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Symmetries and exact solutions of discrete nonconservative systems

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science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1699-1706页

作者： FU JingLi1,LI XiaoWei2,LI ChaoRong1,ZHAO WeiJia3 & CHEN BenYong4 1 Institute of Mathematical Physics,zhejiang sci-tech university,hangzhou 310018,china 2 Department of Physics,Shangqiu Normal university,Shangqiu 476000,china 3 Department of Mathematics,Qingdao university,Qingdao 266071,china 4 faculty of mechanical engineering & automation,zhejiang sci-tech university,hangzhou 310018,china zhejiang sci-tech university Institute of Mathematical Physics Hangzhou China (GRID:grid.413273.0) (ISNI:***) Shangqiu Normal university Department of Physics Shangqiu China (GRID:grid.412544.2) (ISNI:***) Qingdao university Department of Mathematics Qingdao China (GRID:grid.410645.2) (ISNI:***) zhejiang sci-tech university Faculty of Mechanical Engineering &amp automation Hangzhou China (GRID:grid.413273.0) (ISNI:***)

Based on the property of the discrete model entirely inheriting the symmetry of the continuous system,we present a method to construct exact solutions with continuous groups of transformations in discrete nonconservative *** Noether's identity of the discrete nonconservative system is *** symmetric discrete Lagrangian and symmetric discrete nonconservative forces are defined for the *** quasi-extremal equations of discrete nonconservative systems are *** conserved quantities are derived with symmetries associated with the continuous *** have also found that the existence of the one-parameter symmetry group provides a reduction to a conserved quantity;but the existence of a two-parameter symmetry group makes it possible to obtain an exact solution for a discrete nonconservative *** examples are discussed to illustrate these results.

关键词： discrete nonconservative system symmetry conserved quantity quasi-extremal equation exact solution

Factors Affecting Small Axial Cooling Fan Performance

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Journal of Thermal science 2010年第2期19卷 126-131页

作者： Lihong Wang,Yingzi Jin,Baoling Cui,Yuzhen Jin,Jin Lin,Yanping Wang and Chuanyu Wu College of mechanical engineering & automation,zhejiang sci-tech university,Xiasha Education Zone,hangzhou 310018,china College of mechanical engineering & automation Zhejiang Sci-Tech University Xiasha Education Zone Hangzhou China

Many factors such as outer diameter, hub ratio, blade numbers, shape and stagger angle affect the performance of small cooling fans. A small cooling fan was simulated using CFD software for three blade stagger angles （30.5°, 37.5°, 44.5°）and obtained the internal flow field and the static characteristics. Research indicated that the stagger angle has an obvious effect on the static characteristics of a fan. For flow rates below 0.0104 mVs, total pressure is the greatest when the stagger angle is 37.5°; flow rates higher than 0.0104 m^3/s, the total pressure is greatest when the stagger angle is 44.5° For the same flow rates, the velocity at inlet of pressure surface increases with in- creasing stagger angle, but the change of velocity on the suction surface is very small. For one model, vortices and the speed of revolution surfaces decrease with tip clearance increasing. But for other three models, increasing the stagger angle, the vortex intensity and speed of revolution surfaces at same height tip clearance increases, simultaneously, the position of vortex offset from the top of the rotor blade to the suction surface.

关键词： Axial flow fan Stagger angle Revolution surface Vortex intensity

Research on the mechanics of underwater supersonic gas jets

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中国科学：物理学、力学、天文学英文版 2010年第3期53卷 527-535页

作者： SHI HongHui1, WANG BoYi2 & DAI ZhenQing2 1 College of mechanical engineering and automation, zhejiang sci-tech university, hangzhou 310018, china 2 State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of sciences, Beijing 100190, china zhejiang sci-tech university College of Mechanical Engineering and Automation Hangzhou China (GRID:grid.413273.0) (ISNI:***) Chinese Academy of sciences State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Beijing China (GRID:grid.9227.e) (ISNI:***)

An experimental research was carried out to study the fluid mechanics of underwater supersonic gas jets. High pressure air was injected into a water tank through converging-diverging nozzles (Laval nozzles). The jets were operated at different conditions of over-, full- and under-expansions. The jet sequences were visualized using a CCD camera. It was found that the injection of supersonic air jets into water is always accompanied by strong flow oscillation, which is related to the phenomenon of shock waves feedback in the gas phase. The shock wave feedback is different from the acoustic feedback when a supersonic gas jet discharges into open air, which causes screech tone. It is a process that the shock waves enclosed in the gas pocket induce a periodic pressure with large amplitude variation in the gas jet. Consequently, the periodic pressure causes the jet oscillation including the large amplitude expansion. Detailed pressure measurements were also conducted to verify the shock wave feedback phenomenon. Three kinds of measuring methods were used, i.e., pressure probe submerged in water, pressure measurements from the side and front walls of the nozzle devices respectively. The results measured by these methods are in a good agreement. They show that every oscillation of the jets causes a sudden increase of pressure and the average frequency of the shock wave feedback is about 5–10 Hz.

关键词： underwater supersonic gas jet pressure oscillation flow visualization shock wave feedback

Analytical solution and semi-analytical solution for anisotropic functionally graded beam subject to arbitrary loading

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science china(Physics,Mechanics & Astronomy) 2009年第8期52卷 1244-1256页

作者： HUANG DeJin1,2,DING HaoJiang1 & CHEN WeiQiu3 1 Key Laboratory of Soft Soils and Geoenvironmental engineering,Ministry of Education,zhejiang university,hangzhou 310027,china 2 faculty of engineering,Ningbo university,Ningbo 315211,china 3 Department of engineering Mechanics,zhejiang university,hangzhou 310027,china Key Laboratory of Soft Soils and Geoenvironmental engineering Ministry of Education Zhejiang University Hangzhou China faculty of engineering Ningbo University Ningbo China Department of engineering Mechanics Zhejiang University Hangzhou China

Analytical and semi-analytical solutions are presented for anisotropic functionally graded beams subject to an arbitrary load,which can be expanded in terms of sinusoidal *** plane stress problems,the stress function is assumed to consist of two parts,one being a product of a trigonometric function of the longitudinal coordinate(x) and an undetermined function of the thickness coordinate(y),and the other a linear polynomial of x with unknown coefficients depending on *** governing equations satisfied by these y-dependent functions are *** expressions for stresses,resultant forces and displacements are then deduced,with integral constants determinable from the boundary *** the analytical solution is derived for the beam with material coefficients varying exponentially or in a power law along the thickness,the semi-analytical solution is sought by making use of the sub-layer approximation for the beam with an arbitrary variation of material parameters along the *** present analysis is applicable to beams with various boundary conditions at the two *** numerical examples are presented for validation of the theory and illustration of the effects of certain parameters.

关键词： anisotropic material functionally graded arbitrary loading stress function analytical solution semi-analytical solution

Networked Kalman filtering with combined constraints of bandwidth and random delay

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science china(Information sciences) 2012年第10期55卷 2343-2357页

作者： GE QuanBo 1,2,WEN ChengLin 1 & XU TingLiang 1 1 School of automation,hangzhou Dianzi university,hangzhou 310018,china 2 State Key Laboratory of Industrial Control technology,zhejiang university,hangzhou 310027,china School of automation Hangzhou Dianzi University Hangzhou China State Key Laboratory of Industrial Control technology Zhejiang University Hangzhou China

Kalman filter is a powerful tool in target tracking and self-localization across wireless sensor networks with many *** paper considers the filters design for networked systems with combined constraints of bandwidth and random delay,and proposes a kind of universal networked Kalman estimator for given linear time invariant(LTI) or determinate parameters(DP) systems,which are also called linear and determinate parameters(LDP) systems ***,two modeling ways to treat bit quantization error vector are given and the corresponding LDP systems taken after bit quantization are ***,we introduce an equivalent weighted summation form of the conventional linear Kalman filter,which fully uses two essential characteristics,namely offline computation property from the LDP systems and linear weighted summation property from the linear minimum mean square error ***,by adopting the replacement and innovation compensation operations,a kind of integrated networked estimator,involving two estimation algorithms with different modeling ways to bit quantization error actually,is presented based on the weighted summation filter for random delay *** proposed universal networked estimation algorithms have some outstanding advantages such as extensive application,concise algorithm structure,high estimate accuracy,and good running *** examples are demonstrated to validate the proposed networked estimation algorithms.

关键词： Kalman filter LDP systems LMMSE limited bandwidth random delay

Automatic Measurement of Garment Dimensions Based on Image Analysis technology

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Automatic Measurement of Garment Dimensions Based on Image A...

ICEMI'2005第七届国际电子测量与仪器学术会议

作者： Chen Kunchang (College of mechanical engineering and automation zhejiang sci-tech university No.2 Road Xiasha hangzhou 310018 china)

The measurement of garment dimensions remains as a very important procedure in garment making engineering. This paper proposes a novel approach based on image analysis technology to cope with the auto

关键词： Garment dimensions automatic measurement image analysis.

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振动拉削系统振幅衰减特性分析与实验研究

中国机械工程 2017年第5期28卷 518-524页

作者：蒙臻倪敬武传宇浙江理工大学机械与自动控制学院杭州310018 杭州电子科技大学机械工程学院杭州310018

为了探究振动拉削中导致激振幅值衰减的主要因素,以双伺服阀电液激振拉削设备为研究对象,综合考虑双阀电液激振系统动力学特性,以及拉刀多齿接触效应、工件尺寸参数等影响下的动态拉削力特征,建立了振动拉削过程中的激振系统模型;再分... 详细信息

为了探究振动拉削中导致激振幅值衰减的主要因素,以双伺服阀电液激振拉削设备为研究对象,综合考虑双阀电液激振系统动力学特性,以及拉刀多齿接触效应、工件尺寸参数等影响下的动态拉削力特征,建立了振动拉削过程中的激振系统模型;再分别通过理论计算及系统实验,对比研究了电液激振器在非线性负载扰动下实际输出力和输出位移的衰减波形,为振动拉削激振系统参数优化提供理论指导和实验依据。实验结果分析表明:振动频率是导致系统振幅衰减的主要因素,而动态拉削力通过影响激振缸活塞的运动特征使得输出波形的峰值衰减,甚至使位移振幅趋向于0。

关键词：双阀激振拉削负载激振特性幅值衰减

EXPERIMENTAL STUDY ON THE MECHANISM OF THE RICHTMYERMESHKOV INSTABILITY AT A GAS-LIQUID INTERFACE

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Journal of Hydrodynamics 2009年第3期21卷 423-428页

作者： SHI Hong-hui ZHANG Ga DU Kai JIA Hui-xia College of mechanical engineering and automation Zhejiang University of Science and Technology Hangzhou 310018 China

The mechanism of the Richtmyer-Meshkov instability was experimentally studied in a vertical rectangular shock tube. The velocity of the interface driven by the shock wave was measured by a self-designed measurement system, which consists of semiconductor lasers, signal amplification circuits, digital oscilloscope and computer. Tests were carded out at several shock wave Mach numbers. In addition, the movement of the interface and the variation of the mixed zone width with time were recorded by high-speed photography. The experimental results show that the interface velocity increases with the increase of the Mach number, and the distance of the interface＇s movement and the width of the mixed zone vary with time in a linear relationship.

关键词： Richtmyer-Meshkov instability shock wave shock tube laser interface

Two Classes of Models of Granular Computing

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Two Classes of Models of Granular Computing