• 한국항공운항학회지
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• 제25권4호
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• pp.124-129
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• 2017

Clouds are an important factor in aircraft flight. In particular, a significant impact on small aircraft flying at low altitude. Therefore, we have verified and characterized the low level cloud prediction data of the Unified Model(UM) - based Local Data Assimilation and Prediction System(LDAPS) operated by KMA in order to develop cloud forecasting service and contents important for safety of low-altitude aircraft flight. As a result of the low level cloud test for seven airports in Korea, a high correlation coefficient of 0.4 ~ 0.7 was obtained for 0-36 leading time. Also, we found that the prediction performance does not decrease as the lead time increases. Based on the results of this study, it is expected that model-based forecasting data for low-altitude aviation meteorology services can be produced.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2000년도 제15회 학술강연회논문초록집
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• pp.10-10
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• 2000

For low Earth orbit, the atmosphere causes orbit altitude to decrease, If this decrease is not corrected by the satellite propulsive unit, the orbit decoys continuously unit reaches the dense atmosphere and satellite life ends. If active orbit maintenance is mode by satellite propulsive unit then fuel consumption is necessary, which must be considered in the satellite design. Especially interesting is the method for evaluating the fuel consumption role for maintenance of elliptical orbit developed in this paper.(omitted)

• 항공우주기술
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• 제5권2호
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• pp.205-212
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• 2006

고도 800km 이내의 저궤도 위성에 가장 큰 영향을 주는 요소는 지구 대기 항력이다. 지구 저궤도의 대기 밀도는 해수면의 대기 밀도에 비하여 매우 낮지만 항력에 의한 영향이 매 주기 마다 누적되면서 근지점에서 속도가 점진적으로 줄어든다. 근지점에서의 속도 감소는 곧바로 원지점의 고도 감소를 가져오게 되고 이심률이 작아지면서 최종적으로 원궤도로 바뀌게 된다. 본 논문에서는 이러한 대기 항력 및 수명 계산 방법에 대하여 기술하였다. 또한 항력의 크기를 결정하는 대기 밀도에 관해서 알아보고 KSLV-I에 사용될 킥모터와 위성의 수명을 Satellite Tool Kit 프로그램으로 계산하였다.

• The Korean Journal of Ecology
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• 제15권2호
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• pp.181-189
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• 1992

Dictyostelid cellular slime molds were quantitatibly isolated from the soils of mt.halla (above 900m in altitude), korea, according to the 'clonal isolation technique(cavender and raper, 1965a)'. Total fifteen species were found, including 1 new and 6 undescribed species.these are dictyostelium mucorodes, dictostelium minutem,polysphondylium pallidum fasciculatum, polysphondylium violaceum, dictyostelium flavidum,dictyostelium fasciculatum, polysphondylium violaceum, dictyostelium flavidum sp. n.(HL-1),dictyostelium aureo-stipes var. aureo-stipes, dictyostelium capitatum, dictyostelium giganteum,dictyostelium polycephalum,dictyostelium brefeldianum,dictyostelium macrocephalum, and dictyostelium sphaerocephalum, dictyostelium sp. (HL-2), dictyostelium sp. (CJ-9). D. mucoroides was the dominant species, and D. minutam,p.pallidum, d. fasciculatum, and p. violaceum were relatively common. d. polycephalum, d. brefeldianum, d. macrocephalum, dictyostelium sp. (HL-3), and d. sphaerocephalum were very rare. Species diversity appeared to be the highest in the deciduous broad-leaved forest from the soils of which 14 species were isolated. eight species were, including five undescribed species, isolated only from this forest soils. Number of isolates severely decrease at the forests above 1,500m in altitude.

• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.150-155
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• 2017

Proper cooling of PEM fuel cell stack is essential for the high-performance operation of fuel cell system. Insufficient cooling of the stack can cause significant damage to components due to overheating and also can decrease cell performance by dehydration of the polymer electrolyte. In the present study, we performed a computational analysis to assess the condition of the cooling system to secure the proper temperature in fuel cell stack system for high altitude long endurance (HALE) unmanned aerial vehicle (UAV).

• 한국환경과학회지
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• 제21권6호
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• pp.749-755
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• 2012

The effect of elevation and meteorological elements is analyzed in Jeju Island for analysis of evapotranspiration with two different height observation station during 3 years data. The slope of temperature gradient recorded $1.30^{\circ}C$/100 m from the analysis of temperature data. There is much difference evapotranspiration between low elevation and high elevation station because of decrease solar radiation and wind speed with height increase. The evapotranspiration is observed by mini lysimeter at Hankukgonghang. The result of observation is presented 34.2% of global solar radiation changed into evapotranspiration during 4 clear days.

• KIEAE Journal
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• 제14권5호
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• pp.67-73
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• 2014

This study aims at examining kinetic efficient shading systems and their implementation methods. These days, the importance of the shading devices are getting more significant due to the energy problem. Cordially, suitable shade designs are required as an important element for the exterior envelope of the building. This study employs the optimal shading design as an efficient shading method with the kinetic system that can be converted actively by the altitude of the sun. The proposed kinetic shading system works not only as a lightshelf in case the altitude of the sun is high but also as a vertical louver when the sun is getting lower in order to block the direct sunlight. This study has analyzed the thermal performance and shading coefficient of the kinetic shading system in comparison to existing fixed shading devices using the Ecotect. The results, in sum, conclude that the suggested kinetic shading system could decrease direct sunlights 26.2% more than the existing shading methods.

• Journal of Astronomy and Space Sciences
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• 제27권3호
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• pp.205-212
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• 2010

To better understand the physical processes that maintain the high-latitude lower thermospheric dynamics, we have identified relative contributions of the momentum forcing and the heating to the high-latitude lower thermospheric winds depending on the interplanetary magnetic field (IMF) and altitude. For this study, we performed a term analysis of the potential vorticity equation for the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions, with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM). Difference potential vorticity forcing and heating terms, obtained by subtracting values with zero IMF from those with non-zero IMF, are influenced by the IMF conditions. The difference forcing is more significant for strong IMF $B_y$ condition than for strong IMF $B_z$ condition. For negative or positive $B_y$ conditions, the difference forcings in the polar cap are larger by a factor of about 2 than those in the auroral region. The difference heating is the most significant for negative IMF $B_z$ condition, and the difference heatings in the auroral region are larger by a factor of about 1.5 than those in the polar cap region. The magnitudes of the difference forcing and heating decrease rapidly with descending altitudes. It is confirmed that the contribution of the forcing to the high-latitude lower thermospheric dynamics is stronger than the contribution of the heating to it. Especially, it is obvious that the contribution of the forcing to the dynamics is much larger in the polar cap region than in the auroral region and at higher altitude than at lower altitude. It is evident that when $B_z$ is negative condition the contribution of the forcing is the lowest and the contribution of the heating is the highest among the different IMF conditions.

• 한국안광학회지
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• 제12권4호
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• pp.19-22
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• 2007

산악 인구 증가와 더불어 해외원정 등반 인구도 크게 늘고 있다. 6천 미터 이상의 고소등반 시 발생하는 조난사고의 많은 부분이 설맹 때문이다. 설맹의 직접적 원인은 자외선에 의한 각막 및 망막의 손상이다. 고소에서의 자외선의 강도는 기압강하에 따른 고도효과와 설면에서 반사효과의 상승작용에 의해 크게 높아진다. 해발 4천 미터 설산에서의 자외선 강도는 지상에서보다 약 3배, 8천 미터에서는 약 4배 증가하는 것으로 나타났다. 고소등반에서 설맹을 방지하기 위해서는 고글보다 선글라스 형태가 바람직하다. 또 고소등반용 선글라스는 기계적 강도가 높은 프레임, 자외선을 100% 차단하는 플라스틱 렌즈의 사용이 요구된다. 얼굴과 선글라스 틈 사이로 들어오는 자외선을 차단하기 위해 탈부착식 차단막이 필요하다. 또 선글라스가 쉽게 탈착되지 않기 위하여 템플은 귀를 감을 수 있도록 길고 유연성이 좋아야 한다. 안구 주위의 동상을 방지하기 위해 메탈프레임을 합성수지로 피복하는 것이 바람직하다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.195-201
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• 2008

In the jet engines on the aircrafts cruising at high altitude over 20 km and subsonic speed, the Reynolds number in terms of the compressor blades becomes very low. In such an operating condition with low Reynolds number, it is widely reported that total pressure loss of the air flow through the compressor cascades increases dramatically due to separation of the boundary layer and the secondary-flow. But the detail of flow mechanisms causes the total pressure loss has not been fully understood yet. In the present study, two series of numerical investigations were conducted to study the effects of Reynolds number on the aerodynamic characteristics of compressor cascades. At first, the incompressible flow fields in the two-dimensional compressor cascade composed of C4 airfoils were numerically simulated with various values of Reynolds number. Compared with the corresponding experimental data, the numerically estimated trend of total pressure loss as a function of Reynolds number showed good agreement with that of experiment. From the visualized numerical results, the thickness of boundary layer and wake were found to increase with the decrease of Reynolds number. Especially at very low Reynolds number, the separation of boundary layer and vortex shedding were observed. The other series, as the preparatory investigation, the flow fields in the transonic compressor, NASA Rotor 37, were simulated under the several conditions, which corresponded to the operation at sea level static and at 10 km of altitude with low density and temperature. It was found that, in the case of operation at high altitude, the separation region on the blade surface became lager, and that the radial and reverse flow around the trailing edge become stronger than those under sea level static condition.