6,023 research outputs found
MDL Convergence Speed for Bernoulli Sequences
The Minimum Description Length principle for online sequence
estimation/prediction in a proper learning setup is studied. If the underlying
model class is discrete, then the total expected square loss is a particularly
interesting performance measure: (a) this quantity is finitely bounded,
implying convergence with probability one, and (b) it additionally specifies
the convergence speed. For MDL, in general one can only have loss bounds which
are finite but exponentially larger than those for Bayes mixtures. We show that
this is even the case if the model class contains only Bernoulli distributions.
We derive a new upper bound on the prediction error for countable Bernoulli
classes. This implies a small bound (comparable to the one for Bayes mixtures)
for certain important model classes. We discuss the application to Machine
Learning tasks such as classification and hypothesis testing, and
generalization to countable classes of i.i.d. models.Comment: 28 page
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The effects of room design on computer-supported collaborative learning in a multi-touch classroom.
While research indicates that technology can be useful for supporting learning and collaboration, there is still relatively little uptake or widespread implementation of these technologies in classrooms. In this paper, we explore one aspect of the development of a multi-touch classroom, looking at two different designs of the classroom environment to explore how classroom layout may influence group interaction and learning. Three classes of students working in groups of four were taught in the traditional forward-facing room condition, while three classes worked in a centered room condition. Our results indicate that while the outcomes on tasks were similar across conditions, groups engaged in more talk (but not more off-task talk) in a centered room layout, than in a traditional forward-facing room. These results suggest that the use of technology in the classroom may be influenced by the location of the technology, both in terms of the learning outcomes and the interaction behaviors of students. The findings highlight the importance of considering the learning environment when designing technology to support learning, and ensuring that integration of technology into formal learning environments is done with attention to how the technology may disrupt, or contribute to, the classroom interaction practices
On Convergence Properties of Shannon Entropy
Convergence properties of Shannon Entropy are studied. In the differential
setting, it is shown that weak convergence of probability measures, or
convergence in distribution, is not enough for convergence of the associated
differential entropies. A general result for the desired differential entropy
convergence is provided, taking into account both compactly and uncompactly
supported densities. Convergence of differential entropy is also characterized
in terms of the Kullback-Liebler discriminant for densities with fairly general
supports, and it is shown that convergence in variation of probability measures
guarantees such convergence under an appropriate boundedness condition on the
densities involved. Results for the discrete setting are also provided,
allowing for infinitely supported probability measures, by taking advantage of
the equivalence between weak convergence and convergence in variation in this
setting.Comment: Submitted to IEEE Transactions on Information Theor
Playing for Data: Ground Truth from Computer Games
Recent progress in computer vision has been driven by high-capacity models
trained on large datasets. Unfortunately, creating large datasets with
pixel-level labels has been extremely costly due to the amount of human effort
required. In this paper, we present an approach to rapidly creating
pixel-accurate semantic label maps for images extracted from modern computer
games. Although the source code and the internal operation of commercial games
are inaccessible, we show that associations between image patches can be
reconstructed from the communication between the game and the graphics
hardware. This enables rapid propagation of semantic labels within and across
images synthesized by the game, with no access to the source code or the
content. We validate the presented approach by producing dense pixel-level
semantic annotations for 25 thousand images synthesized by a photorealistic
open-world computer game. Experiments on semantic segmentation datasets show
that using the acquired data to supplement real-world images significantly
increases accuracy and that the acquired data enables reducing the amount of
hand-labeled real-world data: models trained with game data and just 1/3 of the
CamVid training set outperform models trained on the complete CamVid training
set.Comment: Accepted to the 14th European Conference on Computer Vision (ECCV
2016
In Memoriam: Daniel J. Meltzer
Sedan Ă„r 2006 har den syntetiskt framstĂ€llda drogen spice existerat i Sverige, men först Ă„r 2008 blev drogen populĂ€r och tidningar började rikta uppmĂ€rksamhet mot den. Genom att drogen kan byta skepnad i uppbyggnaden kan den förbli laglig, dĂ€rför kan egentligen namnet âspiceâ inte betraktas som ett enhetligt begrepp. VĂ„rt syfte med denna studie blev att granska hur drogen spice beskrivs i tidningar och forskning. Ăven hur drogen betraktas gĂ€llande psykosociala och medicinska avseenden. Detta i förhĂ„llande till socialkonstruktivistiskt perspektiv. Den metod som vi valde att anvĂ€nda oss av i studien var kvantitativ innehĂ„llsanalys. Genom analys av 80 stycken svenska tidningsartiklar hĂ€mtade ur databasen mediearkivet, samt vetenskapliga artiklar och litteratur har vi besvarat vĂ„ra frĂ„gestĂ€llningar. De resultat vi fick frĂ„n analyser visade pĂ„ att tidningar kan vara av betydande roll för ungdomars attityder. Tidningar kan utföra bland annat skrĂ€mselpropaganda för att upplysa och förhindra brukandet av spice, dessvĂ€rre visar resultatet en motsatt effekt. Forskning visar att bruk av spice kan pĂ„verka relationer och arbete negativt. Dessutom Ă€r nĂ„gra bieffekter av spice bröstsmĂ€rtor, vanförestĂ€llningar, sjĂ€lvmordstankar och hjĂ€rtstopp
Ubiquity of optical activity in planar metamaterial scatterers
Recently it was discovered that periodic lattices of metamaterial scatterers
show optical activity, even if the scatterers or lattice show no 2D or 3D
chirality, if the illumination breaks symmetry. In this Letter we demonstrate
that such `pseudo-chirality' is intrinsic to any single planar metamaterial
scatterer and in fact has a well-defined value at a universal bound. We argue
that in any circuit model, a nonzero electric and magnetic polarizability
derived from a single resonance automatically imply strong bianisotropy, i.e.,
magneto-electric cross polarizability at the universal bound set by energy
conservation. We confirm our claim by extracting polarizability tensors and
cross sections for handed excitation from transmission measurements on
near-infrared split ring arrays, and electrodynamic simulations for diverse
metamaterial scatterers.Comment: 5 pages, 4 figure
Ab initio parametrised model of strain-dependent solubility of H in alpha-iron
The calculated effects of interstitial hydrogen on the elastic properties of
alpha-iron from our earlier work are used to describe the H interactions with
homogeneous strain fields using ab initio methods. In particular we calculate
the H solublility in Fe subject to hydrostatic, uniaxial, and shear strain. For
comparison, these interactions are parametrised successfully using a simple
model with parameters entirely derived from ab initio methods. The results are
used to predict the solubility of H in spatially-varying elastic strain fields,
representative of realistic dislocations outside their core. We find a strong
directional dependence of the H-dislocation interaction, leading to strong
attraction of H by the axial strain components of edge dislocations and by
screw dislocations oriented along the critical slip direction. We
further find a H concentration enhancement around dislocation cores, consistent
with experimental observations.Comment: part 2/2 from splitting of 1009.3784 (first part was 1102.0187),
minor changes from previous version
dc readout experiment at the Caltech 40m prototype interferometer
The Laser Interferometer Gravitational Wave Observatory (LIGO) operates a 40m prototype interferometer on the Caltech campus. The primary mission of the prototype is to serve as an experimental testbed for upgrades to the LIGO interferometers and for gaining experience with advanced interferometric techniques, including detuned resonant sideband extraction (i.e. signal recycling) and dc readout (optical homodyne detection). The former technique will be employed in Advanced LIGO, and the latter in both Enhanced and Advanced LIGO. Using dc readout for gravitational wave signal extraction has several technical advantages, including reduced laser and oscillator noise couplings as well as reduced shot noise, when compared to the traditional rf readout technique (optical heterodyne detection) currently in use in large-scale ground-based interferometric gravitational wave detectors. The Caltech 40m laboratory is currently prototyping a dc readout system for a fully suspended interferometric gravitational wave detector. The system includes an optical filter cavity at the interferometer's output port, and the associated controls and optics to ensure that the filter cavity is optimally coupled to the interferometer. We present the results of measurements to characterize noise couplings in rf and dc readout using this system
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