• Advances in nano research
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• 제3권4호
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• pp.193-206
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• 2015

The present paper investigate the elastic buckling of chiral double-walled carbon nanotubes (DWCNTs) under axial compression. Using the non-local elasticity theory, Timoshenko beam model has been implemented. According to the governing equations of non-local theory, the analytical solution is derived and the solution for non-local critical buckling loads is obtained. The numerical results show the influence of non-local small-scale coefficient, the vibrational mode number, the chirality of carbon nanotube and aspect ratio of the (DWCNTs) on non-local critical buckling loads of the (DWCNTs). The results indicate the dependence of non-local critical buckling loads on the chirality of single-walled carbon nanotube with increase the non-local small-scale coefficient, the vibrational mode number and aspect ratio of length to diameter.

• 한국시뮬레이션학회논문지
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• 제21권1호
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• pp.1-8
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• 2012

최근들어, 글로벌 조선소들은 친환경 선박 건조와 환경 친화적 생산 공정에 큰 관심을 보이고 있다. 이러한 추세에 따라 이 연구는 조선소 레이아웃에 전 과정 평가를 적용하는 연구를 수행하였다. 전 과정 평가는 제품과 시스템의 전수명주기와 관련된 환경적 영향을 평가하는 기법으로 특정 산업분야에서 ISO 14040 표준에 따라 적용연구가 수행되고 있다. 전 과정 평가를 조선소 레이아웃에 적용하기 위해 조선소 레이아웃 계획 프레임워크를 분석하고, 조선소 레이아웃에 대한 목록분석을 수행하였으며, 환경적 영향에 대한 이산 사건 시뮬레이션 모델을 구축하였다.

• 한국비블리아학회지
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• 제6권1호
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• pp.81-109
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• 1984

The purpose of this research is (i) to establish the principles particularly appropriate for the arrangement of archival collections is korea, and (ii) to produce a workable model of classification scheme in conformity with the established principles. The archival collections in korea are roughly devided into two groups as follows. (1) The collections of professional institutions of archives such as Korean National Archives. (2) The collections preserved by libraries, museums, and other similar institutions as a secondary collection, and these groups of collections are generally non-systematic collecting. For the arrangement of the former collections, the concept of "respect des fonds" which is universally accepted principies in archives are also applicable. But in case of the arrangement of the latter collections, the above mentioned principles are inappropriate because its collections a re built in separate pieces of documents and records without any relevance to the original function or structure of the corporation. Consequantly it is badly needed to make some devices for the arrangement of these archival collections since the archival collections of korea, in the majority of cases, belong to the latter. The author produced a tentative classification scheme, and adapted the korean traditional form (or type) of documents and records as a cardinal principle of the classification. The scheme is presented at the end of this paper.

• Advances in nano research
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• 제4권1호
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• pp.31-44
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• 2016

This article is concerned with the free vibration problem for chiral double-walled carbon nanotube (DWCNTs) modelled using the non-local elasticity theory and Euler Bernoulli beam model. According to the governing equations of non-local Euler Bernoulli beam theory and the boundary conditions, the analytical solution is derived and two branches of transverse wave propagating are obtained. The numerical results obtained provide better representations of the vibration behaviour of double-walled carbon nanotube, where the aspect ratio of the (DWCNTs), the vibrational mode number, the small-scale coefficient and chirality of double-walled carbon nanotube on the frequency ratio (${\chi}^N$) of the (DWCNTs) are significant. In this work, the numerical results obtained can be used to predict and prevent the phenomenon of resonance for the forced vibration analyses of double -walled carbon nanotubes.

• Wind and Structures
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• 제28권1호
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• pp.19-30
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• 2019

This article present the free vibration analysis of simply supported perfect and imperfect (porous) FG beams using a high order trigonometric deformation theory. It is assumed that the material properties of the porous beam vary across the thickness. Unlike other theories, the number of unknown is only three. This theory has a parabolic shear deformation distribution across the thickness. So it is useless to use the shear correction factors. The Hamilton's principle will be used herein to determine the equations of motion. Since, the beams are simply supported the Navier's procedure will be retained. To show the precision of this model, several comparisons have been made between the present results and those of existing theories in the literature.

• Structural Engineering and Mechanics
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• 제70권4호
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• pp.395-405
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• 2019

In the present work, the effects of cutting parameters on surface roughness parameters (Ra), tool wear parameters (VBmax), tool vibration (Vy) and material removal rate (MRR) during hard turning of AISI 4140 steel using coated carbide tool have been evaluated. The relationships between machining parameters and output variables were modeled using response surface methodology (RSM). Analysis of variance (ANOVA) was performed to quantify the effect of cutting parameters on the studied machining parameters and to check the adequacy of the mathematical model. Additionally, Multi-objective optimization based desirability function was performed to find optimal cutting parameters to minimize surface roughness, and maximize productivity. The experiments were planned as Box Behnken Design (BBD). The results show that feed rate influenced the surface roughness; the cutting speed influenced the tool wear; the feed rate influenced the tool vibration predominantly. According to the microscopic imagery, it was observed that adhesion and abrasion as the major wear mechanism.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.191-201
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• 2019

Finite element analysis is one of the most used tools for studying femoral neck fracture. Nerveless, consensus concerning either the choice of material characteristics, damage law and /or geometric models (linear on nonlinear) remains unreached. In this work, we propose a numerical quasi-brittle damage model to describe the behavior of the proximal femur associated with two methods to evaluate the Young modulus. Eight proximal femur finite elements models were constructed from CT scan data (4 donors: 3 women; 1 man). The numerical computations showed a good agreement between the numerical curves (load - displacement) and the experimental ones. A very encouraging result is obtained when a comparison is made between the computed fracture loads and the experimental ones ($R^2=0.825$, Relative error =6.49%). All specific numerical computation provided very fair qualitative matches with the fracture patterns for the sideway fall simulation. Finally, the comparative study based on 32 simulations adopting linear and nonlinear meshing led to the conclusion that the quantitatively results are improved when a nonlinear mesh is used.

• Membrane and Water Treatment
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• 제13권2호
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• pp.73-83
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• 2022

In the present study, we compared the adsorption capacity of Pb (II) from contaminated water of used cardboard (UC) and a commercial powdered activated carbon (PAC), the latter has been characterized by different techniques, namely X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), wavelength dispersion x-ray fluorescence (WDXRF), infrared spectroscopy (IR) and surface area B.E.T analyzer. The effect of various parameters, such as the pH, the contact time, the amount of adsorbent, and the temperature on the adsorption of Pb (II) on both materials was investigated. The Pb (II) adsorptions are perfectly described by a pseudo-second-order model, while the intraparticle diffusion is a decisive step after the first minutes of contact. The fit to the Langmuir and Redlich-Peterson models seems perfect for these adsorption reactions. (PAC) showed a greater affinity for Pb (II) compared to (UC) and the adsorption of Pb (II) ions is strongly pH-dependent, on the other hand, the increase in temperature doesn't have much influence on the two solids. This study showed that the capacity of (UC) to adsorb Pb (II) from an aqueous solution is greater than two-thirds of that of (PAC).

• Composites Research
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• 제26권6호
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• pp.363-372
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• 2013

RTM (Resin Transfer Molding) 공정을 수치해석하기 위해 Level set 방법과 결합된 확장 유한 요소 법을 적용하였다. 유동 전면 부에서 비연속적인 구배를 가지는 압력을 계산하기 위해 확장 유한 요소 법을 이용하여 계산의 정밀성을 높였다. 확장 유한 요소 법에 이용되는 확장 형상 함수는 Level set 값을 이용하여 정의하였다. 이 확장 형상 함수는 요소를 통과하는 수지 유동 전면부의 위치를 반영할 수 있다. 게다가 Level set 법이 금형 충전 동안 수지 유동 전면부의 위치를 계산할 때 적용되었다. 수지 유동 전면부의 위치를 계산하는 미분방정식은 내연적 특성 Galerkin 유한 요소 법을 적용하여 풀었다. 선형 시스템 계산에서는 IPSAP의 다중 프론트 솔버를 이용한다. 본 연구에서 계산한 해석 값은 이론 값과 비교하여 검증하였다. 계산 효율을 높이기 위해 확장 유한 요소 법과 Level set 방법의 국소화 기법이 제안되었다. 이 기법은 계산 영역을 수지 유동 전면 부 근처의 영역으로 축소한다. 그러므로 전체 계산 양은 최소화될 수 있었다. 이 기법의 계산 효율은 채널 유동 모델을 이용하여 평가된다. 본 연구의 해석 능력을 보여주기 위해 몇 가지 적용 예제를 계산하였다. 첫 번째 예제를 이용해서 복잡하게 흘러가는 수지 전면부의 갈라짐과 합쳐지는 현상 해석하였다. 그리고 금형 내부의 Race-tracking 효과와 기공 생성 현상을 확인하기 위해 복잡한 모양의 구조물을 시뮬레이션 하였다.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.53-66
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• 2018

This paper presents an analysis of the bending, buckling and free vibration of functionally graded sandwich beams resting on elastic foundation by using a refined quasi-3D theory in which both shear deformation and thickness stretching effects are included. The displacement field contains only three unknowns, which is less than the number of parameters of many other shear deformation theories. In order to homogenize the micromechanical properties of the FGM sandwich beam, the material properties are derived on the basis of several micromechanical models such as Tamura, Voigt, Reuss and many others. The principle of virtual works is used to obtain the equilibrium equations. The elastic foundation is modeled using the Pasternak mathematical model. The governing equations are obtained through the Hamilton's principle and then are solved via Navier solution for the simply supported beam. The accuracy of the proposed theory can be noticed by comparing it with other 3D solution available in the literature. A detailed parametric study is presented to show the influence of the micromechanical models on the general behavior of FG sandwich beams on elastic foundation.