• 한국지반공학회논문집
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• 제37권10호
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• pp.27-40
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• 2021

동상민감성 지반의 융기 및 침하 방지를 위한 공법을 지반 안정화 공법이라고 하며 열 사이펀은 대표적인 지반 안정화 공법 중 하나이다. 열 사이펀은 최근 간편한 해석모델 개발과 더불어 열 해석이 진행되었지만, 이에 따른 동상민감성 지반의 열적 거동을 고려하지 않았다. 따라서 본 연구는 열 사이펀의 성능에 따른 지반의 온도 변화를 위한 열 해석과 이에 따른 지반의 거동을 예측하기 위한 구조해석을 동시에 수행하기 위해 ABAQUS 내부 사용자 서브루틴을 사용하여 열 사이펀을 적용한 TM(Thermo-Mechanical) 모델을 개발하여 열 사이펀의 성능에 따른 지반 융기 억제성능을 확인하였다. 해석결과 열 사이펀의 성능 증가에 따라 지반의 최종 융기가 감소하였으며 냉매 충전율 25%, 50% 그리고 100%의 열 사이펀 적용 시 각각 5.5%, 14.4%, 21% 융기 억제성능을 나타내었다.

• 한국정밀공학회지
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• 제20권10호
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• pp.183-190
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• 2003

Major device failures such as die cracking, interfacial delamination and warpage in flip chip packages are due to excessive heat and thermal gradients- There have been significant researches toward understanding the thermal performance of electronic packages, but the majority of these studies do not take into account the combined effects of thermo-mechanical interactions of the different package constituents. This paper investigates the thermo-mechanical performance of flip chip package constituents based on the finite element method with thermo-mechanically coupled elements. Delaminations with different lengths between the silicon die and underfill resin interfaces were introduced to simulate the defects induced during the assembly processes. The temperature gradient fields and the corresponding stress distributions were analyzed and the results were compared with isothermal case. Parametric studies have been conducted with varying thermal conductivities of the package components, substrate board configurations. Compared with the uniform temperature distribution model, the model considering the temperature gradients provided more accurate stress profiles in the solder interconnections and underfill fillet. The packages with prescribed delaminations resulted in significant changes in stress in the solder. From the parametric study, the coefficients of thermal expansion and the package configurations played significant roles in determining the stress level over the entire package, although they showed little influence on stresses profile within the individual components. These observations have been implemented to the multi-board layer chip scale packages (CSP), and its results are discussed.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.538-548
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• 2018

The thermo-acoustic instability in the combustion process of a gas turbine is caused by the interaction of the heat release mechanism and the pressure perturbation. These acoustic vibrations cause fatigue failure of the combustor and decrease the combustion efficiency. This study is to develop a segmented dynamic thermo-acoustic model to understand combustion instability of gas turbine. Therefore, this study required a dynamic analysis rather than static analysis, and developed a segmented model that can analyze the performance of the system over time using the Matlab/Simulink. The developed model can confirm the thermo-acoustic combustion instability and exhaust gas concentration in the combustion chamber according to the equivalent ratio change, and confirm the thermo-acoustic combustion instability for the inlet temperature and the load changes. As a result, segmented dynamic thermo-acoustic model has been developed to analyze combustion instability under the operating condition.

• 태양에너지
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• 제18권2호
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• pp.105-113
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• 1998

일반적으로 열 다이오드(thermo-diode)란 임의의 한 방향으로만 열 전달이 가능하도록 설계된 열 전달 기구이나, 열 흐름이 원하는 방향으로 이루어지는 양방향 열 다이오드를 사용한다면 겨울철 난방과 여름철 냉방부하 감소에 모두 효과적으로 적용될 수 있다. 본 연구에서는 루프형 양방향 열 다이오드를 응용한 태양열 이용 시스템을 설계 제작하였으며, test cell을 이용한 옥외 실험을 수행하여 실용 가능성을 확인하였다.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2173-2187
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• 2022

A 3D thermo-elasto-hydrodynamic model is developed to analyze the sealing performance of a notched mechanical seal applied in the reactor coolant pump. In the model, the generalized Reynolds equation, the energy equation coupled with notch heat balance equation, the heat conduction equations, and the deformation equations of the sealing rings are iteratively solved by the finite element method. The film pressure and temperature distribution are obtained, and the deformation of the sealing rings is revealed to study the mechanism of the notched mechanical seals. A parameterized study is conducted to analyze the sealing performance under different operating conditions. As a comparison, the sealing performance of non-notched seals is also studied. The results show that the hydrostatic effect is dominant in the load-carrying capacity of the fluid film due to the radial mechanical and thermal deformations. The notch can cool the fluid film and influence the thermal deformation of seal rings. The sealing performance is sensitive to the pressure difference, ambient temperature, and rotational speed. It is suggested to set the notches on the softer sealing rings to acquire the greater hydrodynamic effect. Compared with the non-notched, the notched end face holds a better lubrication performance, especially under lower rotational speed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2004년도 동계학술대회 논문집
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• pp.42-42
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• 2004

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2004년도 하계학술발표 논문집
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• pp.196-196
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• 2004

• Coupled systems mechanics
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• 제3권1호
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• pp.89-110
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• 2014

In this work we provide the theoretical formulation, discrete approximation and solution algorithm for instability problems combing geometric instability at large displacements and material instability due to softening under combined thermo-mechanical extreme loads. While the proposed approach and its implementation are sufficiently general to apply to vast majority of structural mechanics models, more detailed developments are provided for truss-bar model. Several numerical simulations are presented in order to illustrate a very satisfying performance of the proposed methodology.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1091-1092
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• 2011

• Corrosion Science and Technology
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• 제18권5호
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• pp.182-189
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• 2019

A thin spray coating of inorganic black lithium polysilicate (IBLP) on black anodized AZ31B magnesium alloy was fabricated for better corrosion resistance and thermo-optical properties for thermal control of spacecraft components. The morphology of the specimens with and without IBLP-based spray coating was characterized by SEM-EDS techniques. Impedance and potentiodynamic measurements on the specimens revealed better corrosion resistance for the specimen with a thin coating of lithium polysilicate. This was primarily due to the presence of lithium polysilicate inside the micro-cracks of the black anodized specimen, restricting the diffusion paths for corrosive media. Environmental tests, namely, humidity, thermal cycling, thermo vacuum performance, were used to evaluate the space-worthiness of the coating. The thermo-optical properties of the coating were measured before and after each environmental test to ascertain its stability. The specimen with an IBLP-based spray coating showed enhanced thermo-optical properties, greater than ~0.90. Hence, the proposed coating demonstrated better handling, better corrosion resistance, and space-worthiness during the pre-launch phase owing to its improved thermo-optical properties.