• Journal of Ship and Ocean Technology
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• 제11권2호
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• pp.1-9
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• 2007

This paper describes the design and development of a hovering AUV constructed at Cheju National University and analyses the dynamic performance of the vehicle using simulation programs. The main purpose of this AUV is to carry out fundamental tests in its station keeping, attitude control, and desired position tracking. Its configuration is similar to the general ROV appearance for underwater works and its dimensions are 0.75m*0.5m*0.5m. It has 4 thrusters of 450 watts for longitudinal/lateral/vertical propulsion and is equipped with a pressure sensor for measuring water depth and a magnetic compass for measuring heading angle. The navigation of the vehicle is controlled by an on-board Pentium III-class computer, which runs with the help of the Windows XP operating system. These give us an appropriate environment for developing various algorithms needed for developing and advancing Hovering AUV.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2002년도 제18회 학술발표대회 논문초록집
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• pp.82-83
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• 2002

궤도상에 올려진 위성들은 인형의 궤도 운행을 하게 된다. 그러나 지구가 완전한 구형이 아니고 태양과 달의 인력이 작용하여 위성에 섭동이 발생하게 된다. 그리고 무중력 상태의 우주이므로 태양풍이나 미세 운석 그리고 위성체 내부의 가스 누출이나 내부의 토크 변화에 의해 위성 자세에 조금의 변동을 야기한다. 통신 위성의 경우 지상의 한 지점을 계속 향하고 있어야 하므로 정기적인 자세제어가 필요하다. 위성의 섭동에 의해 EWSK(East-West station keeping)나 NSSK(North-South station keeping)를 하기 위해 추력 모델은 단일 $\Delta$$\upsilon$기동이나 회전 세차 운동(spin precession maneuver)을 지원해야 한다. 위성은 주어진 임무를 수행하는데 필요한 $\Delta$$\upsilon$기동을 위해 적절한 성능의 추력기와 임무기간 동안 사용할 적절한 양의 추진제를 탑재하고 있다. 지상에서 필요한 임무를 수행하기 위해 위성에 지령을 하였을 때, 추력기가 정상작동을 하였는지 그리고 잔류 추진제가 어느 정도 인지를 정확히 알 수 있어야 한다.

• International Journal of Ocean System Engineering
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• 제3권4호
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• pp.218-224
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• 2013

This paper describes the design and control of a hovering AUV test-bed and analyzes the dynamic performance of the vehicle using simulation programs. The main purpose of this vehicle is to carry out fundamental tests of its station keeping, attitude control, and desired position tracking. Its configuration is similar to the general appearance of an ROV for underwater operations, and its dimensions are $0.75m{\times}0.5m{\times}0.5m$. It has four 450-W thrusters for longitudinal/lateral/vertical propulsion and is equipped with a pressure sensor for measuring the water depth and a magnetic compass for measuring its heading angle. The navigation of the vehicle is controlled by an onboard Pentium III-class computer, which runs with the help of the Windows XP operating system. This provides an appropriate environment for developing the various algorithms needed for developing and advancing a hovering AUV.

• Journal of Astronomy and Space Sciences
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• 제3권2호
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• pp.93-102
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• 1986

정지통신위성을 동서방향으로 궤도 조정을 하기 위해서는 평균경도와 궤도의 이심률에 관해서 동시에 조정하여야 한다. 궤도이심률의 효과는 궤도중심방향의 $e_{c}$ 과 $e_{s}$의 위상면상에서 표시되어야 한다. 평균경도와 궤도이심률에 대한 진화도 얻었다.

• Journal of Astronomy and Space Sciences
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• 제4권1호
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• pp.25-33
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• 1987

For a geostationary satellite north-south keeping maneuver must control the inclination elements. The effects on the orbit plane of maneuvers and natural perturbations may be represented by a plane plot of Wc versus, Ws, since these inclination elements represent the projection of the major axis and the inclination elements are obtained.

• 융복합기술연구소 논문집
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• 제2권1호
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• pp.1-6
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• 2012

The cold chain system in South-East Asia is requiring to maintain freshness of refrigerated or frozen food. In this study, Thermal storage system using Phase change material (PCM) was developed and evaluated its performance about temperature and cold keeping time. For various application of cold chain system, we developed portable cold box, cold roll container and freezing station. Keeping time on laboratory tests of portable cold box in case of refrigeration and freezing were 6 hours and 4 hours, respectively. Cold container was developed to 2.5 ton scale. Evaluation in Indonesia, it was showed to keep the setting temperature of $-10^{\circ}C$ over 40 hours at $30^{\circ}C$ of ambient air. Freezing station using PCM was kept over 24 hours under $-20^{\circ}C$.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.142-149
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• 1997

잘 알려진 최적제어 이론의 선형제차조절법을 정지궤도 위성의 위치보존 궤도조정 문제에 적용하였다. 정지궤도 위성의 운동에 가장 큰 영향을 미치는 섭동향을 선택하여 동서방향과 남북방향 궤도조정의 경우 각각 14일간 지구비대칭 중력장의 영향, 28일간 태양과 달의 영향을 예측한 결과로 궤도조정할 경계조건을 적절하게 설정하였다. 비선형방정식을 선형화하여 리카티 방정식(Riccati Equation)을 두 번 적분함으로써 최적궤도와 이에 상응하는 추진 가속도를 알아내었다. 선형제차조절법으로 구한 속도변화량과 기하학적으로 계산한 ${\Delta}V$(속도변화량)을 비교해 봄으로써 제어이론을 통한 궤도조정 방법이 실제상황에 거의 근사한 해를 제공할 수 있는가와 제어이론을 위치보존 궤도조정 문제에 적용한 방법이 경제적인 측면에서의 연료최적화와 이에 따른 정지궤도 위성의 수명연장에 기여할 수 있는가에 대한 해석을 시도하였다.

• 한국농촌건축학회논문집
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• 제14권3호
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• pp.109-119
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• 2012

This study aims to analyze architectural characteristics of railway station facilities which were built with development of railroads from Japanese Colonial Period to 1950's. To achieve this goals, 7 railway stations in Gyeongju area that are worth preserving were set up as research targets. For this study, I analyzed literature of the railway station and drawings which the KORAL Daegu Branch is keeping. Railway stations without a construction drawing investigated a direct visit. After analyzing the railway station facilities, the architectural properties such as plan, elevation and section have been identified. The results are as follows. First, Each modern railway station is usually consisted of waiting room and office, and ancillary spaces have been added. Over the years, however, the space was expanded horizontally. In that case, the structure and finish materials have been changed, like now. Second, Most of the roof shape is 'Matbae'(gable roof), especially Gyeongju station and Bulguksa Station are 'Woojingak roof. The roof structure is truss structure, especially as Pratt and Scissors type, but Gyeongju Station's structure is a reinforced concrete. Third, main doorway of waiting room is located in the center of the front gable. However, small stations like 'Ahwa' and 'Ipsil' station to ensure the passengers' waiting area are placed next to the office area.

• 한국약용작물학회지
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• 제18권2호
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• pp.98-104
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• 2010

Eleuthero(Eleutherococcus senticosus Maxim.) cortex is well known as a herb medicine for tonic. This study was performed to improve the quality of dried E. senticosus cortex. Investigation of quality factor and contents of efficient compounds under different steaming times and drying methods were performed to determine the proper processing and drying conditions of Eleuthero cortex harvested on March in annual stems. The proper steaming time for peeling bark to make high quality Eleuthero cortex took less than 20 mins. Eleutheroside B and E contents among drying methods were significantly different at 5% level DMRT. The $50^{\circ}C$ heat drying was the most advisable condition for drying, when drying and keeping contents of effective compounds.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1996년도 한국우주과학회보 제5권2호
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• pp.19-19
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• 1996

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