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  • Author or Editor: Dae-Won Lee x
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Abstract  

The nucleus23Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the24Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an exact energy calibration within 7 MeV,56Fe(n,γ)57Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the27Al(p,γ)28Si reaction atE p=2046 keV. The neutron binding energy of24Na was determined to be 6959.75 keV.

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Abstract

This study examines the impact of collaborating patterns on the R&D performance of public research institutions (PRIs) in Korea's science and engineering fields. For the construction of R&D collaborating networks based on the co-authorship data of 127 institutions in Scopus, this paper proposes four types of collaborations by categorizing network analyses into two dimensions: structural positions (density, efficiency, and betweeness centrality) and the relational characteristics of individual nodes (eigenvector and closeness centralities). To explore the research performance by collaboration type, we employ a data envelopment analysis window analysis of a panel of 23 PRIs over a 10-year period. Comparing the R&D productivities of each group, we find that the PRIs of higher productivity adhere to a cohesive networking strategy, retaining intensive relations with their existing partners. The empirical results suggest that excessively cohesive alliances might end up in ‘lock-in’ relations, hindering the exploitation of new opportunities for innovation. These findings are implicit in relation to the Korean Government's R&D policies on collaborating strategies to produce sustained research results with the advent of the convergence research era.

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Abstract  

The performances of selective catalytic reduction (SCR) by CO/H2 over two Pd/TiO2/Al2O3 catalysts prepared from PdCl2 and Pd(NO3)2 precursors were compared. The catalytic activities (NOx conversion and N2 yield) were measured on these two catalysts. The catalytic properties of the prepared catalysts were studied by various characterization techniques such as BET, CO-chemisorption, TEM, XPS, and TPD. The Pd precursors influenced the Pd particle distribution, resulting in different catalytic activities.

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Abstract

In this study, a series of imidazolium-based ionic liquids (ILs) having carboxylic acid moieties were synthesized and used as new homogeneous catalysts to synthesize cyclic carbonates from CO2 and epoxides. Even in the absence of any co-catalyst and organic solvent, carboxylic-acid-functionalized ILs showed better catalytic activity in the coupling reaction of CO2 and styrene oxide for the production of styrene carbonate than did hydroxyl-functionalized ILs and conventional ILs without any functional moieties. A detailed investigation was carried out on a variety of factors that affected the reactivity, such as the alkyl chain length and the molecular composition of IL molecules including the halide ions. The effect of various reaction parameters such as reaction time, temperature, CO2 pressure and catalyst amount was also investigated in detail. The mechanism underlying the enhanced rate of the cycloaddition reaction in the presence of carboxylic-acid-functionalized ILs was proposed.

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