2,484 research outputs found
Toward Interpretable Deep Reinforcement Learning with Linear Model U-Trees
Deep Reinforcement Learning (DRL) has achieved impressive success in many
applications. A key component of many DRL models is a neural network
representing a Q function, to estimate the expected cumulative reward following
a state-action pair. The Q function neural network contains a lot of implicit
knowledge about the RL problems, but often remains unexamined and
uninterpreted. To our knowledge, this work develops the first mimic learning
framework for Q functions in DRL. We introduce Linear Model U-trees (LMUTs) to
approximate neural network predictions. An LMUT is learned using a novel
on-line algorithm that is well-suited for an active play setting, where the
mimic learner observes an ongoing interaction between the neural net and the
environment. Empirical evaluation shows that an LMUT mimics a Q function
substantially better than five baseline methods. The transparent tree structure
of an LMUT facilitates understanding the network's learned knowledge by
analyzing feature influence, extracting rules, and highlighting the
super-pixels in image inputs.Comment: This paper is accepted by ECML-PKDD 201
Engineering chromium related single photon emitters in single crystal diamond
Color centers in diamond as single photon emitters, are leading candidates
for future quantum devices due to their room temperature operation and
photostability. The recently discovered chromium related centers are
particularly attractive since they possess narrow bandwidth emission and a very
short lifetime. In this paper we investigate the fabrication methodologies to
engineer these centers in monolithic diamond. We show that the emitters can be
successfully fabricated by ion implantation of chromium in conjunction with
oxygen or sulfur. Furthermore, our results indicate that the background
nitrogen concentration is an important parameter, which governs the probability
of success to generate these centers.Comment: 14 pages, 5 figure
wormholes and topological charge
I investigate solutions to the Euclidean Einstein-matter field equations with
topology in a theory with a massless periodic scalar
field and electromagnetism. These solutions carry winding number of the
periodic scalar as well as magnetic flux. They induce violations of a
quasi-topological conservation law which conserves the product of magnetic flux
and winding number on the background spacetime. I extend these solutions to a
model with stable loops of superconducting cosmic string, and interpret them as
contributing to the decay of such loops.Comment: 18 pages (includes 6 figs.), harvmac and epsf, CU-TP-62
A Study of Obscuration in Catadioptric Lenses
In this paper we will examine the effect of obscuration upon the various features we desired to image with a 157nm microstepper utilising a catadioptric lens. We will show the effect the obscuration has upon imaging when using not only conventional illumination and binary masks, but also when using a range of enhancement techniques such as off-axis illumination and phase-shifting masks. We will show how use of a large obscuration, whilst enhancing the signals for the densest features, actually degrades the signal for more isolated features. The level of obscuration must also take into account cross duty-ratio effects, i.e. the distribution of diffraction energy, for phase shifted features of various sizes. In this situation where a small sigma would be used a large level of obscuration can significantly increase biases. The choice of obscuration can have a major effect upon the imaging capabilities of a tool. In future, when the use of catadioptric lenses may be more widespread (for example this may happen at 157nm) it may be desirable to have the option to vary this obscuration dependant upon the pattern being imaged
Serious Games Application for Memory Training Using Egocentric Images
Mild cognitive impairment is the early stage of several neurodegenerative
diseases, such as Alzheimer's. In this work, we address the use of lifelogging
as a tool to obtain pictures from a patient's daily life from an egocentric
point of view. We propose to use them in combination with serious games as a
way to provide a non-pharmacological treatment to improve their quality of
life. To do so, we introduce a novel computer vision technique that classifies
rich and non rich egocentric images and uses them in serious games. We present
results over a dataset composed by 10,997 images, recorded by 7 different
users, achieving 79% of F1-score. Our model presents the first method used for
automatic egocentric images selection applicable to serious games.Comment: 11 page
The Potential and Challenges of CAD with Equational Constraints for SC-Square
Cylindrical algebraic decomposition (CAD) is a core algorithm within Symbolic
Computation, particularly for quantifier elimination over the reals and
polynomial systems solving more generally. It is now finding increased
application as a decision procedure for Satisfiability Modulo Theories (SMT)
solvers when working with non-linear real arithmetic. We discuss the potentials
from increased focus on the logical structure of the input brought by the SMT
applications and SC-Square project, particularly the presence of equational
constraints. We also highlight the challenges for exploiting these: primitivity
restrictions, well-orientedness questions, and the prospect of incrementality.Comment: Accepted into proceedings of MACIS 201
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