1,721,121 research outputs found
Decoupled Threaded Architecture
No full textDecoupled Threaded Architecture (DTA) is designed to exploit Thread Level Parallelism (TLP) by using a sea of simple cores grouped into cluster for providing a scalable solution that copes with wire delay. Our goals are i) to provide an aggressive mechanisms for decoupling memory accesses deriving from simple and complex data structures; ii) to implement a non-blocking execution of the threads. Here we illustrate some of the concepts related to our research in implementing DTA
Introducing hardware TLP support for the Cell processor
No full textThe focus of our study is the support for fine/medium grained thread level parallelism (TLP) by using a hardware scheduling unit and relying on existing simple cores. Simple cores are grouped into clusters in order to provide a scalable solution. As a proof of concept, we use an implementation based on the cell broadband engine (CBE). Cell is a multiprocessor on a chip developed by Sony, Toshiba and IBM that contains one general purpose core and eight coprocessor elements that accelerate the multimedia and vector processing. The aim of this paper is to present a possible implementation of DTA (decoupled threaded architecture) that is based on the cell processor, while keeping the scalability of the original DTA
Linearization of a 500-W L-band GaN Doherty Power Amplifier by Dual-Pulse Trap Characterization
No full textThis paper describes the linearization of a base-station L-band 500-W GaN Doherty high power amplifier (HPA) driven by OFDM signals. Pre-pulsing characterization is used to extract the gain dispersion of the carrier and peaking PAs due to trap-induced degradation of GaN-on-SiC transistors. Peak drain voltages reached by PA load-lines mainly set the trap states of the carrier and peaking PAs, while the recovery is longer with a dominant time constant of 100μs for this specific GaN technology. When the peak occurrences are below this dominant time constant of 100μs, such as for symbol periods of 16.7 to 66.7μs (i.e., LTE/5G OFDM), the HPA trap-state remains approximately constant in the time interval between voltage peaks, allowing low-complexity linearization of the HPA. With a 10-MHz OFDM signal with peak-to-peak intervals shorter than 100μs, a memory-less digital pre-distortion (DPD) is shown to improve ACLR by 4dB and NRMSE by 1.6 percentage points, as compared to peak-to-peak intervals longer than 100μs when significant trap recovery takes plac
Single-DC-Input Multi-Level Envelope Tracking of a High-Efficiency X-band Power Amplifier
No full textThis paper addresses the efficiency enhancement of microwave power amplifiers (PAs) with discrete-level supply-modulation. We demonstrate an efficient modulator architecture that generates three levels of drain supply voltages from a single dc voltage. Each level is stored in a "flying" capacitor that acts as a temporary voltage supply and is dynamically regulated by feedback through reversal of the PA drain current. A hybrid modulator based on GaN-on-Si technology is tested with a single-stage 2-W X-band MMIC PA with a drain efficiency of 55% at the peak output power. The overall average drain efficiency (PA and modulator) of up to 43% is measured with Gaussian-like pulses for radar and a 5-MHz 6-dB PAPR OFDM signal, and is improved up to 14 percentage points over a constant supply case, with normalized root mean square error below 1.5% when pre-distortion is used
Isotrap Pulsed IV Characterization of GaN HEMTs for PA Design
No full textA pulsed characterization of gallium nitride (GaN) high-electron mobility transistors (HEMTs) under a controlled trap and thermal state is performed to evaluate the trapping-induced degradation in the actual operating conditions, corresponding to different classes of power amplifiers (PAs). Two state-of-the-art GaN-on-SiC technologies are evaluated: 0.15-μm Qorvo and 0.25-μm Wolfspeed HEMTs, with examples relative to class-AB, class-E, and supply modulated operation. It is shown that, in order to get an accurate device characterization, the measurements have to be performed by preconditioning the trap state consistently with the intended application
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
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