• 대한전자공학회논문지SD
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• 제46권9호
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• pp.1-6
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• 2009

본 논문에서는 음극 및 양극으로 동시에 열 방출을 수행할 수 있는 이중 방열 구조의 Gunn 다이오드를 제작하고 음극 방열 구조를 갖는 Gunn 다이오드와 그 특성 차이를 비교하였다. 제작된 다이오드의 DC 특성 측정 결과, 단일 방열 구조의 경우에는 3 V의 문턱전압과 744 mA의 최대 전류 및 4.8 V의 항복 전압 특성을 나타내었고, 이중 방열 구조 다이오드는 2.5 V의 문턱전압, 778 mA의 최대 전류 및 5 V 이상의 항복전압 특성을 나타내었다.

• 대한지리학회지
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• 제42권3호
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• pp.332-343
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• 2007

본 연구에서는 우리나라 열파의 지역별 분포를 파악하고 그 원인을 분석하고자 하였다. 이를 위해 $1973\sim2005$년 $5\sim9$월까지 60개 기상관측지점의 일최고기온과 수증기압, 상층의 바람 자료 등을 사용하여 일최고기온 상위 5% 이상인 날이 3일 이상 지속되는 현상을 열파로 정의하고, 열파일수의 분포와 그 원인을 분석하였다. 우리나라 열파일수는 충청 내륙 및 충청 서해안, 전라 내륙, 경상 내륙, 제주도 남부 지역에서 160일 이상으로 많고 동해안 중부와 제주도 북부 지역에서 110일 이하로 적다. 충청 내륙 및 충청 서해안과 전라 내륙 지역은 열파 발생 시 남서기류의 영향이 크므로 열파가 장기간 지속된다. 경상 내륙 지역은 남서기류에 소백산맥의 지형 효과가 결합되어 고온 건조해진 공기가 분지 지형 때문에 정체되고 지속적인 남서기류의 유입으로 인해 기온 편차가 큰 열파가 장기간 지속된다. 동해안 중부 지역은 태백산맥이 남서기류를 차단하기 때문에 열파일수가 적으나 일단 열파가 발생하면 푄 효과가 결합되어 기온 편차가 크다.

• 대한기계학회논문집B
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• 제20권7호
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• pp.2315-2325
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• 1996

A compression wave is attenuated or distorted as it propagates in a tube. The present study investigated the propagation characteristics of the compression waves which are generated by a train in a high-speed railway tunnel. A Total Variation Diminishing (TVD) difference scheme was applied to one-dimensional, unsteady viscous compressible flow. The numerical calculation involved the effects of wall friction, heat transfer and energy loss due to the friction heat in the boundary layer behind the propagating compression wave, and compared with the measurement results of a shock tube and a real tunnel. The present results show that attenuation of the compression wave in turbulent boundary layer is stronger than in laminar boundary layer, but nonlinear effect of the compression wave is greater in the laminar boundary layer. The energy loss due to the frictional heat had not influence on attenuation and distortion of the propagating compression waves.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.37-49
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• 2004

Four different data reduction methods for the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two heat and mass transfer models and two fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the reduced heat transfer coefficients revealed that the single potential heat and mass transfer model yielded the humidity-independent heat transfer coefficients. Two fin efficiency models-enthalpy model and humidity model-yielded approximately the same fin efficiencies, and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.109-114
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• 2000

본 연구에서는 전파흡수체용 ferrite-Rubber Composite에서 Ferrite의 열처리 온도와 Composite의 전파흡수특성과의 상관관계에 관하여 알아보았다. 이때 Ferrite는 스피넬 구조의 형성과 결정입의 비교적 큰 성장을 위하여 1100, 1200, 1300 $^{\circ}C$에서 각각 2시간 열처리 처리하였다. 열처리 온도를 달리하여 제조한 Ferrite-Rubber Composite는 A가 Mn인 경우에는 열처리 온도가 높을수록 반사감쇠량이 작아지는 경향을 보였다. 그러나 A가 Cu와 Mg인 경우 열처리 은도가 높을수록 페라이트의 반사감쇠량이 커지는 경향을 보였다. 이로부터 전파흡수체용 Ferrite는 화학조성에 따라서 적정 열처리 온도가 존재함을 알 수 있었다.

• 한국태양에너지학회 논문집
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• 제34권6호
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• pp.75-83
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• 2014

Heat loss through windows and doors occupies 20 to 45% of the total heat loss in building. It accounts for a large proportion of the total heat loss in building. In order to suppress the amount of heat flow through the windows and doors were considered actions such as reinforcement of insulation performance of window, adoption of low-e glass, and installation of solar heat shading device. The Purpose of this study is to compare solar heat shading performances of 3 types of internal blinds in the summer. In order to verify the solar heat shading performances of the blinds, a roll blind, blind A(Venetian blind) and blind B(Daylight guiding venetian blind)were installed in the four rooms with the same environmental conditions. As a result of the experiment, the blind B, blind A, roll blind showed an excellent performance in that order. Its because the blind B is made of aluminum materials coated with special paints on surface. It doesn't converted to long wave by short wave light. and it is reflected to short wave to outside.

• 대기
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• 제29권5호
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• pp.627-637
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• 2019

Severe and long-lasting heat waves over Korea and many regions in the Northern Hemisphere (NH) during the 2016 summer, have been attributed to global warming and atmospheric teleconnection coupled with tropical convective activities. Yet, what controls subseasonsal time scale of heat wave has not been well addressed. Here we show a critical role of two dominant boreal summer intraseasonal oscillation (BSISO) modes, denominated as BSISO1 and BSISO2, on modulating temporal structure of heat waves in the midst of similar climate background. The 2016 summer was characterized by La Nina development following decay of strong 2015/2016 El Nino. The NH circumglobal teleconnection pattern (CGT) and associated high temperature anomalies and heat waves were largely driven by convective activity over northwest India and Pakistan during summer associated with La Nina development. However, the heat wave event in Korea from late July to late August was accompanied by the phase 7~8 of 30~60-day BSISO1 characterized by convective activity over the South China Sea and Western North Pacific and anticyclonic circulation (AC) anomaly over East Asia. Although the 2010 summer had very similar climate anomalies as the 2016 summer with La Nina development and CGT, short-lasting but frequent heat waves were occurred during August associated with the phase 1~2 of 10~30-day BSISO2 characterized by convective activity over the Philippine and South China Sea and AC anomaly over East Asia. This study has an implication on importance of BSISO for better understanding mechanism and temporal structure of heat waves in Korea.

• 한국환경과학회지
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• 제29권7호
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• pp.773-784
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• 2020

In order to protect the lives and property of citizens, the central and local governments are responding by enacting municipal ordinances and regulations as the frequency of extreme weather conditions due to climate change increases and intensity increases gradually. Accordingly, the basic contents and strategies of domestic and foreign policies to cope with cold and heat waves were reviewed, referring to measures suitable for application to the Daegu metropolitan area. In addition, it is intended to provide a policy alternative to Daegu metropolitan area to minimize damage from extreme weather by identifying the current status, characteristics, and future prospects of extreme weather in Daegu metropolitan area. Since the damage caused by the cold wave in Daegu area is not as great as that of other regions, it is urgent to come up with cold wave measures for the health and transportation sectors, and to come up with measures against the heat wave as the damage caused by the heat wave is the most serious in the country. Also we will identify spatial characteristics so that the districts and counties with high vulnerability to extreme weather can be identified and implemented first, and present civic life-oriented facilities and civic action guidelines to overcome cold and heat waves.

• 설비공학논문집
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• 제11권4호
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• pp.484-491
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• 1999

Air side heat transfer and pressure drop for ø9.52 fin-tube heat exchanger with various types of slit and louver fins were measured, and compared with wave-slit fin. Longitudinal and transverse tube spacings of the heat exchangers are 21.65mm and 25mm respectively. Actual heat exchanger was tested using water, and the tests were performed for 2 row heat exchangers with 3 different fin spacings, 1.3, 1.5 and 1.7mm. The overall performance of the enhanced fins was evaluated by comparing heat transfer coefficient with respect to fan power.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권2호
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• pp.29-38
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• 2000

Air side heat transfer and pressure drop for f 9.52 fin-tube heat exchanger with various types of slit and louver fins were measured, and compared with wave-slit fin. Longitudinal and transverse tube spacings of the heat exchangers are 21.65 mm and 25mm respectively. Actual heat exchanger was tested using water, and the tests were performed for 2 row heat exchangers with 3 different fin spacings, 1.3, 1.5 and 1.7 mm. The overall performance of the enhanced fins was evaluated by comparing heat transfer coefficient with respect to fan power