Brady 1D seismic velocity model ambient noise prelim
Mellors, Robert J.
Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.
Brady 1D seismic velocity model ambient noise prelim
Mellors, Robert J.
2013-10-25
Preliminary 1D seismic velocity model derived from ambient noise correlation. 28 Green's functions filtered between 4-10 Hz for Vp, Vs, and Qs were calculated. 1D model estimated for each path. The final model is a median of the individual models. Resolution is best for the top 1 km. Poorly constrained with increasing depth.
NASA Astrophysics Data System (ADS)
Graves, R. W.
2012-12-01
I have performed low frequency (f < 1 Hz) ground motion simulations for the 2008 Mw 5.23 Mt. Carmel, Illinois and 2011 Mw 5.74 Mineral, Virginia earthquakes to calibrate a rock-site 1D crustal velocity and Q structure model for central and eastern US (CEUS). For each earthquake, the observed ground motions were simulated at sites extending out to about 900 km from the epicenter. Sites within the Mississippi embayment are not included in the modeling. The initial 1D velocity model was developed by averaging profiles extracted from the CUS V1.3 3D velocity model (Ramirez-Guzman et al, 2012) at each of the recording sites, with the surface shear wave velocity set at 2200 m/s. The Mt. Carmel earthquake is represented as a point double couple (strike=25, dip=90, rake=-175) at a depth of 14 km and a slip-rate function having a Brune corner frequency of 0.89 Hz (Hartzell and Mendoza, 2011). The Mineral earthquake is represented as a point double couple (strike=26, dip=55, rake=108) at a depth of 6 km and a slip-rate function having a corner frequency of 0.50 Hz. Full waveform Green's functions were computed using the FK method of Zhu and Rivera (2002). The initial model does well at reproducing the median level of observed response spectral acceleration (Sa) for most sites out to 300 km at periods of 2 to 5 sec, including the observed flattening in distance attenuation between 70 and 150 km. However, this model under predicts the motions beyond about 400 km distance. Increasing Q in the mid- and lower crust from the original value of 700 to 5000 removes this under prediction of the larger distance motions. Modified Mercalli Intensity (MMI) estimates have been computed from the simulations using the ground motion-intensity conversion equations of Atkinson and Kaka (2007; AK2007) and Dangkua and Cramer (2011; DC2011-ENA) for comparison against the observed "Did You Feel It" intensity estimates. Given the bandwidth limitations of the simulations, I use the conversion relations for 2 sec Sa. For both earthquakes, the MMI values obtained from DC2011-ENA are systematical higher than the AK2007 values for all distances and over predict the median level of the observed values by roughly 1 MMI unit, whereas the AK2007 values provide a close match to the observed median levels.bserved and simulated spectral acceleration levels at 2 second period (left) and MMI (right) for the Mt. Carmel earthquake.
NASA Astrophysics Data System (ADS)
Muench, Thomas; Koch, Manfred; Schlittenhard, Jörg
2010-05-01
On December 5, 2004 a strong earthquake occurred near the city of Waldkirch, about 30 km's north of Freiburg, with a local magnitude of ML = 5.4. This seismic event was one of the strongest observed since the ML = 5.7 'Schwäbische Alb' event of September 3, 1978, 30 years before. In the aftermath of the event several institutions (Bens, BGR, LGBR, LED, SED and NEIC) have attempted to relocate this earthquake that came up with a hypocentral depth range of 9 - 12 km which. In fact, as the exact hypocentral location of the Waldkirch - and other events in the area - namely, the seismic depths, are of utmost importance for the further understanding of the seismotectonics as well as of the seismic hazard in the upper Rhinegraben area, one cannot over stress the necessity for a hypocenter relocation as best as possible. This requires a careful analysis of all factors that may impede an unbiased relocation of such an event. In the present talk we put forward the question whether the Waldkirch seismic event can be relocated with sufficient accuracy by a regional network when, additionally, improved regional 1D- and 3D seismic velocity models for the crust and upper mantle that take into consideration Pn-anisotropy of the upper mantle beneath Germany are employed in the hypocentral determination process. The seismological work starts with a comprehensive analysis of the dataset available for the relocation of the event. By means of traveltime curves a reevaluation of the observed phases is done and it is shown that some of the big observed traveltime residuals are most likely the consequence of wrongly associated phases as well as of the neglect of the anisotropic Pn traveltime correction for the region. Then hypcocenter relocations are done for 1D vertically inhomogeneous and 3D laterally inhomogeneous seismic velocity models, without and with the anisotropic Pn-traveltime correction included. The effects of the - often not well-known - Moho depth and of the VP/VS-ratio across the study area are investigated. Finally a thorough statistical analysis of the hypocentral relocation accuracy and its sensitivity to various observational and model errors is carried out by (1) the classical calculation of covariances and confidence ellipses for the hypocenter and (2) Monte Carlo relocations with random perturbations of the observed arrivaltimes as well as of the choice of the initial hypocenter in the relocation process. The correction of the original phase-data leads to a shift of the hypocenter to about 10 to 15 km depth instead of 0 - 5 km for the uncorrected phases.The importance of the phase correction is also supported by the final RMS which is reduced from 2.22 s to 1.00 s for the isotropic case and, even more so, from 2.29 s to 0.75 s for the anisotropic. The reduced traveltime plots indicate also that a common VP /VS-ratio of 1.72 for both the crust and the upper mantle does not fit the crustal Sg-phases well. From subsequent hypocentral relocations with separate VP/VS-ratio for the crust and the upper mantle optimal values of VP /VS = 1.70 former, respective 1.66 for the latter, are obtained. In a subsequent set of relocations of the Waldkirch event the recently established isotropic and anisotropic 3D- crustal and upper mantle seismic velocity models of (Muench, 2009; Muench et al., 2010) are employed. Compared with the previous 1D hypocentral relocations where the optimal depth range found is 14 to 15 km, those of the 3D models lie about one km higher. The slightly lower depth of the 3D-models is most likely a consequence of traveltime effects of the structural velocity inhomogeneities.
Cerveny, Vlastislav
in studies of induced seismic activity because of the limited distribution of the receivers and induced a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test fails due to the trade-off between the velocity model and event locations. INTRODUCTION Hydraulic
Cerveny, Vlastislav
in studies of induced seismic activity because of the limited distribution of the receivers and induced a distribution of microseismic events induced by hydrofrac treatment to a monitoring geophone array(s), we test fails due to the trade-off between the velocity model and event locations. INTRODUCTION Hydraulic
NSDL National Science Digital Library
2008-05-29
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.
Calibration of a 1D/1D urban flood model using 1D/2D model results in the absence of field data.
Leandro, J; Djordjevi?, S; Chen, A S; Savi?, D A; Stani?, M
2011-01-01
Recently increased flood events have been prompting researchers to improve existing coupled flood-models such as one-dimensional (1D)/1D and 1D/two-dimensional (2D) models. While 1D/1D models simulate sewer and surface networks using a one-dimensional approach, 1D/2D models represent the surface network by a two-dimensional surface grid. However their application raises two issues to urban flood modellers: (1) stormwater systems planning/emergency or risk analysis demands for fast models, and the 1D/2D computational time is prohibitive, (2) and the recognized lack of field data (e.g. Hunter et al. (2008)) causes difficulties for the calibration/validation of 1D/1D models. In this paper we propose to overcome these issues by calibrating a 1D/1D model with the results of a 1D/2D model. The flood-inundation results show that: (1) 1D/2D results can be used to calibrate faster 1D/1D models, (2) the 1D/1D model is able to map the 1D/2D flood maximum extent well, and the flooding limits satisfactorily in each time-step, (3) the 1D/1D model major differences are the instantaneous flow propagation and overestimation of the flood-depths within surface-ponds, (4) the agreement in the volume surcharged by both models is a necessary condition for the 1D surface-network validation and (5) the agreement of the manholes discharge shapes measures the fitness of the calibrated 1D surface-network. PMID:22214046
Crustal Seismic Velocity Model of Southern Ontario
NASA Astrophysics Data System (ADS)
Dineva, S.; Eaton, D.
2004-05-01
Knowledge of crustal thickness and velocity is important to obtain precise hypocenter locations, as well as to constrain tectonic interpretations for a particular region. In southern Ontario, the installation of the POLARIS network started in 2001. At present, there are 23 broad-band stations installed in this region. Together with the information from the Southern Ontario Seismic Network (SOSN), which operated with short-period sensors between 1990-2000, more than 200 recorded events (earthquakes and quarry blast) are available for velocity modeling. The arrival-time data from local events and some well recorded quarry blasts are used for a preliminary estimation of the 1-D and 3-D velocity model of southwestern Ontario. For 1-D velocity tomography the method of Kissling (1984) (VELEST program) is applied. Different initial models are used to obtain a robust result. The Moho depth is constrained independently using results of receiver-function analysis and gravity inversion. . The obtained 1-D `optimum' velocity model is used as the initial model for a subsequent 3-D local tomography using the `Thurber inversion' (Thurber, 1981, 1983, 1993) (SIMULPS program). New hypocenter locations for all local events in southwestern Ontario in 1990-2003 have been calculated using the new 1-D and 3-D velocity models.
Evaluating 1d Seismic Models of the Lunar Interior
NASA Astrophysics Data System (ADS)
Yao, Y.; Thorne, M. S.; Weber, R. C.; Schmerr, N. C.
2012-12-01
A four station seismic network was established on the Moon from 1969 to 1977 as part of the Apollo Lunar Surface Experiment Package (ALSEP). A total of nine 1D seismic velocity models were generated using a variety of different techniques. In spite of the fact that these models were generated from the same data set, significant differences exist between them. We evaluate these models by comparing predicted travel-times to published catalogs of lunar events. We generate synthetic waveform predictions for 1D lunar models using a modified version of the Green's Function of the Earth by Minor Integration (GEMINI) technique. Our results demonstrate that the mean square errors between predicted and measured P-wave travel times are smaller than those for S-wave travel times in all cases. Moreover, models fit travel times for artificial and meteoroid impacts better than for shallow and deep moonquakes. Overall, models presented by Nakamura [Nakamura, 1983] and Garcia et al. [Garcia et al., 2011] predicted the observed travel times better than all other models and were comparable in their explanation of travel-times. Nevertheless, significant waveform differences exist between these models. In particular, the seismic velocity structure of the lunar crust and regolith strongly affect the waveform characteristics predicted by these models. Further complexity is added by possible mantle discontinuity structure that exists in a subset of these models. We show synthetic waveform predictions for these models demonstrating the role that crustal structure has in generating long duration seismic coda inherent in the lunar waveforms.
Ion Cyclotron Waves at Io: 1D Hybrid Modeling
NASA Astrophysics Data System (ADS)
Dols, V. J.; Delamere, P. A.; Bagenal, F.
2012-12-01
On Galileo close flybys of Io (1995-2001), the magnetometers detected ElectroMagnetic Ion Cyclotron (EMIC) waves close to the S, O, SO2 and SO ion gyrofrequencies. These waves are produced when the phase-space distribution function of a minor ion species of the torus is non-Maxwellian, as for instance, the result of a pickup of new ions from Io's neutral corona. They were detected far from Io (~ 10-20 Rio), mainly downstream of the moon, and are powerful diagnostic tools for probing Io's extended atmosphere. We investigate the production of EMIC waves with a 1D hybrid model (fluid electrons and kinetic ions). These 1D simulations represent the lifetime of a field line that is entrained around Io by the plasma flow and experiences a variable mass loading of new ions of different composition when the field line interacts with Io's neutral atmosphere. The time-variable mass loading of this field line is based on former simulations of the multi-species chemistry modeling of Io's interaction (Dols et al., 2008), coupled with a MHD modeling of the local electromagnetic interaction (Dols et al., 2011; 2012): a multi-component neutral atmosphere of Io is prescribed in S, O, SO2 and SO; the flow of the plasma is calculated with a MHD model; the mass loading rate of these ions is calculated for different flow lines around Io that follow the MHD flow. These time dependent multi-ion massloading rates and flow velocities are used as inputs to the 1D hybrid simulation. We then make a Fourier analysis of the hybrid-calculated magnetic field variations close to Galileo trajectories, evaluate the power and the resonant frequencies of the EMIC waves and compare to the Galileo magnetometer data. The ultimate goal of the EMIC analysis is to constrain Io's neutral corona, its longitudinal asymmetries and its time variability.
Lifting the Seismic Lid Beneath Cameroon Volcanic Line Using 1D Shear Wave Velocities
NASA Astrophysics Data System (ADS)
Tokam Kamga, Alain; Durrheim, Ray; Tabod, Charles; Nyblade, Andrew; Nguiya, Severin
2014-05-01
The composition of the lithosphere beneath Cameroon and the origin of the Cameroon Volcanic Line (CVL) is a matter of debate. Although many studies based on regional or global observations provide models for the setting of the CVL, none of them are strong enough to be considered as definitive. We used the joint inversion of Rayleigh wave group velocities and Rayleigh wave group velocities to derive shear wave velocity profiles of the lithosphere beneath Cameroon andshow that lithosphere is, on average, faster beneath the Congo Craton than beneath the Pan-African age crust. Using recently published dispersion curves, we extend the depth of investigation from 60 to 200 km. The calculated velocity-depth profiles do not show any sharp discontinuity that could be interpreted as the lithosphere-asthenosphere transition. Furthermore, there is no clear evidence of the existence of a low velocity zone beneath any geologic province within Cameroon. The smooth velocity variations observed on the velocity models are believed to be influenced by lateral mantle heterogeneities rather than vertical ones. The shear wave velocities for the uppermost mantle are in general greater than 4.3 km/s at all stations. This is higher than the values obtained in the Main Ethiopian Rift, and suggest that the perturbation of the by thermal anomalies does not extend as far as the CVL. This suggests that the source of volcanism along the CVL is from small scale convection in the asthenosphere and controlled by lithospheric fractures that are probably driven by the cold (and fast) edge of the Congo Craton.
Effective-range signatures in quasi-1D matter waves: sound velocity and solitons
NASA Astrophysics Data System (ADS)
Sgarlata, F.; Mazzarella, G.; Salasnich, L.
2015-06-01
We investigate ultracold and dilute bosonic atoms under strong transverse harmonic confinement using a 1D modified Gross–Pitaevskii equation (1D MGPE), which accounts for the energy dependence of the two-body scattering amplitude within an effective-range expansion. We study sound waves and solitons of the quasi-1D system, comparing the 1D MGPE results with the 1D GPE ones. We find that when the finite-size nature of the interaction is taken into account, the speed of sound and the density profiles of both dark and bright solitons show relevant quantitative changes with respect to predictions given by the standard 1D GPE.
Ion velocity distribution at the termination shock: 1-D PIC simulation
Lu Quanming; Yang Zhongwei; Lembege, Bertrand [CAS Key Laboratory of Basic Plasma Physics, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136 (China); LATMOS-UVSQ-IPSL-CNRS, Guyancourt 78280 (France)
2012-11-20
The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.
Modeling an electric motor in 1-D
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1991-01-01
Quite often the dynamicist will be faced with having an electric drive motor as a link in the elastic path of a structure such that the motor's characteristics must be taken into account to properly represent the dynamics of the primary structure. He does not want to model it so accurately that he could get detailed stress and displacements in the motor proper, but just sufficiently to represent its inertia loading and elastic behavior from its mounting bolts to its drive coupling. Described here is how the rotor and stator of such a motor can be adequately modeled as a colinear pair of beams.
GIS-BASED 1-D DIFFUSIVE WAVE OVERLAND FLOW MODEL
KALYANAPU, ALFRED [Los Alamos National Laboratory; MCPHERSON, TIMOTHY N. [Los Alamos National Laboratory; BURIAN, STEVEN J. [NON LANL
2007-01-17
This paper presents a GIS-based 1-d distributed overland flow model and summarizes an application to simulate a flood event. The model estimates infiltration using the Green-Ampt approach and routes excess rainfall using the 1-d diffusive wave approximation. The model was designed to use readily available topographic, soils, and land use/land cover data and rainfall predictions from a meteorological model. An assessment of model performance was performed for a small catchment and a large watershed, both in urban environments. Simulated runoff hydrographs were compared to observations for a selected set of validation events. Results confirmed the model provides reasonable predictions in a short period of time.
Classification of binary textures using the 1-D Boolean model.
García-Sevilla, P; Petrou, M
1999-01-01
The one-dimensional (1-D) Boolean model is used to calculate features for the description of binary textures. Each two-dimensional (2-D) texture is converted into several 1-D strings by scanning it according to raster vertical, horizontal or Hilbert sequences. Several different probability distributions for the segment lengths created this way are used to model their distribution. Therefore, each texture is described by a set of Boolean models. Classification is performed by calculating the overlapping probability between corresponding models. The method is evaluated with the help of 32 different binary textures, and the pros and cons of the approach are discussed. PMID:18267419
Geostatistical Modeling of Pore Velocity
Devary, J.L.; Doctor, P.G.
1981-06-01
A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.
Data Analysis of cGPS stations in central Greece: station velocities and 1-D strain estimates
NASA Astrophysics Data System (ADS)
Ganas, Athanassios; Chousianitis, Konstantinos; Gianniou, Michalis
2013-04-01
We processed 30-s GPS data from permanent GNSS stations in central Greece, available at NOA since 2006. We obtained position time series along with horizontal and vertical velocities using the Kalman filtering approach and accounting for time-correlated noise content. The station distribution allowed us to draw velocity profiles and to calculate rates of baseline length change (1-D strain). In central Greece, the coherent picture of the velocity pattern for Attica and north-eastern Peloponnese (Corinth) stations (effectively a velocity "plateau" at 30 mm/yr) indicates that these areas belong to the same crustal block, although some internal strain is present within Attica's crust as well as across the Saronic Gulf. Our 1-D strain estimates are in general agreement with geological data (fault slip rates) in central Greece, implying accommodation of this crustal extension along E-W striking active normal faults. Some NE-SW directed shortening is mapped in the wider area to the west of the termination of the North Anatolian Fault (Sporades islands).
Brouard, M.; Duxon, S.P.; Enriquez, P.A.; Sayos, R.; Simons, J.P. (Univ. of Nottingham (United Kingdom))
1991-10-17
The secondary reaction of velocity aligned, superthermal atoms generated via molecular photodissociation can lead to aligned secondary reaction products. Their vector properties and their quantum safe distributions can be measured by using Doppler resolved, polarized laser probe techniques. A simple LAB {yields} CM transformation can thus be used to determine the vector correlations among k (the bimolecular collision velocity vectors), k{prime} (the reaction products' velocity vectors), and j{prime} (the reaction products' angular momenta). These are analogous to the ({mu},v,j) correlations in the primary photodissociation. The strategy is demonstrated in a study of the dynamical stereochemistry of the reaction O({sup 1}D) + N{sub 2}O {yields} NO + NO.
Nonlocal Order Parameters for the 1D Hubbard Model
NASA Astrophysics Data System (ADS)
Montorsi, Arianna; Roncaglia, Marco
2012-12-01
We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.
Examination of 1D Solar Cell Model Limitations Using 3D SPICE Modeling: Preprint
McMahon, W. E.; Olson, J. M.; Geisz, J. F.; Friedman, D. J.
2012-06-01
To examine the limitations of one-dimensional (1D) solar cell modeling, 3D SPICE-based modeling is used to examine in detail the validity of the 1D assumptions as a function of sheet resistance for a model cell. The internal voltages and current densities produced by this modeling give additional insight into the differences between the 1D and 3D models.
A simple quasi-1D model of Fibonacci anyons
NASA Astrophysics Data System (ADS)
Aasen, David; Mong, Roger; Clarke, David; Alicea, Jason; Fendley, Paul
2015-03-01
There exists various ways of understanding the topological properties of Ising anyons--from simple free-fermion toy models to formal topological quantum field theory. For other types of anyons simple toy models rarely exist; their properties have to be obtained using formal self-consistency relations. We explore a family of gapped 1D local bosonic models that in a certain limit become trivial to solve and provide an intuitive picture for Fibonacci anyons. One can interpret this model as a quasi-1D wire that forms the building block of a 2D topological phase with Fibonacci anyons. With this interpretation all topological properties of the Fibonacci anyons become manifest including ground state degeneracy and braid relations. We conjecture that the structure of the model is protected by an emergent symmetry analogous to fermion parity. 1) NSF Grant DMR-1341822 2) Institute for Quantum Information and Matter, an NSF physics frontier center with support from the Moore Foundation. 3) NSERC-PGSD.
NASA Astrophysics Data System (ADS)
Dhakal, Y. P.; Tsuno, S.; Yamanaka, H.
2011-12-01
There are several 3-D velocity structural models for the Kanto Basin in Japan. However, the velocity models are different because they have been constructed with separate data sets such as, geophysical, geological, and earthquake data. It is, therefore, important for the reliable prediction of long-period ground motions to validate those models based on the observed earthquake recordings. Tsuno et al. (2011) revised the depths of the seismic basement and sedimentary layer interfaces in the Yamanaka and Yamada (2006) model of the Kanto Basin by the inversion of H/V-spectra of coda waves. In this paper, we perform 1-D simulation of long-period S-waves (2-10 s) to verify the velocity structures in the Kanto Basin inverted from H/V-spectra of earthquake ground motions. Considering the simplicity in the estimation of source parameters, we simulate the long-period S-waves for the nearby intermediate depth moderate earthquakes. We compare only the first cycle of the observed and synthetic S-waveforms. Consequently, the comparison of the time window for velocity waveforms will be sufficiently ahead of the 3-D basin effects. References Tsuno, S., H. Yamanaka, S. Sakai, N. Hirata, K. Kasahara, H. Kimura, T. Aketagawa [2011], "Deep S-wave Velocity Structures in the Tokyo Metropolitan Area estimated by the H/V Spectral Ratio Using coda waves, 4th IASPEI/IAEE International Symposium on Effects of Surface Geology on Seismic Motion, UCSB, Aug 23-26. Yamanaka, H. and N. Yamada [2006], "Modeling 3D S-wave Velocity Structure of Kanto Basin for Estimation of Earthquake Ground Motion", Butsuri-Tansa, Vol. 59, No. 6, pp. 549-560 (in Japanese with English abstract).
A computationally efficient steady-state electrode-level and 1D + 1D cell-level fuel cell model
NASA Astrophysics Data System (ADS)
Bao, Cheng; Bessler, Wolfgang G.
2012-07-01
Computational efficiency is highly important for upscaling detailed electrode-level and cell-level models to the system level required for the design and control of fuel cells. We present a computationally efficient 1D + 1D fuel cell model based on a combination of analytical and numerical approaches. On the electrode level, we develop approximate analytical solutions for the 1D current/potential distribution via a hybrid algorithm of power-law approach and perturbation method. Compared to the conventional perturbation method, this work keeps the intrinsic nonlinearity of electrochemical kinetics, while providing clearer physical meaning than some purely mathematical methods like the Adomian decomposition method. By integrating the resulting overpotential profile into mass transfer models, concentration overpotentials are obtained and the thermodynamic framework is then used for analyzing the H2/CO electrochemical co-oxidation kinetics. A novel expression is also presented to interconvert volume- and area-specific exchange current densities. On the cell level, a linear relationship between local current density and solid temperature is further developed for efficient 1D + 1D thermal along-the-channel numerical simulations without requiring computational iterations. Both the electrode-level and cell-level macroscopic fuel cell models are validated against full numerical solutions available in the open literatures over a wide range of operating conditions. With the hybrid analytical/numerical approximation in two dimensions, the computational framework is predicted to be sufficiently efficient for real-time simulations.
Lanczos diagonalizations of the 1-D Peierls-Hubbard model
Loh, E.Y.; Campbell, D.K.; Gammel, J.T.
1989-01-01
In studies of interacting electrons in reduced dimensions'' one is trapped between the Scylla of exponential growth of the number of states in any exact many-body basis and the Charybdis of the failure of mean-field theories to capture adequately the effects of interactions. In the present article we focus on one technique -- the Lanczos method -- which, at least in the case of the 1-D Peierls-Hubbard model, appears to allow us to sail the narrow channel between these two hazards. In contrast to Quantum Monte Carlo methods, which circumvent the exponential growth of states by statistical techniques and importance sampling, the Lanczos approach attacks this problem head-on by diagonalizing the full Hamiltonian. Given the restrictions of present computers, this approach is thus limited to studying finite clusters of roughly 12--14 sites. Fortunately, in one dimension, such clusters are usually sufficient for extracting many of the properties of the infinite system provided that one makes full use of the ability to vary the boundary conditions. In this article we shall apply the Lanczos methodology and novel phase randomization'' techniques to study the 1-D Peierls-Hubbard model, with particular emphasis on the optical absorption properties, including the spectrum of absorptions as a function of photon energy. Despite the discreteness of the eigenstates in our finite clusters, we are able to obtain optical spectra that, in cases where independent tests can be made, agree well with the known exact results for the infinite system. Thus we feel that this combination of techniques represents an important and viable means of studying many interesting novel materials involving strongly correlated electrons. 26 refs., 6 figs.
Bechtel, S.E.; Forest, M.G.; Holm, D.D.; Lin, K.J.
1988-01-01
In this paper we derive one space dimensional, reduced systems of equations (1-D closure models) for viscoelastic free jets. We begin with the three-dimensional system of conservation laws and a Maxwell-Jeffreys constitutive law for an incompressible viscoelastic fluid. First, we exhibit exact truncations to a finite, closed system of 1-D equations based on classical velocity assumptions of von Karman. Next, we demonstrate that the 3-D free surface boundary conditions overconstrain these truncated systems, so that only a very limited class of solutions exist. We then proceed to derive approximate 1-D closure theories through a slender jet asymptotic scaling, combined with appropriate definitions of velocity, pressure and stress unknowns. Our nonaxisymmetric 1-D slender jet models incorporate the physical effects of inertia, viscoelasticity (viscosity, relaxation and retardation), gravity, surface tension, and properties of the ambient fluid, and include shear stresses and time dependence. Previous special 1-D slender jet models correspond to the lowest order equations in the present asymptotic theory by an a posteriori suppression to leading order of some of these effects, and a reduction to axisymmetry. Solutions of the lowest order system of equations in this asymptotic analysis are presented: For the special cases of elliptical inviscid and Newtonian free jets, subject to the effects of surface tension and gravity, our model predicts oscillation of the major axis of the free surface elliptical cross section between perpendicular directions with distance down the jet, and drawdown of the cross section, in agreement with observed behavior. 15 refs.
Flooding flows in city crossroads: experiments and 1-D modelling.
Rivière, N; Perkins, R J; Chocat, B; Lecus, A
2006-01-01
This study focuses on the discharge distribution in an intersection of four channels, similar to a city crossroad. The channels and the intersection are all horizontal. Flow enters through two of the channels, and leaves through the other two. The flow is subcritical everywhere, and flow depths are controlled by vertical weirs at the exits of the outlet channels. The main variables that are measured are the flow rates in the four channels. When the weir heights in the outlet channels are the same, the ratio of flow rates in the outlet channels depends only on the ratio of flow rates in the inlet channels; if the outlet conditions are different, other parameters, such as the total flow rate also become important. The flow has also been simulated numerically using a solution of the 1-D Saint Venant equations, with a simple model to predict flow distribution in the intersection. A comparison with the experimental data shows that this model works well for the limited range of experimental conditions studied here. However, further work is needed on a wider range of conditions, closer to real conditions, before the model can be considered valid for practical applications. PMID:17120636
Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.
2008-01-01
Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.
A One-Dimensional (1-D) Three-Region Model for a Bubbling Fluidized-Bed Adsorber
Lee, Andrew; Miller, David C.
2012-01-01
A general one-dimensional (1-D), three-region model for a bubbling fluidized-bed adsorber with internal heat exchangers has been developed. The model can predict the hydrodynamics of the bed and provides axial profiles for all temperatures, concentrations, and velocities. The model is computationally fast and flexible and allows for any system of adsorption and desorption reactions to be modeled, making the model applicable to any adsorption process. The model has been implemented in both gPROMS and Aspen Custom Modeler, and the behavior of the model has been verified.
Numerical Modeling of Imploding Plasma liners Using the 1D Radiation-Hydrodynamics Code HELIOS
NASA Astrophysics Data System (ADS)
Davis, J. S.; Hanna, D. S.; Awe, T. J.; Hsu, S. C.; Stanic, M.; Cassibry, J. T.; Macfarlane, J. J.
2010-11-01
The Plasma Liner Experiment (PLX) is attempting to form imploding plasma liners to reach 0.1 Mbar upon stagnation, via 30--60 spherically convergent plasma jets. PLX is partly motivated by the desire to develop a standoff driver for magneto-inertial fusion. The liner density, atomic makeup, and implosion velocity will help determine the maximum pressure that can be achieved. This work focuses on exploring the effects of atomic physics and radiation on the 1D liner implosion and stagnation dynamics. For this reason, we are using Prism Computational Science's 1D Lagrangian rad-hydro code HELIOS, which has both equation of state (EOS) table-lookup and detailed configuration accounting (DCA) atomic physics modeling. By comparing a series of PLX-relevant cases proceeding from ideal gas, to EOS tables, to DCA treatments, we aim to identify how and when atomic physics effects are important for determining the peak achievable stagnation pressures. In addition, we present verification test results as well as brief comparisons to results obtained with RAVEN (1D radiation-MHD) and SPHC (smoothed particle hydrodynamics).
Newberry EGS Seismic Velocity Model
Templeton, Dennise
We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.
Newberry EGS Seismic Velocity Model
Templeton, Dennise
2013-10-01
We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.
1D numerical model of muddy subaqueous and subaerial debris flows
Imran, J.; Parker, G.; Locat, J.; Lee, H.
2001-01-01
A 1D numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows is presented. The model incorporates the Herschel-Bulkley and bilinear rheologies of viscoplastic fluid. The more familiar Bingham model is integrated into the Herschel-Bulkley rheological model. The conservation equations of mass and momentum of single-phase laminar debris flow are layer-integrated using the slender flow approximation. They are then expressed in a Lagrangian framework and solved numerically using an explicit finite difference scheme. Starting from a given initial shape, a debris flow is allowed to collapse and propagate over a specified topography. Comparison between the model predictions and laboratory experiments shows reasonable agreement. The model is used to study the effect of the ambient fluid density, initial shape of the failed mass, and rheological model on the simulated propagation of the front and runout characteristics of muddy debris flows. It is found that initial failure shape influence the front velocity but has little bearing on the final deposit shape. In the Bingham model, the excess of shear stress above the yield strength is proportional to the strain rate to the first power. This exponent is free to vary in the Herschel-Bulkley model. When it is set at a value lower than unity, the resulting final deposits are thicker and shorter than in the case of the Bingham rheology. The final deposit resulting from the bilinear model is longer and thinner than that from the Bingham model due to the fact that the debris flow is allowed to act as a Newtonian fluid at low shear rate in the bilinear model.
Velocity-jump models with crowding effects
NASA Astrophysics Data System (ADS)
Treloar, Katrina K.; Simpson, Matthew J.; McCue, Scott W.
2011-12-01
Velocity-jump processes are discrete random-walk models that have many applications including the study of biological and ecological collective motion. In particular, velocity-jump models are often used to represent a type of persistent motion, known as a run and tumble, that is exhibited by some isolated bacteria cells. All previous velocity-jump processes are noninteracting, which means that crowding effects and agent-to-agent interactions are neglected. By neglecting these agent-to-agent interactions, traditional velocity-jump models are only applicable to very dilute systems. Our work is motivated by the fact that many applications in cell biology, such as wound healing, cancer invasion, and development, often involve tissues that are densely packed with cells where cell-to-cell contact and crowding effects can be important. To describe these kinds of high-cell-density problems using a velocity-jump process we introduce three different classes of crowding interactions into a one-dimensional model. Simulation data and averaging arguments lead to a suite of continuum descriptions of the interacting velocity-jump processes. We show that the resulting systems of hyperbolic partial differential equations predict the mean behavior of the stochastic simulations very well.
GaAs solar cell photoresponse modeling using PC-1D V2.1
NASA Technical Reports Server (NTRS)
Huber, D. A.; Olsen, L. C.; Dunham, G.; Addis, F. W.
1991-01-01
Photoresponse data of high efficiency GaAs solar cells were analyzed using PC-1D V2.1. The approach required to use PC-1D for photoresponse data analysis, and the physical insights gained from performing the analysis are discussed. In particular, the effect of Al(x)Ga(1-x)As heteroface quality was modeled. Photoresponse or spectral quantum efficiency is an important tool in characterizing material quality and predicting cell performance. The strength of the photoresponse measurement lies in the ability to precisely fit the experimental data with a physical model. PC-1D provides a flexible platform for calculations based on these physical models.
Quasi 1D Modeling of Mixed Compression Supersonic Inlets
NASA Technical Reports Server (NTRS)
Kopasakis, George; Connolly, Joseph W.; Paxson, Daniel E.; Woolwine, Kyle J.
2012-01-01
The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.
Validation of 1-D transport and sawtooth models for ITER
Connor, J.W.; Turner, M.F.; Attenberger, S.E.; Houlberg, W.A.
1996-12-31
In this paper the authors describe progress on validating a number of local transport models by comparing their predictions with relevant experimental data from a range of tokamaks in the ITER profile database. This database, the testing procedure and results are discussed. In addition a model for sawtooth oscillations is used to investigate their effect in an ITER plasma with alpha-particles.
Velocity model of the shallow lunar crust
NASA Technical Reports Server (NTRS)
Gangi, A. F.
1980-01-01
The travel times of the seismic waves obtained for the Apollo-14 and -16 active seismic experiments and the Apollo-16 grenade launches are shown to be consistent with a powder-layer model of the shallow lunar crust. The velocity variation with depth determined from these data is: V(z) = approximately 110 z to the 1/6 power m/sec for z less than 10 meters and V(z) is nearly = to 250 m/sec for z greater than 10 meters. The velocity values found for the 10 meter depth are similar to those found by Kovach, et al. (1972). The z to the 1/6 power depth dependence for the velocity of the topmost layer is that predicted on the basis of a powder layer (Gangi, 1972). The Amplitude variation of the direct waves as a function of source-to-receiver separation, x, is A(x) = A(o)x to the -n power exp(-ax) where 1.5 n 2.2 and a is nearly = to 0.047 neper/m. Velocity-spectra analyses of the direct, surface-reflected, bottom-reflected and refracted waves give results that are consistent with the velocity model inferred from the traveltime data.
Kinetic and Stochastic Models of 1D yeast ``prions"
NASA Astrophysics Data System (ADS)
Kunes, Kay
2005-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeasts have proteins, which can undergo similar reconformation and aggregation processes to PrP; yeast ``prions" are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein (1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics along with our own stochastic approach (2). Both models assume reconformation only upon aggregation, and include aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates.
Kinetic Model for 1D aggregation of yeast ``prions''
NASA Astrophysics Data System (ADS)
Kunes, Kay; Cox, Daniel; Singh, Rajiv
2004-03-01
Mammalian prion proteins (PrP) are of public health interest because of mad cow and chronic wasting diseases. Yeast have proteins which can undergo similar reconformation and aggregation processes to PrP; yeast forms are simpler to experimentally study and model. Recent in vitro studies of the SUP35 protein(1), showed long aggregates and pure exponential growth of the misfolded form. To explain this data, we have extended a previous model of aggregation kinetics(2). The model assumes reconformation only upon aggregation, and includes aggregate fissioning and an initial nucleation barrier. We find for sufficiently small nucleation rates or seeding by small dimer concentrations that we can achieve the requisite exponential growth and long aggregates. We will compare to a more realistic stochastic kinetics model and present prelimary attempts to describe recent experiments on SUP35 strains. *-Supported by U.S. Army Congressionally Mandated Research Fund. 1) P. Chien and J.S. Weissman, Nature 410, 223 (2001); http://online.kitp.ucsb.edu/online/bionet03/collins/. 2) J. Masel, V.A.> Jansen, M.A. Nowak, Biophys. Chem. 77, 139 (1999).
Deconvolution of Complex 1D NMR Spectra Using Objective Model Selection
Hughes, Travis S.; Wilson, Henry D.; de Vera, Ian Mitchelle S.; Kojetin, Douglas J.
2015-01-01
Fluorine (19F) NMR has emerged as a useful tool for characterization of slow dynamics in 19F-labeled proteins. One-dimensional (1D) 19F NMR spectra of proteins can be broad, irregular and complex, due to exchange of probe nuclei between distinct electrostatic environments; and therefore cannot be deconvoluted and analyzed in an objective way using currently available software. We have developed a Python-based deconvolution program, decon1d, which uses Bayesian information criteria (BIC) to objectively determine which model (number of peaks) would most likely produce the experimentally obtained data. The method also allows for fitting of intermediate exchange spectra, which is not supported by current software in the absence of a specific kinetic model. In current methods, determination of the deconvolution model best supported by the data is done manually through comparison of residual error values, which can be time consuming and requires model selection by the user. In contrast, the BIC method used by decond1d provides a quantitative method for model comparison that penalizes for model complexity helping to prevent over-fitting of the data and allows identification of the most parsimonious model. The decon1d program is freely available as a downloadable Python script at the project website (https://github.com/hughests/decon1d/). PMID:26241959
NASA Astrophysics Data System (ADS)
Barker, H. W.; Stephens, G. L.; Partain, P. T.; Bergman, J. W.; Bonnel, B.; Campana, K.; Clothiaux, E. E.; Clough, S.; Cusack, S.; Delamere, J.; Edwards, J.; Evans, K. F.; Fouquart, Y.; Freidenreich, S.; Galin, V.; Hou, Y.; Kato, S.; Li, J.; Mlawer, E.; Morcrette, J.-J.; O'Hirok, W.; Räisänen, P.; Ramaswamy, V.; Ritter, B.; Rozanov, E.; Schlesinger, M.; Shibata, K.; Sporyshev, P.; Sun, Z.; Wendisch, M.; Wood, N.; Yang, F.
2003-08-01
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 to partly cloudy atmospheres? (ii) Regardless of the adequacy of their assumptions about unresolved clouds, do 1D solar codes perform as intended?One clear-sky and two plane-parallel, homogeneous (PPH) overcast cloud cases serve to elucidate 1D model differences due to varying treatments of gaseous transmittances, cloud optical properties, and basic radiative transfer. The remaining four cases involve 3D distributions of cloud water and water vapor as simulated by cloud-resolving models. Results for 25 1D codes, which included two line-by-line (LBL) models (clear and overcast only) and four 3D Monte Carlo (MC) photon transport algorithms, were submitted by 22 groups. Benchmark, domain-averaged irradiance profiles were computed by the MC codes. For the clear and overcast cases, all MC estimates of top-of-atmosphere albedo, atmospheric absorptance, and surface absorptance agree with one of the LBL codes to within ±2%. Most 1D codes underestimate atmospheric absorptance by typically 15-25 W m-2 at overhead sun for the standard tropical atmosphere regardless of clouds.Depending on assumptions about unresolved clouds, the 1D codes were partitioned into four genres: (i) horizontal variability, (ii) exact overlap of PPH clouds, (iii) maximum/random overlap of PPH clouds, and (iv) random overlap of PPH clouds. A single MC code was used to establish conditional benchmarks applicable to each genre, and all MC codes were used to establish the full 3D benchmarks. There is a tendency for 1D codes to cluster near their respective conditional benchmarks, though intragenre variances typically exceed those for the clear and overcast cases. The majority of 1D codes fall into the extreme category of maximum/random overlap of PPH clouds and thus generally disagree with full 3D benchmark values. Given the fairly limited scope of these tests and the inability of any one code to perform extremely well for all cases begs the question that a paradigm shift is due for modeling 1D solar fluxes for cloudy atmospheres.
Dynamical Models of SAURON and CALIFA Galaxies: 1D and 2D Rotational Curves
NASA Astrophysics Data System (ADS)
Kalinova, Veselina; van de Ven, G.; Lyubenova, M.; Falcon-Barroso, J.; van den Bosch, R.
2013-01-01
The mass of a galaxy is the most important parameter to understand its structure and evolution. The total mass we can infer by constructing dynamical models that fit the motion of the stars and gas in the galaxy. The dark matter content then follows after subtracting the luminous matter inferred from colors and/or spectra. Here, we present the mass distribution of a sample of 18 late-type spiral (Sb-Sd) galaxies, using two-dimensional stellar kinematics obtained with the integral-field spectrograph SAURON. The observed second order velocity moments of these galaxies are fitted with solutions of the Axisymmetric Jeans equations and give us an accurate estimation of the mass-to-light ratio profiles and rotational curves. The rotation curves of the galaxies are obtained by the Asymmetric Drift Correction (ADC) and Multi-Gaussian Expansion (MGE) methods, corresponding to one- and two-dimensional mass distribution. Their comparison shows that the mass distribution based on the 2D stellar kinematics is much more reliable than 1D one. SAURON integral field of view looks at the inner parts of the galaxies in contrast with CALIFA survey. CALIFA survey provides PMAS/PPAK integral-field spectroscopic data of ~ 600 nearby galaxies as part of the Calar Alto Legacy Integral Field Area. We show the first CALIFA dynamical models of different morphological type of galaxies, giving the clue about the mass distribution of galaxies through the whole Hubble sequence and their evolution from the blue cloud to the red sequence.
Modelling turbulent vertical mixing sensitivity using a 1-D version of NEMO
NASA Astrophysics Data System (ADS)
Reffray, G.; Bourdalle-Badie, R.; Calone, C.
2015-01-01
Through two numerical experiments, a 1-D vertical model called NEMO1D was used to investigate physical and numerical turbulent-mixing behaviour. The results show that all the turbulent closures tested (k+l from Blanke and Delecluse, 1993, and two equation models: generic length scale closures from Umlauf and Burchard, 2003) are able to correctly reproduce the classical test of Kato and Phillips (1969) under favourable numerical conditions while some solutions may diverge depending on the degradation of the spatial and time discretization. The performances of turbulence models were then compared with data measured over a 1-year period (mid-2010 to mid-2011) at the PAPA station, located in the North Pacific Ocean. The modelled temperature and salinity were in good agreement with the observations, with a maximum temperature error between -2 and 2 °C during the stratified period (June to October). However, the results also depend on the numerical conditions. The vertical RMSE varied, for different turbulent closures, from 0.1 to 0.3 °C during the stratified period and from 0.03 to 0.15 °C during the homogeneous period. This 1-D configuration at the PAPA station (called PAPA1D) is now available in NEMO as a reference configuration including the input files and atmospheric forcing set described in this paper. Thus, all the results described can be recovered by downloading and launching PAPA1D. The configuration is described on the NEMO site (1D_PAPA">http://www.nemo-ocean.eu/Using-NEMO/Configurations/C1D_PAPA). This package is a good starting point for further investigation of vertical processes.
A macroscopic 1D model for shape memory alloys including asymmetric behaviors and
Stefanelli, Ulisse
A macroscopic 1D model for shape memory alloys including asymmetric behaviors and transformation behavior of shape memory alloys (SMAs) has been widely growing in last years because of the in- creasing model features and performance. Key words: Shape memory alloys; Tension-compression asymmetry; Variable
A Global 3D P-Velocity Model of the Earth's Crust and Mantle for Improved Event Location
Sanford Ballard; Christopher Young; James Hipp; Marcus Chang; Jennifer E. Lewis; Charlotte Rowe; Michael Begnaud
2010-01-01
Using high-quality 3D Earth models should result in more accurate seismic event locations compared to locations computed with 1D models. To test this hypothesis, we have developed a global P wave velocity model of the Earth's crust and mantle using seismic tomography. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn
Comparison of 1D and 2D modelling with soil erosion model SMODERP
NASA Astrophysics Data System (ADS)
Kavka, Petr; Weyskrabova, Lenka; Zajicek, Jan
2013-04-01
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".
3D Versus 1D Radiative Transfer Modeling of Planetary Nebulae
NASA Astrophysics Data System (ADS)
Pantoja, Blake M.; Ladjal, Djazia
2015-01-01
Planetary nebulae are the products of the fast stellar wind from the end of the AGB star phase. To date, there are many one-dimensional radiative transfer codes, and a few fully 3D codes that can model the ionization of the planetary nebulae. Some limitations on 1D codes are that they can only make spherical or parallel plane models, while 3D codes take much computing power and memory to run. A pseudo-3D code such as pyCloudy can model a planetary nebula in 3D by making multiple runs of a 1D code such as Cloudy in different angles from the center of the nebula. We compared the 1D models with pseudo-3D models to determine if the 1D models give good approximations for the observed parameters of the planetary nebulae. We find that one-dimensional codes can actually give good estimates for electron temperature and density in a bipolar planetary nebula.
DISCRETE VELOCITY MODEL AND IMPLICIT SCHEME FOR THE BGK EQUATION
Mieussens, Luc
DISCRETE VELOCITY MODEL AND IMPLICIT SCHEME FOR THE BGK EQUATION OF RAREFIED GAS DYNAMICS LUC a discrete equilibrium function, a discrete velocity model of this equation is proposed. This model, like. The discrete velocity model is then discretized in space and time by an explicit finite volume scheme which
NASA Astrophysics Data System (ADS)
Haji Mohammadi, M.; Kang, S.; Sotiropoulos, F.
2011-12-01
It is well-known that meander bends impose local losses of energy to the flow in rivers. These local losses should be added together with friction loss to get the total loss of energy. In this work, we strive to develop a framework that considers the effect of bends in meandering rivers for one-dimensional (1-D) homogenous equations of flow. Our objective is to develop a simple, yet physically sound, and efficient model for carrying out engineering computations of flow through meander bends. We consider several approaches for calculating 1-D hydraulic properties of meandering rivers such as friction factor and Manning coefficient. The method of Kasper et al. (2005), which is based on channel top width, aspect ratio and radius of curvature, is adopted for further calculations. In this method, a correction is implemented in terms of local energy loss, due to helical motion and secondary currents of fluid particles driven by centrifugal force, in meanders. To validate the model, several test cases are simulated and the computed results are compared with the reported data in the literature in terms of water surface elevation, shear velocity, etc. For all cases the computed results are in reasonable agreement with the experimental data. 3-D RANS turbulent flow simulations are also carried out, using the method of Kang et al. (Adv. In Water Res., vol. 34, 2011), for different geometrical parameters of Kinoshita Rivers to determine the spatial distribution of shear stress on river bed and banks, which is the key factor in scour/deposition patterns. The 3-D solutions are then cross-sectionally averaged and compared with the respective solutions from the 1-D model. The comparisons show that the improved 1D model, which incorporates the effect of local bend loss, captures key flow parameters with reasonable accuracy. Our results also underscore the range of validity and limitations of 1D models for meander bend simulations. This work was supported by NSF Grants (as part of the National Center for Earth-Surface Dynamics). Computational resources were provided by the University of Minnesota Supercomputing Institute.
1D Modeling of Solar Cells ELEN E9501 Course Project
Lavaei, Javad
..........................................................................11 #12;3 Project Summary Solar energy is in abundance but only a small amount is used to directly. Therefore, the abundant solar energy would be the promi1D Modeling of Solar Cells ELEN E9501 Course Project Columbia University Department of Electrical
1-D modelling of conveyance, boundary shear and sediment transport in overbank flow
S. Atabay; D. W. Knight
2006-01-01
Several sets of experimental data on conveyance capacity, the division of flow between a main river channel and its floodplains, boundary shear, and sediment transport in overbank flow are presented. The strengths and weaknesses of various 1-D modelling approaches are highlighted. The coherence method (COHM) of Ackers [J. Hydraul. Res. 31 (1993) 509] and the weighted divided channel method (WDCM)
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...
Implementation of a 1D k-? model for studying the vertical mixing in Comau fjord, Chile
NASA Astrophysics Data System (ADS)
Sepulveda, O.; De La Fuente, A.; Bouffard, D.; Meruane, C.
2014-12-01
Comau fjord,located in southern Chile (42º22' S, 72º25' W), is a narrow and deep semi-enclosed basin of 68 km-long, 4 km-width and a maximum depth of 500 m. The fjord has a semi-diurnal tidal regime dominated by the M2 component, with maximum oscillations that reach 7,5 m. The stratification and mixing in the Comau fjord was examined in a field campaign during January 2014, using temperature and conductivity sensors and a down-looking ADCP. A very shallow salinity-controlled stratification was detected with a very strong and sharp density change at about 8 m-depth. Furthermore, a surface current of magnitude 5 cm·s-1 due to river discharge was measured and found to interact with both the tide and the wind forcing. A description of the fjord's hydrodynamic was performed using a general 1D vertical k-? model, in which the stratification was forced by exchanges of energy and momentum with the atmosphere. In addition, the river currents and the effects of tidal influence were incorporated through adding terms in the momentum equation that account for non-linear interaction between current and tide, and a periodic barotropic pressure gradient due to the tide. A decomposition in vertical modes were carried out to analyze the velocity data and the results of the model, which showed that the energy is concentrated in the first barotropic mode, in agreement with the fact that the aspect ratio of stratification h1/(h1+h2) is close to 0. Field data and numerical simulations suggest that the energy injected to the system by external forcings is dissipated in the surface region as a consequence of the strong stratification, which acts as a buffer of the energy transfer, controlling the vertical mixing. The model implemented calculates the vertical dissipation rate of turbulent kinetic energy, allowing the estimation of turbulent diffusion parameter, thus connecting the system's hydrodynamics response with the vertical transport of water quality parameters of the system.
NASA Astrophysics Data System (ADS)
Kaystrenko, Victor; Pelinovsky, Efim
2013-04-01
1-D linear inverse problem for initial sea level disturbance in the tsunami source ?0(x) using sea level record f(t) near the shore was investigated. Sea bottom can be considered as the slopping plane and water depthh(x) = k x. Let the function ?(x,t) describing sea level oscillations depending from time t and space coordinate xis satisfying the linear shallow water equation (gkx??x)x = ?tt If initial velocities in the source zone are equal to zero (?t(x,0)=0) than initial sea level disturbance in the tsunami source ?0(x) = ?(x,0) and sea level record (marigram) on the shore f(t) = ?(0,t) are tied by the integral equation of Abel type which has an unique analytical solution. Situation looks different if initial wave field in the tsunami source is related to sea level disturbance and current velocities not equal to zero. In this case specially constructed initial wave field with ?0(x) = ?(x,0) and ?1(x) = ?t(x,0) tied by the integral equation ?0(Z) = -2 ? zZK(° ---- (Z-)2 - 1) z) ? ?1(z)zdz where K is the full elliptic integral and z = 2° -- xkg- = ?2gxh-, gives the tsunami non observed near the shore: ?(0,t)=0. The work was supported by grant 11-05-01054 of the Russian foundation for basic research.
Review of Zero-D and 1-D Models of Blood Flow in the Cardiovascular System
2011-01-01
Background Zero-dimensional (lumped parameter) and one dimensional models, based on simplified representations of the components of the cardiovascular system, can contribute strongly to our understanding of circulatory physiology. Zero-D models provide a concise way to evaluate the haemodynamic interactions among the cardiovascular organs, whilst one-D (distributed parameter) models add the facility to represent efficiently the effects of pulse wave transmission in the arterial network at greatly reduced computational expense compared to higher dimensional computational fluid dynamics studies. There is extensive literature on both types of models. Method and Results The purpose of this review article is to summarise published 0D and 1D models of the cardiovascular system, to explore their limitations and range of application, and to provide an indication of the physiological phenomena that can be included in these representations. The review on 0D models collects together in one place a description of the range of models that have been used to describe the various characteristics of cardiovascular response, together with the factors that influence it. Such models generally feature the major components of the system, such as the heart, the heart valves and the vasculature. The models are categorised in terms of the features of the system that they are able to represent, their complexity and range of application: representations of effects including pressure-dependent vessel properties, interaction between the heart chambers, neuro-regulation and auto-regulation are explored. The examination on 1D models covers various methods for the assembly, discretisation and solution of the governing equations, in conjunction with a report of the definition and treatment of boundary conditions. Increasingly, 0D and 1D models are used in multi-scale models, in which their primary role is to provide boundary conditions for sophisticate, and often patient-specific, 2D and 3D models, and this application is also addressed. As an example of 0D cardiovascular modelling, a small selection of simple models have been represented in the CellML mark-up language and uploaded to the CellML model repository http://models.cellml.org/. They are freely available to the research and education communities. Conclusion Each published cardiovascular model has merit for particular applications. This review categorises 0D and 1D models, highlights their advantages and disadvantages, and thus provides guidance on the selection of models to assist various cardiovascular modelling studies. It also identifies directions for further development, as well as current challenges in the wider use of these models including service to represent boundary conditions for local 3D models and translation to clinical application. PMID:21521508
A 1D model for the description of mixing-controlled reacting diesel sprays
Desantesa, J.M.; Pastor, J.V.; Garcia-Oliver, J.M.; Pastor, J.M. [CMT - Motores Termicos, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022, Valencia (Spain)
2009-01-15
The paper reports an investigation on the transient evolution of diesel flames in terms of fuel-air mixing, spray penetration and combustion rate. A one-dimensional (1D) spray model, which was previously validated for inert diesel sprays, is extended to reacting conditions. The main assumptions of the model are the mixing-controlled hypothesis and the validity of self-similarity for conservative properties. Validation is achieved by comparing model predictions with both CFD gas jet simulations and experimental diesel spray measurements. The 1D model provides valuable insight into the evolution of the flow within the spray (momentum and mass fluxes, tip penetration, etc.) when shifting from inert to reacting conditions. Results show that the transient diesel flame evolution is mainly governed by two combustion-induced effects, namely the reduction in local density and the increase in flame radial width. (author)
Implementation and validation of a 1D fluid model for collapsible channels.
Anderson, Peter; Fels, Sidney; Green, Sheldon
2013-11-01
A 1D fluid model is implemented for the purpose of fluid-structure interaction (FSI) simulations in complex and completely collapsible geometries, particularly targeting the case of obstructive sleep apnea (OSA). The fluid mechanics are solved separately from any solid mechanics, making possible the use of a highly complex and/or black-box solver for the solid mechanics. The fluid model is temporally discretized with a second-order scheme and spatially discretized with an asymmetrical fourth-order scheme that is robust in highly uneven geometries. A completely collapsing and reopening geometry is handled smoothly using a modified area function. The numerical implementation is tested with two driven-geometry cases: (1) an inviscid analytical solution and (2) a completely closing geometry with viscous flow. Three-dimensional fluid simulations in static geometries are performed to examine the assumptions of the 1D model, and with a well-defined pressure-recovery constant the 1D model agrees well with 3D models. The model is very fast computationally, is robust, and is recommended for OSA simulations where the bulk flow pressure is primarily of interest. PMID:24008973
Coupled 1D-3D hydrodynamic modelling, with application to the Pearl River Delta
NASA Astrophysics Data System (ADS)
Twigt, Daniel J.; de Goede, Erik D.; Zijl, Firmijn; Schwanenberg, Dirk; Chiu, Alex Y. W.
2009-12-01
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).
A crustal seismic velocity model for the UK, Ireland and surrounding seas
Kelly, A.; England, R.W.; Maguire, Peter K.H.
2007-01-01
A regional model of the 3-D variation in seismic P-wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity-depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 ?? 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data. ?? 2007 The Authors Journal compilation ?? 2007 RAS.
Thermodynamic nature of vitrification in a 1D model of a structural glass former
NASA Astrophysics Data System (ADS)
Semenov, A. N.
2015-07-01
We propose a new spin-glass model with no positional quenched disorder which is regarded as a coarse-grained model of a structural glass-former. The model is analyzed in the 1D case when the number N of states of a primary cell is large. For N ? ?, the model exhibits a sharp freezing transition of the thermodynamic origin. It is shown both analytically and numerically that the glass transition is accompanied by a significant growth of a static length scale ? pointing to the structural (equilibrium) nature of dynamical slowdown effects in supercooled liquids.
Thermodynamic nature of vitrification in a 1D model of a structural glass former.
Semenov, A N
2015-07-28
We propose a new spin-glass model with no positional quenched disorder which is regarded as a coarse-grained model of a structural glass-former. The model is analyzed in the 1D case when the number N of states of a primary cell is large. For N ? ?, the model exhibits a sharp freezing transition of the thermodynamic origin. It is shown both analytically and numerically that the glass transition is accompanied by a significant growth of a static length scale ? pointing to the structural (equilibrium) nature of dynamical slowdown effects in supercooled liquids. PMID:26233148
SILVA: EDF two-phase 1D annular model of a CFB boiler furnace
Montat, D.; Fauquet, P.; Lafanechere, L.; Bursi, J.M. [Electricite de France (France)
1997-12-31
Aiming to improve its knowledge of CFB boilers, EDF has initiated a R and D program including: laboratory work on mock-ups, numerical modelling and on-site tests in CFB power plants. One of the objectives of this program is the development of a comprehensive steady-state 1D model of the solid circulation loop, named SILVA, for plant operation and design evaluation purposes. This paper describes its mathematical and physical modelling. Promising validation of the model on cold mock-up and industrial CFB is presented.
Zero finite-temperature charge stiffness within the half-filled 1D Hubbard model
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
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.
Scotogenic Z2 or U(1)D model of neutrino mass with ?(27) symmetry
NASA Astrophysics Data System (ADS)
Ma, Ernest; Natale, Alexander
2014-06-01
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.
A 1-D modelling of climatic and chemical effects of greenhouse gases
R. K. R. Vupputuri; K. Higuchi; H. G. Hengeveld
1995-01-01
A coupled 1-D time-dependent radiative-convective-photochemical diffusion model which extends from the surface to 60 km is used to investigate the potential impact of greenhouse trace gas emissions on long-term changes in global climate, atmospheric ozone and surface UV-B radiation, taking into accoont the influence of aerosol loading into the atmosphere from major volcanic eruptions, of thermal inertia of the upper
A Systematic Comparison between 1-D and 3-D Hemodynamics in Compliant Arterial Models
Xiao, Nan; Alastruey, Jordi; Figueroa, C. Alberto
2015-01-01
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
Box model and 1D longitudinal model of flow and transport in Bosten Lake, China
NASA Astrophysics Data System (ADS)
Li, Ning; Kinzelbach, Wolfgang; Li, WenPeng; Dong, XinGuang
2015-05-01
Bosten Lake in the southeast of Yanqi Catchment, China, supports the downstream agricultural and natural environments. Over the last few decades the intensive agricultural activities in Yanqi Catchment resulted in decreased lake levels and deteriorated lake water quality. A two-box model is constructed to understand the evolution of lake level and salinity between 1958 and 2008. The two-box model of the lake indicates that the evaporation does have the same trend as the observed lake area and the annual average evaporation agrees with the value obtained from the Penman-Monteith approach. To achieve a correct salt balance, the ratio of outflow concentration and average lake concentration has to be around 0.7. This is due to the incomplete mixing of the lake caused by short-circuiting between tributary inflow and the main outflow via the pump stations abstracting water from the lake. This short-circuiting is investigated in more detail by a 1D numerical flow and transport model of the lake calibrated with observations of lake level and lake concentrations. The distributed model reproduces the correct time-varying outflow concentration. It is used for the assessment of two basic management options: increasing river discharge (by water saving irrigation, reduction of phreatic evaporation or reduction of agricultural area) and diverting saline drainage water to the desert. Increasing river discharge to the lake by 20% reduces the east basin salt concentration by 0.55 kg/m3, while capturing all the drainage water and discharging it to depressions instead of the lake reduces the east basin salt concentration by 0.63 kg/m3. A combination of increasing river inflow and decreasing drainage salt flux is sufficient to bring future lake TDS below the required 1 kg/m3, to keep a lake level that sustains the lake ecosystem, and to supply more water for downstream development and ecosystem rehabilitation.
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...
Front velocity in models with quadratic autocatalysis Vladimir K. Vanaga)
Epstein, Irving R.
Front velocity in models with quadratic autocatalysis Vladimir K. Vanaga) and Irving R. Epstein the dependence of the front velocity on the diffusion coefficients of X and R, the interconversion rates diffusion coef- ficients of X and R, DX and DR , respectively, raise the ques- tion of how the velocity
A systematic comparison between 1-D and 3-D hemodynamics in compliant arterial models.
Xiao, Nan; Alastruey, Jordi; Alberto Figueroa, C
2014-02-01
We present a systematic comparison of computational hemodynamics in arteries between a one-dimensional (1-D) and a three-dimensional (3-D) formulation with deformable vessel walls. 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 inflow and outflow boundary conditions and have compatible material laws. We also present an iterative algorithm to select the parameters for the outflow boundary conditions by 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 formulations, especially during the diastolic phase of the cycle. PMID:24115509
1D-3D hybrid modeling—from multi-compartment models to full resolution models in space and time
Grein, Stephan; Stepniewski, Martin; Reiter, Sebastian; Knodel, Markus M.; Queisser, Gillian
2014-01-01
Investigation of cellular and network dynamics in the brain by means of modeling and simulation has evolved into a highly interdisciplinary field, that uses sophisticated modeling and simulation approaches to understand distinct areas of brain function. Depending on the underlying complexity, these models vary in their level of detail, in order to cope with the attached computational cost. Hence for large network simulations, single neurons are typically reduced to time-dependent signal processors, dismissing the spatial aspect of each cell. For single cell or networks with relatively small numbers of neurons, general purpose simulators allow for space and time-dependent simulations of electrical signal processing, based on the cable equation theory. An emerging field in Computational Neuroscience encompasses a new level of detail by incorporating the full three-dimensional morphology of cells and organelles into three-dimensional, space and time-dependent, simulations. While every approach has its advantages and limitations, such as computational cost, integrated and methods-spanning simulation approaches, depending on the network size could establish new ways to investigate the brain. In this paper we present a hybrid simulation approach, that makes use of reduced 1D-models using e.g., the NEURON simulator—which couples to fully resolved models for simulating cellular and sub-cellular dynamics, including the detailed three-dimensional morphology of neurons and organelles. In order to couple 1D- and 3D-simulations, we present a geometry-, membrane potential- and intracellular concentration mapping framework, with which graph- based morphologies, e.g., in the swc- or hoc-format, are mapped to full surface and volume representations of the neuron and computational data from 1D-simulations can be used as boundary conditions for full 3D simulations and vice versa. Thus, established models and data, based on general purpose 1D-simulators, can be directly coupled to the emerging field of fully resolved, highly detailed 3D-modeling approaches. We present the developed general framework for 1D/3D hybrid modeling and apply it to investigate electrically active neurons and their intracellular spatio-temporal calcium dynamics. PMID:25120463
Modeling of the diffraction pattern of 1D-disordered silicon carbide
Popenko, V. A.
2008-09-15
A method for calculating the diffraction pattern of a 1D-disordered crystal structure is considered by the example of silicon carbide. One-dimensional disordering is described using a cell setting the mutual position of all close-packed crystal layers. Two models of structure disordering during the polytypic transformation of the silicon carbide cubic modification into hexagonal are discussed. The results of the calculation of the diffraction spectrum in different stages of polytypic transformation are reported. It is shown that 1D disordering leads to the formation of a set of weak diffraction reflections. The experimentally observed changes in the diffraction pattern can be interpreted within the hypothesis on crystal structure disordering through displacement of adjacent close-packed layers.
Evaluation of 2 1-D cloud models for the analysis of VAS soundings
NASA Technical Reports Server (NTRS)
Emmitt, G. D.
1984-01-01
Evaluation of the satellite Visual Infrared Spin Scan Radiometer Atmospheric Sounder (VISSR) has begun to document several of its critical shortcomings as far as numerical cloud models are concerned: excessive smoothing of thermal inversions; imprecise measurement of boundary layer moisture; and tendency to exaggerate atmospheric stability. The sensitivity of 1-D cloud models to their required inputs is stressed with special attention to those parameters obtained from atmospheric soundings taken by the VAS or rawinsonde. In addition to performing model experiments using temperature and moisture profiles having the general characteristics of VAS soundings, standard input sensitivity tests were made and 1-D model performance was compared with observations and the results of a 2-D model experiment using AVE/VAS data (Atmospheric Variability Experiment). Although very encouraging, the results are not sufficient to make any specific conclusions. In general, the VAS soundings are likely to be inadequate to provide the cloud base (and subcloud layer) information needed for inputs to current cumulus models. Above cloud base, the tendency to exaggerate the stability of the atmosphere requires solution before meaningful model experiments are run.
Testing a 1-D Analytical Salt Intrusion Model and the Predictive Equation in Malaysian Estuaries
NASA Astrophysics Data System (ADS)
Gisen, Jacqueline Isabella; Savenije, Hubert H. G.
2013-04-01
Little is known about the salt intrusion behaviour in Malaysian estuaries. Study on this topic sometimes requires large amounts of data especially if a 2-D or 3-D numerical models are used for analysis. In poor data environments, 1-D analytical models are more appropriate. For this reason, a fully analytical 1-D salt intrusion model, based on the theory of Savenije in 2005, was tested in three Malaysian estuaries (Bernam, Selangor and Muar) because it is simple and requires minimal data. In order to achieve that, site surveys were conducted in these estuaries during the dry season (June-August) at spring tide by moving boat technique. Data of cross-sections, water levels and salinity were collected, and then analysed with the salt intrusion model. This paper demonstrates a good fit between the simulated and observed salinity distribution for all three estuaries. Additionally, the calibrated Van der Burgh's coefficient K, Dispersion coefficient D0, and salt intrusion length L, for the estuaries also displayed a reasonable correlations with those calculated from the predictive equations. This indicates that not only is the salt intrusion model valid for the case studies in Malaysia but also the predictive model. Furthermore, the results from this study describe the current state of the estuaries with which the Malaysian water authority in Malaysia can make decisions on limiting water abstraction or dredging. Keywords: salt intrusion, Malaysian estuaries, discharge, predictive model, dispersion
Prediction of car cabin environment by means of 1D and 3D cabin model
NASA Astrophysics Data System (ADS)
Fišer, J.; Pokorný, J.; Jícha, M.
2012-04-01
Thermal comfort and also reduction of energy requirements of air-conditioning system in vehicle cabins are currently very intensively investigated and up-to-date issues. The article deals with two approaches of modelling of car cabin environment; the first model was created in simulation language Modelica (typical 1D approach without cabin geometry) and the second one was created in specialized software Theseus-FE (3D approach with cabin geometry). Performance and capabilities of this tools are demonstrated on the example of the car cabin and the results from simulations are compared with the results from the real car cabin climate chamber measurements.
Modeling velocity dispersion In Gypsy site, Oklahoma
Alsaadan, Sami Ibrahim
2010-01-01
Discrepancies in interval velocities estimated from vertical well measurements made with different source central frequencies at Gypsy site could be primarily explained in terms of intrinsic attenuation. Four intervals ...
N. M. H. Vaytet; T. J. O'Brien; M. F. Bode
2007-04-19
Following the early Swift X-ray observations of the latest outburst of the recurrent nova RS Ophiuchi in February 2006 (Paper I), we present new 1D hydrodynamical models of the system which take into account all three phases of the remnant evolution. The models suggest a novel way of modelling the system by treating the outburst as a sudden increase then decrease in wind mass-loss rate and velocity. The differences between this wind model and previous Primakoff-type simulations are described. A more complex structure, even in 1D, is revealed through the presence of both forward and reverse shocks, with a separating contact discontinuity. The effects of radiative cooling are investigated and key outburst parameters such as mass-loss rate, ejecta velocity and mass are varied. The shock velocities as a function of time are compared to the ones derived in Paper I. We show how the manner in which the matter is ejected controls the evolution of the shock and that for a well-cooled remnant, the shock deceleration rate depends on the amount of energy that is radiated away.
Assessing the impact of different sources of topographic data on 1-D hydraulic modelling of floods
NASA Astrophysics Data System (ADS)
Ali, A. Md; Solomatine, D. P.; Di Baldassarre, G.
2015-01-01
Topographic data, such as digital elevation models (DEMs), are essential input in flood inundation modelling. DEMs can be derived from several sources either through remote sensing techniques (spaceborne or airborne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the light detection and ranging (lidar), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30 to 90 m). On the other hand, the lidar technique is able to produce high-resolution DEMs (at around 1 m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of 1-D hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. To test model selection, the outcomes of the 1-D models were also compared, in terms of flood water levels, to the results of 2-D models (LISFLOOD-FP). The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicate that the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. lidar 1 m) to lower resolution is much less than the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the 1-D hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.
A 1-D model study of Arctic sea-ice salinity
NASA Astrophysics Data System (ADS)
Griewank, P. J.; Notz, D.
2014-03-01
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 SAMSIM sea-ice model 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 modeled Arctic sea-ice salinity that agrees well with ice-core measurements. The simulations hence 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 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. We conclude that for earth system models the impact of fully parametrizing the Arctic temporal salinity evolution is too small to justify the increase in computational cost and model complexity.
Loya, Sudarshan Kedarnath
2011-12-31
Classical one-dimensional (1D) models of automotive catalysts are effective in designing catalyst systems that meet current emission standards. These models use various assumptions in order to simplify the mathematical formulation. Although...
Optimal modeling of 1D azimuth correlations in the context of Bayesian inference
De Kock, Michiel B; Trainor, Thomas A
2015-01-01
Analysis and interpretation of spectrum and correlation data from high-energy nuclear collisions is currently controversial because two opposing physics narratives derive contradictory implications from the same data-one narrative claiming collision dynamics is dominated by dijet production and projectile-nucleon fragmentation, the other claiming collision dynamics is dominated by a dense, flowing QCD medium. Opposing interpretations seem to be supported by alternative data models, and current model-comparison schemes are unable to distinguish between them. There is clearly need for a convincing new methodology to break the deadlock. In this study we introduce Bayesian Inference (BI) methods applied to angular correlation data as a basis to evaluate competing data models. For simplicity the data considered are projections of 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...
NASA Astrophysics Data System (ADS)
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
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
A simple 1D model for the evolution of multi-stranded loops
NASA Astrophysics Data System (ADS)
Lopez Fuentes, Marcelo
We develop a 1D model based on a cellular automaton that reproduces the main qualitative features of the observed evolution of X-ray loops (Lopez Fuentes et al. 2007). The model is inspired in the idea originally proposed by Parker (1988) of coronal loops made of multiple magnetic strands tangled by photospheric motions. When the mutual inclination between adjacent strands reaches a critical value, reconnection occurs and the plasma is heated. In our model the number and intensity of these "nanoflare" events increase until a stationary (or critical) state is reached. This stage corresponds to the so called "main phase" of the evolution of observed loops. Using the 0D EBTEL code (Klimchuk 2008) for the plasma response, we create synthetic light curves and we compare them with the evolution of real loops. We also study and discuss how the properties of the obtained light curves depend on the physical parameters of the model.
Optimal modeling of 1D azimuth correlations in the context of Bayesian inference
Michiel B. De Kock; Hans C. Eggers; Thomas A. Trainor
2015-02-16
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 series (FS) and a Gaussian plus various combinations of individual cosine components. We evaluate model performance with BI methods and with power-spectrum (PS) analysis. We find that the FS-only model is rejected in all cases by Bayesian analysis which always prefers a Gaussian. A cylindrical quadrupole cos(2\\phi) is required in some cases but rejected for most-central Au-Au collisions. Given a Gaussian centered at the azimuth origin "higher harmonics" cos(m\\phi) for m > 2 are rejected. A model consisting of Gaussian + dipole cos(\\phi) + quadrupole cos(2\\phi) provides good 1D data descriptions in all cases.
Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling
NASA Astrophysics Data System (ADS)
Zhang, Pengjie; Zheng, Yi; Jing, Yipeng
2015-02-01
Cosmology based on large scale peculiar velocity prefers volume weighted velocity statistics. However, measuring the volume weighted velocity statistics from inhomogeneously distributed galaxies (simulation particles/halos) suffers from an inevitable and significant sampling artifact. We study this sampling artifact in the velocity power spectrum measured by the nearest particle velocity assignment method by Zheng et al., [Phys. Rev. D 88, 103510 (2013).]. We derive the analytical expression of leading and higher order terms. We find that the sampling artifact suppresses the z =0 E -mode velocity power spectrum by ˜10 % at k =0.1 h /Mpc , for samples with number density 10-3 (Mpc /h )-3 . This suppression becomes larger for larger k and for sparser samples. We argue that this source of systematic errors in peculiar velocity cosmology, albeit severe, can be self-calibrated in the framework of our theoretical modelling. We also work out the sampling artifact in the density-velocity cross power spectrum measurement. A more robust evaluation of related statistics through simulations will be presented in a companion paper by Zheng et al., [Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modelling, arXiv:1409.6809.]. We also argue that similar sampling artifact exists in other velocity assignment methods and hence must be carefully corrected to avoid systematic bias in peculiar velocity cosmology.
A 1-D modelling study of Arctic sea-ice salinity
NASA Astrophysics Data System (ADS)
Griewank, P. J.; Notz, D.
2015-02-01
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.
UCVM: Open Source Software for Understanding and Delivering 3D Velocity Models
NASA Astrophysics Data System (ADS)
Gill, D.; Small, P.; Maechling, P. J.; Jordan, T. H.; Shaw, J. H.; Plesch, A.; Chen, P.; Lee, E. J.; Taborda, R.; Olsen, K. B.; Callaghan, S.
2014-12-01
Physics-based ground motion simulations can calculate the propagation of earthquake waves through 3D velocity models of the Earth. The Southern California Earthquake Center (SCEC) has developed the Unified Community Velocity Model (UCVM) framework to help researchers build structured or unstructured velocity meshes from 3D velocity models for use in wave propagation simulations. The UCVM software framework makes it easy to extract P and S wave propagation speeds and other material properties from 3D velocity models by providing a common interface through which researchers can query earth models for a given location and depth. Currently, the platform supports multiple California models, including SCEC CVM-S4 and CVM-H 11.9.1, and has been designed to support models from any region on earth. UCVM is currently being use to generate velocity meshes for many SCEC wave propagation codes, including AWP-ODC-SGT and Hercules. In this presentation, we describe improvements to the UCVM software. The current version, UCVM 14.3.0, released in March of 2014, supports the newest Southern California velocity model, CVM-S4.26, which was derived from 26 full-3D tomographic iterations using CVM-S4 as the starting model (Lee et al., this meeting), and the Broadband 1D velocity model used in the CyberShake 14.2 study. We have ported UCVM to multiple Linux distributions and OS X. Also included in this release is the ability to add small-scale stochastic heterogeneities to extract Cartesian meshes for use in high-frequency ground motion simulations. This tool was built using the C language open-source FFT library, FFTW. The stochastic parameters (Hurst exponent, correlation length, and the horizontal/vertical aspect ratio) can be customized by the user. UCVM v14.3.0 also provides visualization scripts for constructing cross-sections, horizontal slices, basin depths, and Vs30 maps. The interface allows researchers to visually review velocity models . Also, UCVM v14.3.0 can extract isosurfaces of shear-wave velocities equal to 1 km/s (Z1.0) and 2.5 km/s (Z2.5) for any of the registered velocity models. We have also improved our open source distribution by including a user's guide, an advanced user's guide, and a developer's guide so that users of all levels can get started using and extending the UCVM platform.
VizieR Online Data Catalog: Model 1D (LHD) and 3D (CO5BOLD) spectra (Allende Prieto+, 2013)
NASA Astrophysics Data System (ADS)
Allende Prieto, C.; Koesterke, L. Ludwig H.-G.; Freytag, B.; Caffau, E.
2012-11-01
Model spectral fluxes for late-type stars computed from 3D hydrodynamical simulations of surface convection performed with the CO5BOLD code. Their 1D hydrostatic counterparts are included, based on the LHD code, sharing the same microphysics as the CO5BOLD models. The fluxes for both the 3D and 1D models are calculated with the same opacities and radiative transfer code (ASSET). (6 data files).
Velocity fluctuations in a steadily sheared model foam
NASA Astrophysics Data System (ADS)
Ono, Ian K.; Tewari, Shubha; Langer, Stephen A.; Liu, Andrea J.
2003-06-01
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.
Pool Formation in Boulder-Bed Streams: Implications From 1-D and 2-D Numerical Modeling
NASA Astrophysics Data System (ADS)
Harrison, L. R.; Keller, E. A.
2003-12-01
In mountain rivers of Southern California, boulder-large roughness elements strongly influence flow hydraulics and pool formation and maintenance. In these systems, boulders appear to control the stream morphology by converging flow and producing deep pools during channel forming discharges. Our research goal is to develop quantitative relationships between boulder roughness elements, temporal patterns of scour and fill, and geomorphic processes that are important in producing pool habitat. The longitudinal distribution of shear stress, unit stream power and velocity were estimated along a 48 m reach on Rattlesnake Creek, using the HEC-RAS v 3.0 and River 2-D numerical models. The reach has an average slope of 0.02 and consists of a pool-riffle sequence with a large boulder constriction directly above the pool. Model runs were performed for a range of stream discharges to test if scour and fill thresholds for pool and riffle environments could be identified. Results from the HEC-RAS simulations identified that thresholds in shear stress, unit stream power and mean velocity occur above a discharge of 5.0 cms. Results from the one-dimensional analysis suggest that the reversal in competency is likely due to changes in cross-sectional width at varying flows. River 2-D predictions indicated that strong transverse velocity gradients were present through the pool at higher modeled discharges. At a flow of 0.5 cms (roughly 1/10th bankfull discharge), velocities are estimated at 0.6 m/s and 1.3 m/s for the pool and riffle, respectively. During discharges of 5.15 cms (approximate bankfull discharge), the maximum velocity in the pool center increased to nearly 3.0 m/s, while the maximum velocity over the riffle is estimated at approximately 2.5 cms. These results are consistent with those predicted by HEC-RAS, though the reversal appears to be limited to a narrow jet that occurs through the pool head and pool center. Model predictions suggest that the velocity reversal is produced by a boulder-bedrock constriction that rapidly decreases the channel width above the pool by roughly 25 percent. The width constriction creates highly turbulent flow capable of scouring bed material through the pool. The high velocity core that is produced through the pool center appears to be enhanced by the formation of a large eddy directly below the boulder. Values of unit stream power and shear stress indicate that the pool exit is an area of deposition of bed material due to a decrease in tractive force. The presence of a strong transverse velocity gradient suggests that only a portion of the flow is responsible for scouring bed material. After we eliminate the dead water zone, the lowest five percent of the velocity range, patterns of effective width between pools and riffles begin to emerge. The ratio of flow width between adjacent pools and riffles is one measure of flow convergence. At a discharge of 0.5 cms, the ratio of effective width between pools and riffles is roughly 1:1, implying that there is uniform flow with little flow convergence. At a discharge of 5.15 cms the width ratio between the pool and riffle is about 1:3, demonstrating the strong convergent flow patterns at the pool head. The observed effective width relationship suggests that when considering restoration designs, boulders should be placed in areas that replicate natural convergence and divergence patterns in order to maximize pool area and depth.
Microscopic approach to a class of 1D quantum critical models
K. K. Kozlowski; J. -M. Maillet
2015-01-30
Starting from the finite volume form factors of local operators, we show how and under which hypothesis the $c=1$ free boson conformal field theory in two-dimensions emerges as an effective theory governing the large-distance regime of multi-point correlation functions in a large class of one dimensional massless quantum Hamiltonians. In our approach, in the large-distance critical regime, the local operators of the initial model are represented by well suited vertex operators associated to the free boson model. This provides an effective field theoretic description of the large distance behaviour of correlation functions in 1D quantum critical models. We develop this description starting from the first principles and directly at the microscopic level, namely in terms of the properties of the finite volume matrix elements of local operators.
Reymond, Philippe; Perren, Fabienne; Lazeyras, François; Stergiopulos, Nikos
2012-10-11
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
NASA Astrophysics Data System (ADS)
Powell, C. A.; Vlahovic, G.; Bodin, P.; Horton, S.
2001-12-01
A three-dimensional P wave velocity model has been constructed for the crust in the vicinity of the Mw=7.7 January 26th Bhuj, India earthquake using aftershock data obtained by CERI away teams. Aftershocks were recorded by 8 portable, digital K2 seismographs (the MAEC/ISTAR network) and by a continuously recording Guralp CMG40TD broad-band seismometer. Station spacing is roughly 30 km. The network was in place for 18 days and recorded ground motions from about 2000 aftershocks located within about 100 km of all stations. The 3-D velocity model is based upon an initial subset of 461 earthquakes with 2848 P wave arrivals. The initial 1-D velocity model was determined using VELEST and the 3-D model was determined using the nonlinear travel time tomography method of Benz et al. [1996]. Block size was set at 2 by 2 by 2 km. A 45% reduction in RMS travel time residuals was obtained after 10 iterations holding hypocenters fixed. We imaged velocity anomalies in the range -2 to 4%. Low velocities were found in the upper 6 km and the anomalies follow surface features such as the Rann of Kutch. High velocity features were imaged at depth and are associated with the aftershock hypocenters. High crustal velocities are present at depths exceeding 20 km with the exception of the crust below the Rann of Kutch. The imaged velocity anomaly pattern does not change when different starting models are used and when hypocenters are relocated using P wave arrivals only. The analysis will be extended to an expanded data set of 941 aftershocks.
Huybrechts, Philippe
, School of Geographical Sciences, University of Bristol, Bristol BS81SS, England 2 Alfred for the Greenland ice sheet have been calculated from a new digital-elevation model, accumulation-rates compilation- portant. Partly as a consequence, outlet glaciers and ice streams, which are responsible for most
NASA Astrophysics Data System (ADS)
Holub, Karel; R?žek, Bohuslav; Rušajová, Jana
2012-04-01
The paper presents some results of seismic experiments carried out on the territory of northern Moravia and Silesia, roughly delimited by the coordinates 16°E-19°E and 49°N-51°N. The experiments were aimed at compiling a velocity model of the uppermost Earth's crust using the database of arrival times of Pg and Sg waves recorded at a fairly large number of seismic stations, which enabled us to produce a simple 1D-layered velocity model of the region. The velocity model was computed using the traditional tomographic iterative process composed of consecutive solutions of linear equations. Based on the analysis of velocity distribution, it was found that the velocities of Pg and Sg waves increase from about 5.9 and 3.3 km/s at the surface, to about 6.1 and 3.5 km/s at a depth of 11 km, respectively.
1D finite volume model of unsteady flow over mobile bed
NASA Astrophysics Data System (ADS)
Zhang, Shiyan; Duan, Jennifer G.
2011-07-01
SummaryA one dimensional (1D) finite volume method (FVM) model was developed for simulating unsteady flow, such as dam break flow, and flood routing over mobile alluvium. The governing equation is the modified 1D shallow water equation and the Exner equation that take both bed load and suspended load transport into account. The non-equilibrium sediment transport algorithm was adopted in the model, and the van Rijn method was employed to calculate the bed-load transport rate and the concentration of suspended sediment at the reference level. Flux terms in the governing equations were discretised using the upwind flux scheme, Harten et al. (1983) (HLL) and HLLC schemes, Roe's scheme and the Weighted Average Flux (WAF) schemes with the Double Minmod and Minmod flux limiters. The model was tested under a fixed bed condition to evaluate the performance of several different numerical schemes and then applied to an experimental case of dam break flow over a mobile bed and a flood event in the Rillito River, Tucson, Arizona. For dam break flow over movable bed, all tested schemes were proved to be capable of reasonably simulating water surface profiles, but failed to accurately capture the hydraulic jump. The WAF schemes produced slight spurious oscillations at the water surface and bed profiles and over-estimated the scour depth. When applying the model to the Rillito River, the simulated results generally agreed well with the field measurements of flow discharges and bed elevation changes. Modeling results of bed elevation changes were sensitive to the suspended load recovery coefficient and the bed load adaptation length, which require further theoretical and experimental investigations.
NASA Astrophysics Data System (ADS)
Klimeck, Gerhard
2001-03-01
The quantum mechanical functionality of commercially pursued heterostructure devices such as resonant tunneling diodes (RTDs), quantum well infrared photodetectors, and quantum well lasers are enabled by material variations on an atomic scale. The creation of these heterostructure devices is realized in a vast design space of material compositions, layer thicknesses and doping profiles. The full experimental exploration of this design space is unfeasible and a reliable design tool is needed. The Nanoelectronic Modeling tool (NEMO) is one of the first commercial grade attempts for such a modeling tool. NEMO was developed as a general-purpose quantum mechanics-based 1-D device design and analysis tool from 1993-97 by the Central Research Laboratory of Texas Instruments (later Raytheon Systems). NEMO enables(R. Lake, G. Klimeck, R. C. Bowen, and D. Jovanovic, J. Appl. Phys. 81), 7845 (1997). the fundamentally sound inclusion of the required(G. Klimeck et al.), in the 1997 55th Annual Device Research Conference Digest, (IEEE, NJ, 1997), p. 92^,(R. C. Bowen et al.), J. Appl. Phys 81, 3207 (1997). physics: bandstructure, scattering, and charge self-consistency based on the non-equilibrium Green function approach. A new class of devices which require full 3-D quantum mechanics based models is starting to emerge: quantum dots, or in general semiconductor based deca-nano devices. We are currently building a 3-D modeling tool based on NEMO to include the important physics to understand electronic stated in such superscaled structures. This presentation will overview various facets of the NEMO 1-D tool such electron transport physics in RTDs, numerical technology, software engineering and graphical user interface. The lessons learned from that work are now entering the NEMO 3-D development and first results using the NEMO 3-D prototype will be shown. More information about the publically available NEMO 1-D executables can be found at http://hpc.jpl.nasa.gov/ PEP/gekco/nemo
NASA Astrophysics Data System (ADS)
Iritani, R.; Takeuchi, N.; Kawakatsu, H.
2014-05-01
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.
Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao
2014-10-01
Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.
Background resistivity model from seismic velocities Dieter Werthmller1
data is to extract the structures from the interpreted seismic data and use them in (iterative) EMBackground resistivity model from seismic velocities Dieter Werthmüller1 , Anton Ziolkowski1 , and David Wright1 ABSTRACT We developed a methodology to estimate resistivities from seismic velocities. We
Arroyo-Torres, B; Chiavassa, A; Scholz, M; Freytag, B; Marcaide, J M; Hauschildt, P H; Wood, P R; Abellan, F J
2015-01-01
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 ...
Modeling of a 1-D spherically symmetric experiment on conversion efficiency and thermal transport.
NASA Astrophysics Data System (ADS)
Rosen, M. D.; Dewald, E. L.
2006-10-01
Recently experiments were performed at the Omega laser at URLLE by a joint CEA/LLNL experimental team. Spherical targets, 1 mm in diameter, were coated with high Z materials, such as gold and cocktails, and were spherically illuminated at irradiances that varied from 10^14 W/cm^2 (10 kJ / 3 ns) to 10^15 W/cm^2 (30 kJ / 1 ns). Conversion efficiency of this laser light to x-rays was measured. Spectral information on the 1 keV thermal x-rays, as well as the multi-keV M-band were obtained. Crucial additional constraints on the modeling were provided by temperature measurements, via Thomson scattering, at 2 different radii in the blow-off, and at various times throughout and after the laser pulse. We compare various modeling tools (e.g. flux limiters, non-local transport models, and a variety of non-LTE atomic physics packages) to all of these well-constrained data. The spherical symmetry allows us to model all of this in 1-D, thus allowing very good zoning to fully resolve the radial variations. In particular, the narrow radial region where the density drops and the temperature rises, and in which most of the conversion to x-rays take place, is well resolved. Implications for how to model NIF ignition hohlraums will also be discussed.
NASA Astrophysics Data System (ADS)
Shay, M. A.; Dorland, B.; Drake, J. F.; Stantchev, G.
2005-12-01
We examine a novel simulation scheme called "equation free projective integration"[1] which has the potential to allow global simulations which still include microscale physics, a necessary ingredient in order to model multiscale problems. Such codes could be used to examine the global effects of reconnection and turbulence in the Earth's magnetosphere, and the solar corona, as well as in laboratory Tokamaks. Using this method to simulate the propagation and steepening of a 1D ion acoustic wave, we have already achieved excellent agreement between full particle codes and equation free with a factor of 20 speed-up. This speedup appears to scale linearly with system size, so large scale 2D and 3D simulations using this method will show a speedup of 100 or more. In this method of simulation, the global plasma variables stepped forward in time are not time-integrated directly using dynamical differential equations, hence the name "equation free." Instead, these variables are represented on a microgrid using a kinetic simulation. This microsimulation is integrated forward long enough to determine the time derivatives of the global plasma variables, which are then used to integrate forward the global variables with much larger timesteps. Results will be presented of the successful application of equation free to 1-D ion acoustic wave steepening with a PIC code serving as the underlying kinetic model. Initial results of this technique applied to magnetic reconnection will also be discussed. 1 I. G. Kevrekidis et. al., Equation-free multiscale computation: Enabling microscopic simulators to perform system-level tasks, arXiv:physics/0209043.
Finite element modeling and experimental characterization of crosstalk in 1-D CMUT arrays.
Bayram, Baris; Kupnik, Mario; Yaralioglu, Goksen G; Oralkan, Omer; Ergun, Arif Sanli; Lin, Der-Song; Wong, Serena H; Khuri-Yakub, Butrus T
2007-02-01
Crosstalk is the coupling of energy between the elements of an ultrasonic transducer array. This coupling degrades the performance of transducers in applications such as medical imaging and therapeutics. In this paper, we present an experimental demonstration of guided interface waves in capacitive micromachined ultrasonic transducers (CMUTs). We compare the experimental results to finite element calculations using a commercial package (LS-DYNA) for a 1-D CMUT array operating in the conventional and collapsed modes. An element in the middle of the array was excited with a unipolar voltage pulse, and the displacements were measured using a laser interferometer along the center line of the array elements immersed in soybean oil. We repeated the measurements for an identical CMUT array covered with a 4.5-microm polydimethylsiloxane (PDMS) layer. The main crosstalk mechanism is the dispersive guided modes propagating in the fluid-solid interface. Although the transmitter element had a center frequency of 5.8 MHz with a 130% fractional bandwidth in the conventional operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 2.1 MHz, and had a cut-off frequency of 4 MHz. In the collapsed operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 4.0 MHz, and had a cut-off frequency of 10 MHz. Crosstalk level was lower in the collapsed operation (-39 dB) than in the conventional operation (-24.4 dB). The coverage of the PDMS did not significantly affect the crosstalk level, but reduced the phase velocity for both operation modes. Lamb wave modes, A0 and S0, were also observed with crosstalk levels of -40 dB and -65 dB, respectively. We observed excellent agreement between the finite element and the experimental results. PMID:17328339
Julia, J; Nyblade, A; Hansen, S; Rodgers, A; Matzel, E
2009-07-06
In this project, we are developing models of lithospheric structure for a wide variety of tectonic regions throughout Eurasia and the Middle East by regionalizing 1D velocity models obtained by jointly inverting P-wave and S-wave receiver functions with Rayleigh wave group and phase velocities. We expect the regionalized velocity models will improve our ability to predict travel-times for local and regional phases, such as Pg, Pn, Sn and Lg, as well as travel-times for body-waves at upper mantle triplication distances in both seismic and aseismic regions of Eurasia and the Middle East. We anticipate the models will help inform and strengthen ongoing and future efforts within the NNSA labs to develop 3D velocity models for Eurasia and the Middle East, and will assist in obtaining model-based predictions where no empirical data are available and for improving locations from sparse networks using kriging. The codes needed to conduct the joint inversion of P-wave receiver functions (PRFs), S-wave receiver functions (SRFs), and dispersion velocities have already been assembled as part of ongoing research on lithospheric structure in Africa. The methodology has been tested with synthetic 'data' and case studies have been investigated with data collected at an open broadband stations in South Africa. PRFs constrain the size and S-P travel-time of seismic discontinuities in the crust and uppermost mantle, SRFs constrain the size and P-S travel-time of the lithosphere-asthenosphere boundary, and dispersion velocities constrain average S-wave velocity within frequency-dependent depth-ranges. Preliminary results show that the combination yields integrated 1D velocity models local to the recording station, where the discontinuities constrained by the receiver functions are superimposed to a background velocity model constrained by the dispersion velocities. In our first year of this project we will (i) generate 1D velocity models for open broadband seismic stations in the western half of the study area (Eurasia and the Middle East) and (ii) identify well located seismic events with event-station paths isolated to individual tectonic provinces within the study area and collect broadband waveforms and source parameters for the selected events. The 1D models obtained from the joint inversion will then be combined with published geologic terrain maps to produce regionalized models for distinctive tectonic areas within the study area, and the models will be validated through full waveform modeling of well-located seismic events recorded at local and regional distances.
Modeling Low Velocity Impacts: Predicting Crater Depth on Pluto
NASA Astrophysics Data System (ADS)
Bray, V. J.; Schenk, P.
2014-12-01
The New Horizons mission is due to fly-by the Pluto system in Summer 2015 and provides the first opportunity to image the Pluto surface in detail, allowing both the appearance and number of its crater population to be studied for the first time. Bray and Schenk (2014) combined previous cratering studies and numerical modeling of the impact process to predict crater morphology on Pluto based on current understanding of Pluto's composition, structure and surrounding impactor population. Predictions of how the low mean impact velocity (~2km/s) of the Pluto system will influence crater formation is a complex issue. Observations of secondary cratering (low velocity, high angle) and laboratory experiments of impact at low velocity are at odds regarding how velocity controls depth-diameter ratios: Observations of secondary craters show that these low velocity craters are shallower than would be expected for a hyper-velocity primary. Conversely, gas gun work has shown that relative crater depth increases as impact velocity decreases. We have investigated the influence of impact velocity further with iSALE hydrocode modeling of comet impact into Pluto. With increasing impact velocity, a projectile will produce wider and deeper craters. The depth-diameter ratio (d/D) however has a more complex progression with increasing impact velocity: impacts faster than 2km/s lead to smaller d/D ratios as impact velocity increases, in agreement with gas-gun studies. However, decreasing impact velocity from 2km/s to 300 m/s produced smaller d/D as impact velocity was decreased. This suggests that on Pluto the deepest craters would be produced by ~ 2km/s impacts, with shallower craters produced by velocities either side of this critical point. Further simulations to investigate whether this effect is connected to the sound speed of the target material are ongoing. The complex relationship between impact velocity and crater depth for impacts occurring between 300m/s and 10 km/s suggests that there might be a larger range of 'pristine' crater depths on Pluto than on bodies with higher mean impact velocity. This might affect our ability to define a pristine crater depth as a starting point for crater infill and relaxation studies.
Interactive 1D model for cloud formation and atmospheric chemistry on Mars
NASA Astrophysics Data System (ADS)
Viscardy, S.; Daerden, F.; Neary, L.; Garcia-Munoz, A.; Novak, R.; Villanueva, G.; Mumma, M.
2014-04-01
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.
Dynamic and steady state 1-D model of mediated electron transfer in a porous enzymatic electrode.
Do, T Q N; Varni?i?, M; Flassig, R J; Vidakovi?-Koch, T; Sundmacher, K
2015-12-01
A 1-D mathematical model of a porous enzymatic electrode exhibiting the mediated electron transfer (MET) mechanism has been developed. As a model system, glucose oxidation catalyzed by immobilized glucose oxidase (GOx) in the presence of a co-immobilized tetrathiafulvalene (TTF) mediator in the porous electrode matrix has been selected. The balance equations for potential fields in the electron- and ion-conducting phases as well as concentration field have been formulated, solved numerically and validated experimentally under steady state conditions. The relevant kinetic parameters of the lumped reaction kinetics have been obtained by global optimization. The confidence intervals (CIs) of each parameter have been extracted from the respective likelihood. The parameter study has shown that the parameters related to mediator consumption/regeneration steps can be responsible for the shift of the reaction onset potential. Additionally, the model has shown that diffusion of the oxidized mediator out of the catalyst layer (CL) plays a significant role only at more positive potentials and low glucose concentrations. Only concentration profiles in different layers influence the electrode performance while other state fields like potential distributions in different phases have no impact on the performance. The concentration profiles reveal that all electrodes work through; the observed limiting currents are diffusion-reaction limiting. The normalized electrode activity decreases with an increase of enzyme loading. According to the model, the reason for this observation is glucose depletion along the CL at higher enzyme loadings. Comparison with experiments advices a decrease of enzyme utilization at higher enzyme loadings. PMID:26257008
Velocity dispersion of M87 using a population model
NASA Technical Reports Server (NTRS)
Angione, R. J.; Junkkarinen, V.; Talbert, F. D.; Brandt, J. C.
1980-01-01
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).
1D Chemical Modeling of coupled snow-atmosphere chemistry at Dome C Antarctica
NASA Astrophysics Data System (ADS)
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
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.
Testing the accuracy of a 1-D volcanic plume model in estimating mass eruption rate
NASA Astrophysics Data System (ADS)
Mastin, Larry G.
2014-03-01
During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historical eruptions where plume height Hobs was well observed and mass eruption rate Mobs could be calculated from mapped deposit mass and observed duration. The simulations considered wind, temperature, and phase changes of water. Atmospheric conditions were obtained from the National Center for Atmospheric Research Reanalysis 2.5° model. Simulations calculate the minimum, maximum, and average values (Mmin, Mmax, and Mavg) that fit the plume height. Eruption rates were also estimated from the empirical formula Mempir = 140Hobs4.14 (Mempir is in kilogram per second, Hobs is in kilometer). For these eruptions, the standard error of the residual in log space is about 0.53 for Mavg and 0.50 for Mempir. Thus, for this data set, the model is slightly less accurate at predicting Mobs than the empirical curve. The inability of this model to improve eruption rate estimates may lie in the limited accuracy of even well-observed plume heights, inaccurate model formulation, or the fact that most eruptions examined were not highly influenced by wind. For the low, wind-blown plume of 14-18 April 2010 at Eyjafjallajökull, where an accurate plume height time series is available, modeled rates do agree better with Mobs than Mempir.
1D Modeling of Catalyzed Monopropellant H2O2 Decomposition in Microchannels
NASA Astrophysics Data System (ADS)
Zhou, Xu; Hitt, Darren
2003-11-01
The modeling of the chemical decomposition of hydrogen-peroxide monopropellant flow in a catalytic microchannel is described. This process can be used to provide a micro-propulsion mechanism required for miniaturized satellites (“nanosats”). Based on the largely gaseous nature of the flow and microchannel geometries, a 1D reacting flow model is assumed. The decomposition is modeled by first-order kinetics and a temperature-dependent Arrhenius law; the latter is justified for typical catalysts. Simulations are performed for realistic operating parameters designed to provide thrust levels of 100-500 micro-N. The outcome is a prediction of a critical catalyst chamber length required for complete decomposition; this is shown to depend upon the Damkohler number, Zeldovich number and the non-dimensional heat release rate of the monopropellant. A “thermal detonation” behavior is observed whereby the decomposition process goes to completion instantaneously. Inclusion of heat loss through microchannel walls can significantly increase critical decomposition length and reduce the available energy for the micropropulsion.
NASA Astrophysics Data System (ADS)
Flanagan, M. P.; Myers, S. C.
2003-12-01
We assess the ability of 3-D velocity models to better predict regional seismic travel times, relative to 1-D models, as well as quantify the travel time uncertainties. Accurate travel time prediction and uncertainty characterization is essential for properly identifying regional seismic phases and computing seismic event locations with representative error ellipses. To accomplish this we use an a priori, 3-D velocity model of Western Eurasia developed at LLNL [Pasyanos et al., 2003] and a dataset of P and Pn phase picks from a catalog of calibration events which meet strict network criteria as investigated by Bondar et al., [2003]. We evaluate the predictive power of the model by computing the median residuals between the observed arrivals and those predicted by 3-D finite difference computations. Statistical assessment of prediction accuracy is made in a non-stationary framework. We conclude that 1-D velocity models are not able to accurately characterize travel time uncertainties; not even radially symmetric models will work. Also, statistical estimates of uncertainty must be made in a region-specific framework (i.e., 3-D). These results demonstrate quantitatively that 3-D velocity models accomplish two goals: improving travel-time prediction (by reducing overall variance of residuals), and reducing the dimensionality of the uncertainties by accounting for the non-stationary component. We also investigate improvement in seismic location using an adaptive station correction approach which combines both model predictions and empirical data. We find that no individual Earth model provides optimal travel-time prediction everywhere. We have, therefore, geographically merged travel-time predictions from a variety of different models and empirical observations to form a travel-time model (correction surface) for each station. Our approach combines the extrapolative advantages of model-based corrections and the interpolative/geostatistical advantages of kriging [Schultz et al., 1998] to produce hybrid travel-time predictions and uncertainty models. For ease of use, model-based and empirical corrections are combined to produce one travel-time correction surface (per seismic station) and uncertainty model that is applied on top of the iasp91 global Earth model in our location algorithm. Such 3-D models and uncertainty characterizations help to achieve location accuracy and computation of representative location error ellipses in a regional monitoring environment, particularly for small events not recorded teleseismically. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48, Contribution UCRL-JC-155079-ABS.
Epstein, Sally; Willemet, Marie; Chowienczyk, Phil J.
2015-01-01
Patient-specific one-dimensional (1D) blood flow modeling requires estimating model parameters from available clinical data, ideally acquired noninvasively. The larger the number of arterial segments in a distributed 1D model, the greater the number of input parameters that need to be estimated. We investigated the effect of a reduction in the number of arterial segments in a given distributed 1D model on the shape of the simulated pressure and flow waveforms. This is achieved by systematically lumping peripheral 1D model branches into windkessel models that preserve the net resistance and total compliance of the original model. We applied our methodology to a model of the 55 larger systemic arteries in the human and to an extended 67-artery model that contains the digital arteries that perfuse the fingers. Results show good agreement in the shape of the aortic and digital waveforms between the original 55-artery (67-artery) and reduced 21-artery (37-artery) models. Reducing the number of segments also enables us to investigate the effect of arterial network topology (and hence reflection sites) on the shape of waveforms. Results show that wave reflections in the thoracic aorta and renal arteries play an important role in shaping the aortic pressure and flow waves and in generating the second peak of the digital pressure and flow waves. Our novel methodology is important to simplify the computational domain while maintaining the precision of the numerical predictions and to assess the effect of wave reflections. PMID:25888513
An improved Doppler model for obtaining accurate maximum blood velocities.
Ricci, Stefano; Matera, Riccardo; Tortoli, Piero
2014-09-01
Maximum blood velocity estimates are frequently required in diagnostic applications, including carotid stenosis evaluation, arteriovenous fistula inspection, and maternal-fetal examinations. However, the currently used methods for ultrasound measurements are inaccurate and often rely on applying heuristic thresholds to a Doppler power spectrum. A new method that uses a mathematical model to predict the correct threshold that should be used for maximum velocity measurements has recently been introduced. Although it is a valuable and deterministic tool, this method is limited to parabolic flows insonated by uniform pressure fields. In this work, a more generalized technique that overcomes such limitations is presented. The new approach, which uses an extended Doppler spectrum model, has been implemented in an experimental set-up based on a linear array probe that transmits defocused steered waves. The improved model has been validated by Field II simulations and phantom experiments on tubes with diameters between 2mm and 8mm. Using the spectral threshold suggested by the new model significantly higher accuracy estimates of the peak velocity can be achieved than are now clinically attained, including for narrow beams and non-parabolic velocity profiles. In particular, an accuracy of +1.2±2.5 cm/s has been obtained in phantom measurements for velocities ranging from 20 to 80 cm/s. This result represents an improvement that can significantly affect the way maximum blood velocity is investigated today. PMID:24934798
Asymmetric optimal-velocity car-following model
NASA Astrophysics Data System (ADS)
Xu, Xihua; Pang, John; Monterola, Christopher
2015-10-01
Taking the asymmetric characteristic of the velocity differences of vehicles into account, we present an asymmetric optimal velocity model for a car-following theory. The asymmetry between the acceleration and the deceleration is represented by the exponential function with an asymmetrical factor, which agrees with the published experiment. This model avoids the disadvantage of the unrealistically high acceleration appearing in previous models when the velocity difference becomes large. This model is simple and only has two independent parameters. The linear stability condition is derived and the phase transition of the traffic flow appears beyond the critical density. The strength of interaction between clusters is shown to increase with the asymmetry factor in our model.
A Zonal Climate Model for the 1-D Mars Evolution Code: Explaining Meridiani Planum.
NASA Astrophysics Data System (ADS)
Manning, C. V.; McKay, C. P.; Zahnle, K. J.
2005-12-01
Recent MER Opportunity observations suggest there existed an extensive body of shallow water in the present Meridiani Planum during the late Noachian [1]. Observations of roughly contemporaneous valley networks show little net erosion [2]. Hypsometric analysis [3] finds that martian drainage basins are similar to terrestrial drainage basins in very arid regions. The immaturity of martian drainage basins suggests they were formed by infrequent fluvial action. If similar fluvial discharges are responsible for the laminations in the salt-bearing outcrops of Meridiani Planum, their explanation may require a climate model based on surface thermal equilibrium with diurnally averaged temperatures greater than freezing. In the context of Mars' chaotic obliquity, invoking a moderately thick atmosphere with seasonal insolation patterns may uncover the conditions under which the outcrops formed. We compounded a 1-D model of the evolution of Mars' inventories of CO2 over its lifetime called the Mars Evolution Code (MEC) [4]. We are assembling a zonal climate model that includes meridional heat transport, heat conduction to/from the regolith, latent heat deposition, and an albedo distribution based on the depositional patterns of ices. Since water vapor is an important greenhouse gas, and whose ice affects the albedo, we must install a full hydrological cycle. This requires a thermal model of the regolith to model diffusion of water vapor to/from a permafrost layer. Our model carries obliquity and eccentricity distributions consistent with Laskar et al. [5], so we will be able to model the movement of the ice cap with changes in obliquity. The climate model will be used to investigate the conditions under which ponded water could have occurred in the late Noachian, thus supplying a constraint on the free inventory of CO2 at that time. Our evolution code can then investigate Hesperian and Amazonian climates. The model could also be used to understand evidence of recent climate change, and the specifics of the layering of the northern polar cap. References [1] Hynek, B. M. (2004) Nature 431, 156. [2] Irwin, R. et al. (2004) LPI Conf. 35, 1991. [3] Stepinski, T. F., (2004) JGR E18, 2005 [4] Manning, C. V., et al. (2005Icarus submitted [5] Laskar, J. et al. (2004) Icarus, 170, 343.
Velocity-density twin transforms in the thin disc model
NASA Astrophysics Data System (ADS)
Bratek, ?ukasz; Sikora, Szymon; Ja?ocha, Joanna; Kutschera, Marek
2015-08-01
Ring mass density and the corresponding circular velocity in thin disc model are known to be integral transforms of one another. But it may be less familiar that the transforms can be reduced to one-fold integrals with identical weight functions. It may be of practical value that the integral for the surface density does not involve the velocity derivative, unlike the equivalent and widely known Toomre's formula.
Spontaneous stochasticity of velocity in turbulence models
Mailybaev, Alexei A
2015-01-01
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.
SCEC CVM-Toolkit (CVM-T) -- High Performance Meshing Tools for SCEC Community Velocity Models
NASA Astrophysics Data System (ADS)
Small, P.; Maechling, P. J.; Ely, G. P.; Olsen, K. B.; Withers, K.; Graves, R. W.; Jordan, T. H.; Plesch, A.; Shaw, J. H.
2010-12-01
The SCEC Community Velocity Model Toolkit (CVM-T) enables earthquake modelers to quickly build, visualize, and validate large-scale 3D velocity meshes using SCEC CVM-H or CVM-4. CVM-T is comprised of three main components: (1) a current SCEC community velocity model for Southern California, (2) tools for extracting meshes from this model and visualizing them, and (3) an automated test framework for evaluating new releases of CVMs using 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.
1-D/3-D geologic model of the Western Canada Sedimentary Basin
Higley, D.K.; Henry, M.; Roberts, L.N.R.; Steinshouer, D.W.
2005-01-01
The 3-D geologic model of the Western Canada Sedimentary Basin comprises 18 stacked intervals from the base of the Devonian Woodbend Group and age equivalent formations to ground surface; it includes an estimated thickness of eroded sediments based on 1-D burial history reconstructions for 33 wells across the study area. Each interval for the construction of the 3-D model was chosen on the basis of whether it is primarily composed of petroleum system elements of reservoir, hydrocarbon source, seal, overburden, or underburden strata, as well as the quality and areal distribution of well and other data. Preliminary results of the modeling support the following interpretations. Long-distance migration of hydrocarbons east of the Rocky Mountains is indicated by oil and gas accumulations in areas within which source rocks are thermally immature for oil and (or) gas. Petroleum systems in the basin are segmented by the northeast-trending Sweetgrass Arch; hydrocarbons west of the arch were from source rocks lying near or beneath the Rocky Mountains, whereas oil and gas east of the arch were sourced from the Williston Basin. Hydrocarbon generation and migration are primarily due to increased burial associated with the Laramide Orogeny. Hydrocarbon sources and migration were also influenced by the Lower Cretaceous sub-Mannville unconformity. In the Peace River Arch area of northern Alberta, Jurassic and older formations exhibit high-angle truncations against the unconformity. Potential Paleozoic though Mesozoic hydrocarbon source rocks are in contact with overlying Mannville Group reservoir facies. In contrast, in Saskatchewan and southern Alberta the contacts are parallel to sub-parallel, with the result that hydrocarbon source rocks are separated from the Mannville Group by seal-forming strata within the Jurassic. Vertical and lateral movement of hydrocarbons along the faults in the Rocky Mountains deformed belt probably also resulted in mixing of oil and gas from numerous source rocks in Alberta.
Testing the Early Mars H2-CO2 Greenhouse Hypothesis with a 1-D Photochemical Model
Batalha, Natasha; Ramirez, Ramses; Kasting, James
2015-01-01
A recent study by Ramirez et al. (2014) demonstrated that an atmosphere with 1.3-4 bar of CO2 and H2O, in addition to 5-20% H2, could have raised the mean annual and global surface temperature of early Mars above the freezing point of water. Such warm temperatures appear necessary to generate the rainfall (or snowfall) amounts required to carve the ancient martian valleys. Here, we use our best estimates for early martian outgassing rates, along with a 1-D photochemical model, to assess the conversion efficiency of CO, CH4, and H2S to CO2, SO2, and H2. Our outgassing estimates assume that Mars was actively recycling volatiles between its crust and interior, as Earth does today. H2 production from serpentinization and deposition of banded iron-formations is also considered. Under these assumptions, maintaining an H2 concentration of ~1-2% by volume is achievable, but reaching 5% H2 requires additional H2 sources or a slowing of the hydrogen escape rate below the diffusion limit. If the early martian atmosphere...
Modelling Hydrology of a Single Bioretention System with HYDRUS-1D
Meng, Yingying; Wang, Huixiao; Chen, Jiangang; Zhang, Shuhan
2014-01-01
A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems. PMID:25133240
Droplet size and velocity distributions for spray modelling
NASA Astrophysics Data System (ADS)
Jones, D. P.; Watkins, A. P.
2012-01-01
Methods for constructing droplet size distributions and droplet velocity profiles are examined as a basis for the Eulerian spray model proposed in Beck and Watkins (2002,2003) [5,6]. Within the spray model, both distributions must be calculated at every control volume at every time-step where the spray is present and valid distributions must be guaranteed. Results show that the Maximum Entropy formalism combined with the Gamma distribution satisfy these conditions for the droplet size distributions. Approximating the droplet velocity profile is shown to be considerably more difficult due to the fact that it does not have compact support. An exponential model with a constrained exponent offers plausible profiles.
Comparison of 1D and 2D CSR Models with Application to the FERMI@ELETTRA Bunch Compressors
Bassi, G.; Ellison, J.A.; Heinemann, K.
2011-03-28
We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces [1]. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. As an application, we present numerical results for the Fermi{at}Elettra first bunch compressor with the configuration described in [1].
Fujita, Miki; Himmelspach, Regina; Ward, Juliet; Whittington, Angela; Hasenbein, Nortrud; Liu, Christine; Truong, Thy T; Galway, Moira E; Mansfield, Shawn D; Hocart, Charles H; Wasteneys, Geoffrey O
2013-05-01
Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function. The dwarf mutants have reduced anisotropic growth of roots, aerial organs, and trichomes. Interestingly, cellulose microfibrils were disordered only in the epidermal cells of the any1 inflorescence stem, whereas they were transverse to the growth axis in other tissues of the stem and in all elongated cell types of roots and dark-grown hypocotyls. Overall cellulose content was not altered but both cell wall crystallinity and the velocity of cellulose synthase complexes were reduced in any1. We crossed any1 with the temperature-sensitive radial swelling1-1 (rsw1-1) CesA1 mutant and observed partial complementation of the any1 phenotype in the transheterozygotes at rsw1-1's permissive temperature (21°C) and full complementation by any1 of the conditional rsw1-1 root swelling phenotype at the restrictive temperature (29°C). In rsw1-1 homozygotes at restrictive temperature, a striking dissociation of cellulose synthase complexes from the plasma membrane was accompanied by greatly diminished motility of intracellular cellulose synthase-containing compartments. Neither phenomenon was observed in the any1 rsw1-1 transheterozygotes, suggesting that the proteins encoded by the any1 allele replace those encoded by rsw1-1 at restrictive temperature. PMID:23532584
A 3-mode, Variable Velocity Jet Model for HH 34
NASA Technical Reports Server (NTRS)
Raga, A.; Noriega-Crespo, A.
1998-01-01
Variable ejection velocity jet models can qualitatively explain the appearance of successive working surfaces in Herbig-Haro (HH) jets. This paper presents an attempt to explore which features of the HH 34 jet can indeed be reproduced by such a model.
ABSTRACTION OF INFORMATION FROM 2- AND 3-DIMENSIONAL PORFLOW MODELS INTO A 1-D GOLDSIM MODEL - 11404
Taylor, G.; Hiergesell, R.
2010-11-16
The Savannah River National Laboratory has developed a 'hybrid' approach to Performance Assessment modeling which has been used for a number of Performance Assessments. This hybrid approach uses a multi-dimensional modeling platform (PorFlow) to develop deterministic flow fields and perform contaminant transport. The GoldSim modeling platform is used to develop the Sensitivity and Uncertainty analyses. Because these codes are performing complementary tasks, it is incumbent upon them that for the deterministic cases they produce very similar results. This paper discusses two very different waste forms, one with no engineered barriers and one with engineered barriers, each of which present different challenges to the abstraction of data. The hybrid approach to Performance Assessment modeling used at the SRNL uses a 2-D unsaturated zone (UZ) and a 3-D saturated zone (SZ) model in the PorFlow modeling platform. The UZ model consists of the waste zone and the unsaturated zoned between the waste zone and the water table. The SZ model consists of source cells beneath the waste form to the points of interest. Both models contain 'buffer' cells so that modeling domain boundaries do not adversely affect the calculation. The information pipeline between the two models is the contaminant flux. The domain contaminant flux, typically in units of moles (or Curies) per year from the UZ model is used as a boundary condition for the source cells in the SZ. The GoldSim modeling component of the hybrid approach is an integrated UZ-SZ model. The model is a 1-D representation of the SZ, typically 1-D in the UZ, but as discussed below, depending on the waste form being analyzed may contain pseudo-2-D elements. A waste form at the Savannah River Site (SRS) which has no engineered barriers is commonly referred to as a slit trench. A slit trench, as its name implies, is an unlined trench, typically 6 m deep, 6 m wide, and 200 m long. Low level waste consisting of soil, debris, rubble, wood, etc. is disposed within the trench which is then covered with soil and a cap. The filled trench resembles the surrounding soil, albeit with a higher porosity. As a result, the flow field through the trench is essentially 1-dimensional. This dimensionality makes the abstraction of information from this waste form fairly simple. Engineered waste forms present challenges not seen in the slit trench because of their higher dimensionality. Flow fields must conform to the barriers and are therefore subject to changes in direction. This paper will examine one case and show how this multidimensional flow field can be abstracted into a 1-dimensional flow field while retaining characteristics important to the transport of radioactive contaminants. One complication not addressed by the two preceding examples is that of multiple sources. This presents quite a challenge to the benchmarking exercise, but a fairly robust method has been developed to deal with it. While the PorFlow analyses can treat all sources as independent in space, this is not possible with a 1-D model. This problem has been addressed by constructing multiple 1-D models of the waste forms and using plume overlaps at the assessment points to address the multiple sources which can contribute to a distinct assessment point.
A 1-D radiative conductive model to study the SOIR/VEx thermal profiles
NASA Astrophysics Data System (ADS)
Mahieux, Arnaud; Erwin, Justin T.; Chamberlain, Sarah; Robert, Séverine; Carine Vandaele, Ann; Wilquet, Valérie; Thomas, Ian; Yelle, Roger V.; Bertaux, Jean-Loup
2015-04-01
SOIR is an infrared spectrometer on board Venus Express that probes the Venus terminator region since 2006. The measurements are taken on the morning and evening sides of the terminator, covering all latitudes from the North Pole to the South Pole. Its wavelength range - 2.2 to 4.3 ?m - allows a detailed chemical inventory of the Venus atmosphere [1-5], such as CO2, CO, H2O, HCl, HF, SO2 and aerosols. CO2 is detected from 70 km up to 165 km, CO from 70 km to 140 km, and the minor species typically below 110 km down to 70 km. Number density profiles of these species are computed from the measured spectra. Temperature profiles are obtained while computing the spectral inversion of the CO2 spectra combined with the hydrostatic law [6]. These temperature measurements show a striking permanent temperature minimum (at 125 km) and a weaker temperature maximum (over 100-115 km). The time variability of the CO2 density profiles spans over two orders of magnitude, and a clear trend is seen with latitude. The temperature variations are also important, of the order of 35 K for a given pressure level, but the latitude variation are small. Miss-RT, a 1D radiative transfer model has been developed to reproduce the SOIR terminator profiles, derived from the Mars thermosphere code presented in [7]. This model has been expanded to better account for the CO2, CO, and O non-LTE radiative heating and cooling processes which have to be considered in the dense atmosphere of Venus. Radiative cooling by minor species detected by SOIR (e.g. HCl, SO2, and H2O) are found to be small in comparison to the 15 ?m CO2 cooling. Aerosol cooling in the 60-90km altitude range may be important to the thermal balance. There is a good agreement between the 1D model temperature profile and the mean SOIR temperature profile. Further we can suggest parameters that can be adjusted to improve the agreement between the model and measurements. The remaining differences can be attributed to the atmosphere dynamics at the terminator. 1. Bertaux, J.L., et al., A warm layer in Venus' cryosphere and high altitude measurements of HF, HCl, H2O and HDO. Nature, 2007. 450(29 November): p. 646-649, doi:10.1038/nature05974. 2. Vandaele, A.C., et al., Carbon monoxide short term variability observed on Venus with SOIR/VEX. Planet. Space Sci., 2014. (in press). 3. Mahieux, A., et al., Venus mesospheric sulfur dioxide measurement retrieved from SOIR on board Venus Express. Planet. Space Sci., 2014. (in press). 4. Mahieux, A., et al., Hydrogen Halides measurements in the Venus upper atmosphere retrieved from SOIR on board Venus Express. Planet. Space Sci., 2014. (in press). 5. Wilquet, V., et al., Optical extinction due to aerosols in the upper haze of Venus: Four years of SOIR/VEX observations from 2006 to 2010. Icarus, 2012. 217(2): p. 875-881. 6. Mahieux, A., et al., Update of the Venus density and temperature profiles at high altitude measured by SOIR on board Venus Express. Planet. Space Sci., 2014. (submitted). 7. Yelle, R., et al., Perturbation of the Mars Atmosphere by the Near-Collision with Comet C/2013 A1 (Siding Spring). Icarus, 2014. 237: p. 202-210.
High Velocity Rain: The Terminal Velocity of Model of Galactic Infall
Robert A. Benjamin; Laura Danly
1996-12-18
A model is proposed for determining the distances to falling interstellar clouds in the galactic halo by measuring the cloud velocity and column density and assuming a model for the vertical density distribution of the Galactic interstellar medium. It is shown that falling clouds with $N(H I) \\sim 0.4 kpc$ one or more of the following occurs: (1) the neutral fraction of the cloud decreases to $\\sim 31 \\pm 14%$, (2) the density drops off faster than characterized by Reynolds, or (3) there is a systematic decrease in drag coefficient with increasing z.
Relative-Velocity-Dependent Weber-type Models in Electromagnetism
Santosh Devasia
2008-08-28
This article reconsiders the relative-velocity-dependent approach to modeling electromagnetism that was proposed initially by Weber before data from cathode-ray-tube (CRT) experiments was available. It is shown that identifying the nonlinear, relative-velocity terms using CRT data results in a model, which not only captures standard relativistic effects in optics, high-energy particles, and gravitation, but also explains apparent discrepancies between predicted and measured energy (i) in high-energy-particle absorption experiments and (ii) in the classical beta-ray spectrum of radium-E.
Evaluation of a 1-D snowpack model SMAP applied in the Greenland ice sheet
NASA Astrophysics Data System (ADS)
Niwano, Masashi; Aoki, Teruo; Matoba, Sumito; Yamaguchi, Satoru; Tanikawa, Tomonori; Motoyama, Hideaki; Kuchiki, Katsuyuki
2013-04-01
Snow and ice on the Greenland ice sheet (GrIS) are melting rapidly in recent years. In order to understand the mechanism and to perform reliable future projection on the mass balance of GrIS, we employ the 1-D physical snowpack model named Snow Metamorphism and Albedo Process (SMAP), which was originally developed and validated against seasonal snowpack, and adapt it for the simulation of polar snowpack. In the present study we tested SMAP using the data obtained during the 2012 intensive field observations (30 June to 13 July, 2012) conducted in the site SIGMA-A, which locates on northwest part of GrIS (78° 03'N, 67° 38'W, 1,490 m a.s.l.). During the latter half of the expedition period we encountered the record melt event where surface snow and ice over 97% of GrIS melted abruptly. In the model test the initial physical states of snowpack were given from those obtained by snow-pit observations carried out on 30 June. From the initial state we calculated temporal evolution of physical parameters of snowpack by forcing measured meteorological data, mass concentrations of snow impurities, and snow temperature at the depth of bottom ice formation in the latest annual layer (initial depth was 88 cm). The model performance was evaluated in terms of snow surface temperature, shortwave albedo, relative snow depth (to the ice formation in the latest annual layer), profiles of snow temperature, and snow density. Regarding snow surface temperature and shortwave albedo SMAP overestimated both, nevertheless biases were small (+0.143 ° C and +0.014, respectively), suggesting that the snow-atmosphere energy exchange (snow surface energy balance) is modeled adequately. To calculate accurate relative snow depth it is necessary to simulate mass balance precisely. The acquired small bias (-0.026 m) shows that SMAP estimates mass balance successfully. Finally, as for profiles of snow temperature and snow density we found that SMAP tended to underestimate the former, while overestimate the latter. However, obtained small biases (less than 1 ° C and ranged between 30 and 90 kg m-3, respectively) indicate that SMAP calculates internal physical properties of snowpack in an appropriate manner if relevant upper and lower boundary conditions are imposed.
Testing the early Mars H2-CO2 greenhouse hypothesis with a 1-D photochemical model
NASA Astrophysics Data System (ADS)
Batalha, Natasha; Domagal-Goldman, Shawn D.; Ramirez, Ramses; Kasting, James F.
2015-09-01
A recent study by Ramirez et al. (Ramirez, R.M. et al. [2014]. Nat. Geosci. 7(1), 59-63.) demonstrated that an atmosphere with 1.3-4 bar of CO2 and H2O, in addition to 5-20% H2, could have raised the mean annual and global surface temperature of early Mars above the freezing point of water. Such warm temperatures appear necessary to generate the rainfall (or snowfall) amounts required to carve the ancient martian valleys. Here, we use our best estimates for early martian outgassing rates, along with a 1-D photochemical model, to assess the conversion efficiency of CO, CH4, and H2S to CO2, SO2, and H2. Our outgassing estimates assume that Mars was actively recycling volatiles between its crust and interior, as Earth does today. H2 production from serpentinization and deposition of banded iron-formations is also considered. Under these assumptions, maintaining an H2 concentration of ˜1-2% by volume is achievable, but reaching 5% H2 requires additional H2 sources or a slowing of the hydrogen escape rate below the diffusion limit. If the early martian atmosphere was indeed H2-rich, we might be able to see evidence of this in the rock record. The hypothesis proposed here is consistent with new data from the Curiosity Rover, which show evidence for a long-lived lake in Gale Crater near Mt. Sharp. It is also consistent with measured oxygen fugacities of martian meteorites, which show evidence for progressive mantle oxidation over time.
ccsd-00009406,version1-3Oct2005 Modeling 1-D elastic P-waves in a fractured
Aiguier, 13402 Marseille, France Abstract The one-dimensional propagation of compressional elastic waves is investigated below (in section 2.2). Let us take a plane compressional wave propagating through 0 normally to ccsd-00009406,version1-3Oct2005 Modeling 1-D elastic P-waves in a fractured rock with hyperbolic
Oxidation mechanisms and kinetics of 1D-SiC\\/C\\/SiC composite materials; 2: Modeling
Ludovic Filipuzzi; Roger Naslain
1994-01-01
A model, based on a simple axisymmetrical fiber\\/interphase\\/matrix assembly, is derived to depict the oxidation behavior of 1D-SiC\\/C\\/SiC composites within the temperature range 900--1300 C and for 10
Abstract A coupled 1D physical-biological model of Crater Lake is presented. The model
Boss, Emmanuel S.
the seasonal evolution of two functional phytoplankton groups, total chlorophyll, and zoo- plankton in good in summer and early fall the model displays a marked vertical structure: the phytoplankton biomass 40 m; the phytoplankton biomass of group 2, which repre- sents chlorophyta, chrysophyta, cryptomonads
Velocity prediction errors related to flow model calibration uncertainty
Stephenson, D.E. ); Duffield, G.M.; Buss, D.R. )
1990-01-01
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.
Mass modelling of galaxy clusters via velocity moments
Ewa L. Lokas; Radoslaw Wojtak; Gary A. Mamon; Stefan Gottloeber
2007-12-14
We summarize the method of mass modelling of galaxy clusters based on reproducing the dispersion and kurtosis of the projected velocity distribution of galaxies. The models are parametrized within the framework of the NFW density profile, characterized by the virial mass and concentration, together with the constant anisotropy of galaxy orbits. The use of velocity dispersion alone does not allow to constrain all the three parameters from kinematic data due to the mass-anisotropy degeneracy. The degeneracy is broken by introducing the fourth velocity moment, the kurtosis. We tested the method based on fitting both moments on mock data sets drawn from simulated dark matter haloes and showed it to reproduce reliably the properties of the haloes. The method has been applied to estimate the mass, concentration and anisotropy of more than 20 clusters which allowed us to confirm, for the first time using kinematic data, the mass-concentration relation found in N-body simulations.
Comparison between a 1D and a 2D numerical model of an active magnetic regenerative refrigerator
NASA Astrophysics Data System (ADS)
Petersen, Thomas Frank; Engelbrecht, Kurt; Bahl, Christian R. H.; Elmegaard, Brian; Pryds, Nini; Smith, Anders
2008-05-01
The active magnetic regenerator (AMR) refrigeration system represents an environmentally attractive alternative to vapour-compression refrigeration. This paper compares the results of two numerical AMR models: (1) a 1D finite difference model and (2) a 2D finite element model. Both models simulate a reciprocating AMR and can determine the cyclical steady-state temperature profile of the system as well as performance parameters such as the refrigeration capacity, the work input and the coefficient of performance (COP). The models are used to analyse an AMR with a regenerator made of flat parallel plates of gadolinium operating in the presence of a 1 T magnetic field. The results are used to discuss under which circumstances a 1D model is insufficient and a 2D model is necessary. The results indicate that when the temperature gradients in the AMR perpendicular to the flow are small a 1D model obtains accurate results of overall results such as the refrigeration capacity but that a 2D model is required for a detailed analysis of the phenomena occurring inside the AMR.
NASA Astrophysics Data System (ADS)
Bhattacharya, A.; Mandal, M.
2014-12-01
Model spin-up is the process through which the model is adequately equilibrated to ensure balance between the mass fields and velocity fields. In this study, an offline 1-D Noah land surface model (LSM) has been used to investigate the impact of soil moisture on the model spin up at Kharagpur, India which is a site in monsoonal region. The model is integrated recursively for 3-years to assess its spin-up behavior. Several numerical experiments are performed to investigate the impact of initial soil moisture and subsequent dry or wet condition on model spin-up. These include simulations with different initial soil moisture content (observed soil moisture; dry soil; moderately wet soil; saturated soil), simulations initialized before different rain conditions (no rain; infrequent rain; continuous rain) and simulations initialized in different seasons (Winter, Spring, Summer/Pre-Monsoon, Monsoon and Autumn). It is noted that the model has significantly longer spin-up when initialized with very low initial soil moisture content than with higher soil moisture content. It is also seen that in general, simulations initialized just before a continuous rainfall event have the least spin-up time. In a region affected by the monsoon, such as Kharagpur, this observation is reinforced by the results from the simulations initialized in different seasons. It is seen that for monsoonal region, the model spin-up time is least for simulations initialized during Summer/Pre-monsoon. Model initialized during the Monsoon has a longer spin-up than that initialized in any other season. It appears that the model has shorter spin-up if it reaches the equilibrium state predominantly via drying process. It is also observed that the spin-up of offline 1-D Noah LSM may be as low as two months under quasi-equilibrium condition if the initial soil moisture content and time of start of simulations are chosen carefully.
Three-dimensional seismic velocity model of the West Bohemia/Vogtland seismoactive region
NASA Astrophysics Data System (ADS)
R?žek, Bohuslav; Horálek, Josef
2013-11-01
In this paper, we present a smooth 3-D seismic model WB2012 for the West Bohemia/Vogtland earthquake swarm region derived by means of seismic tomography. Inverted data were represented by a set of 2920 P-wave traveltimes from controlled shots fired in a framework of different experiments and a set of 11339 P- and S-wave arrival times from 661 local earthquakes between 1991 December and 2010 March. We used a standard tomographic approach for independent calculation of P- and S-wave velocity fields in a rectangular grid whose size was 1 km in all coordinates. The traveltimes and rays were calculated by a numerical solution of the eiconal equation. While locating seismic events, our new WB2012 model yielded arrival time residuals on average by 13 per cent lower and hypocentre depths by 0.95 km shallower compared to the locations of the foci in the standard 1-D vertically inhomogeneous isotropic velocity model of the West Bohemia swarm region WB2005. Further, we converted the P- and S-wave velocities to the bulk modulus K and Poisson's ratio ?. The bulk modulus (˜40-70 GPa) correlates acceptably with the tectonic and geological structure of the area. The anomalously low values of the Poisson's ratio (˜0.15) are typical for the most active focal zones of Nový Kostel and Lazy in West Bohemia.
Multi-objective optimisation of cost-benefit of urban flood management using a 1D2D coupled model.
Delelegn, S W; Pathirana, A; Gersonius, B; Adeogun, A G; Vairavamoorthy, K
2011-01-01
This paper presents a multi-objective optimisation (MOO) tool for urban drainage management that is based on a 1D2D coupled model of SWMM5 (1D sub-surface flow model) and BreZo (2D surface flow model). This coupled model is linked with NSGA-II, which is an Evolutionary Algorithm-based optimiser. Previously the combination of a surface/sub-surface flow model and evolutionary optimisation has been considered to be infeasible due to the computational demands. The 1D2D coupled model used here shows a computational efficiency that is acceptable for optimisation. This technological advance is the result of the application of a triangular irregular discretisation process and an explicit finite volume solver in the 2D surface flow model. Besides that, OpenMP based parallelisation was employed at optimiser level to further improve the computational speed of the MOO tool. The MOO tool has been applied to an existing sewer network in West Garforth, UK. This application demonstrates the advantages of using multi-objective optimisation by providing an easy-to-comprehend Pareto-optimal front (relating investment cost to expected flood damage) that could be used for decision making processes, without repeatedly going through the modelling-optimisation stage. PMID:21411958
Sobolev scalar products in the construction of velocity models
Cerveny, Vlastislav
Sobolev scalar products in the construction of velocity models LudÅ¸ek KlimeÅ¸s DepartmentÂmail: klimes@seis.karlov.mff.cuni.cz Summary The Sobolev scalar products are defined, and discussed from, inversion, wave propagation, ray methods. 1 Introduction The Sobolev scalar product of two functions
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...
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...
A new settling velocity model to describe secondary sedimentation.
Ramin, Elham; Wágner, Dorottya S; Yde, Lars; Binning, Philip J; Rasmussen, Michael R; Mikkelsen, Peter Steen; Plósz, Benedek Gy
2014-12-01
Secondary settling tanks (SSTs) are the most hydraulically sensitive unit operations in biological wastewater treatment plants. The maximum permissible inflow to the plant depends on the efficiency of SSTs in separating and thickening the activated sludge. The flow conditions and solids distribution in SSTs can be predicted using computational fluid dynamics (CFD) tools. Despite extensive studies on the compression settling behaviour of activated sludge and the development of advanced settling velocity models for use in SST simulations, these models are not often used, due to the challenges associated with their calibration. In this study, we developed a new settling velocity model, including hindered, transient and compression settling, and showed that it can be calibrated to data from a simple, novel settling column experimental set-up using the Bayesian optimization method DREAM(ZS). In addition, correlations between the Herschel-Bulkley rheological model parameters and sludge concentration were identified with data from batch rheological experiments. A 2-D axisymmetric CFD model of a circular SST containing the new settling velocity and rheological model was validated with full-scale measurements. Finally, it was shown that the representation of compression settling in the CFD model can significantly influence the prediction of sludge distribution in the SSTs under dry- and wet-weather flow conditions. PMID:25243657
Modeling and comparative study of fluid velocities in heterogeneous rocks
NASA Astrophysics Data System (ADS)
Hingerl, Ferdinand F.; Romanenko, Konstantin; Pini, Ronny; Balcom, Bruce; Benson, Sally
2013-04-01
Detailed knowledge of the distribution of effective porosity and fluid velocities in heterogeneous rock samples is crucial for understanding and predicting spatially resolved fluid residence times and kinetic reaction rates of fluid-rock interactions. The applicability of conventional MRI techniques to sedimentary rocks is limited by internal magnetic field gradients and short spin relaxation times. The approach developed at the UNB MRI Centre combines the 13-interval Alternating-Pulsed-Gradient Stimulated-Echo (APGSTE) scheme and three-dimensional Single Point Ramped Imaging with T1 Enhancement (SPRITE). These methods were designed to reduce the errors due to effects of background gradients and fast transverse relaxation. SPRITE is largely immune to time-evolution effects resulting from background gradients, paramagnetic impurities and chemical shift. Using these techniques quantitative 3D porosity maps as well as single-phase fluid velocity fields in sandstone core samples were measured. Using a new Magnetic Resonance Imaging technique developed at the MRI Centre at UNB, we created 3D maps of porosity distributions as well as single-phase fluid velocity distributions of sandstone rock samples. Then, we evaluated the applicability of the Kozeny-Carman relationship for modeling measured fluid velocity distributions in sandstones samples showing meso-scale heterogeneities using two different modeling approaches. The MRI maps were used as reference points for the modeling approaches. For the first modeling approach, we applied the Kozeny-Carman relationship to the porosity distributions and computed respective permeability maps, which in turn provided input for a CFD simulation - using the Stanford CFD code GPRS - to compute averaged velocity maps. The latter were then compared to the measured velocity maps. For the second approach, the measured velocity distributions were used as input for inversely computing permeabilities using the GPRS CFD code. The computed permeabilities were then correlated with the ones based on the porosity maps and the Kozeny-Carman relationship. The findings of the comparative modeling study are discussed and its potential impact on the modeling of fluid residence times and kinetic reaction rates of fluid-rock interactions in rocks containing meso-scale heterogeneities are reviewed.
NASA Astrophysics Data System (ADS)
Huerfano, V. A.; Lopez, A. M.; Castillo, L.; Baez-Sanchez, G.; Soto-Cordero, L.; Lin, G.; Zhang, Q.
2010-12-01
Puerto Rico and the Virgin Islands (PRVI) block lie on the northeastern boundary of the Caribbean plate, where active transpressional tectonics result in the deformation of the boundaries of this block. Every year hundreds of earthquakes occur within and around PRVI region and at least four destructive earthquakes after 1700 are documented in the historical records. The mission of the Puerto Rico Seismic Network (PRSN), Department of Geology of the University of Puerto Rico in Mayagüez is to detect, analyze, disseminate earthquake/tsunami messages and investigate the seismicity in the PR/VI. Currently the PRSN operates 30 seismic stations and receive real time stream from over 75 station installed around the Caribbean. 25 years worth of data recorded by the PRSN has been quality checked and compiled to constrain a new velocity structure using the tomographic package TomoDD. Currently at PRSN, the velocity structure to perform real-time determination of hypocenters consists of a 1-D model. Therefore, this ambitious tomographic study seek to produce a more comprehensive velocity model to be implemented at the PRSN for the daily earthquake locations. Results from this study are a collaborative effort between the University of Miami and the University of Puerto Rico - Mayaguez.
Goedecke, Niels; Maul, Christof; Kauczok, Sebastian; Gericke, Karl-Heinz [Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, Braunschweig (Germany); Chichinin, Alexey I. [Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk (Russian Federation)
2009-08-07
The bimolecular reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO was photoinitiated in the (N{sub 2}O){sub 2} dimer at a wavelength of 193 nm and was investigated by three-dimensional (3D) velocity map imaging. State selective 3D momentum vector distributions were monitored and analyzed. For the first time, kinetic energy resolution and stereodynamic information about the reaction under constrained geometry conditions is available. Directly observable NO products exhibit moderate vibrational excitation and are rotationally and translationally cold. Speed and spatial distributions suggest a pronounced backward scattering of the observed products with respect to the direction of motion of the O({sup 1}D) atom. Forward scattered partner products, which are not directly detectable are also translationally cold, but carry very large internal energy as vibration or rotation. The results confirm and extend previous studies on the complex initiated reaction system. The restricted geometry of the van der Waals complex seems to favor an abstraction reaction of the terminal nitrogen atom by the O({sup 1}D) atom, which is in striking contrast to the behavior observed for the unrestricted gas phase reaction under bulk conditions.
NASA Astrophysics Data System (ADS)
Sinha, Sumit; Rode, Michael; Borchardt, Dietrich
2014-05-01
The Bode River catchment in the Harz Mountain area of central Germany is heavily influenced by anthropogenic factors. 70% of the catchment is dominated by agriculture, 23 % by forest and the rest 7% is urban in nature. The area of the catchment is approximately 3300 km2 and is characterized by sharp gradients in temperature, precipitation and land use. In order to acquire better understanding of the hydrological nature of the catchment and biogeochemical characteristics of the Bode River various monitoring stations have been deployed as a part of the larger earth observation network initiative named Terrestrial Environmental Observatories. One of the major issues with the catchment is the problem of eutrophication due to solute inputs from agriculture. The research presented here evaluated the application and development of 1D and 2D hydrodynamic and water quality models in the downstream area of the Bode River. A stretch of 30 kms between Hadmersleeben and Stassfurt in the downstream area of the Bode River was modeled using 1D model HEC-RAS, the focus of the water quality modeling was transport and uptake of nitrate in the aforementioned modeled stretch. Flood events of varying peak magnitude at different times of the year were modeled. As regards to 2D modeling, TELEMAC-2D model was applied for the same reach. The hydrodynamic simulation results were validated with the help of free surface elevation at Athensleben, 8 kms upstream from the downstream end at Stassfurt. Water quality modeling, focusing on the Nitrate removal for the aforementioned stretch, is applied and developed for both 1D and 2D modeling framework. Results from hydrodynamic and water quality modeling were validated with RMSE (Root Mean Square Error) value of 0.074 and 0.36 for the modeled state variables across various events simulated. For the nutrient-rich reach modeled in this research it was found that the nutrient removal capacity of the stream is directly proportional to the incoming nitrate concentration.
Analytic solutions for seismic travel time and ray path geometry through simple velocity models.
Ballard, Sanford
2007-12-01
The geometry of ray paths through realistic Earth models can be extremely complex due to the vertical and lateral heterogeneity of the velocity distribution within the models. Calculation of high fidelity ray paths and travel times through these models generally involves sophisticated algorithms that require significant assumptions and approximations. To test such algorithms it is desirable to have available analytic solutions for the geometry and travel time of rays through simpler velocity distributions against which the more complex algorithms can be compared. Also, in situations where computational performance requirements prohibit implementation of full 3D algorithms, it may be necessary to accept the accuracy limitations of analytic solutions in order to compute solutions that satisfy those requirements. Analytic solutions are described for the geometry and travel time of infinite frequency rays through radially symmetric 1D Earth models characterized by an inner sphere where the velocity distribution is given by the function V (r) = A-Br{sup 2}, optionally surrounded by some number of spherical shells of constant velocity. The mathematical basis of the calculations is described, sample calculations are presented, and results are compared to the Taup Toolkit of Crotwell et al. (1999). These solutions are useful for evaluating the fidelity of sophisticated 3D travel time calculators and in situations where performance requirements preclude the use of more computationally intensive calculators. It should be noted that most of the solutions presented are only quasi-analytic. Exact, closed form equations are derived but computation of solutions to specific problems generally require application of numerical integration or root finding techniques, which, while approximations, can be calculated to very high accuracy. Tolerances are set in the numerical algorithms such that computed travel time accuracies are better than 1 microsecond.
The Velocity Model of Chinese Continent Established by GNSS Observations
NASA Astrophysics Data System (ADS)
Yao, Y.
2009-04-01
With the high precision repeated GNSS observations, the Multi-quadric equations interpolation method is used to establish the velocity model of Chinese continent's crustal movement. The valuable present-day horizontal and vertical crustal movement velocity images are obtained. The eastwardly movement trend of Chinese continent is quite evident, and there is a trend of clockwise rolling, from northeast to east, then to southeast. At the same time Chinese continent movement show the difference between east and west. In the west the trend is move towards the north and northeast, while in the east the trend is creep towards south and southeast, with a huge north dextral shear zone. The horizontal movement velocity approximately equals to 30-50mm/a.The background velocity model of China mainland in ITRF97 frame is also computed by GNSS velocity observations. The local background velocity model is extremely consistent with Europe -Asia tectonic plate's Euler direction and the spin rate provide by some global background field model such as NNR-NUVEL1A model, Sillard model and Larson model in the magnitude and the major tendency, with which we can analyze the characteristic of Chinese continent's crustal movement.Chinese continent's absolute shift mainly happens in the southwest area. In Ximalaya and Lhasa block the eastern movement is very apparent, and there is an apparent clockwise rotation in Qiangtang, Chuandian, Dianxi block. In Qiangtan block, it shift toward east, but in Chuandian block, it shift toward southeast, and then it shift southwest in Dianxi block. The magnitude is about 10~25mm/a, and they are quite obvious activity deformation belt, and the absolute movement of other area is not evident, mostly less than 10mm/a.The characteristic of vertical crustal movement in Chinese mainland is qualitative analysed: more than 70% of Chinese mainland are descended and the speed of descend is less than 20mm/a , the Qingzang plateau?Huabei plate(excluding Beijing area) and Yanshan plate are ascended with the speed less than 15mm/a. The holistic vertical crustal movement of West-North and East-South?West-South and East-North areas of China are shown an approximate slanting symmetry state.
INFIL1D: a quasi-analytical model for simulating one-dimensional, constant flux infiltration
Simmons, C.S.; McKeon, T.J.
1984-04-01
The program INFIL1D is designed to calculate approximate wetting-front advance into an unsaturated, uniformly moist, homogeneous soil profile, under constant surface-flux conditions. The code is based on a quasi-analytical method, which utilizes an assumed invariant functional relationship between reduced (normalized) flux and water content. The code uses general hydraulic property data in tabular form to simulate constant surface-flux infiltration. 10 references, 4 figures.
Cerveny, Vlastislav
of the Christo#11;el matrix which may rotate rapidly about the ray. In \\weakly anisotropic" models, at moderate seismograms calculated by the coupling ray theory in a 1-D anisotropic model. The e#11;ects of the quasi in the 1-D anisotropic \\oblique twisted crystal" model Petr Bulant & Lud#20;ek Klime#20;s #3; , Department
NASA Astrophysics Data System (ADS)
Dobrynina, Anna; Sankov, Vladimir; Chechelnitsky, Vladimir
2014-05-01
The deep profiles of quality factor were obtained using coda-waves of local strong and moderate earthquakes (epicentral distances up to 50 km) occurred within north-eastern flanc of the Baikal rift system during 2002-2009. We used two methods: 1 - the coda envelope method [Experimental.., 1981; Kopnichev, 1991] and 2 - the sliding window method (lapse time window 10-15 sec with a step of 5 sec). Depth of coda-wave penetration was determined according to Pulli's formulae [1984], the velocity of coda-wave is 3.55 km/s (equal to shear wave velocity). For analysis we used the Q values at frequency 1 Hz since for this frequency the attenuation field heterogeneity is most evident [Aptikaeva and Kopnichev, 1991]. In result Q-profiles for eleven local areas were obtained. The Q-values vary from 50 to 170 for different profiles and depths. Herewith quality factor changes nonuniformly - the alternation of layers with high and low Q-values is observed. This phenomenon can be explained by existing velocity discontinuity. In particular for all profiles this alternation is confined to the depth about 100 km. Analysis VP-anomalies obtained in result of 2D teleseismic tomography along Baikal rift system [Mordvinova, 2009] shows the existence discontinuity on depth about 100 km under most of Baikal rift system structures. Analysis of 1D profiles of shear wave velocities in the crust and upper mantle after inversion of receiver functions [Anan'in et al., 2009] also shows presence of these discontinuity dividing high and low velocity layers. The comparison of Q-values and shear wave velocities [Anan'in et al., 2009] shown that in high velocity layers quality factor is higher too and vice versa. Multilayer quality factor model for the lithosphere in north-eastern flanc of the Baikal rift system with the alternation of layers with high and low attenuation determined by us together with analogous data obtained by Yu.F. Kopnichev [1992] for south-western flanc of the rift system can be one of inferential evidences of passive rifting mechanism in studied area. The reported study was supported by RFBR (research project N12-05-31038-mol_a) and by grant of President of Russian Federation (research project N MK-1171.2014.5).
Thermodynamics of doubly charged CGHS model and D1-D5-KK black holes of IIB supergravity
Youngjai Kiem; Chang-Yeong Lee; Dahl Park
1998-06-22
We study the doubly charged Callan-Giddings-Harvey-Strominger (CGHS) model, which has black hole solutions that were found to be U-dual to the D1-D5-KK black holes of the IIB supergravity. We derive the action of the model via a spontaneous compactification on S^3 of the IIB supergravity on S^1*T^4 and obtain the general static solutions including black holes corresponding to certain non-asymptotically flat black holes in the IIB supergravity. Thermodynamics of them is established by computing the entropy, temperature, chemical potentials, and mass in the two-dimensional setup, and the first law of thermodynamics is explicitly verified. The entropy is in precise agreement with that of the D1-D5-KK black holes, and the mass turns out to be consistent with the infinite Lorentz boost along the M theory circle that is a part of the aforementioned U-dual chain.
Thomas Ingeman-Nielsen; François Baumgartner
2006-01-01
We have constructed a forward modelling code in Matlab, capable of handling several commonly used electrical and electromagnetic methods in a 1D environment. We review the implemented electromagnetic field equations for grounded wires, frequency and transient soundings and present new solutions in the case of a non-magnetic first layer. The CR1Dmod code evaluates the Hankel transforms occurring in the field
NASA Astrophysics Data System (ADS)
Cobb, C. M.; Furukawa, Y.; Keen, T. R.
2005-05-01
The entrainment of cohesive sediments involves coupled sediment-bottom boundary layer processes forced by waves, currents and complex physical, biological, and chemical processes (e.g. consolidation, bioturbation/bioirrigation, geochemistry) that occur within the seafloor sediments. Transition metal contaminants are significantly affected by the redox environment of the surrounding sediments. Therefore, an ability to predict their transport and chemical alteration is necessary for environmental remediation. This study uses a system of coupled models to simulate the 1-D vertical entrainment of heterogeneous coastal sediments and the biogeochemistry of the benthic boundary layer sediments as an initial attempt to create such a predictive tool. An ideal case, forced only by tides and waves, is examined in order to understand the sensitivities of the sediment profiles to the wave-tide forcing and the bottom sediment biogeochemistry to erosion/deposition events generated by the sediment entrainment. In particular, the spatial and temporal changes of the redox species NH4 and SO4 in the pore water of the bottom sediments are analyzed. In addition, the sensitivity of the suspended sediment profile to changes in seafloor properties (% of cohesive sediments, grain size, erosion rate parameters) is investigated. The model is calibrated using suspended sediment concentration data collected at Hunters Point Shipyard (HPS) in San Francisco Bay, California. Realistic sea surface elevation and current velocities, generated using the 3-D baroclinic NCOM hydrodynamic model, are used by the 1-D sediment model to determine the suspended sediment profiles at two locations in the northern and southern regions of HPS. The parameters of the sediment entrainment model are then adjusted to match the measured values of suspended sediment concentration and the response of the biogeochemistry is examined over the entire month of January 2004.
The USGS 3D Seismic Velocity Model for Northern California
NASA Astrophysics Data System (ADS)
Brocher, T. M.; Aagaard, B.; Simpson, R. W.; Jachens, R. C.
2006-12-01
We present a new regional 3D seismic velocity model for Northern California for use in strong motion simulations of the 1906 San Francisco and other earthquakes. The model includes compressional-wave velocity (Vp), shear-wave velocity (Vs), density, and intrinsic attenuation (Qp, Qs). These properties were assigned for each rock type in a 3D geologic model derived from surface outcrops, boreholes, gravity and magnetic data, and seismic reflection, refraction, and tomography studies. A detailed description of the model, USGS Bay Area Velocity Model 05.1.0, is available online [http://www.sf06simulation.org/geology/velocitymodel]. For ground motion simulations Vs and Qs are more important parameters than Vp and Qp because the strongest ground motions are generated chiefly by shear and surface wave arrivals. Because Vp data are more common than Vs data, however, we first developed Vp versus depth relations for each rock type and then converted these to Vs versus depth relations. For the most important rock types in Northern California we compiled measurements of Vp versus depth using borehole logs, laboratory measurements on hand samples, seismic refraction profiles, and tomography models. These rock types include Salinian and Sierran granitic rocks, metagraywackes and greenstones of the Franciscan Complex, Tertiary and Mesozoic sedimentary and volcanic rocks, and Quaternary and Holocene deposits (Brocher, USGS OFR 05-1317, 2005). Vp versus depth curves were converted to Vs versus depth curves using new empirical nonlinear relations between Vs and Vp (Brocher, BSSA, 2005). These relations, showing that Poisson's ratio is a nonlinear function of Vp, were similarly based on compilations of diverse Vs and Vp measurements on a large suite of rock types, mainly from California and the Pacific Northwest. The model is distributed in a discretized form with routines to query the model using C++, C, and Fortran 77 programming languages. The geologic model was discretized at higher resolution near the surface (100m horizontal and 25m vertical) compared with depth (800m horizontal and 200m vertical). The model contains material properties at nearly 190 million locations and is stored as an Etree database (Tu et al., 2003). The query routines provide a simple interface to the database, returning the material properties for a given latitude, longitude, and elevation or depth.
Synthesis of 1D regular arrays of gold nanoparticles and modeling of their optical properties.
Dmitruk, N; Barlas, T; Dmytruk, A; Korovin, A; Romanyuk, V
2008-02-01
Self-organized formation of uniform coating of semiconductor substrate by metal nanoparticles offers a convenient and efficient access to large-scale arrays of uniform metal-semiconductor nanostructures. We used a cheap and facile method of photoinduced chemical gold deposition from an aqueous or alcohol gold salt solution onto semiconductor surface (GaAs, InP). By controlling of both the solution composition and the deposition conditions, gold particles of 10-50 nm in diameter were obtained and the gold covering degree of the semiconductor surface was varied in a wide range. Morphology of the nano/micro structures formed was characterized by atomic force microscopy and scanned electron microscopy with local element analysis. The investigations show that the semiconductor surface patterning can be used for the selective deposition of gold nanoparticles, because they are located predominantly at the tops of the microrelief. We have used specially textured by the anisotropic chemical etching microrelief surfaces of semiconductor single crystal as templates and have obtained nanoparticle arrays in the shape of 1D systems of near parallel quasiperiodical wires. For the periodic 1D array of metal nanowires built into the air-semiconductor interface the spectral and angular dependencies of the transmittance/reflectance of the polarized light have been obtained theoretically using differential formalism. These dependencies demonstrate non-monotonic behaviour at surface plasmon polariton excitation conditions and show possibility of designing functional subwavelength devices. PMID:18464371
Sleipner CCS site: velocity and attenuation model from seismic tomography
NASA Astrophysics Data System (ADS)
Rossi, G.; Chadwick, R. A.; Williams, G. A.
2012-04-01
The results of the travel-time and frequency shift tomographic inversion of the seismic data from one of the high-resolution lines acquired in 2006 on the Sleipner CO2 geological storage site are here presented. The work has been performed within the European project CO2ReMoVe, to produce an accurate model in-depth, of both seismic velocities and attenuation, to constrain better the quantification studies of the project's partners. Tomographic techniques have the advantage of not assuming horizontal layering or uniform lateral velocities, and of enabling an easy comparison of models, even if resulting from seismic data acquired with different geometries, unavoidable in a time-lapse data set. Through an iterative process, the differences in travel-times between observed direct, reflected or refracted arrivals and the same, calculated on a discrete model, with a ray-tracing based on the Fermat's principle, are minimized. Other minimization procedures provide the reflector/refractor geometries in -depth. Analogously, in attenuation tomography, the minimization process takes into account the observed and calculated spectral-centroid frequency-shift, due to the loss of the highest frequency of the seismic wave, while crossing an attenuating medium. The result is a seismic quality factor (Q) model in-depth, and hence of the attenuation that is known to be more sensitive to subtle changes in physical properties than seismic velocity. The model is across the center of the CO2 plume, on the in-line 1838, and is constituted by nine layers, four resulting by a preliminary analysis of the pre-injection 1994 data set, i.e. seabed, a strong reflection in the overburden and the top and bottom of the Utsira Sand, plus additional five horizons, four of which within Utsira Sands, and one just above the top of it. The layers within the reservoir are very close to each other and in some cases they merge together laterally. The accumulation of CO2 in the uppermost layer of the reservoir, observed by other analyses, is confirmed by our analysis, whereas within the plume, lateral variations of both seismic velocity and Q values are observed. The presence of fine shale lenses, and their impact on the CO2 distribution within the plume may be the reason for these lateral variations. The seismic velocity and Q tomographic values have been compared with the theoretical curves from petrophysics studies, so to give to the results an interpretation in terms of effective variations in CO2 saturation and heterogeneity within the plume.
Seismic velocity modelling of the Carboneras Fault Zone, SE Spain
NASA Astrophysics Data System (ADS)
Taylor, R. L.; Rutter, E. H.; Nippress, S. E. J.; Brodie, K. H.
2015-04-01
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.
Velocity Fields with Power-Law Spectra for Modeling Turbulent Mine Caglar
Caglar, Mine
Velocity Fields with Power-Law Spectra for Modeling Turbulent Flows Mine CÂ¸aglar KoÂ¸c UniversityÂ¸inlar velocity fields to capture power-law spectra. The random velocity field is non be generated by varying the stochastic parameters of the model. The velocity field being a functional version
2D MHD and 1D HD models of a solar flare -- a comprehensive comparison of the results
Falewicz, R; Murawski, K; Srivastava, A K
2015-01-01
Without any doubt solar flaring loops possess a multi-thread internal structure that is poorly resolved and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modelling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of 1D hydrodynamic and 2D magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters of the modeled loop are set according to the progenitor M1.8 flare recorded in the AR10126 on September 20, 2002 between 09:21 UT and 09:50 UT. The non-ideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy loss mechanisms, while the non-ideal 2D models take into account viscosity and thermal conduction as energy loss mechanisms only. The 2...
NASA Astrophysics Data System (ADS)
Pandey, S.; Yuan, X.; Debayle, E.; Priestley, K. F.; Kind, R.; Li, X.
2010-12-01
The collision of the Eurasian plate, Indian plate and Philippine sea plate resulted in the tectonic feature of todays; like mountain ranges, fold belts, sedimentary basins and high plateaus in China and the surrounding region. In the Northern part this region is supposed to get some resistance from the Siberian shield. But the collision of Indian plate has left its major imprints and the consequence of this was the uplift of Himalayan Mountain and Tibetan Plateau. This triple junction scenario is the main cause for many inter and intra-plate earthquake in this region. It is generally agreed that the lithosphere is thick in west China while much of the lithospheric root was lost beneath some cratons in east China. Still it's an open debate whether the lithosphere beneath the Tibetan plateau has doubled its thickness as did the crust above or much of the thickened lithosphere was removed by mantle convection and delamination. In our study we try to determine the three dimensional Sv wave speed and azimuthal anisotropy model by analyzing the vertical component multimode Rayleigh wave seismogram. The data which we used are from broadband stations from in and around China. We construct the three dimensional model in two step procedure. In the first step we use the automated version of the Cara and Leveque [1987] waveform inversion technique in terms of secondary observables for modeling each multimode Rayleigh waveform to determine the path-average mantle Sv wave speed structure. In the second stage we combine the 1-D velocity models in a tomographic inversion to obtain the three dimensional Sv wave speed structure and the azimuthal anisotropy as a function of depth. We have taken a source region specific velocity structure from the three dimensional model 3SMAC to improve the source excitation computation. We analyzed the seismograms using a modified (smoothed) version of PREM for the upper mantle velocity structure both for the reference model used in extracting the modal information from the seismogram and for the starting inversion and a priori velocity models employed in determining the path-average mantle structure. However, each path has a path-specific crustal model determined by averaging the crustal part of 3SMAC along the path.
REACTIVE TRANSPORT MODELLING IN THE VADOSE ZONE WITH COUPLED PHREEQC-HYDRUS 1D CODE
Technology Transfer Automated Retrieval System (TEKTRAN)
To model multicomponent transport during transient variably-saturated flow in the vadose zone, complex models are needed. Ideally such models should incorporate simultaneous solutions for the water flow equation, solute transport and equilibrium or kinetically homogeneous and heterogeneous geochemic...
Modeling the exit velocity of a compressed air cannon
NASA Astrophysics Data System (ADS)
Rohrbach, Z. J.; Buresh, T. R.; Madsen, M. J.
2012-01-01
The use of compressed air cannons in an undergraduate laboratory provides a way to illustrate the connection between diverse physics concepts, such as conservation of momentum, the work-kinetic energy theorem, gas expansion, air drag, and elementary Newtonian mechanics. However, it is not clear whether the expansion of the gas in the cannon is an adiabatic or an isothermal process. We built an air cannon that utilizes a diaphragm valve to release the pressurized gas and found that neither process accurately predicts the exit velocity of our projectile. We discuss a model based on the flow of air through the valve, which is in much better agreement with our data.
NASA Astrophysics Data System (ADS)
Zhang, Lianxin; Zhang, Xuefeng; Han, Guijun; Wu, Xinrong; Cui, Xiaojian; Shao, Caixia; Sun, Chunjian; Zhang, Xiaoshuang; Wang, Xidong; Fu, Hongli
2015-09-01
At the interface between the lower atmosphere and sea surface, sea spray might significantly influence air-sea heat fluxes and subsequently, modulate upper ocean temperature during a typhoon passage. The effects of sea spray were introduced into the parameterization of sea surface roughness in a 1-D turbulent model, to investigate the effects of sea spray on upper ocean temperature in the Kuroshio Extension area, for the cases of two real typhoons from 2006, Yagi and Soulik. Model output was compared with data from the Kuroshio Extension Observatory (KEO), and Reynolds and AMSRE satellite remote sensing sea surface temperatures. The results indicate drag coefficients that include the spray effect are closer to observations than those without, and that sea spray can enhance the heat fluxes (especially latent heat flux) considerably during a typhoon passage. Consequently, the model results with heat fluxes enhanced by sea spray simulate better the cooling process of the SST and upper-layer temperature profiles. Additionally, results from the simulation of the passage of typhoon Soulik (that passed KEO quickly), which included the sea spray effect, were better than for the simulated passage of typhoon Yagi (that crossed KEO slowly). These promising 1-D results could provide insight into the application of sea spray in general circulation models for typhoon studies.
Mean velocity and moments of turbulent velocity fluctuations in the wake of a model ship propulsor
NASA Astrophysics Data System (ADS)
Pêgo, J. P.; Lienhart, H.; Durst, F.
2007-08-01
Pod drives are modern outboard ship propulsion systems with a motor encapsulated in a watertight pod, whose shaft is connected directly to one or two propellers. The whole unit hangs from the stern of the ship and rotates azimuthally, thus providing thrust and steering without the need of a rudder. Force/momentum and phase-resolved laser Doppler anemometry (LDA) measurements were performed for in line co-rotating and contra-rotating propellers pod drive models. The measurements permitted to characterize these ship propulsion systems in terms of their hydrodynamic characteristics. The torque delivered to the propellers and the thrust of the system were measured for different operation conditions of the propellers. These measurements lead to the hydrodynamic optimization of the ship propulsion system. The parameters under focus revealed the influence of distance between propeller planes, propeller frequency of rotation ratio and type of propellers (co- or contra-rotating) on the overall efficiency of the system. Two of the ship propulsion systems under consideration were chosen, based on their hydrodynamic characteristics, for a detailed study of the swirling wake flow by means of laser Doppler anemometry. A two-component laser Doppler system was employed for the velocity measurements. A light barrier mounted on the axle of the rear propeller motor supplied a TTL signal to mark the beginning of each period, thus providing angle information for the LDA measurements. Measurements were conducted for four axial positions in the slipstream of the pod drive models. The results show that the wake of contra-rotating propeller is more homogeneous than when they co-rotate. In agreement with the results of the force/momentum measurements and with hypotheses put forward in the literature (see e.g. Poehls in Entwurfsgrundlagen für Schraubenpropeller, 1984; Schneekluth in Hydromechanik zum Schiffsentwurf, 1988; Breslin and Andersen in Hydrodynamics of ship propellers, 1996; Schneekluth and Bertram in Ship design for efficiency and economy, 1998), the co-rotating propellers model showed a much stronger swirl in the wake of the propulsor. The anisotropy of turbulence was analyzed using the anisotropy tensor introduced by Lumley and Newman (J Fluid Mech 82(1):161-178, 1977). The invariants of the anisotropy tensor of the wake flow were computed and were plotted in the Lumley-Newman-diagram. These measurements revealed that the anisotropy tensor in the wake of ship propellers is located near to the borders of the invariant map, showing a large degree of anisotropy. They will be presented and will be discussed with respect to applications of turbulence models to predict swirling flows.
Collision-free nonuniform dynamics within continuous optimal velocity models
NASA Astrophysics Data System (ADS)
Tordeux, Antoine; Seyfried, Armin
2014-10-01
Optimal velocity (OV) car-following models give with few parameters stable stop-and -go waves propagating like in empirical data. Unfortunately, classical OV models locally oscillate with vehicles colliding and moving backward. In order to solve this problem, the models have to be completed with additional parameters. This leads to an increase of the complexity. In this paper, a new OV model with no additional parameters is defined. For any value of the inputs, the model is intrinsically asymmetric and collision-free. This is achieved by using a first-order ordinary model with two predecessors in interaction, instead of the usual inertial delayed first-order or second-order models coupled with the predecessor. The model has stable uniform solutions as well as various stable stop-and -go patterns with bimodal distribution of the speed. As observable in real data, the modal speed values in congested states are not restricted to the free flow speed and zero. They depend on the form of the OV function. Properties of linear, concave, convex, or sigmoid speed functions are explored with no limitation due to collisions.
Traveling waves in an optimal velocity model of freeway traffic.
Berg, P; Woods, A
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137]. PMID:11308709
Traveling waves in an optimal velocity model of freeway traffic
NASA Astrophysics Data System (ADS)
Berg, Peter; Woods, Andrew
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].
Laforest, Marc
velocity models K. C. Assi and M. Laforest Abstract. We study the spatial difference in L1 between two solutions of dif- ferent discrete velocity models in one space dimension using techniques devel- oped by Ha and Tzavaras. We assume that the second (fine) model is obtained by adding new velocities to the first (coarse
NASA Astrophysics Data System (ADS)
Lauer, Wesley; Viparelli, Enrica; Piegay, Herve
2014-05-01
Sedimentary deposits adjacent to rivers can represent important sources and sinks for bed material sediment, particularly on decadal and longer timescales. The Morphodynamics and Sediment Tracers in 1-D model (MAST-1D) is a size-specific sediment transport model that allows for active exchange between channel and floodplain sediment on river reaches of tens to hundreds of kilometers in length. The model is intended to provide a mechanism for performing a first-order assessment of the likely importance of off-channel sediment exchange in controlling decadal-scale geomorphic trends, thereby helping plan and/or prioritize field data collection and higher resolution modeling work. The model develops a sediment budget for short segments of an alluvial valley. Each segment encompasses several active river bends. In each segment, a sediment transport capacity computation is performed to determine the downstream flux of bed material sediment, following the approach of most other 1-D sediment transport models. However, the model differs from most other bed evolution models in that sediment can be exchanged with the floodplain in each segment, and mass conservation is applied to both the active layer and floodplain sediment storage reservoirs. The potential for net imbalances in overall exchange as well as the size specific nature of the computations allows the model to simulate reach-scale aggradation/degradation and/or changes in bed texture. The inclusion of fine sediment in the model allows it to track geochemical tracer material and also provides a mechanism to simulate, to first order, the effects of changes in the supply of silt and clay on overall channel hydraulic capacity. The model is applied to a ~40 km reach of the Ain River, a tributary of the Rhône River in eastern France that has experienced a significant sediment deficit as a result of the construction of several dams between 1920 and 1970. MAST-1D simulations result in both incision and the formation of a bed armor near the upstream end of the study reach, where sediment load has been disrupted. The inclusion of active exchange with the floodplain allows the floodplain evolve into a net source of bed material sediment as the channel incises. This effect prevents the sediment deficit from reaching the confluence with the Rhone for several simulated decades. When spatially variable migration rates similar to those measured from aerial photography are used to drive sediment exchange, the model shows complex interaction between bed and bank sediment, with the relatively fine-grained bank sediment supply mobilizing the coarser fraction of the active layer within rapidly shifting portions of the channel. This increases overall transport rates and leads to additional channel incision relative to what is simulated without bank sediment supply in these rapidly shifting reaches. The model is also helpful for evaluating the potential reach-scale effects of gravel augmentation downstream of the dams.
NASA Astrophysics Data System (ADS)
Pancha, A.; Pullammanappallil, S.; Louie, J. N.; DePolo, C. M.
2012-12-01
Estimation of shallow and deep shear velocity is a key element in the assessment of sites for potential earthquake ground shaking, damage, and the calibration of recorded ground motions. We assess shear-wave velocities across the deepest portion of the Reno-area basin as defined by gravity, as well as at twelve seismic stations in the near-field region of the 26 April 2008 Mw 5.0 Mogul, Nevada earthquake 12 km west of Downtown Reno. To date, no permanent seismic instrumentation is located over this thickest portion of the Reno-area basin and little structural and velocity data is available. Existing velocity models for the region are limited in resolution to intervals of 1 km to 3 km. As a result, 3D basin details are currently insufficient for scenario modeling and ShakeZoning, essential components of seismic hazard evaluation. These efforts contribute towards development of the Western Basin and Range Community Velocity Model and the Reno-Carson urban hazard map. As part of a NEHRP-IMW grant, we measured shear velocities to depths of 500 m using refraction-microtremor (ReMi) arrays across this portion of the basin with 50 m depth resolution. This was achieved through the deployment of 30 stand alone wireless instruments in arrays 2.9 to 5.8 km long, to record ambient urban noise. Data were obtained along two parallel east-west arrays and one shorter north-south array. The ReMi technique was employed to obtain 1D velocity profiles as a function of depth across each array from these noise records. To further characterize and map lateral velocity heterogeneity beneath the arrays, subsets of instruments were used to obtain a series of 1D soundings that were then interpolated to obtain a 2D structural representation of shear-wave velocities. The 1D and 2D velocity soundings along each array are combined produce a 3D shear-velocity volume delineating the deep velocity structure of the basin. Observed lateral velocity variations were identified and correlated with the locations of hypothesized faults in an attempt to constrain their locality. The 26 April 2008 Mw 5.0 Mogul, Nevada earthquake, located at a shallow depth of 3.1 km, was the largest event during a shallow earthquake swarm that began in February 2008 and persisted for several months. The largest peak acceleration vector during this mainshock was recorded at station MOGL (1.19g; 1164 cm/s2), which is among the 25 largest recorded earthquake accelerations worldwide. Strong ground motions were observed at the four closest stations installed at the time of the mainshock, which exceed accelerations of 300 cm/s2 and velocities of 14 cm/s. Both shear-wave (ReMi) and P-wave (refraction) techniques were used to characterize and map lateral velocity heterogeneity beneath the twelve near-field seismic sites. 2D shear-velocity sections together with 2D P-wave refraction tomography sections show complex site conditions beneath these stations. Some of these sites may be crossed by local faults, and the velocity sections reflect this possibility. These resultant site condition assessments at these near-filed sites will contribute towards quantification of local site response and calibration of the high peak ground motions recorded during both the mainshock event and the foreshock/aftershock swarm events.
Modelling the relative velocities of isolated pairs of galaxies
NASA Astrophysics Data System (ADS)
Gonzalez-Perez, V.; Jennings, E.; Cousinou, M.-C.; Escoffier, S.; Tilquin, A.; Ealet, A.
2013-11-01
We study the comoving relative velocities, v_{12}, of model isolated galaxy pairs at z=0.5. For this purpose, we use the predictions from the GAIFORM semi-analytical model of galaxy formation and evolution based on a ? cold dark matter cosmology consistent with the results from WMAP7. In real space, we find that isolated pairs of galaxies are predicted to form an angle t with the line-of-sight that is uniformly distributed as expected if the Universe is homogeneous and isotropic. We also find that isolated pairs of galaxies separated by a comoving distance between 1 and 3 h^{-1}Mpc are predicted to have
Analytical one--way plane--wave solution in the 1D anisotropic ``twisted crystal'' model
Cerveny, Vlastislav
is used. For plane wave u i = u i (x 3 ) propagating along the x 3 axis in 1ÂD anisotropic model a i3k3Analytical one--way plane--wave solution in the 1ÂD anisotropic ``twisted crystal'' model Lud in the simple 1ÂD anisotropic ``twisted crystal'' model, are presented. The analytical equations may be useful
COMPARISON OF QUASIISOTROPIC APPROXIMATIONS OF THE COUPLING RAY THEORY IN 1D MODEL 'OTC'
Cerveny, Vlastislav
with the eigenvectors of the Christoffel matrix which may rotate rapidly about the ray. In ``weakly anisotropic'' models of synthetic seismograms calculated by the coupling ray theory in a 1ÂD anisotropic model. The effects solution for the plane S wave, propagating along the axis of spirality in the 1ÂD anisotropic ``oblique
NASA Astrophysics Data System (ADS)
Cheviron, B.; Moussa, R.
2015-09-01
This review paper investigates the determinants of modelling choices, for numerous applications of 1-D free-surface flow and erosion equations, across multiple spatiotemporal scales. We aim to characterize each case study by its signature composed of model refinement (Navier-Stokes: NS, Reynolds-Averaged Navier-Stokes: RANS, Saint-Venant: SV or Approximations of Saint-Venant: ASV), spatiotemporal scales (domain length: L from 1 cm to 1000 km; temporal scale: T from 1 second to 1 year; flow depth: H from 1 mm to 10 m), flow typology (Overland: O, High gradient: Hg, Bedforms: B, Fluvial: F) and dimensionless numbers (Dimensionless time period T*, Reynolds number Re, Froude number Fr, Slope S, Inundation ratio ?z, Shields number ?). The determinants of modelling choices are therefore sought in the interplay between flow characteristics, cross-scale and scale-independent views. The influence of spatiotemporal scales on modelling choices is first quantified through the expected correlation between increasing scales and decreasing model refinements, identifying then flow typology a secondary but mattering determinant in the choice of model refinement. This finding is confirmed by the discriminating values of several dimensionless numbers, that prove preferential associations between model refinements and flow typologies. This review is intended to help each modeller positioning his (her) choices with respect to the most frequent practices, within a generic, normative procedure possibly enriched by the community for a larger, comprehensive and updated image of modelling strategies.
NASA Astrophysics Data System (ADS)
Cao, H.; Zhou, H.
2007-12-01
Deformable layer tomography is a new layer based tomography method which can be used to integrate forward modeling and inverse approaches of pre-stack analyses of seismic velocity and Q. Traditionally forward modeling generates zero offset synthetic seismic traces based on logging data because such data provide the 1D profiles of reflector depth and rock property. In our work, forward modeling method was integrated with tomographic approach to generate pre-stack synthetic seismic wavelets along certain reflectors. Since the deformable layer tomography is based on layers instead of grids, it can provide 2D geometric information of each reflector and rock property across the reflector to facilitate a comparison with pre-stack seismic traces. We integrate the shot gather modeling with deformable layer tomography at two stages, the pre-inversion stage and post-inversion stage. The pre-inversion stage is to get initial velocity and Q depth models from shot gather modeling based on priori velocity and geology information. This procedure is interactive ¡§C one can select specific layer and then edit the nodes around the layer and rock property inside the layer through graphic user interface to achieve an approximated fit between the observed seismic traces and modeling result. The post- inversion stage is to edit the inverted velocity and Q model based on the difference between the observed seismic traces and the synthetic traces from the inverted depth model. This integration method has been applied to both synthetic and field tests. Those tests show that forward modeling can provide better initial model for the tomography algorithm to stabilize the inversion and shorten the convergent time. In addition, the inverted model can be further edited to get better match between the observed pre-stack seismic traces and the synthetic traces.
NASA Astrophysics Data System (ADS)
Pek?en, Ertan; Yas, Türker; K?yak, Alper
2014-09-01
We examine the one-dimensional direct current method in anisotropic earth formation. We derive an analytic expression of a simple, two-layered anisotropic earth model. Further, we also consider a horizontally layered anisotropic earth response with respect to the digital filter method, which yields a quasi-analytic solution over anisotropic media. These analytic and quasi-analytic solutions are useful tests for numerical codes. A two-dimensional finite difference earth model in anisotropic media is presented in order to generate a synthetic data set for a simple one-dimensional earth. Further, we propose a particle swarm optimization method for estimating the model parameters of a layered anisotropic earth model such as horizontal and vertical resistivities, and thickness. The particle swarm optimization is a naturally inspired meta-heuristic algorithm. The proposed method finds model parameters quite successfully based on synthetic and field data. However, adding 5 % Gaussian noise to the synthetic data increases the ambiguity of the value of the model parameters. For this reason, the results should be controlled by a number of statistical tests. In this study, we use probability density function within 95 % confidence interval, parameter variation of each iteration and frequency distribution of the model parameters to reduce the ambiguity. The result is promising and the proposed method can be used for evaluating one-dimensional direct current data in anisotropic media.
Space-based observational constraints for 1-D fire smoke plume-rise models
NASA Astrophysics Data System (ADS)
Val Martin, Maria; Kahn, Ralph A.; Logan, Jennifer A.; Paugam, Ronan; Wooster, Martin; Ichoku, Charles
2012-11-01
We use a plume height climatology derived from space-based Multiangle Imaging Spectroradiometer (MISR) observations to evaluate the performance of a widely used plume-rise model. We initialize the 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 constrain, and we test the model with four estimates each of active fire area and total heat flux, obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) thermal anomalies available for each MISR plume and other empirical data. 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 entrainment and possibly other less well constrained factors are also likely to be significant. Using atmospheric stability conditions, MODIS FRP, and MISR plume heights, 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 boundary layer, consistent with earlier results. However, over the diversity of conditions studied, the model simulations generally underestimate the plume height dynamic range observed by MISR and do not reliably identify plumes injected into the free troposphere, key information needed for atmospheric models to simulate smoke dispersion. We conclude that embedding in large-scale atmospheric studies an advanced plume-rise model using currently available fire constraints remains a difficult proposition, and we propose a simplified model that crudely constrains plume injection height based on two main physical factors for which some observational constraints often exist. Field experiments aimed at directly measuring fire and smoke plume properties in detail are likely to produce the next major advances in plume-rise modeling.
Rheology, diffusion, and velocity correlations in the bubble model
Arka Prabha Roy; Kamran Karimi; Craig E. Maloney
2015-08-04
We present results on spatio-temporal correlations in the so-called mean drag version of the Durian bubble model in the limit of small, but finite, shearing rates, $\\dot{\\gamma}$. We study the rheology, diffusion, and spatial correlations of the instantaneous velocity field. The quasi-static (QS) effective diffusion co-efficient, $D_e$, shows an anomalous system size dependence indicative of organization of plastic slip into lines along the directions of maximum shearing. At higher rates, $D_e$ decays like $\\dot{\\gamma}^{-1/3}$. The instantaneous velocity fields have a spatial structure which is consistent with a set of spatially uncorrelated Eshelby transformations. The correlations are cut off beyond a length, $\\xi$. $\\xi\\sim \\dot{\\gamma}^{-1/3}$ which explains the $D_e\\sim\\dot{\\gamma}^{-1/3}$ behavior. The shear stress, $\\sigma$, follows a similar rate dependence with $\\delta\\sigma=\\sigma-\\sigma_y\\sim \\dot{\\gamma}^{1/3}$ where $\\sigma_y$ is the yield stress observed in the QS regime.These results indicate that the form for the viscous dissipation can have a profound impact on the rheology, diffusion and spatial correlations in sheared soft glassy systems.
Modeling Cerebral Blood Flow Velocity During Orthostatic Stress.
Mader, Greg; Olufsen, Mette; Mahdi, Adam
2015-08-01
Cerebral autoregulation refers to the physiological process that maintains stable cerebral blood flow (CBF) during changes in arterial blood pressure (ABP). In this study, we propose a simple, nonlinear quantitative model with only four parameters that can predict CBF velocity as a function of ABP. The model was motivated by the viscoelastic-like behavior observed in the data collected during postural change from sitting to standing. Qualitative testing of the model involved analysis of dynamic responses to step-changes in pressure both within and outside the autoregulatory range, while quantitative testing was used to show that the model can fit dynamics observed in data measured from a healthy young and a healthy elderly subject. The latter involved analysis of structural and practical identifiability, sensitivity analysis, and parameter estimation. Results showed that the model is able to reproduce observed overshoot and adaptation and predict the different responses in the healthy young and the healthy elderly subject. For the healthy young subject, the overshoot was significantly more pronounced than for the elderly subject, but the recovery time was longer for the young subject. These differences resulted in different parameter values estimated using the two datasets. PMID:25549771
Turbulent transition in a truncated 1D model for shear flow
Dawes, Jon
relaxes to a purely laminar state. For a review, and substantial numbers of references to the literature meaning in terms of the behaviour of the reduced model comprising nonlinear ODEs. Article submitted
Analysis, simulation and visualization of 1D tapping via reduced dynamical models
NASA Astrophysics Data System (ADS)
Blackmore, Denis; Rosato, Anthony; Tricoche, Xavier; Urban, Kevin; Zou, Luo
2014-04-01
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.
Zeng, Yi
Mathematical models of batteries which make use of the intercalation of a species into a solid phase need to solve the corresponding mass transfer problem. Because solving this equation can significantly add to the ...
Unitary and Complex Matrix Models as 1-d Type 0 Strings
NASA Astrophysics Data System (ADS)
Klebanov, I. R.; Maldacena, J.; Seiberg, N.
2004-12-01
We propose that the double scaling behavior of the unitary matrix models, and that of the complex matrix models, is related to type 0B and 0A fermionic string theories. The particular backgrounds involved correspond to ? < 1 matter coupled to super-Liouville theory. We examine in detail the ? = 0 or pure supergravity case, which is related to the double scaling limit around the Gross-Witten transition, and find that reversing the sign of the Liouville superpotential interchanges the 0A and 0B theories. We also find smooth transitions between weakly coupled string backgrounds with D-branes, and backgrounds with Ramond-Ramond fluxes only. Finally, we discuss matrix models with multicritical potentials that are conjectured to correspond to 0A/0B string theories based on (2,4k) super-minimal models.
NASA Astrophysics Data System (ADS)
Hooshyar, M.; Hagen, S. C.; Wang, D.
2014-12-01
Hydrodynamic models are widely applied to coastal areas in order to predict water levels and flood inundation and typically involve solving a form of the Shallow Water Equations (SWE). The SWE are routinely discretized by applying numerical methods, such as the finite element method. Like other numerical models, hydrodynamic models include uncertainty. Uncertainties are generated due to errors in the discrete approximation of coastal geometry, bathymetry, bottom friction and forcing functions such as tides and wind fields. Methods to counteract these uncertainties should always begin with improvements to physical characterization of: the geometric description through increased resolution, parameters that describe land cover variations in the natural and urban environment, parameters that enhance transfer of surface forcings to the water surface, open boundary forcings, and the wetting/drying brought upon by flood and ebb cycles. When the best possible physical representation is achieved, we are left with calibration and data assimilation to reduce model uncertainty. Data assimilation has been applied to coastal hydrodynamic models to better estimate system states and/or system parameters by incorporating observed data into the model. Kalman Filter is one of the most studied data assimilation methods that minimizes the mean square errors between model state estimations and the observed data in linear systems (Kalman , 1960). For nonlinear systems, as with hydrodynamic models, a variation of Kalman filter called Ensemble Kalman Filter (EnKF), is applied to update the system state according to error statistics in the context of Monte Carlo simulations (Evensen , 2003) & (Hitoshi et. al, 2014). In this research, Kalman Filter is incorporated to simultaneously estimate an influential parameter used in the shallow water equations, bottom roughness, and to adjust the physical feature of bathymetry. Starting from an initial estimate of bottom roughness and bathymetry, and applying EnKF, more accurate bottom roughness and bathymetry are obtained by utilizing measurements available in a limited number of gages. The procedure is examined along five typical near shore transects located in Gulf of Mexico.
On a mean field model for 1D thin film droplet Department of Mathematical Sciences
Dai, Shibin
obtained. Then we study the relation of this model and the mean field model for Ostwald ripening and show rates for the Ostwald ripening. Mathematics Subject Classification: 35B40, 76A20, 35K25, 35K55, 35Q80 1 is described by the lubrication theory [18]. Denote by h = h(x, t) the height of the thin film. The evolution
M. Lam; R. B. Horne; S. A. Glauert; N. P. Meredith
2006-01-01
Existing radial diffusion models of Earth's radiation belt electrons use energy-independent empirical timescales for losses. We present a 1d radial diffusion model using whistler-mode chorus wave and plasmaspheric hiss losses that depend on Kp, electron energy and L-shell. Bounce-averaged diffusion coefficients calculated from PADIE, and scaled by global Kp-driven models of wave intensity, are used to derive timescales for pitch-angle
Assessing the impact of different sources of topographic data on 1-D hydraulic modelling of floods
NASA Astrophysics Data System (ADS)
Ali, A. Md; Solomatine, D. P.; Di Baldassarre, G.
2014-07-01
Topographic data, such as digital elevation models (DEMs), are essential input in flood inundation modelling. DEMs can be derived from several sources either through remote sensing techniques (space-borne or air-borne imagery) or from traditional methods (ground survey). The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM), the Light Detection and Ranging (LiDAR), and topographic contour maps are some of the most commonly used sources of data for DEMs. These DEMs are characterized by different precision and accuracy. On the one hand, the spatial resolution of low-cost DEMs from satellite imagery, such as ASTER and SRTM, is rather coarse (around 30-90 m). On the other hand, LiDAR technique is able to produce a high resolution DEMs (around 1m), but at a much higher cost. Lastly, contour mapping based on ground survey is time consuming, particularly for higher scales, and may not be possible for some remote areas. The use of these different sources of DEM obviously affects the results of flood inundation models. This paper shows and compares a number of hydraulic models developed using HEC-RAS as model code and the aforementioned sources of DEM as geometric input. The study was carried out on a reach of the Johor River, in Malaysia. The effect of the different sources of DEMs (and different resolutions) was investigated by considering the performance of the hydraulic models in simulating flood water levels as well as inundation maps. The outcomes of our study show that the use of different DEMs has serious implications to the results of hydraulic models. The outcomes also indicates the loss of model accuracy due to re-sampling the highest resolution DEM (i.e. LiDAR 1 m) to lower resolution are much less compared to the loss of model accuracy due to the use of low-cost DEM that have not only a lower resolution, but also a lower quality. Lastly, to better explore the sensitivity of the hydraulic models to different DEMs, we performed an uncertainty analysis based on the GLUE methodology.
Photon-mediated qubit interactions in 1D discrete and continous models
Guillermo Diaz-Camacho; Diego Porras; Juan Jose Garcia-Ripoll
2015-02-19
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.
Modeling Bioenhanced DNAPL Dissolution in 1-D and 2-D Flow systems
NASA Astrophysics Data System (ADS)
Wesseldyke, E. S.; Becker, J. G.; Seagren, E. A.; Mayer, A. S.
2011-12-01
Chlorinated ethenes, such as tetrachloroethene (PCE), released into the environment can form dense non-aqueous phase liquids (DNAPLs), which can act as persistent sources of contamination to groundwater. Due to their low aqueous solubility, these DNAPL contaminant sources can persist for up to hundreds of years under natural conditions. Several methods have been investigated to enhance the rate of dissolution of DNAPLs, including bioenhanced dissolution, which consists of stimulating the growth of a microbial population that biodegrades the contaminant, thereby reducing its concentration at the DNAPL-water interface, and creating a greater driving force for contaminant dissolution. This phenomenon has been studied at length in batch reactors and column studies. The hypothesis of this research is that, in modeling DNAPL dissolution bioenhancement via dehalorespiration, it is important to include the effects of microbial competition, as well as spatial effects. A two-dimensional coupled flow-transport model was developed using the finite-volume method (FVM), which includes a DNAPL pool source, and the effects of multiple microbial species. The model has been confirmed to maintain mass balance and has been validated by comparison to an analytical solution for pool dissolution. The model will be used to simulate a pseudo one-dimensional system and a two-dimensional system under multiple microbial competition scenarios and varying hydrodynamic conditions. The results of these simulations will be compared to determine differences in estimations of dissolution bioenhancement, and analyzed for spatial effects that are captured by a two-dimensional model, but not by a pseudo one-dimensional FVM model. Preliminary two-dimensional simulations have shown the effects of large biomass growth near the NAPL source, which could lead to bioclogging and change the flow field. Further simulations are underway and the results will be presented.
Adhikari, K; Pal, S; Chakraborty, B; Mukherjee, S N; Gangopadhyay, A
2014-10-01
The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4-12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11-0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (KS ?=?5.25?×?10(-4) cm/s). The soil containing 47 % silt, 11 % clay, and 1.54% organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R(2)?=?0.977, RMSE?=?1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42-49%. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion point was reached within 12 days of elapsed time. This clearly demonstrated poor attenuation capacity of the soil to retard migration of phenol to the groundwater from the surface outfall site. Suitable liner, based on these data, may be designed to inhibit subsurface transport of phenol and thereby to protect precious groundwater from contamination. PMID:24929358
A linear radio wave velocity model on polythermal glaciers
NASA Astrophysics Data System (ADS)
Ai, Songtao; Wang, Zemin; Geng, Hong
2015-04-01
The glaciers in Svalbard are mostly polythermal type. On these polythermal glaciers, the radio wave velocity (RWV) of ground penetrating radar (GPR) is variable, and the RWV is an important parameter for the ice volume estimation. But the ice volume estimation usually uses a single RWV for one whole glacier in order to simplify the calculation. How about the difference between the actual volume and the estimated result? We used a linear RWV model, derived from common mid-point (CMP) profiles of GPR measurement, to simulate the RWV for each GPR trace on Pedersenbreen in Svalbard. Then a relative accurate volume of glacier Pedersenbreen was acquired. From which we found the difference among those volumes calculated from a single RWV, three RWVs and our RWV model. Our RWV model for polythermal glaciers refined the volume estimation and enhanced the precision in mass change study. And the difference between different models could raise an error up to 10% of the volume results. Moreover, the fixed RWV usually used was probably larger than the actual one in those polythermal glaciers. Acknowledgements: This work was supported by the National Natural Science Foundation of China(41476162) and the Chinese Polar Environment Comprehensive Investigation & Assessment Programmes.
Modeling the velocity field during Haines jumps in porous media
NASA Astrophysics Data System (ADS)
Armstrong, Ryan T.; Evseev, Nikolay; Koroteev, Dmitry; Berg, Steffen
2015-03-01
When nonwetting fluid displaces wetting fluid in a porous rock many rapid pore-scale displacement events occur. These events are often referred to as Haines jumps and any drainage process in porous media is an ensemble of such events. However, the relevance of Haines jumps for larger scale models is often questioned. A common counter argument is that the high fluid velocities caused by a Haines jump would average-out when a bulk representative volume is considered. In this work, we examine this counter argument in detail and investigate the transient dynamics that occur during a Haines jump. In order to obtain fluid-fluid displacement data in a porous geometry, we use a micromodel system equipped with a high speed camera and couple the results to a pore-scale modeling tool called the Direct HydroDynamic (DHD) simulator. We measure the duration of a Haines jump and the distance over which fluid velocities are influenced because this sets characteristic time and length scales for fluid-fluid displacement. The simulation results are validated against experimental data and then used to explore the influence of interfacial tension and nonwetting phase viscosity on the speed of a Haines jump. We find that the speed decreases with increasing nonwetting phase viscosity or decreasing interfacial tension; however, for the same capillary number the reduction in speed can differ by an order of magnitude or more depending on whether viscosity is increased or interfacial tension is reduced. Therefore, the results suggest that capillary number alone cannot explain pore-scale displacement. One reason for this is that the interfacial and viscous forces associated with fluid-fluid displacement act over different length scales, which are not accounted for in the pore-scale definition of capillary number. We also find by analyzing different pore morphologies that the characteristic time scale of a Haines jump is dependent on the spatial configuration of fluid prior to an event. Simulation results are then used to measure the velocity field surrounding a Haines jump and thus, measure the zone of influence, which extends over a distance greater than a single pore. Overall, we find that the time and length scales of a Haines jump are inversely proportional, which is important to consider when calculating the spatial and temporal averages of pore-scale parameters during fluid-fluid displacement.
Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model
Cattin, Rodolphe
Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model.hetenyi@erdw.ethz.ch) Abstract: Low-velocity zones (`bright spots') imaged by the INDEPTH seismic experiment in southern Tibet for the channel flow model. These suggest that a continuous seismic low- velocity zone underlies Tibet
Pushing 1D CCSNe to explosions: model and SN 1987A
Perego, A; Fröhlich, C; Ebinger, K; Eichler, M; Casanova, J; Liebendoerfer, M; Thielemann, F -K
2015-01-01
We report on a method, PUSH, for triggering core-collapse supernova explosions of massive stars in spherical symmetry. We explore basic explosion properties and calibrate PUSH such that the observables of SN1987A are reproduced. Our simulations are based on the general relativistic hydrodynamics code AGILE combined with the detailed neutrino transport scheme IDSA for electron neutrinos and ALS for the muon and tau neutrinos. To trigger explosions in the otherwise non-exploding simulations, we rely on the neutrino-driven mechanism. The PUSH method locally increases the energy deposition in the gain region through energy deposition by the heavy neutrino flavors. Our setup allows us to model the explosion for several seconds after core bounce. We explore the progenitor range 18-21M$_{\\odot}$. Our studies reveal a distinction between high compactness (HC) and low compactness (LC) progenitor models, where LC models tend to explore earlier, with a lower explosion energy, and with a lower remnant mass. HC models are...
The stability and dynamics of a spike in the 1D Keller-Segel model
NASA Astrophysics Data System (ADS)
Kang, K.; Kolokolnikov, T.; Ward, M. J.
2007-04-01
In the limit of a large mass M >> 1 and on a finite interval of length 2L, an equilibrium spike solution to the classical Keller-Segel chemotaxis model with a linear chemotactic function is constructed asymptotically. By calculating an asymptotic formula for the translational eigenvalue for M >> 1, it is shown that the equilibrium spike solution is unstable to translations of the spike profile. If in addition L >> 1, the equilibrium spike is shown to be metastable as a result of an asymptotically exponentially small eigenvalue. For M >> 1 and L >> 1, an asymptotic ordinary differential equation for the metastable spike motion is derived that shows that the spike drifts exponentially slowly towards one of the boundaries of the domain. For a certain reduced Keller-Segel model, corresponding to a domain of small length, a solution with a spike at each of the two boundaries is constructedE This solution is found to be metastable, and it is shown that there is an exponentially slow exchange of mass between the two spikes that occurs over very long timescales. For arbitrary initial conditions, energy methods are used to show the global existence of solutions. The relationship between this reduced Keller-Segel model and a Burgers-type equation modelling the upward propagation of a flame front in a finite channel is emphasized. Full numerical computations are used to confirm the asymptotic results.
Iterative modelling, a new approach to the inversion of 1-D seismograms
Raskin, Greg Steven
1987-01-01
inherent to the earth system. The near-surface of the earth tends to act as a low ? pass filter. The high frequency information necessary to image thin bedding is subsequently lost due to scattering. intrinsic dissipation in the rocks and/or interbed... effectively travelled twice through a low ? pass filter. As most, of the high frequency information has been lost, fine layering cannot be imaged directly. The second aspect of the non ? uniqueness problem is the modelling technique used...
A Simplified 1-D Model for Calculating CO2 Leakage through Conduits
Zhang, Y.; Oldenburg, C.M.
2011-02-15
In geological CO{sub 2} storage projects, a cap rock is generally needed to prevent CO{sub 2} from leaking out of the storage formation. However, the injected CO{sub 2} may still encounter some discrete flow paths such as a conductive well or fault (here referred to as conduits) through the cap rock allowing escape of CO{sub 2} from the storage formation. As CO{sub 2} migrates upward, it may migrate into the surrounding formations. The amount of mass that is lost to the formation is called attenuation. This report describes a simplified model to calculate the CO{sub 2} mass flux at different locations of the conduit and the amount of attenuation to the surrounding formations. From the comparison among the three model results, we can conclude that the steady-state conduit model (SSCM) provides a more accurate solution than the PMC at a given discretization. When there is not a large difference between the permeability of the surrounding formation and the permeability of the conduits, and there is leak-off at the bottom formation (the formation immediately above the CO{sub 2} plume), a fine discretization is needed for an accurate solution. Based on this comparison, we propose to use the SSCM in the rapid prototype for now given it does not produce spurious oscillations, and is already in FORTRAN and therefore can be easily made into a dll for use in GoldSim.
NASA Astrophysics Data System (ADS)
Viganotti, Matteo; Jackson, Ruth; Krahn, Hartmut; Dyer, Mark
2013-05-01
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.
NASA Astrophysics Data System (ADS)
Zhu, D.; Nakamura, N.
2009-12-01
Spontaneous formation of a vorticity staircase and multiple jets is simulated using a one dimensional barotropic model on a beta-plane with parameterized eddy mixing. The model represents nearly inviscid geostrophic turbulence characterized by a uniform forcing of pseudomomentum, nonuniform dissipation due to mixing, and no frictional damping of the mean flow. The dissipation of pseudomomentum (diffusive flux of vorticity) is modeled with the effective diffusivity parameterization proposed recently by Ferrari and Nikurashin(2009). Rossby wave dynamics and upscale energy cascade are not modeled explicitly but implicit in the parameterization. The parameterized effective diffusivity is a decreasing function of squared vorticity gradient, revealing the active role of (potential) vorticity gradient as a barrier to mixing, consistent with the Rossby elasticity idea. Not only does the parameterized diffusivity agree well with the effective diffusivity of a direct numerical simulation, but it allows the 1D model to reproduce other salient features of the direct simulation, most notably the formation of a welldefined vorticity staircase from a uniform vorticity gradient, through inhomogeneous mixing of vorticity. The staircase formation starts as a small-scale, antidiffusive instability in vorticity gradient that develops when the eddy scale is comparable to the Rhines scale. This spawns numerous gaps (barriers) in diffusivity and corresponding small steps in vorticity, but many of them become unstable and disappear later, until a few stable ones remain. The final number of barriers (vorticity steps) is predictable to a good approximation with a few model parameters.
Modelling nonstationary Doppler noise in exoplanetary radial velocity data
NASA Astrophysics Data System (ADS)
Baluev, Roman V.
2015-08-01
We construct a new class of analytic nonstationary noise models for exoplanetary Doppler data. The observable correlated noise is represented as a convolution of a parent activity process with a given memory function. The model honours the casuality principle, meaning that only past values of the activity may affect the observable value. This model does not approximate detailedly any real stellar activity phenomena, but it becomes mathematically simple, simultaneously satisfying the basic natural principles of physical sensibility and self-consistency.Additionally, we develop a new type of periodograms that can be used to detect periodic modulations in the Doppler noise characteristics, rather than in the observed radial velocity curve itself. We present first results of applying this technique to public Doppler time series available for a set of planet-hosting stars.This work was supported by the Russian Foundation for Basic Research (project No. 14-02-92615 KO_a), the UK Royal Society International Exchange grant IE140055, by the President of Russia grant for young scientists (No. MK-733.2014.2), by the programme of the Presidium of Russian Academy of Sciences P21, and by the Saint Petersburg State University research grant 6.37.341.2015.
Authentication Based on Pole-zero Models of Signature Velocity
Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad
2013-01-01
With the increase of communication and financial transaction through internet, on-line signature verification is an accepted biometric technology for access control and plays a significant role in authenticity and authorization in modernized society. Therefore, fast and precise algorithms for the signature verification are very attractive. The goal of this paper is modeling of velocity signal that pattern and properties is stable for persons. With using pole-zero models based on discrete cosine transform, precise method is proposed for modeling and then features is founded from strokes. With using linear, parzen window and support vector machine classifiers, the signature verification technique was tested with a large number of authentic and forgery signatures and has demonstrated the good potential of this technique. The signatures are collected from three different database include a proprietary database, the SVC2004 and the Sabanci University signature database benchmark databases. Experimental results based on Persian, SVC2004 and SUSIG databases show that our method achieves an equal error rate of 5.91%, 5.62% and 3.91% in the skilled forgeries, respectively. PMID:24696797
Modeling Normal Shock Velocity Curvature Relation for Heterogeneous Explosives
NASA Astrophysics Data System (ADS)
Yoo, Sunhee; Crochet, Michael; Pemberton, Steve
2015-06-01
The normal shock velocity and curvature, Dn(?) , relation on a detonation shock surface has been an important functional quantity to measure to understand the shock strength exerted against the material interface between a main explosive charge and the case of an explosive munition. The Dn(?) relation is considered an intrinsic property of an explosive, and can be experimentally deduced by rate stick tests at various charge diameters. However, experimental measurements of the Dn(?) relation for heterogeneous explosives such as PBXN-111 are challenging due to the non-smoothness and asymmetry usually observed in the experimental streak records of explosion fronts. Out of the many possibilities, the asymmetric character may be attributed to the heterogeneity of the explosives, a hypothesis which begs two questions: (1) is there any simple hydrodynamic model that can explain such an asymmetric shock evolution, and (2) what statistics can be derived for the asymmetry using simulations with defined structural heterogeneity in the unreacted explosive? Saenz, Taylor and Stewart studied constitutive models for derivation of the Dn(?) relation on porous `homogeneous' explosives and carried out simulations in a spherical coordinate frame. In this paper, we extend their model to account for `heterogeneity' and present shock evolutions in heterogeneous explosives using 2-D hydrodynamic simulations with some statistical examination. (96TW-2015-0004)
Authentication Based on Pole-zero Models of Signature Velocity.
Rashidi, Saeid; Fallah, Ali; Towhidkhah, Farzad
2013-10-01
With the increase of communication and financial transaction through internet, on-line signature verification is an accepted biometric technology for access control and plays a significant role in authenticity and authorization in modernized society. Therefore, fast and precise algorithms for the signature verification are very attractive. The goal of this paper is modeling of velocity signal that pattern and properties is stable for persons. With using pole-zero models based on discrete cosine transform, precise method is proposed for modeling and then features is founded from strokes. With using linear, parzen window and support vector machine classifiers, the signature verification technique was tested with a large number of authentic and forgery signatures and has demonstrated the good potential of this technique. The signatures are collected from three different database include a proprietary database, the SVC2004 and the Sabanci University signature database benchmark databases. Experimental results based on Persian, SVC2004 and SUSIG databases show that our method achieves an equal error rate of 5.91%, 5.62% and 3.91% in the skilled forgeries, respectively. PMID:24696797
On nonminimal N=4 supermultiplets in 1D and their associated {sigma}-models
Gonzales, Marcelo; Khodaee, Sadi; Toppan, Francesco [CBPF, Rua Dr. Xavier Sigaud 150, cep 22290-180, Rio de Janeiro (RJ) (Brazil)
2011-01-15
We construct the nonminimal linear representations of the N=4 extended supersymmetry in one-dimension. They act on eight bosonic and eight fermionic fields. Inequivalent representations are specified by the mass-dimension of the fields and the connectivity of the associated graphs. The oxidation to minimal N=5 linear representations is given. Two types of N=4{sigma}-models based on nonminimal representations are obtained: the resulting off-shell actions are either manifestly invariant or depend on a constrained prepotential. The connectivity properties of the graphs play a decisive role in discriminating inequivalent actions. These results find application in partial breaking of supersymmetric theories.
On non-minimal N=4 supermultiplets in 1D and their associated sigma-models
Marcelo Gonzales; Sadi Khodaee; Francesco Toppan
2010-06-24
We construct the non-minimal linear representations of the N=4 Extended Supersymmetry in one-dimension. They act on 8 bosonic and 8 fermionic fields. Inequivalent representations are specified by the mass-dimension of the fields and the connectivity of the associated graphs. The oxidation to minimal N=5 linear representations is given. Two types of N=4 sigma-models based on non-minimal representations are obtained: the resulting off-shell actions are either manifestly invariant or depend on a constrained prepotential. The connectivity properties of the graphs play a decisive role in discriminating inequivalent actions. These results find application in partial breaking of supersymmetric theories.
Thermal robustness of multipartite entanglement of the 1-D spin 1/2 XY model
Yoshifumi Nakata; Damian Markham; Mio Murao
2009-03-12
We study the robustness of multipartite entanglement of the ground state of the one-dimensional spin 1/2 XY model with a transverse magnetic field in the presence of thermal excitations, by investigating a threshold temperature, below which the thermal state is guaranteed to be entangled. We obtain the threshold temperature based on the geometric measure of entanglement of the ground state. The threshold temperature reflects three characteristic lines in the phase diagram of the correlation function. Our approach reveals a region where multipartite entanglement at zero temperature is high but is thermally fragile, and another region where multipartite entanglement at zero temperature is low but is thermally robust.
Zeng, Y; Albertus, P; Klein, R; Chaturvedi, N; Kojic, A; Bazant, MZ; Christensen, J
2013-06-07
Mathematical models of batteries which make use of the intercalation of a species into a solid phase need to solve the corresponding mass transfer problem. Because solving this equation can significantly add to the computational cost of a model, various methods have been devised to reduce the computational time. In this paper we focus on a comparison of the formulation, accuracy, and order of the accuracy for two numerical methods of solving the spherical diffusion problem with a constant or non-constant diffusion coefficient: the finite volume method and the control volume method. Both methods provide perfect mass conservation and second order accuracy in mesh spacing, but the control volume method provides the surface concentration directly, has a higher accuracy for a given numbers of mesh points and can also be easily extended to variable mesh spacing. Variable mesh spacing can significantly reduce the number of points that are required to achieve a given degree of accuracy in the surface concentration (which is typically coupled to the other battery equations) by locating more points where the concentration gradients are highest. (C) 2013 The Electrochemical Society. All rights reserved.
1D Unsteady Flow and Sediment Transport Model for Channel Network
NASA Astrophysics Data System (ADS)
bai, Y.; Duan, J. G.
2012-12-01
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.
Comparison of CME radial velocities from a flux rope model and an ice cream cone model
NASA Astrophysics Data System (ADS)
Kim, T.; Moon, Y.; Na, H.
2011-12-01
Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.
Existence of a metallic phase in a 1D Holstein Hubbard model at half filling
NASA Astrophysics Data System (ADS)
Krishna, Phani Murali; Chatterjee, Ashok
2007-06-01
The one-dimensional half-filled Holstein-Hubbard model is studied using a series of canonical transformations including phonon coherence effect that partly depends on the electron density and is partly independent and also incorporating the on-site and the nearest-neighbour phonon correlations and the exact Bethe-ansatz solution of Lieb and Wu. It is shown that choosing a better variational phonon state makes the polarons more mobile and widens the intermediate metallic region at the charge-density-wave-spin-density-wave crossover recently predicted by Takada and Chatterjee. The presence of this metallic phase is indeed a favourable situation from the point of view of high temperature superconductivity.
Electrochemical (de)lithiation of 1D sulfur chains in Li-S batteries: a model system study.
Yang, Chun-Peng; Yin, Ya-Xia; Guo, Yu-Guo; Wan, Li-Jun
2015-02-18
In contrast to the extensive studies of the electrochemical behavior of conventional cyclic S8 molecules in Li-S batteries, there has been hardly any investigation of the electrochemistry of S chains. Here we use S chains encapsulated in single- and double-walled carbon nanotubes as a model system and report the electrochemical behavior of 1D S chains in Li-S batteries. An electrochemical test shows that S chains have high electrochemical activity during lithiation and extinctive electrochemistry compared with conventional S8. The confined steric effect provides Li(+) solid-phase diffusion access to insert/egress reactions with S chains. During lithiation, the long S chains spontaneously become short chains, which show higher discharge plateaus and better kinetics. The unique electrochemistry of S chains supplements the existing knowledge of the S cathode mechanism and provides avenues for rational design of S cathode materials in Li-S batteries. PMID:25650588
NASA Astrophysics Data System (ADS)
Roundy, R. C.; Nemirovsky, D.; Kagalovsky, V.; Raikh, M. E.
2014-06-01
Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations.
Roundy, R C; Nemirovsky, D; Kagalovsky, V; Raikh, M E
2014-06-01
Motivated by recent experiments, where the tunnel magnetoresitance (TMR) of a spin valve was measured locally, we theoretically study the distribution of TMR along the surface of magnetized electrodes. We show that, even in the absence of interfacial effects (like hybridization due to donor and acceptor molecules), this distribution is very broad, and the portion of area with negative TMR is appreciable even if on average the TMR is positive. The origin of the local sign reversal is quantum interference of subsequent spin-rotation amplitudes in the course of incoherent transport of carriers between the source and the drain. We find the distribution of local TMR exactly by drawing upon formal similarity between evolution of spinors in time and of the reflection coefficient along a 1D chain in the Anderson model. The results obtained are confirmed by the numerical simulations. PMID:24949781
An analytical 1-D model for vertical momentum and energy flux through a fully developed wind farm
NASA Astrophysics Data System (ADS)
Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando
2014-05-01
Wind farms capture momentum from the atmospheric boundary layer (ABL) both at the leading edge and from the atmosphere above. Momentum is advected into the wind farm and wake turbulence draws excess momentum in from between turbines until momentum is only available from above the wind farm. This distance can be described by the so-called drag development length scale, which arises from the canopy drag force term in the momentum equation. At this point the flow can be considered fully developed. The horizontally-averaged velocity profile for a fully developed wind farm flow exhibits a characteristic inflection point near the top of the wind farm, similar to that of sparse canopy-type flows (Markfort et al., JoT, 2012). The inflected vertical velocity profile is associated with the presence of a dominant characteristic turbulence scale, which may be responsible for a significant portion of the vertical momentum flux. We evaluate an analytical canopy-type flow model for wind farm-atmosphere interaction by testing it against wind-tunnel experimental data of flow through a model wind farm. The model is adapted to predict the mean flow, vertical momentum flux, and the mean kinetic energy flux as well as kinetic energy dissipation within the wind farm. This model is particularly useful for wind farm configuration optimization, considering wind turbine spacing and surface roughness and can also be useful to represent wind farms in regional scale atmospheric simulations.
NASA Astrophysics Data System (ADS)
Hayek, W.; Sing, D.; Pont, F.; Asplund, M.
2012-03-01
We compare limb darkening laws derived from 3D hydrodynamical model atmospheres and 1D hydrostatic MARCS models for the host stars of two well-studied transiting exoplanet systems, the late-type dwarfs HD 209458 and HD 189733. The surface brightness distribution of the stellar disks is calculated for a wide spectral range using 3D LTE spectrum formation and opacity sampling?. We test our theoretical predictions using least-squares fits of model light curves to wavelength-integrated primary eclipses that were observed with the Hubble Space Telescope (HST). The limb darkening law derived from the 3D model of HD 209458 in the spectral region between 2900 Å and 5700 Å produces significantly better fits to the HST data, removing systematic residuals that were previously observed for model light curves based on 1D limb darkening predictions. This difference arises mainly from the shallower mean temperature structure of the 3D model, which is a consequence of the explicit simulation of stellar surface granulation where 1D models need to rely on simplified recipes. In the case of HD 189733, the model atmospheres produce practically equivalent limb darkening curves between 2900 Å and 5700 Å, partly due to obstruction by spectral lines, and the data are not sufficient to distinguish between the light curves. We also analyze HST observations between 5350 Å and 10 500 Å for this star; the 3D model leads to a better fit compared to 1D limb darkening predictions. The significant improvement of fit quality for the HD 209458 system demonstrates the higher degree of realism of 3D hydrodynamical models and the importance of surface granulation for the formation of the atmospheric radiation field of late-type stars. This result agrees well with recent investigations of limb darkening in the solar continuum and other observational tests of the 3D models. The case of HD 189733 is no contradiction as the model light curves are less sensitive to the temperature stratification of the stellar atmosphere and the observed data in the 2900-5700 Å region are not sufficient to distinguish more clearly between the 3D and 1D limb darkening predictions. Full theoretical spectra for both stars are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/539/A102, as well as at www.astro.ex.ac.uk/people/sing.
NASA Astrophysics Data System (ADS)
Fan, Y.; Brown, W. S.
2002-05-01
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
Development of a Regional Velocity Model Using 3D Broadband Waveform Sensitivity
NASA Astrophysics Data System (ADS)
Panning, M. P.; Romanowicz, B. A.; Kim, A.
2005-12-01
We are developing a new approach which relies on a cascade of increasingly accurate theoretical approximations for computation of the seismic wavefield to develop a model of regional seismic velocity structure for eastern Eurasia using full seismic waveforms. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for standard modeling techniques, but it is well surrounded by earthquake sources and a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The initial model is derived from a large database of teleseismic long period waveforms (surface waves and overtone wavepackets) using well-developed theoretical approximations, the Path Average Approximation (PAVA) and Nonlinear Asymptotic Coupling Theory (NACT). These approaches assume waveforms are only sensitive to the 1D (PAVA) and 2D (NACT) structure in the vertical plane between source and receiver, which is adequate for the development of a smooth initial 3D velocity model. We refine this model using a more accurate theoretical approach. We utilize an implementation of a 3D Born approximation, which takes into account the contribution to the waveform from single scattering throughout the model, giving full 3D waveform sensitivity kernels. We perform verification tests of this approach for synthetic models, and show that it can accurately represent the wavefield as predicted by numerical approaches in several situations where approximations such as PAVA and NACT are insufficient. The Born 3D waveform sensitivity kernels are used to perform a higher resolution inversion of regional waveforms for a smaller subregion between longitudes 90 and 150 degrees E, and latitudes 15 and 40 degrees N. To further increase the accuracy of this model, we intend to utilize a very accurate numerical approach, the coupled spectral elements method (Capdeville et al., 2003), for the forward calculations of synthetics. This accounts for nonlinear effects of the structure on the seismograms in addition to the 3D broadband sensitivity.
Molecular dynamics modelling of granular chute flow: density and velocity profiles
X. M. Zheng; J. M. Hill
1996-01-01
A molecular dynamics simulation technique is applied to the modelling of a granular chute flow, and the density and velocity profiles of the chute flows are examined by considering different inclination angles, rough and smooth boundary conditions, accelerating and fully developed flows. In general, the chute velocity profiles are non-linear, concave in shape and there is a slip velocity at
Kroon, Wilco; Huberts, Wouter; Bosboom, Marielle; van de Vosse, Frans
2012-01-01
A computational method of reduced complexity is developed for simulating vascular hemodynamics by combination of one-dimensional (1D) wave propagation models for the blood vessels with zero-dimensional (0D) lumped models for the microcirculation. Despite the reduced dimension, current algorithms used to solve the model equations and simulate pressure and flow are rather complex, thereby limiting acceptance in the medical field. This complexity mainly arises from the methods used to combine the 1D and the 0D model equations. In this paper a numerical method is presented that no longer requires additional coupling methods and enables random combinations of 1D and 0D models using pressure as only state variable. The method is applied to a vascular tree consisting of 60 major arteries in the body and the head. Simulated results are realistic. The numerical method is stable and shows good convergence. PMID:22654957
The Candy Wrapper Velocity Model for the Earth's Inner Core
NASA Astrophysics Data System (ADS)
Mattesini, M.
2014-12-01
Recent global expansion of seismic data motivated a number of seismological studies of the Earth's inner core that proposed the existence of increasingly complex structure and anisotropy. In the meantime, new hypotheses of dynamic mechanisms have been put forward to interpret seismological results. Here, the nature of hemispherical dichotomy and anisotropy is re-investigated by bridging the observations of PKP(bc-df) differential travel-times with the iron bcc/hcp elastic properties computed from first-principles methods.The Candy Wrapper velocity model introduced here accounts for a dynamic picture of the inner core (i.e., the eastward drift of material), where different iron crystal shapes can be stabilized at the two hemispheres. We show that seismological data are best explained by a rather complicated, mosaic-like, structure of the inner core, where well-separated patches of different iron crystals compose the anisotropic western hemispherical region, and a conglomerate of almost indistinguishable iron phases builds-up the weakly anisotropic eastern side.
High resolution 3D Sv wave velocity model of China and surrounding area
NASA Astrophysics Data System (ADS)
Pandey, S.; Yuan, X.; Debayle, E.; Priestley, K. F.; Kind, R.; Li, X.
2011-12-01
In our study we determine the three dimensional Sv wave speed and azimuthal anisotropy model by analyzing vertical component multimode Rayleigh wave seismograms. We use data of broadband stations from in and around China. We construct the three dimensional model using a two step procedure. In the first step we use the automated version of the Cara and Leveque [1987] waveform inversion technique in terms of secondary observables for modeling each multimode Rayleigh waveform to determine the path-average mantle Sv wave speed structure. We have used the 3SMAC model (as a crustal part) and smooth version of PREM for the upper mantle velocity structure as an initial model. In the second stage we combine the 1-D velocity models in a tomographic inversion to obtain the three dimensional Sv wave speed structure and the azimuthal anisotropy as a function of depth. China is sitting at a triple junction of three major plates: the Eurasian plate, the Indo-Australian plate and the Philippine Sea plate. China itself has three major Precambian cratons: the North China craton (also called Sino-Korean craton), the Yangtze craton (also called South China craton) and the Tarim block. The interactions among different blocks have formed the tectonic features today and caused many intraplate earthquakes. These tectonics setting have made China an interesting place for various kind of study as all of these events have left their imprint on the upper mantle structure. It is generally agreed that the lithosphere is thick in west China while much of the lithospheric root was lost beneath some cratons in east China. Still it's an open debate whether the lithosphere beneath the Tibetan plateau has doubled its thickness as did the crust above or much of the thickened lithosphere was removed by mantle convection and delamination. The upper most part of our model is in good agreement with the finding from the deep seismic profile. It is also evident that the extent of crustal flow of Tibet is being restricted by Tarim in the north and Ordos, Sichuan in the east. Various receiver function and SS precursor results are also comparable with our results in terms of the lithosphere extent.
(abstract) Modeling the Critical Velocity Ionization Experiment Interaction
NASA Technical Reports Server (NTRS)
Wang, J.; Murphy, G.; Biasca, R.
1993-01-01
Proper interpretation of critical velocity ionization experiments depends upon understanding the expected results from in-situ or remote sensors. In particular, the 1991 shuttle based CIV experiment had diagnostics.
Key elements of regional seismic velocity models for long period ground motion simulations
Brocher, T.M.
2008-01-01
Regional 3-D seismic velocity models used for broadband strong motion simulations must include compressional-wave velocity (Vp), shear-wave velocity (Vs), intrinsic attenuation (Qp, Qs), and density. Vs and Qs are the most important of these parameters because the strongest ground motions are generated chiefly by shear- and surface-wave arrivals. Because Vp data are more common than Vs data, many researchers first develop a Vp model and convert it to a Vs model. I describe recent empirical relations between Vs, Vp, Qs, Qp, and density that allow velocity models to be rapidly and accurately calculated. ?? Springer Science+Business Media B.V. 2007.
Quantum distance and the Euler number index of the Bloch band in a 1D spin model
Yu-Quan Ma
2014-10-23
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.
Scale-similarity model for Lagrangian velocity correlations in isotropic and stationary turbulence
NASA Astrophysics Data System (ADS)
He, Guo-Wei; Jin, Guodong; Zhao, Xin
2009-12-01
A scale-similarity model for Lagrangian two-point, two-time velocity correlations (LVCs) in isotropic turbulence is developed from the Kolmogorov similarity hypothesis. It is a second approximation to the isocontours of LVCs, while the Smith-Hay model is only a first approximation. This model expresses the LVC by its space correlation and a dispersion velocity. We derive the analytical expression for the dispersion velocity from the Navier-Stokes equations using the quasinormality assumption. The dispersion velocity is dependent on enstrophy spectra and shown to be smaller than the sweeping velocity for the Eulerian velocity correlation. Therefore, the Lagrangian decorrelation process is slower than the Eulerian decorrelation process. The data from direct numerical simulation of isotropic turbulence support the scale-similarity model: the LVCs for different space separations collapse into a universal form when plotted against the separation axis defined by the model.
An empirical model to forecast solar wind velocity through statistical modeling
NASA Astrophysics Data System (ADS)
Gao, Y.; Ridley, A. J.
2013-12-01
The accurate prediction of the solar wind velocity has been a major challenge in the space weather community. Previous studies proposed many empirical and semi-empirical models to forecast the solar wind velocity based on either the historical observations, e.g. the persistence model, or the instantaneous observations of the sun, e.g. the Wang-Sheeley-Arge model. In this study, we use the one-minute WIND data from January 1995 to August 2012 to investigate and compare the performances of 4 models often used in literature, here referred to as the null model, the persistence model, the one-solar-rotation-ago model, and the Wang-Sheeley-Arge model. It is found that, measured by root mean square error, the persistence model gives the most accurate predictions within two days. Beyond two days, the Wang-Sheeley-Arge model serves as the best model, though it only slightly outperforms the null model and the one-solar-rotation-ago model. Finally, we apply the least-square regression to linearly combine the null model, the persistence model, and the one-solar-rotation-ago model to propose a 'general persistence model'. By comparing its performance against the 4 aforementioned models, it is found that the accuracy of the general persistence model outperforms the other 4 models within five days. Due to its great simplicity and superb performance, we believe that the general persistence model can serve as a benchmark in the forecast of solar wind velocity and has the potential to be modified to arrive at better models.
27 The DNA12 Seismic Velocity Model Robert Porritt, Richard Allen, and Fred Pollitz
Allen, Richard M.
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
van der Lee, Suzan
A new P-velocity model for the Tethyan margin from a scaled S-velocity model and the inversion of P- and PKP-delay times Sung-Joon Chang a, , Suzan Van der Lee a , Megan P. Flanagan b a Dept. of Earth Livermore National Laboratory, P.O. Box 808, L-205, Livermore, CA 94551, USA a r t i c l e i n f o Article
Shuttle data book: SRM fragment velocity model. Presented to the SRB Fragment Model Review Panel
NASA Technical Reports Server (NTRS)
1989-01-01
This study was undertaken to determine the velocity of fragments generated by the range safety destruction (RSD) or random failure of a Space Transportation System (STS) Solid Rocket Motor (SRM). The specific requirement was to provide a fragment model for use in those Galileo and Ulysses RTG safety analyses concerned with possible fragment impact on the spacecraft radioisotope thermoelectric generators (RTGS). Good agreement was obtained between predictions and observations for fragment velocity, velocity distributions, azimuths, and rotation rates. Based on this agreement with the entire data base, the model was used to predict the probable fragment environments which would occur in the event of an STS-SRM RSD or randon failure at 10, 74, 84 and 110 seconds. The results of these predictions are the basis of the fragment environments presented in the Shuttle Data Book (NSTS-08116). The information presented here is in viewgraph form.
NASA Astrophysics Data System (ADS)
Dzierzbicka-Glowacka, L.; Maciejewska, A.; Osi?ski, R.; Jakacki, J.; J?drasik, J.
2009-04-01
This paper presents a one-dimensional Ecosystem Model. Mathematically, the pelagic variables in the model are described by a second-order partial differential equation of the diffusion type with biogeochemical sources and sinks. The temporal changes in the phytoplankton biomass are caused by primary production, respiration, mortality, grazing by zooplankton and sinking. The zooplankton biomass is affected by ingestion, excretion, respiration, fecal production, mortality, and carnivorous grazing. The changes in the pelagic detritus concentration are determined by input of: dead phytoplankton and zooplankton, natural mortality of predators, fecal pellets, and sinks: sedimentation, zooplankton grazing and decomposition. The nutrient concentration is caused by nutrient release, zooplankton excretion, predator excretion, detritus decomposition and benthic regeneration as sources and by nutrient uptake by phytoplankton as sinks. However, the benthic detritus is described by phytoplankton sedimentation, detritus sedimentation and remineralisation. The particulate organic carbon concentration is determined as the sum of phytoplankton, zooplankton and dead organic matter (detritus) concentrations. The 1D ecosystem model was used to simulate the seasonal dynamics of pelagic variables (phytoplankton, zooplankton, pelagic detritus and POC) in the southern Baltic Sea (Gda?sk Deep, Bornholm Deep and Gotland Deep). The calculations were made assuming: 1) increase in the water temperature in the upper layer - 0.008oC per year, 2) increase in the available light - 0.2% per year. Based on this trend, daily, monthly and seasonal and annual variability of phytoplankton, zooplankton, pelagic detritus and particulate organic carbon in different areas of the southern Baltic Sea (Gda?sk Deep, Borrnholm Deep and Gotland Deep) in the euphotic layer was calculated for the years: 2000, 2010, 2020, 2030, 2040 and 2050.
NASA Astrophysics Data System (ADS)
Grin?, Michal; Zeyen, Hermann; Bielik, Miroslav
2014-06-01
Using a very fast 1D method of integrated geophysical modelling, we calculated models of the Moho discontinuity and the lithosphere-asthenosphere boundary in the Carpathian-Pannonian Basin region and its surrounding tectonic units. This method is capable to constrain complicated lithospheric structures by using joint interpretation of different geophysical data sets (geoid and topography) at the same time. The Moho depth map shows significant crustal thickness variations. The thickest crust is found underneath the Carpathian arc and its immediate Foredeep. High values are found in the Eastern Carpathians and Vrancea area (44 km). The thickest crust modelled in the Southern Carpathians is 42 km. The Dinarides crust is characterized by thicknesses more than 40 km. In the East European Platform, crust has a thickness of about 34 km. In the Apuseni Mountains, the depth of the Moho is about 36 km. The Pannonian Basin and the Moesian Platform have thinner crust than the surrounding areas. Here the crustal thicknesses are less than 30 km on average. The thinnest crust can be found in the SE part of the Pannonian Basin near the contact with the Southern Carpathians where it is only 26 km. The thickest lithosphere is placed in the East European Platform, Eastern Carpathians and Southern Carpathians. The East European Platform lithosphere thickness is on average more than 120 km. A strip of thicker lithosphere follows the Eastern Carpathians and its Foredeep, where the values reach in average 160 km. A lithosphere thickness minimum can be observed at the southern border of the Southern Carpathians and in the SE part of the Pannonian Basin. Here, it is only 60 km. The extremely low values of lithospheric thickness in this area were not shown before. The Moesian Platform is characterized by an E-W trend of lithospheric thickness decrease. In the East, the thickness is about 110 km and in the west it is only 80 km. The Pannonian Basin lithospheric thickness ranges from 80 to 100 km.
NASA Astrophysics Data System (ADS)
Cooke, William; Donner, Leo
2015-04-01
Microphysical and aerosol processes determine the magnitude of climate forcing by aerosol-cloud interactions, are central aspects of cloud-climate feedback, and are important elements in weather systems for which accurate forecasting is a major goal of numerical weather prediction. Realistic simulation of these processes demands not only accurate microphysical and aerosol process representations but also realistic simulation of the vertical motions in which the aerosols and microphysics act. Aerosol activation, for example, is a strong function of vertical velocity. Cumulus parameterizations for climate and numerical weather prediction models have recently begun to include vertical velocities among the statistics they predict. These vertical velocities have been subject to only limited evaluation using observed vertical velocities. Deployments of multi-Doppler radars and dual-frequency profilers in recent field campaigns have substantially increased the observational base of cumulus vertical velocities, which for decades had been restricted mostly to GATE observations. Observations from TWP-ICE (Darwin, Australia) and MC3E (central United States) provide previously unavailable information on the vertical structure of cumulus vertical velocities and observations in differing synoptic contexts from those available in the past. They also provide an opportunity to independently evaluate cumulus parameterizations with vertical velocities tuned to earlier GATE observations. This presentation will compare vertical velocities observed in TWP-ICE and MC3E with cumulus vertical velocities using the parameterization in the GFDL CM3 climate model. Single-column results indicate parameterized vertical velocities are frequently greater than observed. Errors in parameterized vertical velocities exhibit similarities to vertical velocities explicitly simulated by cloud-system resolving models, and underlying issues in the treatment of microphysics may be important for both. The dependence of convective microphysical properties on vertical velocities and consequences for microphysics of simulation errors will be illustrated. Underlying limitations in the parameterization and model resolution will be discussed as explanations for differences between observed and simulated vertical velocities.
Novel phase-space Monte-Carlo method for quench dynamics in 1D and 2D spin models
NASA Astrophysics Data System (ADS)
Pikovski, Alexander; Schachenmayer, Johannes; Rey, Ana Maria
2015-05-01
An important outstanding problem is the effcient numerical computation of quench dynamics in large spin systems. We propose a semiclassical method to study many-body spin dynamics in generic spin lattice models. The method, named DTWA, is based on a novel type of discrete Monte-Carlo sampling in phase-space. We demonstare the power of the technique by comparisons with analytical and numerically exact calculations. It is shown that DTWA captures the dynamics of one- and two-point correlations 1D systems. We also use DTWA to study the dynamics of correlations in 2D systems with many spins and different types of long-range couplings, in regimes where other numerical methods are generally unreliable. Computing spatial and time-dependent correlations, we find a sharp change in the speed of propagation of correlations at a critical range of interactions determined by the system dimension. The investigations are relevant for a broad range of systems including solids, atom-photon systems and ultracold gases of polar molecules, trapped ions, Rydberg, and magnetic atoms. This work has been financially supported by JILA-NSF-PFC-1125844, NSF-PIF-1211914, ARO, AFOSR, AFOSR-MURI.
Thermal characterization of large size lithium-ion pouch cell based on 1d electro-thermal model
NASA Astrophysics Data System (ADS)
Vertiz, G.; Oyarbide, M.; Macicior, H.; Miguel, O.; Cantero, I.; Fernandez de Arroiabe, P.; Ulacia, I.
2014-12-01
Thermal management is one of the key factors to keep lithium-ion cells in optimum electrical performance, under safe working conditions and into a reasonably low ageing process. This issue is becoming particularly relevant due to the heterogeneous heat generation along the cell. Cell working temperature is determined by ambient temperature, heat generation and evacuation capacity. Therefore, thermal management is established by: i) the intrinsic thermal properties (heat capacity & thermal conductivity) and ii) the heat generation electro-thermal parameters (internal resistance, open circuit voltage & entropic factor). In this research, different methods - calculated and experimental - are used to characterize the main heat properties of a 14Ah -LiFePO4/graphite-commercial large sizes pouch cell. In order to evaluate the accuracy of methods, two comparisons were performed. First, Newman heat generation estimations were compared with experimental heat measurements. Secondly, empirical thermal cell behaviour was match with 1D electro-thermal model response. Finally, considering the results, the most adequate methodology to evaluate the key thermal parameters of a large size Lithium-ion pouch cell are proposed to be: i) pulse method for internal resistance, ii)heat loss method for entropic factor; and iii)experimental measurement (ARC calorimeter and C-177-97 standard method) for heat capacity and thermal conductivity.
Modeling seismic wave propagation and amplification in 1D/2D/3D linear and nonlinear unbounded media
Semblat, Jean-François
2011-01-01
To analyze seismic wave propagation in geological structures, it is possible to consider various numerical approaches: the finite difference method, the spectral element method, the boundary element method, the finite element method, the finite volume method, etc. All these methods have various advantages and drawbacks. The amplification of seismic waves in surface soil layers is mainly due to the velocity contrast between these layers and, possibly, to topographic effects around crests and hills. The influence of the geometry of alluvial basins on the amplification process is also know to be large. Nevertheless, strong heterogeneities and complex geometries are not easy to take into account with all numerical methods. 2D/3D models are needed in many situations and the efficiency/accuracy of the numerical methods in such cases is in question. Furthermore, the radiation conditions at infinity are not easy to handle with finite differences or finite/spectral elements whereas it is explicitely accounted in the B...
NASA Astrophysics Data System (ADS)
Ichinose, G. A.
2006-12-01
Many scientific issues for the Basin and Range Province (BRP) remain unsettled including structural evolution, strain rates, slip partitioning and earthquake source physics. A catalog of earthquake source parameters including locations and moment tensors is the basis for tectonic and geophysical study. New instrumentation from the Advance National Seismic System, EarthScope Plate Boundary Observatory, Bigfoot and US-Array brings the opportunity for high quality research; therefore, a catalog is an underlying foundation for examining the BRP. We are continuing to generate a moment tensor catalog for the BRP (Mw<3.5) using long-period regional waves spanning back to 1990. Iterative waveform inversion method (e.g., Nolet et al., 1986, Randell, 1994) is used to calibrate the BRP velocity and density structure using two northern and southern BRP earthquakes. The calibrated models generate realistic synthetics for (f<0.5Hz) with ~50-80% variance reduction. We averaged all path specific models to construct a 1-D BRP community background model. The crust is relatively simple between 5-20km (~6.12km/s) and there is a strong velocity gradient in the upper 5- km. There are lower velocities in the upper crust but higher velocities in the mid-crust for the Sierra Nevada paths relative to BRP. There is also a lower crust high-velocity anomaly near Battle Mountain and Elko that is faster by ~5% and may indicate a wider area of under-plating by basaltic magmas. There are significant low velocity zones in the upper and mid crust mainly across the Walker Lane Belt that may indicate the presence of fluids. We are continuing to work on assessing the performance of these newly calibrated models in improving the estimation of moment tensors down to lower magnitudes and mapping out holes in the seismic network which can be filled to improve moment tensor catalog. We also are looking at how these models work at locating earthquakes and comparing synthetics with those computed from models constrained from different data including refraction, surface wave dispersion, and travel-time tomography.
Anisotropic-ray-theory rays in velocity model SC1 II with a split intersection singularity
Cerveny, Vlastislav
Anisotropic-ray-theory rays in velocity model SC1 II with a split intersection singularity Ludek.cz/staff/bulant.htm Summary We show the behaviour of the anisotropicÂrayÂtheory SÂwave rays in a velocity model with a split intersection singularity. The rays crossing the split intersection singularity are smoothly but very sharply
Kirchhoff prestack depth migration in velocity models with and without rotation of the tensor of
Cerveny, Vlastislav
is limited to P-waves. Keywords 3-D Kirchhoff prestack depth migration, anisotropic velocity model, rotation for migration. In: Seismic Waves in Complex 3-D Structures, Report 23 (Department of Geophysics, CharlesKirchhoff prestack depth migration in velocity models with and without rotation of the tensor
Kirchhoff prestack depth migration in triclinic velocity models with differently rotated tensors
Cerveny, Vlastislav
in each Seismic Waves in Complex 3D Structures, 24 (2014), 7793 (ISSN 23363827, online at http://sw3dKirchhoff prestack depth migration in triclinic velocity models with differently rotated tensors homogeneous velocity models in order to demonstrate the impact of rotation of the elasticity tensor
NASA Astrophysics Data System (ADS)
Manful, D. Y.; Kaule, G.; Wieprecht, S.; Rees, J.; Hu, W.
2009-12-01
Hydroelectric Power (HEP) is proving to be a good alternative to carbon based energy. In the past hydropower especially large scale hydro attracted significant criticism as a result of its impact on the environment. A new breed of hydroelectric dam is in the offing. The aim is to have as little a footprint as possible on the environment in both pre and post construction phases and thus minimize impact on biodiversity whilst producing clean renewable energy. The Bui dam is 400 MW scheme currently under development on the Black Volta River in the Bui national park in Ghana. The reservoir created by the Bui barrage is expected to impact (through inundation) the habitat of two species of hippos know to exist in the park, the Hippopotamus amphibius and the Choeropsis liberiensis. Computer-based models present a unique opportunity to assess quantitatively the impact of the new reservoir on the habitat of the target species in this case the H. amphibious. Until this undertaking, there were very few studies documenting the habitat of the H. amphibious let alone model it. The work and subsequent presentation will show the development of a habitat model for the Hippopotamus amphibius. The Habitat Information retrieval Program based on Streamflow Analysis, in short HIPStrA, is a one dimensional (1D) in-stream, spatially explicit hybrid construct that combines physico-chemical evidence and expert knowledge to forecast river habitat suitability (Hs) for the Hippopotamus amphibius. The version of the model presented is specifically developed to assess the impact of a reservoir created by a hydroelectric dam on potential dwelling areas in the Bui gorge for hippos. Accordingly, this version of HIPStrA simulates a special reservoir suitability index (Rsi), a metric that captures the”hippo friendliness” of any lake or reservoir. The impact of measured and simulated flood events as well as low flows, representing extreme events is also assessed. Recommendations are made for the operating rules of the reservoir in the post-construction phase of the dam. A great deal of work has been done on the effects of stream flow changes on fish especially salmonids. Very little work however has been done assessing the impact of hydropower schemes on aquatic mammals especially in Africa. HIPStrA is the first attempt at developing a computer-based habitat model for a large aquatic megaherbivore. The need for energy for development, the availability of large rivers and a rich biodiversity base in Africa makes a case for careful and ecological smart exploitation. The overarching aim of the study is the sustainable development of hydroelectric power through the use of methodologies and tools to rigorously assess changes in instream conditions that impact aquatic mammals.
NASA Astrophysics Data System (ADS)
Chen, M.; Willgoose, G. R.; Saco, P. M.
2009-12-01
This paper investigates the soil moisture dynamics over two subcatchments (Stanley and Krui) in the Goulburn River in NSW during a three year period (2005-2007) using the Hydrus 1-D unsaturated soil water flow model. The model was calibrated to the seven Stanley microcatchment sites (1 sqkm site) using continuous time surface 30cm and full profile soil moisture measurements. Soil type, leaf area index and soil depth were found to be the key parameters changing model fit to the soil moisture time series. They either shifted the time series up or down, changed the steepness of dry-down recessions or determined the lowest point of soil moisture dry-down respectively. Good correlations were obtained between observed and simulated soil water storage (R=0.8-0.9) when calibrated parameters for one site were applied to the other sites. Soil type was also found to be the main determinant (after rainfall) of the mean of modelled soil moisture time series. Simulations of top 30cm were better than those of the whole soil profile. Within the Stanley microcatchment excellent soil moisture matches could be generated simply by adjusting the mean of soil moisture up or down slightly. Only minor modification of soil properties from site to site enable good fits for all of the Stanley sites. We extended the predictions of soil moisture to a larger spatial scale of the Krui catchment (sites up to 30km distant from Stanley) using soil and vegetation parameters from Stanley but the locally recorded rainfall at the soil moisture measurement site. The results were encouraging (R=0.7~0.8). These results show that it is possible to use a calibrated soil moisture model to extrapolate the soil moisture to other sites for a catchment with an area of up to 1000km2. This paper demonstrates the potential usefulness of continuous time, point scale soil moisture (typical of that measured by permanently installed TDR probes) in predicting the soil wetness status over a catchment of significant size.
NASA Astrophysics Data System (ADS)
Reynolds, Dylan; Wood, Stephen E.; Bapst, Jonathan; Mehlhaff, Joshua; Griffiths, Stephen G.
2014-11-01
We have applied a self-consistent 1-D model for heat diffusion, vapor diffusion, and ice condensation/sublimation, and surface energy balance to investigate our hypothesis for the source of the recently observed water vapor around Ceres [1]. As described in a companion presentation [2], we find that the estimated global flux of 6 kg/s can be produced by steady-state sublimation of subsurface ice driven by the “geothermal” temperature gradient for a heat flux of 1 mW/m2 - the value estimated for a chondritic abundance of heat-producing elements [3,4]. We will present a detailed description of our Ceres cryothermal diffusion model and comparisons with previous models. One key difference is the use of a new physics-based analytic model (‘MaxRTCM’) for calculating the thermal conductivity (Kth) of planetary regolith [5] that has been validated by comparisons to a wide range of laboratory data [6]. MaxRTCM predicts much lower Kth values in the upper regolith than those in previous work [3]. It also accounts for a process first modeled in a study of unstable equatorial ground ice on Mars [7,8], where vapor diffusing up from a receding ice table toward the surface can recondense at shallower depths - eventually forming a steady-state profile of pore ice volume fraction that increases with depth and maintains a constant flux of vapor at all depths [7]. Using MaxRTCM we calculate the corresponding Kth(z) profiles and will present predictions and implications of the resulting temperature profile in the upper few kilometers of Ceres’ megaregolith.References: [1] 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.
NASA Astrophysics Data System (ADS)
Ammirati, J. B.; Alvarado, P. M.; Beck, S. L.
2014-12-01
Receiver Function (RF) analyses using teleseismic P waveforms is a technique to isolate P to S conversions from seismic discontinuities in the lithosphere. Using earthquakes with a good azimuthal distribution, RFs recorded at a three-component seismic station can be inverted to obtain detailed lithospheric velocity structures. The technique, however presents a velocity-depth trade-off, which results in a non-unique model because RFs do not depend on the absolute seismic velocities but rather on relative velocity contrasts. Unlike RF, surface wave dispersion is sensitive to the average shear-wave velocity which makes it well suited for studying long period variations of the lithospheric seismic velocities. We performed a joint inversion of RF and Rayleigh-wave phase velocity dispersion to investigate the structure beneath the SIEMBRA network, a 43-broadband-seismic-station array deployed in the Pampean flat slab region of Argentina. Our results indicate: 1) The presence of several mid-crustal discontinuities probably related with terrane accretion; 2) A high seismic velocity in the lower crust suggesting partial eclogitization; 3) A thicker crust (> 50 km) beneath the western Sierras Pampeanas with an abrupt change in the relative timing of the Moho signal indicating a thinner crust to the east; 4) The presence of the subducting oceanic crust lying at ~100 km depth. We then built a 1D regional velocity model for the flat slab region of Argentina and used it for regional moment tensor inversions for local earthquakes. This technique is notably dependent on small-scale variations of Earth structure when modeling higher frequency seismic waveforms. Eighteen regional focal mechanisms have been determined. Our solutions are in good agreement with GCMT source estimations although our solutions for deep earthquakes systematically resulted in shallower focal depths suggesting that the slab seismicity could be concentrated at the top of the subducting Nazca plate. Solutions corresponding to crustal events match well the geological observations from other studies.
NASA Astrophysics Data System (ADS)
Liu, Gang; Kojima, Keitaro; Yoshimura, Kei; Oka, Akira
2014-11-01
The oxygen isotopic ratio in the seawater (?18Osw) recorded in ?18O of coral skeleton for several centuries in tropical regions is an important variable for reconstructing the past climate. However, the relationship between ?18Osw and hydrological balance has not been clearly uncovered yet. In this study, a one-dimensional ocean budget model forced by the global quasi-reanalysis isotope data, which is the output of an isotope-incorporated global spectral model, is employed to simulate ?18Osw. The results from the simulations are compared with 31 coral records in tropical oceanic regions. The 1-D model successfully reproduces ?18Osw in 21 coral records, indicating these corals have the potential to reconstruct the local hydrological budget. The results also confirm that the reproducibility of the 1-D model generally increases with the annual precipitation variability. However, in the regions where the precipitation variability is less, it is more difficult to reconstruct climatic information from the ?18Osw, since the nonlocal physical processes unaccounted for in the 1-D model may affect ?18Osw. The sensitivity analysis of the 1-D model shows that in tropical oceanic regions, the large-scale precipitation is the dominant factor for ?18Osw, confirming that ?18Osw recorded in the coral records is a proxy for the precipitation anomaly. This study implies that ?18Osw is more closely associated with precipitation and local water isotope budget in tropical oceanic regions than elsewhere, and that the 1-D model is a useful approach for the proxy interpretation in tropical oceanic regions.
Cerveny, Vlastislav
Sobolev scalar products in the construction of velocity models --- application to model Hess model building process is the application of Sobolev scalar products. In this paper, we shall describe allows us to construct models optimal for the selected computational method. The Sobolev scalar product
Velocity mapping and models of the elliptical galaxies NGC 720, NGC 1052, and NGC 4697
NASA Technical Reports Server (NTRS)
Binney, J. J.; Davies, Roger L.; Illingworth, Garth D.
1990-01-01
CCD surface photometry and extensive long-slit spectroscopy are used to construct detailed models of the flattened ellipticals NGC 720, 1052, and 4697. The models are combined with the Jeans equations to yield predicted fields of line-of-sight velocity dispersion and streaming velocity. By comparing these fields with observed velocities, it is concluded that none of these systems can have isotropic velocity dispersion tensors, and diminishing the assumed inclination of any given galaxy tends to decrease the line-of-sight velocity dispersion and, counterintuitively, to increase the line-of-sight rotation speeds. The ratio of the line-of-sight velocity dispersion along the minor axis to that along the major axis is found to be a sensitive diagnostic of the importance of a third integral for the galaxy's structure.
Yakovlev, Vadim
-dependent electromagnetic parameters (dielectric constant and the loss factor) and thermal parameters (heat conductivity is off, diffusion is conditioned by both thermal conductivity and additional heat introduced to the load-thermal 1-D Model of Combined Microwave-convective Heating with Pulsing Microwave Energy Erin M. Kiley1, 2
Tullos, Desiree
Simulating dam removal with a 1D hydraulic model: Accuracy and techniques for reservoir erosion of Biological and Ecological Engineering, Oregon State University, 116 Gilmore Hall, Corvallis, OR 97331 and observed sediment erosion and deposition in the reservoir and downstream for the Chiloquin Dam removal
Alice E. Gripp; Richard G. Gordon
1990-01-01
NUVEL-1 is a new global model of current relative plate velocities which differ significantly from those of prior models. Here the authors incorporate NUVEL-1 into HS2-NUVEL1, a new global model of plate velocities relative to the hotspots. HS2-NUVEL1 was determined from the hotspot data and errors used by Minster and Jordan (1978) to determine AM1-2, which is their model of
A Velocity Distribution Model for Steady State Heat Transfer
NASA Technical Reports Server (NTRS)
Hall, Eric B.
1996-01-01
Consider a box that is filled with an ideal gas and that is aligned along Cartesian coordinates (x, y, z) having until length in the 'y' direction and unspecified length in the 'x' and 'z' directions. Heat is applied uniformly over the 'hot' end of the box (y = 1) and is removed uniformly over the 'cold' end (y = O) at a constant rate such that the ends of the box are maintained at temperatures T(sub 0) at y = O and T(sub 1) at y = 1. Let U, V, and W denote the respective velocity components of a molecule inside the box selected at some random time and at some location (x, y, z). If T(sub 0) = T(sub 1), then U, Y, and W are mutually independent and Gaussian, each with mean zero and variance RT(sub 0), where R is the gas constant. When T(sub 0) does not equal T(sub 1) the velocity components are not independent and are not Gaussian. Our objective is to characterize the joint distribution of the velocity components U, Y, and W as a function of y, and, in particular, to characterize the distribution of V given y. It is hoped that this research will lead to an increased physical understanding of the nature of turbulence.
NASA Astrophysics Data System (ADS)
Kanai, Masahiro; Isojima, Shin; Nishinari, Katsuhiro; Tokihiro, Tetsuji
2009-05-01
In this paper, we propose the ultradiscrete optimal velocity model, a cellular-automaton model for traffic flow, by applying the ultradiscrete method for the optimal velocity model. The optimal velocity model, defined by a differential equation, is one of the most important models; in particular, it successfully reproduces the instability of high-flux traffic. It is often pointed out that there is a close relation between the optimal velocity model and the modified Korteweg-de Vries (mkdV) equation, a soliton equation. Meanwhile, the ultradiscrete method enables one to reduce soliton equations to cellular automata which inherit the solitonic nature, such as an infinite number of conservation laws, and soliton solutions. We find that the theory of soliton equations is available for generic differential equations and the simulation results reveal that the model obtained reproduces both absolutely unstable and convectively unstable flows as well as the optimal velocity model.
A global 3D P-velocity model of the Earth's crust and mantle for improved event location.
Ballard, Sanford; Encarnacao, Andre Villanova; Begnaud, Michael A. (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
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.
NASA Astrophysics Data System (ADS)
Spica, Zack J.; Caudron, Corentin; Piña-Flores, José; Perton, Mathieu; Thomas, Lecocq; Camelbeeck, Thierry; Legrand, Denis
2015-04-01
It is now well accepted that the average autocorrelation of seismic noise at a single station is proportional to the imaginary part of the Green's function when both source and receiver are the same. More recently, it has been established that the horizontal and vertical imaginary parts of the Green's function, i.e. the horizontal and vertical transfer functions, should be used to calculate the horizontal to vertical spectral ratio of ambient noise (HVSR). The HVSR is a popular technique that only requires a short-term (20 minutes) 3 components recording of seismic noise. Assuming an unbounded multi-layer model for the computation of the Green function, one can conduct the HVSR inversions to assess the 1D velocity structure of the subsurface. This approach was used to constrain several 1D velocity models (certain up to 3 km deep) of the Ijen caldera (Java, Indonesia) already established by the inversion of dispersion curves. Additionally, 84 HVSR measurements were also performed on Kawah Ijen volcano and allowed to provide a map of the local site effects. The velocity models obtained and the great outcrop of the crater rim allow robust and direct interpretation of the underground geology. Using a first order approximation, some mechanical proprieties of the shallower layers can be derived and the depth of an important lithological interface can be followed all around the Kawah Ijen crater.
NASA Astrophysics Data System (ADS)
Malkov, Mikhail; Diamond, Patrick; Miki, Kazuhiro
2013-10-01
The LH transition crucially depends on the heat and particle deposition, transport and electric field shear suppression. Despite the inhomogeneity of these phenomena, a popular 0D predator-prey model seems to capture the essential transition dynamics, including the limit cycle pre-H-mode oscillations (or I-mode). However, its predictions regarding hysteresis are inconclusive. This is understandable at least because of the known deep fuel lowering of the transition threshold. The readily available fueling devices are the edge neutral penetration and an internal deposition via the supersonic molecular beam injection (SMBI). This suggests a minimal extension of the 0D model by using bi-modal particle distributions. To formulate this extension accurately, a step-by-step comparison with a 1D treatment is required. Fortunately a suitable 1D numerical model has been recently developed specifically for the LH transition studies. In this work, we use the 1D model for the following purposes. First, we explore fueling effects as occurring both by edge neutral penetration, and internal deposition (SMBI) at a finite depth within the separatrix. Second, as the 0D model responds positively to the oscillating heating power, we include a periodic repetitive SMBI firing. The LH transition crucially depends on the heat and particle deposition, transport and electric field shear suppression. Despite the inhomogeneity of these phenomena, a popular 0D predator-prey model seems to capture the essential transition dynamics, including the limit cycle pre-H-mode oscillations (or I-mode). However, its predictions regarding hysteresis are inconclusive. This is understandable at least because of the known deep fuel lowering of the transition threshold. The readily available fueling devices are the edge neutral penetration and an internal deposition via the supersonic molecular beam injection (SMBI). This suggests a minimal extension of the 0D model by using bi-modal particle distributions. To formulate this extension accurately, a step-by-step comparison with a 1D treatment is required. Fortunately a suitable 1D numerical model has been recently developed specifically for the LH transition studies. In this work, we use the 1D model for the following purposes. First, we explore fueling effects as occurring both by edge neutral penetration, and internal deposition (SMBI) at a finite depth within the separatrix. Second, as the 0D model responds positively to the oscillating heating power, we include a periodic repetitive SMBI firing. Supported by the US DoE.
Polynya Modelling A.J. Willmott1, D.M. Holland2 and M.A. Morales Maqueda2
Holland, David
.J. Willmott1, D.M. Holland2 and M.A. Morales Maqueda2 1Department of Mathematics, Keele University, Keele-chemical processes and biological activity. These three phenomena associated with polynyas are discussed in Morales polynyas (Morales Maqueda et al., 2004). Deep water polynyas occur beyond the continental shelf break
ADAPTIVE SIMULATED-ANNEALING VELOCITY MODELING FOR RAYLEIGH SURFACE-WAVE DISPERSION
ADAPTIVE SIMULATED-ANNEALING VELOCITY MODELING FOR RAYLEIGH SURFACE-WAVE DISPERSION Donghong Pei1 is realized using the adaptive simulated annealing (ASA) method. Instead of using uniform probability. Introduction Shallow shear velocity structure is very important for seismic design of engineered structures
Relations Among Fault Behavior, Subsurface Geology, and Three-Dimensional Velocity Models
Andrew J. Michael; Donna Eberhart-Phillips
1991-01-01
The development of three-dimensional P-wave velocity models for the regions surrounding five large earthquakes in California has lead to the recognition of relations among fault behavior and the material properties of the rocks that contact the fault at seismogenic depths; regions of high moment release appear to correlate with high seismic velocities whereas rupture initiation or termination may be associated
NASA Astrophysics Data System (ADS)
Pujol, J. M.; Chiu, J. M.
2014-12-01
When applying seismic tomography to local arrival times from an area with a low-velocity sedimentary cover, the effect of the sediments on travel times should be taken into account. If that is not done, the resulting velocity model(s) cannot be assumed to be correct. This fairly obvious statement has been challenged recently by Powell et al. (JGR, 2010), who claimed that the sediments that cover the New Madrid seismic zone (NMSZ, central United States) can be ignored. This claim is examined here and shown to be incorrect. The NMSZ is covered by low-velocity, poorly consolidated sediments (Vp=1.8 km/s, Vs=3), which are underlain by Paleozoic rocks of much higher velocity. In the central NMSZ the sediment thickness varies between about 0.1 and 0.7 km. The JHD analysis of the data collected in that area by a portable network (PANDA) showed that the P- and S-wave station corrections spanned large ranges (0.35 and 0.63 s, respectively, Pujol et al., Eng. Geol., 1997). This study also showed that a Vp/Vs of 3 for the sediments would be too high if the lateral velocity variations were confined to the sedimentary cover. Here we generate synthetic traveltimes for a model with a sedimentary cover having variable depth (as determined from boreholes) underlain by the high-velocity layers in the 1-D model used for the JHD analysis. The synthetic data were generated for the station and event distributions corresponding to the Panda data. The tomographic inversion of the synthetic times produces spurious anomalies in Vp, Vs, and Vp/Vs, from the surface to a depth of 10 km. In addition, the events are mislocated in depth, with errors between 0 and 1 km for most of them. These results should dispel the notion that the effect of the unconsolidated sediments can be ignored. On the other hand, the inversion of the actual Panda data results in velocity anomalies similar to the synthetic anomalies, although larger, which is consistent with the conclusions of Pujol et al. (1997). Unfortunately, extricating the effects of the sediments from those of deeper velocity anomalies will not be possible with seismic tomography unless in-situ determinations of Vp/Vs for the sediments in the network area become available. Alternatively, analysis techniques that make use of more than just P- and S-wave arrivals (such as S-to-P converted waves) may have to be designed.
Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian
2013-09-09
Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.
Evidence for SrHo2O4 and SrDy2O4 as model 1D J1-J2 zig-zag chain materials
NASA Astrophysics Data System (ADS)
Poole, Amy; Pomjakushin, Vladimir; Uldry, Anne-Christine; Prevost, Bobby; Desilets-Benoit, Alexandre; Bianchi, Andrea; Hansen, Britt; Cava, Robert; Kenzelmann, Michel
2014-03-01
This presentation will focus on the Ho and Dy members of the recently discovered SrR2O4 family of frustrated rare-earth (R) materials. Despite the R sites forming a honeycomb in the ab plane, we demonstrate that the physics is dominated by 1D correlations in the c-direction and that these can be mapped onto the Ising J1-J2 spin chain model. Three-dimensional magnetic order is suppressed from ?w = -16.9 K to TN = 0.66 K in SrHo2O4 and is not observed to 50 mK in SrDy2O4. Our neutron powder diffraction measurements indicate that prior to the 3D order in the SrHo2O4 compound a 1D magnetically correlated state exists and that a similar state is found at the lowest measured temperatures in SrDy2O4. Fits to the diffuse data allow us to identify the 1D nature of the material and the key structural motifs are found from the data collected in the long-range ordered phase of SrHo2O4. Point charge calculations are fitted to the inelastic neutron scattering data and identify a large Ising anisotropy. The combination of neutron scattering and novel modelling techniques has allowed us to unambiguously determine the magnetic structure, identify the key interactions in the system and understand the 1D nature of the system.
NASA Astrophysics Data System (ADS)
Kang, Peter K.; Le Borgne, Tanguy; Dentz, Marco; Bour, Olivier; Juanes, Ruben
2015-02-01
Flow and transport through fractured geologic media often leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity distribution), connectedness in the flow paths through fractures (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of distribution- versus correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on velocity correlation, whereas late-time scaling of breakthrough curves is mainly controlled by velocity distribution. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, velocity distribution and velocity correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model accurately captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of velocity distribution and correlation on transport in fractured media.
NASA Astrophysics Data System (ADS)
Marcq, E.
2012-01-01
In order to understand the early history of telluric interiors and atmospheres during the ocean magma stage, a coupled interior-atmosphere-escape model is being developed. This paper describes the atmospheric part and its first preliminary results. A unidimensional, radiative-convective, H2O-CO2 atmosphere is modeled following a vertical T(z) profile similar to Kasting (1988) and Abe and Matsui (1988). Opacities in the thermal IR are then computed using a k-correlated code (KSPECTRUM), tabulated continuum opacities for H2O-H2O and CO2-CO2 absorption, and water or sulphuric acid clouds in the moist convective zone (whenever present). The first results show the existence of two regimes depending on the relative value of the surface temperature Ts compared to a threshold temperature Tc depending on the total gaseous inventory. For Ts < Tc, efficient blanketing results in a cool upper atmosphere, a cloud cover, and a long lifetime for the underneath magma ocean with a net thermal IR flux between 160 and 200 Wm-2. For Ts > Tc, the blanketing is not efficient enough to prevent large radiative heat loss to space through a hot, cloudless atmosphere. Our current calculations may underestimate the thermal flux in the case of hot surfaces with little gaseous content in the atmosphere.
NASA Astrophysics Data System (ADS)
Pasternack, Gregory B.; Gilbert, Andrew T.; Wheaton, Joseph M.; Buckland, Evan M.
2006-08-01
SummaryResource managers, scientists, government regulators, and stakeholders are considering sophisticated numerical models for managing complex environmental problems. In this study, observations from a river-rehabilitation experiment involving gravel augmentation and spawning habitat enhancement were used to assess sources and magnitudes of error in depth, velocity, and shear velocity predictions made at the 1-m scale with a commercial two-dimensional (depth-averaged) model. Error in 2D model depth prediction averaged 21%. This error was attributable to topographic survey resolution, which at 1 pt per 1.14 m 2, was inadequate to resolve small humps and depressions influencing point measurements. Error in 2D model velocity prediction averaged 29%. More than half of this error was attributable to depth prediction error. Despite depth and velocity error, 56% of tested 2D model predictions of shear velocity were within the 95% confidence limit of the best field-based estimation method. Ninety percent of the error in shear velocity prediction was explained by velocity prediction error. Multiple field-based estimates of shear velocity differed by up to 160%, so the lower error for the 2D model's predictions suggests such models are at least as accurate as field measurement. 2D models enable detailed, spatially distributed estimates compared to the small number measurable in a field campaign of comparable cost. They also can be used for design evaluation. Although such numerical models are limited to channel types adhering to model assumptions and yield predictions only accurate to ˜20-30%, they can provide a useful tool for river-rehabilitation design and assessment, including spatially diverse habitat heterogeneity as well as for pre- and post-project appraisal.
Surface-wave phase-velocity models of the United States: Expanding with USArray coverage
NASA Astrophysics Data System (ADS)
Foster, A. E.; Ekstrom, G.; Nettles, M.
2014-12-01
We update our models of Love and Rayleigh wave phase-velocity structure using USArray data through mid 2014. We make measurements of the phase at periods from 25 to 100 s using a two-station method that assumes a great-circle arrival path for Love waves, and uses the estimated arrival angle for Rayleigh waves to correct the two-station calculation. Arrival-angle estimates are made with a mini-array method that employs a grid search to select the back-azimuth to the source that best predicts the phase observed on a local subset of stations. The two-station phase data with inter-station path lengths between 350 and 750 km are inverted to produce phase-velocity models at discrete periods. The new data set expands the modeled area, covering the entire contiguous United States. The mini-array method also produces an estimate of the local phase-velocity. We calculate this local phase-velocity for both Love and Rayleigh waves, and compare the measurements with the maps resulting from the inversion of the two-station measurements. The local phase velocities, two-station phase velocities, and two-station phase-velocity models are all examined for bias resulting from overtone interference. Based on previous work, we expect overtone interference to affect Love wave measurements but not Rayleigh wave measurements, and to affect the local measurements more than the two-station models.
'A Civil Action' 1-D Transport Game
NSDL National Science Digital Library
Scott Bair
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.
NASA Astrophysics Data System (ADS)
Molin, P.; Pazzaglia, F. J.; Dramis, F.
In active tectonic regions, topography is the result of the interactions of tectonics that deform and move rocks and surface processes that erode rocks. So first-order topo- graphic features including relief, drainage patterns, and stream gradient slope repre- sent ways to quantitatively characterize the interaction between tectonics and geomor- phology, providing a basis for modelling landscape evolution. We characterize tectonic processes through geomorphic investigations in the Sila Massif (Calabria, Italy). Here the Apennines are a narrow and rugged chain, composed of relatively uniform rock- type (crystalline Paleozoic plutonic and metamorphic rocks), that appears to have been affected by extensional tectonics since the early Pliocene and that were rapidly raised above sea level in the Pleistocene. Our study examines the tectonic geomorphology of the northern portion of the Sila Massif focusing on the general topographic met- rics, drainage patterns, and river longitudinal profiles. Our goal is to develop a general picture of the influence of extensional tectonics in the landscape evolution of the Sila Massif in the context of the recent and rapid uplift (0.6-1 mm/yr in the last 700.000 yrs) of the entire Italian peninsula. Our main data base is composed of map and DEM- based topographic analyses, supplemented with field investigations. These data are consistent with a landscape dominated by intra-chain extensional tectonics including block tilting and footwall flexure, superimposed on a regional rock and surface uplift. In particular the flexure of the extensional fault that surround the Sila Massif could have generated the bowl-shape plateau presently located on the Sila top. We develop a simple, flexural,1-D geodynamic model (Turcott and Schubert, 1982) to explain the uplift of the Sila Massif flank. The topographic imprint of the long-wavelength Qua- ternary uplift of the massif is removed by filtering the topography with a low pass filter. The flexural analysis is then performed on the residual topography which nor- malizes the elevation of the plateau flank to sea level. The model generates a plate elastic thickness between 3500-4000 m. This value is consistent with the ones found in the Basin and Range and in Tibet (Masek et al., 1994), confirming a possible flexu- ral isostatic origin of the Sila plateau rim. The uplifted plateau flank fixes the drainage divide and hinders the drainages from integrating into the plateau interior and fully dissecting the rolling upland surface. As a result, the clear geomorphic expression of active normal faulting is well evident around Sila, but is masked within the massif it- 1 self allowing the general perception that it is a vertically uplifted plateau. Furthermore, the marine terrace data on the Ionian coast that suggest an uplift rate of 0.6 mm/yr in the last 350.000 years confirm the broad uplift of the area. These results support the notion of a old landscape less rugged than the modern one that is coincident with a slow uplift related to syn- and late-orogenic exhumation, the eastward migration of the arc, and roll-back in the subducting slab. This old landscape have been preserved by the footwall flexure of the extensional faults surrounding the Sila Massif and uplifted in the Pleistocene as the wavelength of deformation broadened. References Masek J.G., Isacks B.L., and Fielding E.J. (1994) U Rift flank uplift in Tibet: evidence for a viscous lower crust, Tectonics, 13, 659-667. Turcotte D. L. and Schubert G. (1982) U Geodynamics U Applications of continuum physics to ge- ological problems, John Wiley and Sons, pp.450 2
Near-surface ocean velocity from infrared images: Global Optimal Solution to an inverse model
NASA Astrophysics Data System (ADS)
Chen, Wei; Mied, Richard P.; Shen, Colin Y.
2008-10-01
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.
NASA Astrophysics Data System (ADS)
Begnaud, M. L.; Ballard, S.; Young, C. J.; Hipp, J. R.; Encarnacao, A. V.; Maceira, M.; Phillips, W. S.; Chael, E. P.; Rowe, C. A.
2014-12-01
The SALSA3D (SAndia LoS Alamos 3D) global three-dimensional P-velocity tomography model of the Earth's crust and mantle has been shown to significantly improve seismic event location accuracy and precision, compared to standard 1D and 2/2.5D models. This improvement has been demonstrated using data from the International Monitoring System (IMS), a sparse, global seismic network. In relocation tests using the IMS network and a set of seismic events with ground truth (GT) levels of 5 km or better, over 80% of the defining arrivals are regional Pn (15%) or teleseismic P phases (65.1%). There is a small percentage of phases that requires a model that supports secondary phase prediction. We plan to update the SALSA3D model to include an S-velocity component as well as an updated P-velocity model using secondary compressional phases. Our model is derived from the latest version of the GT catalog of travel-time picks assembled by Los Alamos National Laboratory. 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 layer crustal model derived from the Crust 1.0 model, overlying 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 in areas where it is warranted by the available data. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. We compare the travel-time prediction and location capabilities of the updated SALSA3D model to standard 1D and 2/2.5D models via location tests on a global event set with GT of 5 km or better. We compare location results using a subset of these events that have a significant number of phases with which to produce random realizations of actual arrival data. In addition, further tests will involve using GT5 or better events and their arrivals specifically for the IMS network, to test the use of a 3D model on an operational network intended for explosion monitoring.
An analytical model for velocity profiles of settling slurry flow in a horizontal pipe
Sato, H. [Akita Univ. (Japan). Mining College; Xu, Z.; Cui, Y. [Fuxin Mining Institute (China)
1994-12-31
The velocity profile is an important parameter in regarding frictional phenomena between solid particles and pipe wall, critical deposit velocity, and sorting mechanism near the bed in settling slurry flows in a horizontal pipe. The authors propose in this paper an analytical model which could be used for the calculation of the velocity profiles in practical pipeline design. Based on the hypothesis that stayed slurry flow would be produced through the encounter of water flow to stationary suspended solid particles with a fixed distribution of concentration in water, the model has been derived by the analysis of the change in momentums both of solid particles and water with item. This model allows pipeline design engineers to easily calculate velocity profiles of settling slurry flow with a personal computer. Predictions from the model are compared with experimental results obtained from published papers, and are verified to be reliable.
A CONSERVATIVE AND ENTROPIC DISCRETE-VELOCITY MODEL FOR RAREFIED POLYATOMIC GASES
Mieussens, Luc
A CONSERVATIVE AND ENTROPIC DISCRETE-VELOCITY MODEL FOR RAREFIED POLYATOMIC GASES #3; DUBROCA Bruno for modeling rare#12;ed polyatomic gases. This model is based on a polyatomic BGK equation that allows contribution to the rotational energy, this gives Ã? = 2. Modeling the energy exchange in polyatomic gases
NASA Astrophysics Data System (ADS)
Maher Abourabia, Aly; Hassan, Kawsar Mohammad; Abo-Elghar, Eman Mohammad
2015-02-01
We investigate a bio-system composed of a shape memory alloy (SMA) immersed and subjected to heat convection in a blood vessel, affected by heart beats that create a wave motion of long wavelength. The tackled model in (2+1)-D is based on the continuity and momentum equations for the fluid phase, besides; the state of the SMA are described via previous works in the form of statistical distributions of energy for both Martensite and Austenite phases. The solution based on the reductive perturbation technique gives a thermal diffusion-like equation as a key for expressing the temperature and velocity components of the blood. In terms of two cases concerning the difference between the wave numbers in the perpendicular directions, it is found that the system's temperature increases nonlinearly from a minimum initial temperature 293 K (20 °C) up to a maximum value about 316.68 K (43.68 °C), then tends to decrease along the blood flow (anisotropy of K and L) direction. In both cases it is observed that the SMA acquires most of this temperature raising not the blood because of its conventional biological limits (37-40 °C). The range of the heart beats wave numbers characteristic for each person plays an important role in realizing phase changes in the anisotropic case leading to the formation of the hysteresis loops Martensite-Austenite-Martensite or vice versa, according to the energy variation. The entropy generation ? is investigated for the system (Blood + SMA), it predicts that along the flow direction the system gains energy convectively up to a maximum value, then reverses his tendency to gradually loosing energy passing by the equilibrium state, then the system looses energy to the surroundings by the same amount which was gained beforehand. The loss diminishes but stops before arriving to equilibrium again. For certain differences in wave numbers the system starts to store energy again after it passes by the state of equilibrium for the second time. In the curves of ? the common points of intersections can be looked for as the positions where the phase changes take place. It is observed that the effect of heat transfer is dominated over the viscous dissipation substantially; this is illustrated by the irreversibility distribution ratio ? and the Bejan number. On the other hand this is assured by the smallness of the ratio between the initial effect of shear viscosity to the initial thermal effect in the alloy (? ? 10-8). Furthermore, this allows the SMA to reveal the properties of phase change in order, for instance, to prevent the passage of large clots from reaching the lungs.
Gripp, A.E.; Gordon, R.G. (Northwestern Univ., Evanston, IL (USA))
1990-07-01
NUVEL-1 is a new global model of current relative plate velocities which differ significantly from those of prior models. Here the authors incorporate NUVEL-1 into HS2-NUVEL1, a new global model of plate velocities relative to the hotspots. HS2-NUVEL1 was determined from the hotspot data and errors used by Minster and Jordan (1978) to determine AM1-2, which is their model of plate velocities relative to the hotspots. AM1-2 is consistent with Minster and Jordan's relative plate velocity model RM2. Here the authors compare HS2-NUVEL1 with AM1-2 and examine how their differences relate to differences between NUVEL-1 and RM2. HS2-NUVEL1 plate velocities relative to the hotspots are mainly similar to those of AM1-2. Minor differences between the two models include the following: (1) in HS2-NUVEL1 the speed of the partly continental, apparently non-subducting Indian plate is greater than that of the purely oceanic, subducting Nazca plate; (2) in places the direction of motion of the African, Antarctic, Arabian, Australian, Caribbean, Cocos, Eurasian, North American, and South American plates differs between models by more than 10{degree}; (3) in places the speed of the Australian, Caribbean, Cocos, Indian, and Nazca plates differs between models by more than 8 mm/yr. Although 27 of the 30 RM2 Euler vectors differ with 95% confidence from those of NUVEL-1, only the AM1-2 Arabia-hotspot and India-hotspot Euler vectors differ with 95% confidence from those of HS2-NUVEL1. Thus, substituting NUVEL-1 for RM2 in the inversion for plate velocities relative to the hotspots changes few Euler vectors significantly, presumably because the uncertainty in the velocity of a plate relative to the hotspots is much greater than the uncertainty in its velocity relative to other plates.
Wisconsin at Madison, University of
This is a 1D model of an active magnetic regenerative refrigerator (AMRR) that was developed of an Active Magnetic Regenerator Refrigerator 1. Governing Equations Figure 1 shows a schematic of an active
NASA Astrophysics Data System (ADS)
Toyota, K.; Dastoor, A. P.; Staebler, R. M.; McConnell, J. C.
2012-04-01
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).
Propagation of the velocity model uncertainties to the seismic event location
NASA Astrophysics Data System (ADS)
Gesret, A.; Desassis, N.; Noble, M.; Romary, T.; Maisons, C.
2015-01-01
Earthquake hypocentre locations are crucial in many domains of application (academic and industrial) as seismic event location maps are commonly used to delineate faults or fractures. The interpretation of these maps depends on location accuracy and on the reliability of the associated uncertainties. The largest contribution to location and uncertainty errors is due to the fact that the velocity model errors are usually not correctly taken into account. We propose a new Bayesian formulation that integrates properly the knowledge on the velocity model into the formulation of the probabilistic earthquake location. In this work, the velocity model uncertainties are first estimated with a Bayesian tomography of active shot data. We implement a sampling Monte Carlo type algorithm to generate velocity models distributed according to the posterior distribution. In a second step, we propagate the velocity model uncertainties to the seismic event location in a probabilistic framework. This enables to obtain more reliable hypocentre locations as well as their associated uncertainties accounting for picking and velocity model uncertainties. We illustrate the tomography results and the gain in accuracy of earthquake location for two synthetic examples and one real data case study in the context of induced microseismicity.
Quantifying Uncertainty in Velocity Models using Bayesian Methods
NASA Astrophysics Data System (ADS)
Hobbs, R.; Caiado, C.; Majda?ski, M.
2008-12-01
Quanitifying uncertainty in models derived from observed data is a major issue. Public and political understanding of uncertainty is poor and for industry inadequate assessment of risk costs money. In this talk we will examine the geological structure of the subsurface, however our principal exploration tool, controlled source seismology, gives its data in time. Inversion tools exist to map these data into a depth model but a full exploration of the uncertainty of the model is rarely done because robust strategies do not exist for large non-linear complex systems. There are two principal sources of uncertainty: the first comes from the input data which is noisy and bandlimited; the second, and more sinister, is from the model parameterisation and forward algorithms themselves, which approximate to the physics to make the problem tractable. To address these issues we propose a Bayesian approach. One philosophy is to estimate the uncertainty in a possible model derived using standard inversion tools. During the inversion stage we can use our geological prejudice to derive an acceptable model. Then we use a local random walk using the Metropolis- Hastings algorithm to explore the model space immediately around a possible solution. For models with a limited number of parameters we can use the forward modeling step from the inversion code. However as the number of parameters increase and/or the cost of the forward modeling step becomes significant, we need to use fast emulators to act as proxies so a sufficient number of iterations can be performed on which to base our statistical measures of uncertainty. In this presentation we show examples of uncertainty estimation using both pre- and post-critical seismic data. In particular, we will demonstrate uncertainty introduced by the approximation of the physics by using a tomographic inversion of bandlimited data and show that uncertainty increases as the central frequency of the data decreases. This is consistent with the infinite frequency approximation in the tomographic modeling step becoming increasing compromised.
Satellite galaxy velocity dispersions in the SDSS and modified gravity models
Moffat, J W
2009-01-01
The Sloan Digital Sky Survey (SDSS) provides data on several hundred thousand galaxies. Precise location of these galaxies in the sky, along with information about their luminosities and line-of-sight (Doppler) velocities allows one to construct a three-dimensional map of their location and estimate their line-of-sight velocity dispersion. This information, in principle, allows one to test dynamical gravity models, specifically models of satellite galaxy velocity dispersions near massive hosts. A key difficulty is the separation of true satellites from interlopers. We sidestep this problem by not attempting to derive satellite galaxy velocity dispersions from the data, but instead incorporate an interloper background into the mathematical models and compare the result to the actual data. We find that due to the presence of interlopers, it is not possible to exclude several gravitational theories on the basis of the SDSS data.
NASA Technical Reports Server (NTRS)
Gripp, Alice E.; Gordon, Richard G.
1990-01-01
The NUVEL-1 model of current global relative plate velocities is presently incorporated into HS2-NUVEL1, a global model for plate velocities relative to hotspots; the results thus obtained are compared with those of the AM1-2 model of hotspot-relative plate velocities. While there are places in which plate velocities relative to the hotspots differ between HS2-NUVEL1 and AM1-2 by tens of degrees in direction and 15 mm/yr in speed, the hotspot Euler vectors differ with 95 percent confidence only for the Arabian and Indian plates. Plates attached to subducting slabs move faster relative to the hotspots than do plates without slabs.
Feedbacks between vertical velocity and microphysical processes in a single-column model
NASA Astrophysics Data System (ADS)
Igel, A. L.; Saleeby, S. M.; Grant, L. D.; van den Heever, S. C.
2013-12-01
Vertical velocity plays a strong role in determining the formation rates of cloud and rain water. To complicate matters, the release of latent heat during condensation in a growing cloud can have nonlinear feedbacks to vertical velocity. Furthermore, collision-coalescence and hydrometeor fall speed impact the condensate loading of a cloud and hence its buoyancy, which adds to the complexity of the problem. In this study, the Hebrew University Spectral Bin Model (SBM) is run in a single column framework. This simple dynamical framework allows the interactions between vertical velocity and microphysical processes to be analyzed in isolation from other dynamical feedbacks and processes. Warm phase convective clouds are simulated with both fixed and prognosed vertical velocity. Attempts are made to quantify the relationship between latent heat release, acceleration, and vertical velocity. The sensitivity of these relationships to collision-coalescence and fall speed will also be presented.
Comparison of vertical velocities analyzed by a numerical model and measured by a VHF wind profiler
NASA Technical Reports Server (NTRS)
Larsen, M. F.; Rottger, J.; Dennis, T. S.
1986-01-01
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.
A comprehensive dispersion model of surface wave phase and group velocity for the globe
NASA Astrophysics Data System (ADS)
Ma, Zhitu; Masters, Guy; Laske, Gabi; Pasyanos, Michael
2014-10-01
A new method is developed to measure Rayleigh- and Love-wave phase velocities globally using a cluster analysis technique. This method clusters similar waveforms recorded at different stations from a single event and allows users to make measurements on hundreds of waveforms, which are filtered at a series of frequency ranges, at the same time. It also requires minimal amount of user interaction and allows easy assessment of the data quality. This method produces a large amount of phase delay measurements in a manageable time frame. Because there is a strong trade-off between the isotropic part of the Rayleigh-wave phase velocity and azimuthal anisotropy, we include the effect of azimuthal anisotropy in our inversions in order to obtain reliable isotropic phase velocity. We use b-splines to combine these isotropic phase velocity maps with our previous group velocity maps to produce an internally consistent global surface wave dispersion model.
Wave-induced velocities inside a model seagrass bed
Luhar, Mitul
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 ...
NASA Astrophysics Data System (ADS)
Zsom, Andras; Kaltenegger, Lisa; Goldblatt, Colin
2012-11-01
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.
Detailed p- and s-wave velocity models along the LARSE II transect, Southern California
Murphy, J.M.; Fuis, G.S.; Ryberg, T.; Lutter, W.J.; Catchings, R.D.; Goldman, M.R.
2010-01-01
Structural details of the crust determined from P-wave velocity models can be improved with S-wave velocity models, and S-wave velocities are needed for model-based predictions of strong ground motion in southern California. We picked P- and S-wave travel times for refracted phases from explosive-source shots of the Los Angeles Region Seismic Experiment, Phase II (LARSE II); we developed refraction velocity models from these picks using two different inversion algorithms. For each inversion technique, we calculated ratios of P- to S-wave velocities (VP/VS) where there is coincident P- and S-wave ray coverage.We compare the two VP inverse velocity models to each other and to results from forward modeling, and we compare the VS inverse models. The VS and VP/VS models differ in structural details from the VP models. In particular, dipping, tabular zones of low VS, or high VP/VS, appear to define two fault zones in the central Transverse Ranges that could be parts of a positive flower structure to the San Andreas fault. These two zones are marginally resolved, but their presence in two independent models lends them some credibility. A plot of VS versus VP differs from recently published plots that are based on direct laboratory or down-hole sonic measurements. The difference in plots is most prominent in the range of VP = 3 to 5 km=s (or VS ~ 1:25 to 2:9 km/s), where our refraction VS is lower by a few tenths of a kilometer per second from VS based on direct measurements. Our new VS - VP curve may be useful for modeling the lower limit of VS from a VP model in calculating strong motions from scenario earthquakes.
Models of cuspy triaxial stellar systems - III. The effect of velocity anisotropy on chaoticity
NASA Astrophysics Data System (ADS)
Carpintero, D. D.; Muzzio, J. C.; Navone, H. D.
2014-03-01
In several previous investigations, we presented models of triaxial stellar systems, both cuspy and non-cuspy, that were highly stable and harboured large fractions of chaotic orbits. All our models had been obtained through cold collapses of initially spherical N-body systems, a method that necessarily results in models with strongly radial velocity distributions. Here we investigate a different method that was reported to yield cuspy triaxial models with virtually no chaos. We show that such a result was probably due to the use of an inadequate chaos detection technique and that, in fact, models with significant fractions of chaotic orbits result also from that method. Besides, starting with one of the models from the first paper in this series, we obtained three different models by rendering its velocity distribution much less radially biased (i.e. more isotropic) and by modifying its axial ratios through adiabatic compression. All three models yielded much higher fractions of regular orbits than most of those from our previous work. We conclude that it is possible to obtain stable cuspy triaxial models of stellar systems whose velocity distribution is more isotropic than that of the models obtained from cold collapses. Those models still harbour large fractions of chaotic orbits and, although it is difficult to compare the results from different models, we can tentatively conclude that chaoticity is reduced by velocity isotropy.
One-velocity model of a multicomponent heat-conducting medium
NASA Astrophysics Data System (ADS)
Surov, V. S.
2010-03-01
A model of a one-velocity heat-conducting heterogeneous medium with the Fourier relaxation law of heat transfer has been constructed. It is shown that the model’s equations are of hyperbolic type. The results of numerical experiments for a three-component mixture of ideal gases carried out with the use of the Courant-Isaacson-Rees scheme are presented.
Sobolev scalar products in the construction of velocity models Petr Bulant, Ludek Klimes and Karel
Cerveny, Vlastislav
Sobolev scalar products in the construction of velocity models Petr Bulant, LudÅ¸ek Klime of the model, which allows models optimum for ray tracing to be constructed. 1 Sobolev scalar products and Sobolev norms We define the Sobolev scalar product (see, e.g., Tarantola 1987) of real--valued functions f
An upper-mantle S-wave velocity model for East Asia from Rayleigh wave tomography
NASA Astrophysics Data System (ADS)
Li, Yonghua; Wu, Qingju; Pan, Jiatie; Zhang, Fengxue; Yu, Daxin
2013-09-01
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.
An upper-mantle S-wave velocity model for East Asia from Rayleigh wave tomography
NASA Astrophysics Data System (ADS)
Li, Y.; Wu, Q.; Pan, J.; Zhang, F.; Sun, L.
2013-12-01
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).
A subgrid-scale model based on the second-order velocity structure function
NASA Technical Reports Server (NTRS)
Comte, P.; Lee, Sangsan; Cabot, William H.
1990-01-01
A series of tests were performed to help extend the use of a subgrid-scale model to compressible and wall-bounded flows. A priori tests were done in the case of the incompressible turbulent channel flow. They showed that a 1-D formulation of the structure-function model is more appropriate, leading to a satisfactory behavior of the model at the walls without requiring any damping function. This model is consistent with the original formulation of Metais & Lesieur (1990). In large-eddy simulations of compressible isotropic turbulence, both models performed well up to an initial rms Mach number of 0.6.
Thermal blooming threshold computations with a Markov model of velocity turbulence
Viecelli, J.A.
1988-11-30
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.
Modelling vertical structure in circular velocity of spiral galaxy NGC 4244
NASA Astrophysics Data System (ADS)
Ja?ocha, Joanna; Bratek, ?ukasz; Sikora, Szymon; Kutschera, Marek
2015-08-01
We study the vertical gradient in azimuthal velocity of spiral galaxy NGC 4244 in a thin disc model. With surface density accounting for the rotation curve, we model the gradient properties in the approximation of quasi-circular orbits. It is worthy to note that the prediction of our model is consistent with the gradient properties inferred recently from a numerical model implementing the position-velocity diagram of this galaxy. The confirmation of our prediction by the future measurement of the gradient would provide support for the expectation that the mass distribution in this galaxy is flattened.
Turbulence-induced Relative Velocity of Dust Particles V. Testing Previous Models
NASA Astrophysics Data System (ADS)
Pan, Liubin; Padoan, Paolo
2015-10-01
Coagulation models for dust growth in protoplanetary disks usually adopt the prediction of Völk et al. or its later developments (hereafter Völk-type models) for the collision velocity of dust particles induced by turbulent motions. We review the formulation and the underlying physical picture of these models, test their predictions against a numerical simulation, and examine the accuracy of the commonly used prescription for dust particle collisions. We show that Völk-type models typically overestimate the rms of the particle relative velocity by a factor of two, if the particle friction times lie in the inertial range of the flow. The commonly used prescription for the collision kernel has several inaccuracies, and, in particular, it neglects the effect of turbulent clustering. Interestingly, for particles of equal sizes, the inaccuracies happen to cancel out, and by coincidence, the commonly used kernel prescription based on Völk-type models is in good agreement with our simulation result. For particles of different sizes, the prescription shows a larger discrepancy from the measured kernel, and may overestimate the collision rate by up to a factor of 2.5. We find that the predicted rms relative velocity by Völk-type models provides reasonable estimates for the average collision velocity per collision. We also make an effort to improve the accuracy of Völk-type models for the rms relative velocity by tuning the correlation time of turbulent eddies and modifying the criterion for eddy classification.
NASA Astrophysics Data System (ADS)
Kirkegaard, Casper; Foged, Nikolaj; Auken, Esben; Christiansen, Anders Vest; Sørensen, Kurt
2012-09-01
Helicopter borne time domain EM systems historically measure only the Z-component of the secondary field, whereas fixed wing systems often measure all field components. For the latter systems the X-component is often used to map discrete conductors, whereas it finds little use in the mapping of layered settings. Measuring the horizontal X-component with an offset loop helicopter system probes the earth with a complementary sensitivity function that is very different from that of the Z-component, and could potentially be used for improving resolution of layered structures in one dimensional modeling. This area is largely unexplored in terms of quantitative results in the literature, since measuring and inverting X-component data from a helicopter system is not straightforward: The signal strength is low, the noise level is high, the signal is very sensitive to the instrument pitch and the sensitivity function also has a complex lateral behavior. The basis of our study is a state of the art inversion scheme, using a local 1D forward model description, in combination with experiences gathered from extending the SkyTEM system to measure the X component. By means of a 1D sensitivity analysis we motivate that in principle resolution of layered structures can be improved by including an X-component signal in a 1D inversion, given the prerequisite that a low-pass filter of suitably low cut-off frequency can be employed. In presenting our practical experiences with modifying the SkyTEM system we discuss why this prerequisite unfortunately can be very difficult to fulfill in practice. Having discussed instrumental limitations we show what can be obtained in practice using actual field data. Here, we demonstrate how the issue of high sensitivity towards instrument pitch can be overcome by including the pitch angle as an inversion parameter and how joint inversion of the Z- and X-components produces virtually the same model result as for the Z-component alone. We conclude that adding helicopter system X-component to a 1D inversion can be used to facilitate higher confidence in the layered result, as the requirements for fitting the data into a 1D model envelope becomes more stringent and the model result thus less prone to misinterpretation.
Measurement of velocity deficit at the downstream of a 1:10 axial hydrokinetic turbine model
Gunawan, Budi; Neary, Vincent S; Hill, Craig; Chamorro, Leonardo
2012-01-01
Wake recovery constrains the downstream spacing and density of turbines that can be deployed in turbine farms and limits the amount of energy that can be produced at a hydrokinetic energy site. This study investigates the wake recovery at the downstream of a 1:10 axial flow turbine model using a pulse-to-pulse coherent Acoustic Doppler Profiler (ADP). In addition, turbine inflow and outflow velocities were measured for calculating the thrust on the turbine. The result shows that the depth-averaged longitudinal velocity recovers to 97% of the inflow velocity at 35 turbine diameter (D) downstream of the turbine.
Modeling the effect of varying swim speeds on fish passage through velocity barriers
Castro-Santos, T.
2006-01-01
The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption that fish swim at a constant speed regardless of the speed of flow. This paper demonstrates how the maximum distance of ascent through velocity barriers can be estimated from the swim speed-fatigue time relationship, allowing for variation in both swim speed and water velocity.
Modeling velocity in gradient flows with coupled-map lattices with advection.
Lind, Pedro G; Corte-Real, João; Gallas, Jason A C
2002-07-01
We introduce a simple model to investigate large scale behavior of gradient flows based on a lattice of coupled maps which, in addition to the usual diffusive term, incorporates advection, as an asymmetry in the coupling between nearest neighbors. This diffusive-advective model predicts traveling patterns to have velocities obeying the same scaling as wind velocities in the atmosphere, regarding the advective parameter as a sort of geostrophic wind. In addition, the velocity and wavelength of traveling wave solutions are studied. In general, due to the presence of advection, two regimes are identified: for strong diffusion the velocity varies linearly with advection, while for weak diffusion a power law is found with a characteristic exponent proportional to the diffusion. PMID:12241473
Site-Specific Velocity and Density Model for the Waste Treatment Plant, Hanford, Washington.
Rohay, Alan C.; Brouns, Thomas M.
2007-06-27
This report documents the work conducted under the SBP to develop a shear wave and compressional wave velocity and density model specific to the WTP site. Section 2 provides detailed background information on the WTP site and its underlying geology as well as on the Seismic Boreholes Project activities leading up to the Vs and Vp measurements. In Section 3, methods employed and results obtained are documented for measurements of Vs and Vp velocities in basalts and interbeds. Section 4 provides details on velocity measurements in the sediments underlying the WTP. Borehole gravity measurements of density of the subsurface basalt and sediments are described in Section 5. Section 6 describes the analysis of data presented in section 3-5, and presents the overall velocity and density model for the WTP site.
A distributed, dynamic, parallel computational model: the role of noise in velocity storage
Merfeld, Daniel M.
2012-01-01
Networks of neurons perform complex calculations using distributed, parallel computation, including dynamic “real-time” calculations required for motion control. The brain must combine sensory signals to estimate the motion of body parts using imperfect information from noisy neurons. Models and experiments suggest that the brain sometimes optimally minimizes the influence of noise, although it remains unclear when and precisely how neurons perform such optimal computations. To investigate, we created a model of velocity storage based on a relatively new technique–“particle filtering”–that is both distributed and parallel. It extends existing observer and Kalman filter models of vestibular processing by simulating the observer model many times in parallel with noise added. During simulation, the variance of the particles defining the estimator state is used to compute the particle filter gain. We applied our model to estimate one-dimensional angular velocity during yaw rotation, which yielded estimates for the velocity storage time constant, afferent noise, and perceptual noise that matched experimental data. We also found that the velocity storage time constant was Bayesian optimal by comparing the estimate of our particle filter with the estimate of the Kalman filter, which is optimal. The particle filter demonstrated a reduced velocity storage time constant when afferent noise increased, which mimics what is known about aminoglycoside ablation of semicircular canal hair cells. This model helps bridge the gap between parallel distributed neural computation and systems-level behavioral responses like the vestibuloocular response and perception. PMID:22514288
NASA Astrophysics Data System (ADS)
Hawley, B. W.; Zandt, G.; Smith, R. B.
1981-08-01
An iterative inversion technique has been developed that uses the direct P and S wave arrival times from local earthquakes to compute simultaneously a three-dimensional velocity structure and relocated hypocenters. Crustal structure is modeled by subdividing flat layers into rectangular blocks. An interpolation function is used to smoothly vary velocities between blocks, allowing ray trace calculations of travel times in a three-dimensional medium. Tests using synthetic data from known models show that solutions are reasonably independent of block size and spatial distribution but are sensitive to the choice of layer thicknesses. Application of the technique to observed earthquake data from north-central Utah shows the following: (1) lateral velocity variations in the crust as large as 7% occur over 30-km distances, (2) earthquake epicenters computed with the three-dimensional velocity structure were shifted an average of 3.0 km from locations determined assuming homogeneous flat layered models, and (3) the laterally varying velocity structure correlates with anomalous variations in the local gravity and aeromagnetic fields, suggesting that the new velocity information can be valuable in acquiring a better understanding of crustal structure.
SALSA3D : a global 3D p-velocity model of the Earth's crust and mantle for improved event location.
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
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.
A global 3D P-velocity model of the Earth's crust and mantle for improved event location : SALSA3D.
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
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.
No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1
NASA Technical Reports Server (NTRS)
Argus, Donald F.; Gordon, Richard G.
1991-01-01
NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.
No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1
NASA Astrophysics Data System (ADS)
Argus, Donald F.; Gordon, Richard G.
1991-11-01
NNR-NUVEL1 is presented which is a model of plate velocities relative to the unique reference frame defined by requiring no-net-rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model NUVEL-1 (DeMets et al., 1990). In NNR-NUVEL1, the Pacific plate rotates in a right-handed sense relative to the no-net-rotation reference frame at 0.67 deg/m.y. about 63 deg S, 107 deg E. At Hawaii the Pacific plate moves relative to the no-net-rotation reference frame at 70 mm/yr, which is 25 mm/yr slower than the Pacific plate moves relative to the hotspots. Differences between NNR-NUVEL1 and HS2-NUVEL1 are described. The no-net-rotation reference frame differs significantly from the hotspot reference frame. If the difference between reference frames is caused by motion of the hotspots relative to a mean-mantle reference frame, then hotspots beneath the Pacific plate move with coherent motion towards the east-southeast. Alternatively, the difference between reference frames can show that the uniform drag, no-net-torque reference frame, which is kinematically equivalent to the no-net-rotation reference frame, is based on a dynamically incorrect premise.
Hill-type muscle model with serial damping and eccentric force-velocity relation.
Haeufle, D F B; Günther, M; Bayer, A; Schmitt, S
2014-04-11
Hill-type muscle models are commonly used in biomechanical simulations to predict passive and active muscle forces. Here, a model is presented which consists of four elements: a contractile element with force-length and force-velocity relations for concentric and eccentric contractions, a parallel elastic element, a series elastic element, and a serial damping element. With this, it combines previously published effects relevant for muscular contraction, i.e. serial damping and eccentric force-velocity relation. The model is exemplarily applied to arm movements. The more realistic representation of the eccentric force-velocity relation results in human-like elbow-joint flexion. The model is provided as ready to use Matlab and Simulink code. PMID:24612719
NASA Astrophysics Data System (ADS)
Begnaud, M. L.; Ballard, S.; Young, C. J.; Hipp, J. R.; Encarnacao, A.; Phillips, W. S.; Chael, E. P.; Rowe, C. A.
2012-12-01
We are developing a global 3D P wave velocity model of the Earth's crust and mantle using seismic tomography to assess improvement to seismic event locations obtained using high quality 3D Earth models in lieu of 1D and 2/2.5D models. We present the most recent version of SALSA3D (SAndia LoS Alamos 3D) version 1.9, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set 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. For this current version, we employ more robust data quality control measures than previously used, as well as additional global GT data sources. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays into representative rays. 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 layer crustal model derived from the NNSA Unified model in Eurasia and Crust 2.0 model everywhere else, overlying 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 in areas where the data warrant such a refinement. In previous versions, we based this refinement on velocity changes from previous model iterations. For the current version, we utilize the diagonal of the model resolution matrix to control where grid refinement occurs, resulting in more consistent and continuous areas of refinement than before. In addition to the changes in grid refinement, we also employ a more robust convergence criterion between successive grid refinements, allowing a better fit to first broader model features, then progressively to finer ones. 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 ~400 processors. We compare the travel-time prediction and location capabilities to standard 1D and 2/2.5D 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. For the current version of the model, we test using the full 3D covariance matrix to calculate path-dependent travel time uncertainty rather than standard 1D, distance-dependent uncertainty. The SALSA3D model reduces mislocation over the standard 1D ak135 model regardless of Pn to P ratio, with the improvement being most pronounced at higher azimuthal gaps. SALSA3D also reduces mislocation compared to the combined RSTT/ak135 model (2.5D - RSTT for regional phases), with SALSA3D and RSTT performing about the same when using only Pn arrivals in location tests.
NASA Astrophysics Data System (ADS)
Yetirmishli, G. C.; Kazimova, S. E.; Kazimov, I. E.
2011-09-01
We present the method for determining the velocity model of the Earth's crust and the parameters of earthquakes in the Middle Kura Depression from the data of network telemetry in Azerbaijan. Application of this method allowed us to recalculate the main parameters of the hypocenters of the earthquake, to compute the corrections to the arrival times of P and S waves at the observation station, and to significantly improve the accuracy in determining the coordinates of the earthquakes. The model was constructed using the VELEST program, which calculates one-dimensional minimal velocity models from the travel times of seismic waves.
Modelling of developing nearly homogeneous turbulence of velocity and scalar fields
NASA Astrophysics Data System (ADS)
Bondarchuk, V. U.; Kolovandin, B. A.; Martynenko, O. G.
1991-01-01
Based on the second-order model suggested by Kolovandin and Martynenko (1990), numerical modeling of the nearly homogeneous turbulence of the velocity and transported passive scalar field is considered. The work is aimed at a detailed study of the effect exerted by the basic factors of turbulence generation - the gradients of the averaged velocity and scalar values - on the evolution in time of the statistical characteristics of turbulence which, within the framework of the second-order model, determine the processes of turbulent momentum and heat transfer at arbitrary turbulent Reynolds and Peclet numbers.
UCVM: An Open Source Framework for 3D Velocity Model Research
NASA Astrophysics Data System (ADS)
Gill, D.; Maechling, P. J.; Jordan, T. H.; Plesch, A.; Taborda, R.; Callaghan, S.; Small, P.
2013-12-01
Three-dimensional (3D) seismic velocity models provide fundamental input data to ground motion simulations, in the form of structured or unstructured meshes or grids. Numerous models are available for California, as well as for other parts of the United States and Europe, but models do not share a common interface. Being able to interact with these models in a standardized way is critical in order to configure and run 3D ground motion simulations. The Unified Community Velocity Model (UCVM) software, developed by researchers at the Southern California Earthquake Center (SCEC), is an open source framework designed to provide a cohesive way to interact with seismic velocity models. We describe the several ways in which we have improved the UCVM software over the last year. We have simplified the UCVM installation process by automating the installation of various community codebases, improving the ease of use.. We discuss how UCVM software was used to build velocity meshes for high-frequency (4Hz) deterministic 3D wave propagation simulations, and how the UCVM framework interacts with other open source resources, such as NetCDF file formats for visualization. The UCVM software uses a layered software architecture that transparently converts geographic coordinates to the coordinate systems used by the underlying velocity models and supports inclusion of a configurable near-surface geotechnical layer, while interacting with the velocity model codes through their existing software interfaces. No changes to the velocity model codes are required. Our recent UCVM installation improvements bundle UCVM with a setup script, written in Python, which guides users through the process that installs the UCVM software along with all the user-selectable velocity models. Each velocity model is converted into a standardized (configure, make, make install) format that is easily downloaded and installed via the script. UCVM is often run in specialized high performance computing (HPC) environments, so we have included checks during the installation process to alert users about potential conflicts. We also describe how UCVM can create an octree-based database representation of a velocity model which can be directly queried by 3D wave propagation simulation codes using the open source etree library. We will discuss how this approach was used to create an etree for a 4-Hz Chino Hills simulation. Finally, we show how the UCVM software can integrate NetCDF utility code to produce 3D velocity model files compatible with open source NetCDF data viewers. This demonstrates that UCVM can generate meshes from any compatible community velocity model and that the resulting models can be visualized without the need for complex secondary tools. This illustrates how developers can easily write tools that can convert data from one format to another using the UCVM API.
Developing a Crustal and Upper Mantle Velocity Model for the Brazilian Northeast
NASA Astrophysics Data System (ADS)
Julia, J.; Nascimento, R.
2013-05-01
Development of 3D models for the earth's crust and upper mantle is important for accurately predicting travel times for regional phases and to improve seismic event location. The Brazilian Northeast is a tectonically active area within stable South America and displays one of the highest levels of seismicity in Brazil, with earthquake swarms containing events up to mb 5.2. Since 2011, seismic activity is routinely monitored through the Rede 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.
Sotani, Hajime [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Tatekawa, Takayuki [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Department of Physics, Ochanomizu University, 2-1-1 Otsuka, Bunkyo, Tokyo 112-8610 (Japan); Department of Physics, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)
2006-01-15
For the evolution of density fluctuation in nonlinear cosmological dynamics, adhesion approximation (AA) is proposed as a phenomenological model, which is especially useful for describing nonlinear evolution. However, the origin of the artificial viscosity in AA is not clarified. Recently, Buchert and Dominguez report if the velocity dispersion of the dust fluid is regarded as isotropic, it works on a principle similar to viscosity or effective pressure, and they consider isotropic velocity dispersion as the origin of the artificial viscosity in AA. They name their model the Euler-Jeans-Newton (EJN) model. In this paper, we focus on the velocity distribution in AA and the EJN model and examine the time evolution in both models. We find the behavior of AA differs from that of the EJN model, i.e., although the peculiar velocity in the EJN model oscillates, that in AA is monotonically decelerated due to viscosity without oscillation. Therefore it is hard to regard viscosity in AA as effective pressure in the EJN model.
Kirchhoff prestack depth migration in velocity models with and without rotation of the tensor of
Cerveny, Vlastislav
: Seismic Waves in Complex 3-D Structures, Report 23 (Department of Geophysics, Charles University, PragueKirchhoff prestack depth migration in velocity models with and without rotation of the tensor models in order to show the impact of rotation of the tensor of elastic moduli on migrated images
Kirchhoff prestack depth migration in orthorhombic velocity models with differently rotated tensors
Cerveny, Vlastislav
of the tensor of elastic moduli. Seismic Waves in Complex 3D Structures, 24 (2014), 5975 (ISSN 2336Kirchhoff prestack depth migration in orthorhombic velocity models with differently rotated tensors moduli on migrated images. The recorded wave field is generated in models composed of two homogeneous
Fuentes, Olac
to produce a velocity model of the Earth's crust using evolutionary and seismic tomography algorithms search point to a first arrival traveltime seismic tomography algorithm, which then computes the final, and does not require an expert-supplied one-dimensional model for the seismic tomography procedure
HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION
Mellors, R; Gok, R; Sandvol, E
2007-07-10
The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Crustal and upper mantle velocities show great heterogeneity in this region and regional phases display variations in both amplitudes and travel time. Furthermore, due to a lack of quality data, the region has largely been unexplored in terms of the detailed lithospheric seismic structure. A unified high-resolution 3D velocity and attenuation model of the crust and upper mantle will be developed and calibrated. This model will use new data from 23 new broadband stations in the region analyzed with a comprehensive set of techniques. Velocity models of the crust and upper mantle will be developed using a joint inversion of receiver functions and surface waves. The surface wave modeling will use both event-based methods and ambient noise tomography. Regional phase (Pg, Pn, Sn, and Lg) Q model(s) will be constructed using the new data in combination with existing data sets. The results of the analysis (both attenuation and velocity modeling) will be validated using modeling of regional phases, calibration with selected events, and comparison with previous work. Preliminary analyses of receiver functions show considerable variability across the region. All results will be integrated into the KnowledgeBase.
Low velocity impact experiments on the explosive LX-10 with modeling of reaction violence
NASA Astrophysics Data System (ADS)
Chidester, Steven; Garcia, Frank; Vandersall, Kevin S.; Tarver, Craig M.; Ferranti, Louis
2012-03-01
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.
Evaluation of an imputed pitch velocity model of the auditory tau effect.
Henry, Molly J; McAuley, J Devin; Zaleha, Marta
2009-08-01
This article extends an imputed pitch velocity model of the auditory kappa effect proposed by Henry and McAuley (2009a) to the auditory tau effect. Two experiments were conducted using an AXB design in which listeners judged the relative pitch of a middle target tone (X) in ascending and descending three-tone sequences. In Experiment 1, sequences were isochronous, establishing constant fast, medium, and slow velocity conditions. No systematic distortions in perceived target pitch were observed, and thresholds were similar across velocity conditions. Experiment 2 introduced to-be-ignored variations in target timing. Variations in target timing that deviated from constant velocity conditions introduced systematic distortions in perceived target pitch, indicative of a robust auditory tau effect. Consistent with an auditory motion hypothesis, the magnitude of the tau effect was larger at faster velocities. In addition, the tau effect was generally stronger for descending sequences than for ascending sequences. Combined with previous work on the auditory kappa effect, the imputed velocity model and associated auditory motion hypothesis provide a unified quantitative account of both auditory tau and kappa effects. In broader terms, these findings add support to the view that pitch and time relations in auditory patterns are fundamentally interdependent. PMID:19633354
Traffic stability of a car-following model considering driver’s desired velocity
NASA Astrophysics Data System (ADS)
2015-07-01
In this paper, a new car-following model is proposed by considering driver’s desired velocity according to Transportation Cyber Physical Systems. The effect of driver’s desired velocity on traffic flow has been investigated through linear stability theory and nonlinear reductive perturbation method. The linear stability condition shows that driver’s desired velocity effect can enlarge the stable region of traffic flow. From nonlinear analysis, the Burgers equation and mKdV equation are derived to describe the evolution properties of traffic density waves in the stable and unstable regions respectively. Numerical simulation is carried out to verify the analytical results, which reveals that traffic congestion can be suppressed efficiently by taking driver’s desired velocity effect into account.
Fabry-Perot interferometer measurement of static temperature and velocity for ASTOVL model tests
NASA Technical Reports Server (NTRS)
Kourous, Helen E.; Seacholtz, Richard G.
1995-01-01
A spectrally resolved Rayleigh/Mie scattering diagnostic was developed to measure temperature and wing-spanwise velocity in the vicinity of an ASTOVL aircraft model in the Lewis 9 x 15 Low Speed Wind Tunnel. The spectrum of argon-ion laser light scattered by the air molecules and particles in the flow was resolved with a Fabry-Perot interferometer. Temperature was extracted from the spectral width of the Rayleigh scattering component, and spanwise gas velocity from the gross spectral shift. Nozzle temperature approached 800 K, and the velocity component approached 30 m/s. The measurement uncertainty was about 5 percent for the gas temperature, and about 10 m/s for the velocity. The large difference in the spectral width of the Mie scattering from particles and the Rayleigh scattering from gas molecules allowed the gas temperature to be measured in flow containing both naturally occurring dust and LDV seed (both were present).
Quasilinear model for energetic particle diffusion in radial and velocity space
NASA Astrophysics Data System (ADS)
Waltz, R. E.; Bass, E. M.; Staebler, G. M.
2013-04-01
A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 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.
Quasilinear model for energetic particle diffusion in radial and velocity space
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
A quasilinear model for passive energetic particle (EP) turbulent diffusion in radial and velocity space is fitted and tested against nonlinear gyrokinetic tokamak simulations with the GYRO code [J. Candy and R. E. Waltz, Phys. Rev. Lett. 91, 045001 (2003)]. Off diagonal elements of a symmetric positive definite 2 Multiplication-Sign 2 EP diffusion matrix account for fluxes up radial (energy) gradients driven by energy (radial) gradients of the EP velocity space distribution function. The quasilinear ratio kernel of the model is provided by a simple analytic formula for the EP radial and velocity space EP diffusivity relative to radial thermal ion energy diffusivity at each linear mode of the turbulence driven by the thermal plasma. The TGLF [G. M. Staebler, J. E. Kinsey, and R. E. Waltz, Phys. Plasmas 14, 0055909 (2007); ibid. 15, 0055908 (2008)] tokamak transport model provides the linear mode frequency and growth rates to the kernel as well as the nonlinear spectral weight for each mode.
Modeling the effect of humidity on the threshold friction velocity of coal particles
NASA Astrophysics Data System (ADS)
Zhang, Xiaochun; Chen, Weiping; Ma, Chun; Zhan, Shuifen
2012-09-01
Coal particles emission could cause serious air pollution in coal production region and transport region. In coal mining industry, large amounts of water are regularly spayed to coal piles to prevent dust emission from the coal particles. The mechanism behind this measure is to manage the threshold friction velocity, which is an important parameter in controlling wind erosion and dust emission. Bagnold has developed a threshold friction velocity model for soil particles. However, the Bagnold model cannot be applied directly to coal particles as coal particles are quite different from soils in physical and chemical properties. We studied and modeled threshold friction velocity of coal particles under different humidities by using a wind tunnel. Results showed that the effects of humidity on coal particles' threshold friction velocity are related to the hydrophilic effect and adhesive effect. Bagnold model can be corrected by two new parameter items which explained the two effects. The new model, agreed well with wind tunnel measurements for coal particles with different size categories. Despite the fact the new model was developed for coal particles, its physical basis may allow the model application to other wind susceptible particles.
NASA Astrophysics Data System (ADS)
Girshick, Steven; Larriba-Andaluz, Carlos
2014-10-01
It has been hypothesized that deposition of very small silicon nanoparticles during plasma-enhanced chemical vapor deposition of silicon, under conditions where the particle impact velocity is high enough to cause particle melting/amorphization, can lead to epitaxial film growth at low temperature. One way to accomplish this might be by pulsing the RF plasma and applying a positive DC bias during the afterglow of each pulse. The negatively charged particles, trapped in the plasma during the ON phase of each pulse, are accelerated to the substrate during the afterglow. To assess the feasibility of such an approach, we conducted numerical simulations of a pulsed capacitively-coupled RF Ar-silane plasma. We used a modified version of a previously reported 1D model, in which a nanodusty plasma is simulated by self-consistently coupling models for the plasma, chemistry and aerosol. Preliminary results indicate that the approach is feasible, but that parameters such as pulse frequency and duty cycle are important in limiting particle growth and in maximizing fluxes of energetic nanoparticles to the substrate. Partially supported by US Dept. of Energy Office of Fusion Energy Science (DE-SC0001939) and US National Science Foundation (CHE-124752).
NASA Astrophysics Data System (ADS)
Begnaud, M. L.; Ballard, S.; Young, C. J.; Hipp, J. R.; Encarnacao, A.; Phillips, W.; Chael, E. P.; Rowe, C. A.
2013-12-01
We demonstrate the ability of SALSA3D (SAndia LoS Alamos 3D) version 2.1, a global 3D P-wave velocity model of the Earth's crust and mantle, to reduce mislocations compared to those derived from standard 1D and 2-2.5D models, for a set of realizations using only IMS stations - an example of a sparse network whose locations depend heavily on the velocity model employed - and a carefully chosen group of globally-distributed ground truth (GT) events. Our model is derived from the latest version of the GT catalog of P/Pn travel-time picks assembled by Los Alamos National Laboratory. The model uses the GeoTess triangular tessellation system described by Ballard et al. (2009; www.sandia.gov/geotess), which incorporates variable resolution both laterally and radially. For our starting model, we use a simplified version of the NNSA Unified model in Eurasia and the Crust 2.0 model elsewhere. Damping reduces velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness via progressive grid refinement using the diagonal of the model resolution matrix to determine where the data warrant such a refinement. Our approach provides more consistent and continuous areas of refinement, producing a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework of ~400 processors. The global IMS network consists of approximately 150 primary and auxiliary stations, forming a pre-defined, sparse network with which to locate seismic events. We compare the travel-time prediction and location capabilities of SALSA3D to standard 1D and 2/2.5D models via location tests on a global event set with GT of 5 km or better. Using Pn and P picks from IMS stations only, we generate different realizations of station distributions, yielding a range of azimuthal coverage and ratios of teleseismic to regional arrivals, with which we test the accuracy and precision of relocation. We test using the full 3D covariance matrix of the current model to calculate path-dependent travel time uncertainty, rather than applying standard, 1D, distance-dependent uncertainty. SALSA3D reduces mislocation over the standard 1D ak135 model regardless of Pn to P ratio, with the most pronounced improvement at higher azimuthal gaps. SALSA3D also reduces mislocation compared to the combined RSTT/ak135 model (2.5D - RSTT for regional phases), with minimal improvement over RSTT when only regional Pn phases are used to compute locations.
Y. P. Jing; H. J. Mo; G. Boerner
1997-12-15
We show, with the help of large N-body simulations, that the real-space two-point correlation function and pairwise velocity dispersion of galaxies can both be measured reliably from the Las Campanas Redshift Survey. The real-space correlation function is well fitted by the power law $\\xi(r)=(r_0/r)^\\gamma$ with $r_0=(5.06\\pm0.12)\\mpc$ and $\\gamma=1.862\\pm 0.034$, and the pairwise velocity dispersion at $1\\mpc$ is $(570\\pm 80)\\kms$. A detailed comparison between these observational results and the predictions of current CDM cosmogonies is carried out. We construct 60 mock samples for each theoretical model from a large set of high resolution N-body simulations, which allows us to include various observational selection effects in the analyses and to use exactly the same methods for both real and theoretical samples. We demonstrate that such a procedure is essential in the comparison between models and observations. The observed two-point correlation function is significantly flatter than the mass correlation function in current CDM models on scales $\\la 1\\mpc$. The observed pairwise velocity dispersion is also lower than that of dark matter particles in these models. We propose a simple antibias model to explain these discrepancies. This model assumes that the number of galaxies per unit dark matter mass, $N/M$, decreases with the mass of dark haloes. The predictions of CDM models with $\\sigma_8\\Omega_0^{0.6}\\sim 0.4$-0.5 and $\\Omega_0 h\\sim 0.2$ are in agreement with the observational results, if the trend of $N/M$ with $M$ is at the level already observed for rich clusters of galaxies. Thus CDM models with cluster-abundance normalization are consistent with the observed correlation function and pairwise velocity dispersion of galaxies. A high level of velocity bias is not required in these models.
A model of the near-surface seismic velocity: southern San Joaqin Valley, California
Ferry, James Gerard
1987-01-01
A MODEL OF THE NEAR-SURFACE SEISMIC VELOCITY; SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA A Thesis JAMES GERARD FERRY Submitted to the Graduate College of Texas AErM University in partial fulfillment of t, he requirement for the degree of MASTER... OF SCIENCE August iq87 Major Subject: Geophysics A MODEL OF THE NEAR-SURFACE SEISMIC VELOCITY; SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA A Thesis JAMES GERARD FERRY Approved as to style and content by: Richard L. Carlson (Chairman of Committee) Anth y...
NASA Astrophysics Data System (ADS)
Zheng, Yi; Zhang, Pengjie; Jing, Yipeng
2015-02-01
Measuring the volume weighted velocity power spectrum suffers from a severe systematic error due to imperfect sampling of the velocity field from the inhomogeneous distribution of dark matter particles/halos in simulations or galaxies with velocity measurement. This "sampling artifact" depends on both the mean particle number density 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.
NASA Technical Reports Server (NTRS)
Schmitt, G. A.; Abreu, V. J.; Hays, P. B.
1981-01-01
Thermal and nonthermal O(1D) number density profiles are calculated. The two populations are assumed to be coupled by a thermalization cross-section which determines the loss and production in the nonthermal and thermal populations, respectively. The sources, sinks and transport of the two populations are used to model volume emission rate profiles at 6300 A. The 6300 A brightness measured by the Visible Airglow Experiment is then used to establish the presence of the nonthermal population and to determine the thermalization cross-section.
Lin, G.; Thurber, C.H.; Zhang, H.; Hauksson, E.; Shearer, P.M.; Waldhauser, F.; Brocher, T.M.; Hardebeck, J.
2010-01-01
We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP=VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE directionand 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling.
Polar versus Cartesian velocity models for maneuvering target tracking with IMM
NASA Astrophysics Data System (ADS)
Laneuville, Dann
This paper compares various model sets in different IMM filters for the maneuvering target tracking problem. The aim is to see whether we can improve the tracking performance of what is certainly the most widely used model set in the literature for the maneuvering target tracking problem: a Nearly Constant Velocity model and a Nearly Coordinated Turn model. Our new challenger set consists of a mixed Cartesian position and polar velocity state vector to describe the uniform motion segments and is augmented with the turn rate to obtain the second model for the maneuvering segments. This paper also gives a general procedure to discretize up to second order any non-linear continuous time model with linear diffusion. Comparative simulations on an air defence scenario with a 2D radar, show that this new approach improves significantly the tracking performance in this case.
NASA Technical Reports Server (NTRS)
Friesen, W. J.; Moore, J. A.
1973-01-01
Velocity-profile, pitot-pressure, and supplemental probe measurements were made at the nozzle exist of an expansion tunnel (a modification to the Langley pilot model expansion tube) for a nozzle net condition of a nitrogen test sample with a velocity of 4.5 km/sec and a density 0.005 times the density of nitrogen at standard conditions, both with the nozzle initially immersed in a helium atmosphere and with the nozzle initially evacuated. The purpose of the report is to present the results of these measurements and some of the physical properties of the nitrogen test sample which can be inferred from the measured results. The main conclusions reached are that: the velocity profiles differ for two nozzle conditions; regions of the flow field can be found where the velocity is uniform to within 5 percent and constant for several hundred microseconds; the velocity of the nitrogen test sample is reduced due to passage through the nozzle; and the velocity profiles do not significantly reflect the large variations which occur in the inferred density profiles.
NASA Astrophysics Data System (ADS)
Van Eester, Dirk; Lerche, Ernesto
2013-05-01
Both at low and higher cyclotron harmonics, properly accounting for finite Larmor radius effects is crucial in many ion cyclotron resonance frequency heating scenario's creating high energy tails. This paper discusses an extension TOMCAT-U of the 1D TOMCAT tokamak plasma wave equation solver (Van Eester and Koch 1998 Plasma Phys. Control. Fusion 40 1949) to arbitrary harmonics and arbitrary wavelengths while only keeping leading order terms in equilibrium variation terms. Rather than adopting the particle position, the guiding center position is used as the independent variable when writing down an expression for the dielectric response that is suitable for numerical application. This choice of independent variable yields intuitive expressions involving the Kennel-Engelmann operator which can directly be linked to the corresponding expressions in the RF diffusion operator appearing in the Fokker-Planck equation. It also guarantees that a positive definite power transfer from waves to particles is ensured for any of the wave modes in a plasma in which all populations have a Maxwellian distribution, as is expected from first principles. Rather than relying on a truncated Taylor series expansion of the dielectric response, an integrodifferential approach that retains all finite Larmor radius effects is proposed. To keep the required computation time for this generalized description reasonable, tabulation of integrals is intensively used. Although the accent is on the presentation of the upgraded formalism as well as the adopted recursions and tabulations, a few examples are provided to illustrate the potential of the new wave code that relies on these tabulations.
Modeling continuous seismic velocity changes due to ground shaking in Chile
NASA Astrophysics Data System (ADS)
Gassenmeier, Martina; Richter, Tom; Sens-Schönfelder, Christoph; Korn, Michael; Tilmann, Frederik
2015-04-01
In order to investigate temporal seismic velocity changes due to earthquake related processes and environmental forcing, we analyze 8 years of ambient seismic noise recorded by the Integrated Plate Boundary Observatory Chile (IPOC) network in northern Chile between 18° and 25° S. The Mw 7.7 Tocopilla earthquake in 2007 and the Mw 8.1 Iquique earthquake in 2014 as well as numerous smaller events occurred in this area. By autocorrelation of the ambient seismic noise field, approximations of the Green's functions are retrieved. The recovered function represents backscattered or multiply scattered energy from the immediate neighborhood of the station. To detect relative changes of the seismic velocities we apply the stretching method, which compares individual autocorrelation functions to stretched or compressed versions of a long term averaged reference autocorrelation function. We use time windows in the coda of the autocorrelations, that contain scattered waves which are highly sensitive to minute changes in the velocity. At station PATCX we observe seasonal changes in seismic velocity as well as temporary velocity reductions in the frequency range of 4-6 Hz. The seasonal changes can be attributed to thermal stress changes in the subsurface related to variations of the atmospheric temperature. This effect can be modeled well by a sine curve and is subtracted for further analysis of short term variations. Temporary velocity reductions occur at the time of ground shaking usually caused by earthquakes and are followed by a recovery. We present an empirical model that describes the seismic velocity variations based on continuous observations of the local ground acceleration. Our hypothesis is that not only the shaking of earthquakes provokes velocity drops, but any small vibrations continuously induce minor velocity variations that are immediately compensated by healing in the steady state. We show that the shaking effect is accumulated over time and best described by the integrated envelope of the ground acceleration over 1 day which is the discretization interval of the velocity measurements. In our model the amplitude of the velocity reduction as well as the recovery time are proportional to the size of the excitation. This model with the two free scaling parameters for the shaking induced velocity variation fits the data in remarkable detail. Additionally, a linear trend is observed that might be related to a recovery process from one or more earthquakes before our measurement period. For the Tocopilla earthquake in 2007 and the Iquique earthquake in 2014 velocity reductions are also observed at other stations of the IPOC network. However, a clear relationship between the ground shaking and the induced velocity reductions is not visible at other stations. We attribute the outstanding sensitivity of PATCX to ground shaking to the special geological setting of the station, where the material consists of relatively loose conglomerate with high pore volume.
Stabilization of traffic flow in optimal velocity model via delayed-feedback control
NASA Astrophysics Data System (ADS)
Jin, Yanfei; Hu, Haiyan
2013-04-01
Traffic jams may occur due to various reasons, such as traffic accidents, lane reductions and on-ramps. In order to suppress the traffic congestion in an optimal velocity traffic model without any driver's delay taken into account, a delayed-feedback control of both displacement and velocity differences is proposed in this study. By using the delay-independent stability criteria and the H?-norm, the delayed-feedback control can be determined to stabilize the unstable traffic flow and suppress the traffic jam. The numerical case studies are given to demonstrate and verify the new control method. Furthermore, a comparison is made between the new control method and the method proposed by Konishi et al. [K. Konishi, M. Hirai, H. Kokame, Decentralized delayed-feedback control of an optimal velocity traffic model, Eur. Phys. J. B 15 (2000) 715-722]. The results show that the new control method makes the traffic flow more stable and improves the control performance.
NASA Astrophysics Data System (ADS)
Hübsch, Florian; Marheineke, Nicole; Ritter, Klaus; Wegener, Raimund
2013-03-01
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 (thinning). 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- ? 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. Numerical results are discussed for a simplified melt-blowing model consisting of a system of random ordinary differential equations.
Macgregor-Scott, N.; Walter, A.
1988-01-01
Crustal velocity structure for the region near Coalinga, California, has been derived from both earthquake and explosion seismic phase data recorded along a NW-SE seismic-refraction profile on the western flank of the Great Valley east of the Diablo Range. Comparison of the two data sets reveals P-wave phases in common which can be correlated with changes in the velocity structure below the earthquake hypocenters. In addition, the earthquake records reveal secondary phases at station ranges of less than 20 km that could be the result of S- to P-wave conversions at velocity interfaces above the earthquake hypocenters. Two-dimensional ray-trace modeling of the P-wave travel times resulted in a P-wave velocity model for the western flank of the Great Valley comprised of: 1) a 7- to 9-km thick section of sedimentary strata with velocities similar to those found elsewhere in the Great Valley (1.6 to 5.2 km s-1); 2) a middle crust extending to about 14 km depth with velocities comparable to those reported for the Franciscan assemblage in the Diablo Range (5.6 to 5.9 km s-1); and 3) a 13- to 14-km thick lower crust with velocities similar to those reported beneath the Diablo Range and the Great Valley (6.5 to 7.30 km s-1). This lower crust may have been derived from subducted oceanic crust that was thickened by accretionary underplating or crustal shortening. -Authors
Velocity profile method for time varying resistance in minimal cardiovascular system models
NASA Astrophysics Data System (ADS)
Smith, Bram W.; Chase, J. Geoffrey; Nokes, Roger I.; Shaw, Geoffrey M.; David, Tim
2003-10-01
This paper investigates the fluid dynamics governing arterial flow used in lumped parameter cardiovascular system (CVS) models, particularly near the heart where arteries are large. Assumptions made in applying equations conventionally used in lumped parameter models are investigated, specifically that of constant resistance to flow. The Womersley number is used to show that the effects of time varying resistance must be modelled in the pulsatile flow through the large arteries near the heart. It is shown that the equation commonly used to include inertial effects in fluid flow calculations is inappropriate for including time varying resistance. A method of incorporating time varying resistance into a lumped parameter model is developed that uses the Navier-Stokes equations to track the velocity profile. Tests on a single-chamber model show a 17.5% difference in cardiac output for a single-chamber ventricle model when comparing constant resistance models with the velocity profile tracking method modelling time varying resistance. This increase in precision can be achieved using 20 nodes with only twice the computational time required. The method offers a fluid dynamically and physiologically accurate method of calculating large Womersley number pulsatile fluid flows in large arteries around the heart and valves. The proposed velocity profile tracking method can be easily incorporated into existing lumped parameter CVS models, improving their clinical application by increasing their accuracy.
NASA Astrophysics Data System (ADS)
Wilken, Dennis; Rabbel, Wolfgang
2010-05-01
In the years 2006 to 2008 we performed Airgun profiles to excite Scholte-waves at different locations in the North and Baltic sea. Scholte-wave energy was recorded using a specially developed Ocean-Bottom-Seismometer. The system is able to sample signals up to 11kHz and can thus be localised at seafloor with an accuracy of a few meters using traveltimes of high frequent seismic signals that are excited in the watercolumn. Scholte-wave recordings are added to common-receiver-gathers which are then inverted for shear-wave velocity structure by fitting modelled phase-slowness frequency dispersion spectra to spectra of the wavefield. By extracting local wavefields from the profile-gathers, multiple 1D Inversions of these fields at different offset-points lead to a 2D shear-wave velocity model of the profile. A new spectral misfit calculation was developed, working without the requirement of identification of the Scholte-wave dispersed modes in the spectra. For minimization of the misfit we implemented a new hybrid method using a combination of particle swarm optimization and a local downhill-simplex resulting in a resolution of global misfit minimum of about 7%. The method was used for shear-wave velocity inversion at four different locations in North and Baltic sea. Resulting models show very good coherence along each Profile and especially a very good correlation to high resolution reflection seismic sections of the same profiles.
Verley, Jason C.; Axness, Carl L.; Hembree, Charles Edward; Keiter, Eric Richard; Kerr, Bert
2012-04-01
Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools such as SPICE [1] can be used to analyze these threats, and typically rely on compact models for individual electrical components such as transistors and diodes. Compact models consist of a handful of differential and/or algebraic equations, and are derived by making simplifying assumptions to any of the many semiconductor transport equations. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of qualitative approximation, rather than mathematically correct solutions to the ambipolar diffusion equation. A practical consequence of this inaccuracy is that a given model calibration is trustworthy over only a narrow range of operating conditions. This report describes work to produce improved compact models for photocurrent. Specifically, an analytic model is developed for epitaxial diode structures that have a highly doped subcollector. The analytic model is compared with both numerical TCAD calculations, as well as the compact model described in reference [2]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the compact model from reference [2].
Exact realization of integer and fractional quantum Hall phases in U(1)×U(1) models in (2+1)d
Geraedts, Scott D., E-mail: sgeraedt@caltech.edu; Motrunich, Olexei I.
2013-07-15
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.
NASA Astrophysics Data System (ADS)
Simon, E.; Bertino, L.; Samuelsen, A.
2011-12-01
Combined state-parameter estimation in ocean biogeochemical models with ensemble-based Kalman filters is a challenging task due to the non-linearity of the models, the constraints of positiveness that apply to the variables and parameters, and the non-Gaussian distribution of the variables in which they result. Furthermore, these models are sensitive to numerous parameters that are poorly known. Previous works [1] demonstrated that the Gaussian anamorphosis extensions of ensemble-based Kalman filters were relevant tools to perform combined state-parameter estimation in such non-Gaussian framework. In this study, we focus on the estimation of the grazing preferences parameters of zooplankton species. These parameters are introduced to model the diet of zooplankton species among phytoplankton species and detritus. They are positive values and their sum is equal to one. Because the sum-to-one constraint cannot be handled by ensemble-based Kalman filters, a reformulation of the parameterization is proposed. We investigate two types of changes of variables for the estimation of sum-to-one constrained parameters. The first one is based on Gelman [2] and leads to the estimation of normal distributed parameters. The second one is based on the representation of the unit sphere in spherical coordinates and leads to the estimation of parameters with bounded distributions (triangular or uniform). These formulations are illustrated and discussed in the framework of twin experiments realized in the 1D coupled model GOTM-NORWECOM with Gaussian anamorphosis extensions of the deterministic ensemble Kalman filter (DEnKF). [1] Simon E., Bertino L. : Gaussian anamorphosis extension of the DEnKF for combined state and parameter estimation : application to a 1D ocean ecosystem model. Journal of Marine Systems, 2011. doi :10.1016/j.jmarsys.2011.07.007 [2] Gelman A. : Method of Moments Using Monte Carlo Simulation. Journal of Computational and Graphical Statistics, 4, 1, 36-54, 1995.
The National Oceanic and Atmospheric Administration's Multi-Layer Model (NOAA-MLM) is used by several operational dry deposition networks for estimating the deposition velocity of O , SO , HNO , and particles. The NOAA-MLM requires hourly values of meteorological variables and...
Testing Community Velocity Models for Southern California Using the Ambient Seismic Field
Prieto, Germán A.
of community velocity models (Southern California Earthquake Cen- ter [SCEC] CVM 4.0 and CVM-H 5.2) used for strong ground-motion prediction for future scenario earthquakes in southern California. Comparisons- terpretation of wave intensities (e.g., Sato and Fehler, 1998) while the phase information received less
J. O. Egerton; M. G. Rasul; R. J. Brown
The mixing and dispersion created downstream of the marine propeller is critical to the spread and impact of pollutants introduced into the water from outboard motors. Such propulsion systems vent exhaust gases under water where a complex mass transfer of missions occurs to water. This paper presents the modelling and simulation of the propeller velocity profiles and initial plume spread
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...
The mean velocity of two-state models of molecular motor
Yunxin Zhang
2011-08-09
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.
Stochastic optimal velocity model and its long-lived metastability Masahiro Kanai
Stochastic optimal velocity model and its long-lived metastability Masahiro Kanai Graduate School Tetsuji Tokihiro Graduate School of Mathematical Sciences, University of Tokyo, 3-8-1 Komaba, Tokyo 153 simple exclusion process and the zero range process. More- over, it is regarded as a stochastic extension
Optimization of the structural Gabor functions in a homogeneous velocity model
Cerveny, Vlastislav
Optimization of the structural Gabor functions in a homogeneous velocity model for a zero-o#11;set for all shots during seismic re ection survey, based on the correspondence be- tween the structural Gabor consists in specifying the #12;nite set of structural Gabor functions to which the wanted deviations
Robust velocity computation from a biologically motivated model of motion perception
Johnston, Alan
motion pathway do not cope well with image sequences in which a moving pattern is superimposed upon a static texture. The use of non- linear operations and the need for contrast normalization in motion£uence motion computation. A generic model for computing velocity based on a contrast-normalized, opponent
Evaluation of an Imputed Pitch Velocity Model of the Auditory Kappa Effect
ERIC Educational Resources Information Center
Henry, Molly J.; McAuley, J. Devin
2009-01-01
Three experiments evaluated an imputed pitch velocity model of the auditory kappa effect. Listeners heard 3-tone sequences and judged the timing of the middle (target) tone relative to the timing of the 1st and 3rd (bounding) tones. Experiment 1 held pitch constant but varied the time (T) interval between bounding tones (T = 728, 1,000, or 1,600…
Peter Schuck
2000-01-01
A new method for the size-distribution analysis of polymers by sedimentation velocity analytical ultracentrifugation is described. It exploits the ability of Lamm equation modeling to discriminate between the spreading of the sedimentation boundary arising from sample heterogeneity and from diffusion. Finite element solutions of the Lamm equation for a large number of discrete noninteracting species are combined with maximum entropy
Assimilation of moored velocity data in a model of coastal wind-driven circulation off Oregon
Kurapov, Alexander
29 September 2005. [1] Horizontal current measurements from an array of moored acoustic Doppler the upwelling season of MayAugust 2001. Model results are compared against independent moored and ship survey to as K05) that describes assimilation of horizontal velocities from moored acoustic Doppler profilers
NASA Astrophysics Data System (ADS)
Begnaud, M. L.; Ballard, S.; Young, C. J.; Hipp, J. R.; Chang, M.; Encarnacao, A.; Rowe, C. A.; Phillips, W. S.; Steck, L.
2011-12-01
To test the hypothesis that high quality 3D Earth models will produce seismic event locations that are more accurate and more precise than currently used 1D and 2/2.5D models, 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 3D) version 1.7, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth (GT) events, compared to existing models and/or systems. Our model is derived from the latest version of the 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 ~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 layer crustal model derived from the NNSA Unified model in Eurasia and Crust 2.0 model elsewhere, 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 in areas where the data warrant it. In previous versions of SALSA3D, we based this refinement on velocity changes from previous model iterations. For version 1.7, we utilize the diagonal of the model resolution matrix to control where grid refinement occurs, resulting in more consistent and continuous areas of refinement than before. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. 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. 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 the standard 1D ak135 model regardless of Pn to P ratio, with improvement most pronounced at higher azimuthal gaps. We currently are testing the use of the full model covariance matrix to produce realistic path-dependent travel time uncertainty during location tests, replacing the standard, distance-dependent, path-independent uncertainty typically used in location algorithms.
NASA Technical Reports Server (NTRS)
Raphan, T.; Sturm, D.; Cohen, B. (Principal Investigator)
1991-01-01
1. A generalized three-dimensional state space model of visual vestibular interaction was developed. Matrix and dynamical system operators associated with inputs from the semicircular canals, otolith velocity estimator, and the visual system have been incorporated into the model, which focus on their relationship to the velocity storage integrator. 2. A relationship was postulated between the eigenvalues and the direction of the eigenvectors of the system matrix and the orientation of the spatial vertical. It was assumed that the system matrix for a tilted position was a composition of two linear transformations of the system matrix for the upright position. One transformation modifies the eigenvalues of the system matrix, whereas another rotates the eigenvectors of the system matrix. The pitch and roll eigenvectors rotate with the head, whereas the yaw axis eigenvector remains approximately spatially invariant. 3. Based on the three-dimensional model, a computational procedure was formulated to identify the eigenvalues and eigenvectors of the system matrix with the use of a modification of the marquardt algorithm. With the use of data obtained from a monkey, it was shown that the three-dimensional behavior of velocity storage cannot be predicted solely in terms of its time constants, i.e., the inverse of its eigenvalues. With the use of the same eigenvalues the data could either be fit or not fit, depending on the eigenvector directions. Therefore, it is necessary to specify eigenvector directions when characterizing velocity storage in three dimensions. 4. Parameters found with the use of the Marquardt algorithm were incorporated into the model. Diagonal matrices in a head coordinate frame were introduced for coupling the visual system to the integrator and to the direct optokinetic pathway. Simulations of optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) were run. The model predicted the behavior of yaw and pitch OKN and OKAN when the animal is upright. It also predicted the cross-coupling in the side down position. The trajectories in velocity space were also accurately simulated. 5. One of the predictions of the model is that when the stimulus direction is along an eigenvector, the trajectory in velocity space is a straight line. Using the "spectral width" of the residuals from a straight line sequence during OKAN, we developed a methodology to estimate how close the OKAN decay was to an eigenvector trajectory. 6. Thus we have developed a model-based approach for studying and interpreting the response characteristics of velocity storage in three dimensions.(ABSTRACT TRUNCATED AT 400 WORDS).
An extension of the Savage-Hutter gravity driven granular flow model on arbitrary topography in 1D
NASA Astrophysics Data System (ADS)
Fellin, Wolfgang; Ostermann, Alexander; Staggl, Gregor
2015-04-01
In an implementation of the Savage-Hutter model in a GIS (geographic information system, e.g. GRASS GIS) curvature terms must be accounted for. We extend the work of Bouchut et al. (2003) to include friction between flowing mass and bed, as well as the active/passive earth pressure coefficient to model the behavior of the granular flow according to the original Savage-Hutter idea. Conservation of mass and momentum in curvilinear coordinates are integrated over the flow height yielding a shallow water model. This work is part of the project avaflow: http://www.avaflow.org/ References: F. Bouchut, A. Mangeney-Castelnau, B. Perthame, J.-P. Vilotte, A new model of Saint Venant and Savage-Hutter type for gravity driven shallow water flows, C.R. Acad. Sci. Paris, série I 336 (2003), 531-536.
Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling
Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.
1999-01-01
We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data. Copyright 1999 by the American Geophysical Union.
Joint Gas-Phase Velocity-Scalar PDF Modeling for Turbulent EvaporatingSpray Flows
Hai-Wen Ge; Yong Hu; Eva Gutheil
2012-01-01
The article proposes a joint gas-phase velocity-scalar probability\\u000d\\u000a\\u0009density function (PDF) model for turbulent spray flows. The joint\\u000d\\u000a\\u0009gas-phase velocity-mixture fraction PDF transport equation for turbulent\\u000d\\u000a\\u0009spray flows is derived and modeled. The simplified Langevin model\\u000d\\u000a\\u0009and interaction-by-exchange-with-the-mean (IEM) model are extended\\u000d\\u000a\\u0009to account for spray evaporation, and they close the PDF transport\\u000d\\u000a\\u0009equation, which is solved by a Lagrangian
Isothermal velocity and turbulence measurements downstream of a model multilobed turbofan mixer
NASA Astrophysics Data System (ADS)
Koutmos, P.; McGuirk, J. J.
1989-12-01
An isothermal experimental investigation of the three-dimensional flowfield downstream of a model multilobed turbofan forced mixer is presented. LDA measurements of the three mean velocities and corresponding turbulence intensities were obtained in the downstream duct where the turbine (primary) and fan (secondary) streams emerging from the lobes mix together. The flow development in the near field was quantified by measuring the cross-plane velocities. These were found to consist of large radial flows, of order 15 percent of the mean axial velocities at the lobe inlet, with changing sign depending on location. The cross-plane flow is consistent with a large-scale axial vortex pair (per lobe) which persists throughout the downstream duct and enhances mixing in this region.
Low Velocity Impact Experiments plus Modeling of the Resulting Reaction Violence in LX-10 Charges
NASA Astrophysics Data System (ADS)
Chidester, Steven; Garcia, Frank; Vandersall, Kevin; Tarver, Craig
2011-06-01
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.
Effects of geometry and jet velocity on noise associated with an upper-surface-blowing model
NASA Technical Reports Server (NTRS)
Clark, L. R.; Yu, J. C.
1977-01-01
The noise characteristics associated with various upper surface blowing configurations were investigated using a small model consisting of a plate and flap assembly (simulated wing with flap) attached to a rectangular nozzle. Nozzle aspect ratio, flow-run length, and flap-deflection angle were the experimental parameters studied. Three nozzle-exit velocities were used. The normalized noise spectra obtained for different nozzle aspect ratios proved to be similar in terms of Strouhal number based on jet velocity and flow-run length. Consequently, the need for knowing local flow velocity and length scales (for example, at the flap trailing edge) as required in some of the existing noise prediction schemes is eliminated. Data are compared with results computed from three different noise prediction schemes, and the validity of each scheme is assessed. A simple method is proposed to evaluate the frequency dependence of acoustic shielding obtained with the simulated wing flap.
Global plate motion models incorporating the velocity field of ITRF96
Zhang Qiang; Zhu Wenyao; Xiong Yongqin
1999-01-01
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
Koji Takahashi
1997-03-29
The evolution of globular clusters driven by two-body relaxation is investigated by means of numerical integration of the two-dimensional Fokker-Planck equation in energy--angular momentum space. The two- dimensional Fokker-Planck equation allows the development of velocity anisotropy. We include a spectrum of stellar masses in this paper. The radial anisotropy develops, that is, the radial velocity dispersion exceeds the tangential one, in the outer halo of multi-mass clusters as in single-mass clusters. However, the evolution of the velocity anisotropy depends significantly on the stellar mass in some cases. In fact the tangential velocity dispersion becomes dominant around the half-mass radius for massive components in clusters with a steep mass function. The development of this tangential anisotropy is closely related to the initial cooling of the massive components toward energy equipartition. Our simulation results indicate that multi-mass anisotropic King-Michie models are not always appropriate for describing the velocity anisotropy in globular clusters.
Velocity Measurements Near the Empennage of a SmallScale Helicopter Model
NASA Technical Reports Server (NTRS)
Gorton, Susan Althoff; Meyers, James F.; Berry, John D.
1996-01-01
A test program was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to measure the flow near the empennage of a small-scale powered helicopter model with an operating tail fan. Three-component velocity profiles were measured with Laser Velocimetry (LV) one chord forward of the horizontal tail for four advance ratios to evaluate the effect of the rotor wake impingement on the horizontal tail angle of attack. These velocity data indicate the horizontal tail can experience unsteady downwash angle variations of over 30 degrees due to the rotor wake influence. The horizontal tail is most affected by the rotor wake above advance ratios of 0.10. Velocity measurements of the flow on the inlet side of the fan were made for a low-speed flight condition using both conventional LV techniques and a promising, non-intrusive, global, three-component velocity measurement technique called Doppler Global Velocimetry (DGV). The velocity data show an accelerated flow near the fan duct, and vorticity calculations track the passage of main rotor wake vortices through the measurement plane. DGV shows promise as an evolving tool for rotor flowfield diagnostics.
NASA Astrophysics Data System (ADS)
Gaelle, Gibert; Riad, Hassani; Emmanuel, Tric; Tony, Monfret
2010-05-01
Recent analogical models of Heuret et al (2007) and Guillaume et al (2009) showed that the kinematical and mechanical role of the overriding plate is crucial for the slab geometry. We used Hassani et al (1997) 2D finite element numerical code to model subduction with parameters close to analogue models conditions. Our results are coherent with considered previous analogue models. As shown by Heuret et al (2007), after the subducting plate reaches the 660 km discontinuity modeled by a rigid foundation, we obtained two different styles of subduction depending on the overriding plate velocity vop: if vop >0, the slab lays forward on the 660km discontinuity (style 1) if vop ?0, the slab lays backward on the discontinuity (style 2). We also light up two different processes: the subduction evolves in a steady-state regime when vsp ?0 or 2vop + vop ?0 (where vsp stands for the subducting plate velocity) and in non steady-state regime when one of these two conditions is not fulfilled. This result is coherent with Guillaume et al (2009) non steady-state models at vop=0. We checked these conditions by conducting several simulations varying subduction velocities (relative velocity), absolute plates velocities and plate viscosities. When the process is not steady-state, the slab is periodically folding on the 660 km discontinuity leading to episodes of slab flattening (minimal dip of 13° ) followed by slab steepening phases (maximal value of 65° ). The folding period is essentially controlled by slab viscosity and subduction velocity. We then compared our models with the natural case of the Chilean flat slab. Fukao et al (2001) show that the Andean slab does not penetrate the 660 km discontinuity which make possible comparison between our models and nature. For the Andean case, actual velocities are vop? 4.3 cm.an-1 and vsp? 2.9 cm.an-1 for a relative velocity close to vs = vop + vsp? 7.2 cm.an-1, which places us in the case of style 1 with cycles. If we model those velocities with a viscosity of ?=2×1024 Pa.s, we obtain cycle duration of ca. 26 Ma with a period of ca. 3.6 Ma of low dip, with a minimal value of ca. 15° . Haschke et al (2002) work on Andean flat slab region magmatic rocks suggest that evolutionary cycles occurred during the Andean orogeny. Episodes of slab steepening and shallowing with a duration of 30-40 Ma might have occurred, explaining magmatic gaps of ca 5-10. Simplifications imposed by numerical modeling could explain the difference between our values and Andean values. Still, our values are in the range of Haschke et al (2002) estimation of the Andean case. Our models are coherent with Kay et al (2002) results on South American overriding plate: when the Nazca plate slab was steep, the South American margin underwent extension, and that when shallowing occurred, compression occurred in the margin. Therefore, style 1 with cycle may be considered as a possible answer for this natural speacial case.
Towards an improved model of the secular velocities in the western US
NASA Astrophysics Data System (ADS)
Pearson, C. F.; Snay, R. A.; McCaffrey, R.
2009-12-01
Deformation in the western United States, due to tectonic forces associated with the Pacific-North American plate boundary, causes ongoing changes of the positions of points on the Earth’s surface relative to a prescribed reference frame. As a result, accurate surveying in the western US requires an equally accurate description of this deformation to allow survey measurements conducted at different epochs to be corrected for such movement. NOAA’s National Geodetic Survey (NGS) has developed the HTDP (horizontal time dependent positioning) software that enables its users to make these corrections. HTDP contains a model of the secular (continuous) velocity field for the contiguous United States (from 125W to 100W longitude and 31-36N latitude) which is determined using linear interpolation from a series of grid files. The model also contains separate models for the displacements associated with 28 earthquakes. In the contiguous United States, the catalogue of earthquakes is complete since 1984 with the exception of the M 6.7 Nisqually earthquake although in Alaska several major earthquakes are missing. The software is updated periodically to address the displacements associated with new earthquakes, most recently in June 2008 with the release version 3.0. This paper focuses on our model of the secular velocity field. The model of the secular velocities included in HTDP is based on a DEFNODE model containing over 50 blocks in the contiguous US which is later sampled to produce the grid files mentioned above. The model was created in 2007 and has been updated twice to accommodate recent Plate Boundary Observatory velocity solutions. The model contains explicit models of the major faults in the western US and a uniform strain rate tensor for each block. The model currently neglects deformation near major volcanoes in the west or post-seismic effects after great earthquakes. Slip rates on the faults range from over 30 mm/yr for the Juan de Fuca subduction interface and parts of the San Andreas system to near zero (generally sub 1 mm/yr) for faults located in the eastern side of the model. The intra block strain rate tensors are consistent with contraction perpendicular to the coast in blocks immediately adjacent to the west coast and extension further east. NGS is reviewing this model and will update it once reliable velocity vectors are available from an ongoing effort to re-process all existing CORS data back to 1994. The major enhancement that we plan to make to HTDP is the introduction of a vertical velocity field allowing HTDP to map three dimensional positional changes for the first time. In addition we hope to add models of volcanic inflation possibly by adding a Mogi source model. We also plan to add a new grid for the creeping section of the San Andreas fault which will allow for more accurate interpolation of velocities in an area where the velocities often change discontinuously across the fault.
Effects of a space modulation on the behavior of a 1D alternating Heisenberg spin-1/2 model.
Mahdavifar, Saeed; Abouie, Jahanfar
2011-06-22
The effects of a magnetic field (h) and a space modulation (?) on the magnetic properties of a one-dimensional antiferromagnetic-ferromagnetic Heisenberg spin-1/2 model have been studied by means of numerical exact diagonalization of finite size systems, the nonlinear ? model, and a bosonization approach. The space modulation is considered on the antiferromagnetic couplings. At ? = 0, the model is mapped to a gapless Lüttinger liquid phase by increasing the magnetic field. However, the space modulation induces a new gap in the spectrum of the system and the system experiences different quantum phases which are separated by four critical fields. By opening the new gap, a magnetization plateau appears at ½M(sat). The effects of the space modulation are reflected in the emergence of a plateau in other physical functions such as the F-dimer and the bond-dimer order parameters, and the pair-wise entanglement. PMID:21613724
Modeling Compressional and Shear Wave Velocities of Unconsolidated Sediments in the Vadose Zone
NASA Astrophysics Data System (ADS)
Berge, P. A.
2001-12-01
Recent advances in seismic surveys have provided ways to image shallow structure in highly attenuating soils and near-surface rock. Applications include using surface wave methods to find tunnels; mapping landfills with seismic refraction methods; finding faults, the water table, or other strong heterogeneities using seismic reflection surveys. Recent improvements in laboratory ultrasonic measurement techniques have provided reliable data on compressional and shear wave velocities in soils at low pressures analogous to the top few meters to tens of meters of the subsurface. The availability of these data points the way for development of interpretation methods that may allow seismologists to obtain more information from their data in the future. For environmental applications, improvements to interpretation methods could lead to reliable detection of second-order features such as changes in soil saturation, presence of dense non-aqueous phase liquids, or changes in clay content. Traditional modeling techniques developed in the oil industry are optimized for consolidated materials at pressures and depths greater than those typical for environmental applications. The shallow subsurface velocities are highly nonlinear and the soils are highly attenuating, and these characteristics must be considered when modeling velocities (and also when processing seismic data). Various factors, including grain contact roughness, location of clay with respect to sand grains, location of fluid in the partially-saturated case, loose vs. dense packing, all affect the compressional and shear wave velocities and attenuation and their pressure (depth) dependence. Care must be taken when applying effective medium theories or grain-contact theories to model shallow soil velocity behavior. Unconsolidated materials at low pressures show much greater variation in compressional vs. shear wave properties than consolidated materials and high-pressure applications would show. Despite the modeling difficulties, progress in seismic interpretation may be made if data are available for both compressional and shear waves. Examples of pitfalls and methods for successful soil velocity modeling will be presented using lab and field velocity data from the literature, for sands, silty sands, and other unconsolidated materials. The goal is to develop techniques to improve interpretation of seismic data from the vadose zone. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and supported specifically by the DOE Environmental Management Science Program. >http://www.llnl.gov/ees/esd/expgeoph/Berge/EMSP/
Development of a State-Wide 3-D Seismic Tomography Velocity Model for California
NASA Astrophysics Data System (ADS)
Thurber, C. H.; Lin, G.; Zhang, H.; Hauksson, E.; Shearer, P.; Waldhauser, F.; Hardebeck, J.; Brocher, T.
2007-12-01
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.
Three-dimensional P wave velocity model for the San Francisco Bay region, California
NASA Astrophysics Data System (ADS)
Thurber, Clifford H.; Brocher, Thomas M.; Zhang, Haijiang; Langenheim, Victoria E.
2007-07-01
A new three-dimensional P wave velocity model for the greater San Francisco Bay region has been derived using the double-difference seismic tomography method, using data from about 5,500 chemical explosions or air gun blasts and approximately 6,000 earthquakes. The model region covers 140 km NE-SW by 240 km NW-SE, extending from 20 km south of Monterey to Santa Rosa and reaching from the Pacific coast to the edge of the Great Valley. Our model provides the first regional view of a number of basement highs that are imaged in the uppermost few kilometers of the model, and images a number of velocity anomaly lows associated with known Mesozoic and Cenozoic basins in the study area. High velocity (Vp > 6.5 km/s) features at ˜15-km depth beneath part of the edge of the Great Valley and along the San Francisco peninsula are interpreted as ophiolite bodies. The relocated earthquakes provide a clear picture of the geometry of the major faults in the region, illuminating fault dips that are generally consistent with previous studies. Ninety-five percent of the earthquakes have depths between 2.3 and 15.2 km, and the corresponding seismic velocities at the hypocenters range from 4.8 km/s (presumably corresponding to Franciscan basement or Mesozoic sedimentary rocks of the Great Valley Sequence) to 6.8 km/s. The top of the seismogenic zone is thus largely controlled by basement depth, but the base of the seismogenic zone is not restricted to seismic velocities of ?6.3 km/s in this region, as had been previously proposed.
Akhmedov, Novruz G; Gannett, Peter M; Wu, Bulan; Cummings, Matthew M; Train, Brian C
2013-03-01
The (1)H and (13)C NMR spectra of 10-deoxymethynolide (1), 8.9-dihydro-10-deoxymethynolide (2) and its glycosylated derivatives (3-9) were analyzed using gradient-selected NMR techniques, including 1D TOCSY, gCOSY, 1D NOESY (DPFGSENOE), NOESY, gHMBC, gHSQC and gHSQC-TOCSY. The NMR spectral parameters (chemical shifts and coupling constants) of 1-9 were determined by iterative analysis. For the first time, complete and unambiguous assignment of the (1)H NMR spectrum of 10-deoxymethynolide (1) has been achieved in CDCl(3), CD(3)OD and C(6)D(6) solvents. The (1)H NMR spectrum of 8,9-dihydro-10-deoxymethynolide (2) was recorded in CDCl(3), (CD(3))(2)CO and CD(3)OD solutions to determine the conformation. NMR-based conformational analysis of 1 and 2 in conjugation with molecular modeling concluded that the 12-membered ring of the macrolactones may predominantly exist in a single stable conformation in all solvents examined. In all cases, a change in solvent caused only small changes in chemical shifts and coupling constants, suggesting that all glycosylated methymycin analogs exist with similar conformations of the aglycone ring in solution. PMID:23364799
Carlos Moreno; L. A. Sedano
2009-01-01
ITER fuel demands and tritium availability scenarios will determine the pathway to future fusion reactors. Because tritium is not a resource available from natural sources and its emission from the facility should be minimized, to keep the material balance in the entire plant and to control its inventory and safety is an essential issue toward the DEMO reactor. Predictive modeling
Study of fog characteristics by using the 1-D COBEL model at the airport of Thessaloniki, Greece
NASA Astrophysics Data System (ADS)
Stolaki, S.; Pytharoulis, I.; Karacostas, T.
2010-07-01
An attempt is made to couple the one dimensional COBEL - ISBA (COuche Brouillard Eau Liquide - Interactions Soil Biosphere Atmosphere) model with the WRF (Weather Research and Forecasting) numerical weather prediction model. This accomplishment will improve the accuracy on the short-term forecasting of fog events, which is of paramount importance -mainly to the airway companies, the airports functioning and the community as well- and will provide the means for the implementation of extensive studies of fog events formed at the "Macedonia" airport of Thessaloniki. Numerical experiments have been performed to study in depth the thermodynamic structure and the microphysical characteristics of the fog event that was formed on 06/01/2010. Moreover, the meteorological conditions -under the influence of which- the fog event was formed are also investigated. Sensitivity tests with respect to the initial conditions of temperature, relative humidity and geostrophic wind speed profiles have been performed to illustrate the model’s performance. Dew deposition rates have also been examined in order to test the importance of it on controlling the fog formation. The numerical results have been compared with actual measurements and the findings have been evaluated and discussed.
Mench, Matthew M.
-5,11-16 To determine the root cause of freeze/thaw dam- age, a frost heave thermal model has been developed layer CL , which would typically not cause dam- age upon shutdown to freezing in an unconstrained into an existing ice formation by capillary forces, and is known to cause delamination or motion between surfaces
Alessandro Miotti; Alfonso Di Domenico; Yann G Guezennec; Sai Rajagopalan
2005-01-01
Fuel-cell driven vehicles have become the focal point of research and development in all automotive and academic research institutions. The proton exchange membrane fuel cell system which seems to be the forerunner for traction applications, poses a significant challenge for modelling and control design due to a highly nonlinear behavior attributed to the complex interaction of the fluid, thermal, electro-chemical
Arcos, M E M
2014-01-01
The ability to measure, predict, and compute tsunami flow velocities is of importance in risk assessment and hazard mitigation. Substantial damage can be done by high velocity flows, particularly in harbors and bays, even when the wave height is small. Moreover, advancing the study of sediment transport and tsunami deposits depends on the accurate interpretation and modeling of tsunami flow velocities and accelerations. Until recently, few direct measurements of tsunami velocities existed to compare with model results. During the 11 March 2011 Tohoku Tsunami 328 current meters were in place around the Hawaiian Islands, USA, that captured time series of water velocity in 18 locations, in both harbors and deep channels, at a series of depths. We compare several of these velocity records against numerical simulations performed using the GeoClaw numerical tsunami model, based on solving the depth-averaged shallow water equations with adaptive mesh refinement, to confirm that this model can accurately predict velo...
NASA Astrophysics Data System (ADS)
Ashworth, K.; Chung, S. H.; Griffin, R. J.; Chen, J.; Forkel, R.; Bryan, A. M.; Steiner, A. L.
2015-07-01
Biosphere-atmosphere interactions play a critical role in governing atmospheric composition, mediating the concentration of key species such as ozone and aerosol, thereby influencing air quality and climate. The exchange of reactive trace gases and their oxidation products (both gas and particle phase) is of particular importance in this process. The FORCAsT (FORest Canopy AtmoSphere Transfer) one-dimensional model is developed to study the emission, deposition, chemistry and transport of volatile organic compounds (VOCs) and their oxidation products in the atmosphere within and above the forest canopy. We include an equilibrium partitioning scheme, making FORCAsT one of the few canopy models currently capable of simulating the formation of secondary organic aerosols (SOA) from VOC oxidation in a forest environment. We evaluate the capability of FORCAsT to reproduce observed concentrations of key gas-phase species and report modeled SOA concentrations within and above a mixed forest at the University of Michigan Biological Station (UMBS) during the Community Atmosphere-Biosphere Interactions Experiment (CABINEX) field campaign in summer 2009. We examine the impact of two different gas-phase chemical mechanisms on modelled concentrations of short-lived primary emissions, such as isoprene and monoterpenes, and their oxidation products. While the two chemistry schemes perform similarly under high-NOx conditions, they diverge at the low levels of NOx at UMBS. We identify peroxy radical and alkyl nitrate chemistry as the key causes of the differences, highlighting the importance of this chemistry in understanding the fate of biogenic VOCs (bVOCs) for both the modelling and measurement communities.
NASA Astrophysics Data System (ADS)
Riel, Nicolas; Mercier, Jonathan
2014-05-01
It is now widely accepted that the formation and the evolution of high elevation plateaus such as the Tibet and the Altiplano-Puna are strongly linked to mantel magma underplating at crustal root level and partial melting of the lower crust. Understanding the rheological behavior of the deep continental crust during these episodes is therefore crucial to constrain the evolution of such plateau. In this study we present results obtained from pressure-temperature estimates and thermal modeling of gabbro underplating at crustal root level (25km) in the El Oro Metamorphic Complex (Ecuador). The aim of this study is: (1) to complete previously published P-Tmax estimates in the northern part of the migmatitic unit, close to the magmatic contact with the gabbroic unit, to obtain better constraints on the metamorphic gradient during partial melting, (2) to characterize the effects of melt extraction, latent heat capture and release and a temperature-dependent thermal diffusivity on the thermal evolution of the system using a specifically developed numerical model, and (3) in the light of the thermal modeling results, to discuss the geological processes involved during partial melting of the metasedimentary crust. Our modeling results show that the estimate metamorphic gradient cannot be reproduced when solely taking into account latent heat, melt extraction and thermal-dependent diffusivity. In the light of geological, geochemical and modeling evidence we show that the lower migmatitic unit, controlled by biotite-dehydration melting reactions was subject to convective motion that contributed to lower the metamorphic gradient and rapidly transfer heat upward. For a biotite-rich rock (~20%) containing 15-20% of melt, we estimate the maximum viscosity of the rock that allows convection at ~7.5e17 Pa.s. Our results also suggest that convection can be maintained as long as heat is provided and that temperature lies in the stability field of biotite-dehydration melting (750-900°C).
NASA Astrophysics Data System (ADS)
Saleh, F.; Ducharne, A.; Flipo, N.; Oudin, L.; Ledoux, E.
2013-01-01
SummaryRiver cross-sections data are required to represent channel geometry in hydrodynamic models. In the absence of accurate data at regional scale, simplified or parameterized cross sections are often used, which might affect the performance of the hydrodynamic model. In this study we assess the sensitivity of a 1D Saint-Venant hydraulic model to different types of river morphological data. The question is addressed using a 1D unsteady hydraulic model (HEC-RAS), with lateral inflows provided by the hydro(geo)logical model Eau-Dyssée, to explore a wide spectrum of river geometry scenarios, regarding river bed slopes and cross-sectional shapes. The target scale is the one of the Seine River (France). As a gateway for larger and more complex regional hydro(geo)logical applications, our case-study covers a well-described 89-km reach in a sub-tributary of the Seine River. River morphology is described by high-resolution cross-sections, and Manning's roughness coefficient (n) is used for calibration against observed discharges and river stages in a mid-reach control point, with satisfactory performances over the 8-year simulation period. The resulting model still simulates realistic discharge hydrographs when forced with degraded channel geometry data, using either fewer cross-sections or approximated ones. In such cases, however, the hydraulic model does not always satisfactorily predict the associated water levels when compared to observations. In certain geometry scenarios, the RMSE between simulated water levels using degraded geometry and observations may go up to 0.3 m. The study confirms that the accuracy of predicted water levels and maximum water depths simulated by a Saint-Venant model relies on an accurate representation of channel geometry and bed level slopes along the river reach. From the various scenarios, it appears that the longitudinal description of the bed level profiles has a larger impact on the simulation of water levels than the cross-sectional shapes. This offers interesting implications for flood forecast mapping applications and regional scale models that often use simplified river geometry and Digital Elevation Models (DEMs) built by remote sensing technologies to simulate the water levels.
NASA Astrophysics Data System (ADS)
Ma, Shutian; Motazedian, Dariush; Corchete, Victor
2013-04-01
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.
Fisher, Ross; Thomas, Edward
2011-11-15
The spatially resolved phase space distribution was measured for a dusty plasma system. Analysis of the velocity space component of the distributions revealed that the standard assumption of a spherically symmetric velocity space is not applicable to the observed system. The more general, ellipsoidally symmetric, multi-normal distribution function was applied to model the velocity space and is compared to the canonical spherically symmetric model.
Creating Flood Inundation Maps Using 1D Hydrologic Model and GIS for Lower Meric River Basin, Turkey
NASA Astrophysics Data System (ADS)
Sonmez, O.; Dogan, E.; Demir, I.
2012-12-01
In Turkey, one of the areas facing the danger of flooding is Lower Meric River basin, the part between Edirne and Enos, Turkey. Despite being in the flood zone, the region is used widely as an agricultural and settlement land. The State Hydraulic Works (DSI) has built levees to prevent flood damages on the Lower Evros River Basin. However, having floods in the region reaching areas behind levees, clearly showed the need for reviewing and updating the cross-sections of the critical areas in the river bed. In this study, determination of floodplains for various stream-flow values in any cross sections of the river is aimed. The study area is divided into two sections (Study Area 1 & Study Area 2). Available stream flow gauging station data, which is located in study areas, are used in model. Model created using HEC-RAS, is calibrated with 2006 flood which occurred in the study area. After calibration, floodplain maps are created for 1000 m3/s flows from 1000 to6000 m3/s flows for Study Area1. For Study Area 2, floodplain maps are created for 2, 5, 10, 50, 100 years return periods. The models can illustrate the extent of flooding under different conditions allowing residents in the area to see how predicted flood levels could affect their property, and help them make informed decisions.
NASA Technical Reports Server (NTRS)
Reinarts, Thomas R.; Crain, William K.; Stuckey, C. Irvin; Palko, Richard L.
1998-01-01
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.
Thurber, C.; Zhang, H.; Brocher, T.; Langenheim, V.
2009-01-01
We present a three-dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional-scale double-difference tomography algorithm that incorporates a finite-difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled-source explosions, recorded at network and/or temporary stations, were inverted for Vp on a 3D grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km. Our model provides an unprecedented, comprehensive view of the regional-scale structure of northern California, putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features, especially in the middle and lower crust, that have never before been reported. Examples of the former include the complex subducting Gorda slab, a steep, deeply penetrating fault beneath the Sacramento River Delta, crustal low-velocity zones beneath Geysers-Clear Lake and Long Valley, and the high-velocity ophiolite body underlying the Great Valley. Examples of the latter include mid-crustal low-velocity zones beneath Mount Shasta and north of Lake Tahoe. Copyright 2009 by the American Geophysical Union.
NASA Astrophysics Data System (ADS)
Chanamé, Julio; Kleyna, Jan; van der Marel, Roeland
2008-08-01
We present a new Schwarzschild orbit superposition code designed to model discrete data sets composed of velocity measurements 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. The code can handle any combination of velocity components, i.e., only line-of-sight velocities, only proper motions, or both. The code determines the combination of orbital mass weights as a function of the three integrals of motion E, Lz, and I3 that best reproduces, in a maximum likelihood sense, the available kinematic and photometric observations in a given axisymmetric gravitational potential. The fully numerical approach ensures considerable freedom on the form of the distribution function f(E,Lz,I3), avoiding restrictive assumptions about the degree of orbital (an)isotropy. We describe the implementation of the discrete code and present a series of performance tests based on the modeling of simulated data sets generated from a known distribution function. Exploring pseudo-data sets with varying degrees of overall rotation and different inclinations on the sky, we study the results as a function of relevant observational variables such as the size of the data set and the type of velocity information available. The discrete Schwarzschild code recovers the original orbital structure, mass-to-light ratio, and inclination of the input data sets to satisfactory accuracy. The code will be valuable, e.g., for modeling stellar motions in Galactic globular clusters and the motions 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 halos being of particular interest.
NASA Astrophysics Data System (ADS)
Gesret, A.; Noble, M.; Desassis, N.; Romary, T.
2012-12-01
The reservoirs and mines are often monitored by detecting and analyzing the induced seismicity. This microseismicity is interpreted to derive the location and orientation of the fractures and also to derive several physical parameters. Very precise location of the induced seismicity with its associated uncertainties is thus of primary importance. The largest contribution to the microseismic location errors is due to the lack of knowledge of the wave-propagation medium, the velocity model has thus to be preliminary inverted. We here present a tomography algorithm that estimates the true uncertainties on the resulting velocity model. Including these results, we develop an approach that allows to obtain accurate event locations and their associated uncertainties due to the velocity model uncertainties. The inversion of the velocity model is often a totally non-linear inverse problem. To solve it, we choose a Bayesian approach as this formulation allows for a complete understanding of all possible solutions. In a Bayesian context, a large number of samples of statistically near-independent models from the a posteriori probability distribution are sought. Such solutions are consistent with both the data and the prior information, as they fit the data within error bars, and adhere to soft prior constraints given by a prior probability distribution. We apply the Bayesian approach to the tomography of calibration shots for a typical 3D geometry hydraulic fracture context. We develop a Monte-Carlo Markov chain (MCMC) algorithm which generates samples of velocity model distributed according to the posterior distribution. This leads us to express the best and the mean velocity model as well as the associated standard deviation. This allows identifying the regions of the velocity field where the velocities are well constrained and thus reliable and also the regions where the velocities are poorly constrained. This strategy results in the estimation of the true uncertainty on the velocity model, which is much more accurate than the common roughly estimated percentage of uncertainty on the velocity model. We then develop the Bayesian formalism for the event location by including the posterior distribution of the velocity model previously obtained. For the location problem, we use a full grid search algorithm as the whole posterior probability distribution can be explored at a reasonable computational cost. We compute the probability density of the hypocenter location, taking into account the velocity model uncertainties. The resulting probability map shows that the commonly used probability density associated to the picking uncertainties must not be used to represent the probability density associated to the velocity model uncertainties. Traveltime picking and velocity model uncertainties should thus not be mixed.
NASA Technical Reports Server (NTRS)
Minow, Joseph I.; Coffey, Victoria N.; Parker, Linda N.; Blackwell, William C., Jr.; Jun, Insoo; Garrett, Henry B.
2007-01-01
The NUMIT 1-dimensional bulk charging model is used as a screening to ol for evaluating time-dependent bulk internal or deep dielectric) ch arging of dielectrics exposed to penetrating electron environments. T he code is modified to accept time dependent electron flux time serie s along satellite orbits for the electron environment inputs instead of using the static electron flux environment input originally used b y the code and widely adopted in bulk charging models. Application of the screening technique ts demonstrated for three cases of spacecraf t exposure within the Earth's radiation belts including a geostationa ry transfer orbit and an Earth-Moon transit trajectory for a range of orbit inclinations. Electric fields and charge densities are compute d for dielectric materials with varying electrical properties exposed to relativistic electron environments along the orbits. Our objectiv e is to demonstrate a preliminary application of the time-dependent e nvironments input to the NUMIT code for evaluating charging risks to exposed dielectrics used on spacecraft when exposed to the Earth's ra diation belts. The results demonstrate that the NUMIT electric field values in GTO orbits with multiple encounters with the Earth's radiat ion belts are consistent with previous studies of charging in GTO orb its and that potential threat conditions for electrostatic discharge exist on lunar transit trajectories depending on the electrical proper ties of the materials exposed to the radiation environment.
NASA Astrophysics Data System (ADS)
Harel, Marie-Alice; Mouche, Emmanuel
2015-04-01
Despite the recent research focused on runoff pattern connectivity in hydrology, there is a surprising lack of theoretical knowledge regarding hillslope runoff generation and dynamics during a rainfall event. The transient problem is especially unaddressed. In this paper we propose a model based on queueing theory formalism for the infiltration-excess overland flow generation on soils with random infiltration properties. The influence of rainfall intensity and duration on runoff dynamics and connectivity is studied thanks to this model, numerical simulation and available steady-state results. We limit our study to a rainfall intensity that is a rectangular function of time. Exact solutions for the case of spatially random exponential distributions of soil infiltrability and rainfall intensity are developed. Simulations validate these analytical results and allow for the study the rising and recession limbs of the hydrograph for different rainfall characteristics. The case of a deterministic uniform rainfall rate and different infiltrability distributions is also discussed in light of runoff connectivity. We show that the connectivity framework contributes to a better understanding and prediction of runoff pattern formation and evolution with time. A fragmented overland flow is shown to have shorter charge and discharge periods after the onset and offset of rainfall compared to well connected runoff fields. These results demonstrate that the transient regime characteristics are linked with connectivity parameters, rainstorm properties and scale issues.
NASA Astrophysics Data System (ADS)
Fortin, W.; Holbrook, W. S.; Mallick, S.; Everson, E. D.; Tobin, H. J.; Keranen, K. M.
2014-12-01
Understanding the geologic composition of the Cascadia Subduction Zone (CSZ) is critically important in assessing seismic hazards in the Pacific Northwest. Despite being a potential earthquake and tsunami threat to millions of people, key details of the structure and fault mechanisms remain poorly understood in the CSZ. In particular, the position and character of the subduction interface remains elusive due to its relative aseismicity and low seismic reflectivity, making imaging difficult for both passive and active source methods. Modern active-source reflection seismic data acquired as part of the COAST project in 2012 provide an opportunity to study the transition from the Cascadia basin, across the deformation front, and into the accretionary prism. Coupled with advances in seismic inversion methods, this new data allow us to produce detailed velocity models of the CSZ and accurate pre-stack depth migrations for studying geologic structure. While still computationally expensive, current computing clusters can perform seismic inversions at resolutions that match that of the seismic image itself. Here we present pre-stack full waveform inversions of the central seismic line of the COAST survey offshore Washington state. The resultant velocity model is produced by inversion at every CMP location, 6.25 m laterally, with vertical resolution of 0.2 times the dominant seismic frequency. We report a good average correlation value above 0.8 across the entire seismic line, determined by comparing synthetic gathers to the real pre-stack gathers. These detailed velocity models, both Vp and Vs, along with the density model, are a necessary step toward a detailed porosity cross section to be used to determine the role of fluids in the CSZ. Additionally, the P-velocity model is used to produce a pre-stack depth migration image of the CSZ.
Gravity Modeling of a Batholith and Low-Velocity Mantle Zone Beneath the Colorado Mineral Belt
NASA Astrophysics Data System (ADS)
McCoy, A. M.; Roy, M.; Trevino, L.; Keller, R.
2003-12-01
The Colorado Mineral Belt (CMB) is delineated as a belt of mostly Laramide mineralization within a broader zone of Laramide and older magmatism in central Colorado. One of North America's largest Bouguer gravity anomalies coincides with this broad NE-trending zone of protracted magmatic activity. Seismic studies suggest that parts of the CMB region are underlain by anomalously low-density crust and that the CMB lies within a broad zone of low seismic velocities in the uppermost mantle. Our gravity modeling explores simple distributions of subsurface mass deficits that can explain the CMB negative Bouguer gravity anomaly, and are constrained by geologic estimates of the extent of crustal plutonic bodies and by seismically-inferred crustal and upper mantle velocity anomalies. Specifically, our forward models include (1) a low-density batholithic body in a 20-km thick upper crust with a density contrast of 150 kg/m3, (2) a 25-km thick lower crust with a potential low-density body of density contrast 150 kg/m3, and (3) an upper mantle with a low-density body of variable density contrast placed at variable depth. The viability of the crust and mantle low-density bodies in our first-order forward models is tied to their consistency with seismic observations, and we work toward refinement of the models using empirical density/velocity relationships and the upper crustal structure established by the CDROM seismic refraction line.
NASA Astrophysics Data System (ADS)
Tang, Tie-Qiao; Li, Chuan-Yao; Huang, Hai-Jun; Shang, Hua-Yan
2010-12-01
Based on the OV (optimal velocity) model, we in this paper present an extended OV model with the consideration of the honk effect. The analytical and numerical results illustrate that the honk effect can improve the velocity and flow of uniform flow but that the increments are relevant to the density.
A New Open-Loop Fiber Optic Gyro Error Compensation Method Based on Angular Velocity Error Modeling
Zhang, Yanshun; Guo, Yajing; Li, Chunyu; Wang, Yixin; Wang, Zhanqing
2015-01-01
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 u and temperature T 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 u, temperature T 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, u and ?? is established and thus ?? can be calculated automatically to compensate OFOG errors according to T and u. 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 97.0%, 97.1% and 96.5% 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 1.6%, 1.4% and 1.2%, respectively, so the performance of this method is better than that of the direct modeling for gyro angular velocity. PMID:25734642
NASA Astrophysics Data System (ADS)
Bogusz, Janusz; K?os, Anna; Grzempowski, Piotr; Kontny, Bernard
2014-06-01
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.
NASA Astrophysics Data System (ADS)
Shaw, Simon Andrew
2005-11-01
Depth imaging of seismic reflection data plays an important role in discovering and characterizing oil and gas reservoirs. The quality of the image produced by current depth imaging algorithms is inextricably linked to the adequacy of the velocity model, which can be difficult to estimate in geologically complex areas. The inverse scattering series, a multidimensional direct inversion procedure, can be applied to the seismic inverse problem to directly achieve seismic processing objectives without a priori knowledge of the Earth's material properties. Therefore, it has the potential to image reflectors in depth without requiring the velocity model. The inverse series is non-linear in the scattered field, which includes the source wavelet and a chosen reference medium's properties. An imaging subseries of the inverse series for a 1-D constant density variable velocity acoustic medium is isolated and analyzed. This imaging series is a Taylor series expanded about each mislocated reflector whose approximate coefficients are leading order in the scattered field. This leading order imaging series is shown analytically (through the derivation of a closed form) to converge for arbitrarily large finite contrasts between the actual and reference velocities and for bandlimited data whose maximum frequency is finite. A condition is derived which, when satisfied, shows that the leading order imaging series improves the depths of reflectors over a linear imaging algorithm using the reference velocity. Whereas the computational expense of the series algorithm is proportional to the contrast between the actual velocity model and the chosen reference velocity, the closed form efficiently encapsulates an infinite number of terms in a single operation. The impact of missing low frequencies on the leading order imaging series is examined. It is found that, while the predicted depths are more accurate when low frequency information is present, the algorithm can improve upon current linear imaging even when zero and some low frequencies are absent. Some improvement in the effectiveness of the algorithm when low frequency information is missing can be achieved by fixing the limits of the algorithm's integral to be over the known extent of the perturbation. The acquisition of lower frequency data, and the development of low frequency spectral extrapolation techniques will support the progression of this work to eventual field data tests.
A seismic waves velocity model for Gran Canaria Island from ambient noise correlations
NASA Astrophysics Data System (ADS)
García-Jerez, Antonio; Almendros, Javier; Martínez-Arévalo, Carmen; de Lis Mancilla, Flor; Luzón, Francisco; Carmona, Enrique; Martín, Rosa; Sánchez, Nieves
2014-05-01
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.
Global solution to the Cauchy problem for discrete velocity models of vehicular traffic
NASA Astrophysics Data System (ADS)
Bellomo, N.; Bellouquid, A.
This paper offers the proof of the existence for large times of the Cauchy problem for a class of vehicular traffic models with discrete velocities derived from the mathematical tools of the kinetic theory for active particles. This approach has the ability to capture some basic aspects concerning the complexity of the systems under consideration through an appropriate modeling, via stochastic games, of the interactions at the microscopic scale. The proof is related to specific aspects of the real system and hopefully can contribute towards improving the modeling approach.
Numerical Modelling of Glass Fibre Reinforced Laminates Subjected to a Low Velocity Impact
Fan, J. Y.; Guana, Z. W.; Cantwell, W. J. [University of Liverpool, Department of Engineering, Liverpool L69 3GQ (United Kingdom)
2010-05-21
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.
Internal Velocity and Mass Distributions in Clusters of Galaxies for a Variety of Cosmogonic Models
Renyue Cen
1994-04-15
The mass and velocity distributions in the outskirts ($0.5-3.0h^{-1}$Mpc) of clusters of galaxies are examined for a suite of cosmogonic models utilizing large-scale Particle-Mesh (PM) simulations ($500^3$ cells, $250^3$ particles and box size of $100h^{-1}$Mpc, giving a nominal resolution of $0.2h^{-1}$Mpc with the true resolution about $0.5h^{-1}$Mpc). Through a series of model computations, designed to isolate the different effects, we find that both $\\Omega_0$ and $P_k$ ($\\lambda\\le 16h^{-1}$Mpc) are important to the mass and velocity distributions in clusters of galaxies. More details in the full abstract.
A dynamic model for the turbulent burning velocity for large eddy simulation of premixed combustion
Knudsen, E.; Pitsch, H.
2008-09-15
Turbulent premixed combustion is particularly difficult to describe using large eddy simulation (LES). In LES, premixed flame structures typically exist on subfilter length scales. Consequently, premixed LES models must be capable of describing how completely unresolved flame structures propagate under the influence of completely unresolved eddies. This description is usually accomplished through the implementation of a model for the turbulent burning velocity. Here, a dynamic model for describing the turbulent burning velocity in the context of LES is presented. This model uses a new surface filtering procedure that is consistent with standard LES filtering. Additionally, it only uses information that comes directly from the flame front. This latter attribute is important for two reasons. First, it guarantees that the model can be consistently applied when level set methods, where arbitrary constraints can be imposed on field variables away from fronts, are used to track the flame. Second, it forces the model to recognize that the physics governing flame front propagation are only valid locally at the front. Results showing model validation in the context of direct numerical simulation (DNS), and model application in the context of LES, are presented. (author)
NASA Astrophysics Data System (ADS)
Zhou, Wei; Brossier, Romain; Operto, Stéphane; Virieux, Jean
2015-09-01
Full waveform inversion (FWI) aims to reconstruct high-resolution subsurface models from the full wavefield, which includes diving waves, post-critical reflections and short-spread reflections. Most successful applications of FWI are driven by the information carried by diving waves and post-critical reflections to build the long-to-intermediate wavelengths of the velocity structure. Alternative approaches, referred to as reflection waveform inversion (RWI), have been recently revisited to retrieve these long-to-intermediate wavelengths from short-spread reflections by using some prior knowledge of the reflectivity and a scale separation between the velocity macromodel and the reflectivity. This study presents a unified formalism of FWI, named as Joint FWI, whose aim is to efficiently combine the diving and reflected waves for velocity model building. The two key ingredients of Joint FWI are, on the data side, the explicit separation between the short-spread reflections and the wide-angle arrivals and, on the model side, the scale separation between the velocity macromodel and the short-scale impedance model. The velocity model and the impedance model are updated in an alternate way by Joint FWI and waveform inversion of the reflection data (least-squares migration), respectively. Starting from a crude velocity model, Joint FWI is applied to the streamer seismic data computed in the synthetic Valhall model. While the conventional FWI is stuck into a local minimum due to cycle skipping, Joint FWI succeeds in building a reliable velocity macromodel. Compared with RWI, the use of diving waves in Joint FWI improves the reconstruction of shallow velocities, which translates into an improved imaging at deeper depths. The smooth velocity model built by Joint FWI can be subsequently used as a reliable initial model for conventional FWI to increase the high-wavenumber content of the velocity model.
NASA Astrophysics Data System (ADS)
Praveen Kumar, K. A.; Mohan, G.
2014-01-01
The Saurashtra peninsula in the northwestern segment of the Deccan volcanic province of India, is characterized by several high gravity and magnetic anomalies, which correspond to mafic crustal intrusions. This study attempts to quantify the alterations to the crust caused by the Deccan volcanism, by estimating the crustal Poisson's ratio, shear wave velocity (Vs) structure and the shear velocity contrast across the Moho, through teleseismic waveform modeling. The P receiver functions (RFs) for six broadband seismic stations were constructed using about 575 high quality (S/N ? 2.5) teleseismic waveforms of earthquakes (M ? 5.5) recorded during the period 2004-2010. The moveout corrected RF summation stacks were inverted using the Neighborhood algorithm (NA) to estimate the shear velocity structure beneath each station. The crustal thickness is estimated to range from 38 km in western Saurashtra to 33 km close to the southern extension of the Cambay rift. A low velocity zone possibly corresponding to sub-basaltic sediments is detected beneath all the stations. The average crustal Vs and Poisson's ratio are estimated to be 3.68 km/s and 0.276 respectively. The crustal Poisson's ratio indicates an intermediate to mafic composition for the crust. Modeling reveals a relatively high velocity lower crust with an average Vs ? 3.88 ± 0.1 km/s which is consistent with the high Vp ? 7.1 km/s reported for this region through seismic refraction and wide angle reflection studies, overlying a relatively low velocity (Vs ? 4.4 ± 0.1 km/s) upper mantle. The shear velocity contrasts across the Moho, derived from the amplitudes of the P-to-s (Pms) conversions from the Moho range from 0.08 to 0.17 which are much smaller than those (>0.20) observed across the Indian shield, implying a gradational Moho due to underplating. This study reveals that the crust beneath Saurashtra is distinctly different from that of the Archean Indian shield largely due to significant alterations by the Deccan volcanism.
Velocity and pressure characteristics of a model SSME high pressure fuel turbopump
NASA Technical Reports Server (NTRS)
Tse, D. G-N.; Sabnis, J. S.; Mcdonald, H.
1991-01-01
Under the present effort an experiment rig has been constructed, an instrumentation package developed and a series of mean and rms velocity and pressure measurements made in a turbopump which modelled the first stage of the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump. The rig was designed so as to allow initial experiments with a single configuration consisting of a bell-mouth inlet, a flight impeller, a vaneless diffuser and a volute. Allowance was made for components such as inlet guide vanes, exit guide vanes, downstream pumps, etc. to be added in future experiments. This flexibility will provide a clear baseline set of experiments and allow evaluation in later experiments of the effect of adding specific components upon the pump performance properties. The rotational speed of the impeller was varied between 4260 and 7680 rpm which covered the range of scaled SSME rotation speeds when due allowance is made for the differing stagnation temperature, model to full scale. The results at the inlet obtained with rotational speeds of 4260, 6084 and 7680 rpm showed that the axial velocity at the bell-mouth inlet remained roughly constant at 2.2 of the bulk velocity at the exit of the turbopump near the center of the inlet, but it decreased rapidly with increasing radius at all three speeds. Reverse flow occurred at a radius greater than 0.9 R for all three speeds and the maximum negative velocity reduced from 1.3 of the bulk velocity at the exit of the turbopump at 4260 rpm to 0.35 at 7680 rpm, suggesting that operating at a speed closer to the design condition of 8700 rpm improved the inlet characteristics. The reverse flow caused positive prerotation at the impeller inlet which was negligibly small near the center but reached 0.7 of the impeller speed at the outer annulus. The results in the diffuser and the volute obtained at 7680 rpm show that the hub and shroud walls of the diffuser were characterized by regions of transient reverse flow with negative revolution-averaged velocity of 8 percent of the maximum forward revolution-averaged velocity at the center of the diffuser passage near the shroud wall.
NASA Astrophysics Data System (ADS)
Bunthawin, Sakshin; Ritchie, Raymond J.
2013-01-01
Proper models of cell geometry are needed for biophysical analysis of cellular electrical phenomena. This work compares various mathematical volume-models for normal human erythrocytes (discocyte) possessing biconcave-discoid form to simulate translational dielectrophoretic velocity spectra of erythrocyte suspensions induced in a traveling electric field over a frequency range from 1 kHz to 15 MHz. The non-spherical volumes of the oblate-spheroid, the prolate-spheroid, and the oval of Cassini and the "Bun-model" were numerically evaluated according to the normal range of cellular dimension values for mammalian erythrocytes. The latter model is the novel approach derived to provide a more realistic model for the shape of discocytes in the thin biconcave-disc form with a toroidal rim. The bun model is also more rugged than the Cassini equation. Using the actual cell dimensions for calculations, the numerical results among these calculated cell volumes revealed large and significant differences with respect to the Bun-model of +32.09%, +8.95%, and -8.45% for prolate-spheroid, Cassini's equation, and oblate-spheroid, respectively. These large volume deviations shift the magnitude of the sharp peak in dielectrophoretic velocity spectra to lower values with differences of +189.28%, +7.66%, and -9.49%, respectively. For traveling wave dielectrophoresis, similar results were found for the sharp peak of +145.76%, +7.71%, and -9.50%, respectively. The suitability of the Bun-model was verified by curve-fitting of the cell velocity spectra between experimental and theoretical curves, which gave the maximum discrepancies of less than ±10%.
Uncertainty estimation of the velocity model for stations of the TrigNet GPS network
NASA Astrophysics Data System (ADS)
Hackl, M.; Malservisi, R.; Hugentobler, U.
2010-12-01
Satellite based geodetic techniques - above all GPS - provide an outstanding tool to measure crustal motions. They are widely used to derive geodetic velocity models that are applied in geodynamics to determine rotations of tectonic blocks, to localize active geological features, and to estimate rheological properties of the crust and the underlying asthenosphere. However, it is not a trivial task to derive GPS velocities and their uncertainties from positioning time series. In general time series are assumed to be represented by linear models (sometimes offsets, annual, and semi-annual signals are included) and noise. It has been shown that error models accounting only for white noise tend to underestimate the uncertainties of rates derived from long time series and that different colored noise components (flicker noise, random walk, etc.) need to be considered. However, a thorough error analysis including power spectra analyses and maximum likelihood estimates is computationally expensive and is usually not carried out for every site, but the uncertainties are scaled by latitude dependent factors. Analyses of the South Africa continuous GPS network TrigNet indicate that the scaled uncertainties overestimate the velocity errors. So we applied a method similar to the Allan Variance that is commonly used in the estimation of clock uncertainties and is able to account for time dependent probability density functions (colored noise) to the TrigNet time series. Comparisons with synthetic data show that the noise can be represented quite well by a power law model in combination with a seasonal signal in agreement with previous studies, which allows for a reliable estimation of the velocity error. Finally, we compared these estimates to the results obtained by spectral analyses using CATS. Small differences may originate from non-normal distribution of the noise.
HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION
Mellors, R; Gok, R; Pasyanos, M; Skobeltsyn, G; Teoman, U; Godoladze, T; Sandvol, E
2008-07-01
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.
C. A. Powell; G. Vlahovic; P. Bodin; S. Horton
2001-01-01
A three-dimensional P wave velocity model has been constructed for the crust in the vicinity of the Mw=7.7 January 26th Bhuj, India earthquake using aftershock data obtained by CERI away teams. Aftershocks were recorded by 8 portable, digital K2 seismographs (the MAEC\\/ISTAR network) and by a continuously recording Guralp CMG40TD broad-band seismometer. Station spacing is roughly 30 km. The network
Julio Chanamé; Jan Kleyna; Roeland van der Marel
2008-04-21
(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.
Boreal Forest Surface Parameterization in the ECMWF Model--1D Test with NOPEX Long-Term Data.
NASA Astrophysics Data System (ADS)
Gustafsson, D.; Lewan, E.; van den Hurk, B. J. J. M.; Viterbo, P.; Grelle, A.; Lindroth, A.; Cienciala, E.; Mölder, M.; Halldin, S.; Lundin, L.-C.
2003-01-01
The objective of the present study was to assess the performance and recent improvements of the land surface scheme used operationally in the European Centre for Medium-Range Weather Forecasts (ECMWF) in a Scandinavian boreal forest climate/ecosystem. The previous (the 1999 scheme of P. Viterbo and A. K. Betts) and the new (Tiled ECMWF Surface Scheme for Exchange Processes over Land, TESSEL) surface schemes were validated by single-column runs against data from NOPEX (Northern Hemisphere Climate-Processes Land-Surface Experiment). Driving and validation datasets were prepared for a 3-yr period (1994-96). The new surface scheme, with separate surface energy balances for subgrid fractions (tiling), improved predictions of seasonal as well as diurnal variation in surface energy fluxes in comparison with the old scheme. Simulated wintertime evaporation improved significantly as a consequence of the introduced additional aerodynamic resistance for evaporation from snow lying under high vegetation. Simulated springtime evaporation also improved because the limitation of transpiration in frozen soils was now accounted for. However, downward sensible heat flux was still underestimated during winter, especially at nighttime, whereas soil temperatures were underestimated in winter and overestimated in summer. The new scheme also underestimated evaporation during dry periods in summer, whereas soil moisture was overestimated. Sensitivity tests showed that further improvements of simulated surface heat fluxes and soil temperatures could be obtained by calibration of parameters governing the coupling between the surface and the atmosphere and the ground heat flux, and parameters governing the water uptake by the vegetation. Model performance also improved when the seasonal variation in vegetation properties was included.
Stability analysis of singular patterns in the 1D Gray-Scott model: A matched asymptotics approach
NASA Astrophysics Data System (ADS)
Doelman, Arjen; Gardner, Robert A.; Kaper, Tasso J.
1998-11-01
In this work, we analyze the linear stability of singular homoclinic stationary solutions and spatially periodic stationary solutions in the one-dimensional Gray-Scott model. This stability analysis has several implications for understanding the recently discovered phenomena of self-replicating pulses. For each solution constructed in A. Doelman et al. [Nonlinearity 10 (1997) 523-563], we analytically find a large open region in the space of the two scaled parameters in which it is stable. Specifically, for each value of the scaled inhibitor feed rate, there exists an interval, whose length and location depend on the solution type, of values of the activator (autocatalyst) decay rate for which the solution is stable. The upper boundary of each interval corresponds to a subcritical Hopf bifurcation point, and the lower boundary is explicitly determined by finding the parameter value where the solution ‘disappears’, i.e., below which it no longer exists as a solution of the steady state system. Explicit asymptotic formulae show that the one-pulse homoclinic solution gains stability first as the second parameter is decreased, and then successively, the spatially periodic solutions (with decreasing period) become stable. Moreover, the stability intervals for different solutions overlap. These stability results are derived via the reduction of a fourth-order slow-fast eigenvalue problem to a second-order nonlocal eigenvalue problem (NLEP). Explicit determination of these stability intervals plays a central role in understanding pulse self-replication. Numerical simulations confirm that the spatially periodic stationary solutions are attractors in the pulse-splitting regime; and, moreover, whenever, for a given solution, the value of the activator decay rate was taken to lie in the regime below that solution 's stability interval, initial data close to that solution were observed to evolve toward a different spatially periodic stationary solution, one whose stability interval inclucded the parameter value. The main analytical technique used is that of matched asymptotic expansions.
NASA Astrophysics Data System (ADS)
Persson, O. P.; Solomon, A.
2013-12-01
Though leads only represent a small portion of the Arctic sea-ice area, their contribution to the surface turbulent energy and momentum fluxes can be significant. Numerous modeling studies presented in the literature have been conducted examining these effects. The results of such studies have indicated the importance of the environmental large-scale stability, the environmental humidity, the lead width, the ice (lead) concentration, the lead size distribution, the character of the leads (open water, refrozen), etc. Because global climate models (GCMs) show significant sensitivity to the large-scale net energy flux from the heterogeneous sea-ice surface, and because thinner ice in the projected future Arctic climate will likely result in increasing lead fractions, the appropriate GCM representation of this complex system is important. This study presents modeling results based on observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, for which the mid-winter sea-ice was greatly heterogeneous. In mid-January, the 100x100 km region surrounding the SHEBA ice camp consisted of a lead fraction of ~16-33% as revealed by SAR data. This included primarily older refrozen lead areas that were generated at least a month earlier (~16-25% areal coverage), with a smaller fraction of newly opened leads (~4-9% areal coverage). Utilizing the sequence of SAR images, the atmospheric observations at the SHEBA site, and a 1-D snow and ice model, the spatial distribution of sea-ice thickness, snow depth, and surface temperatures within this domain were estimated over a 6-week period, revealing the significant impact of leads in all stages on GCM-scale temperatures and fluxes. This combined observational/model data series is used to evaluate a variety of one-dimensional turbulent flux aggregation techniques (e.g., mosaic) that use different assumptions. Furthermore, by using the spatial distribution of these surface characteristics, three-dimensional large eddy simulations (LES) have been done to a) validate the 1D aggregation techniques and b) to assess how mesoscale circulations generated by the surface heterogeneity impact net surface fluxes. Initially, the LES modeling uses very simple idealized surface conditions and progressively moves towards the much more complex conditions revealed by the SHEBA observations. Our LES studies both validate previous results and address issues not covered in the previous studies in an effort to understand and represent the SHEBA surface fluxes on scales from local point measurements to the GCM grid-box size.
Block modeling of crustal deformation in Tierra del Fuego from GNSS velocities
NASA Astrophysics Data System (ADS)
Mendoza, L.; Richter, A.; Fritsche, M.; Hormaechea, J. L.; Perdomo, R.; Dietrich, R.
2015-05-01
The Tierra del Fuego (TDF) main island is divided by a major transform boundary between the South America and Scotia tectonic plates. Using a block model, we infer slip rates, locking depths and inclinations of active faults in TDF from inversion of site velocities derived from Global Navigation Satellite System observations. We use interseismic velocities from 48 sites, obtained from field measurements spanning 20 years. Euler vectors consistent with a simple seismic cycle are estimated for each block. In addition, we introduce far-field information into the modeling by applying constraints on Euler vectors of major tectonic plates. The difference between model and observed surface deformation near the Magallanes Fagnano Fault System (MFS) is reduced by considering finite dip in the forward model. For this tectonic boundary global plate circuits models predict relative movements between 7 and 9 mm yr- 1, while our regional model indicates that a strike-slip rate of 5.9 ± 0.2 mm yr- 1 is accommodated across the MFS. Our results indicate faults dipping 66- 4+ 6° southward, locked to a depth of 11- 5+ 5 km, which are consistent with geological models for the MFS. However, normal slip also dominates the fault perpendicular motion throughout the eastern MFS, with a maximum rate along the Fagnano Lake.
Applying dynamic wake models to large swirl velocities for optimal propellers
NASA Astrophysics Data System (ADS)
Makinen, Stephen M.
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.
Karoutas, Zeses E.; Liu, Bin; Dzodzo, Milorad; Joffre, Paul F. [Westinghouse Electric Company (United States)
2006-07-01
A numerical investigation was performed to study the variation in axial velocity profiles occurring downstream of the inlet nozzle region of Nuclear PWR fuel assemblies. Computational Fluid Dynamic (CFD) models were prepared for the inlet nozzle region of a section of fuel assembly, simulating the lower support plate located under the fuel assembly, the inlet nozzle of the fuel and the downstream fuel region. Two different nozzle designs were modeled to study how each nozzle impacts the dissipation of the jet velocity profiles occurring downstream of the nozzle. The two different nozzle designs included a standard round chamfered hole flow plate and a chamfered slotted flow plate. The evaluation of the axial velocity profiles occurring downstream of the nozzle flow plate is critical in understanding the fuel rod vibration and rod fretting in the first grid span. Excessive rod vibration in this region can occur due to high axial jet velocities and steep axial velocity gradients generated from the holes in the lower support plate. The excessive rod vibration can lead to fuel rod wear and fuel failure. Axial velocity profiles were predicted for the different nozzle designs using the CFX code. These velocity profiles were compared to air test velocity measurements for the same nozzle designs. Velocity measurements were made in a 3.763/1 over-scale air test section simulating a 6 x 6 rod array of the inlet nozzle region and downstream fuel region. Reasonable agreement was observed between the velocity measurements and CFD model predictions. The results also indicate that nozzle flow plate geometry can have a significant affect on the dissipation of the jet axial velocity profiles and the steepness of the axial velocity gradients downstream on the inlet nozzle. The application of CFD tools can be used to optimize the inlet nozzle geometry to better dissipate jets and reduce axial velocity gradients downstream of the nozzle at a minimal increase in pressure drop. This will help reduce fuel rod vibration and rod fretting. (authors)
Yang, Jun-Qi; Wen, Xiangshu; Liu, Hongzhu; Folayan, Gbolahan; Dong, Xin; Zhou, Min; Van Kaer, Luc; Singh, Ram Raj
2008-01-01
Objective CD1d-reactive invariant natural killer T (iNKT) cells secrete multiple cytokines upon T cell receptor (TCR) engagement and modulate many immune-mediated conditions. The purpose of this study was to examine the role of these cells in the development of autoimmune disease in genetically lupus-prone (NZB × NZW)F1 (BWF1) mice. Methods The CD1d1-null genotype was crossed onto the NZB and NZW backgrounds to establish CD1d1-knockout (CD1d0) BWF1 mice. CD1d0 mice and their wild-type littermates were monitored for the development of nephritis and assessed for cytokine responses to CD1d-restricted glycolipid ?-galactosylceramide (?GalCer), anti-CD3 antibody, and con-canavalin A (Con A). Thymus and spleen cells were stained with CD1d tetramers that had been loaded with ?GalCer or its analog PBS-57 to detect iNKT cells, and the cells were compared between BWF1 mice and class II major histocompatibility complex–matched nonautoimmune strains, including BALB/c, (BALB/c × NZW)F1 (CWF1), and NZW. Results CD1d0 BWF1 mice had more severe nephritis than did their wild-type littermates. Although iNKT cells and iNKT cell responses were absent in CD1d0 BWF1 mice, the CD1d0 mice continued to have significant numbers of interferon-?–producing NKT-like (CD1d-independent TCR?+,NK1.1+ and/or DX5+) cells. CD1d deficiency also influenced cytokine responses by conventional T cells: upon in vitro stimulation of splenocytes with Con A or anti-CD3, type 2 cytokine levels were reduced, whereas type 1 cytokine levels were increased or unchanged in CD1d0 mice as compared with their wild-type littermates. Additionally, numbers of thymic iNKT cells were lower in young wild-type BWF1 mice than in nonautoimmune strains. Conclusion Germline deletion of CD1d exacerbates lupus in BWF1 mice. This finding, together with reduced thymic iNKT cells in young BWF1 mice as compared with nonautoimmune strains, implies a regulatory role of CD1d and iNKT cells during the development of lupus. PMID:17393451
Validation of recent shear wave velocity models in the United States with full-wave simulation
NASA Astrophysics Data System (ADS)
Gao, Haiying; Shen, Yang
2015-01-01
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.
NASA Astrophysics Data System (ADS)
Kalmbach, G.; Goerner, K.; Seeger, M.
A two-color-LDA system including suitable scattering particles and adequate data acquisition software usable for investigation of the flow properties in technical flames was assembled and first tested on an isothermal furnace model. Simultaneous two-dimensional measurements of mean velocities, velocity fluctuations, and their correlations were performed under swirling conditions and without swirl of the inlet air, respectively. With consideration to the planned use of the system in flames, an LDA in backscatter mode was employed. Details of the flow field as recirculation zones and vortices could be quantified by use of frequency shifting. The measured flow fields were compared to those which were obtained by mathematical prediction.
NASA Astrophysics Data System (ADS)
de Almeida, Gustavo; Rodriguez, Jose
2013-04-01
Many gravel bed streams have a typical bed morphology consisting of pool-riffle sequences, which provides important habitat diversity both in terms of flow and substrate. Here we use a 1D unsteady multi-fraction morphodynamic model to explain the formation, self maintenance and degradation of pool-riffle sequences. Previous research has focussed almost exclusively on understanding self-maintenance on existing pool-riffle sequences, leaving formation and degradation at a speculative level. Spontaneous formation of pools and riffles has not been attempted before, even though other similar stable bedforms have been generated numerically and in the laboratory through the interaction of flow and sediment transport, like alternate bars in meanders and central bars in braided rivers. While this previous research substantially simplified flow (constant discharge), geometry (sinusoidal description of curvature or channel width) and sediment (uniform material) it showed the forcing effects of either curvature or width on the location of bedforms. For the formation of pools and riffles we use elements of the previous approach (width forcing) but we also incorporate a much more detailed geometry, flow and sediment description, since our intent is to study driving mechanisms for both the morphology and the sediment composition of the bed in a more realistic setting. We tested two hypotheses using our model. The first hypothesis states that the dynamic interaction of 1D flow and sediment processes can not only maintain but also generate a stable pool-riffle morphology with the corresponding longitudinal sorting on a stream with a non uniform bed material, variations in width and subjected to a variable flow regime. The second hypothesis we investigated is that the two key forming sediment processes of erosion/deposition and sorting have different time scales, which interact with the flow time scales to produce a feedback mechanism that reinforces the pool-riffle morphology, including bed geometry and composition. We performed both variable flow and constant flow simulation imposing the width variations observed in an existing river reach and did experiments starting from both a flat bed (to study formation) and from a pool-riffle sequence (to study degradation). Using measured flows on a stream in which we have removed initial bedforms and sediment sorting our model spontaneously generates pools with finer substrate at narrow sections and riffles with coarser sediment at wider sections, closely resembling the natural bed morphology. Additional experiments show that under our modelling assumptions a variable flow regime is fundamental for development and self-maintenance of the longitudinal grain sorting characteristic of pool-riffle sequences, which could not be obtained or maintained with constant discharges.
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
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.
Janus, Christopher; Flores, Abigail Y; Xu, Guilian; Borchelt, David R
2015-09-01
Alzheimer's disease (AD) is characterized by dysfunction in cognitive and noncognitive domains with clinical diagnosis based on multiple neuropsychological tests. Here, we evaluated cognitive and noncognitive behaviors in 2 age cohorts (8 and 14 months at the start of the study) of APPSwe/PS1dE9 transgenic mice that model AD-like amyloidosis. We used a battery of tests that included fear-conditioned context and tone memories, swimming activity, and orientation to a proximal cue in a visible platform water maze test and burrowing and nest building activity. To compare the performance of mice across all tests, we used z-score normalization of data. The analyses revealed that the behavior of the transgenic mice was significantly compromised in cognitive as well as in noncognitive domains. Combining scores across multiple behavioral tests produced an integrated index characterizing the overall phenotypic abnormality in this model of AD-like amyloidosis. Assessing multiple behavioral domains provides a broader view of the breadth of impairments in multiple behavioral systems. Greater implementation of such approaches could enable reliable and clinically predictive evaluation of therapeutics in mouse models of amyloidosis. PMID:26089165
Discrete Kinetic Models for Molecular Motors: Asymptotic Velocity and Gaussian Fluctuations
NASA Astrophysics Data System (ADS)
Faggionato, Alessandra; Silvestri, Vittoria
2014-12-01
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.
Rock physics model-based prediction of shear wave velocity in the Barnett Shale formation
NASA Astrophysics Data System (ADS)
Guo, Zhiqi; Li, Xiang-Yang
2015-06-01
Predicting S-wave velocity is important for reservoir characterization and fluid identification in unconventional resources. A rock physics model-based method is developed for estimating pore aspect ratio and predicting shear wave velocity Vs from the information of P-wave velocity, porosity and mineralogy in a borehole. Statistical distribution of pore geometry is considered in the rock physics models. In the application to the Barnett formation, we compare the high frequency self-consistent approximation (SCA) method that corresponds to isolated pore spaces, and the low frequency SCA-Gassmann method that describes well-connected pore spaces. Inversion results indicate that compared to the surroundings, the Barnett Shale shows less fluctuation in the pore aspect ratio in spite of complex constituents in the shale. The high frequency method provides a more robust and accurate prediction of Vs for all the three intervals in the Barnett formation, while the low frequency method collapses for the Barnett Shale interval. Possible causes for this discrepancy can be explained by the fact that poor in situ pore connectivity and low permeability make well-log sonic frequencies act as high frequencies and thus invalidate the low frequency assumption of the Gassmann theory. In comparison, for the overlying Marble Falls and underlying Ellenburger carbonates, both the high and low frequency methods predict Vs with reasonable accuracy, which may reveal that sonic frequencies are within the transition frequencies zone due to higher pore connectivity in the surroundings.
Stephenson, William J.
2007-01-01
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.
Mass loading and velocity diffusion models for heavy pickup ions at comet Grigg-Skjellerup
NASA Technical Reports Server (NTRS)
Huddleston, D. E.; Coates, A. J.; Johnstone, A. D.; Neubauer, Fritz M.
1993-01-01
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.
NASA Astrophysics Data System (ADS)
Saar, Steven; Dumusque, Xavier
2015-08-01
The radial velocity (RV) signature of starspots has been well-studied and methods to mitigate for them have been developed. The RV signature of magnetic plage is smaller, but more complex (since plage differs from its surroundings more by velocity than intensity) and less well understood. There are reasons however to expect that RV jitter from plage may be important, especially in low to moderate activity stars. We explore the RV effects of stellar plage by taking spatially resolved solar line bisectors in and out of plage at various limb angles to construct semi-empirical stellar intensity profiles profiles of different strengths. These lines are placed on model stars with various plage configurations, rotated, and disk-integrated. The resulting spectra are analyzed to yield the RV and various line and cross-correlation profile diagnostics as a function of rotational phase. We discuss the results and some ideas for mitigating the inferred RV signatures.
Wall layer models for the calculation of velocity and heat transfer in turbulent boundary layers
NASA Technical Reports Server (NTRS)
Walker, J. D. A.; Scharnhorst, R. K.; Weigand, G. G.
1986-01-01
In the computation of turbulent boundary-layer flows and internal flows, a substantial amount of mesh points and computational effort is required to adequately resolve the intense temperature and velocity profile variations in the near wall region. In this study, analytical profile approximations are obtained for the mean velocity and temperature distribution in the wall layer; these profiles are based upon consideration of the observed coherent structure of the time-dependent wall-layer flow. The profile approximations are relatively simple analytical formulae which satisfy all the required compatibility conditions at the wall and the logarithmic behavior at the edge of the wall layer. The Reynolds analogy for heat transfer is not used in the present theory. A general method for utilizing the present wall-layer profile models in a prediction method is indicated.
Jiang, Beihan; Yang, Kejun; Cao, Shuyou
2015-01-01
Based on the momentum transfer theory, an analytical model is proposed for the velocity and discharge distributions in compound channels with submerged vegetation on the floodplain. The partially vegetated channel was divided into three sub-regions, i.e. the main channel region, the floodplain region with submerged vegetation and the floodplain region without vegetation. For each region, the force balance relationship was established, and the momentum transfer between different regions was presented. Verification by the experimental data and comparison with the traditional method shows that the proposed method is capable of predicting for the velocity and discharge distributions in compound channels with submerged vegetation and is superior to the conventional method. The results also show that when the momentum transfer between different regions is ignored, the computed discharge will be much lager than the measured data, and the error increases with the discharge, especially in the floodplain region. PMID:26161661
Jiang, Beihan; Yang, Kejun; Cao, Shuyou
2015-01-01
Based on the momentum transfer theory, an analytical model is proposed for the velocity and discharge distributions in compound channels with submerged vegetation on the floodplain. The partially vegetated channel was divided into three sub-regions, i.e. the main channel region, the floodplain region with submerged vegetation and the floodplain region without vegetation. For each region, the force balance relationship was established, and the momentum transfer between different regions was presented. Verification by the experimental data and comparison with the traditional method shows that the proposed method is capable of predicting for the velocity and discharge distributions in compound channels with submerged vegetation and is superior to the conventional method. The results also show that when the momentum transfer between different regions is ignored, the computed discharge will be much lager than the measured data, and the error increases with the discharge, especially in the floodplain region. PMID:26161661
A Wiener-Laguerre model of VIV forces given recent cylinder velocities
Maincon, Philippe
2010-01-01
Slender structures immersed in a cross flow can experience vibrations induced by vortex shedding (VIV), which cause fatigue damage and other problems. VIV models in engineering use today tend to operate in the frequency domain. A time domain model would allow to capture the chaotic nature of VIV and to model interactions with other loads and non-linearities. Such a model was developed in the present work: for each cross section, recent velocity history is compressed using Laguerre polynomials. The compressed information is used to enter an interpolation function to predict the instantaneous force, allowing to step the dynamic analysis. An offshore riser was modeled in this way: Some analyses provided an unusually fine level of realism, while in other analyses, the riser fell into an unphysical pattern of vibration. It is concluded that the concept is promissing, yet that more work is needed to understand orbit stability and related issues, in order to further progress towards an engineering tool.
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
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.
NASA Astrophysics Data System (ADS)
Borbon, A.; Ruiz, M.; Bechara, J.; Afif, C.; Huntrieser, H.; Mills, G.; Mari, C.; Reeves, C.; Schlager, H.
2010-12-01
Deep convection plays a key role in determining global atmospheric composition of the upper troposphere by the fast uplift of HOx radical and ozone precursors to the upper troposphere. Formaldehyde (HCHO) is one important gas precursor. It is the most abundant carbonyl compound originating from both primary processes and photooxidation of volatile organic compounds. Thus, determining its source strength to the upper troposphere is important for estimating ozone production. However processes governing its fate are multiple and complex including dynamics (entrainment and detrainment), multiphase chemistry and cloud microphysics. As a result, the flux of formaldehyde to the upper troposphere is still uncertain. The goal of this study is to examine the redistribution of formaldehyde in tropical mesoscale convective systems (MSC) and to estimate its sources and sinks during convective transport to the upper troposphere. The novelty here is to combine 1D modelling (Meso NH model) and formaldehyde aircraft observations. Observations were collected over West Africa during the monsoon period (July-August 2006) of the AMMA experiment. Four aircrafts (English BAe-146, French ATR-42 and Falcon-20 and German Falcon-20) were deployed over a large domain (long.: -8°E-5°W, lat. 4°N-20°N, alt.: 0 12 km) with formaldehyde measuring instruments on board. First, this presentation will point out the construction of a comprehensive and consistent data set of formaldehyde by ensuring data comparability thanks to aircraft intercomparison flights, multiple chemical tracer approach (CO, O3 and relative humidity) and a spatial gridding of the domain. Then formaldehyde spatial variability will be examined under background and convective conditions. Finally, the relative importance of transport (entrainment) and wet scavenging will be discussed from selected AMMA flights. For that purpose, the following equation system has been resolved [HCHO]transported to UT=[HCHO]measured - [HCHO]bckgd [HCHO]transported to UT = x[HCHO]BL + y[HCHO]FT - z[HCHO]bckgd - [HCHO]wet scavenging where : BL: boundary layer; FT: free troposphere; bckgd: background and x, y and z fraction of formaldehyde concentration transported from intermediate layers (BL and FT). Two hypotheses have been tested and compared. The first hypothesis only considers entrainment from the boundary layer (0-2 km) (Bertram et al. 2007). This fraction is derived from non reactive hydrocarbons observations on board the French aircrafts (Bechara et al., 2010). The second hypothesis considers additional entrainment and detrainment from intermediate layers (2-6 km). These terms are determined by 1D-modelling for a non reactive tracer (non soluble).
Schinke, R; Grebenshchikov, S Yu
2007-08-14
In this Comment we present quantum mechanical absorption spectra of the Hartley band originating from the four vibrationally excited levels of the ground electronic state. The calculations are performed using the diabatic B-state potential energy surface and the transition dipole moment vector constructed from the ab initio data of the title paper. The calculated spectra are multimodal (for the symmetric stretch pre-excitation) and strongly structured (for the symmetric stretch and bending pre-excitations). These results agree with the previous theoretical analysis and with the predictions of a simple model based on the reflection principle, but contradict the findings of Baloïtcha amd Balint-Kurti thus questioning the accuracy of their calculations. PMID:17646892
Modeling the exit velocity of a compressed air cannon Z. J. Rohrbach, T. R. Buresh, and M. J. Madsen
Madsen, Martin John
Modeling the exit velocity of a compressed air cannon Z. J. Rohrbach, T. R. Buresh, and M. J; accepted 8 September 2011) The use of compressed air cannons in an undergraduate laboratory provides a way elementary Newtonian kinematics.5 We constructed a compressed air cannon to measure the exit velocity
Nowack, Robert L.
Velocity and Attenuation Structure of the Tibetan Lithosphere Under the Hi-CLIMB Array From earthquakes in Tibet recorded by the Hi-CLIMB experiment, Pn attributes are used to constrain the velocity gradient and attenuation structure of the Tibetan lithosphere under the Hi-CLIMB array. Numerical modeling
Yang Aijun; Wang Xiaohua; Rong Mingzhe; Liu Dingxin; Iza, Felipe; Kong, Michael G.
2011-11-15
In this paper atmospheric-pressure rf He+O{sub 2} cold plasmas are studied by means of a 1-D fluid model. 17 species and 60 key reactions selected from a study of 250+ reactions are incorporated in the model. O{sub 2}{sup +}, O{sub 3}{sup -}, and O are the dominant positive ion, negative ion, and reactive oxygen species, respectively. Ground state O is mainly generated by electron induced reactions and quenching of atomic and molecular oxygen metastables, while three-body reactions leading to the formation of O{sub 2} and O{sub 3} are the main mechanisms responsible for O destruction. The fraction of input power dissipated by ions is {approx}20%. For the conditions considered in the study {approx}6% of the input power is coupled to ions in the bulk and this amount will increase with increasing electronegativity. Radial and electrode losses of neutral species are in most cases negligible when compared to gas phase processes as these losses are diffusion limited due to the large collisionality of the plasma. The electrode loss rate of neutral species is found to be nearly independent of the surface adsorption probability p for p > 0.001 and therefore plasma dosage can be quantified even if p is not known precisely.
A Global Model of The Light Curves and Expansion Velocities of Type II-plateau Supernovae
NASA Astrophysics Data System (ADS)
Pejcha, Ond?ej; Prieto, Jose L.
2015-02-01
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.
Uncertainty estimation of the velocity model for the TrigNet GPS network
NASA Astrophysics Data System (ADS)
Hackl, Matthias; Malservisi, Rocco; Hugentobler, Urs; Wonnacott, Richard
2010-05-01
Satellite based geodetic techniques - above all GPS - provide an outstanding tool to measure crustal motions. They are widely used to derive geodetic velocity models that are applied in geodynamics to determine rotations of tectonic blocks, to localize active geological features, and to estimate rheological properties of the crust and the underlying asthenosphere. However, it is not a trivial task to derive GPS velocities and their uncertainties from positioning time series. In general time series are assumed to be represented by linear models (sometimes offsets, annual, and semi-annual signals are included) and noise. It has been shown that models accounting only for white noise tend to underestimate the uncertainties of rates derived from long time series and that different colored noise components (flicker noise, random walk, etc.) need to be considered. However, a thorough error analysis including power spectra analyses and maximum likelihood estimates is quite demanding and are usually not carried out for every site, but the uncertainties are scaled by latitude dependent factors. Analyses of the South Africa continuous GPS network TrigNet indicate that the scaled uncertainties overestimate the velocity errors. So we applied a method similar to the Allan Variance that is commonly used in the estimation of clock uncertainties and is able to account for time dependent probability density functions (colored noise) to the TrigNet time series. Finally, we compared these estimates to the results obtained by spectral analyses using CATS. Comparisons with synthetic data show that the noise can be represented quite well by a power law model in combination with a seasonal signal in agreement with previous studies.
NASA Astrophysics Data System (ADS)
Shiddiqi, Hasbi Ash; Widiyantoro, Sri; Nugraha, Andri Dian; Ramdhan, Mohamad; Wandono, Sutiyono, Handayani, Titi; Nugroho, Hendro
2015-04-01
We have relocated hypocenters of earthquakes occurring in the Molucca collision zone and surrounding region taken from the BMKG catalog using teleseismic double-difference relocation algorithm (teletomoDD). We used P-wave arrival times of local, regional, and teleseismic events recorded at 304 recording stations. Over 7,000 earthquakes were recorded by the BMKG seismographicnetworkin the study region from April, 2009 toJune, 2014. We used a 3D regional-global nested velocity modelresulting fromprevious global tomographystudy. In this study, the3D seismic velocity model was appliedto theIndonesian region, whilethe1D seismicvelocity model (ak135)wasused for regions outside of Indonesia. Our relocation results show a better improvement in travel-time RMS residuals comparedto those of the BMKG catalog.Ourresultsalso show that relocation shifts were dominated intheeast-west direction, whichmaybeinfluenced by theexistingvelocity anomaly related to the reversed V-shaped slabbeneaththestudy region. Our eventrelocation results refine the geometry of slabs beneath the Halmahera and Sangihe arcs.
Applying the critical velocity model for an off-season interval training program.
Clark, Ida E; West, Brianne M; Reynolds, Sheila K; Murray, Steven R; Pettitt, Robert W
2013-12-01
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
A Three-Dimensional Seismic Velocity Model of the Arabian Plate, Iranian and Turkish Plateaus
NASA Astrophysics Data System (ADS)
Ghalib, Hafidh; Gritto, Roland; Sibol, Matthew; Herrmann, Robert; Aleqabi, Ghassan; Carron, Pierre; Wagner, Robert; Ali, Bakir; Ali, Ali
2010-05-01
Translational and rotational interaction between the Arabian, African and Eurasian plates over time has resulted in a challenging seismotectonic framework that is least understood in the Middle East region, in particular. Sea floor spreading along the Red Sea and Gulf of Aden, transform faulting along the Dead Sea and Own fracture zone, and compressional suture zones form the seismic and tectonic boundaries between the Arabian plate, the Iranian and Turkish plateaus. One objective of this effort is to map the three-dimensional shear-wave velocity variation using surface waves recorded by the broadband stations of North Iraq Seismographic Network (NISN), re-established Iraq Seismographic Network (ISN), and local stations of the Global Seismographic Network (GSN). Analysis of the seismograms netted a new seismicity map for the region consisting of about 2000 well located small to medium size earthquakes using all available phase arrivals including those published by the neighboring Syrian, Iranian and Turkish networks. Analysis of Rayleigh wave pure-path dispersion curves produced detailed maps showing the lateral and vertical variation of seismic velocities throughout the Middle East. These maps show a thick (10-15km) sedimentary layer that overlay the crystalline basement and a Conrad and Moho discontinuities at depths of 20-25km and 45-55km, respectively. The maps also show that the Arabian plate exhibits higher shear-wave velocities than found across the Turkish and Iranian plateaus; imprint of the Zagros Mountain roots extends down as deep as the Moho; and that the tectonic boundaries along the Dead Sea, Taurus and Zagros are more pronounced with depth describing a 60km or thicker Arabian plate. Future plans involving body wave velocity tomography modeling, high frequency wave attenuation, and moment tensor analysis to estimate the focal mechanism and magnitude of events are in preparation.
Jeanjean, Louis
: numerics, existence The coupled problem Small solids in an inviscid fluid: a 1D model, theory and numerics'Alembert paradox : a solid immersed in an inviscid fluid is not submitted to any resultant force ; in other words models of fluid-solid interaction (see e.g. M. Hillairet , for a recent review). Answer 2 (when
NASA Astrophysics Data System (ADS)
Ammirati, Jean-Baptiste; Alvarado, Patricia; Beck, Susan
2015-07-01
In the central Andes, the Nazca plate displays large along strike variations in dip with a near horizontal subduction angle between 28 and 32°S referred to the Pampean flat slab segment. The upper plate above the Pampean flat slab has high rates of crustal seismicity and active basement cored uplifts. The SIEMBRA experiment, a 43-broad-band-seismic-station array was deployed to better characterize the Pampean flat slab region around 31°S. In this study, we explore the lithospheric structure above the flat slab as a whole and its relation to seismicity. We use the SIEMBRA data to perform a joint inversion of teleseismic receiver functions and Rayleigh wave phase velocity dispersion to constrain the shear wave velocity variations in the lithosphere. Our joint inversion results show: (1) the presence of several upper-plate mid-crustal discontinuities and their lateral extent that are probably related to the terrane accretion history; (2) zones of high shear wave velocity in the upper-plate lower crust associated with a weak Moho signal consistent with the hypothesis of partial eclogitization in the lower crust; (3) the presence of low shear-wave velocities at ˜100 km depth interpreted as the subducting oceanic crust. Finally, in order to investigate the relation of the lithospheric structure to seismicity, we determine an optimal velocity-depth model based on the joint inversion results and use it to perform regional moment tensor inversions (SMTI) of crustal and slab earthquakes. The SMTI for 18 earthquakes that occurred between 2007 and 2009 in the flat slab region below Argentina, indicates systematically shallower focal depths for slab earthquakes (compared with inversions using previous velocity models). This suggests that the slab seismicity is concentrated mostly between 90 and 110 km depths within the subducting Nazca plate's oceanic crust and likely related to dehydration. In addition, the slab earthquakes exhibit extensional focal mechanisms suggesting new faulting at the edges of the flat portion of the slab. SMTI solutions for upper-plate crustal earthquakes match well the geological observations of reactivated structures and agree with crustal shortening. Our new constraints on flat slab structure can aid earthquake characterization for regional seismic hazard assessment and efforts to help understand the mechanisms for slab flattening in the central Andes.
Airglow observations and modeling of F region depletion zonal velocities over Christmas Island
NASA Astrophysics Data System (ADS)
Chapagain, Narayan P.; Taylor, Michael J.; Eccles, J. Vincent
2011-02-01
We report image measurements of plasma depletions in the equatorial F region ionosphere over Christmas Island (2.1°N, 157.4°W dip latitude 2.8°N) in the central Pacific Ocean. The observations were made during the equinox period, September-October 1995, using a Utah State University CCD imaging system filtered to observe thermospheric O I (630.0 nm) airglow emissions centered at ˜280 km altitude. Well-defined magnetic field-aligned depletions were observed on 18 nights during the campaign, including strong postmidnight fossilized structures, enabling detailed measurements of their morphology and dynamics. The number of depletions was influenced by their initial onset times and their persistence. The separations between adjacent depletions ranged from ˜150 to ˜250 km in good agreement with prior observations from other sites. However, measurements of their eastward zonal drift speeds indicated normal behavior peaking around 90-100 m/s prior to local midnight, with exceptionally high velocities, ˜80 m/s during the postmidnight period that persisted until dawn. These results differ markedly from optical measurements at similar equatorial latitudes but at different longitude sectors, suggesting that the zonal drift velocities can have a significant longitudinal dependence. Model drift velocities calculated using a simple electric field model with winds defined by the horizontal wind model (HWM-07) produced an eastward drift throughout the night, but their postmidnight magnitudes were much smaller than observed. Using a modified HWM-07 wind field, a basic nighttime trend similar to the Christmas Island trend was successfully obtained.
NASA Astrophysics Data System (ADS)
Arcos, M. M.; Leveque, R. J.
2013-12-01
During the 11 March 2011 Tohoku Tsunami 328 current meters were in place around the Hawaiian Islands, USA, that captured time series of water velocity in 18 locations, in both harbors and deep channels, at a series of depths. We compare several of these velocity records against numerical simulations performed using the GeoClaw numerical tsunami model, based on solving the depth-averaged shallow water equations with adaptive mesh refinement, to confirm that this model can accurately predict velocities at nearshore locations. Model results demonstrate tsunami current velocity is more spatially variable than wave form or height and therefore may be a more sensitive variable for model validation. The ability to measure, predict, and compute tsunami flow velocities is also of great 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.
1 2 3 4 5 6 7 T Mon: Velocity Model Prior Probability
Jefferys, William
.0 0500100020003000 T Mon: log_10 tau_x of Velocity Data log_10 tau_x Frequency -1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 05001000150020002500 T Mon: log_10 tau_z of Color Data log_10 tau_z Frequency 0.3 0.4 0.5 0.6 0.7 050010001500 #12 Model log_10tau.v T Mon: log_10 tau_v of V-Photometry Data log_10 tau_v Frequency -0.1 0.0 0.1 0.2 0
Stochastic microswimming model for the average translational velocity of the ribosome
NASA Astrophysics Data System (ADS)
González-García, José S.; Delgado, Joaquín
2013-07-01
The motion of the ribosome is modeled here, assuming that its two subunits are subject to stochastic rearrangements, thus producing different conformations constituting its deformation cycle, or swimming stroke. Using a general statistical mechanical formulation, the mean propulsion velocity of the ribosome is obtained as a function of the transition rates among the different conformations and of the relevant deformation variables. A calculation with reasonable parameter estimations shows that the ribosome can match the average protein synthesis speed with deformations of a size comparable to its radius.
Scalar potential model of galaxy central mass and central velocity dispersion
John C. Hodge
2006-01-01
The galaxy central mass $M_\\\\mathrm{c}$ and central velocity dispersion\\u000a$\\\\sigma_\\\\mathrm{c}$ have been found to correlate with large scale galaxy\\u000aparameters for samples of galaxies with a limited range of characteristics. A\\u000ascalar potential model (SPM) that derived from considerations of galaxy\\u000aclusters, of redshift, of discrete redshift, of H{\\\\scriptsize{I}} rotation\\u000acurves (RCs) of spiral galaxies and of RC asymmetry is
Sterile neutrinos, dark matter, and pulsar velocities in models with a Higgs singlet.
Kusenko, Alexander
2006-12-15
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
Velocity-gradient probability distribution functions in a lagrangian model of turbulence
NASA Astrophysics Data System (ADS)
Moriconi, L.; Pereira, R. M.; Grigorio, L. S.
2014-10-01
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.
Modelling the transverse distribution of velocity and suspended sediment in tidal estuaries
NASA Astrophysics Data System (ADS)
Huijts, K. M. H.
2011-01-01
An estuary is a semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage. Examples are the Western Scheldt River Estuary and the Chesapeake Bay. Within these environments complex patterns of velocity and suspended sediments are observed in the transversal plane (across-estuary and vertical), and sediments are trapped laterally (across-estuary). The transverse structure of velocity is relevant to the transport of salt, sediment, contaminants, oxygen and other material. High sediment concentrations affect water quality, ecology and wildlife, and may cause siltation of navigation channels and harbors. This work aims at a fundamental understanding of the transverse distributions of estuarine velocity and suspended sediment. The thesis provides two-dimensional (cross-sectional) analytical models to identify the effect of individual forcing mechanisms on the transverse distribution of velocity and suspended sediment in tidally-dominated estuaries. The models are based on the shallow water equations and sediment mass balance. Considered are the residual and the semi-diurnal tidal components of the along-estuary, across-estuary and vertical velocity and of the suspended sediment concentration. The models apply to partially to we