• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.652-654
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• 1999

This paper presents approaches to the control of the DVD(Digital Video Disk) system using DSP(Digital Signal Processor) in order to improve the precision and robustness. To improve the performance of the Pick-Up servo actuator of the digital video drive, the tracking and focusing servo control algorithms is applied to this system. Simulation results show the performance of the robust control algorithm applied the pick-up servo system comparing to the linear controller.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.992-993
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• 2002

We have fabricated the diffractive optical head(DOH) for optical pick up, which one adaptable to a optical recoding information storage. DOH consists of a focusing grating coupler(FGC) and a solid immersion Jens(SIL). FGC is device that the light converge into a focus by surface lattice. FGC have been studied as a potential application of pick up head for the information storage. In this study, FGC was designed and fabricated to make focus near to possible diffraction limit. We also fabricated recording head combined with SIL. The focus was measured in the range of $1.1{\mu}m$ as near to possible diffraction limit in the FGC having a focusing length of $600{\mu}m$ and a lattice area of 500 * $500{\mu}m$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.105-108
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• 2004

The effect of thermal deformation of optical pick-up due to laser diode(LD) and LD driving integrated circuit on the optical performance of digital versatile disk(DVD) optical system was analyzed using the finite element analysis with initial surface residual stress conditions, and results were compared with the measured results with holographic interferometry. Ray tracing was performed using the deformed configuration of optical system.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.98.4-98
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• 2001

A tape feeder of a SMD(Surface Mount Device) mounter is a device that sequentially feeds electronic components on a tape reel to the pick-up system of the mounter. As components are getting much smaller, feeding accuracy of a feeder becomes one of the most important factors for successful component pick-up. Therefore, it is critical to keep the feeding accuracy to a specified level in the assembly and production of tape feeders. This paper describes a tape feeder inspection system that was developed to automatically measure and inspect feeding accuracy using machine vision. It consists of a feeder base, an image acquisition system, and a personal computer. The image acquisition system is composed of CCD cameras with lens ...

• Fashion & Textile Research Journal
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• v.6 no.4
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• pp.511-514
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• 2004

We studied on the bleaching properties of silk fabric by vapor type ozone processing using ozone's strong oxidation instead of 28% $H_2O_2$ chemical treatment. When vapor type ozone processing was directly treated to fabrics retaining water to 50~70% pick up ratio, high concentration ozone was generated 14,000ppm(168 mg/h) approximately and finally its bleaching improved. The fabric's bleaching effect was improved because vapor type ozone generated the highest decomposition to oxidation of surface and inter molecules. The experiment revealed that fabric's bleaching was improved by change of the pick-up ratio of vapor type ozone processing. However, tensile strength and elongation were reduced by increase of time, and the time that was assumed as the most optimized time to minimize the reduction of fabric's tensile strength and elongation as well as maximizing the fabric's bleaching was 30 minutes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.496-503
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• 2001

The suspension of the optical pickup actuator is damped by the presence of silicone rubber damper bond at its termination. In spite of the presence of it, the actuator still exhibits a strong mechanical resonance which affects its settling time and vibrational characteristics. This resonance can cause errors in reading information from the disk, particularly in high speed CD-ROM and DVD-ROM drives. Ferrofluids are stable colloidal suspensions of sub-micron sized magnetic particles in a carrier liquid. In the actuator design, ferrofluid is applied to the surface of the magnets until the quantity is sufficient to maintain intimate contact with the bobbin/carrier assembly. The fluid is retained in the magnetic field and its viscosity provides the desired mechanical damping to the moving assembly, improving the actuators settling time and vibrational characteristics. Access time is also improved, particularly on warped or eccentric discs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.712-717
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• 2001

In order to modify flexible mode frequencies, finite element analysis is applied for a lens-holder in pick-up actuator. Several design parameters like shape and local dimension of a lens-holder were selected adequately and sensitivities of the design variables for vibration modes were obtained by FE analysis and this result was used for updating FE model. A sensitivity matrix between the natural frequencies and the design variables was calculated by finite difference method. By comparing the calculated natural frequencies with target frequencies, modification of the design variables was acquired and used for improving FE model. Calculated natural frequencies after several iterations by FE analysis coincided with target frequencies and the errors between them were minimized.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.183-188
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• 2004

Nowadays optical disc drives have become necessary. As the equipment is popular to use, competition of price and rotating rate have been harder and harder. Shock response analysis for the optical disk drives is rarely studied. In this paper the optical disk drive has 5-DOF system and each motion is presented by using Lagrange Equation. As the motion of the Pick up lens is important to read and write data, it needs to consider the pickup and disk. The lumped parameter model is compared with finite element model in order to make sure of the result. Results of the shock response analysis from various shock inputs are gotten.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.1
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• pp.41-53
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• 2016

Static repositioning is a well-known and commonly used strategy to maximize customer satisfaction in public bike-sharing systems. Repositioning is performed by trucks at night when no customers are in the system. In models that represent the static repositioning problem, the decision variables are truck routes and the number of bikes to pick up and deliver at each rental station. To simplify the problem, the decision on the number of bikes to pick up and deliver is implicitly included in the truck routes. Two relocation-based local search algorithms (1-relocate and 2-relocate) with the best-accept strategy are incorporated into a variable neighborhood search (VNS) to obtain high-quality solutions for the problem. The performances of the VNS algorithm with the effect of local search algorithms and shaking strength are evaluated with data on Tashu public bike-sharing system operating in Daejeon, Korea. Experiments show that VNS based on the sequential execution of two local search algorithms generates good, reliable solutions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.378-380
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• 2002

There has been lower the tilt margin by the increase of coma aberration due to the reduction of wave-length and the increase of numerical aperture for high density recording. The RF signal degradation is increased as the decrease of tilt margin. To compensate the tilt margin, the optical pick-up actuator for high-speed CD/DVD re-writable system should be able to drive the radial-tilt motion. We announce that the 3-axis drive actuator for high-speed CD/DVD rewritable system. And what was more, the DC/AC sensitivities of this actuator are suitable fur the low-speed playability, the high-speed readability and the high-speed rewritability.