• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1700-1711
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• 2015

In the last decade it has been witnessed significant developments in the area of nano particles and nano scale fillers on electrical, thermal, and mechanical properties of polymeric materials such as resins, varnishes, enamel and bakelites. The electric and thermal properties were more important in the electrical equipments for both steady state and transient state conditions. This paper deals with the characterization of the electric and thermal properties of the pure varnish and zirconia (ZrO₂) filler mixed varnish. The electric properties such as dielectric loss (tan δ), dielectric constant (ε), dielectric strength and partial discharge voltage were analyzed and detailed for different samples. It was observed that zirconia nano filler mixed varnish has the superior dielectric and thermal properties when compared to those of standard varnish. It has shown that at power frequency the 1wt% nano composite sample has the higher permittivity value when compared to other samples. It has been examined that the 1wt% sample was having higher inception and extinction voltages when compared to other samples. It has been observed that 1wt% sample has higher dielectric strength when compared with other samples. There has been an improvement of thermal property by adding few weight percent of zirconia nano fillers. There was not much variation in glass transition among the nano mixed composites. The weight loss was improved at 1wt% of the zirconia nano fillers.

• Korean Journal of Dental Materials
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• v.43 no.1
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• pp.81-89
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• 2016

The purpose of this study was to evaluate the effect of the experimental and commercial fluoride varnishes on the Vickers hardness of bovine teeth. The experimental fluoride varnishes with 5 wt.% NaF were fabricated using Bis-GMA or rosin as the resin base. The components were mixed with over-head stirrer under warming up in a double boiler for 30 minutes. Four commercial fluoride varnishes (V-varnish, Flor-opal, Cavity shield, Fluor protector) were compared with the experimental fluoride varnishes. Vickers hardness was measured on the labial surface of bovine anterior teeth after applying fluoride varnish on 5th and 30th day. The surface of bovine teeth was observed with a scanning electron microscope before and after applying fluoride varnish and the change of the components on the bovine teeth surface was measured with EDX. In terms of hardness, the experimental rosin-based fluoride varnish showed significantly higher hardness on the 5th and 30th day than the control (bovine teeth without fluoride treatment)(p<0.05). EDX results showed that the fluoride content on the surface of bovine teeth treated with the experimental rosin-based fluoride varnish was highest on the 1st and 10th day. The higher hardness and fluoride content of experimental rosin-based fluoride varnish can be considered to be used as an effective fluoride varnish to prevent dental caries.

• Geomechanics and Engineering
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• v.33 no.3
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• pp.291-299
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• 2023

Monitoring contaminants in waste landfills on a seabed is important because the leachate affects the marine ecosystem and facility stability. The objective of this study is to optimize a time-domain reflectometry (TDR) probe using different coating materials and several electrodes to estimate contaminants in saline soil. Copper concentrations ranging from 0 mg/L to 10 mg/L were mixed in 3% salinity water to simulate contaminants in the ocean environment. Epoxy, top-coat, and varnish were used as coating materials, and two to seven electrodes were prepared to vary the number and arrangement of the electrodes. Test results showed that the varnish stably captured the increase in copper concentration, while the other coating materials became insensitive or caused leakage current. In addition, a TDR probe with more electrodes exhibited stable and distinct electromagnetic signals. Thus, the TDR probe with seven electrodes coated with varnish was effectively used to estimate contaminants in saline soil.

• Textile Coloration and Finishing
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• v.34 no.4
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• pp.250-260
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• 2022

In this research, a high-elasticity acrylic emulsion binder with core-shell polymerization and self-crosslinking system is mixed with a flame-retardant water-dispersed polyurethane (PUD) binder. In addition, finite element analysis was conducted through virtual engineering software ANSYS by applying three representative nonlinear material models. The most suitable nonlinear material model was selected after the relative comparison between the actual experimental values and the predicted values of the properties derived from simulations. The selected nonlinear material model is intended to be used as a nonlinear material model for computational simulation analysis that simulates the experimental environment of the vibration test (ASTM E1399) and the actual fire safety test (ASTM E1966). When the mass fraction of thermally expandable graphite was 0.7%, the thermal and physical properties were the best. Among the nonlinear material models, the simulation result of the Ogden model showed the closest value to the actual result.

• Conservation Science in Museum
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• v.15
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• pp.78-95
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• 2014

To examine the materials, production techniques, and key features of Goryeo wooden lacquerwares, scientific analysis was conducted on six relevant lacquerware items. All of the items, except for a lacquered bowl ^{duksu 4123}, were found to have been made by first covering the surface of the wood with cloth and then varnishing with lacquer. The wooden frames of flower-shaped lacquered case and pine leaves shape lacquered case were made by wrapping thin wood around either the lid or bottom panel. In most cases, microscopic analysis revealed a lower layer of lacquer mixed with bone ash and bone dust, followed by an upper varnish layer of lacquer. SEM-EDS analysis and μ-XRF ^{Micro-X-ray Fluorescence} analysis showed that vermilion lacquer mixed with cinnabar was used on the surface. A lid decorated with a dot pattern was made by first varnishing the surface with yellow lacquer mixed with orpiment, and then irregular dot pattern with a mixture of black lacquer and soot. The vermilion lacquer used to varnish the side of the lacquered bowls was composed of lacquer mixed with cinnabar and minium ^{Red Lead}.

• Journal of Korean society of Dental Hygiene
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• v.12 no.2
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• pp.335-343
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• 2012

Objectives : The aim of this investigation was to evaluate the remineralization effect of Bamboo salt and NaF+Bamboo salt solutions on bovine enamel formed incipient artificial enamel caries by microcomputed tomography (micro CT). Methods : Experimental solutions were distilled water(negative control), 2% sodium fluoride solution (2% NaF group), 3% bamboo salt solution (3% BS group) and the solution mixed 2% sodium fluoride solution and 3% bamboo salt solution (2% NaF+3% BS group). Specimens were prepared from extracted bovine teeth and divided into 4 groups of 10 specimens each by randomized blocks according to density. Then the specimens surface were divided equally into three parts to observe sound enamel area, incipient enamel carious area and remineralized enamel area. Only one-third of specimen surface was coated with nail varnish and these were exposed to a lactate carbopol buffer system for 72 hours. Then one-half of the demineralized enamel area was coated with nail varnish. The specimens were carried out under pH cycling model for 14 days as follows; samples were immersed in each experimental solution for 2 mins 3 times per day, demineralized for 4 hours and in mixed saliva for the remaining hours. After pH cycling, density was measured using micro CT. Results : All experimental groups showed remineralization effects except for negative control group(p<0.05). The differences of density after experimental solution treatment were statistically significant difference among 4 groups (p<0.01). The density difference values of groups were $0.04{\pm}0.01$ in negative control group, $0.19{\pm}0.01$ in 2% NaF group, $0.14{\pm}0.01$ in 3% BS group, and $0.21{\pm}0.01$ in 2% NaF+3% BS group. Conclusions : The bamboo salt solution showed remineralization effects on incipient artificial enamel caries and the solution mixed sodium fluoride solution and bamboo salt solution showed more remineralization effects than the bamboo salt solution. Thus, it is suggested that bamboo salt can be used as remineralization agent in incipient enamel caries lesion.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.797-810
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• 1998

The purpose of this study was to develop a new way of delivery system of chlorhexidine using self-curing acrylic resin. Different preparations of chlorhexidine, such as chlorhexidine varnish($Chlorzoin^{(R)}$) and chlorhexidine diacetate crystalline, were mixed into self-curing acrylic resin with different methods. Every resin plate was made and was immersed in 100ml of distilled water individually, and kept in an incubator at $37^{\circ}C$. Solution(0.8ml) was collected from the each container at every 24 hours, and the amount of released chlorhexidine in the solution was measured in an ultraviolet spectrophotometer at 255nm. Flexural strength of all of the resin plates in the Experiment 2-A and 2-B were measured using Instron at the end of the experimental periods. The results were as follows: 1. It was found that chlorhexidine was released from the experimental groups in the Experiment 1, 2-A, and 2-B. And the release of chlorhexidine from all of the experimental groups showed a pattern of sustained-release preparation. 2. It seemed likely that a condition of "dryness" reduced a release of chlorhexidine from the chlorhexidine varnish. 3. It may be stated that a method of "chlorhexidine diacetate mix" with the polymer be more efficient than a method of "Chlorzoin mix" with the monomer. 4. Although it was evident that a flexural strength of the acrylic resin plates be reduced by a mix of either Chlorzoin or chlorhexidine diacetate crystalline, it seemed likely that the resin plates except Group 4 and 5 in the Experiment 2-B may be usable in the clinical situation.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.371-376
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• 2009

We evaluated in vitro microleakage of Mineral Trioxide Aggregate (MTA) powder with 4-methacryloxyethyl trimellitate anhydride (4-META) / methyl methacrylate (MMA) & tri-n-butylborane (TBB) resin as a retrograde filling material by using methylene blue dye method. Fifty-two single rooted, extracted teeth were instrumented and obturated with gutta percha and AH plus sealer. The apical 3mm of each root was resected and 3mm deep ultrasonic root end preparation was done. External surface of roots was coated with nail varnish. Prepared teeth were randomly divided into five groups; Negative control: completely covered with nail varnish; Positive control: coated with nail varnish except for apical foramen; Group 1 (retrofilled with Portland cement); Group 2 (retrofilled with MTA); Group 3 (retrofilled with MTA powder mixed with 4-META/MMA & TBB resin). Immediately after completion of root-end filling, all specimens were submerged in methylene blue dye for 72 hours in $37^{\circ}C$incubator. The roots were longitudinally sectioned and measured for extent of dye penetration by three different examiners under microscope (${\times}$10). The results were statistically analyzed using one way ANOVA and Turkey's HSD test. No leakage was evident in negative control and complete leakage in positive control group. Group 3 showed significantly less leakage than group 1 and 2 (p < 0.01). There was no significant difference between group 1 and 2 (p > 0.01). It was concluded that MTA powder with 4-META/MMA & TBB resin was excellent in reducing initial apical microleakage.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1712-1719
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• 2015

In recent days, there was a significant development on the electrical, thermal, mechanical, physical, chemical, magnetic and optical properties of the polyamide enamel, varnish and other insulating materials by the addition of nano fillers to it. Enamel was used in High Voltage Apparatuses used in Medical Electronics as insulation. Insulating materials determine the life time of the electrical apparatuses. The life time of the insulating materials was improved by the addition of nano fillers to it. Hence the life time of the electrical apparatuses was improved by the mixing of nano fillers to the enamel. In this research, the basic dielectric properties of the enamel and enamel mixed with nano composites of silica and alumina were analyzed and compared with each other. The addition of nano fillers has improved the quality factor and capacitance of the enamel. It was also observed that the addition of nano fillers has reduced the dissipation factor and dielectric losses of the enamel. Heat produced by the dielectric losses was also reduced by adding nano fillers to it.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.447-463
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• 1997

The purpose of this study was to evaluate the effectiveness of copal varnish and five bonding agents(Scotchbond Multi-Purpose Plus Dental Adhesive System, Panavia 21, All Bond 2, Superbond D-Liner II plus, Fuji Duet) in reducing microleakage under amalgam restorations. Class V cavity were prepared on both buccal and lingual surface of sixty extracted human molars with cementum margin and were filled with different kinds of liners and amalgam. All teeth were stored at $37^{\circ}C$ in physiologic saline solution. After 1 week they were thermally stressed for 500 cycles between 5 and $55^{\circ}C$ in baths containing 0.5 % basic fuchsin dye. The dye penetrations were observed with a stereomicroscope. Scanning electron micrographs were taken of representative tooth sections from each group to assess the nature of the tooth/liner/amalgam interface. The statistical test were applied to the results using a one way analysis variance (ANOVA) and Duncan's multiple range test. The results were as follows ; 1. In all groups, the enamel margin showed significantly lower leakage value than the cementum margin (p<0.05). 2. At the dentin and enamel margins, the leakage value of Copalite-lined group showed significantly higher than that of no liner group (p<0.05), but showed significantly lower than that of bonding agent lined-groups (p<0.05). 3. There was no significant difference between the bonding agent lined-groups (p>0.05). 4. On the backscattered scanning electron microscopy observation, discontinuous gaps were observed between amalgam and dentin in the bonding agent-lined amalgam restorations and the bonding agents appeared to fill the gap space and were mixed with amalgam particles. At the amalgam/tooth interface, unsealed dentin and continuous gaps were found in both unlined and Copalite-lined restorations.