Levent Kandiller

Profit-oriented disassembly-line balancing

As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower- and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time.

A Decision Support System for the cell formation problem

This paper describes a study involving the development of a Decision Support System (DSS) for the part/machine Cell Formation (CF) problem of cellular manufacturing, to be used as a research oriented as well as operational cell design tool. An overview of the CF problem is presented, followed by the description of efficiency measures and construction algorithms selected from the literature for creation and evaluation of alternative solutions. New modified efficiency measures and a Composite Measure (CM) are proposed and employed in the DSS for more comprehensive comparisons. Improvement heuristics are developed for modifying and enhancing the solutions formed by the construction algorithms. DSS users are enabled to switch among solutions or algorithms for determining the best cell configuration for their particular needs.

Disassembly line balancing with limited supply and subassembly availability

Disassembly line balancing problem (DLBP) aims at finding a feasible assignment of disassembly tasks to workstations such that precedence relations among tasks are satisfied and some measure of effectiveness is optimized. We consider partial disassembly under limited supply of a single product as well as availability of its subassemblies. Hence, in satisfying the demand for revenue generating parts, both discarded products and available subassemblies can be utilized. We assume that part revenues and demand, task times and costs, inventory holding costs, and station opening costs are given. We propose two DLBP formulations. The first one maximizes the profit per disassembly cycle. The second formulation maximizes the profit over the whole planning horizon. Proposed formulations and computational results are presented.

Semi-dynamic modelling of heterogeneous land combat

We propose a semi-dynamic approach to tactical level land combat modelling from the attackers viewpoint. Our approach decomposes a battle between heterogeneous forces into stages and mini battles. For each mini battle in a stage, we use three models: a mathematical programming model for optimizing force allocations, a Lanchester simulation model for predicting whether or not the stage targets are reached under the allocations, and a model for weapon effectiveness update from one stage to the next. These models interact with each other within the framework of a decision support system to help the user with allocation decisions as well as prediction of force requirements to win the battle.

A cell formation algorithm: Hypergraph approximation - Cut tree

A new cell formation technique is presented and analyzed in this paper. The cell formation problem is defined using the hypergraph representation of the manufacturing systems. The proposed method approximates the hypergraph model by graphs so that the cuts are less affected by the approximation. Consequently, a Gomory-Hu cut tree of the graph approximation is obtained. The minimum cuts between all pairs of vertices are calculated easily by means of this tree, and a partition tree is produced. Our cell formation algorithm successively cuts the partition tree. The algorithm is subjected to an experimentation of randomly generated manufacturing situations. The algorithm is compared with other cell formation techniques as well.

Design of a Decision Support System (DSS) for Housekeeping Operations

This paper conducts our senior project at Altin Yunus Hotel located in Cesme, Turkey and it contributes to the improvement of operations management of the hotel, focusing on the front office, reception and housekeeping services. The problem is determined as the housekeeping problem in consideration of other problems described in detail in the following sections. Required data are provided by the hotel management. The aim of the study is to develop a decision support system (DSS) covering and increasing the efficiency in service quality. Through the literature survey, system analysis and the developed mathematical models such as regression, time study, worker assignment, uniform parallel machine scheduling and routing optimization are presented. Finally, achieved time and cost savings are presented.

An alternative MILP model for makespan minimization on assembly lines

The Simple Assembly Line Balancing Problem-2 (SABLP-2) is defined as partitioning the tasks among stations in order to minimize the cycle time, given the number of stations. SALBP-2 reduces to the identical parallel machine scheduling problem with makespan minimization (

Anti-ship missile defense for a naval task group

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