• Journal of Information Processing Systems
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• v.6 no.4
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• pp.575-596
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• 2010

Video-on-Demand services are increasing rapidly nowadays. The load on servers can be very high, even exceeding their capacity. For popular contents, we can use a Periodic Broadcast (PB) strategy using multicast to serve all clients. Recent development of PB uses multiple channels broadcasting for segments of movies in certain patterns, so that users only need to wait for a small segment to start the service. However, users need higher download capacity to download multiple segments at a time. In order to compensate for this, a proxy server can help to reduce download bandwidth requirements by holding some segments for a certain time. This research will focus on more recent PB schemes that couldn't be covered by previous Proxy-Assisted Periodic Broadcast strategies.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.89-102
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• 2010

Future uncertainty on water demand caused by future climate condition and water consumption leads a difficulty to determine the reservoir operation rule for supplying sufficient water to users. It is, thus, important to operate reservoirs not only for distributing enough water to users using the limited water resources but also for preventing floods and drought under the unknown future condition. In this study, the reservoir storage is determined in the first stage when future condition is unknown, and then, water distribution to users and river stream is optimized using the available water resources from the first stage decision using 2-stage stochastic linear programming (2-SLP). The objective function is to minimize the difference between target and actual water storage in reservoirs and the water shortage in users and river stream. Hedging rule defined by a precaution against severe drought by restricting outflow when reservoir storage decreases below a target, is also applied in the reservoir operation rule for improving the model applicability to the real system. The developed model is applied in a system with five reservoirs in the Han River basin, Korea to optimize the multi-reservoir system under various future water demand scenarios. Three multi-purposed dams - Chungju, Hoengseong, and Soyanggang - are considered in the model. Gwangdong and Hwacheon dams are also considered in the system due to the large capacity of the reservoirs, but they are primarily for water supply and power generation, respectively. As a result, the water demand of users and river stream are satisfied in most cases. The reservoirs are operated successfully to store enough water during the wet season for preparing the coming drought and also for reducing downstream flood risk. The developed model can provide an effective guideline of multi-reservoir operation rules in the basin.

• Korean Institute of Interior Design Journal
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• v.21 no.6
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• pp.23-34
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• 2012

There is a demand for a complex cultural space of play, leisure and education, a kids cafe, which will replace a playground just for kids as awareness for the need of a space where parents can spend leisure time with their own children and can take a rest grows, Thus, this study aims to find features for user satisfying kids cafes by conducting observations of the kids cafes and user survey. This study selected 12 kids cafes, 3 kids cafes per type (play focused, cafe or restaurant focused, education focused, multipurpose focused), in Seoul which were built after 2007 and conducted surveys on space planning and spatial characteristics by users and types and the level of satisfaction. As a result, the play focused kids cafes are used the most and the multipurpose focused kids cafes are used the second most. So the reason for using kids cafes is for the play of children. Also the overall satisfaction level for kid cafes were above the average except for the price. The result of this study showed that there was differences of satisfaction based on the type of user satisfaction, size of children space, finishes, colors, furniture and accessories, sanitary conditions. For the overall satisfaction, users were satisfied with the interior space, however, users were unsatisfied with functional parts, such as toys, foods and educational program. The results of the analysis showed that based on the types of the kids cafes, users' satisfaction rate for space size for the children, finishes, colors, furniture and accessories, sanitary conditions were different and for the functional parts, the satisfaction rate was different in all aspects. Also, in overall, the educational focused type users showed higher satisfaction rate than other users. Finally, the level of satisfaction is different by type of kids cafes and we have to consider the level of satisfaction of the users in order to plan kids cafes which meet the demand of the users.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.17 no.2
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• pp.239-259
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• 2006

The purpose of this study is to propose some strategic directions which can promote the government libraries to provide the most effective and efficient information services. The study analyzes user opinion and demand in terms of the Web-based Information Services. For the analysis, the questionnaires were distributed to the 300 users in 18 government libraries. In the results, the study finds that the government libraries with homepage need to advertise homepage service. to provide the training programs, and to improve the system utility for better valuable homepage services. The government libraries without homepage, first of all, must construct their own homepage reflected in the users demand requiring the powerful retrieval ability, the diversity of contents, the high properness of information services.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.662-671
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• 2012

Plug-in hybrid electric vehicles (PHEVs) will be widely used in future transportation systems to reduce oil fuel consumption. Therefore, the electrical energy demand will be increased due to the charging of a large number of vehicles. Without intelligent control strategies, the charging process can easily overload the electricity grid at peak hours. In this paper, we consider a smart charging and discharging process for multiple PHEVs in a building's garage to optimize the energy consumption profile of the building. We formulate a centralized optimization problem in which the building controller or planner aims to minimize the square Euclidean distance between the instantaneous energy demand and the average demand of the building by controlling the charging and discharging schedules of PHEVs (or 'users'). The PHEVs' batteries will be charged during low-demand periods and discharged during high-demand periods in order to reduce the peak load of the building. In a decentralized system, we design an energy cost-sharing model and apply a non-cooperative approach to formulate an energy charging and discharging scheduling game, in which the players are the users, their strategies are the battery charging and discharging schedules, and the utility function of each user is defined as the negative total energy payment to the building. Based on the game theory setup, we also propose a distributed algorithm in which each PHEV independently selects its best strategy to maximize the utility function. The PHEVs update the building planner with their energy charging and discharging schedules. We also show that the PHEV owners will have an incentive to participate in the energy charging and discharging game. Simulation results verify that the proposed distributed algorithm will minimize the peak load and the total energy cost simultaneously.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.5
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• pp.82-96
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• 2020

The Demand Responsive Transit (DRT) system is the flexible public transport service that determines the route and schedule of the service vehicles according to users' requests. With increasing importance of public transport systems in urban areas, the development of stable and fast routing algorithms for DRT has become the goal of many researches over the past decades. In this study, a new heuristic method is proposed to generate fast and efficient routes for multiple vehicles using demand clustering and destination demand priority searching method considering the imbalance of users' origin and destination demands. The proposed algorithm is tested in various demand distribution scenarios including random, concentration and directed cases. The result shows that the proposed method reduce the drop of service ratio due to an increase in demand density and save computation time compared to other algorithms. In addition, compared to other clustering-based algorithms, the walking cost of the passengers is significantly reduced, but the detour time and in-vehicle travel time of the passenger is increased due to the detour burden.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.68-77
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• 2018

Regarding demand response (DR) by residential users (R-users), the users try to reduce electricity costs by adjusting their power consumption in response to the time-varying price. However, their power consumption may be affected not only by the price, but also by user convenience for using appliances. This paper proposes a methodology for appliance scheduling (AS) that considers the user convenience based on historical data. The usage pattern for appliances is first modeled applying the copula function or clustering method to evaluate user convenience. As the modeling results, the comfort distribution or representative scenarios are obtained, and then used to formulate a discomfort index (DI) to assess the degree of the user convenience. An AS optimization problem is formulated in terms of cost and DI. In the case study, various AS tasks are performed depending on the weights for cost and DI. The results show that user convenience has significant impacts on AS. The proposed methodology can contribute to induce more DR participation from R-users by reflecting properly user convenience to AS problem.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.11-19
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• 2018

With the development of smart grid technology, it has become a hotspot to increase benefits of both residential users and electric power companies through demand response technology and interactive technology. In this paper, the game theory is introduced to the interaction between residential users and an electric company, making a mutually beneficial situation for the two. This paper solves the problem of electricity pricing and load shifting in the interactive behavior by building the game-theoretic process, proposing the interaction strategy and doing the optimization. In the simulation results, the residential users decrease their cost by 11% mainly through shifting the thermal loads and the electric company improves its benefits by 5.6% though electricity pricing. Simulation analysis verifies the validity of the proposed method and shows great revenue for the economy of both sides.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.123-132
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• 2020

In contemporary times, there is an increasing demand for a dedicated healthcare environment, all over the world. The main motivation for this demand is the level of awareness manifested by the users and reflected on their expectations. Therefore new research strategies and design actions are investigated in order to answer to the users' needs and to provide objective design tools for the specialist. This study continues a series of previous developments of the Healthcare Environment Color Index that should be used for public facilities in Korea and abroad. The cross-cultural approach is a new opportunity for exchanging know-how and for testing and calibrating the perception of the users on the color index. The gathering of results was made based on the online survey provided in this phase in English version for the Romanian users. The survey was intended as an objective mean of research and an efficient way of disseminating information on the subject thus contributing to increasing the level of awareness of the users. A total of 86 Romanian and 89 Koreans with valid answers took part in the survey. Comparative visualizations of the results showed significant similarities concerning the patterns of color preferences but also cultural and emotional differences. As a result both categories of users proved to be aware of the relation between healthcare environment color and its effects on health. They also showed a common understanding on the potential of the color index. As a result the most appealing colors to be applied to the healthcare environment were the series G and B, and the most effective ones were proved to be the ranges of high lightness and low saturation but also the medium high lightness and medium saturation. Both the similarities and the differences of choice between Romanians and Koreans show that cultural and emotional differences of color recognition are important and that should be taken into consideration in design, in order to generate an inclusive and efficient healthcare environment.

• Journal of Internet Computing and Services
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• v.13 no.1
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• pp.117-124
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• 2012

Recently, the trend of open innovation and web 2.0 change the information portal services. The importance of using information demand analysis is emphasized in planning service strategy. The issues of the study are how we can figure out the demand and how we can use it in enhancing service level. This study aims at presenting the result of green technology information users' interests and the service enhancement directions. For the information types, additive functions, open innovation needs, the relation between users' organization, main job title, and the involved technological area are analysed. Among them, the involved technological area of the user is correlated to the needs, so we illustrate the meaning of planning service strategy according to the technological fields. The main contribution of the study can be the customized service strategy proposal using the users' demand which can be different from one technology field to another.