虫孔寻径无死锁充要条件分析

采用虫孔切换技术容易造成互连网络寻径的死锁。本文通过三个虫孔寻径无死锁的具体实例 ,深入阐述、分析了虫孔寻径无死锁充要条件的研究进展。应用这些充要条件能较好地解决采用虫孔寻径带来的死锁问题     

基于虫孔交换的树型多播无死锁充要条件分析

多播作为其他聚合通信的基础操作,对并行系统的性能有着重要的影响。在无死锁、无拥塞的情况下,基于虫孔交换的树型多播能够取得较高的性能和信道利用率。本文在对树型多播过程中消息依赖关系分析的基础上,给出了基于虫孔交换的树型多播无死锁的充要条件。     

Efficient Deadlock-Free Wormhole Routing and Virtual-Channel Reduction in Shuffle-Based Networks

Many aspects of shuffle-based networks have recently been studied by numerous researchers. However, no attention has been paid to deadlock-free wormhole routing algorithms. In this paper, for a set of shuffle-based networks, we introduce a graph-partitioning technique that enables a deadlock-free routing algorithm with fewer virtual channels than the known algorithms. This is achieved for the de Bruijn digraphs which are shown to require a maximum ofm− ⌊(m− 1)/r⌋ virtual channels per physical channel, wheremis the diameter andris the radix. Algorithms for the generalized de Bruijn graph, the de Bruijn Cube (dBCube) graph and the Shuffle–Exchange network are introduced, and virtual channel requirements are determined. The dBCube graph of size (r,N_b,n) requires a maximum ofm− ⌊(m− 1)/r⌋ virtual channels for the outcluster channels, and a maximum ofm+ 1 − ⌊m/r⌋ virtual channels for the incluster channels in most cases, wherem= ⌊log_rN_b⌋,ris the radix of a generalized de Bruijn graph of sizeN_b, andnrepresents the number of dimensions in a binary hypercube. We also show that a maximum ofm− ⌊(m− 1)/2⌋ virtual channels are required in shuffle-exchange networks with 2^mnodes.     

A Necessary and Sufficient Condition for Consensus Over Random Networks

We consider the consensus problem for stochastic discrete-time linear dynamical systems. The underlying graph of such systems at a given time instance is derived from a random graph process, independent of other time instances. For such a framework, we present a necessary and sufficient condition for almost sure asymptotic consensus using simple ergodicity and probabilistic arguments. This easily verifiable condition uses the spectrum of the average weight matrix. Finally, we investigate a special case for which the linear dynamical system converges to a fixed vector with probability 1.     

反馈严格正实输出的必要与充分条件

本文研究线性多输入多输出系统反馈成为严格正实系统问题，得到了反馈严格正实系统的必要和充分条件，这个条件在表达上十分简洁。由于这个条件的检验仅需考虑系统矩阵，控制矩阵及输出矩阵间的某种确定系统，从而便于实际使用。     

线性时滞系统稳定的充分必要条件

提出一个新的线性时滞系统稳定的充分必要条件,与以前的结论不同的是,我们的结论的表达形式更容易数值计算。开发相应的二种收敛算法,解决系统时滞独立稳定判断和时滞相关稳定的时滞界估计。本文给出范数有界不确定性时,系统稳定的充分条件。文末给出的数值实例证明本文结果降低计算复杂度,改进了时滞估计保守性。     

极点配置问题线性可解的充要条件

本文研究线性系统在输出反馈作用下的极点配置问题,得到了系统可由"线性化"方法任意配置n个(等于系统的维数)闭环极点的充要条件.并给出了一种新的极点配置方法.     

A Necessary and Sufficient Contractivity Condition for the Fractal Transform Operator

This paper revisits the concept of fractal image coding and the contractivity conditions of the fractal transform operator. All such existing conditions are only sufficient. This paper formulates a necessary and sufficient condition for the contractivity of the fractal transform operator associated to a fractal code. Furthermore, analytical results on the convergence of the fractal image decoding will be derived.

分数阶奇异系统容许性的充分必要条件

探讨了阶数在（0,1）区间的分数阶奇异系统的容许性条件. 文中首先给出了正则性,无脉冲性和容许性的定义,然后给出了分数阶奇异系统容许性的充分必要条件,最后通过数值仿真的例子来说明我们给出的容许性条件.     

一种针对虫洞攻击的安全路由方法

Ad Hoc网络的虫洞攻击危害较大且难以防御。为此,提出一种基于时间和跳数的安全路由方法。将时间差值和跳数差值作为2个限制量,分别与规定值进行比较,判断并抛弃可能存在虫洞攻击的路由,并选择相对安全的路由,建立可信的数据传输通道。NS2仿真结果表明,该方法可提高虫洞攻击的检测率,降低数据传输的丢包率。     

一种基于Wormhole Routing的寻径技术*

先锋网(Pionet)是一种具有自主知识产权的网络互连结构,将介绍先锋网寻径技术——先锋信令寻径技术(Pionet-Routing)。先锋网上层协议简单,实验数据显示：该网络系统效率高,适合于进行机群科学计算。     

结构(f,Gi)不变分布的一个充要条件

结构（ｆ,Ｇ_ｉ）不变分布的一个充要条件韩正之,高峰,张钟俊（上海交通大学自动控制系上海２０００３０）关键词非线性分散系统,结构不变分布,结构相容．考虑有干扰的具有两个控制站的非线性分散系统：其中ｕ一【ｕ卜叨”,ｕ;Ｅ炒ｌ和ｌ。一”２分别是第一子系统?..     

A Generic Design Methodology for Deadlock-Free Routing in Multicomputer Networks

This paper introduces a generic methodology for defining deadlock-free wormhole routing schemes in any arbitrary network. The basic strategy is to partition a graph into subdigraphs with no cyclic dependencies and selectively assign virtual channels. The usefulness of our scheme is shown for the n-dimensional hypercube, the n-dimensional mesh, and the k-ary n-cube torus by identifying subdigraph characteristics that ensure acyclic routing. Further generalization which allows partial cyclic dependencies without deadlock is achieved by our extended generic methodology. We also illustrate how to identify shortest fixed path and nonminimal adaptive routing schemes using minimum required channels.     

区间矩阵稳定的新充分必要条件

本文讨论了对称区间矩阵的稳定性并给出了一个简单的充分必要条件，同时还讨论了线性时变区间矩阵和非线性时变区间矩阵的稳定性。     

Necessary and Sufficient Condition for Global Controllability of Planar Affine Nonlinear Systems

In this correspondence, we will investigate the global controllability of general planar affine nonlinear systems, and present a simple necessary and sufficient condition for global controllability. The analysis is carried out in detail, which is based on some basic facts in planar topology such as the Jordan curve Theorem, and in the geometrical theory of ordinary differential equations including the Poincare-Bendixson Theorem. Furthermore, we will also discuss the global controllability for higher dimensional affine nonlinear system with a triangular-like structure.     

不确定线性系统输出反馈鲁棒镇定的充要条件

研究不确定性线性系统的输出反馈鲁棒镇定问题，给出了具有范数有界参数不确定线性系统静态输出反馈鲁棒镇定的充要条件。所给方法的设计过程只需解一个特殊的代数Ｒｉｃｃａｔｉ不等式或代数Ｒｉｃｃａｔｉ方程算法实现简便。最后通过实例验证了本方法的有效性。     

XML模式中隐式冗余不存在的充要条件

XML数据库模式规范化设计是产生一组相关联的、能表示数据间依赖关系、而且消除了冗余的XML模式或DTD,以更好地进行信息检索.XML数据库模式中某些数据依赖的存在是冗余存在的原因,因此在XML数据库模式中数据依赖与冗余的关联是其规范化设计研究的关键问题,但对这一问题目前还没有专门的研究.XML数据库模式的数据依赖包括属性间数据依赖和元素间的数据依赖,给出综合了属性间和元素间数据依赖的XML数据库模式数据依赖的定义,分析与之关联的隐式冗余,并论证XML模式中隐式冗余不存在当且仅当该XML模式是规范的,为XML数据库模式规范化设计更深一层的研究奠定理论基础.     

时不变线性Ito随机系统均方稳定性的充要条件

时不变线性Ｉｔ随机系统均方稳定性的充要条件邓飞其,冯昭枢,刘永清（华南理工大学自动化系广州５１０６４１）关键词：线性随机系统,均方稳定性,充要条件,系数矩阵,Ｈｕｒｗｉｔｚ性质１弓Ｉ言在随机系统模型中,Ｉｔ６型随机系统是最重要的类型之一,许多具有有色...     

Mesh网络耐故障虫孔路由

耐故障是互连网络设计中的一个重要问题。本文提出了一种新的耐故障路由算法,并将其应用于使用虫孔交换技术的Mesh网络。由于使用了较低的路由限制,这一算法具有很强的自适应性,可以在各种不同故障域的Mesh网络中保持路由的连通性和无死锁性;由于使用了最小限度的虚拟通道,这一算法所需的缓冲器资源很少,非常适宜构建低成本的耐故障互连网络;由于根据本地故障信息进行绕行故障节点的决策,这一算法的路由决策速度较快并且易于在互连网络中实现。最后网络仿真试验显示,这一算法具有良好的平滑降级使用的性能。