• 한국대기환경학회지
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• 제10권4호
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• pp.281-288
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• 1994

The hydrodesulfurization (DBT) were Peformed over NiPtMo catalysts supported on HZSM-5, LaY and ${\gamma}$- $Al_2$O$_3$under high H$_2$ pressure. And the acidities of these catalysts were characterized by using TGA and DSC. The result showed that the order of the acid strength for prepared supports was HZSM -5＞LaY＞${\gamma}$- A1$_2$O$_3$. For the acid amount we obtained the same result for the acid strength The acid strength and the acid amount mainly depended on the kinds of supports whose acid site were strong or not The activity of the hydrodesulfurization decreased for catalysts which had strong acid sites. The origin of acid site was Bronsted in NH50 and NY catalysts And it was Lewis in NA catalyst The order of desorption activation energy for Pyridine was NH50＞NY>NA. And the result was the same for thiophene. The activity of the hydrodesulfurization decreased for catalysts which had strong acid sites. The conversion of DBT over NA catalyst was higher than NH and NY catalysts.

• 산업기술연구
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• 제21권A호
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• pp.17-26
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• 2001

The fatigue strength of SM55C has significantly decreased by 83% compared with atmosphere where distilled exists due to strong erosive action of acid fog. The reason is inferred in a way that strong acid erosive material such as acid fog act and give rise to multi-site crack on the surface. Several fatigue clacks occurred under the acid fog repeat the process of division and unification on the surface and form a long non-propagating crack throughout the circumference of experimented steel. However, in the depth, many parts do not show much trace of unification, and the depth is not as big as the one of normal crack shape. 10% of $CaCl_2$ causes strong erosive reaction to material. Then eventually make the life of fatigue shooter. On the other hand, 20% of $CaCl_2$ beings about oxidized material organic crack closing due to weak erosive reaction.

• Journal of the Korean Wood Science and Technology
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• 제30권3호
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• pp.1-11
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• 2002

This study was conducted to investigate the effects of reaction pH conditions and hardener types on the reactivity, chemical structure and adhesion performance of UF resins. Three different reaction pH conditions, such as traditional alkaline-acid (7.5 → 4.5), weak acid (4.5), and strong acid (1.0), were used to synthesize UF resins which were cured by adding three different hardeners (ammonium chloride, ammonium citrate, and zinc nitrate) to measure adhesion strength. Fourier transform infrared (FT-IR) and carbon-13 nuclear magnetic resonance (¹³C-NMR) spectroscopies were employed to study chemical structure of the resin prepared under three different reaction pH conditions. Adhesion strength of the resins cured with three different hardeners was determined with lap shear specimens in tension. The gel time of UF resins decreased with an increasing in the amount of both ammonium chloride and ammonium citrate added in the resins. However, the gel time increased for zinc nitrate. Both FT-IR and ¹³C-NMR spectroscopies showed that the strong reaction pH condition produce uronic structures in UF resin, while both alkaline-acid and weak acid conditions produce quite similar chemical species in the resins. The maximum adhesion strength was occurred with the resin prepared under strong acid pH condition. However, this study indicated that the weak acid reaction condition provide a balance between increasing resin reactivity and improving adhesion strength of UF resin. The measurement of formaldehyde emission from the panels bonded with the UF resins prepared is planned for future work.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.21-22
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• 2022

In order to improve the strength degradation of the cement-based material to which strong alkaline liquid red mud was added, the liquid red mud was neutralized with sulfuric acid and added to the cement paste to examine the mechanical properties according to the amount added. As a result of measuring the compressive strength, the strength was higher when the red mud was neutralized with sulfuric acid and added to the cement paste than the cement paste to which the liquid red mud was added. As a result of hydration heat measurement, when red mud was neutralized with sulfuric acid and added to the cement paste, an initial strength higher than that of liquid red mud was expressed.

• 공업화학
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• 제19권2호
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• pp.214-221
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• 2008

산성도와 세공구조가 다른 제올라이트 촉매에서 폐식용유의 전이에스터화 반응에 의해 바이오디젤을 제조하였다. $H^+$ 이온 교환한 MOR, MFI, BEA, FAU 제올라이트와 산점이 거의 없는 실리카라이트 촉매의 반응 수율을 조사하였다. 산세기가 가장 강하고 산점이 많은 $H^+$ 이온 교환한 MOR(10) 제올라이트에서 메틸에스터 수율이 약 95%로 가장 높았다. 제올라이트 골격에서 알루미늄을 제거하면 산점의 수가 줄어들고 산세기도 약해지면서 메틸에스터 수율도 감소하였다. 폐식용유의 전이에스터화 반응에서 메틸에스터의 수율은 제올라이트 촉매의 산세기와 산량에 따라 비례하는 것으로 나타났다. 메틸에스터의 수율은 제올라이트의 세공구조에는 영향을 받지 않는 것으로 조사되었다.

• The Journal of Advanced Prosthodontics
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• 제8권4호
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• pp.267-274
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• 2016

PURPOSE. This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS. Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (${\alpha}$=.05). RESULTS. Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION. Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia.

• 대한화학회지
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• 제34권4호
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• pp.360-369
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• 1990

보로실리케이트와 HZSM-5 제올라이트 및 이들의 골격에 철이 일부 치환된 촉매를 제조하여 메탄올의 전환반응에서 촉매성질을 조사하였다. 산점의 세기와 양이 생성물 분포에 미치는 영향을 암모니아의 승온 탈착곡선으로부터 얻어진 산성도와 연관지어 고찰하였다. 강한 산점이 적은 보로실리케이트 촉매에서는 프로필렌 선택도가 높았으나, 강한 산점이 많은 HZSM-5 제올라이트 촉매에서는 방향족 화합물의 선택도가 높았다. 약한 산점이 전환반응에 기여하는지 여부는 확인되지 않았으나, 생성물 선택도는 강한 산점의 양과 관련지어 설명할 수 있었다. 철의 치환으로 약한 산점이 많아졌으나, 전화율이나 올레핀 선택도에는 영향이 없었다.

• Bulletin of the Korean Chemical Society
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• 제22권3호
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• pp.263-266
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• 2001

Isopropylation of phenol with 2-propanol has been carried out over Na-exchanged ZSM-5 zeolites to determine the effect of catalyst acidity on phenol conversion and product selectivity. The acid type and strength of the catalyst such as Lewis, weak and strong Bronsted acid sites are measured by pyridine adsorbed XPS and the catalytic properties are interpreted in terms of the acid properties. The active site and mechanism for the reaction are suggested based on evidence of study from the reactant adsorbed FT-IR.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.487-507
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• 1995

Composite resin repair requires strong bond strength between the new and old materials. The objective of the current study was to identify the optimal treatments for sufficient bond strengths. Bondings between same kinds of materials and cross bondings using chemical curing composites and light curing composites were tested. Surface treatments included the methods of sand-blasting, acid etching and coating of bonding agent. Seven kinds cases of combinations from three kinds of methods were experimented and compared with a control group of which surfaces were highly polished. Measurements of shear bond strength and observations of surface morphologic changes using a scanning electron microscope were done. Following conclusions were drawn : 1. The highest bond strength among composite resins were exhibited by the treatment of the sand-blasting and the coating of bonding agent. 2. Acid etched surfaces showed the lowest bond strength. Bond strengths obtained from experimental groups including acid etching were lower than those obtained from same kinds of experimental groups without acid etching. 3. Simple method of the coating of bonding agent produced the slightly increased bond strength on chemical curing composite and reduced bond strength on light curing composite. 4. Bonding surfaces of chemical curing composite resin showed slightly higher bond strengths than light curing composite resin, however significant differences were not confirmed statistically. 5. More significant irregular surfaces were created by sand-blasting method than acid etching method. 6. A principal component of fillers of both resins was silicon. Acid etching method produced the seperations and degradations of fillers, these were significant on light curing composite resins which containing barium fillers.

• 대한화학회지
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• 제57권2호
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• pp.279-288
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• 2013

이 연구에서는 1945년 교수요목기부터 2009 개정 교육과정까지 개발된 화학 교과서에서 강산의 이온화도와 이온화 상수 값이 어떻게 제시되었는지 분석하였다. 또한 설문지를 통해 화학 교사들에게 수용액에서 강산의 세기를 비교하도록 하였다. 그리고 이온화도와 이온화상수 값이 호환되지 않는 이유에 대한 교사들의 인식을 알아보았다. 연구 대상은 화학 교사 46명이었다. 연구 결과, 교사들은 교과서에 제시된 이온화 상수 값과 이온화도를 근거로 수용액에서 강산의 세기를 구분하였으며, 교과서에 제시된 이온화 상수 값이 이온화도와 서로 호환되지 않는 문제를 생각하지 못하거나, 문제로 인식하는 경우에도 그에 대한 해결을 하지 못하고 실험 오차나 측정 오차로 생각하였다.