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1

Brady 1D seismic velocity model ambient noise prelim  

DOE Data Explorer

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.

Robert J. Mellors

2

Brady 1D seismic velocity model ambient noise prelim  

SciTech Connect

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.

Robert J. Mellors

2013-10-25

3

A 1D P wave velocity model under the pacific region using multiply reflected P waves  

NASA Astrophysics Data System (ADS)

In order to constrain the shallow structure of the Earth in global tomography, Love and Rayleigh waves are often used. However these waves are mostly sensitive to the S wave velocity structure. P-wave energy is either evanescent, or leaking away at every surface reflection that generates an S wave which travels much deeper into the mantle. For that reason, to study the shallow P velocity structure of the Earth, we need to study P-waves at regional distances if a good seismic station coverage is available. Otherwise we can use multiply reflected P waves at teleseismic distance when regional data are not available (as in the oceans for instance). We used 203 events of magnitude Mw > 6.0 recorded from the dense network of US ARRAY, which allows us to make a very large number of group arrival and slowness measurements of multiply reflected P waves . Our study shows that two times reflected PPP and three times reflected PPPP waves are very well observed despite the ray- theoretical prediction that at certain distances almost all of their compressional energy is converted to shear waves. We also observed Four times reflected 5P and five times reflected 6P which show a strong interference for epicentral distances larger than 80 degree. These observations of multiply reflected P waves allow us to inferred a 1D P wave model for the shallow structure under the pacific region.

Foundotos, M.; Nolet, G.

2012-12-01

4

Experimental Characterization of 1-D Velocity Selection  

E-print Network

We demonstrate a 1-D velocity selection technique which relies on combining magnetic and optical potentials. We have selected atom clouds with temperatures as low as 2.9% of the initial temperature, with an efficiency of 1%. The efficiency (percentage of atoms selected) of the technique can vary as slowly as the square root of the final temperature. In addition to selecting the coldest atoms from a cloud, this technique imparts a sharp cut-off in the velocity distribution. The cold selected atoms are confined in a small well, spatially separated from higher energy atoms. Such a non-thermal distribution may be useful for atom optics experiments, such as studies of atom tunneling.

S. H. Myrskog; J. K. Fox; A. M. Jofre; L. R. Segal; S. R. Mishra; A. M. Steinberg

2005-03-03

5

Ejs Intro 1D Motion Lab Model  

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

6

A FREEWARE 1D EMITTER MODEL FOR SILICON SOLAR CELLS Keith R. McIntosh  

E-print Network

A FREEWARE 1D EMITTER MODEL FOR SILICON SOLAR CELLS Keith R. McIntosh 1 and Pietro P. Altermatt 2 1, GERMANY ABSTRACT Heavily doped surfaces--often called emitters, diffusions, or back-surface fields that models a 1D emitter in silicon. Given a user- defined dopant profile, a surface recombination velocity

7

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

8

Ejs Group Velocity Model  

NSDL National Science Digital Library

The Ejs Group Velocity model displays the time evolution for the superposition of two traveling waves of similar wave numbers and frequencies. The simulation allows an arbitrarily superposition of two waves for the study of group and phase velocity. The amplitude, wave number, and angular frequency of each wave can be changed via text boxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Group Velocity model 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_ehu_waves_group_velocity.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for wave motion are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-19

9

Modeling Terminal Velocity  

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

Lifting the Seismic Lid Beneath Cameroon Volcanic Line Using 1D Shear Wave Velocities  

NASA Astrophysics Data System (ADS)

The composition of the lithosphere beneath Cameroon and the origin of the Cameroon Volcanic Line (CVL) is a matter of debate. Although many studies based on regional or global observations provide models for the setting of the CVL, none of them are strong enough to be considered as definitive. We used the joint inversion of Rayleigh wave group velocities and Rayleigh wave group velocities to derive shear wave velocity profiles of the lithosphere beneath Cameroon andshow that lithosphere is, on average, faster beneath the Congo Craton than beneath the Pan-African age crust. Using recently published dispersion curves, we extend the depth of investigation from 60 to 200 km. The calculated velocity-depth profiles do not show any sharp discontinuity that could be interpreted as the lithosphere-asthenosphere transition. Furthermore, there is no clear evidence of the existence of a low velocity zone beneath any geologic province within Cameroon. The smooth velocity variations observed on the velocity models are believed to be influenced by lateral mantle heterogeneities rather than vertical ones. The shear wave velocities for the uppermost mantle are in general greater than 4.3 km/s at all stations. This is higher than the values obtained in the Main Ethiopian Rift, and suggest that the perturbation of the by thermal anomalies does not extend as far as the CVL. This suggests that the source of volcanism along the CVL is from small scale convection in the asthenosphere and controlled by lithospheric fractures that are probably driven by the cold (and fast) edge of the Congo Craton.

Tokam Kamga, Alain; Durrheim, Ray; Tabod, Charles; Nyblade, Andrew; Nguiya, Severin

2014-05-01

11

GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL  

SciTech Connect

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

12

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

NASA Astrophysics Data System (ADS)

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; Lembège, Bertrand

2012-11-01

13

Data Analysis of cGPS stations in central Greece: station velocities and 1-D strain estimates  

NASA Astrophysics Data System (ADS)

We processed 30-s GPS data from permanent GNSS stations in central Greece, available at NOA since 2006. We obtained position time series along with horizontal and vertical velocities using the Kalman filtering approach and accounting for time-correlated noise content. The station distribution allowed us to draw velocity profiles and to calculate rates of baseline length change (1-D strain). In central Greece, the coherent picture of the velocity pattern for Attica and north-eastern Peloponnese (Corinth) stations (effectively a velocity "plateau" at 30 mm/yr) indicates that these areas belong to the same crustal block, although some internal strain is present within Attica's crust as well as across the Saronic Gulf. Our 1-D strain estimates are in general agreement with geological data (fault slip rates) in central Greece, implying accommodation of this crustal extension along E-W striking active normal faults. Some NE-SW directed shortening is mapped in the wider area to the west of the termination of the North Anatolian Fault (Sporades islands).

Ganas, Athanassios; Chousianitis, Konstantinos; Gianniou, Michalis

2013-04-01

14

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

SciTech Connect

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

15

Frictional response to velocity steps and 1-D fault nucleation under a state evolution law with stressing-rate dependence  

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

16

3-D velocity model beneath Taal Volcano, Luzon Island Philippines  

NASA Astrophysics Data System (ADS)

We derive a three dimensional velocity model of seismic waves beneath Taal Volcano, Philippines, from about 2300 local earthquakes recorded by the Taal Volcano seismic network during the time period from March 2008 to March 2010. In the early data processing stage, with the cross-correlation functions of continuous record of station pairs, unexpected linear drifting of clock time was clearly identified. The drifting rates of each problematic station were determined and the errors were corrected before further processing. With the corrected data, we first determined initial locations by using the program HYPO71 and the reference 1-D global model ak135. 749 well-located events with 3381 P-wave and 2896 S-wave arrivals were used to derive the 'minimum 1-D velocity model' with the program VELEST developed by Kissling to further improve the 1-D velocity model and event locations. With the robust 1-D velocity model and improved event locations, we inverted a high-resolution 3-D velocity model by using the program LOTOS-10 developed by Koulakov. We present the derived 3-D model and discuss its tectonic implications.

You, S.; Konstantinou, K. I.; Gung, Y.; Lin, C.

2011-12-01

17

Basal Dynamics of a Small Surge-Type Glacier Investigated Using 1-D Geophysical Inverse Modeling  

NASA Astrophysics Data System (ADS)

As part of a study to characterize glacier response to climate in the St. Elias Mountains, Yukon Territory, Canada, the dynamics of a small surge-type valley glacier are investigated. Pole displacements were measured using kinematic global positioning system (GPS) techniques during three consecutive summer field seasons. Calculated surface velocities range from 5 to 10 m/yr over the lower 1.5 km of the 4.5 km-long glacier and increase to around 30 m/yr over the upper 2.5 km. Basal velocities are reconstructed from the measured surface velocities using a 1-D geophysical inverse model. An analytical relationship between the basal velocity, deformational velocity and surface velocity of an ice body flowing in a channel defines the forward model, which is subsequently linearized using a method of longitudinal averaging for variable ice thickness and surface slope. The inversion itself is performed using a spectral decomposition method. Flowline ice thicknesses and surface elevations are required model inputs and are measured with ice- penetrating radar and kinematic GPS surveying, respectively. Sensitivity of the inverse model to uncertain quantities such as the flow-law coefficient, the shape factor and the longitudinal averaging length is quantified through a series of tests. The inversion results show that basal motion accounts for at least 50% and up to 100% of the total surface motion along the flowline. The unexpectedly high flow speeds recorded in the upper reaches of the glacier may explain the formation of fresh crevasses, while the high proportion of basal motion is consistent with observed surface undulations. From these observations and our modeling results, we suggest that the current dynamics of this glacier may be more than a direct response to climate and that the glacier may be undergoing a slow surge. Simple hydrological models are being used to investigate whether spatial variability in the efficiency of the subglacial drainage system may be responsible for the current flow regime.

de Paoli, L.; Flowers, G. E.

2008-12-01

18

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

PubMed

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

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

2006-01-01

19

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

SciTech Connect

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

20

Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves  

USGS Publications Warehouse

Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

21

Variable Selection for 1D Regression Models David J. Olive  

E-print Network

.1) Many important regression models, including generalized linear models (GLM's), sat- isfy (1.1). Another.3) The extraneous terms that can be eliminated given that the subset S is in the model have zero coefficients. Now

Olive, David

22

Isotropic photon drag: Analytic expressions for velocity (3D) and position (1D) with applications to blackbody friction  

NASA Astrophysics Data System (ADS)

The motion of objects traveling at relativistic speeds and subject only to isotropic photon drag (blackbody friction as a special case) is modeled. The objects are assumed to be perfectly absorbing. Analytic expressions for velocity and position as a function of time for objects subject to photon drag are obtained for the case in which the photons are constrained to one-dimensional motion. If the object is also assumed to be a perfect emitter of energy, analytic expressions are found for time as a function of velocity of the body for photons constrained to one-dimensional motion, and for a full three-dimensional isotropic photon background. The derivations are carried out entirely from the point of view of a reference frame at rest relative to the isotropic photon field, so that no changes of reference frame are involved. The results for the three-dimensional model do not agree with work by previous authors, and this discrepancy is discussed. The derivations are suitable for use in the undergraduate classroom. Example cases for a light sail and a micron-sized sand grain are examined for interactions with the cosmic background radiation, assuming a temperature of 3000 K, the temperature at the time the universe became transparent, and it is found that relativistic speeds would decay on a time scale of years.

West, Joseph

2014-03-01

23

1D numerical model of muddy subaqueous and subaerial debris flows  

USGS Publications Warehouse

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

24

Assessing 1D Atmospheric Solar Radiative Transfer Models: Interpretation and Handling of Unresolved Clouds  

Microsoft Academic Search

The primary purpose of this study is to assess the performance of 1D solar radiative transfer codes that are used currently both for research and in weather and climate models. Emphasis is on interpretation and handling of unresolved clouds. Answers are sought to the following questions: (i) How well do 1D solar codes interpret and handle columns of information pertaining

H. W. Barker; G. L. Stephens; P. T. Partain; J. W. Bergman; B. Bonnel; K. Campana; E. E. Clothiaux; S. Clough; S. Cusack; J. Delamere; J. Edwards; K. F. Evans; Y. Fouquart; S. Freidenreich; V. Galin; Y. Hou; S. Kato; J. Li; E. Mlawer; J.-J. Morcrette; W. O'Hirok; P. Räisänen; V. Ramaswamy; B. Ritter; E. Rozanov; M. Schlesinger; K. Shibata; P. Sporyshev; Z. Sun; M. Wendisch; N. Wood; F. Yang

2003-01-01

25

Kinetic and Stochastic Models of 1D yeast ``prions"  

NASA Astrophysics Data System (ADS)

Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeasts have proteins, which can undergo similar reconformation and aggregation processes to PrP; yeast ``prions" are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein (1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics along with our own stochastic approach (2). Both models assume reconformation only upon aggregation, and include aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates.

Kunes, Kay

2005-03-01

26

Kinetic Model for 1D aggregation of yeast ``prions''  

NASA Astrophysics Data System (ADS)

Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeast have proteins which can undergo similar reconformation and aggregation processes to PrP; yeast forms are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein(1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics(2). The model assumes reconformation only upon aggregation, and includes aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates. We will compare to a more realistic stochastic kinetics model and present prelimary attempts to describe recent experiments on SUP35 strains. *-Supported by U.S. Army Congressionally Mandated Research Fund. 1) P. Chien and J.S. Weissman, Nature 410, 223 (2001); http://online.kitp.ucsb.edu/online/bionet03/collins/. 2) J. Masel, V.A.> Jansen, M.A. Nowak, Biophys. Chem. 77, 139 (1999).

Kunes, Kay; Cox, Daniel; Singh, Rajiv

2004-03-01

27

1-D model of bedform-field pattern growth through bedform interactions  

NASA Astrophysics Data System (ADS)

Sediment transport environments that include bedforms also show interactions between these bedforms. These interactions contribute to the emergence of bedform-field patterns. Interactions may be constructive, such as merging between bedforms, regenerative, such as bedform splitting, or neutral, such as bedform or defect repulsion. Our new model addresses the impact of two common interactions, merging and repulsion, on heights and spacing of the bedform field. The 1-D model treats bedforms as similar triangles that migrate at velocities inversely proportional to their heights. In the model, the ratio of the heights of the upstream and downstream bedforms determines whether these bedforms merge or repulse. Merging and repulsion occur when the base of the stoss slopes of the two triangles coincide. Repulsion between an upstream smaller triangle and a downstream larger triangle results in an upstream larger triangle and a downstream smaller triangle, positioned such that the base of the upstream lee slope touches the base of the downstream stoss slope. A repulsion parameter determines what fraction of the dunes masses are exchanged during repulsion. Each process conserves the total area of the triangles as a representation of the conservation of mass, as well as the position of the mass-weighted barycenter of the triangles. If only merging is considered, the decrease in the number of dunes is rapid during the first time steps and slows to a steady state when ninety percent of the dunes have merged. In this scenario, spacing and heights increase over long time scales (100 - 1000 years), but fluctuate at shorter time scales (1-10 years). This simplified model marks an initial effort to understand how pattern growth occurs with different bedform interactions.

Ewing, R. C.; Peyret, A. B.

2008-12-01

28

One-dimensional models of shear wave velocity for the eastern Mediterranean obtained from the inversion of Rayleigh wave phase velocities and tectonic implications  

Microsoft Academic Search

On a SW-NE profile from the Libyan coast towards central Turkey phase velocity curves of the fundamental Rayleigh mode were measured using a two-station method. The inversion of phase velocity curves yields 1-D models of shear wave velocity down to approximately 200 km depths that may be interpreted as estimates of average models between neighbouring stations on the profile. Strong

T. Meier; K. Dietrich; B. Stöckhert; H.-P. Harjes

2004-01-01

29

Newberry EGS Seismic Velocity Model  

SciTech Connect

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.

Dennise Templeton

2013-10-01

30

Newberry EGS Seismic Velocity Model  

DOE Data Explorer

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.

Dennise Templeton

31

Heat-Transfer and Solidification Model of Continuous Slab Casting: CON1D  

E-print Network

Heat-Transfer and Solidification Model of Continuous Slab Casting: CON1D YA MENG and BRIAN G. THOMAS A simple, but comprehensive model of heat transfer and solidification of the continuous casting of steel slabs is described, including phenomena in the mold and spray regions. The model includes a one

Thomas, Brian G.

32

KAM THEORY FOR EQUILIBRIUM STATES IN 1-D STATISTICAL MECHANICS MODELS  

E-print Network

KAM THEORY FOR EQUILIBRIUM STATES IN 1-D STATISTICAL MECHANICS MODELS RAFAEL DE LA LLAVE Abstract-periodic equi- librium solutions in statistical mechanics models. The interactions in the models considered here will consider some mod- els that are very natural from the point of view of statistical mechanics but for which

33

1D finite volume model of unsteady flow over mobile bed  

Microsoft Academic Search

A one dimensional (1D) finite volume model was developed for simulating unsteady flow. The non-equilibrium sediment transport algorithm was adopted in the model. The model was tested under a fixed bed condition and then experimental and field cases. The upwind flux scheme, HLLC approximate Riemann solver and TVD WAF scheme are accurate.

Shiyan Zhang; Jennifer G. Duan

2011-01-01

34

The properties of the hot gas in galaxy groups and clusters from 1D hydrodynamical simulations - I. Cosmological infall models  

Microsoft Academic Search

We report the results of 1D hydrodynamical modelling of the evolution of gas in galaxy clusters. We have incorporated many of the effects missing from earlier 1D treatments: improved modelling of the dark matter and galaxy distributions, cosmologically realistic evolution of the cluster potential, and the effects of a multiphase cooling flow. The model utilizes a fairly standard 1D Lagrangian

P. A. Knight; T. J. Ponman

1997-01-01

35

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

E-print Network

research programs. Many transport models have been partially tested against tokamak data [1]. In order transport codes which are also written in a standardized form and benchmarked against each otherTESTS OF 1-D TRANSPORT MODELS, AND THEIR PREDICTIONS FOR ITER D. R. MIKKELSEN 1 , G. BATEMAN 2 , D

Vlad, Gregorio

36

Inverting full waveforms into 1D seismic (upper) crustal model by Neighborhood Algorithm: example from the Corinth Gulf, Greece  

NASA Astrophysics Data System (ADS)

Constructing seismic models of the Earth crust serves two major purposes: (i) helping to understand a geologic structure, and (ii) enabling investigations of earthquakes in terms of their location, centroid-moment-tensors, and/or slip-history on faults. We follow line (ii) where even good 1D models are still important. Should the 1D models be usable in seismic waveform modeling, the natural way is to derive them from full waveforms. We developed and tested a method in which full waveforms of an earthquake recorded in a network of local-to-regional stations are inverted into a 1D crustal model, optimally representing the seismic wave propagation. A single-point source approximation is used. The hypocenter position, origin time and a double-couple focal mechanism are fixed at previously determined values. The forward problem is solved by the Discrete Wavenumber method (Bouchon, 1981; Coutant 1989). The inverse problem is solved by the Neighborhood Algorithm (Sambridge, 1999), providing a suite of the well-fitting velocity models. The misfit function is the L2 norm of the difference between the observed and synthetic seismograms. The performance of the method is illustrated on the largest event (Mw 5.3) of the 2010 Efpalio earthquake sequence, Greece (Sokos et al., 2012). Broad-band data at 8 stations are used, spanning epicentral distances from 13 to 100 km. Several different parametrizations are tested. The most interesting results are obtained in the frequency range of 0.05-0.20 Hz for varying 7 layer thicknesses, their Vp and Vs. The corresponding waveform match (variance reduction VR~0.6) is significantly better than with the previously existing models of the region. It strengthens a chance to study some details of the space-time rupture process of future significant events in the Corinth Gulf. As revealed by the correlation and covariance matrices, the mutual trade-off between the thicknesses and velocities, as well as between Vp and Vs is negligible. The resolution decreases with depth. The best resolved is a significant Vs increase in the topmost 4 km; the Vp/Vs ratio in this layer is as large as ~2 - 2.5. Several path-dependent (single-station) 1D models were also constructed whose main importance was the stability check. Investigation of lateral crustal variations would require more earthquakes.

Plicka, Vladimir; Zahradnik, Jiri

2013-04-01

37

Modeling measured glottal volume velocity waveforms.  

PubMed

The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use. PMID:12597284

Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S

2003-02-01

38

Comparison of 1D and 2D modelling with soil erosion model SMODERP  

NASA Astrophysics Data System (ADS)

The contribution presents a comparison of a runoff simulated by profile method (1D) and spatially distributed method (2D). Simulation model SMODERP is used for calculation and prediction of soil erosion and surface runoff from agricultural land. SMODERP is physically based model that includes the processes of infiltration (Phillips equation), surface runoff (kinematic wave based equation), surface retention, surface roughness and vegetation impact on runoff. 1D model was developed in past, new 2D model was developed in last two years. The model is being developed at the Department of Irrigation, Drainage and Landscape Engineering, Civil Engineering Faculty, CTU in Prague. 2D model was developed as a tool for widespread GIS software ArcGIS. The physical relations were implemented through Python script. This script uses ArcGIS system tools for raster and vectors treatment of the inputs. Flow direction is calculated by Steepest Descent algorithm in the preliminary version of 2D model. More advanced multiple flow algorithm is planned in the next version. Spatially distributed models enable to estimate not only surface runoff but also flow in the rills. Surface runoff is described in the model by kinematic wave equation. Equation uses Manning roughness coefficient for surface runoff. Parameters for five different soil textures were calibrated on the set of forty measurements performed on the laboratory rainfall simulator. For modelling of the rills a specific sub model was created. This sub model uses Manning formula for flow estimation. Numerical stability of the model is solved by Courant criterion. Spatial scale is fixed. Time step is dynamically changed depending on how flow is generated and developed. SMODERP is meant to be used not only for the research purposes, but mainly for the engineering practice. We also present how the input data can be obtained based on available resources (soil maps and data, land use, terrain models, field research, etc.) and how can the model be used in the assessments of soil erosion risk and in designing of erosion control measures. The research has been supported by the research grants SGS SGS11/148/OHK1/3T/11 "Experimental Research on Rainfall-runoff and Erosion Processes" and by Project No. TA02020647 " Atlas EROZE - a modern tool for soil erosion assessment".

Kavka, Petr; Weyskrabova, Lenka; Zajicek, Jan

2013-04-01

39

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

40

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

SciTech Connect

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

41

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

E-print Network

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

42

submitted to Geophys. J. Int. A 1D modelling of streaming potential dependence on  

E-print Network

submitted to Geophys. J. Int. A 1D modelling of streaming potential dependence on water content: electrokinetics, streaming potential, self potential, water saturation, un- saturated flow, water content, finite of the streaming potential coefficient C as a function of the water saturation Sw is still discussed. We propose

Paris-Sud XI, Université de

43

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

E-print Network

Ensemble Kalman Filter Data Assimilation in a 1D Numerical Model Used for Fog Forecasting SAMUEL RE, a need exists for accurate and updated fog and low-cloud forecasts. Couche Brouillard Eau Liquide (COBEL for the very short-term forecast of fog and low clouds. This forecast system assimilates local observations

Ribes, Aurélien

44

KAM Theory for Equilibrium States in 1-D Statistical Mechanics Models  

Microsoft Academic Search

.  We extend the Lagrangian proof of KAM for twist mappings [34,51] to show persistence of quasi-periodic equilibrium solutions\\u000a in 1-D statistical mechanics models. The interactions in the models considered here do not need to be of finite range but\\u000a they have to decrease sufficiently fast with the distance (a high enough power suffices). In general, these models do not\\u000a admit

Rafael de la Llave

2008-01-01

45

1D Modeling of Catalyzed Monopropellant H2O2 Decomposition in Microchannels  

Microsoft Academic Search

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

Xu Zhou; Darren Hitt

2003-01-01

46

Improved 1D model for calculating hydraulic properties in meandering rivers: Comparisons with measurements and 3D numerical simulations  

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

47

Inversion of MT profiles using laterally coupled 1D piecewise continuous models  

NASA Astrophysics Data System (ADS)

This paper presents a method for constructing coupled, 1D electrical conductivity models of the Earth from surface magnetotelluric measurements. The construction of the individual models is a nonlinear inverse problem that can be approached by linearization techniques combined with iterative methods and Tikhonov's regularization. The standard application of these techniques usually leads to smooth models that represent a continuous variation of conductivity with depth. In a previous work we described how these methods can be modified to incorporate what is known in Computer Vision as the line process (LP) decoupling technique, which has the ability to include discontinuities in the models. This results in piecewise smooth models which are often more adequate for representing stratified media. Now, the 1D models are coupled in order to include information from neighboring sites. We have implemented a relaxation technique to construct 2D profiles using coupled 1D models. We present numerical experiments and application to field data. In both cases we assume that the data is contaminated by static shift effects. The algorithm automatically takes these effects into account. The examples illustrate the performance of the combined LP and Tikhonov's regularization method in the solution of difficult practical problems.

Hidalgo Silva, Hugo; Gomez-Trevino, Enrique; Marroquin Zaleta, Jose L.

1998-10-01

48

Review of Zero-D and 1-D Models of Blood Flow in the Cardiovascular System  

PubMed Central

Background Zero-dimensional (lumped parameter) and one dimensional models, based on simplified representations of the components of the cardiovascular system, can contribute strongly to our understanding of circulatory physiology. Zero-D models provide a concise way to evaluate the haemodynamic interactions among the cardiovascular organs, whilst one-D (distributed parameter) models add the facility to represent efficiently the effects of pulse wave transmission in the arterial network at greatly reduced computational expense compared to higher dimensional computational fluid dynamics studies. There is extensive literature on both types of models. Method and Results The purpose of this review article is to summarise published 0D and 1D models of the cardiovascular system, to explore their limitations and range of application, and to provide an indication of the physiological phenomena that can be included in these representations. The review on 0D models collects together in one place a description of the range of models that have been used to describe the various characteristics of cardiovascular response, together with the factors that influence it. Such models generally feature the major components of the system, such as the heart, the heart valves and the vasculature. The models are categorised in terms of the features of the system that they are able to represent, their complexity and range of application: representations of effects including pressure-dependent vessel properties, interaction between the heart chambers, neuro-regulation and auto-regulation are explored. The examination on 1D models covers various methods for the assembly, discretisation and solution of the governing equations, in conjunction with a report of the definition and treatment of boundary conditions. Increasingly, 0D and 1D models are used in multi-scale models, in which their primary role is to provide boundary conditions for sophisticate, and often patient-specific, 2D and 3D models, and this application is also addressed. As an example of 0D cardiovascular modelling, a small selection of simple models have been represented in the CellML mark-up language and uploaded to the CellML model repository http://models.cellml.org/. They are freely available to the research and education communities. Conclusion Each published cardiovascular model has merit for particular applications. This review categorises 0D and 1D models, highlights their advantages and disadvantages, and thus provides guidance on the selection of models to assist various cardiovascular modelling studies. It also identifies directions for further development, as well as current challenges in the wider use of these models including service to represent boundary conditions for local 3D models and translation to clinical application. PMID:21521508

2011-01-01

49

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

50

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).  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

51

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

PubMed

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

52

The Properties of the Hot Gas in Galaxy Groups and Clusters from 1-D Hydrodynamical Simulations -- I. Cosmological Infall Models  

Microsoft Academic Search

We report the results of 1-D hydrodynamical modelling of the evolution of gas\\u000ain galaxy clusters. We have incorporated many of the effects missing from\\u000aearlier 1-D treatments: improved modelling of the dark matter and galaxy\\u000adistributions, cosmologically realistic evolution of the cluster potential, and\\u000athe effects of a multiphase cooling flow. The model utilises a fairly standard\\u000a1-D Lagrangian

P. A. Knight; T. J. Ponman

1997-01-01

53

Coupled 1D-3D hydrodynamic modelling, with application to the Pearl River Delta  

NASA Astrophysics Data System (ADS)

Within the hydrodynamic modelling community, it is common practice to apply different modelling systems for coastal waters and river systems. Whereas for coastal waters 3D finite difference or finite element grids are commonly used, river systems are generally modelled using 1D networks. Each of these systems is tailored towards specific applications. Three-dimensional coastal water models are designed to model the horizontal and vertical variability in coastal waters and are less well suited for representing the complex geometry and cross-sectional areas of river networks. On the other hand, 1D river network models are designed to accurately represent complex river network geometries and complex structures like weirs, barrages and dams. A disadvantage, however, is that they are unable to resolve complex spatial flow variability. In real life, however, coastal oceans and rivers interact. In deltaic estuaries, both tidal intrusion of seawater into the upstream river network and river discharge into open waters play a role. This is frequently approached by modelling the systems independently, with off-line coupling of the lateral boundary forcing. This implies that the river and the coastal model run sequentially, providing lateral discharge (1D) and water level (3D) forcing to each other without the possibility of direct feedback or interaction between these processes. An additional disadvantage is that due to the time aggregation usually applied to exchanged quantities, mass conservation is difficult to ensure. In this paper, we propose an approach that couples a 3D hydrodynamic modelling system for coastal waters (Delft3D) with a 1D modelling system for river hydraulics (SOBEK) online. This implies that contrary to off-line coupling, the hydrodynamic quantities are exchanged between the 1D and 3D domains during runtime to resolve the real-time exchange and interaction between the coastal waters and river network. This allows for accurate and mass conserving modelling of complex coastal waters and river network systems, whilst the advantages of both systems are maintained and used in an optimal and computationally efficient way. The coupled 1D-3D system is used to model the flows in the Pearl River Delta (Guangdong, China), which are determined by the interaction of the upstream network of the Pearl River and the open waters of the South China Sea. The highly complex upstream river network is modelled in 1D, simulating river discharges for the dry and wet monsoon periods. The 3D coastal model simulates the flow due to the external (ocean) periodic tidal forcing, the salinity distribution for both dry and wet seasons, as well as residual water levels (sea level anomalies) originating from the South China Sea. The model is calibrated and its performance extensively assessed against field measurements, resulting in a mean root mean square (RMS) error of below 6% for water levels over the entire Pearl River Delta. The model also represents both the discharge distribution over the river network and salinity transport processes with good accuracy, resolving the discharge distribution over the main branches of the river network within 5% of reported annual mean values and RMS errors for salinity in the range of 2 ppt (dry season) to 5 ppt (wet season).

Twigt, Daniel J.; de Goede, Erik D.; Zijl, Firmijn; Schwanenberg, Dirk; Chiu, Alex Y. W.

2009-12-01

54

Zero finite-temperature charge stiffness within the half-filled 1D Hubbard model  

SciTech Connect

Even though the one-dimensional (1D) Hubbard model is solvable by the Bethe ansatz, at half-filling its finite-temperature T>0 transport properties remain poorly understood. In this paper we combine that solution with symmetry to show that within that prominent T=0 1D insulator the charge stiffness D(T) vanishes for T>0 and finite values of the on-site repulsion U in the thermodynamic limit. This result is exact and clarifies a long-standing open problem. It rules out that at half-filling the model is an ideal conductor in the thermodynamic limit. Whether at finite T and U>0 it is an ideal insulator or a normal resistor remains an open question. That at half-filling the charge stiffness is finite at U=0 and vanishes for U>0 is found to result from a general transition from a conductor to an insulator or resistor occurring at U=U{sub c}=0 for all finite temperatures T>0. (At T=0 such a transition is the quantum metal to Mott–Hubbard-insulator transition.) The interplay of the ?-spin SU(2) symmetry with the hidden U(1) symmetry beyond SO(4) is found to play a central role in the unusual finite-temperature charge transport properties of the 1D half-filled Hubbard model. -- Highlights: •The charge stiffness of the half-filled 1D Hubbard model is evaluated. •Its value is controlled by the model symmetry operator algebras. •We find that there is no charge ballistic transport at finite temperatures T>0. •The hidden U(1) symmetry controls the U=0 phase transition for T>0.

Carmelo, J.M.P., E-mail: carmelo@fisica.uminho.pt [Center and Department of Physics, University of Minho, Campus Gualtar, P-4710-057 Braga (Portugal) [Center and Department of Physics, University of Minho, Campus Gualtar, P-4710-057 Braga (Portugal); Beijing Computational Science Research Center, Beijing 100084 (China); Institut für Theoretische Physik III, Universität Stuttgart, D-70550 Stuttgart (Germany); Gu, Shi-Jian [Beijing Computational Science Research Center, Beijing 100084 (China) [Beijing Computational Science Research Center, Beijing 100084 (China); Department of Physics and ITP, Chinese University of Hong Kong, Hong Kong (China); Sacramento, P.D. [CFIF, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal) [CFIF, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Beijing Computational Science Research Center, Beijing 100084 (China)

2013-12-15

55

HELIOS-CR - A 1-D Radiation-Magnetohydrodynamics Code with Inline Atomic Kinetics Modeling  

Microsoft Academic Search

HELIOS-CR is a user-oriented 1D radiation-magnetohydrodynamics code to simulate the dynamic evolution of laser-produced plasmas and z-pinch plasmas. It includes an in-line collisional-radiative (CR) model for computing non-LTE atomic level populations at each time step of the hydrodynamics simulation. HELIOS-CR has been designed for ease of use, and is well-suited for experimentalists, as well as graduate and undergraduate student researchers.

J. J. MacFarlane; I. E. Golovkin; P. R. Woodruff

2005-01-01

56

HELIOS-CR – A 1-D radiation-magnetohydrodynamics code with inline atomic kinetics modeling  

Microsoft Academic Search

HELIOS-CR is a user-oriented 1D radiation-magnetohydrodynamics code to simulate the dynamic evolution of laser-produced plasmas and z-pinch plasmas. It includes an in-line collisional-radiative (CR) model for computing non-LTE atomic level populations at each time step of the hydrodynamics simulation. HELIOS-CR has been designed for ease of use, and is well-suited for experimentalists, as well as graduate and undergraduate student researchers.

J. J. MacFarlane; I. E. Golovkin; P. R. Woodruff

2006-01-01

57

HELIOS-CR A 1-D radiation-magnetohydrodynamics code with inline atomic kinetics modeling  

Microsoft Academic Search

HELIOS-CR is a user-oriented 1D radiation-magnetohydrodynamics code to simulate the dynamic evolution of laser-produced plasmas and z-pinch plasmas. It includes an in-line collisional-radiative (CR) model for computing non-LTE atomic level populations at each time step of the hydrodynamics simulation. HELIOS-CR has been designed for ease of use, and is well-suited for experimentalists, as well as graduate and undergraduate student researchers.

J. J. Macfarlane; I. E. Golovkin; P. R. Woodruff

2006-01-01

58

Evaluation of 2 1-D cloud models for the analysis of VAS soundings  

NASA Technical Reports Server (NTRS)

Evaluation of the satellite Visual Infrared Spin Scan Radiometer Atmospheric Sounder (VISSR) has begun to document several of its critical shortcomings as far as numerical cloud models are concerned: excessive smoothing of thermal inversions; imprecise measurement of boundary layer moisture; and tendency to exaggerate atmospheric stability. The sensitivity of 1-D cloud models to their required inputs is stressed with special attention to those parameters obtained from atmospheric soundings taken by the VAS or rawinsonde. In addition to performing model experiments using temperature and moisture profiles having the general characteristics of VAS soundings, standard input sensitivity tests were made and 1-D model performance was compared with observations and the results of a 2-D model experiment using AVE/VAS data (Atmospheric Variability Experiment). Although very encouraging, the results are not sufficient to make any specific conclusions. In general, the VAS soundings are likely to be inadequate to provide the cloud base (and subcloud layer) information needed for inputs to current cumulus models. Above cloud base, the tendency to exaggerate the stability of the atmosphere requires solution before meaningful model experiments are run.

Emmitt, G. D.

1984-01-01

59

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

60

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

PubMed

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

61

EFDC1D - A ONE DIMENSIONAL HYDRODYNAMIC AND SEDIMENT TRANSPORT MODEL FOR RIVER AND STREAM NETWORKS: MODEL THEORY AND USERS GUIDE  

EPA Science Inventory

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...

62

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).  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

63

Boundary-value problem for density-velocity model of collective motion of organisms  

NASA Astrophysics Data System (ADS)

The collective motion of organisms is observed at almost all levels of biological systems. In this paper the density-velocity model of the collective motion of organisms is analyzed. This model consists of a system of nonlinear parabolic equations, a forced Burgers equation for velocity and a mass conservation equation for density. These equations are supplemented with the Neumann boundary conditions for the density and the Dirichlet boundary conditions for the velocity. The existence, uniqueness and regularity of solution for the density-velocity problem is proved in a bounded 1D domain. Moreover, a priori estimates for the solutions are established, and existence of an attractor is proved. Finally, some numerical approximations for asymptotical behavior of the density-velocity model are presented.

Babak, Petro

2008-09-01

64

Dynamic Incompressible Navier-Stokes Model of Catalytic Converter in 1-D Including Fundamental Oxidation Reaction Rate Expressions  

E-print Network

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

65

Evaluation of a Revised Interplanetary Shock Prediction Model: 1D CESE-HD-2 Solar-Wind Model  

NASA Astrophysics Data System (ADS)

We modified the one-dimensional conservation element and solution element (CESE) hydrodynamic (HD) model into a new version [ 1D CESE-HD-2], by considering the direction of the shock propagation. The real-time performance of the 1D CESE-HD-2 model during Solar Cycle 23 (February 1997 - December 2006) is investigated and compared with those of the Shock Time of Arrival Model ( STOA), the Interplanetary-Shock-Propagation Model ( ISPM), and the Hakamada-Akasofu-Fry version 2 ( HAFv.2). Of the total of 584 flare events, 173 occurred during the rising phase, 166 events during the maximum phase, and 245 events during the declining phase. The statistical results show that the success rates of the predictions by the 1D CESE-HD-2 model for the rising, maximum, declining, and composite periods are 64 %, 62 %, 57 %, and 61 %, respectively, with a hit window of ± 24 hours. The results demonstrate that the 1D CESE-HD-2 model shows the highest success rates when the background solar-wind speed is relatively fast. Thus, when the background solar-wind speed at the time of shock initiation is enhanced, the forecasts will provide potential values to the customers. A high value (27.08) of ? 2 and low p-value (< 0.0001) for the 1D CESE-HD-2 model give considerable confidence for real-time forecasts by using this new model. Furthermore, the effects of various shock characteristics (initial speed, shock duration, background solar wind, longitude, etc.) and background solar wind on the forecast are also investigated statistically.

Zhang, Y.; Du, A. M.; Du, D.; Sun, W.

2014-08-01

66

A 1-D modelling of streaming potential dependence on water content during drainage experiment in sand  

E-print Network

The understanding of electrokinetics for unsaturated conditions is crucial for numerous of geophysical data interpretation. Nevertheless, the behaviour of the streaming potential coefficient C as a function of the water saturation Sw is still discussed. We propose here to model both the Richards' equation for hydrodynamics and the Poisson's equation for electrical potential for unsaturated conditions using 1-D finite element method. The equations are first presented and the numerical scheme is then detailed for the Poisson's equation. Then, computed streaming potentials (SPs) are compared to recently published SP measurements carried out during drainage experiment in a sand column. We show that the apparent measurement of DV / DP for the dipoles can provide the SP coefficient in these conditions. Two tests have been performed using existing models for the SP coefficient and a third one using a new relation. The results show that existing models of unsaturated SP coefficients C(Sw) provide poor results in term...

Allègre, Vincent; Ackerer, Philippe; Jouniaux, Laurence; Sailhac, Pascal; 10.1111/j.1365-246X.2012.05371.x

2012-01-01

67

Prediction of changes in landslide movements induced by rainfalls: from the use of a black box model to a 1D mechanical model  

NASA Astrophysics Data System (ADS)

Predicting landslide surface displacements is a challenge for scientists, as it may help save human lives and protect individual housing or transport, energetic facilities. One of the main challenges in active landslide monitoring concerns the prediction of slope's movements in the near future. This study focuses on an innovative methodology to predict landslide surface accelerations, based on a black box tool coupled to a 1D mechanical model. These models are able to predict the evolution of the daily displacements according to the variations of precipitation. More specifically, the impulse response model allows predicting the changes in the landslide movements by computing the transfer function between the input signal (precipitation in this case) and the output signal (the displacements). The second model is based on a simple 1D mechanical assumption, with considering a viscoplastic behavior of the landslide's material, and with taking into account the evolution of the pore water pressure in time. These methods have been applied to the Super-Sauze landslide, located in the Southern French Alps, mountainous region. This site is controlled by complex hydrologic processes leading to active movements within black marls, with velocities ranging between 0.002 and 0.4 m per day. After preliminary tests, results show that the snowmelt has to be taken into account in the models, since the phenomena of freezing /thawing has an influence on the water refills, leading to movement changes. Different approaches to integrate rainfall and/or snow-melting inputs are compared and their complementarity is demonstrated. Finally, a validated methodology for predicting movement changes within landslide based on criteria of comparison between the observed and calculated velocities can be proposed. The results suggest that the impulse response model reproduces the observed data with very good accuracy, whereas the mechanical model seems to be more adapted to predict the movements within 10 days. Moreover, the RMSE criterion permits to highlight the occurrence of the flow, with considering all models, 11 days before the flow itself.

Bernardie, S.; Desramaut, N.; Russo, G.; Grandjean, G.

2012-04-01

68

VizieR Online Data Catalog: Model 1D (LHD) and 3D (CO5BOLD) spectra (Allende Prieto+, 2013)  

NASA Astrophysics Data System (ADS)

Model spectral fluxes for late-type stars computed from 3D hydrodynamical simulations of surface convection performed with the CO5BOLD code. Their 1D hydrostatic counterparts are included, based on the LHD code, sharing the same microphysics as the CO5BOLD models. The fluxes for both the 3D and 1D models are calculated with the same opacities and radiative transfer code (ASSET). (6 data files).

Allende Prieto, C.; Koesterke, L. Ludwig H.-G.; Freytag, B.; Caffau, E.

2012-11-01

69

1D finite volume model of unsteady flow over mobile bed  

NASA Astrophysics Data System (ADS)

SummaryA one dimensional (1D) finite volume method (FVM) model was developed for simulating unsteady flow, such as dam break flow, and flood routing over mobile alluvium. The governing equation is the modified 1D shallow water equation and the Exner equation that take both bed load and suspended load transport into account. The non-equilibrium sediment transport algorithm was adopted in the model, and the van Rijn method was employed to calculate the bed-load transport rate and the concentration of suspended sediment at the reference level. Flux terms in the governing equations were discretised using the upwind flux scheme, Harten et al. (1983) (HLL) and HLLC schemes, Roe's scheme and the Weighted Average Flux (WAF) schemes with the Double Minmod and Minmod flux limiters. The model was tested under a fixed bed condition to evaluate the performance of several different numerical schemes and then applied to an experimental case of dam break flow over a mobile bed and a flood event in the Rillito River, Tucson, Arizona. For dam break flow over movable bed, all tested schemes were proved to be capable of reasonably simulating water surface profiles, but failed to accurately capture the hydraulic jump. The WAF schemes produced slight spurious oscillations at the water surface and bed profiles and over-estimated the scour depth. When applying the model to the Rillito River, the simulated results generally agreed well with the field measurements of flow discharges and bed elevation changes. Modeling results of bed elevation changes were sensitive to the suspended load recovery coefficient and the bed load adaptation length, which require further theoretical and experimental investigations.

Zhang, Shiyan; Duan, Jennifer G.

2011-07-01

70

Calibration and Validation of 1-d and 2-d Flood Flow Models  

NASA Astrophysics Data System (ADS)

The complexity of model required to predict inundation extent at reach lengths of ~10km is unknown. Recent advances in remote sensing have enabled maps of flood extent to be used to assess model predictions, and therefore flood flow models can now be rigorously validated in terms of inundated area. Three flood flow models (HEC- RAS, LISFLOOD-FP and TELEMAC-2D) are tested on a 60km reach of the river Severn, UK, for two flood events for which SAR imagery has been acquired. The use of two events enable one to be used for calibration of model friction parameters and the other for independent validation data. Point discharge measurements can also be used for calibration and validation. When calibrating on one flood event and validating on the other, the results indicated that the 1-D model is capable of predicting flood extent well with only discharge calibration data, whereas the 2-D approaches require inundated area data to be calibrated adequately. All 3 models give similar levels of performance in terms of inundated area.

Horritt, M.; Bates, P.

71

Quantum Cosmological Relational Model of Shape and Scale in 1-d  

E-print Network

Relational particle models are useful toy models for quantum cosmology and the problem of time in quantum general relativity. This paper shows how to extend existing work on concrete examples of relational particle models in 1-d to include a notion of scale. This is useful as regards forming a tight analogy with quantum cosmology and the emergent semiclassical time and hidden time approaches to the problem of time. This paper shows furthermore that the correspondence between relational particle models and classical and quantum cosmology can be strengthened using judicious choices of the mechanical potential. This gives relational particle mechanics models with analogues of spatial curvature, cosmological constant, dust and radiation terms. A number of these models are then tractable at the quantum level. These models can be used to study important issues 1) in canonical quantum gravity: the problem of time, the semiclassical approach to it and timeless approaches to it (such as the naive Schrodinger interpretation and records theory). 2) In quantum cosmology, such as in the investigation of uniform states, robustness, and the qualitative understanding of the origin of structure formation.

Edward Anderson

2010-03-21

72

Evaluation of 1D and 2D numerical models for predicting river flood inundation  

NASA Astrophysics Data System (ADS)

1D and 2D models of flood hydraulics (HEC-RAS, LISFLOOD-FP and TELEMAC-2D) are tested on a 60 km reach of the river Severn, UK. Synoptic views of flood extent from radar remote sensing satellites have been acquired for flood events in 1998 and 2000. The three models are calibrated, using floodplain and channel friction as free parameters, against both the observed inundated area and records of downstream discharge. The predictive power of the models calibrated against inundation extent or discharge for one event can thus be measured using independent validation data for the second. The results show that for this reach both the HEC-RAS and TELEMAC-2D models can be calibrated against discharge or inundated area data and give good predictions of inundated area, whereas the LISFLOOD-FP needs to be calibrated against independent inundated area data to produce acceptable results. The different predictive performances of the models stem from their different responses to changes in friction parameterisation.

Horritt, M. S.; Bates, P. D.

2002-11-01

73

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

PubMed

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

74

HELIOS-CR A 1-D radiation-magnetohydrodynamics code with inline atomic kinetics modeling  

NASA Astrophysics Data System (ADS)

HELIOS-CR is a user-oriented 1D radiation-magnetohydrodynamics code to simulate the dynamic evolution of laser-produced plasmas and z-pinch plasmas. It includes an in-line collisional-radiative (CR) model for computing non-LTE atomic level populations at each time step of the hydrodynamics simulation. HELIOS-CR has been designed for ease of use, and is well-suited for experimentalists, as well as graduate and undergraduate student researchers. The energy equations employed include models for laser energy deposition, radiation from external sources, and high-current discharges. Radiative transport can be calculated using either a multi-frequency flux-limited diffusion model, or a multi-frequency, multi-angle short characteristics model. HELIOS-CR supports the use of SESAME equation of state (EOS) tables, PROPACEOS EOS/multi-group opacity data tables, and non-LTE plasma properties computed using the inline CR modeling. Time-, space-, and frequency-dependent results from HELIOS-CR calculations are readily displayed with the HydroPLOT graphics tool. In addition, the results of HELIOS simulations can be post-processed using the SPECT3D Imaging and Spectral Analysis Suite to generate images and spectra that can be directly compared with experimental measurements. The HELIOS-CR package runs on Windows, Linux, and Mac OSX platforms, and includes online documentation. We will discuss the major features of HELIOS-CR, and present example results from simulations.

Macfarlane, J. J.; Golovkin, I. E.; Woodruff, P. R.

2006-05-01

75

Exploring triggers for polar tropospheric ODEs, using a 1-D snow photochemistry model (MISTRA-SNOW).  

NASA Astrophysics Data System (ADS)

Tropospheric Ozone Depletion Events (ODEs) have been known to occur in polar regions for over 20 years. During such events, ozone concentrations can fall from background amounts to below instrumental detection limits within a few minutes and remain suppressed for on the order of hours to days. The chemical destruction of ozone is driven by halogens (especially bromine radicals) that have a source associated with the sea ice zone. Although our knowledge of ODEs has increased greatly since their discovery, some of the key processes involved are not yet fully understood. We now know that heterogeneous reactions lead to the activation of Br2 and BrCI, via uptake of HOBr onto aqueous salt solutions /aerosol/ surface snowpack (Fickert et al., 1999), and it is widely accepted that bromine catalytic reaction cycles (the 'bromine explosion') in the gas phase are responsible for surface ozone destruction (Simpson et al., 2007). There is still much debate over the source of bromine in the atmosphere that drives ODEs, but there is strong evidence to suggest a source associated with the sea ice zone. A 1D Marine Boundary Layer (MBL) chemistry model (MISTRA; von Glasow et al., 2002) has been modified to be representative of Antarctic conditions. The chemistry module includes chemical reactions in the gas phase, in and on aerosol particles and takes into account transfer between the gas and aqueous phase. A new snow-photochemistry module has been developed which includes chemistry which takes place in the quasi-liquid layer on aerosol (Thomas et al., 2011), which is of great importance to our understanding of the chemistry which initiates a bromine explosion. Here we use this newly developed 1-D snow photochemistry model (MISTRA-SNOW) to look at some of the suggested triggers for, and the different meteorological conditions required to produce, tropospheric ODEs in polar regions.

Buys, Z.; Jones, A. E.; von Glasow, R.

2012-04-01

76

Testing the accuracy of a 1-D volcanic plume model in estimating mass eruption rate  

USGS Publications Warehouse

During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historical eruptions where plume height Hobs was well observed and mass eruption rate Mobs could be calculated from mapped deposit mass and observed duration. The simulations considered wind, temperature, and phase changes of water. Atmospheric conditions were obtained from the National Center for Atmospheric Research Reanalysis 2.5° model. Simulations calculate the minimum, maximum, and average values (Mmin, Mmax, and Mavg) that fit the plume height. Eruption rates were also estimated from the empirical formula Mempir?=?140Hobs4.14 (Mempir is in kilogram per second, Hobs is in kilometer). For these eruptions, the standard error of the residual in log space is about 0.53 for Mavg and 0.50 for Mempir. Thus, for this data set, the model is slightly less accurate at predicting Mobs than the empirical curve. The inability of this model to improve eruption rate estimates may lie in the limited accuracy of even well-observed plume heights, inaccurate model formulation, or the fact that most eruptions examined were not highly influenced by wind. For the low, wind-blown plume of 14–18 April 2010 at Eyjafjallajökull, where an accurate plume height time series is available, modeled rates do agree better with Mobs than Mempir.

Mastin, Larry G.

2014-01-01

77

Velocity Profiles and Unsteady Pipe Friction in Transient Flow  

Microsoft Academic Search

Transient conditions in closed conduits have traditionally been modeled as 1D flows with the implicit assumption that velocity profile and friction losses can be accurately predicted using equivalent 1D velocities. Although more complex fluid models have been suggested, there has been little direct experimental basis for selecting one model over another. This paper briefly reviews the significance of the 1D

Bruno Brunone; Bryan W. Karney; Michele Mecarelli; Marco Ferrante

2000-01-01

78

The Properties of the Hot Gas in Galaxy Groups and Clusters from 1-D Hydrodynamical Simulations; 1, Cosmological Infall Models  

E-print Network

We report the results of 1-D hydrodynamical modelling of the evolution of gas in galaxy clusters. We have incorporated many of the effects missing from earlier 1-D treatments: improved modelling of the dark matter and galaxy distributions, cosmologically realistic evolution of the cluster potential, and the effects of a multiphase cooling flow. The model utilises a fairly standard 1-D Lagrangian hydrodynamical code to calculate the evolution of the intracluster gas. This is coupled to a theoretical model for the growth of dark matter density perturbations. The main advantages of this treatment over 3-D codes are (1) improved spatial resolution within the cooling flow region, (2) much faster execution time, allowing a fuller exploration of parameter space, and (3) the inclusion of additional physics. In the present paper, we explore the development of infall models -- in which gas relaxes into a deepening potential well -- covering a wide range of cluster mass scales. We find that such simple models reproduce ...

Knight, P A

1997-01-01

79

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

80

A crustal seismic velocity model for the UK, Ireland and surrounding seas  

USGS Publications Warehouse

A regional model of the 3-D variation in seismic P-wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity-depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 ?? 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

Kelly, A.; England, R. W.; Maguire, P. K. H.

2007-01-01

81

1D Transient Model for Frost Heave in PEFCs III. Heat Transfer, Microporous Layer, and Cycling Effects  

E-print Network

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.

82

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

83

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

USGS Publications Warehouse

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

84

The Properties of the Hot Gas in Galaxy Groups and Clusters from 1-D Hydrodynamical Simulations -- I. Cosmological Infall Models  

E-print Network

We report the results of 1-D hydrodynamical modelling of the evolution of gas in galaxy clusters. We have incorporated many of the effects missing from earlier 1-D treatments: improved modelling of the dark matter and galaxy distributions, cosmologically realistic evolution of the cluster potential, and the effects of a multiphase cooling flow. The model utilises a fairly standard 1-D Lagrangian hydrodynamical code to calculate the evolution of the intracluster gas. This is coupled to a theoretical model for the growth of dark matter density perturbations. The main advantages of this treatment over 3-D codes are (1) improved spatial resolution within the cooling flow region, (2) much faster execution time, allowing a fuller exploration of parameter space, and (3) the inclusion of additional physics. In the present paper, we explore the development of infall models -- in which gas relaxes into a deepening potential well -- covering a wide range of cluster mass scales. We find that such simple models reproduce many of the global properties of observed clusters. Very strong cooling flows develop in these 1-D cluster models. In practice, disruption by major mergers probably reduces the cooling rate in most clusters. The models overpredict the gas fraction in low mass systems, indicating the need for additional physical processes, such as preheating or galaxy winds, which become important on small mass scales.

P. A. Knight; T. J. Ponman

1997-04-08

85

An 1-D vertically resolved modelling study of the ecosystem dynamics of the middle and southern Adriatic Sea  

Microsoft Academic Search

In order to investigate the regional variations in the physical controls upon the Adriatic Sea ecosystem the European Regional Seas Ecosystem Model (ERSEM) has been coupled to an 1-D vertically resolved water column model. It has been set-up and run to simulate climatological seasonal cycles at two sites, in the open waters of the middle and southern Adriatic Sea. Climatological

J. I. Allen; J. C. Blackford; P. J. Radford

1998-01-01

86

Modeling velocity dispersion In Gypsy site, Oklahoma  

E-print Network

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

87

Comparison of 1D and 2D CSR Models with Application to the FERMI@ELETTRA Bunch Compressors  

SciTech Connect

We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces [1]. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. As an application, we present numerical results for the Fermi{at}Elettra first bunch compressor with the configuration described in [1].

Bassi, G.; Ellison, J.A.; Heinemann, K.

2011-03-28

88

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

89

A marching in space and time (MAST) solver of the shallow water equations. Part I: The 1D model  

NASA Astrophysics Data System (ADS)

A new approach is presented for the numerical solution of the complete 1D Saint-Venant equations. At each time step, the governing system of partial differential equations (PDEs) is split, using a fractional time step methodology, into a convective prediction system and a diffusive correction system. Convective prediction system is further split into a convective prediction and a convective correction system, according to a specified approximated potential. If a scalar exact potential of the flow field exists, correction vanishes and the solution of the convective correction system is the same solution of the prediction system. Both convective prediction and correction systems are shown to have at each x - t point a single characteristic line, and a corresponding eigenvalue equal to the local velocity. A marching in space and time (MAST) technique is used for the solution of the two systems. MAST solves a system of two ordinary differential equations (ODEs) in each computational cell, using for the time discretization a self-adjusting fraction of the original time step. The computational cells are ordered and solved according to the decreasing value of the potential in the convective prediction step and to the increasing value of the same potential in the convective correction step. The diffusive correction system is solved using an implicit scheme, that leads to the solution of a large linear system, with the same order of the cell number, but sparse, symmetric and well conditioned. The numerical model shows unconditional stability with regard of the Courant-Friedrichs-Levi (CFL) number, requires no special treatment of the source terms and a computational effort almost proportional to the cell number. Several tests have been carried out and results of the proposed scheme are in good agreement with analytical solutions, as well as with experimental data.

Aricò, C.; Tucciarelli, T.

2007-05-01

90

Development of a 1D canopy module to couple mesoscale meteorogical model with building energy model  

NASA Astrophysics Data System (ADS)

The actual global warming, highlighted by the scientific community, is due to the greenhouse gases emissions resulting from our energy consumption. This energy is mainly produced in cities (about 70% of the total energy use). Around 36% of this energy are used in buildings (residential/tertiary) and this accounts for about 20% of the greenhouse gases emissions. Moreover, the world population is more and more concentrated in urban areas, 50% of the actual world population already lives in cities and this ratio is expected to reach 70% by 2050. With the obviously increasing responsibility of cities in climate change in the future, it is of great importance to go toward more sustainable cities that would reduce the energy consumption in urban areas. The energy use inside buildings is driven by two factors: (1) the level of comfort wished by the inhabitants and (2) the urban climate. On the other hand, the urban climate is influenced by the presence of buildings. Indeed, artificial surfaces of urban areas modify the energy budget of the Earth's surface and furthermore, heat is released into the atmosphere due to the energy used by buildings. Modifications at the building scale (micro-scale) can thus have an influence on the climate of the urban areas and surroundings (meso-scale), and vice and versa. During the last decades, meso-scale models have been developed to simulate the atmospheric conditions for domain of 100-1000km wide with a resolution of few kilometers. Due to their low resolution, the effects of small obstacles (such as buildings, trees, ...) near the ground are not reproduced properly and parameterizations have been developed to represent such effects in meso-scale models. On the other side, micro-scale models have a higher resolution (around 1 meter) and consequently can better simulate the impact of obstacles on the atmospheric heat flux exchanges with the earth surface. However, only a smaller domain (less than 1km) can be simulated for the same computational time. To simulate the processes at the micro-scale (building) as well as at the meso-scale (city and surroundings), it is necessary to connect these two types of models. It is proposed here to develop a canopy module able to act as an interface between these two scales. The meso-scale model provides the meteorological parameters to the micro-scale model via the canopy module. The micro-scale model then calculates the influence of the different type of surfaces on the variables and gives its back through the module to the meso-scale model. By simulating in a better way the interactions between the atmosphere and the urban surfaces, the model will enhance the estimation of the energy use by building. The tool produced by this research could be coupled in the future with an urban dynamics model to optimize urban planning in order to improve the sustainability of cities.

Mauree, Dasaraden; Kohler, Manon; Blond, Nadège; Clappier, Alain

2013-04-01

91

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

Microsoft Academic Search

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

1985-01-01

92

Using the SPAC Microtremor Method to Identify 2D Effects and Evaluate 1D Shear-Wave Velocity Profile in Valleys  

E-print Network

Microtremor survey methods to evaluate the shear-wave velocity (SWV) profile at specific sites, using in popularity. The microtremor survey methods are ideally suited for urban environment; they are noninvasive

93

INFIL1D: a quasi-analytical model for simulating one-dimensional, constant flux infiltration  

SciTech Connect

The program INFIL1D is designed to calculate approximate wetting-front advance into an unsaturated, uniformly moist, homogeneous soil profile, under constant surface-flux conditions. The code is based on a quasi-analytical method, which utilizes an assumed invariant functional relationship between reduced (normalized) flux and water content. The code uses general hydraulic property data in tabular form to simulate constant surface-flux infiltration. 10 references, 4 figures.

Simmons, C.S.; McKeon, T.J.

1984-04-01

94

Differential cloud models for solar velocity field measurements  

Microsoft Academic Search

The analysis of velocity fields in solar ejecta is an important step in understanding mechanisms of acceleration and energy transfer. Unfortunately, Beckers' cloud model is not quite valid in the case of fast mass flows observed on the disk, because of the fluctuations of the chromospheric background in active regions, and because of strong velocity gradients along the line of

P. Mein; N. Mein

1988-01-01

95

Is flow velocity a significant parameter in flood damage modelling?  

Microsoft Academic Search

Flow velocity is generally presumed to influence flood damage. However, this influence is hardly quantified and virtually no damage models take it into account. Therefore, the influences of flow velocity, water depth and combinations of these two impact parameters on various types of flood damage were investigated in five communities affected by the Elbe catchment flood in Germany in 2002.

H. Kreibich; K. Piroth; I. Seifert; H. Maiwald; U. Kunert; J. Schwarz; B. Merz; A. H. Thieken

2009-01-01

96

1D velocity structure beneath broadband seismic stations in the Gyeongsang Basin and the Okcheon Fold Belt of Korea by receiver function analysis  

NASA Astrophysics Data System (ADS)

The crustal velocity structures beneath four broadband seismic stations (GKP, GSU, HDB, and BUS) in the Gyeongsang Basin and six broadband seismic stations (HKU, JSB, MGB, NPR, SND, and TJN) in the Okcheon Fold Belt of Korea, are estimated by using receiver function analysis employing teleseismic waveforms. The genetic algorithm is adopted to avoid the inherent non-uniqueness problem of the inversion. The inversion results are constrained by surface wave dispersions to complement the shortcoming of the receiver function. The selected records of earthquakes distributed in three quadrants from each seismic station in the years since 2001 are analyzed. Since recent large teleseismic earthquake data of magnitudes larger than 6.0 are included in the analyses, the velocity structures found in the present work are expected to be more reliable than those by the previous independent works. The crustal thickness in the Gyeongsang Basin is estimated to be 28-35 km and that in the Okcheon Fold Belt is estimated to be 32-34 km. The Moho depths under GKP, GSU, HDB, and BUS in the Gyeongsang Basin are 30, 32, 28, and 35 km, respectively. The Moho depths are 32, 34, 32, 32-34, 32, and 32 km beneath HKU, JSB, MGB, NPR, SND, and TJN in the Okcheon Fold Belt, respectively. The Moho depths under GKP and TJN are well coincident with those in nearby velocity cross-sections obtained from crustal-scale seismic profiles. A distinct low velocity anomaly is found at the depth of about 10 km under GSU. An adakitic intrusion which results from the partial melting of a young and hot subducted oceanic crust in the basin during the Cretaceous is suggested as a possible geologic interpretation of the low velocity zone. The significant phase amplitude and arrival time differences in the radial receiver functions conclude the Moho under HDB to dip southwestwardly. This is supported by polarities of direct and in transverse receiver functions. The crustal velocity structures estimated in this work will be able to offer fundamental information to other geologists, and the geological and tectonic interpretation of the velocity structures is expected.

Park, S.; Lee, J. M.; Kang, T.; Han, S.

2009-12-01

97

Continuous model of the regional velocity field for Poland  

NASA Astrophysics Data System (ADS)

The poster presents modern determinations of the regional velocity field for Poland. The research is based on the ASG-EUPOS, Polish multifunctional GNNS network and performed within the developmental project of the Polish Ministry of Science and Higher Education. The network of the satellite-based sites consisted of above 130 Polish sites together with the selected number of European sites operating within EPN (EUREF Permanent Network). Data came from three-year period, which is the minimum number for the horizontal velocity determinations. The velocities were calculated within the discrete network related to the GNSS sites' distribution and then interpolated to the regular grid. The discussion on the interpolation methods is also included. To the interpolation of the velocity field kriging, spline and other functions were used. Assessment of the accuracy of the velocity on the interpolated points and tests of significance were also described. Developed models of the velocities field could indicate geodynamical activity on the area of Poland.

Bogusz, J.; Figurski, M.; Kontny, B.; Grzempowski, P.; Klos, A.

2012-04-01

98

Regional Travel-Time Uncertainty and Seismic Location Improvement Using 3-Dimensional a priori Velocity Models  

NASA Astrophysics Data System (ADS)

We assess the ability of 3-D velocity models to better predict regional seismic travel times, relative to 1-D models, as well as quantify the travel time uncertainties. Accurate travel time prediction and uncertainty characterization is essential for properly identifying regional seismic phases and computing seismic event locations with representative error ellipses. To accomplish this we use an a priori, 3-D velocity model of Western Eurasia developed at LLNL [Pasyanos et al., 2003] and a dataset of P and Pn phase picks from a catalog of calibration events which meet strict network criteria as investigated by Bondar et al., [2003]. We evaluate the predictive power of the model by computing the median residuals between the observed arrivals and those predicted by 3-D finite difference computations. Statistical assessment of prediction accuracy is made in a non-stationary framework. We conclude that 1-D velocity models are not able to accurately characterize travel time uncertainties; not even radially symmetric models will work. Also, statistical estimates of uncertainty must be made in a region-specific framework (i.e., 3-D). These results demonstrate quantitatively that 3-D velocity models accomplish two goals: improving travel-time prediction (by reducing overall variance of residuals), and reducing the dimensionality of the uncertainties by accounting for the non-stationary component. We also investigate improvement in seismic location using an adaptive station correction approach which combines both model predictions and empirical data. We find that no individual Earth model provides optimal travel-time prediction everywhere. We have, therefore, geographically merged travel-time predictions from a variety of different models and empirical observations to form a travel-time model (correction surface) for each station. Our approach combines the extrapolative advantages of model-based corrections and the interpolative/geostatistical advantages of kriging [Schultz et al., 1998] to produce hybrid travel-time predictions and uncertainty models. For ease of use, model-based and empirical corrections are combined to produce one travel-time correction surface (per seismic station) and uncertainty model that is applied on top of the iasp91 global Earth model in our location algorithm. Such 3-D models and uncertainty characterizations help to achieve location accuracy and computation of representative location error ellipses in a regional monitoring environment, particularly for small events not recorded teleseismically. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48, Contribution UCRL-JC-155079-ABS.

Flanagan, M. P.; Myers, S. C.

2003-12-01

99

Quantum correlations in the 1D spin-1/2 Ising model with added Dzyaloshinskii-Moriya interaction  

NASA Astrophysics Data System (ADS)

We have considered the 1D spin-1/2 Ising model with added Dzyaloshinskii-Moriya (DM) interaction and presence of a uniform magnetic field. Using the mean-field fermionization approach the energy spectrum in an infinite chain is obtained. The quantum discord (QD) and concurrence between nearest neighbor (NN) spins at finite temperature are specified as a function of mean-field order parameters. A comparison between concurrence and QD is done and differences are obtained. The macroscopic thermodynamical witness is also used to detect quantum entanglement region in solids within our model. We believe our results are useful in the field of the quantum information processing.

Soltani, M. R.; Vahedi, J.; Mahdavifar, S.

2014-12-01

100

3-D crustal velocity model for Lithuania and its application to local event studies  

NASA Astrophysics Data System (ADS)

PASSEQ 2006-2008 project (PASsive Seismic Experiment in TESZ) aimed at studying the lithosphere-asthenosphere system around the TransEuropean Suture Zone (TESZ)- the transition between old Proterozoic platform of north and east Europe and younger Phanerozoic platform in central and western Europe. The experiment was a seismic array research aiming to retrieve the structure of the crust and Earth's mantle down to the mantle transition zone, including mapping of upper mantle seismic velocity variations and discontinuities (Moho, lithosphere-asthenosphere boundary, mantle transition zone) using all available techniques. During the experiment 26 seismic stations (including four broadband stations) were installed in Lithuania and operated since June, 2006 till January, 2008. One of the main reasons of PASSEQ deployment in Lithuania is identification and characterisation of the local seismic activity. During the data acquisition period a number of local seismic events was identified and preliminary event location was made using LocSat and VELEST algorithms and 1-D velocity models. These standard procedures is not enough precise for Lithuania, however, because the thickness of the crust varies significantly in the region (from 45 to 55 km). Another problem was low quality of S-wave arrivals due to thick (up to 2 km) sediments in most part of Lithuania. In order to improve event location, we compiled a 3-D seismic velocity model of the crust down to a depth of 60 km. The model, consisting of four major layers (sediments, upper crust, middle crust, lower crust and uppermost mantle) was interpolated from 2-D velocity models along previous wide-angle reflection and refraction profiles into a regular grid. The quality of the approximation was analysed using comparison of travel times of P-waves recorded by controlled source experiments and calculated travel times through the 3-D velocity model. The model was converted into a density model using a special procedure, in which the density model is approximated by relationship between seismic velocity and density and the latter is found using inversion of the Bouguer anomaly. Comparison of the inversion result to the observed Bouguer anomaly showed that the upper part of the model needs to be corrected, in particular, in the areas not covered by the profiles. The corrected velocity model was then used to improve location of local events. The epicenters of events relocated with the use of a 3-D model are much less scattered and some of the clusters are confined to known areas of human activity.

Budraitis, M.; Kozlovskaya, E.; Janutyte, I.; Motuza, G.

2009-12-01

101

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

102

1D energy transport in a strongly scattering laboratory model Kasper van Wijk,1  

E-print Network

a grooved model with ul- trasonic surface waves. In ultrasonics, the amplitude and phase of elastic waves provide direct measurements of co- herent and incoherent signal 16,17,23,24 , while surface wave modelsHz tone burst that launches surface waves perpendicular to the grooves 28,29 . The surface waves

Barrash, Warren

103

An Analytical Electrothermal Model of a 1-D Electrothermal MEMS Micromirror  

E-print Network

temperature, maximum temperature, average temperature, and equivalent thermal resistance. The simplest model is used to solve for the temperature distribution of the device upon actuation. Three models are developed and convection and the temperature dependence of the actuator electrical resistor. The temperature distribution

Bowers, John

104

1-D DC Resistivity Modeling and Interpretation in Anisotropic Media Using Particle Swarm Optimization  

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

105

A 1-D Size Specific Numerical Model for Gravel Transport That Includes Sediment Exchange with a Floodplain  

NASA Astrophysics Data System (ADS)

Sedimentary deposits adjacent to rivers can represent important sources and sinks for bed material sediment, particularly on decadal and longer timescales. The Morphodynamics and Sediment Tracers in 1-D model (MAST-1D) is a size-specific sediment transport model that allows for active exchange between channel and floodplain sediment on river reaches of tens to hundreds of kilometers in length. The model is intended to provide a mechanism for performing a first-order assessment of the likely importance of off-channel sediment exchange in controlling decadal-scale geomorphic trends, thereby helping plan and/or prioritize field data collection and higher resolution modeling work. The model develops a sediment budget for short segments of an alluvial valley. Each segment encompasses several active river bends. In each segment, a sediment transport capacity computation is performed to determine the downstream flux of bed material sediment, following the approach of most other 1-D sediment transport models. However, the model differs from most other bed evolution models in that sediment can be exchanged with the floodplain in each segment, and mass conservation is applied to both the active layer and floodplain sediment storage reservoirs. The potential for net imbalances in overall exchange as well as the size specific nature of the computations allows the model to simulate reach-scale aggradation/degradation and/or changes in bed texture. The inclusion of fine sediment in the model allows it to track geochemical tracer material and also provides a mechanism to simulate, to first order, the effects of changes in the supply of silt and clay on overall channel hydraulic capacity. The model is applied to a ~40 km reach of the Ain River, a tributary of the Rhône River in eastern France that has experienced a significant sediment deficit as a result of the construction of several dams between 1920 and 1970. MAST-1D simulations result in both incision and the formation of a bed armor near the upstream end of the study reach, where sediment load has been disrupted. The inclusion of active exchange with the floodplain allows the floodplain evolve into a net source of bed material sediment as the channel incises. This effect prevents the sediment deficit from reaching the confluence with the Rhone for several simulated decades. When spatially variable migration rates similar to those measured from aerial photography are used to drive sediment exchange, the model shows complex interaction between bed and bank sediment, with the relatively fine-grained bank sediment supply mobilizing the coarser fraction of the active layer within rapidly shifting portions of the channel. This increases overall transport rates and leads to additional channel incision relative to what is simulated without bank sediment supply in these rapidly shifting reaches. The model is also helpful for evaluating the potential reach-scale effects of gravel augmentation downstream of the dams.

Lauer, Wesley; Viparelli, Enrica; Piegay, Herve

2014-05-01

106

An Extended Global Sensitivity Analysis Implemented on a 1D Land Biosphere Model  

NASA Astrophysics Data System (ADS)

The implementation of sophisticated mathematical models is undoubtedly becoming increasingly widely used in a variety of fields in geosciences. SimSphere belongs to a special category of land biosphere models called Soil Vegetation Atmosphere Transfer (SVAT) models. Those provide representations, in a vertical profile, of the physical mechanisms controlling the physical interactions occurring in the soil/vegetation/atmosphere continuum at a temporal resolution that is in good agreement with the dynamic timescale of the atmospheric and surface processes. This study builds on previous works conducted by the authors and aims at extending our understanding of this model structure and further establishing its coherence. Herein we present the results from a thorough sensitivity analysis (SA) performed on SimSphere using a cutting edge and robust Global Sensitivity Analysis (GSA) approach, based on the use of the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) tool. In particular, the sensitivity of selected key variables characterising land surface interactions simulated by SimSphere were evaluated at different times of model output. All model inputs were assumed to be normally distributed with their probability distribution functions (PDFs) defined using mean and variance taken from the entire theoretical range that these inputs can take in SimSphere. The sensitivity of the following SimSphere outputs was evaluated: Daily Average Net Radiation, Daily Average Latent Heat flux, Daily Average Sensible Heat flux, Daily Average Air Temperature , Daily Average Radiometric Temperature, Daily Average Surface Moisture Availability, Daily Average Evaporative Fraction and Daily Average Non-Evaporative Fraction. Our results showed largely comparable trends in terms of identifying the most sensitive model inputs in respect to the model outputs examined. In addition, a high percentage of first order interactions between the model inputs were reported, suggesting strong model coherence between inputs and outputs. Among the most sensitive model inputs for the outputs examined were the Fractional Vegetation Cover, Soil Moisture and topographically-related parameters (i.e. slope, aspect). Our study represents a significant step forward in the global efforts towards SimSphere verification given that its use is progressively expanding including present efforts to explore its synergy with Earth Observation for operationally deriving key land surface parameters at a global scale from space. KEYWORDS: Global Sensitivity Analysis, BACCO method, GEM-SA

Ioannou-Katidis, Pavlos; Petropoulos, George; Griffiths, Hywel; Bevan, Rhodri

2014-05-01

107

Iterative modelling, a new approach to the inversion of 1-D seismograms  

E-print Network

impedance structure Demonstration of the effect of' oscillatory impedance structures on the bandlimited seismic response Page 3. Iterative modelling processing flowchart 4. The earth model used to generate all synthetic data The estimated acoustic... impedance structure after one iteration set 6. The structure of Figure 5 after smoothing The structure of Figure 6 after removal of insignificant layering 8. Mechanics of residual error analysis The estimated acoustic impedance structure at the end...

Raskin, Greg Steven

2012-06-07

108

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

109

A 1-D mechanistic model for the evolution of earthflow-prone hillslopes  

NASA Astrophysics Data System (ADS)

In mountainous terrain, deep-seated landslides transport large volumes of material on hillslopes, exerting a dominant control on erosion rates and landscape form. Here, we develop a mathematical landscape evolution model to explore interactions between deep-seated earthflows, soil creep, and gully processes at the drainage basin scale over geomorphically relevant (>103 year) timescales. In the model, sediment flux or incision laws for these three geomorphic processes combine to determine the morphology of actively uplifting and eroding steady state topographic profiles. We apply the model to three sites, one in the Gabilan Mesa, California, with no earthflow activity, and two along the Eel River, California, with different lithologies and varying levels of historic earthflow activity. Representative topographic profiles from these sites are consistent with model predictions in which the magnitude of a dimensionless earthflow number, based on a non-Newtonian flow rheology, reflects the magnitude of recent earthflow activity on the different hillslopes. The model accurately predicts the behavior of earthflow collection and transport zones observed in the field and estimates long-term average sediment fluxes that are due to earthflows, in agreement with historical rates at our field sites. Finally, our model predicts that steady state hillslope relief in earthflow-prone terrain increases nonlinearly with the tectonic uplift rate, suggesting that the mean hillslope angle may record uplift rate in earthflow-prone landscapes even at high uplift rates, where threshold slope processes normally limit further topographic development.

Booth, Adam M.; Roering, Josh J.

2011-12-01

110

Is flow velocity a significant parameter in flood damage modelling?  

NASA Astrophysics Data System (ADS)

Flow velocity is generally presumed to influence flood damage. However, this influence is hardly quantified and virtually no damage models take it into account. Therefore, the influences of flow velocity, water depth and combinations of these two impact parameters on various types of flood damage were investigated in five communities affected by the Elbe catchment flood in Germany in 2002. 2-D hydraulic models with high to medium spatial resolutions were used to calculate the impact parameters at the sites in which damage occurred. A significant influence of flow velocity on structural damage, particularly on roads, could be shown in contrast to a minor influence on monetary losses and business interruption. Forecasts of structural damage to road infrastructure should be based on flow velocity alone. The energy head is suggested as a suitable flood impact parameter for reliable forecasting of structural damage to residential buildings above a critical impact level of 2 m of energy head or water depth. However, general consideration of flow velocity in flood damage modelling, particularly for estimating monetary loss, cannot be recommended.

Kreibich, H.; Piroth, K.; Seifert, I.; Maiwald, H.; Kunert, U.; Schwarz, J.; Merz, B.; Thieken, A. H.

2009-10-01

111

Assessing the impact of different sources of topographic data on 1-D hydraulic modelling of floods  

NASA Astrophysics Data System (ADS)

Topographic data, such as digital elevation models (DEMs), are essential input in flood inundation modelling. DEMs can be derived from several sources either through remote sensing techniques (space-borne or air-borne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the Light Detection and Ranging (LiDAR), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30-90 m). On the other hand, LiDAR technique is able to produce a high resolution DEMs (around 1m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicates the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. LiDAR 1 m) to lower resolution are much less compared to the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.

Ali, A. Md; Solomatine, D. P.; Di Baldassarre, G.

2014-07-01

112

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

113

Velocity prediction errors related to flow model calibration uncertainty  

SciTech Connect

At the Savannah River Site (SRS), a United States Department of Energy facility in South Carolina, a three-dimensional, steady-state numerical model has been developed for a four aquifer, three aquitard groundwater flow system. This model has been used for numerous predictive simulation applications at SRS, and since the initial calibration, the model has been refined several times. Originally, calibration of the model was accomplished using a nonlinear least-squares inverse technique for a set of 50 water-level calibration targets non-uniformly distributed in the four aquifers. The estimated hydraulic properties from this calibration generally showed reasonable agreement with values estimated from field tests. Subsequent model refinements and application of this model to field problems have shown that uncertainties in the model parameterization become much more apparent in the prediction of the velocity field than in the simulation of the distribution of hydraulic heads. The combined use of three types of information (hydraulic head distributions, geologic framework models, and velocity field monitoring) provide valuable calibration data for flow modeling investigations; however, calibration of a flow model typically relies upon measured water levels. For a given set of water-level calibration targets, the uncertainties associated with imperfect knowledge of physical system parameters or groundwater velocities may not be discernable in the calibrated hydraulic head distribution. In this paper, modeling results from studies at SRS illustrate examples of model inadequacy resulting from calibrating only on observed water levels, and the effects of these inadequacies on velocity field prediction are discussed. 14 refs., 6 figs.

Stephenson, D.E. (Westinghouse Savannah River Co., Aiken, SC (USA)); Duffield, G.M.; Buss, D.R. (Geraghty and Miller, Inc., Reston, VA (USA))

1990-01-01

114

Numerical Simulation of Pulse-Tube Refrigerators: 1D model I.A. Lyulina1  

E-print Network

oscillating gas flow using fluid dynamics. Due to the non-linearity of the conservation equations, analytical of pulse-tube cryocoolers is still at an early stage. Only few models are currently in pro- duction to be uniform in space. The 1 #12;Figure 1: A schematic picture of the Stirling-type pulse-tube refrigerators

Eindhoven, Technische Universiteit

115

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

E-print Network

dynamics (i.e. state of charge). � 2007 Elsevier Ltd. All rights reserved. Keywords: Lithium ion battery electrochemical system dynamics [3,4]. Empirical battery models are often favored for their low order (2­5 states and Wang show that a hybrid electric vehicle (HEV) cell may become solid state diffusion limited in sec

116

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

E-print Network

been benchmarked; these 'standard' codes have been relied on for testing most of the transport models been proposed and partially tested against various tokamaks [1]. Before predicting the performance Database, and using transport codes which are also written in a standardized form and benchmarked against

Hammett, Greg

117

Modeling for control of an inflatable space reflector, the nonlinear 1-D case  

Microsoft Academic Search

In this paper we develop a mathematical model of the dynamics for an inflatable space reflector, which can be used to design a controller for the shape of the inflatable structure. Inflatable structures have very nice properties, suitable for aerospace applications. We can construct e.g. a huge light weight reflector for a satellite which consumes very little space in the

Thomas Voss; Jacquelien M. A. Scherpen; Patrick R. Onck

2008-01-01

118

Modeling for control of an inflatable space reflector, the linear 1-D case  

Microsoft Academic Search

In this paper we develop a mathematical model of the dynamics for an inflatable space reflector, which can be used to design a controller for the shape of the inflatable structure. Inflatable structures have very nice properties, suitable for aerospace applications. We can construct e.g. a huge light weight reflector for a satellite which consumes very little space in the

T. Voß; J. M. A. Scherpen; A. J. van der Schaft

2008-01-01

119

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

120

Cellular Dynamical Mean Field Theory for the 1D Extended Hubbard Model  

Microsoft Academic Search

We explore the use of exact diagonalization methods for solving the self\\u000aconsistent equations of the cellular dynamical mean field theory (CDMFT) for\\u000athe one dimensional regular and extended Hubbard models. We investigate the\\u000anature of the Mott transition and convergence of the method as a function of\\u000acluster size as well as the optimal allocation of computational resources\\u000abetween

C. J. Bolech; S. S. Kancharla; G. Kotliar

2002-01-01

121

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

SciTech Connect

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

122

An 1-D vertically resolved modelling study of the ecosystem dynamics of the middle and southern Adriatic Sea  

NASA Astrophysics Data System (ADS)

In order to investigate the regional variations in the physical controls upon the Adriatic Sea ecosystem the European Regional Seas Ecosystem Model (ERSEM) has been coupled to an 1-D vertically resolved water column model. It has been set-up and run to simulate climatological seasonal cycles at two sites, in the open waters of the middle and southern Adriatic Sea. Climatological seasonal cycles of temperature and salinity have been simulated and validated for these sites. On a qualitative level, the response of the biochemical submodels to physical forcing of the type observed in this region is good. They reproduce the deep chlorophyll maxima (DCM) during the summer and show phosphate to be the limiting nutrient for primary production. The comparison of seasonal cycles of chlorophyll, oxygen and nutrients with data shows that the climatological seasonal cycle in the Adriatic Sea can be reproduced.

Allen, J. I.; Blackford, J. C.; Radford, P. J.

1998-12-01

123

A pore network model for calculation of interfacial velocities  

NASA Astrophysics Data System (ADS)

Two-phase flow in porous media is characterized by fluid-fluid interfaces that separate fluid phases at the pore scale. These interfaces support pressure differences between phases, and their dynamics lead to changes in phase saturation within the porous medium. Dynamic pore-scale network models mathematically track the dynamic position of each fluid-fluid interface through a pore network, based on imposed boundary conditions, fluid and solid properties, and geometric characteristics of the network. Because these models produce a detailed description of both phase and interface dynamics, results from these models can be volume-averaged to provide values for many upscaled variables. These include traditional variables such as saturation and macroscopic capillary pressure, as well as non-traditional variables such as amount of interfacial area in the averaging volume. With appropriate geometric definitions in the dynamic pore-scale model, a new algorithm may be included in the pore-scale network model to calculate a new variable: average interfacial velocity. This algorithm uses local information in any pore that contains a fluid-fluid interface to estimate the velocity of that interface over a time step. Summation over all interfaces in the network provides a measure of average velocity. Computations for dynamic drainage experiments indicate that this average interfacial velocity is well defined and exhibits distinct behavior for stable and unstable displacements. Comparison of calculated interfacial velocities to a theoretical conjecture on the functional dependence of this macroscopic variable demonstrates another important use of pore-scale model, namely testing of new theories involving non-traditional variables.

Nordhaug, H. F.; Celia, M.; Dahle, H. K.

2003-10-01

124

3-D crustal velocity model for Lithuania and its application to local event studies  

NASA Astrophysics Data System (ADS)

PASSEQ 2006-2008 project (PASsive Seismic Experiment in TESZ) aimed at studying the lithosphere-asthenosphere system around the TransEuropean Suture Zone (TESZ)- the transition between old Proterozoic platform of north and east Europe and younger Phanerozoic platform in central and western Europe. The experiment was a seismic array research aiming to retrieve the structure of the crust and Earth's mantle down to the mantle transition zone, including mapping of upper mantle seismic velocity variations and discontinuities (Moho, lithosphere-asthenosphere boundary, mantle transition zone) using all available techniques. During the experiment 26 seismic stations (including four broadband stations) were installed in Lithuania. One of the main targets of PASSEQ deployment in Lithuania was identification and characterization of the local seismic activity. The PASSEQ stations in Lithuania were in operation since June, 2006 till January, 2008. During this period a number of local seismic events was recorded and preliminary event location was made using the LocSat algorithm and 1-D velocity model. This standard procedure is not enough precise for Lithuania, however, because the thickness of the crust varies significantly in the region (from 45 to 55 km). In order to improve event location, we separated the events into several groups and located each group separately using a VELEST algorithms and own 1-D velocity model for each group. We also compiled a 3-D seismic velocity of the crust down to a depth of 60 km. The model, consisting of four major layers (sediments, upper crust, middle crust, lower crust and uppermost mantle) was interpolated from 2-D velocity models along previous wide-angle reflection and refraction profiles into a regular grid. The quality of the approximation was analysed using comparison of travel times of P-waves recorded along previous controlled source profiles and synthetic travel times calculated using the 3-D velocity model. The model was converted into a density model using a special procedure, in which the density model is approximated by relationship between seismic velocity and density and the latter is found by inverting of the Bouguer anomaly. Comparison of the inversion results to the observed Bouguer anomaly showed that the upper part of the model needs to be corrected, in particular, in the regions not covered by the profiles. The epicentres of events relocated with the use of both VELEST algorithm and a 3-D velocity model are much less scattered and can be grouped into several clusters, some of which are confined to known areas of human activity. However, one group of events is spatially coincident with the region of two large earthquakes in Kaliningrad region in September, 2004, while another cluster shows good coincidence with known region of historical seismicity in Latvia.

Kozlovskaya, Elena; Budraitis, Mantas; Janutyte, Ilma; Motuza, Gediminas; Lazauskiene, Jurga; Passeq-Working Group

2010-05-01

125

Exploring phase transitions by finite-entanglement scaling of MPS in the 1D ANNNI model  

NASA Astrophysics Data System (ADS)

We use the finite-entanglement scaling of infinite matrix product states (iMPS) to explore supposedly infinite order transitions. This universal method may have lower computational costs than finite-size scaling. To this end, we study possible MPS-based algorithms to find the ground states of the transverse axial next-nearest-neighbor Ising (ANNNI) model in a spin chain with first and second neighbor interactions and frustration. The ground state has four distinct phases with transitions of second order and one of supposedly infinite order, the Kosterlitz-Thouless transition. To explore phase transitions in the model, we study general quantities such as the correlation length, entanglement entropy and the second derivative of the energy with respect to the external field, and test the finite-entanglement scaling. We propose a scaling ansatz for the correlation length of a non-critical system in order to explore infinite order transitions. This method provides considerably less computational costs compared to the finite-size scaling method in [8], and quantities obtained by applying fixed boundary conditions (such as domain wall energy in [8]) are omitted. The results show good agreement with previous studies of finite-size scaling using DMRG.

Nagy, Adam

2011-02-01

126

1D Unsteady Flow and Sediment Transport Model for Channel Network  

NASA Astrophysics Data System (ADS)

This paper presents a one-dimensional unsteady flow and sediment transport model for simulating flood routing and sediment transport over mobile alluvium in channel network. The modified St. Venant equation together with the suspended sediment and bed load transport equations are solved simultaneously to obtain flow properties and sediment transport rates. The Godunov-type finite volume method is employed, and the flux terms are discretized by using the upwind and the HLLC schemes. Then, the Exner equation is used to solve for bed elevation changes. In unsteady flow, sediment transport is non-equilibrium, therefore suspended load adaptation coefficient and bed load adaptation length are used to account for the difference between equilibrium and non-equilibrium sediment transport rate. At river confluences, water surface elevations are kept the same, and the law of mass conservation is used as the internal boundary conditions. An unprecedented flood event occurred in the Santa Cruz River, Tucson, Arizona, in July 2006, is used to test the performances of the model. Simulated results of water surface elevation and bed elevation changes show good agreements with the measurements.

bai, Y.; Duan, J. G.

2012-12-01

127

Calculation of Rayleigh-wave phase velocities due to models with a high-velocity surface layer  

NASA Astrophysics Data System (ADS)

Rayleigh-wave phase velocities have been utilized to determine shear (S)-wave velocities in near-surface geophysics since early 1980s. One of the key steps is to calculate theoretical dispersion curves of an earth model. When the S-wave velocity of the surface layer is higher than some of the layers below, however, the Rayleigh-wave phase velocity in a high-frequency range calculated by existing algorithms approaches the lowest S-wave velocity among the layers above the half-space, rather than a value related to the S-wave velocity of the surface layer. According to our numerical modeling results based on wave equation, trends of the Rayleigh-wave dispersive energy approach about a 91% of the S-wave velocity of the surface layer at a high-frequency range when its wavelength is much shorter than the thickness of the surface layer, which cannot be fitted by a dispersion curve calculated by existing algorithms. We propose a method to calculate Rayleigh-wave phase velocities of models with a high-velocity surface layer by considering its penetration depth. We build a substituted model that only contains the layer with the lowest S-wave velocity among the layers above the half-space and the layers above it. We use the substituted model to replace the original model to calculate phase velocities when the Rayleigh-wave wavelength is not long enough to penetrate the lowest S-wave velocity layer. Several synthetic models are used to verify fitness between the dispersion curve calculated by our proposed method and the trend of the highest dispersive energy. Examples of inversion also demonstrate high accuracy of using our method as the forward calculation method during the inversions.

Pan, Yudi; Xia, Jianghai; Gao, Lingli; Shen, Chao; Zeng, Chong

2013-09-01

128

Point Defects in 3D and 1D Nanomaterials: The Model Case of Titanium Dioxide  

NASA Astrophysics Data System (ADS)

Titanium dioxide is one of the most important oxides for applications in energy and environment, such as solar cells, photocatalysis, lithium-ion batteries. In recent years, new forms of titanium dioxide with unusual structure and/or morphology have been developed, including nanocrystals, nanotubes or nanowires. We have studied in detail the point defect chemistry in nanocrystalline TiO2 powders and ceramics. There can be a change from predominant Frenkel to Schottky disorder, depending on the experimental conditions, e.g. temperature and oxygen partial pressure. We have also studied the local environment of various dopants with similar ion radius, but different ion charge (Zn2+, Y3+, Sn4+, Zr4+, Nb5+) in TiO2 nanopowders and nanoceramics by Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy. Interfacial segregation of acceptors was demonstrated, but donors and isovalent ions do not segregate. An electrostatic "space charge" segregation model is applied, which explains well the observed phenomena.

Knauth, Philippe

2010-11-01

129

Modeling Instruction Program: Curriculum-Velocity vs. Time Worksheet  

NSDL National Science Digital Library

This is an assessment on velocity vs. time graphs, designed for use with the Modeling Cycle method of teaching. It assesses the student's ability to create and interpret v-t graphs when given the motion of an object in a Position vs. Time framework. It is 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.

Dukerich, Larry; Jackson, Jane

2008-11-17

130

1D Modeling of the Initial Stage of Wire Explosions and 2D Modeling of the m=0 Sausage Instability With Sheared Axial Flow  

NASA Astrophysics Data System (ADS)

1D modeling of the initial state of wire explosions (“cold start” with updated SESAME tables) was examined using 1D version of the Eulerian Magnetohydrodynamic Radiative Code (MHRDR). Simulations were carried out for two regimes: with (black body radiative model) and without radiative losses. Results of the simulations revealed strong dependence of the time of explosion and expansion speed of the wire on the implemented radiative model. This shows that it is necessary to accurately include radiative losses to model “cold start” wire explosions. 2D modeling of the m=0 sausage instability with sheared axial flow. The MHRDR simulations were used to obtain the growth rate of the m=0 sausage instability in plasma column with initial Bennett equilibrium profile with and without shear flow. These growth rates appeared to be in good agreement with growth rates calculated from the linearized MHD equations.

Makhin, Volodymyr; Sotnikov, Vladimir; Bauer, Bruno; Lindemuth, Irvin; Sheehey, Peter

2001-10-01

131

Giant fluctuations of local magnetoresistance of organic spin valves and the non-Hermitian 1D Anderson model.  

PubMed

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

132

Effects of the air sac thickness on ventilation by a 1D model of an avian respiratory system.  

PubMed

Airflow in an avian respiratory system was simulated to study why birds affected with airsacculitis have respiratory distress. The airflow in the avian lung was modeled with a 1D electrical circuit and simulated for investigating what effect an increase in wall thickness of air sacs caused by airsacculitis has on flow in lung. The results demonstrated that thickening of the air sac wall caused anti-synchronization between an elastic recoiling force of the air sac walls and an intra-pleural pressure, bringing difficulties in expansion of air sacs to draw in airs during an inspiration period and thereby decreasing air to be pumped out during an expiration period. This was reflected in a decrease in air flow volume in parabronchi where gas exchange takes place. Therefore, it was concluded that airsacculitis causes imbalance in air flow dynamics in the avian lung and thus impairs breathing ability of birds. PMID:24109723

Urushikubo, Akira; Nakamura, Masanori; Hirahara, Hiroyuki

2013-01-01

133

Giant Fluctuations of Local Magnetoresistance of Organic Spin Valves and the Non-Hermitian 1D Anderson Model  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

134

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

SciTech Connect

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

135

RF-sputter fabrication of magnetic garnet thin films and simulation modeling for 1-D magnetic photonic crystal waveguide devices  

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

136

Gap velocity measurements of a blood pump model.  

PubMed

This paper presents the velocity measurements in the gap between the impeller and the pump casing of a 5:1 enlarged centrifugal blood pump model at operating condition. Both the radial and tangential velocity at the gap were measured. It was found that there was no cross flow in both the radial and tangential velocity distributions at the seven radial locations. This implies that the 0.2 mm gap in the prototype should be the optimal clearance of the pump. The vector plot of the resultant velocity showed that the double volute design of the pump, especially the splitter plate that started at theta; = 180 degrees, has created a washout mechanism in the clearance gap; that is, a sector of flow ranging from theta; = 100 degrees to theta; = 190 degrees has directed strongly toward the eye while the rest of the flow in the gap is in a tangential direction. It is important that the blood should flow out of the gap through the eye instead of continuing to circulate in the clearance gap. This explains why the pump has minimum hemolysis and thrombus formation and is able to function with nominal efficiency as compared to other centrifugal pumps. PMID:12139495

Chua, Leok Poh; Ong, Kang Shiu; Yu, Ching Man Simon; Chan, Weng Kong; Wong, Yew Wah

2002-08-01

137

A reduced-order model based on the coupled 1D-3D finite element simulations for an efficient analysis of hemodynamics problems  

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; Oñate, Eugenio

2014-10-01

138

M5.6 Aftershock of the 2009 L'Aquila, Italy, Earthquake: Broadband Composite Source Modeling with 1D Deterministic Green's Functions  

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

139

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

140

Thermal characterization of large size lithium-ion pouch cell based on 1d electro-thermal model  

NASA Astrophysics Data System (ADS)

Thermal management is one of the key factors to keep lithium-ion cells in optimum electrical performance, under safe working conditions and into a reasonably low ageing process. This issue is becoming particularly relevant due to the heterogeneous heat generation along the cell. Cell working temperature is determined by ambient temperature, heat generation and evacuation capacity. Therefore, thermal management is established by: i) the intrinsic thermal properties (heat capacity & thermal conductivity) and ii) the heat generation electro-thermal parameters (internal resistance, open circuit voltage & entropic factor). In this research, different methods - calculated and experimental - are used to characterize the main heat properties of a 14Ah -LiFePO4/graphite-commercial large sizes pouch cell. In order to evaluate the accuracy of methods, two comparisons were performed. First, Newman heat generation estimations were compared with experimental heat measurements. Secondly, empirical thermal cell behaviour was match with 1D electro-thermal model response. Finally, considering the results, the most adequate methodology to evaluate the key thermal parameters of a large size Lithium-ion pouch cell are proposed to be: i) pulse method for internal resistance, ii)heat loss method for entropic factor; and iii)experimental measurement (ARC calorimeter and C-177-97 standard method) for heat capacity and thermal conductivity.

Vertiz, G.; Oyarbide, M.; Macicior, H.; Miguel, O.; Cantero, I.; Fernandez de Arroiabe, P.; Ulacia, I.

2014-12-01

141

Predicting abnormal pressure from 2-D seismic velocity modeling  

SciTech Connect

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

142

A one dimensional numerical model, with an application to the vertical distribution of dissolved oxygen in the ocean. Manual: M1D  

Microsoft Academic Search

This manual describes the one dimensional model M1D, and its application to the vertical distribution of dissolved oxygen in the ocean. Section 2 describes the partial differential equation upon which the model is based, and the required boundary conditions. Section 3 gives the finite difference equations used to approximate the partial differential equations, and the scheme used for their solution.

Eliason

1993-01-01

143

Nondissipative Velocity and Pressure Regularizations for the ICON Model  

NASA Astrophysics Data System (ADS)

A challenging aspect in the numerical simulation of atmospheric and oceanic flows is the multiscale character of the problem both in space and time. The small spacial scales are generated by the turbulent energy and enstrophy cascades, and are usually dealt with by means of turbulence parametrizations, while the small temporal scales are governed by the propagation of acoustic and gravity waves, which are of little importance for the large scale dynamics and are often eliminated by means of a semi-implicit time discretization. We propose to treat both phenomena of subgrid turbulence and temporal scale separation in a unified way by means of nondissipative regularizations of the underlying model equations. More precisely, we discuss the use of two regularized equation sets: the velocity regularization, also know as Lagrangian averaged Navier-Stokes system, and the pressure regularization. Both regularizations are nondissipative since they do not enhance the dissipation of energy and enstrophy of the flow. The velocity regularization models the effects of the subgrid velocity fluctuations on the mean flow, it has thus been proposed as a turbulence parametrization and it has been found to yield promising results in ocean modeling [HHPW08]. In particular, the velocity regularization results in a higher variability of the numerical solution. The pressure regularization, discussed in [RWS07], modifies the propagation of acoustic and gravity waves so that the resulting system can be discretized explicitly in time with time steps analogous to those allowed by a semi-implicit method. Compared to semi-implicit time integrators, however, the pressure regularization takes fully into account the geostrophic balance of the flow. We discuss here the implementation of the velocity and pressure regularizations within the numerical framework of the ICON general circulation model (GCM) [BR05] for the case of the rotating shallow water system, showing how the original numerical formulation can be extended to the regularized systems retaining discrete conservation of mass and potential enstrophy. We also present some numerical results both in planar, doubly periodic geometry and in spherical geometry. These results show that our numerical formulation correctly approximates the behavior of the regularized models, and are a first step toward the use of the regularization idea within a complete, three-dimensional GCM. References [BR05] L. Bonaventura and T. Ringler. Analysis of discrete shallow-water models on geodesic Delaunay grids with C-type staggering. Mon. Wea. Rev., 133(8):2351-2373, August 2005. [HHPW08] M.W. Hecht, D.D. Holm, M.R. Petersen, and B.A. Wingate. Implementation of the LANS-? turbulence model in a primitive equation ocean model. J. Comp. Phys., 227(11):5691-5716, May 2008. [RWS07] S. Reich, N. Wood, and A. Staniforth. Semi-implicit methods, nonlinear balance, and regularized equations. Atmos. Sci. Lett., 8(1):1-6, 2007.

Restelli, M.; Giorgetta, M.; Hundertmark, T.; Korn, P.; Reich, S.

2009-04-01

144

A 1-D Cryothermal Model of Ceres’ Megaregolith: Predictions for Surface Vapor Flux, Subsurface Temperatures and Pore Ice Distribution  

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

145

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

146

1D-Var multilayer assimilation of X-band SAR data into a detailed snowpack model  

NASA Astrophysics Data System (ADS)

The structure and physical properties of a snowpack and their temporal evolution may be simulated using meteorological data and a snow metamorphism model. Such an approach may meet limitations related to potential divergences and accumulated errors, to a limited spatial resolution, to wind or topography-induced local modulations of the physical properties of a snow cover, etc. Exogenous data are then required in order to constrain the simulator and improve its performance over time. Synthetic-aperture radars (SARs) and, in particular, recent sensors provide reflectivity maps of snow-covered environments with high temporal and spatial resolutions. The radiometric properties of a snowpack measured at sufficiently high carrier frequencies are known to be tightly related to some of its main physical parameters, like its depth, snow grain size and density. SAR acquisitions may then be used, together with an electromagnetic backscattering model (EBM) able to simulate the reflectivity of a snowpack from a set of physical descriptors, in order to constrain a physical snowpack model. In this study, we introduce a variational data assimilation scheme coupling TerraSAR-X radiometric data into the snowpack evolution model Crocus. The physical properties of a snowpack, such as snow density and optical diameter of each layer, are simulated by Crocus, fed by the local reanalysis of meteorological data (SAFRAN) at a French Alpine location. These snowpack properties are used as inputs of an EBM based on dense media radiative transfer (DMRT) theory, which simulates the total backscattering coefficient of a dry snow medium at X and higher frequency bands. After evaluating the sensitivity of the EBM to snowpack parameters, a 1D-Var data assimilation scheme is implemented in order to minimize the discrepancies between EBM simulations and observations obtained from TerraSAR-X acquisitions by modifying the physical parameters of the Crocus-simulated snowpack. The algorithm then re-initializes Crocus with the modified snowpack physical parameters, allowing it to continue the simulation of snowpack evolution, with adjustments based on remote sensing information. This method is evaluated using multi-temporal TerraSAR-X images acquired over the specific site of the Argentière glacier (Mont-Blanc massif, French Alps) to constrain the evolution of Crocus. Results indicate that X-band SAR data can be taken into account to modify the evolution of snowpack simulated by Crocus.

Phan, X. V.; Ferro-Famil, L.; Gay, M.; Durand, Y.; Dumont, M.; Morin, S.; Allain, S.; D'Urso, G.; Girard, A.

2014-10-01

147

Mahogany salt images show key role of velocity model  

SciTech Connect

Geophysicists are learning to use basic processing and interpretation tools to fine-tune the very sophisticated techniques now yielding accurate seismic images of subsurface salt. Experience in the Gulf of Mexico's subsalt exploration play shows that careful survey design, use of basic techniques where they are not normally applied, and rigorous quality control can reduce costs and improve accuracy of the ultimate salt imaging technique: 3D prestack depth migration (PSDM). The ability to image structures in sediments below salt led to the landmark Mahogany and Teak discoveries in the Gulf of Mexico. Now, geophysicists are beginning to image relative amplitude data below salt. This points toward subsalt amplitude-vs.-offset (AVO) analysis, a capability that would be extremely valuable but that probably remains 5--10 years in the future. Development and successful application of subsalt imaging technology depend on derivation of an accurate velocity model for salt and surrounding sediments. It is the key step--and the most difficult one--in 3D PSDM. The paper discusses what PSDM does, the building block approach, data acquisition steps, existing technology, time versus depth migration, accurate velocities, and future directions.

Ratcliff, D.W.; Weber, D.J. (Diamond Geophysical Service Co., Houston, TX (United States))

1994-10-24

148

Numerische Methoden 1 B.J.P. Kaus Project: 1D numerical modelling of melt migration in the Earth's  

E-print Network

of the gravity vector). Here, we will focus on solving the equations in 1-D, which means that we have to solve in 2D. Does melt propagate in dikes, waves or in tubes? 1 #12;GEOPHYSICAL RESEARCH LETTERS, VOL. 25, NO

Kaus, Boris

149

A 1-D model evaluation of OH regeneration mechanisms from isoprene oxidation for use in global models.  

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

150

Optical response in two model systems of interacting electrons: The 1D Hubbard model and 2D magnetoexcitons  

SciTech Connect

In Part I of this thesis, we study the real part {sigma}({omega}) of the optical conductivity of a repulsive Hubbard ring of circumference L. At zero temperature, and in the absence of disorder, the dc part of {sigma}({omega}) has the form {sigma}({omega}) = (e{sup 2}/h)D{sub c}{delta}({h_bar}{omega}). The charge stiffness D{sub c} tends to a finite, positive value as L {yields} {infinity} in the metallic phase of the model; however, in the Mott-insulating phase of the model, which occurs at a mean electron density n = 1 (half filling), D{sub c} {approximately} O(L{sup 1/2}exp(-L/{xi}(U)) in the large-L limit, which serves to define the localization length {xi} of the nondisordered Mott insulator. We obtain an analytic expression for {xi}(U) as a function of the on-site repulsion U, and show that {xi} is the correlation length of the equal-time single-particle Green`s function, evaluated at half filling. We interpret {xi} as the correlation length of the electron-hole pairing correlations in the ground state of the Mott insulator. We next consider the metallic phase of the model in the vicinity of the metal-insulator transition. We obtain analytic expressions, valid to leading order in the doping {delta} = {vert_bar}1 - n{vert_bar}, for the charge stiffness D{sub c} = {delta}/{vert_bar}2m{sup *}{vert_bar} and the low-temperature thermopower S = -(k{sup 2}{sub B}T/3e)m{sup *}/{delta}{sup 2} near half filing, where {vert_bar}m{sup *}{vert_bar} is a function of U which we calculate, and sign(m{sup *}) = sign(1 - n). We interpret these results in terms of a physical picture of the charge carriers in the lightly doped Mott insulator as spinless fermionic solitons of size {xi}, effective mass m{sup *}, and number density {delta}, which become noninteracting in the limit {xi}{delta} {yields} 0.

Stafford, C.A.

1992-12-31

151

Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model  

E-print Network

Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model.hetenyi@erdw.ethz.ch) Abstract: Low-velocity zones (`bright spots') imaged by the INDEPTH seismic experiment in southern Tibet for the channel flow model. These suggest that a continuous seismic low- velocity zone underlies Tibet

Demouchy, Sylvie

152

Modeling the Influence of Crew Movement on Boat Velocity Fluctuations during the Rowing Stroke  

Microsoft Academic Search

Caplan and Gardner (2007: Journal of Sports Sciences, 25, 1025-1034) presented a rowing simulation which assumed that each rower moved as a single mass. Although validated against mean on- water shell velocity, instantaneous velocity was not modeled well. As any changes to rowing technique inherently influence the fluctuations in boat velocity throughout each stroke, the previous model was unable to

Nicholas Caplan; Trevor Gardner

153

Air-snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS  

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

154

Development of a Regional Velocity Model Using 3D Broadband Waveform Sensitivity  

NASA Astrophysics Data System (ADS)

We are developing a new approach which relies on a cascade of increasingly accurate theoretical approximations for computation of the seismic wavefield to develop a model of regional seismic velocity structure for eastern Eurasia using full seismic waveforms. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for standard modeling techniques, but it is well surrounded by earthquake sources and a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The initial model is derived from a large database of teleseismic long period waveforms (surface waves and overtone wavepackets) using well-developed theoretical approximations, the Path Average Approximation (PAVA) and Nonlinear Asymptotic Coupling Theory (NACT). These approaches assume waveforms are only sensitive to the 1D (PAVA) and 2D (NACT) structure in the vertical plane between source and receiver, which is adequate for the development of a smooth initial 3D velocity model. We refine this model using a more accurate theoretical approach. We utilize an implementation of a 3D Born approximation, which takes into account the contribution to the waveform from single scattering throughout the model, giving full 3D waveform sensitivity kernels. We perform verification tests of this approach for synthetic models, and show that it can accurately represent the wavefield as predicted by numerical approaches in several situations where approximations such as PAVA and NACT are insufficient. The Born 3D waveform sensitivity kernels are used to perform a higher resolution inversion of regional waveforms for a smaller subregion between longitudes 90 and 150 degrees E, and latitudes 15 and 40 degrees N. To further increase the accuracy of this model, we intend to utilize a very accurate numerical approach, the coupled spectral elements method (Capdeville et al., 2003), for the forward calculations of synthetics. This accounts for nonlinear effects of the structure on the seismograms in addition to the 3D broadband sensitivity.

Panning, M. P.; Romanowicz, B. A.; Kim, A.

2005-12-01

155

Combining flow routing modelling and direct velocity measurement for optimal discharge estimation  

NASA Astrophysics Data System (ADS)

A new procedure is proposed for estimating river discharge hydrographs during flood events, using only water level data measured at a gauged site, as well as 1-D shallow water modelling and sporadic maximum surface flow velocity measurements. During flood, the piezometric level is surmised constant in the vertical plane of the river section, where the top of the banks is always above the river level, and is well represented by the recorded stage hydrograph. The river is modelled along the reach directly located downstream the upstream gauged section, where discharge hydrograph is sought after. For the stability with respect to the topographic error, as well as for the simplicity of the data required to satisfy the boundary conditions, a diffusive hydraulic model is adopted for flow routing. Assigned boundary conditions are: (1) the recorded stage hydrograph at the upstream river site and (2) the zero diffusion condition at the downstream end of the reach. The MAST algorithm is used for the numerical solution of the flow routing problem, which is embedded in the Brent algorithm used for the computation of the optimum Manning coefficient. Based on synthetic tests concerning a broad prismatic channel, the optimal reach length is chosen so that the approximated downstream boundary condition effects on discharge hydrograph assessment at upstream end are negligible. The roughness Manning coefficient is calibrated by using sporadic instantaneous surface velocity measurements during the rising limb of flood that are turned into instantaneous discharges through the solid of velocity estimated by a two-dimensional entropic model. Several historical events, occurring in three gauged sites along the upper Tiber River wherein a reliable rating curve is available, have been used for the validation. The analysis outcomes can be so summarized: (1) criteria adopted for selecting the optimal channel length and based on synthetic tests have been proved reliable by using field data of three gauged river sites. Indeed, for each of them a downstream reach, long not more than 500 m, is turned out fair for achieving good performances of the diffusive hydraulic model, thus allowing to drastically reducing the topographical data of river cross-sections; (2) the procedure for Manning's coefficient calibration allowed to get high performance of the hydraulic model just considering the observed water levels and sporadic measurements of maximum surface flow velocity during the rising limb of flood. Indeed, in terms of errors in magnitude on peak discharge, for the optimal calibration, they were found, in average, not exceeding 5% for all events observed in the three investigated gauged sections, while the Nash-Sutcliff efficiency was, in average, greater than 0.95. Therefore, the proposed procedure, apart from to have turned out reliable for the rating curve assessment at ungauged sites, can be applied in realtime for whatever flood conditions and this is of great interest for the practice hydrology seeing that, looking at new monitoring technologies, it will be possible to carry out velocity measurements by hand-held radar sensors in different river sites and for the same flood.

Corato, G.; Moramarco, T.; Tucciarelli, T.

2011-03-01

156

'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.

Bair, Scott

157

A novel 1D/2D model for simulating conjugate heat transfer applied to flow boiling in tubes with external fins  

NASA Astrophysics Data System (ADS)

This study presents a novel, simplified model for the time-efficient simulation of transient conjugate heat transfer in round tubes. The flow domain and the tube wall are modeled in 1D and 2D, respectively and empirical correlations are used to model the flow domain in 1D. The model is particularly useful when dealing with complex physics, such as flow boiling, which is the main focus of this study. The tube wall is assumed to have external fins. The flow is vertical upwards. Note that straightforward computational fluid dynamics (CFD) analysis of conjugate heat transfer in a system of tubes, leads to 3D modeling of fluid and solid domains. Because correlation is used and dimensionality reduced, the model is numerically more stable and computationally more time-efficient compared to the CFD approach. The benefit of the proposed approach is that it can be applied to large systems of tubes as encountered in many practical applications. The modeled equations are discretized in space using the finite volume method, with central differencing for the heat conduction equation in the solid domain, and upwind differencing of the convective term of the enthalpy transport equation in the flow domain. An explicit time discretization with forward differencing was applied to the enthalpy transport equation in the fluid domain. The conduction equation in the solid domain was time discretized using the Crank-Nicholson scheme. The model is applied in different boundary conditions and the predicted boiling patterns and temperature fields are discussed.

Oc?o?, Pawe?; ?opata, Stanis?aw; Nowak, Marzena

2014-09-01

158

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

E-print Network

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.

159

Control of temperature, pressure gradient and flow law on the formation of crustal-scale shear zones: results from 1D thermo-mechanical modeling  

NASA Astrophysics Data System (ADS)

Localization of deformation plays a major role during tectonic processes at all scale from the formation of deformation bands within single grains up to crustal and lithospheric scale shear zones. Deformation in continental collision belts is typically driven by such localizations resulting in the formation of fold nappes and thrust sheets. There are considerable speculations as to which process dominates the localization behavior. We present a self-consistent pressure-driven thermo-mechanical 1D numerical model to study the formation of shear zones in the upper crust. The numerical model is based on the finite element method and solves the equations for the fluid dynamic force balance and for transient heat conduction. Our model consists of a sediment layer and its underlying basement which is considered rigid. For the sediment layer we apply several calcite flow laws for diffusion creep and dislocation creep. For dislocation creep we use power-law flow laws as well as a flow law based on Peierls mechanism. We study under what thermal and pressure conditions the shear zones form at the base of the sediment layer. We also investigate the impact of thermal coupling through shear heating and of grain size reduction coupled to the Peierls-type flow law on shear zone formation. We apply our model to the Morcles fold nappe in the western Swiss Alps by considering previously published estimates for strain rates, stresses, flow laws and temperatures. Detailed EBSD (electron backscattered diffraction) analyses have been made on the rocks at the contact between the Morcles nappe sediments and the autochthonous cover of the Aiguille rouge massif in order to investigate the deformation mechanisms. We identify the thermal and pressure conditions as well as the different flow laws for calcite for which the model results fit best the field observations and estimates for stress and strain rate. An advantage of the applied 1D thermo-mechanical shear zone model is that neither the strain rate nor the stress is prescribed at any point in depth but is controlled by the applied overall pressure gradient and the temperature profile. Furthermore, the computationally cheap 1D simulations allow a systematic analysis of the control of temperature, pressure gradient and flow law on the formation of shear zones. The results of our 1D model will be used to set up a more elaborated 2D model for the formation of crustal scale shear zones and fold nappes.

Maeder, X.; Schmalholz, S.; Bauville, A.

2012-04-01

160

BMS-181885, a 5HT 1B\\/1D receptor ligand, in experimental models predictive of antimigraine activity and coronary side-effect potential  

Microsoft Academic Search

Many acutely acting antimigraine drugs have the ability to constrict porcine arteriovenous anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively, for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have investigated the effects of BMS-181885 (3-[3-[4-(5-methoxy-4-pyrimidyl)-1-piperazinyl]propyl]-5-(1,2-dioxo-4-methyl-3-cyclobuten-3-yl)amino-1H-indole), a 5-HT1B\\/1D receptor ligand. In anaesthetised pigs,

Pramod R Saxena; Peter De Vries; Jan P. C Heiligers; Willem A Bax; Antoinette MaassenVanDenBrink; Frank D Yocca

1998-01-01

161

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

162

Basin infilling of a schematic 1D estuary using two different approaches: an aggregate diffusive type model and a processed based model.  

NASA Astrophysics Data System (ADS)

Fluvial sediment transport creates great challenges for river scientists and engineers. The interaction between the fluid (water) and the solid (dispersed sediment particles) phases is crucial in morphodynamics. The process of sediment transport and the resulting morphological evolution of rivers get more complex with the exposure of the fluvial systems to the natural and variable environment (climatic, geological, ecological and social, etc.). The earlier efforts in mathematical river modelling were almost exclusively built on traditional fluvial hydraulics. The last half century has seen more and more developments and applications of mathematical models for fluvial flow, sediment transport and morphological evolution. The first attempts for a quantitative description and simulation of basin filling in geological time scales started in the late 60´s of the last century (eg. Schwarzacher, 1966; Briggs & Pollack, 1967). However, the quality of this modelling practice has emerged as a crucial issue for concern, which is widely viewed as the key that could unlock the full potential of computational fluvial hydraulics. Most of the models presently used to study fluvial basin filling are of the "diffusion type" (Flemmings and Jordan, 1989). It must be noted that this type of models do not assume that the sediment transport is performed by a physical diffusive process. Rather they are synthetic models based on mass conservation. In the "synthesist" viewpoint (Tipper, 1992; Goldenfeld & Kadanoff, 1999; Werner, 1999 in Paola, 2000) the dynamics of complex systems may occur on many levels (time or space scales) and the dynamics of higher levels may be more or less independent of that at lower levels. In this type of models the low frequency dynamics is controlled by only a few important processes and the high frequency processes are not included. In opposition to this is the "reductionist" viewpoint that states that there is no objective reason to discard high frequency processes. In this viewpoint the system is broken down into its fundamental components and processes and the model is build up by selecting the important processes regardless of its time and space scale. This viewpoint was only possible to pursue in the recent years due to improvement in system knowledge and computer power (Paola, 2000). The primary aim of this paper is to demonstrate that it is possible to simulate the evolution of the sediment river bed, traditionally studied with synthetic models, with a process-based hydrodynamic, sediment transport and morphodynamic model, solving explicitly the mass and momentum conservation equations. With this objective, a comparison between two mathematical models for alluvial rivers is made to simulate the evolution of the sediment river bed of a conceptual 1D embayment for periods in the order of a thousand years: the traditional synthetic basin infilling aggregate diffusive type model based on the diffusion equation (Paola, 2000), used in the "synthesist" viewpoint and the process-based model MOHID (Miranda et al., 2000). The simulation of the sediment river bed evolution achieved by the process-based model MOHID is very similar to those obtained by the diffusive type model, but more complete due to the complexity of the process-based model. In the MOHID results it is possible to observe a more comprehensive and realistic results because this type of model include processes that is impossible to a synthetic model to describe. At last the combined effect of tide, sea level rise and river discharges was investigated in the process based model. These effects cannot be simulated using the diffusive type model. The results demonstrate the feasibility of using process based models to perform studies in scales of 10000 years. This is an advance relative to the use of synthetic models, enabling the use of variable forcing. REFERENCES • Briggs, L.I. and Pollack, H.N., 1967. Digital model of evaporate sedimentation. Science, 155, 453-456. • Flemmings, P.B. and Jordan, T.E., 19

Laginha Silva, Patricia; Martins, Flávio A.; Boski, Tomász; Sampath, Dissanayake M. R.

2010-05-01

163

An Intriguing Shift Occurs in the Novel Protein Phosphatase 1 Binding Partner, TCTEX1D4: Evidence of Positive Selection in a Pika Model  

PubMed Central

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-Gregorio, Luis; 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 Jose; Fardilha, Margarida

2013-01-01

164

Estimation of flow velocity for a debris flow via the two-phase fluid model  

NASA Astrophysics Data System (ADS)

The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

Guo, S.; Xu, P.; Zheng, Z.; Gao, Y.

2014-06-01

165

Analytical representation of the fault slip velocity from spontaneous dynamic earthquake models  

NASA Astrophysics Data System (ADS)

We have analyzed the most relevant features of three different analytical representations of the time evolution of the cosesimic slip velocity derived from theoretical basis; the so-called modified Yoffe function (MY), which pertains to a singular crack solution, the solution for a nonspontaneous crack obeying a position-weakening governing equation (PR) and the solution for a 1-D fault model subject to a linear slip-weakening friction law (B). By considering the same input parameters, we quantitatively compare these slip velocity functions (SVF) and we found that the time evolutions of the velocity and the correspondent slip predicted by the MY and B functions are very similar, while the PR predicts a very sharp peak. Correspondingly, the PR SVF is richer in high frequency and the fall off of its spectrum at high frequencies goes roughly as ?-1.5, while those of MY and B more closely follow ?-2. Then we select two spontaneous, 3-D, dynamic, subshear models, representing a crack-like or a pulse-like rupture and we account for both homogeneous and heterogeneous configurations. We then compare the three SVF in order to see how they are able to reproduce the 3-D solutions; we also show how the input parameters of the SVF can be constrained from the results of the dynamic models. In the homogeneous cases our results indicate that the MY and the PR SVF reproduce adequately well the main features of a dynamic solution in the case of a crack-like rupture. The PR function overestimates vpeak and the MY SVF predicts a too rapid deceleration. In the case of a pulse-like rupture both the MY and the B SVF tend to underestimate vpeak , but all of them capture very well the final cumulated fault slip. Moreover, the B function fits better that the MY the overall behavior of the fault slip. The considered SVF are able to reproduce the spectral fall off of a 3-D solution at intermediate frequencies (for ? < 20 Hz), the MY and the PR for a crack-like rupture and the MY and the B SVF for a pulse-like rupture. In particular, for ? < 10 Hz the spectral content of the B function is practically indistinguishable from that of the spontaneous pulse-like solution. In the heterogeneous configurations the analytical functions cannot reproduce all the spectral details of the numerical solutions, but we see how it is possible to fit the overall behavior of a single pulse in fault the slip velocity time history. The thorough analysis performed in this work can contribute to the discussion about the debated choice of the source time function to be used in the kinematic models, which in turn is extremely important in the contest of hazard assessment and ground motions generation, although stress heterogeneities, geometrical irregularities, attenuation and free surface effects can definitively smear the details of the analytical functions.

Bizzarri, Andrea

2012-06-01

166

Crustal Structure Modeling of Earthquake Data 1. Simultaneous Least Squares Estimation of Hypocenter and Velocity Parameters  

Microsoft Academic Search

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

167

Modeling of Extinction in Turbulent Diffusion Flames by the Velocity-Dissipation-Composition  

E-print Network

Modeling of Extinction in Turbulent Diffusion Flames by the Velocity-Dissipation-Composition PDF-dissipation-compositionprobabilitydensityfunction(pdf)method is used to model a turbulent CO/H2/N2-air-piloted jet diffusionflamein the regimeof extinction- nomenon of extinction. In this paper, the transport equation for the joint pdf of velocity, dissipation

168

A singular evolutive extended Kalman filter to assimilate real in situ data in a 1-D marine ecosystem model  

Microsoft Academic Search

A singular evolutive extended Kalman (SEEK) filter is used to assimilate real in situ data in a water column marine ecosystem model. The biogeochemistry of the ecosystem is described by the European Regional Sea Ecosystem Model (ERSEM), while the physical forcing is described by the Princeton Ocean Model (POM). In the SEEK filter, the error statistics are parameterized by means

I. Hoteit; G. Triantafyllou; G. Petihakis; J. I. Allen

2003-01-01

169

STP Ising 1D Program  

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

170

Linear velocity fields in non-Gaussian models for large-scale structure  

NASA Technical Reports Server (NTRS)

Linear velocity fields in two types of physically motivated non-Gaussian models are examined for large-scale structure: seed models, in which the density field is a convolution of a density profile with a distribution of points, and local non-Gaussian fields, derived from a local nonlinear transformation on a Gaussian field. The distribution of a single component of the velocity is derived for seed models with randomly distributed seeds, and these results are applied to the seeded hot dark matter model and the global texture model with cold dark matter. An expression for the distribution of a single component of the velocity in arbitrary local non-Gaussian models is given, and these results are applied to such fields with chi-squared and lognormal distributions. It is shown that all seed models with randomly distributed seeds and all local non-Guassian models have single-component velocity distributions with positive kurtosis.

Scherrer, Robert J.

1992-01-01

171

A 3-D velocity model for earthquake location from combined geological and geophysical data: a case study from the TABOO near fault observatory (Northern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

Accurate hypocenter location at the crustal scale strongly depends on our knowledge of the 3D velocity structure. The integration of geological and geophysical data, when available, should contribute to a reliable seismic velocity model in order to guarantee high quality earthquake locations as well as their consistency with the geological structure. Here we present a 3D, P- and S-wave velocity model of the Upper Tiber valley region (Northern Apennines) retrieved by combining an extremely robust dataset of surface and sub-surface geological data (seismic reflection profiles and boreholes), in situ and laboratory velocity measurements, and earthquake data. The study area is a portion of the Apennine belt undergoing active extension where a set of high-angle normal faults is detached on the Altotiberina low-angle normal fault (ATF). From 2010, this area hosts a scientific infrastructure (the Alto Tiberina Near Fault Observatory, TABOO; http://taboo.rm.ingv.it/), consisting of a dense array of multi-sensor stations, devoted to studying the earthquakes preparatory phase and the deformation processes along the ATF fault system. The proposed 3D velocity model is a layered model in which irregular shaped surfaces limit the boundaries between main lithological units. The model has been constructed by interpolating depth converted seismic horizons interpreted along 40 seismic reflection profiles (down to 4s two way travel times) that have been calibrated with 6 deep boreholes (down to 5 km depth) and constrained by detailed geological maps and structural surveys data. The layers of the model are characterized by similar rock types and seismic velocity properties. The P- and S-waves velocities for each layer have been derived from velocity measurements coming from both boreholes (sonic logs) and laboratory, where measurements have been performed on analogue natural samples increasing confining pressure in order to simulate crustal conditions. In order to test the 3D velocity model, we located a selected dataset of the 2010-2013 TABOO catalogue, which is composed of about 30,000 micro-earthquakes (see Valoroso et al., same session). Earthquake location was performed by applying the global-search earthquake location method NonLinLoc, which is able to manage strong velocity contrasts as that observed in the study area. The model volume is 65km x 55km x 20km and is parameterized by constant velocity, cubic cells of side 100 m. For comparison, we applied the same inversion code by using the best 1D model of the area obtained with earthquake data. The results show a significant quality improvement with the 3D model both in terms of location parameters and correlation between seismicity distribution and known geological structures.

Latorre, Diana; Lupattelli, Andrea; Mirabella, Francesco; Trippetta, Fabio; Valoroso, Luisa; Lomax, Anthony; Di Stefano, Raffaele; Collettini, Cristiano; Chiaraluce, Lauro

2014-05-01

172

Current plate velocities relative to the hotspots incorporating the NUVEL-1 global plate motion model  

Microsoft Academic Search

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

173

A singular evolutive extended Kalman filter to assimilate real in situ data in a 1-D marine ecosystem model  

NASA Astrophysics Data System (ADS)

A singular evolutive extended Kalman (SEEK) filter is used to assimilate real in situ data in a water column marine ecosystem model. The biogeochemistry of the ecosystem is described by the European Regional Sea Ecosystem Model (ERSEM), while the physical forcing is described by the Princeton Ocean Model (POM). In the SEEK filter, the error statistics are parameterized by means of a suitable basis of empirical orthogonal functions (EOFs). The purpose of this contribution is to track the possibility of using data assimilation techniques for state estimation in marine ecosystem models. In the experiments, real oxygen and nitrate data are used and the results evaluated against independent chlorophyll data. These data were collected from an offshore station at three different depths for the needs of the MFSPP project. The assimilation results show a continuous decrease in the estimation error and a clear improvement in the model behavior.

Hoteit, I.; Triantafyllou, G.; Petihakis, G.; Allen, J. I.

2003-01-01

174

Status of the solar and infrared radiation submodels in the LLNL 1-D and 2-D chemical-transport models  

SciTech Connect

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

175

Hard-sphere interactions in velocity jump models  

E-print Network

Group-level behaviour of particles undergoing a velocity jump process with hard-sphere interactions is investigated. We derive $N$-particle transport equations that include the possibility of collisions between particles and apply different approximation techniques to get expressions for the dependence of the collective diffusion coefficient on the number of particles and their diameter. The derived approximations are compared with numerical results obtained from individual-based simulations. The theoretical results compare well with Monte Carlo simulations providing the excluded volume fraction is small.

Franz, Benjamin; Yates, Christian; Erban, Radek

2014-01-01

176

Crucial role of sidewalls in velocity distributions in quasi2D granular gases J. S. van Zon, 1, 2 J. Kreft, 1, # Daniel I. Goldman, 1 D. Miracle, 1 J. B. Swift, 1, + and Harry L. Swinney 1  

E-print Network

horizontal dimension of 48d and vertical dimension of 32d. It oscillated with a frequency f = 50 Hz experiments and three­dimensional molecular dynamics simulations of particles confined to a vertical monolayer limiting the motion in one dimension allows the use of a video camera to record the entire velocity field

Texas at Austin. University of

177

Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region  

SciTech Connect

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

178

Study of fog characteristics by using the 1-D COBEL model at the airport of Thessaloniki, Greece  

NASA Astrophysics Data System (ADS)

An attempt is made to couple the one dimensional COBEL - ISBA (COuche Brouillard Eau Liquide - Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting) numerical weather prediction model. This accomplishment will improve the accuracy on the short-term forecasting of fog events, which is of paramount importance -mainly to the airway companies, the airports functioning and the community as well- and will provide the means for the implementation of extensive studies of fog events formed at the "Macedonia" airport of Thessaloniki. Numerical experiments have been performed to study in depth the thermodynamic structure and the microphysical characteristics of the fog event that was formed on 06/01/2010. Moreover, the meteorological conditions -under the influence of which- the fog event was formed are also investigated. Sensitivity tests with respect to the initial conditions of temperature, relative humidity and geostrophic wind speed profiles have been performed to illustrate the model’s performance. Dew deposition rates have also been examined in order to test the importance of it on controlling the fog formation. The numerical results have been compared with actual measurements and the findings have been evaluated and discussed.

Stolaki, S.; Pytharoulis, I.; Karacostas, T.

2010-07-01

179

Can a partially molten metasedimentary sequence convect? Insights from the El Oro Complex (Ecuador) and 1D thermal modelling.  

NASA Astrophysics Data System (ADS)

It is now widely accepted that the formation and the evolution of high elevation plateaus such as the Tibet and the Altiplano-Puna are strongly linked to mantel magma underplating at crustal root level and partial melting of the lower crust. Understanding the rheological behavior of the deep continental crust during these episodes is therefore crucial to constrain the evolution of such plateau. In this study we present results obtained from pressure-temperature estimates and thermal modeling of gabbro underplating at crustal root level (25km) in the El Oro Metamorphic Complex (Ecuador). The aim of this study is: (1) to complete previously published P-Tmax estimates in the northern part of the migmatitic unit, close to the magmatic contact with the gabbroic unit, to obtain better constraints on the metamorphic gradient during partial melting, (2) to characterize the effects of melt extraction, latent heat capture and release and a temperature-dependent thermal diffusivity on the thermal evolution of the system using a specifically developed numerical model, and (3) in the light of the thermal modeling results, to discuss the geological processes involved during partial melting of the metasedimentary crust. Our modeling results show that the estimate metamorphic gradient cannot be reproduced when solely taking into account latent heat, melt extraction and thermal-dependent diffusivity. In the light of geological, geochemical and modeling evidence we show that the lower migmatitic unit, controlled by biotite-dehydration melting reactions was subject to convective motion that contributed to lower the metamorphic gradient and rapidly transfer heat upward. For a biotite-rich rock (~20%) containing 15-20% of melt, we estimate the maximum viscosity of the rock that allows convection at ~7.5e17 Pa.s. Our results also suggest that convection can be maintained as long as heat is provided and that temperature lies in the stability field of biotite-dehydration melting (750-900°C).

Riel, Nicolas; Mercier, Jonathan

2014-05-01

180

Crustal and mantle velocity models of southern Tibet from finite frequency tomography  

E-print Network

Crustal and mantle velocity models of southern Tibet from finite frequency tomography Xiaofeng inversions to image the three dimensional velocity structure beneath southern Tibet to examine the roles beneath the YadongGulu rift, suggesting that rifting in southern Tibet is probably a process that involves

Shen, Yang

181

Vibration measurements using continuous scanning laser vibrometry: velocity sensitivity model experimental validation  

Microsoft Academic Search

This paper builds on a previous study in which the theoretical description of the velocity sensed by a single laser beam incident in an arbitrary direction on a rotating target undergoing arbitrary vibration was extended to continuous scanning laser vibrometer measurements on targets with flexible cross sections. The velocity sensitivity model was written in terms of either laser beam orientation

B. J. Halkon; S. R. Frizzel; S. J. Rothberg

2003-01-01

182

Modeling of the Transient Particle Velocity Distribution in the Fluidized Bed Combustor (FBC) Riser  

Microsoft Academic Search

The geometrical distributions of transient particle velocity in a fluidized bed combustor (FBC) riser are critical to FBC design and manufacturing. Particle image velocimetry (PIV) instrumentation was applied to visualize the particle transient movement in the area of interest (AOI) of an experimental cold model (152 mm ID × 610 mm height) of an FBC. Sixteen (16) PIV particle velocity profiles were generated for

YUN LIU; SEONG W. LEE

2005-01-01

183

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

184

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

USGS Publications Warehouse

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

185

Excitation Spectra of Spin Models constructed from Quantized Affine Algebras of type $B_n^{(1)}$, $D_n^{(1)}$  

E-print Network

The energy and momentum spectrum of the spin models constructed from the vector representation of the quantized affine algebras of type $\\B$ and $\\D$ are computed using the approach of Davies et al. \\cite{DFJMN92}. The results are for the anti-ferromagnetic (massive) regime, and they agree with the mass spectrum found from the factorized S--matrix theory by Ogievetsky et al. \\cite{ORW87}. The other new result is the explicit realization of the fusion construction for the quantized affine algebras of type $\\B$ and $\\D$.}

Brian Davies; Masato Okado

1995-06-30

186

A damage assessment model of slender bridge members based on 1D linear member theory with frequency dependent parameters  

NASA Astrophysics Data System (ADS)

In this study, a linear model with frequency dependent structural property was used to generate the corresponding frequency response function and dynamic stiffness for selected dynamic problems where certain nonlinearity can be resulted from time/space varying characteristics of the bridge vibrations. Derivation of the proposed formula is based on the vibration theory of the elementary member with frequency dependent elastic properties, in which Modulus of Elasticity can be interpreted as serial and parallel connections of springs and dashpots. This paper first describes the use of the proposed formulation to reasonably depict the nonlinear cable vibration associated with the varying tension forces over time. The proposed formulation can also be used to simulate flexural vibration of damage beams in which the elastic property involves certain space varying or time varying characteristics. Simple numerical/experimental data were next used to demonstrate and confirm the potential application of such simulation idea. Consequently, it is concluded that such assessment model with frequency dependent parameters can be practically feasible and serve as a useful tool in the spectral analysis regarding dynamic problems of slender bridge members.

Yu, Chih-Peng; Cheng, Chia-Chi; Lai, Jiunnren; Chiang, Chih-Hung

2012-04-01

187

Impact of river bed morphology on discharge and water levels simulated by a 1D Saint-Venant hydraulic model at regional scale  

NASA Astrophysics Data System (ADS)

SummaryRiver cross-sections data are required to represent channel geometry in hydrodynamic models. In the absence of accurate data at regional scale, simplified or parameterized cross sections are often used, which might affect the performance of the hydrodynamic model. In this study we assess the sensitivity of a 1D Saint-Venant hydraulic model to different types of river morphological data. The question is addressed using a 1D unsteady hydraulic model (HEC-RAS), with lateral inflows provided by the hydro(geo)logical model Eau-Dyssée, to explore a wide spectrum of river geometry scenarios, regarding river bed slopes and cross-sectional shapes. The target scale is the one of the Seine River (France). As a gateway for larger and more complex regional hydro(geo)logical applications, our case-study covers a well-described 89-km reach in a sub-tributary of the Seine River. River morphology is described by high-resolution cross-sections, and Manning's roughness coefficient (n) is used for calibration against observed discharges and river stages in a mid-reach control point, with satisfactory performances over the 8-year simulation period. The resulting model still simulates realistic discharge hydrographs when forced with degraded channel geometry data, using either fewer cross-sections or approximated ones. In such cases, however, the hydraulic model does not always satisfactorily predict the associated water levels when compared to observations. In certain geometry scenarios, the RMSE between simulated water levels using degraded geometry and observations may go up to 0.3 m. The study confirms that the accuracy of predicted water levels and maximum water depths simulated by a Saint-Venant model relies on an accurate representation of channel geometry and bed level slopes along the river reach. From the various scenarios, it appears that the longitudinal description of the bed level profiles has a larger impact on the simulation of water levels than the cross-sectional shapes. This offers interesting implications for flood forecast mapping applications and regional scale models that often use simplified river geometry and Digital Elevation Models (DEMs) built by remote sensing technologies to simulate the water levels.

Saleh, F.; Ducharne, A.; Flipo, N.; Oudin, L.; Ledoux, E.

2013-01-01

188

Velocity model construction, uncertainty evaluation, and two-way travel time to sediment thickness conversion  

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

189

Near-surface ocean velocity from infrared images: Global Optimal Solution to an inverse model  

NASA Astrophysics Data System (ADS)

We address the problem of obtaining ocean surface velocities from sequences of thermal (AVHRR) space-borne images by inverting the heat conservation equation (including sources of surface heat fluxes and vertical entrainment). We demonstrate the utility of the technique by deriving surface velocities from (1) The motion of a synthetic surface tracer in a numerical model and (2) a sequence of five actual AVHRR images from 1 day. Typical formulations of this tracer inversion problem yield too few equations at each pixel, which is often remedied by imposing additional constraints (e.g., horizontal divergence, vorticity, and energy). In contrast, we propose an alternate strategy to convert the underdetermined equation set to an overdetermined one. We divide the image scene into many subarrays and define velocities and sources within each subarray using bilinear expressions in terms of the corner points (called knots). In turn, all velocities and sources on the knots can be determined by seeking an optimum solution to these linear equations over the large scale, which we call the Global Optimal Solution (GOS). We test the accuracy of the GOS by contaminating the model output with up to 10% white noise but find that filtering the data with a Gaussian convolution filter yields velocities nearly indistinguishable from those without the added noise. We compare the GOS velocity fields with those from the numerical model and from the Maximum Cross Correlation (MCC) technique. A histogram of the difference between GOS and numerical model velocities is narrower and more peaked than the similar comparison with MCC, irrespective of the time interval (?t = 2 or 4 h) between images. The calculation of the root mean square error difference between the GOS (and MCC) results and the model velocities indicates that the GOS/model error is only half that of the MCC/model error irrespective of the time interval (?t = 2 or 4 h) between images. Finally, the application of the technique to a sequence of five NOAA AVHRR images yields a velocity field, which we compare with that from a Coastal Ocean Dynamics Radar (CODAR) array. We find that the GOS velocities generally agree more closely with those from the CODAR than they do with those from the MCC. Specifically, the root mean square error obtained by differencing GOS and CODAR velocities is smaller than that from the similar calculation with MCC velocities. The magnitude of the complex correlation between GOS and CODAR is larger than that between MCC and CODAR. The phase of the complex correlation indicates that both MCC and GOS on average yield velocity vectors biased in the clockwise direction relative to the CODAR vectors for the period examined.

Chen, Wei; Mied, Richard P.; Shen, Colin Y.

2008-10-01

190

A neuromusculoskeletal model to simulate the constant angular velocity elbow extension test of spasticity  

Microsoft Academic Search

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

Terry K. K. Koo; Arthur F. T. Mak

2006-01-01

191

IMPROVED THREE-DIMENSIONAL VELOCITY MODELS AND EARTHQUAKE LOCATIONS FOR CALIFORNIA  

Microsoft Academic Search

Our work focused on the development of a three-dimensional (3D) seismic wavespeed model for the greater San Francisco (SF) Bay Area and for Northern California. The model has been used to help validate the USGS 3D velocity model. That model in turn is being used to compute hypothetical strong ground motions in a simulation of the great 1906 San Francisco

Clifford H. Thurber

192

timevarying velocity and density fields from the ORCA model are used as input  

E-print Network

Method: timevarying velocity and density fields from the ORCA model are used as input) western boundary current and (3) interior pathway. Model: · ORCA05, global configuration of the OGCM with the global ocean model ORCA05. The model captures the most important features of the pacific tropical

Döös, Kristofer

193

Mw5.5 Aftershock of the 2009 L'Aquila, Italy, Earthquake: Broadband Composite Source Modeling with 1D Deterministic Green's Functions  

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

194

A vortex-based model of velocity and shear stress in a partially vegetated shallow channel  

E-print Network

This paper presents a method for predicting the distributions of velocity and shear stress in shallow channels with a boundary of emergent vegetation. Experiments in a laboratory channel with model vegetation show that the ...

White, Brian L.

195

Current plate velocities relative to the hotspots incorporating the NUVEL-1 global plate motion model  

SciTech Connect

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

196

Forearc structure beneath southwestern British Columbia: A three-dimensional tomographic velocity model  

Microsoft Academic Search

This paper presents a three-dimensional compressional wave velocity model of the forearc crust and upper mantle and the subducting Juan de Fuca plate beneath southwestern British Columbia and the adjoining straits of Georgia and Juan de Fuca. The velocity model was constructed through joint tomographic inversion of 50,000 first-arrival times from earthquakes and active seismic sources. Wrangellia rocks of the

K. Ramachandran; S. E. Dosso; G. D. Spence; R. D. Hyndman; T. M. Brocher

2005-01-01

197

DEVELOPMENT AND APPLICATION OF GSTAR-1D  

Microsoft Academic Search

GSTAR-1D is a hydraulic and sediment transport numerical model developed to simulate flows in rivers and channels with or without movable boundaries. GSTAR-1D is able to compute water surface profiles in single channels, simple channel networks, and complex channel networks. It has both steady and unsteady flow models, many sediment transport equations, floodplain simulation, and cohesive and non-cohesive sediment transport.

Jianchun Huang; Blair P. Greimann; Travis Bauer

198

Wave-induced velocities inside a model seagrass bed  

E-print Network

Laboratory measurements reveal the flow structure within and above a model seagrass meadow (dynamically similar to Zostera marina) forced by progressive waves. Despite being driven by purely oscillatory flow, a mean current ...

Luhar, Mitul

199

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

200

Impacts of Leads on the Wintertime Sea-ice Environment Using 1D and 3D Models Validated with In-Situ Observations  

NASA Astrophysics Data System (ADS)

Though leads only represent a small portion of the Arctic sea-ice area, their contribution to the surface turbulent energy and momentum fluxes can be significant. Numerous modeling studies presented in the literature have been conducted examining these effects. The results of such studies have indicated the importance of the environmental large-scale stability, the environmental humidity, the lead width, the ice (lead) concentration, the lead size distribution, the character of the leads (open water, refrozen), etc. Because global climate models (GCMs) show significant sensitivity to the large-scale net energy flux from the heterogeneous sea-ice surface, and because thinner ice in the projected future Arctic climate will likely result in increasing lead fractions, the appropriate GCM representation of this complex system is important. This study presents modeling results based on observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, for which the mid-winter sea-ice was greatly heterogeneous. In mid-January, the 100x100 km region surrounding the SHEBA ice camp consisted of a lead fraction of ~16-33% as revealed by SAR data. This included primarily older refrozen lead areas that were generated at least a month earlier (~16-25% areal coverage), with a smaller fraction of newly opened leads (~4-9% areal coverage). Utilizing the sequence of SAR images, the atmospheric observations at the SHEBA site, and a 1-D snow and ice model, the spatial distribution of sea-ice thickness, snow depth, and surface temperatures within this domain were estimated over a 6-week period, revealing the significant impact of leads in all stages on GCM-scale temperatures and fluxes. This combined observational/model data series is used to evaluate a variety of one-dimensional turbulent flux aggregation techniques (e.g., mosaic) that use different assumptions. Furthermore, by using the spatial distribution of these surface characteristics, three-dimensional large eddy simulations (LES) have been done to a) validate the 1D aggregation techniques and b) to assess how mesoscale circulations generated by the surface heterogeneity impact net surface fluxes. Initially, the LES modeling uses very simple idealized surface conditions and progressively moves towards the much more complex conditions revealed by the SHEBA observations. Our LES studies both validate previous results and address issues not covered in the previous studies in an effort to understand and represent the SHEBA surface fluxes on scales from local point measurements to the GCM grid-box size.

Persson, O. P.; Solomon, A.

2013-12-01

201

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

202

Axial flow velocity patterns in a normal human pulmonary artery model: pulsatile in vitro studies.  

PubMed

It has been clinically observed that the flow velocity patterns in the pulmonary artery are directly modified by disease. The present study addresses the hypothesis that altered velocity patterns relate to the severity of various diseases in the pulmonary artery. This paper lays a foundation for that analysis by providing a detailed description of flow velocity patterns in the normal pulmonary artery, using flow visualization and laser Doppler anemometry techniques. The studies were conducted in an in vitro rigid model in a right heart pulse duplicator system. In the main pulmonary artery, a broad central flow field was observed throughout systole. The maximum axial velocity (150 cm s-1) was measured at peak systole. In the left pulmonary artery, the axial velocities were approximately evenly distributed in the perpendicular plane. However, in the bifurcation plane, they were slightly skewed toward the inner wall at peak systole and during the deceleration phase. In the right pulmonary artery, the axial velocity in the perpendicular plane had a very marked M-shaped profile at peak systole and during the deceleration phase, due to a pair of strong secondary flows. In the bifurcation plane, higher axial velocities were observed along the inner wall, while lower axial velocities were observed along the outer wall and in the center. Overall, relatively low levels of turbulence were observed in all the branches during systole. The maximum turbulence intensity measured was at the boundary of the broad central flow field in the main pulmonary artery at peak systole. PMID:2324117

Sung, H W; Yoganathan, A P

1990-01-01

203

Modeling and Simulation of Fixed bed Adsorption column: Effect of Velocity Variation  

Microsoft Academic Search

The kinetic behavior of a fixed-bed adsorber can be explained and the characteristic breakthrough curve of the adsorption phenomena can be obtained through mathematical models. In the earlier models, the kinetics is explained using a mathematical model that takes into account of external and internal mass- transfer resistances with a nonideal plug flow behavior. The variation of fluid velocity along

B. V. Babu; Suresh Gupta

204

Shock waves for discrete velocity nonconservative (except mass) models  

Microsoft Academic Search

Extended discrete kinetic theory (that which we call nonconservative) including sources, sinks, the creation and annihilation of test particles and inelastic scattering etc added to the elastic collisions, was first introduced by Boffi and Spiga. The mass conservation law (or momentum, energy) becomes, by adding polynomials of the mass (or densities), nonconservative. There exist linear and quadratic nonconservative models for

H. Cornille

1999-01-01

205

An upper-mantle S-wave velocity model for East Asia from Rayleigh wave tomography  

NASA Astrophysics Data System (ADS)

We present a new shear velocity model of the upper mantle beneath the East Asia region derived by inverting Rayleigh wave group velocity measurements between 10 and 145 s combined with previously published Rayleigh wave phase velocity measurements between 150 and 250 s. Rayleigh wave group velocity dispersion curves along more than 9500 paths were measured and combined to produce 2D dispersion maps for 10-145 s periods. The group velocity maps benefit from the inclusion of new data recorded by the China National Seismic Network and surrounding global stations. The increase in available data has resulted in enhanced resolution compared with previously published group velocity maps; the horizontal resolution across the region is about 3° for the periods used in this study. The new shear wave velocity models indicate varying velocity structure beneath eastern China, which yields estimates of a lithosphere-asthenosphere boundary depth from around 160 km beneath the Yangtze block to approximately 140 km beneath the western part of the North China Craton (NCC), up to depths of 70-100 km beneath the eastern NCC, Northeast China, and the Cathaysia block. The models reveal the subduction of two opposite-facing continental plates under the southern and northern margin of Tibet. An obvious low-velocity anomaly appears in the top 200 km of the upper mantle beneath northern Tibet, which is inconsistent with the presence of subducted Asian or Indian mantle lithosphere beneath northern Tibet. The Cenozoic volcanism fields in the Mongolian plateau are characterized by an obvious upper mantle negative anomaly, but no signature of deep-seated plume was observed. This study was supported by the international cooperation project of the Ministry of Science and Technology of China (2011DFB20120) and NSFC (41074067).

Li, Y.; Wu, Q.; Pan, J.; Zhang, F.; Sun, L.

2013-12-01

206

An upper-mantle S-wave velocity model for East Asia from Rayleigh wave tomography  

NASA Astrophysics Data System (ADS)

We present a new shear velocity model of the upper mantle beneath the East Asia region derived by inverting Rayleigh wave group velocity measurements between 10 and 145 s combined with previously published Rayleigh wave phase velocity measurements between 150 and 250 s. Rayleigh wave group velocity dispersion curves along more than 9500 paths were measured and combined to produce 2D dispersion maps for 10-145 s periods. The group velocity maps benefit from the inclusion of new data recorded by the China National Seismic Network and surrounding global stations. The increase in available data has resulted in enhanced resolution compared with previously published group velocity maps; the horizontal resolution across the region is about 3° for the periods used in this study. The new shear-wave velocity models indicate varying velocity structure beneath eastern China, which yields estimates of a lithosphere-asthenosphere boundary depth from around 160 km beneath the Yangtze block to approximately 140 km beneath the western part of the North China Craton (NCC), up to depths of 70-100 km beneath the eastern NCC, Northeast China, and the Cathaysia block. The models reveal the subduction of two opposite-facing continental plates under the southern and northern margin of Tibet. An obvious low-velocity anomaly appears in the top 200 km of the upper mantle beneath northern Tibet, which is inconsistent with the presence of subducted Asian or Indian mantle lithosphere beneath northern Tibet. The Cenozoic volcanism fields in the Mongolian plateau are characterized by an obvious upper mantle negative anomaly, but no signature of deep-seated plume was observed.

Li, Yonghua; Wu, Qingju; Pan, Jiatie; Zhang, Fengxue; Yu, Daxin

2013-09-01

207

Focal mechanisms of earthquake multiplets in the western part of the Corinth Rift (Greece): influence of the velocity model and constraints on the geometry of the active faults  

NASA Astrophysics Data System (ADS)

The composite fault plane solutions for 24 large multiplets recorded in the western part of the Corinth Rift between 2000 and 2007 are computed by jointly inverting P polarities and Sv/P, Sh/P, Sv/Sh amplitude ratios of the direct waves. The fault plane solutions are determined using 1-D and 3-D velocity models. Solutions computed with the 3-D velocity model are preferred to the ones computed with the 1-D model because overall, 3-D solutions have a better score function. They correspond essentially to E-NE/W-SW and W-NW/E-SE striking normal faults, which is consistent with the N-S extensional/vertical shortening tectonic regime of the area. For 15 multiplets, one of the nodal planes is similar to the plane delineated by the earthquakes. It is then possible to determine which nodal plane is the fault plane. The analysis of the fault plane solutions highlights a clear decrease of their dip with depth and towards the north. Several multiplets with steeply dipping fault planes (50°-60°) located at depths of 7-8 km are clearly located at the base of onshore and offshore faults that crop out close to the south border of the Corinth Gulf, indicating that these faults are steep down to 7-8 km depth. To the north, multiplets underline a low angle north-dipping structure (20°-30°) on which steep north-dipping faults could take root.

Godano, Maxime; Deschamps, Anne; Lambotte, Sophie; Lyon-Caen, Hélène; Bernard, Pascal; Pacchiani, Francesco

2014-06-01

208

A pore network model for calculation of interfacial velocities  

Microsoft Academic Search

Two-phase flow in porous media is characterized by fluid–fluid interfaces that separate fluid phases at the pore scale. These interfaces support pressure differences between phases, and their dynamics lead to changes in phase saturation within the porous medium. Dynamic pore-scale network models mathematically track the dynamic position of each fluid–fluid interface through a pore network, based on imposed boundary conditions,

H. F. Nordhaug; M. Celia; H. K. Dahle

2003-01-01

209

Quantum Gravity and Maximum Attainable Velocities in the Standard Model  

SciTech Connect

A main difficulty in the quantization of the gravitational field is the lack of experiments that discriminate among the theories proposed to quantize gravity. Recently we showed that the Standard Model(SM) itself contains tiny Lorentz invariance violation(LIV) terms coming from QG. All terms depend on one arbitrary parameter {alpha} that set the scale of QG effects. In this talk we review the LIV for mesons nucleons and leptons and apply it to study several effects, including the GZK anomaly.

Alfaro, Jorge [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)

2007-06-19

210

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

SciTech Connect

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

211

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

USGS Publications Warehouse

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

212

Direct Measurement of Internal Flow Velocities in a Star-Slot Model  

NASA Technical Reports Server (NTRS)

This paper presents the results of a cold flow experiment to make direct measurements of the velocity distribution in a model of a solid rocket motor star grain propellant slot. The experimental procedure utilizes a multi-component laser Doppler velocimeter (LDV) and an apparatus for seeding the flow with aluminum particles to determine the velocity components at various discrete locations within the star slot. The test article used in this investigation was a one-tenth scale, cold flow model based on the geometry of the Space Shuttle solid rocket motor head-end section. The results obtained for the direct measurements of velocity are compared to velocities calculated from measured pressure distributions to data obtained from oil smear experiments and flow visualization videos, and to heat transfer calorimeter data.

Foster, Winfred A., Jr.; Jenkins, Rhonald M.; Hengel, John E.; Smith, Andrew W.

1997-01-01

213

3-D Depth Interval Velocity Model Analysis and Interpretation of the Nankai Trough Margin (Southwest Japan).  

NASA Astrophysics Data System (ADS)

The 3-D Muroto seismic transect images the Nankai Trough margin south of Shikoku island, Japan, where the Philippine Sea plate subducts at a rate of 2-4 cm/y beneath the accretionary prism. The ODP drill sites of Legs 190-196 show the basaltic basement of the incoming plate overlain by the Shikoku Basin Lower Miocene-Lower Pleistocene hemipelagic mudstone, and the Pleistocene-Recent Nankai Trough turbidites. A geological meaningful interval velocity volume has been modeled using 3-D pre-stack depth migration (PSDM) calibrating the seismic volume with known depths at the drill sites, and extended to the entire seaward part of the Muroto transect. Our final PSDM velocity gradients closely resemble the drill holes logging and core velocities. Hence, the PSDM velocity field is representative of the "in-situ" velocities. In the trench area, the velocities increase with depth within the turbidites (1525-1580 m/s), as expected for a section with a normal compaction trend (decreasing porosity with depth). In the Upper Shikoku Basin Facies (USBF) hemipelagic unit (1580-1860 m/s), the P-wave velocity increases downhole although the porosity remains approximately constant within the entire unit. A conclusion of Leg 190 is that velocity in this interval can be controlled by cementation. In the upper part of the Lower Shikoku Basin Facies (LSBF) hemipelagic unit (1860-1920 m/s) the velocity increases until about 50-60 m below the top of LSBF, where a velocity inversion of about 50 m/s is recorded. The velocity inversion can be connected to an anomalously high fluid content at that level in the LSBF unit. We interpret this depth (5200 m below the sea level) as the stratigraphic equivalent of the decollement that occurs landward in the imbricate thrust zone. Below the velocity inversion zone, the PSDM velocities increase again with depth in the rest of the LSBF and the Volcaniclastic units (1870-2160 m/s). This is in agreement with a decrease in porosity versus depth in the underthrusting sediments. At about 5500 m, the velocity sharply increases to 3500-3800 m/s at the top of the oceanic crust. Landward in the accretionary prism, the PSDM vertical gradient maintains a similar trend to the one described in the trench, though the velocity values are slightly higher. The average PSDM vertical gradient above the decollement decreases from 0.99 s-1 seaward of the trench axis to 0.87 s-1 landward near the frontal thrust. The velocity inversion described in the trench extends almost to the first 30 km of the decollement (first 1200 cdps). The velocity inversion is about 150 m/s at the 808 drill site location, and it increases landward to 200-300 m/s (cdps interval 800-1600). The vertical gradient in the underthrusting section decreases from 0.97 s-1 in the basin to 0.72 s-1 beneath the frontal thrust. In this unit, the lateral velocity gradient between the basin and the deformation front is 0.02 s-1, corresponding to a 10% thinning in the direction of the subduction. This has been related to dewatering processes due to compaction of the underthrusting sediments. Velocity variations occurring along strike of the Muroto transect are generally negligible and a similar velocity field pattern is observed all along the data set. More in detail, the southwest sector of the Muroto transect around inline 215, shows lower velocities in the underthrusting section than the northeast sector around inline 284, on the order of 100 to 200 m/s.

Costa Pisani, P.; Kramer, G.; Moore, G. F.; Tobin, H. J.

2005-12-01

214

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

PubMed Central

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

215

Variable aspect ratio method in the Xu-White model for shear-wave velocity estimation  

NASA Astrophysics Data System (ADS)

Shear-wave velocity logs are useful for various seismic interpretation applications, including bright spot analyses, amplitude-versus-offset analyses and multicomponent seismic interpretations. This paper presents a method for predicting the shear-wave velocity of argillaceous sandstone from conventional log data and experimental data, based on Gassmann's equations and the Xu-White model. This variable aspect ratio method takes into account all the influences of the matrix nature, shale content, porosity size and pore geometry, and the properties of pore fluid of argillaceous sandstone, replacing the fixed aspect ratio assumption in the conventional Xu-White model. To achieve this, we first use the Xu-White model to derive the bulk and shear modulus of dry rock in a sand-clay mixture. Secondly, we use Gassmann's equations to calculate the fluid-saturated elastic properties, including compressional and shear-wave velocities. Finally, we use the variable aspect ratio method to estimate the shear-wave velocity. The numerical results indicate that the variable aspect ratio method provides an important improvement in the application of the Xu-White model for sand-clay mixtures and allows for a variable aspect ratio log to be introduced into the Xu-White model instead of the constant aspect ratio assumption. This method shows a significant improvement in predicting velocities over the conventional Xu-White model.

Bai, Jun-Yu; Yue, Cheng-Qi; Liang, Yi-Qiang; Song, Zhi-Xiang; Ling, Su; Zhang, Yang; Wu, Wei

2013-06-01

216

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

217

High Resolution Interseismic Velocity Model of the San Andreas Fault From GPS and InSAR  

NASA Astrophysics Data System (ADS)

We recover the interseismic deformation along the entire San Andreas Fault System (SAFS) at a spatial resolution of 200 meters by combining InSAR and GPS observations using a dislocation model. Previous efforts to compare 17 different GPS-derived strain rate models of the SAFS shows that GPS data alone cannot uniquely resolve the rapid velocity gradients near faults, which are critical for understanding the along-strike variations in stress accumulation rate and associated earthquake hazard. To improve the near-fault velocity resolution, we integrate new GPS observations with InSAR observations, initially from ALOS (Advanced Land Observation Satellite launched by Japan Aerospace Exploration Agency) ascending data (spanning 2006.5-2010), using a remove/restore approach. More than 1100 interferograms were processed with the newly developed InSAR processing software GMTSAR. The integration uses a dislocation-based velocity model to interpolate the Line-Of-Sight (LOS) velocity at the full resolution of the InSAR data in radar coordinates. The residual between the model and InSAR LOS velocity are stacked and high-pass filtered, then added back to the model. This LOS velocity map covers almost entire San Andreas Fault System (see Figure 1) from Maacama Fault to the north to the Superstition Hills Fault to the south. The average standard deviation of the LOS velocity model ranges from 2 to 4 mm/yr. Our initial results show previously unknown details in along-strike variations in surface fault creep. Moreover, the high resolution velocity field can resolve asperities in these "creeping" sections that are important for understanding moment accumulation rates and seismic hazards. We find that much of the high resolution velocity signal is related to non-tectonic processes (e.g., ground subsidence and uplift) sometimes very close to the fault zone. The near-fault deformation signal extracted from this velocity map can provide tighter constraints on fault slip rates and locking depths of the major fault segments along the SAFS.

Tong, X.; Sandwell, D. T.; Smith-Konter, B. R.

2011-12-01

218

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

219

Butyrylcholinesterase is Associated with ?-Amyloid Plaques in the Transgenic APPSWE/PSEN1dE9 Mouse Model of Alzheimer Disease  

PubMed Central

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

220

Comparison of the velocity distribution between the adhesion approximation and the Euler-Jeans-Newton model  

NASA Astrophysics Data System (ADS)

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 Domínguez 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; Tatekawa, Takayuki

2006-01-01

221

Optimal Velocity Profile Generation for given Acceleration Limits; The Half-Car Model Case  

E-print Network

Optimal Velocity Profile Generation for given Acceleration Limits; The Half-Car Model Case E/deceleration and attitude profiles for a half-car model in high-speed cornering is presented. The methodology to experimental results generated by expert-race drivers [5]. On the other hand, these numerical optimization

Tsiotras, Panagiotis

222

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

SciTech Connect

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

223

Mathematical modeling of particle behavior of nanocrystalline Ni during high velocity oxy-fuel thermal spray  

Microsoft Academic Search

The present paper describes a mathematical model predicting the particle behavior of nanocrystalline Ni powders during high velocity oxy-fuel (HVOF) spray. The model development was motivated by successful experimental results as described in the following. The feedstock powders were synthesized by mechanical milling to produce flake-shaped agglomerates with an average grain size of less than 100 nm. The powders were

M. L. Lau; V. V. Gupta; E. J. Lavernia

1998-01-01

224

CELEBRATION 2000: P-wave velocity models of the Bohemian Massif  

NASA Astrophysics Data System (ADS)

Deep structure of the Bohemian Massif (BM), the largest stable outcrop of Variscan rocks in Central Europe, was studied along two refraction profiles, CEL09 that traverses the whole massif in the NW-SE direction, and CEL10 that extends along its eastern edge almost perpendicularly to CEL09. Good quality recordings with clear first arrivals of crustal and upper mantle phases show apparent velocity 5.9 km/s for the upper crust with slightly higher gradient in NW part of the BM and app. velocity 8.0 to 8.1 km/s for the upper mantle. Decrease of amplitudes of crustal phases visible in some sections may be connected with a specific upper crustal structure (zero to negative velocity gradient zone). Pronounced Moho reflections in central part of the BM suggest well-defined Moho in that part and not so clear Moho with smaller velocity contrast in other parts of the BM. For interpretation, the tomographic inversion routine of Hole (1992) was used as an efficient tool to determine seismic P-wave velocity distribution in the crust using first arrivals. Tomographic models were verified by forward ray tracing modelling based on well-established algorithm developed by Cerveny et al. (1983), where apart from first arrivals also further phases were included. 2-D velocity models of first arrivals and reflected phases show high P-wave velocity gradient zone reaching the depth of 5-7 km followed by small gradient and laterally homogeneous P-wave velocity distribution in the middle crust. Differences in velocity distribution in the lower crust delimit central part of the BM (sharp Moho discontinuity) from other tectonic units within the BM (lower crust high gradient transition zone). Position of Moho discontinuity ranging from 32 km to 40 km and reflectors within the crust complement the P-wave velocity distribution. Presented models also show the contact of the BM with its neighbouring units - Carpathians, Paleozoic Platform, Vienna Basin and the Alps. References: Cerveny, V., Psencik, I., 1983. Program SEIS83, Numerical Modelling of Seismic Wave Fields in 2-D Laterally Varying Layered Structures by the Ray Method, Charles University, Prague. Hole, J.A. 1992: Non-linear high-resolution three-dimensional seismic travel time tomography, J. Geophys. Res. 97, 6553-6562.

Hrubcova, P.

2003-04-01

225

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

226

Fabry-Perot interferometer measurement of static temperature and velocity for ASTOVL model tests  

NASA Astrophysics Data System (ADS)

A spectrally resolved Rayleigh/Mie scattering diagnostic was developed to measure temperature and wing-spanwise velocity in the vicinity of an ASTOVL aircraft model in the Lewis 9 x 15 Low Speed Wind Tunnel. The spectrum of argon-ion laser light scattered by the air molecules and particles in the flow was resolved with a Fabry-Perot interferometer. Temperature was extracted from the spectral width of the Rayleigh scattering component, and spanwise gas velocity from the gross spectral shift. Nozzle temperature approached 800 K, and the velocity component approached 30 m/s. The measurement uncertainty was about 5 percent for the gas temperature, and about 10 m/s for the velocity. The large difference in the spectral width of the Mie scattering from particles and the Rayleigh scattering from gas molecules allowed the gas temperature to be measured in flow containing both naturally occurring dust and LDV seed (both were present).

Kourous, Helen E.; Seacholtz, Richard G.

1995-07-01

227

Fabry-Perot interferometer measurement of static temperature and velocity for ASTOVL model tests  

NASA Technical Reports Server (NTRS)

A spectrally resolved Rayleigh/Mie scattering diagnostic was developed to measure temperature and wing-spanwise velocity in the vicinity of an ASTOVL aircraft model in the Lewis 9 x 15 Low Speed Wind Tunnel. The spectrum of argon-ion laser light scattered by the air molecules and particles in the flow was resolved with a Fabry-Perot interferometer. Temperature was extracted from the spectral width of the Rayleigh scattering component, and spanwise gas velocity from the gross spectral shift. Nozzle temperature approached 800 K, and the velocity component approached 30 m/s. The measurement uncertainty was about 5 percent for the gas temperature, and about 10 m/s for the velocity. The large difference in the spectral width of the Mie scattering from particles and the Rayleigh scattering from gas molecules allowed the gas temperature to be measured in flow containing both naturally occurring dust and LDV seed (both were present).

Kourous, Helen E.; Seacholtz, Richard G.

1995-01-01

228

Intercomparison of Eight Forward 1D Vector Radiative Transfer Models, with the Performance of Satellite Aerosol Remote Sensing Algorithms in Mind  

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

229

Acoustic properties of gas hydrate-bearing consolidated sediments and experimental testing of elastic velocity models  

NASA Astrophysics Data System (ADS)

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 consolidated sediments were investigated experimentally. Hydrate saturation (Sh) and acoustic velocities were measured in one system by time domain reflectometry and ultrasonic methods, respectively, during gas hydrate formation and subsequent dissociation in a water-saturated artificial core. Acoustic velocities change little at low hydrate saturations (0% to ˜10%), whereas they increase rapidly when hydrate saturation is between 10% and 30%. We verified two commonly used models, i.e., the weighted equation (WE) and the Biot-Gassmann theory modified by Lee (BGTL). In the 0% to 40% hydrate saturation range, the WE model is consistent with the measured Vp data, while a combination of the WE and the Vp/Vs ratio in the BGTL predicts Vs corresponding to the observed data. As hydrate saturation is more than 30%, however, the BGTL is more suitable for predicting both Vp and Vs. This suggests that gas hydrate may be treated as a component within a matrix of consolidated sediments when hydrate saturation exceeds 30%. However, when Sh is less than 30%, the hydrate locates in the pore fluid or partly adheres to the sediment frame.

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

2010-02-01

230

Understanding 1D Electrostatic Dust Levitation  

NASA Astrophysics Data System (ADS)

Electrostatically-dominated dust motion has been hypothesized since the Lunar Horizon Glow was observed by the Surveyor spacecraft. The hypothesized occurence of this phenomenon was naturally extended to asteroids due to their small gravities. Additionally, it has been suggested that the dust ponds observed on Eros by the NEAR mission may be created by electrostatically-dominated dust transport. Previous attempts to numerically model dust motion on the Moon and Eros have been stymied by poorly understood dust launching mechanisms. As a result, the initial velocity and charge of dust particles used in numerical simulations may or may not have any relevance to the actual conditions occurring in situ. It has been seen that properly tuned initial states (velocity and charge) result in dust particles levitating above the surface in both 1D and 2D simulations. Levitation is of interest to planetary scientists since it provides a way to quickly redistribute the surface dust particles over a body. However, there is currently no method to predict whether or not a certain initial state will result in levitation. We have developed a method to provide constraints on the initial states that result in levitation as a function of dust particle size and central body gravity. Additionally, our method can be applied to several models of the plasma sheath. Thus, we limit the guesswork involved in determining which initial conditions result in levitation. We provide a more detailed understanding of levitation phenomena couched in terms of the commonly recognized spring-mass system. This method of understanding dust motion removes the dependency on the launching mechanism, which remains fraught with controversy. Once a feasible dust launching mechanism is identified (be it micrometeoroid bombardment or electrostatic lofting), our method will allow the community to quickly ascertain if dust levitation will occur in situ or if it is simply a numerical artifact. In addition to constraining the initial states that result in dust levitation, our model provides estimates of the heights and sizes of particles that could be levitated as a function of the central body gravity and plasma sheath potential profile. Thus, given a model of the plasma sheath, we can inform future missions hoping to observe levitating particles.

Hartzell, C. M.; Scheeres, D. J.

2011-12-01

231

Collisionless transport equations derived from a kinetic exospheric solar wind model with kappa velocity distribution functions  

E-print Network

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

232

Calculations of Burning Velocity of Turbulent Premixed Flames Using a Flame Surface Density Model  

NASA Astrophysics Data System (ADS)

The objective of the present paper is to develop and validate a newly formulated Flame Surface Density (FSD) model able to predict realistic turbulent burning velocities of premixed turbulent propagating flames over a wide range of flow conditions. Non-iterative transient numerical calculations of turbulent flame propagation in one-dimensional space are carried out over a range of turbulence Reynolds number using stoichiometric methane-air mixture. It is found that the new model closely predicts experimental data of turbulent burning velocity by Abdel-Gayed et al. (1987) as well as results from KPP (Kolmogorov, Petrovski, Piskonov) analytical method. The model formulation, and subsequent results of turbulent burning velocity and combustion regimes are presented and discussed in terms of the various physical processes that control flame/flow interactions in premixed combustion.

Patel, Samir N. D. H.; Ibrahim, Salah S.

233

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

234

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

235

Quasilinear model for energetic particle diffusion in radial and velocity space  

SciTech Connect

A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 2 Multiplication-Sign 2 EP diffusion matrix account for fluxes up radial (energy) gradients driven by energy (radial) gradients of the EP velocity space distribution function. The quasilinear ratio kernel of the model is provided by a simple analytic formula for the EP radial and velocity space EP diffusivity relative to radial thermal ion energy diffusivity at each linear mode of the turbulence driven by the thermal plasma. The TGLF [G. M. Staebler, J. E. Kinsey, and R. E. Waltz, Phys. Plasmas 14, 0055909 (2007); ibid. 15, 0055908 (2008)] tokamak transport model provides the linear mode frequency and growth rates to the kernel as well as the nonlinear spectral weight for each mode.

Waltz, R. E.; Staebler, G. M. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Bass, E. M. [University of California-San Diego, 9500 Gilman Dr., La Jolla, California 92093 (United States)

2013-04-15

236

Quasilinear model for energetic particle diffusion in radial and velocity space  

NASA Astrophysics Data System (ADS)

A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 2×2 EP diffusion matrix account for fluxes up radial (energy) gradients driven by energy (radial) gradients of the EP velocity space distribution function. The quasilinear ratio kernel of the model is provided by a simple analytic formula for the EP radial and velocity space EP diffusivity relative to radial thermal ion energy diffusivity at each linear mode of the turbulence driven by the thermal plasma. The TGLF [G. M. Staebler, J. E. Kinsey, and R. E. Waltz, Phys. Plasmas 14, 0055909 (2007); ibid. 15, 0055908 (2008)] tokamak transport model provides the linear mode frequency and growth rates to the kernel as well as the nonlinear spectral weight for each mode.

Waltz, R. E.; Bass, E. M.; Staebler, G. M.

2013-04-01

237

a Multiple Data Set Joint Inversion Global 3d P-Velocity Model of the Earth's Crust and Mantle for Improved Seismic Event Location  

NASA Astrophysics Data System (ADS)

SALSA3D is a global 3D P wave velocity model of the Earth's crust and mantle developed specifically to provide seismic event locations that are more accurate and more precise than are locations from 1D and 2.5D models. In this paper, we present the most recent version of our model, for the first time jointly derived from multiple types of data: body wave travel times, surface wave group velocities, and gravity. The latter two are added to provide information in areas with poor body wave coverage, and are down-weighted in areas where body wave coverage is good. To constrain the inversions, we invoked empirical relations among the density, S velocity, and P velocity. We demonstrate the ability of the new SALSA3D model to reduce mislocations and generate statistically robust uncertainty estimates for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. We obtain path-dependent travel time prediction uncertainties for our model by computing the full 3D model covariance matrix of our tomographic system and integrating the model slowness variance and covariance along paths of interest. This approach yields very low travel time prediction uncertainties for well-sampled paths through the Earth and higher uncertainties for paths that are poorly represented in the data set used to develop the model. While the calculation of path-dependent prediction uncertainties with this approach is computationally expensive, uncertainties can be pre-computed for a network of stations and stored in 3D lookup tables that can be quickly and efficiently interrogated using GeoTess software.

Ballard, S.; Begnaud, M. L.; Hipp, J. R.; Chael, E. P.; Encarnacao, A.; Maceira, M.; Yang, X.; Young, C. J.; Phillips, W.

2013-12-01

238

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

E-print Network

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

2012-06-07

239

Potential of high resolution satellite imagery, remote weather data and 1D hydraulic modeling to evaluate flood areas in Gonaives, Haiti  

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 km²), 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

240

The Application of Mean Square Slope Derived Gas Transfer Velocities in a Global General Circulation Model  

NASA Astrophysics Data System (ADS)

An algorithm that estimates gas transfer velocities (k) from the mean square slope of centimetric sea surface waves derived from normalized radar backscatter measured by altimeters was applied to a variant of the NCAR Community Climate System Model-Parallel Ocean Program (CCSM-POP). This ocean general circulation model includes a fully coupled marine ecosystem/carbon cycling sub-model. Historical hindcast simulations were integrated from 1958 to the beginning of 1993 using gas transfer velocities derived from NCEP reanalysis wind speeds and the Wanninkhof quadratic wind speed algorithm. Twin experiments were conducted from 1 Jan 1993 to 1 Jan 2005 using either NCEP reanalysis winds derived transfer velocities or transfer velocities computed from TOPEX data. We focus our analysis on a comparison of the time/space differences in air-sea CO2 and O2 fluxes and surface water pCO2 and pO2 fields between the two experiments. Our objectives are to explore the sensitivity of ocean biogeochemistry to global and basin scale variations in gas transfer velocity, gain greater understanding of the global accuracy of the altimeter algorithm, and provide insight into the various processes influencing the net CO2 and O2 fluxes across the air-sea interface.

Glover, D. M.; Frew, N. M.; Doney, S. C.; Lima, I. D.; Caruso, M. J.; McCue, S. J.

2006-12-01

241

A California statewide three-dimensional seismic velocity model from both absolute and differential times  

USGS Publications Warehouse

We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP=VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE directionand 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling.

Lin, G.; Thurber, C. H.; Zhang, H.; Hauksson, E.; Shearer, P. M.; Waldhauser, F.; Brocher, T. M.; Hardebeck, J.

2010-01-01

242

Polar versus Cartesian velocity models for maneuvering target tracking with IMM  

NASA Astrophysics Data System (ADS)

This paper compares various model sets in different IMM filters for the maneuvering target tracking problem. The aim is to see whether we can improve the tracking performance of what is certainly the most widely used model set in the literature for the maneuvering target tracking problem: a Nearly Constant Velocity model and a Nearly Coordinated Turn model. Our new challenger set consists of a mixed Cartesian position and polar velocity state vector to describe the uniform motion segments and is augmented with the turn rate to obtain the second model for the maneuvering segments. This paper also gives a general procedure to discretize up to second order any non-linear continuous time model with linear diffusion. Comparative simulations on an air defence scenario with a 2D radar, show that this new approach improves significantly the tracking performance in this case.

Laneuville, Dann

243

A New Model for Estimating In Situ Porosities from Seismic Velocities in the Upper Oceanic Crust  

NASA Astrophysics Data System (ADS)

Water is carried into subduction zones by the oceanic crust in hydrous mineral phases and in pore spaces. Estimating the porosity of the crust from its seismic structure is therefore a matter of some interest. Previous estimates of in situ porosity of the oceanic crust have been based on empirical relationships between seismic velocities and bulk densities. An asperity deformation model previously used to demonstrate that (apparent) porosity controls seismic velocities in the upper oceanic crust in Holes 504B and 1256D can also be used to make the reverse calculation - to estimate the in situ porosity from a seismic velocity profile. An advantage of this approach is that the model accounts for the pressure dependence of velocity and porosity. The asperity model parameters are the 'initial pressure', Pi, and the exponent, m, that describes the asperity height distribution, as well as material properties, the modulus of the solid, and densities of the solid and the pore fluid. The porosity then depends on just two variables, the seismic p-wave velocity, V, and the effective pressure, Pe - a function of depth. Then 1/V2= a?2 + b? + c (1) The coefficients a and b are functions of depth, and c is a constant. Given a seismic velocity profile, it is a simple matter to solve this equation for the variation of porosity with depth. The properties of the extrusive section and the underlying dikes in Holes 504B and 1256D are best described by somewhat different model parameters. Fortunately, these units can be distinguished in the seismic profile because velocities in the extrusive sections are typically less than 5.7 km/s, while velocities in the dike sections are higher. The model for the dike section of Hole 504B is well constrained, with an rms difference between the model values and apparent fractional porosities derived from the resistivity log of 0.002. With an rms difference of 0.014, the model for the extrusive section is less well constrained, probably owing to the heterogeneity of the lavas. Nevertheless there is good agreement between the porosities estimated from the sonic log and those estimated from a seismic profile: the mean fractional porosities of the extrusive pile derived from the sonic log and the seismic profile are 0.083(±0.004) and 0.090, respectively, while those for the dike section are 0.012(±0.001) and 0.014.

Carlson, R. L.

2012-12-01

244

Explaining the subpulse drift velocity of pulsar magnetosphere within the space-charge limited flow model  

NASA Astrophysics Data System (ADS)

We try to explain the subpulse drift phenomena adopting the space-charge limited flow model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin, where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalogue of Weltevrede et al. with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.

Morozova, Viktoriya S.; Ahmedov, Bobomurat J.; Zanotti, Olindo

2014-10-01

245

Modeling of liquid ceramic precursor droplets in a high velocity oxy-fuel flame jet  

Microsoft Academic Search

Production of coatings by high velocity oxy-fuel (HVOF) flame jet processing of liquid precursor droplets can be an attractive alternative method to plasma processing. This article concerns modeling of the thermophysical processes in liquid ceramic precursor droplets injected into an HVOF flame jet. The model consists of several sub-models that include aerodynamic droplet break-up, heat and mass transfer within individual

Saptarshi Basu; Baki M. Cetegen

2008-01-01

246

Effects of 1-D versus 3-D velocity models on moment tensor inversion in the Dobr Voda locality at the Little Carpathians region, Slovakia  

E-print Network

;1. Introduction and motivation The mountain region of Little Carpathians in western Slovakia, especially the zone elevation, while its southern border with the Dobrá Voda depression is represented by the distinctive Dobrá

Cerveny, Vlastislav

247

Stabilization of traffic flow in optimal velocity model via delayed-feedback control  

NASA Astrophysics Data System (ADS)

Traffic jams may occur due to various reasons, such as traffic accidents, lane reductions and on-ramps. In order to suppress the traffic congestion in an optimal velocity traffic model without any driver's delay taken into account, a delayed-feedback control of both displacement and velocity differences is proposed in this study. By using the delay-independent stability criteria and the H?-norm, the delayed-feedback control can be determined to stabilize the unstable traffic flow and suppress the traffic jam. The numerical case studies are given to demonstrate and verify the new control method. Furthermore, a comparison is made between the new control method and the method proposed by Konishi et al. [K. Konishi, M. Hirai, H. Kokame, Decentralized delayed-feedback control of an optimal velocity traffic model, Eur. Phys. J. B 15 (2000) 715-722]. The results show that the new control method makes the traffic flow more stable and improves the control performance.

Jin, Yanfei; Hu, Haiyan

2013-04-01

248

Computation of traveltime covariances based on stochastic models of velocity heterogeneity  

NASA Astrophysics Data System (ADS)

We formulate the error covariance for calculated seismic traveltimes (traveltime covariance) along any two propagation paths as a double integral of a covariance function describing velocity-model error (velocity covariance) with sensitivity distributions for the paths. Two numerical techniques are presented for evaluating the traveltime covariance matrix for multiple paths. The first technique evaluates the covariance matrix directly. The second evaluates the inverse of the covariance matrix summed with a covariance matrix for observational errors, as is utilized in event locators. Our approach takes the velocity covariance to be the Green's function of a differential operator, which can be specified in terms of physically meaningful parameters, such as spatially variable velocity variance and correlation lengths. Our numerical algorithms reduce to solving finite-difference equations based on the differential operator. As a demonstration, we compute traveltime covariance using ray-based sensitivity distributions and a suite of depth-dependent models of velocity covariance. We compare our theoretical calculations to empirical estimates of traveltime variance versus event-station distance, derived from observed residuals relative to the `ak135' velocity model. Our calculations predict and explain some key features of the distance dependence of observed residual statistics, such as abrupt changes in variance at crossover points separating branches of the first-arrival traveltime curve. We find that the observed traveltime variances in the distance range 2°-33° are well matched by assuming a velocity standard deviation (relative to `ak135') of >10 per cent in the crust and decaying from ˜2 per cent in the uppermost mantle to near 0 per cent below the 410-km discontinuity. These variance estimates hold over a wide range of assumed correlation lengths of velocity error, which are not well constrained by traveltime variance observations. By providing a physical understanding of traveltime covariance, our approach may help in the development of improved methods for locating seismic events, for estimating path-specific corrections to baseline traveltime models, and for constraining the statistics of velocity variations in the Earth.

Rodi, William L.; Myers, Stephen C.

2013-09-01

249

Comparison of P-, SV- and SH-wave velocity models below Japan and northeast China  

NASA Astrophysics Data System (ADS)

The recent deployment of the NECESSArray seismic network in northeast China has allowed new insights on the velocity structure of this formerly poorly resolved area. This experiment has brought new data to debate about the geodynamical context in this region (stagnant slab, origin of intraplate volcanism, etc...). We use an efficient method for the measurement of travel time residuals by cross-correlating observed and synthetic waveforms. Synthetic seismograms are convolved with high-frequency source-time functions inverted along with focal depths, following a simulated annealing approach. Thus, resulting modeled waveforms take more accurately account for the source effects. The method is used to perform measurements on direct P, SV and SH phases extracted from, respectively, vertical, radial and transverse band-pass-filtered records from NECESSArray and F-NET seismological networks. We finally invert the resulting datasets in order to obtain P-, SV- and SH-wave velocity models. To do so, we use a fast and efficient inversion method using ray theory. Observed structures in the three tomographic models show a very good geographical coherency. Nevertheless, some differences are observed below Songliao basin and Changbaishan volcano between P and SV models and SH model. By measuring velocity ratios, we discuss anisotropy and thermal/compositional origin of these velocity anomalies.

Kawakatsu, H.; Schardong, L.; Takeuchi, N.; Tanaka, S.; Obayashi, M.; Chen, Y. J.; Ning, J.; Niu, F.; Grand, S. P.; Ni, J.

2013-12-01

250

3-D velocity model of the upper mantle in the Northern Eurasia  

NASA Astrophysics Data System (ADS)

In the Northern Eurasia several long-range seismic profiles were carried out using the Peace Nuclear Explosions (PNE). Their total length is around 20000 km. During the last decade the PNE data, were interpreted by different authors with different interpretation methods. As a result a high ambiguity of the wave fields interpretation were revealed. Analysis, systematisation and interpretation of these experimental materials with a common method of the wave field interpretation, enable to determine a 3-D velocity model of the upper mantle to depths of 300 km. Three basic layers with P-velocities 8.1-8.3, 8.3-8.5 and 8.5-8.6 km/s were determined in the upper mantle. The boundaries N and L dividing these layers are observed at depths around 80-120 and 180-200 km. The most variations in thickness and velocities are characteristic for the upper layer. The Timan-Pechora and the West Siberian young plates differs by lower velocities (8.0-8.1 km/s) and higher thickness (up to 150 km) of the upper layer. Anomalous high velocities (up to 8.4 km/s) and an uplift of the N boundary are observed beneath some blocks of the Siberian Craton and of the Urals. The L boundary depths is more stable - around 200-250 km. An important peculiarity of the upper layer are strong reflectors, both horizontal and inclined. The most regular horizontal reflectors are observed at depths of 60-70 km. The reflections at these boundaries are often recorded as apparent first arrivals due to low amplitude of the Pn waves. Their apparent velocities are higher than Pn refraction velocities (up to 8.6 km/s) and the fact has been often misinterpreted as strong variations of the velocities beneath the Moho and as anomalous high average velocities in the uppermost mantle of the East-European Platform. In reality the platform is characterised by stable velocities (8.1-8.2 km/s) and by a stable thickness (80-100 km) of the upper layer. The real high velocities are typical for the uppermost mantle in the Siberian Craton. They might be interpreted as an anisotropy effect.

Pavlenkova, G. A.; Pavlenkova, N. I.

2003-04-01

251

Crustal velocities near Coalinga, California, modeled from a combined earthquake/explosion refraction profile  

USGS Publications Warehouse

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

252

Diurnal Evolution of Organic Aerosols over Paris: Insights from the Combination of Measurements during the MEGAPOLI campaign with a 1D Model  

NASA Astrophysics Data System (ADS)

In spite of rapid developments in our understanding of organic aerosol (OA) physicochemical properties, representing the OA composition and evolution over urban areas remains a challenge. This study addresses the diurnal evolution of OA over Paris during the MEGAPOLI campaign. We analyze the observations with a model that aims at a balanced representation of the various processes that contribute to the diurnal variation of the organic aerosol budget. It is a 1D Eulerian model of the atmospheric boundary layer that contains advanced modules for gas-phase chemistry, gas/particle partitioning, and dry deposition. The model represents a computationally efficient framework for the accurate description of OA formation and photochemical evolution in the boundary layer. Semi-volatile organic components are distributed into volatility bins based on their saturation concentration and are allowed to partition into the aerosol phase. Furthermore, the semi-volatile organics in the gas phase continue to react with OH radical leading to compounds with lower volatility and hence continued OA formation. Model results are evaluated against available observations of OA, gas-phase chemistry and boundary layer dynamics. The model results are used along with the Aerosol Mass Spectrometer (AMS) dataset from the MEGAPOLI campaign to give new insights into the sources and diurnal production of OA over Paris. Furthermore, budget calculations are performed to show the contribution of the various processes (i.e., photochemistry, aerosol thermodynamics, boundary layer dynamics, etc.) to the calculated OA mass. Finally, the influence of uncertainties in several processes that determine the OA budget on the calculated OA properties is systematically analyzed through a series of sensitivity analyses. These include emission fractions of semivolatile and intermediate volatile compounds (SVOC/IVOC), secondary OA yields for the various gas-phase precursors, gas-phase aging of SVOC and IVOC during several generations of oxidation, dry deposition of OA and its gas-phase precursors, the temperature dependence of gas/particle partitioning, and assumptions on the volatility and entrainment of the background OA concentration.

Janssen, Ruud H. H.; Tsimpidi, Alexandra P.; Karydis, Vlassis A.; Lelieveld, Jos

2014-05-01

253

Constraining the NFW Potential with Observations and Modeling of LSB Galaxy Velocity Fields  

E-print Network

We model the NFW potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak IFU velocity fields and rotation curves of axisymmetric and non-axisymmetric potentials that are well-matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that non-axisymmetric potentials with fixed axis ratios change only the normalization of the mock velocity fields and rotation curves and not their shape. The shape of the modeled NFW rotation curves does not reproduce the data: these potentials are unable to simultaneously bring the mock data at both small and large radii into agreement with observations. Indeed, to match the slow rise of LSB galaxy rotation curves, a specific viewing angle of the non-axisymmetric potential is required. For each of the simulated LSB galaxies, the observer's line-of-sight must be along the minor axis of the potential, an arrangement which is inconsistent with a random distribution of halo orientations on the sky.

Rachel Kuzio de Naray; Stacy S. McGaugh; J. Christopher Mihos

2008-10-28

254

Testing Models of North American Seismic Velocity Structure With Traveltimes From Well-Validated Sources  

NASA Astrophysics Data System (ADS)

Surface wave tomography has provided 3D models of the seismic structure of the continents, down to depths of several hundred kilometers (e.g. Van der Lee and Nolet, 1997; Nettles and Dziewonski, 2007). On the one hand, these models are limited by their low horizontal resolution (hundreds of kilometers) and by providing estimates of shear velocity but not compressional velocity. On the other hand, they have the virtue of having a uniform spatial resolution and are based on data (surface wave dispersion) that are only very weakly dependent on the location and origin time of the underlying earthquake sources. This near independence is relevant, for instance, in developing velocity models and/or traveltime models for earthquake location, because the problems associated with circularity-of-results (e.g. the same earthquakes both determining the model and being located by it) are avoided. We discuss the conceptual and practical problems associated with using surface wave results to calculate continental-scale traveltimes and to locate earthquakes. We build such a model of North America and test it against continental-scale traveltimes from five PNE's and the Early Rise series of chemical explosions. Traveltime residuals are reduced by 50 percent compared to the predictions of a radially-stratified model, but some regionally coherent traveltime residuals remain, indicating that the 3D model derived from surface waves is capturing some, but not all, of the actual variability beneath the continents.

Menke, W.; Richards, P. G.; Kim, W.; Waldhauser, F.; Schaff, D.

2007-12-01

255

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

E-print Network

Settling velocities of particulate systems: 14. Unified model of sedimentation, centrifugation August 2002; accepted 30 June 2003 Abstract This paper presents a unified theory of solid, which illustrate the theory. D 2003 Elsevier B.V. All rights reserved. Keywords: sedimentation

Bürger, Raimund

256

Deformation at a Complex Strike-Slip Plate Boundary: Modeling the Southern California GPS Velocity Field  

Microsoft Academic Search

Because of EarthScope and related deployments, Southern California has perhaps the highest Global Positioning System (GPS) station density of any of Earth's seismically active regions. Here we provide an updated analysis of the Southern California velocity field to illustrate both the strengths of high station density and the inherent limitations of surface geodetic measurements for quantifying earthquake-related deformation processes. Modeling

W. R. Thatcher; J. R. Murray-Moraleda

2009-01-01

257

USING METEOROLOGICAL MODEL OUTPUT AS A SURROGATE FOR ON-SITE OBSERVATIONS TO PREDICT DEPOSITION VELOCITY  

EPA Science Inventory

The National Oceanic and Atmospheric Administration's Multi-Layer Model (NOAA-MLM) is used by several operational dry deposition networks for estimating the deposition velocity of O , SO , HNO , and particles. The NOAA-MLM requires hourly values of meteorological variables and...

258

Model Predictive Control of Velocity and Torque Split in a Parallel Hybrid Vehicle  

Microsoft Academic Search

Fuel economy of parallel hybrid electric vehicles is affected by both the torque split ratio and the vehicle velocity. To optimally schedule both variables, information about the surrounding traffic is necessary, but may be made available through telemetry. Consequently, in this paper, a nonlinear model predictive control algorithm is proposed for the vehicle control system to maximise fuel economy while

Tae Soo Kim; Chris Manzie; Rahul Sharma

2009-01-01

259

Considering Ecological Formulations for Estimating Deposition Velocity in Air Quality Models______________________________  

E-print Network

. The same model was tested for its ability to simulate ammonia Vd near an animal agricultural facility of non-industrial, agricultural sources for emissions of nitrogen compounds such as ammonia. Dry to estimate observed deposition velocity estimates for ozone over agricultural fields showed good agreement

Aneja, Viney P.

260

Evaluation of an Imputed Pitch Velocity Model of the Auditory Kappa Effect  

ERIC Educational Resources Information Center

Three experiments evaluated an imputed pitch velocity model of the auditory kappa effect. Listeners heard 3-tone sequences and judged the timing of the middle (target) tone relative to the timing of the 1st and 3rd (bounding) tones. Experiment 1 held pitch constant but varied the time (T) interval between bounding tones (T = 728, 1,000, or 1,600…

Henry, Molly J.; McAuley, J. Devin

2009-01-01

261

Size-Distribution Analysis of Macromolecules by Sedimentation Velocity Ultracentrifugation and Lamm Equation Modeling  

Microsoft Academic Search

A new method for the size-distribution analysis of polymers by sedimentation velocity analytical ultracentrifugation is described. It exploits the ability of Lamm equation modeling to discriminate between the spreading of the sedimentation boundary arising from sample heterogeneity and from diffusion. Finite element solutions of the Lamm equation for a large number of discrete noninteracting species are combined with maximum entropy

Peter Schuck

2000-01-01

262

Development of mathematical model of spring suspension system for microelectromechanical angular Velocity Sensor (MEMS gyroscope)  

Microsoft Academic Search

In the paper a mathematical model for calculating constructive parameters (thickness and length) of the spring element of the spring suspension system for the micromechanical gyroscope (microelectromechanical angular velocity sensor) is developed. The interdependence between the spring suspension system and technical characteristics of the sensor is analyzed.

Mykhaylo Lobur; Andriy Holovatyy; Ihor Motyka

2010-01-01

263

The 2D diffusive shallow water model: validation against experimental data and integration with a 1D module to simulate a meandering river expansion.  

NASA Astrophysics Data System (ADS)

Extreme hydrologic events are increasingly investigated and numerically simulated by means of complete 2D Shallow Water Equations. While the effectiveness of this conceptual model has been proven several times, its numerical integration needs accurate schemes that still require an amount of computational effort. The use of less accurate numerical methods does not justify the complexity of the full dynamic SWE model as they lower the overall correctness of the prediction. An approximation of the full SWE consists in neglecting the inertial terms, degrading the original hyperbolic to a parabolic model (PSWE). The effects of such a choice on simulating real flood events are still not clear. Several conclusions are drawn in this work investigating the behaviour of the PSWE compared to experimental data taken from the Toce physical model (CADAM project). It resembles a dam break event in a steep valley, in which many transitions across critical flow together with multiple reflections occur and whose dynamic is not fully described by the PSWE model. Analysis of results allows to state that the parabolic approximation, even if it fails to reproduce some local phenomena such as high frequency oscillation, bores and run-up, is capable to simulate the propagation of such an impulsive wave over complex topography. The model is able not only to predict the general development of the event, but also to describe inundation arrival times, water levels' distribution and local peak values with precision comparable to other full dynamic numerical models on most parts of the domain. This is due to both the parabolic assumption, which intrinsically allows an easier treatment of wet-dry interfaces, and to the numerical scheme, which adequately deals with such transitions. This can be stated in view of the high impulsiveness of the considered test case. Local discontinuities are proved to have a small influence on the overall dynamic of the event: the application of models which make use of some approximations of the underlying physics is thus justified, and enforced by the minor computational effort they require. This analysis suggests that the PSWE model may effectively reproduce the principal features of an inundation event, even in cases - such as the one examined - for which the diffusive approximation may seem unrealistic. A numerical analysis of a flood event in a meandering reach of Tiber River (Italy) is proposed as well. The study is aimed at assessing the effects induced by the construction of a complex road infrastructure on the floodplain inundation. The 2D PSWE model is linked to a 1D full dynamic module to properly and efficiently simulate both the riverbed and the floodplain flow and to correctly account for complex flow exchanges. This numerical approach allows a quantitative examination of different scenarios and proves to be an effective tool in the decision process within an infrastructure design framework.

Prestininzi, P.

2009-04-01

264

A numerical model for the calculation of the growth velocity of nonisothermal parabolic dendrites  

NASA Astrophysics Data System (ADS)

For a circular paraboloid of revolution growing in a shape preserving manner neither the surface curvature, nor the local interface velocity are constant on the freezing front. Yet within the widely quoted model [J. Lipton, W. Kurz and R. Trivedi, Acta Metall. 35, 957 (1987)] for the calculation of dendritic growth velocities the kinetic and GibbsThomson undercoolings evaluated at the dendrite tip are assumed to apply equally over the whole dendrite surface, approximating the non-isothermal dendrite as an isothermal dendrite with a reduced surface melting temperature. Reasons are discussed why this approach may seriously overestimate the growth velocity at high undercooling, where kinetic effects are important. Using a finite difference model the full, non-isothermal growth problem is solved for the solidification of pure Ni. The model shows that an undercooling of 175 K neglecting non-isothermal effects leads to a 35% error in the calculated growth velocity. Comparison with the available experimental data suggest an adequate fit to the data for Ni can be made without the need for adjustable parameters.

Mullis, Andrew M.

1995-09-01

265

Modeling the 2-D seismic velocity structure across the Kenya rift  

NASA Astrophysics Data System (ADS)

A 460-km-long seismic refraction/wide-angle reflection profile across the East African rift in Kenya has been interpreted using a travel-time inversion method to calculate a two-dimensional crustal and uppermost mantle seismic velocity model. The derived model is consistent with the crustal structure determined by independent interpretation of axial (along the rift) and flank (near the eastern end of the cross profile) data sets. The velocity model indicates that the Kenya rift at this location (near the Equator) is a relatively narrow (about 100 km wide) feature from surface expression (fault-bounded basins) to upper-mantle depths. A 5-km-deep, sediment- and volcanic-filled basin is present beneath the rift valley. Seismic velocities in the underlying crust are slightly higher directly beneath the rift valley than in the adjacent terranes. Additionally, the crust thins by about 8 km (to a thickness of about 30 km) in a 100-km-wide zone beneath the rift valley and anomalously low upper-mantle seismic velocity (Pn ? 7.6 km/s) is present only beneath the thinned crust and extends to depths of greater than 120 km.

Braile, L. W.; Wang, B.; Daudt, C. R.; Keller, G. R.; Patel, J. P.

1994-09-01

266

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

Microsoft Academic Search

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

267

Dynamical Modeling of Velocity Profiles: The Dark Halo around the Elliptical Galaxy NGC 2434  

Microsoft Academic Search

We describe a powerful technique to model and interpret the stellar line-of-sight velocity profiles of galaxies. It is based on Schwarzschild's approach to build fully general dynamical models. A representative library of orbits is calculated in a given potential, and the non-negative superposition of these orbits is determined that best fits a given set of observational constraints. The most significant

Hans-Walter Rix; P. Tim de Zeeuw; Nicolas Cretton; Roeland P. van der Marel; C. Marcella Carollo

1997-01-01

268

Normal-Velocity Relaxation and Higher Order Algebraic Heat Flux Models Applicable to an Axisymmetric Impinging Jet  

Microsoft Academic Search

The present paper encompasses an effort on the prediction of flow and heat transfer characteristics in the turbulent axisymmetric impinging jet. This is achieved by applying the realizability constraint in the normal-velocity relaxation (v  ? f) model and algebraic turbulent heat flux models to flow and thermal fields, respectively. The realizable v  ? f model is capable of improving the predicted velocity

Farzad BAZDIDI-TEHRANI; Alireza IMANIFAR; Siavash KHAJEHHASANI; Mehran RAJABI-ZARGARABADI

2011-01-01

269

Spatial velocity profile in mouse embryonic aorta and Doppler-derived volumetric flow: a preliminary model.  

PubMed

Characterizing embryonic circulatory physiology requires accurate cardiac output and flow data. Despite recent applications of high-frequency ultrasound Doppler to the study of embryonic circulation, current Doppler analysis of volumetric flow is relatively crude. To improve Doppler derivation of volumetric flow, we sought a preliminary model of the spatial velocity profile in the mouse embryonic dorsal aorta using ultrasound biomicroscopy (UBM)-Doppler data. Embryonic hematocrit is 0.05-0.10 so rheologic properties must be insignificant. Low Reynolds numbers (<500) and Womersley parameters (<0.76) suggest laminar flow. UBM demonstrated a circular dorsal aortic cross section with no significant tapering. Low Dean numbers (<100) suggest the presence of minimal skewing of the spatial velocity profile. The inlet length allows for fully developed flow. There is no apparent aortic wall pulsatility. Extrapolation of prior studies to these vessel diameters (300-350 microm) and flow velocities (~50-200 mm/s) suggests parabolic spatial velocity profiles. Therefore, mouse embryonic dorsal aortic blood flow may correspond to Poiseuille flow in a straight rigid tube with parabolic spatial velocity profiles. As a first approximation, these results are an important step toward precise in utero ultrasound characterization of blood flow within the developing mammalian circulation. PMID:12181118

Phoon, Colin K L; Aristizábal, Orlando; Turnbull, Daniel H

2002-09-01

270

Mass Distribution of Spiral Galaxies in a Thin Disk Model with Velocity Curve Extrapolation  

E-print Network

We model a spiral galaxy by a thin axially symmetric disk that includes both visible and dark matter. The surface mass density of the disk is calculated directly from the rotational velocity curve without extra assumptions. We simplify the standard application of the model. Since most velocity curves are known out to some radius, r_{max}, we extrapolate them by attaching a Keplerian tail. The numerical procedure and the extrapolation are tested with a known toy mass density and shown to reconstruct it with a good precision if r_{max} includes a sufficient part of the velocity curve. Mass density curves are calculated for Milky Way and NGC 3198. We vary the extent of the flat part of the velocity curves from 30 kpc to 200 kpc and show that does not affect appreciably the calculated mass density inside r_{max}=30 kpc. The reconstructed masses for Milky Way are 15 x 10^10 solar masses inside the visible disk and 23 x 10^10 solar masses inside 30 kpc. For NGC 3198, the reconstructed mass inside the visible disk is 6.5 x 10^10 solar masses and 11 x 10^10 solar masses inside 30 kpc. The total galactic masses are roughly proportional to the extent of the flat part of the velocity curves which is currently unknown. The high light-to-mass ratios obtained for the visible disks of the galaxies - 11 solar units for Milky way and 9.3 for NGC 3198 - suggest presence of dark matter. The method is also applied to NGC 3031 - a spiral galaxy with a declining velocity curve in which case it is able to reconstruct both the mass density curve and the total mass (14 x 10^10 solar masses).

Valentin Kostov

2006-04-18

271

Prediction of Critical Velocity During Cold Spraying Based on a Coupled Thermomechanical Eulerian Model  

NASA Astrophysics Data System (ADS)

In cold spraying (CS), critical velocity of particles is one of the most important parameters. The impacting particle and substrate inevitably undergo a strong thermomechanical coupling process at the contacting interface and serious plastic deformation in a very short time. In this paper, a coupled thermomechanical Eulerian (CTM-Eulerian) model was, for the first time, developed for CS particles to investigate plastic deformation and heat conduction within the bulk, and to predict the critical velocity. Results show that heat conduction has a significant effect on the temperature distribution within the particle which will influence the atom diffusion at the impacting interface, while a little influence on plastic deformation. Moreover, based on the deformed particle shapes and plastic strain analysis, a calculated critical velocity of about 300 m/s for copper is obtained. Finally, this CTM-Eulerian model is extended to other commonly sprayed materials and the predicted critical velocities of Fe, Ni, SS304, Al, In718, and TC4 are about 350, 380, 395, 410, 490, and 500 m/s, respectively.

Wang, F. F.; Li, W. Y.; Yu, M.; Liao, H. L.

2014-01-01

272

Predicting flow in aortic dissection: comparison of computational model with PC-MRI velocity measurements.  

PubMed

Aortic dissection is a life-threatening process in which the weakened wall develops a tear, causing separation of wall layers. The dissected layers separate the original true aortic lumen and a newly created false lumen. If untreated, the condition can be fatal. Flow rate in the false lumen is a key feature for false lumen patency, which has been regarded as one of the most important predictors of adverse early and later outcomes. Detailed flow analysis in the dissected aorta may assist vascular surgeons in making treatment decisions, but computational models to simulate flow in aortic dissections often involve several assumptions. The purpose of this study is to assess the computational models adopted in previous studies by comparison with in vivo velocity data obtained by means of phase-contrast magnetic resonance imaging (PC-MRI). Aortic dissection geometry was reconstructed from computed tomography (CT) images, while PC-MRI velocity data were used to define inflow conditions and to provide distal velocity components for comparison with the simulation results. The computational fluid dynamics (CFD) simulation incorporated a laminar-turbulent transition model, which is necessary for adequate flow simulation in aortic conditions. Velocity contours from PC-MRI and CFD in the two lumens at the distal plane were compared at four representative time points in the pulse cycle. The computational model successfully captured the complex regions of flow reversal and recirculation qualitatively, although quantitative differences exist. With a rigid wall assumption and exclusion of arch branches, the CFD model over-predicted the false lumen flow rate by 25% at peak systole. Nevertheless, an overall good agreement was achieved, confirming the physiological relevance and validity of the computational model for type B aortic dissection with a relatively stiff dissection flap. PMID:25070022

Cheng, Z; Juli, C; Wood, N B; Gibbs, R G J; Xu, X Y

2014-09-01

273

Coupling method of 1-d/1-d and 1-d/3-d junctions for an implict WCOBRA/TRAC  

SciTech Connect

COBRA/TRAC is an advanced thermal-hydraulic computer code, originally developed by Battelle Pacific Northwest Laboratories. The code combines a two-fluid, three-dimensional (3-d) program, COBRA-TF, with a one-dimensional (1-d) drift flux program, TRAC-PD2. COBRA-TF is designed to be used to model the pressurized water reactor (PWR), and loop components are modeled with TRAC-PD2. An implicit method was proposed for the COBRA part of the code, and some success was achieved as demonstrated by an analysis of a film-boiling experiment for a steady-state and power ascension transient. On the other hand, TRAC-PD2 includes an option to choose a semi-implicit or an implicit method in solving component equations. This implicit option improves running time somewhat, but the junctions among the components are treated semi-implicitly. So, the time step is controlled by the Courant numbers at the 1-d/3-d and 1-d/1-d component junctions. In order to speed up the code further, the solution method for the junctions must be changed to implicit. An implicit method is introduced. It is evaluated by a COBRA/TRAC model of a less-of-fluid test (LOFT) and a two-loop PWR.

Takeuchi, K.; Young, M.Y.

1988-01-01

274

Three-dimensional modeling of shallow shear-wave velocities for Las Vegas, Nevada, using sediment type  

Microsoft Academic Search

A three-dimensional model of near-surface shear-wave velocity in the deep alluvial basin underlying the metropolitan area\\u000a of Las Vegas, Nevada (USA), is being developed for earthquake site response projections. The velocity dataset, which includes\\u000a 230 measurements, is interpolated across the model using depth-dependent correlations of velocity with sediment type. The\\u000a sediment-type database contains more than 1 400 well and borehole

Barbara Luke; Helena Murvosh; Wanda Taylor; Jeff Wagoner

2009-01-01

275

Observation and model of an ellipsoidally symmetric velocity space distribution in a weakly-coupled dusty plasma  

SciTech Connect

The spatially resolved phase space distribution was measured for a dusty plasma system. Analysis of the velocity space component of the distributions revealed that the standard assumption of a spherically symmetric velocity space is not applicable to the observed system. The more general, ellipsoidally symmetric, multi-normal distribution function was applied to model the velocity space and is compared to the canonical spherically symmetric model.

Fisher, Ross; Thomas, Edward [Physics Department, Auburn University, Alabama 36849-5311 (United States)

2011-11-15

276

The Impact of Bdnf Gene Deficiency to the Memory Impairment and Brain Pathology of APPswe/PS1dE9 Mouse Model of Alzheimer's Disease  

PubMed Central

Brain-derived neurotrophic factor (BDNF) importantly regulates learning and memory and supports the survival of injured neurons. Reduced BDNF levels have been detected in the brains of Alzheimer’s disease (AD) patients but the exact role of BDNF in the pathophysiology of the disorder remains obscure. We have recently shown that reduced signaling of BDNF receptor TrkB aggravates memory impairment in APPswe/PS1dE9 (APdE9) mice, a model of AD. The present study examined the influence of Bdnf gene deficiency (heterozygous knockout) on spatial learning, spontaneous exploratory activity and motor coordination/balance in middle-aged male and female APdE9 mice. We also studied brain BDNF protein levels in APdE9 mice in different ages showing progressive amyloid pathology. Both APdE9 and Bdnf mutations impaired spatial learning in males and showed a similar trend in females. Importantly, the effect was additive, so that double mutant mice performed the worst. However, APdE9 and Bdnf mutations influenced spontaneous locomotion in contrasting ways, such that locomotor hyperactivity observed in APdE9 mice was normalized by Bdnf deficiency. Obesity associated with Bdnf deficiency did not account for the reduced hyperactivity in double mutant mice. Bdnf deficiency did not alter amyloid plaque formation in APdE9 mice. Before plaque formation (3 months), BDNF protein levels where either reduced (female) or unaltered (male) in the APdE9 mouse cortex. Unexpectedly, this was followed by an age-dependent increase in mature BDNF protein. Bdnf mRNA and phospho-TrkB levels remained unaltered in the cortical tissue samples of middle-aged APdE9 mice. Immunohistological studies revealed increased BDNF immunoreactivity around amyloid plaques indicating that the plaques may sequester BDNF protein and prevent it from activating TrkB. If similar BDNF accumulation happens in human AD brains, it would suggest that functional BDNF levels in the AD brains are even lower than reported, which could partially contribute to learning and memory problems of AD patients. PMID:23844236

Rantamaki, Tomi; Kemppainen, Susanna; Autio, Henri; Staven, Saara; Koivisto, Hennariikka; Kojima, Masami; Antila, Hanna; Miettinen, Pasi O.; Karkkainen, Elisa; Karpova, Nina; Vesa, Liisa; Lindemann, Lothar; Hoener, Marius C.; Tanila, Heikki; Castren, Eero

2013-01-01

277

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

278

Acoustic reconstruction of the velocity field in a furnace using a characteristic flow model.  

PubMed

An acoustic method can provide a noninvasive, efficient and full-field reconstruction of aerodynamic fields in a furnace. A simple yet reasonable model is devised for reconstruction of a velocity field in a cross section of a tangential furnace from acoustic measurements based on typical physical characteristics of the field. The solenoidal component of the velocity field is modeled by a curved surface, derived by rotating a curve of Gaussian distribution, determined by six characteristic parameters, while the nonrotational component is governed by a priori knowledge. Thus the inverse problem is translated into determination of the characteristic parameters using a set of acoustic projection data. First numerical experiments were undertaken to simulate the acoustic measurement, so as to preliminarily validate the effectiveness of the model. Based on this, physical experiments under different operating conditions were performed in a pilot-scale setup to provide a further test. Hot-wire anemometry and strip floating were applied to compare with acoustic measurements. The acoustic measurements provided satisfactory consistency with both of these approaches. Nevertheless, for a field with a relatively large magnitude of air velocities, the acoustic measurement can give more reliable reconstructions. Extension of the model to measurements of hot tangential furnaces is also discussed. PMID:22712914

Li, Yanqin; Zhou, Huaichun; Chen, Shiying; Zhang, Yindi; Wei, Xinli; Zhao, Jinhui

2012-06-01

279

A comprehensive dispersion model of surface wave phase and group velocity  

NASA Astrophysics Data System (ADS)

In order to complement our large datasets of surface wave group arrival times, we have adapted our cluster analysis method of group velocity measurement to measure phase velocity. When measuring phase, we are no longer working with waveform envelopes and we must be very careful to avoid cycle-skipping. We correct for source phase and the predicted phase shift due to 3d structure by using a nominal phase velocity map. This latter step is important at periods shorter than 100 seconds but is not necessary at longer periods. We have processed all the long period data from IRIS from 1988 to 2007. Currently, we have finished phase measurements for Love wave from 7mHz to 30mHz. This dataset contains about 200,000 measurements at 10mHz and about 100,000 measurements at 30mHz. The phase dataset for Rayleigh waves is complete from 5mHz to 25mHz, and has about 600,000 measurements at 10 mHz and 400,000 measurements at 25mHz. We see no difficulty in extending the Rayleigh wave measurements to, say, 40mHz to complement our group velocity measurements. In order to find a dispersion model that simultaneously matches both phase and group data, we use b-splines to parameterize the frequency dependence of the phase velocity. We find that a parameterization of equally spaced b-splines with an interval of 2mHz is sufficient to explain both our phase and group velocity maps consistently. At long periods, there is a strong tradeoff between the isotropic part of the Rayleigh wave phase velocity and azimuthal anisotropy (e.g. Ekstrom, 2011). This effect is mainly confined to the Pacific basin where azimuthal anisotropy is coherent over large distances and results in significant signal. We include the effect of azimuthal anisotropy in our inversions in order to obtain a reliable isotropic part of the phase velocity. Patterns in the fast directions of Rayleigh wave azimuthal anisotropy and their reliability will also be discussed.

Ma, Z.; Masters, G.; Laske, G.; Pasyanos, M. E.

2012-12-01

280

Metastable fluid flow described via a discrete-velocity coagulation-fragmentation model  

NASA Astrophysics Data System (ADS)

A discrete-velocity Boltzmann model is introduced. It is based on two principles: (i) clusters of particles move in ?3 with seven fixed momenta; (ii) clusters may gain or lose particles according to the rules of Becker-Döring cluster equations. The model provides a kinetic representation of evaporation and condensation. The model is used to obtain macroscopic fluid equations which are valid into the metastable fluid regime,0 ?slant ?< ? _s + O(? ^? ), where ? is any positive number, ? is the inelastic Knudsen number, and ? s is the saturation density.

Slemrod, M.

1996-06-01

281

Improved reflectivity and velocity model for aluminum gratings on YZ LiNbO3.  

PubMed

Lithium niobate has recently been used for SAW tags and temperature sensors because of its high coupling coefficient and high reflectivity. To increase the device operating frequency for a given electrode line resolution, harmonic operation of the reflector is a very attractive option. When used in conjunction with harmonically operated transducers, the device operating frequency can be increased for a given photolithographic line width resolution. To design and accurately predict the behavior of these devices, it is necessary to model the electrode reflectivity and velocity for both fundamental and second-harmonic operation. The coupling of modes (COM) model has been used to model these devices, however the COM model uses empirically determined coefficients to model reflectivity. In this paper, the reflectivity and velocity of aluminum electrodes is extracted experimentally for fundamental and second-harmonic operation versus metalization ratios ranging from 0.2 to 0.9 and versus normalized metal thickness ranging from 0.4% to 4%. A least-squares fit is then performed on the data using physical terms in the transmission line model to yield equations that can be used in the COM model to predict device behavior over varying metallization ratios and normalized metal thicknesses. Orthogonal frequency-coded (OFC) SAW tags were designed and fabricated and experimentally obtained data are compared with the COM modeled responses for the tags at fundamental and second-harmonic operation to verify the predictions. PMID:21507757

Saldanha, Nancy; Malocha, Donald C

2011-04-01

282

A dynamic model for the turbulent burning velocity for large eddy simulation of premixed combustion  

SciTech Connect

Turbulent premixed combustion is particularly difficult to describe using large eddy simulation (LES). In LES, premixed flame structures typically exist on subfilter length scales. Consequently, premixed LES models must be capable of describing how completely unresolved flame structures propagate under the influence of completely unresolved eddies. This description is usually accomplished through the implementation of a model for the turbulent burning velocity. Here, a dynamic model for describing the turbulent burning velocity in the context of LES is presented. This model uses a new surface filtering procedure that is consistent with standard LES filtering. Additionally, it only uses information that comes directly from the flame front. This latter attribute is important for two reasons. First, it guarantees that the model can be consistently applied when level set methods, where arbitrary constraints can be imposed on field variables away from fronts, are used to track the flame. Second, it forces the model to recognize that the physics governing flame front propagation are only valid locally at the front. Results showing model validation in the context of direct numerical simulation (DNS), and model application in the context of LES, are presented. (author)

Knudsen, E.; Pitsch, H. [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States)

2008-09-15

283

Model-based Estimation for Pose, Velocity of Projectile from Stereo Linear Array Image  

NASA Astrophysics Data System (ADS)

The pose (position and attitude) and velocity of in-flight projectiles have major influence on the performance and accuracy. A cost-effective method for measuring the gun-boosted projectiles is proposed. The method adopts only one linear array image collected by the stereo vision system combining a digital line-scan camera and a mirror near the muzzle. From the projectile's stereo image, the motion parameters (pose and velocity) are acquired by using a model-based optimization algorithm. The algorithm achieves optimal estimation of the parameters by matching the stereo projection of the projectile and that of the same size 3D model. The speed and the AOA (angle of attack) could also be determined subsequently. Experiments are made to test the proposed method.

Zhao, Zhuxin; Wen, Gongjian; Zhang, Xing; Li, Deren

2012-01-01

284

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

SciTech Connect

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

285

The IASPEI Reference Event List to Support 3D Velocity Model Validation Studies  

NASA Astrophysics Data System (ADS)

The IASPEI Reference Event List (Ground Truth database) maintained and hosted by the International Seismological Centre (ISC) on behalf of the IASPEI became an indispensable tool for the validation of 3D seismic velocity models. The Ground Truth database is regularly updated and currently consists of some 7,600 GT0-5 events (earthquakes, chemical and nuclear explosions). Recently the CTBTO has launched a global initiative to facilitate the development of the Regional Seismic Travel Time (RSTT) velocity model on a global scale by forming regional expert groups. We make a concentrated effort to increase the number and the coverage of ground truth events in Latin America. To further support the RSTT development and validation studies, the ISC has developed a version of its location software to accommodate local and regional travel-time predictions provided by the RSTT software package. The RSTT-enabled ISC locator is made available through the ISC website.

Bondar, I.; Storchak, D. A.

2013-05-01

286

A new pulsar distance model and some implications for pulsar velocities, populations and searches  

NASA Astrophysics Data System (ADS)

A new model for the free electron density in the Galaxy (Cordes and Lazio, submitted) will be described that builds upon and supercedes the model of Taylor and Cordes (1993). It incorporates all available (as of the end of 2001) independent distance constraints (from HI absorption, timing and interferometric parallaxes, and associations with other objects) and radio wave scattering measurements. New features include structures in the local interstellar medium and a galactic center component. Astrophysical implications that will be discussed include velocities of particular neutron stars, including those with known pulsar wind nebulae; the velocity distribution of radio pulsars; the Galactic distribution of pulsars, and the pulsar birth rate. Comments on pulsar search strategies will also be made.

Cordes, J.; Lazio, T.; Chatterjee, S.; Arzoumanian, Z.; Chernoff, D.

287

Modelling the Velocity Field in a Regular Grid in the Area of Poland on the Basis of the Velocities of European Permanent Stations  

NASA Astrophysics Data System (ADS)

The paper presents the results of testing the various methods of permanent stations' velocity residua interpolation in a regular grid, which constitutes a continuous model of the velocity field in the territory of Poland. Three packages of software were used in the research from the point of view of interpolation: GMT ( The Generic Mapping Tools), Surfer and ArcGIS. The following methods were tested in the softwares: the Nearest Neighbor, Triangulation (TIN), Spline Interpolation, Surface, Inverse Distance to a Power, Minimum Curvature and Kriging. The presented research used the absolute velocities' values expressed in the ITRF2005 reference frame and the intraplate velocities related to the NUVEL model of over 300 permanent reference stations of the EPN and ASG-EUPOS networks covering the area of Europe. Interpolation for the area of Poland was done using data from the whole area of Europe to make the results at the borders of the interpolation area reliable. As a result of this research, an optimum method of such data interpolation was developed. All the mentioned methods were tested for being local or global, for the possibility to compute errors of the interpolated values, for explicitness and fidelity of the interpolation functions or the smoothing mode. In the authors' opinion, the best data interpolation method is Kriging with the linear semivariogram model run in the Surfer programme because it allows for the computation of errors in the interpolated values and it is a global method (it distorts the results in the least way). Alternately, it is acceptable to use the Minimum Curvature method. Empirical analysis of the interpolation results obtained by means of the two methods showed that the results are identical. The tests were conducted using the intraplate velocities of the European sites. Statistics in the form of computing the minimum, maximum and mean values of the interpolated North and East components of the velocity residuum were prepared for all the tested methods, and each of the resulting continuous velocity fields was visualized by means of the GMT programme. The interpolated components of the velocities and their residua are presented in the form of tables and bar diagrams.

Bogusz, Janusz; K?os, Anna; Grzempowski, Piotr; Kontny, Bernard

2014-06-01

288

A GPS velocity field for Fennoscandia and a consistent comparison to glacial isostatic adjustment models  

NASA Astrophysics Data System (ADS)

In Fennoscandia, the process of Glacial Isostatic Adjustment (GIA) drives ongoing crustal deformation. Crustal velocities from GPS observations have proved to be a useful tool in constraining GIA models. However, reference frame uncertainties, plate tectonics, intraplate deformations as well as other geophysical processes contaminate the results. Former studies have shown that different International Terrestrial Reference Frames have large discrepancies, especially in the vertical component, which hamper geophysical interpretation. We present new velocity estimates for the Fennoscandian and North European GPS network. Our GPS velocity field is directly realized in a GIA reference frame. Using this method (named the GIA frame approach) we are able to constrain GIA models with minimal influence of errors in the reference frame or biasing signals from plate tectonics. The drawbacks are more degrees of freedom that might mask real but unmodeled signals. Monte Carlo tests suggest that our approach is robust at the 97% level in terms of correctly separating different models of ice history but, depending on deformation patterns, the identified Earth model may be slightly biased in up to 39% of cases. We compare our results to different one- and three-dimensional GIA models employing different global ice-load histories. The GIA models generally provide good fit to the data but there are still significant discrepancies in some areas. We suggest that these differences are mainly related to inaccuracies in the ice models and/or lateral inhomogeneities in the Earth structure under Fennoscandia. Thus, GIA models still need to be improved, but the GIA frame approach provides a base for further improvements.

Kierulf, Halfdan Pascal; Steffen, Holger; Simpson, Matthew James Ross; Lidberg, Martin; Wu, Patrick; Wang, Hansheng

2014-08-01

289

A Stochastic Non-Gaussian Velocity Model for Tracer Dispersion in Heterogeneous Porous Media  

NASA Astrophysics Data System (ADS)

To model tracer transport in porous media, computationally expensive Monte Carlo (MC) techniques or low-order approximation methods (LOAM) are applicable [1]. The latter are inexpensive but limited to relatively homogeneous media with low conductivity or transmissivity variations, and approximately Gaussian one-point velocity statistics. MC studies have shown that heterogeneous media lead to distinctly skewed non-Gaussian velocity distributions [2]. In addition to MC and LOAM, continuous time random walk (CTRW) or Lévy motion (LM) approaches were proposed for the modeling of dispersion in highly heterogeneous media, e.g, fractured rock [3,4]. Both models involve discontinuous stochastic processes for the displacement of tracer particles. The parameters that determine these processes, however, are not always easy to identify. In this work, a new particle-based model for the simulation of tracer dispersion in homogeneous and heterogeneous porous media is presented. Other than in CTRW or LM models, a continuous stochastic process for the Lagrangian velocity of a tracer particle is formulated. The suggested formulation encompasses Gaussian and skewed velocity statistics, and the model parameters can be related more easily to medium characteristics. Numerical simulations of the tracer plume evolution in the Borden tracer experiment and of breakthrough curves in homogeneous and uniformly heterogeneous sand packs are successfully validated with experimental data [5,6]. Non-Fickian dispersion behavior resulting from the scale effect (plume-size dependent dispersivities) and skewed velocity statistics is demonstrated and analyzed. [1] Zhang, Y. K. and D. Zhang (2004). "Forum: The state of stochastic hydrology." Stochastic Environmental Research and Risk Assessment 18(4): 265-265. [2] Salandin, P. and V. Fiorotto (1998). "Solute transport in highly heterogeneous aquifers." Water Resources Research 34(5): 949-961. [3] Benson, D. A., R. Schumer, et al. (2001). "Fractional Dispersion, Lévy Motion, and the MADE Tracer Tests." Transport in Porous Media 42(1): 211-240. [4] Berkowitz, B., A. Cortis, et al. (2006). "Modeling non-Fickian transport in geological formations as a continuous time random walk." Reviews of Geophysics 44(2). [5] Freyberg, D. L. (1986). "A Natural Gradient Experiment on Solute Transport in a Sand Aquifer. 2. Spatial Moments and the Advection and Dispersion of Nonreactive Tracers." Water Resources Research 22(13): 2031-2046. [6] Silliman, S. E. and E. S. Simpson (1987). "Laboratory Evidence of the Scale Effect in Dispersion of Solutes in Porous-Media." Water Resources Research 23(8): 1667-1673.

Meyer, D. W.; Tchelepi, H. A.

2009-12-01

290

Velocity and pressure characteristics of a model SSME high pressure fuel turbopump  

NASA Technical Reports Server (NTRS)

Under the present effort an experiment rig has been constructed, an instrumentation package developed and a series of mean and rms velocity and pressure measurements made in a turbopump which modelled the first stage of the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump. The rig was designed so as to allow initial experiments with a single configuration consisting of a bell-mouth inlet, a flight impeller, a vaneless diffuser and a volute. Allowance was made for components such as inlet guide vanes, exit guide vanes, downstream pumps, etc. to be added in future experiments. This flexibility will provide a clear baseline set of experiments and allow evaluation in later experiments of the effect of adding specific components upon the pump performance properties. The rotational speed of the impeller was varied between 4260 and 7680 rpm which covered the range of scaled SSME rotation speeds when due allowance is made for the differing stagnation temperature, model to full scale. The results at the inlet obtained with rotational speeds of 4260, 6084 and 7680 rpm showed that the axial velocity at the bell-mouth inlet remained roughly constant at 2.2 of the bulk velocity at the exit of the turbopump near the center of the inlet, but it decreased rapidly with increasing radius at all three speeds. Reverse flow occurred at a radius greater than 0.9 R for all three speeds and the maximum negative velocity reduced from 1.3 of the bulk velocity at the exit of the turbopump at 4260 rpm to 0.35 at 7680 rpm, suggesting that operating at a speed closer to the design condition of 8700 rpm improved the inlet characteristics. The reverse flow caused positive prerotation at the impeller inlet which was negligibly small near the center but reached 0.7 of the impeller speed at the outer annulus. The results in the diffuser and the volute obtained at 7680 rpm show that the hub and shroud walls of the diffuser were characterized by regions of transient reverse flow with negative revolution-averaged velocity of 8 percent of the maximum forward revolution-averaged velocity at the center of the diffuser passage near the shroud wall.

Tse, D. G-N.; Sabnis, J. S.; Mcdonald, H.

1991-01-01

291

Crustal velocity structure beneath Saurashtra, NW India, through waveform modeling: Implications for magmatic underplating  

NASA Astrophysics Data System (ADS)

The Saurashtra peninsula in the northwestern segment of the Deccan volcanic province of India, is characterized by several high gravity and magnetic anomalies, which correspond to mafic crustal intrusions. This study attempts to quantify the alterations to the crust caused by the Deccan volcanism, by estimating the crustal Poisson's ratio, shear wave velocity (Vs) structure and the shear velocity contrast across the Moho, through teleseismic waveform modeling. The P receiver functions (RFs) for six broadband seismic stations were constructed using about 575 high quality (S/N ? 2.5) teleseismic waveforms of earthquakes (M ? 5.5) recorded during the period 2004-2010. The moveout corrected RF summation stacks were inverted using the Neighborhood algorithm (NA) to estimate the shear velocity structure beneath each station. The crustal thickness is estimated to range from 38 km in western Saurashtra to 33 km close to the southern extension of the Cambay rift. A low velocity zone possibly corresponding to sub-basaltic sediments is detected beneath all the stations. The average crustal Vs and Poisson's ratio are estimated to be 3.68 km/s and 0.276 respectively. The crustal Poisson's ratio indicates an intermediate to mafic composition for the crust. Modeling reveals a relatively high velocity lower crust with an average Vs ? 3.88 ± 0.1 km/s which is consistent with the high Vp ? 7.1 km/s reported for this region through seismic refraction and wide angle reflection studies, overlying a relatively low velocity (Vs ? 4.4 ± 0.1 km/s) upper mantle. The shear velocity contrasts across the Moho, derived from the amplitudes of the P-to-s (Pms) conversions from the Moho range from 0.08 to 0.17 which are much smaller than those (>0.20) observed across the Indian shield, implying a gradational Moho due to underplating. This study reveals that the crust beneath Saurashtra is distinctly different from that of the Archean Indian shield largely due to significant alterations by the Deccan volcanism.

Praveen Kumar, K. A.; Mohan, G.

2014-01-01

292

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

SciTech Connect

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. Using data from 25 broadband stations located in the region, new estimates of crustal and upper mantle thickness, velocity structure, and attenuation are being developed. Receiver functions have been determined for all stations. Depth to Moho is estimated using slant stacking of the receiver functions, forward modeling, and inversion. Moho depths along the Caspian and in the Kura Depression are in general poorly constrained using only receiver functions due to thick sedimentary basin sediments. The best fitting models suggest a low velocity upper crust with Moho depths ranging from 30 to 40 km. Crustal thicknesses increase in the Greater Caucasus with Moho depths of 40 to 50 km. Pronounced variations with azimuth of source are observed indicating 3D structural complexity and upper crustal velocities are higher than in the Kura Depression to the south. In the Lesser Caucasus, south and west of the Kura Depression, the crust is thicker (40 to 50 km) and upper crustal velocities are higher. Work is underway to refine these models with the event based surface wave dispersion and ambient noise correlation measurements from continuous data. Regional phase (Lg and Pg) attenuation models as well as blockage maps for Pn and Sn are being developed. Two methods are used to estimate Q: the two-station method to estimate inter-station Q and the reversed, two-station, two event method. The results are then inverted to create Lg and Pg Q maps. Initial results suggest substantial variations in both Pg and Lg Q in the region. A zone of higher Pg Q extends west from the Caspian between the Lesser and Greater Caucasus and a narrow area of higher Lg Q is observed.

Mellors, R; Gok, R; Pasyanos, M; Skobeltsyn, G; Teoman, U; Godoladze, T; Sandvol, E

2008-07-01

293

Regional three-dimensional seismic velocity model of the crust and uppermost mantle of northern California  

Microsoft Academic Search

We present a three-dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional-scale double-difference tomography algorithm that incorporates a finite-difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled-source explosions, recorded at network and\\/or temporary stations, were inverted for Vp on a 3D grid with

Clifford Thurber; Haijiang Zhang; Thomas Brocher; Victoria Langenheim

2009-01-01

294

A California Statewide Three-dimensional Seismic Velocity Model From Both Absolute and Differential Times  

Microsoft Academic Search

We present a tomographic model of the P- and S-wave velocity structure of the crust and uppermost mantle of California. The dataset combines first-arrival times from natural earthquakes (including composite events derived from many nearby earthquakes), explosions, and identified quarry blasts, with differential times from both catalog picks and waveform cross-correlation data. We apply a regional-scale double-difference tomography algorithm, which

G. Lin; C. H. Thurber; H. Zhang; E. Hauksson; P. M. Shearer; F. Waldhauser; J. Hardebeck; T. M. Brocher; D. Schaff

2008-01-01

295

Development of a StateWide 3-D Seismic Tomography Velocity Model for California  

Microsoft Academic Search

We report on progress towards the development of a state-wide tomographic model of the P-wave velocity for the crust and uppermost mantle of California. The dataset combines first arrival times from earthquakes and quarry blasts recorded on regional network stations and travel times of first arrivals from explosions and airguns recorded on profile receivers and network stations. The principal active-source

C. H. Thurber; G. Lin; H. Zhang; E. Hauksson; P. Shearer; F. Waldhauser; J. Hardebeck; T. Brocher

2007-01-01

296

The viscous froth model: steady states and the high-velocity limit  

Microsoft Academic Search

The steady-state solutions of the Viscous Froth Model for foam dynamics are analyzed, and shown to be of finite extent or to asymptote to straight lines. In the high-velocity limi t the solutions consist of straight lines with isolated poin ts of infinite curvature. This analysis is helpful in the interp retation of observations of anomalous features of mobile two-dimensional

S. J. Cox; D. Weaire; G. Mishuris

2009-01-01

297

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

298

Regional Crustal Velocity Models for Northern Arabian Platform and Turkish-Iranian Plateau  

NASA Astrophysics Data System (ADS)

The geological structure of the Northern Arabian platform and surrounding mountains is dominated by the collision and suturing of the Arabian plate with the Eurasian plate and the formation of the Turkish-Iranian plateau. The structure of the Northern Arabian platform and surrounding region is poorly constrained. A recent deployment of 10 broadband seismometers in northern and central Iraq provides an opportunity to refine velocity models of the region. We have applied the Niching Genetic Algorithm waveform inversion technique to Rayleigh and Love waves traversing the Northern Arabian platform, the Zagros fold belt, the southern Turkish Plateau, the Iranian Plateau. Results show variations in crustal thickness and shear wave velocity between the Northern Arabian platform and the Turkish-Iranian plateau. In general the shear wave velocities are higher in the Northern Arabian platform than in the Plateaus. Variation of shear velocities within each of the provinces reflects the diversity in tectonic environment across the Zagros fold belt and the complex tectonic history of the region. Crustal thickness results show little crustal thickening has occurred due to collision.

Aleqabi, G.; Wysession, M.; Ghalib, H.

2008-12-01

299

Sampling Artifact in Volume Weighted Velocity Measurement.--- II. Detection in simulations and comparison with theoretical modelling  

E-print Network

Measuring the volume weighted velocity power spectrum suffers from a severe systematic error, due to imperfect sampling of the velocity field from inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density $\\bar{n}_P$ and the intrinsic large scale structure (LSS) fluctuation in the particle distribution. (1) We report robust detection of this sampling artifact in N-body simulations. It causes $\\sim 12%$ nderestimation of the velocity power spectrum at $k=0.1$h/Mpc for samples with $\\bar{n}_P=6\\times10^{-3}$ (Mpc/h)$^{-3}$. This systematic underestimation increases with decreasing $\\bar{n}_P$ and increasing $k$. Its dependence on the intrinsic LSS fluctuations is also robustly detected. (2) All these findings are expected by our theoretical modelling in paper I \\cite{Zhang14}. In particular, the leading order theoretical approximation agrees quantitatively well with simulation result f...

Zheng, Yi; Jing, Yipeng

2014-01-01

300

Dynamical Modeling of Velocity Profiles The Dark Halo Around the Elliptical Galaxy NGC2434  

E-print Network

We describe a powerful technique to model and interpret the stellar line-of-sight velocity profiles of galaxies. Following Schwarzschild's modeling approach, a representative library of orbits is calculated in a given potential; then the non-negative superposition of these orbits is determined to fit best a given set of observational constraints. Our implementation incorporates several new features: (i) we calculate velocity profiles and represent them by a Gauss-Hermite series. This allows us to constrain the orbital anisotropy in the fit. (ii) we take into account the error on each observational constraint to obtain an objective chi2 measure for the quality-of-fit. Only projected, observable quantities are included in the fit, and aperture binning and seeing convolution of the data are properly taken into account. This scheme is valid for any geometry, but here we focus on spherical geometry and the issue of dark halos around elliptical galaxies. We model radially extended velocity profiles of the E0 galaxy...

Rix, H W; Carollo, M; Cretton, N; Van der Marel, R P; Rix, Hans-Walter; Zeeuw, Tim de; Carollo, Marcella; Cretton, Nicolas; Marel, Roeland van der

1997-01-01

301

Constraining basal hydrology with model inversions of basal friction using new InSAR surface velocities.  

NASA Astrophysics Data System (ADS)

Constraining ice flow models for continental ice sheets such as Antarctica or Greenland can be difficult, especially regarding the specification of basal friction at the ice/bed interface. Historically, two approches have been taken: 1) model the basal hydrology of the ice sheet, and relate the resulting basal water pressure to the basal drag coefficient and 2) invert for the basal drag coefficient using InSAR surface velocities, and infer the resulting basal hydrology. Here, we use both approaches within the Ice Sheet System Model (ISSM), the JPL/UCI developed ice flow model, for which we develop a new hydrological model based on Johnson et al 2002. We compare this model against a massive inversion of Antarctica's basal drag coefficient using new InSAR surface velocities from Rignot et al 2011. We discuss the potential for this model to improve constraints on basal friction evolution, and implications for projections of ice flow dynamics in a changing climate. This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

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

2011-12-01

302

Comparison of CFD Model Velocity Profiles to Test Data for Inlet Nozzle Region of Nuclear PWR Fuel Assemblies  

SciTech Connect

A numerical investigation was performed to study the variation in axial velocity profiles occurring downstream of the inlet nozzle region of Nuclear PWR fuel assemblies. Computational Fluid Dynamic (CFD) models were prepared for the inlet nozzle region of a section of fuel assembly, simulating the lower support plate located under the fuel assembly, the inlet nozzle of the fuel and the downstream fuel region. Two different nozzle designs were modeled to study how each nozzle impacts the dissipation of the jet velocity profiles occurring downstream of the nozzle. The two different nozzle designs included a standard round chamfered hole flow plate and a chamfered slotted flow plate. The evaluation of the axial velocity profiles occurring downstream of the nozzle flow plate is critical in understanding the fuel rod vibration and rod fretting in the first grid span. Excessive rod vibration in this region can occur due to high axial jet velocities and steep axial velocity gradients generated from the holes in the lower support plate. The excessive rod vibration can lead to fuel rod wear and fuel failure. Axial velocity profiles were predicted for the different nozzle designs using the CFX code. These velocity profiles were compared to air test velocity measurements for the same nozzle designs. Velocity measurements were made in a 3.763/1 over-scale air test section simulating a 6 x 6 rod array of the inlet nozzle region and downstream fuel region. Reasonable agreement was observed between the velocity measurements and CFD model predictions. The results also indicate that nozzle flow plate geometry can have a significant affect on the dissipation of the jet axial velocity profiles and the steepness of the axial velocity gradients downstream on the inlet nozzle. The application of CFD tools can be used to optimize the inlet nozzle geometry to better dissipate jets and reduce axial velocity gradients downstream of the nozzle at a minimal increase in pressure drop. This will help reduce fuel rod vibration and rod fretting. (authors)

Karoutas, Zeses E.; Liu, Bin; Dzodzo, Milorad; Joffre, Paul F. [Westinghouse Electric Company (United States)

2006-07-01

303

Modelling the Muscle Force–Velocity Relationship for Multiple Joint Movements  

Microsoft Academic Search

\\u000a The force–velocity relationship for a single muscle fibre is commonly described using a hyperbolic equation. In contrast,\\u000a in-vivo experiments on movements requiring coordination of multiple joints have found a linear relationship for leg press\\u000a and cycling.\\u000a \\u000a \\u000a To investigate this relationship, cycling was modelled using a forward dynamic model incorporating four muscles: rectus femoris,\\u000a a single vastus muscle, a single hamstring

P. J. Sinclair

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 \\cite{FS}. 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

2014-09-01

305

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

306

Velocity and Density Models Incorporating the Cascadia Subduction Zone for 3D Earthquake Ground Motion Simulations  

USGS Publications Warehouse

INTRODUCTION In support of earthquake hazards and ground motion studies in the Pacific Northwest, three-dimensional P- and S-wave velocity (3D Vp and Vs) and density (3D rho) models incorporating the Cascadia subduction zone have been developed for the region encompassed from about 40.2?N to 50?N latitude, and from about -122?W to -129?W longitude. The model volume includes elevations from 0 km to 60 km (elevation is opposite of depth in model coordinates). Stephenson and Frankel (2003) presented preliminary ground motion simulations valid up to 0.1 Hz using an earlier version of these models. The version of the model volume described here includes more structural and geophysical detail, particularly in the Puget Lowland as required for scenario earthquake simulations in the development of the Seattle Urban Hazards Maps (Frankel and others, 2007). Olsen and others (in press) used the model volume discussed here to perform a Cascadia simulation up to 0.5 Hz using a Sumatra-Andaman Islands rupture history. As research from the EarthScope Program (http://www.earthscope.org) is published, a wealth of important detail can be added to these model volumes, particularly to depths of the upper-mantle. However, at the time of development for this model version, no EarthScope-specific results were incorporated. This report is intended to be a reference for colleagues and associates who have used or are planning to use this preliminary model in their research. To this end, it is intended that these models will be considered a beginning template for a community velocity model of the Cascadia region as more data and results become available.

Stephenson, William J.

2007-01-01

307

1D Uniformly Accelerated Motion  

NSDL National Science Digital Library

The representation depicts an object moving along a "track" marked in .5 meter intervals. As the object moves, displacement-time, velocity-time, and acceleration-time graphs record the motion in real time. The user may select various types of motion to be depicted, as well as edit a velocity-time graph and have the resulting motion depicted. As the object moves, color coded vectors display its displacement, velocity and acceleration.

308

A global 3D P-Velocity model of the Earth%3CU%2B2019%3Es crust and mantle for improved event location.  

SciTech Connect

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

309

The thin section rock physics: Modeling and measurement of seismic wave velocity on the slice of carbonates  

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

310

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

311

Correspondence between the adhesion model and the velocity dispersion for the cosmological fluid  

NASA Astrophysics Data System (ADS)

Basing our discussion on the Lagrangian description of hydrodynamics, we studied the evolution of density fluctuation for nonlinear cosmological dynamics. Adhesion approximation (AA) is known as a phenomenological model that describes the nonlinear evolution of density fluctuation rather well and that does not form a caustic. In addition to this model, we have benefited from discussion of the relation between artificial viscosity in AA and velocity dispersion. Moreover, we found it useful to regard whether the velocity dispersion is isotropic produces effective pressure or viscosity terms. In this paper, we analyze plane- and spherical-symmetric cases and compare AA with Lagrangian models where pressure is given by a polytropic equation of state. From our analyses, the pressure model undergoes evolution similar to that of AA until reaching a quasinonlinear regime. Compared with the results of a numerical calculation, the linear approximation of the pressure model seems rather good until a quasinonlinear regime develops. However, because of oscillation arising from the Jeans instability, we could not produce a stable nonlinear structure.

Tatekawa, Takayuki

2004-09-01

312

Probability density functions for velocity in the convective boundary layer, and implied trajectory models  

NASA Astrophysics Data System (ADS)

When a probability density function (pdf) is to be formed on the basis of incomplete information, the "maximum missing information" (mmi) pdf (Jaynes, Phys. Rev.106, 620-630, 1957) is theoretically preferable. We compare the performance of Lagrangian stochastic (LS) models of vertical dispersion in the convective boundary layer, satisfying Thomson's ( J. Fluid Mech.180, 529-556, 1987) well-mixed condition, that derive from the often-used bi-Gaussian pdf (eg. Weil, J. atmos. Sci.47, 501-515, 1990) and from the mmi pdf. The bi-Gaussian based LS model, which we tailor to reproduce velocity moments to fourth order, is less complex than the corresponding mmi based model, and gives similar (good) predictions, which are arguably slightly superior (as regards agreement with convection tank data) to those stemming from the original bi-Gaussian based model (Luhar and Britter, Atmospheric Environment23, 1911-1924, 1989), wherein knowledge of the kurtosis was forsaken.

Du, Shuming; Wilson, John D.; Yee, Eugene

313

Velocity and Attenuation Structure of the Tibetan Lithosphere Under the Hi-CLIMB Array From the Modeling of Pn Attributes  

E-print Network

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

Travelling waves for a velocity-jump model of cell migration and proliferation.  

PubMed

Cell invasion, characterised by moving fronts of cells, is an essential aspect of development, repair and disease. Typically, mathematical models of cell invasion are based on the Fisher-Kolmogorov equation. These traditional parabolic models cannot be used to represent experimental measurements of individual cell velocities within the invading population since they imply that information propagates with infinite speed. To overcome this limitation we study combined cell motility and proliferation based on a velocity-jump process where information propagates with finite speed. The model treats the total population of cells as two interacting subpopulations: a subpopulation of left-moving cells, L(x,t), and a subpopulation of right-moving cells, R(x,t). This leads to a system of hyperbolic partial differential equations that includes a turning rate, ??0, describing the rate at which individuals in the population change direction of movement. We present exact travelling wave solutions of the system of partial differential equations for the special case where ?=0 and in the limit that ???. For intermediate turning rates, 0model and experimental observations of cell invasion. This comparison indicates that the small ? limit produces results that are consistent with experimental observations. PMID:23665453

Simpson, Matthew J; Foy, Brody H; McCue, Scott W

2013-08-01

315

Applying the critical velocity model for an off-season interval training program.  

PubMed

The critical velocity (CV) model offers an opportunity to prescribe and to test empirically different velocity-time (V-t) configurations of high-intensity interval training (HIIT); however, such experiments are lacking. We evaluated a group of competitive, female soccer players (age = 19 ± 1 years, height = 168 ± 6 cm, mass = 61 ± 6 kg) completing 1 of 2 different HIIT regimes: a short group (n = 6) completing higher V and shorter t configurations, and a long group (n = 10) completing lower V, longer t configurations. Both groups trained 2 d·wk for 4 weeks. For each workout, both groups ran at velocities exceeding CV and designed to deplete identical fractional percentages of the finite work capacity above CV (D'). The metrics of CV and D' were evaluated at pretraining and posttraining using the 3-minute all-out exercise test on an indoor track using video digitizing of displacement relative to time. Despite differences in the V-t configurations, both groups increased their CV (+0.22 m·s, +6%) and decreased their D' (-24 m, -13%; p < 0.05). We conclude that 2- to 5-minute HIIT bouts are suitable for increasing CV, in previously trained athletes, but they result in a decline of D'. To increase D', we suggest examining HIIT of intensities that are <2 minutes and >130% of maximum oxygen uptake. PMID:23478481

Clark, Ida E; West, Brianne M; Reynolds, Sheila K; Murray, Steven R; Pettitt, Robert W

2013-12-01

316

Numerical examination of plasmoid-induced reconnection model for solar flares: the relation between plasmoid velocity and reconnection rate  

E-print Network

The plasmoid-induced-reconnection model explaining solar flares based on bursty reconnection produced by an ejecting plasmoid suggests a possible relation between the ejection velocity of a plasmoid and the rate of magnetic reconnection. In this study, we focus on the quantitative description of this relation. We performed magnetohydrodynamic (MHD) simulations of solar flares by changing the values of resistivity and the plasmoid velocity. The plasmoid velocity has been changed by applying an additional force to the plasmoid to see how the plasmoid velocity affects the reconnection rate. An important result is that the reconnection rate has a positive correlation with the plasmoid velocity, which is consistent with the plasmoid-induced-reconnection model for solar flares. We also discuss an observational result supporting this positive correlation.

Keisuke Nishida; Masaki Shimizu; Daikou Shiota; Hiroyuki Takasaki; Tetsuya Magara; Kazunari Shibata

2008-09-04

317

Balloon Rockets in 1D  

NSDL National Science Digital Library

In this structured inquiry activity students will work in groups/ teams to build a balloon rocket of their own design. The rocket will race in one dimension and require that they apply their knowledge of position, time, and velocity.

318

Velocity Modelling Results Of A Pockmark In The Nyegga Region, Norwegian Sea  

NASA Astrophysics Data System (ADS)

Pockmarks are a common indicator of fluid flow through the seafloor at continental margins. They are thought to be of global significance as pathways for the escape of methane from the sediments to the water column beneath continental margins, and also as habitats for chemosynthetic communities of biota. Their mechanism of formation and internal dynamics remain poorly constrained, partly due to a lack of proper three dimensional imaging of their internal structure. Numerous fluid escape features provide evidence for an active fluid-flow system in the Nyegga region of the Norwegian continental margin. In June-July 2006 we conducted a high-resolution seismic experiment using ocean bottom seismometers (OBS) to investigate the detailed 3D structure of a 250-m-wide pockmark in this region, named G11 and hence to determine the distribution of gas and gas hydrate in and around the pockmark . An array of 14 OBS were deployed across the pockmark. Shots fired from two 35 cu. in. mini GI guns were recorded on these OBS and on a near surface hydrophone streamer. Shot and OBS locations were determined with c. 1 m uncertainty using water wave arrivals. The OBS and reflection data reveal many interesting features of the subsurface geology of the chimney. A group of bright reflectors underlies the pockmark at a travel time of c. 1.4 s and at deeper depths some of the reflectors show strong attenuation indicating the presence of gas in the sediments. A pipe ascends from this gas charged zone to where it terminates in the investigated G11 pockmark. We have analysed data from five OBS lying along a line running NE-SW across the pockmark, using both raytracing and reflection tomography. The raytraced forward model, which incorporates signals from six subsurface reflectors, shows, a gradual increase in velocity between the seafloor and the gas charged zone, lying c. 300 m depth below the seabed. The travel-time fit is improved significantly if velocities in the pipe beneath the pockmark are higher than those in the surrounding sediments. The maximum velocity anomaly is c. 6%. An initial tomographic inversion using signals from a single subsurface reflector at the top of the gas-charged zone also recovers a velocity anomaly of c. 6%. This velocity anomaly may be attributed to the presence of increased saturations of methane hydrate beneath the pockmark.

Jose, T.; Minshull, T.; Westbrook, G.; Nouzé, H.; Ker, S.; Exley, R.; Gailler, A.; Berndt, C.

2008-12-01

319

Impact of Rotor Surface Velocity, Leakage Models and Real Gas Properties on Rotordynamic Force Predictions of Gas Labyrinth Seals  

E-print Network

Rotordynamic coefficients of a gas labyrinth seal are assumed to be frequency independent. However, this assumption loses its validity as rotor surface velocity approaches Mach 1. The solution procedure of 1CV model by Childs and Scharrer which...

Thorat, Manish R.

2010-07-14

320

1D Quantum States Applet  

NSDL National Science Digital Library

This simulation shows time-dependent 1D quantum bound state wavefunctions for a number of different wells. Position, momentum, parity, energy, and current can all be viewed, with phase shown with color. Eigentstates can be selected using the energy level diagram. Multiple-energy-eigenstate wavefunctions can be created through changes in the amplitude and phase of the basis states using spinors. Postion and energy measurements can be taken, resulting in new states of the system.

Falstad, Paul

2004-05-17

321

1D Quantum Transitions Applet  

NSDL National Science Digital Library

This simulation explores the transitions between quantum states in a number of 1D systems. The time-dependent wavefunction is displayed. An electric field resonant with the transition between states is applied and the changes in the wavefunction with time are tracked. The dipole transition probability is displayed for different initial to final state transitions, and the user may select the transition they wish to observe.

Falstad, Paul

2004-05-17

322

Assimilation of drifters' trajectories in velocity fields from coastal radar and model via the Lagrangian assimilation algorithm LAVA.  

NASA Astrophysics Data System (ADS)

The Lagrangian assimilation algorithm LAVA (LAgrangian Variational Analysis) is customized for coastal areas in the framework of the TOSCA (Tracking Oil Spills & Coastal Awareness network) Project, to improve the response to maritime accidents in the Mediterranean Sea. LAVA assimilates drifters' trajectories in the velocity fields which may come from either coastal radars or numerical models. In the present study, LAVA is applied to the coastal area in front of Toulon (France). Surface currents are available from a WERA radar network (2km spatial resolution, every 20 minutes) and from the GLAZUR model (1/64° spatial resolution, every hour). The cluster of drifters considered is constituted by 7 buoys, transmitting every 15 minutes for a period of 5 days. Three assimilation cases are considered: i) correction of the radar velocity field, ii) correction of the model velocity field and iii) reconstruction of the velocity field from drifters only. It is found that drifters' trajectories compare well with the ones obtained by the radar and the correction to radar velocity field is therefore minimal. Contrarily, observed and numerical trajectories separate rapidly and the correction to the model velocity field is substantial. For the reconstruction from drifters only, the velocity fields obtained are similar to the radar ones, but limited to the neighbor of the drifter paths.

Berta, Maristella; Bellomo, Lucio; Griffa, Annalisa; Gatimu Magaldi, Marcello; Marmain, Julien; Molcard, Anne; Taillandier, Vincent

2013-04-01

323

An analytical model for lateral depth-averaged velocity distributions along a meander in curved compound channels  

NASA Astrophysics Data System (ADS)

This paper presents an analytical method for modeling the lateral depth-averaged velocity distribution along a half-meander in a curved compound channel. An equation is derived from the momentum equation and the flow continuity equation which contains a velocity term with both streamwise velocity variation and lateral secondary flow variation. A velocity variation parameter is proposed in the main channel and on the floodplain for a series of test sections. To study the validity of these equations experiments were conducted in a large scale meandering compound channel at Sichuan University, China. Based on the experimental data, the generation mechanism of secondary flow in the main channel along half a meander is analyzed. It is shown that the secondary current is enhanced by the centrifugal force and the floodplain flow. Due to the discontinuity of the flow depth and the effect of meandering in the main channel flow, a region divided method is adopted. A new boundary condition is proposed by introducing the angle between the main channel flow and the floodplain flow, and it is shown that this gives better modeling results in cross-over sections. The modeling results indicate that the proposed method, which uses the new boundary condition and includes both the streamwise velocity variation and the lateral secondary flow variation, can model the lateral depth-averaged velocity distributions more accurately. Finally, variations in the velocity term between the main channel and floodplain are discussed and analyzed.

Liu, Chao; Wright, Nigel; Liu, Xingnian; Yang, Kejun

2014-12-01

324

The effect of knockout of sulfotransferases 1a1 and 1d1 and of transgenic human sulfotransferases 1A1/1A2 on the formation of DNA adducts from furfuryl alcohol in mouse models.  

PubMed

Furfuryl alcohol is a rodent carcinogen present in numerous foodstuffs. Sulfotransferases (SULTs) convert furfuryl alcohol into the DNA reactive and mutagenic 2-sulfoxymethylfuran. Sensitive techniques for the isotope-dilution ultra performance liquid chromatography-tandem mass spectrometry quantification of resulting DNA adducts, e.g. N (2)-((furan-2-yl)methyl)-2'-deoxyguanosine (N (2)-MF-dG), were developed. To better understand the contribution of specific SULT forms to the genotoxicity of furfuryl alcohol in vivo, we studied the tissue distribution of N (2)-MF-dG in different mouse models. Earlier mutagenicity studies with Salmonella typhimurium strains expressing different human and murine SULT forms indicated that human SULT1A1 and murine Sult1a1 and 1d1 catalyze furfuryl alcohol sulfo conjugation most effectively. Here, we used three mouse lines to study the bioactivation of furfuryl alcohol by murine SULTs, FVB/N wild-type (wt) mice and two genetically modified models lacking either murine Sult1a1 or Sult1d1. The animals received a single dose of furfuryl alcohol, and the levels of the DNA adducts were determined in liver, kidney, lung, colon and small intestine. The effect of Sult1d1 gene disruption on the genotoxicity of furfuryl alcohol was moderate and limited to kidney and small intestine. In contrast, the absence of functional Sult1a1 had a massive influence on the adduct levels, which were lowered by 33-73% in all tissues of the female Sult1a1 null mice compared with the wt animals. The detection of high N (2)-MF-dG levels in a humanized mouse line expressing hSULT1A1/1A2 instead of endogeneous Sult1a1 and Sult1d1 supports the hypothesis that furfuryl alcohol is converted to the mutagenic 2-sulfoxymethylfuran also in humans. PMID:25053625

Sachse, Benjamin; Meinl, Walter; Glatt, Hansruedi; Monien, Bernhard H

2014-10-01

325

Cluster/PEACE Electron Velocity Distribution Function Modeling in the Solar Wind  

NASA Astrophysics Data System (ADS)

We present a study of the kinetic properties of the electron velocity distribution functions in the solar wind to model the electron heat-flux and temperature anisotropy, to investigate the stability of electron to the excitation of whistler waves. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focused in the mechanisms that control and regulates whistler electron instabilities in the solar wind. These mechanisms are not well understood. We investigate the electron heat-flux and temperature anisotropy as a function of two important parameters, namely the electron parallel plasma ?e\\Vert and the electron collisional age Ae defined as the number of collisions suffered by an electron during the expansion of the solar wind. The goal is to check whether the electrons are constrained and regulated by some instability (e.g., the whistler instability), or are driven by collisions. The electron heat-flux and temperature anisotropy are determined by moments of the velocity distribution functions (VDF) and/or model fitting of the electron VDF using a superposition of a bi-Maxwellian core distribution, bi-Kappa halo and strahl distributions.

Chinchilla, T. N.; Viñas, A. F.; Goldstein, M. L.

2007-12-01

326

Continuous Attractor Network Model for Conjunctive Position-by-Velocity Tuning of Grid Cells  

PubMed Central

The spatial responses of many of the cells recorded in layer II of rodent medial entorhinal cortex (MEC) show a triangular grid pattern, which appears to provide an accurate population code for animal spatial position. In layer III, V and VI of the rat MEC, grid cells are also selective to head-direction and are modulated by the speed of the animal. Several putative mechanisms of grid-like maps were proposed, including attractor network dynamics, interactions with theta oscillations or single-unit mechanisms such as firing rate adaptation. In this paper, we present a new attractor network model that accounts for the conjunctive position-by-velocity selectivity of grid cells. Our network model is able to perform robust path integration even when the recurrent connections are subject to random perturbations. PMID:24743341

Si, Bailu; Romani, Sandro; Tsodyks, Misha

2014-01-01

327

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

NASA Astrophysics Data System (ADS)

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.

Gurgiolo, C.; Viñas, A. F.; Nieves-Chinchilla, T.; Goldstein, M. L.

2008-12-01

328

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

329

Line-of-sight velocity dispersions and a mass distribution model of the Sa galaxy NGC 4594  

E-print Network

In the present paper we develop an algorithm allowing to calculate line-of-sight velocity dispersions in an axisymmetric galaxy outside of the galactic plane. When constructing a self-consistent model, we take into account the galactic surface brightness distribution, stellar rotation curve and velocity dispersions. This algorithm is applied to a Sa galaxy NGC 4594 = M 104, for which there exist velocity dispersion measurements outside of the galactic major axis. The mass distribution model is constructed in two stages. In the first stage we construct a luminosity distribution model, where only galactic surface brightness distribution is taken into account. Thereafter, in the second stage we develop on the basis of the Jeans equations a detailed mass distribution model and calculate line-of-sight velocity dispersions and the stellar rotation curve. Here a dark matter halo is added to visible components. Calculated dispersions are compared with observations along different slit positions perpendicular and parallel to the galactic major axis. In the best-fitting model velocity dispersion ellipsoids are radially elongated. Outside the galactic plane velocity dispersion behaviour is more sensitive to the dark matter density distribution and allows to estimate dark halo parameters.

Elmo Tempel; Peeter Tenjes

2006-06-28

330

Using pressure and seismological broadband ocean data to model shear wave velocities in the north Atlantic.  

NASA Astrophysics Data System (ADS)

Seafloor compliance is the transfer function between pressure and vertical displacement at the seafloor Infragravity waves in the oceanic layer have long periods in the range of 30 - 500 s and obey a simple frequency-wavenumber relation. Seafloor compliance from infragravity waves can be analyzed with single station recordings to determinate sub-seafloor shear wave velocities. Previous studies in the Pacific Ocean have demonstrated that reliable near-surface shear wave profiles can be derived from infragravity wave compliance. However, these studies indicate that, beside the water depth the compliance measurements are limited by instrument sensitivity, calibration uncertainties and possibly other effects. In this work seafloor compliance and infragravity waves are observed at two different locations in the Atlantic Ocean: the Logatchev hydrothermal field at the Mid Atlantic Ridge and the Azores (Sao Miguel Island). The data was acquired with the broadband ocean compliance station developed at the University of Hamburg as well as ocean station from the German instrument pool for amphibian seismology (DEPAS) equipped with broadband seismometers and pressure sensors. Vertical velocity and pressure data were used to calculate power spectral densities and normalized compliance along two profiles (one in each location). Power spectral densities show a dominant peak at low frequencies (0.01-0.035Hz) limited by the expected cut-off frequency, which is dependent on the water depth at each station. The peak has been interpreted as a strong infragravity wave with values between 10-14 and 10-11 (m/s2)2/Hz and 104 and 106 (Pa2)2/Hz for acceleration and pressure respectively. The results show compliance values between 10-10 and 10-8 1/Pa and its estimations take into account the coherence between seismic and pressure signals in order to confirm that the seismic signals in the infragravity waves are caused by pressure sources. Shear wave velocity models, with depth resolution from 200 to 2500 m for the deep water stations, were derived from compliance. Preliminary results indicate shear wave velocity increasing from 200 to 3500 m/s.

Rios, Celia; Dahm, Torsten; Jegen, Marion

2010-05-01

331

Mass Models for Low Surface Brightness Galaxies with High Resolution Optical Velocity Fields  

E-print Network

We present high-resolution optical velocity fields from DensePak integral field spectroscopy, along with derived rotation curves, for a sample of low surface brightness galaxies. In the limit of no baryons, we fit the NFW and pseudoisothermal halo models to the data and find the rotation curve shapes and halo central densities to be better described by the isothermal halo. For those galaxies with photometry, we present halo fits for three assumptions of the stellar mass-to-light ratio. We find that the velocity contribution from the baryons is significant enough in the maximum disk case that maximum disk and the NFW halo are mutually exclusive. We find a substantial cusp mass excess at the centers of the galaxies, with at least two times more mass expected in the cuspy CDM halo than is allowed by the data. We also find that to reconcile the data with LCDM, ~20 km/s noncircular motions are needed and/or the power spectrum has a lower amplitude on the scales we probe.

Rachel Kuzio de Naray; Stacy S. McGaugh; W. J. G. de Blok

2007-12-06

332

Simulation of subice shelf melt rates in a general circulation model: Velocity-dependent transfer and the role of friction  

NASA Astrophysics Data System (ADS)

parameterizations of turbulent boundary layer processes at the interface between an ice shelf and the ocean beneath are investigated in terms of their impact on simulated melt rates and feedbacks. The parameterizations differ in the transfer coefficients for heat and freshwater fluxes. In their simplest form, they are assumed constant and hence are independent of the velocity of ocean currents at the ice shelf base. An augmented melt rate parameterization accounts for frictional turbulence via transfer coefficients that do depend on boundary layer current velocities via a drag law. In simulations with both parameterizations for idealized as well as realistic cavity geometries under Pine Island Ice Shelf, West Antarctica, significant differences in melt rate patterns between the velocity-independent and velocity-dependent formulations are found. While patterns are strongly correlated to those of thermal forcing for velocity-independent transfer coefficients, melting in the case of velocity-dependent coefficients is collocated with regions of high boundary layer currents, in particular where rapid plume outflow occurs. Both positive and negative feedbacks between melt rates, boundary layer temperature, velocities, and buoyancy fluxes are identified. Melt rates are found to increase with increasing drag coefficient Cd, in agreement with plume model simulations, but optimal values of Cd inferred from plume models are not easily transferable. Uncertainties therefore remain, both regarding simulated melt rate spatial distributions and magnitudes.

Dansereau, Véronique; Heimbach, Patrick; Losch, Martin

2014-03-01

333

New approach in the kinematic k-2 source model for generating physical slip velocity functions  

NASA Astrophysics Data System (ADS)

In an attempt to improve the ground motion modelling, the characteristics of the slip velocity functions (SVF) generated using the kinematic k-2 source are investigated and compared to the dynamic solutions proposed in the literature. Several numerical simulations were performed to test the influence of the model parameters on the SVF modelling. Overall, the shapes of SVF are very complex and exhibit a large variability in time and space. However, we found out that the mean SVF is a simple boxcar with duration equal to the largest rise time value. In the areas of weak slip, the SVFs are characterized by the existence of negative values, whereas in large slip areas, the SVF is more impulsive. Overall, on the examples investigated, the SVFs modelled with this k-2 source model are different from a typical Kostrov's solution. The critical analysis of the kinematic k-2 source led us to identify the Fourier decomposition of the slip to be responsible for these difficulties, and to propose a new recombination scheme. It consists of adding a positive correction to the Fourier slip components. The slip is described as the sum of positive contributions at various scales. The SVFs modelled using this new scheme are greatly improved. Moreover, through several parametrical analyses performed to qualify this new approach, we show that the SVF are corrected while preserving the essential quality of the k-2 modelling, that is, the ?2 spectral shape and Cd apparent directivity of the synthetic accelerograms. Strong ground motion modelling in the near-fault region was made and numerical ground motion parameters were compared to the empirical relationships. We show that predicted peak ground motion is consistent with near-source attenuation laws.

Ruiz, J.; Baumont, D.; Bernard, P.; Berge-Thierry, C.

2007-11-01

334

Effects of forward velocity on sound radiation from convecting monopole and dipole sources in jet flow. [subsonic aircraft model  

NASA Technical Reports Server (NTRS)

A theoretical model is presented of the effects of forward velocity of an aircraft at arbitrary subsonic speed on sound radiated from convecting monopole and dipole sources embedded in the jet flow. It is found that with increasing forward velocity there is a steadily increasing amplification (over the static case) of the sound radiated into the forward arc and a large reduction of the sound which is radiated into the rearward arc. The same trend is also shown to result when there is a reduction in the exhaust velocity, with, however, a further rise in amplification in the forward quadrant and a drop in attenuation in the aft quadrant.

Dash, R.

1979-01-01

335

A coupled 1-D atmosphere and 3-D canopy radiative transfer model for canopy reflectance, light environment, and photosynthesis simulation in a heterogeneous landscape  

Microsoft Academic Search

Detailed knowledge of light interactions between the atmosphere and vegetation, and within vegetation are of particular interest for terrestrial carbon cycle studies and optical remote sensing. This study describes a model for 3-D canopy radiative transfer that is directly coupled with an atmospheric radiative transfer model (Forest Light Environmental Simulator, FLiES). The model was developed based on the Monte Carlo

Hideki Kobayashi; Hironobu Iwabuchi

2008-01-01

336

Particle velocity interpolation in block-centered finite difference groundwater flow models  

USGS Publications Warehouse

Reviews linear and bilinear interpolation of velocity and introduces a new interpolation scheme. Linear interpolation of velocity is consistent with the numerical solution of the flow equation and preserves discontinuities in velocity caused by abrupt (blocky) changes in transmissivity or hydraulic conductivity. However, linear interpolation yields discontinuous and somewhat unrealistic velocities in homogeneous aquifers. Bilinear interpolation of velocity yields continuous and realistic velocities in homogeneous and smoothly heterogeneous aquifers but does not preserve discontinuities in velocity at abrupt transmissivity boundaries. The new scheme uses potentiometric head gradients and offers improved accuracy for nonuniform flow in heterogeneous aquifers with abrupt changes in transmissivity. It is equivalent to bilinear interpolation in homogeneous media and is equivalent to linear interpolation where gradients are uniform. -from Author

Goode, D.J.

1990-01-01

337

A Physically Based Coupled Model for Simulating 1D Surface -2D Subsurface Flow and Plant Water Uptake in Irrigation Furrows.  

E-print Network

Uptake in Irrigation Furrows. II: Model Test and Evaluation Th. W�ohling , J.C. Mailhol Abstract A physically based seasonal furrow irrigation model - FIM - was developed which comprises three mod- ules), one literature data set (FW), and data from three irrigations during a corn growing season

Paris-Sud XI, Université de

338

A novel model and behavior analysis for a swarm of multi-agent systems with finite velocity  

NASA Astrophysics Data System (ADS)

Inspired by the fact that in most existing swarm models of multi-agent systems the velocity of an agent can be infinite, which is not in accordance with the real applications, we propose a novel swarm model of multi-agent systems where the velocity of an agent is finite. The Lyapunov function method and LaSalle's invariance principle are employed to show that by using the proposed model all of the agents eventually enter into a bounded region around the swarm center and finally tend to a stationary state. Numerical simulations are provided to demonstrate the effectiveness of the theoretical results.

Wang, Liang-Shun; Wu, Zhi-Hai

2014-09-01

339

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

340

Lithospheric structure of the Arabian Shield and Platform from complete regional waveform modelling and surface wave group velocities  

Microsoft Academic Search

SUMMARY Regional seismic waveforms reveal significant differences in the structure of the Arabian Shield and the Arabian Platform. We estimate lithospheric velocity structure by modelling regional waveforms recorded by the 1995-1997 Saudi Arabian Temporary Broadband Deployment using a grid search scheme. We employ a new method whereby we narrow the waveform modelling grid search by first fitting the fundamental mode

Arthur J. Rodgers; William R. Walter; Robert J. Mellors; Abdullah M. S. Al-Amri; Yu-Shen Zhang

1999-01-01

341

Optimization of a Sea Ice Model Using Basinwide Observations of Arctic Sea Ice Thickness, Extent, and Velocity  

E-print Network

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

342

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

SciTech Connect

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

343

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

NASA Astrophysics Data System (ADS)

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.

Jonsén, P.; Häggblad, H.-A.?.

2007-05-01

344

In-canopy gas-phase chemistry during CABINEX 2009: sensitivity of a 1-D canopy model to vertical mixing and isoprene chemistry  

NASA Astrophysics Data System (ADS)

Vegetation emits large quantities of biogenic volatile organic compounds (BVOC). At remote sites, these compounds are the dominant precursors to ozone and secondary organic aerosol (SOA) production, yet current field studies show that atmospheric models have difficulty in capturing the observed HOx cycle and concentrations of BVOC oxidation products. In this manuscript, we simulate BVOC chemistry within a forest canopy using a one-dimensional canopy-chemistry model (Canopy Atmospheric CHemistry Emission model; CACHE) for a mixed deciduous forest in northern Michigan during the CABINEX 2009 campaign. We find that the base-case model, using fully-parameterized mixing and the simplified biogenic chemistry of the Regional Atmospheric Chemistry Model (RACM), underestimates daytime in-canopy vertical mixing by 50-70% and by an order of magnitude at night, leading to discrepancies in the diurnal evolution of HOx, BVOC, and BVOC oxidation products. Implementing observed micrometeorological data from above and within the canopy substantially improves the diurnal cycle of modeled BVOC, particularly at the end of the day, and also improves the observation-model agreement for some BVOC oxidation products and OH reactivity. We compare the RACM mechanism to a version that includes the Mainz isoprene mechanism (RACM-MIM) to test the model sensitivity to enhanced isoprene degradation. RACM-MIM simulates higher concentrations of both primary BVOC (isoprene and monoterpenes) and oxidation products (HCHO, MACR+MVK) compared with RACM simulations. Additionally, the revised mechanism alters the OH concentrations and increases HO2. These changes generally improve agreement with HOx observations yet overestimate BVOC oxidation products, indicating that this isoprene mechanism does not improve the representation of local chemistry at the site. Overall, the revised mechanism yields smaller changes in BVOC and BVOC oxidation product concentrations and gradients than improving the parameterization of vertical mixing with observations, suggesting that uncertainties in vertical mixing parameterizations are an important component in understanding observed BVOC chemistry.

Bryan, A. M.; Bertman, S. B.; Carroll, M. A.; Dusanter, S.; Edwards, G. D.; Forkel, R.; Griffith, S.; Guenther, A. B.; Hansen, R. F.; Helmig, D.; Jobson, B. T.; Keutsch, F. N.; Lefer, B. L.; Pressley, S. N.; Shepson, P. B.; Stevens, P. S.; Steiner, A. L.

2012-09-01

345

In-canopy gas-phase chemistry during CABINEX 2009: sensitivity of a 1-D canopy model to vertical mixing and isoprene chemistry  

NASA Astrophysics Data System (ADS)

Vegetation emits large quantities of biogenic volatile organic compounds (BVOC). At remote sites, these compounds are the dominant precursors to ozone and secondary organic aerosol (SOA) production, yet current field studies show that atmospheric models have difficulty in capturing the observed HOx cycle and concentrations of BVOC oxidation products. In this manuscript, we simulate BVOC chemistry within a forest canopy using a one-dimensional canopy-chemistry model (Canopy Atmospheric CHemistry Emission model; CACHE) for a mixed deciduous forest in northern Michigan during the CABINEX 2009 campaign. We find that the base-case model, using fully-parameterized mixing and the simplified biogenic chemistry of the Regional Atmospheric Chemistry Model (RACM), underestimates daytime in-canopy vertical mixing by 50-70% and by an order of magnitude at night, leading to discrepancies in the diurnal evolution of HOx, BVOC, and BVOC oxidation products. Implementing observed micrometeorological data from above and within the canopy substantially improves the diurnal cycle of modeled BVOC, particularly at the end of the day, and also improves the observation-model agreement for some BVOC oxidation products and OH reactivity. We compare the RACM mechanism to a version that includes the Mainz isoprene mechanism (RACM-MIM) to test the model sensitivity to enhanced isoprene degradation. RACM-MIM simulates higher concentrations of both primary BVOC (isoprene and monoterpenes) and oxidation products (HCHO, MACR + MVK) compared with RACM simulations. Additionally, the revised mechanism alters the OH concentrations and increases HO2. These changes generally improve agreement with HOx observations yet overestimate BVOC oxidation products, indicating that this isoprene mechanism does not improve the representation of local chemistry at the site. Overall, the revised mechanism yields smaller changes in BVOC and BVOC oxidation product concentrations and gradients than improving the parameterization of vertical mixing with observations, suggesting that uncertainties in vertical mixing parameterizations are an important component in understanding observed BVOC chemistry.

Bryan, A. M.; Bertman, S. B.; Carroll, M. A.; Dusanter, S.; Edwards, G. D.; Forkel, R.; Griffith, S.; Guenther, A. B.; Hansen, R. F.; Helmig, D.; Jobson, B. T.; Keutsch, F. N.; Lefer, B. L.; Pressley, S. N.; Shepson, P. B.; Stevens, P. S.; Steiner, A. L.

2012-05-01

346

Average shear wave velocity models of the crustal structure at Mt. Vesuvius  

Microsoft Academic Search

Some Mt. Vesuvius events recorded in 1989–1999 period at Osservatorio Vesuviano (OSVE)-INGV stations have been processed by means of frequency time analysis (FTAN) method. The group velocities of the fundamental mode of Rayleigh-wave have been extracted in the period range 0.3–2s. Group velocity data, in the period range 10–35s, and phase velocity data in the period range 25–100s, obtained in

M. Natale; C. Nunziata; G. F. Panza

2005-01-01

347

A COMPARISON OF MODEL BASED AND DIRECT OPTIMIZATION BASED FILTERING ALGORITHMS FOR SHEARWAVE VELOCITY RECONSTRUCTION FOR ELECTRODE VIBRATION ELASTOGRAPHY  

PubMed Central

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.

Ingle, Atul; Varghese, Tomy

2014-01-01

348

Observed and modeled tsunami current velocities in Humboldt Bay and Crescent City Harbor, northern California  

NASA Astrophysics Data System (ADS)

A pilot project was initiated in 2009 in Humboldt Bay, about 370 kilometers (km) north of San Francisco, California, to measure the currents produced by tsunamis. Northern California is susceptible to both near- and far-field tsunamis and has a historic record of damaging events. Crescent City Harbor, located approximately 100 km north of Humboldt Bay, suffered US 20 million in damages from strong currents produced by the 2006 Kuril Islands tsunami and an additional US 20 million from the 2011 Japan tsunami. In order to better evaluate these currents in northern California, we deployed a Nortek Aquadopp 600kHz 2D Acoustic Doppler Current Profiler (ADCP) with a one-minute sampling interval in Humboldt Bay, near the existing National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) tide gauge station. The instrument recorded the tsunamis produced by the Mw 8.8 Chile earthquake on February 27, 2010 and the Mw 9.0 Japan earthquake on March 11, 2011. Currents from the 2010 tsunami persisted in Humboldt Bay for at least 30 hours with peak amplitudes of about 0.3 meters per second (m/s). The 2011 tsunami signal lasted for over 86 hours with peak amplitude of 0.95 m/s. Strongest currents corresponded to the maximum change in water level as recorded on the NOAA NOS tide gauge, and occurred 90 minutes after the initial wave arrival. No damage was observed in Humboldt Bay for either event. In Crescent City, currents for the first three and a half hours of the 2011 Japan tsunami were estimated using security camera video footage from the Harbor Master building across from the entrance to the small boat basin, approximately 70 meters away from the NOAA NOS tide gauge station. The largest amplitude tide gauge water-level oscillations and most of the damage occurred within this time window. The currents reached a velocity of approximately 4.5 m/s and six cycles exceeded 3 m/s during this period. Measured current velocities both in Humboldt Bay and in Crescent City were compared to calculated velocities from the Method of Splitting Tsunamis (MOST) numerical model. For Humboldt Bay, the 2010 model tsunami frequencies matched the actual values for the first two hours after the initial arrival however the amplitudes were underestimated by approximately 65%. MOST replicated the first four hours of the 2011 tsunami signal in Humboldt Bay quite well although the peak flood currents were underestimated by about 50%. MOST predicted attenuation of the signal after four hours but the actual signal persisted at a nearly constant level for more than 48 hours. In Crescent City, the model prediction of the 2011 frequency agreed quite well with the observed signal for the first two and a half hours after the initial arrival with a 50% underestimation of the peak amplitude. The results from this project demonstrate that ADCPs can effectively record tsunami currents for small to moderate events and can be used to calibrate and validate models (i.e. MOST) in order to better predict hazardous tsunami conditions and improve planned responses to protect lives and property, especially within harbors. An ADCP will be installed in Crescent City Harbor and four additional ADCPs are being deployed in Humboldt Bay during the fall of 2012.

Admire, A. R.; Dengler, L.; Crawford, G. B.; uslu, B. U.; Montoya, J.

2012-12-01

349

Microseismic monitoring and velocity model building at the Longyearbyen CO2-Lab, Svalbard  

NASA Astrophysics Data System (ADS)

The Longyearbyen CO2 storage lab project addresses the problem to turn Svalbard into a CO2 neutral community. The project has now confirmed that an injective reservoir (800-1000 m depth) and a sealing cap rock section exist around Longyearbyen, and will proceed towards demonstration and monitoring studies of sub surface CO2 storage over time. The progressive construction of the Longyearbyen CO2 storage lab is currently addressing detailed properties and geometry of the reservoir. Liquids other than CO2 have been used in this initial phase (water, brine, gel). The reservoir below Longyearbyen is considered physically open, and, therefore, will likely experience drift of the injected CO2 towards the Northeast, through gradual mixing and expulsion of saline groundwater. This offers a unique opportunity for studying the behavior of CO2 in subsurface saline aquifers. Four wells have been drilled so far and several new monitoring wells are planned for this purpose. In this study, we try to use induced seismicity to monitor the injection fluid in the test site. A precise estimation of the location and magnitude of the microearthquake will be important to investigate the link between the injection and the sudden stress release as a microearthquake. In August 2010 a fluid injection experiment was carried out at the CO2 lab. In parallel, a microseismic monitoring network was deployed close to the injection well. The network consists of a 5-level string of 3-component geophones in a vertical observation well, with 50m distance between the instruments and a maximum depth of 294 meters. In addition, three shallow boreholes of 12 m depth have been drilled at about 500 m distance to the injection well. These additional surface stations are intended to provide more accurate locations for microearthquakes that are large enough to be recorded at the surface. Approximately 17 hours after the 5-days water injection test (from 20th to 25th August, 2010), a relatively strong microseismic event has been recorded at all 8 geophones and is located close to the injection well. An accurate location of this seismic event was not possible yet, due to high uncertainties in our velocity model, affecting mainly the depth of the location. In addition, we use the waveforms of this event as a template (i.e., the "master" event) and search for other events with similar waveforms at lower signal-to-noise ratios based on the matched filter method. After scanning through 78-days of continuous data (10th August to 26th October, 2010), we have detected seven events, with a statistically high correlation coefficient from network average. In order to record any potential seismicity during new injection tests, additional two surface geophones are deployed near the injection well to improve constraining the microearthquake locations. Further improvements on the velocity model are also ongoing, using 2D seismic lines, well logs, VSP and additional explosions at the surface observed with the vertical array. Most improvement of the velocity model is expected in the shallow part of the model, directly enhancing the location accuracy and help to track fluid injection interpreted from microseismicity.

Oye, V.; Zhao, P.; Lecomte, I.; Braathen, A.; Olaussen, S.

2012-04-01

350

Lattice Gas Models for Sound Propagation Simulation  

Microsoft Academic Search

New lattice gas models for sound propagation are studied in this thesis. The one dimensional (1-D) model has zero truncation error, and the group velocity is independent of wave number as is required from the continuum limit. Conventional finite difference approaches do not have these properties in general. Boundary condition treatments, applicable to the 1-D model, are also given. Both

Yasushi Sudo

1994-01-01

351

Upper Mantle Heterogeneities Incorporated into the SCEC Southern California Reference Three-dimensional Seismic Velocity Model Version 3  

NASA Astrophysics Data System (ADS)

We extend the SCEC southern California reference model to the upper mantle by incorporating seismic velocity heterogeneities obtained by teleseismic travel-time inversion. Teleseismic P-wave travel times are obtained from three LARSE passive experiments and SCSN stations; raypath coverage is good over the study area. The inversion is performed using a damped least squares LSQR conjugate gradient method. The inversion model element spacing is 20 km. Prior to the inversion, the effects of crustal velocity heterogeneities (as represented by the SCEC version 2 model) are removed from the teleseismic travel times. This demonstrates the utility of the top-down method of the SCEC model development. The inversion produces a variance reduction of 36 per cent. S-wave velocities are determined from laboratory Vp/Vs relations. The most prominent features imaged in the results are high P-wave velocities (+3 per cent) in the uppermost mantle beneath the northern Los Angeles basin, and the previously reported high velocity anomaly (+3 per cent) to depths of 200 km beneath the San Gabriel Mountains and the San Andreas fault.

Kohler, M. D.; Magistrale, H.; Clayton, R. W.

2001-12-01

352

Different parameterizations of marine snow in a 1D-model and their influence on representation of marine snow, nitrogen budget and sedimentation  

NASA Astrophysics Data System (ADS)

A model is presented that simulates the formation of marine aggregates from particles of different origin inside a model of pelagic biological processes. Experiments are carried out with parameterizations appropriate for different types of aggregates, using different kinds of physical forcing, and compared to observations of dissolved inorganic nitrogen (DIN), particulate organic nitrogen (PON), marine snow concentration, and sedimentation. The occurrence of large, macroscopically visible aggregates (marine snow) can best be simulated with parameterizations that have been derived from in situ observations of marine snow, but not with a parameterization sufficient for dense particles. The parameterization strongly determines the amount and timing of deep export, as well as the post-bloom development of the food web in the upper layers. Detritus in aggregates plays a role mainly during times when zooplankton are abundant, as e.g. in the western Arabian Sea during Southwest Monsoon. Then the large aggregates as fast sinking vehicles may remove detritus quickly from shallow and mid-water depth, preventing the accumulation of nutrients that are produced via detritus decomposition. In this region, detritus contributes strongly to deep sedimentation. The nitrogen budget at this location with regard to the observations cannot be closed: depending on model type, either the model simulates too high sedimentation, or too high DIN. Possible causes for this mismatch include undercollection by sediment traps, inaccurate representation of physical processes in the model and the neglect of biological processes, such as production of dissolved organic matter or denitrification.

Kriest, Iris

2002-12-01

353

Comparison of Velocity, Density, Temperature, and Mass Flux Results with Solar Coronal Models  

NASA Astrophysics Data System (ADS)

We have recently computed a series of global maps of plasma parameters in the extended corona using data from the Solar and Heliospheric Observatory (SOHO). The synoptic maps of velocity, density, temperature, and mass flux were derived from UV and white light coronal data obtained from the Ultraviolet Coronagraph Spectrometer (UVCS) and the Large Angle Spectroscopic Coronagraph (LASCO). The parameters are defined on a sphere at 2.3~ R? from Sun-center and are organized by Carrington Rotations during the 1996 -- 1998 solar minimum for Solar Cycle 23. The data imply that there are large flux tube expansion factors near the coronal hole/streamer boundaries, but these factors change significantly as the corona evolves from minimum to the rising phase. We compare these data to an independently developed theoretical model that includes damping and acceleration by Alfven waves in the corona (see Cranmer et al. 2007, ApJS, 171, 520). The data set will be extended in the future and it will be used for constraining other theoretical models of the corona and solar wind.

Strachan, L.; Cranmer, S. R.; Panasyuk, A.; Kohl, J. L.; Lamy, P. L.

2011-12-01

354

Effects of avitriptan, a new 5HT1B\\/1D receptor agonist, in experimental models predictive of antimigraine activity and coronary side-effect potential  

Microsoft Academic Search

Several acutely acting antimigraine drugs, including ergotamine and sumatriptan, have the ability to constrict porcine arteriovenous\\u000a anastomoses as well as the human isolated coronary artery. These two experimental models seem to serve as indicators, respectively,\\u000a for the therapeutic and coronary side-effect potential of the compounds. Using these two models, we have now investigated\\u000a the effects of avitriptan (BMS-180048; 3-[3-[4-(5-methoxy-4-pyrimidinyl)-1-piperazinyl]propyl]-N-methyl-1H-indole-5-methanesulfonamide monofumarate),

Pramod R. Saxena; Peter De Vries; Wei Wang; Jan P. C. Heiligers; Antoinette MaassenVanDenBrink; Willem A. Bax; Frank D. Yocca

1997-01-01

355

3-D velocity structure model for long-period ground motion simulation of the hypothetical Nankai Earthquake  

NASA Astrophysics Data System (ADS)

Three dimensional velocity structure model of southwest Japan is provided to simulate long-period ground motions due to the hypothetical subduction earthquakes. The model is constructed from numerous physical explorations conducted in land and offshore areas and observational study of natural earthquakes. Any available information is involved to explain crustal structure and sedimentary structure. Figure 1 shows an example of cross section with P wave velocities. The model has been revised through numbers of simulations of small to middle earthquakes as to have good agreement with observed arrival times, amplitudes, and also waveforms including surface waves. Figure 2 shows a comparison between Observed (dash line) and simulated (solid line) waveforms. Low velocity layers have added on seismological basement to reproduce observed records. The thickness of the layer has been adjusted through iterative analysis. The final result is found to have good agreement with the results from other physical explorations; e.g. gravity anomaly. We are planning to make long-period (about 2 to 10 sec or longer) simulations of ground motion due to the hypothetical Nankai Earthquake with the 3-D velocity structure model. As the first step, we will simulate the observed ground motions of the latest event occurred in 1946 to check the source model and newly developed velocity structure model. This project is partly supported by Integrated Research Project for Long-Period Ground Motion Hazard Maps by Ministry of Education, Culture, Sports, Science and Technology (MEXT). The ground motion data used in this study were provided by National Research Institute for Earth Science and Disaster Prevention Disaster (NIED). Figure 1 An example of cross section with P wave velocities Figure 2 Observed (dash line) and simulated (solid line) waveforms due to a small earthquake

Kagawa, T.; Petukhin, A.; Koketsu, K.; Miyake, H.; Murotani, S.; Tsurugi, M.

2010-12-01

356

Modeling of 1-D Deltaic Progradation with a Self-Formed Channel and Floodplain: Implications of a New Slope-Dependent Formative Shields Number  

NASA Astrophysics Data System (ADS)

We consider the case of a river with delta terminus into standing water in which the river channel and floodplain are bounded by well-defined valley walls. In previous analyses of the problem, self-formed channel geometry has been defined in terms of a formative bankfull Shields number that is a prescribed constant. Here we show that a) the condition of constant formative Shields number leads to a channel that over-narrows downstream, b) bankfull Shields number increases with the square root of slope, and c) the inclusion of this variation provides a more realistic model that overcomes the problem of over-narrowing. Our model includes backwater effects and can handle conditions for which the channel bottom is both above and below the basement onto which the delta progrades. We outline model performance under bankfull conditions where the channel and floodplain interact as the delta progrades. Our model represents the first step toward a 2D implementation for axisymmetric deltas such as the Selenga Delta of Lake Baikal, Russia.

Czapiga, M. J.; Li, C.; Viparelli, E.; Eke, E.; Parker, G.

2013-12-01

357

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

358

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

359

Modeling and validation of a 3D velocity structure for the Santa Clara Valley, California, for seismic-wave simulations  

USGS Publications Warehouse

A 3D seismic velocity and attenuation model is developed for Santa Clara Valley, California, and its surrounding uplands to predict ground motions from scenario earthquakes. The model is developed using a variety of geologic and geophysical data. Our starting point is a 3D geologic model developed primarily from geologic mapping and gravity and magnetic surveys. An initial velocity model is constructed by using seismic velocities from boreholes, reflection/refraction lines, and spatial autocorrelation microtremor surveys. This model is further refined and the seismic attenuation is estimated through waveform modeling of weak motions from small local events and strong-ground motion from the 1989 Loma Prieta earthquake. Waveforms are calculated to an upper frequency of 1 Hz using a parallelized finite-difference code that utilizes two regions with a factor of 3 difference in grid spacing to reduce memory requirements. Cenozoic basins trap and strongly amplify ground motions. This effect is particularly strong in the Evergreen Basin on the northeastern side of the Santa Clara Valley, where the steeply dipping Silver Creek fault forms the southwestern boundary of the basin. In comparison, the Cupertino Basin on the southwestern side of the valley has a more moderate response, which is attributed to a greater age and velocity of the Cenozoic fill. Surface waves play a major role in the ground motion of sedimentary basins, and they are seen to strongly develop along the western margins of the Santa Clara Valley for our simulation of the Loma Prieta earthquake.

Hartzell, S.; Harmsen, S.; Williams, R. A.; Carver, D.; Frankel, A.; Choy, G.; Liu, P. -C.; Jachens, R. C.; Brocher, T. M.; Wentworth, C. M.

2006-01-01

360

Size-velocity correlations in hybrid high order moment/multi-fluid methods for polydisperse evaporating sprays: Modeling and numerical issues  

NASA Astrophysics Data System (ADS)

Kah et al. (2010) [30,33] recently developed the Eulerian multi-size moment model (EMSM) which tackles the modeling and numerical simulation of polydisperse multiphase flows. Using a high order moment method in a compact interval, they suggested to reconstruct the number density function (NDF) by entropy maximization, which leads to a unique and realizable NDF, potentially in several size intervals, thus leading to an hybrid method between Multifluid and high order. This reconstruction is used to simulate the evaporation process, by an evaluation of the flux of droplet disappearance at zero size, the fluxes of droplets between size intervals, and an accurate description of the size shift induced by evaporation Massot et al. (2010) [15]. Although this method demonstrated its potential for evaporating polydisperse flows, two issues remain to be addressed. First, the EMSM only considers one velocity for all droplets, thus decoupling size from velocity, which is too restrictive for distributions with a large size spectrum. In most applications size-conditioned dynamics have to be accounted for. Second, the possibility to have separated dynamics for each size can lead to quasi-monodisperse distributions, which corresponds to a hard limiting case for the EM algorithm. So the behavior of the algorithm needs to be investigated, in order to reproduce the entire moment space with a reasonable accuracy. The aim of this paper is thus twofold. The EM and its related algorithm are enhanced by using a more accurate integration method in order to handle NDF close to the frontier of the moment space associated with an adaptive number of parameters to reconstruct the NDF accurately and efficiently, as well as tabulated initial guess to optimize the computational time. Then, a new model called CSVM (coupled size-velocity moments model) is introduced. Size-velocity correlations are addressed either in the evaporation and drag processes, or in the convective transport. To reach this goal, a velocity reconstruction for each size is suggested, using only one additional moment per dimension, and which can be directly applied to several size intervals. Thus, this method is a direct generalization of EMSM. To handle the convective transport, a flux splitting scheme is proposed, based on the underlying kinetic description of the disperse phase. Comparing to existing approaches, a main novelty of the CSVM is that our kinetic approach ensures built-in realizability conditions, no additional corrections of the moments being needed at each time step. The full strategy is first evaluated in 0D and 1D cases, which either demonstrates the ability to reproduce both evaporation, drag force and convection with size-velocity correlations, or the possible extension to several size intervals. Finally, the method is applied on 2D cases with only one section, showing the ability of the CSVM and its related algorithms to capture the main physics of polydisperse evaporating sprays with a minimal number of moments.

Vié, Aymeric; Laurent, Frédérique; Massot, Marc

2013-03-01

361

Experimental measurements and modeling of transient heat transfer in forced flow of He II at high velocities  

NASA Astrophysics Data System (ADS)

An experiment has been built to study heat transfer in forced flow of He II at flow velocities up to 22 m/s. The main part of this experiment is a 10 mm ID, 0.86 m long straight test section instrumented with a heater, thermometers and pressure transducers. The high flow velocities allow clear observation of the effects of the forced convection, counterflow heat transfer and the Joule-Thomson effect. A numerical model based on the He II energy conservation equation and including pressure effects has been developed to compare with the experimental results. The model works well for low flow velocities where the heat flux is primarily driven by the temperature gradient and for high flow velocities where the heat flux is primarily driven by the pressure gradients. In the intermediate velocity region, discrepancies between the model and experiment may result from an inappropriate representation of the heat flux by counterflow when the temperature and pressure gradients have an effect of similar magnitude on the heat flux.

Fuzier, S.; Van Sciver, S. W.

2008-03-01

362

1D modelling of nanosecond laser ablation of copper samples in argon at P = 1 atm with a wavelength of 532 nm  

NASA Astrophysics Data System (ADS)

A one-dimensional model is developed for nanosecond laser ablation of a metal target (Cu) in a background gas (Ar) at any pressure. Simulations are performed with a 6 ns FWHM Gaussian laser pulse at 532 nm with a fluence of 11.3 J.cm-2. Heating, melting, evaporation, and condensation are considered to model the laser-target interaction. Expansion of the plume is investigated solving the Euler equations in a lagrangian formalism. Plasma formation is taken into account by computing the ionic species densities up to the second order of ionization in both the ablated material and the background gas. Such formation implies a strong laser-plasma interaction, assuming that the absorption phenomena are photoionization, electron-atom, and electron-ion inverse Bremsstrahlung. Radiative losses are supposed to be only described by electron-ion Bremsstrahlung. Preliminary results are presented and discussed.

Clair, Guillaume; L'Hermite, Daniel

2011-10-01

363

Velocity Measurements in a Steady Flow Model of an IC Engine using Molecular Tagging Velocimetry  

NASA Astrophysics Data System (ADS)

Velocity measurements are reported in the flow field resulting from the steady discharge of an annular nitrogen jet into a cylindrical geometry. The annular jet is formed by a valve body placed axisymmetrically inside a round inlet manifold. Molecular tagging velocimetry (MTV) is used to obtain two components of the velocity vector over a plane at typically 200 independent points simultaneously. The phosphorescent tracer utilized for these measurements is biacetyl. Results to be presented include instantaneous velocity maps and the spatial distribution of the ensemble average of various properties of the flow such as the mean velocity and the rms velocity fluctuations, the vorticity, and the Reynolds stress. This work was supported primarily by the MRSEC Program of the National Science Foundation under award number DMR-9400417.

Stier, B.; Koochesfahani, M. M.; Nocera, D. G.; Schock, H. J.

1996-11-01

364

Seasonal enhancement of submarine groundwater discharge (SGD)-derived nitrate loading into the Ria Formosa coastal lagoon assessed by 1-D modeling of benthic NO3- profiles  

NASA Astrophysics Data System (ADS)

The role of benthic sandy ecosystems in mitigating NO3- loads carried by Submarine Groundwater Discharge (SGD) to coastal marine ecosystems is uncertain. Benthic biogeochemical mediation of NO3--rich submarine groundwater discharge was studied at the seepage face of a barrier island site in the Ria Formosa coastal lagoon (Southern Portugal). Preliminary analysis of NO3- porewater distributions at the seepage face during discharge indicated that benthic biogeochemical processes could significantly affect the fluxes of groundwater-borne NO3- into the lagoon. In order to discriminate between the relative contribution of transport and reaction processes to shape and concentration range evidenced by in-situ porewater NO3- gradients, an advection-dispersion-reaction (ADR) model of NO3- diagenesis was applied to describe NO3- porewater profiles obtained in March, June, September and December 2006. Good agreement between modeled and measured profiles was obtained. Model-derived apparent benthic nitrification and NO3- reduction rates ranged from 0.01 to 5.2 mmol m-2 h-1, sufficient to explain gross observed changes in NO3- fluxes arriving at the seepage face (up to 70% within the surficial 20 cm depth layer). Results of the analysis indicated that the upper limit of the seepage face promoted mitigation of NO3- fluxes to the lagoon throughout the year. In contrast, the lower limit of the seepage area promoted net amplification of the NO3- fluxes into the lagoon in June and September. These results will help constrain further work aiming to clarify the role of permeable sediments in mitigating nitrogen loading of coastal ecosystems.

Ibánhez, J. Severino P.; Leote, Catarina; Rocha, Carlos

2013-11-01

365

Variation in the Settling Velocity of Suspended Particulate Matter in Shallow Lakes, with Special Implications for Mass Balance Modelling  

NASA Astrophysics Data System (ADS)

Measurements of sedimentation were combined with water samples to calculate settling velocity of suspended particulate matter (SPM) in lakes. The study sites were open water stations and enclosures in Lake Erken (Sweden) and Lake Balaton (Hungary). Settling velocities were found to vary considerably both inside and outside the enclosures. Within sites, the differences between 25th and 75th percentiles of measured settling velocities of SPM were two- or three-fold. Median settling velocities of SPM ranged from around 0.5 m/d in the enclosures of Lake Erken to more than 8 m/d in the open water of Lake Balaton. Special relevance was attributed to flocculation, which is known to be affected by, e.g., SPM concentration and turbulence. Even though not directly measured, the less turbulent environment inside the enclosures was suggested to explain the low settling velocity compared to the open water environment. Settling velocity apparently correlated with water current speed (r2 = 0.66; n = 12). Stepwise multiple linear regressions were used to relate the variability in settling velocity of SPM to the variability of possible controlling factors in a number of data subsets. In most cases, one variable describing the total amount of settling material (e.g., SPM) and one variable reflecting the composition of settling material (e.g., total phosphorus) were chosen. The use of suspended solids concentration to predict settling velocity in mass balance models was discussed. It was found that the mean slope between SPM and vSPM was close to 0.1 (m4d-1 g-1). (

Mikael Malmaeus, Jan

2004-09-01

366

Estimation of urinary flow velocity in models of obstructed and unobstructed urethras by decorrelation of ultrasound radiofrequency signals.  

PubMed

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

367

Scalar potential model of galaxy central mass and central velocity dispersion  

E-print Network

The galaxy central mass $M_\\mathrm{c}$ and central velocity dispersion $\\sigma_\\mathrm{c}$ have been found to correlate with large scale galaxy parameters for samples of galaxies with a limited range of characteristics. A scalar potential model (SPM) that derived from considerations of galaxy clusters, of redshift, of discrete redshift, of H{\\scriptsize{I}} rotation curves (RCs) of spiral galaxies and of RC asymmetry is applied to central region parameters. The $\\sigma_\\mathrm{c}$ and $ M_\\mathrm{c}$ are found to correlate to the host galaxy's and neighboring galaxy's B band luminosity. The sample included galaxies with rising, flat and declining RCs; galaxies with a wide range of characteristics; and galaxies excluded from samples of other studies of $\\sigma_\\mathrm{c}$ relationships. The equations have the same form as the SPM equa