Spacecraft dynamics under the action of Y-dot magnetic control law

The paper investigates the dynamic behavior of a spacecraft when a single magnetic torque-rod is used for achieving a pure spin condition by means of the so-called Y-dot control law. Global asymptotic convergence to a pure spin condition is proven on analytical grounds when the dipole moment is proportional to the rate of variation of the component of the magnetic field along the desired spin axis. Convergence of the spin axis towards the orbit normal is then explained by estimating the average magnetic control torque over one orbit. The validity of the analytical results, based on some simplifying assumptions and approximations, is finally investigated by means of numerical simulation for a fully non-linear attitude dynamic model, featuring a tilted dipole model for Earth׳s magnetic field. The analysis aims to support, in the framework of a sound mathematical basis, the development of effective control laws in realistic mission scenarios. Results are presented and discussed for relevant test cases

Considerations on dynamic soaring

This paper presents an analytical treatment of dynamic soaring, a behaviour that certain sea birds use to extract energy from wind gradient. Theoretical modeling and results of numerical simulations, based on a two-degrees-of-freedom point mass model, are presented

One and two-entry tree volume tables for the new-established ash-sycamore forest types at a pre-alpine territory.

Ash-sycamore stands have been assuming a considerable territorial importance in Northern Italy over the last decades. According to the National Forest and Carbon Sinks Inventory (INFC), these stands form the type of “sycamore-lime mountain & ash forests” and “Apennine maple forests”. These forests amount to 153904 hectares (88% in the Northern regions) and 23600 hectares, respectively. In the Veneto Region, ash-sycamore are mainly secondary forests and occupy 9258 hectares. These stands spread easily throughout the agriculture set-aside lands thanks to their colonizing ability and to the favourable soil conditions in the pre-alpine region. Experimental thinnings framed into a wider project aimed at producing management guidelines according to a single-tree oriented approach, provided a sample of 385 trees. On the basis of this dataset, the first tree volume tables for these ash-sycamore stands have been elaborated. Data collection and data processing are being described in the paper. A two-entry tree volume table was set up by the stepwise analysis procedure and a one tree volume table was derived from the two-entry tree volume table

Prove di diradamento in acero-frassineti di neoformazione nella Comunità Montana Agno-Chiampo (VI). Risultati dopo il secondo intervento

Thinning trials in secondary growth ash-maple stands carried out in the Agno-Chiampo district (VI): results after second thinning. The second thinning results undertaken in four ash-maple stands of different age are described. In three stands a target tree management system (free thinning around few target trees) was applied. In the oldest stand one mixed thinning has been implemented. In the youngest stand 400 target trees have been preselected and numerically half reduced after a second free thinning (aged 18 yr). The basal area of this stand decreased globally with 34%. In the middle aged stand (aged 28 and 31 yr), all the target trees, previously selected, were favoured. Among them, only those seriously damaged (by logging and frost) were cut down. The overall uptake in this stand has been the 30% of basal area. In the oldest stand the second traditional thinning (aged 37 yr) was more intensive, than the previous: the 34% of basal area has been felled. The analysis of target trees diameter growth has revealed that free thinning has been efficient for the youngest stand (a constant diameter increment of 8,6 mm yr-1). Conversely, a progressive reduction of diameter increment (5,5 mm yr-1) has been found in the control plot. The reaction to thinning in the middle aged stand was inferior in terms of homogeneity and diameter increment through years (6 mm yr-1 average), this underline a less reaction of crowns. In the oldest stand, late thinnings had little incremental effect, however the general stability and specific diversity improved . The experimental results confirm the necessity to carry out the first thinning in young stands (aged 15-20 yr) with a frequency of 4-6 yr in a restricted number of target trees (100-200 per hectare). In the oldest stands the chance to improve the production of good quality timber is reduced, but timber with fairly good technological characteristics can be however obtained

A UAS System for Observing Volacanoes and Natural Hazards

Fixed or rotary wing manned aircraft are currently the most commonly used platforms for airborne reconnaissance in response to natural hazards, such as volcanic eruptions, oil spills, wild fires, earthquakes. Such flights are very often undertaken in hazardous flying conditions (e.g., turbulence, downdrafts, reduced visibility, close proximity to dangerous terrain) and can be expensive. To mitigate these two fundamental issues--safety and cost--we are exploring the use of small (<100kg), relatively inexpensive, but effective, unmanned aerial vehicles (UAVs) for this purpose. As an operational test, in 2004 we flew a small autonomous UAV in the airspace above and around Stromboli Volcano. Based in part on this experience, we are adapting the RAVEN- INGV system for such natural hazard surveillance missions. RAVEN- INGV has a 50km range, with a 3.5m wingspan, main fuselage length of 4.60m, and maximum weight of 56kg. It has autonomous flight capability and a ground control station for mission planning and control. It will carry a variety of imaging devices, including a visible camera, and an IR camera. Such flexible, capable, and easy-to-deploy UAV systems may significantly shorten the time necessary to characterize the nature and scale of the natural hazard threats if used from the outset of, and systematically during, natural hazard events. When appropriately utilized, such UAVs can provide a powerful new hazard mitigation and documentation tool for civil protection hazard responders. This research was carried out under the auspices of the Italian government, and, in part, under contract to NASA at the Jet Propulsion Laboratory

Laser irradiated foam targets: absorption and radiative properties

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminium targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target

Diagnostic Methodologies of Laser-Initiated 11B(p,α)2α Fusion Reactions

The detection of the ionic products of low-rate fusion reactions, and in particular of the 11B(p,α)2α, is one of the recognized main problems in experiments where these reactions are initiated by tailored interaction of intense and high-energy lasers with matter. A thorough description of this important issue, with a critical comparison of the diagnostic opportunities, is indeed so far. In this work, we describe the common diagnostic methodologies used for the detection of the alpha particles generated by the 11B(p,α)2α reaction and, for each, we outline advantages and limitations, with considerations that can also be applied to other low-rate fusion reactions. We show here that, in general, the univocal characterization of the α products coming from this reaction can be achieved by the simultaneous use of several diagnostic tools placed in close proximity

Illuminating the Dark Side of Cosmic Star Formation II. A second date with RS-NIRdark galaxies in COSMOS

About 12 billion years ago, the Universe was first experiencing light again after the dark ages, and galaxies filled the environment with stars, metals and dust. How efficient was this process? How fast did these primordial galaxies form stars and dust? We can answer these questions by tracing the Star Formation Rate Density (SFRD) back to its widely unknown high redshift tail, traditionally observed in the Near-InfraRed (NIR), Optical and UV bands. Thus, the objects with a high amount of dust were missing. We aim to fill this knowledge gap by studying Radio Selected NIR-dark (\textit{RS-NIRdark}) sources, i.e. sources not having a counterpart at UV-to-NIR wavelengths. We widen the sample by Talia et al. (2021) from 197 to 272 objects in the COSMic evolution Survey (COSMOS) field, including also photometrically contaminated sources, previously excluded. Another important step forward consists in the visual inspection of each source in the bands from u* to MIPS-24$\mu$m. According to their "environment" in the different bands, we are able to highlight different cases of study and calibrate an appropriate photometric procedure for the objects affected by confusion issues. We estimate that the contribution of RS-NIRdark to the Cosmic SFRD at 3$<$z$<$5 is $\sim$10--25$\%$ of that based on UV-selected galaxies

Ray optics hamiltonian approach to relativistic self focusing of ultraintense lasers in underdense plasmas

The relativistic self focusing of an ultraintense laser propagating through an underdense plasma is analyzed from a geometrical optics point of view, exploiting the classical hamiltonian formalism. The distribution of the laser intensity along the self-generated plasma channel is studied and compared to measurements

Multi-centre and multi-vendor reproducibility of a standardized protocol for quantitative susceptibility Mapping of the human brain at 3T

: Quantitative Susceptibility Mapping (QSM) is an MRI-based technique allowing the non-invasive quantification of iron content and myelination in the brain. The RIN - Neuroimaging Network established an optimized and harmonized protocol for QSM across ten sites with 3T MRI systems from three different vendors to enable multicentric studies. The assessment of the reproducibility of this protocol is crucial to establish susceptibility as a quantitative biomarker. In this work, we evaluated cross-vendor reproducibility in a group of six traveling brains. Then, we recruited fifty-one volunteers and measured the variability of QSM values in a cohort of healthy subjects scanned at different sites, simulating a multicentric study. Both voxelwise and Region of Interest (ROI)-based analysis on cortical and subcortical gray matter were performed. The traveling brain study yielded high structural similarity (∼0.8) and excellent reproducibility comparing maps acquired on scanners from two different vendors. Depending on the ROI, we reported a quantification error ranging from 0.001 to 0.017&nbsp;ppm for the traveling brains. In the cohort of fifty-one healthy subjects scanned at nine different sites, the ROI-dependent variability of susceptibility values, of the order of 0.005-0.025&nbsp;ppm, was comparable to the result of the traveling brain experiment. The harmonized QSM protocol of the RIN - Neuroimaging Network provides a reliable quantification of susceptibility in both cortical and subcortical gray matter regions and it is ready for multicentric and longitudinal clinical studies in neurological and pychiatric diseases