Availability of the system with general repair time distributions and shut-off rules

A model which has main and secondary subsystems subject to shut-off rules is considered. In this model, the system has a single repair facility. The repair discipline that the main subsystem has the pre-emptive repeat priority is considered. Constant failure rate and general repair time distributions are assumed. The system availability is obtained by using the linear ordinary differential equation method and supplementary variable technique.     

Analysis of a degraded multistate system with general repair-time distributions

The system in this paper has good, degraded and (N?1)-failed states. Laplace transforms of state probability for such a system are obtained by using the supplementary variable method. A particular case is considered.     

Availability of non-independent main unit and N-unit series subsystem subject to shut-off rules

Two-unit series system subject to shut-off rules was treated by Osaki et al. [4]. Here a modified model is considered. The system is composed of a main unit and a n-unit series subsystem. The lifetime distributions of the main unit and that of any one of the N-unit of series subsystem are nonindependent. Two repair facilities are introduced. Failure of the main unit shuts off the operation of subsystem, but not vice versa. Failure of the main unit or the subsystem initiates the system shut down. For this model, the system availability is given by using the technique of the Markov renewal process. Moreover, the availability of Osaki's model and that of this model are compared. We found that the availability of this system is generally higher than that of Osaki's system.     

Availability of the 2-out-of-n: F System

Assuming constant failure rate and general repair distribution, this paper treats the availability of the 2-out-of-n:F system by identifying an imbedded Markov renewal process.     

An efficient VLSI design for a residue to binary converter for general balance moduli (2/sup n/-3,2/sup n/+1,2/sup n/-1,2/sup n/+3)

In this paper, we present a new four-moduli set (2/sup n/-3,2/sup n/+1,2/sup n/-1,2/sup n/+3) and an efficient residue to binary (R/B) converter design. The merits of the proposed four-moduli set include 1) larger dynamic range; 2) higher degree of parallelism for conversion; 3) balanced bit-width for internal RNS arithmetic operations; and 4) flexible moduli set selection. According to the relation between the proposed moduli, the divide-and-conquer technique is used to design a two-level converter architecture which has lower hardware cost and shorter critical delay. For the R/B converter designed with 12-b (n=3), our architecture has about 47% saving in hardware cost and 40% saving in critical delay compared to the last work.     

An O(k/sup 2//spl middot/log(n)) algorithm for computing the reliability of consecutive-k-out-of-n: F systems

This study presents an O(k/sup 2//spl middot/log(n)) algorithm for computing the reliability of a linear as well as a circular consecutive-k-out-of-n: F system. The proposed algorithm is more efficient and much simpler than the O(k/sup 3//spl middot/log(n/k)) algorithm of Hwang & Wright.     

An O(k3·log(n/k)) algorithm for theconsecutive-k-out-of-n:F system

The fastest generally-recognized algorithms for computing the reliability of consecutive-k-out-of-n:F systems require O(n) time, for both the linear and circular systems. The authors' new algorithm requires O(k³·log(n/k)) time. The algorithm can be extended to yield an O(n·max{k³·log(n/k), log(n))} total time procedure for solving the combinatorial problem of counting the number of working states, with w working and n-w failed components, w=1,2,...,n     

Optimal self-dual codes over F/sub 2//spl times/F/sub 2/ with respect to the Hamming weight

In this paper, we study optimal self-dual codes and type IV self-dual codes over the ring F/sub 2//spl times/F/sub 2/ of order 4. We give improved upper bounds on minimum Hamming and Lee weights for such codes. Using the bounds, we determine the highest minimum Hamming and Lee weights for such codes of lengths up to 30. We also construct optimal self-dual codes and type IV self-dual codes.     

An approximation analysis for the availability of a parallel redundant system with general distributions

This paper presents an approximation method for deriving the availability of a parallel redundant system with general distributions. The system discussed is composed of two identical units. A single service facility is available for the performance of preventive maintenance(PM) and repair. The failure times, repair times and PM times are assumed to be arbitrarily distributed. The presented method formulates the problem of the availability analysis of a parallel redundant system as a semi-Markov process which represents the state transitions of one specified unit in the system. This method derives the availability easily and accurately. Further, when all the distributions are exponential, the availability obtained by this method is exact.     

Reliability analysis of a two-unit parallel system with dissimilar units and general distributions

We study the reliability characteristics of a parallel system attended by a single repair facility and general failure and repair time probability distribution functions (pdf). The basic mathematical problem is the solution of a pair of simultaneous Wiener-Hopf integral equations.A formal solution procedure of the equations has been discussed in the case of unspecified characteristic functions (cf).Fairly explicit solutions are performed if at least one of the failure time pdf's has a rational cf.We compare some of the results presented in previous literature.     

Availability of K-out-of-N:G systems with M failure modes

Markov models for analyzing the availability of K-out-of-N systems subject to M failure modes are presented. Closed form solutions of the steady-state probabilities of the systems and hence the availability are calculated.     

Lie algebraic stability analysis for switched systems with continuous-time and discrete-time subsystems

We analyze stability for switched systems which are composed of both continuous-time and discrete-time subsystems. By considering a Lie algebra generated by all subsystem matrices, we show that if all continuous-time subsystems are Hurwitz stable, all discrete-time subsystems are Schur stable, and furthermore the obtained Lie algebra is solvable, then there is a common quadratic Lyapunov function for all subsystems and thus the switched system is exponentially stable under arbitrary switching. A numerical example is provided to demonstrate the result.     

IP multimedia subsystems in 3GPP and 3GPP2: overview and scalability issuesP

The Internet has experienced tremendous expansion in the past several years. Demands for IP multimedia services are emerging. The third-generation (3G) wireless networks aim to support mobile users with numerous Internet services. 3G standards organizations are developing IP multimedia subsystems (IMS) to achieve seamless integration between Internet and 3G networks. Moreover, the collaboration between IETF, 3GPP, and 3GPP2 is essential to the development of IMS for next-generation networks. This article first provides an overview of 3GPP and 3GPP2 IMS and illustrates the IMS requirements, architectures, and functional models. We then discuss potential scalability issues in IMS. This article provides guidance for constructing a robust and scalable IMS.     

一种新的22n+1阶QAM星座图设计

该文研究了2²ⁿ⁺¹阶正交幅度调制(Quadrature Amplitude Modulation,QAM)的星座图,提出了一种可以根据格雷映射规则建立映射表的正方形QAM星座图。为了对比正方形星座图与十字形以及矩形星座图的性能,该文以32 QAM为例对3种星座图的信号功率效率进行了分析,并对三者的误码性能进行了仿真。仿真结果表明,与信道编码结合使用时,正方形星座图的误码性能优于十字形星座图和矩形星座图。而且,对于多载波通信系统,正方形星座图和十字形以及矩形星座图具有相同的信号功率效率。     

Pulse broadening in multimode optical fibres with large ?n/n: numerical results

The r.m.s. impulse response width of germania doped fibres having power-law profiles at the carrier wavelength is evaluated with the help of a numerical method and measured values of dn/d?. For ?n/n?0.02, our result exceeds by more than one order of magnitude that obtained from an analytical formula based on the assumption that n dn/d? varies linearly with n2. The optimum profiles are found to differ very significantly from power-law profiles. Our numerical technique is based on scalar-ray optics. It is applicable to any fibre having a large V-number and a smooth profile.     

Normal basis multiplication algorithm for GF(2/sup n/)

A normal basis multiplication algorithm is presented. Its complexity depends on the multiplicative order of the normal element.     

Consecutive-2-of-n:F systems with node and link failures

It has always been assumed that nodes can fail but not links, although most examples given for the consecutive-k-out-of-n :F system show no reason for such an assumption. The system described not only allows links to fail, but allows both nodes and links to fail, with distinct probabilities. For the k=2 case, the authors set up recursive equations for system reliability, and give a closed-form solution. It is proved that for n large, the reliability is decreasing in n (with one exceptional case) and higher reliability should be provided to the nodes, and then to the longer links rather than to shorter links     

Nanoscale potential barrier distributions and their effect on current transport in Ni/n type Si Schottky diode

We have experimentally studied the Ni/n-Si nano Schottky barrier height(SBH) and potential difference between patches in the nano Schottky diodes(SD) using contact atomic force microscopy(C-AFM) in tapping mode and scanning tunneling microscopy(STM). Topology measurement of the surface with C-AFM showed that, a single Ni/n-Si SD consists of many patches with different sizes. These patches are sets of parallel diodes and electrically interacting contacts of 5 to 50 nm sizes and between these individual diodes, there exists an additional electric field. In real metal semiconductor contacts(MSC), patches with quite different configurations, various geometrical sizes and local work functions were randomly distributed on the surface of the metal. The direction and intensity of the additional electric field are distributed in homogenously along the contact metal surface. SBH controls the electronic transport across the MS interface and therefore, is of vital importance to the successful operation of semiconductor devices.