A step‐by‐step approach to compute a consistent initialization for the MNA

One of the difficulties of the numerical integration methods for differential–algebraic equations (DAEs) is the computation of consistent initial values before starting the integration, i.e. calculating values that satisfy the given algebraic constraints as well as the hidden constraints if higher index problems are considered. This paper presents an approach to calculate consistent initial values for index‐2 DAEs starting up from possibly inconsistent ones for systems arising from modified nodal analysis (MNA) in circuit simulation. This article is based on the results from Estévez Schwarz and Tischendorf, International Journal of Circuit Theory and Applications 2000; 28 : 131–162. Several of the denotations and results that we use were introduced there in more detail. Copyright © 2001 John Wiley & Sons, Ltd.     

Mixed-Technology System-Level Simulation

This paper describes a computationally efficient method to simulate mixed-domain systems under the requirements of a system-level framework. The approach is the combined use of Modified Nodal Analysis (MNA) for the representation of a mixed-technology device and piecewise linear (PWL) techniques to overcome the costly numerical evaluation found in conventional circuit or device simulators. This approach makes the simulation computationally fast, as well as more stable when compared with traditional circuit simulation. The PWL solver, based in the frequency domain, is more robust to inconsistencies in initial conditions and impulse changes when compared to integration based solvers in the time domain. The advantage of this method is that the same solver enables the integration of multi-domain devices (e.g., electrical, optical, and mechanical) in the same simulation framework. The use of this technique for the simulation of multi-domain systems has proven to give better performance in simulation time when compared to traditional circuit simulators with a relatively small decrease in the level of accuracy. Comparisons with traditional solvers, such as SPICE, show two to three orders of magnitude speedup with less than 5% relative error. The ability to adjust the level of accuracy, either by varying the sampling rate or the number of regions of operation in the models, allows for both computationally fast and in-depth analysis in the same CAD framework.     

Buckling strength verification of cantilevered cylindrical shells subjected to transverse load using Eurocode 3

At present, there are only a few studies concerning the application of different types of buckling strength verification according to Eurocode 3 at combined loading. Besides the stress design as classical hand calculation method of checking cylindrical steel shells against buckling failure, the new Eurocode 3 also offers two global numerical analyses at different modelling levels. The linear buckling analysis (LBA) combined with a materially nonlinear but geometrically linear analysis (MNA) is the simpler concept from the perspective of the modelling and calculation effort. The more sophisticated method is a geometrically and materially nonlinear analysis of the imperfect structure (GMNIA). This paper presents the application of both numerical concepts to the cantilevered shell subject to a transverse load at the free edge. The results are compared to those from stress design. There are specific features at both types of numerical analysis: As the determination of the plastic reference resistance and the buckling parameters is the main focus at MNA/LBA, the choice of proper equivalent geometric imperfections demands special diligence at GMNIA. The presented analyses show that the GMNIA concept in connection with consistent equivalent geometric imperfections may lead to a safe and economic design of cylinders subject to combined loading. At the particular load case the MNA/LBA concept currently suffers from the lack of proper regulations concerning the determination of the overall buckling reduction factor.     

基于高阶FDTD(2,4)与MNA混合方法求解导弹系统线缆的瞬态电磁脉冲耦合效应

提出一种高阶时域有限差分与改进节点分析的混合方法,计算弹载系统内线缆的强电磁脉冲耦合效应问题。将线与路通过混合单端口模型进行拆分,有效实现了基于线缆分析的FDTD(2,4)与基于电路方程的MNA法独立快速求解。同时,通过采用分布源等效的方式,将外场引入到电报方程组,使得求解更加简便有效。数值算例表明了该方法的高效率及高精度。     

Structural analysis of electric circuits and consequences for MNA

The development of integrated circuits requires powerful numerical simulation programs. Naturally, there is no method that treats all the different kinds of circuits successfully. The numerical simulation tools provide reliable results only if the circuit model meets the assumptions that guarantee a successful application of the integration software. Owing to the large dimension of many circuits (about 10⁷ circuit elements) it is often difficult to find the circuit configurations that lead to numerical difficulties. In this paper, we analyse electric circuits with respect to their structural properties in order to give circuit designers some help for fixing modelling problems if the numerical simulation fails. We consider one of the most frequently used modelling techniques, the modified nodal analysis (MNA), and discuss the index of the differential algebraic equations (DAEs) obtained by this kind of modelling. Copyright © 2000 John Wiley & Sons, Ltd.     

氯代有机物污染场地的监控自然衰减修复初探

氯代有机物因其高毒性、高富集性、高环境残留的特点及其“致癌、致畸、致突变”效应被美国环保局(EPA)列为优先控制污染物。氯代有机物污染场地的传统物理、化学、生物修复方式修复费用相对较高,对污染场地周边环境影响较大。监控自然衰减(MNA)是一种国际上应用较广的污染场地修复和管理技术,近年来在我国逐渐得到关注,其利用污染物自身的自然衰减作用达到修复目标,从而降低修复成本,规避工程风险。本文重点介绍监控自然衰减技术,并结合氯代有机物自然衰减过程中的生物降解作用、降解途径与机理、主要降解菌和酶等要素对氯代有机物污染场地实施监控自然衰减修复的可行性进行初步探究。     

Symbolic analysis of electric networks with higher order summative cofactors and parameter decision diagrams

The paper introduces the concept of higher order summative cofactors (HOSCs) to the circuit analysis. Although the concept is not new, it is not well known. In the paper, some mathematical background of HOSCs is presented. The further development of the concept of HOSC will yield computer implementation arithmetic of HOSC. A cancellation‐free symbolic analysis technique, which is based on HOSC arithmetic, is presented. This technique allows results to be created directly from a netlist in the form of a binary decision diagram, which is called a parameter decision diagram. Additionally, HOSC arithmetic allows the calculation to be started in many places (sometimes distant) simultaneously. The techniques of rolling up the already analyzed parts of a circuit, which is built into HOSC arithmetic, result in a novel multilevel hierarchical analysis method that is called hierarchical parameter decision diagram (HPDD). Unlike in most hierarchical methods, the results that are obtained based on the subcircuit representation in HPDD always maintain a cancellation‐free form. The HPDD always represents the sum of the product form, which is heavily compressed due to the self‐similarities of the actual circuit. The time that is required for any recalculation of the transfer functions is greatly reduced. Analysis of models that are based on pathological components is also a natural consequence of using HOSC arithmetic.     

基于小波加速的三维导体结构频变电感参数提取

本文首次次多分辨率稀疏化技术引入有耗三维导体结构频变电感参数的提取过程中,通过多分辨率分解对稠密的部分电感矩阵进行稀疏比,有效地加速了对紧耦合部分元等效电路的修正节点分析过程。分别计算了单根导体以及一个矩形螺旋电感的例子。数值结果表明该方法可以显著提高参数提取的效率。     

2,4-二硝基苯甲醚为基熔铸炸药的研究进展

由于TNT为熔融介质的熔铸炸药不能满足钝感弹药(IM)要求,人们一直在寻求化学性能和物理性能相适宜的替代物。2,4-二硝基苯甲醚(DNAN)熔点94~96℃,性能适宜,利用它的低感度可研制出IM应用的一类新型低感熔铸炸药,是TN T有前景的替代物。本文详细地综述了其合成现状、物理性能、热性能和相容性等和以DNAN为基的熔铸炸药配方的研制及相关性能的研究进展。     

端接任意负载传输线的分步CN-FDTD分析方法

为了高效精确地求解端接任意负载的传输线结构电磁瞬态响应,该文提出了一种基于分裂时间步技术的Crank-Nicolson(CN)-FDTD方法,通过理论分析证明了该方法具有无条件稳定特性。与混合单端口等效模型相结合,有效地将传输线系统分解为分布参数子系统与集总电路子系统,采用改进节点分析法(Modified Nodal Analysis,MNA)能够快速求解复杂终端电路网络。与以往瞬态分析方法相比,该方法时间步长的选取不受稳定条件的限制,且通过采用精细子时间步技术极大地削减了因大时间步长引入的色散误差。利用该方法计算双导体传输系统的电磁暂态响应,计算结果表明该算法具有很好的稳定性,在保证数值精度的基础上有效地提高了计算效率。