• 대한토목학회논문집
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• 제11권3호
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• pp.37-46
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• 1991

이 논문(論文)은 변단면(變斷面) 보의 자유진동(自由振動)을 해석한 연구(硏究)이다. 보의 기하학적(幾何學的) 형상(形狀)은 보의 단면(斷面)이 직선적으로 변하는 변단면(變斷面) 보(tapered beam)를 택하였으며 균일폭 변화높이의 구형단면(矩形斷面), 균일(均一)높이 변화폭(變化幅)의 구형단면(矩形斷面), 정방형단면(正方形斷面) 또는 원형단면(圓形斷面)의 3가지 단면형상(斷面形狀)을 고려하였다. 보의 동적(動的) 평형방정식(平衡方程式)을 이용하여 변단면(變斷面) 보의 자유진동(自由振動)을 지배하는 미분방정식(微分方程式)을 유도하고, 이를 수치해석 기법인 Runge-Kutta method와 행렬(行列)값 탐사법(探査法)을 이용하여 고유진동수(固有振動數)와 진동형(振動形)을 산출할 수 있는 수치해석 기법을 개발하였다. 또한 타(他) 문헌(文獻)의 결과와 본 연구의 결과를 비교하여 본 연구방법의 타당성을 입증하였다. 실제의 수치해석 예는 힌지-힌지, 힌지-고정, 고정-고정, 자유-고정의 4가지 단부조건(端部條件)에 대하여 수치해석하였다. 수치해석의 결과로 $C_i-d_b/d_a$의 관계를 도시(圖示)하였고, 단부조건(端部條件)과 단면형상(斷面形狀)이 무차원 고유진동수에 미치는 영향을 분석하였다.

• 한국소음진동공학회논문집
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• 제20권1호
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• pp.10-21
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• 2010

Equations of chordwise and flapwise bending motions for the vibration analysis of rotating pre-twisted blades having tapered cross section and setting angle are derived by using hybrid deformation variable modeling. The two motions are couples to each other due to the pre-twisted angle of the beam cross section. The derived equations are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters on the modal characteristics of rotating pre-twisted blades having tapered cross section and orientation angle are investigated. The eigenvalue loci veering phenomena are also investigated and discussed in this work.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.983-986
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• 1998

Inthis paper, we design 4$\times$4 optical star coupler with tapered coupling structure. The 4$\times$4 optical star coupler consists of four 3dB couplers and a 100% coupler with tapered structure. This star coupler is designed by the 2 dimension FD-BPM(finite difference beam propagation method) using TBC(transparent boundary condition). consequently, the maximum power unbalance ratios of relative output power from each of the output waveguides for each of input guides are less than 0.1dB, and the transmission efficiency is more than 99%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.932-937
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• 2002

The polyimide nozzle and silicon restrictor inside a thermal micro actuator have been fabricated using state of the art laser micromachining methods. Numerical models of fluid dynamics inside the actuator chamber and nozzle are presented. The models include fluid flow from reservoir, bubble formation and growth, ejection through the nozzle, and dynamics of refill through restrictor. Since high tapered nozzle and restrictor are very important parameters for overall actuator performance design, a special setup for the beam delivery system has been developed. The effects of variations of nozzle thickness, diameter, taper angles, and restrictor shapes are simulated and some results are compared with the experimental results. It is fecund that the fluid ejection through the thinner and high tapered nozzle is more steady, fast, and robust and the tapered restrictor shows more satisfying refill than the zero taper one.

• 소음진동
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• 제9권4호
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• pp.828-834
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• 1999

The paper describes the vibration and the stability of nonuniform tapered beams resting on two-layered elastic foundations. The two-layered elastic foundations are constructed by discributed Winkler springs and shearing layers as ofen used in oil models. Governing equations are derived from energy experssions using Hamilton's Principle. The associated eigenvalue problems are solved to obtain the free vibration frequencies or the buckling loads. Numerical results for the vibration and the stability of beams under an axial force are presented and compared with other available solutions. Finally, vibration frequencies and critical forces are investigated for various thickness ratios, shear foundation parameters, Winkler foundation parameters, and boundary conditions of tapered beams.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.288-295
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• 2009

Equations of chordwise and flapwise bending motions for the vibration analysis of rotating pre-twisted blades having tapered cross section and orientation angle are derived by using hybrid deformation variable modeling. The two motions are couples to each other due to the pre-twisted angle of the beam cross section. The derived equations are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters on the modal characteristics of rotating pre-twisted blades having tapered cross section and orientation angle are investigated. The eigenvalue loci veering phenomena is also investigated and discussed in this work.

• Structural Engineering and Mechanics
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• 제48권2호
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• pp.195-205
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• 2013

The buckling problem of linearly tapered micro-columns is investigated on the basis of modified strain gradient elasticity theory. Bernoulli-Euler beam theory is used to model the non-uniform micro column. Rayleigh-Ritz solution method is utilized to obtain the critical buckling loads of the tapered cantilever micro-columns for different taper ratios. Some comparative results for the cases of rectangular and circular cross-sections are presented in graphical and tabular form to show the differences between the results obtained by modified strain gradient elasticity theory and those achieved by modified couple stress and classical theories. From the results, it is observed that the differences between critical buckling loads achieved by classical and those predicted by non-classical theories are considerable for smaller values of the ratio of the micro-column thickness (or diameter) at its bottom end to the additional material length scale parameters and the differences also increase due to increasing of the taper ratio.

• Nuclear Engineering and Technology
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• 제28권6호
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• pp.583-593
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• 1996

An elastic stiffness formula of a leaf type holddown spring(HDS) assembly with a uniformly tapered width from $w_0$ to $w_14$ over the length, has been analytically derived based on Euler beam theory and Castigliano's theorem. Elastic stiffnesses of the tapered-width leaf type HDSs(TW-HDSs) designed in the same dimensional design spaces as the KOFA HDSs have been evaluated from the derived formula, in addition, a parametric study on the elastic stiffness of the TW-HDSs has been carried out. Analysis results show that, as the effects of axial and shear force on the elastic stiffness of He TW-HDSs have been 0.15~0.21% of the elastic stiffness, most of the elastic stiffness is attributed to the bending moment, and that elastic stiffnesses of the TW-HDSs have been about 32~33% higher than those of the KOFA HDSs. It is found that the number of leaves composing a HDS assembly could be lessened by one under the conditions that the TW-HDSs have been adopted in KOFA.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.267-274
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• 1999

An understanding of the natural frequencies of a beam is virtually a prerequisite to the understanding of its response in forced vibration due to shock, ground acceleration or moving loads. Contrary to the frequencies of the prismatic bars with arbitrary boundary conditions, those of a tapered bar are hard to determine when one employs convevtional neutral equilibrium or energy method. In this paper, finite element method is adopted to determine the fundamental frequencies of the non-symmetrically tapered bars. The bars assume the shapes of straight lines along the axis. The parameters considered in this study are sectional parameter, m,n and taper parameter, $\alpha$ For the structural engineer's convenience, the results by finite element method are expressed by simple algebraic equations, by which first mode frequencies are easily estimated. And they agree fairy well with those by F.E.M in most cases.

• Structural Engineering and Mechanics
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• 제59권2호
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• pp.243-259
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• 2016

This research develops a finite element code for the transient dynamic analysis of tapered fiber reinforced polymer (FRP) poles with hollow circular cross-section and flexible joints used in power transmission lines. The FRP poles are modeled by tapered beam elements and their flexible joints by a rotational spring. To solve the time equations of transient dynamic analysis, precise time integration method is utilized. In order to verify the utilized formulations, a typical jointed FRP pole under step, triangular and sine pulses is analyzed by the developed finite element code and also ANSYS commercial finite element software for comparison. Thereafter, the effect of joint flexibility on its dynamic behavior is investigated. It is observed that by increasing the joint stiffness, the amplitude of the pole tip deflection history decreases, and the time of occurrence of the maximum deflection is earlier.