782,927 research outputs found
Nonequilibrium stochastic processes: Time dependence of entropy flux and entropy production
Based on the Fokker-Planck and the entropy balance equations we have studied
the relaxation of a dissipative dynamical system driven by external
Ornstein-Uhlenbeck noise processes in absence and presence of nonequilibrium
constraint in terms of the thermodynamically inspired quantities like entropy
flux and entropy production. The interplay of nonequilibrium constraint,
dissipation and noise reveals some interesting extremal nature in the time
dependence of entropy flux and entropy production.Comment: RevTex, 17 pages, 9 figures. To appear in Phys. Rev.
A variational study of some hadron bag models
Quantum chromodynamics (QCD) is the theory of strong interaction and accounts
for the internal structure of hadrons. Physicists introduced phe- nomenological
models such as the M.I.T. bag model, the bag approximation and the soliton bag
model to study the hadronic properties. We prove, in this paper, the existence
of excited state solutions in the symmetric case and of a ground state solution
in the non-symmetric case for the soliton bag and the bag approximation models
thanks to the concentration compactness method. We show that the energy
functionals of the bag approximation model are Gamma -limits of sequences of
soliton bag model energy functionals for the ground and excited state problems.
The pre- compactness, up to translation, of the sequence of ground state
solutions associated with the soliton bag energy functionals in the
non-symmetric case is obtained combining the Gamma -convergence theory and the
concentration-compactness method. Finally, we give a rigorous proof of the
original derivation of the M.I.T. bag equations done by Chodos, Jaffe, Johnson,
Thorn and Weisskopf via a limit of bag approximation ground state solutions in
the spherical case. The supersymmetry property of the Dirac operator is the key
point in many of our arguments
Underwater seismic source
Apparatus for generating a substantially oscillation-free seismic signal for use in underwater petroleum exploration, including a bag with walls that are flexible but substantially inelastic, and a pressured gas supply for rapidly expanding the bag to its fully expanded condition is described. The inelasticity of the bag permits the application of high pressure gas to rapidly expand it to full size, without requiring a venting mechanism to decrease the pressure as the bag approaches a predetermined size to avoid breaking of the bag
Audio Set classification with attention model: A probabilistic perspective
This paper investigates the classification of the Audio Set dataset. Audio
Set is a large scale weakly labelled dataset of sound clips. Previous work used
multiple instance learning (MIL) to classify weakly labelled data. In MIL, a
bag consists of several instances, and a bag is labelled positive if at least
one instances in the audio clip is positive. A bag is labelled negative if all
the instances in the bag are negative. We propose an attention model to tackle
the MIL problem and explain this attention model from a novel probabilistic
perspective. We define a probability space on each bag, where each instance in
the bag has a trainable probability measure for each class. Then the
classification of a bag is the expectation of the classification output of the
instances in the bag with respect to the learned probability measure.
Experimental results show that our proposed attention model modeled by fully
connected deep neural network obtains mAP of 0.327 on Audio Set dataset,
outperforming the Google's baseline of 0.314 and recurrent neural network of
0.325.Comment: Accepted by ICASSP 201
Vapor pressure measured with inflatable plastic bag
Deflated plastic bag in a vacuum chamber measures initial low vapor pressures of materials. The bag captures the test sample vapors and visual observation of the vapor-inflated bag under increasing external pressures yields pertinent data
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