RECONSTRUCTION OF ONE DIMENSIONAL MULTI-LAYERED MEDIA BY USING A TIME DOMAIN SIGNAL FLOW GRAPH TECHNIQUE

A novel inverse scattering method to reconstruct the permittivity profile of one-dimensional multi-layered media is proposed in this paper.Based on the equivalent network ofthe medium,a concept of time domain signal flow graph and its basic principles are introduced,from which the reflection coefficient of the medium in time domain can be shown to be a series ofDirac δ-functions(pulse responses).In terms of the pulse responses,we will reconstruct both thepermittivity and the thickness of each layer will accurately be reconstructed.Numerical examplesverify the applicability of this method     

WDM网状网中的基于平面构造的业务量疏导算法

将多个低于一个波长带宽的低速业务流复用到一个波长上传输的业务量疏导已经得到越来越多 的研究。WDM/SDH环网中的业务量疏导已得到大量研究,WDM网状网中的业务流疏导问题研究相对较少。该文研究静态环境下波长数目受限的业务量疏导问题,提出了一种基于平面构造的启发式业务量疏导算法。仿真结果表明该算法比已知的算法具有更好的性能。     

基于混合图的总体布线调整

本文提出了一种基于混合图的总体布线调整方法。混合图是对表示布局的有向图进行一系列精确的顶点分解而产生的。用得到的图模型来表示总体布线信息,从而可以在总体布局优化的同时估计布线对芯片面积的影响,并对总体布线进行调整。由于总体布线是自动更新的,所以布局同时随着布线的调整和模块的移动而改进。本文还提出了多种瓶颈的概念和瓶颈间走线随模块旋转而变化的规律。最后给出的实验结果表明,这种算法在减小芯片面积上获得比较好的结果。     

线性预编码OFDM系统的迭代接收机

线性预编码是OFDM系统在频率选择性衰落信道中利用频率分集的有效方法.为了进一步提高性能,本文提出了一种线性预编码OFDM系统的迭代接收机,该迭代接收机采用基于线性最小均方误差准则(LMMSE)的turbo均衡算法及其简化方法,具有很低的计算复杂度.本文同时还提出通过使用长度不小于等效离散时间信道的时延扩展长度的线性预编码器和迭代接收机,可获得完全的频率分集增益.仿真表明本文提出的方法在多径干扰严重的信道条件下的误码率性能接近AWGN下界.     

An efficient analysis of repetitive structures generated by graph products

In this paper, an efficient method is developed for the analysis of regular structures. A structure is called regular if its model can be formed by a graph product. Here, instead of direct solution of the equations corresponding to a regular structure or finding the inverse of the stiffness matrix directly, modal analysis is used, and eigenvectors are employed for calculating the displacements and then internal forces of the structures. For this purpose, first an efficient method is developed for calculating the eigenvectors of the product graphs, and then a method is presented for using these eigenvectors for evaluating the displacements of a structure. Copyright © 2010 John Wiley & Sons, Ltd.     

Combined continuum damage‐embedded discontinuity model for explicit dynamic fracture analyses of quasi‐brittle materials

In this paper, a novel constitutive model combining continuum damage with embedded discontinuity is developed for explicit dynamic analyses of quasi‐brittle failure phenomena. The model is capable of describing the rate‐dependent behavior in dynamics and the three phases in failure of quasi‐brittle materials. The first phase is always linear elastic, followed by the second phase corresponding to fracture‐process zone creation, represented with rate‐dependent continuum damage with isotropic hardening formulated by utilizing consistency approach. The third and final phase, involving nonlinear softening, is formulated by using an embedded displacement discontinuity model with constant displacement jumps both in normal and tangential directions. The proposed model is capable of describing the rate‐dependent ductile to brittle transition typical of cohesive materials (e.g., rocks and ice). The model is implemented in the finite element setting by using the CST elements. The displacement jump vector is solved for implicitly at the local (finite element) level along with a viscoplastic return mapping algorithm, whereas the global equations of motion are solved with explicit time‐stepping scheme. The model performance is illustrated by several numerical simulations, including both material point and structural tests. The final validation example concerns the dynamic Brazilian disc test on rock material under plane stress assumption. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental evaluation of the elastic limit of carbon‐fibre reinforced epoxy composites under a large range of strain rate and temperature conditions

The mechanical behaviour of organic matrix composite materials such as T700GC/M21 carbon fibre reinforced polymer (CFRP) is generally considered by the industry as being orthotropic elastic for the sizing of aeronautical structures under normal isothermal “static” flight loads. During the aircraft lifetime, it may be exposed to severe loading conditions at various temperatures. However, the mechanical behaviour of CFRP is known to exhibit a linear behaviour or a non‐linear behaviour according to the types of loads that are considered creep or extreme conditions. The observed non‐linearity can be commonly attributed to several physical phenomena such as non‐linear viscosity, plasticity, or damage. In the literature, different models can be found that are based on three components: a first elastic reversible behaviour, a second non‐linear behaviour, and a failure criterion. An important issue is to understand and characterize the transition between the elastic reversible behaviour and the non‐linear behaviour. To answer this question, the present paper describes an experimental methodology that permits to evaluate this transition thanks to raw experimental data, and its application to a range of constant but different strain rate and temperature tests performed on the T700GC/M21 CFRP material.     

岩石物性参数管理系统开发

岩石物理学的应用建立在岩石物性参数分析及其规律性研究基础之上，因此，需要大量的岩石物性参数支持应用。目前，国内的岩石物性参数处于分散管理状态，没有统一规范的采集、管理体系，造成资源不能共享，数据存储量小等问题。为此，进行了岩石物性参数管理系统的开发研究。从开发目标、框架设计、开发平台等方面概述了系统的设计思想，管理系统由岩石物性参数数据库、数据库前端用户界面和数据应用接口函数库构成，采用C＋＋语言和Qt图形工具为开发平台；介绍了系统的数据管理模型设计、系统软件的实现以及系统的功能。该系统集数据管理、数据查询、数据分析和数据应用接口函数为一体，采用可视化图形界面、人机交互方式实现人机对话，方便、实用、适应性强。     

基于OSG的军用电子沙盘系统的设计与实现

设计实现基于开源跨平台三维渲染引擎OSG的“军用电子沙盘”系统,对其中场景结构的组织和管理、大地形建模等关键技术进行研究。所开发出的系统具有大规模地形展示、军事单元运动轨迹分析、军事目标多分辨率显示控制等特点,对于战场虚拟仿真系统研发有一定的指导意义。     

Robust event correlation scheme for fault identification in communication networks

The complexity of communication networks and the amount of information transferred in these networks have made the management of such networks increasingly difficult. Since faults are inevitable, quick detection, identification, and recovery are crucial to make the systems more robust and their operation more reliable. This paper proposes a novel event correlation scheme for fault identification in communication networks. This scheme is based on the algebraic operations of sets. The causality graph model is used to describe the cause‐and‐effect relationships between network events. For each disorder, and each manifestation, a unique prime number is assigned. The use of the greatest common devisor (GCD) makes the correlation process simple and fast. A simulation model is developed to verify the effectiveness and efficiency of the proposed scheme. From simulation results, we notice that this scheme not only identifies multiple disorders at one time but also is insensitive to noise. The time complexity of the correlation process is close to a function of n, where n is the number of observed manifestations, with order O(n²); therefore, the on‐line fault identification is easy to achieve. Copyright © 1999 John Wiley & Sons, Ltd.