• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.280-285
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• 2001

As an integral part of the probabilistic fracture mechanics analysis, stress intensity factor calculation scheme for semi-elliptical surface flaws in thin-walled cylinder has been introduced. The approximation solution utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for cooldown boundary condition. The analysis results confirmed that the simplified methods provided sufficiently accurate stress intensity factor values for axial semi-elliptcal flaws on the surface of the reactor pressure vessel.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.319-328
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• 2006

A simple approximation method for the stress intensity factor at the tip of the axial semielliptical cracks on the cylindrical vessel is developed. The approximation methods, incorporated in VINTIN (Vessel INTegrity analysis-INner flaws), utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for internal pressure, cooldown, and pressurized thermal shock loading conditions. For these, 3-D finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R=0.1. The approximation solutions are within $\pm2.5%$ of the those of finite element analysis using symmetric model of one-forth of a vessel under pressure loading, and 1-3% higher under pressurized thermal shock condition. The analysis results confirm that the approximation method provides sufficiently accurate stress intensity factor values for the axial semi-elliptical flaws on the surface of the reactor pressure vessel.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제22권11호
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• pp.559-566
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• 2016

전 세계적으로 널리 상용화된 Excel은 수식작성과 계산이 편리해 기업의 세무계산, 보고서나 학교의 성적관리 및 가계부 등에 광범위하게 활용되고 있는 전산프로그램이다. 그러나 초기부터 계산의 부정확성 및 오류들이 꾸준히 제기되어 왔고, 지속적으로 수정되어 발전하여왔다. 소수의 진법변환 과정은 경우에 따라서는 단순한 계산을 반복적으로 여러 번 해야만 하기에, 이러한 단순작업은 컴퓨터에 의한 계산도구들의 도움을 받기에 적절하다. 이번에 발견된 소수의 진법변환과 같은 단순계산과정에서 Excel의 오류는 쉽게 이해되지 않는다. 유사한 오류가 추가적으로 발견될 가능성은 높다. 이번에 발견된 오류의 유형에 대하여 원인을 파악하고, 빠른 수정을 희망한다.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2390-2398
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• 2002

For integrity analysis of nuclear reactor pressure vessel, including the Pressurized thermal shock analysis, the fast and accurate calculation of the stress intensity factor at the crack tip is needed. For this, a simple approximation scheme is developed and the resulting stress intensity factors for axial semi-elliptical cracks in cylindrical vessel under various loading conditions are compared with those of the finite element method and other approximation methods, such as Raju-Newman's equation and ASME Sec. Xl approach. For these, three-dimensional finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R = 0.1. The approximation methods, incorporated in VINTIN (Vessel INTegrity analysis-INner flaws), utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite clement analysis for internal pressure, cooldown, and pressurized thermal shock loading conditions. The approximation solutions are within $\pm$2.5% of the those of FEA using symmetric model of one-forth of a vessel under pressure loading, and 1-3% higher under pressurized thermal shock condition. The analysis results confirm that the VINTIN method provides sufficiently accurate stress intensity factor values for axial semi-elliptical flaws on the surface of the reactor pressure vessel.

• 비파괴검사학회지
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• 제9권1호
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• pp.22-29
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• 1989

The important point of MPI is the analysis of leakage field in the defective regions. The analysis of leakage field depends on many factors such like geometry and character of defect. In general the calculation of magnetic leakage fields arising from such defects presents an extremely complicated mathematical problem and is practically insoluable, since the inhomogeneities have complex geometrical shapes and may differ in physical nature. Therefore, this paper describes Hall probe measurements of residual leakage field around artificial flaws in alloy steel bar, and shows how the results to recent developments in 2D dipole and analytic models of the magnetic field defect interaction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.90-95
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• 2004

The probabilistic fracture analysis is used to determine the effects of uncertainties involved in material properties, location and size of flaws, etc, which can not be addressed using a deterministic approach. In this paper the probabilistic fracture analysis is applied for evaluating the RV(Reactor Vessel) under PTS(Pressurised Thermal Shock). A semi-elliptical axial crack is assumed in the inside surface of RV. The selected random parameters are initial crack depth, neutron fluence, chemical composition of material (copper, nickel and phosphorous) and $RT_{NDT}$. The deterministically calculated $K_I$ and crack tip temperature are used for the probabilistic calculation. Using Monte Carlo simulation, the crack initiation probability for fixed flaw and PNNL(Pacific Northwest National Laboratory) flaw distribution is calculated. As the results show initiation probability of fixed flaw is much higher than that of PNNL distribution, the postulated crack sizes of 1/10t in this paper and 1/4t of ASME are evaluated to be very conservative.

• 한국정밀공학회지
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• 제19권11호
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• pp.174-182
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• 2002

The integrity evaluation of pressure tube is essential for the safety of CANDU reactor, and integrity must be assured when flaws or contacts between pressure tube and surrounding calandria tube are found. In order to complete the integrity evaluation, not only complicated and iterative calculation procedures but also a lot of data and knowledge are required. For this reason, an integrity evaluation system, which provides an efficient way of the evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec.？ and FFSG issued by the AECL, and applicable for the evaluation of blister, sharp flaw and blunt notch. Delayed hydride cracking and blister evaluation modules are included in the general flaw and notch evaluation module. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.

• 한국ITS학회 논문지
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• 제10권3호
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• pp.47-63
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• 2011

교통검지체계는 도로상에서 교통자료 및 정보수집체계로 이해될 수 있는데, 이는 도로 상에서 교통량, 속도 및 점유율 정보를 수집하여 현 상태에서 도로상의 교통소통정보 즉, 혼잡 또는 비혼잡 등의 교통류상태, 또한 이보다 더 구체적인 내용으로서 LOS A~F로 표현되어지는 교통류 상태의 질 등을 파악하여 현 교통체계가 문제가 있는지 없는지에 관한 판단, 그리고 문제가 있다면 어느 지점(또는 구간)이 문제가 있는지, 그리고 문제의 원인은 무엇인지, 문제로 인해 발생되고 파급된 영향은 어느 정도인지, 또한 이를 해결하기 위한 방안은 무엇인지 찾고자하는데 있어서 매우 중요한 역할을 담당하는 체계로 볼 수 있다. 그러나 지점검지체계가 주를 이루고 있는 현재의 교통검지체계는 많은 한계점을 지니고 있으며, 이의 보완을 위해 본 연구에서는 구간검지체계의 이론적 구조 검토, 현장조사를 통한 검지체계별 자료특성 비교, 그리고 최적 구간검지간격 결정을 위한 분석을 수행하였다. 또한, 교통정책, 교통관리 및 이용자서비스 측면의 기능강화를 위해 기존 검지체계의 보완을 위한 새로운 교통검지체계 설치기준을 제시하였다.

• 한국정보통신학회논문지
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• 제20권3호
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• pp.639-646
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• 2016

본 연구에서는 특수한 상황(미끄러짐 발생 및 회전관성이 부하로 작용하는 경우)에서의 회전 엔코더 기반 측정방법의 단점을 극복하기 위하여 광 변위센서(ADNS-9500)를 사용한 비접촉식 변위 측정방법을 제안하였다. 정확한 변위 측정을 위해 데이터 수집 보드와 랩뷰를 활용하여 실험적으로 광 변위센서의 성능을 분석하였으며, 반복실험을 통해 실험조건(측정방향, 속도, 가속도, 높이, 표면 재질)에 따른 광 변위센서의 성능특성을 파악하였다. 성능실험 결과, 광 변위센서를 사용하여 정확하게 평면운동을 측정하기 위해서는 광 변위센서와 지면(대상 물체의 표면)과의 높이를 2.4 mm-3.2 mm로 일정하게 유지시켜야 하며, 각각의 축 방향, 속도, 표면 재질을 고려하여 민감도를 수정하여 변위 계산식에 적용해야 하는 것을 확인하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.245-250
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• 2002

This report describes the effects of following flaws due to ship's propeller on the fish farm structure when the ship's propeller is operated in full power. This study is applied an incompressible newtonian fluid theory, which is governed the Navier-Stokes equation. For the numerical solution, Neumann equation are applied as the boundary conditions. The result shows that the flow velocity near the fish farm is 1.0 m/sec. The actual measurement carries out by using propeller type velocimeter in order to measure the velocity of following flows and currents around the fish farm area. The result shows that the maximum velocity near the fish farm structure is 1.2 m/sec in depth of 1.5 m. This velocity is used for calculation of external force on the fish farm structure. The results of structural strength of the fish farm structures show that the actual maximum bending moment and bending stress are less than the damage strength of material. So the fish farm structure is not affected by the following flows and currents of ship's propeller.