• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.599-603
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• 2012

The enantioselective hydrolysis of racemic styrene oxide in organic solvents was conducted using a recombinant E. coli expressing protein-engineered Mugil cephalus epoxide hydrolase (McEH). The volumetric total activity of the recombinant E. coli was enhanced 2.2-fold by IPTG induction at a mid-exponential growth phase. Among organic solvents with different log P values, isooctane was chosen based on the high activity and the enantioselectivity of McEH. Some lyoprotectants such as skim milk or sucrose enhanced the McEH activity. Enantiopure (S)-Styrene oxide with a 98% ee was obtained from the racemic styrene oxide with a 53.6% yield based on its theoretical yield in isooctane.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.127-134
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• 2016

A series of Ce-doped ZnO (Ce/ZnO) nanostructures were fabricated using the co-precipitation method, then a simply nontoxic hydrothermal approach was proposed for preparation of reduced graphene oxide (rGO)-Ce/ZnO composites. The synthesized composites were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS), UV-vis diffuse reflectance spectroscopy (DRS) techniques and Raman pattern. The as-synthesized rGO-Ce/ZnO composites showed high photodecomposition efficiency in comparison with the rGO-ZnO, Ce/ZnO, pure ZnO under UV, visible-light and sunlight irradiation. The degradation of methylene blue (MB) (10 mg/L, 100ml) by 95.8% within 60 min by using rGO-2 (10 mg) under sunlight irradiation was observed. The repeated use of the rGO-2 was investigated, and the results showed almost no decay in the catalytic activity.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.3
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• pp.367-375
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• 2005

Low-Z particle Electron Probe X-ray Microanalysis was applied to characterize MSW fly- and bottom -ash particle samples originated from two municipal incinerators (denoted as A and B) in Korea. According to their chemical composition, many distinctive particle types were identified. In A fly ash, the major chemical species are carbon-rich, aluminosilicates and many particles are composed of as a mixture of $ CaCO_3$ and other chemical species such as $CaSO_4$ or $CaCl_2$. For B fly ash, Fe, iron oxide, NaCl and NaCl-containing particles are the most abundant. In bottom ash, A and B were composed of similar chemical species such as carbon-rich, Fe, iron oxide, $CaCO_3$, and aluminosilicates. It was demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in the MSW ash samples. In addition, the technique has advantage over conventional analytical techniques in the point that both crystalline and glass-like ash particles can be analyzed at the same time.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3730-3734
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• 2011

The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % $NH_4F$ at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes ($D_{bottom}$) in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops ($D_{top}$) was accompanied by $D_{bottom}$ after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), $D_{top}$ was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.177-184
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• 2001

C3M(chemical mechanical micro machining) is applied for diminishing the size of burr and fabricating the massless patterning for aluminium wafer(thickness of 1${\mu}m$). It is difficult to perform the micro size machining with the radically increased shear stress. While the miniaturization and function-orientation of parts has been needed in the many field such as electronics, optics and medicine. etc., it is not enough to satisfy the industry needs in the machining technology. In this paper feasibility test of diminishing burr and fabricating maskless pattern was experimented and analyzed. In the experiment oxide layer was farmed on the aluminium with chemical reaction by ${HNO_3}$(10wt%), then the surface was grooved with tungsten carbide tool for the different condition such as the load and fred rate. The result was compared with the conventional machining to show the improvement of C3M with SEM for burr diminish and XPS for atomic existence, AFM for more precise image.

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.158-160
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• 2003

We have reported to make nanostructured cobalt oxide electrode that have large capacitance over than 400 F/g (specific capacitance) and good cycleability. But, it had serious demerits of low voltage range under 0.5 V and low power density. Therefore, we need to increase voltage range of cobalt oxide electrode. We report here on the electrochemical properties of sol-gel-derived nanoparticulate cobalt xerogel in 1M KOH solution and aqueous polymeric gel electrolyte. In solution electrolyte, cobalt oxide electrode had over 250 F/g capacitance consisted of EDLC and pseudocapacitance. In gel electrolyte, cobalt oxide electrode had around 100 F/g capacitance. This capacitance was only electric double layer capacitance of active surface area. In solution electrolyte, potassium ion as working ion reacted with both of layers easily. However, In gel electrolyte, reacted with only surface-active layer. Itis very hard to reach resistive layer. So, we have studied on pretreatment of electrode to contain working ions easily. We'll report more details.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.314-317
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• 1997

The electrical and physical characteristics of aluminum oxide and Pt thin films on it, deposited by reactive sputtering and DC magnetron sputtering respectively, were analyzed with increasing annealing temperature(400~80$0^{\circ}C$) by four point probe, SEM and XRD. Under $600^{\circ}C$ of annealing temperature, aluminum oxide had the properties of improving Pt adhesion to SiO$_2$and insulation without chemical reaction to Pt thin films and the resistivity of Pt thin films was improved. But these properties of aluminum oxide and Pt thin films on it were degraded over $700^{\circ}C$ of annealing temperature because aluminum oxide was changed into metal aluminum and then reacted to Pt thin films deposited on it. In the analysis of the thermal charateristics of Pt micro-heater fabricated on Si07/si substrate, the temperature of Pt micro-heater is up to 41$0^{\circ}C$ with the power dissipation 1.8 watts.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.41-45
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• 2012

We observed that in chemical vapor deposition (CVD) tungsten silicide (WSix) poly gate scheme, the gate oxide thickness decreases as gate length is reduced, and it intensifies the roll-off properties of transistor. This is because the fluorine diffuses laterally from WSix to the gate sidewall oxide in addition to its vertical diffusion to the gate oxide during gate re-oxidation process. When the channel length is very small, the gate oxide thickness is further reduced due to a relative increase of the lateral diffusion than the vertical diffusion. In DRAM cells where the channel length is extremely small, we found the thinned gate oxide is a main cause of poor retention time.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.8
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• pp.56-62
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• 1992

This paper is analyzed the charge trapping and electrical properties of 0(Oxide), NO(Nitrided oxide) and ONO(Reoxidized nitrided oxide) as dielectric films in MIS structures. We have processed bottom oxide and top oxide by the thermal method, and nitride(Si$_{3}N_{4}$) by the LPCVD(Low Pressure Chemical Vapor Deposition) method on P-type(100) Silicon wafer. We have studied the charge trapping properties of the dielectrics by using a computer controlled DLTS system. All of the dielectric films are shown peak nearly at 300K. Those are bulk traps. Many trap densities which is detected in NO films, but traps. Many trap densities which is detected in NO films. Varing the nitride thickness, the trap densities of thinner nitride is decreased than the thicker nitride. Finally we have found that trap densities of ONO films is affected by nitride thickness.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.346.2-346.2
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• 2014

To use the GaN based light-emitting diodes (LEDs) as solid state lighting sources, the improvement of light extraction and internal quantum efficiency is essential factors for high brightness LEDs. In this study, we suggested the new materials system of a zinc tin oxide (ZTO) layer formed on blue LED epi-structures to improve the light extraction. ZTO is a representative n-type oxide material consisted of ZnO and SnO system. Moreover, ZTO is one of the promising oxide semiconductor material. Even though ZTO has higher chemical stability than IGZO owing to its SnO2 content this has high mobility and high reliability. After formation of ZTO layer on p-GaN layer by using the spin coating method, structural and optical properties are investigated. The x-ray diffraction (XRD) measurement results show the successful formation of ZTO. The photoluminescence (PL) and absorption spectrum shows that it has 3.6-4.1eV band gap. Finally, the light extraction properties of ZTO/LED chip using electroluminescence (EL) measurement were investigated. The experimental and theoretical analyses were simultaneously conducted.