• Bulletin of the Korean Mathematical Society
• /
• v.50 no.6
• /
• pp.1847-1854
• /
• 2013

The main concern of this paper is to study the dynamics of an n-dimensional ratio-dependent predator-prey system with diffusion. We study the dissipativeness, persistence of the system and it is shown that the unique positive constant steady state is globally asymptotically stable under some assumptions.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1982-1984
• /
• 2002

The admittance of one-port electrostatic actuator are modeled using the steady-state sinusoidal response. Also the admittance of the differential type actuator is derived taking the practical conditions into consideration, although it has no admittance in ideal case. It is a function of biasing error, driving error, and capacitive mismatch including parasitic capacitors. The validity of the admittance model is proved by comparing between the modeled and measured admittances. The distortion in the frequency response curve measured by a capacitive sensor is analyzed and it is concluded that the admittance is the main cause of this distortion.

• Honam Mathematical Journal
• /
• v.30 no.3
• /
• pp.411-423
• /
• 2008

In the field of population dynamics and chemical reaction the possibility or the existence of spatially and temporally nonhomogeneous solutions is a very important problem. For last 50 years or so there have been many results on the pattern formation of chemical reaction systems studying reaction systems with or without diffusions to explain instabilities and nonhomogeneous states arising in biological situations. In this paper we study time-dependent properties of a predator-prey system with functional response and give sufficient conditions that guarantee the existence of stable limit cycles.

• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.1993-1995
• /
• 2001

The subject of nonlinear control is an important area of automatic control. The behavior of nonlinear systems is much more complex. If the operating range of a control system is small, and if the involved nonlinearities are smooth, then the control system may be resonably approximated by a set of linear differential equations. This paper presents the deadbeat response attribute of some nonlinear systems, e.g., magnetic levitation, pendulum, van der pol oscillator etc.. The studied results through the computer simulation are shown a promising attribute of deadbeat response that the outputs of the systems are reached relatively fast the steady state.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.11
• /
• pp.1824-1830
• /
• 2003

The vibrational system of this study is consisted of a rotating cantilever pipe conveying fluid and the tip mass. The equation of motion is derived by using the Lagrange equation. The influences of the rotating angular velocity and the velocity of fluid flow in a cantilever pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by the numerical method. The effects of a tip mass on the dynamic response of a cantilever pipe are also studied. The tip-amplitude and maximum tip-deflection of each direction are directly proportional to the tip mass of the cantilever pipe in steady state. It identifies that the influence of the fluid velocity and the rotating angular velocity of the cantilever pipe give much variation the bending tip-displacement of steady state and the bending tip-displacement of non-steady state, respectively. The influence of the rotating angular velocity gives much the deflection of axial direction.

• Ocean Systems Engineering
• /
• v.1 no.1
• /
• pp.17-28
• /
• 2011

The purpose of this paper is to demonstrate the efficacy of modeling a surface effect ship's air-cushion flexible seal utilizing a two-dimensional beam under steady state conditions. This effort is the initial phase of developing a more complex three-dimensional model of the air-seal-water fluid-structure interaction. The beam model incorporates the seal flexural rigidity and mass with large deformations while assuming linear elastic material response. The hydrodynamic pressure is derived utilizing the OpenFOAM computational fluid dynamic (CFD) solver for a given set of steady-state flow condition. The pressure distribution derived by the CFD solver is compared with the pressure required to deform the seal beam model. The air pressure, flow conditions and seal geometry are obtained from experimental analysis. The experimental data was derived from large-scale experimental tests utilizing a test apparatus of a canonical surface effect ship's flexible seal in a towing tank over a variety of test conditions.

• Nuclear Engineering and Technology
• /
• v.55 no.3
• /
• pp.850-860
• /
• 2023

An industrial control process multiple-input multiple-output (MIMO) coupled system is analyzed in this study as an example of a Loss of Coolant Accident (LOCA) simulation system. Ordinary control algorithms can complete the steady state of the control system and even reduce the response time to some extent, but the entire system still consumes a large amount of energy after reaching the steady state. So a multivariable decoupled energy-saving control method is proposed, and a novel energy-saving function (economic function, Eco-Function) is specially designed based on the active disturbance rejection control algorithm. Simulations and LOCA simulation system tests show that the Eco-function algorithm can cope with the uncertainty of the multivariable system's internal parameters and external disturbances, and it can save up to 67% of energy consumption in maintaining the parameter steady state.

• International Journal of Aeronautical and Space Sciences
• /
• v.8 no.1
• /
• pp.115-121
• /
• 2007

The aeroelastic analysis of rotor blades with trailing edge flaps, focused on reducing vibration while minimizing control effort, are investigated using large deflection-type beam theory in forward flight. The rotor blade aerodynamic forces are calculated using two-dimensional quasi-steady strip theory. For the analysis of forward flight, the nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. The objective function, which includes vibratory hub loads and active flap control inputs, is minimized by an optimal control process. Numerical simulations are performed for the steady-state forward flight of various advance ratios. Also, numerical results of the steady blade and flap deflections, and the vibratory hub loads are presented for various advance ratios and are compared with the previously published analysis results obtained from modal analysis based on a moderate deflection-type beam theory.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.5
• /
• pp.481-486
• /
• 2018

DC motors are classified as DC motors with brush structure and BLDC motors without brush structure. Representing the speed control of the BLDC motor is the PI control. The speed control using the PI controller has a disadvantage that the response characteristic to reach the steady state is slow. Therefore in this paper, a voltage controlled speed controller using a Fuzzy Logic Controller (FLC), which has a short steady response time and usefulness of nonlinear control. The validity and usefulness of the proposed fuzzy speed controller are verified by simulation through Simulink of MATLAB program. Experiments were performed on the PI controller and the proposed fuzzy speed controller in three cases with reference speeds of 500rpm, 800rpm, and 1500rpm. Experimental results show that the proposed fuzzy controller has more 30% improved steady state speed response than PI controller.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.266-267
• /
• 2010