31,170 research outputs found
Bilateral Random Projections
Low-rank structure have been profoundly studied in data mining and machine
learning. In this paper, we show a dense matrix 's low-rank approximation
can be rapidly built from its left and right random projections and
, or bilateral random projection (BRP). We then show power scheme
can further improve the precision. The deterministic, average and deviation
bounds of the proposed method and its power scheme modification are proved
theoretically. The effectiveness and the efficiency of BRP based low-rank
approximation is empirically verified on both artificial and real datasets.Comment: 17 pages, 3 figures, technical repor
Constrained low-tubal-rank tensor recovery for hyperspectral images mixed noise removal by bilateral random projections
In this paper, we propose a novel low-tubal-rank tensor recovery model, which
directly constrains the tubal rank prior for effectively removing the mixed
Gaussian and sparse noise in hyperspectral images. The constraints of
tubal-rank and sparsity can govern the solution of the denoised tensor in the
recovery procedure. To solve the constrained low-tubal-rank model, we develop
an iterative algorithm based on bilateral random projections to efficiently
solve the proposed model. The advantage of random projections is that the
approximation of the low-tubal-rank tensor can be obtained quite accurately in
an inexpensive manner. Experimental examples for hyperspectral image denoising
are presented to demonstrate the effectiveness and efficiency of the proposed
method.Comment: Accepted by IGARSS 201
Spectral theorems for random walks on mapping class groups and
We establish spectral theorems for random walks on mapping class groups of
connected, closed, oriented, hyperbolic surfaces, and on . In
both cases, we relate the asymptotics of the stretching factor of the
diffeomorphism/automorphism obtained at time of the random walk to the
Lyapunov exponent of the walk, which gives the typical growth rate of the
length of a curve -- or of a conjugacy class in -- under a random product
of diffeomorphisms/automorphisms.
In the mapping class group case, we first observe that the drift of the
random walk in the curve complex is also equal to the linear growth rate of the
translation lengths in this complex. By using a contraction property of typical
Teichm\"uller geodesics, we then lift the above fact to the realization of the
random walk on the Teichm\"uller space. For the case of , we
follow the same procedure with the free factor complex in place of the curve
complex, and the outer space in place of the Teichm\"uller space. A general
criterion is given for making the lifting argument possible.Comment: 45 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1506.0724
PadChest: A large chest x-ray image dataset with multi-label annotated reports
We present a labeled large-scale, high resolution chest x-ray dataset for the
automated exploration of medical images along with their associated reports.
This dataset includes more than 160,000 images obtained from 67,000 patients
that were interpreted and reported by radiologists at Hospital San Juan
Hospital (Spain) from 2009 to 2017, covering six different position views and
additional information on image acquisition and patient demography. The reports
were labeled with 174 different radiographic findings, 19 differential
diagnoses and 104 anatomic locations organized as a hierarchical taxonomy and
mapped onto standard Unified Medical Language System (UMLS) terminology. Of
these reports, 27% were manually annotated by trained physicians and the
remaining set was labeled using a supervised method based on a recurrent neural
network with attention mechanisms. The labels generated were then validated in
an independent test set achieving a 0.93 Micro-F1 score. To the best of our
knowledge, this is one of the largest public chest x-ray database suitable for
training supervised models concerning radiographs, and the first to contain
radiographic reports in Spanish. The PadChest dataset can be downloaded from
http://bimcv.cipf.es/bimcv-projects/padchest/
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Gain Modulation by Corticostriatal and Thalamostriatal Input Signals during Reward-Conditioned Behavior.
The cortex and thalamus send excitatory projections to the striatum, but little is known about how these inputs, either individually or collectively, regulate striatal dynamics during behavior. The lateral striatum receives overlapping input from the secondary motor cortex (M2), an area involved in licking, and the parafascicular thalamic nucleus (PF). Using neural recordings, together with optogenetic terminal inhibition, we examine the contribution of M2 and PF projections on medium spiny projection neuron (MSN) activity as mice performed an anticipatory licking task. Each input has a similar contribution to striatal activity. By comparing how suppressing single or multiple projections altered striatal activity, we find that cortical and thalamic input signals modulate MSN gain and that this effect is more pronounced in a temporally specific period of the task following the cue presentation. These results demonstrate that cortical and thalamic inputs synergistically regulate striatal output during reward-conditioned behavior
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