3D numerical modeling and experimental validation of diamagnetic levitated suspension in the static field

Diamagnetic levitation principle opens to promising solutions for innovative powerless and low stiffness suspension applicable to many technological fields. The peculiarities of diamagnetic suspension make this design solution very attractive for some applications such as microdevices and energy harvesters. Low stiffness and powerless functioning are the most appreciable characteristics of this kind of suspension, despite their force-displacement curve is generally hard to predict and strongly nonlinear. The modeling complexity resides in the preliminary prediction of magnetic field distribution and in the calculation of diamagnetic forces as function of the levitation height. This work introduces a modeling approach for calculating the levitation height of a parameterized diamagnetic suspension composed of a ground of permanent magnets and a levitating mass made of pyrolytic graphite. The numerical discretization approach is used and the predicted values are compared with experiments providing good agreement between result

Self-consistent Green's functions calculation of the nucleon mean-free path

The extension of Green's functions techniques to the complex energy plane provides access to fully dressed quasi-particle properties from a microscopic perspective. Using self-consistent ladder self-energies, we find both spectra and lifetimes of such quasi-particles in nuclear matter. With a consistent choice of the group velocity, the nucleon mean-free path can be computed. Our results indicate that, for energies above 50 MeV at densities close to saturation, a nucleon has a mean-free path of 4 to 5 femtometers.Comment: 5 pages, 4 figures. Minor changes, bibliography corrected. Accepted version in Phys. Rev. Let

Diagrammatic calculation of thermodynamical quantities in nuclear matter

In medium T-matrix calculations for symmetric nuclear matter at zero and finite temperatures are presented. The internal energy is calculated from the Galitskii-Koltun's sum rule and from the summation of the diagrams for the interaction energy. The pressure at finite temperature is obtained from the generating functional form of the thermodynamic potential. The entropy at high temperature is estimated and compared to expressions corresponding to a quasiparticle gas.Comment: 9 pages, 5 figure

Self-consistent Green's function approaches

We present the fundamental techniques and working equations of many-body Green's function theory for calculating ground state properties and the spectral strength. Green's function methods closely relate to other polynomial scaling approaches discussed in chapters 8 and 10. However, here we aim directly at a global view of the many-fermion structure. We derive the working equations for calculating many-body propagators, using both the Algebraic Diagrammatic Construction technique and the self-consistent formalism at finite temperature. Their implementation is discussed, as well as the inclusion of three-nucleon interactions. The self-consistency feature is essential to guarantee thermodynamic consistency. The pairing and neutron matter models introduced in previous chapters are solved and compared with the other methods in this book.Comment: 58 pages, 14 figures, Submitted to Lect. Notes Phys., "An advanced course in computational nuclear physics: Bridging the scales from quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor

Experimental methods for the characterization of fatigue in microstructures

The mechanical fatigue behavior of gold microbeams is analyzed. Dedicated devices have been designed and built able to produce alternate loading on gold specimens; the electrostatic actuation is used as driving force. Gold beams are tested under both bending and tensile alternate loadings. Results were used to plot S-N curves and fatigue Goodman-Smith diagram in order to estimate the fatigue limit of the material in presence of mean and alternate stress conditions. The surface topography evolution is studied and failure modes are discussed

Experimental methods for the characterization of fatigue in microstructures

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Experimental methods for the characterization of fatigue in microstructures

The mechanical fatigue behavior of gold microbeams is analyzed. Dedicated devices have been designed and built able to produce alternate loading on gold specimens; the electrostatic actuation is used as driving force. Gold beams are tested under both bending and tensile alternate loadings. Results were used to plot S-N curves and fatigue Goodman-Smith diagram in order to estimate the fatigue limit of the material in presence of mean and alternate stress conditions. The surface topography evolution is studied and failure modes are discussed

Electro-mechanical coupled design of self-powered sensing systems and performances comparison through experiments

Recent advances in low-power sensors and electronic components open to innovative strategies in structural monitoring and real-time data processing, in particular for industrial and vehicular fields. Dedicated devices for harvesting the energy dissipated by mechanical vibrations of machines are showing their applicability in supplying autonomous distributed sensing systems. The harvester will replace cables and storage batteries, with relevant benefits on the sensing system capillarity, accessibility and applicability. The design of the interfaces of the electric, magnetic and structural coupled systems forming the harvester include static and dynamic modeling and simulation of the interactions involved; smart and effective architectures are need to satisfy the general requirements of bandwidth, tunability and efficiency required by each application. This paper reports the research advances in this field as a result of laboratory tests and design studies, with particular focus on the design methodologies involved in the definition of energy harvesters