• Journal of Life Science
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• v.10 no.3
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• pp.229-235
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• 2000

The absorption characteristics of Korean yam powder according to different drying methods were investigated. The physical properties of yam powder by different drying methods were showed the biggest porosity in freeze drying sample, while the smallest in hot air drying sample. No difference was founded in proximate compositions of yam powder by various drying methods. The amount of total phenolic compound and Vit C were showed the bigger decrement in freeze dried sample than other drying methods. The time reaching to equilibrium moisture content were determined in 12 days. Monolayer moisture contents were predicted to 0.0508∼0.0588 by BET equation and 0.0705∼0.0811 g H2O/g solid by GAB equation. BET equation for isothermal absorption curve showed over 0.95 R-square for every drying methods. GAB equation showed over 0.99 in vacuum and freeze drying but a poor R-square in hot air drying.

• Clean Technology
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• v.8 no.2
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• pp.61-66
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• 2002

Recycling method of red mud, byproduct from the aluminium manufacturing process, and paper sludge was investigated in order for them to be utilized as the adsorbent for the removal of volatile organic components(VOCs). Either high density polyethylene(HDPE) or low density polyethylene(LDPE) was added to facilitate the manufacture of adsorbents. The utilization of HDPE in the adsorbents increased the adsorption capacity due to the good physical properties, such as, BET and true density, compared with LDPE. BET values of the manufactured adsorbents were much lower than the commercial activated carbon ($10^{-2}-10^{-3}$). It may be due to the fact that the time for decomposition of the paper sludge was not enough during the manufacturing of adsorbents. But the specific adsorption capacity of the manufactured adsorbents (mole adsorbed per unit surface area) had much higher value than the commercial activated carbon (10-100). Therefore, it is important that BET of manufactured adsorbents needs to be increased to obtain the same adsorption capacity as the commercial activated carbon.

• Nuclear Engineering and Technology
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• v.46 no.1
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• pp.117-124
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• 2014

The effect of various process variables on the powder properties of recycled $U_3O_8$ from MnO-$Al_2O_3$ doped large grain $UO_2$ pellets and the effect of those recycled $U_3O_8$ powders on the sintered density and grain size of MnO-$Al_2O_3$ doped large grain $UO_2$ pellets have been investigated. The evolution of morphology, size, and BET surface area of the recycled $U_3O_8$ powders according to the respective variation of the thermo-mechanical treatment variables of oxidation temperature, powder milling, and sequential cyclic heat treatment of oxidation and then reduction was examined. The correlation between the BET surface area of recycled $U_3O_8$ powder and the sintered pellet properties of MnO-$Al_2O_3$ doped pellets showed that the pellet density and grain size of doped pellets were increased and then saturated by increasing the BET surface area of the recycled $U_3O_8$ powder. The density and grain size of the pellets were maximized when the BET surface area of the recycled $U_3O_8$ powder was in the vicinity of $3m^2/g$. Among the process variables applied in this study, the cyclic heat treatment followed by low temperature oxidation was a potential process combination to obtain the sinter-active $U_3O_8$ powder.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.199-206
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• 2006

Direct decomposition of methane over three types of carbon black (N330-p, N330-f, and HI-900L) was carried out in a fluidized bed quartz reactor. Properties of carbon black before and after reaction were measured and found to be related with surface structure and weight gain. For N330-p and N330-f, some carbon deposit on the surface was considered to be the reason for the increase of BET surface area and pore volume with weight gain. Carbon deposits on the surface and the conglutination of some aggregates may explain the slight increase of particle size. Properties of HI-900L changed much more significantly with weight gain. It is supposed that the increase of aggregate size of HI-900L were due to some unknown oily components. The corresponding agglomeration might be the reason for the decrease of BET surface area with weight gain, as compared with the increase of that for the case of N330 black.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.240-242
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• 2007

The goal of this paper is to investigate effects of three prosodic factors, such as phrasal accent (accented vs. unaccented), prosodic boundary (IP-initial vs. IP-medial) and coda voicing (e.g., bed vs. bet), on acoustic realization of English vowels (/i, $_I/$, $/{\varepsilon}$, ${\ae}/$) as produced by native (Canadian) and nonnative (Korean) speakers. The speech corpus included 16 minimal pairs (e.g., bet-bat, bet-bed) embedded in a sentence. Results show that phonological contrast between vowels are maximized when they were accented, though the contrast maximization pattern was not the same between the English and Korean speakers. However, domain-initial position do not affect the phonetic manifestation of vowels. Results also show that phonological contrast due to coda voicing is maximized only when the vowels are accented. These results propose that the phonetic realization of vowels is affected by phrasal accent only, and not by the location within prosodic position.

• Journal of the Korean Applied Science and Technology
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• v.16 no.1
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• pp.59-65
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• 1999

For a cosmetic plant wastewater containing surfactants of high concentration, adsorption treatment by granular activated carbon(GAC) having different pore size distribution was studied. Three sorts GACs were used and regenerated afterwards with methanol. Experiments were composed of batch process and column test for both virgin and regenerated GACs. Following conclusions were drawn from the study: Methylene blue activating substance(MBAS) adsorption data from the batch tests for three GACs are described well by BET isotherm and Freundich isotherm. Simulation with the BET isotherm shows that maximum adsorption appears to be affected not only by specific surface area but also by pore size distribution. Maximum adsorption from the BET isotherm for MBAS appears to diminish as the number of reactivation increases. The diminishing ratio of maximum adsorption appears to decrease as the pore size decreases. Recovery ratio of the methanol by vacuum evaporation from the spent methanol ranges from 95% to 97%.

• Journal of the Korean Chemical Society
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• v.37 no.4
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• pp.416-422
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• 1993

As a result of adsorbing phthalocyanine (metal free, ${\alpha}\;and\;{\beta}$-Cu) on zinc oxide in aqueous solution using nonionic surfactant, all of the added dye was adsorbed and Na salt of sulfonated phthalocyanine showed the Langmuir monolayer adsorption. To analyze the effect of adsorption on zinc oxide, photovoltage was measured using surface photovoltmeter. The high photovoltaic effect was observed at intrinsic wavelength of zinc oxide and wavelength of adsorbed phthalocyanine dye. Metal free phthalocyanine, ${\alpha}$-copper phthalocyanine and ${\beta}$-copper phthalocyanine showed the highest photovoltaic effect when the percentage of coverage (${\theta}_{BET}$) for zinc oxide is about 80, while sulfonated phthalocyanine showed the highest photovoltaic effect when the percentage of coverage for zinc oxide is about 30.

• Polymer(Korea)
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• v.35 no.1
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• pp.66-71
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• 2011

With the synthesis of hyper crosslinked polymer particle (HCPP), having microporous structure with hydroxyl functional group, synthesized via polymerization reaction consists of three stepssuspension polymerization, hyper crosslinking by Friedel-Craft catalysis and hydrolysis reaction, the effects of the ratio of each monomer, hyper crosslinking conditions and $CO_2$ supercritical drying on the variations of surface morphology, pore size & distribution and BET surface area of HCPP have been investigated. It was observed that the formation of surface crack or fracture of HCPP was intimately related with the degree of hyper crosslinking reaction between microphase separated domains. And the value of BET surface area of HCPP increased with the increase of reaction temperature, time and the amounts of solvent used in hyper crosslinking step. Moreover, $CO_2$ supercritical drying was proven to be a very effective method for removing stabilizer, unreacted monomers and oligomers from HCPP but needed to add methanol as a co-solvent for efficient removing of residual catalyst.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.358-361
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• 2007

Well-ordered mesoporous SiCBN ceramics have been successfully synthesized by infiltrating a polymeric precursor, which was prepared from borazine and 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane via a hydroboration reaction, into a mesoporous carbon (CMK-3) as a hard template. This was followed by pyrolysis at $1400^{\circ}C$ under nitrogen gas and subsequent oxidative removal of the carbon template without chemical etching. The prepared mesoporous SiCBN ceramic was characterized by a small-angle XRD, TEM, and BET surface area. The resulting mesoporous SiCBN ceramic revealed a BET surface area of $275 m^2g^{-1}$ and a pore volume of $0.8 cm^3 g$ with no crystallization.

• Elastomers and Composites
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• v.55 no.4
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• pp.277-280
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• 2020

In this study, mesoporous hollow silica spheres were synthesized using a polystyrene core and cetyltriammonium chloride (CTACl) as a pore template, and a low-cost water glass instead of expensive tetraethyl orthosilicate (TEOS) as a precursor. In addition, the material was synthesized by varying the concentration of polystyrene. Later, the polystyrene core and CTACl were removed by firing in a high-temperature heat-treatment process. The synthesized product was analyzed by various methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and N2-sorption analysis. It was confirmed that the hollow silica sphere had a hexagonal structure with a Brunauer-Emmett-Teller (BET) specific area of 1623 ㎡/g.