• Restorative Dentistry and Endodontics
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• 제26권2호
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• pp.171-179
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• 2001

The purpose of this study was to evaluate the shear bond strength of compomers according to dentin surface treatment. Two materials of compomer were devided into six groups. The compomer used in this study were Dyract AP(D) and F2000(F), Group 1 (DN) and 4(FN) were treated according to manufacturers instructions as control groups. Group 2(DE) and 5(FE) were treated with 37％ phosphoric acid and group 3(DA) and 6(FA) were treated with air abrasion unit (80 psi, 50 m aluminum oxide particles) respectively as experimental groups. After dentin surface treatment, compomers were bonded. Completed samples were stored in 100％ humidity. 37C during 7 days, and then, the shear bond strength of specimens were evaluated. The results were as follows: 1. In the case of Dyract AP, the shear bond strength was showed the highest value of 9.10 MPa in dentin surface treatment with air abrasion unit. but there were no significant differences to the other groups. 2. In the case of F2000. the shear bond strength was showed the highest value of 13.51MPa and there were significant differences to the other groups(p<0.05). 3. The shear bond strength of F2000 was higher than Dyract AP in each dentin surface treatment. and in the case of etching and air abrasion. there were significant differences(p<0.05). 4. As a result of observation of SEM. the most of fracture pattern was adhesive failure in group 1(DN), 2(DE) and 4(FN), and cohesive failure in group 3(DA), S(FE) and 6(FA).

• Restorative Dentistry and Endodontics
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• 제45권3호
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• pp.36.1-36.10
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• 2020

Objectives: This study aims to assess the effect of universal adhesives pretreatment on the bond strength of resin-modified glass ionomer cement to dentin. Materials and Methods: Fifty caries-free human third molars were employed. The teeth were randomly assigned into five groups (n = 10) based on dentin surface pretreatments: Single Bond Universal (3M Oral Care), Gluma Bond Universal (Heraeus Kulzer), Prime&Bond Elect (Dentsply), Cavity Conditioner (GC) and control (no surface treatment). After Fuji II LC (GC) was bonded to the dentin surfaces, the specimens were stored for 7 days at 37℃. The specimens were segmented into microspecimens, and the microspecimens were subjugated to microtensile bond strength testing (1.0 mm/min). The modes of failure analyzed using a stereomicroscope and scanning electron microscopy. Data were statistically analyzed with one-way analysis of variance and Duncan tests (p = 0.05). Results: The surface pretreatments with the universal adhesives and conditioner increased the bond strength of Fuji II LC to dentin (p < 0.05). Single Bond Universal and Gluma Bond Universal provided higher bond strength to Fuji II LC than Cavity Conditioner (p < 0.05). The bond strengths obtained from Prime&Bond Elect and Cavity Conditioner were not statistically different (p > 0.05). Conclusions: The universal adhesives and polyacrylic acid conditioner could increase the bond strength of resin-modified glass ionomer cement (RMGIC) to dentin. The use of universal adhesives before the application of RMGIC may be more beneficial in improving bond strength.

• Environmental Engineering Research
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• 제14권1호
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• pp.41-47
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• 2009

Column experiments were performed in this study to investigate humic acid adhesion to iron oxide-coated sand (ICS) under different experimental conditions including influent humic acid concentration, flow rate, solution pH, and ionic strength/composition. Breakthrough curves of humic acid were obtained by monitoring effluents, and then column capacity for humic acid adsorption ($C_cap$), total adsorption percent (R), and mass of humic acid adsorbed per unit mass of filter media ($q_a$) were quantified from these curves. Results showed that humic acid adhesion was about seven times higher in ICS than in quartz sand at given experimental conditions. This indicates that humic acid removal can be enhanced through the surface charge modification of quartz sand with iron oxide coating. The adhesion of humic acid in ICS was influenced by influent humic acid concentration. $C_cap$ and $q_a$ increased while R decreased with increasing influent humic acid concentration in ICS column. However, the influence of flow rate was not eminent in our experimental conditions. The humic acid adhesion was enhanced with increasing salt concentration of solution. $C_cap$, $q_a$ and R increased in ICS column with increasing salt concentration. On the adhesion of humic acid, the impact of CaCl2 was greater than that of NaCl. Also, the humic acid adhesion to ICS decreased with increasing solution pH. $C_cap$, $q_a$ and R decreased with increasing solution pH. This study demonstrates that humic acid concentration, salt concentration/composition, and solution pH should be controlled carefully in order to improve the ICS column performance for humic acid removal from water.

• 한국염색가공학회지
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• 제5권3호
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• pp.188-193
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• 1993

Aqueous polyurethanes(APU) were prepared from polypropylene glycol(PPG), dimethylol propionic acid(DMPA), and isophoron diisocyanate(IPDI) following a prepolymer mixing process. APUs were applied as binder for nonwoven fabrics processing. APU treated nonwoven fabrics generally showed better tear and tensile strength as compared with the untreated ones. In addition, depending on the soft segment length and crosslinking density of the PU, tear strength of APU treated fabrics was favorably compared with solvent type treated one. Similar results were obtained with microfiber nonwoven fabrics, however, the effect was less significant.

• 대한치과보철학회지
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• 제35권2호
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• pp.413-416
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• 1997

A study of the shear bond strength between dental porcelain and alloy on Ti depostion effect was conducted by Instron universal testing machine. The obtained result was as follows ; The shear bond strengths of Ti-depostion group and acid-etched group were statistically significantly greater than that of untreated control group (p<0.01)

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1213-1216
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• 2000

Localized structures with fronts connecting a Turing patterns and Hopf oscillations are found in discrete reaction-diffusion system. The Chorite-Iodide-Malonic Acid (CIMA) reaction model is used for a reaction scheme. Localized structures in discrete reaction-diffusion system have more diverse and interesting features than ones in continuous system. Various localized structures can be obtained when a single perturbation is applied with variation of coupling strength of two intermediates. Roles of perturbations are not so simple that perturbations are sources of both Turing patterns and Hopf oscillating domains, and spatial distribution of them is determined by strength of a perturbation applied initially.

• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.527-533
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• 1994

In this study, it was studied on dielectric breakdown strength and thennostability properties due to the structure variation of matrix resin and treatment of coupling agent of epoxy insulating materials. The interpenetrating network structure was formed by simultaneous heating curing the epoxy resin with single network structure and the methacrylic acid resin. Also inner structure was observed and the glass transition temperature was measured on these three type specimens. Dielectric breakdown properties were investigated by applying DC, AC and impulse voltage. As a result, the glass transition temperature and the dielectric breakdown strength of specimen with interpenetrating network structure was more higher than another two type specimens.

• 한국안전학회지
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• 제25권3호
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• pp.28-33
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• 2010

Ni alloy steel is able to use during long time because of good acid and corrosion resistance. So, it's research has focused on developing the alternative alloy which is economically feasible. Recently, consumption of Kovar steel is gradually increased in field of the jet engine and the gas turbine because of its low thermal expansive characteristics. The specimens of Kovar steel(29%Ni-17%Co) contain 0.00%C, 0.03%C, 0.06%C, 0.10%C and 0.20%C, respectively. Ingots are manufactured by VIM(vacuum induction melting furnace) and then specimens are made by automatic hot rolling after heat treatment. Strength of Kovar steel according to carbon contents is estimated by hardness, tensile and impact test. Hardness of the 0.20%C specimen is more improved approximately 14.4% than one of base metal. Its strength increases 32.4% of a base metal, and its impact energy is also enhance 11.5%.

• 한국농공학회지
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• 제40권4호
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• pp.103-108
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• 1998

This study examines the physical and mechanical properties of the concrete using rice straw ash. Materials used for this experiment are rice straw ash, normal portland cement, superplasticizer, natural sand and gravel. Test results show that the unit weights of concrete using rice straw ash were decreased 1 ∼ 3% and the highest strengths were achieved by 5% filled rice straw ash concrete, with increase of compressive strength by 19%, tensile strength by 53% and bending strength by 16%, as compared with those of the normal cement concrete. The strength ratio of rice straw ash concrete was higher than that of the normal cement concrete. Also, the durability against sulfuric acid 5% solution was increased with increase of the content of rice straw ash. It was 1.33 times of the normal cement concrete by 10% filled rice straw ash concrete and 1.47 times by 15% filled rice straw ash concrete, respectively Accordingly, rice straw ash concrete will greatly improve the properties of concrete.

• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1136-1141
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• 2003

The primary insulation materials used in an oil filled transformer are kraft paper, wood, porcelain and oil. Modern transformers use chemically treated paper to improve its tensile strength and resistance to aging caused by immersion in oil. But these insulation papers are mainly aged by thermal stress. Over the life time of the insulation paper and oil, it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper used in the layer insulation. We made two aging cells in which insulation papers and mineral oil are conducted to test thermal properties. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.