Quality-of-service and quality-of-protection issues in preplanned recovery schemes using redundant trees

We study quality-of-service (QoS) and quality-of-protection (QoP) issues in redundant tree based preplanned recovery schemes for a single-link failure in two-edge connected graphs and for a single-node failure in two-connected graphs. We present schemes (to be called G-MFBG schemes) that generalize the schemes (to be called MFBG schemes) developed by Me/spl acute/dard et al. (1997) to construct a pair of redundant trees, called red and blue trees, which guarantees fast recovery from any single-link/node failure, as long as the failed node is not the root node. Using the G-MFBG schemes, we study QoS issues relating to red/blue trees. We present effective heuristics for computing a pair of redundant trees with low average delay or small total cost. We develop an optimal algorithm for computing a pair of red/blue trees with maximum bandwidth. Furthermore, a pair of red/blue trees guarantees fast recovery from simultaneous multiple failures if it satisfies certain properties. This leads us to define the concept of QoP of a pair of red/blue trees. We present an effective heuristic to construct a pair of red/blue trees with high QoP. The paper concludes with a discussion of computational results that demonstrate the effectiveness of the different algorithms presented.     

Embedding complete binary trees in product graphs

This paper shows how to embed complete binary trees in products of complete binary trees, products of shuffle‐exchange graphs, and products of de Bruijn graphs with small dilation and congestion. In the embedding results presented here the size of the host graph can be fixed to an arbitrary size, while we define no bound on the size of the guest graph. This is motivated by the fact that the host architecture has a fixed number of processors due to its physical design, while the guest graph can grow arbitrarily large depending on the application. The results of this paper widen the class of computations that can be performed on these product graphs which are often cited as being low‐cost alternatives for hypercubes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Embedded trees: estimation of Gaussian Processes on graphs with cycles

Graphical models provide a powerful general framework for encoding the structure of large-scale estimation problems. However, the graphs describing typical real-world phenomena contain many cycles, making direct estimation procedures prohibitively costly. In this paper, we develop an iterative inference algorithm for general Gaussian graphical models. It operates by exactly solving a series of modified estimation problems on spanning trees embedded within the original cyclic graph. When these subproblems are suitably chosen, the algorithm converges to the correct conditional means. Moreover, and in contrast to many other iterative methods, the tree-based procedures we propose can also be used to calculate exact error variances. Although the conditional mean iteration is effective for quite densely connected graphical models, the error variance computation is most efficient for sparser graphs. In this context, we present a modeling example suggesting that very sparsely connected graphs with cycles may provide significant advantages relative to their tree-structured counterparts, thanks both to the expressive power of these models and to the efficient inference algorithms developed herein. The convergence properties of the proposed tree-based iterations are characterized both analytically and experimentally. In addition, by using the basic tree-based iteration to precondition the conjugate gradient method, we develop an alternative, accelerated iteration that is finitely convergent. Simulation results are presented that demonstrate this algorithm's effectiveness on several inference problems, including a prototype distributed sensing application.     

Reducing average delay after link failure in single-link recovery trees using distributed switching mechanism

Based on the modified MFBG algorithm, the distributed switching mechanism (DSM) is proposed to reduce the average delay after link failure in the preplanned single-link recovery trees. The main principle of the DSM is to use as many links in the blue tree as possible to keep connected, and the key feature is that all the active links comprise a new spanning tree after distributed switching. Simulation results demonstrate the effectiveness of the DSM in reducing the average delay.     

一种变异测试中冗余变异体的寻找方法

变异测试是一种有效的基于故障的测试方法,但大量冗余变异体所带来的昂贵的测试成本问题,阻碍了它在实际工程开发中的应用.为解决该问题,本文针对程序中的顺序语句所产生的变异体,基于故障的可达-感染-传播模型,提出了使用区间抽象域来表示程序状态,通过区间运算判断变异体之间冗余关系的算法;针对程序中的条件语句,基于谓词故障层级,分别给出了面向简单谓词和复合谓词的冗余变异体选择算法.并对这两种算法对冗余变异体的判定效果进行了分析,最后给出了在分层抽样背景下,非冗余变异体生成的约束边界条件.对Siemens和开源项目等共8个工程进行了实验,并与随机选择法进行了对比.结果表明,本文所提方法在减少变异测试时间成本的同时,可以保持较高的变异得分.     

Redundant task-allocation in multicomputer systems

A simple yet effective method for improving multicomputer multiprocessor system reliability via redundant allocation of tasks to computers (processors) is described. Given any known (nonredundant) scheduling strategy, tasks are allocated to processors statically and redundantly using a k-circular shifting (KCS) algorithm. so that if some processors fail during the execution. all tasks can be completed on the remaining processors (but at a longer time). Redundant allocation of independent tasks to identical processors (computers), subject to real-time constraints on total execution time, is discussed in detail, and analytic reliability estimates are derived. The longest processing time scheduling is given as an example of nonredundant deterministic scheduling of independent tasks. Processor utilization for redundant task-allocation is discussed and compared with standby redundancy: the authors' KCS algorithm achieves much higher processor utilization than standby redundancy     

Redundant wireless communication technologies for real-time surveillance

Catastrophic events including those sparked by terrorism have cast a pall over society in recent years. Events such as September 11th or the bombing of the Alfred P. Murrah Federal Building in Okalahoma City demonstrated a sudden surge in telephone call volume. These events indicated that communications systems, including cellular, can fail as a result from damage or capacity overload. Cellular systems have significant capacity given the limited radio spectrum allocated but much like airlines that oversell seats because inevitably some passengers do not show up, cellular providers typically have more customers than operational spectrum can handle in aggregate. Normally this is perfectly acceptable because a high percentage of the customer base would never be making calls simultaneously; except in an emergency. Such emergencies can be active or passive in nature. The release of dangerous airborne agents is one such scenario. The purpose of this study was to use a portable air particulate sensor as a data acquisition platform to evaluate the capability of real-time data throughput using existing wireless topologies, Java, eXtensible Markup Language (XML) and Internet protocols when cellular transmission frequencies are compromised. Results show that high levels of cellular voice traffic in a given area can hamper simultaneous data communications; however, Low Earth Orbiting Satellites (LEOS) can provide redundancy.     

General Expressions for Reliability of Redundant Systems

General expressions for reliability and mean time-to-failure of parallel and standby redundant systems are shown. Each unit in the system has a constant failure rate and need not be good at the beginning.     

功能网络冗余光子学

任何功能的充分稳定发挥是由负反馈机制和冗余机制维持的。将其中的负反馈机制称为功能内稳态(FSH)。维持FSH的非必须子功能(FNS)可以处于FNS特异内稳态(FESH)。打破FSH的特异的应激(FSS)也可以处于FSS特异内稳态(FSSH)。处于/远离FSSH的FSS称为成功/慢性应激。打破FNSH的应激称为常规应激。通过研究控制功能网络的深层网络,假设慢性/成功常规应激是冗余基因/通路的部分/完全激活。弱激光或单色光不能调节完全激活的冗余基因/通路,但可以促进部分激活的冗余基因/通路完全激活。冗余通路的调节已经初步获得了实验证据的支持,但冗余基因的调节有待进一步实验的证实。     

一种基于中间件的RFID系统阅读器去冗余算法

 冗余阅读器判别是大规模RFID系统性能优化的重要问题之一.本文基于EPC网络架构提出一种阅读器去冗余算法MRRE.该算法利用RFID中间件的标签信息判别冗余阅读器,不需阅读器对标签写入信息.仿真结果表明,MRRE算法比LEO+RRE算法在冗余阅读器检测率上提高了6.27%～20.80%,在系统处理的标签信息量上降低了4.50%～35.73%,而且在系统部署合理性方面更具优势.     

A Reliability Model for Dependent Failures in Parallel Redundant Systems

The concept of Equivalent time is introduced to find the hazard rates of elements in a parallel redundant systems which is subject to dependent failures. True acceleration is defined as an adjunct to this concept.     

IC中多余物缺陷对信号串扰的定量研究

该文研究了铜互连线中的多余物缺陷对两根相邻的互连线间信号的串扰,提出了互连线之间的多余物缺陷和互连线之间的互容、互感模型,用于定量的计算缺陷对串扰的影响。提出了把缺陷部分单独看作一段RLC电路模型,通过提出的模型研究了不同互连线参数条件下的信号串扰,主要研究了铜互连线的远端串扰和近端串扰,论文最后提出了一些改进串扰的建议。实验结果证明该文提出的信号串扰模型可用于实际的电路设计中,能够对设计人员设计满足串扰要求的电路提供指导。     

利用冗余进程实现MPI程序错误检测

关注MPI并行程序的运行时错误检测,提出了一种基于冗余进程的检错方法REDReP,能够检测MPI并行程序在运行过程中由于硬件故障导致的数据错误.介绍了REDReP的基本思想,讨论了一些关键问题,最后给出了实验结果,表明REDReP具有较低的检错开销.     

Laplace Transforms for the Two-Unit Cold-Standby Redundant System

A conditional transform approach is applied to the two-unit standby redundant system with instantaneous switchover, and with failure and repair times that follow general well-behaved distributions for each unit. Transforms of distributions are obtained for T, the time to system failure, the number of repairs completed during T, the time spent on repair during T, and the idle time of the repairman during T. Applicable numerical methods are also discussed.     

Scalable Models for Redundant Data Flow Analysis in Online Social Networks

Wireless Personal Communications - Sharing and reception of identical video contents amongst the users of various online social media applications induce enormous amount of redundant data traffic...