Other affiliations: Samsung
Bio: Young-Pil Park is an academic researcher from Yonsei University. The author has contributed to research in topic(s): Actuator & Optical disc. The author has an hindex of 19, co-authored 244 publication(s) receiving 1900 citation(s). Previous affiliations of Young-Pil Park include Samsung.
01 Nov 2018
Abstract: To analyze the effect of slider dynamics on lubricant contact situation, this research conducts the experiment with applied voltage. With applied voltage, lubricant interaction and slider TD/TO power is investigated. Charged disk can avoid the contact with lubricant.
TL;DR: A new low-coherence interferometry system for dual-wavelength off-axis digital holography that enables the fast and accurate measurement of the surface profile with more than a micrometer step height and less noise is proposed.
Abstract: We propose a new low-coherence interferometry system for dual-wavelength off-axis digital holography. By utilizing diffraction gratings, two beams with narrower bandwidths and different center wavelengths could be filtered in a single light-emitting diode. The characteristics of the system are analytically determined to extend the coherence length and field-of-view enough for off-axis configuration. The proposed system enables the fast and accurate measurement of the surface profile with more than a micrometer step height and less noise. The performance of the system is verified by the experimental results of a standard height sample.
••23 Aug 2017
Abstract: We have characterized a new type STED microscope which combines a high numerical aperture (NA) optical head with a solid immersion lens (SIL), and we call it as SIL-STED microscope. The advantage of a SIL-STED microscope is that its high NA of the SIL makes it superior to a general STED microscope in lateral resolution, thus overcoming the optical diffraction limit at the macromolecular level and enabling advanced super-resolution imaging of cell surface or cell membrane structure and function Do. This study presents the first implementation of higher NA illumination in a STED microscope limiting the fluorescence lateral resolution to about 40 nm. The refractive index of the SIL which is made of material KTaO3 is about 2.23 and 2.20 at a wavelength of 633 nm and 780 nm which are used for excitation and depletion in STED imaging, respectively. Based on the vector diffraction theory, the electric field focused by the SILSTED microscope is numerically calculated so that the numerical results of the point dispersion function of the microscope and the expected resolution could be analyzed. For further investigation, fluorescence imaging of nano size fluorescent beads is fulfilled to show improved performance of the technique.
Abstract: With an increased mobility, hard disk drives (HDDs) now use ramp load/unload technology, and multiple disks are used to increase the data capacity This can result in contact between the ramp and the disks, which negatively affects the slider dynamics under operational shock conditions There are several types of ramp–disk contact, such as simultaneous, successive, and single contact, and these depend on the distance between the ramp and each disk in a multi-disk HDD This paper examines the effect of ramp–disk contact on the slider dynamics using a transient shock analysis The ramp–disk contact affects the head stack assembly bending mode and slider dynamics The effect of irregular gaps between the disks and adjacent ramp on the slider dynamics is analyzed with the ramp–disk contact force The simulation shows that the gap irregularity between the ramp and each disk should be as small as possible to improve the stability of the slider dynamics
Abstract: This paper analyzed the effect of lubricant contact on slider dynamics under the unsteady proximity condition, which is related to the intermolecular forces between the slider and disk. To investigate the slider dynamics, an experiment was conducted with a commercial drive, and the slider dynamics were analyzed during touch-down and takeoff (TO) considering the approach and withdrawal speeds of the slider. The instability of the slider dynamics increased under the rapid withdrawal condition during TO.
Abstract: Compliant Mechanisms (CMs) present several desired properties for mechanical applications only depending on elastic deformation of the involved compliant beams/flexures. As reported in the current literature, most CM designs utilize straight beams and initially curved beams (ICBs) as the fundamental flexible members. In CM research community, many great contributions regarding modeling these elementary flexible members have been achieved. In this paper, a comprehensive modeling methodology, based on beam theory, has been established to characterize the static planar deflection of slender beam. Then such a methodology has been applied to solve 8 loading scenarios of large beam-deflection problems that exist in the design of CMs. Essentially speaking, all these beam-deflection problems are treated as a type of boundary value problems (BVPs) of an ordinary differential equation (ODE) and solved by a modified collocation method. After that, this methodology has been used to model some representative CMs with large-deflection strokes, such as compliant parallelograms.
Abstract: Super-hemispherical solid immersion lens (s-SIL) has proved its superiority in high-numerical aperture (NA) and aberration-free characteristics, however, its applications are limited by high cost, difficulty in manufacturing, sample mounting and narrow detection fields. One alternative solution is to utilize a coverslip-based two-piece solid immersion lens (t-SIL) modified from conventional s-SIL. However, one severe issue associated with t-SIL is that its practical imaging performances of t-SIL (e.g. effective NA, aberration, etc.) is not as good as expected. Previous literatures mentioned the problems but gave different explanations. Actually, the fundamental reason is the mismatch among the hemispherical ball, the coupling liquid and the additional coverslip. This work is to investigate the refractive-index-mismatch issues of t-SIL. More specifically, we elaborate two typical cases of mismatches and the corresponding influences on practical aberration and effective NA. In both cases, we prove the feasibility of t-SIL when the refractive indices of three parts are not strictly matched, and give tolerance to mismatch. Besides, solutions to aberration compensation and application suggestions are also given to guide the practical operations.
Yang Liu1•Institutions (1)
TL;DR: A new unloader that slowly releases heavy hammer in the air under gravity has been developed and the experimental result proves the feasibility of flexible unloader.
Abstract: During dynamic compaction , frequent heavy load unloading impacts are the main reasons for crane structural damage. To address this problem, a new method to reduce the unloading impact for a crane is discussed. Firstly, through the energy method, an expression for the energy consumption of the unloader that has been ignored before is established and a mathematical model describing the key parameters of the unloader is obtained. Secondly, a force controlled unloader is designed to convert the pulling force control of the wire rope that suspends the heavy hammer into its own hydraulic control. Thirdly, a rigid-flexible coupling model of a crawler crane used for dynamic compaction is built to predict the relationship between the unloading time and the dynamic response. Finally, a new unloader that slowly releases heavy hammer in the air under gravity has been developed and the experimental result proves the feasibility of flexible unloader.
Author's H-index: 19