2,509 research outputs found
Linear programming of a slate quarry
[Abstract] A new exploitation of roofing slate has several possibilities of marketing
depending on the sizes of the pieces that it makes. Three sizes has been chosen
among aH the possibilities in base of the conditions and the production of the
rock in the quarry, the marketing limitation and the final price of the producto
We've procces aH these data to obtain the optimun output, with the simplex
algorithm. The objective function (week invoicing) and the restrictions of the
problem are created in canonical and standard formo Optimun solution has been
obtained among aH the basic and practical ones, using the graphic and the
analytic method. Sorne conclusions come from the algorithm matrix about the
outputs for each marketing option
Divisive Normalization from Wilson-Cowan Dynamics
Divisive Normalization and the Wilson-Cowan equations are influential models
of neural interaction and saturation [Carandini and Heeger Nat.Rev.Neurosci.
2012; Wilson and Cowan Kybernetik 1973]. However, they have not been
analytically related yet. In this work we show that Divisive Normalization can
be obtained from the Wilson-Cowan model. Specifically, assuming that Divisive
Normalization is the steady state solution of the Wilson-Cowan differential
equation, we find that the kernel that controls neural interactions in Divisive
Normalization depends on the Wilson-Cowan kernel but also has a
signal-dependent contribution. A standard stability analysis of a Wilson-Cowan
model with the parameters obtained from our relation shows that the Divisive
Normalization solution is a stable node. This stability demonstrates the
consistency of our steady state assumption, and is in line with the
straightforward use of Divisive Normalization with time-varying stimuli.
The proposed theory provides a physiological foundation (a relation to a
dynamical network with fixed wiring among neurons) for the functional
suggestions that have been done on the need of signal-dependent Divisive
Normalization [e.g. in Coen-Cagli et al., PLoS Comp.Biol. 2012]. Moreover, this
theory explains the modifications that had to be introduced ad-hoc in Gaussian
kernels of Divisive Normalization in [Martinez et al. Front. Neurosci. 2019] to
reproduce contrast responses. The proposed relation implies that the
Wilson-Cowan dynamics also reproduces visual masking and subjective image
distortion metrics, which up to now had been mainly explained via Divisive
Normalization. Finally, this relation allows to apply to Divisive Normalization
the methods which up to now had been developed for dynamical systems such as
Wilson-Cowan networks
Estimation of the mechanical properties of the eye through the study of its vibrational modes
Measuring the eye's mechanical properties in vivo and with minimally invasive
techniques can be the key for individualized solutions to a number of eye
pathologies. The development of such techniques largely relies on a
computational modelling of the eyeball and, it optimally requires the synergic
interplay between experimentation and numerical simulation. In Astrophysics and
Geophysics the remote measurement of structural properties of the systems of
their realm is performed on the basis of (helio-)seismic techniques. As a
biomechanical system, the eyeball possesses normal vibrational modes
encompassing rich information about its structure and mechanical properties.
However, the integral analysis of the eyeball vibrational modes has not been
performed yet. Here we develop a new finite difference method to compute both
the spheroidal and, specially, the toroidal eigenfrequencies of the human eye.
Using this numerical model, we show that the vibrational eigenfrequencies of
the human eye fall in the interval 100 Hz - 10 MHz. We find that compressible
vibrational modes may release a trace on high frequency changes of the
intraocular pressure, while incompressible normal modes could be registered
analyzing the scattering pattern that the motions of the vitreous humour leave
on the retina. Existing contact lenses with embebed devices operating at high
sampling frequency could be used to register the microfluctuations of the
eyeball shape we obtain. We advance that an inverse problem to obtain the
mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio)
measuring its normal frequencies is doable. These measurements can be done
using non-invasive techniques, opening very interesting perspectives to
estimate the mechanical properties of eyes in vivo. Future research might
relate various ocular pathologies with anomalies in measured vibrational
frequencies of the eye.Comment: Published in PLoS ONE as Open Access Research Article. 17 pages, 5
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A non-conformal multi-resolution preconditioner in the MoM solution of large multi-scale structures
The extension of the surface integral equations (SIEs) [1] to non-conforming meshes has ignited intense research in the last years with the goal of finding a versatile and accurate method to address large and multi-scale complex problems, greatly simplifying computer-aided-design (CAD) generation and meshing processes
A non-conformal multi-resolution preconditioner in the MoM solution of large multi-scale structures
An efficient method to improve the convergence in non-conformal meshes including an automatic quasi-Helmholtz decomposition has been developed for the simulation of nonconforming meshes using the novel Multibranch Rao-Wilton-Glisson (MB-RWG) basis functions. Numerical experiments will be shown to illustrate the great flexibility of this approach for the solution of small-frequency and large multi-scale objects
Strain balanced quantum posts
Quantum posts are assembled by epitaxial growth of closely spaced quantum dot
layers, modulating the composition of a semiconductor alloy, typically InGaAs.
In contrast with most self-assembled nanostructures, the height of quantum
posts can be controlled with nanometer precision, up to a maximum value limited
by the accumulated stress due to the lattice mismatch. Here we present a strain
compensation technique based on the controlled incorporation of phosphorous,
which substantially increases the maximum attainable quantum post height. The
luminescence from the resulting nanostructures presents giant linear
polarization anisotropy.Comment: Submitted to Applied Physics Letters (7th March 2011). 4 pages, 4
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Compositional analysis of InAs-GaAs-GaSb heterostructures by low-loss electron energy loss spectroscopy
As an alternative to Core-Loss Electron Energy Loss Spectroscopy, Low-Loss EELS is suitable for compositional analysis of complex heterostructures, such as the InAs-GaAs-GaSb system, since in this energy range the edges corresponding to these elements are better defined than in Core-Loss. Furthermore, the analysis of the bulk plasmon peak, which is present in this energy range, also provides information about the composition. In this work, compositional information in an InAs-GaAs-GaSb heterostructure has been obtained from Low-Loss EEL spectra
Incidencia de las características mineralógicas y texturales en algunas propiedades de las pizarras de techar
The computer in a roofing slate quarry
[Resumen] Sencillas configuraciones informáticas en base a ordenadores personales con programas comerciales de modelización y diseño asistido por ordenador, facilitan el reiterativo trabajo de planificación minera de una explotación de pizarra a cielo abierto. Su utilización es aplicable a tres fases del proyecto minero: Modelización del yacimiento (investigación), proyecto de explotación (viabilidad) y labores mineras (ejecución).[Abstract] Simple integrated systems based on personal computers and cornmercial programmes about modelling and CAD, make easy the reiterative work on exploitation
planning in roofing slate quarries. We can use this systems in the three phases of the mining project: bed modelling (Research), exploitation (Viability)wand mining (Performance)
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