5,546 research outputs found
A randomized Kaczmarz algorithm with exponential convergence
The Kaczmarz method for solving linear systems of equations is an iterative
algorithm that has found many applications ranging from computer tomography to
digital signal processing. Despite the popularity of this method, useful
theoretical estimates for its rate of convergence are still scarce. We
introduce a randomized version of the Kaczmarz method for consistent,
overdetermined linear systems and we prove that it converges with expected
exponential rate. Furthermore, this is the first solver whose rate does not
depend on the number of equations in the system. The solver does not even need
to know the whole system, but only a small random part of it. It thus
outperforms all previously known methods on general extremely overdetermined
systems. Even for moderately overdetermined systems, numerical simulations as
well as theoretical analysis reveal that our algorithm can converge faster than
the celebrated conjugate gradient algorithm. Furthermore, our theory and
numerical simulations confirm a prediction of Feichtinger et al. in the context
of reconstructing bandlimited functions from nonuniform sampling
Uncovering protein interaction in abstracts and text using a novel linear model and word proximity networks
We participated in three of the protein-protein interaction subtasks of the
Second BioCreative Challenge: classification of abstracts relevant for
protein-protein interaction (IAS), discovery of protein pairs (IPS) and text
passages characterizing protein interaction (ISS) in full text documents. We
approached the abstract classification task with a novel, lightweight linear
model inspired by spam-detection techniques, as well as an uncertainty-based
integration scheme. We also used a Support Vector Machine and the Singular
Value Decomposition on the same features for comparison purposes. Our approach
to the full text subtasks (protein pair and passage identification) includes a
feature expansion method based on word-proximity networks. Our approach to the
abstract classification task (IAS) was among the top submissions for this task
in terms of the measures of performance used in the challenge evaluation
(accuracy, F-score and AUC). We also report on a web-tool we produced using our
approach: the Protein Interaction Abstract Relevance Evaluator (PIARE). Our
approach to the full text tasks resulted in one of the highest recall rates as
well as mean reciprocal rank of correct passages. Our approach to abstract
classification shows that a simple linear model, using relatively few features,
is capable of generalizing and uncovering the conceptual nature of
protein-protein interaction from the bibliome. Since the novel approach is
based on a very lightweight linear model, it can be easily ported and applied
to similar problems. In full text problems, the expansion of word features with
word-proximity networks is shown to be useful, though the need for some
improvements is discussed
CayleyNets: Graph Convolutional Neural Networks with Complex Rational Spectral Filters
The rise of graph-structured data such as social networks, regulatory
networks, citation graphs, and functional brain networks, in combination with
resounding success of deep learning in various applications, has brought the
interest in generalizing deep learning models to non-Euclidean domains. In this
paper, we introduce a new spectral domain convolutional architecture for deep
learning on graphs. The core ingredient of our model is a new class of
parametric rational complex functions (Cayley polynomials) allowing to
efficiently compute spectral filters on graphs that specialize on frequency
bands of interest. Our model generates rich spectral filters that are localized
in space, scales linearly with the size of the input data for
sparsely-connected graphs, and can handle different constructions of Laplacian
operators. Extensive experimental results show the superior performance of our
approach, in comparison to other spectral domain convolutional architectures,
on spectral image classification, community detection, vertex classification
and matrix completion tasks
Joint Optimization Framework for Operational Cost Minimization in Green Coverage-Constrained Wireless Networks
In this work, we investigate the joint optimization of base station (BS)
location, its density, and transmit power allocation to minimize the overall
network operational cost required to meet an underlying coverage constraint at
each user equipment (UE), which is randomly deployed following the binomial
point process (BPP). As this joint optimization problem is nonconvex and
combinatorial in nature, we propose a non-trivial solution methodology that
effectively decouples it into three individual optimization problems. Firstly,
by using the distance distribution of the farthest UE from the BS, we present
novel insights on optimal BS location in an optimal sectoring type for a given
number of BSs. After that we provide a tight approximation for the optimal
transmit power allocation to each BS. Lastly, using the latter two results, the
optimal number of BSs that minimize the operational cost is obtained. Also, we
have investigated both circular and square field deployments. Numerical results
validate the analysis and provide practical insights on optimal BS deployment.
We observe that the proposed joint optimization framework, that solves the
coverage probability versus operational cost tradeoff, can yield a significant
reduction of about in the operational cost as compared to the benchmark
fixed allocation scheme.Comment: 30 pages, 15 figures, submitted to IEEE Transactions on Green
Communications and Networkin
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