5,834 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
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Wintertime Transport of Reactive Trace Gases From East Asia Into the Deep Tropics
Decrease in water clarity of the southern and central North Sea during the 20th century
Light in the marine environment is a key environmental variable coupling physics to marine biogeochemistry and ecology. Weak light penetration reduces light available for photosynthesis, changing energy fluxes through the marine food web. Based on published and unpublished data, this study shows that the central and southern North Sea has become significantly less clear over the second half of the 20th century. In particular, in the different regions and seasons investigated, the average Secchi depth pre-1950 decreased between 25% and 75% compared to the average Secchi depth post-1950. Consequently, in summer pre-1950, most (74%) of the sea floor in the permanently mixed area off East Anglia was within the photic zone. For the last 25+ years, changes in water clarity were more likely driven by an increase in the concentration of suspended sediments, rather than phytoplankton. We suggest that a combination of causes have contributed to this increase in suspended sediments such as changes in sea-bed communities and in weather patterns, decreased sink of sediments in estuaries, and increased coastal erosion. A predicted future increase in storminess (Beniston et al., 2007; Kovats et al., 2014) could enhance the concentration of suspended sediments in the water column and consequently lead to a further decrease in clarity, with potential impacts on phytoplankton production, CO2 fluxes, and fishery production
Soft eSkin:distributed touch sensing with harmonized energy and computing
Inspired by biology, significant advances have been made in the field of electronic skin (eSkin) or tactile skin. Many of these advances have come through mimicking the morphology of human skin and by distributing few touch sensors in an area. However, the complexity of human skin goes beyond mimicking few morphological features or using few sensors. For example, embedded computing (e.g. processing of tactile data at the point of contact) is centric to the human skin as some neuroscience studies show. Likewise, distributed cell or molecular energy is a key feature of human skin. The eSkin with such features, along with distributed and embedded sensors/electronics on soft substrates, is an interesting topic to explore. These features also make eSkin significantly different from conventional computing. For example, unlike conventional centralized computing enabled by miniaturized chips, the eSkin could be seen as a flexible and wearable large area computer with distributed sensors and harmonized energy. This paper discusses these advanced features in eSkin, particularly the distributed sensing harmoniously integrated with energy harvesters, storage devices and distributed computing to read and locally process the tactile sensory data. Rapid advances in neuromorphic hardware, flexible energy generation, energy-conscious electronics, flexible and printed electronics are also discussed. This article is part of the theme issue âHarmonizing energy-autonomous computing and intelligenceâ
Weakly Supervised Learning by a Confusion Matrix of Contexts
© 2019, Springer Nature Switzerland AG. Context consideration can help provide more background and related information for weakly supervised learning. The inclusion of less documented historical and environmental context in researching diabetes amongst Pima Indians uncovered reasons which were more likely to explain why some Pima Indians had much higher rates of diabetes than Caucasians, primarily due to historical, environmental and social causes rather than their specific genetic patterns or ethnicity as suggested by many medical studies. If historical and environmental factors are considered as external contexts when not included as part of a dataset for research, some forms of internal contexts may also exist inside the dataset without being declared. This paper discusses a context construction model that transforms a confusion matrix into a matrix of categorical, incremental and correlational context to emulate a kind of internal context to search for more informative patterns in order to improve weakly supervised learning from limited labeled samples for unlabeled data. When the negative and positive labeled samples and misclassification errors are compared to âhappy familiesâ and âunhappy familiesâ, the contexts constructed by this model in the classification experiments reflected the Anna Karenina principle well - âHappy families are all alike; every unhappy family is unhappy in its own wayâ, an encouraging sign to further explore contexts associated with harmonizing patterns and divisive causes for knowledge discovery in a world of uncertainty
Yukawa Unification and the Superpartner Mass Scale
Naturalness in supersymmetry (SUSY) is under siege by increasingly stringent
LHC constraints, but natural electroweak symmetry breaking still remains the
most powerful motivation for superpartner masses within experimental reach. If
naturalness is the wrong criterion then what determines the mass scale of the
superpartners? We motivate supersymmetry by (1) gauge coupling unification, (2)
dark matter, and (3) precision b-tau Yukawa unification. We show that for an
LSP that is a bino-Higgsino admixture, these three requirements lead to an
upper-bound on the stop and sbottom masses in the several TeV regime because
the threshold correction to the bottom mass at the superpartner scale is
required to have a particular size. For tan beta about 50, which is needed for
t-b-tau unification, the stops must be lighter than 2.8 TeV when A_t has the
opposite sign of the gluino mass, as is favored by renormalization group
scaling. For lower values of tan beta, the top and bottom squarks must be even
lighter. Yukawa unification plus dark matter implies that superpartners are
likely in reach of the LHC, after the upgrade to 14 (or 13) TeV, independent of
any considerations of naturalness. We present a model-independent, bottom-up
analysis of the SUSY parameter space that is simultaneously consistent with
Yukawa unification and the hint for m_h = 125 GeV. We study the flavor and dark
matter phenomenology that accompanies this Yukawa unification. A large portion
of the parameter space predicts that the branching fraction for B_s to mu^+
mu^- will be observed to be significantly lower than the SM value.Comment: 34 pages plus appendices, 20 figure
Using Bayesian Networks and Machine Learning to Predict Computer Science Success
Bayesian Networks and Machine Learning techniques were
evaluated and compared for predicting academic performance of Computer
Science students at the University of Cape Town. Bayesian Networks
performed similarly to other classification models. The causal links AQ1
inherent in Bayesian Networks allow for understanding of the contributing
factors for academic success in this field. The most effective indicators
of success in first-year âcoreâ courses in Computer Science included the
studentâs scores for Mathematics and Physics as well as their aptitude for
learning and their work ethos. It was found that unsuccessful students
could be identified with â91% accuracy. This could help to increase
throughput as well as student wellbeing at university
Implications of large dimuon CP asymmetry in B_{d,s} decays on minimal flavor violation with low tan beta
The D0 collaboration has recently announced evidence for a dimuon CP
asymmetry in B_{d,s} decays of order one percent. If confirmed, this asymmetry
requires new physics. We argue that for minimally flavor violating (MFV) new
physics, and at low tan beta=v_u/v_d, there are only two four-quark operators
(Q_{2,3}) that can provide the required CP violating effect. The scale of such
new physics must lie below 260 GeV sqrt{tan beta}. The effect is universal in
the B_s and B_d systems, leading to S_{psi K}~sin(2beta)-0.15 and S_{psi
phi}~0.25. The effects on epsilon_K and on electric dipole moments are
negligible. The most plausible mechanism is tree-level scalar exchange. MFV
supersymmetry with low tan beta will be excluded. Finally, we explain how a
pattern of deviations from the Standard Model predictions for S_{psi phi},
S_{psi K} and epsilon_K can be used to test MFV and, if MFV holds, to probe its
structure in detail.Comment: 11 pages. v2: References adde
Using technology to deliver cancer follow-up : a systematic review
Peer reviewedPublisher PD
Minimal flavour violation extensions of the seesaw
We analyze the most natural formulations of the minimal lepton flavour
violation hypothesis compatible with a type-I seesaw structure with three heavy
singlet neutrinos N, and satisfying the requirement of being predictive, in the
sense that all LFV effects can be expressed in terms of low energy observables.
We find a new interesting realization based on the flavour group (being and respectively the SU(2) singlet and
doublet leptons). An intriguing feature of this realization is that, in the
normal hierarchy scenario for neutrino masses, it allows for sizeable
enhancements of transitions with respect to LFV processes involving
the lepton. We also discuss how the symmetries of the type-I seesaw
allow for a strong suppression of the N mass scale with respect to the scale of
lepton number breaking, without implying a similar suppression for possible
mechanisms of N productionComment: 14 pages, 6 figure
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