• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.184-191
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• 2003

In this paper, a mathematical framework based on a homogenisation technique to simulate 'umbrella arch reinforcement system' (UARS) and its implementation into a 3D Finite Element program that can consider stage construction situations are presented. The constitutive model developed allows considering the main design parameters of the problem and only requires geometrical and mechanical properties of the constituents. Additionally, the use of a homogenisation approach implies that the generation of the Finite Element mesh can be easily produced and that re-meshing is not required as basic geometrical parameters such as the orientation of the pipes are changed. The model developed is used to simulate tunnelling with the UARS. From the analyses, the effects of the main design parameters on the elastic and the elastoplastic analyses are considered.

• Advances in concrete construction
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• v.9 no.4
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• pp.397-406
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• 2020

The present article deals with post-buckling of geometrically imperfect concrete plates reinforced by graphene oxide powder (GOP) based on general higher order plate model. GOP distributions are considered as uniform and linear models. Utilizing a shear deformable plate model having five field components, it is feasible to verify transverse shear impacts with no inclusion of correction factor. The nonlinear governing equations have been solved via an analytical trend for deriving post-buckling load-deflection relations of the GOP-reinforced plate. Derived findings demonstrate the significance of GOP distributions, geometric imperfectness, foundation factors, material compositions and geometrical factors on post-buckling properties of reinforced concrete plates.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1813-1822
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• 2006

The dynamic analysis of a plate with non-linearity due to large deformation was investigated in this study. There have been many theoretical and numerical analyses of the non-linear dynamic behavior of plates examining theoretically or numerically. The problem is how correctly an analytical model can represent the dynamic characteristics of the actual system. To address the issue, the continuous-time system identification technique was used to generate non-linear models, for stiffness and damping terms, and to explain the observed behaviors with single mode assumption after comparing experimental results with the numerical results of a linear plate model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.498-503
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• 2003

Dynamic analysis of a plate with non-linearity due to large deformation is performed in the study. There have been many researches about the non-linear dynamic behavior of plates examining by means of theoretical or numerical analyses. But it is important how exactly model the actual system. In this respect, the Continuous-Time system identification technique is used to generate non-linear models, for stiffness and damping terms, to explain the observed behaviors with single mode assumptions for the simplicity after comparing the experimental results with the numerical results of a linear plate model.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.223-240
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• 2006

Taking into account the geometrical and material nonlinearities, an ultimate behavior of reinforced concrete cooling tower shell in hyperbolic configuration is presented. The design wind pressures suggested in the guidelines of the US (ACI) and Germany (VGB), with or without the effect of internal suction, are employed in the analysis to examine the qualitative and quantitative characteristics of each design wind pressure. The geometrical nonlinearity is incorporated by the Green-Lagrange strain tensor. The nonlinear features of concrete, such as the nonlinear stress-strain relation in compression, the tensile cracking with the smeared crack model, an effect of tension stiffening, are taken into account. The biaxial stress state in concrete is represented by an improved work-hardening plasticity model. From the perspective of quality of wind pressures, the two guidelines are determined as highly correlated each other. Through the extensive analysis on the Niederaussem cooling tower in Germany, not only the ultimate load is determined but also the mechanism of failure, distribution of cracks, damage processes, stress redistributions, and mean crack width are examined.

• Structural Engineering and Mechanics
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• v.7 no.3
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• pp.259-276
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• 1999

An analytical solution for the shape functions of a beam segment supported on a generalized two-parameter elastic foundation is derived. The solution is general, and is not restricted to a particular range of magnitudes of the foundation parameters. The exact shape functions can be utilized to derive exact analytic expressions for the coefficients of the element stiffness matrix, work equivalent nodal forces for arbitrary transverse loads and coefficients of the consistent mass and geometrical stiffness matrices. As illustration, each distinct coefficient of the element stiffness matrix is compared with its conventional counterpart for a beam segment supported by no foundation at all for the entire range of foundation parameters.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.565-578
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• 2018

This research article reported the nonlinear finite solutions of the nonlinear flexural strength and stress behaviour of nano sandwich graded structural shell panel under the combined thermomechanical loading. The nanotube sandwich structural model is derived mathematically using the higher-order displacement polynomial including the full geometrical nonlinear strain-displacement equations via Green-Lagrange relations. The face sheets of the sandwich panel are assumed to be carbon nanotube-reinforced polymer composite with temperature dependent material properties. Additionally, the numerical model included different types of nanotube distribution patterns for the sandwich face sheets for the sake of variable strength. The required equilibrium equation of the graded carbon nanotube sandwich structural panel is derived by minimizing the total potential energy expression. The energy expression is further solved to obtain the deflection values (linear and nonlinear) via the direct iterative method in conjunction with finite element steps. A computer code is prepared (MATLAB environment) based on the current higher-order nonlinear model for the numerical analysis purpose. The stability of the numerical solution and the validity are verified by comparing the published deflection and stress values. Finally, the nonlinear model is utilized to explore the deflection and the stresses of the nanotube-reinforced (volume fraction and distribution patterns of carbon nanotube) sandwich structure (different core to face thickness ratios) for the variable type of structural parameter (thickness ratio, aspect ratio, geometrical configurations, constraints at the edges and curvature ratio) and unlike temperature loading.

• Journal of The Korean Astronomical Society
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• v.42 no.2
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• pp.27-32
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• 2009

Recently, we suggested a CME earthward direction parameter as an important geoeffective parameter that has been demonstrated by front-side halo CME data. In this study, we present the geometrical implication of this parameter by comparing with the parameters from a CME cone model. Major results from this study can be summarized as follows. First, we derive an analytic relationship between the cone model parameters(the half angular width of a cone and the angle between the cone axis and the plane of sky) and the earthward direction parameter. Second, we demonstrate a close relationship between the earthward direction parameter and the cone axis angle using 32 front-side full halo CMEs. Third, we found that there is noticeable inconsistency between the cone axis angles estimated from the cone model fitting to the CMEs and from their associated flare positions, implying that the flare position should not be considered as a good earthward direction parameter. Finally we present several advantages of our earthward direction parameter in terms of the forecast of a geomagnetic storm based on CME parameters.

• Steel and Composite Structures
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• v.38 no.5
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• pp.583-597
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• 2021

This article develops a nonclassical model to analyze bending response of squared perforated microbeams considering the coupled effect of microstructure and surface stress under different loading and boundary conditions, those are not be studied before. The corresponding material and geometrical characteristics of regularly squared perforated beams relative to fully filled beam are obtained analytically. The modified couple stress and the modified Gurtin-Murdoch surface elasticity models are adopted to incorporate the microstructure as well as the surface energy effects. The differential equations of equilibrium including the Poisson's effect are derived based on minimum potential energy. Exact closed form solution is obtained for bending behavior of the proposed model considering the classical and nonclassical boundary conditions for both uniformly distributed and concentrated loads. The proposed model is verified with results available in the literature. Influences of the microstructure length scale parameter, surface energy, beam thickness, boundary and loading conditions on the bending behavior of perforated microbeams are investigated. It is observed that microstructure and surface parameters are vital in investigation of the bending behavior of perforated microbeams. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams that commonly used in nanoactuators, nanoswitches, MEMS and NEMS systems.

• Journal of Educational Research in Mathematics
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• v.20 no.3
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• pp.323-338
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• 2010

In this study we analyzed the teaching units for the area of geometrical figures by the same method in the previous research of Kang, Wan and Kim, Nam Jun in 2010, where they extracted the teaching units based on the mathematics curriculum based on the theory of Wittmann (1984). Teaching units are a systematic organization of the essential contents for mathematics education according to 4 elements, objectives, data, functions, and backgrounds. In this study, the features and titles of the teaching units, extracted from the area of geometrical figures in revised mathematics curriculums in 2007, are analyzed and categorized as accepting of concept type, application of concept type, and acquiring of relation type. Their meanings for education are investigated, in addition, the way of their practical application to research of education for the area of geometrical figures. The teaching units are a model consistently compensated and evolved rather than fixed. It will be an important material for establishing new educational courses if the teaching units are more systematically studied by mathematics researchers and teachers in educational fields.