• Structural Engineering and Mechanics
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• 제14권1호
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• pp.71-84
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• 2002

A finite element formulation for the time-domain analysis of linear transient elastodynamic problems is presented based on the weak form obtained by applying the Galerkin's method to the integro-differential equations which contain the initial conditions implicitly and does not include the inertia terms. The weak form is extended temporally under the assumptions of the constant and linear time variations of field variables, since the time-stepping algorithms such as the Newmark method and the Wilson ${\theta}$-method are not necessary, obtaining two kinds of implicit finite element equations which are tested for numerical accuracy and convergency. Three classical examples having finite and infinite domains are solved and numerical results are compared with the other analytical and numerical solutions to show the versatility and accuracy of the presented formulation.

• Coupled systems mechanics
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• 제13권3호
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• pp.187-200
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• 2024

This paper presents a numerical model for buckling analysis of slender piles, such as micropiles. The model incorporates geometric nonlinearities to provide enhanced accuracy and a more comprehensive representation of pile buckling behavior. Specifically, the pile is represented using geometrically nonlinear beams with the von Karman deformation measure. The lateral support provided by the surrounding soil is modeled using the spring approach, with the spring stiffness determined according to the undrained shear strength of the soil. The numerical model is tested across a wide range of pile slenderness ratios and undrained shear strengths of the surrounding soil. The numerical results are validated against analytical solutions. Furthermore, the influence of various pile bottom end boundary conditions on the critical buckling force is investigated. The implications of the obtained results are thoroughly discussed.

• 대한가정학회지
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• 제43권8호
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• pp.1-12
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• 2005

Ash solutions derived from vegetation have been known for their good mordanting action. They are used as finishing agents because they are able to promote dye uptake. It is expected that the types of ash solutions may have been different worker by worker since the workers have employed easy-to-get plants, when we reviewed old literature. However, the ash solutions are being used without clear distinctions between their characteristics. In this study, camellia ash solution and rice straw ash solution were prepared according to traditional methods. Using these solutions as mordanting agents, natural dyeing experiments with Caesdpinia Sappan were peformed. Following the dyeing procedure, the effect of the type of ash solution on the color of the dyed fabric was evaluated. The results showed that the ash solution mordanting effect us not dependent upon the components of the ash solution. It was also demonstrated that the mordanting effect was not based on the action of the metallic ions in the ash solution. The pH values of the ash solutions were adjusted in order to investigate the effect of changes in ash solution alkalinity on the dyeing process. The pH values ranged from neutral or weak acidity to the alkaline range in order to evaluate the characteristics of the mordanting tv the ash solutions.

• 한국전자거래학회지
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• 제6권1호
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• pp.17-33
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• 2001

EC(Electronic Commerce) which is done on the virtual space through Internet has strong point like independence from time and space. On the contrary, it also has weak point like security problem because anybody can access easily to the system due to open network attribute of Internet, Therefore, we need the solutions that protect the EC security problem for safe and useful EC activity. One of these solutions is the implementation of strong cipher system. YK2(Young Ku King) cipher system proposed in this paper is good solution for the EC security and it overcome the limit of current block cipher system using 128 bits key length for input, output, encryption key and 32 rounds. Moreover, it is designed for the increase of time complexity by adapting more complex design for key scheduling algorithm regarded as one of important element effected to encryption.

• Korean Journal of Mathematics
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• 제15권2호
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• pp.195-206
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• 2007

We investigate the multiplicity of $2{\pi}$-periodic solutions of the nonlinear Hamiltonian system with perturbed polynomial and exponential potentials, $\dot{z}= JG^{\prime}(z)$, where $z:R{\rightarrow}R^{2n}$, $\dot{z}={\frac{dz}{dt}}$, $J=\(\array{0&-I\\I&0}\)$, I is the identity matrix on $R^n,G:R^{2n}{\rightarrow}R$, G(0, 0) = 0 and $G^{\prime}$ is the gradient of G. We look for the weak solutions $z=(p,q){\in}E$ of the nonlinear Hamiltonian system.

• Korean Journal of Mathematics
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• 제21권2호
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• pp.117-124
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• 2013

We investigate the existence of weak solutions for the biharmonic boundary value problem with nonlinear term decaying at the origin. We get a theorem which shows the existence of nontrivial solutions for the biharmonic boundary value problem with nonlinear term decaying at the origin. We obtain this result by reducing the biharmonic problem with nonlinear term to the biharmonic problem with bounded nonlinear term and then approaching the variational method and using the mountain pass geometry for the reduced biharmonic problem with bounded nonlinear term.

• 한국전자거래학회지
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• 제6권2호
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• pp.159-166
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• 2001

EC(Electronic Commerce) is increasing with high speed based on the expansion of Internet. EC which is done through Internet has strong point like independence from time and space, On the contrary, it also has weak point like security problem because anybody can access easily to the system due to open network attribute of Internet. Therefore, we need the solutions that protect the security problem for safe and useful U activity, One of these solutions is the implementation of strong cipher algorithm. NPC(Non-Polynomial Complete) cipher algorithm proposed in this paper is good for the security and it overcome the limit of current 64bits cipher algorithm using 256bits key for input output and encryption key, Moreover, it is designed for the increase of calculation complexity and probability calculation by adapting more complex design for subkey generation regarded as one of important element effected to encryption.

• Korean Journal of Mathematics
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• 제20권4호
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• pp.507-515
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• 2012

We investigate the number of the solutions for the elliptic boundary value problem. We obtain a theorem which shows the existence of six weak solutions for the elliptic problem with jumping nonlinearity crossing three eigenvalues. We get this result by using the geometric mapping defined on the finite dimensional subspace. We use the contraction mapping principle to reduce the problem on the infinite dimensional space to that on the finite dimensional subspace. We construct a three dimensional subspace with three axis spanned by three eigenvalues and a mapping from the finite dimensional subspace to the one dimensional subspace.

• Steel and Composite Structures
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• 제17권6호
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• pp.951-965
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• 2014

Point bending is commonly used for cambering and curving steel girders to large radii. In this system, a hydraulic ram or press is used to apply concentrated loads at selected points to obtain the required vertical (cambering) or horizontal (curving) curved profile from induced permanent deformations. This paper derives closed form solutions that relate loads to permanent deformations for horizontally curving wide flange steel beams based on their post-yield response. These solutions are presented in a parametric form to identify the relationship between key variables and their impact on the accuracy of the curving operation. It is shown that point bending could yield parabolic curved profiles that are within 1% of a desired circular curve if the span length to radius of curvature ratio (L / R) is less than 1.5 and the point loads are spaced at one third the beam length. Safe limits are then established on loads, strains and curvatures to avoid damaging the steel section. This leads to optimization of the point bending operation for inducing a circular profile in wide flange steel beams of any size.

• Steel and Composite Structures
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• 제27권6호
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• pp.789-801
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• 2018

A weak-form formulation of finite annular prism methods (FAPM) based on Reissner's mixed variational theorem (RMVT), is developed for the quasi three-dimensional (3D) static analysis of two-directional functionally graded (FG) circular plates with various boundary conditions and under mechanical loads. The material properties of the circular plate are assumed to obey either a two-directional power-law distribution of the volume fractions of the constituents through the radial-thickness surface or an exponential function distribution varying doubly exponentially through it. These FAPM solutions of the loaded FG circular plates with both simply-supported and clamped edges are in excellent agreement with the solutions obtained using the 3D analytical approach and two-dimensional advanced plate theories available in the literature.