1,721,051 research outputs found
Designing Trapezoidal Drip Irrigation Units laid on Flat Fields
No full textIn recent years, significant effort has been made to derive simple analytical solutions for designing one-lateral and rectangular drip irrigation units. In contrast, the trapezoidal shape often aligns with the natural subdivision of agricultural fields and serves as a foundational model from which rectangular and triangular forms are particular cases. Following a similar approach to previous works, this paper extends the analytical solutions derived for rectangular shapes to trapezoidal shapes, showing that the rectangular unit (RCT) is a particular case of the new solution. A comprehensive analysis of the performance of trapezoidal units was conducted using novel analytical solutions based on the pressure head tolerance concept. Two distinct types of trapezoidal units were studied based on the feed point: major base-fed (MJR) and minor base-fed (MNR). Interestingly, when the trapezoidal unit is fed from the major base (MJR), the hydraulic performance of the drip irrigation system is more efficient compared to both RCT and MNR. This is because lower manifold inside diameters, inlet pressure heads, and coefficient of variation of pressure head distribution (PHD) are obtained, thus MJR is higher recommended than RCT and MNR. Several applications showing the validity of the suggested procedure are performed and discussed
Settori microirrigui con ali gocciolanti telescopiche
No full textLe ali gocciolanti e le condotte di testata a diametro variabile, cosiddette telescopiche,
consentono di ridurre i costi di impianto e di esercizio dei settori irrigui, nonché
di migliorare l’uniformità di distribuzione delle portate erogate. Per semplificare il dimensionamento
dei settori, sono state proposte differenti metodologie più o meno
complesse che permettono di riprodurre l’andamento delle pressioni nell’impianto
(Sadeghi et al., 2016). Recentemente, con riferimento alla singola ala gocciolante telescopica,
è stata proposta una procedura semplificata basata sull’approccio delle distribuzioni
di pressione normalizzate (Baiamonte et al., 2023). Tale procedura consente di
determinare la lunghezza di ciascun tratto dell’ala, anche utilizzando differenti spaziature
tra i gocciolatori, con errori nella pressione di alimentazione dell’impianto inferiori
a 1.1%. L’obiettivo di questo lavoro è quello di estendere la suddetta metodologia
a un intero settore rettangolare, costituito da numerose ali gocciolanti telescopiche
e da una condotta di testata anch’essa telescopica. I risultati hanno mostrato che il metodo
proposto può essere convenientemente applicato, fornendo un ulteriore risparmio
energetico che si aggiunge a quello previsto nel metodo di calcolo originario con
un solo diametro delle tubazioni, e per cui era stato sviluppato un software denominato
IrriLab
Design Emission Uniformity of Horizontal Tapered Drip Laterals from the Normalized Pressure Head Distribution Approach
No full textA new analytical solution is developed to calculate the hydraulic emission uniformity (EUh) of horizontal tapered drip laterals. Our methodology builds upon normalizing the pressure head profiles along each segment of the lateral. Results indicated that the EUh remains fairly consistent regardless of the total lateral length if a fixed pressure head tolerance () is assigned in the design process. Instead, the EUh is primarily influenced by the number of emitters on each segment, their diameter ratio, and the emitter exponent x. Employing tapered laterals for any given values of and x enhances energy conservation compared to using single diameter laterals. However, it may lead to a reduction in the EUh, particularly when the number of emitters in the smaller diameter segment is low relative to the total number of outlets. It was concluded that the coefficient of variation in emitter pressure heads CV and EUh exhibit a nonlinear behavior in the case of tapered laterals, whereas it has been previously established as linear for single diameter laterals. Interestingly, when applying the newly formulated relationships for EUh and CV while keeping the same diameter for both segments, the results align with those previously obtained for single diameter laterals. Validation of the proposed EUh model against the precise stepwise solution revealed a maximum absolute relative error of ≈ 1%. When excluding the fully laminar flow condition (x = 1), relative errors typically remained below 0.5%. The proposed model could serve as a foundational framework for designing tapered laterals to achieve a targeted uniformity level in future studies
Il metodo di Hardy Cross nelle reti di ali gocciolanti: un confronto con le reti aperte
No full textNel lavoro, viene applicato il metodo di Hardy Cross a reti chiuse di ali gocciolanti,
utilizzando l’equazione di Hazen‐Williams per descrivere le perdite di carico continue
nelle tubazioni in polietilene. Per una prescelta geometria di un settore irriguo rettangolare,
è stato effettuato un confronto tra il comportamento di una rete aperta dimensionata
con il software IrriLab e quello di una rete chiusa di pari geometria, ottenuta
inserendo una condotta di testata secondaria, e dimensionata col metodo di Hardy
Cross. Il confronto ha consentito di valutare il risparmio energetico che offre la rete
chiusa rispetto a quella aperta. I risultati di questo lavoro mostrano che il risparmio
energetico, quantificato con la minore pressione di alimentazione richiesta, può raggiungere
il 54 %. Ovviamente, al risparmio energetico nei costi di esercizio andrebbero
pure messi in conto i maggiori costi di impianto dovuti alla chiusura della rete con una
condotta di testata secondaria. Tuttavia, quest’ultimo aspetto va oltre gli obiettivi di
questo lavoro.In this paper, the Hardy Cross method was applied to closed drip irrigation systems
considering the Hazen‐Williams resistance equation, which is more appropriate
for characterizing friction losses in polyethylene pipes. For a fixed rectangular unit
geometry, a comparison was performed, between an open circuit designed according
to the IrriLab software and a closed circuit obtained by closing the network with a
secondary manifold, and designed according to the Hardy Cross method. The latter
was made to evaluate the energy‐saving that a closed circuit provides compared with
an open circuit. Results showed that the energy‐saving, quantified by the less inlet
pressure head that the closed circuit requires compared to the open circuit, can reach
54 %. Of course, the energy benefit obtained with the closed circuit should also consider
the higher investment costs due to closing the circuit with a secondary manifold.
However, this issue is beyond the purpose of this work
Experimental Tests to Validate a Simple Procedure to Design Dual-Diameter Drip Laterals on Flat Fields
No full textMultiple-diameter laterals reduce the total cost in microirrigation systems, however, the length of each sublateral should be determined carefully to assure appro-priate performance of emitter flow rates. The most accurate method is the numerical trial and error, which is time-consuming. A series of research efforts have been made to propose simple analytical design procedures. By using the power-law form of the Darcy-Weisbach formula, and equal emitters spacing for the sublaterals, Sadeghi et al. (Sadeghi et al. in J Irrig Drain E-ASCE 142:04,016,020, 2016) extended a previously introduced design solution for one-diameter laterals to tapered laterals. Recently, a simplified procedure to design dual-diameter drip laterals has been intro-duced, providing relative errors in pressure heads less than 0.5%, and allowing to set different Hazen-Williams coefficients, flow rates and emitter interspaces for each sublateral. Moreover, this analytical procedure easily detects the required commer-cial emitter characteristics. The objective of this paper is to experimentally test this solution for drip sublaterals with different lengths, flow rates and emitter interspaces. Drip laterals of a major manufacturer (IRRITEC S.p.A) with diameters of 16 and 20 mm and given emitter characteristics were used in the experiments
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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