• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.379-382
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• 2017

Flow characteristics of dual bell nozzle with pintle were investigated. Thrust and thrust coefficient were compared with the pintle-bell nozzle of the same condition, and difference according to the pintle stroke was investigated. At stroke 0 mm, the thrust of the dual bell nozzle was about 13.18% higher than the bell nozzle, and when the pintle was backward, it was similar to the bell nozzle. The change in expansion ratio with stroke was considered to be more advantageous for a dual bell nozzle that performs altitude compensation through separation and transition.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.1-7
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• 2009

As designing PID control on aircraft, we consider a gain scheduling on altitude and velocity. If pitot tube is not installed in the unpowered air vehicle, the control performance is reduced by the difference between ground speed and air speed with a wind considered. In this paper, a simple guidance controller (LOS: Line of Sight) and the wind estimator using Kalman filter are designed. And we minimize the wind effect through the estimator. Finally, we perform the 6-DOF nonlinear simulation with the wind model to verify the performance of the controller with the wind estimator.

• Korean Journal of Remote Sensing
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• v.25 no.3
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• pp.287-294
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• 2009

KOMPSAT-2 like other high-resolution satellites has the time and angle difference in the acquisition of the panchromatic (PAN) and multispectral (MS) images because the imaging systems have the offset of the charge coupled device combination in the focal plane. Due to the differences, high altitude and moving objects, such as clouds, have a different position between the PAN and MS images. Therefore, a mis-registration between the PAN and MS images occurs when a registration algorithm extracted matching points from these cloud objects. To overcome this problem, we proposed a new registration method. The main idea is to discard the matching points extracted from cloud boundaries by using an automatic thresholding technique and a classification technique on a distance disparity map of the matching points. The experimental result demonstrates the accuracy of the proposed method at ground region around cloud objects is higher than a general method which does not consider cloud objects. To evaluate the proposed method, we use KOMPSAT-2 cloudy images.

• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.2
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• pp.137-142
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• 2005

This study was conducted to evaluate the effects of cutting frequency and level of fertilizer application on the botanical composition and forage yield of alpine pasture. Field experiment was established at 600 m (a.s.1) altitude with two cutting frequency schedules (two and three times annually) and two levels of fertilizer application (lower level of fertilizer, 200-200-200 kg / ha and standard level of fertilizer, 280-200-240 kg / ha; N, $P_2O_5$ and $K_2O$, respectively). Higher grass to clover ratio was observed in two cutting frequencies. The clover ratio was highest as $16\%$ in thee cutting frequencies with lower level of fertilizer application End the ratio of weed was low in all treatments ($3.7 {\~} 6.7\%$). No significant difference was observed in forage dry matter (DM) yield among treatments, however forage DM yield in three cutting frequencies tended to be greater in standard level of fertilizer application compared to lower level of fertilizer application. The forage quality was greater in three cutting frequencies, but not changed with different levels of fertilizer application. This result indicates that three cutting frequency and standard level of fertilizer application system are considered to be proper management methods at alpine grassland of 600 m altitude considering the botanical composition, forage DM yield md forage quality.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.2
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• pp.164-172
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• 1983

The present study was conducted to investigate the variations in morphological traits, yield and yield-related components of rice cultivars exposed to different weather conditions by growing at the locations with different altitude but with equal latitude. Three Japonica varieties (Daegoldo, Jinheung, Shin #2) and three Tongil type semi-dwarf varieties(Josaengtongil, Suweon 287, wx 817-65-2-3) were seeded at Suweon on April 21 and transplanted at Suweon ($127^{\circ}$ N37 20', altitude 37m) and Jechun ($128.2^{\circ}$, N37 10', altitude 280-300m) on June 1 with the spacing of 30 $\times$ 15 em. The morphological traits, yield and yield-related components were measured. Culm length, paincle length and 1000-grain weight showed a little increase in Japonica varieties in Jechun as compared to those in Suweon and vice versa in semi-dwarf varieties, showing no significant differences. Number of panicles, per hill and number of spikelets per panicle among yield-related components showed remarkable increase in all varieties in Jechun as compared to those in 'Suweon but such inter-locational differences differed with varieties within varietal group and between varietal groups. On the contrary, grain fertility was higher in Suweon than that in Jechun and in Japonica varieties than that in semi-dwarf varieites , showing greater inter-locational difference in semi-dwarf varieties. Among Japonica varieties Jinheung and Shin #2 showed remarkable increase in yield in Jechun as compared to that in Suweon but in semidwarf varieties it was just the opposite. The importance of each of the yield-related component contributing to yield showed similar tendency 'regardless of locations in Japonica varieties. However, it was evidently different between locations in semidwarf varieties, where number of spikelets per panicle showed greatest direct effect on yield in Suweon but in Jechun so did grain fertility followed by the number of spikelets per panicle.

• Korean Journal of Environment and Ecology
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• v.32 no.6
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• pp.575-581
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• 2018

The relationship between the body size of species and the environment has been an active research subject for many years. Until recently, studies had focused on the relationship between the body size and environment based on the ecogeographic rule for various animal groups. In this study, we examined the relationship between body size of Hyla japonica and the habitat environment in Jeju island located at the southernmost part of the Korean peninsula. We collected H. japonica from three breeding sites, Cheonji, Bonggae, and Aewol, and measured SVL, BW, and HW of the species. We also measured the altitude, longitude, latitude, annual mean temperature, and annual mean precipitation of each site to analyze the relationship between the body size and the habitat environment. The analysis results showed that there was the clear difference of the body size according to the habitat and the body size in Aewol was significantly bigger than others, while the body size in Cheonji was the smallest. The altitude was the most important environmental variable and showed a positive correlation with body size. The body size of H. japonica increased as the altitude increased, and this results were consistent with Bergmann's rule, one of the biological laws related to body size. In conclusion, the environment could affect the body size of H. japonica, and the body size has a certain direction according to the environment.

• Korean Journal of Medicinal Crop Science
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• v.8 no.2
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• pp.134-145
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• 2000

Growth and ecological differences of some important medicinal plants (Carthamus tinctorius, Astragalus membranaceus, Digitalis purpurea, Melissa officinalis, Anethum graveolens, Angelica gigas and Saururus chinensis) were observed at the different attitudinal sites of Mt. Halla in Cheju from 1997 to 1998. Growth of all medicinal plants was generally higher in the northern slope parts than in the southern slope parts. But at 50m above the sea level in the northern slope regions, the germination, growth and yield of Astragalus membranaceus and Digitalis purpurea were reduced by the wind. As the altitude was higher, the temperature was more slowly down in the northern slope regions than in the southern slope regions, while, the moisture was relatively high. The growth of Carthamus tinctorius, Melissa officinalis, Anethum graveolens and Angelica gigas were generally reduced by the higher altitude. On the other hand, growth of Saururus chinensis was good at the 700m above the sea level.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.145-148
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• 2006

In order to design a micro-thruster which controls the altitude of a space vehicle for a very long lifetime, the flow field should be analyzed considering the nozzle geometry and the difference between stagnation and environmental pressures and so on. This paper describes the axisymmetric non-reacted computational results which were carried out to understand the basic flow phenomena according to the high nozzle pressure ratio. The area ratio is about 56 and the diameter of a nozzle exit is about 0.46 inch. The Mach cell and waves are predicted well.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.360-369
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• 2012

Parent material, climate, topography, biological factors, and time are considered five soil forming factors. This study was conducted to elucidate the effects of several environment factors on soil distribution using quantitative analysis method, called soil series estimation algorithm in the soils of Jeju Island. We selected environment factors including mean temperature, annual precipitation, surface geology, altitude, slope, aspect, altitude difference within 1 $km^2$ area, topographic wetness index, distance from the shore, distance from the mountain peak, and landuse for a quantitative analysis. We analyzed the ranges of environment factors for each soil series and calculated probabilities of possible-soil series for certain locations using estimation algorithm. The algorithm can predicted exact soil series on the soil map with correctness of 33% on $1^{st}$ ranking, 62% within $2^{nd}$ ranking, 74% within $5^{th}$ ranking after estimating using randomly extracted environment factors. In predicted soil map, soil sequences of Entisols-Alfisols-Andisols on northern area and Alfisols-Ultisols-Andisols on western area can be suggested along increasing altitude. More modeling studies will be needed for the genesis process of soils in Jeju Island.

• Korean Journal of Ecology and Environment
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• v.46 no.1
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• pp.18-24
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• 2013

The objective of study was to protect seabird breeding site and vegetation restoration of Chilbal and Sokugul island in Shinan county Jeonnam province, April and December 2011. We analyzed the soil properties according to the dominant communities and environmental gradient. As a result, It was highly analyzed to moisture content, organic matter, salinity, total nitrogen in Commelina communis community and low analyzed in Achyranthes japonica community. Carex boottiana community which mainly used as a seabird habitat has a wide range and Achyranthes japonica and Artemisia princeps community was narrowed to soil properties. Soil pH of Carex boottiana community in Sogugul island was the lowest on 3.14 and Peucedanum japonicum community was the highest. Soil moisture content and organic matter was analyzed by the high value in Peucedanum japonicum community. In contrast, Achyranthes japonica was the low value and Carex boottiana community was analyzed the highest on the salinity and total nitrogen. On the soil environmental characteristics according to the environmental gradient, The higher altitude, moisture content, organic matter, salinity and total nitrogen was the lower in Chilbal island. In the case of Sokugul island, the altitude difference did not show the characteristics of soil environmental factors for small area and low altitude. But moisture content is similar to soil property of Chilbal island. Soil property was strongly acid soil because of seabird dropping. This results will be helpful to manage the invasive plants.