1,720,989 research outputs found
Spatial and temporal distribution of precipitation in a Mediterranean area (southern Italy)
Full text linkThe precipitation climate regime of a region is characterized by the distribution of the monthly precipitation contribution. Its temporal and spatial analysis is particularly interesting for many fields of applied sciences, such as climatology, hydrology and water resources management. With the aim to describe the climate regime, its spatial feature and relevant potential temporal shift, for a large area of southern Italy (Mediterranean basin), a database of about 559 stations has been explored through the statistical analysis of rainfall time series spanning between 1917 and 2006. After a change point analysis, aimed at the assessment of data quality, a trend analysis has been performed on both monthly precipitation, monthly percentage of annual rainfall amount and PCI-computed series. The broad extension of the area under investigation highlights a better understanding of precipitation distribution patterns over space. Results of PCI trend analysis show a significant shift, for about 40-50 % of total gauging station, over the time towards a more uniform climate regime, especially for the hilly areas. Moreover, the trend analysis on the monthly rainfall series indicates that the shift is produced by a reduction of rainfall amount during the winter season, particular consistent over the Tyrrhenian side of the peninsula, and an increase during the summer season quite widespread over the whole investigated territory
A combined approach to delineating management zones for precision agriculture
No full textFundamental to the philosophy of precision agriculture is the concept of matching inputs to needs. Recent research in precision agriculture has focused on use of Management Zones which are field areas possessing homogeneous attributes in landscape and soil conditions. There are several methods for delineating management zones, depending on the available resources and the characteristics of the field being mapped. Existing traditional clustering techniques do not account for the spatial correlation between observations and take little account of gradual change, either from one class to another or within any one class. Differently, geostatistics treats variables as continua in a joint attribute and geographic space. Therefore, in geostatistical applications clusters are unnecessary, nevertheless in precision farming it may be sensible to divide the field into a restricted number of practical management zones. It then needs to develop an algorithm of clustering that is also spatially constrained, in order to ensure spatial contiguity. The methods based on nonparametric density estimation are the ones which allow clusters of unequal size and dispersion and with highly irregular shapes to be detected (Castrignan: et al., 2006). The objectives of this work are to propose a combined approach to aggregate soil and crop properties into contiguous management zones, based on multivariate geostatistics and a non-parametric density algorithm of clustering, and to use visualization for displaying data and statistical analysis
Soil loss assessment in the Turbolo catchment (Calabria, Italy)
No full textSoil loss caused by accelerated erosion is a growing problem in the Mediterranean belt in
general, and in many parts of the Calabrian region (Southern Italy), in particular. It is due to
the combination of peculiar geomorphological, pedological and climatic features, very often
exacerbated by unsuitable land management. The aim of this study is to analyze and map
soil loss by water-induced soil erosion at the catchment scale. Soil loss was quantified using
the revised universal soil loss equation (RUSLE) model implemented in a geographical
information system. The RUSLE is an empirical model which estimates the average annual
soil loss that would generally result from splash, sheet and rill erosion. The analysis shows
that total soil loss estimated in the study area is 16,470.88 t yr−1 with an average annual soil
loss of 5.65 t ha−1 yr−1. Spatial variation and rates of soil erosion are mainly linked to land
use, and the rate of soil erosion varies from less than 1 t ha−1 yr−1 in wooded areas to more
than 40 t ha−1 yr−1 in barren land. In addition, the comparison between soil loss and slope
maps shows that ∼47% of the estimated soil loss involves slopes with a gradient >20°. The
map shows seven classes of soil loss, with 8% in the upper three classes and 51% in the
lowest class
Studying the relationship between water-induced soil erosion and soil organic matter using Vis–NIR spectroscopy and geomorphological analysis: A case study in southern Italy
No full textA Combined Approach of Sensor Data Fusion and Multivariate Geostatistics for Delineation of Homogeneous Zones in an Agricultural Field
No full textTo assess spatial variability at the very fine scale required by Precision Agriculture, different proximal and remote sensors have been used. They provide large amounts and different types of data which need to be combined. An integrated approach, using multivariate geostatistical data-fusion techniques and multi-source geophysical sensor data to determine simple summary scale-dependent indices, is described here. These indices can be used to delineate management zones to be submitted to differential management. Such a data fusion approach with geophysical sensors was applied in a soil of an agronomic field cropped with tomato. The synthetic regionalized factors determined, contributed to split the 3D edaphic environment into two main horizontal structures with different hydraulic properties and to disclose two main horizons in the 0–1.0-m depth with a discontinuity probably occurring between 0.40 m and 0.70 m. Comparing this partition with the soil properties measured with a shallow sampling, it was possible to verify the coherence in the topsoil between the dielectric properties and other properties more directly related to agronomic management. These results confirm the advantages of using proximal sensing as a preliminary step in the application of site-specific management. Combining disparate spatial data (data fusion) is not at all a naive problem and novel and powerful methods need to be developed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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