• Elastomers and Composites
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• 제50권2호
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• pp.110-118
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• 2015

In this study, diethylaminoethyl methacrylate-styrene-butadiene terpolymer (DEAEMA-SBR), in which diethylaminoethyl methacrylate (DEAEMA) was introduced to the SBR molecule as a third monomer, was synthesized by cold emulsion polymerization. It is expected that amine group introduced to a rubber molecule would improve dispersion of silica by the formation of hydrogen bond (or ionic coupling) between the amine group and silanol groups of silica surface. The chemical structure of DEAEMA-SBR was analyzed using proton nuclear magnetic resonance spectroscopy (H-NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Then, various properties of DEAEMA-SBR/silica composite such as crosslink density, bound rubber content, abrasion resistance, and mechanical properties were evaluated. As a result, bound rubber content and crosslink density of DEAEMA-SBR/silica compound were higher than those of the SBR 1721 composite. Abrasion resistance and moduli at 300% elongation of the DEAEMA-SBR/silica composite were better than those of SBR 1721 composite due to the high bound rubber content and crosslink density. These results are attributed to high affinity between DEAEMA-SBR and silica. The proposed study suggests that DEAEMA-SBR can help to improve mechanical properties and abrasion resistance of the tire tread part.

• Journal of the Korean Wood Science and Technology
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• 제27권3호
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• pp.31-38
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• 1999

본 연구는 재면이 약한 낙엽송재의 교실용 마루판으로의 재질개량의 일환으로 경도와 내마모성 등 표면성능의 개선을 도모하기 위한 표면강화처리기술을 개발하기 위하여 수행되었다. 낙엽송 마루판의 밑칠을 폴리우레탄 우드실러, 중간칠을 폴리우레탄 샌딩실러도료로 도장한 다음, 마감칠로써 자외선 (UV) 경화형 에폭시아크릴레이트수지도료와 우레탄아크릴레이트수지도료를 이용한 표면강화처리에 의해 경도, 내마모성, 부착성, 내충격성이 향상되었다. 이 처리에 의해 브리넬경도가 1.75에서 2.25~2.27로 개선되어 2.38의 참나무재와 유사한 경도치를 나타내었으며, 약 2배의 내마모성 증대효과가 나타났다. 외부충격에 의한 도막의 갈라짐은 거의 발생하지 않았으며, 에폭시아크릴레이트가 우레탄아크릴레이트에 비해 충격에 의한 크랙의 발생율이 적었다.

• Restorative Dentistry and Endodontics
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• 제27권3호
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• pp.257-269
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• 2002

Objective : The purpose of this study was to evaluate the resin infiltration into dentin of one-bottle adhesive systems and self-etching primer bonded to Class V cavities using confocal laser scanning microscope(CLSM). Material and Methods : Forty Class V cavities were prepared from freshly extracted caries-free Human teeth. These teeth were divided into two groups based on the presence of cervical abrasion: Group I, cervical abrasion : Group II, wedge-shaped cavity preparation. Resin-dentin interfaces were produced with two one-bottle dentin bonding systems-ONE COAT BOND(OCB; Coltene$^R$) and Syntac$^R$SPrint$^{TM}$(SS; VIVADENT)-, one self-etching priming system-CLEARFIL$^{TM}$ SE BOND (SB : KURARAY)- and one multi-step dentin bonding system-Scotchbond$^{TM}$Multi-Purpose (SBMP, 3M Dental Products)-as control according to manufacturers' instructions. Cavities were restored with Spectrum$^{R}$(Dentsply). Specimens were immersed in saline for 24 hours and sectioned longitudinally with a low-speed diamond disc. The resin-dentin interfaces were microscopically observed using CLSM. The quality of resin-infiltrated dentin layers were evaluated by five dentists using 0~4 scale. Results : Confocal laser scanning microscopal investigations using primer labeled with rhodamine B showed that the penetration of the primer occurred along the cavity margins. Statistical analysis using one-way ANOVA followed by Duncan's Multiple Range test revealed that the primer penetration of the group 2(wedge-shaped cavity preparation) was more effective than group 1(cervical abrasion) and that of the gingival interfaces was more effective than the occlusal interfaces. In the one-bottle dentin bonding systems, the resin penetration score of OCB was compatible to SBMP, but those of SS and self-etching priming system, SB were lower than SBMP.

• 한국건축시공학회지
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• 제12권5호
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• pp.490-502
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• 2012

The use of recycled aggregate, even for low-performance concrete, has been very limited because recycled aggregate, which contains a large amount of old mortar, is very low in quality. To produce a high-quality recycled aggregate, removing the paste that adheres to the recycled aggregate is very important. We have conducted research on a complex abrasion method, which removes the component of cement paste from recycled fine aggregate by using both a low-speed wet abrasion crusher as a mechanical process and neutralization as chemical processes, and well as research on the optimal manufacturing condition of recycled fine aggregates. Subsequently, we evaluated the quality of recycled fine aggregate manufactured using these methods, and tested the specimen made by this aggregate. As a result, it was found that recycled fine aggregates produced by considering the aforementioned optimal abrasion condition with the use of sulfuric acid as reactant showed excellent quality, recording a dry density of 2.4 and an absorption ratio of 2.94. Furthermore, it was discovered that gypsum, which is a reaction product occurring in the process, did not significantly affect the quality of aggregates. Furthermore, the test of mortar using this aggregate, when gypsum was included as a reaction product, showed no obvious retarding effect. However, the test sample containing gypsum recorded a long-term strength of 25.7MPa, whereas the test sample that did not contain gypsum posted a long-term strength of 29.4MPa. Thus, it is thought to be necessary to conduct additional research into the soundness and durability because it showed a clear reduction of strength.

• 대한임상독성학회지
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• 제3권2호
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• pp.122-125
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• 2005

Paraquat, is a widely used for its great effect as a herbicide. But the mortality rate by paraquat intoxication is known to be very high. It is thought to act by changing form to superoxide and peroxide free radical. Almost paraquat intoxication is through ingestion. A few intoxication of paraquat is through skin absorption. But there was no known death case through skin absorption. We experienced a case of a expired patient by paraquat intoxication through skin abrasion and scratching wound. A 75-year-old man was visited emergency room after motorcycle accident during transporting paraquat. He has multiple abrasion and scratching wound on extremities, and pelvic bone fracture. There was no evidence of ingestion of paraquat. But serum/urine gramoxone level was all positive. In spite of wound irrigation and hemoperfusion, his condition was been gone form bed to worse. 2 days after, multiple organ failure and the respiratory arrest were developed and he was expired. Paraquat intoxication through skin wound is extremely dangerous and death by that could possibly happen

• 한국재료학회지
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• 제12권5호
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• pp.407-413
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• 2002

Eutectic high chromium cast irons containing 17%Cr and 26%Cr were produced for this research by making each of them solidify unidirectionally. Abrasion wear test against SiC or $Al_2$O$_3$bonded paper was carried out using test pieces cut cross-sectionally at several distances from the chill face of castings. The wear resistance was evaluated in connection with the parameters such as eutectic colony size($E_w$), area fraction of boundary region of the colony($S_B$) where comparatively large massive chromium carbides are crystallized and, average diameter of chromium carbides in the boundary region($D_c$). The wear rate($R_w$), which is a gradient of straight line of wear loss versus testing time, was influenced by the type and the particle size of the abrasives. The $R_w$ value against SiC was found to be larger than that against A1$_2$O$_3$under the similar abrasive particle size. In the case of SiC, the $R_w$ value increased with an increase in the particle size. The $R_w$ value also increased as the eutectic colony size decreased, and that of the 17%Cr iron was larger than that of the 26%Cr iron at the same $E_w$ value. Both of the $S_B$ and $D_c$ values were closely related to the $R_w$ value regardless of chromium content of the specimens. The $R_w$ values of the annealed specimens were greater than those of the as-cast specimens because of softened matrix structures. As for the relationship between wear rate and macro-hardness of the specimens, the hardness resulting in the minimum wear rate was found to be at 550 HV30.

• 자원리싸이클링
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• 제19권1호
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• pp.27-32
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• 2010

리튬이온전지의 양극 전자전도도를 향상시키기 위하여 탄소제를 첨가할 때 기존의 혼합법과는 다르게 abrasive milling에 의하여 $LiCoO_2$ 양극 활물질에 흑연을 균일하게 분산시켜서 충방전시 용량감소를 줄이고자 하였다. 밀링 조건은 300 rpm, 10min으로 하였으며, 흑연 농도는 전기 전도성 향상과 용량의 관계를 고려해 볼 때, 1 wt% 경우가 가장 우수한 전극특성을 보여주었다. Abrasion법은 기존 혼합법에 비하여 10% 이상 capacity retention의 향상을 가져올 수 있었으며, 비가역적인 용량에 있어서도 초기 방전 용량의 효율도 높아 비가역 용량이 감소되는 효과를 얻을 수 있었다. 이는 첨가한 흑연이 균일하게 혼합되고 일부는 $LiCoO_2$ 표면에 코팅되어 전자전도도를 향상시키고 산화물인 활물질의 용해를 억제하기 때문으로 생각된다.

• 터널과지하공간
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• 제8권4호
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• pp.332-341
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• 1998

석판재의 모서리 가공작업은 많은 경우 자동화가 이루어지고 있지만 제품의 형태 가 복잡해지면 여전히 수작업에 의해 연마가 이루어지고 있다. 본 논문을 성형공구의 제작 에 앞서 성형공구의 특성과 장비의 운영요소들의 변화에 따른 연마절삭성능을 파악하기 위 한 기본시험이 수행결과를 나타내는 것이다. 장비의 운영요소는 헤드의 회전속도 및 이송속 도, 가압하중, 급수율, 절삭방향과 이송방향이 포함된다. 실험결과는 연마절삭성능 즉 공구 마모 무게에 대한 판재의 절삭량으로 표시하였고, 각 운영요소들 마다의 적정 운영수준이 제시되어 있다. 또한 연마재 투입략의 변화에 대한 마모시험에서는 마모도는 연마재의 증가 에 따라 증가하지만 어느 이상의 양에서는 오히려 감소하고 있다.

• 한국도로학회논문집
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• 제18권2호
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• pp.61-71
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• 2016

PURPOSES: The objective of this study was to determine the optimum ratio of mix design, for a reclaimed asphalt pavement (RAP) content of 100%, for spray injection application. METHODS: A literature review revealed that spray injection is an efficient and cost-effective application for fixing small defective regions of an asphalt pavement. Rapid-setting polymer-modified asphalt mixtures prepared from two types of rapid-setting polymer asphalt emulsion were subjected to Marshall stability and wet track abrasion tests, in order to identify the optimum mix designs. RESULTS and CONCLUSIONS : Different mix designs of type A and type B emulsions were prepared using RAP and virgin aggregates, in order to compare the performance and determine the optimum mix design. The performance of mixtures prepared with RAP was superior to that of mixtures containing virgin aggregates. Moreover, for optimum ratio of the design, the binder content prepared from RAP was set to 1~2% lower than that consisting of virgin aggregates. Compared to their Type A counterparts, type B mixtures consisting of a reactive emulsion performed better in the Marshall stability and wet track abrasion tests. The initial results confirmed the advantages associated with using RAP for spray injection applications. Further studies will be performed to verify the difference in the optimum mix design and performance obtained in the lab-scale test and tests conducted at the job site by using the spray injection machine.

• Journal of Chest Surgery
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• 제45권5호
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• pp.316-319
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• 2012

Background: The standard operative treatment of primary spontaneous pneumothorax (PSP) is thoracoscopic wedge resection, but necessity of pleurodesis still remains controversial. Nevertheless, pleural procedure after wedge resection such as pleurodesis has been performed in some patients who need an extremely low recurrence rate. Materials and Methods: From January 2000 to July 2010, 207 patients who had undergone thoracoscopic wedge resection and pleurodesis were enrolled in this study. All patients were divided into two groups according to the methods of pleurodesis; apical parietal pleurectomy (group A) and pleural abrasion (group B). The recurrence after surgery had been checked by reviewing medical record through follow-up in ambulatory care clinic or calling to the patients, directly until January 2011. Results: Of the 207 patients, the recurrence rate of group A and B was 9.1% and 12.8%, respectively and there was a significant difference (p=0.01, Cox's proportional hazard model). There was no significant difference in age, gender, smoking status, and body mass index between two groups. Conclusion: This study suggests that the risk of recurrence after surgery in PSP is significantly low in patients who underwent thoracoscopic wedge resection with parietal pleurectomy than pleural abrasion.