• Journal of Hydrogen and New Energy
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• v.22 no.2
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• pp.178-183
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• 2011

Metal hydride alloys are a promising type of material in hydrogen storage applications, allowing for low-pressure, high-density storage. However, while many studies are being performed on enhancing the hydrogen storage properties of such alloys, there has been little research on large-scale storage vessels which make use of the alloys. In particular, large-scale, high-density storage devices must make allowances for the inevitable generation or absorption of heat during use, which may negatively impact functioning properties of the alloys. In this study, we develop a numerical model of the discharge properties of a high-density MH hydrogen storage device. Discharge behavior for a pilot system is observed in terms of temperature and hydrogen flow rates. These results are then used to build a numerical model and verify its calculated predictions. The proposed model may be applied to scaled-up applications of the device, as well as for analyses to enhance future device designs.

• Journal of Drive and Control
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• v.16 no.4
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• pp.93-100
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• 2019

Nuclear and thermal power plants must provide the turbines with an appropriate degree of high temperature and high pressure steam, to produce the optimum electricity. Additionally, in the event of system and power system failure during electrical production, the steam is immediately disabled, to protect the turbines and generators rotating at high speed. The plant thus uses a special steam control valve system for turbine control, which is opened by force of the hydraulic servo actuator and closed by a large steel spring force. In this study, the causes of failure of the turbine control valve system, a key device of the power plants, were analyzed, and the causes of failure were improved relative to reliability of the equipment.

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.55-56
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• 2002

Aflatoxin is a secondary fungal metabolite and is a public health hazard because it is a human carcinogenic and has many deleterious effects in men and animals. Rice is one of the better substrates for the fungus which can produce aflatoxins. This study was performed to investigate aflatoxin reduction during the cooking and processing of rice. Aflatoxin was produced by Aspergillus parasiticus ATCC 15517 on well-milled rice(Japonica type) at the level of 13.2 ppb. Cooked rice, rice cakes (baek-sol-gi, plain steamed rice bread), fermented rice (sik-hye, sweet rice beverage), and popped rice were prepared from the aflatoxin-contaminated rice. Aflatoxin content in the samples was determined by high performance liquid chromatography. The total aflatoxin level was decreased to 46.9％ in the cooked rice, 85.6％ in the rice cakes, 11.4％ in the fermented rice, and 7.6％ in the popped rice, respectively (p＜0.05). This reduction brought the level of aflatoxins down to below the Standard and Specification of Korea (10 ppb), except for the rice cakes. These results indicate that washing, steaming, fermentation, and popping of rice was helpful in reducing the aflatoxin level in the rice and the most helpful factors were high temperature & high pressure. More research is needed to understand why the preparation of rice cakes did not reduce the level of aflatoxin as much as the other cooking methods.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.78-85
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• 2004

The particle amount monitoring technique using ultrasound is proposed to determine the proper maintenance time of the filter in the supply process of pure gas in the unit of oxygen plant. There are advantages that it is adaptable in high temperature and high pressure, and it is not disturbed by being exposed in the gas flow, and it can be implemented very economically. The applicability of the ultrasonic technique is pre-studied through the theoretical analysis for the dependency of attenuation of ultrasonic wave on the particles in the gas flow. For the purpose, absorption, scattering and dispersion models are considered, and the attenuation by absorption and the change rate of the propagation speed are calculated fur the specific range of particle size and the ultrasonic wave frequency. It was expected by simulation that the absorptive attenuation by particles was the most sensitive to the change of particle amount. The experimental result showed high correspondence with the theoretical expectation so that this ultrasound attenuation measurement was proved to be highly effective for monitoring the amount of floating particles in the gas flow.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.69-77
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• 2016

We propose nano-scale Cu direct bonding technology using ultra-high density Cu nano-pillar (CNP) with for high stacking yield exascale 2.5D/3D integration. We clarified the joining mechanism of nano-scale Cu direct bonding using CNP. Nano-scale Cu pillar easily bond with Cu electrode by re-crystallization of CNP due to the solid phase diffusion and by morphology change of CNP to minimize interfacial energy at relatively lower temperature and pressure compared to conventional micro-scale Cu direct bonding. We confirmed for the first time that 4.3 million electrodes per die are successfully connected in series with the joining yield of 100%. The joining resistance of CNP bundle with $80{\mu}m$ height is around 30 m for each pair of $10{\mu}m$ dia. electrode. Capacitance value of CNP bundle with $3{\mu}m$ length and $80{\mu}m$ height is around 0.6fF. Eye-diagram pattern shows no degradation even at 10Gbps data rate after the lamination of anisotropic conductive film.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.212-221
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• 2001

This paper introduces the characteristics and generation of the synchrotron radiation (SR). SR has the very high spectral brilliance, broad spectral range, X-ray wavelength tunability, high degree of polarization and collimation, and pulsed time structure. Also describes the technologies to apply in the fields of geology and environmental sciences. These include X-ray tomography, XRF, EXAFS, XANES, DAC, IVP experiments. Further, nuclear power generation and nuclear waste disposal methods are mentioned relating to energy. Using these, analyses of the chemistry, crystal structure and chemical combining states of minerals and rocks can be carried out. Applications in the fields of the economic geology, paleontology and environmental sciences are open too. Informations of the Earth interior materials' behavior under high pressure-temperature can be acquired.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.6-11
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• 2004

The characteristics of interface layer and the effect of bias voltages on the nucleation density and heteroepitaxial growth of diamond films were studied in the hot filament CVD diamond process. Diamond films were deposited on a high speed steel (SKH-51) substrate by bias-assisted hot filament CVD technique with a titanium interlayer. The bias applied for enhancing the emission of electrons from the filament increased the nucleation density and achieving heteroepitaxial growth of CVD diamond. Diamond films obtained at a gas pressure of 20 torr; a bias voltage of 200 V and a substrate temperature of $700^{\circ}C$. Titanium was a suitable element as an interlayer for the diamond deposition on steel because it has high diffusivity of Fe and C as a carbide forming element.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.595-599
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• 2011

ALC(Autoclaved Lightweight Concrete) is produced using quartz sand, lime and cement and water. And aluminum powder is used for blowing agent. ALC is manufactured by autoclave chamber under high-temperature and high-pressure. Generally, ALC is 1/4 levels lighter than concrete and mortar, because it has a lot of pores. So density of ALC is about 0.45~0.65 g/$cm^3$. But, ALC has a weakness, typically low strength, with its porous structure. So, it is necessary to excellent strength properties for extensive apply of ALC materials in high porosity. In this study, melamine resin was used to improve the strength characteristics of ALC materials. We performed compressive and bending strength measurements. Compressive strength of ALC with 2% melamine resin increased 26.88% than 'melamine-free' ALC. Also we performed functionality evaluation such as thermal conductivity, sound absorption, and flame-resistance.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.326-328
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• 1995

SiC buffer layers were grown on Si(100) substrates by ultra-high-vacuum electron cryclotron resonance plasma (UHV ECR plasma) from $CH_4/H_2$ mixture at 700$^{\circ}C$. The electron densities and temperature were measured by single probe. The axial plasma potentials measured by emissive probe had the double layer structure at positive substrate bias. Piranha cleaning was carried out as ex-situ wet cleaning. Clean and smooth silicon surface were prepared by in-situ hydrogen plasma cleaning at 540$^{\circ}C$. A short exposure to hydrogen plasma transforms the Si surface from 1$\times$1 to 2$\times$1 reconstruction. It was monitored by reflection high energy electron diffraction (RHEED). The defect densities were analysed by the dilute Schimmel etching. The results showed that the substrate bias is important factor in hydrogen plasma cleaning. The low base pressure ($5\times10^{-10}$ torr) restrains the $SiO_2$ growth on silicon surface. The grown layers showed different characteristics at various substrate bias. RHEED and K-ray Photoelectron spectroscopy study showed that grown layer was SiC.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1245-1251
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• 2009

This paper describes the research on the non-eroding throat insert materials under condition of high-temperature, high-pressure, and long-burn time. C/SiC, CIT and W/$Y_2O_3$ were chosen and tested in thermal protection evaluation motor of burning time 20 seconds. From the test results, a heat resistance of W/$Y_2O_3$ was the most excellent among them, but was happened crack on material surface. Thermal reaction characteristics and heat resistance of these materials and feasibility of W/$Y_2O_3$ as throat material were ascertained.