• International Journal of Precision Engineering and Manufacturing
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• 제3권4호
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• pp.64-71
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• 2002

Recently, mechanical systems such as a high-speed vehicles and railway trains moving on flexible beam structures have become a very important issue to consider. Using the general approach proposed in the first part of this paper, it is possible to predict motion of the constrained mechanical system and the elastic structure, with various kinds of foundation supporting conditions. Combined differential-algebraic equation of motion derived from both multibody dynamics theory and finite element method can be analyzed numerically using a generalized coordinate partitioning algorithm. To verify the validity of this approach, results from the simply supported elastic beam subjected to a moving load are compared with the exact solution from a reference. Finally, parametric study is conducted for a moving vehicle model on a simply supported 3-span bridge.

• 한국분말재료학회지
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• 제22권4호
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• pp.247-253
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• 2015

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

• Journal of applied mathematics & informatics
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• 제40권5_6호
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• pp.1199-1215
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• 2022

This article aims to study the dynamical behaviours of a two species model in which non-selective harvesting of a prey-predator system by using a reasonable catch-rate function instead of usual catch-per-unit-effort hypothesis is used. A system of two ordinary differential equations(ODE's) has been proposed and analyzed with the predator functional response to prey density is considered as Hassell-Varley type functional responses to study the dynamics of the system. Positivity and boundedness of the system are studied. We have discussed the existence of different equilibrium points and stability of the system at these equilibrium points. We also analysed the system undergoes a Hopf-bifurcation around interior equilibrium point for a various parametric values which has very significant ecological impacts in this work. Computer simulation are carried out to validate our analytical findings. The biological implications of analytical and numerical findings are discussed critically.

• Advances in Computational Design
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• 제8권1호
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• pp.77-96
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• 2023

Calculating size-dependent mechanical properties of the nano-scale materials usually involves cumbersome numerical and theoretical works. In this paper, we aim to present a closed-form relation to calculate the length-dependent Young's modulus of carbon nanotubes (CNTs) based on nonlocal elasticity theory. In this regard, a single wall carbon nanotube (SWCNT) is considered as a rod structure and the governing nonlocal equations are developed under uniaxial tensile load. The equations are solved using analytical methods and strain distribution, total displacement and the size-dependent equivalent Young's modulus are obtained. Further, the results are compared with the molecular dynamics results from the literature. The outcome indicates that the calculated relations are coincident with the molecular dynamics results.

• 예술경영연구
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• 제54호
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• pp.5-31
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• 2020

이 연구는 전라북도 사례를 중심으로 문화예술단체와 문화예술인이 문화재단 설립에 반대하는 현상이 불거지는 이유를 지역사회권력구조의 정치과정에서 찾아보고, 공정성과 다원성의 측면에서 문화재단 설립 활성화 방안을 모색하는데 목적이 있다. 문화재단 설립과정에서 문화단체와 문화예술인이 제기하는 부정적 인식에는 공적 지원에 의존하는 지역문화시장의 이해관계 속에서 자신의 독점적 지위나 생계기반이 깨지고 향후 지원에서 소외될 수 있다는 우려가 깔려 있다. 전라북도에서 문화재단을 설립할 때 불거진 찬반논쟁은 문화재단의 독점에 따른 배제와 소외의 우려가 권력화, 옥상옥, 전문성 결여, 독립성 훼손, 사업소 전락 등의 공론화된 담론으로 표출되고 있음을 보여준다. 다수의 의사가 아닌 소수의 의사에 의해 정책이 결정되면 권력구조의 불균형과 함께 권력의 집중화가 초래될 수 있다. 기존의 독점적 지위를 가졌던 몇몇 단체에 지원이 집중되면서 나타난 불균형 문제가 문화재단 설립을 통하여 해소될 수 있다는 기대감이 크지만, 자칫 소수의 의사에 의하여 문화재단이 설립되고 운영되면 더 큰 불균형과 불평등이 나타날 수 있다. 문화재단 설립 방향에서 '공정성'과 '다원성'이 중요하게 고려되어야 하는 이유이다. 공정성은 사업 지원에 있어 사회적 자본이나 활동 분야에 상관없이 공정하게 진행될 것이라는 신뢰에 기반을 둔다. 이를 위하여 문화재단 임원 선정에 있어 무엇보다 공정성 확보에 집중하여야 한다. 다원성은 문화재단의 사업방향과 운영방식이 특정집단에 집중되어 행사되지 않고 다양한 집단에 분산되는 것을 말한다. 문화재단 운영 과정이 투명하고 분권적이고 참여적이어야 하며, 이를 토대로 다원적 이익이 실현될 수 있는 사업방향이 마련되어야 한다.

• 한국정밀공학회지
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• 제30권8호
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• pp.824-830
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• 2013

We propose a tracking control system for butterfly valves. A sliding mode controller with a fuzzy-neural network algorithm was applied to the design of the tracking control system. The control scheme used the real-time update law for the unmodeled system dynamics using a fuzzy-neural network algorithm. The performance of the proposed control system was assessed through a range of experiments.

• 토지주택연구
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• 제3권4호
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• pp.451-456
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• 2012

최근에 건설되는 고층 건물들은 지하 3층 이상의 깊은 지하층을 갖는 경우가 일반적이며, 이 경우에 국내 지반의 특성상 기반암 깊이가 얕아 지하층하부가 암반에 장착되거나 지중에 위치하는 경우가 많다. 현행 우리나라 내진설계기준의 지진하중은 자유장인 지표면에서의 응답을 바탕으로 하고 있어 말뚝이 매설된 기초 하부 지반에서의 지진하중과 상이하므로 비교 및 검증이 요구된다. 이를 위하여 본 연구에서는 2차원 동적(2D Dynamic) 수치해석 기법을 이용하여 말뚝기초가 기반암에 근입될 때 말뚝 강성효과에 의한 기초저면에서의 지진하중 감소를 확인하였으며 경제적인 내진설계를 수행할 수 있는 가능성을 확인해 보았다. 현행 내진 설계기준에 따른 자유장 지표면 가속도를 설계 지진 하중산정 과정에서 말뚝 강성을 고려한 지진 하중 저감효과를 평가하기 위해 PLAXIS 2D 프로그램을 사용하여 말뚝 개수 4개, 8개, 12개인 세가지 말뚝 배치 경우에 대하여 지중 및 기초상부의 최대 지진 가속도와 동일 깊이의 자유장 최대 지진 가속도를 수치해석을 통하여 비교한 결과, 지반내 매설된 말뚝 기초에 의해 20~25%가량의 지진하중 저감효과가 있는 것을 확인하였다. 그러나 말뚝의 개수 및 콘크리트 기초의 크기는 지진응답 특성에 큰 영향을 미치지 않는 것으로 평가되었다.

• Structural Engineering and Mechanics
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• 제37권2호
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• pp.149-162
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• 2011

The aim of this research is a comprehensive review and evaluation of beam theories resting on elastic foundations that used to model mode-I delamination in multidirectional laminated composite by DCB specimen. A compliance based approach is used to calculate critical strain energy release rate (SERR). Two well-known beam theories, i.e. Euler-Bernoulli (EB) and Timoshenko beams (TB), on Winkler and Pasternak elastic foundations (WEF and PEF) are considered. In each case, a closed-form solution is presented for compliance versus crack length, effective material properties and geometrical dimensions. Effective flexural modulus ($E_{fx}$) and out-of-plane extensional stiffness ($E_z$) are used in all models instead of transversely isotropic assumption in composite laminates. Eventually, the analytical solutions are compared with experimental results available in the literature for unidirectional ($[0^{\circ}]_6$) and antisymmetric angle-ply ($[{\pm}30^{\circ}]_5$, and $[{\pm}45^{\circ}]_5$) lay-ups. TB on WEF is a simple model that predicts more accurate results for compliance and SERR in unidirectional laminates in comparison to other models. TB on PEF, in accordance with Williams (1989) assumptions, is too stiff for unidirectional DCB specimens, whereas in angle-ply DCB specimens it gives more reliable results. That it shows the effects of transverse shear deformation and root rotation on SERR value in composite DCB specimens.

• Geomechanics and Engineering
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• 제22권5호
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• pp.415-431
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• 2020

In this study, dynamics responses of advanced composite plates resting variable elastic foundations via a quasi-3D theory are developed using an analytical approach. This higher shear deformation theory (HSDT) is included the shear deformation theory and effect stretching that has five unknowns, which is even inferior to normal deformation theories found literature and other theories. The quasi-three-dimensional (quasi-3D) theory accounts for a parabolic distribution of the transverse shear deformation and satisfies the zero traction boundary conditions on the surfaces of the advanced composite plate without needing shear correction factors. The plates assumed to be rest on two-parameter elastic foundations, the Winkler parameter is supposed to be constant but the Pasternak parameter varies along the long side of the plate with three distributions (linear, parabolic and sinusoidal). The material properties of the advanced composite plates gradually vary through the thickness according to two distribution models (power law and Mori-Tanaka). Governing differential equations and associated boundary conditions for dynamics responses of the advanced composite plates are derived using the Hamilton principle and are solved by using an analytical solution of Navier's technique. The present results and validations of our modal with literature are presented that permitted to demonstrate the accuracy of the present quasi-3D theory to predict the effect of variables elastic foundation on dynamics responses of advanced composite plates.

• Steel and Composite Structures
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• 재36권6호
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• pp.689-702
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• 2020

The current study deals with the size-dependent free vibration analysis of graphene nanoplatelets (GNPs) reinforced polymer nanocomposite plates resting on Pasternak elastic foundation containing different boundary conditions. Based on a four variable refined shear deformation plate theory, which considers shear deformation effect, in conjunction with the Eringen nonlocal elasticity theory, which contains size-dependency inside nanostructures, the equations of motion are established through Hamilton's principle. Moreover, the effective material properties are estimated via the Halpin-Tsai model as well as the rule of mixture. Galerkin's mathematical formulation is utilized to solve the equations of motion for the vibrational problem with different boundary conditions. Parametrical examples demonstrate the influences of nonlocal parameter, total number of layers, weight fraction and geometry of GNPs, elastic foundation parameter, and boundary conditions on the frequency characteristic of the GNPs reinforced nanoplates in detail.