• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.77-83
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• 2022

In the last ten years, many researchers have studied the vibrations of carbon nanotubes using different beam theories. The nano- and micro-scale systems have wavy shape and there is a demand for a powerful tool to mathematically model waviness of those systems. In accordance with the above mentioned lack for the modeling of the waviness of the curved tiny structure, a novel approach is employed by implementing the Timoshenko-beam model. Owing to the small size of the micro beam, these structures are very appropriate for designing small instruments. The vibrations of double walled carbon nanotubes (DWCNTs) are developed using the Timoshenko-beam model in conjunction with the wave propagation approach under support conditions to calculate the fundamental frequencies of DWCNTs. The frequency influence is observed with different parameters. Vibrations of the double walled carbon nanotubes are investigated in order to find their vibrational modes with frequencies. The aspect ratios and half axial wave mode with small length are investigated. It is calculated that these frequencies and ratios are dependent upon the length scale and aspect ratio.

• Korean Institute of Interior Design Journal
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• v.24 no.2
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• pp.78-87
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• 2015

This study aims to grasp the vital rhythm of the Chapel at Ronchamp by analyzing its rhythm through Henri Lefebvre's 'rhythmanalysis' in an effort to show the possibility of approaching the presence of this chapel. For the purpose of this study, Lefebvre's thought of rhythmanalysis was first contemplated, and a case study analysis was conducted on the concept and presence of the chapel in the design process. On this basis, examples of the chapel's rhythms were analyzed through Lefebvre's dialectical analysis of the triad of time(melody), space(harmony) and energy(rhythm). The results of analysis are as follows: First, the concept intended by Le Corbusier in the process of designing the Chapel at Ronchamp is expressed as the acoustic form, the modulor corresponding to the scale of the music, the light and shadow of counterpoint, and the opposite composition of musical changes. Consequently, the concept-mediated presence of this chapel is the presence of music. Second, at the Chapel at Ronchamp, a Lefebvre's rhythmanalyst experiences, or rather senses, two vital rhythms of an antithetical unity (i.e., acoustic curved rhythm and modulor-generated linear rhythm), with reference to his/her own rhythms. These rhythms are a dialectical union of spatiality of melodies temporalized through continuity, (i.e., acoustic curved form and modulor-generated linear form), and temporality of harmonies spatialized through simultaneity (i.e., light and shadow, materials and color, form of interpenetration, and stairs or windows/doors). These rhythms carry the measures generated by music-specific repetitions and differences in movements(energy). Consequently, the rhythm-mediated presence of this chapel is also the presence of music. In conclusion, the Chapel of Ronchamp indicates that an approach toward its presence can be realized through vital rhythms derived from Lefebvre's 'rhythmanalysis'. This study holds significance as an analysis of spatial rhythm and presence, employing a philosophical thought.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.341-348
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• 2019

The purpose of this study is to model and analyze retractable large spatial structures by applying parametric modeling techniques. The modeling of wind loads in the analysis of typical structures including curved surfaces can be error-prone, and the processing time increases dramatically when there are many types of variables. However, the method based on StrAuto that was developed in previous research, facilitates the efficacious assignment of wind loads to structures and the rapid arrival of conclusions. As a result, it is possible to compare alternatives with various loads, including wind loads, to determine an optimal alternative much faster than the existing process. Further, it is almost impossible to directly input the wind load by calculating the area of an irregularly curved surface. However, the proposed method automatically assigns the wind load, which allows for automatic optimization in a structural analysis system. The approach was applied and optimized using several models, and the results are presented.

• Plant Journal
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• v.17 no.3
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• pp.42-46
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• 2021

The equation of motion of the drill string along the excavation trajectory was analyzed using the Lagrangian approach together with the finite element method (FEM). A drill string of circular cross section is constructed by combining a plurality of circular axes each having 12 degrees of freedom (DOF). FEM analysis can observe the vibration and dynamic changes of the entire drill string, and it is easy to apply comprehensive boundary conditions to reproduce the simulation of a realistic drill string. In this study, the constructed FEM motel was simulated. In order to apply the FEM program to the actual drill trajectory, the dynamic analysis of the curved beam was verified by comparison with the actual values. The dynamic change over time was observed.

• Steel and Composite Structures
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• v.43 no.1
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• pp.91-106
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• 2022

This paper has focused on presenting a three dimensional theory of elasticity for free vibration of 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) cylindrical panels resting on two-parameter elastic foundations. The elastic foundation is considered as a Pasternak model with adding a Shear layer to the Winkler model. The porous graphene foams possessing 3D scaffold structures have been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the shell thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary at the curved edges. It is explicated that 3D-GrF skeleton type and weight fraction can significantly affect the vibrational characteristics of GrF-PMC panel resting on two-parameter elastic foundations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.581-590
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• 2010

This study introduces a layered sectional analysis for a PSC girder with a vaiable cross section and curved tendons. To consider the shear equilibrium at a concrete layer with curved tendons, the shear stress distribution has been computed at each section. In addition, to improve the convergence to the solution, a system identification technique is newly adopted in the solution process for strain computation. To examine the feasibility of the proposed approach, a static load test has been conducted for a full scale PSC girder with variable cross section. The prediction shows a good agreement with experiment. It is seen that a uniform cross section has the same moment capacity with a variable cross section while the variable cross section has more shear capacity than the uniform cross section. It is also noted that the maximum displacement of a variable cross section is a little smaller than a uniform cross section.

• Structural Engineering and Mechanics
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• v.24 no.4
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• pp.447-461
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• 2006

Here, the axisymmetric free flexural vibrations and thermal stability behaviors of functionally graded spherical caps are investigated employing a three-noded axisymmetric curved shell element based on field consistency approach. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. The material properties are graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents of the material. The effective material properties are evaluated using homogenization method. A detailed numerical study is carried out to bring out the effects of shell geometries, power law index of functionally graded material and base radius-to-thickness on the vibrations and buckling characteristics of spherical shells.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1131-1136
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• 2008

The electrical repulsive energy between two model cylinders was calculated by solving nonlinear Poission- Boltzmann (P-B) equation under Derjaguin approximation. Effects of the surface potential, Debye screening length, and configuration of cylinders on the repulsive interaction energy were examined. Due to the anisotropy of the shape of cylinder, the interaction repulsive energy showed dependence to the configuration of particles; cylinders aligned in end-to-end configuration showed largest repulsive energy and crossed particles had lowest interaction energy. The configuration effect is originated from the curvature effect of the interacting surfaces. The curved surfaces showed less repulsive energy than flat surfaces at the same interacting surface area. The configuration dependency of interaction energy agreed with the previous analytical solution obtained under the linearized P-B equation. The approach and results present in this report would be applicable in predicting colloidal behavior of cylindrical particles.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.61-68
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• 2000

In general, the design of membrane structures takes three steps. The first is shape finding analysis which is determination of initial equilibrium geometry with uniform stresses. The second step involve the computation of the stress-deformation to get completed membrane under various load conditions. The third step is to divide the membrane structures into several plan strips from the initial equilibrium states. This procedure is needed because of the initial shape has usually undevelopable curved surface and is called as "cutting patterns generation". By introducing this work, the deformation due to the initial stress is removed and approximate cutting patterns are generated. In this approach, however, material properties is not considered, therefore the error between the design stresses and actual stresses during the fabrication of plan strips should be occurred. In this paper, actual equilibrium shape analysis procedure for HP shape models is presented. The deviations of stresses between the design stresses and actual stresses are estimated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.06a
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• pp.87-95
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• 1996

The stamping process consists of two stages : First, the blank is held by the blank holder and then it is further formed into the die cavity by punch stroke. In actual stamping process, the accurate prediction of binder wrap is an indispensable step in sheet metal forming analysis because the initial plastic buckling induced by improper die design is directly related with fatal defect at the final stage. In the present work, an approach including the gravity effect of blank material and proper consideration of contact and friction is proposed. Computations are carried out for some actual auto-body parts using 3D FEM code to investigate the validity of the proposed methodology. Comparisons with experimental results show that the suggested scheme can be effectively applied to the precise prediction of binder wrap for arbitrarily curved die faces in which gravity and contact effect must be taken into account.