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우윤환(Yoonhwan Woo),주창업(Changupp Choo) (사)한국CDE학회 2009 한국CDE학회 논문집 Vol.14 No.5
Automatic generation of the mid-surfaces of a CAD model is becoming a useful function in that it can help increase the efficiency of engineering analysis as far as it does not affect the result seriously. Several methods had been proposed previously to automatically generate the mid-surfaces, but they often failed to generate the mid-surfaces of complex CAD models. Due to the inherent difficulty of this mid-surface generation problem, it may not be possible to come up with a complete and general method to solve this problem. Since a method that can handle a specific case may not work for different cases, it seems that developing case-specific methods ends up with solving only a fraction of the problem. In this paper, therefore, we propose a method to generate mid-surfaces based on a divide-and conquer paradigm. This method first decomposes a complex CAD model into simple volumes. The mid-surfaces of the simple volumes are automatically generated by the existing methods, and then they are converted into the mid-surfaces of the original CAD model.
선택적 볼륨분해를 이용한 정적 CAD 모델의 함몰특징형상 수정
우윤환(Yoonhwan Woo),강상욱(Sang Wook Kang) (사)한국CDE학회 2011 한국CDE학회 논문집 Vol.16 No.3
Static CAD models are the CAD models that do not have feature information and modeling history. These static models are generated by translating CAD models in a specific CAD system into neutral formats such as STEP and IGES. When a CAD model is translated into a neutral format, its precious feature information such as feature parameters and modeling history is lost. Once the feature information is lost, the advantage of feature based modeling is not valid any longer, and modification for the model is purely dependent on geometric and topological manipulations. However, the capabilities of the existing methods to modify static CAD models are limited. Direct modification methods such as tweaking can only handle the modifications that do not involve topological changes. There was also an approach to modify static CAD model by using volume decomposition. However, this approach was also limited to modifications of protrusion features. To address this problem, we extend the volume decomposition approach to handle not only protrusion features but also depression features in a static CAD model. This method first generates the model that contains the volume of depression feature using the bounding box of a static CAD model. The difference between the model and the bounding box is selectively decomposed into so called the feature volume and the base volume. A modification of depression feature is achieved by manipulating the feature volume of the static CAD model.
제품개발을 고려한 캐드모델의 응용성 향상을 위한 모델링교육
우윤환(Woo, Yoonhwan) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.3
CAD를 이용한 제품의 설계는 전체적인 제품개발공정의 효율성에 있어 핵심적인 역할을 하고 있다. 따라서 설계자가 어떻게 제품을 모델링 하느냐에 따라 모델의 품질이 달라질 수 있으며 이는 이후에 진행되는 하위 공정의 효율성에 지대한 영향을 끼치게 된다. 이에 본 논문에서는 모델의 품질을 향상할 수 있는 모델링 교육 시 강조하여야 할 3가지 개념을 제시하였다. 이러한 개념을 대학에서의 CAD교육에 적용함으로써, 작게는 모델의 변환과정에 소요되는 시간 및 노력을 현저히 감소시키고, 나아가 제품개발공정의 효율성향상과 동시에 궁극적으로, CAD와 CAM같은 서로 다른 도메인간의 통합에 긍정적인 영향을 줄 것으로 기대한다. The quality of CAD models affects the efficiency of the product development process. However, it seems that CAD modeling education in colleges simply focuses on the creation of CAD models without considering the quality or the applicability of the models. In this paper, we propose educational modeling approaches to help improve the quality and applicability of CAD models. These methods teach students to create models that include a rich set of information, facilitate downstream applications, and are precisely made with the fewest operations. A survey was carried out with students to validate these approaches.
우윤환(Yoonhwan Woo) (사)한국CDE학회 2011 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2011 No.1
In the last two decades, CAD systems have undergone a revolutionary change with the advent of the feature-based, parametric solid modeling. As opposed to the traditional methods which assume that there is one correct representation for a given part, a part can be created using several approaches with different sets of features in solid modeling. The criteria for the quality of a model can be the precision of geometric representation and the level of information that the model contains. It is obvious that the quality of CAD models affects the efficiency of product development process. However, it seems that CAD modeling education in colleges still focus on creations of CAD models without consideration of the quality of the models. In this paper, we propose several education approaches that help improving the quality of CAD models.
기능화된 실리카 비드를 이용한 수용액상의 중금속 이온의 제거공정에 대한 모사 연구
우윤환(Yoonhwan Woo),주창업(Changupp Choo) 한국청정기술학회 2011 청정기술 Vol.17 No.2
본 연구에서는 수용액상의 금속이온을 기능화된 구형의 실리카 담체를 이용하여 제거하는 공정에 대하여 유한 차분법을 이용하여 모사하였다. 평형 모델과 비평형 모델을 수립하여 무차원 변수와 각종 변수에 대한 영향을 살펴보았으며 평형 모델과 비평형 모델의 결과를 비교하였다. 평형모델의 경우 Freundlich 등온식을 사용하였으며 비평형 모델의 경우 1차 반응속도를 가정하였다. 평형모델과 비평형 모델의 경우 변수값에 따라 비숫한 경향을 나타내었으며 금속이온 제거공정의 효율을 예측할 수 있었다. 문헌에 제시된 실험값을 활용하여 평형 모델의 예측 결과를 비교한 결과 부합되는 결과를 나타내었다. The removal process of heavy metal ion in aqueous solution by the functionalized silica bead was simulated using the finite difference method. Equilibrium model and non-equilibrium model were proposed and the effects of dimensionless groups and various parameters were investigated. Freundlich isotherm was used in equilibrium model and 1st order adsorption rate expression was assumed in non-equilibrium model. The comparison results by the predictions of equilibrium and non-equilibrium models showed good agreement. The predictions of equilibrium model were compared with experimental results reported in literature and showed the marginal agreement.