4,963 research outputs found
On Safe Folding
In [3] a general fold operation has been introduced for definite programs wrt computed answer substitution semantics. It differs from the fold operation defined by Tamaki and Sato in [26,25] because its application does not depend on the transformation history. This paper extends the results in [3] by giving a more powerful sufficient condition for the preservation of computed answer substitutions. Such a condition is meant to deal with the critical case when the atom introduced by folding depends on the clause to which the fold applies. The condition compares the dependency degree between the fonding atom and the folded clause, with the semantic delay between the folding atom and the ones to be folded. The result is also extended to a more general replacement operation, by showing that it can be decomposed into a sequence of definition, general folding and unfolding operations
Adaptive Cluster Expansion for Inferring Boltzmann Machines with Noisy Data
We introduce a procedure to infer the interactions among a set of binary
variables, based on their sampled frequencies and pairwise correlations. The
algorithm builds the clusters of variables contributing most to the entropy of
the inferred Ising model, and rejects the small contributions due to the
sampling noise. Our procedure successfully recovers benchmark Ising models even
at criticality and in the low temperature phase, and is applied to
neurobiological data.Comment: Accepted for publication in Physical Review Letters (2011
Probing Low Energy Neutrino Backgrounds with Neutrino Capture on Beta Decaying Nuclei
We study the interaction of low energy neutrinos on nuclei that spontaneously
undergo beta decay showing that the product of the cross section times neutrino
velocity takes values as high as 10^{-42} cm^2 c for some specific nuclei that
decay via allowed transitions. The absence of energy threshold and the value of
the cross section single out these processes as a promising though very
demanding approach for future experiments aimed at a direct detection of low
energy neutrino backgrounds such as the cosmological relic neutrinos.Comment: Includes a discussion of local relic neutrino density effect on
neutrino capture rate. Accepted for publication in JCA
Exponentially hard problems are sometimes polynomial, a large deviation analysis of search algorithms for the random Satisfiability problem, and its application to stop-and-restart resolutions
A large deviation analysis of the solving complexity of random
3-Satisfiability instances slightly below threshold is presented. While finding
a solution for such instances demands an exponential effort with high
probability, we show that an exponentially small fraction of resolutions
require a computation scaling linearly in the size of the instance only. This
exponentially small probability of easy resolutions is analytically calculated,
and the corresponding exponent shown to be smaller (in absolute value) than the
growth exponent of the typical resolution time. Our study therefore gives some
theoretical basis to heuristic stop-and-restart solving procedures, and
suggests a natural cut-off (the size of the instance) for the restart.Comment: Revtex file, 4 figure
On the slip-weakening behavior of rate- and state-dependent constitutive laws
We study the dynamic traction behavior within the cohesive zone during the propagation of earthquake ruptures adopting rate and state dependent constitutive relations. The resulting slip weakening curve displays an equivalent slip weakening distance (D0_eq), which is different from the parameter L controlling the state variable evolution. The adopted constitutive parameters (a, b, L) control the slip weakening behavior and the absorbed fracture energy. The dimension of the nucleation patch scales with L and not with D0_eq. We propose a scaling relation between these two lengthscale parameters which prescribes that D0_eq/L ~ 15
TOWARDS A NOVEL APPROACH TO GEODESIGN ANALYTICS
The adoption of sustainability principles in current European regulatory framework which affect
spatial planning and environmental protection, such as Directive 2001/42/C, introduced the
need for collaboration and participation in spatial planning practices aiming at achieving more
evidence-based, transparent and democratic decision making. However, the involvement of a
wide range of actors, along with traditional collaborative and participatory methods, makes
it often diffi cult to grasp the dynamics which drive the process towards the fi nal decision.
Emerging design methodologies and increased recourse to advanced information technologies
promise unprecedented opportunities not only for applying a system approach and coordinating
involved actors, but also for tracking the evolution of the design alternatives toward the fi nal
plan. In this context, this paper explores the potential offered by the collaborative Planning
Support System Geodesignhub to ease and record the process workfl ow of geodesign studies.
The paper describes underlying theories, research questions formulation and the fi rst results
of the analysis of empirical data on the Cagliari Geodesign case study. The set of variables and
relations identifi ed in this research endeavor represents the fi rst effort towards the development
of an operation framework for geodesign process analysis, which may potentially contribute to
clarify the relationships between the knowledge base and the actors in the planning process.
The aim is to earning a deeper understanding of the process dynamics for more informed,
transparent, and democratic planning, design and decision-making.
KEYWORD
Relaxation and Metastability in the RandomWalkSAT search procedure
An analysis of the average properties of a local search resolution procedure
for the satisfaction of random Boolean constraints is presented. Depending on
the ratio alpha of constraints per variable, resolution takes a time T_res
growing linearly (T_res \sim tau(alpha) N, alpha < alpha_d) or exponentially
(T_res \sim exp(N zeta(alpha)), alpha > alpha_d) with the size N of the
instance. The relaxation time tau(alpha) in the linear phase is calculated
through a systematic expansion scheme based on a quantum formulation of the
evolution operator. For alpha > alpha_d, the system is trapped in some
metastable state, and resolution occurs from escape from this state through
crossing of a large barrier. An annealed calculation of the height zeta(alpha)
of this barrier is proposed. The polynomial/exponentiel cross-over alpha_d is
not related to the onset of clustering among solutions.Comment: 23 pages, 11 figures. A mistake in sec. IV.B has been correcte
Monitoring pit and fissures using transparent sealant and fluorescence intraoral camera, 12 months follow up
The aim of this in vivo study is to report on the combined use
of a fluorescence intraoral camera and transparent sealant for the
clinical monitoring of pits and fissures. 96 permanent molars with
a ICDAS II code 0, 1, or 2, (in 48 patients aged 12–14) were registered
at the First Observation Unit (Oral and Maxillofacial Sciences
Department), Sapienza University, Rome. Clinically selected
teeth were double-checked using a VistaCam iX Proof (Durr Dental
AG) and sealed with a transparent sealant (ControlSeal, VOCO
GmbH), following the established indications for use if a pit and
fissure condition was confirmed within the camera’s internal cutoff
point of 1.5 (“early enamel demineralization”). Clinical followup
was performed using VistaCam at 6 and 12 months to assess
sealant retention and any demineralization trend. At baseline,
57.4% of the registered teeth were sound, both visually and when
using the fluorescence camera, 42.6% presented an early demineralization
(<1.5 with VistaCam and ICDAS II 1- 2). Subsequent
VistaCam assessment of surfaces underlying the transparent sealant
totally confirmed initial evaluations. Complete sealant retention
rated 95% at 6 months, and 91% at 12 months. No case of
complete detachment was observed. At the 12-month follow-up,
VistaCam measurements resulted stable in the whole sample, except
for one permanent molar, which presented a demineralization
increment and partial sealant retention. Visual and fluorescence
assessments were consistent and feasible. Incomplete sealant
retention occurred in 5% of cases at 6 months and 9% of cases at
12 months and was probably due to procedure imperfections. The
combined use of transparent sealant and a fluorescence camera
shows clinical effectiveness and diagnostic efficacy for occlusal
surface monitoring
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