• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.58-68
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• 2003

Accurate estimation of the Earth gravity field plays an important role in understanding the Earth geodynamic activities. After brief discussion on the objective of the gravity estimation, dedicated satellite missions for this purpose are described. Recently launched NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, which consists of two co-orbiting low altitude satellites, is described. For the performance analysis, full numerical simulation was performed. The simulation procedure and its key instrument modelings are described. From the simulation results, a significant improvement on the Earth gravity field accuracy is expected.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.331-339
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• 2014

Determination of an ionospheric delay scale factor, which converts ground-based ionospheric delay into low Earth orbit ionospheric delay, using the international reference ionosphere model is proposed. Ionospheric delay from international GNSS service model combined with IRI-derived scale factor is evaluated with NASA GRACE satellite data. At approximately 480km altitude, mean and standard deviation of the scale factor are 0.25 and 0.01 in 2004. The scale factor reaches high in night time and Spring and Fall seasons. Ionospheric delay error by the proposed method has a mean of 3.50 TECU in 2004.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.2
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• pp.41-50
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• 1999

The purpose of this study is to find out the changes in geomorphic characteristics of a small watershed when a golf course is constructed. The research site is a set of seven small watersheds including an 18-hole golf course that were randomly selected. The size, shape, and drainage network of watersheds were measured by using planimeter, watershed eccentricity, and stream order, respectively. In addition, a 25m$\times$25m mesh was used on topographic maps and grading plans in order to obtain the slope, elevation, and aspect of the watersheds. The major results of this research, while investigating of the changes in geomorphic characteristics of watersheds when a golf course is constructed, are as follows: 1. The size of watersheds is increased in accordance to the difference in elevation between the golf course site and the small watershed. 2. The watershed eccentricities are in general similar except for a few low-valued cases. 3. The changes in the average altitude and the gradient are more drastic with their bigger original values. 4. The aspects are changed more with decreasing elevation. 5. The stream order decreases in the case of a low watershed eccentricity. 6. The surface modification has a closer relationship to the slope rather than the size of effective use area. 7. With a steeper gradient and an excessively low gradient, the height of cutting/filling is increased.

• Journal of Astronomy and Space Sciences
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• v.35 no.1
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• pp.31-37
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• 2018

Pc1 pulsations are geomagnetic fluctuations in the frequency range of 0.2 to 5 Hz. There have been several observations of Pc1 pulsations in low earth orbit by MAGSAT, DE-2, Viking, Freja, CHAMP, and SWARM satellites. However, there has been a clear limitation in resolving the spatial and temporal variations of the pulsation by using a single-point observation by a single satellite. To overcome such limitations of previous observations, a new space mission was recently initiated, using the concept of multi-satellites, named the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE). The SNIPE mission consists of four nanosatellites (~10 kg), which will be launched into a polar orbit at an altitude of 600 km (TBD) in 2020. Four satellites will be deployed in orbit, and the distances between each satellite will be controlled from 10 to 1,000 km by a high-end formation-flying algorithm. One of the possible science targets of the SNIPE mission is observing electromagnetic ion cyclotron (EMIC) waves. In this paper, we report on examples of observations, showing the limitations of previous EMIC observations in low earth orbit, and suggest possibilities to overcome those limitations through a new mission.

• Parasites, Hosts and Diseases
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• v.59 no.1
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• pp.1-8
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• 2021

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.363-369
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• 2021

Since the Global Navigation Satellite System (GNSS) signal received from the low Earth orbit (LEO) satellite is only affected by the upper ionosphere, the magnitude of the ionospheric delay of Global Positioning System (GPS) signal received from ground user is different. Therefore, the ground-based two-dimensional ionospheric model cannot be applied to LEO satellites. The NeQuick model used in Galileo provides the ionospheric delay according to the user's altitude, so it can be used in the ionospheric model of the LEO satellites. However, the NeQuick model is not suitable for space receivers because of the high computational cost. A simplified NeQuick model with reduced computing time was recently presented. In this study, the computing time of the NeQuick model and the simplified NeQuick model was analyzed based on the GPS Klobuchar model. The NeQuick and simplified NeQuick model were applied to the GNSS data from GRACE-B, Swarm-C, and GOCE satellites to analyze the performance of the ionospheric correction and positioning. The difference in computing time between the NeQuick and simplified NeQuick model was up to 90%, but the difference in ionospheric accuracy was not as large as within 4.5%.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.5 no.4
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• pp.789-796
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• 2015

The first phase of architecture design is the field survey of the site and its surroundings. To gather the information there are two methods :the traditional method of an onsite survey, and recently using 3D geometry data and high quality image mapping from online services such as Google Earth. However, the urban condition is fast changing, and information from online services may lack sufficient information. This paper presents the to fast and effective site survey method for urban site using an affordable and fully automated UAV for the architectural design field.

• Korean Journal of Plant Taxonomy
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• v.42 no.3
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• pp.202-206
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• 2012

A new species, Viola ulleungdoensis M. Kim & J. Lee is named and described from Is. Ulleung, Gyeongsangbukdo Province, Korea. Molecular data confirmed that this new taxon was distinguished from other congeneric species. The Viola ulleungdoensis shares several characteristics (acaulescent leaves, beardless lateral petals, glabrous petioles and peduncles, etc.) with its related species V. selkirkii, but is distinct from V. selkirkii which has present adventitious buds, same leaves after flowering, small leaves, and high altitude habitats by having absent adventitious buds, larger leaves after flowering, large leaves, and low altitude habitats.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.5
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• pp.809-815
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• 2020

A number of investigations and studies have been conducted in various fields regarding the sediment disasters of Mt. Woomyeon that occurred in July 2011. We collected and compared the topographic information of the general points where debris flows did not occur and the collapse points where the debris flow occurred in order to find out the characteristics of the collapse points in Woomyeon mountain. The collected topographic information is altitude, curvature, slope, aspect and TPI(topographic position index). As a result of comparison, there were relatively many collapse points at an altitude of 210m to 250m, and at a slope of 30° to 40°. In addition, the risk of collapse was low in a cell where the curvature was close to 0, and the risk was higher in concave terrain than in convex terrain. In the case of TPI, there was no statistical difference between the general points and the collapse points when the analysis radius was larger than 200m, and there was a correlation with the curvature when the analysis radius was smaller than 50m. In the case of debris flows that are affected by artificial structures or facilities, there is a possibility of disturbing the topographic analysis results. Therefore, if a research on debris flow is conducted on a mountain area that is heavily exposed to human activities, such as Woomyeon mountain, diversified factors must be considered to account for this impact.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.345-358
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• 2018

The high altitude scientific balloon has been used for decades in advanced aerospace countries such as United States, France, and Japan to carry out various research objectives. Since the initial cost for development and operation is enormous, it has been conducted by national research institutes. Recently, the advent of open source software/hardware ecosystems with low-cost yet high-performance have lowered barriers to enter into scientific balloon research and development. In this study, a zero pressure balloon prototype was designed considering the cost, usability, compatibility, and development period by using commercial off the shelf (COTS) items. In addition, the flight operation experience was accumulated through eight times of the flight tests, and operational reliability of the balloon system was verified. Finally, the foundation for the operation of the large zero pressure balloon was established.