查询词典 boundary element method

The spring part of this boundary can be determined by Mindlin equations, and frequency dependent viscous material (resistance proportional to velocity) is introduced into the boundary dements to simulate dashpots of the viscous boundary.

提出一种能用于无限域地基动、静力有限元分析的简单人工边界-粘弹边界，采用一层边界单元来实现。

The apparent selective establishment criteria of the new strips may explain the low similarity in species composition between the original boundary and the new boundary plots: only non-woodland perennial monocots and dicots had high establishment rates in the herbaceous strips in all boundary types.

表观选择性建立标准的新带可以解释低，在相似的物种组成与原选区分界及新的边界情节：只有非林地多年生monocots和双子叶植物有较高的建立利率，在绿草带的所有边界类型。

The no-penetration boundary condition is satisfied by placing a vortex sheet along the boundary, which strength must be adapted to cancel the slip velocity on the boundary induced by all the other flow components.

本论文以Leonard之面积扩散涡漩法及Huang之涡泡分裂融合修正法为基础，开发一满足无滑移、无穿透边界条件之数值模拟工具。

Motivated by the i dea o f t he v ariable-structure c ontrol, t he c onception o f a pproaching region and leaving region of the switching boundary is developed. The sufficient conditions of whether sliding mode occurs or not on the switching boundary are obtained. Under the assumption of the switching delay time being positive, the sufficient conditions of quasi-sliding-mode occurring on the switching boundary are given.

受变结构控制思想的启发，提出切换线的趋近域和远离域的概念，进而得出系统在切换线上是否会发生滑动模态的充分条件。

Shadow effect can not be neglected for thermal analysis of spacecraft,Accroding to the angle between solar light and antenna orbit plane and its orbit location,analytical geometry method was used for accurately calculating solar radiation heat flux distribution of reflector surfaces.To analyze the temperature field under heat flux,the formulations of net radiation flux density between two gray elements and the net flux density of gray surface under external thermal flux were deduced.Based on the characteristic of space environment,the nonlinear temperature distribution in transverse direction of reflector shell self radiation were considered,the finite element formulations were given for orthogonal material layered shell by Galerkin method.A layered element including a inner heat source layer was proposed,and the finite element formulation expressed by DOF of the inner heat source layer were put forward with temperature and heat flux boundarys between adjacent layer.

单馈反射面赋形天线是未来星载天线发展的一个重要形式，分析了基于物理光学、几何光学和几何绕射理论的理想反射面辐射场；介绍了基于几何光学的反射面天线赋形方法；针对赋形过程中辐射场的快速分析要求，比较分析了基于物理光学的Fourier-Bessel和Jacobi-Bessel级数展开方法以及GB展开分析方法；利用GB展开快速分析方法在20GHz频率下对0.6m口径的天线进行赋形分析，实现中国大陆的30dB增益覆盖，通过数值计算研究了固定增益期望下的口径尺寸随频率的变化，以及频率为20GHz的不同尺寸天线赋形后的覆盖目标区域最大增益的变化情况。

In order to solve parabolic equation of heat conduction with interval parameters, the regions of space are discretized by finite elements and the regions of time are discretized by finite difference. The interval finite element method based on the element is established via the combination of interval analysis and the traditional finite element method.

对具有区间参数的热传导抛物型方程的求解，在空间域上利用有限单元离散，在时间域上利用差分离散，将区间分析和常规的有限元法相结合，建立了求解不确定温度场的基于单元的区间有限元方法。

Two special cases are discussed: flow due to a constant pressure gradient and flow due to a periodic one; In chapter 4, on the basis of the method of fractional element proposed by Schiessel et al and of the generalized fractional element networks proposed by Xu and Tan and by the use of discretization method for solving the inverse Laplace transform, we obtain the creep compliance of Zener and Poynting-Thomson models which are composed of the generalized fractional element networks.

并讨论了如下两种特殊情形：常压力梯度下的流动和周期性压力梯度下的流动；第四章在Schiessel等提出的分数阶单元法和徐明瑜等提出的广义分数阶单元网络的基础上，应用离散求逆Laplace变换的方法，给出并讨论了广义分数阶单元网络Zener和Poynting-Thomson模型的蠕变柔量。

Compared with the existing finite element eigenanalysis method[8]for asymptotic fields near the crack tip, current method has the following several characteristics: The jump-off that educes the virtue work formula is different; when solving the characteristic formula with FEM, the form of the element is non-confirming element; the singular transformation technique is not used in the assumption of displacement fields surrounding the wedge tip.

该方法与过去的有限元特征分析方法[8]相比的显著特点是：导出虚功原理的出发点不同；有限元单元形式为非协调元；楔形体端部邻域内的位移场假定没有采用奇异变换技术。

This paper, which focused on the structure optimization theory and method, has finished such studies as follows: The three dimension model has been built, which provide the necessary conditions for the building of the dynamics equivalent model. By the launch dynamics simulation, the loads of the key joints when the rocket is launched has been got, which provide the necessary data for the finite element analysis and the structure optimization. The finite element model of the excess weight parts of the rocket has been built, buy the finite element intension analysis of the model in two conditions, the displacement and the stress of the key points have been got, which make us know the distributing of the stress and the transmogrification of the part. To satisfy the intension and the precision design request and to decrease the weight of the part as many as possible, the part has been topology optimized by the structure optimization theory and method. After that, the new model has been analysis in structure and launch dynamics. The contrast of the character change of the old part and the new part and the influence on the rocket system have been studied.

本文以结构优化理论和方法为核心，主要做了以下工作：建立了某自行火箭炮全炮三维实体模型，为建立该火箭炮系统的动力学等效模型提供了必要条件，进行了发射动力学仿真，得到该火箭炮发射装置各关键连接部位在发射状态下的载荷，为有限元分析和结构优化提供了必需的数据；建立了该火箭炮发射装置超重部分的有限元模型，分两种工况，对模型进行了有限元强度分析，得出了关键部位的位移和应力值，对其的应力和变形分布有了具体的了解；运用结构优化的理论和方法，对该火箭炮发射装置超重部分进行了拓扑优化，使其在满足强度和精度的要求下尽可能多地减轻重量，对优化后得到的模型进行了结构分析和发射动力学分析，对比了该部件优化前后的特性变化以及对火箭炮系统的影响。

In this paper, the improvement of the low velocity impact resistance performance of composite plates using shape memory effect of shape memory alloy is analyzed by using finite element method, The constitutive relationship and the model of finite element analysis of SMA hybrid composite plates are established, The finite element equation is solved by using the Newmark direct integration method and the modified Hertzian contact law.

应用有限元方法分析了利用形状记忆合金的记忆特性提高复合材料抵抗低速冲击的能力，建立了SMA复合材料板的本构关系和有限元分析模型，利用修正的Hertzian接触定律确定冲击接触力，应用Newmark直接积分法求解方程；研究结果表明利用SMA的形状记忆功能可有效地改善复合材料板的低速冲击响应性能。

I hope that this success is just the first in a long series.

我希望这只是成功的开始。

Three dimensional stresses on the interface of tire and soil, tire deflection and soil sinkage are measured.

测试轮胎——沙土界面上的三向应力、轮胎变形和沙土沉陷；建立考虑剪切应力对沙土承载特性产生影响的车轮牵引性能预测模型；分析车轮作用下土壤的纵向稳定性。