59,174 research outputs found
A Note on the Shannon Entropy of Short Sequences
For source sequences of length L symbols we proposed to use a more realistic
value to the usual benchmark of number of code letters by source letters. Our
idea is based on a quantifier of information fluctuation of a source, F(U),
which corresponds to the second central moment of the random variable that
measures the information content of a source symbol. An alternative
interpretation of typical sequences is additionally provided through this
approach.Comment: 3 figure
Correction to: Some results on the p(u)-Laplacian problem
Correction to: Mathematische Annalen
https://doi.org/10.1007/s00208-019-01803-w
In the Original Publication of the article, few errors have been identified in section 5
and acknowledgements section.AgĂȘncia financiadora
Ministry of Education and Science, Russian Federation
117198
Portuguese Foundation for Science and Technology (FCT), Portugal
SFRH/BSAB/135242/2017info:eu-repo/semantics/publishedVersio
Chaos and a Resonance Mechanism for Structure Formation in Inflationary Models
We exhibit a resonance mechanism of amplification of density perturbations in
inflationary mo-dels, using a minimal set of ingredients (an effective
cosmological constant, a scalar field minimally coupled to the gravitational
field and matter), common to most models in the literature of inflation. This
mechanism is based on the structure of homoclinic cylinders, emanating from an
unstable periodic orbit in the neighborhood of a saddle-center critical point,
present in the phase space of the model. The cylindrical structure induces
oscillatory motions of the scales of the universe whenever the orbit visits the
neighborhood of the saddle-center, before the universe enters a period of
exponential expansion. The oscillations of the scale functions produce, by a
resonance mechanism, the amplification of a selected wave number spectrum of
density perturbations, and can explain the hierarchy of scales observed in the
actual universe. The transversal crossings of the homoclinic cylinders induce
chaos in the dynamics of the model, a fact intimately connected to the
resonance mechanism occuring immediately before the exit to inflation.Comment: 4 pages. This essay received an Honorable Mention from the Gravity
Research Foundation, 1998-Ed. To appear in Mod. Phys. Lett.
Earthen construction: structural vulnerabilities and retrofit solutions for seismic actions
Earthen structures present very appealing characteristics regarding a more sustainable practice with the
preservation of our natural resources. However, when subjected to earthquake ground motions, this type of
construction may present a deficient performance, which may cause significant human losses and important
structural damage. The seismic response of earthen structures is typically characterized by fragile failures. There
are several examples of recent earthquakes that affected earthen buildings in a severe way, evidencing the
vulnerability of this type of construction, like the El Salvador earthquake, in 2001, the Bam, Iran earthquake, in
2003, the Pisco, Peru earthquake, in 2007 and the Maule, Chile earthquake, in 2010.
The construction of earth structures on earthquake-prone areas must be carefully studied and should include
seismic reinforcement solutions in order to improve their seismic performance.
In this paper, the performance of earthen structures in recent earthquakes will be examined, analyzing failure
modes inherent to these particular construction materials and associated construction techniques. Also, seismic
reinforcement approaches and techniques will be presented in a comprehensive manner. Examples of tests conducted for the assessment of retrofitting solutions efficiency will be presented, and the results obtained will be discussed
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