Journal of Quality Engineering and Management

Abstract Today, the defense of sensitive areas and resources is a fundamental issue that encompasses all key infrastructures, and to achieve the goal of reducing the damage and injuries caused by the attacker, the use of informed and useful strategies is necessary. In this research, modeling is considered to optimize the protection of investment systems that have a series-parallel reliability structure and have a functional correlation with each other. In general, in this study, first considering the functional independence of subsystems, the probabilities of a successful attack, the system reliability structure and the game theory approach to finding the equilibrium point, a nonlinear programming model is proposed to determine the investment defense of systems. Then, by determining the reliability relationships despite the functional correlation between the subsystems, a linear programming model is introduced to determine the correlation coefficient of the subsystems and to redistribute investment to defend the systems. Finally, the proposed research model is used for a numerical example and the results are analyzed.

Abstract Applying preventive maintenance strategies in control chart design, which is one of the main tools in statistical process quality control, not only increases the reliability of the system and reduces its wear and tear, but also reduces the cost of chart design. However, the cost of quality in the classical approach to control chart design, derived from the Crossby football gate philosophy, depends only on whether the quality characteristic is within or outside the control limits. In contrast, using the loss function approach in in-production monitoring activities such as control charts, where quality cost based on Taguchi's concept of social loss quality depends on the amount of quality characteristic deviation from the target value, is a more comprehensive assessment of the process and therefore decisions. It is better guided in planning and management. This paper presents an integrated model of Taguchi loss function, preventive maintenance strategies including incomplete maintenance and early replacement, and economic control diagram design in which the shock model or process failure mechanism has an incremental failure rate. In addition, due to the fact that the data obtained from the measurements related to the output of the production process may not follow the normal distribution or the assumptions of the central limit theorem may not be true for them, it is necessary to study the integrated model in these situations. Normal distribution is necessary. To illustrate the issue, numerical examples based on non-uniform sampling design and Weibull shock model are provided. The adjustment parameters obtained from the integrated model (sample size, sampling intervals, coefficient width of control limits, early replacement time, and cost level and incomplete maintenance time) in addition to significant differences in normal and abnormal conditions, show that with increasing preventive maintenance level, The average design cost will be reduced in both normal and abnormal modes.

Abstract Statistical quality control methods are the basis for measuring process performance and productivity. Control charts are one of the most widely used statistical control tools and play an important role in improving the quality of processes and products. The main purpose of their implementation is to identify the deviation (s) and take corrective measures to eliminate the root of the deviation. The technical applications of control charts are to determine the sample size, sampling frequency and control limits, which is called control chart design. In most nP chart design research, only one reason deviation is considered as the cause of the chart getting out of control, while several industry deviations can play a role. For this purpose, in this research, the design and statistical-economic development of nP control diagram, in order to reduce costs and average detection time and increase the power of the diagram by using gray values ​​and considering deviations for various reasons. In this regard, in order to achieve the optimal values ​​of these parameters, a multi-objective problem with three constraints has been defined, in which we have considered each possible combination of parameters as a decision unit. Then, using data envelopment analysis and ranking methods, the most efficient design for the decision maker is determined. In the continuation of the research, sensitivity analysis has been performed on some parameters of the model and the effect of these parameters on the optimal values ​​has been analyzed.

Abstract Quality of service is the distinguishing factor and the most powerful competitive weapon that many service organizations such as hospitals have. The purpose of this study was to rank selected hospitals in Iran in terms of service quality using a combination of SERVQUAL methods and data envelopment analysis. In this study, first, a systematic search in various scientific databases, to find the research conducted to assess the quality of services provided in Iranian hospitals using the SERVQUAL model, which found 22 related studies. Then, with the help of data envelopment analysis method and considering the five dimensions of service quality as its outputs and considering hospitals as decision-making units by DEAP 2.1 software, the scores related to each were calculated. Most of the published researches were related to 2016 in terms of time and related to Tehran province in terms of location. Zabol Shahid Elmi Field Hospital with a score of 1.000 and D Hospital affiliated to Qazvin University of Medical Sciences with a score of 0.364 won the first and last ranks, respectively. The average score of all hospitals was 0.796. Scores calculated by data envelopment analysis showed that there is an average increase of 20.4% in the quality of hospital services. Also, Shahid Elmi Field Hospital in Zabol can be considered a model for other hospitals under study due to its superior ranking.

Abstract Reliability and accessibility are important features in most systems, especially electronic and mechanical systems, which are in the industries of air communication, Internet networks, telecommunication systems, power generation systems, production facilities, etc., which are among the most important reasons for increasing the complexity of systems. , Hardening and more sensitive market competitive environment, increasing production costs in the event of a stoppage, and so on. In this paper, inspired by research on the reliability and optimization of systems reliability, a model with multiple objective function is presented, the objective function of which includes accessibility optimization and cost of all systems, where the system includes both non-repairable components and Is repairable. In this model, system accessibility, in addition to allocating surplus components to subsystems, allocation of accessibility for components is also considered, which increases the flexibility of the model to increase the accessibility of systems. To solve the designed model, a genetic algorithm based on the arrangement of non-privileged solutions (NSGA-II) is used, which has a high power to solve such problems. Finally, a numerical example is presented to express the efficiency of the proposed model and the method of solving it. In this example, a system is considered in which part of its components is unrepairable and the other part is repairable.

Abstract ehavior is a function of the failure rate of some mechanical systems. The conventional Weibull model is not able to fully model the lifespan of such systems with the ohmic refractive index function. In this paper, a new generalized Weibull distribution is used to model the failure rate functions with vanity-shaped behavior. This model is evaluated on three datasets. In these three datasets, in order to reduce the execution time of the lifetime test, accelerator and censored type one tests have been used. The model parameters are also estimated based on the maximum likelihood method. The Akaike indices, the logarithm of the probability function, and the Bayesian information criterion are obtained, indicating the efficiency of this model for the data obtained from performing the lifetime tests. Therefore, the predicted average lifespan has good validity.