• Journal of Power System Engineering
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• v.9 no.2
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• pp.33-39
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• 2005

Experiments are performed to study the mixed convection flow and heat transfer in an inclined parallel plates with the upper part cooled and the lower part heated uniformly. The Reynolds number ranges from $4.0{\times}10^{-3}\;to\;6.2{\times}10^{-2}$, the angle of inclination, ${\theta}$, from 0 to 45 degree from the horizontal line, and Pr of the high viscosity fluid is 909. In this paper, the PIV(Particle image velocimetry) with TLC(Thermo-sensitive liquid crystal) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature field at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. This paper describes the methods, and presents the quantitative visualization of mixed convection. From this study, it is found that the flow pattern can be classified into three patterns which are affected by Reynolds number and the angle of inclination.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.111-121
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• 2005

As the scale of e-commerce has been increasing, information about products and service become diversified, Most current internet shopping mall. however, provides product information to consumers in collective arrangement. thus they devote a lot of efforts and time to select the product they want, In this paper, as providing consumers convenient interfaces adapting feature inquirer and parallel coordinate, a method for selecting a right product through searching the wanted products easily and comparing their features efficiently has been proposed. To evaluate the efficiency of the method proposed in this paper, several experiments to measure the time spent and the number of clicks of mouse taken in finding the product they want have been conducted. The results verify the effectiveness of the proposed method.

• Wind and Structures
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• v.28 no.6
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• pp.355-367
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• 2019

Control of horseshoe vortex in the circular cylinder-plate juncture using vortex generator (VG) was studied at $Re_D$(where D is the diameter of the cylinder) = $2.05{\times}10^5$. Impact of a number of parameters e.g., the shape of the VG's, number of VG pairs (n), spacing between the VG and the cylinder leading edge (L), lateral gap between the trailing edges of a VG pair (g), streamwise gap between two VG pairs ($S_{VG}$) and the spacing between the two VG's in parallel arrangement ($Z_{VG}$) etc. were investigated on the horseshoe vortex control. The study is conducted using surface oil flow visualization and surface pressure measurements in low speed wind tunnel. It is observed that all the parameters studied have significant control effect, either by reduction in separation region or by lowering the adverse pressure along the symmetric axis upstream of the juncture.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.1
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• pp.25-36
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• 2004

This paper proposes and measures the performance of a distributed EIT (Electrical Impedance Tomography) image reconstruction algorithm which has a master-slave structure. The image construction is a computation based application of which the execute time is proportional to the cube of the unknowns. After receiving a specific frame from the master, each computing node extracts the basic elements by executing the first iteration of Kalman Filter in parallel. Then the master merges the basic element lists into one group and then performs the sequential iterations with the reduced number of unknowns. Every computing node has MATLAB functions as well as extended library implemented for the exchange of MATLAB data structure. The master implements another libraries such as threaded multiplication, partitioned inverse, and fast Jacobian to improve the speed of the serial execution part. The parallel library reduces the reconstruction time of image visualization about by half, while the distributed grouping scheme further reduces by about 12 times for the given target object when there are 4 computing nodes.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.67-76
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• 2011

This paper describes the development of interactive visualization techniques and a program that allow us to visualize the structure of the volume data and interactively select and visualize the isosurface components using contour tree. The main characteristic of this technique is to provide an algorithm that draws the contour tree in 2D plane in a way that users easily understand the tree, and to provide an algorithm that can efficiently extract an isosurface component utilizing GPU's parallel architecture. The main characteristic of the program we developed through implementing the algorithms is to provide us with an interactive user interface based on the contour tree for extracting an isosurface component and visualization that integrates with previous isosurface and volume rendering techniques. To show the excelland vof our methods, we applied 3D biomedical volume data to our algorithms. The results show that we could interactively select the isosurface components that represent a polypeptide chain, a ventricle and a femur respectively using the user interface based on our contour tree layout method, and extract the isosurface components with 3x-4x higher speed compared to previous methods.

• Journal of the Korea Computer Graphics Society
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• v.1 no.2
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• pp.213-225
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• 1995

3 차원 볼륨 데이터를 시각화(visualization)하기 위해서는 많은 계산 량과 메모리 량을 필요로 한다. 단일컴퓨터에서 순차 알고리즘을 이용하여 데이터를 시각화하고 분석하는 것은 실시간 응용 프로그램에는 부적합하다. 기존의 병렬 볼륨 렌더링에서의 데이터 분할 방법은 대부분 정적 로드 밸런싱(static load balancing)에 기반하고 있다. 동적 로드 밸런싱에 기반한 기존의 방법들은 불륨 데이터의 정규성(regularity)을 이용할 수 없다는 단점이 있다. 본 연구에서는 3 차원 볼륨 데이터에 대하여 로컬 태스크 큐(local task queue) 기법에 기반한 새로운 로드밸런싱 알고리즘을 제안한다. 제안한 방법은 계산에 참여할 노드(node)들을 PVM(parallel virtual machine)의 동적 프로세스 그룹(dynamic process group: DPG)을 이용하여 정적으로 그룹화(grouping)한다. 각각의 DPG들은 로컬 태스크 큐를 기반으로 단위 서브-블록에 대하여 동적 로드 밸런싱을 수행한다. 최적화된 레이 캐스팅 알고리즘들을 분산 환경에 새롭게 적용함으로써 로드 밸런싱으로 생길 수 있는 오버 헤드를 최소화하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.286-289
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• 2011

VTK와 OSG는 컴퓨터 그래픽스 분야에서 널리 사용되는 오픈 소스 라이브러리이다. VTK는 데이터 가시화에 초점을 맞추어 개발된 라이브러리로 다양한 격자 구조의 수치 데이터를 위한 고수준의 가시화 알고리즘을 제공한다. OSG는 다수의 폴리곤으로 구성된 복잡한 전경을 빠르고 효율적으로 렌더링할 수 있도록 하는 라이브러리로 전경 그래프(scene graph)와 다양한 실시간 렌더링 기술을 제공한다. VTK와 OSG는 서로 다른 목적으로 개발된 라이브러리이기 때문에 어느 한 라이브러리만을 이용해서 대용량의 수치 데이터를 가시화하는 것은 많은 노력을 필요로 한다. 따라서 VTK의 고수준 가시화 알고리즘과 OSG의 실시간 렌더링 기술을 접목하여 대용량 데이터를 빠르게 가시화하고자 하는 시도가 여러 연구 그룹에서 꾸준히 있어왔다. 본 논문에서는 테라 스케일의 거대 용량 수치 데이터를 빠르게 가시화하기 위한 방법으로 병렬 VTK 엔진과 OSG 실시간 렌더링 엔진을 접목한 병렬 가시화 시스템을 제안하고자 한다. 또, 본 논문에서 제안하는 가시화 시스템을 이용해서 실제 테라 스케일 데이터에 적용한 사례를 소개한다.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.6-10
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• 2005

PIV(Particle image velocimetry) presents the flow velocity of whole flow fields in a fraction of a second. Conventional PIV method uses two optical axis configuration during the image grabbing process. That is, the illumination plane and the recording plane must be parallel. This configuration is very natural to grab the whole field without the image distortion. In the real problem, it is often to meet the situation which this configuration is hard to be fulfilled. In this study, we developed new PIV method which only uses single optical axis to grab the particle images. This new PIV method become possible by utilizing the scanning method similar to echo PIV technique. One particle image of scanning PIV consists of scanned several line images and by repeating this scanning process, two particle images were grabbed and processed to produce the velocity vectors.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.922-924
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• 1992

This paper presents a CAE(Computer Aided Engineering)system for solving electrostatic field problems by means of a small size computer such as a personal computer. The system software operated on the personal computer is composed of a CAD(Computer aided Design), electric field analysis by using FEM(Finite Element Method)and DB(Data Base)of insulating materials. In addition, we discuss an application of the system to analyzing electric field such as parallel plate electrodes with an insulation spacer, which result suggests that the visualization of electric field distribution and tolerance for insulation strength enables us to assure a simplified evaluation of the insulating design.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.671-680
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• 2004

We present numerical and experimental results of the periodic flows inside a rectangular container under a background rotation. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify the fundamental reasons of discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.