• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3626-3631
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• 2009

This study has provided some of the first experimental results of NMOSFET hot-carrier degradation for the analog circuit application. After hot-carrier stress under the whole range of gate voltage, the degradation of NMOSFET characteristics is measured in saturation region. In addition to interface states, the evidences of hole and electron traps are found near drain depending on the biased gate voltage, which is believed to the cause for the variation of the transconductance($g_m$) and the output conductance($g_{ds}$). And it is found that hole trap is a dominant mechanism of device degradation in a low-gate voltage saturation region, The parameter degradation is sensitive to the channel length of devices. As the channel length is shortened, the influence of hole trap on the channel conductance is increased. Because the magnitude of $g_m$ and $g_{ds}$ are increased or decreased depending on analog operation conditions and analog device structures, careful transistor design including the level of the biased gate voltage and the channel length is therefore required for optimal voltage gain ($A_V=g_m/g_{ds}$) in analog circuit.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.527-534
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• 2015

This study offers a novel method for improving the physical contact between the anode and fuel in a direct carbon fuel cell (DCFC): a direct generation of carbon in a porous Ni anode through the thermal decomposition of gaseous hydrocarbons. Three kinds of alkane hydrocarbons with different carbon numbers (CH4, C2H6, and C3H8) are tested. From electron microscope observations of the carbon particles generated from each hydrocarbon, we confirm that more carbon spheres (CS), carbon nanotubes (CNT), and carbon nanofibers (CNF) were identified with increasing carbon number. Raman scattering results revealed that the carbon samples became less crystalline and more flexible with increasing carbon number. DCFC performance was measured at $700^{\circ}C$ with the anode fueled by the same mass of each carbon sample. One-dimensional carbon fuels of CNT and CNF more actively produced and had power densities 148 and 210 times higher than that of the CS, respectively. This difference is partly attributed to the findings that the less-crystalline CNT and CNF have much lower charge transfer resistances than the CS.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.195-200
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• 1998

We have investigated the crystal structure and electrical properties of Pt/SBT/$CeO_2$/Si(MFIS) and Pt/SBT/Si(MFS) structures for the gate oxide of ferroelectric memory. XRD spectra and SEM showed that the SBT film of SBT/$CeO_2$/Si structure had larger grain than that of SBT/Si structure. Furthermore HRTEM showed that SBT/$CeO_2$/Si had 5 nm thick $SiO_2$layer and very smooth interface but SBT/Si had 6nm thick $SiO_2$layer and 7nm thick amorphous intermediate interface. Therefore, $CeO_2$film between SBT film and Si substrate is confirmed as a good candidate for a diffusion barrier. The remanent polarization decreased and coercive voltage increased in Pt/SBT/$CeO_2/Pt/SiO_2$/Si structure. This effect may increase memory window of MFIS structure directly related to the coercive voltage. From the capacitance-voltage characteristics, the memory of Pt/SBT(140 nm)/$CeO_2$(25 nm)/Si structure were in the range of 1~2 V at the applied voltage of 4~6 V. The memory window increased with the thickness of SBT film. These results may be due to voltage applied at SBT films. The leakage currents of Pt/SBT/$CeO_2$/Si and Pt/SBT/Si were $ 10^8A/\textrm{cm}^2$ and $ 10^6 A/\textrm{cm}^2$, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.12
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• pp.851-857
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• 2014

Treatability of heavy metals in marine sediments contaminated with mainly organic matter was investigated on the basis of washing technology using oxidizers and surfactants. Sediment samples were collected at N area which expected for remediation project of contaminated marine sediment. For additives, hydrogen peroxide ($H_2O_2$) and Tween-80 were used at oxidizer and nonionic surfactant, respectively. In experiments, sediments was mixed with sea water at the ratio of 1 : 3 than $H_2O_2$ (1 M, 3 M, 4 M, 5 M) and Tween-80 (0.05%) were added. Samples were gathered at following reaction time (10, 20, 30, 40, 50, 60, 70, 80 min and 24 h). Total Organic Carbon (TOC) was 55.2% at the conditions of 5 M $H_2O_2+0.05%$ Tween-80 24 h. Hence total heavy metals were Cu 29.5%, Zn 42.3%, Cd 73.0% and bioavailable heavy metals were Cu 60.0%, Zn 77.7%, Cd 90.2% at the conditions of 5 M $H_2O_2+0.05%$ Tween-80 10 min. The correlations for between bioavailable metals (Cu, Zn, Cd) and TOC were significant (Cu, Zn, Cd; $r^2=0.94$, 0.85, 0.69, respectively).

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.6-11
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• 2012

In order to understand a process of contaminants removal on surface of Cu seed layer (Cu seed/Ti/Si) by sputter deposition, we investigated the changed morphology and states of Cu seed surface after pretreatment in alkali degreasing Metex TS-40A solution according to dipping time. After TS-40A pretreatment, the surface morphology with clearer grains was observed by Field emission scanning electron microscope and the changed surface chemical states and impurities on surface of samples were checked by X-ray photoelectron spectroscopy. Dipping time in TS-40A solution had very little effect on surface of Cu seed layer. After pretreatment, much carbons and little oxygens on surface of Cu seed were eliminated and the decrease of peaks corresponded to O=C and $Cu(OH)_2$ was estimated. However, Si content (=silicate) was detected on sample surface. We think that the silicate impurity forms on Cu seed by chemical reaction of TS-40A solution included silicate component. By pretreatment of alkali degreasing Metex TS-40A solution, it showed an excellent effect in removal of O=C and $Cu(OH)_2$ on Cu seed layer, but the silicate was formed on surface of Cu seed. Therefore, another cleaning process such as acid cleaning is required for removal of this silicate in use of this alkali degreasing.

• KSBB Journal
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• v.24 no.1
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• pp.41-46
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• 2009

Vegetable oils are desirable inexpensive feedstocks for various bioproducts. The content of unsaturated fatty acids such as oleic and linoleic acids are 22% and 55% for soybean oil, 26% and 60% for corn oil, and 61% and 21% for canola oil, respectively. Keto and hydroxy fatty acids are useful industrial chemicals, used in plasticizer, surfactant, lubricant and detergent formulations because of their special chemical properties such as higher viscosity and reactivity compared with other fatty acids. In this study, a microbial isolate, Flavobacterium sp. strain DS5 (NRRL B-14859), was used to convert oleic acid to 10-ketostearic acid (10-KSA) via 10-hydroxystearic acid (10-HSA). Two bioconversion products, 10-KSA and 10-HSA, were quantitatively and qualitatively analyzed using gas chromatography, gas chromatography-mass spectrometry, and $^1H-$ and $^{13}C$-nuclear magnetic resonance. The maximum production of 10-KSA and 10-HSA in flask cultures were 3.4 g/L and 0.5 g/L, respectively. The optimum concentrations of glucose and yeast extract, addition time and volume of oleic acid for 10-KSA production were less than 20 g/L, more than 5 g/L, 18 hand 0.3 ml/50 ml, respectively.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.3-9
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• 2013

In ultra high strength concrete, when electric arc furnace oxidizing slag is substituted for sea sand as fine aggregate, compressive strength was improved about 15 MPa. To figure out the cause of the improvement in compressive strength, this study considered the dissolution characteristics of Ca component in fine aggregate and examined the microstructure, porosity, microhardness, and Ca/Si mole ratio on the interface of fine aggregate and paste. And to examine the mechanism of strength improvement resulted from the shape of fine aggregate, this study measured the surface roughness of fine aggregate with AFM. According to the result of this experiment, the mechanisms of strength improvement in ultra high strength concrete resulted from the use of electric arc furnace oxidizing slag as fine aggregate can be divided into chemical and physical mechanisms. In the chemical mechanism, the soluble Ca component contained in electric arc furnace oxidizing slag is dissolved and forms a hydrate between fine aggregate and paste to improve the interlocking strength of fine aggregate-paste. Also, it makes the microstructure around the fine aggregate. And in the physical mechanism, electric arc furnace oxidizing slag has a twice greater surface roughness than sea sand, so the interlocking strength between fine aggregate and paste increases, which contributes to the development of compressive strength.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.253-258
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• 2005

Characteristics of electroplated Ni films such as grain size, resistivity, solder wetting angle, and growth rate of intermetallic compound were evaluated as a function of electroplating current density. With increasing the electroplating current density from $5\;mA/cm^2 $ to $40\;mA/cm^2 $, the nodule size on the Ni film surface decreased, grain refinement occurred, and resistivity increased from $7.37\mu\Omega-cm$ to $9.13\mu\Omega-cm$. Compared with Ni film processed at $40\;mA/cm^2 $, Ni films electroplated at $5\;mA/cm^2 $ and $10\;mA/cm^2 $ exhibited low resistivity, dense microstructure, and slow growth rate of intermetallic compound. Ni films electroplated at $5\;mA/cm^2 $ and $10\;mA/cm^2 $ are more suitable for Ni UBM application than that fabricated at $40\;mA/cm^2 $.

• Clean Technology
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• v.23 no.3
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• pp.270-278
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• 2017

This study introduces a method to easily fabricate highly monodisperse pectin hydrogel microfibers in a microfluidic device by using partial gelation. The hydrodynamic parameters between the pectin aqueous solution and the calcium ions containing oil solution are precisely controlled to form a stable elongation flow of the pectin aqueous solution, and partial gelation of the pectin aqueous solution is performed by the chelating of the calcium ions at the interface between the two phases. The partially gelled pectin aqueous solution is phase-separated from the oil solution in an aqueous calcium chloride solution outside the microfluidic device and is completely gelled to produce monodisperse pectin hydrogel microfibers. The thickness of the pectin hydrogel microfiber is controlled in a reproducible manner by controlling the volumetric flow rate of the initially injected pectin aqueous solution. The pectin hydrogel microfibers were 200 to 500 micrometers in diameter and had a coefficient of variation below 5% under all thickness conditions, indicating that the pectin hydrogel microfibers produced by partial gelation are highly monodisperse. In addition, biomaterials can be immobilized to the pectin hydrogel microfibers produced by a single process, demonstrating the possibility that our pectin hydrogel microfiber can be used as carriers for biomaterials or tissue engineering.

• Clean Technology
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• v.23 no.3
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• pp.302-307
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• 2017

This study was conducted to evaluate the feasibility of in situ soil flushing for TPH-contaminated soil remediation with column test. The soil texture of the soil was sand and the initial TPH concentration was $9,369mg\; kg^{-1}$. 0.1% Tween-80 was selected as surfactant solution. And the acrylic and the glass syringe columns were used as reactors. In the acrylic column test, 35% of the initial TPH was removed in 1 PV of flushing and approximately 40% in 5 PV and finally 7 PV showed about 60%. The glass column test showed 3 ~ 12% higher removal efficiency than that of acrylic test until 5 PV of flushing. However, there was no difference in TPH removal efficiency when 7 PV of surfactant was finally flushed. Both of alum only and alum+polymer mixed surfactants showed also the best coagulation efficiency in $150mg\;L^{-1}$ of concentraion. When Tween 80 was newly dissolved in 0.1% to the recovered solution after the coagulation treatment, the removal efficiency was increased from 32.0% to 41.0% in comparison to the new 0.1% Tween 80 solution without reuse by coagulation treatment.