1,281 research outputs found
PADDLE: Proximal Algorithm for Dual Dictionaries LEarning
Recently, considerable research efforts have been devoted to the design of
methods to learn from data overcomplete dictionaries for sparse coding.
However, learned dictionaries require the solution of an optimization problem
for coding new data. In order to overcome this drawback, we propose an
algorithm aimed at learning both a dictionary and its dual: a linear mapping
directly performing the coding. By leveraging on proximal methods, our
algorithm jointly minimizes the reconstruction error of the dictionary and the
coding error of its dual; the sparsity of the representation is induced by an
-based penalty on its coefficients. The results obtained on synthetic
data and real images show that the algorithm is capable of recovering the
expected dictionaries. Furthermore, on a benchmark dataset, we show that the
image features obtained from the dual matrix yield state-of-the-art
classification performance while being much less computational intensive
Directive Emission from Defect-Free Dodecagonal Photonic Quasicrystals: A Leaky-Wave Characterization
In this paper, we study the radiation from embedded sources in
two-dimensional finite-size "photonic-quasicrystal" (PQC) slabs made of
dielectric rods arranged according to a 12-fold symmetric aperiodic tiling. The
results from our investigation, based on rigorous full-wave simulations, show
the possibility of achieving broadside radiation at multiple frequencies, with
high-directivity (e.g., 15 dB) and low-sidelobes (e.g., -12 dB). We also show
that leaky waves are supported by a PQC slab, and that the beamwidth is
directly proportional to the leaky-wave attenuation constant, which provides a
physically-incisive interpretation of the observed radiation characteristics.Comment: 7 pages, 7 figures; slight change in the title, major revision in the
text and figures. Accepted for publication in Phys. Rev.
Reconstruction of Underlying Nonlinear Deterministic Dynamics Embedded in Noisy Spike Trains
An experimentally recorded time series formed by the exact times of occurrence of the neuronal spikes (spike train) is likely to be affected by observational noise that provokes events mistakenly confused with neuronal discharges, as well as missed detection of genuine neuronal discharges. The points of the spike train may also suffer a slight jitter in time due to stochastic processes in synaptic transmission and to delays in the detecting devices. This study presents a procedure aimed at filtering the embedded noise (denoising the spike trains) the spike trains based on the hypothesis that recurrent temporal patterns of spikes are likely to represent the robust expression of a dynamic process associated with the information carried by the spike train. The rationale of this approach is tested on simulated spike trains generated by several nonlinear deterministic dynamical systems with embedded observational noise. The application of the pattern grouping algorithm (PGA) to the noisy time series allows us to extract a set of points that form the reconstructed time series. Three new indices are defined for assessment of the performance of the denoising procedure. The results show that this procedure may indeed retrieve the most relevant temporal features of the original dynamics. Moreover, we observe that additional spurious events affect the performance to a larger extent than the missing of original points. Thus, a strict criterion for the detection of spikes under experimental conditions, thus reducing the number of spurious spikes, may raise the possibility to apply PGA to detect endogenous deterministic dynamics in the spike train otherwise masked by the observational nois
Oral potentially malignant disorders in a large dental population
Objectives Oral cancer (OC) may be preceded by clinically evident oral potentially malignant disorders (OPMDs). Oral carcinogenesis is a multistep process that begins as epithelial hyperplasia and progresses to oral epithelial dysplasia and finally to fully malignant phenotypes. The aim of our study was to estimate the prevalence of OPMDs in a large population of dental patients. Methods Patients were seen in the Oral Diagnosis and Oral Medicine clinics at Boston University Henry M. Goldman School of Dental Medicine between July 2013 and February 2014 and received a comprehensive oral examination to identify any possible mucosal lesions. Patients with a suspected OPMD (submucous fibrosis, oral lichen planus, leukoplakia and erythroplakia) that did not resolve in 2–3 weeks received a biopsy for definitive diagnosis. Logistic regression models were used to explore the relationship between OPMDs and associated risk factors. Results A total of 3,142 patients received a comprehensive oral examination [median age: 43 (range: 18–97); 54.3% females]. Among these, 4.5% had an oral mucosal lesion with 0.9% being an OPMD (one submucous fibrosis, three epithelial dysplasias, fourteen with hyperkeratosis/epithelial hyperplasia and nine with oral lichen planus). Males and current smokers were associated with higher odds of having OPMD (OR 1.7, 95% CI 0.8–3.8; OR 1.9, 95%CI 0.8–4.1). Increasing age was associated with having OPMDs (
Flowmeter and Ground Penetrating Radar: comparison between hydrogeological and geophysical methods
We discuss a comparison between saturated hydraulic conductivity calculated with Electromagnetic Borehole Flowmeter (EBF) and water content obtained by Ground Penetrating Radar (GPR) Zero Offset Profile (ZOP
GPGPU for track finding in High Energy Physics
The LHC experiments are designed to detect large amount of physics events
produced with a very high rate. Considering the future upgrades, the data
acquisition rate will become even higher and new computing paradigms must be
adopted for fast data-processing: General Purpose Graphics Processing Units
(GPGPU) is a novel approach based on massive parallel computing. The intense
computation power provided by Graphics Processing Units (GPU) is expected to
reduce the computation time and to speed-up the low-latency applications used
for fast decision taking. In particular, this approach could be hence used for
high-level triggering in very complex environments, like the typical inner
tracking systems of the multi-purpose experiments at LHC, where a large number
of charged particle tracks will be produced with the luminosity upgrade. In
this article we discuss a track pattern recognition algorithm based on the
Hough Transform, where a parallel approach is expected to reduce dramatically
the execution time.Comment: 6 pages, 4 figures, proceedings prepared for GPU-HEP 2014 conference,
submitted to DESY-PROC-201
Social investment, labour market participation and public debt sustainability: An empirical analysis of European countries
This article explores the role of SI Stock, Flow and Buffer policies by shedding light on their relationships with active labour market participation and public debt sustainability for a panel of 22 European countries from 1997 to 2018. We find SI Stock, Flow and Buffer to be positively correlated with labour market participation and more sustainable public debt. When disaggregating the components of SI, we detect a small degree of heterogeneity, with Active Labour Market Policies (ALMPs) negatively associated with the activity rate and positively associated with the employment rate. This result is coherent with the idea that ALMPs make a significant contribution to increasing opportunities for those already in the labour market rather than creating new jobs for those excluded from the labour market, that is, inactive individuals. In this case, our findings indicate that measures to fight social exclusion and out-of-work expenditure (Buffer), as well as in-kind family benefits, are significantly associated with employability for those excluded from the labour market
- …