• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.52-56
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• 2006

Some of factors affecting photo-conversion efficiency of dye sensitized solar cells (DSCs) are discussed in terms of $TiO_2$ electrodes. The first topic is on the surface modification of $TiO_2$ nano-particles, which is associated with electron traps on the surface of $TiO_2$ nano-particles. The surface is modified with dye molecules under pressurized $CO_2$ atmosphere to increase the surface coverage of $TiO_2$ nano-particles with dye molecules. This increases Jsc because of an increase in the amount of dye molecules and a decrease in the amount of trapping sites on $TiO_2$ nano-particles. In addition, the decrease in the amount of trap sites increases Voc because decreases in Voc are brought about by the recombination of $I_2$ molecules with electrons trapped on the $TiO_2$ surfaces. Selective staining for tandem cells is proposed. The second topic is on the contact between a $SnO_2$/F transparent conductive layer (TCL) and nano-particles. Polishing the TCL surfaces with silica nano-particles increases the contact, resulting in Jsc increases. The third topic is the fabrication of ion-paths in $TiO_2$ layers. Electro-spray coating of $TiO_2$ nano-particles onto TCL is shown to be effective for fabricating ion-paths in $TiO_2$ layers, which increases Jsc.

• Proceedings of the KSRS Conference
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• v.2
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• pp.989-992
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• 2006

The new approach to the problem of oil spill detection consisting in combined use of all available quasiconcurrent satellite information (AVHRR NOAA, TOPEX/Poseidon, Jason-1, MODIS Terra/Aqua, QuikSCAT) is suggested. We present the results of the application of the proposed approach to the operational monitoring of seawater condition and pollution in the coastal zone of northeastern Black Sea conducted in 2006. This monitoring is based on daily receiving, processing and analysis of data different in nature (microwave radar images, optical and infrared data), resolution and surface coverage. These data allow us to retrieve information on seawater pollution, sea surface and air-sea boundary layer conditions, seawater temperature and suspended matter distributions, chlorophyll a concentration, mesoscale water dynamics, near-surface wind and surface wave fields. The focus is on coastal seawater circulation mechanisms and their impact on the evolution of pollutants.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2531-2536
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• 2011

Ethanol is a prototype molecule used in probing catalytic reactivity of oxide catalysts such as $TiO_2$. In the present study, we adsorbed ethanol on $TiO_2$(001) at room temperature (RT) and the corresponding bonding state of ethanol was systematically studied by x-ray photoemission spectroscopy (XPS) using synchrotron radiation. Especially, we compared $TiO_2$(001) surfaces prepared in ultra-high vacuum (UHV) with different surface treatments such as $Ar^+$-sputtering and oxidation with molecular $O_2$, respectively. We find that the saturation coverage of ethanol at RT varies depending on the amount of reduced surface defects (e.g., $Ti^{3+}$) which are introduced by $Ar^+$-sputtering. We also find that the oxidized $TiO_2$(001) surface has other type of surface defects (not related to Ti 3d state) which can dissociate ethanol for further reaction above 600 K. Our C 1s core level spectra indicate clearly resolved features for the two chemically distinct carbon atoms from ethanol adsorbed on $TiO_2$(001), showing the adsorption of ethanol proceeds without C-C bond dissociation. No other C 1s feature for a possible oxidized intermediate was observed up to the substrate temperature of 650 K.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.443-443
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• 2011

Atomic layer deposition (ALD) was used to deposit $TiO_2$ on Ni particles, and changes in the catalytic activity of Ni for $CO_2$ reforming of methane (CRM) were studied. In the presence of $TiO_2$ islands on Ni surfaces, the onset temperature of the CRM reaction was lower than that of bare Ni. During the CRM reaction, carbon was deposited on the surface, reducing the catalytic activity of the surface, but $TiO_2$ was able to remove the carbon deposits from the surface. When the Ni surface was completely covered with $TiO_2$, catalytic activity disappeared, indicating that tuning of $TiO_2$ coverage on Ni is important for maximizing the activity of the CRM reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.216-216
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• 2011

We will investigate the bonding configurations of phenylalanine and tyrosine adsorbed on the Ge(100) surface using CLPES and DFT calculations. First, the C 1s, N 1s, and O 1s spectra obtained at 300 K revealed that both the amine and carboxyl groups of phenylalanine and tyrosine concurrently participated in adsorption on the Ge(100) surface without bond breaking using CLPES, depending on the extent of coverage. In the second place, we confirmed that the "O-H dissociated-N dative bonded structure" is the most stable structure implying kinetically favorable structure, and the "O-H dissociation bonded structure" is another stable structure manifesting thermodynamically advantageous structure using DFT calculations. This tendency turns up both phenylalanine and tyrosine, similarly. Furthermore, through the CLPES data and DFT calculation data, we discovered that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at 0.30 ML and 0.60 ML, respectively. Moreover, we found that the phenyl ring of phenylalanine is located in axial position to Ge(100) surface, but the phenyl ring of tyrosine is located in parallel to Ge(100) surface using DFT calculations.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.581-586
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• 2014

The most stable adsorption structures and their corresponding energies of 4-pyridone, 4-hydroxypyridine, 2-pyridone and 2-hydroxypyridine have been investigated by Density Functional Theory (DFT) calculation and high-resolution photoemission spectroscopy (HRPES). We confirmed that between the two reaction centers of 4- and 2-pyridone, only O atom of carbonyl functional group can act as a Lewis base while both the two reaction centers of 4- and 2-hydroxypyridine (tautomers of 4- and 2-pyridone) can successfully function as a Lewis base. On the other hand, owing to their molecular structures, there is a remarkable difference between the adsorption structures of 4- and 2-hydroxypyridine. Through the analysis of the N 1s and O 1s core level spectra obtained using HRPES, we also could corroborate that two different adducts coexist on the surface at room temperature due to their activation energy investigating the coverage dependent variation of bonding configurations when these molecules are adsorbed on the Ge(100) surface.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.545-551
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• 2013

In this study, shot peening technique was employed with shot peening time for durability improvement and surface modification of copper alloy to investigate the electrochemical characteristics and microstructural variations. As a result of shot peening, roughness was distributed over the surface, and homogenization phenomenon was observed with increasing shot peening time due to the enhancement of coverage. The results revealed that hardness increased for shot peened specimens and particularly 3.5 mins of shot-peening time represented a hardness improvement of 52 %, showing similar electrochemical characteristics to that of the un-peened surface.

• Journal of the Korean institute of surface engineering
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• v.26 no.1
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• pp.3-9
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• 1993

Chemical vapor deposited tungsten films were formed in a cold wall reactor at pressures higher (10~120torr) than those conventionally employed (<1torr). SiH4, in addition to H2, was used as the reduction gas. The effects of pressure and reaction temperature on the deposition rate and morphology of the films were ex-amined under the above conditions. No encroachment or silicon consumption was observed in the tungsten de-posited specimens. A high deposition rate of tungsten and a good step coverage of the deposited films were ob-tained at 40~80 torr and at a temperature range of $360~380^{\circ}C$. The surface roughness and the resistivity of the deposited film increased with pressure. The deposition rate of tungsten increased with the total pressure in the reaction chamber when the pressure was below 40 torr, whereas it decreased when the total pressure ex-ceedeed 40 torr. The deposition rate also showed a maximum value at $360^{\circ}C$ regardless of the gas pressure in the chamber. The results suggest that the deposition mechanism varies with pressure and temperature, the surface reac-tion determines the overall reaction rate and (2) at higher pressures(>40 torr) or temperatures(>36$0^{\circ}C$), the rate is controlled by the dtransportation rate of reactive gas molecules. It was shown from XRD analysis that WSi2 and metastable $\beta$-W were also formed in addition to W by reactions between WF6 and SiH4.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.137-137
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• 2000

The surface collective modes of thin K films deposited on Al(111) have been investigated using frequency dependent photoyield measurements and momentum resolved inelastic electron scattering. Jellium based theoretical calculations have predicted a richer set of features in the thin films than for the surface of a semi-infinite solid because there are th interference between two interfaces (substrate-film and film-vacuum) and heavy damping on the substrate. The use of an optical probe and electron scattering has allowed us to draw a more complete picture of the dynamic screening in thin films. The number, dispersion, damping and optical activity of the collective modes of the thin films have been measured as a function of K film thickness. New overlayer-induced excitations are observed : At qII=0, they correspond to the antisymmetric slab mode and the multipole surface plasmon. At finite qII=0, these modes undergo a transition towards the K multipole and monopole surface plasmons. With increasing coverage, the overlayer excitations turn into the collective modes of semi-infinite K. For a consistent interpretation of photoyield and electron energy loss spectra it is crucial to account for the non-analytic dispersion of the overlayer modes at small parallel wave vectors and for the finite angular resolution of the detector. The observed dispersions confirm predictions based on the time-dependent density functional approach.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.110-116
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• 2021

In this work, the surface of hydrophilic cellulose nanofibrils (CNFs) was modified precisely by varying amounts of cetyltrimethylammonium bromide (CTAB) to produce CNF-based particle surfactants. We found that a critical CTAB density was required to generate amphiphilic CTAB-grafted CNF (CNF-CTAB). Compared to pristine CNF, CNF-CTAB was highly efficient at stabilizing oil-in-water Pickering emulsions. To evaluate their effectiveness as particle surfactants, the surface coverage of oil-in-water emulsion droplets was determined by changing the CNF-CTAB concentration in the aqueous phase. Furthermore, styrene-in-water stabilized by CNF-CTAB surfactants was thermally polymerized to produce CNF-stabilized polystyrene (PS) particles, offering a great potential for various applications including pharmaceuticals, cosmetics, and petrochemicals.