• Proceedings of the Korea Water Resources Association Conference
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• 1980.08a
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• pp.1-6
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• 1980

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.125-135
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• 1995

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.399-405
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• 2000

In this paper, we deal with block cipher algorithm IDEA(international data encryption algorithm), previously known as typical block cipher system. first of all, analysing key scheduler we classify the key sequences with the used key bit and the unused key bits in each round. with this properties we propose the two method, which are differential analysis using differences of plaintext pairs and linear analysis using LSB bit of plaintexts and key sequences.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2731-2736
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• 2007

In this paper, incompressible flow over a cylinder near a plane wall using the Immersed Boundary. Finite Difference Lattice Boltzmann Method (IB-FDLBM) is implemented. In this present method, FDLBM is mixed with IBM by using the equilibrium velocity. We introduce IBM so that we can easy to simulate bluff-bodies. With this numerical procedure, the flow past a circular cylinder near a wall is simulated. We calculated the flow patterns about various Reynolds numbers and gap ratios between a circular cylinder and plane wall. So these are enabled to observe for vortex shedding. The numerical results are found to be in good agreement with those of previous studies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.282-287
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• 2009

본 논문에서는 사각판이 고정단을 경계조건으로 가진 상태에서 충격력을 받았을 때의 굽힘파 전파와 이에 의한 음향 방사가 특정 공간에서 이루는 음장을 유한 차분 시간 영역법을 이용하여 예측하였다. 이와 같은 시도는 향후 구조물에서의 진동과 음장 사이의 관계를 해석하는데 도움이 될 수 있을 것이다. 대상 시뮬레이션 모델은 한 쪽 끝이 철판으로 이루어진 직육면체의 공간이며 예측 결과를 실험값과 비교하였다. 예측 결과는 대체로 파형과 그 특성이 실험값과 잘 일치하였으나, 감쇠 알고리즘을 주파수 대역에 따라 달리 적용하지 못하였고, 사각 평판에서 충격력의 적용 범위가 모호하여, 파형의 크기에 차이가 있었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.108-120
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• 1992

An ADI model for linearized shallow water equation is modified using the method of factorization. In order to show its validity. the computational results are compared both with the analytical solution and with those from existing models, for a rectangualr domain with constant and varying amplitudes at the open boundary. It is shown the accuracy of numerical solutions depends on the size of time step. depth and bottom friction. The modified ADI model is shown to be superior to the existing models such as Leendertse (1971). Butler (1980) and Sheng (1983).

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.408-418
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• 1986

본 연구에서는 표면은 단단하고 내면은 강인한 조직을 얻기위하여 대형 성형 탄 로울에 대하여 노에서의 급속가열 및 대기 상태에서의 자연냉각의 열처리가 수행 되어진다. 급속가열 및 냉각시 성형탄 로울 내부의 온도 분포 예측을 위하여 대류 및 복사 열전달 경계조건을 가지는 1차원 비정상 열전도 방정식이 유한 차분법을 사 용하여 해석되어졌다. 여기서 급속가열시 연소가스로 부터 기체복사에 의하여 성 형탄 로울의 바깥표면을 통하여 흡수되는 열량은

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1276-1293
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• 1993

A numerical and experimental flow visualization study of the louvered fin array, commonly used in a compact heat exchanger was performed. The flow structure which was obtained by using a finite difference method, was compared with an experimental result. The experimental flow visualization was performed by using a dye injection technique with 13:1 scale model. The effects of Reynolds number and fin geometries on flow structure and heat transfer were examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.653-661
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• 1994

In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 supersonic/transonic compressor cascade flow. H-type grid was chosen for its simplicity in applying cyclic tridiagonal matrix algorithm along with conventional slip/no-slip boundary conditions. The thin-layer algebraic model of Baldwin-Lomax was employed for the calculation of turbulent flows. The test case inlet Mach No. was 1.612 and inlet/exit pressure ratio($P_2/P_1$) was 2.15. The results were compared with experimental results from current method were compared well in suction surface with the experiments and other computational results; however, not well in pressure surface. It might be due to the complex flowfields such as shock/boundary layer interaction, turbulence, and flow separation, etc. In the future, a proper turbulence modelling and adaptive grid system will be studied to improve the solution quality.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.713-716
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• 2000

본 논문에서는 프레임간 압축 영상의 열화 과정의 모델과, 동영상에 존재하는 블록화 현상을 제거하는 방법을 제안한다 BDCT기반으로 압축된 정지영상은 DCT계수를 양자화 하는 과정이 블록별로 처리되기 때문에, 블록 경계에 불연속이 발생한다. 동영상의 경우 블록 경계에서 불연속이 발생 할 뿐만 아니라 움직임 보상과정이 합쳐진 혼성 구조로 되어 있어서 블록 내부에서도 불연속이 존재하게 된다. 블록 영계만을 생각한 기존의 처리방법은 동영상의 처리에 있어 적합하지 못하다. 따라서 본 논문에서는 효율적인 블록화 현상 제거를 위해, 양방향 움직임 보상과 반화소 정밀도를 이용한 새로운 평활화 제약조건을 구성하고 차분 영역에서의 정규화 방법을 이용한 알고리듬을 제안한다.