63,515 research outputs found
Storia mondiale dell'Italia
No full textUn racconto fatto di tanti racconti che ci parlano della mobilità degli uomini e delle cose, nello spazio e nel tempo. Conquiste, emigrazioni e immigrazioni, affari, criminalità, viaggi, miserie e ricchezze, invenzioni, vicende di individui, di gruppi e di masse, imperi, stati e città, successi e tracolli.Dall’uomo di Similaun agli sbarchi a Lampedusa, 180 tappe per riscoprire il nostro posto nel mondo.Una storia che coniuga rigore scientifico e gusto della narrazione. Che provoca, spiazza, sorprende e allarga lo sguardo.
«Senza ombra di dubbio la storia è l’arte di lasciarsi sorprendere.» Da Invito al viaggio di Patrick Boucheron, direttore dell’Histoire mondiale de la France
La parola ‘Italia’ definisce uno spazio fisico molto particolare nel bacino del Mediterraneo. Un luogo che è stato nel tempo punto di intersezione tra Mediterraneo orientale e occidentale, piattaforma e base di un grande impero, area di massima espansione del mondo nordico e germanico e poi di relazione e di conflitto tra Islam e Cristianità. E così, via via, fino ai nostri giorni dove l’Italia è uno degli approdi dei grandi flussi migratori che muovono dai tanti Sud del mondo. Questa peculiare collocazione è la vera specificità italiana, ciò che ci distingue dagli altri paesi europei, e ciò che caratterizza la nostra storia nel lungo, o meglio nel lunghissimo periodo. La nostra cultura, la nostra storia, quindi, possono e debbono essere indagate e, soprattutto, comprese anche in termini di relazione tra ciò che arriva e ciò che parte, tra popoli, culture, economie, simboli. La Storia mondiale dell’Italia vuole ripercorrere questo cammino lungo 5000 anni per tappe: ogni fermata corrisponde a una data e ogni data a un evento, noto o ignoto. Le scelte risulteranno spesso sorprendenti, provocheranno interrogativi, faranno discutere sul perché di molte presenze e di altrettante esclusioni. La storia, ancora una volta, si dimostra un antidoto alla confusione e al disorientamento del nostro tempo. Perché ci racconta come le sfide a cui siamo sottoposti non siano inedite. Perché porta in evidenza la complessità ma anche la ricchezza della relazione tra l’Italia e il resto del mondo. Perché, soprattutto, fa comprendere che, quando si è perso l’orientamento della nostra collocazione spaziale, lunghi e disastrosi periodi di decadenza hanno fatto sparire, quasi per magia, l’Italia dalle mappe geografiche
Performance of an imaging system based on silicon pixel detectors of different thickness
No full textTo compare the characteristics of imaging systems based on pixel detectors of different thickness, we have measured the respective imaging capabilities, spatial resolution and spectroscopic characteristics. Each system consists of a single photon counting chip, developed in the framework of the Medipix Collaboration, bump bonded to a silicon detector. The detector is a matrix of 64 x 64, square pixels, with 170 mu m pitch and thickness ranging from 300 to 800 mu m. As expected, the intrinsic detection efficiency increases with the detector thickness; nevertheless the spatial resolution can be affected by a charge sharing mechanism between adjacent pixels due to charge diffusion. The aim of the work reported in this paper is to demonstrate that, optimizing the settings of the image systems, we can increase the detection efficiency without losing in spatial resolution. RI Dalla Betta, Gian-Franco/I-1783-201
Optimized complex signals for Eddy Current Testing
No full textThe choice of optimized excitation devices and strategies is now interesting recent studies about Non Destructive Eddy Current Testing (ND-ECT). Recently, the attention has been paid to the use of complex excitation signals, meant as signals different from the sinusoidal ones and with wide frequency content. In particular, some studies have highlighted their suitability, respect to the sinusoidal one, in supporting the measurement, detection and quantification stages when 'difficult cases' are explored (i.e. very short or annealed cracks). Generally, two class of signal have been proposed in literature. They concern with signals that have to be analysed in the time domain and signals analysed in transformed domains. The former class is represented by signal as the pulsed or pseudo-noise, while the latter contains signal as the chirp or multi-frequency as the best candidate. The author have placed their attention to this second class of signal and in this paper they propose an experimental comparison among different realization of these excitation signals suitably designed to improve the quality of experimental data when difficult cases are experienced
Image quality and spectroscopic characteristics of different silicon pixel imaging systems
No full textImaging capabilities, spatial resolution and analysis have been performed to compare the characteristics of imaging systems based on pixel detectors of different thickness. Each system consists of a single photon counting chip (PCC), developed in the framework of the Medipix Collaboration [1], bump bonded to a silicon detector. The detector is a matrix of 64 x 64 square pixels, with 170 mu m pitch and thickness ranging from 300 to 800 an. As expected, the intrinsic detection efficiency increases with detector thickness (for 22 keV photons the detection efficiency doubles in the examined thickness range [2]), nevertheless the spatial resolution can be affected by a charge sharing mechanism between adjacent pixels due to charge diffusion. We have studied this effect and its dependence on the detector bias voltage and the threshold value of PCC with the aim of optimizing both the detection efficiency and the spatial resolution. RI Dalla Betta, Gian-Franco/I-1783-201
A phenomenological model for predicting the early development of the flame kernel in spark-ignition engines
No full textThis work presents a simple and effective phenomenological model for the prediction of the early growth of the flame kernel in SI engines, including its initiation as a result of the electrical breakdown of the fuel/air mixture between the spark plug electrodes. The present model aims to provide an improved description of the ignition-affected early phases of flame kernel development compared to the majority of models currently available in literature. In particular, these models focus on electrical energy supply and turbulence, whereas the stretch-induced kernel growth slowdown is quantified with linear models that are inconsistent with the small kernel radius. For the flame kernel initiation, this model replaces the current methods that rely on 1D heat diffusion within a plasma column with a more consistent analysis of post-breakdown conditions. Concerning the kernel growth, the present model couples the mass and energy conservation equations of a spherical kernel with the species and temperature profiles outside of it. This combination leads to a non-linear description of the flame stretch, according to which the kernel development is controlled by the Lewis-number-dependent balance between the heat gained via combustion and the heat lost via thermal diffusion. As a result, the kernel temperature differs from the adiabatic flame temperature, causing the laminar flame speed to change from its adiabatic value and ultimately affecting the overall kernel development. Kernel growth predictions are conducted for laminar flames and compared to literature data, showing a satisfactory agreement and highlighting the ability to describe the stretch-induced kernel slowdown, up to its possible extinction. A good agreement with literature data is also obtained for kernel expansions under moderately turbulent conditions, typical of internal combustion engines. The simple formulation of the present model enables swift integration into phenomenological combustion models for spark-ignition engines, while simultaneously offering useful insight into the early kernel development even for CFD-based approaches
The effect of different medium compositions and LAB strains on fermentation Volatile Organic Compounds (VOCs) analysed by Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS)
No full textLactic acid bacteria (LAB) fermentation is a viable approach for producing plant-based flavour compounds; however, little is understood about the impact of different LAB strains and medium compositions on the production of volatile organic compounds (VOCs). This study investigated the impact of the addition of individual amino acids (AAs) (L-leucine, L-isoleucine, L-phenylalanine, L-glutamic acid, L-aspartic acid, L-threonine, or L-methionine) to a defined medium (DM) on the generation of VOCs (after 0, 7, and 14 days) by one of three LAB strains (Levilactobacillus brevis WLP672 (LB672), Lactiplantibacillus plantarum LP100 (LP100), and Pediococcus pentosaceus PP100 (PP100)), using proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS). The concentration of m/z 45.031 (t.i. acetaldehyde) was significantly (p < 0.05) higher after 7 days of fermentation by LP100 in the DM supplemented with threonine compared to all other media fermented by all three strains. The concentrations of m/z 49.012 (t.i. methanethiol) and m/z 95.000 (t.i. dimethyl disulfide) were significantly (p < 0.05) higher after 7 days of fermentation by either LP100, PP100, or LB672 in the DM supplemented with methionine compared to all other media. Information on the role of individual AAs on VOCs generation by different LAB strains will help to guide flavour development from the fermentation of plant-based substrate
Models for optimally controlling varicella and herpes zoster by varicella vaccination: a comparative study
No full textThe introduction of mass vaccination against Varicella-Zoster-Virus (VZV) is being delayed in many European countries mainly because of the “fear” of a subsequent boom in natural herpes zoster (HZ) incidence in the first decades after the initiation of vaccination, caused by the expected decline in the protective effect of natural immunity boosting due to reduced virus circulation. Optimal control theory has proven to be a successful tool in understanding ways to curtail the spread of infectious diseases by devising the optimal disease intervention strategies. In this paper, we describe how a reduced ‘toy’ model can extract the essentials of the dynamics of the VZV transmission and reactivation in case of the study of optimal paths of varicella immunization programs. Results obtained using different optimization approaches are compared with the ones of a more realistic age-structured model. The reduced model shows some unreliable predictions in regards of model time scales about herpes zoster dynamic; nevertheless, it is able to reproduce the main qualitative dynamic of the more realistic model to the different optimization problems, while requiring a minimal number of parameters to be identified. [Figure not available: see fulltext.]
Problematiche di misura in campo della trasmittanza termica negli edifici mediante tecnica termoflussimetrica
No full textUniqueness results for strongly monotone operators related to Gauss measure
No full textIn the present paper we prove some uniqueness results for weak solutions to a class of problems, whose prototype is
−div ((ε + |∇u|^2)^{(p−2)/2 ∇uφ) = f φ in Ω
u = 0 on ∂Ω,
where ε ≥ 0,1 < p < +∞, φ(x) is the density of the N-dimensional Gauss measure, Ω is an open subset of RN (N > 1) with Gauss measure less than one and datum f belongs to the natural dual space. When p ≤ 2 we obtain a uniqueness result for ε = 0. While for p > 2 we have to consider ε > 0 unless the sign of f is constant. Some counterexamples are given too
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