• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.529-538
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• 2021

In this study, the compressive strength and water contact angle were measured before and after surface abrasion of mortar specimens prepared by mixing two types of water repellents and two types of sands. In addition, the hydration products and chemical bonding of cement mortar by repellent were examined using X-ray diffraction(XRD), thermogravimetry-differential thermal analysis(TG-DTA), and Fourier-transform infrared spectroscopy(FT-IR) to evaluate the performance of these cement mortar mixtures as repair materials. We found that the compressive strength of the cement mortar with water repellent added was decreased compared to that of the plain cement mortar, and that of the oligomeric system was higher than that of the monomeric system. We further found that the contact angle of mortar with water repellent added was increased compared to that of the plain cement mortar, and that of the oligomeric system was increased compared to that of the monomer.

• Journal of the Korean Wood Science and Technology
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• v.50 no.4
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• pp.283-298
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• 2022

Wood has always been used for various day-to-day applications such as interior or exterior construction materials, and household products. However, it can undergo photodegradation and discoloration by environmental factors including ultraviolet (UV) light, and thus has shortened its service life. Bleaching or delignification of wood surfaces is a suitable solution to stabilize wood against weathering by UV because these techniques can alter or remove the chromophores in lignin, which is a main factor of wood discoloration. To improve the color stability of wood surface according to the lifespan, surface delignification was conducted using peracetic acid (PAA) and hydrogen peroxide (HP) on the woods of Larix kaempferi and Quercus mongolica. After the PAA treatment, L^* increased considerably from 60-70 to 90-95. Furthermore, wood surface color did not change significantly after UV exposure. The color differences (𝜟E^*) between before and after PPA treatment of wood showed the 4.8-12.2 of L. kaempferi, and 1.7-3.7 of Q. mongolica, respectively. The lignin-related peaks in Fourier transform infrared spectroscopy (FT-IR) spectra disappeared with increased duration of PAA treatment. These results confirmed that the lignin component was partially or completely removed after the PAA treatment; the color differences (𝜟E^*) clearly showed that there was a reduction in redness (a^*) and yellowness (b^*), and an increase in lightness (L^*) owing to the removal of lignin. Based on these results, this study demonstrated that the partial removal of lignin from wood surfaces is a fundamental method for resolving photo-degradation.

• Microbiology and Biotechnology Letters
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• v.51 no.2
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• pp.157-166
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• 2023

Three lactic acid bacteria (LAB) producing exopolysaccharides (EPSs) were isolated from Pa (green onion)-kimchi, and identified as Weissella confusa (SKP 173), Weissella cibaria (SKP 182), and Leuconostoc citreum (SKP 281), respectively by 16S rRNA gene sequencing. The yields of EPS were 21.27, 18.53, and 15.4 g/l for EPS from SKP 173, 182, and 281, respectively when grown in MRS broth containing sucrose (5%, w/v). Total sugar contents were 64.39, 62.84, and 65.16% (w/w) for EPS from SKP 173, 182, and 281, respectively while the protein contents were 0.33, 0.31, and 0.25% (w/w), respectively. EPSs from W. confusa SKP 173 and W. cibaria SKP 182 contained glucose only but EPS from L. citreum SKP 281 contained glucose and glucitol. Viscosities of the 2% (w/w) freeze-dried EPS solution were 9.60, 8.00, and 8.20 centipoise (cP) for EPS from SKP 173, 182, and 281, respectively. Viscosities of culture grown in MRS broth with 5% sucrose (no glucose) were 92.98, 57.19, and 18.8 cP, respectively. The average molecular weights of EPSs were larger than 2 × 10⁷ Da. Fourier transform infrared spectroscopy (FT-IR) analyses of EPSs showed typical carbohydrate peaks, suggesting that the EPSs consisted of pyranose saccharides with α-(1,6) and α-(1,3) glycosidic linkages. L. citreim SKP 281 was used as the starter for yogurt fermentation, and EPS production was confirmed.

• Advances in nano research
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• v.15 no.4
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• pp.295-304
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• 2023

In this paper, a powerful photocatalyst based on carbon nanocomposite is developed in order to obtain a new material applicable in water treatment and especially for the discoloration of effluents used in the textile industry. For that, TiO₂-graphene nanocomposites have been successfully synthesized by a mixture of Functionalized Graphene Sheet (FGS) and tetrachlorotitanium complexes to form FGS-TiO₂ nanocomposite. In the presence of an anionic surfactant, we used a new chemical process to functionalize graphene sheets in order to make them an excellent medium for blocking and preventing the aggregation of TiO₂ nanoparticles. The components of these nanocomposites are characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), which confirms the successful formation of the FGS-TiO₂ nanocomposite. It was found that the TiO₂ nanoparticles were dispersed uniformly on the graphene plane which possesses better charge separation capability than pure TiO₂. The FGS-TiO₂ nanocomposites exhibited higher photocatalytic activity compared to pure TiO₂ for the removal of three dyes: such as Methylene Blue (MB), Bromophenol Blue (BB) and Alizarin Red-S (AR) in water. The removal process was fast and more efficient with FGS-TiO₂ nanocomposite in daylight (in the absence of UV irradiation) compared to pure TiO₂ nanoparticles without and under UV in all pH range.

• Analytical Science and Technology
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• v.37 no.4
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• pp.220-229
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• 2024

This study aims to developing a method for estimating pharmaceutical compounds within a monolith column using high-performance liquid chromatography (HPLC). The monolithic column was prepared using copolymerization of glycidyl methacrylate, co-ethylene dimethacrylate, and co-acrylic acid inside a borosilicate tube of specific dimensions a 60 mm borosilicate tube length with 1.5 mm and 3.5 mm inner and outer diameters, respectively. A UV Ultra violet source with a wavelength of 365 nm was used, and the polymerization process involved mixing glycidyl methacrylate, acrylic acid, ethylene dimethacrylate as a binder, and 2,2-dimethoxy-2-phenyl acetate phenone as an initiator in suitable solvents consisting of ethanol and 1-hexanol. The polymerization process formed the monolith column after 4 minutes, and subsequently, the epoxy groups were altered to diol groups using 0.2 M hydrochloric acid HCl, which were pumped through the column for 3 hours at a flow rate of 10 µL·min^-1. Various techniques, such as Scanning Electron Microscope SEM, Brunauer-Emmett-Teller BET, Fourier-transform infrared spectroscopy FT-IR and HNMR, were utilized to characterize and confirm the structure of the monolith. The prepared monolith was employed to estimate and identify the pharmaceutical compound of warfarin using high-performance liquid chromatography HPLC. The analytical curve of warfarin was linear in the range of 3 to 100 ㎍·mL^-1 with an r² value of 0.999. The detection and quantification limits were 0.932 and 2.788 ㎍·mL^-1, respectively. The molar absorptivity and Sandells sensitivity were 2.99138 × 10⁶ L·mol^-1·cm^-1 and 103.1 × 10^-3 ㎍·cm^-2, respectively.

• Membrane and Water Treatment
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• v.15 no.4
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• pp.163-176
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• 2024

Asymmetric flat sheet poly(vinylidene fluoride) (PVDF) membranes were fabricated using the phase inversion technique, employing four distinct solvents with varying solubility power: N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), Dimethyl sulfoxide (DMSO), and N-Methyl-2-pyrrolidone (NMP). The influence of these solvents on the crystalline properties of the polymers was investigated using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) to elucidate their role in PVDF polymorphism during membrane formation. Our findings revealed significant variations in membrane crystalline phase due to the dissolution of PVDF in different solvents, with α-polymerization predominant in membranes cast with NMP and DMSO, while DMF and DMAc solvents favored β-type polymerization. Further, various additives including PEG-400, TiO2, LiCl, LiBr, acetone, ethanol, propanol, and water were employed to evaluate their impact on membrane morphology and properties. Scanning electron microscopy (SEM) and Ultimate testing machine (UTM) were utilized to analyze membrane morphology, while the tensile strength, contact angle, pore size, and porosity were estimated using the sessile drop method, imageJ, and gravimetric method, respectively. Our results demonstrated that all additives exerted influence on membrane morphology and properties depending on their characteristics and interactions with solvents and polymers. Notably, acetone, being volatile, facilitated the formation of a thin PVDF layer on the membrane surface, resulting in a reduced average pore size (0.18㎛). Conversely, LiCl and LiBr acted as pore-forming additives, yielding membranes with distinct pore characteristics and porosity. Moreover, water as a non-solvent additive induced pregelation during the nonsolvent-induced phase separation (NIPS) process, thereby promoting pore formation (53% porosity) and enhancing membrane hydrophobicity (104° contact angle). To evaluate the quality of synthesized membranes, permeate flux ranging from 16.2 L/m².hr to 27.9 L/m².hr with a salt rejection rate of 98 %, was evaluated using Vacuum Membrane Distillation (VMD).

• Journal of Pharmaceutical Investigation
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• v.31 no.3
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• pp.151-160
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• 2001

The purpose of this study is to investigate the interaction of progesterone with various cyclodextrins (CDs) in the aqueous solution and in solid state, and finally to formulate a parenteral aqueous formulation. CDs used were ${\alpha}-$, ${\beta}-$, and ${\gamma}-CD$, $2-hydroxypropyl-{\beta}-CD$ (HPCD), sulfobutyl $ether-{\beta}-CD$ (SBCD), $dimethyl-{\beta}-CD$ (DMCD) and $trimethyl-{\beta}-CD$ (TMCD). The solubility studies of progesterone were performed in the presence of various CDs as a function of concentration or temperature. The solubility of progesterone increased in the rank order of ${\alpha}-CD$ < ${\beta}-CD$ < ${\gamma}-CD$ < TMCD$ < HPCD < DMCD < SBCD. Addition of SBCD (200 mg/ml) in water increased the aqueous solubility $(9.36\;{\mu}g/ml)$ about 3,200 times, and lowering the temperature facilitated the solubilization of progesterone. However, the addition of HPCD and SBCD in 20:80 (v/v) polyethylene glycol 300-water and propylene glycol-water cosolvents markedly decreased the solubility of progesterone, compared with solubilizing effects in water. Physical mixtures and solid dispersions of progesterone with HPCD or SBCD were prepared, and evaluated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), near IR spectroscopy and dissolution studies. By DSC and IR studies, it was found that progesterone was dispersed in HPCD in monotectic state and dissolved rapidly from both solid dispersions. Based on solubility studies, new aqueous progesterone fonnulations (5 mg/ml) containing SBCD (200 mg/ml) could be prepared and did not form precipitates even after 2 months at $4^{\circ}C$. The solution was transparent when mixed with normal saline and 5% dextrose injection at 1: 1, 1:10 and 1:20 (v/v) even after 7 days. Permeation rates of progesterone through a cellulose membrane from 20% PEG 300 solution $(50\;{\mu}g/ml)$ containing HPCD or SBCD were compared with oily formulation. Permeation of progesterone from oily formulation did not occur up to 8 hr, but aqueous formulations showed fast permeation rates from early stage of permeation study. The addition of HPCD or SBCD retarded the permeation rates of progesterone with the increase of CD concentrations, suggesting the possibility of a controlled absorption from the site administered intramuscularly. These results demonstrate that it is feasible to develop a new progesterone parenteral aqueous injection (5 mg/ml) using SBCD.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.61-69
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• 2009

Statement of problem: Porcelain veneers have become a popular treatment modality for aesthetic anterior prosthesis. Fitting porcelain veneers in the mouth usually involve a try-in appointment, which frequently results in salivary contamination of fitting surfaces. Purpose: An in vitro study was carried out to investigate the effect of silane treatment timing and saliva contamination on the resin bond strength to porcelain veneer surface. Material and methods: Cylindrical test specimens (n=360) and rectangular test specimens (n=5) were prepared for shear bond test and contact angle analysis. Whole cylindrical specimens divided into 20 groups, each of which received a different surface treatment and/or storage condition. The composite resin cement stubs were light-polymerized onto porcelain adherends. The shear bond strengths of cemented stubs were measured after dry storage and thermocycling (3,000 cycles) between 5 and $55^{\circ}C$. The silane and their reactions were chemically monitored by using Fourier Transform Infrared Spectroscopy analysis (FTIR) and contact angle analysis. One-way analysis of variance (ANOVA) and Dunnett's multiple comparison were used to analyze the data. Results: FT-IR analysis showed that salivary contamination and silane treatment timing did not affect the surface interactions of silane. Observed water contact angles were lower on the saliva contaminated porcelain surface and the addition of 37% phosphoric acid for 20 seconds on saliva contaminated porcelain increased the degree of contact angle. Silane applied to the porcelain, a few days before cementation, resulted in increasing the bond strength after thermocycling. Conclusion: Within the limitation of this study, it can be concluded that it would be better to protect porcelain prosthesis before saliva contamination with silane treatment and to clean the contaminated surface by use of phosphoric acid.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.215-225
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• 2015

Recently, the importance of energy saving and alternative energy is significantly increasing due to energy depletion and the phase change material (PCM) research for saving energy is also actively investigating. In this research, the membrane emulsification using SPG membrane was used to make various microencapsulated phase change material (MPCM) particles which were comprised of $Rubitherms^{(R)}$ (RT-21 and RT-24) core and silica coating. We investigated the pressure of the dispersion phase, the concentration of surfactant, and the ratio of $Rubitherm^{(R)}$ and silica to prepare various MPCM particles. The DSC and TGA were used to examine the heat stability and latent heat properties. Also, PSA, SEM, and optical microscopy were used to confirm the size of $Rubitherm^{(R)}$ particles and the thickness of silica shell. The average of particle size was $7-8{\mu}m$. And, FT-IR was also used to enforce the qualitative analysis. Finally, the MPCM particles obtained from membrane emulsification showed monodispersed size distribution and the heat stability and latent heat were kept up to 80% compared to pure $Rubitherm^{(R)}$. So, it can be effectively used for wallpaper, buildings and interior products for energy saving as PCMs.

• Fire Science and Engineering
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• v.30 no.6
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• pp.57-63
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• 2016

In this study, the toxicity of combustion products of wood-based materials (MDF, OSB) were analyzed using experimental animal techniques. The average deed stopping time of MDF was shorter than that of OSB. This means that the toxicity of the combustion products of MDF is higher than that of OSB. To analyze the cause of the result quantitatively, Fourier transform infrared spectroscopy (FT-IR) of the gas phase materials was performed. Qualitative analysis result, CO and $CO_2$ were detected. Quantitative analysis results, the gas generation rate was higher in OSB than in MDF. Blood analysis of mice revealed, COHb to be higher in OSB than MDF. A correlation between the gas generation rate and COHb was found. Currently, the toxicity of the combustion products of the materials is being examined using the toxicity index, such as Fractional Effective Dose (FED). The FED is based on the gas emissions. The average deed stopping time decreased with increasing toxicity of exposed material. On the other hand, the result of this study showed that, the CO emissions of OBS were 186.5% that of MDF. The COHb of OSB was > 129.6% that of MDF. Nevertheless, the average deed stopping time of the OSB is 51 seconds longer than that of MDF. Therefore, more toxicity studies on factors other than the gas phase materials in the combustion products will be needed.