• 한국CDE학회논문집
• /
• 제3권4호
• /
• pp.211-222
• /
• 1998

Parametric design is an important modeling paradigm in CAD/CAM applications, enabling efficient design modifications and variations. One of the major issues in parametric design is to develop a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this appear, we propose a new approach to geometric constraint solving that employs a graph-based method to solve the ruler-and-compass constructible configurations and a numerical method to solve the ruler-and-compass non-constructible configurations, in a way that combines the advantages of both methods. The geometric constraint solving process consists of two phases: 1) planning phase and 2) execution phase. In the planning phase, a sequence of construction steps is generated by clustering the constrained geometric entities and reducing the constraint graph in sequence. in the execution phase, each construction step is evaluated to determine the geometric entities, using both approaches. By combining the advantages of the graph-based constructive approach with the universality of the numerical approach, the proposed approach can maximize the efficiency, robustness, and extensibility of geometric constraint solver.

• 한국CDE학회논문집
• /
• 제6권2호
• /
• pp.78-88
• /
• 2001

In order to adopt feature-based parametric modeling, CAD/CAM applications must have a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this paper, we describe a graph constructive approach to solving geometric constraint problems. Usually, a graph constructive approach is efficient, however it has its limitation in scope; it cannot handle ruler-and-compass non-constructible configurations and under-constrained problems. To overcome these limitations. we propose an algorithm that isolates ruler-and-compass non-constructible configurations from ruler-and-compass constructible configurations and applies numerical calculation methods to solve them separately. This separation can maximize the efficiency and robustness of a geometric constraint solver. Moreover, the solver can handle under-constrained problems by classifying under-constrained subgraphs to simplified cases by applying classification rules. Then, it decides the calculating sequence of geometric entities in each classified case and calculates geometric entities by adding appropriate assumptions or constraints. By extending the clustering types and defining several rules, the proposed approach can overcome limitations of previous graph constructive approaches which makes it possible to develop an efficient and robust geometric constraint solver.

• International Journal of CAD/CAM
• /
• 제6권1호
• /
• pp.173-181
• /
• 2006

In this paper, an integration framework of Geometric Constraint Solving Engine and AutoCAD is presented, and a dynamic geometric constraint system is introduced. According to inherent orientation features of geometric entities and various Object Snap results of AutoCAD, the' proposed system can automatically construct an under-constrained geometric constraint model during interactive drawing. And then the directed constraint graph in a geometric constraint model is realtime modified in order to produce an optimal constraint solving sequence. Due to the open object-oriented characteristics of AutoCAD, a set of user-defined entities including basic geometric elements and graphics constraint relations are defined through derivation. And the custom-made Object Reactor and Command Reactor are also constructed. Several powerful characteristics are achieved based on these user-defined entities and reactors, including synchronously processing geometric constraint information while saving and opening DWG files, visual constraint relations, and full adaptability to Undo/Redo operations. These characteristics of the proposed system can help the designers more easily manage geometric entities and constraint relations between them.

• 한국CDE학회논문집
• /
• 제3권3호
• /
• pp.145-153
• /
• 1998

An approach has been developed to generate parametric models with Boolean operations. The approach combines Boolean operations and graph manipulation on the constraints imposed on primitives. A Boolean operation is first performed on two primitives and new geometric elements such as vertices and edges are computed. Then to generate the constraint graph of the polygon the each constraints graph of two primitives are merged by adding the new geometric elements with its corresponding constraints. In the merging process, some of the geometric elements belonging to the primitives may be eliminated based on its contribution to the polygon. A computer implementation in a 2D space is described to illustrate the approach with examples.

• 한국생물정보학회:학술대회논문집
• /
• 한국생물정보시스템생물학회 2005년도 BIOINFO 2005
• /
• pp.267-271
• /
• 2005

The goal of data mining is to extract new and useful knowledge from large scale datasets. As the amount of available data grows explosively, it became vitally important to develop faster data mining algorithms for various types of data. Recently, an interest in developing data mining algorithms that operate on graphs has been increased. Especially, mining frequent patterns from structured data such as graphs has been concerned by many research groups. A graph is a highly adaptable representation scheme that used in many domains including chemistry, bioinformatics and physics. For example, the chemical structure of a given substance can be modelled by an undirected labelled graph in which each node corresponds to an atom and each edge corresponds to a chemical bond between atoms. Internet can also be modelled as a directed graph in which each node corresponds to an web site and each edge corresponds to a hypertext link between web sites. Notably in bioinformatics area, various kinds of newly discovered data such as gene regulation networks or protein interaction networks could be modelled as graphs. There have been a number of attempts to find useful knowledge from these graph structured data. One of the most powerful analysis tool for graph structured data is frequent subgraph analysis. Recurring patterns in graph data can provide incomparable insights into that graph data. However, to find recurring subgraphs is extremely expensive in computational side. At the core of the problem, there are two computationally challenging problems. 1) Subgraph isomorphism and 2) Enumeration of subgraphs. Problems related to the former are subgraph isomorphism problem (Is graph A contains graph B?) and graph isomorphism problem(Are two graphs A and B the same or not?). Even these simplified versions of the subgraph mining problem are known to be NP-complete or Polymorphism-complete and no polynomial time algorithm has been existed so far. The later is also a difficult problem. We should generate all of 2$^n$ subgraphs if there is no constraint where n is the number of vertices of the input graph. In order to find frequent subgraphs from larger graph database, it is essential to give appropriate constraint to the subgraphs to find. Most of the current approaches are focus on the frequencies of a subgraph: the higher the frequency of a graph is, the more attentions should be given to that graph. Recently, several algorithms which use level by level approaches to find frequent subgraphs have been developed. Some of the recently emerging applications suggest that other constraints such as connectivity also could be useful in mining subgraphs : more strongly connected parts of a graph are more informative. If we restrict the set of subgraphs to mine to more strongly connected parts, its computational complexity could be decreased significantly. In this paper, we present an efficient algorithm to mine frequent subgraphs that are more strongly connected. Experimental study shows that the algorithm is scaling to larger graphs which have more than ten thousand vertices.

• 인터넷정보학회논문지
• /
• 제7권5호
• /
• pp.109-121
• /
• 2006

컴퓨터 시스템이 다양화된 분산시스템 환경으로 발전하면서 시스템에 존재하는 정보를 부적절한 사용자로부터 보호하기 위한 접근통제 정책이 매우 중요하게 되었다 본 논문에서는 강제적 접근통제모델의 등급과 역할기반 접근통제 모델의 제약조건과 역할계층을 체계적으로 변경함으로서 격자기반 역할그래프 보안 관리 모델을 제안한다. 이 모델에서는 기존의 역할그래프 모델의 역할계층에서 상위역할의 권한남용 문제를 해결하였으며 권한간의 충돌발생시 제약조건을 통해 주체의 등급을 재조정함으로서 정보의 무결성을 유지할 수 있다. 또한 역할계층에 의한 권한상속 뿐만 아니라 사용자의 보안레벨에 의해서 통제되도록 함으로서 강화된 보안기능을 제공한다. 그리고 본 모델을 운영하기 위해 역할그래프 보안 관리 알고리즘을 제시하였다.

• 한국컴퓨터그래픽스학회논문지
• /
• 제22권4호
• /
• pp.11-19
• /
• 2016

본 논문에서는 복부 CT 영상에서 다중 확률 아틀라스 기반 형상제한 그래프-컷을 사용한 신실질 자동 분할 방법을 제안한다. 제안 방법은 다음의 세 단계로 구성된다. 첫째, 신실질의 다양한 형상정보를 이용하기 위해 피질기반 유사정합을 통한 다중 확률 아틀라스를 생성한다. 둘째, 최대사후확률 추정을 통해 그래프-컷의 초기 씨앗을 추출하고, 형상제한 그래프-컷을 통해 신실질을 분할한다. 셋째, 확률 아틀라스의 정합 오차를 줄이고 분할 정확도를 높이기 위해, 정합 및 분할을 반복적으로 수행한다. 제안방법의 성능을 평가하기 위해 정성적 평가 및 정량적 평가를 수행하였다. 실험결과 제안방법이 신실질과 유사한 밝기값을 갖는 주변 영역으로의 누출을 방지하여 개선된 분할 정확도를 보여준다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.267-270
• /
• 2001

A lot of efforts have been made to analyze the performance of the vehicle equipped with automatic transmission through simulation. It might be necessary to understand the different types of transmissions, i.e., different power flows, for different models. If there is a module that can be applied to different types of automatic transmission, it could be helpful to transmission-related engineers. This study has started up from this idea. The common bond graph has been obtained from several types of the automatic transmission. The overall generalized equations and kinematic constraint equations have been derived using virtual power sources on common bond graph. They are used to derive state equations and constraints. These equations have been applied as an application to the vehicle equipped with two simple planetary gear set type of Ravigneaux gear type automatic transmission. The state equation, kinematic constraints, and dynamic constraints have been derived in every gear and shift operation using overall generalized equations and kinematic constraint equations. Simulations for constraint speed running, standing-start running, rolling-start running, and LA-4 mode have been conducted to analyze the performance of the vehicle powertrain using GVPS(Generalized Vehicle Powertrain Simulation) program wit pull down menus.

• 한국자동차공학회논문집
• /
• 제5권5호
• /
• pp.73-85
• /
• 1997

An automatic transmission is an important element of automotive power systems that allows a driving convenience. Compared to a manual transmission, however, it has a few problems in efficiency, shift feel, and maintenance. To improve these, it is imperative to understand the dynamics of automatic transmissions. This paper develops a dynamically-correct model of an automatic transmission, using the bond graph method. The bond graph method is ideally suited for modeling power systems, because the method is based on generalized power variables. The bond graph method is capable of providing correct dynamic constraints and kinematic constraints, as well as the governing differential equations of motion. The bond graph method is applied to 1-4 in-gear ranges, as well as various upshifts and downshifts of an automatic transmission, which allows an accurate simulation of an automatic transmission. Conventional automatic transmission models have no dynamic constraint, which do not allow correct simulation studies.

• 대한전자공학회논문지
• /
• 제26권6호
• /
• pp.115-123
• /
• 1989

본 논문은 사용자가 정의한 stick도형으로부터 혼합된 정수 선형프로그래밍 문제를 공식화시키는 새로운 mask compaction 방법을 제시하였는데 이 혼합된 정수 프로그램을 풀므로써 밀집화되고 디자인 rule에 맞는 layout을 얻을 수 있다. 또한 constraint graph에서 최장경로 문제를 풀 수 있는 새로운 효율적인 알고리듬도 기술하였다.