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The role of velocity derivative skewness in understanding non-equilibrium turbulence

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Chinese Physics B 2020年第11期29卷 99-105页

作者： Feng Liu Le Fang liang shao School of Energy and Power Engineering North University of ChinaTaiyuan 030051China Laboratory of Mathematics and Physics Ecole Centrale de PékinBeihang UniversityBeijing 100191China Laboratoire de Mécaniques des Fluides et d’Acoustique Ecole Centrale de Lyon-Université de LyonEcully 69134France

The turbulence governed by the Navier-Stokes equation is paramount in many physical ***,it has been considered as a challenging problem due to its inherent nonlinearity,non-equilibrium,and ***,we review the connections between the velocity derivative skewness Sk and the non-equilibrium properties of ***,a reasonable candidate for describing the non-equilibrium turbulence,which varies during the non-equilibrium procedure.A lot of experimental or numerical evidences have shown that the perturbation of energy spectrum,which associated with the excitation of large scales,results in an obvious variation of Sk,and Sk is a negative value in this rapid energy decay *** variation of positive Sk is closely related to the perturbation of transfer spectrum,and this corresponds to the backward energy transfer *** addition,the skewness characterizes the production(or reduction)rate of enstrophy due to vortex stretching(or compression).Using the transport equation of turbulent energy dissipation rate and enstrophy,it is possible to establish a theoretical connection between skewness and the non-equilibrium *** is expected that this work could trigger the rapid advancement of the future studies of non-equilibrium turbulence,and also the improvement of turbulence models.

关键词： velocity derivative skewness non-equilibrium turbulence turbulence model

Bifurcations of Periodic Solutions and Chaos in Josephson System with Parametric Excitation

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Acta Mathematicae Applicatae Sinica 2015年第2期31卷 335-368页

作者： shao-liang YUAN Zhu-jun JING College of Mathematics and Computer Sciences Yichun University The Center for Dynamical Systems Academy of Mathematics and Systems Science Chinese Academy of Sciences

Josephson system with parametric excitation is investigated. Using second-order averaging method and Melnikov function, we analyze the existence and bifurcations for harmonic,（2, 3, n-order） subharmonics and（2, 3-order） superharmonics and the heterocilinic and homoclinic bifurcations for chaos under periodic perturbation. Using numerical simulation, we check our theoretical analysis and further study the effect of the parameters on dynamics. We find the complex dynamics, including the jumping behaviors, symmetrybreaking, chaos converting to periodic orbits, interior crisis, non-attracting chaotic set, interlocking（reverse）period-doubling bifurcations from periodic orbits, the processes from interlocking period-doubling bifurcations of periodic orbits to chaos after strange non-chaotic motions when the parameter β increases, etc.

关键词： Josephson system bifurcations chaos second-order averaging method Melnikov method

Large eddy simulation of compressible turbulent channel flow with spanwise wall oscillation

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Science China(Physics,Mechanics & Astronomy) 2009年第8期52卷 1233-1243页

作者： FANG Jian LU LiPeng shao liang National Key Laboratory on Aero-engines School of Jet PropulsionBeihang UniversityBeijing 100191China Laboratory of Fluid Mechanics and Acoustics Ecole Centrale de LyonFrance

The influences of the modification of turbulent coherent structures on temperature field and heat transfer in turbulent channel flow are studied using large eddy simulation(LES) of compressible turbulent channel flows with spanwise wall oscillation(SWO).The reliability of the LES on such problems is proved by the comparisons of the drag reduction data with those of other *** high consistency of coherent velocity structures and temperature structures is found based on the analyses of the turbulent flow *** the coherent velocity structures are suppressed,the transportations of momentum and heat are reduced simultaneously,demonstrating the same *** shows that the turbulent coherent structures have the same effects on the transportations of momentum and *** averaged wall heat flux can be reduced with appropriate oscillating parameters.

关键词： large eddy simulation spanwise wall oscillation compressible temperature field heat transportation

Gravitational Field Excitation from the First Term of Quantum Wilson Loop

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Communications in Theoretical Physics 2006年第1X期46卷 77-86页

作者： shao liang shao Dan shao Chang-Gui H. Noda CHEN Yi-Han Department of Applied Physics Wuhan University of Science and Technology Wuhan 430081 China Department of Physics Jianghan University Wuhan 430056 China Institute of Theoretical Physics Hubei University Wuhan 430062 China Department of Mathematical Sciences Ibaraki University Mito 310-8512 Japan

In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation （order k^4） of gravitational field, which is given by the first term of quantum Wilson loop （w） through two-point Green＇s function of the connection. At the same time using the tree diagram propagators of gravitons, the lowest order （k^4） correction to （w） is also calculated through the graviton self-energy in the term. Under the accuracy condition up to order k^4, we have obtained a complete expression of the excitation contributed from the leading term （w^（2））of （w）.

关键词： excitation of gravitational field graviton self-energy correction complete expression of excitation of order k^4 in (w^(2))

Optimization of formation for multi-agent systems based on LQR

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Frontiers of Information Technology & Electronic Engineering 2016年第2期17卷 96-109页

作者： Chang-bin YU Yin-qiu WANG Jin-liang shao School of Automation Hangzhou Dianzi University Hangzhou 310018 China Research School of Engineering The Australian National University Canberra ACT 0200 Australia School of Mathematics Science University of Electronic Science and Technology of China Chengdu 611731 China

In this paper,three optimal linear formation control algorithms are proposed for first-order linear multiagent systems from a linear quadratic regulator(LQR) perspective with cost functions consisting of both interaction energy cost and individual energy cost,because both the collective ob ject(such as formation or consensus) and the individual goal of each agent are very important for the overall ***,we propose the optimal formation algorithm for first-order multi-agent systems without initial physical *** optimal control parameter matrix of the algorithm is the solution to an algebraic Riccati equation(ARE).It is shown that the matrix is the sum of a Laplacian matrix and a positive definite diagonal ***,for physically interconnected multi-agent systems,the optimal formation algorithm is presented,and the corresponding parameter matrix is given from the solution to a group of quadratic equations with one ***,if the communication topology between agents is fixed,the local feedback gain is obtained from the solution to a quadratic equation with one *** equation is derived from the derivative of the cost function with respect to the local feedback *** examples are provided to validate the effectiveness of the proposed approaches and to illustrate the geometrical performances of multi-agent systems.

关键词： Linear quadratic regulator (LQR) Formation control Algebraic Riccati equation (ARE) Optimalcontrol Multi-agent systems

Directional Photo-manipulation of Self-assembly Patterned Microstructures

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Chinese Journal of Polymer Science 2018年第3期36卷 297-305页

作者： Wei Wang Fei Gao Yuan Yao shao-liang Lin Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials of Ministry of EducationSchool of Materials Science and EngineeringEast China University of Science and TechnologyShanghai 200237China

Highly intricate surface architectures derived from patterned polymer microstructures have received increasing concern in recent *** photo-manipulation(DPM)of azopolymers is one of the effective strategies to tune the patterned polymer microstructures through directional mass migration(DMM)upon polarized light *** this feature article,we emphasize the latest advances of DPM on azopatterns created by *** mechanism of DMM,the photo-manipulation performance,and functions of manipulated patterns are introduced in *** presented,DPM can manipulate the as-prepared microstructures feasibly by taking the advantages of non-contacting and nondestructive ***,the challenges and opportunities of DPM strategy are discussed in conclusion.

关键词： Self-assembly Directional photo-manipulation Surface patterning Azopolymer

A REGULARIZED CONJUGATE GRADIENT METHOD FOR SYMMETRIC POSITIVE DEFINITE SYSTEM OF LINEAR EQUATIONS

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Journal of Computational Mathematics 2002年第4期20卷 437-448页

作者： Zhong-zhi Bai shao-liang Zhang LSEC ICMSECAcademy of Mathematics and System SciencesChinese Academy of SciencesBeijing 100080China Department of Applied Physics University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan

A class of regularized conjugate gradient methods is presented for solving the large sparse system of linear equations of which the coefficient matrix is an ill-conditioned symmetric positive definite matrix. The convergence properties of these methods are discussed in depth, and the best possible choices of the parameters involved in the new methods are investigated in detail. Numerical computations show that the new methods are more efficient and robust than both classical relaxation methods and classical conjugate direction methods.

关键词： conjugate gradient method symmetric positive definite matrix regularization ill-conditioned linear system

Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions

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Acta Mechanica Sinica 2009年第2期25卷 205-210页

作者： Youtong Zhang Changsong Zheng Yongfeng Liu liang shao Chenhua Gou School of Mechanical and Vehicular Engineering Beijing Institute of Technology 100081 Beijing China School of Mechanical-Electronic and Automobile Engineering Beijing University of Civil Engineering and Architecture100044 Beijing China

This paper presents two exact explicit solutions for the three dimensional dual-phase lag （DLP） heat conduction equation, during the derivation of which the method of trial and error and the authors＇ previous experiences are utilized. To the authors＇ knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there are few exact solutions up to now. The exact solutions in this paper can be used as benchmarks to validate numerical solutions and to develop numerical schemes, grid generation methods and so forth. In addition, they are of theoretical significance since they correspond to physically possible situations. The main goal of this paper is to obtain some possible exact explicit solutions of the dual-phase lag heat conduction equation as the benchmark solutions for computational heat transfer, rather than specific solutions for some given initial and boundary conditions. Therefore, the initial and boundary conditions are indeterminate before derivation and can be deduced from the solutions afterwards. Actually, all solutions given in this paper can be easily proven by substituting them into the governing equation.

关键词： Exact solution Dual-phase lag Non-Fourier Benchmark solution Heat conduction

基于原位交联增容策略的增强PLA/NR共混物界面相容性和发泡性能研究

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陕西科技大学学报 2025年第1期43卷 73-80,100页

作者：王广静邵亮苏晨阳马春燕姬占有陕西科技大学化学与化工学院中国轻工业轻化工助剂重点实验室陕西西安710021

聚乳酸(PLA)是目前最具发展潜力的生物材料之一,但其韧性差,极大的限制了在塑料领域的发展与应用.已有研究发现天然橡胶(NR)的引入可以改善其韧性差的缺陷,但二者为不相容体系,发泡性能差.因此,本文基于原位交联增容原理,采用1,4-双(叔... 详细信息

聚乳酸(PLA)是目前最具发展潜力的生物材料之一,但其韧性差,极大的限制了在塑料领域的发展与应用.已有研究发现天然橡胶(NR)的引入可以改善其韧性差的缺陷,但二者为不相容体系,发泡性能差.因此,本文基于原位交联增容原理,采用1,4-双(叔丁基过氧异丙基)苯(BIPB)增强PLA和NR的界面相容性,并以超临界二氧化碳(scCO_(2))发泡技术制备了PLA/NR复合发泡材料.探究了不同BIPB含量对复合材料界面相容性、韧性及复合材料发泡行为的影响.结果表明,BIPB的引入显著增强了PLA/NR复合材料的相容性、韧性及发泡性能.当BIPB含量为0.25 phr时,PLA/NR复合材料的断裂伸长率从原来的25.75%增加到35.24%,提升了1.37倍;表观密度从初始的0.565 g·cm^(-3)下降至0.373 g·cm^(-3);平均泡孔尺寸从7.5μm下降至5.0μm.

关键词：聚乳酸天然橡胶 1,4-双(叔丁基过氧异丙基)苯超临界发泡相容性