Numerical and experimental analysis of the bi-stable state for frictional continuous system

Unstable friction-induced vibrations are considered an annoying problem in several fields of engineering. Although several theoretical analyses have suggested that friction-excited dynamical systems may experience sub-critical bifurcations, and show multiple coexisting stable solutions, these phenomena need to be proved experimentally and on continuous systems. The present work aims to partially fill this gap. The dynamical response of a continuous system subjected to frictional excitation is investigated. The frictional system is constituted of a 3D printed oscillator, obtained by additive manufacturing that slides against a disc rotating at a prescribed velocity. Both a finite element model and an experimental setup has been developed. It is shown both numerically and experimentally that in a certain range of the imposed sliding velocity the oscillator has two stable states, i.e. steady sliding and stick–slip oscillations. Furthermore, it is possible to jump from one state to the other by introducing an external perturbation. A parametric analysis is also presented, with respect to the main parameters influencing the nonlinear dynamic response, to determine the interval of sliding velocity where the oscillator presents the two stable solutions, i.e. steady sliding and stick–slip limit cycle

Il primo OBS/H italiano per il monitoraggio e lo studio di faglie e vulcani sottomarini

L’Istituto Nazionale di Geofisica e Vulcanologia (INGV) ha testato con successo, nel luglio 2006, il primo Ocean Bottom Seismometer with Hydrophone (OBS/H) italiano (Fig. 1). Lo strumento, interamente progettato e realizzato all’Osservatorio di Gibilmanna del Centro Nazionale Terremoti, dopo aver superato i test in laboratorio, in camera iperbarica a 600 bar ed in mare a 3412 m di profondità, è stato deposto per 9 giorni (12-21/07/’06) sulla spianata sommitale del vulcano sottomarino Marsili a 790 m di profondità (Fig. 2) ed ha registrato 835 eventi tra cui un telesisma, 8 eventi regionali e circa 800 eventi vulcanici

First long time OBS campaign in the Ionian Sea

The INGV started its interest to extend the seismic monitoring network to the sea in 1995 with GEOSTAR (Geophysical and Oceanographic Station for Abyssal Research) project, coming out with the realization of the first multidisclipinary observatory for deep-sea monitoring [Favali et al. 2002]. At the end of 2004, the National Earthquake Center (CNT) of INGV decided to provide a pool of Ocean Bottom Seismometers to be employed as a submarine mobile network and to study submarine faults and volcanoes. This was possible thanks to an agreement between the INGV and the Italian National Civil Protection Department (DPC). On July 2006, the Gibilmanna OBS Lab, tested the first OBS prototype for nine days on the flat top of the Marsili submarine volcano [D’Anna et al. 2007] and in early 2007 other seven OBS’s were ready to be deployed on the seafloor. In May 2007, within the European project NERIES (activity NA6), the Gibilmanna OBS Lab of the INGV has deployed three Broad Band Ocean Bottom Seismometers (BBOBS) in the southern Ionian Sea at 3500-4000 meters of depth. This area has been chosen during the NERIES – “NA6-BBOBS net” meeting in Rome, on the 11th of September 2006 because at first, there are at the moment few seismological data [Scrocca et al., 2003] to construct a reliable model for the Ionian lithosphere and also the rate and features of the seismicity in the area between the Hyblean-Malta fault system and the accretionary prism of the Calabrian Arc are largely unknown [Catalano et al. 2002]. The Ionian Sea is indeed one of the most seismically active area in the Mediterranean region with several destructive earthquakes sometimes followed by tsunamis [Tinti et al. 2004]. The seismicity occurring in the Ionian basin is characterized by large location uncertainties due to the lack of seafloor seismic stations. In 2002, the quality of the seismic sensing and the location of earthquakes have been improved by the deployment of the real-time submarine observatory SN-1, about 25 km offshore Eastern Sicily [Sgroi et al, 2007]. However, the SN-1 location only allows to characterize the seismicity in the area offshore the eastern Sicily. Two of the three OBS’s were successfully recovered on the 2nd of February 2008; the last one was recovered on the 15th of March 2008 and another OBS was deployed on the same location to accomplish the continuous long-term seismic monitoring task (until May 2010) as planned in NERIES project

Sulfur content in foods consumed in an Italian population and impact of diet quality on sulfur intake

Sulfur is an essential nutrient but data about its intake are scarce. We aimed to measure sulfur content in food samples and assess its habitual intake in relation to adherence to healthy dietary patterns in 719 Italian adults. Using a food frequency questionnaire, we estimated overall sulfur intake, and its relation with adherence to healthy dietary patterns. The highest sulfur content was found in preserved/canned fish (3.0 g/kg), seafood (2.8 g/kg), white meat (2.8 g/kg) and dairy products, particularly aged cheeses (2.1 g/kg) and lowest in fresh fruit (87 mg/kg), oils and fats (157 mg/kg), and beverages (141 mg/kg), with the exception of onion and garlic (1.3 g/kg). The mean sulfur intake in the study population was 1.1 g/day, slightly higher in men than women. The foods contributing most to sulfur intake were meat (29%) and cereals (19%), with also substantial contribution (>10%) from beverages and dairy products. Adherence to dietary patterns had little influence on sulfur intake, except for adherence to MIND diet positively and linearly associated with sulfur intake. Our study provides an updated overview of sulfur content in foods composing the Italian diet, as well as of sulfur intake in an Italian community of Northern Italy

Il nuovo OBS/H dell’INGV

In 2005, thanks to the 3-year agreement between Dipartimento Nazionale della Protezione Civile (DPC) and Istituto Nazionale di Geofisica e Vulcanologia (INGV) - Centro Nazionale Terremoti (CNT), the project of the first Italian “Ocean Bottom Seismometer with Hydrophone” (OBS/H) for long-term deployment was developed at the OBS Lab of the Gibilmanna Observatory (Sicily). The drawing of the instrument started in January 2005 and, after 18 months, the prototype was ready for test in laboratory, in shallow and deep water. Afterwards, the first OBS/H was tested during an oceanographic campaign on the Marsili submarine volcano, from the 10th to the 21st of July 2006.More than 1000 events of several kinds were recorded: 817 VTB (Volcano Tectonic events, B-type), 159 HF (High Frequency events), 53 SDE (Short Duration Event), 8 regional events localized by INGV land network, 10 not localized events, 1 teleseismic event an 2 rockfall events. The INGV OBS/H are equipped with: - Nanometrics Trillium 120p seismometers (theoretical flat response between 120s and 175 Hz) installed in a 17 inches glass sphere on a Nautilus gimbal for the leveling or Guralp CMG40T-OBS (flat response between 60s and 100 Hz); - Cox-Webb Differential Pressure Gauge (bandwidth 500s-2Hz) or OAS E-2PD hydrophone (0-5kHz); - 21 bits, 4 channels SEND Geolon-MLS digitizer with sampling frequency up to 200 Hz

System Level Analysis of Millimetre-wave GaN-based MIMO Radar for Detection of Micro Unmanned Aerial Vehicles

The detection of Unmanned Aerial Vehicles (UAVs) of micro/nano dimensions, is becoming a hot topic, due to their large diffusion, and represents a challenging task from both the system architecture and components point of view. The Frequency Modulated Continuous Wave (FMCW) radar architecture in a Multi-Input Multi-Output configuration has been identified as the most suitable solution for this purpose, due to both its inherent short-range detection capability and compact implementation. This paper describes the operation and technology challenges inherent to the development of a millimeter-wave FMCW MIMO radar for small UAVs detection. In particular it analyzes the sub-systems specifications and the expected system performance with respect to a chip set designed and developed in GaN at 37.5 GHz applications

A novel microbiological approach to impact the aromatic composition of sour loquat beer

The growing interest in novel beer development determined the exploitation of unconventional yeasts isolated from novel ecological niches to generate unexplored sensory profiles. In recent years, there is an increasing interest in generating beers brewed with the addition of fruits. For the first time, Lachancea thermotolerans MNF105 and Saccharomyces cerevisiae MN113 isolated from manna, were tested as starter cultures to process loquat beer to improve the sensory profile. Innovatively, the yeast species L. thermotolerans was investigated for the production of sour fruit beer. Sour fruit beers produced with L. thermotolerans MNF105 were more balanced than the respective control, especially in terms of perceived acidity during sensory analysis. This could be due to the lower lactic acid production (0.49 g/L) compared to the respective control (1.74 g/L). The overall organoleptic investigation showed a preference for S. cerevisiae MN113 (TF1) isolated from manna. Experimental trials conducted with the selected strains demonstrated the absence of off-odour and off-flavour and improved aroma perception. Aldehydes and alcohols were the most abundant compounds emitted from the beers. S. cerevisiae MN113 and L. thermotolerans MNF105, manna related yeasts, showed great technological properties, representing promising starters for the production of fruit beer and sour fruit beer