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김남수,김종보,김인석,최형진,Kim, N.S.,Kim, C.B.,Kim, I.S.,Choi, H.J. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.3
Experimental investigations have been carried out to find the effect of drag reduction caused by effective polymer additives in turbulent flows. The experiments were undertaken with a test section of 9.8mm pipe diameter and 3500 mm pipe length(L/D=357) in a closed loop, and Copolymer-X and Polyacrylamide(PAAM) were used as polymer additives for comparisons. The tests were carried out under different polymer concentrations, and the temperatures of the flow considered were $26^{\circ}C$, $60^{\circ}C$ at the flow velocity of 5.3 m/s. The rate of drag reduction obtained by Copolymer-X is found to be considerably higher than that of PAAM in turbulent flows. Copolymer-X is also found to be very reliable for mechanical degradation, which has not been the case in any other additives. It is concluded that Copolymer-X is considered to be one of the most effective agents as an additive especially for long time hydraulic transports. It is also found that polymer degradation in more likely at lower polymer concentrations in the turbulent flows.
Dual Gate Emitter Switched Thyristor의 전기적 특성
김남수,이응래,최지원,김영석,김경원,주변권,Kim, Nam-Soo,Lee, Eung-Rae,Cui, Zhi-Yuan,Kim, Yeong-Seuk,Kim, Kyoung-Won,Ju, Byeong-Kwon 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.5
Two dimensional MEDICI simulator is used to study the electrical characteristics of Dual Gate Emitter Switched Thyristor. The simulation is done in terms of the current-voltage characteristics with the variations of p-base impurity concentrations and current flow. Compared with the other power devices such as MOS Controlled Cascade Thyristor(MCCT), Conventional Emitter Switched Thyristor(C-EST) and Dual Channel Emitter Switched Thyristor(DC-EST), Dual Gate Emitter Switched Thyristor(DG-EST) shows to have tile better electrical characteristics, which is the high latch-up current density and low forward voltage-drop. The proposed DG-EST which has a non-planer u-base structure under the floating N+ emitter indicates to have the better characteristics of latch-up current and breakover voltage in spite of the same turn-off characteristics.
Wireless Ad-hoc Networks Using Cooperative Diversity-based Routing in Fading Channel
김남수,안병구,김도현,이예훈,Kim, Nam-Soo,An, Beong-Ku,Kim, Do-Hyeon,Lee, Ye-Hoon The Korea Institute of Information and Commucation 2008 韓國通信學會論文誌 Vol.33 No.2b
We propose new routing scheme, Cooperative Diversity-based Routing (CDR)which utilize the cooperative space diversity for power saving and for performance enhancement of wireless ad-hoc networks. The end-to-end performance of the proposed routing, CDR, is analyzed based on the Haenggi's link model. The improved performance is compared with Multi-hop Relay Routing (MRR) by analytical methods. When the required outage probability is $1{\times}10^{-3}$ at the destination node in ad-hoc networks with 7 nodes, we noticed that each node can save power consumption by 21.5 dB in average, by using our proposed CDR compared to MRR.
김남수,이인환,김용근,Kim, Nam-Su,Lee, In-Hwan,Kim, Yong-Geun 한국조경학회 2011 韓國造景學會誌 Vol.39 No.4
도시하천은 산업혁명 이후 산업화 도시화가 진행되면서 무분별하게 복개 개발되어 지역주민들의 일상적 삶의 공간에서 멀어졌다. 최근 도시하천 복원사업이 진행되면서 접근성이 개선되고 쾌적한 환경으로 변모하여 사람들의 유입과 이용이 크게 늘면서 복원된 하천 주변 지역주민들의 커뮤니티 의식에 일정부분 영향을 미치고 있는 것으로 보인다. 본 연구는 도시하천의 복원이 지역주민들의 커뮤니티 의식에 어떠한 영향을 미치는지 규명하고자 수행되었으며, 이를 위해 최근 복원된 서울시 송파구 성내천을 방문한 방문객을 대상으로 설문조사를 시행하였다. 설문분석의 인자는 크게 성내천의 이용현황, 커뮤니티 의식(소속감, 연대의식, 정주의식), 복원사업 전후 비교(커뮤니티 의식변화, 지역효과 변화)등의 항목으로 구성되었다. 분석결과에 따르면 성내천 복원사업 후 일주일에 1~2회 이상 이용하는 방문객이 가장 많았다. 이들의 주된 방문목적은 '휴식 및 운동'이었고, '이웃이나 타인을 만나는 장소'로 이용하는 비율은 낮게 나타났으며, 성내천을 이용하는 주민들의 커뮤니티 의식은 대체로 높은 수준이었다. 방문빈도에 따라 세 집단으로 나누어 집단 간 커뮤니티 의식 차이를 분석한 결과, 집단 간 커뮤니티 의식 수준에 유의한 차이가 있었고, 특히 방문횟수가 많은 집단에서 커뮤니티 의식 수준이 높게 나타났다. 이 같은 결과로 볼 때 복원된 도시하천이 지역주민들의 적극적인 이용과 커뮤니티 활동을 활성화함으로써 지역에 대한 커뮤니티 의식을 고취하기 위해서는 주민들이 이용할 수 있는 적절한 시설과 프로그램 제공이 중요하다고 판단된다. During the industrialization and urbanization of the country, urban rivers have been covered over and developed without forethought and thus became estranged from spaces utilized by area residents in everyday life. Recently, an influx of people and uses have increased largely because accessibility improved through restoration projects which have transformed these river areas into pleasant environments. It thus appears that these projects have an impact on community consciousness for area residents who live near the restored rivers to some extent. The purpose of this study was to determine via questionnaire the effects and influences of urban river restoration on area residents targeting visitors to Seongnaecheon(stream), Songpa-gu, Seoul, which has been restored recently. Factors in the questionnaire analysis included such items as the use status of Seongnaecheon, community consciousness(feeling of belonging, solidarity, feeling settled), and a before and after comparison of the restoration(change of consciousness, regional effects), etc. According to the results of analysis, visitors who have utilized the stream more than 1~2 times per week after the restoration project accounted for the greatest portion. The main purposes of these visits were to 'rest' and 'exercise' while the ratio of using it as a 'meeting space with neighbors and strangers' was low. Community consciousness of area residents using Seongnaecheon was generally high. As a result of an analysis of consciousness differences between groups after dividing visitors into 3 groups according to the frequency of visits, there were significant differences in the consciousness level between groups with high community consciousness levels in visitors who visited frequently. In consideration of these results, the provision of programs along with proper facilities that can be used is deemed important for area residents so as to inspire community consciousness of the area by means of activating both community activities and the progressive use of the restored river.