Consistency of Bayesian inference with Gaussian process priors in an elliptic inverse problem

For $\mathcal{O}$ a bounded domain in $\mathbb{R}^d$ and a given smooth function $g:\mathcal{O}\to\mathbb{R}$, we consider the statistical nonlinear inverse problem of recovering the conductivity $f>0$ in the divergence form equation $$\nabla\cdot(f\nabla u)=g\ \textrm{on}\ \mathcal{O}, \quad u=0\ \textrm{on}\ \partial\mathcal{O},$$ from $N$ discrete noisy point evaluations of the solution $u=u_f$ on $\mathcal O$. We study the statistical performance of Bayesian nonparametric procedures based on a flexible class of Gaussian (or hierarchical Gaussian) process priors, whose implementation is feasible by MCMC methods. We show that, as the number $N$ of measurements increases, the resulting posterior distributions concentrate around the true parameter generating the data, and derive a convergence rate $N^{-\lambda}, \lambda>0,$ for the reconstruction error of the associated posterior means, in $L^2(\mathcal{O})$-distance

Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm

In this article we study the classical nearest-neighbour spin-ice model (nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm. The nnSI describes several of the salient features of the spin-ice materials. Despite its simplicity it exhibits a remarkably rich behaviour. The model has been studied using a variety of techniques, thus it serves as an ideal benchmark to test the capabilities of the Wang Landau algorithm in magnetically frustrated systems. We study in detail the residual entropy of the nnSI and, by introducing an applied magnetic field in two different crystallographic directions ([111] and [100],) we explore the physics of the kagome-ice phase, the transition to full polarisation, and the three dimensional Kasteleyn transition. In the latter case, we discuss how additional constraints can be added to the Hamiltonian, by taking into account a selective choice of states in the partition function and, then, show how this choice leads to the realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure

The regaining of public spaces to enhance the historic urban landscape

Open spaces in the urban landscapes suffer from deterioration caused by man that leads to two major outcomes: on one side they are abandoned because of newer contemporary needs, on the other hand they tend to be “cannibalized” in the attempt to satisfy our society. This has caused a progressive retraction of urban open spaces that have become residual spaces with no shape and no name. This course of crisis has damaged the identity of places and this is more acute in historic urban landscapes that are recognised as cultural heritage and world heritage. The historic urban landscape approach suggested by UNESCO recognises public spaces’ importance for society and promotes the acknowledgement of public spaces and their dynamism aiming to the integration of preservation, social development and economic targets. To understand how “historic urban landscapes” are taking care of their public spaces, a few Management Plans of UNESCO’s World Heritage cities have been compared. Only Italian UNESCO sites with an “urban complex” characterisation have been considered, this means a limited part of a city with homogenous characteristics from a spatial, historic and cultural point of view. We have focused our attention on the specific interventions for the management of open spaces, in order to identify the major targets and their executive tools, projects and actions. In the light of the above-mentioned analyses, we propose some strategies to fight the decline of public spaces (streets, squares, gardens, etc.) and to enhance these spaces with great attention, trying to improve their fruition and comfort according to their historic and cultural values. The need to identify design strategies to enhance public spaces within the historic urban landscape is included in the research and test activities carried out in the UNESCO site of Mantova and Sabbioneta. This site is an excellent area of applicability because of its urban shape, molded in years by the Gonzaga family. Together with the UNESCO Mantova e Sabbioneta office, we have involved citizens in the requalification design to activate regaining process and test the applicability of our analyses in the city of Mantova, a very articulated and complex reality, starting from the fruition of its places and according to its morphological, environmental, cultural and perceptive aspects

Study of a Natural Gas Combined Cycle with Multi-Stage Membrane Systems for CO2 Post-Combustion Capture

Abstract Carbon capture based on membrane process is receiving an increasing attention, due to advances in membrane performances. The aim of this paper is to investigate the integration of a post-combustion capture system based on membrane separation into a natural gas combined cycle (NGCC) power plant. A sensitivity analysis is carried out in order to evaluate the effect of membrane technology and operating conditions on permeate purity, membrane area and energy requirement for CO 2 capture. Hence, energy and environmental performances of the NGCC integrated with the separation unit are assessed and compared to a baseline power plant without carbon dioxide removal

Asymptotic Energy Dependence of Hadronic Total Cross Sections from Lattice QCD

The nonperturbative approach to soft high-energy hadron-hadron scattering, based on the analytic continuation of Wilson-loop correlation functions from Euclidean to Minkowskian theory, allows to investigate the asymptotic energy dependence of hadron-hadron total cross sections in lattice QCD. In this paper we will show, using best fits of the lattice data with proper functional forms satisfying unitarity and other physical constraints, how indications emerge in favor of a universal asymptotic high-energy behavior of the kind B log^2 s for hadronic total cross sections.Comment: Revised and extended version; 29 pages, 4 figure

Critical Temperature tuning of Ti/TiN multilayer films suitable for low temperature detectors

We present our current progress on the design and test of Ti/TiN Multilayer for use in Kinetic Inductance Detectors (KIDs). Sensors based on sub-stoichiometric TiN film are commonly used in several applications. However, it is difficult to control the targeted critical temperature $T_C$, to maintain precise control of the nitrogen incorporation process and to obtain a production uniformity. To avoid these problems we investigated multilayer Ti/TiN films that show a high uniformity coupled with high quality factor, kinetic inductance and inertness of TiN. These features are ideal to realize superconductive microresonator detectors for astronomical instruments application but also for the field of neutrino physics. Using pure Ti and stoichiometric TiN, we developed and tested different multilayer configuration, in term of number of Ti/TiN layers and in term of different interlayer thicknesses. The target was to reach a critical temperature $T_C$ around $(1\div 1.5)$ K in order to have a low energy gap and slower recombination time (i.e. low generation-recombination noise). The results prove that the superconductive transition can be tuned in the $(0.5\div 4.6)$ K temperature range properly choosing the Ti thickness in the $(0\div 15)$ nm range, and the TiN thickness in the $(5\div 100)$ nm rang

Development of microwave superconducting microresonators for neutrino mass measurement in the HOLMES framework

The European Research Council has recently funded HOLMES, a project with the aim of performing a calorimetric measurement of the electron neutrino mass measuring the energy released in the electron capture decay of 163Ho. The baseline for HOLMES are microcalorimeters coupled to Transition Edge Sensors (TESs) read out with rf-SQUIDs, for microwave multiplexing purposes. A promising alternative solution is based on superconducting microwave resonators, that have undergone rapid development in the last decade. These detectors, called Microwave Kinetic Inductance Detectors (MKIDs), are inherently multiplexed in the frequency domain and suitable for even larger-scale pixel arrays, with theoretical high energy resolution and fast response. The aim of our activity is to develop arrays of microresonator detectors for X-ray spectroscopy and suitable for the calorimetric measurement of the energy spectra of 163Ho. Superconductive multilayer films composed by a sequence of pure Titanium and stoichiometric TiN layers show many ideal properties for MKIDs, such as low loss, large sheet resistance, large kinetic inductance, and tunable critical temperature $T_c$. We developed Ti/TiN multilayer microresonators with $T_c$ within the range from 70 mK to 4.5 K and with good uniformity. In this contribution we present the design solutions adopted, the fabrication processes and the characterization results

Drinking water supply in resilient cities: Notes from L'Aquila earthquake case study

Disasters impacts on urban environment are the result of interactions among natural and human systems, which are intimately linked each other. What is more, cities are directly dependent on infrastructures providing essential services (Lifeline Systems, LS). The operation of LS in ordinary conditions as well as after disasters is crucial. Among the LS, drinking water supply deserves a critical role for citizens. The present work summarizes some preliminary activities related to an ongoing EU funded research project. The main aim of the paper is to define a System Dynamic Model (SDM) to assess the evolution of resilience of a drinking water supply system in case of natural disasters, with particular attention to the role of both ‘structural’ and ‘non-structural’ parameters. Reflections are carried out on L’Aquila (Italy) case study, since drinking water infrastructures were significantly stressed during the 2009 earthquake, causing a limited functionality in the aftermath of the event. Furthermore, the reallocation of citizens in temporary shelters determined a change in the demand pattern, requiring a dynamic adaptation of the infrastructure. Based on an innovative approach to resilience, the model was developed also to simulate different emergency management scenarios, corresponding to different disaster management strategies

Permeability characterization of stitched carbon fiber preforms by fiber optic sensors

The in-plane and through thickness permeability of unidirectional stitched carbon fiber preforms have been determined through vacuum infusion tests. The impregnation of various dry preforms with different stitching characteristics has been monitored by fiber optic sensors that have been stitched together with the dry tow to manufacture the dry preform. The experimental infusion times have been fitted by a numerical procedure based on Finite Element (FE) processing simulations. A good agreement between the numerical and experimental infusion times has been found demonstrating the potentiality of the fiber sensor system as suitable tool to evaluate impregnation times and permeability characteristics