[en] Ground-based radar interferometry has recently emerged as an innovative technology of remote sensing, able to accurately measure the static or dynamic displacement of several points of a structure. This technique in the last couple of years has been applied to different types of structures, such as bridges, towers and chimneys. This paper presents a prototype system developed by IDS, originally aimed at measuring the structural vibrations of helicopter rotor blades, based on an interferometric technique and constituted by combination of a radar sensor and a series of transponders installed on the target structure. The main advantages of this solution with respect to conventional interferometric radars, are related to the increased spatial resolution of the system, provided by the possibility to discriminate different transponders installed within the same resolution cell of the radar sensor, and to the reduction of the ambient noise (e.g. multi-path) on the radar measurement. The first feature allows the use of the microwave technology even on target areas with limited dimensions, such as industrial facilities, while the second aspect may extend the use of radar interferometric systems to complex scenarios, where multi-reflections are expected due to the presence of natural targets with high reflectivity to the radar signal. In the paper, the system and its major characteristics are first described; subsequently, application to the measurement of ambient vibration response of a lab set-up is summarized. Then the data acquired on a rotating mock-up are reported and analyzed to identify natural frequencies and mode shapes of the investigated structure.

[en] Even if the demand for energy continues to increase, the European Union Directive 2009/28/EC has set a goal of obtaining 20% of all energy from renewable sources by 2020. In this context, this study investigated two different scenarios: direct combustion and anaerobic digestion. Direct combustion was evaluated using the mass and energy balance method in order to obtain indications of the energy revenue, the emissions, and consequently the necessary flue gas depuration equipment. Anaerobic digestion was evaluated by performing experimental tests in the laboratory, in order to obtain indications of the energy revenue. The results show that both the processes present some advantages: from the energy viewpoint the more suitable process is direct combustion (energy revenue equal to 1.16 MWh/t_input instead to the 0.48 MWh/t_input obtained for the anaerobic digestion), while from the viewpoint of greenhouse gas emissions (GHGs, in particular the CO₂ emissions) the results are rather similar. (We evaluated that the emission is equal to 1.18 kg CO₂/kg_input for the direct combustion and to 1.06 kg CO₂/kg_input for the anaerobic digestion.) The anaerobic digestion presents more advantages from the viewpoint of features a simpler plant layout; the combustion scenario requires a more complex technology, in particular for dealing with NO_x emissions. (The concentration coming from the process is equal to 900 mg/Nm³.) For this specific study, based on the obtained results, the anaerobic digestion proved to be the more suitable treatment process. Furthermore, the analysis considered here demonstrates a general methodology useful for energy production compatibility planning. Graphical Abstract:

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[en] A study on LiNbO₃ crystal irradiation by pulsed KrF excimer laser beam is presented. The interaction with the 248 nm laser light modifies the material properties so that, when the irradiation is switched off, a time-periodic variation in the material reflectivity, depending on the irradiation conditions, was observed. This phenomenon can be explained in terms of the electro-optic effect induced by the buildup of internal electric fields since the compositional characterization, performed by the secondary ion mass spectrometry, showed no modification in the element concentration and the high resolution x-ray diffraction did not detect any structural deformation within the crystal

[en] The damage induced by 5 MeV oxygen ion implantation in x-cut congruent LiNbO₃ has been investigated by Rutherford backscattering spectrometry channeling technique. The dynamics of the damage growth has been described by an analytical formula considering the separate contributions of nuclear and electronic energy deposition. It has been hypothesized that the nuclear damage provides the localization of the energy released to the electronic subsystem necessary for the conversion into atomic displacements. The strong influence of the preexisting defects on the damage pileup, foreseen by the analytical formula, has been experimentally verified by pre-implanting the samples with 500 keV oxygen ions. It has been shown that a subsequent 5 MeV oxygen implantation step gives rise to an impressive damage accumulation, eventually leading to the total amorphization of the surface, even at moderate fluences

[en] In this work x-cut Lithium Niobate crystals were implanted with 0.5 MeV O ions (nuclear stopping regime), 5 MeV O ions (sub-threshold electronic stopping regime) and 12.5 MeV Ti ions (ion track regime) at the fluences required for the formation of a surface fully disordered layer. The damage depth profiles were determined by RBS-channeling. Wet etching was performed at room temperature in 50% HF:H₂O solution. The data indicated an exponential dependence of the etching rate on the damage concentration. Independently of the damage regime, once random level in the RBS-channeling spectra was attained we measured the same etching rate (50-100 nm/s) and the same volume expansion (∼10%) in all samples. These results indicate that the fully disordered layers obtained by electronic damage accumulation have the same chemical properties of those obtained by conventional nuclear damage accumulation and therefore they can be defined 'amorphous'. The impressive etching selectivity of ion implanted regions makes this process suitable for sub-micro machining of Lithium Niobate

[en] The damage formation by implantation of energetic (∼5 MeV) low Z ions (C, N, O, F) in LiNbO₃ has been investigated. The surface damage growth as a function of the fluence is consistent with a mechanism of nucleation and 3D growth of fully disordered clusters. It is possible to describe this behaviour by considering two processes: the first one is the direct generation of nuclear damage whereas the second one is the partial conversion of the electronic excitation into atomic displacements, mediated by the local concentration of defects. Within this simple scenario the damage evolution has been described by an analytical formula. This formula suggested that the existence of pre-damage in the surface region can boost the damage growth. This was demonstrated by introducing nuclear damage in the first 0.6 μm surface layer by 500 keV O implantation followed by a subsequent 5 MeV O implantation. The final surface damage is not the mere sum of the two implantation steps, but it is strongly enhanced by the interaction of the two damage mechanisms (nuclear and electronic) and it is in very good quantitative agreement with the proposed analytical formula. A strong non-linear dependence of the electronic damage formation cross-section on the stopping power was evidenced by repeating the same experiment with carbon ions

[en] High energy implantation of medium-light elements such as oxygen and carbon was performed in X-cut LiNbO₃ single crystals in order to prepare high quality optical waveguides. The compositional and damage profiles, obtained by exploiting the secondary ion mass spectrometry and Rutherford back-scattering techniques respectively, were correlated to the structural properties measured by the high resolution X-ray diffraction. This study evidences the development of tensile strain induced by the ion implantation that can contribute to the decrease of the ordinary refractive index variation through the photo-elastic effect

[en] We show that the approximations used to extract the damage depth profiles from the RBS-channeling spectra of high energy ion implanted lithium niobate lead to incorrect results when two defective regions containing damage generated by electronic and nuclear energy deposition are produced. We demonstrate by high resolution X-ray diffraction analysis that the end-of-range defects formation is not influenced by the onset of different defects in the surface region and it is thus independent of the implantation energy. We propose universal curves, valid for ions Z ≤ 14, for the end-of-range defective fraction and the maximum strain as a function of the density of energy deposited by nuclear processes

[en] We report measurements of the charm-anticharm production asymmetries for Λ_c⁺, Σ_c⁺⁺, Σ_c⁰, Σ_c⁺⁺*, Σ_c⁰*, and Λ_c⁺(2625) baryons from the Fermilab photoproduction experiment FOCUS (E831). These asymmetries are integrated over the region where the spectrometer has good acceptance. In addition, we have obtained results for the photoproduction asymmetries of the Λ_c baryons as functions of p_L, p_T², and x_F. The integrated asymmetry for Λ_c⁺ production, (σ_Λc⁺-σ_Λc^-)/(σ_Λc⁺+σ_Λc^-), is 0.111±0.018±0.012, significantly different from zero. The asymmetries of the excited states are consistent with the Λ_c asymmetry

[en] Using data collected by the FOCUS experiment at Fermilab, we report the discovery of the decay modes D⁰->K^-π⁺π⁺π⁺π^-π^- and D⁰->π⁺π⁺π⁺π^-π^-π^-. With a sample of 48+/-10 reconstructed D⁰->K^-π⁺π⁺π⁺π^-π^- decays and 149+/-17 reconstructed D⁰->π⁺π⁺π⁺π^-π^-π^- decays, we measure the following relative branching ratios: Γ(D⁰->K^-π⁺π⁺π⁺π^-π^-)/Γ(D⁰->K^-π⁺π⁺π^-)=(2.70+/-0.58+/-0.3 8)x10^-3,Γ(D⁰->π⁺π⁺π⁺π^-π^-π^-)/Γ(D⁰->K^-π⁺π⁺π^-)=(5.23+/ -0.59+/-1.35)x10^-3,Γ(D⁰->π⁺π⁺π⁺π^-π^-π^-)/Γ(D⁰->K^-π⁺π⁺π⁺π^-π^-) = 1.93+/-0.47+/-0.48. The first errors are statistical and the second are systematic. The branching fraction of the Cabibbo suppressed six-body decay mode is measured to be a factor of two higher than the branching fraction of the Cabibbo favored six-body decay mode