10,843 research outputs found
Biodegradable polymers based on trimethylene carbonate for tissue engineering applications
In the field of tissue engineering, the search for suitable materials for use in the preparation of scaffolds to host the developing tissue represents a major subject of study. Biodegradable materials show great potential in this area as, by resorbing upon performing their function, they obviate long-term biocompatibility concerns
Civic Education in Basic School: Problems and Challenges in the Digital Age
This paper focus on the analysis of preliminary data of an ongoing study involving Portuguese teachers and
students, in the non-disciplinary curricular area of Civic Education. The project aims at encouraging collaborative behaviour
in educational communities, involving teachers and students in the development of digital contents, and at exploring different
issues on citizenship education, under a case-based methodology. We believe this action research study is of relevance
because it can unveil examples of good practices and innovative teaching strategies that need to be disseminated in this
compulsory subject taking into account the results of recent studies, which exposed some of the inefficiency of the
strategies adopted so far
Extreme values for Benedicks-Carleson quadratic maps
We consider the quadratic family of maps given by with
, where is a Benedicks-Carleson parameter. For each of these
chaotic dynamical systems we study the extreme value distribution of the
stationary stochastic processes , given by , for
every integer , where each random variable is distributed
according to the unique absolutely continuous, invariant probability of .
Using techniques developed by Benedicks and Carleson, we show that the limiting
distribution of is the same as that which would
apply if the sequence was independent and identically
distributed. This result allows us to conclude that the asymptotic distribution
of is of Type III (Weibull).Comment: 18 page
Early aspects: aspect-oriented requirements engineering and architecture design
This paper reports on the third Early Aspects: Aspect-Oriented Requirements Engineering and Architecture Design Workshop, which has been held in Lancaster, UK, on March 21, 2004. The workshop included a presentation session and working sessions in which the particular topics on early aspects were discussed. The primary goal of the workshop was to focus on challenges to defining methodical software development processes for aspects from early on in the software life cycle and explore the potential of proposed methods and techniques to scale up to industrial applications
Caracterização molecular e estrutural do sintase do óxido nítrico de Leishmania
Relatório de projeto no âmbito do Programa de Bolsas Universidade de Lisboa/Fundação Amadeu Dias (2011/2012). Universidade de Lisboa. Faculdade de Ciência
Extreme Value Laws in Dynamical Systems for Non-smooth Observations
We prove the equivalence between the existence of a non-trivial hitting time
statistics law and Extreme Value Laws in the case of dynamical systems with
measures which are not absolutely continuous with respect to Lebesgue. This is
a counterpart to the result of the authors in the absolutely continuous case.
Moreover, we prove an equivalent result for returns to dynamically defined
cylinders. This allows us to show that we have Extreme Value Laws for various
dynamical systems with equilibrium states with good mixing properties. In order
to achieve these goals we tailor our observables to the form of the measure at
hand
Extreme Value Laws for sequences of intermittent maps
We study non-stationary stochastic processes arising from sequential
dynamical systems built on maps with a neutral fixed points and prove the
existence of Extreme Value Laws for such processes. We use an approach
developed in \cite{FFV16}, where we generalised the theory of extreme values
for non-stationary stochastic processes, mostly by weakening the uniform mixing
condition that was previously used in this setting. The present work is an
extension of our previous results for concatenations of uniformly expanding
maps obtained in \cite{FFV16}.Comment: To appear in Proceedings of the American Mathematical Society. arXiv
admin note: substantial text overlap with arXiv:1510.0435
Extreme Value Laws for non stationary processes generated by sequential and random dynamical systems
We develop and generalize the theory of extreme value for non-stationary
stochastic processes, mostly by weakening the uniform mixing condition that was
previously used in this setting. We apply our results to non-autonomous
dynamical systems, in particular to {\em sequential dynamical systems}, given
by uniformly expanding maps, and to a few classes of random dynamical systems.
Some examples are presented and worked out in detail
Speed of convergence for laws of rare events and escape rates
We obtain error terms on the rate of convergence to Extreme Value Laws for a
general class of weakly dependent stochastic processes. The dependence of the
error terms on the `time' and `length' scales is very explicit. Specialising to
data derived from a class of dynamical systems we find even more detailed error
terms, one application of which is to consider escape rates through small holes
in these systems
Complete convergence and records for dynamically generated stochastic processes
We consider empirical multi-dimensional Rare Events Point Processes that keep
track both of the time occurrence of extremal observations and of their
severity, for stochastic processes arising from a dynamical system, by
evaluating a given potential along its orbits. This is done both in the absence
and presence of clustering. A new formula for the piling of points on the
vertical direction of bi-dimensional limiting point processes, in the presence
of clustering, is given, which is then generalised for higher dimensions. The
limiting multi-dimensional processes are computed for systems with sufficiently
fast decay of correlations. The complete convergence results are used to study
the effect of clustering on the convergence of extremal processes, record time
and record values point processes. An example where the clustering prevents the
convergence of the record times point process is given
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