• International Journal of Highway Engineering
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• v.15 no.4
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• pp.155-165
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• 2013

PURPOSES : Benefits for improvement of travel time reliability obtained from construction of new highways should be considered as a major factor in the feasibility study for highway constructions. The purpose of this study is to develop a method of estimation for the value of travel time reliability. METHODS : Highway type (urban/rural highway) and traffic flow type(interrupted/uninterrupted) was considered to estimate he value of travel time reliability. And Double-bounded Dichotomous Choice among Contingent Valuation Method(CVM) was applied to survey the willingness-to-pay of drivers when travel time reliability is improved. Finally the value of travel time reliability was estimated using the results of survey and logit model. The value of travel time reliability was estimated considering travel objectives, time constraint travel and non-time constraint travel. RESULTS: The value of travel time reliability of business trip is higher than that of non-business trip. The value of travel time reliability of time constraint travel is higher than that of non-time constraint travel. The value of travel time reliability in urban area is higher than that in rural area. CONCLUSIONS: It was concluded that the proposed method in this study is more realistic and proper to estimate the value of travel time reliability because it reflects the situations of time constraint travel and non-time constraint travel.

• IE interfaces
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• v.15 no.1
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• pp.49-54
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• 2002

A bus scheduling problem with multiple objective functions and travel time constraint is to determine the allocation of buses to customer service requests minimizing the number of buses and travel costs under the travel time restriction for each bus. For the scheduling, we first represent the scheduling problem using a graph and develop a hierarchical approach. Second, we develop a mathematical model based algorithm for the scheduling problem including heuristic methods. We tested the performance of the algorithm on instances with real data. As a result, the total number of buses and travel costs are reduced over about 10% comparing with that of current practice at the company.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.2
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• pp.140-149
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• 2001

The paper discusses the problem of finding the Origin-Destination(O-D) shortest paths in internodal transportation networks with time-schedule constraints. The shortest path problem on the internodal transportation network is concerned with finding a path with minimum distance, time, or cost from an origin to a destination using all possible transportation modalities. The time-schedule constraint requires that the departure time to travel from a transfer station to another node takes place only at one of pre-specified departure times. The scheduled departure times at the transfer station are the times when the passengers are allowed to leave the station to another node using the relative transportation modality. Therefore, the total time of a path in an internodal transportation network subject to time-schedule constraints includes traveling time and transfer waiting time. In this paper, a genetic algorithm (GA) approach is developed to deal with this problem. The effectiveness of the GA approach is evaluated using several test problems.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.5
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• pp.1-10
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• 2004

This study applied the leisure constraints and negotiation concept to the travel context, especially for traveling in national parks. More specifically, it tries to identify how constraints and negotiation impact a person's travel behavior. The population of this study is the people who intend to visit the national parks for their summer vacations. The data was collected through the panel study, which surveyed the same set of people before and after their trip. Among 527 samples, 39.7％ traveled what they planned without any changes. 24.7％ did not travel or postponed their trip, and 35.7％ enjoyed their vacation but with changes of destination, time or travel periods. These results support that people may use negotiation strategies to overcome their constraints in a travel context. However, there were no statistically significant differences in the impact of constraints on travel behavior among the three groups. The results also confirm that people have to overcome intra-, inter-, and structural constraints for visiting the national parks. Thus, the findings of the study suggest that the concepts of leisure constraints and negotiation is applicable to the travel contexts. Because of its exploratory characteristics, several limitations and cautions were raised.

• Journal of Wetlands Research
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• v.8 no.1
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• pp.73-82
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• 2006

In this study, the hydraulic channel routing model is applied to analyze water surface elevation pattern on the Nakdong river in flood cases. The procedure to apply FLDWAV model is presented to solve the Saint-Venant Equations by using four points implicit finite differential scheme. And the flood travel time is studied for reasonable dam management. As this results, variable assumption and constraint are followed to evaluate flood travelling time by hydraulic model. A guideline of reasonable dam's decision making considering downstream effect is showed by this constructed model, and scientific hydraulic analysis is possible by it.

• Geophysics and Geophysical Exploration
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• v.5 no.1
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• pp.46-55
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• 2002

We investigated the distorting factors of velocity structure reconstructed by traveltime inversion. The set of models that fit the data in a numerical sense usually contains unrealistic models. Reconstructed velocity structure was enhanced because unreasonable models were eliminated by defining constraint of variable grid using a priori information. To correct time delay of source explosion, which distorts traveltime tomograms, terms for correction of time delay was formulated into equation of travel time tomography.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.317-323
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• 2008

Mass transit information can contribute many benefits to users. Especially, transportation information technology is developing highly with information technology in Korea recently. Hereafter, it is expected to give customized transportation information to users individually with the advent of ubiquitous age in earnest. This public transportation information service can be realized by path finding algorithm in public transportation networks including travel and transfer attributes. In this research, constraints are constructed with the primary facts influencing users. Moreover, the method reducing user's path finding condition arbitrarily is proposed by making the maximum value as variables. In this study, transfer frequency, total travel time, seat confirmation, transfer time and travel time become constraint condition based on k path finding algorithm considering service time constraint condition. Moreover, case study about user customized transfer information is performed in Seoul and metropolitan subway networks.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.138-145
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• 2018

In the field of optimization, many studies have been performed on various types of Vehicle Routing Problem (VRP) for a long time. A variety of models have been derived to extend the basic VRP model, to consider multiple truck terminal, multiple pickup and delivery, and time windows characteristics. A lot of research has been performed to find better solutions in a reasonable time for these models with heuristic approaches. In this paper, by considering realtime traffic characteristics in Map Navigation environment, we proposed a method to manage realistic optimal path allocation for the logistics trucks and cargoes, which are dispersed, in order to realize the realistic cargo mixing allowance and time constraint enforcement which were required as the most important points for an online logistics brokerage service company. Then we developed a prototype system that can support above functionality together with delivery status monitoring on Map Navigation environment. First, through Map Navigation system, we derived information such as navigation-based travel time required for logistics allocation scheduling based on multiple terminal multiple pickup and delivery models with time constraints. Especially, the travel time can be actually obtained by using the Map Navigation system by reflecting the road situation and traffic. Second, we made a mathematical model for optimal path allocation using the derived information, and solved it using an optimization solver. Third, we constructed the prototype system to provide the proposed method together with realtime logistics monitoring by arranging the allocation results in the Map Navigation environment.

• The Journal of the Korea Contents Association
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• v.10 no.7
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• pp.317-325
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• 2010

This study aims to deduct the extensive improvement types of leisure activities of private security agents using PPA technique and to examine the influence of leisure constraint on the index of participation. Through this process, this study consequently will draw the priority list of investment on the policy for improving the welfare status of private security agents. In this study, judgement sampling was applied to 6 security agencies located in Seoul, 2010, and 267 cases were used in the final analysis. Collected data went through factor analysis, reliability analysis, paired t test, PPA analysis, and regression analysis by using SPSSWIN 17.0. The conclusions were drawn as follows. In regard to the reliability, Cronbach's $\alpha$ was over .768. First, there was a difference between the preference rate and the participation rate which are the participation index of the private security agents' leisure activities. concentrate here in leisure types turned out to be fitness activities, walking/jogging, tourism, a day-long travel, and keep up the cood work in leisure types are movies, domestic tourist attractions, dating, eating out, personal relationship, watching sports, reading, karaoke, TV video watching, drinking etc. low priority in leisure types are water sports, hiking, biking, soccer, photography, ball games, sky sports, playing go/janggi, inline skates, and cooking. Second, the leisure constraint affects the participation index of leisure activities. As the personal constraint, and surrounding conscious constraint which are the subordinate factors of the leisure constraint get bigger, the participation index of favored leisure activities become lower. In contrast, when the difficulties such as structural constraint, time and economical constraint are overcome, participation index of leisure activities go on the rise.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.4
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• pp.719-728
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• 1997

In the AGV routing a vehicle can select the shortest route on which no conflicts are anticipated. The procedure includes time constraint and the node/arc occupation times of vehicles in order to locate the conflicting paths. The slight differences among AGV routing algorithms exist in identifying the conflict regions encountered while reaching out to the destination node. In this paper, a novel approach to the use of the re-routing scheme is presented. It will be used to minimize the travel distance of vehicles in a regular vehicle routing process rather than to cope with emergency situations. The proposed algorithm provides existing active vehicles with the ability of changing their current paths for a new vehicle whenever the equal-distance paths exist, in on attempt to optimize the AGV transportation system. This ability is possible because of the flexibility of on AGV system controlled by a computer system.