Using rainbow net simulation to measure fault tolerance in a multiprocessor

The Rainbow net simulation technique is applied to modelling the impact of system load and fault handling on the availability of a fault-tolerant multiprocessor architecture. Rainbow nets are described along with the motivation for creating this modelling technique. A Rainbow net fault-handling model is created for the fault-tolerant multiprocessor architecture and the topology is shown to remain constant in size, independent of the number of processor, memory and I/O elements configured in the system. Simulation is performed with a varying load in terms of the number of active jobs the system must support. Results are given showing how the fault-tolerant capability varies with load. Two new metrics for evaluating fault tolerance are introduced; namely full fault-tolerability and partial fault-tolerability. They are based on simple observations in the model.     

Software Process and Product Improvement: A Historical Perspective

In this paper, a historical overview of significant attempts to get over the software crisis is presented. In particular, we trace the development of lifecycle models and information systems development methodologies during the last four decades. Finally, we explore the role of measurements and outline current and future works leading to process and product improvement.     

Objective Information Theory Exemplified in Air Traffic Control System

Information is the core of Air traffic con-trol system (ATCS).In this paper,objective information theory is extended to depict,model and measure the information exemplified in ATCS.The sextuple model is presented with information ontology,state occurrence time,state set,carrier,reflection time,and reflection set.The metric system is given to quantitively measure the information with extensity,detailedness,continuity,richness,containability,delay,pervasiveness,authenticity,and adaptability.The results show that the proposed method is potential to find out actual indexes in ATCS for flight safety.     

A human visual system-driven image segmentation algorithm

This paper presents a novel image segmentation algorithm driven by human visual system (HVS) properties. Segmentation quality metrics, based on perceptual properties of HVS with respect to segmentation, are integrated into an energy function. The energy function encodes the HVS properties from both region-based and boundary-based perspectives, where the just-noticeable difference (JND) model is employed when calculating the difference between the image contents. Extensive experiments are carried out to compare the performances of three variations of the presented algorithm and several representative segmentation and clustering algorithms available in the literature. The results show superior performance of our approach.     

Dynamic Survivability in WDM Mesh Networks Under Dynamic Traffic

Network survivability is a crucial requirement in WDM mesh networks. In this paper, we systematically consider the problem of dynamic survivability with dynamic single link failure in WDM networks under dynamic traffic demands. Specifically, we investigate various protection schemes, such as dedicated path protection (DPP), shared path protection (SPP), dedicated link protection (DLP), shared link protection (SLP), and two restoration schemes, path restoration (PR) and link restoration (LR). Moreover, two new shared protection methods are proposed, i.e., SRLG-based shared link protection (SRLG-SLP) and SRLG-based shared path protection (SRLG-SPP). The SRLG (shared risk link group) constraint defines the availability of protection resources to a working path, which requires that any two working paths sharing the same risk of failure (or in the same SRLG) cannot share the same protection resources. Furthermore, in our study, we consider a more practical dynamic single-link failure model, in which the link-failure-interarrival time and link-failure-holding time are considered as two independent parameters. Based on this link-failure model, extensive simulations are done to analyze and compare the dynamic survivable performance of various protection and restoration schemes. Resource utilization, protection efficiency, restoration efficiency, and service disruption ratio are employed as survivable performance metrics versus traffic load, link-failure frequency, and link-failure reparation time to evaluate the survivable performance. Many meaningful results are given. In addition, we show that the developed SRLG-SLP and SRLG-SPP protection schemes perform very well in terms of protection efficiency and service disruption ratio, while sacrificing some performance in terms of resource utilization.     

内网访问控制策略执行风险度量

VPN网关是众多涉密内网的典型边界防护设备,其网络访问控制策略的执行情况反映了涉密内网安全状况。选取典型的基于VPN网关的涉密内网,研究探讨网络访问控制策略执行过程中的风险度量问题,将安全风险作为一个要素引入网络访问控制策略之中,对策略执行过程中主体、客体和操作等基本信息进行风险分析与度量,从而获得有利于网络访问控制策略动态优化的量化度量结果,改善涉密内网安全状况。     

用非监督式聚类进行视频镜头分割

镜头边界检测是基于内容的视频检索首先要解决的问题。研究人员通常将镜头转换分为突变和渐变,并根据各种转换的特点采用不同的检测算法。在研究中发现,视频镜头的抽象程度与对其进行边界划分的精度相关。为此,提出采用非监督式聚类算法,按照给定的相似尺度对视频数据进行自组织和动态分析,完成层次化的镜头分割。该算法侧重于揭示视频的层次结构,能实现不同精度的视频抽象要求。