24,331 research outputs found
Estimating Carotid Pulse and Breathing Rate from Near-infrared Video of the Neck
Objective: Non-contact physiological measurement is a growing research area
that allows capturing vital signs such as heart rate (HR) and breathing rate
(BR) comfortably and unobtrusively with remote devices. However, most of the
approaches work only in bright environments in which subtle
photoplethysmographic and ballistocardiographic signals can be easily analyzed
and/or require expensive and custom hardware to perform the measurements.
Approach: This work introduces a low-cost method to measure subtle motions
associated with the carotid pulse and breathing movement from the neck using
near-infrared (NIR) video imaging. A skin reflection model of the neck was
established to provide a theoretical foundation for the method. In particular,
the method relies on template matching for neck detection, Principal Component
Analysis for feature extraction, and Hidden Markov Models for data smoothing.
Main Results: We compared the estimated HR and BR measures with ones provided
by an FDA-cleared device in a 12-participant laboratory study: the estimates
achieved a mean absolute error of 0.36 beats per minute and 0.24 breaths per
minute under both bright and dark lighting.
Significance: This work advances the possibilities of non-contact
physiological measurement in real-life conditions in which environmental
illumination is limited and in which the face of the person is not readily
available or needs to be protected. Due to the increasing availability of NIR
imaging devices, the described methods are readily scalable.Comment: 21 pages, 15 figure
Experiences in porting mini-applications to OpenACC and OpenMP on heterogeneous systems
This article studies mini-applications—Minisweep, GenASiS, GPP, and FF—that use computational methods commonly encountered in HPC. We have ported these applications to develop OpenACC and OpenMP versions, and evaluated their performance on Titan (Cray XK7 with K20x GPUs), Cori (Cray XC40 with Intel KNL), Summit (IBM AC922 with Volta GPUs), and Cori-GPU (Cray CS-Storm 500NX with Intel Skylake and Volta GPUs). Our goals are for these new ports to be useful to both application and compiler developers, to document and describe the lessons learned and the methodology to create optimized OpenMP and OpenACC versions, and to provide a description of possible migration paths between the two specifications. Cases where specific directives or code patterns result in improved performance for a given architecture are highlighted. We also include discussions of the functionality and maturity of the latest compilers available on the above platforms with respect to OpenACC or OpenMP implementations
A nucleon in a tiny box
We use Chiral Perturbation Theory to compute the nucleon mass-shift due to
finite volume and temperature effects. Our results are valid up to
next-to-leading order in the "\eps-regime" (mL ~ m\beta << 1) as well as in the
"p-regime" (mL ~ m\beta >> 1). Based on the two leading orders, we discuss the
convergence of the expansion as a function of the lattice size and quark
masses. This result can be used to extrapolate lattice results obtained from
lattice sizes smaller than the pion cloud, avoiding the numerical simulation of
physics under theoretical control. An extraction of the low-energy coefficient
c_3 of the chiral Lagrangean from lattice simulations at small volumes and a
``magic'' ratio \beta=1.22262 L might be possible.Comment: 7 figures, numerical examples and discussion changed. Minor misprints
corrected. Version accepted by Phys Rev
Large gauge invariant non-standard neutrino interactions
Theories beyond the Standard Model must necessarily respect its gauge
symmetry. This implies strict constraints on the possible models of
non-standard neutrino interactions, which we analyze. The focus is set on the
effective low-energy dimension six and eight operators involving four leptons,
decomposing them according to all possible tree-level mediators, as a guide for
model building. The new couplings are required to have sizeable strength, while
processes involving four charged leptons are required to be suppressed. For
non-standard interactions in matter, only diagonal tau-neutrino interactions
can escape these requirements and can be allowed to result from dimension six
operators. Large non-standard neutrino interactions from dimension eight
operators alone are phenomenologically allowed in all flavour channels and
shown to require at least two new mediator particles. The new couplings must
obey general cancellation conditions both at the dimension six and eight
levels, which result from expressing the operators obtained from the mediator
analysis in terms of a complete basis of operators. We illustrate with one
example how to apply this information to model building.Comment: 34 pages, 4 figures, 5 tables. Final version in PR
Intriguing examples of inhomogeneous broadening
Three problems are considered in which inhomogeneous broadening can yield
unusual consequences. One problem involves the energy levels of atoms moving
within nanopores of nearly cylindrical cross section. A second involves atomic
or molecular motion in a quasi-one dimensional interstitial channel within a
bundle of carbon nanotubes. The third problem involves motion within a groove
between two nanotubes at the surface of such a bundle. In each case, the
density of states at low energy is qualitatively different from that occurring
in the perfectly homogeneous case.Comment: 15 pages, 5 figure
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