All calculations are in the hypothesis of " ideal slot " , that is the slots are so narrow that longitudinal field along the slots can be ignored and all fields are independent about the z - coordinate 在当中忽略缝隙口面场随缝隙倾角变化而在z方向上产生的变化? ?即认为场量与z无关。在此前提下可以将三维问题简化为二维问题，用边界元素法直接求解。
Especially , the unknowns of the algebraic equations about 3 - dimensional problems increase as geometrical progression compared with 2 - dimensiond problems . so development of computers can not meet their needs 特别地，三维问题最终产生的代数方程组未知数的个数与二维问题相比，将按几何级数急剧增加，即使计算机技术飞速发展，也难以满足它们的需求。
It overcomes the shortcomings of the traditional algorithms , which deal with the cost and delay separately and need a lot of retrospect and more multimedia services need the network guarantee the real - time requirements , so the network resources can be utilized efficiently 接着提出了一种实时的代价最小动态多播路由算法，利用选择的变换函数使二维问题变为一维问题，这样就避免了传统的将代价和时延分别考虑，大量回溯的弊端。
In this framework , an approach is proposed to transform each of the original 3d geometrical planes of the surface into its canonical reference plane structure . this structure helps to simplify a 3d computational problem into a more manageable 2d problem 为此，本文的系统提出一种加速方法，将模型表面上各种3d几何平面转化到“规范化参考平面” canonical reference plane structure , cprs上，从而将三维计算问题转化为易于处理的二维问题，以加快计算速度。
( 3 ) fem basic theory of foundation pit excavation stimulation is expounded , numerical model and method of construction simulation are determinated , which includes simplification of two - dimension problem and constitutive model of soil mass i . e . constitutive model of duncan - chang hyperbola model , numerical ways of initial situ stress , stimulation of equal nodal load of foundation pit excavation , nonlinear solutions of basic equations , fem disposing of inner supporting and pre - axial force etc . further fem code of stimulation of foundation pit excavation is compiled 阐述了基坑开挖模拟的有限元基本理论，确定计算模型及施工模拟方法。包括二维问题的简化、土体的本构模型，即邓肯-张双曲线本构模型、初始地应力场的计算方法、基坑开挖等效结点荷载模拟、基本方程的非线性解法、内支撑及预加轴力的有限元处理等，并编制了模拟基坑开挖的有限元程序。
Then a kind of military materials are chosed as the research object . combing the pratical demands , the expressing and modeling of the problem are presented also . under the restriction of the cost function and the restricting conditions , a method of converting three dimension problems into two dimension problems is introduced 随后选用一类军用物资器材为具体研究对象,结合问题实际要求,进行了问题的具体描述和建模,并依据问题的目标函数及实际约束条件,提出了将三维问题转化为二维问题的求解思路。
The director in nlc cell may be expressed by one angle parameter 9 or , and it is called one dimension problem ; the director expressed by two angle parameters 6 and , called two dimension problem ; the paper consists of two absolute parts : l . the first order freedricksz transition at saturation point for the weak anchoring nlc cell the first order freedricksz transition ( the first order transition ) at threshold point has been studied by a lot of theoretical works 液晶盒内指向矢可用一个角量或表示称为一维问题，需要用两个角参量和表示称为二维问题。本文由两个独立的工作构成： 1弱锚定向列液晶盒在饱和点的一级freedericksz转变现有的理论工作都讨论在阈值点的一级freedericksz转变(一级转变) 。
Furthermore , the fruits damage will be studied from a new point of view - ? he force applied on the cells . according the structural characteristic of the plant call , a hexagon mechanical model for plant cell was proposed . then , using the mechanical theories and finite element method , the deformation , wall stress and turgor for plant cells , under compression and shear , was analyzed 本文根据植物细胞结构的力学特点和力学原理、利用有限元方法，以二维问题为研究对象，建立了能够描述植物细胞单体受力变形、细胞壁应力和内压变化和便于建立宏观植物组织力学模型的单细胞力学模型。
First , the method of aperture integration - surface integration , which is based on physical optics theory , is used to study the radiating property of the 3 - d radome - enclosed antennas . secondly , the moment method is employed to analyze the electromagnetic radiation from radome - enclosed antennas with axi - symmetric revolving radome 然后应用矩量法针对具有回转体结构天线罩的带罩天线辐射进行分析，分析过程中利用回转体特点，采用适当的基函数将三维问题转化成二维问题解决，以降低计算量提高计算效率。
In this paper the flow field of falling film along the inner of vertical tube is simulated and it ' s the necessary base of the further research that includes characteristics of heat and mass transfer in the absorber under the fluctuant state . in this paper the ocean fisher ' s movement in the ocean is studied and the physical and the mathematical models of fisher are founded , then the expressions of the force caused by the movement are obtained . the expressions are combined with partial different equations of falling film under the static state , thus the mathematical model of the falling film under fluctuant state can be gained 本文首先研究了船舶在海洋中的运动，建立了船舶摇摆运动的简化物理模型和数学模型，得到了运动附加力的表达式；并在此基础上将吸收管的运动附加力表达式代入静止状态下液膜流动的数学模型中，即得到了摇摆状态下液膜流动的数学模型；然后对液膜流动的数学模型进行了简化，在假定了速度分布的条件下，得出了液膜流动的积分方程，经过以上简化就将求解三维问题转化成为求解二维问题；将积分方程离散化后用数值计算的方法模拟了整个流场。
