A new signal processing method, which uses a modified chirp signal for air-coupled ultrasonic imaging, is described. A combination of the elliptical and Tukey window functions has been shown to give a better performance than the Hanning windowing used in most pulse-compression algorithms for air-coupled applications. The elliptical-Tukey chirp signal provides an improvement in both the resolution of images and signal-to-noise ratios. In addition, this type of signal also reduces the level of signal voltages required to drive the source transducer while maintaining the performance of the system. This approach, thus, may have wide interest in all forms of wide bandwidth ultrasonic imaging.
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http://dx.doi.org/10.1109/tuffc.2007.423 | DOI Listing |
Epilepsia
December 2024
Epilepsy Unit, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Istituto Neurologico Carlo Besta, Milan, Italy.
Time-frequency analysis of focal seizure electroencephalographic signals performed with depth electrodes in human temporal lobe structures has revealed the occurrence at onset of oscillations at approximately 30-100 Hz that feature a monotonic rapid decay in frequency content. This seizure onset pattern, referred to as chirp, has been identified as a highly specific and sensitive marker of focal seizures that are characterized by low-voltage fast activity. We report that this chirp pattern is also observed in animal models of temporal lobe epilepsy in both in vivo and in vitro preparations.
View Article and Find Full Text PDFVital signs such as heart rate (HR) and respiration rate (RR) are essential physiological parameters that are routinely used to monitor human health and bodily functions. They can be continuously monitored through contact or contactless measurements performed in the home or a hospital. In this study, a contactless Doppler radar W-band sensing system was used for short-range, contactless vital sign estimation.
View Article and Find Full Text PDFSensors (Basel)
November 2024
Department of Civil Engineering and Architecture, Tallinn University of Technology, 19086 Tallinn, Estonia.
Detecting defects in plates is crucial across various industries due to safety risks. While ultrasonic bulk waves offer point-by-point inspections, they are time-consuming and limited in coverage. In contrast, guided waves enable the rapid inspection of larger areas.
View Article and Find Full Text PDFModern interferometers such as LIGO have achieved sensitivities limited by quantum noise, comprising radiation pressure and shot noise. To mitigate this noise, a static system is employed that minimizes the quantum noise within the measurement band. However, since gravitational wave inspiral signals are a single frequency changing over time, only noise at the chirp frequency needs to be minimized.
View Article and Find Full Text PDFInt J Audiol
December 2024
Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Objective: To evaluate the effects of changes in group delay from a click signal to a chirp signal on the 40-Hz Auditory Steady-State Response (ASSR) using magnetoencephalography (MEG).
Design: In this study, each participant was exposed to 10 chirp signals with gradually varying group delays from the CE chirp to the click at 60 dB nHL. The 40-Hz ASSR was measured using MEG and evaluated for amplitude and latency in the maximum signal channel at the click signal measured in each hemisphere.
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