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Papers by Babak Haji
International Journal of Business Performance and Supply Chain Modelling, 2011
This paper deals with a two-echelon inventory system consisting of one supplier and N retailers. ... more This paper deals with a two-echelon inventory system consisting of one supplier and N retailers. Each retailer faces an independent Poisson demand with the same rate and applies a new ordering policy called one-for-one-period ordering policy for its inventory control. In this ordering policy, the order size is equal to one and the time interval between any two consecutive orders forms a common fixed cycle. Thus, the supplier faces a deterministic demand and adopts a deterministic inventory policy. At each cycle, he orders a batch of size N to his own supplier. Upon receipt of each batch, he sends one unit of the product to each retailer with a transportation cost. In this paper, for the above system, we first derive the total cost function per unit time. Further, we obtain the conditions under which the total cost function is convex. Finally, we obtain the optimal time interval between any two consecutive orders as well as the optimal average inventory for each retailer.
Journal of Applied Probability
We consider a queueing loss system with heterogeneous skill based servers with arbitrary service ... more We consider a queueing loss system with heterogeneous skill based servers with arbitrary service distributions. We assume Poisson arrivals, with each arrival having a vector indicating which of the servers are eligible to serve it. An arrival can only be assigned to a server that is both idle and eligible. Assuming exchangeable eligibility vectors and an idle time ordering assignment policy, the limiting distribution of the system is derived. It is shown that the limiting probabilities of the set of idle servers depend on the service time distributions only through their means. Moreover, conditional on the set of idle servers, the remaining service times of the busy servers are independent and have their respective equilibrium service distributions.
… , Logistics and Informatics, 2009
Abstract-This paper deals with the issue of economic batch quantity (EBQ) in a single machine sys... more Abstract-This paper deals with the issue of economic batch quantity (EBQ) in a single machine system in which defective items are produced in each cycle of production. The accumulated defective items produced in a period, consisting of several equal cycles, are all reworked in the last ...
Operations Research Letters
International Journal of Business Performance and Supply Chain Modelling, 2011
This paper deals with a two-echelon inventory system consisting of one supplier and N retailers. ... more This paper deals with a two-echelon inventory system consisting of one supplier and N retailers. Each retailer faces an independent Poisson demand with the same rate and applies a new ordering policy called one-for-one-period ordering policy for its inventory control. In this ordering policy, the order size is equal to one and the time interval between any two consecutive orders forms a common fixed cycle. Thus, the supplier faces a deterministic demand and adopts a deterministic inventory policy. At each cycle, he orders a batch of size N to his own supplier. Upon receipt of each batch, he sends one unit of the product to each retailer with a transportation cost. In this paper, for the above system, we first derive the total cost function per unit time. Further, we obtain the conditions under which the total cost function is convex. Finally, we obtain the optimal time interval between any two consecutive orders as well as the optimal average inventory for each retailer.
Journal of Applied Probability
We consider a queueing loss system with heterogeneous skill based servers with arbitrary service ... more We consider a queueing loss system with heterogeneous skill based servers with arbitrary service distributions. We assume Poisson arrivals, with each arrival having a vector indicating which of the servers are eligible to serve it. An arrival can only be assigned to a server that is both idle and eligible. Assuming exchangeable eligibility vectors and an idle time ordering assignment policy, the limiting distribution of the system is derived. It is shown that the limiting probabilities of the set of idle servers depend on the service time distributions only through their means. Moreover, conditional on the set of idle servers, the remaining service times of the busy servers are independent and have their respective equilibrium service distributions.
… , Logistics and Informatics, 2009
Abstract-This paper deals with the issue of economic batch quantity (EBQ) in a single machine sys... more Abstract-This paper deals with the issue of economic batch quantity (EBQ) in a single machine system in which defective items are produced in each cycle of production. The accumulated defective items produced in a period, consisting of several equal cycles, are all reworked in the last ...
Operations Research Letters