Repositório Colecção:
http://hdl.handle.net/10198/419
2016-05-02T12:44:10ZMultiple solutions of mixed variable optimization by multistart hooke and jeeves filter method
http://hdl.handle.net/10198/11875
Título: Multiple solutions of mixed variable optimization by multistart hooke and jeeves filter method
Autor: Costa, M. Fernanda P.; Fernandes, Florbela P.; Fernandes, Edite M.G.P.; Rocha, Ana Maria A. C.
Resumo: In this study, we propose a multistart method based on an extended version of the Hooke and Jeeves (HJ) algorithm for computing multiple solutions of mixed variable optimization problems. The inequality and equality constraints of the problem are handled by a ﬁlter set methodology. The basic ideas present in the HJ algorithm, namely the exploratory and pattern moves, are extended to consider two objective functions and to handle continuous and integer variables simultaneously. This proposal is integrated into a multistart method as a local search procedure that is repeatedly invoked to converge to diﬀerent global and non-global optimal solutions starting from randomly generated points. To avoid repeated convergence to previously computed solutions, the concept of region of attraction of an optimizer is implemented. The performance of the new method is tested on benchmark problems. Its eﬀectiveness is emphasized by a comparison with a well-known solver.2014-01-01T00:00:00ZAnosov diffeomorphisms
http://hdl.handle.net/10198/11350
Título: Anosov diffeomorphisms
Autor: Almeida, João P.; Fisher, Albert M.; Pinto, Alberto A.; Rand, David A.
Resumo: We use Adler, Tresser and Worfolk decomposition of Anosov automorphisms
to give an explicit construction of the stable and unstable C^{1+}
self-renormalizable sequences2013-01-01T00:00:00ZGolden tilings
http://hdl.handle.net/10198/11346
Título: Golden tilings
Autor: Almeida, João P.; Pinto, Alberto A.; Portela, A.
Resumo: We introduce the notion of golden tilings, and we prove a one-to-one correspondence between (i) smooth conjugacy classes of Anosov diffeomorphisms, with an invariant measure absolutely continuous with respect to the Lebesgue measure, (ii) affine classes of golden tilings and (iii) solenoid functions. The solenoid functions give a parametrization of the infinite dimensional space consisting of the mathematical objects described in the above equivalences.2012-01-01T00:00:00ZAngular momentum transport by internal waves in the solar interior
http://hdl.handle.net/10198/8290
Título: Angular momentum transport by internal waves in the solar interior
Autor: Zahn, Jean-Paul; Talon, Suzanne; Matias, José
Resumo: The internal gravity waves of low frequency which
are emitted at the base of the solar convection zone are able
to extract angular momentum from the radiative interior. We
evaluate this transport with some simplifying assumptions: we
ignore the Coriolis force, approximate the spectrum of turbulent
convection by the Kolmogorov law, and couple this turbulence
to the internal waves through their pressure fluctuations, following
Press (1981) and Garc´ıa L´opez & Spruit (1991). The
local frequency of an internal wave varies with depth in a differentially
rotating star, and it can vanish at some location, thus
leading to enhanced damping (Goldreich & Nicholson 1989). It
is this dissipation mechanism only that we take into account in
the exchange of momentum between waves and stellar rotation.
The flux of angular momentum is then an implicit function of
depth, involving the local rotation rate and an integral representing
the cumulative effect of radiative dissipation. We find that
the efficiency of this transport process is rather high: it operates
on a timescale of 107 years, and is probably responsible for the
flat rotation profile which has been detected through helioseismology.1997-01-01T00:00:00Z