• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1534-1538
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• 2011

Uniform, hollow nanosilica spheres were prepared by the chemical coating of cationic polystyrene (cPS) with tetraethylorthosilicate (TEOS), followed by calcination at 600 $^{\circ}C$ under air. cPS was synthesized by surfactant-free emulsion polymerization using 2,2'-azobis (2-methyl propionamidine) dihydrochloride as the cationic initiator, and poly(vinyl pyrrolidone) as a stabilizer. The resulting cPS spheres were 280 nm in diameter, and showed monodispersion. After coating, the hollow silica product was spherically shaped, and 330 nm in diameter, with a narrow distribution of sizes. Dispersion was uniform. Wall thickness was 25 nm, and surface area was 96.4 $m^2/g$, as determined by BET. The uniformity of the wall thickness was strongly dependent upon the cPS surface charge. The effects of TEOS and ammonia concentrations on shape, size, wall thickness, and surface roughness of hollow $SiO_2$ spheres were investigated. We observed that the wall thicknesses of hollow $SiO_2$ spheres increased and that silica size was simultaneously enhanced with increases in TEOS concentrations. When ammonia concentrations were increased, the irregularity of rough surfaces and aggregation of spherical particles were more severe because higher concentrations of ammonia result in faster hydrolysis and condensation of TEOS. These changes caused the silica to grow faster, resulting in hollow $SiO_2$ spheres with irregular, rough surfaces.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.439-452
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• 2005

Zinc is ubiquitous in all living cells. Structural and catalytic properties of cellular enzymes are zinc dependent. Zinc deficiency leads to a variety of pathological abnormalities with immune impairment. It is an established fact that nutritional status contributes to overall immune response of individuals. Outcome of zinc deficiency on immune system is so drastic that it is difficult to conceive at the first instance. Zinc supplementation has been advocated to prevent diarrheal disease in children with poor nutritional status. The bioavailability of zinc depends upon its sources. Moreover it varies between monogastrics and ruminants. Controversy still prevails between inorganic and organic sources of zinc with respect to their superiority in bioavailability. Zinc exerts immunostimulatory effects in various laboratory and farm animals. Animals having congenital zinc deficiency diseases like A46 lethal trait usually die due to impairment of the immune system unless treated with zinc. The immune mechanism of zinc and its effect on animals and man are discussed. Zinc has been considered as extremely safe at higher therapeutic doses, but does not provide any beneficial effect but rather may cause immunosuppression. More recently, zinc has been prescribed for immunodeficient hosts, to modulate the immune system so that to a certain extent it can combat against opportunistic pathogens.

• Korean Journal of Environment and Ecology
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• v.20 no.2
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• pp.153-158
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• 2006

The purpose of this study was to provide basic data for developing the effective park management. For this, satisfaction factors and estimated model by satisfaction variables of visitors analyzed through a questionnaire survey in Weolchulsan National Park, Korea. In the evaluation of the satisfaction, variables of 'lack of visit program' was most unsatisfied, and 'lack of facility', 'charge of fee', 'lack of pamphlet & information facility' were more unsatisfied than any other variables. Satisfaction factors by Factor Analysis were loaded with 'facility management', 'usual management'. In estimated model of satisfaction by Multiple Regression Analysis showed in order of 'negative impacts of trail', 'lack of safety facility'.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.12-27
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• 2018

Supercapacitors (SCs) has gained an impressive concentration by the researchers due to its advantages such as high energy and power densities, long cyclic life, rapid charge-discharge rates, low maintenance and desirable safety. Hence it has been widely utilized in energy storage and conversion devices. Among the different components of SC, electrodes play a vital role in the performances of SCs. In this review, we present the recent advances in 2-D nanostructured metal nitrides, carbides, and phosphides based materials for SC electrodes. Finally, the electrochemical stability and designing approach for the future advancement of the electrode materials are also highlighted.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.166-173
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• 2018

In order to investigate the effect of Mn on the dielectric and piezoelectric properties of PMN-PT [$Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$], four different types of 71PMN-29PT samples were prepared using the solid-state single crystal growth (SSCG) method: (1) Undoped single crystals, (2) undoped polycrystalline ceramics, (3) Mn-doped single crystals, and (4) Mn-doped polycrystalline ceramics. In the case of single crystals, the addition of 0.5 mol% Mn to PMN-PT decreased the dielectric constant ($K_3{^T}$), piezoelectric charge constant ($d_{33}$), and dielectric loss (tan ${\delta}$) by about 50%, but increased the coercive electric field ($E_C$) by 50% and the electromechanical quality factor ($Q_m$) by 500%, respectively. The addition of Mn to PMN-PT induced an internal bias electric field ($E_I$) and thus specimens changed from piezoelectrically soft-type to piezoelectrically hard-type. This Mn effect was more significant in single crystals than in ceramics. These results demonstrate that Mn-doped 71PMN-29PT single crystals, because they are piezoelectrically hard and simultaneously have high piezoelectric and electromechanical properties, have great potential for application in fields of SONAR transducers, high intensity focused ultrasound (HIFU), and ultrasonic motors.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.8
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• pp.1194-1198
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• 2005

A computer vision system was designed and validated to recognize an individual Holstein cattle by processing images of their body patterns. This system involves image capture, image pre-processing, algorithm processing, and an artificial neural network recognition algorithm. Optimum management of individuals is one of the most important factors in keeping cattle healthy and productive. In this study, an image-processing system was used to recognize individual Holstein cattle by identifying the body-pattern images captured by a charge-coupled device (CCD). A recognition system was developed and applied to acquire images of 49 cattles. The pixel values of the body images were transformed into input data comprising binary signals for the neural network. Images of the 49 cattle were analyzed to learn input layer elements, and ten cattles were used to verify the output layer elements in the neural network by using an individual recognition program. The system proved to be reliable for the individual recognition of cattles in natural light.

• Ocean and Polar Research
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• v.37 no.4
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• pp.249-263
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• 2015

Standardization work for the ocean data produced by a variety of national oceanographic research projects was conducted in order to establish a national ocean data sharing system. For this work, we first prepared standard proposals for the national research ocean data by reviewing and analyzing of existing international and domestic ocean-data standards. The proposed standards were reviewed and revised by experts in the field of oceanography and academic societies for documentation. The 125-page technical report on the standards of 25 data items was prepared as an output of this research work, which is available free of charge for the public and interested parties. This paper explains the proposed standards of metadata and codes regarding the common properties of all the oceanographic data items. Especially, the standards for the metadata, codes and data formats of 4 physical data items were described in detail. In order to be adopted as the national standards for ocean data, however, the standards suggested here require further development and/or modification based on additional reviews of and ample feedbacks from the relevant academic and technical communities.

• Metals and materials international
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• v.24 no.6
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• pp.1232-1240
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• 2018

Corrosion properties of dissimilar friction stir welded 6061 aluminum and HT590 steel were investigated to understand effects of galvanic corrosion. As cathode when coupled, HT590 was cathodically protected. However, the passivation of AA6061 made the aluminum alloy cathode temporarily, which leaded to corrosion of HT590. From the EIS analysis showing Warburg diffusion plot in Nyquist plots, it can be inferred that the stable passivation layer was formed on AA6061. However, the weld as well as HT590 did not show Warburg diffusion plot in Nyquist plots, suggesting that there was no barrier for corrosion or even if it exists, the barrier had no function for preventing and/or retarding charge transport through the passivation layer. The open circuit potential measurements showed that the potential of the weld was similar to that of HT590, which lied in the pitting region for AA6061, making the aluminum alloy part of the weld keep corrosion state. That resulted in the cracked oxide film on AA6061 of the weld, which could not play a role of corrosion barrier.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.84-89
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• 2009

The turbid/translucent, near colorless(milky) metamorphic sapphire samples from Sri Lanka have been characterized after the heat treatment in $N_2$ at $1650^{\circ}C$. As-received sapphire specimens became bluish-colored and exhibited more clarity after the heat treatment. It was found that the color change at inclusions zoning region is attributed by the dissolution. As received samples contain the micro/nano inclusions such as rutile($TiO_2$), ilmenite($FeTiO_3$), spinel($MgAl_{2}O_{4}$)/ulvospinel($Fe_{2}TiO_{4}$) and apatite($Ca_5(PO_4)_3$), which were dissolved by the heat treatment and form the blue color through $Fe^{2+}/Ti^{4+}$ charge transferring. The microstructures become different because as the dissolution of apatite($Ca_5(PO_4)_3(OH,F,Cl)$) in alumino silicates($Al_{2}SiO_{5}$) occurred, resulting in morphological change with the appearance of(Ca, Mg, Al) silicate on the surface. Both as-received and heat treated samples showed the rhombohedral crystal structure of $Al_{2}O_{3}$.

• Journal of Photoscience
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• v.1 no.1
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• pp.31-37
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• 1994

Photoirradiation at > 300 nm onto a suspension of platinized TiO$_2$ (TiO$_2$-Pt) particles in an aqueous solution. of N$_{\varepsilon}$-carbamyI-L-lysine (Lys(CONH)$_2$) induced the selective N-cyclization of Lys(CONH$_2$) into almost optically pure L-pipecolinic acid (PCA) under argon atmosphere at ambient temperature. Among various TiO$_2$-Pt catalysts, a P-25 (Degussa) powder platinized via impregnation from chloroplatinic acid followed by hydrogen reduction at 753 K exhibited the highest photocatalytic activity for Lys(CONH$_2$) consumption and L-PCA production. GC-MS analyses of L-PCA obtained photocatalytically from $^{15}$N$\alpha$-Lys(CONH$_2$) revealed the selective formation $^{15}$N-substituted L-PCA. This implies that the mechanism for L-PCA production contains selective cleavage of C$_{\varepsilon}$-N bond and intramolecular alkylation at $\alpha$-amino group. Effect of pH on the rate of this photocatalytic reaction was investigated in detail and compared with the pH-dependent charge distribution in Lys(CONH$_2$) molecule. It is clarified that protonation-deprotonation of $\alpha$-amino group gives marked influence on the rate and selectivity of the photocatalytic reaction. On the basis of these results, it is concluded that the selective production of optically pure L-PCA, especially in an acidic suspension of TiO$_2$-Pt, was attributed to the enhanced protonation of $\alpha$-amino group to prevent undesirable oxidation by photogenerated positive holes and blocking of $\varepsilon$-amino group to yield racemic Schiff base intermediate.