• Journal of Hydrogen and New Energy
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• v.18 no.1
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• pp.85-94
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• 2007

Rice straw, produced as an agricultural by-product, is usable biomass as fuels if depolymerized to monomer unit, because the chemical structure are similar to high octane materials found in gasoline. In this study, parameters of thermochemical degradation by solvolysis reaction of rice straw such as the effect of reaction temperature, reaction time and type of solvent on conversion yield and degradation products were investigated. It was found that the effectiveness of the solvent on the solvolysis reaction was as follows; acetone>cresol>butanol. When acetone was used as a solvent, the highest rice straw conversion was observed to be 91.5% at $500^{\circ}C$, 40 min. Combustion heating value of liquid products from thermochemical conversion processes was in the range of 7,380 cal/g. The energy yield and mass yield in acetone-solvolysis of rice straw was as high as 69.0% and 38.2 g-oil/100g-raw material after 40 min of reaction at $350^{\circ}C$. Various aliphatic and aromatic compounds were detected in the rice straw solvolysis products. The major components of the solvolysis products, that could be used as fuel, were 4-methyl-2-pentanone, 3,5,5-trimethyl-2-cyclopentan-1-one as ketones.

• Journal of Hydrogen and New Energy
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• v.28 no.5
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• pp.512-520
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• 2017

This paper is a numerical study of various methods of applying SOFC hot BOP insulation. The application methods are four cases from case 1 to case 4, and the performance difference between the result of applying powdered insulation and the result of zoning using composite multi-layer insulation was examined. Numerical results show that the thermal stability of composite multi-layer insulation is better than that of powder insulation when the thermal conductivity is 0.04 W/mK. In the future, we will increase the thermal conductivity of the composite multi-layer thermal insulation material and find the greatest value of thermal conductivity with a similar result to that of the powder insulation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.61-65
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• 2003

Bottom ash among the coal ash is not used because of its poor properties. But encouraging the use of bottom ash as a construction material is a sensible method of utilization as it avoids the problems and costs associated with disposal and provides an alternative aggregate source. This study was aimed at using bottom ash as an alternative fine aggregate source to provide a solution to disposal and insufficient fine aggregate for the production of concrete. So properties of domestic bottom ash were estimated due to the difference of each domestic bottom ash. And compressive strength and durability were estimated as basic data to use bottom ash in building industries. As a result of the experiment, the very porous surface and angular shape of the bottom ash particles necessitate a higher apparent water-cement ratio. And due to the higher water requirement, the compressive strength and durability of mortar is lower than those of the control samples. But when 25 percent of the total dry weight of the natural fine aggregate was replaced by bottom ash, the engineering characteristics were similar.

• Journal of the Korean Home Economics Association
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• v.36 no.10
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• pp.119-130
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• 1998

This is on the dance costume of ancient Greece. The present study classified the characteristics of Greek dance and dance costume according to the silhouette, quality of material, color and ornaments. Materials of the study are the pictures and figures presented in literatures, sculptures, crockeries, murals, coins. The dances of Greece can be classified into religious dance, educational dance, recreational dance, dramatic dance and various forms of dance on each dances were developed. Especially, it is the greatest character that Greeks gave dances educational value and created composit art including song, lines and dance. As dance costume, Himation, Chiton, Chlamys which Greeks generally wore were widely worn. Also, the beauty of dance costume was maximized by the changes of basic costumes and development of various ways of wearing. Especially, professional dancers wore costumes shorter than knee-length ones forming a A-line silhouette different from a cylindrical one. Thin cloth revealing body silhouette such as fiax hemp, linen, silk were used as materials of dance costumes. As for colors, white was mainly used, But orange, blue and green were used, too. They wore band, scarf, bonnet on the head and seldom used any ornaments except for fibula. They wore the same sandals which Greeks wore, Crepis, front-heeled shoes which is thought to be the origin of modern ballet shoes for the technique of toe in dance. As mentioned above, as the dance costume of Greece were mainly worn as the similar forms of the dance costume of Greeks, various forms of costumes were worn with the development of dance and bold ways of wearing and silhouette were developed unlike the costume of common people.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11b
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• pp.155-180
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• 2000

The pattern of domestic slope construction has been steadily changed from the simpled and small-scale to the large-scale and complicated one, frequently near the existing structures, as the density of population and the traffic increases. In some cases, the slopes become steeper and larger due to the road improvement and construction. For the rock slope, the existence of discontinuity cannot be disregarded and acts as an important factor on the slope stability. Most of the existing methods for stabilizing the slope were focused on reducing the slope angle. Under the specific geographic condition, it is necessary to concentrate more efforts on the research and development of supporting system for the slope stability. As a supporting system, it is often very advantageous to use the FRP pipe grouting method that is similar to the existing soil nailing method or the rock bolting method but uses the high strength FRP pipe as a principal reinforcement in place of steel bar. Through the FRP pipe, the grout material can be injected into the rock mass to improve its shear strength to the required value. .In this study, the characteristics of FRP are investigated by the laboratory tests and the field tests. And, the practical aspects of FRP method are reviewed and analyzed.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.184-192
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• 2002

The purpose of this study was to investigate the abrasion resistance and surface roughness of conventional dental stones and improved dental stones and newly developed dental stones. Materials included in this study were several dental stones and newly developed dental stone; 2 type III. 6 type IV (including newly developed dental stone). 1 type V Ten specimens for each material, total ninety specimens were made. Each specimen was subjected to 50 complete cycle abrasion under constant load 0.42N at speed or 6mm per sec. The depth after abrasion test was measured for each specimen. Surface roughness before and after abrasion test was compared. The results were as follows ; 1. The resin containing die materials such as Tuff Rock and Resin Rock had superior abrasion resistance. 2. Type IV, V dental stone exhibited greater abrasion resistance than Type III dental stone. 3. The results or the surface roughness showed similar pattern with the abrasion resistance.

• Journal of Periodontal and Implant Science
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• v.27 no.1
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• pp.263-290
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• 1997

Homogenization technique is employed to investigate the series of stress analyses of mandible for three different types of dental implants. This technique helps to make proper material model of bone and analyze such a non homogeneous structure at the level of individual microstructural unit. The stress analyses with homogenization technique show much higher stress level in the sponge bone, compared to those of conventional FEM. It also manifested that even a minor lateral force results in crucial stresses in the dental implant system and that the macroscale model should take the shape and size after real mandible to produce reasonable solution in the analyses of dental implant systems. The shapes of dental implants simulated in this study are rectangular-cross-sectioned type, hemi-sphere rooted type, and wedge type implant. The stress states of mandible with hemisphere rooted type implant and wedge type implant show similar levels, while those with sectioned rectangular implant results in higher stresses. It is suggested that the distance between the implant tip and cortical bone be kept far enough to prevent stress concentrations in the mandible.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.257-259
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• 2004

We compare the results of the surveys of starless cores performed with CS (2-1) and (3-2) lines to study inward motions in the cores. The velocity shifts of the CS(3-2) and (2-1) lines with respect to $N_2H^+$ are found to correlate well with each other and to have similar number distributions, implying that, in many cores, systematic inward motions of gaseous material may occur over a range of density of at least a factor ${\~}$4. Fits of the CS spectra to a 2-layer radiative transfer model in ten infall candidates suggest that the median effective line-of-sight speed of the inward-moving gas is ${\~}0.07 km\;s^{-l}$ for CS (3-2) and ${\~} 0.04 km\;s^{-l}$ for CS(2-1). Considering that the optical depth obtained from the fits is usually smaller in CS(3-2) than in (2-1) line, this may indicate that CS(3-2) usually traces inner, denser gas with greater inward motions than CS(2-1) implying that many of the infall candidates have faster infall toward the center. However, this conclusion may not be representative of all starless core infall candidates, due to the statistically small number analyzed here. Further line observations will be useful to test this conclusion.

• Ceramist
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• v.22 no.4
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• pp.452-463
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• 2019

A quartz glass crucible is the essential material for manufacturing silicon ingots such as semiconductors and solar cells. Quartz glass crucibles for semiconductors and solar cells are made similar, but differ in surface purity, structure and durability. Recently, ultra high purity synthetic glass crucibles for semiconductors have become more important due to foreign problems. In Korea, it has succeeded in producing 28-inch quartz glass crucibles through the past 10 years. However, 32-inch synthetic quartz glass for the production of silicon ingots for semiconductors is not up to the level of advanced technology, and the technology gap is expected to be 2 to 3 years. In order to overcome these technological gaps and localize synthetic quartz glass ware, close cooperation between production companies and demand companies and localization of synthetic quartz glass powder must also be made. In addition, if government support can be added, faster results can be expected.

• Transactions on Electrical and Electronic Materials
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• v.3 no.4
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• pp.16-20
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• 2002

The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/㎠/mR and 295 pC/㎠/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.