• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.2
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• pp.129-138
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• 2012

The aim of this in vitro study was to evaluate the effectiveness of experimental 2.26% fluoride-polyvinyl alcohol (F-PVA) tape in inhibition of enamel demineralization using enamel surface microhardness (SMH) analysis and scanning electron microscopy (SEM) examination. Enamel specimens (n=60) randomly assigned to four groups: control group, F-PVA tape group, fluoride varinish (F-varnish) group, casein phosphopeptide-amorphous calcium phosphate (CPP-ACFP) group. After topical application, pH-cycling was processed. Then, SMH was measured and the percentage loss of surface microhardness (%SML) was calculated. For the SEM examination, five sample specimens in each group were treated and the morphologic character was evaluated. After pH-cycling, the SMH values of the enamel specimens of F-PVA tape and F-varnish group were significantly higher than that of CPP-ACFP group, there was no significant difference between F-PVA tape and Fvarnish group. With SEM examination, enamel surfaces in the F-PVA tape group and F-varnish group showed numerous spherical and ovoid crystals formed on the enamel surface were also observed. The density of crystals was higher than that of both control group and CPP-ACFP group. F-PVA tape is effective in inhibition of enamel demineralization. Also, F-PVA tape's inhibition of enamel demineralization is comparable to that of F-vanish and greater than that of CPP-ACFP.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.755-764
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• 2020

Due to pronounced mechanical performance and being environmental friendly, aqueous polymer isocyanate adhesive (API) has been widely applied in the production of formaldehyde-free wood products. In this study, flame retardant formaldehyde-free plywood was prepared by incorporation of flame retardants into the API adhesive. Partially phosphorylated poly (vinyl alcohol) (PPVA) which was prepared by reacting poly (vinyl alcohol) with phosphoric acid was used to replace PVA in API formula. In addition, Mg-Al layered double hydroxides (LDH) was chosen as additive flame retardant, replacing traditional filler CaCO₃ in API adhesive formula. And then, the flame retardant API adhesive with main agent (PPVA replacing PVA70wt.%, SBR emulsion 30wt.%), curing agent 10wt.% (accounts for of the main agent), and 20wt.% LDHs (accounts of the main agent) was used to prepare flame retardant plywood. The effect of application of PPVA and Mg-Al LDH on bonding strength of plywood was investigated. The flammability characteristics of the plywood were determined by cone calorimeter test (CCT). The results revealed that compared with the plywood prepared with API adhesive, the use of PPVA and LDH enhanced the flame retardancy of plywood without negatively affecting bonding strength. The CCT tests indicated that the heat release and smoke production flame retardant API plywood were lower than those of the ordinary API glued plywood. Promising developments for flame retardant API adhesive were expected in future applications of flame retardant formaldehyde-free plywood.

• Journal of Bio-Environment Control
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• v.13 no.1
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• pp.8-15
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• 2004

Seedling mechanization of lettuce is known to be difficult due to the small seed size and the irregular seed shape. The purpose of seed pelleting is to make seedling mechanization possible by enlarging the seed size. After that, it can reduce seedling and thinning labours and can also save seeds. According to the results, there were significant differences on the percent germination and day to 50% final germination in accordance with the pelleting polymer. Among the pelleting polymer, gemination of seeds using polynimyl alcohol (PVA) was generally smooth, and followed by polyvinyl pyrrolidone (PVP), hydroxyethyl cellulose (HEC), methyl cellulose (MC), and wteen 80. The germination rate was also different according to the pelleting particulate matters. Generally, percent germination and speed of seed using the mixture of diatomaceous earth, talc and calcium carbonate were higher and faster than using other polleting materials, respectively. Thus, it should be suitable pelleting particulate matter for the pelleting of lettuce seeds. On the other hands germination of seeds using limestone, calcium oxide and benonite were low. The seed size of lettuce after pelleting was 33 times as large as the raw seed size. During the process of seed pelleting, netrient addition induced the decrement on the germination and the delay of germination speed. Also, there was differences in the germinability of pelleted seeds in accordance with the addition of nutrient sources. MS medium was generally lower than monosodium phosphate in inhibition of seed germination. Germination of pelleted seeds after priming was higher than the seeds without the treatment, and also showed the trend of early germination.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.648-653
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• 2006

As an alternative for the traditional materials packed in biofilters treating gaseous VOCs, a novel packing material has been developed and tested. In the packing material(named as Hydrogel Bead, HB), pollutant-degrading microorganisms were immobilized in hydrogel consisted of alginate, polyvinyl alcohol(PVA), and powdered activated carbon. A closed-bottle study showed that the HB rapidly removed gaseous styrene without the losses of adsorption and biodegradation capacity. Biofilter column experiments using the HBs also demonstrated that greater than 95% of removal efficiencies were found at an inlet styrene loading rate of $245g/m^3/hr$, which was higher biofilter performance than other elimination capacity reported earlier. Furthermore, when the inlet styrene concentration increased stepwise, the adsorption played an important role in overall styrene removals. The absorbed styrene was found to be biodegraded in the following low inlet loading condition. Consequently, the new HB material is able to successfully minimize the drawbacks of activated carbon(necessity of regeneration) and biological processes(low removal capacity at dynamic loading conditions), and maximize the overall performance of biofilter systems treating VOCs.

• Korean Journal of Medicinal Crop Science
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• v.14 no.3
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• pp.130-133
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• 2006

This study was conducted to select Codonopsis lanceolata seed's new pelleting particulate materials and adhesives. Different adhesives (Polyvinyl alcohol (PVA), Carboxymethyl cellulose (CMC), Polyvinyl pyrrolidone (PVP), Xanthan gum (XG), Arabic gum (AG)) and particulate materials (Illite, Diatomite, Pyrophyllite + Illite + Diatomite (PID), Pyrophyllite + Illite + Talc (PIT), Bentonite + Talc (BT)) were tested for seed pelleting. PID for Codonopsis lanceolata seed pelleting appeared to be the best particulate material. Among the pelleting adhesives, PVP was the best adhesive for seed pelleting, and the optimum concentration for germination of pelleting seed was 1 %. Germination rate of the pelleted seeds treated with PID particulate material and PVP adhesive was higher (86.8%) than those of raw seeds (85.5%). $T_{50}$ and MDG of pelleted Codonopsis lanceolata seed required five and eight days at soil moisture content of 50%, respectively.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.513-522
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• 2008

The fiber dispersion performance in fiber-reinforced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion performance in the composite PVA-ECC (Polyvinyl alcohol-Engineered Cementitious Composite) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, an enhanced fiber detection technique is developed and demonstrated. Using a fluorescence technique on the PVA-ECC, PVA fibers are observed as green dots in the cross-section of the composite. After capturing the fluorescence image with a Charged Couple Device (CCD) camera through a microscope. The fibers are more accurately detected by employing a series of process based on a categorization, watershed segmentation, and morphological reconstruction.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.130-137
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• 2023

This study analyzed the effect of mixing order on the flowability, compressive strength, and flexural strength of cement composites reinforced with polyvinyl alcohol(PVA) fibers and multi-walled carbon nanotubes(MWCNTs). The experimental results showed that the addition of CNTs significantly reduced the flowability, and the flowability was considerably affected by the mixing order when CNTs were added. The compressive strength was most effectively improved when water and CNTs solution were mixed first before adding PVA fibers, and the flexural strength was highest when water and CNTs solution were mixed with PVA fibers after dry mixing. However, there was no clear correlation between the flexural toughness and the mixing order. In addition, scanning electron microscopy(SEM) image analysis was conducted to analyze the microstructure. The SEM images showed that CNTs were randomly dispersed through the specimens and contributed to the strength improvement, but the effect of the mixing order was not clearly observed. The main results of this study are expected to be useful for evaluations of workability and material performance of PVA fiber-reinforced cement composites with CNTs.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.5
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• pp.323-330
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• 2023

The development of an analysis model that reflects the microstructure characteristics of polyvinyl alcohol (PVA) fiber-reinforced cementitious composites, which have a highly complex microstructure, enables synergy between efficient material design and real experiments. PVA fiber orientations are an important factor that influences the mechanical behavior of PVA fiber-reinforced cementitious composites. Owing to the difficulty in distinguishing the gray level value obtained from micro-CT images of PVA fibers from adjacent phases, fiber segmentation is time-consuming work. In this study, a micro-CT test with a voxel size of 0.65 ㎛³ was performed to investigate the three-dimensional distribution of fibers. To segment the fibers and generate training data, histogram, morphology, and gradient-based phase-segmentation methods were used. A U-net model was proposed to segment fibers from micro-CT images of PVA fiber-reinforced cementitious composites. Data augmentation was applied to increase the accuracy of the training, using a total of 1024 images as training data. The performance of the model was evaluated using accuracy, precision, recall, and F1 score. The trained model achieved a high fiber segmentation performance and efficiency, and the approach can be applied to other specimens as well.

• KSBB Journal
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• v.26 no.3
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• pp.217-222
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• 2011

Itraconazole is a triazole antifungal agent to inhibit most fungal pathogens. To improve the oral absorption and dissolution of poorly water-soluble itraconazole, microsponge system composed of $Eudragit^{(R)}$ E100 and polyvinyl alcohol(PVA) formulated by quasi-emulsion solvent diffusion method, and its physicochemical properties and pharmacokinetic parameters of itraconazole were studied. The microsponge of itraconazole were discrete free flowing micro sized particles with perforated orange peel like morphology as visualized by scanning electron microscope (SEM). Results showed that the drug loading efficiency, production yield, and particle size of itraconazole microsponge were affected by drug to polymer ratio, the volume of internal phase containing methylene chloride, stirring rate and the concentration of PVA used. Also, the results showed that the dissolution rate of itraconazole from the microsponges was affected by drug to polymer ratio. In other words, the release rate of itraconazole from microsponges was increased from at least 27.43% to 64.72% after 2 h. The kinetics of dissolution mechanism showed that the dissolution data followed Korsmeyer-Peppas model. Therefore, these results suggest that microsponge system can be useful for the oral delivery of itraconazole by manipulating the release profile.

• Journal of Sensor Science and Technology
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• v.1 no.2
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• pp.101-106
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• 1992

pH-ISFETs, the semiconductor pH sensors, were combined with immobilized enzyme membranes to prepare FET type urea and glucose sensors and its operational characteristics were investigated. Photolithography techniques were applied to immobilize enzymes on the $H^{+}$ sensing membrane of the pH-ISFET with photo-sensitive polymers, PVA-SbQ. Fabricated urea and glucose sensors could determine $0.5{\sim}50{\;}mg/dl$ urea concentrations and $10{\sim}1000{\;}mg/dl$ glucose concentrations, respectively.