216 research outputs found
Array Antenna Power Pattern Analysis Through Quantum Computing
A method for the analysis of the power pattern of phased array antennas (PAs)
based on the quantum Fourier transform (QFT) is proposed. The computation of
the power pattern given the set of complex excitations of the PA elements is
addressed within the quantum computing (QC) framework by means of a customized
procedure that exploits the quantum mechanics principles and theory. A
representative set of numerical results, yielded with a quantum computer
emulator, is reported and discussed to assess the reliability of the proposed
method by pointing out its features in comparison with the classical approach
based on the discrete Fourier transform (DFT), as well.Comment: 35 pages, 12 figure
SOCIAL REPORTING PRACTICES IN ITALIAN PUBLIC SECTOR: AN EXPLORATORY STUDY
This paper should be seen in the broad research field that analyses the impact of ICTs on public accountability reports with the objective of understanding whether the institutional websites of public administrations are qualifying and privileged carriers for social reporting and which models they use to draw up their documents. Our analysis refers to the public entities of the Italian regional capital cities that provide the highest number of services for their local communities: municipalities and hospitals. Our research assumption is that, for larger-sized public entities, websites should be the main channel used to meet the accountability expectations of stakeholders, and therefore they are the place where the highest degree of sensitivity to reporting should be observed. The empirical analysis revealed that the approaches to social reporting differ significantly in terms of formal structure, content and communication strength. The analysis seems to suggest that the awareness of the importance of social reporting is still rather scarce, occasional and, in many cases, detached from the criteria set for public accountability processe
Local Search, Semantics, and Genetic Programming:a Global Analysis
Geometric Semantic Geometric Programming (GSGP) is one of the most prominent Genetic Programming (GP) variants, thanks to its solid theoretical background, the excellent performance achieved, and the execution time significantly smaller than standard syntax-based GP. In recent years, a new mutation operator, Geometric Semantic Mutation with Local Search (GSM-LS), has been proposed to include a local search step in the mutation process based on the idea that performing a linear regression during the mutation can allow for a faster convergence to good-quality solutions. While GSM-LS helps the convergence of the evolutionary search, it is prone to overfitting. Thus, it was suggested to use GSM-LS only for a limited number of generations and, subsequently, to switch back to standard geometric semantic mutation. A more recently defined variant of GSGP (called GSGP-reg) also includes a local search step but shares similar strengths and weaknesses with GSM-LS. Here we explore multiple possibilities to limit the overfitting of GSM-LS and GSGP-reg, ranging from adaptive methods to estimate the risk of overfitting at each mutation to a simple regularized regression. The results show that the method used to limit overfitting is not that important: providing that a technique to control overfitting is used, it is possible to consistently outperform standard GSGP on both training and unseen data. The obtained results allow practitioners to better understand the role of local search in GSGP and demonstrate that simple regularization strategies are effective in controlling overfitting
A Self-Replicating Single-Shape Tiling Technique for the Design of Highly Modular Planar Phased Arrays -- The Case of L-Shaped Rep-Tiles
The design of irregular planar phased arrays (PAs) characterized by a
highly-modular architecture is addressed. By exploiting the property of
self-replicating tile shapes, also known as rep-tiles, the arising array
layouts consist of tiles having different sizes, but equal shape, all being
generated by assembling a finite number of smaller and congruent copies of a
single elementary building-block. Towards this end, a deterministic
optimization strategy is used so that the arising rep-tile arrangement of the
planar PA is an optimal trade-off between complexity, costs, and fitting of
user-defined requirements on the radiated power pattern, while guaranteeing the
complete overlay of the array aperture. As a representative instance, such a
synthesis method is applied to tile rectangular apertures with L-shaped tromino
tiles. A set of representative results, concerned with ideal and real antenna
models, as well, is reported for validation purposes, but also to point out the
possibility/effectiveness of the proposed approach, unlike state-of-the-art
tiling techniques, to reliably handle large-size array apertures.Comment: 56 pages, 22 figure
Relating Implicit Bias and Adversarial Attacks through Intrinsic Dimension
Despite their impressive performance in classification, neural networks are
known to be vulnerable to adversarial attacks. These attacks are small
perturbations of the input data designed to fool the model. Naturally, a
question arises regarding the potential connection between the architecture,
settings, or properties of the model and the nature of the attack. In this
work, we aim to shed light on this problem by focusing on the implicit bias of
the neural network, which refers to its inherent inclination to favor specific
patterns or outcomes. Specifically, we investigate one aspect of the implicit
bias, which involves the essential Fourier frequencies required for accurate
image classification. We conduct tests to assess the statistical relationship
between these frequencies and those necessary for a successful attack. To delve
into this relationship, we propose a new method that can uncover non-linear
correlations between sets of coordinates, which, in our case, are the
aforementioned frequencies. By exploiting the entanglement between intrinsic
dimension and correlation, we provide empirical evidence that the network bias
in Fourier space and the target frequencies of adversarial attacks are closely
tied
Phenomenology of a Fake Inert Doublet Model
We introduce a new way of modeling the physics beyond the Standard Model by
considering fake, strictly off-shell degrees of freedom: the fakeons. To
demonstrate the approach and exemplify its reach, we re-analyze the
phenomenology of the Inert Doublet Model under the assumption that the second
doublet is a fakeon. Remarkably, the fake doublet avoids the most stringent
-pole constraints regardless of the chosen mass scale, thereby allowing for
the presence of new effects well below the electroweak scale. Furthermore, the
absence of on-shell propagation prevents fakeons from inducing missing energy
signatures in collider experiments. The distinguishing features of the model
appear at the loop level, where fakeons modify the Higgs boson
decay width and the Higgs trilinear coupling. The running of
Standard Model parameters proceeds as in the usual Inert Doublet Model case.
Therefore, the fake doublet can also ensure the stability of the Standard Model
vacuum. Our work shows that fakeons are a valid alternative to the usual tools
of particle physics model building, with the potential to shape a new paradigm,
where the significance of the existing experimental constraints towards new
physics must necessarily be reconsidered.Comment: 12 pages, 7 figures, version accepted by JHE
The 2012 Ferrara seismic sequence: from a 1D reliable crustal structure for moment tensor solutions to strong implications for seismic hazard
On May 20 2012, an event of Ml 5.9 (Mw 5.6) stuck the southem edge of the Po river plain (Pianura Padana). The earthquake was preceded by a foreshock of Ml 4.1 (Mw 3.8), less than 3 hours before the Mw 5.6 main. Hypocentral depths were 6.3 km for both events. Centroid depths were 5 and 6 km, respectively. The activated fault was a reverse one, dipping to the south. Then a complex seismic sequence started, in which more than six earthquakes with Ml greater than 5 stuck the area, the last one on June 3, 2012. Aftershocks delineated a 50 km long and 10-15 km wide zone, approximately elongated in the WE direction. More than 2100 events were located between May 19 and June 25 2012 by the INGV National Seismic Network, 80 of them with Ml greater than 3.5. The damage due to the Ml 5+ earthquakes was widespread, as they severely hit historical towns and industrial infrastructures. However, a striking inconsistency exists between the relatively small moment magnitudes and the corrisponding high level of damage. In order to define a velocity structure for the crust beneath the Pianura Padana, to be used for waveform inversion of moment tensors, we gathered all the geophysical and geological information available for the area. The model is characterized by very thick and shallow Quaternary sediments, to be used for the inversion of broadband waveforms for moment tensor (MT) solutions, in the frequency band between 0.02-0.1 Hz. We calculated moment tensors for 20 events down to Mw~3.2. We demonstrate how surface waves dominate the seismograms in the region, which may have played a major role in enhancing the damage to industrial structures observed in the epicentral area. Synthetic seismograms computed using the developed model well reproduced the anomalous durations of the ground motion observed in Pianura Padana, also highlighting important implications for the seismic hazard in the entire area. The present seismic hazard assessment as well as the size of the historical earthquakes in the region (and so their recurrence times), may need to be re-evaluated in the light of this new results
SEISMIC SWARM vs MAINSHOCK‐AFTERSHOCKS SEQUENCE: REFINED HYPOCENTERS LOCATIONS AT THE APENNINES‐CALABRIAN ARC BOUNDARY (SOUTHERN ITALY)
In the last years the Apennines-Calabrian arc boundary has been affected by intense seismicity
concentrated in the Pollino mountain region. The Pollino is located at the northernmost edge of the
Calabrian Arc, the last remnant of subduction along the Africa- Eurasian boundary. The area is subject
to Northeast- Southwest extension, which results in a complex system of normal faults striking
Northwest-Southeast, nearly parallel to the Apenninic mountain range. The Italian Seismic Network
between 2010 and 2014 detected more than 5500 earthquakes in the area (Italian Seismological
Instrumental and Parametric Data- Base; http:// iside .rm .ingv .it). In 2010 and 2011 the earthquake
rate has been variable, with increasing and decreasing phases and maximum magnitudes below M=4.
On May 28th 2012, a shallow event with local magnitude of 4.3 struck, about 5 kilometers east of the
previous swarm. The seismic activity remained concentrated in the M=4.3 source region until early
August. At that time seismicity jumped back westward to the previous area, with several earthquakes
of magnitude larger than 3, culminating with a M=5.0 earthquake on 25 October 2012. The seismic
rate remained high for some months, but aftershock magnitudes did not exceed magnitude 3.7. The
seismic rate then suddenly decreased at the beginning of 2013 and stayed quite low for the rest of the
year up to the beginning of 2014. During these years several temporary seismic stations were
deployed in the area, improving the detecting threshold of the Italian Seismic Network and giving us
the opportunity to refine the location of the earthquakes hypocenters. A combined dataset, including
three-component seismic waveforms recorded by both permanent and temporary stations, has been
analyzed in order to obtain an appropriate 1-D and 3D velocity model for earthquake location in the study area. Here we describe the main seismological characteristics of this seismic sequence and,
relying on refined earthquakes location, we make inferences on the geometry of the fault system
responsible for the two strongest shocks. Swarm activity seems to occur on a diffuse crustal volume
more than on fault planes. To yield a better understanding of the origin of the ongoing seismic activity
in the Pollino area, using thousand of seismograms, we analyze vp and vp/vs models and anisotropic
parameters in the crust. The main goal of this study is to increase the understanding of the physical
mechanisms behind the seismic swarm and its influence on the seismic hazard of the Apennines-
Calabrian arc boundary region.EAEE - ESCPublishedIstanbul - August 24-29 20142T. Tettonica attivaope
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