A generalized formulation for the performability indicator

Platis, Agapios Ν.

doi:10.1016/j.camwa.2005.11.009

Cited by 32 publications

(13 citation statements)

References 17 publications

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“…Then the random variable Z T k ð Þ ¼ r CS T k ð Þ refers to the instantaneous reward rate of the girder at time T k [46]. The expected instantaneous reward rate and the variance of the instantaneous reward rate are given by [46,47]:…”

Section: Performabilitymentioning

confidence: 99%

Performance evaluation of corrosion-affected reinforced concrete bridge girders using Markov chains with fuzzy states

Anoop

Rao

2016

Sādhanā

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A methodology for performance evaluation of reinforced concrete bridge girders in corrosive environments is proposed. The methodology uses the concept of performability and considers both serviceability-and ultimate-limit states. The serviceability limit states are defined based on the degree of cracking (characterized by crack width) in the girder due to chloride induced corrosion of reinforcement, and the ultimate limit states are defined based on the flexural load carrying capacity of the girder (characterized in terms of rating factor using the load and resistance factor rating method). The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states. Generally, the classification of condition states is linguistic, while the condition states are considered to be mutually exclusive and collectively exhaustive. In the present study, the condition states of the bridge girder are also represented by fuzzy sets to consider the ambiguities arising due to the linguistic classification of condition states. A non-homogeneous Markov chain (MC) model is used for modeling the condition state evolution of the bridge girder with time. The usefulness of the proposed methodology is demonstrated through a case study of a severely distressed beam of the Rocky Point Viaduct. The results obtained using the proposed approach are compared with those obtained using conventional MC model. It is noted that the use of MC with fuzzy states leads to conservative decision making for the problem considered in the case study.

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Section: Performabilitymentioning

confidence: 99%

Performance evaluation of corrosion-affected reinforced concrete bridge girders using Markov chains with fuzzy states

Anoop

Rao

2016

Sādhanā

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“…We are interested in the total expected cost and hence the first moment of the performability indicator is given by the following equation (see , and the Appendix B for details) As the server runs continuously for a long period of time, the performability indicator (see Appendix) has to be computed in the long run () where s = 0 stands for the high traffic period and s = 1 for the low traffic period, respectively.…”

Section: Performability Indicatorsmentioning

confidence: 99%

“…We are interested in the total expected cost and hence the first moment of the performability indicator is given by the following equation (see [27,30], and the Appendix B for details)…”

Section: Performability Indicatorsmentioning

confidence: 99%

Software rejuvenation and resource reservation policies for optimizing server resource availability using cyclic nonhomogeneous Markov chains

Koutras

Platis

Gravvanis

2012

Appl Stoch Models Bus & Ind

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Software rejuvenation is modeled in a client–server system, which provides resources to priority classes of users. To assure availability, resource reservation policies are adopted for the higher priority classes. In addition software rejuvenation is proposed to optimize resource availability. The system is modeled by a cyclic nonhomogeneous Markov chain to capture the variation of the arrival and service rates during a day period. An optimization problem is solved based on a similar previous work and given the optimal resource reservation policy obtained by its solution, rejuvenation is performed and the optimal rejuvenation policy is determined. As a measure of resource availability the blocking probability of each priority class is used. Performability indicators expressing the total cost are also derived, with respect to the optimal resource reservation and optimal rejuvenation policies, to examine whether rejuvenation benefits the system in terms of cost. To derive the blocking probabilities, the limiting probability distribution is computed using explicit generalized approximate inverse preconditioning for solving efficiently sparse linear systems of algebraic equations. Copyright © 2012 John Wiley & Sons, Ltd.

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“…X(t) is a Homogeneous Continuous Time Markov Chain (HCTMC). The steady-state probability vector of the Markov chain is the solution of the linear system[20],…”

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confidence: 99%

Applying Software Rejuvenation in a Two Node Cluster System for High Availabilit

Koutras

Platis

2006

2006 International Conference on Dependability of Computer Systems

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In order to achieve high availability the idea of cluster systems has been commonly used. In this paper a two node cluster system is considered in which software and hardware failures occur. Hardware failures are permanent and hence they are counteracted by a repair or replacement. On the other side, software failures require a reboot. A reboot though is a reactive action that can be taken when software failures due to degradation are observed. Software rejuvenation, a proactive kind of maintenance, is used to counteract software degradation called "software aging". In the cluster system presented, software rejuvenation is performed when the node's software experiences degradation in order to avoid an unscheduled reboot. The system is modeled under Continuous Time Markov Chains (CTMC). Two different clustering techniques are studied and compared in order to determine the best configuration which provides the highest level of availability.

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A generalized formulation for the performability indicator

Cited by 32 publications

References 17 publications

Performance evaluation of corrosion-affected reinforced concrete bridge girders using Markov chains with fuzzy states

Performance evaluation of corrosion-affected reinforced concrete bridge girders using Markov chains with fuzzy states

Software rejuvenation and resource reservation policies for optimizing server resource availability using cyclic nonhomogeneous Markov chains

Applying Software Rejuvenation in a Two Node Cluster System for High Availabilit

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