• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.77-79
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• 1996

This paper presents an integrated stability analysis by the direct energy function method based on Equivalent Mechanical Model(EMM) which reflects the system behavior related to both angle and voltage stabilities. Actually, angle and voltage stability are intimately related in power system, so complete decoupling of these stability analysis is not possible in general, particularly in stressed power systems. In this paper, it is shown that a identical energy function can be used for angle and voltage stability analysis. The proposed energy function reflects the line resistances and reactive powers under the constraints of the same R/X ratio. The energy margin between UEP and SEP presents a good collapse proximity index in both types of stability analysis.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.198-206
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• 1999

An automobile outside rear view mirror system has been analyzed and designed to reduce vibration with a finite element model. model analysis is conducted for the calculation of natural frequencies. harmonic analysis is utilized to estimate the displacements of the glass surface under dynamic loads. The model is verified with the vibration experiment of the parts and the assembled body. The structure of the mirror system is optimized for the robustness defined by the Taguchi concept. At first, many potential design variables are defined. Final design variables are selected based on the amount of contribution on the objective function. That is, sensitive variables are chose. The SN ratio in the Taguchi method is replaced by an objective function with the mean and the standard deviation of the quality characteristic. The defined objective function is appropriate in the structural design in that the vibration displacements are minimized while the robustness is improved.

• 한국시뮬레이션학회논문지
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• 제27권3호
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• pp.13-21
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• 2018

통신 시스템과 지휘통제 시스템으로 구성된 C3 시스템에 대한 복합체계 기반 분석 방법은 상세한 분석이 가능하다는 장점을 지니지만, 한 번 수행하는데 긴 실행 시간을 요구하고, 이는 다양한 시나리오의 분석을 어렵게 한다. 이를 해결하기 위해, 본 논문에서는 페더레이션으로부터 단일 시뮬레이션으로의 변환 기법을 통한 C3 복합 체계 분석 방법에 대해 제안한다. 본 변환 기법은 분석하고자 하는 이외의 시스템을 추상하여, 정확성을 유지하면서 실행 시간을 단축하고, 이는 model hypothesis와 function identification이 주가 된다. model hypothesis에서는 확장된 DEVS 형식론을 통해 시뮬레이션 가능한 추상화된 모델을 구성할 수 있고, function identification에서는 해당 모델이 타 시스템으로부터 받는 영향을 표현할 수 있다. 통신 및 C2 시스템 분석에 대한 실험을 통해, 제안한 방법은 일정 오차 범위 이내에서 정확성을 보존하면서 시뮬레이션 시간을 단축하였고, 이를 통해 C3 이외의 다양한 복합 체계에 대한 탐색적 분석이 가능할 것으로 기대한다.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1229-1238
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• 2002

In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.

• Journal of the Optical Society of Korea
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• 제8권4호
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• pp.182-187
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• 2004

We synthesized and analyzed the optical transfer function(OTF) of the modified triangular interferometer (MTI) using two-pupil synthesis method. Also, we presented the optimal MTI, which can obtain any bipolar function by combining two wave plates and a linear polarizer. By using the proposed MTI, we can obtain the complex hologram without bias and conjugate image.

• 한국정밀공학회지
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• 제19권5호
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• pp.64-71
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• 2002

A new model utilizing a transfer function was proposed in the previous paper fur analizing motion errors of hydrostatic tables. Validity of the proposed method was theoretically verified as the calculated motion errors were compared with the results by conventional multi pad method. In this paper, relationship between form error of rail and motion errors of hydrostatic table is analized theoretically in order to comprehand so-called ‘averaging effect of oil film’. Experiments on the motion errors of hydrostatic table is conducted with 3 different rails, and the results are compared with the results calculated by Transfer Function Method. The results show good agreement. From the results, it is verified that TFM is very effective to analize the motion errors of hydrostatic table.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.454-458
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• 2001

A new model utilizing a transfer function was proposed in the previous paper for analizing motion errors of hydrostatic tables. Validity of the proposed method was theoretically verified as the calculated motion errors were compared with the results by conventional multi pad method. In this paper, relationship between form error of rail and motion errors of hydrostatic table is analized theoretically in order to comprehand so-called 'averaging effect of oil film'. Experiments on the motion errors of hydrostatic table is conducted with 3 different rails, and the results are compared with the results calculated by Transfer Function Method. The results show good agreement. From the results, it is verified that TFM is very effective to analize the motion errors of hydrostatic table.

• 한국해양공학회지
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• 제34권2호
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• pp.89-96
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• 2020

In this study, the Norbury-Fraenkel family of vortex rings is analyzed using a contour dynamics method for the stream function, which significantly reduces the numerical burden in the calculation. The stream function is formulated as the integral along the contour of the vorticity core. The integration over the logarithmic-singular segment is evaluated analytically, and the positions of the nodal points of the contour are calculated directly. The shapes of the cores and the dividing stream surfaces are found based on the mean core radius. Compared with other studies, the proposed method is verified and found to be more efficient.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2344-2352
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• 2000

Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.

• International Journal of Control, Automation, and Systems
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• 제4권5호
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• pp.660-667
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• 2006

This paper presents a novel region-based snake method for vessel segmentation. According to geometric shape analysis of the vessel structure with different scale, an efficient statistical estimation of vessel branches is introduced into the energy objective function, which applies not only the vessel intensity information, but also geometric information of line-like structure in the image. The defined energy function is minimized using the gradient descent method and a new region-based speed function is obtained, which is more accurate to the vessel structure and not sensitive to the initial condition. The narrow band algorithm in the level set framework implements the proposed method, the solution of which is steady. The segmentation experiments are shown on several images. Compared with other geometric active contour models, the proposed method is more efficient and robust.