arXiv: Computational Physics最新文献_第7页

Electronic Properties of MoS2/MX2/MoS2 Trilayer Heterostructures: A First Principle Study MoS2/MX2/MoS2三层异质结构的电子性质:第一性原理研究

arXiv: Computational Physics Pub Date : 2018-02-26 DOI: 10.1149/2.0011611jss

Kanak Datta, Q. Khosru

引用次数: 7

Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: effects of shear-thinning and viscoelasticity 含高粘度硅油阻尼器内流动的理论研究:剪切减薄和粘弹性的影响

arXiv: Computational Physics Pub Date : 2018-02-16 DOI: 10.1063/1.5011755

A. Syrakos, Y. Dimakopoulos, J. Tsamopoulos

{"title":"Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: effects of shear-thinning and viscoelasticity","authors":"A. Syrakos, Y. Dimakopoulos, J. Tsamopoulos","doi":"10.1063/1.5011755","DOIUrl":"https://doi.org/10.1063/1.5011755","url":null,"abstract":"The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a Finite Volume method, at various excitation frequencies. The oil is modelled by the Carreau-Yasuda (CY) and Phan-Thien & Tanner (PTT) constitutive equations. Both models account for shear-thinning but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from LAOS (Large Amplitude Oscillatory Shear) theory. The CY model also overestimates the damper force relative to the PTT, because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77561011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 32

A Generalized Muon Trajectory Estimation Algorithm with Energy Loss for Application to Muon Tomography 基于能量损失的广义介子轨迹估计算法在介子断层成像中的应用

arXiv: Computational Physics Pub Date : 2018-01-23 DOI: 10.1063/1.5024671

S. Chatzidakis, Zhengzhi Liu, J. Hayward, J. Scaglione

{"title":"A Generalized Muon Trajectory Estimation Algorithm with Energy Loss for Application to Muon Tomography","authors":"S. Chatzidakis, Zhengzhi Liu, J. Hayward, J. Scaglione","doi":"10.1063/1.5024671","DOIUrl":"https://doi.org/10.1063/1.5024671","url":null,"abstract":"This work presents a generalized muon trajectory estimation (GMTE) algorithm to estimate the path of a muon in either uniform or nonuniform media. The use of cosmic ray muons in nuclear nonproliferation and safeguards verification applications has recently gained attention due to the nonintrusive and passive nature of the inspection, penetrating capabilities, as well as recent advances in detectors that measure position and direction of the individual muons before and after traversing the imaged object. However, muon image reconstruction techniques are limited in resolution due to low muon flux and the effects of multiple Coulomb scattering (MCS). Current reconstruction algorithms rely on overly simple assumptions for muon path estimation through the imaged object. For robust muon tomography, efficient and flexible physics based algorithms are needed to model the MCS process and accurately estimate the most probable trajectory of a muon as it traverses an object. In the present work, the use of a Bayesian framework and a Gaussian approximation of MCS are explored for estimation of the most likely path of a cosmic ray muon traversing uniform or nonuniform media and undergoing MCS. The algorithm's precision is compared to Monte Carlo simulated muon trajectories. It was found that the algorithm is expected to be able to predict muon tracks to less than 1.5 mm RMS for 0.5 GeV muons and 0.25 mm RMS for 3 GeV muons, a 50 percent improvement compared to SLP and 15 percent improvement when compared to PoCA. Further, a 30 percent increase in useful muon flux was observed relative to PoCA. Muon track prediction improved for higher muon energies or smaller penetration depth where energy loss is not significant. The effect of energy loss due to ionization is investigated, and a linear energy loss relation that is easy to use is proposed.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85166932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 15

User's guide to Monte Carlo methods for evaluating path integrals 用户指南蒙特卡罗方法评估路径积分

arXiv: Computational Physics Pub Date : 2017-12-22 DOI: 10.1119/1.5024926

Marise J. E. Westbroek, P. King, D. Vvedensky, S. Durr

引用次数: 13

Configurational forces in electronic structure calculations using Kohn-Sham density functional theory 利用Kohn-Sham密度泛函理论计算电子结构中的构型力

arXiv: Computational Physics Pub Date : 2017-12-15 DOI: 10.1103/PhysRevB.97.165132

P. Motamarri, V. Gavini

{"title":"Configurational forces in electronic structure calculations using Kohn-Sham density functional theory","authors":"P. Motamarri, V. Gavini","doi":"10.1103/PhysRevB.97.165132","DOIUrl":"https://doi.org/10.1103/PhysRevB.97.165132","url":null,"abstract":"We derive the expressions for configurational forces in Kohn-Sham density functional theory, which correspond to the generalized variational force computed as the derivative of the Kohn-Sham energy functional with respect to the position of a material point $textbf{x}$. These configurational forces that result from the inner variations of the Kohn-Sham energy functional provide a unified framework to compute atomic forces as well as stress tensor for geometry optimization. Importantly, owing to the variational nature of the formulation, these configurational forces inherently account for the Pulay corrections. The formulation presented in this work treats both pseudopotential and all-electron calculations in single framework, and employs a local variational real-space formulation of Kohn-Sham DFT expressed in terms of the non-orthogonal wavefunctions that is amenable to reduced-order scaling techniques. We demonstrate the accuracy and performance of the proposed configurational force approach on benchmark all-electron and pseudopotential calculations conducted using higher-order finite-element discretization. To this end, we examine the rates of convergence of the finite-element discretization in the computed forces and stresses for various materials systems, and, further, verify the accuracy from finite-differencing the energy. Wherever applicable, we also compare the forces and stresses with those obtained from Kohn-Sham DFT calculations employing plane-wave basis (pseudopotential calculations) and Gaussian basis (all-electron calculations). Finally, we verify the accuracy of the forces on large materials systems involving a metallic aluminum nanocluster containing 666 atoms and an alkane chain containing 902 atoms, where the Kohn-Sham electronic ground state is computed using a reduced-order scaling subspace projection technique (P. Motamarri and V. Gavini, Phys. Rev. B 90, 115127).","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74297054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Efficient time stepping for reactive turbulent simulations with stiff chemistry 具有刚性化学反应性湍流模拟的有效时间步进

arXiv: Computational Physics Pub Date : 2017-12-04 DOI: 10.2514/6.2018-1672

Hao Wu, P. Ma, M. Ihme

引用次数: 13

Phonon-interference resonance effects in nanoparticles embedded in a matrix 嵌入在基质中的纳米颗粒中的声子干涉共振效应

arXiv: Computational Physics Pub Date : 2017-12-02 DOI: 10.1103/PHYSREVB.96.220301

Lei Feng, T. Shiga, Haoxue Han, S. Ju, Y. Kosevich, J. Shiomi

引用次数: 19

Detonation propagation in annular arcs of condensed phase explosives 凝聚相炸药环弧爆轰传播

arXiv: Computational Physics Pub Date : 2017-10-20 DOI: 10.1063/1.4996995

E. Ioannou, Stefan Schoch, N. Nikiforakis, L. Michael

{"title":"Detonation propagation in annular arcs of condensed phase explosives","authors":"E. Ioannou, Stefan Schoch, N. Nikiforakis, L. Michael","doi":"10.1063/1.4996995","DOIUrl":"https://doi.org/10.1063/1.4996995","url":null,"abstract":"We present a numerical study of detonation propagation in unconfined explosive charges shaped as an annular arc (rib). Steady detonation in a straight charge propagates at constant speed but when it enters an annular section, it goes through a transition phase and eventually reaches a new steady state of constant angular velocity. This study examines the speed of the detonation wave along the annular charge during the transition phase and at steady state, as well as its dependence on the dimensions of the annulus. The system is modeled using a recently proposed diffuse-interface formulation which allows for the representation of a two-phase explosive and of an additional inert material. The explosive considered is the polymer-bonded TATB-based LX-17 and is modeled using two JWL equations of state and the Ignition and Growth reaction rate law. Results show that steady state speeds are in good agreement with experiment. In the transition phase, the evolution of outer detonation speed deviates from the exponential bounded growth function suggested by previous studies. We propose a new description of the transition phase which consists of two regimes. The first is caused by local effects at the outer edge of the annulus and leads to a dependence of outer detonation speed on angular position along the arc. The second regime is induced by effects originating from the inner edge of the annular charge and leads to the deceleration of the outer detonation until steady state is reached. The study concludes with a parametric study where the dependence of the steady state and the transition phase on the dimensions of the annulus is investigated.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91080637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 9

Theoretical investigation of the magnetoelectric properties of Bi 2 NiTiO 6 bi2nitio6磁电性质的理论研究

arXiv: Computational Physics Pub Date : 2017-09-30 DOI: 10.1063/1.5029124

L. Patra, P. Ravindran

引用次数: 0

Monte Carlo methods for massively parallel computers 大规模并行计算机的蒙特卡罗方法

arXiv: Computational Physics Pub Date : 2017-09-13 DOI: 10.1142/9789813232105_0006

M. Weigel

{"title":"Monte Carlo methods for massively parallel computers","authors":"M. Weigel","doi":"10.1142/9789813232105_0006","DOIUrl":"https://doi.org/10.1142/9789813232105_0006","url":null,"abstract":"Applications that require substantial computational resources today cannot avoid the use of heavily parallel machines. Embracing the opportunities of parallel computing and especially the possibilities provided by a new generation of massively parallel accelerator devices such as GPUs, Intel's Xeon Phi or even FPGAs enables applications and studies that are inaccessible to serial programs. Here we outline the opportunities and challenges of massively parallel computing for Monte Carlo simulations in statistical physics, with a focus on the simulation of systems exhibiting phase transitions and critical phenomena. This covers a range of canonical ensemble Markov chain techniques as well as generalized ensembles such as multicanonical simulations and population annealing. While the examples discussed are for simulations of spin systems, many of the methods are more general and moderate modifications allow them to be applied to other lattice and off-lattice problems including polymers and particle systems. We discuss important algorithmic requirements for such highly parallel simulations, such as the challenges of random-number generation for such cases, and outline a number of general design principles for parallel Monte Carlo codes to perform well.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88941972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12