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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RTD Fluxgate behavioral model for circuit simulation

Abstract SPICE simulation is universally recognized as a powerful tool in the field of electronic engineering. Simulations are strategic when dealing with a strong non-linear behavior that cannot be easily handled analytically. Magnetic hysteresis is one example of non-linearity that founds many practical applications, especially in the field of magnetometers and magnetic sensors. The aim of this paper is to present a behavioral model of RTD Fluxgate magnetometers easy to implement and adaptive with respect to the dynamic of the driving signal. Even if the whole work is focused on a specific magnetometer, the developed methodology can generalized to the wide class of hysteretic devices

A micro finite element model for soil behaviour: experimental evaluation for sand under triaxial compression

This paper evaluates the ability of a combined discrete-finite element approach to replicate the experimental response of a dry sand under triaxial compression. The numerical sample was created by virtualising the fabric of a Martian regolith-like sand sample obtained from an in-situ test using X-ray micro Computed Tomography and physical properties of the grains obtained from laboratory data were used as input. The boundary and contact conditions were defined according to the experimental test. A key feature of the model is the use of deformable thin-shell elements to represent the numerical membrane, which allows for a realistic failure mode and volumetric deformation. The macroscopic response of the numerical simulation is shown to compare well with the experiment. The contact regions are identified based on their ability to transmit stress and the evolution of the contact normals is shown to correlate well with the macro stress evolution. The computed stress fields within each grain are used to identify the load bearing grains in the assembly, contributing new insights beyond the commonly reported force chains

A lab-scale experiment to measure terminal velocity of volcanic ash

In this paper, a novel methodology to measure trajectory and terminal velocity of volcanic ash in laboratory is presented. The methodology consists of: i) planning a lab-scale experiment in order to reproduce the sedimentation processes of fine volcanic ash based on the principle of dynamic similarity; ii) realizing the experimental set-up using a glass tank filled with glycerine, a web-cam based vision system and a dedicated image post processing tool able to estimate the position and the terminal velocity of any particle falling in the tank; iii) performing a calibration procedure to accurately estimate the uncertainty on particle velocity; iv) comparing the experimental results with estimations obtained by some particle fallout models available in literature. Our results shows that there is a good agreement between experimental terminal velocities and those obtained applying a model which includes information on particle shape. The proposed methodology allows us to investigate how the particle shape affects the sedimentation processes. Since the latter is strategic to improve the accuracy on modeling ash fallout, this work will contribute to reduce risks to aviations during explosive eruptions

Experimental and Theoretical Investigation of a Nonlinear Vibrational Energy Harvester

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Evolution of particle breakage studied using x-ray tomography and the discrete element method

Particle breakage can significantly change the fabric (size and shape of particles and contact network) of a granular material, affecting highly the material's macroscopic response. In this paper, oedometric compression tests are performed on zeolite specimens and x-ray computed micro-tomography is employed, to acquire high resolution 3D images of the specimens throughout the test. The images are processed, to describe breakage spatially and quantify it throughout the test and gain information about the mechanisms leading to particle breakage. In addition to the image processing, the discrete element method (DEM) is used to study the initiation and likelihood of particle breakage, by simulating the experimental test during the early stages of loading and using quantitative results from the images to inform and validate the DEM model. A discrete digital image correlation is used, in order to incrementally identify intact grains and simultaneously get results about the strain field within the specimen, as well as the kinematics of individual grains and fragments. In the initial stages of breakage, there is a clear boundary effect on the spatial distribution of breakage, as it is concentrated at the moving boundary (more than 90% of total breakage) and circumferentially (more than 70% of total breakage) close to the apparatus cell. The DEM model can reproduce the bulk response of the material until the point where substantial breakage governs the macroscopic response and it starts to soften. Additionally, there is an initial indication that the spatial distribution of the force network matches the localisation of breakage radially, but it does not seem to localise close to the loading platen. This analysis will enrich our understanding of the mechanisms and evolution of particle breakage

A Nonlinear Energy Harvester by Direct Printing Technology

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