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Reliability, IEEE Transactions on

Issue 4 • Date Dec. 2014

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Displaying Results 1 - 16 of 16
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Reliability publication information

    Page(s): C2
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  • A Value-Based Assessment Method of the Supportability for a New Aircraft Entering Into Service

    Page(s): 817 - 829
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1456 KB) |  | HTML iconHTML  

    This article starts from an airframer's need to quantitatively assess supportability (logistic support) strategies for the entry-into-service of a new aircraft type. Entries-into-service are often characterized by low maturity and early life failures, for which conventional reliability metrics are not useful. The objective of our project was to develop and implement a value-based assessment method of the supportability for a new aircraft entering into service by exploring the relation between the logistic support resources, the fleet's availability, and the cost. This article applies the general trade-off framework of the Value Operations Methodology, a value engineering method aimed at facilitating decision making. Value in this context represents supportability effectiveness, and describes what is important to a stakeholder during decision making. Based on interviews and literature, Value is found to be determined by both the fleet's availability and the total cost of logistic support. The average stakeholder's preferences indicate a slight preference for maximizing a fleet's availability. To implement the required availability and cost models, data analyses, a survey amongst operators and suppliers, the design of a stochastic fleet simulation, as well as the creation of General Linear Models have been conducted. Three component types are investigated: engine major units, line replaceable units with a NO GO dispatch condition (inoperable), and line replaceable units with a GO IF (operable under certain conditions) dispatch condition. The logistic elements of spare provisioning level and repair capacity are found to be mutually significant. Also, the number of airline operators to be supported is classified as significant, except for components with a GO IF dispatch condition. The final result is a simple assessment tool, able to provide a quick assessment of supportability strategies, implemented at, and accepted by our industrial partner. View full abstract»

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  • Automating the Assembly of Aviation Safety Cases

    Page(s): 830 - 849
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2147 KB) |  | HTML iconHTML  

    Safety cases are among the state of the art in safety management mechanisms, providing an explicit way to reason about system and software safety. The intent is to provide convincing, valid, comprehensive assurance that a system is acceptably safe for a given application in a defined operating environment, by creating an argument structure that links claims about safety to a body of evidence. However, their construction is a largely manual, and therefore a time consuming, error prone, and expensive process. We present a methodology for automatically assembling safety cases which are auto-generated from the application of a formal method to software, with manually created safety cases derived from system safety analysis. Our approach emphasizes the heterogeneity of safety-relevant information, and we show how diverse content can be integrated into a single argument structure. To illustrate our methodology, we have applied it to the Swift Unmanned Aircraft System (UAS) being developed at the NASA Ames Research Center. We present an end-to-end fragment of the resulting interim safety case comprising an aircraft-level argument manually constructed from the safety analysis of the Swift UAS, which is automatically assembled with an auto-generated lower-level argument produced from a formal proof of correctness of the safety-relevant properties of the software autopilot. View full abstract»

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  • Sharp Bounds for Lifetime Variances of Reliability Systems With Exchangeable Components

    Page(s): 850 - 857
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1919 KB) |  | HTML iconHTML  

    We consider coherent and mixed systems with exchangeable components whose lifetimes have positive and finite variances. We present sharp lower and upper bounds on the variance of the system lifetime, expressed in terms of the system signature and the variance of a single component. The bounds are attained for the power and Pareto distributions of the component lifetimes. View full abstract»

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  • The Distribution of Time to Recovery of Enterprise IT Services

    Page(s): 858 - 867
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    The context of this article is the availability of enterprise IT services, a key concern for many enterprises. While there is a plethora of literature concerned with service availability, there is no previous systematic empirical study on IT service time to recovery following outages. The existing literature typically assumes a distribution, or builds on analogies to related areas such as software engineering. Therefore, our objective is to find the statistical distribution of IT service time to recovery. Method-wise, this investigation is based on logs of more than 1800 incidents in a large Nordic bank, corresponding to more than 11000 hours of recorded downtime. Five possible distributions of time to recovery from the literature were investigated using the Akaike Information Criterion to find the distribution offering the best fit. The results show that the log-normal distribution outperformed the others for all tested service channels (collections of IT services). It is concluded that the log-normal distribution offers the best fit of IT service time to recovery. Using this distribution in simulation and decision-support tools offers the prospect of better predictions of downtime and downtime costs to the practitioner community. View full abstract»

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  • Optimal Replacement Last With Continuous and Discrete Policies

    Page(s): 868 - 880
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3751 KB) |  | HTML iconHTML  

    This paper proposes age and periodic replacement last models with continuous, and discrete policies. That is, an operating unit is replaced preventively at time T of operation as a strategic policy, or at a number N of working cycles to satisfy successive job completion, whichever occurs last. Such policies are named as replacement last, and their expected cost rates and optimal policies are obtained. However, the focus of this paper is to compare replacement last with replacement first policies, which are formulated under the classical assumption of whichever occurs first. From the points of cost and performability, different comparative methods for continuous and discrete optimizations are demonstrated to determine in what cases we should adopt replacement last rather than replacement first. All theoretical discussions in this paper are made analytically, and are computed numerically. View full abstract»

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  • Maintaining Partially Observed Systems With Imperfect Observation and Resource Constraint

    Page(s): 881 - 890
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3047 KB) |  | HTML iconHTML  

    The problem of finding the optimal maintenance policy for partially observed systems is considered, where only a limited number of maintenance actions can be performed. The maintenance is assumed to be imperfect in that the system can be only restored to a less deteriorated level rather than to a state as good as new. In addition, the true deterioration state is known just after each replacement action, but the deterioration state at other instants during the system's operation cannot be observed, evolving as a discrete-time Markov chain with a finite state space. In this paper, the described problem can be formulated as a partially observed Markov decision process (POMDP) over the infinite time horizon. To increase the computational efficiency, several key structural properties are developed through minimizing the total expected cost per unit time. The existence of the optimal threshold-type maintenance policy is strictly proved, and the monotonicity of the threshold is obtained. The effectiveness of the optimal policy can be verified by a numerical example. View full abstract»

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  • Semi-Markov Decision Process With Partial Information for Maintenance Decisions

    Page(s): 891 - 898
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (947 KB) |  | HTML iconHTML  

    A critical factor that prevents optimal scheduling of maintenance interventions is the uncertainty regarding the current condition of the asset under consideration, as well as the rate at which deterioration takes place. However, current maintenance modeling and optimization techniques assume that the condition of the asset is either known, or assumed to have an exponential deterioration rate. In this paper, we present a novel approach to maintenance modeling that removes such assumptions. Here, we employ a Partially Observable Semi-Markov Decision Process (POSMDP) for optimizing maintenance decisions, where the condition of the asset is not fully observable, and decision epochs occur at times following any other type of distribution. This method enables a more realistic way of modeling asset deterioration and optimizing maintenance schedules. View full abstract»

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  • Repairable Systems With Dependent Components: Stochastic Process Techniques and Models

    Page(s): 899 - 912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2847 KB) |  | HTML iconHTML  

    We consider three approaches to the modeling of systems with repairable components by a multivariate stochastic on-off process. First, we discuss the Palm calculus framework for stationary processes and its power in the derivation of general formulae for joint downtime statistics in the case of statistically independent components. Second, a class of Generalized Semi-Markov (GSMP) models is proposed for incorporating both arbitrary component downtime distributions and statistical dependence of component failures. The case of two components is studied in detail. Third, we define the property referred to as weakened-by-failures for a system of repairable components, and prove that it implies association under fairly general conditions. We also give sufficient conditions for our GSMP models to possess this property. View full abstract»

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  • Achievements and Challenges in State-of-the-Art Software Traceability Between Test and Code Artifacts

    Page(s): 913 - 926
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (722 KB) |  | HTML iconHTML  

    Testing is a key activity of software development and maintenance that determines the level of reliability. Traceability is the ability to describe and follow the life of software artifacts, and has been promoted as a means for supporting various activities, most importantly testing. Traceability information facilitates the testing and debugging of complex software by modeling the dependencies between code and tests. Actively supplementing traceability to testing enables rectifying defects more reliably and efficiently. Despite its importance, the development of test-to-code traceability has not been sufficiently addressed in the literature, and even worse there is currently no organized review of traceability studies in this field. In this work, we have investigated the main conferences, workshops, and journals of the requirements engineering, testing, and reliability, and identified those contributions that refer to traceability topics. From that starting point, we characterized and analyzed the chosen contributions against three research questions by utilizing a comparative framework including nine criteria. As a result, our study arrives to some interesting points, and outlines a number of potential research directions. This, in turn, can pave the way for facilitating and empowering traceability research in this domain to assist software engineers and testers in test management. View full abstract»

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  • An Automatic Framework for Detecting and Characterizing Performance Degradation of Software Systems

    Page(s): 927 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3075 KB) |  | HTML iconHTML  

    Software systems that run continuously over a long time have been frequently reported encountering gradual degradation issues. That is, as time progresses, software tends to exhibit degraded performance, deflated service capacity, or deteriorated QoS. Currently, the state-of-the-art approach of Mann-Kendall Test & Seasonal Kendall Test & Sen's Slope Estimator & Seasonal Sen's Slope Estimator (MKSK) detects and characterizes degradation via a combination of techniques in statistical trend analysis. Nevertheless, we pinpoint some drawbacks of MKSK in this paper: 1) MKSK cannot be automated for large scale software degradation analysis, 2) MKSK estimates the degradation trend of software in an oversimplified linear way, 3) MKSK is sensitive to noise, and 4) MKSK suffers from high computational complexity. To overcome all these limitations, we propose a more advanced approach called Modified Cox-Stuart Test & Iterative Hodrick-Prescott Filter (CSHP). The superiority of our CSHP approach over MKSK is validated through extensive Monte Carlo simulations, as well as a real performance dataset measured from 99 real-world web servers. View full abstract»

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  • Best Constant-Stress Accelerated Life-Test Plans With Multiple Stress Factors for One-Shot Device Testing Under a Weibull Distribution

    Page(s): 944 - 952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1805 KB) |  | HTML iconHTML  

    We discuss here the design of constant-stress accelerated life-tests for one-shot device testing by assuming a Weibull distribution as a lifetime model. Because there are no explicit expressions for the maximum likelihood estimators of the model parameters and their variances, we adopt the asymptotic approach here to develop an algorithm for the determination of optimal allocation of devices, inspection frequency, and the number of inspections at each stress level, by assuming a Weibull distribution with non-constant scale and shape parameters as the lifetime distribution. The asymptotic variance of the estimate of reliability of the device at a specified mission time is minimized subject to a pre-fixed experimental budget, and a termination time. Examples are provided to illustrate the proposed algorithm for the determination of the best test plan. A sensitivity analysis of the best test plan is also carried out to examine the effect of misspecification of the model parameters. View full abstract»

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  • 2014 Index IEEE Transactions on Reliability Vol. 63

    Page(s): 953 - 962
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    Freely Available from IEEE
  • IEEE Transactions on Reliability institutional listings

    Page(s): C3
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  • IEEE Transactions on Reliability institutional listings

    Page(s): C4
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Aims & Scope

IEEE Transactions on Reliability is concerned with the problems involved in attaining reliability, maintaining it through the life of the system or device, and measuring it.

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Meet Our Editors

Editor-in-Chief
Way Kuo
City University of Hong Kong