• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.92-97
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• 2002

There are a lot of roots of errors in an motion of the optical pick-up actuator being one of the most significant components in a CD-ROM drive. Most of the studies recently performed have a tendency to seek for the causes from an actuator itself. This paper present the dynamic characteristics of an actuator affected by the motion of a feeding deck. The feeding system is modeled as a rigid body with eight degree-of-freedom. Using Largrange's equation, we derive the linear equations of motion with respect to the rectangular coordinate. We found the fact that the ranges of the natural frequencies of a feeding deck and an actuator are close to each other. And the time responses are also computed by the Newmark method and Runge-Kutta method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.160-165
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• 1998

The sub-resonance modes can be easily excited by the assembling tolerance in the asymmetric type optical pick-up actuators, compared with the symmetric type. In this paper, we propose the novel method for reducing the vibration due to the sub-resonance modes where undesirable modes can be decreased by adding the damping, which can be achieved by increasing the flexibility of holder PCB, against to the sub-resonance modes. Using the finite element method, the change of mode shapes is investigated as the shape of holder PCB is modified. Experimental results support that the proposed method reduces remarkably the vibration of sub-resonance modes of the optical pick-up actuator.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.35-44
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• 1999

High negative pressure coefficient is formed in the corner of the bluff body structures. For many curtain wall designers this phenomena is of interest because this high negative pressure coefficient is adopted in structural calculation. The present study is aimed to investigate shedding vortex characteristics of two-dimensional rectangular prism flow. Unsteady calculation by finite difference method based upon SOLA is carried out for three aspect ratios(1:1, 1:2, 1:3) of Re=10$^4$ in viscous incompressible flow within infinite domain. Fluctuation of velocity components at various pick-up points and time variation of drag and lift coefficients are analysed by FFT method to reveal shedding vortex frequency patterns. At aspect ratio 1:1, one primary Strouhal number appears for about all pick-up points. At aspect ratio 1:2, two representative Strouhal numbers are classified by pick-up positions and their flows show two different reattachment patterns. For aspect ratio 1:3, frequency spectrum maintains multiple peaks.

• Journal of Distribution Science
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• v.10 no.12
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• pp.19-24
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• 2012

Purpose - This paper discusses the heterogeneous fixed fleet vehicle routing problem with pick-up and delivery (HFFVRPPD), for vehicles with different capacities, fixed costs, and travel costs. Research Design, data, methodology - This paper made nine assumptions for establishing a mathematical model to describe HFFVRPPD. It established a practical mathematical model, and because of the non-deterministic polynomial-time hard (NP-hard), improved the traditional simulated annealing algorithm and tested a new algorithm using a certain scale model. Result - We calculated the minimum cost of the heterogeneous fixed fleet vehicle routing problem (HFFVRP) with a single task and, on comparing the results with the actual HFFVRP for the single task alone, observed that the total cost of HFFVRPPD reduced significantly by 46.7%. The results showed that the new algorithm provides better solutions and stability. Conclusions - This paper, by comparing the HFFVRP and HFFVRPPD results, highlights certain advantages of using HFFVRPPD in physical distribution enterprises, such as saving distribution vehicles, reducing logistics cost, and raising economic benefits.

• Journal of KSNVE
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• v.8 no.1
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• pp.87-98
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• 1998

A Precise actuator in the pick-up of a DVDR/P(Digital Video Disk Recorder/Player) is required to control position accurately. Therefore, in order to develop a reliable actuator, dynamic characteristics of each part in an actuator should be examined closely. This paper presents systematic design process of an actuator using various analysis methods to confirm fundamental capability and solve performance problems related to dynamic characteristics of an actuator beforehand. Particularly, sensitivity analysis is presented through the program using mass moment of inertia and general equations of rigid body. Through the result of sensitivity analysis, important inferiority causes of actuator are selected and reduced. In the end, dynamic characteristics of manufactured actuators are improved considerably.

• Journal of Korean Institute of Industrial Engineers
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• v.35 no.2
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• pp.160-170
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• 2009

This paper studies a vehicle routing problem variant which considers customers to require simultaneous delivery and pick-up under time windows(VRPSDP-TW). The objective of this paper is to minimize the total travel distance of routes that satisfy both the delivery and pick-up demand. We propose a heuristic algorithm for solving the VRPSDP-TW, based on the ant colony system(ACS). In route construction, an insertion algorithm based ACS is applied and the interim solution is improved by local search. Through iterative processes, the heuristic algorithm drives the best solution. Experiments are implemented to evaluate a performance of the algorithm on some test instances from literature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.115-118
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• 2002

The purpose of this paper is to design a pick-up for the small form factor optical disk drive and to fabricate a micro-compensatory lens for the pick-up using the micro-compression molding process. At design stage, the optical elements including the objective lens and the compensatory lens are miniaturized. The height of pick-up and free working distance are designed as 2mm and 0.2% respectively. To analyze the fabricated micro-compensatory lens, the system was analyzed using the surface profile of the fabricated micro-compensatory lens and CODE V which is commercial software. The RMS wave front aberration of the system using fabricated micro-compensatory lens is 0.01677λ which is lower than Marechal's criterion, 0.07λ.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.246-247
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• 2005

This study suggested fanless thermal design using CAE technique for the information storage system under the serious thermal problem. At first, main heat flow was controlled by CAE based fanless heat sink design not to influence sensitive optical pick-up sensor. Then, vent parametric studies found a thermal solution about highly concentrated case top heat due to fanless. These CAE results were verified by experimental methods. As a consequence of newly designed thermal path, thermal specification of optical pick-up sensor was satisfied and fanless thermal design for the information storage system was achieved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.770-774
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• 2003

We propose the re-design method of modal parameters to depress the 2nd resonance peak of the ultra-slim-height optical pick-up actuator. With the addition of tile counter mode near the 2nd resonance frequency, we can achieve the gain margin which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.1-8
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• 1998

In this paper, the optical pick-up used for general audio/video players having more market share than the others is designed with 4-wire suspension type actuator and the hologram laser diode which laser diode, photo diode, beam splitter, and grating lens are integrated in. This optical pick-up is designed in very simple optical system with the characteristics of hologram laser diode. Thus, it has high productivity, the number of the parts is reduced, and also the shape of the assembling parts becomes simple.