• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1022-1032
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• 2012

In OFDMA-based wireless mesh networks, synchronization of carrier frequencies among adjacent nodes is known to be difficult. In this paper, a distributed synchronization technique is proposed to solve the synchronization problem in OFDMA-based wireless mesh networks by using the bio-inspired algorithm. In the proposed approach, carrier frequencies of all nodes in a mesh network are converged into one frequency by locally synchronizing the frequencies of adjacent nodes. It may take a long time to be converged in some topologies since the convergence characteristic of carrier frequencies in a mesh network may vary depending on the size of the network and deployment of nodes. It is shown that fast frequency synchronization, not heavily depending on the topology, can be achieved through the proposed algorithm with an adjustable weight.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2238-2243
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• 2008

홍수 방류량 하류 도달시간 산정은 댐운영 및 홍수예경보의 기초자료로 인식되고 있어 정확한 유하시간 산정이 필요하다. 수자원공사에서는 댐 방류에 따른 하류도달시간을 댐운영실무편람('06)에 있는 자료를 활용하여 댐 운영에 활용하고 있다. 금강 하류부의 경우 '97년 금강홍수예경보 자료를 활용하고 있으나, 수치모형 결과 자료로 실측에 의한 검증이 이루어지지 않았다. 댐 방류수에 대한 하류도달 시간에 대한 실측 기술을 확보하여 실측을 통한 수치모형의 검증 및 보완 필요하며, 보정된 수치모형을 이용한 홍수도달시간 실시간 예측을 통한 댐운영의 효율성 확보 및 대내외 검증된 결과 제시가 요구되고 있다. 현재 댐 방류에 따른 하류도달 시간에 대한 실측이 요구되고 있으나, 관련 기술에 대한 국내외 개발 및 적용 사례가 전무한 실정으로 본 연구에서는 현장계측과 수치모형을 연계한 신뢰성 높은 도달시간을 분석하는 기술을 개발하고자 하였다. 이를 위해 장구간 내에서 홍수의 흐름과 동일하게 하천에 흘러갈 수 있는 부유물을 개발하였으며, 주야간에 상관없어 주요 계측지점에서 도달시간 산정을 위해 자동 인식될 수 있는 센서기술을 개발하였다. 또한, 인식된 센서를 안정적으로 통신망에 연동하여 실시간 계측이 가능하며, GIS 기반의 원격 모니터링이 가능하도록 시스템을 구성하였다. 나아가. 기존 수치모형에 의존하여 예측된 도달시간 산정방법을 개선하기 위하여 수치모형의 매개변수를 검보정을 위한 시계열 및 지속적으로 자료를 취득하였다. 이러한 센서기술, 모니터링기술, 분석기술을 융합하여 향후 매개변수를 보정한 홍수도달시간 수치모형을 이용하여 신뢰성 높은 예측결과를 홍수예경보 및 댐 운영에 있어 활용함으로써 홍수재해로부터 안전성을 확보하고 물관리의 효율화를 달성할 수 있을 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2184-2188
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• 2008

최근 도시의 발달은 하상공간에 대한 이용도를 높이는 방향으로 개발이 진행되어가는 추세이며, 하상도로 및 하상주차장의 이용은 이제 도시 내에서 이용 가능한 마지막 여유 공간으로 인식될 정도로 그 의존도가 높아져가고 있다. 그러나 하상공간의 활용도가 높아져갈 수록 도시홍수의 발생으로 인한 대피문제가 발생하게 되고 돌발홍수로 인하여 하상도로의 차단 혹은 하상 주차장에 주차된 차량의 소거가 늦어지는 경우 고스란히 피해를 보게 되는 등 그 부작용도 계속 증가되고 있다. 도시홍수의 특성을 살펴보면 국지성 돌발 강우에 의한 유량의 급격한 증가와 짧은 유하시간, 작은 유역면적 등에 의하여 주요 예보지점까지의 도달시간이 매우 짧아 수문학적 홍수예측 모형을 이용하여 홍수예측 업무를 수행하는데 선행시간을 충분히 확보할 수 없다는 단점을 지니고 있다. 이에 따라 본 연구에서는 기존의 하천시스템에 대한 모의모형을 통하여 홍수 예경보를 발령하기에는 선행시간의 확보(대피시간의 확보)라는 측면에서 상당한 어려움을 지닐 수 있으므로 시시각각으로 측정되는 실시간 수위측정 자료 및 실시간 강우자료를 이용하여 모형의 수행과정을 생략하고, 하천의 수위변동을 직접 예측하여 대피할 수 있는 통계학적 모형 (회귀분석 기법) 기반의 수문모형을 개발하였다. 이를 위하여 각 관측 자료로부터 대상 지점(홍수 예보지점)의 수위를 간단한 입력 자료만으로도 직접 구할 수 있는 통계학적 기법을 활용하여 홍수예보 업무를 실시할 수 있도록 하였다. 이에 따라 강우강도 등의 강우정보, 하천 수위정보 등을 이용하여 간단한 홍수예보가 가능한 규칙을 제시하였고, 홍수예보 업무에 신속하게 대응할 수 있는 시스템을 구축하기 위하여 Visual Basic 6.0을 사용한 GUI 기반의 홍수예측 수문모형을 구성하였으며, 제어변수(control variable)로는 강우 관측자료, 수위 등 유출관측 자료로 구분하여 수문모형을 구성함으로써 실무자들이 쉽게 활용할 수 있는 홍수 예경보 시스템의 기본모형을 제시하였다.

• Journal of Environmental Policy
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• v.14 no.4
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• pp.63-101
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• 2015

Banking and borrowing under the ETS may affect the low carbon technology investment level. If the indirect implementation measures are allowed, firms can gradually adjust their carbon reduction costs between implementation periods based on their carbon reduction costs and emission price forecasts. This implies that banking and borrowing may reduce or increase the level of low carbon technology R&D investment. In an oligopoly market, the effects of the measures are quite different from the ones in a perfectly competitive market. This is because the indirect implementation measures can shift market competition in Cournot competition model. The effects of banking and borrowing on the carbon reduction R&D investments depend on emission reduction costs, marginal production costs, discount rate, initial free allocation, and the cost reduction effects of R&D investment.

• International Commerce and Information Review
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• v.13 no.2
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• pp.27-48
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• 2011

Single window has become a critical point of trade facilitation. While Korea has set up the first web based single window 'uTtradeHub', China has also been working on a seamless single window. As strong governmental support, advanced technology, leading agency and legal framework are success factors for single window, China already has solid foundation for this. For the leading agency, this research suggests the CIECC as a leading agency with linkage to E-Port service for seamless trade service for companies. We expect that Chinese single window will materialize in near future by a leading agency with the help of strong governmental support.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.399-404
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• 2020

The purpose of this study is to find out the consumer's purchasing behavior and its factors when a convenience store brand is marketing new PB products online. For this study, we surveyed 2030 millennials about the purchase behavior of convenience store PB products and the paths to encounter PB products. As a result, consumers who purchase convenience store PB products were exposed to the product through SNS or YouTube, and they tended to join the trend by posting on SNS after purchase. In this study, we want to examine the consumption trends of millennials that have this type of consumption and the concept of online marketing that affects them. It is hoped that future consumer purchases will continue to be valuable consumption rather than relying on trends.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.269-278
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• 2010

Today's Virtual Reality(VR) technology has become considerably more affordable and sophisticated with rapidly advancing computer technology. Photo-realistic visual representations along with real-time interactivity are now achievable without special programing knowledge and expensive equipment. The purpose of this paper is to establish how simple, credible user testing methods based on VR simulations can be utilized to improve design decision making towards more sensible design solutions for end-users. Results of a case study demonstrate the value of potential user-testing feedback in a simulated 3D virtual service space, i.e., restaurant interior. User feedback from the VR simulation includes preferences in table location, privacy, and values of seating preferred tables. A new design framework incorporating an empirical testing method for service spaces is presented. The overall design process, the development of the VE, and the user testing method and findings are discussed. This study provides useful guidances for future efforts in the areas where such technology may benefit to understand end-user feedbacks in design process.

• Journal of Korea Game Society
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• v.16 no.6
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• pp.163-172
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• 2016

This study analyzes the attitudes of users who use the automatic-play function of mobile-games. It also observes changes in different emotions to enjoyment. For the analysis, the Q methodology appropriate for the subjectivity study was used, and it classified two types of attitudes based on the analysis. After the classification, it defined the characteristic of each type based on Lazzaro's theory on classification of fun. Types with high rate of convenience feature dependency utilize automatic-play feature to play games for collecting and growth, and they prefer managing the game outdoors. Another type enjoyed the experience of problem solving through games. They want the process to be a good skill to possess in game-play. There was also a tendency to perceive oneself as the game's character. Both types were responded positively to using automatic-play to play mobile-games. This is expected to be used as important data for game production, leading to usability evaluation for analyzing the emotional sensitivity of mobile game users.

• The Korean Journal of Community Living Science
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• v.14 no.2
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• pp.83-92
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• 2003

This study was carried out to investigate the supplementary effects of soybean oil and rice gem oil compared with lard on lipid metabolism of insulin dependent diabetic mice. Streptozotocin-induced diabetic mice were fed three kinds of experimental diets with 20% lipid from lard(L), soy bean oil(SBO) and rice gem oil(RGO) for 7 weeks, respectively. Diet intake, body weight, organs weights and lipids levels of serum, liver and feces were measured. There was no significant difference in diet intake, body and organs weights among experimental groups. But the concentrations of serum triglyceride of SBO and RGO groups, and of serum total cholesterol were lower in RGO group than in the other groups. The hepatic total lipid and total cholesterol levels of RGO group were significantly lower than those of the other groups. The contents of total lipid and total cholesterol excreted in feces of SBO and RGO groups were higher than those of L group, and the significance was shown only in RGO group. These results suggested that soy bean oil and rice germ oil can reduce serum triglyceride and total cholesterol levels and hepatic total lipid concentration of insulin dependent diabetic mice compared with lard as a animal fat source by increasing fecal lipid excretion of these groups. But the significant reducing effects on serum and liver lipid levels were shown only in RGO group, and we need to investigate the hypolipidemic effect of this oil by supplementary level and period.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.131-139
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• 1992

Based on the equi-flooding line theory, this study suggests method of evaluating safety of detent tion reservoirs with drainage pumping facilities in Seoul metropolitan area, and derives equi-flooding lines according to destruction frequency for each detention reservoir. In most part of detention reservoirs, its flood prevention are so much dependent upon drainage capacity that inland flooding prevention can be serious problems in case of its malfunction. In this study, the detention reservoirs which are below 5 year destruction frequency estimated as 29.3%, and below 10 year as 39.6% of the total. To improve reservoir safety, the detention reservoir capacities (including drainage and pumping capacity) should be upgraded above 20 year in its destruction frequency, and its reinforcement capacities are calculated.