331 research outputs found

    Study of flood hazard in the Castelfranco Emilia area (Modena Province, Northern Italy)

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    The Castelfranco Emilia area is located in the Po Plain. The Panaro River have periodically caused flooding in the studyarea. The more recent floods took place between 1966 and 1973 (3 events).In order to reduce flood hazards, several meander cuts were carried out along the river. As these interventions resultedto be ineffective, a flow-regulation system was constructed west of Castelfranco Emilia. It consists of a regulating dambuilt across the riverbed and a storage basin bordered by embankments. This structure is operating since 1985 but wasfinished in 1999: no flooding events have occurred since it is in operation.The paper illustrates some aspects of flood hazard induced by the Panaro River, related to the construction of a highvelocity railway in the study area, a tract of the connection between Milano and Bologna.The relationship between precipitation data and the occurrence of a number of flooding events is studied, in order toestablish whether or not a significant relationship between the two can be identified. Furthermore, a distributed dynamichydrological model is constructed for simulation of the spatial and temporal proceedings of a flood event.On the basis of merely precipitation no predictions can be made with respect to the occurrence of a flood event. Theinclusion of alternative routes for the proposed railway allows for the evaluation and comparison of the spatial effects ofa flood event. Critical points in the model are calibration and the calculation of soil saturation prior to the event

    The survey and mapping of sand-boil landforms related to the Emilia 2012 earthquakes: preliminary results.

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    Sand boils, which are also known as sand blows or sand volcanoes, are among the most common superficial effects induced by high-magnitude earthquakes. These generally occur in or close to alluvial plains when a strong earthquake (M >5) strikes on a lens of saturated and unconsolidated sand deposits that are constrained between silt-clay layers, where the sediments are converted into a fluid suspension. The liquefaction phenomena requires the presence of saturated and uncompacted sand, and a groundwater table near the ground surface. This geological\u2013geomorphological setting is common and widespread for the Po Plain (Italy). The Po Plain (ca. 46,000 km2) represents 15% of the Italian territory. It hosts a population of about 20 million people (mean density of 450 people/km2) and many infrastructures. Thus, the Po Plain is an area of high vulnerability when considering the liquefaction potential in the case of a strong earthquake. Despite the potential, such phenomena are rarely observed in northern Italy, because strong earthquakes are not frequent in this region; e.g., historical data report soil liquefaction near Ferrara in 1570 (M 5.3) and in Argenta 1624 (M 5.5). In the Emilia quakes of May 20 and 29, 2012, the most widespread coseismic effects were soil liquefaction and ground cracks, which occurred over wide areas in the Provinces of Modena, Ferrara, Bologna, Reggio Emilia and Mantov

    Integrated GIS data set and 3d analysis for environmental impact assessment in the Castelfranco Emilia area (Modena Province, Northern Italy).

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    In this work is presented a database sets in order in order to analyse an Environmental Impact Assessment (EIA), Geographical Information System (GIS), Geomorphology, Castelfranco Emilia, Modena Provinc

    The survey and mapping of sand-boil landforms related to the Emilia 2012 earthquakes: preliminary results.

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    Sand boils, which are also known as sand blows or sand volcanoes, are among the most common superficial effects induced by high-magnitude earthquakes. These generally occur in or close to alluvial plains when a strong earthquake (M >5) strikes on a lens of saturated and unconsolidated sand deposits that are constrained between silt-clay layers, where the sediments are converted into a fluid suspension. The liquefaction phenomena requires the presence of saturated and uncompacted sand, and a groundwater table near the ground surface. This geological–geomorphological setting is common and widespread for the Po Plain (Italy). The Po Plain (ca. 46,000 km2) represents 15% of the Italian territory. It hosts a population of about 20 million people (mean density of 450 people/km2) and many infrastructures. Thus, the Po Plain is an area of high vulnerability when considering the liquefaction potential in the case of a strong earthquake. Despite the potential, such phenomena are rarely observed in northern Italy, because strong earthquakes are not frequent in this region; e.g., historical data report soil liquefaction near Ferrara in 1570 (M 5.3) and in Argenta 1624 (M 5.5). In the Emilia quakes of May 20 and 29, 2012, the most widespread coseismic effects were soil liquefaction and ground cracks, which occurred over wide areas in the Provinces of Modena, Ferrara, Bologna, Reggio Emilia and Mantov

    The EL2 trap in highly doped GaAs:Te

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    We have investigated highly doped GaAs:Te at different doping concentrations (>10(17) cm(-3)) to assess the presence of the EL2 trap. We have utilized both capacitance and current transient spectroscopy techniques. The crucial parameter for the detection of EL2 is the relative position of the electron quasi-Fermi level in the depletion region. The observed shift of the EL2 apparent activation energy with increasing doping concentration is also discussed

    Spatial-distribution of recombination centers in gaaste - effects of the doping level

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    The distribution in liquid-encapsulated-Czochralski (LEC) GaAs:Te wafers of point and complex defects has been investigated together with their influence on the minority-carrier diffusion length L. Three wafers with different Te-doping concentration (2.2 X 10(17), 4.5 X 10(17), and 1.5 X 10(18) cm-3) have been studied by means of the electron-beam-induced-current (EBIC) mode of scanning electron microscopy and of the surface photovoltage (SPV) method. The morphology and electrical activity of the defects observed across each wafer have been correlated to the formation and distribution of deep electronic levels, which are significantly affected by the tellurium concentration. The diffusion length has been found to be mainly controlled by deep levels associated with dislocations. EBIC localized measurements of L and of the net ionized free-carrier concentration provide evidence for the influence of Te concentration on impurity segregation at complex defects

    Bias Dependence of the Depletion Layer Width in Semi-Insulating GaAs by Charge Collection Scanning Microscopy

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    A procedure for the evaluation of the depletion region width of a Schottky barrier diode made on semi-insulating materials has been assessed and applied to gallium arsenide nuclear detectors. This procedure, which makes use of the optical beam induced current method of charge collection scanning microscopy, allows the direct measurement of the depletion layer width. By taking into account the high resistivity of the material under examination and measuring the diode reverse current, it is possible to evaluate the actual voltage applied at the depletion layer boundaries. It was found that, at low actual bias values, the voltage dependence of the depletion layer follows the usual square root power law, while at increasing voltages, it changes into a linear behavior. An explanation in terms of deep trap effect and trap field-enhanced capture cross-section is proposed even though further work must be done to explain the space charge width dependence on bias applied in terms of the deep trap influence
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