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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 3.001.,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 3.001.,china Institute of Mathematical Physics Zhejiang Sci-Tech University Hangzhou China Department of Physics Shangqiu Normal University Shangqiu China Department of Mathematics Qingdao University Qingdao China faculty of mechanical engineering & automation Zhejiang Sci-Tech University Hangzhou China

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 3.001.,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 3.001., china 2 State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of sciences, Beijing 100190, china College of mechanical engineering and automation Zhejiang Sci-Tech University Hangzhou China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China

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

Elastohydrodynamic Lubrication Studies on Effects of Crowning Value in Roller Bearings

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Journal of Shanghai university(English Edition) 2001年第1期5卷 76-81页

作者： CHEN Xiao yang, SHEN Xue jin School of Electromechanical engineering and automation, Shanghai university, Shanghai 200072, china XU Wen, MA Jia ju Department of mechanical engineering, zhejiang university, hangzhou 310027, china School of Electromechanical engineering and automation Shanghai University Shanghai China Department of mechanical engineering Zhejiang University Hangzhou China

The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL) problem of Lundberg's profiled cylindrical roller under the conditions of flooded state, moderate load and material parameter. It shows clearly the effects of crowning value on the variations of oil film shape and thickness. The agreement between numerical analysis and experiment results is very good. The results indicate there must be an optimum crowning value that will induce the thickest and most even oil film in EHL state for a given working condition, and this value is larger than the design value in dry contact state for the same working conditions.

关键词： roller bearings crowning value elastohydrodynamic lubrication

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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

Automatic Measurement of Garment Dimensions Based on Image Analysis technology

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

Embedded Microcontroller Based Flat Knitting Machine Controller Design

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 3.001. 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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Embedded Microcontroller Based Flat Knitting Machine Control...

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

第二届先进纺织材料及加工技术国际会议

作者： Zhang Hua Xudong Hu Yanhong Yuan Xianmei Wang Laihu Peng Jianyi Zhang(faculty of mechanical engineering & automation zhejiang sci-tech university hangzhou 3.001. china)

There are kinds of flat knitting machines;they combine basic functions like jacquard,yarn color selection,knit loop traverse,*** machines can be used to knit sweaters or flat pieces of *** this paper,authors design a distributed control based *** the controller,individual functional modules are designed to perform special *** individual functional module is a CAN node of the *** are used to transfer signals and commands between *** control system,based on distributed controls and modularizing designs,are easy to design and can meet the needs of reliability and real-time control with low cost.

关键词： Flat knitting machine CAN Distributed control

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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

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灵巧手操作的重构规划

机器人 2004年第5期26卷 439-443页

作者：杨洋北京航空航天大学机械工程与自动化学院北京100083

根据人类利用滑动或滚动方式进行灵巧操作的几种模式 ,在多指灵巧手—物体的抓持系统中 ,把实现这些灵巧操作模式的规划问题作为一个位形空间的重构问题进行全局和局部级的操作规划 ,开发了实现灵巧操作的规划算法 .仿真结果表明了方法... 详细信息

根据人类利用滑动或滚动方式进行灵巧操作的几种模式 ,在多指灵巧手—物体的抓持系统中 ,把实现这些灵巧操作模式的规划问题作为一个位形空间的重构问题进行全局和局部级的操作规划 ,开发了实现灵巧操作的规划算法 .仿真结果表明了方法的有效性和正确性 .

关键词：灵巧操作多指手操作规划位形重构