1,720,960 research outputs found
Lumped Parameter Modelling of Common Rail High-Pressure Fuel Injection Pump
No full textHigh injection pressure is crucial for both modern and future diesel engines, resulting in enhanced performance, fuel efficiency, and reduced emissions. Fuel atomization, combustion optimization, torque control, and engine NVH are among the critical topics directly influenced by the injection strategy. Common rail diesel injection pumps play a pivotal role in delivering fuel at high pressure, with performance metrics such as flow rate and maximum pressure defining the pump's technology level. Development efforts have consistently focused on improving performance and efficiency since the inception of common rail systems. Future challenges for diesel engines and injection pumps include meeting carbon neutrality goals, which may require adapting to new fuels, engine control strategies (such as hybrid powertrains and drivetrains), and pump drive concepts. In this context, simulating pump operation is essential for optimizing design, predicting performance, and developing control systems. The article deals with the mechanical-hydraulic modelling of a high-pressure pump. The model is based on the lumped parameter simulation of a cylinder-piston pair interacting with intake and delivery volumes via automatically opening valves. Validation of the model relies on dedicated experimental investigation campaigns, enabling measurement of pressure in the pump's working chamber and high-speed visualization of the intake valve's position relative to the pump shaft's angular position. The article reports a detailed description of the model, the experimental approach, and the synthesis of the results
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
INVESTIGATING EXTERNAL GEAR PUMP EFFICIENCY AT VERY LOW SPEEDS WITH GRAPHENE NANOFLUIDS
No full textExperimental investigations are performed to assess the operational efficiency of external gear pumps under high-pressure conditions, with a specific focus on varying shaft rotation speeds. These analyses encompass a broad range of rotational velocities, spanning from conventional to remarkably low speeds, reaching a minimum threshold of 150 RPM. At such reduced speeds, both volumetric and torque losses rise significantly, posing notable challenges to pump performance. Additionally, the lubrication conditions at such modest velocities are often compromised, further constraining the operational range of gear pumps, and limiting the efficiency of pump-controlled systems reliant on speed modulation. The primary objective of the current investigations is to assess the potential effectiveness of nanofluids in enhancing pump performance, particularly under the demanding operational conditions delineated above. This entails scenarios where pump loads are very high, and operational speeds are diminished to reach markedly off-design operating conditions. Consequently, the study presents a comparative analysis of external gear pumps operating with a commercial fluid that is integrated with graphene nanoparticles. Performance metrics, in terms of volumetric and hydro-mechanical efficiency, are evaluated to assess the impact of the nanofluid on overall pump energy performance. The findings of this study provide a first insight into the influence of nanofluids on gear pump efficiency and offer data for pump modeling at low speed. Such analyses hold relevance when control of gear pumps through variable speed logic is needed, as they provide an understanding of the potential benefits and limitations associated with the adoption of nanofluid-enhanced pump systems
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
VARIAZIONI DELLA PROFONDITÀ DELLA CAMERA ANTERIORE PRIMA E DOPO PRK MISURATE CON IL PENTACAM
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