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Finite-Element Shock Analysis of Slim Optical Disk Drives
Seungho Lim,Kyungtae Kim,Chanho Choi,No-Cheol Park,Young-Pil Park,Kyoung-Su Park,Ik-Joo Cha IEEE 2009 IEEE transactions on magnetics Vol.45 No.5
<P>In this paper, a finite-element model of a slim optical disk drive is developed to investigate the transient response of the sled base and disk. The model is simplified by using beam, shell and lumped parameter elements, in order to decrease the computational time. After the dynamic characteristics of the finite-element model have been verified by modal test, the shock response is obtained and compared with the results of a drop test. Finally, dynamic characteristics are modified to improve the shock performance.</P>
Park, Kwi Woo,Chae, Jeong Geun,Song, Se Phil,Son, Seok Bo,Choi, Seungho,Park, Chansik The Institute of Positioning 2017 Journal of Positioning, Navigation, and Timing Vol.6 No.1
In this study, to design a multi-GNSS receiver using single RF front-end, the receiving performances for various frequency plans were evaluated. For the fair evaluation and comparison of different frequency plans, the same signal needs to be received at the same time. For this purpose, two synchronized RF front-ends were configured using USRP X310, and PC-based software was implemented so that the quality of the digital IF signal received at each front-end could be evaluated. The software consisted of USRP control, signal reception, signal acquisition, signal tracking, and C/N0 estimation function. Using the implemented software and USRP-based hardware, the signal receiving performances for various frequency plans, such as the signal attenuation status, overlapping of different systems, and the use of imaginary or real signal, were evaluated based on the C/N0 value. The results of the receiving performance measurement for the various frequency plans suggested in this study would be useful reference data for the design of a multi-GNSS receiver in the future.
Cantilever Dynamic Vibration Absorber for Reducing Optical Disk Drive Vibration
Seungho Lim,Kyungtae Kim,Ungrae Cho,No-Cheol Park,Young-Pil Park,Kyoung-Su Park,Wook-Young Soh IEEE 2009 IEEE transactions on magnetics Vol.45 No.5
<P>This research explores the design of a dynamic vibration absorber (DVA) using a cantilever beam with tip mass. Compared to a conventional DVA using a rubber bobbin, the proposed DVA isolates vibrations more effectively due to the low damping properties of its structure, which are the principal reason for its excellent anti-vibration performance near the anti-resonance frequency. This low damping decreases the harmonic response at the rotational frequency of the disk. To design the proposed DVA, the dynamic characteristics of the optical disk drive were represented with lumped parameter and finite element models. The dimensions of the beam were tuned to reduce the vibration in multiple axes based on this model. Tolerance analysis were performed so the drive would be robust against normal dimension variance due to the manufacturing process, and the variation in the dynamic characteristics with respect to the pickup position was investigated. The anti-vibration performance of the DVA was also measured experimentally.</P>
Molecular Dynamics Simulation for Size-Dependent Properties and Various Nanoscale Phenomena
Seungho Park,Joon Sik Lee,Young Ki Choi,Sung San Cho,Jung Soo Kim 한국정밀공학회 2004 International Journal of Precision Engineering and Vol.5 No.4
Stimulated by novel phenomena observed in molecular aggregates, recent developments in engineering fields of microscopic scales are creating tremendous opportunities for future nanotechnology-based applications. Investigation in the field involves sub-nanosecond or sub-micrometer interactions between extremely small systems, but researches to date in these physical extremes have been quite limited. Here, we shed light on some of nanoscale phenomena using molecular dynamics simulation: visualization of various phenomena of nanoscales and exploration of size-dependent mechanical properties.
Park, Hyanjoo,Choe, Seunghoe,Kim, Hoyoung,Kim, Dong-Kwon,Cho, GeonHee,Park, YoonSu,Jang, Jong Hyun,Ha, Don-Hyung,Ahn, Sang Hyun,Kim, Soo-Kil Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.444 No.-
<P><B>Abstract</B></P> <P>Pt catalysts for water electrolysis were prepared on carbon paper by using both direct current and pulse electrodeposition. Controlling the mass transfer of Pt precursor in the electrolyte by varying the deposition potential enables the formation of various Pt particle shapes such as flower-like and polyhedral particles. Further control of the deposition parameters for pulse electrodeposition resulted in changes to the particle size and density. In particular, the upper potential of pulse was found to be the critical parameter controlling the morphology of the particles and their catalytic activity. In addition to the typical electrochemical measurements, Pt samples deposited on carbon paper were used as cathodes for a proton exchange membrane water electrolyser. This single cell test revealed that our Pt particle samples have exceptional mass activity while being cost effective.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt catalysts were directly prepared on carbon paper by pulse electrodeposition. </LI> <LI> Pulse electrodeposited Pt catalysts significantly enhanced HER performance. </LI> <LI> The prepared Pt catalysts with low loading mass showed excellent performance in PEMWE. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>