• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.69-70
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• 2008

Automatic control systems(AVR, Governor, Synchronizer) installed $1970{\sim}1980$ in K-water were considered to be rehabilitated around 2000. Moreover, Korea Power Exchange market system was changed from PPA (Power Purchase Agreement) to a bidding system. Therefore, depending on the power quality, the power provider could achieve additional profits. It is the excitation system and governor that have the functions of enhancing power necessities. During the 20 to 30 years of generator operation, there were many major and minor problems. Examples are SCR burnout (Andong: Excitation system), hunting (Imha: governor), field circuit breaker failure (Chungju 1st: excitation system), the rise of leakage current (Chungju 2nd: excitation system), power supply burnout (Chungju 2nd: governor). These are the typical examples of malfunction which hindered the generator operation and, consequently, diminished the profit of power business. In order to satisfy the needs of the power market and prevent malfunctions mentioned above, the rehabilitation of AVRs and governors were executed. A new system was made to have the flexibility of ancillary service (GF, AGC, etc.), PSS function. With user friendly HMI software, it is more convenient for the operator to fulfill suitable maintenance. It was possible to connect SCADA system by opening protocol of AVR, governor for the efficiency of operation and maintenance.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.45-54
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• 2011

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1423-1428
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• 2011

This paper proposes a learning input shaper with nonlinear actuator dynamics to reduce the residual vibration of flexible systems. The controller is composed of an estimator of the time constant of the nonlinear actuator dynamics, a recursive least squares method, and an iterative updating algorithm. The updating mechanism is modified by introducing a vibration measurement function to cope with the dynamics of nonlinear actuators. The controller is numerically evaluated with respect to parameter convergence and control performance by using a benchmark pendulum system. The feasibility and applicability of the controller are demonstrated by comparing its control performance to that of an existing controller algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.260-266
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• 2015

The warship is run based on the combat system which shares tactical information collected by target detection systems and navigation devices across a network, and conducts the command and control of weapons from target detection to kill assessment. The short-range air defense missile system defends a warship from anti-ship missiles, aircraft, helicopter and other threats in order to contribute to the survival of a warship and the success of missions. The short-range air defense missile system is applied to a various combat systems. In this paper, we have proposed the interface design between the short-range air defense missile and dissimilar combat systems. To employ the short-range air defense missile at dissimilar combat systems, each system is driven by independent processor, and the tasks which are performed by each system are assigned. The information created by them is exchanged through the interface, and the flow of messages is designed.

• Nuclear Engineering and Technology
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• v.41 no.7
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• pp.885-892
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• 2009

This manuscript will discuss a numerical method where the six equations of two-phase flow, the solid heat conduction equations, and the two equations that describe neutron diffusion and precursor concentration are solved together in a tightly coupled, nonlinear fashion for a simplified model of a nuclear reactor core. This approach has two important advantages. The first advantage is a higher level of accuracy. Because the equations are solved together in a single nonlinear system, the solution is more accurate than the traditional "operator split" approach where the two-phase flow equations are solved first, the heat conduction is solved second and the neutron diffusion is solved third, limiting the temporal accuracy to $1^{st}$ order because the nonlinear coupling between the physics is handled explicitly. The second advantage of the method described in this manuscript is that the time step control in the fully implicit system can be based on the timescale of the solution rather than a stability-based time step restriction like the material Courant limit required of operator-split methods. In this work, a pilot code was used which employs this tightly coupled, fully implicit method to simulate a reactor core. Results are presented from a simulated control rod movement which show $2^{nd}$ order accuracy in time. Also described in this paper is a simulated rod ejection demonstrating how the fastest timescale of the problem can change between the state variables of neutronics, conduction and two-phase flow during the course of a transient.

• Journal of Acupuncture Research
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• v.18 no.1
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• pp.76-87
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• 2001

Objective : Zusanli(ST36) and Hoku(Li4) are analgesic acupuncture points frequently used for acupuncture in Oriental medicine. The present study was conducted to see the antinociceptive effects produced by electroacupuncture combined two frequencies(Low, High) and two different acupuncture points(LI4, ST36) in the rat tail flick test. Method : In this study the Rats (Sprague-Dawley, 250-300g) were partially anesthetized with thiopental sodium(40mg/kg, i.p.). The basal reaction time for the tail-flick was 3${\pm}$0.5 sec. Low frequency(3Hz, 5V, biphasic) and high frequency(100Hz, 5V, biphasic) were applied to the inserted needle for the period of insertion(twenty minutes). Experimental groups are divied as follow; a) electroacupuncture stimulation groups at Hoku with or high frequency(L-EA, H-EA), b) electroacupuncture stimulation groups at Zusanli with low or high frequency(1-EA, h-EA), c) low frequency at Hoku and Zusanli(LIEA), d) low frequency at Hoku and high frequency at Zusanli(LhEA), e) high frequency at Hoku and low frequency at Zusanli(HIEA), f) high frequency at Hoku and Zusanli(HhEA) Results : The individual stimulation at either Hoku or Zusanli with low frequency has stronger and longer analgesic effect than high frequency stimulation. In addition, the combined stimulation at Hoku and Zusanli with low frequency has superior effect to individual stimulation with low frequency. LhEA and LIEA have superior effect to other stimulation groups among the combined groups. In order to determine the involvement of opioid system on the different antinociceptive effects, Naloxone, an opioid antagonist, was used in the combined groups. LIEA is the most sensitive when naloxone was administrated among study groups. HhEA is the least sensitive in the administration of naloxone. Conclusion : From results, this study confirmed that the opioid system is involved in analgesic effect of low frequency stimulation of acupuncture point, and we also can suggest the stronger analgesic effect of combining stimulation points is due to the theory of spatial summation in the nervous system.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.4
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.6
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• pp.619-628
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• 2021

In order to compare numerical analyses made by Song and Kim needed for predicting gas and water filling with experimental results we conducted an experiment to recover a test projectile (43.7 kg with a 155 mm diameter) at a velocity of 775 m/s in a soft recovery system with a length of 179 m using pressurized gas and filled water. The soft recovery system consisting of a series of pressure tubes had a diaphragm, piston, and water plug for filling the pressurized gas and water. We installed a continuous wave Doppler radar system for velocity measurements of the test projectile travelling in the pressure tubes and pressure transducers for measuring the pressure in the soft recovery system. Continuous wave Doppler radar has the advantage of achieving real-time measurements of the velocity of a test projectile. The velocity-time curve of the test projectile, measured using the continuous wave Doppler radar, and the pressure profile were compared with the numerical analysis results. The experiment results show good agreement with the numerical analysis results based on the one-dimensional Euler equation with an HLL Riemann solver.

• Korean Journal of Materials Research
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• v.5 no.1
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• pp.63-74
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• 1995

Process optimization experiments based on the Taguchi method were performed in order to set up the optimal process conditions for the contact oxide etching process module which was built in order to be attached to the cluster system of multi-processing purpose. From the two times experiments of Taguchi method, the overall behaviors of the etchmg characteristics depending upon the equipment parameters were understood at the 1st Taguchi experiment, the detail and optimal process conditions were extracted from the 2nd Taguchi experiment. As a final analysis of experimental results, the optimal etching characteristics were obtalned at the process conditions of $CHF_{3}/CF_{4}$ gas flow rate=72/8 sccm, chamber pressure=50 mTorr, RF power=300 Watts, magnetic field intensity=90 Gauss.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.319-328
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• 2014

Dorang - the Korean term for headwater streams - occupy a large portion of the total stream length in a basin, and contribute significantly towards the quantitative and qualitative characteristics, and the ecosystem, of the main river. The Ministry of Environment of South Korea has supported the investigation of the status of Dorang in the nation's four major basins, since 2007. Without a widely accepted academic or legal definition of Dorang, however, there are limits to understand the distribution of Dorang at the national scale and to systematically compile a Dorang database. This paper, through a review of the stream classification system and Korean legal system delineating streams, defines Dorang as 1st and 2nd order streams according to the Strahler ordering method, in a 1:25,000 geographical scale. Analysis of the Geum River basin, with this definition, reveals that the total length of Dorang is 20,622.4 km (73.6% of total stream length), and the number of Dorang catchments is 23,639 (71.3% of the basin area). Further analysis of the geomorphological characteristics of Dorang catchments shows that the average total stream length is 1.1 km, average catchment length is 1.2 km, average drainage area is $0.4km^2$, and average drainage density is 3.08/km.