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Citation - WoS: 62
Citation - Scopus: 69
Estimation in Coherent Reliability Systems Through Copulas
(Elsevier Sci Ltd, 2011) Eryilmaz, Serkan
The problem of estimating the parameter of a common distribution of components' lifetimes from system's lifetime data is of interest and importance in reliability engineering. The present paper deals with this problem when the common component distribution is exponential with mean it and the lifetimes of components have an exchangeable joint distribution which is constructed by the help of Archimedean copula. In particular we obtain moment estimator of p for Clayton and Ali-Mikhail-Haq copulas. We illustrate the findings of the paper for a special class of coherent systems called consecutive k-within-m-out-of-n:F system. A simulation study is performed to investigate the properties of the moment estimator. The method presented in this paper can be applied to all coherent systems. (C) 2010 Elsevier Ltd. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 9
The Number of Failed Components Upon System Failure When the Lifetimes Are Discretely Distributed
(Elsevier Sci Ltd, 2022) Eryilmaz, Serkan; Yalcin, Femin
The number of failed components at the time when the system fails is an important quantity which can be effectively used in the determination of the optimal number of spares. This paper is concerned with the distribution and expected value of this quantity when the lifetimes of a given coherent system are discretely distributed. In particular, the distribution of the corresponding random quantity is derived for all coherent systems of order three and four. The mean number of the failed components upon system failure is exactly derived for a linear consecutive-2-out-of-n:F structure. The mean of the quantity under concern is also computed for series and parallel systems consisting of disjoint modules. The latter computation provides an efficient way to obtain the corresponding mean for a larger system via the modules which have smaller number of components.
Citation - WoS: 15
Citation - Scopus: 17
The Lost Capacity by the Weighted k-out-of-n< System Upon System Failure
(Elsevier Sci Ltd, 2021) Eryilmaz, Serkan; Ucum, Kaan Ayberk
A k-out-of-n. system with weighted components is a system that consists of components contribute differently to the overall performance of the system, and functions if the total weight/contribution of all working components exceeds or equal to the level k.. Such a system is useful and suitable for modeling capacity based systems such as power systems, transportation systems and manufacturing systems. This paper is concerned with the lost capacity by the weighted-k-out-of-n. system at the time when the system fails. This random quantity is useful for making an optimal decision about the spare capacity that should be available to renew the system upon its failure. In particular, the distribution of this random quantity is derived and the theoretical results are illustrated for a power system consisting of a specified number of generating units.
Citation - WoS: 15
Citation - Scopus: 20
A Decision Theoretic Framework for Reliability-Based Optimal Wind Turbine Selection
(Elsevier Sci Ltd, 2022) Eryilmaz, Serkan; Navarro, Jorge
The problem of choosing the optimal wind turbine for a specific site is of special importance in the design process of wind farm. Manifestly, the selection of the optimal wind turbine should depend on a certain criteria. In this paper, optimal wind turbine selection is studied in terms of the capacity factor of wind turbine generator and the Expected Energy not Supplied which is one of the most commonly used reliability indices for power systems. The latter one considers the load profile of the system and is suitable to compare different wind farm compositions while the former one completely ignores the load profile of the system. This paper presents general theoretical results that are helpful to compare performance of wind turbines and wind farms without data collection and further numerical assessment. In particular, the conditions on wind turbine characteristics and availability values of wind turbines are determined to compare wind turbines and wind farms in terms of the capacity factor and Expected Energy not Supplied.
Citation - WoS: 36
Citation - Scopus: 44
An Algorithmic Approach for the Dynamic Reliability Analysis of Non-Repairable Multi-State Weighted k-out-of-n< System
(Elsevier Sci Ltd, 2014) Eryilmaz, Serkan; Bozbulut, Ali Riza
In this paper, we study a multi-state weighted k-out-of-n:G system model in a dynamic setup. In particular, we study the random time spent by the system with a minimum performance level of k. Our method is based on ordering the lifetimes of the system's components in different state subsets. Using this ordering along with the Monte-Carlo simulation algorithm, we obtain estimates of the mean and survival function of the time spent by the system in state k or above. We present illustrative computational results when the degradation in the components follows a Markov process. (C) 2014 Elsevier Ltd. All rights reserved.
Citation - WoS: 45
Citation - Scopus: 48
Age-Based Preventive Maintenance for Coherent Systems With Applications To Consecutive-k-out-of-n< and Related Systems
(Elsevier Sci Ltd, 2020) Eryilmaz, Serkan
This article presents a signature-based representation for the expected cost rate of age-based preventive maintenance policy for a binary coherent system consisting of independent exponential components, and then specializes the method to consecutive k-out-of-n system and its generalizations. According to the age-based preventive maintenance policy, the system is replaced at failure or before failure. For an arbitrary coherent system, the number of failed components at replacement time is a random variable. Thus, the expected cost per unit of time involves the mean number of failed components at replacement time. This mean is represented in terms of signature. Extensive numerical and graphical examples are presented for m-consecutive k-out-of-n:F and consecuthre-k-within-m-out-of-n:F systems.
Citation - WoS: 44
Citation - Scopus: 53
On Reliability Analysis of a k-out-of-n< System With Components Having Random Weights
(Elsevier Sci Ltd, 2013) Eryilmaz, Serkan
Consider a system consisting of n components each with its own positive integer-valued random weight (capacity). The system is assumed to have a performance level above c if there are at least k working components, and the total weight of all working components is above c. We study the reliability properties of such a system. A recursive formula is obtained for computing the system state probabilities. We present a Monte-Carlo simulation algorithm to observe the time spent by the system in state c or above. The algorithm is based on the use of ordered lifetimes of components. We illustrate the results with numerical computations. (C) 2012 Elsevier Ltd. All rights reserved.
Citation - WoS: 17
Citation - Scopus: 25
On the Theoretical Distribution of the Wind Farm Power When There Is a Correlation Between Wind Speed and Wind Turbine Availability
(Elsevier Sci Ltd, 2020) Kan, Cihangir; Devrim, Yilser; Eryilmaz, Serkan
It is important to elicit information about the potential power output of a wind turbine and a wind farm consisting of specified number of wind turbines before installation of the turbines. Such information can be used to estimate the potential power output of the wind farm which will be built in a specific region. The output power of a wind turbine is affected by two factors: wind speed and turbine availability. As shown in the literature, the correlation between wind speed and wind turbine availability has an impact on the output of a wind farm. Thus, the probability distribution of the power produced by the farm depending on the wind speed distribution and turbine availability can be effectively used for planning and risk management. In this paper, the theoretical distribution of the wind farm power is derived by considering the dependence between turbine availability and the wind speed. The theoretical results are illustrated for real wind turbine reliability and wind speed data.
Citation - WoS: 18
Citation - Scopus: 21
Theoretical Derivation of Wind Plant Power Distribution With the Consideration of Wind Turbine Reliability
(Elsevier Sci Ltd, 2019) Eryilmaz, Serkan; Devrim, Yilser
The wind power generated by a wind plant has a stochastic nature due to randomness in the wind speed. Although the empirical distribution of the wind power has been extensively studied by using data sets in different regions, several works focused on theoretical distribution of the wind power produced by wind turbines. In this paper, the theoretical distribution of the wind plant power is obtained. In the derivation of the distribution of the wind plant power, wind turbine reliability is taken into account. The wind plant power distribution can be effectively used if the wind speed probability distribution is known. Theoretical results are illustrated for Weibull and Bimbaum-Saunders wind speed distributions which have been found to be suitable for real data collected at two different locations.
Citation - WoS: 21
Citation - Scopus: 24
Optimization Problems for a Parallel System With Multiple Types of Dependent Components
(Elsevier Sci Ltd, 2020) Eryilmaz, Serkan; Ozkut, Murat
This paper is concerned with two optimization problems for a parallel system that consists of dependent components. First, the problem of finding the number of elements in the system that minimizes the mean cost rate of the system is considered. The second problem is concerned with the optimal replacement time of the system. Previous work assumes that the components are independent. We discuss the impact of dropping this assumption. In particular, we numerically examine how the dependence between the components affects the optimal number of units and replacement time for the system which minimize mean cost rates. We first consider the case when the components are exchangeable and dependent, i.e. the system consists of single type of dependent components. Subsequently, we consider a system that consists of multiple types of dependent components. Comparative numerical results are presented for particularly chosen dependence models.

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