The present work explores the theoretical basis of sound propagation through periodic media and provides experimental evidences of stop-band properties of sonic crystals, periodic arrays of scatterers immersed in air. In order to investigate the sound field generated by sonic crystals, three theoretical models are used. The band structures are analysed with the Plane Wave Expansion method, while the Multiple Scattering Theory is used to calculate the magnitude of the scattered sound field. The Finite Element analysis is used for both purposes and to provide a stronger bond between the calculations of the theoretical models and the experimental results. Experimental measurement campaigns are performed at the Open University, Milton Keynes (UK) and at the University of Bologna. The two laboratories offer different testing facilities, respectively an anechoic chamber and a large industrial hall. Three square unit cells are analysed, varying the lattice constant and/or the filling fraction in order to provide a correlation between the two experimental setups. Measurements are performed to assess the characteristics of the sound field transmitted and reflected from the arrays, posing a special attention to the contribution of side and top edge diffraction. The evanescent behaviour of modes inside the lattice has been investigated by carrying out Impulse Response measurements inside the crystal and testing, with an intensity probe, the components of the sound field that exit the crystal in the two main directions. Finally, standardised indices are calculated that allow to compare the screening performance of sonic crystals to those of common noise barriers. All measurements setups report coherent results among them and with respect to the theoretical calculations, representing a solid platform for further developments.

The world is stochastic and chaotic, and organisms have access to limited information to take decisions. For this reason, brains are continuously required to deal with probability distributions, and experimental evidence confirms that they are dealing with these distributions optimally or close to optimally, according to the rules of Bayesian probability theory. Yet, a complete understanding of how these computations are implemented at the neural level is still missing. We assume that the “computational” goal of neurons is to perform Bayesian inference and to represent the state of the world efficiently. Starting from this assumption, we derive from first principles two distinct models of neural functioning, one in single neuron and one in neural populations, which explain known biophysics and molecular processes of neurons. The models we propose suggest a new original interpretation for various neural quantities. Action potentials, which are usually considered the paramount form of communication between neurons, in our model of single neuron dynamics are reinterpreted as an internal communication channel. On the contrary, intracellular calcium concentration is interpreted as the most explicit representation of the external world inside the neuron. Specifically, we propose that calcium level represents the log-odds probability ratio of a particular hidden state in the world. Furthermore, we reinterpret synaptic vesicle release as a sampling process, which simulates the external world given all the available information. Finally, the neural population dynamics we propose interpret spontaneous neural activity as a process of sampling from the prior world statistics. This enables the system to implement a Markov Chain Monte Carlo algorithm that produces inference by sampling. The proposed models generate various observable predictions, which match experimental results about synaptic vesicle release, short-term synaptic potentiation, ions channels open probability, intracellular calcium dynamics and propagation, spike rate adaptation and neural receptive fields.

The first part of this work reports the elementary theory of the atomic photoeffect presented in a form that is suited for practical numerical calculation. A detailed derivation of subshell cross sections for both excitation and ionization, comprising the angular distributions of emitted photoelectrons, is presented taking into account the effect of the polarization of the photons. The theoretical formulas have been implemented in a computer program PHOTACS that calculates tables of excitation and ionization cross sections for any element and subshell. Numerical calculations are practicable for excitations to final states with the principal quantum number up to about 20 and for ionization by photons with energy up to about 2 MeV. The effect of the finite width of atomic energy levels is accounted for by convolving the calculated subshell cross section with a Lorentzian profile. The second part of this work reports unfolding strategies for correcting a radiation measurement from the effects of the detector-pulse handling circuitry system. These strategies comprise the correction from the effects of pulse pile-up (PPU) and the detector response function (DRF). A first principles balance equation for second order PPU is derived and solved for the particular case of rectangular pulse shape. A Monte Carlo (MC) strategy is then implemented in the code MCPPU (Multi-shape pulse pile-up correction) allowing handling more general cases. Regarding the DRF, computed with deterministic or MC codes, it is presented the new tool RESOLUTION which introduces in the computed DRF the effects of energy resolution and incomplete charge collection. In the end the computer program UMESTRAT (Unfolding Maximum Entropy STRATegy) is presented in an updated version which include a new constrain to the total number of photons of the spectrum, which can be easily determined by inverting the diagonal efficiency matrix.

In modern nuclear technology, integral reactor parameter uncertainty evaluation plays a crucial role for both economic and safety purposes. Target accuracies for operating and future nuclear facilities can be obtained only if the available simulation tools, such that computational platforms and nuclear data, are precise enough to produce reduced biases and uncertainties on target reactor parameters. The quality of any engineering parameter uncertainty quantification analysis strongly depends on the reliability related to the covariance information contained in evaluated libraries. To propagate properly nuclear data uncertainty on nuclear reactor parameters, science-based variance-covariance matrices are then indispensable. The present work is devoted to nuclear data covariance matrices generation for reactivity loss uncertainty estimations regarding the Jules Horowitz Reactor (JHR), a material testing facility under construction at CEA-Cadarache (France). During depletion, in fact, various fission products appear and the related nuclear data are often barely known. In particular, the strenuous and worldwide recognized problem of generating fission product yields covariances has been mainly considered. Present nuclear data libraries such as JEFF or ENDF/B do not have complete uncertainty information on fission yields, which is limited to only variances. The main goal of this work is to generate science-based and physically consistent fission yields covariances to be associated to the existing European library JEFF-3.1.1. Variance-covariance matrices have been evaluated using CONRAD (COde for Nuclear Reaction Analysis and Data assimilation, developed at CEA-Cadarache) for the most significant fissioning systems.

The dissertation focuses on several aspects of non-equilibrium atmospheric plasma technology, also known as cold atmospheric plasma (CAP) technology, including the design, the diagnostic and the optimization of CAP sources for biomedical applications. The first part of the dissertation concerns the characterization of a single electrode atmospheric pressure plasma jet (APPJ) through various diagnostic techniques, including ICCD and Schlieren high speed imaging. First, the results for the APPJ freely expanding in atmosphere are presented along with the detailed description of the methodology developed for the ICCD analysis of plasma discharges driven by sub-microsecond voltage pulses. Second, results on the investigation on the APPJ source while impinging on a liquid substrate are shown to highlight the influence of the presence of the liquid substrate on the characteristics of the plasma discharge. In the second part of the dissertation focuses on the application of CAP technology in various branches of the medical field. The applications reported in this dissertation include: plasma treatment of soft reline palatal obturators prostheses for bacterial decontamination and reduction of bacteria adhesion; plasma direct and indirect treatment of L5178Y lymphoma cells to investigate the fundamental mechanisms promoting cell death and cell-cycle arrest; plasma treatment of tooth root canal dentin in standard dental procedures for the enhancement of the adhesion of resin composites for dental restorations. Overall, all findings support the feasibility of these plasma applications and help in the understanding of some of their governing mechanisms.

In this Thesis, new simulation codes for the evaluation of a heat pump system seasonal performance are presented. The codes apply to electric air-to-water and ground-coupled heat pump systems based on a vapor compression cycle, used for building heating, cooling and domestic hot water production. Numerical models are developed to simulate different kinds of air-to-water heat pumps by means of the bin-method. The models take into account the different operating modes of mono-compressor on-off, multi-compressor and inverter-driven heat pumps. The heat pump system seasonal performance is analyzed in terms of SCOP and SEER in relation to the thermal characteristics of the building, the climate of the location and the kind of heat pump control system. Furthermore, numerical codes for the hourly simulation of air-to-water heat pump systems are developed. The dynamic codes are implemented in the software MATLAB and apply to on-off and inverter-driven heat pumps for building heating, cooling and domestic hot water production, coupled with storage tanks and integrated by a gas boiler or electric heaters. The codes are used, in particular, to evaluate the seasonal performance and the primary energy consumption of the inverter-driven air-to-water heat pump employed in the retrofit of a residential building in Bologna (Italy). A code for the hourly simulation of ground-coupled heat pump systems is developed. The code, implemented in MATLAB, employs g-functions expressed in analytic form and applies to on-off and inverter-driven heat pumps, used for building heating and/or cooling. The whole system, composed by the heat pump and the coupled borehole heat exchanger field, can be simulated for several years. The code is applied to analyze the effects of the inverter and of the total length of the borehole field on the mean seasonal performance of a ground-coupled heat pump system designed for a residential house with dominant heating loads.

This PhD dissertation deals with the use of optical, non-invasive measurement techniques for the investigation of single and two-phase flows in microchannels. Different experimental techniques are presented and the achieved results are critically discussed. Firstly, the inverse use of the micro Particle Image Velocimetry technique for the detection of the real shape of the inner cross-section of an optical accessible microchannel is shown by putting in evidence the capability of this technique to individuate the presence of singularities along the wetted perimeter of the microchannel. Then, the experimental measurement of the local fluid temperature using non-encapsulated Thermochromic Liquid Crystal particles is discussed. A deep analysis of the stability of the color of these particles when exposed to different levels of shear stress has been conducted by demonstrating that these particles can be used for simultaneous measurements of velocity and temperature in water laminar flows characterized by low Reynolds numbers (Re < 10). A preliminary experiment where the TLC thermography is coupled to the APTV method for the simultaneous measurement of the three-dimensional velocity and temperature distribution in a microchannel is shown. Finally, an experimental analysis of the different flow patterns observed for an adiabatic air-water mixture generated by means of a micro T-junction is discussed. The main air-water mixture features have been deeply observed in 195 different experimental conditions in which values of superficial velocity ranging between 0.01 m/s and 0.15 m/s for both the inlet flows (air and water) are imposed. The flow patterns of the air-water mixture are strongly influenced by the value of the water superficial velocity; on the contrary, the air superficial velocity plays a secondary role for the determination of the characteristics of the bubbles (i.e. length).

The present PhD thesis summarizes the three-years study about the neutronic investigation of a new concept nuclear reactor aiming at the optimization and the sustainable management of nuclear fuel in a possible European scenario. A new generation nuclear reactor for the nuclear reinassance is indeed desired by the actual industrialized world, both for the solution of the energetic question arising from the continuously growing energy demand together with the corresponding reduction of oil availability, and the environment question for a sustainable energy source free from Long Lived Radioisotopes and therefore geological repositories. Among the Generation IV candidate typologies, the Lead Fast Reactor concept has been pursued, being the one top rated in sustainability. The European Lead-cooled SYstem (ELSY) has been at first investigated. The neutronic analysis of the ELSY core has been performed via deterministic analysis by means of the ERANOS code, in order to retrieve a stable configuration for the overall design of the reactor. Further analyses have been carried out by means of the Monte Carlo general purpose transport code MCNP, in order to check the former one and to define an exact model of the system. An innovative system of absorbers has been conceptualized and designed for both the reactivity compensation and regulation of the core due to cycle swing, as well as for safety in order to guarantee the cold shutdown of the system in case of accident. Aiming at the sustainability of nuclear energy, the steady-state nuclear equilibrium has been investigated and generalized into the definition of the ``extended'' equilibrium state. According to this, the Adiabatic Reactor Theory has been developed, together with a New Paradigm for Nuclear Power: in order to design a reactor that does not exchange with the environment anything valuable (thus the term ``adiabatic''), in the sense of both Plutonium and Minor Actinides, it is required indeed to revert the logical design scheme of nuclear cores, starting from the definition of the equilibrium composition of the fuel and submitting to the latter the whole core design. The New Paradigm has been applied then to the core design of an Adiabatic Lead Fast Reactor complying with the ELSY overall system layout. A complete core characterization has been done in order to asses criticality and power flattening; a preliminary evaluation of the main safety parameters has been also done to verify the viability of the system. Burn up calculations have been then performed in order to investigate the operating cycle for the Adiabatic Lead Fast Reactor; the fuel performances have been therefore extracted and inserted in a more general analysis for an European scenario. The present nuclear reactors fleet has been modeled and its evolution simulated by means of the COSI code in order to investigate the materials fluxes to be managed in the European region. Different plausible scenarios have been identified to forecast the evolution of the European nuclear energy production, including the one involving the introduction of Adiabatic Lead Fast Reactors, and compared to better analyze the advantages introduced by the adoption of new concept reactors. At last, since both ELSY and the ALFR represent new concept systems based upon innovative solutions, the neutronic design of a demonstrator reactor has been carried out: such a system is intended to prove the viability of technology to be implemented in the First-of-a-Kind industrial power plant, with the aim at attesting the general strategy to use, to the largest extent. It was chosen then to base the DEMO design upon a compromise between demonstration of developed technology and testing of emerging technology in order to significantly subserve the purpose of reducing uncertainties about construction and licensing, both validating ELSY/ALFR main features and performances, and to qualify numerical codes and tools.

No description available.

Quantum physics lends a view of space-time geometry as an emergent structure that shows classical features only at some observational level. The space-time manifold can be viewed as a purely theoretical arena, where quantum states and observables are defined, with the additional freedom of changing coordinates. We focus on spherically symmetric quantum sources, and determine the probability they are black holes. The gravitational radius is promoted to quantum mechanical operator acting on the ``horizon wave-function''. This formalism is applied to several sources with mass around the fundamental scale, as natural candidates of quantum black holes. This horizon quantum mechanics supports some features of BEC models of black holes. The Klein-Gordon equation for a toy graviton field coupled to a static matter current classically reproduces the Newtonian potential, while the corresponding quantum state is given by a coherent superposition of scalar modes. When N such bosons are self-confined in a volume of the size of the Schwarzschild radius, the horizon shows that their radius corresponds to a proper horizon whose related uncertainty is connected to the typical energy of Hawking modes: it is suppressed as N increases, contrarily to a single very massive particle. The spectrum of these systems is formed by a discrete ground state and a continuous Planckian distribution at the Hawking temperature representing the radiation. Assuming the internal scatterings give rise to the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function. The partition function follows together with the usual entropy law, with a logarithmic correction related to the Hawking component. The backreaction of radiating modes is also shown to reduce the Hawking flux, and eventually stop it.