• Progress in Superconductivity
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• v.8 no.1
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• pp.93-97
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• 2006

YBCO films were deposited on a moving substrate by a spray pyrolysis method using nitrate aqueous solution as precursors. Deposition was made on $LaAlO_3$(100) single crystal substrate by spraying precursor droplets generated by a concentric nozzle. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:4.5. The distance between nozzle and substrate was 15 cm. Substrate was transported with a speed ranging from 0.23 cm/min to 0.5 cm/min. Films were deposited at the pressure ranging from 10 Torr to 20 Torr and the deposition temperature was ranged from $740^{\circ}C\;to\;790^{\circ}C$. Oxygen partial pressure was controlled between 1 Tow and S Torr. Superconducting YBCO films were obtained from $740^{\circ}C\;to\;790^{\circ}C$ with an oxygen partial pressure of 3 Torr. Scanning electron microscope(SEM) and X-ray diffraction(XRD) observation revealed that films are smooth and highly texture with(001) plans parallel to substrate plane. Highest Jc was 0.72 $MA/cm^2$ at 77K and self-field for the film with a thickness of 0.15 m prepared at a substrate temperature of $740^{\circ}C$ and $PO_2$=3 Torr.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.118-124
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• 2001

When particles are dissolved in solution, they have different zeta-potentials depending on pH. Zeta-potential has an influence on particle separation, which can control particle size. And the size of $WO_3$ particle affects the sensitivity of $WO_3$ sensor for detecting NO gas. Therefore we study influence of pH on NO-sensing $WO_3$ gas sensor fabricated by Sol-Coprecipitation method. As pH increases from 2 to 7, dynamic mobility of $WO_3$ precursor was increased. When pH was 7, it showed the largest distribution separation. It means when pH is 7, we can make $WO_3$ powder which has smaller particle size. And it is confirmed by particle size analysis of $WO_3$ powder, X-ray diffration result of $WO_3$ sensing layer and surface morphology. It also affect NO sensing characteristics of $WO_3$ gas sensor. The sensing film synthesized at pH 7 showed the largest sensitivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.101-101
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• 2010

ZnO shows a direct band gap of 3.37eV, large exciton binding energy (~60 meV), high oxidation ability, high sensitivity to many gases, and low cost, and it has been used in various applications such as transparent electrodes, light emitting diodes (LEDs), gas sensors and photocatalysts. Among these applications ZnO as photocatalyst has considerably attracted attention over the past few years because of its high activities in removing organic contaminants generated from industrial activities. In this research, ZnO nanoparticles were synthesized by spray-pyrolysis method using the zinc acetate dihydrate as starting material at synthesis temperature of $900^{\circ}C$ with concentration varied from 0.01 to 1.0M. The physical and chemical properties of the synthesized ZnO nanoparticles were examined by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transformation Infrared (FT-IR), and UV-vis spectroscopy. The Miller indices of XRD patterns indicate that the synthesized ZnO nanoparticles showed a hexagonal wurtzite structure. With increased precursor concentration, a primary, secondary particle sizes of ZnO nanoparticles increased by 0.8 to $1.5{\mu}m$ and 15 to 35nm, and their crystallinity was improved. Methyleneblue (MB) solution ($1{\mu}M$) as a test comtaminant was prepared for evaluating the photocatalytic activities of ZnO nanoparticles synthesized in different precursor concentration. The results show that the photocatalytic efficiency of ZnO nanoparticles was gradually enhanced by increased precursor concentration.

• Journal of Surface Science and Engineering
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• v.57 no.4
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• pp.338-347
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• 2024

𝛼-MnO₂ as a cathode material for Zn-ion batteries allows insertion and extraction of Zn ions within its tunnel structure during charge and discharge. The morphology and crystal structure of 𝛼-MnO₂ particles critically determine their electrochemical behavior and energy storage performance. In this study, 𝛼-MnO₂ was synthesized from precursor solutions under varying pH conditions using a hydrothermal method. The effects of pH values on the morphology, crystal structure, and electrochemical performance were systematically analyzed. The analysis revealed that materials synthesized at higher pH levels exhibited elongated and narrow nanorods with a lower specific surface area. In contrast, those formed at lower pH levels showed shorter, thicker nanorods with a higher specific surface area. This increased surface area at a lower pH enhanced the specific capacitance by providing a greater electrode/electrolyte interfacial area. By contrast, the material synthesized at higher pH conditions demonstrated superior rate capability, attributed to its crystal structure with wider lattice spacings. Wide lattice parameters in the material synthesized at higher pH conditions facilitated easier ion transport than at lower pH levels. Consequently, the study confirms that adjusting the pH of the precursor solution can optimize the electrochemical properties of 𝛼-MnO₂ for Zn-ion batteries.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1028-1030
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• 1995

In the fields of the optics, precise machine, semiconducting processing, the micro-positioning actuators are required for the control of position in the submicron range. In this study, $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb({Zn}_{1/3}Nb_{2/3})O_3-Pb({Zr}_{1/2}Ti_{1/2})O_3$ ceramics were fabricated by solid state reaction. The structural, dielectric and electric properties were investigated for sintering condition. The specimen sintered at $1,150(^\circ}C)$ for 1hr, had the highest density and dielectric contant. The resistivity, dielectric and density were increased with increasing PZN contents.

• Journal of Environmental Health Sciences
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• v.23 no.2
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• pp.28-34
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• 1997

This study was carried out to investigate the effects of prechlorination and algae growth on THMs generation. The sample water obtained from Paldang Dam which is a main source of raw water for the Seoul metropolitan area. THMs concentration in the sample water was investigated in water treatment process prechlorifiation, chemical coagulation, and sand filtration. And also, THMs concentration were analyzed in the water which cultured algae in laboratory. The results were as follows 1. The THMs concentration produced by prechlorination unit process were increased in control (not purified) but decreased in process of purification. 2. The THMs concertration can reduce by increasing the number of cleaning filters. 3. The main precursor in raw water for the THMs generation was supplied by algae growth. So as to reduce the THMs concentration in water supplying system, it is the best method to manage algae growth in water body of Paldang reservoir.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.6
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• pp.828-835
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• 2014

GC-TSQ CI technique was applied for analysis of samples for the $32^{nd}$ OPCW proficiency test. Eight chemical weapon convention(CWC) related chemicals were identified by product ion mode analysis with GC-TSQ in the samples. Choice of specific precursor ion made it possible to supply selective total ion chromatograms(TICs) of target molecule. GC-TSQ CI anaylsis technique was useful method for chemical warfare agent verification because analysis selectivity was improved by choice of mother molecule as precursor ion and gave mass spectra.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.771-774
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• 2001

NADPH has been known as a regulating factor the biosynthesis of polyhydroxyalkanote(PHA), and the flux of NADPH for PHA biosynthesis could be enforced by the amplification of zwf gene encoding glucose 6-phosphate dehydrogenase. The recombinant plasmid pCZWF harboring PHA synthase, phbC from R. eutropha and zwf from E. coli were constructed, and were transformed to R. eutropha by electroporation. The biosynthesis of P(3HB-3HV) copolymer were carried out in transformant R. eutropha through the two-stage cultivation method using valerate as a precursor. The biosynthesis rate and PHA content of transformant R. eutropha harboring pCZWF were increased compared with transformant R. eutropha harboring only phbC. Especially, the molar fraction of 3HV was increased from 68% to 74% due to amplification of zwf gene. And the biosynthesis P(3HB-3HV) and P(3HB-4HB) carried out using propionate and ${\gamma}-butyrolactone$ as a precursor, respectively. But the rate, content, and molar fraction of biosynthesis copolymers were not influenced appreciably. This may be due to the reduced availability of NADPH.

• Journal of the Korean Ceramic Society
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• v.47 no.3
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• pp.205-209
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• 2010

In the last (fourth) section, the discussion will entail a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.83-84
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• 2009

Thin film solar cells based on CIGS continue to be a leading candidate for thin film photovoltaic devices due to their appropriate bandgap, long-term stability, and low-cost production. To date, the most successful technique for the deposition of a CIGS absorber layer has been based on the co-evaporation However, the evaporation process is difficult to scale-up for large-area manufacturing the sputtering and Selenizaton process has been a promising method for low-cost and large-scale production of high quality CIGS In this study, we have used Cu and CuIn alloy targets for precursor deposition the precursor deposited by sputtering Cu and CuIn targets and $CuInSe_2$ thin film is manufactured by Selenization process