• Journal of Industrial Technology
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• v.24 no.A
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• pp.127-131
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• 2004

In this paper, we proposed an optical balance using a Michelson Interferometer structure. The frequency of the interference signal is changed nonlinearly related with a weight to be measured, and this frequency change is processed by a processor to give a measured weight. Several measurements were performed and the good results were obtained with the fluctuation of about 1g.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.230-235
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• 1997

During laser welding, a laser induced matal vapour and plasuma is formed. The plasma shows strong fluctuation combined with acoustic sound emission. On-line monitoring of the process is possible by measuring and analysing the plasma and acoustic sound emission. This paper introduce the method of on line process monitoring in the laser beam welding and analysis being monitoring signal. The results show the complementary information on the process.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.65-68
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• 2001

The selection transmit diversity is an effective way to avoid the deep fading in a wireless channel. However, it may not completely eliminate the SNR fluctuation of a received signal at the receiver. This letter presents an application of an adaptive modulation effectively exploiting the SNR variation over time for a higher spectral efficiency to the conventional selection transmit diversity. Numerical results show that the proposed scheme can achieve a SNR gain of about 7 dB over the conventional selection diversity in a flat Rayleigh fading environment, when a BER of 10$^{-3}$ and a spectral efficiency of 2 bps/Hz are required..

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.133-139
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• 1995

In this paper, the frequency separation locking and interval stabilization of 4-channel DFB-LDs have been demonstrated using a fiber Fabry-Perot filter with an free spectral range of 100GHz. Frequency fluctuation and locking range of each channel were appeared to be within 15MHz and over 12GHz, respectively. Back-reflection curve from the fiber Fabry-Perot filter was used for the extraction of an error signal in order to increase the number of accomodable channels and extinction ratio.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.856-859
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• 2003

The switched reluctance motor(SRM) drive system provides a good adjustable speed and torque characteristics. However, because of the torque production mechanism, it also has some disadvantage such as higher torque ripple and fluctuation in speed. To reduce torque ripple and to control speed precisely, digital signal processor(BSP) is adopted. The DSP TMS320F241 was used to be realized this drive system. Test results show that the suggested control system has the ability of dynamic and precise speed control.

• The Journal of the Acoustical Society of Korea
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• v.26 no.3
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• pp.123-128
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• 2007

This Paper Presents new transient signal classification algorithms for underwater transient signals. In general. the ambient noise has small spectral deviation and energy variation. while a transient signal has large fluctuation. Hence to detect the transient signal, we use the spectral deviation and power variation. To classify the detected transient signal. the feature Parameters are obtained by using the Wigner-Ville distribution based eigenvalue decomposition. The correlation is then calculated between the feature vector of the detected signal and all the feature vectors of the reference templates frame-by-frame basis, and the detected transient signal is classified by the frame mapping rate among the class database.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.575-600
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• 2024

During an earthquake on December 29th 2020, the Krško NPP automatically shutdown due to the trigger of the negative neutron flux rate signal on the power range nuclear instrumentation. From the time course of the detector signal, it can be concluded that the fluctuation in the detector signal may have been caused by the mechanical movement of the ex-core neutron detectors or the pressure vessel components rather than the actual change in reactor power. The objective of the analysis was to evaluate the sensitivity of the neutron flux at the ex-core detector position, if the detector is moved in the radial or axial direction. In addition, the effect of the core barrel movement and core inside the baffle movement in the radial direction were analysed. The analysis is complemented by the calculation of the thermal and total neutron flux gradient in radial, axial and azimuthal directions. The Monte Carlo particle transport code MCNP was used to study the changes in the response of the ex-core detector for the above-mentioned scenarios. Power and intermediate-range detectors were analysed separately, because they are designed differently, positioned at different locations, and have different response characteristics. It was found that the movement of the power range ex-core detector has a negligible effect on the value of the thermal neutron flux in the active part of the detector. However, the radial movement of the intermediate-range detector by 5 cm results in 7%-8% change in the thermal neutron flux in the active part of the intermediate-range detector. The analysis continued with an evaluation of the effects of moving the entire core barrel on the ex-core detector response. It was estimated that the 2 mm core barrel radial oscillation results in ~4% deviation in the power and intermediate-range detector signal. The movement of the reactor core inside baffle can contribute ~6% deviation in the ex-core neutron detector signal. The analysis showed that the mechanical movement of ex-core neutron detectors cannot explain the fluctuations in the ex-core detector signal. However, combined core barrel and reactor core inside baffle oscillations could be a probable reason for the observed fluctuations in the ex-core detector signal during an earthquake.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.5 no.1
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• pp.38-43
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• 1994

Though normal vocal cords show regular vibration, pathologic vocal cords show irregularity between peaks. Jitter means fluctuation in the time interval between peaks, and Shimmer means cycle to cycle variation in the amplitude of the peaks. We investigated the vocal vibration of Korean normal persons objectively. The fundamental frequency, Jitter, Shimmer and SNR(signal to noise ratio) of normal persons were compared with that of vocal Polyp Patients with CSpeech Program for the possibility of distinguishing the pathologic vocal vibration from normal. The results were as follows ; Comparing the fundamental frequency of vocal Polyp Patients with normal persons, great change was noted only in female cases. But the Jitter and Shimmer of vocal polyp patients were greater than normal significantly in both male and female cases. SNR was lower than normal in vocal polyp patients. In the conclusion, fundamental frequency, Jitter, Shimmer and SNR might be meaningful parameters distinguisuing pathologic vibration from normal.

• Journal of Biomedical Engineering Research
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• v.31 no.2
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• pp.170-175
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• 2010

A method of measuring heart rate using photoplethysmograph(PPG) signal during exercise is proposed. PPG's are composed of strong base tones and their harmonics, and the strong base tones are trackable by the adaptive notch filter (ANF) which adjusts its coefficients to minimize the output power. The proposed heart rate measurement algorithm continuously notches the frequency component with the maximum power in the measured PPG, so that the fundamental frequency corresponding to heart rate is traced. We also presents methods of detecting degeneration and impulsive noise blocks to minimize the coefficient fluctuation. Experiments were conducted using real PPG signals captured during exercise. Results showed that the proposed algorithm is capable of consistently tracking the heart rate embedded in the noisy PPG's.

• The Journal of the Acoustical Society of Korea
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• v.8 no.1
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• pp.75-80
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• 1989

A Mach-Zehnder interferometer using single mode optical fiber was constructed which operates in homodyne detection scheme. Its response to air-borne soun pressure was examined experimentally. A signal stabilizer was developed for maintaining optical fiber interferometer in quadrature condition using a cylindrical piezoelectric stretcher. This maintains the optical fiber sensor at a maximum sensitivity in the presence of the phase drift caused by temperature fluctuation and other types of environmental disturbances.