For comprehensive and current results, perform a real-time search at Science.gov.

1

Brady 1D seismic velocity model ambient noise prelim

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.

Mellors, Robert J.

2

Brady 1D seismic velocity model ambient noise prelim

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.

Mellors, Robert J.

2013-10-25

3

NASA Astrophysics Data System (ADS)

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.

Graves, R. W.

2012-12-01

4

NASA Astrophysics Data System (ADS)

On December 5, 2004 a strong earthquake occurred near the city of Waldkirch, about 30 km's north of Freiburg, with a local magnitude of ML = 5.4. This seismic event was one of the strongest observed since the ML = 5.7 'Schwäbische Alb' event of September 3, 1978, 30 years before. In the aftermath of the event several institutions (Bens, BGR, LGBR, LED, SED and NEIC) have attempted to relocate this earthquake that came up with a hypocentral depth range of 9 - 12 km which. In fact, as the exact hypocentral location of the Waldkirch - and other events in the area - namely, the seismic depths, are of utmost importance for the further understanding of the seismotectonics as well as of the seismic hazard in the upper Rhinegraben area, one cannot over stress the necessity for a hypocenter relocation as best as possible. This requires a careful analysis of all factors that may impede an unbiased relocation of such an event. In the present talk we put forward the question whether the Waldkirch seismic event can be relocated with sufficient accuracy by a regional network when, additionally, improved regional 1D- and 3D seismic velocity models for the crust and upper mantle that take into consideration Pn-anisotropy of the upper mantle beneath Germany are employed in the hypocentral determination process. The seismological work starts with a comprehensive analysis of the dataset available for the relocation of the event. By means of traveltime curves a reevaluation of the observed phases is done and it is shown that some of the big observed traveltime residuals are most likely the consequence of wrongly associated phases as well as of the neglect of the anisotropic Pn traveltime correction for the region. Then hypcocenter relocations are done for 1D vertically inhomogeneous and 3D laterally inhomogeneous seismic velocity models, without and with the anisotropic Pn-traveltime correction included. The effects of the - often not well-known - Moho depth and of the VP/VS-ratio across the study area are investigated. Finally a thorough statistical analysis of the hypocentral relocation accuracy and its sensitivity to various observational and model errors is carried out by (1) the classical calculation of covariances and confidence ellipses for the hypocenter and (2) Monte Carlo relocations with random perturbations of the observed arrivaltimes as well as of the choice of the initial hypocenter in the relocation process. The correction of the original phase-data leads to a shift of the hypocenter to about 10 to 15 km depth instead of 0 - 5 km for the uncorrected phases.The importance of the phase correction is also supported by the final RMS which is reduced from 2.22 s to 1.00 s for the isotropic case and, even more so, from 2.29 s to 0.75 s for the anisotropic. The reduced traveltime plots indicate also that a common VP /VS-ratio of 1.72 for both the crust and the upper mantle does not fit the crustal Sg-phases well. From subsequent hypocentral relocations with separate VP/VS-ratio for the crust and the upper mantle optimal values of VP /VS = 1.70 former, respective 1.66 for the latter, are obtained. In a subsequent set of relocations of the Waldkirch event the recently established isotropic and anisotropic 3D- crustal and upper mantle seismic velocity models of (Muench, 2009; Muench et al., 2010) are employed. Compared with the previous 1D hypocentral relocations where the optimal depth range found is 14 to 15 km, those of the 3D models lie about one km higher. The slightly lower depth of the 3D-models is most likely a consequence of traveltime effects of the structural velocity inhomogeneities.

Muench, Thomas; Koch, Manfred; Schlittenhard, Jörg

2010-05-01

5

NASA Astrophysics Data System (ADS)

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.

Jechumtálová, Zuzana; Bulant, Petr

2014-07-01

6

NASA Astrophysics Data System (ADS)

The paper will present a theoretical model for the prediction of undertow velocity profiles in the surf zone due to near-normally incident waves. The waves may be periodic or narrow-banded random waves, and the beach may be plane or barred. The theoretical model consists of three components: (i) breaking wave model; (ii) surface roller model; and (iii) undertow velocity profile model. \\textit{The breaking wave model} (Tajima and Madsen, 2002) is based on the concept of an equivalent linear wave and predicts linear wave characteristics for shoaling, breaking and broken waves. Non-linear wave characteristics, e.g., near-bottom orbital velocity, are obtained from equivalent linear wave characteristics and local bottom slope through use of simple transform formulae. \\textit{The surface roller model} is based on the same principle as Dally et al. (1985), but differs from this by transferring only the potential energy lost from the wave motion into the surface roller and calculating the decay of surface roller energy using a decay coefficient equal to that obtained for the breaking wave dissipation model. \\textit{The undertow velocity profile model} assumes a linearly varying shear stress over the water depth combined with an assumed form of the turbulent eddy viscosity. The shear stress at the surface is obtained from the breaking wave and surface roller models, whereas the bottom shear stress is obtained from considerations of mass conservation, i.e., depth-integrated undertow velocity must equal the volume transport of waves and surface roller above trough level. The near-bottom undertow velocity is calculated at the edge of the wave-bottom boundary layer, from knowledge of near-bottom orbital velocity, bottom shear stress and bottom roughness, using the combined wave-current bottom boundary layer theory by Madsen (1994). Comparison of predicted and measured undertow velocity profiles are performed for periodic and random waves normally incident on plane and barred concrete beaches as well as random waves near-normally incident on barred movable bed beach profiles. In general the agreement between predicted and observed undertow velocities is excellent. It is shown that model predictions are fairly insensitive to the choice of turbulent eddy viscosity, which is the only adjustable quantity in the model.

Tajima, Y.; Madsen, O. S.

2002-12-01

7

NSDL National Science Digital Library

The Introductory Physics 1D Motion Lab program asks students to develop a model for a ball moving vertically under the influence of gravity. It is distributed as a ready-to-run (compiled) Java archive. Double-clicking the ejs_intro_1DMotionLab.jar file will run the program if Java is installed. In order to modify this simulation (and see how it is designed), if you have Ejs installed, you can right-click within the simulation window and select Open Ejs Model from the pop-up menu. Information about Ejs (Easy Java Simulations) is available at: http://www.um.es/fem/Ejs/. The Intro 1D Motion Lab program is one of a suite of Easy Java Simulations (Ejs) models used in Introductory Physics Labs. Ejs, a part of the Open Source Physics Project, and is designed to make it easier to access, modify and generate computer models. Additional models can be found by searching ComPADRE for Ejs.

Cox, Anne; Christian, Wolfgang; Belloni, Mario

2008-05-30

8

A 1-D model of sinking particles

NASA Astrophysics Data System (ADS)

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.

Jokulsdottir, T.; Archer, D.

2006-12-01

9

ERIC Educational Resources Information Center

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…

Brand, Neal; Quintanilla, John A.

2013-01-01

10

Point Charge Forces in 1D Model

NSDL National Science Digital Library

The Point Charge Forces in One-Dimension model investigates the electric force that one charged particle exerts on another. The electric force is shown in three ways. First, particle 2 can be dragged left or right to sample the force at various locations - the force on each particle is shown with an arrow. Second, the numerical value of each force is shown in the table at the bottom. Third, you can check the box at the top of the menu to plot a graph of the electric force as a function of position. For the graph (and the numerical values), we define positive force as a force pointing to the right, and negative force as a force pointing to the left. The Point Charge Forces in One-Dimension was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_Point_Charge_Force_1D.jar file will run the program if Java is installed.

Duffy, Andrew

2010-04-16

11

Ion Cyclotron Waves at Io: 1D Hybrid Modeling

NASA Astrophysics Data System (ADS)

On Galileo close flybys of Io (1995-2001), the magnetometers detected ElectroMagnetic Ion Cyclotron (EMIC) waves close to the S, O, SO2 and SO ion gyrofrequencies. These waves are produced when the phase-space distribution function of a minor ion species of the torus is non-Maxwellian, as for instance, the result of a pickup of new ions from Io's neutral corona. They were detected far from Io (~ 10-20 Rio), mainly downstream of the moon, and are powerful diagnostic tools for probing Io's extended atmosphere. We investigate the production of EMIC waves with a 1D hybrid model (fluid electrons and kinetic ions). These 1D simulations represent the lifetime of a field line that is entrained around Io by the plasma flow and experiences a variable mass loading of new ions of different composition when the field line interacts with Io's neutral atmosphere. The time-variable mass loading of this field line is based on former simulations of the multi-species chemistry modeling of Io's interaction (Dols et al., 2008), coupled with a MHD modeling of the local electromagnetic interaction (Dols et al., 2011; 2012): a multi-component neutral atmosphere of Io is prescribed in S, O, SO2 and SO; the flow of the plasma is calculated with a MHD model; the mass loading rate of these ions is calculated for different flow lines around Io that follow the MHD flow. These time dependent multi-ion massloading rates and flow velocities are used as inputs to the 1D hybrid simulation. We then make a Fourier analysis of the hybrid-calculated magnetic field variations close to Galileo trajectories, evaluate the power and the resonant frequencies of the EMIC waves and compare to the Galileo magnetometer data. The ultimate goal of the EMIC analysis is to constrain Io's neutral corona, its longitudinal asymmetries and its time variability.

Dols, V. J.; Delamere, P. A.; Bagenal, F.

2012-12-01

12

Ion velocity distribution at the termination shock: 1-D PIC simulation

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.

Lu Quanming; Yang Zhongwei; Lembege, Bertrand [CAS Key Laboratory of Basic Plasma Physics, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136 (China); LATMOS-UVSQ-IPSL-CNRS, Guyancourt 78280 (France)

2012-11-20

13

GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL

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.

KALYANAPU, ALFRED [Los Alamos National Laboratory; MCPHERSON, TIMOTHY N. [Los Alamos National Laboratory; BURIAN, STEVEN J. [NON LANL

2007-01-17

14

Geostatistical Modeling of Pore Velocity

A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.

Devary, J.L.; Doctor, P.G.

1981-06-01

15

Cell polarisation model : the 1D case Thomas Lepoutre

Cell polarisation model : the 1D case Thomas Lepoutre , Nicolas Meunier and Nicolas Muller (x)dx = M. (2) INRIA Rh^one Alpes (team DRACULA) Batiment CEI-1, 66 Boulevard NIELS BOHR, 69603.meunier@parisdescartes.fr, nicolas.muller@parisdescartes.fr 1 hal-00776613,version1-16Jan2013 #12;The previous model (1) comes from

Boyer, Edmond

16

MODELING HYDRODYNAMICS AND CHANNEL MORPHOLOGY USING CCHE1D

CCHE1D is a one-dimensional unsteady flow and sediment transport model for channel networks designed to be used in combination with rainfall-runoff and upland erosion models. Its sediment transport module computes non-equilibrium transport of non-uniform sediment mixtures, which allows the simulation of processes such as hydraulic sorting and armoring, and the determination of changes in bed sediment gradation. Bank toe erosion

Dalmo A. Vieira; Weiming Wu; Sam S. Y. Wang

17

NASA Astrophysics Data System (ADS)

A new state evolution law has recently been proposed by Nagata et al. (2012) that includes a dependence upon stressing rate through a laboratory derived proportionality constant c. It has been claimed that this law, while retaining the time-dependent healing of the Dieterich (or Aging) law, can also match the symmetric response of the Ruina (or Slip) law to velocity step tests. We show through analytical approximations and numerical results that the new law transitions between the responses of the traditional Aging and Slip laws in velocity step-up/step-down experiments when the value of c is tuned properly. Particularly, for c=0, the response is pure Aging, while for finite, nonzero c one observes Slip law type behavior for small velocity jumps but Aging law type response for larger jumps. The magnitude of the velocity jump required to see this transition between aging and slip behaviors increases as c increases. In the limit of c?1 the response becomes purely Slip law type for all geologically plausible velocity jumps. We also present results from detailed analytical and numerical studies of the mechanism of rupture nucleation on 1-D faults under this new state evolution law to demonstrate that the style of nucleation can also be made to switch from Aging-type (expanding cracks) to Slip-type (slip pulses) by adjusting the value of c as indicated by the velocity step results.

Bhattacharya, P.; Rubin, A. M.

2014-03-01

18

Examination of 1D Solar Cell Model Limitations Using 3D SPICE Modeling: Preprint

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.

McMahon, W. E.; Olson, J. M.; Geisz, J. F.; Friedman, D. J.

2012-06-01

19

Nonlocal Order Parameters for the 1D Hubbard Model

NASA Astrophysics Data System (ADS)

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.

Montorsi, Arianna; Roncaglia, Marco

2012-12-01

20

High Velocity Rain: The Terminal Velocity Model of Galactic Infall

A model is proposed for determining the distances to falling interstellar clouds in the galactic halo by measuring the cloud velocity and column density and assuming a model for the vertical density distribution of the Galactic interstellar medium. It is shown that falling clouds with N(H I) terminal velocity which increases with increasing height above the Galactic plane. This terminal velocity model correctly predicts the distance to high velocity cloud Complex M and several other interstellar structures of previously determined distance. It is demonstrated how interstellar absorption spectra alone may be used to predict the distances of the clouds producing the absorption. If the distance, velocities, and column densities of enough interstellar clouds are known independently, the procedure can be reversed, and the terminal velocity model can be used to estimate the vertical density structure (both the mean density and the porosity) of the interstellar medium. Using the data of Danly and assuming a drag coefficient of CD ? = 1, the derived density distribution is consistent with the expected density distribution of the warm ionized medium, characterized by Reynolds. There is also evidence that for z> ? 0.4 kpc one or more of the following occurs: (1) the neutral fraction of the cloud decreases to ? 31 ± 14%, (2) the density drops off faster than characterized by Reynolds, or (3) there is a systematic decrease in CD with increasing z. Current data do not place strong constraints on the porosity of the interstellar medium.

Robert A. Benjamin; Laura Danly

1996-01-01

21

Normal Modes on 1D Monatomic Lattice Model

NSDL National Science Digital Library

The Normal Modes on 1D Monatomic Lattice Model shows the motion and the dispersion relation of N identical ions of mass M separated by a lattice distance a. Ionic vibrations in a crystal lattice form the basis for understanding many thermal properties found in materials. These vibrations are described as displacement waves traveling through the lattice. These vibrational modes can also be described as bosonic particles called phonons which have quantized energy in much the same way photons do for light. Using a spring model for the inter-ionic interactions, the dispersion relation between the vibrational frequencies and the allowed wave vectors can be analytically solved for the simple one dimensional case. It is sometimes difficult for students to visualize these modes of vibration and how they relate to the resulting ionic motions in the underlying crystal lattice. This simulation facilitates the understanding of the analytical solution by graphically representing these modes. The analytical form of the dispersion relation is shown along with the allowed normal mode points. Based on the chosen normal mode, the motion of the ions as a function of time is displayed to help visualize the mode. It is easy to see how the chosen mode affects the ion motions from unit cell to unit cell. The Normal Modes on 1D Monatomic Lattice Model was developed by Richard Charles Andrew using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Andrew, Richard C.

2013-10-08

22

Point Charge Electric Field in 1D Model

NSDL National Science Digital Library

The Point Charge Electric Field in 1D model investigates the electric field at various positions along a line, when there are either one or two charged particles on that line. The electric field is represented in two ways. First, there is a movable positive test charge that you can move along the line to sample the field at various locations - the direction of the force on that test charge is the same as the direction of the electric force on the test charge. The second way to represent the electric field is to plot a graph of the electric field as a function of position. For the graph, we define positive field as a field pointing to the right, and negative field as a field pointing to the left.

Duffy, Andrew

2009-10-21

23

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.

Bechtel, S.E.; Forest, M.G.; Holm, D.D.; Lin, K.J.

1988-01-01

24

Flooding flows in city crossroads: experiments and 1-D modelling.

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

Rivičre, N; Perkins, R J; Chocat, B; Lecus, A

2006-01-01

25

Normal Modes on 1D Diatomic Lattice Model

NSDL National Science Digital Library

The Normal Modes on 1D Diatomic Lattice Model shows the motion and the dispersion relation of N diatomic unit cells. Ionic vibrations in a crystal lattice form the basis for understanding many thermal properties found in materials. These vibrations are described as displacement waves traveling through the lattice. These vibrational modes can also be described as bosonic particles called phonons which have quantized energy in much the same way photons do for light. Using a spring model for the inter-ionic interactions, the dispersion relations between the vibrational frequencies and the allowed wave vectors can be analytically solved for the simple one dimensional case with a two atom basis. It is sometimes difficult for students to visualize these modes of vibration and how they relate to the resulting ionic motions in the underlying crystal lattice. This simulation facilitates the understanding of the analytical solutions by graphically representing these modes. The analytical forms of the two dispersion relations (the optical and acoustic branches) are shown along with the allowed normal mode points. Based on the chosen normal mode, the motion of the ions as a function of time is displayed to help visualize the mode. It is easy to see how the chosen mode affects the ion motions inside a unit cell as well as the motions from unit cell to unit cell. Also, the optical and acoustic motions can be readily compared. This model was developed by Richard Charles Andrew using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Andrew, Richard C.

2013-10-14

26

A One-Dimensional (1-D) Three-Region Model for a Bubbling Fluidized-Bed Adsorber

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.

Lee, Andrew; Miller, David C.

2012-01-01

27

Newberry EGS Seismic Velocity Model

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.

Templeton, Dennise

2013-10-01

28

On a 2D 'zoom' for the 1D shallow water model: coupling and data assimilation

On a 2D 'zoom' for the 1D shallow water model: coupling and data assimilation I.Yu. Gejadze a,1, J global model. The zoom model (2D shallow water equations) describes additional physical phenomena, which are not repre- sented by the global model (1D shallow water equations with storage areas). Both models

Paris-Sud XI, UniversitĂ© de

29

NASA Astrophysics Data System (ADS)

We propose a new quantitative determination of shear wave velocities for distinct geological units in the Bohemian Massif, Czech Republic (Central Europe). The phase velocities of fundamental Love wave modes are measured along two long profiles (~200 km) crossing three major geological units and one rift-like structure of the studied region. We have developed a modified version of the classical multiple filtering technique for the frequency-time analysis and we apply it to two-station phase velocity estimation. Tests of both the analysis and inversion are provided. Seismograms of three Aegean Sea earthquakes are analyzed. One of the two profiles is further divided into four shorter sub-profiles. The long profiles yield smooth dispersion curves; while the curves of the sub-profiles have complicated shapes. Dispersion curve undulations are interpreted as period-dependent apparent velocity anomalies caused both by different backazimuths of surface wave propagation and by surface wave mode coupling. An appropriate backazimuth of propagation is found for each period, and the dispersion curves are corrected for this true propagation direction. Both the curves for the long and short profiles are inverted for a 1D shear wave velocity model of the crust. Subsurface shear wave velocities are found to be around 2.9 km/s for all four studied sub-profiles. Two of the profiles crossing the older Moldanubian and Teplá-Barrandian units are characterized by higher velocities of 3.8 km/s in the upper crust while for the Saxothuringian unit we find the velocity slightly lower, around 3.6 km/s at the same depths. We obtain an indication of a shear wave low velocity zone above Moho in the Moldanubian and Teplá-Barrandian units. The area of the Eger Rift (Teplá-Barrandian-Saxothuringian unit contact) is significantly different from all other three units. Low upper crust velocities suggest sedimentary and volcanic filling of the rift as well as fluid activity causing the earthquake swarms. Higher velocities in the lower crust together with weak or even missing Moho implies the upper mantle updoming.

Kolínský, Petr; Málek, Ji?í; Brokešová, Johana

2011-01-01

30

Icequake sources location on Triftgletscher (Switzerland) using different velocity models.

NASA Astrophysics Data System (ADS)

In the last 15 years Triftgletscher (Bernese Alps, Switzerland) has substantially retreated and a proglacial lake has been formed in the glacier forefield. Because of the glacier retreat, especially the thinning of the lower flat tongue, the stability of the steep section behind it is affected. As a consequence, the likelihood of large ice avalanches with several millions cubic meters releasing from this dangerous area and reaching the new formed lake will increase. In order to improve the understanding of the mechanisms leading to such instabilities, 8 seismometers were installed in the ice right above the unstable part and a continuous recording of the local seismic activity was carried out from 16th July to 4th August 2010. Considering a set of 214 icequakes, we performed a location of the seismic sources using an homogeneous velocity model where only the ice is considered, a two layers (ice+rock) 1D model, and finally a 3D velocity model including both ice and bedrock precise topographies. The velocity models are implemented in the software NonLinLoc. Results showed surface, shallow and deep icequakes and could precisely describe the associated uncertainties. We discussed the sources locations found and compared the results obtained with the different velocity models. We also analyzed the findings with the help of both surface motion and water pressure measurements and tried to link the icequakes locations to the glacier dynamics.

Dalban Canassy, P.; Maurer, H.; Husen, S.

2012-04-01

31

Multivalued velocity field model of turbulence

The considered study is based on new theoretical concepts regarding a post-instability model of a fluid discussed by Zak (1980). The model permits the completion of the governing equations of turbulence by introducing multivalued fields of velocities. Attention is given to the mechanism of energy dissipation, the characteristic wave propagation, a simplified model, the formation of turbulence around stagnation points,

M. Zak

1981-01-01

32

Velocity-jump models with crowding effects

NASA Astrophysics Data System (ADS)

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.

Treloar, Katrina K.; Simpson, Matthew J.; McCue, Scott W.

2011-12-01

33

2+1-D Insoluble Surfactant Model for a Vertical Draining Free Film

NASA Astrophysics Data System (ADS)

A 2+1-D mathematical model is constructed to study the evolution of a vertically-oriented thin liquid free film draining under gravity when there is an insoluble surfactant with finite surface viscosity on its free surface. Lubrication theory for this free film results in four coupled nonlinear partial differential equations (PDEs) describing the time-evolution of the free surface shape, the surface velocities and the surfactant transport at leading order. The draining film is assumed to terminate on a 1-D static meniscus. Numerical experiments are performed to understand the stability of the system to perturbations across the film. The limit of large surface viscosities recover the tangentially-immobile film and is also found to have a stabilizing influence on transverse perturbations due to their energy dissipating effect. An instability is seen in the mobile film case; this is caused by a competition between gravity and the Marangoni effect. The instability is closely related to that calculated by Miller and coworkers in nonaxisymmetric film drainage in a ring. This work is partially supported by the NSF and Dow Corning.

Naire, S.; Braun, R. J.; Snow, S. A.

2000-11-01

34

1D numerical model of muddy subaqueous and subaerial debris flows

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.

Imran, J.; Parker, G.; Locat, J.; Lee, H.

2001-01-01

35

Servo Motor Position and Velocity Control Model

NSDL National Science Digital Library

The Servo Motor Position and Velocity Control Model simulates the use of a proportional-integral-derivative (PID) controller to run a DC motor. The motor is modeled as a first order system and the simulation allows the user to control either the position of the motor or its velocity. This EJS simulation is based on a real system running at the Spanish Open University for Distance Education (UNED).Â The real DC motor is used as a remote laboratory for learning purposes and a different application created with EJS (visually identical to this simulation) serves as graphical user interface to operate the remote laboratory.

De La Torre, Luis; Oyarzun, Hector V.

2014-03-18

36

Velocity model of the shallow lunar crust

NASA Technical Reports Server (NTRS)

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.

Gangi, A. F.

1980-01-01

37

Models of high velocity impact phenomena

Models of craters formed by impacts at velocities of up to 27 km/sec have been computed using the Smooth Particle Hydrodynamics, MESA, EPIC and CALE codes. These modeling efforts will be compared to data obtained from the Hypervelocity Microparticle Impact project at Los Alamos using the van de Graaff accelerator. This work aids in understanding the fine features and scaling laws found in the experimental results.

Wingate, C.A.; Stellingwerf, R.F.; Davidson, R.F.; Burkett, M.W.

1992-09-01

38

Quasi 1D Modeling of Mixed Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

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.

Kopasakis, George; Connolly, Joseph W.; Paxson, Daniel E.; Woolwine, Kyle J.

2012-01-01

39

On a 2D ‘zoom’ for the 1D shallow water model: Coupling and data assimilation

In the context of river hydraulics we elaborate the idea of a ‘zoom’ model locally superposed on an open-channel network global model. The zoom model (2D shallow water equations) describes additional physical phenomena, which are not represented by the global model (1D shallow water equations with storage areas). Both models are coupled using the optimal control approach when the zoom

I. Yu. Gejadze; J. Monnier

2007-01-01

40

Coupled Drives Tension and Velocity Control Model

NSDL National Science Digital Library

The Coupled Drives Tension and Velocity Control Model simulates the use of a proportional-integral-derivative (PID) controller to he tension and the angular velocity of the pulley in a coupled drive system. This system consist in two drive motors and a pulley which are connected through elastic belts. The jockey pulley is mounted on an arm, that is supported by a spring whose elongation is an indirect measure of the tension in the drive belt. The motors torque can be controlled either manually or with PID, while the motor movement affect the tension and velocity in the pulley. The velocity can be obtained immediately and using the jockey pulley measurements (angle or position) we obtain the tension. This EJS simulation is based on a real system running at the Spanish Open University for Distance Education (UNED).Â The real system is used as a remote laboratory for learning purposes and a different application created with EJS (visually identical to this simulation) serves as graphical user interface to operate the remote laboratory.

Saenz, Jacobo; De La Torre, Luis

2014-04-15

41

Superposition of local zoom models and simultaneous calibration for 1D-2D shallow

Superposition of local zoom models and simultaneous calibration for 1D-2D shallow water flows J: Shallow Water equations, Saint-Venant equation, coupling, zoom model, superposition, optimal control, data Shallow Water equa- tions with storage areas (also called 1.5D model) since 2D models cannot be solved

Boyer, Edmond

42

(2+1)d Thirring model at quantum criticality Lukas Janssen, Holger Gies

at quantum criticality 23/03/2012 6 / 17 #12;(2+1)d fermions with maximal symmetry Dirac equation for Nf| described by relativistic massless Dirac fermions! SB - Lukas Janssen (FSU Jena) (2+1)d Thirring model fermions: S = d3 x ÂŻa iÂµÂµa , a = 1, . . . , Nf, Âµ = 1, 2, 3 Dirac matrices Âµ fulfill Clifford algebra: {Âµ

Rossak, Wilhelm R.

43

Strong solutions for a 1D viscous bilayer Shallow Water model

Strong solutions for a 1D viscous bilayer Shallow Water model Jean De Dieu ZabsonrÂ´e , Carine Lucas , Adama Ouedraogo Abstract In this paper, we consider a viscous bilayer shallow water model. Keywords. Strong solutions, shallow water, viscous models, bilayer, stabil- ity. AMS classification: 35Q30

Paris-Sud XI, UniversitĂ© de

44

Modelling turbulent vertical mixing sensitivity using a 1-D version of NEMO

NASA Astrophysics Data System (ADS)

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.

Reffray, G.; Bourdalle-Badie, R.; Calone, C.

2015-01-01

45

Locating earthquakes in west Texas oil fields using 3-D anisotropic velocity models

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.

Hua, Fa; Doser, D.; Baker, M. (Univ. of Texas, El Paso, TX (United States). Dept. of Geological Sciences)

1993-02-01

46

DATA ASSIMILATION IN A COMBINED 1D-2D FLOOD MODEL USING THE ENSEMBLE KALMAN FILTER

The combined 1D-2D numerical flood modelling system MIKE FLOOD is considered in a data assimilation setting. Data assimilation facilities have been implemented in MIKE FLOOD for assimilation of water level measurements. The data assimilation system is based on the ensemble Kalman filter methodology. In the ensemble Kalman Filter method the probability density of the model state is represented by an

JOHAN N. HARTNACK; HENRIK MADSEN; JACOB V. T. SŘRENSEN

47

Verification of 1D numerical model for heat conduction in human tissue by means of thermography

The paper presents the results of simulation of the heat transport in the human tissue by means of 1D numerical model and experimentally obtained data. The model is based on the control volume numerical method with the skin temperature and heat losses to the surrounding as the boundary conditions. The thermodynamical properties of the tissue were taken from the relevant

I. Boras; S. Švai?

48

3D Versus 1D Radiative Transfer Modeling of Planetary Nebulae

NASA Astrophysics Data System (ADS)

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.

Pantoja, Blake M.; Ladjal, Djazia

2015-01-01

49

NASA Astrophysics Data System (ADS)

It is well-known that meander bends impose local losses of energy to the flow in rivers. These local losses should be added together with friction loss to get the total loss of energy. In this work, we strive to develop a framework that considers the effect of bends in meandering rivers for one-dimensional (1-D) homogenous equations of flow. Our objective is to develop a simple, yet physically sound, and efficient model for carrying out engineering computations of flow through meander bends. We consider several approaches for calculating 1-D hydraulic properties of meandering rivers such as friction factor and Manning coefficient. The method of Kasper et al. (2005), which is based on channel top width, aspect ratio and radius of curvature, is adopted for further calculations. In this method, a correction is implemented in terms of local energy loss, due to helical motion and secondary currents of fluid particles driven by centrifugal force, in meanders. To validate the model, several test cases are simulated and the computed results are compared with the reported data in the literature in terms of water surface elevation, shear velocity, etc. For all cases the computed results are in reasonable agreement with the experimental data. 3-D RANS turbulent flow simulations are also carried out, using the method of Kang et al. (Adv. In Water Res., vol. 34, 2011), for different geometrical parameters of Kinoshita Rivers to determine the spatial distribution of shear stress on river bed and banks, which is the key factor in scour/deposition patterns. The 3-D solutions are then cross-sectionally averaged and compared with the respective solutions from the 1-D model. The comparisons show that the improved 1D model, which incorporates the effect of local bend loss, captures key flow parameters with reasonable accuracy. Our results also underscore the range of validity and limitations of 1D models for meander bend simulations. This work was supported by NSF Grants (as part of the National Center for Earth-Surface Dynamics). Computational resources were provided by the University of Minnesota Supercomputing Institute.

Haji Mohammadi, M.; Kang, S.; Sotiropoulos, F.

2011-12-01

50

Heat-transfer and solidification model of continuous slab casting: CON1D

A simple, but comprehensive model of heat transfer and solidification of the continuous casting of steel slabs is described,\\u000a including phenomena in the mold and spray regions. The model includes a one-dimensional (1-D) transient finite-difference\\u000a calculation of heat conduction within the solidifying steel shell coupled with two-dimensional (2-D) steady-state heat conduction\\u000a within the mold wall. The model features a detailed

Ya Meng; Brian G. Thomas

2003-01-01

51

Decorrelation estimates for a 1D tight binding model in the localized regime

In this article, we prove decorrelation estimates for the eigenvalues of a 1D discrete tight binding model near two distinct energies in the localized regime. Consequently, with an arbitrary, fixed number n, the asymptotic independence for local level statistics near n distinct energies is obtained.

Trinh Tuan Phong

2012-12-17

52

Ensemble Kalman Filter Data Assimilation in a 1D Numerical Model Used for Fog Forecasting

Ensemble Kalman Filter Data Assimilation in a 1D Numerical Model Used for Fog Forecasting SAMUEL RE significant. This led to the implementation of an ensemble Kalman filter (EnKF) within COBEL-ISBA. The new by using an ensemble Kalman filter (EnKF; Evensen 1994, 2003). Theoreti- cally, ensemble filters

Ribes, AurĂ©lien

53

Minimal representations of supersymmetry and 1D N-Extended {sigma} models

We discuss the minimal representations of the 1D N-Extended Supersymmetry algebra (the Z{sub 2}-graded symmetry algebra of the Supersymmetric Quantum Mechanics) linearly realized on a finite number of fields depending on a real parameter t, the time. Their knowledge allows to construct onedimensional sigma-models with extended off-shell supersymmetries without using superfields.

Toppan, F., E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisa Fisicas (Brazil)

2010-03-15

54

Velocity Structure Determination Through Seismic Waveform Modeling and Time Deviations

NASA Astrophysics Data System (ADS)

Through the use of seismic waveforms recorded by TriNet, a dataset of earthquake focal mechanisms and deviations (time shifts) relative to a standard model facilitates the investigation of the crust and uppermost mantle of southern California. The CAP method of focal mechanism determination, in use by TriNet on a routine basis, provides time shifts for surface waves and Pnl arrivals independently relative to the reference model. These shifts serve as initial data for calibration of local and regional seismic paths. Time shifts from the CAP method are derived by splitting the Pnl section of the waveform, the first arriving Pn to just before the arrival of the S wave, from the much slower surface waves then cross-correlating the data with synthetic waveforms computed from a standard model. Surface waves interact with the entire crust, but the upper crust causes the greatest effect. Whereas, Pnl arrivals sample the deeper crust, upper mantle, and source region. This natural division separates the upper from lower crust for regional calibration and structural modeling and allows 3-D velocity maps to be created using the resulting time shifts. Further examination of Pnl and other arrivals which interact with the Moho illuminate the complex nature of this boundary. Initial attempts at using the first 10 seconds of the Pnl section to determine upper most mantle structure have proven insightful. Two large earthquakes north of southern California in Nevada and Mammoth Lakes, CA allow the creation of record sections from 200 to 600 km. As the paths swing from east to west across southern California, simple 1-D models turn into complex structure, dramatically changing the waveform character. Using finite difference models to explain the structure, we determine that a low velocity zone is present at the base of the crust and extends to 100 km in depth. Velocity variations of 5 percent of the mantle in combination with steeply sloping edges produces complex waveform variations. Characteristics of this complex propagation appear from the southern Sierra Nevada Mountains, in the west, to Death Valley in the east. The structure does not cross the Garlock fault to the south, but we are unsure of the structures northern extent.

Savage, B.; Zhu, L.; Tan, Y.; Helmberger, D. V.

2001-12-01

55

Incremental “model-build-test” validation exercise for a 1-D biomedical ultrasonic imaging array

Quantitative validation is critical to the effective utilization of large-scale modeling in advanced biomedical ultrasonic imaging applications. This work describes an incremental “model-build-test” validation exercise centered around a nonproprietary, 5 MHz, 1D linear array design. The step-by-step sequence reported here includes piezoceramic slivers, slivers with matching and slivers with both backing and matching. Furthermore, prior to the fabrication process, all

D. J. Powell; G. L. Wojcik; C. S. Desilets; T. R. Gururaja; K. Guggenberger; S. Sherrit; B. K. Mukherjee

1997-01-01

56

Finite Time Blow Up for a 1D Model of 2D Boussinesq System

NASA Astrophysics Data System (ADS)

The 2D conservative Boussinesq system describes inviscid, incompressible, buoyant fluid flow in a gravity field. The possibility of finite time blow up for solutions of this system is a classical problem of mathematical hydrodynamics. We consider a 1D model of the 2D Boussinesq system motivated by a particular finite time blow up scenario. We prove that finite time blow up is possible for the solutions to the model system.

Choi, Kyudong; Kiselev, Alexander; Yao, Yao

2014-08-01

57

Behavioral Responses in Animal Model of Congenital Muscular Dystrophy 1D.

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

Comim, Clarissa M; Schactae, Aryadnne L; Soares, Jaime A; Ventura, Letícia; Freiberger, Viviane; Mina, Francielle; Dominguini, Diogo; Vainzof, Mariz; Quevedo, Joăo

2014-12-01

58

Implementation and validation of a 1D fluid model for collapsible channels.

A 1D fluid model is implemented for the purpose of fluid-structure interaction (FSI) simulations in complex and completely collapsible geometries, particularly targeting the case of obstructive sleep apnea (OSA). The fluid mechanics are solved separately from any solid mechanics, making possible the use of a highly complex and/or black-box solver for the solid mechanics. The fluid model is temporally discretized with a second-order scheme and spatially discretized with an asymmetrical fourth-order scheme that is robust in highly uneven geometries. A completely collapsing and reopening geometry is handled smoothly using a modified area function. The numerical implementation is tested with two driven-geometry cases: (1) an inviscid analytical solution and (2) a completely closing geometry with viscous flow. Three-dimensional fluid simulations in static geometries are performed to examine the assumptions of the 1D model, and with a well-defined pressure-recovery constant the 1D model agrees well with 3D models. The model is very fast computationally, is robust, and is recommended for OSA simulations where the bulk flow pressure is primarily of interest. PMID:24008973

Anderson, Peter; Fels, Sidney; Green, Sheldon

2013-11-01

59

NASA Astrophysics Data System (ADS)

- Seismic event locations based on regional 1-D velocity-depth sections can have bias errors caused by travel-time variations within different tectonic provinces and due to ray-paths crossing boundaries between tectonic provinces with different crustal and upper mantle velocity structures. Seismic event locations based on 3-D velocity models have the potential to overcome these limitations. This paper summarizes preliminary results for calibration of IMS for North America using 3-D velocity model. A 3-D modeling software was used to compute Source-Station Specific Corrections (SSSCs(3-D)) for Pn travel times utilizing 3-D crustal and upper mantle velocity model for the region. This research was performed within the framework of the United States/Russian Federation Joint Program of Seismic Calibration of the International Monitoring System (IMS) in Northern Eurasia and North America.An initial 3-D velocity model for North America was derived by combining and interpolating 1-D velocity-depth sections for different tectonic units. In areas where no information on 1-D velocity-depth sections was available, tectonic regionalization was used to extrapolate or interpolate. A Moho depth map was integrated. This approach combines the information obtained from refraction profiles with information derived from local and regional network data. The initial 3-D velocity model was tested against maps of Pn travel-time residuals for eight calibration explosions; corrections to the 3-D model were made to fit the observed residuals. Our goal was to find a 3-D crustal and upper mantle velocity model capable predicting Pn travel times with an accuracy of 1.0-1.5 seconds (r.m.s.).The 3-D velocity model for North America that gave the best fit to the observed travel times, was used to produce maps of SSSCs(3-D) for seismic stations. The computed SSSCs(3-D) vary approximately from +5 seconds to -5 seconds for the western USA and the Pre-Cambrian platform, respectively. These SSSCs(3-D) along with estimated modeling and measurement errors were used to relocate, using regional data, an independent set of large chemical explosions (with known locations and origin times) detonated within various tectonic provinces of North America. Utilization of the 3-D velocity model through application of the computed SSSCs(3-D) resulted in a substantial improvement in seismic event location accuracy and in a significant decrease of error ellipse area for all events analyzed in comparison both with locations based on the IASPEI91 travel times and locations based on 1-D regional velocity models.

Ryaboy, V.; Baumgardt, D. R.; Firbas, P.; Dainty, A. M.

60

Modeling velocity dispersion In Gypsy site, Oklahoma

Discrepancies in interval velocities estimated from vertical well measurements made with different source central frequencies at Gypsy site could be primarily explained in terms of intrinsic attenuation. Four intervals ...

Alsaadan, Sami Ibrahim

2010-01-01

61

Evidence for BCS Diquark Condensation in the 3+1d Lattice NJL Model

We present results of numerical simulations of the 3+1d Nambu - Jona-Lasinio model with a non-zero baryon chemical potential mu, with particular emphasis on the superfluid diquark condensate and associated susceptibilities. The results, when extrapolated to the zero diquark source limit, are consistent with the existence of a non-zero BCS condensate at high baryon density. The nature of the infinite volume and zero temperature limits are discussed.

Simon Hands; David N. Walters

2002-09-19

62

Cenozoic ice volume and temperature simulations with a 1-D ice-sheet model

Ice volume and temperature for the past 35 Million years is investigated with a 1-D ice-sheet model, simulating ice-sheets on both hemispheres. The simulations include two continental Northern Hemisphere (NH) ice-sheets representative for glaciation on the two major continents, i.e. Eurasia (EAZ) and North America (NAM). Antarctic glaciation is simulated with two separate ice-sheets, respectively for West and East Antarctica.

B. de Boer; R. Bintanja; L. J. Lourens; E. Tuenter

2009-01-01

63

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...

64

P, S wave velocity model of the crust and upper most mantle of Albania region

NASA Astrophysics Data System (ADS)

This paper describes the one-dimensional (1D) velocity model computed by VELEST in the SEISAN seismic analysis system, inverting re-picked P-wave and S-wave arrival times recorded during 2002-2006 by the Albanian, Montenegro, Thessalonica and Macedonia seismic networks. The re-picked data yield P-wave and S-wave velocities proved to be more suitable compared to bulletin data for this detailed inversion study. Seismic phases recorded by the Albania seismic network and integrated with data from the Montenegro, Thessalonica and Macedonia networks are used to prepare the Albanian seismic bulletin. Earthquake hypocenters from the Albanian bulletins have also location errors that are negligible for civil protection purposes, large scale seismotectonic analyses and more accurate hypocentral determinations which are necessary for detailed seismotectonic and geodynamic studies. It was noted that the smoothness of the velocity variation increased with depth. A velocity of 5.5 km/s was calculated for the upper crust, 6.1 km/s was calculated for the middle crust and 6.9 km/s was computed for the lower crust. P wave velocity was 7.85 km/s at depth of 50 km and for the upper mantle it is 8.28 km/s. Using the improved velocity model, the earthquakes which occurred in Albania in the past 5 years were able to be relocated, achieving constrained hypocentral determinations for events in Albania. The interpretation of the 1 D velocity models infers interesting features of the deep structure of Albania. These results represent an important step towards more detailed seismotectonic analyses.

Ormeni, Rrapo

2011-01-01

65

1D-3D hybrid modeling—from multi-compartment models to full resolution models in space and time

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

Grein, Stephan; Stepniewski, Martin; Reiter, Sebastian; Knodel, Markus M.; Queisser, Gillian

2014-01-01

66

Velocity autocorrelation functions in model liquid metals

NASA Technical Reports Server (NTRS)

Starting from interatomic potentials and static radial distribution functions, a self-consistent iteration scheme has been used to calculate velocity autocorrelation functions in liquid metals. The interatomic forces are treated directly. The calculation bypasses the details of the many-body dynamics and it is not necessary to introduce any additional parameters. Several simplifications may be used without introducing appreciable deviations. The results are in good agreement with computer experiments on liquid sodium at 383 K, suggesting that the velocity autocorrelation function may be a simpler quantity than previously supposed.

Tsang, T.; Maclin, A. P.

1975-01-01

67

Modeling of the diffraction pattern of 1D-disordered silicon carbide

A method for calculating the diffraction pattern of a 1D-disordered crystal structure is considered by the example of silicon carbide. One-dimensional disordering is described using a cell setting the mutual position of all close-packed crystal layers. Two models of structure disordering during the polytypic transformation of the silicon carbide cubic modification into hexagonal are discussed. The results of the calculation of the diffraction spectrum in different stages of polytypic transformation are reported. It is shown that 1D disordering leads to the formation of a set of weak diffraction reflections. The experimentally observed changes in the diffraction pattern can be interpreted within the hypothesis on crystal structure disordering through displacement of adjacent close-packed layers.

Popenko, V. A., E-mail: pvapds@mail.ru [Research Industrial Association Luch (Russian Federation)

2008-09-15

68

Verification and comparison of four numerical schemes for a 1D viscoelastic blood flow model.

A reliable and fast numerical scheme is crucial for the 1D simulation of blood flow in compliant vessels. In this paper, a 1D blood flow model is incorporated with a Kelvin-Voigt viscoelastic arterial wall. This leads to a nonlinear hyperbolic-parabolic system, which is then solved with four numerical schemes, namely: MacCormack, Taylor-Galerkin, monotonic upwind scheme for conservation law and local discontinuous Galerkin. The numerical schemes are tested on a single vessel, a simple bifurcation and a network with 55 arteries. The numerical solutions are checked favorably against analytical, semi-analytical solutions or clinical observations. Among the numerical schemes, comparisons are made in four important aspects: accuracy, ability to capture shock-like phenomena, computational speed and implementation complexity. The suitable conditions for the application of each scheme are discussed. PMID:25145651

Wang, Xiaofei; Fullana, Jose-Maria; Lagrée, Pierre-Yves

2015-11-01

69

Optimisation of A 1d-ecosystem Model To Observations In The North Atlantic Ocean

NASA Astrophysics Data System (ADS)

An optimisation experiment is performed with a vertically resolved, nitrogen based ecosystem model, comprising four state variables (1D-NPZD model): dissolved inor- ganic nitrogen (N), phytoplankton (P), herbivorous zooplankton (Z) and detritus (D). Parameter values of the NPZD-model are optimised while regarding observational data from three locations in the North Atlantic simultaneously: Bermuda Atlantic Time-series Study (BATS), data of the North Atlantic Bloom Experiment (NABE) and observations from Ocean Weather Ship-India (OWS-INDIA). The simultaneous opti- misation yields a best parameter set which can be utilized for basin wide simulations in coupled physical-biological (general circulation) models of the North Atlantic. After optimisation of the 1D-NPZD model, systematic discrepancies between 14C-fixation rates and modelled primary production are emphasized. Using the optimal parame- ter estimates for coupled 3D-simulations, the biogeochemical fluxes show substantial differences in contrast to previous model results. For instance, rapid recycling of or- ganic matter enhances primary production rates. This becomes most evident within the oligotrophic regions of the subtropical gyre.

Schartau, M.; Oschlies, A.

70

Testing a 1-D Analytical Salt Intrusion Model and the Predictive Equation in Malaysian Estuaries

NASA Astrophysics Data System (ADS)

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

Gisen, Jacqueline Isabella; Savenije, Hubert H. G.

2013-04-01

71

Prediction of car cabin environment by means of 1D and 3D cabin model

NASA Astrophysics Data System (ADS)

Thermal comfort and also reduction of energy requirements of air-conditioning system in vehicle cabins are currently very intensively investigated and up-to-date issues. The article deals with two approaches of modelling of car cabin environment; the first model was created in simulation language Modelica (typical 1D approach without cabin geometry) and the second one was created in specialized software Theseus-FE (3D approach with cabin geometry). Performance and capabilities of this tools are demonstrated on the example of the car cabin and the results from simulations are compared with the results from the real car cabin climate chamber measurements.

Fišer, J.; Pokorný, J.; Jícha, M.

2012-04-01

72

Classical one-dimensional (1D) models of automotive catalysts are effective in designing catalyst systems that meet current emission standards. These models use various assumptions in order to simplify the mathematical ...

Loya, Sudarshan Kedarnath

2011-12-31

73

Resistivity structure of Sumatran Fault (Aceh segment) derived from 1-D magnetotelluric modeling

NASA Astrophysics Data System (ADS)

Sumatran Fault Zone is the most active fault in Indonesia as a result of strike-slip component of Indo-Australian oblique convergence. With the length of 1900 km, Sumatran fault was divided into 20 segments starting from the southernmost Sumatra Island having small slip rate and increasing to the north end of Sumatra Island. There are several geophysical methods to analyze fault structure depending on physical parameter used in these methods, such as seismology, geodesy and electromagnetic. Magnetotelluric method which is one of geophysical methods has been widely used in mapping and sounding resistivity distribution because it does not only has the ability for detecting contras resistivity but also has a penetration range up to hundreds of kilometers. Magnetotelluric survey was carried out in Aceh region with the 12 total sites crossing Sumatran Fault on Aceh and Seulimeum segments. Two components of electric and magnetic fields were recorded during 10 hours in average with the frequency range from 320 Hz to 0,01 Hz. Analysis of the pseudosection of phase and apparent resistivity exhibit vertical low phase flanked on the west and east by high phase describing the existence of resistivity contras in this region. Having rotated the data to N45°E direction, interpretation of the result has been performed using three different methods of 1D MT modeling i.e. Bostick inversion, 1D MT inversion of TM data, and 1D MT inversion of the impedance determinant. By comparison, we concluded that the use of TM data only and the impedance determinant in 1D inversion yield the more reliable resistivity structure of the fault compare to other methods. Based on this result, it has been shown clearly that Sumatra Fault is characterized by vertical contras resistivity indicating the existence of Aceh and Seulimeum faults which has a good agreement with the geological data.

Nurhasan, Sutarno, D.; Bachtiar, H.; Sugiyanto, D.; Ogawa, Y.; Kimata, F.; Fitriani, D.

2012-06-01

74

Optimal modeling of 1D azimuth correlations in the context of Bayesian inference

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 2D angular correlations onto 1D azimuth from three centrality classes of 200 GeV Au-Au collisions. We consider several data models typical of current model choices, including Fourier seri...

De Kock, Michiel B; Trainor, Thomas A

2015-01-01

75

Using overlapping sonobuoy data from the Ross Sea to construct a 2D deep crustal velocity model

NASA Astrophysics Data System (ADS)

Sonobuoys provide an alternative to using long streamers while conducting multi-channel seismic (MCS) studies, in order to provide deeper velocity control. We present analysis and modeling techniques for interpreting the sonobuoy data and illustrate the method with ten overlapping sonobuoys collected in the Ross Sea, offshore from Antarctica. We demonstrate the importance of using the MCS data to correct for ocean currents and changes in ship navigation, which is required before using standard methods for obtaining a 1D velocity profile from each sonobuoy. We verify our 1D velocity models using acoustic finite-difference (FD) modeling and by performing depth migration on the data, and demonstrate the usefulness of FD modeling for tying interval velocities to the shallow crust imaged using MCS data. Finally, we show how overlapping sonobuoys along an MCS line can be used to construct a 2D velocity model of the crust. The velocity model reveals a thin crust (5.5 ± 0.4 km) at the boundary between the Adare and Northern Basins, and implies that the crustal structure of the Northern Basin may be more similar to that of the oceanic crust in the Adare Basin than to the stretched continental crust further south in the Ross Sea.

Selvans, M. M.; Clayton, R. W.; Stock, J. M.; Granot, R.

2012-03-01

76

Stochastic patterns in a 1D Rock-Paper-Scissors model with mutation

NASA Astrophysics Data System (ADS)

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.

Cianci, Claudia; Carletti, Timoteo

2014-09-01

77

Tuning a physically-based model of the air-sea gas transfer velocity

NASA Astrophysics Data System (ADS)

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.

Jeffery, C. D.; Robinson, I. S.; Woolf, D. K.

78

High Velocity Rain: The Terminal Velocity of Model of Galactic Infall

A model is proposed for determining the distances to falling interstellar clouds in the galactic halo by measuring the cloud velocity and column density and assuming a model for the vertical density distribution of the Galactic interstellar medium. It is shown that falling clouds with $N(H I) terminal velocity which increases with increasing height above the Galactic plane. This terminal velocity model correctly predicts the distance to high velocity cloud Complex M and several other interstellar structures of previously determined distance. It is demonstrated how interstellar absorption spectra alone may be used to predict the distances of the clouds producing the absorption. If the distances to the clouds are already known, we demonstrate how the model may be used to determine the vertical density structure of the ISM. The derived density distribution is consistent with the expected density distribution of the warm ionized medium, characterized by Reynolds. There is also evidence that for $z >\\sim 0.4 kpc$ one or more of the following occurs: (1) the neutral fraction of the cloud decreases to $\\sim 31 \\pm 14%$, (2) the density drops off faster than characterized by Reynolds, or (3) there is a systematic decrease in drag coefficient with increasing z.

Robert A. Benjamin; Laura Danly

1996-12-18

79

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.

Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao

2014-10-01

80

Phenomenological 3D and 1D consistent models for shape-memory alloy materials

NASA Astrophysics Data System (ADS)

The paper deals with the modeling and the development of a numerical procedure for the analysis of shape-memory alloy (SMA) elements in order to predict the main features of SMA devices. A 3D SMA model in the framework of small strain theory is developed starting from the thermo-mechanical model proposed by Souza et al. (Eur J Mech A/Solids 17:789-806, 1998) and modified by Auricchio and Petrini (Int J Numer Methods Eng 55:1255-1284, 2002). The aim of this paper is to propose some more modifications to the original model, to derive its consistent 1D formulation, to clarify the mechanical meaning of the material parameters governing the constitutive model. A robust time integration algorithm is developed in the framework of the finite element method and a new beam finite element is proposed. Some numerical applications and a comparison with experimental data available in literature are carried out in order to assess the ability of the proposed model to describe the SMA behavior.

Evangelista, Veronica; Marfia, Sonia; Sacco, Elio

2009-08-01

81

Application of HYDRUS 1D model for assessment of phenol-soil adsorption dynamics.

Laboratory-scale batch, vertical, and horizontal column experiments were conducted to investigate the attenuative capacity of a fine-grained clayey soil of local origin in the surrounding of a steel plant wastewater discharge site in West Bengal, India, for removal of phenol. Linear, Langmuir, and Freundlich isotherm plots from batch experimental data revealed that Freundlich isotherm model was reasonably fitted (R (2) = 0.94). The breakthrough column experiments were also carried out with different soil bed heights (5, 10, and 15 cm) under uniform flow to study the hydraulic movements of phenol by evaluating time concentration flow behavior using bromide as a tracer. The horizontal migration test was also conducted in the laboratory using adsorptive phenol and nonreactive bromide tracer to explore the movement of solute in a horizontal distance. The hydrodynamic dispersion coefficients (D) in the vertical and horizontal directions in the soil were estimated using nonlinear least-square parameter optimization method in CXTFIT model. In addition, the equilibrium convection dispersion model in HYDRUS 1D was also examined to simulate the fate and transport of phenol in vertical and horizontal directions using Freundlich isotherm constants and estimated hydrodynamic parameters as input in the model. The model efficacy and validation were examined through statistical parameters such as the coefficient of determination (R (2)), root mean square error and design of index (d). PMID:24407784

Pal, Supriya; Mukherjee, Somnath; Ghosh, Sudipta

2014-04-01

82

Exactly solvable 1D lattice model for the Laughlin states on torus geometries

NASA Astrophysics Data System (ADS)

We study the fractional quantum Hall (FQH) states on a thin torus where the 2D continuum system in a magnetic field can be reduced into a 1D lattice model with short-range interaction. We introduce a minimal model with exact ground states in Laughlin series (flling factors of the lowest Landau level ?=1/q).The model has the same degrees of freedom as that of the pseudo-potential for the Laughlin wave function, and it naturally derives general properties of the Laughlin wave function such as the Z2 properties (the FQH effect is limited only odd q for fermions). The obtained exact ground states have high overlaps with the Laughlin states and well describe their properties, the incompressibility and the fractional charge excitations. The physical quantities such as the correlation functions are calculated analytically by using matrix product method. We also compute the entanglement spectrum and show the diamond structure of the FQH states on torus geometries. Thus, our model gives a simple reference model to describe the Laughlin states. (arXiv:1206.3071)

Wang, Zheng-Yuan; Nakamura, Masaaki

2013-03-01

83

We present the atmospheric structure and the fundamental parameters of three red supergiants, increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. We carried out spectro-interferometric observations of 3 RSGs in the near-infrared K-band with the VLTI/AMBER instrument at medium spectral resolution. To comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3-D convection, and new 1-D self-excited pulsation models of RSGs. Our near-infrared flux spectra are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict ...

Arroyo-Torres, B; Chiavassa, A; Scholz, M; Freytag, B; Marcaide, J M; Hauschildt, P H; Wood, P R; Abellan, F J

2015-01-01

84

Finite element modeling and experimental characterization of crosstalk in 1-D CMUT arrays.

Crosstalk is the coupling of energy between the elements of an ultrasonic transducer array. This coupling degrades the performance of transducers in applications such as medical imaging and therapeutics. In this paper, we present an experimental demonstration of guided interface waves in capacitive micromachined ultrasonic transducers (CMUTs). We compare the experimental results to finite element calculations using a commercial package (LS-DYNA) for a 1-D CMUT array operating in the conventional and collapsed modes. An element in the middle of the array was excited with a unipolar voltage pulse, and the displacements were measured using a laser interferometer along the center line of the array elements immersed in soybean oil. We repeated the measurements for an identical CMUT array covered with a 4.5-microm polydimethylsiloxane (PDMS) layer. The main crosstalk mechanism is the dispersive guided modes propagating in the fluid-solid interface. Although the transmitter element had a center frequency of 5.8 MHz with a 130% fractional bandwidth in the conventional operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 2.1 MHz, and had a cut-off frequency of 4 MHz. In the collapsed operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 4.0 MHz, and had a cut-off frequency of 10 MHz. Crosstalk level was lower in the collapsed operation (-39 dB) than in the conventional operation (-24.4 dB). The coverage of the PDMS did not significantly affect the crosstalk level, but reduced the phase velocity for both operation modes. Lamb wave modes, A0 and S0, were also observed with crosstalk levels of -40 dB and -65 dB, respectively. We observed excellent agreement between the finite element and the experimental results. PMID:17328339

Bayram, Baris; Kupnik, Mario; Yaralioglu, Goksen G; Oralkan, Omer; Ergun, Arif Sanli; Lin, Der-Song; Wong, Serena H; Khuri-Yakub, Butrus T

2007-02-01

85

Interactive 1D model for cloud formation and atmospheric chemistry on Mars

NASA Astrophysics Data System (ADS)

Atmospheric water vapor is the main driver for the chemistry in the lower atmosphere of Mars. Its photolysis products control the abundances of species such as ozone which, in turn, is photolyzed by UV photons (? ? 310 nm) penetrating down to the Martian surface. This results in the production of the excited molecular oxygen O2(1) and then in the dayglow emission at 1.27 ?m [1] observable from Earth [2]. The water abundance in the atmosphere of Mars is controlled by its release from the northern permanent cap and subsequent transport over the planet and locally by cloud formation, precipitation and surface exchanges (e.g. frost deposition and adsorption) [3,4]. Moreover the isotopic ratio [HDO]/[H2O] is also controlled by cloud formation and photochemistry [5]. It has also been suggested that water ice clouds may be serving as surfaces for heterogeneous chemistry processes on Mars [6]. The present work focuses on the local scale and intends to investigate in detail the impacts of the water vapor profile shape and of cloud formation on the chemical composition of the Martian atmosphere. To this purpose, we have coupled two 1D atmospheric models: (1) the detailed microphysical cloud model and (2) the photochemistry model described in Refs. [4] and [1], respectively. The resulting coupled 1D model is driven by timedependent temperature profiles and diffusive mixing coefficients from the GEM-Mars 3D global circulation model (GCM) [7]. The model calculates the diurnal cycle of the water vapor profile as well as the formation of ice clouds. In addition, it also computes their impact on the atmospheric chemistry, especially on the O2(1) dayglow. It will be tested against recent groundbased observations of H2O, HDO, and O2(1) dayglow on Mars [2, 8]. In particular, a rapid decrease of the dayglow in the afternoon has recently been observed [2]. We thus aim to understand the origins of the resulting asymmetry in the diurnal cycle of emission from O2(1) and investigate especially the role of ice clouds in this behavior.

Viscardy, S.; Daerden, F.; Neary, L.; Garcia-Munoz, A.; Novak, R.; Villanueva, G.; Mumma, M.

2014-04-01

86

NASA Astrophysics Data System (ADS)

The structure of the Earth's inner core boundary (ICB) is complex. Hemispherical differences and local variations of velocity and attenuation structures, as well as the ICB topography have been reported in previous studies. We are using an automatic waveform modeling method to improve the resolution of the ICB structures. The full waveforms of triplicated PKP phases at distance ranges from 120 to 165 degrees are used to model the lowermost 200 km of the outer core and the uppermost 600km of the inner core. Given a 1D velocity and attenuation model, synthetic seismograms are generated by Generalized Ray Theory. We are also experimenting 2D synthetic methods (WKM, AXISEM, and 2D FD) for 2D models (in the mantle and the inner core). The source time function is determined by observed seismic data. We use neighborhood algorithm to search for a group of models that minimize the misfit between predictions and observations. Tests on synthetic data show the efficiency of this method in resolving detailed velocity and attenuation structures of the ICB simultaneously. We are analyzing seismic record sections at dense arrays along different paths and will report our modeling and inversion results in the meeting.

Jin, J.; Song, X.; Sun, D.; Helmberger, D. V.

2013-12-01

87

1D Transient Model for Frost Heave in PEFCs III. Heat Transfer, Microporous Layer, and Cycling 446-912, Korea A computational model based on a frost heave mechanism has been developed to simulate-5,11-16 To determine the root cause of freeze/thaw dam- age, a frost heave thermal model has been developed

Mench, Matthew M.

88

SCEC CVM-Toolkit (CVM-T) -- High Performance Meshing Tools for SCEC Community Velocity Models

NASA Astrophysics Data System (ADS)

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 SCEC’s 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 Ely’s 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.

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

89

Random Texture Defect Detection Using 1-D Hidden Markov Models Based on Local Binary Patterns

NASA Astrophysics Data System (ADS)

In this paper a novel method for the purpose of random texture defect detection using a collection of 1-D HMMs is presented. The sound textural content of a sample of training texture images is first encoded by a compressed LBP histogram and then the local patterns of the input training textures are learned, in a multiscale framework, through a series of HMMs according to the LBP codes which belong to each bin of this compressed LBP histogram. The hidden states of these HMMs at different scales are used as a texture descriptor that can model the normal behavior of the local texture units inside the training images. The optimal number of these HMMs (models) is determined in an unsupervised manner as a model selection problem. Finally, at the testing stage, the local patterns of the input test image are first predicted by the trained HMMs and a prediction error is calculated for each pixel position in order to obtain a defect map at each scale. The detection results are then merged by an inter-scale post fusion method for novelty detection. The proposed method is tested with a database of grayscale ceramic tile images.

Hadizadeh, Hadi; Baradaran Shokouhi, Shahriar

90

1D Modeling of Catalyzed Monopropellant H2O2 Decomposition in Microchannels

NASA Astrophysics Data System (ADS)

The modeling of the chemical decomposition of hydrogen-peroxide monopropellant flow in a catalytic microchannel is described. This process can be used to provide a micro-propulsion mechanism required for miniaturized satellites (“nanosats”). Based on the largely gaseous nature of the flow and microchannel geometries, a 1D reacting flow model is assumed. The decomposition is modeled by first-order kinetics and a temperature-dependent Arrhenius law; the latter is justified for typical catalysts. Simulations are performed for realistic operating parameters designed to provide thrust levels of 100-500 micro-N. The outcome is a prediction of a critical catalyst chamber length required for complete decomposition; this is shown to depend upon the Damkohler number, Zeldovich number and the non-dimensional heat release rate of the monopropellant. A “thermal detonation” behavior is observed whereby the decomposition process goes to completion instantaneously. Inclusion of heat loss through microchannel walls can significantly increase critical decomposition length and reduce the available energy for the micropropulsion.

Zhou, Xu; Hitt, Darren

2003-11-01

91

A 3-mode, Variable Velocity Jet Model for HH 34

NASA Technical Reports Server (NTRS)

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.

Raga, A.; Noriega-Crespo, A.

1998-01-01

92

Behaviour of ion velocity distributions for a simple collision model

NASA Technical Reports Server (NTRS)

Calculation of the ion velocity distributions for a weakly ionized plasma subjected to crossed electric and magnetic fields. An exact solution to Boltzmann's equation has been obtained by replacing the Boltzmann collision integral with a simple relaxation model. At altitudes above about 150 km, where the ion collision frequency is much less than the ion cyclotron frequency, the ion distribution takes the shape of a torus in velocity space for electric fields greater than 40 mV/m. This shape persists for one to two hours after application of the electric field. At altitudes where the ion collision and cyclotron frequencies are approximately equal (about 120 km), the ion velocity distribution is shaped like a bean for large electric field strengths. This bean-shaped distribution persists throughout the lifetime of ionospheric electric fields. These highly non-Maxwellian ion velocity distributions may have an appreciable affect on the interpretation of ion temperature measurements.

St-Maurice, J.-P.; Schunk, R. W.

1974-01-01

93

1D Tight-Binding Models Render Quantum First Passage Time "Speakable"

NASA Astrophysics Data System (ADS)

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.

Ranjith, V.; Kumar, N.

2014-12-01

94

Modeling Instruction Program: Unit Assessment-Displacement and Velocity

NSDL National Science Digital Library

This page is a comprehensive unit review for high school students on graphing velocity and position. It assesses the student's ability to both create and interpret graphical representations of an object's displacement and velocity over time. Students must be familiar with motion maps and coordinate graphing. This resource is freely downloadable in pdf format. This item is part of a larger collection of resources and pedagogic materials developed by the Modeling Instruction team at Arizona State University to be used with the Modeling method of teaching.

Dukerich, Larry; Jackson, Jane

2008-11-18

95

Deriving snow hardness from density and its application to the 1-D snow cover model SNOWPACK

NASA Astrophysics Data System (ADS)

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

Monti, F.; Schweizer, J.

2012-04-01

96

Embedding a 1D calving ice model into a large-scale 3D ice dynamical model for Greenland.

NASA Astrophysics Data System (ADS)

With a large-scale 3D ice dynamical model a reconstruction of the Greenland ice sheet is carried out over the period 1960-2100 with boundary conditions from the latest Ice2Sea topographic data set and the RACMO regional climate forcing fields. The Ice2Sea and RACMO fields have been remapped with an optimal centered oblique stereographic projection. The spatial resolution of most of the large scale ice sheet models is not enough to resolve the dynamics of narrow deep outlet glaciers. Processes acting at the marine boundary such as calving and submarine melt can not be represented in enough detail. To improve the large-scale ice model, a detailed 1D calving ice model is embedded at the location of an important outlet system. Here we present results for Jakobshavn Isbrć. Both models exchange information with the mapping tool OBLIMAP at as many time steps as required by the user. The coupling can be done at various levels of detail. A first order coupling considers the geometrical adaptation of the ice sheet. A more sophisticated coupling takes in addition the ice fluxes precisely into account. Results are compared with stand-alone 1D flow line results indicating the importance of the coupling process.

Reerink, Thomas; Nick, Faezeh; van de Wal, Roderik

2013-04-01

97

Parameter sensitivities in a 1-D model for DMS and sulphur cycling in the upper ocean

NASA Astrophysics Data System (ADS)

We have developed a marine DMS (dimethylsulfide) module and implemented it in a 1-D coupled atmosphere-ocean-biogeochemical model. In developing the marine sulphur model we have found that several parameters used in the model are not known to even an order of magnitude. Our approach is used to test the model's sensitivity to these parameters. A parameter change of ±25% is applied to test the respective range of changes in the DMS fluxes. The model is run for a 3-year time period as well as for the time period of the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) in July 2002. The simulated seasonal cycle is in agreement with available observations: Near surface DMS concentrations vary from 1.5nmolL-1 in winter to 13.5nmolL-1 in summer. Simulated DMS production is found to be most sensitive to variations of the S:N ratio and the bacterial consumption rate of DMS. Implementing light or UV limited bacterial activity shows a negligible effect in winter and increases DMS concentrations by 0.2- 0.6nmolL-1 in summer. Similarly a yield increase under UV stress increases summer values by 1- 2nmolL-1. The simulated diel cycle in surface DMS concentration is no more than 2.5nmolL-1, even when light-dependent changes in bacterial activity are considered. Simulating the DMS response to iron fertilization with the standard run leads to overestimation during an initial bloom of small phytoplankton. While implementing light-dependent bacterial activity has a minor effect, the implementation of yields that depend on nutrient availability significantly improves the results. The model confirms earlier results showing the importance of including atmospheric DMS concentrations in gas flux calculations when there are high surface concentrations and small atmospheric boundary layer heights. Simulated summer concentrations in the upper layer can be underestimated by 2nmolL-1 or more if the atmospheric concentration is set to zero. Our study shows that inclusion of mechanistic DMS modules in comprehensive climate models requires better knowledge of the variation of key parameters in the marine sulphur cycle. Even though there are still open questions, the model reasonably reproduces the mean annual cycle; and including variable DMS yield improves the simulation of the DMS response to iron fertilization during SERIES.

Steiner, N.; Denman, K.

2008-07-01

98

Evaluation of six fracture models in high velocity perforation

A systematic evaluation of six ductile fracture models is performed to identify the most suitable fracture criterion for high velocity perforation problems. Included in the paper are the Wilkins, the Johnson–Cook, the maximum shear stress, the modified Cockcroft–Latham, the constant fracture strain, and the Bao–Wierzbicki fracture models. These six fracture models are implemented into ABAQUS\\/Explicit by means of a user

X. Teng; T. Wierzbicki

2006-01-01

99

A 3-mode, Variable Velocity Jet Model for HH 34

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. From previously published data on this object, we find evidence for the existence of a 3-mode ejection velocity variability, and then explore the implications of such a variability. From simple, analytic considerations it is possible to show that the longer period modes produce a modulation on the shorter period modes, resulting in the formation of ``trains'' of multiple knots. The knots observed close to the source of HH-34 could correspond to such a structure. Finally, a numerical simulation with the ejection velocity variability deduced from the HH-34 data is computed. This numerical simulation shows a quite remarkable resemblance with the observed properties of the HH-34 jet.

A. Raga; A. Noriega-Crespo

1998-08-25

100

1D and 2D urban dam-break flood modelling in Istanbul, Turkey

NASA Astrophysics Data System (ADS)

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.

Ozdemir, Hasan; Neal, Jeffrey; Bates, Paul; Döker, Fatih

2014-05-01

101

1-D/3-D geologic model of the Western Canada Sedimentary Basin

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.

Higley, D.K.; Henry, M.; Roberts, L.N.R.; Steinshouer, D.W.

2005-01-01

102

Open boundary conditions for the Diffuse Interface Model in 1-D

NASA Astrophysics Data System (ADS)

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.

Desmarais, J. L.; Kuerten, J. G. M.

2014-04-01

103

NASA Astrophysics Data System (ADS)

Modeling of hydrological water transfers in the unsaturated zone of a watershed requires hydraulic characterization of soils. This characterization is commonly described by the hydraulic conductivity curve and the water retention curve which, for the purposes of flux calculations, are approximated by mathematical functions. With traditional methods, assessment of the involved parameters requires considerable amounts of time and resources when a great number of grid sampling points is needed. We present a simple and accurate method to determine the hydraulic conductivity at saturation (Ks) and the normalisation parameter of the water retention curve (alpha) of the van Genuchten functions for the case of 1-D vertical infiltration under a constant pressure head at the soil surface. The method is based on the optimization of cumulative infiltration versus time data using a numerical dimensionless solution of the Richards' equation. Other data requirements are: shape parameters of the retention curve, obtained from textural information, and initial and saturated water contents of the soil. The method is tested for experimental data contrasting two soils: a well graded silt and a structured coarse sand, both having uniform initial water contents and a null pressure heads at the surface. The results show that the parameters Ks and alpha can be accurately predicted but further research is necessary to test different initial and pressure head conditions.

Soria Ugalde, J. M.

2006-12-01

104

Modelling hydrology of a single bioretention system with HYDRUS-1D.

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

Meng, Yingying; Wang, Huixiao; Chen, Jiangang; Zhang, Shuhan

2014-01-01

105

ABSTRACTION OF INFORMATION FROM 2- AND 3-DIMENSIONAL PORFLOW MODELS INTO A 1-D GOLDSIM MODEL - 11404

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.

Taylor, G.; Hiergesell, R.

2010-11-16

106

Finite-Source Inversion for the 2004 Parkfield Earthquake using 3D Velocity Model Green's Functions

NASA Astrophysics Data System (ADS)

We determine finite fault models of the 2004 Parkfield earthquake using 3D Green's functions. Because of the dense station coverage and detailed 3D velocity structure model in this region, this earthquake provides an excellent opportunity to examine how the 3D velocity structure affects the finite fault inverse solutions. Various studies (e.g. Michaels and Eberhart-Phillips, 1991; Thurber et al., 2006) indicate that there is a pronounced velocity contrast across the San Andreas Fault along the Parkfield segment. Also the fault zone at Parkfield is wide as evidenced by mapped surface faults and where surface slip and creep occurred in the 1966 and the 2004 Parkfield earthquakes. For high resolution images of the rupture process"Ait is necessary to include the accurate 3D velocity structure for the finite source inversion. Liu and Aurchuleta (2004) performed finite fault inversions using both 1D and 3D Green's functions for 1989 Loma Prieta earthquake using the same source paramerization and data but different Green's functions and found that the models were quite different. This indicates that the choice of the velocity model significantly affects the waveform modeling at near-fault stations. In this study, we used the P-wave velocity model developed by Thurber et al (2006) to construct the 3D Green's functions. P-wave speeds are converted to S-wave speeds and density using by the empirical relationships of Brocher (2005). Using a finite difference method, E3D (Larsen and Schultz, 1995), we computed the 3D Green's functions numerically by inserting body forces at each station. Using reciprocity, these Green's functions are recombined to represent the ground motion at each station due to the slip on the fault plane. First we modeled the waveforms of small earthquakes to validate the 3D velocity model and the reciprocity of the Green"fs function. In the numerical tests we found that the 3D velocity model predicted the individual phases well at frequencies lower than 0.25 Hz but that the velocity model is fast at stations located very close to the fault. In this near-fault zone the model also underpredicts the amplitudes. This implies the need to include an additional low velocity zone in the fault zone to fit the data. For the finite fault modeling we use the same stations as in our previous study (Kim and Dreger 2008), and compare the results to investigate the effect of 3D Green's functions on kinematic source inversions. References: Brocher, T. M., (2005), Empirical relations between elastic wavespeeds and density in the Earth's crust, Bull. Seism. Soc. Am., 95, No. 6, 2081-2092. Eberhart-Phillips, D., and A.J. Michael, (1993), Three-dimensional velocity structure and seismicity in the Parkfield region, central California, J. Geophys. Res., 98, 15,737-15,758. Kim A., D. S. Dreger (2008), Rupture process of the 2004 Parkfield earthquake from near-fault seismic waveform and geodetic records, J. Geophys. Res., 113, B07308. Thurber, C., H. Zhang, F. Waldhauser, J. Hardebeck, A. Michaels, and D. Eberhart-Phillips (2006), Three- dimensional compressional wavespeed model, earthquake relocations, and focal mechanisms for the Parkfield, California, region, Bull. Seism. Soc. Am., 96, S38-S49. Larsen, S., and C. A. Schultz (1995), ELAS3D: 2D/3D elastic finite-difference wave propagation code, Technical Report No. UCRL-MA-121792, 19pp. Liu, P., and R. J. Archuleta (2004), A new nonlinear finite fault inversion with three-dimensional Green's functions: Application to the 1989 Loma Prieta, California, earthquake, J. Geophys. Res., 109, B02318.

Kim, A.; Dreger, D.; Larsen, S.

2008-12-01

107

NASA Astrophysics Data System (ADS)

In the past several years we have systematically analysed long-period seismograms for the study of large-scale P and S velocity variations in the mantle [J. Ritsema, H.J. van Heijst, and J. H. Woodhouse, Science, 286, 1925--1928, 1999; J. Ritsema and H.J. van Heijst, Geophysical Journal International, submitted, 2001]. This new data set consists of 250,000 travel times and more than 2 million phase velocities. It is several orders of magnitude larger than seismic data sets available two decades ago due to the expansion of digital seismic networks. When combined with data from other research groups (e.g., free-oscillation splitting measurements), it will enable the construction of better constrained reference 1-D and 3-D Earth models. In our presentation we demonstrate that reliable surface-wave phase-velocity and body-wave travel-time measurements can be obtained with automatic procedures by systematic presentation of phase velocity maps and the spatial characteristics of differential travel times. We point out characteristics of the Preliminary Reference Earth model (e.g., 220-km discontinuity, upper mantle P velocity structure) that are inconsistent with our data. Furthermore, we compare our 3-D models of S and P velocity (obtained by joint inversion) with models from other groups to indicate robust features in global seismic models.

Ritsema, J.; van Heijst, H.

2001-05-01

108

Modeling and comparative study of fluid velocities in heterogeneous rocks

NASA Astrophysics Data System (ADS)

Detailed knowledge of the distribution of effective porosity and fluid velocities in heterogeneous rock samples is crucial for understanding and predicting spatially resolved fluid residence times and kinetic reaction rates of fluid-rock interactions. The applicability of conventional MRI techniques to sedimentary rocks is limited by internal magnetic field gradients and short spin relaxation times. The approach developed at the UNB MRI Centre combines the 13-interval Alternating-Pulsed-Gradient Stimulated-Echo (APGSTE) scheme and three-dimensional Single Point Ramped Imaging with T1 Enhancement (SPRITE). These methods were designed to reduce the errors due to effects of background gradients and fast transverse relaxation. SPRITE is largely immune to time-evolution effects resulting from background gradients, paramagnetic impurities and chemical shift. Using these techniques quantitative 3D porosity maps as well as single-phase fluid velocity fields in sandstone core samples were measured. Using a new Magnetic Resonance Imaging technique developed at the MRI Centre at UNB, we created 3D maps of porosity distributions as well as single-phase fluid velocity distributions of sandstone rock samples. Then, we evaluated the applicability of the Kozeny-Carman relationship for modeling measured fluid velocity distributions in sandstones samples showing meso-scale heterogeneities using two different modeling approaches. The MRI maps were used as reference points for the modeling approaches. For the first modeling approach, we applied the Kozeny-Carman relationship to the porosity distributions and computed respective permeability maps, which in turn provided input for a CFD simulation - using the Stanford CFD code GPRS - to compute averaged velocity maps. The latter were then compared to the measured velocity maps. For the second approach, the measured velocity distributions were used as input for inversely computing permeabilities using the GPRS CFD code. The computed permeabilities were then correlated with the ones based on the porosity maps and the Kozeny-Carman relationship. The findings of the comparative modeling study are discussed and its potential impact on the modeling of fluid residence times and kinetic reaction rates of fluid-rock interactions in rocks containing meso-scale heterogeneities are reviewed.

Hingerl, Ferdinand F.; Romanenko, Konstantin; Pini, Ronny; Balcom, Bruce; Benson, Sally

2013-04-01

109

MODIFYING PC1D TO MODEL SPONTANEOUS AND PIEZOELECTRIC POLARIZATION IN III-V NITRIDE SOLAR CELLS

efficiency caused by polarization-induced electric fields at the GaN/InGaN heterojunction. Scope for future and thus, have significant consequence on solar cell design. Polarization in the III-nitrides induce sheetMODIFYING PC1D TO MODEL SPONTANEOUS AND PIEZOELECTRIC POLARIZATION IN III-V NITRIDE SOLAR CELLS M

Honsberg, Christiana

110

Numerical modeling of shallow non-Newtonian flows: Part I. The 1D horizontal dam break problemÂ´e Cassin, BP 7151, 97715 Saint-Denis cedex 09, France October 6, 2012 Abstract Â The dam break problem subject to the horizontal dam break problem. Keywords Â power-law fluid; dam break problem; shallow flows

Paris-Sud XI, UniversitĂ© de

111

The Velocity Model of Chinese Continent Established by GNSS Observations

NASA Astrophysics Data System (ADS)

With the high precision repeated GNSS observations, the Multi-quadric equations interpolation method is used to establish the velocity model of Chinese continent's crustal movement. The valuable present-day horizontal and vertical crustal movement velocity images are obtained. The eastwardly movement trend of Chinese continent is quite evident, and there is a trend of clockwise rolling, from northeast to east, then to southeast. At the same time Chinese continent movement show the difference between east and west. In the west the trend is move towards the north and northeast, while in the east the trend is creep towards south and southeast, with a huge north dextral shear zone. The horizontal movement velocity approximately equals to 30-50mm/a.The background velocity model of China mainland in ITRF97 frame is also computed by GNSS velocity observations. The local background velocity model is extremely consistent with Europe -Asia tectonic plate's Euler direction and the spin rate provide by some global background field model such as NNR-NUVEL1A model, Sillard model and Larson model in the magnitude and the major tendency, with which we can analyze the characteristic of Chinese continent's crustal movement.Chinese continent's absolute shift mainly happens in the southwest area. In Ximalaya and Lhasa block the eastern movement is very apparent, and there is an apparent clockwise rotation in Qiangtang, Chuandian, Dianxi block. In Qiangtan block, it shift toward east, but in Chuandian block, it shift toward southeast, and then it shift southwest in Dianxi block. The magnitude is about 10~25mm/a, and they are quite obvious activity deformation belt, and the absolute movement of other area is not evident, mostly less than 10mm/a.The characteristic of vertical crustal movement in Chinese mainland is qualitative analysed: more than 70% of Chinese mainland are descended and the speed of descend is less than 20mm/a , the Qingzang plateau?Huabei plate(excluding Beijing area) and Yanshan plate are ascended with the speed less than 15mm/a. The holistic vertical crustal movement of West-North and East-South?West-South and East-North areas of China are shown an approximate slanting symmetry state.

Yao, Y.

2009-04-01

112

Comparison between a 1D and a 2D numerical model of an active magnetic regenerative refrigerator

NASA Astrophysics Data System (ADS)

The active magnetic regenerator (AMR) refrigeration system represents an environmentally attractive alternative to vapour-compression refrigeration. This paper compares the results of two numerical AMR models: (1) a 1D finite difference model and (2) a 2D finite element model. Both models simulate a reciprocating AMR and can determine the cyclical steady-state temperature profile of the system as well as performance parameters such as the refrigeration capacity, the work input and the coefficient of performance (COP). The models are used to analyse an AMR with a regenerator made of flat parallel plates of gadolinium operating in the presence of a 1 T magnetic field. The results are used to discuss under which circumstances a 1D model is insufficient and a 2D model is necessary. The results indicate that when the temperature gradients in the AMR perpendicular to the flow are small a 1D model obtains accurate results of overall results such as the refrigeration capacity but that a 2D model is required for a detailed analysis of the phenomena occurring inside the AMR.

Petersen, Thomas Frank; Engelbrecht, Kurt; Bahl, Christian R. H.; Elmegaard, Brian; Pryds, Nini; Smith, Anders

2008-05-01

113

Composite memory variable velocity-stress viscoelastic modelling

NASA Astrophysics Data System (ADS)

The full 3-D viscoelastic wave equations have been reformulated,using the velocity-stress formulation for a curved grid, to include a set of memory variables for each particle velocity component. The earlier standard formulation includes a set of memory variables for each stress component. In 3-D this reduces the number of memory variables by three for each extra relaxation parameter above 1. This reformulation requires transforming the usual first order differential equation for velocity-stress modelling to a second order differential equation which again requires storage of two consecutive time step values of the particle velocities. No memory saving therefore is achieved using just one relaxation mechanism. However, the memory saved by the new formulation increases with increasing number of included relaxation mechanisms, and is around 30 per cent for 5-7 relaxation mechanisms, which is often required for accurate Q modelling. Incidentally, for media of heterogeneous Q , the new formulation is two to three times slower in simulations than the old formulation, so the new formulation should be used in memory critical applications and/or for heterogeneous media with layers/blocks of homogeneous Q , for which also CPU will be saved.

Hestholm, Stig

2002-01-01

114

Modeling of general 1-D periodic leaky-wave antennas in layered media using EIGER.

This paper presents a mixed-potential integral-equation formulation for analyzing 1-D periodic leaky-wave antennas in layered media. The structures are periodic in one dimension and finite in the other two dimensions. The unit cell consists of an arbitrary-shaped metallic/dielectric structure. The formulation has been implemented in the EIGER{trademark} code in order to obtain the real and complex propagation wavenumbers of the bound and leaky modes of such structures. Validation results presented here include a 1-D periodic planar leaky-wave antenna and a fully 3-D waveguide test case.

Wilton, Donald R. (University of Houston); Basilio, Lorena I.; Celepcikay, Ferhat T. (University of Houston); Johnson, William Arthur; Baccarelli, Paolo (Sapienza Universita de Roma); Valerio, Guido (Sapienza Universita de Roma); Paulotto, Simone (University of Houston); Langston, William L.; Jackson, David R. (University of Houston)

2010-09-01

115

Modeling of general 1-D periodic leaky-wave antennas in layered media with EIGER.

This paper presents a mixed-potential integral-equation formulation for analyzing 1-D periodic leaky-wave antennas in layered media. The structures are periodic in one dimension and finite in the other two dimensions. The unit cell consists of an arbitrary-shaped metallic/dielectric structure. The formulation has been implemented in the EIGER{trademark} code in order to obtain the real and complex propagation wavenumbers of the bound and leaky modes of such structures. Validation results presented here include a 1-D periodic planar leaky-wave antenna and a fully 3-D waveguide test case.

Wilton, Donald R.; Basilio, Lorena I.; Celepcikay, F. T. (University of Houston, Houston TX); Johnson, William Arthur; Baccarelli, Paolo (University of Rome); Valerio, G. (University of Rome); Paulotto, Simone (University of Houston, Houston TX); Langston, William L.; Jackson, David R. (University of Houston, Houston TX)

2010-06-01

116

Analytic solutions for seismic travel time and ray path geometry through simple velocity models.

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.

Ballard, Sanford

2007-12-01

117

Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.

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

Ekama, G A; Marais, P

2004-01-01

118

1D Runoff-runon stochastic model in the light of queueing theory : heterogeneity and connectivity

NASA Astrophysics Data System (ADS)

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)*?x , 0) where Qn is the runoff arriving on pixel n of size ?x [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.

Harel, M.-A.; Mouche, E.; Ledoux, E.

2012-04-01

119

The bimolecular reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO was photoinitiated in the (N{sub 2}O){sub 2} dimer at a wavelength of 193 nm and was investigated by three-dimensional (3D) velocity map imaging. State selective 3D momentum vector distributions were monitored and analyzed. For the first time, kinetic energy resolution and stereodynamic information about the reaction under constrained geometry conditions is available. Directly observable NO products exhibit moderate vibrational excitation and are rotationally and translationally cold. Speed and spatial distributions suggest a pronounced backward scattering of the observed products with respect to the direction of motion of the O({sup 1}D) atom. Forward scattered partner products, which are not directly detectable are also translationally cold, but carry very large internal energy as vibration or rotation. The results confirm and extend previous studies on the complex initiated reaction system. The restricted geometry of the van der Waals complex seems to favor an abstraction reaction of the terminal nitrogen atom by the O({sup 1}D) atom, which is in striking contrast to the behavior observed for the unrestricted gas phase reaction under bulk conditions.

Goedecke, Niels; Maul, Christof; Kauczok, Sebastian; Gericke, Karl-Heinz [Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, Braunschweig (Germany); Chichinin, Alexey I. [Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2009-08-07

120

Sleipner CCS site: velocity and attenuation model from seismic tomography

NASA Astrophysics Data System (ADS)

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.

Rossi, G.; Chadwick, R. A.; Williams, G. A.

2012-04-01

121

A new velocity-pressure-compaction model for uncemented sediments

NASA Astrophysics Data System (ADS)

Knowledge of the pressure dependence of rock properties is useful for a wide range of earth science problems, especially related to pore pressure changes caused by fluid injection or withdrawal, as often occurs in groundwater, hydrocarbon and CO2 sequestration reservoirs. A long-standing problem is that theoretical models of velocity-pressure response often do not match laboratory measurements, and alternately, empirical regressions fit to such data do not extrapolate accurately to wider pressure ranges since they have little or no physical basis. Accurate determination of the dry rock frame properties at low effective pressure is a key aspect of the problem, particularly when ultrasonic laboratory measurements are not available in this pressure range. We present a new model to describe the pressure sensitivity of the bulk and shear moduli for uncemented sedimentary rocks. Our model incorporates effects of sedimentary compaction and critical porosity, including a relationship to account for porosity and density change with pressure. The model is tested on laboratory measurements for various rock samples and fits well over a wide range of pressures. The new velocity-pressure model should be useful for improved prediction and interpretation of pressure-dependent rock properties and seismic data.

Saul, M. J.; Lumley, D. E.

2013-05-01

122

Improving sub-salt imaging using 3D basin model derived velocities

The quality of depth imaging is directly related to the accuracy of the underlying velocity model. In most sub-salt settings, lack of angular illumination severely degrades the resolution and accuracy of velocity information derived from the seismic data itself. A standard approach for building a starting velocity model uses more reliable velocity information outboard of salt which is subsequently extrapolated

R. Stephan Petmecky; Martin L. Albertin; Nick Burke

2009-01-01

123

Central United States Velocity Model Version 1: Description and Validation

NASA Astrophysics Data System (ADS)

We describe and test via numerical simulations a velocity model of the Central United States (CUSVM Version 1). Our model covers an area of 650,000 km2 and includes parts of Arkansas, Mississippi, Alabama, Illinois, Missouri, Kentucky and Tennessee. The model represents the compilation of research carried out for decades consisting of seismic refraction and reflection lines, geophysical logs, and inversions of the regional seismic properties. The CUSVM has a higher resolution description around Memphis and St. Louis, two of the largest urban areas in the Central United States. The density, p- and s-wave velocities are synthesized in a stand-alone spatial data base that can be queried to generate the required input for numerical simulations. We calibrate the CUSVM using three earthquakes located N, SW and SE of the zone encompassed by the model to sample different paths of propagation. The selected stations in the comparisons reflect different geological site conditions and cover distances ranging from 50 to 450 km away from the epicenters. The results indicate that both within and outside the Mississippi embayment, the CUSVM satisfactorily reproduces: a) the body wave arrival times and b) the observed regional variations in ground motion amplitude and duration in the frequency range 0-0.75Hz.

Ramirez Guzman, L.; Williams, R. A.; Boyd, O. S.; Hartzell, S.

2009-12-01

124

Pressure and velocity profiles in a static mechanical hemilarynx model.

This study examined pressure and velocity profiles in a hemilarynx mechanical model of phonation. The glottal section had parallel walls and was fabricated from hard plastic. Twelve pressure taps were created in the vocal fold surface and connected to a differential pressure transducer through a pressure switch. The glottal gap was measured with feeler gauges and the uniform glottal duct was verified by use of a laser system. Eight pressure transducers were placed in the flat wall opposite the vocal fold. Hot-wire anemometry was used to obtain velocity profiles upstream and downstream of the glottis. The results indicate that the pressure distribution on the vocal fold surface was consistent with pressure change along a parallel duct, whereas the pressures on the opposite flat wall typically were lower (by 8%-40% of the transglottal pressure just past mid-glottis). The upstream velocity profiles were symmetric regardless of the constriction shape and size. The jet flow downstream of the glottis was turbulent even for laminar upstream conditions. The front of the jet was consistently approximately 1.5 mm from the flat wall for glottal gaps of 0.4, 0.8 and 1.2 mm. The turbulence intensity also remained approximately at the same location of about 4 mm from the flat wall for the two larger gaps. PMID:12509021

Alipour, Fariborz; Scherer, Ronald C

2002-12-01

125

Predicting abnormal pressure from 2-D seismic velocity modeling

Seismic velocities are the only data available, before drilling, on which to base a quantitative, present-day estimate of abnormal pressure. Recent advances in seismic velocity processing have enabled them to obtain, using an in-house approach, an optimized 2-D interval velocity field and consequently to better define the lateral extension of pressure regimes. The methodology, interpretation and quantification of overpressure-related anomalies are supported by case studies, selected in sand-shale dominated Tertiary basins, offshore West Africa. Another advantage of this approach is that it can also account for the presence of reservoir-potential intervals at great depth and thus provide significant insight, from a prospective standpoint, into very poorly explored areas. Although at the outset the 2-D seismic tool legitimately merits being favored, optimization of the final predictive pressure model, prior to drilling, will depend upon the success of its combined use with other concepts and approaches, pertaining to structural geology, sedimentology, rock mechanics and fluid dynamics.

Grauls, D.; Dunand, J.P.; Beaufort, D.

1995-12-01

126

Modeling the exit velocity of a compressed air cannon

NASA Astrophysics Data System (ADS)

The use of compressed air cannons in an undergraduate laboratory provides a way to illustrate the connection between diverse physics concepts, such as conservation of momentum, the work-kinetic energy theorem, gas expansion, air drag, and elementary Newtonian mechanics. However, it is not clear whether the expansion of the gas in the cannon is an adiabatic or an isothermal process. We built an air cannon that utilizes a diaphragm valve to release the pressurized gas and found that neither process accurately predicts the exit velocity of our projectile. We discuss a model based on the flow of air through the valve, which is in much better agreement with our data.

Rohrbach, Z. J.; Buresh, T. R.; Madsen, M. J.

2012-01-01

127

A 1D model for tides waves and fine sediment in short tidal basins—Application to the Wadden Sea

NASA Astrophysics Data System (ADS)

In order to simulate the dynamics of fine sediments in short tidal basins, like the Wadden Sea basins, a 1D cross-sectional averaged model is constructed to simulate tidal flow, depth-limited waves, and fine sediment transport. The key for this 1D model lies in the definition of the geometry (width and depth as function of the streamwise coordinate). The geometry is computed by implementing the water level and flow data, from a 2D flow simulation, and the hypsometric curve in the continuity equation. By means of a finite volume method, the shallow-water equations and sediment transport equations are solved. The bed shear stress consists of the sum of shear stresses by waves and flow, in which the waves are computed with a depth-limited growth equation for wave height and wave frequency. A new formulation for erosion of fines from a sandy bed is proposed in the transport equation for fine sediment. It is shown by comparison with 2D simulations and field measurements that a 1D schematization gives a proper representation of the dynamics in short tidal basins.

van Prooijen, Bram Christiaan; Wang, Zheng Bing

2013-12-01

128

NASA Astrophysics Data System (ADS)

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.

Zhang, MingLiang; Xu, YuanYuan; Hao, ZiNing; Qiao, Yang

2014-04-01

129

Mean velocity and moments of turbulent velocity fluctuations in the wake of a model ship propulsor

NASA Astrophysics Data System (ADS)

Pod drives are modern outboard ship propulsion systems with a motor encapsulated in a watertight pod, whose shaft is connected directly to one or two propellers. The whole unit hangs from the stern of the ship and rotates azimuthally, thus providing thrust and steering without the need of a rudder. Force/momentum and phase-resolved laser Doppler anemometry (LDA) measurements were performed for in line co-rotating and contra-rotating propellers pod drive models. The measurements permitted to characterize these ship propulsion systems in terms of their hydrodynamic characteristics. The torque delivered to the propellers and the thrust of the system were measured for different operation conditions of the propellers. These measurements lead to the hydrodynamic optimization of the ship propulsion system. The parameters under focus revealed the influence of distance between propeller planes, propeller frequency of rotation ratio and type of propellers (co- or contra-rotating) on the overall efficiency of the system. Two of the ship propulsion systems under consideration were chosen, based on their hydrodynamic characteristics, for a detailed study of the swirling wake flow by means of laser Doppler anemometry. A two-component laser Doppler system was employed for the velocity measurements. A light barrier mounted on the axle of the rear propeller motor supplied a TTL signal to mark the beginning of each period, thus providing angle information for the LDA measurements. Measurements were conducted for four axial positions in the slipstream of the pod drive models. The results show that the wake of contra-rotating propeller is more homogeneous than when they co-rotate. In agreement with the results of the force/momentum measurements and with hypotheses put forward in the literature (see e.g. Poehls in Entwurfsgrundlagen für Schraubenpropeller, 1984; Schneekluth in Hydromechanik zum Schiffsentwurf, 1988; Breslin and Andersen in Hydrodynamics of ship propellers, 1996; Schneekluth and Bertram in Ship design for efficiency and economy, 1998), the co-rotating propellers model showed a much stronger swirl in the wake of the propulsor. The anisotropy of turbulence was analyzed using the anisotropy tensor introduced by Lumley and Newman (J Fluid Mech 82(1):161-178, 1977). The invariants of the anisotropy tensor of the wake flow were computed and were plotted in the Lumley-Newman-diagram. These measurements revealed that the anisotropy tensor in the wake of ship propellers is located near to the borders of the invariant map, showing a large degree of anisotropy. They will be presented and will be discussed with respect to applications of turbulence models to predict swirling flows.

Pęgo, J. P.; Lienhart, H.; Durst, F.

2007-08-01

130

Collision-free nonuniform dynamics within continuous optimal velocity models

NASA Astrophysics Data System (ADS)

Optimal velocity (OV) car-following models give with few parameters stable stop-and -go waves propagating like in empirical data. Unfortunately, classical OV models locally oscillate with vehicles colliding and moving backward. In order to solve this problem, the models have to be completed with additional parameters. This leads to an increase of the complexity. In this paper, a new OV model with no additional parameters is defined. For any value of the inputs, the model is intrinsically asymmetric and collision-free. This is achieved by using a first-order ordinary model with two predecessors in interaction, instead of the usual inertial delayed first-order or second-order models coupled with the predecessor. The model has stable uniform solutions as well as various stable stop-and -go patterns with bimodal distribution of the speed. As observable in real data, the modal speed values in congested states are not restricted to the free flow speed and zero. They depend on the form of the OV function. Properties of linear, concave, convex, or sigmoid speed functions are explored with no limitation due to collisions.

Tordeux, Antoine; Seyfried, Armin

2014-10-01

131

NASA Technical Reports Server (NTRS)

Subgrid-scale models for Large Eddy Simulation (LES) in both the velocity-pressure and the vorticity-velocity formulations were evaluated and compared in a priori tests using spectral Direct Numerical Simulation (DNS) databases of isotropic turbulence: 128(exp 3) DNS of forced turbulence (Re(sub(lambda))=95.8) filtered, using the sharp cutoff filter, to both 32(exp 3) and 16(exp 3) synthetic LES fields; 512(exp 3) DNS of decaying turbulence (Re(sub(Lambda))=63.5) filtered to both 64(exp 3) and 32(exp 3) LES fields. Gaussian and top-hat filters were also used with the 128(exp 3) database. Different LES models were evaluated for each formulation: eddy-viscosity models, hyper eddy-viscosity models, mixed models, and scale-similarity models. Correlations between exact versus modeled subgrid-scale quantities were measured at three levels: tensor (traceless), vector (solenoidal 'force'), and scalar (dissipation) levels, and for both cases of uniform and variable coefficient(s). Different choices for the 1/T scaling appearing in the eddy-viscosity were also evaluated. It was found that the models for the vorticity-velocity formulation produce higher correlations with the filtered DNS data than their counterpart in the velocity-pressure formulation. It was also found that the hyper eddy-viscosity model performs better than the eddy viscosity model, in both formulations.

Winckelmans, G. S.; Lund, T. S.; Carati, D.; Wray, A. A.

1996-01-01

132

Excitons in the 1D Hubbard Model: a Real-Time Study

NASA Astrophysics Data System (ADS)

We study the real-time dynamics of a pair hole/doubly-occupied-site, namely a holon and a doublon, in a 1D Hubbard insulator with on-site and nearest-neighbor Coulomb repulsion. Our analysis shows that the pair is long-lived and the expected decay mechanism to underlying spin excitations is actually inefficient. For a nonzero inter-site Coulomb repulsion, we observe that part of the wave-function remains in a bound state. Our study also provides insight on the holon-doublon propagation in real space. Due to the one-dimensional nature of the problem, these particles move in opposite directions even in the absence of an applied electric field. The potential relevance of our results to solar cell applications is discussed.

Al-Hassanieh, Khaled; Feiguin, Adrian; Reboredo, Fernando; Gonzalez, Ivan; Dagotto, Elbio

2008-03-01

133

Cardiac segmentation by a velocity-aided active contour model.

Heart disease is one of the more life-threatening diseases. Accurate diagnosis and treatment are central to the survival of patients. Numerous diagnostic methods that can assess abnormalities of the heart have been developed. Among these methods, cardiac functional analysis has been widely used to derive cardiac functional parameters that describe the functionality of the heart and are frequently used in diagnosis of various heart diseases. Segmentation of the myocardial boundaries is an essential step for deriving these cardiac functional parameters, and the accuracy of parameters depends much on the correctness of the segmented boundaries. Therefore, it is essential that cardiac segmentation be accurate and reliable. However, current segmentation techniques still have difficulty both extracting accurate myocardial boundaries, especially the endocardial boundary and performing a fully automatic process because of low image quality, the complex shape and motion pattern of the heart, and lack of clear delineation between the myocardium and adjacent anatomic structures. A velocity-aided cardiac segmentation method based a modified active contour model, the tensor-based orientation gradient force (OGF) and phase contrast magnetic resonance imaging (MRI) has been developed to improve the accuracy of segmentation of the myocardial boundaries, especially the endocardial boundary. Furthermore, the initial seed contour tracking (SCT) algorithm has been also developed to improve the accuracy of automatic sequential frame segmentation in conjunction with the OGF-based segmentation method. The performance of the proposed method was assessed by experimentations on a phase contrast MRI data set of three normal human volunteer. The results of the individual frame segmentation showed that the accuracy and reproducibility of segmentation of the endocardial boundary by the use of the OGF was generally improved around the lower level of the LV and end systole. The results of the sequential frame segmentation showed that the propagation of errors caused was significantly reduced by the use of the SCT in addition to the OGF and improvements in the accuracy and reproducibility of segmentation of the endocardial boundary were much higher than the individual frame segmentation. However, improvements were generally negligible around the upper level of the LV and end diastole, and the velocity wrap-around problem and blood turbulence around the basal level of the ventricles even degraded the performance of boundary segmentation. Although this work demonstrates the potential of using the velocity information from phase contrast MRI for cardiac segmentation, the velocity wrap-around artifacts in phase contrast MRI data sets can degrade the performance. Therefore, future work must include the development of appropriate methods to cope with these artifacts. PMID:16378714

Cho, Jinsoo; Benkeser, Paul J

2006-01-01

134

NASA Astrophysics Data System (ADS)

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.

Zhang, Lianxin; Zhang, Xuefeng; Han, Guijun; Wu, Xinrong; Cui, Xiaojian; Shao, Caixia; Sun, Chunjian; Zhang, Xiaoshuang; Wang, Xidong; Fu, Hongli

2015-01-01

135

Unsteady velocity measurements in a realistic intracranial aneurysm model

NASA Astrophysics Data System (ADS)

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.

Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György

2012-01-01

136

TESTS OF 1-D TRANSPORT MODELS, AND THEIR PREDICTIONS FOR ITER

models ITER's predicted fusion power depends strongly on the 'pedestal' temperature, but ~ 1GW (Q=10) is predicted for most models if the pedestal temperature is at least 4 keV. 1. INTRODUCTION We seek predictions how well each model represents the wide range of existing tokamak data. This has led

Hammett, Greg

137

Although elastic velocities (Vp, Vs) can be used to assess the distribution and concentration of marine gas hydrates in situ and several existing models relate hydrate saturation to acoustic velocity, the accuracy of these models is uncertain because of the difficulty in determining hydrate saturations and velocities of intact hydrate-bearing sediments. In this paper, the acoustic properties of gas hydrate–bearing

Gao W. Hu; Yu G. Ye; Jian Zhang; Chang L. Liu; Shao B. Diao; Jia S. Wang

2010-01-01

138

Although elastic velocities (Vp, Vs) can be used to assess the distribution and concentration of marine gas hydrates in situ and several existing models relate hydrate saturation to acoustic velocity, the accuracy of these models is uncertain because of the difficulty in determining hydrate saturations and velocities of intact hydrate-bearing sediments. In this paper, the acoustic properties of gas hydrate-bearing

Gao W. Hu; Yu G. Ye; Jian Zhang; Chang L. Liu; Shao B. Diao; Jia S. Wang

2010-01-01

139

Authentication Based on Pole-zero Models of Signature Velocity

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

Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad

2013-01-01

140

Comparison of CME radial velocities from a flux rope model and an ice cream cone model

NASA Astrophysics Data System (ADS)

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.

Kim, T.; Moon, Y.; Na, H.

2011-12-01

141

NASA Astrophysics Data System (ADS)

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.

Pek?en, Ertan; Yas, Türker; K?yak, Alper

2014-09-01

142

The 1D Ising model and the topological phase of the Kitaev chain

NASA Astrophysics Data System (ADS)

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 Jordan-Wigner 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.

Greiter, Martin; Schnells, Vera; Thomale, Ronny

2014-12-01

143

Control oriented 1D electrochemical model of lithium ion battery Kandler A. Smith a

Available online 28 June 2007 Abstract Lithium ion (Li-ion) batteries provide high energy and power density/charge behavior of a Li-ion battery. Validated against a 313th order nonlinear CFD model of a 6 Ah HEV cell, a 12 work is to develop a fundamental lithium-ion (Li-ion) bat- tery model in a low order state variable

144

Nuclear quantum effects in a 1-D model of hydrogen bonded ferroelectrics

NASA Astrophysics Data System (ADS)

A one dimensional model of a coupled hydrogen (H) bonding chain is developed and parametrized to density functional theory (DFT) calculations on squaric acid, a prototypical H-bonded antiferroelectric crystal. The energetics of single and collective proton jumps and its dependence on H-bond length, as obtained by DFT, is reproduced quite well in the model despite its simplicity where only hydrogen and oxygen atom positions in (O-H...O) H-bonds and nearest-neighbor coupling between H positions are explicitly included. Classical and path- integral molecular dynamics simulations are performed to shed light on nuclear quantum effects and how they influence the paraelectric phase transition. A large H/D isotope shift in the transition temperature TC as well as a geometric isotope effect is obtained in good agreement with experiment. Fixing the O-O bond length results in shifts of TC to higher temperature but a pronounced isotope shift of TC remains, highlighting the importance of quantum effects beyond the geometrical changes in H-bonds accompanying isotopic substitution. Intermediate between fully atomistic models and simpler Ising-type models, the proposed H-bond chain model is a useful toy model for investigating microscopic mechanisms behind phase transitions in H-bonded ferroelectrics and the detailed role of quantum fluctuations.

Wikfeldt, K. T.

2014-12-01

145

Space-based Observational Constraints for 1-D Plume Rise Models

NASA Technical Reports Server (NTRS)

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.

Martin, Maria Val; Kahn, Ralph A.; Logan, Jennifer A.; Paguam, Ronan; Wooster, Martin; Ichoku, Charles

2012-01-01

146

NASA Astrophysics Data System (ADS)

Knowledge of the spatial distribution of seismic properties within an earthquake rupture zone is essential to our understanding of rupture mechanics. Following the Maule earthquake, there was an international collaborative effort to deploy a dense network of seismic instruments in order to record the aftershock sequence; this means a large dataset is available to perform seismic velocity tomography in the area of the rupture zone. Since most co-seismic slip occurred in the offshore region, it is important to interpret the velocity structure of the marine forearc and the underlying oceanic crust. However, since many aftershocks are located offshore, and thus outside of the land network, both the offshore velocity structure and the location of these aftershocks are inherently poorly resolved. During the period July - December 2010, The National Taiwan Ocean University and The University of Liverpool each deployed ocean-bottom seismometer (OBS) networks in the northern and southern ends of the rupture zone, respectively, comprising a total of 43 stations. We use a catalogue of ~500 seismic events recorded at both land and OBS stations, containing ~60000 hand-picked P- and S-wave travel-times. We use a staggered 1D inversion scheme, which initially incorporates a separate velocity model for the marine forearc in order to form better hypocentral locations for the offshore events. Based on previous estimates for slab geometry, we find that the location of offshore seismicity is more tightly constrained along and above the interface. Taking these improved locations into account, we then re-invert for a new 1D model with station corrections. We present a 3D local earthquake tomography model based on manually-picked arrival times. The incorporation of OBS picks into the inversion elucidates better both the up-dip geometry of the subducting plate and the structure of the marine forearc. Beneath the low vp marine forearc (vp < 6.0 km/s), at depths of 7-15 km, we infer the presence of a high velocity structure (vp > 7.0 km/s); the upper interface of which dips at 10-15°, interpreted as the top of the downgoing oceanic crust. These first-order features are in accordance with results from previous active source studies in the region. We continue to analyse the nature and geometry of velocity anomalies along and around the megathrust, and their relation to rupture models and aftershock distribution.

Hicks, Stephen; Rietbrock, Andreas; Ryder, Isabelle; Miller, Matthew; Lee, Chao-Shing

2013-04-01

147

Radon exhalation from uranium mill tailings: experimental validation of a 1-D model.

TRACI, a model based on the physical mechanisms governing the migration of radon in unsaturated soils, has been developed to evaluate the radon flux density at the surface of uranium mill tailings. To check the validity of the TRACI model and the effectiveness of cover layers, an in situ study was launched in 1997 with the French uranium mining company, COGEMA. The study consisted of continuous measurements of moisture content, suction, radon concentration at various depths inside a UMT cover, and flux density at its surface. An initial analysis has shown that radon concentration and flux density, as calculated with a steady-state diffusion model using monthly averaged moisture contents, are in good agreement with measured monthly averaged concentrations and flux densities. PMID:11379078

Ferry, C; Richon, P; Beneito, A; Robé, M C

2001-01-01

148

Application of the Dual Fermion-Dynamical Cluster Approach to the 1D Falicov Kimball Model

NASA Astrophysics Data System (ADS)

The Falicov Kimball model is the simplest model for correlated electrons. It was introduced to study metal-insulator transitions. In one dimension, it is known to possess a charge density wave (CDW) instability at zero transition temperature (Tc). However, finite cluster methods like Dynamical Mean Field Theory (DMFT), Dynamical Cluster Approximation (DCA), Cellular Dynamical Mean Field Theory (CDMFT) , etc. show finite temperature CDW transition. In this paper, we study the model using the recently developed Dual Fermion-Dynamical Cluster approach that takes into account large length scale correlations through the auxiliary particles known as dual Fermions. We find that Tc obtained from this method is lower than that obtained from the cluster methods. In particular, we study the scaling behavior of Tc with the linear cluster size and also the scaling of other one-particle and two-particle quantities near the criticality.

Pathak, Sandeep; Meng, Zi Yang; Yang, S.-X.; Jarrell, Mark; Moreno, Juana

2012-02-01

149

Modeling Bioenhanced DNAPL Dissolution in 1-D and 2-D Flow systems

NASA Astrophysics Data System (ADS)

Chlorinated ethenes, such as tetrachloroethene (PCE), released into the environment can form dense non-aqueous phase liquids (DNAPLs), which can act as persistent sources of contamination to groundwater. Due to their low aqueous solubility, these DNAPL contaminant sources can persist for up to hundreds of years under natural conditions. Several methods have been investigated to enhance the rate of dissolution of DNAPLs, including bioenhanced dissolution, which consists of stimulating the growth of a microbial population that biodegrades the contaminant, thereby reducing its concentration at the DNAPL-water interface, and creating a greater driving force for contaminant dissolution. This phenomenon has been studied at length in batch reactors and column studies. The hypothesis of this research is that, in modeling DNAPL dissolution bioenhancement via dehalorespiration, it is important to include the effects of microbial competition, as well as spatial effects. A two-dimensional coupled flow-transport model was developed using the finite-volume method (FVM), which includes a DNAPL pool source, and the effects of multiple microbial species. The model has been confirmed to maintain mass balance and has been validated by comparison to an analytical solution for pool dissolution. The model will be used to simulate a pseudo one-dimensional system and a two-dimensional system under multiple microbial competition scenarios and varying hydrodynamic conditions. The results of these simulations will be compared to determine differences in estimations of dissolution bioenhancement, and analyzed for spatial effects that are captured by a two-dimensional model, but not by a pseudo one-dimensional FVM model. Preliminary two-dimensional simulations have shown the effects of large biomass growth near the NAPL source, which could lead to bioclogging and change the flow field. Further simulations are underway and the results will be presented.

Wesseldyke, E. S.; Becker, J. G.; Seagren, E. A.; Mayer, A. S.

2011-12-01

150

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

Adhikari, K; Pal, S; Chakraborty, B; Mukherjee, S N; Gangopadhyay, A

2014-10-01

151

BCS Diquark Condensation in the 3+1d Lattice NJL Model

We present preliminary evidence of BCS diquark condensation in the 3+1 dimensional Nambu-Jona-Lasinio (NJL) model at non-zero chemical potential (mu) on the lattice. Large N results are used to match the model's parameters to low energy, zero density phenomenology. A diquark source j is added in a partially quenched approximation to enable the measurement of lattice diquark observables. In particular measurements are made of the diquark condensate and susceptibilities as functions of j which support the existence of a BCS phase at high mu.

David N. Walters

2002-08-06

152

Pushing 1D CCSNe to explosions: model and SN 1987A

We report on a method, PUSH, for triggering core-collapse supernova explosions of massive stars in spherical symmetry. We explore basic explosion properties and calibrate PUSH such that the observables of SN1987A are reproduced. Our simulations are based on the general relativistic hydrodynamics code AGILE combined with the detailed neutrino transport scheme IDSA for electron neutrinos and ALS for the muon and tau neutrinos. To trigger explosions in the otherwise non-exploding simulations, we rely on the neutrino-driven mechanism. The PUSH method locally increases the energy deposition in the gain region through energy deposition by the heavy neutrino flavors. Our setup allows us to model the explosion for several seconds after core bounce. We explore the progenitor range 18-21M$_{\\odot}$. Our studies reveal a distinction between high compactness (HC) and low compactness (LC) progenitor models, where LC models tend to explore earlier, with a lower explosion energy, and with a lower remnant mass. HC models are...

Perego, A; Fröhlich, C; Ebinger, K; Eichler, M; Casanova, J; Liebendoerfer, M; Thielemann, F -K

2015-01-01

153

Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment.

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

Vanpoucke, Danny E P

2014-04-01

154

A Simplified 1-D Model for Calculating CO2 Leakage through Conduits

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.

Zhang, Y.; Oldenburg, C.M.

2011-02-15

155

Biot-JKD model: Simulation of 1D transient poroelastic waves with fractional derivatives

NASA Astrophysics Data System (ADS)

A time-domain numerical modeling of Biot poroelastic waves is presented. The viscous dissipation occurring in the pores is described using the dynamic permeability model developed by Johnson-Koplik-Dashen (JKD). Some of the coefficients in the Biot-JKD model are proportional to the square root of the frequency: in the time-domain, these coefficients introduce order 1/2 shifted fractional derivatives involving a convolution product. Based on a diffusive representation, the convolution kernel is replaced by a finite number of memory variables that satisfy local-in-time ordinary differential equations. Thanks to the dispersion relation, the coefficients in the diffusive representation are obtained by performing an optimization procedure in the frequency range of interest. A splitting strategy is then applied numerically: the propagative part of Biot-JKD equations is discretized using a fourth-order ADER scheme on a Cartesian grid, whereas the diffusive part is solved exactly. Comparisons with analytical solutions show the efficiency and the accuracy of this approach.

Blanc, Emilie; Chiavassa, Guillaume; Lombard, Bruno

2013-03-01

156

NASA Astrophysics Data System (ADS)

Earthen flood defence embankments are linear structures, raised above the flood plain, that are commonly used as flood defences in rural settings; these are often relatively old structures constructed using locally garnered material and of which little is known in terms of design and construction. Alarmingly, it is generally reported that a number of urban developments have expanded to previously rural areas; hence, acquiring knowledge about the flood defences protecting these areas has risen significantly in the agendas of basin and asset managers. This paper focusses, by reporting two case studies, on electromagnetic induction (EMI) methods that would efficiently complement routine visual inspections and would represent a first step to more detailed investigations. Evaluation of the results is presented by comparison with ERT profiles and intrusive investigation data. The EM data, acquired using a GEM-2 apparatus for frequency sounding and an EM-31 apparatus for geometrical sounding, has been handled using the prototype eGMS software tool, being developed by the eGMS international research consortium; the depth sounding data interpretation was assisted by 1D inversions obtained with the EM1DFM software developed by the University of British Columbia. Although both sounding methods showed some limitations, the models obtained were consistent with ERT models and the techniques were useful screening methods for the identification of areas of interest, such as material interfaces or potential seepage areas, within the embankment structure: 1D modelling improved the rapid assessment of earthen flood defence embankments in an estuarine environment; evidence that EMI sounding could play an important role as a monitoring tool or as a first step towards more detailed investigations.

Viganotti, Matteo; Jackson, Ruth; Krahn, Hartmut; Dyer, Mark

2013-05-01

157

Constraining the temporal evolution of a deep hypersaline anoxic basin by 1D geochemical modelling

NASA Astrophysics Data System (ADS)

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.

Goldhammer, Tobias; Aiello, Ivano; Zabel, Matthias

2014-05-01

158

On nonminimal N=4 supermultiplets in 1D and their associated {sigma}-models

We construct the nonminimal linear representations of the N=4 extended supersymmetry in one-dimension. They act on eight bosonic and eight fermionic fields. Inequivalent representations are specified by the mass-dimension of the fields and the connectivity of the associated graphs. The oxidation to minimal N=5 linear representations is given. Two types of N=4{sigma}-models based on nonminimal representations are obtained: the resulting off-shell actions are either manifestly invariant or depend on a constrained prepotential. The connectivity properties of the graphs play a decisive role in discriminating inequivalent actions. These results find application in partial breaking of supersymmetric theories.

Gonzales, Marcelo; Khodaee, Sadi; Toppan, Francesco [CBPF, Rua Dr. Xavier Sigaud 150, cep 22290-180, Rio de Janeiro (RJ) (Brazil)

2011-01-15

159

Constraining quantum critical dynamics: 2+1D Ising model and beyond

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 non-perturbative constraints on the linear-response dynamics of conformal QC systems, in spatial dimensions above one. Specifically, we analyze the large frequency/momentum asymptotics, which we use to derive powerful sum rules. 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 interacting gauge theories are made.

Witczak-Krempa, William

2015-01-01

160

High resolution 3D Sv wave velocity model of China and surrounding area

NASA Astrophysics Data System (ADS)

In our study we determine the three dimensional Sv wave speed and azimuthal anisotropy model by analyzing vertical component multimode Rayleigh wave seismograms. We use data of broadband stations from in and around China. We construct the three dimensional model using a two step procedure. In the first step we use the automated version of the Cara and Leveque [1987] waveform inversion technique in terms of secondary observables for modeling each multimode Rayleigh waveform to determine the path-average mantle Sv wave speed structure. We have used the 3SMAC model (as a crustal part) and smooth version of PREM for the upper mantle velocity structure as an initial model. In the second stage we combine the 1-D velocity models in a tomographic inversion to obtain the three dimensional Sv wave speed structure and the azimuthal anisotropy as a function of depth. China is sitting at a triple junction of three major plates: the Eurasian plate, the Indo-Australian plate and the Philippine Sea plate. China itself has three major Precambian cratons: the North China craton (also called Sino-Korean craton), the Yangtze craton (also called South China craton) and the Tarim block. The interactions among different blocks have formed the tectonic features today and caused many intraplate earthquakes. These tectonics setting have made China an interesting place for various kind of study as all of these events have left their imprint on the upper mantle structure. It is generally agreed that the lithosphere is thick in west China while much of the lithospheric root was lost beneath some cratons in east China. Still it's an open debate whether the lithosphere beneath the Tibetan plateau has doubled its thickness as did the crust above or much of the thickened lithosphere was removed by mantle convection and delamination. The upper most part of our model is in good agreement with the finding from the deep seismic profile. It is also evident that the extent of crustal flow of Tibet is being restricted by Tarim in the north and Ordos, Sichuan in the east. Various receiver function and SS precursor results are also comparable with our results in terms of the lithosphere extent.

Pandey, S.; Yuan, X.; Debayle, E.; Priestley, K. F.; Kind, R.; Li, X.

2011-12-01

161

Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations. PMID:24949781

Roundy, R C; Nemirovsky, D; Kagalovsky, V; Raikh, M E

2014-06-01

162

Evaluation of the WEN II and DENN-1D steady-state, fixed-bed gasifier models

In this study, the steady-state, one-dimensional WEN II and DENN-1D fixed-bed gasifier models were compared theoretically and with experimental data to determine their advantages and disadvantages in predicting the operating characteristics of fixed-bed gasification. Initially, the models were compared in terms of their major assumptions, limitations, and unique characteristics. Many of the major assumptions in the models are similar. The main differences occur in the way the models handle drying of coal, predict devolatilization, and represent the kinetics of gasification and combustion reactions. To test the predictive capabilities of the model, each was run with Pittsburgh No. 8 and Illinois No. 6 bituminous coals, Montana Rosebud subbituminous coal, and North Dakota Indianhead lignite. Both air- and oxygen-blow cases were tested as well as both dry-ash and slagging operation. The dry-ash cases utilized data from the METC, General Electric (GE), and British Gas Corporation (BGC)/Lurgi dry-ash gasifiers. Data from the BGC/Lurgi slagging gasifier and the former Grand Forks Energy Technology Center (GFETC) gasifier were used for the slagging gasification cases. In all, 12 cases were tested, 10 dry-ash and 2 slagging cases. Results are discussed. 14 refs., 38 figs., 14 tabs.

Stefano, J.M.

1985-05-01

163

NASA Astrophysics Data System (ADS)

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.

Gallovic, F.; Pacor, F.; Zahradnik, J.; Luzi, L.; Puglia, R.

2013-12-01

164

An empirical model to forecast solar wind velocity through statistical modeling

NASA Astrophysics Data System (ADS)

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.

Gao, Y.; Ridley, A. J.

2013-12-01

165

Determination of soil hydraulic parameters with an inverse model for 1D and 2D infiltration

NASA Astrophysics Data System (ADS)

Determination of soil hydraulic parameters is important for modelling of hydrological transfer processes in the unsaturated zone of a watershed. However, assessment of these parameters at a great number of grid locations with traditional methods requires considerable time and resources. In this work, a simple method is developed to determine the hydraulic conductivity at saturation (Ks) and the normalisation parameter of the water retention curve (hg which equals 1/alfa for the van Genuchten water retention curve) for the cases of vertical and axisymmetrical infiltration subject to a constant pressure head at the soil surface. While the method is based on the optimisation of a dimensionless solution of the Richards equation, the data requirements are: i) a cumulative infiltration-time curve (e.g., obtained with a disk permeameter); ii) the pressure shape parameters of the soil characteristic curves (e.g., m, n) which can easily be obtained from textural information; and iii) the initial volumetric water content and the surface boundary condition hs < 0. The method is tested for synthetic data generated with the Hydrus-2D code for the Mualem-van Genuchten soil characteristic functions. Obviously, the method can be applied for any other set of functions. The results show that the parameters Ks and hg can be accurately predicted independent of the number of points and the time span of infiltration. However, further research is necessary to test the sensitivity of other variables.

Soria, J. M.; Angulo-Jaramillo, R.; Haverkamp, R.; Leij, F. J.

2003-04-01

166

NASA Astrophysics Data System (ADS)

A reduced-order model for an efficient analysis of cardiovascular hemodynamics problems using multiscale approach is presented in this work. Starting from a patient-specific computational mesh obtained by medical imaging techniques, an analysis methodology based on a two-step automatic procedure is proposed. First a coupled 1D-3D Finite Element Simulation is performed and the results are used to adjust a reduced-order model of the 3D patient-specific area of interest. Then, this reduced-order model is coupled with the 1D model. In this way, three-dimensional effects are accounted for in the 1D model in a cost effective manner, allowing fast computation under different scenarios. The methodology proposed is validated using a patient-specific aortic coarctation model under rest and non-rest conditions.

Soudah, Eduardo; Rossi, Riccardo; Idelsohn, Sergio; Ońate, Eugenio

2014-10-01

167

27 The DNA12 Seismic Velocity Model Robert Porritt, Richard Allen, and Fred Pollitz

27 The DNA12 Seismic Velocity Model Robert Porritt, Richard Allen, and Fred Pollitz 27.1 Introduction The DNA velocity models have been following the rolling USArray from west to east. The initial model, DNA07 (Xue and Allen, 2010), used data from the earli- est USArray deployment, the BDSN

Allen, Richard M.

168

A new P-velocity model for the Tethyan margin from a scaled S-velocity model and the inversion of P- and PKP-delay times Sung-Joon Chang a, , Suzan Van der Lee a , Megan P. Flanagan b a Dept. of Earth Livermore National Laboratory, P.O. Box 808, L-205, Livermore, CA 94551, USA a r t i c l e i n f o Article

van der Lee, Suzan

169

The velocity-density relation in the spherical model

We study the cosmic velocity-density relation using the spherical collapse model (SCM) as a proxy to non-linear dynamics. Although the dependence of this relation on cosmological parameters is known to be weak, we retain the density parameter Omega_m in SCM equations, in order to study the limit Omega_m -> 0. We show that in this regime the considered relation is strictly linear, for arbitrary values of the density contrast, on the contrary to some claims in the literature. On the other hand, we confirm that for realistic values of Omega_m the exact relation in the SCM is well approximated by the classic formula of Bernardeau (1992), both for voids (delta<0) and for overdensities up to delta ~ 3. Inspired by this fact, we find further analytic approximations to the relation for the whole range delta from -1 to infinity. Our formula for voids accounts for the weak Omega_m-dependence of their maximal rate of expansion, which for Omega_m < 1 is slightly smaller that 3/2. For positive density contrasts, we find a simple relation div v = 3 H_0 (Omega_m)^(0.6) [ (1+delta)^(1/6) - (1+delta)^(1/2) ], that works very well up to the turn-around (i.e. up to delta ~ 13.5 for Omega_m = 0.25 and neglected Omega_Lambda). Having the same second-order expansion as the formula of Bernardeau, it can be regarded as an extension of the latter for higher density contrasts. Moreover, it gives a better fit to results of cosmological numerical simulations.

Maciej Bilicki; Micha? Chodorowski

2008-09-21

170

NASA Astrophysics Data System (ADS)

One dimensional magnetic photonic crystals (1D-MPC) are promising structures for integrated optical isolator applications. Rare earth substituted garnet thin films with proper Faraday rotation are required to fabricate planar 1D-MPCs. In this thesis, flat-top response 1D-MPC was proposed and spectral responses and Faraday rotation were modeled. Bismuth substituted iron garnet films were fabricated by RF magnetron sputtering and structures, compositions, birefringence and magnetooptical properties were studied. Double layer structures for single mode propagation were also fabricated by sputtering for the first time. Multilayer stacks with multiple defects (phase shift) composed of Ce-YIG and GGG quarter-wave plates were simulated by the transfer matrix method. The transmission and Faraday rotation characteristics were theoretically studied. It is found that flat-top response, with 100% transmission and near 45° rotation is achievable by adjusting the inter-defect spacing, for film structures as thin as 30 to 35 mum. This is better than 3-fold reduction in length compared to the best Ce-YIG films for comparable rotations, thus allows a considerable reduction in size in manufactured optical isolators. Bismuth substituted iron garnet thin films were prepared by RF magnetron sputtering. We investigated or measured the deposition parameters optimization, crystallinity, surface morphologies, composition, magnetic and magnetooptical properties. A very high crystalline quality garnet film with smooth surface has been heteroepitaxially grown on (111) GGG substrate for films less than 1mum. Dual layer structures with two distinct XRD peaks (within a single sputtered film) start to develop when films exceed this thickness. The development of dual layer structure was explained by compositional gradient across film thickness, rather than strain gradient proposed by other authors. We also investigated the elimination of linear birefringence by thickness tuning method for our sputtered films. We examined the compressively and tensilely strained films and analyze the photoelastic response of the sputter deposited garnet films. It has been found that the net birefringence can be eliminated under planar compressive strain conditions by sputtering. Bi-layer GGG on garnet thin film yields a reduced birefringence. (Abstract shortened by UMI.)

Yang, Haichun

171

A computational method of reduced complexity is developed for simulating vascular hemodynamics by combination of one-dimensional (1D) wave propagation models for the blood vessels with zero-dimensional (0D) lumped models for the microcirculation. Despite the reduced dimension, current algorithms used to solve the model equations and simulate pressure and flow are rather complex, thereby limiting acceptance in the medical field. This complexity mainly arises from the methods used to combine the 1D and the 0D model equations. In this paper a numerical method is presented that no longer requires additional coupling methods and enables random combinations of 1D and 0D models using pressure as only state variable. The method is applied to a vascular tree consisting of 60 major arteries in the body and the head. Simulated results are realistic. The numerical method is stable and shows good convergence. PMID:22654957

Kroon, Wilco; Huberts, Wouter; Bosboom, Marielle; van de Vosse, Frans

2012-01-01

172

Constraints on shear velocity in the cratonic upper mantle from Rayleigh wave phase velocity

NASA Astrophysics Data System (ADS)

The standard model of the thermal and chemical structure of cratons has been scrutinized in recent years as additional data have been collected. Recent seismological and petrological studies indicate that the notion of cratonic lithosphere as a thick thermal boundary layer with a very depleted and dehydrated composition may be too simplistic and does not fully explain all aspects of the seismological and petrological observations. We hypothesized that the cratonic lithosphere may be more complicated and designed an experiment to investigate its thermal, chemical, and mineralogical properties using a global database of fundamental mode Rayleigh surface waves. To test this hypothesis, the phase velocities of Rayleigh wave that travel paths primarily over cratons were selected. A 1-D global craton phase velocity profile was generated from these observations and compared to predicted phase-velocity curves using two different forward modeling techniques. With the first approach, profiles of shear velocity were generated based on educated guesses of upper mantle temperatures using geotherms. With the second approach, profiles of shear velocity were generated using random permutations about 1-D global model STW105. In total 5,625 geotherm and 80,000 random 1-D forward models were generated for comparison. Each shear velocity model was converted to phase velocity and compared to the observed range of cratonic phase velocities, defined as within one standard deviation of the mean. This method was able to constrain shear velocity in cratons relatively well though the 1-D profiles deviate at depths shallower than 100 km. Shear velocity is faster than PREM/STW105 to depths greater than 200 km with constantly increasing velocity with depth in the random model and a low velocity layer at 100-150 km.

Hirsch, Aaron C.

173

Shuttle data book: SRM fragment velocity model. Presented to the SRB Fragment Model Review Panel

NASA Technical Reports Server (NTRS)

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.

1989-01-01

174

Modeling students' conceptual understanding of force, velocity, and acceleration

NASA Astrophysics Data System (ADS)

We have developed a multiple choice test designed to probe students' conceptual understanding of the relationships among the directions of force, velocity, and acceleration. The test was administered to more than 800 students enrolled in standard or honors introductory physics courses or a second-year physics majors course. The test was found to be reasonably statistically reliable, and correlations of test score with grade, course level, and the Force Concept Inventory were moderate to strong. Further analysis revealed that in addition to the common incorrect response that velocity must be in the direction of the acceleration or net force, up to 30% of students gave "partially correct" responses, for example that velocity can be either opposite to or in the direction of the acceleration or net force but not zero. The data also suggests that for some students their evolution of understanding may progress through this kind of partially incorrect understanding.

Rosenblatt, Rebecca; Sayre, Eleanor C.; Heckler, Andrew F.

2009-11-01

175

Modeling studentsâ conceptual understanding of force, velocity, and acceleration

NSDL National Science Digital Library

We have developed a multiple choice test designed to probe studentsâ conceptual understanding of the relationships among the directions of force, velocity, and acceleration. The test was administered to more than 800 students enrolled in standard or honors introductory physics courses or a second-year physics majors course. The test was found to be reasonably statistically reliable, and correlations of test score with grade, course level, and the Force Concept Inventory were moderate to strong. Further analysis revealed that in addition to the common incorrect response that velocity must be in the direction of the acceleration or net force, up to 30% of students gave âpartially correctâ responses, for example that velocity can be either opposite to or in the direction of the acceleration or net force but not zero. The data also suggests that for some students their evolution of understanding may progress through this kind of partially incorrect understanding.

Rosenblatt, Rebecca; Sayre, Eleanor C.; Heckler, Andrew F.

2010-01-19

176

Modeling students’ conceptual understanding of force, velocity, and acceleration

We have developed a multiple choice test designed to probe students’ conceptual understanding of the relationships among the directions of force, velocity, and acceleration. The test was administered to more than 800 students enrolled in standard or honors introductory physics courses or a second-year physics majors course. The test was found to be reasonably statistically reliable, and correlations of test

Rebecca Rosenblatt; Eleanor C. Sayre; Andrew F. Heckler

2009-01-01

177

Modeling students' conceptual understanding of force, velocity, and acceleration

We have developed a multiple choice test designed to probe students' conceptual understanding of the relationships among the directions of force, velocity, and acceleration. The test was administered to more than 800 students enrolled in standard or honors introductory physics courses or a second-year physics majors course. The test was found to be reasonably statistically reliable, and correlations of test

Rebecca Rosenblatt; Eleanor C. Sayre; Andrew F. Heckler

2009-01-01

178

Modeling students' conceptual understanding of force, velocity, and acceleration

Concept Inventory were moderate to strong. Further analysis revealed that in addition to the common to be reasonably statistically reliable, and correlations of test score with grade, course level, and the Force understanding of all paired relations among the concepts of force, velocity, and acceleration. Here, we report

Zollman, Dean

179

NASA Astrophysics Data System (ADS)

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.

Pradel, J.-L.; David, C.; Quinebčche, S.; Blondel, P.

2014-05-01

180

Arrival times from an ensemble of discrete earthquakes independently contain information on hypocenter locations and jointly provide information on the velocity model. A properly formulated least squares estimation procedure can be used to determine simultaneously both hypocenter and velocity model parameters. By means of this procedure a sufficiently well distributed set of earthquakes provides information on crustal structure without some

Robert S. Crosson

1976-01-01

181

A Three-mode, Variable Velocity Jet Model for HH 34

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. From previously published data on this object, we find evidence for the existence of a three-mode ejection velocity variability and

A. Raga; A. Noriega-Crespo

1998-01-01

182

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

Alice E. Gripp; Richard G. Gordon

1990-01-01

183

Modelling of composite sandwich structures with honeycomb core subjected to high-velocity impact

In this study the perforation of composite sandwich structures subjected to high-velocity impact was analysed. Sandwich panels with carbon\\/epoxy skins and an aluminium honeycomb core were modelled by a three-dimensional finite element model implemented in ABAQUS\\/Explicit. The model was validated with experimental tests by comparing numerical and experimental residual velocity, ballistic limit, and contact time. By this model the influence

Brenda L. Buitrago; Carlos Santiuste; Sonia Sánchez-Sáez; Enrique Barbero; Carlos Navarro

2010-01-01

184

NASA Astrophysics Data System (ADS)

This study presents 3D shear-wave velocity model beneath the East Sea (Sea of Japan). The region, which lies between the Korean peninsula and Japanese arc, plays important role to understand the crustal evolution at the continental margin. Long-period waveforms from 292 earthquake recorded on 251 stations of IRIS, F-net, and KS Networks were analyzed to estimate group arrival velocities of Rayleigh waves. A careful determination of the group velocities were carried out by determining velocity deviation to theoretical dispersion curves, and 3,666 dispersion curves were finally selected. A surface wave tomography technique using the fast marching method was applied to examine spatial group velocity variations between 10 s and 100 s. 3D shear-wave velocity model is constructed after inversion of the group velocities. Our shear-wave velocity model shows a shallow crust of the East Sea and a relatively thick crust of the Korean peninsula and Japanese arc. Depths of Moho-discontinuity inferred from steepest velocity gradient of the vertical velocity profiles were estimated. Estimated depths are 15-25 km beneath the East Sea and ~35 km beneath the Korean peninsula, respectively. Differences of Moho-depths are clearly depicted between sea basins and highs. Crustal thickness of the Yamato rise and Korea plateau, which are known as continental fragments formed during the East Sea opening, are found to be ~25 km, while 3 major basins, Japan, Ulleung, and Yamato show about 15 km-thick crust. Shear-wave velocities of the uppermost mantle down to 100 km show ±4% variation to 4.3 km/s of the average velocity. There exist a low velocity zone with -4% perturbation at ~70 km-depth beneath the East Sea. We consider that the thin crustal thickness and the low velocity zones are strong indications that the origin of the East Sea is the back-arc opening.

Jo, B. G.; Jung, S.; Jang, Y.

2013-05-01

185

The pairwise velocity probability density function in models with local primordial non-Gaussianity

NASA Astrophysics Data System (ADS)

We study how primordial non-Gaussianity affects the pairwise velocity probability density function (PDF) using an analytical model and cosmological N-body simulations. We adopt the local type non-Gaussian models characterized by fnl, and examine both the linear velocity difference PDF and the linear pairwise velocity PDF. We show explicitly how fnl induces correlations between originally independent velocities along the parallel and the perpendicular to the line of separation directions. We compare the model results with measurements from N-body simulations of the non-Gaussian models. Linear theory fails to predict the PDF in the fnl models. Therefore, we develop an analytic model based on the Zeldovich approximation to describe the evolution of the velocity PDF. Our analytical model and simulation results show remarkably good agreement in both the parallel and the perpendicular directions for the PDF profiles, as well as the change in the PDF due to primordial non-Gaussianity. The agreement is particularly good for relatively small separations (<10 h-1 Mpc). The inclusion of the evolution of the velocity PDF is important to obtain a good description on the signature of primordial non-Gaussianity in the PDF. Our model provides the foundation to constrain fnl using the peculiar velocity in future surveys.

Lam, Tsz Yan; Nishimichi, Takahiro; Yoshida, Naoki

2011-06-01

186

NASA Astrophysics Data System (ADS)

We investigate departures from local thermodynamic equilibrium (LTE) in the line formation of Fe for a number of well-studied late-type stars in different evolutionary stages. A new model of the Fe atom was constructed from the most up-to-date theoretical and experimental atomic data available so far. Non-LTE (NLTE) line formation calculations for Fe were performed using 1D hydrostatic MARCS and MAFAGS-OS model atmospheres, as well as the spatial and temporal average stratifications from full 3D hydrodynamical simulations of stellar convection computed using the STAGGER code. It is shown that the Fe I/Fe II ionization balance can be well established with the 1D and mean 3D models under NLTE including calibrated inelastic collisions with H I calculated from Drawin's formulae. Strong low-excitation Fe I lines are very sensitive to the atmospheric structure; classical 1D models fail to provide consistent excitation balance, particularly so for cool metal-poor stars. A better agreement between Fe I lines spanning a range of excitation potentials is obtained with the mean 3D models. Mean NLTE metallicities determined for the standard stars using the 1D and mean 3D models are fully consistent. Moreover, the NLTE spectroscopic effective temperatures and gravities from ionization balance agree with that determined by other methods, e.g. the infrared flux method and parallaxes, if one of the stellar parameters is constrained independently.

Bergemann, Maria; Lind, K.; Collet, R.; Magic, Z.; Asplund, M.

2012-11-01

187

NASA Astrophysics Data System (ADS)

In this paper, we propose the ultradiscrete optimal velocity model, a cellular-automaton model for traffic flow, by applying the ultradiscrete method for the optimal velocity model. The optimal velocity model, defined by a differential equation, is one of the most important models; in particular, it successfully reproduces the instability of high-flux traffic. It is often pointed out that there is a close relation between the optimal velocity model and the modified Korteweg-de Vries (mkdV) equation, a soliton equation. Meanwhile, the ultradiscrete method enables one to reduce soliton equations to cellular automata which inherit the solitonic nature, such as an infinite number of conservation laws, and soliton solutions. We find that the theory of soliton equations is available for generic differential equations and the simulation results reveal that the model obtained reproduces both absolutely unstable and convectively unstable flows as well as the optimal velocity model.

Kanai, Masahiro; Isojima, Shin; Nishinari, Katsuhiro; Tokihiro, Tetsuji

2009-05-01

188

NASA Astrophysics Data System (ADS)

An algorithm is developed to model the three-dimensional velocity distribution function of a sample of stars using only measurements of each star's two-dimensional tangential velocity. The algorithm works with ``missing data'': it reconstructs the three-dimensional distribution from data (velocity measurements) that all have one dimension that is unmeasured (the radial direction). It also accounts for covariant measurement uncertainties on the tangential velocity components. The algorithm is applied to tangential velocities measured in a kinematically unbiased sample of 11,865 stars taken from the Hipparcos catalog, chosen to lie on the main sequence and have well-measured parallaxes. The local stellar velocity distribution function of each of a set of 20 color-selected subsamples is modeled as a mixture of two three-dimensional Gaussian ellipsoids of arbitrary relative responsibility. In the fitting, one Gaussian (the ``halo'') is fixed at the known mean velocity and velocity variance tensor of the Galaxy halo, and the other (the ``disk'') is allowed to take an arbitrary mean and an arbitrary variance tensor. The mean and variance tensors (commonly known as the ``velocity ellipsoid'') of the disk velocity distribution are both found to be strong functions of stellar color, with long-lived populations showing larger velocity dispersion, slower mean rotation velocity, and smaller vertex deviation than short-lived populations. The local standard of rest (LSR) is inferred in the usual way, and the Sun's motion relative to the LSR is found to be (U,V,W)solar=(10.1,4.0,6.7)+/-(0.5,0.8,0.2) km s-1. Artificial data sets are made and analyzed, with the same error properties as the Hipparcos data, to demonstrate that the analysis is unbiased. The results are shown to be insensitive to the assumption that the velocity distributions are Gaussian.

Hogg, David W.; Blanton, Michael R.; Roweis, Sam T.; Johnston, Kathryn V.

2005-08-01

189

A global 3D P-velocity model of the Earth's crust and mantle for improved event location.

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.

Ballard, Sanford; Encarnacao, Andre Villanova; Begnaud, Michael A. (Los Alamos National Laboratories); Rowe, Charlotte A. (Los Alamos National Laboratories); Lewis, Jennifer E.; Young, Christopher John; Chang, Marcus C.; Hipp, James Richard

2010-04-01

190

NASA Astrophysics Data System (ADS)

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] Küppers 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.

Reynolds, Dylan; Wood, Stephen E.; Bapst, Jonathan; Mehlhaff, Joshua; Griffiths, Stephen G.

2014-11-01

191

Noise Induced Congested Traffic Flow in Coupled Map Optimal Velocity Model

NASA Astrophysics Data System (ADS)

The optimal velocity traffic flow model is one of the car-followingmodels which describe the behavior of cars by differential equations.In that model, each car controls its speed toward an optimal (safety)velocity, which depends only on the headway. We constructed a newcar-following type simulation model for traffic flow in a coupled mapform based on the optimal velocity model. We can easily simulate openroad systems with the model. The emergence of weakly congested flowinduced by noise is investigated. We observe the enhancement of thecar density induced by noise. The strong traffic jam hardly occurs inopen road systems. We discuss the problems of unrealisticacceleration in the optimal velocity model and the possibility ofspontaneous formation of strong traffic jams.

Tadaki, Shin-ichi; Kikuchi, Macoto; Sugiyama, Y?ki; Yukawa, Satoshi

1999-09-01

192

Relations Among Fault Behavior, Subsurface Geology, and Three-Dimensional Velocity Models

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

Andrew J. Michael; Donna Eberhart-Phillips

1991-01-01

193

An Innovative Model-Based Velocity Integration Procedure with an Application in Eastern Saudi Arabia

NASA Astrophysics Data System (ADS)

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.

Al-Moqbel, Abdulaziz Mohammed Saleh

194

A MATHEMATICAL MODEL FOR TSUNAMI GENERATION USING A CONSERVATIVE VELOCITY-PRESSURE HYPERBOLIC SYSTEM

A MATHEMATICAL MODEL FOR TSUNAMI GENERATION USING A CONSERVATIVE VELOCITY-PRESSURE HYPERBOLIC enable to propagate as a SaintVenant water wave and to become a tsunami when reaching the shore. We. We conclude by some discussions about the emergence of a tsunami wave or not. 1. The velocity

Paris-Sud XI, UniversitĂ© de

195

New, High Resolution, Three-Dimensional Velocity Models for the New Madrid Seismic Zone

NASA Astrophysics Data System (ADS)

We are developing high resolution three-dimensional P and S wave velocity models for the New Madrid seismic zone (NMSZ) using arrival times recorded by the 90 station New Madrid seismic network operated by the Center for Earthquake Research and Information. The new velocity models will be much more detailed than prior velocity images produced by inverting arrival times recorded by the 40 station PANDA array and will be the first models produced for the southwest portion of the NMSZ. The new models will use arrival times associated with 1,100 earthquakes recorded from 1995 until mid 2003. This data set comprises roughly 25,000 P and S wave arrivals. Previous three-dimensional velocity models determined using PANDA data imaged high velocity regions interpreted to be mafic intrusions along the axis and edges of the Reelfoot rift. Hypocenters in the depth range 4 to 10 km in the NW trending central arm of seismicity occur along the borders of the mafic intrusions. A region of low shear wave velocity was imaged at the SE end of the central arm of seismicity and was attributed to the presence of highly fractured, fluid saturated crust. This region is characterized by a high earthquake swarm rate and shallower than normal seismicity. The new velocity models will provide increased resolution along the NW trending central arm of seismicity and will help illuminate the relationship between earthquake activity and velocity perturbations. In particular, the apparent association of earthquakes and mafic intrusions will be thoroughly investigated. The station configuration will allow detailed velocity models to be constructed for the SW trending arm of seismicity; these models may provide insight into why seismicity terminates near Marked Tree, Arkansas.

Vlahovic, G.; Powell, C.; Withers, M.

2003-12-01

196

A Multi-scale Approach to 1-D Finite-Frequency Inversions

NASA Astrophysics Data System (ADS)

One-dimensional velocity models are representative of regional tectonic units. They are important in determining the locations and focal mechanisms of earthquakes, and provide initial models for tomographic studies. However, resolution of velocity models are quite dependent on the distribution of stations and earthquakes. Making use of finite-frequency travel-times which afford better resolution on the velocity structures, we formulated a multi-scale approach to reveal 1-D model from a single or more seismogram of local records. From a series of synthetic tests, it shows how 1-D multi-scale velocity models could be obtained from data with limited quality. Sensitivity kernels to parameters involved in the model, such as P- and S-wave speeds and depths of seismic discontinuities, are computed numerically by perturbing the reference model and measuring the resulting travel-times. An iterative inversion is carried out with updates of travel-time and amplitude measurements and sensitivity kernels following each iteration. According to the resolution of different phases and their Fréchet kernels, models at different scales were determined to explain the corresponding parts of data. In a synthetic test we reconstructed the input model into a series of reasonable models with multiple scale levels, assuming this method to be accurate and quickly in modeling 1-D structures from limited local records. This approach was also applied to the inversions of velocity structures in South Africa using real seismic records from Kimberley Array, revealing lateral structural variations in Kaapvaal Craton.

Wan, K.; Ni, S.; Zhao, L.

2011-12-01

197

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 [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia and Meteorological, Climatological, and Geophysical Agency, Jl. Angkasa 1 No. 2, Kemayoran, Jakar (Indonesia)] [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132, Indonesia and Meteorological, Climatological, and Geophysical Agency, Jl. Angkasa 1 No. 2, Kemayoran, Jakar (Indonesia); Widiyantoro, Sri [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia)] [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia); Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technologyc Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia)] [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technologyc Bandung, Jl. Ganesha No. 10, Bandung 40132 (Indonesia)

2013-09-09

198

Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

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.

Beeler, N.M.; Tullis, T.E.

1996-01-01

199

-dependent electromagnetic parameters (dielectric constant and the loss factor) and thermal parameters (heat conductivity is off, diffusion is conditioned by both thermal conductivity and additional heat introduced to the load-thermal 1-D Model of Combined Microwave-convective Heating with Pulsing Microwave Energy Erin M. Kiley1, 2

Yakovlev, Vadim

200

NASA Astrophysics Data System (ADS)

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.

Li, Q.; Shimeld, J.; Dickie, K.; Dehler, S. A.; Desroches, K.

2013-12-01

201

NASA Astrophysics Data System (ADS)

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.

Lin, G.

2010-12-01

202

Settling velocities of particulate systems: 14. Unified model of sedimentation, centrifugation

Settling velocities of particulate systems: 14. Unified model of sedimentation, centrifugationÂliquid separation of flocculated suspensions including sedimentation- thickening, centrifugation and filtration. After identifying the variables and equations for each of the operations, thickening, centrifugation

BĂĽrger, Raimund

203

Code package MAG c user tool for numerical modeling of 1D shock wave and dynamic processes in solids

NASA Astrophysics Data System (ADS)

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.

Rudenko, Vladimir; Shaburov, Michail

1999-06-01

204

Estimating V??s(30) (or NEHRP site classes) from shallow velocity models (depths < 30 m)

The average velocity to 30 m [V??s(30)] is a widely used parameter for classifying sites to predict their potential to amplify seismic shaking. In many cases, however, models of shallow shear-wave velocities, from which V??s(30) can be computed, do not extend to 30 m. If the data for these cases are to be used, some method of extrapolating the velocities must be devised. Four methods for doing this are described here and are illustrated using data from 135 boreholes in California for which the velocity model extends to at least 30 m. Methods using correlations between shallow velocity and V??s(30) result in significantly less bias for shallow models than the simplest method of assuming that the lowermost velocity extends to 30 m. In addition, for all methods the percent of sites misclassified is generally less than 10% and falls to negligible values for velocity models extending to at least 25 m. Although the methods using correlations do a better job on average of estimating V??s(30), the simplest method will generally result in a lower value of V??s(30) and thus yield a more conservative estimate of ground motion [which generally increases as V??s(30) decreases].

Boore, D.M.

2004-01-01

205

Modeling of meteoroid streams: The velocity of ejection of meteoroids from comets (a review)

NASA Astrophysics Data System (ADS)

An analytical review of the models of ejection of meteoroids from cometary nuclei is presented. Different formulas for the ejection velocity of meteoroids and the corresponding parameters are discussed and compared with the use of comet Halley and the Geminids meteoroid stream as examples. The ejection velocities obtained from observations of the dust trails of comets are discussed, and the values for comets 2P/Encke, 4P/Faye, 17P/Holmes, 22P/Kopff, and 67P/Churyumov-Gerasimenko are compared to the velocities yielded by Whipple's model. The uncertainty intervals of the results are estimated.

Ryabova, G. O.

2013-05-01

206

Analysis of Hook Formation Mechanism in Ultra Low Carbon Steel using CON1D Heat Flow carbon steel, Continuous casting process, Hook formation, Heat flow, Initial solidification Abstract Subsurface hook formation at the meniscus during the continuous casting of steel slabs is an important cause

Thomas, Brian G.

207

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.

Gripp, A.E.; Gordon, R.G. (Northwestern Univ., Evanston, IL (USA))

1990-07-01

208

NASA Astrophysics Data System (ADS)

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.

Daskalakis, Nikos; Krol, Maarten; Kanakidou, Maria

2014-05-01

209

Propagation of the velocity model uncertainties to the seismic event location

NASA Astrophysics Data System (ADS)

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.

Gesret, A.; Desassis, N.; Noble, M.; Romary, T.; Maisons, C.

2015-01-01

210

NASA Astrophysics Data System (ADS)

Dust emission schemes in climate models are relatively simple and are often tuned to represent observed background aerosol concentrations many of which are thousands of kilometres from source regions. Parameterisations of dust emission in numerical models were developed from idealised experiments such as those conducted in wind tunnels. Improvement of current model dust emission schemes has been difficult to achieve because of the paucity of observations from key dust sources. The Dust Observations for Models project (DO4Models) aims to gather data from source regions at a scale appropriate to climate model grid box resolution. Here we present the results of 1D box model simulations in which three commonly used parameterisations for the horizontal and vertical dust emission flux (Marticorena and Bergametti 1995, Alfaro and Gomez 2001, Shao et al. 2004) are applied and compared with Do4Models field campaign data retrieved over a typical salt pan dust source (Sua Pan, Botswana). The sensitivity of the schemes to input parameters such as soil moisture content, aerodynamic surface roughness length, shear velocity, soil texture class, and particle size is tested with particular regard to the representation of horizontal-to-vertical-mass-flux ratio. The effects of spatial averaging over 11 field sites is evaluated as is the average dust emission flux of a typical 12x12km model grid box. It is analysed whether the full range of surface processes (temporal changes in roughness, moisture, and soil conditions) is represented sufficiently well after averaging yet. Furthermore, the application of the dispersed soil size distribution on the performance of the emission schemes compared to the typically used undisturbed soil size distribution provided from soil databases is examined. Preliminary results suggest that the current schemes do not describe the observed emission process well. The scheme after Shao et al. (2004) provides the most accurate horizontal flux estimate so far. However, as our observed horizontal-to-vertical-dust-flux ratio is fairly variable compared to other field sites (e.g. Owens Lake), an accurate representation of the saltating flux does not assure a good simulation of the vertical emission flux. The simpler scheme after Marticorena and Bergametti (1995) can therefore compete in terms of total vertical dust flux despite its deficiencies in representing the full range of physics involved. We show that the moisture correction strongly affects the simulated dust flux and that the drag partition correction after Marticorena and Bergametti (1997) needs a little revision to be applicable to the whole range of observed roughness lengths. The dispersed soil texture data allow for a better representation of the deflatable dust fraction which controls the horizontal flux. It is more consistently constrained with regard to the measured saltating flux.

Haustein, Karsten; King, James; Wiggs, Giles; Washington, Richard

2013-04-01

211

Measurements and a model for convective velocities in the turbulent boundary layer

NASA Technical Reports Server (NTRS)

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.

Cliff, W. C.; Sandborn, V. A.

1973-01-01

212

A comprehensive dispersion model of surface wave phase and group velocity for the globe

NASA Astrophysics Data System (ADS)

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.

Ma, Zhitu; Masters, Guy; Laske, Gabi; Pasyanos, Michael

2014-10-01

213

A multifractal model for linking Lagrangian and Eulerian velocity structure functions

NASA Astrophysics Data System (ADS)

A multifractal model is developed to connect the Lagrangian multifractal dimensions with their Eulerian counterparts. We propose that the characteristic time scale of a Lagrangian quantity should be the Lagrangian time scale, and it should not be the Eulerian time scale which was widely used in previous studies on Lagrangian statistics. Using the present model, we can obtain the scaling exponents of Lagrangian velocity structure functions from the existing data or models of scaling exponents of Eulerian velocity structure functions. This model is validated by comparing its prediction with the results of experiments, direct numerical simulations, and the previous theoretical models. The comparison shows that the proposed model can better predict the scaling exponents of Lagrangian velocity structure functions, especially for orders larger than 6.

Dong, Yu-Feng; Jin, Guo-Dong

2014-08-01

214

A three-dimensional P wave velocity model for the Charlevoix seismic zone, Quebec, Canada

NASA Astrophysics Data System (ADS)

A three-dimensional P wave velocity model has been developed for the Charlevoix seismic zone (CSZ). The CSZ is located along the St. Lawrence River 100 km northeast of Quebec City, Canada, and is one of the most active seismic zones in eastern North America. Five earthquakes with magnitudes equal to or exceeding 6.0 have occurred in the CSZ in historic time, and around 200 earthquakes occur annually. Hypocenters are located in Precambrian basement rocks. Basement rocks have been affected by numerous tectonic events including Grenvillian collision, Iapetan rifting, and meteor impact. We performed a sequential, tomographic inversion for P wave velocity structure based upon 3093 P wave arrivals from 489 earthquakes recorded by 12 stations. High velocity is associated with the center of the impact crater. The region of high velocity is surrounded by low velocities interpreted to be highly disrupted rocks. An elongated, high-velocity region is present at midcrustal depths that trends parallel to the St. Lawrence River. Earthquakes avoid the high-velocity body and separate into two bands, one on either side of the feature. Larger earthquakes (magnitude ? 4) have occurred along the northern edges of the high-velocity region.

Vlahovic, Gordana; Powell, Christine; Lamontagne, Maurice

2003-09-01

215

'A Civil Action' 1-D Transport Game

NSDL National Science Digital Library

The 'A Civil Action' 1-D Contaminant Transport Game is an EXCEL spreadsheet that enables students to compute concentrations of TCE traveling in the groundwater flow system toward well H that emanate from the W.R. Grace site. The idea of the game is to draw students into learning some of the fundamental concepts about (1) how contaminants move in the subsurface and (2) how models can be used to test hypotheses. These concepts are taught within the context of the famous 'A Civil Action' trial described in the book by Jonathan Harr (1996) and the movie starring John Travolta (1998). The spreadsheet computes values of hydraulic head, advective flow velocities and traveltimes, contaminant velocities, and contaminant concentrations at 20 locations along the flowpath from W.R. Grace to the Aberjona River. Breakthrough curves showing changes in concentration versus distance and changes in concentration versus time pop-up automatically (see below). The spreadsheet also creates graphs of advective and contaminant velocities versus distance.

Scott Bair

216

Volumetric Velocity Measurements of Pulsating Flow through a Model Aneurysm

NASA Astrophysics Data System (ADS)

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.

Troolin, Daniel; Amatya, Devesh; Longmire, Ellen

2010-11-01

217

Specified discharge velocity models for numerical simulations of laminar vortex rings

NASA Astrophysics Data System (ADS)

We numerically and theoretically investigate the flow generated at the exit section of a piston/cylinder arrangement that is generally used in experiments to produce vortex rings. Accurate models for the velocity profile in this section (also called specified discharge velocity, SDV models) are necessary in (i) numerical simulations of laminar vortex rings that do not compute the flow inside the cylinder and (ii) in slug-models that provide a formula for the total circulation of the flow. Based on the theoretical and numerical analysis of the flow evolution in the entrance region of a pipe, we derive two new and easy to implement SDV models. A first model takes into account the unsteady evolution of the centerline velocity, while the second model also includes the time variation of the characteristics of the boundary layer at the exit plane of the vortex generator. The models are tested in axisymmetric direct numerical simulations of vortex rings. As distinguished from classical SDV model, the new models allow to accurately reproduce the characteristics of the flow. In particular, the time evolution of the total circulation is in good agreement with experimental results and previous numerical simulations including the vortex generator. The second model also provides a more realistic time evolution of the vortex ring circulation. Using the classical slug-model and the new correction for the centerline velocity, we finally derive a new and accurate analytical expression for the total circulation of the flow.

Danaila, Ionut; Vadean, Claudiu; Danaila, Sterian

2009-09-01

218

Measurement of velocity deficit at the downstream of a 1:10 axial hydrokinetic turbine model

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.

Gunawan, Budi [ORNL] [ORNL; Neary, Vincent S [ORNL] [ORNL; Hill, Craig [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414] [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414; Chamorro, Leonardo [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414] [St. Anthony Falls Laboratory, 2 Third Avenue SE, Minneapolis, MN 55414

2012-01-01

219

Modeling the effect of varying swim speeds on fish passage through velocity barriers

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.

Castro-Santos, T.

2006-01-01

220

Site-Specific Velocity and Density Model for the Waste Treatment Plant, Hanford, Washington.

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.

Rohay, Alan C.; Brouns, Thomas M.

2007-06-27

221

NASA Astrophysics Data System (ADS)

A dynamic exchange of halogens between the ocean, sea ice, snowpack, and the atmosphere is a main driver for the occurrence of ozone depletion episodes (ODEs) and atmospheric mercury depletion episodes (AMDEs) in the polar boundary layer particularly during the spring. Oxidized mercury is deposited to the snow/ice surface efficiently concurrent with the AMDEs and can be transformed to methyl-mercury, which subsequently bio-magnifies and imposes various health threats to northern communities and wild life. However, some field measurements of mercury in the snowpack and overlying ambient air, including but not limited to those in the polar region, indicate the photochemical reduction of oxidized mercury back to gaseous elemental mercury (GEM) on timescales of days to weeks whereas other studies show no evidence of rapid reduction. Such differences could be attributed not only to meteorological factors like temperature but also to chemical/biological factors that control the abundance of halogens and organic compounds, with a link to the redox chemistry of mercury. In order to understand the role of each driving process in the overall behaviors of mercury in the polar region, we have developed a one-dimensional model, PHANTAS (a model of PHotochemistry ANd Transport in Air and Snowpack), which describes multiphase chemistry in the gas phase, aerosols and the brine layer assumed to exist on the grain surface of saline snowpack. Henry's law for Hg(II) gases and aqueous-phase stability constants for Hg(II)-halide complexes are re-evaluated including their temperature dependence. Photochemical reduction of Hg(II) to Hg(0) in the aqueous phase is handled simply by a prescribed first-order rate constant with diurnal variations. The model also handles the transport of gases and aerosols across the snowpack and the turbulent atmospheric boundary layer. The atmospheric profile of turbulent diffusivity down to the interfacial sublayer is diagnosed from an arbitrary chosen set of measured surface sensible heat fluxes, reference-height wind speed and static stability in the free troposphere. The model yields a shallower boundary layer depth with decreasing wind speed, leading to more rapid ODEs and AMDEs. On the other hand, the amount of Hg(II) deposition is simulated to increase with increasing wind speed. Ozone and GEM are actively destroyed in the snowpack interstitial air via bromine radical chemistry. However, apparent dry deposition velocities for ozone (and GEM where efficient Hg(II) reduction is not included in the model) reached only up to the order of 10-3 cm/s. The gas-particle partitioning of oxidized mercury in the air is strongly connected to bromine chemistry in that particulate mercury starts to build up mainly as HgBr42- in sulfate aerosols after ozone is significantly depleted. In the saline snowpack above the sea ice, mixed-halide complexes like HgCl3Br2- and HgCl2Br22-, as well as HgCl42-, are simulated to comprise a major component of inorganic Hg(II). A predominant fraction of Hg(II) entering from the atmosphere is captured in the top millimeter of the snowpack, whereas molecular diffusion in the brine and re-emission of GEM followed by re-oxidation in the interstitial air contribute to the downward migration of some of the Hg(II).

Toyota, K.; Dastoor, A. P.; Staebler, R. M.; McConnell, J. C.

2012-04-01

222

Solid velocity correction schemes for a temperature transforming model for convection phase change

Purpose – To study the effects of velocity correction schemes for a temperature transforming model (TTM) for convection controlled solid-liquid phase-change problem. Design\\/methodology\\/approach – The effects of three different solid velocity correction schemes, the ramped switch-off method (RSOM), the ramped source term method (RSTM) and the variable viscosity method (VVM), on a TTM for numerical simulation of convection controlled solid-liquid

Zhanhua Ma; Yuwen Zhang

2006-01-01

223

A distributed, dynamic, parallel computational model: the role of noise in velocity storage

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

Merfeld, Daniel M.

2012-01-01

224

No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1

NASA Astrophysics Data System (ADS)

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.

Argus, Donald F.; Gordon, Richard G.

1991-11-01

225

Variations in global ice volume and temperature over the Cenozoic era have been\\u000ainvestigated with a set of one-dimensional (1-D) ice-sheet models. Simulations include three ice sheets\\u000arepresenting glaciation in the Northern Hemisphere, i.e. in Eurasia, North America and Greenland, and\\u000atwo separate ice sheets for Antarctic glaciation. The continental mean Northern Hemisphere surface-air\\u000atemperature has been derived through an

B. de Boer; R. Bintanja; L. J. Lourens; E. Tuenter

2010-01-01

226

Thermal maturity information has been compiled for one of the deepest parts of the Central European Basin system, the Schleswig-Holstein\\u000a area in northern Germany. New vitrinite reflectance data were obtained and old data were evaluated from a total of 31 wells.\\u000a Furthermore, numerical 1D basin modelling was performed in order to interpolate\\/extrapolate vitrinite reflectance data to\\u000a base Zechstein and base

Sabine Rodon; Ralf Littke

2005-01-01

227

Hill-type muscle model with serial damping and eccentric force-velocity relation.

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

Haeufle, D F B; Günther, M; Bayer, A; Schmitt, S

2014-04-11

228

A math model for high velocity sensoring with a focal plane shuttered camera.

NASA Technical Reports Server (NTRS)

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.

Morgan, P.

1971-01-01

229

Rectangular nozzle plume velocity modeling for use in jet noise prediction

NASA Technical Reports Server (NTRS)

A modeling technique for predicting the axial and transverse velocity characteristics of rectangular nozzle plumes is developed. In this technique, modeling of the plume cross section is initiated at the nozzle exit plane. The technique is demonstrated for the plume issuing from a rectangular nozzle having an aspect ratio of 6.0 and discharging into quiescent air. Application of the present procedures to a nozzle discharging into a moving airstream (flight effect) are then demonstrated. The effects of plume shear layer structure modification on the velocity flowfield are discussed and modeling procedures are illustrated by example.

Vonglahn, U. H.

1989-01-01

230

NASA Astrophysics Data System (ADS)

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.

Yetirmishli, G. C.; Kazimova, S. E.; Kazimov, I. E.

2011-09-01

231

SALSA3D : a global 3D p-velocity model of the Earth's crust and mantle for improved event location.

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.

Encarnacao, Andre Villanova; Begnaud, Michael A. (Los Alamos National Laboratories); Rowe, Charlotte A. (Los Alamos National Laboratories); Young, Christopher John; Chang, Marcus C.; Ballard, Sally C.; Hipp, James Richard

2010-06-01

232

A global 3D P-velocity model of the Earth's crust and mantle for improved event location : SALSA3D.

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.

Young, Christopher John; Steck, Lee K. (Los Alamos National Laboratory); Phillips, William Scott (Los Alamos National Laboratory); Ballard, Sanford; Chang, Marcus C.; Rowe, Charlotte A. (Los Alamos National Laboratory); Encarnacao, Andre Villanova; Begnaud, Michael A. (Los Alamos National Laboratory); Hipp, James Richard

2010-07-01

233

UCVM: An Open Source Framework for 3D Velocity Model Research

NASA Astrophysics Data System (ADS)

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.

Gill, D.; Maechling, P. J.; Jordan, T. H.; Plesch, A.; Taborda, R.; Callaghan, S.; Small, P.

2013-12-01

234

NASA Astrophysics Data System (ADS)

One significant difference between the atmospheres of stars and exoplanets is the presence of condensed particles (clouds or hazes) in the atmosphere of the latter. In current 1D models clouds and hazes are treated in an approximate way by raising the surface albedo, or adopting measured Earth cloud properties. The former method introduces errors to the modeled spectra of the exoplanet, as clouds shield the lower atmosphere and thus modify the spectral features. The latter method works only for an exact Earth-analog, but it is challenging to extend to other planets. The main goal of this paper is to develop a self-consistent microphysical cloud model for 1D atmospheric codes, which can reproduce some observed properties of Earth, such as the average albedo, surface temperature, and global energy budget. The cloud model is designed to be computationally efficient, simple to implement, and applicable for a wide range of atmospheric parameters for planets in the habitable zone. We use a 1D, cloud-free, radiative-convective, and photochemical equilibrium code originally developed by Kasting, Pavlov, Segura, and collaborators as basis for our cloudy atmosphere model. The cloud model is based on models used by the meteorology community for Earth’s clouds. The free parameters of the model are the relative humidity and number density of condensation nuclei, and the precipitation efficiency. In a 1D model, the cloud coverage cannot be self-consistently determined, thus we treat it as a free parameter. We apply this model to Earth (aerosol number density 100 cm-3, relative humidity 77%, liquid cloud fraction 40%, and ice cloud fraction 25%) and find that a precipitation efficiency of 0.8 is needed to reproduce the albedo, average surface temperature and global energy budget of Earth. We perform simulations to determine how the albedo and the climate of a planet is influenced by the free parameters of the cloud model. We find that the planetary climate is most sensitive to changes in the liquid water cloud fraction and precipitation efficiency. The advantage of our cloud model is that the cloud height and the droplet sizes are self-consistently calculated, both of which influence the climate and albedo of exoplanets.

Zsom, Andras; Kaltenegger, Lisa; Goldblatt, Colin

2012-11-01

235

A California Statewide Three-Dimensional Seismic Velocity Model from Both Absolute and Differential of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin using S picks from both the Southern California Seismic Network and USArray, assuming a starting model

Shearer, Peter

236

HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION

The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Crustal and upper mantle velocities show great heterogeneity in this region and regional phases display variations in both amplitudes and travel time. Furthermore, due to a lack of quality data, the region has largely been unexplored in terms of the detailed lithospheric seismic structure. A unified high-resolution 3D velocity and attenuation model of the crust and upper mantle will be developed and calibrated. This model will use new data from 23 new broadband stations in the region analyzed with a comprehensive set of techniques. Velocity models of the crust and upper mantle will be developed using a joint inversion of receiver functions and surface waves. The surface wave modeling will use both event-based methods and ambient noise tomography. Regional phase (Pg, Pn, Sn, and Lg) Q model(s) will be constructed using the new data in combination with existing data sets. The results of the analysis (both attenuation and velocity modeling) will be validated using modeling of regional phases, calibration with selected events, and comparison with previous work. Preliminary analyses of receiver functions show considerable variability across the region. All results will be integrated into the KnowledgeBase.

Mellors, R; Gok, R; Sandvol, E

2007-07-10

237

For the evolution of density fluctuation in nonlinear cosmological dynamics, adhesion approximation (AA) is proposed as a phenomenological model, which is especially useful for describing nonlinear evolution. However, the origin of the artificial viscosity in AA is not clarified. Recently, Buchert and Dominguez report if the velocity dispersion of the dust fluid is regarded as isotropic, it works on a principle similar to viscosity or effective pressure, and they consider isotropic velocity dispersion as the origin of the artificial viscosity in AA. They name their model the Euler-Jeans-Newton (EJN) model. In this paper, we focus on the velocity distribution in AA and the EJN model and examine the time evolution in both models. We find the behavior of AA differs from that of the EJN model, i.e., although the peculiar velocity in the EJN model oscillates, that in AA is monotonically decelerated due to viscosity without oscillation. Therefore it is hard to regard viscosity in AA as effective pressure in the EJN model.

Sotani, Hajime [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Tatekawa, Takayuki [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Department of Physics, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610 (Japan); Department of Physics, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

2006-01-15

238

TWO PROPERTIES OF TWO-VELOCITY TWO-PRESSURE MODELS FOR TWO-PHASE FLOWS

that each phase is described by its own pressure, velocity and temperature and on the use of void fractions-MARC HÂ´ERARD , KHALED SALEH , AND NICOLAS SEGUIN Â§ Abstract. We study a class of models of compressible The modeling of compressible two-phase flows is a challenging task in Thermo- hydraulics. It is a crucial issue

239

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 rsw1-1’s permissive temperature (21°C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29°C). 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

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

240

Low velocity impact experiments on the explosive LX-10 with modeling of reaction violence

NASA Astrophysics Data System (ADS)

A new gas gun capability designed for the velocity range of ~20-400 m/s was used to study the mechanisms of low-velocity impact ignition and reaction violence of explosive targets in safety studies. Hemispherical charges of the HMX-based explosive LX-10 (95% HMX, 5% Viton binder) assembled in a polycarbonate target ring were impacted by a 6.35 mm diameter hardened steel rod protruding from a projectile at velocities ranging from 36 to 374 m/s. Digital high-speed (Phantom v12) cameras were utilized to capture the times of first ignition and a Photonic Doppler Velocimetry (PDV) probe placed at the rear of the target was used to measure the free surface velocity histories of an aluminum foil on the LX-10 surface to quantify the resulting reaction violence. The Ignition and Growth reactive flow model for LX-10 was used to compare the relative violence of these reactions to the intentional detonation of an equivalent LX-10 charge. It was found that comparing the model results to that of the experiment using this impactor geometry within the tested velocity range, the reaction violence increased with velocity from 45-374 m/s and only a small fraction of material appears to react during the impact.

Chidester, Steven; Garcia, Frank; Vandersall, Kevin S.; Tarver, Craig M.; Ferranti, Louis

2012-03-01

241

Modeling of the Terminal Velocities of the Dust Ejected Material by the Impact

We compute the distribution of velocities of the particles ejected by the impact of the projectile released from NASA Deep Impact spacecraft on the nucleus of comet 9P/Tempel 1 on the successive 20 hours following the collision. This is performed by the development and use of an ill-conditioned inverse problem approach, whose main ingredients are a set of observations taken by the Narrow Angle Camera (NAC) of OSIRIS onboard the Rosetta spacecraft, and a set of simple models of the expansion of the dust ejecta plume for different velocities. Terminal velocities are derived using a maximum likelihood estimator. We compare our results with published estimates of the expansion velocity of the dust cloud. Our approach and models reproduce well the velocity distribution of the ejected particles. We consider these successful comparisons of the velocities as an evidence for the appropriateness of the approach. This analysis provides a more thorough understanding of the properties of the Deep Impact dust cloud.

M. Rengel; M. Kueppers; H. U. Keller; P. Gutierrez

2007-01-03

242

Modeling of the Terminal Velocities of the Dust Ejected Material by the Impact

We compute the distribution of velocities of the particles ejected by the impact of the projectile released from NASA Deep Impact spacecraft on the nucleus of comet 9P/Tempel 1 on the successive 20 hours following the collision. This is performed by the development and use of an ill-conditioned inverse problem approach, whose main ingredients are a set of observations taken by the Narrow Angle Camera (NAC) of OSIRIS onboard the Rosetta spacecraft, and a set of simple models of the expansion of the dust ejecta plume for different velocities. Terminal velocities are derived using a maximum likelihood estimator. We compare our results with published estimates of the expansion velocity of the dust cloud. Our approach and models reproduce well the velocity distribution of the ejected particles. We consider these successful comparisons of the velocities as an evidence for the appropriateness of the approach. This analysis provides a more thorough understanding of the properties of the Deep Impact dust cloud. 2

M. Rengel; H. U. Keller; P. Gutierrez

2007-01-01

243

Crustal P-wave velocity model for the central-western region of Mexico

NASA Astrophysics Data System (ADS)

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.

Ochoa, J.; Escudero, C. R.; Perez, O. G.; Nunez-Cornu, F. J.

2012-12-01

244

In this paper we discuss the collisionless transport equations, continuity, momentum and energy conservation, derived from a kinetic exospheric model of the solar wind based on a kappa velocity distribution function of the electrons. The model is stationary and is based on a non-monotonic potential energy for the protons. The present study is carried out for an exobase located at 1.5 solar radii and for two different values of the kappa index. The maximum radial distance considered is equal to one astronomical unit. The moments of the velocity distribution function computed with the kinetic exospheric model for both electrons and protons are introduced into the mass continuity equation, momentum conservation equation and energy conservation equation. The relative importance of various terms in the macroscopic transport equations for each component species are analyzed and discussed. The results obtained show that the kinetic description based on kappa velocity distribution functions satisfies rigorously the t...

Voitcu, Gabriel; Lamy, Herve; Lemaire, Joseph; Echim, Marius

2014-01-01

245

A Community Velocity Model (CVM) for the Sichuan basin and Longmen Shan, China

NASA Astrophysics Data System (ADS)

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; Süss and Shaw, 2003). The model extends from 27.5°-34.5°N and 100°-110°E, 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.

Wang, M.; Hubbard, J.; Shaw, J. H.; Plesch, A.; Jia, D.

2012-12-01

246

Bow shock models for the velocity structure of ultracompact H II regions

NASA Technical Reports Server (NTRS)

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.

Van Buren, Dave; Mac Low, Mordecai-Mark

1992-01-01

247

A model of the near-surface seismic velocity: southern San Joaqin Valley, California

A MODEL OF THE NEAR-SURFACE SEISMIC VELOCITY; SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA A Thesis JAMES GERARD FERRY Submitted to the Graduate College of Texas AErM University in partial fulfillment of t, he requirement for the degree of MASTER... OF SCIENCE August iq87 Major Subject: Geophysics A MODEL OF THE NEAR-SURFACE SEISMIC VELOCITY; SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA A Thesis JAMES GERARD FERRY Approved as to style and content by: Richard L. Carlson (Chairman of Committee) Anth y...

Ferry, James Gerard

1987-01-01

248

NASA Astrophysics Data System (ADS)

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.

Mastin, L. G.; Sherrod, D. R.; Vallance, J. W.; Thornber, C. T.; Ewert, J. W.

2005-12-01

249

A crustal model for Bavaria (Southern Germany) - 3D structure and seismic velocity

NASA Astrophysics Data System (ADS)

A regional 3-D model of the variation of discontinuities and seismic P-wave velocity in the crust of Bavaria has been compiled. Using available regional compilations and published reflection/refraction profiles we created a refined structural model of the Bavarian subsurface down to the Moho-discontinuity. Our recently published maps of the top of the crystalline basement and the base of the Bavarian Molasse basin are used as additional constraints. The model is further supplemented by a velocity model derived from VSP-borehole data throughout the whole of the Molasse basin as well as a local model calculated from a thorough analysis of several thousands of kilometres of seismic reflection profiles. Each model is the result of anisotropic kriging interpolation; the state-wide model makes use of structural assumptions in the form of layer-conformable interpolation. With a block size of 5 km x 5 km x 1 km the resulting model provides a significantly higher resolution of the 3-D variation in structure and seismic velocity distribution than previous existing models for Bavaria. Among other, it will be of great value for more accurate earthquake localisation carried out by the Bavarian seismological service. First comparisons with standard earth models are under way.

Geiss, Erwin; Pamer, Robert; Sattler, Sabine

2010-05-01

250

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

251

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; da Cruz e Silva, Edgar F; Esteves, Pedro José; Fardilha, Margarida

2013-01-01

252

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

Macgregor-Scott, N.; Walter, A.

1988-01-01

253

NASA Astrophysics Data System (ADS)

Surviving in a diverse environment requires corresponding organism responses. At the cellular level, such adjustment relies on the transcription factors (TFs) which must rapidly find their target sequences amidst a vast amount of non-relevant sequences on DNA molecules. Whether these transcription factors locate their target sites through a 1D or 3D pathway is still a matter of speculation. It has been suggested that the optimum search time is when the protein equally shares its search time between 1D and 3D diffusions. In this paper, we study the above problem using Monte Carlo simulations by considering a simple physical model. A 1D strip, representing a DNA, with a number of low affinity sites, corresponding to non-target sites, and high affinity sites, corresponding to target sites, is considered and later extended to a 2D strip. We study the 1D and 3D exploration pathways, and combinations thereof by considering three different types of molecules: a walker that randomly walks along the strip with no dissociation; a jumper that represents dissociation and then re-association of a TF with the strip at later time at a distant site; and a hopper that is similar to the jumper but it dissociates and then re-associates at a faster rate than the jumper. We analyze the final probability distribution of molecules for each case and find that TFs can locate their targets on the experimental time scale even if they spend only 15% of their search time diffusing freely in the solution. This agrees with recent experimental results obtained by Elf et al (2007 Science 316 1191) and is in contrast to previously reported theoretical predictions. Our results also agree with the experimental evidence for the role of chaperons and proteasomes in stabilizing and destabilizing TFs binding, respectively, during the regulation process. Therefore, the results of our manuscript can provide a refined theoretical framework for the process.

Rezania, Vahid; Tuszynski, Jack; Hendzel, Michael

2007-12-01

254

Abstract: Terminal velocity of chickpea, rice and lentil seeds has been experimentally measured by suspending the seeds in an air stream. In order to assessment the effects of seed size and moisture content on terminal velocity a completely randomized design in factorial experiment was carried out. The results showed that size and moisture content have significant effects (pterminal velocityin each three crops. Terminal velocity of chickpea,rice and lentil seeds varied within the 11.13- 15.08, 4.25- 5.01 and 5.08- 6.41 m/s, respectively. In this research the shape of chickpea, rice and lentil respectively were assumed to be spherical, cylindrical and flat and on the basis of this, the mathematical models for predicting the terminal velocity were obtained. The 2 coefficient of determination (R) for chickpea, rice and lentil were respectively 0.977, 0.922 and 0.895. Also the root mean square error (RMSE) for chickpea, rice and lentil were 0.05, 0.087 and 0.097 respectively. Key words: Mathematical model Moisture content Seed shape Seed size Terminal velocity

Salah Ghamari; Hekmat Rabbani; Javad Khazaei

255

NASA Astrophysics Data System (ADS)

A new 1-D velocity model along the southern Cuban margin has been determined using local earthquake data, which are the result of the merged Cuban and Jamaican catalogues. Simultaneous inversion using joint-hypocentre determination was applied to solve the coupled hypocentre-velocity model problem. We obtained a seven-layer model with an average Moho interface at 20 km. The average velocity was found to be 7.6 km s-1 on the top of the crust-mantle transition zone and 6.9 km s-1 in the basaltic layer of the crust. The improvement in the earthquake locations allowed us for the first time to use local seismicity to characterize the activity on local faults and the stress regime in the area. For this purpose, 34 earthquake focal mechanisms were determined along the eastern segments of the Oriente Fault. These solutions are consistent with the known left-lateral strike-slip motion along this major structure as well as with the stress regime of two local structures: (1) the Cabo Cruz Basin and (2) the Santiago deformed belt. The first structure is dominated by normal faults with minor strike-slip components and the second by reverse faults. The shallow seismicity in the Cabo Cruz Basin is associated with fault planes trending N55°-58°E and dipping 38°-45° to the north. The Santiago deformed belt, on the other hand, exhibits diverse fault plane orientations. These local structures account for most of the earthquake activity along the southern Cuban margin. Deep seismicity observed in the Santiago deformed belt, supported by focal mechanisms, suggests underthrusting of the Gonave Microplate beneath the Cuban Block in this area. The principal stress orientations obtained from stress inversion of earthquake focal mechanisms suggest a thrust faulting regime along the Southern Cuban margin. We obtained a nearly horizontal ?1 and nearly vertical ?3, which indicates active compressional deformation along the major Oriente transcurrent fault in agreement with the dominant structural trend associated with the Santiago deformed belt.

Moreno, Bladimir; Grandison, Margaret; Atakan, Kuvvet

2002-11-01

256

NASA Astrophysics Data System (ADS)

In recent years there is an increased interest in solute transport processes in large rivers given their role in delivering nutrients, bacteria and sediment to coastal regions (e.g., rivers in the US Midwest contributing to the Gulf of Mexico hypoxia). While small to medium rivers received a lot of attention in the past few decades, especially from the point of hyporheic exchange and nutrient uptake, relatively few studies have focused on solute transport in large rivers, especially on the dynamics of surface storage zones. Here we report the results of a large-scale tracer study on the St. Clair River, a large international river (discharge ~ 5000 cms) straddling the border between the U.S and Canada that serves as the outflow for Lake Huron. We first describe a fully three-dimensional hydrodynamic model and a 3D particle transport model of the St. Clair River based on FVCOM (Finite Volume Coastal Ocean Model). We then use the 3D particle transport model to generate breakthrough data for evaluating the surface storage dynamics in the river using several classes of one-dimensional solute transport models. In particular, we evaluate the ability of the 1D models to describe both the magnitude and the timing of the peaks. The one-dimensional models examined include multi-rate transient storage (MRTS) models in which the storage zones are arranged either in series or in parallel as well as models based on time and space fractional derivatives. Results indicate that for the 1D models to describe data adequately, the timing of solute pulses which corresponds to various in-channel features such as sand bars or islands should be taken into account.

Anderson, E. J.; Phanikumar, M. S.

2010-12-01

257

Testing Waveform Predictions of 3D Velocity Models against Two Recent

Testing Waveform Predictions of 3D Velocity Models against Two Recent Los Angeles Earthquakes by En). In this paper, we compare the low-frequency seismograms observed in two recent Los Angeles earthquakes, 17 March million synthetic seismograms, have been computed for the Los Angeles region (Graves et al., 2010; Wang et

Chen, Po

258

A mathematical model of turbulence in flows with uniform stationary velocity gradients

Summary The simplest mathematical models of turbulence as a regime of auto-oscillations are considered. Based on the governing equations proposed in Ref. [1], some analytical solutions are obtained for flows with uniform velocity gradients where the equations of the average flow are decoupled from the equations of pulsations. The conditions of stability of these solutions are analyzed.

M. A. Zak

1982-01-01

259

TWO PROPERTIES OF TWO-VELOCITY TWO-PRESSURE MODELS FOR TWO-PHASE FLOWS

that each phase is described by its own pressure, velocity and temperature and on the use of void fractions is the void fraction, k -MARC HÂ´ERARD , KHALED SALEH , AND NICOLAS SEGUIN Â§ Abstract. We study a class of models of compressible

Saleh, Khaled

260

Hyperbolic trigonometry in the Einstein relativistic velocity model of hyperbolic geometry

Hyperbolic geometry is a fundamental aspect of modern physics. We explore in this paper the use of Einstein's velocity addition as a model of vector addition in hyperbolic geometry. Guided by analogies with ordinary vector addition, we develop hyperbolic vector spaces, called gyrovector spaces, which provide the setting for hyperbolic geometry in the same way that vector spaces provide the

A. A. Ungar

2000-01-01

261

Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling

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.

Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.

1999-01-01

262

NASA Astrophysics Data System (ADS)

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.

Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

2014-05-01

263

Effects of geometry and jet velocity on noise associated with an upper-surface-blowing model

NASA Technical Reports Server (NTRS)

The noise characteristics associated with various upper surface blowing configurations were investigated using a small model consisting of a plate and flap assembly (simulated wing with flap) attached to a rectangular nozzle. Nozzle aspect ratio, flow-run length, and flap-deflection angle were the experimental parameters studied. Three nozzle-exit velocities were used. The normalized noise spectra obtained for different nozzle aspect ratios proved to be similar in terms of Strouhal number based on jet velocity and flow-run length. Consequently, the need for knowing local flow velocity and length scales (for example, at the flap trailing edge) as required in some of the existing noise prediction schemes is eliminated. Data are compared with results computed from three different noise prediction schemes, and the validity of each scheme is assessed. A simple method is proposed to evaluate the frequency dependence of acoustic shielding obtained with the simulated wing flap.

Clark, L. R.; Yu, J. C.

1977-01-01

264

Global plate motion models incorporating the velocity field of ITRF96

In this paper, incorporating the ITRF96 velocity field that is free of any tectonic plate model assumption, a new present-day plate motion model relative to the ITRF96 reference frame, called the ITRF96VEL, is determined. The total angular momentum of all tectonic plates with regards to the ITRF96VEL shows that the ITRF96 rotates in a right-handed sense relative to the no-net-rotation

Zhang Qiang; Zhu Wenyao; Xiong Yongqin

1999-01-01

265

Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling

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

M. B. Helgerud; J. Dvorkin; A. Nur; A. Sakai; T. Collett

1999-01-01

266

A model for sound velocity in a two-phase air-water bubbly flow

In this paper, wave propagation in a homogeneous, low void fraction, two-phase air-water bubbly flow is analyzed through the compressibility of a single bubble to derive a P(Ď) relation; the dispersion relation is then derived by a homogeneous model. The phase velocity and attenuation calculated from the model are compared with existing data and are in good agreement. The momentum

N. M. Chung; W. K. Lin; B. S. Pei; Y. Y. Hsu

1992-01-01

267

Three-dimensional P wave velocity model for the San Francisco Bay region, California

A new three-dimensional P wave velocity model for the greater San Francisco Bay region has been derived using the double-difference seismic tomography method, using data from about 5,500 chemical explosions or air gun blasts and approximately 6,000 earthquakes. The model region covers 140 km NE-SW by 240 km NW-SE, extending from 20 km south of Monterey to Santa Rosa and

Clifford H. Thurber; Thomas M. Brocher; Haijiang Zhang; Victoria E. Langenheim

2007-01-01

268

Numerical modelling of foam-cored sandwich plates under high-velocity impact

This paper studies the high-velocity impact response of sandwich plates, with E-glass fibre\\/polyester face-sheets and foam core, using finite-element models developed in ABAQUS\\/explicit code. The failure of the face-sheets was predicted by implementing Hou failure criteria and a procedure to degrade material properties in a user subroutine (VUMAT). The foam core was modelled as a crushable foam material. The numerical

I. Ivańez; C. Santiuste; E. Barbero; S. Sanchez-Saez

2011-01-01

269

Wall effects on terminal falling velocity of spherical particles moving in a Carreau model fluid

Experimental verification of our previous numerical simulation of wall effects on the terminal falling velocity of spherical\\u000a particles moving slowly along the axis of a cylindrical vessel filled with a Carreau model fluid is presented. Dependences\\u000a of the wall correction factor F\\u000a W on the sphere to tube ratio d\\/D and on the dimensionless Carreau model parameters m, ?, and

Jaroslav Strnadel; Miloslav Simon; Ivan Macha?

2011-01-01

270

Towards an improved model of the secular velocities in the western US

NASA Astrophysics Data System (ADS)

Deformation in the western United States, due to tectonic forces associated with the Pacific-North American plate boundary, causes ongoing changes of the positions of points on the Earth’s surface relative to a prescribed reference frame. As a result, accurate surveying in the western US requires an equally accurate description of this deformation to allow survey measurements conducted at different epochs to be corrected for such movement. NOAA’s National Geodetic Survey (NGS) has developed the HTDP (horizontal time dependent positioning) software that enables its users to make these corrections. HTDP contains a model of the secular (continuous) velocity field for the contiguous United States (from 125W to 100W longitude and 31-36N latitude) which is determined using linear interpolation from a series of grid files. The model also contains separate models for the displacements associated with 28 earthquakes. In the contiguous United States, the catalogue of earthquakes is complete since 1984 with the exception of the M 6.7 Nisqually earthquake although in Alaska several major earthquakes are missing. The software is updated periodically to address the displacements associated with new earthquakes, most recently in June 2008 with the release version 3.0. This paper focuses on our model of the secular velocity field. The model of the secular velocities included in HTDP is based on a DEFNODE model containing over 50 blocks in the contiguous US which is later sampled to produce the grid files mentioned above. The model was created in 2007 and has been updated twice to accommodate recent Plate Boundary Observatory velocity solutions. The model contains explicit models of the major faults in the western US and a uniform strain rate tensor for each block. The model currently neglects deformation near major volcanoes in the west or post-seismic effects after great earthquakes. Slip rates on the faults range from over 30 mm/yr for the Juan de Fuca subduction interface and parts of the San Andreas system to near zero (generally sub 1 mm/yr) for faults located in the eastern side of the model. The intra block strain rate tensors are consistent with contraction perpendicular to the coast in blocks immediately adjacent to the west coast and extension further east. NGS is reviewing this model and will update it once reliable velocity vectors are available from an ongoing effort to re-process all existing CORS data back to 1994. The major enhancement that we plan to make to HTDP is the introduction of a vertical velocity field allowing HTDP to map three dimensional positional changes for the first time. In addition we hope to add models of volcanic inflation possibly by adding a Mogi source model. We also plan to add a new grid for the creeping section of the San Andreas fault which will allow for more accurate interpolation of velocities in an area where the velocities often change discontinuously across the fault.

Pearson, C. F.; Snay, R. A.; McCaffrey, R.

2009-12-01

271

NASA Astrophysics Data System (ADS)

In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles - WTB - occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station Săo Joăo do Cariri (Geographic 7.45°S, 36.5°W, dip 20°S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between 20 and 40 ms-1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July-September. No WTB have been observed from November until April in all years 2001-2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds.

Sobral, José H. A.; de Castilho, Vivian M.; Abdu, M. A.; Takahashi, Hisao; Paulino, I.; Gasparelo, Ulisses A. C.; Arruda, Daniela C. S.; Mascarenhas, Matheus; Zamlutti, C. J.; Denardini, C. M.; Koga, Daiki; de Medeiros, A. F.; Buriti, R. A.

2011-07-01

272

NSDL National Science Digital Library

The STP 1DIsing program is a Monte Carlo simulation of a one-dimensional Ising model in equilibrium with a heat bath at temperature T using the Metropolis algorithm. The default is N=64 spins up (s = 1) with no external field with heat bath temperature T=1. STP Ising1D is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp_Ising1D.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-05-28

273

NASA Astrophysics Data System (ADS)

The correlation between the velocity helicity and the energy backscatter is proved in a DNS case of 256 3-grid homogeneous isotropic decaying turbulence. The helicity is then proposed to be employed to improve turbulence models and SGS models. Then Spalart-Allmaras turbulence model (SA) is modified with the helicity to take account of the energy backscatter, which is significant in the region of corner separation in compressors. By comparing the numerical results with experiments, it can be concluded that the modification for SA model with helicity can appropriately represent the energy backscatter, and greatly improves the predictive accuracy for simulating the corner separation flow in compressors.

Liu, Yangwei; Lu, Lipeng; Fang, Le; Gao, Feng

2011-06-01

274

The ability to measure, predict, and compute tsunami flow velocities is of importance in risk assessment and hazard mitigation. Substantial damage can be done by high velocity flows, particularly in harbors and bays, even when the wave height is small. Moreover, advancing the study of sediment transport and tsunami deposits depends on the accurate interpretation and modeling of tsunami flow velocities and accelerations. Until recently, few direct measurements of tsunami velocities existed to compare with model results. During the 11 March 2011 Tohoku Tsunami 328 current meters were in place around the Hawaiian Islands, USA, that captured time series of water velocity in 18 locations, in both harbors and deep channels, at a series of depths. We compare several of these velocity records against numerical simulations performed using the GeoClaw numerical tsunami model, based on solving the depth-averaged shallow water equations with adaptive mesh refinement, to confirm that this model can accurately predict velo...

Arcos, M E M

2014-01-01

275

Exact realization of integer and fractional quantum Hall phases in U(1)×U(1) models in (2+1)d

In this work we present a set of microscopic U(1)×U(1) models which realize insulating phases with a quantized Hall conductivity ?{sub xy}. The models are defined in terms of physical degrees of freedom, and can be realized by local Hamiltonians. For one set of these models, we find that ?{sub xy} is quantized to be an even integer. The origin of this effect is a condensation of objects made up of bosons of one species bound to a single vortex of the other species. For other models, the Hall conductivity can be quantized as a rational number times two. For these systems, the condensed objects contain bosons of one species bound to multiple vortices of the other species. These systems have excitations carrying fractional charges and non-trivial mutual statistics. We present sign-free reformulations of these models which can be studied in Monte Carlo, and we use such reformulations to numerically detect a gapless boundary between the quantum Hall and trivial insulator states. We also present the broader phase diagrams of the models. -- Highlights: •We present a set of models of two species of bosons which realize topological phases. •The models exist on a lattice, and can be realized by local Hamiltonians. •These models exhibit both integer and fractional bosonic Hall effects. •The models can be studied in sign-free Monte Carlo.

Geraedts, Scott D., E-mail: sgeraedt@caltech.edu; Motrunich, Olexei I.

2013-07-15

276

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].

Verley, Jason C.; Axness, Carl L.; Hembree, Charles Edward; Keiter, Eric Richard; Kerr, Bert (New Mexico Institute of Mining and Technology, Socorro, NM)

2012-04-01

277

We developed a neuromusculoskeletal model to simulate the stretch reflex torque induced during a constant angular velocity elbow extension by tuning a set of physiologically-based parameters. Our model extended past modeling efforts in the investigation of elbow spasticity by incorporating explicit musculotendon, muscle spindle, and motoneuron pool models in each prime elbow flexor. We analyzed the effects of changes in motoneuron pool and muscle spindle properties as well as muscle mechanical properties on the biomechanical behavior of the elbow joint observed during a constant angular velocity elbow extension. Results indicated that both motoneuron pool thresholds and gains could be substantially different among muscles. In addition, sensitivity analysis revealed that spindle static gain and motoneuron pool threshold were the most sensitive parameters that could affect the stretch reflex responses of the elbow flexors during a constant angular velocity elbow extension, followed by motoneuron pool gain, and spindle dynamic gain. It is hoped that the model will contribute to the understanding of the underlying mechanisms of spasticity after validation by more elaborate experiments, and will facilitate the future development of more specific treatment of spasticity. PMID:15908257

Koo, Terry K K; Mak, Arthur F T

2006-01-01

278

A 1-D elastic–plastic sea-ice model solved with an implicit Eulerian–Lagrangian method

A physical model for an elastic–plastic rheology is developed and implemented in a numerical sea-ice model. The rheology describes sea ice as behaving as an elastic material for relatively small deformations and as a plastic material for larger ones. The model equations are solved using an Eulerian–Lagrangian method in which the displacement of granular aggregates from an original Eulerian grid

David M. Holland

2007-01-01

279

Comparative Experimental and Modeling Study of Fluid Velocities in Heterogeneous Rocks

NASA Astrophysics Data System (ADS)

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.

Hingerl, F.; Romanenko, K.; Pini, R.; Balcom, B.; Benson, S. M.

2013-12-01

280

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...

281

Structure of the Northern Cascadia Subduction Zone: A 3-D Tomographic P-wave Velocity Model

NASA Astrophysics Data System (ADS)

A large-scale 3D P-wave velocity model to ~60 km depth has been constructed for SW British Columbia and NW Washington through tomographic inversion of first-arrival times from controlled source experiments together with local and regional earthquake travel-time data recorded at permanent stations. 150000 first-arrival times recorded at 225 temporary stations from the 1998 Seismic Hazards Investigation in Puget Sound (SHIPS) experiment, and 60000 first-arrival times from 3000 earthquakes recorded at 91 permanent recording stations are inverted for a minimum structure velocity model. The RMS residuals for the initial and final models are 764 and 132 ms, respectively, which represents a 97% variance reduction. Checkerboard resolution tests indicate a horizontal resolution of 30 km down to 20 km depth, and 50 km down to 60 km depth. The velocity model images the structure of the forearc crust/upper mantle, and the subducting Juan de Fuca plate geometry beneath the region. The sedimentary basins in the Straits of Georgia and Juan de Fuca and Puget Sound are well defined by the velocity model. The mafic Eocene Crescent Terrane (Metchosin Igneous Complex in southern Vancouver Island) is shown to dip beneath the margin to at least 20 km depth. This terrane is regionally extensive beneath the Strait of Juan de Fuca and the Puget lowland, with higher than average velocities of ~7 km/s at approximately 15 km depth. Beneath the Olympic Peninsula, the Core rocks (accretionary sedimentary prism) are under-thrust beneath the Crescent Terrane to a depth of at least 30 km. At this location most seismicity lies within the overlying Crescent Terrane; the under-thrusting Core rocks are aseismic. The strong Crescent terrane seismicity may be due to deformation induced by the underthrusting. Beneath southern Vancouver Island, the subduction thrust zone above the Juan de Fuca plate is characterized by low velocities of 6.4-6.6 km/s at a depth of 25-35 km. Such low velocities may be due to trapped fluids, sheared lower crustal rocks, and possibly underthrust accretionary sedimentary or metamorphic rocks. This low velocity region coincides with the high conductivity region mapped in previous magneto-telluric studies and with a dipping band of seismic reflectors; it is devoid of seismicity. It probably represents a zone of aseismic slip. Low velocities of 7.2-7.6 km/s are observed in the forearc upper mantle beneath the Strait of Georgia and Puget Sound. Such low upper mantle velocities are interpreted to be due to regional serpentinization of cool forearc mantle peridotite by fluids rising from the dehydrating underlying Juan de Fuca crust. The Tertiary sedimentary basins in the Strait of Georgia and Puget lowland lie directly above the zone of forearc upper mantle serpentinization. In contrast, the sedimentary basins in the Strait of Juan de Fuca lie in a synclinal depression in the Crescent volcanic Terrane.

Ramachandran, K.; Hyndman, R. D.; Brocher, T. M.

2004-12-01

282

Towards a Rational Model for the Triple Velocity Correlations of Turbulence

NASA Technical Reports Server (NTRS)

This paper presents a rational approach to modelling the triple velocity correlations that appear in the transport equations for the Reynolds stresses. All existing models of these correlations have largely been formulated on phenomenological grounds and are defective in one important aspect: they all neglect to allow for the dependence of these correlations on the local gradients of mean velocity. The mathematical necessity for this dependence will be demonstrated in the paper. The present contribution lies in the novel use of Group Representation Theory to determine the most general tensorial form of these correlations in terms of all the second- and third-order tensor quantities that appear in the exact equations that govern their evolution. The requisite representation did not exist in the literature and therefore had to be developed specifically for this purpose by Professor G. F. Smith. The outcome of this work is a mathematical framework for the construction of algebraic, explicit, and rational models for the triple velocity correlations that are theoretically consistent and include all the correct dependencies. Previous models are reviewed, and all are shown to be an incomplete subset of this new representation, even to lowest order.

Younis, B. A.; Gatski, T. B.; Speziale, C. G.

1999-01-01

283

NASA Astrophysics Data System (ADS)

Seismic forward modeling is an integral component of microseismic location algorithms, yet there is generally no one correct approach, but rather a range of acceptable approaches that can be used. Since seismic signals are band limited, the length scale of heterogeneities can significantly influence the seismic wavefronts and waveforms. This can be especially important for borehole microseismic monitoring, where subsurface heterogeneity can be strong and/or vary on length scales equivalent to or less than the dominant source wavelength. In this paper, we show that ray-based approaches are not ubiquitously suitable for all borehole microseismic applications. For unconventional reservoir settings, ray-based algorithms may not be suitably accurate for advanced microseismic imaging. Here we focus on exploring the feasibility of using one-way wave equations as forward propagators for full waveform event location techniques. As a feasibility study, we implement an acoustic wide-angle wave equation and use a velocity model interpolation approach to explore the computational efficiency and accuracy of the solution. We compare the results with an exact solution to evaluate travel-time and amplitude errors. The results show that accurate travel-times can be predicted to within 2 ms of the true solution for modest velocity model interpolation. However, for accurate amplitude prediction or for higher dominant source frequencies, a larger number of velocity model interpolations is required.

Angus, D. A.; Aljaafari, A.; Usher, P.; Verdon, J. P.

2014-12-01

284

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.

Grant, K.E.; Taylor, K.E.; Ellis, J.S.; Wuebbles, D.J.

1987-07-01

285

NASA Astrophysics Data System (ADS)

Based on the OV (optimal velocity) model, we in this paper present an extended OV model with the consideration of the honk effect. The analytical and numerical results illustrate that the honk effect can improve the velocity and flow of uniform flow but that the increments are relevant to the density.

Tang, Tie-Qiao; Li, Chuan-Yao; Huang, Hai-Jun; Shang, Hua-Yan

2010-12-01

286

A seismic waves velocity model for Gran Canaria Island from ambient noise correlations

NASA Astrophysics Data System (ADS)

We have analysed continuous ambient seismic noise recorded by a temporary array in Gran Canaria (Canary Islands, Spain) in order to find a velocity model for the top few kilometers. The SISTEVOTENCAN-IGN seismic array consisted of five broadband stations surrounding a sixth central one placed close to Pico de las Nieves, at the center of the island. The array had a radius of 12-14 km, with interstation distances ranging from 10 to 27 km. This network was operative from December 2009 to November 2011. The Green's functions between the 15 pairs of stations have been estimated in the time domain by stacking cross-correlations of 60-s time windows for the whole recording period (~2 years). The effects of several processing adjustments such as 1-bit normalization and spectral whitening are discussed. We observe significant differences (mainly in amplitude) between causal and acausal parts of the estimated Green's functions, which can be associated to an uneven distribution of the seismic noise sources. The application of a phase-matched filter based on an average dispersion curve allowed the effective reduction of some spurious early arrivals and the selection of fundamental-mode Rayleigh wave pulses, making possible an automatic extraction of their group velocities. Then, Rayleigh-wave dispersion curves were retrieved for the set of paths by using frequency-time analysis (FTAN) as well as by following the procedure described by Herrin and Goforth (1977, BSSA) based on the iterative fitting of a phase-matched filter which optimally undisperses the signal. Reliable curves were obtained from 1 s to 6-7 s with group velocities ranging between 1.5 and 2.2 km/s. Some lateral variations in velocity have been detected in spite of the limited spatial coverage and path density, which substantially restricted the resolution. A mean S-wave velocity model has been inverted for this area down to ~3 km.

García-Jerez, Antonio; Almendros, Javier; Martínez-Arévalo, Carmen; de Lis Mancilla, Flor; Luzón, Francisco; Carmona, Enrique; Martín, Rosa; Sánchez, Nieves

2014-05-01

287

The H_2O(+) Velocity Field in Comet Hale-Bopp, Observations and MHD Models

NASA Astrophysics Data System (ADS)

The 3.5-meter WIYN Telescope and its Multi-Object Spectrograph (MOS)obtained simultaneous spectra at many points in the coma of Comet Hale-Bopp between 1996 October and 1997 April. The "Hydra" fiber positioner was used to sample a ring pattern of points about the nucleus with a minimum spacing of 40 arc seconds and a maximum radius of 22.5 arc minutes. A integral field device called "Densepak" was also used to sample a 7 x 13 rectangular pattern of 91, 3 arc second fibers on 4 arc second centers. The bench spectrograph was used in the echelle mode with an interference filter to isolate a single order and covered the wavelength range from 6100 Angstroms to 6400 Angstroms with resolution of approximately 15,000. This spectral region contains the emission features of H_2O(+) . From these data we have extracted the radial velocity of the H_2O(+) . We find the acceleration in the anit-sun direction to be of the order of 20 cm sec(-) (2) . The measured velocity fields have been compared to full 3D MAUS-MHD models. The models suggest that the degree ofconfinement of the coma and the velocities attained in the anti-sun direction depend sensitively upon the velocity of the ambient solar wind. The observed velocity fields are consistent with the confinement of the near coma by a relatively slow solar wind while the speeds attained at distances of the order of a million kilometers in the anti-sun direction are more like those produced by a fast solar wind. The observations were obtained at a time when Hale-Bopp was at intermediate heliocentric latitudes where the solar wind speed is known to change rapidly from slow to fast modes. This situation is under further investigation.

Anderson, C. M.; Combi, M. R.; Gombosi, T.; Hansen, K. C.

1998-09-01

288

Modeling Blast and High-Velocity Impact of Composite Sandwich Panels

NASA Astrophysics Data System (ADS)

Analytical models for predicting the deformation and failure of composite sandwich panels subjected to blast and projectile impact loading are presented in this paper. The analytical predictions of the transient deformations and damage initiation in the composite sandwich panels were compared with finite element solutions using ABAQUS Explicit. For the blast model, the predicted transient deformation of the sandwich panel was within 7%of FEA results, while the predicted damage initiation using Hashin's composite failure criteria was about 15%higher than FEA results in most cases. For the high velocity impact model, the predicted transient deformations were within 20%of FEA results.

Fatt, Michelle S. Hoo; Palla, Leelaprasad; Sirivolu, Dushyanth

289

Numerical Modelling of Glass Fibre Reinforced Laminates Subjected to a Low Velocity Impact

This paper presents a series of numerical predictions of the perforation behaviour of glass fibre laminates subjected to quasi-static and low-velocity impact loading. Both shear and tensile failure criteria were used in the finite element models to simulate the post-failure processes via an automatic element removal procedure. The appropriate material properties, obtained through a series of uniaxial tension and bending tests on the composites, were used in the numerical models. Four, eight and sixteen ply glass fibre laminates panels were perforated at quasi-static rates and under low-velocity impact loading. Reasonably good correlation was obtained between the numerical simulations and the experimental results, both in terms of the failure modes and the load-deflection relationships before and during the penetration phase. The predicted impact energies of the GFRP panels were compared with the experimental data and reasonable agreement was observed.

Fan, J. Y.; Guana, Z. W.; Cantwell, W. J. [University of Liverpool, Department of Engineering, Liverpool L69 3GQ (United Kingdom)

2010-05-21

290

Using measurements in urban areas to estimate turbulent velocities for modeling dispersion

NASA Astrophysics Data System (ADS)

This study extends a study [Princevac, M., Venkatram, A., 2007. Estimating micrometeorological inputs for modeling dispersion in urban areas during stable conditions. Atmospheric Environment, doi:10.1016/j.atmosenv.2007.02.029.] in which mean winds and temperatures measured at one or two levels on towers located in urban areas were fitted to Monin-Obukhov similarity equations to obtain estimates of micrometeorological variables required in modeling dispersion in the stable boundary layer. This study shows that such methods are also useful in unstable conditions: measurements of the mean wind speed and the standard deviation of temperature fluctuations, ?T, at one level on a tower yield estimates of surface heat flux, surface friction velocity, and standard deviations of turbulent velocities that are within a factor of two of values observed at two urban sites over 80% of the time.

Venkatram, Akula; Princevac, Marko

2008-05-01

291

NASA Astrophysics Data System (ADS)

Our knowledge of the inter-annual evolution of glacier dynamics suggests that subglacial water pressure is one of the major variables that impact glacier velocities. This coupling is confirmed by a number of observations of water related speed-ups on mountain glaciers as well as larger ice streams. Subglacial hydrological models that assess the water pressure at the base of glaciers along with their sliding velocities are emerging. These models are designed to account for inefficient and efficient drainage systems at the base of the ice. The different methods which are used are based on a number of parameters that are difficult to quantify and for which the only fitting method seems to be the comparison of model results to field observations. Here, we present a new approach, based on the double continuum method, in which water pressure is computed using the Darcy equation for two different media. A sediment layer with small hydraulic conductivity represents the inefficient drainage system and another layer with a much larger conductivity plays the role of an efficient drainage system. The application of this model to a small Alpine glacier yields convincing results, even when relying to a weakly constrained subset of parameters. The present study further investigates model parameterization and the applicability to larger ice streams. The choice of Russell Glacier (West Greenland) as a baseline experiment for our model is natural given the amount of hydrological and surface velocity data gathered in this area. These sets of data allow a realistic parameterization of the hydrological model for the former and a mean of validating the coupled model results for the latter.

de Fleurian, B.; Morlighem, M.; Seroussi, H. L.; Larour, E. Y.; Rignot, E. J.

2013-12-01

292

NASA Astrophysics Data System (ADS)

Proper models of cell geometry are needed for biophysical analysis of cellular electrical phenomena. This work compares various mathematical volume-models for normal human erythrocytes (discocyte) possessing biconcave-discoid form to simulate translational dielectrophoretic velocity spectra of erythrocyte suspensions induced in a traveling electric field over a frequency range from 1 kHz to 15 MHz. The non-spherical volumes of the oblate-spheroid, the prolate-spheroid, and the oval of Cassini and the "Bun-model" were numerically evaluated according to the normal range of cellular dimension values for mammalian erythrocytes. The latter model is the novel approach derived to provide a more realistic model for the shape of discocytes in the thin biconcave-disc form with a toroidal rim. The bun model is also more rugged than the Cassini equation. Using the actual cell dimensions for calculations, the numerical results among these calculated cell volumes revealed large and significant differences with respect to the Bun-model of +32.09%, +8.95%, and -8.45% for prolate-spheroid, Cassini's equation, and oblate-spheroid, respectively. These large volume deviations shift the magnitude of the sharp peak in dielectrophoretic velocity spectra to lower values with differences of +189.28%, +7.66%, and -9.49%, respectively. For traveling wave dielectrophoresis, similar results were found for the sharp peak of +145.76%, +7.71%, and -9.50%, respectively. The suitability of the Bun-model was verified by curve-fitting of the cell velocity spectra between experimental and theoretical curves, which gave the maximum discrepancies of less than ±10%.

Bunthawin, Sakshin; Ritchie, Raymond J.

2013-01-01

293

Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight

NASA Technical Reports Server (NTRS)

Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 13 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage.

Berry, John D.

1997-01-01

294

Effects of a space modulation on the behavior of a 1D alternating Heisenberg spin-1/2 model

NASA Astrophysics Data System (ADS)

The effects of a magnetic field (h) and a space modulation (?) on the magnetic properties of a one-dimensional antiferromagnetic-ferromagnetic Heisenberg spin-1/2 model have been studied by means of numerical exact diagonalization of finite size systems, the nonlinear ? model, and a bosonization approach. The space modulation is considered on the antiferromagnetic couplings. At ? = 0, the model is mapped to a gapless Lüttinger liquid phase by increasing the magnetic field. However, the space modulation induces a new gap in the spectrum of the system and the system experiences different quantum phases which are separated by four critical fields. By opening the new gap, a magnetization plateau appears at \\frac {1}{2}M_{ {sat}} . The effects of the space modulation are reflected in the emergence of a plateau in other physical functions such as the F-dimer and the bond-dimer order parameters, and the pair-wise entanglement.

Mahdavifar, Saeed; Abouie, Jahanfar

2011-06-01

295

Accounting for uncertainty in the analysis of overlap layer mean velocity models

NASA Astrophysics Data System (ADS)

When assessing the veracity of mathematical models, it is important to consider the uncertainties in the data used for the assessment. In this paper, we study the impact of data uncertainties on the analysis of overlap layer models for the mean velocity in wall-bounded turbulent flows. Specifically, the tools of Bayesian statistics are used to calibrate and compare six competing models of the mean velocity profile, including multiple logarithmic and power law forms, using velocity profile measurements from a zero-pressure-gradient turbulent boundary layer and fully developed turbulent pipe flow. The calibration problem is formulated as a Bayesian update of the joint probability density function for the calibration parameters, which are treated as random variables to characterize incomplete knowledge about their values. This probabilistic formulation provides a natural treatment of uncertainty and gives insight into the quality of the fit, features that are not easily obtained in deterministic calibration procedures. The model comparison also relies on a Bayesian update. In particular, the relative probabilities of the competing models are updated using the calibration data. The resulting posterior probabilities quantify the relative plausibility of the competing models given the data. For the boundary layer, results are shown for five subsets of the turbulent boundary layer data due to Österlund, including different Reynolds number and wall distance ranges, and multiple assumptions regarding the magnitude of the uncertainty in the velocity measurements. For most choices, multiple models have relatively high posterior probability, indicating that it is difficult to distinguish between the models. For the most inclusive data sets—i.e., the largest ranges of Reynolds number and wall distance—the first-order logarithmic law due to Buschmann and Gad-el-Hak is significantly more probable, given the data, than the other models evaluated. For the pipe flow, data from the Princeton Superpipe is analyzed for the region where McKeon et al. find a logarithmic layer (600 ? y+ ? 0.12?+). As in the boundary layer case, the first-order logarithmic law by Buschmann and Gad-el-Hak is most probable. However, the parameter values required to fit the data are different from those necessary for the boundary layer. Thus, the present analysis confirms the differences between the boundary layer and pipe flow results observed elsewhere in the literature, casting serious doubt on the universality of overlap layer model parameters.

Oliver, Todd A.; Moser, Robert D.

2012-07-01

296

It is now well established that non-thermal, high-pressure plasmas can be initiated and sustained between a microhollow cathode discharge (MHCD) acting as a plasma cathode and a third electrode placed some distance away. To investigate the properties of the plasma created in such a microcathode sustaind (MCS) discharge configuration, we have developed a 2D quasi-neutral model of a radially expanding

E. Munoz-Serrano; G. Hagelaar; J. P. Boeuf; L. C. Pitchford

2006-01-01

297

NASA Technical Reports Server (NTRS)

The purpose of the work is to demonstrate that the flat test panel substrate temperatures are consistent with analysis predictions for MCC-1 applied to a aluminum substrate. The testing was performed in an aerothermal facility on samples of three different thicknesses of MCC-1 on an aluminum substrate. The results of the test were compared with a Transient Thermal model. The key assumptions of the Transient Thermal model were: (1) a one-dimensional heat transfer; (2) a constant ablation recession rate (determined from pre and post-test measurements); (3) ablation temperature of 540 degrees F; (4) Char left behind the ablation front; and (5) temperature jump correction for incident heat transfer coefficient. Two methods were used to model the heating of bare MCC-1: (1) Directly input surface temperature as a function of time; and (2) Aerothermal heating using calibration plate data and subtracting the radiation losses to tunnel walls. The results are presented as graphs. This article is presented in Viewgraph format.

Reinarts, Thomas R.; Crain, William K.; Stuckey, C. Irvin; Palko, Richard L.

1998-01-01

298

NASA Astrophysics Data System (ADS)

The ability to measure, predict, and compute tsunami flow velocities is of importance in risk assessment and hazard mitigation. Substantial damage can be done by high velocity flows, particularly in harbors and bays, even when the wave height is small. Moreover, advancing the study of sediment transport and tsunami deposits depends on the accurate interpretation and modeling of tsunami flow velocities and accelerations. Until recently, few direct measurements of tsunami velocities existed to compare with model results. During the 11 March 2011 Tohoku Tsunami 328 current meters were in place around the Hawaiian Islands, USA, that captured time series of water velocity in 18 locations, in both harbors and deep channels, at a series of depths. We compare several of these velocity records against numerical simulations performed using the GeoClaw numerical tsunami model, based on solving the depth-averaged shallow water equations with adaptive mesh refinement, to confirm that this model can accurately predict velocities at nearshore locations. Model results demonstrate tsunami current velocity is more spatially variable than wave form or height and therefore may be a more sensitive variable for model validation.

Arcos, M. E. M.; LeVeque, Randall J.

2014-11-01

299

NASA Astrophysics Data System (ADS)

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.

Gallovic, Frantisek; Pacor, Francesca; Zahradnik, Jiri; Luzi, Lucia; Puglia, Rodolfo; D'Amico, Maria

2014-05-01

300

Finite Element Modeling (FEM) is increasingly used as a tool in the field of injury biomechanics. One challenge in validating human body FEMs is quantifying the effect that variability of input parameters from experiments can have on the model?s predictions. The objective of this study was to conduct a parametric study on a validation simulation of the Global Human Body Models Consortium?s 50th percentile male model. The selected case was an oblique hub impact to the thoracoabdominal region of the model?s right side. The hub impactor was a 23.4 kg cylinder, with a 15cm diameter, given an initial velocity. The location and velocity of the impactor were varied based on the reported variance of the experiments used as the basis of these simulations. The effect that these changes have on the peak force was observed. Fifteen cases were simulated, giving results for five locations and three velocities based on a nominal velocity (6.7 m/s) and placement. The nominal impactor location was 7.5 cm below the xiphoid process and 30° from lateral, as described in the literature. The nominal velocity was varied ± 2 standard deviations from the average experimental velocity. The study results indicate that there were both location-based and velocity-based dependencies. There was a 5.5% increase in peak force when increasing the velocity by 0.3 m/s and a 6.4% decrease in peak force when decreasing the velocity by 0.3 m/s. Additionally, the Force vs. Time curves of the same impactor location showed a trend of similar curve shapes. The impactor location also had an impact on the number of rib fractures predicted by the model as well as the time of the peak force. The parameters used in this study represent typical experimental variation in location and velocity and show the model is reasonably robust within range of plausible impacts. PMID:22846319

Vavalle, Nicholas A; Moreno, Daniel P; Stitzel, Joel D; Gayzik, F Scott

2012-01-01

301

Modeling shock-unsteadiness and pressure-velocity correlation in shock/turbulence interaction

NASA Astrophysics Data System (ADS)

The RANS (Reynolds Averaged Navier Stokes) equations can yield significant error when applied to practical flows involving shock waves (Knight et al, AIAA Paper 2002-0437, 2002). We use the interaction of homogeneous isotropic turbulence with a normal shock to suggest improvements in k-? models applied to shock/turbulence interaction. Mahesh et al (Journal of Fluid Mechanics, vol. 334, pp. 353-379, 1997) and Lee et al (Journal of Fluid Mechanics, vol. 340, pp. 225-247, 1997) present direct numerical simulation and linear analysis of this flow, where it is found that shock unsteadiness and distortion, pressure-velocity correlation and upstream entropy fluctuations play an important role in the interaction. These effects are not included in current RANS models which yield very high amplification of the turbulent kinetic energy, k, across the shock. We modify the k-equation to include terms due to shock unsteadiness and distortion, and model these additional terms using linear analysis. The effect of pressure- velocity correlations and dissipation rate are similarly modeled based on linear analysis results. These modifications improve the model predictions considerably, and the new model is found to match the DNS data well. The work is supported by AFOSR and AHPCRC.

Sinha, Krishnendu; Mahesh, Krishnan; Candler, Graham V.

2002-11-01

302

NASA Astrophysics Data System (ADS)

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.

Petropoulos, George P.; Carlson, Toby N.

2013-04-01

303

Markov random field modelling for fluid distributions from the seismic velocity structures

NASA Astrophysics Data System (ADS)

Recent development of geophysical observations, such as seismic tomography, seismic reflection method and geomagnetic method, provide us detailed images of the earth's interior. However, it has still been difficult to interpret these data geologically, including predicting lithology and fluid distributions, mainly because (1) available data usually have large noise and uncertainty, and (2) the number of observable parameters is usually smaller than the number of target parameters. Therefore, the statistical analyses of geophysical data sets are essential for the objective and quantitative geological interpretation. We propose the use of Markov random field (MRF) model to geophysical image data as an alternative to classical deterministic approaches. The MRF model is a Bayesian stochastic model using a generalized form of Markov Chains, and is often applied to the analysis of images, particularly in the detection of visual patterns or textures. The MRF model assumes that the spatial gradients of physical properties are relatively small compared to the observational noises. By hyperparameter estimation, the variances of noises can be appropriately estimated only from available data sets without prior information about observational noises. In this study, we try to image the fluid distributions based on the seismic velocity structure by using the Markov random field model. According to Nakajima et al. (2005), seismic velocities (Vp and Vs) are expressed as functions of porosity and pore geometry using the unified formulation proposed by Takei (2002). Additionally, the spatial continuity of porosity and pore geometry is incorporated by Gaussian Markov Chains as prior probabilities. The most probable estimation can be obtained by maximizing the posterior probability of the fluid distribution given the observed velocity structures. In the present study, the steepest descent method was implemented in order to minimize the free energy (i.e. maximize the posterior probability) using the Markov chain Monte Carlo (MCMC) algorithm. First, synthetic inversion tests are conducted in order to investigate the effectiveness and validity of the proposed model. Then, we apply the model to the natural data sets of the seismic velocity structures in the mantle wedge of the NE Japan (Matsubara et al. 2008), by assuming the physical properties other than porosity and pore geometry, such as temperature and type of fluid. Finally, we discuss the validity of the assumptions and possible developments of our model.

Kuwatani, T.; Nagata, K.; Okada, M.; Toriumi, M.

2011-12-01

304

Discrete Kinetic Models for Molecular Motors: Asymptotic Velocity and Gaussian Fluctuations

NASA Astrophysics Data System (ADS)

We consider random walks on quasi one dimensional lattices, as introduced in Faggionato and Silvestri (Random Walks on Quasi One Dimensional Lattices: Large Deviations and Fluctuation Theorems, 2014). This mathematical setting covers a large class of discrete kinetic models for non-cooperative molecular motors on periodic tracks. We derive general formulas for the asymptotic velocity and diffusion coefficient, and we show how to reduce their computation to suitable linear systems of the same degree of a single fundamental cell, with possible linear chain removals. We apply the above results to special families of kinetic models, also catching some errors in the biophysics literature.

Faggionato, Alessandra; Silvestri, Vittoria

2014-12-01

305

Spectral analysis of surface waves method to assess shear wave velocity within centrifuge models

NASA Astrophysics Data System (ADS)

The method of the spectral analysis of surface waves (SASW) is tested out on reduced scale centrifuge models, with a specific device, called the mini Falling Weight, developed for this purpose. Tests are performed on layered materials made of a mixture of sand and clay. The shear wave velocity VS determined within the models using the SASW is compared with the laboratory measurements carried out using the bender element test. The results show that the SASW technique applied to centrifuge testing is a relevant method to characterize VS near the surface.

Murillo, Carol Andrea; Thorel, Luc; Caicedo, Bernardo

2009-06-01

306

NASA Technical Reports Server (NTRS)

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.

Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.

2007-01-01

307

NASA Astrophysics Data System (ADS)

The characteristic features of the marine boundary layer (MBL) over the Bay of Bengal during the southwest monsoon and the factors influencing it are investigated. The Bay of Bengal and Monsoon Experiment (BOBMEX) carried out during July-August 1999 is the first observational experiment under the Indian Climate Research Programme (ICRP). A very high-resolution data in the vertical was obtained during this experiment, which was used to study the MBL characteristics off the east coast of India in the north and south Bay of Bengal. Spells of active and suppressed convection over the Bay were observed, of which, three representative convective episodes were considered for the study. For this purpose a one-dimensional multi-level PBL model with a TKE-? closure scheme was used. The soundings, viz., the vertical profiles of temperature, humidity, zonal and meridional component of wind, obtained onboard ORV Sagar Kanya and from coastal stations along the east coast are used for the study. The temporal evolution of turbulent kinetic energy, marine boundary layer height (MBLH), sensible and latent heat fluxes and drag coefficient of momentum are simulated for different epochs of monsoon and monsoon depressions during BOBMEX-99.The model also generates the vertical profiles of potential temperature, specific humidity, zonal and meridional wind. These simulated values compared reasonably well with the observations available from BOBMEX.

Sam, N. V.; Mohanty, U. C.; Satyanarayana, A. N. V.

2003-06-01

308

NASA Astrophysics Data System (ADS)

This paper discusses a new approach for investigating the seismic wave velocity of rock, specifically carbonates, as affected by their pore structures. While the conventional routine of seismic velocity measurement highly depends on the extensive laboratory experiment, the proposed approach utilizes the digital rock physics view which lies on the numerical experiment. Thus, instead of using core sample, we use the thin section image of carbonate rock to measure the effective seismic wave velocity when travelling on it. In the numerical experiment, thin section images act as the medium on which wave propagation will be simulated. For the modeling, an advanced technique based on artificial neural network was employed for building the velocity and density profile, replacing image's RGB pixel value with the seismic velocity and density of each rock constituent. Then, ultrasonic wave was simulated to propagate in the thin section image by using finite difference time domain method, based on assumption of an acoustic-isotropic medium. Effective velocities were drawn from the recorded signal and being compared to the velocity modeling from Wyllie time average model and Kuster-Toksoz rock physics model. To perform the modeling, image analysis routines were undertaken for quantifying the pore aspect ratio that is assumed to represent the rocks pore structure. In addition, porosity and mineral fraction required for velocity modeling were also quantified by using integrated neural network and image analysis technique. It was found that the Kuster-Toksoz gives the closer prediction to the measured velocity as compared to the Wyllie time average model. We also conclude that Wyllie time average that does not incorporate the pore structure parameter deviates significantly for samples having more than 40% porosity. Utilizing this approach we found a good agreement between numerical experiment and theoretically derived rock physics model for estimating the effective seismic wave velocity of rock.

Wardaya, P. D.; Noh, K. A. B. M.; Yusoff, W. I. B. W.; Ridha, S.; Nurhandoko, B. E. B.

2014-09-01

309

NASA Astrophysics Data System (ADS)

In this paper the reformulation of Trofimov-Park (TP) model, [V.I. Trofimov, Appl. Surf. Sci. 219 (2003) 93), of thin film roughness evolution during nucleation and growth of islands in case of simultaneous nucleation is presented. The calculation of TP restricted to one-dimensional triangular islands has been extended to both the one-dimensional elliptical case and to the pyramidal two-dimensional one. The kinetics of the interface width, w, and the height-height autocorrelation function G, through which the correlation length ? has been defined, have been estimated. Moreover, w(?) and ?(?), where ? is the fraction of the covered substrate, if properly rescaled to the density of nuclei N and to the aspect ratio of islands, are universal functions that, for a conspicuous range of ?, obey a power law with the exponent depending upon island shape.

Pacchiarotti, Barbara; Fanfoni, Massimo; Tomellini, Massimo

2005-12-01

310

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.

Santini, E.; Steinheimer, J.; Bleicher, M. [Institut fuer Theoretische Physik, Goethe-Universitaet, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main (Germany); Schramm, S. [Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main (Germany)

2011-07-15

311

Development of the EUREF Velocity Model - Status and Roadmap for Future Work

NASA Astrophysics Data System (ADS)

Interplate and intraplate deformations are present all over Europe. They can be subdivided by their spatial or temporal nature as well as their magnitude. For example, different, partly overlapping processes are related to several geodynamic zones such as plate boundaries, micro-plates, volcanoes, (formerly) glaciated areas, hydrological basins etc. On the other side, there are long-term processes such as the Fennoscandian post-glacial rebound, episodic events such as earthquakes and many temporarily intermediate deformations from e.g. volcanic swelling or anthropogenic influences due to oil or gas extraction or CO2 sequestration. The corresponding deformations of different scales are measured as three-dimensional crustal velocities by Global Navigation Satellite System (GNSS) reference stations with meanwhile sufficient detail and accuracy. The IAG Reference Frame Sub-Commission for Europe (EUREF) working group on "Deformation models" aims at obtaining velocity models for Europe and adjacent areas and significantly improving the prediction of the time evolution of coordinates, thus overcoming the limitations in the use of the European Terrestrial Reference System 1989 (ETRS89). A general understanding of the physics behind such a velocity field is also a major goal. In particular, the working group will model and correct for interplate and intraplate deformations, while using the reference frame, and thus extend the useful lifetime of a realisation of the ETRS89. Hence, the purpose of this working group are twofold; first, pure scientific interests in improved knowledge of the surface deformations of Eurasia and adjacent areas, and second, providing a valuable tool in the management and use of the national realisations of the ETRS89. The work will strongly benefit from sophisticated infrastructures such as the European Plate Observing System (EPOS). Key information for improved knowledge of crustal deformations is observed motions at stations. This includes station velocities, and possible station position shifts for the case of episodic events, where the European Permanent Network (EPN) is considered as the core infrastructure. However, a denser network of GNSS stations than EPN will be needed to sample the crustal deformations sufficiently well. The availability of velocity solutions including additional stations compared to the EPN stations provided by other initiatives and projects is therefore of high interest for this initiative. The key input for the working group is the EPN densification where the dense national permanent GNSS networks are integrated with the EPN on the weekly SINEX level. There are three major activities for the development of this solution: An evaluation of station velocities, Development of a crustal deformation model for Europe, and Consideration of such a deformation model in maintenance and use of national realisations of ETRS89. The presentation will give an overview of the current status in the evaluation of station velocities based on initiatives and projects in the last two decades as well as an outlook to future work including details to the model development.

Lidberg, Martin; Steffen, Holger; Altamimi, Zuheir; Bruyninx, Carine; Caporali, Alessandro; Dousa, Jan; Habrich, Heinz; Kenyeres, Ambrus; da Silva Fernandes, Rui Manuel; Stangl, Günter

2013-04-01

312

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.

Ballard, Sanford; Encarnacao, Andre Villanova; Begnaud, Michael A. (Los Alamos National Laboratories); Rowe, Charlotte A. (Los Alamos National Laboratories); Lewis, Jennifer E.; Young, Christopher John; Chang, Marcus C.; Hipp, James Richard

2010-05-01

313

Velocity and Attenuation Structure of the Tibetan Lithosphere Under the Hi-CLIMB Array From earthquakes in Tibet recorded by the Hi-CLIMB experiment, Pn attributes are used to constrain the velocity gradient and attenuation structure of the Tibetan lithosphere under the Hi-CLIMB array. Numerical modeling

Nowack, Robert L.

314

A Global Model of The Light Curves and Expansion Velocities of Type II-plateau Supernovae

NASA Astrophysics Data System (ADS)

We present a new self-consistent and versatile method that derives photospheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photometric measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ~230 velocity and ~6800 mag measurements distributed over 21 photometric passbands spanning wavelengths from 0.19 to 2.2 ?m. The light-curve differences among the Type II-Plateau supernovae are well modeled by assuming different rates of photospheric radius expansion, which we explain as different density profiles of the ejecta, and we argue that steeper density profiles result in flatter plateaus, if everything else remains unchanged. The steep luminosity decline of Type II-Linear supernovae is due to fast evolution of the photospheric temperature, which we verify with a successful fit of SN 1980K. Eliminating the need for theoretical supernova atmosphere models, we obtain self-consistent relative distances, reddenings, and nickel masses fully accounting for all internal model uncertainties and covariances. We use our global fit to estimate the time evolution of any missing band tailored specifically for each supernova, and we construct spectral energy distributions and bolometric light curves. We produce bolometric corrections for all filter combinations in our sample. We compare our model to the theoretical dilution factors and find good agreement for the B and V filters. Our results differ from the theory when the I, J, H, or K bands are included. We investigate the reddening law toward our supernovae and find reasonable agreement with standard \\mathscr{R}_V? 3.1 reddening law in UBVRI bands. Results for other bands are inconclusive. We make our fitting code publicly available.

Pejcha, Ond?ej; Prieto, Jose L.

2015-02-01

315

NASA Astrophysics Data System (ADS)

Apart from some exceptions (e.g. certain convection movements, small scale turbulence, or surface gravity wave), vertical velocities in the ocean are generally too weak to be measured. In particular, that is the case of the vertical movements associated to the coastal upwelling dynamics. This prevents any accurate assessment of the vertical fluxes (mass, heat, oxygen and carbon) which are of particular importance when it comes to quantify the nutrient enrichment. As a result, questions related to the source, position, and debit of a coastal upwelling are still largely opened. In a first part, we analyze the vertical velocity field in a series of models of increasing complexity : from Ekman theory (unstratified theory in which the upwelling structure is controlled by the interaction of the surface and bottom boundary layers) to the primitive equation of a realistic simulation of the Senegalese coastal upwelling (ROMS). Then in the second part, we present preliminary results from the Upsen cruise (9-18 march 2012) in which we will seek to measure horizontal flows associated with the South Senegal upwelling in order to estimate the corresponding vertical velocities.

Estrade, P.

2012-04-01

316

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

Sénégond, Nicolas; Boulmé, Audren; Plag, Camille; Teston, Franck; Certon, Dominique

2013-07-01

317

Velocity-gradient probability distribution functions in a lagrangian model of turbulence

NASA Astrophysics Data System (ADS)

The Recent Fluid Deformation Closure (RFDC) model of lagrangian turbulence is recast in path-integral language within the framework of the Martin–Siggia–Rose functional formalism. In order to derive analytical expressions for the velocity-gradient probability distribution functions (vgPDFs), we carry out noise renormalization in the low-frequency regime and find approximate extrema for the Martin–Siggia–Rose effective action. We verify, with the help of Monte Carlo simulations, that the vgPDFs so obtained yield a close description of the single-point statistical features implied by the original RFDC stochastic differential equations.

Moriconi, L.; Pereira, R. M.; Grigorio, L. S.

2014-10-01

318

Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

NASA Astrophysics Data System (ADS)

The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the ?nie?nik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model's performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation's performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model's performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity = 1.0 m/s and mean absolute error of direction = 30°. The author concludes that, within specific meteorological conditions (relatively strong and constant synoptic forcing) and using the aforementioned input data, the Canyon model provides fairly acceptable results. Similarly, the quality of the presented remote sensing data is suitable for wind velocity modelling in the proposed resolution. However, CLC 2006 land use data should be first verified with a higher-resolution satellite or aerial imagery.

Jancewicz, Kacper

2014-06-01

319

NASA Astrophysics Data System (ADS)

The Lower Tagus Valley, in Portugal, has a complex tectonic history and a seismic activity determined by the proximity to the Eurasian - Nubian tectonic plate boundary. Some of these earthquakes were destructive and produced in large ruptures in offshore structures located southwest of the Portuguese coastline; other moderate earthquakes were produced by local (onshore) sources. In the last years, various studies have successfully obtained strong-ground motion synthesis for the Lower Tagus Valley using the finite difference method. To improve the velocity model of this sedimentary basin obtained by geophysical and geological data, we analyse ambient seismic noise measurements by applying the horizontal to vertical spectral ratio method (HVSR). The study reveals the dependence of the frequency and the amplitude of the low frequency peaks (0.2-2 Hz) of the HVSR with the sediments thickness. We have obtained the depth of the basement of the Cenozoic basin by inversion of such ratios imposing constraints from seismic reflection, boreholes, seismic sounding, and gravimetric and magnetic data. The obtained velocity model was confirmed by comparison between real HVSR curves with synthetic ones obtained by 3D seismic wave simulation using a finite-difference method. This technique proved to be practical and useful to improve the subsurface structures and the three-dimensional model of the basin.

Borges, José; Torres, Ricardo; Silva, Hugo; Caldeira, Bento; Bezzeghoud, Mourad; Carvalho, Joăo; Furtado, Augusto

2014-05-01

320

Comparing the 2MTF and 6dFGS Peculiar Velocity Surveys to models from redshift surveys

NASA Astrophysics Data System (ADS)

The 6dF Galaxy Survey (6dFGS) and 2MASS Tully-Fisher Survey (2MTF) are large galaxy peculiar velocity surveys of the local universe, providing distances and peculiar velocities for thousands of galaxies, derived via the Fundamental Plane and Tully-Fisher relations respectively. We compare these observed velocity fields to reconstructed peculiar velocity field models derived from redshift surveys such as the 2MASS Redshift Survey (2MRS) and the IRAS Point Source Redshift Survey (PSCz), addressing the question of whether the galaxy distribution traces the matter distribution, and whether the observed velocity fields include a "residual bulk flow" not predicted by the models. This research was conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020.

Springob, Christopher M.; Hong, Tao; Magoulas, Christina; Colless, Matthew; Staveley-Smith, Lister; Erdogdu, Pirin; Jones, D. Heath; Lucey, John R.; Masters, Karen; Mould, Jeremy R.; Jarrett, Tom; Koribalski, Baerbel; Macri, Lucas M.; Scrimgeour, Morag

2015-01-01

321

Feasible domain of Walker's unsteady wall-layer model for the velocity profile in turbulent flows.

The present work studies, in detail, the unsteady wall-layer model of Walker et al. (1989, AIAA J., 27, 140 - 149) for the velocity profile in turbulent flows. Two new terms are included in the transcendental non-linear system of equations that is used to determine the three main model parameters. The mathematical and physical feasible domains of the model are determined as a function of the non-dimensional pressure gradient parameter (p+). An explicit parameterization is presented for the average period between bursts (), the origin of time () and the integration constant of the time dependent equation (A0) in terms of p+. In the present procedure, all working systems of differential equations are transformed, resulting in a very fast computational procedure that can be used to develop real-time flow simulators. PMID:25590746

Mikhailov, Mikhail D; Freire, Atila P Silva

2014-12-01

322

NASA Astrophysics Data System (ADS)

Deep convection plays a key role in determining global atmospheric composition of the upper troposphere by the fast uplift of HOx radical and ozone precursors to the upper troposphere. Formaldehyde (HCHO) is one important gas precursor. It is the most abundant carbonyl compound originating from both primary processes and photooxidation of volatile organic compounds. Thus, determining its source strength to the upper troposphere is important for estimating ozone production. However processes governing its fate are multiple and complex including dynamics (entrainment and detrainment), multiphase chemistry and cloud microphysics. As a result, the flux of formaldehyde to the upper troposphere is still uncertain. The goal of this study is to examine the redistribution of formaldehyde in tropical mesoscale convective systems (MSC) and to estimate its sources and sinks during convective transport to the upper troposphere. The novelty here is to combine 1D modelling (Meso NH model) and formaldehyde aircraft observations. Observations were collected over West Africa during the monsoon period (July-August 2006) of the AMMA experiment. Four aircrafts (English BAe-146, French ATR-42 and Falcon-20 and German Falcon-20) were deployed over a large domain (long.: -8°E-5°W, lat. 4°N-20°N, alt.: 0 12 km) with formaldehyde measuring instruments on board. First, this presentation will point out the construction of a comprehensive and consistent data set of formaldehyde by ensuring data comparability thanks to aircraft intercomparison flights, multiple chemical tracer approach (CO, O3 and relative humidity) and a spatial gridding of the domain. Then formaldehyde spatial variability will be examined under background and convective conditions. Finally, the relative importance of transport (entrainment) and wet scavenging will be discussed from selected AMMA flights. For that purpose, the following equation system has been resolved [HCHO]transported to UT=[HCHO]measured - [HCHO]bckgd [HCHO]transported to UT = x[HCHO]BL + y[HCHO]FT - z[HCHO]bckgd - [HCHO]wet scavenging where : BL: boundary layer; FT: free troposphere; bckgd: background and x, y and z fraction of formaldehyde concentration transported from intermediate layers (BL and FT). Two hypotheses have been tested and compared. The first hypothesis only considers entrainment from the boundary layer (0-2 km) (Bertram et al. 2007). This fraction is derived from non reactive hydrocarbons observations on board the French aircrafts (Bechara et al., 2010). The second hypothesis considers additional entrainment and detrainment from intermediate layers (2-6 km). These terms are determined by 1D-modelling for a non reactive tracer (non soluble).

Borbon, A.; Ruiz, M.; Bechara, J.; Afif, C.; Huntrieser, H.; Mills, G.; Mari, C.; Reeves, C.; Schlager, H.

2010-12-01

323

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

NASA Astrophysics Data System (ADS)

P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, that constitute alpine rock walls, has been denied in prior studies. These explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimeter-large low-porosity (<6 %) metamorphic, magmatic and sedimentary permafrost rock samples with a natural texture (>100 micro-fissures) from 25 °C to -15 °C in 0.3 °C increments close to the freezing point. P-wave velocity increases by 7-78 % when freezing parallel to cleavage/bedding and matrix velocity increases from 5-59 % coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's 2-phase equation implementing changes in matrix velocity dependent on lithology and demonstrate the physical basis for refraction seismics in low-porosity bedrock.

Draebing, D.; Krautblatter, M.

2012-02-01

324

P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

NASA Astrophysics Data System (ADS)

P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large low-porosity (< 10%) metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (> 100 micro-fissures) from 25 °C to -15 °C in 0.3 °C increments close to the freezing point. When freezing, p-wave velocity increases by 11-166% perpendicular to cleavage/bedding and equivalent to a matrix velocity increase from 11-200% coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's two-phase-equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.

Draebing, D.; Krautblatter, M.

2012-10-01

325

NASA Astrophysics Data System (ADS)

Teleseismic arrivals recorded by a network distributed over the northern part of the Kenya Rift in 1981 have been interpreted in terms of the structure of an anomalously low P-wave velocity upper mantle zone beneath the Kenya dome. The travel time residuals through a Jeffreys-Bullen Earth model have been compared with those derived previously by Savage and Long (1985). Their equivalence suggests that the large delays of up to about 1.9 seconds determined at stations well to the north of the apex of the Kenya dome are caused by a similar upper mantle low velocity zone as that presumed to exist beneath the centre and south of the dome. Slowness and azimuth anomalies of teleseismic arrivals recorded at a small aperture array at Ngurunit (NGU) in the Ndoto Mountains of the Turkana District on the north-eastern flank of the Kenya Rift show a relatively simple variation with azimuth and epicentral distance of event. It is suggested that this variation may be related to the shape of the upper surface of the anomalous mantle zone beneath the array. 3-dimensional ray-tracing through a low velocity mantle zone whose upper surface is described by a simple quadratic surface, enables a reasonable fit between observed and synthetic slowness and azimuth anomalies. The attitude of the quadratic surface implies a surprising thickening of the anomalous mantle zone to the north-east of the array. This together with previous geophysical results suggests a possible local thickening of the anomalous zone exists along most of the eastern flank of the Kenya Rift. Such a model has previously been proposed to explain the Quaternary volcanic activity from the Huri Hills in the north, through the Nyambeni range to the Chyulu Hills in the south, all lying about 150 - 200 km to the east of the main rift.

Pointing, A. J.; Maguire, P. K. H.

326

Histochemical analysis of Alzheimer disease (AD) brain tissues indicates that butyrylcholinesterase (BuChE) is present in ?-amyloid (A?) plaques. The role of BuChE in AD pathology is unknown but an animal model developing similar BuChE-associated A? plaques could provide insights. The APPSWE/PSEN1dE9 mouse (ADTg), which develops A? 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 A? plaques. A?-, 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 A? immunostaining but a greater number of plaques than were visualized with thioflavin-S. Double-labelling experiments demonstrated that all BuChE-positive plaques were A?-positive while only some BuChE-positive plaques were thioflavin-S-positive. These observations suggest that BuChE is associated with a subpopulation of A? 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

Darvesh, Sultan; Cash, Meghan K.; Reid, G. Andrew; Martin, Earl; Mitnitski, Arnold; Geula, Changiz

2011-01-01

327

Community Velocity Model for the New Madrid Region, Central U.S.

NASA Astrophysics Data System (ADS)

In 1811-1812, a series of three major earthquakes struck the Central United States in the New Madrid Seismic Zone. Having magnitudes near 7.5 and being located within the relatively stable interior of the North American Continent, these events produced widespread strong shaking. If these events were to occur today, there would be substantial devastation to people, buildings and transportation and communication infrastructure. To better understand this threat and in preparation for the upcoming bicentennial, the US Geological Survey is planning to produce and support sophisticated numerical simulations of earthquake rupture and seismic wave propagation due to a repeat of these events. To kick off this effort, the USGS began the development and construction of a community seismic velocity model for use in these numerical simulations. We have collected existing research regarding the p- and s-wave velocities, impedance contrasts and densities of the lithosphere in the New Madrid region and synthesized these results into a single model that can be used in earthquake simulations. We have identified areas of missing or incomplete information for further study. The region covers an area of approximately 600,000 km2 from Little Rock, Arkansas across to Nashville Tennessee, up to St Louis, Missouri. The model has currently been gridded at 3 km lateral resolution and from 5-m resolution near the surface to 10-km resolution at 100 km depth. Less but still substantial uncertainty exists for the Mississippi Embayment where a majority of the research has been done. Newer regional models such as those by van der Lee and others and Liang and Langston have improved regional resolution beyond a 1-dimensional model, but for ground motion simulations, greater resolution outside the Embayment is desired.

Boyd, O. S.

2008-12-01

328

NASA Astrophysics Data System (ADS)

We report a well constrained velocity model of the Central (Kumaon-Garhwal) Himalaya, based on a rigorous analysis of over 5,000 seismograms generated at 50 digital broadband seismic stations in the region between April 2005 and June 2008. These include data from 385 local earthquakes with azimuth gaps of less than 180°, each of which had a minimum of 7P and 5S phase readings. This velocity model was then used to map the locations of 1150 earthquakes of magnitude between 1 and 5, that occurred in the region during the recording period.A majority of these occur in the upper 20 km of the crust and form a 50 km wide band along the surface trace of the Main Central Thrust, as first shown by Gaur et al.(1984). However, we also find another parallel band of earthquakes about 70 km to its southwest, and a significant number both in the Tethys Himalaya and within the flexed crust of the under-thrusting Indian plate beneath the Ganga basin, notably along an arc-normal band through Chamoli which has witnessed two moderate earthquakes (of magnitude more than 5 ) over the past dozen years. Furthermore, unlike the reported absence of seismicity (Monsalve et al. 2006) in the lower crust of Nepal Himalaya, and its reappearance in the shallow mantle, the Central Himalayan crust is found to be seismically active throughout, with no event reliably recorded in the shallow mantle of this region during the epoch of our seismic recording.

Rai, S. S.; Perugu, M.; Krishnavajjhala, S.; Paul, A.; Parimi, R.; Gupta, S.; Gaur, V. K.

2011-12-01

329

A global shear velocity model of the mantle from normal modes and surface waves

NASA Astrophysics Data System (ADS)

We present SEISGLOB1, a new global shear wave velocity model of the mantle based on the inversion of all published normal mode, splitting and coupling coefficients, and the large surface wave dataset measured by Debayle & Ricard (2012). Normal mode and surface wave data are sensitive to lateral heterogeneities of elastic parameters (Vs, Vp, ?, ?, ?) and density. We first only consider spheroidal modes and Rayleigh waves and restrict the inversion to Vsv (imposing an a priori correlation between Vp-Vsv and density-Vsv). Before the inversion, we correct the data from the crust effect using 3SMAC (Nataf & Ricard ,1996). The data are inverted up to the degree 20 of spherical harmonics. Vertical smoothing is imposed by splines and we discuss the effect of coupling/decoupling the inverted structure above and below the '670' discontinuity. The obtained model is in good agreement with existing ones and an interesting result is that the high velocity slabs do cross the '670' discontinuity and are still observed down to 800 km depth whatever the parameterization is, coupled or not at the '670' discontinuity.

durand, stephanie; debayle, eric; ricard, yanick; lambotte, sophie

2014-05-01

330

Calculation of vertical velocity in three-dimensional, shallow water equation, finite element models

NASA Astrophysics Data System (ADS)

Computation of vertical velocity within the confines of a three-dimensional, finite element model is a difficult but important task. This paper examines four approaches to the solution of the overdetermined system of equations arising when the first-order continuity equation is solved in conjunction with two boundary conditions. The traditional (TRAD) method neglects one boundary condition, solving the continuity equation with the remaining boundary condition. The vertical derivative of continuity (VDC) method involves solution of the second-order equation obtained by differentiation of the continuity equation with respect to the vertical co-ordinate. The least squares (LS) method minimizes the residuals of the continuity equation (in discrete form) and the two boundary conditions. The adjoint (ADJ) method minimizes the residuals of the continuity equation (in continuous form) and the two boundary conditions.Two domains are considered: a quarter-annular harbour and the southwest coast of Vancouver Island. Results indicate that the highest-quality solution is obtained with both LS and ADJ. Furthermore, ADJ requires less CPU and memory than LS. Therefore the optimal method for computation of vertical velocity in a three-dimensional finite element model is the adjoint (ADJ) method.

Muccino, J. C.; Gray, W. G.; Foreman, M. G. G.

1997-10-01

331

NASA Astrophysics Data System (ADS)

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.

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

332

NASA Astrophysics Data System (ADS)

Quantification and characterization of the omnipresent atmospheric aerosol by remote sensing methods is key to answering many challenging questions in atmospheric science, in climate modeling and in air quality monitoring foremost. In recent years, accurate measurement of the state of polarization of photon fluxes at optical sensors in the visible and near-IR spectrum has been hailed as a very promising approach to aerosol remote sensing. Consequently, there has been a flurry of activity in polarized or 'vector' radiative transfer (vRT) model development. This covers the multiple scattering and ground reflection aspects of sensor signal prediction that complement single-particle scattering computation, and lies at the core of all physics-based retrieval algorithms. One can legitimately ask: What level of model fidelity (representativeness of natural scenes) and what computational accuracy should be achieved for this task in view of the practical constraints that apply? These constraints are, at a minimum: (i) the desired accuracy of the retrieved aerosol properties, (ii) observational uncertainties, and (iii) operational efficiency requirements as determined by throughput. We offer a rational and balanced approach to address these questions and illustrate it with a systematic inter-comparison of the performance of a diverse set of 1D vRT models using a small but representative set of test cases. This 'JPL' benchmarking suite of cases is naturally divided into two parts. First the emphasis is on stratified atmospheres with a continuous mixture of molecular and aerosol scattering and absorption over a black surface, with the corresponding pure cases treated for diagnostic purposes. Then the emphasis shifts to the variety of surfaces, both polarizing and not, that can be encountered in real observations and may confuse the aerosol retrieval algorithm if not properly treated.

Davis, Anthony B.; Kalashnikova, Olga V.; Diner, David J.; Garay, Michael J.; Lyapustin, Alexei I.; Korkin, Sergey V.; Martonchik, John V.; Natraj, Vijay; Sanghavi, Suniti V.; Xu, Feng; Zhai, Pengwang; Rozanov, Vladimir V.; Kokhanovsky, Alexander A.

2014-05-01

333

The objective of this work is to model the viscoelastic behaviour of polymer from the solid state to the liquid state. With this objective, we perform experimental tensile tests and compare with simulation results. The chosen polymer is a PMMA whose behaviour depends on its temperature. The computation simulation is based on Navier-Stokes equations where we propose a mixed finite element method with an interpolation P1+/P1 using displacement (or velocity) and pressure as principal variables. The implemented technique uses a mesh composed of triangles (2D) or tetrahedra (3D). The goal of this approach is to model the viscoelastic behaviour of polymers through a fluid-structure coupling technique with a multiphase approach.

Pham, VT.; Silva, L.; Digonnet, H.; Combeaud, C.; Billon, N.; Coupez, T. [Centre for Material Forming (CEMEF), MINES ParisTech, Rue Claude Daunesse, Sophia Antipolis cedex (France)

2011-05-04

334

Cluster/Peace Electrons Velocity Distribution Function: Modeling the Strahl in the Solar Wind

NASA Technical Reports Server (NTRS)

We present a study of kinetic properties of the strahl electron velocity distribution functions (VDF's) in the solar wind. These are used to investigate the pitch-angle scattering and stability of the population to interactions with electromagnetic (whistler) fluctuations. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focuses on the mechanisms that control and regulate the pitch-angle and stability of strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the electron heat-flux and temperature anisotropy. The goal is to check whether the strahl electrons are constrained by some instability (e.g., the whistler instability), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by fitting the VDF's to a spectral spherical harmonic model from which the moments are derived directly from the model coefficients.

Figueroa-Vinas, Adolfo; Gurgiolo, Chris; Goldstein, Melvyn L.

2008-01-01

335

A model to predict the critical velocity for liquid loss from a receding meniscus

NASA Astrophysics Data System (ADS)

This paper is a revision of the authors' previous work entitled "Experimental characterization of the receding meniscus under conditions associated with immersion lithography," presented in Optical Microlithography XIX, edited by Donis G. Flagello, Proceedings of SPIE Vol. 6154 (SPIE, Bellingham, WA, 2006) 61540R. Several engineering challenges accompany the insertion of the immersion fluid in a production tool, one of the most important being the confinement of a relatively small amount of liquid to the under-lens region. The semiconductor industry demands high throughput, leading to relatively large wafer scan velocities and accelerations. These result in large viscous and inertial forces on the three-phase contact line between the liquid, air, and substrate. If the fluid dynamic forces exceed the resisting surface tension force then residual liquid is deposited onto the substrate that has passed beneath the lens. Liquid deposition is undesirable; as the droplets evaporate they will deposit impurities on the substrate. In an immersion lithography tool, these impurities may be transmitted to the printed pattern as defects. A substantial effort was undertaken relative to the experimental investigation of the static and dynamic contact angle under conditions that are consistent with immersion lithography. A semi-empirical model is described here in order to predict the velocity at which liquid loss occurs. This model is based on fluid physics and correlated to measurements of the dynamic and static contact angles. The model describes two regimes, an inertial and a capillary regime, that are characterized by two distinct liquid loss processes. The semi-empirical model provides the semiconductor industry with a useful predictive tool for reducing defects associated with film pulling.

Shedd, Timothy A.; Schuetter, Scott D.; Nellis, Gregory F.; Van Peski, Chris K.

2006-10-01

336

Aftershock Seismicity of the Mw 8.8 Maule Earthquake of 27 February 2010 Using a 2D Velocity Model

NASA Astrophysics Data System (ADS)

On 27 February 2010 a magnitude 8.8 earthquake occurred along the subduction zone in central Chile, rupturing a 350 km long section of the dipping fault interface. The southern part ruptured previously in 1835 during the M 8.5 Concepcion earthquake and the northern part ruptured in 1906 during the Mw 8.5 Valparaiso event. Immediately after the earthquake struck, a coordinated multinational effort took place to capture in great detail the aftershock activity. In total 142 seismic stations were deployed by Chilean, French, USA, UK and German institutions, making this one of the best-observed aftershock sequences of a megathrust earthquake until now. We will present earthquake locations based on different optimized automatic arrival time picking algorithms (STA/LTA, Kurtosis, TpD, Akaike) and a newly-developed event association algorithm based on a backward time migration approach. So far we have carried out a preliminary analysis of the IRIS dataset, which covers the first two deployment months (end of March to beginning of June).. In total 34,192 seismic events could be identified which were associated with at least 6 P wave arrivals (51,947 for 5 P wave arrivals). Since most of the seismicity is located offshore, automatic locations based solely on P wave arrival times have very poorly-constrained depth estimates. We therefore used an iterative approach to increase the number of arrival time picks, to obtain S wave arrival times and also to increase the accuracy of the automatic picks. Using the preliminary locations, we calculated expectation time windows for both P and S wave arrivals at all stations based on a 1D velocity model for the region. Inside these time windows the sensitivity of the picking algorithm was raised, increasing significantly the amount and accuracy of P and S wave pciks. Random manual checks were carried out to optimize the parameters. Finally, events were relocated in a 2D velocity model based on a tomographic model developed for the southern end of the rupture in a previous study. Seismicity is distributed both along the subduction interface and in the overriding South American crust. Seismicity rates are considerably higher in the northern rupture area as compared with the southern one. Crustal seismicity is most intense in the region of Pichilemu, where the largest aftershock (Mw 6.9) took place. Most of the seismicity associated with the plate interface is located in a depth range between 15 km and 35 km. Deeper seismicity can be seen between 40 km and 50 km but seems to be separated from the upper region. Along the active volcanic chain distinct clusters of seismicity can be associated with Planchan volcano and along a line comprising Nevado, Blancas and Resago volcanoes. Sparse seismicity is also located close to Antuco volcano. The relocated seismicity distribution will also be compared to currently developed co-seismic slip models.

Rietbrock, A.; Ryder, I. M.; Haberland, C. A.; Nippress, S.; Agurto, H.; Barrientos, S. E.; Bataille, K.; Beck, S. L.; Bernard, P.; Campos, J. A.; Comte, D.; Heit, B.; Lange, D.; Miller, M. R.; Peyrat, S.; Roecker, S.; Schurr, B.; Tilmann, F. J.; Vilotte, J.

2010-12-01

337

NASA Astrophysics Data System (ADS)

The detailed analysis of the background microseismicity (M< 3) of the Southern Apennines (Italy) is used to identify the present active faults and stress field acting in a structurally complex area characterized by high seismic potential. The used refined techniques for the analysis and the high data quality allow to obtain a sharper picture of the spatial distribution of microseismicity and to determine the fine-scale geometry and extent of existing faults. We analysed a microearthquake data set consisting of 980 events with moment magnitude ranging between 0.9 and 3.1 occurred from August 2005 to April 2010 by integrating the data recorded by ISNet (AMRA Scarl) and the National Seismic Network managed by INGV. The first P- and S-wave arrival times have been manually picked on the raw waveforms for a total of 8663 P and 4358 S arrival times. The 3D crustal velocity model is retrieved using a delay travel times linearized, iterative tomographic algorithm. In the tomographic inversion we used as starting velocity model the minimum 1D model obtained with the same dataset using VELEST code. In this model all the events have been located using the probabilistic, non-linear, global-search earthquake location method (NonLinLoc code). The refined seismicity location well delineates a sequence of sub-parallel, NW-SE striking normal faults along the Apenninic chain and an approximately E-W oriented, strike-slip fault, transversely cutting the chain. The found fault trending and extent as suggested by the imaged earthquake locations indicate that low magnitude seismicity is likely generated along the major fault segments activated during the most recent earthquakes occurred in the Irpinia region on 23 November 1980 and between 1990 and 1991 in the Potenza region. This evidence suggests that major fault segments are still active today thirty years after the mainshock occurrences. In order to study the relation of this complex fault system with the stress field acting in the study area we performed a stress inversion from microearthquakes. We used the algorithm developed by Rivera and Cisternas (1990) that allows for the estimation of the orientation and shape of the stress tensor directly using the polarities of the P arrivals and the take-off angles. Moreover, the errors on the principal stress axes direction are estimated by computing the 95% confidence regions with a bootstrap procedure. Results show a dominant extensional regional stress field characterized by a nearly horizontal NE-SW minimum compressive stress axis (?3), and a nearly vertical maximum compressive stress axis (?1). These findings are consistent with the results obtained from the analysis of other surface geological, breakout and seismic data. Our study suggests that the existence of a unique, dominant anti-Apenninic extensional regional stress can explain the microearthquake generation along both the NW-SE striking normal faults and the E-W oriented fault, with a dominant dextral strike-slip motion.

De Matteis, R.; Amoroso, O.; Matrullo, E.; Stabile, T. A.; Rivera, L. A.; Zollo, A.

2011-12-01

338

NASA Astrophysics Data System (ADS)

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

Lea, J. M.; Mair, D.; Nick, F. M.; Rea, B. R.; Schofield, E.; Nienow, P. W.

2012-12-01

339

Modeling of Sediment Bed Behavior for Critical Velocity in Horizontal Piping

This paper compares results from a predictive tool for modeling transport of a multiphase mixture (solids in a liquid) in a pipeline, (up to and including plugging) with experiments performed to support the Hanford site’s Waste Treatment and Immobilization Plant (WTP). The treatment of high-level waste at the DOE Office of River Protection’s WTP will involve the transfer of high solid content suspensions through pipelines. Pipeline plugging was identified as a significant potential issue by a panel of external experts. In response to their concerns an experimental effort was initiated at PNNL to determine the critical velocities for a variety of operating conditions. A computational method has been developed to predict the dynamic behavior of a sediment bed in response to the surrounding suspension flow. The flow field is modeled using a lattice kinetics method, similar to the lattice Boltzmann method, which scales very well on highly parallel computers. Turbulent quantities are calculated using a k-epsilon RANS model. This work is part of a larger effort to develop a process simulation capability for a wide range of applications. Solids are represented using two different continuum fields. The suspended solids are treated as passive scalars in the flow field, including terms for hindered settling and Brownian diffusion. Normal stresses created by the irreversible collisions of particles during shearing are added to the pressure tensor. The sediment bed interface is represented using a continuum phase field with a diffuse interface. The bed may change with time due to settling, erosion and deposition through convection. The erosion rates are calculated using the local shear stress obtained from the turbulence model. The method is compared with data from the PNNL pipeline experiments conducted at PNNL (Poloski et al. 2008). The experimental flow loop consists of 3-inch schedule 40 piping with instrumentation for determining flow rate and pressure gradient. The simulant test particles ranged in density from 2.5 to 8 g/cc while the nominal particle size ranged from 10 to 100 ?m. At the beginning of each test, the slurry flow velocity was nominally set to 8 ft/sec. The flow was incrementally ramped down, and a steady-state pressure gradient was obtained at each flow condition. A rise in pressure gradient as the flow rate drops indicates that the pipe cross-sectional area is beginning to fill with sediment. This point is referred to as the “critical velocity”. Visualization information is provided using Electrical Resistance Tomography (ERT). The paper will show favorable comparison of results with data.

Rector, David R.; Stewart, Mark L.; Poloski, Adam P.

2009-10-01

340

The velocity pattern of the blood flow in the pulmonary artery was investigated in an animal model of acute pulmonary hypertension. Nine anesthetized, open-chest dogs were embolized with polystyrene microspheres, and the velocity pattern of the blood flow in the pulmonary artery was studied with use of an invasive pulsed Doppler technique. Phasic intraluminal velocity was recorded with use of a miniature piezoelectric crystal activated by 20-MHz Doppler pulses and mounted on the tip of a needle probe introduced into the pulmonary artery. The recorded Doppler quadrature signals were processed by spectral analysis. Significant increases occurred in mean, systolic, and diastolic pulmonary arterial pressures (p less than 0.0002), in pulmonary vascular resistance (p less than 0.005), and in negative velocity time (duration in milliseconds that the mean velocity was directed toward the pulmonic valve) (p less than 0.002). Significant decreases occurred in right ventricular ejection time (p less than 0.006) and in positive velocity time (duration in milliseconds that the mean velocity was directed away from the pulmonic valve) (p less than 0.005). A significant shortening in the time to peak velocity (acceleration time) was found (p less than 0.005). Second-order regression analyses demonstrated an inverse correlation between the ratio of positive velocity time to negative velocity time and the mean pulmonary artery pressure in all animals (r = 0.71). These findings should be compared with the velocity patterns of the blood flow in the pulmonary artery obtained under pulmonary hypertensive conditions due to various causes to facilitate interpretation and understanding of clinical investigations. PMID:1864122

Henry, G W; Katayama, H; Lores, M E; Lucas, C L; Ferreiro, J I

1991-08-01

341

NASA Astrophysics Data System (ADS)

We report on earthquake and temperature-related velocity changes in high-frequency autocorrelations of ambient noise data from seismic stations of the Integrated Plate Boundary Observatory Chile project in northern Chile. Daily autocorrelation functions are analyzed over a period of 5 years with passive image interferometry. A short-term velocity drop recovering after several days to weeks is observed for the Mw 7.7 Tocopilla earthquake at most stations. At the two stations PB05 and PATCX, we observe a long-term velocity decrease recovering over the course of around 2 years. While station PB05 is located in the rupture area of the Tocopilla earthquake, this is not the case for station PATCX. Station PATCX is situated in an area influenced by salt sediment in the vicinity of Salar Grande and presents a superior sensitivity to ground acceleration and periodic surface-induced changes. Due to this high sensitivity, we observe a velocity response of several regional earthquakes at PATCX, and we can show for the first time a linear relationship between the amplitude of velocity drops and peak ground acceleration for data from a single station. This relationship does not hold true when comparing different stations due to the different sensitivity of the station environments. Furthermore, we observe periodic annual velocity changes at PATCX. Analyzing data at a temporal resolution below 1 day, we are able to identify changes with a period of 24 h, too. The characteristics of the seismic velocity with annual and daily periods indicate an atmospheric origin of the velocity changes that we confirm with a model based on thermally induced stress. This comprehensive model explains the lag time dependence of the temperature-related seismic velocity changes involving the distribution of temperature fluctuations, the relationship between temperature, stress and velocity change, plus autocorrelation sensitivity kernels.

Richter, Tom; Sens-Schönfelder, Christoph; Kind, Rainer; Asch, Günter

2014-06-01

342

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

Jiang, Shuang; Pang, Liping; Buchan, Graeme D; Sim?nek, Jirí; Noonan, Mike J; Close, Murray E

2010-02-01

343

NASA Technical Reports Server (NTRS)

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.

Dobson, Chris C.; Hrbud, Ivana

2004-01-01

344

NASA Astrophysics Data System (ADS)

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.

Bozza, Andrea; Durand, Arnaud; Allenbach, Bernard; Confortola, Gabriele; Bocchiola, Daniele

2013-04-01

345

In this paper we address the problem of PID stabilization of a single-link inverted pendulum-based biomechanical model with force feedback, two levels of position and velocity feedback, and with delays in all the feedback loops. The novelty of the proposed model lies in its physiological relevance, whereby both small and medium latency sensory feedbacks from muscle spindle (MS), and force feedback from Golgi tendon organ (GTO) are included in the formulation. The biomechanical model also includes active and passive viscoelastic feedback from Hill-type muscle model and a second-order low-pass function for muscle activation. The central nervous system (CNS) regulation of postural movement is represented by a proportional-integral-derivative (PID) controller. Padé approximation of delay terms is employed to arrive at an overall rational transfer function of the biomechanical model. The Hermite-Biehler theorem is then used to derive stability results, leading to the existence of stabilizing PID controllers. An algorithm for selection of stabilizing feedback gains is developed using the linear matrix inequality (LMI) approach. PMID:15796343

Iqbal, Kamran; Roy, Anindo

2004-12-01

346

NASA Astrophysics Data System (ADS)

Faddeev and Vershik proposed the Hamiltonian and Lagrangian formulations of constrained mechanical systems that are invariant from the differential geometry standpoint. In both formulations, the description is based on a nondegenerate symplectic 2-form defined on a cotangent bundle T*Q (in the Hamiltonian formulation) or on a tangent bundle TQ (in the Lagrangian formulation), and constraints are sets of functions in involution on these manifolds. We demonstrate that this technique does not allow "invariantization" of the Dirac procedure of constraint "proliferation." We show this in an example of a typical quantum field model in which the original Lagrange function is a quadratic form in velocities with a degenerate coefficient matrix. We postulate that the initial phase space is a manifold where all arguments of the action functional including the Lagrange multipliers are defined. The Lagrange multipliers can then be naturally interpreted physically as velocities (in the Hamiltonian formulation) or momenta (in the Lagrangian formulation) related to "nonphysical" degrees of freedom. A quasisymplectic 2-form invariantly defined on such a manifold is degenerate. We propose new differential-geometric structures that allow formulating the Dirac procedure invariantly.

Pavlov, V. P.

2014-03-01

347

NASA Astrophysics Data System (ADS)

The analysis of travel time delays from 94 teleseisms recorded at The Geysers-Clear Lake, California, region reveals a broad area of delay centered at Mount Hannah and encompassing The Geysers geothermal field. A three-dimensional velocity inversion of the delays indicates that the source of the delays is a low-velocity body largely within the top 30 km of the lithosphere. Velocity decreases of as much as 20% are observed in the top 15 km near Mount Hannah and diminish with depth. No significant velocity fluctuations are observed below 60 km. The block model of velocity perturbations resulting from the teleseismic residual inversion is used to predict the observed Bouguer gravity field by solving for the relation between velocity and density perturbation. Comparison between the predicted gravity and observed gravity indicates that the same body responsible for the teleseismic delays accounts for the long-wave-length 30-mGal Bouguer gravity minima at Mount Hannah. The results of the velocity-density modeling suggest that the material beneath Mount Hannah and The Geysers may be partially molten and somewhat more silicic than the surrounding medium. Supplemental table is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J81-006; $1.00. Payment must accompany order.

Oppenheimer, David H.; Herkenhoff, Ken E.

1981-07-01

348

NASA Astrophysics Data System (ADS)

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.

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

349

Human running can be modelled as either a spring-mass model or multiple springs in series. A force is required to stretch or compress the spring, and thus stiffness, the variable of interest in this paper, can be calculated from the ratio of this force to the change in spring length. Given the link between force and length change, muscle stiffness and mechanical stiffness have been areas of interest to researchers, clinicians, and strength and conditioning practitioners for many years. This review focuses on mechanical stiffness, and in particular, vertical, leg and joint stiffness, since these are the only stiffness types that have been directly calculated during human running. It has been established that as running velocity increases from slow-to-moderate values, leg stiffness remains constant while both vertical stiffness and joint stiffness increase. However, no studies have calculated vertical, leg or joint stiffness over a range of slow-to-moderate values to maximum values in an athletic population. Therefore, the effects of faster running velocities on stiffness are relatively unexplored. Furthermore, no experimental research has examined the effects of training on vertical, leg or joint stiffness and the subsequent effects on running performance. Various methods of training (Olympic style weightlifting, heavy resistance training, plyometrics, eccentric strength training) have shown to be effective at improving running performance. However, the effects of these training methods on vertical, leg and joint stiffness are unknown. As a result, the true importance of stiffness to running performance remains unexplored, and the best practice for changing stiffness to optimize running performance is speculative at best. It is our hope that a better understanding of stiffness, and the influence of running speed on stiffness, will lead to greater interest and an increase in experimental research in this area. PMID:18620465

Brughelli, Matt; Cronin, John

2008-01-01

350

Although the neural basis of balance control remains unknown, recent studies suggest that a feedback law on center-of-mass (CoM) kinematics determines the temporal patterning of muscle activity during human postural responses. We hypothesized that the same feedback law would also explain variations in muscle activity to support-surface translation as perturbation characteristics vary. Subject CoM motion was experimentally modulated using 34 different anterior-posterior support-surface translations of varying peak acceleration and velocity but the same total displacement. Electromyographic (EMG) recordings from several muscles of the lower limbs and trunk were compared to predicted EMG patterns from an inverted pendulum model under delayed feedback control. In both recorded and predicted EMG patterns, the initial burst of muscle activity scaled linearly with peak acceleration, whereas the tonic "plateau" region scaled with peak velocity. The relatively invariant duration of the initial burst was modeled by incorporating a transient, time-limited encoding of CoM acceleration inspired by muscle spindle primary afferent dynamic responses. The entire time course of recorded and predicted muscle activity compared favorably across all conditions, suggesting that the initial burst of muscle activity is not generated by feedforward neural mechanisms. Perturbation conditions were presented randomly and subjects maintained relatively constant feedback gains across all conditions. In contrast, an optimal feedback solution based on a trade-off between CoM stabilization and energy expenditure predicted that feedback gains should change with perturbation characteristics. These results suggest that an invariant feedback law was used to generate the entire time course of muscle activity across a variety of postural disturbances. PMID:19357335

Welch, Torrence D J; Ting, Lena H

2009-06-01

351

The APPswe/PS1dE9 mouse is a double transgenic model of Alzheimer's disease, which harbors mutant mouse/human amyloid precursor protein (Swedish K594N/M595L) and presenilin-1 genes (PS1-dE9). These mice develop beta-amyloid plaques and exhibit visuo-spatial learning and memory impairment in the Morris water maze (MWM) at 8-12 and 16-18 months of age. To extend these findings, we tested visuo-spatial learning and memory of male and female APPswe/PS1dE9 mice at 16 months of age on the Barnes maze. APPswe/PS1dE9 mice showed impaired acquisition learning using measures of latency, distance traveled, errors and hole deviation scores, and were less likely to use the spatial search strategy to locate the escape hole than wild-type mice. APPswe/PS1dE9 mice also showed a deficit in memory in probe tests on the Barnes maze relative to wild-type mice. Learning and memory deficits, however, were not found during reversal training and reversal probe tests. Sex differences were observed, as male APPswe/PS1dE9 mice had smaller reversal effects than male wild-type mice, but females of each genotype did not differ. Overall, these results replicate previous findings using the MWM, and indicate that APPswe/PS1dE9 mice have impaired visuo-spatial learning and memory at 16 months of age. PMID:19428625

O'Leary, Timothy P; Brown, Richard E

2009-07-19

352

NASA Astrophysics Data System (ADS)

A cellular automata (CA) model, which adopts the findings of tenability analysis, is proposed to simulate the evacuation from a smoke-filled room. Two algorithms, viz., direct algorithm and indirect algorithm, are used to model the behavior of a crowd consisting of people with different movement velocities. In the indirect algorithm, the movement velocity is related to probability so that the CPU time is greatly reduced. Another novelty is that an experimental formula for estimating the survival duration when exposed to constant concentration of toxic gases in a static environment is extended to one that involves varying degree of toxic gases. This has been incorporated into the CA model.

Weifeng, Yuan; Kang Hai, Tan

2007-06-01

353

Lateral heterogeneity scales in regional and global upper mantle shear velocity models

NASA Astrophysics Data System (ADS)

We analyse the lateral heterogeneity scales of recent upper mantle tomographic shear velocity (Vs) global and regional models. Our goal is to constrain the spherical harmonics power spectrum over the largest possible range of scales to get an estimate of the strength and statistical distribution of both long and small-scale structure. We use a spherical multitaper method to obtain high quality power spectral estimates from the regional models. After deconvolution of the employed taper functions, we combine global and regional spectral estimates from scales of 20 000 to around 200 km (degree 100). In contrast to previous studies that focus on linear power spectral densities, we interpret the logarithmic power per harmonic degree l as heterogeneity strength at a particular depth and horizontal scale. Throughout the mantle, we observe in recent global models, that their low degree spectrum is anisotropic with respect to Earth's rotation axis. We then constrain the uppermost mantle spectrum from global and regional models. Their power spectra transfer smoothly into each other in overlapping spectral bands, and model correlation is in general best in the uppermost 250 km (i.e. the `heterosphere'). In Europe, we see good correlation from the largest scales down to features of about 500 km. Detailed analysis and interpretation of spectral shape in this depth range shows that the heterosphere has several characteristic length scales and varying spectral decay rates. We interpret these as expressions of different physical processes. At larger depths, the correlation between different models drops, and the power spectrum exhibits strong small scale structure whose location and strength is not as well resolved at present. The spectrum also has bands with elevated power that likely correspond to length scales that are enhanced due to the inversion process.

Meschede, Matthias; Romanowicz, Barbara

2015-02-01

354

Optimization of a Sea Ice Model Using Basinwide Observations of Arctic Sea Ice Thickness, Extent 2004, in final form 27 June 2005) ABSTRACT A stand-alone sea ice model is tuned and validated using satellite-derived, basinwide observations of sea ice thickness, extent, and velocity from the years 1993

Feltham, Daniel

355

We synthesize relocated regional seismicity and 3D velocity and Qp models to infer structure and deformation in the transpressive zone of southern California. These models provide a comprehensive synthesis of the tectonic fabric of the upper to middle crust, and the brittle ductile transition zone that in some cases extends into the lower crust. The regional seismicity patterns in southern

E. Hauksson; P. Shearer

2004-01-01

356

Measuring and modelling the frictional velocity u*, turbulence and heat fluxes above the North Sea

NASA Astrophysics Data System (ADS)

In this study, we analyse the frictional velocity u*, drag coefficient, vertical wind speed and turbulence profiles observed at different met-masts in the German North and Baltic Sea. We present an analysis of different models for the frictional velocity u* in convective, neutral and stable thermal stratification of the atmosphere. Atmospheric turbulent momentum and heat flux measurements performed with ultra-sonic anemometers are compared to profile-derived values and a bulk Richardson number formulation of the atmospheric thermal stability. Modelling: An improved approach to model the vertical wind speed profile is presented and compared against meso-scale model results (WRF, COSMO): Bye-Ekman-Coupling (BEC) describes the flux of momentum from the Ekman layer of the atmosphere through the Prandtl layer down to the air-sea interface by a modified wave boundary layer with enhanced Charnock dynamics (Bye et al. 2010). The BEC model is based on the coupled pair of similarity relations for "aerodynamically rough flow" in both fluids (air and sea). The derived drag law is of Charnock form, almost independent of the wave age and consistent with the transfer of momentum to the wave spectrum - which takes place in the smaller rather than the dominant wavelengths. Measurements: It was found that the frictional velocity u* is considerably smaller than predicted by conventional approaches using the Charnock relation: For wind speeds between 10 m/s and 15 m/s at 40 m height above the sea surface, u*(observed) is 14% smaller than u*(Charnock). Most important, we found unexpected, strong and obviously artificial distortions concerning the three wind speed components in the 10Hz data of the three ultra-sonic anemometers at the offshore met-mast FINO1 at 40 m, 60 m and 80 m height. The pattern of these distortions is independent from different post-processing procedures (planar-fit etc.). We anticipate that these artefacts imply severe problems for the eddy covariance technique. Moreover, these artefacts may be relevant in other (previous and on-going) ultra-sonic measurement campaigns where turbulent parameters such as u* and heat fluxes are derived. A simple, but innovative analysis is proposed to check ultra-sonic measurements with respect to these artefacts, using the original temporal 10Hz resolution of the data: The instantaneous vertical wind speed component w is analysed versus the instantaneous wind direction (called wind.dir in the following), computed from the instantaneous horizontal components u and v. The observational density is then plotted in the (w; wind.dir)-space. We found a pattern of stripes of very strong densities for specific wind direction bins, which are thinner than 1° and which cannot be attributed directly to the geometry of the anemometer (transducers, physical structure etc.). The source of this artificial pattern is still unclear and open for discussion. References: Bye JAT, Ghantous M, Wolff J-O (2010) On the variability of the Charnock constant and the functional dependence of the drag coefficient on wind speed. Ocean Dynamics 60(4) 851-860

Tambke, Jens; Bye, John A. T.; Schmidt, Michael; Wolff, Jörg-Olaf

2014-05-01

357

Modelling and Simulation of Tensile Fracture in High Velocity Compacted Metal Powder

In cold uniaxial powder compaction, powder is formed into a desired shape with rigid tools and a die. After pressing, but before sintering, the compacted powder is called green body. A critical property in the metal powder pressing process is the mechanical properties of the green body. Beyond a green body free from defects, desired properties are high strength and uniform density. High velocity compaction (HVC) using a hydraulic operated hammer is a production method to form powder utilizing a shock wave. Pre-alloyed water atomised iron powder has been HVC-formed into circular discs with high densities. The diametral compression test also called the Brazilian disc test is an established method to measure tensile strength in low strength material like e.g. rock, concrete, polymers and ceramics. During the test a thin disc is compressed across the diameter to failure. The compression induces a tensile stress perpendicular to the compressed diameter. In this study the test have been used to study crack initiation and the tensile fracture process of HVC-formed metal powder discs with a relative density of 99%. A fictitious crack model controlled by a stress versus crack-width relationship is utilized to model green body cracking. Tensile strength is used as a failure condition and limits the stress in the fracture interface. The softening rate of the model is obtained from the corresponding rate of the dissipated energy. The deformation of the powder material is modelled with an elastic-plastic Cap model. The characteristics of the tensile fracture development of the central crack in a diametrically loaded specimen is numerically studied with a three dimensional finite element simulation. Results from the finite element simulation of the diametral compression test shows that it is possible to simulate fracturing of HVC-formed powder. Results from the simulation agree reasonably with experiments.

Jonsen, P.; Haeggblad, H.-A. [Division of Solid Mechanics, Department of Applied Physics and Mechanical Engineering, Luleaa University of Technology, 971 87 Luleaa (Sweden)

2007-05-17

358

Tissue stiffness estimation plays an important role in cancer detection and treatment. The presence of stiffer regions in healthy tissue can be used as an indicator for the possibility of pathological changes. Electrode vibration elastography involves tracking of a mechanical shear wave in tissue using radio-frequency ultrasound echoes. Based on appropriate assumptions on tissue elasticity, this approach provides a direct way of measuring tissue stiffness from shear wave velocity, and enabling visualization in the form of tissue stiffness maps. In this study, two algorithms for shear wave velocity reconstruction in an electrode vibration setup are presented. The first method models the wave arrival time data using a hidden Markov model whose hidden states are local wave velocities that are estimated using a particle filter implementation. This is compared to a direct optimization-based function fitting approach that uses sequential quadratic programming to estimate the unknown velocities and locations of interfaces. The mean shear wave velocities obtained using the two algorithms are within 10%of each other. Moreover, the Young’s modulus estimates obtained from an incompressibility assumption are within 15 kPa of those obtained from the true stiffness data obtained from mechanical testing. Based on visual inspection of the two filtering algorithms, the particle filtering method produces smoother velocity maps. PMID:25285187

Ingle, Atul; Varghese, Tomy

2014-01-01

359

Imaging Rayleigh wavefronts and new 3D S-velocity model of South America

NASA Astrophysics Data System (ADS)

In this study we analyse data recorded at the densely spaced Chile Ridge Subduction Project (CRSP) stations, to image fundamental mode Rayleigh wavefronts as they pass through the region. The processing involves first cleaning the seismograms by means of frequency time analysis (FTAN), whereby we test different filtering techniques, and cross-correlating the seismograms at a series of frequencies. Wavefronts are fit to the relative arrival times with a least squares fitting procedure. Our results show that the shape of the wavefronts change within the study region and that for certain events, particularly those with wavepaths that follow the west coast line of South America, wavefronts are not perpendicular to the great circle path between the source and the receiver. We discuss the implications of this discrepancy and interpret the frequency dependent wavefront modulations in terms of interstation velocity structure. Additionally, we combine the dispersion curves obtained during the FTAN with existing data to present an updated tomographic model of the whole South American continent. This marks a step forward from existing models, which typically suffer from poor data coverage in the southernmost parts of continental South America.

Lloyd, S.; van der Lee, S.; Russo, R.; Mocanu, V.; Callego, A.; Comte, D.; Murdie, R.; Vandecar, J.

2008-05-01

360

Velocity-Dependent Models for Non-Abelian/Entangled String Networks

We develop velocity-dependent models describing the evolution of string networks that involve several types of interacting strings, each with a different tension. These incorporate the formation of Y-type junctions with links stretching between colliding strings, while always ensuring energy conservation. These models can be used to describe network evolution for non-abelian strings as well as cosmic superstrings. The application to $Z_{N}$ strings in which interactions are topologically constrained, demonstrates that a scaling regime is generally reached which involves a hierarchy of string densities with the lightest most abundant. We also study hybrid networks of cosmic superstrings, where energetic considerations are more important in determining interaction outcomes. We again find that networks tend towards scaling, with the three lightest network components being dominant and having comparable number densities, while the heavier string states are suppressed. A more quantitative analysis depends on the precise calculation of the string interaction matrix using the underlying string or field theory. Nevertheless, these results provide further evidence that the presence of junctions in a string network does not obstruct scaling.

A. Avgoustidis; E. P. S. Shellard

2009-12-28

361

A mathematical model for Tsunami generation using a conservative velocity-pressure hyperbolic system

By using the Hugoniot curve in detonics as a Riemann invariant of a velocity-pressure model, we get a conservative hyperbolic system similar to the Euler equations. The only differences are the larger value of the adiabatic constant (= 8.678 instead of 1.4 for gas dynamics) and the mass density replaced by a strain density depending on the pressure. The model is not homogeneous since it involves a gravity and a friction term. After the seismic wave reaches up the bottom of the ocean, one gets a pressure wave propagating toward the surface, which is made of a frontal shock wave followed by a regular decreasing profile. Since this regular profile propagates faster than the frontal shock waves, the amplitude of the pressure wave is strongly reduced when reaching the surface. Only in the case of a strong earth tremor the residual pressure wave is still sufficient to generate a water elevation with a sufficient wavelengths enable to propagate as a SaintVenant water wave and to become a tsunami when reaching the sh...

Roux, Alain-Yves Le

2009-01-01

362

Modeling of Geodetic Crustal Motion Velocities in Southern California: Undergraduate Research

NASA Astrophysics Data System (ADS)

With funding from the National Science Foundation's Opportunities for Enhancing Diversity in the Geosciences, we have undertaken a project with two primary goals: (1) to introduce undergraduate students and K-14 educators to research in geology/geophysics, and (2) to use GPS to monitor deformation across the boundary between the Pacific and North American plates in southern California, and to model the slip on specific faults that could be responsible for that deformation. Starting in July 2002, we collected campaign-style GPS data twice a year from 13 sites along a line across the San Andreas and San Jacinto faults from Norco through San Bernardino to Lucerne Valley. We are also modeling data from the SCEC Crustal Deformation Velocity Map 2.0 [http://www.scecdc.scec.org/group_e/release.v2/]. Our initial approach has been to use a one-dimensional model of dislocations in an elastic half-space. We are studying the portion of the plate boundary from San Bernardino southward to the U.S.-Mexico border. We have divided this region into seven transects that are perpendicular to the plate boundary. We used a spreadsheet macro to systematically model a range of slip rates and locking depths for each fault. Out of hundreds or thousands of possible combinations for each transect, we sorted the models according to their goodness of fit, using the sum of the squares of the residuals as a criterion. We are also beginning to use the program Simplex (G. Lyzenga. J. Parker) to model the velocity data from all transects simultaneously. This will allow us to take into account the complex fault geometry of the region. Our preliminary results from the one-dimensional modeling suggest that the best-fitting slip rate of the San Andreas fault is 26 mm/yr for the section from Indio to Durmid. However, slip rates in the range of 20-30 mm/yr also fit the geodetic data relatively well. Slip rates of 15 or 35 mm/yr do not fit well. For the San Jacinto fault, the best-fitting slip rate is 13 mm/yr for the section from Anza to Borrego Mountain and 15 mm/yr for the section farther south, which ruptured in 1968. However, slip rates within the range 10-20 mm/yr also fit these data relatively well. The best-fitting rate for the Superstition Hills fault is 15 mm/yr, with rates of 10-15 mm/yr fitting reasonably well, whereas a rate of 20 mm/yr does not fit well. The best-fitting slip rate for the Elsinore fault was 5 mm/yr for the section near Julian, but rates ranging from 2-8 mm/yr also fit relatively well. For the southernmost section of the Elsinore fault, from Agua Caliente Springs to the Coyote Mountains, the best-fitting slip rate was 2 mm/yr, but rates from 2-4 mm/yr fit relatively well. The best-fitting rate for the Laguna Salada fault was 4 mm/yr, with rates from 2-6 mm/yr also fitting fairly well. These results generally agree with geologic estimates of the Holocene slip rates for these faults. There has been considerable debate as to whether the San Andreas and San Jacinto faults contribute approximately equally to the plate boundary deformation in southern California or whether the San Andreas fault contributes substantially more than the San Jacinto fault. Our preliminary results suggest that the San Andreas fault most likely is contributing more to the plate boundary deformation than is the San Jacinto fault, but we cannot rule out the possibility that they are equal contributors.

McGill, S. F.; Barley, M. E.; Hams, J. E.; Hobart, K.; Ramirez, J.; Fryxell, J. E.; Lyzenga, G. A.; McGill, J. D.

2003-12-01

363

The modified Biot-Attenborough (MBA) model for acoustic wave propagation in porous media has been found useful to predict wave properties in cancellous bone. The present study is aimed at applying the MBA model to predict the dependence of phase velocity on porosity in cancellous bone. The MBA model predicts a phase velocity that decreases nonlinearly with porosity. The optimum values for input parameters of the MBA model, such as compressional speed c(m) of solid bone and phase velocity parameter s(2), were determined by comparing the predictions with previously published measurements in human calcaneus and bovine cancellous bone. The value of the phase velocity parameter s(2)=1.23 was obtained by curve fitting to the experimental data for 53 human calcaneus samples only, assuming a compressional speed c(m)=2500 m/s of solid bone. The root-mean-square error (RMSE) of the curve fit was 15.3m/s. The optimized value of s(2) for all 75 cancellous bone samples including 22 bovine samples was 1.42 with a value of 55 m/s for the RMSE of the curve fit. The latter fit was obtained by using of a value of c(m)=3200 m/s. Although the MBA model relies on the empirical parameters determined from experimental data, it is expected that the model can be usefully employed as a practical tool in the field of clinical ultrasonic bone assessment. PMID:17573089

Lee, Kang Il; Humphrey, Victor F; Leighton, Timothy G; Yoon, Suk Wang

2007-11-01

364

Resolution of group velocity models obtained by adjoint inversion in the Czech Republic region

NASA Astrophysics Data System (ADS)

We performed tomographic inversion of crosscorrelation traveltimes of group waves in the Bohemian massif. The traveltimes used for inversion come from ambient seismic noise measurements between pairs of stations filtered for several period ranges between 2-20s. The inverse problem was solved by the conjugate gradients, which were calculated using efficient adjoint method. Assuming that the propagation of group waves can be approximated by membrane waves for each period separately, the computations are reduced to 2D domain. The numerical calculations were carried out using adjoint version of SeisSol, which solves elastodynamic system using Discontinuous Galerkin method with arbitrary high order time derivatives (ADER-DG). The adjoint inversion is based on computation of so called sensitivity kernels for each data, which are then combined into Fréchet kernel of misfit gradient. Therefore, if using only the longest wavelength data i.e. the traveltimes of 20s and 16s group waves, structures of even shorter wavelengths can be obtained by the inversion. However, these smaller-scale structures are possibly more affected by data noise and thus require careful treatment. Note that in the classical tomography based on ray method, such structures are subdued by regularization. This leads to question on the influence of data noise on the obtained models. Several synthetic tests were carried out to reveal the effect of data errors on the resulting model. Firstly, we tested the level of data noise required to obtain artificial small scale structures. As a target model we constructed simple heterogenous model consisting of one very long wavelength structure. The synthetic traveltime data were modified using random shifts for several distributions with different variances. The method appears to be extremely sensitive even for relatively small level of noise. The other set of tests concentrated on the main feature of models obtained from the real data. All models inverted using longer period data contain distinct decrease in velocity with well defined boundary in SE of our domain, where the station coverage is rather poor. The synthetic tests show us whether this feature originates in the real model or is only an artifact of data coverage in this part of domain. We tested several types of structures in order to find out, whether they could produce results similar to the one obtained by the inversion of real data.

Valentova, Lubica; Gallovic, Frantisek; Ruzek, Bohuslav; de la Puente, Josep

2013-04-01

365

The feasibility of estimating urinary flow velocity from the decorrelation of radiofrequency (RF) signals was investigated in soft tissue-mimicking models of obstructed and unobstructed urethras. The decorrelation was studied in the near field, focal zone and far field of the ultrasound beam. Furthermore, the effect of beam width was investigated. The results of this study suggest that it is feasible to estimate flow velocity in models of the urethra by quantifying the decorrelation of RF ultrasound signals. The decorrelation slope increased more rapidly and more linearly with increasing velocity in the focal zone than in the near and far field. A preliminary example of an in vivo measurement in a healthy volunteer illustrated that this method has potential for clinical use in the future. PMID:24412180

Arif, Muhammad; Idzenga, Tim; van Mastrigt, Ron; de Korte, Chris L

2014-05-01

366

NASA Astrophysics Data System (ADS)

We are studying the influence on DT ignition of the Li-Petrasso ^1 model for energy loss of charged particles in non-degenerate plasmas. This model is more general than an older model due to Corman and Zimmerman ^2, which is valid only when the velocity of the projectile particle is much smaller than the velocity of background thermal electrons and simultaneously much greater than the velocity of background thermal ions. The Li-Petrasso model, by contrast, is valid for all projectile velocities; it accounts for large-angle Coulomb interactions through the inclusion of a term proportional to 1/ln ? i (where ? i is the Coulomb logarithm for binary collisions between the projectile and background particle of species i); and it includes a contribution for the effect of collective plasma oscillations. In general, the Li-Petrasso model gives smaller stopping powers and hence longer ranges for the charged products of fusion reactions, in comparison to the Corman/Zimmerman approach. We investigate its implications for the ignition of simple two-component static DT spheres based on the fuel configuration of a compressed NIF capsule, in which a hot low-density region is surrounded by a cold high-density region. 1. CK Li and RD Petrasso, Phys. Rev. Lett. 70, 3059, 1993. 2. EG Corman, WE Loewe, GE Cooper, AM Winslow, Nucl. Fusion 15, 377, 1975; GB Zimmerman, UCRL 84776, 1980.

Hoffman, Nelson M.; Lee, Charles L.

2001-10-01

367

NSDL National Science Digital Library

The RandomWalk1D program simulates a random walk in one dimension for steps of unit length and equal time intervals. The default number of steps is N = 16 and the probability of going right or left at any step is the same (the probability p of going to the right for a single step is 0.5). RandomWalk1D is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp RandomWalk1D