• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.859-866
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• 2003

When calcium sulfoaluminate-based expansive cement was hydrated, ettringite and monosulfate were mainly formed. The crack of hardened cement was prevented by compensating drying shrinkage due to formation of the above hydrates. In order to study the hydration properties of calcium sulfoaluminate-based expanding cement, 3CaOㆍ3Al$_2$O$_3$ㆍCaSO$_4$(C$_4$A$_3$S) was prepared by chemical synthesis, and then the hydration of $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$.$2H_2O$-C$_3$A system_was characterized. Good $C_4$A$_3$S phase was prepared at $1300^{\circ}C$ by chemical synthesis, and the main hydration product of $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$.2$H_2O$ system was ettringite. In the case of hydration $C_4$A$_3$S-Ca(OH)$_2$-CaSO$_4$ㆍ 2$H_2O$-C$_3$A system, ettringite was formed in the early period and it was transformed into monosulfate while consumed gypsum.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.588-592
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• 1988

A chiral recognition was observed in aminolysis of 3-acyl-4(S)-isopropyl-1,3-thiazolidine-2-thione by racemic amine to give an optically active amide (S-excess) and amine (R-excess). This procedure can be applied to synthesis of macrocyclic diamide macrocyclic spermidine alkaloid, and peptide. The rate of this aminolysis is remarkably affected by steric surrounding; completion of reaction can be easily judged by the disappearance of the original yellow color of 4(S)-AITT. These features of the aminolysis suggested a potential recognition racemic amines by a chiral 4 (S)-AITT derivative. Thus 4 (S)-AITT was synthesized from 4 (S)-isopropyl-1, 3-thiazolidine-2-thione and carboxylic acids.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.213-221
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• 2002

Activated carbons with high surface area of 2,600 $m^{2}/g$ and high pore volume of 1.2 cc/g could be prepared by KOH activation of rice hulls at a KOH:char ratio of 4:1 and $850^{\circ}C$. In order to increase the adsorption capacity of hydrogen sulfide, which is one of the major malodorous component in the waste water treatment process, various contents of $Na_{2}CO_{3}$ and $KIO_{3}$ were impregnated to the rice-hull activated carbon. The impregnated activated carbon with 5 wt.% of $Na_{2}CO_{3}$ showed improved $H_{2}S$ adsorption capacity of 75 mg/g which is twice of that for the activated carbon without impregnation and the impregnated activated carbon with 2.4 wt.% of $KIO_{3}$ showed even higher $H_{2}S$ adsorption capacity of 97 mg/g. The improvement of $H_{2}S$ adsorption capacity by the introduction of those chemicals could be due to the $H_{2}S$ oxidation and chemical reaction with impregnated materials in addition to the physical adsorption of activated carbon.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.1-5
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• 1985

CulnSe2 single crystals were grown by the Bridgman method. The n.CulnSe2 single cry seals with a carrier concentration of 2.6$\times$1016/㎤ were obtained by a thermal treatment of the grown CulnSe2 single crystals in selenium atmosphere. The solar cell of n.CulnSe2-3M KOH+3M Na2 S+4M S junction was prepared by using n.Culnsel single crystal as a photoanode, 3M KOH+SM Nat S+4M S as Polysulfide solutions. The FF of the solar cell was 0.44 under 100 mW/cml illumination condition, and the conversion efficiency was 5.67%.

• Journal of Sasang Constitutional Medicine
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• v.18 no.3
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• pp.75-93
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• 2006

1. Objectives and Methods Sasang Constitutional Medicine is the original Korean Medicine. The purpose of this study was to objectify the diagnosis of Sasang Constitution. 212 Women's sentences were analyzed into 228 factors like Pitch, APQ, Shimmer, Octave and Energy, etc. Women's sentences were classified into 3 categories: total group, under 54 years old group and over 55 years old group. 2. Results 1) In Total group Soyangin's Center feq.(3) was significantly high compared with Taeyangin and Taeumin groups. Taeumin's Pitch2 was significantly high compared with Soeumin and Taeyangin groups. Taeyangin's Pitch S.D. was significantly high compared with Soyangin group. Taeyangin's Octave6 was significantly high compared with Soeumin group. There were no significant differences among constitutional groups in APQ and Shimmer segment. On the point of Energy, Taeyangin's G Tot E(1), G# Tot E(1), G dev.(1), G# dev.(1), G Tot E(2), G# Tot E(2), G dev.(4) and G# dev.(4) were significantly high compared with other groups. Soyangin's A#S.D.(2) was significantly high compared with Taeyangin group. Taeyangin's A#S.D.(3) was significantly high compared with Taeumin group. Taeyangin's F S.D.(5), F# S.D.(5) and Max Average were significantly high compared with Soeumin group. Taeumin's Peak3 and Peak4 were significantly high compared with Taeyangin group. Taeumin's PeakValue1 was significantly high compared with Soeumin group. Taeyangin's PeakValue2 was significantly high compared with Soeumin group. Taeyangin's PeakValue3 and PeakValue5 were significantly high compared with Other groups. 2) In Under 54 years old group, there were no significant differences among constitutional groups in APQ, Shimmer and Octave segment. Taeumin's Center freq.(2) was significantly high compared with Taeyangin and Soyangin groups. Taeumin's Pitch(2) and Pitch(3) were significantly high compared with Taeyangin and Soeumin groups. Taeyangin's and Taeumin's Pitch S.D. were significantly high compared with Soyangin group. Taeyangin's and Soyangin's Octave2 were significantly high compared with Taeumin group. On the point of Energy, Taeyangin's and Soyangin's A# S.D.(2) were significantly high compared with Soeumin group. Taeyangin's and Soyangin's G# dev.(1), G# dev.(2) were significantly high compared with Taeumin group. Taeyangin's and Taeumin's F# S.D.(3) were significantly high compared with Soeumin group. Taeyangin's and Soyangin's Max Average were significantly high compared with Soeumin group. Taeumin's Peak3 was significantly high compared with Taeyangin and Soeumin groups. Taeyangin's and Taeumin's PeakValue2 were significantly high compared with Soeumin group. Taeyangin's and Soeumin's PeakValue3 were significantly high compared with Taeumin group. Taeyangin's and Soyangin's PeakValue5 were significantly high compared with Soeumin group. Taeyangin's and Soyangin's PeakValue9 were significantly high compared with Taeumin group 3) In Over 55 years old group, there were no significant differences among constitutional groups in Pitch, APQ, and Peak segment. Soeumin's F Shimmer(1) and F Shimmer(2) were significantly high compared with Taeyangin and Taeumin groups. Soeumin's G# Shimmer(1) and G# Shimmer(2) were significantly high compared with Soyangin group. Taeyangin's Octave5 and Octave6 were significantly high compared with Soeumin group. On the point of Energy, Soyangin's C S.D., F# S.D.(1), F# S.D.(2) and G dev.(2) were significantly high compared with other groups. Soyangin's F# S.D.(3) was significantly high compared with Taeumin and Soeumin groups. Taeyangin's and Taeumin's G# S.D.(2) and G# S.D.(3) were significantly high compared with Soyangin group 3. Conclusions From above result, there is the possibility of efficient standard guide for constitution diagnosis by analysis of voice

• Journal of Wetlands Research
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• v.9 no.2
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• pp.33-43
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• 2007

Distribution area, actual vegetation map, standing crop biomass, relative growth, and primary productivity of Salix spp.were investigated to provide the basic data necessary for conservation and ecotechnological application of Salix community in the Upo wetland, Changryeong County, Gyeongsangnamdo Province, Korea from April 2005 to April 2006. 1. Among seven Salix species, the dominant species was S. nipponica and S. glandulosa was subdominant. There were six kinds of Salix communities such as S. nipponica, S. glandulosa, S. koreensis, S. nipponica-S. glandulosa, S. glandulosa-S. nipponica, and S. nipponica-S. koreensis. 2. Distribution area of S. nipponica community was largest as 28.46 ha among Salix communities and those of S. nipponica-S. glandulosa community, S. glandulosa-S. nipponica community, S. nipponica-S. koreensis community, S. glandulosa community, and S. koreensis community were 6.12 ha, 6.12 ha, 2.92 ha, 1.86 ha, and 0.81 ha, respectively. 3. The tree age, tree height, and DBH of S. nipponica were 5~13year, 4.1~7.2 m, and 3.0~14.0 cm and those of S. glandulosa were 2~36year, 3.5~10.1 m, and 3.2~26.0 cm, respectively. 4. The standing crop of S. nipponica was 408 ton and that of S. glandulosa was 336 ton in the study area. 5. The productivity of S. nipponica was $235g\;m^{-2}yr^{-1}$ and the annual production was 86.4 ton, and those of S. glandulosa were $1,006g\;m^{-2}yr^{-1}$ and 80.3 ton in the study area.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.197-205
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• 2000

Factors most strongly related to zooplankton growth rates were studied along a lake and a river stretch in the middle part of the lowland River Spree. The study was conducted at the lake inflow (S1), the lake outflow (S2), and at the end of a 21 km stretch of the outflow (S3) from March to November of 1999. Total zooplankton biomass increased significantly at S2 and then sharply decreased at S3. The abundance of microzooplankton (rotifers and nauplii) was strongly higher than macrozooplankton (cladocerans and copepodids) at all station. However, macrozooplankton biomass (${\mu}$g dw 1$^{-1}$) was similar or much higher than microzooplankton biomass. Large-bodied cladocerans (Daphnia cucullata) dominated at S2 while small-bodied cladocerans (Bosmina longirostris) dominated at S1 and S3. Patterns in growth rates (r$_{t}$ in d$^{-1}$ of the major zooplankton community were greatly different between S1 and S2 (lake stretch) and between S2 and S3 (river stretch). In the lake, growth rates generally were positive, while values of growth rates were negative in the river stretch. Among the environmental variables considered, partial retention time (PRT, d$^{-1}$) seemed to play the most important role in determining characteristics of the zooplankton community structure in the middle part of River Spree.

• Microbiology and Biotechnology Letters
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• v.24 no.2
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• pp.213-216
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• 1996

Optically active carboxylic acid, D-(-)-$\beta$-hydroxyisobutyric acid {(D)-(-)-HIBA} is a useful chiral starting material for the preparation of enantiomerically pure bioactive compounds which have a chiral methyl carbon center in the molecule such as captopril, $\alpha$-tocopherol, erythromycin A, muscone and so on. (S)-3-Acetoxy-2-methylpropanol can be used as the precursor of (D)-(-)-HIBA, that is, chemical oxidation of the hydroxyl group and subsequent hydrolysis of acyl group in (S)-3-acetoxy-2-methylpropanol affords D-(-)-$\beta$-hydroxyisobutyric acid. (S)-3-Acetoxy-2-methyl-propanol was prepared by lipase-catalyzed asymmetric hydrolysis. In the enzymatic hydrolysis system, lipase AY (Candida rugosa) provided the expected (S)-3-acetoxy-2-methylpropanol in 60% e.e. of the enantiomeric purity under the phosphate buffer and organic co-solvent system.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.1-7
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• 1980

Solvolysis rate constants for methylchloroformate, methylthionochloroformate, methylthiolchloroformate and methyldithiochloroformate have been determined conductometrically in methanol, ethanol and ethanol-water mixtures and activation parameters have been derived. Results show that methylchloroformate solvolyzes through $S_N2$ process while methyldithiochloroformate solvolyzes by $S_N1$ process in all the solvent systems. The rate of hydrolysis decreased in the order, $CH_3S(CS)Cl>CH_3S(CO)Cl>CH_3O(CS)Cl>CH_3O(CO)Cl$ which corresponds to the order of decreasing $S_N1$ character. In methanol, $CH_3S(CS)Cl$ solvolyzed via the $S_N1$ mechanism while the others solvolyzed via the $S_N2$ process. In ethanol, however, $S_N2$ character was dominant for all the compounds, except methyldithiochloroformate, for which $S_N1$ character was still strong enough to accelerate the rate of ethanolysis. In ethanol-water mixtures, $CH_3S(CS)Cl$ and $CH_3S(CS)Cl$ solvolyzed via $S_N2$ process in ethanol-rich region while the $S_N1$ character increased greatly in water-rich region for the solvolysis of these compounds. The order of $S_N1$ character for solvolysis in water-rich region was the same as the order of hydrolysis rate.

• Advances in environmental research
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• v.3 no.3
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• pp.185-197
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• 2014

Efficient defluorination of perfluorooctanoic acid (PFOA) was achieved by integrating UV irradiation and $Fe^{2+}$ activation of persulfate ($S_2O{_8}^{2-}$). It was found that the UV-$Fe^{2+}$, $Fe^{2+}-S_2O{_8}^{2-}$, and UV-$S_2O{_8}^{2-}$ processes caused defluorination efficiency of 6.4%, 1.6% and 23.2% for PFOA at pH 5.0 within 5 h, respectively, but a combined system of UV-$Fe^{2+}-S_2O{_8}^{2-}$ dramatically promoted the defluorination efficiency up to 63.3%. The beneficial synergistic behavior between $Fe^{2+}-S_2O{_8}^{2-}$ and UV-$S_2O{_8}^{2-}$ was demonstrated to be dependent on $Fe^{2+}$ dosage, initial $S_2O{_8}^{2-}$ concentration, and solution pH. The decomposition of PFOA resulted in generation of shorter-chain perfluorinated carboxylic acids (PFCAs), formic acid and fluoride ions. The generated PFCAs intermediates could be further defluorinated by adding supplementary $Fe^{2+}$ and, $S_2O{_8}^{2-}$ and re-adjusting solution pH in later reaction stage. The much enhanced PFOA defluorination in the UV-$Fe^{2+}-S_2O{_8}^{2-}$ system was attributed to the fact that the simultaneous employment of UV light and $Fe^{2+}$ not only greatly enhanced the activation of $S_2O{_8}^{2-}$ to form strong oxidizing sulfate radicals ($SO{_4}^{\cdot-}$), but also provided an additional decarboxylation pathway caused by electron transfer from PFOA to in situ generated $Fe^{3+}$.