共查询到17条相似文献，搜索用时 234 毫秒
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An effective metric is developed on the background of light field in the plasma.Consistency with effective metric and Gordon‘s metric is under the ideal fluid approximation.The validity of effective metric is verified in the limit of non-relativistic limit.Finally the effective metric for plasma electrons is obtained. 相似文献
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One dimensional electron density perturbation is derived by using the cold fluid equation,Possion‘s equation and the continuity equation.The perturbation is generated by a driving laser pulse propagating through a plasma,The upshifting of the frequency of a trailing pulse induced by density perturbation is studide by using optical metric.The results show that it is possible that the photon will gain energy from wht wakefield when assuming photon‘s number to be conserved.i.e..,thd photon will be accelerated. 相似文献
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A numerical simulation of the interaction between laminar flow with low Reynolds number and a highly flexible elastic sheet is presented. The mathematical model for the simulation includes a three-dimensional finitevolume based fluid solver for incompressible viscous flow and a combined finite-discrete element method for the three-dimensional deformation of solid. An immersed boundary method is used to couple the simulation of fluid and solid. It is implemented through a set of immersed boundary points scattered on the solid surface. These points provide a deformable solid wall boundary for the fluid by adding body force to Navier-Stokes equations. The force from the fluid is also obtained for each point and then applied on the boundary nodes of the solid. The vortex-induced vibration of the highly flexible elastic sheet is simulated with the established mathematical model. The simulated results for both swing pattern and oscillation frequency of the elastic sheet in low Reynolds number flow agree well with experimental data. 相似文献
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XIANG Yu-min 《重庆大学学报(英文版)》2008,7(3):210-215
To determine the motion of a charged particle in a magnetic field produced by a current flowing along a long column conductor, the equation of the motion was established on the basis of Lorentz force. Qualitative analysis and quantitative solutions demonstrated that the motion contains nonlinear oscillation. The oscillation can be treated as the perturbation of the helical motion, Which the particle undergoes in a special condition. The general motion is superposition of two helixes, one as an axis spiraled by another. It is proven that the oscillation is stable. 相似文献
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Thermal-mechanical behavior of functionally graded thick plates, with one pair of opposite edges simply supported, is investigated based on 3D thermoelasticity. As for the arbitrary boundary conditions, a semi-analytical solution is presented via a hybrid approach combining the state space method and the technique of differential quadrature. The temperature field in the plate is determined according to the steady-state 3D thermal conduction. The Mori-Tanaka method with a power-law volume fraction profile is used to predict the effective material properties including the bulk and shear moduli, while the effective coefficient of thermal expansion and the thermal conductivity are estimated using other micromechanics-based models. To facilitate the implementation of state space analysis through the thickness direction, the approximate laminate model is employed to reduce the inhomogeneous plate into a homogeneous laminate that delivers a state equation with constant coefficients. The present solutions are validated by comparisons with the exact ones for both thin and thick plates. Effects of gradient indices, volume fraction of ceramics, and boundary conditions on the thermomechanical behavior of functionally graded plates are discussed. 相似文献
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Mathematical modelling of translational motion of rail-guided cart with suspended payload 总被引：1，自引：0，他引：1
MITREV Rosen 《浙江大学学报(A卷英文版)》2007,8(9):1395-1400
In this paper modelling of the translational motion of transportation rail-guided cart with rope suspended payload is considered. The linearly moving cart,driven by a travel mechanism,is modelled as a discrete six degrees of freedom (DOF) dynamic system. The hoisting mechanism for lowering and lifting the payload is considered and is included in the dynamic model as one DOF system. Differential equations of motion of the cart elements are derived using Lagrangian dynamics and are solved for a set of real-life constant parameters of the cart. A two-sided interaction was observed between the swinging payload and the travel mechanism. Results for kinematical and force parameters of the system are obtained. A verification of the proposed model was conducted. 相似文献
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Ren-peng CHEN Yun-min CHEN Wei XU Zhi-gang LIANG Wei FENG 《浙江大学学报(A卷英文版)》2008,9(3):293-302
Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a fre- quency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different fre- quency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry （TDR） measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak＇s model. 相似文献
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The base stress of the opened bottom cylinder structure differs greatly from that of the structure with a closed bottom. By investigating the inner soil pressure on the cylinder wall and the base stress of the cylinder base, which were obtained from the model experiments, the interactions among the filler inside the cylinder, subsoil and cylinder are analyzed. The adjusting mechanism of frictional resistance between the inner filler and the wall of the cylinder during the overturning of the cylinder is discussed. Based on the experimental study, a method for calculating the base stress of the opened bottom cylinder structure is proposed. Meanwhile, the formulas for calculating the effective anti-overturning ratio of the opened bottom cylinder are derived. 相似文献
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The technique of adaptive tree mesh is an effective way to reduce computational cost through automatic adjustment of cell size according to necessity. In the present study, the 2D numerical N-S solver based on the adaptive quadtree mesh system was extended to a 3D one, in which a spatially adaptive octree mesh system and multiple particle level set method were adopted for the convenience to deal with the air-water-structure multiple-medium coexisting domain. The stretching process of a dumbbell was simulated and the results indicate that the meshes are well adaptable to the free surface. The collapsing process of water column impinging a circle cylinder was simulated and from the results, it can be seen that the processes of fluid splitting and merging are properly simulated. The interaction of second-order Stokes waves with a square cylinder was simulated and the obtained drag force is consistent with the result by the Morison’s wave force formula with the coefficient values of the stable drag component and the inertial force component being set as 2.54. 相似文献
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The purpose of this study was to build a flexible mechanical system with a hydrostatic skeleton. The main components of this system are two type flexible bags. One is a structural bag with constant inner pressure. The other is an actuator bag with controlled inner pressure. To design the system, it was necessary to estimate both structural deformation and driving force. Nu- merical analysis of flexible bags, however, is difficult because of large nonlinear deformation. This study analyzed structural strength and driving force of flexible bags with the nonlinear finite element analysis （FEA） software ABAQUS. The stress con- centration dependency on the bag shape is described and the driving force is calculated to include the large deformation. From the analytical results, this study derives an empirical equation of driving force. The validity of the equation was confirmed by condition-changed analyses and experimental results. 相似文献
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邱承媛 《阿坝师范高等专科学校学报》2003,(2):98-100
圆周运动按运动物体所受力的种类,可分为:1.在万有引力作用下的匀速圆周运动,2.在电场中的匀速圆周运动,3.在磁场中的匀速圆周运动,4.在复合场中的圆周运动。文章以近年高考题为例对此进行讨论。 相似文献
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该文介绍了用正则方程求解受平方反比引力作用的质点轨道方程的方法,推导了质点的角动量守恒定律(mh=恒量)和机械能守恒定律(E=恒量)及其轨道方程。以往用比耐公式求解质点的轨道方程,通常没有给出积分常数的具体形式。该文用E和h确定了用比耐公式法求解的积分常数。这样用比耐公式方法与用机械能守恒方法求解的轨道方程形成了统一的形式,有利于学生更深入地理解受平方反比引力作用质点运动的物理内涵。 相似文献
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关于卢瑟福模型中电子的运动是加速还是减速,不同文献给出不同描述,甚至是截然相反的描述.本文分别从能量和力的角度定量、定性地分析了卢瑟福模型中电子的运动情况,得出了卢瑟福模型中电子绕原子核旋转、辐射能量时作加速运动的结论. 相似文献
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分析受摩擦力约束条件下的机械系统运动，利用广义坐标系的扩展方法，引入辅助坐标。将摩擦力包含在广义力的扩展坐标系中。论文构建了速度变换矩阵和反变换矩阵，用三阶玻尔茨曼方程求解，所得结果与动力学普遍方程是一致的。 相似文献