1,721,121 research outputs found
Design and fabrication of fiber optic sensors and systems for aerospace applications
Full text linkThe rapid evolution of fiber optic technology has revolutionized the field of communication
and sensing, enabling unprecedented levels of accuracy, miniaturization,
and scalability. This thesis describes the results obtained during my Ph.D.
activity and concerning the development of fiber optic sensors, optical fiber
components, and light sources tailored to advance the field of aerospace structure
monitoring. The work has required the exploration of the research forefront in
this field.
The first part of the thesis focuses on the design, fabrication, and characterization
of non-conventional fiber optic sensors. These sensors leverage Bragg
gratings to detect several physical parameters, including temperature, strain, and
bending, matching the stringent requirement of structural health monitoring of
Carbon Fiber Reinforced Polymers (CFRP). The findings have been obtained in
collaboration with the University of Southampton (Optoelectronic Research
Centre - ORC, UK) trying to give a contribution to the ongoing evolution of
aerospace sensor technologies.
Bragg gratings are wavelength-selective structures also employed for multiplexing
optical signals or for the construction of laser cavities. By considering
these aspects and the growing interest in Medium-Infrared (Mid-IR) spectral
range, the second part of the thesis delves into the design, fabrication, and characterization
of Mid-IR optical fiber components, based on soft glasses, operating
between 0.5 μm and 12 μm. Optical fiber combiners/couplers are essential elements
in communication and sensing systems that enable the splitting (or combining)
of optical signals into (from) a single optical fiber preserving beam quality.
The development of a custom manufacturing procedure for fluoride and chalcogenide
glasses, in collaboration with the company Le Verre Fluoré (Bruz,
France) made it possible, for the first time, to address the results described in the
doctoral thesis.
Moreover, Bragg gratings in combination with these optical fiber components
allow the development of all-in-fiber Mid-IR amplifiers, lasers, and wavelength
division multiplexing (WDM) systems. In particular, optical fiber lasers, operating in the Mid-IR spectral range, can be employed for material inspection
purposes to assess the integrity and quality of composite materials via Non-Destructive
Testing (NDT) techniques. Therefore, the design and optimization of
Mid-IR continuous wave (CW) lasers, are reported in the last part of the Ph.D.
research work.
Part of the obtained results have been published in International Journals and
in the Proceedings of National and International Conferences, as listed at the end
of the thesis
Precision Impedance Measurements by the Three-Voltage Method with a Novel High-Stability Multiphase DDS Generator
No full textAmplitude and frequency noise sensitivities of optical frequency discriminators based on Fabry-Perot interferometers and the FM technique
No full textClaimants in vascular surgery
No full textLitigation concerning medical activities is constantly increasing, as society becomes more and more “protective” of citizens who may have suffered any wrong due to malpractice. However, we should bear in mind that the percentage of claims liquidated is minimal.
Methods. From January 2009 to December 2011, 63 claims involving vascular procedures were analyzed. The rate of claimants receiving payment was very low: only 8 of the 63 (12.7%) claims having been settled. The most important thing we noted was that in 5 of the 8 claims settled the key element that defined the sentence was time: time to take a decision, to perform a diagnostic examination, to decide on a surgical procedure.
Results. We have sought to assess the role of the “time factor” in the occurrence of errors in a surgical specialty considered at high risk of litigation such as vascular surgery. This analysis of our experience over the past three years has shown that the central element in the genesis of the error was the erroneous timing of intervention. It interesting to note that, in contrast to what might be expected, time-related errors are much more common in cases treated electively than in urgent or emergency cases.
Conclusion. Our experience demonstrates that the “time factor” plays a primary role in the genesis of errors in vascular surgery. This delay in deciding and acting probably depends on the fact that the vascular surgeon was the patient’s first contact in only one of the cases examined. This should emphasize the need to equip all emergency departments with a Vascular Surgery Unit
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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