scholarly journals A Recursive Algorithm for Indoor Positioning Using Pulse-Echo Ultrasonic Signals

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5042
Author(s):  
Salvatore A. Pullano ◽  
Maria Giovanna Bianco ◽  
Davide C. Critello ◽  
Michele Menniti ◽  
Antonio La Gatta ◽  
...  
Keyword(s):  
Communication Systems ◽  
Polyvinylidene Fluoride ◽  
Cross Correlation ◽  
Recursive Algorithm ◽  
Low Frequency ◽  
Correlation Method ◽  
Experimental Results ◽  
Ultrasonic Signals ◽  
Average Improvement ◽  
Pulse Echo

Low frequency ultrasounds in air are widely used for real-time applications in short-range communication systems and environmental monitoring, in both structured and unstructured environments. One of the parameters widely evaluated in pulse-echo ultrasonic measurements is the time of flight (TOF), which can be evaluated with an increased accuracy and complexity by using different techniques. Hereafter, a nonstandard cross-correlation method is investigated for TOF estimations. The procedure, based on the use of template signals, was implemented to improve the accuracy of recursive TOF evaluations. Tests have been carried out through a couple of 60 kHz custom-designed polyvinylidene fluoride (PVDF) hemicylindrical ultrasonic transducers. The experimental results were then compared with the standard threshold and cross-correlation techniques for method validation and characterization. An average improvement of 30% and 19%, in terms of standard error (SE), was observed. Moreover, the experimental results evidenced an enhancement in repeatability of about 10% in the use of a recursive positioning system.

scholarly journals Датчик скорости потока жидкости на основе волоконных брэгговских решеток с индукционным нагревом

2021 ◽  
Vol 47 (17) ◽  
pp. 22
Author(s):  
А.В. Умнова ◽  
А.С. Алейник ◽  
В.Е. Стригалев ◽  
В.А. Новикова ◽  
А.Н. Аширов
Keyword(s):  
Flow Velocity ◽  
Induction Heating ◽  
Cross Correlation ◽  
Fiber Bragg Gratings ◽  
Correlation Method ◽  
Temperature Sensors ◽  
Heat Pulse ◽  
Experimental Results ◽  
Time Response ◽  
Velocity Range

The paper presents simulating and experimental results of flowmeter operation with induction heating, where fiber Bragg gratings were used as sensitive elements of temperature sensors. The operating principle of flowmeter based on cross-correlation method. During the experiment, it was detected time response of heat pulse from 0.2 s to 0.5 s that corresponds to a flow velocity range 0.1-0.5 m/s.

Electrophysiologic Assessment of Low-Frequency Hearing: Sedation Effects

1989 ◽  
Vol 101 (4) ◽  
pp. 434-441 ◽  
Author(s):  
Constantine W. Palaskas ◽  
Michael J. Wilson ◽  
Robert A. Dobie
Keyword(s):  
Cross Correlation ◽  
Low Frequency ◽  
Correlation Method ◽  
Normal Hearing ◽  
Hearing Level ◽  
Evoked Responses ◽  
Middle Latency Response ◽  
Latency Response ◽  
Middle Latency ◽  
40 Hz

Sixteen normal-hearing adults were tested in both awake and sedated states for several evoked responses to low-frequency stimuli. Responses obtained by cross-correlation function, middle latency responses, and the 40-Hz response proved most sensitive; all had mean thresholds of less than 20 dB normal hearing level for the awake-alert state, but 40-Hz and middle latency response mean thesholds were shifted about 10 dB under sedation. The cross-correlation method seems to offer promise for pediatric auditory assessment.

scholarly journals Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

2020 ◽  
Author(s):  
Bin Sun ◽  
Kai Xie ◽  
Yan Liu ◽  
Yujin Zhang ◽  
Shaoshuai Guo ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Phase Shift ◽  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Low Frequency ◽  
Experimental Results ◽  
Time Varying ◽  
Dynamic Effects ◽  
Shared Time ◽  
Theoretical Results

In this paper, we reveal the dynamic effects of time-varying plasma on low-frequency (LF) electromagnetic (EM) wave propagation. The time-varying attenuation, time-varying phase shift, and power spectrum of the LF EM waves are presented. By using the frequency division multiplexing method, LF EM waves at the four discrete frequencies simultaneously penetrate through a shared time-varying plasma in one shock tube experiment. The experimental results indicate that the time-varying attenuation and phase shift of the LF EM wave are determined by the time-varying behavior of the plasma, and they are positively related to the electron density and frequency of the LF EM waves. The theoretical results are well consistent with the experimental results. Moreover, in the frequency domain, the time-varying plasma causes spectrum expansion of the LF EM waves. These results help us deeply understand the propagation process of LF EM waves in time-varying plasma and design LF communication systems.

scholarly journals Experimental Investigation of the Dynamic Effects of Time-Varying Plasma on Low-Frequency Electromagnetic Wave Propagation

2020 ◽  
Author(s):  
Bin Sun ◽  
Kai Xie ◽  
Yan Liu ◽  
Yujin Zhang ◽  
Shaoshuai Guo ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Phase Shift ◽  
Communication Systems ◽  
Electromagnetic Wave Propagation ◽  
Low Frequency ◽  
Experimental Results ◽  
Time Varying ◽  
Dynamic Effects ◽  
Shared Time ◽  
Theoretical Results

In this paper, we reveal the dynamic effects of time-varying plasma on low-frequency (LF) electromagnetic (EM) wave propagation. The time-varying attenuation, time-varying phase shift, and power spectrum of the LF EM waves are presented. By using the frequency division multiplexing method, LF EM waves at the four discrete frequencies simultaneously penetrate through a shared time-varying plasma in one shock tube experiment. The experimental results indicate that the time-varying attenuation and phase shift of the LF EM wave are determined by the time-varying behavior of the plasma, and they are positively related to the electron density and frequency of the LF EM waves. The theoretical results are well consistent with the experimental results. Moreover, in the frequency domain, the time-varying plasma causes spectrum expansion of the LF EM waves. These results help us deeply understand the propagation process of LF EM waves in time-varying plasma and design LF communication systems.

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