• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.484-492
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• 1994

Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets have been investigated during sintering under H$_2$ and $CO_2$ atmospheres. Pellets are sintered at 1$700^{\circ}C$ in H$_2$ atmosphere and at 130$0^{\circ}C$ in $CO_2$ atmosphere for 1 to 41 hr. The addison of Nb$_2$O$_{5}$ causes the formation of large pores, which shrink to some extent in H$_2$ atmosphere but very little in $CO_2$. Fine pores in the Nb$_2$O$_{5}$-doped UO$_2$ pellet are almost annihilated when sintered under H$_2$ atmosphere but little changed under $CO_2$ atmosphere. The increase in grain size due to Nb$_2$O$_{5}$ addition is much larger in H$_2$ atmosphere than in $CO_2$. Thus the enhancement of uranium diffusion in UO$_2$ due to the Nb$_2$O$_{5}$ addition is thought to be more significant in H$_2$ atmosphere. Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets sintered in H$_2$ atmosphere are discussed from the viewpoint of in-reactor performance. Possible defects formation due to Nb$_2$O$_{5}$ addition is discussed to explain the enhancement of uranium diffusion in H$_2$ and $CO_2$ atmospheres.> atmospheres.

• Corrosion Science and Technology
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• v.7 no.2
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• pp.69-76
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• 2008

Common methods for large scale hydrogen production, such as steam reforming and coal gasification, also involve production of carbonaceous gases. It is therefore necessary to handle process gas streams involving various mixtures of hydrocarbons, $H_2$, $H_2O$, CO and $CO_2$ at moderate to high temperatures. These gases pose a variety of corrosion threats to the alloys used in plant construction. Carbon is a particularly aggressive corrodent, leading to carburisation and, at high carbon activities, to metal dusting. The behaviour of commercial heat resisting alloys 602CA and 800, together with that of 304 stainless steel, was studied during thermal cycling in $CO/CO_2$ at $650-750^{\circ}C$, and also in $CO/H_2/H_2O$ at $680^{\circ}C$. Thermal cycling caused repeated scale separation, which accelerated chromium depletion from the alloy subsurface regions. The $CO/H_2/H_2O$ gas, with $a_C=2.9$ and $p(O_2)=5\times10^{-23}$ atm, caused relatively rapid metal dusting, accompanied by some internal carburisation. In contrast, the $CO/CO_2$ gas, with $a_C=7$ and $p(O_2)=10^{-23}-10^{-24}$ atm caused internal precipitation in all three alloys, but no dusting. Inward diffusion of oxygen led to in situ oxidation of internal carbides. The very different reaction morphologies produced by the two gas mixtures are discussed in terms of competing gas-alloy reaction steps.

• BMB Reports
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• v.32 no.2
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• pp.154-160
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• 1999

A calcium-independent phospholipase $A_2$ ($iPLA_2$) was identified from the cytosolic fraction of rat liver cells. On gel filtration chromatography, the $iPLA_2$ activity was eluted as broad peaks of 150 to 500 kDa. The enzyme was maximally active at pH 7.5, retained 75% of its original activity after heating at $50^{\circ}C$ for 5 h, and was inhibited by $Ca^{2+}$, $Mg^{2+}$, and $Zn^{2+}$ ions, but was not affected by $Na^+$ and $K^+$ ions. The enzymatic activity was increased up to 150% by 1 to 4 mM DTT and was inhibited up to 25% by 0.1 to 1 mM PMSF. The $iPLA_2$ activity had preference for the head group of phospholipids, where phosphatidylethanolamine was preferred to phosphatidylcholine. The results suggest that the $iPLA_2$ may be a novel enzyme distinct from the previously reported $iPLA_2s$.

• Journal of Astronomy and Space Sciences
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• v.34 no.2
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• pp.111-118
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• 2017

A ultra low frequency (ULF) wave, Pi2, has been reported to occur during periods of extremely quiet magnetospheric and solar wind conditions. And no statistical study on the Pi2 has been performed during extremely quiet conditions, using satellite observations to the author's knowledge. Also Pi2 pulsations in the space fluxgate magnetometers near perigee failed to attract scientist's attention previously. In this paper, Pi2 pulsations detected by the Van Allen probe satellites (VAP-A & VAP-B) were investigated statistically. During the period from October 2012 to December 2014, ninety six Pi2 events were identified using VAP when Kp = 0 while using Kakioka (KAK, L = 1.23) as a reference ground station. Seventy five events had high coherence between VAP-Bz and H components at KAK station. As a result, it was found that 77 % of the events had power spectra between 5 and 12 mHz, which differs from the regular Pi2 band range of from 6.7 to 25 mHz. In addition, it was shown that it is possible to observe Pi2 pulsations from space fluxgate magnetometers near perigee. Twenty two clean Pi2 pulsations were found where L < 4 and four examples of Pi2 oscillations at different L shells are presented in this paper.

• Environmental Mutagens and Carcinogens
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• v.22 no.2
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• pp.76-82
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• 2002

In human U-937 cell exposed to ${\gamma}$-irradiation and $H_2O$$_2$, the level of mRNA efrpression in ceruloplasmin gene was measured by using comparative RT.PCR (reverse transcriptase-polymerase chain reaction). At the normal growth condition, the level of ceruloplasmin transcript was estimated as 8.2% and 0.0068% of hprt (hypoxantine phosphoribosyl transferase) transcript and of $\beta$-actin transcript, respectively. In U-937 cells exposed to a dose of 100 rad ${\gamma}$-irradiation, the level of ceruloplasmin transcript was increased about 2.7 and 1.6 fold compared to un-treated cell by using compensation with the levels of hprt and $\beta$-actin transcript. By contrast, the expression of ceruloplasmin gene in U-937 cells exposed to $H_2O$$_2$(50 $\mu$M, 24 h), was shown no significant difference compared to un-treated cell. These results indicated that the expression system of ceruloplasmin gene may react only some specific oxygen species, such as reactive oxygen species induced by ${\gamma}$-irradiation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1105-1117
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• 2017

Financial technology, also known as FinTech, is one of the fast growing global businesses in since its inception in 2008. Fintech is a new economic industry, comprised of companies that adopted the latest technologies to provide more efficient financial services than the traditional financial services. Fintech companies are generally small to medium sized startups trying to disintermediate existing financial systems. FinTech companies can be differentiated in several areas, based on its business solutions and target customers. In Korea, the Peer-to-Peer (P2P) lending companies are the most prominent in the FinTech sector. P2P lending is a method of borrowing or lending money to individuals through online services without the use of an official financial institution as an intermediary. The P2P lending companies operate their services entirely online or mobile environment. Consequently, mobile P2P lending application users are dramatically increasing. Thus, it is worth evaluating the acceptance of the mobile apps of the P2P lending companies from a user's perspective. This paper discusses user acceptance of the mobile P2P lending apps, guided by the Technology Acceptance Model. We conclude that the users' acceptance of mobile P2P lending apps are significantly influenced by perceived ease of use, perceived usefulness, and user satisfaction. These in turn influenced their attitude towards using mobile P2P lending apps and intention to use.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.553-560
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• 1997

A fine $\alpha$-Al2O3 powder was prepared by sol-gel process for membrane application. And it was carried out by adding 1.5wt% $\alpha$-Al2O3 powders(mean size : 87 nm) as seeds to the prepared sols and by controlling the heating schedule (the heating rate and the soaking time) to prevent the microstructural change, which occured during $\theta$-to $\alpha$Al2O3 phase transformation. The seeded $\alpha$-Al2O3 particles acted as the heterogeneous nucleation sites for the $\alpha$-Al2O3 nucleation during the transformation of $\theta$- to $\alpha$-Al2O3 and resulted in increasing the driving force of phase transformation to activate the formation of $\alpha$-Al2O3 phase at 82$0^{\circ}C$. By $\alpha$-Al2O3 seeding and controlling of heating condition the phase transformation of $\theta$- to $\alpha$-Al2O3 was accomplished at low temperature and the grain growth process was depressed. Therefore, the unsupported membrane could be fabricated in $\alpha$-Al2O3 . The average diameter of pores in the fabricated membrane was 7 nm and the porosity was 47%.

• Magazine of the Korean Society of Agricultural Engineers
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• v.18 no.4
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• pp.4226-4231
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• 1976

The objective of this study is to investigate the characteristics of the concrete mixture and the plastic shrinkage of concrete exposed to a rapid evaporation immediately after placement, and to measure the shringkage rate according to the cement-mixture. Drying of concrete was conducted under a controlled chamber in which the temperature was 36${\pm}$2$^{\circ}C$, the relative humidity 45${\pm}$2%, and the wind velocity 4${\pm}$1m/sec. All of the concrete mo1ds were made to have good workability as 6${\pm}$0.5cm in slump. The results obtained are as follows; 1) The evaporation rate was 3.36kg/$\textrm{km}^2$, 2.98kg/$\textrm{km}^2$ and 2.91kg/$\textrm{km}^2$ respectively for each concretemixtures 365kg, 335kg and 317kg after 5 hour exposure, and the evaporation was measured at all 55∼57% after 2 hours and additional in 10% on after 5 hours exposure. 2) The weight of the concrete were was reduced to 3.0%, 2.6% and 2.4% respectively for each of them. 3) The shrinkage of concrete was 0.87 mm/m, 0.56mm/m and 0.31 mm/m after 5 hour exposure, and the shringkage of concrete was measured at 84%, 59% and 45% after 2 hours and it in 1∼5% after 5 hour exposure and then stopped. 4) A recommendation for good concrete is that the evaporation should be minimized during 2 hours after placement of concrete, if possible.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.704-712
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• 1988

In order to investigate the effect of the second phase on Al2O3 matrix, SiC whisker was dispersed in Al2O3 matrix as a second phase over the content range of 5vol% to 20vol%. To this mixture, Y2O3 or TiO2 powder was added as a sintering additive before isostatically pressing and pressureless sintering at 1800-190$0^{\circ}C$ for 90min in N2 atmosphere. With increasing SiC whisker content, relative densities of composites were decreased and the grain growth of Al2O3 was restricted. When Y2O3 was added as a sintering aid the sintering temperature was 180$0^{\circ}C$, the maximum values of flexural strength, hardness and fracture toughness were 537MPa, 12.1GPa, 3.7MPa.m1/2, respectively. However, when the sintering temperature was elevated to 190$0^{\circ}C$, maximum values of flexural strength, hardness and fracture toughness were 453MPa, 17.5GPa, 4.9MPa.m1/2, respectively. Improved mechanical properties are assumed to be attributed to the crack deflection by the second phase SiC whisker and whisker pullout mechanism.