• Food Science of Animal Resources
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• v.33 no.3
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• pp.317-324
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• 2013

Radio-frequency driven atmospheric pressure plasma using argon gas was studied in the inactivation of Campylobacter jejuni in order to investigate its applicability. First, the inactivation study was conducted on an agar surface. C. jejuni NCTC11168 was reduced by more than 7 Log CFU after an 88 s treatment. Another strain, ATCC49943, was studied; however, the inactivation was less efficient, with a 5 Log CFU reduction after a 2 min treatment. Then, chicken breast ham was studied at the $10^6$ CFU inoculation level. The inactivation efficiency was much lower for both strains compared to that on the agar plates. C. jejuni NCTC11168 and ATCC49943 were reduced by 3 Log CFU after a 6 min treatment and by 1.5 Log CFU after a 10 min treatment, respectively. The scanning electron microscopy analysis indicated that C. jejuni cells were deformed or transformed into coccoid form under the plasma treatment. During the plasma treatment, the temperature of the samples did not rise above $43^{\circ}C$, suggesting that heat did not contribute to the inactivation. Meanwhile, water activity significantly decreased after a 10 min treatment (p<0.05). This study conveyed that radio-frequency atmospheric pressure plasma can effectively inactivate C. jejuni with strain-specific variation.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.29-32
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• 2010

In this study, transparent and conductive Al-doped zinc oxide (AZO) films were prepared on a glass substrate by an radio frequency (RF) magnetron sputtering method using a 150-nm-thick AZO target (Al: 2 wt.%) at room temperature. We investigated the effects of RF power between 100-350 W (in steps of 50 W) on the structural, electrical, and optical properties of the AZO films. The thickness and cross-sectional images of the films were observed by field emission scanning electron microscopy. The thicknesses of all films were kept constant at 150 nm and grown on a glass substrate. The grain sizes of the AZO films were determined with the X-ray diffraction by using the Scherrer' equation, and their electrical properties were investigated using a Hall effect electronic transport measurement system. The transmittance of the AZO films was also measured by an ultraviolet-visible spectrometer.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.3
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• pp.246-254
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• 2007

The scanning laser source (SLS) technique is a promising new laser ultrasonic tool for the detection of small surface-breaking defects. The SLS approach is based on monitoring the changes in laser-generated ultrasound as a laser source is scanned over a defect. Changes in amplitude and frequency content are observed for ultrasound generated by the laser over uniform and defective areas. The SLS technique uses a point or a short line-focused high-power laser beam which is swept across the test specimen surface and passes over surface-breaking or subsurface flaws. The ultrasonic signal that arrives at the Rayleigh wave speed is monitored as the SLS is scanned. It is found that the amplitude and frequency of the measured ultrasonic signal have specific variations when the laser source approaches, passes over and moves behind the defect. In this paper, the setup for SLS experiments with full B-scan capability is described and SLS signatures from small surface-breaking and subsurface flaws are discussed using a point or short line focused laser source.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1295-1302
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• 2005

This paper shows experimental evaluation results of the nano-positioning planar scanner used in the scanning probe microscope. The planar scanner is composed of flexure guides, piezoelectric actuators and feedback sensors as like explained in detail in Ref. (5). First, the fabrication methods were explained. Second, as the static Properties of the Planar scanner. we evaluated the maximum travel range & crosstalk. Also, we presented the correcting method for crosstalk using electric circuits finally. as the dynamic properties of the planar scanner, we evaluated the first resonant frequency. Also, we presented the actual AFM(atomic force microscope) imaging results with up to 2Hz imaging scan rate. Experimental results show that properties of the proposed planar scanner are well enough to be used in SPM applications like AFM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.661-663
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• 2021

Network performance is degraded when the UE is disconnected because the outage occurs at the base station in a mobile communication system. Therefore it is important to detect and recover the outage. In this paper, detecting the outage base station by using the KPI and the network scanning in the neighbor base station, and increasing the transmit power and changing the frequency band to recovery the outage scheme is proposed. The proposed scheme uses not only the KPI of the base station but also the network scanning of the neighbor base stations to detect the outage base station, so that it is possible to detect the outage base station more accurately. In addition, when the outage occurred, the neighbor base station changes the transmit power and frequency band to recover the outage with less signal interference.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.61.2-61.2
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• 2013

We study chromospheric oscillations including umbral flashes and running penumbral waves in a sunspot using scanning spectroscopy in H-alpha and Ca II 8542A, with the Fast Imaging Solar Spectrograph (FISS) at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. A bisector method is applied to spectral observations to construct chromospheric Doppler velocity maps. Temporal sequence analysis of these shows enhanced high-frequency oscillations inside the sunspot umbra in both lines. Their peak frequency gradually decreases outward from the umbra. The oscillation power is found to be associated with magnetic-field strength and inclination, with different relationships in different frequency bands.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.673-674
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• 2008

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.120-121
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• 2001

고분해능을 장점으로 하는 근접장 광학 현미경(NSOM)은 최근 높은 관심을 모으고 있으나, 그 촬영 속도가 너무 느린 이유로 실제적인 활용이 미비한 상황이다. scanning 속도를 높이고자 하는 노력들이 많이 진행되고 있으나[1-2] 아직도 실시간 촬영과는 거리가 멀다. 기존의 근접장 광학 현미경(NSOM)은 tuning fork를 사용하여 탐침을 진동시키고 그 진동의 진폭 또는 위상의 변화를 측정함으로써 탐침과 시료의 거리를 측정하는 방식을 사용한다. (중략)

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.149-154
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• 2004

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the relationship of transporting speed according to the change of flexural beam shape and the effect of transporting speed according to the change of weight and amplification voltage are verified. The vibration behavior of flexural beam in the ultrasonic transport system is experimented using Laser Scanning Vibrometer.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.48-58
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• 2011

In this paper, an attempt has been made to design the current and speed proportional and integral (PI) regulators of self-commutating current source inverter-fed induction motor drive having capacitors at the machine end and to investigate the transient performance of the same for step changes in reference speed. The mathematical model of the complete drive system is developed in closed loop, and the characteristic equations of the systems are derived using perturbation about steady-state operating point in order to develop the characteristic equations. The D-partition technique is used for finding the stable region in the parametric plane. Frequency scanning technique is used to confirm the stability region. Final selection of the regulator parameters is done by comparing the transient response of the current and speed loops for step variations in reference. The performance of the drive is observed analytically through MATLAB simulation.