곡률 단조성을 유지하는 Bezier Spiral의 설계

李玄燦,洪錫瑢 弘益大學校 科學技術硏究所 2000 科學技術硏究論文集 Vol.11 No.-

Many spiral segments are useful in the design of fair curves. They can be used in CAD/CAM systems, the design of highway and railway and the design of trajectories of mobile robots. In this paper, we propose a new method to calculate Bezier spirals under the condition that the curvature of the Bezier spirals is absolutely monotone. The main purpose of this paper is to find a unique Bezier spiral that matches given G¹ Hermite data. Using the G¹ Hermite data, Bezier spiral can be calculated with a equation. However, the equation for calculating the Bezier spiral is not derived from the first derivative of curvature of a Bezier curve. Instead, the equation is derived from approximation values of discrete curvatures for the control points of the Bezier curve. Designers can control the degree of Bezier spirals freely with our new Bezier spirals.

CAD에서의 물체의 기하학적 및 위상학적 요소들의 매개변수화 전략

李玄燦 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.5 No.-

Parametric design is a very useful tool for product modeling and modification. In this paper, we propose a 2D parametric design system is based on macro programming in the AutoCAD design system. Using AutoLISP, we define new commands which provide parametric design. User can design a product parametrically using the new commands and the sequence of design is stored in a history file. When design changes are occurred, the history file is used for producing new product model. The 3D parametric design system is based on features. Features are local shapes of a product which are directly related to manufacturing methods. To utilize features in design, features are defined parametrically in the form of primitive instancing and stored in a feature library. A product model is represented by a CSG tree, a binary tree. By evaluating the CSG tree, a product model is produced.

제품 정보 국제 표준 STEP에서의 공통 형상 표현 지원 내용 연구

李玄燦 弘益大學校 科學技術硏究所 2004 科學技術硏究論文集 Vol.15 No.-

The STEP stands for standard for exchange of product model data. It represents ISO 10303. In the STEP, common shape representation is supported by various part groups. In this paper, four major part groups are investigated. The first part group is part 40's, the integrated generic resources, which provide the fundamental framework for shape representation. The second part group is part 500's, the AIC (Application Interpreted Constructs), which provide common shape representation for APs (Application Protocol). The third part group is part 50's and 100's, the parametrics, which provide the representation schemes for variational design and history-based parametric design. The fourth part group is the rest of STEP parts which are involved in shape representation such as AP 203. In this paper, these part groups are summarized in terms of common shape representation supports and relationship among these parts are analysed. Finally, based on the analysis, future works in these fields in Korea are proposed.

제4차산업혁명과 로봇기술, 관광산업에의 영향

이현찬,양위주 동북아시아문화학회 2017 동북아시아문화학회 국제학술대회 발표자료집 Vol.2017 No.10

The purpose of this study is to review the effect of the fourth industrial revolution on robotics of tourism industry in China. The related cases were taken and briefly reviewed. The findings suggested that the communication channel between the central government and public sector resulted in the current top leader in the relevant around the world.

제품 정보 국제 표준 STEP에서의 매개변수 설계 방법론 지원 내용 연구

李玄燦,洪忠成 弘益大學校 科學技術硏究所 2003 科學技術硏究論文集 Vol.14 No.-

The STEP stands for standard for exchange of product model data. It represents ISO 10303. In the STEP, parametric design methodology is supported by various parts. The first part is ISO 10303-55: integrated generic resource: procedural and hybrid representation. The second part is 10303-108: integrated application resource: parameterization and constraint for explicit geometric product models. The third part is ISO 10303-NWI: integrated application resource: 2D standard modeling commands for the procedural parametric exchange. And the last part is ISO 10303-111: integrated application resource: construction history features. In this paper, these parts are summarized in terms of parametric design supports and relationship among these parts are analysed.

소수의 불규칙적인 이차원 모양군이 지속적으로 반복되는 경우의 재료절단 알고리즘 개발

이현찬 대한산업공학회 1993 대한산업공학회 춘계학술대회논문집 Vol.1993 No.5

기존의 곡면 분할 알고리듬 비교 연구

李玄燦,朱柄俊,洪忠成 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

Recently, designing and visualizing 3D objects become getting more important issues in related industrial fields due to new trends such as Virtual Design using CAD(Computer-Aided Design) systems and high-speeded internet. In this paper, we compare the existing surface subdivision algorithms. Subdivision algorithm is a 3D modeling technique that generates a very smooth surface through many times of refinement processes that split polygons of control mesh into several smaller polygons. We examine the methods of calculating new vertices and topological algorithms of three existing subdivision algorithms, Doo-Sabin, Catmull-Clark, and Loop subdivision scheme in detail, and compare them to find the differences, merits and demerits. In calculating new vertices, Doo-Sabin scheme is simpler than Catmull-Clark and Loop schemes. But in topological algorithm, Catmull-Clark and Loop schemes are simpler than Doo-Sabin scheme.

기하학적 모형을 위한 꼭지점 중심의 쿼드트리와 옥트리

이현찬,이철동,Lee, Hyeon-Chan,Lee, Cheol-Dong 한국전자통신연구원 1989 전자통신 Vol.11 No.1

We developed new quadtree and octree representation schemes which reduce the storage requirements from exponential to polynomial. The new schemes not only lessen the large storage requirements of the existing quadtree and octree representation schemes but guarantee an exact representation of the original object. These are made possible by adopting a new set of termination conditions that ensure finiteness of the quadtree and octree during the decomposition. These new data structures are analyzed theoretically and tested empirically. For space complexity, we analyzed its best case, worst case, and average case. Given an $n_e$-gon, we show that the expected number of nodes in our quadtree isO($$$n_e^1.292$) For a polyhedron with $n_f$ faces, the expected number of nodes in the new octree is O($$$n_f^1.667$). For time complexity, we again analyzed the best, worst, and average cases for constructing such quadtree and octree and find the average to be the same as those of the space complexity. Finally, random $n_e$- gons are generated as test data. Regression equations are fitted and are shown to support the claims on the average case performance.

솔리드 모델링

이현찬 한국CDE학회 1997 한국CAD/CAM학회학회지 Vol.3 No.2

솔리드 모델링은 형상 모델링(geometric modeling) 기법 중 3차원 형상을 솔리드의 형태로 표현하기 위한 기법으로 컴퓨터가 디자인에 사용되기 시작하면서 3차원 형상을 컴퓨터에 어떻게 표현할 것인가를 연구하는 분야이다. 이 분야는 다른 CAD분야의 핵심이 되고 있게 때문에 이들과 중복되는 내용이 많으나 다른 분야에 대한 내용이 별도로 서술되기 때문에 본 고에서는 이들과 중복되지 않는 내용을 중심으로 최근의 연구동향에 대하여 알아보기로 한다.

펜타센 분자의 배향 각도에 따른 전하 수송 특성의 이론적 연구

이현찬,이현복 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.10

유기물 반도체는 그 기계적 유연성으로 인해 늘어나는 전자 소자에 사용될 수 있어 많은 주목을 받고 있다. 유기물 반도체의 고유한 특성 중 하나는 전하이동도가 분자 배향에 따라 크게 변화한다는 것이다. 따라서, 고효율 유기물 반도체 소자를 설계하기 위해서는 적절한 이론 모델을 사용하여 다양한 분자 배향에 따른 유기 반도체의 전하 수송 특성을 이해하는 것이 중요하다. 본 연구에서는 대표적 $p$형 유기물 반도체인 펜타센(pentacene)의 이론적 전하 수송 특성을 1 차원 분자 배열을 가정하여 계산하였다. 밀도범함수이론(DFT)과 이론적 모델을 사용하여 기판에 대한 펜타센 분자 각도 변화에 따른 재구조에너지, 전자결합도, Marcus 이론에 기초한 전하수송률 및 이론적인 전하이동도를 계산하였다. 이러한 방법을 통해 계산된 전하이동도를 3 차원 결정 구조에서의 전하이동도와 비교하였다. 계산된 결과들에 기초하여 분자 배향 제어를 통한 유기물 반도체 소자의 전하이동도 향상법에 대해 논의하였다. Organic semiconductors are receiving much attention because they can be utilized in stretchable electronics due to their mechanical flexibility. One of the unique properties of organic semiconductors is that the carrier mobility is significantly changed with molecular orientation. Therefore, a fundamental understanding of the charge transport properties of organic semiconductors with various molecular orientations based on a proper theoretical model is of great importance in designing efficient organic electronic devices. In this study, we investigated the theoretical charge-transport properties of pentacene, a benchmark $p$-type organic semiconductor, with various molecular orientations under the assumption of a 1-dimensional molecular array. The reorganization energy, electronic coupling, charge transport rate based on the Marcus theory, and theoretical mobility were calculated for various pentacene molecular angles relative to the substrate by using density functional theory and a theoretical model.