1,720,964 research outputs found
Can LSE Reduce Noise in Sensing Applications?
No full textThis work reports an experimental investigation of Large Scale Excitation (LSE) in sensing applications. This technique aims at mitigating flicker noise by suppressing its originating, signal-dependent, phenomena. Differently from modulation/chopping, which is not effective in these situations (flicker noise is modulated just as the signal is), LSE aims at switching on/off the source of signal generation without leaving enough time for carrier trapping or mobility changing, so blocking random telegraph noise phenomena which build up 1/f noise. As 1/f noise appears both in transistors and thin-film resistors, which are both key elements in the front-end of various sensors types, this work, after providing a simplified model for the scenario, experimentally verifies LSE. Results confirm the possibility of consistent flicker noise reduction in MOS transistors, by as much as a factor 3.3, whereas no flicker noise reduction is observed on piezoresistors, hinting that the source of 1/f is here a different process
State-Space Modeling of a Novel 2-output, single-L Driver for PZT Actuators with Charge Recovery
No full textThe growing need for larger transduction forces to be applied by piezoelectric actuators leads to the increase of their footprint, capacitance and voltage level. This is in trade-off with low power dissipation needs, and thus new driving circuits shall be conceived. In this work a novel architecture based on a two-output, single-inductor, DC-AC converter is presented, which exploits a charge-recovery technique. It is of utmost importance to derive a linear time-invariant (LTI) model for such a switching circuit, so that a target driving waveform can be obtained on the piezoelectric actuators, depending on the duty cycle applied to the circuit switches. A state-space averaging technique and linearization is used to extract the LTI model of the proposed driver. The so computed equations are then exploited to predict the required duty cycles to generate, as a real-case scenario, a 56-V, 120-Hz sawtooth signal, typically used to drive MEMS micromirrors. The entire circuit model is finally validated by an open-loop behavioral simulation, showing a relative error deviation between the target and the obtained voltage waveforms smaller than 2.7%, with zero power dissipation in the assumption of ideal switches
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
Nested Closed-loop Control of Quasi-Static MEMS Scanners with Large Dynamic Range
Full text linkThis article discusses the challenges in implementing a fully electrical closed-loop control system for high-end applications of quasi-static microscanners, accounting at the same time for wide aperture, high accuracy, and wide bandwidth. The discussion highlights how not only the ringing of the main mode but also the presence of spurious modes and nonlinearity impacts the closed-loop stability and accuracy. A novel control approach based on nested loops is conceived and implemented in the digital domain in a mixed-signal application-specific integrated circuit (ASIC). The developed versatile ASIC is designed to be coupled to different types of micromirrors, with fundamental frequency ranging from few hundred hertz to few kilohertz, by simply adjusting coefficients in the digital domain. The ASIC is here successfully operated with two micromirrors, and results demonstrate sawtooth position control at 28-32 degrees field of view and up to 120-Hz refresh rate, while holding at the same time a tilt angle resolution of 25 m degrees rms (dynamic range of 60 dB) and a linearity error below +/- 1%
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
Efficient Phase and Quadrature Control of a PZT Resonant MEMS Microscanner with Piezoresistive Position Sensor
No full textThis work discloses a closed-loop driving architecture for piezoelectric resonant micromirrors with piezoresistive position sensing, applied to a novel mirror design. The circuit topology is based on two digital negative feedback loops to control the mirror actuation phase and oscillation amplitude. The system design is specifically conceived to handle spurious actuator resonances coupling to the embedded position sensor, which otherwise may cause loop instability in conventional feedback-based oscillators. Additionally, the system ensures operation on the peak of the actuator transfer function, maximizing the efficiency and minimizing actuation voltages. Experimental results show how the proposed approach enables start-up oscillation without locking to any spurious resonant mode. For field-of-view up to 60 degrees, the oscillating frequency is stable within 0.1 ppm and the amplitude within 0.4%, at voltages <30 V
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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