• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.176-176
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• 2007

Flat-panel direct conversion detectors used in compound substance of semiconductor are being studied for digital x-ray imaging. Recently, such detectors are deposited by physical vapor deposition(PVD) generally. But, most of materials (HgI2, PbI2, TlBr, PbO) deposited by PVD have shown difficult fabrication and instability for large area x-ray imaging. Consequently, in this paper, we propose applicable potentialities for screen printing method that is coated on a substrate easily. It is compared to electrical properties among semiconductors such as $HgI_2$, $PbI_2$, PbO, HgBrI, InI, and $TlPbI_3$ under investigation for direct conversion detectors. Each film detector consists of an ~25 to $35\;{\mu}m$ thick layer of semiconductor and was coated onto the substrate. Substrates of $2cm{\times}2cm$ have been used to evaluate performance of semiconductor radiation detectors. Dark current, sensitivity and physics properties were measured. Leakage current of $HgI_2$ as low as $9pA/mm^2$ at the operation bias voltage of ${\sim}1V/{\mu}m$ was observed. Such a value is not better than PVD process, but it is easy to be fabricated in high quality for large area x-ray Imaging. Our future efforts will concentrate on optimization of growth of film thickness that is coated onto a-Si TFT array.

• Resources Recycling
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• v.13 no.4
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• pp.11-16
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• 2004

In this study, treatment conditions for monazite concentrate in Hong-Cheon area deposit were studied with NaOH fritting decomposition and HCl leaching experiments. At condition of NaOH fritting decomposition, it was appropriate to adopt particle size of -200 mesh monazite, reaction temperature of about $460^{\circ}C$ and NaOH/TREO mole ratio of 6. In case of HCl leaching for decomposed product, it was appropriate to use hydrochloric acid of above 8N with leaching temperature of above $80^{\circ}C$, leaching time of 2 hrs and pulp density of about 10%. A rate of decomposition and leaching for monazite was above 90% under optimum conditions. Sodium phosphate compound was effectively recovered from NaOH decomposed solution, and mixed rare earth chloride solution was prepared with HCl leaching of decomposed product.

• Resources Recycling
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• v.20 no.2
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• pp.54-59
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• 2011

An investigation on the synthesis of aluminum tartrate, one of the aluminum organic compounds, has been performed using aluminum chloride solution as a raw material. For this aim, the effect of the ratio of ethanol/Al solution and pH on the synthesis of aluminum tartrate has been examined and aluminum tartrate synthesized has also been characterized in terms of the chemical composition, X-ray diffraction pattern, particle size distribution, and SEM analysis. As a result, the synthesis more than 97% could be obtained under the conditions of pH more than 3.0 at the ratio of ethanol/Al solution of 3.0. From the chemical analysis of aluminum tartrate synthesized in this work, the content of $NH_4$, Al and C was found to be 9.10, 4.83 and 25.8%, respectively. In addition, aluminum tartrate synthesized from the aluminum chloride solution was found to be $(NH_4)_3Al(C_4H_4O_6)_3$.

• Journal of the Korean Institute of Gas
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• v.2 no.3
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• pp.1-11
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• 1998

To increase peel strength, low temperature properties and flowability of pressure sensitive adhesives(PSA) used in a heat shrinkable sheet, these properties were evaluated by changing each components in type and content. In this study, Isobutylene-co-Isoprene Rubber (IIR) which has good wetherability was selected as a base polymer. Instead of rosin ester, petroleum resin was selected as a tackifier because of superior peel strength. By decreasing petroleum resin contents, flowability of PSA was decreased. High molecular weight of polybutene was better than low molecular weight for the peel strength of PSA. Large particle size of carbon black showed better properties than small one in peel strength and brittleness temperature. By adding calcium carbonate, the cost of compound was able to be reduced. But it must be used with carbon black.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.78-85
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• 2012

Aluminum nitride(AlN) is a compound (III-V group) of hexagonal system with a crystal structure. Its Wurzite phase is a very wide band gap semiconductor material. It has not only a high thermal conductivity, a high electrical resistance, a high electrical insulating constant, a high breakdown voltage and an excellent mechanical strength but also stable thermal and chemical characteristics. This study is on the preferred orientation characteristics of AlN thin films by reactive evaporation using $NH_3$. We have manufactured an AlN thin film and then have checked the crystal structure and the preferred orientation by using an X-ray diffractometer and have also observed the microstructure with TEM and AlN chemical structure with FT-IR. We can manufacture an excellent AlN thin film by reactive evaporation using $NH_3$ under 873 K of substrate temperature. The AlN thin film growth is dependent on Al supplying and $NH_3$ has been found to be effective as a source of $N_2$. However, the nuclear structure of AlN did not occur randomly around the substrate a particle of the a-axis orientation in fast growth speed becomes an earlier crystal structure and is shown to have an a-axis preferred orientation. Therefore, reactive evaporation using $NH_3$ is not affected by provided $H_2$ amount and this can be an easy a-axis orientation method.

• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.346-355
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• 2021

Ngoc Linh ginseng is one of the most valuable endemic medicinal herbs in Vietnam. In this study, Ngoc Linh ginseng callus was fermented by Lactobacillus plantarum ATCC 8014 (at 6, 7, and 8 log CFU/ml) to evaluate the extraction efficiency of bioactive compounds. The post-fermentation solution was spray-dried using maltodextrin with or without Stevia rebaudiana (3% and 6% v/v) as the wall material. Bioactive compounds such as polyphenols, polysaccharides, and total saponins, and L. plantarum viability during fermentation and after spray-drying, as well as under simulated gastric digestion, were evaluated in this study. The results showed that probiotic density had a significant effect on bioactive compounds, and L. plantarum at 8 log CFU/ml showed the best results with a short fermentation time compared to other tests. The total content of polyphenols, polysaccharides, and saponins reached 5.16 ± 0.18 mg GAE/g sample, 277.2 ± 6.12 mg Glu/g sample, and 4.17 ± 0.15 mg/g sample, respectively after 20 h of fermentation at the initial density of L. plantarum (8 log CFU/ml). Although there was no difference in the particle structure of the preparation, the microencapsulation efficiency of the bioactive compound in the samples containing S. rebaudiana was higher than that with only maltodextrin. The study also indicated that adding S. rebaudiana improved the viability of L. plantarum in gastric digestion. These results showed that S. rebaudiana, a component stimulating probiotic growth, combined with maltodextrin as a co-prebiotic, improved the survival rate of L. plantarum in simulated gastric digestion.

• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.329-337
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• 2008

During the continuous casting of boron-bearing steel, the corner cracks on the slab are formed by deformation with low strain rate and rapid cooling at the unbending temperature within the range of 800- $1000^{\circ}C$. Especially, the rapid cooling in the corner of slab during the continuous casting leads to as corner cracking. Therefore, in this study, the hot tensile tests applied to the different cooling rates were taken into account in order to study the effect of cooling rate on the hot ductility of boron-bearing steel. The results revealed that increasing cooling rate deteriorate the hot ductility of boron- bearing steel. Rapid decreasing of the hot ductility is caused by formation of a film-like ferrite and precipitate at the austenite grain boundaries. The morphology of the precipitates in the boron-bearing steel was monitored by PTA (Particle Tracking Autoradiography) and TEM, we observed MnS and BN compound and their morphology was quite different depending on the cooling rates. When the cooling rate is increased, rodshape MnS and BN precipitates can be formed along the austenite grain boundaries. It can cause that weakening the boundary region and decreasing the hot ductility of boron-bearing steel.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.690-695
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• 2012

Gas hydrate is an inclusion compound consisting of water and low molecular weight gases, which are incorporated into the lattice structure of water. Owing to its promising aspect to application technologies, gas hydrate has been widely studied recently, especially $CO_2$ hydrate for the CCS (Carbon Capture and Storage) issue. The key point of $CO_2$ hydrate technology for the CCS is how to produce gas hydrate in an efficient and economic way. In this study, we have tried to study the characteristic of gas hydrate formation using micro-sized ice through an ultrasonic nozzle which generate 2.4 MHz frequency wave. $CO_2$ as a carrier gas brings micro-sized mist into low-temperature reactor, where the mist and carrier gas forms $CO_2$ hydrate under $-55^{\circ}C$ and atmospheric pressure condition and some part of the mist also remains unreacted micro-sized ice. Formed gas hydrate was average 10.7 of diameter at average. The starting ice particle was set to constant pressure to form $CO_2$ hydrate and the consumed amount of $CO_2$ gas was simultaneously measured to calculate the conversion of ice into gas hydrate. Results showed that the gas hydrate formation was highly suitable because of its extremely high gas-solid contact area, and the formation rate was also very high. Self-preservation effect of $CO_2$ hydrate was confirmed by the measurement of $CO_2$ hydrate powder at normal and at pressed state, which resulted that this kind of gas storage and transport could be feasible using $CO_2$ hydrate formation.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.553-558
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• 2012

A simple new method was developed for the determination of betaine in Fructus Lycii using hydrophilic interaction liquid chromatography with evaporative light scattering detection (HILIC-ELSD). Good chromatographic separation and reasonable betaine retention was achieved on a Kinetex HILIC column ($2.1{\times}100mm$, $2.6{\mu}m$) packed with fused-core particle. The mobile phase consisted of (A) acetonitrile and (B) 10 mM ammonium formate (pH 3.0)/acetonitrile (90/10, v/v). It was used with gradient elution at a flow rate of 0.7 mL/min. The column temperature was set at $27.5^{\circ}C$ and the injection volume was $10{\mu}L$. The ELSD drift tube temperature was $50^{\circ}C$ and the nebulizing gas (nitrogen) pressure was 3.0 bar. Stachydrine, a zwitterionic compound, was used as an internal standard. Calibration curve over $10-250{\mu}g/mL$ showed good linearity ($R^2$ > 0.9992) and betaine in the 70% methanol extract of Fructus Lycii was well separated from other peaks. Intraand inter-day precision ranged from 1.1 to 3.0% and from 2.4 to 5.3%, respectively, while intra- and inter-day accuracy ranged from 100.0 to 107.0% and from 94.3 to 103.9%, respectively. The limit of quantification (LOQ) was $10{\mu}g/mL$ and the recoveries were in the range of 98.2-102.7%. The developed HILIC-ELSD method was successfully applied to quantitatively determine the amount of betaine in fourteen Fructus Lycii samples from different locations, demonstrating that this method is simple, rapid, and suitable for the quality control of Fructus Lycii.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.89-91
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• 2000

Polynuclear aromatic hydrocarbon (PAH) compounds are highly carcinogenic chemicals and common groundwater contaminants that are observed to persist in soils. The adherence and slow release of PAHs in soil is an obstacle to remediation and complicates the assessment of cleanup standards and risks. Biological degradation of PAHs in soil has been an area of active research because biological treatment may be less costly than conventional pumping technologies or excavation and thermal treatment. Biological degradation also offers the advantage to transform PAHs into non-toxic products such as biomass and carbon dioxide. Ample evidence exists for aerobic biodegradation of PAHs and many bacteria capable of degrading PAHs have been isolated and characterized. However, the microbial degradation of PAHs in sediments is impaired due to the anaerobic conditions that result from the typically high oxygen demand of the organic material present in the soil, the low solubility of oxygen in water, and the slow mass transfer of oxygen from overlying water to the soil environment. For these reasons, anaerobic microbial degradation technologies could help alleviate sediment PAH contamination and offer significant advantages for cost-efficient in-situ treatment. But very little is known about the potential for anaerobic degradation of PAHs in field soils. The objectives of this research were to assess: (1) the potential for biodegradation of PAH in field aged soils under denitrification conditions, (2) to assess the potential for biodegradation of naphthalene in soil microcosms under denitrifying conditions, and (3) to assess for the existence of microorganisms in field sediments capable of degrading naphthalene via denitrification. Two kinds of soils were used in this research: Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS). Results presented in this seminar indicate possible degradation of PAHs in soil under denitrifying conditions. During the two months of anaerobic degradation, total PAH removal was modest probably due to both the low availability of the PAHs and competition with other more easily degradable sources of carbon in the sediments. For both Harbor Point sediment (HPS-2) and Milwaukee Harbor sediment (MHS), PAH reduction was confined to 3- and 4-ring PAHs. Comparing PAH reductions during two months of aerobic and anaerobic biotreatment of MHS, it was found that extent of PAHreduction for anaerobic treatment was compatible with that for aerobic treatment. Interestingly, removal of PAHs from sediment particle classes (by size and density) followed similar trends for aerobic and anaerobic treatment of MHS. The majority of the PAHs removed during biotreatment came from the clay/silt fraction. In an earlier study it was shown that PAHs associated with the clay/silt fraction in MHS were more available than PAHs associated with coal-derived fraction. Therefore, although total PAH reductions were small, the removal of PAHs from the more easily available sediment fraction (clay/silt) may result in a significant environmental benefit owing to a reduction in total PAH bioavailability. By using naphthalene as a model PAH compound, biodegradation of naphthalene under denitrifying condition was assessed in microcosms containing MHS. Naphthalene spiked into MHS was degraded below detection limit within 20 days with the accompanying reduction of nitrate. With repeated addition of naphthalene and nitrate, naphthalene degradation under nitrate reducing conditions was stable over one month. Nitrite, one of the intermediates of denitrification was detected during the incubation. Also the denitrification activity of the enrichment culture from MHS slurries was verified by monitoring the production of nitrogen gas in solid fluorescence denitrification medium. Microorganisms capable of degrading naphthalene via denitrification were isolated from this enrichment culture.