1,720,957 research outputs found
Low power, MEMS liquid flow sensor with silicone coating electrical insulation
No full textA flow sensor based on a differential microcalorimeter integrated onto a silicon chip is presented. A tunable readout interface, capable of compensating for the sensor offset and offset drift, is integrated on the same chip as the sensing structures. The liquid flow is conveyed to the sensing structure by means of a proper package provided of micro-channels. A simple technique is used to deposit a silicone film onto the flow channel walls, including the chip surface exposed to the liquid. In this way electrical insulation between the sensing chip and the liquid flow is obtained. Results of test performed in deionized water flow are presented
Low voltage acoustic particle velocity sensor with integrated low noise chopper pre-amplifier
Get PDFNovel acoustic particle velocity (APV) sensors suitable for low voltage, battery-powered systems are proposed. The sensing structure consists of four silicide polysilicon wires placed over suspended dielectric membranes and arranged in a Wheatstone full-bridge configuration. The device has been fabricated combining a commercial CMOS process with a simple and low cost post-processing technique. An ultra low noise chopper pre-amplifier has been integrated on the same chip. Preliminary noise and acoustic characterization is presented
Characterization and modeling of CMOS-compatible acoustical particle velocity sensors for applications requiring low supply voltages
Get PDFAcoustic particle velocity sensors have been obtained applying simple low resolution micromachining steps to chips fabricated using a standard microelectronic process. Each sensor consists of four silicided polysilicon wires, suspended over cavities etched into the substrate, and connected to form a heatstone bridge. Full compatibility of the micromachining procedure with the original process is demonstrated by integrating a simple pre-amplifier on the same chip as the sensors and showing that both blocks are functional. Proper design of the sensing structures allows them to operate with a single 3.3 V power supply. Sensitivity and noise measurements, performed to estimate the sensor detection limit, are described. Excess noise with a flicker-like behavior, not ascribable to the amplifier, is found when the bridges are biased in working conditions. In addition, the dependence of the sensitivity on the dc bias voltage of the bridges is investigated, comparing the experimental data with the results of a simple analytical model and finite element method simulations
An integrated thermal flow sensor for liquids based on a novel technique for electrical insulation
No full textA novel method to electrically insulate integrated thermal flow sensors from liquids is proposed. The sensor is fabricated with a post-processing technique applied to chips designed with a commercial CMOS process. A low cost packaging technique is used to convey the liquid to the sensing structures. After packaging, a simple technique is used to coat the flow channel and the chip area exposed to the fluid with silicone. Preliminary tests in water confirm the effectiveness of the proposed method
Isolation and electrical characterization of a multi-walled carbon nanotube
No full textCarbon nanotubes (CNTs) are currently the focus of intense interdisciplinary
research activity, because they display remarkable physical and chemical properties
and because of their prospects for novel technologies. The experimental
motivation of this thesis are recent results on individual single-walled carbon nanotubes
(SWCNTs) and multi-walled carbon nanotubes (MWCNTs), due to
the necessity of their physical characterization before any potential application,
which spans a wide range, from mechanical to electrical and thermal ones.
We introduce the basic concepts and theoretical expectations for the electrical
transport properties of CNTs. In particular, we review the electronic properties
of graphene, SWCNTs and MWCNTs first, and then the electrical transport
properties of nanotubes in zero magnetic field at room temperature. Finally, we
present our local and non-local electrical transport measurements on an individual
MWCNT performed in zero magnetic field at room temperature, since our
goal is to characterize individual pristine MWCNTs. Experimentally MWCNTs
are found to be either conducting or non-conducting and currently there are no
production or separation methods that can yield bulk quantities (milligram or
larger) of metallic nanotubes. As a result, we aim at determining whether our
MWCNT is conducting or non-conducting, that is, metallic or insulator.
For the purposes of physical characterization, we have previously aimed at
developing an original and creative method for separation first and then isolation of a pristine MWCNT, because pristine nanotubes are packed together in bundles
due to strong van der Waals attraction. Few solvents disperse pristine CNTs,
but one point of concern with them is that they may influence substantially the
physical properties of the nanomaterial and induce unwanted chemical reactions
such as protonation and oxidation. So, we have striven to study a non-destructive
process that avoids damages to tube walls or tips and preserves the
integrity of nanotubes, even during atomic force microscope (AFM) and focused
ion beam (FIB) imaging of the collected samples. Moreover, we have striven to
establish Ohmic contacts to these individual, clean and undamaged MWCNTs
by means of FIB deposition onto metal electrodes of a silicon device, since, when
the contact is not good, non-linear current-voltage (I-V) curves are obtained,
even though the contacted nanotube is metallic. These are key issues from
a physical standpoint, as we then focus our efforts on investigating the intrinsic
properties of MWCNTs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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