965 research outputs found
Alternating Back-Propagation for Generator Network
This paper proposes an alternating back-propagation algorithm for learning
the generator network model. The model is a non-linear generalization of factor
analysis. In this model, the mapping from the continuous latent factors to the
observed signal is parametrized by a convolutional neural network. The
alternating back-propagation algorithm iterates the following two steps: (1)
Inferential back-propagation, which infers the latent factors by Langevin
dynamics or gradient descent. (2) Learning back-propagation, which updates the
parameters given the inferred latent factors by gradient descent. The gradient
computations in both steps are powered by back-propagation, and they share most
of their code in common. We show that the alternating back-propagation
algorithm can learn realistic generator models of natural images, video
sequences, and sounds. Moreover, it can also be used to learn from incomplete
or indirect training data
Relativistic mean-field approximation with density-dependent screening meson masses in nuclear matter
The Debye screening masses of the , and neutral
mesons and the photon are calculated in the relativistic mean-field
approximation. As the density of the nucleon increases, all the screening
masses of mesons increase. It shows a different result with Brown-Rho scaling,
which implies a reduction in the mass of all the mesons in the nuclear matter
except the pion. Replacing the masses of the mesons with their corresponding
screening masses in Walecka-1 model, five saturation properties of the nuclear
matter are fixed reasonably, and then a density-dependent relativistic
mean-field model is proposed without introducing the non-linear self-coupling
terms of mesons.Comment: 14 pages, 3 figures, REVTEX4, Accepted for publication in Int. J.
Mod. Phys.
Learning Generative ConvNets via Multi-grid Modeling and Sampling
This paper proposes a multi-grid method for learning energy-based generative
ConvNet models of images. For each grid, we learn an energy-based probabilistic
model where the energy function is defined by a bottom-up convolutional neural
network (ConvNet or CNN). Learning such a model requires generating synthesized
examples from the model. Within each iteration of our learning algorithm, for
each observed training image, we generate synthesized images at multiple grids
by initializing the finite-step MCMC sampling from a minimal 1 x 1 version of
the training image. The synthesized image at each subsequent grid is obtained
by a finite-step MCMC initialized from the synthesized image generated at the
previous coarser grid. After obtaining the synthesized examples, the parameters
of the models at multiple grids are updated separately and simultaneously based
on the differences between synthesized and observed examples. We show that this
multi-grid method can learn realistic energy-based generative ConvNet models,
and it outperforms the original contrastive divergence (CD) and persistent CD.Comment: CVPR 201
In-Process Global Interpretation for Graph Learning via Distribution Matching
Graphs neural networks (GNNs) have emerged as a powerful graph learning model
due to their superior capacity in capturing critical graph patterns. To gain
insights about the model mechanism for interpretable graph learning, previous
efforts focus on post-hoc local interpretation by extracting the data pattern
that a pre-trained GNN model uses to make an individual prediction. However,
recent works show that post-hoc methods are highly sensitive to model
initialization and local interpretation can only explain the model prediction
specific to a particular instance. In this work, we address these limitations
by answering an important question that is not yet studied: how to provide
global interpretation of the model training procedure? We formulate this
problem as in-process global interpretation, which targets on distilling
high-level and human-intelligible patterns that dominate the training procedure
of GNNs. We further propose Graph Distribution Matching (GDM) to synthesize
interpretive graphs by matching the distribution of the original and
interpretive graphs in the feature space of the GNN as its training proceeds.
These few interpretive graphs demonstrate the most informative patterns the
model captures during training. Extensive experiments on graph classification
datasets demonstrate multiple advantages of the proposed method, including high
explanation accuracy, time efficiency and the ability to reveal class-relevant
structure.Comment: Under Revie
Poly[diimidazole-μ4-oxalato-μ2-oxalato-dicopper(II)]
The title compound, [Cu2(C2O4)2(C3H4N2)2]n, was obtained as an unexpected product under hydrothermal conditions. The CuII atom is in a Jahn–Teller-distorted octahedral environment formed by one imidazole N atom and five O atoms from three oxalate anions. The two independent oxalate anions are situated on centres of inversion and coordinate to the CuII atom in two different modes, viz. bidentate and monodentate. The bidentate anions bridge two CuII atoms, whereas the monodentate anions bridge four CuII atoms, leading to a layered arrangement parallel to (100). These layers are further linked into a final three-dimensional network structure via intermolecular N—H⋯O hydrogen bonds. The title compound is isotypic with the Zn analogue
Effective photon mass in nuclear matter and finite nuclei
Electromagnetic field in nuclear matter and nuclei are studied. In the
nuclear matter, because the expectation value of the electric charge density
operator is not zero, different in vacuum, the U(1) local gauge symmetry of
electric charge is spontaneously broken, and consequently, the photon gains an
effective mass through the Higgs mechanism. An alternative way to study the
effective mass of photon is to calculate the self-energy of photon
perturbatively. It shows that the effective mass of photon is about
in the symmetric nuclear matter at the saturation density and about at the surface of . It seems that
the two-body decay of a massive photon causes the sharp lines of
electron-positron pairs in the low energy heavy ion collision experiments of
.Comment: 10 pages, 2 figures, 1 table, REVTEX4, submitted to Int. J. Mod.
Phys.
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