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

1

1D wind model: sinusoidal piston

1D wind model: sinusoidal piston For comparison, we also show a wind model with a sinusoidally moving piston and a correÂ sponding velocity amplitude of 5 km/s. This amplitude is comparable to the nonÂsinusoidal wind model (but with smaller temporal variÂ ations). A sinusoidal model with a piston

Freytag, Bernd

2

Pulse Compression with Superluminal Group Velocity in 1-D Photonic

of photonic crystals or Photonic BandGap (PBG) for optical devices [1] has induced the emergence of novelPulse Compression with Superluminal Group Velocity in 1-D Photonic Bandgap Coplanar Waveguide Marc of a Photonic BandGap coplanar waveguide (CPW) that jointly exhibits pulse compression and superluminal group

Brest, UniversitÃ© de

3

fluids under pressure high enough to fracture the formation and create conductive paths in the reservoir a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test. The velocity model used is composed of homogeneous layers, derived from sonic logging. Results for the case

Cerveny, Vlastislav

4

fluids under pressure high enough to fracture the formation and create conductive paths in the reservoir a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test. The velocity model used is composed of homogeneous layers, derived from sonic logging. Results for the case

Cerveny, Vlastislav

5

NSDL National Science Digital Library

The Introductory Physics 1D Motion Lab asks students to develop a computer model for a ball moving vertically under the influence of gravity. When the file is opened, it is initially programmed with a mass moving at constant velocity. It is assumed that students have first collected data of a basketball or volleyball bouncing under a motion detector. The lab instructions fully explain how to build the computer model using Easy Java Simulations modeling tool. The students will learn how to modify the model to simulate a bouncing ball, define variables, calculate relationships, and change the properties for plotting the graph. The calculus is done for the student. *Editor's Note: The Easy Java Simulation tool greatly reduces the amount of programming required to develop computer models. Exercises in student-generated modeling are becoming much more widespread in physics education because of the opportunities for students to test and apply their own prototypes to explain and predict physical phenomena.* This resource is distributed as a ready-to-run (compiled) Java archive. In order to modify the simulation (and see how it is designed), users must install the *Easy Java Simulations Modeling and Authoring Tool*. SEE RELATED MATERIALS for a link to install the EJS modeling tool.

2008-05-29

6

NASA Astrophysics Data System (ADS)

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

Tajima, Y.; Madsen, O. S.

2002-12-01

7

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

8

GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL

This paper presents a GIS-based 1-d distributed overland flow model and summarizes an application to simulate a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the 1-d diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. Simulated runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.

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

2007-01-17

9

Simple 1D Discrete Hidden Markov Models for Face Recognition

We propose an approach to cope with the problem of 2D face image recognition system by using 1D Discrete Hidden Markov Model (1D-DHMM). The Haar wavelet transform was applied to the image to lessen the dimension of the observation vectors. The system was tested on the facial database obtained from AT&T Laboratories Cambridge (ORL). Five images of each individuals were

Hung-son Le; Haibo Li

2003-01-01

10

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

11

Non-cooperative Brownian donkeys: A solvable 1D model

NASA Astrophysics Data System (ADS)

A paradigmatic 1D model for Brownian motion in a spatially symmetric, periodic system is tackled analytically. Upon application of an external static force F the system's response is an average current which is positive for F < 0 and negative for F > 0 (absolute negative mobility). Under suitable conditions, the system approaches 100% efficiency when working against the external force F.

Jiménez de Cisneros, B.; Reimann, P.; Parrondo, J. M. R.

2003-12-01

12

Cell polarisation model : the 1D case Thomas Lepoutre

Cell polarisation model : the 1D case Thomas Lepoutre , Nicolas Meunier and Nicolas Muller-diffusion equation set in the half-line, with the coupling involving the trace value on the boundary. The initial on the initial data. Keywords: Cell polarisation, global existence, blow-up, asymptotic convergence, entropy

Boyer, Edmond

13

Crossed-beam reaction of O( 1D)+D 2?OD+D by velocity map imaging

NASA Astrophysics Data System (ADS)

The technique of velocity map imaging [Eppink and Parker, Rev. Sci. Instrum. 68 (1997) 3477] has been applied to the reaction O( 1D)+D 2?OD+D under single-collision conditions in crossed molecular beams at a collision energy ( Ecoll) of 2.4 kcal/mol. Images of the reactively scattered D-atom product were recorded, yielding the full double differential cross-sections (energy and angle) for the reaction. The translational energy and angular distributions are observed to be strongly coupled, with the forward-scattered products showing the largest translational energy release and the sideways-scattered products the lowest translational energy release.

Ahmed, Musahid; Peterka, Darcy S.; Suits, Arthur G.

1999-02-01

14

Nonlocal Order Parameters for the 1D Hubbard Model

NASA Astrophysics Data System (ADS)

We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.

Montorsi, Arianna; Roncaglia, Marco

2012-12-01

15

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

To examine the limitations of one-dimensional (1D) solar cell modeling, 3D SPICE-based modeling is used to examine in detail the validity of the 1D assumptions as a function of sheet resistance for a model cell. The internal voltages and current densities produced by this modeling give additional insight into the differences between the 1D and 3D models.

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

2012-06-01

16

A 1-D model for highly sensitive tubular reactors

We consider the steady state operation of wall-cooled, fixed-bed tubular reactors. In these reactors the temperature rise ..delta..T must normally be limited to small fractions of the adiabatic temperature rise ..delta..T/sub ad/, both to avoid runaway and maintain product selectivity. Yet ..delta..T/..delta..T/sub ad/ << 1 can only occur if eta = t/sub dif//t/sub reac/ << 1, where t/sub dif/ is the timescale on which heat escapes the reactor by ''diffusing'' to the cooled walls, and t/sub reac/ is the timescale over which the reaction occurs. So here we use asymptotic methods based on eta << 1 to analyze the 2-d reactor equations, and find the radial concentration and temperature profiles to leading order in eta. We then obtain a 1-d model of the reactor by substituting these asymptotically correct profiles into the reactor equations and averaging over r. This model, the ..cap alpha..-model, is identical to the standard (Beek and Singer) 1-d model, except that the reactor's overall heat transfer coefficient U is a decreasing function of the temperature rise ..delta..T. This occurs because as ..delta..T increases, the reaction becomes increasingly concentrated near r = 0, causing a decreased heat transfer efficiency through the reactor's walls. By comparing it with numerical solutions of the original 2-d reactor equations, we find that the ..cap alpha..-model simulates the 2-d equations very accurately, even for highly sensitive reactors operated near runaway. We also find that a runaway criterion derived from the ..cap alpha..-model predicts the runaway transition of the original 2-d equations accurately, especially for highly sensitive reactors. 19 refs.

Hagan, P.S.; Herskowitz, M.; Pirkle, J.C.

1987-01-01

17

Derivation of generalized Maxwell velocity slip model

NASA Astrophysics Data System (ADS)

Based on the conservation of momentum and energy fluxes in the Knudsen layer, a generalized Maxwell velocity slip boundary model is derived in detail using the velocity distribution function from the Grad thirteen moment approximation. The study shows that the generalized Maxwell velocity slip boundary model has the same form as the slip model given by Lockerby. In addition, it is consistent with the typical Maxwell velocity slip model when the temperature gradient along the surface and the normal velocity of gas flow are neglected.

Yang, Qin; Liu, Yulu; Zhang, Haijun; Zuo, Chuncheng

2014-12-01

18

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

This study focuses on the discharge distribution in an intersection of four channels, similar to a city crossroad. The channels and the intersection are all horizontal. Flow enters through two of the channels, and leaves through the other two. The flow is subcritical everywhere, and flow depths are controlled by vertical weirs at the exits of the outlet channels. The main variables that are measured are the flow rates in the four channels. When the weir heights in the outlet channels are the same, the ratio of flow rates in the outlet channels depends only on the ratio of flow rates in the inlet channels; if the outlet conditions are different, other parameters, such as the total flow rate also become important. The flow has also been simulated numerically using a solution of the 1-D Saint Venant equations, with a simple model to predict flow distribution in the intersection. A comparison with the experimental data shows that this model works well for the limited range of experimental conditions studied here. However, further work is needed on a wider range of conditions, closer to real conditions, before the model can be considered valid for practical applications. PMID:17120636

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

2006-01-01

19

In this paper we derive one space dimensional, reduced systems of equations (1-D closure models) for viscoelastic free jets. We begin with the three-dimensional system of conservation laws and a Maxwell-Jeffreys constitutive law for an incompressible viscoelastic fluid. First, we exhibit exact truncations to a finite, closed system of 1-D equations based on classical velocity assumptions of von Karman. Next, we demonstrate that the 3-D free surface boundary conditions overconstrain these truncated systems, so that only a very limited class of solutions exist. We then proceed to derive approximate 1-D closure theories through a slender jet asymptotic scaling, combined with appropriate definitions of velocity, pressure and stress unknowns. Our nonaxisymmetric 1-D slender jet models incorporate the physical effects of inertia, viscoelasticity (viscosity, relaxation and retardation), gravity, surface tension, and properties of the ambient fluid, and include shear stresses and time dependence. Previous special 1-D slender jet models correspond to the lowest order equations in the present asymptotic theory by an a posteriori suppression to leading order of some of these effects, and a reduction to axisymmetry. Solutions of the lowest order system of equations in this asymptotic analysis are presented: For the special cases of elliptical inviscid and Newtonian free jets, subject to the effects of surface tension and gravity, our model predicts oscillation of the major axis of the free surface elliptical cross section between perpendicular directions with distance down the jet, and drawdown of the cross section, in agreement with observed behavior. 15 refs.

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

1988-01-01

20

NASA Astrophysics Data System (ADS)

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.

Luo, Yinhe; Xia, Jianghai; Liu, Jiangping; Xu, Yixian; Liu, Qingsheng

2008-04-01

21

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

A general one-dimensional (1-D), three-region model for a bubbling fluidized-bed adsorber with internal heat exchangers has been developed. The model can predict the hydrodynamics of the bed and provides axial profiles for all temperatures, concentrations, and velocities. The model is computationally fast and flexible and allows for any system of adsorption and desorption reactions to be modeled, making the model applicable to any adsorption process. The model has been implemented in both gPROMS and Aspen Custom Modeler, and the behavior of the model has been verified.

Lee, Andrew; Miller, David C.

2012-01-01

22

Numerical Modeling of Imploding Plasma liners Using the 1D Radiation-Hydrodynamics Code HELIOS

NASA Astrophysics Data System (ADS)

The Plasma Liner Experiment (PLX) is attempting to form imploding plasma liners to reach 0.1 Mbar upon stagnation, via 30--60 spherically convergent plasma jets. PLX is partly motivated by the desire to develop a standoff driver for magneto-inertial fusion. The liner density, atomic makeup, and implosion velocity will help determine the maximum pressure that can be achieved. This work focuses on exploring the effects of atomic physics and radiation on the 1D liner implosion and stagnation dynamics. For this reason, we are using Prism Computational Science's 1D Lagrangian rad-hydro code HELIOS, which has both equation of state (EOS) table-lookup and detailed configuration accounting (DCA) atomic physics modeling. By comparing a series of PLX-relevant cases proceeding from ideal gas, to EOS tables, to DCA treatments, we aim to identify how and when atomic physics effects are important for determining the peak achievable stagnation pressures. In addition, we present verification test results as well as brief comparisons to results obtained with RAVEN (1D radiation-MHD) and SPHC (smoothed particle hydrodynamics).

Davis, J. S.; Hanna, D. S.; Awe, T. J.; Hsu, S. C.; Stanic, M.; Cassibry, J. T.; Macfarlane, J. J.

2010-11-01

23

Global Models of Surface Wave Group Velocity

v--vMeasurements of group velocity are derived from phase-velocity dispersion curves and modeled with global laterally-varying isotropic structure. Maps for both Love and Rayleigh waves are created in the period range 35 s to 175 s. The data set of group-velocity measurements includes over 50,000 minor-arc observations and 5,000 major-arc observations. The errors in the measurements are estimated by an empirical

E. W. F. Larson; G. Ekström

2001-01-01

24

SCEC UCVM - Unified California Velocity Model

NASA Astrophysics Data System (ADS)

The SCEC Unified California Velocity Model (UCVM) is a software framework for a state-wide California velocity model. UCVM provides researchers with two new capabilities: (1) the ability to query Vp, Vs, and density from any standard regional California velocity model through a uniform interface, and (2) the ability to combine multiple velocity models into a single state-wide model. These features are crucial in order to support large-scale ground motion simulations and to facilitate improvements in the underlying velocity models. UCVM provides integrated support for the following standard velocity models: SCEC CVM-H, SCEC CVM-S and the CVM-SI variant, USGS Bay Area (cencalvm), Lin-Thurber Statewide, and other smaller regional models. New models may be easily incorporated as they become available. Two query interfaces are provided: a Linux command line program, and a C application programming interface (API). The C API query interface is simple, fully independent of any specific model, and MPI-friendly. Input coordinates are geographic longitude/latitude and the vertical coordinate may be either depth or elevation. Output parameters include Vp, Vs, and density along with the identity of the model from which these material properties were obtained. In addition to access to the standard models, UCVM also includes a high resolution statewide digital elevation model, Vs30 map, and an optional near-surface geo-technical layer (GTL) based on Ely's Vs30-derived GTL. The elevation and Vs30 information is bundled along with the returned Vp,Vs velocities and density, so that all relevant information is retrieved with a single query. When the GTL is enabled, it is blended with the underlying crustal velocity models along a configurable transition depth range with an interpolation function. Multiple, possibly overlapping, regional velocity models may be combined together into a single state-wide model. This is accomplished by tiling the regional models on top of one another in three dimensions in a researcher-specified order. No reconciliation is performed within overlapping model regions, although a post-processing tool is provided to perform a simple numerical smoothing. Lastly, a 3D region from a combined model may be extracted and exported into a CVM-Etree. This etree may then be queried by UCVM much like a standard velocity model but with less overhead and generally better performance due to the efficiency of the etree data structure.

Small, P.; Maechling, P. J.; Jordan, T. H.; Ely, G. P.; Taborda, R.

2011-12-01

25

Using H/V spectral ratios to constrain 1-D subsurface models for seismic hazard assessment

NASA Astrophysics Data System (ADS)

In recent years, considerable research has been focused on establishing reliable methods to predict earthquake ground motions for seismic hazard assessment. The seismic motions are significantly affected by the soil layers at the site and by the impedance ratio between surficial and underlying deposits. These yield frequency selective amplification effects that are important parameters in the process of earthquake resistance design of buildings and in the process of preparing earthquake damage scenarios. Numerical methods for estimating site effects require modeling of the subsurface, primarily shear-wave velocities of the sedimentary layers and underlying rock and thickness of each layer. In many cases, it is difficult to construct such models by only using conventional geophysical methods and borehole information, especially with regard to the deeper sediments. We have encountered such difficulties at several sites for bridge design in Israel, located along or near the seismically active Dead Sea transform. There, and in many other places we found it very useful to constrain the subsurface models by considering site response functions evaluated by using the H/V spectral ratio techniques. A number of bridge construction sites where instrumented with three-component seismometers. We evaluated the empirical site response function from H/V spectral rations of weak motions from local and regional earthquakes and measurements of ambient noise. The average spectral ratio estimated for soil sites showed amplification factor up to 5 in the frequency range of 0.4 to 0.8 Hz. Regional geology data, S-wave refraction surveys in different areas for similar geological units and borehole information were used to construct 1D subsurface model for each site from which an analytical site response function is calculated. The uncertainty associated with the proposed subsurface model models yield a too high variability between the analytical site response functions. Hence, we found it useful to compare the possible analytical functions with those obtained empirically. The later were used to define and constrain the average shear wave velocities and thickness of the unconsolidated materials overlying the bedrock. After a trial and error process, we obtained 1D models that yield response functions consistent with our H/V observations and with the known, yet limited, geological and geophysical information. Owing to the fact that the H/V spectral ratio techniques are relatively simple and inexpensive, we would strongly recommend that they should be performed in site response investigations to support and verify theoretical calculations.

Shapira, A.; Zaslavsky, Y.

2003-04-01

26

1D numerical model of muddy subaqueous and subaerial debris flows

A 1D numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows is presented. The model incorporates the Herschel-Bulkley and bilinear rheologies of viscoplastic fluid. The more familiar Bingham model is integrated into the Herschel-Bulkley rheological model. The conservation equations of mass and momentum of single-phase laminar debris flow are layer-integrated using the slender flow approximation. They are then expressed in a Lagrangian framework and solved numerically using an explicit finite difference scheme. Starting from a given initial shape, a debris flow is allowed to collapse and propagate over a specified topography. Comparison between the model predictions and laboratory experiments shows reasonable agreement. The model is used to study the effect of the ambient fluid density, initial shape of the failed mass, and rheological model on the simulated propagation of the front and runout characteristics of muddy debris flows. It is found that initial failure shape influence the front velocity but has little bearing on the final deposit shape. In the Bingham model, the excess of shear stress above the yield strength is proportional to the strain rate to the first power. This exponent is free to vary in the Herschel-Bulkley model. When it is set at a value lower than unity, the resulting final deposits are thicker and shorter than in the case of the Bingham rheology. The final deposit resulting from the bilinear model is longer and thinner than that from the Bingham model due to the fact that the debris flow is allowed to act as a Newtonian fluid at low shear rate in the bilinear model.

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

2001-01-01

27

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

28

A statistical model for unwarping of 1-D electrophoresis C.A. Glasbey

A statistical model for unwarping of 1-D electrophoresis gels C.A. Glasbey Biomathematics, which relates density profiles in 1-D electrophoresis gels, such as those produced by pulsed-field gel electrophoresis (PFGE), to databases of profiles of known genotypes. The warp in each gel lane is described

Stone, J. V.

29

Despite a high degree of conservation, subtle but important differences exist between the CD1d antigen presentation pathways of humans and mice. These differences may account for the minimal success of natural killer T (NKT) cell-based antitumor therapies in human clinical trials, which contrast strongly with the powerful antitumor effects in conventional mouse models. To develop an accurate model for in vivo human CD1d (hCD1d) antigen presentation, we have generated a hCD1d knock-in (hCD1d-KI) mouse. In these mice, hCD1d is expressed in a native tissue distribution pattern and supports NKT cell development. Reduced numbers of invariant NKT (iNKT) cells were observed, but at an abundance comparable to that in most normal humans. These iNKT cells predominantly expressed mouse V?8, the homolog of human V?11, and phenotypically resembled human iNKT cells in their reduced expression of CD4. Importantly, iNKT cells in hCD1d knock-in mice exert a potent antitumor function in a melanoma challenge model. Our results show that replacement of mCD1d by hCD1d can select a population of functional iNKT cells closely resembling human iNKT cells. These hCD1d knock-in mice will allow more accurate in vivo modeling of human iNKT cell responses and will facilitate the preclinical assessment of iNKT cell-targeted antitumor therapies. PMID:23382238

Wen, Xiangshu; Rao, Ping; Carreño, Leandro J; Kim, Seil; Lawrenczyk, Agnieszka; Porcelli, Steven A; Cresswell, Peter; Yuan, Weiming

2013-02-19

30

Quasi 1D Modeling of Mixed Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.

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

2012-01-01

31

GaAs solar cell photoresponse modeling using PC-1D V2.1

NASA Technical Reports Server (NTRS)

Photoresponse data of high efficiency GaAs solar cells were analyzed using PC-1D V2.1. The approach required to use PC-1D for photoresponse data analysis, and the physical insights gained from performing the analysis are discussed. In particular, the effect of Al(x)Ga(1-x)As heteroface quality was modeled. Photoresponse or spectral quantum efficiency is an important tool in characterizing material quality and predicting cell performance. The strength of the photoresponse measurement lies in the ability to precisely fit the experimental data with a physical model. PC-1D provides a flexible platform for calculations based on these physical models.

Huber, D. A.; Olsen, L. C.; Dunham, G.; Addis, F. W.

1991-01-01

32

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

M. P. Flanagan; S. C. Myers

2003-01-01

33

Control oriented 1D electrochemical model of lithium ion battery

Lithium ion (Li-ion) batteries provide high energy and power density energy storage for diverse applications ranging from cell phones to hybrid electric vehicles (HEVs). For efficient and reliable systems integration, low order dynamic battery models are needed. This paper introduces a general method to generate numerically a fully observable\\/controllable state variable model from electrochemical kinetic, species and charge partial differential

Kandler A. Smith; Christopher D. Rahn; Chao-Yang Wang

2007-01-01

34

We compare results from numerical simulations of pulsatile blood flow in two patient-specific intracranial arterial networks using one-dimensional (1D) and three-dimensional (3D) models. Specifically, we focus on the pressure and flowrate distribution at different segments of the network computed by the two models. Results obtained with 1D and 3D models with rigid walls show good agreement in massflow distribution at tens of arterial junctions and also in pressure drop along the arteries. The 3D simulations with the rigid walls predict higher amplitude of the flowrate and pressure temporal oscillations than the 1D simulations with compliant walls at various segments even for small time-variations in the arterial cross-sectional areas. Sensitivity of the flow and pressure with respect to variation in the elasticity parameters is investigated with the 1D model. PMID:20661645

Grinberg, L; Cheever, E; Anor, T; Madsen, J R; Karniadakis, G E

2011-01-01

35

Fractal velocity models in refraction seismology

The introduction of noise components to a simple crustal velocity model is shown to markedly affect the appearance of synthetic seismograms calculated according to ray theory applied to refraction experiments. Here we simulate noise by a self-similar process with a power spectral density which falls off as inverse wavenumber to a simple power (0–2). The major effect is to destroy

David J. Crossley; Oliver G. Jensen

1989-01-01

36

1D thermonuclear model for x-ray transients

The thermonuclear evolution of a 1.41 M solar mass neutron star, with a radius of 14.3 km, accreting various mixtures of hydrogen, helium, and heavy elements at rates of 10/sup -11/ to 10/sup -10/ M solar mass/yr is examined, in conjunction with S.E. Woosley and T.A. Weaver, using a one-dimensional numerical model. We have ignored any effects due to general relativity or magnetic fields. Two cases shall be discussed. In both models, the accretion rate is such that the hydrogen shell burns to helium in steady state, with the hydrogen burning stabilized by the ..beta..-limited CNO cycle. A thick helium shell is produced, which is eventually ignited under extremely degenerate conditions, producing a thermonuclear runaway.

Wallace, R.K.

1982-01-01

37

Dielectric Breakdown in the 1-D Hubbard Model

Nonequilibrium transport in the one dimensional Hubbard model at half-filling is studied by the time-dependent density matrix renormalization group method. It is clearly demonstrated that dielectric breakdown of the Mott insulating phase to a nonequilibrium steady state occurs when an external voltage is larger than the charge gap. From the numerically obtained current-voltage characteristics we find that the current is

Shunsuke Kirino; Kazuo Ueda

2011-01-01

38

A new 1-D velocity model along the southern Cuban margin has been determined using local earthquake data, which are the result of the merged Cuban and Jamaican catalogues. Simultaneous inversion using joint-hypocentre determination was applied to solve the coupled hypocentre-velocity model problem. We obtained a seven-layer model with an average Moho interface at 20 km. The average velocity was found

Bladimir Moreno; Margaret Grandison; Kuvvet Atakan

2002-01-01

39

Cosmological velocity correlations - Observations and model predictions

NASA Technical Reports Server (NTRS)

By applying the present simple statistics for two-point cosmological peculiar velocity-correlation measurements to the actual data sets of the Local Supercluster spiral galaxy of Aaronson et al. (1982) and the elliptical galaxy sample of Burstein et al. (1987), as well as to the velocity field predicted by the distribution of IRAS galaxies, a coherence length of 1100-1600 km/sec is obtained. Coherence length is defined as that separation at which the correlations drop to half their zero-lag value. These results are compared with predictions from two models of large-scale structure formation: that of cold dark matter and that of baryon isocurvature proposed by Peebles (1980). N-body simulations of these models are performed to check the linear theory predictions and measure sampling fluctuations.

Gorski, Krzysztof M.; Davis, Marc; Strauss, Michael A.; White, Simon D. M.; Yahil, Amos

1989-01-01

40

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

NASA Astrophysics Data System (ADS)

Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k + l from Blanke and Delecluse, 1993 and two equation models: Generic Lengh Scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a one-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between -2 and 2 °C during the stratified period (June to October). However the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 °C during the stratified period and from 0.03 to 0.15 °C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (1D_PAPA">http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D_PAPA). This package is a good starting point for further investigation of vertical processes.

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

2014-08-01

41

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

NASA Astrophysics Data System (ADS)

Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k+l from Blanke and Delecluse, 1993, and two equation models: generic length scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a 1-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between -2 and 2 °C during the stratified period (June to October). However, the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 °C during the stratified period and from 0.03 to 0.15 °C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (1D_PAPA">http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D_PAPA). This package is a good starting point for further investigation of vertical processes.

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

2015-01-01

42

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

43

3D Versus 1D Radiative Transfer Modeling of Planetary Nebulae

NASA Astrophysics Data System (ADS)

Planetary nebulae are the products of the fast stellar wind from the end of the AGB star phase. To date, there are many one-dimensional radiative transfer codes, and a few fully 3D codes that can model the ionization of the planetary nebulae. Some limitations on 1D codes are that they can only make spherical or parallel plane models, while 3D codes take much computing power and memory to run. A pseudo-3D code such as pyCloudy can model a planetary nebula in 3D by making multiple runs of a 1D code such as Cloudy in different angles from the center of the nebula. We compared the 1D models with pseudo-3D models to determine if the 1D models give good approximations for the observed parameters of the planetary nebulae. We find that one-dimensional codes can actually give good estimates for electron temperature and density in a bipolar planetary nebula.

Pantoja, Blake M.; Ladjal, Djazia

2015-01-01

44

HYDRUS-1D Modeling of an Irrigated Agricultural Plot with Application to Aquifer Recharge Estimation

Technology Transfer Automated Retrieval System (TEKTRAN)

A variety of methods are available for estimating aquifer recharge in semi-arid regions, each with advantages and disadvantages. We are investigating a procedure for estimating recharge in an irrigated basin. The method involves computing irrigation return flows based on HYDRUS-1D modeling of root z...

45

Revisiting the capture velocity of a cesium magneto-optical trap: model, simulation and experiment

NASA Astrophysics Data System (ADS)

In this work, we have explored ab initio the capture process in a magneto-optical trap by theory, simulation and experiment. We measured the capture velocity vc of a cesium vapor cell magneto-optical trap (VCMOT) from its capture rate R and developed an exact model for the capture rate of a VCMOT in terms of its capture velocity, background density and trap laser beam diameter. We measured the capture velocity of a cesium VCMOT for various trap laser intensities and magnetic field gradients. We observed that the capture velocity is a damping force as well as a restoring force phenomenon. We supported our findings by performing simulations for single atom trajectories in a 1D cesium MOT. Finally, we concluded that two MOTs can have the same capture velocities but very different capture rates, thereby revealing that these are two fundamentally different characteristics of the MOT.

Anwar, Muhammad; Magalhães, Daniel V.; Müller, Stella T.; Faisal, Muhammad; Nawaz, Muhammad; Ahmed, Mushtaq

2014-12-01

46

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

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

47

1-D Controlled source electromagnetic forward modeling for marine gas hydrates studies

We discuss the feasibility of using controlled-source electromagnetic (CSEM) in the frequency domain for prospecting marine\\u000a gas hydrates. Based on the Ocean Drilling Program (ODP) Leg 164 log data, we have established several 1-D resistivity models\\u000a which have different gas hydrate concentrations. Meanwhile, we analyzed the electromagnetic response of marine gas hydrates\\u000a in the frequency domain based on these models.

Zhao Luanxiao; Geng Jianhua; Zhang Shengye; Yang Dikun

2008-01-01

48

A design model for circular porous air bearings using the 1D generalized flow method

Although the working principles of porous air bearings have been known for many years, most calculation procedures still involve specialized 3D CFD techniques which are not very useful to design engineers who initially require first-order engineering models for feasibility studies. This paper presents a simple design model for a circular porous air bearing based on well-established 1D generalized flow theory.

Jean-Sébastien Plante; John Vogan; Tarek El-Aguizy; Alexander H. Slocum

2005-01-01

49

The investigations on the pressure wave propagation along the arterial network and its relationships with vascular physiopathologies can be supported nowadays by numerical simulations. One dimensional (1D) mathematical models, based on systems of two partial differential equations for each arterial segment suitably matched at bifurcations, can be simulated with low computational costs and provide useful insights into the role of wave reflections. Some recent works have indeed moved in this direction. The specific contribution of the present paper is to illustrate a 1D numerical model numerically coupled with a model for the heart action. Typically, the action of the heart on the arterial system is modelled as a boundary condition at the entrance of the aorta. However, the left ventricle (LV) and the vascular network are a strongly coupled single mechanical system. This coupling can be relevant in the numerical description of pressure waves propagation, particularly when dealing with pathological situations. In this work, we propose a simple lumped parameter model for the heart and show how it can be coupled numerically with a 1D model for the arteries. Numerical results actually confirm the relevant impact of the heart-arteries coupling in realistic simulations. PMID:17132614

Formaggia, Luca; Lamponi, Daniele; Tuveri, Massimiliano; Veneziani, Alessandro

2006-10-01

50

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

51

Modeling coiled tubing velocity strings for gas wells

Multiphase flowing pressure and velocity prediction models are necessary to coiled tubing velocity string design. A model used by most of the coiled tubing service companies or manufacturers is reviewed. Guidance is provided for selecting a coiled tubing of the proper size. The steps include: (1) Measured data matching; (2) Fluid property adjustment; (3) Pressure, velocity, and holdup selection; (4) Correlation choice; (5) Coiled tubing selection. A velocity range for the lift of liquid is given.

Martinez, J.; Martinez, A.

1995-12-31

52

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

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

53

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

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

54

Scotogenic Z2 or U(1)D model of neutrino mass with ?(27) symmetry

NASA Astrophysics Data System (ADS)

The scotogenic model of radiative neutrino mass with Z2 or U(1)D dark matter is shown to accommodate ?(27) symmetry naturally. The resulting neutrino mass matrix is identical to either of two forms, one proposed in 2006, the other in 2008. These two structures are studied in the context of present neutrino data, with predictions of CP violation and neutrinoless double beta decay.

Ma, Ernest; Natale, Alexander

2014-06-01

55

Pitchfork-Hopf bifurcations in 1D neural field models with transmission delays

NASA Astrophysics Data System (ADS)

Recently, local bifurcation theory for delayed neural fields was developed. In this paper, we show how symmetry arguments and residue calculus can be used to simplify the computation of the spectrum in special cases and the evaluation of the normal form coefficients, respectively. This is done hand in hand with an extensive study of two pitchfork-Hopf bifurcations for a 1D neural field model with 'Wizard hat' type connectivity.

Dijkstra, K.; Gils, S. A. van; Janssens, S. G.; Kuznetsov, Yu. A.; Visser, S.

2015-03-01

56

A Systematic Comparison between 1-D and 3-D Hemodynamics in Compliant Arterial Models

SUMMARY In this article, we present a systematic comparison of computational hemodynamics in arterial models with deformable vessel walls using a one-dimensional (1-D) and a three-dimensional (3-D) method. The simulations were performed using a series of idealized compliant arterial models representing the common carotid artery, thoracic aorta, aortic bifurcation, and full aorta from the arch to the iliac bifurcation. The formulations share identical outflow boundary conditions and have compatible material laws. We also present an iterative algorithm to select the parameters for the outflow boundary conditions using the 1-D theory to achieve a desired systolic and diastolic pressure at a particular vessel. This 1-D/3-D framework can be used to efficiently determine material and boundary condition parameters for 3-D subject-specific arterial models with deformable vessel walls. Finally, we explore the impact of different anatomical features and hemodynamic conditions on the numerical predictions. The results show good agreement between the two schemes, especially during the diastolic phase of the cycle. PMID:24115509

Xiao, Nan; Alastruey, Jordi; Figueroa, C. Alberto

2015-01-01

57

Multicomponent Geochemical Transport Modeling Using Hydrus-1D and HP1

NASA Astrophysics Data System (ADS)

The transport of reactive contaminants in the subsurface is generally affected by a large number of nonlinear and often interactive physical, chemical, and biological processes. Simulating these processes requires a comprehensive reactive transport code that couples the physical processes of water flow and advective-dispersive transport with a range of biogeochemical processes. Two recently developed coupled geochemical models that are both based on the HYDRUS-1D software package for variably saturated flow and transport are summarized in this paper. One model resulted from coupling HYDRUS1D with the UNSATCHEM module. While restricted to major ion chemistry, this program enables quantitative predictions of such problems as analyzing the effects of salinity on plant growth and the amount of water and amendments required to reclaim salt-affected soil profiles. The second model, HP1, resulted from coupling HYDRUS-1D with the PHREEQC biogeochemical code. The latter program accounts for a wide range of instantaneous or kinetic chemical and biological reactions, including complexation, cation exchange, surface complexation, precipitation dissolution and/or redox reactions. The versatility of HP1 is illustrated in this paper by means of two examples: the leaching of toxic trace elements and the transport of the explosive TNT and its degradation products.

Simunek, Jirka; Jacques, Diederik; van Genuchten, Martinus Th.; Mallants, Dirk

2006-12-01

58

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

NASA Astrophysics Data System (ADS)

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=Uc=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.

Carmelo, J. M. P.; Gu, Shi-Jian; Sacramento, P. D.

2013-12-01

59

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...

60

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

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

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

2015-11-01

61

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

62

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

NASA Astrophysics Data System (ADS)

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

Schartau, M.; Oschlies, A.

63

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,

Haichun Yang

2005-01-01

64

NASA Astrophysics Data System (ADS)

Three dimensional velocity models constructed through seismic tomography are seldom digitally processed further for imaging structural features. A study conducted to evaluate the potential for imaging subsurface discontinuities in horizontal and vertical direction from three dimensional velocity models using image processing/computer vision techniques has provided significant results. Three-dimensional velocity models constructed through tomographic inversion of active source and/or earthquake traveltime data are generally built from an initial 1-D velocity model that varies only with depth. Regularized tomographic inversion algorithms impose constraints on the roughness of the model that help to stabilize the inversion process. Final velocity models obtained from regularized tomographic inversions have smooth three-dimensional structures that are required by the data. Final velocity models are usually analyzed and interpreted either as a perturbation velocity model or as an absolute velocity model. Compared to perturbation velocity model, absolute velocity model has an advantage of providing constraints on lithology. Both velocity models lack the ability to provide sharp constraints on subsurface faults. However, results from the analysis of the 3-D velocity model from northern Cascadia using Roberts, Prewitt, Sobel, and Canny operators show that subsurface faults that are not clearly interpretable from velocity model plots can be identified through this approach. This analysis resulted in inferring the locations of Tacoma Fault, Seattle Fault, Southern Whidbey Island Fault, and Darrington Devils Mountain fault much clearly. The Coast Range Boundary Fault, previously hypothesized on the basis of sedimentological and tectonic observations is inferred clearly from processed images. Many of the fault locations so imaged correlate with earthquake hypocenters indicating their seismogenic nature.

Ramachandran, K.

2011-12-01

65

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 (spaceborne or airborne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the light detection and ranging (lidar), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30 to 90 m). On the other hand, the lidar technique is able to produce high-resolution DEMs (at around 1 m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of 1-D hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. To test model selection, the outcomes of the 1-D models were also compared, in terms of flood water levels, to the results of 2-D models (LISFLOOD-FP). The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicate that the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. lidar 1 m) to lower resolution is much less than the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the 1-D hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.

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

2015-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

67

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

Analysis and interpretation of spectrum and correlation data from high-energy nuclear collisions is currently controversial because two opposing physics narratives derive contradictory implications from the same data-one narrative claiming collision dynamics is dominated by dijet production and projectile-nucleon fragmentation, the other claiming collision dynamics is dominated by a dense, flowing QCD medium. Opposing interpretations seem to be supported by alternative data models, and current model-comparison schemes are unable to distinguish between them. There is clearly need for a convincing new methodology to break the deadlock. In this study we introduce Bayesian Inference (BI) methods applied to angular correlation data as a basis to evaluate competing data models. For simplicity the data considered are projections of 2D angular correlations onto 1D azimuth from three centrality classes of 200 GeV Au-Au collisions. We consider several data models typical of current model choices, including Fourier seri...

De Kock, Michiel B; Trainor, Thomas A

2015-01-01

68

An electro-mechanically coupled 1-D polycrystalline model for piezoelectric stack actuators

NASA Astrophysics Data System (ADS)

Piezoelectric actuators used in nano-positioning devices exhibit highly non-linear behavior and strong hysteresis, which limits the efficiency of conventional non-model-based controllers. This paper presents a free energy model based on the theory of thermal activation for single crystal piezoceramics that couples mechanical stress and electric field. It is capable of predicting the hysteretic behavior along with the frequency-dependence present in these materials. The model is then coupled with a spring as a first step toward a 1-D model of a commercial nano-positioning stage and is the basis for future control applications. Quasi-static simulations are conducted to illustrate the effects of spring loading on the actuator behavior. A first step towards adapting the model for polycrystalline material is also presented. Simulations are shown to predict the rate-dependent strain response of a spring loaded polycrystalline stack actuator for various pre-stresses.

York, Alexander; Seelecke, Stefan

2009-03-01

69

NASA Astrophysics Data System (ADS)

Aims: This research has two main goals. First, we present the atmospheric structure and the fundamental parameters of three red supergiants (RSGs), increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. Methods: We carried out spectro-interferometric observations of the RSGs V602 Car, HD 95687, and HD 183589 in the near-infrared K-band (1.92-2.47 ?m) with the VLTI/AMBER instrument at medium spectral resolution (R ~ 1500). To categorize and comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3D convection, and new 1D self-excited pulsation models of RSGs. Results: Our near-infrared flux spectra of V602 Car, HD 95687, and HD 183589 are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict the large observed extensions of molecular layers, most remarkably in the CO bands. Likewise, the 3D convection models and the 1D pulsation models with typical parameters of RSGs lead to compact atmospheric structures as well, which are similar to the structure of the hydrostatic PHOENIX models. They can also not explain the observed decreases in the visibilities and thus the large atmospheric molecular extensions. The full sample of our RSGs indicates increasing observed atmospheric extensions with increasing luminosity and decreasing surface gravity, and no correlation with effective temperature or variability amplitude. Conclusions: The location of our RSG sources in the Hertzsprung-Russell diagram is confirmed to be consistent with the red limits of recent evolutionary tracks. The observed extensions of the atmospheric layers of our sample of RSGs are comparable to those of Mira stars. This phenomenon is not predicted by any of the considered model atmospheres including available 3D convection and new 1D pulsation models of RSGs. This confirms that neither convection nor pulsation alone can levitate the molecular atmospheres of RSGs. Our observed correlation of atmospheric extension with luminosity supports a scenario of radiative acceleration on Doppler-shifted molecular lines. Based on observations made with the VLT Interferometer (VLTI) at Paranal Observatory under programme ID 091.D-0275.Figures 2-6 are available in electronic form at http://www.aanda.org

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

2015-03-01

70

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

71

Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling

NASA Astrophysics Data System (ADS)

Cosmology based on large scale peculiar velocity prefers volume weighted velocity statistics. However, measuring the volume weighted velocity statistics from inhomogeneously distributed galaxies (simulation particles/halos) suffers from an inevitable and significant sampling artifact. We study this sampling artifact in the velocity power spectrum measured by the nearest particle velocity assignment method by Zheng et al., [Phys. Rev. D 88, 103510 (2013).]. We derive the analytical expression of leading and higher order terms. We find that the sampling artifact suppresses the z =0 E -mode velocity power spectrum by ˜10 % at k =0.1 h /Mpc , for samples with number density 10-3 (Mpc /h )-3 . This suppression becomes larger for larger k and for sparser samples. We argue that this source of systematic errors in peculiar velocity cosmology, albeit severe, can be self-calibrated in the framework of our theoretical modelling. We also work out the sampling artifact in the density-velocity cross power spectrum measurement. A more robust evaluation of related statistics through simulations will be presented in a companion paper by Zheng et al., [Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modelling, arXiv:1409.6809.]. We also argue that similar sampling artifact exists in other velocity assignment methods and hence must be carefully corrected to avoid systematic bias in peculiar velocity cosmology.

Zhang, Pengjie; Zheng, Yi; Jing, Yipeng

2015-02-01

72

A 1-D modelling study of Arctic sea-ice salinity

NASA Astrophysics Data System (ADS)

We use a 1-D model to study how salinity evolves in Arctic sea ice. To do so, we first explore how sea-ice surface melt and flooding can be incorporated into the 1-D thermodynamic Semi-Adaptive Multi-phase Sea-Ice Model (SAMSIM) presented by Griewank and Notz (2013). We introduce flooding and a flushing parametrization which treats sea ice as a hydraulic network of horizontal and vertical fluxes. Forcing SAMSIM with 36 years of ERA-interim atmospheric reanalysis data, we obtain a modelled Arctic sea-ice salinity that agrees well with ice-core measurements. The simulations thus allow us to identify the main drivers of the observed mean salinity profile in Arctic sea ice. Our results show a 1.5-4 g kg-1 decrease of bulk salinity via gravity drainage after ice growth has ceased and before flushing sets in, which hinders approximating bulk salinity from ice thickness beyond the first growth season. In our simulations, salinity interannual variability of first-year ice is mostly restricted to the top 20 cm. We find that ice thickness, thermal resistivity, freshwater column, and stored energy change by less than 5% on average when the full salinity parametrization is replaced with a prescribed salinity profile.

Griewank, P. J.; Notz, D.

2015-02-01

73

Velocity fluctuations in a steadily sheared model foam.

Numerical simulations are conducted to calculate velocity fluctuations in a simple two-dimensional model of foam under steady shear. The width of the velocity distribution increases sublinearly with the shear rate, indicating that velocity fluctuations are large compared to the average flow at low shear rates (stick-slip flow) and small compared to the average flow at large shear rates. Several quantities reveal a crossover in behavior at a characteristic strain rate gamma(x), given by the yield strain divided by the duration of a bubble rearrangement event. For strain rates above gamma(x), the velocity correlations decay exponentially in space and time, and the velocity distribution is a Gaussian. For strain rates below gamma(x), the velocity correlations decay as stretched exponentials in space and time, and the velocity distribution is broader than a Gaussian. PMID:16241229

Ono, Ian K; Tewari, Shubha; Langer, Stephen A; Liu, Andrea J

2003-06-01

74

Velocity fluctuations in a steadily sheared model foam

NASA Astrophysics Data System (ADS)

Numerical simulations are conducted to calculate velocity fluctuations in a simple two-dimensional model of foam under steady shear. The width of the velocity distribution increases sublinearly with the shear rate, indicating that velocity fluctuations are large compared to the average flow at low shear rates (stick-slip flow) and small compared to the average flow at large shear rates. Several quantities reveal a crossover in behavior at a characteristic strain rate ??x, given by the yield strain divided by the duration of a bubble rearrangement event. For strain rates above ??x, the velocity correlations decay exponentially in space and time, and the velocity distribution is a Gaussian. For strain rates below ??x, the velocity correlations decay as stretched exponentials in space and time, and the velocity distribution is broader than a Gaussian.

Ono, Ian K.; Tewari, Shubha; Langer, Stephen A.; Liu, Andrea J.

2003-06-01

75

The stability analysis of the full velocity and acceleration velocity model

NASA Astrophysics Data System (ADS)

The stability analysis is one of the important problems in the traffic flow theory, since the congestion phenomena can be regarded as the instability and the phase transition of a dynamical system. Theoretically, we analyze the stable conditions of the full velocity and acceleration difference model (FVADM), which is proposed by introducing the acceleration difference term based on the previous car-following models (the optimal velocity model and the full velocity difference model, OVM and FVDM). By numerical simulations, it is found that when the traffic flow is unstable, the traffic jam in the FVADM is weaker than that in the FVDM. Also it is observed that the spreading speed of the jam is slower in the FVADM than that in the FVDM and the fluctuations of vehicles in the FVADM are smaller than those in the FVDM. Therefore, the acceleration difference term has strong effects on traffic dynamics and plays an important role in stabilizing the traffic flow.

Xiaomei, Zhao; Ziyou, Gao

2007-03-01

76

NASA Astrophysics Data System (ADS)

In the context of an ongoing study on seismic response of landslide-prone hill-slopes in Central Italy (area of Caramanico Terme), we tested the applicability of the Refraction Microtremor (ReMi) analysis technique (Louie, 2001) to obtain geometrical and physical parameters needed for numerical modelling. In particular, we used this technique to determine one-dimensional shear-wave velocity profiles (Vs) at sites located on and close to a recent landslide that mobilized 30-40 m thick Quaternary colluvium overlying Pliocene mudstones. The use of this technique in unstable slope areas presents difficulties related to rough topography and lateral lithological heterogeneities, which prevent the extension of geophone array up to the minimum lengths (100 - 200 m) commonly adopted in standard applications. Moreover, sites distant from anthropic sources of microtremors can have unfavourable noise conditions in comparison with other well established cases of application. To check the stability of the ReMi data in these operative conditions and the confidence level of the results, three ReMi campaigns were conducted at different times using different acquisition parameters (seismograph channel number, geophone frequency and spacing). We also tested simultaneous noise recording along orthogonal arrays to investigate a possible presence of directional variations of soil properties. The Rayleigh wave velocity dispersion data derived from picking carried out on p (slowness)-f (frequency) matrix showed the presence in noise recordings of different Rayleigh wave vibration modes (fundamental and first two higher modes), which prevail at different frequency intervals. This indicates that it is essential to correctly identify the different vibration modes to avoid erroneous data interpretation (e.g. fictitious identification of velocity decrease with depth). An analysis of the influence of changing environmental conditions and of different acquisition parameters was conducted through the comparison of data obtained from different campaigns with equal acquisition parameters and from simultaneous acquisition with different parameters. We show that different data acquisition can give quite stable results if spatial aliasing does not contaminate the signal in the p-f matrix near the picking area. Regarding the presence of directional variations, the differences found between velocities measured in two orthogonal directions were not very large (up to 10-20 %). These differences were more probably due to an anisotropic distribution of the noise sources rather than to lateral variations in material properties. The Rayleigh wave velocity dispersion curves, obtained from microseismic noise recording, were then inverted with the software Dinver (Wathelet, 2005) to derive shear-wave vertical distribution. This resulted in a large number of models compatible with data uncertainties estimated from measurement repetitions. The major variability characterizing the models at depth implies that this part of profiles is poorly constrained. However, if different vibration modes are recognised, the number of solutions can be considerably reduced by simultaneously inverting the relative dispersion curves and also by introducing into the models additional constraints (e.g. subsurface information from boreholes and seismic refraction data). References Louie J.N.; 2001: Shear wave velocity to 100 meters depth from refraction microtremor arrays. Bull. Seism. Soc. Am., 91, (2), 347-364. Wathelet M.; 2005: Array recordings of ambient vibrations: surface-wave inversion. PhD thesis, Université de Liège, Belgium.

Coccia, S.; Del Gaudio, V.; Venisti, N.; Wasowski, J.

2009-04-01

77

One-dimensional models of the systemic arterial tree are useful tools for studying wave propagation phenomena, however, their formulation for frictional losses is approximate and often based on solutions for developed flow in straight non-tapered arterial segments. Thus, losses due to bifurcations, tortuosity, non-planarity and complex geometry effects cannot be accounted for in 1-D models. This may lead to errors in the estimation of mean pressure. To evaluate these errors, we simulated steady flow in a patient specific model of the entire systemic circulation using a standard CFD code with Newtonian and non-Newtonian blood properties and compared the pressure evolution along three principal and representative arterial pathlines with the prediction of mean pressure, as given by the 1-D model. Pressure drop computed from aortic root up to iliac bifurcation and to distal brachial is less than 1 mmHg and 1-D model predictions agree well with the 3-D model. In smaller vessels like the precerebral and cerebral arteries, the losses are higher (mean pressure drop over 10 mmHg from mean aortic pressure) and are consistently underestimated by the 1-D model. Complex flow patterns resulting from tortuosity, non-planarity and branching yield shear stresses, which are higher than the ones predicted by the 1-D model. In consequence, the 1-D model overestimates mean pressure in peripheral arteries and especially in the cerebral circulation. PMID:22884968

Reymond, Philippe; Perren, Fabienne; Lazeyras, François; Stergiopulos, Nikos

2012-10-11

78

1-D COMPUTATIONAL MODEL OF A MOTIVE NOZZLE FOR THE R744

The paper presents the results of a theoretical analysis performed for a motive nozzle of a two-phase R744 ejector at steady-state conditions. The model takes into consideration one-dimensional flow of real fluid through the converging-diverging nozzle. The proposed approach allows the determination of one- dimensional distributions of pressure, velocity and density. The simulated profiles take account of local values of

TWO-PHASE EJECTOR

2010-01-01

79

a Revised Stochastic Optimal Velocity Model Considering the Velocity Gap with a Preceding Vehicle

NASA Astrophysics Data System (ADS)

The stochastic optimal velocity (SOV) model, which is a cellular automata model, has been widely used because of its good reproducibility of the fundamental diagram, despite its simplicity. However, it has a drawback: in SOV, a vehicle that is temporarily stopped takes a long time to restart. This study proposes a revised SOV model that suppresses this particular defect; the basic concept of this model is derived from the car-following model, which considers the velocity gap between a particular vehicle and the preceding vehicle. A series of simulations identifies the model parameters and clarifies that the proposed model can reproduce the three traffic phases: free, jam, and even synchronized phases, which cannot be achieved by the conventional SOV model.

Shigaki, Keizo; Tanimoto, Jun; Hagishima, Aya

80

1-D and 2-D modeling of U-Ti alloy response in impact experiments

NASA Astrophysics Data System (ADS)

Dynamie response of a U-0.75wt%Ti alloy bas been studied in planar (disk-on-disk), reverse (disk-on-rod) and symmetric (rod-on-rod) ballistic impact experiments performed with a 25 mm light-gas gun. The impact velocities ranged between 100 and 500 m/see and the samples were softly recovered for further examination, revealing different degrees of spall fracture (planar impact) and of adiabatic shear bands (ballistic experiments). The back (planar experiments) and the lateral (ballistic experiments) surface velocities were continuously monitored by VISAR. The velocity profiles and the damage maps were simulated using a 2-D AUTODYN^TM Lagrangian finite differences code. Simulations of the planar experiments were performed with special attention to the compressive path of the loading cycle in order to calibrate a modified Steinberg-Cochran-Guinan (SCG) constitutive model. The Bauschinger effect and a single-parameter spall model were added to describe the unloading and tensile paths. The calibrated SCG model was then employed to simulate the ballistic experiments. An erosion AUTODYN built-in subroutine with a threshold value of plastic strain was chosen to describe the failure in the ballistic impact experiments. The results of the suggested experimental-numerical technique can be taken into account in estimating the different contributions to the shock-induced plastic deformation and failure.

Hermann, B.; Favorsky, V.; Landau, A.; Shvarts, D.; Zaretsky, E. B.

2003-09-01

81

Study on Effects of the Stochastic Delay Probability for 1d CA Model of Traffic Flow

NASA Astrophysics Data System (ADS)

Considering the effects of different factors on the stochastic delay probability, the delay probability has been classified into three cases. The first case corresponding to the brake state has a large delay probability if the anticipant velocity is larger than the gap between the successive cars. The second one corresponding to the following-the-leader rule has intermediate delay probability if the anticipant velocity is equal to the gap. Finally, the third case is the acceleration, which has minimum delay probability. The fundamental diagram obtained by numerical simulation shows the different properties compared to that by the NaSch model, in which there exist two different regions, corresponding to the coexistence state, and jamming state respectively.

Xue, Yu; Chen, Yan-Hong; Kong, Ling-Jiang

82

NASA Astrophysics Data System (ADS)

We apply a waveform inversion method based on simulated annealing to complex core phase data observed by globally deployed seismic arrays, and present regional variation of depth profiles of attenuation and velocity for the top half of the inner core. Whereas measured attenuation parameters exhibit consistent trends for data sampling the eastern hemisphere of the inner core, for the western hemisphere, there is a remarkable difference between data sampling the inner core beneath Africa (W1) and beneath north America (W2). Obtained attenuation profiles suggest that intricate heterogeneities appear to be confined in the top 300 km. The profile for the eastern hemisphere has a high attenuation zone in the top 150 km that gradually diminishes with depth. Conversely, for the western hemisphere, the profile for W1 shows constant low attenuation and that for W2 represents a gradual increase from the inner core boundary to a peak at around 200 km depth. Velocity profiles, obtained from differential traveltimes between PKP(DF) and PKP(CD, BC) phases, for the eastern and western hemispheres are respectively about 0.8% faster and 0.6% slower than the reference model at the top of the inner core, and the difference nearly disappears at about 200 km depth. Our result suggests the presence of intricate quasi-hemispherical structures in the top ˜200-300 km of the inner core.

Iritani, R.; Takeuchi, N.; Kawakatsu, H.

2014-05-01

83

Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.

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

2014-10-01

84

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

NASA Astrophysics Data System (ADS)

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

Evangelista, Veronica; Marfia, Sonia; Sacco, Elio

2009-08-01

85

Entanglement properties of the nontrivial Haldane insulator in the 1D extended Bose-Hubbard model

NASA Astrophysics Data System (ADS)

We investigate the entanglement properties of a nontrivial topological phase in the one-dimensional (1D) Bose-Hubbard model with additional nearest-neighbor repulsion. Employing the large-scale density-matrix renormalization group technique we show that a gapped insulating phase protected by lattice inversion symmetry, the so-called Haldane insulator, appears between the Mott and density wave phases in the intermediate-coupling regime. The phase boundaries were determined from the central charge via the von Neumann entropy. The Haldane insulator reveals a characteristic degeneracy in the entanglement spectra. Breaking the lattice inversion symmetry strongly affects the distinctive gapped dispersion of the dynamical charge response of the bosonic Haldane insulator.

Ejima, Satoshi; Fehske, Holger

2015-03-01

86

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

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

Pal, Supriya; Mukherjee, Somnath; Ghosh, Sudipta

2014-04-01

87

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

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

2015-01-01

88

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

89

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

90

In this project, we are developing models of lithospheric structure for a wide variety of tectonic regions throughout Eurasia and the Middle East by regionalizing 1D velocity models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities. We expect the regionalized velocity models will improve our ability to predict travel-times for local and regional phases, such as Pg, Pn, Sn and Lg, as well as travel-times for body-waves at upper mantle triplication distances in both seismic and aseismic regions of Eurasia and the Middle East. We anticipate the models will help inform and strengthen ongoing and future efforts within the NNSA labs to develop 3D velocity models for Eurasia and the Middle East, and will assist in obtaining model-based predictions where no empirical data are available and for improving locations from sparse networks using kriging. The codes needed to conduct the joint inversion of P-wave receiver functions (PRFs), S-wave receiver functions (SRFs), and dispersion velocities have already been assembled as part of ongoing research on lithospheric structure in Africa. The methodology has been tested with synthetic 'data' and case studies have been investigated with data collected at an open broadband stations in South Africa. PRFs constrain the size and S-P travel-time of seismic discontinuities in the crust and uppermost mantle, SRFs constrain the size and P-S travel-time of the lithosphere-asthenosphere boundary, and dispersion velocities constrain average S-wave velocity within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D velocity models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background velocity model constrained by the dispersion velocities. In our first year of this project we will (i) generate 1D velocity models for open broadband seismic stations in the western half of the study area (Eurasia and the Middle East) and (ii) identify well located seismic events with event-station paths isolated to individual tectonic provinces within the study area and collect broadband waveforms and source parameters for the selected events. The 1D models obtained from the joint inversion will then be combined with published geologic terrain maps to produce regionalized models for distinctive tectonic areas within the study area, and the models will be validated through full waveform modeling of well-located seismic events recorded at local and regional distances.

Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E

2009-07-06

91

Velocity dispersion of M87 using a population model

NASA Technical Reports Server (NTRS)

The velocity dispersion of M 87 (NGC 4486) is determined using (1) a single star of class K0 III and (2) two different population models to represent the spectral region of the G-band. Although the models fit the overall spectrum better than the single-star, there is only a small difference in the derived velocity dispersion. This work revises the earlier velocity dispersion result of Brandt and Roosen (1969) down to 350 km/sec, in agreement with Faber and Jackson (1976) and Sargent et al. (1978).

Angione, R. J.; Junkkarinen, V.; Talbert, F. D.; Brandt, J. C.

1980-01-01

92

Prediction of changes in landslide movements induced by rainfalls: from the use of a black box model to a 1D mechanical model S. Bernardie (1), N. Desramaut(2), G. Russo(2), G. Grandjean(2) (1) BRGM to predict landslide surface accelerations, based on a black box tool coupled to a 1D mechanical model

Boyer, Edmond

93

1D Chemical Modeling of coupled snow-atmosphere chemistry at Dome C Antarctica

NASA Astrophysics Data System (ADS)

High levels of nitrogen oxides NOx (NOx=NO+NO2) generated by the photolysis of nitrate present in surface snow profoundly impact atmospheric composition and oxidizing capacity in the Antarctic boundary layer. In particular, NOx emissions from sunlit snow increase OH values by effectively recycling HO2 to OH. In order to better characterize this chemistry the OPALE campaign was conducted in December 2011/January 2012 at Dome C, Antarctica (altitude of 3,233 meters, 75 ° S, 123 ° E). The campaign included boundary layer profiling, measurements of the physical properties of snow, as well as a comprehensive suite of atmospheric chemistry measurements (including NOx, HONO, OH and RO2, H2O2, CH2O, O3). We present results using the 1-D coupled snow-boundary layer model MISTRA-SNOW in combination with observations made during the measurement campaign to understand this chemistry. The model includes both chemistry at the surface of snow grains (aqueous chemistry), in firn air (gas phase chemistry), and gas/aerosol chemistry in the boundary layer. Model predictions of NOx mixing ratios using a model sensitivity analysis approach are presented. The model was initialized using measured snow properties, including temperature, density, and snow grain size. In addition, the model dynamics are driven using the measured surface temperature at Dome C. To calculate the rate of snowpack ventilation, measured wind speeds during the campaign were used. The model was run varying the amount of nitrate and bromide available for reaction at the surface of snow grains and results are compared to measurements made in the atmospheric boundary from 2-4 January 2012. We test the hypothesis that very low concentrations of bromine may alter the ratio of NO/NO2. We also investigate the influence of NOx emissions from snow, and bromine (if present), on OH concentrations in the boundary layer on the Antarctic plateau.

Gil, Jaime E.; Thomas, Jennie; von Glasgow, Roland; Bekki, Slimane; Kukui, Alexandre; Frey, Markus; Jourdain, Bruno; Kerbrat, Michel; Genthon, Christophe; Preuknert, Susanne; Legrand, Michel

2013-04-01

94

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

NASA Astrophysics Data System (ADS)

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

Hadizadeh, Hadi; Baradaran Shokouhi, Shahriar

95

Car Deceleration Considering Its Own Velocity in Cellular Automata Model

NASA Astrophysics Data System (ADS)

In this paper, we propose a new cellular automaton model, which is based on NaSch traffic model. In our method, when a car has a larger velocity, if the gap between the car and its leading car is not enough large, it will decrease. The aim is that the following car has a buffer space to decrease its velocity at the next time, and then avoid to decelerate too high. The simulation results show that using our model, the car deceleration is realistic, and is closer to the field measure than that of NaSch model.

Li, Ke-Ping

2006-01-01

96

Velocity Correlations in the Nagel-Schreckenberg Model

NASA Astrophysics Data System (ADS)

The correlation between the velocity of two successive vehicles as a function of time headway is studied in the one-dimensional cellular automata (CA) NaSch model within parallel dynamic update. It is found that a strong correlation occurs in short time headway. The behavior of the correlation velocity as a function of the car density in different traffic states is also investigated. Moreover, our study is also extended to a more complicated situation where the two vehicles are separated by a number n of other vehicles. It is shown that the velocity correlation coefficient depends strongly on the number n of vehicles in between and on their positions.

Lakouari, N.; Jetto, K.; Ez-Zahraouy, H.; Benyoussef, A.

2014-09-01

97

Spontaneous stochasticity of velocity in turbulence models

We analyze the phenomenon of spontaneous stochasticity in fluid dynamics formulated as the nonuniqueness of solutions resulting from viscosity at infinitesimal scales acting through intermediate on large scales of the flow. We study the finite-time onset of spontaneous stochasticity in a real version of the GOY shell model of turbulence. This model allows high-accuracy numerical simulations for a wide range of scales (up to ten orders of magnitude) and demonstrates non-chaotic dynamics, but leads to an infinite number of solutions in the vanishing viscosity limit after the blowup time. Thus, the spontaneous stochasticity phenomenon is clearly distinguished from the chaotic behavior in turbulent flows. We provide the numerical and theoretical description of the system dynamics at all stages. This includes the asymptotic analysis before and after the blowup leading to universal (periodic and quasi-periodic) renormalized solutions, followed by nonunique stationary states at large times.

Mailybaev, Alexei A

2015-01-01

98

A P wave velocity model of Earth's core

NASA Astrophysics Data System (ADS)

Present Earth core models derived from the retrieval of global Earth structure are based on absolute travel times, mostly from the International Seismological Centre (ISC), and/or free-oscillation eigenfrequencies. Many core phase data are left out of these constructions, e.g., PKP differential travel times, amplitude ratios, and waveforms. This study is an attempt to utilize this additional information to construct a model of core P wave velocity which is consistent with the different types of core phase data available. In conjunction with our waveform modeling we used 150 differential time measurements and 87 amplitude ratio measurements, which were the highest-quality observations chosen from a large population of Global Digital Seismograph Network (GDSN) records. As a result of fitting these various data sets, a one-dimensional P wave velocity model of the core, PREM2, is proposed. This model, modified from the Preliminary Reference Earth Model (PREM) (Dziewonski and Anderson, 1981), shows a better fit to the combined data set than any of the existing core models. Major features of the model include a sharp velocity discontinuity at the inner core boundary (ICB), with a large jump (0.78 km/s), and a low velocity gradient at the base of the fluid core. The velocity is nearly constant over the lower 100 km of the outer core. The model features a depth-dependent Q? structure in the inner core such that a constant t* for the inner core fits the amplitude ratios and waveforms of short-period waves moderately well. This means the top of the inner core is more attenuating than the deeper part of the inner core. In addition, the P velocity in the lowermost mantle is reduced from that of PREM as a baseline adjustment for the observed separations of the DF and AB branches of PKP at large distances.

Song, Xiaodong; Helmberger, Don V.

1995-06-01

99

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

100

New petrophysical model describing the pressure dependence of seismic velocity

NASA Astrophysics Data System (ADS)

Seismic data are increasingly applied to predict the characteristics of reservoirs, as their quality improves. Since the change of pressure is a major component in exploitation of reservoirs, a thorough understanding of the influence of pressure on seismic velocity is also important. In this study we introduce the first results of the developed petrophysical model which describes the pressure dependence of seismic velocity. The model is based on the idea that microcracks in rocks open and close under the change of pressure. Laboratory measurements are presented on several sandstone samples. Longitudinal wave velocities were measured at various incremental pressures increased from 0 to 20 MPa. During the measurements, the pulse transmission technique was used and the parameters of the model were determined by using a linearized inversion method. The inversion results proved that the proposed petrophysical model well applies in practice.

Dobróka, Mihály; Somogyi Molnár, Judit

2012-04-01

101

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

102

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

The 3-D geologic model of the Western Canada Sedimentary Basin comprises 18 stacked intervals from the base of the Devonian Woodbend Group and age equivalent formations to ground surface; it includes an estimated thickness of eroded sediments based on 1-D burial history reconstructions for 33 wells across the study area. Each interval for the construction of the 3-D model was chosen on the basis of whether it is primarily composed of petroleum system elements of reservoir, hydrocarbon source, seal, overburden, or underburden strata, as well as the quality and areal distribution of well and other data. Preliminary results of the modeling support the following interpretations. Long-distance migration of hydrocarbons east of the Rocky Mountains is indicated by oil and gas accumulations in areas within which source rocks are thermally immature for oil and (or) gas. Petroleum systems in the basin are segmented by the northeast-trending Sweetgrass Arch; hydrocarbons west of the arch were from source rocks lying near or beneath the Rocky Mountains, whereas oil and gas east of the arch were sourced from the Williston Basin. Hydrocarbon generation and migration are primarily due to increased burial associated with the Laramide Orogeny. Hydrocarbon sources and migration were also influenced by the Lower Cretaceous sub-Mannville unconformity. In the Peace River Arch area of northern Alberta, Jurassic and older formations exhibit high-angle truncations against the unconformity. Potential Paleozoic though Mesozoic hydrocarbon source rocks are in contact with overlying Mannville Group reservoir facies. In contrast, in Saskatchewan and southern Alberta the contacts are parallel to sub-parallel, with the result that hydrocarbon source rocks are separated from the Mannville Group by seal-forming strata within the Jurassic. Vertical and lateral movement of hydrocarbons along the faults in the Rocky Mountains deformed belt probably also resulted in mixing of oil and gas from numerous source rocks in Alberta.

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

2005-01-01

103

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

NASA Astrophysics Data System (ADS)

The SCEC Community Velocity Model Toolkit (CVM-T) enables earthquake modelers to quickly build, visualize, and validate large-scale 3D velocity meshes using SCEC CVM-H or CVM-4. CVM-T is comprised of three main components: (1) a current SCEC community velocity model for Southern California, (2) tools for extracting meshes from this model and visualizing them, and (3) an automated test framework for evaluating new releases of CVMs using SCEC’s AWP-ODC forward wave propagation software and one, or more, ground motion goodness of fit (GoF) algorithms. CVM-T is designed to help SCEC modelers build large-scale velocity meshes by extracting material properties from the most current version of Community Velocity Model H (CVM-H) and to provide a consistent interface as new CVM-H versions are developed. The CVM-T software provides a highly-scalable interface to CVM-H 6.2 (and later) voxets. Along with an improved interface to CVM-H material properties, the CVM-T software adds a geotechnical layer (GTL) to CVM-H 6.2+ based on Ely’s Vs30-derived GTL. The initial release of CVM-T also extends the coverage region for CVM-H 6.2 with a Hadley-Kanamori 1D background. Smoothing is performed within the transition boundary between the core model and the 1D background. The user interface now includes a C API that allows applications to query the model either by elevation or depth. The Extraction and Visualization Tools (EVT) include a parallelized 3D mesh generator which can quickly generate meshes (consisting of Vp, Vs, and density) from either CVM-H or CVM-4 with over 100 billion points. Python plotting scripts can be employed to plot horizontal or profile slices from existing meshes or directly from either CVM. The Automated Test Framework (ATF) is a system for quantitatively evaluating new versions of CVM-H and ensuring that the model improves against prior versions. The ATF employs the CruiseControl build and test framework to run an AWP-ODC simulation for the 2008 Chino Hills event (Mw = 5.39) and perform a goodness of fit statistics calculation on the generated synthetic and recorded observed seismograms using the GoF algorithm, based on comparison of synthetic peak amplitudes to observed peak amplitudes, used in the SCEC Broadband platform. CVM-T produced plots include comparisons of synthetic and observed seismograms, plots of bias versus period, and spatial plots of the pseudo-AA bias over the entire region.

Small, P.; Maechling, P. J.; Ely, G. P.; Olsen, K. B.; Withers, K.; Graves, R. W.; Jordan, T. H.; Plesch, A.; Shaw, J. H.

2010-12-01

104

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

NASA Astrophysics Data System (ADS)

New techniques are developed for solving multi-phase flows in unbounded domains using the Diffuse Interface Model in 1-D. They extend two open boundary conditions originally designed for the Navier-Stokes equations. The non-dimensional formulation of the DIM generalizes the approach to any fluid. The equations support a steady state whose analytical approximation close to the critical point depends only on temperature. This feature enables the use of detectors at the boundaries switching between conventional boundary conditions in bulk phases and a multi-phase strategy in interfacial regions. Moreover, the latter takes advantage of the steady state approximation to minimize the interface-boundary interactions. The techniques are applied to fluids experiencing a phase transition and where the interface between the phases travels through one of the boundaries. When the interface crossing the boundary is fully developed, the technique greatly improves results relative to cases where conventional boundary conditions can be used. Limitations appear when the interface crossing the boundary is not a stable equilibrium between the two phases: the terms responsible for creating the true balance between the phases perturb the interior solution. Both boundary conditions present good numerical stability properties: the error remains bounded when the initial conditions or the far field values are perturbed. For the PML, the influence of its main parameters on the global error is investigated to make a compromise between computational costs and maximum error. The approach can be extended to multiple spatial dimensions.

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

2014-04-01

105

Modelling Hydrology of a Single Bioretention System with HYDRUS-1D

A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems. PMID:25133240

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

2014-01-01

106

NASA Astrophysics Data System (ADS)

We present a 3D seismic velocity model for the extended Barents Sea region, including Svalbard, Novaya Zemlya, the Kara Sea and the Kola-Karelia Regions. The purpose of developing a higher-resolution velocity model is to improve generally the seismic event localization in the target region. The model should improve the future monitoring facilities and the accompanied travel-time modeling. Initial testing of the model will base on the modeling of a series of seismic ground-truth events recorded by the surrounding stations. The model has a spatial resolution of 50x50 km and includes 1490 nodes. Each node is filled with a 5-layer crustal model (plus water/ice- and additional mantle layers): Nodes within the oceanic and continental domains bear two sedimentary layers (low/high vp) and three "crystalline" crustal layers (low/intermediate/high vp). Basis of this model is a recent compilation of seismic velocities taken from published wide-angle profiles, unpublished ESP profiles and additional gravity modeling along deep MSC-profiles. Over 700 1D velocity profiles are collected. In order to interpolate the velocity/depth-information from the randomly distributed 1D profiles on the equal-spaced grid, the following technique was applied: Analyzing the database, we found a strong linear trend between the total thickness of the sediment layers and the remaining crystalline crust within pre-defined continental provinces (e.g. distinct sedimentary basins, plateaus, basement highs, etc.). Area-wide depth-to-basement information, based on the integrated analysis of seismic, gravity and magnetic data is used to calculate the crystalline and total crustal thicknesses as functions of sediment thickness. The mean seismic velocities and thickness-rates for each of the 5 crustal layers are calculated from the compiled database. Analysis of the regressions show that about 75-90% of the data input is fitted by the calculated functions with a maximum of 20% deviation relative to its total thickness. The compiled database provides further excellent statistical background for composition of crystalline crustal rocks in the target region. The overall distribution of seismic velocities within crystalline crust shows a clear bimodal structure with velocity peaks at 6.4 and 6.8 km/s. First modeling tests along four selected transects were carried out to evaluate the constructed 3D seismic model. According to the tests travel-time deviations can exceed 2 s at distances of 300-800 km (by comparison to a standard 1D model).

Ritzmann, O.; Faleide, J.; Bungum, H.; Maercklin, N.; Schweitzer, J.; Mooney, W. D.; Detweiler, S. T.; Leith, W. S.

2004-12-01

107

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

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

108

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

The Savannah River National Laboratory has developed a 'hybrid' approach to Performance Assessment modeling which has been used for a number of Performance Assessments. This hybrid approach uses a multi-dimensional modeling platform (PorFlow) to develop deterministic flow fields and perform contaminant transport. The GoldSim modeling platform is used to develop the Sensitivity and Uncertainty analyses. Because these codes are performing complementary tasks, it is incumbent upon them that for the deterministic cases they produce very similar results. This paper discusses two very different waste forms, one with no engineered barriers and one with engineered barriers, each of which present different challenges to the abstraction of data. The hybrid approach to Performance Assessment modeling used at the SRNL uses a 2-D unsaturated zone (UZ) and a 3-D saturated zone (SZ) model in the PorFlow modeling platform. The UZ model consists of the waste zone and the unsaturated zoned between the waste zone and the water table. The SZ model consists of source cells beneath the waste form to the points of interest. Both models contain 'buffer' cells so that modeling domain boundaries do not adversely affect the calculation. The information pipeline between the two models is the contaminant flux. The domain contaminant flux, typically in units of moles (or Curies) per year from the UZ model is used as a boundary condition for the source cells in the SZ. The GoldSim modeling component of the hybrid approach is an integrated UZ-SZ model. The model is a 1-D representation of the SZ, typically 1-D in the UZ, but as discussed below, depending on the waste form being analyzed may contain pseudo-2-D elements. A waste form at the Savannah River Site (SRS) which has no engineered barriers is commonly referred to as a slit trench. A slit trench, as its name implies, is an unlined trench, typically 6 m deep, 6 m wide, and 200 m long. Low level waste consisting of soil, debris, rubble, wood, etc. is disposed within the trench which is then covered with soil and a cap. The filled trench resembles the surrounding soil, albeit with a higher porosity. As a result, the flow field through the trench is essentially 1-dimensional. This dimensionality makes the abstraction of information from this waste form fairly simple. Engineered waste forms present challenges not seen in the slit trench because of their higher dimensionality. Flow fields must conform to the barriers and are therefore subject to changes in direction. This paper will examine one case and show how this multidimensional flow field can be abstracted into a 1-dimensional flow field while retaining characteristics important to the transport of radioactive contaminants. One complication not addressed by the two preceding examples is that of multiple sources. This presents quite a challenge to the benchmarking exercise, but a fairly robust method has been developed to deal with it. While the PorFlow analyses can treat all sources as independent in space, this is not possible with a 1-D model. This problem has been addressed by constructing multiple 1-D models of the waste forms and using plume overlaps at the assessment points to address the multiple sources which can contribute to a distinct assessment point.

Taylor, G.; Hiergesell, R.

2010-11-16

109

NASA Astrophysics Data System (ADS)

Compared to solid ground, lakes tend to have decreased albedo, increased ground heat conductance, and increased effective ground heat capacity. These features alter local surface fluxes compared to nearby vegetation, which in turn alter the climate of the nearby atmosphere and surrounding land areas. Interest in feedbacks between lake behavior and climate change provides motivation for including lakes in global climate models, as does the desire to do effective regional downscaling of climate model predictions over regions with large lake area fraction, like the Great Lakes region. Finally, the initiation, warming, and expansion of Arctic thermokarst lakes could provide an important geophysical and biogeochemical feedback to climate warming. The Community Land Model (CLM) 3.5 currently uses a 1D Hostetler lake scheme. We have updated this model to improve the characterization of surface fluxes, eddy diffusivity, and convective mixing. We also link the lake model with the full snow physics found over other land surface types (including 5 snow layers, aerosol deposition, partial transparency of snow layers, and snow aging), add phase change & ice physics to the lake model, and include soil layers beneath lakes. These soil layers will be an important component of future thermokarst lake modeling, as thermokarst lakes tend to form regions of unfrozen soil (talik) beneath them that become active sites for anaerobic decomposition of pre-modern peat. We have also integrated the updated lake model into a modified version of the Weather Research and Forecasting (WRF) Model 3.0. We will present comparisons between predicted and observed thermal conditions, snow and ice depths, and surface energy fluxes at several lake sites, using local meteorological forcing or integrated regional atmospheric coupling. The thermal predictions are generally reasonable and show a marked improvement from runs performed with the baseline CLM 3.5 version of the lake model. Over Sparkling Lake, the lake model simulates the hourly lake water temperatures from 2002-2005 in very good agreement (<3 K error) with observations at all depths when the model is forced with the observed climatology. Over other relatively shallow (2 m - 50 m) lakes, thermal depth profiles are generally well reproduced, with maximum summer surface temperatures generally within ~3 K of the observations and mixing depths accurate to about 20% of lake depth. Snow depths, ice depths, and freezing duration are evaluated. Over very deep lakes like Lake Geneva, the model predicts insufficient mixing below about 30 m depth, which is a known deficiency of the Hostetler Lake Model, although the surface temperature is well replicated. We conclude that the model is suitable for inclusion into regional and global climate models for evaluating climate feedbacks, particularly for shallow thermokarst lakes. Finally, we present a comparison of the simulated historical surface climatology to observations for the Great Lakes region in WRF, both with and without the new lake model.

Subin, Z. M.; Riley, W. J.

2009-12-01

110

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

111

Measuring refraction and modeling velocities of surface waves

Recent high-resolution global models of lateral variations in surface-wave velocities contradict each other. While the models parameterize structures as small as 500 km, they are consistent only for wavelengths longer than 4000 km. This disagreement causes confusion and frustration on the part of Earth scientists who try to make use of the models. This thesis addresses this ambiguity in surface-wave

Erik William Feldmeth Larson

2000-01-01

112

Velocity prediction errors related to flow model calibration uncertainty

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

113

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

Paris-Sud XI, UniversitÃ© de

114

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

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

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

2010-09-01

115

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

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

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

2010-06-01

116

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

117

Solutions for the velocity-dependent Krook (VDK) model using Helmoltz equations

NASA Astrophysics Data System (ADS)

Our previous treatment for the solutions of the VDK model involved the use of a Green's function [1]. We now solve directly the Helmoltz equation describing the model in 1D (and 2D as previously described in ref.2). This involves the numerical solution of a diffusion-like equation for each energy group in steady-state. We present comparisons between the two methods of solution on test problems and on one typical implosion calculation [2]. Sensitivity of the solution to the number of energy (velocity) groups is also presented since this is an important component affecting the total computing time for this model. Further work will also be discussed. [4pt] [1] W. Manheimer, D. Colombant and V. Goncharov, Phys. Plasmas 15, 083103 (2008).[0pt] [2] W. Manheimer, D. Colombant and A.J. Schmitt, Phys. Plasmas 19, 056317 (2012).

Colombant, Denis; Manheimer, Wallace; Schmitt, Andrew

2012-10-01

118

Representation of Velocity Gradient Effects in a Gaussian Puff Model

The Gaussian puff model framework is extended to provide a description of velocity shear distortion effects. An efficient splitting-merging algorithm is presented so that a maximum puff size can be specified for a calculation. This localizes the Gaussian puffs so that they represent only a limited region of the flow and the accuracy of the representation is therefore controlled. The

R. I. Sykes; D. S. Henn

1995-01-01

119

Analysis of optimal velocity model with explicit delay

NASA Astrophysics Data System (ADS)

We analyze the optimal velocity model (OVM) with explicit delay. The properties of congestion and the delay time of car motion are investigated by analytical and numerical methods. It is shown that the small explicit delay time has almost no effects. In the case of the large explicit delay time, a new phase of congestion pattern of OVM seems to appear.

Bando, Masako; Hasebe, Katsuya; Nakanishi, Ken; Nakayama, Akihiro

1998-11-01

120

MODELLING TRANSIENT VARIABLY SATURATED FLOW UNDER NATURAL CONDITIONS USING HYDRUS-1D

Technology Transfer Automated Retrieval System (TEKTRAN)

The Hydrus-1D software package (Simunek et al., 1998), based on the Richards equation, was used to study variably saturated flow and deep drainage in an old abandoned terraced area under grass. The field site was located in the Vallcebre research catchment of the Eastern Pyrenees in North-Eastern Sp...

121

MODELLING TRANSIENT VARIABLY SATURATED FLOW IN SILT LOAM SOILS USING HYDRUS-1D

Technology Transfer Automated Retrieval System (TEKTRAN)

The Hydrus-1D software package (Simunek et al., 1998), based on the Richards equation, was used to study variably saturated flow and deep drainage in an old abandoned terraced area under grass. The field site was located in the Vallcebre research catchment of the Eastern Pyrenees in North-Eastern Sp...

122

1-D Modelling rock compaction in sedimentary basins using a visco-elastic rheology

NASA Astrophysics Data System (ADS)

Recent experimental studies on unlithified sediments suggest that the compaction is in part viscous. At the basin scale and on a geological time scale, processes such as pressure solution can be approached by creep deformation, subjected to a viscous rheology. In the present work, we have studied porosity reduction and fluid pressure development resulting from the visco-elastic compaction of a sedimentary basin during its formation. Model equations include continuity equations, Darcy's law and a visco-elastic rheology law which relates the strain rate to the effective stress and to the rate of change of this effective stress. Under the assumption that permeability is a power law function of porosity, the equations become essentially non-linear. Model results illustrate how the decrease of porosity starts at the base of the basin and spreads upward with increasing time. In a wide range of input parameter values calculations indicate a zone of almost linear increasing of pore pressure just below the basin surface, a transition zone of rapidly increasing fluid pressure with a large pressure gradient and a zone of lithostatic fluid pressure below. This is consistent with the general features of zoning of fluid pressure distribution in overpressured areas but zones with high pressure also correspond to low porosity at depth. The relative thickness of the zones depends on time, subsidence velocity and the physical parameters of sediments which can be combined in order to define a characteristic compaction length and a characteristic compaction time. In the upper zone, the decrease of porosity results in a boundary layer; within this layer, the porosity decreases from its initial value down to its minimum value. The deeper zone appears when the time of formation of the given depth basin exceeds the characteristic compaction time and the thickness of the basin is in order of compaction length. Zones of fluid overpressure may also develop due to the spatial variations of the physical properties of the sediments.

Suetnova, Elena; Vasseur, Guy

2000-05-01

123

Developing a Low-Velocity Collision Model Based on the Nasa Standard Breakup Model

We have conducted a series of low-velocity impact experiments to understand the dispersion properties of fragments newly created by low-velocity impacts possible in space, especially in geostationary Earth orbit. The test results are utilized to establish a mathematical prediction model to be used in debris generation and propagation codes. Since the expected collision velocity between catalogued objects in geostationary Earth

Toshiya Hanada; Mail Code SX; Lyndon B. Johnson

2000-01-01

124

NASA Astrophysics Data System (ADS)

Single-zone modelling is used to assess different collections of impeller 1D loss models. Three collections of loss models have been identified in literature, and the background to each of these collections is discussed. Each collection is evaluated using three modern automotive turbocharger style centrifugal compressors; comparisons of performance for each of the collections are made. An empirical data set taken from standard hot gas stand tests for each turbocharger is used as a baseline for comparison. Compressor range is predicted in this study; impeller diffusion ratio is shown to be a useful method of predicting compressor surge in 1D, and choke is predicted using basic compressible flow theory. The compressor designer can use this as a guide to identify the most compatible collection of losses for turbocharger compressor design applications. The analysis indicates the most appropriate collection for the design of automotive turbocharger centrifugal compressors.

Harley, P.; Spence, S.; Early, J.; Filsinger, D.; Dietrich, M.

2013-12-01

125

The International Photolysis Frequency Measurement and Modeling Intercomparison (IPMMI) took place at Boulder, Colorado, from 15 to 19 June 1998 and offered the opportunity to test how well experimental techniques and theoretical models can determine the photolysis frequency of O3 ? O(1D) in the troposphere. Different techniques measured the downwelling 2? sr component of j(O1D) at the ground and were

A. Hofzumahaus; B. L. Lefer; P. S. Monks; S. R. Hall; A. Kylling; B. Mayer; R. E. Shetter; W. Junkermann; A. Bais; J. G. Calvert; C. A. Cantrell; S. Madronich; G. D. Edwards; A. Kraus; M. Müller; B. Bohn; R. Schmitt; P. Johnston; R. McKenzie; G. J. Frost; E. Griffioen; M. Krol; T. Martin; G. Pfister; E. P. Röth; A. Ruggaber; W. H. Swartz; S. A. Lloyd; M. Van Weele

2004-01-01

126

The International Photolysis Frequency Measurement and Modeling Intercomparison (IPMMI) took place at Boulder, Colorado, from 15 to 19 June 1998 and offered the opportunity to test how well experimental techniques and theoretical models can determine the photolysis frequency of O3 -> O(1D) in the troposphere. Different techniques measured the downwelling 2pi sr component of j(O1D) at the ground and were

A. Hofzumahaus; B. L. Lefer; P. S. Monks; S. R. Hall; A. Kylling; B. Mayer; R. E. Shetter; W. Junkermann; A. Bais; J. G. Calvert; C. A. Cantrell; S. Madronich; G. D. Edwards; A. Kraus; M. Müller; B. Bohn; R. Schmitt; P. Johnston; R. McKenzie; G. J. Frost; E. Griffioen; M. Krol; T. Martin; G. Pfister; E. P. Röth; A. Ruggaber; W. H. Swartz; S. A. Lloyd; M. Van Weele

2004-01-01

127

Intraglottal velocity and pressure measurements in a hemilarynx model.

Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model. PMID:25698025

Oren, Liran; Gutmark, Ephraim; Khosla, Sid

2015-02-01

128

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

The geometry of ray paths through realistic Earth models can be extremely complex due to the vertical and lateral heterogeneity of the velocity distribution within the models. Calculation of high fidelity ray paths and travel times through these models generally involves sophisticated algorithms that require significant assumptions and approximations. To test such algorithms it is desirable to have available analytic solutions for the geometry and travel time of rays through simpler velocity distributions against which the more complex algorithms can be compared. Also, in situations where computational performance requirements prohibit implementation of full 3D algorithms, it may be necessary to accept the accuracy limitations of analytic solutions in order to compute solutions that satisfy those requirements. Analytic solutions are described for the geometry and travel time of infinite frequency rays through radially symmetric 1D Earth models characterized by an inner sphere where the velocity distribution is given by the function V (r) = A-Br{sup 2}, optionally surrounded by some number of spherical shells of constant velocity. The mathematical basis of the calculations is described, sample calculations are presented, and results are compared to the Taup Toolkit of Crotwell et al. (1999). These solutions are useful for evaluating the fidelity of sophisticated 3D travel time calculators and in situations where performance requirements preclude the use of more computationally intensive calculators. It should be noted that most of the solutions presented are only quasi-analytic. Exact, closed form equations are derived but computation of solutions to specific problems generally require application of numerical integration or root finding techniques, which, while approximations, can be calculated to very high accuracy. Tolerances are set in the numerical algorithms such that computed travel time accuracies are better than 1 microsecond.

Ballard, Sanford

2007-12-01

129

NASA Astrophysics Data System (ADS)

HYDRUS 1D and other similar hydrologic models can estimate the soil water profile with reasonable accuracy. Uncertainty in soil texture parameters leads to error in water balance simulations, which can affect crop yield predictions when the hydrologic model is coupled with a crop growth model. Assimilation of soil moisture observations into these hydrologic models is a novel method for improving estimates of hydrologic variables and predicting crop yield. The Ensemble Kalman Filter (EnKF) is a computational procedure commonly implemented for these data assimilation problems. Our objective was to test an EnKF for soil moisture data assimilation into HYDRUS 1D coupled with a generic crop growth model. Measurements of in-situ soil moisture were used as the filter observations. These measurements were taken using neutron scattering probes twice weekly during an irrigated wheat cropping experiment conducted at Maricopa, Arizona. The generic crop model coupled to HYDRUS 1D was based on the plant growth module used in the WEPP model. This pairing provided a model with both a rigorous solution for the water balance as well as a simple crop model for yield prediction. Prior to applying the EnKF the crop growth parameters were manually calibrated using biomass, leaf area index, and yield data collected during the field experiment. Implementing the EnKF for the coupled models presented several challenges when modifying model structure and execution. For example, tracking time discretization and time steps was essential for convergence of the numerical solution to the water movement in HYDRUS. Evaluation of the EnKF was based on its ability to accurately estimate soil moisture. The effects of soil moisture assimilation on other simulated hydrological variables and crop yield were also assessed. Further research will explore the value and applicability of remote or in-situ soil moisture measurements for use in EnKF data assimilation algorithms with an overall goal of improving crop yield predictions.

Groenendyk, D.; Thorp, K. R.; Ferre, P. A.; Crow, W. T.

2012-12-01

130

NASA Astrophysics Data System (ADS)

With the advent of airborne electromagnetic (AEM), large areas can be investigated with a high density of geophysical soundings: flight lines are typically tens of kilometers long with a sounding for each 3-30m and line spacing of 200-1000m. AEM soundings are usually inverted to 1D layered-earth resistivity models, possibly with spatially constrained inversion algorithms which take into account neighboring soundings for the inversion and provide a more consistent set of resistivity models. But as 3D inversion of AEM data remains unsolved, the visualization of these rich datasets representing 3D geological structures is often limited to 2D cross-sections and thematic maps. We present a new methodology to tackle the need for 3D visualization of resistivity structures. Our method is based on the regional 2D interpolation of the geophysical model parameters: layer thicknesses and resistivities obtained from geophysical inversion are mapped in the 2D horizontal space. From these maps, a 3D irregular mesh is generated according to the geometry of the 1D geophysical models. The cells constituting the 3D grid are irregular hexahedra which accurately follow the geometry of geophysical interfaces. This produces very fine, but memory-light 3D grids of resistivity at low computational cost. The 3D grid is then written to VTK standards and can be read with a powerful 3D visualization software which is freely available. The error from inversion, expressed as the standard deviation of model parameters, is used to weight each sounding during interpolation, which gives more importance to 1D models with a low residual between the sounding data and the 1D geophysical model. The propagation of uncertainty during interpolation is quantified and expressed as a standard deviation factor in each cell of the model. This is made possible by the use of kriging for interpolation, and allows the extraction of regions of the 3D grid which match given quality criteria. The reliability of the 3D grid, and its ability to represent heterogeneities present in the 1D models depend on the resolution of the 3D grid and the quality of the interpolation. The 3D grid is provided with a quantification of the loss of detail due to gridding process. The method is largely illustrated with a case study based on a SkyTEM airborne transient electromagnetic geophysical survey conducted on two islands in Galápagos Archipelago in 2006. The 3D resistivity grid of this extensive survey provides unprecedented images. Resistivity thresholds applied to the 3D grid allows the delineation of 3D geological bodies, providing unprecedented insights into the hydrogeology and geological structures of these volcanic islands.

Pryet, A.; Ramm, J.; Auken, E.; Chilès, J.; Violette, S.; D'Ozouville, N.; Deffontaines, B.

2010-12-01

131

NASA Astrophysics Data System (ADS)

The deep profiles of quality factor were obtained using coda-waves of local strong and moderate earthquakes (epicentral distances up to 50 km) occurred within north-eastern flanc of the Baikal rift system during 2002-2009. We used two methods: 1 - the coda envelope method [Experimental.., 1981; Kopnichev, 1991] and 2 - the sliding window method (lapse time window 10-15 sec with a step of 5 sec). Depth of coda-wave penetration was determined according to Pulli's formulae [1984], the velocity of coda-wave is 3.55 km/s (equal to shear wave velocity). For analysis we used the Q values at frequency 1 Hz since for this frequency the attenuation field heterogeneity is most evident [Aptikaeva and Kopnichev, 1991]. In result Q-profiles for eleven local areas were obtained. The Q-values vary from 50 to 170 for different profiles and depths. Herewith quality factor changes nonuniformly - the alternation of layers with high and low Q-values is observed. This phenomenon can be explained by existing velocity discontinuity. In particular for all profiles this alternation is confined to the depth about 100 km. Analysis VP-anomalies obtained in result of 2D teleseismic tomography along Baikal rift system [Mordvinova, 2009] shows the existence discontinuity on depth about 100 km under most of Baikal rift system structures. Analysis of 1D profiles of shear wave velocities in the crust and upper mantle after inversion of receiver functions [Anan'in et al., 2009] also shows presence of these discontinuity dividing high and low velocity layers. The comparison of Q-values and shear wave velocities [Anan'in et al., 2009] shown that in high velocity layers quality factor is higher too and vice versa. Multilayer quality factor model for the lithosphere in north-eastern flanc of the Baikal rift system with the alternation of layers with high and low attenuation determined by us together with analogous data obtained by Yu.F. Kopnichev [1992] for south-western flanc of the rift system can be one of inferential evidences of passive rifting mechanism in studied area. The reported study was supported by RFBR (research project N12-05-31038-mol_a) and by grant of President of Russian Federation (research project N MK-1171.2014.5).

Dobrynina, Anna; Sankov, Vladimir; Chechelnitsky, Vladimir

2014-05-01

132

Density waves in traffic flow model with relative velocity

NASA Astrophysics Data System (ADS)

The car-following model of traffic flow is extended to take into account the relative velocity. The stability condition of this model is obtained by using linear stability theory. It is shown that the stability of uniform traffic flow is improved by considering the relative velocity. From nonlinear analysis, it is shown that three different density waves, that is, the triangular shock wave, soliton wave and kink-antikink wave, appear in the stable, metastable and unstable regions of traffic flow respectively. The three different density waves are described by the nonlinear wave equations: the Burgers equation, Korteweg-de Vries (KdV) equation and modified Korteweg-de Vries (mKdV) equation, respectively.

Yu, L.; Shi, Z.-K.

2007-05-01

133

Bifurcation phenomena in the optimal velocity model for traffic flow.

In the optimal velocity model with a time lag, we show that there appear multiple exact solutions in some ranges of car density, describing a metastable uniform flow, a metastable congested flow, and an unstable congested flow. This establishes the presence of subcritical Hopf bifurcations. Our analytical results have implications for continuum traffic flow, such as hysteresis phenomena associated with discontinuous transitions between uniform and congested flow. PMID:11690176

Igarashi, Y; Itoh, K; Nakanishi, K; Ogura, K; Yokokawa, K

2001-10-01

134

Unsteady cases of validation for a 1-D sediment transport model

Downstream the dam, the dam-break wave may reach high velocities. In such a case, erosion may occur due to the high bottom shear stress. This creates an evolution of the topography which may influence the maximum water level. In order to estimate this impact of sediment transport, we propose to solve the system of equations constituted by de Saint Venant

André PAQUIER; Pierre BALAYN

135

The USGS 3D Seismic Velocity Model for Northern California

NASA Astrophysics Data System (ADS)

We present a new regional 3D seismic velocity model for Northern California for use in strong motion simulations of the 1906 San Francisco and other earthquakes. The model includes compressional-wave velocity (Vp), shear-wave velocity (Vs), density, and intrinsic attenuation (Qp, Qs). These properties were assigned for each rock type in a 3D geologic model derived from surface outcrops, boreholes, gravity and magnetic data, and seismic reflection, refraction, and tomography studies. A detailed description of the model, USGS Bay Area Velocity Model 05.1.0, is available online [http://www.sf06simulation.org/geology/velocitymodel]. For ground motion simulations Vs and Qs are more important parameters than Vp and Qp because the strongest ground motions are generated chiefly by shear and surface wave arrivals. Because Vp data are more common than Vs data, however, we first developed Vp versus depth relations for each rock type and then converted these to Vs versus depth relations. For the most important rock types in Northern California we compiled measurements of Vp versus depth using borehole logs, laboratory measurements on hand samples, seismic refraction profiles, and tomography models. These rock types include Salinian and Sierran granitic rocks, metagraywackes and greenstones of the Franciscan Complex, Tertiary and Mesozoic sedimentary and volcanic rocks, and Quaternary and Holocene deposits (Brocher, USGS OFR 05-1317, 2005). Vp versus depth curves were converted to Vs versus depth curves using new empirical nonlinear relations between Vs and Vp (Brocher, BSSA, 2005). These relations, showing that Poisson's ratio is a nonlinear function of Vp, were similarly based on compilations of diverse Vs and Vp measurements on a large suite of rock types, mainly from California and the Pacific Northwest. The model is distributed in a discretized form with routines to query the model using C++, C, and Fortran 77 programming languages. The geologic model was discretized at higher resolution near the surface (100m horizontal and 25m vertical) compared with depth (800m horizontal and 200m vertical). The model contains material properties at nearly 190 million locations and is stored as an Etree database (Tu et al., 2003). The query routines provide a simple interface to the database, returning the material properties for a given latitude, longitude, and elevation or depth.

Brocher, T. M.; Aagaard, B.; Simpson, R. W.; Jachens, R. C.

2006-12-01

136

Sleipner CCS site: velocity and attenuation model from seismic tomography

NASA Astrophysics Data System (ADS)

The results of the travel-time and frequency shift tomographic inversion of the seismic data from one of the high-resolution lines acquired in 2006 on the Sleipner CO2 geological storage site are here presented. The work has been performed within the European project CO2ReMoVe, to produce an accurate model in-depth, of both seismic velocities and attenuation, to constrain better the quantification studies of the project's partners. Tomographic techniques have the advantage of not assuming horizontal layering or uniform lateral velocities, and of enabling an easy comparison of models, even if resulting from seismic data acquired with different geometries, unavoidable in a time-lapse data set. Through an iterative process, the differences in travel-times between observed direct, reflected or refracted arrivals and the same, calculated on a discrete model, with a ray-tracing based on the Fermat's principle, are minimized. Other minimization procedures provide the reflector/refractor geometries in -depth. Analogously, in attenuation tomography, the minimization process takes into account the observed and calculated spectral-centroid frequency-shift, due to the loss of the highest frequency of the seismic wave, while crossing an attenuating medium. The result is a seismic quality factor (Q) model in-depth, and hence of the attenuation that is known to be more sensitive to subtle changes in physical properties than seismic velocity. The model is across the center of the CO2 plume, on the in-line 1838, and is constituted by nine layers, four resulting by a preliminary analysis of the pre-injection 1994 data set, i.e. seabed, a strong reflection in the overburden and the top and bottom of the Utsira Sand, plus additional five horizons, four of which within Utsira Sands, and one just above the top of it. The layers within the reservoir are very close to each other and in some cases they merge together laterally. The accumulation of CO2 in the uppermost layer of the reservoir, observed by other analyses, is confirmed by our analysis, whereas within the plume, lateral variations of both seismic velocity and Q values are observed. The presence of fine shale lenses, and their impact on the CO2 distribution within the plume may be the reason for these lateral variations. The seismic velocity and Q tomographic values have been compared with the theoretical curves from petrophysics studies, so to give to the results an interpretation in terms of effective variations in CO2 saturation and heterogeneity within the plume.

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

2012-04-01

137

Representation of velocity gradient effects in a Gaussian puff model

The Gaussian puff model framework is extended to provide a description of velocity shear distortion effects. An efficient splitting-merging algorithm is presented so that a maximum puff size can be specified for a calculation. This localizes the Gaussian puffs so that they represent only a limited region of the flow and the accuracy of the representation is therefore controlled. The model is shown to perform well on the deformational flow of Smolarkiewicz, providing an accurate calculation of the highly distorted solution. The extended puff methodology allows practical applications of an efficient Lagrangian dispersion technique in complex flow fields. 14 refs., 7 figs., 1 tab.

Sykes, R.I.; Henn, D.S. [Titan Corp., Princeton, NJ (United States)] [Titan Corp., Princeton, NJ (United States)

1995-12-01

138

Seismic velocity modelling of the Carboneras Fault Zone, SE Spain

NASA Astrophysics Data System (ADS)

The Carboneras fault zone forms part of a major strike-slip fault system in SE Spain, striking NE-SW, and accommodating up to 40 km displacement. It affects basement metamorphic rocks and unconformably overlying upper Miocene sediments and volcanic rocks. High-resolution shallow seismic tomographic sections were made across the fault zone in two localities. From the same areas, fault rocks and their wallrocks were collected for laboratory seismic velocity measurements. The laboratory data were corrected for the substantial effects of near-surface crack damage. By combining these results with geological cross sections, forward velocity models for the fault zone were constructed to compare with field seismic measurements and hence to 'ground-truth' the inferences made from them. These velocity/depth relationships matched moderately well with those extracted from the in-situ tomography results. Aspects of the in-situ seismic sections matched features on the forward-modelled sections, but the comparisons showed that it is important to have some degree of foreknowledge of the geology to be able successfully to interpret seismic tomography sections as an exploration tool.

Taylor, R. L.; Rutter, E. H.; Nippress, S. E. J.; Brodie, K. H.

2015-04-01

139

In this note we present a numerical parameterization of the results of the LLNL one-dimensional model for total column ozone change in terms of surface emissions or abundances of the various source species. The LLNL model was used in an earlier study to evaluate a significant number of time-dependent scenarios of future trends in the emissions or atmospheric abundances of CFC-11, CFC-12, CFC-22, CFC-113, CCl/sub 4/, CH/sub 3/CCl/sub 3/, CO/sub 2/, CH/sub 4/, N/sub 2/O, Halon-1301 and Halon-1211. This parameterization produces calculated ozone changes within about 2% (column ozone change relative to the 1985 model atmosphere) of the actual complete model calculation for a wide range of scenarios and ozone changes. It therefore can approximately represent the actual 1-D model for the purposes of economic analysis of regulatory strategies. It is, however, crucial to note that the 1-D model results, and consequently this parameterization, are subject to substantial uncertainties. Future improvements in our knowledge of atmospheric photochemical kinetics and transport in the troposphere and stratosphere should be expected to modify these current results in unpredictable directions.

Connell, P.S.

1986-05-01

140

NASA Astrophysics Data System (ADS)

In this note we present a numerical parameterization of the results of the LLNL one-dimensional model for total column ozone change in terms of surface emissions or abundances of the various source species. The LLNL model was used in an earlier study to evaluate a significant number of time-dependent scenarios of future trends in the emissions or atmospheric abundances of CFC-11, CFC-12, CFC-22, CFC-113, CCl, CHCCl, CO, CH, NO, Halon-1301 and Halon-1211. This parameterization produces calculated ozone changes within about 2% (column ozone change relative to the 1985 model atmosphere) of the actual complete model calculation for a wide range of scenarios and ozone changes. It therefore can approximately represent the actual 1-D model for the purposes of economic analysis of regulatory strategies. It is, however, crucial to note that the 1-D model results, and consequently this parameterization, are subject to substantial uncertainties. Future improvements in our knowledge of atmospheric photochemical kinetics and transport in the troposphere and stratosphere should be expected to modify these current results.

Connell, P. S.

1986-05-01

141

About the Efficiency of Numerical 1-D and 2-D Modelling of Site Effects in Basin Structures

NASA Astrophysics Data System (ADS)

In the present study we compare results obtained from experimental estimates of local site amplification effects with those from numerical modelling using four different techniques. We benefit from an extremely precise knowledge of the near-surface structure and experimental estimates of the local amplification factors which are determined from seismic weak-motion data recorded by a dense array across a sedimentary basin at a European test-site in Northern Greece. The possibilities and limitations of the different modelling techniques (a 1-D technique, and three 2-D techniques) to model the effects of local amplification effects are tested. Amplifications calculated by the numerical techniques are only qualitatively compared with observed data from experimental studies in the time domain and directly in the frequency domain.As a result we conclude that, in the case of a complex subsurface geometry, 1-D modelling underestimates the amplification patterns in terms of absolute amplification level, and cannot correctly account for resonant frequencies, at least for modes higher than the fundamental mode. If a more realistic incident wave field than just a plane wave is taken into account, 2-D modelling reveals the fundamental frequency and shows adequate amplifications not only at the fundamental frequency but also at higher frequencies. The general trend of the amplifications at the lowest frequencies is well determined by the 2-D numerical modelling, and can therefore supply information for seismic risk analysis.

Riepl, J.; Zahradník, J.; Plicka, V.; Bard, P.-Y.

142

Predicting abnormal pressure from 2-D seismic velocity modeling

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

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

1995-12-01

143

NASA Astrophysics Data System (ADS)

H/V spectral ratios are regularly used for estimating the bedrock depth in 1-D like basins exhibiting smooth lateral variations. In the case of 2-D or 3-D pronounced geometries, observational and numerical studies have shown that H/V curves exhibit peculiar shapes and that the H/V frequency generally overestimates 1-D theoretical resonance frequency. To investigate the capabilities of the H/V method in complex structures, a detailed comparison between measured and 3-D-simulated ambient vibrations was performed in the small-size lower Romanche valley (French Alps), which shows significant variations in geometry, downstream and upstream the Séchilienne basin. Analysing the H/V curve characteristics, two different wave propagation modes were identified along the valley. Relying on previous geophysical investigation, a power-law relationship was derived between the bedrock depth and the H/V peak frequency, which was used for building a 3-D model of the valley geometry. Simulated and experimental H/V curves were found to exhibit quite similar features in terms of curve shape and peak frequency values, validating the 3-D structure. This good agreement also evidenced two different propagation modes in the valley: 2-D resonance in the Séchilienne basin and 1-D resonance in the external parts. This study underlines the interest of H/V curves for investigating complex basin structures.

Le Roux, Olivier; Cornou, Cécile; Jongmans, Denis; Schwartz, Stéphane

2012-09-01

144

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

145

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

146

Towards improved 1-D settler modelling: impact on control strategies using the

traditional SST models (Figure 2, left) Â· More pronounced effect of storm peak on MLSS concentration (Figure 2 model recommended for controller design and evaluation of control strategies BÃ¼rger-Diehl model A new 1: Dynamic simulation of the underflow concentration (left) and the sludge blanket height (right) under storm

BÃ¼rger, Raimund

147

NASA Astrophysics Data System (ADS)

Earthquake hazard in the Salt Lake City, Utah region is strongly dominated by the potential for a M7 event on the Salt Lake segment of the Wasatch fault. The lack of instrumental records due to the long recurrence intervals on the fault and the inability of ground motion prediction equations to capture the effects of the basin structure make the estimation of earthquake ground motions from 3-D deterministic simulations an attractive approach to characterizing hazard in the region. Our simulations investigate the effect of velocity perturbations in the seismic material model on earthquake ground motions for a M7 event on the Wasatch fault. The reference seismic velocity model is the Wasatch Front community velocity model (WCVM). Earthquake simulations are carried out with the reference seismic material model and for models in which we make perturbations to the regional seismic velocity model and to the seismic velocities of the deep sedimentary basins. We construct a kinematic fault model that defines the slip amplitudes, rupture velocities and rise times and model seismic wave propagation using the Hercules finite element tool-chain (Tu et al., 2006). We obtain displacement time histories and compare ground motion parameters from the reference and perturbed velocity models. Ground motion parameters that are of greatest importance in engineering seismology (e.g., peak ground motions, spectral accelerations, etc.) are selected for the comparisons. Differential wave propagation through the reference and perturbed seismic velocity models explains the variations in earthquake ground motions. We also present recent results from a comprehensive validation of the WCVM and the perturbed velocity models to characterize the fit between observed and synthetic seismograms from small magnitude (M3-4.5) earthquakes in the region. Overall, we find that the WCVM can reproduce the waveform parameters that are of greatest interest in seismic hazard studies to a fair degree, up to a high-frequency corner of 0.5 Hz for two of the simulated earthquakes and to 0.1 Hz for one of the events. Spatial variation in the GOF is high but strong-motion records generally show poorer fits at the seismographs located atop thick sediments and near basin-edges. In addition, we find a correlation between the discrepancies in peak ground motions (velocity and acceleration) for the observed and synthetic seismograms and distance for two of the modeled earthquakes for the higher frequency band measurements. The effect of velocity perturbations in the sedimentary basins on ground motions increases with the frequency band of the measurement and suggests that knowledge about the velocity structure of the sedimentary basins has important consequences for accurately predicting earthquake ground motions. Our results suggest that future modifications to the WCVM focus on improving the seismic velocity structure of the deeper parts of the sedimentary basins.

Moschetti, M. P.; Ramirez Guzman, L.

2011-12-01

148

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

dependent, convection coefficients are temperature dependent, and/or radiation causes a significant source of a microbridge gas sensor [3]. This model considered conduction, convection, and the temperature dependent using different thermal conditions on the device. The models consider heat dissipation from conduction

Bowers, John

149

Mapping thin resistors and hydrocarbons with marine EM methods: Insights from 1D modeling

The use of marine controlled-source electromagnetic EM (CSEM) sounding to detect thin resistive layers at depths below the seafloor has been exploited re- cently to assess the resistivity of potential hydrocar- bon reservoirs before drilling. We examine the sensitiv- ity of the CSEM method to such layers with forward and inverse modeling in one and three dimensions. The 3D modeling

Steven Constable; Chester J. Weiss

2006-01-01

150

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

151

Velocity response curves demonstrate the complexity of modeling entrainable clocks.

Circadian clocks are biological oscillators that regulate daily behaviors in organisms across the kingdoms of life. Their rhythms are generated by complex systems, generally involving interlocked regulatory feedback loops. These rhythms are entrained by the daily light/dark cycle, ensuring that the internal clock time is coordinated with the environment. Mathematical models play an important role in understanding how the components work together to function as a clock which can be entrained by light. For a clock to entrain, it must be possible for it to be sped up or slowed down at appropriate times. To understand how biophysical processes affect the speed of the clock, one can compute velocity response curves (VRCs). Here, in a case study involving the fruit fly clock, we demonstrate that VRC analysis provides insight into a clock?s response to light. We also show that biochemical mechanisms and parameters together determine a model?s ability to respond realistically to light. The implication is that, if one is developing a model and its current form has an unrealistic response to light, then one must reexamine one?s model structure, because searching for better parameter values is unlikely to lead to a realistic response to light. PMID:25193284

Taylor, Stephanie R; Cheever, Allyson; Harmon, Sarah M

2014-12-21

152

Analysis, simulation and visualization of 1D tapping via reduced dynamical models

NASA Astrophysics Data System (ADS)

A low-dimensional center-of-mass dynamical model is devised as a simplified means of approximately predicting some important aspects of the motion of a vertical column comprised of a large number of particles subjected to gravity and periodic vertical tapping. This model is investigated first as a continuous dynamical system using analytical, simulation and visualization techniques. Then, by employing an approach analogous to that used to approximate the dynamics of a bouncing ball on an oscillating flat plate, it is modeled as a discrete dynamical system and analyzed to determine bifurcations and transitions to chaotic motion along with other properties. The predictions of the analysis are then compared-primarily qualitatively-with visualization and simulation results of the reduced continuous model, and ultimately with simulations of the complete system dynamics.

Blackmore, Denis; Rosato, Anthony; Tricoche, Xavier; Urban, Kevin; Zou, Luo

2014-04-01

153

A 1D mechanistic model for the evolution of earthflowprone hillslopes

landscape evolution model to explore interactions between deepseated earthflows, soil creep, and gully and are more than several meters deep, in contrast to shallow landslides, which incorporate only soil

Roering, Joshua J.

154

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

155

An electro-mechanically coupled 1-D polycrystalline model for piezoelectric stack actuators

Piezoelectric actuators used in nano-positioning devices exhibit highly non-linear behavior and strong hysteresis, which limits the efficiency of conventional non-model-based controllers. This paper presents a free energy model based on the theory of thermal activation for single crystal piezoceramics that couples mechanical stress and electric field. It is capable of predicting the hysteretic behavior along with the frequency-dependence present in

Alexander York; Stefan Seelecke

2009-01-01

156

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

NASA Astrophysics Data System (ADS)

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

Wikfeldt, K. T.

2014-12-01

157

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

158

physical model includes the effects of a conducting external cylindrical housing. Motional effects of bidirectional motion, most Terfenol-D transducers are compressively prestressed and magnetically biased. This prestressed and biased point would then be the transducer's quiescent state. Typically, the origin

Flatau, Alison B.

159

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

160

Photon-mediated qubit interactions in 1D discrete and continous models

In this work we study numerically and analytically the interaction of two qubits in a one-dimensional waveguide, as mediated by the photons that propagate through the guide. We develop strategies to assert the Markovianity of the problem, the effective qubit-qubit interactions and their individual and collective spontaneous emission. We prove the existence of collective Lamb-shifts that affect the qubit-qubit interactions and the dependency of coherent and incoherent interactions on the qubit separation. We also develop the scattering theory associated to these models and prove single photon spectroscopy does probes the renormalized resonances of the single- and multi-qubit models, in sharp contrast with earlier toy models where individual and collective Lamb shifts cancel.

Guillermo Diaz-Camacho; Diego Porras; Juan Jose Garcia-Ripoll

2015-02-19

161

Unsteady velocity measurements in a realistic intracranial aneurysm model

NASA Astrophysics Data System (ADS)

The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.

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

2012-01-01

162

A 1D Model for N-level Atoms Coupled to an EM Field

We construct a model for n-level atoms coupled to quantized electromagnetic fields in a fibrillar geometry. In the slowly varying envelope and rotating wave approximations, the equations of motion are shown to satisfy a zero curvature representation, implying integrability of the quantum system.

Z. S. Bassi; A. LeClair

1997-03-28

163

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

on the solid and liquid interfacial slag layers, and the effect of oscillation marks. The model predicts, or "slag," adjacent to the mold wall cools and greatly increases in viscosity, thus acting like a solid. It is thicker near and just above the meniscus, where it is called the "slag rim." The slag cools rapidly

Thomas, Brian G.

164

1D Computational model of a two-phase R744 ejector for expansion work recovery

A one-dimensional mathematical model of the R744 two-phase ejector for expansion work recovery is presented in this paper. Governing equations were formulated for all passages of the ejector based on the differential equations for mass, momentum, and energy balance as well as a differential representation for the equation of state. For two-flow sections (mixer and diffuser) closing equations for mass,

Krzysztof Banasiak; Armin Hafner

2011-01-01

165

A 1-D model of physical chemistry in Saturn's inner magnetosphere

NASA Astrophysics Data System (ADS)

Water vapor spewed out of Enceladus' geysers spreads across the Saturn system through dissociation, charge exchange, and neutral-neutral collisions. The combined effects of impact ionization by suprathermal electrons, charge-exchange between ions and neutrals, and radial transport of the plasma produce the observed distribution of ions and their temperature in the magnetosphere of Saturn. In this paper we combine our physical chemistry model with the neutral cloud model of Cassidy and Johnson (2010) to explore how the spatial distributions of hot electrons and of neutrals, as well as radial transport rates, produce the observed ion properties between 4 and 10 RS (where RS is the radius of Saturn). We investigate the sensitivity of the model output to radial transport rates and the radial profile of hot electron density. Selected results are as follows: (1) Hot electrons (e.g., tens to hundreds eV) at 4 RS (Enceladus' orbit) make up between ?0.25% and 0.5% of the total electron density, consistent with our previous findings, increasing to ˜10% at 10 RS. (2) The region over which chemistry plays a dominant role extends to 7 RS. Beyond 7 RS radial transport takes over, establishing the rate of plasma outflow from Saturn's plasma torus. (3) The plasma radial transport rate at 10 RS is found to be between 20 and 80 kg/s for reasonable choices of hot electron density, radial transport rate, and neutral hydrogen and H2O densities.

Fleshman, B. L.; Delamere, P. A.; Bagenal, F.; Cassidy, T.

2013-08-01

166

Authentication Based on Pole-zero Models of Signature Velocity

With the increase of communication and financial transaction through internet, on-line signature verification is an accepted biometric technology for access control and plays a significant role in authenticity and authorization in modernized society. Therefore, fast and precise algorithms for the signature verification are very attractive. The goal of this paper is modeling of velocity signal that pattern and properties is stable for persons. With using pole-zero models based on discrete cosine transform, precise method is proposed for modeling and then features is founded from strokes. With using linear, parzen window and support vector machine classifiers, the signature verification technique was tested with a large number of authentic and forgery signatures and has demonstrated the good potential of this technique. The signatures are collected from three different database include a proprietary database, the SVC2004 and the Sabanci University signature database benchmark databases. Experimental results based on Persian, SVC2004 and SUSIG databases show that our method achieves an equal error rate of 5.91%, 5.62% and 3.91% in the skilled forgeries, respectively. PMID:24696797

Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad

2013-01-01

167

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

168

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

169

Thermally driven classical Heisenberg model in 1D with a local time varying field

NASA Astrophysics Data System (ADS)

We study thermal transport in the one-dimensional classical Heisenberg model driven by boundary heat baths and in the presence of a local time varying magnetic field. We find that, in the steady state, the energy current shows thermal resonance as the frequency of the time-periodic forcing is varied. Even in the absence of a thermal bias a steady nonzero energy current can be induced in the system, whereas for the thermally driven system a current reversal can be achieved in the bulk by suitably tuning the system parameters. When the amplitude of the forcing field is increased the system exhibits multiple resonance peaks. Thermal resonance survives in the thermodynamic limit and their magnitude increases as the temperature of the system is decreased. We find that the resonance frequency is an intrinsic frequency of the model and is related to its spin wave dispersion spectrum. Finally we show that, similar to other generic force-driven systems, there is no thermal pumping despite the current reversal in the bulk of the system.

Bagchi, Debarshee

2013-12-01

170

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

NASA Astrophysics Data System (ADS)

Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.

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

2011-12-01

171

Comprehensive 1D Modelling of Reactive Chemical Transport in Unsaturated Soil

NASA Astrophysics Data System (ADS)

Computer models for simulating environmental processes of water flow, solute transport and geochemical reactions have greatly advanced during recent years. However, there is still demand for the development of programs that a capable of simulating the numerous interactions between physical transport processes and biogeochemical reactions in natural soils. We present a new tool for simulating transient vadose zone flow and solute transport according to the moisture- based form of Richards' equation within the widely used geochemical software PHREEQC. The direct implementation into the geochemical framework provides access to comprehensive geochemical models, giving capabilities beyond existing software for coupled unsaturated flow and reaction. Possible reactions include complex aqueous speciation, cation exchange, equilibrium phase dissolution and precipitation, formation of solid solutions, redox reactions, gas phase exchange, surface adsorption considering electrostatics and kinetic reactions with user-defined rate equations, among others. As a result of the close coupling procedure, the influence of geochemical reactions on water content, e.g., through dissolution or precipitation of water-containing phases, can be investigated. For the solution of the partial differential equations of flow and transport, an explicit finite-difference formulation with a second-order space discretization and first-order time discretization was employed. The use of integrated diffusivities transforms Richards' equation into a simple advection-diffusion equation. Changes in water content and solute concentration were conceptualized as local kinetic reactions of individual elements where changes in moisture content result from fluxes of oxygen and hydrogen across cell boundaries. Reactions and chemical element transport are coupled via sequential two-step operator splitting. The scheme was implemented into PHREEQC without any source code modification such that it can be applied by an experienced user within the existing freely available software. In this presentation, we show results from extensive code verification and demonstrate the unique capabilities of the model for simulating surface sorption to variable charge surface sites including the development of a diffuse double layer as well as dissolution reactions with effects on soil moisture.

Wissmeier, L.; Barry, D. A.

2007-12-01

172

Hyperbolic reformulation of a 1D viscoelastic blood flow model and ADER finite volume schemes

The applicability of ADER finite volume methods to solve hyperbolic balance laws with stiff source terms in the context of well-balanced and non-conservative schemes is extended to solve a one-dimensional blood flow model for viscoelastic vessels, reformulated as a hyperbolic system, via a relaxation time. A criterion for selecting relaxation times is found and an empirical convergence rate assessment is carried out to support this result. The proposed methodology is validated by applying it to a network of viscoelastic vessels for which experimental and numerical results are available. The agreement between the results obtained in the present paper and those available in the literature is satisfactory. Key features of the present formulation and numerical methodologies, such as accuracy, efficiency and robustness, are fully discussed in the paper.

Montecinos, Gino I.; Müller, Lucas O.; Toro, Eleuterio F.

2014-06-01

173

As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes

A. Rodgers; A. Petersson; S. Nilsson; B. Sjogreen; K. McCandless

2006-01-01

174

An analytical 1-D model for vertical momentum and energy flux through a fully developed wind farm

NASA Astrophysics Data System (ADS)

Wind farms capture momentum from the atmospheric boundary layer (ABL) both at the leading edge and from the atmosphere above. Momentum is advected into the wind farm and wake turbulence draws excess momentum in from between turbines until momentum is only available from above the wind farm. This distance can be described by the so-called drag development length scale, which arises from the canopy drag force term in the momentum equation. At this point the flow can be considered fully developed. The horizontally-averaged velocity profile for a fully developed wind farm flow exhibits a characteristic inflection point near the top of the wind farm, similar to that of sparse canopy-type flows (Markfort et al., JoT, 2012). The inflected vertical velocity profile is associated with the presence of a dominant characteristic turbulence scale, which may be responsible for a significant portion of the vertical momentum flux. We evaluate an analytical canopy-type flow model for wind farm-atmosphere interaction by testing it against wind-tunnel experimental data of flow through a model wind farm. The model is adapted to predict the mean flow, vertical momentum flux, and the mean kinetic energy flux as well as kinetic energy dissipation within the wind farm. This model is particularly useful for wind farm configuration optimization, considering wind turbine spacing and surface roughness and can also be useful to represent wind farms in regional scale atmospheric simulations.

Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando

2014-05-01

175

NASA Astrophysics Data System (ADS)

Grant and Madsen (1979) showed that the nonlinear interaction between steady near bottom currents and oscillatory surface wave currents can produce enhanced bottom stress relative to what a quadratic drag law formulation would indicate. A numerical study of this process has been conducted by combining a bottom boundary layer model (BBLM) with the Dartmouth one-dimensional (1-D) finite element dynamic model called NUBBLE. This model system is forced to dynamic equilibrium by typical Gulf of Maine storm-related 12-second surface waves and prescribed steady geostrophic currents. The results of a suite of sensitivity tests show that: (1) the combined wave and current influence on bottom stress calculations is very important in water depth less than 80 m; (2) the equivalent drag coefficient (Cd) associated with the combination of wave and current interactions is larger than that due to either forcing process alone; and (3) the quadratic drag law is practical for simulating the bottom stress in ''deep'' water. The model results in various forms of the bottom Ekman spiral that are strongly modified by wave-enhanced bottom stress in depths less than 60 m. For cases of greater bottom stress in the depth range 2.4D

Fan, Y.; Brown, W. S.

2002-05-01

176

Initial velocity model construction of seismic tomography in near-surface applications

NASA Astrophysics Data System (ADS)

The impact of initial velocity models on final image reconstruction results and how to construct a proper initial velocity model in near-surface tomography studies are investigated on a two-layer synthetic model with gradually increasing velocity with depth. Refraction initial velocity models and linear velocity function models are tested on both synthetic and field data to obtain images close to reality. It is concluded that velocity function type initial models should be preferred in soft alluvial deposits that exist within the investigated depths, whereas refraction initial models should be preferred in the groundwater table or with strong refractors' existence within the investigated depths to obtain optimum subsurface images in refraction-diving wave seismic tomography.

Kanl?, Ali Ismet

2009-01-01

177

Some T cells react with lipid antigens bound to antigen-presenting molecule CD1d. Numbers and functions of a subset of such lipid-reactive T cells are reduced in patients with systemic lupus erythematosus (SLE) and their relatives, as well as in genetically susceptible and chemically induced animal models of lupus-like disease. We have reported that the germline deletion of CD1d exacerbates lupus, suggesting a protective role of these cells in the development of lupus. The use of a knockout mouse model in this study, however, did not allow examination of the role of these cells at different stages of disease. Here, we describe an approach to deplete CD1d-dependent T cells, which allowed us to investigate the role of these cells at different stages of disease in genetically lupus-prone NZB/NZW F1 (BWF1) mice. Repeated intravenous injections of large numbers of CD1d-transfected cells resulted in ~50–75% reduction in these cells, as defined by the expression of CD4, NK1.1 and CD122, and lack of expression of CD62 ligand. TCR ?? +NK1.1+ cells were also reduced in the recipients of CD1d-transfected cells as compared with control recipients. Such depletion of CD1d-reactive T cells in preclinical BWF1 mice resulted in disease acceleration with a significant increase in proteinuria and mortality. In older BWF1 mice having advanced nephritis, however, such depletion of CD1d-reactive T cells resulted in some disease improvement. Taken together, these data as well as our published studies suggest that CD1d-reactive T cells protect against the development of lupus in animal models. However, these cells appear to be unable to suppress established lupus nephritis in these animals, and might even play a disease aggravating role in late stages of disease. PMID:22065098

Jacinto, J; Kim, PJ; Singh, RR

2012-01-01

178

NASA Astrophysics Data System (ADS)

Elementary statistical models for collision-sequence interference effects usually assume Gaussian-distributed velocities with zero persistence of velocity. Here we extend the treatment to arbitrary persistences of velocity in the range zero to just less than unity. For vector collision-sequence interference the results show the interference dip narrowing with increasing persistence of velocity as expected. Only partial agreement is obtained with some observations in a molecular dynamics simulation in Lennard-Jonesium.

Wheeler, H. T.; Lewis, J. C.

2012-12-01

179

Transport of a 1D viscoelastic actin myosin strip of gel as a model of a crawling cell

NASA Astrophysics Data System (ADS)

Cell crawling is an important biological phenomenon because it underlies coordinated cell movement in morphogenesis, cancer and wound healing. This phenomenon is based on protrusion at the cell's leading edge, retraction at the rear, contraction and graded adhesion powered by the dynamics of actin and myosin protein networks. A few one-dimensional models successfully explain an anteroposterior organization of the motile cell, but don’t sufficiently explore the viscoelastic nature of the actin-myosin gel. We develop and numerically solve a model of a treadmilling strip of viscoelastic actin-myosin gel. The results show that the strip translocates steadily as a traveling pulse, without changing length, and that protein densities, velocities and stresses become stationary. The simulations closely match the observed forces, movements and protein distributions in the living cell.

Larripa, Kamila; Mogilner, Alex

2006-12-01

180

Key elements of regional seismic velocity models for long period ground motion simulations

Regional 3-D seismic velocity models used for broadband strong motion simulations must include compressional-wave velocity (Vp), shear-wave velocity (Vs), intrinsic attenuation (Qp, Qs), and density. Vs and Qs are the most important of these parameters because the strongest ground motions are generated chiefly by shear- and surface-wave arrivals. Because Vp data are more common than Vs data, many researchers first develop a Vp model and convert it to a Vs model. I describe recent empirical relations between Vs, Vp, Qs, Qp, and density that allow velocity models to be rapidly and accurately calculated. ?? Springer Science+Business Media B.V. 2007.

Brocher, T.M.

2008-01-01

181

Quantum distance and the Euler number index of the Bloch band in a 1D spin model

We study the Riemannian metric and the Euler characteristic number of the Bloch band in a 1D spin model with multi-site spins exchange interactions. The Euler number of the Bloch band originates from the Gauss-Bonnet theorem on the topological characterization of the closed Bloch states manifold in the first Brillouin zone. We study this approach analytically in a transverse field XY spin chain with three-site spin coupled interactions. We define a class of cyclic quantum distance on the Bloch band and on the ground state, respectively, as a local characterization for quantum phase transitions. Specifically, we give a general formula for the Euler number by means of the Berry curvature in the case of two-band models, which reveals its essential relation to the first Chern number of the band insulators. Finally, we show that the ferromagnetic-paramagnetic phases transition in zero-temperature can be distinguished by the Euler number of the Bloch band.

Yu-Quan Ma

2014-10-23

182

Insights into brine dynamics and sea ice desalination from a 1-D model study of gravity drainage

NASA Astrophysics Data System (ADS)

We study gravity drainage using a new 1-D, multiphase sea ice model. A parametrization of gravity drainage based on the convective nature of gravity drainage is introduced, whose free parameters are determined by optimizing model output against laboratory measurements of sea ice salinity evolution. Optimal estimates of the free parameters as well as the parametrization performance remain stable for vertical grid resolutions from 1 to 30 mm. We find a strong link between sea ice growth rate and bulk salinity for constant boundary conditions but only a weak link for more realistic boundary conditions. We also demonstrate that surface warming can trigger brine convection over the whole ice layer. Over a growth season, replacing the convective parametrization with constant initial salinities leads to an overall 3% discrepancy of stored energy, thermal resistance, and salt release. We also derive from our convective parametrization a simplified, numerically cheap and stable gravity-drainage parametrization. This parametrization results in an approximately 1% discrepancy of stored energy, thermal resistance, and salt release compared to the convective parametrization. A similarly low discrepancy to our complex parametrization can be reached by simply prescribing a depth-dependent salinity profile.

Griewank, Philipp J.; Notz, Dirk

2013-07-01

183

NASA Astrophysics Data System (ADS)

In this paper atmospheric-pressure rf He+O2 cold plasmas are studied by means of a 1-D fluid model. 17 species and 60 key reactions selected from a study of 250+ reactions are incorporated in the model. O2+, O3-, and O are the dominant positive ion, negative ion, and reactive oxygen species, respectively. Ground state O is mainly generated by electron induced reactions and quenching of atomic and molecular oxygen metastables, while three-body reactions leading to the formation of O2 and O3 are the main mechanisms responsible for O destruction. The fraction of input power dissipated by ions is ˜20%. For the conditions considered in the study ˜6% of the input power is coupled to ions in the bulk and this amount will increase with increasing electronegativity. Radial and electrode losses of neutral species are in most cases negligible when compared to gas phase processes as these losses are diffusion limited due to the large collisionality of the plasma. The electrode loss rate of neutral species is found to be nearly independent of the surface adsorption probability p for p > 0.001 and therefore plasma dosage can be quantified even if p is not known precisely.

Yang, Aijun; Wang, Xiaohua; Rong, Mingzhe; Liu, Dingxin; Iza, Felipe; Kong, Michael G.

2011-11-01

184

NASA Astrophysics Data System (ADS)

Industrial scale-up (or scale down) in Compounding and Reactive Extrusion processes is one of the most critical R&D challenges. Indeed, most of High Performances Polymers are obtained within a reactive compounding involving chemistry: free radical grafting, in situ compatibilization, rheology control... but also side reactions: oxidation, branching, chain scission... As described by basic Arrhenius and kinetics laws, the competition between all chemical reactions depends on residence time distribution and temperature. Then, to ensure the best possible scale up methodology, we need tools to match thermal history of the formulation along the screws from a lab scale twin screw extruder to an industrial one. This paper proposes a comparison between standard scale-up laws and the use of Computer modeling Software such as Ludovic® applied and compared to experimental data. Scaling data from a compounding line to another one, applying general rules (for example at constant specific mechanical energy), shows differences between experimental and computed data, and error depends on the screw speed range. For more accurate prediction, 1D-Computer Modeling could be used to optimize the process conditions to ensure the best scale-up product, especially in temperature sensitive reactive extrusion processes. When the product temperature along the screws is the key, Ludovic® software could help to compute the temperature profile along the screws and extrapolate conditions, even screw profile, on industrial extruders.

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

2014-05-01

185

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

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

Allen, Richard M.

186

A stochastic model of fluid flow in porous rocks has been previously developed to explain the measured distribution of local velocity. The theoretical predictions of this model agree well with experimental results obtained from the magnetic resonance imaging-based measurements of the spatial variation of velocity of water permeating through Bentheimer and Clashach sandstones. To further verify previous results, we have performed new velocity measurement experiments using an efficient velocity encoded pi-echo planar imaging sequence on glass bead phantoms that exhibit more regular pore size distribution than rocks. The results show that velocity distributions in glass bead phantoms also exhibit Gaussian profiles and the linear relationship between the velocity variance and the mean velocity (the Mansfield-Issa equation). PMID:9803919

Bencsik, M; Issa, B; al-Mugheiry, M A; Bowtell, R W; Mansfield, P

1998-01-01

187

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 the velocity for a debris flow.

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

2015-02-01

188

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

189

NASA Astrophysics Data System (ADS)

Many scientific issues for the Basin and Range Province (BRP) remain unsettled including structural evolution, strain rates, slip partitioning and earthquake source physics. A catalog of earthquake source parameters including locations and moment tensors is the basis for tectonic and geophysical study. New instrumentation from the Advance National Seismic System, EarthScope Plate Boundary Observatory, Bigfoot and US-Array brings the opportunity for high quality research; therefore, a catalog is an underlying foundation for examining the BRP. We are continuing to generate a moment tensor catalog for the BRP (Mw<3.5) using long-period regional waves spanning back to 1990. Iterative waveform inversion method (e.g., Nolet et al., 1986, Randell, 1994) is used to calibrate the BRP velocity and density structure using two northern and southern BRP earthquakes. The calibrated models generate realistic synthetics for (f<0.5Hz) with ~50-80% variance reduction. We averaged all path specific models to construct a 1-D BRP community background model. The crust is relatively simple between 5-20km (~6.12km/s) and there is a strong velocity gradient in the upper 5- km. There are lower velocities in the upper crust but higher velocities in the mid-crust for the Sierra Nevada paths relative to BRP. There is also a lower crust high-velocity anomaly near Battle Mountain and Elko that is faster by ~5% and may indicate a wider area of under-plating by basaltic magmas. There are significant low velocity zones in the upper and mid crust mainly across the Walker Lane Belt that may indicate the presence of fluids. We are continuing to work on assessing the performance of these newly calibrated models in improving the estimation of moment tensors down to lower magnitudes and mapping out holes in the seismic network which can be filled to improve moment tensor catalog. We also are looking at how these models work at locating earthquakes and comparing synthetics with those computed from models constrained from different data including refraction, surface wave dispersion, and travel-time tomography.

Ichinose, G. A.

2006-12-01

190

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

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

191

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

192

Analysis of peripheral artery velocity tracing in a porcine model

Background The aim of the study was to trace the peripheral artery velocity with ultrasound in pigs and provide inference on diagnosis of the type, location and severity of vascular diseases. Materials and methods Limb tightening, adrenaline administration and arterial wall pinching were performed independently in six pigs, and then the evolution of the external iliac artery or femoral artery velocity tracing were monitored. Results With the increase of the extents of hindlimb tightening, peak systolic velocity (PSV) of ipsilateral external iliac artery turned from 36.33±1.77 cm/s to 59.72±2.67 cm/s, minimum post-principal wave velocity (MPV from 13.68±1.11 cm/s to ?7.48±0.82 cm/s, peak diastolic velocity (PDV) from 19.31±0.86 cm/s to 8.98±0.45 cm/s, and, end diastolic velocity (EDV) from 13.2±0.45 cm/s to 0. With the increase of the dose of the epinephrine injection, PSV increased from 36.33±1.77 cm/s to 43.97±2.15 cm/s but then decreased to 35.43±3.01 cm/s, and MPV negatively increased to ?23.53±0.82 cm/s after decreasing from 13.68±1.11 cm/s to 0. PDV and EDV gradually decreased to zero. With the increase of the stenosis severity in the abdominal aortic wall pinching, PSV was reduced and had a linearly negative correlation with the stenosis severity (R=0.983, R2=0.967). MPV gradually increased, and its direction reversed when the stenosis severity increased, then diminished when the blood flow was occluded by more than 2/3. Conclusions The formation of peripheral artery velocity is the result of concurrent effects of cardiac ejection, vascular resistance, effective circulating blood volume and elastic recoil. Vascular resistance exerts pronounced effects on the diastolic waveform, and the occurrence of backward wave indicates that the downstream circulation resistance significantly increases. PMID:22933940

Meng, Qingxin; Ding, Weiwei; Yang, Bin; Fu, Ninghua; Lu, Guangming

2011-01-01

193

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

194

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

195

Floodplain mapping via 1D and quasi-2D numerical models in the valley of Thessaly, Greece

NASA Astrophysics Data System (ADS)

The European Union Floods Directive defines a flood as 'a covering by water of land not normally covered by water'. Human activities, such as agriculture, urban development, industry and tourism, contribute to an increase in the likelihood and adverse impacts of flood events. The study of the hydraulic behaviour of a river is important in flood risk management. Here, we investigate the behaviour of three hydraulic models, with different theoretical frameworks, in a real case scenario. The area is located in the Penios river basin, in the plain of Thessaly (Greece). The three models used are the one-dimensional HEC-RAS and the quasi two-dimensional LISFLOOD-FP and FLO-2D which are compared to each other, in terms of simulated maximum water depth as well as maximum flow velocity, and to a real flood event. Moreover, a sensitivity analysis is performed to determine how each simulation is affected by the river and floodplain roughness coefficient, in terms of flood inundation.

Oikonomou, Athanasios; Dimitriadis, Panayiotis; Koukouvinos, Antonis; Tegos, Aristoteles; Pagana, Vasiliki; Panagopoulos, Panayiotis-Dionisios; Mamassis, Nikolaos; Koutsoyiannis, Demetris

2013-04-01

196

Velocity mapping and models of the elliptical galaxies NGC 720, NGC 1052, and NGC 4697

NASA Technical Reports Server (NTRS)

CCD surface photometry and extensive long-slit spectroscopy are used to construct detailed models of the flattened ellipticals NGC 720, 1052, and 4697. The models are combined with the Jeans equations to yield predicted fields of line-of-sight velocity dispersion and streaming velocity. By comparing these fields with observed velocities, it is concluded that none of these systems can have isotropic velocity dispersion tensors, and diminishing the assumed inclination of any given galaxy tends to decrease the line-of-sight velocity dispersion and, counterintuitively, to increase the line-of-sight rotation speeds. The ratio of the line-of-sight velocity dispersion along the minor axis to that along the major axis is found to be a sensitive diagnostic of the importance of a third integral for the galaxy's structure.

Binney, J. J.; Davies, Roger L.; Illingworth, Garth D.

1990-01-01

197

A Velocity Distribution Model for Steady State Heat Transfer

NASA Technical Reports Server (NTRS)

Consider a box that is filled with an ideal gas and that is aligned along Cartesian coordinates (x, y, z) having until length in the 'y' direction and unspecified length in the 'x' and 'z' directions. Heat is applied uniformly over the 'hot' end of the box (y = 1) and is removed uniformly over the 'cold' end (y = O) at a constant rate such that the ends of the box are maintained at temperatures T(sub 0) at y = O and T(sub 1) at y = 1. Let U, V, and W denote the respective velocity components of a molecule inside the box selected at some random time and at some location (x, y, z). If T(sub 0) = T(sub 1), then U, Y, and W are mutually independent and Gaussian, each with mean zero and variance RT(sub 0), where R is the gas constant. When T(sub 0) does not equal T(sub 1) the velocity components are not independent and are not Gaussian. Our objective is to characterize the joint distribution of the velocity components U, Y, and W as a function of y, and, in particular, to characterize the distribution of V given y. It is hoped that this research will lead to an increased physical understanding of the nature of turbulence.

Hall, Eric B.

1996-01-01

198

, electromagnetic induction and transport of heat are Â· Solve these equations (in a spherical geometry and model description The induction equation, neglecting diffusion of magnetic fields is For a 2D flow

Finlay, Christopher

199

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

To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D (SAndia LoS Alamos) version 1.4, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is > 55%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method, as well as by directly estimating the diagonal of the model resolution matrix based on the technique developed by Bekas, et al. We compare the travel-time prediction and location capabilities of this model over standard 1D models. We perform location tests on a global, geographically-distributed event set with ground truth levels of 5 km or better. These events generally possess hundreds of Pn and P phases from which we can generate different realizations of station distributions, yielding a range of azimuthal coverage and proportions of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135, especially with increasing azimuthal gap. The 3D model appears to perform better for locations based solely or dominantly on regional arrivals, which is not unexpected given that ak135 represents a global average and cannot therefore capture local and regional variations.

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

2010-04-01

200

Velocity spectra of quantum turbulence: experiments, numerics and models

Superfluid Turbulence is unusual and presents a challenge to fluid dynamicists because it consists of two coupled, inter penetrating turbulent fluids: the first is inviscid with quantised vorticity, the second is viscous with continuous vorticity. Despite this double nature, the observed spectra of the superfluid turbulent velocity at sufficiently large length scales are similar to those o ordinary turbulence. We present experimental, numerical and theoretical results which explain these similarities, and illustrate the limits of our present understanding of superfluid turbulence at smaller scales.

Carlo F. Barenghi; Victor L'vov; Philippe-E. Roche

2013-06-26

201

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

202

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

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

Paris-Sud XI, UniversitÃ© de

203

PPPL3196 Preprint: June 1996, UC420 Modeling of Neutral Hydrogen Velocities in

Monte Carlo neutral transport simulations of hydrogen velocities in the Tokamak Fusion Test ReactorPPPL3196 Preprint: June 1996, UC420 Modeling of Neutral Hydrogen Velocities in the Tokamak Fusion Test Reactor D. P. Stotler, C. H. Skinner, R. V. Budny, and A. T. Ramsey Princeton Plasma Physics

204

PPPL-3196 -Preprint: June 1996, UC-420 Modeling of Neutral Hydrogen Velocities in

Monte Carlo neutral transport simulations of hydrogen velocities in the Tokamak Fusion Test ReactorPPPL-3196 - Preprint: June 1996, UC-420 Modeling of Neutral Hydrogen Velocities in the Tokamak Fusion Test Reactor D. P. Stotler, C. H. Skinner, R. V. Budny, and A. T. Ramsey Princeton Plasma Physics

205

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

The development of three-dimensional P-wave velocity models for the regions surrounding five large earthquakes in California has lead to the recognition of relations among fault behavior and the material properties of the rocks that contact the fault at seismogenic depths; regions of high moment release appear to correlate with high seismic velocities whereas rupture initiation or termination may be associated

Andrew J. Michael; Donna Eberhart-Phillips

1991-01-01

206

A Velocity-Separation Difference Model for Car-Following Theory and Simulation Tests

This paper attempts to introduce a velocity-separation difference model that modifies the previous models in the literature. The improvement of this new model over the previous ones lies in that it performs more realistically than others in the dynamical evolution of congestion. Furthermore, the proposed model is investigated with analytic and numerical method, with the finding that this model can

Zhipeng Li; Xiaobo Gong; Yuncai Liu

2006-01-01

207

Velocity Field Modelling for Pollutant Plume Using 3-D Adaptive Finite Element Method

\\u000a Air pollution models usually start from the computation of the velocity field of a fluid. In this paper, we present a model\\u000a for computing that field based on the contribution of the observed wind flow and the vertical buoyancy or momentum plume rise\\u000a defined by a Gaussian plume model. This initial velocity field is adjusted to verify incompressibility and impermeability

Gustavo Montero; Rafael Montenegro; José María Escobar; Eduardo Rodríguez; José María González-yuste

2004-01-01

208

NASA Astrophysics Data System (ADS)

Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian

2013-09-01

209

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

210

NASA Astrophysics Data System (ADS)

Sediment transport in mountain rivers and torrents is a substantial process within the assessment of flood related hazard potential and vulnerability in alpine catchments. Focusing on fluvial transport processes, river bed erosion and deposition considerably affects the extent of inundation. The present work deals with scenario-specific bed-load transport modelling in a large alpine valley in the Austrian Alps. A routing scheme founding on empirical equations for the calculation of transport capacities, incipient motion conditions and drag forces is set up and applied to the case study area for two historic flood events. The required hydraulic data result from a distributed hydrological-1-D-hydraulic model. Hydraulics and bed-load transport are simulated sequentially providing a technically well-founded and feasible methodology for the estimation of bed-load transport rates during flood events.

Gems, B.; Achleitner, S.; Plörer, M.; Schöberl, F.; Huttenlau, M.; Aufleger, M.

2012-12-01

211

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

212

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

213

NASA Astrophysics Data System (ADS)

We analyze earthquakes occurring in and around the Rotorua and Kawerau geothermal systems, Taupo Volcanic Zone, New Zealand. The two data sets contain 504 and 1875 shallow (? 20 km deep) earthquakes, respectively, and span the 21 year period between 1984 and 2004. The arrival time data for these earthquakes are first used to calculate 1-D P- and S-wave seismic velocity models and accompanying station correction terms for both areas. In order to address the non-uniqueness of the joint hypocenter-velocity model estimation problem, we analyze suites of 1000 velocity models computed from random initial models. The final velocity models are well constrained, particularly at depths between 4 and 15 km, and consistent with the results obtained in previous seismic refraction studies of the central Taupo Volcanic Zone. Using a combination of cross-correlation-derived and catalog-based arrival times, we relocate subsets of the Rotorua and Kawerau data sets. In Rotorua, the relocated earthquakes cluster near the geothermally active parts of Rotorua City and beneath the Mount Ngongotaha rhyolite dome. Earthquake clusters and alignments reveal seismogenic structures in the mid-crust whose positions and geometries are consistent with previously published fault mechanisms and known near-surface faults. In Kawerau, the earthquakes within the geothermal field align along northeast-trending lineations, consistent with the predominant alignment of surface-mapped faults in the area.

Clarke, D.; Townend, J.; Savage, M. K.; Bannister, S.

2009-02-01

214

Alzheimer's disease (AD), the most common cause of dementia, is neuropathologically characterized by accumulation of insoluble fibrous inclusions in the brain in the form of intracellular neurofibrillary tangles and extracellular senile plaques. Perturbation of the ubiquitin-proteasome system (UPS) has long been considered an attractive hypothesis to explain the pathogenesis of AD. However, studies on UPS functionality with various methods and AD models have achieved non-conclusive results. To get further insight into UPS functionality in AD, we have crossed a well-documented APPswe/PS1dE9 AD mouse model with a UPS functionality reporter, GFPu, mouse expressing green fluorescence protein (GFP) fused to a constitutive degradation signal (CL-1) that facilitates its rapid turnover in conditions of a normal UPS. Our western blot results indicate that GFPu reporter protein was accumulated in the cortex and hippocampus, but not striatum in the APPswe/PS1dE9 AD mouse model at 4 weeks of age, which is confirmed by fluorescence microscopy and elevated levels of p53, an endogenous UPS substrate. In accordance with this, the levels of ubiquitinated proteins were elevated in the AD mouse model. These results suggest that UPS is either impaired or functionally insufficient in specific brain regions in the APPswe/PS1dE9 AD mouse model at a very young age, long before senile plaque formation and the onset of memory loss. These observations may shed new light on the pathogenesis of AD. PMID:24363091

Liu, Yanying; Hettinger, Casey L; Zhang, Dong; Rezvani, Khosrow; Wang, Xuejun; Wang, Hongmin

2014-04-01

215

A velocity-difference-separation model for car-following theory

We introduce a velocity-difference-separation model that modifies the previous models in the literature. The improvement of this new model over the previous ones lies in that it not only theoretically retains many strong points of the previous ones, but also performs more realistically than others in the dynamical evolution of congestion. Furthermore, the proposed model is investigated with analytic and

Zhi-Peng Li; Yun-Cai Liu

2006-01-01

216

'A Civil Action' 1-D Transport Game

NSDL National Science Digital Library

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

Scott Bair

217

Toward Understanding and Modeling Compressibility Effects on Velocity Gradients in Turbulence

Development of improved turbulence closure models for compressible fluid flow simulations requires better understanding of the effects of compressibility on various underlying processes of turbulence. Fundamental studies of turbulent velocity...

Suman, Sawan

2011-02-22

218

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

219

NASA Astrophysics Data System (ADS)

We investigate a bio-system composed of a shape memory alloy (SMA) immersed and subjected to heat convection in a blood vessel, affected by heart beats that create a wave motion of long wavelength. The tackled model in (2+1)-D is based on the continuity and momentum equations for the fluid phase, besides; the state of the SMA are described via previous works in the form of statistical distributions of energy for both Martensite and Austenite phases. The solution based on the reductive perturbation technique gives a thermal diffusion-like equation as a key for expressing the temperature and velocity components of the blood. In terms of two cases concerning the difference between the wave numbers in the perpendicular directions, it is found that the system's temperature increases nonlinearly from a minimum initial temperature 293 K (20 °C) up to a maximum value about 316.68 K (43.68 °C), then tends to decrease along the blood flow (anisotropy of K and L) direction. In both cases it is observed that the SMA acquires most of this temperature raising not the blood because of its conventional biological limits (37-40 °C). The range of the heart beats wave numbers characteristic for each person plays an important role in realizing phase changes in the anisotropic case leading to the formation of the hysteresis loops Martensite-Austenite-Martensite or vice versa, according to the energy variation. The entropy generation ? is investigated for the system (Blood + SMA), it predicts that along the flow direction the system gains energy convectively up to a maximum value, then reverses his tendency to gradually loosing energy passing by the equilibrium state, then the system looses energy to the surroundings by the same amount which was gained beforehand. The loss diminishes but stops before arriving to equilibrium again. For certain differences in wave numbers the system starts to store energy again after it passes by the state of equilibrium for the second time. In the curves of ? the common points of intersections can be looked for as the positions where the phase changes take place. It is observed that the effect of heat transfer is dominated over the viscous dissipation substantially; this is illustrated by the irreversibility distribution ratio ? and the Bejan number. On the other hand this is assured by the smallness of the ratio between the initial effect of shear viscosity to the initial thermal effect in the alloy (? ? 10-8). Furthermore, this allows the SMA to reveal the properties of phase change in order, for instance, to prevent the passage of large clots from reaching the lungs.

Maher Abourabia, Aly; Hassan, Kawsar Mohammad; Abo-Elghar, Eman Mohammad

2015-02-01

220

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

221

Anomalous Kinetics in Velocity Space: equations and models

Equation for anomalous diffusion in momentum space, recently obtained in the recent paper (S.A. Trigger, ArXiv 0907.2793 v1, [cond-matt. stat.-mech.], 16 July 2009) is solved for the stationary and non-stationary cases on basis of the appropriate probability transition function (PTF). Consideration of diffusion for heavy particles in a gas of the light particles can be essentially simplified due to small ratio of the masses of the particles. General equation for the distribution of the light particles, shifted in velocity space, is also derived. For the case of anomalous diffusion in momentum space the closed equation is formulated for the Fourier-component of the momentum distribution function. The effective friction and diffusion coefficients are found also for the shifted distribution. If the appropriate integrals are finite the equations derived in the paper are applicable for both cases: the PT-function with the long tails and the short range PT-functions in momentum space. In the last case the results are equivalent to the Fokker-Planck equation. Practically the new results of this paper are applicable to strongly non-equilibrium physical systems.

S. A. Trigger

2009-09-05

222

Propagation of the velocity model uncertainties to the seismic event location

NASA Astrophysics Data System (ADS)

Earthquake hypocentre locations are crucial in many domains of application (academic and industrial) as seismic event location maps are commonly used to delineate faults or fractures. The interpretation of these maps depends on location accuracy and on the reliability of the associated uncertainties. The largest contribution to location and uncertainty errors is due to the fact that the velocity model errors are usually not correctly taken into account. We propose a new Bayesian formulation that integrates properly the knowledge on the velocity model into the formulation of the probabilistic earthquake location. In this work, the velocity model uncertainties are first estimated with a Bayesian tomography of active shot data. We implement a sampling Monte Carlo type algorithm to generate velocity models distributed according to the posterior distribution. In a second step, we propagate the velocity model uncertainties to the seismic event location in a probabilistic framework. This enables to obtain more reliable hypocentre locations as well as their associated uncertainties accounting for picking and velocity model uncertainties. We illustrate the tomography results and the gain in accuracy of earthquake location for two synthetic examples and one real data case study in the context of induced microseismicity.

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

2015-01-01

223

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

NASA Technical Reports Server (NTRS)

A physical model is presented which describes convective velocities within a flat plate turbulent boundary layer. A production zone concept is used as a basis for the physical model. The production zone concept employs the idea that packets of turbulent fluid are generated near the viscous sublayer. These packets are found to be discernible from the mean motion and may move either outward from the production zone or inward depending on their circulation relative to the fluid surrounding the packet. The packets are predicted to travel with a convective velocity different from the local mean velocity throughout most of the boundary layer. The model also predicts that the convective velocities will be functions of wave number outside the production zone.

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

1973-01-01

224

Comparison of vertical velocities analyzed by a numerical model and measured by a VHF wind profiler

NASA Technical Reports Server (NTRS)

The use of wind profilers for measuring vertical velocities in the troposphere and lower stratosphere is potentially of great interest for verification of forecasts, diagnosis of mesoscale circulations, and studies of wave motions. The studies of profiler vertical velocities to date have shown that the observed patterns of ascent and subsidence are reasonable when compared to the synoptic conditions. However, difficulties arise when a direct verification of the profiler vertical winds is sought. Since no other technique can measure the vertical velocities over the same height range and with the same claimed accuracy as the profilers, direct comparisons are impossible. The only alternative is to compare the measurements to analyzed vertical velocity fields. Here, researchers compare vertical measurements made with the SOUSY VHF radar over a period of 11 days at the beginning of November 1981 to the analyzed vertical velocities produced by the European Center for Medium-range Weather Forecasting (ECMWF) model for grid points near the radar site.

Larsen, M. F.; Rottger, J.; Dennis, T. S.

1986-01-01

225

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

226

Wave-induced velocities inside a model seagrass bed

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

227

Economic analysis of the costs and benefits of regulation of chlorofluorocarbon (CFC) emissions with respect to changes in the total atmospheric ozone column abundance depends on the availability of an accurate means to predict future ozone changes as a function of CFC emissions and trends in other atmospheric species. Over about the last decade, these predictive calculations have been made chiefly with one-dimensional numerical models of the stratosphere. Although these models, run time-dependently, are substantially more computationally efficient than the more desirable multi-dimensional models, they remain expensive from the viewpoint of the requirements of cost/benefit analysis. In this note we present a numerical parameterization of the results of the LLNL one-dimensional model for total column ozone change in terms of surface emissions or abundances of the various source species. Previous versions of the LLNL model have been used in earlier studies to evaluate time-dependent scenarios of future trends in the emissions or atmospheric abundances of CFC-11, CFC-12, CFC-22, CFC-113, CCl/sub 4/, CH/sub 3/CCl/sub 3/, CO/sub 2/, CH/sub 4/, N/sub 2/O, Halon-1301 and Halon-1211. The numerical fit reported here produces calculated ozone changes within about 2% (column ozone change relative to the 1985 model atmosphere) of the current LLNL 1-D model results, for a range of scenarios and ozone changes. It therefore can approximately represent the actual 1-D model for the purposes of economic analysis of regulatory strategies. It is, however, crucial to note that the 1-D model results, and consequently this parameterization, are subject to substantial uncertainties. Future improvements in our knowledge of atmospheric photochemical kinetics and transport in the troposphere and stratosphere should be expected to modify these current results in unpredictable directions.

Connell, P.S.

1986-11-01

228

NASA Astrophysics Data System (ADS)

Economic analysis of the costs and benefits of regulation of chlorofluorocarbon (CFC) emissions with respect to changes in the total atmospheric ozone column abundance depends on the availability of an accurate means to predict future ozone changes as a function of CFC emissions and trends in other atmospheric species. For the past decade, these predictive calculations have been made chiefly with one-dimensional numerical models of the stratosphere. Although these models, run time-dependently, are substantially more computationally efficient than the more desirable multi-dimensional models, they remain expensive from the viewpoint of the requirements of cost/benefit analysis. Therefore, a numerical parameterization is presented of the results of the LLNL one-dimensional model for total column ozone change in terms of surface emissions or abundances of the various source species. Previous versions of the LLNL model have been used in earlier studies to evaluate time-dependent scenarios of future trends in the emissions or atmospheric abundances of CFC-11, CFC-12, CFC-22, CFC-113, CCl4, CH3CCl3, CO2, CH4, N2O, Halon-1301, Halon-1211. The numerical fit reported here produces calculated ozone changes within about 2% (column ozone change relative to the 1985 model atmosphere) of the current LLNL 1-D model results, for a range of scenarios and ozone changes. It therefore can approximately represent the actual 1-D model for the purposes of economic analysis of regulatory strategies. It is, however, crucial to note that the 1-D model results, and consequently this parameterization, are subject to substantial uncertainties. Future improvements in the knowledge of atmospheric photochemical kinetics and transport in the troposphere and stratosphere are expected to modify these current results.

Connell, P. S.

1986-11-01

229

NASA Astrophysics Data System (ADS)

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

Zsom, Andras; Kaltenegger, Lisa; Goldblatt, Colin

2012-11-01

230

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

231

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

232

Modeling coiled-tubing velocity strings for gas wells

Because of its ability to prolong well life, its relatively low expense, and the relative ease with which it is installed, coiled tubing has become a preferred remedial method of tubular completion for gas wells. Of course, the difficulty in procuring wireline-test data is a drawback to verifying the accuracy of the assumptions and predictions used for coiled-tubing selection. This increases the importance of the prediction-making process, and, as a result, places great emphasis on the modeling methods that are used. This paper focuses on the processes and methods for achieving sound multiphase-flow predictions by looking at the steps necessary to arrive at coiled-tubing selection. Furthermore, this paper examines the variables that serve as indicators of the viability of each tubing size, especially liquid holdup. This means that in addition to methodology, emphasis is placed on the use of a good wellbore model. The computer model discussed is in use industry wide.

Martinez, J. [Martinez (John), Houston, TX (United States); Martinez, A. [Martinez (Alec), Houston, TX (United States)

1998-02-01

233

Thermal blooming threshold computations with a Markov model of velocity turbulence

A model of velocity turbulence based on first order Markov statistics is discussed. The coherence time of the scintillations in the optical intensity of a low power beam passing through the turbulence depends inversely on the root mean square amplitude of the velocity fluctuations. The relationship between coherence time and level of velocity turbulence is independent of both the velocity correlation length and the index structure constant. Application of the Markov model to atmospheric scintillation data yields estimates for the rms amplitude of velocity turbulence consistent with convective boundary layer theory. Computations of the optical field show that velocity turbulence introduces a threshold for stimulated thermal Rayleigh scattering. The threshold can be expressed in terms of a formula relating the limit on absorbed power to the rms amplitude of the velocity fluctuations. Above threshold the instability grows approximately exponentially reaching saturation after only a few waves of phase distortion have accumulated. Below threshold the instability is suppressed but there is a slow increase in the level of index turbulence caused by incoherent heating of the propagation medium. 15 refs., 15 figs.

Viecelli, J.A.

1988-11-30

234

Seismic traveltime inversion of 3D velocity model with triangulated interfaces

NASA Astrophysics Data System (ADS)

Seismic traveltime tomographic inversion has played an important role in detecting the internal structure of the solid earth. We use a set of blocks to approximate geologically complex media that cannot be well described by layered models or cells. The geological body is described as an aggregate of arbitrarily shaped blocks, which are separated by triangulated interfaces. We can describe the media as homogenous or heterogeneous in each block. We define the velocities at the given rectangle grid points for each block, and the heterogeneous velocities in each block can be calculated by a linear interpolation algorithm. The parameters of the velocity grid positions are independent of the model parameterization, which is advantageous in the joint inversion of the velocities and the node depths of an interface. We implement a segmentally iterative ray tracer to calculate traveltimes in the 3D heterogeneous block models. The damped least squares method is employed in seismic traveltime inversion, which includes the partial derivatives of traveltime with respect to the depths of nodes in the triangulated interfaces and velocities defined in rectangular grids. The numerical tests indicate that the node depths of a triangulated interface and homogeneous velocity distributions can be well inverted in a stratified model.

Li, Fei; Xu, Tao; Zhang, Minghui; Wu, Zhenbo; Wu, Chenglong; Zhang, Zhongjie; Teng, Jiwen

2014-04-01

235

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

2015-04-01

236

Volumetric Velocity Measurements of Pulsating Flow through a Model Aneurysm

NASA Astrophysics Data System (ADS)

Volumetric 3-component velocimetry (V3V) was used to examine the flow structure inside of a scaled-up transparent urethane model of a saccular aneurysm. The model was fabricated to match the geometry of an in vivo case. Index matching was used to minimize optical distortions caused by the curved walls of the model. The model and a surrounding visualization box were integrated into a custom-built pulse duplicator system with in-line flow meter and pressure transducers. The pulsing frequency and amplitude were controlled independently to generate two flow conditions each having a non-dimensional peak Reynolds (Re) and Womersley (Wo) Number: Re = 250, Wo = 10.4 and Re = 125, Wo = 7.4. Phase-locked and instantaneous measurements of the pulsatile flow upstream, downstream, and within the aneurysm reveal significant three-dimensional features including zones of separation, recirculation, impingement, and relative inactivity. Plots and movies will be shown, and a detailed discussion of the flow and various experimental considerations will be included.

Troolin, Daniel; Amatya, Devesh; Longmire, Ellen

2010-11-01

237

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

The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption that fish swim at a constant speed regardless of the speed of flow. This paper demonstrates how the maximum distance of ascent through velocity barriers can be estimated from the swim speed-fatigue time relationship, allowing for variation in both swim speed and water velocity.

Castro-Santos, T.

2006-01-01

238

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

Wake recovery constrains the downstream spacing and density of turbines that can be deployed in turbine farms and limits the amount of energy that can be produced at a hydrokinetic energy site. This study investigates the wake recovery at the downstream of a 1:10 axial flow turbine model using a pulse-to-pulse coherent Acoustic Doppler Profiler (ADP). In addition, turbine inflow and outflow velocities were measured for calculating the thrust on the turbine. The result shows that the depth-averaged longitudinal velocity recovers to 97% of the inflow velocity at 35 turbine diameter (D) downstream of the turbine.

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

2012-01-01

239

a Modified Cellular Automaton Model for Ring Road Traffic with Velocity Guidance

NASA Astrophysics Data System (ADS)

We present a modified cellular automaton model to study the traffic flow on a signal controlled ring road with velocity guidance. The velocity guidance is such a strategy that when vehicles approach the traffic light, suggested velocities are provided for avoiding the vehicles' sharp brakes in front of red light. Simulation results show that this strategy may significantly reduce the vehicles' stopping rate and the effect size is dependent upon the traffic density, the detector position, the signal's cycle time and the obedience rate of vehicles to the guidance.

Mei, C. Q.; Huang, H. J.; Tang, T. Q.

240

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

This report documents the work conducted under the SBP to develop a shear wave and compressional wave velocity and density model specific to the WTP site. Section 2 provides detailed background information on the WTP site and its underlying geology as well as on the Seismic Boreholes Project activities leading up to the Vs and Vp measurements. In Section 3, methods employed and results obtained are documented for measurements of Vs and Vp velocities in basalts and interbeds. Section 4 provides details on velocity measurements in the sediments underlying the WTP. Borehole gravity measurements of density of the subsurface basalt and sediments are described in Section 5. Section 6 describes the analysis of data presented in section 3-5, and presents the overall velocity and density model for the WTP site.

Rohay, Alan C.; Brouns, Thomas M.

2007-06-27

241

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

Networks of neurons perform complex calculations using distributed, parallel computation, including dynamic “real-time” calculations required for motion control. The brain must combine sensory signals to estimate the motion of body parts using imperfect information from noisy neurons. Models and experiments suggest that the brain sometimes optimally minimizes the influence of noise, although it remains unclear when and precisely how neurons perform such optimal computations. To investigate, we created a model of velocity storage based on a relatively new technique–“particle filtering”–that is both distributed and parallel. It extends existing observer and Kalman filter models of vestibular processing by simulating the observer model many times in parallel with noise added. During simulation, the variance of the particles defining the estimator state is used to compute the particle filter gain. We applied our model to estimate one-dimensional angular velocity during yaw rotation, which yielded estimates for the velocity storage time constant, afferent noise, and perceptual noise that matched experimental data. We also found that the velocity storage time constant was Bayesian optimal by comparing the estimate of our particle filter with the estimate of the Kalman filter, which is optimal. The particle filter demonstrated a reduced velocity storage time constant when afferent noise increased, which mimics what is known about aminoglycoside ablation of semicircular canal hair cells. This model helps bridge the gap between parallel distributed neural computation and systems-level behavioral responses like the vestibuloocular response and perception. PMID:22514288

Merfeld, Daniel M.

2012-01-01

242

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

243

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

To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D version 1.5, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is {approx}50%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D models via location tests on a global event set with GT of 5 km or better. These events generally possess hundreds of Pn and P picks from which we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135 regardless of Pn to P ratio, with the improvement being most pronounced at higher azimuthal gaps.

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

2010-06-01

244

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

To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D version 1.5, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is {approx}50%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with {approx}400 processors. Resolution of our model is assessed using a variation of the standard checkerboard method. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D models via location tests on a global event set with GT of 5 km or better. These events generally possess hundreds of Pn and P picks from which we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the robustness and quality of relocation. The SALSA3D model reduces mislocation over standard 1D ak135 regardless of Pn to P ratio, with the improvement being most pronounced at higher azimuthal gaps.

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

2010-07-01

245

Rectangular nozzle plume velocity modeling for use in jet noise prediction

NASA Technical Reports Server (NTRS)

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

Von Glahn, U. H.

1989-01-01

246

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

247

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

248

Developing a Crustal and Upper Mantle Velocity Model for the Brazilian Northeast

NASA Astrophysics Data System (ADS)

Development of 3D models for the earth's crust and upper mantle is important for accurately predicting travel times for regional phases and to improve seismic event location. The Brazilian Northeast is a tectonically active area within stable South America and displays one of the highest levels of seismicity in Brazil, with earthquake swarms containing events up to mb 5.2. Since 2011, seismic activity is routinely monitored through the Rede Sismográfica do Nordeste (RSisNE), a permanent network supported by the national oil company PETROBRAS and consisting of 15 broadband stations with an average spacing of ~200 km. Accurate event locations are required to correctly characterize and identify seismogenic areas in the region and assess seismic hazard. Yet, no 3D model of crustal thickness and crustal and upper mantle velocity variation exists. The first step in developing such models is to refine crustal thickness and depths to major seismic velocity boundaries in the crust and improve on seismic velocity estimates for the upper mantle and crustal layers. We present recent results in crustal and uppermost mantle structure in NE Brazil that will contribute to the development of a 3D model of velocity variation. Our approach has consisted of: (i) computing receiver functions to obtain point estimates of crustal thickness and Vp/Vs ratio and (ii) jointly inverting receiver functions and surface-wave dispersion velocities from an independent tomography study to obtain S-velocity profiles at each station. This approach has been used at all the broadband stations of the monitoring network plus 15 temporary, short-period stations that reduced the inter-station spacing to ~100 km. We expect our contributions will provide the basis to produce full 3D velocity models for the Brazilian Northeast and help determine accurate locations for seismic events in the region.

Julia, J.; Nascimento, R.

2013-05-01

249

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

Shearer, Peter

250

Integrated Modeling of 3D Velocity Structure Beneath the Tokyo Metropolitan Area

We are carrying out integrated modeling of 3D velocity structure in the Tokyo metropolitan area under the Special Project for Earthquake Disaster Mitigation in Urban Area (Daidaitoku Project) in order to upgrade strong ground motion prediction. Several models have been proposed using refraction\\/reflection, borehole, microtremor, and gravity data by Koketsu and Higashi (1992), Yamanaka and Yamada (2002), Afnimar et al.

Y. Tanaka; K. Koketsu; H. Miyake; T. Furumura; H. Sato; N. Hirata; H. Suzuki; T. Masuda

2005-01-01

251

T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4) contains the canonical phosphoprotein phosphatase 1 (PPP1) binding motif, composed by the amino acid sequence RVSF. We identified and validated the binding of TCTEX1D4 to PPP1 and demonstrated that indeed this protein is a novel PPP1 interacting protein. Analyses of twenty-one mammalian species available in public databases and seven Lagomorpha sequences obtained in this work showed that the PPP1 binding motif 90RVSF93 is present in all of them and is flanked by a palindromic sequence, PLGS, except in three species of pikas (Ochotona princeps, O. dauurica and O. pusilla). Furthermore, for the Ochotona species an extra glycosylation site, motif 96NLS98, and the loss of the palindromic sequence were observed. Comparison with other lagomorphs suggests that this event happened before the Ochotona radiation. The dN/dS for the sequence region comprising the PPP1 binding motif and the flanking palindrome highly supports the hypothesis that for Ochotona species this region has been evolving under positive selection. In addition, mutational screening shows that the ability of pikas TCTEX1D4 to bind to PPP1 is maintained, although the PPP1 binding motif is disrupted, and the N- and C-terminal surrounding residues are also abrogated. These observations suggest pika as an ideal model to study novel PPP1 complexes regulatory mechanisms. PMID:24130861

Korrodi-Gregório, Luís; Margarida Lopes, Ana; Esteves, Sara L. C.; Afonso, Sandra; Lemos de Matos, Ana; Lissovsky, Andrey A.; da Cruz e Silva, Odete A. B.; Esteves, Pedro José; Fardilha, Margarida

2013-01-01

252

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

253

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

254

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

255

Quasilinear model for energetic particle diffusion in radial and velocity space

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

256

a Dynamical Model with Next-Nearest Interaction in Relative Velocity

NASA Astrophysics Data System (ADS)

By introducing the velocity difference between the preceding car and the car before the preceding one into the optimal velocity model (OVM), we present an extended dynamical model which takes into account the next-nearest-neighbor interaction in relative velocity. The stability condition of this model is derived by considering a small perturbation around the uniform flow solution and the validity of our theoretical analysis is also confirmed by direct simulations. The analytic and simulation results indicate that traffic congestion is suppressed efficiently by incorporating the effect of new consideration. Moreover, the effect of the new consideration is investigated by numerical simulation. In particular, the jamming flow, the current-density relation, and the propagation speed of small disturbance are examined in detail by varying various values of the parameter.

Li, Zhipeng; Liu, Yuncai; Liu, Fuqiang

257

NASA Astrophysics Data System (ADS)

An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6oC, a maximum of 20.5oC and a minimum of -54.3oC) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal regime well. Detailed temperature comparison suggests that the 1-D thermal diffusion model results closely approximate the measured temperature at all depths with the average square root of the mean squared error (SRMSE) of 0.15oC; a linear correlation between modeled and measured temperatures yields an average R2 value of 0.9997. Prominent seasonal temperature variations diminish with depth, and it equilibrates to mean annual temperature at about 21.5 m depth. The amount of heat generated/consumed by ice condensation/sublimation is insufficient to significantly impact the thermal regime.

Liu, L.; Sletten, R. S.; Hallet, B.; Waddington, E. D.; Wood, S. E.

2013-12-01

258

NASA Astrophysics Data System (ADS)

This work focuses on the numerical treatment of 1D flow in channels with arbitrary shape using energy balanced arguments. The system of equations is defined using the mass and momentum conservation equations, allowing the resolution of hydraulic jumps where energy conservation arguments are not valid. When necessary, conservation of mechanical energy takes part actively in the numerical scheme when evaluating the source terms. The numerical scheme is based on an augmented Roe solver that involves the presence of source terms by adding an extra stationary wave. The characteristics of the numerical scheme include the energy balanced property, and being only first order accurate in time and space, leads to exact numerical solutions for steady solutions with independence of the grid refinement in channels with general geometries. Riemann problems considered here involve non-prismatic channels, bed variations and the resonance regime, including the limiting situation when the Riemann data belong to the resonance hypersurface. Numerical results point out that the finite volume numerical scheme with nonconservative terms presented here, converges to the exact solution. The well balanced property is ensured, as it is a particular case of the energy balanced property in cases of quiescent equilibrium.

Murillo, J.; García-Navarro, P.

2014-03-01

259

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

not account for significant spatial variations in the near-surface velocity. As a result, the inverse model accounts for false time-structure as great as 180 ms in seismic-reflection data shot betiveen 1966 and 1983. The model also indicates that there have... at velocity-survey locations during this time perh&d. Afore recent crater-table data consist of hydr?graph plot~ supplied by I'enneco %Vest, formerly the Kern County Land Company. These plots show water-table depths measured semi-annually during the period...

Ferry, James Gerard

1987-01-01

260

A universal framework for modelling measured velocity in laser vibrometry with applications

NASA Astrophysics Data System (ADS)

This paper presents a novel, universally applicable framework for modelling measured velocity in laser vibrometry systems. The framework is introduced generically before demonstration of its application to three scanning vibrometer systems, each configured to measure vibration of a tracked point on a rotating target. The novelty in this vectorial framework lies in the combination of its elements, which include vector descriptions of target velocity, optical device velocity at deflection points, laser beam orientations, incorporating reflection and refraction, and surface normals. Initial alignment and a full set of inevitable misalignments are incorporated by the modification of position vectors and the use of rotation matrices. Inclusion of components of measured velocity associated with moving optical devices is an important feature of the framework. The models derived and their validation against published data demonstrate how this versatile framework can be applied to any optical configuration measuring target motions with any level of complexity. The individual models are explored extensively and quantitatively through simulation. Small but inevitable misalignments are shown to generate measurable low order velocity components and their effects on the sensitivities to in-plane and out-of-plane components of target vibration are quantified.

Rothberg, Steve J.; Tirabassi, Mario

2012-01-01

261

NASA Astrophysics Data System (ADS)

Measuring the volume weighted velocity power spectrum suffers from a severe systematic error due to imperfect sampling of the velocity field from the inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density 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 ˜12 % underestimation of the velocity power spectrum at k =0.1 h /Mpc for samples with n¯ P=6 ×10-3 (Mpc /h )-3 . This systematic underestimation increases with decreasing n¯P and increasing k . Its dependence on the intrinsic LSS fluctuations is also robustly detected. (2) All of these findings are expected based upon our theoretical modeling in paper I [P. Zhang, Y. Zheng, and Y. Jing, Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling, arXiv:1405.7125.]. In particular, the leading order theoretical approximation agrees quantitatively well with the simulation result for n¯ P?6 ×10-4 (Mpc /h )-3 . Furthermore, we provide an ansatz to take high order terms into account. It improves the model accuracy to ?1 % at k ?0.1 h /Mpc over 3 orders of magnitude in n¯P and over typical LSS clustering from z =0 to z =2 . (3) The sampling artifact is determined by the deflection D field, which is straightforwardly available in both simulations and data of galaxy velocity. Hence the sampling artifact in the velocity power spectrum measurement can be self-calibrated within our framework. By applying such self-calibration in simulations, it is promising to determine the real large scale velocity bias of 1013M? halos with ˜1 % accuracy, and that of lower mass halos with better accuracy. (4) In contrast to suppressing the velocity power spectrum at large scale, the sampling artifact causes an overestimation of the velocity dispersion. We prove that a correlation between the signal field (v ) and the sampling field (D ) is a major cause. This complexity, among other issues, is carefully investigated to further improve understanding of the sampling artifact.

Zheng, Yi; Zhang, Pengjie; Jing, Yipeng

2015-02-01

262

NASA Astrophysics Data System (ADS)

We demonstrate the ability of SALSA3D (SAndia LoS Alamos 3D) version 2.1, a global 3D P-wave velocity model of the Earth's crust and mantle, to reduce mislocations compared to those derived from standard 1D and 2-2.5D models, for a set of realizations using only IMS stations - an example of a sparse network whose locations depend heavily on the velocity model employed - and a carefully chosen group of globally-distributed ground truth (GT) events. Our model is derived from the latest version of the GT catalog of P/Pn travel-time picks assembled by Los Alamos National Laboratory. The model uses the GeoTess triangular tessellation system described by Ballard et al. (2009; www.sandia.gov/geotess), which incorporates variable resolution both laterally and radially. For our starting model, we use a simplified version of the NNSA Unified model in Eurasia and the Crust 2.0 model elsewhere. Damping reduces velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness via progressive grid refinement using the diagonal of the model resolution matrix to determine where the data warrant such a refinement. Our approach provides more consistent and continuous areas of refinement, producing a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework of ~400 processors. The global IMS network consists of approximately 150 primary and auxiliary stations, forming a pre-defined, sparse network with which to locate seismic events. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D and 2/2.5D models via location tests on a global event set with GT of 5 km or better. Using Pn and P picks from IMS stations only, we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the accuracy and precision of relocation. We test using the full 3D covariance matrix of the current model to calculate path-dependent travel time uncertainty, rather than applying standard, 1D, distance-dependent uncertainty. SALSA3D reduces mislocation over the standard 1D ak135 model regardless of Pn to P ratio, with the most pronounced improvement at higher azimuthal gaps. SALSA3D also reduces mislocation compared to the combined RSTT/ak135 model (2.5D - RSTT for regional phases), with minimal improvement over RSTT when only regional Pn phases are used to compute locations.

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

2013-12-01

263

Anisotropic shear-wave velocity structure of the Earth's mantle: A global model

NASA Astrophysics Data System (ADS)

We combine a new, large data set of surface wave phase anomalies, long-period waveforms, and body wave travel times to construct a three-dimensional model of the anisotropic shear wave velocity in the Earth's mantle. Our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model, simultaneous inversion for velocity and anisotropy, as well as discontinuity topographies, and implementation of nonlinear crustal corrections for waveforms. A comparison of our new three-dimensional model, S362ANI, with two other models derived from comparable data sets but using different techniques reveals persistent features: (1) strong, ˜200-km-thick, high-velocity anomalies beneath cratons, likely representing the continental lithosphere, underlain by weaker, fast anomalies extending below 250 km, which may represent continental roots, (2) weak velocity heterogeneity between 250 and 400 km depths, (3) fast anomalies extending horizontally up to 2000-3000 km in the mantle transition zone beneath subduction zones, (4) lack of strong long-wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle-lower mantle boundary, and (5) slow-velocity superplumes beneath the Pacific and Africa. The shear wave radial anisotropy is strongest at 120 km depth, in particular beneath the central Pacific. Lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths. Tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle.

Kustowski, B.; EkströM, G.; Dziewo?Ski, A. M.

2008-06-01

264

NASA Technical Reports Server (NTRS)

Thermal and nonthermal O(1D) number density profiles are calculated. The two populations are assumed to be coupled by a thermalization cross-section which determines the loss and production in the nonthermal and thermal populations, respectively. The sources, sinks and transport of the two populations are used to model volume emission rate profiles at 6300 A. The 6300 A brightness measured by the Visible Airglow Experiment is then used to establish the presence of the nonthermal population and to determine the thermalization cross-section.

Schmitt, G. A.; Abreu, V. J.; Hays, P. B.

1981-01-01

265

A Reference Crustal and Plate-Boundary Velocity Model of Japan

NASA Astrophysics Data System (ADS)

The study of velocity structure using earthquake data has been remarkably progressed by development of seismic observation networks, improvement of the methodology, and increase in processing power. Recent studies on 3D velocity structures have produced tomographic images with resolution of a few kilometers (e.g., Matsubara et al., 2005; Nakamichi et al., 2007). In addition to these traveltime analyses, waveform studies such as receiver function analyses have been developed to image the configuration of continental Moho and oceanic plate boundaries (e.g., Yamauchi et al., 2003; Shiomi et al., 2004). Reflection and refraction surveys with controled sources have also been providing information on 2D and 3D velocity structures (e.g., Sato et al., 2005; Special Project for Earthquake Disaster Mitigation in Urban Areas). Thus, plenty of structural property models exist over the Japan islands, but the validity of an individual model is confined to its study area. Therefore, it is essential to build a reference crustal and plate-boundary velocity model for the whole Japan by combining them all together. If this sort of reference velocity model over the Japan islands is available under a unified criterion, it will be valuable for many fields of seismology and Earth sciences. We here construct a reference crustal and plate-boundary velocity model of Japan by integrating 2D models from seismic profiling and receiver functions, 3D models of seismic tomography, and other geophysical data such as gravity anomalies. The goal of this study is to construct a 3D laterally heterogeneous seismic velocity structure model, which clarifies the topography of the Conrad and Moho discontinuities and shapes of the oceanic plates, like the SCEC Unified Velocity Model (e.g., Magistrale et al., 1996). We first make a preliminary Japan model by compiling information on the topography of the Conrad and Moho discontinuities and subducting plates. To this end, we collect 2D seismic velocity models obtained by seismic profiling of reflection/refraction surveys and receiver function analyses, and then integrate them to a 3D velocity model, using complementary information on 3D structures, such as 3D boundary shapes obtained by travel time and gravity anomaly analyses. At this stage, maintaining local structural continuity is a key challenge in the process. We also have to clarify major tectonic features such as the Median Tectonic Line and the Itoigawa-Shizuoka Tectonic Line, and consider the continuity between land-based and offshore models. The integrated 3D reference model will improve the reliability of strong ground motion prediction. Improvements will be the most critical for large-scale ground motion simulations for plate-boundary earthquakes in the Nankai and Tokai regions, which can cause strong shaking in major metropolitan areas of Japan. So, this modeling should be one of the most essential parts of earthquake damage mitigation in Japan.

Ishise, M.; Koketsu, K.; Miyake, H.

2007-12-01

266

NASA Technical Reports Server (NTRS)

Velocity-profile, pitot-pressure, and supplemental probe measurements were made at the nozzle exist of an expansion tunnel (a modification to the Langley pilot model expansion tube) for a nozzle net condition of a nitrogen test sample with a velocity of 4.5 km/sec and a density 0.005 times the density of nitrogen at standard conditions, both with the nozzle initially immersed in a helium atmosphere and with the nozzle initially evacuated. The purpose of the report is to present the results of these measurements and some of the physical properties of the nitrogen test sample which can be inferred from the measured results. The main conclusions reached are that: the velocity profiles differ for two nozzle conditions; regions of the flow field can be found where the velocity is uniform to within 5 percent and constant for several hundred microseconds; the velocity of the nitrogen test sample is reduced due to passage through the nozzle; and the velocity profiles do not significantly reflect the large variations which occur in the inferred density profiles.

Friesen, W. J.; Moore, J. A.

1973-01-01

267

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

268

Line-of-sight velocity in a semiempirical model of a disappearing granule

NASA Astrophysics Data System (ADS)

The behaviour of the line-of-sight velocity in the centre of a disappearing granule is analyzed using an inversion method applied to a time-series of spectra containing the Fe I 522.5 nm, 557.6 nm and 557.7 nm lines. The temporal evolution of the line-of-sight velocity vLOS is presented in the form of the functional dependence of vLOS(log?5, t) on the optical depth ?5 at 500 nm and time t. An oscillatory behaviour is found in the velocity stratification with nearly constant phase through the photosphere. The amplitude of variations increases from log?5 = -0.3 to log?5 = -2.5 reaching a maximum of ~1.2 km s-1. A zero velocity layer is detected in every instantaneous model of the velocity stratification. The results suggest, that the zero velocity may occur in a considerable range of the optical depths from log?5 ~ -2 to log?5 ~ -3.5.

Koza, J.; Bellot Rubio, L. R.; Ku?era, A.; Hanslmeier, A.; Rybák, J.; Wöhl, H.

2002-12-01

269

NASA Astrophysics Data System (ADS)

Soil develops as a result of interacting processes, many of which have been described in more or less detailed models. A key challenge in developing predictive models of soil function is to integrate processes that operate across a wide range of temporal and spatial scales. Many soil functions could be classified as "emergent", since they result from the interaction of subsystems. For example, soil organic matter (SOM) dynamics are commonly considered in relation to carbon storage, but can have profound effects on soil hydraulic properties that are conventionally considered to be static. Carbon fixed by plants enters the soil as litterfall, root turnover or via mycorrhizae. Plants need water and nutrients to grow, and an expanding root system provides access to a larger volume of soil for uptake of water and nutrients. Roots also provide organic exudates, such as oxalate, which increase nutrient availability. Carbon inputs are transformed at various rates into soil biota, CO2, and more persistent forms of organic matter. The SOM is partly taken up into soil aggregates of variable sizes, which slows down degradation. Water availability is an important factor as both plant growth and SOM degradation can be limited by shortage of water. Water flow is the main driver for transport of nutrients and other solutes. The flow of water in turn is influenced by the presence of SOM as this influences soil water retention and hydraulic conductivity. Towards the top of the unsaturated zone, bioturbation by the soil fauna transports both solid material and solutes. Weathering rates of minerals determine the availability of many nutrients and are in turn dependent on parameters such as pH, water content, CO2 pressure and oxalate concentration. Chemical reactions between solutes, dissolution and precipitation, and exchange on adsorption sites further influence solute concentrations. Within the FP7 SoilTrEC project, we developed a model that incorporates all of these processes, to explore the complex interactions involved in soil development and change. We were unable to identify appropriately-detailed existing models for plant productivity and for the dynamics of soil aggregation and porosity, and so developed the PROSUM and CAST models, respectively, to simulate these subsystems. Moreover, we applied the BRNS generator to obtain a chemical equilibrium model. These were combined with HYDRUS-1D (water and solute transport), a weathering model (derived from the SAFE model) and a simple bioturbation model. The model includes several feedbacks, such as the effect of soil organic matter on water retention and hydraulic conductivity. We encountered several important challenges when building the integrated model. First, a mechanism was developed that initiates the execution of a single time step for an individual sub-model and accounts for the relevant mass transfers between sub-models. This allows for different and sometimes variable time step duration in the submodels. Secondly, we removed duplicated processes and identified and included relevant solute production terms that had been neglected. The model is being tested against datasets obtained from several Soil Critical Zone Observatories in Europe. This contribution focuses on the design strategy for the model.

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

2014-05-01

270

of these terms is studied for proper inclusion in the model. Furthermore, it is evident from the history of catalyst modeling that precise reaction rate expressions are needed for accurate predictions. In order to determine the correct reaction rate expression...

Loya, Sudarshan Kedarnath

2011-12-31

271

NASA Astrophysics Data System (ADS)

Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenario's creating high energy tails. This paper discusses an extension TOMCAT-U of the 1D TOMCAT tokamak plasma wave equation solver (Van Eester and Koch 1998 Plasma Phys. Control. Fusion 40 1949) to arbitrary harmonics and arbitrary wavelengths while only keeping leading order terms in equilibrium variation terms. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response that is suitable for numerical application. This choice of independent variable yields intuitive expressions involving the Kennel-Engelmann operator which can directly be linked to the corresponding expressions in the RF diffusion operator appearing in the Fokker-Planck equation. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integrodifferential approach that retains all finite Larmor radius effects is proposed. To keep the required computation time for this generalized description reasonable, tabulation of integrals is intensively used. Although the accent is on the presentation of the upgraded formalism as well as the adopted recursions and tabulations, a few examples are provided to illustrate the potential of the new wave code that relies on these tabulations.

Van Eester, Dirk; Lerche, Ernesto

2013-05-01

272

A one-dimensional model was developed for the forced flow-thermal gradient chemical vapor infiltration of carbon\\/carbon composites. The infiltration time predicted by the model agreed very well with experiments, where propylene and propane were used as the hydrocarbon source. The model was also validated by interrupting the infiltration and comparing predicted with observed densities.

S. Vaidyaraman; W. J. Lackey; P. K. Agrawal; T. L. Starr

1996-01-01

273

The properties of the surface wavefield at Kilauea Volcano are analysed using data from small-aperture arrays of short-period seismometers deployed in and around the Kilauea caldera. Tremor recordings were obtained during two Japan-US cooperative experiments conducted in 1996 and 1997. The seismometers were deployed in three semi-circular arrays with apertures of 300, 300 and 400 m, and a linear array with length of 1680 m. Data are analysed using a spatio-temporal correlation technique well suited for the study of the stationary stochastic wavefields of Rayleigh and Love waves associated with volcanic activity and scattering sources distributed in and around the summit caldera. Spatial autocorrelation coefficients are obtained as a function of frequency and are inverted for the dispersion characteristics of Rayleigh and Love waves using a grid search that seeks phase velocities for which the L-2 norm between data and forward modelling operators is minimized. Within the caldera, the phase velocities of Rayleigh waves range from 1400 to 1800 m s-1 at 1 Hz down to 300-400 m s-1 at 10 Hz, and the phase velocities of Love waves range from 2600 to 400 m s-1 within the same frequency band. Outside the caldera, Rayleigh wave velocities range from 1800 to 1600 m s-1 at 1 Hz down to 260-360 m s-1 at 10 Hz, and Love wave velocities range from 600 to 150 m s-1 within the same frequency band. The dispersion curves are inverted for velocity structure beneath each array, assuming these dispersions represent the fundamental modes of Rayleigh and Love waves. The velocity structures observed at different array sites are consistent with results from a recent 3-D traveltime tomography of the caldera region, and point to a marked velocity discontinuity associated with the southern caldera boundary.

Saccorotti, G.; Chouet, B.; Dawson, P.

2003-01-01

274

Models of Seismic Velocity and Anisotropy For the Great Basin, Nevada

NASA Astrophysics Data System (ADS)

The Great Basin, which lies in the northern Basin and Range Province in the western United States, has a complex deformation history and is currently characterized by significant crustal extension. The region is marked by a semi-circular shear-wave splitting pattern around a weak azimuthal anisotropy zone in central Nevada. This observation led to various interpretations, including the presence of an upwelling, toroidal mantle flow around a slab, and lithospheric drip. Recent research, however, showed that a similar signal of anisotropy can be found in Rayleigh wave phase velocity maps at periods of 16 s and 18 s around a region of locally reduced phase velocities (Beghein, et al., EPSL, 2010). Since surface waves at these periods mostly sample the crust, this suggests that at least part of the observed shear-wave splitting pattern has a crustal origin. In the present study, we employ a forward modeling approach to model the three-dimensional (3-D) variations in shear-wave velocities and azimuthal anisotropy in this area. We first use a fully non-linear forward modeling approach based on the Neighbourhood Algorithm (Sambridge, 1999) to model the isotropic velocity variations. This method enables us to quantitatively assess parameter trade-offs and uncertainties. We use prior constraints for the Moho depth based on receiver function results (Miller and Levander, 2009), but we allow it vary by up to 3%. Our results display uniform S-wave velocities of 3.6 km/s in the crust with a standard deviation of ~0.3 km/s. We also find the presence of a mantle lid of ~45 km thickness, with S-wave velocities up to 4.9 km/s (+/- 0.2 km/s). The posterior Moho depth roughly follows the prior model, and we find that the locally thicker crust located in the southwestern part of the region is sufficient to explain the reduction in phase velocities seen at short periods at the center of the circular anisotropy pattern. Velocities are lower down to at least 100 km depth with Vs=3.9 km/s (+/- 0.3 km/s). We see significant lateral variations in velocity below that depth, accompanied by large uncertainties, which makes the interpretation of the results at those depths difficult. Unlike results from P-wave tomography, we do not observe a faster velocity region in the central Great Basin. This implies that it may be located at larger depths than previously estimated. We also employ the Neighbourhood Algorithm to constrain 3-D variations in azimuthal anisotropy. Our preliminary models display up to 6% Vsv anisotropy in the crust. The uncertainties are relatively small and there are little trade-offs with anisotropy at larger depths. In the upper mantle, our models have a stronger dependence on the regularization and thus have larger uncertainties. Despite the small uncertainties in our crustal anisotropy models, however, the shortest period phase velocities are the most difficult to fit. This suggests that our 16 s and 8 s data are not compatible with the longer period phase velocities, possibly because due to scattering effects that may have affected the measurements. Nevertheless, our most reliable result, which fits the short periods data well, is the amount of crustal anisotropy in central Nevada, where we find ~3% azimuthal anisotropy. This contributes to 3-4 s of shear-wave splitting delay times.

Beghein, C.

2010-12-01

275

An Empirical Model of Human Aspiration in Low-Velocity Air Using CFD Investigations.

Computational fluid dynamics (CFD) modeling was performed to investigate the aspiration efficiency of the human head in low velocities to examine whether the current inhaled particulate mass (IPM) sampling criterion matches the aspiration efficiency of an inhaling human in airflows common to worker exposures. Data from both mouth and nose inhalation, averaged to assess omnidirectional aspiration efficiencies, were compiled and used to generate a unifying model to relate particle size to aspiration efficiency of the human head. Multiple linear regression was used to generate an empirical model to estimate human aspiration efficiency and included particle size as well as breathing and freestream velocities as dependent variables. A new set of simulated mouth and nose breathing aspiration efficiencies was generated and used to test the fit of empirical models. Further, empirical relationships between test conditions and CFD estimates of aspiration were compared to experimental data from mannequin studies, including both calm-air and ultra-low velocity experiments. While a linear relationship between particle size and aspiration is reported in calm air studies, the CFD simulations identified a more reasonable fit using the square of particle aerodynamic diameter, which better addressed the shape of the efficiency curve's decline toward zero for large particles. The ultimate goal of this work was to develop an empirical model that incorporates real-world variations in critical factors associated with particle aspiration to inform low-velocity modifications to the inhalable particle sampling criterion. PMID:25438035

Anthony, T Renée; Anderson, Kimberly R

2015-04-01

276

Model for toroidal velocity in H-mode plasmas in the presence of internal transport barriers

NASA Astrophysics Data System (ADS)

A model for predicting toroidal velocity in H-mode plasmas in the presence of internal transport barriers (ITBs) is developed using an empirical approach. In this model, it is assumed that the toroidal velocity is directly proportional to the local ion temperature. This model is implemented in the BALDUR integrated predictive modelling code so that simulations of ITB plasmas can be carried out self-consistently. In these simulations, a combination of a semi-empirical mixed Bohm/gyro-Bohm (mixed B/gB) core transport model that includes ITB effects and NCLASS neoclassical transport is used to compute a core transport. The boundary is taken to be at the top of the pedestal, where the pedestal values are described using a theory-based pedestal model based on a combination of magnetic and flow shear stabilization pedestal width scaling and an infinite-n ballooning pressure gradient model. The combination of the mixed B/gB core transport model with ITB effects, together with the pedestal and the toroidal velocity models, is used to simulate the time evolution of plasma current, temperature and density profiles of 10 JET optimized shear discharges. It is found that the simulations can reproduce an ITB formation in these discharges. Statistical analyses including root mean square error (RMSE) and offset are used to quantify the agreement. It is found that the averaged RMSE and offset among these discharges are about 24.59% and -0.14%, respectively.

Chatthong, B.; Onjun, T.; Singhsomroje, W.

2010-06-01

277

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 accreted Paleozoic and Mesozoic island arc assemblage underlying southern Vancouver Island in the Cascadia forearc are imaged at some locations with higher than average lower crustal velocities of 6.5-7.2 km/s, similar to observations at other island arc terranes. The mafic Eocene Crescent terrane, thrust landward beneath southern Vancouver Island, exhibits crustal velocities in the range of 6.0-6.7 km/s and is inferred to extend to a depth of more than 20 km. The Cenozoic Olympic Subduction Complex, an accretionary prism thrust beneath the Crescent terrane in the Olympic Peninsula, is imaged as a low-velocity wedge to depths of at least 20 km. Three zones with velocities of 7.0-7.5 km/s, inferred to be mafic and/or ultramafic units, lie above the subducting Juan de Fuca plate at depths of 25-35 km. The forearc upper mantle wedge beneath southeastern Vancouver Island and the Strait of Georgia exhibits low velocities of 7.2-7.5 km/s, inferred to correspond to ???20% serpentinization of mantle peridotites, and consistent with similar observations in other warm subduction zones. Estimated dip of the Juan de Fuca plate beneath southern Vancouver Island is ???11??, 16??, and 27?? at depths of 30, 40, and 50 km, respectively. Copyright 2005 by the American Geophysical Union.

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

2005-01-01

278

NASA Astrophysics Data System (ADS)

As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes recorded on broadband stations. Satisfactory prediction of ground motions from these events will provide hope for accurate modeling of future scenario earthquakes. Simulations were performed on large parallel computer(s) with a new elastic finite difference code developed at LLNL. We simulated broadband ground motions (0-0.25 Hz) for several moderate (magnitude 3.5-5.0) earthquakes in the region observed at Berkeley Digital Seismic Network (BDSN) broadband stations. These events are well located and can be modeled with simple point moment tensor sources (taken from the Berkeley Seismological Laboratory catalog), helping to isolate the effects of structure on the waveforms. These data sample the region's diverse tectonic structures, such as the bay muds, sedimentary basins and hard rock complexes. Preliminary results indicate that the simulations reproduce many important features in the data. For example, observed long duration surface waves are often predicted for complex paths (traveling across contrasting structures) and through sedimentary basins. Excellent waveform fits were frequently obtained for long-period comparisons (0.02-0.1) and good fits were often obtained for shorter periods. We will attempt higher frequency simulations to test the ability of the model to match the high frequency response. Finally, we performed large scenario earthquake simulations for the Hayward Fault. These simulations predict large amplifications across the Santa Clara and San Ramon/Livermore Valley sedimentary basins and with the Sacramento/San Joaquin River Delta.

Rodgers, A.; Petersson, A.; Nilsson, S.; Sjogreen, B.; McCandless, K.

2006-12-01

279

Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools such as SPICE [1] can be used to analyze these threats, and typically rely on compact models for individual electrical components such as transistors and diodes. Compact models consist of a handful of differential and/or algebraic equations, and are derived by making simplifying assumptions to any of the many semiconductor transport equations. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of qualitative approximation, rather than mathematically correct solutions to the ambipolar diffusion equation. A practical consequence of this inaccuracy is that a given model calibration is trustworthy over only a narrow range of operating conditions. This report describes work to produce improved compact models for photocurrent. Specifically, an analytic model is developed for epitaxial diode structures that have a highly doped subcollector. The analytic model is compared with both numerical TCAD calculations, as well as the compact model described in reference [2]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the compact model from reference [2].

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

2012-04-01

280

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

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

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

2013-07-15

281

This is a 1D model of an active magnetic regenerative refrigerator (AMRR) that was developed in MATLAB. The model uses cycle inputs such as the fluid mass flow and magnetic field profiles, fluid define the number of time steps in each cycle and the number of nodes in the axial direction

Wisconsin at Madison, University of

282

Simulation results for the velocity autocorrelation function in a bond percolation model

NASA Astrophysics Data System (ADS)

Computer simulation results for the velocity autocorrelation function in a two-dimensional bond percolation model are presented, both below and above threshold. Comparison with the effective medium approximation shows an excellent agreement for short and intermediate times, whereas significant discrepancies appear in the long-time region.

Brey, J. J.; Ordóñez, J. Gómez; Santos, A.

1989-03-01

283

The mean velocity of two-state models of molecular motor

The motion of molecular motor is essential to the biophysical functioning of living cells. In principle, this motion can be regraded as a multiple chemical states process. In which, the molecular motor can jump between different chemical states, and in each chemical state, the motor moves forward or backward in a corresponding potential. So, mathematically, the motion of molecular motor can be described by several coupled one-dimensional hopping models or by several coupled Fokker-Planck equations. To know the basic properties of molecular motor, in this paper, we will give detailed analysis about the simplest cases: in which there are only two chemical states. Actually, many of the existing models, such as the flashing ratchet model, can be regarded as a two-state model. From the explicit expression of the mean velocity, we find that the mean velocity of molecular motor might be nonzero even if the potential in each state is periodic, which means that there is no energy input to the molecular motor in each of the two states. At the same time, the mean velocity might be zero even if there is energy input to the molecular motor. Generally, the velocity of molecular motor depends not only on the potentials (or corresponding forward and backward transition rates) in the two states, but also on the transition rates between the two chemical states.

Yunxin Zhang

2011-08-09

284

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

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

285

Finite element modelling of low velocity impact of composite sandwich panels

This paper outlines a finite element procedure for predicting the behaviour under low velocity impact of sandwich panels consisting of brittle composite skins supported by a ductile core. The modelling of the impact requires a dynamic analysis that can also handle non-linearities caused by large deflections, plastic deformation of the core and in-plane degradation of the composite skins. Metal honeycomb,

T Besant; G. A. O Davies; D Hitchings

2001-01-01

286

Modeling the Effect of Varying Swim Speeds on Fish Passage through Velocity Barriers

The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption

Theodore Castro-Santos

2006-01-01

287

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

288

Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities

Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.

Lee, Myung W.

2008-01-01

289

Hyperbolic trigonometry in the Einstein relativistic velocity model of hyperbolic geometry

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

A. A. Ungar

2000-01-01

290

Modeling the Coupled Effects of Pore Space Geometry and Velocity on Colloid Transport and Retention

Technology Transfer Automated Retrieval System (TEKTRAN)

Recent experimental and theoretical work has demonstrated that pore space geometry and hydrodynamics can play an important role in colloid retention under unfavorable attachment conditions. Computer models that only consider the average pore-water velocity and a single attachment rate coefficient a...

291

Technology Transfer Automated Retrieval System (TEKTRAN)

Watershed modeling is a key component of watershed management that involves the simulation of hydrological and fluvial processes for predicting flow and sediment transport within a watershed. For practical purposes, most numerical models have been developed to simulate either runoff and soil erosion...

292

NASA Technical Reports Server (NTRS)

1. A generalized three-dimensional state space model of visual vestibular interaction was developed. Matrix and dynamical system operators associated with inputs from the semicircular canals, otolith velocity estimator, and the visual system have been incorporated into the model, which focus on their relationship to the velocity storage integrator. 2. A relationship was postulated between the eigenvalues and the direction of the eigenvectors of the system matrix and the orientation of the spatial vertical. It was assumed that the system matrix for a tilted position was a composition of two linear transformations of the system matrix for the upright position. One transformation modifies the eigenvalues of the system matrix, whereas another rotates the eigenvectors of the system matrix. The pitch and roll eigenvectors rotate with the head, whereas the yaw axis eigenvector remains approximately spatially invariant. 3. Based on the three-dimensional model, a computational procedure was formulated to identify the eigenvalues and eigenvectors of the system matrix with the use of a modification of the marquardt algorithm. With the use of data obtained from a monkey, it was shown that the three-dimensional behavior of velocity storage cannot be predicted solely in terms of its time constants, i.e., the inverse of its eigenvalues. With the use of the same eigenvalues the data could either be fit or not fit, depending on the eigenvector directions. Therefore, it is necessary to specify eigenvector directions when characterizing velocity storage in three dimensions. 4. Parameters found with the use of the Marquardt algorithm were incorporated into the model. Diagonal matrices in a head coordinate frame were introduced for coupling the visual system to the integrator and to the direct optokinetic pathway. Simulations of optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) were run. The model predicted the behavior of yaw and pitch OKN and OKAN when the animal is upright. It also predicted the cross-coupling in the side down position. The trajectories in velocity space were also accurately simulated. 5. One of the predictions of the model is that when the stimulus direction is along an eigenvector, the trajectory in velocity space is a straight line. Using the "spectral width" of the residuals from a straight line sequence during OKAN, we developed a methodology to estimate how close the OKAN decay was to an eigenvector trajectory. 6. Thus we have developed a model-based approach for studying and interpreting the response characteristics of velocity storage in three dimensions.(ABSTRACT TRUNCATED AT 400 WORDS).

Raphan, T.; Sturm, D.; Cohen, B. (Principal Investigator)

1991-01-01

293

Local Mass Conservation and Velocity Splitting In Pv-conserving Balanced Models

NASA Astrophysics Data System (ADS)

The most accurate potential-vorticity-conserving balanced models (PVBMs) do not conserve mass locally. A PVBM, in the sense understood here, has two defining prop- erties. First, a PVBM is a balanced model formulated in terms of a unique velocity field v , which advects the model's potential vorticity (PV) and which is obtainable by PV inversion. Second, the model's PV is given by the exact (primitive-equation, RossbyErtel) PV formula evaluated with the same v . Not conserving mass locally means that the velocity field v fails to satisfy the local mass-conservation equation, except possibly for some special flows such as steady circular vortices. There exists an infinite class C of PVBMs that do conserve mass locally. Its best-known member is the ``BolinCharney balance" model, in the shallow-water and isentropic-coordinate versions described by Gent and McWilliams and Whitaker. The present work char- acterizes the class C, and shows that most of its members are less accurate than the Bolin-Charney model. It shows furthermore, in full detail for the simplest, f-plane case, that the most accurate known PVBMs are not members of C. That is, the most accurate known PVBMs have velocity fields v that fail to satisfy local mass conserva- tion exactly, in general, even though the error may be tiny. Paradoxical though it may seem, this means that all the most accurate known PVBMs have one velocity field, v , to advect PV and another, vm , implicitly defined, to advect mass, the difference v - vm being nonzero in general even if tiny. The second field vm is computable by solving a Poisson equation at each timestep. The fact that v - vm is nonzero in general can be seen as a non-Hamiltonian counterpart of the ``schizophre- nia" or ``velocity splitting" already known to be characteristic of all Hamiltonian bal- anced models derived from the primitive equations by Salmon's method, in which imposing balance always splits the primitive equations' unique velocity field into two or more distinct velocity fields each of which has an essential role in the balanced dynamics.

Mohebalhojeh, A. R.; McIntyre, M. E.

294

NASA Astrophysics Data System (ADS)

The objective of this study was to fit a simple ecosystem model to climatological nitrogen cycle data in the Gulf of Maine, in order to calibrate the biological model for use in future 3-D modelling studies. First depth-dependent monthly climatologies of nitrate, ammonium, chlorophyll, zooplankton, detritus and primary production data from Wilkinson Basin, Gulf of Maine, were created. A 6-box nitrogen-based ecosystem model was objectively fitted to the data through parameter optimization. Optimization was based on weighted least squares with model-data misfits nondimensionalized by assigned uncertainties in the monthly climatological estimates. These uncertainties were estimated as the standard deviations of the raw data from the 6-meter and monthly bin averages. On average the model fits the monthly means almost within their assigned uncertainties. Several statistics are examined to assess model-data misfit. Pattern statistics such as the correlation coefficient lack practical significance when data errors are large relative to the signal, as in this application. Thus Taylor diagrams were not found to be useful. The RMSE and model bias normalized by the data error were found to be the most useful skill metrics as they indicate whether the model fits the data within its estimated error. The optimal simulated nitrogen cycle budgets are presented, as an estimate of the seasonal nitrogen cycle in Wilkinson Basin, and discussed in context of the available data. Wilkinson Basin has spring and fall phytoplankton blooms, and strong summer stratification with a deep chlorophyll maximum near 21 m, just above the nitracline. The mean euphotic zone depth is estimated to be 25 m, relatively constant with season. The model estimates annual primary production as 176 g C m - 2 yr - 1 , annual new production as 71 g C m - 2 yr - 1 and sinking PON fluxes of 9.7 and 4.7 g N m - 2 yr - 1 at 24 and 198 m respectively. Areas for improvement in the biological model, the model optimization method, and significant data gaps are identified.

Anderson, Laurence A.

2009-08-01

295

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

296

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

We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data. Copyright 1999 by the American Geophysical Union.

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

1999-01-01

297

This article is dedicated to the study of Piezoelectric Transformers (PTs), which offer promising solutions to the increasing need for integrated power electronics modules within autonomous systems. The advantages offered by such transformers include: immunity to electromagnetic disturbances; ease of miniaturisation for example, using conventional micro fabrication processes; and enhanced performance in terms of voltage gain and power efficiency. Central to the adequate description of such transformers is the need for complex analytical modeling tools, especially if one is attempting to include combined contributions due to (i) mechanical phenomena owing to the different propagation modes which differ at the primary and secondary sides of the PT; and (ii) electrical phenomena such as the voltage gain and power efficiency, which depend on the electrical load. The present work demonstrates an original one-dimensional (1D) analytical model, dedicated to a Rosen-type PT and simulation results are successively compared against that of a three-dimensional (3D) Finite Element Analysis (COMSOL Multiphysics software) and experimental results. The Rosen-type PT studied here is based on a single layer soft PZT (P191) with corresponding dimensions 18mm×3mm×1.5mm, which operated at the second harmonic of 176kHz. Detailed simulational and experimental results show that the presented 1D model predicts experimental measurements to within less than 10% error of the voltage gain at the second and third resonance frequency modes. Adjustment of the analytical model parameters is found to decrease errors relative to experimental voltage gain to within 1%, whilst a 2.5% error on the output admittance magnitude at the second resonance mode were obtained. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for Rosen-type PT design and behavior understanding. PMID:25753623

Boukazouha, F; Poulin-Vittrant, G; Tran-Huu-Hue, L P; Bavencoffe, M; Boubenider, F; Rguiti, M; Lethiecq, M

2015-07-01

298

Low Velocity Impact Experiments plus Modeling of the Resulting Reaction Violence in LX-10 Charges

NASA Astrophysics Data System (ADS)

A new gas gun facility and improved instrumentation were used to study the mechanisms of low velocity impact ignition and growth of violent reaction. Cylindrical charges of the HMX based explosive LX-10 (95% HMX, 5% Viton binder) encased by lexan were impacted by 6.35 mm diameter hardened steel projectiles at velocities ranging from 47 to 500 m/s. Fast Phantom v12 cameras were employed to capture the times of first ignition. The degrees of resulting reaction violence were determined using Photonic Doppler Velocimetry (PDV) probes to measure the free surface velocity histories of attached aluminum foils. Analytical and hydrodynamic reactive flow models were used to estimate the relative violence of these LX-10 reactions compared to the intentional detonation of an equivalent LX-10 charge. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Chidester, Steven; Garcia, Frank; Vandersall, Kevin; Tarver, Craig

2011-06-01

299

In melt-blowing very thin liquid fiber jets are spun due to high-velocity air streams. In literature there is a clear, unsolved discrepancy between the measured and computed jet attenuation. In this paper we will verify numerically that the turbulent velocity fluctuations causing a random aerodynamic drag on the fiber jets -- that has been neglected so far -- are the crucial effect to close this gap. For this purpose, we model the velocity fluctuations as vector Gaussian random fields on top of a k-epsilon turbulence description and develop an efficient sampling procedure. Taking advantage of the special covariance structure the effort of the sampling is linear in the discretization and makes the realization possible.

Florian Hübsch; Nicole Marheineke; Klaus Ritter; Raimund Wegener

2012-08-30

300

The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force-velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate. PMID:20162474

Domire, Zachary J; Challis, John H

2010-12-01

301

A DERIVATION OF THE COMPUTER-FRAME VELOCITY ERROR MODEL FOR INS AIDING

Recent developments in robotics, the automotive industry, and autonomous vehicles involves integrating measure- ments from on-board strapdown inertial sensors and external data collected by various sensors. This paper briefly revisits the equations of terrestrial inertial navigation, presents a novel derivation of the computer-frame velocity error model, makes explicit the equivalence to the computer-frame position error model, and presents an insightful

JACQUES WALDMANN

302

Global plate motion models incorporating the velocity field of ITRF96

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

Zhang Qiang; Zhu Wenyao; Xiong Yongqin

1999-01-01

303

Velocity Measurements Near the Empennage of a SmallScale Helicopter Model

NASA Technical Reports Server (NTRS)

A test program was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a small-scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with Laser Velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady downwash angle variations of over 30 degrees due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the fan were made for a low-speed flight condition using both conventional LV techniques and a promising, non-intrusive, global, three-component velocity measurement technique called Doppler Global Velocimetry (DGV). The velocity data show an accelerated flow near the fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane. DGV shows promise as an evolving tool for rotor flowfield diagnostics.

Gorton, Susan Althoff; Meyers, James F.; Berry, John D.

1996-01-01

304

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

NASA Astrophysics Data System (ADS)

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 datasets are Geysers-San Pablo Bay, Imperial Valley, Livermore, W. Mojave, Gilroy-Coyote Lake, Shasta region, Great Valley, Morro Bay, Mono Craters-Long Valley, PACE, S. Sierras, LARSE 1 and 2, Loma Prieta, BASIX, San Francisco Peninsula and Parkfield. Our beta-version model is coarse (uniform 30 km horizontal and variable vertical gridding) but is able to image the principal features in previous separate regional models for northern and southern California, such as the high-velocity subducting Gorda Plate, upper to middle crustal velocity highs beneath the Sierra Nevada and much of the Coast Ranges, the deep low-velocity basins of the Great Valley, Ventura, and Los Angeles, and a high- velocity body in the lower crust underlying the Great Valley. The new state-wide model has improved areal coverage compared to the previous models, and extends to greater depth due to the data at large epicentral distances. We plan a series of steps to improve the model. We are enlarging and calibrating the active-source dataset as we obtain additional picks from investigators and perform quality control analyses on the existing and new picks. We will also be adding data from more quarry blasts, mainly in northern California, following an identification and calibration procedure similar to Lin et al. (2006). Composite event construction (Lin et al., in press) will be carried out for northern California for use in conventional tomography. A major contribution of the state-wide model is the identification of earthquakes yielding arrival times at both the Northern California Seismic Network and the Southern California Seismic Network. These events are critical to the determination of the seismic velocity model in central California, in the former `no-mans-land' between the Northern and Southern California networks. Ultimately, a combination of active-source datasets, composite events, original catalog picks, and differential times from both waveform cross-correlation and catalog picks will be used in a double-difference tomography inversion.

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

2007-12-01

305

NASA Astrophysics Data System (ADS)

Femtoscopy is providing information on system size and its dynamics in heavy-ion collisions. At ultrarelativistic energies, such as those obtained at the Large Hadron Collider (LHC), significant production of pions, kaons, and protons enables femtoscopic measurements for these particles. In particular, the dependence of system size on pair momentum and particle type is interpreted as evidence for strong collective flow. Such phenomena are naturally modeled by hydrodynamics. We present calculations within the (3+1)D hydrodynamic model coupled to statistical hadronization code therminator 2, corresponding to Pb-Pb collisions at ?{sNN}=2.76 TeV. We obtain femtoscopic radii for pions, kaons, and protons, as a function of pair transverse momentum and collision centrality. We find that an approximate universal scaling of radii with pair transverse mass and final-state event multiplicity is observed and discuss the consequences for the interpretation of experimental measurements.

Kisiel, Adam; Ga?a?yn, Mateusz; Bo?ek, Piotr

2014-12-01

306

NASA Astrophysics Data System (ADS)

The real-space renormalization group (RSRG) method introduced previously for the Brownian landscape is generalized to obtain the joint probability distribution of the subset of the important extrema at large scales of other one-dimensional landscapes. For a large class of models we give exact solutions obtained either by the use of constrained path-integrals in the continuum limit, or by solving the RSRG equations via an Ansatz which leads to the Liouville equation. We apply in particular our results to the toy model energy landscape, which consists in a quadratic potential plus a Brownian potential, which describes, among others, the energy of a single domain wall in a 1D random field Ising model (RFIM) in the presence of a field gradient. The measure of the renormalized landscape is obtained explicitly in terms of Airy functions, and allows to study in detail the Boltzmann equilibrium of a particle at low temperature as well as its non-equilibrium dynamics. For the equilibrium, we give results for the statistics of the absolute minimum which dominates at zero temperature, and for the configurations with nearly degenerate minima which govern the thermal fluctuations at very low-temperature. For the dynamics, we compute the distribution over samples of the equilibration time, or equivalently the distribution of the largest barrier in the system. We also study the properties of the rare configurations presenting an anomalously large equilibration time which govern the long-time dynamics. We compute the disorder averaged diffusion front, which interpolates between the Kesten distribution of the Sinai model at short rescaled time and the reaching of equilibrium at long rescaled time. Finally, the method allows to describe the full coarsening (i.e., many domain walls) of the 1D RFIM in a field gradient as well as its equilibrium.

Le Doussal, Pierre; Monthus, Cécile

2003-01-01

307

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

308

NASA Astrophysics Data System (ADS)

Many crucial tasks in seismology, such as locating seismic events and estimating focal mechanisms, need crustal velocity models. The velocity models of shallow structures are particularly important in the simulation of ground motions. In southern Ontario, Canada, many small shallow earthquakes occur, generating high-frequency Rayleigh ( Rg) waves that are sensitive to shallow structures. In this research, the dispersion of Rg waves was used to obtain shear-wave velocities in the top few kilometers of the crust in the Georgian Bay, Sudbury, and Thunder Bay areas of southern Ontario. Several shallow velocity models were obtained based on the dispersion of recorded Rg waves. The Rg waves generated by an m N 3.0 natural earthquake on the northern shore of Georgian Bay were used to obtain velocity models for the area of an earthquake swarm in 2007. The Rg waves generated by a mining induced event in the Sudbury area in 2005 were used to retrieve velocity models between Georgian Bay and the Ottawa River. The Rg waves generated by the largest event in a natural earthquake swarm near Thunder Bay in 2008 were used to obtain a velocity model in that swarm area. The basic feature of all the investigated models is that there is a top low-velocity layer with a thickness of about 0.5 km. The seismic velocities changed mainly within the top 2 km, where small earthquakes often occur.

Ma, Shutian; Motazedian, Dariush; Corchete, Victor

2013-04-01

309

Study of the mixed layer depth variations within the north Indian Ocean using a 1-D model

Mixed layer depth (MLD) over the north Indian Ocean (30°S to 30°N and 40°E to 110°E) is computed using the simple one-dimensional model of Price et al. [1986] forced by satellite-derived parameters (winds and chlorophyll). Seasonal chlorophyll observations obtained from the Coastal Zone Color Scanner allow us to examine how biology interacts with physics in the upper ocean by changing

K. N. Babu; Rashmi Sharma; Neeraj Agarwal; Vijay K. Agarwal; R. A. Weller

2004-01-01

310

Creating Flood Inundation Maps Using 1D Hydrologic Model and GIS for Lower Meric River Basin, Turkey

NASA Astrophysics Data System (ADS)

In Turkey, one of the areas facing the danger of flooding is Lower Meric River basin, the part between Edirne and Enos, Turkey. Despite being in the flood zone, the region is used widely as an agricultural and settlement land. The State Hydraulic Works (DSI) has built levees to prevent flood damages on the Lower Evros River Basin. However, having floods in the region reaching areas behind levees, clearly showed the need for reviewing and updating the cross-sections of the critical areas in the river bed. In this study, determination of floodplains for various stream-flow values in any cross sections of the river is aimed. The study area is divided into two sections (Study Area 1 & Study Area 2). Available stream flow gauging station data, which is located in study areas, are used in model. Model created using HEC-RAS, is calibrated with 2006 flood which occurred in the study area. After calibration, floodplain maps are created for 1000 m3/s flows from 1000 to6000 m3/s flows for Study Area1. For Study Area 2, floodplain maps are created for 2, 5, 10, 50, 100 years return periods. The models can illustrate the extent of flooding under different conditions allowing residents in the area to see how predicted flood levels could affect their property, and help them make informed decisions.

Sonmez, O.; Dogan, E.; Demir, I.

2012-12-01

311

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

312

Comparative Experimental and Modeling Study of Fluid Velocities in Heterogeneous Rocks

NASA Astrophysics Data System (ADS)

Understanding the spatial distribution of fluid velocities and effective porosities in rocks is crucial for predicting kinetic reaction rates and fluid-rock interactions in a plethora of geo-engineering applications, ranging from geothermal systems, Enhanced Oil Recovery to Carbon Capture and Storage. Magnetic Resonance Imaging can be used to measure spatially resolved porosities and fluid velocities in porous media. Large internal field gradients and short spin relaxation times, however, constrain the usability of the conventional MRI technique in natural rock samples. The combination of three-dimensional Single Point Ramped Imaging with T1 Enhancement (SPRITE) and the 13-interval Alternating-Pulsed-Gradient Stimulated-Echo (APGSTE) scheme - a method developed at the UNB MRI Center - is able to compensate for those challenges and quantitative 3 dimensional maps of porosities and fluid velocities can be obtained. In this study we measured velocities and porosities using MRI in a sandstone rock sample showing meso-scale heterogeneities. Then we generated permeabilities using three independent approaches, employed them to model single-phase fluid flow in the measured rock sample and compared the generated velocity maps with the respective MRI measurements. For the first modeling approach, we applied the Kozeny-Carman relationship to create a permeability map based on porosities measured using MRI. For the second approach we used permeabilities derived from CO2-H2O multi-phase experiments performed in the same rock sample assuming the validity of the J-Leverett function. The permeabilities in the third approach were generated by applying a new inverse iterative-updating technique. The resulting three permeability maps were then used as input for a CFD simulation - using the Stanford CFD code AD-GPRS - to create a respective velocity map, which in turn was then compared to the measured velocity map. The results of the different independent methods for generating permeability maps as well as their correlation with the measured velocity maps are evaluated. Furthermore the implication of this study on understanding kinetic reaction rates and fluid-rock interaction is discussed.

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

2013-12-01

313

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

314

NASA Astrophysics Data System (ADS)

The indentation of the Adria plate into the Southern and Eastern Alps is an ongoing collisional process accompanied by seismicity, uplift and lateral escape. We attempt a first 3D quantitative description of the process by combining GPS and structural data with an elastic dislocation model. Horizontal velocities of 75 Austrian and Italian permanent GPS stations in the Eastern and Southern Alps serve as boundary condition on the free surface of an elastic half space containing six rectangular faults, each with an uniform slip rate. Using the Okada (1985) algorithm, and taking into account the structural setting of the area and the geographic distribution of the velocity data, the geometry of the rectangular faults and the slip rate vector are constrained by least squares. We find that the surface velocities of the order of some mm/yr require slips at crustal depth ranging for 1 to 5 cm/yr, with rake mostly reverse, occasionally transpressional. The horizontal gradient of the moment rate associated to each rectangular fault positively correlates with seismicity. The regional stress pattern computed from fault plane solutions agrees with the principal directions of our rectangular fault planes. The model, although constrained by horizontal velocities only, predicts a pattern of vertical motion which qualitatively agrees with known phenomena such as the uplift in the Tauern and subsidence in the Po Plain, of the order of up to few mm/yr.

Caporali, A.; Neubauer, F.; Stangl, G.; Zuliani, D.

2012-04-01

315

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

316

An Unique SPICE Model of Photodiode with Slowly Changeable Carriers' Velocities

NASA Astrophysics Data System (ADS)

This paper deals with a relatively new SPICE model of a P-i-N photodiode. The model includes a change of velocities of electrons and holes, due to the voltage drop on the edges of the photodiode, which depends on the time form of input excitation. We have derived the model of the P-i-N photodiode for digital input excitation i.e. for Heaviside's square wave time excitation. The model is incorporated in SPICE program and simulated with it. The model and the limitations of the model itself are observed. The output results are compared with the similar ones. It is suggested when it is practical to use the model, and determined the photodiode working domain regime when the model gives accurate results.

Matavulj, Petar S.; Lazovi?, Miomira V.; Radunovi?, Jovan B.

2011-01-01

317

NASA Technical Reports Server (NTRS)

The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.

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

2007-01-01

318

Exact electron addition spectrum in 1D supersymmetric t-J model with 1/r2 interaction

NASA Astrophysics Data System (ADS)

The electron addition spectrum A(k,?) is obtained analytically for the one-dimensional supersymmetric t- J model with 1/r interaction. The spectral function A(k,?) has a simple analytic form with contributions from one spinon, one holon and one antiholon all of which obey fractional statistics. The upper edge of A(k,?) in the (k,?) plane includes a delta-function peak which reduces to that of the single-electron band in the low-density limit. This peak is interpreted as a result of spin-charge recombination. Our derivation relies on the ideas of Yangian highest weight states and Jack polynomials adapted to the SU(1,1) supersymmetry.

Arikawa, M.; Yamamoto, T.; Saiga, Y.; Kuramoto, Y.

2004-12-01

319

NASA Astrophysics Data System (ADS)

This work deals with the numerical solution of a complex mathematical model arising in theoretical glaciology. The global moving boundary problem governs thermomechanical processes jointly with ice sheet hydrodynamics. One major novelty is the inclusion of the ice velocity field computation in the framework of the shallow ice model so that it can be coupled with profile and temperature equations. Moreover, the proposed basal velocity and shear stress laws allow the integration of basal sliding effects in the global model. Both features were not taking into account in a previous paper (Math. Model. Methods Appl. Sci. 12 (2) (2002) 229) and provide more realistic convective terms and more complete Signorini boundary conditions for the thermal problem. In the proposed numerical algorithm, one- and two-dimensional piecewise linear Lagrange finite elements in space and a semi-implicit upwinding scheme in time are combined with duality and Newton's methods for nonlinearities. A simulation example involving real data issued from Antarctic shows the temperature, profile and velocity qualitative behaviour as well as the free boundaries and basal effects.

Calvo, N.; Durany, J.; Vazquez, C.

2003-09-01

320

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

321

A new open-loop fiber optic gyro error compensation method based on angular velocity error modeling.

With the open-loop fiber optic gyro (OFOG) model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a modeling scheme with OFOG output voltage and temperature as the input variables and angular velocity error as the output variable. Firstly, the angular velocity error is extracted from OFOG output signals, and then the output voltage , temperature and angular velocity error are used as the learning samples to train a Radial-Basis-Function (RBF) neural network model. Then the nonlinear mapping model over T, and is established and thus can be calculated automatically to compensate OFOG errors according to and . The results of the experiments show that the established model can be used to compensate the nonlinear OFOG errors. The maximum, the minimum and the mean square error of OFOG angular velocity are decreased by , and relative to their initial values, respectively. Compared with the direct modeling of gyro angular velocity, which we researched before, the experimental results of the compensating method proposed in this paper are further reduced by , and , respectively, so the performance of this method is better than that of the direct modeling for gyro angular velocity. PMID:25734642

Zhang, Yanshun; Guo, Yajing; Li, Chunyu; Wang, Yixin; Wang, Zhanqing

2015-01-01

322

NASA Astrophysics Data System (ADS)

Using seismic data from regional 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 is performed using the spectral-element method (SEM) for laterally varying upper-mantle velocity and attenuation, and the seismic attributes considered include the Pn travel-time, envelope amplitude, and pulse frequency. The results from the SEM modeling provide two alternative models for the upper-mantle beneath the Hi-CLIMB array in Tibet. The first model is derived from the 3D velocity model of G riffin et al. (Bull Seism Soc Am 101:1938-1947, 2011) with a constant upper-mantle velocity gradient, and laterally varying upper mantle attenuation. The second model has a laterally varying upper-mantle velocity gradient, and constant upper-mantle attenuation. In both cases, the Qiangtang terrane is distinguished from the Lhasa terrane by a change in Moho depth and upper-mantle velocities. The lower upper-mantle velocities, as well as higher Pn attenuation, suggest hotter temperatures beneath the Qiangtang terrane as compared to the Lhasa terrane. Although the fits to the Pn amplitude and pulse frequency data are comparable between the two models, the first model with the constant upper-mantle velocity gradient fits the travel times somewhat better in relation to the data errors.

Bakir, Ali C.; Nowack, Robert L.

2012-12-01

323

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

324

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

325

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

NASA Astrophysics Data System (ADS)

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.

2010-05-01

326

Analytical modeling of helicopter static and dynamic induced velocity in GRASP

NASA Technical Reports Server (NTRS)

The methodology used by the General Rotorcraft Aeromechanical Stability Program (GRASP) to model the characteristics of the flow through a helicopter rotor in hovering or axial flight is described. Since the induced flow plays a significant role in determining the aeroelastic properties of rotorcraft, the computation of the induced flow is an important aspect of the program. Because of the combined finite-element/multibody methodology used as the basis for GRASP, the implementation of induced velocity calculations presented an unusual challenge to the developers. To preserve the modelling flexibility and generality of the code, it was necessary to depart from the traditional methods of computing the induced velocity. This is accomplished by calculating the actuator disk contributions to the rotor loads in a separate element called the air mass element, and then performing the calculations of the aerodynamic forces on individual blade elements within the aeroelastic beam element.

Kunz, Donald L.; Hodges, Dewey H.

1988-01-01

327

Analytical modeling of helicopter static and dynamic induced velocity in GRASP

NASA Technical Reports Server (NTRS)

The methodology used by the General Rotorcraft Aeromechanical Stability Program (GRASP) to model the characteristics of the flow through a helicopter rotor in hovering or axial flight is described. Since the induced flow plays a significant role in determining the aeroelastic properties of rotorcraft, the computation of the induced flow is an important aspect of the program. Because of the combined finite-element/multibody methodology used as the basis for GRASP, the implementation of induced velocity calculations presented an unusual challenge to the developers. To preserve the modelling flexibility and generality of the code, it was necessary to depart from the traditional methods of computing the induced velocity. This is accomplished by calculating the actuator disc contributions to the rotor loads in a separate element called the air mass element, and then performing the calculations of the aerodynamic forces on individual blade elements within the aeroelastic beam element.

Kunz, Donald L.; Hodges, Dewey H.

1987-01-01

328

We propose a way to introduce in microscopic pedestrian models a "social norm" in collision avoiding and overtaking, i.e. the tendency, shared by pedestrians belonging to the same culture, to avoid collisions and perform overtaking in a preferred direction. The "social norm" is implemented, regardless of the specific collision avoiding model, as a rotation in the perceived velocity vector of the opponent at the moment of computation of the collision avoiding strategy, and justified as an expectation that the opponent will follow the same "social norm" (for example a tendency to avoid on the left and overtake on the right, as proposed in this work for Japanese pedestrians). By comparing with real world data, we show that the introduction of this norm allows for a better reproduction of macroscopic pedestrian density and velocity patterns. PMID:23227202

Zanlungo, Francesco; Ikeda, Tetsushi; Kanda, Takayuki

2012-01-01

329

Velocity selection at large undercooling in a two-dimensional nonlocal model of solidification

NASA Technical Reports Server (NTRS)

The formation of needle-crystal dendrites from an undercooled melt is investigated analytically, applying the method of Caroli et al. (1986) to Langer's (1980) symmetric two-dimensional nonlocal model of solidification with finite anisotropy in the limit of large undercooling. A solution based on the WKB approximation is obtained, and a saddle-point evaluation is performed. It is shown that needle-crystal solutions exist only if the capillary anisotropy is nonzero, in which case a particular value of the growth velocity can be selected. This finding and the expression for the dependence of the selected velocity on the singular perturbation parameter and the strength of the anisotropy are found to be in complete agreement with the results of a boundary-layer model (Langer and Hong, 1986).

Barbieri, Angelo

1987-01-01

330

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

331

Brans-Dicke Cosmology in an Anisotropic Model When Velocity of Light Varies

NASA Astrophysics Data System (ADS)

In this paper, we have studied Brans-Dicke (BD) Cosmology in an anisotropic Kantowski-Sachs space-time model; considering variation of the velocity of light. We have addressed the flatness problem considering both cases namely (i) when the Brans-Dicke scalar field ? is constant (ii) when ? varies, specially for radiation dominated era perturbatively and non-perturbatively and asymptotic behaviour have been studied.

Chakraborty, Subenoy; Chakraborty, Narayan Chandra; Debnath, Ujjal; Dolgov, A.

332

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

The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. 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

333

(ABRIDGED) We present a new Schwarzschild orbit-superposition code designed to model discrete datasets composed of velocities of individual kinematic tracers in a dynamical system. This constitutes an extension of previous implementations that can only address continuous data in the form of (the moments of) velocity distributions, thus avoiding potentially important losses of information due to data binning. Furthermore, the code can handle any combination of available velocity components, i.e., only line-of-sight velocities, only proper motions, or a combination of both. It can also handle a combination of discrete and continuous data. The code finds the distribution function (DF, a function of the three integrals of motion E, Lz, and I3) that best reproduces the available kinematic and photometric observations in a given axisymmetric gravitational potential. The fully numerical approach ensures considerable freedom on the form of the DF f(E,Lz,I3). This allows a very general modeling of the orbital structure, thus avoiding restrictive assumptions about the degree of (an)isotropy of the orbits. We describe the implementation of the discrete code and present a series of tests of its performance based on the modeling of simulated datasets generated from a known DF. We find that the discrete Schwarzschild code recovers the original orbital structure, M/L ratios, and inclination of the input datasets to satisfactory accuracy, as quantified by various statistics. The code will be valuable, e.g., for modeling stellar motions in Galactic globular clusters, and those of individual stars, planetary nebulae, or globular clusters in nearby galaxies. This can shed new light on the total mass distributions of these systems, with central black holes and dark matter halos being of particular interest.

Julio Chanamé; Jan Kleyna; Roeland van der Marel

2008-04-21

334

Global bifurcation investigation of an optimal velocity traffic model with driver reaction time.

We investigate an optimal velocity model which includes the reflex time of drivers. After an analytical study of the stability and local bifurcations of the steady-state solution, we apply numerical continuation techniques to investigate the global behavior of the system. Specifically, we find branches of oscillating solutions connecting Hopf bifurcation points, which may be super- or subcritical, depending on parameters. This analysis reveals several regions of multistability. PMID:15447565

Orosz, Gábor; Wilson, R Eddie; Krauskopf, Bernd

2004-08-01

335

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

336

Applying dynamic wake models to large swirl velocities for optimal propellers

NASA Astrophysics Data System (ADS)

The dynamic wake model is applied to the optimal propeller systems originally studied by the classic aerodynamicists: Betz, Prandtl and Goldstein. Several modified forms of the model are theoretically developed to extend the applicable range to flight conditions with a large swirl velocity component. Dynamic wake model calculations accurately predict the inflow behavior for helicopter rotors, including axial flow for large tip-speed ratios, (OR/V infinity) ? 20. The swirl velocity is a prominent component for small tip-speed ratios (?5), typical of forward flight for tiltrotor craft such as the V-22 Osprey and the BA609. Dynamic wake calculation results are compared to the closed-form solutions by Prandtl and Goldstein. The exact and approximate solutions correlate strongly for infinite blade cases and finite blade cases with a large tip-speed ratio. The original form of the He-Peters and Morillo-Peters dynamic wake models converge poorly for small tip-speed ratios, due to neglect of the swirl velocity. Derivations are presented for several adaptations of the models to account for the large apparent mass at the inboard blade region. A best modified form is chosen and the associated empirical factor is optimized to correlate well with Prandtl's solution. Error norms for the original and modified forms of the dynamic wake model are presented for propellers of various number of blades and a range of tip-speed ratios. The Goldstein solution is also studied in depth and conclusions are drawn for improving the dynamic wake model.

Makinen, Stephen M.

337

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

338

Validation of recent shear wave velocity models in the United States with full-wave simulation

NASA Astrophysics Data System (ADS)

Interpretations of dynamic processes and the thermal and chemical structure of the Earth depend on the accuracy of Earth models. With the growing number of velocity models constructed with different tomographic methods and seismic data sets, there is an increasing need for a systematic way to validate model accuracy and resolution. This study selects five shear wave velocity models in the U.S. and simulates full-wave propagation within the 3-D structures. Surface-wave signals extracted from ambient seismic noise and regional earthquakes are compared with synthetic waveforms at multiple-frequency bands. Phase delays and cross-correlation coefficients between observed and synthetic waveforms allow us to compare and validate these models quantitatively. In general, measurements from regional earthquakes are consistent with ambient noise results, but appear more scattered, which may result from uncertainty of the earthquake source location, origin time, and moment tensor. Our results show the improvement of model prediction with the increase of seismic data sets and implement of advanced methods. There exists a positive linear trend between phase delay and interstation distance for three models, indicating that on average, these models are faster than the real Earth structure. The phase delays from the jointly inverted model of ambient noise and receiver function have negative means at all periods while without obvious dependence on the interstation distance. The full-wave ambient noise tomographic model predicts more accurate phase arrivals compared to other models. This study suggests a need for an integrated model constructed with multiple seismic waveforms and consideration of anisotropy and attenuation.

Gao, Haiying; Shen, Yang

2015-01-01

339

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

340

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., E-mail: pongga.wardaya@utp.edu.my; Noh, K. A. B. M., E-mail: pongga.wardaya@utp.edu.my; Yusoff, W. I. B. W., E-mail: pongga.wardaya@utp.edu.my [Petroleum Geosciences Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Ridha, S. [Petroleum Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Nurhandoko, B. E. B. [Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Dept. of Physics, Institute of Technology Bandung, Bandung, Indonesia and Rock Fluid Imaging Lab, Bandung (Indonesia)

2014-09-25

341

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

NASA Astrophysics Data System (ADS)

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

Faggionato, Alessandra; Silvestri, Vittoria

2014-12-01

342

Accurate calibration of the velocity-dependent one-scale model for domain walls

NASA Astrophysics Data System (ADS)

We study the asymptotic scaling properties of standard domain wall networks in several cosmological epochs. We carry out the largest field theory simulations achieved to date, with simulation boxes of size 20483, and confirm that a scale-invariant evolution of the network is indeed the attractor solution. The simulations are also used to obtain an accurate calibration for the velocity-dependent one-scale model for domain walls: we numerically determine the two free model parameters to have the values cw=0.34±0.16 and kw=0.98±0.07, which are of higher precision than (but in agreement with) earlier estimates.

Leite, A. M. M.; Martins, C. J. A. P.; Shellard, E. P. S.

2013-01-01

343

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

344

We report a fast time-domain model of fluid-coupled cMUTs developed to predict the transient response-i.e., the impulse pressure response--of an element of a linear 1-D array. Mechanical equations of the cMUT diaphragm are solved with 2-D finite-difference schemes. The time-domain solving method is a fourth--order Runge-Kutta algorithm. The model takes into account the electrostatic nonlinearity and the contact with the bottom electrode when the membrane is collapsed. Mutual acoustic coupling between cells is introduced through the numerical implementation of analytical solutions of the impulse diffraction theory established in the case of acoustic sources with rectangular geometry. Processing times are very short: they vary from a few minutes for a single cell to a maximum of 30 min for one element of an array. After a description of the model, the impact of the nonlinearity and the pull-in/pull-out phenomena on the dynamic behavior of the cMUT diaphragm is discussed. Experimental results of mechanical displacements obtained by interferometric measurements and the acoustic pressure field are compared with simulations. Different excitation signals-high-frequency bandwidth pulses and toneburst excitations of varying central frequency-were chosen to compare theory with experimental results. PMID:25004518

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

2013-07-01

345

Mass loading and velocity diffusion models for heavy pickup ions at comet Grigg-Skjellerup

NASA Technical Reports Server (NTRS)

We compare model predictions of cometary water group ion densities and the solar wind slow down with measurements made by the Giotto Johnstone plasma analyzer implanted ion sensor at the encounter with comet Grigg-Skjellerup (G-S) on July 10, 1992. The observed slope of the ion density profile on approach to the comet is unexpectedly steep. Possible explanations for this are discussed. We present also a preliminary investigation of the quasilinear velocity-space diffusion of the implanted heavy ion population at G-S using a transport equation including souce, convection, adiabatic compression, and velocity diffusion terms. Resulting distributions are anisotropic, in agreement with observations. We consider theoretically the waves that may be generated by the diffusion process for the observed solar wind conditions. At initial ion injections, waves are generated at omega approximately Omega(sub i) the ion gyrofrequency, and lower frequencies are predicted for diffusion toward a bispherical shell.

Huddleston, D. E.; Coates, A. J.; Johnstone, A. D.; Neubauer, Fritz M.

1993-01-01

346

NASA Astrophysics Data System (ADS)

The dynamics of edge dislocations with parallel Burgers vectors, moving in the same slip plane, is mapped onto Dyson's model of a two-dimensional Coulomb gas confined in one dimension. We show that the tail distribution of the velocity of dislocations is power law in form, as a consequence of the pair interaction of nearest neighbors in one dimension. In two dimensions, we show the presence of a pairing phase transition in a system of interacting dislocations with parallel Burgers vectors. The scaling exponent of the velocity distribution at effective temperatures well below this pairing transition temperature can be derived from the nearest-neighbor interaction, while near the transition temperature, the distribution deviates from the form predicted by the nearest-neighbor interaction, suggesting the presence of collective effects.

Jafarpour, Farshid; Angheluta, Luiza; Goldenfeld, Nigel

2013-10-01

347

The dynamics of edge dislocations with parallel Burgers vectors, moving in the same slip plane, is mapped onto Dyson's model of a two-dimensional Coulomb gas confined in one dimension. We show that the tail distribution of the velocity of dislocations is power law in form, as a consequence of the pair interaction of nearest neighbors in one dimension. In two dimensions, we show the presence of a pairing phase transition in a system of interacting dislocations with parallel Burgers vectors. The scaling exponent of the velocity distribution at effective temperatures well below this pairing transition temperature can be derived from the nearest-neighbor interaction, while near the transition temperature, the distribution deviates from the form predicted by the nearest-neighbor interaction, suggesting the presence of collective effects. PMID:24229132

Jafarpour, Farshid; Angheluta, Luiza; Goldenfeld, Nigel

2013-10-01

348

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

349

NASA Astrophysics Data System (ADS)

The indentation of the Adria plate into the Southern and Eastern Alps is an ongoing collisional process accompanied by seismicity, surface and rock uplift and lateral escape. We present a 3D quantitative description of the process by combining GPS and structural data with an elastic dislocation model. Horizontal velocities of 70 Austrian and Italian permanent GPS stations in the Eastern and Southern Alps serve as boundary condition on the free surface of an elastic half space containing six rectangular faults, each with an uniform slip rate. The geometry of the rectangular faults and the slip rate vector are constrained by least squares, taking into account the structural setting of the area and the geographic distribution of the velocity data. We find that the surface velocities of the order of some mm/yr require reverse (North side of the Tauern window), transpressional (Giudicarie, North Alpine Wrench Corridor, Pustertal, Dinarids) and normal (Brenner fault) slips at crustal depth ranging from 10 to 30 mm/yr. The regional stress pattern computed from fault plane solutions agrees with the principal directions of our rectangular fault planes. The model, although constrained by horizontal velocities only, predicts a pattern of vertical motion which qualitatively agrees with known phenomena such as the surface uplift in the Tauern Window area, of the order of up to few mm/yr. If the heat on the shearing fault planes is removed mostly by upwards diffusion, the absence of large heat anomalies on the Earth surface suggests, for nominal geotherms, shear stresses and concentration of subcrustal radiogenic elements, that time of initiation of the slip dates back to Pliocene, hence more recent than late Oligocene - Miocene time of collision of the Adria indenter.

Caporali, Alessandro; Neubauer, Franz; Stangl, Guenter; Ostini, Luca; Zuliani, David

2013-04-01

350

NASA Astrophysics Data System (ADS)

The indentation of the Adria plate into the Southern and Eastern Alps is an ongoing collisional process accompanied by seismicity, surface and rock uplift and lateral escape. We present a 3D quantitative description of the process by combining GPS and structural data with an elastic dislocation model. Horizontal velocities of 70 Austrian and Italian permanent GPS stations in the Eastern and Southern Alps serve as boundary condition on the free surface of an elastic half space containing six rectangular faults, each with a uniform slip rate. The geometry of the rectangular faults and the slip rate vector are constrained by least squares, taking into account the structural setting of the area and the geographic distribution of the velocity data. We find that the surface velocities of the order of some mm/yr require reverse (North side of the Tauern Window), transpressional (Giudicarie, North Alpine Wrench Corridor, Pustertal, Dinarides) and normal (Brenner fault) slips ranging from 10 to 30 mm/yr at crustal depths. The regional stress pattern computed from fault plane solutions agrees with the principal directions of our rectangular fault planes. The model, although constrained by horizontal velocities only, predicts a pattern of vertical motion, which qualitatively agrees with known phenomena such as the surface uplift in the Tauern Window area, of the order of up to few mm/yr. If the heat on the shearing fault planes is removed mostly by upwards diffusion, the absence of large heat anomalies on the Earth's surface suggests, for nominal geotherms, shear stresses and concentration of subcrustal radiogenic elements, that the time of initiation of the slip dates to Pliocene, hence more recent than Late Oligocene-Miocene time of collision of the Adria indenter.

Caporali, A.; Neubauer, F.; Ostini, L.; Stangl, G.; Zuliani, D.

2013-04-01

351

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

352

Measurement and modelling of high resolution flow- velocity data under simulated rainfall on a low to start. A rainfall-simulation experiment was carried out to produce high- resolution flow-velocity data a small rill formed in the middle. The experiment consisted of a 2 h 15'-long rainfall at a constant

Boyer, Edmond

353

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

NASA Astrophysics Data System (ADS)

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

Pejcha, Ond?ej; Prieto, Jose L.

2015-02-01

354

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

355

A velocity-difference-separation model for car-following theory

NASA Astrophysics Data System (ADS)

We introduce a velocity-difference-separation model that modifies the previous models in the literature. The improvement of this new model over the previous ones lies in that it not only theoretically retains many strong points of the previous ones, but also performs more realistically than others in the dynamical evolution of congestion. Furthermore, the proposed model is investigated with analytic and numerical methods, with the finding that it can demonstrate some complex physical features observed in real traffic such as the existence of three phases: free flow, synchronized flow, and wide moving jam; sudden flow drop in flow-density plane; and traffic hysteresis in transition between the free and the synchronized flow.

Li, Zhi-Peng; Liu, Yun-Cai

2006-07-01

356

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

357

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

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

358

Lattice Botlzmann Solution to the 1D MHD-Burgers Equation

NASA Astrophysics Data System (ADS)

Recently, Fleischer & Diamond [2000] have considered the 1D MHD-Burgers equation as a paradigm for the spatio-temporal intermittency involving coherent structures. This is the simplest model to exhibit Alvenization - the exchange of fluid and magnetic energies. In the limit B 0, the equations reduce to the familiar Burgers equation, which exbibits shocks. Our lattice Boltzmann solution introduces two scalar distribution functions - one for the velocity field and one for the magnetic field. The coupled BGK equations require only a simple phase space velocity lattice of (+1,-1,+2,-2). A linear stability analysis is performed and simulation results are presented. The need for adaptive grids is discussed.

Vahala, Linda; Vahala, George

2002-11-01

359

NASA Astrophysics Data System (ADS)

The diurnal variation of HOCl and the related species ClO, HO2 and HCl measured by satellites has been compared with the results of a one-dimensional photochemical model. The study compares the data from various limb-viewing instruments with model simulations from the middle stratosphere to the lower mesosphere. Data from three sub-millimetre instruments and two infrared spectrometers are used, namely from the Sub-Millimetre Radiometer (SMR) on board Odin, the Microwave Limb Sounder (MLS) on board Aura, the Superconducting Submillimeter-wave Limb-Emission Sounder (SMILES) on the International Space Station, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT, and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board SCISAT. Inter-comparison of the measurements from instruments on sun-synchronous satellites (SMR, MLS, MIPAS) and measurements from solar occultation instruments (ACE-FTS) is challenging since the measurements correspond to different solar zenith angles (or local times). However, using a model which covers all solar zenith angles and data from the SMILES instrument which measured at all local times over a period of several months provides the possibility to verify the model and to indirectly compare the diurnally variable species. The satellite data were averaged for latitudes of 20° S to 20° N for the SMILES observation period from November 2009 to April 2010 and were compared at three altitudes: 35, 45 and 55 km. Besides presenting the SMILES data, the study also shows a first comparison of the latest MLS data (version 3.3) of HOCl, ClO, and HO2 with other satellite observations, as well as a first evaluation of HO2 observations made by Odin/SMR. The MISU-1D model has been carefully initialised and run for conditions and locations of the observations. The diurnal cycle features for the species investigated here are generally well reproduced by the model. The satellite observations and the model agree well in terms of absolute mixing ratios. The differences between the day and night values of the model are in good agreement with the observations although the amplitude of the HO2 diurnal variation is 10-20% lower in the model than in the observations. In particular, the data offered the opportunity to study the reaction ClO+HO2 ? HOCl+O2 in the lower mesosphere at 55 km. At this altitude the HOCl night-time variation depends only on this reaction. The result of this analysis points towards a value of the rate constant within the range of the JPL 2006 recommendation and the upper uncertainty limit of the JPL 2011 recommendation at 55 km.

Khosravi, M.; Baron, P.; Urban, J.; Froidevaux, L.; Jonsson, A. I.; Kasai, Y.; Kuribayashi, K.; Mitsuda, C.; Murtagh, D. P.; Sagawa, H.; Santee, M. L.; Sato, T. O.; Shiotani, M.; Suzuki, M.; von Clarmann, T.; Walker, K. A.; Wang, S.

2013-08-01

360

We present a dynamical study of NGC 4697, an almost edge-on, intermediate-luminosity, E4 elliptical galaxy, combining new surface brightness photometry, new as well as published long-slit absorption line kinematic data, and published planetary nebulae (PNe) velocity data. The combined kinematic data set extends out to ~= 5' ~= 4.5 R_e and allows us to probe the galaxy's outer halo. For the first time, we model such a dataset with the new and flexible Chi^2-made-to-measure particle code NMAGIC. We extend NMAGIC to include seeing effects, introduce an efficient scheme to estimate the mass-to-light ratio, and incorporate a maximum likelihood technique to account for discrete velocity measurements. For modelling the PNe kinematics we use line-of-sight velocities and velocity dispersions computed on two different spatial grids, and we also use the individual velocity measurements with the likelihood method, in order to make sure that our results are not biased by the way we treat the PNe measurements. We generate axisymmetric self-consistent models as well models including various dark matter halos. These models fit all the mean velocity and velocity dispersion data with Chi^2/N~ 2R_e.

Flavio De Lorenzi; Ortwin Gerhard; Roberto P. Saglia; Niranjan Sambhus; Victor P. Debattista; Maurilio Pannella; Roberto H. Mendez

2008-02-12

361

Sterile neutrinos, dark matter, and the pulsar velocities in models with a Higgs singlet

We identify the range of parameters for which the sterile neutrinos can simultaneously explain the cosmological dark matter and the observed velocities of pulsars. To satisfy all cosmological bounds, the relic sterile neutrinos must be produced sufficiently cold. This is possible in a class of models with a gauge-singlet Higgs boson coupled to the neutrinos. Sterile dark matter can be detected by the x-ray telescopes. The presence of the singlet in the Higgs sector can be tested at the Large Hadron Collider.

Alexander Kusenko

2006-12-06

362

NASA Astrophysics Data System (ADS)

In this article, we propose to study two issues associated with the use of the incremental projection method for solving the incompressible Navier-Stokes equation. The first one is the combination of this time splitting algorithm with an adaptive local refinement method. The second one is the reduction of spurious velocities due to the right-hand side of the momentum balance. We propose a new variant of the incremental projection method for solving the Navier-Stokes equations with variable density and illustrate its behavior with the example of two phase flows simulations using a Cahn-Hilliard/Navier-Stokes model.

Minjeaud, Sebastian

2013-03-01

363

Sterile neutrinos, dark matter, and pulsar velocities in models with a Higgs singlet.

We identify the range of parameters for which the sterile neutrinos can simultaneously explain the cosmological dark matter and the observed velocities of pulsars. To satisfy all cosmological bounds, the relic sterile neutrinos must be produced sufficiently cold. This is possible in a class of models with a gauge-singlet Higgs boson coupled to the neutrinos. Sterile dark matter can be detected by the x-ray telescopes. The presence of the singlet in the Higgs sector can be tested at the CERN Large Hadron Collider. PMID:17280266

Kusenko, Alexander

2006-12-15

364

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

365

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

366

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

367

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

The present work studies, in detail, the unsteady wall-layer model of Walker et al. (1989, AIAA J., 27, 140 – 149) for the velocity profile in turbulent flows. Two new terms are included in the transcendental nonlinear system of equations that is used to determine the three main model parameters. The mathematical and physical feasible domains of the model are determined as a function of the non-dimensional pressure gradient parameter (p+). An explicit parameterization is presented for the average period between bursts (T+B), the origin of time (t+0 ) and the integration constant of the time dependent equation (A0) in terms of p+. In the present procedure, all working systems of differential equations are transformed, resulting in a very fast computational procedure that can be used to develop real-time flow simulators. PMID:25590746

Mikhailov, Mikhail D; Freire, Atila P Silva

2014-12-01

368

High-velocity impacts in regolith: insight from numerical models and experiments

NASA Astrophysics Data System (ADS)

High-velocity impacts are common events on planetary surfaces, from a constant micrometeoroid bombardment to infrequent but catastrophic large asteroid impacts that form giant craters. The consequences of such impacts depend, in part, on the properties of the planet surface, such as strength, porosity and surface gravity. The near-surface of many solar system bodies is a loose granular material composed of dust, soil and broken rock, known as regolith. Planetary regolith could have a range of material properties, hence it is difficult to specify its material model. As a result, experimental investigations of impacts on planetary surfaces often use sand as a regolith analogue material and hydrocode simulations of impact often assume a sand-like equation of state and strength model. In this study, we compare iSALE hydrocode simulations of impacts in sand and other porous granular materials with results from laboratory impact experiments to test and refine material models for regolith materials.

Miljkovic, Katarina; Collins, Gareth; Patel, Manish; Chapman, David; Proud, William

2011-06-01

369

NASA Technical Reports Server (NTRS)

Electron density measurements have been made in steady-state plasmas in a spherical inertial electrostatic confinement (IEC) discharge using microwave interferometry. Plasma cores interior to two cathodes, having diameters of 15 and 23 cm, respectively, were probed over a transverse range of 10 cm with a spatial resolution of about 1.4 cm for buffer gas pressures from 0.2 to 6 Pa in argon and deuterium. The transverse profiles are generally flat, in some cases with eccentric symmetric minima, and give mean densities of from approx. = 0.4 to 7x 10(exp 10)/cu cm, the density generally increasing with the neutral gas pressure. Numerical solutions of the 1-D Poisson equation for EC plasmas are reviewed and energy distribution functions are identified which give flat transverse profiles. These functions are used with the plasma approximation to obtain solutions which also give densities consistent with the measurements, and a double potential well solution is obtained which has minima qualitatively similar to those observed. Explicit consideration is given to the compatibility of the solutions interior and exterior to the cathode, and to grid transparency. Deuterium fusion neutron emission rates were also measured and found to be isotropic, to within the measurement error, over two simultaneous directions. Anisotropy was observed in residual emissions during operation with non-fusing hydrogen-1. The deuterium rates are consistent with predictions from the model.

Dobson, Chris C.; Hrbud, Ivana

2004-01-01

370

NASA Astrophysics Data System (ADS)

The Lower Rhine Delta, a transitional area between the River Rhine and Meuse and the North Sea, is at risk of flooding induced by infrequent events of a storm surge or upstream flooding, or by more infrequent events of a combination of both. A joint probability analysis of the astronomical tide, the wind induced storm surge, the Rhine flow and the Meuse flow at the boundaries is established in order to produce the joint probability distribution of potential flood events. Three individual joint probability distributions are established corresponding to three potential flooding causes: storm surges and normal Rhine discharges, normal sea levels and high Rhine discharges, and storm surges and high Rhine discharges. For each category, its corresponding joint probability distribution is applied, in order to stochastically simulate a large number of scenarios. These scenarios can be used as inputs to a deterministic 1-D hydrodynamic model in order to estimate the high water level frequency curves at the transitional locations. The results present the exceedance probability of the present design water level for the economically important cities of Rotterdam and Dordrecht. The calculated exceedance probability is evaluated and compared to the governmental norm. Moreover, the impact of climate change on the high water level frequency curves is quantified for the year 2050 in order to assist in decisions regarding the adaptation of the operational water management system and the flood defense system.

Zhong, H.; van Overloop, P.-J.; van Gelder, P. H. A. J. M.

2013-07-01

371

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

372

NASA Astrophysics Data System (ADS)

Continuum damage mechanics is a promising alternative to fracture mechanics for representing rifting, crevassing and calving processes in ice sheet models. The constitutive relations describing ice rheology can be modified using state variables which describe the effects of cracking and damage without explicitly seeking to resolve individual cracks. The challenge in formulating a damage model for application in a large-scale ice sheet model is in the computational cost associated with the increase in model complexity and the addition of a differential equation describing the evolution of damage. We present an investigation of the spatial distribution of damage for the Larsen C ice shelf using a scalar isotropic damage model implemented in the Ice Sheet System Model (ISSM). The representation of damage using a single scalar is a simple but numerically efficient approach to accounting for the effects of fractures on ice flow. InSAR-derived surface velocities are used to invert for the scalar damage variable, leading to a spatial map of damage analogous to that produced by inverting for the ice rigidity itself. The key distinction in inverting for the damage variable is that thermal and mechanical components of the constitutive relation are formally separated in the inversion. This spatial mapping of damage is a key first step in forward modeling of the stability of ice shelves using damage mechanics, and we discuss ongoing work to implement a transient damage model in ISSM to project the mechanical integrity of ice shelves in a warming climate.

Borstad, C.; Larour, E.; Morlighem, M.; Seroussi, H.; Rignot, E.

2012-04-01

373

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 1