• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.233-239
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• 2013

This study is interested in manufacturing the self-cleaning silicate concrete surface impregnant including tetra ethyl ortho silicate, lithium silicate for the repair of the exposed concrete surface and the color concrete requiring the advanced function in view of the concrete appearance. The concrete surface layer change and static contact angel was tested for the review of application. The result of this study shows that the effective silicate is tetra ethyl ortho silicate and lithium silicate. The adhesion in tension is satisfied with performance requirement of KS standard but the reinforcement of concrete substrate is slight. So, The self-cleaning silicate concrete impregnant of this study is more desirable for the improvement of durability rather than the reinforcement.

• The Korean Journal of Mycology
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• v.15 no.3
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• pp.158-168
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• 1987

Several species of the fungi were isolated from cassava(Manihot esculenta Gruntz) starch which had formed into pellet, those had been stored for a while in southern part of Thailand. The species of Rhizopus, Aspergillus niger, and Aspergillus fumigatus were identified. The experimental results are as follows; Dry weight increases were checked during the static liquid culture with modified Czapek Dox medium to which cassava starch was partly replaced to sugar, Aspergillus niger and Aspergillus fumigatus had grown more than Rizopus species when 6% cassava starch was replaced to sugar and had been cultured for 72 hours. Amounts of mycelial protein of Aspergillus niger were checked, the highest amount was shown in 6% cassava starch involved medium. When nitrogen sources were varied such as ammonium sulfate or urea against sodium nitrate, there was no significant difference in mycelial production. Alpha amylase activity of each fungus isolated here was checked, those of Aspergillus niger have shown the highest peak at 72 hours.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.155-171
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• 2023

Aiming at the grouting treatment of water inflow in karst conduits, a visualized experiment system for conduit-type grouting blocking was developed. Through the improved water supply system and grouting system, and the optimized multisource information monitoring system, the real-time observation of diffusion and deposition of slurry, and the data acquisition of pressure and velocity during the whole process of grouting were realized, which breaks through the problem that the monitoring element is easy to fail due to slurry adhesion in conventional test system. Based on the grouting experiments in static and flowing water, the diffusion and deposition behavior of the quick-setting slurry under different working conditions were analyzed. The temporal and spatial variation behavior of the pressure and velocity were studied, and the blocking mechanism of the grouting were further revealed. The results showed that: (1) Under the flowing water condition, the counter-flow diffusion distance of slurry was negatively correlated with the flow water velocity and the volume ratio of cement and sodium silicate (C-S ratio), and positively correlated with the grouting volume. The slurry deposition thickness was negatively correlated with the flowing water velocity, and positively correlated with the grouting volume and C-S ratio. (2) The pressure increased slowly before blocking of the flowing water and rapidly after blocking in karst conduits. (3) With the continuous progress of grouting, the flowing water velocity decreased slowly first, then significantly, and finally tended to be stable. According to the research results, some engineering recommendations were put forward for the grouting treatment of the conduit-type water inflow disaster, which has been successfully applied in the treatment project of the China Resources Cement (Pingnan) Limestone Mine. This study provided some guidance and reference for the parameter optimization of grouting for the treatment projects of water inflow in karst conduits.

• Journal of Adhesion and Interface
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• v.20 no.3
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• pp.87-95
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• 2019

In the present study, the effect of alkali treatment of rice straw on the flexural properties and impact strength of rice straw/recycled polyethylene composite was investigated. Alkali treatments were performed by means of two different methods at various sodium hydroxide (NaOH) concentrations. One is static soaking method and the other is dynamic shaking method. The composites were made by compression molding technique using rice straw/recycled polyethylene pellets produced by twin-screw extrusion process. The result strongly depends on the alkali treatment method and concentration. The shaking method done with a low concentration of 1 wt% NaOH exhibits the highest flexural and impact properties whereas the soaking method done with a high concentration of 10 wt% NaOH exhibits the highest properties, being supported qualitatively by the fiber-matrix interfacial bonding of the composites. The properties between the two highest property cases above-described are comparable each other. The study suggests that such a low concentration of 1 wt% NaOH may be used for alkali treatment of natural fibers to improve the flexural and impact properties of resulting composites, rather than using high concentrations of NaOH, 10 wt% or higher. Considering of environmental concerns of alkali treatment, the shaking method is preferable to use.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.4
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• pp.361-368
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• 2021

The objective of this study was to establish technology for removing bacteria with human- and eco-friendly material. Staphylococcus aureus as an important component for balanced equilibrium among microbiomes, was cultured under various concentrations of phosphate. Experimental observation relating to physical properties was performed in an addition of phosphate buffer. Statistically minimum value of size and hardness using atomic force microscope was observed on the matured biofilm at 5 mM concentration of phosphate. As a result of absorbance for the biofilm tagged with dye, concentration of biofilm was reduced with phophate, too. To identify whether this reduction by phosphate at the 5 mM is caused by counter ion or not, sodium chloride was treated to the biofilm under the same condition. To elucidate components of the biofilm counting analysis of the biofilm using time-of-flight secondary ion mass spectrometry was employed. The secondary ions from the biofilm revealed that alteration of physical properties is consistent to the change of extracellular polymeric substrate (EPS) for the biofilm. Viscoelastic characterization of the biofilm using a controlled shear stress rheometer, where internal change of physical properties could be detected, exhibited a static viscosity and a reduction of elastic modulus at the 5 mM concentration of phosphate. Accordingly, bacteria at the 5 mM concentration of phosphate are attributed to removing the EPS through a reduction of elastic modulus for bacteria. We suggest that the reduction of concentration of biofilm induces dispersion which assists to easily spread its dormitory. In conclusion, it is elucidated that an addition of phosphate causes removal of EPS, and that causes a function of antibiotic.