Search results for "Time series"
showing 10 items of 247 documents
Information Transfer in Linear Multivariate Processes Assessed through Penalized Regression Techniques: Validation and Application to Physiological N…
2020
The framework of information dynamics allows the dissection of the information processed in a network of multiple interacting dynamical systems into meaningful elements of computation that quantify the information generated in a target system, stored in it, transferred to it from one or more source systems, and modified in a synergistic or redundant way. The concepts of information transfer and modification have been recently formulated in the context of linear parametric modeling of vector stochastic processes, linking them to the notion of Granger causality and providing efficient tools for their computation based on the state&ndash
Study of vegetation evolution in Sicily using time series analysis of remote sensing and climatic data.
2007
During last 10 years, several studies confirmed that drought phenomena are affecting southern Mediterranean areas. One of the effects of a persistent drought is a modification of the vegetation cover and biomass. The aim of our research is to investigate and monitor the evolution of this phenom- enon in Sicily using remote sensing techniques. To do this, a data set of NOAA-AVHRR multispectral images, acquired monthly from 1988 to 2005, has been calibrated and processed. A time series analysis (TSA) has been applied both on the NDVI and precipitation data sets in order to study the main characteristics of vegetation distribution during the period under investigation and to compare the vegeta…
Malthusian checks in pre-industrial Sweden and Finland: a comparative analysis of the demographic regimes
2015
In this article, the existence of the Malthusian preventive and positive checks in pre-industrial Sweden and Finland are studied using demographic and economic data from circa 1750–1860. By applying time series analysis, we are able to identify strong preventive and positive checks for Sweden. The preventive check is considered to work both directly through births and indirectly through marriages. Although the Finnish data also indicate the existence of the preventive check, the positive check is only detected with differenced data. Our findings contradict the initial hypothesis that, due to poverty, Finland would display a higher sensitivity of mortality to living standards than Sweden. In…
Nonlinear Time-Series Adaptation for Land Cover Classification
2017
Automatic land cover classification from satellite image time series is of paramount relevance to assess vegetation and crop status, with important implications in agriculture, biofuels, and food. However, due to the high cost and human resources needed to characterize and classify land cover through field campaigns, a recurrent limiting factor is the lack of available labeled data. On top of this, the biophysical–geophysical variables exhibit particular temporal structures that need to be exploited. Land cover classification based on image time series is very complex because of the data manifold distortions through time. We propose the use of the kernel manifold alignment (KEMA) method for…
Assessing the Beneficial Effects of Economic Growth: The Harmonic Growth Index
2011
In this paper we introduce the multidimensional notion of harmonic growth as a situation of diffused well-being associated to an increase of per capita GDP. We say that a country experienced a harmonic growth if during the observed period all the key indicators, proxies of the endogenous and exogenous forces driving population well-being, show a significantly common pattern with the income dynamics. The notion is operationalized via an index of time series harmony which follows the functional data analysis approach. This Harmonic Growth Index (HGI) is based on comparisons between the coefficients from cubic B-splines interpolation. Such indices are then synthesized in order to provide the g…
Estimating finite mixtures of semi-Markov chains: an application to the segmentation of temporal sensory data
2019
Summary In food science, it is of great interest to obtain information about the temporal perception of aliments to create new products, to modify existing products or more generally to understand the mechanisms of perception. Temporal dominance of sensations is a technique to measure temporal perception which consists in choosing sequentially attributes describing a food product over tasting. This work introduces new statistical models based on finite mixtures of semi-Markov chains to describe data collected with the temporal dominance of sensations protocol, allowing different temporal perceptions for a same product within a population. The identifiability of the parameters of such mixtur…
Insar time-series analysis for management and mitigation of geological risk in urban area
2010
This work shows the capabilities of InSAR time series analyses to support civil protection activities in the framework of geological risk management and mitigation. We discuss the outcomes from an integrated analysis of conventional in situ investigations and observations with advanced InSAR analyses carried out for the test sites of Agrigento and Naro (Italy), affected by ground instability respectively due to landsliding and tectonic forces. The study of past ground deformations provided valuable insights into the spatial and temporal patterns and behaviors of these phenomena, helping local civil protection authorities to focus resources on the areas of maximum need and to identify the mo…
Harmonic growth: a new approach to the measurement of countries development
2009
The paper defines harmonic growth as a situation of diffuse well-being associated to an increase of GDP, and proposes a measures of time series similarity between GDP and each one from a set of social and economic indicators of development. Such indexes are then synthesized in order to provide the global degree of harmony in growth inside a country. A first Harmonic Growth Index is based on comparisons between couples of polynomials fitting the series. The second version of the index is obtained from cubic B-splines estimates. With an accurate selection of social indicators, both indexes can also be used to rank countries according to their level of development, offering effective complemen…
Relation between training load and recovery-stress state in high-performance swimming
2018
\(\bf Background:\) The relation between training load, especially internal load, and the recovery-stress state is of central importance for avoiding negative adaptations in high-performance sports like swimming. The aim of this study was to analyze the individual time-delayed linear effect relationship between training load and recovery-stress state with single case time series methods and to monitor the acute recovery-stress state of high-performance swimmers in an economical and multidimensional manner over a macro cycle. The Acute Recovery and Stress Scale (ARSS) was used for daily monitoring of the recovery-stress state. The methods session-RPE (sRPE) and acute:chronic workload-ratio (…
Measuring the Rate of Information Exchange in Point-Process Data With Application to Cardiovascular Variability
2022
The amount of information exchanged per unit of time between two dynamic processes is an important concept for the analysis of complex systems. Theoretical formulations and data-efficient estimators have been recently introduced for this quantity, known as the mutual information rate (MIR), allowing its continuous-time computation for event-based data sets measured as realizations of coupled point processes. This work presents the implementation of MIR for point process applications in Network Physiology and cardiovascular variability, which typically feature short and noisy experimental time series. We assess the bias of MIR estimated for uncoupled point processes in the frame of surrogate…