383 research outputs found
Plate-Like Structure Damage Acoustic Emission Beamforming Array Technique and Probability-Based Diagnostic Imaging Method
A novel beamforming array technique and probability-based diagnostic imaging method are proposed to determine the acoustic emission (AE) source in plate-like structures. The technique that differs from common beamforming array techniques, in particular a sensor network, is used instead of a linear sensor array, to highlight information on the AE source location in one coordinate system as energy distribution. To reduce the uncertainty, avoid the boundary reflection effect, and ensure the rationality of the signal superposition, a Hilbert transform-based signal processing is applied before the delay-and-sum algorithm and a probability-based diagnostic imaging method is developed for AE source localization. The finite element numerical simulation method and the pencil-lead-broken experiment on aluminum plate are also conducted, and a thin-walled cylinder pipe-like structure is also tested by the pencil-lead-broken experiment to develop the application of the proposed method in various fields. The results indicate that this method is efficient and capable of visually showing the localization results highlighted in the probability images
Reexamination of the resonance contributions in B->X_s e^+ e^-
With help of the recent developments in the heavy quarkonium physics, we
reexamine the long distance(LD) effects in \Bsee dominantly from the charmonium
resonances and through the decay chains B\ra X_s
J/\Psi (\Psi^{\prime}) \ra X_s e^+ e^-. We find that the resonance to
nonresonance interference are reduced substantially.Comment: Revtex file,11 pages,1 figures,Phys.Lett.B in pres
Regularity and analyticity of solutions in a direction for elliptic equations
In this paper, we study the regularity and analyticity of solutions to linear elliptic equations with measurable or continuous coefficients. We prove that if the coefficients and inhomogeneous term are Hölder-continuous in a direction, then the second-order derivative in this direction of the solution is Hölder-continuous, with a different Hölder exponent. We also prove that if the coefficients and the inhomogeneous term are analytic in a direction, then the solution is analytic in that direction
Nonfactorization Effects in Inclusive Decay B->J/\Psi X_s
We discuss the nonfactorization effects in , which is
similar to the nonperturbative effect found by Voloshin in the decay . The QCD sum rule has been used to estimate the hadron matrix
elements. We find that the correction from this effect is very large and the
large discrepancy between the theory and the experimental data can be reduced
considerably.Comment: LaTex, 9 pages, 4 figures. Two references added and typo correcte
CONVECTIVE FLOW AND HEAT TRANSFER OF NANO-ENCAPSULATED PHASE CHANGE MATERIAL (NEPCM) DISPERSIONS ALONG A VERTICAL SURFACE
Nano-encapsulated phase change suspension is a novel type of functional fluid in which the nanoparticles undergo phase change that contribute to heat transfer. Thus, the working fluid carries heat not only by sensible heat but also in the form of latent heat stored in the particles. The natural convection and heat transfer of Nano-Encapsulated Phase Change Materials (NEPCMs) suspensions within a boundary layer along a heated flat surface are theoretically investigated in this work. The nanoparticles are core-shell structured with the core fabricated from PCMs covered by a solid shell. A similarity solution approach along with the finite element method is employed to address the phenomena. The outcomes indicate that a decisive factor in boosting the heat transfer is the temperature at which NEPCM particles undergo the phase transition. The heat transfer parameter can be enhanced by about 25% by just adding 5% of NEPCM particles, compared to the case with no NEPCM particles
SERCA2a gene transfer improves electrocardiographic performance in aged mdx mice
<p>Abstract</p> <p>Background</p> <p>Cardiomyocyte calcium overloading has been implicated in the pathogenesis of Duchenne muscular dystrophy (DMD) heart disease. The cardiac isoform of sarcoplasmic reticulum calcium ATPase (SERCA2a) plays a major role in removing cytosolic calcium during heart muscle relaxation. Here, we tested the hypothesis that SERCA2a over-expression may mitigate electrocardiography (ECG) abnormalities in old female mdx mice, a murine model of DMD cardiomyopathy.</p> <p>Methods</p> <p>1 × 10<sup>12 </sup>viral genome particles/mouse of adeno-associated virus serotype-9 (AAV-9) SERCA2a vector was delivered to 12-m-old female mdx mice (N = 5) via a single bolus tail vein injection. AAV transduction and the ECG profile were examined eight months later.</p> <p>Results</p> <p>The vector genome was detected in the hearts of all AAV-injected mdx mice. Immunofluorescence staining and western blot confirmed SERCA2a over-expression in the mdx heart. Untreated mdx mice showed characteristic tachycardia, PR interval reduction and QT interval prolongation. AAV-9 SERCA2a treatment corrected these ECG abnormalities.</p> <p>Conclusions</p> <p>Our results suggest that AAV SERCA2a therapy may hold great promise in treating dystrophin-deficient heart disease.</p
Timing the Transient Execution: A New Side-Channel Attack on Intel CPUs
The transient execution attack is a type of attack leveraging the
vulnerability of modern CPU optimization technologies. New attacks surface
rapidly. The side-channel is a key part of transient execution attacks to leak
data. In this work, we discover a vulnerability that the change of the EFLAGS
register in transient execution may have a side effect on the Jcc (jump on
condition code) instruction after it in Intel CPUs. Based on our discovery, we
propose a new side-channel attack that leverages the timing of both transient
execution and Jcc instructions to deliver data. This attack encodes secret data
to the change of register which makes the execution time of context slightly
slower, which can be measured by the attacker to decode data. This attack
doesn't rely on the cache system and doesn't need to reset the EFLAGS register
manually to its initial state before the attack, which may make it more
difficult to detect or mitigate. We implemented this side-channel on machines
with Intel Core i7-6700, i7-7700, and i9-10980XE CPUs. In the first two
processors, we combined it as the side-channel of the Meltdown attack, which
could achieve 100\% success leaking rate. We evaluate and discuss potential
defenses against the attack. Our contributions include discovering security
vulnerabilities in the implementation of Jcc instructions and EFLAGS register
and proposing a new side-channel attack that does not rely on the cache system
Direct imaging of a zero-field target skyrmion and its polarity switch in a chiral magnetic nanodisk
A target skyrmion is a flux-closed spin texture that has two-fold degeneracy
and is promising as a binary state in next generation universal memories.
Although its formation in nanopatterned chiral magnets has been predicted, its
observation has remained challenging. Here, we use off-axis electron holography
to record images of target skyrmions in a 160-nm-diameter nanodisk of the
chiral magnet FeGe. We compare experimental measurements with numerical
simulations, demonstrate switching between two stable degenerate target
skyrmion ground states that have opposite polarities and rotation senses and
discuss the observed switching mechanism.Comment: 18 pages, 4 figure
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