• Journal of Korean Dental Science
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• 제2권2호
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• pp.5-11
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• 2009

Objectives : This study investigated the hypothesis that the dentin bond strength of self-etching adhesives (SEAs) may be improved by applying a coat of hydrophobic, neutral adhesive resin in addition to SEA. Method and Materials : The bond strengths of two SEAs - Experimental SEA (EX) and Adper Prompt (AP) - were measured with three bonding protocols. The D/E resin of All-Bond 2 was applied as the hydrophobic, neutral adhesive. Clearfil SE Bond (SE, self-etching primer system) and All-Bond 2 (AB, total etching system) were used as references. The following protocols were used: (1) EX1 (EX 1 coat); (2) EX2 (EX 2 coats); (3) EX+ (EX 1 coat + D/E resin); (4) AP1 (AP 1 coat); (5) AP2 (AP 2 coats); (6) AP+ (AP 1 coat + D/E resin); (7) SE (SE primer + SE bond); (8) SE+ (SE primer + D/E resin); (9) AB (etching + AB primer + D/E resin). Filtek Z250 composite resin was built up and the microtensile bond strength (MTBS) values of the specimens were compared. The fractured surfaces were observed using SEM. Results : When SEA was used as self-etching primer and hydrophobic, neutral adhesive was applied as well, MTBS was significantly higher than that when either one coat or two coats of SEA only were used (p < 0.05). Conclusion : The hydrophobic, neutral adhesive improved the integrity of the bonded interface obtained with SEA.

• Restorative Dentistry and Endodontics
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• 제32권5호
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• pp.445-458
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• 2007

단일과정 접착제를 이용함에 있어 복합레진과의 부적합성을 개선하고자 중간레진이 결합에 영향을 미칠 것으로 사료된다. Experimental single step system (Bisco Ltd., Schaumburg, IL)을 대조군으로 하고 6종의 중간레진을 접착제의 중합여부, 복합레진의 광중합-자가중합 여부로 분류하였다. 상아질에 대한 광중합 또는 자가중합형 복합레진의 결합강도를 측정하고 접착계면에 대한 투과전자현미경 관찰하여 다음과 같은 결론을 얻었다. 1. 중간레진의 적용은 광중합형 복합레진의 결합강도를 증가시키지 않았다. 2. 자가중합형 복합레진의 결합강도는 중간레진을 적용할 경우 증가하였다. 3. 중간레진의 적용 전 접착제의 중합여부는 결합강도의 변화에 영향을 미치지 않았다. 4. 중간레진이 친수성일 때 소수성 중간레진을 적용할 때 보다 높은 결합강도를 나타냈으나 통계적 유의차는 없었다. 광중합형 복합레진의 수복 시 단일과정 접착제를 사용하는 것은 초기 결합강도에 영향을 미치지 않으며, 자가중합형 복합레진을 단일과정 접착제와 사용할 때는 접착층의 투과도를 감소시키는 소수성의 중간레진을 적용하여 부적합성을 해소할 수 있을 것이다.

• 한국대기환경학회지
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• 제27권3호
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• pp.337-346
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• 2011

24-hr integrated measurements of water-soluble organic carbon (WSOC) in PM2.5 were made between May 5 and September 25, 2010, on a six-day interval basis, at the Metropolitan Area Air Pollution Monitoring Supersite. A macro-porous XAD7HP resin was used to separate hydrophilic and hydrophobic WSOC. Compounds that penetrate the XAD7HP column are referred to hydrophilic WSOC, while those retained by the column are defined as hydrophobic WSOC. Laboratory calibrations using organic standards suggest that hydrophilic WSOC includes lowmolecular aliphatic dicarboxylic acids and carbonyls with less than 4 or 5 carbons, amines, and saccharides. While the hydrophobic WSOC is composed of compounds of aliphatic dicarboxylic acids with carbon numbers larger than 4~5, phenols, aromatic acids, cyclic acid, and humic-like Suwannee River fulvic acid. Over the entire study period, total WSOC accounted for on average 48% of OC, ranging from 32 to 65%, and hydrophilic WSOC accounted for on average 30.5% (9.3~66.7%) of the total WSOC. Based on the previous results, our measurement result suggests that significant amounts of hydrophobic WSOC during the study period were probably from primary combustion sources. However, on June 9 when 1-hr highest ozone concentration of 130 ppb was observed, WSOC to OC was 0.61, driven by increases in the hydrophilic WSOC. This result also suggests that processes, such as secondary organic aerosol formation, produce significant levels of hydrophilic WSOC compounds that add substantially to the fine particle fraction of the organic aerosol.

• Tribology and Lubricants
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• 제36권5호
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• pp.267-273
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• 2020

This study experimentally investigates hydrophobic surfaces fabricated via additive manufacturing. Additive manufacturing, commonly known as 3D printing, is the process of joining materials to fabricate parts from 3D model data, usually in a layer-upon-layer manner. Digital light processing is used to fabricate hydrophobic surfaces in this study. This method uses photo-curable resins and ultraviolet (UV) sources. Moreover, this technique generally has faster shaping speeds and is advantageous for the fabrication of small components because it enables the fabrication of one layer at a time. Two photo-curable resins with different compositions are used to fabricate micro-patterns of hydrophobic surfaces. The resins are composed of a photo-initiator, monomer, and oligomer. Experiments are conducted to determine suitable process conditions for the fabrication of hydrophobic surfaces depending on the type of resin. The most important factors affecting the process conditions are the UV exposure time and slice thickness. The fabrication capability according to the process conditions is evaluated using the side and top views of the micro-patterns observed using a microscope. The micro-patterns are collapsed and intertwined when the exposure time is short because sufficient light (heat) is not applied to cure the photo-curable resin with a given slice thickness. On the other hand, the micro-patterns are attached to each other when the exposure time is prolonged because the over-curing time can cure the periphery of a given shape. When the slice is thicker, the additional curing area is enlarged in each slice owing to the straightness of UV light, and the slice surface becomes rough.

• International Journal of Concrete Structures and Materials
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• 제2권1호
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• pp.21-25
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• 2008

Surface treatments act as a barrier between the environment and the concrete, preventing or retarding the entry of harmful substances and cutting off the transportation path into concrete. The effectiveness of a surface protection preventing the permeation depends on how close and strongly connected are the resin molecules. This work intends to contribute to a better understanding of the performance of protected concrete in chemically aggressive environments, by presenting results of ion diffusion and resistance to aggressive solutions of several hydrophobic agents and coatings used to protect concrete. Three different types of surface protections were tested: silicone hydrophobic agent, acrylic and epoxy coatings. The obtained results indicate that the overall performance of epoxy resin was better than the other selected types of protections.

• KSBB Journal
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• 제15권4호
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• pp.366-369
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• 2000

택서스속 식물세포인 Taxus chinensis 배양에서 식물세포, 세포조각 및 여액에 있는paclitaxel 의 분포는 paclitaxel 생 산량에 의존하였다. 즉, 여액에 녹을 수 있는 paclitaxel에 힌계가 있기 때문에 발효조에서의 생산량이 적을 경우 여 액 에 녹아 있는 paclitaxel양은 상대 적 으로 증가하여 수율 증가 측면에서 이를 반드시 회수하여야 한다. 여러가지 종 류의 흡착제 중에서 HP20 (stylene, high porous polymer)의 경우 흡착 및 탈착 효율이 좋고 가격도 저렴하여 가장 경 제적인 흡착제 임을 알 수 있었다. 식물세포와 세포조각이 포함되어 있는 배양액의 경우 흡착효율이 상당히 떨어져 10 g/l흡착제로 3일 동안 반응시켜도 여액내 paclitaxel은 여 전히 잔존함을 알 수 있었다 데칸터 여 액, 식불세포만 제 거된 배양액의 경우에는 흡착효율이 향상되어 5 g/l흡착제 처리로 1일 정도면 배양액내 paclitaxel이 완전히 흡착됨을 말 수 있었다. 또한 고속원심분리기 여액, 식물세포와 세 포조각이 제거된 여액의 경우 3 g/l흡착제 처리로 1일 정 도면 여 액내 paclitaxel이 완전히 흡착되 어 여 액내 paclitaxel 을 완전히 회수할 수 있었다. 이상의 결과로부터 여액에 녹아 있는 paclitaxel 회수를 위하여 식물세포와 세포조각을 미리 제거한 여액, 즉 고체 함량을 줄인 여액이 더욱 효과 적임을 알 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1576-1581
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• 2004

An experimental study has been carried out to investigate the frosting behaviors of thermally conductive plastic(PBT based resin) resin by comparing with those of aluminum and some plastic(PTFE based resin) test specimens. It is found that the frosting behavior of plastic specimens with 1 mm thickness show similar trend with aluminum except PTFE. The properties of frost formed on the specimens are affected by both thermal conductivityand surface characteristics (hydrophilic/hydrophobic) of the materials. It can be said that the heat and mass transfer rate of plastic materials are almost equivalent with those of aluminum.

• 한국물환경학회지
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• 제26권6호
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• pp.976-985
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• 2010

In this study, characteristics of dissolved organic matter (DOM) from Lake Paldang and seven other DOM sources (lake plankton, plants, soil, composite, treated sewage) were studied using XAD resin fractionation and 28-day microbial incubation experiment. Distribution patterns of DOM-fractions, which include hydrophilic acids (HiA), hydrophilic bases (HiB), hydrophilic neutrals (HiN), hydrophobic acids (HoA), hydrophobic neutrals (HoN) and the extent of DOM biodegradation (i.e., biodegradability) were different depending on the origins of the DOM samples. The DOM distribution pattern and the biodegradability were found to be effective for distinguishing the different DOM sources. The biodegradability (%) had negative correlations with the content (%) of hydrophobic fractions (Ho) and specific UV absorbance of DOM, which indicate that the Ho fractions contain more aromatic carbon structures and relatively stable during biodegradation, irrespective of the sources. To gain additional insight into the microbial transformation of the DOM, we also investigated the changes in the fraction's distribution for plankton, leaf litter and composite samples after the incubation. The results showed that biodegradation of hydrophilic fraction (Hi) causes an increase in the proportion of Ho (HoA, HoN), while biodegradation of HoA increases the HoN production.

• 한국물환경학회지
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• 제38권3호
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• pp.133-142
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• 2022

Natural organic matter (NOM) is a heterogeneous mixture of organic matter with various polarities and molecular weights in an aquatic environment. This study investigated the effects of separation conditions (resin volume, organic matter, etc.) and the repeated use of the resin for the fractionation of organic components in the DAX resin fractionation method. The distribution characteristics of the organic components ((hydrophilic [Hi], hydrophobic acid [HoA], and hydrophobic neutral [HoN]) under the derived fractionation conditions were also analyzed. Constant fractionation results (i.e. HoA/Hi ratio) were obtained in the column capacity factor (i.e. the packed resin volume) in the range of 50 to 100. The resin-packed column maintained constant separation efficiency for up to two repeated uses. The above conditions were applied to wastewater and stream water samples (before and after rainfall). The results showed that the concentration of organic matter in the wastewater effluent was 2-15 times lower with an increased ratio of hydrophilicity to hydrophobicity (i.e. Ho/Hi) compared to the influent depending on the industrial wastewater classification. Particularly, HoN was found to have a high content distribution, 10.2-50.4% of the total dissolved organic matter (DOM), in the effluents. For the stream water, the content of Hi or HoN increased significantly after rainfall, suggesting a correlation with the distribution characteristics of pollutants from the stream watershed. The results provide useful data to enhance the reliability of the DAX resin fractionation and its application to environmental samples.

• 한국미생물·생명공학회지
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• 제15권2호
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• pp.122-128
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• 1987

Candida rugosa와 Rhizopus arrhizus 리파제를 photocrosslinkable resin prepolymer에 고정화시켜서 이소옥탄을 유기용매로 사용한 이상계를 이용해서 유지분해 및 에스테르교환 반응을 보고자했다. Dioctylsulfosuccinate가 가장 좋은 surfactant였다. 소수성 젤인 ENTP-3000에 고정된 리파제가 좋은 활성을 나타냈고 친수성 젤인 ENT-4000에 고정된 리파제가 유기용매에 대해 안정했다. 고정화 matrix의 소수성이 증가될수록Vm(app)는 증가되었으나 Km(app)는 거의 일정했다. 리파제의 최적 pH는 소수성 젤인 ENTP-3000에 고정된 경우 C. rugosa와 R. arrhizus 리파제에 대해서 각각 6.0과 6.5였으나, 친수성 젤에 고정된 리파제는 짧은 시간 반응에는 pH에 크게 영향을 받지 않았으나 긴 시간 동안 반응시킬 때는 역시 pH6.0과 6.5에서 각각 C. rugosa와 R. arrhizus 리파제가 높은 양의 지방산을 분해시켰다. 리파제를 entrapment 시키면 열안정성이 증가됨을 알 수 있었다.