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Chinhae, South Korea

Lim T.,University of Texas at Austin | Kim O.-H.,Republic of Korea Naval Academy | Sung Y.-E.,Seoul National University | Kim H.-J.,Korea Institute of Industrial Technology | And 3 more authors.
Journal of Power Sources | Year: 2016

Onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt-Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt-Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability. © 2016 Elsevier B.V. Source

Kim O.-H.,Republic of Korea Naval Academy | Cho Y.-H.,Korea Basic Science Institute | Cho Y.-H.,Seoul National University | Jeon T.-Y.,Pohang University of Science and Technology | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Core-shell structure nanoparticles have been the subject of many studies over the past few years and continue to be studied as electrocatalysts for fuel cells. Therefore, many excellent core-shell catalysts have been fabricated, but few studies have reported the real application of these catalysts in a practical device actual application. In this paper, we demonstrate the use of platinum (Pt)-exoskeleton structure nanoparticles as cathode catalysts with high stability and remarkable Pt mass activity and report the outstanding performance of these materials when used in membrane-electrode assemblies (MEAs) within a polymer electrolyte membrane fuel cell. The stability and degradation characteristics of these materials were also investigated in single cells in an accelerated degradation test using load cycling, which is similar to the drive cycle of a polymer electrolyte membrane fuel cell used in vehicles. The MEAs with Pt-exoskeleton structure catalysts showed enhanced performance throughout the single cell test and exhibited improved degradation ability that differed from that of a commercial Pt/C catalyst. (Figure Presented). © 2015 American Chemical Society. Source

Kim Y.K.,Korea Institute of Intellectual Property | Lee K.,Seoul National University | Park W.G.,American University of Washington | Choo K.,Republic of Korea Naval Academy
Research Policy | Year: 2012

This paper examines how the role of patents and utility models in innovation and economic growth varies by level of economic development. Using a panel dataset of over 70 countries, we find that patent protection is an important determinant of innovation and that patentable innovations contribute to economic growth in developed countries, but not in developing. Instead, in developing economies, a minor form of intellectual property rights (IPRs) - namely utility models - is conducive to innovation and growth, controlling for other factors. Using Korean firm level data as a case study, we find that utility model innovations contribute to firm performance when firms are technologically lagging and that those minor innovations can be a learning device and thus a stepping stone for developing more patentable inventions later on. Upon reaching higher levels of technological capabilities, firms become more reliant upon patents and less on utility models. Thus the lesson here is that patent protection enhances innovation and economic growth in countries where the capacity to conduct innovative research exists. Where this capacity is weaker, a system that provides incentives to conduct minor, incremental inventions is more conducive to growth. The significance of this paper is to emphasize the importance not just of the strength of IPRs but of the appropriate type of IPRs for economic development. © 2011 Elsevier B.V. Source

Park I.-S.,Korea Institute of Geoscience and Mineral Resources | Kim O.-H.,Republic of Korea Naval Academy | Kim J.W.,Kangwon National University | Cho Y.-H.,Kangwon National University | And 2 more authors.
Journal of Applied Electrochemistry | Year: 2016

A carbon-supported Pt-RuS2 nanocomposite (Pt-RuS2/C) that contained extremely small amount of Pt compared with commercial Pt/C was prepared by the deposition of Pt nanoparticles (NPs) onto carbon-supported RuS2 NPs. This Pt-RuS2/C NP was demonstrated to be an electrocatalyst for hydrogen oxidation reaction catalyst for polymer electrolyte membrane fuel cells using membrane electrode assembly in a single-cell performance test and CO-stripping measurements. The results of structural analysis on prepared nanocomposite showed highly dispersed Pt (ca. 2.5 nm in diameter) and RuS2 (ca. 5.5 nm in diameter) NPs on carbon particles. Pt existed in an unalloyed phase in Pt-RuS2/C, and RuS2 NPs were in physical contact with Pt NPs. Although the amount of Pt in the Pt-RuS2/C NP was only 21.7 % of commercial Pt/C, the Pt-RuS2/C exhibited comparable single-cell performance to commercial Pt/C as an anode electrocatalyst, owing to the promoting effect of RuS2 on the reactivity of Pt. © 2015, Springer Science+Business Media Dordrecht. Source

Lee S.-H.,Republic of Korea Naval Academy | Joo Y.,Seoul National University | Back J.,Kwangwoon University | Seo J.-H.,Seoul National University | Choy I.,Kwangwoon University
Journal of Power Electronics | Year: 2011

We propose a torque and pitch control scheme for variable speed wind turbines with permanent magnet synchronous generator (PMSG). A torque controller is designed to maximize the power below the rated wind speed and a pitch controller is designed to regulate the output power above the rated wind speed. The controllers exploit the sliding mode control scheme considering the variation of wind speed. Since the aerodynamic torque and rotor acceleration are difficult to measure in practice, a finite time convergent observer is designed which estimates them. In order to verify the proposed control strategy, we present stability analysis as well as simulation results. Source

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