• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1898-1902
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• 2012

In this paper, we consider the delay-dependent robust stability condition for polytopic uncertain systems with interval time-varying delay using various combinations of quantization and overflow nonlinearities. A robust stability condition for uncertain systems with time-varying delay and quantization/overflow nonlinearities is proposed by LMI(linear matrix inequality) and Lyapunov technique. It is shown that the proposed method is less conservative compared to the recent results by numerical examples.

• Structural Engineering and Mechanics
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• v.6 no.2
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• pp.217-227
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• 1998

An elasto-plastic finite element procedure using degenerated shell element with assumed strain field technique considering both material and geometric nonlinearities has been developed. This assumes von-Mises yield criterion, von-Karman strain displacement relations and isotropic hardening. A few numerical examples are presented to demonstrate the correctness and applicability of the method to different kinds of engineering problems. From present study, it is seen that there is a considerable improvement in the displacement valuse when both material and geometric nonlinearities are considered. An example of the spread of plastic zones for isotropic and anisotropic materials has been illustrated.

• Coupled systems mechanics
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• v.13 no.3
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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.

• Journal of the Korean Mathematical Society
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• v.39 no.2
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• pp.319-330
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• 2002

The method of quasilinearization generates a monotone iteration scheme whose iterates converge quadratically to a unique solution of the problem at hand. In this paper, we apply the method to two families of three-point boundary value problems for second order ordinary differential equations: Linear boundary conditions and nonlinear boundary conditions are addressed independently. For linear boundary conditions, an appropriate Green\`s function is constructed. Fer nonlinear boundary conditions, we show that these nonlinearities can be addressed similarly to the nonlinearities in the differential equation.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.362-365
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• 1990

This paper proposes the precise positioning controller. The pricision of this controller is improved by considering stiction, coulomb friction and biscous friction. These frictions have nonlinearities both typical and mechanical. According to the result in this paper, good precision is abstained by adding a simple friction compensator to a PI controller.

• Structural Engineering and Mechanics
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• v.30 no.1
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• pp.67-76
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• 2008

Limit cycle oscillations of a two-dimensional airfoil with quadratic and cubic pitching nonlinearities are investigated. The equivalent stiffness of the pitching stiffness is obtained by combining the linearization and harmonic balance method. With the equivalent stiffness, the equivalent linearization method for nonlinear flutter analysis is generalized to address aeroelastic system with quadratic nonlinearity. Numerical example shows that good approximation of the limit cycle can be obtained by the generalized method. Furthermore, the proposed method is capable of revealing the unsymmetry of the limit cycle; however the ordinary equivalent linearization method fails to do so.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.245-250
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• 1998

This thesis is concerned with the development of useful engineering techniques to detect and analyze nonlinearities in mechanical systems. The methods developed are based on the concepts of higher order spectra, in particular the bispectrum and trispectrum, and the Volterra series. The study of higher order statistics has been dominated by work on the bispectrum. The bispectrum can be viewed as a decomposition of the third moment(skewness) of a signal over frequency and as such is blind to symmetric nonlinearities.

• Journal of the Korean Mathematical Society
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• v.57 no.4
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• pp.825-844
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• 2020

We obtain infinitely many solutions for a class of fractional Schrödinger equation, where the nonlinearity is superquadratic or involves a combination of superquadratic and subquadratic terms at infinity. By using some weaker conditions, our results extend and improve some existing results in the literature.

• Journal of the Korean Mathematical Society
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• v.59 no.1
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• pp.205-216
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• 2022

This paper deals with a nonlinear wave equation with boundary damping and source terms of variable exponent nonlinearities. This work is devoted to prove a global nonexistence of solutions for a nonlinear wave equation with nonnegative initial energy as well as negative initial energy.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.691-704
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• 2011

This paper presents an investigation on the ultimate behavior of steel cable-stayed bridges in the construction stage, considering various geometric nonlinearities and material nonlinearities. To numerically determine the state of cable-stayed bridges in the construction stage, initial shape analysis and construction stage analysis via backward process analysis were done sequentially. Then nonlinear analysis of the state under the construction load condition, considering the weight of the derrick crane and the key segment of the girder loaded onto the tip of the center span, was performed to investigate the ultimate behavior of the structure. The effects of the girder-mast stiffness ratio, the cable-arrangement types, and the area of the stay cables on the ultimate behavior were also extensively investigated. Moreover, the results of the ultimate analysis, considering both geometric nonlinearities and material nonlinearities, were compared with the results of the geometric nonlinear analysis, for a more meaningful investigation of the ultimate behavior of steel cable-stayed bridges in the construction stage.