• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2003년도 Proceeding
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• pp.50-56
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• 2003

In the development of complex software system, it is important to use hierarchical use case model due to the complex scope of development procedure. The use case model is core factor of the OMG (Object Management Group)'s UML (Unified Modeling Language) diagrams. In this paper, we propose a novel method to check syntactic consistency automatically in use case models at the different level of abstraction. This method is a rule-based approach which utilizes actor tree, use case tree and use case description. The proposed method is simulated on ITS (Intelligent Transportation System) architecture for the verification.

• 한국정보처리학회논문지
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• 제3권7호
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• pp.1781-1791
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• 1996

전문가시스템의 지식획득, 적합한 추론기구의 설계 및 구현, 지식의 정제 등 다단계 과정으로 이뤄져 있다. 각각을 하나의 연구이슈로 다양한 연구가 진행되어 왔으나 전체를 하나로 연계해 통합적 개발에 관해서는 상대적으로 연구가 활발히 진행되지 못한 실정이다. 지식획득은 전문가에 의해 수행되는 추론과정에서 특징 응용분야의 필요한 지식이 전달되어야 하므로 시식획득과 추론을 서로 밀접한 연관성을 갖는다. 지식의 정제는 추론과정에서 일어나는 문에의 제기와 이의 해결을 통해 지식베이스의 불완전하거나 논리적 모순을 찾아 해결함으로 지식베이스를 보다 완벽하고 정확한 것으로 만드는 것이다. ㅂㄴ 연구에서는 서로 연관된 다단계 과정이 통합적으로 개발될 수 있는 환경의 설저엥 대한 하나의 방안을 제시하려한다. 특히 도메인 모델이 잘 정립되기 어려운 분야에 학습기법을 활용햇 초기 지식 베이스를 구성할 수 있는 점진적 지식획득방법과 이를 통해 만들어진 지식베이스 규칙들을 학습기법의 일종인 개념적 클러스터링 기법을 이용하여 규칙모델을 구축하고 이를 이용해 효율적인 추론이 가능하게 하며, 지식획득 과정에서는 규칙의 오류를 제시할 수 있고 이에 대한 규칙의 수정이나 새로운 규칙이 기존의 지식구조에 합당한지를 결정하는 통합적 설계방안에 대해 연구한다. 지식의 정제는 설명기구와 규칙모델을 활용하여 문제의 원인을 찾고 해결점을 제시해 그에 대한 유효성을 검증합으로 이뤄지게 한다.뤄지게 한다.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1528-1534
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• 2001

In order to improve Leak-Be(ore-Break methodology, more precisely the crack growth evaluation, a round robin analysis was proposed by the CEA Saclay. The aim of this analysis was to evaluate the crack initiation life, penetration life and shape of through wall crack under cyclic bending loads. The proposed round robin analysis is composed of three main topic; fatigue crack initiation, crack propagation and crack penetration. This paper deals with the first topic, crack initiation in a notched pipe under four point bending. Both elastic-plastic finite element analysis and Neuber's rule were used to estimate the crack initiation life and the finite element models were verified by mesh-refinement, stress distribution and global deflection. In elastic-plastic finite element analysis, crack initiation life was determined by strain amplitude at the notch tip and strain-life curve of the material. In the analytical method, Neuber's rule with the consideration of load history and mean stress effect, was used for the life estimation. The effect of notch tip radius, strain range, cyclic hardening rule were examined in this study. When these results were compared with the experimental ones, the global deformation was a good agreement but the crack initiation cycle was higher than the experimental result.

• 한국항만학회지
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• 제13권1호
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• pp.167-174
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• 1999

Numerical analysis of two-fluid flows for both water and air is carried out. Free-Surface flows with an arbitrary deformation have been simulated around two dimensional submerged hydrofoil. The computation is performed using a finite volume method with unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell-wise local mesh refinement. the integration in space is of second order based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels The linear equation systems are solved by conjugate gradient type solvers and the non-linearity of equations is accounted for through picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations the continuity equation the conservation equation of one species and the equations or two turbulence quantities.

• Structural Engineering and Mechanics
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• 제48권1호
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• pp.125-150
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• 2013

This paper intends to present an application of isogeometric analysis in crack problems. An isogeometric formula is developed based on NURBS basis functions - enriched and adopted via X-FEM enrichment functions. The proposed method which is represented by the combination of the two above-mentioned methods, first by using NURBS functions models the geometry exactly and then by defining level set function on domain, identifies available discontinuity in elements. Additional DOFs are allocated to elements containing the crack and X-FEM enrichment functions enrich approximate solution. Moreover, a subelement refinement technique is used to improve the accuracy of integration by the Gauss quadrature rule. Finally, several numerical examples are illustrated to demonstrate the effectiveness, robustness and accuracy of the proposed method during calculation of crack parameters.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1215-1220
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• 2008

To obtain the shape of the free surface more accurately, computations are carried out by a finite volume method using unstructured meshes and an interface capturing method. Free-surface flow, which is very important in the fields of ship and marine engineering, is numerically simulated for flows of both water and air. Control volumes are used with an arbitrary number of faces and allows a local mesh refinement. The integration is of second order, with a midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation. The solution method of pressure-correction type solves sequentially equations of momentum, continuity, conservation, and two-equations turbulence model. Comparison are quantitatively made between the computation and experiment in order to confirm the solution method.

• Journal of Mechanical Science and Technology
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• 제14권7호
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• pp.789-795
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• 2000

Free-surface flows with an arbitrary deformation, induced by a submerged hydrofoil, are simulated numerically, considering two-fluid flows of both water and air. The computation is performed by a finite volume method using unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell wise local mesh refinement. The integration in space is of second order, based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels. The linear equations are solved by conjugate gradient type solvers, and the non-linearity of equations is accounted for through Picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations, the continuity equation, the conservation equation of one species, and the equations for two turbulence quantities. Finally, a comparison is quantitatively made at the same speed between the computation and experiment in which the grid sensitivity is numerically checked.

• Journal of information and communication convergence engineering
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• 제11권4호
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• pp.258-267
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• 2013

New incremental learning algorithm using extended data expression, based on probabilistic compounding, is presented in this paper. Incremental learning algorithm generates an ensemble of weak classifiers and compounds these classifiers to a strong classifier, using a weighted majority voting, to improve classification performance. We introduce new probabilistic weighted majority voting founded on extended data expression. In this case class distribution of the output is used to compound classifiers. UChoo, a decision tree classifier for extended data expression, is used as a base classifier, as it allows obtaining extended output expression that defines class distribution of the output. Extended data expression and UChoo classifier are powerful techniques in classification and rule refinement problem. In this paper extended data expression is applied to obtain probabilistic results with probabilistic majority voting. To show performance advantages, new algorithm is compared with Learn++, an incremental ensemble-based algorithm.

• 접착 및 계면
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• 제3권1호
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• pp.43-51
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• 2002

Advanced adhesive technologies and demanding applications of adhesive joints can no longer be developed successfully by the traditional "trial and error" approach. Appropriate technical solutions require reference to a reliable basis of well-established scientific knowledge about the elementary mechanisms of adhesion (i.e. the 'fundamental adhesion') as they are responsible for the capability of the compound w transmit mechanical force between the adhesive and the substrate surface (i.e. the 'practical adhesion'). Adhesion mechanisms also influence the formation of polymer structure in the adhesive and the resulting macromolecular dynamics in the interphase that is formed in the adhesive near to the substrate. These manifold molecular factors rule the macroscopic behaviour of an adhesive bond line in terms of mechanical and other physical properties as well as in terms of durability. This paper reviews the level of refinement that understanding of fundamental adhesion has achieved up to now.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1253-1255
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• 1993

Double Injection(DI) switching devices consist of p+ and n+ contact separated by a nearly intrinsic semiconductor region containing deep trap. The FEM is chosen as a simulation method for DI switching device, because of the advantage in local mesh refinement and computer memory comparing with other methods. And Scharfetter-Gummel(S-G) scheme is applied, with which an accurate-seven point Gaussian Quadrature rule is combined. The existance of deed trap requires the modification of conventional equation set. So recombination rate equation is modified and a new equation is included in the equation set which conventionally consists of Poisson equation and current continuity equations.