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Java: Preprocessing Closures in Java
No full textThe paper adds a mechanism of {\em closure} to Java. We apply to closures the same technique we exploited in extending Java with methods as parameters \cite{bellia2008,bellia2008c} and we obtain a formal definition and a prototype of Java with closures. The formal definition consists of a set of source to source translation rules that state the meaning of the new construct in terms of compositions of well known ordinary Java structures. Two variants of the transformation are discussed to allow recursive defined closures and other mechanisms. The notion of {\em shared variable} as a local variable that is allocated in the heap is also discussed. Eventually, since the resulting transformation is one pass process, it can be implemented through a source to source, one pass, preprocessor \cite{bellia2007,bellia2008b}, easy to write using standard development tools \cite{levine1995,donnely2006}
Strong-disorder paramagnetic-ferromagnetic fixed point in the square-lattice +- J Ising model
No full textWe consider the random-bond +- J Ising model on a square lattice as a
function of the temperature T and of the disorder parameter p (p=1 corresponds
to the pure Ising model). We investigate the critical behavior along the
paramagnetic-ferromagnetic transition line at low temperatures, below the
temperature of the multicritical Nishimori point at T*= 0.9527(1),
p*=0.89083(3). We present finite-size scaling analyses of Monte Carlo results
at two temperature values, T=0.645 and T=0.5. The results show that the
paramagnetic-ferromagnetic transition line is reentrant for T<T*, that the
transitions are continuous and controlled by a strong-disorder fixed point with
critical exponents nu=1.50(4) and eta=0.128(8), and beta = 0.095(5). This fixed
point is definitely different from the Ising fixed point controlling the
paramagnetic-ferromagnetic transitions for T>T*. Our results for the critical
exponents are consistent with the hyperscaling relation 2 beta/nu - eta = d - 2
= 0
The wandering token: Congestion avoidance of a shared resource
No full textIn a distributed system where scalability is an issue, the problem of enforcing mutual exclusion often arises in a soft form: the infrequent failure of the mutual exclusion predicate is tolerated, without compromising the consistent operation of the overall system. For instance this occurs when the operation subject to mutual exclusion requires massive use of a shared resource. We introduce a scalable soft mutual exclusion algorithm, based on previous termtokennext term passing: one distinguished feature of our algorithm is that instead of introducing an overlay topology we adopt a random walk approach. The consistency of our proposal is evaluated by simulation, and we exemplify its use in the coordination of large data transfers in a backbone based network. This algorithm is studied in the frame of the CoreGRID Institute of Grid Information, Resource and Workflow Monitoring Services, in cooperation with the FORTH Institute, in Greece
S.Maria Maggiore di Francavilla a mare:progetto, costruzione, arredo
Get PDFRIASSUNTO La chiesa di S. Maria Maggiore in Francavilla a Mare (Chieti) venne costruita sulle ceneri della precedente chiesa settecentesca, distrutta durante il secondo conflitto mondiale. Il progetto vincitore del concorso indetto nel 1948, elaborato da Ludovico Quaroni, si distingueva per l’uso del cemento armato nelle parti strutturali portanti e per l'adozione di un linguaggio neorealista per le pareti di tamponamento che inseriva la chiesa nel più ampio contesto delle sperimentazioni architettoniche postbelliche. S. Maria Maggiore rappresenta anche il primo tentativo quaroniano di rispondere ai problemi dell'interpretazione del tema dell'edificio sacro e del suo inserimento nel tessuto urbano, alla luce delle esigenze di culto poste dalla committenza e dalla natura stessa dell'edificio . Nel corso del tempo gli interventi dello scultore Pietro Cascella hanno contribuito a modificare la percezione dello spazio interno dell’edificio, riplasmato nel rispetto della riforma liturgica operata dal Concilio Vaticano II. L’articolo ricostruisce le fasi principali dell’elaborazione progettuale e della costruzione della chiesa, evidenziando il rapporto tra l'architetto, la committenza e l'artista. SUMMARY The church of S. Maria Maggiore, Francavilla a Mare (Chieti) was built on the ashes of the previous Eighteenth-Century church, destroyed during the Second World War. A project developed by Ludovico Quaroni won the competition held in 1948. It was distinguished by the use of reinforced concrete in structural parts and the adoption of a neorealist language for the walls that inserted the church in the broader context of post-conflict experiments. S. Maria Maggiore is also Quaroni's first attempt to answer to the problems of interpretation of a sacred theme and of its insertion into the urban fabric, according to the requirements imposed by the liturgy and by the nature of the building. The sculptor Pietro Cascella changed the perception of the interior space of the building, reshaped in accordance with the liturgical reform made by Vatican II. This paper describes the main stages of the project and the construction of the church, highlighting the relationship between the architect, the client and the artist
Masking Patterns in Sequences: A New Class of Motif Discovery with Don't Cares
No full textSUMMARY We introduce a new notion of motifs, called masks, that succinctly represents the repeated patterns for an input sequence T of n symbols drawn from an alphabet. We show how to build the set of all frequent maximal masks of length L in O.2Ln/ time and space in the worst case, using the KarpMillerRosenberg approach. We analytically show that our algorithm performs better than the method based on constant-time enumerating and checking all the potential .jj C 1/L candidate patterns in T , after a polynomial-time preprocessing of T . Our algorithm is also cache-friendly, attaining O.2L sort.n// block transfers, where sort.n/ is the cache complexity of sorting n items
Preventing the collision of requests from slave clocks in the Precision Time Protocol (PTP)
No full textSUMMARY The Precision Time Protocol (PTP) distributes a time reference across a network: it specifically addresses demanding environments, where it can reach sub microsecond precision using appropriate technologies. Its scalability is primarily limited by packet delay variations induced by packet collisions. While it is possible to avoid collisions with non-PTP packets using traffic management technologies, collision between PTP packets is an open problem in large systems with critical clock precision requirements. We propose a coordination algorithm that avoids the occurrence of such collisions. It assumes that the timing reference source, the master clock, can send a packet in multicast to the slaves: this is not a restrictive hypotesis, since PTP itself takes advantage of this kind of connectivity, and it is also compatible with typical wireless environments. The algorithm operates without introducing additional traffic, it ensures an upper bound to the time between two successive synchronizations of any given slave, it does not alter the structure of the standard PTP messages, it envisions a dynamic number of slaves, it tolerates the replacement of the master with a hot spare in case of failure, and does not rely on specialized hardware. The algorithm has a footprint that does not insist on activities that are already time sensitive, and its operation is mostly concentrated on the master. The algorithm inherits security and fault tolerance limits from PTP: in particular this refers to malicious nodes, and to broken devices that may jam the network
The future challenges for "clean coal technologies": joining efficiency increase and pollutant emission control
No full textSUMMARY Coal offers an abundant widely spread fossil energy resource. It is available at a quite stable price from many international suppliers and it will continue to play a significant role in new generating capacity, if security and diversity of supply remain fundamental. In this paper we point out the state of the art in the field of “Clean Coal Technologies” evidencing the perspectives of improvement and the critical elements. Both the emission control of NOx, SOx and Particle Matter and the advanced coal conversion pathways like USC, PFBC and IGCC are reviewed and analysed. At the end some elements concerning the perspectives of CO2 emission control strategies are outlined
Molecular phylogeography of the asp viper Vipera aspis (Linnaeus, 1758) in Italy: evidence for introgressive hybridization and mitochondrial DNA capture
No full textSUMMARY Owing to its temperature dependence and low vagility, the asp viper (Vipera aspis) is an interesting model species to study the effects of Pleistocene climatic fluctuations on vertebrate genomes. We genotyped 102 specimens from the whole Italian distribution range at three mitochondrial DNA regions (2278 characters, total) and six microsatellite DNA loci (Short Tandem Repeats, STR). The molecular phylogeny was constructed according to Bayesian, Neighbour-Joining, Maximum Parsimony and Maximum Likelihood procedures. All methods grouped individuals of the three morphological subspecies (V. a. aspis, V. a. francisciredi, V. a. hugyi) into five different haploclades. Specimens assigned to hugyi clustered in two highly differentiated clades, one being sister group to the complex comprising the second clade of hugyi (i.e., a paraphyletic status), plus two clades of francisciredi. The Bayesian clustering of the STR variability disclosed only two groups, the first including aspis and francisciredi, the second all hugyi. Introgressive hybridization and capture of francisciredi-like lineages in the hugyi mitochondrial genome were suggested to explain the discordance between mitochondrial and nuclear data. The phylogeographic pattern was compatible with population contractions in three glacial refuges. Plausibility of derived hypothesis was checked using coalescence simulations as post hoc tests. Long-term drift and serial founder-effects, rather than selection, appeared the main factors affecting the genetic make-up of the Italian asp viper
Transparent Process Monitoring in a Virtual Environment
Get PDFPsycoTrace is a system that integrates static and dynamic tools to protect a process from attacks that alter the process self as specified by the program source code. The static tools build a context-free grammar that describes the sequences of system calls the process may issue and a set of assertions on the process state, one for each invocation. The dynamic tools parse the call trace of the process to check that it belongs to the grammar language and evaluate the assertions. This paper describes the architecture of PsycoTrace, which exploits virtualization to introduce two virtual machines, the monitored and the monitoring virtual machines, to increase both the robustness and the transparency of the monitoring because the machine that implements all the checks is strongly separated from the monitored one. We discuss the modification to the kernel of the monitored machine to trace system call invocations, the definition of the legal traces and the checks to prove the trace is valid. We describe how PsycoTrace applies introspection to evaluate the assertions and analyze the state of the monitored machine and of its data structures. Finally, we present the security and performance results of the dynamic tools, and the implementation of the static tools. Sommario Il lavoro descrive PsycoTrace, uno strumento per la protezione da attacchi informatici basato su virtualizzazione. PsycoTrace fonde virtualizzazione ed introspezione per valutare asserzioni sullo stato di un processso in modo da rilevare attacchi che modifichino lo stato del processo. Inoltre, ad ogni processo viene associata una grammatica che descrive le tracce generate dall'esecuzione del processo. Una traccia definisce le invocazioni al sistema operativo del processo
Relation between configurational entropy and relaxation dynamics of glass-forming systems under volume and temperature reduction
No full textSUMMARY The structural relaxation dynamics of two molecular glass-forming systems have been analyzed by means of dielectric spectroscopy, under cooling and compression conditions. The relation of the dynamic slowing down with the reduction of the configurational entropy, SC, as predicted by Adam and Gibbs (AG), was also investigated. As SC is not directly accessible by experiments, it was estimated, following a common procedure in literature, from the excess entropy Sexc of the supercooled liquid with respect to the crystal, determined from calorimetric and expansivity measurements over the same T–P range of dynamics investigation. The AG relation, predicting linear dependence between the logarithmic of structural relaxation time and the reciprocal of the product of temperature with configurational entropy, was successfully tested. Actually, a bilinear relation between Sexc and SC was found, with different proportionality factors in isothermal and isobaric conditions. Using such results, we derived an equation for predicting the pressure dependence of the glass transition temperature, in good accordance with the experimental values in literature