1,720,979 research outputs found
Optimization of the design of labyrinth emitter for agriculture irrigation using computational fluid dynamic analysis
No full textFluid dynamic simulations are used to improve the efficiency of flat drippers commonly used in agriculture to optimize the irrigation system.. These emitters have a particular configuration of the labyrinth channel appropriately shaped to ensure high turbulence and dissipation of the hydraulic load. The analysis was carried out investigating the labyrinth geometry by means of computational fluid dynamics technique. Several simulations were performed in order to investigate on the relationship between the flow rate, in liters per hour, and the pipe pressure. Seven different dripper models were analyzed to change the size of the dissipation channel and therefore the flow rate. The emitter discharge was investigated for three inlet pressure values 50, 100 and 150 kPa. This way it was possible to calculate the law that rules the pressure-flow curve. Basically, the geometry was modified thus to optimize the exponent of the emitter. The value of the exponent is closely linked to the conformation of the channel and is standardized by the International Organization for Standardization (ISO) 9261:2004. Furthermore, the relation between the cross sectional area of the labyrinth channel and the flow rate was investigated
Effect of roughness on elongated particles in turbulent channel flow
No full textIn this paper, we examine the deposition and resuspension of rigid elongated particles transported by turbulence in a channel bounded by two-dimensional roughness. To analyze these processes, we use an Euler–Lagrange approach based on Direct Numerical Simulation of the carrier phase and Lagrangian Particle Tracking of the dispersed phase. Four different channel configurations are considered: One is the classical channel flow bounded by smooth flat walls, whereas the other three correspond to a channel with walls of increasing roughness. The roughness shape is obtained by superimposition of sinusoidal functions with different amplitude k and is characterized by the mean absolute value of the amplitude, k̄= 0.012, 0.024 and 0.050 (k̄= 0 for a smooth wall). The friction Reynolds number is Reτ=150 for all cases. Particles are modeled as prolate ellipsoids and classified according to their aspect ratio λ. Three different particles sets are considered: λ=1, corresponding to the reference case of spheres, λ=3, corresponding to slightly elongated particles, and λ=10, corresponding to long fiber-like particles. The particle response time is St+=5 for all sets. In turbulent flow bounded by smooth walls, particles are known to accumulate preferentially in the near-wall region, leaving the central region of the channel scarcely populated. Wall roughness produces a completely different scenario: Particles exhibit a more homogeneous distribution along the wall-normal direction. We show that the aspect ratio does not affect the preferential distribution and the velocity statistics of the particles. The effect of elongation, however, becomes important for their preferential orientation, which is much weaker than in the smooth-walls case, in the near-wall region, while recovering the smooth-walls case in the outer region of the channel. This finding supports the validity of Townsend's similarity hypothesis, namely that the bulk flow dynamics are unaffected by the roughening of the bounding walls
Numerical simulation for water loss estimation in water supply pipes: Discharge estimation and deformation analysis
No full textIn recent decades, the changing scenario in the availability and the use of water has made the efficiency of water distribution systems (WDSs) management a topic of great importance, particularly in terms of leakage detection and control. The definition of the relationships, which relates the leak outflow and the relevant hydraulic parameters has received more and more increasing attention in literature. Here, the attention is mainly focused on the analysis of the behavior of different types of leak openings in pressurized pipes, taking into account the effect of rigid and deformable materials
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
Policy and political challenges for a better world: The United States and China pathways towards the 2030 Agenda
Full text linkThe Agenda 2030 poses critical elements regarding the transition towards a more sustainable development. This paper aims at exploring and comparing the path of sustainable development within the United States and China at the subnational level. An index of Integrated Sustainable Development is introduced to measure local sustainable development on an internationally-comparable scale. This Index is computed both at the national and subnational level and the resulting scores are compared within and across the two countries, also through the adoption of convergence and cluster analysis, allowing to answer four questions: Are the US and China moving towards a sustainable development agenda? Are the current achievements uniformly distributed within the two countries? Are states/provinces converging towards a more uniform level of sustainable development? Do the existing differences and analogies between states and provinces give rise to common clusters across the two countries? The results lead to one robust conclusion: while the US can claim a better result in the national and subnational rankings of sustainable development, China exhibits a more balanced achievement in terms of synergies across Goals and spatial distribution. Nonetheless, both countries are characterized by subnational disparities and scarce achievements of Planet-related Goals. Policy recommendations are discussed accordingly
Performance of Emitters in Drip Irrigation Systems Using Computational Fluid Dynamic Analysis
Full text linkFlat drippers are widely used in agricultural irrigation systems to ensure precise water distribution. This study investigates the optimization of flat drippers through Computational Fluid Dynamics (CFDs) simulations, focusing on the channel geometry. These emitters have a particular configuration of the labyrinth channel appropriately shaped to ensure high turbulence and dissipation of the hydraulic load. CFDs techniques are particularly suitable to investigate the labyrinth design and optimization. Here, by analyzing seven different dripper models with varying dissipation channel sizes, the relationship between flow rate (liters per hour) and pipe pressure (kPa) was studied. Simulations were performed for six inlet pressures in the range between 50 and 175 kPa, with steps of 25 kPa, allowing for the derivation of the pressure-flow curve and the optimization of the emitter exponent. The value of the exponent is closely linked to the conformation of the channel and is standardized by the International Organization for Standardization (ISO) 9261:2004. Additionally, the influence of the labyrinth channel's cross-sectional area on flow rate was examined, providing insights into design improvements for enhanced hydraulic performance. The proposed optimization could lead to significant water savings and enhanced agricultural productivity by improving the efficiency of irrigation systems
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
New Evidence on the Link between Ethnic Fractionalization and Economic Freedom
Full text linkAmong the determinants of economic freedom, the presence of different ethnic groups within a country has sometimes been explored by the empirical literature, without conclusive evidence on the sign of the relation, its drivers, and the conditions under which it holds. This paper offers new evidence by empirically modelling how ethnic fragmentation is related to economic freedom, as measured by the Economic Freedom Index and by each of its numerous areas, components and sub-components. The results provide insights on the components driving the effect and, interestingly, detect notable differences between developed and developing countries
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