• Steel and Composite Structures
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• v.43 no.5
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• pp.533-552
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• 2022

The current article deals with the dynamic stability, and structural improvement of vibrating electrically curved screen on the viscoelastic substrate. By considering optimum value for radius curvature of the electrically curved screen, the structure improvement of the system occurs. For modeling the electrically system, the Maxwell's' equation is developed. Hertz contact model in employed to obtain contact forces between impactor and structure. Moreover, variational methods and nonlinear von Kármán model are used to derive boundary conditions (BCs) and nonlinear governing equations of the vibrating electrically curved screen. Galerkin and Multiple scales solution approach are coupled to solve the nonlinear set of governing equations of the vibrating electrically curved screen. Along with the analytical solution, 3D finite element simulation via ABAQUS package is provided with the aid of a FE package for simulating the current system's response. The results are categorized in 3 different sections. First, effects of geometrical and material parameters on the vibrational performance and stability of the curves panel. Second, physical properties of the impactor are taken in to account and their effect on the absorbed energy and velocity profile of the impactor are presented. Finally, effect of the radius and initial velocity on the mode shapes of the current structure is demonstrated.

• Journal of the Korean Mathematical Society
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• v.32 no.4
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• pp.869-876
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• 1995

Piezo devices such as piezoceramic patches knwon as collocated rate sensor and actuators are commonly used in control of flexible structure (see, e.g., [1]) and noise reduction. Recently, Ito and Kang ([4]) developed a nonlinear feedback control synthesis for regulating fluid flow using these devices.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.463-467
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• 1991

A continuous variable structure system control as a DC servomotor trackhig controller is proposed for the improvement of the chattering problems. The stability property of the proposed algorithms is analyzed. The prescribed trackfiig error is gauranteed in the existence of load variations based on the stability analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.999-1000
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• 2010

• Structural Engineering and Mechanics
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• v.32 no.3
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• pp.429-445
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• 2009

Thermal stability of quasi-isotropic composite and polymeric structures is considered one of the most important criteria in predicting life span of building structures. The outdoor applications of these structures have raised some legitimate concerns about their durability including moisture resistance and thermal stability. Exposure of such quasi-isotropic composite/polymeric structures to various and severe climatic conditions such as heat flux and frigid climate would change the material behavior and thermal viability and may lead to the degradation of material properties and building durability. This paper presents an analytical model for the generalized problem. This model accommodates the non-linearity and the non-homogeneity of the internal heat generated within the structure and the changes, modification to the material constants, and the structural size. The paper also investigates the effect of the incorporation of the temperature and/or material constant sensitive internal heat generation with four encountered climatic conditions on thermal stability of infinite cylindrical quasi-isotropic composite/polymeric structures. This can eventually result in the failure of such structures. Detailed critical analyses for four case studies which consider the population of the internal heat generation, cylindrical size, material constants, and four different climatic conditions are carried out. For each case of the proposed boundary conditions, the critical thermal stability parameter is determined. The results of this paper indicate that the thermal stability parameter is critically dependent on the cylinder size, material constants/selection, the convective heat transfer coefficient, subjected heat flux and other constants accrued from the structure environment.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.2
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• pp.116-124
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• 2008

Current paper investigates the dynamic behavior and stability of an infrared search and track subjected to external disturbance having gimbal structure with three rotating axes keeping constant angular velocity in the azimuth direction. Euler-Lagrange equation is applied to derive the coupled nonlinear dynamic equation of motion of infrared search and track and the characteristics of dynamic coupling are investigated. Two equilibrium points with small variations from the nonlinear coupling system are derived and the specific condition from which a coupled equation can be three independent equations is derived. Finally, to examine the stability of system, Lyapunov direct method was used and system stability and stability boundaries are investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1035-1046
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• 2002

Time Delay Control(TDC) is a robust nonlinear control scheme using Time Delay Estimation(TDE) and also has a simple structure. To apply TDC to a real system, we must design Time Delay Controller to guarantee stability. The earlier research stated sufficient stability condition of TDC for general plants. In that research, it was assumed that time delay is infinitely small. But, it is impossible to implement infinitely small time delay in a real system. So, in this research we propose a new sufficient stability condition of TDC for general plants with finite time delay. And the simulation results indicate that the previous sufficient stability condition does not work even for small time delay, while our proposed condition works well.

• Journal of information and communication convergence engineering
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• v.12 no.1
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• pp.39-45
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• 2014

A numerical method for solving Hamiltonian equations is said to be symplectic if it preserves the symplectic structure associated with the equations. Various symplectic methods are widely used in many fields of science and technology. A symplectic method preserves an approximate Hamiltonian perturbed from the original Hamiltonian. It theoretically supports the effectiveness of symplectic methods for long-term integration. Although it is also related to long-term integration, numerical stability of symplectic methods have received little attention. In this paper, we consider explicit symplectic methods defined for Hamiltonian equations with Hamiltonians of the special form, and study their numerical stability using the harmonic oscillator as a test equation. We propose a new stability criterion and clarify the stability of some existing methods that are visually based on the criterion. We also derive a new method that is better than the existing methods with respect to a Courant-Friedrichs-Lewy condition for hyperbolic equations; this new method is tested through a numerical experiment with a nonlinear wave equation.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.3-6
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• 2001

Power system stability is correlated with system structure, disturbances and operating conditions. and power flows in transmission lines are closely related with those conditions. This paper discusses a methodology to identify crucial transmission lines for stability diagnosis with respect to transient stability and small-signal stability. On-line monitoring of the selected lines enables to predict system stability in real-time. Also, a Procedure to make a priority list of monitored transmission lines using contingency analysis. The procedure is applied to the PSS/E test system. and it shows capabilities of the proposed method.

• Wind and Structures
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• v.6 no.4
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• pp.279-290
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• 2003

Flutter stability is one of major concerns on the design of long-span cable-stayed bridges. Considering the geometric nonlinearity of cable-stayed bridges and the effects due to the nonlinear wind-structure interactions, a nonlinear method is proposed to analyze the flutter stability of cable-stayed bridges, and a computer program NFAB is also developed. Taking the Jingsha bridge over the Yangtze River as example, parametric analyses on flutter stability of the bridge are carried out, and some important design parameters that affect the flutter stability of cable-stayed bridges are pointed out.