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دسترسی آزاد مقاله
1 - A Goal Programming Linear Model for Simultaneous Project Scheduling and Resource Leveling - a Huge Civil Project as a Case Study
Yousef RabbaniWe have a huge civic project, includes several sub-projects, which are divided into activities. This project is a project to rehabilitate 550,000 hectares of agricultural land in the provinces of Khuzestan and Ilam. The project has been divided according to the plots of چکیده کاملWe have a huge civic project, includes several sub-projects, which are divided into activities. This project is a project to rehabilitate 550,000 hectares of agricultural land in the provinces of Khuzestan and Ilam. The project has been divided according to the plots of land. The Jehad in Tehran is managing the projects. They need project scheduling as well as resource levelling and "lot-sizing". Levelling and lot sizing are the most important issues in utilizing the limited resources. For determining the scope and the size of those sub-projects as well as their parallel activities, so far, many models have been proposed. However, the models are weak either in higher resource utilization or in solving numerically the problems. In this paper, our effort has been concentrated on developing scheduling, resource levelling, and lot sizing model, based on balancing utilization of resources, so that the real size civil project could be solved within an acceptable duration time. This paper proposes a goal programming linear model for simultaneous project scheduling and resource levelling. This model determines the best schedule of sub-activities (optimal "lot size" of each sub-activity) to reach the minimum amount of diversion of resources consumed from the number of resources available for the entire periods of the planning horizon. In fact, if the best "lot sizes" have been taken, then minimum fluctuation of the active resources is reached. The proposed model has been used to schedule a project with 87 activities. This project has been scheduled and, accordingly, the optimal volume (the "lot size") of sub-activities have been determined for each activity at any period of time. In this way, only 4 resources out of a total of 32 resources are in shortage. In contrast, the scheduling of this project, using the CPM, results in a shortage of 13 resources. پرونده مقاله -
دسترسی آزاد مقاله
2 - توسعه و حل یک مدل تعیین اندازه انباشته دو سطحی با چند روش تولید بوسیله الگوریتم بهینه سازی میرایی ارتعاش
محمد ابراهیمی مقصود امیریمسئله تعیین اندازه انباشته شامل تعیین مقدار محصول و زمان بندی برای چندین قلم بر روی یک واحد تسهیل با بیش از یک تعداد متناهی از دوره به طوری که تقاضا و ظرفیت محدود می تواند با حداقل هزینه ارضا شود، می باشد. در این مقاله، یک مدل تعیین اندازه انباشته دو سطحی با چند روش تول چکیده کاملمسئله تعیین اندازه انباشته شامل تعیین مقدار محصول و زمان بندی برای چندین قلم بر روی یک واحد تسهیل با بیش از یک تعداد متناهی از دوره به طوری که تقاضا و ظرفیت محدود می تواند با حداقل هزینه ارضا شود، می باشد. در این مقاله، یک مدل تعیین اندازه انباشته دو سطحی با چند روش تولید ارائه می شود. هدف مدل ارائه شده مینیمم سازی هزینه می باشد. از الگوریتم بهینه سازی میرایی ارتعاش برای حل مدل استفاده می شود. از آنجایی که کیفیت حل همه الگوریتم های فرا ابتکاری به پارامترهای آن ها وابسته است، برای تنظیم پارامتر الگوریتم میرایی ارتعاش از روش تاگوچی استفاده شده است. سپس برای اثبات عملکرد مناسب روش حل ارائه شده، ابتدا مسائل آزمایشی با ابعاد مختلف تولید شده و سپس توسط نرم افزار لینگو و الگوریتم بهینه سازی میرایی ارتعاش حل گردید. در نهایت پاسخ لینگو و الگوریتم بهینه سازی میرایی ارتعاش را با هم از نظر زمان حل مقایسه می کنیم که نتایج بدست آمده نشان می دهد، جواب الگوریتم بهینه سازی میرایی ارتعاش در مسائل با اندازه بزرگ کیفیت بهتری نسبت لینگو داشته است. پرونده مقاله -
دسترسی آزاد مقاله
3 - Optimal Manufacturer-Retailer Policies in a Supply Chain with Defective Product and Price Dependent Demand
Abbas Ahmadi Samira Mohabbatdar Mohsen SajadiehThis study deals with a two-level supply chain consisting of one manufacturer and one retailer. We consider an integrated production inventory system where the manufacturer processes raw materials in order to deliver finished product with imperfect quality to the retail چکیده کاملThis study deals with a two-level supply chain consisting of one manufacturer and one retailer. We consider an integrated production inventory system where the manufacturer processes raw materials in order to deliver finished product with imperfect quality to the retailer, where number of defective product has a uniform distribution. The retailer receives product and conducts a 100% inspection. We assume that unit price charged by the retailer influences the demand of the product. Thereby, this study establishes a link between the literature on shipment, ordering, pricing policies, imperfect quality and the joint economic lot-sizing literature. The objective is to maximize the total joint annual profits incurred by the manufacturer and the retailer. The retailer inspects the product and delivers perfect-quality product to the first market and the rejected products sent back to the manufacture to be sold in the second market. Shortages are permitted for the retailer and are completely backordered. The researchers assume the policy in which the shipment quantity is delivered to the retailer is identical at each shipment.The numerical study shows that coordination between supply chain members increases when the defective percentage is reduced, and the warranty cost increases. The warranty cost has more effect on decreasing maximum total profit under individual optimization. پرونده مقاله -
دسترسی آزاد مقاله
4 - Economic Lot Sizing and Scheduling in Distributed Permutation Flow Shops
Mohammad Alaghebandha Bahman Naderi Mohammad MohammadiThis paper addresses a new mixed integer nonlinear and linear mathematical programming economic lot sizing and scheduling problem in distributed permutation flow shop problem with number of identical factories and machines. Different products must be distributed between چکیده کاملThis paper addresses a new mixed integer nonlinear and linear mathematical programming economic lot sizing and scheduling problem in distributed permutation flow shop problem with number of identical factories and machines. Different products must be distributed between the factories and then assignment of products to factories and sequencing of the products assigned to each factory has to be derived. The objective is to minimize the sum of setup costs, work-in-process inventory costs and finished products inventory costs per unit of time. Since the proposed model is NP-hard, an efficient Water Cycle Algorithm is proposed to solve the model. To justify proposed WCA, Monarch Butterfly Optimization (MBO), Genetic Algorithm (GA) and combination of GA and simplex are utilized. In order to determine the best value of algorithms parameters that result in a better solution, a fine-tuning procedure according to Response Surface Methodology is executed. پرونده مقاله -
دسترسی آزاد مقاله
5 - Economic order quantity model for growing items with incremental quantity discounts
Makoena Sebatjane Olufemi AdetunjiCertain inventory items are living organisms, for example livestock, and are therefore capable of growing during the replenishment cycle. These items often serve as various saleable food items downstream in supply chains. The purpose of this paper is to develop a lot si چکیده کاملCertain inventory items are living organisms, for example livestock, and are therefore capable of growing during the replenishment cycle. These items often serve as various saleable food items downstream in supply chains. The purpose of this paper is to develop a lot sizing model for growing items if the supplier of the items offers incremental quantity discounts. A mathematical model is derived to determine the optimal inventory policy which minimises the total inventory cost in both the owned and rented facilities. A solution procedure for solving the model is developed and illustrated through a numerical example. Sensitivity analysis is performed to demonstrate the response of the order quantity and total costs to some key input parameters. Incremental quantity discounts result in reduced purchasing costs; however, ordering very large quantities has downsides as well. The biggest downsides include the increased holding costs, the risks of running out of storage capacity and item deterioration since the cycle time increases if larger quantities are purchased. Owing to the importance of growing items in the food supply chains, the model presented in this article can be used by procurement and inventory mangers when making purchasing decisions. پرونده مقاله
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