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A management architecture for active networks
In this paper we present an architecture for network and applications management, which is based on the Active Networks paradigm and shows the advantages of network programmability. The stimulus to develop this architecture arises from an actual need to manage a cluster of active nodes, where it is often required to redeploy network assets and modify nodes connectivity. In our architecture, a remote front-end of the managing entity allows the operator to design new network topologies, to check the status of the nodes and to configure them. Moreover, the proposed framework allows to explore an active network, to monitor the active applications, to query each node and to install programmable traps. In order to take advantage of the Active Networks technology, we introduce active SNMP-like MIBs and agents, which are dynamic and programmable. The programmable management agents make tracing distributed applications a feasible task. We propose a general framework that can inter-operate with any active execution environment. In this framework, both the manager and the monitor front-ends communicate with an active node (the Active Network Access Point) through the XML language. A gateway service performs the translation of the queries from XML to an active packet language and injects the code in the network. We demonstrate the implementation of an active network gateway for PLAN (Packet Language for Active Networks) in a forty active nodes testbed. Finally, we discuss an application of the active management architecture to detect the causes of network failures by tracing network events in time
Optimal pressure boundary control of steady multiscale fluid-structure interaction shell model derived from koiter equations
Fluid-structure interaction (FSI) problems are of great interest, due to their applicability in science and engineering. However, the coupling between large fluid domains and small moving solid walls presents numerous numerical difficulties and, in some configurations, where the thickness of the solid wall can be neglected, one can consider membrane models, which are derived from the Koiter shell equations with a reduction of the computational cost of the algorithm. With this assumption, the FSI simulation is reduced to the fluid equations on a moving mesh together with a Robin boundary condition that is imposed on the moving solid surface. In this manuscript, we are interested in the study of inverse FSI problems that aim to achieve an objective by changing some design parameters, such as forces, boundary conditions, or geometrical domain shapes. We study the inverse FSI membrane model by using an optimal control approach that is based on Lagrange multipliers and adjoint variables. In particular, we propose a pressure boundary optimal control with the purpose to control the solid deformation by changing the pressure on a fluid boundary. We report the results of some numerical tests for two-dimensional domains to demonstrate the feasibility and robustness of our method
Higher Curvature Gravity and the Holographic fluid dual to flat spacetime
Recent works have demonstrated that one can construct a (d+2) dimensional
solution of the vacuum Einstein equations that is dual to a (d+1) dimensional
fluid satisfying the incompressible Navier-Stokes equations. In one important
example, the fluid lives on a fixed timelike surface in the flat Rindler
spacetime associated with an accelerated observer. In this paper, we show that
the shear viscosity to entropy density ratio of the fluid takes the universal
value 1/4\pi in a wide class of higher curvature generalizations to Einstein
gravity. Unlike the fluid dual to asymptotically anti-de Sitter spacetimes,
here the choice of gravitational dynamics only affects the second order
transport coefficients. We explicitly calculate these in five-dimensional
Einstein-Gauss-Bonnet gravity and discuss the implications of our results.Comment: 13 pages; v2: modified abstract, added references; v3: added
clarifying comments, modified discussio
The universal viscosity to entropy density ratio from entanglement
We present evidence that the universal Kovtun-Son-Starinets shear viscosity
to entropy density ratio of 1/4\pi can be associated with a Rindler causal
horizon in flat spacetime. Since there is no known holographic (gauge/gravity)
duality for this spacetime, a natural microscopic explanation for this
viscosity is in the peculiar properties of quantum entanglement. In particular,
it is well-known that the Minkowski vacuum state is a thermal state and carries
an area entanglement entropy density in the Rindler spacetime. Based on the
fluctuation-dissipation theorem, we expect a similar notion of viscosity
arising from vacuum fluctuations. Therefore, we propose a holographic Kubo
formula in terms of a two-point function of the stress tensor of matter fields
in the bulk. We calculate this viscosity assuming a minimally coupled scalar
field theory and find that the ratio with respect to the entanglement entropy
density is exactly 1/4\pi in four dimensions. The issues that arise in
extending this result to non-minimally coupled scalar fields, higher spins, and
higher dimensions provide interesting hints about the relationship between
entanglement entropy and black hole entropy.Comment: 30 pages; v2: footnote added, minor editin
Gravity from Quantum Information
It is suggested that the Einstein equation can be derived from Landauer's
principle applied to an information erasing process at a local Rindler horizon
and Jacobson's idea linking the Einstein equation with thermodynamics. When
matter crosses the horizon, the information of the matter disappears and the
horizon entanglement entropy increases to compensate the entropy reduction. The
Einstein equation describes an information-energy relation during this process,
which implies that entropic gravity is related to the quantum entanglement of
the vacuum and has a quantum information theoretic origin.Comment: 7 pages, revtex4-1, 2 figures, recent supporting results adde
Sicilian byzantine icons through the use of non-invasive imaging techniques and optical spectroscopy: The case of the madonna dell’elemosina
The iconographic heritage is one of the treasures of Byzantine art that have enriched the south of Italy, and Sicily in particular, since the early 16th century. In this work, the investigations of a Sicilian Icon of Greek-Byzantine origin, the Madonna dell’Elemosina, is reported for the first time. The study was carried out using mainly non-invasive imaging techniques (photography in reflectance and grazing visible light, UV fluorescence, infrared reflectography, radiography, and computed tomography) and spectroscopic techniques (X-ray fluorescence and infrared spectroscopy). The identification of the constituent materials provides a decisive contribution to the correct historical and artistic placement of the Icon, a treasure of the Eastern European historical community in Sicily. Some hidden details have also been highlighted. Most importantly, the information obtained enables us to define its conservation state, the presence of foreign materials, and to direct its protection and restoration
Campionamento biologico delle catture commerciali Sezione III.C - Variabili biologiche relative al mestiere e dei parametri biologici Sezione III.E - Variabili biologiche relative agli stock del Programma Nazionale
Il campionamento biologico delle catture/sbarcati commerciali, sezione C – Relative al mestiere ed E – Relative agli stock (Campbiol), nell’ambito del Programma Nazionale per la Raccolta Dati Alieutici (PNRDA) (Reg. Ce. N°199/2008; N°665/2008 e decisione della commissione N°949/2008) risulta di grande importanza per conoscere come agisce il prelievo dei diversi ”metiers” sulle diverse specie, in termini di variazioni dell’abbondanza e struttura demografica delle risorse da pesca.
Il campionamento biologico risponde, quindi, principalmente alle seguenti esigenze:
1. Ricostruire la struttura demografica delle catture commerciali/sbarchi di ogni specie (in taglia/età ), considerando tutti i ”métiers” che incidono significativamente sull’ammontare globale delle catture.
2. Ricostruire il pattern di sfruttamento dei diversi ”métiers” per le diverse specie.
3. Consentire lo studio dei fenomeni biologici rilevanti, quali la crescita ed il ciclo sessuale, che variano nel corso dell’anno.
4. Acquisire informazioni sulla struttura demografica con specifico riferimento allo stadio di maturazione gonadica (maturitĂ /taglia-etĂ ) ed alla relazione fra lunghezza e peso corporeo (taglia-peso/etĂ ).
Il Programma Nazionale prevede il rilievo dei parametri significativi ai fini della caratterizzazione biologica del prodotto della pesca, principalmente nell’ambito di due differenti moduli:
Modulo di valutazione del settore della pesca
Sezione C – “Variabili biologiche relative al mestiere”
Sezione E – “Variabili biologiche relative agli stock
Campionamento biologico delle catture commerciali Sezione III.C - Variabili biologiche relative al mestiere e dei parametri biologici Sezione III.E - Variabili biologiche relative agli stock del Programma Nazionale Sub-area Geografica (GSA16) – Stretto di Sicilia Anno 2015
Il campionamento biologico delle catture/sbarcati commerciali, sezione C – Relative al mestiere ed E – Relative agli stock, nell’ambito del Programma Nazionale per la Raccolta Dati Alieutici (PNRDA) (Reg. Ce. N°199/2008; N°665/2008 e decisione della commissione N°949/2008), ha l’obiettivo di valutare la composizione in taglia e/o età del pescato ed ottenere altre informazioni sulla biologia delle specie bersaglio, quali le chiavi età /lunghezza, la relazione lunghezza/peso, i parametri di crescita, la composizione in sesso e le condizioni di maturità sessuale.
Il campionamento delle catture/sbarchi commerciali (campionamento biologico - CAMPBIOL) risulta di grande importanza per conoscere come agisce il prelievo dei diversi ”metiers” sulle diverse specie, in termini di variazioni dell’abbondanza e struttura demografica delle risorse da pesca.
Il campionamento biologico risponde, quindi, principalmente alle seguenti esigenze:
1. Ricostruire il pattern di sfruttamento dei diversi ”métiers” per le diverse specie.
2. Ricostruire la struttura demografica delle catture commerciali/sbarchi di ogni specie (in taglia/età ), considerando tutti i ”métiers” che incidono significativamente sull’ammontare globale delle catture.
3. Consentire lo studio dei fenomeni biologici rilevanti, quali la crescita ed il ciclo sessuale, che variano nel corso dell’anno.
4. Acquisire informazioni sulla struttura demografica con specifico riferimento allo stadio di maturazione gonadica (maturitĂ /taglia-etĂ ) ed alla relazione fra lunghezza e peso corporeo (taglia-peso/etĂ ).
Il Programma Nazionale prevede il rilievo dei parametri significativi ai fini della caratterizzazione biologica del prodotto della pesca, principalmente nell’ambito di due differenti moduli:
Modulo di valutazione del settore della pesca
Sezione C – “Variabili biologiche relative al mestiere”
Sezione E – “Variabili biologiche relative agli stock
Local Entropy Current in Higher Curvature Gravity and Rindler Hydrodynamics
In the hydrodynamic regime of field theories the entropy is upgraded to a
local entropy current. The entropy current is constructed phenomenologically
order by order in the derivative expansion by requiring that its divergence is
non-negative. In the framework of the fluid/gravity correspondence, the entropy
current of the fluid is mapped to a vector density associated with the event
horizon of the dual geometry. In this work we consider the local horizon
entropy current for higher-curvature gravitational theories proposed in
arXiv:1202.2469, whose flux for stationary solutions is the Wald entropy. In
non-stationary cases this definition contains ambiguities, associated with
absence of a preferred timelike Killing vector. We argue that these ambiguities
can be eliminated in general by choosing the vector that generates the subset
of diffeomorphisms preserving a natural gauge condition on the bulk metric. We
study a dynamical, perturbed Rindler horizon in Einstein-Gauss-Bonnet gravity
setting and compute the bulk dual solution to second order in fluid gradients.
We show that the corresponding unambiguous entropy current at second order has
a manifestly non-negative divergence.Comment: 28 pages, 2 appendices; v2: added references, fixed typos, one
clarifying commen
Conservative entropic forces
Entropic forces have recently attracted considerable attention as ways to
reformulate, retrodict, and perhaps even "explain'" classical Newtonian gravity
from a rather specific thermodynamic perspective. In this article I point out
that if one wishes to reformulate classical Newtonian gravity in terms of an
entropic force, then the fact that Newtonian gravity is described by a
conservative force places significant constraints on the form of the entropy
and temperature functions. (These constraints also apply to entropic
reinterpretations of electromagnetism, and indeed to any conservative force
derivable from a potential.)
The constraints I will establish are sufficient to present real and
significant problems for any reasonable variant of Verlinde's entropic gravity
proposal, though for technical reasons the constraints established herein do
not directly impact on either Jacobson's or Padmanabhan's versions of entropic
gravity. In an attempt to resolve these issues, I will extend the usual notion
of entropic force to multiple heat baths with multiple "temperatures'" and
multiple "entropies".Comment: V1: 21 pages; no figures. V2: now 24 pages. Two new sections (reduced
mass formulation, decoherence). Many small clarifying comments added
throughout the text. Several references added. V3: Three more references
added. V4: now 25 pages. Some extra discussion on the relation between
Verlinde's scenario and the Jacobson and Padmanabhan scenarios. This version
accepted for publication in JHE
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