109,252 research outputs found
Addressing Model Vulnerability to Distributional Shifts over Image Transformation Sets
We are concerned with the vulnerability of computer vision models to
distributional shifts. We formulate a combinatorial optimization problem that
allows evaluating the regions in the image space where a given model is more
vulnerable, in terms of image transformations applied to the input, and face it
with standard search algorithms. We further embed this idea in a training
procedure, where we define new data augmentation rules according to the image
transformations that the current model is most vulnerable to, over iterations.
An empirical evaluation on classification and semantic segmentation problems
suggests that the devised algorithm allows to train models that are more robust
against content-preserving image manipulations and, in general, against
distributional shifts.Comment: ICCV 2019 (camera ready
Learning Deep Similarity Metric for 3D MR-TRUS Registration
Purpose: The fusion of transrectal ultrasound (TRUS) and magnetic resonance
(MR) images for guiding targeted prostate biopsy has significantly improved the
biopsy yield of aggressive cancers. A key component of MR-TRUS fusion is image
registration. However, it is very challenging to obtain a robust automatic
MR-TRUS registration due to the large appearance difference between the two
imaging modalities. The work presented in this paper aims to tackle this
problem by addressing two challenges: (i) the definition of a suitable
similarity metric and (ii) the determination of a suitable optimization
strategy.
Methods: This work proposes the use of a deep convolutional neural network to
learn a similarity metric for MR-TRUS registration. We also use a composite
optimization strategy that explores the solution space in order to search for a
suitable initialization for the second-order optimization of the learned
metric. Further, a multi-pass approach is used in order to smooth the metric
for optimization.
Results: The learned similarity metric outperforms the classical mutual
information and also the state-of-the-art MIND feature based methods. The
results indicate that the overall registration framework has a large capture
range. The proposed deep similarity metric based approach obtained a mean TRE
of 3.86mm (with an initial TRE of 16mm) for this challenging problem.
Conclusion: A similarity metric that is learned using a deep neural network
can be used to assess the quality of any given image registration and can be
used in conjunction with the aforementioned optimization framework to perform
automatic registration that is robust to poor initialization.Comment: To appear on IJCAR
Statistical Model of Shape Moments with Active Contour Evolution for Shape Detection and Segmentation
This paper describes a novel method for shape representation and robust image segmentation. The proposed method combines two well known methodologies, namely, statistical shape models and active contours implemented in level set framework. The shape detection is achieved by maximizing a posterior function that consists of a prior shape probability model and image likelihood function conditioned on shapes. The statistical shape model is built as a result of a learning process based on nonparametric probability estimation in a PCA reduced feature space formed by the Legendre moments of training silhouette images. A greedy strategy is applied to optimize the proposed cost function by iteratively evolving an implicit active contour in the image space and subsequent constrained optimization of the evolved shape in the reduced shape feature space. Experimental results presented in the paper demonstrate that the proposed method, contrary to many other active contour segmentation methods, is highly resilient to severe random and structural noise that could be present in the data
A Powerful Optimization Tool for Analog Integrated Circuits Design
This paper presents a new optimization tool for analog circuit design. Proposed tool is based on the robust version of the differential evolution optimization method. Corners of technology, temperature, voltage and current supplies are taken into account during the optimization. That ensures robust resulting circuits. Those circuits usually do not need any schematic change and are ready for the layout.. The newly developed tool is implemented directly to the Cadence design environment to achieve very short setup time of the optimization task. The design automation procedure was enhanced by optimization watchdog feature. It was created to control optimization progress and moreover to reduce the search space to produce better design in shorter time. The optimization algorithm presented in this paper was successfully tested on several design examples
Data-driven Identification and Prediction of Power System Dynamics Using Linear Operators
In this paper, we propose linear operator theoretic framework involving
Koopman operator for the data-driven identification of power system dynamics.
We explicitly account for noise in the time series measurement data and propose
robust approach for data-driven approximation of Koopman operator for the
identification of nonlinear power system dynamics. The identified model is used
for the prediction of state trajectories in the power system. The application
of the framework is illustrated using an IEEE nine bus test system.Comment: Accepted for publication in IEEE Power and Energy System General
Meeting 201
Deep reinforcement learning for robust quantum optimization
Machine learning techniques based on artificial neural networks have been
successfully applied to solve many problems in science. One of the most
interesting domains of machine learning, reinforcement learning, has natural
applicability for optimization problems in physics. In this work we use deep
reinforcement learning and Chopped Random Basis optimization, to solve an
optimization problem based on the insertion of an off-center barrier in a
quantum Szilard engine. We show that using designed protocols for the time
dependence of the barrier strength, we can achieve an equal splitting of the
wave function (1/2 probability to find the particle on either side of the
barrier) even for an asymmetric Szilard engine in such a way that no
information is lost when measuring which side the particle is found. This
implies that the asymmetric non-adiabatic Szilard engine can operate with the
same efficiency as the traditional Szilard engine, with adiabatic insertion of
a central barrier. We compare the two optimization methods, and demonstrate the
advantage of reinforcement learning when it comes to constructing robust and
noise-resistant protocols.Comment: 9 pages, 8 figure
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