1,425 research outputs found
Los sentidos en el Jardín Mediterráneo: la vista y la percepción de las formas
El trabajo se titula: “Los Sentidos en el Jardín Mediterráneo: La vista y la percepción de las
formas” y forma parte de un conjunto de proyectos de investigación ofertados por el Área de
Jardinería y Paisajismo del Departamento de Ciencias Agroforestales que estudian los sentidos
en el Jardín Mediterráneo; como se relacionan estos entre sí (sinestesias) y como son asociados
a diferentes emociones y sentimientos.
El TFG trata en concreto la relación entre cuatro formas básicas perceptibles por la vista
(cuadrada, triangular, circular y sinusoidal) con todos los Sentidos (gusto, oído, olfato, tacto y
vista (colores)), y con diferentes Emociones y Sentimientos.
La vista es el principal sentido a la hora de percibir el diseño de un jardín (sin quitar valor
sensorial al resto de los sentidos), por ello resulta interesante estudiar el efecto que causan la
forma de los objetos y plantas, y su disposición espacial, en las sensaciones, percepciones,
emociones y sentimientos que nos trasmite un jardín.
Para analizar las repercusiones que dichas asociaciones y sinestesias conllevan en el diseño y la
percepción de nuestro jardín, nos basaremos en las opiniones de personas elegidas al azar. Dicha
información se obtiene mediante una encuesta, que utiliza la aplicación de Formularios Online
de Google para la recaudación de los datos. Esta encuesta fue realizada por un mínimo de 500
personas de gran diversidad sociológica (sexo, edad, ocupación, estudios, etc.).
Con intención de evaluar dichas opiniones de forma objetiva nos serviremos de un estudio
estadístico, y una vez obtenidos y tratados dichos datos, serán codificados e interpretados, con
lo que se podrán obtener conclusiones para determinar el papel de la vista y la percepción de
las formas en la Jardinería y el Paisajismo, tratando de determinar cuáles de estas formas
podrían ser útiles en el jardín, teniendo en cuenta: las Sensaciones, y Emociones y Sentimientos asociados a la observación de formas básicas; y los preconceptos previos sobre el tema. Por lo que se pretende conocer:
1. Si la observación de distintas Formas provoca distintas Emociones y Sentimientos.
1.1. Si estas asociaciones dependen de factores sociológicos (edad, sexo, estudios, etc.).
2. Si existe alguna relación sinestésica entre la Vista (en concreto de la percepción de Formas) y el resto de Sentidos (Vista (color), Oído, Gusto, Olfato y Tacto).
2.1. Si estas sinestesias dependen de factores sociológicos (edad, sexo, estudios, etc.).
3. Los preconceptos de la población sobre ciertas cuestiones relacionadas con el jardín, las formas, y el estudio sensorial y emocional de estos.Universidad de Sevilla. Grado en Ingeniería Agrícol
Long wave expansions for water waves over random topography
In this paper, we study the motion of the free surface of a body of fluid
over a variable bottom, in a long wave asymptotic regime. We assume that the
bottom of the fluid region can be described by a stationary random process
whose variations take place on short length scales and which
are decorrelated on the length scale of the long waves. This is a question of
homogenization theory in the scaling regime for the Boussinesq and KdV
equations. The analysis is performed from the point of view of perturbation
theory for Hamiltonian PDEs with a small parameter, in the context of which we
perform a careful analysis of the distributional convergence of stationary
mixing random processes. We show in particular that the problem does not fully
homogenize, and that the random effects are as important as dispersive and
nonlinear phenomena in the scaling regime that is studied. Our principal result
is the derivation of effective equations for surface water waves in the long
wave small amplitude regime, and a consistency analysis of these equations,
which are not necessarily Hamiltonian PDEs. In this analysis we compute the
effects of random modulation of solutions, and give an explicit expression for
the scattered component of the solution due to waves interacting with the
random bottom. We show that the resulting influence of the random topography is
expressed in terms of a canonical process, which is equivalent to a white noise
through Donsker's invariance principle, with one free parameter being the
variance of the random process . This work is a reappraisal of the paper
by Rosales & Papanicolaou \cite{RP83} and its extension to general stationary
mixing processes
The effect of the solar corona on the attenuation of small-amplitude prominence oscillations. I. Longitudinal magnetic field
Context. One of the typical features shown by observations of solar
prominence oscillations is that they are damped in time and that the values of
the damping times are usually between one and three times the corresponding
oscillatory period. However, the mechanism responsible for the attenuation is
still not well-known. Aims. Thermal conduction, optically thin or thick
radiation and heating are taken into account in the energy equation, and their
role on the attenuation of prominence oscillations is evaluated. Methods. The
dispersion relation for linear non-adiabatic magnetoacoustic waves is derived
considering an equilibrium made of a prominence plasma slab embedded in an
unbounded corona. The magnetic field is orientated along the direction parallel
to the slab axis and has the same strength in all regions. By solving the
dispersion relation for a fixed wavenumber, a complex oscillatory frequency is
obtained, and the period and the damping time are computed. Results. The effect
of conduction and radiation losses is different for each magnetoacoustic mode
and depends on the wavenumber. In the observed range of wavelengths the
internal slow mode is attenuated by radiation from the prominence plasma, the
fast mode by the combination of prominence radiation and coronal conduction and
the external slow mode by coronal conduction. The consideration of the external
corona is of paramount importance in the case of the fast and external slow
modes, whereas it does not affect the internal slow modes at all. Conclusions.
Non-adiabatic effects are efficient damping mechanisms for magnetoacoustic
modes, and the values of the obtained damping times are compatible with those
observed.Comment: Accepted in A&
Artificial Intelligence for breast cancer detection:Technology, challenges, and prospects
Purpose: This review provides an overview of the current state of artificial intelligence (AI) technology for automated detection of breast cancer in digital mammography (DM) and digital breast tomosynthesis (DBT). It aims to discuss the technology, available AI systems, and the challenges faced by AI in breast cancer screening. Methods: The review examines the development of AI technology in breast cancer detection, focusing on deep learning (DL) techniques and their differences from traditional computer-aided detection (CAD) systems. It discusses data pre-processing, learning paradigms, and the need for independent validation approaches. Results: DL-based AI systems have shown significant improvements in breast cancer detection. They have the potential to enhance screening outcomes, reduce false negatives and positives, and detect subtle abnormalities missed by human observers. However, challenges like the lack of standardised datasets, potential bias in training data, and regulatory approval hinder their widespread adoption. Conclusions: AI technology has the potential to improve breast cancer screening by increasing accuracy and reducing radiologist workload. DL-based AI systems show promise in enhancing detection performance and eliminating variability among observers. Standardised guidelines and trustworthy AI practices are necessary to ensure fairness, traceability, and robustness. Further research and validation are needed to establish clinical trust in AI. Collaboration between researchers, clinicians, and regulatory bodies is crucial to address challenges and promote AI implementation in breast cancer screening.</p
Wreath products and representations of p-local finite groups
Peer reviewedPostprin
The role of Rayleigh-Taylor instabilities in filament threads
Many solar filaments and prominences show short-lived horizontal threads
lying parallel to the photosphere. In this work the possible link between
Rayleigh-Taylor instabilities and thread lifetimes is investigated. This is
done by calculating the eigenmodes of a thread modelled as a Cartesian slab
under the presence of gravity. An analytical dispersion relation is derived
using the incompressible assumption for the magnetohydrodynamic (MHD)
perturbations. The system allows a mode that is always stable, independently of
the value of the Alfv\'en speed in the thread. The character of this mode
varies from being localised at the upper interface of the slab when the
magnetic field is weak, to having a global nature and resembling the transverse
kink mode when the magnetic field is strong. On the contrary, the slab model
permits another mode that is unstable and localised at the lower interface when
the magnetic field is weak. The growth rates of this mode can be very short, of
the order of minutes for typical thread conditions. This Rayleigh-Taylor
unstable mode becomes stable when the magnetic field is increased, and in the
limit of strong magnetic field it is essentially a sausage magnetic mode. The
gravity force might have a strong effect on the modes of oscillation of
threads, depending on the value of the Alfv\'en speed. In the case of threads
in quiescent filaments, where the Alfv\'en speed is presumably low, very short
lifetimes are expected according to the slab model. In active region
prominences, the stabilising effect of the magnetic tension might be enough to
suppress the Rayleigh-Taylor instability for a wide range of wavelengths
Seismology of Standing Kink Oscillations of Solar Prominence Fine Structures
We investigate standing kink magnetohydrodynamic (MHD) oscillations in a
prominence fine structure modeled as a straight and cylindrical magnetic tube
only partially filled with the prominence material, and with its ends fixed at
two rigid walls representing the solar photosphere. The prominence plasma is
partially ionized and a transverse inhomogeneous transitional layer is included
between the prominence thread and the coronal medium. Thus, ion-neutral
collisions and resonant absorption are the considered damping mechanisms.
Approximate analytical expressions of the period, the damping time, and their
ratio are derived for the fundamental mode in the thin tube and thin boundary
approximations. We find that the dominant damping mechanism is resonant
absorption, which provides damping ratios in agreement with the observations,
whereas ion-neutral collisions are irrelevant for the damping. The values of
the damping ratio are independent of both the prominence thread length and its
position within the magnetic tube, and coincide with the values for a tube
fully filled with the prominence plasma. The implications of our results in the
context of the MHD seismology technique are discussed, pointing out that the
reported short-period (2 - 10 min) and short-wavelength (700 - 8,000 km) thread
oscillations may not be consistent with a standing mode interpretation and
could be related to propagating waves. Finally, we show that the inversion of
some prominence physical parameters, e.g., Alfv\'en speed, magnetic field
strength, transverse inhomogeneity length-scale, etc., is possible using
observationally determined values of the period and damping time of the
oscillations along with the analytical approximations of these quantities.Comment: Accepted for publication in Ap
Kink oscillations of flowing threads in solar prominences
Recent observations by Hinode/SOT show that MHD waves and mass flows are
simultaneously present in the fine structure of solar prominences. We
investigate standing kink magnetohydrodynamic (MHD) waves in flowing prominence
threads from a theoretical point of view. We model a prominence fine structure
as a cylindrical magnetic tube embedded in the solar corona with its ends
line-tied in the photosphere. The magnetic cylinder is composed of a region
with dense prominence plasma, which is flowing along the magnetic tube, whereas
the rest of the flux tube is occupied by coronal plasma. We use the WKB
approximation to obtain analytical expressions for the period and the amplitude
of the fundamental mode as functions of the flow velocity. In addition, we
solve the full problem numerically by means of time-dependent simulations. We
find that both the period and the amplitude of the standing MHD waves vary in
time as the prominence thread flows along the magnetic structure. The
fundamental kink mode is a good description for the time-dependent evolution of
the oscillations, and the analytical expressions in the WKB approximation are
in agreement with the full numerical results. The presence of flow modifies the
period of the oscillations with respect to the static case. However, for
realistic flow velocities this effect might fall within the error bars of the
observations. The variation of the amplitude due to the flow leads to apparent
damping or amplification of the oscillations, which could modify the real rate
of attenuation caused by an additional damping mechanism.Comment: Accepted for publication in A&
Magnetohydrodynamic kink waves in two-dimensional non-uniform prominence threads
We analyse the oscillatory properties of resonantly damped transverse kink
oscillations in two-dimensional prominence threads. The fine structures are
modelled as cylindrically symmetric magnetic flux tubes with a dense central
part with prominence plasma properties and an evacuated part, both surrounded
by coronal plasma. The equilibrium density is allowed to vary non-uniformly in
both the transverse and the longitudinal directions.We examine the influence of
longitudinal density structuring on periods, damping times, and damping rates
for transverse kink modes computed by numerically solving the linear resistive
magnetohydrodynamic (MHD) equations. The relevant parameters are the length of
the thread and the density in the evacuated part of the tube, two quantities
that are difficult to directly estimate from observations. We find that both of
them strongly influence the oscillatory periods and damping times, and to a
lesser extent the damping ratios. The analysis of the spatial distribution of
perturbations and of the energy flux into the resonances allows us to explain
the obtained damping times. Implications for prominence seismology, the physics
of resonantly damped kink modes in two-dimensional magnetic flux tubes, and the
heating of prominence plasmas are discussed.Comment: 12 pages, 9 figures, A&A accepte
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