1,439 research outputs found
Multi-wavelet residual dense convolutional neural network for image denoising
Networks with large receptive field (RF) have shown advanced fitting ability
in recent years. In this work, we utilize the short-term residual learning
method to improve the performance and robustness of networks for image
denoising tasks. Here, we choose a multi-wavelet convolutional neural network
(MWCNN), one of the state-of-art networks with large RF, as the backbone, and
insert residual dense blocks (RDBs) in its each layer. We call this scheme
multi-wavelet residual dense convolutional neural network (MWRDCNN). Compared
with other RDB-based networks, it can extract more features of the object from
adjacent layers, preserve the large RF, and boost the computing efficiency.
Meanwhile, this approach also provides a possibility of absorbing advantages of
multiple architectures in a single network without conflicts. The performance
of the proposed method has been demonstrated in extensive experiments with a
comparison with existing techniques.Comment: 9 pages, 9 figure
A primal-dual interior-point relaxation method with adaptively updating barrier for nonlinear programs
Based on solving an equivalent parametric equality constrained mini-max
problem of the classic logarithmic-barrier subproblem, we present a novel
primal-dual interior-point relaxation method for nonlinear programs. In the
proposed method, the barrier parameter is updated in every step as done in
interior-point methods for linear programs, which is prominently different from
the existing interior-point methods and the relaxation methods for nonlinear
programs. Since our update for the barrier parameter is autonomous and
adaptive, the method has potential of avoiding the possible difficulties caused
by the unappropriate initial selection of the barrier parameter and speeding up
the convergence to the solution. Moreover, it can circumvent the jamming
difficulty of global convergence caused by the interior-point restriction for
nonlinear programs and improve the ill conditioning of the existing primal-dual
interiorpoint methods as the barrier parameter is small. Under suitable
assumptions, our method is proved to be globally convergent and locally
quadratically convergent. The preliminary numerical results on a well-posed
problem for which many line-search interior-point methods fail to find the
minimizer and a set of test problems from the CUTE collection show that our
method is efficient.Comment: submitted to SIOPT on April 14, 202
Self-Organized Time Crystal in Driven-Dissipative Quantum System
Continuous time crystals (CTCs) are characterized by sustained oscillations
that break the time translation symmetry. Since the ruling out of equilibrium
CTCs by no-go theorems, the emergence of such dynamical phases has been
observed in various driven-dissipative quantum platforms. The current
understanding of CTCs is mainly based on mean-field (MF) theories, which fail
to address the problem of whether the long-range time crystalline order exists
in noisy, spatially extended systems without the protection of all-to-all
couplings. Here, we propose a new kind of CTC realized in a quantum contact
model through self-organized bistability (SOB). The exotic CTCs stem from the
interplay between collective dissipation induced by the first-order absorbing
phase transitions (APTs) and slow constant driving provided by an incoherent
pump. The stability of such oscillatory phases in finite dimensions under the
action of intrinsic quantum fluctuations is scrutinized by the functional
renormalization group method and numerical simulations. Occurring at the edge
of quantum synchronization, the CTC phase exhibits an inherent period and
amplitude with a coherence time diverging with system size, thus also
constituting a boundary time crystal (BTC). Our results serve as a solid route
towards self-protected CTCs in strongly interacting open systems.Comment: 15 pages, 7 figure
Large-deviation analysis for counting statistics in mesoscopic transports
We present an efficient approach, based on a number-conditioned master
equation, for large-deviation analysis in mesoscopic transports. Beyond the
conventional full-counting-statistics study, the large-deviation approach
encodes complete information of both the typical trajectories and the rare
ones, in terms of revealing a continuous change of the dynamical phase in
trajectory space. The approach is illustrated with two examples: (i) transport
through a single quantum dot, where we reveal the inhomogeneous distribution of
trajectories in general case and find a particular scale invariance point in
trajectory statistics; and (ii) transport through a double dots, where we find
a dynamical phase transition between two distinct phases induced by the Coulomb
correlation and quantum interference.Comment: 8 pages, 3 figure
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