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A laboratory experimental system for infiltration studies
No full textThe investigation of a few hydrological processes under natural conditions can be distorted by their interactions. In this context, a laboratory system that allows a few mechanisms of the infiltration process to be studied univocally is presented. The core component of the system is a physical model consisting of a soil tank with slope angle, γ, adjustable from 1 ° to 15 °. A generator of artificial rainfall can produce rainfall rates up to 50 mm h−1. Surface runoff and deep flow, Qd, are continuously monitored. An overall analysis of three previous investigations performed by the physical system and directed to clarify the infiltration process is also briefly reported. These investigations, that concerned the validation of a local conceptual model for erratic rainfalls, the role of run-on and the effects of sloping soil surfaces, were all carried out by using different configurations of the system. Great slope effects in bare soils were observed. For example, under steady conditions, a ratio Qd(γ = 1 °) / Qd(γ = 10 °) equal to about 4 was observed in a loam soil. Finally, on the basis of the acquired knowledge, further investigations to be realized with the same basic elements are proposed to derive a conceptual model that describes the soil surface gradient effects
Hydropower in Central Italy: current status and future prospects
No full textThe largest source of renewable energy comes from a proven technology, hydropower. Hydropower is renewable because it draws its essential energy from the sun which drives the hydrological cycle which, in turn, provides a continuous renewable supply of water. The main goal of this paper is to optimize the use of hydropower resources in Umbria, a region of Central Italy. To this scope, we initially analyse the currently operating hydroelectric plants, taking into account both those of great size and the very small installations. Successively, we discuss the perspectives of this area in terms of exploitable hydraulic potential. It has been found that in Umbria are currently working 38 hydropower installations: 84% of them are run-of-river power plants, 10% are hydropower stations with a reservoir, while 6% works in both ways. Currently, 70 turbines are working: 41 are Francis, while the remaining, excluding a small Pelton and a Banki-Michell, are characterized by high degrees of reaction (Kaplan or helixes). The total installed hydroelectric capacity is over 650 MW, corresponding to an average annual production of approximately 1415 GWh. Most of these hydropower plants, 35 corresponding to 92% of the total, is privately owned: 13 from a big multinational company, 16 from small and medium size companies, 6 from private people. Only 3 installations are owned by municipalities. The described situation characterizes the Umbria region as a geographic area where the ratio between the exploited potential and the economically feasible potential has already reached a value not far from its physiological limit. In this context it is clear that in Umbria no large installations (> 10 MW) can be planned; instead, considering also the low number of existing hydropower stations with respect to the extension of the area (currently equal to 1 plant for each 222 Km2), a significant potential for the realization of small run-of-river power plants exists. At the moment 5 new hydropower plants are under construction, while about 100 small installations (<2 MW) are waiting to finalize their authorization process, during which the following issues are typically addressed and resolved by the local scientific community: 1) the increase of hydraulic risk produced during extreme precipitation events; 2) the management of hydrometric stations located near the new installations; 3) the environmental impact; 4) the definition of selection criteria when in the same location there are two or more requests of hydropower installations
Are heavy rainfalls in central Italy influenced by climate changes?
No full textIn recent years there is a growing concern by the community, scientific and not, about global warming and climate changes. The fact that the global temperature is growing up after the increase of the greenhouse gases emissions is already known, but there is still wondering about its effect on the hydrological cycle and most of all on rainfalls. Many studies supported by the Intergovernmental Panel on Climate Change (IPPC) showed that there is a general increase of heavy rainfalls also in areas where total annual precipitation is not prominently changed. Changings about frequency, intensity, duration in rainfalls and in weather events in general are still object of wonderings and past studies referred to different regions don’t give an unanimous answer about their trends. Mediterranean Area, which includes Italy, is supposed to be one of the most reactive to the climate changes and strong effects of them are expected. This paper deals with the rainfall tendencies in Umbria Region, Central Italy, since almost all the regional territory is included in the Upper Tiber River Basin and many areas are prone to risk of flooding. The climate of Umbria region is variable from areas to areas, in fact the weather is cold and wet in the East areas, near the Apennine Mountains and hotter and drier in the West, close to Tuscany region. Because of this variability a lot of raingauges had been placed in the last 10-15 years and nowadays a very dense raingauge network is present (more than 90 raingauges for a regional area of 8464,33 Km2, about one station each 90 Km2). The aim of this paper is to analyse if the climate changes caused effects on the rainfalls’ intensity in Umbria. Three meteorological stations have been selected: Città di Castello, Todi and Orvieto. They provide the longest series of data and the best quality in their measurements because raingauges have never been relocated. Rainfall measurements began in the thirties and have gone on until nowadays even if there are some interruptions (most of all during the years of the Second World War). For each year there are maxima for 6 durations:1, 2, 3, 6, 12 and 24 hours. The analyses of the data of the three stations, and most of all the one referred to Todi, whose geographical position is barycentric in the regional territory, show that there are not considerable changes in rainfall maxima and intensities in the last seventy years
IL PROCESSO DI INFILTRAZIONE SU UN SUOLO CON SUPERFICIE INCLINATA E INERBITA
No full text• Nelle situazioni reali il processo di infiltrazione di acqua nel suolo avviene quasi sempre in corrispondenza di superfici inclinate e in presenza di copertura vegetale
• Le modellistiche matematiche comunemente utilizzate per rappresentare il processo di infiltrazione assumono sempre una superficie del suolo orizzontale
• Esperimenti di laboratorio condotti su un modello fisico a scala ridotta hanno evidenziato che l’infiltrazione dipende significativamente dall’inclinazione della superficie del suolo e dalla copertura vegetal
The Influence of Climate Change on Heavy Rainfalls in Central Italy
No full textAbstractIn recent years there is a growing concern by the community, scientific and not, about global warming and climate changes. The fact that the global temperature is growing up after the increase of the greenhouse gases emissions is already known, but there is still wondering about its effect on the hydrological cycle and most of all, on rainfalls. Many studies supported by the Intergovernmental Panel on Climate Change (IPCC) showed that there is a general increase of heavy rainfalls also in areas where total annual precipitation is not prominently changed. Changings about frequency, intensity, duration in rainfalls and in weather events in general are still objects of uncertainty and past studies referred to different regions do not give an unanimous answer about their trends. The Mediterranean area, which includes Italy, is supposed to be one of the most reactive to climate change and deep effects are expected. This paper deals with rainfall tendencies in the Umbria Region, Central Italy, since almost all the regional territory is included in the Upper Tiber River Basin and many areas are prone to risk of flooding. The climate in the Umbria region is different from zone to zone, in fact the weather is cold and wet in the East areas, near the Apennine Mountains and hotter and drier in the West, close to Tuscany region.Because of this variability a lot of rain gauges were placed in the last 10-15 years. Nowadays a very dense rain gauge network is present (more than 90 rain gauges for a regional area of 8464.33 km2, about one station each 90 km2). The aim of this paper is to analyze if climate change affects rainfall intensity in Umbria. Three meteorological stations have been selected: Città di Castello, Todi and Orvieto. They provide the longest series of data and the best quality in rainfall measurements. Rainfall measurements began in the thirties and have gone on until nowadays even if there are some interruptions (most of all during the years of the Second World War). The analyses of heavy rainfalls of the three stations, and most of all the data referred to Todi, whose geographical position is barycentric in the regional territory; show that there are not considerable changes in rainfall maxima and intensities in the last seventy years
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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