2,638 research outputs found
PAC-Bayes and Domain Adaptation
We provide two main contributions in PAC-Bayesian theory for domain
adaptation where the objective is to learn, from a source distribution, a
well-performing majority vote on a different, but related, target distribution.
Firstly, we propose an improvement of the previous approach we proposed in
Germain et al. (2013), which relies on a novel distribution pseudodistance
based on a disagreement averaging, allowing us to derive a new tighter domain
adaptation bound for the target risk. While this bound stands in the spirit of
common domain adaptation works, we derive a second bound (introduced in Germain
et al., 2016) that brings a new perspective on domain adaptation by deriving an
upper bound on the target risk where the distributions' divergence-expressed as
a ratio-controls the trade-off between a source error measure and the target
voters' disagreement. We discuss and compare both results, from which we obtain
PAC-Bayesian generalization bounds. Furthermore, from the PAC-Bayesian
specialization to linear classifiers, we infer two learning algorithms, and we
evaluate them on real data.Comment: Neurocomputing, Elsevier, 2019. arXiv admin note: substantial text
overlap with arXiv:1503.0694
A New PAC-Bayesian Perspective on Domain Adaptation
We study the issue of PAC-Bayesian domain adaptation: We want to learn, from
a source domain, a majority vote model dedicated to a target one. Our
theoretical contribution brings a new perspective by deriving an upper-bound on
the target risk where the distributions' divergence---expressed as a
ratio---controls the trade-off between a source error measure and the target
voters' disagreement. Our bound suggests that one has to focus on regions where
the source data is informative.From this result, we derive a PAC-Bayesian
generalization bound, and specialize it to linear classifiers. Then, we infer a
learning algorithmand perform experiments on real data.Comment: Published at ICML 201
PAC-Bayesian Learning and Domain Adaptation
In machine learning, Domain Adaptation (DA) arises when the distribution gen-
erating the test (target) data differs from the one generating the learning
(source) data. It is well known that DA is an hard task even under strong
assumptions, among which the covariate-shift where the source and target
distributions diverge only in their marginals, i.e. they have the same labeling
function. Another popular approach is to consider an hypothesis class that
moves closer the two distributions while implying a low-error for both tasks.
This is a VC-dim approach that restricts the complexity of an hypothesis class
in order to get good generalization. Instead, we propose a PAC-Bayesian
approach that seeks for suitable weights to be given to each hypothesis in
order to build a majority vote. We prove a new DA bound in the PAC-Bayesian
context. This leads us to design the first DA-PAC-Bayesian algorithm based on
the minimization of the proposed bound. Doing so, we seek for a \rho-weighted
majority vote that takes into account a trade-off between three quantities. The
first two quantities being, as usual in the PAC-Bayesian approach, (a) the
complexity of the majority vote (measured by a Kullback-Leibler divergence) and
(b) its empirical risk (measured by the \rho-average errors on the source
sample). The third quantity is (c) the capacity of the majority vote to
distinguish some structural difference between the source and target samples.Comment: https://sites.google.com/site/multitradeoffs2012
Drop impact on a flexible fiber
When droplets impact fibrous media, the liquid can be captured by the fibers
or contact then break away. Previous studies have shown that the efficiency of
drop capture by a rigid fiber depends on the impact velocity and defined a
threshold velocity below which the drop is captured. However, it is necessary
to consider the coupling of elastic and capillary effects to achieve a greater
understanding of the capture process for soft substrates. Here, we study
experimentally the dynamics of a single drop impacting on a thin flexible
fiber. Our results demonstrate that the threshold capture velocity depends on
the flexibility of fibers in a non-monotonic way. We conclude that tuning the
mechanical properties of fibers can optimize the efficiency of droplet capture.Comment: Soft Matter (2015
Acousto-optical coherence tomography with a digital holographic detection scheme
Acousto-optical coherence tomography (AOCT) consists in using random phase
jumps on ultrasound and light to achieve a millimeter resolution when imaging
thick scattering media. We combined this technique with heterodyne off-axis
digital holography. Two-dimensional images of absorbing objects embedded in
scattering phantoms are obtained with a good signal-to-noise ratio. We study
the impact of the phase modulation characteristics on the amplitude of the
acousto-optic signal and on the contrast and apparent size of the absorbing
inclusion
Damping of liquid sloshing by foams: from everyday observations to liquid transport
We perform experiments on the sloshing dynamics of liquids in a rectangular
container submitted to an impulse. We show that when foam is placed on top of
the liquid the oscillations of the free interface are significantly damped. The
ability to reduce sloshing and associated splashing could find applications in
numerous industrial processes involving liquid transport.Comment: Accepted for publication in Journal of Visualizatio
Wetting morphologies on randomly oriented fibers
We characterize the different morphologies adopted by a drop of liquid placed
on two randomly oriented fibers, which is a first step toward understanding the
wetting of fibrous networks. The present work reviews previous modeling for
parallel and touching crossed fibers and extends it to an arbitrary orientation
of the fibers characterized by the tilting angle and the minimum spacing
distance. Depending on the volume of liquid, the spacing distance between
fibers and the angle between the fibers, we highlight that the liquid can adopt
three different equilibrium morphologies: (1) a column morphology in which the
liquid spreads between the fibers, (2) a mixed morphology where a drop grows at
one end of the column or (3) a single drop located at the node. We capture the
different morphologies observed using an analytical model that predicts the
equilibrium configuration of the liquid based on the geometry of the fibers and
the volume of liquid
- âŠ