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A geometrically attractive and covariant derivation of the balance laws from the principle of energy balance in terms of this stress is presented.


From the results of tensile, compression, and threepoint bend testing of specimens, the parameters of elasticity and strength for an "equivalent" orthotropic body have been determined on the basis of Bolotin's principle of energy smoothing.


Then based on principle of energy equilibrium we propose a global infrared image synthesis model for urban scene, discuss the specific forms for various parts of the scene and compute their surface temperature.


We propose to reconcile these apparently contradictory results by combining the virial theorem and a principle of energy partitioning between energy storage elements in a system with dissipation.


During this period, Helmoltz (über die Erhaltung der Kraft, 1847) showed that the principle of energy conservation may be applied to living systems.

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 The dynamic properties of the unstable (fast) propagation of cracks, especially the rule of the variation of propagating velocity, are discussed. The case to be considered is that the extension of cracks is not very long (as the cases of rapid crack propagation under impulsive load) , the main idea of this paper is that the rapid propagation of cracks may be treated as a vibration problem and is connected to the basic conceptions of fracture mechanics (such as criterior of fracture, etc.) by the principle... The dynamic properties of the unstable (fast) propagation of cracks, especially the rule of the variation of propagating velocity, are discussed. The case to be considered is that the extension of cracks is not very long (as the cases of rapid crack propagation under impulsive load) , the main idea of this paper is that the rapid propagation of cracks may be treated as a vibration problem and is connected to the basic conceptions of fracture mechanics (such as criterior of fracture, etc.) by the principle of energy equivalence. The rapid propagation of cracks is essentially a specific type of the transient vibration of elastic bodies, with the boundary conditions varying with the time. Under the assumption of equivalence, the above problem may be treated as the initialvalue problem of a damped system with multiple degrees of freedom, considering the nonlinear effect of stiffness due to the extension of crack. After further simplification, it is deduced to a transient response problem of a damped nonlinear system of single degree of freedom under the initial condition of displacement, so that the solution can be obtained numerically. The fundamental conceptions for which the model is constituted, is the principle of the whole amount of energies being equivalent between the model and practical element, and the primary (main) hypothesis is that the fracture energy dissipated during the propagation oi crack is equivalent to the damping energy of the model system. The DCB specimens are taken as an example for explaining the theory and computing procedure. Numerical examples are calculated and compared with experimental results.In order to record the complete procedure of the rapid propagation and arrest of the crack by experiments, a new method of eddycurrent type is developed.Computational results of several specimens of different materials are all coincided well with the experiments. So it can be concluded that the computational model can be used at least for such cases. Further research would be studied for more compli cate cases.  本文研究裂纹快速扩展的动力特性,特别是裂纹扩展速度的规律.主要考虑在裂纹扩展量不很大的情况(如冲击载荷下裂纹快速扩展的情况)下,将裂纹快速扩展止裂过程作为一种瞬态振动问题求解,而通过能量相当(等效)的原则与断裂力学基本概念(断裂准则等)相联系.计算模型的主要假设是:在裂纹快速扩展过程中,断裂能的消耗用等效的阻尼能来表达.经过近似处理,最后归结为求解有阻尼的单自由度非线性系统在初位移下的瞬态响应计算问题.以DCB试件为例说明计算程序,并给出实例计算结果与实验结果和其他工作的比较.用涡流检测法记录裂纹快速扩展的全过程,以提供实验数据。计算结果与各种实验结果符合较好,初步证明所用的计算模型的有效性,可以作进一步的推广研究以及用于更复杂的问题.  A triangular plate bending hybrid element is constructed according to Reisner's principle. It has 9 degrees of freedom and takes, the shear effect into account. The C0 formulation of the thick plate is extended to the thin plate and the"shear locking"phenomenon can be avoided through imposing the discrete type of Kirchhoff's constraints. It is interesting to note that the kind of discrete constraints can be directly imposed by means of Hermite interpolation. This is one of the features which distinguish the... A triangular plate bending hybrid element is constructed according to Reisner's principle. It has 9 degrees of freedom and takes, the shear effect into account. The C0 formulation of the thick plate is extended to the thin plate and the"shear locking"phenomenon can be avoided through imposing the discrete type of Kirchhoff's constraints. It is interesting to note that the kind of discrete constraints can be directly imposed by means of Hermite interpolation. This is one of the features which distinguish the paper from ref. [ 5 ]and [ 1 ]. On the other hand, the specific matching between bending and shearing is discussed in the analysis of the thick plate. It is shown that the reasonable matching between bending and shearing complementary energies may be destroyed by inhomogeneous magnification of the discretization errors. Furthermore, a principle of energy regulation is put forward, with the aid of which this matching problem is effectively treated so that the unified analysis of the thick and thin plates is achieved. Finally, numerical examples are given.  本文从Reissner变分原理出发,构造一计入剪切效应的9自由度板弯曲杂交元。通过离散型Kirchhoff约束的实施,把厚板公式直接推广于薄板计算而不出现解的“闭锁”现象。文中提出的能量调整原理有效地解决了厚板元素中的弯、剪匹配问题,从而实现了厚薄板分析的统一性。文章最后给出计算实例。  In this paper, a new mixed variational principle of energy in linear elasticity the stateparted variational principle of energy is presented.If an elastic body with complex surface S is in static equilibrium, Let the part Su1 transform into Sσ1 and the part Sσ1 into Su1. The body having the surface is called the BASIC SYSTEM of the original body.Let us divide the state of the basic system into two substates called substates (1) and (2).Let us consider the substate (1) having potential energy... In this paper, a new mixed variational principle of energy in linear elasticity the stateparted variational principle of energy is presented.If an elastic body with complex surface S is in static equilibrium, Let the part Su1 transform into Sσ1 and the part Sσ1 into Su1. The body having the surface is called the BASIC SYSTEM of the original body.Let us divide the state of the basic system into two substates called substates (1) and (2).Let us consider the substate (1) having potential energy and the substate (2) having complementary energy and define the energy H. The functional of the stateparted variational principle of energy are as following: + H and so on.Problems dealing with a body having complex boundary conditions can be solved by means of the stateparted variational principle of energy.  本文提出了线弹性体力学的一类混合能量变分原理——分态能量变分原理。 文中首先定义了对弹性体施行边界变换以后获得的基本体系状态,然后把基本体系状态分解成两个子状态。对这两个子状态分别建立位能泛函和余能泛函,并定义两子状态之间的附加能量。从而可以构造出一族分态混合能量泛函。除了详细地论证了三种典型的分态能量变分原理以外,文中还列出了分态能量泛函的其它一些形式。 最后,说明了分态能量变分原理在计算具有复杂边界条件薄板问题中的应用。   << 更多相关文摘 
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