Journal of Operational Research in its Applications
Year:2020 | Volume:17 | Issue:2 (65)|Papers Count:8

Data envelopment analysis (DEA) is a widely used modeling technique in the field of operations research that its various applications have been reported in different sectors of industry in the last three decades. In this paper, a performance evaluation model is proposed to analyze the performance of provincial gas companies when there are undesirable outputs. The managerial disposability assumption is used to handle undesirable outputs. In the following, a ranking procedure based on common weights is proposed. Finally, twenty-nine provincial gas companies will be evaluated and analyzed.

In the present century, environmentalism has become an important global issue. Electric vehicles (EVs) are becoming an attractive alternative to gasoline vehicles owing to the environmentalism constraints and the increase of greenhouse gas emissions and gasoline prices. However, the rapid growth in electricity demand may cause large and undesirable peak loads in the power grid. Fortunately, electric vehicles can flexibly coordinate charge schedules, which requires smart charge and discharge scheduling algorithms. In this paper, we consider a mathematical model of Mixed Integer Linear Programming (MILP) to schedule charging and discharging of electric vehicles to smart grid power and the considered model is solved by using the exact Benders decomposition method and Benders' method with Pareto-optimal cuts. Finally, we will check the performance of the proposed model and algorithms with numerical results.

This paper deals with a two-level inventory system consisting of a central warehouse and an arbitrary number of non-identical retailers with (1, T) ordering policy. It is assumed that the fi xed ordering cost at retailers is negligible; however, it has a positive value at central warehouse. Perishable items with fixed shelf life are considered for which the aging begins immediately on their arrival at central warehouse. Although the demand of retailers is random and follows Poisson distribution, demand of the central warehouse could be determined deterministically due to the (1, T) ordering policy of retailers. Therefore, the central warehouse employs a periodic policy with a fixed time period. In this study, the approximated total cost function of the inventory system is derived. Then due to the complexity of the cost function, a metaheuristic algorithm named Differential Evolutionary algorithm, is utilized to find the optimal or near-optimal solutions. Finally, a numerical experiment is carried out to demonstrate the accuracy of the model, which shows that the used approximation works rather well.

ATMs are one of the most important cash-distribution channels, their inventory management is some of the most important tasks of banks. This paper provides a dynamic and optimized model for managing ATM inventory, based on the time and location of the devices. The number of devices examined is 368 in Tehran, which were surveyed during the quarterly period in 2018, which includes 189657 records. This model with data clustering succeeds in learning the pattern in the data, and then the proposed decision tree can predict the number of costumers for each scenario. By simulating the obtained scenarios, the system costs are determined, and finally, by optimizing the proposed model for each scenario, the average cost of the whole system is reduced by 12%.

Knowledge based economy as an emerging paradigm has a fundamental role in the economic success of organizations and countries. Taking into account that the core of this paradigm is consisted of knowledge-based labor (talents), talent management has much importance in human resource management. Accordingly, the current study aims to identify the critical factors which form the talent management in knowledge based companies based upon them provide the basis for attracting and retaining talent workforce. Considering research method, it’ s a descriptive-survey study and in term of the data analysis method, it’ s a quantitative-mathematical modeling one. The statistical population of the research consisted of 230 directing managers, senior managers (supervisors and assistant directors) and human resource managers of knowledge based companies in Rasht city. In the process of conducting the research, at first, the determinants of talent management in knowledge based organizations were identified by reviewing the literature and deep semi-structured interview with experts, based on the Colaizzi method. After dealing with the content validity and test-retest the reliability of the questionnaire, coding the fuzzy DEMATEL technique in MATLAB software was used for modeling the feedback relationships among identified factors and determining the critical factors. The results of data analysis indicate that "team work and cooperative spirit", "make a creative and innovative workplace", "defining challenging and motivating tasks", "encouraging talents to dynamic thinking and making ideas", “ make a pleasant workplace" and "creating opportunities for knowledge and expertise sharing among talents" are of significant importance in the system. Therefore, paying special attention to these key factors will lead to success of knowledge based companies in talent management.

Recently, the nurse scheduling problem has attracted considerable attention in different areas. In this problem, the number of the required nurses for the daily shifts has been given during the planning horizon and the objective is assigning the shifts to the nurses in order to meet the required demands. In this paper, first, a mathematical programming model is presented to maximize the nurses’ preferences for the working shifts. Then, to investigate the uncertainty on the nurses’ preferences, a fuzzy modeling approach based on the Werner’ s fuzzy operator is proposed for the research problem. Finally, to evaluate the proposed fuzzy model, several random test problems are generated and solved using the fuzzy model. Moreover, a sensitivity analysis is implemented to investigate the effects of the changes of the parameters on the obtained results. Regarding the results, high quality schedules can be generated by the proposed fuzzy model.

Through this study, we are going to introduce a new aspect of cut sets for hesitant fuzzy sets. Compared to the rare researches in regard of cut sets for hesitant fuzzy sets, not only this study does not deal with extra parameters, but also the proposed concept of cut set conforms with the accepted principles, and further, it is extension of existing cut set concept of fuzzy sets, intuitionistic fuzzy sets, interval-valued fuzzy sets, interval-valued intuitionistic fuzzy sets and three-dimensional fuzzy sets. In the sequel, using proposed concept of cut sets for hesitant fuzzy sets, we extend the corresponding theorems of decomposition and representation for hesitant fuzzy sets. The current research can be a basis for the future work on the application of cut sets in multiple criteria decision making problems under hesitant fuzzy environment.

Performance analysis of organizations is one of the most important issues in the field of optimization and operations research in operations. Benchmarking is one of the most effective ways to do this, and perhaps one of the most important tools for benchmarking is data envelopment analysis, which has attracted researchers' attention in the last three decades. Cross efficiency is one of the ranking methods in data envelopment analysis technique which unfortunately does not provide a unique rank of units due to the multiple optimal solutions in the multivariate form of basic data envelopment analysis models. Secondary goals were used to address this problem. In this paper, using the perturbed problems and the relationship between linear and dual linear programming problems, a new model is proposed so that the weights obtained from this model and then the ranking obtained by the cross-efficiency method are uniquely represented. The results of the proposed method have been studied with real data from bank branches in Iran.