1,720,966 research outputs found
Design of SiC-Si Hybrid Interleaved 3-Phase 5-Level E-Type Back-to-Back Converter
Full text linkIn modern applications, such as variable frequency electric drives, aircraft propulsion, electric vehicles, and uninterruptible power supply units, high power-dense, and efficient AC-AC power converters are the key to reducing power losses, thus limiting the overall costs, and improving the system's reliability. Power electronic equipment can be enhanced thanks to the continuous evolution of conversion topologies and advancements in power semiconductor technology. The design and the optimization strategy of the AC-AC 5-Level converter, called Interleaved 3-Phase 5-Level E-Type Back-to-Back Converter (I3Φ5L BTB E-Type Converter), has been proposed in this paper. The converter is analyzed and experimentally characterized to prove the configuration's high efficiency and high-power density. An introduction to the characteristics of the I-3Φ5L BTB E-Type Converter is described, and afterward, the optimization methodology to design the multilevel converter is presented. The converter prototype is illustrated, which achieves a peak efficiency of 98.2% and a total weight of 6.18 kg using hybrid technology for power semiconductor
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
Symmetrical three-phase seven-level E-type inverter for PV systems: Design and operation
No full textSolar photovoltaic (PV) is one of the most favourable renewable energy types today, the use of which has grown throughout the world, and much more is expected in the future due to the continuous price drop. It is important to further develop renewable systems to generate green energy, which results in the reduction of air pollution and in enabling a future sustainable society for the next generation of people. Accordingly, new topologies of the multilevel converter have been proposed and investigated for PV applications to achieve high efficiency and high-power density. This study presents the analysis and design of the symmetrical three-phase E-type inverter (S-3Φ7L E-type). The proposed topology is directly derived from the T-type converter and exhibits seven voltage levels at the output offering interesting performance in terms of power semiconductors current and voltage stress. The hardware design process of the converter has been carried out to enhance the efficiency conversion. Finally, theoretical results are carefully verified by testing the converter prototype, featuring a peak efficiency of 99%
Li-Ion Battery Fast Charging Methods: Review and Comparison
No full textIn this paper a comprehensive review and analysis on fast charging methods for Li-Ion batteries is reported and assessment of their impact on battery performance addressed. Existing literature proposed and compared several pulse charging strategies, e.g., Positive Pulse Charging (PPC) and Sinusoidal Ripple Current (SRC), with the standard Constant Current Constant Voltage (CCCV) approach, asserting superior outcomes in term charging time, lifetime, and temperature rising. However, it is crucial to highlight that the Electric Vehicles (EVs) typically charge up to 80% to 90% State of Charge (SoC), leading to irrelevant contribution of the CV phase in terms of SoC but heavily contributing to the full charging time, therefore biasing the comparison. A comparative analysis of PPC, SRC against both Constant Current (CC) and CCCV charging methods based on past literatures data and tests is reported here, aiming at highlighting that PC does not significantly impact charging time as compared to CC charging. However, the advantages of PC, including extended battery lifetime, reduced capacity fade, and efficient charging, making it a promising option for the future e-mobility applications. Our evaluation considers several crucial parameters, namely charging time, temperature rise, lifetime, capacity fade, energy efficiency and charge efficiency. Additionally, we considered the practical implementation of pulsed charging strategies with respect to standard ones, considering the challenges and constraints in an actual battery charger. By addressing the feasibility and limitations, our research aims to provide valuable insights for the potential integration of pulsed charging into commercial EV charging infrastructure
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
FPGA-Based Permanent Magnet Synchronous Machine Emulator with SiC Power Amplifier
No full textPower-Hardware-in-the-Loop (PHIL) platforms are gaining increasing attention as a valid solution for testing of converters operating in power electronics systems. When the Device-Under-Test (DUT) is represented by a power converter designed to supply a Variable Speed Drive (VSD), electrical machine emulation must be performed by the PHIL. However, emulation of electrical machines imposes several requirements to the design of the PHIL test platform. Indeed, the emulable range of the machine operating points is constrained by the choice of the DC-bus voltage and of the coupling network. Furthermore, coupling network sizing strongly affects the stability of the emulation. In this paper, the analytical relation between the coupling network, the emulator DC-bus voltage and the machine operating range is described. A design procedure is then derived for both the DC-bus voltage and the coupling network. Afterwards, a stability analysis is carried out to determine the stability characteristic of the PHIL emulation as a function of the coupling network choice and of the main parameters of the DUT control loop. The FPGA implementation of the PHIL is then described. Simulation and experimental results show the capability of the proposed implementation, with respect to both transient and steady state machine emulation
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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