Upwinding of the source term at interfaces for Euler equations with high friction

We consider Euler equations with a friction term that describe an isentropic gas flow in a porous domain. More precisely, we consider the transition between low and high friction regions. In the high friction region the system is reduced to a parabolic equation, the porous media equation. In this paper we present a hyperbolic approach based on a finite volume technique to compute numerical solutions for the system in both regimes. The Upwind Source at Interfaces (USI) scheme that we propose satisfies the following properties. Firstly it preserves the nonnegativity of gas density. Secondly, and this is the motivation, the scheme is asymptotically consistent with the limit model (porous media equation) when the friction coefficient goes to infinity. We show analytically and through numerical results that the above properties are satisfied. We shall also compare results given with the use of USI, hyperbolic–parabolic coupling and classical centered sources schemes.     

电涡流方法在输电线损伤检测中的应用

结合高压输电线的特点 ,在论述了电涡流检测方法的基本原理之后 ,进一步论述了差动式检测线圈的电涡流检测原理与方法。通过试验确定了高压输电导线电涡流检测的最佳激励频率。最后对试验波形进行了分析 ,表明此种方法用于检测高压输电线的外部铝导线是可行的。     

Capacitance of microstrip lines on anisotropic substrate using the method of lines and finite elements

A finite elements-based Method of Lines is used to calculate static capacitances for microstrip line structures with layered substrates of arbitrary permittivity tensor. The problem is solved by discretizing the associated static equations in one coordinate variable using finite elements, and obtaining an analytical solution with respect to the remaining variable. Proper boundary and transition conditions are imposed. To validate the solution, comparison is made with results derived from other methods. A significant increase in numerical efficiency afforded by the presented method, relative to the conventional, fully discrete, finite element solution, is demonstrated quantitatively.     

Invariant imbedding and the method of lines for parallel computers

Recursion relations have been used to allow the solution of the invariant imbedding equations with singularities. We demonstrate that these same relations can be used in an efficient implementation of invariant imbedding for massively parallel computers. The parallel implementation of invariant imbedding can be used in conjuction with the method of lines to solve partial differential equations. We consider the problem of assigning lines to processors to minimize communication delays and the effect of asynchronous relaxation. Each algorithm is implemented and run on the NCUBE/ten hypercube, and timing data, speedup and normalized speedup are given. Operation counts are also given for each algorithm.     

An adaptive method of lines solution of the Korteweg-de Vries equation

Following a method of lines formulation, the Korteweg-de Vries equation is solved using a static spatial remeshing algorithm based on the equidistribution principle, which allows the number of nodes to be significantly reduced as compared to a fixed-grid solution. Several finite difference schemes, including direct and stagewise procedures, are compared and the results of a large number of computational experiments are presented, which demonstrate that the selection of a spatial approximation scheme for the third-order derivative term is the primary determinant of solution accuracy.     

架空线路的防护及故障诊断方法

架空电力线路及其设备是电力系统的重要组成部分,是发电、输电、变配电、用电的中心环节,它的作用是分配电能。架空线路由于暴露在野外,外部的恶劣环境,可能会发生许多事故以及故障,影响电网的安全运行。分析了架空线路的防护及故障诊断方法,包括架空线路的防护,架空线路设备故障诊断等。     

Determination of the strengths of doubled lines by the method of equivalent widths

A technique for the measurement of line strengths of doubled lines using the equivalent width method is developed. The line profile is represented by the Voigt function and the prototype doubling is the lambda doubling in NO. The lambda doubling is incorporated into the algorithm for the theoretical calculations of the equivalent widths. The dependence of the equivalent width on the half width at half intensity, the line strength and splitting is demonstrated. Comparisons of the Voigt, Lorentz and Doppler function properties are included.     

Nonlinear transient analysis of coupled RLGC lines by the method of characteristics

A computationally efficient numerical technique for the evaluation of the time domain response of coupled lossy uniform and nonuniform transmission lines terminated in general nonlinear elements is presented. The technique is based on the method of characteristics where the original system of coupled transmission line equations is transformed into a system of ordinary differential equations which hold along a family of characteristic curves. An algorithm to solve these equations is presented. The procedure is applicable to both uniform and nonuniform coupled systems and examples of two and three line structures terminated in linear and nonlinear elements are included to demonstrate the versatility and the usefulness of the algorithm.     

A new method of analysis for discrete straight lines

The problem of finding the set of all continuous straight lines which lead to the same digitization is quite well known and has been studied in [1, 2, 3]. In this paper, we propose a new method of analysis which is simple and straightforward but is shown to be as powerful as the other techniques. Moreover, our scheme, being algebraic in nature, can be generalized to more complex shapes and figures and thus has a wider applicability.     

A MATLAB method of lines template for transport equations

Many environmental problems involve diffusion and convection processes, which can be described by partial differential equations (PDEs). This paper will describe the development of a MATLAB template that generates a numerical solution to PDEs using the method of lines. The template will be applied to various unsaturated flow problems within soil physics to demonstrate the versatility of the method. In particular, the template will generate solutions for three cases (1) one-dimensional Richards’ equation for vertical infiltration; (2) coupled one-dimensional Richards’ equation and solute transport equation for horizontal water and contaminant flow; and (3) two-dimensional Richard’s equation for unsaturated flow over a complex geometry. Where possible, the results from the template will be compared against analytical solutions to determine the accuracy of the numerical solution. In addition, the paper will provide a discussion on possible extensions to the template and future directions.     

基于自相似的风格化线条纹理合成方法

针对动画风格化线条渲染中需要权衡线条纹理滑动和线条纹理缩放两种不同的走样现象,提出了一种新的线条纹理(自相似样图),从而避免了这两种走样现象。自相似样图的纹理可以连续地无限放大,并且可以从单一样本自动生成。自相似样图可替代传统笔画纹理用于2D插图和动画。此外,自相似样图应用新的简单的方法,可以连贯地渲染3D路径,适用于交互式应用程序。     

Extending the reflexion method for consolidating software variants into product lines

Software variants emerge from ad-hoc copying in-the-large with adaptations to a specific context. As the number of variants increases, maintaining such software variants becomes more and more difficult and expensive. In contrast to such ad-hoc reuse, software product lines offer organized ways of reuse, taking advantage of similarities of different products. To re-gain control, software variants may be consolidated as organized software product lines. In this paper, we describe a method and supporting tools to compare software variants at the architectural level extending the reflexion method to software variants. Murphy’s reflexion method allows one to reconstruct the module view, a static architectural view describing the static components, their interfaces and dependencies and their grouping as layers and subsystems. The method consists of the specification of the module view and the mapping of implementation components onto the module view. An automatic analysis determines differences between the module view and its implementation. We extend the reflexion method from single systems to software variants. Because software variants share a very large amount of code, we can expect components of one variant to re-occur in the other variant either identically or at least similarly. We use similarity metrics to determine this type of correspondence among implementation components between two variants. Because the similarity metrics are expensive to compute, we use clone detection techniques to reduce the number of candidate pairs of implementation components for which the similarity is computed. The correspondence is then used to transfer as much as possible of the mapping for the analyzed variants to the next variant to be analyzed. Furthermore, we describe how to unify the individual product architectures into a software product line architecture.     

Analysis of coupled or single nonuniform transmission lines using the method of moments

A method is proposed for the analysis of arbitrarily loaded lossy and dispersive single or coupled nonuniform transmission lines (NTLs). In this method, the integral equations of the NTLs, converted from their differential equations, are solved using the method of moments. It is assumed that per‐unit‐length matrices are known at all or even some points along the length of the coupled NTLs. The validity of the method is verified using a comprehensive example. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Pseudo-characteristic method of lines solution of first-order hyperbolic equation systems

First-order hyperbolic partial differential equations are difficult to solve numerically because of their ability to transmit steep waves. It is well known that the method of characteristics is the natural method for such equations, as it precisely follows wave interactions. However, a characteristic solution is expensive, as it requires repeated solution of non-linear algebraic equations. This gives considerable motivation to the development of fixed grid numerical schemes.Unfortunately any attempt to use a finite fixed grid generates spurious numerical oscillation and dispersion, which must be minimized by artificial damping or directional differentiation. For sets of hyperbolic equations, the appropriate assignment of damping or direction is difficult to determine, as variables are coupled in non-linear form. However, a clear definition of directionality is given in the characteristic form of the equations, and may be used to develop a pseudo characteristic fixed grid statement of the equations, which is readily solved by the method of lines, is simple to implement, and produces stable accurate solutions.Applications are illustrated for the solution of equations describing shallow water flow, and compressible gaseous flow.     

Real-time information driven intelligent navigation method of assembly station in unpaced lines

This paper considers the assembly station as a breakthrough to improve the real-time information driven control and optimization of assembly process in unpaced asynchronous line. By adopting automatic identification technologies, the overall architecture of the real-time intelligent navigation of assembly station (INoAS) is put forward. Under this architecture, three core services, namely the real-time assembly operating guidance service (OGS), collaborative production service (CPS) among assembly stations and real-time queuing service (RQS) of the jobs at each station, are designed to provide optimal and dynamical navigation for assembly activities for each station. Then, the disturbances and exceptions could be timely captured by installing the INoAS at each station, and the operating guidance, collaborative production information sharing and real-time queuing could be easily achieved. The presented architecture and services of INoAS will facilitate the real-time information driven process monitor and control between the line and stations.     

Convergence of method of lines approximations to partial differential equations

Many existing numerical schemes for evolutionary problems in partial differential equations (PDEs) can be viewed as method of lines (MOL) schemes. This paper treats the convergence of one-step MOL schemes. Our main purpose is to set up a general framework for a convergence analysis applicable to nonlinear problems. The stability materials for this framework are taken from the field of nonlinear stiff ODEs. In this connection, important concepts are the logarithmic matrix norm and C-stability. A nonlinear parabolic equation and the cubic Schrödinger equation are used for illustrating the ideas.     

A novel method for crosstalk reduction in coupled pair microstrip lines

This article demonstrates novel ideas for mitigation of far‐end as well as near‐end crosstalk in coupled pair microstrip lines (CPMLs) by means of defected microstrip structure (DMS). Simple equations and models for analysis and design of a DMS are presented and extracted. Different configurations of DMS‐CPMLs are introduced, and their performances in crosstalk reduction are compared. Finally, the best configuration for far‐end crosstalk reduction is fabricated and tested. A maximum of 35 dB reduction in far‐end and 38 dB reduction in near‐end crosstalk are achieved. The signal integrity performance of the structure is also verified by eye‐diagrams. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.