• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.299-307
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• 2007

In this study, a new concept for simulating a physical damage of tunnel shotcrete lining due to a long-term chemical deterioration has been proposed. It is known that the damage takes place mainly by internal cracks, reduction of stiffness and strength, which results mainly from volume expansion of the lining and corrosion of cement materials, respectively. This damage mechanism of shotcrete lining appears similar in most kinds of chemical reactions in tunnels. Therefore, the mechanical deterioration mechanism induced by a series of chemical reactions was generalized in this study and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of tunnel structures undergoing external loads as well as chemical deterioration in time. A number of illustrative examples were given to show a feasibility of the model in tunnel designs.

• Radioisotope journal
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• v.15 no.3
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• pp.78-92
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• 2000

낮은 선량의 방사선피폭으로 인한 건강 위해의 여부에 대하여 과학적 현황을 고찰하였다. 선량과 영향 사이에 문턱 없는 선형비례 모델(LN-T모델)에 대해 역학적, 수학적, 방사선생물학적 측면의 긍정적 논리와 호메시스, 적응반응, 통계적 관점의 비판적 논거를 대비하여 평가하였다. 방사선 피폭이력자에게 발현한 확률적 영향 특히 백혈병을 포함한 암에 대해 그 질환의 방사선 인과성 판단에 대한 애로와 접근 방향을 논의하였다. 객관적인 평가 지표의 하나로 기인확률(PC)을 적용하되 근로자에 대한 제도적 배려 등 고려할 사항을 논의하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.516-516
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• 2022

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.189-193
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• 2005

Thermal effect of finite-rate chemistry on linear combustion stability and film cooling effect are investigated in sample rocket engine. The flow variables required to evaluate stability limits are obtained from CFD data with finite-rate chemistry adopted in three dimensional chamber. Major flow variables are affected appreciably by finite-rate chemistry and thereby, the calculated stability limits are modified. It is found that finite-rate chemistry contributes to stability enhancement in thermal point of view. And film cooling also has the effect of combustion stabilization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.75-81
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• 2006

Thermal effect of finite-rate chemistry on linear combustion stability and film-cooling effect are investigated in sample rocket engines. The flow variables required to evaluate stability limits are obtained from CFD data with finite-rate chemistry adopted in three dimensional chamber. Major flow variables are affected appreciably by finite--rate chemistry and thereby, the calculated stability limits are modified. It is found that finite-rate chemistry contributes to stability enhancement in thermal point of view. And film cooling also has the effect of combustion stabilization.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.157-163
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• 2010

Solid oxide fuel cells (SOFCs) are commonly composed of ceramic compartments, and it is known that the physical properties of the ceramic materials can be changed according to the operating temperature. Thus, the physical properties of the ceramic materials have to be properly predicted to develop a highly reliable simulation model. In this study, several physical properties that can affect the performance of SOFCs were selected, and simulation models for those physical properties were developed using our own code. The Gibbs free energy for the open circuit voltage, exchange current densities for the activation polarization, and electrical conductivity for the electrolyte were calculated. In addition, the diffusion coefficient-including the binary and Knudsen diffusion mechanisms-was calculated for mass transport analysis at the porous electrode. The physical property and electrochemical reaction models were then simulated simultaneously. The numerical results were compared with the experimental results and previous works studied by Chan et al. for code validation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.291-299
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• 2018

Under a pyro-processing concept, an electrolytic reduction process has been developed to reduce uranium oxide in molten salt by electrochemical means as a part of spent fuel treatment process development. Accordingly, a model based on electrochemical theory is required to design a reactor for the electrolytic reduction process. In this study, a 1D model based on the phase-field theory, which explains phase separation behaviors was developed to simulate electrolytic reduction of uranium oxide. By adopting parameters for diffusion of oxygen elements in a pellet and electrochemical reaction rate at the surface of the pellet, the model described the behavior of inward reduction well and revealed that the current depends on the internal diffusion of the oxygen element. The model for the electrolytic reduction is expected to be used to determine the optimum conditions for large scale reactor design. It is also expected that the model will be applied to simulate the integration of pyro-processing.

• Journal of Acupuncture Research
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• v.25 no.2
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• pp.105-117
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• 2008

목적 : 만성 염증성 질환에 대한 전침효과를 알아보기 위해 complete Freund's adjuvant(CFA) 유발 관절염 모델의 거퇴 관절 내 염증관련 단백질 및 복합당질의 변화를 살펴보았다. 방법 : Sprague-Dawley계 흰쥐의 족부에 CFA를 주사한 다음 3일 간격으로 2Hz, 15Hz 및 120Hz 전침자극을 주며 부종 형성여부를 plethysmometer로 측정하여 판정하였으며 30일째 거퇴관절을 취하여 4% paraformaldehyde에 고정하고 EDTA용액에서 탈회시켜 파라핀연속 절편을 얻어 $NF-{\kappa}B$를 비롯한 5종의 염증관련 단백질의 발현 및 복합당질 변화를 살펴보았다. 결과 : 관절연골 내 면역반응 중 연골기질은 반응이 없거나 약하고 연골세포는 $NF-{\kappa}Bp65$, $I-{\kappa}B{\alpha}$, iNOS 반응이 강하며 특히 유리연골층에서 더 현저하였으나 염증 및 전침자극에 따른 변화는 없었다. 관절낭에서 면역반응을 살펴보면 염증유발시 활액세포의 면역반응세포는 $I-{\kappa}B{\alpha}$가 감소한 반면 iNOS, $IL-1{\beta}$는 증가하며 특히 iNOS 증가가 현저하였으며 전침자극에 의해 iNOS 가 감소하였다. 활액막조직에서 모든 면역반응이 증가하며 특히 $NF-{\kappa}Bp65$, $I-{\kappa}B{\alpha}$, iNOS 반응이 현저한데 전침자극에 의해 $IL-1{\beta}$를 제외한 모든 반응이 감소하였다. 복합당질 염색성은 CFA를 주사한 염증유발 흰쥐군이 정상군에 비해 감소하였다. 관절연골 중 구역간질의 중성복합당질 및 연골세포피막의 산성복합당질이 현저히 감소하였다 Lectin반응도 DBA을 제외한 모든 발현이 염증유발시 감소하였다. 그러나 전침처리에 의해 정상군과 유사한 염색성과 lectin반응을 유지하였다. 특히 구역간질의 중성복합당질과 연골세포의 sWGA와 RCA-1 반응이 현저하였다. 결론 : 만성 염증성 동물모델의 거퇴 관절 내 염증관련 단백질은 관절연골보다 관절낭에서, 복합당질의 변화는 관절연골에서 큰 변화를 보였으며 전침의 자극에 의해 이들 변화가 억제되는 것을 알 수 있다. 이상의 결과로 보아 전침처치는 염증관련 단백질 발현 및 복합당질의 변화 억제를 통해 만성 관절염 질환에 효과적임을 알 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.327-330
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• 2006

Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base homing process. Overall fluid dynamic process is modeled by Wavier-Stokes equations for reacting flows with two-equation $k-\omega$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.22-25
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• 2005

The thermal degradation of carbon/phenolic composite have been studied at high temperature by using thermogravimetric (TGA). A heating .ate of 5, 10, 15, 30 and $50^{\circ}C/min$ was used for the determination of thermal decomposition parameters of composite materials at high-temperature service. It has been shown that as the heating rates is increased, the peak decomposition rates are occur at higher temperature. Based on results of thermogravimetric analysis, the pyrolysis process is analyzed and physical and mathematical models for the process are proposed. The thermal analysis also has been conducted using transient heat conduction and the in-depth temperature distribution and the density profile were evaluated along the solid rocket nozzle. As a future effort the thermal decomposition parameter determined in this investigation will be used as input to thermal and mechanical analysis when subjected to solid rocket propulsion environment.