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General solutions to a class of time fractional partial differential equations

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Applied Mathematics and Mechanics(English Edition) 2010年第7期31卷 815-826页

作者：黄凤辉郭柏灵 Department of Mathematics School of SciencesSouth China University of Technology Institute of Applied Physics and computational Mathematics

A class of time fractional partial differential equations is considered, which in- cludes a time fractional diffusion equation, a time fractional reaction-diffusion equation, a time fractional advection-diffusion equation, and their corresponding integer-order partial differential equations. The fundamental solutions to the Cauchy problem in a whole-space domain and the signaling problem in a half-space domain are obtained by using Fourier- Laplace transforms and their inverse transforms. The appropriate structures of the Green functions are provided. On the other hand, the solutions in the form of a series to the initial and boundary value problems in a bounded-space domain are derived by the sine- Laplace or cosine-Laplace transforms. Two examples are presented to show applications of the present technique.

关键词： fractional differential equation Caputo fractional derivative Green function Laplace transform Fourier transform sine (cosine) transform

A fast multipole BEM for solving thin plate bending problems

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A fast multipole BEM for solving thin plate bending problems

Nonequilibrium Green＇s function method for quantum thermal transport

中国力学大会——2013

作者： Liu Yijun Huang Shuo Mechanical Engineering University of Cincinnati Institute for computational Mechanics and Its applications(NPUiCMA) Northwestern Polytechnical University

A fast multipole boundary element method(BEM) for solving large-scale thin plate bending problems will be presented in this *** plate bending problems are governed by bihannonic equation under given boundary conditions. This PDE can be transformed into two direct boundary integral equations(BIEs) that are sufficient to solve the unknown boundary variables—deflection,rotation,shear force,or bending moment—two at each boundary *** multipole formulations are developed for the two direct BIEs based on the

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Frontiers of physics 2014年第6期9卷 673-697页

作者： Jian-Sheng Wangt Bijay Kumar Agarwalla Huanan Li Juzar Thingna Department of Physics and Centre for computational Science and Engineering National University of Singapore Singapore 117542 Republic of Singapore

This review deals with the nonequilibrium Green＇s function （NEGF） method applied to the problems of energy transport due to atomic vibrations （phonons）, primarily for small jtmction systems. We present a pedagogical introduction to the subject, deriving some of the well-known results such as the Laudauer-like formula for heat current in ballistic systerms. The main aim of the review is to build the machinery of the method so that it can be applied to other situations, which are not directly treated here. In addition to the above, we consider a nmnber of applications of NEGF, not in routine model system calculations, but in a few new aspects showing the power and usefulness of the formalism. In partkaflar, we discuss the problems of multiple leads, coupled left-right-lead system, and system without a center. We also apply the method to the problem of full counting statisties. In the case of nonlinear svstems, we make general comments on the thermal expansion effect. phonon relaxation timv. and a certain class of mean-field approximations. Lastly, we examine the relationship between NEGF. reduced density matrix, and master equation approaches to thermal transport,

关键词： nonequilibrium Green's function (NEGF) contour ordered Green's function thermal transport

Theoretical study of the electronic structures and spectroscopic properties of [(4'-XC≡Ctrpy)PtCl]^+ (trpy=2,2':6',2"-terpyridine;X=H,Me and Ph)

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Science China Chemistry 2009年第12期52卷 2226-2236页

作者： WANG Xin,BAI FuQuan,ZHOU Xin,LIU Tao & ZHANG HongXing State Key Laboratory of Theoretical and computational Chemistry,Institute of Theoretical Chemistry,Jilin University,Changchun 130023,China State Key Laboratory of Theoretical and computational Chemistry Institute of Theoretical Chemistry Jilin University Changchun China

The electronic structures and spectroscopic properties of [(4'-XC≡Ctrpy)PtCl]+(trpy = 2,2':6',2″-terpyridine; X = H (1),methyl (Me) (2),and phenyl (Ph) (3) were studied by the ab initio method. The structures at the ground and excited state were optimized at the B3LYP and CIS levels,respectively. The absorption and emission spectra in the dichloromethane solution were obtained by using the TD-DFT (B3LYP) method associated with the pcm model. The molecular orbital energy of the HOMOs of 1-3 with the d(Pt),p(Cl),π(trpy),and π(XC≡C) character is sensitive to the substituents on the acetylide ligand,but that of the trpy-based LUMOs with the π*(trpy) character varies slightly. The lowest lying emission at 503 nm for 1 is mainly attributed to the 3ILCT perturbed by the 3MLCT and 3LLCT transitions,but that at 535 nm for 2,and that at 558 nm for 3 are mainly attributed to the 3LLCT perturbed by the 3ILCT and 3MLCT transitions. The different electron-donating ability of H,Me,and Ph is responsible for the differences in emission character. Moreover,the calculation results show that the phosphorescent color can be turned by adjusting the substituents. Both the lowest energy absorption and emission of 1―3 are red-shifted in the order of 1<2<3,consistent with the electron-donating of H

关键词： platinum(Ⅱ) complexes TD-DFT absorption spectra charge transfer luminescence

TWO-SCALE FINITE ELEMENT GREEN'S FUNCTION APPROXIMATIONS WITH applications TO ELECTROSTATIC POTENTIAL COMPUTATION

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Journal of Systems Science & Complexity 2010年第1期23卷 177-193页

作者： Ying YANG Aihui ZHOU Department of computational Science and Mathematics Guilin University of Electronic Technology Guilin 541004 China. The State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China.

In this paper,a two-scale finite element approach is proposed and analyzed for approximationsof Green's function in *** approach is based on a two-scale finite elementspace defined,respectively,on the whole domain with size H and on some subdomain containing singularpoints with size h (h << H).It is shown that this two-scale discretization approach is very *** particular,the two-scale discretization approach is applied to solve Poisson-Boltzmann equationssuccessfully.

关键词： Error analysis finite element Green's function Poisson-Boltzmann equation two-scale.

Developments and challenges ahead in blue perovskite light-emitting devices

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Journal of Energy Chemistry 2022年第8期31卷 418-433,I0011页

作者： Lin Zhang Run Long College of Chemistry Key Laboratory of Theoretical&Computational Photochemistry of Ministry of EducationBeijing Normal UniversityBeijing 100875China

Recently,perovskite light-emitting diodes(Pe LEDs)have developed rapidly in the green,red,and nearinfrared light emissions,owing to the unique optoelectronic characteristics of halide perovskites,such as high carrier mobility,narrow emission linewidths,high photoluminescence quantum yield,as well as bandgap ***,the efficiency improvement in blue(especially deep-blue)Pe LEDs is still inferior to other analogs,which severely restricts the Pe LED ***,we systematically summarize the substantial progress in the performance of blue Pe LEDs based on different blue perovskite candidates,and recent advances from three aspects(i.e.,the sky-blue,pure-blue,and deep-blue light emissions).Then,we point out several challenges existing in deep-blue Pe LEDs,such as the effect of Cl-ions incorporation,spectral instability,ion migration,and the difficulty of charge injection,and highlight the strategies to improve device efficiency,to motivate further research and development of blue Pe LEDs.

关键词： Perovskite Blue emission Light-emitting diodes Stability Efficiency

Dynamic Control of Tunneling Conductance in Ferroelectric Tunnel Junctions

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Chinese Physics Letters 2013年第10期30卷 178-182页

作者： ZOU Ya-Yi CHEW Khian-Hooi ZHOU Yan Department of Physics University of Hong KongHong Kong Department of Physics Peking UniversityBeijing 100871 Centre for Theoretical and computational Physics Department of PhysicsUniversity of Malaya50480 Kuala LumpurMalaysia Center of Theoretical and computational Physics University of Hong KongHong Kong

We investigate the dynamic characteristics of electric polarization P(t)in a ferroelectric junction under ac applied voltage and stress,and calculate the frequency response and the cut-off frequency f0,which provides a reference for the upper limit of the working *** study might be significant for sensor and memory applications of nanodevices based on ferroelectric junctions.

关键词： polarization Tunnel ferroelectric

First principle study of LiXS_2(X=Ga, In) as cathode materials for Li ion batteries

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Chinese Physics B 2016年第2期25卷 522-527页

作者：饶凤雅宁芳华蒋礼威曾祥明吴木生徐波欧阳楚英 Department of Physics Laboratory of Computational Materials Physics Jiangxi Normal University School of New Energy Science and Engineering Xinyu University

From first principle calculations, we demonstrate that LiXS_2（X = Ga, In） compounds have potential applications as cathode materials for Li ion batteries. It is shown that Li can be extracted from the LiXS_2 lattice with relatively small volume change and the XS_4 tetrahedron structure framework remains stable upon delithiation. The theoretical capacity and average intercalation potential of the LiGaS_2（LiInS_2） cathode are 190.4（144._2） m Ah/g and 3.50 V（3.53 V）. The electronic structures of the LiXS_2 are insulating with band gaps of _2.88 eV and 1.99 eV for X = Ga and In, ***, Li vacancies, which are formed through delithiation, change the electronic structure substantially from insulating to metallic structure, indicating that the electrical conductivities of the LiXS_2 compounds should be good during *** ion migration energy barriers are also calculated, and the results show that Li ion diffusions in the LiXS_2 compounds can be as good as those in the currently widely used electrode materials.

关键词： lithium batteries sulfide electrolyte cathode materials first principle calculations

High-fidelity image reconstruction for compressed ultrafast photography via an augmented-Lagrangian and deep-learning hybrid algorithm

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Photonics Research 2021年第2期9卷 I0023-I0030页

作者： CHENGSHUAI YANG YUNHUA YAO CHENGZHI JIN DALONG QI FENGYAN CAO YILIN HE JIALI YAO PENGPENG DING LIANG GAO TIANQING JIA JINYANG LIANG ZHENRONG SUN SHIAN ZHANG State Key Laboratory of Precision Spectroscopy School of Physics and Electronic ScienceEast China Normal University Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign Institut National de la Recherche Scientifique Centreénergie Matériaux TélécommunicationsLaboratory of Applied Computational Imaging Collaborative Innovation Center of Extreme Optics Shanxi University Collaborative Innovation Center of Light Manipulations and applications Shandong Normal University

Compressed ultrafast photography(CUP) is the fastest single-shot passive ultrafast optical imaging technique,which has shown to be a powerful tool in recording self-luminous or non-repeatable ultrafast ***, the low fidelity of image reconstruction based on the conventional augmented-Lagrangian(AL)and two-step iterative shrinkage/thresholding(Tw IST) algorithms greatly prevents practical applications of CUP, especially for those ultrafast phenomena that need high spatial resolution. Here, we develop a novel AL and deep-learning(DL) hybrid(i.e., AL+DL) algorithm to realize high-fidelity image reconstruction for CUP. The AL+DL algorithm not only optimizes the sparse domain and relevant iteration parameters via learning the dataset but also simplifies the mathematical architecture, so it greatly improves the image reconstruction accuracy. Our theoretical simulation and experimental results validate the superior performance of the AL+DL algorithm in image fidelity over conventional AL and Tw IST algorithms, where the peak signalto-noise ratio and structural similarity index can be increased at least by 4 d B(9 d B) and 0.1(0.05) for a complex(simple) dynamic scene, respectively. This study can promote the applications of CUP in related fields, and it will also enable a new strategy for recovering high-dimensional signals from low-dimensional detection.

关键词： image algorithm luminous