1,720,977 research outputs found
Power-efficient gate control of synchronous boost converters with high output voltage
No full textA half output voltage swing gate driving scheme is presented for high voltage single chip DC/DC converters. In the proposed scheme the energy for the PMOS gate drive is reused for the NMOS gate drive, and switching loss is reduced. A high speed and area-efficient high voltage level shifter is also realised. A prototype is implemented using a 0.5 mu m 40 V power BiCMOS process
Voltage-clamped class-E inverter with harmonic tuning, network for magnetron drive
No full textA passive lossless snubber utilizing harmonic resonance is proposed for the voltage-driven class-E inverter. This snubber reduces the peak resonant voltage stress across the switch in class-E operation by adding the third-order harmonic current into the fundamental resonant part and can be extended to a higher-order network for further reduction. Though the principle is actually equivalent to the class-F operation in RF power amplifiers, it is first tried for the class-E inverter without a current source inductor. A series of analyses is performed to find component values that provide the optimum harmonic condition, and the experimental results from the inverter power supply for driving a magnetron are presented
Detection and regulation of CCFL current and open-lamp voltage while keeping floating condition of the lamp
No full textA new simple balanced circuitry using four printed circuit board trace capacitors effectively detects the cold-cathode fluorescent lamp current and the transformer voltage of the inverter without grounding either side of the lamp. The inverter employing this circuit is free from the problems caused by grounding one side of the lamp, and it provides a stable and wide dimming control as well as an open-lamp voltage regulation with a better efficacy
A low-cost high-efficiency CCFL inverter with new capacitive sensing and control
No full textA new low-cost and efficient cold cathode fluorescent lamp (CCFL) inverter for liquid crystal display (LCD) application is suggested in this paper. The topology of the inverter is derived from modified class E-type resonant electronic ballasts and has a dc-like input current. In addition, a new sensing circuit for lamp current and transformer voltage is proposed. A simple RC-network measures the voltage of a ballasting capacitor in series with the lamp instead of the lamp current itself while the lamp is floated. Utilizing the printed circuit board capacitors for the sensing capacitors and integrating small-valued sensing resistors into a control integrated circuit make the inverter very simple, efficient, and cost-effective. The new sensing circuit can solve many problems that arise when a terminal of the lamp is grounded to sense the lamp current. The control circuits for the prototype experiments are also described in detail. The frequency control scheme with a fixed off-time and a varying on-time was chosen to maintain the operation of zero-voltage switching in the entire dimming range and to reduce the complexity of the control circuits. The control circuits have an analog dimming function using a current control loop, a low frequency pulsewidth modulation dimming, open-lamp protection and voltage regulation, and soft-on/off functions
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
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