Search results for "Random"
showing 10 items of 3931 documents
Non-Periodic Systems with Continuous Diffraction Measures
2015
The present state of mathematical diffraction theory for systems with continuous spectral components is reviewed and extended. We begin with a discussion of various characteristic examples with singular or absolutely continuous diffraction, and then continue with a more general exposition of a systematic approach via stationary stochastic point processes. Here, the intensity measure of the Palm measure takes the role of the autocorrelation measure in the traditional approach. We furthermore introduce a ‘Palm-type’ measure for general complex-valued random measures that are stationary and ergodic, and relate its intensity measure to the autocorrelation measure.
Risonanza stocastica non dinamica in una popolazione di Nezara Viridula (L.)
2009
In questo lavoro viene studiato l’effetto del rumore sul comportamento, durante il periodo di accoppiamento, di individui di Nezara viridula (L.). Analizzando la risposta di insetti maschi a segnali sotto soglia, prodotti da individui di sesso femminile, si osserva, in presenza di una sorgente esterna di rumore bianco Gaussiano, un’attivazione “comportamentale”, con un andamento non monotono in funzione dell’intensit`a di rumore, chiara indicazione della presenza di risonanza stocastica non dinamica. Lo studio `e ripetuto utilizzando una sorgente di rumore colorato. Infine, i risultati sperimentali vengono riprodotti attraverso un modello a soglia “morbida”, in cui la funzione di cross-corr…
GENERAZIONE DI SECONDA ARMONICA MEDIANTE RANDOM QUASI-PHASE-MATCHING IN TANTALATO DI LITIO POLATO PERIODICAMENTE
2009
We experimentally observed and explained bulk Second Harmonic Generation via Random Quasi-Phase-Matching, derived from a periodically poled Lithium Tantalate sample with a randomly patterned mark-to-space-ratio.
Parallel Random Search and Tabu Search for the Minimal Consistent Subset Selection Problem
1998
The Minimal Consistent Subset Selection (MCSS) problem is a discrete optimization problem whose resolution for large scale instances requires a prohibitive processing time. Prior algorithms addressing this problem are presented. Randomization and approximation techniques are suitable to face the problem, then random search and meta-heuristics are proposed and consequently Tabu Search strategies are applied and evaluated. Parallel computing helps to reduce processing time and/or produce better results; different approaches for designing parallel tabu search are analyzed.
Analysis of the railway network operations safety, with of different obstacles along the route, by the study of Buffon-Laplace type problems: the cas…
2016
In this paper we use an approach based on a Buffon-Laplace type problem for an irregular hexagonal lattice and obstacles to study some problems about analysis of the railway network operations safety in the presence of different obstacles on the route.
Dynamic integration of classifiers in the space of principal components
2003
Recent research has shown the integration of multiple classifiers to be one of the most important directions in machine learning and data mining. It was shown that, for an ensemble to be successful, it should consist of accurate and diverse base classifiers. However, it is also important that the integration procedure in the ensemble should properly utilize the ensemble diversity. In this paper, we present an algorithm for the dynamic integration of classifiers in the space of extracted features (FEDIC). It is based on the technique of dynamic integration, in which local accuracy estimates are calculated for each base classifier of an ensemble, in the neighborhood of a new instance to be pr…
Models of Dynamical Modelling Under Uncertainty
1986
The objective of this work is to modelize the evolution of a Model-System to be adapted to a Random System. This evolution is described by means of the change of a probabilistic function, through deterministic rules and in function of the random responses of the modelized System. This probabilistic function can describe the relative weight of distinct submodels (deterministic or random Systems, with constant or variable stimulus), or the stimulus-response relation in the Model-System (Adaptative Random System). We conclude that the Adaptative Random Model permits a more precise, simple and economical modelling.
Analysis of random walks on a hexagonal lattice
2019
We consider a discrete-time random walk on the nodes of an unbounded hexagonal lattice. We determine the probability generating functions, the transition probabilities and the relevant moments. The convergence of the stochastic process to a 2-dimensional Brownian motion is also discussed. Furthermore, we obtain some results on its asymptotic behavior making use of large deviation theory. Finally, we investigate the first-passage-time problem of the random walk through a vertical straight-line. Under suitable symmetry assumptions we are able to determine the first-passage-time probabilities in a closed form, which deserve interest in applied fields.
Ureteral Stones: Shockwave Lithotripsy or Ureteroscopy, Which is Best?
2021
Background Renal stone disease is common and can cause emergency presentation with acute pain due to ureteric colic. International guidelines have stated the need for a multicentre randomised controlled trial (RCT) to determine whether a non-invasive outpatient (shockwave lithotripsy [SWL]) or surgical (ureteroscopy [URS]) intervention should be the first-line treatment for those needing active intervention. This has implications for shaping clinical pathways. Objective To report a pragmatic multicentre non-inferiority RCT comparing SWL with URS. Design, setting, and participants This trial tested for non-inferiority of up to two sessions of SWL compared with URS as initial treatment for ur…
Diuretic vs. placebo in intermediate-risk acute pulmonary embolism: a randomized clinical trial
2022
Abstract Aims The role of diuretics in patients with intermediate-risk pulmonary embolism (PE) is controversial. In this multicentre, double-blind trial, we randomly assigned normotensive patients with intermediate-risk PE to receive either a single 80 mg bolus of furosemide or a placebo. Methods and results Eligible patients had at least a simplified PE Severity Index (sPESI) ≥1 with right ventricular dysfunction. The primary efficacy endpoint assessed 24 h after randomization included (i) absence of oligo-anuria and (ii) normalization of all sPESI items. Safety outcomes were worsening renal function and major adverse outcomes at 48 hours defined by death, cardiac arrest, mechanical ventil…