• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.159-166
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• 1999

The physical properties and microstructural changes with heat-treatment of opacified silica aerogels doped by TiO2 were investigated. Monolithic SiO2-TiO2 aerogels were prepared by supercritical drying (25$0^{\circ}C$, 1250 psig) of wet gel obtained by adding titanium isopropoxide to prehydrolyzed TEOS-isopropanol solutions. The density and the porosity of SiO2-10 mol% TiO2 aerogels were 0.23 g/㎤ and 90%, respectively. During supercritical drying, the linear shrinkage of aerogels increased with increase in the titanium content an TiO2 was transformed to the anatase phase as well as particls agglomerates led to TiO2 clusters of 100~800 nm dispersed homogeneoulsy in the silica matrix. The IR transmittance of opacified silica aerogels was very low in the region of wavelengths below 8 ${\mu}{\textrm}{m}$ compared with pure silica aerogels and SiO2-TiO2 aerogels showed the high thermal stability of microstructures up to $600^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.553-559
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• 2003

PDP rib is one of the important parts of manufacturing process and the sintering degree of rib plays an important role to prevent some problems such as cross talk. Nowadays, the screen-printing method, which is a low price and high production, is used to make a rib. However, it is hard to judge and value the sintering ratio of sintered body itself. In this study, we measured the sintering degree by the dielectric breakdown of pores with the potentiostat. We conformed that this has similar tendency to density of sintered samples and an error being expected by open and closed pores was inspected by change of the microstructure to scanning electron microscope. This result showed that the sintering degree of PDP rib could be analyzed into the electro-chemical method.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.195-201
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• 1997

The present paper describes the effect of dry mixed grinding on kaolinite-aluminum trihydroxide mixture with a planetary ball mill before sintering and its influence on mullite formation during sintering. The size reduction of the mixture is market in the early stage of grinding and the obtained fine particles agglomerate subsequently with an increase of grinding time. The crystal structure of the mixture is collapsed easily into an amorphous one by planetary ball milling, of which amount increases with an increase of grinding time. Only mullite phase except for anatase as an inherent impurity in kaolinite appeared in the sintered body of the mixtures with mixed grinding as relatively lower temperature 1523K, while corundum, cristobalite, and Al-Si spinel phases, besides mullite were formed in the sintered body of the mixture without mixed grinding. Therefore, the mixed grinding treatment is very effective to improve the homogeneous mixing and disp-ersion of the mixture of raw materials on a micro scale and to decrease the thermal decomposition tem-perature by crystal structure change of them so as to obatin direct preparation of mullite with high purity at relatively low temperature.

• Journal of Korean Library and Information Science Society
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• v.48 no.1
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• pp.291-318
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• 2017

In this study, We found out that bibliotherapy program for university student has its strong point and effectiveness. The result of this study are follows: 1) bibliotherapy program is a safe method which covers the advantage of group psychotherapy and make up for the disadvantages. 2) significant changes in imitational behavior, cohesion and acceptance of reality suggest the necessity of bibliotherapy program that focuses on university career. 3) In light of the gloomy reality of young people, the fact that university students discuss love and hope for romance was meaningful phenomenon. It is necessary to study the after reading activities that can enhance the effectiveness of the bibliotherapy program and the specific topics and media that is needed by universities. The study is an approach that is widely available in university and will be the first step to establish the professional direction for bibliotherapy program.

• The Journal of Society for e-Business Studies
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• v.8 no.2
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• pp.77-98
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• 2003

A web-based information system, that is a dominant type of information systems, suffers from the "web crisis" in development and maintenance of the system. To cope with the problem, a technology of software clustering to web-based application, which is one of web engineering, is strongly needed. In this paper, we propose a Form Clustering Algorithm along with an application example, which are used for internal-system reengineering to web-based information system. A Form Clustering Algorithm focuses on Page-model which is the feature of the web among the various web-based information system's structural model. Specially, we applying distance matrix to navigation model of graph form for easily analyzing, and web log analysis for identifying core function object that have a highly loading. Also, we create web software structure that can be used to maximize reusability and assign hardware effectively through 2-phase clustering step. Form Clustering Algorithm might be used at web-based information system development and maintenance for reusable web component development and hardware assignment, respectively.

• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.103-111
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• 2018

Mineralogical properties of two Asian dust (Hwangsa) samples collected during dust events in April 6 and 15, 2018 were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analyses showed that Asian dusts were dominated by phyllosilicates (62 wt%) comprising illite-smectite series clay minerals (ISCMs) (55%), chlorite (3%) and kaolinite (4%). Nonphyllosilicate minerals were quartz (18%), plagioclase (9%), K-feldspar (3%), calcite (3%), and gypsum (2-4%). Mineral compositions determined by SEM chemical analyses were consistent with XRD data. ISCMs occur as submicron grains forming aggregate particles or coating coarse mineral grains such as quartz, plagioclase, K-feldspar, chlorite, and calcite. The ISCMs are often associated with calcite nanofibers and gypsum blades. Mineralogical properties of 2018 dusts were similar to those of previous dusts although clay contents were higher than that of coarse 2012 dust.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.168-172
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• 1999

We have studied the formation of Co/Ti bilayer silicide with low resistivity and good thermal stability on the heavily boron doped $\textrm{p}^{+}$-Si region. In this paper, Co/Ti bilayer silicides were fabricated by depositing Co($150\AA$)/Ti($50\AA$) films on the clean $\textrm{p}^{+}$-Si substrates in an E-beam evaporator and performing the two step RTA process (first annealing: 650$50^{\circ}C$/20sec, second annealing: $800^{\circ}C$/20sec) in a $N_2$ambient with the pressure of $\textrm{10}^{-1}$atm. Co/Ti bilayer silicides obtained from our experiments exhibited the low resistivity of about $18\mu\Omega$-cm and the uniform thickness of about $500\AA$ without change of sheet resistance and agglomeration under the long post0annealing time up to $1000^{\circ}C$.

• Parasites, Hosts and Diseases
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• v.36 no.2
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• pp.121-126
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• 1998

Hemagglutination-inhibition titers (log2) to Newcastle disease (ND) vims were chronologically observed in chicks, which were orally inoculated with 5 × 105 oocysts of Cwptospori,drum bcileyi at 2 days of age and subsequently vaccinated with inactivated ND virus at 4 and 21 days postinoculation. In general, the titers were considerably lower in the infected chicks than those in the uninfected control throughout the experimental period (p < 0.01), and rapid negative seroronversions were observed in the infected chicks. The titers reached a peak on weeks 2 and 4 post-booster-vaccination in the control and infected chicks, respectively. Thus, C. bciLeWi infection was shown to have an immunosuppressive effect on ND vaccination when the agent was given to 2-day-old chicks. It is suggested that C. bniLeWi infection in chicks may increase the host susceptibility to ND virus.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.685-691
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• 2009

Dispersions of fumed silica are made in 6 kinds of mono-solvents and mixed solvents which have hydroxyl group, non hydroxyl group, different polarity, and different molecular size. The viscosity and rheology behaviors of the each dispersion are investigated according to the viewpoint of solvent characteristic. The silica dispersion in polar solvent with hydroxyl group is stable and low viscous sol. The silica dispersion in non-polar solvent with non-hydroxyl group is high viscous gel. When the solvent with hydroxyl group is added to the silica dispersions with non-polar solvents, they show the reduction of viscosity with solvent content. They have minimum critical content which shows no viscosity change. The minimum critical solvent content is decreased according to the polarity of solvents with no hydroxyl group. The solvation layer which is formed on the silica surface through hydrogen bonding between hydroxyl-containing solvent and the silanol group of silica surface is the reason of stable and low viscous sol. In case of non-polar solvent, silanol on adjacent silica particles interacted directly by hydrogen bonding show high viscous and flocculated gel.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.487-493
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• 1993

The changes of cooked rice stored in an electric rice cooker at different temperature were investigated using sensory and mechanical methodology. The desirability of cooked rice was deteriorated during storage, particulary cooked rice stored at $80^{\circ}C$ had the lowest desirability. As the storage time increased, glossiness, clumpiness, adhesiveness, moistness and sweet flavor of cooked rice decreased but browning and off-flavor increased. The higher storage temperature resulted in the lower in glossiness, firmness, cohesiveness, moistness, sweet flavor and in the more browning, adhesiveness and off-flavor. L and b values measured by Hunter Color Difference Meter were highly correlated with the sensory glossiness and color.