• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.221-226
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• 1998

Ternary heavy metal oxide glasses in the $PbO-Bi_2O_3-Ga_2O_3$ system doped with $Er_2O_3$ were prepared and their spectroscopic properties, such as radiative transition probability, calculated and measured radiative lifetimes and cross-sections of 1.5 $\mu\textrm{m}$ and 2.7 $\mu\textrm{m}$ emissions were analyzed. Enhanced quantum efficiencies of some electronic transitions were evident mainly because of the low vibrational phonon energy ($~500cm^{-1}$) inherent in the host glasses. This seems to be the main reason for obtaining the 2.7 $\mu\textrm{m}$ luminescence which is normally quenched in the conventional oxide glasses. In addition, green and red fluorescence emissions were observed through the frequency upconversion processes of the 798 nm excitation. Non-radiative transition due to the multiphonon relaxation is a dominant lifetime-shortening mechanism in the 4f-4f transitions in $Er^{3+}$ ion except for the $^4S_{3/2}{\rightarrow}^4I_{15/2}$ transition where a non-radiative transfer to band-gap excitation of the host glasses is dominant. Melting of glasses under an inert gas atmosphere and (or) addition of the typical glass-network former into glasses is necessary in order to enhance the quantum efficiency of the transition.

• Resources Recycling
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• v.30 no.1
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• pp.66-76
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• 2021

Electric arc furnace dust (EAFD) contains compounds, such as oxides and chlorides, including large quantities of Zn, Pb and Fe. An efficient and stable method for the extraction of metal elements from EAFD is the Rotary Kiln Process. This method is used to recover Zn in the form of crude ZnO (approximately 60%) via the addition of a reducing agent (coke, anthracite) and limestone (for basicity control) to EAFD. This process is commonly used in industry as well as in research and development. Currently, this method is used in many Korean commercial plants, producing approximately 150,000 tons of Crude ZnO per year. The majority of Zn is found in crude ZnO (approximately 76%). In addition components such as Pb, Cd, Sn, In, Fe, Cl, and F are present as oxides, chlorides, and alkaline compounds. This elements have an adverse effect on the zinc smelting process. Therefore, a refining process that eliminates these impurities is essential. In this study, we developed a process technology that efficiently separates Zn and Pb from byproducts (mainly chlorides). A bag filter was used to collect Zn and Pb generated during the dry purification process of crude ZnO. Pure components were recovered as metals or metal carbonate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.6
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• pp.339-344
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• 2017

An all-transparent photodetector was fabricated by structuring $Cu_2O$/ZnO/AZO/ITO on a glass substrate. The visible-range transmittance was as high as 80%, which ensures clear vision forhuman eyes. High-transparency metal conductive oxides (p-type $Cu_2O$ and n-type ZnO) were appliedto form the transparent p/n junction. The functional AZO layer was adopted to improve the transparent photodetector performance between the ZnO and ITO, improving the photoresponses because of its electrical conductivity. To clarify the AZO functionality, a comparator device was prepared without the AZO layer in the formation of $Cu_2O$/ZnO/ITO/Glass. The $Cu_2O$/ZnO/AZO/ITO device provided a rectifying ratio of 113.46, significantly better than the 9.44 of the $Cu_2O$/ZnO/ITO device. In addition, the $Cu_2O$/ZnO/AZO/ITO device's photoresponses at short wavelengths were better than those of the comparator. The functioning AZO layer provides ahigh-performing transparent Cu oxide photodetector and may suggest a route for the design of efficient photoelectric devices.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.463-468
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• 1998

When sulfuric acid was added in HCl etching solution, corrosion of aluminum metal was inhibited by the chemical adsorption of sulfate ions. In the presence of $SO_4^{-2}$, cyclic voltammetry showed that the protective oxide film was formed on the inner surfaces of etch pits and, pit density was increased by nucleation on both the aluminum surface and the pits inside. Structure and distribution of etch pits found in AC etching of aluminum were strongly influenced by the concentration of $SO_4^{-2}$ and the amount of cathodic pulse charging. Below $0.8mC/cm^2$ of cathodic pulse charging, oxide films formed inside actively dissolving pits indicated the higher resistance to pit nucleation as the concentration of $SO_4^{-2}$ increases. However, the structural change of oxide films occurred above the $0.8mC/cm^2$ charging and the effect of $SO_4^{-2}$ was minimized, and it resulted in the rapid formation of etch pits.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.168-174
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• 2016

A conductive oxide-based sapphire glass indium tin oxide/metal electrode and the optical coating, through patterning process was studied in excellent optical properties and integrated touch panel has a high strength. Indium tin oxide conductive oxides of the sapphire glass to 0.3 A at DC magnetron sputtering method of 10 min, gas flow Ar 10 Sccm Ar, $O_2$ 1.0 Sccm the formation conditions of the thin film after annealing at $550^{\circ}C$ for 30min was achieved through a 86% transmittance. In addition, the coating 130 nm hollow silica sol-gel was to improve the optical transmittance of the indium tin oxide to 91%. For the measurement by the modeling hollow silica sol by Macleod simulation and calculated the average values of silica part to the presence or absence in analogy to actual. Refractive index value and the actual value of the material on the simulation the transmittance difference is it does not completely match the air region similar to the actual value (transmission) could be confirmed that the measurement is set to a value of between 5 nm and 10 nm.

• Journal of Sensor Science and Technology
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• v.20 no.5
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• pp.300-304
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• 2011

Exhaled breath gases include gases generated in the body. When there is disease in the body, exhalation can include gas components from the disease. If we can find these specific elements through analysis of the exhalation gases, this can be an effective way to diagnose the disease. The lung has a close relationship with exhalation. Lung cancer refers to malignant tumors which originate in the lungs. Exhalation from the lung causes direct jets of gas to be ejected through the mouth and nose, so by analyzing these jets it may be possible to diagnose lung cancer. In our study we attempt to diagnose lung cancer from patient's exhaled gases. Exhalation of lung cancer patients was analyzed using gas chromatography-mass spectroscopy(GC-MS) and the expiratory gas was also measured using a sensor system. The system was designed to use a metal oxide sensor and solid phase micro extraction(SPME) fiber. The GC-MS analysis of the healthy subject's and cancer patient's exhalation gases both showed the presence of decane in the breath of patients with lung cancer. In addition, the results from the sensor system showed significant difference between the lung cancer patients and the healthy subjects.

• Culinary science and hospitality research
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• v.21 no.1
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• pp.235-249
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• 2015

This study was carried out to investigate the flavor changes of Lentinus edodes at different storage temperatures, time and natural additives using an electronic nose with six metal oxide sensors. To preserve good quality of modified atmosphere packaged Lentinus edodes, Four natural additives(Artemisia princeps, Artemisia capillaries, green tea, and activated charcoal) were used. The mushrooms were packaged in polyethylene films with each treatment and were stored at 5, 10 and $20^{\circ}C$. Increase in storage temperature and storage time decreased the ratio of resistance in the electronic nose as well as first principal component scores. In addition, indicating quality of mushroom reduced at high temperature and long storage time. The results of the electronic nose and the principal component analysis(PCA) in the mushrooms with Artemisia princeps and Artemisia capillaries that were stored at $5^{\circ}C$, and green tea and activated charcoal which were stored at $10^{\circ}C$ showed the good effects to maintain the freshness along with reducing off-flavor. However, there were no differences between control and treatment groups at $20^{\circ}C$.

• Transactions on Electrical and Electronic Materials
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• v.12 no.6
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• pp.262-266
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• 2011

A simulation study of a current-mode direct current (DC)-DC boost converter is presented in this paper. This converter, with a fully-integrated power module, is implemented by using bipolar complementary metal-oxide semiconductor (BiCMOS) technology. The current-sensing circuit has an op-amp to achieve high accuracy. With the sense metal-oxide semiconductor field-effect transistor (MOSFET) in the current sensor, the sensed inductor current with the internal ramp signal can be used for feedback control. In addition, BiCMOS technology is applied to the converter, for accurate current sensing and low power consumption. The DC-DC converter is designed with a standard 0.35 ${\mu}m$ BiCMOS process. The off-chip inductor-capacitor (LC) filter is operated with an inductance of 1 mH and a capacitance of 12.5 nF. Simulation results show the high performance of the current-sensing circuit and the validity of the BiCMOS converter. The output voltage is found to be 4.1 V with a ripple ratio of 1.5% at the duty ratio of 0.3. The sensing current is measured to be within 1 mA and follows to fit the order of the aspect ratio, between sensing and power FET.

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.115-118
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• 2009

The use of dolomite refractories has increased during the past several years in the manufacturing of clean steel during the stainless steelmaking process. However, at the same time, the use of dolomite refractories has led to what is known as the skull formation. In the present work, to understand the skull formation, the wetting characteristics of dolomite substrates by liquid Fe-19wt%Cr-10wt%Ni alloys in various oxygen partial pressures were initially investigated at 1753K using the sessile drop technique. For comparison, the wetting characteristics of alumina substrates were investigated with the same technique. It was found that the wetting index, (1+$cos{\theta}$), of dolomite is approximately 40% higher compared to those of alumina. In addition, the oxygen partial pressure to generate the surface oxide, which may capture the liquid metal on the refractory surface, for dolomite is much lower than that for alumina. From this study, it was concluded that the use of dolomite is much more closely associated with the skull formation compared to the use of alumina due to the stronger wettability and the surface oxide formation at a lower oxygen partial pressure of dolomite.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.981-987
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• 1998

$La_{0.5}Sr_{0.5}MnO_{3-\delta}$ as air electrode for soild oxide fuel cell was synthesized by a citrate process and its cathodic polarization was determinated by the current interruption method on the Gd-doped ceria as electrolyte. The addition of citric acid increased the exothermic heat for the formation of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ perovskite oxide. The degree of the initial particle agglomeration was affected by the exothermic heat. Also the increase of cal-cination temperature enlarged the particle size and the higher sintering temperature accelerated the den-sification of $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ layer after its being painted on $Ce_{0.8}Gd_{0.2}O_{1.9}$ electrolyte. In this study $La_{0.5}Sr_{0.5}MnO_{3-\delta}$ synthesized by citrate process of which the molar ratio of citric acid to metal nitrate was 2 calcined at $650^{\circ}C$ for 2hr and sintered at 1100 at $1200^{\circ}C$ for 4 hrs after slurry coating on Ce0.8Gd0.2O1.9 electrlyte showed the lowest cathodic polarization.