Search results for "sampling"
showing 10 items of 788 documents
A Spatial-Temporal Correlation Approach for Data Reduction in Cluster-Based Sensor Networks
2019
International audience; In a resource-constrained Wireless Sensor Networks (WSNs), the optimization of the sampling and the transmission rates of each individual node is a crucial issue. A high volume of redundant data transmitted through the network will result in collisions, data loss, and energy dissipation. This paper proposes a novel data reduction scheme, that exploits the spatial-temporal correlation among sensor data in order to determine the optimal sampling strategy for the deployed sensor nodes. This strategy reduces the overall sampling/transmission rates while preserving the quality of the data. Moreover, a back-end reconstruction algorithm is deployed on the workstation (Sink)…
Wide bandwidth impedance meter using low rate random sampling
2008
A novel impedance measurement method based on random sampling of voltage and current signals is proposed. This technique dramatically reduces the sampling frequency requirements, thus circumventing the limitations imposed by maximum speed of the analog to digital converter and the signal processing unit. The lowering of the sampling frequencies allows the design and the implementation of an almost all digital architecture by using a simple microprocessor based embedded system and a digital frequency synthesizer. The basic principles are presented, and the implemented algorithms are described. Experimental results show the instrument performances compared to others commercial alternatives.
Selection of Large Sub-Samples from the Continuous Sample of Working Lives Representative of the Benefits Provided by the Spanish Public Pension Syst…
2016
The Continuous Sample of Working Lives (CSWL) is a set of anonymized microdata with information about individuals taken from Spanish Social Security records. It provides very valuable information, which is used in many studies on labor economics and in the analysis of the Spanish public pension system. This article presents two major contributions: The first is an analysis of how representative CSWL is of the population of pensioners for the period 2005-2013. It is concluded that the CSWL does not follow the same distribution as the population with respect to some types of benefits, and that this happens in most waves. One of the reasons is that it is obtained by simple random sampling, so …
Dataset of the COVID-19 lockdown survey conducted by GIPEyOP in Spain
2022
This article introduces a dataset that captures relevant in- formation about the living conditions, feelings, and habits of residents in Spain during ninety nine days of home confinement. This and other measures, imposed by the Government of Spain to mitigate the impact of the pandemic on the population, have brought with them important economic, labor, and social changes, which have been accompanied by various modifications (some only temporary) in Spaniards habits and behaviours. Data collection was carried out through the implementation of a questionnaire with 33 questions, which was sent by email to the collaborators of GIPEyOP (Elections and Public Opinion Research Group from the Unive…
Integrating geophysical and geostatistical techniques to map the spatial variation of clay
2012
Abstract The development of subsoil models represents an important aspect of land resource evaluation, because they can provide an accurate description of the spatial variability in soil properties. Although direct soil sampling provides the best information in terms of soil properties, sample density is rarely adequate to accurately describe the horizontal and vertical variability of the physical properties of soil. Geophysical methods, such as Ground Penetrating Radar (GPR) and electromagnetic induction (EMI) sensors, provide rapid, non-invasive and exhaustive ways for subsoil characterization. Moreover, geophysical methods can be integrated with geostatistics to map soil properties. This…
Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania
2014
Abstract. Fire is a natural phenomenon with important implications on soil properties. The degree of this impact depends upon fire severity, the ecosystem affected, topography of the burned area and post-fire meteorological conditions. The study of fire effects on soil properties is fundamental to understand the impacts of this disturbance on ecosystems. The aim of this work was to study the short-term effects immediately after the fire (IAF), 2, 5, 7 and 9 months after a low-severity spring boreal grassland fire on soil colour value (assessed with the Munsell colour chart), soil organic matter content (SOM) and soil water repellency (SWR) in Lithuania. Four days after the fire a 400 m2 plo…
Factors Influencing Point Measurement of Near-surface Saturated Soil Hydraulic Conductivity in a Small Sicilian Basin
2017
Hydraulic conductivity of saturated soil, Ks, controls many hydrological processes. Parameterization of basin hydrological models in terms of Ks is complicated and uncertain owing to the very high spatial variability of this soil property. A small Sicilian basin was intensively sampled by the simplified falling head technique to obtain spatially distributed Ks data, and an attempt to explain their spatial variability on the basis of soil physical characteristics, digital elevation model-derived topographic attributes and land cover was carried out. High Ks values were obtained when clay content was low and both elevation and mean slope were high. Moreover, differences in Ks among land cover…
Biodiversity dynamics and their driving factors during the Cretaceous diversification of Spatangoida (Echinoidea, Echinodermata)
2004
Abstract Variations in recorded diversity over time present a scrambled signal that is modulated by a large number of variables: the potential of particular life forms to generate evolutionary innovations, external constraints induced by the environment in its broad sense, the heterogeneity of the fossil record and the analytical artefacts due to sampling bias. A key question is how to characterise and quantify the separate input of any given factor in the overall diversity signal. This paper explores the structure of diversity data for spatangoid heart urchins and the sensitivity of recorded diversity to different factors of analytical bias (length of geological periods, proportion of pala…
The Fluorescence Explorer (FLEX) Mission: From Spectral Measurements to High-Level Science Products
2021
The Fluorescence Explorer (FLEX) mission was selected in 2015, by the European Space Agency (ESA), as an Earth Explorer mission, with a launch planned for 2024. The key scientific objective of the mission is the quantitative global mapping of actual photosynthetic activity of terrestrial ecosystems, as a function of variable vegetation health status and environmental stress conditions. The measurements will have a spatial resolution of 300 m, adequate to resolve land surface processes associated to vegetation dynamics at a global scale. To be able to accomplish such objective, the FLEX mission carries the FLORIS spectrometer, specially optimized to map vegetation fluorescence with a spectra…
Conditions of dust sampling in pneumatic conveying through the horizontal pipeline
2007
Abstract The paper presents the results of examinations on the reciprocal relation between the isokinetic coefficient H of sampling, the quantity of measured mass concentration and the measuring usefulness of a dust sample aspired from the stream of solgas conveyed pneumatically in the horizontal pipeline. In gravimetric measurements of two-phase flows, the conditions under which aspiration is carried out, are extremely important. Available theoretical considerations and practical experiments usually concern aspiration in the vertical channels, where the manner of making measurements is universally known and it does not express any reservations. However, it is often necessary to conduct tes…