26,278 research outputs found
Behavioral Equivalences
Beahvioral equivalences serve to establish in which cases two reactive (possible concurrent) systems offer similar interaction capabilities relatively to other systems representing their operating environment. Behavioral equivalences have been mainly developed in the context
of process algebras, mathematically rigorous languages that have been used for describing and verifying properties of concurrent communicating systems. By relying on the so called structural operational semantics (SOS), labelled transition systems, are associated to each term of a process
algebra. Behavioral equivalences are used to abstract from unwanted details and identify those labelled transition systems that react āsimilarlyā to external experiments. Due to the large number of properties which may be relevant in the analysis of concurrent systems, many different theories
of equivalences have been proposed in the literature. The main contenders consider those systems equivalent that (i) perform the same sequences of actions, or (ii) perform the same sequences of actions and after each sequence are ready to accept the same sets of actions, or (iii) perform the
same sequences of actions and after each sequence exhibit, recursively, the same behavior. This approach leads to many different equivalences that preserve significantly different properties of systems
Process Algebras
Process Algebras are mathematically rigorous languages with well defined semantics that permit describing and verifying properties of concurrent communicating systems.
They can be seen as models of processes, regarded as agents that act and interact continuously with other similar agents and with their common environment. The agents may be real-world objects (even people), or they may be artifacts, embodied perhaps in computer hardware or software systems.
Many different approaches (operational, denotational, algebraic) are taken for describing the meaning of processes. However, the operational approach is the reference one. By relying on the so called Structural Operational Semantics (SOS), labelled transition systems are built and composed by using the different operators of the many different process algebras. Behavioral equivalences are used to abstract from unwanted details and identify those systems that react similarly to external
experiments
Refinement of a previous hypothesis of the Lyapunov analysis of isotropic turbulence
The purpose of this brief comunication is to improve a hypothesis of the
previous work of the author (de Divitiis, Theor Comput Fluid Dyn,
doi:10.1007/s00162-010-0211-9) dealing with the finite--scale Lyapunov analysis
of isotropic turbulence. There, the analytical expression of the structure
function of the longitudinal velocity difference is derived
through a statistical analysis of the Fourier transformed Navier-Stokes
equations, and by means of considerations regarding the scales of the velocity
fluctuations, which arise from the Kolmogorov theory. Due to these latter
considerations, this Lyapunov analysis seems to need some of the results of the
Kolmogorov theory.
This work proposes a more rigorous demonstration which leads to the same
structure function, without using the Kolmogorov scale. This proof assumes that
pair and triple longitudinal correlations are sufficient to determine the
statistics of , and adopts a reasonable canonical decomposition of
the velocity difference in terms of proper stochastic variables which are
adequate to describe the mechanism of kinetic energy cascade.Comment: 6 page
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