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The classical economic batch quantity (EBQ) model assumes that all produced items have a perfect quality. But in real-life production systems, generation of defective items is inevitable. A portion of these defective items is considered to be scrap , while the other is assumed to be reworkable and reworking them can reduce costs and increase productivity. In this thesis we have studied the economic batch quantity for a single stage production system with rework and scrapping . We want to satisfy the customer demand and minimize total costs of the system like set up costs , production costs , rework costs , holding costs , shortage costs and scrapping costs . In the first chapter of this... 

Based on the latest statistical figures, more than 50 billion Rials worth of medical equipment exists in Iran’s medical centers. In spite of this, Breakdown maintenance is used in all hospitals, which means that the equipment is utilized as long as it is not out of order and only in such a situation, i.e. a breakdown, the necessary repair operation is conducted on the equipment. In fact, no maintenance is carried out to prevent a breakdown, while the “prevention from breakdown” concept has long been introduced in the majority of industries in many countries including Iran and its positive impacts are undisputable. This thesis aims at proposing a solution for the implementation of a “planned... 

This research deals with a supply chain consisting of one vendor and several retailers. Every retailer orders a fixed discrete quantity in fixed discrete time intervals. Order quantity and order cycle of each retailer could be different from the others. The vendor orders the required quantity to a supplier to fulfill the received demands. Also the vendor orders a discrete quantity, which will be immediately received at the vendor’s warehouse. In this supply chain system, the lead-time is assumed to be zero and shortage is allowed for vendor. The aim is to find minimum vendor’s inventory cost. We proposed a backward Dynamic Programming algorithm for the model. The algorithm creates vendor’s... 

Production scheduling is such a key issue that directly influences on the performance of the machines and efficiency of production line. This category of problems is to find simultaneously the lot sizes and their sequence over a finite set of planning periods.
In this Thesis a multi objective production planning and job shop scheduling problem is investigated. The objectives are minimization of the production cost and minimization of production time smoothness in consecutive periods. As the problem is shown to be NP-hard, two multi-objectives genetic algorithms with two approaches in selection of parents and crowding distance index are proposed to solve this problem. In these two meta... 

EOQ and EPQ models have been among the most important and commonly used techniques for about 100 and 60 years respectively .But, they are involved in some assumptions that sometimes prevent them from being implemented in real situation of industry and production. One of these unrealistic assumptions is that all of items received or produced are of perfect quality. In order to overcome this constraint and make the mentioned models closer to the real environmentsome researches have been done. To this end,following the previous attemptsin this project we assumed to have destructive inspections and existence of imperfect and rejected items after rework. In our models, considering 3 circumstances... 

Hub and Spoke networks come into play when considering direct link between all origins and destinations is either impossible or expensive in a transportation system. In this kind of problems, some nodes are chosen as hub from all origin and destination nodes to collect flows and then distribute them. Implementing hub network leads to minimizing transportation cost, sorting flows and conveying them in economies of scale. Otherwise, shipping flows directly may cause decreasing the travelling distance and the delivery time consequently. In this dissertation, combination of hub network and direct shipment is investigated. To obtain the optimal hub locations and direct links between non-hub nodes... 

In this paper, we studied a two-echelon inventory system which consists of one central warehouse and one retailer. All installations follow base stock inventory management policy. The customers arrive at retailer according to Poisson distribution. The demand is satisfied when both central warehouse and retailer have positive on-hand inventory. Otherwise, the demand is lost. The lead time of central warehouse and the time needed to replenish orders of retailer are assumed to be exponentially distributed. The purpose of this study is to minimize the expected long-run total cost of the system per unit time. Total cost of the system includes holding costs of central warehouse and retailer, cost... 

This dissertation attempts to develop four inventory control models for two-echelon supply chains. For the all models, the retailers face Poisson demand and lost sales during a stockout. There is also a time-dependent holding cost and a cost per unit of lost sales. However, there is no (or negligible) cost associated with placing an order.
For the first model, we consider a two-echelon inventory system with one central warehouse and a number of retailers. The central warehouse applies (R, Q) policy and retailers apply base stock policy. In this model, we approximate the arrival process of the central warehouse and obtain the total cost of the system, as well as the optimal solution.... 

In this study we consider a two-level supply chain, with a supplier and a number of identical retailers, demand process is Poisson with random rate. All retailers apply (R,Q) policy with backorder case for their inventory control supplier fulfills the orders of retailers according to FIFO discipline. At any point of time the supplier has online information about inventory position of all retailers.
Whenever the inventory position of a retailer reaches to a fixed value (s) above its reorder point, the supplier orders a batch of size Q to an outside source with infinite capacity. Lead-time of each retailer is equal to the sum of a constant transportation time and a delay time which is... 

Fulfilling the demands of customers, used to be the main purpose of Supply Chain Network Designers. Soon after that, the environmental concerns created the concept of Reverse Logistic in order to prevent goods from being scattered in the environment after their disposal. Governmental regulations and people's concerns, forced the factories to gather the created pollutions of the environment. They gradualy confessed the positive impacts of these ruturns on their financials. The flow of forward and reverse logistics establishes a Closed-Loop in which the returning economical circumstances were transferd into original factories. Later, Open-Loops were created. In open-loops the returns have to... 

Although inventory control under discrete demand in dynamic quantities and time intervals are very common in reality, existing literature has largely ignored them. In this thesis, we investigate the inventory control decisions in a two echelon supply chain. The vendor supplies a product to several retailers, buying discrete quantities in pre-determined time intervals. The order quantity and order cycles for each retailer can be different from others. We have developed a new efficient algorithm to find the optimal ordering policy involves the scheduling and the order quantity of vendor to his supplier to minimize his cost function in infinite time horizon. Moreover, we have designed a revenue...