• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.184-189
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• 1997

A prompt fission gas release model incorporating the resistance to gas flow in the gap was developed and the effects of gap resistance and failure location on prompt fission gas release from the cladding breach were assessed. The process of prompt fission gas release from the plenum and gap into the coolant was modeled in accordance with three major phenomena: (1) transient gas flow in the gap, (2) the growth of the fission gas bubble while it is still attached to the breach, and (3) the detachment of the fission gas bubble from the breach and mixing with the coolant. The cumulative mass release fraction by the present model was calculated for the case of Young-Gwang 3 & 4 nuclear fuel rod as a typical example. The results showed that the release behavior of prompt fission gas with time was different from the frictionless model which has frequently been used in a simplified approach, and that the location of cladding failure was another key factor for the prompt fission gas release process due to the resistance in the gap.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.3
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• pp.139-144
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• 2005

[ $SF_6$ ] gas circuit breakers are widely used short circuit current interruption in EHV or UHV power system. For a $SF_6$ gas circuit breaker development, the $SF_6$ gas velocity measurement is necessary during $SF_6$ circuit breaker's trip operation. Small-gap flashover characteristics are used for this measurement. So, small-gap measuring system which will be used to develope GCB should be developed. This study shows the characteristic analysis and experimental results of small-gap measuring system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.3
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• pp.155-158
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• 2006

$SF_6$ gas circuit breakers we widely used for short circuit current interruption in EHV or UHV power system. For a $SF_6$ gas circuit breaker development, the hot gas velocity measurement is necessary during $SF_6$ gas circuit breaker's trip operation. Small-gap flashover characteristics are used for this hot gas velocity measurement. This study sho was the hot gas velocity measurement results during $SF_6$ gas circuit breaker' trip operation.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2760-2770
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• 2020

A model for calculation of fuel temperature profile using binary gas mixture of Helium and Xenon for gap gas conductance is proposed here. In this model, the temperature profile of a fuel pencil from fuel centreline to fuel surface has been calculated by taking into account the dilution of Helium gas filled during fuel manufacturing due to accumulation of fission gas Xenon. In this model an explicit calculation of gap gas conductance of binary gas mixture of Helium and Xenon has been carried out. A computer code Fuel Characteristics Calculator (FCCAL) is developed for the model. The phenomena modelled by FCCAL takes into account heat conduction through the fuel pellet, heat transfer from pellet surface to the cladding through the gap gas and heat transfer from cladding to coolant. The binary noble gas mixture model used in FCCAL is an improvement over the parametric model of Lassmann and Pazdera. The results obtained from the code FCCAL is used for fuel temperature calculation in 3-D neutron diffusion solver for the coolant outlet temperature of the core at steady operation at full power. It is found that there is an improvement in calculation time without compromising accuracy with FCCAL.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.11
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• pp.796-805
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• 1987

The flashover voltages have been investigated for spacer and unbridged-gap in SF6-N2 gas mixtures up to the value of 760(torr. cm), The gap was stressed by DC source The results obtained are as follows` 1) The flashover voltages for an unbridged gap and for a spacer in SF6, N2 and SF6-N2 gas mixtures follow the Paschen's curve. 2) The polarity effects was not observed in both unbridged gap and a spacer which had per ect contact with an electrode. The flashover voltages for negative polatity are lower than those for positive polarity in case of imperfect contact. 3) 3%flashover voltage is decreased by putting a spacer which had perfect contact with an electrode. The spacer which has a gap void shows the lowest flashover voltage. 4) The lowest spacer efficiency was obtained with higher gas pressure & large amount of N2 content. The flashover voltages depend on the gas pressure rather than the spacer efficienty at low value of pd. 5) The flashover voltages of gas mixtures of N2 with SF6 are relatively high, even though the amount of SF6 gas content is small.

• International Journal of Clinical Preventive Dentistry
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• v.14 no.4
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• pp.247-255
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• 2018

Objective: Osseointegration is essential process for successful implants and effects to implant in long term, therefore, passive fitness of good prosthesis is necessary. To make a good prosthesis, at first it should be done a sectioned casting and then joined method of sectioned casting body is recommended. Methods: In this study, to provide the fundamental data on stable connection method for successful implants, the author tested fitness of casting body, and compared difference between gas soldering technique and laser welding technique. Results: In fitness test of 2 abutment (test A, C), gas soldering group's fitness in the opposite part of connection was worse than laser welding group. In fitness test of 3 abutment (test B, D), gap distance was increased both in gas soldering technique and laser welding technique. Gap distance at the connecting part and the opposite part of the abutment in gas soldering technique was worse than laser welding technique and the more additional abutment, the worse gap distance in gas soldering technique. In fitness test of 3 abutment (test B, D), there's little variation in No. 2 abutment when connecting soldering process was done and there's little influence on already soldered connection part when the additional soldering connection was done. Conclusion: On weak loading condition and the part which is needed an accuracy, laser welding technique is more effective and on long-span prosthesis and frequent chewing loading part, laser welding technique is recommended first and applying additional gas soldering technique would be better for making much more successful prosthesis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.10
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• pp.86-92
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• 2013

In studies on an alternative insulating gas of $SF_6$ gas, the section of the alternative gas and an insulation technique to improve its low dielectric strength have been reported, but very few attempts have been made at the dependence of a gas pressure and a gap as well as the medium effect in the alternative gas. The purpose of this paper is to analyze the dependence of the gas pressure and the gap at surface flashover voltage in dry air. The dependence is analyzed based on the medium effect. The medium effect by the gas pressure and the gap can be explained by surface roughness of a solid dielectric and an electrode as well as an electric field which decreases due to the correlation between the collision ionization coefficient and the gap, respectively. In addition, an insulation technique which can fabricate a compact eco-friendly gas insulated switchgear is proposed by the results of this paper.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1921-1923
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• 2004

V-p characteristics and the discharge luminous characteristics in inhomogeneous $SF_6$ gas gap under the positive and negative lightning impulse voltages are presented. The test gap was composed of the plane-to-plane with a needle-shaped protrusion. The applied voltage and the predischarge current were measured by the electric field sensor and the shunt of 50 ${\Omega}$, respectively. The light emission signals were observed by a photomultiplier tube, and a high-speed camera. In a consequence, the dielectric strengths of $SF_6$ gas gap under positive lightning impulse voltages were independent of the gas pressure. In the presence of the positive polarity, the branches of discharge channel were created and the directions of the discharge paths were random. On the other hands, the discharge paths of the negative polarity were more thicker and brighter.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.1-9
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• 2000

To understand the thermal characteristics around the piston ring gap ring gap positions and piston temperatures are measured simultaneously. The locations of piston ring gap are measured by the radio-tracer method and piston temperature are measured by a K-type thermocouple and scissors type linkage system. From these experiments following facts are clarified. Piston temperatures fluctuate according to the piston ring rotation. And the temperature fluctuation is mainly affected by top ring gap position irrelevant to the second ring fop position. If the top ring gap position increases and the temperature of top ring groove shows maximum value when top rin gap position coincide with temperature measuring point. The maximum amplitude of temperature fluctuation which is proportional to the blow by gas rate is around 12-15$^{\circ}C$.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.201-210
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• 2000

The noncontacting groove end face seal is one of various approaches to sealing gases with a single seal. Gas pumped into groove maintains operating gap and lubricates between primary ring and mating ring. So it removes heat and decreases face wear. In this paper, K-type and T-type grooved seals have been analyzed numerically using the finite element method. It explains the effects of groove shapes in gas seals along rotating speeds with a temperature gradient, face distortion, stress and so on. The calculated FEM results show the operating gap and rotating speed are strongly related to the leakages of a gas seal and that T-type groove seal shows a good thermal performance compared to K-type groove seal.