12,702 research outputs found
Virtual Element Method for fourth order problems: estimates
We analyse the family of -Virtual Elements introduced in
\cite{Brezzi:Marini:plates} for fourth-order problems and prove optimal
estimates in and in via classical duality arguments
Serendipity Face and Edge VEM Spaces
We extend the basic idea of Serendipity Virtual Elements from the previous
case (by the same authors) of nodal (-conforming) elements, to a more
general framework. Then we apply the general strategy to the case of
and conforming Virtual Element Methods, in two and three dimensions
Serendipity Nodal VEM spaces
We introduce a new variant of Nodal Virtual Element spaces that mimics the
"Serendipity Finite Element Methods" (whose most popular example is the 8-node
quadrilateral) and allows to reduce (often in a significant way) the number of
internal degrees of freedom. When applied to the faces of a three-dimensional
decomposition, this allows a reduction in the number of face degrees of
freedom: an improvement that cannot be achieved by a simple static
condensation. On triangular and tetrahedral decompositions the new elements
(contrary to the original VEMs) reduce exactly to the classical Lagrange FEM.
On quadrilaterals and hexahedra the new elements are quite similar (and have
the same amount of degrees of freedom) to the Serendipity Finite Elements, but
are much more robust with respect to element distortions. On more general
polytopes the Serendipity VEMs are the natural (and simple) generalization of
the simplicial case
Lowest order Virtual Element approximation of magnetostatic problems
We give here a simplified presentation of the lowest order Serendipity
Virtual Element method, and show its use for the numerical solution of linear
magneto-static problems in three dimensions. The method can be applied to very
general decompositions of the computational domain (as is natural for Virtual
Element Methods) and uses as unknowns the (constant) tangential component of
the magnetic field on each edge, and the vertex values of the
Lagrange multiplier (used to enforce the solenoidality of the magnetic
induction ). In this respect the method can be seen
as the natural generalization of the lowest order Edge Finite Element Method
(the so-called "first kind N\'ed\'elec" elements) to polyhedra of almost
arbitrary shape, and as we show on some numerical examples it exhibits very
good accuracy (for being a lowest order element) and excellent robustness with
respect to distortions
Comment on "Entropy Production and Fluctuation Theorems for Active Matter"
This is a comment to a letter by D. Mandal, K. Klymko and M. R. DeWeese
published as Phys. Rev. Lett. 119, 258001 (2017).Comment: 2 pages without figures, in press as a Comment on Physical Review
Letter
Yambo: an \textit{ab initio} tool for excited state calculations
{\tt yambo} is an {\it ab initio} code for calculating quasiparticle energies
and optical properties of electronic systems within the framework of many-body
perturbation theory and time-dependent density functional theory. Quasiparticle
energies are calculated within the approximation for the self-energy.
Optical properties are evaluated either by solving the Bethe--Salpeter equation
or by using the adiabatic local density approximation. {\tt yambo} is a
plane-wave code that, although particularly suited for calculations of periodic
bulk systems, has been applied to a large variety of physical systems. {\tt
yambo} relies on efficient numerical techniques devised to treat systems with
reduced dimensionality, or with a large number of degrees of freedom. The code
has a user-friendly command-line based interface, flexible I/O procedures and
is interfaced to several publicly available density functional ground-state
codes.Comment: This paper describes the features of the Yambo code, whose source is
available under the GPL license at www.yambo-code.or
Efficacy of Two Common Methods of Application of Residual Insecticide for Controlling the Asian Tiger Mosquito, Aedes albopictus (Skuse), in Urban Areas
After its first introduction in the 1980's the Asian tiger mosquito, Aedes albopictus (Skuse), has spread throughout Southern Europe. Ae. albopictus is considered an epidemiologically important vector for the transmission of many viral pathogens such as the yellow fever virus, dengue fever and Chikungunya fever, as well as several filarial nematodes such as Dirofilaria immitis or D. repens. It is therefore crucial to develop measures to reduce the risks of disease transmission by controlling the vector populations. The aim of the study was to compare the efficacy of two application techniques (mist vs. stretcher sprayer) and two insecticides (Etox based on the nonester pyrethroid Etofenprox vs. Microsin based on the pyrethroid type II Cypermetrin) in controlling adult tiger mosquito populations in highly populated areas. To test the effect of the two treatments pre- and post-treatment human landing rate counts were conducted for two years. After one day from the treatment we observed a 100% population decrease in mosquito abundance with both application methods and both insecticides. However, seven and 14 days after the application the stretcher sprayer showed larger population reductions than the mist sprayer. No effect of insecticide type after one day and 14 days was found, while Etox caused slightly higher population reduction than Microsin after seven days. Emergency measures to locally reduce the vector populations should adopt adulticide treatments using stretcher sprayers. However, more research is still needed to evaluate the potential negative effects of adulticide applications on non-target organisms
A Comparison of Predictive Validity of the Norton Scale, the Daly Scale and the Braden Scale
The purpose of this study was to compare the predictive ability of three tools (the Norton Scale, the Braden Scale and the Daly Scale) to predict risk of skin breakdown in a hospitalized population. Neuman\u27s theoretical framework served as the organizational framework for the study.; A convenience sample of 27 patients who were admitted to one of three medical/surgical floors in an acute care hospital were selected for the study. The Braden Scale and the Norton 14 each identified 50% of those subjects who developed pressure ulcers. The Norton Scale 12 identified 96% of those subjects without pressure ulcers who were not predicted and had the lowest false positive rate at 4%. The lowest false negative rate was scored by the Braden and Norton 14 at 50%. The Norton 12 scored highest at 33% for predictive value of a positive test while all three scales scored high at 95% and 96% for predictive value of a negative test
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