1,720,958 research outputs found
Optimal operation of pressurised irrigation distribution systems operating by gravity
No full textOn-demand pressurized irrigation distribution networks (IDN) operating by gravity may face pressure
failures especially during the peak period. Several methods have been developed for irrigation sectoring where farmers are organized in turns. In general, the optimization methods used for pressurized systems consider, in the formulation of the problem, energy saving as objective function, which is not suitable for gravity-fed networks. In this study, an optimization model for pressurized IDN fed by gravity was developed to provide an optimal operating strategy based on irrigation periods. The model uses genetic algorithm to assign an irrigation period to each hydrant taking into account the minimization of pressure deficit at the most unfavorable hydrant of the network. The method is applied to a large scale irrigation distribution network in Italy. It shows to significantly improve the hydraulic performance of the network by insuring a satisfactory pressure at all hydrants, under the actual peak demand as well as higher water demands
Multi-Objective Optimization Model Based on Localized Loops for the Rehabilitation of Gravity-fed Pressurized Irrigation Networks
No full textNowadays, some of the existing irrigation distribution networks (IDNs) are facing hydraulic performance problems, due partly to the ageing of pipe networks, initial design flaws, improper management or/and the increase in water demand. Rehabilitation of these networks may become an inevitable need to provide the best services to farmers. To this end, a comprehensive computer model was developed to assist planners and decision makers in the determination of the most cost-effective strategy for the rehabilitation of irrigation networks. This model incorporates an innovative algorithm for the automatic search of the best looping positions in the network. Two multi-objective optimizations were applied for the rehabilitation of a real medium-size network operating on-demand and by gravity, one included the looping option while the other excluded this option. The two Pareto fronts, associated with each optimization, clearly indicated that it is imperative to consider the localized loops option during the rehabilitation process as it provided superior cost-effective solutions. The comparison between two selected cases from each front showed that even though the two solutions offered the same magnitude of improvement to the network, a cost saving of about 77% is obtained by choosing the case with the looping option. The model developed in the framework of this work represents a powerful optimization tool for cost-effective rehabilitation of irrigation networks
Development of an Integrated Computer Aided Design Tool for Microirrigation Systems
Full text linkPlanning, design and management of microirrigation systems require extensive numerical calculations. The introduction of computers in these processes removes much of the complications in calculation and results in more accurate analysis. Not many of the available software can be used to deal with an overall irrigation system implementation. Usually, separate software are used for irrigation planning and irrigation systems design. Consequently, this increases the investment cost for using the software in irrigation schemes. Hence, an integrated approach for both planning and
system design is required. In this study, an integrated computer aided design for microirrigation systems was developed. The program was written in Visual Basic (version 6.0) and it runs in Windows environment. A user-friendly interface is provided to give more flexibility to the user. This program uses menu bar and toolbar which takes the user to all data entry and results dialogs. Additionally, it is designed in such a way that extensive use of tables tables and graphics will be provided. This program also provides a help file that can be used as a guide for selecting the appropriate data during data entry processes. The developed program has the ability to estimate crop water requirements and design of microirrigation system pipelines. The computation of reference crop evapotranspiration from the available climatic data can be done for daily and monthly
time steps, using F AO Penman-Monteith method. Crop water requirement during the whole crop growing season can be calculated. Using these data, the program estimates
irrigation requirement taking into consideration the available rainfall. All the inputted data and the obtained results can be displayed in tabular or graphical forms. The program is also capable of performing analysis of either lateral or submain unit. All the emitter flows along a lateral or in a submain unit can be determined. Additionally, maximum and minimum emitter flows and their locations can also be determined. Finally, emitter flow variation and pressure variation along a lateral or in a
submain unit are computed. In this stage, tables and graphics are also provided. The overall laterals' layout and emitter flows profile can be displayed in the screen.
The developed program can be considered as a tool for preliminary design of micro irrigation systems. It is recommended to extend it to more powerful software by
including the design of all irrigation system
An Integrated Decision Support System for the Planning, Analysis, Management and Rehabilitation of Pressurised Irrigation Distribution Systems
Full text linkWater scarcity is a mounting problem in arid and semi-arid regions such as the Mediterranean. Therefore, smarter and more effective water management is required, especially in irrigated agriculture. Irrigation infrastructure such as pressurized irrigation distribution systems (PIDSs) play an important role for the intensification of agricultural production in the Mediterranean region. However, the operation and management of these systems can be complex as they involve several intertwined processes, which need to be considered simultaneously. For this reason, numerous decision support systems (DSSs) have been developed and are available to deal with these processes, but as independent components.
To this end, a comprehensive DSS called DESIDS has been developed and tested in the framework of this research. This DSS has been developed bearing in mind the need of irrigation district managers for an integrated tool that can assist them in taking strategic decisions for managing and developing reliable, adequate and sustainable water distribution plans, which provide the best services to farmers. Hence, four modules were integrated in DESIDS: i) the irrigation demand and scheduling module; ii) the hydraulic analysis module; iii) the operation and management modules; and iv) the design and rehabilitation module.
DESIDS was tested on different case studies located in the Apulia region, where it proved to be a valuable tool for irrigation district managers as it provides a wide range of decision options for proper operation and management of PIDSs. All this is obtained through a DSS that offers: i) high level of interactivity; ii) complete control of the irrigation managers; iii) adaptability and flexibility to the problems related to the operation of PIDSs; and iv) effectiveness in assisting irrigation managers with the decision making.
The developed DSS can be used as a platform for future integrations and expansions to include other processes needed for better decision-making support
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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