• 대한환경공학회지
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• 제34권3호
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• pp.189-194
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• 2012

본 연구는 유로변경식 3단 BAF를 사용하여, C/N ($TCOD_{cr}$/TKN)비가 낮은 생활하수를 대상으로 질소 처리 효율을 향상시키기 위해 제안되었다. 체류시간 6시간에서의 유로변경 3단 BAF의 효과를 평가하기 위해 실험실 규모로 실시하였다. 유로변경식 3단 BAF 공정이 3단 BAF보다 총 질소 제거효율이 약 7% 높은 것으로 나타났는데, 이것은 유기물을 효율적으로 사용하였기 때문이다. 또한 암모니아성 질소의 제거는 독립적인 호기조에서 질산화만을 수행하였기 때문에 질산화 효율이 안정적이었다. 이것은 본 연구에서 제안한 유로변경식 3단 BAF공정이 유기물 흡착을 이용하여 질소의 제거, 탈질 및 질산화에서 우수한 효율을 보였다.

• 한국해양공학회지
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• 제6권2호
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• pp.76-84
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane behavior of base metal (BM) and heat affected zone (HAZ) of SAPH45. The main results obtained are as follows: 1) The more aspect ratio (b/t) of corner crack decreases, the more aspect ratio (b/a) takes greatly effect by corrosion. 2) The correlation between the stress intensity factor range ($\Delta$k) and crack growth rate (da/dN) for weldment in seawater is given by Paris rule as follow: da/dN=C($\Delta$K) super(m). Where m is constant, and the value is 3.82-3.84. 3) The accelerative factor ($\alpha$) of BM and HAZ under seawater is about 1.1-1.9, and ($\alpha$) of HAZ increases more and more under the low $\Delta$K region. 4) HAZ is more susceptible to corrowion than BM because of potential of electrode (E sub(c)) of HAZ becomes more less noble potential than that of BM.

• 폴리머
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• 제24권2호
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• pp.168-173
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• 2000

자유 라디칼 개시제인 2,2'-azobisisobutyronitrile (AIBN)을 사용하여 1,4-dioxane 용매하에서 N-isopropylacrylamide (NIPAAM)와 methyl methacrylate (MMA)를 공중합하였다. 온도에 따른 NIPAAM과 MMA의 반응성비를 알아보기 위해 각각 50, 60, 7$0^{\circ}C$에서 중합하여 전환율이 10 wt%이하가 되도록 반응을 정지시켰다. 단량체 반응성비는 Finemann-Ross법으로 구하였으며, 그 값은 5$0^{\circ}C$에서는 ${\gamma}$$_2$=0.259, ${\gamma}$$_2$=2.782, 6$0^{\circ}C$에서는 ${\gamma}$$_1$=0.271, ${\gamma}$$^2$=0.819, 그리고 7$0^{\circ}C$에서는 ${\gamma}$$_1$=0.286, ${\gamma}$$_2$=2.915로 나타나, 반응온도가 높아질수록 ${\gamma}$$_1$, ${\gamma}$$_2$ 값이 증가함을 알 수 있었다. 또한 반응온도와 반응성비와의 관계로부터 활성화에너지의 차를 구할 수 있었으며, 그 결과 반응성비는 온도 의존성이 있는 것으로 나타났다.

• 한국재료학회지
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• 제11권3호
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• pp.236-242
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• 2001

고속도 공구강 기판에 반응성 스퍼터링법으로 증착된 HfN/Si$_3$N$_4$와 NbN/Si$_3$N$_4$다층박막의 기계적인 성질들을 막 증착 조건에 따라 평가하였다. HfN/Si$_3$N$_4$와 NbN/Si$_3$N$_4$ 다층박막의 강도는 $N_2$/Ar비가 0.4일 때가지 증가하다가 유량비가 증가함에 따라 더 이상 증가하지 않았다. 두 다층박막의 강도는 낮은 온도에서의 열처리에 의해서는 거의 변화가 업지만 80$0^{\circ}C$ 정도의 고온에서는 열처리에 의한 산화로 인하여 감소하였다. 낮은 온도에서의 열처리는 밀착성을 향상시키는 반면 고온에서의 열처리는 강도의 감소 이외에 밀착성이 감소하므로 바람직하지 못하다.

• 상하수도학회지
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• 제26권6호
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• pp.889-896
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• 2012

In this study, simulation results of nitrogen and phosphorus removals and microbial activities for an $A_2O$ process in wastewater treatment plant are presented by using Activated Sludge Models (ASMs). Simulations were performed using pre-calibrated model and layout implemented in GPS-X simulation software. The models were used to investigate variations of SRT, water temperature, DO and C/N ratio effect on nutrients removal and microbial activity. According to the simulated results, the successful nitrification required SRT higher than 10.3 days, whereas increase of $NO_3$-N loading in the anaerobic reactor caused phosphorus release by PAOs; the effluent $NH_4$-N showed rapid change between $12^{\circ}C$(21.7 mg/L) and $13^{\circ}C$(3.2 mg/L); the effluent phosphorus was increased up to 1.9 mg/L at water temperature of $25^{\circ}C$; the DO increase was positive for heterotrophs and autotrophs growths but negative for PAOs growth; the PAOs showed low activity when C/N ratio was lower than 2.5. The experimental results indicated that the calibrated models can assure the prediction quality of the ASMs and can be used to optimize the $A_2O$ process.

• 대한금속재료학회지
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• 제49권10호
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• pp.774-779
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• 2011

S-N fatigue behavior of cast 304 stainless steel was studied at 25, -50 and $-196^{\circ}C$ and at a stress ratio of -1 in uniaxial and bending loading condition. It was found that the resistance to S-N fatigue was greatly improved with decreasing testing temperature. The normalized S-N fatigue curves by tensile strength at three different testing temperatures matched each other, suggesting that tensile strength determines the S-N fatigue resistance of cast 304 stainless steel at low temperatures. The effects of different loading on the resistance to S-N fatigue of cast 304 stainless steel were quantified. The S-N fatigue curves at 25, -50 and $-196^{\circ}C$ were described by using Basquin's law the relationship between the S-N fatigue curve and the testing temperature was obtained by using a simple regression method.

• 한국초지조사료학회지
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• 제20권3호
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• pp.193-198
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• 2000

Plant characteristics of four winter crop hairy vetch, red clover, crimson clover and rye as green manure were evaluated at three harvesting time(Apri1 23, May 9, May 28) in spring to select superior winter green manure crop. Rye and hairy vetch had superior wintering ability and produced high dry matter compared with crimson clover and red clover. But N amount of rye was small because of its low plant N% despite of early dry matter accumulation. Wintering ability of crimson clover was very poor, so its dry matter decreased rapidly with low seeding rate. Hairy vetch had high N % (4%, C:N ratio 11) and produced high N yield among four plant. It is estimated that hairy vetch have high N-fixing ability because its N% was not changed largely despite of dry matter accumulation at late harvesting time contrast to the other legume. It was thought that hairy vetch was superior green manure crop in considering yield of dry matter and N. (Key words : Winter legumes, Hairy vetch, Green manure yield, Nitrogen concentration)

• 한국응용과학기술학회지
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• 제27권2호
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• pp.137-143
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• 2010

Oxide semiconductors Thin-film transistors are an exemplified one owing to its excellent ambient stability and optical transparency. In particular zinc oxide (ZnO) has been reported because It has stability in air, a high electron mobility, transparency and low light sensitivity, compared to any other materials. For this reasons, ZnO TFTs have been studied actively. Furthermore, we expected that would be satisfy the demands of flexible display in new generation. In order to do that, ZnO TFTs must be fabricated that flexible substrate can sustain operating temperature. So, In this paper we have studied low-temperature process of zinc oxide(ZnO) thin-film transistors (TFTs) based on silicon nitride ($SiN_x$)/cross-linked poly-vinylphenol (C-PVP) as gate dielectric. TFTs based on oxide fabricated by Low-temperature process were similar to electrical characteristics in comparison to conventional TFTs. These results were in comparison to device with $SiN_x$/low-temperature C-PVP or $SiN_x$/conventional C-PVP. The ZnO TFTs fabricated by low-temperature process exhibited a field-effect mobility of $0.205\;cm^2/Vs$, a thresholdvoltage of 13.56 V and an on/off ratio of $5.73{\times}10^6$. As a result, We applied experimental for flexible PET substrate and showed that can be used to ZnO TFTs for flexible application.

• 한국미생물·생명공학회지
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• 제33권2호
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• pp.117-122
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• 2005

Beijerinckia indica를 통한 Heteropolysaccharide-7(PS-7)생산 최적화를 위해 다양한 탄소원과 질소원을 첨가하여 다른 배지 조성들이 PS-7에 미치는 영향을 조사하였다. 높은 C/N ratio에서 PS-7 생산을 배양 40시간까지 효과적으로 증가시킬 수 있었으며 낮은 C/N ratio에선 탄소원으로 첨가한 glucose가 균체의 생산에 사용되었을뿐 PS-7의 생산은 낮았다. 하지만, 높은 C/N ratio에서는 배양액의 점도로 균체의 생산이 정체하는 것으로 보아 본 실험에서는 20g/l glucose와 $NH_{4}NO_3$ 7.5 mM으로 33.3의 C/N ratio가 PS-7 생산에 적절한 비율인 것으로 관찰되었다. 다양한 탄소원을 첨가한 결과, B. indica는 PS-7 생산을 위하여 탄소원으로 hexose 또는 glucose-generating 당을 효율적으로 이용할 수 있었다. Beijerinckia indica를 이용한 PS-7 생산을 위해 첨가한 다양한 탄소원 중 sucrose 농도가 최고의 PS-7(6.96 g/L)을 생산 하였다. 51 배양기를 이용한 배양에서 탄소원 20 g/L glucose, 질소원 7.5 mM $NH_{4}NO_3$이 포함된 MSM 배지내 배양된 B. indica의 세포 농도가 최고 2.5 g/L이였고, 생산된 최고 PS-7농도는 7.5 g/L(35174 cp)으로 나타났다. 질소원이 완전히 소모된 12시간 이후, 7.5 mM의 $NH_{4}NO_3$, glutamine, glutamate을 첨가한 MSM 배지에서의 B. indica 배앙 결과, 질소원이 B. indica 내에서 탄소원 대사를 조절하는 역할을 하는 것을 관찰할 수 있었으며 최종적으로 PS-7의 생산을 조절할 수 있었다.

• Journal of Nutrition and Health
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• 제29권1호
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• pp.122-133
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• 1996

As ciarette smoking adversely affects vitamin C metabolism in humans, smokers need substantially more vitamin C intake than do non-smokers to achieve similar serum vitamin C concentration. To provide the basic information currently available for the determination of vitamin C requirement for Korean smokers, we investigated the differences the serum vitamin C values between smokers(n=53) and non-smokers(n=62) in relation to their intake of the vitamin through diet in 115 male college students, who had not been using vitamin C supplements. Dietary intakes of vitamin C were determined by a 24-hour recall, and serum vitamin C was determined using the 2, 4-dinitrophenylhydrazine method. The mean vitamin C intakes of smokers and non-smokers were consuming less than 75% of the Koeran RDA for vitamin c in their diet. Smokers consumed yellow and green leafy vegetables more often (P=0.02) and fresh fruits less often(P=0.006) than non-smokers. The mean serum vitamin C concentration of smokers consuming the same amounts of vitamine C as non-smokers, 64.3 umol/1, were 20% lower than for non-smokers, 80.1 umol/l(P<0.05). The risk of low serum vitamin C concentration (LoC) among smokers were 3.8% compared with 1.6% in non-smokers, and the odd ratio for LoC risk was 2.43. There were no correlations between dietary and serum vitamin C for smokers and non-smokers. It was concluded that smokers might require at least 20% more vitamin C to reach the same concentration comparable to non-smokers.