• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.3
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• pp.174-187
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• 2011

The flowed soil is able to be estimated from topographic data of before and after the debris flow. However, it is often difficult to obtain airborne LiDAR data before the debris flow area. Thus, this study tries to develop a topographic restoration method that can provide spatial distribution of flowed soil and reconstruct the topography before the debris flow using airborne LiDAR data. The topographic restoration method can express a numerical formula induced from a Gaussian mixture model after extracting the cross sections of linear or non-linear in debris flowed area. The topographic restoration method was verified by two ways using airborne LiDAR data of before and after the debris flow. First, each cross section extracted from the debris flow sites to restore the topography was compared with airborne LiDAR data of before the debris flow. Also, the topographic data produced after the topographic restoration method applied to the debris flow sites was verified by airborne LiDAR DEM. Verifying the results of the topographic restoration method, overall fitting accuracy showed high accuracy close to 0.5m.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.277-277
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• 2021

합류부는 인공수로 또는 자연하천에서 흔히 존재하며 매우 복잡한 흐름 구조가 발생하는 곳이다. 특히 본류와 지류의 유속장의 차이에 따라 발생하는 전단층은 흐름과 물질이 혼합되는 경계면이 되며, 흐름 구조가 전단층을 따라 발달한다는 특징으로 인해 수리학적으로 매우 중요하다. 최근 원격탐사 기법의 발전에 따라 위성이나 드론과 같은 무인 이동체를 이용한 하천 계측법이 수질 및 지형변화 연구들에 광범위하게 적용되고 있다. 그 중 RGB 항공영상은 해상도가 높고 취득 비용이 저렴하여 확장성 및 활용도가 높다. 본 연구에서는 합류부 전단층이 촬영된 RGB 항공 영상을 이용해 합류부 전단층 분석에 활용하는 방법을 제안한다. 제안되는 방법은 RGB 항공 영상에서 본류와 지류의 수체 영역을 각각 추출하기 위해 가우시안 혼합 모형(Gaussian mixture model)을 이용한다. 추출된 수체 영역에는 자기조직화지도(self-organizing map)을 적용하고 좌표 변환을 하여 정량적인 특징을 추출한다. 본 연구에서는 알고리듬의 적용 예로서 구글어스를 통해 확보된 낙동강-남강 합류부의 항공 영상을 분석한다. 본 추출법을 이용하면 접촉식 센서를 이용하는 기존의 전단층 계측 방법들에 비해 경제적이고 안전하며 합류부 흐름의 평면적 분석을 가능하게 할 수 있을 것으로 기대된다.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.5
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• pp.617-623
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• 2010

In this research an LMI based mixed $H_2/H_{\infty}$ controller for a Wheeled Inverted Pendulum is designed and a numerical simulation of that is carried out. The Wheeled Inverted Pendulum is a kind of an inverted pendulum that has two equivalent points. To keep that the naturally unstable equivalent point, a controller should control the wheels persistently. Dynamic equations of the Wheeled Inverted Pendulum are derived with considering inclined road that is one of the representative road conditions. A Linear Matrix Inequality method is used to construct a controller that is able to stabilize the Wheeled Inverted Pendulum with considering the inclined road condition aggressively. Various numerical simulations show that the LMI based controller is doing well on not only flat road but also inclined road condition.

• Journal of the Korean Geotechnical Society
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• v.31 no.2
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• pp.65-73
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• 2015

The bank revetment work which is conducted on the slope of river bank to protect against flowing water as a geotechnical structure has been applied as an average value of critical tractive force based on domestic and international standard design. Currently, an appropriate evaluation is needed for the hydraulic stability and geotechnical behavior analysis of bank revetments because of the effects of climate change and ambiguous design criterion. This study has compared the critical tractive forces of soil improvement material and conventional materials used for the bank revetment work. Through various experiments, the shear strength of mixtures with soil improvement material was investigated by curing time and mixture ratio. It was found that the critical tractive force of the mixture obtained from a scour test is suitable to the reinforcement of the slope of river bank which has problems such as seepage erosion and scour.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.41-46
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• 2010

In this paper, we propose a detection method of reduced computational complexity aimed at separating the moving objects from the background in a generic video sequence. In generally, indoor environments, it is difficult to accurately detect the object because environmental factors, such as lighting changes, shadows, reflections on the floor. First, the background image to detect an object is created. If an object exists in video, on a previously created background images for similarity comparison between the current input image and to detect objects through several operations to generate a mixture image. Mixed-use video and video inputs to detect objects. To complement the objects detected through the labeling process to remove noise components and then apply the technique of morphology complements the object area. Environment variable such as, lighting changes and shadows, to the strength of the object is detected. In this paper, we proposed that environmental factors, such as lighting changes, shadows, reflections on the floor, including the system uses mixture images. Therefore, the existing system more effectively than the object region is detected.

• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.94-97
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• 2001

Electro-conducting Polypyrrole(PPy) films were Prepared by applying constant current in various electrolytes solutions and their capacitance properties were investigated using cyclic voltammetry. Capacitance values were strongly dependent on the electrolytes solution used in electrochemical polymerization. PPy prepared in PC/AN mixture solution containing 0.5M $LiClO_4$ with small amount water showed 401 F/g and that electrogenerated in $AN/H_2O$ mixture solution containing 0.5M $LiClO_4$ retained $70\%$ of initial capacitance after 2000 cycles.

• Fire Science and Engineering
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• v.23 no.6
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• pp.111-115
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• 2009

Acetone LIF and Rayleigh scattering measurements were performed to identify the entrainment of ambient air in the buoyant jet qualitatively. The air entrainment near nozzle exit was enhanced with increasing both an axial distance and Reynolds number. The results supported that the air entrainment had to be considered in isothermal model for the development of its accuracy. Also, this paper provided an isothermal model based on the ideal plume, of which radiative heat loss fraction was assumed to 0.35 and the entainment of isothermal jet was considered. This simple model could be used in compartment or semi-enclosure fires such as tunnel, and it is more reliable because of introducing entrainment effect in isothermal jet.

• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.57-66
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• 2000

OH radical and NO distributions have been measured in methane/air partially premixed counterflow flames(${\alpha}$=1.0, 0.8, 0.6) using PLIF technique. The results are discussed and compared with the numerical analysis results obtained under the same flame conditions. Measured OH and NO LIF signals agree with the computed concentration distributions. Both numerical and experimental results indicate that the structural change in a flame alters the NO formation characteristics of a partially premixed counterflow flame. The nitrogen dilution also changes flame structure, temperature and OH radical distributions and results in the decreased NO concentrations in a flame. The levels of decrease in NO concentrations, however, depends on the premixedness(${\alpha}$) of a flame. The larger change in the flame structure and NO concentrations have been observed in a premixed flame($\alpha$=1.0), which implies that the premixedness is likely to be a factor in the dilution effect on NO formation of a flame.

• Fire Science and Engineering
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• v.15 no.2
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• pp.91-95
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• 2001

Decays of the ceiling jet front velocity under a circular ceiling are investigated. To simulate the ceiling jet in fires He and $N_2$gas were injected from a nozzle to the center of the ceiling. The jet fronts in the form of turbulent eddies were traced by a high-speed camera system. The instantaneous locations of the front were obtained from visual readings of visualized front, and the radial velocity was calculated from the information of the time and the location with respect to the front. The similarity and dimensional analysis were also carried out to reveal the relationship between the velocity decay and the radial distance. It was shown that the radial velocity of the front was inversely proportional to the radial distance in the fully developed region from the experimental results and the theoretical analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.77-83
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• 2002

A computational study on the performance prediction of a two-stage axial compressor has been performed. A quasi-steady mixing-plane method is used on the rotor/stator interface to simulate the unsteady interaction phenomena. Detail flow mechanisms, for example, choke, stall, shock/boundary interaction, etc., have been observed and discussed in conjunction with performance characteristics. Calculational data agree reasonably well with the experimental data in terms of the performance characteristics showing the applicability of computational methods to the design validation of multistage axial compressors instead of experimental methods. But it is found that the stall margin of the original compressor was rather small, thus the design modification adopting a simple 1D/2D method has been conducted and its corresponding computations are also carried out. As a result of the redesign process, the stall margin becomes wide enough, but the overall performance is unsatisfactory, therefore, it seems that the redesign of the blades using 3-D methods is needed in the future work.