• Steel and Composite Structures
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• v.38 no.5
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• pp.523-531
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• 2021

The generalized thermoelastic analysis problem of a two-dimension porous medium with and without energy dissipation are obtained in the context of Green-Naghdi's (GNIII) model. The exact solutions are presented to obtain the studying fields due to the pulse heat flux that decay exponentially in the surface of porous media. By using Laplace and Fourier transform with the eigenvalues scheme, the physical quantities are analytically presented. The surface is shocked by thermal (pulse heat flux problems) and applying the traction free on its outer surfaces (mechanical boundary) through transport (diffusion) process of temperature to observe the analytical complete expression of the main physical fields. The change in volume fraction field, the variations of the displacement components, temperature and the components of stress are graphically presented. Suitable discussion and conclusions are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.333-341
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• 2013

In this paper, a feedback linearization control is proposed to regulate the output voltages of a three-phase four-wire inverter under the unbalanced and nonlinear load conditions. First, the nonlinear model of system including the output LC filters is derived in the d-q-0 synchronous reference frame. Then, the system is linearized by the multi-input multi-output feedback linearization. The tracking controllers for d-q-0-components of three-phase line-to-neutral load voltages are designed by linear control theory. The experimental results have shown that the proposed control method gives the good performance in response to the load conditions.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.05a
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• pp.203-206
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• 2002

This paper describes fuzzy control methodologies of the steam generator which have nonlinear characteristics in the nuclear power plant. Actually, the steam generator part of the power generator has a problem to control water level because it has complex components and nonlinear characteristics. In order to control nonlinear terms of the model, Takagj-Sugeno (75) fuzzy system is used to design a controller. In designing procedure, intelligent digital redesign method is used to control the nonlinear system. This digital controller keeps the performance of the analog controller. Simulation examples are included for ensuring the proposed control method.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.265-273
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• 2016

A water wall system is one of the most important components of a boiler in a thermal power plant, and it is a nonlinear Multi-Input and Multi-Output (MIMO) system, with 6 inputs and 3 outputs. Three models are developed and comp for the controller design, including a linear model, a multilayer feed-forward neural network (MFNN) model and an Echo State Network (ESN) model. First, the linear model is developed by linearizing a given nonlinear model and is analyzed as a function of the operating point. Second, the MFNN and the ESN are developed by using training data from the nonlinear model. The three models are validated using Matlab with nonlinear input-output data that was not used during training.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.9-18
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• 1993

Numerical wave tank is a robust tool by which the nonlinear interactions between the body and the free-surface can be treated in time-domain. In this paper, a two-dimensional numerical wave tank based on the Spectral/Boundary-Element Method is developed, and applied successfully to the study of nonlinear wave diffraction around a submerged circular cylinder. Particularly, it is shown that the high-order wave components of significant wave height are developed in the lee-side of the cylinder and that these waves result in a negative drift force on the circular cylider.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2272-2283
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• 1994

In scanning tunneling microscopy, the piezoelectric actuator is popuilarly used in stacked type as it can provide remarkable positioning resolution and stiffness. The actuator, however, exhibits a considerable amount of hystereic nonlinearity, resulting in losses of overall measuring accuracy when a linear model is used for its control and calibration, In this study, a nonlinear model is proposed for predicting the precise relationship between the input connand voltage and the output displacement of the actuator itself, cross-coupled electrical behaviours of the driving circuit with the actuator, and mechanical characteristics of the driven components of the actuator. Finally experimental results prove that the nonlinear model enhances the measuring of scanning tunneling microscopy by an order ten in comparison with a conventional linear model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.410-413
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• 2001

In this paper, we present results of this that design of the multi-layer VCO(Voltage Controlled Oscillator), which is composed of the resonation circuit and the oscillation circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for acquiring EM(Electromagnetic) characteristics of conductor pattern as well as designing multi-layer VCO, Acquired EM characteristics of the circuit pattern was used like real components at nonlinear RF circuit simulator. Finally VCO is simulated at nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was DuPont #9599, which is applied for L TCC process. The structure is constructed with 4 conducting layer. Simulated results showed that the output level was about 1[dBm], the phase noise was 102 [dBc/Hz] at 30[kHz] offset frequency, the harmonics -8dBc, and the control voltage sensitivity of 30[MHz/V] with a DC current consumption of l0[mA]

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.849-855
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• 2010

Damping may change the response characteristics of nonlinear oscillations due to the parametric excitation of a thin cantilever beam. When the natural frequencies of the first bending and torsional modes are of the same order of magnitude, we can observe the one-to-one combination resonance in the perturbation analysis depending on the characteristic parameters. The nonlinear behavior about the combination resonance reveals a chaotic motion depending on the natural frequencies and damping ratio. We can analyze the chaotic dynamics by using the eigenvalue analysis of the perturbed components. In this paper, we derived the equations for autonomous system and solved them to obtain the characteristic equation. The stability analysis was carried out by examining the eigenvalues. Numerical integration gave the physical behavior of each mode for given parameters.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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• pp.465-472
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• 2016

A nonlinear load causes harmonic distortion and hampers the performance of other loads or distributed generation (DG) sources connected to the point of common coupling (PCC). This study proposes a new control strategy to reduce harmonic components, such as fifth and seventh harmonics, at the PCC under nonlinear loads in islanded microgrids, which comprise more than two DG sources. The proposed control scheme enables the DG source to share the power commanded by the control center as well as to compensate for the voltage harmonics at the PCC. The reference current is estimated from the voltage harmonics and injecting power; thus, the control scheme is implemented without any additional hardware devices. The simulation and experimental results are presented to verify the effectiveness of the proposed control method.

• ETRI Journal
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• v.29 no.1
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• pp.89-94
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• 2007

A mathematical model for the input-output characteristic of an amplifier exhibiting gain expansion and weak and strong nonlinearities is presented. The model, basically a Fourier-series function, can yield closed-form series expressions for the amplitudes of the output components resulting from multisinusoidal input signals to the amplifier. The special case of an equal-amplitude two-tone input signal is considered in detail. The results show that unless the input signal can drive the amplifier into its nonlinear region, no gain expansion or minimum intermodulation performance can be achieved. For sufficiently large input amplitudes that can drive the amplifier into its nonlinear region, gain expansion and minimum intermodulation performance can be achieved. The input amplitudes at which these phenomena are observed are strongly dependent on the amplifier characteristics.