绘制二维单元等值线的一种简单方法

等值线是二维标量场可视化的一种主要手段,提出一种画二维单元等值线的简单方法。首先把母元等分成4个子块,然后利用子块顶点的自然坐标和单元的形函数,求出实际单元中对应子块的顶点温度,利用子块顶点温度判断是否有等值线通过。对于有等值线通过的子块,求出其包围盒的尺寸,如果小于等于一个像素,则把对应的像素设置为相应的颜色,否则,在母元中把子块继续4等分,直到实际坐标系中子块的包围盒尺寸小于一个像素为止。应用实践表明,这种方法原理简单,精度高,易于编写程序。     

A new method for contour plotting in finite element analysis

A simple method has been developed in order to get a contour plot in an element with given nodal values. The contour lines are obtained by solving a differential equation obtained from the shape function using symbolic computation. This method can be applied to any kind of shape (interpolation) function of a two-dimensional element.     

Generalized transport vortex method

In this paper, a novel vortex method - generalized transport vortex method is introduced. Being a Lagrangian-Eulerian Approach, this method determines the vorticity field through studying the vortex/circulation’s generalized transport in an artificial velocity (generalized velocity) field of Lagrangian frame. The velocity field is then determined through the use of Poisson’s equation in Eulerian frame. The “generalized transport process” refers the movement and area variation of vortex/circulation, which takes consideration of both diffusion and convection processes. Comparing with traditional vortex-in-cell methods and hybrid vortex methods, it does not use splitting algorithm in math, instead, handle diffusion as a part of the convection process. There is no region decomposition issue in the computation, and its expression is rather simple and easy to realize numerically. Being a numerical application, the present method is used to compute flow past one impulsively started circular cylinder. It is capable of calculating the evolution of the fine structure of the flow field with time precisely.     

GIS中Jpg图形的地图绘制

利用ArcGIS软件中的ArcMap模块对Jpg图形进行地理图像配准,对Jpg图形加控制点并进行点的地理位置设置,可直接进行地图设置,也可根据这些控制点的信息与该软件中的数据文件进行叠加,这样就可将该图形作为一个图层,并与数据文件一起,运用GIS中的一些特性对Jpg图片进行处理,如加入经纬度设置,加入站点信息等。通过这种方法,在面对精细的地理数据文件短缺的情况下,可以利用扫描地图或网络截屏等方式,与GIS软件结合,为初学者处理图片提供方便。     

广义q-ROF TODIM方法及应用

基于Pythagorean模糊迭代多准则决策(TODIM)方法和简化的TODIM方法,首先给出简化的q-ROF TODIM方法,并分析该方法产生的悖论;其次,结合广义TODIM方法的思想,提出广义q-ROF TODIM方法;再次,通过一个实例来说明广义q-ROF TODIM方法的可行性和有效性;最后,结合该实例,将所提出的方法与其他q-ROF决策方法进行比较分析,同时分析参数的变化对决策结果的影响,进一步阐明所提出方法的优越性.     

A phase-plane approach to time-optimal control of single-DOF mechanical systems with friction

In this paper, we attempt to solve the time-optimal control problem for single-degree-of-freedom (DOF) mechanical systems with friction, while taking into account not only the velocity-dependent control input constraint but also the state constraint. Direct application of the Pontryagin's maximum principle (PMP) leads to a sixth-order nonlinear two-point boundary-value problem (TPBVP) which is very difficult to solve numerically. In this context, we take a phase-plane analysis without resorting to the PMP. Thereby, the exact time-optimal solution can be obtained simply by solving a set of first-order differential equations with continuous right-hand sides. We also present some simulation results to demonstrate the practical use of the time-optimal solution.     

On the Newton-type method with admissible trajectories for mixed complementatiry problems

A new strategy is suggested for globalization of the convergence of the Newton method, which we proposed earlier, of the active set for the solution of mixed complementarity problems. The most important feature of the new algorithm is the admissibility of the trajectories generated by it.     

A method for the construction of cloud trajectories from series of satellite images

Knowledge of the trajectories of atmospheric structures is useful in meteorology, in particular for the study of the persistence of clouds at mesoscale and for studies of the large-scale atmospheric circulation. For this purpose, a method for the construction of cloud trajectories has been developed and is presented in this article. This method extends traditional techniques used to calculate cloud motion vectors from satellite images, representing the wind at a single instant and the motion over a short time interval (typically ½h), to the measurement of the motion of the same clouds over a long duration, up to 60 h. Trajectories of clouds have been constructed from series of Meteosat images in the thermal IR, the WV (water vapour) and the VISible channels. Similarly, pure WV structures have been tracked in the WV channel. The duration of a trajectory is mainly related to the lifetime of the tracked structure, but also dependent on its spatial scale. A lesser image quality or a larger time interval between images reduces this duration. The use of severe quality tests enables reliable tracking of a limited number of clouds or WV structures, whereas more tolerant tests lead to larger groups of less precise trajectories nevertheless suitable for the study of large-scale motions.     

Generalized perturbation-based stochastic finite element method in elastostatics

Generalised nth order stochastic perturbation technique that can be applied to solve some boundary value or boundary initial problems in computational physics and/or engineering with random coefficients is presented here. This technique is implemented in conjunction with the finite element method (FEM) to model 1D linear elastostatics problem with a single random variable. Main motivation of this work is to improve essentially the accuracy of the stochastic perturbation technique, which in its second order realization was ineffective for large variations of the input random fields. The nth order approach makes it possible to specify the accuracy of the computations a priori for the expected values and variances separately. The symbolic computer program is employed to perform computational studies on convergence of the first two probabilistic moments for simple unidirectional tension of the bar. These numerical studies verify the influence of coefficient of variation of the random input and, in the same time, of the perturbation parameter on the first four probabilistic moments of the final solution vector.     

基于共轭梯度搜索的广义特征对追踪算法

研究广义特征对追踪算法,通过探索基于共轭梯度搜索的标准特征向量追踪算法,将其引入到广义特征对的提取.所提算法具有自适应步长机制,使不同特征搜索方向上的广义瑞利熵达到最优,并适用于提取平稳矩阵束和非平稳矩阵束的广义特征对.数值仿真中将所提算法与多个自适应广义特征向量提取算法进行了比较,实验结果验证了所提算法的有效性.     

基于粒子群优化算法的广义逆控制分配方法

为了获取具有最高分配效率的加权矩阵,将粒子群算法应用于广义逆控制分配法设计,通过计算不同广义逆阵所能有效分配的转矩可达集体积,来选择具有最高分配效率的加权矩阵。以某飞机的控制效率矩阵进行基于广义逆分配法分配器设计,通过粒子群算法对加权矩阵进行寻优,有效地选取了具有最优分配效率的广义逆阵,显著地提高了分配器的分配效率。     

Generalized dynamic programming: A variables freezing method

A variables freezing method is designed for widening the possibilities of numerical application of generalized dynamic programming algorithms. Reducing the size of the memory under certain conditions, the method surmounts the “dimensional curse.” This paper is the continuation of [1–3].     

基于进化策略的广义积分计算方法研究

提出了一种基于进化策略算法的广义积分计算新方法,该方法根据被积函数的变量区间任意选取分割点,作为进化策略的初始的群体,通过进化策略算法来优化这些分割点,最终可得到一些最优的分割点,然后再求和,再根据和函数定义适应度函数,在给定的终止条件下,可获的精度较高的积分值.最后,以广义积分(无穷积分),二重广义积分(瑕积分)为例,仿真结果表明,该算法相比传统的一些方法,具有计算精度高,自适应性强等特点.     

Application of bilinear transformation to root locus plotting

Use of the bilinear transformations = (z + 1)/(z - 1)is suggested as an alternative to the log root locus method for plotting root loci which cannot be accommodated satisfactorily on linear scales. Familiar rules for locus construction are applicable in thezplane.     

Shmoo plotting: the black art of IC testing

Obtaining higher yields from IC fabrication is a never ending goal. Toward that end, shmoo plotting can help bridge the gap between design and test and ultimately show ways to improve a product, process, or manufacturing test program