检索结果-南通市图书馆

Feedback minimization of first-passage failure of quasi integrable Hamiltonian systems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2007年第4期23卷 437-444页

作者： Maolin Deng Weiqiu Zhu Department of Mechanics,state key {2. of {2. power transmission and control,zhejiang university,Hangzhou 31002.,china Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

Abstract A nonlinear stochastic optimal control strategy for minimizing the first-passage failure of quasi integrable Hamiltonian systems （multi-degree-of-freedom integrable Hamiltonian systems subject to light dampings and weakly random excitations） is proposed. The equations of motion for a controlled quasi integrable Hamiltonian system are reduced to a set of averaged It6 stochastic differential equations by using the stochastic averaging method. Then, the dynamical programming equations and their associated boundary and final time conditions for the control problems of maximization of reliability and mean first-passage time are formulated. The optimal control law is derived from the dynamical programming equations and the control constraints. The final dynamical programming equations for these control problems are determined and their relationships to the backward Kolmogorov equation governing the conditional reliability function and the Pontryagin equation governing the mean first-passage time are separately established. The conditional reliability function and the mean first-passage time of the controlled system are obtained by solving the final dynamical programming equations or their equivalent Kolmogorov and Pontryagin equations. An example is presented to illustrate the application and effectiveness of the proposed control strategy.

关键词： Nonlinear stochastic system First-passage time Reliability Stochastic control Dynamical programming

SIMULATION OF fluid FLOW IN CHANNEL OF A NOVEL HYDRAULIC SHOCK GENERATOR

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2000年第4期13卷 258-262页

作者： Fu XinYang Huayong (state key {2. of {2. power transmission and control, zhejiang university) 浙江大学流体传动及控制国家重点实验室浙江杭州

In order to improve the engineering performance of a novel hydraulic shock generator, the fluid flow inside its complex passages is numerically investigated. The effects of the inlet flow velocity upon the turbulence intensity of the jet flow are analyzed. The calculated pressure loss is experimentally verified with the consideration of temperature determined viscosity shifting. The results are used as the reference in the further development of the hydraulic shock generator

关键词： Shock generator Numerical simulation Jet flow Turbulence

Numerical simulation of the efficiency of mixing in heterogeneous microchannels with patterned surface potentials

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第12期16卷 1322-1328页

作者： ZHANG Kai~1, LIN Jianzhong~ 1,2.** and LI Huijun~1(1. state key {2. of {2. power transmission and control, zhejiang university, Hangzhou 31002., china 2. china Jiliang university, Hangzhou 310018, china) [a]state key {2. of {2. power transmission and control Zhejiang University Hanghou China [b]china Jiliang university Hangzhou China

The mixing of samples in heterogeneous microchannels with a periodically stepwise surface potential was analyzed numerically using the control volume method. The equations describing the wall potential and external potential were solved first to get the distribution of wall potential and external potential, respectively, then the momentum equation was solved to get the developed flow field. Finally, the mass transport equation was solved to get the concentration field. The simulation results show that the distribution of samples at the inlet of the microchannel determines its theoretical value of concentration, therefore, the pattern of the distribution of samples at the inlet and its corresponding velocity can be changed to get the desirable concentration of solute. The heterogeneous wall potential almost has no effect on the mixing of samples in two-inlet microfluidic devices. For three-inlet microfluidic devices, the comprehensive ability of transportation and mixing has an optimization when the ratio of periodic length of wall potential to the height of the microchannel is about 4.88. The above conclusions are helpful to the optimization of the design of microfluidic devices.

关键词： microchannel mixing efficiency electroosmosis numerical simulation.

STUDY ON MECHANISM OF HYDRODYNAMIC OSCILLATION IN VORTEX PRECESSION METER USING LARGE EDDY SIMULATION

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2001年第1期14卷 9-11页

作者： Fu Xin Yang Huayong state key {2. of {2. power transmission and control,zhejiang university 浙江大学流体传动及控制国家重点实验室浙江杭州

In order to improve the anti jamming performance of a vortex precession meter, the disciplinarian of the vortex precession and the mechanism of hydrodynamic oscillation inside the vortex precession meter are numerically investigated by using the large eddy simulation The results show that the periodical eccentric motion of the vortexes initiates a hydrodynamic oscillation inside the vortex precession meter The visualized time dependent flow fields indicate that the pressures at axisymmetric points oscillate with a same intensity and frequency but 180° phase shift By using differential sensing technique,a new prototype of double sensor vortex precession meter,aimed to improve measurement accuracy, is developed

关键词： Flow measurement Vortex precession Hydrodynamic oscillation Flow visualization

Exact stationary solutions independent of energy for strongly nonlinear stochastic systems of multiple degrees of freedom

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2009年第8期52卷 2424-2431页

作者： HUANG ZhiLong1,2.& JIN XiaoLing1 1 Department of Mechanics, zhejiang university, Hangzhou 31002., china {2., zhejiang university, Hangzhou 31002., china Department of Mechanics Zhejiang University Hangzhou 310027 China The state key {2. of {2. power transmission and control Zhejiang University Hangzhou 310027 China

A new procedure is proposed to construct strongly nonlinear systems of multiple degrees of freedom subjected to parametric and/or external Gaussian white noises, whose exact stationary solutions are independent of energy. Firstly, the equivalent Fokker-Planck-Kolmogorov (FPK) equations are derived by using exterior differentiation. The main difference between the equivalent FPK equation and the original FPK equation lies in the additional arbitrary antisymmetric diffusion matrix. Then the exact stationary solutions and the structures of the original systems can be obtained by using the coefficients of antisymmetric diffusion matrix. The obtained exact stationary solutions, which are generally independent of energy, are for the most general class of strongly nonlinear stochastic systems multiple degrees of freedom (MDOF) so far, and some classes of the known ones dependent on energy belong to the special cases of them.

关键词： exact stationary solution nonlinear stochastic system equivalent system independent of energy

Stochastic stability of quasi-integrable Hamiltonian systems with time delay by using Lyapunov function method

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第3期53卷 703-712页

作者： LING Quan 1,JIN XiaoLing 1 &HUANG ZhiLong 2.1 Department of Mechanics,zhejiang university,Hangzhou 31002.,{2. 2.state key laboratory of fluid power transmission and control,zhejiang university,Hangzhou 31002.,{2. 1. Department of Mechanics Zhejiang University Hangzhou 310027 China2. State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

The asymptotic Lyapunov stability of one quasi-integrable Hamiltonian system with time-delayed feedback control is studied by using Lyapunov functions and stochastic averaging ***,a quasi-integrable Hamiltonian system with time-delayed feedback control subjected to Gaussian white noise excitation is approximated by a quasi-integrable Hamiltonian system without time ***,stochastic averaging method for quasi-integrable Hamiltonian system is used to reduce the dimension of the original system,and after that the Lyapunov function of the averaged It equation is taken as the optimal linear combination of the corresponding independent first integrals in ***,the stability of the system is determined by using the largest eigenvalue of the linearized *** examples are used to illustrate the proposed procedure and the effects of delayed time on the Lyapunov stability are discussed as well.

关键词： Lyapunov stability Lyapunov function time delay stochastic averaging

STRUCTURAL PARAMETERS CALIBRATION BY POSTURE MEASUREMENT ON PARALLEL 6-DOF PLATFORM

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2002年第4期15卷 334-338,343页

作者： Wu Jiangning Li Shilunstate key {2. of {2. power transmission and control, zhejiang university,Hangzhou 31002., china state key {2. of {2. power transmission and control Zhejiang University Hangzhou 310027 China

Some approaches to measure parallel 6-degree of freedom platform's posturestatically and to calibrate the platform's actual structural parameters by measuring a series of theplatform's varying postures are studied. In the case where high posture accuracy is requiredrelatively, to obtain the platform's actual structural parameters is very important. Threedimensions measurement with 2.theodolites are used to obtain the platform's postures statically andNewton iterative method is adopted to calibrate structural parameters. Some measures taken in themeasurement and the calibration are discussed in detail. And the experiment results of theplatform's posture control before and after the calibration are given. The results show that theplatform's posture control accuracy after the calibration is improved notably.

关键词： parallel 6-DOF platform theodolite posture measurement nonlinearequation group structural parameters calibration

INVESTIGATION OF VORTEX SHEDDING INDUCED HYDRODYNAMIC VIBRATION IN VORTEX STREET FLOWMETER

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2001年第4期14卷 310-313页

作者： Fu Xin,Xu Bing,Yang Huayong (state key {2. of {2. power transmission and control,zhejiang university) 浙江大学流体传动及控制国家重点实验室浙江

Vortex street flowmeter has been used in steady flow measurement for about three decades The benefits of this type of flowmeter include high accuracy,good linearty,wide measuring range,and excellent reliability However,in unsteady flow measurement,the pressure disturbance as well as the noise from the system or surrounding can reduce the signal to noise ratio of the flowmeter seriously Aimed to use vortex street flowmeters in unsteady flow measurement,the characteristics of the vortex shedding induced hydrodynamic vibration around the prism bluff body in a vortex street flowmeter are investigated numerically and by expriments The results show that the hydrodynamic vibrations with 180° phase shift occur at the axisymmetric points of the channel around the bluff body The most intense vibration occurs at the points on the lateral faces close to the base of the prism The results provide therefore a useful reference for developing an anti interference vortex flowmeter using the different ial sensing technique.

关键词： Vortex street flowmeter Vortex shedding induced hydrodynamic vibration Unsteady flow measurement Anti-interference performance

STABILITY IN THE CIRCULAR PIPE FLOW OF FIBER SUSPENSIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2003年第2期15卷 12-18页

作者： You Zhen jiang, Lin Jian zhong Department of Mechanics, state key {2. of {2. power transmission and control, zhejiang university, Hangzhou 31002., china DepartmentofMechanics StateKeyLaboratoryofFluidPowerTransmissionandControlZhejiangUniversityHangzhou310027China

A linear stability analysis on the circular pipe flow of fiber suspensions ispresented. The fiber orientation tensors are used to describe the characteristics of theorientation dislribution of fibers. The constitutive equation for the fiber suspensions is set upand the modified Orr-Sommerfeld stability equation is derived. An improved finite difference methodwith high order accuracy is employed to solve the e-quation. The Newtonian pipe Poiseuille flowcorresponding to H = 0 is also analyzed for comparison. The results reveal that the fiber additiveswill enhance the flow stability, the degree of enhancement becomes high with the increases of theparameter H which accounts for the fiber resistance to the stretching along its axis. Fibersuspensions with large H can suppress the influence of high Reynolds number on the flow ***, fibers give a higher attenuation of the short waves of disturbance.

关键词： flow stability circular pipe flow fiber suspensions numerical simulation