1,721,019 research outputs found
Design, fabrication and characterization of electromagnetic resonators for medical and environmental applications
Get PDFIn this Ph.D. thesis, the feasibility investigation, design, and characterization of different resonant structures optimized to improve the performance of microwave devices for environmental monitoring and medical applications, such as cancer therapy, have been illustrated. In particular:
▪ A metamaterial lens based on a split ring resonator (SRR) has been designed to improve the focusing of an external applicator for superficial hyperthermia tumour therapy. A prototype has been fabricated by using the standard printed board circuits (PCB) technology and then characterized. The experimental results suggest that a metamaterial based on SRR is a potentially effective option for external microwave applicators in the field of dermatology [1].
▪ An interstitial microwave applicator has been investigated for deep-seated tumours, a coaxial antenna working in the Industrial, Scientific, and Medical (ISM) frequency band at f=2.45 GHz. Several simulations have been performed to explore various configurations, impedance matching techniques, and radiating sections. The insertion of a metamaterial lens based on Closed Loop Resonator (CLR) around the radiating section of the applicator has been numerically investigated for a further improvement of the performance. Two prototypes of mini-invasive needle applicators have been constructed and characterized [2-5].
▪ Metamaterial lenses have been designed to improve the radiation performance of an antipodal Vivaldi antenna for wideband applications. Prototypes have been fabricated and characterized. The experimental results are in good agreement with simulations. The metalens allows the increase of the maximum gain, preserving the antenna bandwidth, and a more symmetrical radiation pattern [6-9].
▪ A microwave sensor based on a substrate integrated waveguide (SIW) technology has been designed and characterized for the detection of water contamination in the fuel. A suitable radiating slot placed on the top of the SIW applicator allows the interaction between the microwave electromagnetic field and the fuel contaminated. The sensor is low-cost, low profile and ensures a good sensitivity for constant and real-time monitoring [10]. In addition, during the Ph.D. course, I have contributed to the following side research activities concerning optical electromagnetic field applications:
▪ The design, fabrication, and characterization of a 2×2 optical fiber coupler based on indium fluoride optical fibers [11]. In particular, I have contributed to the fabrication by means the glass processing system, Vytran® GPX2400, supplied by the “Electromagnetic Fields” laboratory led by Prof. Francesco Prudenzano, by developing preliminary silica glass samples and by searching the fabrication parameters used for obtaining fluoride glass combiners.
▪ The design of a gain-switched pulsed laser based on a commercial, heavily holmium-doped fluoroindate glass fiber, emitting in the middle-infrared range, at the wavelength λ = 3.92 μm [12]. In particular, I have contributed to run several cases and discuss the obtained results
Design and fabrication of mid-infrared devices for IoT applications
Get PDFThe advancement of photonics has transformed the fields of communication and sensing, allowing for outstanding improvements in transmission speed, accuracy, miniaturization, and scalability. This Ph.D. thesis reports the design and fabrication of Mid-InfraRed (Mid-IR) devices tailored for Internet of Things (IoT) applications, focusing on the use of optical fibers based on soft glasses. The research encompasses various optical components, including Bragg gratings inscribed on flat fibers and planar substrates, and optical fiber devices based on stretching and heating fabrication technique such as combiners, couplers, photonic lanterns, long period gratings (LPGs), non-adiabatic tapers, and S-tapers. Additionally, the modelling and design of a Praseodymium-doped laser is explored to enhance Mid-IR light generation.
The initial section of this thesis concentrates on the design, fabrication, and characterization of innovative Bragg gratings. These are wavelength-selective mirrors, essential for the construction of laser cavities. Moreover, they can be used as sensors exploiting the Bragg wavelength shift to measure various physical parameters, such as strain, curvature, and temperature. These results were achieved in collaboration with the University of Southampton (Optoelectronic Research Centre - ORC, UK) and the University of Bristol (School of Civil, Aerospace and Design Engineering, UK).
Considering the increasing interest in the Mid-IR spectral range, the second part of the thesis investigates the design, fabrication, and characterization of Mid-IR optical fiber components based on soft glasses, mainly operating within the wavelength range from λ=0.5 μm to λ=5.5 μm. Optical fiber combiners and couplers are key building blocks in communication and sensing systems, serving for spectral splitting/combining and the increasing of optical power. Photonic lanterns offer an efficient interface between multi-mode and single-mode waveguides, proving beneficial in astrophotonics where “every photon counts”. LPGs and tapers enable sensing capabilities in the Mid-IR, spectral range that allows to identify the typical bonds of many molecules. In collaboration with Le Verre Fluoré (Bruz, France), the development of a specialized manufacturing process for soft glasses permitted the fabrication and characterization of these devices.
Finally, Bragg gratings in combination with some of the developed building blocks allow the fabrication of all-in-fiber Mid-IR amplifiers, and lasers systems. In this context, optical fiber lasers, emitting in the Mid-IR wavelengths, can be employed for novel communication and sensing schemes. Therefore, the design and optimization of a Mid-IR continuous wave (CW) laser based on Praseodymium, is reported in the last part of the Ph.D. research work.
Some of the findings from this research have been published in International Journals and presented at National and International Conferences, as detailed in the list at the end of the thesis
5-GHz repetition-rate dual-wavelength pulse-train generation from an intracavity frequency-modulated Er-Yb:glass laser
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Measurement of the energy transfer and upconversion constants in Er-Yb-doped phosphate glass
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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
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