• Journal of Aerospace System Engineering
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• v.15 no.1
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• pp.72-79
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• 2021

In this study, as part of the development of an autonomous flying personal aircraft, an equivalent model of the main wing assembly of an Optionally Piloted Personal Air Vehicle (OPPAV) was developed. Reliability of the developed equivalent model was verified by eigenvalue analysis. The main wing assembly consisted of a main wing, an inboard pod, and an outboard pod. First, for developing an equivalent model of each component, components to produce the equivalent model were divided into several sections. Nodes were then created on the axis of the equivalent model at both ends of each section. In addition, static analysis with unit force and unit moment was performed to calculate the deformation or the amount of rotation at the node to be used in the equivalent model. Equivalent axial, bending, and torsional stiffness of each section were calculated by applying the beam theory. Once the equivalent stiffness of each section was calculated, information of a mass and moment of inertia for each section was entered by creating a lumped mass in the center of each section. An equivalent model was developed using beam element. Finally, the reliability of the developed equivalent model was verified by comparison with results of mode analysis of the fine model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.119-126
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• 2008

방위산업분야의 항공기용 전자장비는 신뢰성 설계를 위하여 MIL규격이나 실측된 PSD데이터를 이용하여 보수적으로 설계하는 것이 일반적이다. 하나의 프로젝트에서 개발되는 PCB는 수십 종에 이르고 그 장착위치나 설계변경이 병행되므로 PSD랜덤 진동해석의 대안으로 등가정적해석을 수행하게 된다. 등가정적해석결과의 보수성을 확인하기 위하여 PSD랜덤진동해석으로부터 추출된 정규분포를 갖는 각 방향 응력에 대해 Monte Carlo모의를 수행하여 결과를 비교분석하였다. 결론적으로 PSD랜덤진동 해석의 대안으로 등가정적해석결과의 유용성과 보수성을 통계적으로 비교하였고 실험을 통하여 결과의 타당성을 보였다.

• Annual Conference on Human and Language Technology
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• 1989.10a
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• pp.29-34
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• 1989

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.57
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• pp.65-70
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• 2006

• Journal of the Korea Computer Graphics Society
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• v.3 no.2
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• pp.85-97
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• 1997

This study is intended to propose methods of iso-surfaces representation in visualizing the stress distribution in 3-dimensional solids computed by finite element method, and to develop efficient algorithms related to iso-surfaces, and also to exploit the practical application to various data visualizations. This paper suggests practical methods of creating and rendering iso-surfaces, and methods of surface smoothing which removes local irregularity on the surface. Also devised in this study are various methods of rendering stress distribution with the aid of iso-surfaces. Their effectiveness and usefulness have been tested and verified through actual implementaion of a finite element analysis software and case studies using the software.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.187-196
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• 2003

Today, the Working Stress Rating (WSR) is being widely used for the capacity-rating and the safety assessment of railroad steel bridges. Since it cannot incorporate the uncertainties, several studies have been carried out in order to get over the incompleteness of the conventional capacity-rating and safety assessment. A system reliability-based equivalent capacity-rating method, which can evaluate the capacity of existing bridges, has been recently proposed. For more efficient reliability analysis, probabilistic parameters of the random variables in the limit-state models should be reasonably evaluated. Especially, uncertainties for live load effects must be realistically included. In this study, an improved limit-state model was used for the system reliability-based equivalent strength method. This model can incorporate the probabilistic parameters obtained from ambient measurement data. To demonstrate the applicability of the improved system reliability-based equivalent capacity rating method, this was applied to the existing steel plate girder bridge for comparison with the conventional capacity-rating and safety assessment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.3
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• pp.239-246
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• 2007

In this paper a new equivalent static analysis method of dynamic behavior during progressive collapse is presented. The proposed analysis method uses the equivalent nodal load for the element stiffness which represents the dynamic behavior influence caused by the deletion of elements during progressive collapse analysis. The proposed analysis method improves the efficiency of progressive collapse analysis haying the iterative characteristic because the inverse of the structural stiffness matrix is roused in the reanalysis. By comparing the results obtained by this analysis method with those of GSA code analysis and time history analysis, it is shown that the results obtained by this analysis method more closely approach to those of time history analysis than by GSA code analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1811-1820
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• 2010

Most components in the real world show nonlinear response. The nonlinearity may arise because of contact between the parts, nonlinear material, or large deformation of the components. Structural optimization considering nonlinearities is fairly expensive because sensitivity information is difficult to calculate. To overcome this difficulty, the equivalent load method was proposed for nonlinear response optimization. This method was originally developed for size and shape optimization. In this study, the equivalent load method is modified to perform topology optimization considering all kinds of nonlinearities. Equivalent load is defined as the load for linear analysis that generates the same response field as that for nonlinear analysis. A simple example demonstrates that results of the topology optimization using equivalent load are very similar to the numerical results. Nonlinear response topology optimization is performed with a practical example and the results are compared with those of conventional linear response topology optimization.

• Electrical & Electronic Materials
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• v.3 no.4
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• pp.315-324
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• 1990

저저항(DuPont 1721, 100.OMEGA./sq.)과 고저항(1741, 10K.OMEGA./sq.)의 두 Ru계 후막저항체를 여러 조건에서 소결하여 소결막의 복소임피던스 특성과 임피던스의 주파수의존성을 1KHz-13MHz의 주파수 범위에서 조사하였다. 저저항 1721계의 경우 600.deg.C이상에서 소결한 모든 시편이 거의 저항성분(R)만으로 구성된 등가회로에 해당되는 복소임피던스 거동을 보였으며 임피던스에 미치는 주파수 의존성은 크게 나타나지 않았는데 5KHz까지는 주파수에 따라 변화가 없다가 그 이상의 주파수에서 주파수 증가에 따라 약간씩 증가하였다. 고저항 1741 후막저항체의 경우는 소결조건에 따라 복소임피던스 거동과 임피던스에 미치는 주파수 의존성이 달리 나타났다. 600.deg.C에서는 용량(C) 성분만으로 구성된 등가회로에 해당하는 복소임피던스 거동을 얻었고 주파수 증가에 따라 임피던스가 직선적으로 감소하였으며 700.deg.C이상 900.deg.C까지는 저항(R)과 용량(C)이 병렬로 연결되는 형태의 등가회로에 해당하는 복소임피던스 거동을 얻었고 이때의 임피던스의 주파수 의존성은 저주파수 영역에서는 임피던스가 주파수에 변함없이 일정하다가 5KHz이상의 주파수에서는 주파수 증가에 따라 임피던스가 직선적으로 감소하였다. 1000.deg.C반응에서의 복소임피던스 거동은 RCL성분이 병렬로 연결된 형태의 등가회로에 해당되는 결과를 얻었으며 임피던스도 작아지고 주차수 의존성도 현저하지 않았다.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.288-293
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• 2009

Polarization characteristics of a composite film composed of two optically anisotropic films are analyzed. The procedure to determine the effective optics axis and the equivalent retardation of the composite film is suggested in conjuction with the related ellipsometric expressions. The explicit expressions of the effective optic axis and the equivalent retardation of a non-uniform anisotropic film are derived when all optic axes are parallel. Those expressions of the composite film where optic axes of two constituting anisotropic films are not parallel are also derived. Dependence of those expressions on the polarization state of the incident light or the azimuth angle of the linearly polarized light and their limit when applied to practical use are discussed.