• 천문학회지
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• 제18권1호
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• pp.15-31
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• 1985

Making use of the arbitrary shock theory developed by Ulmschneider (1967, 1971) and Ulmschneider and Kalkofen (1978), we have calculated the dissipation rates of upward-travelling slow-mode acoustic shock waves in umbral chromospheres for two umbral chromosphere models, a plateau model by Avrett (1981) and a gradient model by Yun and Beebe (1984). The computed shock dissipation rates are compared with the radiative cooling rate given by Avrett (1981). The results show that the slow-mode acoustic shock waves with a period of about 20 second can heat the low umbral chromospheres travelling with a mechanical energy flux of $2.6{\times}10^6\;erg/cm^2s$ at a height of $300{\sim}400km$ above the temperature minimum region.

• Journal of Advanced Marine Engineering and Technology
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• 제41권3호
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• pp.176-181
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• 2017

본 연구는 저온환경에서의 평판형 열교환기에 대해 제빙을 억제할 수 있는 방법을 살펴보았으며, 그 방법으로 초음파의 발생에 따른 제빙특성을 관찰하였다. 본 실험에서 최적의 조건을 찾아내기 위해 에틸렌글리콜을 브라인으로 사용하고, 온도는 $-8{\sim}-16^{\circ}C$로 순환시켰으며, 제빙에 사용된 물은 1~3mm 두께로 공급하여 데이터를 기록하였다. 또한 초음파의 발생정도에 따른 변화를 확인하기 위해 출력을 조절하여 실험을 진행하였다. 그 결과 제빙억제 효과는 브라인 온도, 제빙두께, 초음파 주파수의 영향을 받는 것을 알 수 있었다.

• 한국해양학회지:바다
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• 제3권1호
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• pp.9-15
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• 1998

기상청에서는 1996년 7월부터 1997년 2월까지 목포앞바다의 칠발도 인접 해역에 1시간 간격으로 해양기상을 관측할 수 있는 부이를 설치하고 자료를 얻었다. 이 자료로부터 이 해역의 1일 평균 해양-대기 열교환량을 산출하고, 해양기상 상태의 특성을 조사하였다. 현열속의 경우, 7월에 최소(평균 -5.5 $Wm^{-2}$)이고, 1월에 최대(평균 12.6 $Wm^{-2}$)를 나타내고 있는데 이는 여름철에 대기가 해양으로 열을 공급하고 겨울철에는 반대로 해양에서 대기로 열을 공급하지만 그 크기는 여름철이 겨울철에 비해 작다는 것을 의미한다. 잠열속의 경우 7월에 최소(평균 -4.6 $Wm^{-2}$)를 보이고, 최대값은 11월에 월 평균 86.5 $Wm^{-2}$이고 10월에 일평균 최대값이 250$Wm^{-2}$까지 나타났다. 잠열 속은 대기가 건조해지고 바람이 강해지는 가을철에 최대가 나타나서 겨울철까지 지속된다. 파랑분석에 의하면 바람이 강한 겨울철이 여름철에 비해 높은 파의 출현율이 많았다 파주기는 4~6초의 출현율이 가장 많았고, 파향은 계절풍의 영향으로 겨울에는 북 또는 북동방향에서 유입되는 파가 우세하고, 여름에는 남, 남서 또는 서쪽에서 유입되는 파가 비교적 자주 출현하였다.

• 한국가구학회지
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• 제22권1호
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• pp.72-81
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• 2011

These days, beds have been developed not as furniture to sleep in but Healthcare Furniture. The function of heating, non-electronic-waves and far-infrared rays have been added. Also, eco-friendly materials such as stone, mud, rubber and wood are combined to them together with the radiation-heating method using heat conduction through electronic coil and hot water circulation. Modern people suffer from stress and fatigue. The hot issue is "health." Focused on the health, the development of design for beds considering the influence electronic waves, anions, deep sleep and the density of toxic materials have on human bodies has become urgent. In this study, the trend, specification and efficiency of the functional health-related electronic coil technology are analyzed. Through the analysis, the environmental standards are set. According to them, technology, eco-friendly materials and additional functions for the development of the design are considered. Also, the government is promoting the IEC international standardization for the Korean traditional floor heating style beds. In preparation for that, we adopted new HPT method technology. It enables non-electronic-waves, low electricity and stable temperature maintenance control for the warm top and the cool bottom. Also, the head boards and the frames of the beds can be separated. Through this separation, the beds can be easily moved or installed. Eco-friendly materials such as Hinoki cypress wood and red clay and the existing tables function are combined to the head boards so they can be used as drawers and display shelves. If they are used as separate items, they can be used as covers. This is how we suggest the design for the heating beds.

• 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.

• 한국가시화정보학회지
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• 제22권1호
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• pp.6-17
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• 2024

This study examined the natural convection heat flow characteristics of the melting process of PCM (palm oil) inside a liquid flexitank(bag) for a cargo container. A film heating element was installed on the bottom of the container, and numerical analysis was performed under heat flux conditions of 1,000 to 4,000 W/m². As a result, the melt interface of the PCM rises to a nearly horizontal state over time. In the initial stage, conduction heat transfer dominates, but gradually waves at the cell flow and melt interfaces are formed due to natural convection heat transfer. As melting progresses, the Ra number increases parabolically, and the Nu number increases linearly and has a constant value. The Nu number rises slowly under low heat flux conditions, whereas under high heat flux conditions, the Nu number rises rapidly. As the heat flux increases, the internal temperature oscillation of the liquid phase after melting increases. However, under high heat flux conditions, excess heat exceeding the latent heat is generated, and the temperature of the molten liquid is raised, so the increase in melting rate decreases. Therefore, the appropriate heating element specification applied to a 20-ton palm oil container is 2,000 W/m².

• 한국습지학회지
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• 제21권4호
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• pp.344-353
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• 2019

폭염은 전 세계에서 나타나고 있는 현상으로 열 노출과 관련된 위험을 악화시키고, 치명적인 인명피해를 초래한다. 본 연구에서는 폭염의 한 가지 형태 중 하나인 열대야를 대상으로 한국의 열대야 추세가 어떻게 변화하고 있는 지를 살펴보았다. 1973년부터 2018년까지 한국 기상청 ASOS 60개 지점의 일 최저 기온을 이용하여 여섯 개의 열대야 특성의 시간적인 변화를 분석하였다. 이러한 분석으로부터 열대야 관심지역은 인천, 강릉, 청주, 전주, 광주, 장흥, 여수, 거제, 구미, 영덕 등 10개 지역, 열대야 우심지역은 홍천, 양평, 수원, 원주, 보령, 대전, 부안, 정읍, 목포, 거창, 밀양, 포항, 제주, 서귀포 등 14개 지역이 식별되었다. 제안된 열대야 우심지역에는 특별한 열대야 대책이 수립될 필요가 있을 것이다.

• 대기
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• 제29권2호
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• pp.131-147
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• 2019

On the urban scale, Micro-climate analysis models for urban scale have been developed to investigate the atmospheric characteristics in urban surface in detail and to predict the micro-climate change due to the changes in urban structure. BioCAS (Biometeorological Climate Impact Assessment System) is a system that combines such analysis models and has been implemented internally in the Korea Meteorological Administration. One of role in this system is the analysis of the health impact by heat waves in urban area. In this study, the vegetation cooling models A and B were developed and linked with BioCAS and evaluated by the temperature drop at the vegetation areas during ten selected heat-wave days. Smaller prediction errors were found as a result of applying the vegetation cooling models to the heat-wave days. In addition, it was found that the effects of the vegetation cooling models produced different results according to the distribution of vegetation area in land cover near each observation site - the improvement of the model performance on temperature analysis was different according to land use at each location. The model A was better fitted where the surrounding vegetation ratio was 50% or more, whereas the model B was better where the vegetation ratio was less than 50% (higher building and impervious areas). Through this study, it should be possible to select an appropriate vegetation cooling model according to its fraction coverage so that the temperature analysis around built-up areas would be improved.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1069-1074
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• 2004

This study investigated the effect of pressure variations on augmentation of heat transfer when the ultrasonic waves were applied. The augmentation ratio of heat transfer was experimentally investigated and was compared with the profiles of pressure distributions calculated applying a coupled finite element-boundary element method (coupled FE-BEM). As the ultrasonic intensities increase from 70W to 340W, the velocity of the liquid paraffin is found to increase as well as kinetic energy, This physical behavior known as quasi-Eckart streaming results from acoustic pressure variations in the liquid. Especially, the higher acoustic pressure distribution near two ultrasonic transducers develops more intensive flow (quasi-Eckart streaming), destroying the flow instability. Also, the profile of acoustic pressure variation is consistent with that of augmentation of heat transfer. This mechanism is believed to increase the ratio of hear transfer coefficient.

• 농업과학연구
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• 제45권3호
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• pp.493-498
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• 2018

There has been widespread warming and a general increase in summer temperatures over the Korean peninsula ($0.5^{\circ}C$/10 years from 2001 to 2010). South Korea is transforming into a subtropical region, and the productivity of livestock is affected by the climatic changes. In this study, we investigated whether the summer heat waves affect the developmental competency of Korean native cattle (Hanwoo), a taurine type of cattle with a small portion of indicine varieties. We collected oocytes during the summer (heat stress, HS) and autumn (non-HS condition) and examined the developmental competencies including in vitro maturation and preimplantation embryo development. No significant differences were observed between the HS and non-HS oocytes in nuclear maturation (extrusion of the polar body); however, the cleavage and blastocyst rates were significantly lower in the HS group than those in the non-HS group. The lower developmental competence of the HS oocytes compared to the non-HS is, in part, due to insufficient cytoplasmic maturation because of a higher production of Reactive oxygen species (ROS) levels as well as peri/cortical distributed mitochondria in the HS oocytes after in vitro maturation. Next, we examined the ROS and mitochondria distribution and found a significant increase in the levels of ROS in the HS oocytes and a polarized distribution (pericortical cytoplasm) of mitochondria in the HS oocytes. In summary, impaired cytoplasmic maturation of oocytes from exposure to HS affects the preimplantation embryo development by dysfunction of mitochondria. To improve reproductive performance, embryo transfer using cryopreserved embryos/oocytes is recommended in the hot summer season of South Korea.