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SPIRA: Screw Wheel-Based Mobile Robot for Switching Primitives
ChangKook Seo,DongHan Son,KyungUk Lee,KyoungMin Ko,JongMyeong Lee,TaeWon Seo 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.2
In this study, we propose a novel movement mechanism for a mobile robot that combines screw-based and general wheel-based mechanisms via switching. As mobile robots developed, their areas of activity gradually expanded to environments including rough terrain such as granular surfaces. Accordingly, the need for a suitable movement mechanism in an environment in which a general rigid surface and a granular surface are combined has increased. To address the limitations of existing movement mechanisms, we develop a switching mechanism that combines a screw-based wheel mechanism that is optimized for rough terrain with general rigid-surface-based mechanisms that exhibit good driving performance. The two individual mechanisms are configured to be used according to the external environment using a switching mechanism. The validity of the proposed mechanism is verified through experiments conducted in a realistic setting using mobile robots. Experimental results show that granular surfaces that cannot be traversed using conventional wheels can be overcome through screw-based wheels through switching mechanisms. In summary, a switching mechanism combining screw-based wheels and normal wheels is presented as a movement mechanism capable of multi-locomotion not only on rough terrain but also on flat land.
Characterization and in vivo evaluation of calcium phosphatecoated cp-titanium by dip-spin method
Changkook You,여인성,Myung-Duk Kim,Tae-Kwan Eom,이재열,김석영 한국물리학회 2005 Current Applied Physics Vol.5 No.5
Calcium phosphate ceramics like hydroxyapatite (HA) and tricalcium phosphate (TCP) are good candidates for bone substitutesdue to their chemical similarity to bone minerals. Additionally, the biodegradation property of bone substitutes may allow theorganism to replace the foreign material by fully functional new bone in a balanced time schedule. Thus, the coating of biodegrad-able calcium phosphate ceramics on dental implants was conducted in this study to enhance the biocompatibility and eliminate thelong-term adverse eects of HA coated implants. First, biodegradable calcium metaphosphate(CMP) sol was prepared and thencoated on cp-Ti substrates by a dip-spin coating technique. The coated specimens were heat-treated at 600.C for 6 h. CMP coatedlayer on cp-Ti was smooth and uniform with ne grains. It is observed that bone-to-implant contact area of CMP coated specimenat both 2 and 6 weeks was signicantly higher than that of non-coated group. The biocompatibility and cytotoxicity of the CMPcoated specimen were better than those of the non-coated specimen. Therefore, the CMP coating on cp-Ti is a good candidate for. improving bone-to-implant osseointegration, although it is difficult to extrapolate in vitro results directly to in vivo situation.
Low-temperature reactivity of coals for evaluation of spontaneous combustion propensity
Changkook Ryu,Jungsoo Kim,류창국,Ho Young Park,Hyunsoo Lim 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.7
Low rank coals are more reactive at low temperatures than high rank coals, which leads to spontaneous combustion if not controlled. Due to the increased use of low rank coals, preventing spontaneous combustion during storage and size reduction has become an important issue in power plants. The present study evaluates the low-temperature reactivity for various coals in terms of their rank and country of origin. The experimental method determined the temperature and its gradient for coals in a small fixed bed at the point surpassing that of input oxygen, which were defined as the crossing-point temperature (CPT) and slope (CPS), respectively. Combining the two parameters, a low-temperature reactivity index (LTR index) was proposed. The method tested 17 coals collected from a power plant that yielded CPTs ranging between 168-190 oC and CPSs between 0.862-1.228 oC/min. The LTR index for the coals was calculated to be 0.696 to 1.542. The LTR index was positively correlated with the moisture content and volatile matter/fixed carbon (VM/FC) ratio, and inversely correlated with the ash content. The ignition temperature, measured by thermogravimetric tests, also exhibited a positive relationship with the LTR index. However, no single property of coal was sufficiently correlated with the self-heating propensity for all the coals tested, illustrating the complex mechanisms involved.
Robust design of a screw-based crawling robot on a granular surface
ChangKook Seo(서창국),KyungUK Lee,DongHan Son,TaeWon Seo 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In this paper, a robust design of a screw wheel is presented, based on the Taguchi method to accelerate a screw-based crawling robot. Screw-based crawling robots have been studied before, but their application is limited because of their limited speed. To solve this problem, robust design is applied for the screw wheel geometry driving on granular surfaces, such as desert sand. Each of the four parameters determining the screw wheel geometry and two user conditions were set at three levels, and the Taguchi method was applied through the L_9 (3^4) orthogonal array. The experimentally optimized parameters were as follows: the slope angle was 35°, the height of the blade was 14 mm, the number of spirals was one, and the blade had a semicircular cross-section. In conclusion, the robust design using the Taguchi method is suitable for solving the speed problem of a screw-based crawling robot on a granular surface.
You, Changkook,Lee, Moon-Hwan,Lee, Hyo-Jin,Han, Myung-Ho,Kwon, Tae-Yub,Kim, Kyo-Han,Oh, Daniel S. Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.4
<P><B>Abstract</B></P> <P>Cellular responses such as adhesion, spreading, growth and proliferation can be altered by macro and micro pores as well as surface patterns on its surface. In this study, the scaffold was prepared with interconnected macro pores by the polymeric sponge method and with interconnected micro pores by BCP slurry coating with different particle sizes on sintered porous body and necking sintering process. Two particle sizes for micro pores, 200–400nm and 600–800nm, were coated on a pre-sintered porous body. A combined macro and micro pore structure of the BCP scaffold can improve osteoblast cellular activity. <I>In vitro</I> study of MG63 cells suggest that the modified scaffolds improved cell response such as cell spreading, proliferation and differentiation. The scaffold that has a uniform distribution of micro pores ranging 1~5µm in diameter on its surface yields the highest rate of cellular response.</P>