1,720,955 research outputs found
The impact of DC-bus impedance on the switching performance of low-voltage silicon power MOSFETs
No full textTypical DC-bus stabilization for low-voltage power circuits consists primarily of ceramic capacitors due to the capacity density and low equivalent series resistance (ESR) resulting in low conduction losses. Particularly in hard-switching and hard-commutation operation, the low ESR and high equivalent series inductance (ESL) of the capacitors in the commutation path restrict the damping of the switch node voltage overshoot and introduce high-frequency ringing, reducing the voltage margin of the transistor. Therefore, this paper analyzes the impact of the DC-bus impedance and proposes a DC-bus snubber based on an RC network to form the DC-bus impedance’s characteristic, which minimizes the overshoot voltage. A comprehensive simulation using measurement-derived component models is shown, which is verified by an in-situ measurement on a test PCB. Furthermore, transient measurements using a double pulse test setup show the effectiveness of the proposed approach
CM EMI Evaluation of Totem-Pole and HERIC Single-Phase PFC Converters
No full textThe totem-pole PFC stage is a commonly used and widely accepted topology in industry. With the newest emerging power semiconductor technologies, such as the M-BDS, different concepts like the HERIC PFC converter are becoming increasingly more attractive and provide numerous benefits. The presence of a bidirectional switch in the HERIC converter results in a symmetric structure and avoids a problem of the totem-pole topology, the unfolding. This leads to improved performance in terms of conducted common-mode emissions and to lower control complexity. This paper presents a detailed analysis of both topologies, examining and comparing their performance in terms of conducted electro-magnetic interferences. The influence of the design aspects of the magnetic components, i.e., the grid-side boost inductor, is considered, highlighting that the conducted emissions can be effectively mitigated by a proper balancing and coupling strategy. The measurement-based evaluation utilizes a hardware demonstrator that can be operated as HERIC or totem-pole-PFC stage and fully demonstrate the effectiveness of the proposed solution, with CM noise reductions of up to 30 dB
Verification of Envelope Tracking Concepts for High Frequency TCM/ZVS in Two-Level AC/DC Converter Applications
No full textTriangular current mode (TCM) enables the benefit of zero voltage switching, but it is accompanied by two significant functional limitations. Initially, it often requires expensive FPGA, ASIC, and/or specialized hardware-based sensing. Secondly, the time delays linked with such sensing and processing can lead to a trade-off between the achievable switching frequency and the precision of the triangular inductor current waveform. This paper delivers the experimental verification of an alternative method where the inductor current envelopes are measured using straightforward analog quasi-peak detectors. The sampling rate needed for these envelopes is in first approximation independent of the applied switching frequency. The control behavior is mainly unaffected by time and signal delays due to the low frequency envelope signals being used, allowing for an affordable standard DSP to implement the proposed method. Importantly, the same control loop can also facilitate continuous conduction mode (CCM) operation, whereby a normal CCM operation at constant switching frequency and a mode with variable switching frequency and constant ripple current can be featured. Using a standard two-level grid-tied inverter configuration as a case study, this paper shows a measurement based verification of the concept of the envelope tracking-based TCM (E-TCM) and CCM (E-CCM) method. A prototype is presented to demonstrate the behavior of an envelope tracking hardware solution, including a measurement-based evaluation of the proposed circuits in operation with a 0.5 kVA, two-level SiC-based converter. This converter, together with its envelope tracking circuit, is capable of operating in TCM at frequencies up to several hundred kHz and can dynamically transition to CCM during operation
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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