Search results for "Autore"
showing 10 items of 352 documents
Comparison of gap-filling techniques applied to the CCI soil moisture database in Southern Europe
2021
Abstract Soil moisture (SM) is a key variable that plays an important role in land-atmosphere interactions. Monitoring SM is crucial for many applications and can help to determine the impact of climate change. Therefore, it is essential to have continuous and long-term databases for this variable. Satellite missions have contributed to this; however, the continuity of the series is compromised due to the data gaps derived by different factors, including revisit time, presence of seasonal ice or Radio Frequency Interference (RFI) contamination. In this work, the applicability of different gap-filling techniques is evaluated on the ESA Climate Change Initiative (CCI) SM combined product, whi…
Dynamical model identification of population of oysters for water quality monitoring
2014
International audience; The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight and tide levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. Through this application, it is demonstrated that the developed dynamical model can be used for estimation of the normal physiological rhythms of permanently immersed oyste…
Forecasting the volatility of biofuel feedstock prices: the US evidence
2019
Given that, nowadays, 40% of the US corn crop is used for biofuel production, there is a growing concern that the rise in biofuel production might lead to an increase in food prices. However, it is also obvious that significant growth in biofuel use has minimized the demand for fossil fuel and has hence reduced the volume of carbon emissions. It is therefore crucial to model corn market volatility precisely because such an estimate could play a vital role in stabilizing food and biofuel market prices. For this purpose, we consider using the information content of the corn implied volatility (CIV) index to predict the corn futures market return volatility. Using symmetric and asymmetric GARC…
Health Indicator for Low-Speed Axial Bearings Using Variational Autoencoders
2020
This paper proposes a method for calculating a health indicator (HI) for low-speed axial rolling element bearing (REB) health assessment by utilizing the latent representation obtained by variational inference using Variational Autoencoders (VAEs), trained on each speed reference in the dataset. Further, versatility is added by conditioning on the speed, extending the VAE to a conditional VAE (CVAE), thereby incorporating all speeds in a single model. Within the framework, the coefficients of autoregressive (AR) models are used as features. The dimensionality reduction inherent in the proposed method lowers the need of expert knowledge to design good condition indicators. Moreover, the sugg…
A Dirichlet Autoregressive Model for the Analysis of Microbiota Time-Series Data
2021
Growing interest in understanding microbiota dynamics has motivated the development of different strategies to model microbiota time series data. However, all of them must tackle the fact that the available data are high-dimensional, posing strong statistical and computational challenges. In order to address this challenge, we propose a Dirichlet autoregressive model with time-varying parameters, which can be directly adapted to explain the effect of groups of taxa, thus reducing the number of parameters estimated by maximum likelihood. A strategy has been implemented which speeds up this estimation. The usefulness of the proposed model is illustrated by application to a case study.
Housing market shocks in italy: A GVAR approach
2020
Abstract In this paper, we use a Global Vector Autoregression (GVAR) model to assess the spatio-temporal mechanism of house price spillovers, also known as “ripple effect”, among 93 Italian provincial housing markets, over the period 2004 − 2016 . In order to better capture the local housing market dynamics, we use data not only on house prices but also on transaction volumes. In particular, we focus on estimating, to what extent, exogenous shocks, interpreted as negative housing demand shocks, arising from 10 Italian regional capitals, impact on their house prices and sales and how these shocks spill over to neighbours housing markets. The negative housing market demand shock hitting the G…
Modeling Conditional Skewness in Stock Returns
2007
Abstract In this paper, we propose a new GARCH-in-Mean (GARCH-M) model allowing for conditional skewness. The model is based on the so-called z distribution capable of modeling skewness and kurtosis of the size typically encountered in stock return series. The need to allow for skewness can also be readily tested. The model is consistent with the volatility feedback effect in that conditional skewness is dependent on conditional variance. Compared to previously presented GARCH models allowing for conditional skewness, the model is analytically tractable, parsimonious and facilitates straightforward interpretation.Our empirical results indicate the presence of conditional skewness in the mon…
Filiación derivada de técnicas de reproducción humana asistida: Bebés medicamento
2018
En España, entre las novedades de la Ley 14/2006, se regula la selección embrionaria con fines terapéuticos para terceros. Hay que esperar hasta 2014 para que esta técnica sea sufragada por el sistema sanitario público español. Se hace alusión a los argumentos en contra y a favor de la utilización de esta técnica, siendo mayoritarios los autores que la apoyan, tanto en el sector biomédico como en el bioético
Addictive-like behaviour for Acetaldehyde: involvement of D2 receptors
2013
Acetaldehyde (ACD), ethanol's first metabolite, is centrally active and shows rewarding and motivational properties. It is able to activate mesolimbic dopamine system, since it enhances neuronal firing of dopamine cells in ventral tegmental area and exerts dopamine release in the nucleus accumbens (Foddai et al., 2004; Melis et al., 2007; Deehan et al., 2013). ACD motivational properties are demonstrated by self-administration studies in rodents (Rodd et al., 2005), particularly behavioural evidence suggests that ACD could produce positive reinforcing effects in operant-conflict paradigms (Cacace et al., 2012). In order to shed light on neurobiological substrate underpinning ACD-related beh…