20,873 research outputs found
Building and Equipment Trends: II
published or submitted for publicatio
Random deep neural networks are biased towards simple functions
We prove that the binary classifiers of bit strings generated by random wide
deep neural networks with ReLU activation function are biased towards simple
functions. The simplicity is captured by the following two properties. For any
given input bit string, the average Hamming distance of the closest input bit
string with a different classification is at least sqrt(n / (2{\pi} log n)),
where n is the length of the string. Moreover, if the bits of the initial
string are flipped randomly, the average number of flips required to change the
classification grows linearly with n. These results are confirmed by numerical
experiments on deep neural networks with two hidden layers, and settle the
conjecture stating that random deep neural networks are biased towards simple
functions. This conjecture was proposed and numerically explored in [Valle
P\'erez et al., ICLR 2019] to explain the unreasonably good generalization
properties of deep learning algorithms. The probability distribution of the
functions generated by random deep neural networks is a good choice for the
prior probability distribution in the PAC-Bayesian generalization bounds. Our
results constitute a fundamental step forward in the characterization of this
distribution, therefore contributing to the understanding of the generalization
properties of deep learning algorithms
On the use of self-organizing maps to accelerate vector quantization
Self-organizing maps (SOM) are widely used for their topology preservation
property: neighboring input vectors are quantified (or classified) either on
the same location or on neighbor ones on a predefined grid. SOM are also widely
used for their more classical vector quantization property. We show in this
paper that using SOM instead of the more classical Simple Competitive Learning
(SCL) algorithm drastically increases the speed of convergence of the vector
quantization process. This fact is demonstrated through extensive simulations
on artificial and real examples, with specific SOM (fixed and decreasing
neighborhoods) and SCL algorithms.Comment: A la suite de la conference ESANN 199
Electron-Ion Structure Factors and the General Accuracy of Linear Response
We show that electron-ion structure factors in fluid metallic systems can be
well understood from an application of linear response in the electron system,
combined with hard-sphere like correlation for the ionic component. In
particular, we predict that electron-ion structure factors fall into two
general classes, one for high () and one for low () valence
metals, and make suggestions for experiments to test these ideas. In addition,
we show how the general success of electronic linear response for most metallic
systems stems in part from an intrinsic interference between atomic and
electronic length scales which weakens the nonlinear response. The main
exception to this is metallic hydrogen.Comment: to appear in J. Non-Crystalline Solids, part of LAM-10 conference
proceedings. RevTex, 12 pages, 2 figure
Light-addressable liquid crystal polymer dispersed liquid crystal
Scattering-free liquid crystal polymer-dispersed liquid crystal polymer (LCPDLC)
films are fabricated by combining a room temperature polymerizable liquid crystal (LC)
monomer with a mesogenic photosensitive LC. The morphological and photosensitive
properties of the system are analysed with polarized optical microscopy and high resolution
scanning and transmission electron microscopy. A two-phase morphology comprised of
oriented fibril-like polymeric structures interwoven with nanoscale domains of phase
separated LC exists. The nanoscale of the structures enables an absence of scattering which
allows imaging through the LCPDLC sample without optical distortion. The use of a
mesogenic monomer enables much smaller phase separated domains as compared to nonmesogenic systems. All-optical experiments show that the transmitted intensity, measured
through parallel polarizers, can be modulated by the low power density radiation (31
mW/cm2) of a suitable wavelength (532 nm). The reversible and repeatable transmission
change is due to the photoinduced trans-cis photoisomerization process. The birefringence
variation (0.01) obtained by optically pumping the LCPDLC films allow their use as an alloptical phase modulato
Why the governmentâs Help to Buy scheme wonât reach the right people
The governmentâs Help to Buy scheme intends to boost homeownership by reducing the down payment required. Analysis by Robbie de Santos and Toby Lloyd of Shelter, also detailed in a report launched today, shows that overall affordability is a bigger problem than the big deposits required by mortgage lenders. Easy finance into a supply constrained market can only boost up house prices, pushing them further out of reach for the millions of lower and middle income households already frozen out of the housing market
Keplerian discs around post-AGB stars: a common phenomenon?
Aims: We aim at showing that the broad-band SED characteristics of our sample
of post-AGB stars are best interpreted, assuming the circumstellar dust is
stored in Keplerian rotating passive discs.
Methods: We present a homogeneous and systematic study of the Spectral Energy
Distributions (SEDs) of a sample of 51 post-AGB objects. The selection criteria
to define the whole sample were tuned to cover the broad-band characteristics
of known binary post-AGB stars. The whole sample includes 20 dusty RV Tauri
stars from the General Catalogue of Variable Stars (GCVS). We supplemented our
own Geneva optical photometry with literature data to cover a broad range of
fluxes from the UV to the far-IR.
Results: All the SEDs display very similar characteristics: a large IR excess
with a dust excess starting near the sublimation temperature, irrespective of
the effective temperature of the central star. Moreover, when available, the
long wavelength fluxes show a black-body slope indicative of the presence of a
component of large mm sized grains.
Conclusions: We argue that in all systems, gravitationally bound dusty discs
are present. The discs must be puffed-up to cover a large opening angle for the
central star and we argue that the discs have some similarity with the passive
discs detected around young stellar objects. We interpret the presence of a
disc to be a signature for binarity of the central object, but this will need
confirmation by long-term monitoring of the radial velocities. We argue that
dusty RV Tauri stars are those binaries which happen to be in the Population II
instability strip.Comment: 29 pages, 5 figures, accepted for publication in A&
Infant cortex responds to other humans from shortly after birth
A significant feature of the adult human brain is its ability to selectively process information about conspecifics. Much debate has centred on whether this specialization is primarily a result of phylogenetic adaptation, or whether the brain acquires expertise in processing social stimuli as a result of its being born into an intensely social environment. Here we study the haemodynamic response in cortical areas of newborns (1â5 days old) while they passively viewed dynamic human or mechanical action videos. We observed activation selective to a dynamic face stimulus over bilateral posterior temporal cortex, but no activation in response to a moving human arm. This selective activation to the social stimulus correlated with age in hours over the first few days post partum. Thus, even very limited experience of face-to-face interaction with other humans may be sufficient to elicit social stimulus activation of relevant cortical regions
Dose response severity functions for acoustic disturbance in cetaceans using recurrent event survival analysis
This work was financially supported by the U. S. Office of Naval Research grant N00014â12â1â0204, under the project âMultiâstudy Ocean acoustics Human effects Analysisâ (MOCHA). . L. Tyack received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. The case study data were provided by the 3S project, which was funded by the U.S. Office of Naval Research, the Norwegian Ministry of Defense, the Netherlands Ministry of Defense, and WWF Norway.Behavioral response studies (BRSs) aim to enhance our understanding of the behavior changes made by animals in response to specific exposure levels of different stimuli, often presented in an increasing dosage. Here, we focus on BRSs that aim to understand behavioral responses of free-ranging whales and dolphins to manmade acoustic signals (although the methods are applicable more generally). One desired outcome of these studies is dose-response functions relevant to different species, signals and contexts. We adapted and applied recurrent event survival analysis (Cox proportional hazard models) to data from the 3S BRS project, where multiple behavioral responses of different severities had been observed per experimental exposure and per individual based upon expert scoring. We included species, signal type, exposure number and behavioral state prior to exposure as potential covariates. The best model included all main effect terms, with the exception of exposure number, as well as two interaction terms. The interactions between signal and behavioral state, and between species and behavioral state highlighted that the sensitivity of animals to different signal types (a 6â7 kHz upsweep sonar signal [MFAS] or a 1â2 kHz upsweep sonar signal [LFAS]) depended on their behavioral state (feeding or nonfeeding), and this differed across species. Of the three species included in this analysis (sperm whale [Physeter macrocephalus], killer whale [Orcinus orca] and long-finned pilot whale [Globicephala melas]), killer whales were consistently the most likely to exhibit behavioral responses to naval sonar exposure. We conclude that recurrent event survival analysis provides an effective framework for fitting dose-response severity functions to data from behavioral response studies. It can provide outputs that can help government and industry to evaluate the potential impacts of anthropogenic sound production in the ocean.Publisher PDFPeer reviewe
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