• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.832-835
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• 2001

We report the structural and electrical properties of hafnium oxide (HfO$_2$) films with tungsten silicide (WSi$_2$) metal gate. In this study, HfO$_2$thin films were fabricated by oxidation of sputtered Hf metal films on Si, and WSi$_2$was deposited directly on HfO$_2$by LPCVD. The hysteresis windows in C-V curves of the WSi$_2$HfO$_2$/Si MOS capacitors were negligible (<20 mV), and had no dependence on frequency from 10 kHz to 1 MHz and bias ramp rate from 10 mV to 1 V. In addition, leakage current was very low in the range of 10$^{-9}$ ~10$^{-10}$ A to ~ 1 V, which was due to the formation of interfacial hafnium silicate layer between HfO$_2$and Si. After PMA (post metallization annealing) of the WSi$_2$/HfO$_2$/Si MOS capacitors at 500 $^{\circ}C$ EOT (equivalent oxide thickness) was reduced from 26 to 22 $\AA$ and the leakage current was reduced by approximately one order as compared to that measured before annealing. These results indicate that the effect of fluorine diffusion is negligible and annealing minimizes the etching damage.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.21-27
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• 2011

A nano-porous structure of tin oxide was prepared using an anodic oxidation process and the sample's electrochemical properties were evaluated for application as an anode in a rechargeable lithium battery. Microscopic images of the as-anodized sample indicated that it has a nano-porous structure with an average pore size of several tens of nanometers and a pore wall size of about 10 nanometers; the structural/compositional analyses proved that it is amorphous stannous oxide (SnO). The powder form of the as-anodized specimen was satisfactorily lithiated and delithiated as the anode in a lithium battery. Furthermore, it showed high initial reversible capacity and superior rate performance when compared to previous fabrication attempts. Its excellent electrode performance is probably due to the effective alleviation of strain arising from a cycling-induced large volume change and the short diffusion length of lithium through the nano-structured sample. To further enhance the rate performance, the attempt was made to create porous tin oxide film on copper substrate by anodizing the electrodeposited tin. Nevertheless, the full anodization of tin film on a copper substrate led to the mechanical disintegration of the anodic tin oxide, due most likely to the vigorous gas evolution and the surface oxidation of copper substrate. The adhesion of anodic tin oxide to the substrate, together with the initial reversibility and cycling stability, needs to be further improved for its application to high-power electrode materials in lithium batteries.

• Membrane Journal
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• v.15 no.2
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• pp.105-113
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• 2005

Silica membranes were prepared on a porous metal sheet by ultrasonic spray pyrolysis method for gas separation at high temperatures. In order to improve the permselectivity, silica was deposited in the sol-gel derived $silica/\gamma-alumina$ intermediate layer by pyrolysis of tetraethyl orthosilicate (TEOS) at 873 K. The pyrolysis with forced cross flow through the porous wall of the support was very effective in plugging mesopores, Knudsen diffusion regime, that were left unplugged in the membranes. At permeation temperature of 523 K, the silica/alumina composite membrane showed $H_2/N_2$ and water/methanol selectivity as high as 17 and 16, respectively, by molecular sieve effect.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1993-1997
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• 2008

In the present work, Diels-Alder reaction of cyclopentadiene with ethylacrylate has been carried out by using two types of mesoporous solid acid catalysts (Al-MCM-41, Al-MCM-48) with different pore structures. The specific topology of Al-MCM-48 (cubic Ia3d structure composed of two independent 3-D channel systems) exhibit higher activity and stereo-control than those of Al-MCM-41 (hexagonal packing of 1-D channels). The physical properties of Al-MCM-48 catalyst, such as high accessibility of reactants to the acid sites, spatial confinement in the nanoscopic reactors, and 3-D channel network structure that are effective adsorption and diffusion of reactants, play a crucial role in the present study.

• Journal of Environmental Health Sciences
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• v.19 no.2
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• pp.46-54
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• 1993

This study was carried out on the stabilized/solidified treatment for the reducing leachability of hazardous heavy metals copper, lead, chromium and cadmium in the hazardous sludge which treated to be unleached heavy metals by sodium diethyl dithiocarbamate. Cement matrix was analyzed for the leachability of 24 hrs and dynamic leaching test, structure and the optimum condition for the stabilization and solidification of the hazardous sludge. In 28 days of curing time the unconfined compressive strength was 21.5 kg/cm$^2$ at the ratio of portland cement (0.5)+fly ash (0.25) and 23.5 kg/cmz at the ratio of portland cement (0.5)+fly ash (0.25) + cake (0.25). High concentration of Pb, Cr and Cd in the sea water and Cu in the distilled water were leached at the dynamic leaching test. The concentration of leaching heavy metals for specimens which were tested 24 hrs were found low leachability with decreasing pH of leachant. According to dynamic leaching test, the low level of copper, lead, cadmium and chromium were leached in the cement matrix with sodium diethyl dithiocarbamate. But the effective diffusion coefficient of unleached cement matrix which was treated sodium diethyl dithiocarbamate was decreased above 2 times than that of cement matrix. The relation of leachant renewal period (Y) and cumulative fraction ion leached (X) was the following regression equations. Solidification with unleached agent. Y$_{Cu}$ = 1413752X + 247, Y$_{Pb}$ = 223501IX + 214, Y$_{Cr}$ = 8310601X - 472, Y$_{Cd}$ = 168787X + 1061 The structure of' solidified matrix with X-ray diffraction analysis was composed more Ca(OH)$_2$, Si, Mg(OH)$_2$ and Al in the unleached cement matrix than those in cement matrix.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1429-1436
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• 1994

We have prepared Ba0.5Sr0.5TiO3 thin films on Si substrate without buffer layer. Deposition was carried out by off-axis rf magnetron sputtering method using Ba0.5Sr0.5TiO3 stoichiometric target. The substrate temperature was changed from 40$0^{\circ}C$ to $700^{\circ}C$ during deposition. As the substrate temperature increased, relative intensity of (110) peak increased up to $600^{\circ}C$, however preferred orientation changed from (110) to (h00) beyond $650^{\circ}C$ of substrate temperature. Deposited films showed microstructures with fine grains whose diameters are less than 100 nm, and columnar structure was observed in the cross-sectional SEM micrograph. AES depth profile showed no significant diffusion at the interfacial reaction area. The effective dielectric constant of films showed maximum value at $600^{\circ}C$, and the leakage current increased with increasing substrate temperature, which may be ascribed to the crystallization of amorphous phases at grain boundary.

• Preventive Nutrition and Food Science
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• v.6 no.1
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• pp.10-15
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• 2001

Antimicrobial activities of volatile flavor, water and methanol extracts from Agastache rugosa were investigated. The volatile flavor extract was obtained from A. rugosa by simulataneous distillation-extraction (SDE) method. Antimicrobial activity was investigated by disc diffusion method against several microorganisms, four species of Gram positive, three species of Gram negative and tow species of yeast. The volatile flavor extracts had strong antimicrobial activity againstc. utilisand S. cerevisiae. During the growth period, a difference in antimicrobial activity among volatile flavor extracts from A. rugosa was not shown. The water extract of above 10 mg/disc showed antimicrobial activity. Methanol extracts from A. rugosa harvested in June showed antimicrobial activity against tested Gram positive and Gram negative bacteria, showed weak antimicrobial activity against the bacteria from those harvested in July and August. In particular, antimicrobial activity against V. parahaemolyticus was stronger than that against other bacteria. Water and methanol extracts did not inhibit yeast. C. utilis and S. cerevisiae. To further elucidate the effective components, volatile flavor extracts was analyzed by GC/MS. harvested in June, the components included 8 phenols (93.031%), 18 terpenes (5.230%), 12 alcohols (1.300%) 8 alkanes (0.181%), 1 ester (0.056%), 2 ketones (0.033%), 2 aldehydes (0.011%) and 1 pyrrole (0.007%). In July, the components included 6 phenols (94.366%), 19 terpenes (3.394%), 11 alcohols (2.045%), 1 ester (0.039%), 2 ketones (0.028%), 1 furan (0.005%) and 1 aldehyde (0.005%). And in August, the components included 7 phenols (95.270%), 19 terpenes (2.951%), 13 alcohols (1.399%), 1 ester (0.063%), 2 aldehydes (0.016%), 2 ketones (0.011%), 1 alkane (0.006%), 1 acid (0.005%) and 1 pyrrole (0.005%). The major component of volatile flavors was estragole, a phenolic compound.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.3
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• pp.39-45
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• 2016

In this paper, prcess modeling of germanium condensation has been performed and a germanium PMOSFET having nanowire channel implented by the condensation process has been designed and characterized by device simulations. Based on the previous experimental results, our modeling results demonstrate that the ratio of germanium concentration at the silicon germanium-silicon dioxide interface ($C_S$) to that in the bulk region ($C_B$) which are obtainable during the germanium condensation is approximately 4.03 and the effective diffusion coefficient ($D_{eff}$) of germanium atom is $3.16nm^2/s$. Furthermore, a germanium nanowire-channel PMOSFET having the ultra-thin germanium channel on the silicon core that can be fabricated by the germanium condensation has been designed and characterized. As the result, it is confirmed that the proposed device having the coaxial nanowire consisting of silicon core and germanium channel might have superior performances over the device with either all-silicon or all-germanium channel.

• Journal of Periodontal and Implant Science
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• v.40 no.6
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• pp.257-264
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• 2010

Purpose: Connective tissue reattachment to periodontally damaged root surfaces is one of the most important goals of periodontal therapy. The aim of this study was to develop a root conditioning agent that can demineralize and detoxify the infected root surface. Methods: Dentin slices obtained from human teeth were treated with a novel root planing agent for 2 minutes and then washed with phosphate-buffered saline. Smear layer removal and type I collagen exposure were observed by scanning electron microscopy (SEM) and type I collagen immunostaining, respectively. Cell attachment and lipopolysaccharides (LPS) removal demonstrated the efficiency of the root conditioning agent. Results: SEM revealed that the smear layer was entirely removed and the dentinal tubules were opened by the experimental gel. Type I collagen was exposed on the surfaces of the dentin slices treated by the experimental gel, which were compared with dentin treated with other root planing agents. Dentin slices treated with the experimental gel showed the highest number of attached fibroblasts and flattened cell morphology. The agar diffusion assay demonstrated that the experimental gel also has effective antimicrobial activity. Escherichia coli LPS were effectively removed from well plates by the experimental gel. Conclusions: These results demonstrated that this experimental gel is a useful tool for root conditioning of infected root surfaces and can also be applied for detoxification of ailing implant surface threads.

• Information Systems Review
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• v.11 no.2
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• pp.131-145
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• 2009

Knowledge management is systematic management of vital knowledge resources and its associated processes of creating, gathering, organizing, diffusion, use and exploitation. A key challenge emerging for such organizations is how to encourage knowledge sharing within organization because knowledge is the organization's intellectual capital, of increasing importance in promoting competitive advantages. Isolated initiatives for promoting knowledge sharing and team collaboration, without taking consideration of the knowledge sharing limitations and constraints can defeat further development of KM culture. This article investigates knowledge sharing bottlenecks and proposes the use of community of practice as an effective instrument for knowledge sharing. The article demonstrates the opportunity for overcoming barriers of knowledge sharing through the application of communities of practice. The article introduces a steel company case as the best practice of communities of practice. Then, the paper empirically analyzes the case study to provide evidence for the feasibility and effectiveness of the proposed approach.