Reliability and performance analysis of hardware–software systems with fault-tolerant software components

This paper presents an algorithm for evaluating reliability and expected execution time for systems consisting of fault-tolerant software components running on several hardware units. The components are built from functionally equivalent but independently developed versions characterized by different reliability and execution time. Different number of versions can be executed simultaneously depending on the number of available units. The system reliability is defined as the probability that the system produces a correct output in a specified time.     

Reliability analysis of shuffle-exchange network systems

Shuffle-exchange networks (SENs) have been widely considered as practical interconnection systems due to their size of its switching elements (SEs) and uncomplicated configuration. SEN is a network among a large class of topologically equivalent multistage interconnection networks (MINs) that includes omega, indirect binary n-cube, baseline, and generalized cube. In this paper, SEN with additional stages that provide more redundant paths are analyzed. A common network topology with a 2×2 basic building block in a SEN and its variants in terms of extra-stages is investigated. As an illustration, three types of SENs are compared: SEN, SEN with an additional stage (SEN+), and SEN with two additional stages (SEN+2). Finally, three measures of reliability: terminal, broadcast, and network reliability for the three SEN systems are analyzed.     

Reliability analysis of electronic devices with multiple competing failure modes involving performance aging degradation

This paper presents an extension of reliability analysis of electronic devices with multiple competing failure modes involving performance aging degradation. The probability that a product fails on a specific mode is derived. Using this probability, the dominant failure mode on the product can be predicted. A practical example is presented to analyze an electronic device with two kinds of major failure modes–solder/Cu pad interface fracture (a catastrophic failure) and light intensity degradation (a degradation failure). Reliability modeling of an individual failure mode and device reliability analysis is presented and results are discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Reliability and performance analysis for fault-tolerant programs consisting of versions with different characteristics

This paper presents a simple straightforward algorithm for evaluating reliability and expected execution time for software systems consisting of fault-tolerant components. The components are built from functionally equivalent but independently developed versions characterized by different reliability and performance. Both N-version programming (with parallel and sequential execution of the versions) and the recovery block scheme are considered within a universal model.     

Distributed multicast routing algorithm with dynamic performance in multimedia networks

The delay and delay variation-bounded multicast tree (DVBMT) problem is known to be NP-complete. In this paper, we propose an efficient distributed dynamic multicast routing algorithm to produce routing trees with delay and delay variation constraints. The proposed algorithm is fully distributed, and supports the dynamic reorganizing of the multicast tree in response to changes for the destination. Simulations demonstrate that our algorithm is better in terms of tree delay and routing success ratio as compared with other existing algorithms, and performs excellently in delay variation performance under lower time complexity, which ensures it to support the requirements of real-time multimedia communications more effectively.     

多时滞无线通信网络的功率和速率最优跟踪

研究了无线通信网络的功率和速率控制这一热点问题。针对传统的无线通信网络模型并没有同时考虑状态时滞和输入时滞,已有的功率和速率控制算法也不能保证系统具有最优输出跟踪性能的情况,重新建立了无线通信网络的模型,在建模过程中考虑了多时滞,得到了含有不同的状态时滞和输入时滞的功率和速率控制系统模型,在此基础上,研究了一般形式的多时滞模型的时滞补偿算法,并将该算法应用在提出的多时滞模型中,给出了无线通信网络功率和速率的最优跟踪控制律。经过计算机仿真验证,提出的最优控制律具有良好的控制性能。     

Reliability analysis of laminated composite structures using finite elements and neural networks

Saving of computer processing time on the reliability analysis of laminated composite structures using artificial neural networks is the main objective of this work. This subject is particularly important when the reliability index is a constraint in the optimization of structural performance, because the task of looking for an optimum structural design demands also a very high processing time. Reliability methods, such as Standard Monte Carlo (SMC), Monte Carlo with Importance Sampling (MC–IS), First Order Reliability Method (FORM) and FORM with Multiple Check Points (FORM–MCPs) are used to compare the solution and the processing time when the Finite Element Method (FEM) is employed and when the finite element analysis (FEA) is substituted by trained artificial neural networks (ANNs). Two ANN are used here: the Multilayer Perceptron Network (MPN) and the Radial Basis Network (RBN). Several examples are presented, including a shell with geometrically non-linear behavior, which shows the advantages using this methodology.     

Prediction of flow stress in Ti–6Al–4V alloy with an equiaxed α + β microstructure by artificial neural networks

Flow stress during hot deformation depends mainly on the strain, strain rate and temperature, and shows a complex and nonlinear relationship with them. A number of semi-empirical models were reported by others to predict the flow stress during hot deformation. This work attempts to develop a back-propagation neural network model to predict the flow stress of Ti–6Al–4V alloy for any given processing conditions. The network was successfully trained across different phase regimes (α + β to β phase) and various deformation domains. This model can predict the mean flow stress within an average error of 5.6% from the experimental values, using strain, strain rate and temperature as inputs. This model seems to have an edge over existing constitutive model, like hyperbolic sine equation, and has a great potential to be employed in industries.     

Reliability and validity of risk analysis

In this paper we investigate to what extent risk analysis meets the scientific quality requirements of reliability and validity. We distinguish between two types of approaches within risk analysis, relative frequency-based approaches and Bayesian approaches. The former category includes both traditional statistical inference methods and the so-called probability of frequency approach. Depending on the risk analysis approach, the aim of the analysis is different, the results are presented in different ways and consequently the meaning of the concepts reliability and validity are not the same.     

Reliability graph with general gates: an intuitive and practical method for system reliability analysis

In this paper, we propose an intuitive and practical method for system reliability analysis. Among the existing methods for system reliability analysis, reliability graph is particularly attractive due to its intuitiveness, even though it is not widely used for system reliability analysis. We provide an explanation for why it is not widely used, and propose a new method, named reliability graph with general gates, which is an extension of the conventional reliability graph. An evaluation method utilizing existing commercial or free software tools are also provided. We conclude that the proposed method is intuitive, easy-to-use, and practical while as powerful as fault tree analysis, which is currently the most widely used method for system reliability analysis.     

Buckling analysis of tri-layer beams with multiple separated delaminations

In the present work, nondimensionalized axial and bending stiffnesses are used to investigate the buckling behavior of tri-layer beams having asymmetric double separated delaminations. A generalized analytical analysis using the Euler–Bernoulli beam theory is developed. Appropriate boundary and kinematic conditions are used to formulate the systematic homogeneous equations. The model is verified with the previously published data for homogeneous beam case and an excellent agreement between the results is observed. Effective-slenderness ratio, a new nondimensionalized parameter, is defined and introduced which strongly influences the buckling phenomenon.     

Reliability analysis of multi‐state series systems with performance sharing mechanism under epistemic uncertainty

For real engineering systems, it is sometimes difficult to obtain sufficient data to estimate the precise values of some parameters in reliability analysis. This kind of uncertainty is called epistemic uncertainty. Because of the epistemic uncertainty, traditional universal generating function (UGF) technique is not appropriate to analyze the reliability of systems with performance sharing mechanism under epistemic uncertainty. This paper proposes a belief UGF (BUGF)‐based method to evaluate the reliability of multi‐state series systems with performance sharing mechanism under epistemic uncertainty. The proposed BUGF‐based reliability analysis method is validated by an illustrative example and compared with the interval UGF (IUGF)‐based methods with interval arithmetic or affine arithmetic. The illustrative example shows that the proposed BUGF‐based method is more efficient than the IUGF‐based methods in the reliability analysis of multi‐state systems (MSSs) with performance sharing mechanism under epistemic uncertainty.     

Comments on ‘Reliability and performance analysis for fault-tolerant programs consisting of versions with different characteristics’ by Gregory Levitin [Reliability Engineering and System Safety 86 (2004) 75–81]

This paper [Levitin G. Reliability and performance analysis for fault-tolerant programs consisting of versions with different characteristics. Reliab Eng Syst Safety 2004;86:75–81] presents a detailed reliability and performance analysis of fault-tolerant programs. Unfortunately, the treatment is dependent upon a key assumption: ‘Failures of versions for each component are statistically independent…’ (Section 2). Such an assumption is not justified.     

System performance analysis of flexible flow shop with match processing constraint

Blocking makes the analytical modelling of open queuing networks with finite buffers intractable because the product-form solutions are unavailable. In this paper, about mould manufacturing, a four-stage flexible flow shop with match processing constraint is first modelled as an open queuing network with finite buffers. According to the characteristics of the matching node, the inter-arrival time distributions of parts arriving at the nodes are assumed to be exponential or general. Next, based on approximation of queuing theory, the Decomposition of State Space Method and the Generalized Expansion Method are developed for system performance evaluation. Then, experiments to assess the accuracy of the proposed methods are reported by comparing the analytical results with simulations. Finally, a case of a real-life production system of mould manufacturing is studied to show the application of the proposed methods. The results of experiments reveal that the proposed methods are feasible and effective for system performance evaluation and they can even solve large-size practical problems in a reasonable time. The results in this paper can provide a basis for system design or resource planning, to solve buffer allocation problems and capacity configuration problems.     

Reliability analysis of reinforced concrete grids with nonlinear material behavior

Reinforced concrete grids are usually used to support large floor slabs. These grids are characterized by a great number of critical cross-sections, where the overall failure is usually sudden. However, nonlinear behavior of concrete leads to the redistribution of internal forces and accurate reliability assessment becomes mandatory. This paper presents a reliability study on reinforced concrete (RC) grids based on coupling Monte Carlo simulations with the response surface techniques. This approach allows us to analyze real RC grids with large number of failure components. The response surface is used to evaluate the structural safety by using first order reliability methods. The application to simple grids shows the interest of the proposed method and the role of moment redistribution in the reliability assessment.     

Manganese waste mud immobilization in cement – natural zeolite – lime blend: Process optimization using artificial neural networks and multi‐criteria functions

In this study, stabilization/solidification process of manganese contaminated mud using portland cement was optimized. For that purpose, immobilization process was modeled applying artificial neural networks with radial basis activation function. The optimal model presented satisfactory prediction characteristics (R² value for manganese leaching was 0.9615 while and for concrete flexural strength 0.8748). Therefore, it was used in combination with seven in‐house developed multi‐criteria optimization functions, separately, in order to optimize concrete formulation. The used approach proved itself as efficient and cost effective alternative in ecological material formulation process. The best properties (i. e. high flexural strength and lowest manganese leaching) manifested stabilization/solidification matrix consisted of 350 g of portland cement, 20 g of lime, 70 g of natural zeolite, 10 g of manganese waste mud and 180 g of water.     

European patent filings in 1985–1990: National time series with comparative analysis

This article concerns patent statistics. The number of published European Patent Applications field between 1985 and 1990 is considered. It appears that, during this period, eight countries have filed 90% of the totality, while all the other nations are individually below the threshold of 1.5%. In this set of eight nations, three groups can be identified: United States of America, Japan and Federal Republic of Germany are above 6000 applications per year, France and United Kingdom between 2500 and 6000 per year, and Italy, The Netherlands and Switzerland are below 2500 applications per year. For these nations, the number of applications filed, arranged according to filing year and applicant's country, is presented by tables and graphics. National trends are considered, and a comparison is presented.     

Transient analysis of stochastic switches and trajectories with applications to gene regulatory networks

Many gene regulatory networks are modelled at the mesoscopic scale, where chemical populations change according to a discrete state (jump) Markov process. The chemical master equation (CME) for such a process is typically infinite dimensional and unlikely to be computationally tractable without reduction. The recently proposed finite state projection (FSP) technique allows for a bulk reduction of the CME while explicitly keeping track of its own approximation error. In previous work, this error has been reduced in order to obtain more accurate CME solutions for many biological examples. Here, it is shown that this dasiaerrordasia has far more significance than simply the distance between the approximate and exact solutions of the CME. In particular, the original FSP error term serves as an exact measure of the rate of first transition from one system region to another. As such, this term enables one to (i) directly determine the statistical distributions for stochastic switch rates, escape times, trajectory periods and trajectory bifurcations, and (ii) evaluate how likely it is that a system will express certain behaviours during certain intervals of time. This article also presents two systems-theory based FSP model reduction approaches that are particularly useful in such studies. The benefits of these approaches are illustrated in the analysis of the stochastic switching behaviour of Gardnerdasias genetic toggle switch.     

Reliability and failure analysis of GaAs mesfets on GaAs and Si substrates

Reliability of GaAs MESFET's on GaAs and Si was studied using high-temperature storage tests. Tested MESFETs were back etched and analysed by SEM, EDX and TEM. The major failure modes have been identified as gate sinking and an increase of ohmic contact resistance through Au particle formation.