• Korean Journal of Child Studies
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• v.29 no.1
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• pp.33-48
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• 2008

This study analyzed social development and self-efficacy in use of internet in adolescents. Subjects were 510 7th, 8th, 10th, and 11th grade students in Daegu. Instruments were the modified Activities Questionnaire for Students (Heitner & Erica, 2(02), the Personality Inventory for Youth (Heitner & Erica, 2002) and the Self-Efficacy Scale (Song, 1998). Findings were that (1) male students use more synchronous (multi-game) but female students use more asynchronous (e-mail) and asocial (web-surfing) internet activity. (2) Synchronous social internet (multi-game) users were more social and more efficient than asynchronous (e-mail) and asocial (web-surfing) internet users.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.822-839
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• 2011

Group key agreement protocols derive a shared secret key for a group of users to ensure data confidentiality or/and integrity among the users in the subsequent communications. In this paper, we inspect two group key agreement schemes which have been proposed by Shi et al. and Zheng et al. in 2005 and 2007 respectively. Although both schemes were claimed to be secure in a heuristic way, we reveal several flaws using the Bellare-Rogaway security model extended to multi-party setting by Bresson et al. These flaws are found to be originated from inappropriate selection of key derivation function, inadvertent exclusion of partners' identities from the protocol specification and insufficient consideration in preserving known temporary information security and key freshness properties. Furthermore, we suggest and discuss proper countermeasures to address such flaws.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2001.11a
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• pp.3-17
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• 2001

In this paper, we compare the market performances under circuit pricing whereby users are charged based on their length of usage time and under packet pricing whereby users are charged based on the amount of information received. We show that, if packet pricing is introduced, the market price rises contrary to the government's expectation but that the overall social welfare is unambiguously increased because packet pricing reflects the social cost properly while circuit pricing does not. Also, we show that, if delivery of multi-media files requires a much higher speed, a move to packet pricing lowers the price of multi-media transmission, thereby increasing the usage of multimedia data in the absence of congestion, which may not be the case in the presence of congestion.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.297-299
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• 2012

In this paper, we introduce a joint flow control and scheduling algorithm for multi-hop cognitive radio networks with spectrum underlay. Our proposed algorithm maximizes the total utility of secondary users while stabilizing the cognitive radio network and still satisfies the total interference from secondary users to primary network is less than an accepted level. Based on Lyapunov optimization technique, we show that our scheme is arbitrarily close to the optimal.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.594-598
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• 2003

In this paper, we analyze the performance of UWB(Ultra-WideBand) communication system employing Bi-phase modulation and RAKE Receiver under the MAI(Multiple Access Interference) and the OSI(Other System Interference) environment. Using the multi-path channel model recommended by IEEE P802.15.TG3a, the performance degradation Is described with the number of users, the number of RAKE fingers and training sequences. To meet BER 10e-4 for 20 users at the same time, the number of RAKE fingers are proposed from 3 to 32. And the number of training sequences are limited less than 8 to keep the channel estimation error within 3dB

• The Journal of the Korea Contents Association
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• v.13 no.11
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• pp.533-540
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• 2013

Currently, as the Android platform only supports single-user protection, it needs security solution for multi-users. Specially, it has to protect specific applications which have personal and financial information, and be available to support authority management for contents access. Thus, this paper proposes an integrated user authority manger model for the Android platform. It helps application authority which is capable to divide into three statuses: installation, execution, deletion with the help of information technology.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.12 no.4
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• pp.270-276
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• 2012

With the increase in amount of data and information available on the web, there have been high demands on personalized information retrieval services to provide context-aware services for the web users. This paper proposes a novel dynamic multi-agent context-awareness user profile construction method based on ontology to incorporate concepts and properties to model the user profile. This method comprehensively considers the frequency and the specific of the concept in one document and its corresponding domain ontology to construct the user profile, based on which, a fuzzy c-means clustering method is adopted to cluster the user's interest domain, and a dynamic update policy is adopted to continuously consider the change of the users' interest. The simulation result shows that along with the gradual perfection of the our user profile, our proposed system is better than traditional semantic based retrieval system in terms of the Recall Ratio and Precision Ratio.

• Korean Institute of Interior Design Journal
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• v.15 no.4 s.57
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• pp.73-80
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• 2006

As ubiquitous technology(uT) is offered in the future space, human will find their life more convenient and prosperous, and the space efficiency will be improved with virtual displays within a limited space. In an living space with ubiquitous environments, all information of family members will be an essential source creating advanced future spaces both for users and for those maintaining the space. In recent studies of uT environment, development of scenario is mostly being carried out based on user and service. It is unsatisfactory, however, when it comes to the study of how these studies can be developed on the basis of architectural space. In this paper, we study about applying scenarios created through space analysis to suggest ways to predict the analysis of the relationship between digital devices/services and the building elements based on physical space with uT and to offer services smoothly to uT environment, intelligent devices and their users.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.05a
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• pp.114-116
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• 2022

The advent of the Multi-access Edge Computing (MEC) paradigm allows mobile users to offload resource-intensive and delay-stringent services to nearby servers, thereby significantly enhancing the quality of experience. Due to erratic roaming of mobile users in the network environment, maintaining maximum quality of experience becomes challenging as they move farther away from the serving edge server, particularly due to the increased latency resulting from the extended distance. The services could be migrated, under policies obtained using Deep Reinforcement Learning (DRL) techniques, to an optimal edge server, however, this operation incurs significant costs in terms of service downtime, thereby adversely affecting service quality of experience. Thus, this study addresses the service mobility problem of deciding whether to migrate and where to migrate the service instance for maximized migration benefits and marginal service downtime.

• Speech Sciences
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• v.14 no.2
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• pp.43-53
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• 2007

The purpose of this study was to observe the effect of eating a raw egg by professional or nonprofessional voice users on their voice quality and the duration of the effect. 20 professional voice users and 20 nonprofessional voice users participated in the experiment and they had gone through stroboscopy to have no vocal or laryngeal diseases. The voice exam was performed three times: before eating a raw egg (1st period), right after eating it (2nd period), and 10 minutes later (3rd period). By using Multi-dimensional Voice Program which is a software of Computerized Speech Lab 4500 as a voice analysis instrument, the authors checked the F0, Jitter, Shimmer, Noise to harmonic ratio (NHR), and Voice Range Profile (VRP). Results showed as follows: Firstly, vocal hygiene was good in 57.5% of the total subjects and was poor in 42.5%. 40% of professional voice users and 75% of nonprofessional voice users hand good quality. 77.5% of the total subjects had the vocal fatigue while 22.5% of the subjects did not. 95% of the professional voice users and 60% of nonprofessional voice users complained the vocal fatigue. 60% of the total subjects reported a subjective vocal symptom. 65.0% professional voice users and 70.0% of nonprofessional voice users reported a voice symptom. From the results above, we suggest that eating a raw egg may lead to imporve voice quality of the professional voice users.