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Quasi-Hamiltonian principle of liquid-filled elastic body dynamics

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Science China(Physics,Mechanics & Astronomy) 2010年第6期53卷 1116-1123页

作者： HAO MingWang & YE ZhengYin National key laboratory of Aerodynamic Design and Research,northwestern polytechnical university,Xi’an 710072,China National key laboratory of Aerodynamic Design and Research Northwestern Polytechnical University Xi’an China

Liquid-filled elastic body dynamics is an important branch of fluid-solid coupling mechanics. It deals with the study of motion of a body and the liquid contained in the body under the interaction between the two,for example,a liquid-filled satellite,a fuel tank of an airplane,etc. The research on liquid-filled elastic body dynamics is usually done by the variational method since the method has a feature of treating things as a whole. Considering the elastic motion of the liquid-filled body and the surface tension effect on the liquid-gas interface,liquid-solid interface and gas-solid interface,the present paper establishes a quasi-Hamiltonian variational principle for the above-mentioned system. After finding the stationary-value conditions of its functional obtained,a complete system of governing equations consisting of the stationary value conditions,preconditions and constraint conditions is established,and then the equations are reduced into some known ones in a special case.

关键词： fluid-solid coupling quasi-Hamiltonian variational principle liquid-filled elastic body incompressible fluid

Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

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Science China(Technological Sciences) 2010年第2期53卷 326-342页

作者： YAN Jing, YANG He, ZHAN Mei & LI Heng College of Materials Science and Engineering, State key laboratory of Solidification Processing, northwestern polytechnical university, Xi’an 710072, China College of Materials Science and Engineering State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China

With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

关键词： forming limit NC tube bending aluminum alloy thin-walled tubes with large diameters multi-index constraints finite element method

Research on the expanding deformation of ring radius in cold profiled ring rolling process

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Science China(Technological Sciences) 2010年第3期53卷 813-821页

作者： YANG He,LI LanYun,WANG Min&GUO LiangGang State key laboratory of Solidification Processing,School of Material Science and Engineering,northwestern polytechnical university,Xi’an 710072,China State key laboratory of Solidification Processing School of Material Science and Engineering Northwestern Polytechnical University Xi’an China

Cold profiled ring rolling is an advanced local plastic deformation technology widely used to precisely manufacture various complex seamless ring *** plays an important role in many industrial fields such as aeronautics,astronautics,automobile,bearings,*** the cold ring rolling process,the ring radius expands gradually with the increase of the feeding amount(*** reduction),and the expanding deformation of the ring radius is closely related to the rolling *** is very important to investigate the expanding deformation of ring radius for the precise control of ring dimensions and the design of feeding *** this paper,the relation between the expanding deformation of the ring radius and the rolling reduction in the stepped ring rolling process,a typical profiled ring rolling process,is analyzed by using analytical *** results show that the growth amount of the filling depth of groove can't exceed the rolling reduction,that in the inner stepped ring rolling process,the curves of the outer radius and big inner radius with the rolling reduction are monotonous,ascending and concave,i.e.,the outer radius and big inner radius expand faster and faster with the increase of the rolling reduction,and that in the outer stepped ring rolling process,the curves of the inner radius and small outer radius with the rolling reduction are also monotonous,ascending and concave,i.e.,the inner radius and small outer radius expand faster and faster with the increase of the roll reduction.

关键词： cold ring rolling inner stepped ring outer stepped ring rolling reduction expanding deformation of ring radius

2D/3D-QSAR comparative study on mutagenicity of nitroaromatics

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Science China Chemistry 2005年第3期48卷 246-252页

作者： WANG Xiaodong1, LIN Zhifen2, YIN Daqiang1, LIU Shushen1 & WANG Liansheng1 1. State key laboratory of Pollution control and Resources Reuse, School of the Environment at Nanjing university, Nanjing 210093, China 2. key laboratory of Tropical Marine Environmental dynamics, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301,China State key laboratory of Pollution control and Resources Reuse School of the Environment at Nanjing University Nanjing China key laboratory of Tropical Marine Environmental dynamics South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou China

Nitroaromatics are typical toxic organic pollutants and are ubiquitous in environment with diverse structures. They are widely used in many industries and formed during many natural and anthropogenic processes. Most of these pollutants are potentially carcinogenic and the as-sessment and prediction of the mutagenicity of nitroaromatics are of great interest. In this paper the structure-mutagenicity relationships of 219 nitroaromatics are investigated by molecular or-bital theory based classic structure-activity relationships and comparative molecular field analysis (CoMFA). A comparison is undertaken in respect of the interpretation of mechanism and predic-tive ability for these two categories of QSAR approaches and highly predictive QSAR models have been developed.

关键词： nitroaromatics, mutagenicity, mechanism, 3D-QSAR, CoMFA.

Stress distribution rule of roadway affected by overhead mining in gently inclined coal seams group

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中国有色金属学会会刊：英文版 2011年第S3期21卷 529-535页

作者： KANG Qin-rong1, 2, TANG Jian-xin1, 2, HU Hai1, 2, ZHANG Wei-zhong1, 3 1. College of Resource and Environmental Sciences, Chongqing university, Chongqing 400030, China 2. State key laboratory of Coal Mine Disaster dynamics and control, Chongqing university, Chongqing 400030, China 3. School of Safety Science and Administration, Zhongnan university of Economics and Law, Wuhan 430074, China College of Resource and Environmental Sciences Chongqing University Chongqing 400030 China State key laboratory of Coal Mine Disaster dynamics and control Chongqing University Chongqing 400030 China School of Safety Science and Administration Zhongnan University of Economics and Law Wuhan 430074 China

In light of the severe deformation and destruction of the district raise tunnel in the mining area at the northern part of the Lubanshan colliery, by the theoretic analysis and numerical simulation, both the mining stress distribution in seams group and the deformation and destruction mechanism of floor district raise were investigated. The results show that, at the maximum vertical distance of 40 m, the abutment stress has an influence on the recovery of 2# and 3# coal seam and 8# coal seam at distance of 30 m. As a result, the recovery of 8# is rather than those of 2# or 3# coal seam, which contributes to the deformation and destruction of the district raise surrounding rock. The major factors affecting the abutment stress include the mining depth, mining height, residual gob space, adjacent working faces and short spacing coal seam recovery.

关键词： coal seams group stress distribution district raise surrounding rock deformation and destruction abutment stress

Simulation of molecular dynamics of silver subcritical nuclei and crystal clusters during solidification

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Science China(Technological Sciences) 2010年第12期53卷 3203-3208页

作者： JIAN ZengYun1, CHEN Ji1, CHANG FangE1, ZENG Zhao1, HE Tan1 & JIE WanQi2 1 School of Materials Science and Engineering, Xi’an Technological university, Xi’an 710032, China 2 State key laboratory of Solidification Processing, northwestern polytechnical university, Xi’an 710072, China School of Materials Science and Engineering Xi’an Technological University Xi’an China State key laboratory of Solidification Processing Northwestern Polytechnical University Xi’an China

Molecular dynamics simulation is carried out to investigate the effects of cooling rate on the final configurations of silver after rapid solidification. The cooling rate for the formation of a silver amorphous phase is determined by analyzing its pair distribution function, H-A bond index, and the largest crystal cluster. Further, the equilibrium structures of the subcritical nuclei and crystal clusters are studied. The results show that the solidified microstructure is composed of a mixture of crystal clusters and amorphous phases at a certain cooling rate range. The size of the largest crystal cluster decreases with the increasing cooling rate, and it completely disappears when the cooling rate exceeds a critical value. The structures of the subcritical nuclei and the largest crystal cluster are composed of lamellar structures of fcc and hcp atoms, indicating that the lamellar structure of fcc and hcp atoms in the silver crystal originates from nucleation, and not from the growth of crystals.

关键词： molecular dynamics simulation amorphous phase subcritical nuclei crystal cluster cooling rate

controlling uncertain fuzzy neutral dynamic systems with Markov jumps

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Journal of systems Engineering and Electronics 2010年第3期21卷 476-484页

作者： Shuping He1,2 and Fei Liu1,2,1.key laboratory of Advanced Process control for Light Industry,Ministry of Education,Jiangnan university,Wuxi 214122,P.R.China 2.Institute of Automation,Jiangnan university,Wuxi 214122,P.R.China key laboratory of Advanced Process control for Light Industry Ministry of Education Jiangnan University Wuxi 214122 P. R. China Institute of Automation Jiangnan University Wuxi 214122 P. R. China

The robust H∞ control problems for stochastic fuzzy neutral Markov jump systems（MJSs） with parameters uncertainties and multiple time-delays are *** delays are respectively considered as constant and time varying,and the uncertain parameters are assumed to be norm *** means of Takagi-Sugeno fuzzy models,the overall closed-loop fuzzy dynamics are constructed through selected membership *** selecting the appropriate Lyapunov-Krasovskii functions,the sufficient condition is given such that the uncertain fuzzy neutral MJSs are stochastically stability for all admissible uncertainties and satisfies the given H∞ control *** stability and H∞ control criteria are formulated in the form of linear matrix inequalities,which can be easily checked in *** examples illustrate the effectiveness of the developed techniques.

关键词： neutral Markov jump system(MJS) Takagi-Sugeno fuzzy model time-delay uncertainty linear matrix inequality(LMI).

Consensus of high-order dynamic multi-agent systems with switching topology and time-varying delays

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控制理论与应用（英文版） 2010年第1期8卷 52-60页

作者： Fangcui JIANG,Long WANG,Guangming XIE(Institute of Intelligent Engineering,Center for systems and control,College of Engineering,and key laboratory of Machine Perception(Ministry of Education),Peking university,Beijing 100871,China) Institute of Intelligent Engineering Center for Systems and Control College of Engineering and Key Laboratory of Machine Perception (Ministry of Education) Peking University Beijing China

This paper studies the consensus problems for a group of agents with switching topology and time-varying communication delays, where the dynamics of agents is modeled as a high-order integrator. A linear distributed consensus protocol is proposed, which only depends on the agent＇s own information and its neighbors＇ partial information. By introducing a decomposition of the state vector and performing a state space transformation, the closed-loop dynamics of the multi-agent system is converted into two decoupled subsystems. Based on the decoupled subsystems, some sufficient conditions for the convergence to consensus are established, which provide the upper bounds on the admissible communication delays. Also, the explicit expression of the consensus state is derived. Moreover, the results on the consensus seeking of the group of high-order agents have been extended to a network of agents with dynamics modeled as a completely controllable linear time-invariant system. It is proved that the convergence to consensus of this network is equivalent to that of the group of high-order agents. Finally, some numerical examples are given to demonstrate the effectiveness of the main results.

关键词： Consensus problems Distributed control Multi-agent systems Switching topology Time-varying delays Lyapunov-Krasovskii approach

A HIGH-ORDER-ACCURATE DIFFERENCE SCHEME WITH UNCONDITIONAL STABILITY FOR THE DIFFUSION EQUATION ON NONUNIFORM GRIDS

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Journal of Hydrodynamics 2001年第1期13卷 92-98页

作者： Wang Xuan, Yang Zhi-feng State key laboratory of Environment Simulation and Pollution control, Institute of Environmental Sciences, Beijing Normal university, Beijing 100875, China[WT5”HZ] Beijing Normal Univ. Beijing 100875 China

WT5”BZ]A high-order-accurate difference scheme with unconditional stability is developed for the diffusion equation on nonuniform grids. The theoretical analysis shows that the accuracy of this scheme is between third order and fourth order, and fourth-order accuracy is achieved in the case of the same grid steps being used within the computational domain. Two numerical examples are given to demonst ate the advantages of the proposed scheme. Compared with the conventional difference scheme, more accurate numerical solution can be obtained by using the proposed scheme even with relatively larger grid sizes. It is also pointed out that the appropriate structure of the nonuniform grid can not only make the proposed scheme more practical, but lead to a solution superior to that for a uniform grid structure. [WT5”HZ]

关键词： ]finite difference scheme diffusion equation nonuniform grid high accuracy computational fluid dynamics