A flow sensor exploiting magnetic fluids

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A Low Cost Multi-sensor Strategy for Early Warning in Structural Monitoring Exploiting a Wavelet Multiresolution Paradigm

AbstractThis paper deals with a novel approach to validate alerts provided by an early warning system (EWS) for structural monitoring implemented through low cost multi-sensor nodes. In particular, a dedicated wavelet multiresolution methodology is presented to implement a reliable assessment of the structural behavior. Such strategy allows to discriminate the structural response to seismic sources from other exogenous inertial components. Results obtained demonstrate the suitability of the proposed solution in the framework of the development of low cost multi-sensor strategies for the early warning of anomalous structural behaviors

A Ferrofluid Inclinometer with a Time Domain Readout Strategy

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Smart virtual sensors for real-time assessment of Volcanic activity

Monitoring is mandatory in hazardous areas with active volcanoes. South Italy countries are seriously affected by continuous risk of volcanic ash emissions, explosions and eruptions. In particular, Mt. Etna and Stromboli volcanoes requires great efforts by the scientific community to develop efficient monitoring systems. Several tasks in surveillance are already being managed by authority; anyway, innovative techniques are required to improve the performance of the monitoring task which is mandatory to improve the quality of public safety. Synergy between competence on geophysical and engineer disciplines must be reinforced to develop monitoring systems aimed to increase information needed to promptly manage crisis arising from volcanic activities. In this paper an innovative monitoring system is proposed. The system is based on smart virtual sensors, which assures real-time management of the volcanic activity by providing a large amount of information on the time evolution of the observed phenomena. The system performs in two parallel tasks: the first aims to optimise the amount of the recorded data by a smart real-time processing of the gathered images and gives very rough set of information on the ongoing events (explosions, eruptions, ash emissions, etc.), while the second task is aimed to a deep analysis of the recorded data to compute statistic indexes characterizing the evolution of the volcanic activity observed (area, height, width, aspect ratio, magma flow rate, etc.). The prototype of the proposed system is composed by a thermal camera sensor and a PC-based environment for data analysis. In particular, two computation tools were developed in the LabVIEW environment which provide the above mentioned information on the ongoing activity along with a smart processing of the acquired data. The system will be aimed to give useful information to the surveillance authority which, on the basis of the obtained results, can suitably manage the incoming events

Experimental and Theoretical Investigation of a Nonlinear Vibrational Energy Harvester

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Experimental characterisation of (localised) Deformation Phenomena in Granular Geomaterials from Sample Down to Inter-and Intra-grain Scales

AbstractThis paper outlines some recent advances in the full-field experimental characterisation of the mechanics of granular geomaterials (in particular, sands) using a range of methods that provide characterisation at different scales, from the sample-scale down to the inter- and intra-grain scale. The techniques used are “full-field” approaches involving in-situ x-ray micro-tomography, 3D-volumetric digital image analysis/correlation and grain ID-tracking, in-situ 3D x-ray diffraction and in-situ, spatially-resolved neutron diffraction. These methods provide new data on the mechanics of sand at different scales, including continuum measures of strain, porosity, and fabric plus discrete measures of particle kinematics and force transmission. The results of such measurements might be used to advance higher-order continuum theories, and provide the necessary input parameters, or to calibrate discrete grain-scale simulations of sand behaviour to explore loading paths that are inaccessible in the laboratory

Zircon as a provenance tracer: Coupling Raman spectroscopy and Usingle bondPb geochronology in source-to-sink studies

Usingle bondPb zircon geochronology is one of the most widely used techniques in sedimentary provenance analysis. Unfortunately, the ability of this method to identify sediment sources is often degraded by sediment recycling and mixing of detritus from different source rocks sharing similar age signatures. These processes create non-unique zircon Usingle bondPb age signatures and thereby obscure the provenance signal. We here address this problem by combining detrital zircon Usingle bondPb geochronology with Raman spectroscopy. The position and width of the Raman signal in zircon scales with its degree of metamictization, which in turn is sensitive to temperature. Thus, combined U-Pb + Raman datasets encode information about the crystallization history of detrital zircons as well as their thermal history. Using three borehole samples from Mozambique as part of a source-to-sink study of interest for hydrocarbon exploration, we show that zircon populations with similar Usingle bondPb age distributions can exhibit different Raman signatures. The joint U-Pb + Raman analysis allowed us to identify three different annealing trends, which were linked to specific thermal events. Thus we were able to differentiate a dominant Pan-African Usingle bondPb age peak into several sub-populations and highlight the major effect of Karoo tectono-magmatic events. In our case study, we used Raman also as a means to systematically identify all zircon grains in heavy-mineral mounts, resulting in considerable time savings. Raman spectroscopy is a non-destructive and cost-effective method that is easily integrated in the zircon Usingle bondPb dating workflow to augment the resolution power of detrital zircon Usingle bondPb geochronology

Indoor free space optics link under the weak turbulence regime: measurements and model validation

This paper is a postprint of a paper submitted to and accepted for publication in [journal] and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital LibraryIn this study, the authors present the measurements performed on a free space optics (FSO) communications link using an indoor atmospheric chamber. In particular, the authors have generated several different optical turbulence conditions, demonstrating how even the weak turbulence regime can strongly affect the FSO link performance. The authors have carried out an in-depth analysis of the data collected during the measurements, and calculated the turbulence strength (i.e. scintillation index and Rytov variance) and the important performance metrics (i.e. the Q-factor and bit error rate) to evaluate the FSO link quality. Moreover, the authors have tested, for the first time, an appositely developed temporally-correlated gamma-gamma channel model to generate the temporal irradiance fluctuations observed at the receiver. This has been accomplished by using a complete analysis tool that enables the authors to fully simulate the experimental FSO link. Finally, the authors compare the generated time-series with the collected experimental data, showing a good agreement and thus proving the effectiveness of the model.This work was supported by the European Space Agency under grant no. 5401001020. We are very grateful to Dr. E. Armandillo for enlightening discussions. J. Perez's work was support by Spanish MINECO Juan de la Cierva Fellowship JCI-2012-14805. This research project falls within the frame of COST ICT Action IC1101 - Optical Wireless Communications - An Emerging Technology (OPTICWISE).Pernice, R.; Ando, A.; Cardinale, M.; Curcio, L.; Stivala, S.; Parisi, A.; Busacca, AC.... (2015). Indoor free space optics link under the weak turbulence regime: measurements and model validation. IET Communications. 9(1):62-70. https://doi.org/10.1049/iet-com.2014.0432S627091Tsukamoto, K., Hashimoto, A., Aburakawa, Y., & Matsumoto, M. (2009). The case for free space. IEEE Microwave Magazine, 10(5), 84-92. doi:10.1109/mmm.2009.933086Suriza, A. Z., Md Rafiqul, I., Wajdi, A. K., & Naji, A. W. (2013). Proposed parameters of specific rain attenuation prediction for Free Space Optics link operating in tropical region. Journal of Atmospheric and Solar-Terrestrial Physics, 94, 93-99. doi:10.1016/j.jastp.2012.11.008Nebuloni, R. (2005). Empirical relationships between extinction coefficient and visibility in fog. Applied Optics, 44(18), 3795. doi:10.1364/ao.44.003795García-Zambrana, A., Castillo-Vázquez, C., & Castillo-Vázquez, B. (2011). Outage performance of MIMO FSO links over strong turbulence and misalignment fading channels. Optics Express, 19(14), 13480. doi:10.1364/oe.19.013480Shokrollahi, A. (2006). Raptor codes. IEEE Transactions on Information Theory, 52(6), 2551-2567. doi:10.1109/tit.2006.874390MacKay, D. J. C. (2005). Fountain codes. IEE Proceedings - Communications, 152(6), 1062. doi:10.1049/ip-com:20050237Uysal, M., Jing Li, & Meng Yu. (2006). Error rate performance analysis of coded free-space optical links over gamma-gamma atmospheric turbulence channels. IEEE Transactions on Wireless Communications, 5(6), 1229-1233. doi:10.1109/twc.2006.1638639Tsiftsis, T. A. (2008). Performance of heterodyne wireless optical communication systems over gamma-gamma atmospheric turbulence channels. Electronics Letters, 44(5), 373. doi:10.1049/el:20083028Popoola, W. O., & Ghassemlooy, Z. (2009). BPSK Subcarrier Intensity Modulated Free-Space Optical Communications in Atmospheric Turbulence. Journal of Lightwave Technology, 27(8), 967-973. doi:10.1109/jlt.2008.2004950Nistazakis, H. E., Tsiftsis, T. A., & Tombras, G. S. (2009). Performance analysis of free-space optical communication systems over atmospheric turbulence channels. IET Communications, 3(8), 1402. doi:10.1049/iet-com.2008.0212Bayaki, E., Schober, R., & Mallik, R. (2009). Performance analysis of MIMO free-space optical systems in gamma-gamma fading. IEEE Transactions on Communications, 57(11), 3415-3424. doi:10.1109/tcomm.2009.11.080168Anguita, J. A., Neifeld, M. A., Hildner, B., & Vasic, B. (2010). Rateless Coding on Experimental Temporally Correlated FSO Channels. Journal of Lightwave Technology, 28(7), 990-1002. doi:10.1109/jlt.2010.2040136Andò, A., Mangione, S., Curcio, L., Stivala, S., Garbo, G., Pernice, R., & Busacca, A. C. (2013). Recovery Capabilities of Rateless Codes on Simulated Turbulent Terrestrial Free Space Optics Channel Model. International Journal of Antennas and Propagation, 2013, 1-8. doi:10.1155/2013/692915Ghassemlooy, Z., Le Minh, H., Rajbhandari, S., Perez, J., & Ijaz, M. (2012). Performance Analysis of Ethernet/Fast-Ethernet Free Space Optical Communications in a Controlled Weak Turbulence Condition. Journal of Lightwave Technology, 30(13), 2188-2194. doi:10.1109/jlt.2012.2194271Xiaoming Zhu, & Kahn, J. M. (2002). Free-space optical communication through atmospheric turbulence channels. IEEE Transactions on Communications, 50(8), 1293-1300. doi:10.1109/tcomm.2002.800829Xu, F., Khalighi, A., Caussé, P., & Bourennane, S. (2009). Channel coding and time-diversity for optical wireless links. Optics Express, 17(2), 872. doi:10.1364/oe.17.00087

Evolution of deformation and breakage in sand studied using X-ray tomography

International audienceParticle breakage of a granular material can cause significant changes in its microstructure, which will govern its macroscopic behaviour; this explains why the mechanisms leading to particle breakage have been a common subject within several fields, including geomechanics. In this paper, X-ray computed micro-tomography is used, to obtain three-dimensional images of entire specimens of sand, during high-confinement triaxial compression tests. The acquired images are processed and measurements are made on breakage, local variations of porosity, volumetric strain, maximum shear strain and grading. The evolution and spatial distribution of quantified breakage and the resulting particle size distribution for the whole specimen and for specific areas are presented here for the first time and are further related to the localised shear and volumetric strains. Before peak stress is reached, compaction is the governing mechanism leading to breakage; neither compressive strains nor breakage are significantly localised and the total amount of breakage is rather low. Post peak, in areas where strains localise and breakage is present, a dilative volumetric behaviour is observed locally, as opposed to the overall compaction of the specimen. Some specimens exhibited a compaction around the shear band at the end of the test, but there was no additional breakage at that point. From the grading analysis, it is found that mainly the grains with diameter close to the mean diameter of the specimen are the ones that break, whereas the biggest grains that are present in the specimen remain intact

Comparison of nanosecond laser ablation at 1064 and 308 nm wavelength

Abstract To study the solid Cu ablation in vacuum, two different laser sources operating at 1064 and 308 nm wavelength are employed at similar values of laser fluences. The infrared laser is a Q-switched Nd:Yag having 9 ns pulse width (INFN-LNS, Catania), while the ultraviolet one is a XeCl excimer having 20 ns pulse width (INFN-LEA, Lecce). Both experiments produced a narrow angular distribution of the ejected material along the normal to the target surface. The ablation showed a threshold laser power density, of about 7 and 3 J/cm 2 at 1064 and 308 nm, respectively, below which the ablation effect was negligible. The laser interaction produces a plasma at the target surface, which expands very fast in the vacuum chamber. Time-of-flight (TOF) measurements of the ion emission indicated an average ion velocity of the order of 4:7 Â 10 4 and 2:3 Â 10 4 m/s for the infrared and ultraviolet radiation, respectively. We also estimated approximately the corresponding temperature of the plasma from which ions originated, i.e. about 10 6 and 10 5 K for IR and UV wavelength, respectively. A discussion of the analysis of the ablation mechanism is presented. At the used laser power densities the produced Cu ions showed ionisation states between 1þ and 5þ in both cases.