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  • Author or Editor: Hyun Park x
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Abstract  

This paper examines how Korean technological development is linked with scientific activities and spreads to industrial fields through knowledge flows. It empirically assesses the linkages between scientific and technological knowledge flows and technological innovation by determining whether the quantity and quality of scientific papers cited by, and the knowledge being absorbed in, Korean patents filed in USPTO varied over time, and between technology fields. We conducted MANOVA and then canonical discriminate analysis. Our findings are: the patterns of both the absorption of scientific knowledge and the diffusion of technological knowledge differ by period and by field, and the speed of knowledge diffusion differs by technology field. This implies that the time required for Korean investment in basic and applied research to impact her industrial innovation differs by technology field.

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Abstract  

The hydrogen concentration for the reference material low-alloy steel was estimated using prompt gamma neutron activation analysis. The hydrogen concentration had a range of 0.91–1.14 mg/kg as measured by the prompt gamma activation method but the reference value was about 1.0 mg/kg as measured by the ICP/AES method. The relative error appeared to be 14% and the differences showed as the background by blank. The standard reference material (NIST SRM) was used for the analytical control.

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Abstract

Binary CeO2–MgO oxides with various Ce/Mg mol ratios were prepared by the co-precipitation method and were tested in the dehydrogenation of ethylbenzene to styrene. The obtained materials were characterized by N2 adsorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The N2 adsorption showed that CeO2–MgO oxides were mesoporous materials and the BET surface area increased with increasing magnesia content. The fluorite type structure of ceria was observed in samples with low magnesia content while the mixture of the ceria phase and the magnesia phase existed simultaneously in samples with high magnesia content. The results showed that the Ce4+–Mg2+–O2− couple in CeO2/MgO catalyst could be supposed to be an active site in the dehydrogenation of ethylbenzene.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Saet Byul Kim, Mi Ran Lee, Eun Duck Park, Sang Min Lee, HyoKyu Lee, Ki Hyun Park, and Myung-June Park

Abstract

A kinetic model of the homogeneous conversion of d-xylose in high temperature water (HTW) was developed. Experimental testing evaluated the effects of operating conditions on xylose conversion and furfural selectivity, with furfural yields of up to 60% observed without the use of acid catalysts. The reaction order for the decomposition of d-xylose was assumed to be above two, while the conversion of d-xylose to furfural and the degradation of furfural were first order reactions. Estimated kinetic parameters were within the range of values reported in the literature. The activation energy of furfural production showed that the ionization rate was high enough for HTW to replace acid catalysts. Simulated results from this model were in good agreement with experimental data, allowing the model to aid reactor design for the maximization of productivity.

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Abstract

Platinum catalysts supported on silicas with various physicochemical properties were prepared in order to investigate the effect of silica characteristics on their platinum dispersion and catalytic activity in the oxidation of carbon monoxide. Although titania-incorporation into silica and further treatment of the impregnated platinum precursor with hydrogen peroxide were effective for improving the dispersion and stability of platinum catalysts supported on silicas, regardless of the characteristic of the silicas, the platinum catalysts supported on fumed silica with a medium level of surface hydroxyl group concentration exhibited the highest catalytic activity among those supported on mesoporous silica, silica gel, and precipitated silica. The required properties of the highly active platinum catalyst seemed to be a high dispersion of platinum, the formation of a stable titania layer, and the generation of strong acid sites. By contrast, the precipitated silica with a small surface area and high concentration of surface hydroxyl groups was not appropriate for a catalytic support for platinum catalysts.

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Abstract  

The electrochemical redox behavior of nitric acid was studied using a glassy carbon fiber column electrode system, and its reaction mechanism was suggested and confirmed in several ways. Electrochemical reactions in less than 2.0M nitric acid was not observed. However, in more than 2.0M nitric acid, the reduction of nitric acid to nitrous acid occurred and the reduction rate was slow so that the nitric acid solution had to be in contact with an electrode for a period of time long enough for an apparent reduction current of nitric acid to nitrous acid to be observed. The nitrous acid generated in more than 2.0M nitric acid was rapidly and easily reduced to nitric oxide by an autocatalytic reaction. Sulfamic acid was confirmed to be effective to destroy the nitrous acid. At least 0.05M sulfamic acid was necessary to scavenge the nitrous acid generated in 3.5M nitric acid.

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Ixeris dentata (Thunb. ex Thunb.) Nakai (Asteraceae), a well-known edible vegetable in Asia, contains various bioactive secondary metabolites, including sesquiterpene lactones. In this study, a high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method has been developed and validated for simultaneous determination of seven sesquiterpene lactone glucosides isolated from the roots of I. dentata. In addition, these compounds were evaluated in terms of their antiviral activities against coxsackievirus B3 (CVB3) and human enterovirus 71 (EV71). The developed method was validated in terms of linearity (R 2 > 0.9996), precision (RSD < 2.24%), accuracy (96.30–102.77%), and stability (RSD < 1.94%) and successfully applied to the quantitation of the I. dentata root samples collected from six different regions of Korea. The content of sesquiterpene lactone glucosides varied significantly based on the region. For the antiviral activities, guaianolides with an ester group at C-8 (compounds 6 and 7) showed the most potent activities against CBV3, while germacranolide (compound 5) showed the most consistent antiviral activity against both CVB3 and EV71. The method was validated to be simple and reliable to simultaneously determine seven putative bioactive sesquiterpene lactone glucosides, the substantial chemotaxonomic markers, in I. dentata root samples.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Bo-Hyun Kim, Tae-Hee Lim, Jin-Woong Roh, Sang-Geun Lee, Chang Ju, Seong Park, Seong Hong, and Gun Lee

Abstract  

Undoped and Cr-doped Bi12TiO20 (BTO) were prepared and used as photocatalysts for the degradation of formic acid both under visible light and UV irradiation. The effects of the Cr doping on the visible light response and the photocatalytic activity of BTO were investigated. The prepared catalysts were characterized by using XRD, XPS, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The doping of Bi12TiO20 with low concentration of Cr leads to noticeable increase in visible light absorption and decrease in the recombination rate of photo-generated electrons and holes. As a result, the Cr-doped BTO showed a higher photocatalytic activity for the degradation of formic acid both under visible light and UV irradiation, as compared with undoped BTO.

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Journal of Behavioral Addictions
Authors: Ji-Won Chun, Chang-Hyun Park, Jin-Young Kim, Jihye Choi, Hyun Cho, Dong Jin Jung, Kook-Jin Ahn, Jung-Seok Choi, Dai-Jin Kim, and In Young Choi

Abstract

Background and aims

Although the Internet has provided convenience and efficiency in many areas of everyday life, problems stemming from Internet use have also been identified, such as Internet gaming disorder (IGD). Internet addiction, which includes IGD, can be viewed as a behavioral addiction or impulse control disorder. This study investigated the altered functional and effective connectivity of the core brain networks in individuals with IGD compared to healthy controls (HCs).

Methods

Forty-five adults with IGD and 45 HCs were included in this study. To examine the brain networks related to personality traits that influence problematic online gaming, the left and right central executive network (CEN) and the salience network (SN) were included in the analysis. Also, to examine changes in major brain network topographies, we analyzed the default mode network (DMN).

Results

IGD participants showed lower functional connectivity between the dorsal lateral prefrontal cortex (DLPFC) and other regions in the CEN than HC participants during resting state. Also, IGD participants revealed reduced functional connectivity between the dorsal anterior cingulate cortex and other regions in the SN and lower functional connectivity in the medial prefrontal cortex of the anterior DMN. Notably, in IGD individuals but not HC individuals, there was a positive correlation between IGD severity and effective connectivity and a positive correlation between reward sensitivity and effective connectivity within the ventral striatum of the SN.

Conclusions

Problematic online gaming was associated with neurofunctional alterations, impairing the capacity of core brain networks.

Open access
Journal of Behavioral Addictions
Authors: Sam-Wook Choi, Hyun Kim, Ga-Young Kim, Yeongju Jeon, Su Park, Jun-Young Lee, Hee Jung, Bo Sohn, Jung-Seok Choi, and Dai-Jin Kim

Open access