• 한국의류학회지
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• 제24권5호
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• pp.686-695
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• 2000

Recently, with a growing interest of health and environment, chitosan which was good in no harmful effect to human body and environment, has been watched as the finish treatment of hygiene and pleasantness. The purpose of this study is to develop multifunctional fabric that was improved antimicrobial activity and deodorization rate, water absorption, static voltage and dye absorption by treatment of nylon 6 grafted with acrylic acid added in chitosan. FT-IR spectra of the grafted with acrylic acid added in chitosan shows peaks of COOH and NH2. Antimicrobial activity and deodorization rate of chitosan and grafted with acrylic acid added in chitosan were increased greatly than the control, durability of laundry of grafted with acrylic acid added in chitosan was good. In case of chitosan was dyed acid dyes and grafted with acrylic acid added in chitosan was dyed basic dyes, dye absorption of them were increased than the control. Moisture regain, absorption time and tensile strength of grafted with acrylic acid added in chitosan was increased greatly than the control.

• 대한기계학회논문집A
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• 제32권1호
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• pp.13-20
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• 2008

The purpose of this study is to investigate the effect of acid fog on the rust formation behavior of weathering steel (SMA50) which is used in un-coated bridges. Weathering steel didn't form the passive film under the environment of acid fog(pH5,6), whereas the environment of distilled water formed the protective oxide film. Therefore, the construction of weathering steel under the environment extremely exposed to SOx and NOx which are the main compositions of acid fog is not adequate. Fatigue limits of weathering steel under acid fog environment are remarkably decreased as compared with environment of distilled water. The corrosive constituents in acid fog has piled up the corrosion products on specimen surface and generated the corrosion pits. Because of the high stress concentration arising at this corrosion pit, relatively low fatigue limits were obtained for acid fog specimens.

• 대한소아치과학회지
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• 제37권4호
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• pp.445-452
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• 2010

최근 CPP-ACP의 초기 우식증의 재광화 및 예방 효과에 대한 연구가 많이 진행되고 있다. 그러나, CPP-ACP 적용으로 인한 법랑질 산부식 저항성 증가가 치면열구전색제 접착에 미치는 영향에 대해서는 연구가 부족한 실정이다. 본 연구에서는 CPP-ACP의 치면 도포 여부와 치면열구전색제의 접착 방법의 차이가 법랑질과 치면열구전색제의 결합력에 미치는 영향에 대하여 미세전단결합강도 측정법으로 알아보고자 하였다. 건전한 제3대구치를 사용하여 150개의 시편을 제작하였으며, 다음과 같이 6군으로 나누었다. I군: 인공타액에 2주 보관 후 35% 인산 산부식 II군: 인공타액에 2주 보관 후 35% 인산 산부식 + 접착제 III군: 인공타액에 2주 보관 후 자가 부식 접착제 IV군: CPP-ACP 2주 적용 후 35% 인산 산부식 V군: CPP-ACP 2주 적용 후 35% 인산 산부식 + 접착제 VI군: CPP-ACP 2주 적용 후 자가 부식 접착제 6군의 시편에 치면열구전색제 접착 후 미세전단결합강도를 측정하여 다음과 같은 결과를 얻었다. CPP-ACP 적용은 전통적인 산부식 방법으로 치면열구전색제를 접착하는 경우에는 결합강도와 산부식 양상에 영향을 미치지 않으나, 자가 부식 접착제를 사용한 경우에는 치면열구전색제의 결합강도를 약화시켰다.

• 대한치과보철학회지
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• 제42권5호
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• pp.501-513
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• 2004

Purpose : The purpose of this study was to evaluate the effects of etching time on shear bond strength of four resin cements to IPS Empress 2 ceramic. Material and Methods: Forty rectangular shape ceramic specimens ($10{\times}15{\times}3.5mm$ size) were used for this study. The ceramic specimens divided into four groups and were etched with 10% hydrofluoric acid for 0, 10, 30, 60, 180, 300, 420, 600, and 900 seconds respectively. Etched surfaces of ceramic specimens were coated with ceramic adhesive system and bonded with four resin cement (Variolink II, Panavia F, Panavia 21, Super-Bond C&B) using acrylic glass tube. All cemented specimens were tested under shear loading untill fracture on universal testing machine at a crosshead speed 1mm/min: the maximum load at fracture (kg) was recored. Shear bond strengh data were analyzed with oneway analysis of variance and Tukey HSD tests (p<.05). Etched ceramic surfaces (0-, 60-, 300-, and 600-seconds etching period) and fracture surfaces after shear testing were examined mophologically using scanning electron microscopy. Results : Ceramic surface treatment with 10% hydrofluoric acid improved the bond strength of three resin cement except for Super-Bond C&B cement. Variolink II (41.0$\pm$2.4 MPa) resin cement at 300-seconds etching time showed statistically higher shear bond strength than the other resin cements (Panavia F: 28.3$\pm$2.3 MPa, Panavia 21: 21.5$\pm$2.2 MPa, Super-Bond C&B: 16.7$\pm$1.6 MPa). Ceramic surface etched with 10% hydrofluoric acid for 300 seconds showed more retentive surface texture. Conclusion: Within the limitation of this study, Variolink II resin cement are suitable for cementation of Empress 2 all-ceramic restorations and etching with 10% hydrofluoric acid for 180 to 300 seconds is required to enhance the bond strength.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.144-155
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• 1997

This study evaluated shear bond strength between porcelain and resin cement according to various surface treatments of porcelain, and surface condition of debonded porcelain. 50 porcelain specimens(Celay block A2M7) and composite resin specimens(Clearfil Photo-Bright) were prepared, and divided into 5 experimental groups according to the treatment method of porcelain surface. 5 experimental groups by surface treatments were as follows; CONTROL Group : No surface treatment was done on the surface of porcelains. SAND Group : The surface of porcelains were sandblasted with $50{\mu}m$ aluminum oxide for 5 seconds. HF Group: The surface of porcelains were etched with 8% Hydrofluoric acid for 4 minutes. SIL Group: The surface of porcelains were coated with silane coupling agent and heated at $100^{\circ}C$ for 5 minutes. SAND+HF+SIL Group : The surface of porcelains were sandblasted with $50{\mu}m$ aluminum oxide for 5 seconds and etched with 8% Hydrofluoric acid for 4 minutes, and coated with silane coupling agent and heated at $100^{\circ}C$ for 5 minutes. After surface treatments on the prepared porcelain surface two pastes of Panavia 21$^{(R)}$ were mixed, they were applied between composite resin block and porcelain surface, and then excessive resin cements were removed, and its margin was surrounded with Oxyguard II. All specimens were stored for 24 hours in water at $37^{\circ}C$ and tested with Instron testing machine between porcelains and resin cements, and debonded porcelain surfaces were observed under Scanning Electon Microscope(Hitachi S-2300) at 20kvp. The values from each group were compared statistically by Student's t-test. The obtained results were as follows; 1. The shear bond strength without surface treatment of porcelain was the lowest among all experimental groups(p<0.05). 2. The detached porcelain surface with sandblasting alone had more remarkable cracks than with only Hydrofluoric Acid or Silane coupling 2gent, but showed the lowest value of shear bond strength among surface treated groups(p<0.05), 3. When porcelain surface was treated by hydrofluoric acid, it affected shear bond strength more than silane coupling agent, but there were no significant statistical differences(p>0.05). 4. When three methods were combined to increase shear bond strength between porcelains and resin cements, its value was the highest than the others(p<0.05). 5. In Scannig Electron Micrograph of detached porcelain surface with no treatment, the sample revealed adhesive failure between the porcelain and resin cement whereas detached porcelain surface with combination of three method cohesive failure on the porcelain.

• 한국건축시공학회지
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• 제23권3호
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• pp.231-240
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• 2023

본 연구에서는 액상 레드머드를 첨가한 시멘트 모르타르의 활용 가능성을 검토하기 위하여 pH 10~12 인 액상 레드머드(LR)를 황산으로 중화하여 액상 레드머드(SR)를 제조하였으며, 액상 레드머드의 활용가능성을 확인하고자 플로우, 응결시간, 압축강도를 측정하고 XRD, SEM을 통해 화학적 특성을 분석하였다. 플로우 측정결과 MS-LR과 MS-SR의 경우 Plain과 비교하여 플로우 값이 감소하였다. 응결시간 측정결과 Plain과 비교하여 MS-LR 및 MS-SR의 응결시간은 단축되었다. 압축강도 측정결과 Plain과 비교하여 MS-LR의 1d와 MS-SR의 1d 및 3d의 압축강도가 Plain보다 증가하였으며 28d 압축강도 측정결과에서는 MS-LR 및 MS-SR의 압축강도가 Plain과 비교하여 감소하였다. XRD 분석결과 28일의 경우 Plain과 MS-SR의 XRD 패턴이 유사하게 나타나고, MS-LR에서는 새로운 피크가 관찰되었다. SEM 이미지를 분석한 결과 Plain과 MS-SR의 미세구조는 유사하게 관찰되고 있지만, MS-LR의 미세구조는 미세한 섬유상 조직으로 미세구조가 다르게 나타났다. 따라서 중화하지 않은 레드머드 보다 황산으로 중화한 액상레드머드를 시멘트 모르타르에 대체하였을 때 강도개선 효과가 있는 것으로 사료되며 이의 활용가능성을 확인하였다.

• 대한치과보철학회지
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• 제45권2호
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• pp.159-168
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• 2007

Statement of problem: Literature showed different results on the durability of bonded ceramic restoration. Purpose: The purpose of this article is to review the effect of surface treatment of ceramics in resin-ceramic bond to get predictable results. Material and method: PubMed data base was utilized to search the articles which were written in English and published in 1986 and 2006. Some electronic published articles which are forthcoming to publish in paper were also included for this review. This review article focused on the effect of acid etching and silane application on the silica based ceramics. The durability of resin-ceramic bonding, the methodology for bond strength test and resin bonding to alumina or zirconia based ceramics were compared in brief at the end of the review. Results and Conclusion: the effect of silane application can be influenced by the contaminations of saliva or solutions. Micromechanical retention by acid etching as well as silane application plays an important role in initial and durable bond strength between resin and ceramic. The use of phosphate modified resin cement following tribochemical silica coating and silane application produced best bond strength for alumina or zirconia based ceramics.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.142-147
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• 1995

In this study, styrene-maleic anhydride copolymer (SMA) was synthesized from styrene and maleic anhydride and further reacted with sulfuric acid to obtain water-soluble SMA and the flow and strength tests of cement mortar mixed with copolymers were carried out to evaluate the capability of copolymers as high range water reducer for the concrete. It was found from flow experiment that the fluidity of cement mortar mixed with sulfonated SMA (SSMA) was larger than that miced with aminophenol-substituted SSMA (SmSMA). The decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was decreasing rate of the flow of cement mortar mixed with SSMA and SmSMA was significantly lower than that mixed with naphthalene condensate (NSC). The compressive strength of the hardened cement mortars containing 0.5% copolymers after 28 days curing was examined. The compressive strength of hardened cement mortar containing SSMA and SmSMA was increased up to 32% and 13%, respectively, when compared to the plain. As the results, the copolymers (SSMA and SmSMA) used in this study are greatly expected as a good high range water reducers for the concrete.

• 한국구조물진단유지관리공학회 논문집
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• 제12권5호
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• pp.55-64
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• 2008

유해 환경하에 노출된 숏크리트는 시간이 경과함에 따라 각종 유해이온의 침식으로 인하여 열화하게 된다. 본 연구에서는 이와 같은 환경에 노출된 숏크리트의 열화특성을 평가하기 위하여 황산염 및 산에 대한 화학적침식에 대하여 유해이온에 각각 60주 동안 침지한 숏크리트 코어 공시체를 대상으로 외관조사, 압축강도, 부착강도 및 기기분석을 실시하였다. 그 결과 용액의 종류에 관계없이 침지재령 60주에서 균열, 박리 등으로 인한 표면손상이 심각한 상태였으며, 압축 및 부착강도는 초기재령에서는 수중양생한 공시체보다 상회하는 결과를 보였으나 장기재령에서는 역전되는 현상을 보여주었다.

• Composites Research
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• 제26권3호
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• pp.160-164
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• 2013

In this study, the effect of phosphoric acid (PA) as a fiber spinning aid on the strength increase of polyacrylonitrile (PAN) nano-fibers by using modified mechano-electrospinning technologies has been analyzed. The medium carbonization temperature of $800^{\circ}C$ has been selected for the future economic production of these new materials. The concentration of PAN in dimethyl sulfoxide (DMSO) was fixed as 5 wt%. The weight fraction of PA was selected as being 2%, 4%, 6%, and 8% in comparison to PAN. These solutions have been used to make the nanofibers. The mechano-electrospinning apparatus installed in KRICT was made by our own design. By using this apparatus the continous and highly aligned precursor nano-fibers have been obtained. The bundle of 50 well aligned nano diameter continuous fibers with the diametr of 10 microns with 6 wt% phosphoric acid for addition showed maximum mechanical properties of 1.6 GPa as tensile strength and 300 GPa as Young's modulus. The weight of final product can be increased 19%, which can improve the economical benefits for the application of these new materials.