• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.805-817
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• 2016

This study considered the existing approximation theories of solitary wave for stable generation of it with different waveforms in a hydraulic/numerical wave tank for coping with the tsunami. Based on the approximation theory equations, two methods were proposed to estimate various waveforms of solitary wave. They estimate different waveforms and flow rates by applying waveform distribution factor and virtual depth factor with the original approximate expressions of solitary wave. Newly proposed estimation methods of solitary wave were applied in the wave generation of hydraulic/numerical wave tank. In the result, it was able to estimate the positional information signal of wave generator in the hydraulic wave tank and to find that the signal was very similar to an input signal of existing hydraulic model experiment. The waveform and velocity of solitary wave was applied to the numerical wave tank in order to generate wave, which enabled generate waveform of tsunami that was not reproduced with existing solitary wave approximation theory and found that the result had high conformity with existing experiment result. Therefore, it was able to validate and verify the two proposed estimation methods to generate stable tsunami in the hydraulic/numerical wave tank.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.1
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• pp.19-30
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• 2007

Modeling 3D buildings is an essential process to revive the real world into a computer. There are two ways to create a 3D building model. The first method is to use the building layer of 1:1000 digital maps based on high density point data gained from airborne laser surveying. The second method is to use LiDAR point data with digital images achieved with LiDAR. In this research we tested one sheet area of 1:1000 digital map with both methods to process a 3D building model. We have developed a process, analyzed quantitatively and evaluated the efficiency, accuracy, and reality. The resulted differed depending on the buildings shape. The first method was effective on simple buildings, and the second method was effective on complicated buildings. Also, we evaluated the accuracy of the produced model. Comparing the 3D building based on LiDAR data and digital image with digital maps, the horizontal accuracy was within ${\pm}50cm$. From the above we derived a conclusion that 3D building modeling is more effective when it is based on LiDAR data and digital maps. Using produced 3D building modeling data, we will be utilized as digital contents in various fields like 3D GIS, U-City, telematics, navigation, virtual reality and games etc.

• The Journal of the Acoustical Society of Korea
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• v.27 no.3
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• pp.140-148
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• 2008

In this study, a numerical method for a time-domain acoustic wave backscattering analysis is established based on a physical optics and a Fourier transform. The frequency responses of underwater targets are calculated based on physical optics derived from the Kirchhoff-Helmholtz integral equation by applying Kirchhoff approximation and the time-domain signals are simulated taking inverse fast Fourier transform to the obtained frequency responses. Particularly, the adaptive triangular beam method is introduced to calculate the areas impinged directly by acoustic incident wave and the virtual surface concept is adopted to consider the multiple reflection effect. The numerical analysis result for an acoustic plane wave field incident normally upon a square flat plate is coincident with the result by the analytic time-domain physical optics derived theoretically from a conventional physical optics. The numerical simulation result for a hemi-spherical end-capped cylinder model is compared with the measurement result, so that it is recognized that the presented method is valid when the specular reflection effect is predominant, but, for small targets, gives errors due to higher order scattering components. The numerical analysis of an idealized submarine shows that the established method is effectively applicable to large and complex-shaped underwater targets.

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.419-426
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• 2009

To realistically simulate fluid, the Navier-Stokes equations are generally used. Solving these Navier-Stokes equations on the Eulerian framework, the non-linear advection terms invoke heavy computation and thus Semi-Lagrangian methods are used as an approximated way of solving them. In the Semi-Lagrangian methods, the locations of advection sources are traced and the physical values at the traced locations are interpolated. In the case of Stam's method, there are relatively many chances of numerical losses, and thus there have been efforts to correct these numerical errors. In most cases, they have focused on the numerical interpolation processes, even simultaneously using particle-based methods. In this paper, we propose a new approach to reduce the numerical losses, through improving the tracing method during the advection calculations, without any modifications on the Eulerian framework itself. In our method, we trace the grids with the velocities which will let themselves to be moved to the current target position, differently from the previous approaches, where velocities of the current target positions are used. From the intuitive point of view, we adopted the simple physical observation: the physical quantities at a specific position will be moved to the new location due to the current velocity. Our method shows reasonable reduction on the numerical losses during the smoke simulations, finally to achieve real-time processing even with enhanced realities.

• Journal of the Korean Operations Research and Management Science Society
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• v.5 no.1
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• pp.89-90
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• 1980

원래 다량자료의 정리(Large Scale Data Screening)는 어떤 정립된 이론에 의해 수행되는 것보다는 그 자료자체가 가지는 성격과 자원의 Availability 등을 고려하여 수행되는 것이 상례이다. 여기서는 여러 방법 중 자료가 모두 수치로 나타나는 경우 자료정리의 한 유용한 방법으로 회귀분석을 사용하는 방법에 대해 설명코자 한다.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.2
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• pp.24-33
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• 1989

본 고에서는 이러한 추세에 따라서, 보다 효율적인 optimization program에 대해서 소개하고자 한다. 사용한 최적화 알고리즘은 ALM(augmented lagrange multiplier) 방법을 적용해서 구속조건이 있는 문제를 구속조건이 없는 문제로 변환한 후, self-scaling BFGS(broydon-flecher-goldfarb-schanno)를 적용한다. BFGS의 각 descent 방향에서의 step 길이는, sequential search로 unimodal point를 구해서, golden section 방법으로 refine을 한후, cubic approximation을 적용해서 구한다.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.54-61
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• 2008

The drawdown distribution due to pumping by horizontal or slanted wells is analyzed by numerical modelling. In the numerical modelling uses 1-D discrete element feature included in commercial groundwater modeling program FEFLOW (version 5.1) and the results are compared with the semi analytic solution which uses superposition of successive point sources proposed by Zhan and Zlotnik (2002). Results of the numerical modeling agree well with the semi analytic solution except for very near field region of sink sources. The drawdown distribution due to pumping in riverbank filtration(RBF) plan site can be evaluated quantitatively by the numerical modeling in this study.

• The Journal of Internal Korean Medicine
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• v.26 no.4
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• pp.753-760
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• 2005

목적 : 본 연구는 100명의 암환자를 대상으로 항암단의 항혈관형성 효과를 측정하기 위하여 고안되었다. 방법 : 100명의 암환자 전체의 치료전후의 VEGF, bFGF 및 혈소판 수치의 변화량을 측정하였고, 병기, 삶의 질 및 암종별로 환자를 나누어 각각의 치료전후의 VEGF, bFGF 및 혈소판 수치의 변화량을 측정하여 통계적 유의성을 살펴보았다. 결과 : 항암단으로 치료한 암환자의 bFGF 수치는 치료전 후 통계적으로 유의성 있게 감소하였다. 특히 유방암 환자에서 bFGF 수치의 감소가 눈에 띄었다. 비록 통계적으로 유의하지는 않았지만 VEGF수치도 항암단으로 치료 후 다소 감소하는 경향을 보였다. 결론 : 따라서 항암단이 암환자 치료에 있어 항혈관형성 약물로써 작용한다고 추론할 수 있다.

• Current Research on Agriculture and Life Sciences
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• v.8
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• pp.115-118
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• 1990

The packed cell volume(PCV) of chicken, volume percentage of erythrocytes in whole blood, was reshuffled of 20%, 40% and 60% using autoplasma, and the red blood cell sedimentation rate was measured in Westergren tubes at room temperature($27{\pm}1^{\circ}C$) and low temperature ($8{\pm}1^{\circ}C$). The results obtained were summarized as follows. 1. The sedimentation rates of chicken red blood cell were settled faster at low PCV than higher PCV, i,e., there was a reverse relationship between the sedimentation rate and PCV. 2. The sedimentation rate of chicken red blood cell was accelerated more at high temperature than low temperature. 3. The sedimentation rate of reshuffled chicken red blood cell by time was almost linear for several hours.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.321-321
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• 2011

최근 기상이변으로 인하여 예측이 어려운 게릴라성 집중호우 등의 증가로 재해 및 재난이 빈번하게 발생하고 있으며, 특히 도시지역에서의 홍수피해로 막대한 인명과 재산피해가 발생하고 있다. 도시지역내로 유입되는 홍수는 다양한 형태와 크기를 가지는 건물과 도로의 배치에 의해 크게 영향을 받으며, 매우 복잡한 흐름특성을 나타내는 것으로 알려져 있다. 도시지역이 조밀한 건물군으로 구성되어 있을 경우 홍수의 대부분은 도로와 교차점을 통해 흐르므로 도시지역 내에서 홍수로 인한 피해를 저감하기 위해서는 도로 교차로에서의 홍수파의 전파특성을 분석하는 것이 중요하다. 교차로는 세 개 또는 네 개의 도로가 대칭 또는 비대칭으로 연결되어 있으며, 일반적으로 교차로에서의 흐름은 유입되는 유량이 상대적으로 적고 도로의 경사가 비교적 완만한 경우 상류 특성을 나타내나 이와 반대일 경우에는 상류 및 사류가 공존하는 복잡한 수면형을 나타낸다. 본 연구에서는 도지지역 내 도로 교차점에서 유입경사 변화에 따른 도로 교차부에서의 흐름특성을 수치모의 결과와 수리실험 결과와 비교하였다. Case 1은 수로의 유입경사가 3%일 경우 도로 교차로에서 수위 및 흐름특성을 수치모의결과와 비교한 결과 조도계수가 0.0086일 경우 RMSE 값은 X축에서는 0.0023, Y축에서는 0.0042로 수로중심에서의 수심분포가 잘 일치 하였으며, 흐름특성 또한 수치모의결과와 잘 일치하는 경향을 보였다. Case 2에서는 검증결과를 바탕으로 유입경사가 3%와 5%일 경우 도로와 교차점에서의 흐름특성을 수치적 방법을 통해 분석하였으며, 유입경사가 변화함에 따른 수면흐름특성을 모의하였다.