MODARES TECHNICAL AND ENGINEERING
Year:2003 | Volume:- | Issue:11|Papers Count:16

In this paper an approximate method for calculating performance measures of production flow line with finite buffer is proposed. The exact performance measures of production flow line can be found by Markov chain when the system is relatively small. However, as the system gets larger, the number of the states increases explosively. So exact models are not available for these systems.One of the main performance measures of production flow line is "throughput." In this paper, it is assumed that the flow line consists of m single server stations with exogenous Poisson arrival process and exponentially distributed service times.The procedure reduces the problem from multiple machines to one machine, i.e., the first machine by backward method. The effective input rate is approximated by considering the blocking probability of stations and their effects on upstream stations. In the steady-state conditions, the effective input rate is equal to throughput rate, so throughput and the other performance measures are approximated. Numerical results demonstrate the accuracy of proposed formulas.

Decision making is an important activity for today’s organizations at all levels. Due to the complexity of activities in the context of uncertain economic, social, and political situations, the need for a tool to evaluate the efficiency of the decision making units (DMU’s) is obvious. Parliaments of course are important decision making units whose decisions affect all aspects of societies.In this paper we propose a fuzzy common set of weights (CSW) model to evaluate the decisions of the past five courses of Iran’s Parliament. The performance of the parliament was measured by using criteria developed for this purpose. Due to the qualitative nature of the problem a fuzzy approach was used to process the criteria. 78 such criteria were used as inputs and outputs of the model. The model was solved using GAMS and the results determined the efficiency ranks of the past five terms of parliament. And finally discussions were made on how to improve the efficiency of the parliament based on the input output criteria.

This paper focuses on the formulation and solution of the problem of Just-In-Time provision of required materials or parts from suppliers for a production system. The unique characteristic of this problem is that the quantity of required material to be delivered to the central depot is a function of the route taken by a vehicle assigned to serve some selected suppliers. Minimizing number of required vehicles and minimizing average inventories at the central depot are the objectives of this problem. The problem is modeled and then two heuristic solution procedures are suggested. The performances of the heuristic solution procedures are evaluated against the mathematical model. The heuristic procedures are shown to provide generally good results.

The problem of scheduling n Jobs on m machines in Job Shops to minimize Make Span is analyzed through a simple Two Phase Technique and Branch and Bound algorithm. In the first phase of the algorithm method by a forward scheduling process the earliest starting and finishing times for each operation considering the logical and technological constraints are determined. If two or more operations are ready to be processed by one machine at a time, two branches are generated. On one branch theSPT→MWKR priority rules and on the other one the MWKR →SPT rules are applied.The second phase starts with the best Make Span calculated in the first phase and by using a backward scheduling process and a combination of SPT, MWKR priority rules and a branch and bound approach the scheduling task is performed. The minimum Make Span calculated in both phases is considered as the final solution.

A massive challenge for innovating new business models recently has risen to Transform the brick-and-mortar companies to the click-and-mortar companies. It is not possible to transform these organizations without utilizing its internal knowledge. This paper reviews the literature of knowledge management and organizational learning and then explains their roles in the creation of innovative business models. By elaborating the specifications of traditional business models and considering the requirements of knowledge management systems, the paper describes the specifications of knowledge-based business models and proposes a conceptual framework for a knowledge-based business model. Utilization of organizational learning concepts is the most significance of the proposed model. Application of UML (Unified Modeling Language) in defining the proposed business model is also described.

This paper presents a solution of a cellular manufacturing system (CMS) considering flow (routing) flexibility and machine flexibility in stochastic and dynamic states. In most research carried out in the past, CMS problems have been solved in static production flow and deterministic production demand. However, there are dynamic flow and stochastic demand in a real-world situation. In this paper, we present a non-linear mixed-integer mathematical model for a CMS problem in dynamic and stochastic production environments. Due to the complexity of the above model, it is so difficult to solve such a model by traditional optimization methods in a reasonable computation time. Thus, tabu search (TS) known as a meta-heuristic algorithm is proposed and a special design of this algorithm is carried out solving the above CMS model.Finally, solutions obtained by tabu search method are compared with solutions reported by the Lingo 6 software in order to validate the efficiency of the proposed algorithms.

This paper analyzes the partial productivity of Iran National Railways (INR). Partial productivity is defined as the ratio of output (i.e. unit of transportation) and the input factors such as road lines, employees, fuel, locomotive, freight wagons, and passenger stations. Using 30 years of INR’s data, the affect of different input factors on the partial productivity is investigated. The results show INR consummed some extra inputs such as freight wagons due to inappropriate usage of resources combinations.The paper also investigates the performance of INR, using Capdoglas production functions. Then, regarding sound combinations of resources, some practical suggestions are derived.

This paper explores a qualitative research approach to relationship between organizational change and learning capability based on the grounded theory building. Particular emphasis is placed on developing a pre-existing construct and the research design. The preexisting construct portrays the interaction between change processes, interval dynamic of change and learning capabilities. This pre-construct which is pure literature base data, help researchers to conduct a research to induct insight from field data.

In this paper after providing four criteria, a method is provided that can determine the information systems situation in the firms that have supply chain. For this purpose, development of information systems is classified into four periods. New concepts are provided: four essential criteria (Information Sharing, Acquiring Technical Knowledge, Learning, Response to Customers) in supply chain information systems. These four criteria are measures for determining the information systems situation in enterprises supply chain for the first time.Finally, results of two case studies, conclusion, and suggestions for future research are provided.

In some of the papers on Data Envelopment Analysis (DEA), it has been explained that if correlation coefficient between each pair of input (output) vectors is strong and positive, one of the input (output) vectors should be omitted. In this paper, a threshold is identified for correlation coefficient beyond which one of the input vectors could be omitted without altering the mean efficiency of the DMUs. The threshold identification in terms of some of the DEA models including CCR, CCRCSW, BCC and BCCCSW is performed. First, the effect of the factor of before and after omission of one of the input vectors on the mean efficiency is determined by analysis of variance (ANOVA). Then, the effect of the factor of different correlation coefficients between two input vectors on the mean efficiency is determined. Third, interaction effect of the factor of different correlation coefficients between two input vectors and factor of before and after omission of one of the input vectors on the mean efficiency is determined. Finally, the interaction effect of the factor of different correlation coefficients between two input vectors and factor of size of DMUs on the mean efficiency is determined.