Non-convex scenario optimization

Scenario optimization is an approach to data-driven decision-making that has been introduced some fifteen years ago and has ever since then grown fast. Its most remarkable feature is that it blends the heuristic nature of data-driven methods with a rigorous theory that allows one to gain factual, reliable, insight in the solution. The usability of the scenario theory, however, has been restrained thus far by the obstacle that most results are standing on the assumption of convexity. With this paper, we aim to free the theory from this limitation. Specifically, we focus on the body of results that are known under the name of “wait-and-judge” and show that its fundamental achievements maintain their validity in a non-convex setup. While optimization is a major center of attention, this paper travels beyond it and into data-driven decision making. Adopting such a broad framework opens the door to building a new theory of truly vast applicability

Liquid-Gas Phase Transition in Nuclear Equation of State

A canonical ensemble model is used to describe a caloric curve of nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze out densities of all the possible initial temperatures for a given total reaction energy, the first order characteristics of liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low beam energy and one at high beam energy show different caloric behaviors and are discussed.Comment: 12 pages in Revtex including two Postscript figure

VANTAGGI DELL’UTILIZZO DEL SISTEMA DOSIMETRICO OSL IN CASO DI EMERGENZA

VANTAGGI DELL’UTILIZZO DEL SISTEMA DOSIMETRICO OSL IN CASO DI EMERGENZA S. Abate, F. Campi, L. Garlati, O. Tambussi Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano [email protected] Il sistema dosimetrico per corpo intero OSL (Optically Stimulated Luminescence) è un tipo di dosimetria che si sta sempre più diffondendo in vari paesi. In Europa molti centri di ricerca si sono dotati di un proprio sistema dosimetrico, mentre commercialmente Landauer rappresenta il maggior fornitore di tale servizio dosimetrico, ma anche del sistema stesso (dosimetri e apparecchio di lettura). Il vantaggio di questo tipo di dosimetro consiste nella semplicità e velocità di lettura e azzeramento, anche se risulta meno affidabile dei film-badge. Inoltre, rispetto ai dosimetri a TL, risultano essere più stabili nel tempo, non dovendo subire cicli termici che ne alterano la struttura cristallina e di conseguenza le loro performance. Questo permette di utilizzare, leggere e azzerare anche il singolo dosimetro e non l’intero lotto di appartenenza. Questa caratteristica permette di utilizzare il dosimetro a OSL come un dosimetro passivo, ma col vantaggio della lettura indiretta al termine delle operazioni, proprio come per un dosimetro elettronico viene effettuata la lettura diretta su display. In questo lavoro si vogliono paragonare i vantaggi e gli svantaggi dei sistemi dosimetrici tradizionali (film-badge e TLD) con il sistema OSL. Si presentano i risultati sperimentali delle performance (dipendenza energetica, dosimetrica e angolare) del sistema dosimetrico OSL Inlight con sistema di lettura MicroStar. Infine si presentano i risultati degli irraggiamenti condotti in parallelo presso un centro LAT tra il sistema OSL e i dosimetri elettronici DMC 2000 (Mirion Technologies). Le caratteristiche di questo dosimetro permettono di concludere che questo tipo di sistema dosimetrico ha degli aspetti positivi per il suo utilizzo in caso di emergenza radiologica senza i costi di una dosimetria con strumentazione attiva

Active shielding design and optimization of a wireless power transfer (WPT) system for automotive

This study deals with the optimization of a shielding structure composed by multiple active coils for mitigating the magnetic field in an automotive wireless power transfer (WPT) system at 85 kHz. Each active coil is independently powered and the most suitable excitation is obtained by an optimization procedure based on the Gradient Descent algorithm. The proposed procedure is described and applied to shield the magnetic field beside an electric vehicle (EV) equipped with SAE standard coils, during wireless charging. The obtained results show that the magnetic field in the most critical area is significantly reduced (i.e., approximately halved) with a very limited influence on the electrical performances (i.e., WPT efficiency decreases by less than 1 percentage point compared to the case without active shielding)

Sc substitution for Mg in MgB2: effects on Tc and Kohn anomaly

Here we report synthesis and characterization of Mg_{1-x}Sc_{x}B_{2} (0.12T_{c}>6 K. We find that the Sc doping moves the chemical potential through the 2D/3D electronic topological transition (ETT) in the sigma band where the ``shape resonance" of interband pairing occurs. In the 3D regime beyond the ETT we observe a hardening of the E_{2g} Raman mode with a significant line-width narrowing due to suppression of the Kohn anomaly over the range 0<q<2k_{F}.Comment: 8 pages, 4 EPS figures, to be published in Phys. Rev.

Indium selenide: An insight into electronic band structure and surface excitations

We have investigated the electronic response of single crystals of indium selenide by means of angle-resolved photoemission spectroscopy, electron energy loss spectroscopy and density functional theory. The loss spectrum of indium selenide shows the direct free exciton at similar to 1.3 eV and several other peaks, which do not exhibit dispersion with the momentum. The joint analysis of the experimental band structure and the density of states indicates that spectral features in the loss function are strictly related to single-particle transitions. These excitations cannot be considered as fully coherent plasmons and they are damped even in the optical limit, i.e. for small momenta. The comparison of the calculated symmetry-projected density of states with electron energy loss spectra enables the assignment of the spectral features to transitions between specific electronic states. Furthermore, the effects of ambient gases on the band structure and on the loss function have been probed

Exploring the Lattice Gas Model for isoscaling

Isotopic spin dependent lattice gas model is used to examine if it produces the isoscaling behaviour seen in intermediate energy heavy ion collisions. Qualitative features are reproduced but quantitative agreement with experiments is lacking.Comment: 13 pages including 6 figures. (Some typing mistakes in the references have been corrected in the 2nd version

Lattice Simulation of Nuclear Multifragmentation

Motivated by the decade-long debate over the issue of criticality supposedly observed in nuclear multifragmentation, we propose a dynamical lattice model to simulate the phenomenon. Its Ising Hamiltonian mimics a short range attractive interaction which competes with a thermal-like dissipative process. The results here presented, generated through an event-by-event analysis, are in agreement with both experiment and those produced by a percolative (non-dynamical) model.Comment: 8 pages, 3 figure