• Korean Journal of Remote Sensing
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• v.32 no.5
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• pp.435-452
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• 2016

Land Surface Temperature (LST) has been operationally retrieved from the Communication, Ocean, and Meteorological Satellite (COMS) data by the spilt-window method (CSW_v2.0) developed by Cho et al. (2015). Although the CSW_v2.0 retrieved the LST with a reasonable quality compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) LST data, it showed a relatively poor performance for the strong inversion and lapse rate conditions. To solve this problem, the LST retrieval algorithm (CSW_v2.0) was updated using the simulation results of radiative transfer model (MODTRAN 4.0) by considering the diurnal variations of air temperature. In general, the upgraded version, CSW_v3.0 showed a similar correlation coefficient between the prescribed LSTs and retrieved LSTs (0.99), the relatively smaller bias (from -0.03 K to-0.012 K) and the Root Mean Square Error (RMSE) (from 1.39 K to 1.138 K). Particularly, CSW_v3.0 improved the systematic problems of CSW_v2.0 that were encountered when temperature differences between LST and air temperature are very large and/or small (inversion layers and superadiabatic lapse rates), and when the brightness temperature differences and surface emissivity differences were large. The bias and RMSE of CSW_v2.0 were reduced by 10-30% in CSW_v3.0. The indirect validation results using the MODIS LST data showed that CSW_3.0 improved the retrieval accuracy of LST in terms of bias (from -0.629 K to -0.049 K) and RMSE (from 2.537 K to 2.502 K) compared to the CSW_v2.0.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.6
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• pp.111-121
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• 2019

Evapotranspiration (ET) of vegetation is one of the major components of the hydrologic cycle, and its accurate estimation is important for hydrologic water balance, irrigation management, crop yield simulation, and water resources planning and management. For agricultural crops, ET is often calculated in terms of a short or tall crop reference, such as well-watered, clipped grass (reference crop evapotranspiration, $ET_o$). The Penman-Monteith equation recommended by FAO (FAO 56-PM) has been accepted by researchers and practitioners, as the sole $ET_o$ method. However, its accuracy is contingent on high quality measurements of four meteorological variables, and its use has been limited by incomplete and/or inaccurate input data. Therefore, this study evaluated the applicability of Backpropagation Neural Network (BPNN) model for estimating $ET_o$ from less meteorological data than required by the FAO 56-PM. A total of six meteorological inputs, minimum temperature, average temperature, maximum temperature, relative humidity, wind speed and solar radiation, were divided into a series of input groups (a combination of one, two, three, four, five and six variables) and each combination of different meteorological dataset was evaluated for its level of accuracy in estimating $ET_o$. The overall findings of this study indicated that $ET_o$ could be reasonably estimated using less than all six meteorological data using BPNN. In addition, it was shown that the proper choice of neural network architecture could not only minimize the computational error, but also maximize the relationship between dependent and independent variables. The findings of this study would be of use in instances where data availability and/or accuracy are limited.

• Journal of Life Science
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• v.26 no.5
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• pp.620-631
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• 2016

Viroids are about 250-400 base pair of short single strand RNA fragments have been associated with economically important plant diseases. Due to the lack of protein expression capacity associated with replication, it is very difficult to diagnosis viroid diseases in serological methods. For detecting viroid at plants, molecular-based techniques such as agarose gel electrophoresis, polyacrylamide gel electrophoresis (PAGE), DNA-hybridization, blotting analysis and conventional RT-PCR are reliable. Real-time RT-PCR methods that grafted on RT-PCR methods with improved confirmation methods have been also utilized. However, they are still labor-intensive, time-consuming, and require personnel with expertise. Loop-mediated Isothermal Amplification (LAMP) method is a nucleic acid amplification method under the isothermal condition. The LAMP methodology has been reported to be simple, rapid, sensitive and field applicable in detecting a variety of pathogens. The results of LAMP method can be colorized by adding a visible material such as SYBR green I, Evagreen, Calcein, Berberine and Hydroxy naphthol blue (HNB) with simple equipment or naked eyes. The combination of LAMP method and nucleic pathogens, viroids, can be used to realize simple diagnosis platform for the genetic point-of care testing system. The aim at this review is to summary viroid-caused diseases and the simple visible approach for diagnosing viroids using Loop-mediated Isothermal Amplification (LAMP) method.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.75-85
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• 2017

A method to estimate hourly temperature profiles on calm and clear nights was developed based on temporal changes of inversion height and strength. A meteorological temperature profiler (Model MTP5H, Kipp and Zonen) was installed on the rooftop of the Highland Agriculture Research Institute, located in Daegwallyeong-myeon, Pyeongchang-gun, Gangwon-do. The hourly vertical distribution of air temperature was measured up to 600 m at intervals of 50 m from May 2007 to March 2008. Temperature and relative humidity data loggers (HOBO U23 Pro v2, Onset Computer Corporation, USA) were installed in the Jungdae-ri Valley, located between Gurye-gun, Jeollanam-do and Gwangyang-si, Jeollanam-do. These loggers were used to archive measurements of weather data 1.5 m above the surface from October 3, 2014, to November 23, 2015. The inversion strength was determined using the difference between the temperature at the inversion height, which is the highest temperature in the profile, and the temperature at 100 m from the surface. Empirical equations for the changes of inversion height and strength were derived to express the development of temperature inversion on calm and clear nights. To estimate air temperature near the ground on a slope exposed to crops, the equation's parameters were modified using temperature distribution of the mountain slope obtained from the data loggers. Estimated hourly temperatures using the method were compared with observed temperatures at 19 weather sites located within three watersheds in the southern Jiri-mountain in 2015. The mean error (ME) and root mean square error (RMSE) of the hourly temperatures were $-0.69^{\circ}C$ and $1.61^{\circ}C$, respectively. Hourly temperatures were often underestimated from 2000 to 0100 LST the next day. When temperatures were estimated at 0600 LST using the existing model, ME and RMSE were $-0.86^{\circ}C$ and $1.72^{\circ}C$, respectively. The method proposed in this study resulted in a smaller error, e.g., ME of $-0.12^{\circ}C$ and RMSE of $1.34^{\circ}C$. The method could be improved further taking into account various weather conditions, which could reduce the estimation error.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1027-1031
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• 2008

본 연구는 한반도 영역을 대상으로 2001년 7, 8월과 2002년 6월로 홍수기를 대상으로 RDAPS 모형, AWS, 상층기상관측(upper-air sounding)의 자료를 이용하였다. 또한 수치예보자료를 범주적 예측확률로 변환하고 인공신경망기법(ANN)을 이용하여 강수발생확률의 예측정확성을 향상시키는데 있다. 신경망의 예측인자로 사용된 대기변수는 500/ 750/ 1000hpa에서의 지위고도, 500-1000hpa에서의 층후(thickness), 500hpa에서의 X와 Y의 바람성분, 750hpa에서의 X와 Y의 바람성분, 표면풍속, 500/ 750hpa/ 표면에서의 온도, 평균해면기압, 3시간 누적 강수, AWS관측소에서 관측된 RDAPS모형 실행전의 6시간과 12시간동안의 누적강수, 가강수량, 상대습도이며, 예측변수로는 강수발생확률로 선택하였다. 강우는 다양한 대기변수들의 비선형 조합으로 발생되기 때문에 예측인자와 예측변수 사이의 복잡한 비선형성을 고려하는데 유용한 인공신경망을 사용하였다. 신경망의 구조는 전방향 다층퍼셉트론으로 구성하였으며 역전파알고리즘을 학습방법으로 사용하였다. 강수예측성과의 질을 평가하기 위해서 $2{\times}2$ 분할표를 이용하여 Hit rate, Threat score, Probability of detection, Kuipers Skill Score를 사용하였으며, 신경망 학습후의 강수발생확률은 학습전의 강수발생확률에 비하여 한반도영역에서 평균적으로 Kuipers Skill Score가 0.2231에서 0.4293로 92.39% 상승하였다.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.18-20
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• 2005

일반적으로 저압계통의 고장전류를 차단하기 위해 설치된 차단기의 차단원리는 주로 역전압발생법올 이용하고 있다. 역전압발생법은 효과적으로 저압계통의 고장전류를 차단할 수 있으나, 제한된 한류성능과 긴 아킹 시간은 차단기는 물론 주변 전력기기에 전기적/열적/기계적 스트레스를 주게 된다. 국내외 업체는 고장전류를 보다 빠르고 효과적으로 제한 및 차단을 할 수 있는 한류형 차단기를 제안하고 있는 실정이다. 저압계통의 경우, 정온도계수 (Positive Temperature Coefficient, PTC) 특성을 가지는 한류소자를 기존 차단기에 직렬 혹은 병렬로 연결하여 저압계통의 고장전류를 매우 빠르고 효과적으로 제한 및 차단하는 추세에 있으며, 또한 PTC 한류소자를 이용함으로써 저압계통의 차단보호협조를 효과적으로 구현하고자 하고 있다. PTC 한류소자는 소자는 열팽창이 큰 비전도성 성분과 열팽창이 작은 전도성 성분이 혼합되어 구성되며, 소자의 온도가 증가함에 따라 비전도성 성분이 상대적으로 큰 부피 팽창을 하여 저항이 증가하게 된다. 이러한 PTC 소자를 전력계통에 적용함으로써 고장전류에 따른 줄열에 의한 저항증가로 고장전류를 제한하게 된다. 본 연구에서는 일반적으로 배터리 보호용으로 사용되는 폴리에틸렌 수지 및 카본블랙으로 구성된 폴리머 PTC 한류소자를 이용하여, 기존의 저전력 배터리 보호 폴리머 PTC 소자로부터, 저압계통의 단락사고시 발생하는 단락전류를 효과적으로 제한할 수 있는 대전력 폴리머 PTC 소자를 개발하였다.

• Journal of the Korean earth science society
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• v.36 no.4
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• pp.315-329
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• 2015

We investigated the characteristics of meteorological conditions related to the strong downslope wind over the leeward side of the Taebaek Mountains during the period 2005~2010. The days showing the strong wind exceeding $14ms^{-1}$ in Gangwon province were selected as study cases. A total of 15 days of strong wind were observed at Sokcho, Gangneung, Donghae, and Taebaek located over the Yeongdong region. Seven cases related to tropical cyclone (3 cases) and heavy snowfall (2 cases) and heavy rainfall (2 cases) over the Yeongdong region were excluded. To investigate the characteristics of the remaining 8 cases, we used synoptic weather chart, Sokcho radiosonde, Gangneung wind profiler and numerical model. The cases showed no precipitation (or ${\leq}1mm\;day^{-1}$). From the surface and upper level weather chart, we found the pressure distribution of southern high and northern low pattern over the Korean peninsula and warm ridge over the Yeongdong region. Inversion layer (or stable layer) and warm ridge with strong wind were located in about 1~3 km (925~700 hPa) over mountains. The Regional Data Assimilation and Prediction System (RDAPS) indicated that warm core and temperature ridge with horizontal temperature gradient were $0.10{\sim}0.23^{\circ}C\;km^{-1}$ which were located on 850 hPa pressure level above mountaintop. These results were summarized as a forecasting guidance of downslope windstorm in the Yeongdong region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.23-26
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• 2009

General characteristics of hydrogen and the ratio change of the two forms of hydrogen(ortho-hydrogen and para-hydrogen) as a function of the temperature were introduced. The unique characteristics of hydrogen, such as a wide range of flammability limits, low minimum ignition energy, low maximum inverse temperature, and hydrogen embrittlement were introduced. The process of producing the liquid hydrogen using pre-cooling and expansion engine and ortho-para conversion using the catalyst were introduced. Finally, the characteristics and the considerations as a propellant for liquid rocket were reviewed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.498-504
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• 1984

가열된 곡면에 의한 자연대류에서는 유동의 박리현상이 존재하지 않음이 알려져 있다. 이에 반해 날카로운 모서리를 갖는 가열된 정방형 수평실린더에 의한 자연대류에서는 그라소프 수가 4.66*$10^{4}$ 전후로 부착 혹은 박리현상이 윗쪽 양 모서리 부근에서 일어남을 광학간섭 계(Mach Zehnder Inter-ferometer)를 이용하여 온도장을 가시화하고 이를 이용하여 좌우 대칭 선상에서의 속도분포를 간단한 대수적인 방법으로 구하여 수평정방형 윗쪽 수평면 위에 유동의 박리현상을 시사하는 "쌍동이 소용돌이"의 존재를 입증하였고, 이에 의해 온도역전현상과 평균 열전달량의 급격한 증가를 설명 할 수 있다.설명 할 수 있다.

• 전기의세계
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• v.26 no.4
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• pp.8-11
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• 1977

공업기술의 발전에 따라 전동기의 용도도 다양화되고 기계의 기진 정상 정전에서 역전으로 바꾸는것을 기계적 방법보다 전동기의 기동제동 plugging운전방법으로 이송할 때 기계의 고효율화, 기구의 간소화가 된다. 그러나 이러한 다송운전이 빈번할 때 일반전동기로서는 신뢰도가 문제가 되므로, 이 용도에 적합한 특성을 가지는 운동기를 개정함으로서 신뢰도가 높도록 해야 한다. 이런 종류의 용도로 사용되는 용형전동기로서는 특성상 기동 Torque, 가속 Torque가 크고 단시간에 기동하며 Plugging에 적합하고 Dynamic Brake에도 지장이 없어야 하며, 온도상승의 점에서는 기동중에 1차동손이 적고 2차고저항인것이 요구된다. 또 구조상에서는 Inertia가 작으며 급속한 기동이 제일 먼저 요구된다. 만약 기동중에 발열하는 부분의 열용량이 크며 부하 Inertia도 커서 기동시간이 수10초를 걸린다면 국부적으로 대단히 높은 온도상승을 하게 되고, 가혹한 Plugging운전을 하는 경우는 열적 및 기계적으로 고도의 신뢰성이 요구된다. 이에 적합한 Cycle Starting Motor를 시작하여 본 결과를 경험을 토대로 다목적으로 연구검토하여 여기에 소개하고자 한다.