排序方式: 共有74条查询结果,搜索用时 15 毫秒
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R. Petrini M. Pennisi L. Vittori Antisari R. Cidu G. Vianello U. Aviani 《Environmental Earth Sciences》2014,71(12):5099-5111
This paper examines the issues related to salinization and water quality in the complex drainage system of the historical land reclamation of Lamone basin (Ravenna coastal plain, northern Italy), with the aim of guiding ongoing agricultural-related decisions. Major and trace element concentration and O–H–B–Sr isotope-ratios were measured on surface water from a network of canals and ditches. Sampling was carried out during the winter period and in summer, to assess the effects of agricultural water management on the aquatic system. Results show widespread salinization of waters over the entire crop, due to both the direct saltwater inland flushing through the canals in proximity of the mouths, and sea salt leaching from soils. During winter, salinization is partly mitigated by rainfalls, while in summer dilution processes are due to freshwater input from outside the watershed, planned to assist the agricultural water demand. In the winter season, the concentration of some elements such as Fe, Mn, Al, and Cu in waters exceeds the maximum permissible limits imposed by the Italian regulations, while during summer the concentration of these elements is significantly reduced. A seasonal cycling is established, where the bottom sediments of canals and ditches act as sinks of harmful elements, mostly through adsorption by Fe–Mn–Al oxy-hydroxide solid phases. The irrigation practice, although improving the water quality, increases water turbidity by re-mobilization of sediments which act as transport agents of contaminants, with detrimental effects that may become significant over the years. 相似文献
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Luiz G. de Carvalho Marcelo de Carvalho Alves Marcelo S. de Oliveira Rubens L. Vianello Gilberto C. Sediyama Luis M. T. de Carvalho 《Theoretical and Applied Climatology》2010,102(3-4):417-428
The objective of the present study was to assess for Minas Gerais the cokriging methodology, in order to characterize the spatial variability of Thornthwaite annual moisture index, annual rainfall, and average annual air temperature, based on geographical coordinates, altitude, latitude, and longitude. The climatic element data referred to 39 INMET climatic stations located in the state of Minas Gerais and in nearby areas and the covariables altitude, latitude, and longitude to the SRTM digital elevation model. Spatial dependence of data was observed through spherical cross semivariograms and cross covariance models. Box–Cox and log transformation were applied to the positive variables. In these situations, kriged predictions were back-transformed and returned to the same scale as the original data. Trend was removed using global polynomial interpolation. Universal simple cokriging best characterized the climate variables without tendentiousness and with high accuracy and precision when compared to simple cokriging. Considering the satisfactory implementation of universal simple cokriging for the monitoring of climatic elements, this methodology presents enormous potential for the characterization of climate change impact in Minas Gerais state. 相似文献
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Jean-Pierre Raulin Pedro Correia de Matos David Rubens Hadano Antonio C. V. Saraiva Emilia Correia Pierre Kaufmann 《Earth, Moon, and Planets》2009,104(1-4):247-261
In this paper we present the South America VLF NETwork (SAVNET), a new observing facility at very low frequencies. It has been recently installed at different locations spread over Latin America, in Brazil, Peru and Argentina. It consists of a network of seven Very Low Frequency (VLF) receivers with the main scientific objective of monitoring the solar activity on short (minutes to hours) and long (years) time scales. Other objectives include a better understanding of the spatial structure of the South Atlantic Magnetic Anomaly, the study of atmospheric phenomena and the search for genuine seismic-electromagnetic effects. After discussing the scientific goals, the details of the installation are presented as well as the first results recently obtained. 相似文献
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Lucas May Petry Camila Leite Da Silva Andrea Esuli Chiara Renso Vania Bogorny 《International journal of geographical information science》2020,34(7):1428-1450
ABSTRACT The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score. 相似文献
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Vajapeyam S. Srinivasan Hugo M. de Alcântara Carlos de O. Galvão Ulisses A. Bezerra John E. de Brito Leite Cunha 《水文研究》2021,35(5):e14194
Catchments have highly variable yields of runoff and soil erosion. The size, land use and the surface cover play a significant role and influence the catchment response and parameter values of simulation models. Two experimental basins—the Cariri basins—were equipped in a semi-arid region of Brazil, for obtaining runoff and sediment yield at different catchment scales, as well as, to evaluate the influence of the land use and surface cover. In the first basin, located in the municipality of Sumé, the field studies were carried out at two different scales: four micro-catchments with an area of around 0.5 ha and nine standard Wischmeier-type erosion plots of 100 m2. The experimental units had varied vegetation and management. They were subjected only to natural rainfall events, and were monitored from 1982 to 1991. The total runoff and total sediment yield were determined for each of the events. The installations in the second basin, in the municipality of São João do Cariri, from 1999, include two erosion plots, three micro-catchments, and two sub-catchments of a small basin. These basins are still being monitored for runoff and sediment production. Among the micro-catchments two are nested to detect any scale effect at the micro-catchment level. Nearly 600 events of precipitation, that produced runoff in at least one of the experimental units, have been registered. These data have been used to evaluate the influence of various factors, including cultivation practices and to calibrate hydrological models for plots and micro-catchments. Parameters have been tested by means of cross validations among micro-catchments and sub-catchments. The data sets are made available to all the catchment hydrology researchers and others at https://doi.org/10.5281/zenodo.4690886 . 相似文献
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Leandro Ismael de Azevedo LACERDA José Augusto Ribeiro da SILVEIRA Celso Augusto Guimar 《地理学报(英文版)》2021,31(10):1529-1552
Urban forests play an important role in the thermal comfort and overall life of local populations in large-and medium-sized cities.This study analyzes urban forest loss and maps land use and land cover (LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in Jo~o Pessoa,Brazil.For this purpose,satellite-derived LULC images from 1991,2006,2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used.In addi-tion,this paper also discusses the instruments used for integrated urban planning,which are(a) the legal sector,responsibility and nature;(b) the urban expansion process;and (c) the elements of urban infrastructure.The results show a clear shift in land use in the study area.The major changes in LULC classes occurred in urban areas and herbaceous vegetation,while the greatest loss was in arboreal/shrub vegetation.Thus,an increase in the pressure to occupy zones intended for environmental preservation could be estimated.Our results showed similar accuracies with other studies and more spatial details.The characteristics of the patterns,traces,and hotspots of urban expansion and forest cover loss were explored.We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of ur-ban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches. 相似文献
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Rafael Moniz Caixeta Diniz Tamantini Ribeiro João Felipe Coimbra Leite Costa Péricles Lopes Machado 《Natural Resources Research》2017,26(2):213-221
Multiple Random Walk Simulation consists of a methodology adapted to run fast simulations if close-spaced data are abundant (e.g., short-term mining models). Combining kriging with the simulation of random walks attempts to approximate traditional simulation algorithm results but at a computationally faster way when there is a large amount of conditioning samples. This paper presents this new algorithm illustrating the situations where the method can be used properly. A synthetic study case is presented in order to illustrate the Multiple Random Walk Simulation and to analyze the speed and goodness of its results against the ones from using Turning Bands Simulation and Sequential Gaussian Simulation. 相似文献
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R. F. S. Andrade O. Oliveira A. L. Cardoso L. S. Lucena F. E. A. Leite M. J. Porsani R. C. Maciel 《Computational Geosciences》2009,13(2):155-163
Self-affine properties have been observed in a large variety of rough profiles and time series from natural data sets. In
this work, seismograms used for oil prospecting, which contain information of distinct subsurface features collected by seismic
waves reflected or scattered at their interfaces, are taken into consideration. It is expected that any self-affine property,
measured by the Hurst exponent H, depends on the depth. For each seismic trace, H is evaluated locally within a moving window, which is chosen narrow enough to reveal space dependency but also wide enough
to display scale invariance. With the use of color code diagrams, it is possible to draw two-dimensional diagrams that show
the local dependence of H for the analyzed seismogram. The reliability of the method is tested by the investigation of seismograms that contain ground
roll components, as well as multiple reflections. The effect of different kinds of filter in the scaling properties is also
investigated. In this case, comparisons are drawn among the diagrams obtained from original seismograms and those subjected
to appropriate filter to eliminate spurious components.
Work supported by the Brazilian agencies CNPq, FINEP-CTPETRO and Petrobras. 相似文献
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Marcelo Accioly Teixeira de Oliveira Jorge Luis Porsani Gisele Leite de Lima Vivian Jeske-Pieruschka Hermann Behling 《Quaternary Research》2012,77(3):397-407
Paleoenvironmental interpretation of proxy data derived from peatlands is largely based upon an evolutionary model for ombrotrophic bogs, in which peat accumulates in still environments. Reports on proxies obtained from minerotrophic fens, where hydrologic inputs are variable, are less common. In this study, a highland peatland in southern Brazil is presented through ground penetrating radar (GPR) and sedimentological, palynological and geochronologic data. The radar stratigraphic interpretation suggests a relatively complex history of erosion and deposition at the site since the beginning of Marine Isotope Stage 3 (MIS 3) interstadial period. In spite of this, radar stratigraphic and palynologic interpretations converge. Electromagnetic reflections tend to group in clusters that show lateral coherence and correlate with different sediment types, while pollen grains abound and are well preserved. As a result, the study of minerotrophic fens provides a source of proxies, suggesting that ombrotrophic bogs are not the only reliable source of data in wetlands for palynological analysis. 相似文献