1,721,942 research outputs found
OPTIMAL OPERATION OF POWER-SPLIT HYBRID ELECTRIC POWERTRAIN: COMPARISON BETWEEN TWO PERFORMANCE INDICES
No full textAmong all the current environmentally-friendly ground vehicles proposed to reduce fuel consumption and emissions, power-split hybrid electric vehicles represent one of the most promising solutions. Their operation is based on the cooperation of the thermal engine and the electric unit enabled by mechanical transmissions consisting of planetary and ordinary gear sets. However, implementing proper energy management strategies to realise the best powertrain operations is crucial to maximise the environmental gain without compromising performance and drivability. For this purpose, an initial comprehensive analysis of the powertrain response is required. In this respect, this paper relies on a unified parametric approach, available in the literature, to investigate the acceleration response of an output-split hybrid electric powertrain by also considering the transmission mechanical power losses. The efficiency maps of the engine and electric machines are introduced to assess two performance indices. These are the powertrain real global efficiency and a fictitious equivalent efficiency where the efficiency of each actuator is normalised to the respective maximum value. The aim is to compare the optimal powertrain operation resulting from the maximisation of each performance index for a given vehicle speed and acceleration
Analysis of hybrid vehicle transmissions with any number of modes and planetary gearing: kinematics, power flows, mechanical power losses
Full text linkThis paper is focused on upgrading a unified parametric model, available in the literature, that can perform both the analysis and the design of Power-Split Continuously Variable Transmissions (PS-CVTs), which are particularly promising to deploy in the hybrid electric powertrain. In particular, this work is focused on the analysis of PS-CVTs and proposes a new matrix approach for identifying the basic functional parameters underlying the model from the constructive layout of the transmission. This new method does not rely on a case-specific formulation, thus befits any power-split transmission, regardless of the number of planetary and ordinary gear sets and their constructive arrangement. Moreover, it handles the clutches operations that perform the shift between different constructive layouts, therefore it is suitable even for multimode PS-CVTs. As a case study, we applied it to the complex multimode PS-CVT of the Cadillac CT6 and carried out a comprehensive analysis of its kinematics, mechanical power losses and power flows
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
Castellano A
No full textCastellano A es el primero de una serie de volúmenes que avanzan de lo más simple
a lo más complejo. Este volumen presenta 15 lecciones. Cada unidad comienza con una lectura que introduce la lección. Estas lecturas son variadas para incluir vocabulario y conceptos tanto del ambiente comunal como de la cultura mayoritaria
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
- …
