673 research outputs found
CODEWEAVE: exploring fine-grained mobility of code
This paper is concerned with an abstract exploration of code mobility constructs designed for use in settings where the level of granularity associated with the mobile units exhibits significant variability. Units of mobility that are both finer and coarser grained than the unit of execution are examined. To accomplish this, we take the extreme view that every line of code and every variable declaration are potentially mobile, i.e., it may be duplicated or moved from one program context to another on the same host or across the network. We also assume that complex code assemblies may move with equal ease. The result is CODEWEAVE, a model that shows how to develop new forms of code mobility, assign them precise meaning, and facilitate formal verification of programs employing them. The design of CODEWEAVE relies greatly on Mobile UNITY, a notation and proof logic for mobile computing. Mobile UNITY offers a computational milieu for examining a wide range of constructs and semantic alternatives in a clean abstract setting, i.e., unconstrained by compilation and performance considerations traditionally associated with programming language design. Ultimately, the notation offered by CODEWEAVE is given exact semantic definition by means of a direct mapping to the underlying Mobile UNITY model. The abstract and formal treatment of code mobility offered by CODEWEAVE establishes a technical foundation for examining competing proposals and for subsequent integration of some of the mobility constructs both at the language level and within middleware for mobility
Further evidence of the absence of Replica Symmetry Breaking in Random Bond Potts Models
In this short note, we present supporting evidence for the replica symmetric
approach to the random bond q-state Potts models. The evidence is statistically
strong enough to reject the applicability of the Parisi replica symmetry
breaking scheme to this class of models. The test we use is a generalization of
one formerly proposed by Dotsenko et al. and consists in measuring scaling laws
of disordered-averaged moments of the spin-spin correlation functions.
Numerical results, obtained via Monte Carlo simulations for several values of
q, are shown to be in fair agreement with the replica symmetric values computed
by using perturbative CFT for the second and third moments of the q=3 model.
RSB effects, which should increase in strength with moment, are unobserved.Comment: 7 pages, some minor modifications (mainly misprints). To Appear in
Europhysics Letter
Programming Wireless Sensor Networks with Logical Neighborhoods: A Road Tunnel Use Case
Wireless sensor networks (WSNs) involving actuation are increasingly envisioned in a range of fields [1]. Among these, there is considerable interest in leveraging off WSNs to improve safety in road tunnels [4]. Researchers are envi- sioning tunnels equipped with WSN nodes that gather physi- cal readings such as temperature and light, monitor the struc- tural integrity of the tunnel, and sense the presence of vehi- cles to detect a possible traffic congestion. Based on sensed data, the system operates a variety of devices, such as ven- tilation fans inside the tunnel, and traffic lights at the en- trances. For instance, when a sensor detects the presence of a fire in a sector, the fans in the same sector are activated, and the traffic lights are turned red to prevent further vehicles from entering the tunnel
Scale Invariance and Self-averaging in disordered systems
In a previous paper we found that in the random field Ising model at zero
temperature in three dimensions the correlation length is not self-averaging
near the critical point and that the violation of self-averaging is maximal.
This is due to the formation of bound states in the underlying field theory. We
present a similar study for the case of disordered Potts and Ising ferromagnets
in two dimensions near the critical temperature. In the random Potts model the
correlation length is not self-averaging near the critical temperature but the
violation of self-averaging is weaker than in the random field case. In the
random Ising model we find still weaker violations of self-averaging and we
cannot rule out the possibility of the restoration of self-averaging in the
infinite volume limit.Comment: 7 pages, 4 ps figure
3_D modeling using TLS and GPR techniques to characterize above and below-ground wood distribution in pyroclastic deposits along the Blanco River (Chilean Patagonia)
To date, the study of in-stream wood in rivers has been focused mainly on quantifying wood pieces deposited above
the ground. However, in some particular river systems, the presence of buried dead wood can also represent an
important component of wood recruitment and budgeting dynamics. This is the case of the Blanco River (Southern
Chile) severely affected by the eruption of Chait\ue9n Volcano occurred between 2008 and 2009. The high pyroclastic
sediment deposition and transport affected the channel and the adjacent forest, burying wood logs and standing
trees. The aim of this contribution is to assess the presence and distribution of wood in two study areas (483 m2 and
1989 m2, respectively) located along the lower streambank of the Blanco River, and covered by thick pyroclastic
deposition up to 5 m. The study areas were surveyed using two different devices, a Terrestrial Laser Scanner (TLS)
and a Ground Penetrating Radar (GPR). The first was used to scan the above surface achieving a high point cloud
density ( 48 2000 points m-2) which allowed us to identify and measure the wood volume. The second, was used
to characterize the internal morphology of the volcanic deposits and to detect the presence and spatial distribution
of buried wood up to a depth of 4 m. Preliminary results have demonstrated differences in the numerousness and
volume of above wood between the two study areas. In the first one, there were 43 wood elements, 33 standing
trees and 10 logs, with a total volume of 2.96 m3 (109.47 m3 km-1), whereas the second one was characterized
by the presence of just 7 standing trees and 11 wood pieces, for a total amount of 0.77 m3 (7.73 m3 km-1). The
dimensions of the wood elements vary greatly according to the typology, standing trees show the higher median
values in diameter and length (0.15 m and 2.91 m, respectively), whereas the wood logs were smaller (0.06 m and
1.12 m, respectively). The low dimensions of deposited wood can be probably connected to their origin, suggesting
that these elements were generated by toppling and breaking of surrounding dead trees. Results obtained with the
GPR confirm the ability of this instrument to localize the presence and distribution of buried wood. From the 3-
D analysis it was possible to assess the spatial distribution and to estimate, as first approach, the volume of the
buried wood which represents approximately 0.04% of the entire volcanic deposit. Further analysis will focus on
additional GPR calibration with different wood sizes for a more accurate estimation of the volume. The knowledge
of the overall wood amount stored in a fluvial system that can be remobilized over time, represent an essential
factor to ensure better forest and river management actions
Pervasive Games in a Mote-Enabled Virtual World Using Tuple Space Middleware
Pervasive games are a new and exciting field where the user experience benefits from the blending of real and virtual elements. Players are no longer confined to computer screens. Rather, interactions with devices embedded within the real world and physical movements become an integral part of the gaming experience. Several prototypes of pervasive games have been proposed by both industry and academia. However, in such games the issues arising from the integration of players and real world, the management of the context surrounding the players, and the need for communication and distributed coordination are often addressed in an ad-hoc fashion. Therefore, the underlying software fabric is often not reusable, ultimately slowing down the diffusion of pervasive games.
In this paper we describe the design and implementation of a pervasive game on top of TinyLIME, a middleware system supporting data sharing among mobile and embedded devices. By illustrating the design of a pervasive game we developed, we argue concretely that the programming abstractions supported by TinyLIME greatly simplify the data and context management characteristics of pervasive games, and provide an effective and reusable building block for their development.
TinyLIME was originally designed to support applications where mobile users collect data from sensors scattered in the physical environment. We build upon this capability to put forth a second contribution, namely, the use of wireless sensor devices (or motes) as a computing platform for pervasive games. Besides reporting physical data for the sake of the game, we use motes to store information relevant to the game plot, e.g., virtual objects. Motes are typically very small in size, and therefore can be hidden in the environment, enhancing the sense of immersion in a virtual world. To the best of our knowledge, this original use of wireless sensor devices is novel in the scientific and gaming literature. Furthermore, it is naturally supported by TinyLIME, yielding a unified programming abstraction that spans the heterogeneous gaming platform we propose
4D Spin Glasses in Magnetic Field Have a Mean Field like Phase
By using numerical simulations we show that the 4D Edwards Anderson
spin glass in magnetic field undergoes a mean field like phase transition. We
use a dynamical approach: we simulate large lattices (of volume ) and work
out the behavior of the system in limit where both and go to infinity,
but where the limit is taken first. By showing that the dynamic
overlap converges to a value smaller than the static one we exhibit replica
symmetry breaking. The critical exponents are compatible with the ones obtained
by mean field computations.Comment: Physrev format, 5 ps figures include
A general method to determine replica symmetry breaking transitions
We introduce a new parameter to investigate replica symmetry breaking
transitions using finite-size scaling methods. Based on exact equalities
initially derived by F. Guerra this parameter is a direct check of the
self-averaging character of the spin-glass order parameter. This new parameter
can be used to study models with time reversal symmetry but its greatest
interest concerns models where this symmetry is absent. We apply the method to
long-range and short-range Ising spin glasses with and without magnetic field
as well as short-range multispin interaction spin glasses.Comment: 5 pages, 4 figures, Revtex fil
Magnetic-glassy multicritical behavior of the three-dimensional +- J Ising model
We consider the three-dimensional model defined on a simple cubic
lattice and study its behavior close to the multicritical Nishimori point where
the paramagnetic-ferromagnetic, the paramagnetic-glassy, and the
ferromagnetic-glassy transition lines meet in the T-p phase diagram (p
characterizes the disorder distribution and gives the fraction of ferromagnetic
bonds). For this purpose we perform Monte Carlo simulations on cubic lattices
of size and a finite-size scaling analysis of the numerical results.
The magnetic-glassy multicritical point is found at , along the
Nishimori line given by . We determine the
renormalization-group dimensions of the operators that control the
renormalization-group flow close to the multicritical point, ,
, and the susceptibility exponent . The
temperature and crossover exponents are and , respectively. We also investigate the model-A dynamics, obtaining
the dynamic critical exponent .Comment: 17 page
A Flexible and Modular Framework for Implementing Infrastructures for Global Computing
We present a Java software framework for building infrastructures to support the development of applications for systems where mobility and network awareness are key issues. The framework is particularly useful to develop run-time support for languages oriented towards global computing. It enables platform designers to customize communication protocols and network architectures and guarantees transparency of name management and code mobility in distributed environments. The key features are illustrated by means of a couple of simple case studies
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