• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.693-698
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• 2009

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, the test facility was set up composed of fan, duct and silencer. Using the test facility, insertion loss tests were carried out to improve the acoustic performance in the low-frequency ranges. Through a series of tests, it was found out that the array resonators having multi-perforated holes inside the exhaust silencer, might be very effective in the low frequency range. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer, was proposed and its high performance in the low-frequency range was also verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.30-35
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• 2007

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, test equipment composed of fan, duct and silencer was set up. Using the test equipment, insertion loss tests were carried out to improve the performance in the low-frequency ranges. Through a series of tests, the fact that array resonators may be effective in the low-frequency noise has been verified. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer were proposed and its high acoustic performance in the low-frequency range has also been verified.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.3
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• pp.45-55
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• 2000

This study was carried out to derive optimal design low flows bythe Weibull-3 and Wakeby distributions for the partial consecutive duration series at seven watersheds along Han. nagdong, Geum Yeongsan and Seomjin river systems. L-coefficient of variation L-skewness and L-kurtosis were calculated by the L-moment ratio respectively. Parameters were estimated by the method of L-Moments with consecutive duration. Design low flows obtained by method of L-Moments using with consecutive duration, Design low flows obtained by method of L-Moments using different methods for plotting positions formulas in the Weibull-3 and Wakeby distributions were compared by the Root Mean Square Errors(RMSE). It has shown that design low flows derived by the method of L-moments using Weivull plotting position formula in Wakeby distribution were much closer to those of the observed data in comparison with those obtained by the methods of L-moments with the different formulas for plotting positions in Weibull-3 distribution from the viewpoint of Root Mean Square Errors.

• Korean Institute of Interior Design Journal
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• v.22 no.1
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• pp.247-255
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• 2013

In this study, the colors and characteristics of Gwangbok-ro of Busan were analyzed in the standpoint of local images based on the examination of the facade designs of stores along the road of Gwangbok-ro, Busan a main street with massive population flow. To that end, the facades of stores, correlation with the city, color and locality were examined, and after the status of facade designs in Gwangbok-ro were identified through case survey by it, color images were analyzed. For color analysis, Munsell color system was used as basic tool. As a result of examining the colors in Gwangbok-ro area, the following status could be analyzed on 3 attributes of hue, brightness and chroma: First, analysis results of hue indicated that dominant color that covers 70% or more of the area represented mid brightness and low chroma in GY(36.1%) series, subsidiary color which covers 25% or more of the area mid brightness and low chroma in YR(26.5%) series, and accent color that covers less than 5% of the area high brightness and low chroma of GY(40%) series. Second, in brightness analysis, dominant color mostly represented mid brightness, subsidiary color mid brightness and accent color high brightness respectively. In particular accent color showed more intensive crowding phenomenon in high brightness. Third, as for chroma, dominant color, subsidiary color and accent color all are gathered in low chroma, however in small number of accent colors, peculiar high chroma appeared notable. In conclusion, the colors of Gwangbok-ro area analyzed based on the facade design of the stores along the road in this study were superficial colors that reflect the life of people in the area, artificial colors by improvement of the local environment. This study is meaningful in that the image of Gwangbok-ro was found through building colors in one part of the city Busan. It is judged that the study results would become useful as reference document in planning out environment colors later on.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.91-96
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• 1998

The broadband noise generated aerodynamically from a two-bladed axial flow fan has been measured and compared to the result of a self-noise prediction method. The prediction scheme is based on the experimental data set acquired from a series of aerodynamic and acoustic tests of two and three-dimensional airfoil blade sections. For low blade loading case the comparison showed a reasonably good agreement, but as the loading becomes larger the empirical formula overpredict the sound pressure level at high frequency range. This is probably due to the use of stationary wing data for the prediction of rotating blade case, which will be quite different in their vortex strength at the blade tip.

• Journal of Ship and Ocean Technology
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• v.4 no.1
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• pp.1-10
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• 2000

A low-order potential based boundary element method is applied for the prediction of the performance of flapped rudders as well as all-movable rudders in steady inflow. In order to obtain a reasonable solution at large angles of attack, the location of the trailing wake sheet is determined by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap of a flapped rudder is modeled as Couette flow and its effect is introduced into the kinematic boundary conditions for flux at both the inlet and the outlet of the gap. In order to validate the present method, the method is applied for a series of rudders and the computational results on forces and moments are compared with experimental data. The effect of the gap size on the forces and moments is also presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.8
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• pp.405-412
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• 2003

This paper presents a three-phase Line-Interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using synchronous reference frame (SRF) based controller, which allows an effective power factor correction, source harmonic voltage compensation, load harmonic current suppression, and output voltage regulation. The three-phase UPS system consists of two active power compensator topologies. One is a series active compensator, which works as a voltage source in phase with the source voltage to have the sinusoidal source current and high power factor under the deviation and distortion of the source voltage. The other is a parallel active compensator which works as a conventional sinusoidal voltage source in phase with the source voltage, providing to the load a regulated and sinusoidal voltage with low THD (total harmonic distortion). The control algorithm using SRF method and the active power flow through the Line-interactive UPS systems are described and studied. The simulation and experimental results are depicted in this paper to show the effect of the proposed algorithm.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.82-87
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• 1996

To find the effects of pressure on critical heat flux (CHF) for the conditions of low pressures (especially up to 10 bar) and low mass flux (~300 kg/$m^2$s), a series of experiments have been accomplished by using uniformly heated Inconel-625 tube. The experimental ranges are as follows: pressure (from 1.2 to 8 bar). mass velocities (from 100 to 250 kg/$m^2$s) and the inlet subcooling ($\Delta$h$_{i}$ ＝ 350 kJ/kg). According to the experimental data, it is found that the CHF is nearly independent of the pressure and increases with mass flux. From the results of the CHF correlation assessment for this experimental data, we could find somewhat different tendency of CHF behavior from every other CHF prediction correlation and table.ation and table.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.504-504
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• 2000

The flow ratio in the industrial process is usually accomplished by using PID controller with series type ratio. But always the large overshoot and a long rise time may be achieved from this conventional control. These problems are involved to the inexact flow ratio control. In order to avoid this poor performance. the paper presents a designing of the two controller modes for the flow ratio plants. This proposed controller combine the lookup table technique and the well-known PID controller to obtain the fast response and low overshoot of flow ratio control. The PID controller mode will be operated when the flow ratio reaches the preset value while the lookup table technique mode is applied for initial operation. The data in tile table is calculated by the valve sizing equation and convened to the valve position control signal. The experimental results show that the transient and steady state responses of the control systems using the proposed technique can be efficiently obtained when compared with tile conventional controller.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.45-58
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• 2006

In order to grasp physical characteristics of Ganajin Bay receiving the effluents from land, a comprehensive field surve)'has been conducted at the north of Wando and Gogeumdo in 2002. Water temperature was most high in September while most low in December. A high temperature in September was inferred to have caused by the dispersion of warm fresh water with favor of a dominant wind in autumn. However, salinity and sigma-t in situ was most low in September while most high in December. A low salinity (or density) in September turned out to reflect the influence of a dense rainfall in summer. Water temperature, salinity and density at the surface layer were lower than those at the bottom layer, except for December. Their horizontal profiles suggested the influence of effluents such as Tamjin River. Particularly, time series of water temperature acquired near the sluice and at the north channel of Wando tended to rise at the flood flow but fall at the ebb flow in accordance with the tide. The form ratio of the tide in the study area was $0.31\~0.32$ and the amplitude of the tide appeared to increase towards the west. Northeastward or southwestward flows prevailed in this area but the residual flows were all northeastward with a magnitude of $3\~4cm/s$.