• 대한기계학회논문집A
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• 제24권8호
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• pp.1991-1999
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• 2000

This research has been performed to reveal the hysteresis phenomena of the hunting motion in a railway passenger car having a bolster. Since linear analysis can not explain them, bifurcation analysis is used to predict its outbreak velocities in this paper. However bifurcation analysis is attended with huge computing time, thus this research proposes more effective numerical algorithm to reduce it than previous researches. Stability of periodic solution is obtained by adapting of Floquet theory while stability of equilibrium solutions is obtained by eigen-value analysis. As a result, linear and nonlinear critical speed are acquired. Full scale roller rig test is carried out for the validation of the numerical result. Finally, it is certified that there are many similarities between numerical and test results.

• Computers and Concrete
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• 제32권3호
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• pp.303-311
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• 2023

An analysis of the Poisson's ratios influence of single walled carbon nanotubes (SWCNTs) based on Sander's shell theory is carried out. The effect of Poisson's ratio, boundary conditions and different armchairs SWCNTs is discussed and studied. The Galerkin's method is applied to get the eigen values in matrix form. The obtained results shows that, the decrease in ratios of Poisson, the frequency increases. Poisson's ratio directly measures the deformation in the material. A high Poisson's ratio denotes that the material exhibits large elastic deformation. Due to these deformation frequencies of carbon nanotubes increases. The frequency value increases with the increase of indices of single walled carbon nanotubes. The prescribe boundary conditions used are simply supported and clamped simply supported. The Timoshenko beam model is used to compare the results. The present method should serve as bench mark results for agreeing the results of other models, with slightly different value of the natural frequencies.

• Advances in nano research
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• 제12권5호
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• pp.467-482
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• 2022

In the current work, static and free torsional vibration of functionally graded (FG) nanorods are investigated using Fourier sine series. The boundary conditions are described by the two elastic torsional springs at the ends. The distribution of functionally graded material is considered using a power-law rule. The systems of equations of the mechanical response of nanorods subjected to deformable boundary conditions are achieved by using the modified couple stress theory (MCST) and taking the effects of torsional springs into account. The idea of the study is to construct an eigen value problem involving the torsional spring parameters with small scale parameter and functionally graded index. This article investigates the size dependent free torsional vibration based on the MCST of functionally graded nano/micro rods with deformable boundary conditions using a Fourier sine series solution for the first time. The eigen value problem is constructed using the Stokes' transform to deformable boundary conditions and also the convergence and accuracy of the present methodology are discussed in various numerical examples. The small size coefficient influence on the free torsional vibration characteristics is studied from the point of different parameters for both deformable and rigid boundary conditions. It shows that the torsional vibrational response of functionally graded nanorods are effected by geometry, small size effects, boundary conditions and material composition. Furthermore, for all deformable boundary conditions in the event of nano-sized FG nanorods, the incrementing of the small size parameters leads to increas the torsional frequencies.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1970-1979
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• 2017

Ultra Lift Luo Converter (ULC) gained considerable research interest in recent years. The stability analysis of voltage mode and peak current mode controlled ULC in continuous conduction mode is analyzed in this paper. The Eigen value theory is used for the stability analysis of voltage mode controlled ULC. Then to characterize the dynamics of inner current loop, the expressions of closed loop transfer function and loop gain are determined. An algorithm has been developed to analyze the stability of the peak current mode controlled ULC. The theoretical results are correlated with the simulation results obtained using PSIM 9.1(SMARTCTRL 1.0) software. Finally it is proposed to fabricate a prototype and validate the performance by suitable experimental setup.

• 대한가정학회지
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• 제27권1호
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• pp.141-164
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• 1989

The Purpose of this study is to investigate the relationship between the urban home-maker's view of homemanagement and the domestic courtesy and ritual (wedding ceremany, ancestral service, funeral rites). The data for this study was obtained from the 661 homemakers who live in Seoul, Busan, Inchon etc. The data were analyzed by the method described below with SPSS Computer programs. Such methods as frequence, percentile, analysis of variance (t-test, one-way ANOVA), Pearson's correlation and Factor analysis, Multiple regression were used. The major results the study can be summaried as follows; 1) As the result of factor analysis about view of homemanagement, 10 factors (which Eigen Value was above 1.0) out of 28 guestions were extracted. 2) In general, it can be said that the urban Homemaker's View of homemanagement varies by age, level of education, religion. 3) The domestic courtesy and ritual (wedding ceremony, ancestral servic, funeral rites) varies by age, level of education, religion. 4) There is a positive relation in analyzing the correlation between the urban homemaker's view of homemanagement and domestic courtesy and ritual (wedding ceremony, ancestral service, funeral rites)(p<.001).

• 한국전산구조공학회논문집
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• 제22권4호
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• pp.307-314
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• 2009

본 논문은 기하학적 비선형성을 가진 보존적 단일 하중 매개변수의 탄성 상태 공간구조의 탄성 분기 좌굴해석을 위한 공간프레임의 정식화, 분기경로 추적을 위한 pin-pointing 및 분기경로 전환알고리즘을 기술하고 있다. 복잡한 좌굴 후 거동특성을 파악하기 위한 본 연구의 공간프레임요소는 오일러리안 좌표계에 의한 유한회전이론으로 강체변형을 계산하였고, 굽힘효과가 고려된 보-기둥식을 적용하여 적은 개수의 요소의 사용으로도 정해를 얻을 수 있도록 하였으며, 후좌굴해석과 같은 고도의 비선형해석을 수행하기 위해 기하강성행렬의 모멘트에 대한 영향을 고려하였다. 분기좌굴에 의한 좌굴후 평형상태인 주경로와 분기경로의 pin-pointing 알고리즘으로 특이점을 계산하였으며, 고유치 및 고유모드를 이용한 본 연구의 수치알고리즘에 의해 분기경로를 추적하였다. 분기좌굴 해석예제로 평면프레임, 평면아치 및 공간돔에 대한 분기좌굴 해석을 수행하여 본문에서 제시한 수치해석법의 정확성 및 적용성을 검증한다.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.197-202
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• 2009

Active Appearance Models(AAMs)은 얼굴인식, 얼굴추적, 표정인식 뿐만 아니라 눈동자 추적과 같은 분야에도 적용되어 좋은 성능을 보여 주었다. 보통 AAM 을 생성하기 위해서는 얼굴 영상과 얼굴의 특징을 나타내는 점으로 구성된 매쉬로 이루어 지는 트레이닝 셋이 필요하다. AAM fitting algorithm 은 학습한 얼굴과 유사한 얼굴을 Fitting 할 때에는 뛰어난 성능을 보이지만 조명에 의한 그림자 또는 액세서리에 의한 얼굴의 피부 가림과 같이 전체 얼굴이 잘 나타나지 않는 불완전한 영상의 Fitting 은 입력영상과 템플릿 영상간의 오차가 커지기 때문에 실패할 가능성이 매우 높다. 본 논문에서 우리는 AAMs 에서 사용되는 PCA를 Higher-order Singular Value Decomposition(HOSVD)로 대체하여 이 문제를 보완하는 강화된 AAM 을 제안한다. 제안된 AAM 에는 기존에 사용하던 고유벡터와 함께 HOSVD 를 통해 획득할 수 있는 Eigen-Modes 를 추가하여 사용한다. 또한 우리는 Yale Face Database를 이용한 평가를 통해 제안된 AAM 이 기존 AAM 보다 불완전한 영상에 효과적으로 대응하는 것을 보여준다.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1319-1326
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• 2012

본 논문은 구동력이 자전거의 self-stability 에 미치는 영향을 해석한다. 운전자의 제어를 고려하지 않는 자전거의 self-stability 는 자전거의 선형 모델로부터 고유치를 구하여 해석 할 수 있다. 전륜과 후륜에 작용하는 자전거 구동력을 고려한 선형모델을 개발하고 이로부터 구동력이 안정성에 미치는 영향을 규명하였다. 선형모델의 결과가 다물체 동역학 모델의 시뮬레이션을 통한 비선형 자전거 모델에서도 같은 결과를 보임을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.756-759
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• 2001

The purpose of this paper is to investigate the buckling and dynamic characteristics for the cylindrical shell under shear loading. To do this, a vibration model tests and analyses and static buckling analyses were performed for the reduced scale model of nuclear reactor vessel. From the results of vibration modal analysis with the pre-shear displacement loads, it is known that the beam vibration mode is not affected by the shear displacement, however shell vibration modes are significantly affected by it. As the pre-shear displacement increases to the critical buckling displacement, the 1st shell vibration frequency in greatly reduces and approaches to zero value.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.328-335
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• 2005

For high speed railway vehicles, we consider a vibration of flexible track/wheel system. It is very important to deal with the complex phenomena of high-speed vehicles that can be occurred in the vertical vibration of the system. From a viewpoint of multibody dynamics, this kind of problem needs accurate analysis because the system includes mutual dynamic behaviors of rigid body and flexible body. The simulation technique for the complex problems is also discussed. We consider the high-speed translation, rail elasticity, elastic supports under the rail and contact rigidity. Eigen value analysis is also completed to verify the mechanism of the coupled vertical vibration of the system.