Browsing by Subject "Heuristic search"
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Item Open Access A collaborative system for providing routes between locations(Bilkent University, 2008) Uluğ, Kerem AliMany systems, such as in-car GPS devices and airline company web sites, provide route information between locations. Although such systems are used widely and can provide route information successfully, users of these systems cannot contribute to the data entry process. In these systems, data is entered by the administrators and these systems cannot take advantage of the route expertise of their users. In this work, we present a collaborative system, which provides routes between locations upon user queries. The data in the system is entered by the users of the system. We present a model which is containing locations, links between locations and relationships between locations (containment, neighborhood and intersection) in order to store the data. For the route finding purpose, we present a customized version of the A* search algorithm. This customized version, named A*CD (A* for Collaborative Data), uses heuristics for estimating the cost remaining to the target location while processing the nodes. A*CD can also provide alternative routes, exclude certain link types in the searches according to user preferences and handle the problems associated with multiple stop transportation lines. As the cost models, we use duration and financial cost. We also present the intuitive connections concept. Even if a route does not exist between the selected locations, the system can provide a route with missing links. The gap(s) between the disconnected locations are filled by the help of the relationships between locations. In order to evaluate the performance of the A*CD algorithm, we present automated tests. These tests show that the costs of the routes that are provided by the A*CD algorithm are close to the actual shortest routes. In order to demonstrate the intuitive connections concept, we also present manual test queries.Item Open Access Mobility and optimal tenure choice(Elsevier, 2005) Özyıldırım, S.; Önder, Z.; Yavas, A.In this paper, we offer a dynamic model of the optimal tenure behavior of an individual who faces the possibility of moving multiple times during his lifetime. We also investigate the lifetime effects of such factors as income tax, property tax, transaction costs, and mortgage rates on the household's tenure choice. The agents in the model utilize a genetic algorithm, a probabilistic search approach, to determine their optimal lifetime tenure choice path. The agents are forward looking in that they anticipate such possible events as changes in jobs, marital status, household size, or dissatisfaction with current residence. Our results suggest several housing policy implications and explain some of the empirical findings in the literature.Item Open Access Scheduling preventive maintenance on a single CNC machine(Taylor & Francis, 2008) Gurel, S.; Akturk, M. S.In this study we attempt to deal with process planning, scheduling and preventive maintenance (PM) decisions, simultaneously. The objective is to minimize the total completion time of a set of jobs on a CNC machine. During the process planning, we decide on the processing times of the jobs which are controllable (i.e. they can be easily changed) on CNC machines. Using shorter processing times (higher production rates) would result in greater deterioration of the machine, and we would need to plan more frequent PM visits to the machine, during which it would not be available. Therefore, the selected processing times determine not only the completion times but also the PM visit times. We first provide optimality properties for the joint problem. We propose a new heuristic search algorithm to determine simultaneously the processing times of the jobs, their sequence and the PM schedule.