• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1192-1207
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• 2014

Dynamic spectrum sharing is a key technology to improve spectrum utilization in wireless networks. The elastic spectrum management provides a new opportunity for licensed primary users and unlicensed secondary users to efficiently utilize the scarce wireless resource. In this paper, we present a game-theoretic framework for dynamic spectrum allocation where the primary users rent the unutilized spectrum to the secondary users for a monetary profit. In reality, due to the ON-OFF behavior of the primary user, the quantity of spectrum that can be opportunistically shared by the secondary users is limited. We model this situation with the renewal theory and formulate the spectrum pricing scheme with the Bertrand game, taking into account the scarcity of the spectrum. By the Nash-equilibrium pricing scheme, each player in the game continually converges to a strategy that maximizes its own profit. We also investigate the impact of several properties, including channel quality and spectrum substitutability. Based on the equilibrium analysis, we finally propose a decentralized algorithm that leads the primary users to the Nash-equilibrium, called DST. The stability of the proposed algorithm in terms of convergence to the Nash equilibrium is also studied.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.39-46
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• 2007

The blasting load induced by the explosion of the powder generation the vibration of the ground and affects on nearby ground and underground structures. The structures are possibly damaged and it may create the social problems such as noneconomic construction due to the delay of the construction period especially in urban areas. Therefore, the stability of the nearby structures need to be evaluated. In this study, the stability of the tunnel is estimated and examined by the analytical solution and by using $FLAC^{2D}$ which is one of the programs based on the finite difference analysis.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.105-113
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• 2018

This paper proposes pre-analysis on planning of high-voltage direct current (HVDC) transmission system applied to Korea electric power grid. HVDC transmission system for interface lines has been considered as alternative solution for high-voltage AC transmission line in South Korea since constructing new high-voltage AC transmission lines is challenging due to political, environmental and social acceptance problems. However, the installation of HVDC transmission system as interface line in AC grid must be examined carefully. Thus, this paper suggests three scenarios to examine the influences of the installation of HVDC transmission system in AC grid. The power flow and contingency analyses are carried out for the proposed scenarios. Power reserves in metro area are also evaluated. And then the transient stability analysis focusing on special protection scheme (SPS) operations is analyzed when critical lines, which are HVDC lines or high voltage AC lines, are tripped. The latest generic model of HVDC system is considered for evaluating the impacts of the SPS operations for introducing HVDC system in the AC grid. The analyses of proposed scenarios are evaluated by electromechanical simulation.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.1-10
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• 2021

This study examines the dynamic pattern of the exchange rate volatilities of the ASEAN-5 currencies from January 2006 to August 2020. The exchange rates applied in this study comprise bilateral and effective exchange rates in order to investigate the influence of the US dollar on the stability of the ASEAN-5 currencies. Since a volatility model employed in this study is a natural cubic spline volatility model, the Monte Carlo simulation is consequently conducted to determine an appropriate criterion to select a number of quantile knots for this model. The simulation results reveal that, among four candidate criteria, Generalized Cross-Validation is a suitable criterion for modeling the ASEAN-5 exchange rate volatilities. The estimated volatilities showed the inconstant dynamic patterns reflecting the uncertain exchange rate risk arising in international transactions. The bilateral exchange rate volatilities of the ASEAN-5 currencies to the US dollar are more variable than their corresponding effective exchange rate volatilities, indicating the influence of the US dollar on the stability of the ASEAN-5 currencies. The findings of this study suggest that the natural cubic spline volatility model with the quantile knots selected by Generalized Cross-Validation is practical and can be used to examine the dynamic patterns of the financial volatility.

• Korea Trade Review
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• v.44 no.6
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• pp.285-302
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• 2019

Good faith is difficult to define due to the facts that there is not an objective and concrete concept of good faith, and good faith in contracts for the international sale of goods is a principle that parties to the contract must act with sincerity as members of a social community. The Korean Supreme Court shall pay attention to setting the applicable standards that can be universally applied to good faith based on the self-established criteria. Through such effort, it is possible not only to realize the value of concrete validity pursued by the general clause of good faith but also to realize the value of legal stability by assuring the predictability of results when applying good faith. In the modern sense, it can be said that the arbitrary application of general rules rather than the escape and general clauses is a problematic situation in the application of good faith, but this problem can be solved by setting a reasonable standard of good faith. This paper studies good faith in the view of Korean law, international laws, and related cases in contract law. The purpose of this paper is to find the problems and solutions of the practical application of good faith by analyzing the Korean case (2009Da86000), which undermined the legal stability of good faith in Korea.

• The Korean Journal of Food & Health Convergence
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• v.9 no.2
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• pp.7-18
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• 2023

Through these research results, I would like to present some implications for promoting and revitalizing local food sales in Daejeon and establishing a local food system. First, in terms of local food direct stores, when establishing a local food store, location conditions should be considered. If the location cannot be changed, the quality of agricultural products should be improved to improve consumer satisfaction and purchase intention so that consumers can directly feel the value of the product. Second, efforts at the local government level are needed to improve the stability of local food. There are still many consumers who are not properly aware of local food. It is necessary to improve consumers' interest in the value of local food by providing education including social and environmental information on the production and distribution process of local food. Third, policy efforts on local food are needed. It is necessary to introduce and reorganize the local food certification system to emphasize the stability of local food to consumers and form trust. Finally, for the continuous development of local food, research on the satisfaction and purchase intention of local food consumers must be continuously conducted.

• Journal of Information Processing Systems
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• v.19 no.1
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• pp.55-66
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• 2023

Community portraits can deeply explore the characteristics of community structures and describe the personalized knowledge needs of community users, which is of great practical significance for improving community recommendation services, as well as the accuracy of resource push. The current community portraits generally have the problems of weak perception of interest characteristics and low degree of integration of topic information. To resolve this problem, the reader community portrait method based on the thematic and timeliness characteristics of interest labels (UIT) is proposed. First, community opinion leaders are identified based on multi-feature calculations, and then the topic features of their texts are identified based on the LDA topic model. On this basis, a semantic mapping including "reader community-opinion leader-text content" was established. Second, the readers' interest similarity of the labels was dynamically updated, and two kinds of tag parameters were integrated, namely, the intensity of interest labels and the stability of interest labels. Finally, the similarity distance between the opinion leader and the topic of interest was calculated to obtain the dynamic interest set of the opinion leaders. Experimental analysis was conducted on real data from the Douban reading community. The experimental results show that the UIT has the highest average F value (0.551) compared to the state-of-the-art approaches, which indicates that the UIT has better performance in the smooth time dimension.

• Journal of The Korea Institute of Healthcare Architecture
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• v.30 no.1
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• pp.19-26
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• 2024

Purpose: Autism spectrum disorder impacts children's social, sensory, and language development, necessitating specialized educational support. Special classrooms play a crucial role in providing an appropriate learning environment for children with autism. However, there is a lack of systematic research on creating effective environments in these special classrooms. Methods: This study aims to gain a comprehensive and systematic understanding of the environmental composition of special classrooms for children with autism spectrum disorder, using the following systematic methodologies including literature review and case study. Results: Sensory spaces in special classrooms for children with autism help regulate sensory stimuli and promote sensory development. They provide stability, reducing stress from excessive stimuli, and enhance emotional stability. These spaces also promote communication and interaction among children and expand the diversity of learning activities, enriching experiences and stimulating interest in learning. Implications: Based on the results, we propose suggestions for improving the environment of special classrooms for children with autism spectrum disorder and provide direction for the design of such environments.

• Journal of Korea Entertainment Industry Association
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• v.14 no.5
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• pp.115-130
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• 2020

The purpose of this study is to analyze the difference between A Study on the Weight Change and Exercise Immersion for Activation of Aerobic Dance and to suggest the continuous activation of Aerobic Dance. To achieve this purpose, a questionnaire was conducted using a convenience sampling method, which is one of non-probability sampling, in April 2020, targeting general aerobic dance members in Gyeongnam. The results of this study are as follows. First, the demographic characteristics were partially different. The age was 40 to 49 years, height was more than 160cm, occupation was housewives, weight change was more than -3kg, participation intensity was more than 100 minutes, participation frequency was 4 days, and participation period was less than 5 years. Second, the results of this study are as follows: Weight Change(Body Confidence, Activity Confidence, Dance Confidence, Psychological Stability Effect, Dance Activity Effect, Perform-motion Effect) and Exercise Immersion(Behavior immersion, Cognitive immersion) were partially high There was a difference. Third, the results of this study are as follows: Weight Change(Body Confidence, Activity Confidence, Dance Confidence, Psychological Stability Effect, Dance Activity Effect, Perform-motion Effect) and Exercise Immersion(Behavior immersion, Cognitive immersion) were partially high It was shown that the influence was.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.196-203
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• 2020

In this study, we tried to explore the actual direction for the play culture by looking at the social perception of the change of play culture due to the Corona 19 using big data analysis. For this research, we used Textom, a website specializing in collecting big data, and collected 10,216 data using keywords of "Corona + Play," "Play Culture" and "Leisure" from January 19, 2020 to September 30, 2020, when the first confirmed case of Corona 19 occurred in Korea on various portal sites at home and abroad. The results of this paper showed that the social perception of the play culture in Corona 19 was 51.61%, not much different from the negative image of 48.15%. It is necessary to develop a play culture program that can identify people's various desires and emotions under the premise that situations similar to the current With Corona period and Corona19 can occur at any time, and find mental and physical stability and vitality in unstable situations. In addition, the results of this study can be used as basic data for the development of play culture policies or programs, with the significance that this study helped vitalize big data utilization research in the fields of play, leisure, and culture.