• 항공우주기술
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• 제3권2호
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• pp.217-228
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• 2004

본 논문은 복합재 패들형 블레이드를 장착한 축소 힌지없는 로터 시스템의 정지 및 전진 비행조건에 대한 회전시험 기술과 결과에 대한 것이다. 축소 로터 시스템은 실물크기 로터 시스템의 구조 자료를 이용하여 프루드 축소화하였고, 허브 flexure는 동일한 로터의 동력학적 특성을 기준으로 금속재와 복합재 2가지를 제작하였다. 2종류의 힌지없는 허브시스템을 KARI의 GSRTS에 장착후 회전 시험을 실시하여 로터 시스템의 리드래그 감쇠비와 공력 하중을 측정하였다. 리드래그 모드의 감쇠비를 산출하기 위해 MBA(Moving Block Analysis)기법을 사용하였고, 허브와 주축 사이에 6분력 발란스를 장착하고, 블레이드에 스트레인게이지를 부착하여 공력하중을 측정하였다. 시험은 제자리 및 전진비행 조건에 따라 지상 및 풍동에서 각각 수행하였다.

• 한국농공학회논문집
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• 제57권1호
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• pp.69-78
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• 2015

The objective of this study was to investigate characteristics of irrigation return flow from paddy block in a reservoir irrigated district during growing seasons. The irrigation return flow was divided into three parts, quick return flow from irrigation canal (RFI), quick return flow from drainage canal (RFD), and delayed return flow (DRF). The RFI was calculated from water level and stage-discharge relationships at the ends of the irrigation canals. The DRF was estimated using measured infiltration amount from paddy fields of the irrigated district. A combined monitoring and modeling method was used to estimate the RFD by subtracting surface runoff from surface drainage. The paddy block irrigated from the Idong reservoir was selected to study the irrigation return flow components. The results showed that daily agricultural water supply (AWS), the RFI, and the RFD were $27.4mm\;day^{-1}$, $4.9mm\;day^{-1}$, and $19.8mm\;day^{-1}$, respectively in May, which were greater than other months (p<0.05). The return flow ratio of the RFI and the RFD were the greatest in July (34.6%) and May (72.3%), respectively. The daily AWS was closely correlated with the RFD (correlation coefficients of 0.76~0.86) in except for July with, while correlation coefficient with the RFI were 0.56 and 0.42 in June and July, respectively (p<0.01). The total irrigation return flow was 1,965 mm in 2011, and 1,588 mm in 2012, resulting in total return flow ratio of 84.6% and 79.1%, respectively. This results indicate that substantial amounts of agricultural water were returned to streams as irrigation return flow. Thus, irrigation return flow should be fully considered into the agricultural water resources planning in Korea.

• 한국수자원학회논문집
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• 제52권spc2호
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• pp.823-833
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• 2019

This study presents the impact of natural flow patterns on downstream fish habitat and economic outcomes in the Dal Stream, Korea. The study reach is 3.35 km long, located downstream form the Goesan Dam. To assess such impact, this study performed physical habitat simulations. The River2D model was used for the computation of the flow and the HSI model for the habitat simulation. Two physical habitat variables, flow depth and velocity, were used. The Zacco platypus, Zacco temminckii, Coreoleuciscus splendidus, and Opsariichthys bidens were selected as the target species in the study area. Using the building block approach (BBA), the scenarios for the hydropeaking mitigation were presented. Scenario 1 and scenario 2 were proposed by using the magnitude - duration concept and averaged the hydrologic data over the each month, respectively. Simulation results indicated that the scenarios effects significantly increased by about 18.6% for the weighted usable area (WUA). In addition, hydroelectric power benefits with both scenarios were investigated. It was revealed that the change of storing and releasing water decreased by about 27% for hydroelectric power benefits. In order to increase economic benefits, the scenario was modified with the discharges corresponding to the hydropeaking condition except the flood season. As a result, the hydroelectric power benefits were almost the same, however the aquatic habitat for the target species increased by about 5%. The change of dam re-operations through natural flow patterns provides an opportunity to minimize environmental and economic benefits in order to balance water management.

• Industrial Engineering and Management Systems
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• 제4권2호
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• pp.117-122
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• 2005

An assembly system (AS), a valuable tool for mass production, is generally composed of a number of workstations and a transport system. While the workstations perform some preplanned operations, the transport system moves the assemblies by special designed pallets from one station to another. One common problem associated with automatic assembly systems is that some assembly operations may have relatively long cycle times. As a consequence, the productivity, as determined by the operations with the longest cycle time, can be reduced significantly. Therefore, special forms of parallel workstations were developed to improve the performance of an assembly system. In this paper, three most commonly used parallel stations: on-line, off-line and tunnel-gated stations in a free transfer assembly system are studied via discrete event simulation. Our findings revealed that the off-line parallel system has the best performance because the two independent parallel stations can lower the buffer requirement; reduce the sensitivity to variability of processing time and balance of a line. On-line parallel systems were found to have a relatively poor performance, because the operations of two parallel stations block each other, and higher buffer capacity is required to achieve similar capacity. The tunnel-gated system was more efficient than the on-line system since the first parallel station can operate independently. More importantly, we have quantified the productivity of the three different strategies mentioned. Engineers can choose the optimal strategies for installing parallel stations under their working environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3607-3623
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• 2014

The increasing demand in promoting cloud computing in either business or other areas requires more security of a cloud storage system. Traditional cloud storage systems fail to protect data integrity information (DII), when the interactive messages between the client and the data storage server are sniffed. To protect DII and support public verifiability, we propose a data integrity verification scheme by deploying a designated confirmer signature DCS as a building block. The DCS scheme strikes the balance between public verifiable signatures and zero-knowledge proofs which can address disputes between the cloud storage server and any user, whoever acting as a malicious player during the two-round verification. In addition, our verification scheme remains blockless and stateless, which is important in conducting a secure and efficient cryptosystem. We perform security analysis and performance evaluation on our scheme, and compared with the existing schemes, the results show that our scheme is more secure and efficient.

• 기계저널
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• 제35권7호
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• pp.593-602
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• 1995

수출주도형 산업구조를 가지고 있는 우리 나라의 경제여건은 1960년대 초 경제개발 5개년 계획을 수립한 이래 지속적인 성장을 기록하여 왔다. 그러나 1986년도에 3저라는 국제경제여건을 호기로 삼아 국제무역수지 흑자를 기록한 이후 선진국의 보호장벽 강화, 세계적인 BLOCK 경제화, WTO 출범에 따른 국내시장 개방압력, 국내임금의 급속한 상승 등 수많은 대내외적 여건으로 인하여 우리경제의 성장에 큰 부담으로 작용하고 있다. 1994년의 경우 전체무역적자가 63억 3천만 달 러를 기록함으로써 한국경제의 계속적인 무역역조현상이 큰 문제점으로 대두되고 있고 1994년 기준으로 전체무역적자의 188%이상에 해당하는 118억 7천만 달러가 대일무역에서 발생한 대일 역조라는 사실과 최근 몇년간 대일무역적자는 다소 개선되고 있으나 전체 무역적자에서 차지하는 비중이 더욱더 높아가고 있는 것에 대한 대책이 시급한 실정이다. 이같은 대일무역적자 문제는 1960년대 이후 급속한 경제성장만을 추구하여 노동집약형 사업이 주가된 경제성장의 결과이며, 산업재, 특히 기계분야에 대한 기술축적의 부족으로 대부분의 자본재 및 중간재와 기술력에 대한 대일의존도의 심화 등에 그 원인이 있다고 할 수 있다. 이러한 점에서 수출 주도형의 한국경제 하에서는 대일무역역조 특히 기계공업분야의 역조현상은 반드시 해결해야 할 중요한 정책과제 임을 인식해야 하며, 이 글에서는 이에 대한 다각적인 대책을 검토하여 해결방안을 제시해 보 고자 한다.

• Natural Product Sciences
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• 제12권4호
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• pp.175-192
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• 2006

Screening for the cytotoxicity from plant origin is the first stage for anti-cancer drug development. A variety of terpenoids with exomethylene, epoxide, allyl, $\alpha,\beta-unsaturated$ carbonyl, acetylenes, and $\alpha-methylene-\gamma-lactone$ induces apoptosis and/or differentiation as well as cytotoxicity through the ROS signal transduction pathways. These are found among monoterpenes, sesquiterpenes, triterpenes, flavonoids, coumarins, diarylheptanoids, and even organosulfuric compounds. The most essential characteristics of natural cytotoxic substances is to possess the strong electrophilicity that is susceptible to nucleophilic biomolecules in the cell. Thiol-reductants and superoxide dismutase can block or delay apoptosis. Thus, ROS and the resulting cellular redox-potential changes can be parts of the signal transduction pathway during apoptosis. Disturbance of the balance of oxireduction by the pigment of natural quinones also caused the induction of the differentiation and apoptosis. Saponins with the cytotoxicity are restricted to their monodesmosides, rather than to bisdesmosides. Those saponins exhibited calcium ion-mediated apoptosis in addition to cytotoxicity whereas they showed also differentiation without extracellular calcium ion. The properties on cytotoxicity, apoptosis, and differentiation were assumed to depend on resultant oxidative stress to the cells. In this review, we describe a spectrum of cytotoxic compounds with various action mechanisms.

• 대한통합의학회지
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• 제1권4호
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• pp.75-83
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• 2013

Purpose : This research was conducted to see the correlation between sway speed and muscle activity for lower extremity of stroke patients through unstable surface training. Methods : A total of 60 patients were randomly divided unstable surface group (30 peoples) and stable surface group (30 people). Then they were asked to carry out the same exercise program for 6 weeks. The unstable surface group and stable surface group performed the exercise program on the balance mat and on the hard wood block. We checked the changes of sway speed and the changes in muscle activity for lower extremity. Results : The unstable surface group displayed significantly reduced sway speed, and improved muscle activity of lower extremity. There were significant correlation between change amount of muscle activity and sway velocity in Gastrocnemius, Biceps femoris during unstable surface training(r=.373, p<.05)(r=.369, p<.05). And there were not show significant differences during stable surface training. Conclusion : Judging from this, we can have knowledge that the correlation between increase of muscle activity and decrease of sway velocity for Gastrocnemius, Biceps femoris in the unstable surface training.

• The Korean Journal of Pain
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• 제8권2호
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• pp.347-349
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• 1995

A 43 year old man who suffered from right facial palsy was treated successfully with the application of both magnetic resonance diagnostic analyser(MRA) and drug therapy. Treatment of facial palsy is generally composed of stellate ganglion block(SGB), drug therapy and operative intervention. Short periods of exposure to appropriate magnetic resonance can beneficially modulate the balance of autonomic nervous system that are responsible for sympathetic overflow. It was concluded that recovery of facial palsy by application of both MRA and drug therapy was effective in patient who refused SGB.

• 한국정보과학회논문지:정보통신
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• 제28권3호
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• pp.426-434
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• 2001

병렬 VOD 시스템에서 스트라이핑 정책은 비디오 데이터를 분할 하여 각 노드에 잘 정의된 순서로 분배함으로서 노드간에 부하 균등을 통한 시스템의 성능을 높일 수 있는 중요한 기법이다. 본 논문운 노드를 추가할 경우 노드간의 부하 균등을 고려한 데이터 스트라이핑 기법을 제시한다. 병렬 VOD 서버의 추가된 노드에 새 비디오 파일을 저장할 경우 그 노드에 부하가 집중되어 시스템의 성능이 떨어질수 있기 때문에 적절한 새 노드에 이동시켜 배치시키고 새 비디오 파일을 각 노드에 분배시키는 3 가지 스트라이핑 기법들을 제시한후 실험 분석을 통하여 이 기법들을 비교 평가하였다. 그 결과 FSM 양방향 기법이 가장 좋은 성능을 보였다.