3,587 research outputs found
Acoustic meta-stethoscope for cardiac auscultation
Straight cylindrical stethoscopes serve as an important alternative to
conventional stethoscopes whose application in the treatment of infectious
diseases might be limited by the use of protective clothing. Yet their
miniaturization is challenging due to the low-frequency of bioacoustics signal.
Here, we design and experimentally implement a meta-stethoscope with
subwavelength size, simple fabrication, easy assembly yet high sensitivity,
which simply comprises multiple round perforated plate units and a cylindrical
shell. We elucidate our proposed mechanism by analytically deriving the
frequency response equation, which proves that the equivalent acoustic
propagation path is substantially increased by the high-index metamaterial,
enabling downscaling of the meta-stethoscope to subwavelength footprint. The
acoustic performance of meta-stethoscope is experimentally characterized by
monitoring the cardiac auscultation on clothed human body. The simulated and
measured results agree well, with both showing the expected enhancement of
sensitivity of our proposed meta-stethoscope (~ 10 dB) within the predicted
working frequency range from 80 to 130 Hz despite its compactness and
simplicity. Our designed portable, detachable yet effective meta-stethoscope
opens a route to metamaterial-enabled stethoscope paradigm, with potential
applications in diverse scenarios such as medical diagnosis and acoustic
sensing.Comment: 14 pages, 3 figure
Deep unfolding as iterative regularization for imaging inverse problems
Recently, deep unfolding methods that guide the design of deep neural
networks (DNNs) through iterative algorithms have received increasing attention
in the field of inverse problems. Unlike general end-to-end DNNs, unfolding
methods have better interpretability and performance. However, to our
knowledge, their accuracy and stability in solving inverse problems cannot be
fully guaranteed. To bridge this gap, we modified the training procedure and
proved that the unfolding method is an iterative regularization method. More
precisely, we jointly learn a convex penalty function adversarially by an
input-convex neural network (ICNN) to characterize the distance to a real data
manifold and train a DNN unfolded from the proximal gradient descent algorithm
with this learned penalty. Suppose the real data manifold intersects the
inverse problem solutions with only the unique real solution. We prove that the
unfolded DNN will converge to it stably. Furthermore, we demonstrate with an
example of MRI reconstruction that the proposed method outperforms conventional
unfolding methods and traditional regularization methods in terms of
reconstruction quality, stability and convergence speed
Inpatient care burden due to cancers in Anhui, China: a cross-sectional household survey
Raw dataset of inpatient cancer care costs and related variables studied. (XLSX 32 kb
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