• 한국전산유체공학회지
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• 제19권4호
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• pp.20-28
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• 2014

An efficient solution algorithm for simulating free surface problem is presented. Navier-Stokes equations for variable density incompressible flow are employed as the governing equation on Cartesian meshes. In order to describe the free surface motion efficiently, VOF(Volume Of Fluid) method utilizing THINC(Tangent of Hyperbola for Interface Capturing) scheme is employed. The most time-consuming part of the current free surface flow simulations is the solution step of the linear system, derived by the pressure Poisson equation. To solve a pressure Poisson equation efficiently, the PCG(Preconditioned Conjugate Gradient) method is utilized. This study showed that the proper application of the preconditioner is the key for the efficient solution of the free surface flow when its pressure Poisson equation is solved by the CG method. To demonstrate the efficiency of the current approach, we compared the convergence histories of different algorithms for solving the pressure Poisson equation.

• 해양환경안전학회지
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• 제20권6호
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• pp.746-751
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• 2014

본 논문에서는 소스 코드가 공개된 라이브러리를 이용하여 선박의 성능을 예측할 수 있는 해석 코드를 개발하였다. 질량보존 방정식, 모멘튼 보존방정식, 난류를 고려하기 위해 난류모델과 벽함수를 고려하였다. 자유수면 계산을 위해 볼륨비 수송방정식을 고려하였고, 자유수면의 정확도 높은 계산을 위해 고차 도식을 포함하는 라이브러리를 개발하였다. 개발한 프로그램을 컨테이너선인 KCS에 적용한 결과 실험에서 포착된 자유수면 분포를 잘 예측하였다. 자항성능 평가 시 추진기 회전을 위해 GGI 라이브러리를 사용하였다. 계산결과 실험과 비교해 약 7 % 정도의 정확도로 자항성능을 예측하였다. 캐비테이션 예측을 위해 이상 균질 모델을 포함하는 새로운 라이브러리를 개발하였다. 이상 균질 모델을 추진기에 적용한 결과 일반적으로 발생하는 얇은 층 캐비테이션을 잘 예측하는 것을 확인하였다. 오픈 소스 라이브러리를 이용하여 개발한 수치수조를 KCS에 적용한 결과 오픈 소스 라이브러리에 대한 가능성을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.74-78
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• 1992

This paper describes an intelligent system to automatic evaluation of eddy current(EC) signal for Inspection of steam generator(SG) tubes in nuclear power plant. Some features of the intelligent system design in the proposed system are : (1) separation of representation scheme ,or event capturing knowledge in EC signal and for structural inspection knowledge in SG tubes inspection; (2) each representation scheme is implemented in different methods, one is syntactic pattern grammar and the other is rule based production. This intelligent system also includes an data base system and an user interface system to support integration of the hybrid knowledge processing methods. The intelligent system based on the proposed concept is useful in simplifying the knowledge elicitation process of the rule based production system, and in increasing the performance in real time signal inspection application.

• 대한인간공학회지
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• 제31권4호
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• pp.601-607
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• 2012

Objective: The aim of this study is to classify between intentional and natural blinks in vision based eye tracking system. Through implementing the classification method, we expect that the great eye tracking method will be designed which will perform well both navigation and selection interactions. Background: Currently, eye tracking is widely used in order to increase immersion and interest of user by supporting natural user interface. Even though conventional eye tracking system is well focused on navigation interaction by tracking pupil movement, there is no breakthrough selection interaction method. Method: To determine classification threshold between intentional and natural blinks, we performed experiment by capturing eye images including intentional and natural blinks from 12 subjects. By analyzing successive eye images, two features such as eye closed duration and pupil size variation after eye open were collected. Then, the classification threshold was determined by performing SVM(Support Vector Machine) training. Results: Experimental results showed that the average detection accuracy of intentional blinks was 97.4% in wearable eye tracking system environments. Also, the detecting accuracy in non-wearable camera environment was 92.9% on the basis of the above used SVM classifier. Conclusion: By combining two features using SVM, we could implement the accurate selection interaction method in vision based eye tracking system. Application: The results of this research might help to improve efficiency and usability of vision based eye tracking method by supporting reliable selection interaction scheme.