1,720,973 research outputs found
Modelli matematici per la taratura di trasformatori di corrente continua mediante multimetri numerali, derivatori e trasformatori di corrente
No full textI trasformatori di corrente per correnti in regime continuo (DCCT) sono tra i più diffusi sensori di forti correnti oggi commercialmente disponibili con ampia variabilità nell’accuratezza di misura, per cui è possibile utilizzare sistemi più o meno complessi ed accurati per effettuarne la taratura.
Nel presente rapporto tecnico vengono presentati alcuni modelli matematici di misura per sistemi di taratura in corrente continua “semplificati” che utilizzano come campioni di riferimento multimetri numerali (DMM), derivatori di corrente (shunt) o altri DCCT.Direct-current current transformers (DCCTs) are nowaday the most popular high current sensors commercially available with a wide variability of measurement acuracy, therefore it is possible using more o less complex and accurate systems to carry out their calibration.
In the present tecnical report some measurement mathematical models for “simplified” dc calibration systems are presented, which they use digital multimeters (DMMs), resistance shunts or other DCCTs as reference standards
Taratura di derivatori e resistori campioni nel campo da 1 μΩ a 1 mΩ, con correnti fino a 2000 A
No full textIl presente rapporto tecnico descrive nel dettaglio il sistema INRIM di trasferimento della riferibilità a campioni di resistenza elettrica, impiegati come derivatori di corrente, nel campo di valori da 1 μΩ a 1 mΩ con correnti sino a 2 kA.
Vengono anche riportate le migliori capacità di misura (CMC) dell’Istituto per questo tipo di tarature.This technical report describes in detail the INRIM transfer traceability system to electrical resistance standards, used as current shunts, in the range of values from 1 μΩ to 1 mΩ with currents up to 2 kA.
The best measurement capabilities (CMC) of the Institute for this type of calibration are also reported
Confronti di resistenza con il ponte a comparatore criogenico di correnti Magnicon
No full textL’avvenuta revisione del Sistema Internazionale di unità di misura (SI) permette, a partire da maggio 2019, la realizzazione pratica dell’unità di resistenza elettrica, l’ohm (Ω), direttamente dall’effetto Hall quantistico (Quantum Hall Effect, QHE), che ne diventa di fatto la mise en pratique.
Il presente rapporto tecnico illustra le misure di confronto, eseguite tra il 11 novembre al 3 dicembre 2020 nell’ambito della campagna di misura n° 128, finalizzate alla caratterizzazione del ponte a comparatore criogenico di correnti (Cryogenic Current Comparator, CCC) e alla miglior definizione del circuito di misura da realizzare per il trasferimento della riferibilità a partire dal QHE.The revision of the International System of Units (SI) allows, since May 2019, the practical realization of the electrical resistance unit, the ohm (Ω), directly from the Quantum Hall Effect (QHE), which effectively becomes its mise en pratique.
This technical report illustrates the comparison measurements, carried out between 11th November and 3rd December 2020 as a part of the measurement campaign n° 128, aimed to characterize the Cryogenic Current Comparator (CCC) bridge and to find the best definition of the measurement circuit to be implemented for the traceability transfer starting from the QHE
On the calibration of DC resistance ratio bridges
Full text linkCurrent comparator bridges are employed for the realization of the resistance scale from the quantum Hall effect in several National Metrology Institutes and calibration centers. Quantum resistance standards under development, based on novel materials and tabletop dry cryostats, make the more achievable DC current comparator bridges (DCCs) a viable alternative to the more accurate but more expensive cryogenic current comparator bridges (CCCs). A DCC ratios' calibration against a reference CCC is a straightforward way to improve the DCC's performances and the resistance scale overall accuracy.The paper reports the calibration results of two DCCs on the ratios employed in a 1 omega to 10 k omega resistance scale traceable to a 12.906 k omega quantized Hall resistance, showing a good reproducibility and stability of the DCC readings over the measurement period and supporting the possibility of a DCC errors' correction and of a realization of the primary resistance scale at the 10-8 level
Fabrication of Nanoscale SQUIDs Using Vertical Nb Nanoconstrictions
No full textThe measurement of ultra-weak magnetic fields with nanometer-scale spatial resolution is a powerful tool for investigating several biological, chemical and physical systems. Among the available detectors, SQUIDs are the most sensitive magnetic field and flux detectors and are rapidly approaching the quantum sensitivity limit. To reach such sensing capability, technological advances in the fabrication of nanoscale SQUIDs with submicrometric loops are needed. In this work we present a novel process for the fabrication of nanoscale SQUIDs, based on superconducting vertical Nb nanoconstrictions. The fabrication process uses laser lithography to define the device geometry, focused ion beam to mill the top surface of the Nb in a nanometer-sized region across the width of the film and anodization to define the final thickness of the nanoconstriction and at the same time to embed the ion-implanted amorphous layer produced by the FIB milling step. A preliminary electrical characterization of nano-sized single Josephson junctions and SQUIDs fabricated with this process is also reported
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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