By applying the theory of semigroups, we generalize an earlier result of Komornik and Loreti  on the observability of compactly
perturbed systems. As an application, we answer a question of the same authors concerning the observability of weakly coupled
linear distributed systems.
Authors:Paul Delfabbro, Anna Thomas, and Andrew Armstrong
about the likelihood of such information being observable on any one occasion. Similar reviews were expressed in a paper by Hafeli and Schneider ( 2006 ) who conducted research into the potential value of indicators in Swiss casinos. In contrast to
Authors:Claudio Baiocchi, Vilmos Komornik, and Paola Loreti
Completing a series of works begun by Wiener , Paley and Wiener  and Ingham , a far-reaching generalization of
Parseval"s identity was obtained by Beurling  for nonharmonic Fourier series whose exponents satisfy a uniform gap condition.
Later this gap condition was weakened by Ullrich , Castro and Zuazua , Jaffard, Tucsnak and Zuazua  and then in
 in some particular cases. In this paper we prove a general theorem which contains all previous results. Furthermore, applying
a different method, we prove a variant of this theorem for nonharmonic Fourier series with vector coefficients. This result, partly motivated by control-theoretical applications, extends several earlier results obtained
in  and . Finally, applying these results we obtain an optimal simultaneous observability theorem concerning a system
of vibrating strings.
We characterize the stabilization for some coupled infinite dimensional systems. The proof of the main result uses the methodology
introduced in Ammari and Tucsnak , where the exponential stability for the closed loop problem is reduced to an observability
estimate for the corresponding uncontrolled system combined to a boundedness property of the transfer function of the associated
open loop system and a result in .
This paper is a review of recent developments of a research line proposed on the turn of the decades, 1980s to 1990s. The
main results concern basic qualitative properties of nonlinear models of population biology, such as controllability and observability.
The methods applied are different for the density-dependent models of population ecology and for the frequency-dependent models
of population genetics and evolutionary theory. While in the first case the classical theorems of nonlinear systems theory
can be used, in the second one an extension of classical results to systems with invariant manifold is necessary.
Biome interfaces are expected to exhibit chorological symmetry, i.e., decreasing trends in the number of species associated with each of the two neighbouring biomes as we progress from one into the other. Our aim was to test for such a pattern within the forest steppe biome, which is a transition zone in itself between the temperate deciduous forests and the steppe biome. Presence of chorological symmetry would provide indirect evidence for the prehuman presence of zonal steppes in the Carpathian basin. We also whished to provide an example with this analysis for drawing biogeographical conclusions based on quantitative species occurrence data, an information source hitherto neglected in Central Europe. Occurrence patterns of forest and steppe species were analysed at the Duna-Tisza köze (Danube-Tisza Interfluve) by the traditional qualitative biogeographic method and by hierarchical classification of predicted spatial pattern based on Generalized Linear Models with logistic link function. Species presences were explained by variables describing spatial orientation. In this approach, an outgroup of sand grassland species was also added to characetrise the discrimination ability of the approach. The quantitative method discriminated the out-group of sand grassland species, providing evidence of its suitability for our purpose. The results of the quantitative investigations were also in accordance with the qualitative evaluation. Surprisingly, forest and steppe species showed similar distributional patterns, i.e., no chorological symmetry was discernable. The quantitative biogeographic approach unveiled important evidence for deciding about the potential presence of zonal steppes in the Carpathian basin. Although the observed similarity of the distribution of forest and steppe species may have multiple reasons, the major cause of the lack of chorological symmetry is most probably the lack of zonal steppe South of the forest steppe biome in the Carpathian basin. Additional explanations include land use pattern and the mountain belt around the basin acting as a refugium in the ice ages.
eigenvectors can be expected to change with a dynamics different from those of the networks of observable relations. A “duality of structure” is generated because the events take place in two concurrent spaces (Giddens 1979 ).
From a systems