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IoT(Internet of Things) based Smart City Services for The Creative Economy
Jaehak Byun,Sooyeop Kim,Jaehun Sa,Sangphil Kim,Yong-Tae Shin,Jong-Bae Kim 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.7
The Internet of Things (IoT) is a pervasive technology in the IT industry, and several companies and governments have tried to make references with the IoT in the past. However, in the manufacturing, retail, and social overhead capital (SOC) industries, successful best practices are built recently. In this paper, I have outlined the tangible IoT based service models, which are helpful to the academic and industrial world for a better understanding of the IoT business. The South Korean government has suggested a “creative economy” as the country’s new economic development paradigm, and strived to establish a creative economic ecosystem by building platforms. IoT is one of the technologies focused on the implementation of the “creative economy”. Therefore, the central government and many local governments are eager to invest on the IoT area in order to build smart cities.
Jaehak Park,Seongbaek Park,Yujin Lim 한국철도학회 2018 International Journal of Railway Vol.11 No.2
In the case of concrete slab track, construction sites have steadily increased since the opening of the second stage of the Gyeongbu Express Railway in 2008. Even though it has many advantages in respects of maintenance and track safety, unlike the initial healthy concrete track condition, defects have been found recently. Therefore, it is necessary to develop a new detection system capable of checking the defects and of performing logical decision-making process for the trackbed condition based on NDT. In this study, an impact echo test was introduced to check the possibility of developing a new NDT system for investigating cavities underneath the concrete slab track. For this purpose, small concrete slabs were constructed in backyard and have been tested by the newly proposed NDT system with impact echo. It has been shown that the new NDT system can be adapted for condition monitoring to check cavities underneath the concrete slab track.
Stabilization and dynamical switching of skyrmions and skyrmioniums in magnetic hemispherical shells
Jaehak Yang,Hyeon-Kyu Park,Gyuyoung Park,Claas Abert,Dieter Suess,Sang-Koog Kim 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
We explored the topological magnetic textures of vortices, skyrmions, and skyrmioniums in magnetic hemispherical shells by varying surface-normal uniaxial magnetic anisotropy constant (Ku), Dzyaloshinskii-Moriya interaction (DMI) constant (Dint), and the shell diameter 2R. For given values of 2R, the combination of Ku and Dint plays a crucial role in the stabilization of those different spin textures. With decreasing 2R, the geometrical confinement of hemispherical shells more significantly affects the stabilization of skyrmions owing to curvature-induced DM-like interaction. This effect is contrastingly dependent on the sign of Dint: skyrmion formation is more favorable for positive Dint values, whereas it is less favorable for negative ones. A quite promising feature is that skyrmions can be stabilized even in the absence of intrinsic DMI for 2R < 25 nm. We also explored characteristic dynamic properties of skyrmions excited by in-plane and out-of plane oscillating magnetic fields. Similar to the fundamental dynamic modes found in planar dots, in-plane gyration and azimuthal spin-wave modes as well as out-of-plane breathing modes were found, but additional higher-frequency hybrid modes also appeared due to coupling between radially quantized and azimuthal spin-wave modes. Finally, we found a switching behavior of skyrmion polarity through a transient skyrmionium state using very-low-strength AC magnetic fields. This work provides further physical insight into the static and dynamic properties of skyrmions in curved-geometry nanodots and suggests potential applications to low-power consumption and ultra-high-density information-storage devices.
Jaehak Lee,Jae Young Seok,Minyang Yang,Bongchul Kang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.1
Hybrid supercapacitors are considered as one of the most promising next-generation energy storage devices, owing to highenergy, high-power density, and long-cycle life. In this work, a simple and low-cost fabrication method of the nanostructured anode with a high capacity and power is proposed for fabrication of high-performance hybrid supercapacitors. This is achieved by a one-step in-situ growth of numerous copper nanopillars on a commercially available copper foil though the galvanic displacement reaction in an aqueous ionic solution. The copper nanopillar forest-based structure with a high surface area, ion accessibility, and electron transportability provides excellent current collecting characteristics for the anode of a lithium-ion battery. The electrochemical performance of a Li half-cell incorporating the copper nanopillar-based current collector exhibits a high capacity (880 mAh g − 1 at 0.2 °C), excellent rate capability, and extremely high durability (97% after 1000 cycles). These results show that the fabricated anode structure can improve the electrochemical performance of the hybrid supercapacitors. To demonstrate the feasibility of an alternative power source, the full cell was fabricated by combining the copper nanopillar anode and an activated carbon cathode. This device provided a high energy density (98.9 Wh kg − 1 at 248 W kg − 1 ), high power density (7018 W kg − 1 ), and long-cycle life (> 1000 cycles).