• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.693-696
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• 2005

We propose a robust adaptive fuzzy controller for the transient stability and voltage regulation of a single-machine inflnite bus power system. The proposed control scheme is based on the input-output linearization to eliminate the system nonlinearities. To deal with uncertainties due to a parameter variation or a fault, we introduce fuzzy systems with universal function approximating capability which estimate the uncertainties on-line.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1255-1265
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• 2001

A numerical study has been conducted to characterize the transient flow in a utility gas turbine burning natural gas. The solution domain encompasses the supply gas pressure regulator to the combustor of the gas turbine that employs multi-nozzle fuel injectors. Some results produced for verification in the present study agree suite well with the experimental ones. It is found that the total gas flow may decrease noticeably during its combustion mode change, which would be the reason of momentary combustion upset, when a reference case of opening ratios of control valves in the system is applied. Several parameters are then varied in order to make the total gas flow stable over that period of time. Results of this study may be useful to understand the unsteady behavior of combustion system burning natural gas.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.314.2-314.2
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• 2002

DNA topoisomerases catalyze changes in DNA topology through cycles of transient DNA strand breakage and religation. During this process. the active site tyrosine in human DNA topoisomerase Ⅰ(Top Ⅰ) becomes covalently linked to the 3'-ends of a single-stranded nick in the DNA duplex, Stabilization of the Top Ⅰ-DNA cleavable complex is the common initial event leading to the cytotoxicity of top 1 inhibitors. (omitted)

• Journal of the military operations research society of Korea
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• v.3 no.1
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• pp.83-96
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• 1977

The combustion chamber and nozzle of an end burning, small spherical rocket is designed. A spherical external shape has a number of advantages such as fixed center-of-gravity and minimum aerodynamic precession torques during flight and a better mass distribution for gyro-stabilization as contrasted to a conventional ogive rocket shape. It is shown that the cross-sectional variation of the end burning solid propellant with length is an exponential geometry to provide a constant thrust-weight ratio of the rocket device during the propellant burning period, and that the factors which affect the attainment of the constant relationship of thrust to weight in the design are the initial propellant area, initial weight of the rocket and propellant density. The measurement of the transient thrust in the ground static test using black powder propellant supports the predicted results. A wind tunnel having a $30{\times}30{\times}75cm$ test section and Mach number 0.11 is constructed, and a simple balance-type device is designed for the measurement of the drag of a spinning sphere. The experimental results indicate that the. spinning has no effect on the magnitude of the drag up to the Reynolds number $3{\times}10^5$. Numerical computation of the flight trajectories for various launching angles is presented, and the gyro-stabilization of spinning sphere is discussed.

• Corrosion Science and Technology
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• v.16 no.4
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• pp.194-200
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• 2017

Stress-corrosion cracking (SCC) of alloy 600 and alloy 800 in 0.5 mol/L thiosulfate solution during constant strain was investigated using electrochemical noise (EN) combined with 3-D microscope techniques. The in-situ morphology observation and EN results indicate that the SCC process could be divided into three stages: (1) passive film stabilization and growth, (2) crack initiation, (3) and crack growth. Power Spectral Density (PSD) and the probability distribution obtained from EN were used as the "fingerprint" to distinguish the different processes. During passive film stabilization and growth, the current noise signals resembled "white noise": when the crack initiated, many transient peaks could be seen in the current noise and the wavelet energy at low frequency as well as the noise resistance decreased. After crack propagation, the noise amplitudes increased, particularly the white noises at low and high frequencies ($W_L$ and $W_H$) in the PSDs. Finally, the detection of metal structure corrosion in a simulated sea splash zone and pipeline corrosion in the atmosphere are established.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.8
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• pp.718-722
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• 2015

This paper proposes a fractional-order PID (Proportional-Integral-Derivative) control used electromagnetic strip stabilization controller in a continuous galvanizing line. Compared to a conventional PID controller, a fractional-order PID controller has integration-fractional-order and derivation-fractional-order as additional control parameters. Thanks to increased control parameters, more precise controller adjustment is available. In addition, accurate transfer function of a real system generally has a fractional-order form. Therefore, it is more adequate to use a fractional-order PID controller than a conventional PID controller for a real world system. Finite element models of a $1200{\times}2000{\times}0.8mm$ strip, which were extracted using a commercial software ANSYS were used as simulation plants, and Gaussian mixture models were used to find optimized control parameters that can reduce the strip vibrations to the lowest amplitude. Simulation results show that a fractional-order PID controller significantly reduces strip vibration and transient response time than a conventional PID controller.

• Journal of the Korean Institute of Intelligent Systems
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• v.8 no.2
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• pp.117-127
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• 1998

Power systems have uncertain dynamics due to a variety of effects such as lightning, severe storms and equipment failures. The variation of the effective reactance of a transmission line due to a fault is an example of uncertainty in power system dynamics. Hence, a robust controller to cope with these uncertainties is needed. Recently, fuzzy controllers are becoming quite popular for robust control due to its potential of dealing with uncertain systems. Thus in this paper we design an adaptive fuzzy controller based on an input-output linearization approach for the transient stabilization and voltage regulation of a power system under a sudden fault. Also this paper proposes a fuzzy system that estimates the upper bound of uncertain term in the system dynamics to guarantee the Lyapunov stability. Simulation results show that good performance is achieved by the proposed controller.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.533-544
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• 2006

The amplitude and phase lag of surface deformation were determined for a compliant coating under the action of turbulent pressure fluctuations. For this purpose, pressure fluctuations were measured experimentally. The amplitude and duration of coherent wave train of pressure fluctuations were investigated using digital filtration. The transient response was calculated for stabilization of forced oscillations of the coating in approximation of local deformation. The response of coating was analyzed with considerations of its inertial properties and limited duration of coherent harmonics action of pressure fluctuations. It is shown that a compliant coating interacts not with the whole spectrum of pressure fluctuations, but only with a frequency range near the first resonance. According to the analysis, with increasing elasticity modulus of the coating material E, deformation amplitude decreases as 1/E, and dimensionless velocity of the coating surface decreases as $1/\sqrt{E}$. For sufficiently hard coatings, deformation amplitude becomes smaller than the thickness of viscous sublayer, while surface velocity remains comparable to vertical velocity fluctuations of the flow.

• Journal of Chest Surgery
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• v.27 no.7
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• pp.563-570
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• 1994

Effect of ischemic preconditioning on left ventricular function after cardiac arrest in isolated rat heart.Ischemic preconditioning reduces infarct size caused by sustained ischemia. However, the effects of preconditioning on post ischemic cardiac function are not well-known. The objective of the present study was to determine whether preconditioning would improve the recovery of left ventricular functions after cardiac arrest in isolated rat heart model.Isolated rat hearts were allowed to equilibrate for 20 minutes and were then subjected to either 5 minutes of global, normothermic transient ischemia [Group 2 and 4] or not [Group 3]. A stabilization period of perfusion lasting 5 minutes after the termination of transient ischemia was followed by a standard global, normothermic 20 minute-ischemia and 35-minute reperfusion challenge [Group 3 and 4]. These following results were odtained.1. The recovery of left ventricular developed pressures showed no significant differences between Group 3 and Group 4 at 50 [P>0.3] and 85 minute [P>0.2].2. Heart rates showed no significant differences throughout all the course of experiment and between groups [P>0.5].3. The recovery of left ventricular maximum dP/dt showed no significant differences between Group 3 and Group 4 at 50 [P>0.1] and 85 minute [P>0.2].4. The recovery of pressure-rate products showed no significant differences between Group3 and Group 4 at 50 [P>0.5] and 85 minute [P>0.1].These results suggest that ischemic preconditioning does not provide significant benefit for the postischemic left ventricular functions in isolated rat hearts.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.3
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• pp.1-12
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• 2003

The complexity of the papermaking system accelerates interactions between a large number of variables involved. The process operation, therefore, is subject to frequent perturbations by disturbance. Dynamic modelling is a useful tool for characterizing the transient behavior and selecting the best control strategies to reject disturbances. In this study we developed a dynamic simulation model of a fine paper production process, which consists of stock preparation, wire sections, white water circulations, and broke system. It focused on dynamic simulation in its role for developing control strategies and studying control loop dynamics related to filler loading for ash control. The results emphasized the importance of filler-loading position and length of control loop for rapid ash control and process stabilization.