• 한국항행학회논문지
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• 제22권6호
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• pp.585-590
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• 2018

GPS 위성의 궤도는 위성의 GPS 측정치와 정밀한 위성의 동역학을 함께 고려하여 정밀하게 추정 할 수 있다. 대부분의 위성 동역학 성분은 위성의 위치와 속도와 알려진 모델 식의 수식과 계수 값을 활용하여 정밀한 구현이 가능하다. 그러나 태양풍에 의한 힘은 모델을 선정하고, 모델의 계수를 추정해야 한다. 이 때, 모델에 따라 구현 성능이 달라질 수 있다. 따라서 본 논문은 CODE에서 생성한 정밀 궤도력을 활용해, 다양한 태양풍 모델의 계수를 추정하고 각 모델을 활용한 궤도 전파 모델의 정확도를 비교 분석했다. 결과적으로 ECOM 모델과reduced ECOM을 활용하는 경우, CODE 1일궤도와 cm level 오차를 가지는 궤도전파모델을 구현할 수 있음을 확인했다. 또한 SRP 모델을 구현하지 않는 경우 수십 m의 오차를 가짐을 확인할 수 있었다.

• 한국농공학회논문집
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• 제65권3호
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• pp.57-67
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• 2023

A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike general droughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study, Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flash drought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the drought severity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-do showed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show that FDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 하계종합학술발표회논문초록집
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• pp.330-330
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• 2004

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 공동학술발표회
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• pp.171-171
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• 2017

• Journal of Astronomy and Space Sciences
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• 제29권1호
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• pp.23-31
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• 2012

Thermal analysis and control design are prerequisite essential to design the satellite. In the space environment, it makes satellite survive from extreme hot and cold conditions. In recent years CubeSat mission is developed for many kinds of purpose. Triplet Ionospheric Observatory (TRIO)-CubeSat for Ion, Neutral, Electron, MAgnetic fields (CINEMA) is required to weigh less than 3 kg and operate on minimal 3 W power. In this paper we describe the thermal analysis and control design for TRIO-CINEMA mission. For this thermal analysis, we made a thermal model of the CubeSat with finite element method and NX6.0 TMG software is used to simulate this analysis model. Based on this result, passive thermal control method has been applied to thermal design of CINEMA. In order to get the better conduction between solar panel and chassis, we choose aluminum 6061-T6 for the material property of standoff. We can increase the average temperature of top and bottom solar panels from $-70^{\circ}C$ to $-40^{\circ}C $ and decrease the average temperature of the magnetometer from $+93^{\circ}C$ to $-4^{\circ}C$ using black paint on the surface of the chassis, inside of top & bottom solar panels, and magnetometer.

• 한국전자파학회논문지
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• 제17권1호
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• pp.24-38
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• 2006

본 논문에서는 인공위성의 원격 측정, 명령 및 제어(TT&C)용에 적합한 원뿔 나선 안테나의 설계 및 제작에 관해 검토하였다. $2.0{\sim}2.3\;GHz$ 대역에서 동작하며 반구면상에서 양호한 이득 특성과 축비 특성을 가지도록 나선의 형상을 상용 전자장 소프트웨어를 이용하여 최적 설계하였다. 원뿐 나선의 급전을 위한 동축선 무한 벌룬은 실험적인 방법으로 구현하였다. 설계된 나선의 형상을 정밀하게 제작하는 방법을 제시하였다. 설계한 안테나를 제작하여 측정한 결과 $2.0{\sim}2.3\;GHz$ 대역에서 -18 dB 이하의 반사 계수, 4 dB 이상의 이득, 이득이 0 dB 이상인 각도가 안테나 축으로부터 ${\pm}75^{\circ}$, 축비가 5 dB 이하인 각도가 안테나 축으로부터 ${\pm}90^{\circ}$, 15 dB 이상의 전후 방비 등 양호한 특성을 얻었다.

• 한국식생활문화학회지
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• 제9권2호
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• pp.159-170
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• 1994

Central commissary school foodservice operations' practices and their dietitians' job duties were assessed and compared with those of their counterpart of conventional school foodservice operations to find out strategies for early settlement and better management for commissary system. Survey qestionnaires consisted of general background, employees' work schedule and dietitians' job duties. 12 commissary schools(out of 22 existing in Korea) and 77 conventional schools from Kyungkido were participated in the survey. The results of this study can be summarized as follows: 1. Central commissary school foodservice was presently utilized at 5 schools from islands type, 11 schools from rural type, and 6 schools from urban type, consisting total of 22 commissary schools, and 52 satellite schools. 2. Dietitians were evenly employed with their experiences, 55.5% were those with less than 2 years of experience, 44.6% were those with more than 2 years of experience. 3. Commissary schools employed more full-time empolyees$(1.8{\pm}0.7)$ than conventional schools$(0.3{\pm}0.5)$, however as far as the production capacity was concerned, only the part-time employees played significant roles(p<.01). Regardless of the number of students, an absolute number of full-time employees were employed, and their duties were not carried out efficiently. The part-time employees of commissary schools performed more loaded work compared to their counterparts in conventional schools. 4. Out of the dietitians' foodservice duties, 'basic food service production$(3.9{\pm}0.7)$' were carried out adequately, whereas 'nutrition education and advertisement$(2.5{\pm}0.6)$' and 'administrative affairs and information related duties$(2.8{\pm}0.9)$' were not. In order to enhance their working capacity, systematic organizational reforms are imminent. 5. Survey results also showed that dietitians performed less duties at satellite school than at the central commissary. This indicates more systematic foodservice management practices are urgently needed.

• 대한원격탐사학회지
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• 제38권5_2호
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• pp.685-694
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• 2022

건물 정보는 다양한 도시 공간 분석에 활용되는 필수 정보 중 하나이기에 지속적인 모니터링이 필요하지만 현실적으로 어려움이 존재하고 있다. 이를 위해 광범위한 지역에 대해서도 지속적인 관찰이 가능한 위성영상으로부터 건물을 추출하기 위한 연구가 진행되고 있으며, 최근에는 딥러닝 기반의 시맨틱 세그멘테이션 기법들이 활용되고 있다. 본 연구에서는 SpaceNet의 건물 v2 무료 오픈 데이터를 이용하여 30 cm 급 Worldview-3 RGB 영상으로부터 건물을 자동으로 추출하기 위해, context-based ResU-Net의 일부 구조를 변경하여 학습을 진행하였다. 분류 정확도 평가 결과, f1-score가 2회차 SpaceNet 대회 수상작의 분류 정확도보다 높은 것으로 나타났다. 앞으로 지속적으로 Worldview-3 위성 영상을 확보할 수 있다면 본 연구의 성과를 활용하여 전세계 건물 자동 추출 모델을 제작하는 것도 가능할 것으로 판단된다.

• Asian-Australasian Journal of Animal Sciences
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• 제33권12호
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• pp.1922-1929
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• 2020

Objective: The present study aimed to survey seasonal changes in reproductive performance of local cows receiving artificial insemination (AI) in the Pursat province of Cambodia, a tropical country, to investigate if ambient conditions affect the reproductive performance of cows as to better understand the major problems regarding cattle production. Methods: The number of cows receiving AI, resultant number of calving, and calving rate were analyzed for those receiving the first AI from 2016 to 2017. The year was divided into three seasons: cool/dry (from November to February), hot/dry (from March to June), and wet (from July to October), based on the maximal temperature and rainfall in Pursat, to analyze the relationship between ambient conditions and the reproductive performance of cows. Body condition scores (BCS) and feeding schemes were also analyzed in these seasons. Results: The number of cows receiving AI was significantly higher in the cool/dry season than the wet season. The number of calving and calving rate were significantly higher in cows receiving AI in the cool/dry season compared with the hot/dry and wet seasons. The cows showed higher BCSs in the cool/dry season compared to the hot/dry and wet seasons probably due to the seasonal changes in the feeding schemes: these cows grazed on wild grasses in the cool/dry season but fed with a limited amount of grasses and straw in the hot/dry and wet seasons. Conclusion: The present study suggests that the low number of cows receiving AI, low number of calving, and low calving rate could be mainly due to poor body condition as a result of the poor feeding schemes during the hot/dry and wet seasons. The improvement of body condition by the refinement of feeding schemes may contribute to an increase in the reproductive performance in cows during the hot/dry and wet seasons in Cambodia.

• 한국항행학회논문지
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• 제22권5호
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• pp.384-390
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• 2018

본 논문에서는 KASS (korea augmentation satellite system) 의 가용성 성능 평가를 위한 MATLAB GUI (graphical user interface)기반의 소프트웨어에 대해 소개한다. 본 소프트웨어는 MV (minimum variance) estimator 와 Kriging 알고리즘을 이용해 한반도 지역의 지상 사용자 및 항공기 사용자에 대해 UDRE (user differential range error) 와 GIVE (grid ionospheric vertical error) 와 같은 무결성 정보를 생성한다. 또한 본 소프트웨어는 생성한 정보를 이용하여 사용자의 각 위치에 대해 정확도, 보호 수준, 가용성 지도를 제공한다. 특히 항공기 경로에 대해 경로에 따른 보호 수준 값을 계산하는 기능을 수행한다. 항공기 사용자에 대한 보호 수준 값 계산 결과는 EGNOS (european geostationary navigation overlay service) 의 시뮬레이션 툴인 SBASimulator#2의 결과와 비교하여 검증하였다. 그 결과 본 소프트웨어가 생성한 보호 수준의 값의 오차가 약 2% 정도로 정확하게 나온 것을 확인하였다.