majid Esmaelian; ahmad jafarnajad
Volume 15, Issue 2 , May 2011, , Pages 47-70
Abstract
The purpose of preventive maintenance management is to perform a series of tasks that prevents or minimizes production breakdowns and improves the reliability of production facilities. The inspection, repair, and replacement of production equipment are tasks that are central to preventive maintenance ...
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The purpose of preventive maintenance management is to perform a series of tasks that prevents or minimizes production breakdowns and improves the reliability of production facilities. The inspection, repair, and replacement of production equipment are tasks that are central to preventive maintenance management.
An important objective of preventive maintenance management is to minimize the downtime of production facilities. In order to accomplish this objective, management personnel has to efficiently allocate resources and determine an effective maintenance schedule. Mathematical models have been developed to solve the preventive maintenance-scheduling problem of assigning skilled personnel to work with tasks that require a set of corresponding skills.
However, there are several limitations in the prior work in this area of research. The craft-combination problem has not been solved because the craft-combinations is assumed to be given. The craft-combination problem concerns the computation of all combinations of assigning multi-skilled workers to accomplishing a particular task. In fact, determining craft-combinations is difficult because of the exponential number of craft-combinations that are possible.
This research provides an integrated solution for the preventive maintenance-scheduling problem with multi-skilled workforce constraints.
Two novel preventive maintenance-scheduling model is formulated to automatically produce the optimal solution and craft combination.
Ahmad Jafarnejhad; Majid Esmaelian; Masood Rabieh
Volume 12, Issue 4 , January 2009, , Pages 127-153
Abstract
One of the most important permanence factors in today’s competition environment is decreasing of the cost of the products. Selecting the appropriate suppliers can significantly reduce the purchasing cost and increase organization competitiveness. It is due to the fact that in most industries, the cost ...
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One of the most important permanence factors in today’s competition environment is decreasing of the cost of the products. Selecting the appropriate suppliers can significantly reduce the purchasing cost and increase organization competitiveness. It is due to the fact that in most industries, the cost of raw material and component parts includes the main cost of a product. The aim of this paper was to introduce a fuzzy decision making approach for supplier selection problems in supply chain. Most of such decisions are unstructured and many of the performance criteria such as quality, cost, flexibility and delivery time to determine the best supplier should be considered. In this paper, verbal variables were used for evaluation and determination of the performance of supplier under each criterion and determination of the weight of the criteria. Verbal variables were described by means of the triangular and trapezoid fuzzy numbers. Furthermore, the priority and the rank of suppliers by fuzzy multi-criteria decision making were determined. Finally, an example was presented to the process of decision making.
Ahmad Jafarnejhad; Majid Esmaelian; Mehradn Rzvani
Volume 12, Issue 1 , March 2008, , Pages 105-125
Abstract
In this research We introduce a new distribution center (DC) location model that incorporates working inventory and safety stock inventory costs at the distribution centers. In addition, the model incorporates transport costs from the suppliers to the DCs that explicitly reflect economies of scale through ...
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In this research We introduce a new distribution center (DC) location model that incorporates working inventory and safety stock inventory costs at the distribution centers. In addition, the model incorporates transport costs from the suppliers to the DCs that explicitly reflect economies of scale through the use of a fixed cost term.
The model was formulated as a non-linear integer-programming problem. The algorithms were tested on the problems with 15 retailers and 5 distribution centers. We uses SOLVER of Excel for modeling, solution and sensitivity analysis of the results.
Finally, the sensitivity of the results to changes in key parameters including the fixed cost of placing orders was discussed. Significant reductions in these costs might be expected from e-commerce technologies. The model suggests that as these costs decrease, it is optimal to locate additional facilities.