• Tribology and Lubricants
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• 제13권2호
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• pp.60-67
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• 1997

ER(electro-rheological) fluids, which are represented as Bingham fluids, have large and reversible changes in yield shear stresses by application of an electric field. In this paper, ER fluids are employed in a short squeeze film damper. The modified Reynolds equation for an ER short squeeze film damper is theoretically solved to get the approximate solutions of pressure profiles and damping coefficients. The theoretical approximate solutions are compared with numerical ones and both results are coincided very well. Both the direct and cross coupled damping coefficients substantially increase with increasing the yield shear stress of ER fluids. Furthermore, the synchronous response analysis of a rigid rotor supported on ER short squeeze film dampers is performed to show the improved damping capability of an ER short squeeze film damper.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.965-972
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• 1997

An approximate molecular theory of classical fluids based on the nonrandom lattice statistical-mechanical theory is presented. To obtain configurational Helmholtz free energy and equation of state (EOS), the lattice-hole theory of the Guggenheim combinatorics is approximated by introducing the nonrandom two-fluid theory. The approximate nature in the derivation makes the model possible to unify the classical lattice-hole theory and to describe correctly the configurational properties of real fluids including macromolecules. The theory requires only two molecular parameters for a pure fluid. Results obtained to date have demonstrated that the model correlates quantitatively the first- and second-order thermodynamic properties of real fluids. The basic simplicity of the model can readily be generalized to multicomponent systems. The model is especially relevant to (multi) phase equilibria of systems containing molecularly complex species.

• Korean Journal of English Language and Linguistics
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• 제1권3호
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• pp.497-508
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• 2001

This study tested whether non-native speakers approximated native-like locus equation slopes. Russian learners of English acquired native-like values of the locus equation slope for the English bilabial, and English learners of Russian made slight modifications to the locus equation slope of the Russian bilabial. The acquisition of the locus equations occurred gradually with experience. While English speakers, with limited experience with Russian, failed to approximate Russian-typical value of the locus equations slope, Russian speakers, with more extensive experience with English, succeeded in approximating the locus equation for English bilabial. The observation of locus equation transfer effect supports for the locus equation hypothesis as the unit of acquisition over CV-by-CV learning.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.188-192
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• 1996

It is shown that the inversion of the undamped Bloch equation for an amplitude-modulated broadband π/2 pulse can be precisely treated as an inverse scattering problem for a Schrodinger equation on the positive semiaxis. The pulse envelope is closely related to the central potential and asymptotically the wave function takes the form of a regular solution of the radial Schrodinger equation for s-wave scattering. An integral equation, which allows the calculation of the pulse amplitude (the potential) from the phase shift of the asymptotic solution, is derived. An exact analytical inversion of the integral equation shows that the detuning-independent π/2 pulse amplitude is given by a delta function. The equation also provides a means to calculate numerically approximate π/2 pulses for broadband excitation.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제16권4호
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• pp.431-437
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• 2003

In this paper, an approximate optimization program based on GUI(graphic user interface) environment is developed. This program is coded by using Fortran and Visual basic. Fortran is used to Progress approximate optimization process. Visual basic is used to make user environment for user to use conveniently. Inside of this program, it uses two independent programs. One is commercial program, ANSYS, and the other is optimization program, PLBA(Pshenichny-Lim-Belegundu Arora). The former is used to obtain approximate equation of stress and displacement of a structure. The latter is used to solve approximate optimization. This algorithm uses second-order information of a function and active set strategy. This program is connecting ANSYS and PLBA. And it progress the process repeatedly until it obtain optimum value. As a method of approximate optimization, sequential design domain(SDD) is introduced. SDD starts with a certain range which is offseted from midpoint of an initial design domain and then SDD of the next step is determined by optimal point of a prior step.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권11호
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• pp.19-26
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• 2019

To construct buildings on limited land, the size of the building is important. The development process needs to be minimized because determining the size of a structurally safe building at the planning stage incurs considerable time and cost. This study proposes the Limit Slenderness Ratio Approximation Equation. This study examined an outrigger structure system among several systems proposed for controlling the lateral displacement in tall buildings. This study compared the Limit Slenderness Ratio Approximation Equation with the approximate equation by changing the variables of the building model, and examined the size of the building using the approximate Equation. As an analysis program, the MAIDAS architectural structural analysis program was used to conduct model-specific analysis. The appropriate scale of the building to minimize the error between the approximate value calculated by the Limit Slenderness Ratio Approximation Equation and the analysis result of the structural analysis program is as follows. As the number of outrigger installation increases, the error can be reduced; the ratio of the cores is reasonable, from 20% to 30%, and the arrangement of the column is suitable only for the outer column without an internal column.

• Computational Structural Engineering
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• 제11권1호
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• pp.171-178
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• 1998

The added viscoelastic dampers increase damping and stiffness of buildings and results in so called non-classical or non-proportional damping problem. In this system the eigenvectors of the undamped system may not diagonalize the damping matrix, and the system is generally analyzed by converting the equation of motion into a 2n first order state-space form. As this approach is complex and time-consuming compared to the classically damped problem, the system is often analyzed by neglecting the off-diagonal terms in the damping matrix. In this paper the theoretical background of the approximate approach is studied, and the vibration characteristics of a three-story shear building with a viscoelastic damper are investigated using the exact and approximate method. It is found that the approximate method may produce good result when the additional damping is small, but as the damping increases the error also increase.

• East Asian mathematical journal
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• 제33권5호
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• pp.511-525
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• 2017

We introduce an extrapolated higher order characteristic finite element method to construct approximate solutions of a Sobolev equation with a convection term. The higher order of convergence in both the temporal direction and the spatial direction in $L^2$ normed space is established and some computational results to support our theoretical results are presented.

• The Pure and Applied Mathematics
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• 제24권3호
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• pp.147-153
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• 2017

In this paper, we propose a numerical method to solve fuzzy differential equations. Numerical experiments show that when the step size is small, the new method has significantly good approximate solutions of fuzzy differential equation. Graphical representation of fuzzy solutions in three-dimension is also provided as a reference of visual convergence of the solution sequence.

• Bulletin of the Korean Mathematical Society
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• 제49권4호
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• pp.829-850
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• 2012

In this paper, we adopt symmetric interior penalty discontinuous Galerkin (SIPG) methods to approximate the solution of nonlinear viscoelasticity-type equations. We construct finite element space which consists of piecewise continuous polynomials. We introduce an appropriate elliptic-type projection and prove its approximation properties. We construct semidiscrete discontinuous Galerkin approximations and prove the optimal convergence in $L^2$ normed space.