• 한국미생물·생명공학회지
• /
• 제6권4호
• /
• pp.187-196
• /
• 1978

미생물이 하는 생산하는 대사길항물질을 screening 한 결과 최소검정배지상에서 Gram 양성균과 Gram 음성균에 다같이 강한 항균작용을 나타내고 L-aspar tic acid와 L-g1utamic acid에 의하여 길항당하는 물질 N-2292를 생산하는 방선균을 분리하였다. 본 생산균을 분류동정한 결과, Streptomyces albulus 로 보거나 혹은 그 유연균으로 동정하였다. N-2292물질의 배양조건을 검토하여 최적조건에서 대량 배양하고 주로 ion 교환수지, Dowex 50을 사용하여 활성물질을 분리정제하였으며 배양액 약 10ι에서 약 40mg의 백색분말을 얻었다. 본물질은 그 의 이화학적 성질로 보아 indole 화합물을 함유하는 peptide 양 물질임을 추정할 수가 있었다. 생물학적 성질은 최소검정배지상에서 Gram 양성 및 Gram 음성세균에 항균력을 나타냈다. 이러한 항균력은 L-Asp. 및 L-Glu.의 첨가에 의해서 조해당하였다.

• 콘크리트학회논문집
• /
• 제12권3호
• /
• pp.39-46
• /
• 2000

This study is to investigate the watertightness properties of waterproofing admixture mixed redispersible polymer and siliceous powder. Series I deals with change in micro-structure of mortar by waterproofing admixture according to the water/cement ratios of 0.5, 0.6, 0.7 and 0.8 Crystal growth in micro-structure was observed through SEM to estimate on the watertightness effect of it. SeriesII deals with watertightness properties of waterproofing admixture on water permeability coefficient, crack restoration capacity and carbonation depth. SeriesII deals with watertightness properties of waterproofing admixture on water permeability coefficient, crack restoration capacity and carbonation depth. The result of this study can be summarized as follows. 1) Fluidity of mortar and concrete was increased by adding waterproofing admixture. 2) From observation through SEM. Crystals grew larger and denser in micro-structure as fiberic crystalization. 3) Waterproofing admixture is good watertightness properties in a level of high water/cement ratios and long limit of time. 4) Crack restoration capacity was appeared and durability was progressed by waterproofing admixture.

• Composites Research
• /
• 제14권3호
• /
• pp.77-89
• /
• 2001

초고속 일체형 주축의 공진주파수가 일체형 주축 시스템의 모터 회전자의 질량과 주축의 굽힘 강성에 의존하기 때문에 초고속 주축 시스템의 동적 특성을 향상시키기 위해 주축과 회전자를 각각 고분자 기지 섬유강화 복합재료와 자성분말이 함침된 에폭시 수지를 이용하여 설계하였다. 설계된 복합재료 회전자의 자기 특성을 향상시키기 위해 내부에 강철 코어를 삽입하였으며, 강철 코어와 전도체 봉의 기하학적 형상의 변화가 전동기의 성능에 미치는 효과를 파악하기 위해 자기 해석을 수행하였다. 유한요소해석을 통해 복합재료 회전자의 최적의 기하학적 조건을 제안하였다. 또한 복합 재료 회전자 재료의 열특성을 파악하기 위해 TMA, DMA및 VSM을 이용한 기계적, 전자기적 물성측정을 수행하여 복합재료 회전자의 최적 설계에 적용하였다.

• 한국응용과학기술학회지
• /
• 제31권2호
• /
• pp.329-336
• /
• 2014

The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the epoxy resins filled with nickel. The sample was prepared using vehicle such as epoxy resin replenished with nickel powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 4.666~13.074 when using nickel powder. Weight loss of the conductive composites took place at $350^{\circ}C{\sim}470^{\circ}C$.

• 자원리싸이클링
• /
• 제17권5호
• /
• pp.60-65
• /
• 2008

고순도 동 제조를 위해 황산동 전해액중에 존재하는 은(Ag)을 제거하기 위한 기초연구를 실시하였다. 이온교환수지법, 활성탄 흡착법, 구리분말 및 세선을 이용한 치환법, CuS침전법 등을 이용하여 Ag제거에 대한 실험을 실시하였으며, 은(Ag)제거 반응에 영향을 미칠 수 있는 반응온도, 반응시간, 첨가량 등에 대해 고찰하였다. 이들 방법중 CuS 침전법과 Lewatit TP214를 이용한 이온교환수지 방법이 효과적이었는데 특히 Lewatit TP214를 사용한 경우 초기 동전해액중, Ag 농도가 10ppm서 0.1ppm 이하 수준까지 제거가 가능하였다.

• 한국농공학회논문집
• /
• 제50권5호
• /
• pp.19-27
• /
• 2008

This study was performed to evaluate the compressive strength and acid-resistant of polymer concrete using redispersible polymer powder(RPP) and blast furnace slag powder(BSP). Material used were ordinary portlant cement, recycled coarse aggregate, natural fine aggregate, redispersible polymer powder and blast furnace slag powder. The main experimental variables were the substitution ratio of redispersible polymer powder and blast furnace slag powder, when the substitution ratios of RPP were 0, 1, 2, 3, 4, 5 and 6%, and those of BSP were 10%. The compressive strength and acid-resistant of polymer concrete using RPP and BSP were compared with those of ordinary concrete(Basis). When the substitution ratio of RPP was 1%, at age of 28 days, the compressive strength were more higher than those of Basis by 24%, and it was decreased with increasing the RPP content, respectively. Also, the water absorption ratio was decreased with increasing the RPP content. But, the acid-resistant was improved with increasing the RPP content.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2005년도 학술발표논문집
• /
• pp.128-134
• /
• 2005

This study was performed to evaluate the strength and durability properties of recycled concrete containing water - redispersible copolymer powder(WRP) and blast furnace slag powder(BSP) [RCWS]. Material used were cemente, recycled coarse aggregare, natural fine aggregate, water-redispersible copolymer powder, blast-furnace slag powder. Especially, Water-redispersible powder was used for blending with Inorganic binders such as cemente, gypsum and hydrated lime etc. First of all, Mixed ratio method of RCWS made Two Type. One was called type-1 which used to BSP content 5% and WRP(Water-redispersible powder) content 0%, 1%, 2%, 3%, 4%, 5%, 6%. respectively. Another was called Type-2 which used to BSP(blast furnace slag powder)content 10% and WRP(Water-redispersible powder) content 0%, 1%, 2%, 3%, 4%, 5%, 6%. respectively. According to the experimental results of (RCWS), Incase Type-2 at curing age 28days, Compressive strength, pulse velocity and dynamic modulous of elasticity were shown higher than Type-1 and The more WRP content increasing($0%{\sim}6%$) was the lower Compressive strength, Pulse velocity and Dynamic modulous of elasticity. Water absorption ratio was in the range of $3.85%\;{\sim}\;3.23%$, it was almost equal to Type-1, 2 but Increasing the WRP content($0%{\sim}6%$), The water absorption ratio is decreased.

• 한국표면공학회지
• /
• 제49권5호
• /
• pp.416-422
• /
• 2016

We have investigated the effects of applied potential, deposition time and electrolyte types on shapes and physical properties of Cu dendrites by potentiostatic electrodeposition. Finer shape of dendrites was observed at less cathodic potential by 100mV than at the limiting current, due to 'effective overpotential'. The shape of copper dendrite is related to the deposition time, too. The dendrite depositing for 10 min showed the finest shape. The finer dendrite has the less apparent density and the larger specific surface area. Dendrite from chloride solution has the lowest density and the largest surface area among three plating solutions, sulfate, chloride and pyrophosphate.

• 한국주조공학회지
• /
• 제19권1호
• /
• pp.54-65
• /
• 1999

The present work is an attempt to evaluate the relationship between dendrite arm spacing and average cooling rate in gasatomized $Al_{87.3}misch$ $metal_{8.3}Ni_{4.4}$ powder by means of the following methods. One is calculation of heat transfer coefficient and average cooling rate, which are derived from estimated particle velocity during gas-atomization. The other is measurement of secondary dendrite arm spacing, which are observed on the particle surface. Then, we make experimental equation for this relationship in case of permanent mold casting and compare it with similar equation in case of rapidly solidified powder. Both average cooling rates and solidification rates are considered to represent the variance of dendrite arm spacings in two types soidification route. Even though there is a considerable difference in each average cooling rate, the dendrite arm spacing values are similar in two cases; particle diameter, $100\;{\mu}m$, and casting width, 2.05 mm. It is because that each solidification route has similar solidification rate.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권12호
• /
• pp.561-566
• /
• 2005

This paper describes electrical resistivity, dielectric strength, thermal conductivity, thermal stability and tensile strength of mica sheet impregnated with silicone rubber resin or silicone rubber resin containing alumina powder. The mica sheet impregnated with silicone rubber resin had higher electrical resistivity, dielectric strength and tensile strength than those of virgin mica sheet. Electrical resistivity of mica sheet impregnated with silicone rubber resin containing alumina increased with increasing the amount of alumina. However, dielectric strength and tensile strength of mica sheet impregnated with silicone rubber resin containing alumina decreased with increasing the amount of alumina. The mica sheet impregnated with silicone rubber resin had lower thermal conductivity than that of virgin mica sheet. However, thermal conductivity of mica sheet impregnated with silicone rubber resin conatining alumina increased with increasing the amount of alumina. In the case of thermal stability, thermal degradation of virgin mica sheet and impregnated mica sheet with silicone rubber resin did not occur up to $1100^{\circ}C$ and $400^{\circ}C$, respectively.