• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.299-308
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• 2016

This paper presents an investigation of the mechanical and microstructural properties on hardened samples that were synthesized using blended binder(fly ash(FA) and blast furnace slag cement(BFSC)), alkali activator and sea water or distilled water. Binders were prepared by mixing the FA and BFSC in different blend weight ratios of 6:4, 7:3 and 8:2. Sodium hydroxide and sodium silicate were used 5 wt% of binder, respectively, as an alkaline activator. The compressive strength and absorption were measured at the age of 3, 7 and 28 days, and the XRD, TGA and MIP tests were performed at the age of 28 days. An increase in the content of BFSC leads to an increase in the quantities of ettringite and C-S-H formed, regardless of the type of mixing water. And it also shows higher strength due to the reduction of pores larger than ~50 nm. All hardened samples in this study have common hydration products of C-S-H, $Ca(OH)_2$ and calcite. Hydrocalumite of all reaction products formed was only present in hardened sample mixed with sea water. For each FA/BFSC mixing ratio, the compressive strength of hardened sample mixed with sea water was similar to that mixed with distilled water. It is proposed that the slight increase of strength of samples mixed with sea water is mainly due to the presence of hydrocalumite phase containing chlorine ion, contributing to the change of total porosity and pore size distribution in samples.

• Applied Biological Chemistry
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• v.12
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• pp.75-81
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• 1969

In order to obtain a method of scouring of raw silk and degumming of cocoon by the appling of bacterial enzyme of sericinase, a strain of proper bacteria was isolated and some properties of the enzyme produced by the isolated bacteria were studied and the following results were obtained. 1) Optimum pH and temperature were indicating 7.5 and $50^{\circ}C$. and on these conditions, the silk fibroin will get no modification at all. 2) Sericinase activity was inhibited by calcium ion in the free incubation but same ions reacted as an activator in the reaction with substrate. So, degumming of Tussah cocoon which contains calcium oxalate in the cocoon layer will be possible by the treatment of this enzyme. 3) This bacterial sericinase never gives any affection to the fibroin layer of the silk. 4) The factors of smooth-surface condition, damage of fibroin layer, touching, luster and degumming effect of the silk resulting by the enzyme treatment were more appropriate than the results of other scouring methods, saponin, alkali and saponin-alkali using methods. We expect to get the same scouring result that compared with the papain or pancreatin were applied.

• Journal of the Korean Society of Radiology
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• v.7 no.1
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• pp.85-91
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• 2013

The selective transport characteristics of $K^+$ and $Na^+$ of cell membrane model which irradiated by 60Co ${\gamma}$-ray was investigated. The cell membrane model used in this experiment was a Na+ type sulfonated copolymerized membrane of styrene and divinylbenezene. The initial flux of the ion was increased with increase of both $H^+$ ion concentration. In this experiment range(pH 0.5-3, temperature $15-65^{\circ}C$), first, the selectivity of $K^+$ and the ratio K+/Na+ of membrane which was not irradiated was about 1.06 - 1.13 and second, that of K+ and the ratio $K^+/Na^+$ of membrane which was irradiated was near about 0. And the driving force of pH of irradiated membrane was significantly increased about 4-5 times than membrane which was not irradiated. As selective transport of K+ and Na+ of cell membrane model were abnormal, cell damages were appeared at cell.

• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.531-538
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• 1998

The ion selective membrane electrode made of calix[4]arene-based host 1 as ionophore, poly (vinyl chloride) (PVC) as matrix and dioctylsebacate (DOS) as a plasticizer was studied. The potential responses of this membrane electrode to alkali, alkaline earth and transition metal cations were investigated. Especially this membrane electrode was turned out to be affinitive for $Pb^{2+}$ in the deionized water. It was observed that the response was linear in the concentration range from $1.0 \times 10^{-1} M to 1.0 \times 10^{-6} M of Pb^{2+}$ and its slope (26.5 mV/decade) was near to the sub-Nernstian response in deionized water. Also, the potential was maintained constantly in the range of pH $4.00 \sim 12.00$, which supports the potential usage as $Pb^{2+}$ affinitive electrode in the deionized water.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.258-263
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• 2018

This study attempted to utilize ultrafine precipitated calcium carbonate for fluoride removal from the wastewater of electronics industries. An average particle size of the calcium carbonate was $0.96{\mu}m$, and pH of the aqueous slurry was 10 with 70% in mass. The suspension solution showed approximately 2 mL/hr of the sedimentation rate. The present calcium carbonate solution could be comparable to the conventional aqueous calcium source, $Ca(OH)_2$, for the neutralization and removal of fluoride ions. Depending on the amount of an additional alkali source, less amounts of test Ca-source slurries were required to reach the solution pH of 7.0 than that of using the aqueous calcium hydroxide. It was also found from XRD analysis that more calcium fluoride precipitates were formed by the addition of calcium carbonate solution rather than that of calcium hydroxide. In addition, Minteq equilibrium modelling estimated various ion complexes of fluoride and calcium in this process.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.2
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• pp.67-73
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• 2015

The microcystin is a cyclic heptapeptide from metabolites of cyanobacteria in the genera mycrocystis, anabaeba as a result of eutrophication. It has been known that microcystin-LR is a potent inhibitor of the catalytic subunits of protein phosphatase-1 (PP-1) as well as powerful tumor promoter. The active site of microcystin actually has two metal ions $Fe^{2+}/Zn^{2+}$ close to the nucleophilic portion of PP-1-microcystin complex. We report the isolation and purification of this microcystin-LR from cyanobacteria (blue-green algae) obtained from Daechung Dam in Chung-cheong Do, Korea. Microcystin-LR was extracted from solid-phase extraction (SPE) sample preparation using a CN cartridge. The cyanobacteria extract was purified to obtain microcystin-LR by HPLC method and identified by LC/MS. The detail structural studies that can elucidate the possible role of monovalent and divalent metal ions in PP-1-microcystin complexation were carried out by utilizing molecular dynamics. Conformational changes in metal binding for ligands were monitored by molecular dynamic computation and potential of mean force (PMF) using the method of the free energy perturbation. The microcystin-metal binding PMF simulation results exhibit that microcystin can have very stable binding free energy of -10.95 kcal/mol by adopting the $Mg^{2+}$ ion at broad geometrical distribution of $0.5{\sim}4.5{\AA}$, and show that the $K^+$ ion can form a stable metal complex rather than other monovalent alkali metal ions.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.1
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• pp.39-49
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• 2002

In this study, limits of detection (LOD), accuracy and precision of four sampling/ analytical methods were evaluated and compared for the determination of airborne hexavalent chromium, Cr (VI). The methods include : (1) a combination of the National Institute for Occupational Safety and Health (NIOSH) Method 7600/U. S. Environmental Protection Agency (EPA) Method 218.6 (NIOSH/EPA Method) proposed by Shin and Paik, 2) two impinger methods using 2% NaOH/3% Na$_2$CO$_3$. (3) same as (2) but with 0.02 N NaHCO$_3$absorbing solution, and (4) the Occupational Safety and Health (OSHA) Method ID-215. An ion chromatograph/visible absorbance detector was used for the analysis of Cr (VI) in sample solution. Limit of detection (LOD) , analytical accuracy, and precision were also tested using Cr (VI) spike samples. Recoveries (as index of accuracy) and coefficient of variation (CV) (as a index of precision) were determined. Two-way ANOVA and Turkey's test were performed to test the significance in differences among recoveries and CVs of the methods. In all the methods, the peaks of Cr (VI) were separated sharply on chromatograms and exhibited a strong linearity with Cr (VI) concentrations in solution. The correlation coefficients of calibration curves typically ranged from 0.9997 to 0.9999, and the analytical LODs from 0.025 to 0.1$\mu\textrm{g}$/sample. All the method had good sensitivities and linearities between Cr (VI) levels and peak areas. The accuracies (% mean recoveries) of the methods ranged from 80.1 to 104.2%, while the precisions (pooled coefficient of variation) ranged from 3.16 to 4.43%. The impinger methods showed higher recoveries ( > 95%) than those of the PVC filter methods (the OSHA Method and the NIOSH/EPA Method). It was assumed that Cr (VI) on PVC filter was exposed to air and reduced to trivalent chromium, Cr (III), whereas it was stabilized in alkali solution contained in impinger. Thus, a special treatment of Cr (VI) samples collected on PVC filters may be required.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.583-589
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• 2010

In this paper, the properties of reclaimed ash(RA) from various domestic thermal power plants(S, D and H) were analyzed, and the possibility of fabricating the artificial lightweight aggregate(ALA) using RA was studied. The chemical compositions of RA are similar to the clay, but it had higher concentrations of alkali earth metal oxides(CaO, MgO) and unburned-carbon. The TCLP(Toxicity Characteristic Leaching Procedure) results showed that the dissolution concentrations of heavy metal ions of RA were below the limitation defined by the enforcement regulation of wastes management law in Korea. The results of IC analysis showed that leaching concentration of $Cl^-$ ion was 124 ppm for RA of HN and ${SO_4}^{2-}$ ion was leached a few hundreds ppm for all RA in this study. The ALAs with various mass ratio of clay to reclaimed ash(RA:Clay = 7:3, 6:4, 5:5, 4:6, 3:7) were sintered with a electric muffle furnace at the temperature of $1050{\sim}1200^{\circ}C$. The specific gravity and water absorption(%) of the sintered ALAs were 1.1~1.8 and 10~30% respectively. The ALA sintered in the rotary kiln at $1125^{\circ}C$ showed a bulk density of 1.7 and water absorption of 15.2%.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.85-92
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• 1992

A new potassium sensitive field effect transistor modified with 4'-aminobenzo-15-crown-5 was prepared and its response characteristics were evaluated. The response slope of $K^{+}-ISFET$ for pH was 30.0 mV/decade and the response time was mere than 3 minutes. And the response slope and time of the $K^{+}-ISFET$ for potassium ion as $19.5{\pm}0.2{\;}mV/decade$ and about 3 minutes, respectively. The linear response range of the sensor for potassium ion was $2.0{\times}10^{-4}{\sim}1.0{\times}10^{-2}M$. The selectivity coefficients of the $K^{+}-ISFET$ for the alkali and alkaline earth metal ions were also evaluated. Sodium, ammonium and calcium ions exhibited relatively significant interference. The long term stability of the sensor was remarkably improved and it could be used for more than 50 days.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.303-306
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• 2006

Using a variety of chemical geothermometers we estimate the temperature of a deep geothermal reservoir in relation to thermal groundwater in the Bugok area, southern Korea, in order to assess the potential use of geothermal energy in South Korea. Thermal water at Bugok has been exploited down to about 400 m below the land surface and shows the highest outflow temperatures (up to $78{\circ}C$) in South Korea. Based on the hydrochemical data and occurrence, groundwater in Bugok can be classified into three groups: $Na-SO_4$ type thermal groundwater (CTGW) occurring in the central part (about 0.24 $km^2$) $Ca-HCO_3$ type cold groundwater (SCGW) occurring in shallow peripheral parts of CTGW; and the intermediate type groundwater (STGW). CTGW waters are typical of thermal water in the area, because they have the highest outflow temperatures and contain very high concentrations of Na, K and $SiO_2$ due to the sufficient reaction with silicate minerals in deep reservoir. Their enriched $SO_4$ was likely formed by gypsum dissolution. The major ion composition of CTGW shows the general approach to a partial equilibrium state with rocks at depth. The application of various alkali ion geothermometers yields temperature estimates in the range of 88 to $198{\circ}C$ for the thermal reservoir. Multiple mineral equilibrium calculation indicates asimilar but narrower temperature range between about 100 and $155{\circ}C$. These temperature estimates are not significantly higher than the measured outflow temperatures for CTGW Considering the heat loss during the ascent- of thermal waters, this fact may suggest that a thermal reservoir in the study area is likely located at relatively shallow depths (possibly close to the depth of preexisting wells). Therefore, we suggest a high potential for geothermal energy development around the Bugok area in southern Korea.