• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.597-600
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• 2001

In order to investigate the electrical properties of X-ray tube oils for insulating and cooling, the breakdown characteristics in temperature range of $20\sim100[^{\circ}C]$, that of AC breakdown in 0.5~2.5[mm] of gap length, we are made researches. The classification for the physical properties of oil for X-ray tube by FTIR and H-NMR experiments was confirmed to type of mineral oils. As for the dependance of breakdown characteristics due to electrode gap length, breakdown voltage was found nearly uniform by impurity effect according to the increase of gap. As a result the characteristics for AC breakdown, the dielectric strength was increased to $90[^{\circ}C]$ but decreased over $90[^{\circ}C]$ in the temperature range.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.138-140
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• 2005

Plasma arc welding(PAW) technology is a proven process that has already been adopted by other industrial fields and recently has been considered to join the tank structure of LNG carrier. The purpose of this study is to introduce PAW process for the root welding of stainless steel pipes instead of TIG welding. There are distinctive features of the PAW compared to TIG welding; higher energy density that can increase welding speed by more than twofold, and longer arc length that can be controlled to trace seam line easily because of allowable gap between workpiece and torch. However, PAW process is also very sensitive to the root gap and misalignment due to the characteristics of long and narrow arc shape. So, we have done various experiments to establish the allowable fit-up condition by changing welding parameters including arc length, with or without filler metal, groove shape, and obtained satisfactory result.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.484-485
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• 1987

The characteristics of leader development in rod -to- plane air gap (20cm gap length) under positive impulse potentials have been studied by means of 2-photomultiplier technique and image intensifier camera. It was shown that the streamers radiate relatively short wavelength light (${\sim}340nm$) while the leaders radiate a plenty of long wave length light ($400{\sim}800nm$). It was also known that the streamers propagate very fast with a velocity of $6{\times}l0^7cm/sec$ but the leaders have average velocity of $5{\times}10^6cm/sec$ and they proceed gradually fast by step-wise development.

• 전기의세계
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• v.25 no.1
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• pp.87-94
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• 1976

The characteristic of flashover electric discharge has been brought to light in this paper for the situation in which the space and creeping gaps are laid out in series. The result of this study has disclosed the facts that the over all flashover characteristics have three kind of features such as unilateral increase after increase, and increase after decrease in compliance with varied layout method and relative magnitude of gap length, and accordingly there exist a ratio among the magnitudes of gap length and a proper layort method through which the over all flashover voltage reaches the highest. Also involved with this study is the theoretic analysis of flashover characteristics even in the case of creeping electric discharge from hand tip of the gauge, where the over all value of flashover voltage can be estimated from the peculiar value of flashover voltage and flicker voltage for the space and creeping gap within the extent of 5% error.

• 전기의세계
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• v.21 no.4
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• pp.27-38
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• 1972

This paper discusses the characteristics about the ignition of D.C. main discharge is a plasma jet generator, manufactured for trial as non-transferred type, when the electrical energy appropriate to the ignition is supplied to the gap between the electrodes by using advance discharge of attenuating high frequency voltage generated by a high frequency oscillator with mercury spark gap. These characteristics are under the influences of (a) the length of mercury gap in high frequency oscillator and the quantity of hydrogen flow supplied to it, (b) the condenser capacity of the high frequency oscillator circuit, (c) the length of plasma jet torch in D.C. main discharge circuit and the quantity of argon flow supplied to it, (d) the circuit constants of D.C. main discharge circuit. The results for these characteristics, obtained by this research, are considered to be helpful to the designs for the ignition of a plasma jet as well as the welding arc stabilizer by high frequency discharge and the high frequency arc welder.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.597-600
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• 2001

In order to investigate the electrical properties of X-ray tube oils for insulating and cooling, the breakdown characteristics in temperature range of 20∼100[$^{\circ}C$], that of AC breakdown in 0.5∼2.5(mm) of gap length, we are made researches. The classification for the physical properties of oil for X-ray tube by FTIR and $^1$H-NMR experiments was confirmed to type of mineral oils. As for the dependance of breakdown characteristics due to electrode gap length, breakdown voltage was found nearly uniform by impurity effect according to the increase of gap. As a result the characteristics for AC breakdown, the dielectric strength was increased to 90[$^{\circ}C$] but decreased over 90[$^{\circ}C$] in the temperature range.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.513-523
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• 2016

The stress concentration factors and stress intensity factors for a simple beam and a cantilever are analyzed by using finite element method and phtoelasticity. Using the analyzed results, the estimated graphs on stress concentration factors and stress intensity factors are obtained. To analyze stress concentration factors of notch, the dimensionless notch length H(height of specimen)/h=1.1~2 and dimensionless gap space r(radius at the notch tip)/h=0.1~0.5 are used. where h=H-c and c is the notch length. As the notch gap length increases and the gap decreases, the stress concentration factors increase. Stress concentration factors of a simple beam are greater than those of a cantilever beam. However, actually, the maximum stress values under a load, a notch length and a gap occur more greatly in the cantilever beam than in the simple beam. To analyze stress intensity factors, the normalized crack length a(crack length)/H=0.2~0.5 is used. As the length of the crack increases, the normalized stress intensity factors increase. The stress intensity factors under a constant load and a crack length occur more greatly in the cantilever beam than in the simple beam.

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.204-217
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• 2016

Modified poplar has emerged as a potential raw material for furniture production. Lack of specific modified poplar strength information; however, restricts applications in the furniture industry especially as related to strength in corner-joints. Optimization of strength in L-shaped corner dowel modified poplar joints under compression loads utilizing finite element analysis (FEA) by Taguchi method with the focus of this study. Four experiment factors (i.e., Structure Style, Tenon Length, Tenon Diameter, and Tenon Gap), each at three levels, were conducted by adopting a $L_9-3^4$ Taguchi orthodoxy array (OA) to determine the optimal combination of factors and levels for the von Mises stress utilizing ANSYS software. Results of Signal-to-Noise ratio (S/N) analysis and the analysis of variance (ANOVA) revealed the optimal L-shaped corner dowel joint in modified poplar is $45^{\circ}$ Bevel Butt in structure style, 24 mm in tenon length, 6 mm in tenon diameter, and 20 mm in tenon gap. Tenon length and tenon gap are determined to be significant design factors for affecting von Mises Stress. Confirmation tests with optimal levels and experimental test indicated the predicted optimal condition is comparable to the actual experimental optimal condition.

• Journal of radiological science and technology
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• v.9 no.1
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• pp.73-81
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• 1986

This paper carried out an experiment on the characteristics of time, temperature, electric field and the dependense of electrode materials and gap length by the conduction current of the insulating oil used for x-ray tube housing. The obtained results can be summarized as following: 1. In the x-ray tube housing insulating oil with vacuum condition, conduction current is declined more than the x-ray tube housing insultaing oil with the air, and is held stable states. 2. At the low electric field the higher temperature of the x-ray tube housing insulating oil is increased, the more conduction current. 3. The dependence of electrode material is appeared at the low electric field and the short gap length than the high and the long with Fe> Cu >Al. 4. At the I-E characteristics, the low electric field than 1000 [V/cm] is appeared Ohm's law region, and the high become saturation region. 5. At the same electric field, the longer gap length become, the more conduction current is increased, and the same applied voltage, the longer, the less conduction current is decreased, the less low than high temperature x-ray tube housing insulating oil.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.103-106
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• 2000

The electronic properties of carbon nanotube are currently the focus of considerable interest. In this paper, the electronic properties of finite length effect in carbon nanotube for cabon nanoscale device is presented. To calculate the electronic properties of carbon nanotube, Empirical potential method (Brenner' hydrocarbon potential) for carbon and Tight binding molecular dynamic (TBMD) simulation are used. As a result of study, we have known that the value of the band gap decreases with increasing the length of the tube. The energy band gap of (6, 6) armchair carbon nanotube have the ranges between 0.3 eV and 2.5 eV. Also, our results were compared with the results of the other computational techniques. As that result, our results are very well united.