17,201 research outputs found
Spatiotemporal instability of a confined capillary jet
Recent experimental studies on the instability appearance of capillary jets
have revealed the capabilities of linear spatiotemporal instability analysis to
predict the parametrical map where steady jetting or dripping takes place. In
this work, we present an extensive analytical, numerical and experimental
analysis of confined capillary jets extending previous studies. We propose an
extended, accurate analytic model in the limit of low Reynolds flows, and
introduce a numerical scheme to predict the system response when the liquid
inertia is not negligible. Theoretical predictions show a remarkable accuracy
with results from the extensive experimental exploration provided.Comment: Submitted to the Physical Review E (20-March-2008
Dynamics of a 1-D model for the emergence of the plasma edge shear flow layer with momentum conserving Reynolds stress
A one-dimensional version of the second-order transition model based on the
sheared flow amplification by Reynolds stress and turbulence supression by
shearing is presented. The model discussed in this paper includes a form of the
Reynolds stress which explicitly conserves momentum. A linear stability
analysis of the critical point is performed. Then, it is shown that the
dynamics of weakly unstable states is determined by a reduced equation for the
shear flow. In the case in which the flow damping term is diffusive, the
stationary solutions are those of the real Ginzburg-Landau equation.Comment: 21 pages, 8 figure
An Enactive Theory of Need Satisfaction
In this paper, based on the predictive processing approach to cognition, an enactive theory of need satisfaction is discussed. The theory can be seen as a first step towards a computational cognitive model of need satisfaction
Eye Tracking Impact on Quality-of-Life of ALS Patients
Chronic neurological disorders in their advanced phase are characterized by a progressive loss of mobility (use of upper and lower limbs), speech and social life. Some of these pathologies, such as amyotrophic lateral sclerosis and multiple sclerosis, are paradigmatic of these deficits. High technology communication instruments, such as eye tracking, can be an extremely important possibility to reintroduce these patients in their family and social life, in particular when they suffer severe disability. This paper reports and describes the results of an ongoing experimentation about Eye Tracking impact on the quality of life of amyotrophic lateral sclerosis patients. The aim of the experimentation is to evaluate if and when eye tracking technologies have a positive impact on patients' live
Dual branes in topological sigma models over Lie groups. BF-theory and non-factorizable Lie bialgebras
We complete the study of the Poisson-Sigma model over Poisson-Lie groups.
Firstly, we solve the models with targets and (the dual group of the
Poisson-Lie group ) corresponding to a triangular -matrix and show that
the model over is always equivalent to BF-theory. Then, given an
arbitrary -matrix, we address the problem of finding D-branes preserving the
duality between the models. We identify a broad class of dual branes which are
subgroups of and , but not necessarily Poisson-Lie subgroups. In
particular, they are not coisotropic submanifolds in the general case and what
is more, we show that by means of duality transformations one can go from
coisotropic to non-coisotropic branes. This fact makes clear that
non-coisotropic branes are natural boundary conditions for the Poisson-Sigma
model.Comment: 24 pages; JHEP style; Final versio
Mapping the structural diversity of C60 carbon clusters and their infrared spectra
The current debate about the nature of the carbonaceous material carrying the
infrared (IR) emission spectra of planetary and proto-planetary nebulae,
including the broad plateaus, calls for further studies on the interplay
between structure and spectroscopy of carbon-based compounds of astrophysical
interest. The recent observation of C60 buckminsterfullerene in space suggests
that carbon clusters of similar size may also be relevant. In the present work,
broad statistical samples of C60 isomers were computationally determined
without any bias using a reactive force field, their IR spectra being
subsequently obtained following local optimization with the
density-functional-based tight-binding theory. Structural analysis reveals four
main structural families identified as cages, planar polycyclic aromatics,
pretzels, and branched. Comparison with available astronomical spectra
indicates that only the cage family could contribute to the plateau observed in
the 6-9 micron region. The present framework shows great promise to explore and
relate structural and spectroscopic features in more diverse and possibly
hydrogenated carbonaceous compounds, in relation with astronomical
observations
Thermal analysis applied to estimation of solidification kinetics of Al–Si aluminium alloys
Evaluation of solidification kinetics by thermal analysis is a useful tool for quality control of Al–Si melts before pouring provided it is rapid and highly reproducible. Series of thermal analysis records made with standard cups are presented that show good reproducibility. They are evaluated using a Newton’s like approach to get the instantaneous heat evolution and from it solidification kinetics. An alternative way of calculating the zero line is proposed which is validated by the fact that the latent heat of solidification thus evaluated is within 5% of the value calculated from thermodynamic data. Solidification kinetics was found highly reproducible provided appropriate experimental conditions were achieved: high enough casting temperature for the cup to heat up to the metal temperature well before solidification starts; and equal and homogeneous temperatures of the metal and of the cup at any time in the temperature range used for integration
Carlos Rojas: su primera obra narrativa (1957-1962)
En las obras narrativas de este primer período de Carlos Rojas se encuentran ya algunos de los elementos básicos de su novelística posterior, como la temática sobre la condición humana, Europa y sus valores, el carácter destructivo del poder y el mal. Igualmente hallamos los componentes de la actitud de Rojas ante la novela: la independencia y autocrítica, el criterio personal en la manera de concebir la novela, el ensayo constante de nuevas formas, la fusión de lo cerebral y lo vital, la conjugación de los elementos de la realidad visible y de la invisible en un «realismo total» y la búsqueda de la transcendencia que apunta a niveles metafísicos y religiosos.In Carlos Rojas' first period narrative works were already some of the basic elements of his later personality, as the theme of the human condition, Europe and its values, the destructive nature of power and evil. Equally, we find the components of Rojas' attitude before the novel: the independence and self-criticism, the personal discretion in the way of conceiving the novel, the constant test of new forms, the merger of the cerebral and vital, the combination of the elements of visible reality and invisible in a "total realism" and the search for the transcendence that aims at metaphysical and religious levels
Melting of aluminium clusters
The melting of Al clusters in the size range 49 <= N <= 62 has been studied
using two model interatomic potentials. The results for the two models are
significantly different. The glue potential exhibits a smooth relatively
featureless heat capacity curve for all sizes except for N = 54 and N = 55,
sizes at which icosahedral structures are favoured over the polytetrahedral.
Gupta heat capacity curves, instead, show a well-defined peak that is
indicative of a first-order-like transition. The differences between the two
models reflect the different ground-state structures, and neither potential is
able to reproduce or explain the size dependence of the melting transition
recently observed in experiments
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