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Item Open Access An Input/Output control system for the dynamic job shop(Taylor & Francis, 1987) Onur, L.; Fabrycky, W. J.Show more A combined input/output control system is presented for periodically determining the set of jobs to be released (input variables) and the capacities of processing centers (output variables) in the dynamic job shop, so that a composite cost function is minimized. An interactive heuristic optimizing algorithm incorporating a 0-1 linear mixed integer program is formulated. The resulting control system is compared by simulation with an alternate system for which only input is subject to control. Significant improvements are obtained for most performance measures evaluated. © 1987 Taylor & Francis Group, LLC.Show more Item Open Access An algorithmic proof of the polyhedral decomposition theorem(John Wiley & Sons, 1988) Akgül, M.Show more It is well‐known that any point in a convex polyhedron P can be written as the sum of a convex combination of extreme points of P and a non‐negative linear combination of extreme rays of P. Grötschel, Lovász, and Schrijver gave a polynomial algorithm based on the ellipsoidal method to find such a representation for any x in P when P is bounded. Here we show that their algorithm can be modified and implemented in polynomial time using the projection method or a simplex‐type algorithm : in n(2n + 1) simplex pivots, where n is the dimension of x. Extension to the unbounded case is immediate.Show more Item Open Access A transportation type aggregate production model with bounds on inventory and backordering(Elsevier, 1988) Erenguc, S. S.; Tufekci, S.Show more We consider a certain T period aggregate production planning model, where the two sources of production are regular and overtime. The model allows for time varying production, holding and backordering costs and includes bounds on inventory and backorders. We show that the problem has a rather interesting network structure and exploit this structure to develop a greedy algorithm to solve the problem. The procedure is easy to implement and has a computational complexity of O(T2). We report computational experience with the greedy procedure and demonstrate its superiority to a well known network simplex code, Gnet, implemented on the classical network formulation of the problem. © 1988.Show more Item Open Access A heuristic procedure for a single-item dynamic lot sizing problem(Pergamon Press, 1988) Benli, O. S.; Sabuncuoglu, I.; Tufekci, S.Show more An O(T) heuristic proceudre for a single-item dynamic lot sizing problem is introduced in this paper. The algorithm tries to establish the regeneration points of the problem whether either the production or the beginning inventory must be equal to zero. The proposed algorithm is very easy to implement and compares very favourably with the existing heuristic procedures. © 1988.Show more Item Open Access A sequential dual simplex algorithm for the linear assignment problem(Elsevier, 1988) Akgül, M.Show more We present a sequential dual-simplex algorithm for the linear problem which has the same complexity as the algorithms of Balinski [3,4] and Goldfarb [8]: O(n2) pivots, O(n2 log n + nm) time. Our algorithm works with the (dual) strongly feasible trees and can handle rectangular systems quite naturally.Show more Item Open Access Optimal pickup point location on material handling networks(1989) Kiran, A.S.; Tansel, C. BarbarosShow more The optimal location of a pickup point on a material handling network is considered. The pickup point is defined as the material exchange point between the material handling system (MHS) and a station. The problem is defined as that of choosing the location of the pickup point to minimize the total cost of material movement in the MHS. A facility location model on directed networks has been developed, and strongly polynomial solution methods are presented.Show more Item Open Access An expert system for selecting attribute sampling plans(Taylor & Francis, 1990) Fard, N. S.; Sabuncuoglu, I.Show more A considerable portion of quality control managers lime in a production system is spent in routine and complex decision-making processes that have significant impact on average outgoing quality, quality improvement, and quality cost. The quality control manager must decide among various statistical process control methods and sampling plans for each part (or characteristic). These decisions arc usually based on how critical a part is, historical information about the quality of the parts, and other factors. Many of these factors require subjective judgments by the quality control manager. For a production facility with an inventory system of thousands of different parls l determination of feasible sampling plans and process control charts is a time-consuming and difficult task. As demons: rated in this paper, an expert system has been designed 10 faciliratc the selection of an appropriate sampling plan for each part . The system is referred to as Adviser for Selecting Auribute Sampling Plan (ASASP). © 1990 Taylor & Francis Ltd.Show more Item Open Access Training an artificial neural network the pure pursuit maneuver(Pergamon Press, 1991) Hommertzheim, D.; Huffman, J.; Sabuncuoglu, IhsanShow more Artificial neural networks' ability to learn, categorize, generalize and self organize make them potentially very useful for a variety of application areas. This paper discusses some experiences in attempting to teach a neural network how to perform the pure pursuit maneuver. Several problems were encountered in defining a proper training set. Three and four layer backpropagation networks were utilized to capture the input to output mappings.Show more Item Open Access Optimal order quantity and pricing decisions in single-period inventory systems(1991) Polatoğlu, Lütfi HakanShow more In this paper, we consider simultaneous pricing and procurement decisions associated with a one-period pure inventory model under deterministic or probabilistic demand. We investigate the necessary and sufficient conditions for an (σ, Σ) type policy to be optimal for the determination of the procurement quantity. We also show how the corresponding optimal price can be obtained. © 1991.Show more Item Open Access Incorporating just-in-time into a decision support system environment(Elsevier BV, 1991) Oǧuz, Ceyda; Dinçer, CemalShow more In this paper, a Decision Support System is proposed for a Just-In-Time production system. The Decision Support System includes three components: database, model base, and interface. The database contains the predefined parameters together with the data generated for the considered Just-In-Time production system. In the model base, both deterministic and stochastic aspects of the system are considered. The deterministic system is examined by constructing a linear programming model whereas simulation is used as a tool for the stochastic system. Furthermore, a sensitivity analysis is performed on the Just-In-Time production system with the help of the Decision Support System environment for the unit load size changes under different demand patterns by using the alternative solutions obtained from the model base.Show more Item Open Access Data dependent worst case bound improving techniques in zero-one programming(Elsevier BV, 1991) Oğuz, OsmanShow more A simple perturbation of data is suggested for use in conjunction with approximation algorithms for the purpose of improving the available bounds (upper and lower), and the worst case bounds. The technique does not require the approximation algorithm (heuristic) to provide a worst case bound to be applicable.Show more Item Open Access Separation and normalization in multi-attribute decision models for investment evaluation(Taylor & Francis, 1991) Falkner, C. H.; Verter, V.Show more The separation of the evaluation attributes into two distinct subsets, objective and subjective measures, is discussed. The use of normalization over the alternatives for each subjective attribute is shown to lead to erroneous choices in certain situations. © 1991 Taylor and Francis Group, LLC.Show more Item Open Access On the optimality of the greedy solutions of the general knapsack problems(Taylor & Francis, 1992) Vizvári, BelaShow more In this paper we submit a unified discussion of some closely related results which were achieved independently in number theory and integer programming, and we partially generalize them. In the unified discussion we treat together two problems where the greedy method has different characters, in the first one it is an internal-point algorithm, in the second one it is an outer-point method. We call a knapsack problem “pleasant” if the greedy solution is optimal for every right-hand side. A sufficient and two finite necessary and sufficient conditions for the pleasantness of a problem are discussed. The sufficient condition can be checked very easily. The paper is finished with an error analysis of some nonpleasant problems. AMS 1980 Subject Classification: Primary: 90C 10.Show more Item Open Access The linear assignment problem(Springer, 1992) Akgül, Mustafa; Akgül, Mustafa; Hamacher, H. W.; Tüfekçi, S.Show more We present a broad survey of recent polynomial algorithms for the linear assignment problem. They all use essentially alternating trees and/or strongly feasible trees. Most of them employ Dijkstra’s shortest path algorithm directly or indirectly. When properly implemented, each has the same complexity: O (n 3) for dense graphs with simple data structures and O (n 2 log n+nm) for sparse graphs using Fibonacci Heaps.Show more Item Open Access An integrated evaluation of facility location, capacity acquisition, and technology selection for designing global manufacturing strategies(Elsevier BV, 1992) Verter, Vedat; Dincer, Mehmet CemalShow more Emergence of global markets enhanced the emergence of global firms which have plants in different countries and implement an integrated management style. Due to the intensive competition in global markets, manufacturing performance is conceived as an important strategic weapon. Facility location, capacity acquisition and technology selection decisions constitute means to implement manufacturing strategies. We review the literature in order to contribute to a better understanding of global manufacturing strategies. As a result we observe that an integrated analysis of the location, capacity and technology decisions is vital for the design of effective global manufacturing strategies.Show more Item Open Access A comparison of hazard rate estimators for left truncated and right censored data(1992) Uzunoğulları, Ü.; Wang, J.-L.Show more SUMMARY: Left truncation and right censoring arise frequently in practice for life data. This paper is concerned with the estimation of the hazard rate function for such data. Two types of nonparametric estimators based on kernel smoothing methods are considered. The first one is obtained by convolving a kernel with a cumulative hazard estimator. The second one is in the form of a ratio of two statistics. Local properties including consistency, asymptotic normality and mean squared error expressions are presented for both estimators. These properties facilitate locally adaptive bandwidth choice. The two types of estimators are then compared based on their theoretical and empirical performances. The effect of overlooking the truncation factor is demonstrated through the Channing House data.Show more Item Open Access Experimental investigation of FMS machine and AGV scheduling rules against the mean flow-time criterion(Taylor & Francis, 1992) Sabuncuoglu, Ihsan; Hommertzheim, D. L.Show more Although a significant amount of research has been carried out in the scheduling of flexible manufacturing systems (FMSs), it has generally been focused on developing intelligent scheduling systems. Most of these systems use simple scheduling rules as a part of their decision process. While these scheduling rules have been investigated extensively for a job shop environment, there is little guidance in the literature as to their performance in an FMS environment. This paper attempts to investigate the performances of machine and AGV scheduling rules against the mean flow-time criterion. The scheduling rules are tested under a variety of experimental conditions by using an FMS simulation model.Show more Item Open Access Dynamic dispatching algorithm for scheduling machines and automated guided vehicles in a flexible manufacturing system(Taylor & Francis, 1992) Sabuncuoglu, Ihsan; Hommertzheim, D. L.Show more In this paper, an on-line dispatching algorithm is proposed for the FMS scheduling problem. The algorithm uses various priority schemes and relevant information concerning the load of the system and the status of jobs in the scheduling process. This information is organized into hierarchical levels. The scheduling decision process is hierarchical in the sense that different decision criteria are applied sequentially to identify the most appropriate part and the machine to be served. The algorithm schedules the jobs on a machine or an automated guided vehicle (AGV) one at a time as the scheduling decision is needed (or as the status of the system changes). Performance of the proposed algorithm is compared with several machine and AGV scheduling rules by using the mean flow-time and the mean tardiness criteria. Simulation results indicate that the proposed algorithm produces significant mean flow-time and mean tardiness improvements over existing scheduling rules for a variety of experimental conditions.Show more Item Open Access Preface(Springer, 1992) Akgül, Mustafa; Hamacher, H. W.; Tüfekçi, S.; Akgül, Mustafa; Hamacher, H. W.; Tüfekçi, S.Show more Item Open Access Beam search based algorithm for scheduling machines and AGVs in an FMS(Institute for Industrial Engineers, 1993) Karabük, S.; Sabuncuoğlu, İhsanShow more This paper presents a beam search based scheduling algorithm for a random FMS. The proposed algorithm considers finite buffer capacity, routing and sequence flexibilities and generates machine and AGV schedules in varying time windows. The performance of the algorithm is measured using makespan, flow time, and tardiness criteria under various experimental conditions.Show more