نشریه بین المللی مهندسی صنایع و مدیریت تولید
سال بیست و دوم شماره 4 (زمستان 1390)

The dynamic facility layout problem involves the design of facility layouts in which the flows of materials between activities can change during a multi-period planning horizon. In the static layout problem, it is assumed that all the activities are constant. However, in today’s volatile markets, the business conditions are changing. So the similar changes are imposed on the facility projects and the flows of material between activities. In this paper, a new model of the dynamic facility layout problem is studied that the flows of materials are considered as fuzzy numbers with different membership functions. For modeling the problem, the expected value, the chance programming and the probabilistic programming methods are utilized using fuzzy programming. A new method is proposed for solving the model and a numerical example is given to describe the method.

Knowing about the real time of a change in the parameter(s) of a statistical process would enable users to identify root causes more quickly and precisely. Due to the sensitivity and importance of reaching zero defects in high quality processes, to be aware of the change time would be so precious. In this paper, we consider the performance of the Maximum Likelihood Estimator in comparison with built-in change point estimators of Cumulative Sum (CUSUM) and Exponential Weighted Moving Average (EWMA) control charts. Using likelihood function approach, we also proposed a confidence set for the change point. The results of a Monte-Carlo simulation have shown the priority of the MLE in identifying the real time of the change.

Flexible job shop scheduling problem)FJSP(is an extension of the classical job shop scheduling problem which allows an operation to be processed by any machine from a given set. FJSP is NP-hard and mainly presents two difficulties. The first one is to assign each operation to a machine out of a set of capable machines, and the second one deals with sequencing the assigned operations on the machines. However, it is quite difficult to achieve an optimal solution to this problem in medium and large size problems with traditional optimization approaches. In this paper a memetic algorithm (MA) or flexible job shop scheduling with overlapping in operation is proposed that solves the FJSP to minimize makespan time and obtain the optimum solution for small problem and best solution for medium and large scale problems. In this paper we also used preemption to improve the results of memetic algorithm and reduce the makespan.

Population growth and industrial development cause the growth in electricity demand. Supply of this energy needs investment for installation of new power stations and more fuel consumption with different consequences. Furthermore, Demand side management is an approach to rationalize and reduce the rate of demand growth. With attention to the cause and effect nature in energy sector, interaction of variables in this sector, and also its complexities; it is required that the policies be tested by some advanced tools. In this paper, a system dynamics based model has been presented. By this model, the results of two approaches-demand side control and supply side development can be compared.

One of methods that used in product mix problems is theory of constraints (TOC). However, unfortunately it is not efficient in some situations. So many researchers have tried to solve these inefficiencies. In this way, Revised Theory of Constraints is proposed to use the advantage of this method for certainty conditions.Nevertheless, in the real world situations many parameters such as processing time, capacity and profit are not completely certain. Furthermore, Fuzzy set theory has been used to model systems that are hard to define precisely and represents an attractive tool to aid research in production management when the dynamics of the production environment limit the specification of model objectives, constraints and the precise measurement of model parameter. So In this paper, an algorithm based on RTOC and fuzzy logic is proposed. The results have shown this algorithm is an effective and flexible algorithm.

One of the main efforts in a pull system to meet the final goal of Just-In-Time (JIT) is to decrease Work-In-Process (WIP) without reducing throughput rate and service level. This paper proposes a new hybrid control policy using Kanban, Base Stock and CONWIP to form the final construction of production plan, and then the function of new model is shown by a 3 stage case study with probabilistic parameters. The results obtained using simulation and solving various problems indicate that the inventory level is reduced to an acceptable range. Also, Data Envelopment Analysis (DEA) is implemented for the evaluation and verification of the proposed policy with functional indicatives.

Recently, due to growth in sport branches and increase in constraints and complications in sport competitions, mathematical models and operations research approaches have been significantly used for preparing sport schedules. Football leagues are also among such these competitions. In this paper, the scheduling problem of Iranian football league in which the goal is to minimize breaks and carry over effect is investigated. A new criterion, so-called “breaks for most popular teams” is introduced that has never been taken into account in literature. Final schedule will be obtained through three stages with different objective for each stage in which graph theory and simulated annealing algorithm have been used to solve the problem. Finally, comparing the results of the proposed algorithm with those in the literature shows effectiveness of the proposed algorithm.

The main objective of facilities location and service system design is covering of potential customers’ demand. Many location models are extended with the covering objective and considered constraints, details of problem and its different aspects. In this paper the maximal covering location-allocation model for congested system is extended in the competitive environment. In the proposed model, several important characteristics such as spatial interaction model, congestion, the competitive user-choice environment and probabilistic demand are considered. The objective of the model is maximization of the demand captured by each facility in the competitive environment. The optimization software of lingo 8 and the genetic algorithm are used for solving the small-size problems. Due to the complexity of problem and its nonlinear nature, the software of lingo 8 cant solved the large-size problems and the genetic algorithm is applied to solve the larger size problems. Numerical results verify the effectiveness of proposed algorithm for solving the model and show that the use of queuing theory in service system design can improve different service strategies, promote organization’s business process and increase customer’s satisfaction.

Due to the rapid development of knowledge and information technology (IT), business environments have become much more complicated. In order to cope with ensuing complications, enterprises ought to incessantly innovate otherwise, it will be very difficult for them to survive in the marketplace. Hence, IT can help a company to gain a competitive advantage. In addition, many studies have argued that business value comes mainly from intangible assets, such as knowledge. Thus, knowledge workers will be able to replace clerical workers as the new mainstream of manpower resources, a field in which the development of IT is the major force for change in knowledge management system (KMS). Therefore, based on the proposed definition of the six gaps in KMS by Tseng, this study explores the role and effect of IT in the implementation of KMS moreover, relationships between KMS and IT are analyzed and demonstrated by means of the literature reviews, expert interviews and questionnaire analyses. Finally according to these gaps and mentioned IT tools for covering them, new conceptual model is proposed. Based on proposed model and statistical analysis situation of each gap in the company had been assessed and discussed how to enhance the effectiveness and efficiency of implementing KMS through appropriate IT.