1,720,997 research outputs found
On the approximation of distributed demands as nodal demands in WDN analysis
No full textThe analysis of a looped water distribution network, operating under pressure and in steady flow conditions, can be accomplished once the topology of the network, the geometry of the pipes, the water demands delivered at the nodes and the head value at least one node are known. In a water distribution network (WDN) model water demands are represented as delivered at the nodes although they occur along the pipes. This classical approximation represents the total demand along the pipe as two lumped demands at its ending nodes. This paper demonstrates that the above approximation is wrong, because it generates head loss errors which may be significant when the network analysis is performed for calibration or for network design purposes. Therefore, an extension of the Global Gradient Algorithm for network analysis is here proposed which allows to correctly introduce the lumped nodal demands without loosing the physical correct representation of head losses
Pipe hydraulic resistance correction in WDN analysis
No full textThe analysis of a looped water distribution network, operating under pressure and in steady flow conditions, can be accomplished once the topology of the network, the geometry of the pipes, the water demands at the nodes and the head value of at least one node are known. In a water distribution network (WDN), water de-mands are assigned to the nodes, although in reality they are distributed along the pipes converging at such nodes. This classical assumption represents the total demand along a pipe as two lumped withdrawals at its terminal nodes. This paper demonstrates that the above approximation is wrong because it generates head loss errors which may be significant when network analysis is performed for calibration, system design, real-time operations, rehabilitation strategies, optimal operation studies, reliability analyses, etc. Therefore, an extension of the Global Gradient Algorithm (GGA) for network analysis is proposed which entails a modified GGA permitting the effective introduction of the lumped nodal demands, and without forfeiting a correct physical representation of head losses, by means of a pipe hydraulic resistance correction
New Modularity-Based Approach to Segmentation of Water Distribution Networks
No full textComplex and/or large size water distribution networks (WDNs) require the division of the hydraulic system into modules to simplify the analysis and the management tasks. In the modern science of networks, the modularity index has been proposed to detect communities, i.e., groups/clusters of nodes characterized by stronger interconnections. The modularity index is a measure of the strength of the network division into communities and it is maximized to identify them. Therefore, the division into modules of WDNs, also named segmentation, could be performed by using the modularity index as metric to identify cluster of nodes. Nevertheless, modularity index needs to be revised considering the specificity of the hydraulic systems, which are infrastructure networks. In fact, the division into modules for infrastructure networks, although it can be based on the identification of clusters of nodes, is not aimed at investigating network features. Differently, the aim is the practical issue of simplifying system analysis, planning and management; therefore, the division is constrained by the technical needs. Accordingly, in the present work the classic modularity index is firstly presented. Successively, it is tailored and modified for WDNs. Furthermore, a MO strategy for optimal segmentation is presented and discussed also using a real test network. The optimization framework is based on the maximization of the WDN-oriented modularity-based index versus the minimization of the cost of newly installed devices to obtain network segments. Those are a set of optimal divisions into modules of the hydraulic system which are the basis for an integrated, dynamical plannin
Studio del moto vario in uno schema complesso misto gallerie a pelo libero - condotte in pressione
No full textViene studiato un modello di moto unidimensionale per correnti gradualmente variate in uno schema idraulico complesso costituito da tre canali a pelo libero intervallati da due passaggi in pressione (sifoni rovesci).
Si fa riferimento ad uno schema idraulico esistente costruito per il trasporto idrico di una portata di dieci metri cubi al secondo dal fiume Bradanoagli invasi di Acerenza e Genzano (in Basilicata) attraverso un canale adduttore di circa 22 Km.
Il modello di moto vario è stato realizzato considerando le equazioni differenziali del moto e di continuità, per i canali a pelo libero e per i passaggi in pressione interposti, adottando un semplice e generale schema per la loro differenziazione (Preissmann a quattro punti) e linearizzando succrssivamente il sistema dio equazioni risolventi. Si è posta particolare attenzione alla concettualizzazione delle connessioni canali a pelo libero-condotte im pressione, al fine di mantenere le equazioni risolutive dell'intero schema sempre accoppiate nonché di computare la capacità di invaso dei sifoni rovesci
A novel infrastructure modularity index for the segmentation of water distribution networks
Full text linkThe search for suitable segmentations is a challenging and urgent issue for the analysis, planning and management of complex water distribution networks (WDNs). In fact, complex and large size hydraulic systems require the division into modules in order to simplify the analysis and the management tasks. In the complex network theory, modularity index has been proposed as a measure of the strength of the network division into modules and its maximization is used in order to identify community of nodes (i.e., modules) which are characterized by strong interconnections. Nevertheless, modularity index needs to be revised considering the specificity of the hydraulic systems as infrastructure systems. To this aim, the classic modularity index has been recently modified and tailored for WDNs. Nevertheless, the WDN-oriented modularity is affected by the resolution limit stemming from classic modularity index. Such a limit hampers the identification/design of small modules and this is a major drawback for technical tasks requiring a detailed resolution of the network segmentation. In order to get over this problem, we propose a novel infrastructure modularity index that is not affected by the resolution limit of the classic one. The rationale and good features of the proposed index are theoretically demonstrated and discussed using two real hydraulic networks
New concepts and tools for pipe network design
No full textWater Distribution Network design has been traditionally approached as a cost minimization problem, constrained by some additional restrictions intended to ensure an acceptable level of customer service. Although the ideas have existed for same time, it was only recently that various researchers developed new network optimization approaches trying to address the minimization of design costs, while maximizing the benefits through some other performance indicators assessment in a risk-based scenario. Unfortunately, network simulation is still performed within a demand-driven context, even when reliability is considered among the benefits, and leakages are given as a constant percentage of nodal demands instead of being computed as a function of pipe pressure. This article introduces a more realistic approach to network design and simulation, performed using pressure-driven leakages employing a recently developed simulation model. Thus, the design procedure is conceived as multi-objective optimization, performed considering the minimization of pipe cost and together with total network leakage flow. The approach was tested on a small-size Italian real network which supplies an industrial area, and on a simpler network that yielded some interesting observations about the proposed paradigm
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
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