Stochastic Dynamics in Quenched-in Disorder and Hysteresis

The conditions under which relaxation dynamics in the presence of quenched-in disorder lead to rate-independent hysteresis are discussed. The calculation of average hysteresis branches is reduced to the solution of the level-crossing problem for the stochastic field describing quenched-in disorder. Closed analytical solutions are derived for the case where the disorder is characterized by Wiener-Levy statistics. This case is shown to be equivalent to the Preisach model and the associated Preisach distribution is explicitly derived, as a function of the parameters describing the original dynamic problem.Comment: 7 pages, 3 figures, MMM Conference, to be published on J.Appl.Phy

Heritage education through serious games. A web-based proposal for primary schools to cope with distance learning

[EN] In recent years a growing amount of research has shown interest in studying how virtual reality (VR) could be relevant in many fields. In this respect, VR has gained consideration throughout many applications such as education. Among other aims for its use in education, serious games based on VR were used to promote heritage and make students experience either far or inaccessible scenarios. Until now, VR-based applications have been mainly implemented using head mounted displays (HMD), which actually reduced their circulation. This gap is particularly remarkable in the current Sars-CoV19 pandemic because students, being at home or being at school without sharing equipment, cannot exploit educational programs based on this technology. The current paper proposes a web-based platform on which VR applications could be accessed on any device, either desktop- or mobile-based. The serious game was initially set up on a computer with a specialized software using a HMD, while the process of turning it into a web-based platform is described so that the used methodology could be available to those, who would like to follow it. This project is probably also able to cope with the general aim of making inaccessible objects available to students and, thus, to make the application useful even beyond the current pandemic emergency.The VAR.HEE. project – Virtual and Augmented Reality for Heritage and art Education in school and museum Experiences – was funded by the Free University of Bozen/Bolzano with a competitive call for proposals by the Central Research Commission in 2017. The project lasts three years, started in January 2018 and will end in December 2020 (June 2021, after Covid-19 health emergency).Luigini, A.; Fanini, B.; Basso, A.; Basso, D. (2020). Heritage education through serious games. A web-based proposal for primary schools to cope with distance learning. VITRUVIO - International Journal of Architectural Technology and Sustainability. 5(2):73-85. https://doi.org/10.4995/vitruvio-ijats.2020.14665OJS73855

Non-equilibrium thermodynamics of the spin Seebeck and spin Peltier effects

We study the problem of magnetization and heat currents and their associated thermodynamic forces in a magnetic system by focusing on the magnetization transport in ferromagnetic insulators like YIG. The resulting theory is applied to the longitudinal spin Seebeck and the spin Peltier effects. By focusing on the specific geometry with one YIG layer and one Pt layer, we obtain the optimal conditions for generating large magnetization currents into Pt or large temperature effects in YIG. The theoretical predictions are compared with experiments from the literature permitting to derive the values of the thermomagnetic coefficients of YIG: the magnetization diffusion length $l_M \sim 0.4 \, \mu$m and the absolute thermomagnetic power coefficient $\epsilon_M \sim 10^{-2}$ TK$^{-1}$.Comment: accepted for publication on Physical Review

PADDLE: Proximal Algorithm for Dual Dictionaries LEarning

Recently, considerable research efforts have been devoted to the design of methods to learn from data overcomplete dictionaries for sparse coding. However, learned dictionaries require the solution of an optimization problem for coding new data. In order to overcome this drawback, we propose an algorithm aimed at learning both a dictionary and its dual: a linear mapping directly performing the coding. By leveraging on proximal methods, our algorithm jointly minimizes the reconstruction error of the dictionary and the coding error of its dual; the sparsity of the representation is induced by an $\ell_1$-based penalty on its coefficients. The results obtained on synthetic data and real images show that the algorithm is capable of recovering the expected dictionaries. Furthermore, on a benchmark dataset, we show that the image features obtained from the dual matrix yield state-of-the-art classification performance while being much less computational intensive

Non-equilibrium thermodynamics of the longitudinal spin Seebeck effect

In this paper we employ non equilibrium thermodynamics of fluxes and forces to describe magnetization and heat transport. By the theory we are able to identify the thermodynamic driving force of the magnetization current as the gradient of the effective field $\nabla H^*$. This definition permits to define the spin Seebeck coefficient $\epsilon_M$ which relates $\nabla H^*$ and the temperature gradient $\nabla T$. By applying the theory to the geometry of the longitudinal spin Seebeck effect we are able to obtain the optimal conditions for generating large magnetization currents. Furthermore, by using the results of recent experiments, we obtain an order of magnitude for the value of $\epsilon_{M} \sim 10^{-2}$ TK$^{-1}$ for yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$).Comment: accepted for publication on Physics Procedi

Enhancing the digital heritage, educating with the heritage. The Charles V Fort of the harbor of Girgenti

[EN] The essay proposes a project of enhancement and valorization of the Fort of Charles V to guard the harbor of Agrigento, in 1549. Starting from those visual references testified by the sixteenth and seventeenth century representations between the defensive fort, the harbor of Agrigento, and the ancient Greek city taking shape in the landscape configurations of Camiliani and Spannocchi, the article proposes the enhancement of the building starting from a photogrammetric digital survey with a phase of digital elaboration of the model on virtual platforms for the immersive exploration to be concluded with the definition of paths differentiated by users from a wide range of sources (scholars, citizens, students of different ages).Basso, A.; Vattano, S.; Luigini, A. (2020). Enhancing the digital heritage, educating with the heritage. The Charles V Fort of the harbor of Girgenti. Editorial Universitat Politècnica de València. 231-238. https://doi.org/10.4995/FORTMED2020.2020.11354OCS23123

Experimental proof of the reciprocal relation between spin Peltier and spin Seebeck effects in a bulk YIG/Pt bilayer

We verify for the first time the reciprocal relation between the spin Peltier and spin Seebeck effects in a bulk YIG/Pt bilayer. Both experiments are performed on the same YIG/Pt device by a setup able to accurately determine heat currents and to separate the spin Peltier heat from the Joule heat background. The sample-specific value for the characteristics of both effects measured on the present YIG/Pt bilayer is (6.2 \pm 0.4)\times 10^{-3} \,\, \mbox{KA^{-1}}. In the paper we also discuss the relation of both effects with the intrinsic and extrinsic parameters of YIG and Pt and we envisage possible strategies to optimize spin Peltier refrigeration.Comment: 11 pages, 3 figure

Chapter Visualità digitale applicata a metodologie di rilievo integrato. Sinergie collaborative tra sperimentazione e tecnologia

The 43rd UID conference, held in Genova, takes up the theme of ‘Dialogues’ as practice and debate on many fundamental topics in our social life, especially in these complex and not yet resolved times. The city of Genova offers the opportunity to ponder on the value of comparison and on the possibilities for the community, naturally focused on the aspects that concern us, as professors, researchers, disseminators of knowledge, or on all the possibile meanings of the discipline of representation and its dialogue with ‘others’, which we have broadly catalogued in three macro areas: History, Semiotics, Science / Technology. Therefore, “dialogue” as a profitable exchange based on a common language, without which it is impossible to comprehend and understand one another; and the graphic sign that connotes the conference is the precise transcription of this concept: the title ‘translated’ into signs, derived from the visual alphabet designed for the visual identity of the UID since 2017. There are many topics which refer to three macro sessions: - Witnessing (signs and history) - Communicating (signs and semiotics) - Experimenting (signs and sciences) Thanks to the different points of view, an exceptional resource of our disciplinary area, we want to try to outline the prevailing theoretical-operational synergies, the collaborative lines of an instrumental nature, the recent updates of the repertoires of images that attest and nourish the relations among representation, history, semiotics, sciences

Structure constants of short operators in planar N=4\mathcal{N}=4 SYM theory

We present an integrability-based conjecture for the three-point functions of single-trace operators in planar $\mathcal{N}=4$ super-Yang-Mills theory at finite coupling, in the case where two operators are protected. Our proposal is based on the hexagon representation for structure constants of long operators, which we complete to incorporate operators of any length using data from the TBA/QSC formalism. We perform various tests of our conjecture, at weak and strong coupling, finding agreement with the gauge theory through 5 loops for the shortest three-point function and with string theory in the classical limit.Comment: 6 pages, 4 figures, 1 appendi

A novel approach to water softening based on graphene oxide-activated open cell foams

This work focuses on exploring a new configuration for the reduction of water hardness based on the surface modification of polyurethane (PU) open cell foams by the deposition of thin graphene oxide (GO) washcoat layers. GO was deposited by the dip–squeeze coating procedure and consolidated by thermal treatment. The final washcoat load was controlled by performing consecutive depositions, after three of which, a GO inventory up to 27 wt% was obtained onto PU foams of 60 pores per inch (PPI). The GO-coated PU foams were assembled into a filter, and the performance of the system was tested by continuously feeding water with hardness in the 190–270 mgCa2+,eq·L−1 range. Remarkable results were demonstrated in terms of total adsorbing capacity, which was evaluated by measuring the outlet total hardness by titration and exhibited values up to 63 mgCa2+,eq·gGO−1 at a specific filtered water volume of 650 mLH2O·gGO−1, outperforming the actual state-of-the-art adsorbing capacity of similar GO-based materials