• Geomechanics and Engineering
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• v.1 no.4
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• pp.307-321
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• 2009

The paper employs a feed forward neural network with back-propagation algorithm for modeling time dependent swell in clays containing carbonate in the presence of sulfuric acid. The oedometer swell percent is estimated at a nominal surcharge pressure of 6.25 kPa to develop 612 data sets for modeling. The input parameters used in the network include time, sulfuric acid concentration, carbonate percentage, and liquid limit. Among the total data sets, 280 (46%) were assigned to training, 175 (29%) for testing and the remaining 157 data sets (25%) were relegated to cross validation. The network was programmed to process this information and predict the percent swell at any time, knowing the variable involved. The study demonstrates that it is possible to develop a general BPNN model that can predict time dependent swell with relatively high accuracy with observed data ($R^2$=0.9986). The obtained results are also compared with generated non-linear regression model.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.21-22
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• 2022

In order to improve the strength degradation of the cement-based material to which strong alkaline liquid red mud was added, the liquid red mud was neutralized with sulfuric acid and added to the cement paste to examine the mechanical properties according to the amount added. As a result of measuring the compressive strength, the strength was higher when the red mud was neutralized with sulfuric acid and added to the cement paste than the cement paste to which the liquid red mud was added. As a result of hydration heat measurement, when red mud was neutralized with sulfuric acid and added to the cement paste, an initial strength higher than that of liquid red mud was expressed.

• Restorative Dentistry and Endodontics
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• v.6 no.1
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• pp.37-50
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• 1980

Scanning Electron Microscopic (SEM) examination on the labial surface of 91 permanent upper incisors were made after etching procedure with phosphoric acid, sulfuric acid, nitric acid, hydro chloric acid, oxalic acid, formic acid, citric acid and zinc phosphate liquid for 2 minutes. Following results were obtained. 1. In the surfaces etched by 10%. 50% phosphoric acid, 50% sulfuric acid, 10%. 30% nitric acid, 10%. 50% oxalic acid, 10%. 30%. 50% formic acid, 30%. 50% citric acid and zinc phosphate liquid, there appeared to be a preferential removal of prism cores, but in the surfaces etched by 10% phosphoric acid, 50% nitric acid, 10%. 30% hydrochloric acid and 30% oxalic acid, the prism peripheries were removed preferentially. 2. According to Silverstone classification on enamel etching pattern the surface treated by zinc phosphate liquid, 30. 50% citric acid, 10%. 30%. 50% formic acid, 10%. 50% oxalic acid, 10%. 30% nitric acid, 50% sulfuric acid and 10%. 50%. phosphoric acid showed Type 1, and etched by 30% oxalic acid, 10%. 30% hydrochloric acid, 50% nitric acid and 10% phosphoric acid showed Type II. Etching of prism cores was by far the most common occurence. The changes produced could be related to intrinsic differences in histology and / or solubility of enamel.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1854-1856
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• 2007

• Bulletin of the Korean Chemical Society
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• v.26 no.9
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• pp.1431-1433
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• 2005

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.137-138
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• 2015

The use of the cement and increased with the recent development of the construction industry. If the cement is the environmental problems caused by generating a large quantity of CO₂ and the production process. Accordingly, this study is the test to determine the sulfuric acid and hydrochloric acid resistance properties of the Light weight matrix product of blast furnace slag-based light. A result, the compression strength of the sulfuric acid and hydrochloric acid immersion showed alower strength than the Plain.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.128-135
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• 2021

In this study, the acid polyols containing acid groups were synthesized, the novel polyurethane adhesive was developed by introducing the acid polyol by content. The acid polyols were introduced, the mechanical properties showed the maximum value when the acid content was 0.1 to 0.3 wt%, and it was confirmed that the mechanical properties and adhesive strength decreased at the content higher than 0.5 wt%. As the acid group, carboxylic acid and sulfuric acid were introduced to compare properties, and carboxylic acid showed stronger hydrogen bonding potential than sulfuric acid and improved mechanical properties. In addition, the correlation between particle size and mechanical properties was confirmed by introducing ZnO and CaCO₃. When ZnO and CaCO₃ were introduced, an ionic bond was formed with an acid group, and it was confirmed that mechanical properties were increased.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.114-119
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• 2016

In this study, we tried to add the conductivity to natural polymer like bacterial cellulose (BC) coated with the conductive polymer PEDOT:PEG, graphene and silver nano-wire (AgNW). Sulfuric acid of 10 to 20% was previously mixed with PEDOT:PEG and then the solution was electron spin-coated on the BC membrane. And then, additive coating with graphene and AgNW were done to improve conductivity, which was examined by hall effect. As the result, we confirmed a considerable improvement of conductivity compared to BC-coated film without sulfuric acid treatment as $2.487{\times}10^{10}$ vs $8.093{\times}10^{15}$ ($1/cm^3$), showing higher electron density with $3.25{\times}10^5$ times. Also, we identified that changed particle type to the polymer type by sulfuric acid using SEM analysis. For FT-IR analysis, it was confirmed that S-O radical ($1200cm^{-1}$) increased in the sulfuric acid treatment than non-treated sulfuric acid. As the method used very small amount of PEDOT:PEG, its transparency could be kept, and pre-treatment process of sulfuric acid will be able to simplify the production process.

• Resources Recycling
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• v.32 no.3
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• pp.38-44
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• 2023

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150℃ in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200℃, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H₂SO₄, 100℃, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.

• Journal of the Korean institute of surface engineering
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• v.57 no.1
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• pp.8-13
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• 2024

Anodizing of Al6061 alloy was conducted in two different electrolytes of 20% sulfuric acid and 8% sulfuric acid + 3 % oxalic acid solutions at a constant current or decreasing current density conditions, and its dielectric breakdown voltage was measured. The surface morphology of anodic oxide films was observed by TEM and thermal treatment was carried out at 400 ℃ for 2 h to evaluate the resistance of the anodic oxide films to crack initiation. The anodic oxide film formed in 8% sulfuric acid + 3 % oxalic acid solution showed higher dielectric breakdown voltage and better resistance to crack initiation at 400 ℃ than that formed in 20% sulfuric acid solution. The dielectric breakdown voltage increased 6 ~12% by applying decreasing current density comparing with a constant current density.