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Öğe An Overview of Energy Technologies for a Sustainable Future(Springer Int Publishing Ag, 2015) Esen, Ayse Nur; Duzgit, Zehra; Toy, A. Ozgur; Gunay, M. ErdemPopulation and the economic growth are highly correlated with the energy demand. The world population was multiplied by a factor of 1.59 (reaching above 7 billion) from 1980 to 2013, while the total energy consumption of the world was multiplied by 1.84 (getting beyond 155,000 TWh) in the same time interval. Furthermore, the demand for energy is expected to increase even more with an average annual rate of 1.2 % in the near future. However, for the last 30 years, about 85-90 % of the energy demand is supplied by petroleum, natural gas, and coal, even though they are harmful for the environment and estimated to be depleted soon. Hence, building energy policies to satisfy the needs of increasing population and growing economy in a sustainable, reliable, and secure fashion has become quite important. This may involve optimizing the energy supplies, minimizing the environmental costs, promoting the utilization of clean and renewable energy resources and diversifying the type of energy sources. Thus, not only the conventional energy generation technologies must be developed more, but also environmentally friendly alternative energy sources (such as wind, solar, geothermal, hydro, and bio) must become more widespread to sustain the energy needs for the future. However, this requires a significant amount of research on energy technologies and an effective management of the energy sources.Öğe Design of a Routing Algorithm for Efficient Order Picking in a Non-traditional Rectangular Warehouse Layout(Springer-Verlag Singapore Pte Ltd, 2022) Sancakli, Edin; Dumlupinar, Irem; Akcin, Ali Osman; Cinar, Ezgi; Geylani, Ipek; Duzgit, ZehraWarehouses have gained considerable attention in recent years, especially due to the increasing interest for e-commerce. Order picking is the process of finding and removing products from a warehouse to fulfil customer orders. Order picking is the most time-consuming and costly operation in manual picker-to-parts warehouses. Order picking problem is similar to Traveling Salesman Problem in the sense that the order picker corresponds to the salesman whereas items to be picked correspond to cities to be visited. Hence, order picking problem is known to be NP-hard. The objective of order picking problem is to minimize total travelled distance of an order picker. For only single-block and two-block traditional rectangular warehouses, optimal picker routing can be found. However, there is no optimal algorithm for three or more block traditional rectangular warehouses. Some popular routing heuristics are applied for single-block and multi-block traditional rectangular warehouses, such as S-Shape, Largest Gap, Aisle-by-aisle, Combined/Combined+ heuristics. In this study, we consider the order picking problem of a merchandising company. The objective of the company is to minimize total travelled distance during order picking which leads to an increase in throughput (the number of picks per time). The warehouse under consideration can be said to be non-traditional rectangular due to its block and aisle configuration. Therefore, order picking heuristics, which are proposed for traditional rectangular warehouses, cannot be directly implemented. Accordingly, we modified popular picker routing heuristics to apply for the non-traditional rectangular warehouse layout. Then, a meta-heuristic algorithm is implemented to obtain the best picking sequence of items and order picking route. Finally, we examined the impact of different storage assignment policies on total travelled distance.Öğe Hybrid Flowshop Scheduling with Setups to Minimize Makespan of Rubber Coating Line for a Cable Manufacturer(Springer-Verlag Singapore Pte Ltd, 2022) Balci, Diyar; Yuksel, Burak; Taskiran, Eda; Aslim, Guliz Hande; Ozkorkmaz, Hande; Duzgit, ZehraWe consider the hybrid flowshop scheduling problem of a cable manufacturing company. We focus on rubber coating line to minimize the makespan. Industrial cables differ based on the number of cores and core colors. The rubber coating line is composed of three stages with two identical parallel machines in each stage. These stages are i) Isolation; ii) Bunching; iii) Sheathing. The input of the isolation stage is copper wire whereas the output of the isolation stage is cores with different colors. Before the isolation stage, a sequence-dependent setup time is required based on a cross-section of cables and a sequence-independent setup time is required to change the color of cores. The input of the bunching stage is cores with different colors whereas the output of the bunching stage is bunched cores. Before the bunching stage, a sequence-independent setup time is necessary based on the number of cores. The input of the sheathing stage is bunched cores whereas the output of the sheathing stage is rubber-coated cables. Before the sheathing stage, a sequence-dependent setup time is needed based on area. Since the problem is NP-hard, genetic algorithm is employed. With the help of genetic algorithm, we can determine the best job-machine assignments for each stage, the best job sequence on each machine at each stage, start and completion times of jobs on each stage, and the best makespan.Öğe PERFORMANCE COMPARISON OF META-HEURISTICS FOR THE MULTIBLOCK WAREHOUSE ORDER PICKING PROBLEM(Univ Cincinnati Industrial Engineering, 2021) Duzgit, Zehra; Toy, Ayhan Ozgur; Saner, Ahmet CanThis study focuses on streamlining the order-picking process in a warehouse. We consider determining the picking sequence of items in a pick-list to minimize the total traveled distance in a multiblock warehouse, where a low-level picker-to-parts manual picking system is employed. We assume that the items are stored randomly in the warehouse. First, we construct a distance matrix of the shortest path between any pair of items. Next, using the distance matrix, we implement two meta-heuristics-the tabu search algorithm and the iterated greedy algorithm-to determine the picking sequence with the minimum total traveled distance. Through a numerical study, the performances of the meta-heuristic algorithms are compared with those of popular rule-based heuristics (S-shape, largest gap, and Combined+) and the bestknown solutions. We conducted the numerical study in two stages. In the first stage, we considered a two-block rectangular warehouse, and in the second stage, we considered a three-block rectangular warehouse. The performance of the heuristics was calculated based on the optimal solution when available or the best calculated bound when the optimal solution is not available. We observed that the iterated greedy algorithm significantly outperforms the other heuristics for both stages.Öğe PERIODIC DUE DATE ASSIGNMENT WITH FAMILY SETUPS(Univ Cincinnati Industrial Engineering, 2019) Sertdemir, Sevilay; Unal, Ali Tamer; Duzgit, ZehraIn this study we consider a single machine due date assignment problem involving dynamic job arrivals and family setups. The due date quotation process is based on periodically generating schedules of new and old jobs. We want to keep the tardiness of old jobs below an allowable threshold while minimizing total completion time of new arriving jobs. We propose a mixed integer linear programming formulation to solve the scheduling problem. We also present a function to quote due dates for new jobs. An experimental analysis is conducted to analyze the proposed due date quotation process under various shop and solution procedure parameters. Three performance measures are considered: average quoted lead time, average tardiness, number of setups perfouned. The first significant outcome of our analysis is that existence of family setups plays a crucial role; the second significant observation is that batching plays a double-edged sword role in due date management.
