559 research outputs found
Signal Separation Using a Mathematical Model of Physiological Signals for the Measurement of Heart Pulse Wave Propagation With Array Radar
The arterial pulse wave, which propagates along the artery, is an important
indicator of various cardiovascular diseases. By measuring the displacement at
multiple parts of the human body, pulse wave velocity can be estimated from the
pulse transit time. This paper proposes a technique for signal separation using
an antenna array, so that pulse wave propagation can be measured in a
non-contact manner. The body displacements due to the pulse wave at different
body parts are highly correlated, and cannot be accurately separated using
techniques that assume independent or uncorrelated signals. The proposed method
formulates the signal separation as an optimization problem, based on a
mathematical model of the arterial pulse wave. The objective function in the
optimization comprises four terms that are derived based on a
small-displacement approximation, unimodal impulse response approximation, and
a causality condition. The optimization process was implemented using a genetic
algorithm. The effectiveness of the proposed method is demonstrated through
numerical simulations and experiments.Comment: This paper has been published in IEEE Access (Early Access), 12
pages, 17 figure
Generating a Super-resolution Radar Angular Spectrum Using Physiological Component Analysis
In this study, we propose a method for generating an angular spectrum using array radar and physiological component analysis. We develop physiological component analysis to separate radar echoes from multiple body positions, where echoes are phase-modulated by propagating pulse waves. Assuming that the pulse wave displacements at multiple body positions are constant multiples of a time-shifted waveform, the method estimates echoes using a simplified mathematical model. We exploit the mainlobe and nulls of the directional patterns of the physiological component analysis to form an angular spectrum. We applied the proposed method to simulated data to demonstrate that it can generate a super-resolution angular spectrum
Personal Identification Using Ultrawideband Radar Measurement of Walking and Sitting Motions and a Convolutional Neural Network
This study proposes a personal identification technique that applies machine
learning with a two-layered convolutional neural network to spectrogram images
obtained from radar echoes of a target person in motion. The walking and
sitting motions of six participants were measured using an ultrawideband radar
system. Time-frequency analysis was applied to the radar signal to generate
spectrogram images containing the micro-Doppler components associated with limb
movements. A convolutional neural network was trained using the spectrogram
images with personal labels to achieve radar-based personal identification. The
personal identification accuracies were evaluated experimentally to demonstrate
the effectiveness of the proposed technique.Comment: 9 pages, 7 figures, and 3 table
Noncontact Measurement of Autonomic Nervous System Activities Based on Heart Rate Variability Using Ultra-Wideband Array Radar
The noncontact measurement of vital signs using ultra-wideband radar has been attracting increasing attention because it can unobtrusively provide information about the physical and mental condition of people. In particular, the continuous measurement of a person's time-varying instantaneous heart rate can estimate the activity level of the autonomic nervous system without the person wearing any sensors. Continuous heart rate measurement using radar is, however, a difficult task because accuracy is compromised by numerous factors, such as the posture and motion of the target person. In this study, we introduce techniques for increasing the accuracy and reliability of the noncontact measurement of heart rate variability. We demonstrate the performance of the proposed techniques by applying them to radar measurement data from a sleeping person, and we also compare its accuracy with electrocardiogram data
Radar-based Measurement of Pulse Wave using Fast Physiological Component Analysis
2022 International Workshop on Antenna Technology (iWAT), 16-18 May 2022, Dublin, IrelandThis study proposes a fast blind signal separation technique for human arterial pulse wave propagation measurement. One of the authors previously developed a blind signal separation method called physiological component analysis that uses mathematical modeling of the measured physiological signals, including the pulse wave propagation, and this method improves the signal separation accuracy when applied to array signal processing. Physiological component analysis, however, is known to require long computation times because it is based on high-dimensional global optimization. In this paper, we propose a method to reduce the dimensionality of the decision variables for the optimization process that uses the Schelkunoff polynomial method. Using this dimension reduction technique, we propose a new algorithm, called fast physiological component analysis, and the performance of this algorithm is evaluated using numerical simulations
Noncontact measurement of heartbeat of humans and chimpanzees using millimeter-wave radar with topology method
チンパンジーの瞬時心拍間隔を非接触で測定することに成功 --ミリ波レーダを用いた非接触バイタル測定技術の確立へ--. 京都大学プレスリリース. 2023-10-18.This study proposes a method to determine the filter parameters required for the topology method, which is a radar-based noncontact method for measurement of heart inter-beat intervals. The effectiveness of the proposed method is evaluated by performing radar measurements involving both human participants and chimpanzee subjects. The proposed method is designed to enable setting of the filter cutoff frequency to eliminate respiratory components while maintaining the higher harmonics of the heartbeat components. Measurements using a millimeter-wave radar system and a reference contact -type electrocardiogram sensor demonstrate that the smallest errors that occur when measuring heart inter-beat intervals using the proposed method can be as small as 4.43 and 2.55 ms for humans and chimpanzees, respectively. These results indicate the possibility of using noncontact physiological measurements to monitor both humans and chimpanzees
Yang-Baxter deformations of Minkowski spacetime
We study Yang-Baxter deformations of 4D Minkowski spacetime. The Yang-Baxter
sigma model description was originally developed for principal chiral models
based on a modified classical Yang-Baxter equation. It has been extended to
coset curved spaces and models based on the usual classical Yang-Baxter
equation. On the other hand, for flat space, there is the obvious problem that
the standard bilinear form degenerates if we employ the familiar coset
Poincar\'e group/Lorentz group. Instead we consider a slice of AdS by
embedding the 4D Poincar\'e group into the 4D conformal group . With
this procedure we obtain metrics and -fields as Yang-Baxter deformations
which correspond to well-known configurations such as T-duals of Melvin
backgrounds, Hashimoto-Sethi and Spradlin-Takayanagi-Volovich backgrounds, the
T-dual of Grant space, pp-waves, and T-duals of dS and AdS. Finally we
consider a deformation with a classical -matrix of Drinfeld-Jimbo type and
explicitly derive the associated metric and -field which we conjecture to
correspond to a new integrable system.Comment: 27 pages, no figure, LaTe
Noncontact monitoring of heartbeat and movements during sleep using a pair of millimeter-wave ultra-wideband radar systems
We experimentally evaluate the performance of a noncontact system that measures the heartbeat of a sleeping person. The proposed system comprises a pair of radar systems installed at two different positions. We use millimeter-wave ultra-wideband multiple-input multiple-output array radar systems and evaluate the performance attained in measuring the heart inter-beat interval and body movement. The importance of using two radar systems instead of one is demonstrated in this paper. We conduct three types of experiments; the first and second experiments are radar measurements of three participants lying on a bed with and without body movement, while the third experiment is the radar measurement of a participant actually sleeping overnight. The experiments demonstrate that the performance of the radar-based vital measurement strongly depends on the orientation of the person under test. They also show that the proposed system detects 70% of rolling-over movements made overnight
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