• 한국CDE학회논문집
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• 제5권4호
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• pp.293-300
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• 2000

The non-manifold geometric modeling technique is to improve design process and to Integrate design, analysis, and manufacturing by handling mixture of wireframe model, surface model, and solid model in a single data structure. For the non-manifold geometric modeling, Euler operators and other high level modeling methods are necessary. Boolean operation is one of the representative modeling method for the non-manifold geometric modeling. This thesis studies Boolean operations of non-manifold model with the data structure of selective storage. The data structure of selective storage is improved non-manifold data structure in that existing non-manifold data structures using ordered topological representation method always store non-manifold information even if edges and vortices are in the manifold situation. To implement Boolean operations for non-manifold model, intersection algorithm for topological cells of three different dimensions, merging and selection algorithm for three dimensional model, and Open Inventor(tm), a 3D toolkit from SGI, are used.

• 한국국방경영분석학회지
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• 제10권1호
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• pp.15-22
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• 1984

오일러의 미분 방정식은 보조 방정식을 이용하면 쉽게 일반해를 구할 수 있다. 정의된 유사-오일러 미분 방정식을 풀기 위해 규정된 조건을 만족토록 하면 보조 방정식을 이용하여 일반해를 쉽게 구할 수 있음을 보였다.

• Structural Engineering and Mechanics
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• 제48권5호
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• pp.697-709
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• 2013

A simulation method called modified differential transform is studied to solve the free vibration problems of uniform Euler-Bernoulli beam. First of all, the modified differential transform method is derived. Secondly, the modified differential transformation is applied to uniform Euler-Bernoulli beam free-free vibration. And then a set of differential equations are established. Through algebraic operations on these equations, we can get any natural frequency and normalized mode shape. Thirdly, the FEM is applied to obtain the numerical solutions. Finally, mode experimental method (MEM) is conducted to obtain experimental data for analysis by signal processing with LMS Test.lab Vibration testing and analysis system. Experimental data and simulation results are illustrated to be in comparison with the analytical solutions. The results show that the modified differential transform method can achieve good results in predicting the solution of such problems.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.96-99
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• 1996

본 연구는 CAD/CAM에서 3차원 물체를 표현하는 기법중 하나인 Solid Modeling을 구성하는 데이터 구조를 객체지향화 함으로써 보다 효율적이고 유연한 설계개발환경을 제공하고자 한다. 이를 위해서 가장 일반적으로 Solid Modeling을 표현하는 데이터 구조인 기존의 Half-Edge Data Structure를 기본모델로 하여 점(Vortex), 선(Edge), 면(Face), 입체(Solid)를 객체 Class로 하고 Euler Operator를 Method로 하는 객체지향 반모서리 데이터 구조(Object Oriented Half-Edge Data Structure)를 개발하였다.

• 한국정밀공학회지
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• 제13권7호
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• pp.100-114
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• 1996

In order to create a solid model more efficiently for a plastic or sheet metal product with a thin and constant thickness, various methods have been proposed up to now. One of the most typical approaches is to create a sheet model initially and then transform it into a solid model automatically for a given thickness. The sheet model as well as the transitive model in sheet modeling procedure is a non-manifold model. However, the previous methods adopted the boundary representations for a solid model as their topological framework. Thus, it is difficult to represent the exact adjacency relationship between topological entities and to implement the topological operations for sheet modeling and the transformation procedure of a sheet into a solid. In this paper, we proposed a sheet modeling system based on a non-manifold topological representation which can represent solids, sheets, wireframes, and their mixture. A set of generalized Euler operators for non-manifold topology as well as the sheet modeling capabilities including adding, bending, and punching functions are provided for easy modeling of sheet objects, and they are perfomed interactively with a two dimensional curve editor. Once a sheet model is completed, it can be transformed into a solid automatically. The transformation procedure is composed of the offset functions and the Boolean operations of sheet models, and it is even more comprehensive and easier to be implemented than the precious methods.

• 전자공학회논문지CI
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• 제40권6호
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• pp.127-140
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• 2003

본 논문은 2차원 Discrete Cosine Transform (2D-DCT)의 계산을 새로운 Polynomial 변환을 통하여 1차원 DCT의 합으로 변환하여 계산하는 알고리즘을 개발한다. 기존의 2차원 계산방법인 row-column 으로는 N×M 크기의 2D-DCT에서 3/2NMlog₂(NM)-2NM＋N＋M의 합과 1/2NMlog₂(NM)의 곱셈이 필요한데 비하여 본 논문에서 제시한 알고리즘은 3/2NMlog₂M＋NMlog₂N-M-N/2＋2의 합과 1/2NMlog₂M의 곱셈 수를 필요로 한다. 또한 기존의 polynomial 변환에 의한 2D DCT는 Euler 공식을 적용하였기 때문에 복소 연산이 필요하지만 본 논문에서 제시한 polynomial 변환은 DCT의 modular 규칙을 이용하여 2D DCT를 ID DCT의 합으로 직접 변환하므로 복소 연산이 필요하지 않다.

• 한국컴퓨터그래픽스학회논문지
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• 제4권1호
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• pp.11-19
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• 1998

오일러 연산과 집합 연산과 같은 비다양체 위상 연산은 모델링의 다양한 환경을 제공한다. 이들 연산들은 주어진 모델의 위상 정보를 적합하게 유지하도록 하기 위하여 기하학적인 문제를 발생시킨다. 꼭지점, 모서리와 면과 같은 요소들이 서로 접촉할 때 이들 연산의 내부에서 수행되는 접합 연산은 비다양체 모델의 위상을 수정하는 기본적인 방법이다. 비다양체 모델을 접합할 때는 위상 관계를 추론하여야 한다. 위상 관계의 추론 방법은 위상학적인 방법과 기하학적인 방법의 2 가지 경우로 분류할 수 있다. 위상학적인 방법은 저장되어 있는 위상 정보만을 이용하여 위상 관계를 추론한다. 반면에, 기하학적인 방법은 접합이 일어나는 부분적인 영역에서 기하학적인 형상을 고려하여 위상의 관계를 찾아내는 방법이다. 본 연구에서는 이들 중에서 기하학적인 방법에 관하여 기술한다.

• 한국CDE학회논문집
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• 제5권3호
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• pp.242-254
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• 2000

This paper describes an efficient solid modeling method for thin-walled plastic or sheet metal parts, based on the non-manifold offsetting operations. Since the previous methods for modeling and converting a sheet into a solid have adopted the boundary representations for solid object as their topological framework, it is difficult to represent the exact adjacency relationship between topological entities of a sheet model and a mixture of wireframe and sheet models that can appear in the meantime of modeling procedure, and it is hard to implement topological operations for sheet modeling and transformation of a sheet into a solid. To solve these problems, we introduce a non-manifold B-rep and propose a sheet conversion method based on a non-manifold offset algorithm. Because the non-manifold offset aigorithm based on mathematical definitions results in an offset solid with tubular and spherical thickness-faces we modify it to generate the ruled or planar thickness-faces that are mostly shown in actual plastic or sheet metal parts. In addition, in order to accelerate the Boolean operations used the offset algorithm, we also develope an efficient face-face intersection algorithm using topological adjacency information.

• 한국전산구조공학회논문집
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• 제26권4호
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• pp.247-254
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• 2013

본 논문에서는 해상 시추작업을 위한 heave compensation system의 시뮬레이션 모델을 개발하였다. 우선 시뮬레이션을 위하여, 다물체계 동역학 커널을 개발하였다. 다물체계 동역학 커널은 입력 받은 heave compensation system 시뮬레이션 모델의 운동학적 정보를 이용하여 recursive Newton-Euler formulation 방법을 기반으로 운동방정식을 자동으로 구성하고, 수치적으로 해를 계산하는 기능을 한다. 그리고 해상 시추선에 작용하는 외력을 계산하기 위하여 유체 정역학적 힘과 유체 동역학적 힘을 계산하는 모듈을 개발하였다. 이와 같이 개발한 커널과 모듈들을 적용하여 해상 시추선의 hoisting system 동적거동 해석을 수행하고, 관절에서의 구속력을 계산하였다.

• 한국경영과학회지
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• 제38권1호
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• pp.201-216
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• 2013

Diffusion is a basic mathematical tool for modern financial engineering. The theory of the estimation methods for diffusion models is an important topic of the financial engineering. Many researches have been tried to apply the likelihood estimation method for estimating diffusion models. However, the likelihood estimation method for diffusion is complicated and needs much amount of computing. In this paper we develop the estimation methods which are simple enough to be compared to the Euler approximation method, and efficient enough statistically to be compared to the likelihood estimation method. We devise pseudo-likelihood and propose the maximum pseudo-likelihood estimation methods. The pseudo-likelihoods are obtained by approximating the transition density with normal distributions. The means and the variances of the distributions are obtained from the delta expansion suggested by Lee, Song and Lee (2012). We compare the newly suggested estimators with other existing estimators by simulation study. From the simulation study we find the maximum pseudo-likelihood estimator has very similar properties with the maximum likelihood estimator. Also the maximum pseudo-likelihood estimator is easy to apply to general diffusion models, and can be obtained by simple numerical steps.