Search results for "Secondary"
showing 10 items of 1765 documents
On resampling schemes for particle filters with weakly informative observations
2022
We consider particle filters with weakly informative observations (or `potentials') relative to the latent state dynamics. The particular focus of this work is on particle filters to approximate time-discretisations of continuous-time Feynman--Kac path integral models -- a scenario that naturally arises when addressing filtering and smoothing problems in continuous time -- but our findings are indicative about weakly informative settings beyond this context too. We study the performance of different resampling schemes, such as systematic resampling, SSP (Srinivasan sampling process) and stratified resampling, as the time-discretisation becomes finer and also identify their continuous-time l…
Order-distance and other metric-like functions on jointly distributed random variables
2013
We construct a class of real-valued nonnegative binary functions on a set of jointly distributed random variables, which satisfy the triangle inequality and vanish at identical arguments (pseudo-quasi-metrics). These functions are useful in dealing with the problem of selective probabilistic causality encountered in behavioral sciences and in quantum physics. The problem reduces to that of ascertaining the existence of a joint distribution for a set of variables with known distributions of certain subsets of this set. Any violation of the triangle inequality or its consequences by one of our functions when applied to such a set rules out the existence of this joint distribution. We focus on…
Unbiased Estimators and Multilevel Monte Carlo
2018
Multilevel Monte Carlo (MLMC) and unbiased estimators recently proposed by McLeish (Monte Carlo Methods Appl., 2011) and Rhee and Glynn (Oper. Res., 2015) are closely related. This connection is elaborated by presenting a new general class of unbiased estimators, which admits previous debiasing schemes as special cases. New lower variance estimators are proposed, which are stratified versions of earlier unbiased schemes. Under general conditions, essentially when MLMC admits the canonical square root Monte Carlo error rate, the proposed new schemes are shown to be asymptotically as efficient as MLMC, both in terms of variance and cost. The experiments demonstrate that the variance reduction…
Pattern statistics in faro words and permutations
2021
We study the distribution and the popularity of some patterns in $k$-ary faro words, i.e. words over the alphabet $\{1, 2, \ldots, k\}$ obtained by interlacing the letters of two nondecreasing words of lengths differing by at most one. We present a bijection between these words and dispersed Dyck paths (i.e. Motzkin paths with all level steps on the $x$-axis) with a given number of peaks. We show how the bijection maps statistics of consecutive patterns of faro words into linear combinations of other pattern statistics on paths. Then, we deduce enumerative results by providing multivariate generating functions for the distribution and the popularity of patterns of length at most three. Fina…
Unbiased Inference for Discretely Observed Hidden Markov Model Diffusions
2021
We develop a Bayesian inference method for diffusions observed discretely and with noise, which is free of discretisation bias. Unlike existing unbiased inference methods, our method does not rely on exact simulation techniques. Instead, our method uses standard time-discretised approximations of diffusions, such as the Euler--Maruyama scheme. Our approach is based on particle marginal Metropolis--Hastings, a particle filter, randomised multilevel Monte Carlo, and importance sampling type correction of approximate Markov chain Monte Carlo. The resulting estimator leads to inference without a bias from the time-discretisation as the number of Markov chain iterations increases. We give conver…
The infinite dihedral group
2022
We describe the infinite dihedral group as automaton group. We collect basic results and give full proofs in details for all statements.
Using the transit of Venus to probe the upper planetary atmosphere
2015
The atmosphere of a transiting planet shields the stellar radiation providing us with a powerful method to estimate its size and density. In particular, because of their high ionization energy, atoms with high atomic number (Z) absorb short-wavelength radiation in the upper atmosphere, undetectable with observations in visible light. One implication is that the planet should appear larger during a primary transit observed in high energy bands than in the optical band. The last Venus transit in 2012 offered a unique opportunity to study this effect. The transit has been monitored by solar space observations from Hinode and Solar Dynamics Observatory (SDO). We measure the radius of Venus duri…
The wild boar (Sus scrofa Linnaeus, 1758) as secondary reservoir of Fasciola hepatica in Galicia (NW Spain)
2013
Fasciolosis is an emerging or reemerging human and animal disease in numerous parts of the world. In Galicia (NW, Spain), the wild boar (Sus scrofa) is the main wild ungulate in terms of abundance and distribution. Its population has continuously increased over the past decades and this population growth has been accompanied by a reduction of habitats, so that the wild boar populations encroach more and more frequently onto agricultural lands. The increase of the interface area between livestock and the wild boars frequently involves the sharing of pastures and water sources, so that the circulation of common pathogens is propitiated. This is the first report concerning the importance of th…
Banks, Firms and Economic Culture: Economists and Research Centres in Interwar Italy
2020
In the interwar years, Italy experimented a strong growth of applied economic research. The foundation of research centers can be read and placed in a much wider international trend that emerged during the Great War. In this essay, we offer a map of the most important research centers, exploring the extensive web of relationships between the academia and the productive world. We then focus on a set of case studies, selected for their relevance. Section 2 is devoted to the banking sector, with reference to four important cases (Banca Commerciale Italiana, Banca d’Italia, Associazione Bancaria Italiana and Banco di Sicilia); section 3 to the industrial sector (IRI, Finsider, Ansaldo, Edison, …
Hacia una mayor autonomía en la construcción de identidades de género partiendo de la mirada crítica de Mernissi y el Hachmi
2021
[Resumen] En este trabajo destacamos dos problemas en la construcción de identidades de género por parte del alumnado adolescente: la escasa incorporación de contribuciones culturales femeninas en manuales escolares y cánones literarios, y la imagen distorsionada de las mujeres de origen marroquí instaurada en el imaginario colectivo, que oculta sus manifestaciones de autonomía y perjudica las relaciones interculturales. Nuestro objetivo fundamental es realizar un análisis discursivo de cuatro títulos de Fatema Mernissi y Najat El Hachmi en relación a la identidad de género para establecer las claves del modelo subyacente y valorar, a continuación, las posibilidades de explotación didáctica…