• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.144-152
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• 2011

In order to investigate the operation performance behaviors of the UAV's propulsion system to be operated long time in high altitude, the engine performance tests, which are simulated in the altitude engine test facility should be needed. If the test is performed in a existing altitude engine test facility, additional test apparatuses are required. Among them a proper design of the inlet and exhaust ducts that may directly affect the engine performance is very important. If the design is not adequate, the engine performance loss due to the flow behavior change and the pressure loss may be not similar to the real engine performance. In this work, firstly the engine inlet and exhaust ducts to be mounted to the existing altitude facility are modelled in 3D and its flow behaviors and pressure losses are analyzed using a commercial CFD tool, ANSYS's CFX, and the engine performance with the duct losses is calculated using the performance analysis program developed by C. Kong et al. Finally, the optimized inlet and exhaust ducts' configurations are proposed through the repeated analyses of various duct configurations.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.594-602
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• 2020

This study investigated the effect of geography and altitude on epigeic spider communities in rice field levees in Jeollabuk-do. Spider communities in the mountainous and plain areas were compared to determine the effect of geography on the cultivation periods. The effect of altitude was compared between the Jeongeup and Jangsu areas during non-cultivation periods. Analysis using nMDS (non-metric multidimensional scaling), MRPP (multiple response permutation procedure), and ANOSIM (analysis of similarity) revealed differences in spider community structures between the two types of study areas. Lycosidae predominated at the family level, and its abundance was greater in the mountainous area than in the plains area. The total abundance did not differ between the two areas with different altitudes, but the abundance of three Pardosa species was greater at lower altitudes than at higher altitudes. Geography and altitude had a minimal effect on species richness and diversity indices at the community level. However, several Lycosidae species showed species-specific responses to both geography and altitude in the rice fields.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.4
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• pp.1-12
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• 2021

Recently, the use of unmanned aerial vehicles (UAVs) is increasing in the field of land information acquisition and terrain exploration through high-altitude aerial photography. High-altitude aerial photography is suitable for large-scale geographic information collection, but has the disadvantage that it is difficult to accurately collect small-scale geographic information. Therefore, this study used low-altitude UAV to monitor changes in small rural spaces around rural resources, and the results are as follows. First, the low-altitude aerial imagery had a very high spatial resolution, so it was effective in reading and analyzing topographic features. Second, an area with a large number of aerial images and a complex topography had a large amount of point clouds to be extracted, and the number of point clouds affects the three-dimensional quality of rural space. Third, 3D mapping technology using point cloud is effective for monitoring rural space and rural resources because it enables observation and comparison of parts that cannot be read from general aerial images. In this study, the possibility of rural space analysis of low-altitude UAV was verified through aerial photography and analysis, and the effect of 3D mapping on rural space monitoring was visually analyzed. If data acquired by low-altitude UAV are used in various forms such as GIS analysis and topographic map production it is expected to be used as basic data for rural planning to maintain and preserve the rural environment.

• Journal of Environmental Science International
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• v.33 no.8
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• pp.591-604
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• 2024

To investigate the frequency and trajectories of volcanic ash from Mt. Baekdu reaching the Korean Peninsula, a forward trajectory analysis was conducted using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Through a cluster analysis of air parcel trajectories, we identified the main pathways of the volcanic ash from Mt. Baekdu entering the Korean Peninsula and analyzed the synoptic meteorological conditions on those days. The frequency of volcanic ash reaching the Korean Peninsula was 82 times at an altitude of 1000 m and 70 times at 2000 m, with an increasing trend from 2016 to 2022. This increase is attributed to the weakening of westerly winds and the strengthening of north-south winds due to global warming. Five and three trajectory clusters were classified at 1000 m and 2000 m, respectively. At a starting altitude of 1000 m, most air parcels originating from Mt. Baekdu entered the Korean Peninsula under weather conditions (C2, C3) where the pressure gradient from the northwest to the southeast was small, resulting in weak northerly winds. C2 and C3 showed shorter trajectories, which occurred in all seasons, except summer. At a starting altitude of 2000 m, air parcels mostly passed over the Korean Peninsula in a synoptic pattern similar to that at 1000 m in altitude; however, the air parcels had simpler paths and less frequent inflow. C2, at a starting altitude of 2000 m, originates from Mount Baekdu, crosses the center of the Korean Peninsula, and continues to the central region. At a starting altitude of 1000 m, volcanic ash can enter the Korean Peninsula when there is no strong low-pressure system to the southeast of the Korean Peninsula, whereas at 2000 m, volcanic ash can enter the Korean Peninsula when the Siberian high-pressure system is weak.

• Journal of Astronomy and Space Sciences
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• v.25 no.2
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• pp.167-180
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• 2008

The resolution of Earth images taken from a satellite has close relation with satellite's altitude. If a satellite has lower altitude, it gets a picture having better resolution. However the satellite will be exposed to heavier air drag and will spend more fuel to maintain its altitude for a desired mission. Therefore, in this study, the required fuel to maintain very low earth orbit(LEO) with severe air drag is analyzed using optimization method such as collocation method. The required fuel to maintain the low altitude has significantly increased as the mission altitude is lowered and the solar activity is maximized. This study also shows that the fuel reduced by increasing the period of the satellite maneuver is very small, and that slightly increasing the satellite's mission altitude is much effective in reducing the amount of fuel to maintain its altitude. The calculated fuel to maintain very low earth orbit in this study would give useful information in planning the budget of fuel and cost for LEO satellites.

• Korean Journal of Environment and Ecology
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• v.27 no.4
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• pp.449-461
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• 2013

This study is contributed to examine the vegetation characteristics of the Quercus mongolica which are located in between two summits, hyangnobong and gitdaebaggybong, with dividing two regions(I, II). A total of 63 Quercus mongolica communities were enrolled in this survey. A~E, 5 communities were the result of analysed classification by TWINSPAN. Spatial distribution of the communities; 'A' community is concentrated at an altitude of about 1,300 meters in Mt. Taebaek(II region). 'B' and 'C' communities are concentrated at an altitude of between 700 and 1500 meters in Mt. Seorak and Odae(Iregion). 'D' and 'E' communities are concentrated at an altitude of below 1,100 meters in Mt. Cheongok and geumdaebong(II region), and also Mt. Seorak and Odae(Iregion). Arboral and shrub populations, maximum species diversity and height of arboral of each communities have a characteristic of decreasing according to increasing altitude gradually. And the result of studying on arboreal growth increment with up to 40-year-old trees, there is no special tendency with growth increment in the altitude of subnormal 1,100 meters, but there is a tendency that growth increment becomes lower in the altitude of more than 1,100 meters. In correlation analysis, it is -0.53 in the Quercus mongolica and Betula costata community at an altitude of over 1,000 meters, the correlation shows negative(-). It is +0.59 in the Quercus mongolica and Rubus crataegifolius community at an altitude of less than 1,000 meters, the correlation shows positive(+). And those are cognate trees with the correlation of Betula costata, Betula costata Trautv., Tripterygium regelii Sprague&Takeda., Acer barbinerve Maxim. With a summary of the results, the changes in the environment according to the elevation affect Quercus mongolica community.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.100-106
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• 2019

Ground and high altitude simulated combustion experiments were conducted using a liquid rocket engine with hydrogen peroxide and kerosene as the propellant. A ground and high altitude simulated combustion test facility was constructed by installing a high altitude model diffuser and TMS (Thrust Measuring System) on a vertical combustion test bench. The thrust characteristics according to altitude were investigated using the combustion test equipment. The diffuser was designed on a 1:4.8 scale to verify the characteristics of the high diffusing diffuser and starting pressure. The cold flow tests were conducted using nitrogen gas, and the performance characteristics and starting characteristics of the scale down diffuser were verified. A diffuser and TMS were installed on the vertical combustion test bench, and the thrust correction equations for the system resistance were derived. The thrust correction equations were derived from the step test and vacuum step test before the actual hot firing test. Nozzles with an operating altitude of 10km were designed. Hot firing tests were conducted to analyze the thrust characteristics according to the operating altitude changes. The actual thrust was calculated using each correction equation with the thrust value measured by the TMS.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.12
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• pp.1801-1808
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• 2019

Objective: As an iconic symbol of Qinghai-Tibetan Plateau and of high altitude, yak are subjected to hypoxic conditions that challenge aerobic metabolism. Matrix metalloproteinases-3 (MMP3) is assumed to be a key target gene of hypoxia-inducible factor-$1{\alpha}$ that function as a master regulator of the cellular response to hypoxia. Therefore, the aim of this investigation was to identify the DNA polymorphism of MMP3 gene in domestic yak and to explore its possible association with high-altitude adaptation. Methods: The single-nucleotide polymorphisms (SNPs) genotyping and mutations scanning at the MMP3 locus were conducted in total of 344 individuals from four domestic Chinese yak breeds resident at different altitudes on the Qinghai-Tibetan Plateau, using high-resolution melting analysis and DNA sequencing techniques. Results: The novel of SNPs rs2381 $A{\rightarrow}G$ and rs4331 $C{\rightarrow}G$ were identified in intron V and intron VII of MMP3, respectively. Frequencies of the GG genotype and the G allele of SNP rs2381 $A{\rightarrow}G$ observed in high-altitude Pali yak were significantly higher than that of the other yak breeds resident at middle or low altitude (p<0.01). No significant difference was mapped for SNP rs4331 $C{\rightarrow}G$ in the yak population (p>0.05). Haplotype GC was the dominant among the 4 yak breeds, and Pearson correlation analysis showed that the frequencies of GC was significantly lower in Ganan (GN), Datong (DT), and Tianzhu white yaks (TZ) compared with Pali (PL) yak. The two SNPs were in moderate linkage disequilibrium in high-altitude yaks (PL) but not in middle-altitude (GN, DT) and low-altitude (TZ) yaks. Conclusion: These results indicate that MMP3 may have been subjected to positive selection in yak, especially that the SNP rs2381 $A{\rightarrow}G$ mutation and GC haplotypes might contribute to adaptation for yak in high-altitude environments.

• Atmosphere
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• v.27 no.3
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• pp.359-370
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• 2017

In this study, the oceanic Total Precipitable Water (TPW) retrieval algorithm at 16 km altitude of High Altitude Long Endurance Unmanned Aerial Vehicle (HALE UAV) is described. Empirical equation based on Wentz method (1995) that uses the 18.7 and 22.235 GHz channels is developed using the simulated brightness temperature and SeeBor training dataset. To do radiative simulation, Satellite Data Simulator Unit (SDSU) Radiative Transfer Model (RTM) is used. The data of 60% (523) and 40% (349) in the SeeBor training dataset are used to develop and validate the TPW retrieval algorithm, respectively. The range of coefficients for the TPW retrieval at the altitude of 3~18 km with 3 km interval were 153.69~199.87 (${\alpha}$), 54.330~58.468 (${\beta}$), and 84.519~93.484 (${\gamma}$). The bias and RMSE at each altitude were found to be about $-0.81kg\;m^{-2}$ and $2.17kg\;m^{-2}$, respectively. Correlation coefficients were more than 0.9. Radiosonde observation has been generally operated over land. To validate the accuracy of the oceanic TPW retrieval algorithm, observation data from the Korea Meteorological Administration (KMA) Gisang 1 research vessel about six clear sky cases representing spring, autumn, and summer season is used. Difference between retrieved and observed TPW at 16 km altitude were in the range of $0.53{\sim}1.87kg\;m^{-2}$, which is reasonable for most applications. Difference in TPW between retrieval and observation at each altitude (3~15 km) is also presented. Differences of TPW at altitudes more than 6 km were $0.3{\sim}1.9kg\;m^{-2}$. Retrieved TPW at 3 km altitude was smaller than upper level with a difference of $-0.25{\sim}0.75kg\;m^{-2}$ compared to the observed TPW.

• Korean Business Review
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• v.22 no.2
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• pp.139-156
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• 2009

Mountain tourism is regarded as an important inbound tourist destination for the whole world. The Himalayan Mountains are house of world's highest peaks that includes over 100 mountains exceeding 8,500 meters. However limited dimension of visitors constraints and motivation has been reported about the high altitude mountain. This research work permits the identification of some of the motivation and constraints related to the decision making of tourism in high altitude mountains. The study was conducted in Korea, Indian state (Sikkim), and Nepal (Kathmandu) due to the popularity and the major destination for mountain tourism. A set of 9 motive, 45 motivation items and 40 constraints were initially generated from a review of research pertaining to visitor motivation and constraints. They were considered to be the most appropriate for measuring visitors motivation and constraints for experiencing high altitude mountain tourism. Validity of dimensionality and inter correlation was evaluated by factor analysis investigation and analysis of obtained data revealed that constraints of Korean are significantly higher than Indian and other inbound tourist. Among the major constraints structural constraints were recorded higher for Indian, Korean and other visitors. Similarly, motives of different visitors varied significantly. This analysis also revealed that Korean motives for travelling were influenced by health and pleasure, whereas, Indian and others motives were mostly related to knowledge seeking and adventure. The environmental importance were given priority by all the countries. The purpose of this study includes; (1) To identify the motives of visitors in high altitude destinations. (2) To analysis the major motivation factor for the altitude tourism. (3) To report the major constraints of visitors travelling to the high altitude. (4) To study whether the strength of motivation help to overcome the constraints.