• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1105-1110
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• 2011

It is possible to synchronize the spatio-temporal data with a server using a wireless network. These data has the benefit to be up-to-date and able to service to the user efficiently. However, the mobile devices or the wireless network are very vulnerable to various hard or soft failures. If an failure occurs during a synchronization process, the spatio-temporal data which is synchronizing could be inconsistent state. In this paper, we propose the recovery scheme to solve the problem caused by the errors which occur during the synchronization on mobile environments. The proposed scheme writes the log records for the synchronization process into the both local storages of the server and the mobile client. When the errors arise, the data which are synchronizing are recovered using the written log records. Also, we design and implement the proposed recovery scheme on the synchronization system.

• Journal of KIISE:Software and Applications
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• v.33 no.11
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• pp.953-964
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• 2006

Due to the usefulness of the collaborative filtering, it has been widely used in both the research and commercial field. However, there are still some challenges for it to be more efficient, especially the scalability problem, the sparsity problem and the cold start problem. In this paper. we address these problems and provide a novel distributed approach based on agents collaboration for the problems. We have tried to solve the scalability problem by making each agent save its users ratings and broadcast them to the users friends so that only friends ratings and his own ratings are kept in an agents local database. To reduce quality degradation of recommendation caused by the lack of rating data, we introduce a method using friends opinions instead of real rating data when they are not available. We also suggest a collaborative filtering algorithm based on user profile to provide new users with recommendation service. Experiments show that our suggested approach is helpful to the new user problem as well as is more scalable than traditional centralized CF filtering systems and alleviate the sparsity problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.24-33
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• 2007

In this paper, two different dynamic cell coordination strategies for frequency flat and selective fading are proposed for efficient subcarrier allocation in the joint consideration of adaptive modulation and variable frequency reuse in the channel-aware OFDMA downlink multicellular environment. Compared to a conventional OFDMA system without cell coordination, where system throughput may become degraded due to the persistent interference from other cells, the proposed system dynamically allows RNC to apply different reuse factors on each subchannel and scheduling in consideration of channel and interference conditions of individual users so as to increase the system throughput and guarantee QoS of each user. In a frequency flat fading, the dynamic scheme with the proposed scheduling achieves on average three times larger throughput than the conventional dynamic scheme [8]. In a selective fading channel, the proposed schemes showed 2.6 times as large throughput as that of a single reuse factor of one for all subchannels.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.316-322
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• 2019

A probabilistic approach considering uncertainties was employed to investigate the effects on the material characteristics and strength of nuclear bio-logical shield concrete walls, when exposed to long-term radiation during the entire service life. Time-dependent compressive and tensile strengths were estimated by conducting the neutron fluence analysis. For the contaminated concrete, individual compressive and tensile failure probabilities can be possibly evaluated by not only establishing limit-state function withthe predefined critical values but also performing Monte Carlo Simulation. Nuclear power plant types similar to the Kori Unit 1, which was shut off permanently in 2017 after the 40-year operation, were herein selected for an illustrative purpose. Consequently, the probability-based performance assessment and prediction of contaminated concrete walls were well demonstrated.

• Journal of Environmental Impact Assessment
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• v.21 no.1
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• pp.119-132
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• 2012

Biodiversity is a key element of ecosystem of which function provides essential product and service in human life. In the course since development projects often causes damages to biodiversity, environmental impact assessment technique must be capable of accurately assessing potential impact from flora and fauna and to entire ecosystem. Korea needs improvement of its assessment technique that is compatible with Korean environmental regulatory standard that is generally stricter than that of most countries. This study attempts to explore both domestic and overseas biodiversity assessment techniques and analyze each stage of environmental impact assessment. The data is collected from numbers of literatures selected by navigating both domestic and overseas literature database with certain keywords. Among the 44 selected papers, overseas publications outnumber those of domestics, and there are more researches on assessment methodology of biodiversity than assessment tool and model. In terms of environmental impact assessment, the number of papers on environmental impact forecast exceeds the numbers of papers on current state of environment and the impact minimizing solution. Therefore, contents and trends of those researches in the different stages of environmental impact assessment discussed in this paper not only suggest potential impact on biodiversity and minimization solutions in detail, but is also a valuable resource particularly for biodiversity relevant environmental assessment technique improvement in Korea. Proposing of a new direction of improvement in biodiversity assessment techniques makes this study significant, and further research for preservation of biodiversity should follow up to provide an improvement scheme for biodiversity assessment techniques in the future.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.6
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• pp.968-979
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• 2008

Since community growth and vitality frequently depend on local businesses and community inhabitants depend on local retailers for their daily necessities, studying small businesses in rural areas is important to community sustainability. The purpose of our research was to investigate what marketing, merchandising, customer service, or business operation strategies were being implemented by successful independent rural retailers(i.e., clothing, jewelry, floral, hardware etc.), in competition with large discount stores in the U.S.. In addition, social capital as indicated by community involvement was examined for its use as a business strategy that contributes to the success of small retailers. In-depth interviews were conducted with 27 rural retailers representing three communities within a Midwestern state. Data were content analyzed. Participants were following several of the recommended business strategies but opportunities existed to implement changes. Results are discussed in terms of key practices followed by these successful small business owners.

• Journal of the Korean Society for information Management
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• v.22 no.1 s.55
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• pp.209-228
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• 2005

This study is a preliminary work in examining how to manage resources for collaboratively interactive help systems. The purpose of this article is to describe significant patterns of behaviors and cognitive state in collaborative problem-solving situation, and further to explore the relationship between the behavior and the perception of service evaluation. Based on the concept of 'cognitive motion' in Dervin's Sense-Making theory, this study conducted a time-line interview. The sample of this study consists of 22 IT personnel helping other person solve IT problems and 36 users being helped for a IT problem-solving. This study presents a model of collaborative problem-solving behaviors and discusses some implications for designing help systems which collaborative interactions can happen.

• The Korean Journal of Archival Studies
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• no.66
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• pp.317-355
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• 2020

Moon Ik-hwan's prison letters are valuable historical materials managed by the Moon Ik-hwan House of Unification, reflecting an aspect of modern and contemporary South Korea. He wrote these prison letters during a period of approximately 11 years and three months. Today about 800 of them remain and are in an urgent need for measures to ensure their long-term preservation and Use. This study set out to introduce their current state that had been made to the public only in fragments, analyze their characteristics as objects of records management, and propose directions and strategies to provide them as part of online service. For these purposes, the investigator analyzed Moon's personal life and life in prison as the backgrounds of their creation and examined their unique characteristics as prison letters according to the scope and size, recipients, reproduction and circulation process, and the medium of lettercards. Based on these efforts, the study shed new light on the significance of use in private archives and provided a case of online utilization tasks and strategies based on the characteristics of letters as one of the representative types of personal records.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.297-312
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• 2005

The multimedia traffic of continuous video and audio data via streaming service accounts for a significant and expanding portion of the Internet traffic. This streaming data delivery is mostly based on RTP with UDP. However, UDP does not support congestion control. For this reason, UDP causes the starvation of congestion controlled TCP traffic which reduces its bandwidth share during overload situation. In this paper, we propose a new TCP-friendly rate control scheme called 'TF-RTP(TCP-Friendly RTP)'. In the congested network state, the TF-RTP exactly estimates the competing TCP's throughput by using the modified parameters. Then, it controls the sending rate of the video streams. Therefore, the TF-RTP adjusts its sending rate to TCP-friendly and fair share with competing TCP traffics. Through the simulation, we prove that the TF-RTP correctly estimates the TCP's throughput and improves the TCP-friendliness and fairness.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.72-77
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• 2011

Spectrum sensing is a critical functionality of CR network; it allow secondary user to detect spectral holes and to opportunistically use under-utilized frequency bands without causing harmful interference to primary use. Recently, wideband service has been increase for processing abundance of data traffic. So CR network needs a realizable implementation design of spectrum sensing for wideband. To get high resolution performance of wideband sensing must precede algorithm processing for reliability signal detection. By the way, the performance of spectrum sensing can be degraded due to fading and shadowing. In order to overcome this problem, we propose system model of wideband sensing scheme on energy detected collaborative technique. we divide wideband into narrowbands and use narrowbands to detect signal excepting some narrowbands including bad channel through the CSI. And we simulate and analyze in terms of detection probability with various SNR.