• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.133-138
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• 1987

In this paper the tuning characteristics of resonant frequencies are experimentally studied through the variation of the length of the inner conducting rod in a re-enterant eavity resonator. The re-enterant eavity resonator consists of a coaxial cable and a cylindrical wave guide. The length of the inner conducting rod can be varied to the longitudinal direction. The resonant frequencies of TMonq modes are measured according to the arbitrary length. In order to verify the propriety of experimental results, experimental results are compared with other theoretical results. The results in this paper can be applied to wave meter and resonant circuit of amplifier. They will be use to vary resonant frequencies of a dielectric resonator in MIC and filter.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.125-133
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• 2016

In this paper, we propose a vertical axis water turbine with dual blades. A parametric study was conducted using numerical analyses. First, a two-dimensional finite-volume analysis with a commercial code was used to find the pitch angle of the main blade under different tip speed ratio conditions. Second, we developed a potential-based panel method to find the best configuration of the inner blades. Experimental tests were conducted at the circulating water channel of Chungnam National University. Various configurations of the dual blades were considered, and their performances were comparatively investigated. The results showed that the turbine with movable dual blades produces a constant torque and tip speed ratio at various flow rates.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.13-18
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• 2000

This paper presents the result of a technique to enhance TDAC in the AC-3 algorithm. To reduce block boundary noise without decreasing the performance of transform coding, We propose new special windows which improve the defect of the AC-3 algorithm that could not properly cancel aliasing in the transient period. In addition, a fast MDCT calculation algorithm based on a fast Fourier transform, is adopted.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.715-720
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• 2001

The main reason for applying positive pressure variable clearance packing in fossil power plant is high efficiency and energy saving movement in the government. This study intends to analyze the turbine efficiency through the shaft packing improvement in thermal power plant and makes its comparison to that of the used packing.

• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.202-207
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• 2018

This paper presents the efficiency of a floating vertical axis wind turbine with variable-pitch. A model was designed to use the lift force and drag force for blades with various pitch angles. The blade's pitch angle is controlled by the stopper. To validate the efficiency of the wind turbine discussed in this paper, a model test was carried out through a single model efficiency experiment and wave tank experiment. The parameters of the single model efficiency experiment were the wind speed, electronic load, and pitch angle. The wave tank experiment was performed using the most efficient pitch angle from the results of the single model efficiency experiment. According to the results of the wave tank experiment, the surge and pitch motion of a structure slightly affect the efficiency of a wind turbine, but the heave motion has a large effect because the heights of the wind turbine and wind generator are almost the same.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.142-149
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• 2004

PMLSM(Permanent Magnet linear Synchronous Motor) has widely applied to industrial automations, machine tools and semiconductor equipments due to the merit on the reduction of noise, vibration and the superior dynamic characteristics in comparison to the conventional method, which uses mechanical transfer equipments. Especially, in the case of applying to Z-axis operation structure, control system needs the method of an initial angle setting and the improvement of up/down operation characteristics. This paper proposes an initial angle setting algorithm and a variable gain schedule using real speed and moving direction to improve up/down operation characteristics. The effectiveness of proposed algorithms Is demonstrated by comparing to a conventional gain system via 4-point absolute positions profile with each velocity, acceleration and deceleration.

• Journal of the Korean Geosynthetics Society
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• v.14 no.3
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• pp.1-12
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• 2015

During installing sheet piles for an impermeable wall or a retaining wall, vibratory hammers are widely used. Among vibratory hammers, a hydraulic hammer is used most commonly. However, a hydraulic hammer causes excessive vibration and noise due to resonance by change of natural frequency according to movements of eccentric shaft when the hammer starts and stops. In this study, new variable amplitude type hammer is developed in order to reduce the vibration and noise due to resonance produced in starting and stopping the hammer. By controlling horizontal angle in two pairs of eccentric body inside of the hammer, the amplitude and vibration of the new hammer can be controlled. The performance tests with the new hammer and existing hammers such as the hydraulic hammer and electric hammer are carried out, and the new hammer shows reduced vibration and noise results in comparison with existing hammers from performance tests. Also, this study shows that penetration rates of sheet pile using the new hammer increase due to impellent force of a backhoe in comparison with the electric hammer and penetration rate increase in comparison with a general hydraulic hammer, since the new hammer can control the amplitude during penetration of sheet pile according to soil condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.437-442
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• 2014

The equipment or with a constant torque and a variable stress due to axial vibration such as the turbine-generator system in nuclear power plant show the fatigue fracture behavior. Thus this study whoul aim to measure the torsional stress and analyze the fatigue fracture behavior. To achieve this, we manufactured the equipment similar with turbine-generator system and applied various torsional vibration stress due to external load. In particular, the evaluation was conducted with the existing evaluation methods of the fatigue behavior of known stress-life, strain-life, crack growth assessment methods. With increasing the external load and independent methods tends to decrease the fatigue life was confirmed up to 10 times in 5 kV external load compared to without external load.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1400-1405
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• 2004

Experimental study is performed to investigate the effect of heat load and operating temperature on the thermal performance of a heat pipe with screen mesh wick. The heat pipe was designed in 200 screen meshes, 500mm length and 12.7mm O.D tube of copper, water as working fluid(4.8g) and nitrogen as non-condensible gas(NCG). The heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Experimental data of axial wall temperature distribution is presented for heat transport capacity, the temperature of cooling water of condenser, inclination angle, and operating temperature. For the results from this study, it is found that, for the same charging mass of working fluid, the initial operating temperature and the overall wall temperatures of heat pipe are higher for NCG charging mass of $5.0{\times}10^{-6}kg$ and $3.4{\times}10^{-6}kg$, than that of $1.0{\times}10^{-6}kg$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.77-82
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• 2010

In this paper, a haptic fishing robot, Fishbot, for a Virtual Fishing System is presented. Fishbot is 3DOF robot and it consists of a XY table and a wheel motor. To simulate the motion of fish, XY table is controlled by position servo drivers with variable torque constraint, and wheel axis is controlled by torque servo driver. Finally, Fishibot detects the end point of fishing pole with cameras to recognize the pose of user, and it can interface with a Virtual Reality System.