5,488 research outputs found
Weighted Schatten -Norm Minimization for Image Denoising and Background Subtraction
Low rank matrix approximation (LRMA), which aims to recover the underlying
low rank matrix from its degraded observation, has a wide range of applications
in computer vision. The latest LRMA methods resort to using the nuclear norm
minimization (NNM) as a convex relaxation of the nonconvex rank minimization.
However, NNM tends to over-shrink the rank components and treats the different
rank components equally, limiting its flexibility in practical applications. We
propose a more flexible model, namely the Weighted Schatten -Norm
Minimization (WSNM), to generalize the NNM to the Schatten -norm
minimization with weights assigned to different singular values. The proposed
WSNM not only gives better approximation to the original low-rank assumption,
but also considers the importance of different rank components. We analyze the
solution of WSNM and prove that, under certain weights permutation, WSNM can be
equivalently transformed into independent non-convex -norm subproblems,
whose global optimum can be efficiently solved by generalized iterated
shrinkage algorithm. We apply WSNM to typical low-level vision problems, e.g.,
image denoising and background subtraction. Extensive experimental results
show, both qualitatively and quantitatively, that the proposed WSNM can more
effectively remove noise, and model complex and dynamic scenes compared with
state-of-the-art methods.Comment: 13 pages, 11 figure
Experimental study of guided waves propagation characteristics under the changing temperatures
Structural Health Monitoring (SHM) plays an important role in ensuring the safe use of aerospace, architecture and other fields. At present, SHM based on piezoelectric and guided waves is a hot spot for real-time monitoring and nondestructive testing. However, the effect of environmental temperatures may mask the signal changes caused by damage and lead to failure of guided wave SHM methods. In this paper, the influence mechanism of the changing temperatures on the propagation characteristics of the guided wave is analyzed. Piezoelectric constants changed with the changing temperatures due to the amplitude variation of the guided wave with the changing temperatures. The effect of temperature on material properties of the plate structures will result in the influence of the guided wave propagation speed. An experiment is performed to study the propagation characteristics of the guided wave on an aluminium plate under changing temperatures. The experimental results indicate that the temperature can change the guide wave amplitude and velocity. At the same time, the temperature effect has the same variation trend at different frequencies, and the slopes of the linear fitting of the propagation characteristics of guided waves with the changing temperatures are also almost consistent
Embeddable Advanced Sensors for Harsh Environment Sensing Applications
Research and development in advanced sensors with embedded monitoring capability have experienced significant growth in recent years, fueled by their broad applications in real-time measurement of a wide variety of physical, chemical, and biological quantities. Compared with conventional sensors with bulky assemblies, recent progress in 3D manufacturing technologies (e.g., ultrafast laser micromachining and additive manufacturing) has opened up a new avenue in one-step fabrication of assembly-freemicro devices in various materials as well as the development of compact, customized, and intricate smart structures/components. The merits of these advanced manufacturing techniques enable the integration of embeddable advanced sensors into smart structures and components for improved robustness, enriched functionality, enhanced intelligence, and unprecedented performance
Underlaid Sensing Pilot for Integrated Sensing and Communications
This paper investigates a novel underlaid sensing pilot signal design for
integrated sensing and communications (ISAC) in an OFDM-based communication
system. The proposed two-dimensional (2D) pilot signal is first generated on
the delay-Doppler (DD) plane and then converted to the time-frequency (TF)
plane for multiplexing with the OFDM data symbols. The sensing signal underlays
the OFDM data, allowing for the sharing of time-frequency resources. In this
framework, sensing detection is implemented based on a simple 2D correlation,
taking advantage of the favorable auto-correlation properties of the sensing
pilot. In the communication part, the sensing pilot, served as a known signal,
can be utilized for channel estimation and equalization to ensure optimal
symbol detection performance. The underlaid sensing pilot demonstrates good
scalability and can adapt to different delay and Doppler resolution
requirements without violating the OFDM frame structure. Experimental results
show the effective sensing performance of the proposed pilot, with only a small
fraction of power shared from the OFDM data, while maintaining satisfactory
symbol detection performance in communication.Comment: 13 pages, 6 figure
Threshold Effects in the Decay of Heavy b' and t' Quarks
A sequential fourth generation is still viable, but the t' and b' quarks are
constrained to be not too far apart in mass. The t'{\to}bW and b'{\to}tW decay
channels are still being pursued at the Tevatron, which would soon be surpassed
by the LHC. We use a convolution method with up to five-body final state to
study t' and b' decays. We show how the two decay branches for m_{b'} below the
tW threshold, b'{\to}tW^* and t^*W, merge with b'{\to}tW above the threshold.
We then consider the heavy-to-heavy transitions b'{\to}t^{\prime(*)}W^{(*)} (or
t'{\to}b^{\prime(*)}W^{(*)}), as they are not suppressed by quark mixing. We
find that, because of the threshold sensitivity of the branching fraction of
t'{\to}b'W^* (or b'{\to}t'W^*), it is possible to measure the strength of the
CKM mixing element V_{t'b} (or V_{tb'}), especially when it is rather small. We
urge the experiments to pursue and separate the t'{\to}b'W^* (or b'{\to}t'W^*)
decay in their search program
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