• Progress in Superconductivity
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• v.2 no.1
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• pp.20-26
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• 2000

A 40-channel superconducting quantum interference device (SQUID) system was constructed for measuring neuromagnetic fields. Main features of the system are the use of double relaxation oscillation SQUIDs (DROSs), and planar gradiometers measuring magnetic field components tangential to the head surface. The DROSs with high flux-to-voltage transfers enabled direct readout of the SQUID output by room-temperature dc preamplifiers and simple flux-locked loop circuits could be used for SQUID operation. The pickup coil is an integrated first-order planar gradiometer with a baseline of 40 mm. Average noise level of the 40 channels is around 1.2 $fT/cm/{\surd}Hz$ at 100 Hz, corresponding to a field noise of 5 $fT/{\surd}Hz$, operated inside a magnetically shielded room. The SQUID insert was designed to have low thermal load, minimizing the loss of liquid helium. The constructed system was applied to measure auditory-evoked neuromagnetic fields.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.205-210
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• 1999

The 250ppm hydrogen-charged Zircaloy-4 sheets, homogenized at $400^{\circ}C$ for 72hrs in vacuum, were corroded under the autoclave conditions of $350^{\circ}C$, 2350psi. The corrosion behavior of the Zircaloy-4 sheets was evaluated by measuring their weight gains with the exposure time. The electrical characteristics were investigated in the ranges of 5000~1x10\ulcornerHz using AC impedance technique in 1N $H_2$$SO_4$aqueous solution. The corrosion rate of the hydrogen charged specimen was more rapid than the normal specimen at the early stage of the corrosion. With a longer corrosion time, however, the normal specimen corroded faster than the hydrogen-charged specimen. At the same time the hydrogen pickup in the hydrogen-charged specimen was more suppressed compared with the normal specimen. Such appears to be occurred because the impedance for the movement of the hydrogen ion into the metal was higher in the hydrogen-charged specimen compared to normal specimen at the interface between the oxide layer and the uncorroded metal. Thus the corrosion rate of the hydrogen-charged specimen was likely to be decreased with a longer corrosion time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.981-988
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• 2013

In this paper, we propose a method to generate defocusing images at the focusing plane using the 3D spatial information of object through pickup process of integral imaging technique. In the proposed method, the focusing and defocusing images are generated by the convolution operation between elemental images and ${\delta}$ function array. We observed the image difference by defocusing degree according to the distance of focusing plane. To show the feasibility of the proposed method, some preliminary experiments are carried out and the results are presented.

• Tribology and Lubricants
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• v.11 no.5
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• pp.99-107
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• 1995

This paper reported research results to develop an algorithm of on-lin evaluation of surface profiles and roughness generated by turning. The developed module consisted of computer simulation of surface profiles using mechanism of cutting mark formation and cutting vibrations, and online measurement of cutting vibrations. The relative cutting vibrations between tool and worpkiece were measured through an inductance pickup at the rate of one sample per rotation of the workpiece. The sampling process was monitored using an encoder to avoid conceling out the phase lag between waves. The digital cutting signals from the Analog-to-Digital converter were transferred to the simulation module of surface profile where the surface profiles were generated. The developed algorithm or surface generation in a hard turning was analyzed through computer simulations to consider the stochastic and dynamic nature of cutting process. Cutting tests were performed using AISI 304 Stainless Steel and carbide inserts in practical range of cutting conditions. Experimental results showed good correlation between the surface profiles and roughness obtained using the developed algorithm and the surface texture measured using a surface profilemeter. The research provided the feasibility to monitor surface characteristics during tribelogical tests considering wear effect on surface texture in machining.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.424-429
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• 2003

This paper proposes a swing-arm type dual-stage actuator, which consists of a PZT actuator for fine motion and a VCM(Voice Coil Motor) for coarse motion, for SFF ODD(Small Form Factor Optical Disk Drive), in order to achieve fast access speed and precise track following control. We focus our attention on the design and control of the PZT actuator, because there have been a lot of previous researches related to the VCM and dual-stage actuators. Due to the dual cantilever structure, the PZT actuator can generate precise translational tracking motion at its tip where optical pickup is attached at, and the effect of hysteric behavior of the PZT element is reduced. The dynamic model of the PZT actuator is derived by using the Hamilton's principle, and verified by comparing with the experimental frequency response. The sliding mode control is designed in order to be robust against modeling uncertainties. Simulations and experimental results confirm the effectiveness of the suggested control scheme.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.177-183
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• 2006

A tape feeder is an important feeding device to supply micro-chips such as 1005 and 0603 components to PCB in SMT process. Traditionally, tape feeding methods using sprocket wheel mechanism has been used for the pickup system of chip-mounters. However, there is growing needs for new feeding mechanism with high accuracy and confidence as electric components are getting much smaller. Thus, recently, a tape feeder using cam-slider mechanism is developed to meet such requirements. The major advantages of developed system are; significantly reduced indexing and backlash errors, slim and compact design, and improved repetitive capacity compared to existing system. In this paper, the performance evaluation criteria for the developed tape feeder are suggested. Stability against induced vibration, positioning accuracy, cycle time, durability and supply error rate are estimated using developed self testers. As a result, the excellence of developed tape feeding mechanism is validated using the effective rating methods.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.38-49
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• 1998

The 3rd generation optical pick-up used popularly in resent years is composed of many optical and electronic components such as laser diode, photo diode, beam splitter, objective lens, grating lens, concave lens, collimator lens etc. Therefore, the design of its optical system and its main base which the said optical and electronic components are set on, is complicated and needs high precision. Its assembly and adjustment in the production line is also difficult. This complication and the demand of high precision get its production cost to be high and its reliability to be low. In this paper, the 4th generation optical pick-up is designed and developed, with the hologram device which laser diode. photo diode, beam splitter. and grating lens are integrated in. This optical pick-up reduces the number of points of adjustment by 3, compared with the 3rd generation optical pick-up of which the number of points of adjustment is 6. This optical pickup also decreases by 4 the number of points of W bonding to have bad influence on environmental reliability, decreases by about 10 the number of parts, and establishes about 20% cost-down of material cost, compared with the 3rd generation optical pick-up.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.420-427
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• 2015

This paper statistically reviewed for the USNCAP frontal crash test results carried out by NHTSA. Vehicle samples were selected on total 20 vehicles which were included on 15 vehicles for MPV&SUV and 5 Pickup. The results was summarized as followings. The performance for the driver was better than the passenger's in the average sense. There exist distinctions between the driver and the passenger on the USNCAP front test procedure, for example dummy size, seating position and airbag style. Therefore these differences originated in the statistical results. Main effect was Neck injury for crash performance on both dummies on the average value. Root cause of neck injury was different for each dummy, ie, the driver caused from Nte & Ntf, but the passenger did absolutely Nte mode. Reliability evaluated from the standard deviation was highly dependent upon chest injury on the driver and neck injury on the passenger. Restraint system was also summarized.

• Journal of Magnetics
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• v.18 no.2
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• pp.159-162
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• 2013

We present how to optimize the operation condition including frequency of the orthogonal fluxgate sensor in this paper. The orthogonal fluxgate sensor was fabricated with a Co-based amorphous wire with 10 mm long and 100 ${\mu}m$ in the diameter and a 270-turn pickup coil wound on the amorphous wire. In order to investigate the frequency dependence of the sensitivity, output spectra of the sensor which was connected by using a coaxial cable with various lengths of 0.5-5 m were measured with a RF lock-in amplifier. The maximum sensitivities were obtained at different frequencies according to coaxial cable lengths. It was found that the optimal operation frequencies, at which maximum sensitivities were appeared, were almost identical to the frequencies of impedance resonance. The maximum sensitivity and optimal operation frequency were 1.1 V/Oe (${\approx}$ 11000 V/T) and 1.25 MHz respectively.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.680-686
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• 1995

It has been known that water-side corrosion of fuel rods in nuclear reactor is accompanied with the loss of metallic wall thickness and pickup of hydrogen. This corrosion is one of the important limiting factors ill the operating life of fuel rods. In connection with the fuel cladding corrosion, a device to measure the water-side oxide layer thickness by means of the eddy-current method without destructing the fuel rod was developed by KAERI. The device was installed on the multi-function testing bench in the nondestructive test hot-cell and its calibration was carried out successfully for the standard rod attached with plastic thin films whose thicknesses are predetermined. It shows good precision within about 10% error. And a PWR fuel rod, one of the J-44 assembly discharged from Kori nuclear power plant Unit-2, has been selected for oxide layer thickness measurements. With the result of data analysis, it appeared that the oxide layer thicknesses of Zircaloy cladding vary with the length of the fuel rod, and their thicknesses were compared with those of the destructive test results to confirm the real thicknesses.