• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.63-64
• /
• 2019

Due to the rapid deterioration of the domestic atmosphere, people are suffering from inconveniences such as wearing fine dust masks all the time during outdoor activities. In this study, light transmitting concrete, LEFC(Light Emotion Friendly Concrete), using TiO2 photocatalyst was produced. Since the characteristics of LEFC where acrylic rods are inserted require self-consolidating performance, the purpose was to utilize UHPC(Ultra High Performance Concrete) materials to obtain high-flowability. Further, the compressive strength and flexural strength were evaluated to prevent the reduction of epidemiological performance by utilizing UHPC materials. As such, a basic study was carried out to develop LEFC materials using photocatalyst that can purify the air and stimulate human sensibility.

• Proceedings of the KACD Conference
• /
• 2003.11a
• /
• pp.570-571
• /
• 2003

This study was done to evaluate the shear bond strength between light-cured glass ionomer cement base and resin cement for luting indirect resin inlay and to observe bonding aspects which is produced at the interface between them by SEM(Scanning Electron Microscope). 1)Shear bond strength. Light-cured glass ionomer cement base were made in plastic molds(10mm diameter, 5mm thickness). Two type of light cured glass-ionomer cement were uesd.(중략)

• The Journal of Advanced Prosthodontics
• /
• v.7 no.1
• /
• pp.47-50
• /
• 2015

PURPOSE. This study aimed to discover a way to increase the bond strength between bis-acryl resins, using a comparison of the shear bond strengths attained from bis-acryl resins treated with light curing, pressure, oxygen inhibition, and heat. MATERIALS AND METHODS. Self-cured bis-acryl resin was used as both a base material and as a repair material. Seventy specimens were distributed into seven groups according to treatment methods: pressure - stored in a pressure cooker at 0.2 Mpa; oxygen inhibition- applied an oxygen inhibitor around the repaired material,; heat treatment - performed heat treatment in a dry oven at $60^{\circ}C$, $100^{\circ}C$, or $140^{\circ}C$. The shear bond strength was measured with a universal testing machine, and the shear bond strength (MPa) was calculated from the peak load of failure. A comparison of the bond strength between the repaired specimens was conducted using one-way ANOVA and Tukey multiple comparison tests (${\alpha}$=.05). RESULTS. There were no statistically significant differences in the shear bond strength between the control group and the light curing, pressure, and oxygen inhibition groups. However, the heat treatment groups showed statistically higher bond strengths than the groups treated without heat, and the groups treated at a higher temperature resulted in higher bond strengths. Statistically significant differences were seen between groups after different degrees of heat treatment, except in groups heated at $100^{\circ}C$ and $140^{\circ}C$. CONCLUSION. Strong bonding can be achieved between a bis-acryl base and bis-acryl repair material after heat treatment.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.1
• /
• pp.76-92
• /
• 1998

The purpose of this study was to evaluate the possible efficacy of Nd-YAG laser as a dentin conditioner by observing the laser irradiation dentin surface under scanning electron micrograph and measuring shear bond strength of restored light-cured glass ionomer mold. Fifty intact premolars were prepared for shear bond strength tests. The teeth were randomly divided into five groups as follows; Group I. no treatment Group II. 10% poly acrylic acid, 20 sec Group III. laser treatment 2 w, 20 Hz, 2 sec Group IV. laser treatment 2 w, 20 Hz, 5 sec Group V. laser treatment 2 w, 20 Hz, 10 sec Samples of each group were restored with light-cured glass ionomer cement after dentin conditioning and then measuring the shear bond strength of each specimen were measured using universal testing machine. Additional ten premolars were prepared for SEM analysis The result from the this study can be summarized as follows. 1. Shear bond strength of polyacrylic acid-treated group (II) was significantly higher than other groups (p<0.05). 2. No statistically significant difference could be found between three laser-treated groups (III, IV, V) in shear bond strength(p>0.05) 3. According to the result of observation under SEM, Polyacrylic acid was shown to have removed the smear layer effectively and opened the dentinal tubules, whereas the laser has produced the irregular surface mainly composed of melted and fused structure. The microcracks found in laser-treated groups increased in number with irradiation time and formed the regular mesh-type in 10 sec-irradiation group. 4. The ultrastructural change of dentin surface created by laser irradiation was found to the improper for bonding of the glass ionomer restorative materials. And the lower shear bond strength of laser irradiated group might have been due to the failure to form the suit able dentin surface for the glass ionomer to penetrated into and form the proper micromechanical retention.

• Textile Coloration and Finishing
• /
• v.34 no.4
• /
• pp.241-249
• /
• 2022

As for military backpacks in Korea, utility backpack products equipped with various functions along with comfort and convenience are being developed. As a result, the volume and weight of the backpack increase, and many lightweight studies of the materials forming the backpack are being conducted. This study is a basic study on frame lightweight using fiber-reinforced composites to deal with aluminum, a back frame that maintains the shape of a backpack and provides stability when worn by combatants. As is known, only fiber-reinforced composites have sufficient light weight and mechanical properties, but the mechanical properties were reviewed by drilling holes to maximize the light weight. Tensile strength and flexural strength were measured by drilling 6mm, 12mm, 18mm, and 24mm holes, and the tensile strength and flexural strength were measured when 1, 3, 5, and 7 holes of 12mm were increased. As a result, even when the number of holes was increased, tensile strength did not change significantly, and the flexural strength showed to be higher in the case of 3 holes and 5 holes than in the case of 1 hole.

• Textile Coloration and Finishing
• /
• v.15 no.3
• /
• pp.176-184
• /
• 2003

This research aimed at scrutinizing the dyeability of some solvent dyes on polyester and their light fastness to be exploited as a breakthrough in light fastness where utmost fastness is required such as ultramicrofibers and industrial markets. Dyeability on polyester was mainly evaluated by HT exhaust dyeing according to the general procedure. Light fastness has been tested by a preliminary UV test followed by HT xenon test in compliance with standard SAE J1885, 224 KJ. Fading has been determined quantitatively by evaluating the shade deviation and the strength difference between unexposed and exposed samples by means of CIELab values.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.1
• /
• pp.73-79
• /
• 2011

The various properties of concrete have been required, as civil engineering structures are getting larger and complicated. Therefore, the high performance of concrete, such as high strength, high fluidity, and low hydration heat, has been investigated largely. In this study, the properties of lightweight concrete-reducing self-weight of structure member have been studied in order to check the applicability of lightweight aggregate concrete to structural material. The experiments on compressive strength, splitting tensile strength, unit weight, and modulus of elasticity have been conducted with varying PLC, LWCI, LWCII, LWCII-SF5, LWCII-SF15 to check the basic properties. The compressive strength of 21MPa was obtained easily by using lightweight aggregate concrete and the addition of silica fume to increase the compressive strength slightly. To use lightweight aggregate concrete for civil engineering structures, systematic and rigorous studies are necessary.

• Journal of Integrative Natural Science
• /
• v.11 no.2
• /
• pp.113-120
• /
• 2018

This study was planned to prepare the high strength hydrogel ophthalmic lens containing isocyanate group and nanoparticles. HDI with carbon nanoparticles were used as additives for the basic combination of HEMA, MA and MMA, and the materials were copolymerized with EGDMA as the cross-linking agent and AIBN as the initiator. The mixture was heated at $100^{\circ}C$ for an hour to produce the high performance hydrogel ophthalmic lens by cast mold method. Measurement of the physical characteristics of the produced material showed that the refractive index was in the range of 1.4027~1.4600, water content 25.21~44.01%, contact angle $54.18{\sim}72.94^{\circ}$, visible light transmittance 53.03~92.09%, and tensile strength 0.1024~0.2359 kgf and breaking strength was 0.0872~0.2825 kgf. The results showed an increase of refractive index while the decrease in water content. And also, the breaking strength was highest when the addition ratio of HDI was 5%(wt). As a result of the absorbance measurement, no significant difference was observed in all the samples, so it can be judged that the stabilization of nanoparticles in the polymer was maintained.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.26 no.10
• /
• pp.1401-1411
• /
• 2002

To Save energy and cost one bath/one step dyeing and finishing on cotton/polyester blends is carried out with disperse dyes in the presence of crosslinking agent. Cotton 100 %, cotton/polyester 70/30, 50/50, 35/65, polyester 100 % fabrics were used. wrinkle recovery angle, tensile strength retention and tearing strength retention were determined in according to the dyebath composition, and also determined while the concentration of DMDHEU, molecular weight and concentration of PEG were varied. Colorfastness to abrasion, washing and light were tested. For cotton and cotton/polyester blends dyed in the presence of DMDHEU/PEG, wrinkle recovery was improved. Tensile strength retention and tearing strength retention were decreased, in compared with dyed fabrics without DMDHEU. Colorfastness to abrasion was good but colorfastness to washing and to light were poor for the fabrics dyed in the presence of DMDHEU/PEG.

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.1
• /
• pp.33-39
• /
• 1999

This study has been performed to develop an efficient electrocharged scrubber. To improve collection efficiency of the scrubber, electric-charger was installed at the forefront of the packed crossflow scrubbers, and an experiment of changing discharge electrode shape and fluctuating electric field strength was undertaken. After using a light-oil boiler for generation of particles in the about 80% weight of submicron size particles was exhausted. Collection characteristics of the electrocharged scrubber were similar to those of two-stage electrostatic precipitator. In this study the collection efficiency of submicron size particles has been much improved, compared with the previous ones. In an experiment of changing discharge electrode and electric field strength, a needle-spike shape wire electrode showed a higher collection efficiency than round shape wire. The collection efficiency becomes increased with an increase of electric field strength.