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Gyroscopic modes decoupling method in parametric instability analysis of gyroscopic systems

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Acta Mechanica Sinica 2018年第5期34卷 963-969页

作者： Y.J.Qian X.D.yang H.Wu W.zhang T.z.yang College of Mechanical Engineering Beijing University of TechnologyBeijing 100124China Department of Mechanics Tianjing UniversityTianjing 300072China

Traditional procedures to treat vibrations of gyroscopic continua involve direct application of perturbation methods to a system with both a strong gyroscopic term and other weakly coupled *** this study,a gyroscopic modes decoupling method is used to obtain an equivalent system with decoupled gyroscopic modes having only weak *** the axially moving string as an example,the instability boundaries in the vicinity of parametric resonances are detected using both the traditional coupled gyroscopic system and our system with decoupled gyroscopic modes,and the results are compared to show the advantages and disadvantages of each method.

关键词： Axially moving material Decoupling of gyroscopic modes Parametric instability Perturbation method Gyroscopic system

Predicting the variation of stacking fault energy for binary Cu alloys by first-principles calculations

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Journal of Materials Science & Technology 2020年第18期52卷 61-65页

作者： T.Cai K.Q.Li z.J.zhang P.zhang R.Liu J.B.yang z.F.zhang Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province College of Advanced Materials and EnergyInstitute of Surface Micro and Nano MaterialsXuchang UniversityXuchang 461000China Laboratory of Fatigue and Fracture for Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)*** calculated results show that some solute atoms(Mg,Al,Si,zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the ***,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of *** intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.

关键词： Cu-alloy Deformation behavior First-principles calculation Stacking fault energy

On the topological number in Kelvin's circulation of inviscid fluids

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Communications in Theoretical Physics 2024年第12期76卷 176-180页

作者： z B Guo State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University

Kelvin's circulation,as a loop integral of the velocity field,is first shown to be equal to Γc=2πΔnΓ1+constant in an inviscid fluid,with Γ1a unit *** integer Δn is interpreted as the number of net 27r-rotations of the velocity vector in one cyclicality along the circulation loop and hence it is a topological *** from the linkage number in the helicity invariant,which only exists in 3D space,the topological number in the circulation invariant is independent of the spatial dimension.A further study reveals that this new topological phase 2πΔn is rooted at the gauge invariance of the circulation and it is a counterpart of the Berry's phase in the quantum system.

关键词： Berry's phase fluids Kelvin’s circulation topological number

Fire hazard in transportation infrastructure:Review,assessment,and mitigation strategies

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Frontiers of Structural and Civil Engineering 2021年第1期15卷 46-60页

作者： Venkatesh KODUR M.z.NASER Department of Civil and Environmental Engineering Michigan State UniversityEast LansingMI 48824-1226USA Glenn Department of Civil Engineering Clemson UniversityClemsonSC 29634USA

This paper reviews the fire problem in critical transportation infrastructures such as bridges and *** magnitude of the fire problem is illustrated,and the recent increase in fire problems in bridges and tunnels is *** research undertaken to address fire problems in transportation structures is reviewed,as well as critical factors governing the performance of those ***,key strategies recommended for mitigating fire hazards in bridges and tunnels are presented,and their applicability to practical situations is demonstrated through a practical case ***,research needs and emerging trends for enhancing the“state-of-the-art”in this area are discussed.

关键词： fire hazard bridges tunnels fire resistance mitigation strategies transportation infrastructure

Centrality of the collision and random matrix theory

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Chinese Physics C 2010年第10期34卷 1593-1597页

作者： z.Wazir Department of Physics COMSATS Institute of Information Technology

I discuss the results from a study of the central ^12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.

关键词： random matrix theory UrQMD central collisions multiplicity

Opportunities and challenges of biodegradable zn-based alloys

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Journal of Materials Science & Technology 2020年第11期42卷 136-138页

作者： H.F.Li z.z.Shi L.N.Wang Beijing Advanced Innovation Center for Materials Genome Engineering School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing100083China

Following the footsteps of biodegradable Mg-based and Fe-based alloys,biodegradable zn-based alloy is a newcomer and rising star in the family of biodegradable metals and *** combined superior mechanical properties,appropriate degradation rates,excellent biocompatibility of biodegradable zn-based alloys have brought worldwide research interest on the design,development and clinical translation of zn-based *** present perspective has summarized opportunities and challenges in the development of biodegradable zn-based alloys.

关键词： Biodegradable zn-based alloys Clinical applications Mechanical properties Degradation behavior Biocompatibility Corrosion fatigue Bio-tribocorrosion

Discrete-frequency Convergence of Iterative Learning Control for Linear Time-invariant systems with Higher-order Relative Degree

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International Journal of Automation and computing 2015年第3期12卷 281-288页

作者： Xiao-E Ruan zhao-zhen Li z.z.Bien School of Mathematics and Statistics Xi an Jiaotong University Department of Electrical Engineering Korea Advanced Institute of Science and Technology

In this paper, a discrete-frequency technique is developed for analyzing sufficiency and necessity of monotone convergence of a proportional higher-order-derivative iterative learning control scheme for a class of linear time-invariant systems with higher-order relative degree. The technique composes of two steps. The first step is to expand the iterative control signals, its driven outputs and the relevant signals as complex-form Fourier series and then to deduce the properties of the Fourier coefficients. The second step is to analyze the sufficiency and necessity of monotone convergence of the proposed proportional higher-order-derivative iterative learning control scheme by assessing the tracking errors in the forms of Paserval s energy modes. Numerical simulations are illustrated to exhibit the validity and the effectiveness.

关键词： Iterative learning control monotone convergence discrete frequency-domain spectrum Fourier series Parseval s energy equality rel

FINITE ELEMENT ANALYSIS FOR MICROSTRUCTURE EVOLUTION IN HOT FINISHING ROLLING OF STEEL STRIPS

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 79-86页

作者： z.D. Qu S.H. zhang D.z. Li z.T. Wang Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China College of Material Science and Engineering Taiyuan University of Science andTechnology Taiyuan 030024 China Shenyang Ligong University Shenyang 110168 China

A computer model that describes the evolution of microstructures during the hot finishing rolling of SS400 steel has been proposed. It has been found that the microstructure strongly depends on processing of materials and on their parameters, which affected the history of the thermomechanical variables, such as temperature, strain, and strain rate. To investigate the microstructural evolutions during the hot finishing rolling process, the rigid-thermoviscoplastic finite element method （FEM） has been combined with dynamic recrystallization, static recrystallization, and grain growth models. The simulation results show a good agreement with those from the prediction software online.

关键词： finite element method (FEM) finishing rolling microstructure evolution recrystallization

Calculation of Collective Variable-based PMF by Combining WHAM with Umbrella Sampling

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Chinese Physics Letters 2012年第6期29卷 291-294页

作者： XU Wei-Xin LI yang zHANG John z.H. State Key Laboratory of Precision Spectroscopy Department of PhysicsEast China Normal UniversityShanghai 200062 Institute of Theoretical and Computational Science Institutes for Advanced Interdisciplinary ResearchEast China Normal UniversityShanghai 200062 Department of Chemistry New York UniversityNew YorkNew York 10003USA

Potential of mean force (PMF) with respect to localized reaction coordinates (RCs) such as distance is often applied to evaluate the free energy profile along the reaction pathway for complex molecular ***,calculation of PMF as a function of global RCs is still a challenging and important problem in computational *** examine the combined use of the weighted histogram analysis method and the umbrella sampling method for the calculation of PMF as a function of a global RC from the coarse-grained Langevin dynamics simulations for a model *** method yields the folding free energy profile projected onto a global RC,which is in accord with benchmark *** this method rare global events would be sufficiently sampled because the biased potential can be used for restricting the global conformation to specific regions during free energy *** strategy presented can also be utilized in calculating the global intra- and intermolecular PMF at more detailed levels.

关键词： coordinates utilized calculating