The First AGILE Solar Flare Catalog

We report the Astrorivelatore Gamma ad Immagini LEggero (AGILE) observations of solar flares, detected by the on board anticoincidence system in the 80-200 keV energy range, from 2007 May 1st to 2022 August 31st. In more than 15 yr, AGILE detected 5003 X-ray, minute-lasting transients, compatible with a solar origin. A cross-correlation of these transients with the Geostationary Operational Environmental Satellites (GOES) official solar flare database allowed to associate an intensity class (i.e., B, C, M, or X) to 3572 of them, for which we investigated the main temporal and intensity parameters. The AGILE data clearly revealed the solar activity covering the last stages of the 23rd cycle, the whole 24th cycle, and the beginning of the current 25th cycle. In order to compare our results with other space missions operating in the high-energy range, we also analyzed the public lists of solar flares reported by RHESSI and Fermi Gamma-ray Burst Monitor. This catalog reports 1424 events not contained in the GOES official dataset, which, after statistical comparisons, are compatible with low-intensity, short-duration solar flares. Besides providing a further dataset of solar flares detected in the hard X-ray range, this study allowed to point out two main features: a longer persistence of the decay phase in the high-energy regime, with respect to the soft X-rays, and a tendency of the flare maximum to be reached earlier in the soft X-rays with respect to the hard X-rays. Both these aspects support a two-phase acceleration mechanism of electrons in the solar atmosphere.Comment: 22 pages, 10 figure

The design and validation of the R1 personal humanoid

In recent years the robotics field has witnessed an interesting new trend. Several companies started the production of service robots whose aim is to cooperate with humans. The robots developed so far are either rather expensive or unsuitable for manipulation tasks. This article presents the result of a project which wishes to demonstrate the feasibility of an affordable humanoid robot. R1 is able to navigate, and interact with the environment (grasping and carrying objects, operating switches, opening doors etc). The robot is also equipped with a speaker, microphones and it mounts a display in the head to support interaction using natural channels like speech or (simulated) eye movements. The final cost of the robot is expected to range around that of a family car, possibly, when produced in large quantities, even significantly lower. This goal was tackled along three synergistic directions: use of polymeric materials, light-weight design and implementation of novel actuation solutions. These lines, as well as the robot with its main features, are described hereafter

An X-ray burst from a magnetar enlightening the mechanism of fast radio bursts

Fast radio bursts (FRBs) are millisecond radio pulses originating from powerful enigmatic sources at extragalactic distances. Neutron stars with large magnetic fields (magnetars) have been considered as the sources powering the FRBs, but the connection requires further substantiation. Here we report the detection by the AGILE satellite on 28 April 2020 of an X-ray burst in temporal coincidence with a bright FRB-like radio burst from the Galactic magnetar SGR 1935+2154. The burst observed in the hard X-ray band (18-60 keV) lasted about 0.5 s, it is spectrally cut off above 80 keV and implies an isotropically emitted energy of about 1040 erg. This event demonstrates that a magnetar can produce X-ray bursts in coincidence with FRB-like radio bursts. It also suggests that FRBs associated with magnetars can emit X-ray bursts. We discuss SGR 1935+2154 in the context of FRBs with low-intermediate radio energies in the range 1038-1040 erg. Magnetars with magnetic fields B ≈ 1015 G may power these FRBs, and new data on the search for X-ray emission from FRBs are presented. We constrain the bursting X-ray energy of the nearby FRB 180916 to be less than 1046 erg, smaller than that observed in giant flares from Galactic magnetars

Effect of the fiber orientation on the tensile and flexural behavior of continuous carbon fiber composites made via fused filament fabrication

Recent years have seen the wide diffusion of composite materials in many manufacturing fields and the rapid evolution of additive manufacturing. Lately, these technologies have been combined practically allowing the fabrication of continuous-fiber reinforced polymer parts via 3D-printing. This topic is gaining attention both in the research community and among industrial users. Because of their novelty, such manufacturing methods are, however, still not thoroughly understood, and their performance limits have not yet been fully characterized. This study aims at analyzing the mechanical resistance of components made with continuous carbon fiber (CCF) thermoplastic materials by means of fused filament fabrication (FFF), focusing on the influence of the fiber orientation on such properties. In particular, both the tensile and the bending characteristics are evaluated according to the relative test standards, in specimens with both unidirectional and mixed-isotropic configurations. The experimental findings are compared with a set of reference specimens made with a base polymer filled with chopped \u201cshort\u201d carbon fibers, allowing one to appreciate the advantages or limitations of the different fiber arrangements

Adhesive bonding of 3D-printed short- and continuous-carbon-fiber composites: An experimental analysis of design methods to improve joint strength

This experimental work focuses on the effect of various joint-design factors on the adhesive bonding of mixed short-(Onyx) and continuous-carbon-fiber reinforced Nylon-6 parts, 3D-printed via Fused Filament Fabrication technology. A low-pressure plasma treatment has been preliminarily performed to maximize the adhesion at the composite's surface-adhesive interface. This approach has allowed the definition of a performance benchmark beyond which the intrinsic non-homogeneity of the composite determines joint failures due to delamination of substrates. Starting from this condition, adhesive-bonding parameters such as adherend overlap length (12.5, 25, or 50 mm) and geometry, adhesive type (epoxy or polyurethane), and substrate configuration are considered, investigating their influence on both the mechanical behavior of single-lap joints and modality of crack propagation across the bonded laminates. Supported by failure analysis, the experimental findings highlight that higher load levels (up to +251.4%) can be achieved by increasing the joint stiffness using higher values of overlap length thanks to lower peel stresses at the adherend ends where material discontinuities are mainly concentrated. Alternatively, joining of continuous-fiber-only adherends is considered to provide a further high-performing approach that involves the exclusion of the Onyx shell from the areas designed to be bonded. Moreover, heterogeneous joining between additively-manufactured composites and conventional carbon-fiber-reinforced-polymer materials is also investigated, providing pivotal insights about the applicability of 3D-printed composites also in pre-existing composite structures

A Systematic Approach to Evaluating and Benchmarking Robotic Hands—The FFP Index

The evaluation of robotic hands is a subjectively biased, complex process. The fields pertaining to robotic hands are human-centric in nature, making human hands a good standard for benchmark comparisons of robotic hands. To achieve this, we propose a new evaluation index, where we evaluate robotic hands on three fronts: their form, features and performance. An evaluation on how anthropomorphic robotic hands are in basic mobility, and appearance constitutes the “Form„, while features that can be read, changed and actuated for effective control of robotic hands constitutes the “Features„. We derived these key features from an extensive analysis of robotic hands in literature. Finally, the robotic hands carry out a series of tasks that evaluate their “Performance„. An individual score for each category is drawn and we carry out a three-pronged analysis. We also propose an additional feature in the form of price to provide context when analysing multiple hands

Setup prototype for safe interaction between a humanoid robot (iCub) and children with autism-spectrum condition

Socially-assistive robotics has the potential to become powerful assistance to healthcare professionals working with neurodevelopmental disorders (NDDs). A growing body of literature suggests that robot-mediated and robot-assisted activities might be beneficial for children with a neuro-developmental disorder. The robot could represent, for individuals with neurodevelopmental disorders, a safe and predictable environment in which they can practice simplified versions of social interaction. Here, we propose a solution to test the efficacy of robot-assisted training activity aimed at improving social skills in children with autism spectrum conditions (ASC)

Design and Validation of a Talking Face for the iCub

International audienceRecent developments in human–robot interaction show how the ability to communicate with people in a natural way is of great importance for artificial agents. The implementation of facial expressions has been found to significantly increase the interaction capabilities of humanoid robots. For speech, displaying a correct articulation with sound is mandatory to avoid audiovisual illusions like the McGurk effect (leading to comprehension errors) as well as to enhance the intelligibility in noisy conditions. This work describes the design, construction and testing of an animatronic talking face developed for the iCub robot. This talking head has an articulated jaw and four independent lip movements actuated by five motors. It is covered by a specially designed elastic tissue cover whose hemlines at the lips are attached to the motors via connecting linkages. The mechanical design and the control scheme have been evaluated by speech intelligibility in noise (SPIN) perceptual tests that demonstrate an absolute 10% intelligibility gain provided by the jaw and lip movements over the audio-only display

An articulated talking face for the iCub

International audienceRecent developments in human-robot interaction show how the ability to communicate with people in a natural way is of great importance for artificial agents. The implementation of facial expressions has been found to significantly increase the interaction capabilities of humanoid robots. For speech, displaying a correct articulation with sound is mandatory to avoid audiovisual illusions like the McGurk effect (leading to comprehension errors) as well as to enhance the intelligibility in noise. This work describes the design, construction and testing of an animatronic talking face developed for the iCub robot. This talking head has an articulated jaw and four independent lip movements actuated by five motors. It is covered by a specially designed elastic tissue cover whose hemlines at the lips are attached to the motors via connecting linkages

From science to technology: Orientation and mobility in blind children and adults

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