• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.7
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• pp.239-246
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• 2001

The present study addresses the open correction associated with the reflection and discharge phenomena of a weak shock wave from an open end of a duct. The open correction of the weak shock wave is investigated experimentally and by numerical computation. An experiment is made using a simple shock tube with an open end. and computaion is performed to simulate the experimental flow field using the unsteady, axisymmetric compressible. flow governing equations. The results obtained show the an open correction should be involved for shock wave discharge and reflection problems generated from the exit of the duct with an open baffle plate. With a baffle plate less than three times the duct diameter, it is found that the open end correction is a function of both the diameter of the baffle plate and normal shock wave magnitude However, for a baffle plate larger than three the duct diameter it is independent of the baffle plate diametre, The present computations predict the results of shock tube experiment with good accuracy. A new empirical equation for prediction of the open correction is found for the weak shock reflection and discharge phenomena occurring at the open of the duct with and without a baffle plate.

• Water for future
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• v.24 no.2
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• pp.109-119
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• 1991

The river-bed variation and the sediment transport in an alluvial stream are very complicated physical phenomena, especially in a stream where the dam construction prevents the supply of earth and sand from upper tributaries Therefore, the mathematical modeling is needed to establish. The purpose of this study is to apply river-bed variation to the Han River downstream by the conception of gradually varied unsteady flow instead of that of steady flow in order to decrease errors. For the variation and forecast of river-bed, the numerical analysis has been made in this study by way of discharge variation and river-bed variation. In conclusion, the numerical analysis shows that river-bed variation, sediment transport , and their forecast have similarity to natural phenomena and that river-bed variation is greatly affected in sediment transport by discharge variation and retention time(duration). Therefore, the errors of numerical analysis can be reduced by the application of flood data instead of continuous discharge data.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1598-1600
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• 1998

When dielectric surface electric field exceed any electric field strength on air, corona discharge is occurred from the dielectric surface. This paper presents corona discharge phenomena on the dielectric in high field were studied under application of ${\pm}DC$ voltage, constitute of the point to plane 20mm gap. The results obtained in experimental are summarized as follow :(1) Corona pulse is appeared periodically after first corona pulse is occurred and the number of corona pulse increases with the instantaneous applied voltage but peak value is not changed greatly.(2)Applied voltage to beccrite and characteristics and peak value of current are almost a straight line. That kind of tendency accorded with characteristics of beccrite resistance.(3)In case of Positive corona, Positive streamers, were progressed greatly to plane electrodes but In case of negative corona, negative streamers smaller than that of Positive corona.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.1
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• pp.1-12
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• 2001

Based on mixed-mode transient analyses utilizing a 2-dimensional device simulator, we have suggested the methodology to analyze the HBM ESD phenomena in CMOS chips utilizing NMOS transistors for ESD protection, and have analyzes the HBM discharge mechanisms in detail. Also the second breakdown characteristics in the protection device have been successfully simulated based on mixed-mode simulations, to explain the discharge mechanisms leading to device failure. To analyze the effects of the device structure changes on the discharge characteristics, we have compared the results of DC analyses and mixed-mode transient analyses, and have discussed about more robust designs of NMOS transistor structures against HBM ESD based on the analyses.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.94-100
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• 2002

As the use of automatic handling equipment for sensitive semiconductor devices is rapidly increased, manufacturers of electronic components and equipments need to be more alert to the problem of electrostatic discharges(ESD). In order to analyze damage characteristics of semiconductor device damaged by ESD, this study adopts a new charged-device model(CDM), field-induced charged model(FCDM) simulator that is suitable for rapid, routine testing of semiconductor devices and provides a fast and inexpensive test that faithfully represents ESD hazards in plants. High voltage applied to the device under test is raised by the field of non-contacting electrodes in the FCDM simulator, which avoids premature device stressing and permits a faster test cycle. Discharge current and time are measured and calculated. The characteristics of electrostatic attenuation of domestic semiconductor devices are investigated to evaluate the ESD phenomena in the semiconductors. Also, the field charging mechanism, the device thresholds and failure modes are investigated and analyzed. The damaged devices obtained in the simulator are analyzed and evaluated by SEM. The results obtained in this paper can be used to prevent semiconductor devices form ESD hazards and be a foundation of research area and industry relevant to ESD phenomena.

• The Journal of the Acoustical Society of Korea
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• v.21 no.7
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• pp.614-623
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• 2002

In this paper, it was manufactured an interferometric optical fiber sensor and measured partial discharge acoustic signal caused by defect of power facilities such as power cables, transformers and gas insulation. Acrylic and aluminium mandrels wound with fiber-optic were chosen as optical fiber sensor, Sagnac and Mach-Zehnder interferometers were chosen to detect discharge acoustic signals. The two fiber optic interferometers were identified by using the PZT. Discharge experimentation set in the discharge imitation cell in oil tank and the discharge phenomena was generated. Based on the experimental result, to detect the discharge acoustic signal, Sagnac interferometer can detect stably the acoustic signal than the Mach-Zehnder interferometer. It is shown that Sagnac optical fiber sensor can detect the discharge acoustic signals effectively.

• Fire Science and Engineering
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• v.18 no.4
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• pp.22-26
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• 2004

The static eliminator is used for prevention of disasters by static discharge, improvement of production efficiency, protection of a sensitive electronic element on the discharge of static, and it is handled for elimination of static in the painting plant, the film manufacturing plant, the producing semi-conductor factory. This study described on the explosion appearance by discharge phenomena on the voltage input type eliminator's ion generation bar of inflammable gas through an experimental tests. It was used Hydrogen, Ethylene, Propane, Methane gas with the inflammable gas and it was studied on the ignition phenomena by the length of ion-generation static bar, the number of ion-generation electrode and the variation of input voltage to the ion-generation electrode. As a result of this study it was confirmed that the shorter of the bar's length, the greater of explosion danger. And it is considered that there will not ignite at general using inflammable gas, in case of more than 900 mm bar and one electrode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.4
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• pp.43-50
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• 2001

In this paper, the discharge phenomena and electromagnetic waves caused by discharge with insertion of a solid insulator and flame between sphere-sphere electrodes in air ware investigated. The surface discharge light and patterns of flame generated on a solid insulator surface were observed by using a CCD(Charged Coupled Device) camera. Also, the radiated electromagnetic waves were measured by using a biconical antenna and a spectrum analyzer. The surface discharge light generated on the solid insulator surface was larger and the size of flame was smaller by increasing allied voltages. Also, voltage distortion by voltage drop was strongly revealed when a insulator surface was polluted. When a solid insulator surface was not polluted, the electric field stength of electromagnetic waves was 10∼17[dBuV/m] higher than a polluted solide insulator, and 5∼9[dBuV/m] higher than a polluted solide insulator and flame.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.99-105
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• 2003

The influence of discharge conditions, including the resistance of the sparking circuit, the shape of the electrodes and the width of the falling dust on the ignitability of lycopodium streams were investigated. Discharge characteristics and the ignition phenomena were also explored. When a 100 ㏀ resistor was connected in series with the sparking circuit, the lowest level of minimum ignition energy (MIE) was attained for lycopodium streams. Simultaneously, the area where flammable gas generated increased and the duration of flammable gas generation decreased. That is, the ignita-bility of lycopodium streams depended strongly on the discharge power and discharge duration. Electrodes with sharp tips gave smaller MIEs than those with round tips in a capacitive-inductive sparking circuit, while shape made no difference in a capacitive-resistive circuit. Streams that were too narrow required a considerable amount of energy for ignition.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2562-2564
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• 1999

We have development the electronic ballast for metal halide discharge (MHD) lamp. The ballast consists of the boost pre-converter for power factor correction (PFC), a flyback a converter, half-bridge inverter and ignitor. To reject acoustic resonance phenomena, we have designed electronic ballast driving with the low frequency square wave. As results of this study, the ballast had not flicker phenomena and promoted corrected the factor (PF) highly