• 한국해안·해양공학회논문집
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• 제21권6호
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• pp.462-469
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• 2009

파랑과 흐름이 공존하는 해안에서의 비점착성 퇴적물이동에 대하여 육지-외해방향 총 퇴적물 이동률을 산정할 수 있는 경험식을 제안한다. 본 경험식은 파랑만 존재하는 경우와 흐름만 존재하는 경우에도 범용적으로 사용할 수 있다. 해수면 기준 비대칭인 파랑을 이용하여 퇴적물의 부상률과 이동거리의 곱으로 단위면적당 총 퇴적물 이동률을 계산할 수 있다. 대체로 파고가 큰 파랑이 입사하는 경우 퇴적물은 외해방향으로 이동하는 반면 파고가 작은 파랑의 경우 육지방향으로 퇴적물을 이동시키는 경향을 본 예측식이 잘 재현하고 있다. 또한 장주기 파랑의 경우 퇴적물을 육지방향으로 이동시키려는 경향을 본 예측식이 잘 보여준다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.512-514
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• 2008

In this paper, a new electromagnetic circuit is proposed for an optical pickup actuator with high sensitivity. Contrary to those of conventional actuators, the proposed circuit has two focusing coils which are diagonally placed at the front and rear of a moving part. The configuration which makes the effective length of the focusing coil longer and the moving part lighter, is helpful in increasing the sensitivity of the actuator. However, the asymmetry of the moving part by two focusing coils causes flexible node vibrations in quite low frequency range. This paper shows that the design modification of the moving part for the reconfiguration of mass moment of inertia can reduce the mode vibrations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.479-483
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• 2006

As high-definition television(HDTV) broadcasting were generalized, there have been many researches and developments about large storage capacity and fast data transfer rate in optical disk drives(ODD). Pickup actuators must have high flexible mode frequencies and gain margins. Flexible modes are caused by the flexibility of moving parts in the actuator and a servo bandwidth is limited by them. As a result, the system becomes unstable for high-speed operations in high density reading and recording. In this paper, we suggest improved modeling method that considers the bonding layer. And, flexible mode frequency of actuator is improved by Design of Experiment of lens holder. Magnet circuit is designed considering the relation with moving part. Through improving yoke design, the magnetic flux is changed and DC tilt is reduced. Consequently, we designed actuator which has high flexible mode frequency and gain margins.

• 한국정보통신학회논문지
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• 제16권6호
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• pp.1285-1290
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• 2012

3D 산업이 발달하고 3D와 관련된 콘텐츠 및 장비가 점차 보편화 되면서 사람들은 3D 다음 세대의 미디어 및 서비스에 대한 관심을 보이고 있다. 많은 사람들은 그 강력한 후보자로 디지털 홀로그램을 생각하고 있다. 홀로그램 기술은 일반적인 비디오 시스템들과 마찬가지로 획득(혹은 생성), 처리, 그리고 재생으로 나누어질 수 있다. 본 논문에서는 하이브리드 영상획득 장치를 이용한 디지털 홀로그래픽 디스플레이 시스템에 대해 논의하고 새로운 시스템의 구조를 제안한다. 제안한 방식을 통해서 다양한 해상도를 갖는 디스플레이, 수신단의 연산 능력, 그리고 네트워크의 대역폭에 따라 적응적으로 홀로그래픽 비디오를 서비스할 수 있다는 것을 보였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.1010-1014
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• 2002

A new type actuator has been designed and investigated to overcome thermal problems in slim optical disc drive which is adopted in mobile storage devices. Recently, in optical storage device technical trends, the size of optical disc drives is slimmer to adopt notebook computer and the spindle rotate velocity is faster to achieve high transfer rate and the power of actuator is higher to perform tilting, etc. However, these trends of optical disc drives tend to raise the environment temperature of drives, actuator power and parts temperature. Moreover, it is more difficult to remove the heat inside a drive and the temperature of an actuator increases and drive slims. As a result, increase of surface temperature of actuator body caused that second resonance of an actuator moves down to a lower frequency band and the performance of optical parts also deteriorates. Especially objective lens, coil and magnet of the actuator parts are easily damaged. To manage these thermal problems, in this paper an actuator with a hybrid blade, which is composed of vectra which has low thermal conductivity and magnesium which has high thermal conductivity, has been suggested and verified. Despite the high temperature environment, the proposed actuator showed good dynamic performance.

• Progress in Superconductivity
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• 제6권1호
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• pp.19-23
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• 2004

YBCO do superconducting quantum interference device (SQUID) magnetometers based on bicrystal Josephson junctions on 10 mm ${\times}$ 10 mm $SrTiO_3$ substrates have been fabricated. The pickup coil of the device was designed to have 16 parallel loops with 50-fm-wide lines. We could obtain optimised direct coupled YBCO SQUID magnetometer design with field sensitivity $B_{N}$ $\Phi$/ of $4.5 nT/\Phi_{0}$ and magnetic field noise $B_{N}$ of about $22 fT/Hz^{1}$2/ with an I/f corner frequency of 2 Hz measured inside a magnetically shielded room. Preliminary results of magnetocardiograph measurement using the HTS SQUID magnetometers show signal to noise ratio of about 110, which is comparable to the quality of a commercial MCG system based on Nb-SQUIDs.

• 대한기계학회논문집A
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• 제24권3호
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• pp.728-734
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• 2000

An asymmetric actuator can be used to reduce the distance between the reflective mirror and objective lens of a small optical disk drive for use in the notebook-sized personal computer data storage devices. However, this asymmetric actuator is very sensitive to the subsidiary resonance which is caused by its rigid body motion. In this paper, an analytical approach using a simple lumped parameter system model is presented with a physical insight to investigate why the subsidiary resonance occurs. The finite element method is used to figure out the force and torque characteristics of the asymmetric actuator which are essential to understand the subsidiary vibration characteristics. The frequency responses are presented to examine how the subsidiary resonance is altered for various situations of having different thickness of a yoke and permanent magnet and of having a different magnet circuit. Finally, the design guidelines to avoid the subsidiary resonance will be presented.

• 대한기계학회논문집A
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• 제31권1호
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• pp.43-49
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• 2007

A new electric coil design methodology using the notion of topology optimization is developed. The specific design problem in consideration is to find optimal coil configuration that maximizes the Lorentz force under given magnetic field. Topology optimization is usually formulated using the finite element method, but the novel feature of this method is that no such partial differential equation solver is employed during the whole optimization process. The proposed methodology allows the determination of not only coil shape but also the number of coil turns which is not possible to determine by any existing topology optimization concept and to perform single coil strand identification algorithm. The specific applications are made in the design of two-dimensional fine-pattern focusing coils of an optical pickup actuator. In this method, the concept of equivalent magnetizing current is utilized to calculate the Lorentz force, and the optimal coil configuration is obtained without any initial layout. The method is capable of generating the location and shape of turns of coil. To confirm the effectiveness of the proposed method in optical pickup applications, design problems involving multipolar permanent magnets are considered.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.856-860
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• 2008

Wire-suspensions in the conventional actuators mechanically support the moving part and guarantee the accuracy of the actuator without tangential tilt actuation. However, such a suspension configuration has considerable stiffness in the tangential tilt direction with two additional wire beams for the tangential tilt. Thus, we performed a design sensitivity analysis for the wire-suspension stiffness of 4-axis actuator and controlled the main parameters such as distance among wire-suspensions and wire-suspension length to allow tangential tilt flexibility. The elasticity of frame PCB that supports the moving part by wire-suspensions was also exploited to improve the flexibility of wire-suspension in the tangential tilt direction. A novel suspension structure was devised by establishing eight wire-suspensions at both sides of the moving part for electrical connection to coils. The magnetic circuit according to the proposed 4-axis actuator using multi-polar magnet and coils was also suggested for the generation of electromagnetic forces in the focusing, tracking, radial and tangential tilt directions.

• 한국자기학회지
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• 제15권4호
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• pp.250-255
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• 2005

8 MA/m급 펄스자석과 픽업코일, 아날로그 전자적분기, 계수기록형 오실로스코우프, 퍼스널컴퓨터 등을 이용하여 펄스고자장하에서 자성을 정밀 측정할 수 있는 펄스마그네토미터를 구성하였다. 픽업코일은 작은 공간에서 정밀측정이 가능하도록 3-축보상원리를 채용하여 제작하였으며 펄스자장에 대한 신호 보상은 $10^{-6}$수준이었고 적분기와 오실로스코우프를 거친 후의 최종 자기모멘트의 측정감도는 $5{\cdot}10^{-7}\;Am^2$이었다. 본 실험을 통하여 구성된 펄스마스네토미터는 지름 $3\;mm{\phi}$, 이하의 소형 및 박막형 희토류 영구자석의 특성평가에 적합하였다.