Browsing by Subject "Materials management."

Now showing 1 - 4 of 4

Open Access
Design of cellular manufacturing systems using a holonistic approach
(1998) Türkcan, Ayten
Cellular manufacturing is application of group technology to mcinufacturing. Cellular manufacturing system design problem involves the identification of part families, machine groups and layout of cells, and the selection of tools, fixtures and material handling equipment. In this study, part family and machine cell formation, and within-cell hiyout problems are solved simultaneously by using a holonistic approach. A mixed integer programming (MIP) model is proposed to form completely independent cells. The model maximizes total profit under cell size, within-cell layout, machine capacity, low utilization and low profit level constraints. Since it is difficult to obtain a feasible solution to the proposed model in a reasonable computation time, a local search heuristic based algorithm is proposed. The first two stages of the algorithm are used to find a feasible solution to the MIP model and the third stage provides an alternative solution with intercell movements. The proposed algorithm finds feasible solutions to the problem in recisonable computation times.
Open Access
Exact solutions and heuristics for multi-product inventory pricing problem
(2014) Çetin, Oğuz
We study the multi-product inventory pricing problem under stochastic and price sensitive demand. We have initial inventory of m resources whose different combinations form n products. Products are perishable and need to be sold by a deadline. Demand for each product is modeled as a non-homogeneous Poisson process whose intensity is a function of the current price of the product itself. The aim is to set the price of each product over the selling period to maximize the expected revenue. This problem is faced in various industries including retail, airlines, automobile, apparel, hotels and car rentals. Our contributions are twofold. First, we provide a closed form solution for the special case of exponential price response where the elasticity parameter of the demand function of all products are equal. Second, we develop two classes of dynamic pricing heuristics: one using the value approximation approach of dynamic programming and the other using the deterministic version of the problem. Our numerical analysis indicates that dynamic pricing yields significantly higher revenues compared to fixed price policies. One of the dynamic pricing heuristics based on the deterministic problem provides around 5−15% additional revenue compared to fixed price policies. Moreover, two value approximation heuristics that we suggest result in at most ∼ 0.5% and ∼ 3.4% gaps in the expected revenue compared to the optimal dynamic pricing policy for general form of exponential price response. These additional revenues can have a profound effect on the profitability of firms, so dynamic pricing should be preferred over fixed price policies in practice.
Open Access
Financial valuation of flexible supply chain contracts
(2008) Erön, Ali Gökay
We consider a single buyer - single supplier multiple period quantity flexibility contract in which the buyer has options to buy in case of a higher than expected demand in addition to the committed purchases at the beginning of each period of the contract. We take the buyer’s point of view and find the maximum value of the contract for the buyer by analyzing the financial and real markets simultaneously. We assume both markets evolve as discrete scenario trees. Furthermore, under the assumption that the demand of the item correlates perfectly with the price of the risky security we present a model to find the buyer’s maximum acceptable price of the contract. Applying duality, we develop sufficient conditions on some parameters to decrease the value of the contract. Then, an experimental study is presented to illustrate the impacts of all the parameters on the value of the contract and the option. We show that the model can also be extended to the case of partially correlated demand and the risky asset price under the assumption that the markets evolve as binomial trees. Finally, we apply duality and perform numerical analysis for the latter assumption.
Open Access
Integration of production, transportation and inventory decisions in supply chains
(2012) Koç, Utku
This dissertation studies the integration of production, transportation and inventory decisions in supply chains, while utilizing the same vehicles in the inbound and outbound. The details of integration is studied in two levels: operational and tactical. In the first part of the thesis, we provide an operational level model for coordination of production and shipment schedules in a single stage supply chain. The production scheduling problem at the facility is modelled as belonging to a single process. Jobs that are located at a distant origin are carried to this facility making use of a finite number of capacitated vehicles. These vehicles, which are initially stationed close to the origin, are also used for the return of the jobs upon completion of their processing. In the first part, a model is developed to find the schedules of the facility and the vehicles jointly, allowing effective utilization of the vehicles for both in the inbound and outbound transportation. In the second part of the dissertation, we provide a tactical level model and study a manufacturer’s production planning and outbound transportation problem with production capacities to minimize transportation and inventory holding costs. The manufacturer in this setting can use two vehicle types for outbound shipments. The first type of vehicle is available in unlimited number. The availability of the second type, which is less expensive, changes over time. For each possible combination of operating policies affecting the problem structure, we either provide a pseudo-polynomial algorithm for general cost structure or prove that no such algorithm exists even for linear cost structure. We develop general optimality properties, propose a generic model formulation that is valid for all problems and evaluate the effects of the operating policies on the system performance. The third part of the dissertation considers one of the problems defined in the second part in detail. Motivated by some industry practices, we present formulations for three different solution approaches, which we refer to as the uncoordinated solution, the hierarchically-coordinated solution and the centrallycoordinated solution. These approaches vary in how the underlying production and transportation subproblems are solved, i.e., sequentially versus jointly, or, heuristically versus optimally. We provide intractability proofs or polynomialtime exact solution procedures for the subproblems and their special cases. We also compare the three solution approaches to quantify the savings due to integration and explicit consideration of transportation availabilities.