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Feedback control of wave segments in an excitable medium

Chinese Physics B 2013年第5期22卷 187-190页

作者：吴宁杰高洪俊应和平 Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical SciencesNanjing Normal University Institute of Modern Physics and Department of Physics Zhejiang University

Depending on the excitability of the medium, a propagating wave segment will either contract or expand to fill the medium with spiral waves. This paper aims to introduce a simple mechanism of feedback control to stabilize such an expansion or contraction. To do this, we lay out a feedback control system in a block diagram and reduce it into a bare, universal formula. Analytical and experimental findings are compared through a series of numerical simulations of the Barkley model.

关键词： feedback control wave segments excitable medium

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Dynamical energy equipartition of the Toda model with additional on-site potentials

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Chinese Physics B 2017年第10期26卷 107-111页

作者：张振俊唐春梅康静童培庆 College of Science Hohai University School of Physics and Technology Nanjing Normal University Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University

We study the dynamical energy equipartition properties in the integrable Toda model with additional uniform or disordered on-site energies by extensive numerical simulations. The total energy is initially equidistributed among some of the lowest frequency linear modes. For the Toda model with uniform on-site potentials, the energy spectrum keeps its profile nearly unchanged in a relatively short time scale. On a much longer time scale, the energies of tail modes increase slowly with time. Energy equipartition is far away from being attached in our studied time scale. For the Toda model with disordered on-site potentials, the energy transfers continuously to the high frequency modes and eventually towards energy equipartition. We further perform a systematic study of the equipartition time teq depending on the energy density ε and the nonlinear parameter α in the thermodynamic limit for the Toda model with disordered on-site potentials. We find teq∝ （1/ε）^a（1/α）^b, where b≈ 2a. The values of a and b are increased when increasing the strengths of disordered on-site potentials or decreasing the number of initially excited modes.

关键词： energy transport behaviors Toda model uniform or disordered on-site potentials

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Dynamical quantum phase transition in XY chains with the Dzyaloshinskii-Moriya and XZY-YZX three-site interactions

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Chinese Physics B 2022年第6期31卷 260-266页

作者： Kaiyuan Cao Ming Zhong Peiqing Tong Department of Physics and Institute of Theoretical Physics Nanjing Normal UniversityNanjing 210023China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal UniversityNanjing 210023China

We study the dynamical quantum phase transitions(DQPTs)in the XY chains with the Dzyaloshinskii-Moriya interaction and the XZY-YZX type of three-site interaction after a sudden *** the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form■where the quasiparticle excitation spectraεkmay be smaller than 0 for some k and are asymmetrical■It is found that the factors of Loschmidt echo equal 1 for some k corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfyingε_(k)·ε_(-k)<0,when the quench is from the gapless *** considering the quench from different ground states,we obtain the conditions for the occurrence of DQPTs for the general XY chains with gapless phase,and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless *** is different from the DQPTs in the case of quench from the gapped phase to gapped phase,in which the DQPTs will always ***,we analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped *** conclusion can also be extended to the general quantum spin chains.

关键词： dynamical quantum phase transition gapless phase asymmetry excitation spectra

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Semileptonic decays B/Bs→(D^(?),D^(?)s)lνl in the PQCD approach with the lattice QCD input

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Chinese Physics C 2020年第5期44卷 8-21页

作者： Xue-Qing Hu Su-Ping Jin Zhen-Jun Xiao Department of Physics and Institute of Theoretical Physics Nanjing Normal UniversityNanjing 210023China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal UniversityNanjing 210023China

We study the semileptonic B/Bs→(D^(?),D^(?)s)lνl decays in the framework of the Standard Model(SM),by employing the perturbative QCD(PQCD)factorization formalism combined with the lattice QCD input for the relevant transition form *** calculate the branching ratios B(B(s)→D^(?)(s)lνl)with l=(e,μ,τ),the ratios of the branching fractions R(D^(?))and R(D^(?)s),and the physical observables Pτ(D^(?)(s)),FL(D?(s))and AFB(τ).The“PQCD+Lattice”predictions for B(B→D^(?)lνl)and R(D^(?))agree with the available experimental measurements within *** the ratios R(Ds)and R(D^?s),the"PQCD+Lattice"predictions agree with the other *** Pτ(D^?)and FL(D^?),our theoretical predictions agree with the measured values within *** theoretical predictions of the semileptonic B/Bs decays considered could be tested in the near future by the LHCb and Belle II experiments.

关键词： semileptonic decays form factor PQCD Bs meson

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Semileptonic decays B_c■(η_c, J/ψ)l■_l in the “PQCD+Lattice” approach

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Chinese Physics C 2020年第2期44卷 51-61页

We study the semileptonic decaysBc-→(ηc,J/ψ)l-■lusing the PQCD factorization approach with the newly defined distribution amplitudes of the B c meson and a new kind of parametrization for extrapolating the form factors which takes into account the recent lattice QCD *** find the following main results:(a)the PQCD predictions of the branching ratios of theBc→(ηc,J/ψ)l■decays are smaller by about 5%-16%when the lattice results are taken into account in the extrapolation of the relevant form factors;(b)the PQCD predictions of the ratio Rηc,RJ/ψand of the longitudinal polarization PτareRηc=0.34±0.01,RJ/ψ=0.28±0.01,Pτ(ηc)=0.37±0.01and Pτ(J/ψ)=-0.55±0.01;and(c)after including the lattice results,the theoretical predictions slightly change:Rηc=0.31±0.01,RJ/ψ=0.27±0.01,Pτ(ηc)=0.36±0.01andPτ(J/ψ)=-0.53±*** theoretical predictions of RJ/ψagree with the measurements within the *** other predictions could be tested by the LHCb experiment in the near future.

关键词： semileptonic Bc decays PQCD approach lattice QCD results ratio of branching ratios longitudinal polarization

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On Compressible Smooth Viscous Fluids in Slowly Expanding Balls

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Analysis in Theory and Applications 2019年第1期35卷 28-65页

作者： Huicheng Yin Lin Zhang School of Mathematical Sciences Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University

In[17]and[19,20],the global existence and large time behaviors of smooth compressible fluids(including inviscid gases of Euler equations,viscous gases of Navier-Stokes equations,and rarified gases of Boltzmann equation,respectively)have been established in an infinitely expanding ball with a constant expansion *** paper concerns with the viscous fluids in a slowly expanding *** involved analy-sis on the density function and the weighted energy estimates,we show that the fluid in the slowly expanding ball smoothly tends to a vacuum state and there is no appearance of vacuum in any part of the expansive *** present result is a meaningful supplement to the one in[19].

关键词： Compressible Navier-Stokes equations slowly expanding ball weighted energy estimate global existence

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numerical Validations of the Tangent Linear Model for the Lorenz Equations

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Computer Modeling in Engineering & Sciences 2019年第7期120卷 83-104页

作者： Tengjin Zhao Jing Zhang Zhilin Li Zhiyue Zhang School of Mathematical Sciences Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex SystemsNanjing Normal UniversityNanjing210023China Department of Mathematics North Carolina State UniversityRaleighNC 27695-8205USA

The validity of the tangent linear model(TLM)is studied numerically using the example of the Lorenz equations in this *** relationship between the limit of the validity time of the TLM and initial perturbations for the Lorenz equations is investigated using the Monte Carlo sampling method.A new error function between the nonlinear and the linear evolution of the perturbations is ***,numerical sensitivity analysis is carried to establish the relationship between parameters and the validity of the TLM,such as the initial perturbation,the prediction time,the time step size and so on,by the method of mathematical statistics.

关键词： Lorenz model tangent linear model nonlinear model Monte Carlo

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The two-body hadronic decays of B_c meson in the perturbative QCD approach:a short review

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Chinese Science Bulletin 2014年第29期59卷 3748-3759页

作者： Zhen-Jun Xiao Xin Liu Department of Physics and Institute of Theoretical Physics Nanjing Normal University Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University School of Physics and Electronic Engineering Jiangsu Normal University

Along with the running of large Hadron Collider(LHC)located at CERN in November 2009,a large number of data samples of Bc meson have been collected and some hadronic Bc decay modes have been measured by the LHC *** view of the special and important roles of Bc meson decays playing in the heavy flavor sector,we here give a short review on the status of two body hadronic decays Bc!M1M2at both experimental and theoretical *** the theoretical progresses,specifically,we will show lots of theoretical studies on two body hadronic Bcdecays involving pseudoscalar,vector,scalar,axial-vector,even tensor meson(s)in the final states by employing the perturbative QCD(pQCD)factorization *** will present a general analysis about the twobody hadronic decays of the heavy Bc meson and also provide some expectations for the future developments.

关键词：微扰QCD 强子衰变介子评论欧洲核子研究中心大型强子对撞机实验测量衰减模式

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A Novel Class of Energy-Preserving Runge-Kutta Methods for the Korteweg-de Vries Equation

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numerical Mathematics(Theory,Methods and Applications) 2022年第3期15卷 768-792页

作者： Yue Chen Yuezheng Gong Qi Hong Chunwu Wang Department of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Mathematical Modelling and High Performance Computing of Air Vehicles(NUAA) MIITNanjing 211106China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing 210023China

In this paper,we present a quadratic auxiliary variable approach to develop a new class of energy-preserving Runge-Kutta methods for the Korteweg-de Vries *** quadratic auxiliary variable approach is first proposed to reformulate the original model into an equivalent system,which transforms the energy conservation law of the Korteweg-de Vries equation into two quadratic invariants of the reformulated *** the symplectic Runge-Kutta methods are directly employed for the reformulated model to arrive at a new kind of time semi-discrete schemes for the original *** consistent initial conditions,the proposed methods are rigorously proved to maintain the original energy conservation law of the Korteweg-de Vries *** addition,the Fourier pseudo-spectral method is used for spatial discretization,resulting in fully discrete energy-preserving *** implement the proposed methods effectively,we present a very efficient iterative technique,which not only greatly saves the calculation cost,but also achieves the purpose of practically preserving *** numerical results are addressed to confirm the expected order of accuracy,conservative property and efficiency of the proposed algorithms.

关键词： Quadratic auxiliary variable approach symplectic Runge-Kutta scheme energypreserving algorithm Fourier pseudo-spectral method

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Supertetragonal BaZrS_(3):A promising perovskite sulphide with giant ferroelectricity and low band gap

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Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 126-133页

作者： Menglu Li Sa Zhang Chenhan Liu Xiaotao Zu Liang Qiao Haiyan Xiao School of Physics University of Electronic Science and Technology of ChinaChengdu 611731China College of Mathematics and Physics Chengdu University of TechnologyChengdu 610059China Micro-and Nano-scale Thermal Measurement and Thermal Management Laboratory Ministry of Education Key Laboratory of Numerical Simulation of Large-Scale Complex SystemsSchool of Energy and Mechanical EngineeringNanjing Normal UniversityNanjing 210023China

Over the past century,ferroelectricity has offered exciting opportunities for fundamental research and device ***,most of the discovered excellent ferroelectrics are oxide materials with large band gaps,limiting their potential for optoelectronics *** using first-principles calculations we identify a new narrow-gap ferroelectric beyond oxides,i.e.,ferroelectric perovskite sulphide BaZrS_(3).Under large compressive strains,BaZrS_(3)can be stabilized into a unique supertetragonal phase with an extraordinary polarization of 67.16μC/cm^(2),which is even stronger than that of conventional oxide ***,the supertetragonal BaZrS_(3)exhibits a direct narrow band gap of 1.2 eV and excellent electronic *** on the chemical bonding analysis,we attribute the formation of supertetragonal phase to charge re-ordering in which theπbond overlap along the long〈Zr-S〉bond completely vanishes and the antibonding states of theσbond appear below the Fermi *** work provides a conceptual strategy for designing new ferroelectrics for electronic and photovoltaic applications.

关键词： supertetragonal phase perovskite sulphide ferroelectricity

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