• Journal of Bio-Environment Control
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• 제9권3호
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• pp.166-170
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• 2000

Three methods for heat collection, which were the flat solar collector, two fan with radiator, and square pipe method, were studied to sue efficiently solar energy in the three different glasshouses for two years. The flat plate solar collector method was made use of the commercial solar collector with collection area of 24$m^2$, the method of two fans with radiators collected solar energy at the top of the glasshouse. An thermal storage tank was constructed underneath in teach glasshouses. When an area of 1,000$m^2$ was heated to the minimum temperature of 9$^{\circ}C$, the decrease rate of heating fuel for the flat plate solar collector, the fan attached radiator and the square pipe methods were 7%, 19% and 28% respectively. The flat plate solar collector method, which could be heated approximately 40-50$m^2$, was currently used by most of the farmer. Under the condition, the decrease rate of annual heating fuel was 14% which was not better for an economic annual heating fuel. If the fan with radiator method was operated, the use of installation and maintenance were required. So, it could not be good economic efficiency of solar heating. The heating efficiency of the square pipe method was relatively better thant those of the flat plate solar collector or the fan attached radiator. Since the cost of materials and its installation of the use of square pipe method was lower than any other method. However, corrosion of the pipe, greater shade in the greenhouse and strength against the square pipe were problems that should be overcome in the square pipe method.

• Journal of the Korean Society for Marine Environment & Energy
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• 제9권1호
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• pp.14-20
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• 2006

In this study, the feasibility of simultaneous removal of organic materials and nitrogen in the waste-water from fisheries processing plant was evaluated using entrapped mixed microbial cell technique(EMMC) process. The experiment was performed using activated sludge from municipal sewage treatment plant which was immobilized with gel matrix by cellulose triacetate. It was found that the stable operation at the treatment system which is composed of anoxic and oxic tank, was possible when the organic and nitrogen loading rates were increased stepwise. The organic and nitrogen loading rates were applied from 0.65 to $1.72kgCOD/m^3/d$ and from 0.119 to $0.317kgT-N/m^3$ with four steps, respectively. The maximum nitrogen loading rate which could satisfy the regulated effluent standard of nitrogen concentration, was $0.3kgT-N/m^3/d$. The removal efficiency of total nitrogen was decreased apparently as increasing nitrogen loading rates, whereas the removal efficiency of ammonium nitrogen was effective at the all tested nitrogen loading rates. Therefore, it was concluded that nitrification was efficient at the system. Nitrate removal efficiency ranged from 98.62% to 99.51%, whereas the nitrification efficiency at the oxic tank ranged 94.0% to 96.9% at the tested loading rates. The removal efficiencies of chemical oxygen demand(COD) and those of total nitrogen at the entire system ranged from 94.2% to 96.6% and 73.4% to 83.4%, respectively.

• Journal of the Korean Society for Marine Environment & Energy
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• 제9권4호
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• pp.203-215
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• 2006

Field observations on the spatio-temporal distribution of organic matter of the surface sediment were carried out at 15 stations in the central parts of the South Sea of Korea from April 2002 to January 2003. The range of water temperature and salinity in bottom waters, mud content and water content of surface sediment were $8.06{\sim}23.35^{\circ}C,\;29.20{\sim}34.51\;psu,\;71.2{\sim}99.9%$ and $38.7{\sim}68.9%$, respectively. Measured parameters on the surface sediments of ignition loss (IL), chemical oxygen demand (CODs), phaeopigment, particulate organic carbon (POC) and particulate organic nitrogen (PON) also ranged in $3.9{\sim}l2.5%,\;9.60{\sim}44.05\;mgO_2/g-dry,\;1.58{\sim}29.51\;{\mu}g/g-dry,\;3.12{\sim}13.01\;mgC/g-dry$ and $0.49{\sim}2.00\;mgN/g-dry$, respectively. The spatio-temporal distribution of organic matter demonstrated higher concentrations offshore than at lesions near the coastal line. Higher concentrations occurred in the summer and spring. The results indicated that the origin of organic matter in surface sediments in the central part of the South Sea was autochthonous rather than allocthonous because the organic matter had an average C/N ratio of 6.44 (${\pm}0.51$). However, the composition of autochthonous organic matter was mainly derived from detritus rather than living phytoplankton, which was Indicated by the results of the POC/phaeopigment ratio. A principal component analysis (PCA) indicated that 73.2% of the variability in the data was described by two factors: 1) an 'environmental factor concerning the accumulation of materials (57.3%)' and 2) 'origin of organic matter and the composition by primary production (15.9%)'. The sedimentary environment in the central part of the South Sea was divided into four regions from the factor score of the PCA by the concentrations of organic matter and the composition ratio of organic matters from phytoplankton in surface sediments.

• Journal of Korean Society of Environmental Engineers
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• 제27권7호
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• pp.746-752
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• 2005

In this study, the effect of reaction parameters including reaction temperature, time, and pressure on sludge degradation and conversion to intermediates such as organic acids were investigated at low critical wet air oxidation(LC-WAO) conditions. Degradation pathways and a modified kinetic model in LC-WAO were proposed and the kinetics model predictions were compared with experimental data under various conditions. Results in the batch experiments showed that reaction temperature directly affected the thermal hydrolysis reaction rather than oxidation reaction. The efficiencies of sludge degradation and organic acid formation increased with the increase of the reaction temperature and time. The removal of SS at $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 10 min of reaction time were 52.6%, 68.3%, 72.6%, and 74.4%, respectively, indicating that most organic suspended solids were liquified at early stage of reaction. At $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 40 min of reaction time, the amounts of organic acids formed from 1 g of sludge were 93.5 mg/g SS, 116.4 mg/g SS, 113.6 mg/g SS, and 123.8 mg/g SS, respectively, and the amounts of acetic acid from 1 g of sludge were 24.5 mg/g SS, 65.5 mg/g SS, 88.1 mg/g SS, and 121.5 mg/g SS, respectively. This suggested that the formation of sludge to organic acids as well as the conversion of organic acids to acetic acid increased with reaction temperature. Based on the experimental results, a modified kinetic model was suggested for the liquefaction reaction of sludge and the formation of organic acids. The kinetic model predicted an increase in kinetic parameters $k_1$ (liquefaction of organic compounds), $k_2$ (formation of organic acids to intermediate), $k_3$ (final degradation of intermediate), and $k_4$ (final degradation of organic acids) with reaction temperature. This indicated that the liquefaction of organic solid materials and the formation of organic acids increase according to reaction temperature. The calculated activation energy for reaction kinetic constants were 20.7 kJ/mol, 12.3 kJ/mol, 28.4 kJ/mol, and 54.4 kJ/mol, respectively, leading to a conclusion that not thermal hydrolysis but oxidation reaction is the rate-limiting step.

• Journal of Hydrogen and New Energy
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• 제10권2호
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• pp.119-130
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• 1999

After preparing $Mg_2Ni_{1-x}{^{57}}Fe_x$(x=0.015, 0.03, 0.06, 0.12 and 0.24) alloys, they were studied by $M{\ddot{o}}ssbauer$ resonance. The $M{\ddot{o}}ssbauer$ spectra of x=0.015 and 0.03 alloys exhibit two doublets (doublet 1, 2). That of x=0.06 alloys shows two doublets (doublet 1,2) and one six-line, and those of x=0.12 and 0.24 alloys have only one six-line. The doublet 1 for x=0.015, 0.03 and 0.06 alloys is considered to result from a fraction of Fe in excess showing a superparamagnetic behavior. The doublet 2 is considered to result from the Fe substituted for Ni in the $Mg_2Ni$ phase. The values of isomer shift 0.24 ~ 0.28 mm/s suggest that the iron exist in the state $Fe^{+3}$. The result that the quadrapole splitting of the doublet 2 is not zero shows that the distribution of electrons around the iron is asymmetric. Their values for the doublet 2, 1.20 ~ 1.38 mm/s, approach the value of quadrapole for the oxidation number +3. The six-line showing the magnetic hyperfine interactions results from the iron which has not substituted the nickel in the $Mg_2Ni$ phase. The $M{\ddot{o}}ssbauer$ spectra of the hydrided alloys with x=0.015 and 0.03 show six-line. This suggests that the iron segregates with the hydriding reaction. The analysis results of the $M{\ddot{o}}ssbauer$ spectrum, the variation of magnetization with magnetic field, Auger electron spectroscopy and electron diffraction show the segregation of Ni and the formation of MgO. This is considered to result from the reaction of the $Mg_2Ni$ phase with the oxygen contained in the hydrogen as impurity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제48권6호
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• pp.1-6
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• 2011

A transparent oxide thin film transistors (Transparent Oxide-TFT) have been fabricated by RF magnetron sputtering at room temperature using amorphous indium zinc oxide (a-IZO) as both of active channel and source/drain, gate electrodes and co-sputtered $HfO_2-Al_2O_3$ (HfAIO) as gate dielectric. In spite of its high dielectric constant > 20), $HfO_2$ has some drawbacks including high leakage current and rough surface morphologies originated from small energy band gap (5.31eV) and microcrystalline structure. In this work, the incorporation of $Al_2O_3$ into $HfO_2$ was obtained by co-sputtering of $HfO_2$ and $Al_2O_3$ without any intentional substrate heating and its structural and electrical properties were investigated by x-ray diffraction (XRD), atomic force microscopy (AFM) and spectroscopic ellipsometer (SE) analyses. The XRD studies confirmed that the microcrystalline structures of $HfO_2$ were transformed to amorphous structures of HfAIO. By AFM analysis, HfAIO films (0.490nm) were considerably smoother than $HfO_2$ films (2.979nm) due to their amorphous structure. The energy band gap ($E_g$) deduced by spectroscopic ellipsometer was increased from 5.17eV ($HfO_2$) to 5.42eV (HfAIO). The electrical performances of TFTs which are made of well-controlled active/electrode IZO materials and co-sputtered HfAIO dielectric material, exhibited a field effect mobility of more than $10cm^2/V{\cdot}s$, a threshold voltage of ~2 V, an $I_{on/off}$ ratio of > $10^5$, and a max on-current of > 2 mA.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제10권6호
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• pp.425-433
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• 2000

The stochiometric mix of evaporating materials for the $CuGaTe_2$single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0 and c_0$ were 6.025 $\AA$ and 11.931 $\AA$, respectively. To obtain the single crystal thin films, $CuGaTe_2$mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is 2.1$\mu\textrm{m}$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of $CuGaTe_2$single crystal thin films deduced from Hall data are $8.72{\times}10{23}$개 $\textrm m^3$, $3.42{\times}10^{-2}$ $\textrm m^2$/V.s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuGaTe_2$single crystal thin film, we have found that the values of spin orbit coupling $\Delta$s.o and the crystal field splitting $\Delta$cr were 0.0791 eV and 0.2463 eV at 10 K, respectively. From the PL spectra at 10 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470 eV and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be 0.0490 eV, 0.0558 eV, respectively.

• Economic and Environmental Geology
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• 제47권6호
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• pp.563-569
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• 2014

Ruby is one of the most favor colored gem, for beautiful red tone, be high in scarcity value. However, rubies with high quality are produced in restricted regions, such as in Thailand, Sri Lanka, Myanmar, and Tanzania etc., and they have been gradually exhausted by mining for a long period. Therefore, improving qualities of low level rubies with various treatments is arising an alternative way to obtain better rubies. Gemological and mineralogical properties of the natural ruby from Tanzanian were studied with heat treatments. Those characteristics were compared between only heat and adding flux materials under heating. Tanzanian raw rubies were applied a heat treatment ($1,600^{\circ}C$ for 6 hours). However, chromameter and UV-Vis analyses found that a simple heat treatment is inappropriated for the Tanzanian ruby. Although $Cr^{3+}$ containing for red color in the ruby increased with heat treatment, the ruby displays dark medium red because of Fe in the ruby as a form of $Fe_2O_3$. The low transparency after heat treatment is attributed to the recrystallization of $SiO_2$ which has a low melting point. Chromameter confirmed adding Pb-containing flux under heating greatly improves the clarity and color of Tanzanian rubies with micro-fractures and cavities on the surface. EMPA results show that Pb as an additive fills the cavities and cracks on raw Tanzanian rubies during the heat treatment. As a rewult of it, the quality of the Tanzanian ruby raw dramatically improved. These results indicate that the heat treatment with an additive (Pb in this study) is an effective way to obtain better quality of the Tanzanian ruby. Consequently, this study suggests a suitable method to improve the properties of the Tanzanina ruby. The result of this study would provide useful information to upgrade the qualities of similar gem stones such as corundum and sapphire.

• The Journal of Korean Society for Radiation Therapy
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• 제30권1_2호
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• pp.17-25
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• 2018

Purpose : To compare the radiation doses of prostate cancer patients according to changes in abdominal body shape and energy during Volumetric modulated arc therapy(VMAT). Materials and Methods : Seven patients with prostate cancer were enrolled in this study. VMAT treatment plan was established at 6, 10, and 15 MV while changing from -2.0 cm to 2 cm by 0.5 cm. Conformal index(CI), homogeneous index(HI), $D_{max}$, $D_{95%}$, $D_{50%}$ and $D_{2%}$ of PTV were examined in order to evaluate the change of dose in the target organ according to body shape change. Normal organ of the femoral head, rectum and bladder was analyzed to evaluate dose changes. Results : The dose of $D_{max}$ 6 MV in PTV increased to 107.2 % in 1.0 cm body shape reduction, and 10 MV and 15 MV dose increased to 107.1 % and 107.0 % in 1.5 cm body reduction, respectively. The dose of $D_{50%}$ 6 MV in PTV decreased to 99.64 % in 1.0 cm body shape increase, and in 10 MV and 15 MV dose decreased to 99.79 % and 99.97 % in 1.5 cm body increase, respectively. In 2.0 cm body type increase, the dose was decreased to 99.30 % and 99.52 %, respectively. Doses for rectum and bladder gradually increased with decreasing weight, and dose decreased with decreasing weight. 6 MV, and $V_{70Gy}$ at 10 MV increased from 11.50 % to 12.76 % when the external shape decreased by 2.0 cm. The bladder $V_{70Gy}$ also increased from 14.0 % to 15.2 %. It was also shown that the dose increased as the body weight decreased in the femoral head. Conclusion : In the treatment of VMAT, dose distribution can be changed according to the change of abdominal shape. SSD and CBCT were used to decrease the body shape by more than 1cm or more than 1.0 cm at 6 MV and the body shape by more than 1.5 cm or more than 1.5 cm at 10 MV or 15 MV. It is considered that a new treatment plan should be established through re-simulation.

• The Journal of Korean Society for Radiation Therapy
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• 제32권
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• pp.31-39
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• 2020

Purpose: The aims of this study were to compare the superficial dose with Optically Stimulated Luminescence Dosimeter(OSLD) measurement and Treatment Planning System(TPS) calculation for 6MV-Flattening Filter Free(FFF) energy using HalcyonTM and TrueBeamTM. Materials and methods: Phantom study was performed using the CT images of human phantom. In the treatment planning system, the Planning Target Volume(PTV) was contoured which is similar to Glottic cancer. Furthermore, Point(M), Point(R), and Point(L) were contoured at the iso-center of head and neck region and 5mm bolus was applied to the body contour. Each treatment plans using 6MV-FFF energy from HalcyonTM and TrueBeamTM with static Intensity Modulated Radiation Therapy(IMRT) and Volumetric Modulated Arc Therapy(VMAT) were established with eclipse. To reproduce the same position as the TPS, OSLDs were placed at the iso-center point and 5mm bolus was applied to compare the error rate after the dose delivery. Result: The results of the study using human phantom are as follows. In case of HalcyonTM, the mean absolute error rates of the point dose using the treatment planning system and the dose measured by OSLD were 1.7%±1.2% for VMAT and 4.0±2.8% for IMRT. Also TrueBeamTM was identified as 2.4±0.4% and 8.6±1.8% respectively for VMAT and IMRT. Conclusion: Through the results of this study, TrueBeamTM confirmed that the average error rate was 2.4 times higher for VMAT and 3.6 times higher for IMRT than HalcyonTM. Therefore, based on the results of this study, If we need a more accurate dose assessment for the superficial dose, It is expected that using HalcyonTM would be better than TrueBeamTM.