• 대한토목학회논문집
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• 제29권2A호
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• pp.155-162
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• 2009

이 논문은 정다각형 중실단면을 갖는 최강보에 관한 연구이다. 이 연구에서 보의 체적은 항상 일정하다. 이러한 보에 집중하중과 만재 사다리꼴 분포하중이 작용하는 경우에 탄성곡선의 미분방정식을 유도하고 이를 수치해석하여 정적 거동을 산정하였다. 미분방정식은 Runge-Kutta법을 이용하여 수치적분을 하였고 미지수인 보의 초기치는 shooting method를 이용하여 산정하였다. 수치해석 예에서는 단순보를 채택하였고, 단면깊이의 형상함수로는 선형, 포물선형 및 정현형의 함수를 채택하였다. 이 연구에서 얻은 수치해석의 결과로부터 보의 정적 최대거동값이 최소가 되는 단면형상 즉 최강단면비를 산정하였다.

• 대한토목학회논문집
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• 제29권3A호
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• pp.251-258
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• 2009

이 논문은 정다각형 중실 단면을 갖는 최강보에 관한 연구이다. 이 연구에서 보의 체적은 항상 일정하다. 이러한 보에 집중하중과 만재 사다리꼴 분포하중이 작용하는 경우에 탄성곡선의 미분방정식을 유도하고 이를 중적분법을 이용하여 풀어 정적 거동을 산정하였다. 미분방정식의 정적분은 Simpson 공식을 이용하였다. 수치해석 예에서는 고정-고정 보 및 고정-회전보를 채택하였고, 단면깊이의 형상함수로는 선형, 포물선형 및 정현형의 함수를 채택하였다. 이 연구에서 얻은 수치해석의 결과로부터 보의 정적 최대거동값이 최소가 되는 단면형상 즉 최강단면비를 산정하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.79-86
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• 2005

This paper deals with the static optimal shapes of simple beams which are subjected to a vertical point load. The area and second moment of inertia of the regular polygon cross-section of the tapered beams are determined, which have always same volume and same length for the parabolic taper. The differential equation governing the elastic curve is derived using the small deflection theory and solved numerically. By using the numerical results of deflections, rotations and bending stresses of such beams, the optimal shapes, namely, optimal section ratios, of the beams subjected to a single point load according to variation of load position parameters are determined and presented in the figures. Examples of the static optimal shapes for beams with a single load and multiple loads are reported. The design process of this study can be used directly for the minimum weight design of simple beams.

• Steel and Composite Structures
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• 재36권6호
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• pp.643-656
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• 2020

This article presents a comprehensive static analysis of simply supported cross-ply carbon nanotubes reinforced composite (CNTRC) laminated nanobeams under various loading profiles. The nonlocal strain gradient constitutive relation is exploited to present the size-dependence of nano-scale. New higher shear deformation beam theory with hyperbolic function is proposed to satisfy the zero-shear effect at boundaries and parabolic variation through the thickness. Carbon nanotubes (CNTs), as the reinforced elements, are distributed through the beam thickness with different distribution functions, which are, uniform distribution (UD-CNTRC), V- distribution (FG-V CNTRC), O- distribution (FG-O CNTRC) and X- distribution (FG-X CNTRC). The equilibrium equations are derived, and Fourier series function are used to solve the obtained differential equation and get the response of nanobeam under uniform, linear or sinusoidal mechanical loadings. Numerical results are obtained to present influences of CNTs reinforcement patterns, composite laminate structure, nonlocal parameter, length scale parameter, geometric parameters on center deflection ad stresses of CNTRC laminated nanobeams. The proposed model is effective in analysis and design of composite structure ranging from macro-scale to nano-scale.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.1-4
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• 2005

A higher order zig-zag shell theory is developed to refine accurately predict deformation and stress of smart shell structures under the mechanical, thermal, and electric loading. The displacement fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. The mechanical, thermal, and electric loading is applied in the sinusoidal distribution function in the in-surface direction. Thermal and electric loading is given in the linear variation through the thickness. Especially, in electric loading case, voltage is only applied in piezo-layer. The layer-dependent degrees of freedom of displacement fields are expressed in terms of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses. In order to obtain accurate transverse shear and normal stresses, integration of equilibrium equation approach is used. The numerical examples of present theory demonstrate the accuracy and efficiency of the proposed theory. The present theory is suitable for the predictions of behaviors of thick smart composite shell under mechanical, thermal, and electric loadings combined.

• Journal of Pharmaceutical Investigation
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• 제22권3호spc1호
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• pp.65-76
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• 1992

The superoxide dismutase (SOD)-mimetic activities of copper complexes of a series of salicylic acid (SA) analogs were tested and compared to the activity of bovine erythrocyte SOD using ferricytochrome c reduction assay. Stability constants of copper complexes were measured potentiometrically using SCOGS2 program. In the presence of 10 g/l albumin, all the copper complexes lost their SOD mimetic activities. Multiple regression analysis was employed for the statistical comparisons between the SOD mimetic activity and their physicochemical properties. Correlation exists for the SOD mimetic activity and steric parameter $(E_s)$ and/or electronic parameter $({\Sigma}{\sigma})$ in xanthine/xanthine oxidase (XOD) system, demonstrating that E, plays a key role in SOD activity whereas ${\Sigma}{\sigma}$ influences it to a lesser extent. The protective effect of copper complexes against membrane damage was measured by counting D-glucose released frm $EG_s$. D-glucose and XOD were entrapped within $EG_s$ and acetaldehyde was used as a substrate for XOD. In this membrane model system using $EG_s$, hydrophobic parameter $({\Sigma}{\pi})$ is of most importance, producing parabolic equation while $E_s$, and ${\Sigma}{\sigma}$ appear to playa minor role in protection against D-glucose release. In summary, to design an efficient SOD mimetic, stability, steric factor, lipophilicity and redox potential should be considered.

• 한국군사과학기술학회지
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• 제18권5호
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• pp.538-547
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• 2015

The goal of this study is to develop an algorithm to propose optimal deployment of detection sensor nodes in the target area, based on a performance surface, which represents detection performance of active and passive acoustic sonar systems. The performance surface of the active detection system is calculated from the azimuthal average of maximum detection ranges, which is estimated with a transmission loss and a reverberation level predicted using ray-based theories. The performance surface of the passive system is calculated using the transmission loss model based on a parabolic equation. The optimization of deployment configurations is then performed by a hybrid method of a virtual force algorithm and a particle swarm optimization. Finally, the effectiveness of deployment configurations is analyzed and discussed with the simulation results obtained using the algorithm proposed in this paper.

• 소음진동
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• 제6권5호
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• pp.587-594
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• 1996

이 논문에서는 일정체적의 정다각형 단면을 갖는 보-기둥의 자유진동 및 좌굴하중을 지배하는 비분방정식을 유도하고 이를 수치해석하였다. 정다각형 단면의 단면깊이 변화식으로는 포물선식과 정현식을 채택하였고, 고정-고정, 회전-고정 및 회전-회전의 단부조건에 대하여 고유진동수 및 좌굴하중을 산출하였다. 수치해석의 결과로 무차원 고유진동수와 무차원변들 사이의 관계 및 무차원 좌굴하중과 단면비 사이의 관계를 그림에 나타내었다. 또한, 최강기둥의 단면비와 좌국하중을 산출 하였다.

• 한국해안해양공학회지
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• 제11권3호
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• pp.135-140
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• 1999

에너지 감쇠역으로 인한 파의 변형을 모의하기 위하여 타원형 수치모형을 구성하였다. 해석방정식은 에너지 감쇠항이 추가된 타원형 완경사 방정식을 사용하였다. 개방경계조건에는 포물형 가정을 도입하였고 이를 위해 수치기법으로는 GCGM을 사용하였다. 원형감쇠역에 대한 수치실험을 통하여 감쇠역 전부에서의 반사파의 생성, 감쇠효과에 의한 파고감소 등을 확인할 수 있었고 해석해와 잘 일치하였다. 사각형 감쇠역에 대한 실험을 통하여 감쇠계수의 크기에 따른 파고분포의 변화를 살펴보았고 감쇠역 주변에서는 회절효과에 의한 파고의 증가가 매우 완만히 진행됨을 확인하였다. 이러한 수치실험을 통하여 에너지 감쇠구조 또한 반복기법을 사용한 타원형 수치모형으로 잘 모의할 수 있음을 확인하였다.

• 대한수학회지
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• 제49권3호
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• pp.585-604
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• 2012

In this paper we consider the evolution of the rolling stone with a rotationally symmetric nonconvex compact initial surface ${\Sigma}_0$ under the Gauss curvature flow. Let $X:S^n{\times}[0,\;{\infty}){\rightarrow}\mathbb{R}^{n+1}$ be the embeddings of the sphere in $\mathbb{R}^{n+1}$ such that $\Sigma(t)=X(S^n,t)$ is the surface at time t and ${\Sigma}(0)={\Sigma}_0$. As a consequence the parabolic equation describing the motion of the hypersurface becomes degenerate on the interface separating the nonconvex part from the strictly convex side, since one of the curvature will be zero on the interface. By expressing the strictly convex part of the surface near the interface as a graph of a function $z=f(r,t)$ and the non-convex part of the surface near the interface as a graph of a function $z={\varphi}(r)$, we show that if at time $t=0$, $g=\frac{1}{n}f^{n-1}_{r}$ vanishes linearly at the interface, the $g(r,t)$ will become smooth up to the interface for long time before focusing.