Age and lifetime based policies for perishable items

buir.advisorGürler, Ülkü
dc.contributor.authorPoormoaied, Saeed
dc.departmentDepartment of Industrial Engineeringen_US
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (Ph.D.): Bilkent University, Department of Industrial Engineering, İhsan Doğramacı Bilkent University, 2018.en_US
dc.descriptionIncludes bibliographical references (leaves 178-182).en_US
dc.description.abstractMany inventory systems hold items which perish after a specific time. Upon perishing, the inventory level falls down to zero which may incur irreparable costs to the system. Therefore, developing a genius control policy for managing such inventories is a crucial task. Since the lifetime of items are now affecting the inventory level, applying the traditional inventory policies which are based only on the stock level causes some shortcomings. The traditional inventory policies lack the information regarding the lifetime of items. On the other hand, the optimal policy for perishable items is known to be a periodic review policy keeping the complete information regarding the remaining lead times of orders, inventory onhand, and lifetimes of items. Optimal control policy class for continuous review is still an open question. In this regard, we attempt to contribute the remaining lifetime of items into the inventory policy for perishable items with positive lead time and fixed lifetime under a continuous review with a service level constraint. We develop a class of hybrid control policies which utilize the remaining lifetimes of items in addition to stock levels. We study a stochastic single item inventory system where demand follows a Poisson process and unmet demand is lost. The aging process of a new batch starts when it joins the inventories. We provide an exact analytic model by using an embedded Markov chain process to derive the stationary distribution of the effective lifetimes in the presence of both one and more than one outstanding orders assumptions. Operating characteristics of the system are derived using the renewal reward theorem. Additionally, we propose some control policies based on only the remaining lifetime of items. Our results reveal that the hybrid policies consistently outperform the stock level and remaining lifetime-based polices, especially when demand during the lifetime is sufficiently small and unit perishing cost is high. It is observed that the dominance relations among these two policy classes depend on the particular parameter setting. In particular, when the lifetime of items is long enough, the stock level based policy performs very well. Finally, we present our methodology for finding the optimal solution thorough a heuristic algorithm derived by considering the structure of the objective function and service level constraint, and a sensitivity analysis is performed to evaluate the impact of the key input parameters.en_US
dc.description.statementofresponsibilityby Saeed Poormoaieden_US
dc.format.extentxvi, 185 leaves : charts ; 30 cm.en_US
dc.publisherBilkent Universityen_US
dc.subjectPerishable Inventoryen_US
dc.subjectInventory Policyen_US
dc.subjectEffective Lifetimeen_US
dc.subjectEmbedded Markov Chainen_US
dc.subjectRenewal Theoremen_US
dc.titleAge and lifetime based policies for perishable itemsen_US
dc.title.alternativeKısa ömürlü ürünler için yaş ve raf ömrüne dayalı politikalaren_US
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Thesis. Last version.pdf
9.84 MB
Adobe Portable Document Format
Full printable version
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
1.71 KB
Item-specific license agreed upon to submission