scholarly journals Amplitude–phase calibration of tri-axial accelerometers in the low-frequency range by a LDV

2019 ◽  
Vol 8 (1) ◽  
pp. 223-231 ◽  
Author(s):  
Giulio D'Emilia ◽  
Antonella Gaspari ◽  
Emanuela Natale
Keyword(s):  
Cross Correlation ◽  
Laser Doppler Vibrometer ◽  
Low Frequency ◽  
Frequency Range ◽  
Critical Aspect ◽  
Calibration Uncertainty ◽  
Cross Correlation Analysis ◽  
Phase Calibration ◽  
Linear Slide ◽  
Phase Evaluation

Abstract. A method for amplitude–phase calibration of tri-axial accelerometers in the low-frequency range (0 to 20 Hz) is proposed, based on a linear slide, used to excite all the axes of the accelerometer at the same time, and a laser Doppler vibrometer (LDV) as a reference. For the phase evaluation different methods, like cross-correlation analysis and cross-spectrum analysis, have also been used for validation purposes. The procedure includes many further validation actions in order to verify the correctness of modelling of the systems being tested, of the data processing and to reduce the calibration uncertainty. Results show that the phase is a critical aspect to consider in calibration, more than the amplitude, and the comparison with the theoretical model is useful to verify the hypotheses. Different behaviours result depending on the elements of the measurement chain and not only on the type of accelerometer.

Neural Drive to Muscles in Stuttering

1989 ◽  
Vol 32 (2) ◽  
pp. 252-264 ◽  
Author(s):  
Anne Smith
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Cross Correlation ◽  
Frequency Range ◽  
Neural Drive ◽  
Activation Patterns ◽  
Fluent Speech ◽  
Muscle Activation Patterns ◽  
Cross Correlation Analysis ◽  
Cross Correlations

EMG recordings were made from muscles of the jaw, lip, and neck during speech of 10 stutterers and 10 nonstutterers. One-second records of disfluent behaviors of stutterers and of fluent speech of the normal speakers were analyzed by computing cross correlations between all possible muscle pairs and spectra for each muscle channel. The cross correlation analysis indicated that for both the disfluent behavior of stutterers and the fluent speech of nonstutterers, jaw muscles (including antagonistic pairs), lip muscles, and neck muscles tend to be coactivated. Thus, no dramatic differences in muscle activation patterns were revealed in the correlational analysis. In contrast, spectral analysis revealed differences between muscle activity during disfluent behavior and fluent speech. During disfluencies the muscles of 6 of the stutterers showed large, rhythmic oscillations in the frequency range of 5 to 12 Hz. Large oscillations were not observed in this frequency range in the muscle activity of normal speakers. The oscillations in muscle activity during disfluencies generally occurred at the same frequency in the various muscle systems studied. These results suggest that diverse muscles are subject to common oscillatory synaptic drive during disfluent behaviors and that this drive is disruptive to speech production. A reasonable speculation is that the disruptive oscillatory drive is produced by tremorogenic mechanisms.

scholarly journals WAVE GROUPINESS AS A SOURCE OF NEARSHORE LONG WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 38 ◽  
Author(s):  
Jeffrey H. List
Keyword(s):  
Wave Amplitude ◽  
Cross Correlation ◽  
Surf Zone ◽  
Low Frequency ◽  
Long Waves ◽  
Progressive Wave ◽  
Wave Groups ◽  
Long Wave ◽  
Cross Correlation Analysis ◽  
Limited Usefulness

Data from a low energy swell-dominated surf zone are examined for indications that observed low frequency motions are simply group-forced bounded long waves. Time series of wave amplitude are compared to filtered long wave records through cross-spectral and cross-correlation analysis. These methods are found to have limited usefulness until long waves are separated into seaward and shoreward components. Then a clear picture of a rapidly shoaling bounded long wave emerges, with a minimum of nearly one fourth of the long wave amplitude being explainable by this type of motion close to shore. Through the zone in which waves were breaking, and incident wave amplitude variability decreased by 50%, the contribution from the bounded long wave continued to increase at a rate much greater than a simple shoaling effect. Also present are clear signs that this amplified bounded long wave is reflected from a position close to the shoreline, and is thus released from wave groups as a free, offshore-progressive wave.

scholarly journals Magnetic storm free ULF analysis in relation with earthquakes in Taiwan

2012 ◽  
Vol 12 (5) ◽  
pp. 1747-1754 ◽  
Author(s):  
S. Wen ◽  
C.-H. Chen ◽  
H.-Y. Yen ◽  
T.-K. Yeh ◽  
J.-Y. Liu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Cross Correlation ◽  
Low Frequency ◽  
Magnetic Anomalies ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Geomagnetic Data ◽  
Before And After ◽  
The Cross ◽  
The Fourier Transform

Abstract. Despite early optimism, pre-earthquake anomalous phenomena can be determined by using enhanced amplitude at the ultra-low-frequency range from geomagnetic data via the Fourier transform. In reality, accuracy of the enhanced amplitude in relation to earthquakes (deduced from time-varied geomagnetic data) would be damaged by magnetic storms and/or other unwanted influences resulting from solar activity and/or variations in the ionosphere, respectively. We substitute values of the cross correlation between amplitudes, summarized from the earthquake-related (0.1–0.01 Hz) and the comparable (0.01–0.001 Hz) frequency bands, for isolated amplitude enhancements as indexes of determination associated with seismo-magnetic anomalies to mitigate disturbance caused by magnetic storms. A station located about 300 km away from the others is also taken into account to further examine whether changes of the cross correlation values are caused by seismo-magnetic anomalies limited within local regions or not. Analytical results show that the values suddenly decrease near epicenters a few days before and after 67% (= 6/9) of earthquakes (M > = 5) in Taiwan between September 2010 and March 2011. Seismo-magnetic signals determined by using the values of cross correlation methods partially improve results yielded from the Fourier transform alone and provide advantageous information of earthquake locations.

The Effects of Restricted Preview on Driver Steering Control and Performance

1973 ◽  
Vol 15 (4) ◽  
pp. 421-430 ◽  
Author(s):  
John R. McLean ◽  
Errol R. Hoffmann
Keyword(s):  
Cross Correlation ◽  
Peak Frequency ◽  
Steering Wheel ◽  
Vehicle Speed ◽  
Frequency Range ◽  
Steering Control ◽  
Sight Distance ◽  
Cross Correlation Analysis ◽  
Heading Angle ◽  
And Performance

Driver steering control and performance were studied for straight-lane driving under conditions of restricted far-sight distance. The far-sight distance necessary for the driver to adequately align the car was found to be 70 ft. and was independent of vehicle speeds of 20 and 30 m.p.h. With far-sight distances beyond 70 ft., there was no improvement in driver steering performance. Spectral analysis of steering wheel angle showed peaks in the frequency range 0.1 to 0.3 Hz. The value of the peak frequency was affected by allowed preview time, where preview time was far-sight distance divided by vehicle speed. Cross-correlation analysis suggested that the peaks were associated with the driver's control of vehicle heading angle. Higher frequency peaks were observed in the range 0.35 to 0.6 Hz. These peaks were more likely to occur under conditions of severely reduced preview.

scholarly journals Calibration of tri-axial MEMS accelerometers in the low-frequency range – Part 1: comparison among methods

2018 ◽  
Vol 7 (1) ◽  
pp. 245-257 ◽  
Author(s):  
Giulio D'Emilia ◽  
Antonella Gaspari ◽  
Fabrizio Mazzoleni ◽  
Emanuela Natale ◽  
Alessandro Schiavi
Keyword(s):  
Low Cost ◽  
Laser Doppler Vibrometer ◽  
Low Frequency ◽  
Frequency Range ◽  
Mems Accelerometer ◽  
Primary Reference ◽  
Pros And Cons ◽  
Standard Calibration ◽  
Capacitive Mems ◽  
Range Part

Abstract. Two alternative experimental procedures for the calibration of tri-axial accelerometers have been compared with traditional methods, performed according the procedures stated in the standard ISO 16063-21. Standard calibration is carried out by comparison with a laser Doppler vibrometer (LDV), used as a primary reference transducer. The main sensitivities have been investigated and, where applicable, also transverse ones. Many aspects have been evaluated: the hypotheses about transverse sensitivities, the simplicity of the procedure, the number of measurements needed, and the effect of typology of transducer, depending on electrical and geometrical contributions. Two different accelerometers have been tested, a piezo-electric accelerometer and a capacitive MEMS accelerometer. A low-frequency range of vibration has been investigated, 3 and 6 Hz, with amplitude of acceleration ranging from 2 to 20 ms−2. A satisfactory reproducibility of methods has been verified, with percentage differences less than 2.5 %. Anyway, pros and cons of each method are also discussed with reference to their possible use for easy and quick calibration of low-cost tri-axial accelerometers.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
Author(s):  
G. Jianmin ◽  
R. Gall ◽  
W. Zuomin
Keyword(s):  
Dynamic Behavior ◽  
Variable Parameter ◽  
Low Frequency ◽  
Vertical Load ◽  
Frequency Range ◽  
Inflation Pressure ◽  
Vehicle Simulation ◽  
Dynamic Damping ◽  
Speed Range ◽  
Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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