• Architectural research
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• 제11권1호
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• pp.7-14
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• 2009

In this paper, we take advantage of Wavelet Transform to identify damping ratios of membrane structures under wind action. Due to the lightweight and flexibility of membrane structures, they are very sensitive to the wind load, and show a type of fluid-structure interaction phenomenon simultaneously. In this study, we firstly obtain the responses of an air-supported membrane structure by ADINA with the consideration of this characteristic, and then conduct Wavelet Transform on these responses. Based on the Wavelet Transform, damping ratios could be obtained from the slope of Wavelet Transform in a semi-logarithmic scale at a certain dilation coefficient. According to this principle, damping ratios could eventually be obtained. There are two numerical examples in this study. The first one is a simulated signal, which is used to verify the accuracy of the Wavelet Transform method. The second one is an air-supported membrane structure under wind action, damping ratios obtained from this method is about 0.05~0.09. The Wavelet Transform method could be regarded as a very good method for the the damping analysis, especially for the large spatial structures whose natural frequencies are closely spaced.

• Journal of Astronomy and Space Sciences
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• 제22권2호
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• pp.89-112
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• 2005

We determine the rotation velocities of 108 spiral and irregular galaxies (XV-Sample) from first-order rotation curves from position-velocity maps, based on short 21-cm observations with the Westerbork Synthesis Radio Telescope (WSRT). To test the usual random motion corrections, we compare the global HI linewidths and the rotation velocities, obtained from kinematical fits to two-dimensional velocity fields for a sample of 28 galaxies (RC-Sample), and find that the most frequently used correction formulae (Tully & Fouque 1985) are not very satisfactory. The rotation velocity parameter (the random-motion corrected HI linewidth: W?), derived with these corrections, may be statistically equal to two times the true rotation velocity, but in individual cases the differences can be large. We analyse, for both RC- and XV-Samples, the dependence of the slope of, and scatter in the Tully-Fisher relation on the definition of the rotation velocity parameters- For the RC-Sample, we find that the scatter in the Tully-Fisher relation can be reduced considerably when the rotation velocities derived from rotation curves are used instead of the random-motion corrected global H I linewidths. No such reduction in the scatter is seen for XV-Sample. We conclude that the reduction of the scatter in the Tully-Fisher relation seems to be related to the use of two-dimensional velocity information: accurate rotation velocity and kinematical inclination.

• 한국농공학회논문집
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• 제56권1호
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• pp.71-79
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• 2014

In this study, an experiment with large-scale model was performed according to raising the embankment in order to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The pore water pressure, earth pressure, settlement and failure pattern by a rapid drawdown and overtopping were compared and analyzed. The pore water pressure and earth pressure at spillway transitional zone by overtopping increased a rapidly with the expansion of seepage erosion, but the crest showed a smally change due to effect of the inclined core type. And it is considered an useful data that can accurately estimate the possibility of failure of the reservoirs. A settlement at overtopping decreased a rapidly due to failure of crest. The relative settlement difference due to change of the water level at the upstream and downstream slope cause increase largely crack of crest. The behavior of failure by overtopping was gradually enlarged towards reservoirs crest from the bottom of the spillway transition zone, the inclined core after the raising the embankment was influenced significantly to prevent the seepage erosion.

• 천문학회보
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• 제41권2호
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• pp.49.1-49.1
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• 2016

Asteroid taxonomy dates back to the mid-1970's and is based mostly on broadband photometric and spectroscopic observations in the visible wavelength. Different taxonomic classes have long been characterized by spectral slope shortward of 0.75 microns and the absorption band in 1 micron, the principal components. In this way, taxonomic classes are grouped and divided into four broad complexes; silicates (S), carbonaceous (C), featureless (X), Vestoids (V), and the end-members that do not fit well within the S, C, X and V complexes. The past decade witnessed an explosion of data due to the advent of large-scale asteroid surveys such as SDSS. The classification scheme has recently been expanded with the analysis of the SDSS 4th Moving Object Catalog (MOC 4) data. However, the boundaries of each complex and subclass are rather ambiguously defined by hand. Furthermore, there are only few studies on asteroid taxonomy using Johnson-Cousins filters, and those were conducted on a small number of objects, with significant uncertainties. In this paper, we present our preliminary results for a new taxonomic classification of asteroids using SMASS, Bus and DeMeo (2014) and the SDSS MOC 4 datasets. This classification scheme is simply represented by a triplet of photometric colors, either in SDSS or in Johnson-Cousins photometric systems.

• 한국환경복원기술학회지
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• 제1권1호
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• pp.119-132
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• 1998

In recent Japan, the demand for woodland creation on revegetation sites is increasing. In the forests and woodlands, we can find many functions of environmental conservation, in addition of biomaterial production, and all of these existences with such functions are defined as environmental woodlands. Many woodlands has been created from old times for the purpose of forest conservation and flood control, and most of these technology are handed down to present time. After Edo era (from the beginning of Meiji era, 1867), some valuable examples of woodlands were created, like Meiji shrine woodland in Tokyo. After the World War II, a lot of technology for woodland revegetation, such as ecological tree planting, have been developed. At present, many revegetation sites are aiming at woodland creation, like on man-made slope, etc.. In the great change of social structure, revegetation technology is also required to keep in close relationships to the restoration of devastated existing forests and woodlands, and to provide many technology for the restoration of secondary woodland, preservation of soil, mitigation, reclamation, etc.. Now in Japan, the improvement of environment including all the member of biosphere is demanded on a large scale. Therefore, revegetation technology should also try to make an activity taking a broad view of the restoration of natural vegetation in addition to the traditional and new woodland creation.

• Journal of Forest and Environmental Science
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• 제35권1호
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• pp.61-68
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• 2019

The purpose of this study is to evaluate the natural habitat of Hotaria unmunsana Doi, which was first discovered at Mt. Unmun also represents a landscape indicator species for Daegu and Gyeongbuk provinces, and Luciola lateralis Motschulsky, which is the object of experiential activation at festivals in some cities in the region. The spatial range of this study is limited by Daegu City and Gyeongbuk province, and is used to predict the preference of firefly for altitude, slope, direction, shaded relief, riparian buffer zone, river environment, and farmland to analyze the area that best matches the habitat of fireflies. As a result, fireflies are highly influenced by altitude and there may be no large-scale habitats in some areas through the Nakdong and the Baekdu mountain ranges, which occur at high altitude. In most of the cities, we found major habitats around the streams and wetlands. By region, the sites were widely distributed around the cities focused on Nakdong River, and many habitats emerged around the Nakdong River tributary and gentle slopes. In order to preserve and spread the habitat of fireflies, the physical environment as well as their relationship with food chains and symbiotic organisms should be established, and excessive use of pesticides and herbicides in agricultural areas should be avoided.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.329-343
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• 2019

In order to simulate the evacuation simulation of a ship during a sinking, the slope angle change of the ship must be reflected during the simulation. In this study, the passenger evacuation simulation is implemented by continuously applying the heeling angle change during sinking. To reflect crowd behavior, the human density and the congestion algorithm were developed in this research and the walking speed experiment in the special situation occurring in the inclined ship was conducted. Evacuation simulation was carried out by applying the experimental results and the change of the walking speed according to the heeling angle of the ship. In order to verify the evacuation simulation, test items suggested by International Maritime Organization (IMO) and SAFEGUARD Validation Data Set conducted on a large Ro-PAX ferry (SGVDS 1) which performed real evacuation trial in full-scale ships were performed and the results of simulation were analyzed. Based on hypothetical scenario of when a normal evacuation command is delivered to the passengers of MV SEWOL in time, we predicted and analyzed the evacuation process and the number of casualties.

• 지질공학
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• 제30권4호
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• pp.497-514
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• 2020

본 연구는 강원도 삼척시 소재의 삼도 석회석광산에서 발생한 채굴공동 상부의 대규모 지반침하지를 대상으로 그 발생원인을 규명하는데 있다. 현장에서 채광, 측량도면 및 지질도 등을 토대로 지반침하지 인근의 갱도 및 산사면 붕괴지에 대한 지질조사 및 전기비저항탐사를 수행하였으며, 그 결과들로부터 지질공학적 평가를 수행하고 다양한 경험식과 수치해석 방법에 의해 지반침하의 원인을 분석하였다. 해석 결과로부터 다양한 불연속면이 발달한 불안정한 지반 내에서 채굴공동의 폭이 넓고 불규칙한 Pillar 설치로 인하여 오랜 기간 동안 채굴적 천단부 및 Pillar가 점진적으로 이완되면서 지반응력의 증가로 단층면을 따라 붕락되어 지반침하가 발생된 것으로 판단된다.

• 지질공학
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• 제32권4호
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• pp.571-583
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• 2022

On 7 August 2020, a large-scale catastrophic landslide was triggered by extreme rainfall at Osan village, Gokseong County, South Jeolla Province, South Korea. The initiation mechanism of the Gokseong landslide was different from those typical landslides that occurred in South Korea. Despite the relatively low elevation and slope degree, the landslide had a long runout distance of about 640 m over a total vertical distance of 90 m. A detailed field investigation and chemical analysis were conducted to understand the possible mechanisms for the high-speed and long-runout behavior of the landslide. The terrain controlled the motion behavior of the landslide and the seepage was observed at the whole landslide body. The clay-rich soils covered on granite bedrock of the landslide deposition area from the rice paddy field to the landslide crown. The results of this study may provide basic data for further research on the mechanisms for landslide initiation and propagation.

• 대한지리학회지
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• 제47권5호
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• pp.641-653
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• 2012

강원 영동지역의 천진호와 쌍호에서 확보한 석호 퇴적물을 분석한 결과, 천진호는 AD 780에, 쌍호는 100 BC에 벼농경이 개시된 것으로 추정된다. 두 지점이 멀지 않은 거리 내에 있고 해안으로 연결되어 있음에도 불구하고 벼농경 시작 시점에 큰 차이가 나타나고 있다. 이는 화분자료를 활용하여 특정지역 벼농경문화의 정확한 전파 시점을 파악하는 것이 쉽지 않음을 시사한다. 강원 영동 지역의 경우, 낮은 농경 생산성으로 말미암아 벼농경 문화가 최초로 전파된 시점과 벼농경이 본격적으로 시작된 시점 간에 시간적인 차이가 있었던 것으로 사료된다. 천진호 및 쌍호 분석 자료 모두에서 벼농경이 본격적으로 시작된 지 약 250년 후부터 농경지시화분들의 중요도가 더욱 커지고 산지의 침식이 빠르게 증가하는 모습이 나타난다. 이는 벼농경의 활성화로 인구가 증가함에 따라 저지대에서 산지로 거주지역의 확대가 나타났고 이로 인해 산림이 영향을 받았음을 시사한다.