• Korean Journal of Optics and Photonics
• /
• v.18 no.2
• /
• pp.171-177
• /
• 2007

We prepared $TiO_2$ thin films by electron-beam evaporation at various oxygen pressures, and investigated their optical and structural properties as a function of the annealing temperature. The physical properties of the $TiO_2$ thin films depend upon the injection oxygen content. With the increased injection of oxygen, the phase transformation temperature and the transmittance of $TiO_2$ thin films in the range of visible wavelength were increased. For low injection of oxygen, the absorption edges of $TiO_2$ thin films were more red-shifted when annealed at temperatures from $700^{\circ}C$ to $1100^{\circ}C$.

• Clean Technology
• /
• v.28 no.1
• /
• pp.63-78
• /
• 2022

Electronics industrial wastewater treatment facilities release organic wastewaters containing high concentrations of organic pollutants and more than 20 toxic non-biodegradable pollutants. One of the major challenges of the fourth industrial revolution era for the electronics industry is how to treat electronics industrial wastewater efficiently. Therefore, it is necessary to develop an electronics industrial wastewater modeling technique that can evaluate the removal efficiency of organic pollutants, such as chemical oxygen demand (COD), total nitrogen (TN), total phosphorous (TP), and tetramethylammonium hydroxide (TMAH), by digital twinning an electronics industrial organic wastewater treatment facility in a cyber physical system (CPS). In this study, an electronics industrial wastewater activated sludge model (e-ASM) was developed based on the theoretical reaction rates for the removal mechanisms of electronics industrial wastewater considering the growth and decay of micro-organisms. The developed e-ASM can model complex biological removal mechanisms, such as the inhibition of nitrification micro-organisms by non-biodegradable organic pollutants including TMAH, as well as the oxidation, nitrification, and denitrification processes. The proposed e-ASM can be implemented as a Water Digital Twin for real electronics industrial wastewater treatment systems and be utilized for process modeling, effluent quality prediction, process selection, and design efficiency across varying influent characteristics on a CPS.

• Journal of the Korean Chemical Society
• /
• v.63 no.6
• /
• pp.453-458
• /
• 2019

Synthesis of ZnCo₂O₃ oxide is performed by sol-gel method via nitrate-citrate route. Powder X-ray diffraction (XRD) study shows monoclinic unit cell having lattice parameters: a = 5.721(1) Å, b = 8.073(2) Å, c = 5.670(1) Å, β = 93.221(8)°, space group P_2/m and Z = 4. Average crystallite sizes determined by Scherrer equation are the range ~14-32 nm, whereas SEM micrographs show nano-micro meter size particles formed in ZnCo₂O₃. Endothermic peak at ~798 K in the Differential scanning calorimetric (DSC) trace without weight loss could be due to structural transformation and the endothermic peak ~1143 K with weight loss is due to reversible loss of O₂ in air atmosphere. Energy Dispersive X-ray (EDX) analysis profile shows the presence of elements Zn, Co and O which indicates the purity of the sample. Magnetic measurements in the range of +12 kOe to -12 kOe at 10 K, 77 K, 120 K and at 300 K by PPMS-II Physical Property Measurement System (PPMS) shows hysteresis loops having very low values of the coercivity and retentivity which indicates the weakly ferromagnetic nature of the oxide. Observed X-band EPR isotropic lineshapes at 300 K and 77 K show positive g-shift at g_iso ~2.230 and g_iso ~2.217, respectively which is in agreement with the presence of paramagnetic site Co²⁺(3d⁷) in the oxide. DC conductivity value of 2.875 ×10^-8 S/cm indicates very weakly semiconducting nature of ZnCo₂O₃ at 300 K. DRS absorption bands ~357 nm, ~572 nm, ~619 nm and ~654 nm are due to the d-d transitions ⁴T_1g(⁴F)→²E_g(²G), ⁴T_1g(⁴F)→⁴T_1g(⁴P), ⁴T_1g(⁴F)→⁴A_2g(⁴F), ⁴T_1g(⁴F)→⁴T_2g(⁴F), respectively in octahedral ligand field around Co²⁺ ions. Direct band gap energy, E_g~ 1.5 eV in the oxide is obtained by extrapolating the linear part of the Tauc plot to the energy axis indicates fairly strong semiconducting nature of ZnCo₂O₃.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.24 no.1
• /
• pp.21-26
• /
• 2014

Red clay has been used for making rakuyaki for the past 400 years. Because the resources for red clay in Japan are being depleted, many potters in Japan began to develop new materials which can replace red clay. In this study, It is analyzed that the chemical and physical properties of red clay from Shigaraki (Shiga, Japan), and developed a novel engobe which can be used for making Rakuyaki instead of Shigaraki red clay. Results from Raman spectroscopic examination showed that ferric oxide content in Shigaraki red clay is 9.4 % (Goethite 5 %, Wustite 4.4 %), and that the mechanism of red color development by the firing at $900^{\circ}C$ for 10 min is the chemical transformation of Goethite into Hematite, and the subsequent formation of solid solution with Alumina and Silica. To make similar ferric oxide content to that of Shigaraki red clay, we added 5 g of Goethite and 9 g of Wustite to 100 g of White kaolin from Hadong area (Gyeongsangnam-do, Korea). The $L^*a^*b^*$ color scale of the mixture was 56.83, 27.22, and 23.28, respectively, and stable red color was successfully developed under the same firing condition used for Shigaraki red clay.

• Korean Journal of Optics and Photonics
• /
• v.16 no.2
• /
• pp.168-173
• /
• 2005

Ag-doped $TiO_2$ thin films were prepared by RF magnetron co-sputtering method, and their physical and chemical properties were examined as a function of calcination temperature. XRD results showed that the crystallite size of Ag-doped films was smaller than that of the $TiO_2$ thin films. SEM results showed that the particle size of $Ag/TiO_2$ film was smaller and more uniform than pure $TiO_2$ film. The films had high transparency in the visible range. The films calcined at $600^{\circ}C$ were the anatase phase, and the films calcined at $900^{\circ}C$ were a mixture of anatase and rutile phases. The absorption edge of films calcined at $900^{\circ}C$ was red-shifted. This is due to the augmented absorption resulting from the phase transformation from anatase to rutile phase. And the transmittance of films decreased by the light scattering and absorption in the films. Photocatalytic activity of $Ag/TiO_2$ thin films was higher than that of the pure $TiO_2$ thin films.

• KSBB Journal
• /
• v.24 no.6
• /
• pp.527-532
• /
• 2009

Lignocellulose represents a key sustainable source of biomass for transformation into biofuels and bio-based products. Unfortunately, lignocellulosic biomass is highly recalcitrant to biotransformation, both microbial and enzymatic, which limits its use and prevents. As a result, effective pretreatment strategies are necessary. The vast majority of pretreatment strategies have focused on achieving a reduction of lignin content. In this work, an ethanosolv pretreatment has been evaluated for extracting lignin from barley straw. 75% ethanol was used as a pretreatment solvent to extract lignin from barley straw. The influence on delignification of three independent variables are temperature, time, catalyst (1 M $H_2SO_4$) dose. The best pretreatment condition observed was $180^{\circ}C$, 120 min, 0.2% $H_2SO_4$ and delignification was 38%. A combined roasting and ethanosolv, 2-step pretreatment, was developed in order to improve the delignification. Roasting didn't increase the delignification but reduced the pretreatment time. X-ray diffraction results indicated that these physical changes enhance the enzymatic digestibility in the ethanosolv treated barley straw. The cellulose in the pretreated barley straw becomes more crystalline without undergoing ethanosolv.

• Korean Journal of Veterinary Research
• /
• v.9 no.1
• /
• pp.23-62
• /
• 1969

Throughout the studies the following experimental results were obtained and are summarized: 1. Multiplication of agents in primary cell cultures of both GF classical and CR-64 acute strain of Marek's disease infected chicken kidneys was accompanied by the formation of distinct transformed cell foci. This characteristic nature of cell transformation was passaged regularly by addition of dispersed cell from infected cultures to normal chicken kidney cell cultures, and also transferred was the nature of cell transformation to normal chick-embryo liver and neuroglial cell cultures. No cytopathic changes were noticed in inoculated chick-embryo fibroblast cultures. 2. The same cytopathic effects were noticed in normal kidney cell monolayers after the inoculation of whole blood and huffy coat cells derived from both forms of Marek's disease infected chickens. In these cases, however, the number of transformed cell foci appearing was far less than that of uninoculated monolayers prepared directly from the kidneys of Marek's disease infected chickens. 3. The change in cell culture IS regarded as a specific cell transformation focus induced by an oncogenic virus rather than it plaque in slowly progressing cytopathic effect by non-oncogenic viruses, and it is quite similar to RSV focus in chick-embryo fibroblasts in many respects. 4. The infective agent (cell transformable) were extremely cell-associated and could not be separated in an infective state from cells under the experimental conditions. 5. The focus assay of these agents was valid as shown by the high degree of linear correlation (r=0.97 and 0.99) between the relative infected cell concentration (in inoculum) and the transformed cell foci counted. 6. No differences were observed between the GF classical strain and the CR-64 acute strain of Marek's disease as far as cell culture behavior. 7. Characterization of the isolates by physical and chemical treatments, development of internuclear inclusions in Infected cells, and nucleic acid typing by differential stainings and cytochemical treatments indicated that the natures of these cell transformation agents closely resemble to those described fer the group B herpes viruses. 8. Susceptible chicks inoculated with infected kidney tissue culture cells developed specific lesions of Marek's disease, and in a case of prolonged observation after inoculation (5 weeks) the birds developed clinical symptoms and gross lesions of Marek's disease. Kidney cell cultures prepared from those inoculated birds and sacrificed showed a superior recovery of cell transformation property by formation of distinct foci. 9. Electron microscopic study of infected kidney culture cells (GF agent) by negative staining technique revealed virus particles furnishing the properties of herpes viruses. The particle was measured about $100m{\mu}$ and, so far, no herpes virus envelop has been seen from these preparations. 10. No relationship of both isolates to avian leukosis/sarcoma group viruses and PPLO was observed.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.4
• /
• pp.25-31
• /
• 2007

Characterizing the risk posed by a mixture of chemicals is a challenging task due to the chemical interactions of individual components that may affect their physical behavior and hence alter their exposure to receptors. In this study, cell tests that represent subsurface environment were carried out using benz[a]anthracene (BaA) and p-xylene focusing on phasetransforming interaction to verify increased mobility and risk of highly sorbed pollutants in the presence of less sorbed, mobile liquid pollutants. A transport model was also developed to interpret results and to simulate the same process on a field scale. The experimental results showed that BaA had far greater mobility in the presence of p-xylene than in the absence of that. The main transport mechanisms in the vadose zone were by dissolution to p-xylene or water. The transport model utilizing Defined Time Steps (DTS) was developed and tested with the experimental results. The predicted and observed values showed similar tendency, but the more work is needed in the future study for more precise modeling. The field-scale simulation results showed that transport of BaA to groundwater table was significantly faster in the presence of NAPL, and the oral carcinogenic risk of BaA calculated with the concentration in groundwater was 15${\sim}$87 times larger when mixed with NAPL than when solely contaminated. Since transport rate of PAHs is very slow in the subsurface without NAPL and no degradation of PAHs was considered in this simulation during the transport, the increase of risk in the presence of NAPL is expected to be greater for the actual contaminated site.