• 한국결정성장학회지
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• 제5권4호
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• pp.358-369
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• 1995

SIC와 금속박막의 반응에 의한 표면구조 및 부착력이 550$^{\circ}C$에서 1450$^{\circ}C$의 온도범위에서 조사되어졌다. SiC/Co계에서는 850$^{\circ}C$ 이상에서, SiC/Ni계에서는 650$^{\circ}C$ 이상에서 여러 가지 규소화물이 형성된 반응이 최초로 나타났다. 코발트는 1050$^{\circ}C$, 0.5 h에서 니켈은 950$^{\circ}C$, 2h에서 SiC와 완전히 반응하여 소모되었다. SiC/Co에서는 CoSi상이 SiC/Ni에서는 Ni$_{2}$Si상이 1250$^{\circ}C$와 1050$^{\circ}C$의 반응에서까지 각각 열역학적으로 안정하게 관찰되어졌다. 탄소는 SiC/Co 반응표면에서는 1450$^{\circ}C$ 이상에서 그리고 SiC/Ni 반응표면에서는 1250$^{\circ}C$ 이상에서의 온도에서 흑연으로 결정화되었다. SiC기판과 금속박막의 임계하중이 scratch test 방법에 의하여 정성적으로 비교되어져, 850$^{\circ}C$에서 1050$^{\circ}C$의 온도범위에서 SiC/Ni couple이 20~33N의 상대적으로 높은 값을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2178-2182
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• 2011

Recently, the synthesis of ordered macroporous materials has received much attention due to its potential use as photonic band gap materials.$^1$ In this study, we have used the three-dimensional (3D) latex array template impregnated with benzenesulfonic acid (BSA), which is capable of catalyzing the reaction using tetraethyl orthosilicate (TEOS) as a precursor and distilled water. The polystyrene (PS) templates were reacted with TEOS in $scCO_2$ at 40 $^{\circ}C$ and at 80 bar. In the reactor, TEOS was filtrated into the PS particle lattice. After the reaction, porous silica materials were obtained by calcinations of the template. The stability test of the PS template in pure $CO_2$ was conducted before the main experiment. Scanning electron microscopy (SEM) images showed that the reaction in $scCO_2$ takes place only on the particle surface. This new method using $scCO_2$ has advantages over conventional sol-gel processes in its capability to control the fluid properties such as viscosity and interfacial tension. It has been found that the reaction in $scCO_2$ occurs only on the particle surface, making the proposed technique as more rapid and sustainable method of synthesizing inverse opal materials than conventional coating processes in the liquid phase and in the vapor phase.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.279-286
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• 2020

In this article, we develop a reactive distillation (RD) column configuration for the production of hydrogen. This RD column is in the HI decomposition section of the sulphur - iodine (SI) thermochemical cycle, in which HI decomposition and H₂ separation take place simultaneously. The section plays a major role in high hydrogen production efficiency (that depends on reaction conversion and separation efficiency) of the SI cycle. In the column simulation, the rigorous thermodynamic phase equilibrium and reaction kinetic model are used. The tuning parameters involved in phase equilibrium model are dependent on interactive components and system temperature. For kinetic model, parameter values are adopted from the Aspen flowsheet simulator. Interestingly, there is no side reaction (e.g., solvation reaction, electrolyte decomposition and polyiodide formation) considered aiming to make the proposed model simple that leads to a challenging prediction. The process parameters are determined on the basis of optimal hydrogen production as reflux ratio = 0.87, total number of stages = 19 and feeding point at 8th stage. With this, the column operates at a reasonably low pressure (i.e., 8 bar) and produces hydrogen in the distillate with a desired composition (H₂ = 9.18 mol%, H₂O = 88.27 mol% and HI = 2.54 mol%). Finally, the results are compared with other model simulations. It is observed that the proposed scheme leads to consume a reasonably low energy requirement of 327 MJ/kmol of H₂.

• 한국분말재료학회지
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• 제21권6호
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• pp.467-472
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• 2014

RBSC (reaction-bonded silicon carbide) represents a family of composite ceramics processed by infiltrating with molten silicon into a skeleton of SiC particles and carbon in order to fabricate a fully dense body of silicon carbide. RBSC has been commercially used and widely studied for many years, because of its advantages, such as relatively low temperature for fabrication and easier to form components with near-net-shape and high relative density, compared with other sintering methods. In this study, RBSC was fabricated with different size of SiC in the raw material. Microstructure, thermal and mechanical properties were characterized with the reaction-sintered samples in order to examine the effect of SiC size on the thermal and mechanical properties of RBSC ceramics. Especially, phase volume fraction of each component phase, such as Si, SiC, and C, was evaluated by using an image analyzer. The relationship between microstructures and physical properties was also discussed.

• 대한수의학회지
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• 제41권1호
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• pp.89-98
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• 2001

This study was conducted to detect the toxoplasma specific-DNA in circulating blood and organs collected from slaughtered pigs at slaughtering house and experimentally infected pigs with Toxoplasma gondii tachyzoites by polymerase chain reaction(PCR), and also PCR was applied to diagnose for acute phase of swine toxoplasmosis as a newly developed diagnostic test. The sensitivity of oligonucleotide primer, T-1 & T-2, designed from toxoplasma B1 gene amplification method was compared with Tp parasite detection by mouse inoculation(MI). On the other hand, latex agglutination test(LAT) was conducted to detect the serum antibodies comparing with the detection of toxoplasma by PCR and MI. The results obtained were summarized as follows. PCR was able to determine at the lowest level of $10^0/ml$ T. gondii in blood samples which were blended with a serial diluted T gondii in vitro. On the other hand, $10^2/5g$ of T gondii could detect from a variety of tissues including lung, diaphragm, liver, heart, spleen and brain in vitro. The primer was proved to specifically determine T gondii in blood and tissues in vitro but it did not detect Neospora caninum used as a negative control. DNA of T. gondii was effectively extracted by freezing, thawing and grinding twice both tissues mixed with T gondii in vitro and in experimentally infected pig's tissues. PCR detected specific DNA in the blood of experimentally infected pigs at 108 hrs and 120 hrs post-infection, it was the same time that the pigs showed fever and parasitaemia. In case of tissue, specific DNA was, however, detected only lung from experimentally infected pigs. Even though the duration of acute phase was from 3 to 7 days post-infection, but the latex agglutination test (LAT) results appeared from 8 days post-infection. A comparison of sensitivity in determining T gondii in blood samples between PCR and MI, PCR positive rate ranged from 25 to 33.3%, but that of MI covered from 75 to 100%.

• 공업화학
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• 제7권3호
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• pp.580-587
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• 1996

소성법을 이용하여 반응은도 $1050^{\circ}C$, 반응시간 3시간, $K_2CO_3$에 대한 $TiO_2$(rutile)의 mole ratio 2.8 그리고 $1^{\circ}C/min$의 서냉속도로 서냉하여 초생상을 합성하였으며, 이를 비등수로 10시간 처리하여 층상구조를 갖는 장섬유의 $K_2Ti_4O_9$을 효과적으로 합성하였다. 또한 합성된 $K_2Ti_4O_9$의 열적안정성을 조사하였으며, 이 결과 $K_2Ti_4O_9$은 열적으로 매우 불안정하여 온도가 올라감에 따라 $K_2O$와 $K_2Ti_6O_{13}$으로 분리됨을 확인하였다.

• KSBB Journal
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• 제9권3호
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• pp.312-318
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• 1994

Ac-Tyr-OH의 에스테르화 반응은 water/water­m miscible organic solvent를 이용하여 단일상계 (one phase system) 조건 하에서 ${\alpha}$-chymotrypsin의 촉 매작용으로 진행하였으며, 그 결과는 다음과 같다. Ac- Tyr-OH(1OmM)이 함유된 에탄올(lOml)[ 4 % %(v/v) buffer 함유] 용액에서 ${\alpha}$-chymotrypsin의 촉매작용에 의한 에스테르화 반응에 영향을 마치는 흡착물질 chitin, chitosan, Sephadex G-25 및 G-50, CM 및 DEAE-Sephadex, CM 및 DEAE cellulose 중 chitin을 첨가하였을 경우, 에스테르화 수율이 62%로 가장 높았다. 그리고 에스테르화 수 율에 마치는 최적반응조건은 chitin/${\alpha}$-chymotry psm의 비가 20(w/w), 온도 $35^{\circ}C$, pH 8.0 빛 유기 용매에 첨가된 수용액의 농도는 2%(v/v)였다. 또한, water/water-miscible organic solvent system 에서 chitin의 첨가는 효소의 안정성에 기여하는 것으로 나타났다. 최적반응조건 하에서 에스테르화 반응의 수율, Km 및 Vmax 값은 각각 93%, 3.093mM 및 1.088mM/mg/hr이었다.

• 대한화학회지
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• 제55권4호
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• pp.691-696
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• 2011

CTAB 혹은 CTAB-나피온 촉매를 속빈 실리콘 튜브형 MCM-41에 담지시켰다. 이들 촉매들을 XRD, SEM, BET 등으로 분석하였다. 이들을 1,7-heptanediol 의 브롬화 반응 촉매로 사용하였고 다른 촉매들과 비교하였다. 이들 촉매들은 CTAB 보다 효과가 좋았으며 CTAB-Nafion/MCM-41 이 성능이 가장 우수하였다.

• Carbon letters
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• 제15권4호
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• pp.247-254
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• 2014

In this work, thermal treatment accompanied with different acid treatments was applied to a commercial coal tar pitch (CTP) to obtain a spinnable precursor pitch for carbon fiber. In the case of thermal treatment only, a relatively high reaction temperature of between $380^{\circ}C$ and $400^{\circ}C$ was required to obtain a softening point (SP) range of $220^{\circ}C-260^{\circ}C$ and many meso-phase particles were created during the application of high reaction temperature. When nitric acid or sulfuric acid treatment was conducted before the thermal treatment, the precursor pitch with a proper SP range could be obtained at reaction temperatures of $280^{\circ}C-300^{\circ}C$, which were about $100^{\circ}C$ lower than those for the case of thermal treatment only. With the acid treatments, the yield and SP of the precursor pitch increased dramatically and the formation of meso-phase was suppressed due to the lower reaction temperatures. Since the precursor pitches with acid and thermal treatment were not spinnable due to the inhomogeneity of properties such as molecular weight distribution and viscosity, the CTP was mixed with ethanol before the consecutive nitric acid and thermal treatments. The precursor pitches with ethanol, nitric acid, and thermal treatments were easily spinnable, and their spinning and carbon fiber properties were compared to those of air blowing and thermal treated CTP.

• 한국환경농학회지
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• 제6권1호
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• pp.44-49
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• 1987

본 연구는 제초제인 alachlor이 가지는 선택성이 식물고유의 생화학적 차이에 기인한다는 가정하에, 이의 규명을 목적으로 수행하였다. 공시작물인 대두, 배추 및 피는 alachlor 수용액의 처리로 경중의 약해를 입었으며 그 피해는 해당식물의 glutathione 또는 homoglutathione 함량이 많을 수록 적었다. 비효소적 반응조건 하에서 가한 alachlor의 17.7%가 GS-alachlor conjugate로 전환됨을 관찰하였으며, 이어 수행한 공시작물의 유묘시험에서는 처리한 C-14 표지 alachlor이 단시간(24hrs)에 4∼5개의 수용성 대사물로 전환되 었으며, 주요대사물로 대두에서는 homoglutathione-alachlor, 깨, 배추 그리고 피에서는 glutathione-alachlor conjugates를 잠정적으로 확인하였다. 본 연구에서 채택한 3종의 공시식물의 경우, 식물체 내에서 glutathione (및 homoglutathione)과 alachlor와의 phase Ⅱreaction인 conjugation 반응이 해독반응으로 작용, alachlor의 선택성에 공헌하는 것으로 해석하였다.