438 research outputs found
Uniqueness for the electrostatic inverse boundary value problem with piecewise constant anisotropic conductivities
We discuss the inverse problem of determining the, possibly anisotropic,
conductivity of a body when the so-called
Neumann-to-Dirichlet map is locally given on a non empty curved portion
of the boundary . We prove that anisotropic
conductivities that are \textit{a-priori} known to be piecewise constant
matrices on a given partition of with curved interfaces can be
uniquely determined in the interior from the knowledge of the local
Neumann-to-Dirichlet map
Opposite effects of NO on electrical injection in porous silicon gas sensors
The electrical conductance of porous silicon fabricated with heavily doped
p-type silicon is very sensitive to NO. A concentration of 10 ppb can be
detected by monitoring the current injection at fixed voltage. However, we show
that the sign of the injection variations depends on the porous layer
thickness. If the thickness is sufficiently low -- of the order of few
\micro\meter{} -- the injection decreases instead of increasing. We discuss the
effect in terms of an already proposed twofold action of NO, according to
which the free carrier density increases, and simultaneously the energy bands
are bent at the porous silicon surface.Comment: 3 pages, 3 figures, requires SIunits packag
Lipschitz stability for the electrostatic inverse boundary value problem with piecewise linear conductivities
We consider the electrostatic inverse boundary value problem also known as
electrical impedance tomography (EIT) for the case where the conductivity is a
piecewise linear function on a domain and we show
that a Lipschitz stability estimate for the conductivity in terms of the local
Dirichlet-to-Neumann map holds true.Comment: 28 pages. arXiv admin note: text overlap with arXiv:1405.047
Photon energy lifter
We propose a time-dependent photonic structure, in which the carrier
frequency of an optical pulse is shifted without changing its shape. The
efficiency of the device takes advantage of slow group velocities of light
attainable in periodic photonic structures. The frequency shifting effect is
quantitatively studied by means of Finite Difference Time Domain simulations
for realistic systems with optical parameters of conventional silicon
technology.Comment: 4 pages 5 figure
High order direct Arbitrary-Lagrangian-Eulerian schemes on moving Voronoi meshes with topology changes
We present a new family of very high order accurate direct
Arbitrary-Lagrangian-Eulerian (ALE) Finite Volume (FV) and Discontinuous
Galerkin (DG) schemes for the solution of nonlinear hyperbolic PDE systems on
moving 2D Voronoi meshes that are regenerated at each time step and which
explicitly allow topology changes in time.
The Voronoi tessellations are obtained from a set of generator points that
move with the local fluid velocity. We employ an AREPO-type approach, which
rapidly rebuilds a new high quality mesh rearranging the element shapes and
neighbors in order to guarantee a robust mesh evolution even for vortex flows
and very long simulation times. The old and new Voronoi elements associated to
the same generator are connected to construct closed space--time control
volumes, whose bottom and top faces may be polygons with a different number of
sides. We also incorporate degenerate space--time sliver elements, needed to
fill the space--time holes that arise because of topology changes. The final
ALE FV-DG scheme is obtained by a redesign of the fully discrete direct ALE
schemes of Boscheri and Dumbser, extended here to moving Voronoi meshes and
space--time sliver elements. Our new numerical scheme is based on the
integration over arbitrary shaped closed space--time control volumes combined
with a fully-discrete space--time conservation formulation of the governing PDE
system. In this way the discrete solution is conservative and satisfies the GCL
by construction.
Numerical convergence studies as well as a large set of benchmarks for
hydrodynamics and magnetohydrodynamics (MHD) demonstrate the accuracy and
robustness of the proposed method. Our numerical results clearly show that the
new combination of very high order schemes with regenerated meshes with
topology changes lead to substantial improvements compared to direct ALE
methods on conforming meshes
Three Pillars of Automated Home-Cage Phenotyping of Mice: Novel Findings, Refinement, and Reproducibility Based on Literature and Experience
Animal models of neurodegenerative and neuropsychiatric disorders require extensive behavioral phenotyping. Currently, this presents several caveats and the most important are: (i) rodents are nocturnal animals, but mostly tested during the light period; (ii) the conventional behavioral experiments take into consideration only a snapshot of a rich behavioral repertoire; and (iii) environmental factors, as well as experimenter influence, are often underestimated. Consequently, serious concerns have been expressed regarding the reproducibility of research findings on the one hand, and appropriate welfare of the animals (based on the principle of 3Rs—reduce, refine and replace) on the other hand. To address these problems and improve behavioral phenotyping in general, several solutions have been proposed and developed. Undisturbed, 24/7 home-cage monitoring (HCM) is gaining increased attention and popularity as demonstrating the potential to substitute or complement the conventional phenotyping methods by providing valuable data for identifying the behavioral patterns that may have been missed otherwise. In this review, we will briefly describe the different technologies used for HCM systems. Thereafter, based on our experience, we will focus on two systems, IntelliCage (NewBehavior AG and TSE-systems) and Digital Ventilated Cage (DVC®, Tecniplast)—how they have been developed and applied during recent years. Additionally, we will touch upon the importance of the environmental/experimenter artifacts and propose alternative suggestions for performing phenotyping experiments based on the published evidence. We will discuss how the integration of telemetry systems for deriving certain physiological parameters can help to complement the description of the animal model to offer better translation to human studies. Ultimately, we will discuss how such HCM data can be statistically interpreted and analyzed.Peer reviewe
Solar Reector Design
The design of solar panels is investigated. Different aspects of this problem are presented. A formula averaging the solar energy received on a given location is derived rst. The energy received by the collecting solar panel is then calculated using a specially designed algorithm. The geometry of the device collecting the energy may then be optimised using different algorithms. The results show that for a given depth, devices of smaller width are more energy efficient than those of wider dimensions. This leads to a more economically efficient design
Lipschitz stability for the inverse conductivity problem for a conformal class of anisotropic conductivities
We consider the stability issue of the inverse conductivity problem for a
conformal class of anisotropic conductivities in terms of the local Dirichlet\u2013
Neumann map. We extend here the stability result obtained by Alessandrini
and Vessella (Alessandrini G and Vessella S 2005 Lipschitz stability for the
inverse conductivity problem Adv. Appl. Math. 35 207\u2013241), where the
authors considered the piecewise constant isotropic case
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