1,843 research outputs found
Responsables, Sostenibles, Universitarios como vía de lucha contra el cambio climático: El caso de la ETSIMontes, Forestal y del Medio Natural (UPM)
La universidad responsable juega un rol importante en el cambio climático. Le compete promover la responsabilidad empresarial, la responsabilidad social científica y la responsabilidad social ciudadana, y lo hace a través de tres enfoques distintos: Gerencial, basado en la rendición de cuentas a sus grupos de interés; Transformacional, muy comprometida socialmente, a través de actividades de voluntariado o cooperación al desarrollo; o Normativo, con el propósito de fortalecer el papel de la educación superior desde el servicio público, la relevancia y la Responsabilidad Social Universitaria. En este sentido, la Escuela Técnica de Ingeniería de Montes, Forestal y del Medio Natural de la Universidad Politécnica de Madrid, primera entidad pública española con la validación de la
ISO 26000, se erige como entidad de transformación, como modelo de actuación y, especialmente, de lucha contra el cambio climático, dada la naturaleza de sus enseñanzas y el enfoque de su estrategia RSU: Responsables, Sostenibles
y Universitarios
Robust Cardiac Motion Estimation using Ultrafast Ultrasound Data: A Low-Rank-Topology-Preserving Approach
Cardiac motion estimation is an important diagnostic tool to detect heart
diseases and it has been explored with modalities such as MRI and conventional
ultrasound (US) sequences. US cardiac motion estimation still presents
challenges because of the complex motion patterns and the presence of noise. In
this work, we propose a novel approach to estimate the cardiac motion using
ultrafast ultrasound data. -- Our solution is based on a variational
formulation characterized by the L2-regularized class. The displacement is
represented by a lattice of b-splines and we ensure robustness by applying a
maximum likelihood type estimator. While this is an important part of our
solution, the main highlight of this paper is to combine a low-rank data
representation with topology preservation. Low-rank data representation
(achieved by finding the k-dominant singular values of a Casorati Matrix
arranged from the data sequence) speeds up the global solution and achieves
noise reduction. On the other hand, topology preservation (achieved by
monitoring the Jacobian determinant) allows to radically rule out distortions
while carefully controlling the size of allowed expansions and contractions.
Our variational approach is carried out on a realistic dataset as well as on a
simulated one. We demonstrate how our proposed variational solution deals with
complex deformations through careful numerical experiments. While maintaining
the accuracy of the solution, the low-rank preprocessing is shown to speed up
the convergence of the variational problem. Beyond cardiac motion estimation,
our approach is promising for the analysis of other organs that experience
motion.Comment: 15 pages, 10 figures, Physics in Medicine and Biology, 201
Cosmography and constraints on the equation of state of the Universe in various parametrizations
We use cosmography to present constraints on the kinematics of the Universe,
without postulating any underlying theoretical model. To this end, we use a
Monte Carlo Markov Chain analysis to perform comparisons to the supernova Ia
Union 2 compilation, combined with the Hubble Space Telescope measurements of
the Hubble constant, and the Hubble parameter datasets. We introduce a sixth
order cosmographic parameter and show that it does not enlarge considerably the
posterior distribution when comparing to the fifth order results. We also
propose a way to construct viable parameter variables to be used as
alternatives of the redshift . These can overcome both the problems of
divergence and lack of accuracy associated with the use of . Moreover, we
show that it is possible to improve the numerical fits by re-parameterizing the
cosmological distances. In addition, we constrain the equation of state of the
Universe as a whole by the use of cosmography. Thus, we derive expressions
which can be directly used to fit the equation of state and the pressure
derivatives up to fourth order. To this end, it is necessary to depart from a
pure cosmographic analysis and to assume the Friedmann equations as valid. All
our results are consistent with the CDM model, although alternative
fluid models, with nearly constant pressure and no cosmological constant, match
the results accurately as well.Comment: 23 pages. 1 reference added. Minor correction
Constant mean curvature solutions of the Einstein-scalar field constraint equations on asymptotically hyperbolic manifolds
We follow the approach employed by Y. Choquet-Bruhat, J. Isenberg and D.
Pollack in the case of closed manifolds and establish existence and
non-existence results for the Einstein-scalar field constraint equations on
asymptotically hyperbolic manifolds.Comment: 15 page
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