that of a three-dimensional (3D) Finite Element Analysis (COMSOL Multiphysics software) and experimental results. The Rosen-type PT studied here is based on a single layer soft PZT (P191) with corresponding dimensions 18 mm × 3 mm × 1.5 mm, which operated at the second harmonic of 176 kHz. Detailed simulational and experimental results show that the presented 1D model predicts experimental measurements to within less than 10% error of the voltage gain at the second and third resonance frequency modes. Adjustment of the analytical model parameters is found to decrease errors relative to experimental voltage gain to within 1%, whilst a 2.5% error on the output admittance magnitude at the second resonance mode were obtained. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for Rosen-type PT design and behavior understanding. PMID:25753623
Velocity measurements in jets with application to noise source modeling
NASA Astrophysics Data System (ADS)
Morris, Philip J.; Zaman, K. B. M. Q.
2010-02-01
This paper describes an experimental investigation of the statistical properties of turbulent velocity fluctuations in an axisymmetric jet. The focus is on those properties that are relevant to the prediction of noise. Measurements are performed using two single hot-wire anemometers as well as a two-component anemometer. Two-point cross correlations of the axial velocity fluctuations and of the fluctuations in the square of the axial velocity fluctuations are presented. Several reference locations in the jet are used including points on the jet lip and centerline. The scales of the turbulence and the convection velocity are determined, both in an overall sense as well as a function of frequency. The relationship between the second and fourth order correlations is developed and compared with the experimental data. The implications of the use of dimensional as well as non-dimensional correlations are considered. Finally, a comparison is made between the length scales deduced from the flow measurements and a RANS CFD calculation.
NASA Astrophysics Data System (ADS)
Carmelo, J. M. P.; Gu, Shi-Jian; Sampaio, M. J.
2014-06-01
Finite-temperature T > 0 transport properties of integrable and nonintegrable one-dimensional (1D) many-particle quantum systems are rather different, showing ballistic and diffusive behavior, respectively. The repulsive 1D Hubbard model is a prominent example of an integrable correlated system. For electronic densities n ? 1 (and spin densities m ? 0) it is an ideal charge (and spin) conductor, with ballistic charge (and spin) transport for T ? 0. In spite of the fact that it is solvable by the Bethe ansatz, at n = 1 (and m = 0) its T > 0 charge (and spin) transport properties are an issue that remains poorly understood. Here we combine this solution with symmetry and the explicit calculation of current-operator matrix elements between energy eigenstates to show that for on-site repulsion U > 0 and at n = 1 the charge stiffness D?(T) vanishes for T > 0 in the thermodynamic limit. A similar behavior is found by such methods for the spin stiffness Ds(T) for U > 0 and T > 0, which vanishes at m = 0. This absence of finite temperature n = 1 ballistic charge transport and m = 0 ballistic spin transport are exact results that clarify long-standing open problems.
NASA Astrophysics Data System (ADS)
Cooke, William; Donner, Leo
2015-04-01
Microphysical and aerosol processes determine the magnitude of climate forcing by aerosol-cloud interactions, are central aspects of cloud-climate feedback, and are important elements in weather systems for which accurate forecasting is a major goal of numerical weather prediction. Realistic simulation of these processes demands not only accurate microphysical and aerosol process representations but also realistic simulation of the vertical motions in which the aerosols and microphysics act. Aerosol activation, for example, is a strong function of vertical velocity. Cumulus parameterizations for climate and numerical weather prediction models have recently begun to include vertical velocities among the statistics they predict. These vertical velocities have been subject to only limited evaluation using observed vertical velocities. Deployments of multi-Doppler radars and dual-frequency profilers in recent field campaigns have substantially increased the observational base of cumulus vertical velocities, which for decades had been restricted mostly to GATE observations. Observations from TWP-ICE (Darwin, Australia) and MC3E (central United States) provide previously unavailable information on the vertical structure of cumulus vertical velocities and observations in differing synoptic contexts from those available in the past. They also provide an opportunity to independently evaluate cumulus parameterizations with vertical velocities tuned to earlier GATE observations. This presentation will compare vertical velocities observed in TWP-ICE and MC3E with cumulus vertical velocities using the parameterization in the GFDL CM3 climate model. Single-column results indicate parameterized vertical velocities are frequently greater than observed. Errors in parameterized vertical velocities exhibit similarities to vertical velocities explicitly simulated by cloud-system resolving models, and underlying issues in the treatment of microphysics may be important for both. The dependence of convective microphysical properties on vertical velocities and consequences for microphysics of simulation errors will be illustrated. Underlying limitations in the parameterization and model resolution will be discussed as explanations for differences between observed and simulated vertical velocities.
NASA Astrophysics Data System (ADS)
Ismail, Norilmi Amilia
2016-02-01
The motorized momentum exchange tether (MMET) is capable of generating useful velocity increments through spin-orbit coupling. This study presents a comparative study of the velocity increments between the rigid body and flexible models of MMET. The equations of motions of both models in the time domain are transformed into a function of true anomaly. The equations of motion are integrated, and the responses in terms of the velocity increment of the rigid body and flexible models are compared and analysed. Results show that the initial conditions, eccentricity, and flexibility of the tether have significant effects on the velocity increments of the tether.
Malo, Marcus; Brive, Lars; Luthman, Kristina; Svensson, Peder
2012-01-01
The aim of this study was to use a combined structure and pharmacophore modeling approach to extract information regarding dopamine D1 receptor agonism and D1/D2 agonist selectivity. A 3D structure model of the D1 receptor in its agonist-bound state was constructed with a full D1 agonist present in the binding site. Two different binding modes were identified using (+)-doxanthrine or SKF89626 in the modeling procedure. The 3D model was further compared with a selective D1 agonist pharmacophore model. The pharmacophore feature arrangement was found to be in good agreement with the binding site composition of the receptor model, but the excluded volumes did not fully reflect the shape of the agonist binding pocket. A new receptor-based pharmacophore model was developed with forbidden volumes centered on atom positions of amino acids in the binding site. The new pharmacophore model showed a similar ability to discriminate as the previous model. A comparison of the 3D structures and pharmacophore models of D1 and D2 receptors revealed differences in shape and ligand-interacting features that determine selectivity of D1 and D2 receptor agonists. A hydrogen bond pharmacophoric feature (Ser-TM5) was shown to contribute most to the selectivity. Non-conserved residues in the binding pocket that strongly contribute to D1/D2 receptor agonist selectivity were also identified; those were Ser/Cys3.36, Tyr/Phe5.38, Ser/Tyr5.41, and Asn/His6.55 in the transmembrane (TM) helix region, together with Ser/Ile and Leu/Asn in the second extracellular loop (EC2). This work provides useful information for the design of new selective D1 and D2 agonists. The combined receptor structure and pharmacophore modeling approach is considered to be general, and could therefore be applied to other ligand–protein interactions for which experimental information is limited. PMID:22315216
Solar velocity references from 3D HD photospheric models
NASA Astrophysics Data System (ADS)
de la Cruz Rodrguez, J.; Kiselman, D.; Carlsson, M.
2011-04-01
Context. The measurement of Doppler velocities in spectroscopic solar observations requires a reference for the local frame of rest. The rotational and radial velocities of the Earth and the rotation of the Sun introduce velocity offsets in the observations. Normally, good references for velocities are missing (e.g. telluric lines), especially in filter-based spectropolarimetric observations. Aims: We determine an absolute reference for line-of-sight velocities measured from solar observations for any heliocentric angle, calibrating the convective line shift of spatially-averaged profiles on quiet sun from a 3D hydrodynamical simulation. This method works whenever there is quiet sun in the field-of-view, and it has the advantage of being relatively insensitive to uncertainties in the atomic data. Methods: We carry out radiative transfer computations in LTE for selected C i and Fe i lines, whereas the Ca ii infrared lines are synthesized in non-LTE. Radiative transfer calculations are done with a modified version of Multi, using the snapshots of a non-magnetic 3D hydrodynamical simulation of the photosphere. Results: The resulting synthetic profiles show the expected C-shaped bisector at disk center. The degree of asymmetry and the line shifts, however, show a clear dependence on the heliocentric angle and the properties of the lines. The profiles at ? = 1 are compared with observed profiles to prove their reliability, and they are tested against errors induced by the LTE calculations, inaccuracies in the atomic data and the 3D simulation. Conclusions: Theoretical quiet-sun profiles of lines commonly used by solar observers are provided to the community. Those can be used as absolute references for line-of-sight velocities. The limb effect is produced by the projection of the 3D atmosphere along the line of sight. Non-LTE effects on Fe i lines are found to have a small impact on the convective shifts of the lines, reinforcing the usability of the LTE approximation in this case. We estimate the precision of the disk-center line shifts to be approximately 50 m s-1, but the off-center profiles remain to be tested against observations. The spectral profiles are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/528/A113
NASA Astrophysics Data System (ADS)
Saleh, F.; Ducharne, A.; Flipo, N.; Oudin, L.; Ledoux, E.
2013-01-01
SummaryRiver cross-sections data are required to represent channel geometry in hydrodynamic models. In the absence of accurate data at regional scale, simplified or parameterized cross sections are often used, which might affect the performance of the hydrodynamic model. In this study we assess the sensitivity of a 1D Saint-Venant hydraulic model to different types of river morphological data. The question is addressed using a 1D unsteady hydraulic model (HEC-RAS), with lateral inflows provided by the hydro(geo)logical model Eau-Dysse, to explore a wide spectrum of river geometry scenarios, regarding river bed slopes and cross-sectional shapes. The target scale is the one of the Seine River (France). As a gateway for larger and more complex regional hydro(geo)logical applications, our case-study covers a well-described 89-km reach in a sub-tributary of the Seine River. River morphology is described by high-resolution cross-sections, and Manning's roughness coefficient (n) is used for calibration against observed discharges and river stages in a mid-reach control point, with satisfactory performances over the 8-year simulation period. The resulting model still simulates realistic discharge hydrographs when forced with degraded channel geometry data, using either fewer cross-sections or approximated ones. In such cases, however, the hydraulic model does not always satisfactorily predict the associated water levels when compared to observations. In certain geometry scenarios, the RMSE between simulated water levels using degraded geometry and observations may go up to 0.3 m. The study confirms that the accuracy of predicted water levels and maximum water depths simulated by a Saint-Venant model relies on an accurate representation of channel geometry and bed level slopes along the river reach. From the various scenarios, it appears that the longitudinal description of the bed level profiles has a larger impact on the simulation of water levels than the cross-sectional shapes. This offers interesting implications for flood forecast mapping applications and regional scale models that often use simplified river geometry and Digital Elevation Models (DEMs) built by remote sensing technologies to simulate the water levels.
NASA Astrophysics Data System (ADS)
Gallovic, Frantisek; Pacor, Francesca; Zahradnik, Jiri; Luzi, Lucia; Puglia, Rodolfo; D'Amico, Maria
2014-05-01
We perform an extended study of the largest aftershock of the Mw6.3 2009 L'Aquila, Italy, earthquake, based on low-frequency inversion and broadband simulation of strong-motion data. The Mw5.5 aftershock occurred on April 7 and was recorded by ~30 permanent and temporal accelerometric stations located within 50km from the epicenter. Using ISOLA software we perform a CMT inversion, finding the centroid at 15km depth in agreement with previous studies. Distribution of relocated small aftershocks by Valoroso et al. (2013) suggests that the event ruptured a normal fault dipping NE at 60 degrees, antithetic to the major L'Aquila fault. To better constrain the source model, we invert strong-motion data in the frequency range 0.1-0.5 Hz, considering a finite-extent fault with homogenous slip and radial propagation at constant speed. We estimate fault dimension of 6x6km, static stress drop of 10 MPa (relatively low with respect to other studies), and find a weak indication of bilateral rupture propagation. These features are used to setup a broadband (0-10Hz) composite source model with fractal number-size distribution of overlapping subsources. The Green's functions are calculated in 1D layered medium in the full frequency range, assuming shallow site-specific structure, wherever available, and an average profile for generic rock stations; no stochastic Green's functions are used. At stations with not very strong site effects, the fit between synthetic and observed waveforms is generally good. Careful analysis of S-wave group polarization at high frequencies reveals that while some stations retain the predominantly linear polarization in accordance with the 1D modeling, other stations show a peculiar mismatch. The high-frequency mismatch appears either as the occurrence of random circular polarization, or as a variation of the angle characterizing the linear polarization. We discuss these observations in terms of crustal heterogeneity and azimuthally dependent site amplification.
A Velocity Distribution Model for Steady State Heat Transfer
NASA Technical Reports Server (NTRS)
Hall, Eric B.
1996-01-01
Consider a box that is filled with an ideal gas and that is aligned along Cartesian coordinates (x, y, z) having until length in the 'y' direction and unspecified length in the 'x' and 'z' directions. Heat is applied uniformly over the 'hot' end of the box (y = 1) and is removed uniformly over the 'cold' end (y = O) at a constant rate such that the ends of the box are maintained at temperatures T(sub 0) at y = O and T(sub 1) at y = 1. Let U, V, and W denote the respective velocity components of a molecule inside the box selected at some random time and at some location (x, y, z). If T(sub 0) = T(sub 1), then U, Y, and W are mutually independent and Gaussian, each with mean zero and variance RT(sub 0), where R is the gas constant. When T(sub 0) does not equal T(sub 1) the velocity components are not independent and are not Gaussian. Our objective is to characterize the joint distribution of the velocity components U, Y, and W as a function of y, and, in particular, to characterize the distribution of V given y. It is hoped that this research will lead to an increased physical understanding of the nature of turbulence.
NASA Astrophysics Data System (ADS)
Ichinose, G. A.
2006-12-01
Many scientific issues for the Basin and Range Province (BRP) remain unsettled including structural evolution, strain rates, slip partitioning and earthquake source physics. A catalog of earthquake source parameters including locations and moment tensors is the basis for tectonic and geophysical study. New instrumentation from the Advance National Seismic System, EarthScope Plate Boundary Observatory, Bigfoot and US-Array brings the opportunity for high quality research; therefore, a catalog is an underlying foundation for examining the BRP. We are continuing to generate a moment tensor catalog for the BRP (Mw<3.5) using long-period regional waves spanning back to 1990. Iterative waveform inversion method (e.g., Nolet et al., 1986, Randell, 1994) is used to calibrate the BRP velocity and density structure using two northern and southern BRP earthquakes. The calibrated models generate realistic synthetics for (f<0.5Hz) with ~50-80% variance reduction. We averaged all path specific models to construct a 1-D BRP community background model. The crust is relatively simple between 5-20km (~6.12km/s) and there is a strong velocity gradient in the upper 5- km. There are lower velocities in the upper crust but higher velocities in the mid-crust for the Sierra Nevada paths relative to BRP. There is also a lower crust high-velocity anomaly near Battle Mountain and Elko that is faster by ~5% and may indicate a wider area of under-plating by basaltic magmas. There are significant low velocity zones in the upper and mid crust mainly across the Walker Lane Belt that may indicate the presence of fluids. We are continuing to work on assessing the performance of these newly calibrated models in improving the estimation of moment tensors down to lower magnitudes and mapping out holes in the seismic network which can be filled to improve moment tensor catalog. We also are looking at how these models work at locating earthquakes and comparing synthetics with those computed from models constrained from different data including refraction, surface wave dispersion, and travel-time tomography.
NASA Astrophysics Data System (ADS)
Simon, Ehouarn; Bertino, Laurent
2012-01-01
We consider the problem of combined state-parameter estimations in biased nonlinear models with non-Gaussian extensions of the Deterministic Ensemble Kalman Filter (DEnKF). We focus on the particular framework of ocean ecosystem models. Such models present important obstacles to the use of data assimilation methods based on Kalman filtering due to the non-linearity of the models, the constraints of positiveness that apply to the variables and parameters, and the non-Gaussian distribution of the variables in which they result. We present extensions of the DEnKF dealing with these difficulties by introducing a nonlinear change of variables (anamorphosis function) in order to execute the analysis step with Gaussian transformed variables and parameters. Several strategies to build the anamorphosis functions are investigated and compared within the framework of twin experiments realized in a simple 1D ocean ecosystem model. A solution to the problem of the specification of the observation error for transformed observations is suggested. The study highlights the inability of the plain DEnKF with a simple post-processing of the negative values to properly estimate parameters when constraints of positiveness apply to the variables. It goes on to show that the introduction of the Gaussian anamorphosis can remedy these assimilation biases.
Kinematic and diabatic vertical velocity climatologies from a chemistry climate model
NASA Astrophysics Data System (ADS)
Hoppe, C. M.; Ploeger, F.; Konopka, P.; Müller, R.
2015-11-01
The representation of vertical velocity in chemistry climate models is a key element for the representation of the large scale Brewer-Dobson-Circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic vertical velocities in the ECHAM/Messy Atmospheric Chemistry (EMAC) model. The calculation of kinematic vertical velocity is based on the continuity equation, whereas diabatic vertical velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of vertical velocity from a 10 year simulation are provided for both, kinematic and diabatic vertical velocity representations. In general, both vertical velocity patterns show the main features of the stratospheric circulation, namely upwelling at low latitudes and downwelling at high latitudes. The main difference in the vertical velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic vertical velocity. Diabatic vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two vertical velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different vertical velocities. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic vertical velocities. Further, the age of air climatology from the transport scheme using diabatic vertical velocities shows younger mean age of air in the inner tropical upwelling branch and older mean age in the extratopical tropopause region.
Velocity mapping and models of the elliptical galaxies NGC 720, NGC 1052, and NGC 4697
NASA Technical Reports Server (NTRS)
Binney, J. J.; Davies, Roger L.; Illingworth, Garth D.
1990-01-01
CCD surface photometry and extensive long-slit spectroscopy are used to construct detailed models of the flattened ellipticals NGC 720, 1052, and 4697. The models are combined with the Jeans equations to yield predicted fields of line-of-sight velocity dispersion and streaming velocity. By comparing these fields with observed velocities, it is concluded that none of these systems can have isotropic velocity dispersion tensors, and diminishing the assumed inclination of any given galaxy tends to decrease the line-of-sight velocity dispersion and, counterintuitively, to increase the line-of-sight rotation speeds. The ratio of the line-of-sight velocity dispersion along the minor axis to that along the major axis is found to be a sensitive diagnostic of the importance of a third integral for the galaxy's structure.
Velocity mapping and models of the elliptical galaxies NGC 720, NGC 1052, and NGC 4697
Binney, J.J.; Davies, R.L.; Illingworth, G.D. Oxford Univ. National Optical Astronomy Observatories, Tucson, AZ California Univ., Santa Cruz )
1990-09-01
CCD surface photometry and extensive long-slit spectroscopy are used to construct detailed models of the flattened ellipticals NGC 720, 1052, and 4697. The models are combined with the Jeans equations to yield predicted fields of line-of-sight velocity dispersion and streaming velocity. By comparing these fields with observed velocities, it is concluded that none of these systems can have isotropic velocity dispersion tensors, and diminishing the assumed inclination of any given galaxy tends to decrease the line-of-sight velocity dispersion and, counterintuitively, to increase the line-of-sight rotation speeds. The ratio of the line-of-sight velocity dispersion along the minor axis to that along the major axis is found to be a sensitive diagnostic of the importance of a third integral for the galaxy's structure. 48 refs.
NASA Astrophysics Data System (ADS)
Persson, O. P.; Solomon, A.
2013-12-01
Though leads only represent a small portion of the Arctic sea-ice area, their contribution to the surface turbulent energy and momentum fluxes can be significant. Numerous modeling studies presented in the literature have been conducted examining these effects. The results of such studies have indicated the importance of the environmental large-scale stability, the environmental humidity, the lead width, the ice (lead) concentration, the lead size distribution, the character of the leads (open water, refrozen), etc. Because global climate models (GCMs) show significant sensitivity to the large-scale net energy flux from the heterogeneous sea-ice surface, and because thinner ice in the projected future Arctic climate will likely result in increasing lead fractions, the appropriate GCM representation of this complex system is important. This study presents modeling results based on observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, for which the mid-winter sea-ice was greatly heterogeneous. In mid-January, the 100x100 km region surrounding the SHEBA ice camp consisted of a lead fraction of ~16-33% as revealed by SAR data. This included primarily older refrozen lead areas that were generated at least a month earlier (~16-25% areal coverage), with a smaller fraction of newly opened leads (~4-9% areal coverage). Utilizing the sequence of SAR images, the atmospheric observations at the SHEBA site, and a 1-D snow and ice model, the spatial distribution of sea-ice thickness, snow depth, and surface temperatures within this domain were estimated over a 6-week period, revealing the significant impact of leads in all stages on GCM-scale temperatures and fluxes. This combined observational/model data series is used to evaluate a variety of one-dimensional turbulent flux aggregation techniques (e.g., mosaic) that use different assumptions. Furthermore, by using the spatial distribution of these surface characteristics, three-dimensional large eddy simulations (LES) have been done to a) validate the 1D aggregation techniques and b) to assess how mesoscale circulations generated by the surface heterogeneity impact net surface fluxes. Initially, the LES modeling uses very simple idealized surface conditions and progressively moves towards the much more complex conditions revealed by the SHEBA observations. Our LES studies both validate previous results and address issues not covered in the previous studies in an effort to understand and represent the SHEBA surface fluxes on scales from local point measurements to the GCM grid-box size.
NASA Astrophysics Data System (ADS)
Ammirati, J. B.; Alvarado, P. M.; Beck, S. L.
2014-12-01
Receiver Function (RF) analyses using teleseismic P waveforms is a technique to isolate P to S conversions from seismic discontinuities in the lithosphere. Using earthquakes with a good azimuthal distribution, RFs recorded at a three-component seismic station can be inverted to obtain detailed lithospheric velocity structures. The technique, however presents a velocity-depth trade-off, which results in a non-unique model because RFs do not depend on the absolute seismic velocities but rather on relative velocity contrasts. Unlike RF, surface wave dispersion is sensitive to the average shear-wave velocity which makes it well suited for studying long period variations of the lithospheric seismic velocities. We performed a joint inversion of RF and Rayleigh-wave phase velocity dispersion to investigate the structure beneath the SIEMBRA network, a 43-broadband-seismic-station array deployed in the Pampean flat slab region of Argentina. Our results indicate: 1) The presence of several mid-crustal discontinuities probably related with terrane accretion; 2) A high seismic velocity in the lower crust suggesting partial eclogitization; 3) A thicker crust (> 50 km) beneath the western Sierras Pampeanas with an abrupt change in the relative timing of the Moho signal indicating a thinner crust to the east; 4) The presence of the subducting oceanic crust lying at ~100 km depth. We then built a 1D regional velocity model for the flat slab region of Argentina and used it for regional moment tensor inversions for local earthquakes. This technique is notably dependent on small-scale variations of Earth structure when modeling higher frequency seismic waveforms. Eighteen regional focal mechanisms have been determined. Our solutions are in good agreement with GCMT source estimations although our solutions for deep earthquakes systematically resulted in shallower focal depths suggesting that the slab seismicity could be concentrated at the top of the subducting Nazca plate. Solutions corresponding to crustal events match well the geological observations from other studies.
NASA Astrophysics Data System (ADS)
Latorre, Diana; Lupattelli, Andrea; Mirabella, Francesco; Trippetta, Fabio; Valoroso, Luisa; Lomax, Anthony; Di Stefano, Raffaele; Collettini, Cristiano; Chiaraluce, Lauro
2014-05-01
Accurate hypocenter location at the crustal scale strongly depends on our knowledge of the 3D velocity structure. The integration of geological and geophysical data, when available, should contribute to a reliable seismic velocity model in order to guarantee high quality earthquake locations as well as their consistency with the geological structure. Here we present a 3D, P- and S-wave velocity model of the Upper Tiber valley region (Northern Apennines) retrieved by combining an extremely robust dataset of surface and sub-surface geological data (seismic reflection profiles and boreholes), in situ and laboratory velocity measurements, and earthquake data. The study area is a portion of the Apennine belt undergoing active extension where a set of high-angle normal faults is detached on the Altotiberina low-angle normal fault (ATF). From 2010, this area hosts a scientific infrastructure (the Alto Tiberina Near Fault Observatory, TABOO; http://taboo.rm.ingv.it/), consisting of a dense array of multi-sensor stations, devoted to studying the earthquakes preparatory phase and the deformation processes along the ATF fault system. The proposed 3D velocity model is a layered model in which irregular shaped surfaces limit the boundaries between main lithological units. The model has been constructed by interpolating depth converted seismic horizons interpreted along 40 seismic reflection profiles (down to 4s two way travel times) that have been calibrated with 6 deep boreholes (down to 5 km depth) and constrained by detailed geological maps and structural surveys data. The layers of the model are characterized by similar rock types and seismic velocity properties. The P- and S-waves velocities for each layer have been derived from velocity measurements coming from both boreholes (sonic logs) and laboratory, where measurements have been performed on analogue natural samples increasing confining pressure in order to simulate crustal conditions. In order to test the 3D velocity model, we located a selected dataset of the 2010-2013 TABOO catalogue, which is composed of about 30,000 micro-earthquakes (see Valoroso et al., same session). Earthquake location was performed by applying the global-search earthquake location method NonLinLoc, which is able to manage strong velocity contrasts as that observed in the study area. The model volume is 65km x 55km x 20km and is parameterized by constant velocity, cubic cells of side 100 m. For comparison, we applied the same inversion code by using the best 1D model of the area obtained with earthquake data. The results show a significant quality improvement with the 3D model both in terms of location parameters and correlation between seismicity distribution and known geological structures.
Sngond, Nicolas; Boulm, Audren; Plag, Camille; Teston, Franck; Certon, Dominique
2013-07-01
We report a fast time-domain model of fluid-coupled cMUTs developed to predict the transient response-i.e., the impulse pressure response--of an element of a linear 1-D array. Mechanical equations of the cMUT diaphragm are solved with 2-D finite-difference schemes. The time-domain solving method is a fourth--order Runge-Kutta algorithm. The model takes into account the electrostatic nonlinearity and the contact with the bottom electrode when the membrane is collapsed. Mutual acoustic coupling between cells is introduced through the numerical implementation of analytical solutions of the impulse diffraction theory established in the case of acoustic sources with rectangular geometry. Processing times are very short: they vary from a few minutes for a single cell to a maximum of 30 min for one element of an array. After a description of the model, the impact of the nonlinearity and the pull-in/pull-out phenomena on the dynamic behavior of the cMUT diaphragm is discussed. Experimental results of mechanical displacements obtained by interferometric measurements and the acoustic pressure field are compared with simulations. Different excitation signals-high-frequency bandwidth pulses and toneburst excitations of varying central frequency-were chosen to compare theory with experimental results. PMID:25004518
Janus, Christopher; Flores, Abigail Y; Xu, Guilian; Borchelt, David R
2015-09-01
Alzheimer's disease (AD) is characterized by dysfunction in cognitive and noncognitive domains with clinical diagnosis based on multiple neuropsychological tests. Here, we evaluated cognitive and noncognitive behaviors in 2 age cohorts (8 and 14 months at the start of the study) of APPSwe/PS1dE9 transgenic mice that model AD-like amyloidosis. We used a battery of tests that included fear-conditioned context and tone memories, swimming activity, and orientation to a proximal cue in a visible platform water maze test and burrowing and nest building activity. To compare the performance of mice across all tests, we used z-score normalization of data. The analyses revealed that the behavior of the transgenic mice was significantly compromised in cognitive as well as in noncognitive domains. Combining scores across multiple behavioral tests produced an integrated index characterizing the overall phenotypic abnormality in this model of AD-like amyloidosis. Assessing multiple behavioral domains provides a broader view of the breadth of impairments in multiple behavioral systems. Greater implementation of such approaches could enable reliable and clinically predictive evaluation of therapeutics in mouse models of amyloidosis. PMID:26089165
Jet stream velocity errors in general circulation models
NASA Technical Reports Server (NTRS)
Tenenbaum, J.
1987-01-01
The longitude and time dependence of excessive wind speed errors above subtropical jets in current GCM forecasts is studied for 14 five-day winter forecasts using the NASA Goddard Laboratory for Atmospheres fourth-order GCM. Several distinct phenomena, which may be divided into four categories, are found to contribute to the excess winds. These categories are: (1) error growth above the jet near the Himalayas; (2) error growth above the jet initiated elsewhere followed by advection; (3) tropical moisture bursts appearing in equatorial regions and migrating northeastward to merge with and distort the jet; and (4) undulatory growth of waves in the meridional component of the jet stream velocity. The results of additional sensitivity studies of the Himalayan region error are also reported.
A global 3D P-velocity model of the Earth's crust and mantle for improved event location.
Ballard, Sanford; Encarnacao, Andre Villanova; Begnaud, Michael A.; Rowe, Charlotte A.; Lewis, Jennifer E.; Young, Christopher John; Chang, Marcus C.; Hipp, James Richard
2010-04-01
To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D (SAndia LoS Alamos) version 1.4, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is > 55%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method, as well as by directly estimating the diagonal of the model resolution matrix based on the technique developed by Bekas, et al. We compare the travel-time prediction and location capabilities of this model over standard 1D models. We perform location tests on a global, geographically-distributed event set with ground truth levels of 5 km or better. These events generally possess hundreds of Pn and P phases from which we can generate different realizations of station distributions, yielding a range of azimuthal coverage and proportions of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135, especially with increasing azimuthal gap. The 3D model appears to perform better for locations based solely or dominantly on regional arrivals, which is not unexpected given that ak135 represents a global average and cannot therefore capture local and regional variations.
An Innovative Model-Based Velocity Integration Procedure with an Application in Eastern Saudi Arabia
NASA Astrophysics Data System (ADS)
Al-Moqbel, Abdulaziz Mohammed Saleh
During the workflow of seismic data processing, approximately one third of the processing time is allocated to estimate initial stacking velocity functions. The precision of the current available methods of estimating stacking velocity is limited in vertical and horizontal velocity resolution, especially in cases involving multiples and limited-offset data sets. A new procedure is proposed in this study to effectively build initial stacking velocity functions for processing new seismic lines with improved productivity, increased accuracy and interpretation consistency. The procedure builds a 3-D velocity model from previous surface and borehole seismic surveys as well as interpretation data for seven key horizons. A common-model platform has been used to allow for integration of otherwise independent data types. Results show that using the estimated integrated velocity model has allowed velocity picking in seismic data sets with poor signal-to-noise ratio due to excessive ambient noise or karsting. The model also helped in discriminating stacking velocities in areas with stretched or poor semblance peaks.
NASA Astrophysics Data System (ADS)
Spica, Zack J.; Caudron, Corentin; Pia-Flores, Jos; Perton, Mathieu; Thomas, Lecocq; Camelbeeck, Thierry; Legrand, Denis
2015-04-01
It is now well accepted that the average autocorrelation of seismic noise at a single station is proportional to the imaginary part of the Green's function when both source and receiver are the same. More recently, it has been established that the horizontal and vertical imaginary parts of the Green's function, i.e. the horizontal and vertical transfer functions, should be used to calculate the horizontal to vertical spectral ratio of ambient noise (HVSR). The HVSR is a popular technique that only requires a short-term (20 minutes) 3 components recording of seismic noise. Assuming an unbounded multi-layer model for the computation of the Green function, one can conduct the HVSR inversions to assess the 1D velocity structure of the subsurface. This approach was used to constrain several 1D velocity models (certain up to 3 km deep) of the Ijen caldera (Java, Indonesia) already established by the inversion of dispersion curves. Additionally, 84 HVSR measurements were also performed on Kawah Ijen volcano and allowed to provide a map of the local site effects. The velocity models obtained and the great outcrop of the crater rim allow robust and direct interpretation of the underground geology. Using a first order approximation, some mechanical proprieties of the shallower layers can be derived and the depth of an important lithological interface can be followed all around the Kawah Ijen crater.
Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength
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.
NASA Astrophysics Data System (ADS)
Bryan, Alexander M.; Cheng, Susan J.; Ashworth, Kirsti; Guenther, Alex B.; Hardiman, Brady S.; Bohrer, Gil; Steiner, Allison L.
2015-11-01
Foliar emissions of biogenic volatile organic compounds (BVOC)-important precursors of tropospheric ozone and secondary organic aerosols-vary widely by vegetation type. Modeling studies to date typically represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height variation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homogeneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting foliage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.
Yang Aijun; Wang Xiaohua; Rong Mingzhe; Liu Dingxin; Iza, Felipe; Kong, Michael G.
2011-11-15
In this paper atmospheric-pressure rf He+O{sub 2} cold plasmas are studied by means of a 1-D fluid model. 17 species and 60 key reactions selected from a study of 250+ reactions are incorporated in the model. O{sub 2}{sup +}, O{sub 3}{sup -}, and O are the dominant positive ion, negative ion, and reactive oxygen species, respectively. Ground state O is mainly generated by electron induced reactions and quenching of atomic and molecular oxygen metastables, while three-body reactions leading to the formation of O{sub 2} and O{sub 3} are the main mechanisms responsible for O destruction. The fraction of input power dissipated by ions is {approx}20%. For the conditions considered in the study {approx}6% of the input power is coupled to ions in the bulk and this amount will increase with increasing electronegativity. Radial and electrode losses of neutral species are in most cases negligible when compared to gas phase processes as these losses are diffusion limited due to the large collisionality of the plasma. The electrode loss rate of neutral species is found to be nearly independent of the surface adsorption probability p for p > 0.001 and therefore plasma dosage can be quantified even if p is not known precisely.
Bryan, Alexander M.; Cheng, Susan J.; Ashworth, Kirsti; Guenther, Alex B.; Hardiman, Brady; Bohrer, Gil; Steiner, A. L.
2015-11-01
Foliar emissions of biogenic volatile organic compounds (BVOC)dimportant precursors of tropospheric ozone and secondary organic aerosolsdvary widely by vegetation type. Modeling studies to date typi-cally represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height vari-ation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homo-geneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting fo-liage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.
Darvesh, Sultan; Cash, Meghan K.; Reid, G. Andrew; Martin, Earl; Mitnitski, Arnold; Geula, Changiz
2011-01-01
Histochemical analysis of Alzheimer disease (AD) brain tissues indicates that butyrylcholinesterase (BuChE) is present in β-amyloid (Aβ) plaques. The role of BuChE in AD pathology is unknown but an animal model developing similar BuChE-associated Aβ plaques could provide insights. The APPSWE/PSEN1dE9 mouse (ADTg), which develops Aβ plaques, was examined to determine if BuChE associates with these plaques, as in AD. We found that in mature ADTg mice, BuChE activity associated with Aβ plaques. Aβ-, thioflavin-S- and BuChE-positive plaques mainly accumulated in olfactory structures, cerebral cortex, hippocampal formation, amygdala and cerebellum. No plaques were stained for acetylcholinesterase activity. The distribution and abundance of plaque staining in ADTg closely resembled many aspects of plaque staining in AD. BuChE staining consistently showed fewer plaques than were detected with Aβ immunostaining but a greater number of plaques than were visualized with thioflavin-S. Double-labelling experiments demonstrated that all BuChE-positive plaques were Aβ-positive while only some BuChE-positive plaques were thioflavin-S-positive. These observations suggest that BuChE is associated with a subpopulation of Aβ plaques and may play a role in AD plaque maturation. Further study of this animal model could clarify the role of BuChE in AD pathology. PMID:22157615
NASA Astrophysics Data System (ADS)
Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian
2013-09-01
Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.
Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian
2013-09-09
Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.
NASA Astrophysics Data System (ADS)
Kang, Peter K.; Le Borgne, Tanguy; Dentz, Marco; Bour, Olivier; Juanes, Ruben
2015-02-01
Flow and transport through fractured geologic media often leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity distribution), connectedness in the flow paths through fractures (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of distribution- versus correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on velocity correlation, whereas late-time scaling of breakthrough curves is mainly controlled by velocity distribution. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, velocity distribution and velocity correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model accurately captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of velocity distribution and correlation on transport in fractured media.
Surface-wave phase-velocity models of the United States: Expanding with USArray coverage
NASA Astrophysics Data System (ADS)
Foster, A. E.; Ekstrom, G.; Nettles, M.
2014-12-01
We update our models of Love and Rayleigh wave phase-velocity structure using USArray data through mid 2014. We make measurements of the phase at periods from 25 to 100 s using a two-station method that assumes a great-circle arrival path for Love waves, and uses the estimated arrival angle for Rayleigh waves to correct the two-station calculation. Arrival-angle estimates are made with a mini-array method that employs a grid search to select the back-azimuth to the source that best predicts the phase observed on a local subset of stations. The two-station phase data with inter-station path lengths between 350 and 750 km are inverted to produce phase-velocity models at discrete periods. The new data set expands the modeled area, covering the entire contiguous United States. The mini-array method also produces an estimate of the local phase-velocity. We calculate this local phase-velocity for both Love and Rayleigh waves, and compare the measurements with the maps resulting from the inversion of the two-station measurements. The local phase velocities, two-station phase velocities, and two-station phase-velocity models are all examined for bias resulting from overtone interference. Based on previous work, we expect overtone interference to affect Love wave measurements but not Rayleigh wave measurements, and to affect the local measurements more than the two-station models.
NASA Astrophysics Data System (ADS)
Pujol, J. M.; Chiu, J. M.
2014-12-01
When applying seismic tomography to local arrival times from an area with a low-velocity sedimentary cover, the effect of the sediments on travel times should be taken into account. If that is not done, the resulting velocity model(s) cannot be assumed to be correct. This fairly obvious statement has been challenged recently by Powell et al. (JGR, 2010), who claimed that the sediments that cover the New Madrid seismic zone (NMSZ, central United States) can be ignored. This claim is examined here and shown to be incorrect. The NMSZ is covered by low-velocity, poorly consolidated sediments (Vp=1.8 km/s, Vs=3), which are underlain by Paleozoic rocks of much higher velocity. In the central NMSZ the sediment thickness varies between about 0.1 and 0.7 km. The JHD analysis of the data collected in that area by a portable network (PANDA) showed that the P- and S-wave station corrections spanned large ranges (0.35 and 0.63 s, respectively, Pujol et al., Eng. Geol., 1997). This study also showed that a Vp/Vs of 3 for the sediments would be too high if the lateral velocity variations were confined to the sedimentary cover. Here we generate synthetic traveltimes for a model with a sedimentary cover having variable depth (as determined from boreholes) underlain by the high-velocity layers in the 1-D model used for the JHD analysis. The synthetic data were generated for the station and event distributions corresponding to the Panda data. The tomographic inversion of the synthetic times produces spurious anomalies in Vp, Vs, and Vp/Vs, from the surface to a depth of 10 km. In addition, the events are mislocated in depth, with errors between 0 and 1 km for most of them. These results should dispel the notion that the effect of the unconsolidated sediments can be ignored. On the other hand, the inversion of the actual Panda data results in velocity anomalies similar to the synthetic anomalies, although larger, which is consistent with the conclusions of Pujol et al. (1997). Unfortunately, extricating the effects of the sediments from those of deeper velocity anomalies will not be possible with seismic tomography unless in-situ determinations of Vp/Vs for the sediments in the network area become available. Alternatively, analysis techniques that make use of more than just P- and S-wave arrivals (such as S-to-P converted waves) may have to be designed.
Quantifying Uncertainty in Velocity Models using Bayesian Methods
NASA Astrophysics Data System (ADS)
Hobbs, R.; Caiado, C.; Majda?ski, M.
2008-12-01
Quanitifying uncertainty in models derived from observed data is a major issue. Public and political understanding of uncertainty is poor and for industry inadequate assessment of risk costs money. In this talk we will examine the geological structure of the subsurface, however our principal exploration tool, controlled source seismology, gives its data in time. Inversion tools exist to map these data into a depth model but a full exploration of the uncertainty of the model is rarely done because robust strategies do not exist for large non-linear complex systems. There are two principal sources of uncertainty: the first comes from the input data which is noisy and bandlimited; the second, and more sinister, is from the model parameterisation and forward algorithms themselves, which approximate to the physics to make the problem tractable. To address these issues we propose a Bayesian approach. One philosophy is to estimate the uncertainty in a possible model derived using standard inversion tools. During the inversion stage we can use our geological prejudice to derive an acceptable model. Then we use a local random walk using the Metropolis- Hastings algorithm to explore the model space immediately around a possible solution. For models with a limited number of parameters we can use the forward modeling step from the inversion code. However as the number of parameters increase and/or the cost of the forward modeling step becomes significant, we need to use fast emulators to act as proxies so a sufficient number of iterations can be performed on which to base our statistical measures of uncertainty. In this presentation we show examples of uncertainty estimation using both pre- and post-critical seismic data. In particular, we will demonstrate uncertainty introduced by the approximation of the physics by using a tomographic inversion of bandlimited data and show that uncertainty increases as the central frequency of the data decreases. This is consistent with the infinite frequency approximation in the tomographic modeling step becoming increasing compromised.
Iwamoto, Masami; Nakahira, Yuko
2015-11-01
Accurate prediction of occupant head kinematics is critical for better understanding of head/face injury mechanisms in side impacts, especially far-side occupants. In light of the fact that researchers have demonstrated that muscle activations, especially in neck muscles, can affect occupant head kinematics, a human body finite element (FE) model that considers muscle activation is useful for predicting occupant head kinematics in real-world automotive accidents. In this study, we developed a human body FE model called the THUMS (Total HUman Model for Safety) Version 5 that contains 262 one-dimensional (1D) Hill-type muscle models over the entire body. The THUMS was validated against 36 series of PMHS (Post Mortem Human Surrogate) and volunteer test data in this study, and 16 series of PMHS and volunteer test data on side impacts are presented. Validation results with force-time curves were also evaluated quantitatively using the CORA (CORrelation and Analysis) method. The validation results suggest that the THUMS has good biofidelity in the responses of the regional or full body for side impacts, but relatively poor biofidelity in its local level of responses such as brain displacements. Occupant kinematics predicted by the THUMS with a muscle controller using 22 PID (Proportional-Integral- Derivative) controllers were compared with those of volunteer test data on low-speed lateral impacts. The THUMS with muscle controller reproduced the head kinematics of the volunteer data more accurately than that without muscle activation, although further studies on validation of torso kinematics are needed for more accurate predictions of occupant head kinematics. PMID:26660740
NASA Astrophysics Data System (ADS)
Li, Q.; Shimeld, J.; Dickie, K.; Dehler, S. A.; Desroches, K.
2013-12-01
Sediment thickness determinations play a key role in positioning the most seaward fixed points of the outer limits of continental shelves for coastal states. Seismic reflection surveying is an invaluable technique for estimating the sediment thickness required for the positioning. However, such seismic reflection surveying records the two way travel time (twtt) of vertically incident seismic waves. An accurate seismic velocity model is required for the conversion between twtt and sediment thickness. In this approach, a velocity model is constructed, its uncertainty is evaluated, and twtt is converted to sediment thickness. All of these procedures are programmed for batch and script processing. First, a slowness (the inverse of velocity) function, which is based on the solid sediment compaction theory, is selected and it is fitted using all available velocity observations using the reduced major axis (RMA) method, which can minimize errors from both velocity and depth observations. Second, the velocity uncertainty is estimated using a bootstrapping method by simulating a non-replace re-sampling procedure; thus it is also used in the estimation of sediment thickness uncertainty that is caused by velocity model errors. Moreover, with the constructed velocity model, conversion from sediment depth to twtt is resolved analytically and the conversion from twtt to depth is completed by solving a nonlinear equation with Newton iteration method, having approved convergence efficiency and a predefined accuracy (0.1 m). Finally, all these processes have been implemented in C# and JavaScript for integration with GeoFrame file format (seismic horizon interpretation) or embedded in any document with power batch processing and flexible verification facilities. As an example, publicly available velocity observations in the Labrador Sea region are used in the construction of a velocity model and the evaluation of velocity and sediment thickness uncertainty. The conversion between twtt and sediment thickness, based on the constructed velocity model, is derived and their excellent performance is demonstrated by simulating and comparing with published velocity models in the deep water region of the global oceans.
NASA Astrophysics Data System (ADS)
Khosravi, M.; Baron, P.; Urban, J.; Froidevaux, L.; Jonsson, A. I.; Kasai, Y.; Kuribayashi, K.; Mitsuda, C.; Murtagh, D. P.; Sagawa, H.; Santee, M. L.; Sato, T. O.; Shiotani, M.; Suzuki, M.; von Clarmann, T.; Walker, K. A.; Wang, S.
2013-08-01
The diurnal variation of HOCl and the related species ClO, HO2 and HCl measured by satellites has been compared with the results of a one-dimensional photochemical model. The study compares the data from various limb-viewing instruments with model simulations from the middle stratosphere to the lower mesosphere. Data from three sub-millimetre instruments and two infrared spectrometers are used, namely from the Sub-Millimetre Radiometer (SMR) on board Odin, the Microwave Limb Sounder (MLS) on board Aura, the Superconducting Submillimeter-wave Limb-Emission Sounder (SMILES) on the International Space Station, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT, and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board SCISAT. Inter-comparison of the measurements from instruments on sun-synchronous satellites (SMR, MLS, MIPAS) and measurements from solar occultation instruments (ACE-FTS) is challenging since the measurements correspond to different solar zenith angles (or local times). However, using a model which covers all solar zenith angles and data from the SMILES instrument which measured at all local times over a period of several months provides the possibility to verify the model and to indirectly compare the diurnally variable species. The satellite data were averaged for latitudes of 20 S to 20 N for the SMILES observation period from November 2009 to April 2010 and were compared at three altitudes: 35, 45 and 55 km. Besides presenting the SMILES data, the study also shows a first comparison of the latest MLS data (version 3.3) of HOCl, ClO, and HO2 with other satellite observations, as well as a first evaluation of HO2 observations made by Odin/SMR. The MISU-1D model has been carefully initialised and run for conditions and locations of the observations. The diurnal cycle features for the species investigated here are generally well reproduced by the model. The satellite observations and the model agree well in terms of absolute mixing ratios. The differences between the day and night values of the model are in good agreement with the observations although the amplitude of the HO2 diurnal variation is 10-20% lower in the model than in the observations. In particular, the data offered the opportunity to study the reaction ClO+HO2 ? HOCl+O2 in the lower mesosphere at 55 km. At this altitude the HOCl night-time variation depends only on this reaction. The result of this analysis points towards a value of the rate constant within the range of the JPL 2006 recommendation and the upper uncertainty limit of the JPL 2011 recommendation at 55 km.
NASA Astrophysics Data System (ADS)
Lin, G.
2010-12-01
We present preliminary results of a recent development of three-dimensional (3D) P-wave velocity and attenuation models for the Salton Trough, California. We obtain first arrival times and waveform data for all the local events in our study area recorded by the Southern California Seismic Network. Over 1000 master events are selected for the tomographic inversions. Arrival times from explosions and quarry blasts are also included to improve constraints on the shallow crustal structure. The simul2000 algorithm is applied to solve for both the velocity and attenuation models. We start with a one-dimensional velocity model with uniform 5 km horizontal and variable (2 to 5 km) vertical gridding. Our velocity model shows strong velocity contrast across the Southern San Andreas Fault (SSAF) through all the depth layers. Preliminary 3D relocated seismicity shows ~2 km shift towards the surface trace of the SSAF compared to the starting catalog locations, indicating that part of the separations between the seismicity and the fault surface may be due to the velocity anomalies in the local structure. A checkerboard test is also performed to evaluate the resolution of our results. Seismic attenuations can also provide important constraints on Earth properties. We determine the 3D attenuation structure using the t* values computed from the velocity spectra for vertical component seismograms from each event recorded by each station. Our 3D velocity model is used to trace the ray paths along which the t* values are accumulated. The resulting attenuation model generally agrees with the previous studies, but we also observe some new features, such as the locally low Q at shallow depths north of the Salton Sea. Our high-resolution velocity and attenuation studies may reveal fine-scale structures that are not resolved in the previous regional-scale studies.
NASA Astrophysics Data System (ADS)
Concha-Dimas, A.; Rasmussen, T.; Louie, J. N.; Smith, S.; Thelen, W.; Pancha, A.; Anderson, J. G.
2002-12-01
We are developing a three-dimensional reference seismic velocity model for Las Vegas and surrounding basins. We will use this model to help determine the importance of the basin response to any possible large seismic source, and the contribution of this response to seismic hazards in the urban area. Assessment of seismic-shaking amplification by deep sedimentary basins needs detailed characterization of basin geometry, fill velocities, and geotechnical velocities. We are compiling velocity information from sources in the literature, results of previous seismic experiments, earthquake monitoring, and geotechnical, petroleum, and ground water projects. We are developing for public release in early 2003 a model-assembly code and web interface that generates elastic-property grids for input to finite-difference codes. The model assembler is rule-based. It incorporates location and geological information to specify basin depth, seismic velocities, and densities for bedrock, sedimentary basins, and volcanic rift-basins. It adds the results of more detailed studies where they are available, such as those from Langenheim's gravity analysis of Las Vegas basin. This community velocity model is a part of a regional model we are developing for the western Great Basin. With a new parallel computer facility, we are validating the obtained rule-based models by generating synthetic seismograms and comparing them to recordings of old NTS explosions and past earthquakes (as the Little Skull Mountain earthquake) at broadband seismic stations and urban strong-motion stations.
NASA Astrophysics Data System (ADS)
Lea, J. M.; Mair, D.; Nick, F. M.; Rea, B. R.; Schofield, E.; Nienow, P. W.
2012-12-01
The ability to successfully model the behaviour of Greenlandic tidewater glaciers is pivotal for the prediction of future behaviour and potential impact on global sea level. However, to have confidence in the results of numerical models, they must be capable of replicating the full range of observed glacier behaviour (i.e. both advance and retreat) when realistic forcings are applied. Due to the paucity of observational records recording this behaviour, it is therefore necessary to verify calving models against reconstructions of glacier dynamics. The dynamics of Kangiata Nunaata Sermia (KNS) can be reconstructed with a high degree of detail using a combination of sedimentological and geomorphological evidence, photographs, historical sources and satellite imagery. Since the LIA-maximum KNS has retreated a total of 21 km with multiple phases of rapid retreat evident between topographic pinning points. A readvance attaining a position 9 km from the current terminus associated with the '1920 stade' is also identified. KNS therefore represents an ideal test location for calving models since it has both advanced and retreated over known timescales, while the scale of fluctuations implies KNS is sensitive to parameter(s) controlling terminus stability. Using the known stable positions for verification, we present the results of an array of sensitivity tests conducted on KNS using the 1-D flowband calving model of Nick et al (2009). The model is initially tuned to an historically stable position where the glacier configuration is accurately known (in this case 1985), and forced by varying surface mass balance, crevasse water depth, submarine melt rate at the calving front, in addition to the strength and pervasiveness of sikussak in the fjord. Successive series of experiments were run using each parameter to test model sensitivity to the initial conditions of each variable. Results indicate that the model is capable of stabilising at locations that are in agreement with the geomorphic/historical record. Reference: Nick FM, Vieli A, Howat IM, Joughin I. 2009. Large-scale changes in Greenland outlet glaciers triggered at the terminus. Nature Geoscience 2 : 110-114
NASA Technical Reports Server (NTRS)
Dobson, Chris C.; Hrbud, Ivana
2004-01-01
Electron density measurements have been made in steady-state plasmas in a spherical inertial electrostatic confinement (IEC) discharge using microwave interferometry. Plasma cores interior to two cathodes, having diameters of 15 and 23 cm, respectively, were probed over a transverse range of 10 cm with a spatial resolution of about 1.4 cm for buffer gas pressures from 0.2 to 6 Pa in argon and deuterium. The transverse profiles are generally flat, in some cases with eccentric symmetric minima, and give mean densities of from approx. = 0.4 to 7x 10(exp 10)/cu cm, the density generally increasing with the neutral gas pressure. Numerical solutions of the 1-D Poisson equation for EC plasmas are reviewed and energy distribution functions are identified which give flat transverse profiles. These functions are used with the plasma approximation to obtain solutions which also give densities consistent with the measurements, and a double potential well solution is obtained which has minima qualitatively similar to those observed. Explicit consideration is given to the compatibility of the solutions interior and exterior to the cathode, and to grid transparency. Deuterium fusion neutron emission rates were also measured and found to be isotropic, to within the measurement error, over two simultaneous directions. Anisotropy was observed in residual emissions during operation with non-fusing hydrogen-1. The deuterium rates are consistent with predictions from the model.
Gripp, A.E.; Gordon, R.G. )
1990-07-01
NUVEL-1 is a new global model of current relative plate velocities which differ significantly from those of prior models. Here the authors incorporate NUVEL-1 into HS2-NUVEL1, a new global model of plate velocities relative to the hotspots. HS2-NUVEL1 was determined from the hotspot data and errors used by Minster and Jordan (1978) to determine AM1-2, which is their model of plate velocities relative to the hotspots. AM1-2 is consistent with Minster and Jordan's relative plate velocity model RM2. Here the authors compare HS2-NUVEL1 with AM1-2 and examine how their differences relate to differences between NUVEL-1 and RM2. HS2-NUVEL1 plate velocities relative to the hotspots are mainly similar to those of AM1-2. Minor differences between the two models include the following: (1) in HS2-NUVEL1 the speed of the partly continental, apparently non-subducting Indian plate is greater than that of the purely oceanic, subducting Nazca plate; (2) in places the direction of motion of the African, Antarctic, Arabian, Australian, Caribbean, Cocos, Eurasian, North American, and South American plates differs between models by more than 10{degree}; (3) in places the speed of the Australian, Caribbean, Cocos, Indian, and Nazca plates differs between models by more than 8 mm/yr. Although 27 of the 30 RM2 Euler vectors differ with 95% confidence from those of NUVEL-1, only the AM1-2 Arabia-hotspot and India-hotspot Euler vectors differ with 95% confidence from those of HS2-NUVEL1. Thus, substituting NUVEL-1 for RM2 in the inversion for plate velocities relative to the hotspots changes few Euler vectors significantly, presumably because the uncertainty in the velocity of a plate relative to the hotspots is much greater than the uncertainty in its velocity relative to other plates.
Jiang, Shuang; Pang, Liping; Buchan, Graeme D; Simůnek, Jirí; Noonan, Mike J; Close, Murray E
2010-02-01
HYDRUS-1D was used to simulate water flow and leaching of fecal coliforms and bromide (Br) through six undisturbed soil lysimeters (70 cm depth by 50 cm diameter) under field conditions. Dairy shed effluent (DSE) spiked with Br was applied to the lysimeters, which contained fine sandy loam layers. This application was followed by fortnightly spray or flood water irrigation. Soil water contents were measured at four soil depths over 171 days, and leachate was collected from the bottom. The post-DSE period simulations yielded a generally decreased saturated water content compared to the pre-DSE period, and an increased saturated hydraulic conductivity and air-entry index, suggesting that changes in soil hydraulic properties (e.g. via changes in structure) can be induced by irrigation and seasonal effects. The single-porosity flow model was successful in simulating water flow under natural climatic conditions and spray irrigation. However, for lysimeters under flood irrigation, when the effect of preferential flow paths becomes more significant, the good agreement between predicted and observed water contents could only be achieved by using a dual-porosity flow model. Results derived from a mobile-immobile transport model suggest that compared to Br, bacteria were transported through a narrower pore-network with less mass exchange between mobile and immobile water zones. Our study suggests that soils with higher topsoil clay content and soils under flood irrigation are at a high risk of bacteria leaching through preferential flow paths. Irrigation management strategies must minimize the effect of preferential flow to reduce bacterial leaching from land applications of effluent. PMID:19775719
NASA Astrophysics Data System (ADS)
Bozza, Andrea; Durand, Arnaud; Allenbach, Bernard; Confortola, Gabriele; Bocchiola, Daniele
2013-04-01
We present a feasibility study to explore potential of high-resolution imagery, coupled with hydraulic flood modeling to predict flooding risks, applied to the case study of Gonaives basins (585 km), Haiti. We propose a methodology working at different scales, providing accurate results and a faster intervention during extreme flood events. The 'Hispaniola' island, in the Caribbean tropical zone, is often affected by extreme floods events. Floods are caused by tropical springs and hurricanes, and may lead to several damages, including cholera epidemics, as recently occurred, in the wake of the earthquake upon January 12th 2010 (magnitude 7.0). Floods studies based upon hydrological and hydraulic modeling are hampered by almost complete lack of ground data. Thenceforth, and given the noticeable cost involved in the organization of field measurement campaigns, the need for exploitation of remote sensing images data. HEC-RAS 1D modeling is carried out under different scenarios of available Digital Elevation Models. The DEMs are generated using optical remote sensing satellite (WorldView-1) and SRTM, combined with information from an open source database (Open Street Map). We study two recent flood episodes, where flood maps from remote sensing were available. Flood extent and land use have been assessed by way of data from SPOT-5 satellite, after hurricane Jeanne in 2004 and hurricane Hanna in 2008. A semi-distributed, DEM based hydrological model is used to simulate flood flows during the hurricanes. Precipitation input is taken from daily rainfall data derived from TRMM satellite, plus proper downscaling. The hydraulic model is calibrated using floodplain friction as tuning parameters against the observed flooded area. We compare different scenarios of flood simulation, and the predictive power of model calibration. The method provide acceptable results in depicting flooded areas, especially considering the tremendous lack of ground data, and show the potential of remote sensing information in prediction of flood events in this area, for the purpose of risk assessment and land use planning, and possibly for flood forecast during extreme events.
Propagation of the velocity model uncertainties to the seismic event location
NASA Astrophysics Data System (ADS)
Gesret, A.; Desassis, N.; Noble, M.; Romary, T.; Maisons, C.
2015-01-01
Earthquake hypocentre locations are crucial in many domains of application (academic and industrial) as seismic event location maps are commonly used to delineate faults or fractures. The interpretation of these maps depends on location accuracy and on the reliability of the associated uncertainties. The largest contribution to location and uncertainty errors is due to the fact that the velocity model errors are usually not correctly taken into account. We propose a new Bayesian formulation that integrates properly the knowledge on the velocity model into the formulation of the probabilistic earthquake location. In this work, the velocity model uncertainties are first estimated with a Bayesian tomography of active shot data. We implement a sampling Monte Carlo type algorithm to generate velocity models distributed according to the posterior distribution. In a second step, we propagate the velocity model uncertainties to the seismic event location in a probabilistic framework. This enables to obtain more reliable hypocentre locations as well as their associated uncertainties accounting for picking and velocity model uncertainties. We illustrate the tomography results and the gain in accuracy of earthquake location for two synthetic examples and one real data case study in the context of induced microseismicity.
Velocity Modeling of Land 3-D Surface Seismic Data for Prestack Depth Migration
NASA Astrophysics Data System (ADS)
Duncan, W. S.; Zhou, H.
2005-05-01
Since the early 1990's prestack depth migrations (PSDM) have been routinely applied to 3-D seismic data. Using current methods building an accurate velocity model is dependent on the quality of the seismic data. Data quality is a reason why PSDM have been applied nearly exclusively to marine data. To apply the power of PSDM to land 3-D surface seismic data deriving an initial sediment velocity model that overcomes limitations of data quality associated with land 3-D seismic data is essential. In this study I use a non-seismic approach to generate an initial sediment velocity model for PSDM of land 3-D surface seismic data. Differences in data quality between marine and land 3-D seismic data provided the motivation to investigate innovative velocity modeling techniques for land 3-D surface seismic data. In this study current practices primarily for marine data were reviewed and problems with land 3-D surface seismic data were identified. An approach that integrates the efficiency and accuracy of current methods and overcomes the limitations imposed by data quality was implemented. Data were acquired over Vinton Dome in southwest Louisiana and used in this case study to derive an initial sediment velocity model using sonic logs. Comparing the results with a prestack time migration (PSTM) and a PSDM that had been migrated using a seismically derived velocity model demonstrated that this approach enhanced the fidelity of the Vinton Dome 3-D surface seismic data.
Johnson, G. R.; Holmquist, T. J.
2007-12-12
Constitutive models for brittle materials such as glass can be very complex as they are dependent on strains, strain rates, pressures, temperatures, damage and other parameters. There may also be significant (pressure-dependent) strength after failure such that the constitutive response is much different for intact material and failed material. A large number of laboratory tests is required to develop a comprehensive constitutive model. Another approach is to develop simple models by using penetration-velocity data obtained from ballistic experiments. Here various functional forms of simple models (with a limited number of constants) can be used to (computationally) match the penetration velocity over a range of impact velocities. This allows for the determination of the most important parameters and it provides an approximation of the stresses that occur during penetration. This article presents several simple computational models for borosilicate glass, including single-state models and dual-state models (that include an intact strength and a failed strength)
Subgrid scale updraft velocity in km-scale models: implication for the aerosol indirect effect
NASA Astrophysics Data System (ADS)
Malavelle, F.; Haywood, J.; Field, P.; Hill, A.; Abel, S.; Lock, A.; Shipway, B.; McBeath, K.
2013-12-01
Aerosol-cloud-interactions (ACI) span a large range of spatial and temporal scales. The coarse resolution used in Global Circulation Models and Earth System models is unable to resolve the fine scale processes (e.g. vertical velocity, turbulent mixing) or the microphysical and dynamic feedbacks that are important for ACI, which leads to important uncertainties. The microphysical link between aerosols and clouds is activation, which is a strong function of the cloud-scale updraft velocity. To bridge the gap between the cloud scale and the global scale, a potential approach is using high-resolution large-scale models such as those from operational Numerical Weather Prediction (NWP). However, even for non-hydrostatic km-scale NWP models, vertical velocities are only partially resolved. This work focuses on the parameterisation of the sub-grid vertical velocity and aerosol activation in such models. In order to estimate the contribution of the unresolved sub-grid variability, we analyse the updraft velocity at cloud resolving scales. Our strategy relies on running Large Eddy Simulation (LES) models and analysing hi-resolution aircraft observations of stratocumulus and shallow cumulus clouds to devise the scale-linking partition function of the total updraft velocity variability. To construct such a function, the resolved and sub-grid parts of the variables at coarser grid sizes are deduced after coarse graining the initial high resolution datasets. On this basis, we have developed and tested a framework for a parameterization that represents the sub-grid variability of updraft velocity in UK-Met Office NWP model, the Unified Model (UM), which is applicable to resolutions up to a few km. We show that without correction, the variability of updraft velocity decreases with decreasing model resolution. Applying our parameterization leads to consistent estimates of vertical velocity variability across the different resolutions. The contribution of the sub-grid variability to the vertical velocity standard deviation is factor of ~4-8 increase in simulations at a 1 km horizontal grid resolution. Offline calculations of CCN activated fraction using two activation schemes have been performed to investigate the sensitivity of the activation processes when the sub-grid scale vertical velocity variability is accounted for. These tests show significant increases in the CCN activated fraction, from +20% up to +100% depending on CCN concentration and the scheme considered. This highlights important implications for future ACI simulations at km-scale.
Volumetric Velocity Measurements of Pulsating Flow through a Model Aneurysm
NASA Astrophysics Data System (ADS)
Troolin, Daniel; Amatya, Devesh; Longmire, Ellen
2010-11-01
Volumetric 3-component velocimetry (V3V) was used to examine the flow structure inside of a scaled-up transparent urethane model of a saccular aneurysm. The model was fabricated to match the geometry of an in vivo case. Index matching was used to minimize optical distortions caused by the curved walls of the model. The model and a surrounding visualization box were integrated into a custom-built pulse duplicator system with in-line flow meter and pressure transducers. The pulsing frequency and amplitude were controlled independently to generate two flow conditions each having a non-dimensional peak Reynolds (Re) and Womersley (Wo) Number: Re = 250, Wo = 10.4 and Re = 125, Wo = 7.4. Phase-locked and instantaneous measurements of the pulsatile flow upstream, downstream, and within the aneurysm reveal significant three-dimensional features including zones of separation, recirculation, impingement, and relative inactivity. Plots and movies will be shown, and a detailed discussion of the flow and various experimental considerations will be included.
NASA Astrophysics Data System (ADS)
Khosravi, M.; Baron, P.; Urban, J.; Froidevaux, L.; Jonsson, A. I.; Kasai, Y.; Kuribayashi, K.; Mitsuda, C.; Murtagh, D. P.; Sagawa, H.; Santee, M. L.; Sato, T. O.; Shiotani, M.; Suzuki, M.; von Clarmann, T.; Walker, K. A.; Wang, S.
2012-08-01
The diurnal variation of HOCl and the related species ClO, HO2 and HCl measured by satellites has been compared with the results of a one-dimensional photochemical model. The study compares the data from various limb-viewing instruments with model simulations from the middle stratosphere to the lower mesosphere. Data from three sub-millimeter instruments and two infrared spectrometers are used, namely from the Sub-Millimeter Radiometer (SMR) on board Odin, the Microwave Limb Sounder (MLS) on board Aura, the Superconducting Submillimeter-wave Limb-Emission Sounder (SMILES) on the International Space Station, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT, and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board SCISAT. Inter-comparison of the measurements from instruments on sun-synchronous satellites (SMR, MLS, MIPAS) and measurements from solar occultation instruments (ACE-FTS) is challenging since the measurements correspond to different solar zenith angles (or local times). However, using a model which covers all solar zenith angles and the new SMILES instrument which measures at all local times over a period of several months provides the possibility to indirectly compare the diurnally variable species. The satellite data were averaged for latitudes of 20 S to 20 N for the SMILES observation period from November 2009 to April 2010 and were compared at three altitudes: 35, 45 and 55 km. This study presents the first evaluation of HO2 Odin/SMR data and also the first comparison of the new SMILES data and the latest version of MLS (version 3.3) with other satellite observations. The MISU-1D model has been run for conditions and locations of the observations. The diurnal cycle features for the species investigated here are generally well reproduced by the model. The satellite observations and the model generally agree well in terms of absolute mixing ratios as well as differences between the day and night values. This confirms that gas phase chemistry of these species based on latest recommendations of reaction rate constants is fairly well understood.
NASA Astrophysics Data System (ADS)
Driba, D. L.; De Lucia, M.; Peiffer, S.
2014-12-01
Fluid-rock interactions in geothermal reservoirs are driven by the state of disequilibrium that persists among solid and solutes due to changing temperature and pressure. During operation of enhanced geothermal systems, injection of cooled water back into the reservoir disturbs the initial thermodynamic equilibrium between the reservoir and its geothermal fluid, which may induce modifications in permeability through changes in porosity and pore space geometry, consequently bringing about several impairments to the overall system.Modeling of fluid-rock interactions induced by injection of cold brine into Groß Schönebeck geothermal reservoir system situated in the Rotliegend sandstone at 4200m depth have been done by coupling geochemical modeling Code Phreeqc with OpenGeoSys. Through batch modeling the re-evaluation of the measured hydrochemical composition of the brine has been done using Quintessa databases, the results from the calculation indicate that a mineral phases comprising of K-feldspar, hematite, Barite, Calcite and Dolomite was found to match the hypothesis of equilibrium with the formation fluid, Reducing conditions are presumed in the model (pe = -3.5) in order to match the amount of observed dissolved Fe and thus considered as initial state for the reactive transport modeling. based on a measured composition of formation fluids and the predominant mineralogical assemblage of the host rock, a preliminary 1D Reactive transport modeling (RTM) was run with total time set to 30 years; results obtained for the initial simulation revealed that during this period, no significant change is evident for K-feldspar. Furthermore, the precipitation of calcite along the flow path in the brine results in a drop of pH from 6.2 to a value of 5.2 noticed over the simulated period. The circulation of cooled fluid in the reservoir is predicted to affect the temperature of the reservoir within the first 100 -150m from the injection well. Examination of porosity change in this simulation reveals that, porosity and permeability near the wellbore are enhanced after injection. This is chiefly due to the dissolution of calcite near the injection well and less extent by dolomite The porosity is improved by more than 14% at the injection well, but then decreases away from the well.
Measurements and a model for convective velocities in the turbulent boundary layer
NASA Technical Reports Server (NTRS)
Cliff, W. C.; Sandborn, V. A.
1973-01-01
A physical model is presented which describes convective velocities within a flat plate turbulent boundary layer. A production zone concept is used as a basis for the physical model. The production zone concept employs the idea that packets of turbulent fluid are generated near the viscous sublayer. These packets are found to be discernible from the mean motion and may move either outward from the production zone or inward depending on their circulation relative to the fluid surrounding the packet. The packets are predicted to travel with a convective velocity different from the local mean velocity throughout most of the boundary layer. The model also predicts that the convective velocities will be functions of wave number outside the production zone.
Preliminary velocity and resistivity models of the Loma Prieta earthquake region
Eberhart-Phillips, D.; Michael, A.J. ); Labson, V.F.; Stanley, W.D.; Rodriguez, B.D. )
1990-07-01
A preliminary three-dimensional velocity model of the Loma Prieta epicentral region in the Santa Cruz Mountains of California has been derived using raypaths from aftershocks recorded by the U.S.G.S. seismic network. In addition, magnetotelluric sounding profile was completed prior to the earthquake and a two-dimensional resistivity model computed. The velocity and resistivity models include a low-resistivity (3-10 ohm-m), low-velocity (3.3-5.8 km/s) wedge of material between the Zayante and San Andreas faults that extends to depths of over 8 km and is interpreted to be largely Tertiary marine sedimentary rocks. A high-resistivity (>1,000 ohm-m), high-velocity (6.4-6.7 km/s) zone between the San Andreas and Sargent faults may represent largely mafic intrusive rocks.
NASA Technical Reports Server (NTRS)
Gripp, Alice E.; Gordon, Richard G.
1990-01-01
The NUVEL-1 model of current global relative plate velocities is presently incorporated into HS2-NUVEL1, a global model for plate velocities relative to hotspots; the results thus obtained are compared with those of the AM1-2 model of hotspot-relative plate velocities. While there are places in which plate velocities relative to the hotspots differ between HS2-NUVEL1 and AM1-2 by tens of degrees in direction and 15 mm/yr in speed, the hotspot Euler vectors differ with 95 percent confidence only for the Arabian and Indian plates. Plates attached to subducting slabs move faster relative to the hotspots than do plates without slabs.
A comprehensive dispersion model of surface wave phase and group velocity for the globe
NASA Astrophysics Data System (ADS)
Ma, Zhitu; Masters, Guy; Laske, Gabi; Pasyanos, Michael
2014-10-01
A new method is developed to measure Rayleigh- and Love-wave phase velocities globally using a cluster analysis technique. This method clusters similar waveforms recorded at different stations from a single event and allows users to make measurements on hundreds of waveforms, which are filtered at a series of frequency ranges, at the same time. It also requires minimal amount of user interaction and allows easy assessment of the data quality. This method produces a large amount of phase delay measurements in a manageable time frame. Because there is a strong trade-off between the isotropic part of the Rayleigh-wave phase velocity and azimuthal anisotropy, we include the effect of azimuthal anisotropy in our inversions in order to obtain reliable isotropic phase velocity. We use b-splines to combine these isotropic phase velocity maps with our previous group velocity maps to produce an internally consistent global surface wave dispersion model.
The Last Variable: Speculations on Mapping Stream Velocity using Imagery and Models
NASA Astrophysics Data System (ADS)
Fonstad, M. A.
2009-12-01
The past decade has seen a revolution in the use of remote sensing to map quantitative river forms such as water depth, slope, and particle sizes. Despite these advances, researchers focusing on river remote sensing have been hampered in describing river processes directly because of the lack of mapped river flow velocities at high resolution and over large extents. The same transparency which often allows many of the other variables makes it difficult to detect the flow field. Nevertheless, several options already exist for potentially mapping velocity remotely, including (1) Use of a resistance formula w/estimated slope and depth information and a hydraulic model, (2) augmenting option number 1 with directly detected water elevations using radar, lidar, or optical parallax to increase precision, (3) natural and artificial PIV approaches, (4) motion blur, (5) classification and regression of velocity zones from spectral information, (6) Water surface feature interpretation combined with hydraulic theory, and (7) water surface superelevation in bends. Direct observations and numerical sensitivity analysis of these approaches show that there is not a single solution to best map stream velocity. In many cases, using two or more techniques simultaneous will increase precision and accuracy. Along with depth, slope, and particle sizes, the addition of velocity as a remotely mapped variable would profoundly alter the study of rivers. Mapped velocity would allow more precise habitat maps and, potentially, calibration and validation of hydraulic models and resistance formulas. In addition to these direct uses of velocity maps, the knowledge of velocity combined with the other remotely measurable variables would allow direct calculation of a large number of derived river indices, such as stream power, shear stress, Froude number, Bisson habitat class, and many others. The number of possible roads to remote velocity mapping is large and expanding, but it requires specifically dedicated time for basic research. Flume experiments, high-resolution field observations, and numerical modeling will all be useful in delimiting the needs and precisions of these techniques in different river situations.
Velocity field measurements in oblique static divergent vocal fold models
NASA Astrophysics Data System (ADS)
Erath, Byron
2005-11-01
During normal phonation, the vocal fold cycle is characterized by the glottal opening transitioning from a convergent to a divergent passage and then closing before the cycle is repeated. Under ordinary phonatory conditions, both vocal folds, which form the glottal passage, move in phase with each other, creating a time-varying symmetric opening. However, abnormal pathological conditions, such as unilateral paralysis, and polyps, can result in geometrical asymmetries between the vocal folds throughout the phonatory cycle. This study investigates pulsatile flow fields through 7.5 times life-size vocal fold models with included divergence angles of 5 to 30 degrees, and obliquities between the vocal folds of up to 15 degrees. Flow conditions were scaled to match physiological parameters. Data were taken at the anterior posterior mid-plane using phase-averaged Particle Image Velocimetry (PIV). Viscous flow phenomena including the Coanda effect, flow separation points, and jet "flapping" were investigated. The results are compared to previously reported work of flow through symmetric divergent vocal fold models.
NASA Astrophysics Data System (ADS)
Habert, J.; Ricci, S.; Le Pape, E.; Thual, O.; Piacentini, A.; Goutal, N.; Jonville, G.; Rochoux, M.
2016-01-01
This paper presents a data-driven hydrodynamic simulator based on the 1-D hydraulic solver dedicated to flood forecasting with lead time of an hour up to 24 h. The goal of the study is to reduce uncertainties in the hydraulic model and thus provide more reliable simulations and forecasts in real time for operational use by the national hydrometeorological flood forecasting center in France. Previous studies have shown that sequential assimilation of water level or discharge data allows to adjust the inflows to the hydraulic network resulting in a significant improvement of the discharge while leaving the water level state imperfect. Two strategies are proposed here to improve the water level-discharge relation in the model. At first, a modeling strategy consists in improving the description of the river bed geometry using topographic and bathymetric measurements. Secondly, an inverse modeling strategy proposes to locally correct friction coefficients in the river bed and the flood plain through the assimilation of in situ water level measurements. This approach is based on an Extended Kalman filter algorithm that sequentially assimilates data to infer the upstream and lateral inflows at first and then the friction coefficients. It provides a time varying correction of the hydrological boundary conditions and hydraulic parameters. The merits of both strategies are demonstrated on the Marne catchment in France for eight validation flood events and the January 2004 flood event is used as an illustrative example throughout the paper. The Nash-Sutcliffe criterion for water level is improved from 0.135 to 0.832 for a 12-h forecast lead time with the data assimilation strategy. These developments have been implemented at the SAMA SPC (local flood forecasting service in the Haute-Marne French department) and used for operational forecast since 2013. They were shown to provide an efficient tool for evaluating flood risk and to improve the flood early warning system. Complementary with the deterministic forecast of the hydraulic state, the estimation of an uncertainty range is given relying on off-line and on-line diagnosis. The possibilities to further extend the control vector while limiting the computational cost and equifinality problem are finally discussed.
NASA Astrophysics Data System (ADS)
Pondaven, P.; Ruiz-Pino, D.; Fravalo, C.; Tréguer, P.; Jeandel, C.
2000-02-01
Interannual variability of nutrients and plankton cycles were studied at the time-series station KERFIX (50°40'S, 68°25'E) using a 1-D coupled physical-biogeochemical model that is descended from that of Pondaven et al. (1998). At KERFIX, a high half saturation constant for silicic acid uptake ( KSi) and a high Si/ N uptake ratio are required to reproduce the Si and N cycles. Although very high in comparison with most data from temperate systems, these values are consistent with KSi and Si/ N uptake ratios measured in the Indian sector of the Southern Ocean. Past and recent finding on the role of light and iron limitation on nutrient consumption ratios might explain these "unusual" silicon uptake kinetic parameters. Comparison of model results with observations show that the model correctly reproduces the observed interannual variability of nutrients and plankton cycles at KERFIX between 1992 and 1995. Characteristic features of this region are a spring phytoplankton bloom of 1.0-1.5 mg Chlorophyll a m -3 and a net excess of silicic acid utilisation over that of nitrate. This high silicic acid utilisation leads to low Si concentrations in late summer and subsequent Si limitation of diatom growth. The interannual variability of production of silicon and nitrogen predicted by the model is 1.93±0.04 mol Si m -2 yr -1 and 1.35±0.07 mol N m -2 yr -1 (±SD). In parallel, the predicted export is 1.12±0.04 mol Si m -2 yr -1 and 0.06±0.01 mol N m -2 yr -1. It is shown that diatoms may contribute significantly to export if diatom sinking is taken into account. An interannual variability of the predicted Si and N cycles is detected. This variability is associated with changes in the mixed layer properties, which have been documented to be linked to the Pacific El Niño Southern Oscillation or displacement of the Polar Front.
Turbulence-induced Relative Velocity of Dust Particles V. Testing Previous Models
NASA Astrophysics Data System (ADS)
Pan, Liubin; Padoan, Paolo
2015-10-01
Coagulation models for dust growth in protoplanetary disks usually adopt the prediction of Vlk et al. or its later developments (hereafter Vlk-type models) for the collision velocity of dust particles induced by turbulent motions. We review the formulation and the underlying physical picture of these models, test their predictions against a numerical simulation, and examine the accuracy of the commonly used prescription for dust particle collisions. We show that Vlk-type models typically overestimate the rms of the particle relative velocity by a factor of two, if the particle friction times lie in the inertial range of the flow. The commonly used prescription for the collision kernel has several inaccuracies, and, in particular, it neglects the effect of turbulent clustering. Interestingly, for particles of equal sizes, the inaccuracies happen to cancel out, and by coincidence, the commonly used kernel prescription based on Vlk-type models is in good agreement with our simulation result. For particles of different sizes, the prescription shows a larger discrepancy from the measured kernel, and may overestimate the collision rate by up to a factor of 2.5. We find that the predicted rms relative velocity by Vlk-type models provides reasonable estimates for the average collision velocity per collision. We also make an effort to improve the accuracy of Vlk-type models for the rms relative velocity by tuning the correlation time of turbulent eddies and modifying the criterion for eddy classification.
Mathematical model for logarithmic scaling of velocity fluctuations in wall turbulence
NASA Astrophysics Data System (ADS)
Mouri, Hideaki
2015-12-01
For wall turbulence, moments of velocity fluctuations are known to be logarithmic functions of the height from the wall. This logarithmic scaling is due to the existence of a characteristic velocity and to the nonexistence of any characteristic height in the range of the scaling. By using the mathematics of random variables, we obtain its necessary and sufficient conditions. They are compared with characteristics of a phenomenological model of eddies attached to the wall and also with those of the logarithmic scaling of the mean velocity.
Relations among fault behavior, subsurface geology, and three-dimensional velocity models
Michael, A.J.; Eberhart-Phillips, D.
1991-01-01
The development of three-dimensional P-wave velocity models for the regions surrounding five large earthquakes in California has lead to the recognition of relations among fault behavior and the material properties of the rocks that contact the fault at seismogenic depths; regions of high moment release appear to correlate with high seismic velocities whereas rupture initiation or termination may be associated with lower seismic velocities. These relations point toward a physical understanding of why faults are divided into segments that can fail independently, an understanding that could improve our ability to predict earthquakes and strong ground motion.
Modeling the effect of varying swim speeds on fish passage through velocity barriers
Castro-Santos, T.
2006-01-01
The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption that fish swim at a constant speed regardless of the speed of flow. This paper demonstrates how the maximum distance of ascent through velocity barriers can be estimated from the swim speed-fatigue time relationship, allowing for variation in both swim speed and water velocity.
Measurement of velocity deficit at the downstream of a 1:10 axial hydrokinetic turbine model
Gunawan, Budi; Neary, Vincent S; Hill, Craig; Chamorro, Leonardo
2012-01-01
Wake recovery constrains the downstream spacing and density of turbines that can be deployed in turbine farms and limits the amount of energy that can be produced at a hydrokinetic energy site. This study investigates the wake recovery at the downstream of a 1:10 axial flow turbine model using a pulse-to-pulse coherent Acoustic Doppler Profiler (ADP). In addition, turbine inflow and outflow velocities were measured for calculating the thrust on the turbine. The result shows that the depth-averaged longitudinal velocity recovers to 97% of the inflow velocity at 35 turbine diameter (D) downstream of the turbine.
Site-Specific Velocity and Density Model for the Waste Treatment Plant, Hanford, Washington.
Rohay, Alan C.; Brouns, Thomas M.
2007-06-27
This report documents the work conducted under the SBP to develop a shear wave and compressional wave velocity and density model specific to the WTP site. Section 2 provides detailed background information on the WTP site and its underlying geology as well as on the Seismic Boreholes Project activities leading up to the Vs and Vp measurements. In Section 3, methods employed and results obtained are documented for measurements of Vs and Vp velocities in basalts and interbeds. Section 4 provides details on velocity measurements in the sediments underlying the WTP. Borehole gravity measurements of density of the subsurface basalt and sediments are described in Section 5. Section 6 describes the analysis of data presented in section 3-5, and presents the overall velocity and density model for the WTP site.
Modeling velocity in gradient flows with coupled-map lattices with advection.
Lind, Pedro G; Corte-Real, Joo; Gallas, Jason A C
2002-07-01
We introduce a simple model to investigate large scale behavior of gradient flows based on a lattice of coupled maps which, in addition to the usual diffusive term, incorporates advection, as an asymmetry in the coupling between nearest neighbors. This diffusive-advective model predicts traveling patterns to have velocities obeying the same scaling as wind velocities in the atmosphere, regarding the advective parameter as a sort of geostrophic wind. In addition, the velocity and wavelength of traveling wave solutions are studied. In general, due to the presence of advection, two regimes are identified: for strong diffusion the velocity varies linearly with advection, while for weak diffusion a power law is found with a characteristic exponent proportional to the diffusion. PMID:12241473
Direct Measurement of Internal Flow Velocities in a Star-Slot Model
NASA Technical Reports Server (NTRS)
Foster, Winfred A., Jr.; Jenkins, Rhonald M.; Hengel, John E.; Smith, Andrew W.
1997-01-01
This paper presents the results of a cold flow experiment to make direct measurements of the velocity distribution in a model of a solid rocket motor star grain propellant slot. The experimental procedure utilizes a multi-component laser Doppler velocimeter (LDV) and an apparatus for seeding the flow with aluminum particles to determine the velocity components at various discrete locations within the star slot. The test article used in this investigation was a one-tenth scale, cold flow model based on the geometry of the Space Shuttle solid rocket motor head-end section. The results obtained for the direct measurements of velocity are compared to velocities calculated from measured pressure distributions to data obtained from oil smear experiments and flow visualization videos, and to heat transfer calorimeter data.
NASA Astrophysics Data System (ADS)
Mogensen, Ditte; Aaltonen, Hermanni; Aalto, Juho; Bäck, Jaana; Kieloaho, Antti-Jussi; Gierens, Rosa; Smolander, Sampo; Kulmala, Markku; Boy, Michael
2015-04-01
Volatile organic compounds (VOCs) are emitted from the biosphere and can work as precursor gases for aerosol particles that can affect the climate (e.g. Makkonen et al., ACP, 2012). VOC emissions from needles and leaves have gained the most attention, however other parts of the ecosystem also have the ability to emit a vast amount of VOCs. This, often neglected, source can be important e.g. at periods where leaves are absent. Both sources and drivers related to forest floor emission of VOCs are currently limited. It is thought that the sources are mainly due to degradation of organic matter (Isidorov and Jdanova, Chemosphere, 2002), living roots (Asensio et al., Soil Biol. Biochem., 2008) and ground vegetation. The drivers are biotic (e.g. microbes) and abiotic (e.g. temperature and moisture). However, the relative importance of the sources and the drivers individually are currently poorly understood. Further, the relative importance of these factors is highly dependent on the tree species occupying the area of interest. The emission of isoprene and monoterpenes where measured from the boreal forest floor at the SMEAR II station in Southern Finland (Hari and Kulmala, Boreal Env. Res., 2005) during the snow-free period in 2010-2012. We used a dynamic method with 3 automated chambers analyzed by Proton Transfer Reaction - Mass Spectrometer (Aaltonen et al., Plant Soil, 2013). Using this data, we have developed empirical parameterizations for the emission of isoprene and monoterpenes from the forest floor. These parameterizations depends on abiotic factors, however, since the parameterizations are based on field measurements, biotic features are captured. Further, we have used the 1D chemistry-transport model SOSAA (Boy et al., ACP, 2011) to test the seasonal relative importance of inclusion of these parameterizations of the forest floor compared to the canopy crown emissions, on the atmospheric reactivity throughout the canopy.
Predicting Ground Motions In Seattle Using A New Shear Wave Velocity Model
NASA Astrophysics Data System (ADS)
Delorey, A. A.; Vidale, J. E.
2010-12-01
Much of Seattle lies atop a deep sedimentary basin. The Seattle Basin amplifies and distorts seismic waves in ways that modulate the hazard from earthquakes. Seismic hazard assessments heavily depend upon upper crustal and near-surface S-wave velocity models. Improving the accuracy and resolution of basin S-wave models is key to improving predictions of ground shaking. Tomography, with short-period Rayleigh waves extracted using noise interferometry, can refine S-wave velocity models in urban areas with dense arrays of short period and broadband instruments. We applied this technique to develop a new S-wave velocity model encompassing the upper 3-4 km and covering Seattle and several neighboring cities. We then embed this updated model into the regional velocity model that was used in the development of the USGS seismic hazard maps for Seattle. We collected data from two local earthquakes, one crustal and one Benioff Zone event, which were recorded on many strong motion stations operated by the Pacific Northwest Seismic Network and the USGS Earthquake Hazards program. For the two local earthquakes, we compared amplitudes and waveforms predicted by our new velocity model to predictions made using the older velocity model at stiff soil sites. For the crustal event, the amplitudes predicted by simulations with our new model are closer to the data than those predicted by the previous model. At periods between 1.25-5 seconds our new model makes considerably better predictions, while at periods between 1-1.25 seconds our new model makes better predictions, but the difference is smaller. For the Benioff zone event, the two models’ predictions are both good, but also favor our model. At periods between 1.6-3.3, the previous model makes better predictions while our model makes better predictions at periods between 1-1.6 and 3.3-5 seconds. Our simulations confirm that amplitudes are determined by a complex set of variables including basin velocity structure, wave-guides, and soil type. We are working to improve predicted amplifications to improve seismic hazard assessments. Many new strong motion instruments have been installed within the last year, including Netquakes seismographs operated by the USGS, providing us with a valuable data set for improving our predictions. Shear wave velocities in the Seattle Basin
No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1
NASA Technical Reports Server (NTRS)
Argus, Donald F.; Gordon, Richard G.
1991-01-01
NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.
A distributed, dynamic, parallel computational model: the role of noise in velocity storage
Merfeld, Daniel M.
2012-01-01
Networks of neurons perform complex calculations using distributed, parallel computation, including dynamic “real-time” calculations required for motion control. The brain must combine sensory signals to estimate the motion of body parts using imperfect information from noisy neurons. Models and experiments suggest that the brain sometimes optimally minimizes the influence of noise, although it remains unclear when and precisely how neurons perform such optimal computations. To investigate, we created a model of velocity storage based on a relatively new technique–“particle filtering”–that is both distributed and parallel. It extends existing observer and Kalman filter models of vestibular processing by simulating the observer model many times in parallel with noise added. During simulation, the variance of the particles defining the estimator state is used to compute the particle filter gain. We applied our model to estimate one-dimensional angular velocity during yaw rotation, which yielded estimates for the velocity storage time constant, afferent noise, and perceptual noise that matched experimental data. We also found that the velocity storage time constant was Bayesian optimal by comparing the estimate of our particle filter with the estimate of the Kalman filter, which is optimal. The particle filter demonstrated a reduced velocity storage time constant when afferent noise increased, which mimics what is known about aminoglycoside ablation of semicircular canal hair cells. This model helps bridge the gap between parallel distributed neural computation and systems-level behavioral responses like the vestibuloocular response and perception. PMID:22514288
Hill-type muscle model with serial damping and eccentric force-velocity relation.
Haeufle, D F B; Gnther, M; Bayer, A; Schmitt, S
2014-04-11
Hill-type muscle models are commonly used in biomechanical simulations to predict passive and active muscle forces. Here, a model is presented which consists of four elements: a contractile element with force-length and force-velocity relations for concentric and eccentric contractions, a parallel elastic element, a series elastic element, and a serial damping element. With this, it combines previously published effects relevant for muscular contraction, i.e. serial damping and eccentric force-velocity relation. The model is exemplarily applied to arm movements. The more realistic representation of the eccentric force-velocity relation results in human-like elbow-joint flexion. The model is provided as ready to use Matlab and Simulink code. PMID:24612719
A math model for high velocity sensoring with a focal plane shuttered camera.
NASA Technical Reports Server (NTRS)
Morgan, P.
1971-01-01
A new mathematical model is presented which describes the image produced by a focal plane shutter-equipped camera. The model is based upon the well-known collinearity condition equations and incorporates both the translational and rotational motion of the camera during the exposure interval. The first differentials of the model with respect to exposure interval, delta t, yield the general matrix expressions for image velocities which may be simplified to known cases. The exposure interval, delta t, may be replaced under certain circumstances with a function incorporating blind velocity and image position if desired. The model is tested using simulated Lunar Orbiter data and found to be computationally stable as well as providing excellent results, provided that some external information is available on the velocity parameters.
NASA Astrophysics Data System (ADS)
Godano, Maxime; Deschamps, Anne; Lambotte, Sophie; Lyon-Caen, Hlne; Bernard, Pascal; Pacchiani, Francesco
2014-06-01
The composite fault plane solutions for 24 large multiplets recorded in the western part of the Corinth Rift between 2000 and 2007 are computed by jointly inverting P polarities and Sv/P, Sh/P, Sv/Sh amplitude ratios of the direct waves. The fault plane solutions are determined using 1-D and 3-D velocity models. Solutions computed with the 3-D velocity model are preferred to the ones computed with the 1-D model because overall, 3-D solutions have a better score function. They correspond essentially to E-NE/W-SW and W-NW/E-SE striking normal faults, which is consistent with the N-S extensional/vertical shortening tectonic regime of the area. For 15 multiplets, one of the nodal planes is similar to the plane delineated by the earthquakes. It is then possible to determine which nodal plane is the fault plane. The analysis of the fault plane solutions highlights a clear decrease of their dip with depth and towards the north. Several multiplets with steeply dipping fault planes (50-60) located at depths of 7-8 km are clearly located at the base of onshore and offshore faults that crop out close to the south border of the Corinth Gulf, indicating that these faults are steep down to 7-8 km depth. To the north, multiplets underline a low angle north-dipping structure (20-30) on which steep north-dipping faults could take root.
NASA Astrophysics Data System (ADS)
Yetirmishli, G. C.; Kazimova, S. E.; Kazimov, I. E.
2011-09-01
We present the method for determining the velocity model of the Earth's crust and the parameters of earthquakes in the Middle Kura Depression from the data of network telemetry in Azerbaijan. Application of this method allowed us to recalculate the main parameters of the hypocenters of the earthquake, to compute the corrections to the arrival times of P and S waves at the observation station, and to significantly improve the accuracy in determining the coordinates of the earthquakes. The model was constructed using the VELEST program, which calculates one-dimensional minimal velocity models from the travel times of seismic waves.
NASA Astrophysics Data System (ADS)
Johnson, Gordon; Holmquist, Timothy
2007-06-01
Constitutive models for brittle materials such as glass can be very complex as they are dependent on strains, stain rates, pressures, temperatures, damage and other parameters. There may also be significant (pressure-dependent) strength after failure such that the constitutive response is much different for intact material and failed material. A great number of laboratory tests are required to develop a comprehensive constitutive model. Another approach is to develop simple models using penetration-velocity data obtained from ballistic experiments. Here, various functional forms of simple models (with a limited number of constants) are used to (computationally) match the penetration velocity over a range of impact velocities. This allows for the determination of the most important parameters and it provides an approximation of the stresses that occur during penetration. This paper presents constitutive models for high-density DEDF glass. They are based on penetration-velocity data reported by Behner et al. (Proceedings of the 22^nd International Symposium on Ballistics, Vancouver BC, Canada, November 2005) for gold rods impacting DEDF glass at impact velocities from 400 to 2500 m/s.
Detailed Three-Dimensional P and S Wave Velocity Models for the New Madrid Seismic Zone
NASA Astrophysics Data System (ADS)
Powell, C.; Withers, M.; Vlahovic, G.
2005-05-01
Detailed P and S wave velocity models and Vp/Vs values have been determined for the New Madrid Seismic Zone (NMSZ) based upon arrival times recorded by the New Madrid seismic network and by PANDA stations. The combined data set consists of 11,778 P wave arrivals and 8,579 S wave arrivals recorded by 97 stations. We used a modified version of the Benz et al., 1996 algorithm that inverts simultaneously for both P and S velocities and hypocentral locations (Tryggvason et al., 2002). The ability to specify independent P and S wave starting velocity models, rather than an S wave model linked to the P wave model via a constant Vp/Vs ratio, is particularly important for the NMSZ because the surface sediments have highly variable Vp/Vs ratios. Block size was reduced to 2x2x2 km, yielding the most detailed image of the NMSZ ever obtained. Inversion results were tested using chessboard models, spike tests and reconstruction techniques. Intrusions are imaged in great detail. Low P wave velocity and high S wave velocity appear to be correlated with earthquake occurrence; this results in distinct regions of low Vp/Vs values that correspond to the major arms of seismicity. The unusual low Vp/Vs values could be due to lithology variations but may be related to fluid saturation and porosity variations.
NASA Astrophysics Data System (ADS)
Murray, Keenan A.; Kramer, Louisa J.; Doskey, Paul V.; Ganzeveld, Laurens; Seok, Brian; Van Dam, Brie; Helmig, Detlev
2015-09-01
Observed depth profiles of nitric oxide (NO), nitrogen dioxide (NO2), and ozone (O3) in snowpack interstitial air at Summit, Greenland were best replicated by a 1-D process-scale model, which included (1) geometrical representation of snow grains as spheres, (2) aqueous-phase chemistry confined to a quasi-liquid layer (QLL) on the surface of snow grains, and (3) initialization of the species concentrations in the QLL through equilibrium partitioning with mixing ratios in snowpack interstitial air. A comprehensive suite of measurements in and above snowpack during a high O3 event facilitated analysis of the relationship between the chemistry of snowpack and the overlying atmosphere. The model successfully reproduced 2 maxima (i.e., a peak near the surface of the snowpack at solar noon and a larger peak occurring in the evening that extended down from 0.5 to 2 m) in the diurnal profile of NO2 within snowpack interstitial air. The maximum production rate of NO2 by photolysis of nitrate (NO3-) was approximately 108 molec cm-3 s-1, which explained daily observations of maxima in NO2 mixing ratios near solar noon. Mixing ratios of NO2 in snowpack interstitial air were greatest in the deepest layers of the snowpack at night and were attributed to thermal decomposition of peroxynitric acid, which produced up to 106 molec NO2 cm-3 s-1. Highest levels of NO in snowpack interstitial air were confined to upper layers of the snowpack and observed profiles were consistent with photolysis of NO2. Production of nitrogen oxides (NOx) from NO3- photolysis was estimated to be two orders of magnitude larger than NO production and supports the hypothesis that NO3- photolysis is the primary source of NOx within sunlit snowpack in the Arctic. Aqueous-phase oxidation of formic acid by O3 resulted in a maximum consumption rate of ∼106-107 molec cm-3 s-1 and was the primary removal mechanism for O3.
Developing a Crustal and Upper Mantle Velocity Model for the Brazilian Northeast
NASA Astrophysics Data System (ADS)
Julia, J.; Nascimento, R.
2013-05-01
Development of 3D models for the earth's crust and upper mantle is important for accurately predicting travel times for regional phases and to improve seismic event location. The Brazilian Northeast is a tectonically active area within stable South America and displays one of the highest levels of seismicity in Brazil, with earthquake swarms containing events up to mb 5.2. Since 2011, seismic activity is routinely monitored through the Rede Sismogrfica do Nordeste (RSisNE), a permanent network supported by the national oil company PETROBRAS and consisting of 15 broadband stations with an average spacing of ~200 km. Accurate event locations are required to correctly characterize and identify seismogenic areas in the region and assess seismic hazard. Yet, no 3D model of crustal thickness and crustal and upper mantle velocity variation exists. The first step in developing such models is to refine crustal thickness and depths to major seismic velocity boundaries in the crust and improve on seismic velocity estimates for the upper mantle and crustal layers. We present recent results in crustal and uppermost mantle structure in NE Brazil that will contribute to the development of a 3D model of velocity variation. Our approach has consisted of: (i) computing receiver functions to obtain point estimates of crustal thickness and Vp/Vs ratio and (ii) jointly inverting receiver functions and surface-wave dispersion velocities from an independent tomography study to obtain S-velocity profiles at each station. This approach has been used at all the broadband stations of the monitoring network plus 15 temporary, short-period stations that reduced the inter-station spacing to ~100 km. We expect our contributions will provide the basis to produce full 3D velocity models for the Brazilian Northeast and help determine accurate locations for seismic events in the region.
UCVM: An Open Source Framework for 3D Velocity Model Research
NASA Astrophysics Data System (ADS)
Gill, D.; Maechling, P. J.; Jordan, T. H.; Plesch, A.; Taborda, R.; Callaghan, S.; Small, P.
2013-12-01
Three-dimensional (3D) seismic velocity models provide fundamental input data to ground motion simulations, in the form of structured or unstructured meshes or grids. Numerous models are available for California, as well as for other parts of the United States and Europe, but models do not share a common interface. Being able to interact with these models in a standardized way is critical in order to configure and run 3D ground motion simulations. The Unified Community Velocity Model (UCVM) software, developed by researchers at the Southern California Earthquake Center (SCEC), is an open source framework designed to provide a cohesive way to interact with seismic velocity models. We describe the several ways in which we have improved the UCVM software over the last year. We have simplified the UCVM installation process by automating the installation of various community codebases, improving the ease of use.. We discuss how UCVM software was used to build velocity meshes for high-frequency (4Hz) deterministic 3D wave propagation simulations, and how the UCVM framework interacts with other open source resources, such as NetCDF file formats for visualization. The UCVM software uses a layered software architecture that transparently converts geographic coordinates to the coordinate systems used by the underlying velocity models and supports inclusion of a configurable near-surface geotechnical layer, while interacting with the velocity model codes through their existing software interfaces. No changes to the velocity model codes are required. Our recent UCVM installation improvements bundle UCVM with a setup script, written in Python, which guides users through the process that installs the UCVM software along with all the user-selectable velocity models. Each velocity model is converted into a standardized (configure, make, make install) format that is easily downloaded and installed via the script. UCVM is often run in specialized high performance computing (HPC) environments, so we have included checks during the installation process to alert users about potential conflicts. We also describe how UCVM can create an octree-based database representation of a velocity model which can be directly queried by 3D wave propagation simulation codes using the open source etree library. We will discuss how this approach was used to create an etree for a 4-Hz Chino Hills simulation. Finally, we show how the UCVM software can integrate NetCDF utility code to produce 3D velocity model files compatible with open source NetCDF data viewers. This demonstrates that UCVM can generate meshes from any compatible community velocity model and that the resulting models can be visualized without the need for complex secondary tools. This illustrates how developers can easily write tools that can convert data from one format to another using the UCVM API.
CELEBRATION 2000: P-wave velocity models of the Bohemian Massif
NASA Astrophysics Data System (ADS)
Hrubcova, P.
2003-04-01
Deep structure of the Bohemian Massif (BM), the largest stable outcrop of Variscan rocks in Central Europe, was studied along two refraction profiles, CEL09 that traverses the whole massif in the NW-SE direction, and CEL10 that extends along its eastern edge almost perpendicularly to CEL09. Good quality recordings with clear first arrivals of crustal and upper mantle phases show apparent velocity 5.9 km/s for the upper crust with slightly higher gradient in NW part of the BM and app. velocity 8.0 to 8.1 km/s for the upper mantle. Decrease of amplitudes of crustal phases visible in some sections may be connected with a specific upper crustal structure (zero to negative velocity gradient zone). Pronounced Moho reflections in central part of the BM suggest well-defined Moho in that part and not so clear Moho with smaller velocity contrast in other parts of the BM. For interpretation, the tomographic inversion routine of Hole (1992) was used as an efficient tool to determine seismic P-wave velocity distribution in the crust using first arrivals. Tomographic models were verified by forward ray tracing modelling based on well-established algorithm developed by Cerveny et al. (1983), where apart from first arrivals also further phases were included. 2-D velocity models of first arrivals and reflected phases show high P-wave velocity gradient zone reaching the depth of 5-7 km followed by small gradient and laterally homogeneous P-wave velocity distribution in the middle crust. Differences in velocity distribution in the lower crust delimit central part of the BM (sharp Moho discontinuity) from other tectonic units within the BM (lower crust high gradient transition zone). Position of Moho discontinuity ranging from 32 km to 40 km and reflectors within the crust complement the P-wave velocity distribution. Presented models also show the contact of the BM with its neighbouring units - Carpathians, Paleozoic Platform, Vienna Basin and the Alps. References: Cerveny, V., Psencik, I., 1983. Program SEIS83, Numerical Modelling of Seismic Wave Fields in 2-D Laterally Varying Layered Structures by the Ray Method, Charles University, Prague. Hole, J.A. 1992: Non-linear high-resolution three-dimensional seismic travel time tomography, J. Geophys. Res. 97, 6553-6562.
Traffic stability of a car-following model considering driver’s desired velocity
NASA Astrophysics Data System (ADS)
Zhang, Geng; Sun, Di-Hua; Liu, Wei-Ning; Liu, Hui
2015-07-01
In this paper, a new car-following model is proposed by considering driver’s desired velocity according to Transportation Cyber Physical Systems. The effect of driver’s desired velocity on traffic flow has been investigated through linear stability theory and nonlinear reductive perturbation method. The linear stability condition shows that driver’s desired velocity effect can enlarge the stable region of traffic flow. From nonlinear analysis, the Burgers equation and mKdV equation are derived to describe the evolution properties of traffic density waves in the stable and unstable regions respectively. Numerical simulation is carried out to verify the analytical results, which reveals that traffic congestion can be suppressed efficiently by taking driver’s desired velocity effect into account.
Fabry-Perot interferometer measurement of static temperature and velocity for ASTOVL model tests
NASA Technical Reports Server (NTRS)
Kourous, Helen E.; Seacholtz, Richard G.
1995-01-01
A spectrally resolved Rayleigh/Mie scattering diagnostic was developed to measure temperature and wing-spanwise velocity in the vicinity of an ASTOVL aircraft model in the Lewis 9 x 15 Low Speed Wind Tunnel. The spectrum of argon-ion laser light scattered by the air molecules and particles in the flow was resolved with a Fabry-Perot interferometer. Temperature was extracted from the spectral width of the Rayleigh scattering component, and spanwise gas velocity from the gross spectral shift. Nozzle temperature approached 800 K, and the velocity component approached 30 m/s. The measurement uncertainty was about 5 percent for the gas temperature, and about 10 m/s for the velocity. The large difference in the spectral width of the Mie scattering from particles and the Rayleigh scattering from gas molecules allowed the gas temperature to be measured in flow containing both naturally occurring dust and LDV seed (both were present).
A global 3D P-velocity model of the Earth's crust and mantle for improved event location : SALSA3D.
Young, Christopher John; Steck, Lee K.; Phillips, William Scott; Ballard, Sanford; Chang, Marcus C.; Rowe, Charlotte A.; Encarnacao, Andre Villanova; Begnaud, Michael A.; Hipp, James Richard
2010-07-01
To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D version 1.5, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is {approx}50%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D models via location tests on a global event set with GT of 5 km or better. These events generally possess hundreds of Pn and P picks from which we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135 regardless of Pn to P ratio, with the improvement being most pronounced at higher azimuthal gaps.
SALSA3D : a global 3D p-velocity model of the Earth's crust and mantle for improved event location.
Encarnacao, Andre Villanova; Begnaud, Michael A.; Rowe, Charlotte A.; Young, Christopher John; Chang, Marcus C.; Ballard, Sally C.; Hipp, James Richard
2010-06-01
To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D version 1.5, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is {approx}50%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D models via location tests on a global event set with GT of 5 km or better. These events generally possess hundreds of Pn and P picks from which we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135 regardless of Pn to P ratio, with the improvement being most pronounced at higher azimuthal gaps.
Crustal P-wave velocity model for the central-western region of Mexico
NASA Astrophysics Data System (ADS)
Ochoa, J.; Escudero, C. R.; Perez, O. G.; Nunez-Cornu, F. J.
2012-12-01
Several studies require a p-wave velocity model to obtain accurate results moreover such models could provide an insight of the tectonic structure of the study area. Accordingly, in this study we estimate the crustal 3D p-wave velocity model for the Jalisco Block located at the central-western region of Mexico. The Jalisco Block is limited on its eastern side by the Colima and Tepic-Zacoalcos Rifts, and the Trans-Mexican Volcanic Belt; while on its western side it is limited by the Mesoamerican Trench. Cocos and Rivera plates are subducting beneath the Jalisco Block conforming a tectonically complex region. We used earthquakes occurring within the limits of lithosphere volume from which we want to estimate the velocity model. Such events were registered by the Mapping the Rivera Subduction Zone experiment (MARS) and the Seismic and Acelerometric Network of Jalisco (RESAJ). During MARS experiment 51broadband stations active from January 2006 to June 2007 were deployed while RESAJ by July of 2012consists of nine active stations however more stations will be deployed until reach 30 stations. The velocity model is estimated using the Fast Marching Tomography (FMTOMO) software. FMTOMO uses the Fast Marching Method (FMM) in order to solve the forward problem; the FMM is a numerical algorithm that tracks the interfaces evolution along a nodes narrow band, and travel times are updated solving the eikonal equation. Finally , the inverse problem is about adjusting the model parameters (interface depth, velocity, hypocenter location) in order to try to satisfy the observed data (travel times). We perform a resolution test using several events that show good resolution results up to a 60 km depth. We present a 3D p-wave velocity model, we compare our results within the MARS data with previous results for greater depths, approximately the upper mantle, finally we also present studies towards the northern portion of the Jalisco Block using the RESAJ data.
Bow shock models for the velocity structure of ultracompact H II regions
NASA Technical Reports Server (NTRS)
Van Buren, Dave; Mac Low, Mordecai-Mark
1992-01-01
The velocity structure of ultracompact H II regions is modeled assuming that O stars moving supersonically through molecular clouds sweep up bow shocks to produce the observed objects. The expected radio recombination line emission is calculated for the case of an optically thin continuum and the strong effect of changing the viewing angle is shown. The kinematic information removes the degeneracy with ram pressure of a previous model, allowing measurement of stellar velocity vectors and cloud densities. A detailed model for G29.96-0.02 shows good agreement with observations by Wood and Churchwell, supporting the bow shock hypothesis. It is found that the exciting star of G29 is moving at 20 km/s relative to the gas, suggesting that O stars acquire a large velocity dispersion early in their lives.
Quasilinear model for energetic particle diffusion in radial and velocity space
NASA Astrophysics Data System (ADS)
Waltz, R. E.; Bass, E. M.; Staebler, G. M.
2013-04-01
A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 22 EP diffusion matrix account for fluxes up radial (energy) gradients driven by energy (radial) gradients of the EP velocity space distribution function. The quasilinear ratio kernel of the model is provided by a simple analytic formula for the EP radial and velocity space EP diffusivity relative to radial thermal ion energy diffusivity at each linear mode of the turbulence driven by the thermal plasma. The TGLF [G. M. Staebler, J. E. Kinsey, and R. E. Waltz, Phys. Plasmas 14, 0055909 (2007); ibid. 15, 0055908 (2008)] tokamak transport model provides the linear mode frequency and growth rates to the kernel as well as the nonlinear spectral weight for each mode.
A Community Velocity Model (CVM) for the Sichuan basin and Longmen Shan, China
NASA Astrophysics Data System (ADS)
Wang, M.; Hubbard, J.; Shaw, J. H.; Plesch, A.; Jia, D.
2012-12-01
We present a new three-dimensional velocity model of the crust and upper mantle for the eastern margin of the Tibetan Plateau, developed using the concept of a Community Velocity Model (CVM) (Magistrale et al., 2000; Sss and Shaw, 2003). The model extends from 27.5-34.5N and 100-110E, and describes the velocity structure of the Sichuan basin and surrounding fold-and-thrust belt systems (including the Longmen Shan, Micang Shan, Daba Shan, Eastern Sichuan and Kangdian), as well as the Kunlun and Xianshuihe-Anninghe strike fault systems in the eastern Tibetan Plateau. The model consists of 3D surfaces representing major geologic unit contacts and faults, and is parameterized with velocity-depth curves (Boore and Joyner, 1997) calibrated using sonic logs from wells. The model incorporates data from 1166 oil wells, industry isopach maps, surface geological maps and digital elevation models. The model was developed in the program GoCAD, a geological computer-aided design application (Mallet, 1992). The geological surfaces were modeled based on industry isopach maps for various units augmented by stratigraphic picks in oil and gas wells and regional seismic reflection profiles. These surfaces include base Quaternary, Cretaceous, Jurassic, Triassic, and Paleozoic horizons. These surface are locally cut by major faults, which are compatible with the locations and displacements of major faults systems in the Sichuan Community Fault Model (CFM) (Hubbard et al., 2012). The velocity profiles for each layer are calibrated with high-resolution sonic log as well as stacking velocities from seismic reflection profiles and vertical seismic profiles. This upper crustal model extends down to ~10-15 km depth, and is embedded into a regional tomographic model (Xu and Song, 2010). The Sichuan basin is an atypical basin in terms of its velocity structure. The rocks exposed at the surface are primarily Mesozoic in age, with limited patch of Cenozoic rocks in the southwestern part of the basin. As a consequence, the velocities (Vp) in the basin are generally fast. They range from about 3000 to ~7500 m/s, exhibiting increasing velocities with age and depth. We divide the rock in the Sichuan basin and Longmen Shan region into five basic types: (1) Cenozoic alluvium; (2) Mesozoic sedimentary and metamorphic rocks; (3) Paleozoic sedimentary and metamorphic rocks; (4) Proterozoic sedimentary and metamorphic rocks and (5) granite. Cenozoic alluvium is thin (0~500 m) and limited primarily to the southwestern basin. Mesozoic sedimentary rocks are thick (2600-9800 m) and widely exposed at the surface and in boreholes in the basin. Their velocities vary from about 3000-6000 m/s. Paleozoic sedimentary and metamorphic rocks are also common, exposed primarily in the Longmen Shan and in regions to the north, east, and south of the basin. These units vary in thickness from 400-4100 m, and have velocities from about 5000-7000 m/s. Proterozoic sedimentary and metamorphic rocks crop out in narrow regions around the boundary of the basin, but are disturbed within the basin. Two exploration wells penetrate the base of Sinian, giving a velocity of about 6500-7500 m/s. The model will serve as a basic community resource for strong ground motion prediction and seismic hazard assessments in the densely populated Sichuan basin.
Quasilinear model for energetic particle diffusion in radial and velocity space
Waltz, R. E.; Staebler, G. M.; Bass, E. M.
2013-04-15
A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 2 Multiplication-Sign 2 EP diffusion matrix account for fluxes up radial (energy) gradients driven by energy (radial) gradients of the EP velocity space distribution function. The quasilinear ratio kernel of the model is provided by a simple analytic formula for the EP radial and velocity space EP diffusivity relative to radial thermal ion energy diffusivity at each linear mode of the turbulence driven by the thermal plasma. The TGLF [G. M. Staebler, J. E. Kinsey, and R. E. Waltz, Phys. Plasmas 14, 0055909 (2007); ibid. 15, 0055908 (2008)] tokamak transport model provides the linear mode frequency and growth rates to the kernel as well as the nonlinear spectral weight for each mode.
Modeling the effect of humidity on the threshold friction velocity of coal particles
NASA Astrophysics Data System (ADS)
Zhang, Xiaochun; Chen, Weiping; Ma, Chun; Zhan, Shuifen
2012-09-01
Coal particles emission could cause serious air pollution in coal production region and transport region. In coal mining industry, large amounts of water are regularly spayed to coal piles to prevent dust emission from the coal particles. The mechanism behind this measure is to manage the threshold friction velocity, which is an important parameter in controlling wind erosion and dust emission. Bagnold has developed a threshold friction velocity model for soil particles. However, the Bagnold model cannot be applied directly to coal particles as coal particles are quite different from soils in physical and chemical properties. We studied and modeled threshold friction velocity of coal particles under different humidities by using a wind tunnel. Results showed that the effects of humidity on coal particles' threshold friction velocity are related to the hydrophilic effect and adhesive effect. Bagnold model can be corrected by two new parameter items which explained the two effects. The new model, agreed well with wind tunnel measurements for coal particles with different size categories. Despite the fact the new model was developed for coal particles, its physical basis may allow the model application to other wind susceptible particles.
NASA Astrophysics Data System (ADS)
Fosdick, J. C.; Hilley, G. E.; Graham, S. A.
2011-12-01
This study investigates the effects of inelastic bending of attenuated lithosphere on foreland flexure and basin geometry in the Upper Cretaceous Magallanes Basin of southern South America. The lack of correlation between topographic load from the present-day Patagonian Andes and the distribution of total sediment thickness in the adjacent Magallanes Basin suggests that that foreland lithosphere has accumulated irrecoverable strain and thus, inelastic flexure should be considered. We present a 1-D numerical analysis using an elastic-plastic model for plate bending and explore the effects of yield stress, spatially-variable flexural rigidity, and size of the tapered topographic load. The Upper Cretaceous Magallanes retroforeland basin formed during Andean orogenesis after closure of a Late Jurassic quasi-oceanic backarc basin. The unusually thick (>5 km) succession of Cenomanian-Maastrichtian sedimentary rocks were deposited in a deep-marine axial foredeep. Sediment thickness profiles across the Cenomanian-Turonian basin fill define a curve with high amplitude and long-wavelength deflection and a substantially suppressed forebulge. Secondly, observed thicknesses across the basin show a distinct inflection point, located ~200 km east of the palinspastically-restored thrust front, that separates a deep (>2.5 km thick) depocenter that thins abruptly toward the craton. Linear elastic models using a range of flexural rigidities (3.6 x 1022 to 2.8 x 1023 N-m) corresponding to elastic thicknesses of 20-40 km for both line loads and distributed loads do not fit observed sediment thicknesses. We explore the effects of obducted high-density oceanic blocks in the thrust belt, spatial variations in elastic thickness of attenuated lithosphere, and permanent strain on foreland flexure. In elastic-plastic models, the plate deforms elastically when the fiber stress is less than the maximum yield stress. When the bending stress in the plate reaches the yield stress, the outer portions of the plate behaves plastically. We compare the observed sedimentary thickness with derived deflection curves. Preliminary results show that spatial variations in elastic thickness (Te) strongly affect the geometry of flexural profiles. Increasing Te toward the foreland transmits deflection farther toward the craton. A higher contrast in Te between the foredeep and craton region amplifies this effect. Plasticity also affects the overall geometry of the deflection profile. As the yield stress decreases, maximum deflection increases, the forebulge increases in height, and the backbulge basin shallows considerably. Lastly, we find that the position of the transition point between mechanical properties exerts a control on the location and height of the forebulge but does not affect the amplitude of the maximum foredeep deflection. The inclusion of inelastic strain significantly changes the basin geometry and mechanical strength of the lithosphere. Our preliminary work has important implications for predicting the distribution and character of sedimentary infill and rates of basin depocenter migration in foreland basins that evolve on narrow plates and attenuated lithosphere.
NASA Astrophysics Data System (ADS)
Zheng, Yi; Zhang, Pengjie; Jing, Yipeng
2015-02-01
Measuring the volume weighted velocity power spectrum suffers from a severe systematic error due to imperfect sampling of the velocity field from the inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density nP and the intrinsic large scale structure (LSS) fluctuation in the particle distribution. (1) We report robust detection of this sampling artifact in N -body simulations. It causes 12 % underestimation of the velocity power spectrum at k =0.1 h /Mpc for samples with n P=6 10-3 (Mpc /h )-3 . This systematic underestimation increases with decreasing nP and increasing k . Its dependence on the intrinsic LSS fluctuations is also robustly detected. (2) All of these findings are expected based upon our theoretical modeling in paper I [P. Zhang, Y. Zheng, and Y. Jing, Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling, arXiv:1405.7125.]. In particular, the leading order theoretical approximation agrees quantitatively well with the simulation result for n P?6 10-4 (Mpc /h )-3 . Furthermore, we provide an ansatz to take high order terms into account. It improves the model accuracy to ?1 % at k ?0.1 h /Mpc over 3 orders of magnitude in nP and over typical LSS clustering from z =0 to z =2 . (3) The sampling artifact is determined by the deflection D field, which is straightforwardly available in both simulations and data of galaxy velocity. Hence the sampling artifact in the velocity power spectrum measurement can be self-calibrated within our framework. By applying such self-calibration in simulations, it is promising to determine the real large scale velocity bias of 1013M? halos with 1 % accuracy, and that of lower mass halos with better accuracy. (4) In contrast to suppressing the velocity power spectrum at large scale, the sampling artifact causes an overestimation of the velocity dispersion. We prove that a correlation between the signal field (v ) and the sampling field (D ) is a major cause. This complexity, among other issues, is carefully investigated to further improve understanding of the sampling artifact.
NASA Technical Reports Server (NTRS)
Friesen, W. J.; Moore, J. A.
1973-01-01
Velocity-profile, pitot-pressure, and supplemental probe measurements were made at the nozzle exist of an expansion tunnel (a modification to the Langley pilot model expansion tube) for a nozzle net condition of a nitrogen test sample with a velocity of 4.5 km/sec and a density 0.005 times the density of nitrogen at standard conditions, both with the nozzle initially immersed in a helium atmosphere and with the nozzle initially evacuated. The purpose of the report is to present the results of these measurements and some of the physical properties of the nitrogen test sample which can be inferred from the measured results. The main conclusions reached are that: the velocity profiles differ for two nozzle conditions; regions of the flow field can be found where the velocity is uniform to within 5 percent and constant for several hundred microseconds; the velocity of the nitrogen test sample is reduced due to passage through the nozzle; and the velocity profiles do not significantly reflect the large variations which occur in the inferred density profiles.
NASA Astrophysics Data System (ADS)
Morozova, Viktoriya S.; Ahmedov, Bobomurat J.; Zanotti, Olindo
2014-10-01
We try to explain the subpulse drift phenomena adopting the space-charge limited flow model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin, where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalogue of Weltevrede et al. with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.
Subpulse drift velocity of pulsar magnetosphere within the space-charge limited flow model
NASA Astrophysics Data System (ADS)
Ahmedov, Bobomurat; Morozova, Viktoriya; Zanotti, Olindo
We attempt to explain the subpulse drift phenomena adopting the space-charge limited flow (SCLF) model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin (2012), where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalog of Weltevrede, Edwards & Stappers (2006) with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.
Lin, G.; Thurber, C.H.; Zhang, H.; Hauksson, E.; Shearer, P.M.; Waldhauser, F.; Brocher, T.M.; Hardebeck, J.
2010-01-01
We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP=VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE directionand 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling.
Saccorotti, G.; Chouet, B.; Dawson, P.
2003-01-01
The properties of the surface wavefield at Kilauea Volcano are analysed using data from small-aperture arrays of short-period seismometers deployed in and around the Kilauea caldera. Tremor recordings were obtained during two Japan-US cooperative experiments conducted in 1996 and 1997. The seismometers were deployed in three semi-circular arrays with apertures of 300, 300 and 400 m, and a linear array with length of 1680 m. Data are analysed using a spatio-temporal correlation technique well suited for the study of the stationary stochastic wavefields of Rayleigh and Love waves associated with volcanic activity and scattering sources distributed in and around the summit caldera. Spatial autocorrelation coefficients are obtained as a function of frequency and are inverted for the dispersion characteristics of Rayleigh and Love waves using a grid search that seeks phase velocities for which the L-2 norm between data and forward modelling operators is minimized. Within the caldera, the phase velocities of Rayleigh waves range from 1400 to 1800 m s-1 at 1 Hz down to 300-400 m s-1 at 10 Hz, and the phase velocities of Love waves range from 2600 to 400 m s-1 within the same frequency band. Outside the caldera, Rayleigh wave velocities range from 1800 to 1600 m s-1 at 1 Hz down to 260-360 m s-1 at 10 Hz, and Love wave velocities range from 600 to 150 m s-1 within the same frequency band. The dispersion curves are inverted for velocity structure beneath each array, assuming these dispersions represent the fundamental modes of Rayleigh and Love waves. The velocity structures observed at different array sites are consistent with results from a recent 3-D traveltime tomography of the caldera region, and point to a marked velocity discontinuity associated with the southern caldera boundary.
Polar versus Cartesian velocity models for maneuvering target tracking with IMM
NASA Astrophysics Data System (ADS)
Laneuville, Dann
This paper compares various model sets in different IMM filters for the maneuvering target tracking problem. The aim is to see whether we can improve the tracking performance of what is certainly the most widely used model set in the literature for the maneuvering target tracking problem: a Nearly Constant Velocity model and a Nearly Coordinated Turn model. Our new challenger set consists of a mixed Cartesian position and polar velocity state vector to describe the uniform motion segments and is augmented with the turn rate to obtain the second model for the maneuvering segments. This paper also gives a general procedure to discretize up to second order any non-linear continuous time model with linear diffusion. Comparative simulations on an air defence scenario with a 2D radar, show that this new approach improves significantly the tracking performance in this case.
NASA Astrophysics Data System (ADS)
Rodgers, A.; Petersson, A.; Nilsson, S.; Sjogreen, B.; McCandless, K.
2006-12-01
As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes recorded on broadband stations. Satisfactory prediction of ground motions from these events will provide hope for accurate modeling of future scenario earthquakes. Simulations were performed on large parallel computer(s) with a new elastic finite difference code developed at LLNL. We simulated broadband ground motions (0-0.25 Hz) for several moderate (magnitude 3.5-5.0) earthquakes in the region observed at Berkeley Digital Seismic Network (BDSN) broadband stations. These events are well located and can be modeled with simple point moment tensor sources (taken from the Berkeley Seismological Laboratory catalog), helping to isolate the effects of structure on the waveforms. These data sample the region's diverse tectonic structures, such as the bay muds, sedimentary basins and hard rock complexes. Preliminary results indicate that the simulations reproduce many important features in the data. For example, observed long duration surface waves are often predicted for complex paths (traveling across contrasting structures) and through sedimentary basins. Excellent waveform fits were frequently obtained for long-period comparisons (0.02-0.1) and good fits were often obtained for shorter periods. We will attempt higher frequency simulations to test the ability of the model to match the high frequency response. Finally, we performed large scenario earthquake simulations for the Hayward Fault. These simulations predict large amplifications across the Santa Clara and San Ramon/Livermore Valley sedimentary basins and with the Sacramento/San Joaquin River Delta.
Modeling continuous seismic velocity changes due to ground shaking in Chile
NASA Astrophysics Data System (ADS)
Gassenmeier, Martina; Richter, Tom; Sens-Schnfelder, Christoph; Korn, Michael; Tilmann, Frederik
2015-04-01
In order to investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing, we analyze 8 years of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC) network in northern Chile between 18 and 25 S. The Mw 7.7 Tocopilla earthquake in 2007 and the Mw 8.1 Iquique earthquake in 2014 as well as numerous smaller events occurred in this area. By autocorrelation of the ambient seismic noise field, approximations of the Green's functions are retrieved. The recovered function represents backscattered or multiply scattered energy from the immediate neighborhood of the station. To detect relative changes of the seismic velocities we apply the stretching method, which compares individual autocorrelation functions to stretched or compressed versions of a long term averaged reference autocorrelation function. We use time windows in the coda of the autocorrelations, that contain scattered waves which are highly sensitive to minute changes in the velocity. At station PATCX we observe seasonal changes in seismic velocity as well as temporary velocity reductions in the frequency range of 4-6 Hz. The seasonal changes can be attributed to thermal stress changes in the subsurface related to variations of the atmospheric temperature. This effect can be modeled well by a sine curve and is subtracted for further analysis of short term variations. Temporary velocity reductions occur at the time of ground shaking usually caused by earthquakes and are followed by a recovery. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. Our hypothesis is that not only the shaking of earthquakes provokes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by the integrated envelope of the ground acceleration over 1 day which is the discretization interval of the velocity measurements. In our model the amplitude of the velocity reduction as well as the recovery time are proportional to the size of the excitation. This model with the two free scaling parameters for the shaking induced velocity variation fits the data in remarkable detail. Additionally, a linear trend is observed that might be related to a recovery process from one or more earthquakes before our measurement period. For the Tocopilla earthquake in 2007 and the Iquique earthquake in 2014 velocity reductions are also observed at other stations of the IPOC network. However, a clear relationship between the ground shaking and the induced velocity reductions is not visible at other stations. We attribute the outstanding sensitivity of PATCX to ground shaking to the special geological setting of the station, where the material consists of relatively loose conglomerate with high pore volume.
Stabilization of traffic flow in optimal velocity model via delayed-feedback control
NASA Astrophysics Data System (ADS)
Jin, Yanfei; Hu, Haiyan
2013-04-01
Traffic jams may occur due to various reasons, such as traffic accidents, lane reductions and on-ramps. In order to suppress the traffic congestion in an optimal velocity traffic model without any driver's delay taken into account, a delayed-feedback control of both displacement and velocity differences is proposed in this study. By using the delay-independent stability criteria and the H∞-norm, the delayed-feedback control can be determined to stabilize the unstable traffic flow and suppress the traffic jam. The numerical case studies are given to demonstrate and verify the new control method. Furthermore, a comparison is made between the new control method and the method proposed by Konishi et al. [K. Konishi, M. Hirai, H. Kokame, Decentralized delayed-feedback control of an optimal velocity traffic model, Eur. Phys. J. B 15 (2000) 715-722]. The results show that the new control method makes the traffic flow more stable and improves the control performance.
A study of bath velocity distribution in a 3-D water model
Chen, J.J.J.; Shen, X.; Welch, B.J.; Taylor, M.P.
1996-10-01
A probe consisting of a sphere and an embedded thermocouple was used for measuring point velocities in a 3-D air-water model. Prior to testing in the model, the probe was calibrated in a water flow channel. Results measured in a full-scale 3-D model covering various parts of the cell including various positions of the center channel, the side channel and the anode-anode gap are reported. Flow directions can also be detected using this measurement technique.
NASA Astrophysics Data System (ADS)
Ballard, S.; Begnaud, M. L.; Hipp, J. R.; Chael, E. P.; Encarnacao, A.; Maceira, M.; Yang, X.; Young, C. J.; Phillips, W.
2013-12-01
SALSA3D is a global 3D P wave velocity model of the Earth's crust and mantle developed specifically to provide seismic event locations that are more accurate and more precise than are locations from 1D and 2.5D models. In this paper, we present the most recent version of our model, for the first time jointly derived from multiple types of data: body wave travel times, surface wave group velocities, and gravity. The latter two are added to provide information in areas with poor body wave coverage, and are down-weighted in areas where body wave coverage is good. To constrain the inversions, we invoked empirical relations among the density, S velocity, and P velocity. We demonstrate the ability of the new SALSA3D model to reduce mislocations and generate statistically robust uncertainty estimates for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. We obtain path-dependent travel time prediction uncertainties for our model by computing the full 3D model covariance matrix of our tomographic system and integrating the model slowness variance and covariance along paths of interest. This approach yields very low travel time prediction uncertainties for well-sampled paths through the Earth and higher uncertainties for paths that are poorly represented in the data set used to develop the model. While the calculation of path-dependent prediction uncertainties with this approach is computationally expensive, uncertainties can be pre-computed for a network of stations and stored in 3D lookup tables that can be quickly and efficiently interrogated using GeoTess software.
An Empirical Model of Human Aspiration in Low-Velocity Air Using CFD Investigations
Anthony, T. Rene; Anderson, Kimberly R.
2016-01-01
Computational fluid dynamics (CFD) modeling was performed to investigate the aspiration efficiency of the human head in low velocities to examine whether the current inhaled particulate mass (IPM) sampling criterion matches the aspiration efficiency of an inhaling human in airflows common to worker exposures. Data from both mouth and nose inhalation, averaged to assess omnidirectional aspiration efficiencies, were compiled and used to generate a unifying model to relate particle size to aspiration efficiency of the human head. Multiple linear regression was used to generate an empirical model to estimate human aspiration efficiency and included particle size as well as breathing and freestream velocities as dependent variables. A new set of simulated mouth and nose breathing aspiration efficiencies was generated and used to test the fit of empirical models. Further, empirical relationships between test conditions and CFD estimates of aspiration were compared to experimental data from mannequin studies, including both calm-air and ultra-low velocity experiments. While a linear relationship between particle size and aspiration is reported in calm air studies, the CFD simulations identified a more reasonable fit using the square of particle aerodynamic diameter, which better addressed the shape of the efficiency curves decline toward zero for large particles. The ultimate goal of this work was to develop an empirical model that incorporates real-world variations in critical factors associated with particle aspiration to inform low-velocity modifications to the inhalable particle sampling criterion. PMID:25438035
NASA Astrophysics Data System (ADS)
Jones, Alan G.; Afonso, Juan Carlos; Fullea, Javier; Salajegheh, Farshad
2014-02-01
Modeling the continental lithosphere's physical properties, especially its depth extent, must be done within a self-consistent petrological-geophysical framework; modeling using only one or two data types may easily lead to inconsistencies and erroneous interpretations. Using the LitMod approach for hypothesis testing and first-order modeling, we show how assumptions made about crustal information and the probable compositions of the lithospheric and sub-lithospheric mantle affect particular observables, particularly especially surface topographic elevation. The critical crustal parameter is density, leading to ca. 600 m error in topography for 50 kg m- 3 imprecision. The next key parameter is crustal thickness, and uncertainties in its definition lead to around ca. 4 km uncertainty in LAB for every 1 km of variation in Moho depth. Possible errors in the other assumed crustal parameters introduce a few kilometers of uncertainty in the depth to the LAB. We use Ireland as a natural laboratory to demonstrate the approach. From first-order arguments and given reasonable assumptions, a topographic elevation in the range of 50-100 m, which is the average across Ireland, requires that the lithosphere-asthenosphere boundary (LAB) beneath most of Ireland must lie in the range 90-115 km. A somewhat shallower (to 85 km) LAB is permitted, but the crust must be thinned (< 29 km) to compensate. The observations, especially topography, are inconsistent with suggestions, based on interpretation of S-to-P receiver functions, that the LAB thins from 85 km in southern Ireland to 55 km in central northern Ireland over a distance of < 150 km. Such a thin lithosphere would result in over 1000 m of uplift, and such rapid thinning by 30 km over less than 150 km would yield significant north-south variations in topographic elevation, Bouguer anomaly, and geoid height, none of which are observed. Even juxtaposing the most extreme probable depleted composition for the lithospheric mantle beneath southern Ireland against the most extreme fertile composition beneath northern Ireland only allows some 20 km of LAB variation; any further variations would produce effects that are well beyond those observed. One model that satisfies almost all the extant data to first order includes a spinel-peridotite upper lithospheric mantle layer to 85 km in southern Ireland and to 55 km in northern Ireland, thinning over a lateral distance of 150 km. Below this in southern Ireland is a garnet peridotite layer extending down to 115 km, and in northern Ireland a refertilized layer down to 95 km. The mid-lithospheric chemical discontinuity (MLD) at the base of the Spinel Peridotite zone may explain the observed discontinuity in S-to-P (Sp) receiver functions.
NASA Astrophysics Data System (ADS)
Begnaud, M. L.; Ballard, S.; Young, C. J.; Hipp, J. R.; Encarnacao, A.; Phillips, W.; Chael, E. P.; Rowe, C. A.
2013-12-01
We demonstrate the ability of SALSA3D (SAndia LoS Alamos 3D) version 2.1, a global 3D P-wave velocity model of the Earth's crust and mantle, to reduce mislocations compared to those derived from standard 1D and 2-2.5D models, for a set of realizations using only IMS stations - an example of a sparse network whose locations depend heavily on the velocity model employed - and a carefully chosen group of globally-distributed ground truth (GT) events. Our model is derived from the latest version of the GT catalog of P/Pn travel-time picks assembled by Los Alamos National Laboratory. The model uses the GeoTess triangular tessellation system described by Ballard et al. (2009; www.sandia.gov/geotess), which incorporates variable resolution both laterally and radially. For our starting model, we use a simplified version of the NNSA Unified model in Eurasia and the Crust 2.0 model elsewhere. Damping reduces velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness via progressive grid refinement using the diagonal of the model resolution matrix to determine where the data warrant such a refinement. Our approach provides more consistent and continuous areas of refinement, producing a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework of ~400 processors. The global IMS network consists of approximately 150 primary and auxiliary stations, forming a pre-defined, sparse network with which to locate seismic events. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D and 2/2.5D models via location tests on a global event set with GT of 5 km or better. Using Pn and P picks from IMS stations only, we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the accuracy and precision of relocation. We test using the full 3D covariance matrix of the current model to calculate path-dependent travel time uncertainty, rather than applying standard, 1D, distance-dependent uncertainty. SALSA3D reduces mislocation over the standard 1D ak135 model regardless of Pn to P ratio, with the most pronounced improvement at higher azimuthal gaps. SALSA3D also reduces mislocation compared to the combined RSTT/ak135 model (2.5D - RSTT for regional phases), with minimal improvement over RSTT when only regional Pn phases are used to compute locations.
Macgregor-Scott, N.; Walter, A.
1988-01-01
Crustal velocity structure for the region near Coalinga, California, has been derived from both earthquake and explosion seismic phase data recorded along a NW-SE seismic-refraction profile on the western flank of the Great Valley east of the Diablo Range. Comparison of the two data sets reveals P-wave phases in common which can be correlated with changes in the velocity structure below the earthquake hypocenters. In addition, the earthquake records reveal secondary phases at station ranges of less than 20 km that could be the result of S- to P-wave conversions at velocity interfaces above the earthquake hypocenters. Two-dimensional ray-trace modeling of the P-wave travel times resulted in a P-wave velocity model for the western flank of the Great Valley comprised of: 1) a 7- to 9-km thick section of sedimentary strata with velocities similar to those found elsewhere in the Great Valley (1.6 to 5.2 km s-1); 2) a middle crust extending to about 14 km depth with velocities comparable to those reported for the Franciscan assemblage in the Diablo Range (5.6 to 5.9 km s-1); and 3) a 13- to 14-km thick lower crust with velocities similar to those reported beneath the Diablo Range and the Great Valley (6.5 to 7.30 km s-1). This lower crust may have been derived from subducted oceanic crust that was thickened by accretionary underplating or crustal shortening. -Authors
Numerical Study of CME-like disturbances. 1-D simulations
NASA Astrophysics Data System (ADS)
Corona-Romero, P.; Gonzalez-Esparza, A.; Jeyakumar, S.; Casillas Perez, G.
2007-05-01
We present a parametric study of ICME-like disturbances from close to the Sun (18 solar radii) to 1 AU. This is a 1-D HD model using the ZEUS 3D code (Stone and Norman, 1992). With this study we illuminate some basic aspects of the heliocentric evolution of these disturbances in the inner heliosphere. After their injection, the fast ICME-like disturbances present two deceleration steps: a slow deceleration propagation in the inner trajectory, and, after reaching a critical distance (at about .45 AU), an exponential deceleration propagation where the ICME- like velocity tends to equalize the ambient wind speed. This critical distance depends on the ICME initial parameters and the ambient wind characteristics.
The National Oceanic and Atmospheric Administration's Multi-Layer Model (NOAA-MLM) is used by several operational dry deposition networks for estimating the deposition velocity of O , SO , HNO , and particles. The NOAA-MLM requires hourly values of meteorological variables and...
Evaluation of an Imputed Pitch Velocity Model of the Auditory Kappa Effect
ERIC Educational Resources Information Center
Henry, Molly J.; McAuley, J. Devin
2009-01-01
Three experiments evaluated an imputed pitch velocity model of the auditory kappa effect. Listeners heard 3-tone sequences and judged the timing of the middle (target) tone relative to the timing of the 1st and 3rd (bounding) tones. Experiment 1 held pitch constant but varied the time (T) interval between bounding tones (T = 728, 1,000, or 1,600
Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities
Lee, Myung W.
2008-01-01
Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.
Modeling the Coupled Effects of Pore Space Geometry and Velocity on Colloid Transport and Retention
Technology Transfer Automated Retrieval System (TEKTRAN)
Recent experimental and theoretical work has demonstrated that pore space geometry and hydrodynamics can play an important role in colloid retention under unfavorable attachment conditions. Computer models that only consider the average pore-water velocity and a single attachment rate coefficient a...
NASA Technical Reports Server (NTRS)
Raphan, T.; Sturm, D.; Cohen, B. (Principal Investigator)
1991-01-01
1. A generalized three-dimensional state space model of visual vestibular interaction was developed. Matrix and dynamical system operators associated with inputs from the semicircular canals, otolith velocity estimator, and the visual system have been incorporated into the model, which focus on their relationship to the velocity storage integrator. 2. A relationship was postulated between the eigenvalues and the direction of the eigenvectors of the system matrix and the orientation of the spatial vertical. It was assumed that the system matrix for a tilted position was a composition of two linear transformations of the system matrix for the upright position. One transformation modifies the eigenvalues of the system matrix, whereas another rotates the eigenvectors of the system matrix. The pitch and roll eigenvectors rotate with the head, whereas the yaw axis eigenvector remains approximately spatially invariant. 3. Based on the three-dimensional model, a computational procedure was formulated to identify the eigenvalues and eigenvectors of the system matrix with the use of a modification of the marquardt algorithm. With the use of data obtained from a monkey, it was shown that the three-dimensional behavior of velocity storage cannot be predicted solely in terms of its time constants, i.e., the inverse of its eigenvalues. With the use of the same eigenvalues the data could either be fit or not fit, depending on the eigenvector directions. Therefore, it is necessary to specify eigenvector directions when characterizing velocity storage in three dimensions. 4. Parameters found with the use of the Marquardt algorithm were incorporated into the model. Diagonal matrices in a head coordinate frame were introduced for coupling the visual system to the integrator and to the direct optokinetic pathway. Simulations of optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) were run. The model predicted the behavior of yaw and pitch OKN and OKAN when the animal is upright. It also predicted the cross-coupling in the side down position. The trajectories in velocity space were also accurately simulated. 5. One of the predictions of the model is that when the stimulus direction is along an eigenvector, the trajectory in velocity space is a straight line. Using the "spectral width" of the residuals from a straight line sequence during OKAN, we developed a methodology to estimate how close the OKAN decay was to an eigenvector trajectory. 6. Thus we have developed a model-based approach for studying and interpreting the response characteristics of velocity storage in three dimensions.(ABSTRACT TRUNCATED AT 400 WORDS).
Local Mass Conservation and Velocity Splitting In Pv-conserving Balanced Models
NASA Astrophysics Data System (ADS)
Mohebalhojeh, A. R.; McIntyre, M. E.
The most accurate potential-vorticity-conserving balanced models (PVBMs) do not conserve mass locally. A PVBM, in the sense understood here, has two defining prop- erties. First, a PVBM is a balanced model formulated in terms of a unique velocity field v , which advects the model's potential vorticity (PV) and which is obtainable by PV inversion. Second, the model's PV is given by the exact (primitive-equation, RossbyErtel) PV formula evaluated with the same v . Not conserving mass locally means that the velocity field v fails to satisfy the local mass-conservation equation, except possibly for some special flows such as steady circular vortices. There exists an infinite class C of PVBMs that do conserve mass locally. Its best-known member is the ``BolinCharney balance" model, in the shallow-water and isentropic-coordinate versions described by Gent and McWilliams and Whitaker. The present work char- acterizes the class C, and shows that most of its members are less accurate than the Bolin-Charney model. It shows furthermore, in full detail for the simplest, f-plane case, that the most accurate known PVBMs are not members of C. That is, the most accurate known PVBMs have velocity fields v that fail to satisfy local mass conserva- tion exactly, in general, even though the error may be tiny. Paradoxical though it may seem, this means that all the most accurate known PVBMs have one velocity field, v , to advect PV and another, vm , implicitly defined, to advect mass, the difference v - vm being nonzero in general even if tiny. The second field vm is computable by solving a Poisson equation at each timestep. The fact that v - vm is nonzero in general can be seen as a non-Hamiltonian counterpart of the ``schizophre- nia" or ``velocity splitting" already known to be characteristic of all Hamiltonian bal- anced models derived from the primitive equations by Salmon's method, in which imposing balance always splits the primitive equations' unique velocity field into two or more distinct velocity fields each of which has an essential role in the balanced dynamics.
Relationship between Elastic wave Velocity and Permeability of Rock Model with penny-shaped cracks
NASA Astrophysics Data System (ADS)
Yamabe, H.; Tsuji, T.; Matsuoka, T.
2011-12-01
Estimating underground fluid-flow is of great importance in petroleum engineering and carbon capture and storage (CCS). Permeability is one of the most important parameters which show how easily fluid passes through rock mass. It could be acquired just by measuring rock samples near borehole in lab-experiments. It means that permeability except near borehole should be estimated, considering other information. In this research, elastic wave velocity is focused as a tool of estimating permeability, because it is one of the most popular parameter which has underground information. The relationship between permeability and elastic wave velocities should be revealed, in order to establish a methodology to estimate rock permeability from elastic wave velocity. These two parameters are controlled by pore geometry of rock. Therefore, we focused on pore geometry as connecting bridge between the two parameters: permeability, elastic wave velocity. We modeled the considering rock as a solid mass containing a lot of same-sized penny-shaped cracks randomly. LBM (Lattice Boltzmann Method), which is one of the computational fluid dynamics methods, is adopted for calculating permeability in our study. This method has a storing point especially under complicated fluid-solid boundary condition. Elastic wave velocities are derived from effective elastic moduli (i.e., bulk modulus, stiffness). They are estimated by self-consistent approximation, which needs porosity of rock model, aspect ratio of penny-shaped cracks and volume fraction of each phase. In this research, we assume that solid phase is composed only by quartz and rock's pore space is filled with water. The simulated results demonstrate that aspect ratio of crack can be estimated by P- and S-wave velocity, and aspect ratio and P-wave velocity can determine porosity. Whereas, the relationship between porosity and permeability is dependent on aspect ratio, which means permeability can be estimated by aspect ratio and porosity. Therefore, this research reveals that permeability can be estimated by P-wave velocity and S-wave velocity if the rock is composed by same-sized penny cracks.
Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling
Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.
1999-01-01
We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data. Copyright 1999 by the American Geophysical Union.
Modeling and simulation of continuous wave velocity radar based on third-order DPLL
NASA Astrophysics Data System (ADS)
Di, Yan; Zhu, Chen; Hong, Ma
2015-02-01
Second-order digital phase-locked-loop (DPLL) is widely used in traditional Continuous wave (CW) velocity radar with poor performance in high dynamic conditions. Using the third-order DPLL can improve the performance. Firstly, the echo signal model of CW radar is given. Secondly, theoretical derivations of the tracking performance in different velocity conditions are given. Finally, simulation model of CW radar is established based on Simulink tool. Tracking performance of the two kinds of DPLL in different acceleration and jerk conditions is studied by this model. The results show that third-order PLL has better performance in high dynamic conditions. This model provides a platform for further research of CW radar.
Velocity Measurements Near the Empennage of a SmallScale Helicopter Model
NASA Technical Reports Server (NTRS)
Gorton, Susan Althoff; Meyers, James F.; Berry, John D.
1996-01-01
A test program was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a small-scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with Laser Velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady downwash angle variations of over 30 degrees due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the fan were made for a low-speed flight condition using both conventional LV techniques and a promising, non-intrusive, global, three-component velocity measurement technique called Doppler Global Velocimetry (DGV). The velocity data show an accelerated flow near the fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane. DGV shows promise as an evolving tool for rotor flowfield diagnostics.
NASA Astrophysics Data System (ADS)
Gaelle, Gibert; Riad, Hassani; Emmanuel, Tric; Tony, Monfret
2010-05-01
Recent analogical models of Heuret et al (2007) and Guillaume et al (2009) showed that the kinematical and mechanical role of the overriding plate is crucial for the slab geometry. We used Hassani et al (1997) 2D finite element numerical code to model subduction with parameters close to analogue models conditions. Our results are coherent with considered previous analogue models. As shown by Heuret et al (2007), after the subducting plate reaches the 660 km discontinuity modeled by a rigid foundation, we obtained two different styles of subduction depending on the overriding plate velocity vop: if vop >0, the slab lays forward on the 660km discontinuity (style 1) if vop ?0, the slab lays backward on the discontinuity (style 2). We also light up two different processes: the subduction evolves in a steady-state regime when vsp ?0 or 2vop + vop ?0 (where vsp stands for the subducting plate velocity) and in non steady-state regime when one of these two conditions is not fulfilled. This result is coherent with Guillaume et al (2009) non steady-state models at vop=0. We checked these conditions by conducting several simulations varying subduction velocities (relative velocity), absolute plates velocities and plate viscosities. When the process is not steady-state, the slab is periodically folding on the 660 km discontinuity leading to episodes of slab flattening (minimal dip of 13 ) followed by slab steepening phases (maximal value of 65 ). The folding period is essentially controlled by slab viscosity and subduction velocity. We then compared our models with the natural case of the Chilean flat slab. Fukao et al (2001) show that the Andean slab does not penetrate the 660 km discontinuity which make possible comparison between our models and nature. For the Andean case, actual velocities are vop? 4.3 cm.an-1 and vsp? 2.9 cm.an-1 for a relative velocity close to vs = vop + vsp? 7.2 cm.an-1, which places us in the case of style 1 with cycles. If we model those velocities with a viscosity of ?=21024 Pa.s, we obtain cycle duration of ca. 26 Ma with a period of ca. 3.6 Ma of low dip, with a minimal value of ca. 15 . Haschke et al (2002) work on Andean flat slab region magmatic rocks suggest that evolutionary cycles occurred during the Andean orogeny. Episodes of slab steepening and shallowing with a duration of 30-40 Ma might have occurred, explaining magmatic gaps of ca 5-10. Simplifications imposed by numerical modeling could explain the difference between our values and Andean values. Still, our values are in the range of Haschke et al (2002) estimation of the Andean case. Our models are coherent with Kay et al (2002) results on South American overriding plate: when the Nazca plate slab was steep, the South American margin underwent extension, and that when shallowing occurred, compression occurred in the margin. Therefore, style 1 with cycle may be considered as a possible answer for this natural speacial case.
Modeling Compressional and Shear Wave Velocities of Unconsolidated Sediments in the Vadose Zone
NASA Astrophysics Data System (ADS)
Berge, P. A.
2001-12-01
Recent advances in seismic surveys have provided ways to image shallow structure in highly attenuating soils and near-surface rock. Applications include using surface wave methods to find tunnels; mapping landfills with seismic refraction methods; finding faults, the water table, or other strong heterogeneities using seismic reflection surveys. Recent improvements in laboratory ultrasonic measurement techniques have provided reliable data on compressional and shear wave velocities in soils at low pressures analogous to the top few meters to tens of meters of the subsurface. The availability of these data points the way for development of interpretation methods that may allow seismologists to obtain more information from their data in the future. For environmental applications, improvements to interpretation methods could lead to reliable detection of second-order features such as changes in soil saturation, presence of dense non-aqueous phase liquids, or changes in clay content. Traditional modeling techniques developed in the oil industry are optimized for consolidated materials at pressures and depths greater than those typical for environmental applications. The shallow subsurface velocities are highly nonlinear and the soils are highly attenuating, and these characteristics must be considered when modeling velocities (and also when processing seismic data). Various factors, including grain contact roughness, location of clay with respect to sand grains, location of fluid in the partially-saturated case, loose vs. dense packing, all affect the compressional and shear wave velocities and attenuation and their pressure (depth) dependence. Care must be taken when applying effective medium theories or grain-contact theories to model shallow soil velocity behavior. Unconsolidated materials at low pressures show much greater variation in compressional vs. shear wave properties than consolidated materials and high-pressure applications would show. Despite the modeling difficulties, progress in seismic interpretation may be made if data are available for both compressional and shear waves. Examples of pitfalls and methods for successful soil velocity modeling will be presented using lab and field velocity data from the literature, for sands, silty sands, and other unconsolidated materials. The goal is to develop techniques to improve interpretation of seismic data from the vadose zone. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and supported specifically by the DOE Environmental Management Science Program. >http://www.llnl.gov/ees/esd/expgeoph/Berge/EMSP/
Crustal Velocity Model of Watusi Data Integrated With Legacy Data, Clark County, Nevada
NASA Astrophysics Data System (ADS)
Zaragoza, S. A.; Snelson, C. M.
2004-12-01
The Las Vegas Valley, Nevada is located in the central Basin and Range Province, about 100 km southeast of the Nevada Test Site (NTS). Las Vegas sits atop a basin up to 5 km deep (Langenheim et al., 2001) that has been shown to amplify energy from strong ground motion (Su et al., 1998). Rapid population growth has led to concerns that future nuclear testing at NTS may pose a hazard from strong ground motion. Studies performed when nuclear testing was ongoing were limited to the central basin and were insufficient to adequately assess ground motion hazard for the entire Valley. In September 2002, 400 single-channel seismic recorders were deployed to record a chemical blast (Watusi) at NTS. Forward modeling of these data as well as Legacy data from the 1960s (Prodehl, 1979) produced a 268 km two-dimensional crustal velocity model from Kingman, Arizona to NTS with higher resolution than the previous model. Crustal velocities range from 3.5 to 6.2 km/s. Velocities at the Moho range from 7.9-8.0 km/s. Crustal depth ranges from 28-29 km near Kingman to 33-34 km near NTS. A structural feature in model space at 12-15 km underneath Indian Springs, Nevada appears to focus seismic energy into the Las Vegas basin, and may pose a significant seismic hazard. The feature has a dip in model space of 45 toward the southeast. A density model was also produced and tied to the velocity model. The density model is consistent with the velocity model, confirming crustal depth ranges from 28-29 km near Kingman to 33-34 km near NTS. The density model also confirms the 45 southeast-dipping structural feature and indicates the location of a mafic body in model space at a depth of 5-12 km beneath the Las Vegas Basin. Possible interpretations of the dipping structure include a relict thrust or metamorphic core complex. However, these interpretations are difficult due to the steep dip angle of the feature, and more evidence would be needed to verify one of these conclusions. A more likely interpretation would be that this feature represents apparent dip on the Las Vegas Valley Shear Zone.
Mapping high Pn velocity beneath the Colorado Plateau constrains uplift models
NASA Astrophysics Data System (ADS)
Beghoul, Noureddine; Barazangi, Muawia
1989-06-01
The massive International Seismological Centre data set of the past 20 years and the two-station method are used to determine Pn velocities in the mantle lid beneath the Colorado plateau. In this method the event is located at distances where Pn is the first arrival (2-16) and the path is in or very near the azimuth of the two-station pair and crosses the plateau. This technique to a large extent minimizes the hypocenter mislocation effect and possible errors due to variations in the crustal structure near the source, since only the difference in travel times at the two stations is used. However, this technique has a few underlying assumptions and possible sources of errors (such as the quality of the Pn data base and station delays caused by varying crustal structure) that require an extremely careful application of the method. A detailed study of the source of errors and a methodology of selection of the data are presented. Application of this method to the Colorado plateau using all possible two-station pairs from 53 stations located within or along the margin of the plateau yields an average high Pn velocity of 8.120.09 km/s. This value is considerably larger than the average value of 7.83 km/s based on available but very limited seismic refraction profiles but is remarkably similar to the average value of 8.1 km/s for the relatively stable midcontinent region. Our new Pn velocity for the Colorado plateau eliminates the paradox in the literature that emphasizes the rather close similarity between average Pn velocities beneath the Colorado plateau and the Basin and Range Province while their tectonic and magmatic Cenozoic history is dramatically different. Previous models for the structure and evolution of the plateau have used the low Pn velocity as an important constraint on density and thermal state of the lithosphere. Hence such models should be reexamined on the basis of this new uppermost mantle Pn velocity determination. There are two main models that have been proposed to explain the 2-km uplift of the Colorado plateau. One is based on a combination of thermal thinning of the lithosphere and crustal thickening, and the other involves a combination of the delamination of the subducted, subhorizontal Farallon oceanic plate from the overriding North American plate and crustal thickening. We show that the delamination model is more readily consistent not only with our velocity determination and the elevation of the plateau but also with varied geological observations reported in the literature that concern the Cenozoic evolution of western North America.
Comparative Experimental and Modeling Study of Fluid Velocities in Heterogeneous Rocks
NASA Astrophysics Data System (ADS)
Hingerl, F.; Romanenko, K.; Pini, R.; Balcom, B.; Benson, S. M.
2013-12-01
Understanding the spatial distribution of fluid velocities and effective porosities in rocks is crucial for predicting kinetic reaction rates and fluid-rock interactions in a plethora of geo-engineering applications, ranging from geothermal systems, Enhanced Oil Recovery to Carbon Capture and Storage. Magnetic Resonance Imaging can be used to measure spatially resolved porosities and fluid velocities in porous media. Large internal field gradients and short spin relaxation times, however, constrain the usability of the conventional MRI technique in natural rock samples. The combination of three-dimensional Single Point Ramped Imaging with T1 Enhancement (SPRITE) and the 13-interval Alternating-Pulsed-Gradient Stimulated-Echo (APGSTE) scheme - a method developed at the UNB MRI Center - is able to compensate for those challenges and quantitative 3 dimensional maps of porosities and fluid velocities can be obtained. In this study we measured velocities and porosities using MRI in a sandstone rock sample showing meso-scale heterogeneities. Then we generated permeabilities using three independent approaches, employed them to model single-phase fluid flow in the measured rock sample and compared the generated velocity maps with the respective MRI measurements. For the first modeling approach, we applied the Kozeny-Carman relationship to create a permeability map based on porosities measured using MRI. For the second approach we used permeabilities derived from CO2-H2O multi-phase experiments performed in the same rock sample assuming the validity of the J-Leverett function. The permeabilities in the third approach were generated by applying a new inverse iterative-updating technique. The resulting three permeability maps were then used as input for a CFD simulation - using the Stanford CFD code AD-GPRS - to create a respective velocity map, which in turn was then compared to the measured velocity map. The results of the different independent methods for generating permeability maps as well as their correlation with the measured velocity maps are evaluated. Furthermore the implication of this study on understanding kinetic reaction rates and fluid-rock interaction is discussed.
A comparison of measured and modeled velocity fields for a laminar flow in a porous medium
NASA Astrophysics Data System (ADS)
Wood, B. D.; Apte, S. V.; Liburdy, J. A.; Ziazi, R. M.; He, X.; Finn, J. R.; Patil, V. A.
2015-11-01
Obtaining highly-resolved velocity data from experimental measurements in porous media is a significant challenge. The goal of this work is to compare the velocity fields measured in a randomly-packed porous medium obtained from particle image velocimetry (PIV) with corresponding fields predicted from direct numerical simulation (DNS). Experimentally, the porous medium was comprised of 15 mm diameter spherical beads made of optical glass placed in a glass flow cell to create the packed bed. A solution of ammonium thiocyanate was refractive-index matched to the glass creating a medium that could be illuminated with a laser sheet without distortion. The bead center locations were quantified using the imaging system so that the geometry of the porous medium was known very accurately. Two-dimensional PIV data were collected and processed to provide high-resolution velocity fields at a single plane within the porous medium. A Cartesian-grid-based fictitious domain approach was adopted for the direct numerical simulation of flow through the same geometry as the experimental measurements and without any adjustable parameters. The uncertainties associated with characterization of the pore geometry, PIV measurements, and DNS predictions were all systematically quantified. Although uncertainties in bead position measurements led to minor discrepancies in the comparison of the velocity fields, the axial and normal velocity deviations exhibited normalized root mean squared deviations (NRMSD) of only 11.32% and 4.74%, respectively. The high fidelity of both the experimental and numerical methods have significant implications for understanding and even for engineering the micro-macro relationship in porous materials. The ability to measure and model sub-pore-scale flow features also has relevance to the development of upscaled models for flow in porous media, where physically reasonable closure models must be developed at the sub-pore scale. These results provide valuable data in support of that goal.
Cheng, Z; Juli, C; Wood, N B; Gibbs, R G J; Xu, X Y
2014-09-01
Aortic dissection is a life-threatening process in which the weakened wall develops a tear, causing separation of wall lay