scholarly journals Reliability Analysis of Random Fuzzy Unrepairable Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Ying Liu ◽  
Xiaozhong Li ◽  
Jianbin Li
Keyword(s):  
Mathematical Models ◽  
Parallel Systems ◽  
Time To Failure ◽  
Numerical Examples ◽  
Fuzzy Variables ◽  
Cold Standby ◽  
Random Fuzzy Variables ◽  
Lamp System ◽  
Series Systems ◽  
Mean Time

The lifetimes of components in unrepairable systems are considered as random fuzzy variables since randomness and fuzziness are often merged with each other. Then we establish the fundamental mathematical models of random fuzzy unrepairable systems, including series systems, parallel systems, series-parallel systems, parallel-series systems, and cold standby systems with absolutely reliable conversion switches. Furthermore, the expressions of reliability and mean time to failure (MTTF) are given for the above five random fuzzy unrepairable systems, respectively. Finally, numerical examples are given to show the application in a lighting lamp system and a hi-fi system.

scholarly journals The Optimal System for Complex Series-Parallel Systems with Cold Standby Units: A Comparative Analysis Approach

2021 ◽  
Author(s):  
Ibrahim Yusuf ◽  
Ismail Muhammad Musa
Keyword(s):  
Parallel Systems ◽  
Optimal Configuration ◽  
Profit Function ◽  
Time To Failure ◽  
Mean Time To Failure ◽  
Reliability Models ◽  
System Parameters ◽  
Cost Benefits ◽  
Cold Standby ◽  
Mean Time

The purpose of this research is to propose three reliability models (configurations) with standby units and to study the optimum configuration between configurations analytically and numerically. The chapter considered the need for 60 MW generators in three different configurations. Configuration 1 has four 15 MW primary units, two 15 MW cold standby units and one 30 MW cold standby unit; Configuration 2 has three 20 MW primary units, three 20 cold standby units; Configuration 3 has two 30 MW primary units and three 30 MW cold standby units. Some reliability features of series–parallel systems under minor and complete failure were studied and contrasted by the current. Failure and repair time of all units is assumed to be exponentially distributed. Explanatory expressions for system characteristics such as system availability, mean time to failure (MTTF), profit function and cost benefits for all configurations have been obtained and validated by performing numerical experiments. Analysis of the effect of different system parameters on the function of profit and availability has been carried out. Analytical comparisons presented in terms of availability, mean time to failure, profit function and cost benefits have shown that configuration 3 is the optimal configuration. This is supported by numerical examples in contrast to some studies where the optimal configuration of the system is not uniform as it depends on some system parameters. Graphs and sensitivity analysis presented reveal the analytical results and accomplish that Configuration 3 is the optimal in terms of design, reliability physiognomies such as availability of the system, mean time to failure, profit and cost benefit. The study is beneficial to engineers, system designers, reliability personnel, maintenance managers, etc.

Reliability optimization for non-repairable series-parallel systems with a choice of redundancy strategies and heterogeneous components: Erlang time-to-failure distribution

2020 ◽  
pp. 1748006X2095257
Author(s):  
Meisam Sadeghi ◽  
Emad Roghanian ◽  
Hamid Shahriari ◽  
Hassan Sadeghi
Keyword(s):  
Lower Bound ◽  
Closed Form ◽  
System Reliability ◽  
Parallel Systems ◽  
Closed Form Expression ◽  
Erlang Distribution ◽  
Time To Failure ◽  
Form Expression ◽  
Integrodifference Equation ◽  
Cold Standby

The redundancy allocation problem (RAP) of non-repairable series-parallel systems considering cold standby components and imperfect switching mechanism has been traditionally formulated with the objective of maximizing a lower bound on system reliability instead of exact system reliability. This objective function has been considered due to the difficulty of determining a closed-form expression for the system reliability equation. But, the solution that maximizes the lower bound for system reliability does not necessarily maximize exact system reliability and thus, the obtained system reliability may be far from the optimal reliability. This article attempts to overcome the mentioned drawback. Under the assumption that component time-to-failure is distributed according to an Erlang distribution and switch time-to-failure is exponentially distributed, a closed-form expression for the subsystem cold standby reliability equation is derived by solving an integrodifference equation. A semi-analytical expression is also derived for the reliability equation of a subsystem with mixed redundancy strategy. The accuracy and the correctness of the derived equations are validated analytically. Using these equations, the RAP of non-repairable series-parallel systems with a choice of redundancy strategies is formulated. The proposed mathematical model maximizes exact system reliability at mission time given system design constraints. Unlike most of the previous formulations, the possibility of using heterogeneous components in each subsystem is provided so that the active components can be of one type and the standby ones of the other. The results of an illustrative example demonstrate the high performance of the proposed model in determining optimal design configuration and increasing system reliability.

scholarly journals Portfolio Selection Based on Distance between Fuzzy Variables

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Weiyi Qian ◽  
Mingqiang Yin
Keyword(s):  
Mathematical Models ◽  
Portfolio Selection ◽  
Expected Value ◽  
Simple Method ◽  
Numerical Examples ◽  
Fuzzy Variables ◽  
Fuzzy Environment ◽  
Investment Return ◽  
New Models ◽  
Different Types

This paper researches portfolio selection problem in fuzzy environment. We introduce a new simple method in which the distance between fuzzy variables is used to measure the divergence of fuzzy investment return from a prior one. Firstly, two new mathematical models are proposed by expressing divergence as distance, investment return as expected value, and risk as variance and semivariance, respectively. Secondly, the crisp forms of the new models are also provided for different types of fuzzy variables. Finally, several numerical examples are given to illustrate the effectiveness of the proposed approach.

scholarly journals A Holistic Solution for Reliability of 3D Parallel Systems

2022 ◽  
Vol 18 (1) ◽  
pp. 1-27
Author(s):  
Javad Bagherzadeh ◽  
Aporva Amarnath ◽  
Jielun Tan ◽  
Subhankar Pal ◽  
Ronald G. Dreslinski
Keyword(s):  
Performance Improvement ◽  
Parallel Systems ◽  
Time To Failure ◽  
High Failure Rate ◽  
Core System ◽  
Holistic View ◽  
Reliability Management ◽  
Promising Solution ◽  
Detection And Diagnosis ◽  
Mean Time

Monolithic 3D technology is emerging as a promising solution that can bring massive opportunities, but the gains can be hindered due to the reliability issues exaggerated by high temperature. Conventional reliability solutions focus on one specific feature and assume that the other required features would be provided by different solutions. Hence, this assumption has resulted in solutions that are proposed in isolation of each other and fail to consider the overall compatibility and the implied overheads of multiple isolated solutions for one system. This article proposes a holistic reliability management engine, R2D3, for post-Moore’s M3D parallel systems that have low yield and high failure rate. The proposed engine, comprising a controller, reconfigurable crossbars, and detection circuitry, provides concurrent single-replay detection and diagnosis, fault-mitigating repair, and aging-aware lifetime management at runtime. This holistic view enables us to create a solution that is highly effective while achieving a low overhead. Our solution achieves 96% coverage of defect; reduces V th degradation by 53%, leading to a 78% performance improvement on average over 8 years for an eight-core system; and ultimately yields a 2.16× longer mean-time-to-failure (MTTF) while incurring an overhead of 7.4% in area, 6.5% in power, and an 8.2% decrease in frequency.

scholarly journals Availability of periodically inspected systems with Markovian wear and shocks

2006 ◽  
Vol 43 (02) ◽  
pp. 303-317 ◽  
Author(s):  
Jeffrey P. Kharoufeh ◽  
Daniel E. Finkelstein ◽  
Dustin G. Mixon
Keyword(s):  
Markov Chain ◽  
Continuous Time ◽  
Lifetime Distribution ◽  
Time To Failure ◽  
Continuous Time Markov Chain ◽  
Mean Time To Failure ◽  
Numerical Examples ◽  
Shock Process ◽  
Hidden Failures ◽  
Mean Time

We analyze a periodically inspected system with hidden failures in which the rate of wear is modulated by a continuous-time Markov chain and additional damage is induced by a Poisson shock process. We explicitly derive the system's lifetime distribution and mean time to failure, as well as the limiting average availability. The main results are illustrated in two numerical examples.

scholarly journals Interval Availability Distribution for A 1-out-of-2 Reliability System with Repair

1987 ◽  
Vol 1 (2) ◽  
pp. 211-223 ◽  
Author(s):  
M. C. van der Heijden
Keyword(s):  
Approximate Method ◽  
Time To Failure ◽  
Numerical Investigations ◽  
Satisfactory Performance ◽  
Time Period ◽  
Alternating Renewal Process ◽  
Cold Standby ◽  
The Mean ◽  
Mean Time ◽  
Operating Unit

This paper deals with a two-unit reliability model having one operating unit and one cold standby unit and with ample repair facilities. An approximate method is given for the calculation of the probability distribution of the proportion of time that the system is available in a given time period. The approximate method first computes the mean-time-to-failure and the meantime-to-repair and next approximates the up-and-down process of the two-unit reliability system by an alternating renewal process having exponentially distributed on and off periods. Numerical investigations show a satisfactory performance of the approximation. Also, a sensitivity analysis is given.

scholarly journals Availability of periodically inspected systems with Markovian wear and shocks

2006 ◽  
Vol 43 (2) ◽  
pp. 303-317 ◽  
Author(s):  
Jeffrey P. Kharoufeh ◽  
Daniel E. Finkelstein ◽  
Dustin G. Mixon
Keyword(s):  
Markov Chain ◽  
Continuous Time ◽  
Lifetime Distribution ◽  
Time To Failure ◽  
Continuous Time Markov Chain ◽  
Mean Time To Failure ◽  
Numerical Examples ◽  
Shock Process ◽  
Hidden Failures ◽  
Mean Time

We analyze a periodically inspected system with hidden failures in which the rate of wear is modulated by a continuous-time Markov chain and additional damage is induced by a Poisson shock process. We explicitly derive the system's lifetime distribution and mean time to failure, as well as the limiting average availability. The main results are illustrated in two numerical examples.

Reliability Analysis of Cold Standby Parallel System Possessing Failure And Repair Rate Under Geometric Distribution

2019 ◽  
Vol 13 ◽  
Author(s):  
Jasdev Bhatti ◽  
Mohit Kumar Kakkar
Keyword(s):  
Failure Rate ◽  
Geometric Distribution ◽  
Discrete Distribution ◽  
Maintenance Cost ◽  
Discrete Problem ◽  
New Techniques ◽  
Testing Strategies ◽  
Cold Standby ◽  
Mean Time ◽  
Iteration Technique

Background and Aim: With an increase in demands about reliability of industrial machines following continuous or discrete distribution, the important thing to be noticed is that in all previous researches where systems are having more than one failure no iteration technique has been studied to separate the failed unit on basis of its failure. Therefore, aim of our paper is to analyze the real industrial discrete problem following cold standby units arranged in parallel manner with newly concept of inspection procedure for failed units to inspect the exact failure and being communicator to the repairman for repairing exact failed part of unit for saving time and maintenance cost. Methods: The geometric distribution and regenerative techniques had been applied for calculating different reliability measures like mean time to system failure, availability of a system, inspection, repair and failed time of unit. Results: Graphical and analytical study had also been done to analyze the increasing/decreasing behavior of profit function w.r.t repair and failure rate. The system responded properly in fulfilling his basic needs. Conclusion: The calculated value of all reliability parameter is helpful for studying any other models following same concept under different environmental conditions. Thus, it concluded that, reliability increases/decreases with increase in repair/failure rate. Also, the evaluated results by this paper provides the better reliability testing strategies that helps to develop new techniques which leads to increase the effectiveness of system.

scholarly journals Surveillance System in Smart Cities: A Dependability Evaluation Based on Stochastic Models

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 876
Author(s):  
Igor Gonçalves ◽  
Laécio Rodrigues ◽  
Francisco Airton Silva ◽  
Tuan Anh Nguyen ◽  
Dugki Min ◽  
...  
Keyword(s):  
Surveillance System ◽  
Smart Cities ◽  
Heterogeneous Data ◽  
Time To Failure ◽  
Video Streams ◽  
Dependability Evaluation ◽  
The Mean ◽  
Mean Time ◽  
The Internet Of Things

Surveillance monitoring systems are highly necessary, aiming to prevent many social problems in smart cities. The internet of things (IoT) nowadays offers a variety of technologies to capture and process massive and heterogeneous data. Due to the fact that (i) advanced analyses of video streams are performed on powerful recording devices; while (ii) surveillance monitoring services require high availability levels in the way that the service must remain connected, for example, to a connection network that offers higher speed than conventional connections; and that (iii) the trust-worthy dependability of a surveillance system depends on various factors, it is not easy to identify which components/devices in a system architecture have the most impact on the dependability for a specific surveillance system in smart cities. In this paper, we developed stochastic Petri net models for a surveillance monitoring system with regard to varying several parameters to obtain the highest dependability. Two main metrics of interest in the dependability of a surveillance system including reliability and availability were analyzed in a comprehensive manner. The analysis results show that the variation in the number of long-term evolution (LTE)-based stations contributes to a number of nines (#9s) increase in availability. The obtained results show that the variation of the mean time to failure (MTTF) of surveillance cameras exposes a high impact on the reliability of the system. The findings of this work have the potential of assisting system architects in planning more optimized systems in this field based on the proposed models.

On classes of life distributions based on the mean time to failure function

2021 ◽  
Vol 58 (2) ◽  
pp. 289-313
Author(s):  
Ruhul Ali Khan ◽  
Dhrubasish Bhattacharyya ◽  
Murari Mitra
Keyword(s):  
Damage Model ◽  
Replacement Policy ◽  
Time To Failure ◽  
Mean Time To Failure ◽  
Moment Convergence ◽  
Life Distributions ◽  
Cumulative Damage Model ◽  
The Mean ◽  
Age Replacement ◽  
Mean Time

AbstractThe performance and effectiveness of an age replacement policy can be assessed by its mean time to failure (MTTF) function. We develop shock model theory in different scenarios for classes of life distributions based on the MTTF function where the probabilities $\bar{P}_k$ of surviving the first k shocks are assumed to have discrete DMTTF, IMTTF and IDMTTF properties. The cumulative damage model of A-Hameed and Proschan [1] is studied in this context and analogous results are established. Weak convergence and moment convergence issues within the IDMTTF class of life distributions are explored. The preservation of the IDMTTF property under some basic reliability operations is also investigated. Finally we show that the intersection of IDMRL and IDMTTF classes contains the BFR family and establish results outlining the positions of various non-monotonic ageing classes in the hierarchy.

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