查询词典 finite difference approximation

A new scheme for approximating the solution of 2D Maxwell's equations-the high order symplectic scheme is proposed to overcome the shortcoming of the conventional finite difference time domain. The scheme is obtained by discretizing the Maxwell's equations in time domain based on symplectic scheme with high order, and then evaluating the equation in spatial domain with second or fourth order finite difference approximation.

为克服标准时域有限差分方法的缺陷，引入一种新的数值计算方法－高阶辛算法求解Maxwell方程，即在时间上用高阶辛差分格式离散，空间分别采用二阶及四阶精度的差分格式离散。

The fluid film bearing-flexible rotor nonlinear system with squeeze film damper is modeled practically using the finite element method and the Hamilton principle.(3) The film forces produced by fluid film bearing and squeeze film damper are determined by finite element method at any moment, and the Jacobian matrix is also determined.(4) A method for analyzing the dynamics of a large system with local nonlinearities is presented. The stability and bifurcation of the equilibrium position and the unbalance responce of a fluid film bearing-flexible rotor system with squeeze film damper are investigated based on the assumption of an incompressible lubricant together with the long bearing approximation for fluid film bearing, short bearing approximation for squeeze film damper and the"π"film cavitation model.

主要研究内容包括下面几个方面：（1）对挤压油膜阻尼器-滑动轴承-转子非线性动力系统中的非线性现象进行了机理方面的研究；（2）应用有限元方法及Hamilton原理对复杂的挤压油膜阻尼器-滑动轴承-转子非线性动力系统进行了建模分析；（3）对滑动轴承及挤压油膜阻尼器中任一时刻的油膜力及相应的Ja-cobi矩阵的确定进行了分析；（4）对一类具有局部非线性的多自由度动力系统，提出了一种可以有效地分析其动力特性的方法；（5）采用实验与理论分析相结合的方法，对挤压油膜阻尼器-滑动轴承-转子非线性动力系统的动力特性进行了分析。

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。

The plane adopts the joint method of both the finite element and the finite difference to divide plane domain by means of irregular triangular net in order to fit topography and coastal line complicated sea zone; Vertical application σcoordinate conversion and the finite difference method.

平面采用有限元法和有限差分法相结合的方法，用不规则三角形网格剖分计算域，以适应地形和岸线复杂的海区；垂向应用σ-坐标变换及有限差分法。

The results showed:among the 7 isolates, five isolates of HY3、GY1－3、ZJ1－1、HP1、FC3 had same colony shape, irregular shape, liquidlike, slimy, opacity with smooth surface;the other two isolates had same shape, irregular shape, dry, opacity with coarse surface. By inoculating eucalyptus with the 7 isolates, the plants were infected apparently, and the young plants of eucalyptus in control experiment with tap water were not infected. By cultivating eucalyptus cuttings with the bacterial suspensions without EPS, the incidence of disease was very distinct,but compared with the former bacteria suspension,the incidence of disease has decreased at different degrees. By screening out two isolates of strong pathogenicity and two isolates of weak pathogenicity from the 7 isolates,making the bacterial suspensions with them to inoculate the young plants of eucalyptus, two treatments of cutlings and ramets with rats were set with 5 repetitions in every treatment, the results of data analysis showed: for the cutlings, the bacterial contents in upper and middle parts、upper and lower had significant difference;for ramets with roots, the bacterial contents in upper, middle parts, lower had significant difference between each other; For both the cutlings and ramets with roof, the bacterial contents in xylem and phloem had significant difference. The interaction between vertical and horizontal parts for the bacterial content had significant difference. For the two isolates of HY3 and 93B which were screened out at last,their activities of the cellulase were: 1.955ug/ and 1.288ug/ respectively, and had significant difference; the activities of pectase were: 1.325 ug/and 1.24ug/ respectively, and had no significant difference. The content of EPS extracted from the two isolates of HY3 and 93B was very different: 7.08x10-8ug/cell and 5.17x10-8ug/cell.

结果显示：7个菌株中，其中5个菌株HY3、GY1－3、ZJ1－1、HP1、FC3的菌落形态相同：不规则形状、流体、粘性、不透明、表面光滑；另外2个菌株93B、GN1菌落形态相同：不规则形状、干燥、不透明、表面粗糙；用7个菌株接种剪根桉树苗，发病情况非常明显，而自来水对照实验中桉树苗却不发病；无EPS菌悬液培养桉树剪根苗，发病率也很明显，但是相比原菌液，则发病率有不同程度的下降；从7个菌株中间筛选出来2个强致病性菌株和2个弱致病性菌株，用它们配制菌悬液培养桉树苗，设置剪根和不剪根两个处理，每个处理设置五个重复，数据分析结果显示：对于剪根苗，上部和中部、上部和下部的含菌量有显著的差异，中部和下部含菌量差异不显著；带根苗，上部、中部、下部含菌量彼此之间差异显著；不管是剪根苗还是带根苗，木质部和韧皮部含菌量之间的差异都非常显著；上中下与木韧交互作用中，含菌量差异非常显著；最后筛选出来的强弱2个菌株HY3和93B，它们的纤维素酶活性分别为：1.955ug/和1.288ug/，具有显著的差别；果胶酶的活性分别为：1.325 ug/和1.24ug/，没有显著的差别，而且HY3和93B两个菌株细胞分泌的胞外多糖的含量差异很显著，分别为：7.08×10-8ug/cell和5.17×10-8ug/cell。

The difference schema of the initial boundary value problem was converted to the step-by-step form,which was similar to the difference schema of the initial value problem.It is concluded that the difference schema satisfying the Von Neumann condition is a stable schema,and that,under the consistency condition,such stable schema is convergent.Moreover,with error estimate expression for the difference approximation to the classical solution,the linearity condition is unnecessary.

引入反投影算子将发展方程初边值问题的差分格式转化为与初值问题差分格式类似的逐步推进的形式，从而得出：满足Von Neumann条件的差分格式是稳定的格式；在相容条件下，差分格式若稳定(或满足VonNeumann条件)则格式收敛，且对古典解的差分逼近有误差估计式，不再需要线性的条件。

A one-sided difference approximation is used for convection terms and a second-order central difference approximation for diffusion term.

二阶一边差分逼近用于对流项的离散，二阶中心差分逼近用于扩散项的离散。

For the given endpoint interpolation conditions, a new approximation method of multidegree reduction is presented. Using Chebyshev polynomial approximation theory, the nearly best uniform approximation under the interpolation conditions of endpoints can be obtained.

对于给定的首末端点的各阶插值条件，给出了一种新的一次降多阶逼近算法，应用Chebyshev多项式逼近理论达到了满足端点插值条件下的近似最佳一致逼近。

Applying the Euler method to the equation and particularly using the interpolation technique on variable delay, the Euler approximation is obtained. The discrete Euler approximation is extended to the continuous Euler approximation. It is proved that the Euler numerical solutions will converge strongly to the true solution under the local Lipschitz condition.

对方程应用欧拉方法，特别地对变延迟部分运用插值技巧进行数值离散后，将离散的欧拉格式延拓为连续的欧拉格式，从而得到欧拉格式在局部Lipschitz条件下强收敛到解析解。

The main results are as follows: the relations between local fractional integrated semigroups and the corresponding Cauchy problem, global fractional integrated semigroups and regularized semigroups are given; introduction of the notion of regularized resolvent families, and the generation theorem and analyticity criterions for regularized resolvent families are obtained; the spectral inclusions between fractional resolvent family and its generator, and the approximation for fractional resolvent families in the cases of generators approximation and fractional orders approximation; elliptic operators with variable coefficients generating fractional resolvent family on L^2 by using numerical range techniques; and the L^p theory for elliptic operators with real coefficients highest order are obtained by Sobolev''s inequalities and the a priori estimates for elliptic operators; and a kind of coercive differential operators generates fractional regularized resolvent family by applying the Fourier multiplier method, functional calculus and some basic properties of Mittag-Leffler functions.

主要结论是：给出了局部分数次积分半群和相应的Cauchy问题的关系以及分数次积分半群和正则半群的关系；引入了正则预解族的概念，并给出了其生成定理和解析生成法则；给出了分数次预解族与其生成元的谱包含关系，并研究了在生成元逼近和分数阶逼近两种情况下相应的预解族的逼近问题；利用数值域方法证明了具变系数的椭圆算子在L^2上生成分数次预解族；利用Sobolev不等式和椭圆算子的先验估计证明了具变系数的椭圆算子在其最高项系数为实数时在L^p上生成分数次预解族；运用Fourier乘子理论、泛函演算和Mittag-Leffler函数证明了一类强制微分算子可以生成分数次正则预解族，并给出了该预解族的范数估计。

It's rather showy.I'd like something plainer.

赶花了，我想要素净些的。

The Kremlins Spassky Tower and passers-by are reflected in the wet cobblestones of Moscows Red Square on Feb.

克里姆林宫的斯巴斯克塔和旅客的身影倒映在潮湿的鹅卵石墙上。