• 한국재난관리표준학회지
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• 제1권4호
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• pp.65-71
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• 2008

본 논문은 국지성 호우에 따른 성토사변의 내부 침식의 특성에 대한 것이다. 기존 성토재료의 필터조건 분석방법에 대하여 검토하였다. 근접 성토재료로부터 재료업자의 이동을 억제하기 위한 필터층의 조건을 이론적 배경을 기초로 새로운 분석법을 제안하였다. 이러한 필터거동에 대한 새로운 분석기법에 따라 성토재료 내 침식에 의한 입자간의 거동 특성을 규명하기 위하여 사면의 내부 침식에 영향을 주는 주요원인인자(강우강도, 사면구배, 성토재료 특성 등)를 변화하여 총 3가지 Case의 축소모형실험을 실시하였다. 본 연구로부터 새로운 필터조건 분석법이 실질적인 성토구배 내의 성토재료에 대한 필터 설계시보다 더 적용성이 높은 방법이라는 결론을 얻었다. 이에 따라 새로운 필터조건검토 기준 또는 방법을 제안하였다.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.409-428
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• 1994

Endodontic surgery is performed when conventional endodontic therapy fails or is contraindicated. In such cases, retrograde filling materials including amalgam, composite resin, and various cements have been used. Biocompatibilty and margin sealing ability of retrograde filling materials are important for the long term success of endodontic surgery. In vitro cell culture is frequently used as the method of measuring the biocompatibilty of dental materials. The purpose of this study was to evaluate the cytotoxicity of six kinds of retrograde filling materials including newly developed light curing glass ionomer cements. Each material was mixed according to. the manufacture's instruction and evaluated as : freshly mixed, 24-hour after mixing, and 168-hour after mixing respectively. The elution solution was extracted after 24-hour contact with materials using media. Cytotoxicity was evaluated by direct contact, or elution contact. Test results of radiochromium($^{51}Cr$) release, cell viability using tetrazolium dye (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl dimethyltetrazolium bromide(MTT) test and lactate dehydrogenase(LD) of damaged L929 cells were analyzed. In the $^{51}Cr$ release of direct contact, all experimental retrograde filling materials except amalgam and glass ionomer cement showed increased cytotoxicity compared to control. In the $^{51}Cr$ release of elution solution, the released $^{51}Cr$ was so minimal that it was impossible. to evlauate the cytotoxicity exactly. The elution solutions of glass ionomer cement and IRM showed marked cytotoxicity in MTT test. LD enzyme activity was highest in tests of direct contact with composite, light curing composite, and light curing glass ionomer cement and IRM. Amalgam revealed least cytotoxicity while IRM showed cytotoxicity using all three methods. Composite, light curing composite and light curing glass iomomer cement were cytotoxic in the tests of $^{51}Cr$ release and LD activity. Glass ionomer cement showed cytotoxic effect only in the MTT method. From these results it is suggested that the standardization and optimization of cytotoxicity testing, especially using elution solutions, should be strongly advised.

• Journal of the Korean Wood Science and Technology
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• 제42권2호
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• pp.163-171
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• 2014

Environmental issues about indoor air quality have been increased and focused on volatile organic compounds (VOCs) caused cancer, asthma, and skin disease. Reducing VOCs has been attempted in many different methods such as using environmentally friendly materials and air cleaner or purifier. Charcoal is well known material for absorbing VOCs. Therefore, carbonized board from medium density fiberboard has been developed. We assumed that the source of carbonized boards can be any type of wood-based panels. In this study, carbonized boards were manufactured from oriented strand board (OSB) at 400, 600, 800, and $1000^{\circ}C$. Each carbonized OSB (c-OSB) was evaluated and determined physiomechanical characteristics such as exterior defects, dimensional shrinkage, modulus of elasticity, and bending strength. No external defects were observed on c-OSBs at all carbonizing conditions. As carbonizing temperature increased, less porosity between carbonized wood fibers was observed by SEM analysis. The higher rate of dimensional shrinkage was observed on c-OSB at $1000^{\circ}C$ (66%) than c-OSB at 400, 600, and $800^{\circ}C$ (47%, 58%, and 63%, respectively). The densities of c-OSBs were lower than original OSB, but there was no significant different among the c-OSBs. The bending strength of c-OSB increased 1.58 MPa (c-OSB at $400^{\circ}C$) to 8.03 MPa (c-OSB at $1000^{\circ}C$) as carbonization temperature increased. Carbonization temperature above $800^{\circ}C$ yielded higher bonding strength than that of gypsum board (4.6 MPa). In conclusion, c-OSB may be used in sealing and wall for decorating purpose without additional artwork compare to c-MDF which has smooth surface.

• 방사성폐기물학회지
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• 제3권4호
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• pp.341-348
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• 2005

벤토나이트는 낮은 침투성, 높은 수착성, 자체밀봉특성, 내구성 등으로 인해 고준위 방사성 폐기물 처분을 위한 지하처분장에서 완충재 후보물질로 고려되고 있다. 적절한 처분장 조건에서 국내 Ca-벤토나이트에 대하여 지하수 침식에 의한 벤토나이트 입자의 발생 가능성과 발생된 벤토나이트 입자들의 영향에 대한 실험적 연구를 수행하였다. 실험결과 비록 벤토나이트의 팽윤압에 의한 암반 균열로의 벤토나이트의 침투는 적었지만 벤토나이트/화강암 경계에서 벤토나이트 입자가 발생될 수 있고 지하수 흐름에 의해 유동될 수 있음을 보였다. 압축된 벤토나이트 블록으로부터 이러한 벤토나이트 입자들의 유동화에는 각기 다른 과정들이 기여하고 있음을 확인하였다. 유량이 크면 클수록, 유출되는 벤토나이트 입자들의 농도가 높게 나타났다. 따라서 실험결과는 지하수 흐름에 의한 벤토나이트 표면의 침식은 침투과정과 함께 화강암 균열에서의 벤토나이트 입자들을 유동시키는 주요한 과정임을 보여준다.

• 한국도로학회논문집
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• 제19권2호
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• pp.45-53
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• 2017

PURPOSES: The objectives of this study are to develop a new cold-applied crack sealant and to evaluate its properties and field applicability by comparing with other conventionally used crack sealants. METHODS : A new cold-applied crack sealant was developed by using neoprene latex to improve material properties. The fundamental properties such as viscosity, residue %, penetration, and softening point of the developed crack sealant were tested by TxDOT criteria to evaluate crack sealing capability. Moreover, the performance of the developed cold-applied crack sealant was evaluated under both laboratory and field conditions. In the laboratory, the bond property was evaluated using the developed cold-applied crack sealant and conventional hot-applied crack sealant by the bond-properties test standardized under ASTM D 6690. In the field, test sections were constructed on three areas: a trunk road, bus-only lane, and motorway, with the developed crack sealant and three conventional crack sealants. After construction, early field-inspection was performed on the test sections. RESULTS AND CONCLUSIONS : Overall, the developed cold-applied crack sealant demonstrates reasonable storage stability, durability, and bond property compared to conventional hot-applied crack sealants. From the test sections, it was established that the developed cold-applied crack sealant does not pose construction issues. Moreover, the early performance was verified through field inspection. However, as the field inspection was conducted a week after the construction, it is necessary to conduct an inspection of performance from a long-term point of view.

• 한국추진공학회지
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• 제18권4호
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• pp.67-73
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• 2014

고온고압의 밸브에서 연소가스의 유입을 방지하는 흑연 씰은 밸브 축의 구동으로 인한 마찰 및 마모에 노출된다. 흑연 씰의 마모로 인해 고온 가스 제어가 불가능해지기 때문에 씰의 마모 특성을 예측하는 것은 매우 중요하다. 본 논문은 비마모율을 마모 특성에 대한 척도로 설정하고 접촉하중, 미끄럼 속도, 온도 등을 변수로 하여 흑연의 왕복동 마모 시험을 수행하였다. 반응표면분석법에 근거하여 실험계획을 정립하고 시험 결과에 대하여 분산분석법을 통하여 유효한 수학적 모델을 제시하였다. 또한, 마모된 표면의 SEM 분석을 통해 특정 조건에서의 마모 메커니즘을 분석하고 비교하였다.

• Restorative Dentistry and Endodontics
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• 제26권2호
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• pp.111-120
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• 2001

Calcium hydroxide pastes is widely used in conventional endodontics. Along with the expanded clinical use of calcium hydroxide, literatures suggest mixing calcium hydroxide with other substance. Among added substances the vehicle plays the most importance role in the overall process because it is directly related with the velocity of ionic dissociation of $Ca^{2+}$ and OH ion. In this study, we evalutated and compared periapical tissue response and root resorption after canal was filled with mixture of saline and calcium hydroxide(Junsei Chemical Co.. Japan) as a aqueous vehicle, Metapaste(Meta Co., Korea) as a viscous vehicle paste, Vitapex(Neo Dental, Japan) as a oily vehicle paste and IRM(Caulk Dentsply, USA) in replantation of rat molar. A total of 31 maxillary first molars of Sprague-Dawley female rats, 30 days old were used. The upper 1st molar was extracted and the mesiobuccal canal was filled with mixture of saline and calcium hydroxide, Metapaste, Vitapex. IRM and then replanted. Rats were sacrificed 3 weeks after replantation. the maxillae were removed. section of 4 micron were cut and stained with hematoxylin-eosin, Apical tissue response were observed under light microscope. The results were as follows: 1. Saline mixing group and Metapaste group were significant different in fibrous capsule width compared to Vitapex group and IRM group(P<0.05). 2. Saline mixing group. Metapaste group. Vitapex group and IRM group did not prevent root resorption and there were no statistical difference. 3. In saline mixing group and Metapaste group. loss of pastes were observed in all samples. From the results of our study. we observed loss of pastes in saline mixing group and Metapaste group because of water soluble property and assumed it was related to inflammation in apical area and sealing ability of material. So, we should study and develop calcium hydroxide vehicle which is easily removed and more stable and because of only 3 weeks observation we need more evaluation in long period.

• Restorative Dentistry and Endodontics
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• 제37권1호
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• pp.29-33
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• 2012

Objectives: The purpose of this study was to evaluate the microleakage of 4 temporary materials in teeth with Class II-type endodontic access preparations by using a glucose penetration model. Materials and Methods: Glucose reaction test was performed to rule out the presence of any reaction between glucose and temporary material. Class II-type endodontic access preparations were made in extracted human premolars with a single root (n = 10). Each experimental group was restored with Caviton (GC), Spacer (Vericom), IRM (Dentsply-Caulk), or Fuji II(GC). Microleakage of four materials used as temporary restorative materials was evaluated by using a glucose penetration model. Data were analyzed by the one-way analysis of variance followed by a multiplecomparison Tukey test. The interface between materials and tooth were examined under a scanning electron microscope (SEM). Results: There was no significant reaction between glucose and temporary materials used in this study. Microleakage was significantly lower for Caviton and Spacer than for Fuji II and IRM. SEM observation showed more intimate adaptation of tooth-restoration interfaces in Caviton and Spacer than in IRM and Fuji II. Conclusions: Compared to IRM and Fuji II, Caviton and Spacer can be considered better temporary sealing materials in Class II-type endodontic access cavities.

• Elastomers and Composites
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• 제45권3호
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• pp.212-216
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• 2010

리튬 이온 전지의 가스켓 재료로 사용되기 위해서는 내전해액성, 전기절연성, 낮은 압축 영구 줄음률, 비오염성, 내열성이 요구된다. Perfluoroalkoxy (PFA)보다 압축 영구 줄음률이 우수한 고무의 적합성을 평가하기 위하여 Ethylene Propylene Diene Monomer (EPDM), Nitrile Butadiene(NBR), Fluoro Elastomers(FKM), Methyl-Vinyl Silicone Rubber (VMQ), Fluorosilicone(FVMQ)을 이용하여 최적상태의 compound를 제작하고 특성을 살펴보았다. 시험편을 $80^{\circ}C$의 propylene carbonate액에 침적하여 경도 및 체적변화를 1,000시간까지 시간별로 측정하였다. EPDM과 VMQ가 내전해액성이 우수하였으며, 전기절연성에서도 체적저항 기준 $10^{10}{\Omega}cm$이상의 결과를 얻을 수 있었다. 따라서, EPDM과 VMQ가 적절한 것으로 판단되었다.

• Elastomers and Composites
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• 제42권3호
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• pp.159-167
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• 2007

산업기계에서 공기압 또는 유압용 액추에이터(actuator)가 넓이 사용되는데 액추에이터의 중요 부품으로 탄성중합체로 만들어진 시일을 사용한다. 우수한 밀봉특성을 요구하는 시일의 재료로 내유성과 내마모성이 비교적 우수한 NBR(nitrile butadiene rubber) 재료가 가장 많이 사용한다. 산업기계의 액추에이터는 적용환경에 따라 낮거나 혹은 높은 온도에서 사용되는데 여러 온도에서 NBR은 그에 따른 특성이 다르게 나타난다. 본 연구에서는 새롭게 만들어지고 있는 재료 중 공기압, 유압용 시일(Seal)재료로 사용하는 Hs70, 80, 90등 3종의 NBR을 각각 $-10^{\circ}C,\;20^{\circ}C,\;80^{\circ}C,\;100^{\circ}C$온도에서 소재의 비선형(nonlinear) 특성의 시험과 유한요소해석에 필요한 재료상수를 알아보고 각각의 온도에서 하중 반복조건에 따른 소성변형 경향을 살펴보았다.