3,200 research outputs found
An Adaptive Moving Mesh Method for Two-Dimensional Relativistic Hydrodynamics
No full textThis paper extends the adaptive moving mesh method developed by Tang and Tang [36] to two-dimensional (2D) relativistic hydrodynamic (RHD) equations. The algorithm consists of two "independent" parts: the time evolution of the RHD equations and the (static) mesh iteration redistribution. In the first part, the RHD equations are discretized by using a high resolution finite volume scheme on the fixed but nonuniform meshes without the full characteristic decomposition of the governing equations. The second part is an iterative procedure. In each iteration, the mesh points are first redistributed, and then the cell averages of the conservative variables are remapped onto the new mesh in a conservative way. Several numerical examples are given to demonstrate the accuracy and effectiveness of the proposed method.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000301923300006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, MathematicalSCI(E)15ARTICLE1114-1461
Learning an Ensemble of Semantic Parsers for Building Dialog-Based Natural Language Interfaces
No full textStability of Atomic Simulations with Matching Boundary Conditions
No full textWe explore the stability of matching boundary conditions in one space dimension, which were proposed recently for atomic simulations (Wang and Tang, Int. J. Numer. Mech. Eng., 93 (2013), pp. 1255-1285). For a finite segment of the linear harmonic chain, we construct explicit energy functionals that decay along with time. For a nonlinear atomic chain with its nonlinearity vanished around the boundaries, an energy functional is constructed for the first order matching boundary condition. Numerical verifications are also presented.Mathematics, AppliedMechanicsSCI(E)[email protected]; [email protected]
Gravitational collapse of massless scalar field in f(R) gravity
No full textWe study the spherically symmetric gravitational collapse of massless scalar matter field in asymptotic flat spacetime in the Starobinsky R-2 gravity, one specific model in the f(R) gravity. In the Einstein frame of f(R) gravity, an additional scalar field arises due to the conformal transformation. We find that in addition to the usual competition between gravitational energy and kinetic energy in the process of gravitational collapse, the new scalar field brought by the conformal transformation adds one more competing force in the dynamical system. The dynamical competition can be controlled by tuning the amplitudes of the initial perturbations of the new scalar field and the matter field. To understand the physical reasons behind these phenomena, we analyze the gravitational potential behavior and calculate the Ricci scalar at center with the change of initial amplitudes of perturbations. We find rich physics on the formation of black holes through gravitational collapse in f(R) gravity.NNSF of ChinaSCI(E)[email protected]; [email protected]; [email protected]
The use of a multi-set-up, reduced-scale accelerated trafficking simulator for evaluating roadway systems and products
No full textThis paper describes the use of an accelerated trafficking device, the one-third scale model mobile load simulator (MMLS3), for evaluating roadway systems and products. While the majority of accelerated load testers have focused on investigating rutting behaviours and moisture damage susceptibility of bituminous materials, this paper sheds light on broader applications using the MMLS3, including accelerated tests on field sections, scaled pavement structures, roadway reflective markings, roadway slip-resistant plates, in addition to performance evaluation tests on hot-mix asphalt mixtures. Results of experiments for the various applications indicate that the MMLS3, when equipped with ancillary instrumentation and devices, is a valuable tool for investigating the structural responses of a roadway system and for evaluating the effectiveness and durability of roadway pavement products. This study shows that the results of accelerated trafficking tests using the MMLS3 are comparable with field full-scale accelerated tests due to the nature of similitude in the MMLS3 design. Using the MMLS3 for accelerated traffic testing for practical and research purposes in the area of pavement engineering is a reliable and economical alternative to full-scale accelerated testing, given the savings in the required time and resources. © 2012 Copyright Taylor and Francis Group, LLC.Aktan F, 2004, TRANSPORT RES REC, P38; Al-Qadi L., 2007, TRB 2007 ANN M; Anderson D., 1984, 4 CYCLE PAVEMENT RES, V1; [Anonymous], 2007, ANN BOOK ASTM STAND; [Anonymous], 2007, ANN BOOK ASTM STAND; Barksdale R. D., 1989, 315 NCHRP TRANSP BOA; Bhattacharjee S., 2005, THESIS WORCESTER POL; Chehab G.R., 2007, FHWAPA2007009050110; Cooley Jr L. A., 2000, EC016 TRB NAT RES CO; Donnell ET, 2009, TRANSP RES RECORD, P76, DOI 10.3141-2107-08; Epps A. L., 2003, J TRANSPORTATION ENG, V129, P451, DOI 10.1061-(ASCE)0733-947X(2003)129:4(451); Epps A. L., 2001, 21341 TEX A M U TEX; Hufenus R, 2006, GEOTEXT GEOMEMBRANES, V24, P21, DOI 10.1016-j.geotexmem.2005.06.002; Hugo F. H., 2006, NCHRP SYNTHESIS HIGH; Kim S-M., 1995, 29141F U TEX CTR TRA; Lee S., 2003, THESIS N CAROLINA ST; Metcalf J. B., 1996, NCHRP SYNTHESIS HIGH; MLS Test Systems, 2003, MMLS3 OP MAN; Palacios C, 2008, PAVEMENT CRACKING: MECHANISMS, MODELING, DETECTION, TESTING AND CASE HISTORIES, P721; Pennsylvania Department of Transportation (PennDOT, 1995, PENNS DEP TRANSP PUB; Perkins S. S., 1999, FHWAMT990018138 US D; Smit A., 2004, P 2 INT APT C US SEA; Smit A., 1999, FHWATX00018142 U TEX; Smit A., 2003, TRB 82 ANN M; Tang X., 2008, GEOTECHNICAL SPECIAL, P1049; Tang X., 2008, GEOTECHNICAL SPECIAL, P1089; Xiaochao Tang, 2008, INT J PAVEMENT ENG, V9, P413, DOI 10.1080-102984308022798270
A direct Eulerian GRP scheme for relativistic hydrodynamics: Two-dimensional case
No full textThis paper develops a direct Eulerian generalized Riemann problem (GRP) scheme for two-dimensional (2D) relativistic hydrodynamics (RHD). It is an extension of the GRP scheme for one-dimensional (1D) RHDs [Z.C. Yang, P. He, H.Z. Tang, J. Comput. Phys. 230 (2011) 7964-7987] and the GRP scheme for the non-relativistic hydrodynamics [M. Ben-Artzi, J.Q. Li, G. Warnecke, J. Comput. Phys. 218 (2006) 19-43]. In order to derive the direct Eulerian GRP scheme, the (local) GRP of the split 2D RHD equations in the Eulerian formulation has to be directly resolved by using corresponding Riemann invariants and Rankine-Hugoniot jump conditions so that the crucial and delicate Lagrangian treatment in the original GRP scheme [M. Ben-Artzi, J. Falcovitz, J. Comput. Phys. 55 (1984) 1-32] may be avoided. An important difference of resolving the GRP of the split 2D RHD equations from the GRP of the 1D RHD equations or the non-relativistic hydrodynamical equations is coming from the fact that the flow regions across the shock or rarefaction wave in the GRP of the split 2D RHD equations are nonlinearly coupled through the Lorentz factor which is also built in terms of the tangential velocities. It is a purely multi-dimensional relativistic feature. Several numerical examples are given to demonstrate the accuracy and effectiveness of the proposed 2D GRP scheme. (C) 2011 Elsevier Inc. All rights reserved.Computer Science, Interdisciplinary ApplicationsPhysics, MathematicalSCI(E)8ARTICLE42116-213923
On the regularity of approximate solutions to conservation laws with piecewise smooth solutions
No full textIn this paper we address the questions of the convergence rate for approximate solutions to conservation laws with piecewise smooth solutions in a weighted W-1,W-1 space. Convergence rate for the derivative of the approximate solutions is established under the assumption that a weak pointwise-error estimate is given. In other words, we are able to convert weak pointwise-error estimates to optimal error bounds in a weighted W-1,W-1 space. For convex conservation laws, the assumption of a weak pointwise-error estimate is veri ed by Tadmor [SIAM J. Numer. Anal., 28 (1991), pp. 891-906]. Therefore, one immediate application of our W-1,W-1-convergence theory is that for convex conservation laws we indeed have W-1,W-1-error bounds for the approximate solutions to conservation laws. Furthermore, the O (epsilon)-pointwise-error estimates of Tadmor and Tang [SIAM J. Numer. Anal., 36 (1999), pp. 1739-1758] are recovered by the use of the W-1,W-1-convergence result.Mathematics, AppliedSCI(E)0ARTICLE51483-14953
Surveying silk fibre degradation by crystallinity determination: a study on the Tang-Dynasty silk treasure from Famen Temple, China
No full textWhen Chinese archaeologists opened an unknown vault under the collapsed pagoda of Famen Temple near Xian (Shaanxi Province, NW China) in 1987, they found a vast amount of valuable silk textiles. The degraded textiles were part of a treasure comprising hundreds of artifacts deposited by Tang dynasty (ad 618–907) emperors as a gift to the temple. Run as a bilateral German-Chinese project, the Roemisch-Germanisches Zentralmuseum Mainz established a textile conservation laboratory in Shaanxi´s provincial capital Xian in 2001, joining numerous other laboratories that have existed there since the early 1990s.This preliminary study represents part of an ongoing investigation programme that accompanies the conservation work. The Tang dynasty silk is generally in a very poor state of preservation as a result of its long burial period. Large sections have only survived as an amorphous brown mass of fibre debris. Some parts are better preserved, however, offering the unique opportunity to study the whole range of degradation stages on ancient silks.This preliminary scientific investigation focuses on the determination of the silk fibres’ crystallinity and its relation to the ageing process. As we know from modern material, silk is mainly crystalline, albeit in a somewhat amorphous state. The methods of investigation used were X-ray diffraction (XRD) using synchrotron radiation, which is a new way to determine crystallinity of ancient silk fibres; and polarized Fourier transform infrared spectroscopy (FTIR) for the determination of crystallite orientation. Both methods were specifically devised to gain information on small single fibres
Static spherically symmetric solutions to modified Horava-Lifshitz gravity with a projectability condition
No full textIn this paper we seek static spherically symmetric solutions of Horava-Lifshitz-like gravity with the projectability condition. We consider the most general form of gravity action without detailed balance, and require the spacetime metric to respect the projectability condition. We find that for any value of lambda, the solutions of topology R x M-3 may exist, where R is the time direction and M-3 is a three-dimensional maximally symmetric space depending on the value of cosmological constant and the potential of the action. Besides, in the UV region where lambda not equal 1, we find Minkowski or de Sitter spacetime as the solution, while in the IR region where lambda = 1, we prove that (dS-)Schwarzschild solution is the only nontrivial solution. We also notice that the other static spherically symmetric solutions found in the literature do not satisfy the projectability condition and are not the solutions we get. Our study shows that in Horava-Lifshitz gravity with the projectability condition, there is no novel correction to Einstein's general relativity in solar system tests.Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)25ARTICLE4null8
Information disclosure and price discovery
No full textIn this paper. I present a parsimonious, theoretical model to examine the influence of disclosure on market efficiency and on the cost of capital in the presence of endogenous information acquisition. Because disclosure "crowds out" private-information production, disclosure can either improve or harm market efficiency and the cost of capital, depending on whether investors' private-information production is sensitive to disclosure. This non-monotonic disclosure-cost-of-capital relation helps reconcile the existing mixed empirical evidence and has implications for the disclosure policies of firms. (C) 2014 Elsevier B.V. All rights reserved.Business, [email protected]
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