• Journal of Microbiology and Biotechnology
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• 제26권1호
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• pp.80-88
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• 2016

The enzyme-catalyzed Henry reaction was realized using deep eutectic solvents (DESs) as a reaction medium. The lipase from Aspergillus niger (lipase AS) showed excellent catalytic activity toward the substrates aromatic aldehydes and nitromethane in choline chloride:glycerol at a molar ratio of 1:2. Addition of 30 vol% water to DES further improved the lipase activity and inhibited DES-catalyzed transformation. A final yield of 92.2% for the lipase AS-catalyzed Henry reaction was achieved under optimized reaction conditions in only 4 h. In addition, the lipase AS activity was improved by approximately 3-fold in a DES-water mixture compared with that in pure water, which produced a final yield of only 33.4%. Structural studies with fluorescence spectroscopy showed that the established strong hydrogen bonds between DES and water may be the main driving force that affects the spatial conformation of the enzyme, leading to a change in lipase activity. The methodology was also extended to the aza-Henry reaction, which easily occurred in contrast to that in pure water. The enantioselectivity of both Henry and aza-Henry reactions was not found. However, the results are still remarkable, as we report the first use of DES as a reaction medium in a lipase-catalyzed Henry reaction.

• 한국분말재료학회지
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• 제16권3호
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• pp.217-222
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• 2009

This paper presents a novel single-step method to prepare the Ag nanometallic particle dispersed fluid (nanofluid) by electrical explosion of wire in liquid, deionized water (DI water). X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) were used to investigate the characteristics of the Ag nanofluids. Zeta potential was also used to measure the dispersion properties of the as-prepared Ag nanofluid. Pure Ag phase was detected in the nanofluids using water. FE-SEM analysis shows that the size of the particles formed in DI water was about 88 nm and Zeta potential value was about -43.68 without any physical and chemical treatments. Thermal conductivity of the as-prepared Ag particle dispersed nanofluid shows much higher value than that of pure DI water.

• 한국멀티미디어학회논문지
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• 제23권11호
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• pp.1372-1382
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• 2020

This paper proposes a core technology for a micro river monitoring terminal device suitable for flood monitoring in small rivers and valleys. Our proposed device is basically equipped with a 77GHz radar, gyro and accelerometer sensors. To measure the flow velocity and water level, we proposed a signal processing technique that extracts pure water energy components from the observed Doppler velocity and reflection intensity from the radar. And to determine the stability of the river structure equipped with our device, we constantly monitor the displacement of the measured values of the gyro and accelerometer sensors. Experimental result verified that our method detects pure water energy in various river environments and distinguishes between flow velocity and water level well. And we verified that vibration and position change of structures can be determined through a gyro sensor. In future research, we will work to build a secure digital twin river network by lowering the cost of supplying RF-WAV devices. Also we expect our device to contribute to securing a preventive golden time in rivers.

• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1200-1205
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• 2014

The effect of nanofluids on the heat transfer performance of a pulsating heat pipe has been experimentally investigated. Water-based diamond nanofluid and aluminium oxide ($Al_2O_3$) nanofluid were tested in the concentration range of 0.5-5%. The pulsating heat pipe was constructed using clear Pyrex tubes of 1.85 mm in inner diameter in order to visualize the pulsating action. The total number of turns was eight each for heated and cooled parts. The supply temperatures of heating water and cooling water were fixed at $80^{\circ}C$ and $25^{\circ}C$ respectively. The liquid charging ratio of the nanofluid was 50-70%. The test results showed that the case of 5% concentration of diamond nanofluid showed 18% increase in heat transfer rate compared to pure water. The case of 0.5% concentration of $Al_2O_3$ nanofluid showed 24% increase in heat transfer rate compared to pure water. But the increase of $Al_2O_3$ nanofluid concentration up to 3% did not show further enhancement in heat transfer. It is also observed that the deposited nanoparticles on the tube wall played a major role in enhanced evaporation of working fluid and this could be the reason for the enhancement of heat transfer by a nanofluid, not the enhanced thermal conductivity of the nanofluid.

• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.69-75
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• 1999

The silica-pillared H-kenyaites were prepared by interlarmellar base-catalyzed reaction of tetraethylorthosilicate [TEOS, Si(OC2H5)4] intercalated into the interlayer of H-kenyaite. The intercalation of TEOS was conducted by the octylamine preswelling process, resulting in a dramatic increase in gallery height to 24.7 Å. The interlamellar hydrolysis of octylamine-TEOS/H-kenyaite paste were conducted between 10 min and 40 min in 0.00%, 0.05% and 0.10% NH3-water solution respectively, and resulting in siloxane-pillared H-kenyajte with gallery height of 28.2-31.8 Å. The calcination of samples at 538 ℃ resulted in silica-pillared H-kenyaites with a large surface areas between 411 m2/g and 885 m2/g, depending on the aging time and NH3 concentration. Samples with optimum specific surface areas and well ordered-basal spacing were obtained by reaction between 10 min and 40 min in pure water and 0.05% NH3-water solution. Mesoporous samples with narrow pore size distribution were also prepared by reaction for 10-40 min in 0.05% NH3 solution. Rapid interlamellar reaction of TEOS in pure water showed that intercalated octylamine itself could act as a base catalyst during interlamellar polycondensation of TEOS.

• Corrosion Science and Technology
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• 제9권6호
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• pp.325-330
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• 2010

Many surface protection methods have been developed to apply for constructional steels used under severe corrosive environment. Thermal spray coating has been known to be an attractive technique due to its relatively high coating speed. Furthermore high corrosion resistance of coated film with thermal spray is required to expand its application. Four types of coated films(DFT:300 um) such as pure zinc, pure aluminum and two Al-Zn alloy (Al:Zn=85:15 and Al:Zn=95:5) onto the carbon steel (SS401) were prepared with arc spray, and the corrosion behavior of their samples were evaluated by electrochemical method in this study. Pure aluminum sample showed high corrosion resistance behavior exposed to sea water solution and pure zinc and alloy (Al:Zn=95:5) samples followed pure aluminum sample. The other alloy(Al:Zn=85:15) so called galvalume coated onto the carbon steel ranks the 4th corrosion resistance in this study. The results of porosity ratio of those samples by observation are well matched with the electrochemical data.

• Journal of the Korean Wood Science and Technology
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• 제48권3호
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• pp.405-413
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• 2020

Recycling of ionic liquid (1-ethyl-3-methylimidazolium acetate, [EMIM]Ac) after the pretreatment of Salix gracilistyla Miq. was conducted and the effect of the recycling number on the enzymatic saccharification yield was investigated. Enzymatic saccharification was performed using an enzyme cocktail (Acremonium cellulase and Optimash BG) at 50 ℃ for 72 h. All recycled [EMIM]Ac samples showed a lower amount of water soluble fraction than pure [EMIM]Ac. On increasing the recycling number from 1 to 4, the amount of water soluble fraction decreased from 18% to 15%. The X-ray diffraction pattern of the products pretreated with recycled [EMIM]Ac showed cellulose I crystalline polymorph. The crystallinity of the product pretreated with recycled [EMIM]Ac was 47-49%, which was lower than 33% of that with pure [EMIM]Ac. The yields of glucose and xylose decreased in the pretreatment with recycled [EMIM]Ac compared to that with pure [EMIM]Ac.

• 상하수도학회지
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• 제14권2호
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• pp.157-163
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• 2000

An experimental study was conducted to evaluate the treatment efficiency of paper-mill wastewater using pure oxygen activated sludge process. Effects of hydraulic retention time (HRT) and organic loading on process performance and kinetics were investigated. The raw paper-mill wastewater(BOD concentration ${\leq}500mg/L$) and the effluent from dissolved air flotation(DAF) treatment(BOD concentration ${\geq}500mg/L$) were used as influent for pure oxygen activated sludge process. Average BOD removal efficiencies were above 89.3% under 6hours or longer of HRT, while under 3hours of HRT they decreased to about 82%. With the effluent from DAF process, the half saturation constants($K_S$) and the maximum specific substrate removal rate($K_{max}$) were 85 mg/L and 2.25 L/day, respectively. However, with the raw paper-mill wastewater, both $K_S$ and $K_{max}$ increased to 156 mg/L and 3.84 L/day, respectively. The microbial yield coefficient(Y) and the decay coefficient($K_d$) were 0.46 gVSS/gBOD and 0.03 L/day, respectively, with effluent from DAF process. While, Y and $K_d$ were 0.24 gVSS/gBOD and 0.035 L/day, respectively, with the raw paper-mill wastewater.

• 한국안전학회지
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• 제14권1호
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• pp.86-92
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• 1999

This study was carried out to investigate the effect of chemical cleaning of corrosion product on cooling system made of copper as a basic material and using cooling water as pure water. We studied chemical cleaning condition that minimizes the influence on basic material by means of EDTA solution so as to eliminate the slurry in cooling system. In addition, the proper amount of NALCO-39L (Nitrite-Borate-BZT mixture) as a inhibitor was determined in order to protect the copper in cooling system against corrosion after chemical cleaning and the effect of corrosion resistance on the copper surface treated was excelent in comparison with surface untreated. As a result, we found that the main components of sludge in cooling system produced by corrosion of copper were $Cu_2O$, CuO, Cu, and Fe. The optimum condition of chemical cleaning was 400ppm EDTA solution at $60^{\circ}C$. Inhibitor concentration needed to treat the surface of pure copper was 15～20ppm per unit area and corrosion rate of copper treated with 500ppm inhibitor solution for 72 hrs at $60^{\circ}C$ was remarkably decreased as compared with that of pure copper.

• 한국전기전자재료학회논문지
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• 제30권8호
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• pp.514-519
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• 2017

TiN (titanium nitride) films were prepared using the RF magnetron sputtering technique. The films were deposited by pure $N_2$ plasma sputtering. Their mechanical properties, such as nano-indentation hardness, friction coefficient, and surface wettability, have been investigated. X-ray diffraction (XRD) studies revealed that the orientation of $TiN_X$ films changed towards the (111) orientation with decreasing working pressure due to a strong compressive stress during deposition. The strongest TiN (111) orientation was found when the film was deposited at a working pressure of 1 Pa. This film showed the largest hardness (16 GPa) and smallest friction coefficient (0.17) among the studied samples. Moreover, this film was found to be accompanied by a water-repellent surface with water contact angle more than $100^{\circ}$.