• Structural Engineering and Mechanics
• /
• 제40권2호
• /
• pp.257-277
• /
• 2011

In this paper the geometrically nonlinear continuum plate finite element model, hitherto not reported in the literature, is developed using the total Lagrange formulation. With the layerwise displacement field of Reddy, nonlinear Green-Lagrange small strain large displacements relations (in the von Karman sense) and linear elastic orthotropic material properties for each lamina, the 3D elasticity equations are reduced to 2D problem and the nonlinear equilibrium integral form is obtained. By performing the linearization on nonlinear integral form and then the discretization on linearized integral form, tangent stiffness matrix is obtained with less manipulation and in more consistent form, compared to the one obtained using laminated element approach. Symmetric tangent stiffness matrixes, together with internal force vector are then utilized in Newton Raphson's method for the numerical solution of nonlinear incremental finite element equilibrium equations. Despite of its complex layer dependent numerical nature, the present model has no shear locking problems, compared to ESL (Equivalent Single Layer) models, or aspect ratio problems, as the 3D finite element may have when analyzing thin plate behavior. The originally coded MATLAB computer program for the finite element solution is used to verify the accuracy of the numerical model, by calculating nonlinear response of plates with different mechanical properties, which are isotropic, orthotropic and anisotropic (cross ply and angle ply), different plate thickness, different boundary conditions and different load direction (unloading/loading). The obtained results are compared with available results from the literature and the linear solutions from the author's previous papers.

• 영어어문교육
• /
• 제3호
• /
• pp.141-183
• /
• 1997

This paper aims to find out the current state of early English education in the world(including Korea) and to suggest its more desirable direction, with special reference to TEFL in elementary schools of Korea. In fact English teaching in elementary schools of Korea has been put into practice as an extracurricular activity since 1982. But in 1995 the Ministry of Education proclaimed a policy to establish a TEFL program as the regular course in elementary schools of Korea since 1997. In this connection, the writer surveyed several kinds of theories about early English education to verify the necessity and validity of Korea's elementary school English education. The logical result from these theories is that younger children are better equipped to learn foreign languages with efficiency than older children or adults. However, as most studies are based on logical inferences rather than on direct observation or experimental evidence, we are not sure that those theories are right. In this view, the writer put stress on the preparation of educational environments to establish a more desirable direction of early English education in Korea, since Korea's elementary school English education will be practiced under EFL environment, not ESL environment. The writer also pointed out some problems of educational finances, the curriculum development process and its content, teaching materials(textbooks and tapes), English teachers, teaching methods, evaluation, educational facilities. This paper concludes that we have to try to solve these problems to succeed in a TEFL program in elementary schools of Korea and suggests several things for a more desirable direction of Korea's elementary school English education.