7,497 research outputs found
Adaptable processes
We propose the concept of adaptable processes as a way of overcoming the
limitations that process calculi have for describing patterns of dynamic
process evolution. Such patterns rely on direct ways of controlling the
behavior and location of running processes, and so they are at the heart of the
adaptation capabilities present in many modern concurrent systems. Adaptable
processes have a location and are sensible to actions of dynamic update at
runtime; this allows to express a wide range of evolvability patterns for
concurrent processes. We introduce a core calculus of adaptable processes and
propose two verification problems for them: bounded and eventual adaptation.
While the former ensures that the number of consecutive erroneous states that
can be traversed during a computation is bound by some given number k, the
latter ensures that if the system enters into a state with errors then a state
without errors will be eventually reached. We study the (un)decidability of
these two problems in several variants of the calculus, which result from
considering dynamic and static topologies of adaptable processes as well as
different evolvability patterns. Rather than a specification language, our
calculus intends to be a basis for investigating the fundamental properties of
evolvable processes and for developing richer languages with evolvability
capabilities
Synchronization and local convergence analysis of networks with dynamic diffusive coupling
In this paper, we address the problem of achieving synchronization in networks of nonlinear units coupled by dynamic diffusive terms. We present two types of couplings consisting of a static linear term, corresponding to the diffusive coupling, and a dynamic term which can be either the integral or the derivative of the sum of the mismatches between the states of neighbouring agents. The resulting dynamic coupling strategy is a distributed proportional-integral (PI) or a proportional-derivative (PD) law that is shown to be effective in improving the network synchronization performance, for example, when the dynamics at nodes are nonidentical. We assess the stability of the network by extending the classical Master Stability Function approach to the case where the links are dynamic ones of PI/PD type. We validate our approach via a set of representative examples including networks of chaotic Lorenz and networks of nonlinear mechanical systems
Very low bias stress in n-type organic single crystal transistors
Bias stress effects in n-channel organic field-effect transistors (OFETs) are
investigated using PDIF-CN2 single-crystal devices with Cytop gate dielectric,
both under vacuum and in ambient. We find that the amount of bias stress is
very small as compared to all (p-channel) OFETs reported in the literature.
Stressing the PDIF-CN2 devices by applying 80 V to the gate for up to a week
results in a decrease of the source drain current of only ~1% under vacuum and
~10% in air. This remarkable stability of the devices leads to characteristic
time constants, extracted by fitting the data with a stretched exponential -
that are \tau ~ 2\cdot10^9 s in air and \tau ~ 5\cdot10^9 s in vacuum -
approximately two orders of magnitude larger than the best values reported
previously for p-channel OFETs.Comment: Submitted to Applied Physics Letters; 14 pages, 3 figure
First record of brown long-eared bat Plecotus auritus (Chiroptera: Vespertilionidae) for Sicily island (Italy)
The knowledge of the bat fauna of Sicily (Southern Italy) is scarce,
fragmentary or sometimes even confusing. A recent review mentioned 20
species for the region, but it is likely that the checklist of bats of
Sicily is still far from being exhaustive. To help fill this gap, in
the past few years specific studies were carried out on the
distribution of bat species in Sicily, especially in the woodlands of
the Nebrodi Mountains. In the municipality of Caronia (Messina
province) has captured a young female brown long-eared bat Plecotus
auritus (Linneaus, 1758). The capture of P. auritus in Sicily
represents the first record of brown long-eared bat Plecotus auritus
for Sicily island, an interesting biogeographical record, as this bat
is mostly known for the north and centre of the Italian peninsul
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