• 유변학
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• 제10권4호
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• pp.202-216
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• 1998

기존의 'Orthotropic' 근사모델의 개선된 형태인 ORW를 새로운 유동 자료를 이용하여 수치적으로 구하였다. 기존의 'Orthotropic' 근사모델인 ORF나 ORL은 특히 전단유동 하에서 상호작용상수 $C_1$<0.001인 경우 비물리적 진동특성을 나타낸다. 물론 center-gated disk와 같은 비균일 유동하에서도 비물리적 진동특성을 나타내고 'Distribution Function Calculation'과 비교하여 배향 상태를 낮게 예측한다. 이런 현상들은 바로 least-square 최적화 시 사용된 유동 자료에 기인한 것을 알 수 있었다. 작은 상호작용계수의 균일 유동 자료를 이용하여 최적화를 한 ORW의 경우 비물리적 진동특성도 나타나지 않았고 균일 및 비균일 유동하에서 모두 정성적으로 잘 일치함을 확인할 수 있었다. 최적화 시 사용된 함수의 선택은 근사모델을 발전시키는데 그다지 영향을 미치지 못하였다. 하지만, 모든 배향 텐서의 eigenvalue들을 고려하면 보다 정량적으로 발전시킬 수 있지만 이들의 함수모양 선택은 중요하고 어려운 문제다. 비교를 위하여 ORW와 다른 여러 가지 근사모델을 이용하여 Film-gated strip과 Center-gated disk에 대한 연계효과 및 평면속도구배를 포함한 사출성형 충전공정의 수치모사를 수행하였다. ORW가 'Distribution Function Calculation' 과 비교하여 정량적으로도 거의 비슷한 결과를 예측함을 보여주지만 실제 실험자료와 비교하였을 때 약간의 차이가 있음을 확인하였다. 따라서 좀 더 정확히 섬유의 배향도를 예측하기 위해서는 섬유들의 상호작용을 나타내는 항의 모델링의 변화가 요구된다.

• 한국건축시공학회지
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• 제1권1호
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• pp.143-150
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• 2001

Permanent-Form is one of system forms for reducing human labor, work costs, oscillation, noise, construction wastes and so on. Permanent-Form is made from precast method in facilities, and carried in construction site to assemble with no demolding. The biggest expense to produce permanent-Form is about manufacturing mold. This papers about structural efficiency evaluation, construction efficiency test. The result of this study is below. (1) In the compressive strength test of column. Fly ash specimen and polymer specimen's strength developed as each 8%, 14% to comparison with standard specimen. The reason of this result from form section area increase and form's reinforcing bar (2) The Degree of column crack in permanent form is lower than another one's The glass fiber's fiber reinforcement effect brings like this. (3) In the flexural load test of beam, the early crack load and maximum load of permanent form use specimen showed 20% higher than standard specimen's. (4) In field application experiment, an constructional error is satisfied with the allowable margin of error, $\pm$5mm (5) When the concrete is placed into the form inside, The transformation degree of permanent form is lower than plywood form's. (6) The concrete packing ability of permanent form is satisfactory. (7) The bonding strength of permanent form shows enough strength - 6kgf/$\textrm{cm}^2$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.43-46
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• 2005

Micro molding technology is a promising mass production technology for polymer based microstructures. Mass production technologies such as the micro injection/compression molding, hot embossing, and micro reaction molding are already in use. In the present study, we have developed a numerical analysis system to simulate three-dimensional non-isothermal cavity filling for hot embossing, with a special emphasis on the free surface capturing. Precise free surface capturing has been successfully accomplished with the level set method, which is solved by means of the Runge-Kutta discontinuous Galerkin (RKDG) method. The RKDG method turns out to be excellent from the viewpoint of both numerical stability and accuracy of volume conservation. The Stokes equations are solved by the stabilized finite element method using the equal order tri-linear interpolation function. To prevent possible numerical oscillation in temperature Held we employ the streamline upwind Petrov-Galerkin (SUPG) method. With the developed code we investigated the detailed change of free surface shape in time during the mold filling. In the filling simulation of a simple rectangular cavity with repeating protruded parts, we find out that filling patterns are significantly influenced by the geometric characteristics such as the thickness of base plate and the aspect ratio and pitch of repeating microstructures. The numerical analysis system enables us to understand the basic flow and material deformation taking place during the cavity filling stage in microstructure fabrications.