• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.15 no.3
• /
• pp.511-521
• /
• 2002

A simple numerical modelling technique is proposed for estimating the shear stress distribution in beams of framed tube structures with multiple internal tubes. The structures arc analysed using a continuum approach in which each tube is individually modelled by a tube beam that accounts for the flexural and shear deformations, as well as the shear lag effects. The numerical analysis of shear stress is based on the mathematical analogy in conjunction with the elastic theory By simplifying assumptions regarding the form of strain distributions in external and internal tubes, the shear stress distributions are expressed in terms of a series of lineal functions of the second moments of area of the structures and the corresponding geometric and material properties, as well as the applied loads. Previous studies for axial stresses and shear lag phenomenon are further developed lot the numerical analysis of shear stresses in the tubes. The simplicity and accuracy of the proposed method are demonstrated through the solutions of throe numerical examples.

• Steel and Composite Structures
• /
• v.20 no.3
• /
• pp.623-649
• /
• 2016

Most of the early studies on plates vibration are focused on two-dimensional theories, these theories reduce the dimensions of problems from three to two by introducing some assumptions in mathematical modeling leading to simpler expressions and derivation of solutions. However, these simplifications inherently bring errors and therefore may lead to unreliable results for relatively thick plates. The main objective of this research paper is to present 3-D elasticity solution for free vibration analysis of continuously graded carbon nanotube-reinforced (CGCNTR) rectangular plates resting on two-parameter elastic foundations. The volume fractions of oriented, straight single-walled carbon nanotubes (SWCNTs) are assumed to be graded in the thickness direction. In this study, an equivalent continuum model based on the Eshelby-Mori-Tanaka approach is employed to estimate the effective constitutive law of the elastic isotropic medium (matrix) with oriented, straight carbon nanotubes (CNTs). The proposed rectangular plates have two opposite edges simply supported, while all possible combinations of free, simply supported and clamped boundary conditions are applied to the other two edges. The formulations are based on the three-dimensional elasticity theory. A semi-analytical approach composed of differential quadrature method (DQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence of the method is demonstrated and comparison studies are carried out to establish its very high accuracy and versatility. The 2-D differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and to implement the boundary conditions. The convergence of the method is demonstrated and to validate the results, comparisons are made between the present results and results reported by well-known references for special cases treated before, have confirmed accuracy and efficiency of the present approach. The novelty of the present work is to exploit Eshelby-Mori-Tanaka approach in order to reveal the impacts of the volume fractions of oriented CNTs, different CNTs distributions, various coefficients of foundation and different combinations of free, simply supported and clamped boundary conditions on the vibrational characteristics of CGCNTR rectangular plates. The new results can be used as benchmark solutions for future researches.

• Korean Institute of Interior Design Journal
• /
• no.40
• /
• pp.26-33
• /
• 2003

Contemporary architecture has two different movements that one is the utilization of digital technology and the other is the inclination to nature. After deconstructivism in architecture, the tendency of design shows the fusion between digitalism and organicism and as a consequence the phenomena of 'skin expression' has emerged which can be thought as 'organic digitalism' or 'digital organicism'. The definition of skin tendency in environmental design is the design of nature based on the technology. As a result, the surface becomes the design issue compared to structure and the momentum for new aesthetic value. There are post-structuralism, complex system theory and the organic architecture as theoretical background for the tendency of skin expression. Specially the ideas of post-structural philosophy has effected deeply to the formation of its movement and also offered the theoretical nutrition for digital architecture. The characteristics of the skin tendency can be analyzed as topological transformation, smooth continuum, deterritorialization, ecological response system, and tactility. These design characteristics has combined with conventional material and design vocabulary to transform and develope new spatial conception.

• Advances in concrete construction
• /
• v.9 no.3
• /
• pp.301-312
• /
• 2020

This research deals with the study of the orthotropic vibrational features of single-walled carbon nanotubes according to Kelvin's model and to check the accuracy of the models, the results have been compared with earlier modeling/simulations. Obtaining rough approximations of the natural frequencies of CNTs using continuum equations are still a common procedure, even at high harmonics. The effects of different physical and material parameters on the fundamental frequencies are investigated for zigzag and chiral single-walled carbon nanotubes invoking Kelvin's theory. By using nonlocal Kelvin's model, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes (SWCNTs) have been calculated. The influence of frequencies with nonlocal parameters and bending rigidity are investigated in detail for these tubes. Computer software MATLAB is utilized for the frequencies of SWCNTs and current results shows a good stability with comparison of other studies.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1147-1150
• /
• 2004

We studied on an electro-optical (EO) hysteresis, coming from the in-plane modulation of the molecular reorientation, in highly twisted nematic liquid crystal devices. Varying a ratio d/$P_0$ of the cell thickness d to the natural pitch $P_0$, the EO hysteresis and the twisted angle transition were observed and analyzed in terms of the periodicity of the in-plane modulation within the continuum theory.

• Journal of the Korea Computer Graphics Society
• /
• v.12 no.1
• /
• pp.21-25
• /
• 2006

This paper proposes a real-time simulation technique for thin shells undergoing large deformation. Thin shells are almost two-dimensional structures visually well approximated as surfaces, such as leaves, paper sheets, hats, aluminum cans. Unfortunately accurate simulation of these structures requires one of the most complex formulations in continuum mechanics, shell theory [4]. Moreover, there has not yet been any work reported to produce visually convincing animation of them while achieving real-time performance. Motivated by discrete shells [5] and modal warping [3], we formulate dynamics of thin shells using mass-spring models instead of finite element models, and then apply the modal warping technique to cope with large rotational deformation of thin shells. Experiments show that the proposed technique runs in real-time, and that it can simulate large bending and/or twisting deformations with acceptable realism.

• The Korean Journal of Ecology
• /
• v.14 no.3
• /
• pp.257-271
• /
• 1991

Two types in the species-importance, one type of carpinus laxiflora, carpinus tschonoskii, quercus serrata, quercus grosseserrata and pnus densiflora community and another type of abeies koreana community classified by zurich-montpellier method, were recognized based on the data from 81 sample plots. The forme species sequence-importance curves were coincidred with the ideal curve calculated by preston's lognormal-distribution theory(1948), with small variations among five communities, and the latter with that of motomura's niche pre-emption hypothesis(1932). It seems that plant community classified by phytosociological method based on the unit concept coincide with the vegetation type recognized by species population analyse based on the continuum concept and the dominance-diversity reflrcts on the difference in the coenocline among their plant communities.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.1
• /
• pp.60-66
• /
• 1999

This study is to develop design sensitivity analysis method based on continuum theory for the actual buckling load of vehicle passenger compartment with respect to sizing design variables. For nonlinear structural analysis, both geometric and material nonlinear effects are considered. The total Lagrangian formulation for incremental equilibrium analysis and one-point linear eigenvalue problem for buckling analysis are utilized. Numerical methods are presented to evaluate design sensitivity expressions, using structural analysis results from FEM code. Optical design of vehicle passenger compartment with buckling constraint solved using Gradient projection method.

• Geomechanics and Engineering
• /
• v.8 no.3
• /
• pp.377-390
• /
• 2015

The governing equations of wave propagation in one dimension of elastic continuum materials are investigated by taking the influence of the initial stress into account. After a short review of the theory of elastic wave propagation in a rock mass with an initial stress, results indicate that the initial stress differentially influences P-wave and S-wave propagation. For example, when the initial stress is homogeneous, for the P-wave, the initial stress only affects the magnitude of the elastic coefficients, but for the S-wave, the initial stress not only influences the elastic coefficients but also changes the governing equation of wave propagation. In addition, the P-wave and S-wave velocities were measured for granite samples at a low initial stress state; the results indicate that the seismic velocities increase with the initial stress. The analysis of the previous data of seismic velocities and elastic coefficients in rocks under ultra-high hydrostatic initial stress are also investigated.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2382-2388
• /
• 2007

A series of dimethine cyanine dyes were synthesized in a fast, efficient and high yield by the condensation of quaternary salts with 1H-indole-3-carbaldehyde in the presence of piperidine under solvent-free microwave irradiation. The products were identified by 1H NMR, IR, UV-Vis spectra and elemental analysis. The absorption and fluorescence properties of these dyes were investigated both experimentally and theoretically. Calculations performed at a combination of time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π-π* type absorption bands of the dyes. Regression analysis was used for studying theoretical results of the absorption maxima in different solvents. Compared with experimental counterparts, estimated overall uncertainties in the absorption maxima were about ±2%.