1,721,162 research outputs found
Streamflow variability and optimal capacity of run-of-river hydropower plants
No full textThe identification of the capacity of a run-of-river plant which allows for the optimal utilization of the available water resources is a challenging task, mainly because of the inherent temporal variability of river flows. This paper proposes an analytical framework to describe the energy production and the economic profitability of small run-of-river power plants on the basis of the underlying streamflow regime. We provide analytical expressions for the capacity which maximize the produced energy as a function of the underlying flow duration curve and minimum environmental flow requirements downstream of the plant intake. Similar analytical expressions are derived for the capacity which maximize the economic return deriving from construction and operation of a new plant. The analytical approach is applied to a minihydro plant recently proposed in a small Alpine catchment in northeastern Italy, evidencing the potential of the method as a flexible and simple design tool for practical application. The analytical model provides useful insight on the major hydrologic and economic controls (e.g., streamflow variability, energy price, costs) on the optimal plant capacity and helps in identifying policy strategies to reduce the current gap between the economic and energy optimizations of run-of-river plants
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
Water management strategies for run-of-river power plants: Profitability and hydrologic impact between the intake and the outflow
No full textIn Alpine regions, especially when energy production by run-of-river plants is subsidized through state incentives, the indiscriminate growth of small plants built in cascade along the same river threatens aquatic ecosystems by depleting significant fractions of the river network. This paper compares the economic profitability of small run-of-river power plants and the ensuing hydrologic disturbance between the intake and the outflow, as resulting from the adoption of two alternative management strategies, namely the minimum flow discharge and a percent-of-flow rule. The capacity that maximizes the produced energy or the economic value of the plant, as well as the flow regime between the intake and the outflow, are analytically expressed as a function of the frequency distribution of the available streamflows. A quantitative framework relying on a set of synthetic hydrologic and economic indices is then proposed to compare the effectiveness of management strategies. The application of the method to three case studies in North-Eastern Italy evidences that the compliance of the minimum flow discharge does not prevent huge alterations of some key attributes of the flow regime, especially the temporal flow correlation. For a given and equal economic profitability of the investment, the two management strategies produce similar ecodeficits and an analogous reduction of the mean discharge between the intake and the outflow. However, the percent-of-flow strategy allows a reduced disturbance on the temporal correlation and the skewness of river discharges. Furthermore, when a percent-of-flow strategy is implemented, possible policy redefinitions aimed at reducing the hydrologic disturbance of the plant in the reach between the intake and the outflow can be complied with at reduced costs in terms of missed energy production. The framework developed may be a valuable tool to assess the ability of water management strategies to trade between hydrologic disturbance and anthropogenic uses of fresh water
Regional Calibration for a Distributed Catchment Model: an Application in North-Western Italy
No full textOne major challenge in large scale modeling is the estimation of spatially consistent distributed parameters, with a robust functional relationship to climate and landscape characteristics. We use here the newly developed PArameter Set Shuffling (PASS) approach, which is able to provide such regionally consistent parameter sets, for the calibration of the SALTO (SAme Like The Others) distributed hydrological model for about 80 catchments in North-Western Italy. The PASS method is a machine learning technique that does not require a priori assumptions on the relationship between model parameters and catchment descriptors. It instead derives these relationships from observed patterns of calibrated parameters and available catchment descriptors. The application demonstrates that the performance of the regionally calibrated distributed parameter sets is consistent with the one obtained locally, calibrating each catchment individually, implying robust results also for ungauged catchments in the area. To allow the reproducibility and repeatability of experiments, and to ease the application of the PASS approach to other case studies, an R package is under development which will be soon made available in GitHub
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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