• Proceedings of the KSME Conference
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• 2003.11a
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• pp.670-675
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• 2003

With the increase in recording density and higher rotation speeds, the aerodynamic aspect of hard disk drives (HDDs) is now quite significant. To achieve high TPI (tracks per inch) for hard disk drives, the actuator must induce less air turbulence. Also, alternative cross sections for the actuator arms are proposed for the reduction of air turbulence. In this study, off-track vibration of actuator arms used in of 3.5" hard disk drives with different cross sections have been measured by using Laser Doppler Vibrometer (LDV). It has been found that the vibration of the actuator arms with modified cross sections is lower than the conventional one.

• Current Optics and Photonics
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• v.6 no.2
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• pp.171-182
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• 2022

A single-photon laser and mid-wave infrared (MWIR) common aperture optical system was designed and developed to detect and range a long-distance civil aviation aircraft. The secondary mirror of the Ritchey-Chretien (R-C) optical system was chosen as a dichroic lens to realize the design of a common aperture system for the laser and MWIR. Point spread function (PSF) ellipticity was introduced to evaluate the coupling efficiency of the laser receiving system. A small aperture stop and narrow filter were set in the secondary image plane and an afocal light path of the laser system, respectively, and the stray light suppression ability of the small aperture stop was verified by modeling and simulation. With high-precision manufacturing technology by single point diamond turning (SPDT) and a high-efficiency dichroic coating, the laser/MWIR common aperture optical system with a 𝜑300 mm aluminum alloy mirror obtained images of buildings at a distance of 5 km with great quality. A civil aviation aircraft detection experiment was conducted. The results show that the common aperture system could detect and track long-distance civil aviation aircraft effectively, and the coverage was more than 450 km (signal-to-noise ratio = 6.3). It satisfied the application requirements for earlier warning and ranging of long-range targets in the area of aviation, aerospace and ground detection systems.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.89-98
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• 2009

In this study, the YLPODS (Yonsei Laser-ranging Precision Orbit Determination System) is developed for POD using SLR (Satellite Laser Ranging) NP (Normal Point) observations. The performance of YLPODS is tested using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite. JPL's POE (Precision Orbit Ephemeris) is assumed to be true orbit, the measurement residual RMS (Root Mean Square) and the orbit accuracy (radial, along-track, cross-track) are investigated. The validation of POD using GPS (Global Positioning System) raw data is achieved by YLPODS performance and highly accurate SLR NP observations. YGPODS (Yonsei GPS-based Precision Orbit Determination System) is used for generating GPS based precise orbits for TOPEX/POSEIDON. The initial orbit for YLPODS is derived from the YGPODS results. To validate the YGPODS results the range residual of the first adjustment of YLPODS is investigated. The YLPODS results using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite show that the range residual is less than 10 cm and the orbit accuracy is about 1 m level. The validation results of the YGPODS orbits using SLR NP observations of the TOPEX/POSEIDON satellite show that the range residual is less than 10 cm. This result predicts that the accuracy of this GPS based orbits is about 1m level and it is compared with JPL's POE. Thus this result presents that the YLPODS can be used for POD validation using SLR NP observations such as STSAT-2 and KOMPSAT-5.

• The Journal of Korean Physical Therapy
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• v.13 no.3
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• pp.569-578
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• 2001

The purpose of the present study was to examine the functional recovery of the crushed sciatic nerve of rats after low-power laser irradiation applied to the corresponding segments of the spinal cord. After a crushed injury on the left sciatic nerve in rats. low-power laser irradiation was applied transcutaneously to corresponding segments of the spinal cord immediately after suture the wound by using 2000 mW, 2000Hz, 830 nm CaAIAs(Gallium-aluminum-arsenide) semiconductor diode laser. The laser treatment was performed with 10 minutes daily for 4 successive weeks. Functional recovery was evaluated per weekly following injury by sciatic function index(SFI),using data obtained by walking track analysis. For four weeks after crush injury, experimental group had significantly greater functional improvement than control group(${\alpha}$=0.05). In a experimental group, SFI was significantly increased for three weeks, but control group not increased for two weeks. This study suggests that low-power laser irradiation applied directly to the spinal cord can improve functional recovery of the crushed sciatic nerve in rats.

• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.30-37
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• 2004

There have been continuous efforts on automating welding processes. This automation process could be said to fall into two categories, weld seam tracking and weld quality evaluation. Recently, the attempts to achieve these two functions simultaneously are on the increase. For the study presented in this paper, a vision sensor is made, a vision system is constructed and using this, the 3 dimensional geometry of the bead is measured on-line. For the application as in welding, which is the characteristic of nonlinear process, a fuzzy controller is designed. And with this, an adaptive control system is proposed which acquires the bead height and the coordinates of the point on the bead along the horizontal fillet joint, performs seam tracking with those data, and also at the same time, controls the bead geometry to a uniform shape. A communication system, which enables the communication with the industrial robot, is designed to control the bead geometry and to track the weld seam. Experiments are made with varied offset angles from the pre-taught weld path, and they showed the adaptive system works favorable results.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.211-220
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• 2002

Optical disk drives read information by replacing a laser beam on the disk track. As information has become larger, the more accurate position control of a laser beam is necessary. In this paper, we report the analysis and fabrication of the micro mirror for optical disk drivers. A coupled simulation of gas flow and structural displacement of the micro mirror using the Finite-Element-Method is applied to this. The mirror was fabricated by using MEMS technology. Especially, the process using the lapping and polishing step after the bonding of the mirror and electrode plates was employed for the Process reliability. The mirror size was 2.5mm${\times}$3mm and it needed about 35V for displacement of 3.2 ${\mu}$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.782-787
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• 2002

In optical disk drives (ODD), the demands of high data density and high speed have been increasing rapidly to achieve high data capacity and data transfer rate. The short wavelength laser, High NA objective lens, and high track following performance are needed to raise data density and data rate. For high-performance actuator, the improvement of linearity and acceleration become more important. Also, 3-axis actuator for active tilt compensation is introduced to overcome the decrease in disk tilt tolerance which is induced by short wavelength laser. In this paper, a hybrid type 3-axis actuator is presented and a new yoke structure, which can reduce the interaction between yoke and moving magnet, is designed to keep the efficiency of magnetic circuit. Experimental results show the validity of the yoke in the hybrid type actuator.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.653-657
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• 2005

AGV is very useful equipment to transfer containers in automated container terminal. AGV must have Obstacle Detection System (ODS) for port automation. ODS needs the function to classify some specified object from background in acquired data. And it must be able to track classified moving objects. Finally, ODS could determine its next action for safe driving whether it should do emergency stop or speed down, or it should change its deriving lane. For these functions, ODS can have many different kinds of algorithm. In this paper, we present one of AGV to be used in automated container terminal.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.4
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• pp.36-42
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• 2003

Theodolite measurement system is non-contacted 3-dimensional measurement system. The system accuracy is ${\pm}0.5mm$or better for distance 0~100m. And the system is used for the measurement of a product of middle and large scale. This study is performed for the measurement error factors of the system. We could know that the main measurement error factors are temperature, illumination and skill. Also, we performed the study for the effect according to the height difference of scale bar.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.872-878
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• 2009

Passenger safety is a primary concern of the railway system. However, dozens of people are killed every year when they accidently fall on to the track from the boarding platform. This is one of the most urgent issues to solve regarding the railway platform. The installation environment, and the blind area problems as well as maintenance and operating costs which are not efficient have to be looked at. To solve these problems, we propose a 3D laser radar sensor based monitoring system for the railway platform. This paper introduces an overview, the detecting method, and the interface with the signalling system in detecting a fallen passenger from the platform using the 3D laser radar sensor.