• 한국작물학회지
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• 제34권2호
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• pp.204-210
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• 1989

오리엔트종 연초에서 전조조건에 따른 품질과 화학성분의 변화를 구명하기 위하여 수확엽을 황변시킨 후 각각 벌크건조 4$0^{\circ}C$, 5$0^{\circ}C$, 6$0^{\circ}C$구, 양건 및 음건으로 처리하여 분석한 결과는 다음과 같다. 1. 품질은 음건엽이 유의하게 낮았으며, 양건과 벌크건조엽은 차이가 적었다. 2. 음건엽은 양건엽과 벌크건조엽에 비해 암모니아태 질소, 단백태 질소, 전질소, 회분함량 및 pH가 높고 당함량이 낮았으며, 석유에텔 추출물과 휘발성 유기산함량은 차이가 적었다. 3. 석유에텔 추출물, 휘발성 유기산과 대부분의 정유성분 중성부함량은 벌크건조 온도가 높을수록 감소하거나 변화가 없었다. 4. 오리엔트종 잎담배의 품질평가 지수로 (총 휘발성 유기산(mg/100g)+석유에텔추출물(%)) / (회분(%)+pH) $\times$ 10 이 추천된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.139-142
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• 1995

Polyimide(PI) thin films are fabricated by vapor deposition polymerization(VDP) from PMDA and DDE. The IR spectrum show that PAA the films are changed into PI films by curing. The activation energy of PI films is estimated to be 0.32 [eV] at the electric field of 0.133 [Mv/cm]. The resistivity is about 4.5${\times}$10$\_$16/ [$\Omega$$.$cm] at room temperature.

• 한국건설순환자원학회논문집
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• 제6권2호
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• pp.67-73
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• 2011

본 연구에서는 산업부산물을 다량으로 사용하는 콘크리트의 건설현장의 구조체 적용을 위한 기초자료를 확보하기 위해 혼화재를 다량 사용한 콘크리트의 압축강도 발현 특성을 검토하였다. 이를 위해 본 연구에서는 일반강도 영역을 대상으로 하여 단위결합재량($310{\sim}410kg/m^3$), 혼화재 치환율(70~90%), 단위수량($140{\sim}150kg/m^3$) 및 양생온도에 따른 압축강도 발현 특성을 검토하였으며, 실제 부재에서의 특성을 검토하기 위해 $2,000{\times}2,000{\times}2,000mm$ 크기의 모의부재를 제작한 후, 수화발열 특성 및 압축강도 발현 특성을 검토하였다. 검토 결과를 토대로, 본 연구에서 검토한 산업부산물을 다량 사용한 콘크리트의 경우 대기온도 평균 약 $13^{\circ}C$ 이상의 양생온도 조건에서는 재령 28일에서 24MPa 이상의 강도를 확보할 수 있는 것으로 나타나, 건설현장에서 골조용 콘크리트로 적용이 가능할 것으로 판단된다.

• 폴리머
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• 제38권6호
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• pp.774-781
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• 2014

4-ethynylaniline(4-EA) 혹은 4-phenylethynyl phthalic anhydride(4-PEPA)을 end-capper로 사용하여 분자량이 2500 g/mol 혹은 5000 g/mol로 조절되고, 반응성 ethynyl 기를 갖는 4,4'-diamino diphenyl ether(4,4'-ODA)/3,3',4,4'-benzophenone tetracarboxylic acid dianhydride(BTDA), 4,4'-ODA/4,4'-oxydiphthalic anhydride(ODPA)계 폴리아이소이미드 올리고머를 합성하여 이들의 중합 및 경화거동을 연구하였다. FTIR 분광분석을 통하여 이들 폴리아이소이미드 올리고머 말단에 반응성 ethynyl 기가 포함되어 있음을 확인할 수 있었다. 이미드화 반응은 폴리아이소이미드 올리고머의 화학구조에도 영향을 받을 뿐 아니라 올리고머의 분자량에도 영향을 받아 분자량 2500 g/mol 올리고머가 5000 g/mol 올리고머보다 대략 $10^{\circ}C$ 정도 낮은 온도에서 이미드화 반응이 일어났다. Ethynyl기의 가교반응은 이미드화 반응보다 높은 온도에서 일어났으며 4-EA로 end-cap된 폴리아이소이미드 올리고머에 대해서는 이 두 반응이 DSC 그래프에서 겹쳐서 나타났다. 4-PEPA로 end-cap된 4,4'-ODA/ODPA 폴리아이소이미드 올리고머에 대해 등 속도 가열 DSC 실험을 통해 이미드화 반응 및 가교반응에 대한 활성화 에너지와 지수앞인자를 구하였다. 이미드화 반응에 대한 활성화 에너지는 141 kJ/mol, 지수앞인자 값은 $1.45{\times}10^{13}min^{-1}$, 가교반응에 대한 활성화 에너지는 177 kJ/mol, 지수앞인자 값은 $2.90{\times}10^{13}min^{-1}$이 얻어졌다.

• Computers and Concrete
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• 제2권1호
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• pp.19-30
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• 2005

We study the kinetics of absorption of water in Portland cement concretes added with 60, 70 and 80% of granulated blast furnace slag (GGBS) cured in water and at open air and preheated at 50 and $100^{\circ}C$. A mathematical model is presented that allows describing the process not only in early ages where the capillary sorption is predominant but also for later and long times where the diffusive processes through the finer and gel pores are considered. The fitting of the model by computerized methods enables us to determine the parameters that characterize the process: i.e., the sorptivity coefficient (S) and diffusion coefficient (D). This allows the description of the process for all times and offers the possibility to know the contributions of both, the diffusive and capillary processes. The results show the influence of the curing regime and the preheating temperature on the behavior of GGBS mortars.

• Elastomers and Composites
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• 제26권3호
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• pp.193-201
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• 1991

Epoxy resin and CTBN(carboxyl terminated butadiene acrylonitrile) rubber were reacted at $150^{\circ}C$. Epoxy mixtures containing reactant in a ratio $0{\sim}75%(wt%)$ of total liquid component were with dicyandiamide(DICY) at $130{\sim}200^{\circ}C$. Cure, thermal and adhesive properties were investigated in relation to rubber content, cure temperature, hardner content and promoter content. $CTBN{\times}13$ showed better properties in miscibility, curing time and adhesive strength. 2PZ-CNS was more excellent in Tg, and melamine was in adhesive strength. Adhesive strength represented best at rubber content $12{\times}15%$.

• 한국초지조사료학회지
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• 제16권2호
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• pp.169-176
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• 1996

An experiment was carried out to determine the effect of cultivar and tedding frequency on changes of moisture content of oat(Avena sativa L.) hay during field drying and on quality of baled oat hay after storage. The experimental design was a split-plot with the four oat cultivm such as 'Magnum', 'Cayuse', 'West' and 'Murray' as main plots and the two tedding frequencies such as 1 or 3 times a day as subplots in three replications. Moisture content of fresh cut oat cultivar was higher in the order of 'Magnum', 'Cayuse', 'West', and 'Murray' and the moisture content difference among the cultivm was maintained to the final curing day(P< 0.05). Moisture loss from the oat hay during the last 3 curing days was greater with 3 tedding a day than I tedding a day. Temperature of baled oat hay began to rise critically from the 6th day of storage and wa5 highest in 'Magnum' oat cultivar($45.3^{\circ}C$). Total nitrogen and ADIN contents of late maturing oat hay 'Magnum' and 'Cayuse' were higher than those of early maturing 'Murray' and 'West'. Tedding frequency did not influence total nitrogen and ADIN contents. ADF and NDF contents of early maturing oat hay were higher than those of late maturing oat hay. Relative feed value (RFV) of 'Magnum' oat hay was the highest(l06) and classified as Grade 2 in forage quality standard. Quality grade difference between early and late maturing oat cultivan was only 1 or 2.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.827-834
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• 2011

Epoxy/graphite/expanded graphite composites have been prepared in various weight ratios and thermal degradation and electrical properties were estimated in order to use for the bipolar plate materials in PEMFC. Thermogravimetric analysis (TGA) showed that the epoxy/graphite system cured by a curing agent GX-533 was most proper because its weight loss until $80^{\circ}C$ at which PEMFC would be operated was 0.3 wt%, and differential scanning calorimetry (DSC) analysis showed its cure temperature would be sufficient at $80^{\circ}C$. The activation energy for the cure reaction was 132.0 kJ/mol and the pre-exponential factor was $1.76{\times}10^{17}min^{-1}$. Electrical conductivity on the surface of the bipolar plate prepared under a pressure of 200 $kgf/cm^2$ was increased from 4 to 25 $S/cm^2$ by increasing expanded graphite (EG) content from 50 phr to 90 phr. The percolation threshold was initiated around 75 phr and the corrosion rate at 80 phr was 1.903 $uA/cm^2$.

• 대한치과보철학회지
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• 제35권4호
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• pp.697-705
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• 1997

The purpose of this study was to evaluate the effects of two metal adhesive primers on the shear bond strengths of self-curing resin to Ni-Cr a]toy and the effects of 1000 thermal cycling on the durability of the bond. The two selected metal adhesive primers were Metal Primer II(G-C corp., Japan) and MR Bond(Tokuyama corp., Japan) and no treatment groups were used as control. All specimens were divided into two groups according to thermal cycling. In the group without thermal cycling, the specimens were stored in water for 24 hours. In the group with thermal cycling, the specimens were thermocycled 1000 times at temperature of $5^{\circ}C\;and\;55^{\circ}C$. Shear bond strengths were measured using the Universal testing machine(Zwick 145641, Germany) with a crosshead speed of 0.5 mm/min. The results were as follows: 1. MR Bond significantly improved the shear bond strength of resin to Ni-Cr alloy before and after thermal cycling. 2. There were no difference in the shear bond strength of resin to Ni-Cr alloy between Metal Primer II treated group and no treatment group. 3. Regardless of the type and the use of adhesive primers, there were tendency of decrease in shear bond strength with 1000 thermal cycling.

• 대한소아치과학회지
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• 제25권2호
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• pp.368-382
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• 1998

The purpose of this study is to evaluate and compare the results of argon laser for 5 seconds, argon laser for 10 seconds, and visible light for 40 seconds photo-polymerization in compressive strength, microhardness, curing depth, temperature rising during polymerization, and polymerization shrinkage. Hybrid type composite resin(Z-100) and compomer(Dyract) were used to be compared. The compressive strength was measured by an Instron(1mm/min cross head speed) in 60 specimens and the microhardness of the surface was expressed by Vickers Hardness Number(VHN) in 30 specimens. The curing depth was evaluated comparing the different values of upper and lower VHN according to irradiation time and thickness for the light source polymerization in 60 specimens. The temperature rising during photopolymerization was observed by the temperature change with thermocouple sensitizer beneath 40 specimens at the argon laser for 10 seconds and visible light 40 seconds irradiation. The polymerization shinkage was evaluated by calculating the decrease of % volume by using a dilatometer in 30 specimens. The results were as follows ; 1. In the case of compressive strength, the argon laser polymerization groups were higher than visible light group in Z-100 (p<0.05). In Dyract, the argon laser 5 seconds group did not show a significant difference with the visible light 40 seconds group. The argon laser 10 seconds group showed the markedly low value when compared with other groups (p<0.05) 2. In microhardness, Z-100 was better than Dyract when comparing by VHNs (p<0.05); however, there was not a significant difference between two materials in the visible light 40 seconds group and the argon laser 10 seconds group. 3. In the study of curing depth, Z-100 showed the consistent polymerization in argon laser irradiation because there was no difference in the VHN decrease according to the thickness change. Over the thickness control, the results did not show a significant difference between visible light and argon laser group in Z-100; however, in the case of Dyract, the visible light 40 seconds group was better than the argon laser groups(p<0.05). 4. There was a significant difference between the two materials in temperature rising during polymerization (p<0.05), but not a significant difference between irradiation times, 5. There was not a significant difference between the two materials in polymerization shrink age. The argon laser 5 seconds group was smaller than the other groups (p<0.05). It could be concluded that Z-100 polymerization was recommended to use the argon laser for reduction of the irradiation time while Dyract was recommended to use the visible light polymerization.