Search results for "Statistical"
showing 10 items of 4960 documents
Una nuova teoria per lo studio dei processi di efflusso dagli stramazzi
2011
Il processo di efflusso da uno stramazzo, di notevole interesse per le applicazioni pratiche, viene studiato applicando l’analisi dimensionale e la teoria dell’autosimilitudine incompleta. La nuova scala teorica di efflusso dedotta per gli stramazzi, in parete sottile e grossa e di differente forma geometrica, viene verificata facendo ricorso sia alle misure disponibili in letteratura sia ad apposite sperimentazioni di laboratorio.
Comparison of machine learning models for gully erosion susceptibility mapping
2020
© 2019 China University of Geosciences (Beijing) and Peking University Gully erosion is a disruptive phenomenon which extensively affects the Iranian territory, especially in the Northern provinces. A number of studies have been recently undertaken to study this process and to predict it over space and ultimately, in a broader national effort, to limit its negative effects on local communities. We focused on the Bastam watershed where 9.3% of its surface is currently affected by gullying. Machine learning algorithms are currently under the magnifying glass across the geomorphological community for their high predictive ability. However, unlike the bivariate statistical models, their structu…
Propagation failure in discrete bistable reaction-diffusion systems: Theory and experiments
2001
International audience; Wave front propagation failure is investigated in discrete bistable reaction-diffusion systems. We present a theoretical approach including dissipative effects and leading to an analytical expression of the critical coupling beyond which front propagation can occur as a function of the nonlinearity threshold parameter. Our theoretical predictions are confirmed by numerical simulations and experimental results on an equivalent electrical diffusive lattice.
Elastic waves in random-fibre networks
1997
The propagation of the first displacement maximum of a semi-infinite wavetrain in a two-dimensional random-fibre network is analysed. Model calculations and numerical simulations are used for demonstrating that two qualitatively different wavefront velocities appear in the network. A transient wave, which travels fast and whose amplitude decreases exponentially, dominates the short-time behaviour when the bending stiffness of the fibres is small and the driving frequency is high. This mode can be described by a one-dimensional model. The transient-wave mode propagates even if the bending stiffness of the fibres vanishes, in which case the normal sound velocity is zero. The usual, and slower…
Weakly nonlinear analysis of Turing patterns in a morphochemical model for metal growth
2015
We focus on the morphochemical reaction–diffusion model introduced in Bozzini et al. (2013) and carry out a nonlinear bifurcation analysis with the aim to characterize the shape and the amplitude of the patterns arising as the result of Turing instability of the physically relevant equilibrium. We perform a weakly nonlinear multiple scales analysis, and derive the normal form equations governing the amplitude of the patterns. These amplitude equations allow us to construct relevant solutions of the model equations and reveal the presence of multiple branches of stable solutions arising as the result of subcritical bifurcations. Hysteretic type phenomena are highlighted also through numerica…
Well-posedness of Prandtl equations with non-compatible data
2013
In this paper we shall be concerned with Prandtl's equations with incompatible data, i.e. with initial data that, in general, do not fulfil the boundary conditions imposed on the solution. Under the hypothesis of analyticity in the streamwise variable, we shall prove that Prandtl's equations, on the half-plane or on the half-space, are well posed for a short time.
Modelling wet and dry spells for daily rainfall data series: an application to irrigation management in North-West Italy
2016
Rainfall time variability is relevant for agricultural production. The daily time scale is often used in modelling crop and soil water balance. In this work a novel statistical analysis of wet and dry spells is presented, together with an application in an Italian area characterised by a relevant climate spatial variability, due to the presence of both high mountains (e.g.: Mont Blanc) and of the Mediterranean Sea. Statistical analysis of the sequences of rainy days, wet spells (WS), and that of no-rainy days, dry spells (DS), could be carried out separately (as widely applied in the past) or jointly, by introducing the inter-arrival time (IT), representing the time elapsed between two subs…
On the classification of type D space–times
2002
We give a classification of the type D spacetimes based on the invariant differential properties of the Weyl principal structure. Our classification is established using tensorial invariants of the Weyl tensor and, consequently, besides its intrinsic nature, it is valid for the whole set of the type D metrics and it applies on both, vacuum and non-vacuum solutions. We consider the Cotton-zero type D metrics and we study the classes that are compatible with this condition. The subfamily of spacetimes with constant argument of the Weyl eigenvalue is analyzed in more detail by offering a canonical expression for the metric tensor and by giving a generalization of some results about the non-exi…
The effect of whole genome amplification on samples originating from more than one donor
2006
Abstract In this study, the GenomiPhi™ DNA Amplification Kit (Amersham Biosciences) was used to investigate the potential of whole genome amplification (WGA) when considering samples originating from more than one donor. DNA was extracted from blood samples, quantified and normalised before being mixed in ratios of 1:1, 1:3, 1:7 and 1:15. Proportions were checked using standard STR analysis before being subjected to WGA. Once amplified using GenomiPhi™, the ratios were again checked. Relative proportions were found to be maintained in the 1:1 and 1:3 ratios following WGA; the observed peak ratios were found to match the expected peak ratios regardless of the starting concentration of DNA. W…
Joint probability distributions for wind speed and direction. A case study in Sicily
2015
In this study we analyze data of hourly average wind speed and direction measured at three different sampling stations located in Sicily (Italy) and provide a statistical model for their joint probability density function. Singly truncated from below Normal Weibull mixture distribution and a linear combination of von Mises distributions are used to model wind speed and direction. Sites with heterogeneous local conditions (prevailing wind direction and/or elevation) have been considered in order to investigate the reliability of the model here taken into consideration.