查询词典 calculus of finite differences

In this paper, the maximum likelihood algorithm with process and measurement noise for nonlinear continuous-discrete system given by Jategaonkar and Plaetschke is improved in two aspects: 1 to avoid the disadvantages of sensitivities computation by common finite-difference method, in which the perturbation sizes should be selected optionally, an improved finite-difference method with best perturbations, is presented. 2 to improve the numerical stability of Jategaonkar's algorithm, maximum likelihood algorithm with fast triangular square-root decomposition filter is given.

摘要对Jategaonkar等人给出的同时计及过程及观测噪声的非线性连续-离散系统的极大似然算法从两个方面进行了改进：1给出了计算灵敏度的最佳摄动有限差分算法，避免了普通有限差分法计算灵敏度矩阵时需人为选择参数摄动量大小而带来的缺点；2给出了具有快速三角化平方根滤波的极大似然算法，提高了原算法的数值稳定性。

The finite element model of DN200 type metal bellow was set up,based on the finite element theory.

基于有限元理论建立了DN200型金属波纹管的仿真模型。

The "compressed sparse row data format" is adopted to save storage and the "mode multiplication" is used to improve the computation efficiency, so that the finite integration equation is obtained with low storage and high efficiency. To solve the finite integration equation, which is a large-scale sparse algebraic eigenvalue problem under the condition specified, the Krylov subspace iteration method is introduced and the shift-invert Arnoldi method is proposed to exclude the unphysical static electro-magnetic solution and get the needed eigensolution around the specified eigenvalue.

采用"行索引稀疏格式"压缩存贮技术节约内存，采用大型稀疏矩阵的模式乘法，提高矩阵计算效率，高效获得了离散电场分量满足的有限积分方程；针对有限积分特征方程的求解，论文介绍了大型稀疏矩阵Krylov子空间迭代方法，并提出了位移求逆Arnoldi算法，以排除非物理的静态电磁场解，获得指定频率附近的特征值。

It adopts Reynolds time-average N-S equation and k-s turbulence model to calculate the inner 3-D viscid turbulence flow of hydraulic turbine. In the unstructured grid, the governing equations are discredited with Finite Volume Method based on Finite Element Method. And the pressure correction method is proposed in numerical calculations.

然后采用基于雷诺时均N-S方程与标准k-ε湍流模型来计算水轮机三维粘性湍流场，在非结构化网格中，采用基于有限元的有限体积法对方程进行离散，用压力校正法进行数值求解。

In chapter 2, we investigate the structure of finite groups under the condition that all special subgroups are conjugate-permutable subgroups and obtain some sufficient conditions for solvability, Abelian property of finite groups.

第二章主要是利用一些特殊子群的共轭置换性得到了有限群成为可解群、交换群的一些充分条件，改进和推广了文[1]和[4]中的部分结果，有些结果是新的。

In order to investigate buckling mode, buckling load and failure mode of structure, shear experiments were conducted for stiffened thin-walled composite plate. Finite element method was also used to analyze the buckling behavior of that composite structure. Analysis results reveal buckling mode and buckling loading of finite element analysis are accordable with experimental results.

通过对复合材料薄壁加筋板结构进行剪切载荷下的屈曲试验研究，得到结构的屈曲模态、屈曲失稳载荷以及破坏形式，并通过有限元方法对结构的屈曲进行数值分析，分析得到的复合材料薄壁加筋板结构的屈曲模态和试验结果一致，屈曲载荷与试验结果吻合较好。

So the braking prescription should be performed strictly, furthermore, the sudden and urgent braking should be avoided to the best of our abilities.In the end, the thermal fatigue lives were evaluated by the finite element method. It was proved that the thermal fatigue life of improved steel (ZG35CrMoRE) was higher than that of the formers. It was also found that the quantitative evaluations of the thermal fatigue lives of brake disc were acquirable, by putting the equivalent plastic strain, which was analyzed with finite element methods, and the material mechanical property parameters into the formula of Manson-Coffon to calculate its lives. Therefore, theoretical method can be provided to develop new brake disc steel and to prolong its lives.

为了进一步提高刹车鼓的使用寿命，对新试制的钢种进行了热疲劳寿命评估，验证了改进后的钢种在相同的使用工况下具有更高的热疲劳寿命；评估结果还表明利用有限元数值分析计算相应的等效塑性应变，结合材料力学性能参数，代入Manson-Coffin热疲劳寿命公式可以对刹车鼓的热疲劳寿命做出定量评估，从而为刹车鼓用钢的研制和刹车鼓寿命的提高提供了理论依据。

In theory, firstly, the numerical simulation methods, such as the boundary element method, the finite difference method and the finite element method, were utilized to calculate the distribution of electric field intensity and potential of the electron-gun system, the focusing system and the whole equipment, respectively. Then, the trajectories of the electron-beam were traced by using of the Runge-Kutta method and the Monte-Carlo method associatively. The point spread function was also calculated.

在理论分析中，先后采用边界元方法、差分方法、有限元方法等科学数值计算方法，编制程序，对X射线源的电子枪发射系统、聚焦系统以及发射系统与聚焦系统的组合系统等的电场分布进行了严格的计算，在准确求得各系统电场内各个剖分点的电场场强、偏导数等参量的基础上，采用蒙特-卡罗模拟方法和不等距龙格-库塔方法相结合，追踪由LaB_6单晶阴极表面发射出的大量电子束在电场内的运动轨迹，求出点扩展函数，并根据点扩展函数的优劣，反复调节、大量计算对比，挑选出X射线源最佳的电极结构及其组合。

In order to analyze vertical bearing behavior of large diameter belled pile in soft substratum, three-dimensional non-linear finite-difference numeric models are established with finite-difference program, calculated and measured results are contrasted, and it proves that the calculation models and the chosen parameters are rational.

为分析存在软弱下卧层的大直径扩底桩的竖向承载性状，本文利用有限差分程序建立三维非线性有限差分数值模型，将计算结果与实测数据进行对比，验证了计算模型与参数选取的合理性。

The technology of bending by bendable roller was introduced briefly. A finite element model of the process of BBBR was built by the general finite element program.

简单介绍了可弯曲辊卷板成形技术，利用通用有限元程序建立了可弯曲辊卷板成形过程的有限元模型。

These are places without aristocratic baggage; egalitarian places open to talent, self-improving, engaged in learning and innovation through networks that were at once competitive and cooperative.

这些地方没有贵族遗风作祟，而且对于那些有天分的人是开放的平等之地，这些人善于通过那些曾经很具有竞争力与合作精神的关系网进行自我提高以及学习创新。

Christine: You don't want to see me?

你不想见我？