Piezo-electromechanical smart materials with distributed arrays of piezoelectric transducers: Current and upcoming applications

This review paper intends to gather and organize a series of works which discuss the possibility of exploiting the mechanical properties of distributed arrays of piezoelectric transducers. The concept can be described as follows: on every structural member one can uniformly distribute an array of piezoelectric transducers whose electric terminals are to be connected to a suitably optimized electric waveguide. If the aim of such a modification is identified to be the suppression of mechanical vibrations then the optimal electric waveguide is identified to be the 'electric analog' of the considered structural member. The obtained electromechanical systems were called PEM (PiezoElectroMechanical) structures. The authors especially focus on the role played by Lagrange methods in the design of these analog circuits and in the study of PEM structures and we suggest some possible research developments in the conception of new devices, in their study and in their technological application. Other potential uses of PEMs, such as Structural Health Monitoring and Energy Harvesting, are described as well. PEM structures can be regarded as a particular kind of smart materials, i.e. materials especially designed and engineered to show a specific andwell-defined response to external excitations: for this reason, the authors try to find connection between PEM beams and plates and some micromorphic materials whose properties as carriers of waves have been studied recently. Finally, this paper aims to establish some links among some concepts which are used in different cultural groups, as smart structure, metamaterial and functional structural modifications, showing how appropriate would be to avoid the use of different names for similar concepts. © 2015 - IOS Press and the authors

Rock physics in four dimensions

The measurement of the seismic velocity of a medium is fundamental to many applications in geoscience and engineering. Examples include the monitoring of: ice sheet melting, the health of concrete structures, temperature in volcanic regions, and sub-surface fluid pressure due to hydrocarbon extraction or the injection of CO2 to mitigate climate change. Velocities are also used to infer elastic properties, such as bulk and shear moduli and density, which can then be used to develop a wide range of rock physics models. This thesis addresses two key areas of research related to the seismic velocity: first, the improvement in the methodology of measuring changes in velocity in the time-lapse or four dimensional mode; and second, the interpretation of changing velocity measurements in terms of underlying processes, using various rock physics models. First, I investigate the use of coda wave interferometry (CWI) for measuring temporal changes in bulk velocity, particularly in an experimental rock physics setting. CWI uses the diffuse, multiply-scattered waves that arrive in the tail of the seismogram, sampling the entire medium and sampling the same sub-volumes many times, thus coda waves are far more sensitive to changes in a medium compared to the first arriving ballistic waves. Compared to conventional methods of phase picking of first arriving waves, CWI provides significant improvements in the accuracy and precision of estimates of velocity changes and is far more robust in the presence of background noise. CWI is also capable of jointly estimating changing source locations, allowing the estimation of the relative locations of a cluster of acoustic emissions with simultaneous velocity perturbations, all with a single receiver. Previously, the estimate of velocity change made by CWI has been an average of changes in compressional (P) and shear (S) wave velocities, which has previously been a major limitation to the application of the CWI method. I present a new method to use CWI for estimating changes in both P and S wave velocities individually. I then validate this method using numerical simulations on a range of media and the results of triaxial rock deformation experiments. The second part of this thesis is based on understanding the relationship between seismic velocity and time-dependent variables, including the evolving differential stress during deformation and changes in porosity during cementation. I investigate the seismic velocity-differential stress relationship during the experimental deformation of two finely laminated carbonate samples, using CWI to measure the temporal changes in both P and S wave velocity, allowing the inversion of crack density to interpret the mechanical behaviour of these carbonate samples. I then investigate the velocity-porosity relationship with an entirely digital method, using digital rocks where deposition and cementation are computationally simulated. I then simulate wavefield propagation through the digital rocks using a 3D finite-difference method to estimate the velocity of the medium. I statistically test two competing inclusion models for modelling elastic moduli-porosity data and find one that allows variable inclusion aspect ratio to be the most appropriate for fitting the data. I find CWI to be an effective method characterising changes in a medium in a rock physics environment. By providing a method for estimating separate changes in P and S wave velocity, I greatly improve the relevance and applicability of CWI for experimental rock physics. The method can be extended for the characterisation of media for a variety of applications in geoscience and engineering

proceedings of a workshop held at Göttingen September 27 - 29, 2006

An international workshop entitled: Modern Solar Facilities - Advanced Solar Science was held in Göttingen from September 27 until September 29, 2006. The workshop, which was attended by 88 participants from 24 different countries, gave a broad overview of the current state of solar research, with emphasis on modern telescopes and techniques, advanced observational methods and results, and on modern theoretical methods of modelling, computation, and data reduction in solar physics. This book collects written versions of contributions that were presented at the workshop as invited or contributed talks, and as poster contributions.Vom 27. bis 29. September 2006 fand in Göttingen ein internationaler Workshop zum Thema: Modern Solar Facilities - Advanced Solar Science statt, der von 88 Teilnehmern aus 24 verschiedenen Ländern besucht wurde und der einen breiten Überblick über den gegenwärtigen Stand der sonnenphysikalischen Forschung gab, unter Betonung moderner Teleskope und Techniken, fortschrittlicher Beobachtungsmethoden und Ergebnisse, sowie zu modernen theoretischen Verfahren der Modellierung, Berechnung und Datenreduktion in der Sonnenphysik. Dieser Band fasst die schriftlichen Versionen von Beiträgen zusammen, die auf der Konferenz als eingeladene oder angemeldete Vorträge, sowie als Posterbeiträge präsentiert worden sind.conferenc

Mathematical Modeling and Simulation in Mechanics and Dynamic Systems

The present book contains the 16 papers accepted and published in the Special Issue “Mathematical Modeling and Simulation in Mechanics and Dynamic Systems” of the MDPI “Mathematics” journal, which cover a wide range of topics connected to the theory and applications of Modeling and Simulation of Dynamic Systems in different field. These topics include, among others, methods to model and simulate mechanical system in real engineering. It is hopped that the book will find interest and be useful for those working in the area of Modeling and Simulation of the Dynamic Systems, as well as for those with the proper mathematical background and willing to become familiar with recent advances in Dynamic Systems, which has nowadays entered almost all sectors of human life and activity

Single-station inversion of seismic data for the InSight mission to Mars

Terrestrial planets, such as Earth and Mars, possess a crust that forms during the accretion phase, preserving impressions of the fundamental processes involved in their formation and evolution. Unlike Earth, where most of the ancient crust has been recycled, Mars retains most of it as it does not possess plate tectonics. Investigation of its crustal thickness and structure can thus help constrain its early evolution and formation. In November 2018, NASA’s InSight mission successfully deployed a three-component, very broad-band seismometer on the surface of Mars. With continuous seismic monitoring of Mars for over three Earth years, the seismic data from InSight now presents us with an opportunity for in-situ investigation of the Martian crust for the very first time. This thesis presents the development and application of a single-station seismic method to image the crust of Mars and evaluate its crustal thickness and structure below the InSight landing site using recorded marsquakes

Microwave resonant sensors

Microwave resonant sensors use the spectral characterisation of a resonator to make high sensitivity measurements of material electromagnetic properties at GHz frequencies. They have been applied to a wide range of industrial and scientific measurements, and used to study a diversity of physical phenomena. Recently, a number of challenging dynamic applications have been developed that require very high speed and high performance, such as kinetic inductance detectors and scanning microwave microscopes. Others, such as sensors for miniaturised fluidic systems and non-invasive blood glucose sensors, also require low system cost and small footprint. This thesis investigates new and improved techniques for implementing microwave resonant sensor systems, aiming to enhance their suitability for such demanding tasks. This was achieved through several original contributions: new insights into coupling, dynamics, and statistical properties of sensors; a hardware implementation of a realtime multitone readout system; and the development of efficient signal processing algorithms for the extraction of sensor measurements from resonator response data. The performance of this improved sensor system was verified through a number of novel measurements, achieving a higher sampling rate than the best available technology yet with equivalent accuracy and precision. At the same time, these experiments revealed unforeseen applications in liquid metrology and precision microwave heating of miniature flow systems.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Physics from Time Variability of the VHE Blazar PKS 2155-304

Blazars are the principal extragalactic sources of very high energy gamma-ray emission in the Universe. These objects constitute a sub-class of Active Galactic Nuclei whose emission is dominated by Doppler boosted non-thermal radiation from plasma outflowing at relativistic speeds from the central engine. This plasma outflow happens in the form of large-scale collimated structures called jets, which can extend for Mpc in length and transport energy from the central engine of the galaxy to the larger scale intergalac- tic medium. Over thirty such sources have been discovered to date by ground-based gamma-ray telescopes such as H.E.S.S., and PKS 2155-304 is the prototypical southern-hemisphere representative of this population of objects. In this thesis I have studied in detail some aspects of the temporal variability of the jet emission from PKS 2155-304, combining coordinated observations across the electromagnetic spectrum, from optical polarimetric measurements to X-ray and ground-based gamma-ray data. The temporal properties of the dataset allowed us to derive important physical information about the structure and emission mechanisms of the source and put constraints to the location of the sites of VHE emission and particle acceleration within the jet. We have also derived a sensitive statistical measure, called Kolmogorov distance, which we applied to the large outburst observed from PKS 2155-304 in July 2006, to derive the most stringent constraints to date on limits for the violation of Lorentz invariance induced by quantum-gravity effects from AGN measurements

The Antares Collaboration : Contributions to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague)

The ANTARES detector, completed in 2008, is the largest neutrino telescope in the Northern hemisphere. Located at a depth of 2.5 km in the Mediterranean Sea, 40 km off the Toulon shore, its main goal is the search for astrophysical high energy neutrinos. In this paper we collect the 21 contributions of the ANTARES collaboration to the 34th International Cosmic Ray Conference (ICRC 2015). The scientific output is very rich and the contributions included in these proceedings cover the main physics results, ranging from steady point sources, diffuse searches, multi-messenger analyses to exotic physics