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Relation concentration-débit et évolution temporelle du nitrate dans 25 rivières de la région Bretagne (France) ArchiMer
Guillaud, Jean-francois; Bouriel, Luc.
The study of the twenty-five largest rivers of Brittany showed that nitrate concentrations are positively correlated with river flow, in 90 % of the cases. The hydrogeological characteristics of the watersheds had an influence on these relationships. In this respect, river basins characterized by prevalent surficial water runoff exhibited higher correlation coefficients and lower lag times between river flow sequences and nitrate concentrations. The multi-year trend in riverine nitrate concentrations indicated a fourfold increase over 30 years. Nevertheless, 80% of rivers exhibited a recent decrease in nitrate concentrations, independent of inter-annual river flow fluctuations. The highest annual rates of nitrate decrease corresponded to river basins for...
Tipo: Text Palavras-chave: Eutrophication; River flow; Multiple regression analysis; Multi year trend; Nitrate; Brittany; Eutrophisation; Débit fluvial; Régression multiple; Évolution pluriannuelle; Nitrate; Bretagne.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2568.pdf
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Boron adsorption in soils from the State of São Paulo, Brazil PAB
ALLEONI,LUÍS REYNALDO FERRACCIÚ; CAMARGO,OTÁVIO ANTONIO DE.
Boron adsorption was studied in five representative soils (Rhodic Hapludox, Arenic Paleudalf and three Typic Hapludox) from the State of São Paulo, Brazil. Adsorption was higher in the clayey Oxisols, followed by the Alfisol and the coarser Oxisols. Calcium carbonate promoted an increase in the amount of adsorbed boron in all soils, with the most pronounced effect in the coarser-textured Oxisols. High correlation coefficients were found between adsorbed boron and clay and amorphous aluminum oxide contents and specific surface area (r = 0.79, 0.76 and 0.73, respectively, p < 0.01). Clay content, free aluminum oxide, and hot CaCl2 (0.01 mol L-1)-extracted boron explained 93% of the variation of adsorbed boron. Langmuir and Freundlich isotherms fitted well...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Tropical soils; Simple correlation; Multiple regression analysis.
Ano: 2000 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-204X2000000200020
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MODEL TREE: AN APPLICATION IN REAL ESTATE APPRAISAL AgEcon
Acciani, Claudio; Fucilli, Vincenzo; Sardaro, Ruggiero.
In the last twenty years in real estate appraisal there has been a growing interest for new and reliable assessment techniques essentially through the introduction of pluriparametric estimate, in particular of linear regression. However, also these techniques seem having not a great deal of adherence to very complex markets, for which the detection of best suited techniques to investigate market segments is necessary. The aim of the research is to test the applicative possibilities of model tree to land market, in order to highlight possible market segments in the original data set not detectable a priori.
Tipo: Conference Paper or Presentation Palavras-chave: Data mining; Model tree; Multiple regression analysis; Land market appraisal; Research Methods/ Statistical Methods; C01.
Ano: 2008 URL: http://purl.umn.edu/44853
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Remaining phosphorus estimated by pedotransfer function Rev. Bras. Ciênc. Solo
Cagliari,Joice; Veronez,Maurício Roberto; Alves,Marcelo Eduardo.
Although the determination of remaining phosphorus (Prem) is simple, accurate values could also be estimated with a pedotransfer function (PTF) aiming at the additional use of soil analysis data and/or Prem replacement by an even simpler determination. The purpose of this paper was to develop a pedotransfer function to estimate Prem values of soils of the State of São Paulo based on properties with easier or routine laboratory determination. A pedotransfer function was developed by artificial neural networks (ANN) from a database of Prem values, pH values measured in 1 mol L-1 NaF solution (pH NaF) and soil chemical and physical properties of samples collected during soil classification activities carried out in the State of São Paulo by the Agronomic...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Artificial neural networks; Modeling; Multiple regression analysis.
Ano: 2011 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832011000100019
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Modelling air temperature for the state of São Paulo, Brazil Scientia Agricola
Rodríguez-Lado,Luis; Sparovek,Gerd; Vidal-Torrado,Pablo; Dourado-Neto,Durval; Macías-Vázquez,Felipe.
Spatial modelling of air temperature (maximum, mean and minimum) of the State of São Paulo (Brazil) was calculated by multiple regression analysis and ordinary kriging. Climatic data (mean values of five or more years) were obtained from 256 meteorological stations distributed uniformly over the State. The correlation between the climatic dependent variables, with latitude and altitude as independent variables was significant and could explain most of the spatial variability. The coefficients of determination (P < 0.05) varied in the range of 0.924 and 0.953, showing that multiple regression analysis is an accurate method for the modelling of air temperature for the State of São Paulo. Finally, these regression equations were used together with the...
Tipo: Info:eu-repo/semantics/article Palavras-chave: DEM; GIS; Multiple regression analysis; Kriging; Climate modelling.
Ano: 2007 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162007000500002
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CORRELATIONS BETWEEN HOT CALCIUM CHLORIDE-EXTRACTED BORON AND CHEMICAL AND PHYSICAL ATTRIBUTES OF SOME BRAZILIAN SOILS Scientia Agricola
Alleoni,Luís Reynaldo Ferracciú; Camargo,Otávio Antonio de; Valadares,José Maria Aires Silva.
Relationship between soluble boron extracted with a hot CaCl2 0.01 mol L-1 solution and pH; organic carbon; exchangeable cations; cation exchange capacity (CEC); base saturation; total, free and amorphous iron and aluminum oxide contents; clay content; and specific surface area were performed for surface and subsurface samples of five soils. The soils were a Rhodic Hapludox, an Arenic Paleudalf and three Typic Hapludox, all representative soils of the State of São Paulo, Brazil. To quantify the relations between soluble boron and the different soil characteristics, simple linear correlations and multiple regressions, using a stepwise regression program, were performed. Hot-CaCl2 extractable boron (HCB) was significantly correlated with clay content (r =...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Soluble boron; Tropical soils; Simple correlation; Multiple regression analysis.
Ano: 1999 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90161999000200006
Registros recuperados: 6
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