• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.735-738
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• 2000

The most important issue in database security is correct concurrency control under the restrictive security policy. The goal of secure transaction management is to keep security and provide many concurrent users with the high availability of database. In this paper, we consider the security environment of multidatabase system with replicated data. The read-from relationship in the existed serializability is improper in security environment. So, we define new read-from relationship and propose new secure 1-copy quasi-seriailzability by utilizing this relationship and display some examples. This security environment requires both the existed local autonomy and the security autonomy as newly defined restriction. To solve covert channel problem is the most difficult issue in developing secure scheduling scheme. The proposed secure 1-copy quasi-serializability is very proper for global transactions in that this serializability not violates security autonomy and prevents covert channel between global transactions.

• Journal of KIISE:Information Networking
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• v.37 no.6
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• pp.415-419
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• 2010

Bandwidth is an extremely valuable and scarce resource in a wireless network. Therefore, efficient bandwidth management is necessary in order to provide high quality service to users with different requirements. In this paper, we propose a bandwidth reservation algorithm based on Nash Bargaining Solution. The proposed algorithm has low complexity and are quite flexible in the different situations of network. Simulation results indicate that the proposed scheme has excellent performance than other existing schemes.

• Annual Conference of KIPS
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• 2024.05a
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• pp.137-140
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• 2024

가상 및 증강현실(VR/AR), 원격 제어, 산업 자동화를 위한 실시간 애플리케이션이 증가함에 따라 무선 통신 네트워크의 처리량과 지연시간 성능이 중요해졌다. 이에 따라 Wi-Fi 8 에서는 초고신뢰 (Ultra-High Reliable, UHR)을 목표로 표준화가 진행 중이며 다수의 AP가 협력하여 데이터를 전송하는 다중 AP 협력 기법이 핵심 기술로 논의되고 있다. 하지만 기존의 다중 AP 협력 환경에서 협력 전송을 위한 제어 정보로 인한 간섭 증가와 OBSS(Overlapped Basic Service Set) 간섭 문제를 고려하지 못하고 있다. 따라서 본 논문에서는 효율적인 다중 AP 협력 전송을 위한 단순화된 채널 관리 방법(Simplified Channel Management Mechanism, SCMM)을 제안한다. 실험 결과에 따르면, SCMM 이 종래모델 대비 처리량은 평균 21.23% 증가했고, 지연시간은 평균 51.02% 감소했다.

• Journal of Internet Technology
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• v.21 no.3
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• pp.841-847
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• 2020

In this paper, a novel technique that improves the performance of generalized mixture decomposition algorithm (GMDA) based on pre-training phase unwrapping. From the investigation of the GMDA scheme, it was discovered that the conventional GMDA technique cannot fully consider phase unwrapping, because the estimated inter-channel phase difference (IPD) slope is initialized randomly. To avoid this phenomenon, the proposed GMDA approach initialized the IPD slope from the data of low-frequency bins. Experimental results show that comparing to the conventional GMDA technique, the proposed GMDA technique based on pre-training phase unwrapping obtains a lower estimation error. When integrated into a source localization system, the result of source localization is improved.

• Journal of Korean Society for Quality Management
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• v.45 no.3
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• pp.503-520
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• 2017

Purpose: In the near future, it is expected that UGV(unmanned ground vehicle) will be put into battle due to IT technology and unmanned technology development. In this study, we analyze the combat effectiveness considering communication effect where complex combat information and commands are transmitted. Methods: We use ABM(agent-based modeling) and wireless channel module which provides sophisticated communication effect through geographic information and UGV performance. And UGV combat simulation using wireless channel module is used to grasp the combat effectiveness according to the number of packets, which is a unit for storing all information and commands having high complexity. Results: The result of this study is to derive the optimal number of packets which does not decrease the combat effectiveness and the number of lost tanks. The number of packet increases, the survival ratio of our tanks are decreased. Conclusion: In this study, we reveal that the communication success or failure could affect the combat effectiveness. Also, it helps develope the standard communication protocol between UGVs and could be applied to analyze the cost effectiveness analysis in UGV combat environment.

• Journal of Distribution Research
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• v.17 no.3
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• pp.93-113
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• 2012

Early conflict research in channel and organization area have focused on the definition of conflict construct, its cause, consequence and identified conflict resolution management. Recent studies about conflict, however, have explored new assumption of complexity, a multidimensional conflict construct, contextual conflict management strategies, positive and negative conflict/consequence, and the conflict resolution strategy. Although many literatures exists on channel conflict resolution, little research has been done about relationship learning and performance from conflict resolution perspective. This study explores how channel members can achieve a relationship learning, as a conflict resolution mechanism, which enhance co-created value in marketing channel relationship. Therefore we propose that conflict resolution strategies(collaborating behavior and avoiding behavior) influence channel performance(effectiveness and efficiency) through relationship learning processes(learning via information exchange, joint interpretation and coordination, relationship-specific knowledge memory), in view of buyer-seller relationship. The research model is shown at

• Journal of Digital Convergence
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• v.13 no.10
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• pp.319-325
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• 2015

We proposed the blocking channel to reduce the performance decrease using the low correlation with cyclic delay scheme in LED-ID system. LED-ID is based on the visible light to transmit the data. However, It is occurred the block channel by structure or environment of indoor for light of straightness. LED-ID system is degraded the performance by the block channel as loss of data, and burst error. To solve the block channel, the proposed system is overcome the burst error by low correlation among data, which is able to obtain the maximize time diversity gain to improve the performance of BER by cyclic delay scheme. The BER performance is evaluated by computer simulation according to channel parameter. The simulation results shows that proposed system gives much better performance than conventional system and constant cyclic delay scheme system.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.547-559
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• 2012

Abandoned channel is vestiges of running in the past. Abandoned channels have been formed mostly by artificial river maintenance through channel straightening in Korea. Managed properly, these now abandoned channels can provide habitat for wildlife, maintain biodiversity of aquatic life, security against flooding and recreation area for human. However, because the areas are officially classified as abandoned, the channels is collapsing and decaying from years of neglect. This study suggested functional assessment for wetland-type abandoned channel in order to provide appropriate management and investment. For this reason, The study will examine and evaluate these channels with regard to the following four major criteria (Natureless, Habitat, Water-friendliness and Water quality) and 21 indices. Consequently, abandoned channel in two Nakdong river sites, site 1 was needed for protection or improvement in the medium to longer term, while site 2 was in good condition. This evaluation method will be helpful to manage wetland-type abandoned channel in Korea and will be able to use National River Health Program.

• Journal of Information Processing Systems
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• v.11 no.4
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• pp.583-600
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• 2015

Generally, the wireless network provides priority to handover calls instead of new calls to maintain its quality of service (QoS). Because of this QoS provisioning, a call admission control (CAC) scheme is essential for the suitable management of limited radio resources of wireless networks to uphold different factors, such as new call blocking probability, handover call dropping probability, channel utilization, etc. Designing an optimal CAC scheme is still a challenging task due to having a number of considerable factors, such as new call blocking probability, handover call dropping probability, channel utilization, traffic rate, etc. Among existing CAC schemes such as, fixed guard band (FGB), fractional guard channel (FGC), limited fractional channel (LFC), and Uniform Fractional Channel (UFC), the LFC scheme is optimal considering the new call blocking and handover call dropping probability. However, this scheme does not consider channel utilization. In this paper, a CAC scheme, which is termed by a uniform fractional band (UFB) to overcome the limitations of existing schemes, is proposed. This scheme is oriented by priority and non-priority guard channels with a set of fractional channels instead of fractionizing the total channels like FGC and UFC schemes. These fractional channels in the UFB scheme accept new calls with a predefined uniform acceptance factor and assist the network in utilizing more channels. The mathematical models, operational benefits, and the limitations of existing CAC schemes are also discussed. Subsequently, we prepared a comparative study between the existing and proposed scheme in terms of the aforementioned QoS related factors. The numerical results we have obtained so far show that the proposed UFB scheme is an optimal CAC scheme in terms of QoS and resource utilization as compared to the existing schemes.

• Journal of agriculture & life science
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• v.44 no.1
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• pp.69-80
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• 2010

The purpose of this study is to analyse current marketing practices and marketing efficiency using operational efficiency. Through field survey on marketing situations and channels, we found that major marketing channels of paprika were classified into six types : channels in exporting market included (1) producer's organization leading channel (type I), (2) regional cooperative leading channel (type II), (3) individual producer leading channel (type III), and channels in domestic market included (4) wholesale markets targeting channel (type IV), (5) distribution agents targeting channel (type V), (6) cooperative system selling channel (type VI). According to the estimated result of operational efficiency of marketing channels, marketing efficiency of type III and IV was relatively higher than type I,II and type V, VI respectively.