Generic rules to evaluate system-failure frequency

Frequency of failure of a system with s-independent components can be obtained from the system availability (unavailability) expression and failure and repair rates of the components. Although, Grouped Variable Inversion is an efficient technique to find the system availability, there is no convenient method to convert the “availability expression obtained by this technique” into an “expression for system-failure frequency.” This paper present generic rules to find system-failure frequency, particularly, when the availability or unavailability expression of a system is obtained using this technique. The rules are straightforward, and produce appreciably shorter expressions for system-failure frequency. Examples illustrate the simplicity and efficiency of the proposed rules     

Transient phase conjunction in a two-level system

An analytical expression for conjugate signals is developed for a case where three rectangular pulses with the same center frequency are injected into a two-level system. The Maxwell's equation is solved with the slowly varying envelope approximation and with the perturbative third-order nonlinear polarization expression of a two-level system. Numerical examples are discussed in such a way that the input pulsewidth is changed relative to the energy relaxation and dephasing times. As the optical pulsewidth becomes short, ripples appear in the signal pulse due to the beat between the optical field and the resonant oscillation of the atomic system     

A Heuristic Algorithm for System Failure Frequency

For reliability analysis, the choice between tie-sets and cut-sets is not a matter of convenience but depends on assessment of computational effort. The system configuration alone determines the preference of the approach. The present paper offers a faster algorithm for evaluating system failure frequency using both approaches. An expression for system failure frequency between two specified nodes is derived using either tie-sets or cut-sets. The expression is in terms of failure frequency, availability, and unavailability of the system elements. A heuristic algorithm to obtain the expression can be programmed for a computer. The algorithm is illustrated through an example. The manner in which Abraham's algorithm can be used to determine system probability of failure using cut-sets is suggested. The algorithms are also useful for evaluating sensitivity coefficients.     

Symmetrized Split-Step Fourier Scheme to Control Global Simulation Accuracy in Fiber-Optic Communication Systems

Analytical expressions involving both system parameters and step-size are proposed to represent the local simulation error for the symmetrized split-step Fourier (SSSF) simulation method. This analytical expression can be used for a step-size selection rule to achieve comparable local simulation accuracy for SSSF simulations. This can lead to computational savings since there is no waste of computation in each simulation step. Furthermore, based on the local error expression, scaling rules are derived to achieve comparable global simulation accuracy for wide ranges of key system parameter values. This is significant in enhancing the computational efficiency in optical fiber communication system design and optimization. Extensive validation tests were performed to explore the application range of the proposed step-size selection and scaling rules. The desired global accuracy can be achieved with the use of our local error expression and scaling rules by only a couple of test trial simulation runs for a variety of practical applications.     

Characterization of noncoherent spread-spectrum multiple-accesscommunications

An expression for the decision statistic of the receiver in a noncoherent DS/SSMA communication system is obtained, and conditions are identified that allow key parameters in the expression to be modeled as a set of Gaussian random variables. The decision statistic is then characterized as an inhomogeneous quadratic form in Gaussian random variables. An applicable theorem is applied to obtain a new expression, a function of a set of independent Gaussian random variables, with the same distribution as the decision statistic. The results are used to determine the distribution for the decision statistic and to compute the average probability of error for the system. The effects of the length of the signature sequences and the number of interfering transmitters are illustrated     

电光偏转器的矩阵表示和应用

用光线追述的方法，导出了电光偏转器的矩阵表达式，是著名的ＡＢＣＤ矩阵的扩展，它包含了电光偏转器的时变项。井用矩阵光学的理论对由电光偏转器对构成的激光脉冲整形系统进行了研究，对实际应用的电光偏转器对参数的一致性、电脉冲的同步精度及光路排布提出了要求。     

Average bit-error-rate performance of band-limited DS/SSMA communications

Direct-sequence spread-spectrum multiple-access (DS/SSMA) communications, strictly band-limited transmitter chip waveforms with excess bandwidth in the interval between zero and one, pseudo-random spreading sequences, an additive white Gaussian noise channel, and matched filter receivers are considered. First, a new expression for the average bit error rate (BER) is derived for systems with quaternary phase-shift keying (QPSK) spreading, the conventional matched filter receiver, a coherent detector for binary phase-shift keying (BPSK) data symbols, and chip waveforms that result in no interchip interference. The expression consists of a well known BER expression based on the standard Gaussian approximation to multiple-access interference and a few correction terms. It enables accurate BER evaluations without any numerical integration for various choices of system parameters of interest. The accuracy of the expression is guaranteed as long as the conditional Gaussian approximation to the cross-correlation coefficients between the desired user's spreading sequence and the interfering users' spreading sequences is valid. The expression well reflects the effect of filtering on the system performance. Extensions of the expression are discussed for systems with QPSK spreading and different detection schemes, systems with BPSK spreading, and systems with different transmit and receive filters. Monte Carlo simulation results are also provided to verify the accuracy.     

The State Variable Approach to System Effectiveness

Expressions are given in the literature for the availability, mean-time-between-failures, mean uptime, and mean downtime for systems consisting of a number of identical modules in redundancy. Using the concept of superstates, vector expressions for these parameters are presented which apply to a system consisting of an arbitrary interconnection of different types of modules. A vector expression for system effectiveness is presented which is formally the same as the expression for availability in the case of a single-function system and which can be extended easily to cover multifunction systems.     

Average BER Analysis for $M$-ary FSK Signals in Nakagami-$q$ (Hoyt) Fading With Noncoherent Diversity Combining

This paper analyzes the average bit error rate (BER) of noncoherent M-ary frequency-shift keying (FSK) signals over multichannel nonidentically distributed Nakagami-q (Hoyt) fading employing diversity combining. The first part of the paper considers the conventional postdetection noncoherent equal-gain combiner (NC-EGC), in which a Fourier series inversion formula is employed to derive a simple and rapidly converging series-based expression for the system average BER. This expression is valid for arbitrary values of received average signal-to-noise ratios (SNRs) and fading parameters. The derived expression is then compared with some existing ones in the literature, and the results show a large reduction in computational complexity, particularly when M and/or the diversity order increases. In the second part, a new noncoherent combiner is proposed to achieve improvements over the conventional NC-EGC. It is also shown that this new combiner results in a simple closed-form expression for the system average BER that is given in terms of elementary functions; hence, it can be easily numerically evaluated with noticeable computation efficiency.     

分布式天线系统中的系统下行中断概率分析

本文针对分布式天线系统的系统下行中断概率问题展开研究.文章首先建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型.接着,在接收端采用最大比合并的方式接收信号,并运用矩生成函数推导出输出信噪比的概率密度函数.然后,对分布式天线采用选择传输策略,并分析出给定移动台位置时的中断概率的表达式.最后,考虑小区内移动台任意分布特...     

Performance of coherent receiver with weighted despreading sequencefor DS-CDMA

The performance of a DS-CDMA system using coherent receivers with the despreading sequences weighted by adjustable chip waveforms is presented. A new expression for the signal to interference plus noise ratio (SINR) of the decision variable is derived for the proposed receiver. When the system parameters are given, the derived SINR expression is determined only by one parameter of the weighted despreading sequence. As a result, the parameter can be simply tuned in practice for multiple access interference (MAI) rejection     

可生存性控制系统的有限状态机的设计

文章提出一种基于布尔表达式的可生存性控制系统的有限状态机的设计方法。基于系统服务、节点功能和故障元素之间的布尔函数关系．给出可生存性控制系统的有限状态机的形式化规范，并自动满足受控系统的可生存性。     

On Reliability Evaluation by Network Decomposition

A simple algorithm for evaluating the symbolic terminal-pair reliability of a complex system is presented. The system graph is decomposed into two subgraphs through a minimal cut. The system success is expressed in terms of certain successes of these subgraphs, and then changed into an equivalent disjoint expression which is directly converted on a one-to-one basis into a reliability expression. It yields unusually simple reliability expressions. The algorithm can be computerized but has not been done. Three examples illustrate the algorithm and compare it with other algorithms.     

Calculating the Time-Specific Frequency of System Failure

This paper develops a formula for converting the expression for time-specific probability of system success into time-specific frequency of system failure. This conversion rule is then used to derive an expression for time-specific frequency of system failure using the tie-set approach. The calculation of interval frequency from time-specific frequency is also presented.     

Capacity analysis of M-SC receivers over TWDP fading channels

An expression for the probability distribution function (PDF) of the signal-to-noise ratio of a selection combining receiver in two-wave with diffuse power fading channel is derived. Using this PDF expression, the capacity for the different adaptive transmission techniques employing selection combining (SC) are obtained. The study presents the effects of the ratio of total dominant signal power to the scattered signal power on the system capacity. The change in the capacity of the system with the diversity order for a SC receiver in the fading channel is also presented.     

Performance of two-way amplify-and-forward relaying with adaptive modulation over Nakagami-m fading channels

This paper investigates the performance of a two-way amplify-and-forward(AF)relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels.The tight closed-form cumulative distribution function(CDF)expression of the instantaneous end-to-end signal-to-noise ratio(SNR)is provided.Further,approximate closed-form expression for the average spectral efficiency of the two-way AF system with adaptive modulation is obtained.Then,a tight lower bound of outage probability is deriv...     

Automatic Facial Expression Exaggeration System with Parallelized Implementation on a Multi-Core Embedded Computing Platform

In this paper, we propose an automatic facial expression exaggeration system, which consists of face detection, facial expression recognition, and facial expression exaggeration components, for generating exaggerated views of different expressions for an input face video. In addition, the parallelized algorithms for the automatic facial expression exaggeration system are developed to reduce the execution time on a multi-core embedded system. The experimental results show satisfactory expression exaggeration results and computational efficiency of the automatic facial expression exaggeration system under cluttered environments. The quantitative experimental comparisons show that the proposed parallelization strategies provide significant computational speedup compared to the single-processor implementation on a multi-core embedded platform.     

Partial-band jamming rejection of FFH/BFSK with product combiningreceiver over a Rayleigh-fading channel

An exact closed-form expression of the characteristic function is derived for a fast frequency-hopping (FFH) binary orthogonal frequency-shift-keying (FSK) spread-spectrum (SS) communication system. The FFH system employs a product combining receiver over a Rayleigh-fading channel with partial-band jamming and additive white Gaussian noise (AWGN). The derived characteristic function is then used to obtain a compact bit error rate (BER) expression for different diversity levels. Our study shows that there exists an optimum diversity level under certain channel conditions     

Software reliability of programs with network structure

The aim of this paper is to present the reliability expression of programs/packages with general network structure, which is not sequential, branch or parallel in logic flow of the concerned algorithm. The reliability expression for logic flow (R_L) of an example program of a general network structure (whose segments are listed in Appendix 1) is discussed and thereby overall reliability expression for the entire program which can be built in several different ways is derived. Such evaluations help increase the probability of programs having complex structure to be executed without errors on the computer system. The problem is obviously of great interest to programmers/system analysts while designing the flow system, debugging or testing the program.     

二维数字系统的系数灵敏度和结构优化

本文从二维数字系统的Roesser模型出发,在Kawamata等人定义的灵敏度的基础上,导出了系统传输函数对全体系数的标量灵敏度的新的表达式,并给出了一种降低灵敏度的优化方法,该优化方法不仅可以降低系数灵敏度,还可以提高结构的效率.举例结果表明,新的表达式与Kawamata等人的表达式相比,能更好地与计算机模拟结果相符.