arXiv: Computational Physics最新文献_第9页

Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem 利用反亥姆霍兹问题的数值解析确定表面阻抗

arXiv: Computational Physics Pub Date : 2017-06-05 DOI: 10.2514/6.2017-3695

D. Patel, Prateek Gupta, C. Scalo

{"title":"Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem","authors":"D. Patel, Prateek Gupta, C. Scalo","doi":"10.2514/6.2017-3695","DOIUrl":"https://doi.org/10.2514/6.2017-3695","url":null,"abstract":"Assigning boundary conditions, such as acoustic impedance, to the frequency domain thermoviscous wave equations (TWE), derived from the linearized Navier-Stokes equations (LNSE) poses a Helmholtz problem, solution to which yields a discrete set of complex eigenfunctions and eigenvalue pairs. The proposed method -- the inverse Helmholtz solver (iHS) -- reverses such procedure by returning the value of acoustic impedance at one or more unknown impedance boundaries (IBs) of a given domain, via spatial integration of the TWE for a given real-valued frequency with assigned conditions on other boundaries. The iHS procedure is applied to a second-order spatial discretization of the TWEs on an unstructured staggered grid arrangement. Only the momentum equation is extended to the center of each IB face where pressure and velocity components are co-located and treated as unknowns. The iHS is finally closed via assignment of the surface gradient of pressure phase over the IBs, corresponding to assigning the shape of the acoustic waveform at the IB. The iHS procedure can be carried out independently for different frequencies, making it embarrassingly parallel, and able to return the complete broadband complex impedance distribution at the IBs in any desired frequency range to arbitrary numerical precision. The iHS approach is first validated against Rott's theory for viscous rectangular and circular ducts. The impedance of a toy porous cavity with a complex geometry is then reconstructed and validated with companion fully compressible unstructured Navier-Stokes simulations resolving the cavity geometry. Verification against one-dimensional impedance test tube calculations based on time-domain impedance boundary conditions (TDIBC) is also carried out. Finally, results from a preliminary analysis of a thermoacoustically unstable cavity are presented.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89974664","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: 6

Effects of the Functional Group on the Lithium Ions Across the Port of Carbon Nanotube 官能团对碳纳米管端部锂离子的影响

arXiv: Computational Physics Pub Date : 2017-05-18 DOI: 10.1166/jctn.2016.5337

Xie Hui, L. Geng, Yang Cheng-bing, L. Chong, L. Chao

{"title":"Effects of the Functional Group on the Lithium Ions Across the Port of Carbon Nanotube","authors":"Xie Hui, L. Geng, Yang Cheng-bing, L. Chong, L. Chao","doi":"10.1166/jctn.2016.5337","DOIUrl":"https://doi.org/10.1166/jctn.2016.5337","url":null,"abstract":"The mean axial velocity of lithium irons across the entrance of carbon nanotube VLi is an important factor for the charge-discharge performances of rechargeable Lithium battery. The molecular dynamics simulation method is adopted to evaluate the factors and their effects on VLi which include the diameter of carbon nanotube, functional group type on the port and the number of a given type of functional group. The statistical analysis of the calculation results shows that: In the selected carbon nanotubes of four different diameters, VLi will gradually rise with the increase of CNT diameter due to lithium irons migration resistance decreasing; as the port of CNT is successively modified to hydrogen (-H), hydroxyl (-OH), amino (-NH2) and carboxyl (-COOH), the corresponding migration resistance of lithium ions is enhanced resulting in the dropping of VLi; in comparison to the effect strength of four types of functional groups on VLi, -COOH shows strongest, -NH2 and -OH perform relatively weaker, and the effect difference between -NH2 and -OH is very small, -H displays weakest; When the number of a given non-hydrogen functional group on the port sequentially increases, it also shows a trend that lithium ion migration resistance gradually increases which makes VLi decreases in turn. The more influential the functional group, the greater the impact of functional group number changes on VLi. The results of this paper have some significance on the precise production of lithium-ion battery electrode materials, enhancing the overall battery cycle efficiency and charging speed.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76087138","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: 6

$bar{textrm{H}}^{+}$ Sympathetic Cooling Simulations with a Variable Time Step $bar{textrm{H}}^{+}$变时间步长的交感冷却模拟

arXiv: Computational Physics Pub Date : 2017-05-09 DOI: 10.7566/JPSCP.18.011014

N. Sillitoe, J. Karr, J. Heinrich, T. Louvradoux, A. Douillet, L. Hilico

引用次数: 5

Flat borophene films as anode materials for Mg, Na or Li-ion batteries with ultra high capacities: A first-principles study 作为超高容量镁、钠或锂离子电池负极材料的硼罗芬薄膜:第一性原理研究

arXiv: Computational Physics Pub Date : 2017-05-06 DOI: 10.1016/j.apmt.2017.04.010

B. Mortazavi, O. Rahaman, S. Ahzi, T. Rabczuk

引用次数: 118

Reconstructing Detailed Line Profiles of Lamellar Gratings from GISAXS Patterns with a Maxwell Solver 用Maxwell求解器重建GISAXS图的片层光栅详细线轮廓

arXiv: Computational Physics Pub Date : 2017-04-26 DOI: 10.1107/S1600576717012742

V. Soltwisch, A. Herrero, Mika Pfluger, A. Haase, J. Probst, C. Laubis, M. Krumrey, F. Scholze

{"title":"Reconstructing Detailed Line Profiles of Lamellar Gratings from GISAXS Patterns with a Maxwell Solver","authors":"V. Soltwisch, A. Herrero, Mika Pfluger, A. Haase, J. Probst, C. Laubis, M. Krumrey, F. Scholze","doi":"10.1107/S1600576717012742","DOIUrl":"https://doi.org/10.1107/S1600576717012742","url":null,"abstract":"Laterally periodic nanostructures were investigated with grazing incidence small angle X-ray scattering (GISAXS) by using the diffraction patterns to reconstruct the surface shape. To model visible light scattering, rigorous calculations of the near and far field by numerically solving Maxwell's equations with a finite-element method are well established. The application of this technique to X-rays is still challenging, due to the discrepancy between incident wavelength and finite-element size. This drawback vanishes for GISAXS due to the small angles of incidence, the conical scattering geometry and the periodicity of the surface structures, which allows a rigorous computation of the diffraction efficiencies with sufficient numerical precision. To develop dimensional metrology tools based on GISAXS, lamellar gratings with line widths down to 55 nm were produced by state-of-the-art e-beam lithography and then etched into silicon. The high surface sensitivity of GISAXS in conjunction with a Maxwell solver allows a detailed reconstruction of the grating line shape also for thick, non-homogeneous substrates. The reconstructed geometrical line shape models are statistically validated by applying a Markov chain Monte Carlo (MCMC) sampling technique which reveals that GISAXS is able to reconstruct critical parameters like the widths of the lines with sub-nm uncertainty.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82580732","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: 26

Quantum-Accurate Molecular Dynamics Potential for Tungsten 钨的量子精确分子动力学势

arXiv: Computational Physics Pub Date : 2017-02-22 DOI: 10.2172/1365473

M. Wood, A. Thompson

引用次数: 18

The Planar Sandwich and Other 1D Planar Heat Flow Test Problems in ExactPack ExactPack中平面夹层及其他一维平面热流测试问题

arXiv: Computational Physics Pub Date : 2017-01-25 DOI: 10.2172/1340981

R. Singleton

引用次数: 1

An Improved Adaptive Minimum Action Method for the Calculation of Transition Path in Non-gradient Systems 非梯度系统过渡路径计算的改进自适应最小作用法

arXiv: Computational Physics Pub Date : 2017-01-15 DOI: 10.4208/CICP.OA-2016-0230

Y. Sun, X. Zhou

{"title":"An Improved Adaptive Minimum Action Method for the Calculation of Transition Path in Non-gradient Systems","authors":"Y. Sun, X. Zhou","doi":"10.4208/CICP.OA-2016-0230","DOIUrl":"https://doi.org/10.4208/CICP.OA-2016-0230","url":null,"abstract":"The minimum action method (MAM) is to calculate the most probable transition path in randomly perturbed stochastic dynamics, based on the idea of action minimization in the path space. The accuracy of the numerical path between different metastable states usually suffers from the \"clustering problem\" near fixed points. The adaptive minimum action method (aMAM) solves this problem by relocating image points equally along arc-length with the help of moving mesh strategy. However, when the time interval is large, the images on the path may still be locally trapped around the transition state in a tangle, due to the singularity of the relationship between arc-length and time at the transition state. Additionally, in most non-gradient dynamics, the tangent direction of the path is not continuous at the transition state so that a geometric corner forms, which brings extra challenges for the aMAM. In this note, we improve the aMAM by proposing a better monitor function that does not contain the numerical approximation of derivatives, and taking use of a generalized scheme of the Euler-Lagrange equation to solve the minimization problem, so that both the path-tangling problem and the non-smoothness in parametrizing the curve do not exist. To further improve the accuracy, we apply the Weighted Essentially non-oscillatory (WENO) method for the interpolation to achieve better performance. Numerical examples are presented to demonstrate the advantages of our new method.","PeriodicalId":8424,"journal":{"name":"arXiv: Computational Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78817331","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

Numerical evidence of Sinai diffusion of random-mass Dirac particles 随机质量狄拉克粒子西奈扩散的数值证据

arXiv: Computational Physics Pub Date : 2016-12-27 DOI: 10.4208/cicp.oa-2016-0239

S. Palpacelli, S. Succi

引用次数: 0

Field- and damping-like spin-transfer torque in magnetic multilayers 磁性多层膜中类场和类阻尼自旋传递转矩

arXiv: Computational Physics Pub Date : 2016-12-01 DOI: 10.1103/PhysRevApplied.7.054007

C. Abert, H. Sepehri-Amin, F. Bruckner, C. Vogler, M. Hayashi, D. Suess

引用次数: 16