• 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.

• Journal of the Korean Chemical Society
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• v.37 no.2
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• pp.244-248
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• 1993

Nitroalcohols were prepared by a substitution reaction from the corresponding bromoalcohols. The second nitro group was introduced via different methods depending on the carbon chain length. 3,3-Dinitro-1-propanol was obtained by an intramolecular varient of the alkaline nitration method. Whereas 5,5-dinitro-1-pentanol was given by the catalytic oxidative nitration. 3,3-Dinitro-1-propanol and 5,5-dinitro-1-pentanol were converted to 3,3-dinitro-1,6-hexanediol and 4,4-dinitro-1,8-octanediol via Michael reaction with acrolein followed by the reduction of the resulting aldehydes. Acetyl group was a good protecting group for the substitution reaction while THP was for the catalytic oxidative nitration.

• ETRI Journal
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• v.42 no.4
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• pp.619-632
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• 2020

Highly dispersive S-boxes are desirable in cryptosystems as nonlinear confusion sublayers for resisting modern attacks. For a near optimal cryptosystem resistant to modern cryptanalysis, a highly nonlinear and low differential probability (DP) value is required. We propose a method based on a piecewise linear chaotic map (PWLCM) with optimization conditions. Thus, the linear propagation of information in a cryptosystem appearing as a high DP during differential cryptanalysis of an S-box is minimized. While mapping from the chaotic trajectory to integer domain, a randomness test is performed that justifies the nonlinear behavior of the highly dispersive and nonlinear chaotic S-box. The proposed scheme is vetted using well-established cryptographic performance criteria. The proposed S-box meets the cryptographic performance criteria and further minimizes the differential propagation justified by the low DP value. The suitability of the proposed S-box is also tested using an image encryption algorithm. Results show that the proposed S-box as a confusion component entails a high level of security and improves resistance against all known attacks.

• Journal of the Korean Chemical Society
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• v.31 no.2
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• pp.123-132
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• 1987

Nucleophilic substitution reactions of methylthiocyanate(MTC) with anion nucleophiles,$SH^-,\;CN^-$ and $OH^-$, have been investigated using MNDO method. For the three reaction centers of MTC, gas-phase and solution-phase selectivities are discussed for each nucleophile by considering potential energy profiles calculated(intrinsic term) and magnitudes of negative charge on the nucleophile at the transition state(solvation term). It was found that both components of the selectivity for $SH^-$agreed with the experimental results obtained for 4-methylbenzylthiocyanate (4-MBTC), but the selectivity order for TEX>$CN^-$ was found to agree only with that of the intrinsic term and that of $OH^-$disagreed with any theoretical selectivity order. The MNDO optimized geometries for all species at the stationary points are reported.

• Korean Journal of Materials Research
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• v.27 no.8
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• pp.416-421
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• 2017

V-substituted $SrTiO_3$ thermoelectric oxide materials were fabricated by the conventional solid state reaction method. From X-ray diffraction pattern analysis, it can be clearly seen that almost every vanadium atom incorporated into the $SrTiO_3$ provided charge carriers. The electrical conductivity ${\sigma}$, Seebeck coefficient S, and thermal conductivity k were investigated in a high temperature regime above 1000 K. The addition of vanadium significantly reduced the thermal conductivity and enhanced the Seebeck coefficient, as well as the electrical conductivity, thus enhancing the ZT value. A maximum ZT value of 0.084 at 673 K was observed for the sample with 1.0 mole% of vanadium substitution. In this study, the reason for the enhanced thermoelectric properties via vanadium addition was also investigated.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.166-166
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• 1996

A series of 6-(N-arylamino)-7-alkylthio-5,8-quinolinedione derivatives(SQ1-12) were newly synthesized for the evaluation of antifungal activities. 6-(N-Arylamino)-7-chloro-5,8-quinolinediones (RCKs) were treated with Na$_2$S/(CH$_3$)$_2$SO$_2$ in EtOH In give SQs. RCKs were prepared by regioselective nucleophilic substitution of 6,7-dichloro-5,8-quinolinediones with arylamines. In the presence of CeCl$_3$, the N-arylamino groups were introduced at the 6-position of 5,8-quinolinedione ring by the regioselective substitution. These derivatives 1-12 were tested for antifungal and also antibacterial activities, in vitro, against Candida sp., Aspergillus niger and Trichophyton mentagrophytes. The MIC values were determined by the two-fold dilution method.

• Journal of the Korean Applied Science and Technology
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• v.26 no.4
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• pp.428-433
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• 2009

Cellulose triacetate (CTA) was prepared from cotton linter and pulps which contain various contents of $\alpha$-cellulose. CTA which contains 2.8 of degree of substitution (DS) and 222 of degree of polymerization (DP) was obtained from V-81 pulp under the heterogeneous system. The DS was measured by the titration method, and the DP was obtained by measurement of viscosity. FT-IR spectometer (FT-IR 6300, JASCO) was used to analyze the chemical structure of raw materials and cellulose triacetate, and X-ray diffractometer (X-pert MPD PW3040, Philips) was used to confirm the crystal structure and to calculate the relative crystallinity index (RCI). As $\alpha$-cellulose content in pulp increased, the acetylation yield increased. Besides with a kind of pulp, it contains insoluble residue which was mainly formed due to the formation of glucomannan triacetate and xylan diacetate during the esterification.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.160-166
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• 2002

In this paper, we implement a new vocabulary-independent speech recognition system that uses CV, VCCV, VC recognition unit. Since these recognition units are extracted in the trowel region of syllable, the segmentation is easy and robust. And in the case of not existing VCCV unit, the units are replaced by combining VC and CV semi-syllable model. Clustering of vowel group and applying combination rule to the substitution model in the case of not existing of VCCV model lead to 5.2% recognition performance improvement from 90.4% (Model A) to 95.6% (Model C) in the first candidate. The recognition results that is 98.8% recognition rate in the second candidate confirm the effectiveness of the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.210-220
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• 2006

Dense $((Na_{0.5}K_{0.5})_{1-x}Li_x)(Nb_{0.8}Ta_{0.2})O_3$ ceramics were developed by conventional sintering process. The electrical properties of $((Na_{0.5}K_{0.5})_{1-x}Li_x)(Nb_{0.8}Ta_{0.2})O_3$ ceramics were investigated as a function of Li substitution. When the sample sintered at $1100^{\circ}C$ for 4 h with the Substitution of 2 mol% Li, electro-mechanical coupling factor ($k_p$) and piezoelectric coefficient ($d_{33}$) were found to reach the highest values of 0.42 and 210 pC/N, respectively.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.225-231
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• 2003

To search and development a new material with superior melanogenesis inhibitory activity, the bioactivities (obs. pl$_{50}$) of alkyl-3,4-dihydroxybenzoyl esters and N-alkyl-3,4-dihydroxybenz-oyl amides as substrate molecules were measured in mouse melanoma cells. And also, we have studied that 3-D QSARs (3 dimensional Quantitative Structure-Activity Relationships) between molecular interaction field of substrates and the bioactivities were analyzed using CoMFA (Comparative Molecular Field Analyses) method. When cross-validation value (q$^2$) is 0.68 at 3 components, the Pearson correlation coefficient ($r^2$) is 0.900. From the basis on the findings, the model was appeared by the contour map such as steric field and electrostatic field relationships between quantitative structure and the bioactivity of the various substrate derivatives. Measured bioactivities (obs. pl$_{50}$) of unknown compounds are very similar to predicted activity (pred. pl$_{50}$) according to the CoMFA model. As the results of prediction, we could conclude that the bioactivities were increased by creation of R$_1$ substitution of 5,5-dime-thylhexoxy, 6,6-dimethylheptyl, 1-amino-6,6-dimethylheptyl group etc and R$_2$ substitution of hydroxy, methyl, methoxy group etc.p etc.