1,721,105 research outputs found
U-tipi esnek montaj hattı tasarım problemi.
No full textThis study considers a U-shaped assembly line where the operators are allowed to work on both legs of the U-shaped line. We assume that the number of workstations and the cycle time are fixed. Each task uses a specified set of equipments where each type of equipment has a specified cost. The problem is to assign the tasks together with their equipments to the workstations so as to minimize the total equipment cost. We propose a branch and bound algorithm that uses efficient precedence relations and lower bounds. We find that the algorithm is able to solve moderate size problem instances with up to 21 tasks-10 workstations and 30 tasks-8 workstations in reasonable time.M.S. - Master of Scienc
Tip-2 transfer hattı dengeleme problemi.
No full textIn this thesis, we consider Type II Transfer Line Balancing that assigns the operation to the blocks and blocks to the stations so as to maximize the production rate, i.e., to minimize the cycle time. A mixed integer programming model is developed and a branch and bound algorithm is proposed for the exact solutions. The efficiency of the branch and bound algorithm is enhanced by lower and upper bounding procedures. The computational results have revealed the satisfactory behavior of the model and branch and bound algorithm on moderate size problem instances.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Industrial Engineering
k-Çinli postacı dengeleme problemi üzerine.
No full textIn this thesis, we consider a k-Chinese Postmen Problem with the objective of minimizing total squared workloads. Our aim is to balance the workloads of the postmen, while maintaining low total workload. We develop an efficient subtour elimination constraint and incorporate it to our integer program. We develop exact and approximate solution procedures that run in exponential and polynomial time respectively. The results of our computational experiment reveal the satisfactory behaviors of our algorithms in terms of solution speed and solution quality.M.S. - Master of Scienc
Montaj hatlarında yeniden dengeleme.
No full textAssembly line balancing is an important and well recognized operations research problem. The current balancing might not stay optimal for a long time due to the changing conditions. The changing conditions, like disruptions in one or more workstations, may cause some inefficiencies, even infeasibilities, for the current balance. In this study, after the disruption, we aim to rebalance the assembly line by considering the trade-off between workload balancing (efficiency measure) and total displacement amount for the tasks assigned to the different workstations (stability measure). We try to generate all non-dominated objective function vectors for the defined efficiency and stability measures. Two algorithms are developed: classical approach and tabu search algorithm. Our experiments have shown that the classical approach returns exact non dominated objective vectors with up to 40 tasks and 7 workstations in one hour and the tabu search algorithm returns approximate non dominated objective vectors that are very close to their exact counterparts and can solve large sized instances, very quickly.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Industrial Engineering
Sabit sayıda iş istasyonu içeren esnek montaj hattı tasarımı problemi.
No full textIn this thesis, we study a Flexible Assembly Line Design problem. We assume the task times and equipment costs are correlated in the sense that for all tasks the cheaper equipment gives no smaller task time. Given the cycle time and number of workstations we aim to find the assignment of tasks and equipments to the workstations that minimizes the total equipment cost. We study a special case of the problem with identical task times. For the general case, we develop a branch and bound algorithm that uses powerful lower bounds and reduction mechanisms. We test the performance of our branch and bound algorithm on randomly generated test problems. The results of our experiments have revealed that we are able to solve large-sized problem instances in reasonable times.M.S. - Master of Scienc
Önleyici bakım varlığında makine çizelgeleme.
No full textIn manufacturing environments, machines are usually subject to down periods due to various reasons such as preventive maintenance activities, pre-accepted jobs and pre-known material shortages. Among these reasons, preventive maintenance, which is defined as the pre-planned maintenance activities to keep the machine in its operating state, has gained much more importance in recent years. In this thesis, we consider the single machine total flow time problem where the jobs are non-resumable and the machine is subject to preventive maintenance activities of known starting times and durations. We propose a number of optimality properties together with the upper and lower bounding procedures. Using these mechanisms, we build a branch and bound algorithm to find the optimal solution of the problem. Our extensive computational study on randomly generated test instances shows that our algorithm can solve large-sized problem instances with up to 80 jobs in reasonable times. We also study a two-alternative maintenance planning problem with minor and major maintenances. We give an optimizing algorithm to find the timing of the maintenances, when the job sequence is fixed.M.S. - Master of Scienc
Proje ağlarında bütçe kısıtlı kesikli zaman/maliyet ödünleşim problemi.
No full textThe time/cost trade-off models in project management aim to compress the project completion time by accelerating the activity durations at an expense of additional resources. The budget problem in discrete time/cost trade-off scheduling selects the time/cost mode -among the discrete set of specified modes- for each activity so as to minimize the project completion time without exceeding the available budget. There may be alternative modes that solve the budget problem optimally, however each solution may have a different total cost value. In this study we aim to find the minimum cost solution among the optimal solutions of the budget problem. We analyze the structure of the problem together with its linear programming relaxation and derive some mechanisms for reducing the problem size. We solve the reduced problem by linear programming relaxation and branch and bound based approximation and optimization algorithms. We find that our branch and bound algorithm finds optimal solutions for medium-sized problem instances in reasonable times and the approximation algorithms produce high quality solutions. We also discuss the way our algorithms could be used to construct the time/cost trade-off curve.M.S. - Master of Scienc
Tek yenilenemeyen kaynak ile çoklu modlu proje çizelgeleme problemi.
No full textIn this thesis, we consider a multi-mode project scheduling problem with a single nonrenewable resource. We assume that the resource is released in pre-specified times at pre-specified quantities and the resource is consumed at activity completions. The activities can be processed at different modes where a mode is defined by a processing time and a resource requirement amount. Our problem is to select the modes and timings of the activities so as to minimize the project completion time. We develop a mixed integer linear model and present a branch and bound algorithm. The results of our experiments have revealed that the mathematical model can handle only small-sized problem instances with up to 20 tasks and branch and bound algorithm can solve problem instances with up to 100 tasks for some resource release profiles.M.S. - Master of Scienc
İki boyutlu stok kesme problemi.
No full textIn this study, we consider a two dimensional cutting stock problem with multiple stock sizes and two stage guillotine cuts. Our objective is to maximize the difference between total revenue over all items and total cost over all used panels. We propose two mathematical models and discuss their relative performances. We enhance the performances of the models by incorporating the properties of optimal solution that we derive. The results of our computational study have revealed the satisfactory performance of one of our models with optimal properties for medium sized problem instances. We develop decomposition-based heuristics that produce high quality solutions in reasonable time.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Industrial Engineering
Sürdürülebilir sistemler mühendisliğinde ödünleşim modelleri.
No full textPrior to concerns of sustainability, almost all industrial engineering models tried to minimize cost or maximize profit. Sustainability awareness has recently forced the decision makers to also take into consideration such aspects as clean water use, or carbon dioxide emissions. In an effort to incorporate more aspects of sustainability in optimizing production efforts, we present a network model to handle trade-offs among dissimilar sustainability criteria. Since typically there are alternative choices for the various operations, the network allows parallel arcs between the same nodes. We also introduce the concept of generalized cost. Generalized cost is a vector quantity that includes not only a monetary measure, but also measures relevant to sustainability, such as carbon use or embodied energy. The approach leads to a multi-criteria decision making model, whose efficient frontier is obtained by the epsilon constraint method. Numerical work shows that the computational effort to obtain the efficient frontier is reasonable, allowing products of up to about a hundred activities to be solved with the current generation of personal computers.M.S. - Master of Scienc
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