• Journal of dental hygiene science
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• v.18 no.6
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• pp.367-373
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• 2018

The consumption of beverages among children is rising. The purpose of this study was to examine the effect of kid's drink on dental resin-based pit and fissure sealant. Pororo, I-kicker, Sunkist kids were included in the experimental groups, and Samdasu was included in the control group. A conventional dental sealant material ($Clinpro^{TM}Sealant^{(R)}$) was selected for this study. Resin specimens (8 mm in diameter and 1 mm in thickness) were prepared according to manufacturers' instructions and the initial roughness (Ra) was then measured. The pH of all the four groups was measured using a pH meter. The specimens were individually immersed in 5 ml of the experimental solutions and stored at $37^{\circ}C$ for 72 hours. Following this, the surface roughness of the resin specimens was measured by Surftest. The concentration of residual monomer released was determined by high performance liquid chromatography (HPLC). The surface morphology of the resin specimen was evaluated before and after storage by scanning electron microscopy (SEM). Data were statistically analyzed using Kruskal-Wallis and Duncan's test. The results showed that all the children's beverages examined in this study contained citric acid. The pH of I-kicker was the lowest ($3.03{\pm}0.01$), followed by that of Sunkist kids ($3.26{\pm}0.02$) and Pororo ($3.47{\pm}0.02$). We observed an increase in the surface roughness of resin specimens after 72 h of immersion in all the beverages tested (p<0.05). There was matrix degradation after immersion, visualized on SEM image, in all the beverage groups. Bisphenol-A-glycidyl methacrylate was not detected after 72 hours, but triethylene glycol dimethacrylate levels were increased in all the beverages tested during the 72 hours by HPLC. These results suggest that intake of beverages containing acid can cause degradation of the resin-based pit and fissure sealants in children.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.150-159
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• 2019

The bond analysis model equation was proposed through the regression analysis of the experimental values of bond behavior for each rebar. In order to verify the appropriateness of the bond analysis model equation, the bond behaviors calculated by the proposed bond analysis model, BPE model and CMR model were compared with experimental values. The proposed bond model showed the closest behavior to the experimental values when compared to other analysis models. The former models can not consider the different properties of GFRP rebar according to composed materials, mixing and manufacturing method and the latter has limitation to express the relationships between bond behavior because of derived formula by numerical analysis. This study proposed the analytical model different considering bond mechanism according to surface type. In order to verity the appropriateness of the bond analytical model, the bond behaviors calculated by the proposed bond analytical model, BPE model and CMR model were compared with experimental values. The proposed bond model showed the closest behavior to the experimental values when compared to other analysis models.

• The Korean Journal of Nuclear Medicine Technology
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• v.23 no.1
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• pp.40-44
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• 2019

Purpose Glomerular filtration rate (GFR) is an important index for evaluation of renal function, renal disease diagnosis and progress monitoring. Therefore, accurate measurement of GFR is clinically important. Among the factors that affect the GFR result, there have been many discussions on the methods such as the correction of the kidney depth, net syringe count, and the method of setting the ROI. However there has been no consideration of counting in the most basic factors like height and weight measurement. In this study, we investigate how height and weight changes affects the result of GFR and review the importance of standardized body measurements. Materials and Methods Fifty patients who underwent GFR test were randomly sampled and examined for changes in height and body weight within one month. From the normal patients without renal disease to the patients with severely decreased GFR, we applied the GFR formula of Gate with varying height and weight. Results: The result showed variation of the height at maximum three centimeters and six kilograms of weight. The first calculation of GFR was done with fixed height value and control variable as weight. Weight was incremented by one kilogram each time up to six kilograms. The GFR showed increased result with increasing weight. The result of GFR showed ten percent increase with six kilograms of weight increase. On the other hand, when height value was incremented by one centimeter up to three centimeters showed decreased GFR result with fixed weight value. Up to three centimeters of height increase showed two percent of decreased GFR with fixed weight. Conclusion This study showed varying GFR result when height and weight changes. Therefore it is clinically crucial not only to maintain and manage body measuring instrument but also to have a standardized measurement methods to derive accurate measured values and to achieve reproducibility.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.5
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• pp.187-191
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• 2019

Perovskite-type oxides have consistently attracted considerable attention for their applications in high-temperature electrochemical devices, such as electrolytes and electrodes of solid oxide fuel cells, oxygen permeating membranes and sensors etc. Among them, the electrical conductivity of 10 % Sr and 10 % Mg doped $LaAlO_3$ (LSAM9191) was measured using impedance spectroscopy and 4-probe d.c. method. Below $550^{\circ}C$, the grain boundary resistance mostly determined the overall conductivity; however, it nearly disappeared above $800^{\circ}C$. Using the defect model and curve fitting, the ionic and electronic conductivity contributions were also separated. In the temperature region where the sample resistance is mostly determined by the grain volume property, LSAM9191 was an oxygen ion conductor at low $Po_2$ and a mixed conductor at high $Po_2$. With increasing temperature, the ionic conduction region only slightly increased. Thus, LSAM9191 is a promising material as an oxygen ion conductor at high temperature and in low $Po_2$.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.101-110
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• 2019

The aim of this study was to evaluate and compare the microstructural properties and mineralization quality of mesiodens with permanent and primary central incisors. Fifteen mesiodens, permanent and primary central incisors were collected. The enamel rod diameter and enamel thickness were observed and measured using field emission scanning electron microscope (FE-SEM). Chemical composition of the enamel was analyzed using energy dispersive X-ray spectrometer (EDS). The measurements were then assessed using the one-way ANOVA and Tukey test. There was no statistically significant difference in the enamel rod diameter between mesiodens and permanent central incisors. However, enamel rods of primary central incisors were smaller than remaining two groups. The thickness of enamel was thick in order of permanent central incisors, mesiodens, primary central incisors. In the composition analysis using EDS, there was no difference in the Ca/P ratio and Ca/C ratio between mesiodens and permanent central incisors, but small in primary central incisors. In conclusion, the microstructural properties of mesiodens were more similar to those of permanent central incisors compared to primary central incisors. Futher, the mineralization quality of mesiodens did not differ significantly from that of permanent central incisors.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.173-177
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• 2011

In this study, the formation of $AlPO_4$-type porous materials from alum sludge was investigated. The materials were synthesized by the reaction of aluminum hydroxide and phosphoric acid with an organic template. Cationic surfactant, natural humic acid, and amino acids were used for the organic template. The residual organic templates were removed by calcination at $600^{\circ}C$ in the air. Powder X-ray diffraction patterns showed the charicteristic patterns of the $AlPO_4$-type porous materials. The morphology of the material was examined using a scanning electron microscopy. The coordination environment of $Al^{3+}$ ion was investigated by $^{27}Al$ MAS NMR technique. Both tetrahedrally and octahedrally coordinated$Al^{3+}$ ions were found in the as-synthesized samples while all $Al^{3+}$ ions were tetrahedrally coordinated in the calcined products. The development of mesopore in the solid material was confirmed by the measurement of BET specific surface area. Finally, they were used for removal of toxic formaldehyde from the air and the formaldehyde molecules were adsorbed on the surface of pores. In conclusion, $AlPO_4$-type porous materials from alum sludge might be applicable in the removal of toxic volatile organic compounds from the air.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.551-554
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• 2011

One of the key issues in the research of organic field-effect transistors (OFETs) is the low-voltage operation. To address this issue, we synthesized poly(styrene-r-benzocyclobutene-r-methyl methacrylate) (P(S-r-BCB-r-MMA)) as a thermally cross-linkable gate dielectrics. The P(S-r-BCB-r-MMA) showed high quality dielectric properties due to the negligible volume change during the cross-linking. The pentacene FETs based on the 34 nm-thick P(S-r-BCB-r-MMA) gate dielectrics operate below 5 V. The P(S-r-BCB-r-MMA) gate dielectrics yielded high device performance, i.e. a field-effect mobility of $0.25cm^2/Vs$, a threshold voltage of -2 V, an sub-threshold slope of 400 mV/decade, and an on/off current ratio of ${\sim}10^5$. The thermally cross-linkable P(S-r-BCB-r-MMA) will provide an attractive candidate for solution-processable gate dielectrics for low-voltage OFETs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.94-100
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• 2021

To improve the productivity of cargo containment construction for a membrane LNG carrier, it is important to shorten the installation period and process of the scaffolding system, which is a construction workbench of a cargo containment for a membrane LNG carrier. As an effective method, opinions are being gathered to enlarge the lifting unit from the existing two stages to eight stages. On the other hand, the stresses around the pin and hole will increase significantly because of the increase in lifting load according to the large size of the module. The purpose of this study was to establish a new large module-lifting plan by introducing TRIZ to solve these problems. This study adopted a method to utilize 40 inventive principles, which is one of the various problem-solving tools of TRIZ. First, technical contradictions were derived, the engineering parameters were selected. Second, efficient inventive principles were selected to overcome the technical contradictions using a contradiction matrix. Finally, the general and specific solutions were derived through the selected inventive principle, and structural analysis confirmed that the stress generated in the structure was low. The utility of TRIZ was confirmed by the successful lifting of large modules using the established lifting method.

• Conservation Science in Museum
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• v.26
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• pp.67-82
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• 2021

Two golden beads (Buyeo 5336) housed at the Buyeo National Museum were discovered in 1993 near the site of an ancient workshop in Neungsan-ri in Buyeo-gun, Chungcheongnam-do Province. These rare examples from the Baekje Kingdom of an application of granulation have maintained their original form intact, and thus serve as important materials for the investigation of production techniques applied. This study analyzed the composition of the golden beads using a portable X-ray fluorescence analyzer, a stereo microscope, and a scanning electron microscope with an energy dispersive X-ray spectrometer. The manufacturing technique was examined through the observation of the micro-shape and the surface condition and by a composition analysis of the joint part. In both beads, a hole was pierced in a hollow body and the bead was decorated with golden wires around the hole and gold granules in other parts. In some areas, golden granules had been attached to the gold plate and golden wires were then placed over the granules. The purity of both the wires and the granules was analyzed as 23.6 - 23.7K. A high copper content was detected in some of the parts where the granules were attached. The findings of a previous reproduction experiment and study of production methods suggest that the beads were made using the copper diffusion technique.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.367-375
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• 2021

This study evaluated the fluoride release of alkasite restorative material (ARM) and giomer penetrating the dentin adhesive layer. Twenty specimens were prepared for each restorative material, and dentin adhesive with uniform thickness was applied to half of them. The prepared specimens were placed in a polyethylene tube containing 2.0 mL of deionized water and deposited in a 37.0℃ water bath for the study duration. The amount of fluoride release was measured on the 1^st, 3^rd, 7^th, 14^th, 21^st, and 28^th days after deposition. The dentin adhesive applied to the ARM and giomer could not completely block the fluoride release; however, it significantly reduced its amount. The cumulative amount of fluoride release of the ARM after 28 days was higher than that of the giomer regardless of the application of dentin adhesive.