• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.212-216
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• 2004

In this paper, we have fabricated a triode field emitter using carbon nanotubes (CNTs) directly grown by thermal chemical vapor deposition(CVD) method as an electron omission source. Vertically aligned CNTs have been grown in the center of the gate hole, to the size of 1.5 ${\mu}{\textrm}{m}$ in diameter, with help of a sacrificial layer of a type generally used in metal tip process. By the method of tilling the substrate, we made CNTs emitters both with and without SiO$_2$layer, a sidewall protector, deposited on sidewall of gate. After that we researched the electrical characteristics about two types of emitters. In effect, a sidewall protector can enhance the electrical characteristics by suppressing the problem of short circuits between the gate and the CNTs. The leakage current of an emitter with a sidewall protector is approximately sevenfold lower than that of an emitter without it at a gate voltage of 100 V.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2868-2873
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• 2008

Carbon Monoxide(CO) poisoning accident is higher than any other gas accident in the rate of deaths/incidents. In the last five years, 36 people died and 104 were wounded because of carbon monoxide poisoning accident. Most of these CO poisoning accidents were caused by defective exhaust tube in the old gas boiler and multi-use facility. In this study, the spread of incomplete combustion gas(CO) released from leakage hole of exhaust tube was analyzed by computational flow modeling and concentration measuring test. CO gas leaked form exhaust tube in a building was highest concentrated near the ceiling and formed the circular currents along the walls. Through these experiments and simulation, the reasonable installation location of carbon monoxide alarm was made certain and suggested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.87-94
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• 1983

The successful oil storage in the underground cavern is dependent on how to keep the water-tightness around the cavern by the groundwater. If the water-tightness is not secured, gas bubles will leak out and oil migrate to the adjacent empty cavern. An electrical analogy method was employed in studying the influences of the position of horizontal and vertical water curtains, the head of water curtain and the intervals of the cavern spacings and boreholes on the gas leakage and the oil migration into the adjacent empty cavern. The result shows that if the cavern spacing is narrow, the vertical water curtain should be established and if the cavern spacing is more than twice the cavern height, its establishment is not necessary. All the detailed factors required to prevent the oil migration are shown on graphs.

• Journal of the Korean Institute of Gas
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• v.11 no.4
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• pp.47-53
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• 2007

The safe operation of high pressure pipe line systems is of significant importance. Leaks due to faulty operation from the pipelines can lead to considerable product losses and to exposure of community to dangerous gases. There are several leak detection methods, which have been recently suggested on pipeline network. The negative pressure wave detection technology, which has advantages of short time detection availability, accurate leaking location estimate capability and cost effective, is concentrated in this study. Theoretical analysis of the flow characteristics for leaking through a hole on the pipe wall has been performed by using CFD++, commercial CFD package. The results of 3-dimensional analysis near leaking hole confirm the occurrence of negative pressure wave and verify the characteristics of propagation of the wave which travels with speed equal to the speed of sound in the pipeline contents. For the application of long pipe line system. The method of 1-dimensional analysis has been suggested and verified with results of CFD++.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.800-805
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• 2017

The accelerated thermal ageing of CSPE (chlorosulfonated polyethylene) was carried out for 16.82, 50.45, and 84.09 days at $110^{\circ}C$, equivalent to 20, 60, and 100 years of ageing at $50^{\circ}C$ in nuclear power plants, respectively. As the accelerated thermally aged years increase, the insulation resistance and resistivity of the CSPE decrease, and the capacitance, relative permittivity and dissipation factor of those increase at the measured frequency, respectively. As the accelerated thermally aged years and the measured frequency increase, the phase degree of response voltage vs excitation voltage of the CSPE increase but the phase degree of response current vs excitation voltage decrease, respectively. As the accelerated thermally aged years increase, the apparent density, glass transition temperature and the melting temperature of the CSPE increase but the percent elongation and % crystallinity decrease, respectively. The differential temperatures of those are $0.013-0.037^{\circ}C$ and, $0.034-0.061^{\circ}C$ after the AC and DC voltages are applied to CSPE-0y and CSPE-20y, respectively; the differential temperatures of those are $0.011-0.038^{\circ}C$ and $0.002-0.028^{\circ}C$ after the AC and DC voltages are applied to CSPE-60y and CSPE-100y, respectively. The variations in temperature for the AC voltage are higher than those for the DC voltage when an AC voltage is applied to CSPE. It is found that the dielectric loss owing to the dissipation factor($tan{\delta}$) is related to the electric dipole conduction current. It is ascertained that the ionic (electron or hole) leakage current is increased by the partial separation of the branch chain of CSPE polymer as a result of thermal stress due to accelerated thermal ageing.

• Journal of the Korean Society of Safety
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• v.29 no.2
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• pp.24-30
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• 2014

There have been controversies over whether explosion hazardous area(EHA) should be classified for facilities which use lighter-than-air gases such as city gas, hydrogen and ammonia. Two view points are confronting each other: an economic piont of view that these gases are lighter than air and disperse rapidly, hence do not form EHA upon release into the atmosphere, and a safety point of view that they are also inflammable gases, hence can form EHA although the extent is limited compared to heavy gases. But various standards such as KS, IEC, API, NFPA do not exclude light gases when classifying EHA and present examples of EHA for light gas facilities. This study calculates EHA using the hypothetical volume in the IEC code where the hole sizes required for the calculation were selected according to various nominal pipe sizes in such a way to conform to the EHA data in the API code and HSL. Then, 25 leakage scenarios were suggested for 5 different pipe sizes and 5 operating pressures that cover typical operating conditions of light gas facilities. The EHA for the minimum leakage scenario(25 mm pipe, 0.01MPa pressure) was found to correspond to a hypothetical volume larger than 0.1 $m^3$(medium-level ventilation). This confirms the validity of classifying EHA for facilities using lighter-than-air gases. Finally, a computer program called HACPL was developed for easy use by light gas facilities that classifies EHA according to operating pressures and pipe sizes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1671-1680
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• 2014

There are always much concern about the leakage of radiation materials in the event of dismantle or unexpected accident of nuclear power plant. In order to remove the leakage of radiation materials, appropriate dispersion detection techniques for radiation materials are necessary. However, because direct handling of radiation materials is highly restricted and risky, developing radiation-related techniques needs computer simulation in advance to evaluate the feasibility. In this paper, we propose a radiation imaging technique which can acquire 3D dispersion information of radiation materials and tested by simulation. Using two virtual 1D radiation sensors, we obtain stereo radiation images and acquire the 3D depth to virtual radiation materials using stereo disparity. For point and plane type virtual radiation materials, the possibility of the acquisition of stereo radiation image and 3D information are simulated.

• The Journal of the Convergence on Culture Technology
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• v.8 no.2
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• pp.337-342
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• 2022

Although printing technology has recently been widely used in IT fields including displays and fuel cells, residual and thermal stress are generated by a manufacturing process of stacking the layers of the print head and result in the substrate deformation and nozzle plate crack, which may cause ink leaks or not be ejected onto a desired region. Therefore, in this paper, we propose a new design of thermal inkjet print head with a robust and reliable structure. Diverse types of inkjet print head such as a rib, pillar, support wall and individual feed hole are designed to reduce the deformation of the substrate and nozzle plate, and their feasibility is numerically investigated through FEA analysis. The numerical results show that the maximum stress and deformation of proposed print head dramatically drops to at least 40~50%, and it is confirmed that there is no nozzle plate cracks and ink leakage through the fabrication of pillar and support wall typed print head. Therefore, it is expected that the proposed head shape can be applied not only to ink ejection in the normal direction, but also to large-area printing technology.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.42-51
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• 2021

Facilities that supply specialty gases used in semiconductor manufacturing mainly handles with hazardous and dangerous substances with flammable, toxic, and corrosive properties, and gas cabinets are mainly used as such supply facilities. The effects of the supply facilities were analyzed for each leak through the rupture disk in the gas cabinet and a leak where the leak hole. In this case, gas leaked to the outside depending on the leak area. It is a factor that creates a risk depending on the concentration of the leaked gas. Depending on the risk of leakage, all measures such as safe operation procedures should be reviewed again.

• Journal of the Korean Geophysical Society
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• v.6 no.3
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• pp.165-177
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• 2003

The purpose of this paper is to analyze the behavior and to study the safety evaluation of the Unmun Dam located in Cheongdo-Gun of GyeongBuk Province, Korea. For this purpose, soil analyses including boring data, geophysical surveys were conducted. In this paper, especially many geophysical methods were adopted to configure out the subsurface situation of dam. Applied geophysical methods were: 1) electric resistivity survey, 2) high frequency magnetotelluric (HFMT) survey, 3) ground penetrating radar (GPR) survey, 4) seismic refraction survey, 5) seismic cross-hole tomography survey, and 6) high frequency impedance (ZHF) survey. Each of geophysical surveys were analyzed and joint analyses between geophysical surveys were also performed to deduce the more reliable subsurface information of Dam by using the features and characteristics of each geophysical survey. Since many defects, such as gravel and weathered rock blocks in the dam core, and lots of amounts of leakage, by boring analyses were found, reinforcement by compaction grouting system (CGS) has been conducted in some range of dam. Some geophysical data and data of geotechnical gauges were also used to confirm the effects of reinforcement. Electric resistivity, EM, GPR, ZHF, seismic refraction and seismic tomography surveys show that left side of dam is weak, which means the possibility of existence of gravel, rock block, water and cavities in the core of dam. This result coincides with the boring data. Especially, electric survey after reinforcement shows that even the right side of the dam has been deformed by the strong pressure during the reinforcement itself. As a conclusion, some problems in the dam found. Especially, the dam near spillway shows the high possibility of leakage. It should be pointed out that only the left side of he dam has not a leakage problem. As a whole, the dam has problems of weakness, because of unsatisfactory construction. It is strongly recommended that highly intensive monitoring is required.