• Journal of Adhesion and Interface
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• v.18 no.2
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• pp.68-74
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• 2017

Epoxy resins are widely used in various fields due to their excellent thermal, mechanical and chemical properties. In order to improve the mechanical properties of the epoxy composition after curing, various materials are mixed in the epoxy resin. Among the nano materials, CNT is the most widely used. However, CNT has limitations in terms of manufacturing process and manufacturing cost. Therefore, there is a growing interest in naturally occurring HNTs having similar structure to that of CNT. In this study, the thermal and mechanical properties of epoxy compositions containing HNTs treated with two types of silane compounds were investigated. The mechanical properties of silane-treated HNT were measured by using a universal testing machine. The differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA) were used to measure thermal properties. As a result of the above tests, when the HNT was surface-treated with aminosilane, the tensile strength of the epoxy composition containing the HNT was higher than that of the epoxy composition containing epoxy silane treated HNT. The linear thermal expansion coefficients (CTE) obtained from the thermomechanical analysis of the two epoxy compositions for the comparison of dimensional stability showed that the HNT composition treated with aminosilane showed a lower value of CTE than that of epoxy composition including the pristine HNT.

• Restorative Dentistry and Endodontics
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• v.32 no.3
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• pp.198-207
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• 2007

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration. Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then $Ca(OH)_2$ and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at $36.5^{\circ}C$ for experiment period (7 days, 30 days). After removing IRM and $Ca(OH)_2$, each dentin adhesives were treated on dentin surfaces. Composite resin (Z-250, 3M) was placed with S mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into $1.0\times1.0mm^2$ cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and ${\mu}TBS$ test was performed. SEM analysis was performed to examine the fractured surfaces. The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.269-281
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• 2006

This study evaluated the effectiveness and safety of an experimental bleaching strip (Medison dental whitening strip. Samsung medical Co., Anyang, Korea) containing 2.9% hydrogen peroxide. Twenty-three volunteers used the bleaching strips for one and a half hour daily for 2 weeks. As control group. the same strips in which hydrogen peroxide was not included were used by 24 volunteers with the same protocol. The shade change (${\Delta}E^{*}$, color difference) of twelve anterior teeth was measured using Shade Vision (X-Rite Inc., S.W. Grandville, MI, USA). Chroma Meter (Minolta Co., Ltd. Osaka. Japan) and Vitapan classical shade guide (Vita Zahnfabrik, Germany). The shade change of overall teeth in the experimental group was significantly greater than that in the control group (p < 0.05) and was easily perceivable. The change resulted from the increase of lightness (CIE $L^{*}$ value) and the decrease of redness (CIE $a^{*}$ value) and yellowness (CIE $b^{*}$ value). The shade change of individual tooth was greatest in canine. and smallest in central incisor. The safety of the bleaching strip was also confirmed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.400-406
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• 2023

In this study, the relationship between the material properties and air permeability characteristics was examined, an experimental method to analyze the air permeability characteristics was presented, and experimental results were derived. The effects of compressive strength and apparent density of hardened concrete on air permeability characteristics were evaluated experimentally. Focusing on the mix proportions used in nuclear power plant concrete structures, concrete test specimens were manufactured and air permeability characteristics were measured according to changes in binder, maximum aggregate size, and water-binder ratio. The apparent density was over 2,400 kg/m³ for the OPC mix and the FA-35 mix, and the air permeability for both mixes were low, in the range of 0.1-0.2 L/min. On the other hand, in the case of the combination of FA-40, FA-45, and FA-M, the apparent density was measured to be less than 2,400 kg/m³ and the air permeability was measured to be more than 0.3 L/min, experimentally verifying that the apparent density is an important factor in air permeability characteristics.

• Journal of Korean Society of Disaster and Security
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• v.16 no.2
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• pp.85-98
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• 2023

Flood is one of the most frequent natural disasters worldwide. In Korea, the probability of urban flooding is greatly increasing due to complex factors such as global warming, an increase in impervious areas, and limitations in expanding water supply facilities in existing urban areas. However, large-scale civil engineering works to prevent urban inundation are socially and economically difficult to obtain national consent. Recently the importance of resilience, which is the ability to return to the original state after a disaster through rapid recovery while preparing for natural disasters to a level that the local community can afford socially and economically, is increasing. Accordingly, various studies on urban resilience have been conducted, but the resilience measurement method related to the lifeline that provides essential services of the city is insufficient. However, among lifelines, road networks are important facilities for the transportation of recovery resources and rapid recovery in the event of a natural disaster, so road networks are a major factor that must be considered when measuring the degree of recovery of a city in the field of natural disasters. Therefore, this study proposes a recovery evaluation method considering the characteristics of resilience and road networks in the urban flooding field and analyzes the effect of road networks on urban resilience.

• The korean journal of orthodontics
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• v.29 no.3 s.74
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• pp.361-374
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• 1999

Intraoral filled type of orthodontic appliance can cause reversible or irreversible damages such as gingivitis, periodontitis, enamel decalcification, dental caries, root resorption, and pulpal changes. Such adverse effects are brought by increase in dental plaque as well as oral flora. Such an increase causes gingival inflammation and enamel decalcification. The purpose of this study is to get klowledge on initial changes in dental plaque, gingivitis, and enamel decalcification after bonding fixed orthodontic appliances according to time flow, gender, and sides(right/left) of premolar region. For control group, 48 students of dental college, Yonsei university(26 males, 22 females) were chosen; for experimental group, 73 orthodontic patients(36 males, 37 females) who will be treated with fixed appliances were chosen. All the subjects had no systemic disease, juvenile periodontitis and all the females had passed their ,menarche. Tooth brushing instruction was given to all the subjects prior to the experiment. For control group, plaque index, gingival index, and decalcification index were measured twice at 3 weeks interval ; for experimental group, the same was done prior to, 3, 6, 9 weeks after bonding fixed appliances. The following results were obtained: 1. In plaque index 3 weeks after placement of appliances, and it showed gradual increase afterwards. 2. In gingival index3 weeks after placement of appliances, and afterwards it showed increase at a faster rate than plaque index. 3. Enamel decalcification began to show between 3 and 6 weeks after bonding fixed appliances. Decalcification index began to increase 6 weeks after appliance placement, but there was no statistical significance. 4. When the comparison was made between two sides of premolar region, the right side showed greater index in plaque and gingival index of experimental group.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.619-626
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• 2020

This study aimed to identify the error rates in Catheter Calibration Mode, Auto Calibration Mode, and Segment Calibration Mode among many calibration modes as a quantitative evaluation tool used for predicting the diameter and length of balloon or stent in percutaneous intravascular balloon dilatation or stent insertion. Our experiment was conducted with Copper Wire of 2 mm × 80 mm (diameter × length) manufactured elaborately for quantitative evaluation in calibration and Metal Ball of 5, 10, 15, 30, and 40 mm and Acryl Phantom of 25 mm, 50 mm, 75mm, 100 mm, 125 mm, 150mm, 175 mm, and 200 mm. At each height, subtraction images were acquired with a cineangiograph and Stenosis Analysis Tool as a software provided by the equipment company was used for measurement. To evaluate the error rates in Catheter Calibration Mode, Copper Wire was put on each acryl phantom before shooting. Copper Wire of 2 mm in diameter was set as a diameter for catheter, and Copper Wire of 8 mm in length was measured with Multi-segments. As a result, the error rates appeared at 1.13 ~ 5.63%. To evaluate the error rates in Auto Calibration Mode, the height of acryl was entered at each height of acryl phantom and the length of 8 mm Copper Wire was measured with Multi-segments and as a result, the error rates appeared at 0 ~ 0.26%. To evaluate the error rates in Segment Calibration Mode, each metal ball on the floor of table was calibrated and the length of 8 mm Copper Wire on each acryl phantom was measured and the length of 8 mm Copper Wire depending on the changes of acryl phantom height was measured with Mutli-segments and as a result, the error rates appeared at 1.05 ~ 19.04%. And in the experiment on OID changes in Auto Calibration Mode, the height of acryl phantom was fixed at 100mm and OID only changed within the range of 450 mm ~ 600 mm and as a result, the error rates appeared at 0.13 ~ 0.38%. In conclusion, it was found that entering the height values in Auto Calibration Mode, among these Calibration Modes for evaluating quantitative vascular dimensions provided by the software was the calibration method with the least error rates and it is thus considered that for calibration using a metal ball or other objects, putting them in the same height as that of treatment sites before calibrating is the method that can reduce the error rates the most.

• Restorative Dentistry and Endodontics
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• v.31 no.5
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• pp.390-397
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• 2006

The purpose of this study was to evaluate the accuracy and the consistency of four different electronic apex locators in an in vitro model. Fourty extracted premolars were used for the study. Four electronic apex locators (EAL) were Root ZX, Smarpex, Elements Diagnostic Unit (EDU), and E-Magic Finder Deluxe (EMF). After access preparation, the teeth were embedded in an alginate model and the length measurements were carried out at '0.5' and 'Apex' mark using four EALs. The file was cemented at the location of the manufacturers' instruction (Root ZX, EDU, EMF: 0.5 mark, SmarPex: Apex mark). The apical 4mm of the apex was exposed and the distance from the file tip to the major foramen was measured by Image ProPlus (${\times}100$). The distance from the file tip to the major foramen was calculated at 0.5 and Apex mark and the consistency of 0.5 and Apex mark was compared by SD and Quartile of Box plots. In this study, Root ZX and EMF located the apical constriction accurately within ${\pm}0.5 mm$ in 100%, whereas SmarPex and EDU located in 90% and in 70% respectively. For Root ZX and EMF, there was no significant difference between the consistency of 0.5 and Apex mark. However, for the EDU and SmarPex, Apex mark was more consistent than 0.5 mark. From the evaluation of the consistency in this study, for Root ZX and EMF, both 0.5 and Apex mark can be used as a standard mark. And for EDU and SmarPex, the Apex mark can be recommended to be used as a standard mark.

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.452-459
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• 2006

Competition will usually develop between the opposing walls as the restorative resin shrinks during polymerization. Magnitude of this phenomenon may be depended upon cavity configuration and volume. The purpose of this sturdy was to evaluate the effect of cavity configuration and volume on microleakage of composite resin restoration that has margins on the enamel site only. The labial enamel of forty bovine teeth was ground using a model trimmer to expose a flat enamel surface. Four groups with cylindrical cavities were defined, according to volume and configuration factor(Depth x Diameter / C-factor) - Group I : 1.5 mm ${\times}$ 2.0 mm / 4.0, Group II : 1.5 mm ${\times}$ 6.0 mm / 2.0, Group III : 2.Omm ${\times}$ 1.72 mm / 5.62, Group IV : 2.0 mm ${\times}$ 5.23 mm / 2.54. After treating with fifth-generation one-bottle adhesive - BC Plus$^{TM}$ (Vericom, AnYang, Korea), cavities were bulk flted with microhybrid composite resin - Denfill$^{TM}$ (Vericom). Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Specimens were thermocycled 500 times between 5$^{\circ}$C and 55$^{\circ}$C for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (${\mu}$A) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. The results were as follows: 1. Small cavity volume showed lower microleakage score than large one, however, there was no statistically significant difference. 2. There was no relationship between cavity configuration and microleakage. Factors of cavity configuration and volume did not affect on microleakage of resin restorations with enamel margins only.

• Fashion & Textile Research Journal
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• v.1 no.3
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• pp.252-258
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• 1999

The aims of this study is to classify the lower somatotype of adult women and appearance analysis on the shape of flare skirts by using the image processing. Also We have made skirts in order to analyze the various types of appearance of flare skirts by using the image processing. The subjects for our wear test lower somatotype, who were controlled in their waist, abdomen and hip shapes. The flare skirts used for wear test were 112 types(combinated 14 fabric type and 8 lower somatotype). The effect of lower somatotype on the shape of flare skirts was determined by the horizontally hem line section shape and the silhouette of flare skirts with image processing. The data were analyzed by using analysis of variance and Turkey, Duncan multiple range test. The results obtained are summarized as follows: It is shown that the fabric weight elongation differs in fabrics properties, in direction of textures. The shape horizontal section of flare skirt hem line has differed with the number of nodes, wave-height of nodes and breadth of silhouette by fabrics properties and lower somatotype. It is noticed that the breadth of flare skirts by the silhouette has high correlation with the drape ability of fabrics and lower somatotype. Results for our flare skirts show changes in amplitude and mean with fabrics, somatotype. Therefore we can say that gray-level histograms are correlated with changes in appearance, differences in drape spacing and related fabric properties and their somatotype.