• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.197-204
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• 2007

Ultra thin Er-silicide layers formed by Er deposition on the clean p-silicon and in situ post annealing technique were investigated with respect to change of the Schottky barrier height. The formation of Er silicides was confirmed by XPS results. UPS measurements revealed that the workfunction of the silicide decreased and was saturated as the deposited Er thickness increased up to $10{\AA}$. We found that the silicides were mainly composed of Er5Si3 phase through the XRD experiments. After Schottky diodes were fabricated with the Er silicide/p-Si junctions, the Schottky barrier heights were calculated $0.44{\sim}0.78eV$ from the I-V measurements of the Schottky diodes. There was large discrepancy in the Schottky barrier heights deduced from the UPS with the ideal junction condition and the real I-V measurements, so that we attributed the discrepancy to the $Er_5Si_3$ phase in the Er-silicides and the large interfacial density of trap state of it.

• Membrane Journal
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• v.24 no.5
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• pp.375-385
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• 2014

NaA zeolite/${\alpha}$-alumina composite membranes were hydrothermally synthesized at $100^{\circ}C$ for 24 hr by using nanosize seed of 100 nm in diameter and an ${\alpha}$-alumina support of $0.1{\mu}m$ in pore diameter, and then effect of seed coating layer on the microstructure of NaA zeolite separation layer was systematically investigated. In cases when nanosize seed was coated with a monolayer, increment in seed coverage induced small grained and thick NaA zeolite separation layer. On the other hand, in case when nanosize seed was coated with a multilayer, much small grained and thick separation layer was formed. It was clear that an uniform monolayer seed coating is required to grow hydrothermally a thin and defect-free NaA zeolite separation layer. In the present study, it was clearly announced that seed coating layer is a key factor to determine the microstructure of NaA zeolite layer, secondary grown on a porous support.

• Membrane Journal
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• v.24 no.5
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• pp.367-374
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• 2014

In the present study, disc-type LSCF/GDC (20 : 80 vol%) dual-phase membranes having porous LSC/GDC (50 : 50 vol%) active layers were prepared and effect of active layers on oxygen ion transport behavior was investigated. Introduction of active layers improved drastically oxygen flux due to enhanced electron conductivity and oxygen surface exchange activity. As firing temperature of active layer increased from $900^{\circ}C$ to $1000^{\circ}C$, oxygen flux increased due to improved contact between membrane and active layer or between grains of active layer. The enhanced contact would improve oxygen ion and electron transports from active layer to membrane. Also, as thickness of active layer increased from 10 to $20{\mu}m$, oxygen flux decreased since thick active layer rather prevented oxygen molecules diffusing through the pores. And, STF infiltration improved oxygen flux due to enhanced oxygen reduction reaction rate. The experimental data announces that coating and property control of active layer is an effective method to improve oxygen flux of dual-phase oxygen transport membrane.

• Korean Journal of Environmental Agriculture
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• v.16 no.1
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• pp.48-54
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• 1997

This study was performed to develop the biological treatment technology of wastewater polluted with heavy metals. The copper-tolerant bacteria, Pseudomonas stutzeri which possessed the ability to accumulate copper, was isolated from mine wastewaters polluted with various heavy metals. The characteristics of copper accumulation in the cells and the recovery of the copper from the cells accumulating zinc, were investigated. Removal rate of copper from the solution containing 100mg/l of copper by copper-tolerant bacteria was more than 78% at 2 days after inoculation with the cells. A large number of the electron-dense granules were found mainly on the cell wall and cell membrane fractions, when determined by transmission electron microscopy. Energy dispersive X-ray spectroscopy revealed that the electron-dense granules were copper complex with the substances binding copper. The copper accumulated into the cells was not desorbed by deistilled water, but more than 80% of the copper accumulated was desorbed by 0.1M-EDTA solution. The residues of the cells after combustion at $550^{\circ}C$ amounted to about 23.2% of the dry weight of the cells. EDS analysis showed that residues were relatively pure copper compound containing more than 78.4% of copper.

• Membrane Journal
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• v.17 no.3
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• pp.269-275
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• 2007

Sodium type faujasite(FAU) zeolite membranes with a thickness of 5${\mu}m$ and a Si/Al molar ratio of 1.5 were prepared by the secondary growth process. The $CO_2/N_2$ separation in the vacuum mode was investigated at $30^{\circ}C$ for an equimolar $CO_2-N_2$ mixed gas before and after embedding 13X zeolite beads in the permeate side. The embedded 13X zeolite beads improved both $CO_2$ permeance and $CO_2/N_2$ separation factor, simultaneously. The phenomenon was explained by an increment in the $CO_2$ desorption rate at the FAU zeolite/$\alpha-Al_2O_3$ phase boundary due to an enhanced $CO_2$ escaping through the pore channels of the $\alpha-Al_2O_3$ support layer. In the present paper, it will be emphasized that a hybridization of a membrane with an adsorbent can provide a key to break through the trade-off between permeance and separation factor, generally shown in a membrane separation.

• Membrane Journal
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• v.17 no.3
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• pp.254-268
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• 2007

Sodium type faujasite(FAU) zeolite layers with diverse materials characteristics(Si/Al ratio, thickness, and structural discontinuity) were hydrothermally grown on a porous $\alpha-Al_2O_3$ tube, and then the $CO_2/N_2$ separation was evaluated at $30^{\circ}C$ for an equimolar mixture of $CO_2$ and $N_2$. Among hydrothermal conditions, $SiO_2$ content in hydrothermal solution seriously affected materials characteristics: with an increment in the $SiO_2$ content, Si/Al ratio, thickness, and structural discontinuity of grown FAU zeolite layer simultaneously increased. The present study reveals that structural discontinuity(intercrystalline voids due to an incomplete densification and cracks induced by GIS Na-P1 phase) is the most important variable affecting the $CO_2/N_2$ separation. Also, it was suggested that the $CO_2$ desorption in permeate side be the rate-determining(slowest) step in the overall $CO_2$ permeation.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.86-93
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• 1997

Purpose: To assess the ability of in vivo H-1 MRS to determine the degree of malignancy and to characterize the histopathologic type of intracranial solid tumors. Materials and Methods: In vivo H-1 MR spectra of the pathologically-proven 81 intracranial soild tumors (low-grade glioma 17 cases, high-grade glioma 31 cases, lymphoma 9 cases, meningioma 8 cases, central neurocytoma 4 cases, medulloblastoma 3 cases, PNET 3 cases, metastasis 2 cases, others 4 cases) were analyzed. H-1 MR spectroscopy was performed on a 1.5T MR unit using PRESS sequence with a TR of 2000ms, a TE of 270 or 135ms and a voxel size of $2{\times}2{\times}2cm^3$ for all spectra. N-acetyl aspartate (NAA)/Creatine complex(Cr), Choline complex (Cho)/Cr, and lactate (Lac)/Cr ratios were measured on the peak heights of each resonance and compared among the different tumors. Results: All intracranial solid tumors demonstrated decreased NAA, elevated Cho and lactate, and variable Cr levels. All tumors showed increased Cho/Cr and Lac/Cr, whereas NAA/Cr level was decreased. Mean Cho/Cr and Lac/Cr ratios were significantly higher in high-grade gliomas than in low-grade gliomas. However, NAA/Cr ratio showed no significant difference between low-grade and high-grade gliomas. Very high Cho peaks were seen in lymphomas, meningiomas, medulloblastomas, and neurocytomas in addition to high-grade gliomas. Conclusion: H-1 MRS may be useful in differentiating between low-grade and high-grade gliomas, however cannot characterize the histologic types or subtypes of tumors.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.2
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• pp.125-133
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• 2005

Methodologies of NEWTRIT model, NRC model and AIRDOS-EPA model, which are off-site dose assessment models for regulatory compliance from routine releases of tritium into the environment, were investigated. Using the domestic data, if available, the predictive results of the models were compared. Among them, recently developed NEWTRIT model considers only doses from organically bounded tritium (OBT) due to environmental releases of tritiated water (HTO) . A total dose from all exposure pathways predicted from AIRDOS-EPA model was 1.03 and 2.46 times higher than that from NEWTRIT model and NRC model, respectively. From above result, readers should not have an understanding that a predictive dose from NRC model may be underestimated compared with a realistic dose. It is because of that both mathematical models and corresponding parameter values for regulatory compliance are based on the conservative assumptions. For a dose by food consumption predicted from NEWTRIT model, the contribution of OBT was nearly equivalent to that of HTO due to relatively high consumption of grains in Korean. Although a total dose predicted from NEWTRIT model is similar to that from AIRDOS-EPA model, NEIIfTRIT model may be have a meaning in the understanding of phenomena for the behavior of HTO released into the environment.

• Korean Journal of Environmental Agriculture
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• v.11 no.1
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• pp.77-85
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• 1992

Of the cadmium-tolerant 162 bacterial strains isolated from soils, river waters or active sludges of waste-water disposal plants in the Gyeongnam province a strain C1, which showed considerably higher growth rate in the agar plate containing 2000 ppm than any other strains isolated, was identified as a Pseudomonas putida or its similar strain when analyzed by taxonomical characteristics. Optimum pH and temperature for the growth of the P, putida were 7.0 and $30^{\circ}C$, respectively. This strain was resistant to antibiotics(ampicillin, chloramphenicol and streptomycin), and heavy metals(lithium, cupper, lead and zinc). This strain utilized salicylate, naphthalene or xylene as a sole carbon source. The rate of cadmium accumulation in P. putida cell was enhanced at low concentration of Cd in the growth media. The maximum cadmium absorption by this strain grown in 1 and l0ppm of Cd was respectively 78% and 60% 24 hrs after culture, but in 100 ppm Cd, 40% 48 hrs after culture. Addition of a non-ionic surfactant Triton X-100(0.1%) to the medium enhanced the accumulation of cadmium in the P. putida up to approximately 37%.

• Korean Journal of Environmental Agriculture
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• v.11 no.1
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• pp.67-76
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• 1992

A mechanistic study by which Cadmium-tolerant P.Putida C1 accumulates high conc of Cd in its cell body was performed. Approximately 57% Cd accumulated was distributed on the cell wall and the other 43% portion was in cytoplasm. 84% Cd of the Cd in the cell wall fractions present in the polyphosphate-polysaccharide fractions, but most of Cd in the cytoplasm fraction was in protein and nucleic acid. Cadmium affected the protein synthesis in P. Putida. The intracellular protein content was decreased by cadmium addition, but the soluble protein precipitated by ammonium sulfate($30{\sim}75%$ satruation) was increased as compared to that from the cells grwon without cadmium. Furthermore, in the cells grown with of cadmium, high-molecular-weight soluble protein was increased, with of cadmium, high-molecular-weight soluble protein was increased, compared with the cells grown without cadmium, but low-molecular-weight soluble protein was decreased. These results indicate that Cd inhibited the intracellular protein biosynthesis but enhance biosynthesis of the high-molecular-weight soluble protein precipitate by ammonium sulfate($30{\sim}75%$ saturation).