检索结果-南通市图书馆

太原理工大学学报 2008年第S2期39卷 291-294,298页

作者：郑利锋张年梅太原理工大学应用力学与生物医学工程研究所山西太原030024

分析了大挠度矩形板在横向周期激励和面内静载下的强非线性振动,在考虑几何非线性的同时,结合不同面内静载条件,利用能量法求解了矩形板的振动响应模式,并研究了横向动载荷对矩形板周期解的存在区域和稳定性的影响。

关键词：强非线性振动周期运动稳定性矩形板

LASIK术后眼球受力变形的有限元模拟研究

在线全文

学校读者我要写书评

暂无评论

太原理工大学学报 2008年第S2期39卷 257-260页

作者：祝雅利陈维毅太原理工大学应用力学与生物医学工程研究所山西太原030024

用Solidworks绘图软件对眼球建模,然后将几何模型导入到Adina有限元分析软件中,选用粘弹性材料模型,根据实验得到的数据处理导入,对眼球的受力进行模拟分析,模拟基于LASIK术后眼球的实验数据,得到眼球受内压作用和变形的关系。结果表明... 详细信息

用Solidworks绘图软件对眼球建模,然后将几何模型导入到Adina有限元分析软件中,选用粘弹性材料模型,根据实验得到的数据处理导入,对眼球的受力进行模拟分析,模拟基于LASIK术后眼球的实验数据,得到眼球受内压作用和变形的关系。结果表明术后角膜基质层越薄,角膜抵抗变形的能力越差,在眼内压作用下变形也越明显,术后容易发生角膜膨胀;眼压越高,角膜顶点相对边缘的位移越明显。因此,手术必须保留足够的角膜基质层厚度;低眼压的人不适宜用准分子激光手术治疗近视。

关键词： LASIK 眼内压有限元分析粘弹性

THEORY OF DIELECTRIC ELASTOMERS

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2010年第6期23卷 549-578页

作者： Zhigang Suo (School of engineering and applied Sciences,Kavli institute for Nanobio Science and technology,Harvard university,Cambridge,MA 02138,USA) School of engineering and applied Sciences Kavli Institute for Nanobio Science and Technology Harvard University Cambridge USA

In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material （SAM）. This review focuses on one class of soft active materials： dielectric elastomers. When a membrane of a dielectric elastomer is subject to a voltage through its thickness, the membrane reduces thickness and expands area, possibly straining over 100%. The dielectric elastomers are being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. This paper reviews the theory of dielectric elastomers, developed within continuum mechanics and thermodynamics, and motivated by molecular pictures and empirical observations. The theory couples large deformation and electric potential, and describes nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity. The theory enables the finite element method to simulate transducers of realistic configurations, predicts the efficiency of electromechanical energy conversion, and suggests alternative routes to achieve giant voltage-induced deformation. It is hoped that the theory will aid in the creation of materials and devices.

关键词： soft active material, dielectric elastomer, electromechanical instability, large deformation transducer

EXPERIMENTAL STUDY ON THE VORTEX FORMATION AND ENTRAINMENT CHARACTERISTICS FOR A ROUND TRANSVERSE JET IN SHALLOW WATER

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第3期21卷 386-393页

作者： FAN Jing-yu ZHANG Yan WANG Dao-zeng Shanghai institute of applied Mathematics and mechanics Shanghai University Shanghai 200072 China Key Laboratory of Advanced Display and System Applications Ministry of Education and SMIT Center School of Mechatronics Engineering and Automation Shanghai University Shanghai 200072 China

The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex wrapped around the main body of the jet is formed in the near-wall region due to the interaction between the resulting wall jet and sufficiently shallow crossflow, with some more or less unsteady flow properties and with spreading ranges as functions of both the velocity ratio and the water depth within the near field. The entrainment of the ambient crossflow fluid into the jet main body is closely associated with the time-evolving features of the shear layer between the jet and surrounding fluid as well as the induced vortical structures near the wall. In the case of slight impingement upon the wall, the interaction between the jet shear layer and the weak, unstable scarf vortex gives rise to an appreciable local entrainment enhancement, confined in the near-wall region in the vicinity of the stagnation point. While in the case of intense impingement upon the wall, the well-organized and stable scarf vortex gives rise to a greatly enhanced entrainment and a greatly increased lateral spreading rate nearly throughout the overall near field as compared to the conventional wall jet. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex in this case occurs largely on the surface of the unique spiral roller structure by itself due to the presence of smaller and unorganized eddies, and accordingly the scarf vortex is likely to keep its spiral roller structure steadily to a relatively great downstream distance within the near field.

关键词： transverse jet shallow water vortex formation entrainment PIV measurement

Spinning Deformation Criteria of Thin-walled Tubular Part with Longitudinal Inner Ribs

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of technology(Materials Science) 2006年第4期21卷 169-172页

作者：江树勇 engineering Training Center Harbin Engineering University Harbin 150001China

As a successive and local plastic deformation process, backward ball spinning was applied for the purpose of prodacing thin-walled tubular parts with longitudinal inner ribs. According to the local plastic deformation theoo,, the application of yield criterion to the spinning process and the influence of the radial spinning force component on the formability of inner ribs were analyzed. Based on yield criterion and plastic mechanics, the stable flow rule of metal material and forming criteria of the inner ribs were obtained aad conformed to the experimental results so as to contribute greatly to improving the ball spinning process and optimizing the process variables, such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank, which have a significant influenee on the formability of the inner ribs. The knowledge of the influence of the process variables such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank on the spinning process is essential to preventing the quality defects of the spun parts and obtaining the desired spun parts.

关键词： ball spinning power spinning spinning force criterion

Fabrication of sub-micro size PZT array and their ferroelectric properties

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2006年第6期49卷 693-700页

作者： ZHAO Gaoyang1, ZHANG Weihua1, XU Guomin1, DENG Xiaocui1, JIANG Bailing1 & ZHAO Wei2 1. School of Materials Science and engineering, Xi’an university of technology, Xi’an 710048, china 2. Xi’an institute of Optics and Precision mechanics of CAS, Xi’an 710048, china School of Materials Science and engineering Xi’an University of Technology Xi’an China Xi’an institute of Optics and Precision mechanics of CAS Xi’an China

The photosensitive PZT sols and their gel films were prepared by sol-gel process. Based on the photosensitivity of the PZT gel films, two-dimensional (2D) array of the PZT gel film was fabricated using twice-exposure of double-beam interference on the gel film. PZT gel films coated on ITO/quartz substrate were exposed to an interference fringe of 325 He-Cd laser beams, the substrate was rotated by 90° between the first and second irradiation steps. Island type periodic 2D array structures with a pitch of 1 μm and cell size of about 480 nm × 480 nm × 40 nm were formed after the irradiation, and followed by leaching with organic solvent, and then by heat treatment at 600°C for 15 min. The hysteresis loops of the cell in PZT array were in-situ measured by the online-operation of TF analyzer and atomic force microscope (AFM). The probe can be located on the locked cell of PZT array in the AFM image. The alternating voltage applied to the locked cell is supplied by the TF analyzer through the conductive coating probe, and then the test signal is fed back to the TF analyzer to obtain the hysteresis loop of the locked cell of array in the absence of top electrode. The results show that the sub-micro size PZT arrays prepared in this way are of polarization reversal characteristics with the alternating electric fields, thereby exhibiting obvious ferroelectricity.

关键词： PZT, ferroelectric films, photosensitivity, hysteresis loop.

NUMERICAL SIMULATION OF TWO-DIMENSIONAL DAM-BREAK FLOWS IN CURVED CHANNELS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第6期19卷 726-735页

作者： BAI Yu-chuan XU Dong LU Dong-qiang institute for Sediment on River and Coast 300072 China Shanghai institute of applied Mathematics engineering School of Civil Engineering Tianjin University Tianjin and Mechanics Shanghai University Shanghai 200072 China

Two-dimensional transient dam-break flows in a river with bends were theoretically studied. The river was modeled as a curved channel with a constant width and a flat bottom. The water was assumed to be an incompressible and homogeneous fluid. A channel-fitted orthogonal curvilinear coordinate system was established and the corresponding two-dimensional shallow-water equations were derived for this system. The governing equations with well-posed initial and boundary conditions were numerically solved in a rectangular domain by use of the Godunov-type finite-difference scheme, which can capture the hydraulic jump of dam-break flows. The comparison between the obtained numerical results and the experimental data of Miller and Chaudry in a semicircle channel shows the validity of the present numerical scheme. The mathematical model and the numerical method were applied to the dam-break flows in channels with various curvatures. Based on the numerical results, the influence of river curvatures on the dam-break flows was analyzed in details.

关键词： dam-break flow shallow-water equations,channel bend curvilinear coordinate Godunov-type finite-difference scheme

LINEAR ACTIVE STRUCTURES AND MODES (Ⅱ) —DISCRETE SYSTEMS AND BEAMS

在线全文

学校读者我要写书评

暂无评论

applied Mathematics and mechanics(English Edition) 2004年第8期25卷 854-862页

作者：王永刚龚靖School of Civil engineering and mechanics Xi'an Jiaotong university Xi'an 710049 P.R.china Department of Civil engineering Northeast china institute of Electric Power Jilin 132012 P.R.china 张景绘School of Civil engineering and mechanics Xi'an Jiaotong university Xi'an 710049 P.R.china School of Civil engineering and mechanics Xi'an Jiaotong University Xi'an 710049 P.R.ChinaSchool of Science Chang'an University Xi'an 710064 P.R.China

The basic concepts about the active structures and some attributes of the modes were presented in paper “Liner Active Structures and Modes]( I) ". The characteristics of the active discrete systems and active beams were discussed, especially, the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-storeyed building with sensors and actuators. The concept of the adjoint active structure was extended from the discrete systems to the beams that were the representations of the continuous structures. Two types of beams with different placements of the measuring and actuating systems were discussed in detail. One is the beam with the discrete sensors and actuators, and the other is the beam with distributed sensor and actuator function. The orthogonality conditions were derived with the modal shapes of the active beam and its adjoint active beam. An example shows that the variation of eigenvalues with feedback amplitude for the homo-configuration and non-homo-configuration active structures.

关键词： I) ". The characteristics of the active discrete systems and active beams were discussed especially the stability of the active structures and the orthogonality of the eigenvectors. The notes about modes were portrayed by a model of a seven-s

Stability Robustness Measures of Linear Discrete-Time Systems with Structured Perturbations

在线全文

学校读者我要写书评

暂无评论

Systems Science and Systems engineering 1999年第1期9卷 58-64页

作者： CAO Dengqing(institute of applied mechanics, Southwest Jiaotong university, Chengdu 610031, china)

This paper consider the robust stability of linear discrete-time systems subjected toreal structured perturbations. The "zero exclusion principle", which is based on the properties of theKronecker product and the bialternate product, is employed to derive the new robust stability boundsfor time-invariant perturbations. A numerical examples is Presented to demonstrate the merit of theproposed method. The example shows that the new bounds are easy to compute numerically and canhave an arbitrary degree of improvement over the Previous ones reported by the Lyapunov stabilitymethod.

关键词： robust stability linear discrete-time systems structured perturbations matrix approach

NUMERICAL SIMULATION OF THE DISPERSION IN OSCILLATING FLOWS WITH REVERSIBLE AND IRREVERSIBLE WALL REACTIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第4期21卷 482-490页

作者： ZHANG Dao-xiang LU Zhi-ming LIU Yu-lu NG Chiu-On Shanghai institute of applied Mathematics and mechanics Shanghai University Shanghai 200072 China College of Mathematics and Computer Science Anhui Normal University Wuhu 241000 China Department of Mechanical engineering The University of Hong Kong Hong Kong China

This is a study on the mass transport of a solute or contaminant in oscillating flows through a circular tube with a reactive wall layer. The reaction consists of a reversible component due to phase exchange between the flowing fluid and the wall layer, and an irreversible component due to absorption into the wall. The short-time dispersion characteristics are numerically investigated, incorporating the coupling effects between the flow oscillation, sorption kinetics, and retardation due to phase partitioning. The effects of various dimensionless parameters e.g., Da （the Damkoehler number）, α （phase partitioning number）, F （dimensionless absorption number）, and δ （dimensionless Stokes boundary layer number） on dispersion are discussed. In particular, it is found that there exist trinal peaks of the breakthrough curves in some cases.

关键词： dispersion flow oscillation wall reactions