352 research outputs found
Activity recognition from videos with parallel hypergraph matching on GPUs
In this paper, we propose a method for activity recognition from videos based
on sparse local features and hypergraph matching. We benefit from special
properties of the temporal domain in the data to derive a sequential and fast
graph matching algorithm for GPUs.
Traditionally, graphs and hypergraphs are frequently used to recognize
complex and often non-rigid patterns in computer vision, either through graph
matching or point-set matching with graphs. Most formulations resort to the
minimization of a difficult discrete energy function mixing geometric or
structural terms with data attached terms involving appearance features.
Traditional methods solve this minimization problem approximately, for instance
with spectral techniques.
In this work, instead of solving the problem approximatively, the exact
solution for the optimal assignment is calculated in parallel on GPUs. The
graphical structure is simplified and regularized, which allows to derive an
efficient recursive minimization algorithm. The algorithm distributes
subproblems over the calculation units of a GPU, which solves them in parallel,
allowing the system to run faster than real-time on medium-end GPUs
Probing the phase diagram of cuprates with YBaCuO thin films and nanowires
We have grown and characterized 30 nm thick YBaCuO
(YBCO) films, deposited by pulsed laser deposition on both MgO (110) and
SrTiO (001) substrates, which induce opposite strain to the superconducting
layer. By carefully tuning the in-situ post-annealing oxygen pressure, we
achieved, in a reproducible way, films at different oxygen doping, spanning
from the slightly overdoped down to the strongly underdoped region of the phase
diagram. The transport properties of the films, investigated through resistance
versus temperature measurements, are in perfect qualitative agreement with
single crystals. Starting from these films, we have also successfully
fabricated nanowires with widths down to 65 nm, at different oxygen doping. The
nanostructures exhibit characteristic temperatures (as the critical temperature
and the pseudogap temperature ) similar to those of the
as-grown films and carry critical current densities close to
the critical depairing value, limited by vortex entry. This implies that the
superconducting and the normal state properties of underdoped YBCO are
preserved in our films, and they can be studied as a function of the
dimensionality of the system, down to the nanoscale.Comment: 11 pages, 9 figures, submitted to Phys. Rev. Material
Normal forms with exponentially small remainder : application to homoclinic connections for the reversible 0 2+ iω resonance
International audienceIn this note we explain how the normal form theorem established in [2] for analytic vector fields with a semi-simple linearization enables to prove the existence of homoclinic connections to exponentially small periodic orbits for reversible analytic vector fields admitting a 0 2+ iω resonance where the linearization is precisely not semi simple
Arthroscopic transosseous rotator cuff repair: A prospective study on cost savings, surgical time, and outcomes
Objectives: Health expenditures in the United States are outpacing national income, and affordability has become a major policy issue. Over 500,000 rotator cuff repairs (RCR) are performed annually in the United States making RCR a potential source of cost savings. Arthroscopic trans-osseous equivalent (TOE) repair using a double row of anchors has shown superior biomechanical strength compared to other techniques, but at a higher cost. The arthroscopic transosseous (TO) repair is a novel technique allowing arthroscopic rotator cuff repair to be performed without suture anchors. Arthroscopic TO repair may be a means to provide similarly excellent patient outcomes while lowering the cost of care. The primary purpose is to compare the price differential and time of surgery for an arthroscopic rotator cuff repair using anchorless TO repair verses an anchor trans-osseous equivalent (TOE) repair. A secondary purpose of the study was to evaluate outcomes at 6 months postoperatively. Methods: A prospective, case-controlled study evaluating arthroscopic rotator cuff repair using two techniques was performed. The study group consisting of 21 patients undergoing TO repair was compared to a control group consisting of 22 patients undergoing TOE repair. The groups were controlled for size of tear, biceps treatment, acromioplasty, distal clavicle excision, and labral pathology. The primary outcome measures were surgical time as well as total cost of implants and equipment for each surgery, determined by an independent third party, Atlanticare Hospital. Secondary outcomes were changes in the SST, VAS, and SANE scores. Results: Mean total surgical implant/equipment cost per procedure for TOE repair was 1204.97 (SD 330.69; p\u3c0.0001). Mean cut to close time for TOE repair was 85 minutes (95% CI is 77-90) verses 74 (95% CI = 71-98) for TO repair. A log rank test revealed no difference in time (p =0.95). A linear regression model was developed to evaluate the change in SST, VAS, and SANE scores from pre-op to 6 months follow-up. Our study was underpowered but no difference in outcome was observed. Conclusion: Arthroscopic TO rotator cuff repair is a cost savings and time neutral technique compared to TOE repair. A mean of $1100 can be saved in surgical cost per case. In a country that performs over 500,000 RCRs annually, utilizing a TO repair technique can provide substantial cost savings to the healthcare system. © The Author(s) 2015
Observations of Extrasolar Planets During the non-Cryogenic Spitzer Space Telescope Mission
Precision infrared photometry from Spitzer has enabled the first direct
studies of light from extrasolar planets, via observations at secondary eclipse
in transiting systems. Current Spitzer results include the first longitudinal
temperature map of an extrasolar planet, and the first spectra of their
atmospheres. Spitzer has also measured a temperature and precise radius for the
first transiting Neptune-sized exoplanet, and is beginning to make precise
transit timing measurements to infer the existence of unseen low mass planets.
The lack of stellar limb darkening in the infrared facilitates precise radius
and transit timing measurements of transiting planets. Warm Spitzer will be
capable of a precise radius measurement for Earth-sized planets transiting
nearby M-dwarfs, thereby constraining their bulk composition. It will continue
to measure thermal emission at secondary eclipse for transiting hot Jupiters,
and be able to distinguish between planets having broad band emission versus
absorption spectra. It will also be able to measure the orbital phase variation
of thermal emission for close-in planets, even non-transiting planets, and
these measurements will be of special interest for planets in eccentric orbits.
Warm Spitzer will be a significant complement to Kepler, particularly as
regards transit timing in the Kepler field. In addition to studying close-in
planets, Warm Spitzer will have significant application in sensitive imaging
searches for young planets at relatively large angular separations from their
parent stars.Comment: 12 pages, 7 figures, to appear in "Science Opportunities for the Warm
Spitzer Mission
Fabrication and electrical transport characterization of high quality underdoped YBa2Cu3O7-δ nanowires
We present the fabrication and electrical transport characterization of underdoped YBa2Cu3O7-δnanowires. The nanowires have been realized without any protective capping layer and theyshow transport properties similar to those of the parent thin film, demonstrating that they havenot been damaged by the nanopatterning. The current-voltage characteristics of the underdopednanowires show large hysteretic voltage switching at the critical current, in contrast to theflux-flow like characteristics of optimally doped nanostructures, indicating the formation of aself-stabilizing hot spot. These results open up new possibilities for using the underdopednanowires as single photon detectors and for exploring the underdoped side of the YBa2Cu3O7-δphase diagram at the nanoscale
Mapping the Phase Diagram of a YBa2Cu3 O7-δ Nanowire Through Electromigration
We use electromigration (EM) to tune the oxygen content of YBa2Cu3O7-δ (YBCO) nanowires. During EM, the dopant oxygen atoms in the nanowire are moved under the combined effect of electrostatic force and Joule heating. The EM current can be tuned to either deplete or replenish nanowires with oxygen, allowing fine tuning of its hole-doping level. Electrical transport measurements and Kelvin probe microscopy corroborate good homogeneity of the doping level along the electromigrated nanowires. Thus, EM provides an effective method to study transport properties of YBCO in a wide doping range at the nanoscale in one and the same device
Polynomial normal forms with exponentially small remainder for analytic vector fields
International audienceA key tool in the study of the dynamics of vector fields near an equilibrium point is the theory of normal forms, invented by Poincaré, which gives simple forms to which a vector field can be reduced close to the equilibrium. In the class of formal vector valued vector fields the problem can be easily solved, whereas in the class of analytic vector fields divergence of the power series giving the normalizing transformation generally occurs. Nevertheless the study of the dynamics in a neighborhood of the origin, can very often be carried out via a normalization up to finite order. This paper is devoted to the problem of optimal truncation of normal forms for analytic vector fields in R m. More precisely we prove that for any vector field in R m admitting the origin as a fixed point with a semi-simple linearization, the order of the normal form can be optimized so that the remainder is exponentially small.We also give several examples of non semi-simple linearization for which this result is still true
SQUID magnetometer based on Grooved Dayem nanobridges and a flux transformer
We report noise measurements performed on a SQUID magnetometer implementing
Grooved Dayem nanobridge of YBCO as weak-links. The SQUID shows magnetic flux
noise as low as 10 /Hz. The magnetometer is realized by
coupling the SQUID to a flux transformer with a two-level coupling scheme using
a flip-chip approach. This improves the effective area of the SQUID and result
in a magnetic field noise of 50 fT/Hz at T=77 K.Comment: 4 pages, 4 figure
The IPAC Image Subtraction and Discovery Pipeline for the intermediate Palomar Transient Factory
We describe the near real-time transient-source discovery engine for the
intermediate Palomar Transient Factory (iPTF), currently in operations at the
Infrared Processing and Analysis Center (IPAC), Caltech. We coin this system
the IPAC/iPTF Discovery Engine (or IDE). We review the algorithms used for
PSF-matching, image subtraction, detection, photometry, and machine-learned
(ML) vetting of extracted transient candidates. We also review the performance
of our ML classifier. For a limiting signal-to-noise ratio of 4 in relatively
unconfused regions, "bogus" candidates from processing artifacts and imperfect
image subtractions outnumber real transients by ~ 10:1. This can be
considerably higher for image data with inaccurate astrometric and/or
PSF-matching solutions. Despite this occasionally high contamination rate, the
ML classifier is able to identify real transients with an efficiency (or
completeness) of ~ 97% for a maximum tolerable false-positive rate of 1% when
classifying raw candidates. All subtraction-image metrics, source features, ML
probability-based real-bogus scores, contextual metadata from other surveys,
and possible associations with known Solar System objects are stored in a
relational database for retrieval by the various science working groups. We
review our efforts in mitigating false-positives and our experience in
optimizing the overall system in response to the multitude of science projects
underway with iPTF.Comment: 66 pages, 21 figures, 7 tables, accepted by PAS
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