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Design and Evaluation of Micro-Cutting Tools for Local Planarization
Erkhes Bilegt,윤해성,이현택,김은섭,김충수,안성훈 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.10
Following the skyrocketing demands for micro applications, various micro-cutting tools have been investigated up to a diameter of a few μm; however, most of them are limited in terms of tool geometry due to the fabrication techniques used. In this study, we present 30-μm-diameter micro-mechanical cutting tools with 3D cutting edges fabricated using FIB systems. Their geometries were inspired by macroscale cutting tools. Tools were fabricated with one, two, four, and multiple-lattice cutting edges, and their performances were compared with a bulk cylinder tool with no pattern. A local planarization system was constructed for the nanoporous structure. To assess performances, the height and roughness of the structures were measured after the planarization. The structure height was controlled at 1 μm, and a surface roughness of 20 nm was achieved. Among the patterns, the best surface roughness was obtained with the multiple-lattice cutting edges, and surface roughness improved as the number of edges increased. The tool showed little wear at the edges after several rounds of planarization. These results will contribute to the development of an intermediate process for nanoscale 3D printing, and also to direct microscale cutting of a structure.
Design and performance evaluation of Korean traditional heating system—Ondol: Case study of Nepal
Chu, Won-Shik,Kim, Min-Soo,Lee, Kyung-Tae,Bhandari, Binayak,Lee, Gil-Yong,Yoon, Hae-Sung,Kim, Hyung-Soo,Park, Jae-Il,Bilegt, Erkhes,Lee, Jang-Yeob,Song, Ji-Hyun,Park, Gee-Hoon,Bhandari, Pratibha,Lee, Elsevier 2017 Energy and buildings Vol.138 No.-
<P><B>Abstract</B></P> <P>Poor infrastructure in developing countries, combined with challenging geographical characteristics, is associated with problems of limited access to resources, poor transportation and environmental health issues. In some developing countries, there are no heating systems during the winter season, which causes problems for both people and livestock. The most common heating source is from open fires using biomass from animal and plant residue, which are also used for cooking. Fireplaces are typically located inside the house, which can lead to respiratory health problems because of limited ventilation. Thus, heating systems with proper ventilation are desirable to mitigate health problems and improve living conditions. Here we describe the application of ‘Ondol’, a traditional Korean heating system that was redesigned for improved efficiency, in remote villages in a mountainous region of Nepal. Total 10 models of Ondol were designed and fabricated, and the temperature profile and uniformity were characterized to select the optimal design. The height and type of the ‘Gorae’ were the most important factors in determining the efficiency. The optimal design was provided to local people, who were trained to replicate and build the Ondol on their own. A post-installation survey was carried out to evaluate the effectiveness of the system.</P>