130,770 research outputs found
L'évolution de la frontière entre la Provence et le comté de Nice
No full textAndreis D. L'évolution de la frontière entre la Provence et le comté de Nice. In: Cahiers de la Méditerranée, n°11, 1, 1975. Migrants et travailleurs. pp. 101-115
Coexistence of Stable Limit Cycles in a Generalized Curie–Weiss Model with Dissipation
No full textIn this paper, we modify the Langevin dynamics associated to the generalized Curie–Weiss model by introducing noisy and dissipative evolution in the interaction potential. We show that, when a zero-mean Gaussian is taken as single-site distribution, the dynamics in the thermodynamic limit can be described by a finite set of ODEs. Depending on the form of the interaction function, the system can have several phase transitions at different critical temperatures. Because of the dissipation effect, not only the magnetization of the systems displays a self-sustained periodic behavior at sufficiently low temperature, but, in certain regimes, any (finite) number of stable limit cycles can exist. We explore some of these peculiarities with explicit examples
Serie dinamica del bosco a Rovere: il caso del Parco nazionale Val Grande (VCO)
No full textViene ricostruita la serie dinamica del bosco a rovere nel
Parco Nazionale Val Grande (VCO), quale caso di studio esportabile
a tutta l’area prealpina occidentale suboceanica, per analogia di clima
e substrato. Sono state cartografate, in ambiente GIS, le aree di pertinenza
della serie sulla base delle caratteristiche climatiche e fi siche del
territorio. Entro tali aree sono stati effettuati 48 rilievi fi tosociologici
che hanno compreso tutti gli stadi serali della vegetazione, per poi procedere
con l’analisi delle fi tocenosi individuate e la loro interpretazione
in chiave dinamica. Risultato dello studio è l’individuazione di sei fi -
tocenosi, quattro delle quali (pteridieti, calluneti, betuleti, rovereti) fra
loro collegate da un legame dinamico, suggerito da analisi fl oristiche
quali-quantitative sull’abbondanza delle specie e dall’analisi dei parametri
ecologico-stazionali tramite CCA.Ecological succession of sessile oak woods: Val Grande
National Park (Italian Western Alps) as a case study. We assessed the
ecological succession of sessile oak (Quercus petraea) woods in Val
Grande National Park (Verbano-Cusio-Ossola, Italian Western Alps), as
an example available for all the western prealpine insubric area. With
GIS we have deduced the map of the areas of pertinence of Quercus
petraea, based on climatic and physical characteristics of the territory.
Within these areas we carried out 48 phytosociological relevés according
to Braun-Blanquet method, assessing all stages of the ecological succession.
As a main result the Cluster Analysis individuated 6 phytocenoses
and 4 of the them (Pteridium aquilinum grasslands, Calluna vulgaris
moors, Betula pendula woods, Quercus petraea woods) have a dynamic
link suggested by quali-quantitative analysis about species ecology and
abundance and by several environmental parameters analyzed by CCA
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