• Proceedings of the KSME Conference
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• 2001.06c
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• pp.451-456
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• 2001

Today, most of data storage devices use digital storage type. In this thesis, a new digital storage media called rainbow disk was introduced. It doesn't use 1-bit digital signal, but 2 or 4 bits digital signal using colors, so it can increase $2{\sim}4$ times more capacity than existing digital media in case of having the same spot size. It has made possible by means of technological advancement of devices and software. The photo quality paper was used for writing data by color inkjet or laser printing, and high resolution scanner was used for reading data. To extract data from image, the converting program was used. This paper shows the concept of rainbow disk as well as its performance and capacity. Axiomatic design was used for evaluating and developing the whole system.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.194-201
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• 1998

The beam rotating actuator has been developed. It can be utilized to improve the data transfer rate for the optical disk systems, Newly developed laser beam rotating actuator is applied to put multi-beam spots on more than one track on the optical disk simultaneously. The beam rotating actuator is made of piezoelectric ceramic bimorph as the form of cantilever, Piezoelectric actuators with high resolution, high stiffness and fast frequency response are widely assembled in micropositioning applications. Therefore, the actuator has above 50Hz natural frequency. Beam array is rotated using the dove prism in the end of beamrotator. The dynamic equation of beam rotating actuator is derived theoretically. The actuator is designed on the ground of this analysis. The performance of the beam rotating actuator is verified as the dynamics frequency performance is measured using the dynamic analyzer and sensor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.450-453
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• 1995

The beam rotating actuator, which can be utilized to improve the data transfer rate for the optical disk systems, has been developed. It can employ a newly developed laser beam rotating actuator for putting multi-beam spots on more than one track on the optical disk simultaneously. Therefore, It has to maintain up to .+-.0.01 .deg. resolution and high bandwidth performance. In this these, the Dove prism is used for the beam rotating actuator based on bimorph piezo material. The performance of the beam rotating actuator is verified since the dynamics ferquency performance is measured using the dynamic analyzer and the attached stain gage sensor. the beam rotating angle performance is also examined since the long range beam reflection character is utilized.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.187-192
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• 2002

In-plane ESPI(Electronic Speckle Patten Interferometry)was devised to measure in~plane defamation and rotation of a specimen with laser in this study. The conventional measuring methods of surface deformations such as the strain gauge have many demerits because they are contact and point-to-point measuring ones. But that ESPI is noncontact, nondestructive and whole field measuring method can overcome previous disadvantages. We used ESPI which is sensitive to in-plane displacement for measuring in-plane deformations of a disk. First of all, the system calibration was done due to an in-plane rotation before getting deformations of a disk. Finally we showed good agreement between theexperiment results and those of the FEA(Finit Element Analysis).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2646-2653
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• 2000

The performance of slider of a hard disk drive affects the durability of the system. Particularly, the flying ability of the slider is critical in terms of surface damage and head crash. In this work, the take-off characteristics of the slider for various types of laser zone textured bump geometries were investigated. Also, the effect of ambient pressure on the flying characteristics of the slider was experimentally observed. An index of air density which can be used as a parameter for evaluating the flying characteristic is introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1577-1582
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• 2000

In this study, the experimental modal analysis is performed to investigate the dynamic characteristics of slider-air bearings in hard disk drives. Bump response of the slider is acquired by measuring the relative velocity for two points using the laser interferometer, in which the disk is scratched lightly by a sharp knife to make a bump. From the measurements, the modal parameters of the head slider, modal frequencies and damping ratios of roll and pitch, are estimated by data processing and parameter estimation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.720-725
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• 2000

A new ultrasonic pulse-echo technique was developed and described for vibration measurement of the suspension assembly in hard disk drives. The method is based upon the difference in magnitude of two consecutive reflection waves from a moving object(suspension), while the traditional ultrasonic vibrometer uses the phase shift of the reference wave and the reflection wave. A cone-shape delay line is designed to access the small structure. A simple mathematical model is presented and analyzed with experimental results to show the feasibility of the method. The advantages of this ultrasonic vibration measurement method are relatively high resolution, low cost, and ease of implementation comparing with the Laser Doppler vibrometer.

• Journal of Wellbeing Management and Applied Psychology
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• v.5 no.3
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• pp.1-5
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• 2022

Purpose: The purpose of this study is to investigate whether wetland has antimicrobial activity on pathogenic bacteria in the toilet bowl. Research design, data and methodology: Air-dried mud obtained from "Jilmoe Bog" wetland was packed and dissolved in the autoclaved saline. Antimicrobial susceptibility was assessed against three Gram-negative bacteria using disk diffusion method and broth dilution method. Identification of specific bacterium presented in wetland supernatant was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Results: Incubation of three Gram-negative bacteria with wetland supernatant inhibited bacterial growth of the bacteria, otherwise increased prevalence of specific bacterium. It was confirmed that Pseudomonas putida was presented in wetland supernatant. Conclusions: The results presented in this study might provide the possibility to utilize wetland supernatant as a bioremediation of toilet bowl bacteria.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.463-470
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• 2016

In this paper, the characteristics analysis of LMD track, such as including track structure, track wear resistance and track thickness, were analyzed to enhance the deposition efficiency using a diode-pumped disk laser. SKD61 hot work steel plate and Fe based AISI M2 alloy were used as a the substrate and powder for the LMD process, respectively. The laser power, track pitch and powder feed rate among LMD parameters were adopted to estimate the deposition efficiency. As the laser power is increased, heat input and melting pool on the substrate is grown also increases, so resulting in the increased LMD track thickness was increased. Through EPMA mapping analysis of the cross-section in the LMD track, it was observed that all the elements are evenly distributed inside. Therefore, the entire hardness in the LMD track is expected to be almost uniform regardless of location. The characteristics of the LMD specimen were excellent compared to the STD11 specimen in terms of the wear track width and the wear rate as well as the coefficient of friction. Especially the wear rate of LMD specimen has been significantly reduced by 60 % or more. From Based on the experimental results, the prediction formula of LMD thickness was calculated by using laser power, track pitch and powder feed rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.89-94
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• 2015

This study was conducted to compare the laser weldability of boron steel and hot-stamped steel. In general, boron steel is used in the hot-stamping process. Hot-stamping is a method for simultaneously forming and cooling boron steel in a press die after heating it to the austenitizing temperature. Hot-stamped steel has a strength of 1500 MPa or more. Thus, in this study, the laser weldability of boron steel and thet of hot-stamped steel were investigated and compared. A continuous wave disk laser was used to produce butt and lap joints. In the butt welding, the critical cooling speed at which full penetration was obtained in the hot-stamped steel was lower than that of boron steel. In the lap welding, the joint widths were similar regardless of the welding speed when full penetration was obtained.