• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.731-734
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• 2013

Reduced tungsten bronze nanoparticles of ternary and quaternary compounds were prepared by adding sodium and cesium to crystal structures of tungsten trioxides ($Na_xCs_{0.33-x}WO_3$, x = 0, 0.11) while maintaining the overall alkali metal fraction at 0.33, in an attempt to control near infrared (NIR) shielding property in the particular wavelength range of 780 to 1200 nm. The structure and composition analysis of the quaternary compound, $Na_{0.11}Cs_{0.22}WO_3$, revealed that 93.1% of the hexagonal phase was formed, suggesting that both alkali metals were mainly inserted in hexagonal channel. The NIR shielding property for $Na_{0.11}Cs_{0.22}WO_3$ was remarkable, as this material demonstrated efficient transmittance of visible light up to 780 nm and enhancement in NIR shielding because of the blue-shifted absorption maximum in comparison to $Cs_{0.33}WO_3$.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.431-441
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• 2023

The aim of this paper is to present a new sustainable ternary and quaternary binder by partially replacing ordinary Portland cement (OPC) with different percentages of supplementary cementitious materials. The motivation is to reduce our dependency on OPC to reduce CO₂ emission and carbon foot print. As the main substitute for the OPC, siliceous fly ash was used. Moreover, silica fume and nanosilica were also used. During examinations the main mechanical parameters of concrete composites, i.e., compressive strength (f_cm) and splitting tensile strength (f_ctm) were assed. The microstructure of these materials was also analysed. It was found that the concrete incorporating pozzolanic materials is characterized by a well-developed structure and has high values of mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good strength parameters as well as the most favourable microstructure, whereas the worst mechanical parameters with microstructure containing microcracks at phase interfaces were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Nevertheless, all concretes made on quaternary binders had better parameters than the reference one. It can be stated that sustainable concrete incorporating pozzolanic materials could be good substitute of ordinary concretes.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.372-382
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• 2022

In this study, anion exchange membranes were prepared by synthesizing the main chain into a poly(arylene ether) (PAE) structure, and the structures capable of improving the physical and chemical stability of the membrane by introducing a heterocyclic quaternary ammonium functional groups were studied. The chemical structure and thermal properties of the prepared polymer were confirmed by ¹H-NMR, FT-IR, TGA, and DSC, and surface analysis was performed through AFM measurement. Additionally, dimensional stability and chemical properties was studied by measuring water uptake and swelling ratio, IEC and ionic conductivity. At 90℃, the quaternized poly(arylene ether) (QPAE)/1-methylpiperidine (MP) membrane exhibited the highest ionic conductivity of 27.2 mS cm^-1, while the QPAE/1-methylimidazole (MI) membrane and QPAE/1-methylmorpholine (MM) membrane exhibited values of 14.5 mS cm^-1 and 11.5 mS cm^-1, respectively. In addition, the prepared anion exchange membrane exhibited high chemical stability in alkaline solution.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.701-704
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• 2007

• BMB Reports
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• v.40 no.5
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• pp.690-696
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• 2007

There are conflicting views for the polymerization process of human UDP-glucose dehydrogenase (UGDH) and no clear evidence has been reported yet. Based on crystal coordinates for Streptococcus pyogenes UGDH, we made double mutant A222Q/S233G. The double mutagenesis had no effects on expression, stability, and secondary structure. Interestingly, A222Q/S233G was a dimeric form and showed an UGDH activity, although it showed increased $K_m$ values for substrates. These results suggest that Ala222 and Ser233 play an important role in maintaining the hexameric structure and the reduced binding affinities for substrates are attributable to its altered subunit communication although quaternary structure may not be critical for catalysis.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.485-490
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• 2004

Silver-needle shaped crystals of $KLa_2Sb_3S_9$ from $K_2S_x$ flux and $KSm_2Sb_3Se_8$ from NaCl/KCl flux reactions were obtained and their crystal structures were determined by the single crystal X-ray diffraction method. $KLa_2Sb_3S_9$ crystallizes in the orthorhombic noncentrosymmetric space group $P2_12_12_1$ (No.19) with a unit cell of a = 4.220(3) ${\AA}$, b = 24.145(2) ${\AA}$, c = 14.757(5) ${\AA}$ and Z = 4. $KSm_2Sb_3Se_8$ crystallizes in the orthorhombic space group Pnma (No.62) with a unit cell of a = 16.719(3) ${\AA}$, b = 4.1236(8) ${\AA}$, c = 22.151(4) ${\AA}$ and Z = 4. Both structures have three-dimensional tunnel frameworks filled with $K^+$ ions. $KSm_2Sb_3Se_8$ is an ordered version of $ALn_{1{\pm}X}B_i{4{\pm}X}S_8$, and it is made up of NaCl-type and $Gd_2S_3$-type fragments. $KLa_2Sb_3S_9$ also contains building fragments similar to those of $KSm_2Sb_3Se_8$, however, there are chalcogen-chalcogen bonds in the $Gd_2S_3$-type fragment. The formula of $KLa_2Sb_3S_9$ can be described as $(K^+ )(La^{3+})_2(Sb^{3+})^3(S^{2-})_7(S_2^{2-})$.

• Polymer(Korea)
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• v.31 no.1
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• pp.80-85
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• 2007

Maleic anhydride (MA) modified ethylene-propylene-diene terpolymer (MEPDM) was pre-pared from solution polymerization. MEPDM-g-PST copolymer was prepared by melt polymerization of male ate d EPDM and quaternary ammonium silyl polydimethylsiloxane -7,7,8,8- tetracyanoquinodimethane (TCNQ) adduct (PST) in internal mixer and MEPDM-g-PST/HDPE/CB (MPEC) was prepared by com-pounding HDPE, MEPDM-g-PST copolymer and carbon black (CB, 5, 10, 15, and 20 phr), and HDPE/ CB (PEC) by compounding HDPE and CB (5, 10, 15, and 20 phr), respectively. The structure of MEPDM-g-PST copolymer was confirmed by measuring the FTIR. The maximum grafting ratio of MA onto EPDM was 2.35%. The thermal and mechanical properties of the composites were measured and dispersion characteristics of CB in matrix show that CB in MPEC was better dispersed than that in PEC composite.

• Applied Microscopy
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• v.25 no.3
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• pp.82-89
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• 1995

High resolution transmission electron microscopic observations on quaternary $Zn_{1-x}Mg_{x}S_y$ $S_{1-y}$(x=0.13, y=0.16) on (001) GaAs substrate grown up to $1.2{\mu}m$ with 20nm ZnSe buffer layer at $300^{\circ}C$ by RIBER MBE system which has a single growth chamber were investigated by HRTEM working at 300kV with point resolution of 0.18nm. The ZnSe buffer layer maintains the coherency with the GaAs substrate. The stacking faults had begun at ZnSe buffer/$Zn_{1-x}Mg_{x}S_{y}S_{1-y}$ interface, whose length and spacing became larger than 60nm and wider than 40nm, respectively. The inverse triangular stacking fault was bounded by stacking faults which were formed on {111} planes with different variants. There exists rare stacking faults inside the triangular defect. The epilayer surrounded by the straight stacking faults, which had formed in the same direction, became the columnar structure.

• Advances in concrete construction
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• v.9 no.4
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• pp.387-395
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• 2020

This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

• Advances in nano research
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• v.16 no.3
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• pp.217-229
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• 2024

This paper presents results of visual analysis of cracks formation and propagation of concretes made of quaternary binders (QBC). A composition of the two most commonly used mineral additives, i.e. fly ash (FA) and silica fume (SF) in combination with nanosilica (nS), has been proposed as a partial replacement of the cement. The principal objective of the present study is to achieve information about the effect of simultaneous incorporation of three pozzolans as partial replacement to the OPC on the fracture processes in concretes made from quaternary binders (QBC). The modern and precise non-contact measurement method (NCMM) via digital image correlation (DIC) technique was used, during the studies. In the course of experiments it was established that the substitution of OPC with three pozzolans including the nanoadditive in FA+SF+nS FA+SF+nS combination causes a clear change of brittleness and behavior during fractures in QBCs. It was found that the shape of cracks in unmodified concrete was quasi-linear. Substitution of the binder by SCMs resulted in a slight heterogeneity of the structure of the QBC, including only SF and nS, and clear heterogeneity for concretes with the FA additive. In addition, as content of FA rises throughout each of QBC series, material becomes more ductile and shows less brittle failure. It means that an increase in the FA content in the concrete mix causes a significant change in fracture process in this composite in comparison to concrete with the addition of silica modifiers only.