• Solar Energy
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• v.17 no.1
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• pp.103-111
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• 1997

The purpose of this research is the study of characteristics of heat transfer in a heat pipe controlled by solenoid valve. A solenoid valve located to the adiabatic section between evaporator and condenser of heat pipe was used to control the valve action for effective energy transfer of the industrial exchanger machine. By the results presented in this study temperature difference between evaporator and condenser increases with increasing the temperature frequency and with decreasing the temperature amplitude. When inclination angle and flow rate of cooling water increases, the temperature amplitude is reached to the steady state rapidly with increasing the temperature frequncy.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.27-33
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• 2006

Fault diagnosis and condition monitoring for rotating machines are important for efficiency and accident prevention. The process of fault diagnosis is to extract the feature of signals and to classify each state. Conventionally, fault diagnosis has been developed by combining signal processing techniques for spectral analysis and pattern recognition, however these methods are not able to diagnose correctly for certain rotating machines and some faulty phenomena. In this paper, we add a minimum detection error algorithm to the previous method to reduce detection error rate. Vibration signals of the induction motor are measured and divided into subband signals. Each subband signal is processed to obtain the RMS, standard deviation and the statistic data for constructing the feature extraction vectors. We make a study of the fault diagnosis system that the feature extraction vectors are applied to K-means clustering algorithm and minimum detection error algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.11
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• pp.846-853
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• 2014

High performance intake silencer with low pressure drop are developed for a household oxygen generator. First, the acoustic power of the target oxygen generator are experimentally evaluated according to ISO code. Then, the transmission loss of and the flow characteristics inside the existing intake silencer are predicted and analyzed. On a basis of these results, two intake silencers are proposed, which are designed to induce the swirling flow inside the intake silencer and thus to reduce the flow loss. The predicted TL and the pressure drop for these two new silencers are compared to the existing one, which shows that the proposed ones have higher TL as well as low pressure drop. The reason for these improvements are explained by investigating the flow characteristics of the new silencers in detail.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.150-152
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• 2019

In this study, the effects of the wave field changes due to the coastal structure on the hydrodynamic performance of the OWC wave energy, converter are analyzed using a three-dimensional numerical wave tank technique (NWT). The OWC device is simulated numerically by introducing a linear pressure drop model, considering the coupling effect between the turbine and the OWC chamber in the time domain. The flow distribution around the chamber is different due to the change of reflection characteristics depending on the consideration of the breakwater model. The wave energy captured from the breakwater is spatially distributed on the plane of the front of the breakwater, and the converted pneumatic power increased when concentrated in front of the chamber. The change of the standing wave distribution is repeated according to the relationship between the incident wavelength and the length of the breakwater, and the difference in energy conversion performance of the OWC was confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1332-1335
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• 2003

This paper presents the enhancement of oxygen transfer efficiency using the vibrating intravascular lung assist device (VIVLAD) in in-vitro experiments for patients having chronic respiratory problems. The test section was a cylinder duct with the inner diameter of 30 mm. The flow rate was controlled by the pump and monitored by a built-in flow meter. The vibration apparatus was composed of a piezo-vibrator, a function generator. and a power amplifier. The direction of vibration was radial to the fluid flow. Gas flow rates of up to 6 l/min through the 120-cm-Jong hollow fibers have been achieved by exciting a piezo-vibrator. The output of PVDF sensor were investigated by various frequencies in VIVLAD. The experimental results showed that VIVLAD would be enhance oxygen transfer efficiency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.180-187
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• 2017

Major design targets such as test cell type, cell flow, cell bypass ratio, approach velocity, cell depression, front cell distortion, noise level and vibration level to construct a new 150,000 lbf thrust aircraft engine test facility were established. Based on the final aerodynamic and acoustic performance tests conducted at the newly constructed test facility, it was found that the new test facility is judged to be excellent and meets design targets.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.26-32
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• 2005

The volumetric efficiency is significantly affected by the behavior of pressure wave in induction system and exhaust pipe. By the motion of the piston, there exist pressure fluctuation in induction system which produce waves. Waves are propagated along a pipe bi-directional as they propagated through it, making compression wave and rare-faction(expansion) wave. These wave phenomena can affect to the volumetric efficiency. As a method of improvement of the volumetric efficiency, fuel economy and pollutant emission reduction particularly in low engine speeds, a side-branch additional tunable helmholtz resonator on the secondary pipe of intake system is proposed by use of their acoustic vibrations. Some of results are presented which deal with their physical phenomena for the wave action of intake system in a four-stroke three cylinders diesel engine.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.129-136
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• 2008

The purpose of this study is to find an effective operating system for water supply of Andong Dam. The reliability of water supply was assessed by HEC-5 model based on operated water supply data of Andong Dam and data of Jin-dong water level gauge station in Nak- dong river. In addition, estimated additional amount of water supply was evaluated for each alternative by additional retention of Andong Dam in rainy season from June to September. As the result, additional amount of water supply of each alternative in non-rainy season (excluding rainy season) is increased as $1.35m^3/s{\sim}2.12m^3/s$, it shows that additional amount of water supply can be made by effective operating system for water supply in every dam as Andang Dam.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.64-72
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• 1997

Since the average speed calculated with encoder pulses inevitably has time delay, the control performance as well as the system stability is deteriorated. especially at the low speed region. Additionally, the distorted inverter output voltage due to the dead time effects and the forward voltage drops of the VSI (Voltage Source Inverter) causes torque ripples and their effects are more severe at the low speed operation of an induction motor. In this paper, an accurate speed estimation method using Kalman Filter Algorithm is presented to improve the performance of an induction motor speed control with a low precision encoder at low speed legion. The dead time effects and the forward voltage drops of the VSI are feedforwardly compensated to produce an exact inverter output voltage.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.33-39
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• 2006

Parameters including the seismic sources and the elastic wave propagation characteristics were analysed using the observed ground motions from 3 Kyoungju region earthquakes. The Levenberg-Marquardt algorithm was applied to invert all the variables non-linearly and simultaneously with S wave energy In frequency domain. Average stress drop of 3 events and local attenuation parameter ${\kappa}$ were estimated to about 48-bar and 0.0312 respectively. Regional attenuation parameter, Qo and ${\eta}$, were also estimated to be about 417 and 0.83. ${\kappa}$ values are much higher than that of EUS, even though smaller than that of WUS. All these values resultant from this study show that there are differences in some parameters of other studios due to differences in the governing equation. of acceleration motions