• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.48-52
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• 2005

The research topic of super-RENS technology is shifting from the signal intensity (CNR; Carrier to Noise Ratio) to the signal uniformity (Jitter or bER). To achieve an uniform signal characteristics, it is important to reduce signal fluctuation in a super-RENS disc. In this study, we investigated the relation between signal fluctuation and low frequency noise (LFN), and analyzed LFN increase in recording and readout processes. It was found that signal fluctuation had a close relationship with the LFN. Also, it was found that the recorded mark shape such a bubble type and high readout power increased the LFN in recording and readout process of a super-RENS disc. So, using non-bubble type recording material and low super-resolution readout material, we markedly improved the LFN in a super-RENS disc.

• Current Optics and Photonics
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• v.7 no.1
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• pp.28-32
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• 2023

Frequency characteristics of gain-saturated erbium-doped fiber amplifier (EDFA) are experimentally evaluated to mitigate the optical signal fluctuation induced by atmospheric turbulence in terrestrial freespace optical communication systems. Here, an acousto-optic modulator (AOM) is used to emulate optical signal fluctuations induced by atmospheric turbulence. The waveform which is generated in proportion to the refractive-index structural parameters is used to drive the AOM at various periodic frequencies. Thus, the dependence of the signal fluctuation suppression on the frequency is evaluated. The experiment is conducted using a periodic frequency sweep of the AOM driving voltage waveform and signal input power variation of the amplifier. It is observed that a low periodic frequency and high input signal power effectively suppress the optical signal fluctuation. This study evaluates the experimental results from the high-pass filter and gain-saturation characteristics of the EDFA.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.5-9
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• 2019

Optical emission spectroscopy is used to identify chemical species and monitor the changes of process results during the plasma process. However, plasma process monitoring or fault detection by using emission signal variation monitoring is vulnerable to background signal fluctuations. IR heaters are used in semiconductor manufacturing chambers where high temperature uniformity and fast response are required. During the process, the IR lamp output fluctuates to maintain a stable process temperature. This IR signal fluctuation reacts as a background signal fluctuation to the spectrometer. In this research, we evaluate the effect of infrared background signal fluctuation on plasma process monitoring and improve the plasma process monitoring accuracy by using simple infrared background signal subtraction method. The effect of infrared background signal fluctuation on plasma process monitoring was evaluated on $SiO_2$ PECVD process. Comparing the $SiO_2$ film thickness and the measured emission line intensity from the by-product molecules, the effect of infrared background signal on plasma process monitoring and the necessity of background signal subtraction method were confirmed.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.242-247
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• 1990

By self-homodyne method we measured the relative phase fluctuation of a light wave. Balanced detection system can eliminate local oscillator excess noise and multiport detection makes it possible ot measure the phase change of the signal beam. Deriving the SB(Signal Beam) and the LO(Local Oscillator) from the same laser source, we find the SB maintain constant phase relative to that of the LO. We have introduced a phase fluctuation in the SB by modulating the beam path of the SB. The measured phase fluctuation agreed well with the predicted one, thereby we confirmed the reliability of our system.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.158-165
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• 2005

KOGAS(Korea Gas Corporation) has about a hundred of local stations to supply natural gas to the city gas companies and the power stations. As some severe flow fluctuation phenomena are observed in several governor stations, the investigation about the reasons and factors which are relating to flow fluctuation has been started. Some field surveys hav been carried out and experimental studies have been performed to find the fluctuation mechanism. As a result, it is found that the flow fluctuation is related with the length of straight pipe in front of the meter, the size of the header pipe and the variation of demand at the city gas company and the power station. Furthermore. it is also proved that both the length of the transmitter cable and the status of the coating of signal transmission cable do not affect flow fluctuation, but the measurement range of the differential pressure transmitter influences flow fluctuation. On the other hand, as the averaging the flow fluctuation is converged to less than 0.1 % in almost all of the cases, it is concluded that the quantity of flow fluctuation do not relates to metering accuracy directly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.272-278
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• 2008

This paper investigated the a-si:H gate driver with the stepwise gate signal. In 1-chip type mobile LCD application the stepwise gate signal for low power consumption can be used by adding simple switching circuit. The power consumption of the a-Si:H gate driver can be decreased by employing the stepwise gate signal in the conventional circuit. In conventional one, the effect of stepwise gate signal can decrease slew rate and increase the fluctuation of gate-off state voltage, In order to increase the slew rate and decrease the gate off state fluctuation, we proposed a new a-Si:H TFT gate driver circuit. The simulation data of the new circuit show that the slew rate and the gate-off state fluctuation are improved, so the circuit can work reliably.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.330-332
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• 2003

In this paper, It is introduced new sound quality method, FI(Fluctuation Index) and the example applied Outdoors side Air-conditioner noise evaluation. Because FI is applied with very simple algebraic calculation algorithm, it can be applied some other application without spending high time and cost.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1085-1093
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• 2010

This paper proposes a multiple filter for reduction of received signal fluctuation and enhancement of step altitude edge detection in FMCW radar altimeter. The proposed filter was composed of alpha-trimmed mean filter, frequency variation limiter, and 1/3 order static filter. Simulations by analysis of received signal show that the proposed filter provides better performance than moving average and standard median filters with error reduction. In particular, the proposed filter was improved in the ability of reducing fluctuation for ground hovering.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1759-1766
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• 2001

Vibration transient generated by developing localized fault in gear can be used as indicators in gear fault detection. In this paper, we propose the zoomed phase map for a fault signal using continuous wavelet transfers to detect this vibration transient. Local fault induces the abrupt fluctuation of load exciting tooth and phase lag in the vibration signal measured on the gearbox. The relatively large fault like "tip breakage" easily can be detected by the clear fluctuation of exciting load. However, minor fault like "initial pitting"cannot be detected using the load fluctuation. To defect this kind of minor fault, the phase map for a fault signal is taken into account. The phase lag by minor fault is observed well in the zoomed phase map.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.590-595
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• 2001

Vibration transient generated by developing localized fault in gear can be used as indicators of condition monitoring in a gear. In this paper, we propose the phase map for a fault signal using continuous wavelet transform to detect this vibration transient. Local fault induces the abrupt fluctuation of load exciting tooth and phase lag in the vibration signal measured on the gearbox. The relatively large fault like "tip breakage" easily can be detected by the clear fluctuation of exciting load. However, minor fault like "initial pitting" cannot be detected using the load fluctuation. To detect this kind of minor fault, the phase map for a fault signal is taken into account. The phase lag by minor fault is observed well in the phase map.