• Proceedings of the Korean Society of Crop Science Conference
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• 2005.10b
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• pp.318-319
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• 2005

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.161-164
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• 2005

The flexural behavior of a strengthened beam, that is a reinforced. concrete beam with externally bonded fiber sheets, was theoretically and experimentally investigated. The effects of the amount of glass fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. The flexural rigidity of the strengthened beam was enhanced compared with RC beam. In addition, the failure mode and load-deflection relationship for the strengthened beam and the comparison of analysis with experiment are extensive investigated. Finally, the determination of the nominal moment capacity $M_n$ of the strengthened beam will be discussed

• Ceramist
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• v.22 no.4
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• pp.429-451
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• 2019

Quartz glass is a key material for making semiconductor process components because of its purity, low thermal expansion, high UV transmittance and relatively low cost. Domestic quartz glass has a market worth about 500 billion won in 2018, and the market power of Japanese materials is very high. Quartz glass for semiconductor process can be divided into general process and exposure. For general process, molten quartz glass is mainly used, but synthetic quartz glass with higher purity is preferred. Synthetic quartz glass is used as the photomask for the exposure process. Recently, as semiconductors started the sub-nm process, the transition from the transmission type using ArF ultraviolet (194 nm) to the reflection type using EUV ultraviolet (13.5 nm) began. Therefore, the characteristics required for the synthetic quartz glass substrates used so far are also rapidly changing. This article summarizes the current technical trends of quartz glass and recent technical issues. Lastly, the present situation and development possibility of quartz glass technology in Korea were diagnosed.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.114-119
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• 2007

Dielectric properties of quartz glass and $Si_3N_4$ are investigated using the waveguide method from room temperature to $800^{\circ}C$. For the case of dielectric constant, $Si_3N_4$ showed similar increase with quartz glass up to $300^{\circ}C$, but less increase from $300^{\circ}C$ to $800^{\circ}C$. For the case of loss tangent, those showed gradual increase with temperature except of some temperature points. The loss tangent of $Si_3N_4$ and quartz glass increased up to 18.2% and 12.5% respectively. Through these researches, high temperature dielectric properties of silicon nitride materials are characterized.

• Journal of Nutrition and Health
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• v.32 no.2
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• pp.189-196
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• 1999

This study was conducted to investigate the relationships among the levels of fasting serum insulin, free fatty acid, lipids and anthropometry in normal-weight female college students. Serum insulin and free fatty acid levels were negatively correlated. However, insulin, triglyceride, and cholesterol levels were not correlated with fat mass or BMI(body mass index). The ability of anthropometric and biochemical indicators to predict fatness could be important for epidemiologic and clinical research. In the subjects, waist cirumference was correlated with BMI, fat mass and percent body fat, and HDLC/CHOL (high density lipoprotein cholesterol/cholesterol)was correlated with body weight, BMI, and fat mass. Our data suggests than waist circumference and HDLC/CHOL are predictors of fatness, whereas WHR apears to be a less important contributor to fatness in female college students.

• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.73-82
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• 2015

This work demonstrates the indoor SI-traceable calibration of a transmissometer with a 75-m baseline for the measurement of visibility in MOR (Meteorological Optical Range). The calibration is performed using a set of neutral density (ND) filters (OD 0.1-2.5) and a set of high-transmission quartz glass plates (a bare quartz glass plate and antireflective-coated quartz glass plates), the collection consisting of 20 artifacts in total. The luminous transmittance values of the reference artifacts had been calibrated traceable to the KRISS spectral transmittance scale, which ranges from 0.2 % to 99.5 %. The transmissometer to be calibrated typically consists of a loosely collimated light source based on a white LED (CCT ~5000 K) and a luminous intensity detector with a CIE 1924 V(${\lambda}$) spectral response. As a result of calibration, we obtained the MOR error and its uncertainty for the transmissometer in 20 m - 40 km of MOR. Based on the results, we investigated the applicability of the calibration method and the conformity of the transmissometer to the ICAO's (International Civil Aviation Organization) accuracy requirement for meteorological visibility measurement. We expect that this work will establish the standard procedure for the SI-traceable calibration of a transmissometer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.128-135
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• 2022

The inside of a quartz glass crucible for semiconductor processing, called a transparent layer, is manufactured using synthetic silica powder. Bubbles existing in the transparent layer of the crucible cause a problem of reducing the quality of the crucible as well as the yield of the silicon ingot. Therefore, the main goal of the synthetic silica powder, which is the raw material of the transparent layer, is to minimize the bubble generation factor. For this purpose, in the case of synthetic silica powder, it is necessary to minimize silanol groups, carbon and pores. In this study, synthetic silica gel was prepared using the sol-gel method, and changes in carbon content and specific surface area were investigated according to calcination temperature and dwelled time in a two-stage calcination process. The first-stage calcination process was performed between 500℃ and 600℃ and the second-stage calcination process was performed between 1000℃ and 1100℃. The dwelled time was carried out from 10 minutes to a maximum of 12 hours. The carbon content of the powder calcined at 1000℃ for 1 hour was 0.0031 wt.%, and the specific surface area of the powder calcined at 1100℃ for 12 hours was 16.6 m²/g.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.147-163
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• 2015

Chemical and mineralogical properties of coal ash samples from the nine thermal power plants of Korea were investigated to acquire basic data for estimating the potential of rare metal recovery. Chemical compositions of coal ash were consistent with those of average shale and foreign coal ashes. However, there were small differences between the metal contents of domestic anthracitic and imported bituminous coal ashes. Unburned coal particles were much abundant in the ash of domestic anthracitic coal. Chalcophile elements were relatively enriched in the fly ash compared to bottom ash. Silicate glass was the major component of coal ash with minor minerals such as quartz, illite (muscovite), mullite, magnetite, lime, and anhydrite. Al and Si were the major components of the glass with varying contents of Ca, Fe, K, and Mg. Glass occurred in a form of porous sphere and irregular pumace-like grain often fused with iron oxide spheres or other glass grains. Iron oxide spheres were fine intergrowth of fast-grown iron oxide crystals in the matrix of silicate glass. Chemical, microstructural, and mineralogical properties would guide successful rare metal recovery from coal ash.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.123-129
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• 2016

This study is conducted to estimate the firing temperature and condition of the 4-6th Century earthenwares excavated from the ancient tombs in the Seonggok-ri, Cheongdo through mineralogical approaches, and to contrast to the characteristics of the earthenware from the Changnyeong the adjacent area to the Cheongdo. The Cheongdo earthenware was mainly composed of quartz, pores and vitric matrix with minor parts of feldspars, felsic volcanic fragments and opaque minerals, of which quartz crystals frequently show embayed texture and pores was partly filled with amorphous quartz. Mullite, hematite and cristobalite were found by XRD spectrometer additionally, and in the SEM image the Mullite contents are evenly distributed from the central part to the marginal part. As a result, the firing temperature of the Cheongdo earthenware could be 1,100 to $1,200^{\circ}C$, which is higher than that of the Changnyeong. Distribution characteristics of mullite in the Cheongdo and the Changnyeong earthenware indicate that the Cheongdo earthenware was under the longer firing time or more homogeneous thermal condition in the kiln than the Changnyeong.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.99-105
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• 2018

In order to avoid un-uniform crystallization on the surface of a quartz glass crucible that is known to affect the production yield of the single crystal silicon, Ba (barium) was selected as a crystallization promotor and the inner surface of the crucible was coated using Ba (barium hydroxide octahydrate)-solution by the spray pyrolysis method. For un-coated crucible, it was found that the crystallization of its surface started at $1350^{\circ}C$, and at $1450^{\circ}C$ the surface was uniformly crystallized with ${\beta}$-cristobalite phase. It was found that the crucible coated with Ba began to be crystallized from $1000^{\circ}C$ and was uniformly crystallized on the crucible surface at $1300^{\circ}C$. In this case, ${\alpha}$-cristobalite and needle-shaped $BaSi_2O_5$ phase were created and disappeared as a crystal phase, and the ${\beta}$-cristobalite phase was eventually evenly distributed over the Ba-coated crucible surface.