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排序方式: 共有439条查询结果,搜索用时 15 毫秒
321.
Abstract Recent investigations demonstrated that inter‐year NOAA‐AVHRR NDVI variations at the middle of the rainy season can provide information on annual crop yields in Sahelian countries. This line of research is presently extended to the consideration of multitemporal NDVI data for several years (1986-1991) pre‐processed by a proven methodology. The investigation was conducted using NDVI and crop yield data from the sahelian sub‐districts of Niger. The results confirm that geographically standardized NDVI data are efficient for crop yield forecasting, but notable differences exist in this prediction capability depending on the beginning of the season. Late beginnings of the growing (rainy) season (after the end of June) allow optimum forecasting only after mid‐August, while early beginnings lead to anticipate the forecasting capability but also to decrease its accuracy. The importance of these findings in the context of an early warning system is finally discussed. 相似文献
322.
Giancarlo Biotto Lucia Gobbo Elisa Furlan Sonia Valenti Roberto Rosselli 《International journal of geographical information science》2013,27(10):1233-1244
This work deals with the identification of potentially contaminated areas using remote sensing, geographic information systems (GIS) and multi‐criteria spatial analysis. The identification of unknown illegal landfills is a crucial environmental problem in all developed and developing countries, where a large number of illegal waste deposits exist as a result of fast, and relatively unregulated, industrial growth over the past century. The criteria used to perform the spatial analysis are here selected by considering the characteristics which are ‘desirable’ for an illegal waste disposal site, chiefly related to the existence of roads for easy access and to a low population density which facilitates unnoticed dumping of illegal waste materials. A large dataset describing known legal and illegal landfills and the context of their location (population, road network, etc.) was used to perform a spatial statistical analysis to select factors and criteria allowing for the identification of the known waste deposits. The final result is a map describing the likelihood of an illegal waste deposit to be located at any arbitrary location. Such a probability map is then used together with remote sensing techniques to narrow down the set of possibly contaminated sites (Silvestri and Omri, 2008), which are candidates for further analyses and field investigations. The importance of the integration of GIS and remote sensing is highlighted and represents a key instrument for environmental management and for the spatially‐distributed characterization of possible uncontrolled landfill sites. 相似文献
323.
Carolina Perpiña Castillo Carlo Lavalle Claudia Baranzelli Sarah Mubareka 《International journal of geographical information science》2013,27(10):1807-1825
This paper presents a modelling approach for the spatial allocation of second-generation feedstock (lignocellulosic crops) under a reference policy scenario in European Union of 28 Member State (EU-28). The land-use modelling platform (LUMP) was used in order to simulate the land-use changes from 2010 to 2050. Within the LUMP, the land demand for these lignocellulosic energy crops was derived from the Common Agricultural Policy Regionalised Impact analysis model. Suitability maps were generated for two main energy crop groups: herbaceous and woody lignocellulosic crops, using multicriteria analysis techniques. Biophysical factors (climate, soil properties and topographical aspects), natural and artificial constraints and location-specific land categories were defined as relevant components within the platform. A sensitivity analysis determined the most influential factors to be temperature, precipitation, length of growing period and number of frost-free days. The results of the modelling exercise in the LUMP reflect the significant renewable energy contribution from energy crops in EU-28, which was estimated to be between 2.3 EJ/year (in 2020) and 6.3 EJ/year (in 2050), accounting for 2.3% and 9.6% of total energy consumption in the EU-28. The results of the allocation were aggregated at regional level to analyse trends. Regions with considerably high demand were identified in Germany, the United Kingdom and Poland. 相似文献
324.
Bulk and trace lithophilic elements (Al, Ca, Fe, Mn, Ti, Cr, Sr, V and Zn) have been determined in individual chondrules and in other constituents of the H-4 Mafra chondrite by means of flameless A.A. microanalysis. Twenty-four large sized (> 1 mg) chondrules, composite samples of minor-sized (0.1 and 0.2 mg) chondrules and fine-grained “interchondrular” material have been examined. Data on the large-sized chondrules exhibit large compositional variations among cosmochemically coherent groups of elements. A weak anti-correlation was found between the geochemically coherent refractory V and volatile Zn. A possible mass-composition relationship is suggested by the apparent concentration of lithophile high-temperature condensing elements (Ca, Al, Ti) in the minor-sized chondrules. Compositional features tend to support the hypothesis that chondrules originate from a large number of precursor components constituting a distinct grain population in the solar nebula. Melting through a sudden heating of random mixtures of these precursor grains was possibly followed by further condensation of volatiles and accretion. 相似文献
325.
Stochastic energy analysis of seismic isolated bridges 总被引:1,自引:0,他引:1
In this paper, a parametric stochastic analysis of isolated bridge is proposed with the aim to assess isolation performance and to investigate effects of energetic influence on protection efficiency. The analysis has been carried out in terms of two stochastic parameters of pear-deck maximum displacement and hysteretic energy response, of which a qualitative trend has been observed.Isolated bridge is described by a simple two degree of freedom (TDoF) Bouc–Wen hysteretic model, which has been introduced for its intrinsic ability in reproducing a wide range of real devices behavior. With the aim of taking into consideration intrinsic stochastic nature of seismic events, the ground motion and the structural response have been described by random vibration approach. Results obtained show that protection achieved by shifting structural natural period and reducing input energy by devices dissipation have counteracting effects if related to deck lateral displacement. 相似文献
326.
Middle to Late Holocene glacial variations, periglacial processes and alluvial sedimentation on the higher Apennine massifs (Italy) 总被引:1,自引:0,他引:1
Carlo Giraudi 《Quaternary Research》2005,64(2):176-184
The major climatic variations that have affected the summit slopes of the higher Apennine massifs in the last 6000 yr are shown in alternating layers of organic matter-rich soils and alluvial, glacial and periglacial sediments. The burial of the soils, triggered by environmental-climatic variations, took place in several phases. For the last 3000 yr chronological correlations can be drawn between phases of glacial advance, scree and alluvial sedimentation and development of periglacial features. During some periods, the slopes were covered by vegetation up to 2700 m and beyond, while in other phases the same slopes were subject to glacial advances and periglacial processes, and alluvial sediments were deposited on the high plateaus. Around 5740-5590, 1560-1370 and 1300-970 cal yr B.P., organic matter-rich soils formed on slopes currently subject to periglacial and glacial processes; the mean annual temperature must therefore have been higher than at present. Furthermore, on the basis of the variations in the elevation of the lower limit reached by gelifraction, it can be concluded that the oscillations in the minimum winter temperatures could have ranged between 3.0°C lower (ca. 790-150 cal yr B.P.) and 1.2°C higher (ca. 5740-5590 cal yr B.P.) than present minimum winter temperatures. During the last 3000 yr the cold phases recorded by the Calderone Glacier advance in the Apennines essentially match basically the phases of glacial advance in the Alps. 相似文献
327.
Heinz Wanner Stefan Brönnimann Carlo Casty Dimitrios Gyalistras Jürg Luterbacher Christoph Schmutz David B. Stephenson Eleni Xoplaki 《Surveys in Geophysics》2001,22(4):321-381
This paper aims to provide a comprehensive review of previous studies and concepts concerning the North Atlantic Oscillation. The North Atlantic Oscillation (NAO) and its recent homologue, the Arctic Oscillation/Northern Hemisphere annular mode (AO/NAM), are the most prominent modes of variability in the Northern Hemisphere winter climate. The NAO teleconnection is characterised by a meridional displacement of atmospheric mass over the North Atlantic area. Its state is usually expressed by the standardised air pressure difference between the Azores High and the Iceland Low. ThisNAO index is a measure of the strength of the westerly flow (positive with strong westerlies, and vice versa). Together with the El Niño/Southern Oscillation (ENSO) phenomenon, the NAO is a major source of seasonal to interdecadal variability in the global atmosphere. On interannual and shorter time scales, the NAO dynamics can be explained as a purely internal mode of variability of the atmospheric circulation. Interdecadal variability maybe influenced, however, by ocean and sea-ice processes. 相似文献
328.
Carlo Gavarini 《Soil Dynamics and Earthquake Engineering》2001,21(5):480
In the first part the paper outlines the current conceptions relevant to seismic risk for constructions in urban centres analysing seismic hazard, vulnerability and exposure. In the second part there are some details about the vulnerability assessment of ordinary buildings, and about the differences that arise when monumental or historical buildings are in question. Then the concept of seismic scenario is given (third part), so that the specific question of seismic vulnerability of historical centres may be treated (part four), presenting an appropriate methodology recently proposed by the author. Finally part five presents an introduction to the theme of risk mitigation for historical centres and monuments, a very difficult question, where the two aspects of preservation and seismic safety must be considered together. 相似文献
329.
330.
Sergio Grauso Andrea Pagano Grazia Fattoruso Piero De Bonis Filippo Onori Pasquale Regina Carlo Tebano 《Environmental Geology》2008,54(2):219-234
In the present work on-going research is discussed whose primary goal is to test some statistical methods to estimate the
average yearly area-specific sediment yield (SSY). Using geomorphological and climatic parameters various multiple regression
formulae have been set up based on SSY observed data from 16 catchments of Sicily. Three distinct techniques were adopted
to select the parameters to be used in the equations: simple correlation, stepwise regression analysis and a supervised geomorphological–statistical
correlation. The comparison of the results showed the effectiveness of the stepwise analysis, which led to a regression equation
with a coefficient of determination (r
2) of 0.87. Nevertheless, even this methodology showed some elements of uncertainty that have caused, in some cases, appreciable
differences between observed and predicted values (mean percentage error equal to 26%). These differences are likely either
due to the hydraulic regime of most of Sicilian watercourses (typical of semi-arid regions) or to hidden factors (e.g., topography,
human impact and concentrated erosion), which can greatly affect the processes of sediment production and transport. The study
has pointed out the need to take into account a larger number of observations and to perform the analysis of relations between
suitable variables and SSY at a more detailed time resolution. 相似文献