• Restorative Dentistry and Endodontics
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• 제25권2호
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• pp.243-253
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• 2000

The purpose of this in vitro study was to evaluate dentin bonding by two different dentin bonding systems(DBS) using acetone based primer or adhesive [All Bond 2(AB2), One Step(OS)] when they were applied by wet or dry bonding technique. Morphology of resin-dentin interface and hybrid layer thickness(HLT) were investigated using Confocal Laser Scanning Microscope(CLSM) and compared to shear bond strength(SBS). 72 extracted sound human molars were randomly divided into 4 groups of 18 teeth each - Group 1.(AW); AB2 by wet bonding. Group 2(AD); AB2 by dry bonding. Group 3.(OW); OS by wet bonding, Group 4.(OD); OS by dry bonding. In 6 teeth of each group, notch-shaped class V cavities(depth 2mm) were prepared on buccal and lingual surface at the cementoenamel juction(12 cavities per group). To obtain color contrast in CLSM observation, bonding resins of each DBS were mixed with rhodamine B and primer of AB2 was mixed with sodium fluorescein. Prepared teeth of each group were treated with AB2, OS, respectively according to the manufacturer's instructions except for dentin surface moisture treatment after acid etching. In group 1 and 3, after acid etching, excess water was removed with wet tissue(Kimwipes), leaving consistently shiny, visibly hydrated dentin surface. In group 2 and 4, dentin surface was dried for 10 seconds at 1 inch distance. The treated teeth were then packed with composite resin(${\AE}$litefil) and light-cured. 12 microscopic samples($60{\sim}80{\mu}m$ thickness) of each group were obtained after longitudinal section and grinding(Exakt cutting and grinding system). Morphological investigation of resin-dentin interface and HLT measurement using CLSM were done. For measurement of SBS, remaining 12 teeth of each group were flattened occlusally to remove all enamel and grinded to 500 grit SiC(Pedemet Specimen Preparation Equipment). After applying DBS on the exposed dentin surface, composite resin was applied in the shape of cylinder, which has 5mm diameter, 1.5mm thickness, and light cured. SBS was measured using Instron with a crosshead speed of 0.5mm/min. It was concluded as follows, 1. HLT of AW(mean: $2.59{\mu}m$) was thicker than any other group, and followed by AD, OW, OD in descending order(mean; 2.37, 2.28, $1.92{\mu}m$). Only OD had statistically significant differences(p<0.05) to AW and AD. 2. There were intimate contact of resin and dentin at the interface in wet bonding groups, but gaps or irregular interfaces were observed in dry bonding groups. 3. The length, diameter, density of resin tags were various even in the same group without significant differences between groups and lots of adhesive lateral branches were observed. 4. There were no statistically significant difference of SBS between AB2 and OS, but SBS of wet bonding groups were significantly higher(p<0.05) than dry bonding groups. 5. There were no consistent relationships between HLT and SBS.

• Restorative Dentistry and Endodontics
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• 제35권6호
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• pp.486-491
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• 2010

Objectives: This study examined the effect of 2% chlorhexidine on the ${\mu}TBS$ of a direct composite restoration using one-step self-etch adhesives on human dentin. Materials and Methods: Twenty-four extracted permanent molars were used. The teeth were assigned randomly to six groups (n = 10), according to the adhesive system and application of chlorhexidine. With or without the application of chlorhexidine, each adhesive system was applied to the dentin surface. After the bonding procedure, light-cure composite resin buildups were produced. The restored teeth were stored in distilled water at room temperature for 24 hours, and then cut and glued to the jig of the microtensile testing machine. A tensile load was applied until the specimen failed. The failure mode was examined using an operating microscope. The data was analyzed statistically using one-way ANOVA, Student's t-test (p < 0.05) and Scheffet's test. Results: Regardless of the application of chlorhexidine, the Clearfil $S^3$ Bond showed the highest ${\mu}TBS$, followed by G-Bond and Xeno V. Adhesive failure was the main failure mode of the dentin bonding agents tested with some samples showing cohesive failure. Conclusions: The application of 2% chlorhexidine did not affect the ${\mu}TBS$ of the resin composite to the dentin using a one-step self-etch adhesive.

• Food Science and Preservation
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• 제18권3호
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• pp.271-278
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• 2011

Considering the importance of cassava as food crops in humid tropics, the effect of feed moisture (20, 25%) and barrel temperature (110, $130^{\circ}C$) on physical properties (piece density, expansion, mechanical properties, color, water solubility index, water absorption index) and pasting properties of extruded cassava starch was investigated. The feed moisture used during extrusion processing had a significant effect on extrudates SME input, specific length and piece density at (p<0.05) while effect on cross-sectional expansion index, apparent elastic modulus and breaking strength in bending shown significantly at p<0.1. Furthermore, the interaction effect of feed moisture and barrel temperature gave a significantly affected the SME input and piece density (p<0.1), specific length (p<0.05) and on redness (p<0.01). The increase in water injection rate led to increase in piece density, apparent elastic modulus, breaking strength in bending, cold peak viscosity, breakdown and final viscosity and decrease in cross-sectional expansion index and specific length. It was found that the extrusion cooking process did not affect the value of color L, color b, water solubility index and water absorption index. Thus, the results of this study can be useful to some extent in developing extruded cassava starch as human and animal feeds.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• 제9권6호
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• pp.711-718
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• 2019

Spectrum analyzer and electromagnetic field meter were used to investigate the EM generation behaviour in different types of home electrical appliances. During microwave oven operation, the EM power measured at a point 30cm apart was measured in the range of 8~11mW/㎡, the strength of the low frequency magnetic field was 60~80mG and the electric field strength was measured at 150~160V/m. For smart phone wireless charging pad, it was measured at an electromagnetic power of 0.4mW/㎡, an electric field of 160 V/m and a magnetic field of 1mG at a point 10cm away. For microwave oven and wireless charging pad, if used within 10cm, the size of the electric field has been measured at a large value that exceeds the human body protection standard and may be hazardous to humans. On the other hand, home appliances such as TVs, hairdryers and refrigerators all showed very low levels of electromagnetic waves, electric fields and magnetic fields, with no harmful effects seen. For electromagnetic shielding, the metal Cu fabric and metal foil had a high level of EM shielding, while polymer films had a low EM shielding characteristic.

• Journal of the Korea Institute of Building Construction
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• 제19권1호
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• pp.9-18
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• 2019

Concrete, which is the most widely used building material in modern times, has been improved not only in strength but also in structural performance such as increase in toughness and ductility, weight reduction, and improvement in quality of human life. Due to the surge in demand for the building, there is a tendency to be used variously from architectural panel and architecture to interior accessories. In Korea, a light-transmitting concrete, LEFC(Light Emotion Friendly Concrete), that insert plastic rods to stimulate emotional sensation through the combination of light and concrete has developed. In previous research, it was confirmed that the use of a synthetic foam agent rather than an animal foam agent did not cause a fogging phenomenon. In this study, lightweight by applying foaming agent to LEFC and two types of fiber (Nylon Fiber, Polyvinyl Alcohol) were compared to achieve to investigate the fiber to be applied in future. An equation that can predict the loss and adhesion reduction of the concrete section according to the diameter of the rod (5mm, 10mm) and the interval (10mm, 15mm, 20mm) was proposed.

• Journal of the Korea Institute of Building Construction
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• 제19권4호
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• pp.361-371
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• 2019

In 2017, the ratio of the number of victims and deaths in the construction industry was the highest with 25.2% and 29.6%, respectively. Especially, as safety accidents at construction sites continue to increase, the economic loss is greatly increased too. Therefore, in order to prevent safety accidents in the construction work, the safety risk assessment index by type of construction was developed, and the main results of this study are as follows. First, 17 factors related to safety accidents at construction sites were derived through survey and interview survey, and this study suggested 9 items(process, type of construction, progress rate, contract amount, number of floors, safety education, working days and weather) throughout the expert advisory meeting. Second, the risk assessment index for safety accidents was developed based on the ratio and intensity of safety accidents. Third, to verify the risk assessment model, the construction safety risk assessment index by type of construction was derived by surveying and analyzing the statistics of the construction accident. In addition, the risk strength was calculated by dividing human damage caused by construction safety accidents into those killed and injured. The risk assessment index based on the frequency and intensity of safety accidents by type of construction is expected to be utilized as basic data when assessing the risk of similar projects in the future.

• Journal of Marine Bioscience and Biotechnology
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• 제13권2호
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• pp.76-85
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• 2021

Crassostrea gigas were fermented using L. brevis BJ20 to prepare fermented oyster extract (FO). The participants of this study were randomly assigned to FO and placebo (CON) groups. The FO group was given 1.0 g of FO supplementation and the CON group was given sucrose each day for eight weeks. The effects of FO supplementation on body composition, muscula r strength, and blood factors associated with muscle growth were assessed. The FO supplement was enriched with arginine (6,183.3 mg), phenylalanine (217.9 mg), leucine (122.6 mg), isoleucine (59.8 mg), valine (16.4 mg), and γ-amino butyric acid (GABA, 1,053.7 mg). The total fat was significantly decreased in the FO group compared with the CON group (p < 0.05). 60D/S Ext.T/Wo rk and 60D/S Flex.T/Work concomitantly with 60D/S Flex.PeakTQ/BW were significantly increase d by FO treatment compared to CON group (p < 0.05). However, posture stability was not significa ntly different between the groups. The levels of angiotensin-converting enzyme were significantly decreased within the FO group (p < 0.05). The FO group showed significantly decreased levels of tumor necrosis factor-α and increased levels of human growth hormone compared with the CON group (p < 0.01). The levels of insulin-like growth factor-1 increased (p < 0.01) in the FO group while that of creatine kinase and triglyceride decreased significantly compared with the CON group (p < 0.05). These results demonstrated that FO supplementation is effective in preventing sarcopenic obesity and maintaining and strengthening muscular function in elderly wom en. Hence, FO supplements can be used as functional ingredients for these benefits.

• Journal of the Korean Geosynthetics Society
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• 제23권2호
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• pp.63-75
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• 2024

Drinking water is an essential element to ensure the basic human right to live, and the quality of clean water must always be ensured. However, domestic water facilities, which were installed intensively in the early 2000s, are deteriorating. The accidents such as discoloration of water such as chromaticity and turbidity as well as leakage of substances frequently occur. However, since it is virtually impossible to replace all water pipes, the detailed standards for maintenance of water pipe network facilities established in 2021 require water pipe cleaning. The swab pig method, one of the water pipe cleaning methods, is a method of physically removing substances in pipes and is evaluated as having the highest cleaning efficiency. However, Swab is highly likely to be damaged or deformed during the cleaning process, and may even be lost. Therefore, in this study, the material of the pig was changed to a material with high compressibility, and it was made as close as possible to the inner wall of the water pipe. And, to maximize cleaning efficiency, a rotation swab pig with a rotation blade was developed. In addition, high-strength wire and winding equipment were additionally developed to eliminate the possibility of loss and to determine the location of the pig. The inlet and outlet are connected with wires, and after verifying the performance of each detailed technology, the technology was applied on a test bed with a 30m section. As a result of the application, the performance of the technology was verified by measuring the process time and evaluating applicability.

• Journal of the Korean Geotechnical Society
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• 제40권2호
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• pp.95-103
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• 2024

The global increase in population and subsequent scarcity of terrestrial living spaces necessitates exploration of alternative habitats. Research into the development of underwater living areas provides promising avenues for the expansion of human living spaces and the use of marine environments. This study focuses on the failure envelope of suction caisson foundations subjected to combined loads in a marine setting, utilizing finite element analysis. The foundation is assumed to be embedded in clay characterized by a linear increase in undrained shear strength with depth, employing the von Mises constitutive model for the clay. The resulting failure envelope is represented as a tilted ellipse which expands as the undrained shear strength increases, maintaining a constant ratio between the major and minor axes. A comparative analysis of two suction caisson foundations with varying length-to-diameter ratios revealed that this ratio influences the dimensions of the failure envelope, with a tendency for the major-to-minor axis ratio to increase as the length-to-diameter ratio increases. These findings are critical for the design of suction caisson foundations in offshore environments.

• Journal of Radiation Protection and Research
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• 제33권4호
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• pp.161-166
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• 2008

In order to determine the effect of extremely low frequency electromagnetic fields (ELF-EMF) on the frequency of micronuclei (MN), aneuploidy and chromosomal rearrangement induced by bleomycin (BLM) in human fibroblast cells, a 60 Hz ELF-EMF of 0.8 mT field strength was applied either alone or with ELM throughout the culture period and a micronucleus-centromere assay was performed. Our results indicate that the frequencies of MN, aneuploidy and chromosomal rearrangement induced by ELM increased in a dose-dependent manner. The exposure of cells to 0.8 mT ELF-EMF followed by ELM exposure for 3 hours led to significant increases in the frequencies of MN and aneuploidy compared to BLM treatment for 3 hours alone (p<0.05), but no significant difference was observed between field exposed and sham exposed control cells. The obtained results suggest that low density ELF-EMF could act as an enhancer of the initiation process of BLM rather than as an initiator of mutagenic effects in human fibroblast.