Hadi Akbarzade Khorshidi

On Reliability Evaluation of Multistate Weighted -out-of- System Using Present Value

A new reliability evaluation methodology for multistate weighted k-out-of-n systems is presented in this article. The present value of the cash flow generated by the system components is used as a reliability value. We take a financial view of reliability and consider functioning periods and the time value of money in system reliability analysis. Two approaches, the universal generating function (UGF) and recursive algorithm, are applied to evaluate the reliability of the multistate weighted k-out-of-n system. An illustrative example is calculated based on the proposed system reliability evaluation methodology. It is shown that this evaluation method can also be used to find the value of the maintenance policy. Finally, the UGF and recursive algorithm approaches are compared with each other for large system reliability assessment.

Data-Driven System Reliability and Failure Behavior Modeling Using FMECA

System reliability modeling needs a large amount of data to estimate the parameters. In addition, reliability estimation is associated with uncertainty. This paper aims to propose a new method to evaluate the failure behavior and reliability of a large system using failure modes, effects, and criticality analysis (FMECA). Therefore, qualitative data based on the judgment of experts are used when data are not sufficient. The subjective data of failure modes and causes have been aggregated through the system to develop an overall failure index (OFI). This index not only represents the system reliability behavior, but also prioritizes corrective actions based on improvements in system failure. In addition, two optimization models are presented to select optimal actions subject to budget constraint. The associated costs of each corrective action are considered in risk evaluation. Finally, a case study of a manufacturing line is introduced to verify the applicability of the proposed method in industrial environments. The proposed method is compared with conventional FMECA approach. It is shown that the proposed method has a better performance in risk assessment. A sensitivity analysis is provided on the budget amount and the results are discussed.

An improved similarity measure for generalized fuzzy numbers and its application to fuzzy risk analysis

Display Omitted A new method for similarity measure of the generalized trapezoidal fuzzy numbers.Proven properties of the new proposed method.Better performance in comparison with the previous methods.Application on fuzzy risk analysis.An example of risk level classification. This paper presents an improved method to compute the degree of similarity between generalized trapezoidal fuzzy numbers. The proposed similarity measure contains many features of fuzzy numbers such as geometric distance, center of gravity (COG), area, perimeter, and height. The previous methods are criticized via presenting some examples. In addition, the performance of the proposed methods is compared by the existing similarity measures using twenty different sets of generalized trapezoidal fuzzy numbers. Furthermore, the proposed method is used for fuzzy risk analysis based on similarity measures. Finally, an example is introduced to illustrate the fuzzy risk analysis.

Investigation on system reliability optimization based on classification of criteria

System reliability optimization has been considered as an area to improve the operational availability of electrical and manufacturing systems. This research area addresses system reliability estimation and mathematical model development. This paper presents a -review on system reliability optimization techniques based on different classification of criteria. The main criteria considered in this study are system structure, system state, optimization model, allocation model, modeling and solution methods. The classification can provide an overview of all criteria that should be used to make optimal decisions in a system by taking the reliability into account. Not only it can assist the researchers to develop new optimization models, but also it presents the practitioners how system reliability optimization models can help industries. The paper also discusses the limitations of the present techniques in this area.

Applying UGF concept to enhance the assessment capability of FMEA

The purpose of this paper is to propose a modified version of Failure Mode and Effects Analysis (FMEA) to alleviate its drawbacks. FMEA is an important tool in risk evaluation and finding the priority of potential failure modes for corrective actions. In the proposed method, the Universal Generating Function (UGF) approach has been used to improve the assessment capability of the conventional Risk Priority Number (RPN) in ranking. The new method is named as URPN. It generates the most number of unique values in comparison with the previous methods and considers relative importance for the parameters while it is easy to compute. More unique numbers help to avoid from having the same priority level for different failure modes which represent various risk levels. A case study has been employed to demonstrate that the URPN not only can improve the shortcomings but also is able to provide accurate values for risk assessment. Copyright

Reliability centered maintenance using system dynamics approach

This paper presents a system dynamic modeling technique for reliability centered maintenance (RCM). It provides a simulation model to analyze the impact of maintenance strategies such as preventive and corrective maintenance on system availability. Also, maintenance cost is associated with the model to have an optimization view for a manufacturing system. As a result, the optimal decisions can be made based on the results of the model. In addition, sensitivity analysis has been conducted for various parameters in the simulation model. The results were compared and discussed for various conditions.

Optimising service quality translating via quantitative quality function deployment

This study aims to create a model to use internal measures for service quality evaluation. Using internal measures provides continuous (daily) service quality measurement and faster improvement efforts allocation, we find them more applicable and useful for service quality measurement. This paper demonstrates that using SERVQUAL lonely cannot be efficient, so we need some new improvements. This study proposes a model that can use internal measures for continuous and more effective evaluation. The quality function development method is used for translating customer expectation to internal measures. SERVQUAL dimensions or statements are employed as customer expectation that they are perceived by SERVQUAL questionnaire. Moreover, this paper tries to optimise this translation by a mixed integer linear programming mathematical model. This model can optimise the service quality translation to enrich the internal evaluation with customer opinions. Finally, the proposed model is employed for optimising the evaluation of the train’s internal service quality.

Fuzzy risk analysis by similarity-based multi-criteria approach to classify alternatives

Abstract In this paper, a new method for fuzzy risk analysis based on similarity of fuzzy numbers is presented. First of all, the similarity-based multi-criteria approach is used to find the similarity between generalized trapezoidal fuzzy numbers and the desired fuzzy number to rank them. The geometry distance, spread difference, perimeter ratio, area ratio, and height ratio have been considered as criteria. Secondly, the proposed ranking approach is used for fuzzy risk analysis. Severity of loss, probability of failure, and failure ignorance possibility are the parameters to assess the risk of various alternatives. In the proposed fuzzy risk analysis, the alternatives can be classified into different levels in terms of their risk. Therefore, fuzzy risk analysis leads to classification and prioritization of the alternatives. Finally, a numerical example is presented to illustrate the applicability of the proposed method.

A new modified FMEA model for ranking the risk of maintenance waste considering hierarchy of root causes and effects

Implementing sustainable manufacturing practice requires efficiency of the resource utilisation and activities which add value to the operations. From this point of view, development of an improved methodology to access the criticality of non-added value (waste) is important and believed to support the realisation of sustainable manufacturing operation. While previous studies on improving methodology to support sustainable operation from product and process design are abundantly available in the references, the contribution from maintenance field is in contrary. The goal of this study is to modify the quality improvement tool, failure mode and effect analysis (FMEA) to access the criticality of waste in maintenance operation. In an attempt to realise the above goal, an empirical study to propose the theoretical and actual maintenance waste from industrial practice is undertaken. In order to assist maintenance decision maker to quantify criticality of maintenance waste occurrence, a new model to rank waste maintenance mode, called the waste priority number (WPN) is given. Illustrative on using model for practical purpose is given.

Social impact assessment on metro development with a case study in Eastern District of Tehran

Development is an important issue to which the major part of people’s efforts has been allocated. Nowadays, it is perceived that development could have undesirable results in addition to its advantageous outcomes. These undesirable results are emerged in different themes such as social, environmental and cultural aspects. As a result, the ones who work on development plans try to predict and prevent the unwanted results of projects in order to reach the sustainable development. Due to this fact, social impact assessment (SIA) of projects and plans has been considered by decision makers. SIA identifies the consequences of development projects and it aims to notify managers to prevent unintended impacts. Transportation development is not apart from other development projects, so its social impacts should be assessed. Metro network as a transportation system plays a critical role in urban transportation and its development has a special importance. In this study, social impacts of metro development in eastern district of Tehran have been assessed. These impacts are classified in three categories including accessibility, mobility, and social wellbeing. The survey’s outcomes show that metro has the positive impact on mobility and accessibility items. Also, it has affected social wellbeing and general living condition of district’s local people differently.