• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.109-109
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• 2019

본 연구에서는 강우-유출 과정 모의를 위한 GPU 기반 확산파 모형을 개발하였다. 확산파 방정식을 풀기위한 수치기법으로는 유한체적법을 이용하였으며, van Leer TVD limiter를 적용한 MUSCL 기법을 이용하여 각 셀의 인터페이스의 물리적 성질을 재구성하여 구하였다. 또한, 침투를 고려하기 위하여 Horton 침투 모형을 이용하였다. 개발된 모형을 이용하여 1D single overland plane과 2D V-shaped overland에서 강우-유출 과정을 모의실험을 하였으며, 각각 해석해와 dynamic wave model을 이용하여 계산된 수치 결과와 비교하여 본 모형의 정확성을 검증하였다. 또한, 1D와 2D의 기복이 심한 지형에 적용하여 강우-유출과정이 본 모형을 통하여 물리적으로 타당한 해석이 가능함을 검증하였다. 마지막으로 복잡한 실제 지형에 적용하였으며, 측정값과의 비교를 통하여 실제 유역에서의 확산파 모형의 적정성을 검증하였다. 또한, 본 연구에서는 NVIDIA사의 GPU인 Geforce GTX 1050과 GPU의 병렬 연산 처리 능력을 활용할 수 있는 NVIDIA사의 CUDA-Fortran을 이용하여 GPU 기반 확산파 모형을 개발하였다. PC windows에서 CPU(Intel i7, 4.70 GHz) 기반 모형 대비 GPU 기반 모형의 계산속도 성능을 비교한 결과, 격자 간격이 증가할수록 CPU 기반 모형 대비 GPU 기반 모형의 연산 효율이 증가하였으며, 격자 간격이 $3200{\times}3200$일 때, CPU 기반 모형 대비 GPU 기반 모형의 연산 효율이 최대 약 150배 증가하였다.

• Fire Science and Engineering
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• v.18 no.1
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• pp.24-30
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• 2004

In this work the dynamic heat transfer occurring in a cable penetration fire stop system built in the firewall of nuclear power plants is three-dimensionally investigated to develop a test-simulator that can be used to verify effectiveness of the sealants. Here was carried out an experiment to observe the heat transfer in the cable penetration fire stop system made of DOW CORNING products. The dynamic heat transfer occurring in the fire stop system is formulated in a parabolic partial differential equation subjected to a set of initial and boundary conditions. And it was modeled, simulated, and analyzed. The simulation results were illustrated in three-dimensional graphics and were compared with experimental data. Through the simulations, it was shown clearly that the temperature distribution was influenced very much by the number, position, and temperature of the cable streams. It also was found that the dynamic heat transfer through the cable streams was one of the most dominant factors, and the feature of heat conduction could be understood as an unsteady-state process. It is certain that these numerical results are useful for making a performance-based design for the cable penetration fire stop system.

• The korean journal of orthodontics
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• v.32 no.4 s.93
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• pp.275-291
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• 2002

Of various factors indicated for effective use of straight wire appliances, there was a great lack of studies both domestic and international about the curvatures of tooth crowns. This study was performed to investigate the labio/buccal clinical crown curvatures of Korean permanent teeth. For this study, three-dimensional laser scanning was performed on 36 dental casts with normal anatomic structures. Andrews plane and Facial axis of clinical crown (FACC) were designated as horizontal and vertical reference planes respectively. 2 or 3 lines, 1mm apart, were drawn superior, inferior, left and right of these reference planes. A three-dimensional coordinate table was made for points formed by crossing these lines, and averages of each coordinate point on the 36 dental casts were obtained. The curvature equation was made using three-dimensional coordinate points (x,y,z) and by this curvature equation, the curve ratio of each tooth was obtained. Curve ratio changes of each section of teeth were calculated by curve ratios of simplified curves. These two dimensional curves were simplified horizontally and vertically Conclusions for this study are as follows. 1. The basic data of labial and buccal clinical crown curvatures were obtained about Korean permanent teeth. 2. No significant difference was found between male and females. 3. Individual tooth characteristics 1) In maxillary central incisors, the difference in the curve ratio between the gingival and incisal sides was greater than for the other teeth. And the gingival side showed a greater curve ratio. 2) Maxillary canines showed more curvatures in the mesio-occlusal surface than the other surfaces. 3) In maxillary $1^{st}$ premolars, more curvatures were found in mesio-occlusal and disto-gingival surface, thus showing a twisted crown surface, but in maxillary $2^{nd}$ premolars, the crown curvatures of mesial and distal ends became parallel to each other. 4) No significant difference in crown curvatures was found between mandibular central and lateral incisors. 5) Occluso-gingival curvatures of mandibular$2^{nd}$ premolar turned out to be more rounded than mandibular $1^{st}$ premolars or maxillary $2^{nd}$ premolars. From the above conclusions, it can be deduced that the same bracket bases can be used for mandibular central and lateral incisors. But for maxillary $1^{st}\;and\;2^{nd}$ premolars and for mandibular $1^{st}\;and\;2^{nd}$ premolars, because crown curvatures showed significant differences, when making bracket bases there is ample reason to make bracket base curves differently for each type of tooth.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.517-534
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• 2021

Hydrogen fuel is emerging as an new energy source to replace fossil fuels in that it can solve environmental pollution problems and reduce energy imbalance and cost. Since hydrogen is eco-friendly but highly explosive, there is a high concern about fire and explosion accidents of hydrogen fueled vehicles. In particular, in semi-enclosed spaces such as tunnels, the risk is predicted to increase. Therefore, this study was conducted on the applicability of the equivalent TNT model and the numerical analysis method to evaluate the hydrogen explosion pressure in the tunnel. In comparison and review of the explosion pressure of 6 equivalent TNT models and Weyandt's experimental results, the Henrych equation was found to be the closest with a deviation of 13.6%. As a result of examining the effect of hydrogen tank capacity (52, 72, 156 L) and tunnel cross-section (40.5, 54, 72, 95 m²) on the explosion pressure using numerical analysis, the explosion pressure wave in the tunnel initially it propagates in a hemispherical shape as in open space. Furthermore, when it passes the certain distance it is transformed a plane wave and propagates at a very gradual decay rate. The Henrych equation agrees well with the numerical analysis results in the section where the explosion pressure is rapidly decreasing, but it is significantly underestimated after the explosion pressure wave is transformed into a plane wave. In case of same hydrogen tank capacity, an explosion pressure decreases as the tunnel cross-sectional area increases, and in case of the same cross-sectional area, the explosion pressure increases by about 2.5 times if the hydrogen tank capacity increases from 52 L to 156 L. As a result of the evaluation of the limiting distance affecting the human body, when a 52 L hydrogen tank explodes, the limiting distance to death was estimated to be about 3 m, and the limiting distance to serious injury was estimated to be 28.5~35.8 m.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.405-413
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• 2017

In this paper, we study the biaxial buckling analysis of nonlocal MEE(magneto-electro-elastic) nano plates based on the first-order shear deformation theory. The in-plane electric and magnetic fields can be ignored for MEE(magneto-electro-elastic) nano plates. According to magneto-electric boundary condition and Maxwell equation, the variation of magnetic and electric potentials along the thickness direction of the MME plate is determined. In order to reformulate the elastic theory of MEE(magneto-electro-elastic) nano-plate, the nonlocal differential constitutive relations of Eringen is used. Using the variational principle, the governing equations of the nonlocal theory are discussed. The relations between nonlocal and local theories are investigated by computational results. Also, the effects of nonlocal parameters, in-plane load directions, and aspect ratio on structural responses are studied. Computational results show the effects of the electric and magnetic potentials. These computational results can be useful in the design and analysis of advanced structures constructed from MEE(magneto-electro-elastic) materials and may be the benchmark test for the future study.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.59-66
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• 2012

The purpose of this study is to estimate the behavior and the mechanism of debris flow on the slope, which has specially various gradient plane. The numerical simulation was performed by using the Finite Differential Element method (FDM) based on the equation for the mass conservation and momentum conservation. The mechanism of flow type for debris flow is divided into three flow types which are stony debris flow, immature debris flow, and turbulent water flow, respectively. First, flow discharge, water flow depth, sediment volume concentration was investigated by variable input of flow discharge at the straight slope angle and two step inclined plane. As the input of flow discharge was decrease, flow discharge and water flow depth was increased, after the first coming debris flow only reached at the downstream. As the input of flow discharge was increased, the curve of flow discharge and flow depth was highly fluctuated. As the results of RMS ratio, the flow discharge and flow depth was lower two step slope angle than the straight slope angle. Second, the behavior of debris flow was investigated by the four cases of gradient degree at the downstream of slope angle. The band width of flow discharge and flow depth for $14^{\circ}$ between $16^{\circ}$ was higher than other gradient degree, and fluctuation curve was continuously high after 10 seconds.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.2
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• pp.125-132
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• 2019

This paper presents a seismic reliability analysis method for an offshore wind turbine with a twisted tripod support structure under earthquake loading. A three dimensional dynamic finite element model is proposed to consider the nonlinearity of the ground-pile interactions and the geometrical characteristics of the twisted tripod support structure where out-of-plane displacement occurs even under in-plane lateral loadings. For the evaluation of seismic reliability, the failure probability was calculated for the maximum horizontal displacement of the pile head, which is calculated from time history analysis using artificial earthquakes for the design return periods. The application of the subset simulation method using the Markov Chain Monte Carlo(MCMC) sampling is proposed for efficient reliability analysis considering the limit state equation evaluation by the nonlinear time history analysis. The proposed method can be applied to the reliability evaluation and design criteria development of the offshore wind turbine with twisted tripod support structure in which two dimensional models and static analysis can not produce accurate results.

• Journal of Korean Association for Spatial Structures
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• v.8 no.5
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• pp.47-58
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• 2008

Spatial structure is an appropriate shape that resists external force only with in-plane force by reducing the influence of bending moment, and it maximizes the effectiveness of structural system. With this character of the spatial structure, generally long span is used. As a result, large deflection is accompanied from the general frame. the structure is apt to result in a large deflection even though this structure experiences a small displacement in absence. Usually, nonlinear analysis in numerical analysis means geometric nonlinearity and material nonlinearity and complex nonlinearity analysis considers both of them. In this study, nonlinear equation of equilibrium considering geometric nonlinearity as per finite element method was applied and also considered the material nonlinearity using the relation of stress-strain in element. It is applied to find unstable result for tracing load-deflection curve in the numerical analysis tech. especially Arc-length method, and result of the analysis was studied by ABAQUS a general purpose of the finite element program. It is found that the present analysis predicts accurate nonlinear behavior of plane and space truss.

• Journal of Korea Multimedia Society
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• v.15 no.4
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• pp.425-438
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• 2012

In this paper, We propose Augmented Reality (AR) System for the interaction between user's hand motion and virtual object motion based on computer vision. The previous AR system provides inconvenience to user because the users have to control the marker and the sensor like a tracker. We solved the problem through hand motion and provide the convenience to the user. Also the motion of virtual object using a physical phenomenon gives a reality. The proposed system obtains geometrical information by the marker and hand. The system environments like virtual space of moving virtual ball and bricks are made by using the geometrical information and user's hand motion is obtained from the hand's information with extracted feature point through the taping hand. And it registers a virtual plane stably by getting movement of the feature points. The movement of the virtual ball basically is parabolic motion with a parabolic equation. When the collision occurs either the planes or the bricks, we show movement of the virtual ball with ball position and normal vector of plane and the ball position is faulted. So we showed corrected ball position through experiment. and we proved that this system can replaced the marker system to compare to jitter of augmented virtual object and progress speed with it.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.238-244
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• 2001

A method of estimating the fluid drag of a fishing gear and otter board spread in a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of the towing cable (warp) of a trawl system with the field experiments obtained with the SCANMAR system. The shape of hand rope, bridle and float(or ground) rope attached behind otter boards in a horizontal plane was assumed to be of form $y_r=Ax_r^B$. The distance between otter boards (otter board spread) obtained by the three dimensional analysis of a towing cable must be equal to that obtained by the functional equation of the shape of ropes behind otter boards, The angle of attack of ropes which can be obtained from the functional equation enables one to estimate the fluid drag of trawl net (net drag) by subtracting the fluid drag of the hand rope and bridles from the drag component of the tension of hand rope attached just behind the otter boards.