• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.385-393
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• 1995

Akali-resistant porous glass was prepared by phase separation in Na2O-B2O3-SiO2 system containing ZrO2 and MgO. ZrO2 was added for alkali-resistance and MgO for anti-cracking during leaching. Optimal content of ZrO2 for alkali-resistance was 7wt% and devitrification by heat treatment resulted from further addition. Pore size and pore volume were decreased and specific surface area was increased with ZrO2 addition due to depression in phase separation. Addition of 3mol% MgO to mother glass containing 7wt% ZrO2 was effective for anti-crack during leaching. In this case, with phase separation at 55$0^{\circ}C$ and 5$25^{\circ}C$ for 20 hrs. crack-free porous glasses could be prepared. The relation between pore size r and heat treatment time t at 55$0^{\circ}C$ was D=25.58＋18.16t. According to measurement of gas permeability, the mechanism of gas permeation was Knudsen flow. N2 and He permeability of porous glass which was prepared by heat treatment at 55$0^{\circ}C$ for 20 hrs. were 0.843$\times$10-7mol/$m^2$.s.Pa and 2.161$\times$10-7mol/$m^2$.s.Pa respectively.

• Textile Coloration and Finishing
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• v.14 no.4
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• pp.214-222
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• 2002

In order to give a silk-like touch to PET fabrics, the PET fabrics were treated with NaOH alkaline solution in various conditions. In alkaline treatment, the liquor flow type pilot weight reduction apparatus with magnetostrictive ultrasonic transducer was used for the study. The weight loss of PET fabrics hydrolyzed in 4% and 6% NaOH solution, at $95^\circ{C}$ and $99^\circ{C}$ for 60min. with ultrasonic application showed 3.7~4.6% higher than that of treated fabric without ultrasonic application. From the difference of specific weight loss, the treatment condition of the maximum of hydrolyzation effect appeared at $95^\circ{C}$ in $4^\circ{C}$ and at $90^\circ{C}$ in 6% NaOH solution, respectively. During the alkali hydrolysis of PET fabrics, the decomposition rate constant(k) increased exponentially with the treatment temperature and were not related with ultrasonic cavitation. The activation energy$(E_a)$ in decomposition of PET fabrics were 21.06kcal/mol with ultrasonic application and 21.10kcal/mol without ultrasonic application. The ultrasonic application gave a little higher value of the activation entropy$(\Delta{S}^\neq)$ and a little lower value of Gibbs free energy$(\Delta{S}^\neq)$ compared with not used ultrasonic apparatus.

• Journal of Microbiology and Biotechnology
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• v.3 no.3
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• pp.139-145
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• 1993

The nucleotide sequence of the xylanase gene (xynS) from alkali-tolerant Bacillus sp. YA.14 was determined and analyzed. A 639 base pairs open reading frame for xynS gene was observed and encoded for a protein of 213 amino acids with a molecular weight of 23, 339. S1 nuclease mapping showed that the transcription initiation site of the xynS gene did not exist in the cloned DNA. Ribosome binding site sequence with the free energy of -18.8 Kcal/mol was observed 8 base pairs upstream from the initiation codon, ATG. The proposed signal sequence consisted of 28 amino acids, of which 3 were basic amino acid residues and 21 were hydrophobic amino acid residues. When the amino acid sequences of xylanases were compared, Bacillus sp. YA-14 xylanase showed 48% homology with Bacillus sp. YC-335 xylanase and 96% homology with xylanases from B. subtilis and B. circulans.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.123-131
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• 2020

The bond performance of glass fibre reinforced polymer (GFRP) bars and that of steel bars embedded in Alkali Activated Cement (AAC) concrete are analysed and compared using pull-out specimens. The bond failure modes, the average bond strength and the free end bond stress-slip curves are used for comparison. Tepfers' concrete ring model is used to further analyse the splitting failure in ribbed steel bar and GFRP bar specimens. The angle the bond forces make with the bar axis was calculated and used for comparing bond behaviour of ribbed steel bar and GFRP bars in AAC concrete. The results showed that bond failure mode plays a significant role in the comparison of the average bond stress of the specimens at failure. In case of pull-out failure mode, specimens with ribbed steel bars showed a higher bond strength while specimens with GFRP bars showed a higher bond stress in case of splitting failure mode. Comparison of the bond stress-slip curves of ribbed steel bars and GFRP bars depicted that the constant bond stress region at the peak is much smaller in case of GFRP bars than ribbed steel bars indicating a basic bond mechanism difference in GFRP and ribbed steel bars.

• Geomechanics and Engineering
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• v.19 no.1
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• pp.21-28
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• 2019

Use of cement in stabilizing the sulfate-bearing clay soils forms ettringite/ thaumasite in the presence of moisture leads to excessive swelling and causes damages to structures built on them. The development and use of non-traditional stabilisers such as alkali activated ground granulated blast-furnace slag (AGGBS) and enzyme for soil stabilisation is recommended because of its lower cost and the non detrimental effects on the environment. The objective of the study is to investigate the effectiveness of AGGBS and enzyme on improving the volume change properties of sulfate bearing soil as compared to ordinary Portland cement (OPC). The soil for present study has been collected from Tilda, Chhattisgarh, India and 5000 ppm of sodium sulfate has been added. Various dosages of the selected stabilizers have been used and the effect on plasticity index, differential swell index and swelling pressure has been evaluated. XRD, SEM and EDX were also done on the untreated and treated soil for identifying the mineralogical and microstructural changes. The tests results show that the AGGBS and enzyme treated soil reduces swelling and plasticity characteristics whereas OPC treated soil shows an increase in swelling behaviour. It is observed that the swell pressure of the OPC-treated sulfate bearing soil became 1.5 times higher than that of the OPC treated non-sulfate soil.

• Korean Journal of Materials Research
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• v.33 no.4
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• pp.135-141
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• 2023

The volatilization of alkali ions in (K,Na)NbO₃ (KNN) ceramics was inhibited by doping them with alkaline earth metal ions. In addition, the grain growth behavior changed significantly as the sintering duration (t_s) increased. At 1,100 ℃, the volatilization of alkali ions in KNN ceramics was more suppressed when doped with alkaline earth metal ions with smaller ionic size. A Ca²⁺-doped KNN specimen with the least alkali ion volatilization exhibited a microstructure in which grain growth was completely suppressed, even under long-term sintering for t_s = 30 h. The grain growth in Sr²⁺-doped and Ba²⁺-doped KNN specimens was suppressed until t_s = 10 h. However, at t_s = 30 h, a heterogeneous microstructure with abnormal grains and small-sized matrix grains was observed. The size and number of abnormal grains and size distribution of matrix grains were considerably different between the Sr²⁺-doped and Ba²⁺-doped specimens. This microstructural diversity in KNN ceramics could be explained in terms of the crystal growth driving force required for two-dimensional nucleation, which was directly related to the number of vacancies in the material.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.313-317
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• 2003

The study is the results of accelerated tests and the specimens, mortars, are submerged in a 5% sulfuric acid solution. The deterioration of specimens is followed up by investigating the change in weight and compressive strength of the specimens and techniques such as XRD and XRF are used to examine the chemical changes. Sulfuric acid is a very aggressive acid that reacts with the free lime [$Ca(OH)_2$] in the concrete forming gypsum($CaSO_{4}.2H_{2}O$). This reaction is associated with an increase in volume of the concrete, and the corroded surface becomes soft and white. The results showed that the OPC mortar caused an decrease in weight above 18% and strength loss about 57%. On the other hand, AASC(alkali-activated slag composites) did not cause any decrease in weight and in the case of strength caused an decrease below 10%. In addition, this mechanical results was verified to XRD and XRF.

• Computers and Concrete
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• v.12 no.4
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• pp.431-442
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• 2013

This study attempted to find a proper method applicable to simulating practical equifield lines of two-dimensional Accelerate Lithium Migration Technique (ALMT), and evaluate the feasibility of using the theoretical ion migration model of one-dimensional ALMT to predict the ion migration behavior of two-dimensional ALMT. The result showed that the electrolyte or carbon plate can be used as matrix to draw equifield line graph similar to that by using mortar as matrix. Using electrolyte electrode module for simulation has advantages of simple production, easy measurement, rapidness, and economy. The electrolyte module can be used to simulate the equifield line distribution diagram in practical two-dimensional electrode configuration firstly. Then, several equifield line zones were marked, and several subzones under one-dimensional ALMT were separated from various equifield line zones. The theoretical free content distribution of alkali in concrete under two-dimensional electric field effect could be obtained from duration analysis.

• Resources Recycling
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• v.27 no.1
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• pp.106-117
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• 2018

The present study was carried out to find a suitable drying method for the determination of non-evaporable water in hydraulic inorganic materials. In Part 1 of the paper, the case ordinary Portland cement was discussed and, in this Part 2, the case of alkali active slag (AAS) was investigated. Various drying methods including vacuum and oven drying, and an ignition, were used for the AAS system having different w/b, types and amounts of alkali activators. It was found that a combination of the vacuum and oven drying was a suitable drying method for the AAS case. Although a part of the crystallized water in hydration products was decomposed, but the free and adsorbed water could be completely evaporated and the deviation of the results was small.

• Journal of Life Science
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• v.10 no.2
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• pp.131-139
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• 2000

Lecithin-free egg yolk protein (EYP), the by-product of lecithin extraction from egg yolk, which is denatured with an organic solvent, would normally be discarded. In this study, the denatured protein was renatured with alkali, and hydrolyzed with Alcalase in order to utilize by-product. The hydrolysate was separated through a series of ultrafiltration membranes with molecular weight cut-off (MWOO) of 10, 5 and 1 kDa, and the antioxidative activities of the hydrolysates was investigated. The 5K hydrolysate, permeate from 5 kDa membrane, showed stronger antioxidative activity than 10 K and 1 K hydrolysate which were permeated from 10 kDa and 1 kDa membrane, in a linoleic acid autoxidation system. In addition, the optimum concentration of antioxidative activity for 5 K hydrolysate was 1%, and the activity was about 37% higher as compared with α-tocopherol. The synergistic effect was also increased by using the hydrolysates with α-tocopherol.