• 한국자원식물학회지
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• 제24권4호
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• pp.343-350
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• 2011

유사미소중력, 진동 그리고 저온과 같은 물리적 스트래스하에서 4일간 자란 약용식물인 스테비아(Stevia rebaudiana Bertoni)는 대조구에 비해 3.6%, 21% 그리고 8.7%의 생체 중량의 감소를 보였다. 합성 항산화물질인 AA(ascorbic acid)와 BHA(beta-hydroxyacetic acid)는 비교적 약한 22%와 27%의 항산화 활성을 보였다. 유사미소중력하에서 스테비아의 DPPH(2,2-diphenyl-1-picryl hydrazal)의 음이온 소거효과는 대조구보다 지속적으로 더 높게 나타났으나, 진동과 저온처리의 처리효과는 급히 증가했다가 진동의 경우는 6시간 후에 감소되고 저온처리의 경우는 24시간 후에 대조구 수준으로 감소되었다. 유사미소중력하에서 SOD활성은 대조구에 비해 147%, 진동과 저온처리는 각각 121%와 125%로 증가를 보였다. 이상의 결과로부터 유사미소중력스트레스는 다른 스트레스보다 스테비아의 항산화 활성에 더 효과적인 영향을 미치는 것이 분명해졌다.

• 한국산학기술학회논문지
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• 제20권7호
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• pp.599-606
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• 2019

위험물질에 의한 제조물을 취급하는 설비와 시설은 대부분 고온, 고압으로 공정을 운전을 한다. 이로 인해 화재폭발로 인한 위험성이 증대되고 있다. 특히, 폭발 사고는 석유 화학 가스설비 등 위험물 시설의 가장 주된 위험요인으로 작용하고 있으며, 그 중, 프로필렌은 석유화학 플랜트의 기초 원료 및 첨가 중합반응에 의한 합성물질을 제조하는 현장에서 많이 사용되고 있다. 산소농도의 변화에 대한 폭발범위를 구함으로써 프로필렌을 사용하는 사업장에서 발생 될 수 있는 폭발을 예방하기 위하여 불활성 가스인 $CO_2$를 이용하여 온도와 압력의 변화에 따라 산소농도의 변화에 대한 폭발범위를 구하였다. 온도는 $25^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$로 변화시켜 측정하였으며, 용기 내 압력을 $1.0kgf/cm^2.G$, $1.5kgf/cm^2.G$, $2.0kgf/cm^2.G$, $2.5kgf/cm^2.G$로 $CO_2$를 가압시켜 측정하였다. 폭발한계는 온도, 압력 및 산소농도와 관계가 있으며, 온도와 압력이 높아질수록 최소산소농도는 낮아지고, 산소농도가 낮아질수록 폭발범위는 좁아졌다. 또한, 최소산소농도 이하의 농도에서는 프로필렌의 증기와 점화원이 존재하여도 폭발이 발생하지 않는 것을 알 수 있다.

• 대한화학회지
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• 제59권3호
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• pp.215-224
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• 2015

Unsymmetrical tetradentate Schiff base N-(2-hydroxy-5-methylacetophenone)-N'-(2-hydroxy acetophenone) ethylene diamine (H₂L) and its complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, IR, electronic spectra and thermogravimetric analyses. ¹H, ¹³C-NMR and FAB Mass spectra of ligand clearly indicate the presence of OH and azomethine groups. Elemental analyses of the complexes indicate that the metal to ligand ratio is 1:1 in all complexes. Infrared spectra of complexes indicate a dibasic quadridentate nature of the ligand and its coordination to metal ions through phenolic oxygen and azomethine nitrogen atoms. The thermal behavior of these complexes showed the loss of lattice water in the first step followed by decomposition of the ligand in subsequent steps. The thermal data have also been analyzed for the kinetic parameters by using Horowitz-Metzger method. The dependence of the electrical conductivity on the temperature has been studied over the temperature range 313-403 K and the complexes are found to show semiconducting behavior. XRD and SEM images of some representative complexes have been recorded. The antimicrobial activity of the ligand and its complexes has been screened against various microorganisms and all of them were found to be active against the test organisms. The Fe(III) and Ni(II) complex have been tested for the catalytic oxidation of styrene.

• 한국응용과학기술학회지
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• 제23권3호
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• pp.207-214
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• 2006

$Y_{2-x}Gd_xO_3:Eu$, phosphors for plasma display panel(PDP), were prepared by Pechini method which use yttriun chloride, gadolinium chloride, and europium oxide as starting materials. This method is a different way to the synthesis of europium(Eu)-doped phosphors, and it consists of the formation of a polymeric resin obtained by polyesterification between metal chelate compounds and a polyfunctional alcohol. This needs lower temperature than solid-state synthetic method. The prepared $Y_{2-x}Gd_xO_3:Eu$ phosphor particles had spherical shape and coherence. The luminescence intensity of $Y_{2-x}Gd_xO_3:Eu$ phosphor particles increased according to the increase of gadolinium(Gd) content(to 0.8mol%), and $Y_{1.2}Gd_{0.8}O_3:Eu$ phosphors had the highest luminescence intensity under vacuum ultra violet(VUV) excitation. The optimum concentration of Eu in the phosphor and optimum calcination temperature was 3wt% and $1100^{\circ}C$. The prepared phosphors were consist of particle, and its size was between 100nm and 150nm. Among the different polyfunctional alcohols, diethylene glycol(DEG) improved the luminescence intensities of phosphors more than other additives. The Pechini method proved that it is demonstrated to be suitable for the synthesis of phosphors used in PDP.

• 한국미생물·생명공학회지
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• 제25권1호
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• pp.89-95
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• 1997

The current processer of the textile wastewater treatment are mostly consisted of a combination of a physico-chemical and a biological treatment. The overall efficiency of these processes is, however, assessed to be fairly low. It is even worse during the summer season when temperature of the wastewater rises above 40$\circ $C. Therefore, a feasible process of the textile wastewater treatment which can work efficiently at higher temperatures was investigated in this work. We used a bench scale reactor consisted of one 4 liter anaerobic and one 8 liter aerobic tank, and the thermophilic symbiotic PVA degraders, Pasteruella hemolytica KMG1 and Pseudomonas sp. KMG6 that had been isolated in our laboratory. In the preliminary flask experiments, we observed that the thermophilic symbiotic PVA degraders could not grow in the wastewater substrate. Then, we isolated the mutant strains by acclimating the KMG1and KMG6 strains to the wastewater medium. The mutant symbionts (KMG1-1 and KMG6-1) were isolated through 6 times successive transfers into the fresh wastewater medium after 5 days culture for each. The mutant strains obtained grew well in the mixed medium composed of 75% wastewater and 25% synthetic medium, and supplemented with 0.5% PVA as a sole carbon source. During the culture for 14 days at pH 7.0 and 40$\CIRC $C, the bacteria assimilated about 89% of the added PVA. The symbionts degraded equally well all the PVA substrates of different molecular weight (nd=500~30000). In contrast to the flask experiments, in the reactor system the mutant strains showed very low levels of the PVA and COD removal rates. However, the new reactor system with an additional aerobic tank attained 82% removal rate of COD, 94% of PVA degradation and 71% of color index under the conditions of 5% inoculm on the tank 2, incubation temperature of 40$\circ $C, dissolved oxygen level of 2~3 mg/l and retention time of 30 hours. This result ensures that the process described above could be an efficient and feasible treatment for the PVA contained textile wastewater at higher temperatures.

• 공업화학
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• 제28권4호
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• pp.485-489
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• 2017

Polyethylene terephthalate (PET)는 화학적 안정성과 높은 기계적 강도를 가지고 있어 식품, 의류 등 다양한 분야에서 사용되고 있으며, 이로 인해 PET는 주요 폐플라스틱 폐기물 중 하나이다. 본 연구에서 PET를 재활용하기 위해 ethylene glycol (EG)와 glycolysis의 반응을 이용하여 단량체 회수에 관한 연구를 수행하였다. 마이크로 튜빙 반응기를 사용하여 EG/PET비율 1~4, 반응시간 15~90 min, 반응온도 $250{\sim}325^{\circ}C$에서 망간, 구리 촉매 조건하에서 연구를 진행하였다. 10 wt% $Cu/{\gamma}-Al_2O_3$ 촉매에서 반응온도, 시간과 EG/PET의 비가 각각 $300^{\circ}C$, 30 min와 1 : 2였을 때 가장 높은 89.46%의 bis (2-hydroxyethyl) terephthalate monomer (BHET) 수율을 나타내었다.

• 한국해양학회지
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• 제30권6호
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• pp.543-549
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• 1995

연속된 AVHRR/SST 자료를 이용한 표층유속의 추정에 역행렬법이 이용되어 왔다. 본 모델에서 방정식체계는 열방정식과 제한요소로서 가중치가 있는 발산최소화이다. 제한요소는 열방정식의 속도해중에서 null space(Menke, 1984)에 해당하는 해를 구하기 위하여 도입되었으며 이 식들은 격자화한 영역에서 AVHRR/SST의 수온경사에 의해 선형화된다. 실험은 열방정식에 대한 발산최소화의 상대적 중요성을 나타내는 가중치의 크기를 설정하기 위하여 수행하였으며 행렬식은 SVD(Singular Value Decomposion)에 의해 해를 구했다. 실험에서 가상온도분포의 수온경사와 가상유속장의 발산의 크기는 실제해역에 근사시켰다. 열방정식은 착산의 효과를 무시하고 열속이 공간적으로 일정한 것으로 가정하여 구성하였으며 이와같은 가정에 의한 오류를 고려하기 위하여 가상 온도자료에 무작위오류를 도입하였다. 실험결과에 의하면 가중치를 설정하는 기준으로서 상대오차 최소화가 잔차최소화보다 바람직한 것으로 나타났으며 가중치가 $10^{-1}$의 크기일 때 추정유속의 오류가 가장 작은것으로 나타났다.

• Tribology and Lubricants
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• 제36권3호
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• pp.124-132
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• 2020

The effect of the stoichiometry on the sliding wear properties of NiAl coatings has been investigated. Three different powder mixtures with the compositions of Ni-50at%Al, Ni-54at%Al and Ni-42at%Al were diepressed respectively, and which were subsequently coated on mild steel through combustion synthesis in an induction heating system. Sliding wear behavior of the coatings was examined against an alloyed tool steel using a pin-on-disc type sliding wear test machine. As results, it could be seen that powder mixture(Ni-54at%Al) with displaying Al-rich deviations from the stoichiometry of NiAl(Ni-50at%Al) was promoted the most the synthetic reactivity. The microstructure of the coating layer with the compositions of Ni-54at%Al exhibits the porous NiAl single phase structure. However, the microstructure of the coating layer of the compositions of Ni-42at%Al exhibits the denser multi-phase structure containing several intermediate phases in addition to NiAl. Densification of the coating layer was enhanced by increasing the reacting temperature. On the other hand, the wear properties of the coating layers showed that the wear mode at speeds of around 1 m/s was severe wear, regardless of the stoichiometry and reacting temperature. However, wear properties of coating layer with the compositions of Ni-42at%Al were superior to those of coating layer with the compositions of Ni-54at%Al. This would be attributed by the fact that coating layer with the compositions of Ni-42at%Al develops little void and much intermediate phases with high strength.

• 한국광물학회지
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• 제16권2호
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• pp.161-169
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• 2003

한성 비정질 투휘석$(Ca,Mg)SiO_3$에 대한 상변이 연구를 압력은 다이아몬드앤빌기기를 이용하여 ∼30 GPa까지, 온도는 약(YAG) 레이저 가열기기를 이용하여 ∼$1000^{\circ}C$에서 조사(scanning)하여 시행하였다. 비정질 투휘석은 고온-고압 하에서 곧바로 등축정계에 속하는 단상의 $(Ca,Mg)SiO_3$페롭스카이트 결정구조로 상변이 하였다. 이러한 결과는 고온-고압 하에서 사방정계에 속하는 $MgSiO_3$페롭스카이트 상과 등축정계에 속하는 $CaSiO_3$페롭스카이트 상으로 분리되는 상변이를 하는 결정질 투휘석의 상변이 계통과는 큰 차이를 보이고 있다. 이러한 차이는 출발시료의 차이점이나 특히 온도가 상변이에 큰 영향인자로 작용하여 기인한 것으로 판단된다. 이러한 강변이 관계는 맨틀의 온도, 압력 및 산소분압 차이 등에 의해 맨틀전이대나 하부맨틀을 구성하는 광물상의 조합에 영향을 줄 수 있다.

• Journal of Microbiology and Biotechnology
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• 제16권3호
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• pp.360-367
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• 2006

The endoinulinase gene (inu1) from Pseudomonas mucidolens was expressed on the cell surface of Saccharomyces cerevisiae by fusing with Aga2p linked to the membrane anchored protein, Aga1p. The inu1 gene of P. mucidolens was subcloned into the surface display vector, pCTcon (GAL1 promoter). The constructed plasmid, pCTENIU (8.5kb), was then introduced to S. cerevisiae EBY100 cells and the yeast transformants selected on synthetic defined media lacking uracil and inulin-containing media. The inu1 gene under the control of the GAL1 promoter was successfully expressed in the yeast transformants, and the surface display of endoinulinase confirmed by immunofluorescence microscopy, along with its enzymatic ability to form inulooligosaccharides (IOSs) from inulin. The total endoinulinase activity reached about 2.31 units/ml when the yeast transform ants were cultivated on a YPDG medium. To efficiently hydrolyze the inulin, various reaction conditions were examined, including the pH, temperature, and inulin source. The optimized conditions were then determined as follows: pH, 7.0; temperature, $50^{\circ}C$; inulin source, Jerusalem artichoke. Under the optimized condition and 46 units of endoinulinase per g of inulin, IOSs started to be produced after 10 min of enzymatic reaction. The highest yield, 71.2% of IOSs, was achieved after 30 h of reaction without any significant loss of the initial enzyme activity. As a result of the reaction with inulin, IOSs consisting of inulobiose (F2), inulotriose (F3), inulotetraose (F4), and inulopentaose (F5) were produced, and F4 was the major product.