• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.299-302
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• 2000

본 연구에서는 원형실린더에 의한 음향파의 산란현상을 전산공력음향학 기법을 이용하여 계산하였다. 특히 전산공력음항학에서 정확도를 위해 요구되는 좌표의 직교성을 유지하기 위해서 그에 대한 적절한 관계식을 유도하였으며 정확성의 검증을 위해서 수치적인 해를 이론적인 해와 비교, 분석하였다. 공간차분법으로는 Taylor 전개를 통하여 차 정확도를 가진 차분법을 바탕으로 주파수 공간에서 최적화 된 DRP(Dispersion Relation Preserving) 기법을 사용하였으며, 시간차분법으로는 Adams-Bashford 방법을 기준으로 최적화된 4단계 외재적(explicit) 적분방법을 사용하였다 벽면 경계조건으로는 가상점 개념을 이용한 경계조건을 사용하였으며 원방 경계조건으로서는 선형화 된 Euler 방정식의 점근해(Asymptotic Solution)을 이용한 방사경계조건(Radiation Boundary Condition)을 사용하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.104-113
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• 1997

In this paper, the effects of intake manifold systems on volumetric efficiency were investigated in the 4-cylinder 4-stroke cycle diesel engines. The effects of intake manifold system were analyzed on resonant speed and on volumetric efficiency. Resonant speed was calculated by acoustic theory and volumetric efficiency by the method of characteristics. The calculation results agreed well with rest results. It was assured that between the resonant speed and the volumetric efficiency there exists good correlation in multi-cylinder engines. As the results, the prediction of resonant speed was useful to design the optimum intake system. It was assured that the intake manifold systems for BOX-type and RAM-type have different characteristics on the trend of volumetric efficiency. Also a procedure to design the desirable intake manifold system was proposed.

• Journal of KSNVE
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• v.10 no.3
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• pp.536-550
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• 2000

Inversitgated in this study are the modal characteristics of the eccentric cylindrical shells with fluid-filled annulus. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier expansion and their results are compared with those of finite element method to verify the validation of the method developed. The effect of eccentricity on the modal characteristics of the shells is investigated using a finite element modeling.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.1
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• pp.44-52
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• 2008

In this paper we consider detecting collisions between characters whose motion is specified by motion capture data. Since we are targeting on massive crowd simulation, we only consider rough collisions, modeling the characters as a disk in the floor plane. To provide efficient collision detection, we introduce a hierarchical bounding volume, the Motion Oriented Bounding Box tree (MOBB tree). A MOBBtree stores space-time bounds of a motion clip. In crowd animation tests, MOBB trees performance improvements ranging between two and an order of magnitude.

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.542-545
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• 2010

통상 분 당 $0.6{\ell}$, 최대 $2{\ell}$의 유량과 토출 압력 5atg의 운전 조건을 만족시키는 미세기포발생기용 소형 왕복동식 공기압축기를 개발하는 것이 본 연구의 목적이다. 미세기포발생기는 현재 농업, 어업, 미용, 수질오염방지 등 여러 방면에서 매우 널리 사용되고 있는데, 이러한 미세 기포를 발생시키기 위해서는 고압의 소형 공기압축기가 요구 된다. 이를 위해 비교적 간단한 구동방식의 왕복동식 압축방법을 선정하여 핵심 설계 항목인 실린더와 피스톤형상, 간극체적, 압축비, 구동모터 출력을 이론적 예측과 실험적 방법을 통하여 최적화하였다. 그 결과 미세기포 발생장치 시스템에서 가장 큰 공간을 차지하고 있는 압축기를 소형화시켰으며 압축기 개발 목표 성능을 달성하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.149-156
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• 2000

Sedimentation and self-weight consolidation tests in cylinder and large model tank and field measurement such as settlement and pore water pressure at each layer by wireless automatic instrumentation system were carried out to investigate the behaviour of dredged marine clay fill. The consolidation behaviour for each reclaimed layer was analyzed from these measured data and numerical analysis result using finite strain consolidation theory. It was fond from this study that the consolidation behaviour of dredged clay fill is heavily dependent on the filling process.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.149-152
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• 2001

The Linear compressor is widely used in Stirling cryocooler for cooling of infrared sensor. The performance of Stirling cryocooler was mainly depending on how much pressure difference can be generated by compressor. The gap between cylinder and piston should be minimized to get high pressure difference, but too small gap cause failure in the cryocooler. In this study, the leakage rate through gap was investigated by using CFD method and simple thermodynamic relation. The results show compression ratio is decreased and leakage rate increased according to increasing gap.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.404-409
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• 2000

Characteristics of secondary vortices is topologically investigated in the near-wake region of a circular cylinder where the Taylor hypothesis does not hold. The three-dimensional flow fields in the wake-transition regime were measured by a time-resolved PIV. For the analysis in a moving frame of reference, the convection velocity of the Karman vortices is evaluated from the trajectory of vortex center which is defined as the centroid of the vorticity field. Then, a saddle point is obtained by applying the critical point theory. Science the distributions of fluctuating Reynolds stresses defined by triple-decomposition are closely related with the existence of secondary vortices. the physical meaning of them is explained in conjunction with vortex center and saddle point trajectories. Finally, the temporal evolution of streamwise vortex is also discussed.

• International Journal of Highway Engineering
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• v.16 no.4
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• pp.87-95
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• 2014

PURPOSES: Evaluation of thermal conductivity and convection properties of asphalt mixture by using thermodynamics. METHODS: In this research, temperature prediction model based on thermodynamics is derived for asphalt mixture in transient state and it is verified with laboratory test results. RESULTS: The derived temperature prediction model shows good agreement with laboratory test results. CONCLUSIONS: It is concluded that the derived model based on thermodynamics and thermal properties in the literature are good enough to capture temperature variation in laboratory test. The approach based on thermodynamics can be applied to more complex temperature simulations.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.6
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• pp.541-548
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• 2000

An area light source in the three dimensional space shines past a scene polygon, to generate two types of shadow volumes for each scene polygon, i.e., one with partial occlusion and the other with the complete occlusion. These are called, penumbra and umbra, respectively. In this paper, consider the problem for computing the umbra of a convex polygon from convex quadric light sources such as circles, ellipses, spheres, ellipsoids and cylinders. First, we give characteristics of the boundary surfaces of the umbra and then propose an algorithm for generating the umbra using them.