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Understanding the condensation process of turbulent steam jet using the PDPA system
Lim, Seungho,Cha, Jinho,Lee, Haneol,Kim, Taejoon,Shin, Weon Gyu Elsevier 2018 International journal of multiphase flow Vol.98 No.-
<P><B>Abstract</B></P> <P>In the present study, we investigated condensation characteristics of water droplets in a turbulent steam jet with the Reynolds number from 78,400 to 140,700, such as Particle Size Distribution (PSD), Total Number Concentration (TNC), and Liquid Water Content (LWC) obtained from the Phase Doppler Particle Analyzer (PDPA) system and measured the temperature profile. The temperature decay rate and the temperature half width (<I>r<SUB>T, 0.5</SUB> </I>) were obtained for steam jets. The increased latent heat release due to condensation was found to have an effect on the decreased temperature decay rate and the increased spread rate with an increase of the steam jet's Reynolds number. Along the radial direction at <I>z/d</I> = 10, TNC and LWC increased up to the range within <I>r / r<SUB>T, 0.5</SUB> </I> = 1.2, but the turbulence intensity continued to increase beyond the range. These results suggest that the evaporation effect started to occur due to the mixing with the surrounding air. Along the axial direction, we used the effective diameter in order to confirm the Reynolds number effect. As the Reynolds number became larger, particle formation started to occur further downstream along the axial direction. At the downstream of the peak position, the values of TNC and LWC were found to decrease due to the mixing process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Condensation process in a turbulent steam jet with a high <I>Re</I> was investigated. </LI> <LI> Temperature profiles in a turbulent steam jet with a high <I>Re</I> are presented. </LI> <LI> Condensation region of steam jets was determined based on the temperature half width. </LI> </UL> </P>
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>
Lim, Seungho,Park, Hyunseol,Shin, Weon Gyu Informa UK (TaylorFrancis) 2017 AEROSOL SCIENCE AND TECHNOLOGY Vol.51 No.3
<P>In the present study, we measured the penetration of silver nanowires with the mobility diameter in the range from 200 to 400 nm through two different types of polyester filters: the screen filter with the solidity of 0.505 and fibrous filter with the solidity of 0.278. The orientation angles of silver nanowires passing through the single layer and multi-layers of polyester filter were experimentally estimated on the basis of the single fiber efficiency theory. In the case of the screen filter, the orientation angle obtained by fitting the experimental data for single layer was found to be close to 408, indicating a random orientation of nanowires near the filter. However, the fibrous filter has the orientation angle much larger than 40 degrees. The orientation angle can be affected by inhomogeneity of the filter. In particular, in the case of the fibrous filter, the solidity and fiber diameter may affect the orientation angle. For multi-layers of both screen and fibrous filters, it is difficult to determine the typical orientation angle and the fibrous filter tends to have a larger orientation angle than the screen filter. In addition, we carried out numerical simulations on the penetration of silver nanowires through the five layers of screen filter and the single layer of both screen and fibrous filters. Numerical prediction was carried out by using the three-dimensional numerical model determined by solidity and thickness of fibrous filter. Numerical predictions are highly congruent with experimental results and theoretical prediction.</P>
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>
Lim, Seungho,Yoon, Hong Yeol,Jang, Hee Jeong,Song, Sukyung,Kim, Woojun,Park, Jooho,Lee, Kyung Eun,Jeon, Sangmin,Lee, Sangmin,Lim, Dong-Kwon,Kim, Byung-Soo,Kim, Dong-Eog,Kim, Kwangmeyung American Chemical Society 2019 ACS NANO Vol.13 No.10
<P>Noninvasive and precise stem cell tracking after transplantation in living subject is very important to monitor both stem cell destinations and their <I>in vivo</I> fate, which is closely related to their therapeutic efficacy. Herein, we developed bicyclo[6.1.0]nonyne (BCN)-conjugated glycol chitosan nanoparticles (BCN-NPs) as a delivery system of dual-modal stem cell imaging probes. Near-infrared fluorescent (NIRF) dye Cy5.5 was chemically conjugated to the BCN-NPs, and then oleic acid-coated superparamagnetic iron oxide nanoparticles (OA-Fe<SUB>3</SUB>O<SUB>4</SUB> NPs) were encapsulated into BCN-NPs, resulting in Cy5.5-labeled and OA-Fe<SUB>3</SUB>O<SUB>4</SUB> NP-encapsulated BCN-NPs (BCN-dual-NPs). For bioorthogonal labeling of human adipose-derived mesenchymal stem cells (hMSCs), first, hMSCs were treated with tetra-acetylated <I>N</I>-azidoacetyl-<SMALL>D</SMALL>-mannosamine (Ac<SUB>4</SUB>ManNAz) for generating azide (−N<SUB>3</SUB>) groups onto their surface <I>via</I> metabolic glycoengineering. Second, azide groups on the cell surface were successfully chemically labeled with BCN-dual-NPs <I>via</I> bioorthogonal click chemistry <I>in vitro</I>. This bioorthogonal labeling of hMSCs could greatly increase the cell labeling efficiency, safety, and imaging sensitivity, compared to only nanoparticle-derived labeling technology. The dual-modal imaging-guided precise tracking of bioorthogonally labeled hMSCs was tested in the photothrombotic stroke mouse model <I>via</I> intraparenchymal injection. Finally, BCN-dual-NPs-labeled hMSCs could be effectively tracked by their migration from the implanted site to the brain stroke lesion using NIRF/<I>T</I><SUB>2</SUB>-weighted magnetic resonance (MR) dual-modal imaging for 14 days. Our observation would provide a potential application of bioorthogonally labeled stem cell imaging in regenerative medicine by providing safety and high labeling efficiency <I>in vitro</I> and <I>in vivo</I>.</P> [FIG OMISSION]</BR>