• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.95-96
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• 2022

Carbon nanotubes has a positive effect on the mechanical properties, functionality, and durability of cement-based materials. In this study, carbon nanotube solutions mixed with two different types of superplasticizers were dispersed by high-pressure homogenizer, and used for preparation of cement paste. The 7and 28day compressive strength were evaluated.

• Analytical Science and Technology
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• v.24 no.5
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• pp.401-405
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• 2011

The efficient removal of bromate ($BrO_3^-$) from aqueous solutions was investigated using activated alumina. Bromate is a disinfection by-product, generally formed by the reaction of ozone and bromide in drinking water during ozonation process. The removal efficiency was about 90% for bromate (500 ng/mL) ion with acidic activated alumina but over 95% with silver or aluminum treated acidic activated alumina without any treatments of neutral water within 1~2 min.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.10
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• pp.1475-1483
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• 2006

This study was carried out to examine the optimum processing conditions of seasoned semi-dried oyster, and to investigate its food component characteristics. Three types of semi-dried oyster were prepared: semi-dried oyster prepared without seasoning and coating (C), seasoned semi-dried oyster without coating (S) and seasoned semi-dried oyster coated with alginate (SA). SA was high in moisture (48.6%), while low in lipid (2.8%), and crude protein (25.9%) compared to those of C and S. Hardness and sensory scores of SA were $209.8g/cm^2$ and $3.9\sim4.5$ points, respectively. Total amino acid content (24,299 mg/100 g) of SA was lower than that (27,181 mg/100 g) of C, and the major amino acids were aspartic acid, glutamic acid, leucine and Lysine. The major fatty acids of SA were 16:0 (25.5%) as saturates and EPA (23.5%) and DHA (9.3%) as polyenes. Calcium and phosphorus contents of SA were 42.6 mg/100 g and 245.5 mg/100 g, respectively.

• Korean Journal of Food Science and Technology
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• v.11 no.3
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• pp.188-191
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• 1979

The heat decomposition rate of guanosine-5'-monophosphate was investigated in pH range from 5.52 to 7.00, and 0.1 of the ionic strength. The result showed that the rate was a first-order reaction and the rate of guanosine-5'-monophosphate loss was maximum near $pKa_2$. The loss of guanosine-5'-monophosphate was temperature dependent and followed to the Arrhenius equation in the temperature region from $93^{\circ}C$ to $108^{\circ}C$. The rate constant as function of temperature ($93^{\circ}C$ to $108^{\circ}C$) and neutral pH($pKa_2$, 6.0, to 7.0) was correlated by least-square fit of the experimental data; $$K=4.19{\times}10^{26}\;{\exp}\;[-1.3(pH+E/RT)]$$

• Resources Recycling
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• v.10 no.5
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• pp.16-21
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• 2001

Ultrafine $Mg(OH)l_2$and MgO powders were recovered from the waste solution containing $Mg^{++}$ which was a by-product of SHS (Self-propagating High temperature Synthesis)process. The optimum experimental conditions to prepare $Mg(OH)_2$were 13.0 of pH and 0.7M of $Mg^{++}$ content with addition of 9M of KOH as a pH regulator in acid leaching solution. Complete pre-cipitation of Mg(OH)$_2$from $Mg^{++}$ was realized at that condition. The dehydration reaction of the prepared Mg(OH)$_2$was studied by DSC, and the result was used for calcination process. In order to obtain MgO powder, dried Mg(OH)2 powder was calcined at $400~450^{\circ}C$. Particle size and shape of the prepared $Mg(OH)_2$and MgO powder was similar to those of the commercial powders.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.73-79
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• 1997

Removal of the Arsenic components from the closed mine tailings has been attempted by the alkali-leaching method. Two tailings collected from the Daduck and Yuchon mine which were already closed many years ago were leached with caustic soda solutions. The Arsenic components in the leach liquor resulted from the alkali treatment of tailings could be removed fairly well in the form of insoluble calcium-Arsenic compound by the precipitation with calcium chloride. As a result, the extraction of about 60~90% Arsenic from the tailings could be obtained depending on the leaching conditions and the influence of temperature and the slurry density on the extraction of Arsenic was also found to be very small at the NaOH concentration more than 0.5N. In addition, it seemed that a caustic soda solution over 0.5N NaOH could be used repeatedly for the leaching of tailings since the consumption of NaOH was not so great in a leaching of them. As far as the precipitation of Arsenic components was concerned, more than 99% of Arsenic could be precipitated within 10 minutes by the addition of 2wt% CaC12 in to the leach liquor.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.10
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• pp.1420-1426
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• 2006

To establish a rapid and effective method for the analysis of soy isoflavone which is known to have lots of variation in derivatives of glucoside, conversion rate from isoflavone conjugates to its aglycones, and decomposition of conversed aglycones were investigated with various acid hydrolysis conditions. A number of heating conditions for acid hydrolysis including heating at convection oven $(105^{\circ}C)$, water bath $(95^{\circ}C)$, heating block $(120^{\circ}C)$, and hot plate $(120^{\circ}C)$ were applied. Acid hydrolysis in heating block with reflux was chosen as the best heating condition. From the stability test of isoflavone aglycone during acid hydrolysis, genistein, daidzein, and glycitein did not show any significant changes in their contents for 60 min of hydrolysis. Ten to thirty milligram of sample per 1 mL HCl was the best ratio of sample to acid. As conclusion, acid hydrolysis for 60 min after addition of 15 mL HCl solution to 0.5 g soybean, and then fill up to 50 mL with methanol, followed by HPLC analysis was set as a final analysis method. From this method, isoflavone contents expressed as total aglycone of feed meal was the highest with content of $1288.5{\mu}g/g$ followed by those of dehulled meal.

• Analytical Science and Technology
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• v.10 no.2
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• pp.119-125
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• 1997

A stripping voltammetric procedure for determining ruthenium was developed, based on the adsorptive accumulation of ruthenium in the presence of hydrazine in acidic acetate buffer. After preconcentration of ruthenium compelex and reduction, the ruthenium-catalyzed hydrogen current at -0.84V was measured by differential pulse voltammetry. Optimal experimental conditions were found to be a stirred acetate buffer solution(pH 2.0) containing 0.01M acetate and 0.01M hydrazine, accumulation potential of -0.76V, and a scan rate of 5mV/s. The detection limit was $2{\times}10^{-9}M$ for a 7 min accumulation period. The possible interferences by other platinum group metals were also investigated.

• Economic and Environmental Geology
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• v.12 no.1
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• pp.41-49
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• 1979

A literature review is made on the physical and chemical characteristics of clay minerals in acidic solutions from the mineralogical and hydrometallurgical viewpoints. Some of the important characteristics of clays are their ability to cation exchange, swelling, and incongruent dissolution in acidic solutions. Various clay minerals can take up metallic ions from solution via cation exchange mechanism. Generally, cation exchange capacity increases in the following order : kaolinite, halloysite, illite, vermiculite, and montmorillonite. In acidic solutions, the cation uptake such as copper by clay minerals is strongly inhibited by hydrogen and aluminum ions and thus is not economically significant factor for recovery of metals such as uranium and copper. In acidic solutions, the cation uptake is substial. Swelling is minimal at lower pH, possibly due to lattice collapse. Swelling may be controllable with montmorillonite type clays by exchanging interlayer sodium with lithium and/or hydroxylated aluminum species. The effect of add on clay minerals are : 1. Division of aggregates into smaller plates with increase in surface area and porosity. 2. Clay-acid reactions occur in the following order: (i) $H^+$ replacement of interlayer cations, (ii) removal of octahedral cations, such as Al, Fe, and Mg, and (iii) removal of tetrahedral Al ions. Acid attack initiates, around the edges of the clay particles and continued inward, leaving hydrated silica gel residue around the edges. 3. Reaction rates of (ii) and (iii) are pseudo-1st order and proportional to acid concentration. Rate doubles for every temperature increment of $10^{\circ}C$. Implications in in-situ leaching of copper or uranium with acid are : 1. Over the life span of the operation for a year or more, clays attacked by acid will leave silica gel. If such gel covers the surface of valuable mineral surfaces being leached, recovery could be substantially delayed. 2. For a copper deposit containing 0.5% each of clay minerals and recoverable copper, the added cost due to clay-acid reaction is about 1.5c/lb of copper (or 0.93 lbs of $H_2SO_4/1b$ of copper). This acid consumption by clay may be a factor for economic evaluation of in-situ leaching of an oxide copper deposit.

• Polymer(Korea)
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• v.28 no.4
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• pp.291-297
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• 2004

Water-soluble chitosan micro spheres were prepared by emulsification of chitosan solution in mineral oil followed by cross linking reaction with different amount of the cross linking agent (glutraraldehyde), different chitosan concentration. Then, the physicochemical properties such as morphological change by degradation, drug loading efficiency, and drug release profiles were investigated with the drug loaded water-soluble chitosan microspheres. Norfloxacin loaded water-soluble chitosan micro spheres showed excellent drug entrapping capacities without burst release caused by surface bound drug. The absence of the surface bound drug also confirmed by X-ray diffraction study. Degradation and drug release studies showed that the amount of the crosslinking agent played a crucial role for drug loading, release and degradation. The water-soluble chitosan micro spheres showed more sustained drug release profiles with slower degradation and larger particle size by increasing crosslinking agent.