• 전기학회논문지
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• 제61권12호
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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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• 제6권2호
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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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• 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.

• 대한수학회지
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• 제39권2호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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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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• 제30권1호
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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.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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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.

• 대한수학회지
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• 제57권4호
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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.

• 대한수학회지
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• 제59권1호
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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.

• 한국강구조학회 논문집
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• 제23권6호
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• pp.691-704
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• 2011

본 연구는 데릭크레인과 인양중인 새그먼트 자중에 의한 외력이 작용하는 시공중인 폐합 직전 사장교의 기하비선형성 및 재료비선형성을 고려한 비선형 해석을 통해 극한 거동을 규명하였다. 시공중 사장교의 상태를 수치적으로 구현하기 위해 초기형상 해석과 역방향 시공단계 해석을 순차적으로 진행하였고, 이후에는 데릭크레인 및 인양중인 새그먼트 자중을 중앙경간 최 측단에 재하 하여 폐합 전 강사장교의 주요한 거동을 모사하였다. 또한 주요 매개변수에 따른 극한거동 및 극한하중계수의 변화를 정량적으로 분석하기 위한 방법으로 주탑-거더간 강성비와 케이블 면적을 변화하면서 거동을 관찰하였고, 기하비선형성과 재료비선형성 모두를 고려한 극한해석 결과를 기하비선형성만을 고려한 기하비선형 해석과 비교하여 보다 구체적이고 정량적인 극한거동에 대해 분석하였다.