1,720,958 research outputs found
Novel solutions for tracked crane electrification
No full textNowadays regulators, industry and academy are pushing toward electrification to reduce air pollution and energy consumption in a variety of sectors, including non-road mobile machinery.
All-electric heavy-duty equipment is already available, not just due to lower energy consumption and emissions, but as there is a demand for equipment that can operate in noise-sensitive locations and indoors. Often electrification of these machines is achieved just substituting the internal combustion engine with an electric motor, which is not optimal. This work aims to propose novel solutions for a better exploitation of the advantages offered by electric motors. Some novel solutions to address the energy efficiency issue typical of traditional fluid power systems were identified in literature, but there is still a lack of proposals for mobile cranes. The suitability for mobile cranes of the identified solutions was evaluated and two of them, decentralization and electronic load sensing, were selected for a deeper study. Decentralization is realized splitting the centralized hydraulic system in separated subsystems, for which electric-driven pumps are the most practical solution. In the first part of this work, a simulation model for fast energetic analyses of centralized and decentralized system was developed. Following experimental tests conducted on a prototype crane, the developed model was used to compare energy consumption of the two concepts through some operating cycles. The study highlighted that savings offered by decentralization are strongly-dependent on the considered operating conditions and on the low-speed operation ability of the pumps. Moving to a decentralized system, thus, must be carefully evaluated, due to the higher initial cost. As for electronic load sensing, an algorithm based on accurate control of fixed-displacement pump speed to achieve pressure control is proposed. Controllability offered by electric drives is exploited to realize a behavior similar to the one achieved with more complex variable-displacement pumps, which often are not adopted on small-size, low-cost machines. The proposed pressure controller is tuned relying on an purpose-built analytical model that takes into account the dynamics of the speed control loop. Compared to the traditional fixed-speed, fixed-displacement concept adopted on small-size machines, which makes use of unloading valves to control pump pressure, the proposed approach saves approximately 10% energy, without introducing costly components
Feasibility Evaluation of Hybrid Electric Agricultural Tractors Based on Life Cycle Cost Analysis
Full text linkThis paper presents a method to evaluate the economic feasibility of tractor powertrain electrification based on life cycle cost analysis. For a parallel hybrid, the best combustion engine downsizing, among some discrete values, was evaluated. The methodology was applied to three case studies with different power levels and operating cycles: a 76 kW orchard tractor, a 175 kW row crop tractor with medium duty use, and a 210 kW row crop tractor with heavy duty use. Fuel and electrical energy consumption were estimated through simulation. A range of powertrain components prices and fuel and electrical energy prices was taken into account, in order to cover price uncertainty and to show its effects. The results show that operating cost savings decrease when more power-intensive operations are performed. Considering a combination of system and energy prices deemed realistic by the authors, the operating cost savings, respectively for orchard, row crop medium duty, and row crop heavy duty, are approximately 8%, 3%, and 0.5%, which result in 6%, 1%, and 0.1% life cycle cost savings. Thus, powertrain electrification of high-power tractors should probably be avoided, whereas it could be beneficial for specialized orchard tractors. The developed method has proved to be suitable for such analyses
Feasibility Evaluation of Hybrid Electric Agricultural Tractors Based on Life Cycle Cost Analysis
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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
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