1,720,965 research outputs found
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
A Novel and Robust Security Approach for Authentication, Integrity, and Confidentiality of Lithium-ion Battery Management Systems
Full text linkBattery management systems (BMSs) play a critical and crucial role in ensuring the safety and the efficiency of the batteries. The increasing BMS complexity, the expanding interconnections between batteries and applications, and the introduction of cloud-based energy storage system structures have led to growing concerns about battery cybersecurity. For instance, the data exchange between the local and remote BMS parts can be exposed to cybersecurity attacks. Classic BMSs are not equipped with security mechanisms that are instead essential to protect their integrity and reliability and prevent serious consequences such as loss of data, equipment damage, and counterfeiting of battery components. This work highlights the importance of securing BMSs against cyber threats and discusses the current state of the art of cybersecurity in BMSs. The main outcome is the proposal of a novel and robust security approach to design a BMS able to prevent misuse and undesired manipulation of battery equipment and data. The proposed design approach can be used as enabling technology to support the application to the BMSs of the most diffused security mechanisms adopted by the state of the art as cybersecurity protections
A Dynamic Equalization Topology Based on Auxiliary Cell: Theoretical and Simulative Analyses
No full textThe dynamic equalization approach can significantly increase the use of electric vehicle second-life batteries in stationary applications. Dynamic equalization aims to face the very high variability of the capacity values of the second-life battery cells that strongly reduces the battery usable capacity. This work proposes an alternative dynamic equalization architecture based on an auxiliary cell to support the less-performing cells, maximizing the battery usable capacity. A theoretical methodology has been presented to analyze the proposed architecture. The obtained preliminary theoretical results are then validated using a simulation platform. The final results show a potential increase in usable battery energy of up to 16 % using an ideal DC/DC converter, and 13 % with a DC/DC converter efficiency of 0.8
Analysis of Thermal-Induced Shunt Current Sensor Errors in a Low-Cost Battery Management System
No full textLithium-Ion batteries are becoming a standard solution for automotive applications. These batteries must be equipped with a Battery Management System that monitors and controls the battery avoiding hazardous situations. The battery current measurement is crucial for both safety and control tasks. Shunt-based current sensors are widely used in automotive applications, thanks to the affordability and linearity of the measurement. This article discusses an unexpected current measurement error occurred during the test of a prototypal Battery Management System for a 12 V cranking battery. The current error only shows up during the cell balancing procedure, pointing to a thermal related effect. A theoretical assessment of the problem suggests the thermoelectric effect as the best candidate to explain the error. The thermal simulation of the circuit validated the hypothesis with perfect match. Finally, the guidelines for a correct shunt choice in a Battery Management System are provided
A novel methodology to study and compare active energy-balance architectures with dynamic equalization for second-life battery applications
Full text linkThe continuous growth of the electric vehicles market and the increasing environmental awareness impose to search for innovative solutions to reuse the exhausted vehicle batteries in different applications. One of the main problems of second-life batteries is the very high mismatch among their cell capacities which reduces the overall battery performance. The mismatch effect can be overcome by using dynamic equalization. This technique aims to keep balanced as much as possible the State of Charge of the cells during the battery operation, i.e. in both the charge and discharge phases. In order to do this, the dynamic equalization approach requires a high-current active energy balancing system able to move a quantity of charge among the battery cells much higher than the active balancing circuits sometimes used in first-life batteries. The use of a high equalization current increases the design complexity of the balance system.
A methodology to study and compare the main balance system topologies suitable for second-life batteries with dynamic equalization approach is presented in this work. The Adjacent Cell-to-Cell, Direct Cell-to-Cell, Cell-to-Pack, and Pack-to-Cell active balance topologies are analyzed considering the case study of a second-life battery composed of 10 series-connected cells with capacity values uniformly distributed around
15 % of the nominal value.
The investigation proves that the Direct Cell-to-Cell topology has the best performance. This balancing topology improves the usable battery capacity of around 16 % with respect to the case in which no dynamic equalization is applied if a DC/DC converter with a power efficiency of only 70 % is used. Finally, the results show that the Adjacent Cell-to-Cell performance is strongly affected by the position of the cell mismatches in the battery
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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