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Collision avoidance for Delay_Req messages in broadcast media
No full textThe time accuracy of the Precision Time Protocol deteriorates in consequence to Delay req/Delay resp session collisions common for applications using shared broadcast media. In this paper we propose a protocol that coordinates Delay_req/Delay_resp sessions with minimum changes to the original PTP protocol. Simulations illustrate protocol’s operation and demonstrate significant reduction of session collisions
TERMGRAPH 2009 Preliminary Proceedings
No full textPREFACE
TERMGRAPH 2009 took place in York (UK) on March 22, 2009, as a one-day
satellite event of ETAPS 2009. Previous editions of the TERMGRAPH
workshops series took place in Barcelona (2002), in Rome (2004), in
Vienna (2006), and in Braga (2007).
The advantage of computing with graphs rather than terms (strings or
trees) is that common subexpressions can be shared, which improves the
efficiency of computations in space and time. Sharing is ubiquitous in
implementations of programming languages: many implementations of
functional, logic, object-oriented and concurrent calculi are based on
term graphs. Term graphs are also used in symbolic computation systems
and automated theorem proving.
The aim of TERMGRAPH 2009 was to bring together researchers working in
these different domains and to foster their interaction, to provide a
forum for presenting new ideas and work in progress, and to enable
newcomers to learn about current activities in term graph rewriting.
Topics of interest for the workshop are all aspects of term graphs and sharing of
common subexpressions in rewriting, programming, automated reasoning
and symbolic computation. This includes (but is not limited to) term
rewriting, graph transformation, programming languages, models of
computation, graph-based languages, semantics and implementation of
programming languages, compiler construction, pattern recognition,
databases, bioinformatics, and system descriptions.
This report contains the eight contributions presented during the workshop:
they were selected by the Program Committee according to originality,
significance, and general interest. In addition to these presentations,
the programme included two invited lectures by Helene Kirchner
and Fabio Gadducci
About LTR recurrence in yeast strains
No full textHere we report a preliminary analysis of transposons Long Terminal Repeats (LTR) within several yeast strains
Overdetermined boundary value problems for the -Laplacian
No full textSUMMARY We consider overdetermined boundary value problems for the -Laplacian
in a domain of and discuss what kind of implications on the
geometry of the existence of a solution may have. The classical
-Laplacian, the normalized or game-theoretic -Laplacian and the
limit of the -Laplacian as are considered and provide
different answers
Advent of Non-Abelian Vortices and Monopoles-- further thoughts about duality and confinement
No full textRecent development on non-Abeliann vortices and monopoles is reviewed with an
emphasis on their relevance on confinement and duality. A very recent
construction of non-Abelian vortices which do not dynamically Abelianize is
crucial in this context
0-1 Reformulations of the Multicommodity Capacitated Network Design Problem
No full textWe study 0-1 reformulations of the multicommodity capacitated network design problem, which is usually modeled with general integer variables to represent design decisions on the number of facilities to install on each arc of the network. The reformulations are based on the multiple choice model, a generic approach to represent piecewise linear costs using 0-1 variables. This model is improved by the addition of extended linking inequalities, derived from variable disaggregation techniques. We show that these extended linking inequalities for the 0-1 model are equivalent to the residual capacity inequalities, a class of valid inequalities derived for the model with general integer variables. In this paper, we compare two cutting-plane algorithms to compute the same lower bound on the optimal value of the problem: one based on the generation of residual capacity inequalities within the model with general integer variables, and another based on the addition of extended linking inequalities to the 0-1 reformulation. To further improve the computational results of the latter approach, we develop a column-and-row generation approach; the resulting algorithm is shown to be competitive with the approach relying on residual capacity inequalities
Echi raciniani nella Clemenza di Tito di Metastasio-Hasse (1759)
No full textRIASSUNTO Il libretto della Clemenza di Tito (1734) è fra quelli in Metastasio che affiancano più lucidamente il contenuto politico e la magnificenza dell’apparato pubblico con implicazioni e problematiche connesse allo sviluppo dei caratteri. Come per solito, Metastasio trae l’argomento da fonti di matrice classica (in particolare le Vite di Svetonio), poggiando per la stesura dell’ordito sulla griglia elaborata da tragedie e melodrammi coevi, secondo la prassi del riuso citazionistico tipica di tutta una maniera letteraria. In questo caso suggestioni corneilliane e raciniane, divise prevalentemente fra Cinna (1640-1641) e Andromaque (1667), avvalorano il duplice aspetto della materia e somministrano i momenti salienti del dramma, che il libretto ridispone con impareggiabile ingegno in equilibri affatto nuovi, talora attraverso metamorfosi profonde dei modelli riguardo all’impianto e alla caratterizzazione dei personaggi: una riscrittura adeguata alle diverse convenzioni di genere, valide anche per il passaggio inverso dal melodramma alla tragedia nella traduzione francese di Pierre-Laurent Buirette de Belloy (Titus, 1757). Da Cinna discendono la cornice politica e il motivo della cospirazione, cui Andromaque porge le ragioni psicologiche sotto forma di una sequenza di relazioni amorose frustrate che in Metastasio, come già in Racine, conducono all’attentato contro il sovrano. L’ispirazione, tuttavia, appare attratta non dal celebre dilemma di Andromaca bensì dallo sdegnato orgoglio di Ermione, i cui confronti con Oreste illuminano le scene fra Vitellia e Sesto nel libretto. I punti dell’intreccio che riscrivono il motivo raciniano offrono la sostanza per analizzare la qualità delle scelte interpretative di Hasse nella sua ultima intonazione del libretto (Napoli, 1759). Anche ad un esame superficiale risultano tendenze significative rispetto al testo metastasiano, come per esempio la valorizzazione del ruolo di Sesto oppure il rilievo garantito ad aspetti quali nostalgia e ripiegamento nella caratterizzazione di Tito. In particolare, l’attenzione al rapporto fra poesia, musica e gesto si giova nel commento delle prospettive critiche maturate negli ultimi trent’anni, soprattutto grazie agli studi di Reinhard Strohm, nella convinzione che al linguaggio musicale di Hasse (e della sua epoca) vada riconosciuta la possibilità di sottintendere azioni e di possedere forza espressiva. SUMMARY La clemenza di Tito is one of Metastasio’s most famous (and often studied) dramas. Musicologists have been attracted by its late setting by Mozart, just as literary scholars have shown interest in its relationship with authoritative sources such as Corneille’s Cinna and Tite et Bérénice, and Racine’s Bérénice and Andromaque. From Corneille’s Cinna Metastasio derives the treatment of the conspiracy motive, but then combines the political issues with a Racinian psychological situation. Andromaque provides a chain of frustrated love relationships. In these Metastasio, like Racine, finds personal reasons that lead to the attempt on the king’s life. Out of jealousy and offended pride, Vitellia and Hermione first urge Sesto and Oreste to take revenge on the ‘unfaithful’ Tito and Pyrrhus, and then deny any responsibility for the crime. In La clemenza di Tito Metastasio seems to combine the political and intimate themes that he derives from Corneille’s Cinna and Racine’s Andromaque. This favours the organization of the libretto in larger units containing from three to six scenes, where both recitatives and arias determine the dramatic situation. In the analysis, I shall thus discuss how Hasse’s music reacts to the level of the Racinian themes, trying to highlight the dramatic and musical coherence of selected sequences of scenes
On the Choice of Explicit Stabilizing Terms in Column Generation
No full textColumn generation algorithms are instrumental in many areas of applied optimization, where linear programs with an enormous number of columns need to be solved. Although succesfully employed in many applications, these approaches suffer from well-known instability issues that somewhat limit their efficiency. Building on the theory developed for nondifferentiable optimization algorithms, a large class of stabilized column generation algorithms can be defined which avoid the instability issues by using an explicit stabilizing term in the dual; this amounts at considering a (generalized) augmented Lagrangian of the primal master problem. Since the theory allows for a great degree of flexibility in the choice and in the management of the stabilizing term, one can use piecewise-linear or quadratic functions that can be efficiently dealt with off-the-shelf solvers. The effectiveness in practice of this approach is demonstrated by extensive computational experiments on large-scale Vehicle and Crew Scheduling problems. Also, the results of a detailed computational study on the impact of the different choices in the stabilization term (shape of the function, parameters), and their relationships with the quality of the initial dual estimates, on the overall effectiveness of the approach are reported, providing practical guidelines for selecting the most appropriate variant in different situations
Optimal design of binary cycle power plants for water-dominated, medium-temperature geothermal fields
No full textSUMMARY Exploitation of lower temperature, water-dominated geothermal fields is analyzed, and a methodology for optimizing geothermal binary plants is discussed. The geothermal fluid inlet temperatures considered are in the 110-160 °C range, while the return temperature of the brine is assumed to be between 70 and 100 °C. The analysis shows that the brine specific consumption, ranging from 20 to 120 kg/s for each net MW produced, and the efficiency of the plants, ranging from 20 to 45% in terms of Second Law efficiency, are dictated mainly by the combination of the brine inlet temperature, the brine rejection temperature and the energy conversion cycle being used. For given operating conditions and with correct matching between working fluid and energy conversion cycle, it is possible to obtain very similar performances in a number of different cases. It is shown that optimization of the plant can yield improvements of up to 30-40% in terms of reduction of brine specific consumption compared to conventional design
Multiple Solutions in Preliminary Orbit Determination from Three Observations
No full textSUMMARY Charlier's theory (1910) provides a geometric interpretation of the occurrence of multiple solutions in Laplace's method of preliminary orbit determination, assuming geocentric observations. We introduce a generalization of this theory allowing to take into account topocentric observations, that is observations made from the surface of the rotating Earth. The generalized theory works for both Laplace's and Gauss' methods. We also provide a geometric definition of a curve that generalizes Charlier's limiting curve, separating regions with a different number of solutions. The results are generically different from Charlier's: they may change according to the value of a parameter that depends on the observations