1,721,255 research outputs found
Confinement loss and nonlinearity analysis of air-guiding modified honeycomb photonic bandgap fibers
No full textAir-guiding photonic bandgap fibers based on a modified honeycomb lattice have been numerically investigated through the finite element method. Results confirm that an extra hole in the unit cell of a honeycomb lattice can be exploited to enlarge the photonic bandgap, allowing air-guiding with confinement losses lower than 0.1 dB/km and nonlinear coefficient lower than 3.5 (.) 10(-3) (W (.) km)(-1) at 1.55 um
The figure and work of Riccardo felici
No full textRiccardo Felici (1819-1902) was Professor of Experimental Physics at the University of Pisa from
1859 to 1893. However, his main scientific contributions go back to the Fifties of the XIX century,
when he studied the electromagnetic induction phenomena both from an experimental and a
theoretical point of view. His formulation was very rigorous, probably the best of his time, and it
was quite appreciated also by J.C. Maxwell. His school of physics was the most important and
influential in Italy for the best part of the XIX century, and he gave also a substantial contribution to
the formation of the Italian Physics community, especially through his direction of the journal Il
Nuovo Cimento and his participation in founding the Italian Physics Society
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
Study of Raman amplification properties in triangular photonic crystal fibers
No full textIn this paper, the Raman properties of triangular photonic crystal fibers (PCFs) are analyzed in order to design a fiber for Raman amplification with enhanced performances. By casting the Raman intensity propagation equations, the Raman effective area and the Raman gain coefficient are introduced-two meaningful parameters that take into account the overlap between the pump and signal profiles. The behavior of these two parameters is examined in silica PCFs as a function of the geometrical characteristics of the triangular lattice. The numerical results show that a proper design of the hole diameter and the spacing between air holes can minimize the Raman effective area and maximize the Raman gain coefficient. The paper then focuses on the PCFs with germania-doped core. It is found that, for a given PCF cross section and dimension of the doped region, the Raman gain coefficient increases linearly with the germania concentration. Moreover, by enlarging the doped region, it is discovered that a PCF with a germania-doped area internally tangent to the first ring of air holes has a maximum Raman gain coefficient. Finally, the calculated values of the Raman gain coefficient are compared with those of other highly nonlinear fibers presented in literature, showing that a well-designed triangular PCF can significatively improve the Raman gain performances
Raman Amplification Properties of Silica and Tellurite Photonic Crystal Fibers
No full textRaman properties of silica and tellurite photonic crystal fibers are investigated and compared. A significant increase in Raman gain coefficient is possible by tailoring the triangular lattice holes
Harmonic tuning for Ku band dielectric resonator antennas
No full textThe design of a rectangular dielectric resonator antenna
(DRA) operating in the Ku frequency band is addressed in
this letter. Since the DRA has to be used as the radiating element
of a transmitting array of active integrated antennas, its input
impedance must exhibit a proper resistive load at the fundamental
resonance frequency, as well as a dominant reactive behavior,
either inductive or capacitive, at higher harmonics. Then, the configuration
here proposed is a slot-coupled DRA where harmonic
tuning is performed by resorting to the introduction of a couple
of additional slots parallel to the conventional main coupling slot.
The modified DRA is characterized by the same complexity level
as the nontunable counterpart. Samples of simulation results are
shown to demonstrate the capabilities of the proposed slot-based
harmonic tuning technique for rectangular DRAs
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