• Title/Summary/Keyword: isoparametric type

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Elliptic Linear Weingarten Surfaces

  • Kim, Young Ho
    • Kyungpook Mathematical Journal
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    • v.58 no.3
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    • pp.547-557
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    • 2018
  • We establish some characterizations of isoparametric surfaces in the three-dimensional Euclidean space, which are associated with the Laplacian operator defined by the so-called II-metric on surfaces with non-degenerate second fundamental form and the elliptic linear Weingarten metric on surfaces in the three-dimensional Euclidean space. We also study a Ricci soliton associated with the elliptic linear Weingarten metric.

SPHERICAL SUBMANIFOLDS WITH FINITE TYPE SPHERICAL GAUSS MAP

  • Chen, Bang-Yen;Lue, Huei-Shyong
    • Journal of the Korean Mathematical Society
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    • v.44 no.2
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    • pp.407-442
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    • 2007
  • The study of Euclidean submanifolds with finite type "classical" Gauss map was initiated by B.-Y. Chen and P. Piccinni in [11]. On the other hand, it was believed that for spherical sub manifolds the concept of spherical Gauss map is more relevant than the classical one (see [20]). Thus the purpose of this article is to initiate the study of spherical submanifolds with finite type spherical Gauss map. We obtain several fundamental results in this respect. In particular, spherical submanifolds with 1-type spherical Gauss map are classified. From which we conclude that all isoparametric hypersurfaces of $S^{n+1}$ have 1-type spherical Gauss map. Among others, we also prove that Veronese surface and equilateral minimal torus are the only minimal spherical surfaces with 2-type spherical Gauss map.

On Curvature-Adapted and Proper Complex Equifocal Sub-manifolds

  • Koike, Naoyuki
    • Kyungpook Mathematical Journal
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    • v.50 no.4
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    • pp.509-536
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    • 2010
  • In this paper, we investigate curvature-adapted and proper complex equifocal submanifolds in a symmetric space of non-compact type. The class of these submanifolds contains principal orbits of Hermann type actions as homogeneous examples and is included by that of curvature-adapted and isoparametric submanifolds with flat section. First we introduce the notion of a focal point of non-Euclidean type on the ideal boundary for a submanifold in a Hadamard manifold and give the equivalent condition for a curvature-adapted and complex equifocal submanifold to be proper complex equifocal in terms of this notion. Next we show that the complex Coxeter group associated with a curvature-adapted and proper complex equifocal submanifold is the same type group as one associated with a principal orbit of a Hermann type action and evaluate from above the number of distinct principal curvatures of the submanifold.

A Study on the Finite Element Analysis of Three Dimensional Plate Structures (3차원 공간 판구조물의 유한요소 해석에 관한 연구)

  • 권오영;남정길
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.35 no.1
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    • pp.54-59
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    • 1999
  • High-speed electronic digital computers have enabled engineers to employ various numerical discretization techniques for solutions of complex problems. The Finite Element Method is one of the such technique. The Finite Element Method is one of the numerical analysis based on the concepts of fundamental mathematical approximation. Three dimensional plate structures used often in partition of ship, box girder and frame are analyzed by Finite Element Method. In design of structures, the static deflections, stress concentrations and dynamic deflections must be considered. However, these problem belong to geometrically nonlinear mechanical structure analysis. The analysis of each element is independent, but coupling occurs in assembly process of elements. So, to overcome such a difficulty the shell theory which includes transformation matrix and a fictitious rotational stiffness is taken into account. Also, the Mindlin's theory which is considered the effect of shear deformation is used. The Mindlin's theory is based on assumption that the normal to the midsurface before deformation is "not necessarily normal to the midsurface after deformation", and is more powerful than Kirchoff's theory in thick plate analysis. To ensure that a small number of element can represent a relatively complex form of the type which is liable to occur in real, rather than in academic problem, eight-node quadratic isoparametric elements are used. are used.

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A 3-D Finite Element Model For R/C Structures Based On Orthotropic Hypoelastic Constitutive Law

  • Cho, Chang-Geun;Park, Moon-Ho
    • KCI Concrete Journal
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    • v.13 no.1
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    • pp.19-25
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    • 2001
  • Based on the orthotropic hypoelasticity formulation, a constitutive material model of concrete taking account of triaxial stress state is presented. In this model, the ultimate strength surface of concrete in triaxial stress space is described by the Hsieh's four-parameter surface. On the other hand, the different ultimate strength surface of concrete in strain space is proposed in order to account for increasing ductility in high confinement pressure. Compressive ascending and descending behavior of concrete is considered. Concrete cracking behavior is considered as a smeared crack model, and after cracking, the tensile strain-softening behavior and the shear mechanism of cracked concrete are considered. The proposed constitutive model of concrete is compared with some results obtained from tests under the states of uniaxial, biaxial, and triaxial stresses. In triaxial compressive tests, the peak compressive stress from the predicted results agrees well with the experimental results, and ductility response under high confining pressure matches well the experimental result. The reinforcing bars embedded in concrete are considered as an isoparametric line element which could be easily incorporated into the isoparametric solid element of concrete, and the average stress - average strain relationship of the bar embedded in concrete is considered. From numerical examples for a reinforced concrete simple beam and a structural beam type member, the stress state of concrete in the vicinity of talc critical region is investigated.

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Development of 3-Dimensional Static Infinite Elements with Various Decay Characteristics for Tunnel Analysis (터널해석을 위한 다양한 감쇠특성의 3차원 정적무한요소 개발)

  • Koo, Hee-Dae;Koh, Hyun-Moo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.3A
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    • pp.439-445
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    • 2006
  • Analysis problems of tunnels whose geometrical dimensions are very small compared with surrounding media can be treated as infinite region problems. In such cases, even if finite element models can be applied, excessive number of elements is required to obtain satisfactory accuracy. However, inaccurate results may be produced due to assumed artificial boundary conditions. To solve these problems, a hybrid model, which models the region of interest with finite elements and the surrounding infinite media with infinite elements, is introduced for the analysis of infinite region. Three-dimensional isoparametric infinite elements with various decay characteristics are formulated in this paper and the corresponding parameters are presented by means of parametric studies. Three-dimensional tunnel analysis performed on a representative example verifies the applicability of hybrid model using infinite elements.

Development of Efficient Plate Element Considering Variable Thickness and Nonuniform Pressure (단면과 압력변화를 고려한 효율적인 평판 요소의 개발)

  • 이성우;심규점
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1993.10a
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    • pp.1-7
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    • 1993
  • Most of wall or plate structures subjected to nonuniform earth or water pressure has variable thickness. These problems were generally solved by models with uniform thickness and pressure. To obtain more accurate and economic solution for this type of problem. efficient isoparametric plate element considering variable thickness and nonuniform pressure were developed. Some example problems demonstrated efficiency of the proposed element.

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Finite Element Modeling for Free Vibration Control of Beam Structures using Piezoelectric Sensors and Actuators (압전감지기와 압전작동기를 이용한 보구조물의 자유진동제어에 대한 유한요소 모형화)

  • 송명관;한인선;김선훈;최창근
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2003.04a
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    • pp.269-278
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    • 2003
  • In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived, The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free vibration control for the beam structures with bonded plate-type piezoelectric sensors and actuators is proposed.

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Finite Element Modeling of Piezoelectric Sensors and Actuators based on Timoshenko Beam Theory

  • 최창근;송명관
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.10a
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    • pp.3-10
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    • 2000
  • In this study, a new smart beam finite element is proposed for the finite element modeling of the beam-type smart structure with bonded plate-type piezoelectric sensors and actuators. Constitutive equations far the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived. The presented 2-node beam finite element is isoparametric element based on Timoshenko beam theory. The validity of the proposed beam element is shown through comparing the analysis results of the verification examples with those of other previous researches. Therefore, by analyzing smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by piezoelectric actuators with applied voltages and the monitoring of the structure behavior by piezoelectric sensors with sensed voltages.

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Thermal frequency analysis of FG sandwich structure under variable temperature loading

  • Sahoo, Brundaban;Mehar, Kulmani;Sahoo, Bamadev;Sharma, Nitin;Panda, Subrata Kumar
    • Structural Engineering and Mechanics
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    • v.77 no.1
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    • pp.57-74
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    • 2021
  • The thermal eigenvalue responses of the graded sandwich shell structure are evaluated numerically under the variable thermal loadings considering the temperature-dependent properties. The polynomial type rule-based sandwich panel model is derived using higher-order type kinematics considering the shear deformation in the framework of the equivalent single-layer theory. The frequency values are computed through an own home-made computer code (MATLAB environment) prepared using the finite element type higher-order formulation. The sandwich face-sheets and the metal core are discretized via isoparametric quadrilateral Lagrangian element. The model convergence is checked by solving the similar type published numerical examples in the open domain and extended for the comparison of natural frequencies to have the final confirmation of the model accuracy. Also, the influence of each variable structural parameter, i.e. the curvature ratios, core-face thickness ratios, end-support conditions, the power-law indices and sandwich types (symmetrical and unsymmetrical) on the thermal frequencies of FG sandwich curved shell panel model. The solutions are helping to bring out the necessary influence of one or more parameters on the frequencies. The effects of individual and the combined parameters as well as the temperature profiles (uniform, linear and nonlinear) are examined through several numerical examples, which affect the structural strength/stiffness values. The present study may help in designing the future graded structures which are under the influence of the variable temperature loading.