Reliability Theory

... Suprasad V. Amari, Member, IEEE ... Notation label of component , [failure, repair] rate of component system-failure frequency “mean number of system-failures” per time-unit , Boolean variable indicating that component is [working, failed]; is the complement of , steady state ...

We present a foundational theory of software system re-liability based on components. The theory describes how component developers can design and test their components to produce measurements that are later used by system de-signers to calculate composite system reliability — ...

Key Words -Positive and complementary indexes, Mean normalized capacity, Pseudo-switching function, Map method, Reduction rule, Generalized Max-Flow Min-Cut Theorem Rcodrr Aids -Purpose: Tutorial Special math needed for explanations: Probability Special math needed to use results: Same Results useful to: Reliability and telecommunication analysts Abstract -Two recently proposed performance indexes for telecommunication networks are shown to be the s-t and overall versions of the same measure, vlz, the mean normalized network capacity. The network capacity is a pseudo-switching function of the branch successes, and hence its mean value is readily obtainable from its sum-of-products expression. Three manual techniques of conventional reliability analysis are adapted for the computation of the new performance indexes, viz, a map procedure, reduction rules, and a generalized cutset procedure. Four tutorial examples illustrate these techniques and demonstrate their computational advantages over the stateenumeration technique.

which approaches one uniformly on .H2 as n increases for any a.o. p, since H(Q) 2 2. The same procedure is used for &',, but the sequence is-+ KL.LMhk,). *-+ p(h(j,,j,))p(h(k,,k,)) * *. so that the 2" integers mapped by h" are always drawn from the same distribution (Q, or Q,). Using this encoding on the rows of the array in Fig. I, sending representations of 2" runs of zeros and 2" runs of ones from each row, and using the appropriate marker-moving algorithm gives an a.o. sequence of universal codes for SZZ~, A, and JZ'.

We present a hierarchical model for the analysis of proactive fault management in the presence of system resource leaks. At the low level of the model hierarchy is a degradation model, in which we use a nonhomogeneous Markov chain to establish an explicit connection between resource leaks and the failure rate. With the degradation model we prove that the failure rate is asymptotically constant in the absence of resource leaks and it is increasing as leaks occur and accumulate, which confirms the resource leaks as an aging source. The proactive fault management (PFM) is modeled at the higher level as a semi-Markov process. The PFM model takes as input the degradation analysis from the low-level model and allows us to determine optimal rejuvenation schedules with respect to various system measures.

This paper proposes a hierarchical modeling approach for the reliability analysis of phased-mission systems with repairable components. The components at the lower level are described by continuous time Markov chains which allow complex component failure/repair behaviors to be modeled. At the upper level, there is a combinatorial model whose structure function is represented by a binary decision diagram (BDD). Two BDD ordering strategies, and consequently two evaluation algorithms, are proposed to compute the phased-mission system (PMS) reliability based on Markov models for components, and a BDD representation of system structure function. The performance of the two evaluation algorithms is compared. One algorithm generates a smaller BDD, while the other has shorter execution time. Several examples, and experiments are presented in the paper to illustrate the application, and the advantages of our approach.

The main objective of this study is to run a complete structural reliability analysis of an existing villa, located in Lebanon. The structural components, such as slabs, beams, columns, and footings, are first analyzed independently, and the reliability index for each failure mode, is being evaluated at the component level. The structural failure modes are grouped into two categories: the

In this research, it was aimed to develop an instrument for determining problematic
internet usage of university students. Factorial structure of the data collected from
1658 university students revealed three factors. Of these, the first factor is called negative
consequences of the internet and accounted for 25.36% of the variance, the second
factor is called social benefit / social comfort and accounted for 14.62% of the variance,
and the third factor is called excessive usage and explained 8.98 % of the variance.
All three factors consisting of 33 items accounted for the 48.96% of the total
variance. It was found that the scale was able to discriminate problematic internet use
with respect to the time spent on the internet and individuals’ perception of themselves
as the internet addicts. The correlation between the scale and the Davis’s Online
Cognitive Scale-Turkish adaptation (Keser Özcan ve Buzlu, 2005) was found as
0.61. Internal consistency coefficient of the scale (α) was found to be 0.94. Item total
correlations ranged between 0.31 and 0.70 (p<.001). Test-re-test reliability coefficient
was found to be 0.81 and split half reliability coefficient was found to be 0.83. Thus,
the scale called as “the Problematic Internet Usage Scale” was developed.

The numerical integration scheme developed by Becke in 1988 is the popular choice to calculate the integrals that arise in density functional theory, DFT. Although complex, numerical integration is an essential part of a DFT code. The new features offered by Fortran 90 such as dynamic allocation, derived types, pointers, and modules were used to develop a numerical integration code that is both efficient and easy to manage. In this paper we discuss in detail our Fortran 90 numerical integration code.

Mathematical education is essential for the study of psychology, and is especially important for individuals who will engage themselves in research work in this field of social sciences. The variance and covariance are statistical concepts which are important primarily in the analysis of variance, regression analysis, calculating reliability coefficients, as well as determining the extent of variation in the raw scores of the tasks and the overall test. Psychology students often have difficulties in understanding these concepts, which can be improved by providing practical examples in the form of carefully selected problems for exercise and for testing their knowledge. In this paper, it has also been given a short discussion about statistical reasoning.

Development of an autonomous fault diagnosis and recovery system for unmanned aerial vehicles has recently attracted a lot of interest in the research community. Design of a reliable control system that can cope with faults and anomalies plays an important role in ensuring efficient performance of small aerial vehicles due to hardware redundancy limitations.

This paper is concerned with estimation of the scale and shape parameters of the Power function distribution through the use of symmetrically located percentiles from a sample. The process requires algebraic solution of two equations derived from the cumulative distribution function. Sampling behavior of the estimates is indicated by a Monte Carlo simulation. Three alternative methods of estimated distribution function are compared, for precision and variability, with maximum likelihood (M.L.E), Ridge Regression and Least squares estimators (L.S.E). The best percentile estimator (using the 5 th and 95 th ) is inferior to M.L.E in variability. The said estimator is also substandard to least square estimator in accuracy and variability to a small degree.

This paper develops the asymptotic sampling distribution of the inverse of the coefficient of variation (InvCV). This distribution is used for making statistical inference about the population CV (coefficient of variation) or InvCV without making an assumption about the population distribution. It applies to making inferences (point and interval estimation, and hypothesis-testing) about the shape parameter of some popular lifetime distributions like the Gamma, Weibull, and log-normal, when the scale parameter is unknown. The test procedure is used to test exponentiality against a Gamma or a Weibull alternative. The results are compared with those in the literature

The computational work and the time required to decode with reliability E at code rate R on noisy channels are defined, and hounds on the size of these measures are developed. A number of ad hoc decoding procedures are ranked on the basis of the computational work they require.

In this article results of researches of strategies of maintenances of fault-tolerant informative systems are described. A design process is carried out on the basis of original approach. This approach is realized on application of structurally - automatics models for construction of Markov models.

Improvement factors in hazard rate and age for a sequential preventative maintenance (PM) policy are introduced. Two imperfect PM models are analyzed: (1) PM reduces the hazard rate while it increases with the number of PMs, and (2) PM reduces the age. The PM is done at intervals xk (k=1,2, . . . , N) and is imperfect. The optimal

A National Aeronautics and Space Administration (NASA) supported Reliability, Maintainability, and Availability (RMA) analysis team developed a RMA analysis me thodology that uses cut set and importance measure analyses to compare model proposed avionics computing architectures. In this paper we will present an effective and efficient application of the RMA analysis methodology for importance measures that includes Reliability Block Diagram (RBD) Analysis, Comparison modeling, Cut Set Analysis, and Importance Measure Analysis. In addition, we will also demonstrate that integrating RMA early in the system design process is a key and fundamental decision metric that supports design selection. The RMA analysis methodology presented in this paper and applied to the avionics architectures enhances the usual way of predicting the need for redundancy based on failure rat es or subject matter expert opinion. Typically, RBDs and minimal cut sets along with the Fussell-Vesely (FV) method is used to calculate importance measures are calculated for each functional element in the architecture [1]. This paper presents an application of the FV importance measures and presents it as a methodology for using importance measures in success space to compare architectures. These importance measures are used to identify which functional element is most likely to cause a system failure, thus, quickly identifying the path to increase the overall system reliability by either procuring more reliable functional elements or adding redundancy [2]. This methodology that used RBD analysis, cut set analysis, and the FV importance measures allowed the avionics design team to better understand and compare the vulnerabilities in each scenario of the architectures. It also enabled the design team to address the deficiencies in the design architectures more efficiently, while balancing the need to design for optimum weight and space allocations.

The reliability index ß is a parameter used to estimate the safety of a structure or an element during the design stage or service. This parameter defined in other codes in the world (European Committee for Standardisation (Eurocode), EN 1990:2002; American Association of State Highway and Transportation Officials (AASHTO), 2012), is not specified in the Colombian Code of Bridges Seismic Design (CCDSP-95) (1995). In this paper, it will be presented a study on the estimation of the reliability index ß of the interior and exterior girders of a beam and slab bridge with reinforced concrete, 30 m in length, simply supported and designed according to the CCDSP-95. In the evaluation of the resistant moments, there were considered properties of materials using a normal distribution, and moreover, a Monte Carlo simulation was used to estimate load effect of moment at mid-span of the live load.

A sequence of n microwave stations transmit information spaced between places A and B. Each microwave station is able to transmit information a distance up to k microwave stations. General purpose: Widen state of art This system fails iff at least k consecutive microwave stations Special math needed for explanations: Theoretical statistics fail. 4 Special math needed to use results: Statistics Results useful to: Reliability theoreticians, statisticians Key Words -Series system, Consecutive-k-out-of-n:F system, Linearly connected system, Cut, Path, Poisson convergence from place A to place B. The microwave stations are Reader Aids -Example 2 Abstract -The consecutive-k-out-of-n:F & related systems have caught the attention of many researchers since the early 1980s. The studies of these systems lead to better understanding of the reliability of general series systems, in computation & structure.

In this paper the improvement of method of automated building of state space models of complex technical systems for critical application was proposed. On the basis of the developed model with the split state of critical failure the reliability and safety indexes of studied system can be obtained. Developed approach allows to estimate of reliability and safety indexes, that makes the impact of maintenance strategies on safety and reliability, impact of the fault tolerance on safety to be considered. This will increase the accuracy (certainty) of efficiency indexes estimation of complex technical systems for critical application.

Estimators of the reliability function in a GLM (generalized life model) are considered. The class of the GLM includes (among others) the Weibull, Pareto, Beta, Gompertz, and Rayleigh distribution. A proper general prior density and the predictive function for general class of distribution proposed by Al-Hussaini [1] are used to obtain the exact estimate. Also, the Bayes estimates relative to symmetric loss function (quadratic loss), and asymmetric loss function (LINEX loss, and GE loss), are obtained. Comparisons are made between those estimators and the MLE applying to the Burr-XII model using the Bayes approximation due to Lindley. Monte Carlo simulation was used.

Majority voted redundant systems are widely used. A re-(N = 2n + 1, N > 1). liability model is developed and analyzed for N-tuple Modular Redun-n Degree of active redundancy, N = 2n + 1 in dancy-NMR: (n + I)-out-of-2n + 1)-where the units are subject to majority logic; (n > 0). stuck-at-0, stuck-at-1 or stuck-at-X failures and where failures can occur T Mission time; (T> 0). in a mutually compensatory manner. A reconfiguration of the NMR mmyvles (T O). redundancy, the NMR/Simplex strategy, is proposed and evaluated and t or z Dummy variables for time; (0. t, z S 1)

The aim of the current study was to develop a short form of Coping Styles Scale based on COPE
Inventory. A total of 275 undergraduate students (114 female, and 74 male) were administered in
the first study. In order to test factors structure of Coping Styles Scale Brief Form, principal components
factor analysis and direct oblique rotation was used. Factor analysis Results indicated
that Coping Styles Scale Brief Form had 14 factors with two items. All factors explained 80.37% of
the variance in the scale. In order to test concurrent validity of CSS-BF, the relationship between
coping styles, social desirability, self-esteem, life satisfaction and A type personality were examined.
Cronbach’s alfa coefficient of subscales ranged from 0.39 (Restraint Coping) to 0.92 (Humor)
and test re-tests (two weeks interval) coefficients were ranged from .44 (Restraint Coping) to .90
(Religion).

Mathematical optimization provides a formal framework that enables systematic and transparent decision making. Significant progress has been made in recent years in applications of formal optimization techniques for competitive market based resource commitment, scheduling, pricing and dispatch. This paper describes experiences with the application of optimization technology for electricity market operation. Experiences with and the status of the latest development in the security-constrained unit commitment and economic dispatch algorithms are described with references to actual market practices. key words-Electricity market operation, optimal power flow, security-constrained unit commitment and economic dispatch, locational marginal pricing, formal optimization.

Since the late 90's IP telephony, commonly referred to as Voice over IP (VoIP), has been presented as a revolution on communications enabling the possibility to converge historically separated voice and data networks, reducing costs, and integrating voice, data and video on applications. This paper presents a study over the standard VoIP protocols H.323, session initiation protocol (SIP), media gateway control protocol (MGCP), and H.248/Megaco. Given the fact that H.323 and SIP are more widespread than the others, we focus our study on them. For each of these protocols we describe and discuss its main capabilities, architecture, stack protocol, and characteristics. We also briefly point their technical limitations. Furthermore, we present the advanced multimedia system (AMS) project, a new system that aims to operate on Next Generation Networks (NGN) taking the advantage of its features, and it is viewed as the successor to H.323 and SIP.

This paper presents a methodology for the design of reliable control systems by using multiple identical controllers to a given plant. The resulting closed-loop control system is reliable in the sense that it provides guaranteed internal stability and H 1 performance (in terms of disturbance attenuation), not only when all controllers are operational but also when some controller outages (sensor and/or actuator) occur. A numerical example is given to illustrate the proposed design procedures.

This paper examines the theoretical and practical role of testing in software development. We prove a fundamental theorem showing that properly structured tests are capable of demonstrating the absence of errors in a program. The theoremts proof hinges on our definition of test reliability and validity, but its practical utility hinges on being able to show when a test is ac-tuaUy reliable.

The commenter maintains that an expression in the above-mentioned paper (ibid., vol.R-31, p.194-7, June 1982) on which the results are based is wrong, and therefore the results are wrong. The author rebuts the commenter&amp;amp;amp;#39;s argument point by point

probability that at least one path exists between the two nodes Ugo G. Montanari in the worst conditions. This is a good measure of the grade of service given to the unluckiest pair of users. Any pair of nodes in the network has, on the average, a viable connection for a Abstract-In order to design an available network efficiently, a fraction of time not smaller than TA. Even if the existing parameter characterizing the network availability is needed. The global methods [10-24] for computing TA have an exponential or availability is suggested and algorithms are given for its exact or approx-f c ( ..

& Conclusions -This paper generalizes 2-state (binary-state) reliability parameters 'It@), fit), A@), and mean-timeto-failure' to multi-state reliability parameters 'R(t,z), G(t,z), X(t,f), mean-life-span-at-specified-performance-level(z), for each state'. By using these generalized reliability parameters, multi-state reliability dynamic analysis can be transformed to a set of 2-state reliability dynamic analyses. Then, we extend some theoretical results in 2-state reliability analysis to the multi-state case. Measures for evaluating performance degradation of multi-state system are developed. By combining Markov processes and s-coherent multistate system structure functions, the dynamic multi-state reliability can be analyzed, Several examples are given.

ABSTRACT A generalized notion of source divisibility or in other words successive refinement of information with an additional requirement of exponential decrease of error probability is considered. A necessary and sufficient condition for the possibility of such successive refinement is established

Moore & Shannon's theorem is the cornerstone in reliability theory, but cannot be applied to human systems in its original form. A generalization to human systems would therefore be of considerable interest because the choice of organization structure can remedy reliability problems that notoriously plaque business operations, financial institutions, military intelligence and other human activities. Our main result is a proof that provides answers to the following three questions. Is it possible to design a reliable social organization from fallible human individuals? How many fallible human agents are required to build an economic system of a certain level of reliability? What is the best way to design an organization of two or more agents in order to minimize error? On the basis of constructive proofs, this paper provides answers to these questions and thus offers a method to analyze any form of decision making structure with respect to its reliability.

In this paper, based on the switching cell approach, a unified steady state analysis for families of soft-switching dc-dc converters with complete unified design equations will be presented. The concept of the unified approach and step by step procedure for a generalized process are discussed and applied to selected soft-switching families such as zero-voltage-switching (ZVS) and zero-current-switching (ZCS)-quasi-resonant converter families, ZVS-clamped voltage quasi-square-wave (QSW) family, ZCS-clamped-current (CC) QSW family, and zero-voltagetransition and zero-current-transition pulse-width modulation families. Also, it has been noted that all the analyzed families have one generalized transformation table. The basic unified equations will be summarized and the cell-to-cell comparison will be introduced. It will be shown that the unified analysis leads to several advantages such as improving the computer-aided analysis and design, simplified mathematical modeling, and giving more insight into the converter-cell operation. . His power electronics research focuses on the development of high frequency power converters to improve power density, power factor, efficiency, and performance. The research includes the analysis and design of high frequency dc-to-dc resonant converter topologies, low-voltage dc-dc converters, small signal modeling and control of PWM and resonant converters, power factor correction techniques, and power electronic circuits for distributed power systems applications.

This paper deals with the relationship between system design, reliability and dependent failure. A hierarchical multi-level system model is developed to characterize system design mapping from the functional domain to the physical domain. Based on this modeling framework, the reliability and cost of reliability are linked to system functions, design structures and dependent failures. The evaluation method for analyzing product system designs from a reliability perspective is proposed.