Numerical treatment of a quasilinear initial value problem with boundary layer

The paper deals with the singularly perturbed quasilinear initial value problem exhibiting initial layer. First the nature of solution of differential problem before presenting method for its numerical solution is discussed. The numerical solution of the problem is performed with the use of a finite-fitted difference scheme on an appropriate piecewise uniform mesh (Shishkin-type mesh). An error analysis shows that the method is first-order convergent except for a logarithmic factor, in the discrete maximum norm, independently of the perturbation parameter. Finally, numerical results supporting the theory are presented.     

四芯建筑低压配电电缆的谐波阻抗研究

电缆的阻抗在供电系统以及谐波评估中是一重要参数,通常认为在已确定电缆型号的情况下,其电阻值不变,谐波电抗的大小是基频电抗的谐波倍数,即电感值不变。通过实验的方法对横截面为95、300 mm2的四芯铠装电力电缆谐波阻抗进行测试,得到谐波次数从基波到49次的谐波阻抗。实验结果表明,电缆电感具有频率依赖性,它随着谐波次数的增加而下降。最后应用实测数据和曲线拟合技术得到电缆电阻和电感的计算公式。     

Variances of Plane Parameters Fitted to Range Data

Formulas for variances of plane parameters fitted with Nonlinear Least Squares to point clouds acquired by 3D imaging systems (e.g., LADAR) are derived. Two different error objective functions used in minimization are discussed: the orthogonal and the directional functions. Comparisons of corresponding formulas suggest the two functions can yield different results when applied to the same dataset.     

“booster method” for singularly perturbed robin problems-II

Singularly perturbed Robin problems are considered in this paper. In order to get an improved numerical solution to these problems, a computational method (“Booster Method”) is suggested. In this method, an asymptotic approximation is incorporated into a finite difference scheme to improve the numerical solution. Error estimates are proposed when implemented in known difference schemes. Numerical examples are presented to illustrate the present method.     

Effect of cross derivatives in discretization schemes in structured non-orthogonal meshes for compositional reservoir simulation

Corner-point meshes have been implemented in several commercial reservoir simulators due to their flexibility to deal with several important features of the hydrocarbon bearing-reservoirs, such as irregular boundaries, geologic fractures, and faults. Although this type of mesh presents an important step in discretization of the domains for reservoirs, some parts of the approximate equation in discretized formulations are neglected in most commercial simulators. The neglected terms are related to the cross derivatives and, in general, are neglected to produce the same Jacobian stencil as when Cartesian grids are employed. This work presents an investigation of the effect of cross derivatives in discretization schemes using structured non-orthogonal boundary-fitted meshes in conjunction with a compositional reservoir simulator. The main goal is to investigate the difference between the numerical results with and without the cross derivatives that arise when the Cartesian equations are written for a transformed plane. We used an in-house compositional reservoir simulator to carry out this study. The component mass balance equations for a compositional, multiphase, multi-component fluid flow are solved using a fully implicit reservoir simulator in conjunction with the finite volume method. The results of several reservoir simulation case studies that were performed to carry out this study are presented in this paper.     

平衡贴体两片袖合理配制的探讨

本文介绍了由于过度依赖公式,使得袖型配制达不到预期的合理效果。通过深入研究,得知衣身袖窿条件状况是影响袖型的关键。通过改变以往传统应付式配袖为主动出击式配袖,可以达到贴体两片袖的合理配制。     

基于合体两片袖的内旋造型结构设计

为探究袖身内旋造型的形成机制及影响因素,增强合体两片袖的活动性和机能性,从立裁角度提出分割线借量法、袖中线偏移法与袖中线旋转法3种结构设计方法。借助三维虚拟试衣技术进行单变量试验设计,确定每种方法中各变量的取值范围;通过正交试验设计,完成16款袖子的结构设计、虚拟试衣及实样制作;最后建立评价体系,进行主客观评价与分析。结果表明:各变量对内旋夹角影响程度的大小依次为袖中线旋转量、分割线借量、袖中线偏移量;结合动静态指标、主客观评价数据,得到的美观与舒适俱佳的袖子变量组合为分割线借量 0.5 cm, 袖中线偏移量2 cm,袖中线旋转量1 cm。     

输电线路上风速的分布式监测

风、雨等外界因素对输电线路的有一定危害,风对输电线路上的影响最为频繁且持续时间较长,输电线路上风速的分布式监测可观测到整条线路的风速分布,对输电线路的防振及防振定位有一定的指导作用,因此输电线路上的风速的分布式监测极为重要。本文以两条实验线路为例,根据卡门漩涡理论,由于风速的影响在线路圆柱体周围形成上下交替周期性的交变力的作用,这个交变力是一个瞬时稳定的力,使得输电线形成一个瞬时稳定的振动频率,利用卡门漩涡理论公式中振动频率与风速的关系计算相应时刻和相应位置的风速,并与微气象风速进行对比分析,结果显示这一稳定的振动频率能够很好地反映风速在输电线路上风速随时间的变化,预测风速的精度较高,为输电线路上振动研究提供理论依据,有一定的实用价值。     

两种催化油浆的热重反应动力学研究

采用SDT 2960Simultaneous DSC-TGA差热-热重分析仪,考察了辽河石化炼油厂两种油浆在N2保护下的热重反应性能,在Coats-Redfern积分法的基础上,对油浆的热重反应数据进行了线性拟合,取得了令人满意的结果。两种油浆在低温区均表现为一级动力学行为,表观活化能分别为29.685kJ/mol和32.35kJ/mol;在高温区间均表现为二级动力学行为,表观活化能分别为71.84kJ/mol和32.095kJ/mol。低温区间以裂化反应为主,高温区间以缩合反应为主。     

时域有限面积法解手征介质涂层导体柱的电磁散射

本文将时域有限面积法推广应用于研究任意截面复合手征介质涂层导体柱的电磁散射问题,建立了数值求解复合手征介质问题的时域基本方程.本文使用正交贴体计算网格,并选用适合正交曲线坐标系的二阶精度吸收边界条件,提高了计算精度.对典型的复合手征介质涂层导体柱的RCS计算表明,数值计算结果与级数解相吻合.