• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.9-16
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• 2019

In the present study, to investigate flows around space launch vehicles at mid-high altitudes efficiently, a three-dimensional unstructured mesh Navier-Stokes solver employing a Maxwell slip boundary condition was developed. Validation of the present flow solver was made for a blunted cone-tip configuration by comparing the results with those of the DSMC simulation and experiment. It was found that the present flow solver works well by capturing the velocity slip and the temperature jump on the solid surface more efficiently than the DSMC simulation. Flow simulations of space launch vehicles were conducted by using the flow solver. Mach number of 6 at the mid-high altitude around 86km was considered, and the flow phenomena at the mid-high altitude was discussed.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.433-440
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• 2022

High Altitude Long Endurance(HALE) solar powered UAV is the vehicle that flies for a long time as solar power energy sources. It can be used to replace satellites or provide continuous service because it can perform long-term missions at high altitudes. Due to the property of the mission, it is very important for HALE solar powered UAV to have maximum flight time. It is required for mission performance to fly at high altitudes continuously except a return for temporary maintenance. Therefore mission availability time analysis is a critical factor in the commercialization of HALE solar powered UAV. In this paper, we presented an analytic model and logic for available time analysis based on the design parameters of HALE solar powered UAV. This model can be used to analyze the possibility of applying UAV according to the UAV's mission in concept design before the UAV detail design stage.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.775-784
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• 2023

Drone images are being used more and more actively in the fields of surveying and spatial information, and are rapidly replacing existing aerial and satellite images. The technology of quickly acquiring real-time data at low cost and processing it is now being applied to actual industries beyond research. However, there are also problems encountered as this progresses. When high-resolution spatial information is acquired using a general 2D flight plan for a terrain with sever undulations, problems arise due to the difference in resolution of the data. In particular, when a low-altitude high-resolution image is taken using a drone in a mountainous or steep terrain, there may be a problem in image matching due to a resolution difference caused by terrain undulations. This problem occurs because a drone acquires data while flying on a 2D plane at a fixed altitude, just like conventional aerial photography. In order to acquire high-quality 3D data using a drone, the scale difference for the shooting distance should be considered. In addition, in order to obtain facade images of large structures, it is necessary to take images in 3D space. In this study, in order to improve the disadvantages of the 2D flight method, a 3D flight plan was established for the study area, and it was confirmed that high-quality 3D spatial information could be obtained in this way.

• Journal of Forest and Environmental Science
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• v.29 no.1
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• pp.29-37
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• 2013

The study was carried out in two different forest types viz., Banj oak and Chir pine forests to assess the variation in forest species composition and soil properties along altitudinal gradients in the Garhwal Himalayas. The results of the study showed that between the forests soil moisture was higher in Banj oak forest because of closed canopy and dense forest compared to Chir pine forest. The sand particles were reported higher in Banj oak forest which might be due to the addition of organic matter favouring coarse structure of soil, helping in holding maximum water in soils. However in the Chir pine forest low amount of soil organic matter and presence of clayey soil, develops soil compactness which reduces the penetration of water resulting in high soil bulk density. The higher accumulation of litter and presence of moisture in Banj oak forest favours higher nutrient level of nitrogen, phosphorus and potassium compared to Chir pine forest. The soil organic carbon also reduced with increasing altitude at both gradients. While bulk density has reverse trend with soil organic carbon in both the forests at different peaks of same region. In Banj oak forest, the highest density and total basal cover was reported 1,100 tree $ha^{-1}$ and 58.86 $m^2\;ha^{-1}$ respectively. However, the highest values of density and total basal cover of Chir pine forest was 560 tree$ha^{-1}$ and 56.94 $m^2\;ha^{-1}$ respectively. The total density and basal cover of both the forests reduced with increasing altitude. The study concludes that Banj oak forest has better nutrient cycling ability, well developed foest floor and has a greater protective and productive features compared to the Chir pine forest which is without lower vegetation cover and having only pine litter accumulation which does not allow any other species to grow.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.5
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• pp.47-56
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• 2004

This study was carried out to analyze forest vegetation of the Jangtaesan, Haetaesan, Ahnpyoungsan and Gubongsan in Daejeon. Employing the releve method of Braun-Blanquet, 76 plots were sampled. The communities were classified into Quercus mongolica community, Quercus variabilis community, and Pinus densiflora community. Average coverage rate was 85% in tree layer, 44% in subtree layer, 37% in shrub layer, 25% in herb layer, respectively. The importance values were 58.76 in Pinus densiftora, 44.86 in Quercus monegolica, 44.06 in Quercus variabilis, 33.00 in Quercus serrata, 18.73 in Rhus trichocarpa, 18.07 in Prunus sargentii. DBH range of most Pinus densiflora, Quercus mongolica and Quercus variabilis was between 5cm and 20cm. Therefore, Pinus densiflora, Quercus mongolica and Quercus variabilis will be dominant species in the study area for several more decades. Quercus mongolica community was distributed mainly on the north and east slope in a high-altitude and relative good nutrition condition. Querucus variabilis community was distributed mainly on the south slope in a middle-altitude and medium nutrition condition. Pinus densiflora community was distributed mainly in a low-altitude and poor nutrition condition.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.512-522
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• 2012

This study is focused on fish fauna and distributional features along with physical gradients and stream orders in the Tamjin River basin, Korea. Fish sampling and investigation were conducted for 2 years from 2009 to 2010. Total number of fish species collected were 47 species of 16 family. The group of cyprinidae was mostly abundant. Both fish abundance and biotic index were declined with increasing altitude and longitudinal distance from the river mouth. Two species of Zacco temminckii and Pungtungia herzi were prevalent in most of sampling sites and showed no altitudinal and longitudinal differences. Most other species, however, were spatially restricted to specific regional altitudes. Several species including Zacco platypus, Squalidus gracilis majimae and P. herzi were broadly distributed from river mouth to 50 km. Eight species including Z. temminckii and Rhynchocypris oxycephalus only appeared in over 10 km from the river mouth. Both Odontobutis platycephala and Pseudobagrus koreanus were classified as "upstream dewelling species" observed only in over 30 km from the river mouth. High proportion of tolerant and omnivorous species were more dominated in the downstream zone of the dam, whereas intolerant and insectivorous species were abundant in the upstream zone of the dam. The variable of stream order showed positive relationship between number of fish species and total individuals collected. Sensitive species including insectivore had a declining tendency with increasing stream order, while tolerant specie including omnivore species had relatively increased with stream order. Overall, our study suggested that fish distribution considerably depends on altitudinal gradient and longitudinal distance from the river mouth as well as physical habitat.

• Journal of Environmental Science International
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• v.22 no.1
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• pp.99-107
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• 2013

This study surveyed the distribution and characteristics of epiphytes and host trees in Jejudo's warm-temperate evergreen forests area. The gathered data will be used for evaluating ecological changes according to climate change. The study found 46 species of epiphytes in Jejudo; 12 of which were species of pteridophytes and 5 species of orchids, totaling 17 species of epiphytes. The appearance frequency was the greatest with Lepisorus thunbergianus, followed by Lemmaphyllum microphyllum and Lepisorus onoei. The area with the greatest diversity of epiphytes was nutmeg tree forests which have the largest number of 2.89 average species. Lemmaphyllum microphyllum had the greatest percent cover of the epiphytes whose importance was found to be the greatest. The factors involved were the epiphytes' diversity index (0.64), maximum species diversity (1.23), evenness (0.52), and dominance (0.48). The study has noted the distribution characteristics of epiphytes according to altitudes above sea level. The Lemmaphyllum microphyllum can survive at an altitude of 600 m above sea level, Lepisorus thunbergianus at 200 - 1,400m above sea level, Lepisorus onoei. at 400 - 1,000 m, and Gonocormus minutus at an altitude above 800 m. The host trees, consisting of Quercus serrata, Castanopsis cuspidata var. sieboldii, and Carpinus laxiflora, stands at 2-19 m high and 2.5 - 120 cm wide, showing diverse kinds of trees and sizes. Jejudo's warm-temperate evergreen forests have lower epiphyte diversity compared with those of subtropical and tropical areas in Japan and China. Based on the characteristics of the host trees order, epiphytes' distribution associated with the altitude above sea level was typical.

• Journal of Korean Society of Rural Planning
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• v.21 no.2
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• pp.127-135
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• 2015

In recent years, meteorological disasters have frequently occurred in rural areas. As a result, there have been growing concerns over the protective measures needed. In order to avoid natural risks and damage, and to strengthen countermeasure to meteorological disasters, local governments needs to be prepared. Therefore, this paper seeks to prevent meteorological disasters through mapping of inundation vulnerability in agricultural land, Chungcheongnam-do. In doing so, this study were considered 5 variables (i.e. precipitation, region of altitude below 50m, region of slope gradient is below 10 degree, distance from river within less 50m) for creating vulnerability map. The precipitation was excluded in five variables. Since, the precipitation which include Daily maximum precipitation, 2-Daily maximum precipitation, summer precipitation was not any correlation among them. The results of analysing four variables, exclusive of precipitation, were showed that the agricultural lands where located in Dangjin, Buyeo, Hongseong and Asan were low correlation of inundation vulnerability by overlapping analysis. Moreover, The correlation analysis was showed low correlation between each factors and the annual average area of agricultural lands' inundation, whereas, the correlation analysis which was overlapping each factor showed high correlation. In conclusion, in order to create reliable vulnerability map in agricultural lands, Chungcheongnam-do, it must be considered to overlap analysis of the four main factors such region of altitude below 50m, region of slope gradient is below 10 degree, distance from river within less 50m. We suppose that this study's analysis can help to set the preparedness site of agricultural lands inundation.

• The Korean Journal of Ecology
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• v.25 no.2
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• pp.109-117
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• 2002

This study was conducted to clarify the characteristics of attitudinal bled communities in Mt. Seoraksan National Park from May to Oct. 2001. Marsh tit Parus palustris, Arctic warbler Phylloscipus borealis, coal tit Parus ater and Eurasian nuthatchh Sitta europaea evenly distributed in almost elevational ranges. Goshawk Accipiter gentilis, black grouse Tetrao tetrix, white-rumped swift Apus pacificus, Siberian rubythroat Luscinia calliope, red-flanked bluetail Tarsiger cyanurus, dusky warbler Phylloscopus fuscatus, yellow-browned warbler Phylloscopus inomatus, siskin Carduelis spinus and rook Corvus frugilegus were only observed in high altitude area. Distribution pattern of birds in Mt. Seoraksan National Park showed differences by elevation. There was difference in altitudinal distribution pattern of birds in Mt. Seoraksan National Park. It seems that habitat preference or selection is different in each species. Altitudinal habitat preference of each bird species need further studies.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.615-625
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• 2012

To measure the athletic information of exercisers, the applications of smartphone are programmed based on the sensing data from GPS device. These applications provide exercisers for running or walking distance, exercising time, calorie consumption, average speed, and so on. Among them, the exercising distance should measure accurately because it directly affects the other athletic information for exercisers. However, the existing methods for measuring the exercising distance makes errors because they are worked on the simple sphere or ellipse earth models. Actually, the surface of real earth is composed of inclined ground like hills and valleys. In this paper, a new exercising distance measuring algorithm is proposed to compensate the errors of existing method. It considers the altitude of slopes in exercising routes. To evaluate exercising distance measuring algorithms, we implement the athletic life-guide system based on the smartphone platform. In experiments, the proposed method shows that it provides more accurate distance measurement.