Ω-模糊软环

将软集理论的概念应用到Ω-模糊环中,提出了Ω-模糊软环的概念,给出了Ω-模糊软环的交与并的定义;探讨了交与并的一些相关性质;讨论了Ω-模糊软环的同态的一些性质,并提出了Ω-模糊软子环和模糊软同构的概念,研究了与其相关的性质。     

Flood Avoidance Mechanisms for Bridged Resilient Packet Rings

Resilient Packet Ring (RPR), or the Standard IEEE 802.17, is a new IP-based network technology proposed to replace SONET/SDH in metropolitan area networks. RPR is well-adapted to handle multimedia traffc and is effcient. However, when RPR networks are bridged, inter-ring packets, or packets with the destination on a remote RPR network other than on the source network, are flooded on the source and the destination networks, and also on the path of the intermediate networks between the source and the destination networks. This decreases the available bandwidth for other traffc in those networks and is ineffcient. As a result, we propose two solutions based on topology discovery, global topology discovery (GTD) and enhanced topology discovery (ETD), that prevent the flooding of inter-ring packets. GTD enables the bridges to determine the next-hop bridge for each destination. ETD enables the source node to determine a default ringlet, so that packets reach the next-hop bridge without flooding the source network. The proposed solutions were analyzed and the overhead bandwidth and stabilization time were shown to be bounded. Simulations performed showed that the proposed solutions successfully avoid flooding and achieve optimal effciency in the intermediate and destination networks, and in the source networks with one bridge.     

针对环状流形数据的非线性降维

近年来出现了多种新型的非线性降维方法,且在一些应用中体现出良好的效果.然而,当面对球体、柱体等环状流形产生的非线性流形数据时,这些方法往往会失效.针对这一问题,提出了针对环状流形数据的环结构检测算法与非线性降维方法.理论上,基于目前极受关注的Isomap降维方法的运行原理,给出了一个判断环状流形的充要条件;算法上利用所得的判断定理,制订了基于数据的环状流形检测算法:最后基于所找到的环结构,利用极坐标展开的思想设计了针对环状流形数据的非线性降维策略.针对一系列典型环状流形数据集的仿真实验结果表明,与其他流形学习降维方法相比,该方法对环状流形数据进行降维具有显著优势.     

Global data computation in chordal rings

Existing Global Data Computation (GDC) protocols for asynchronous systems are round-based algorithms designed for fully connected networks. In this paper, we discuss GDC in asynchronous chordal rings, a non-fully connected network. The virtual links approach to solve the consensus problem may be applied to GDC for non-fully connected networks, but it incurs high message overhead. To reduce the overhead, we propose a new non-round-based GDC protocol for asynchronous chordal rings with perfect failure detectors. The main advantage of the protocol is that there is no notion of rounds. Every process creates two messages initially, with one message traversing in a clockwise direction and visiting each and every process in the chordal ring. The second message traverses in a counterclockwise direction. When there is direct connection between two processes, a message is sent directly. Otherwise, the message is sent via virtual links. When the two messages return, the process decides according to the information maintained by the two messages. The perfect failure detector of a process need only detect the crash of neighboring processes, and the crash information is disseminated to all other processes. Analysis and comparison with two virtual links approaches show that our protocol reduces message complexity significantly.     

Coding with skew polynomial rings

In analogy to cyclic codes, we study linear codes over finite fields obtained from left ideals in a quotient ring of a (non-commutative) skew polynomial ring. The paper shows how existence and properties of such codes are linked to arithmetic properties of skew polynomials. This class of codes is a generalization of the θ-cyclic codes discussed in [Boucher, D., Geiselmann, W., Ulmer, F., 2007. Skew cyclic codes. Applied Algebra in Engineering, Communication and Computing 18, 379–389]. However θ-cyclic codes are powerful representatives of this family and we show that the dual of a θ-cyclic code is still θ-cyclic. Using Groebner bases, we compute all Euclidean and Hermitian self-dual θ-cyclic codes over of length less than 40, including a [36,18,11] Euclidean self-dual θ-cyclic code which improves the previously best known self-dual code of length 36 over .     

不同通信模型下的全光树环网波长分配算法

研究了波分复用全光树环网在不同通信模型下的波长分配算法及其最坏性能分析.对于静态模型,证明了5L/2是树环网所需波长数的紧界.对于动态模型,提出了一种近似比为∑_i=1^hmax_r∈Ri[log|V(r)|]+h的波长分配算法,其中h为树环网的基树的层数,R_i为树环网中处于第i层的环的集合,|V(r)|为环r上的节点数.对于增量模型,提出了一种近似度为O[log₂(t+1)]的波长分配算法,其中t为树环网中的环数.     

Bases for projective modules in An(k)

Let A_n(k) be the Weyl algebra, with k a field of characteristic zero. It is known that every projective finitely generated left module is free or isomorphic to a left ideal. Let M be a left submodule of a free module. In this paper we give an algorithm to compute the projective dimension of M. If M is projective and rank(M)≥2 we give a procedure to find a basis.     

Closed-form solution for reliability of SCI-based multiprocessor systems using Weibull distribution and self-healing rings

This paper introduces a new closed-form solution for the reliability of large-scale multiprocessor systems. The systems are based on SCI rings interconnected in hierarchical structures. Reliability expressions using enumeration technique are derived assuming Weibull failure process. The reliability function derived in this paper is general and valid for any hierarchical ring-based system with arbitrary number of levels. The hierarchical interconnections are constructed from self-healing rings and basic rings. The analysis shows the improvement achieved in reliability when self-healing rings are used. Although we used hierarchical systems based on SCI rings, the technique followed in this work is applied for any type of rings such as slotted or token rings.     

Realisation of linear time-varying systems

In this paper, the realisation problem of linear multi-input multi-output, time-varying systems is studied. The approach, based on the theory of non-commutative polynomial rings, yields explicit and simple formulas for computation of the state coordinates as well as for state equations in observable canonical form. The formulas are based on (left) Euclidean polynomial division.     

航空发动机轴承剥落分析

航空发动机轴承在使用过程中出现早期剥落。采用宏观检验、化学分析、力学性能测试、金相检验、能谱等手段对轴承内滚道表面剥落原因进行了分析,结果表明:剥落轴承内圈存在锻造过烧,形成孔洞缺陷,破坏了金属连续性,降低了轴承接触疲劳强度,在交变应力的作用下,以孔洞为核心,其周围形成“蝶形”组织,产生显微裂纹向滚动接触表面扩展,形成剥落,引起轴承疲劳失效。由此提出,通过控制锻造工艺及增加锻造缺陷的检测手段来防止锻造过烧,进而提高轴承使用寿命。