1,354,465 research outputs found
LA BIBLIOTECA DI UN RE. LIBRI, MINIATURE E UMANISTI ALLA CORTE DI ALFONSO IL MAGNANIMO
No full textLA RELAZIONE HA PRESENTATO AD UNA PLATEA DI STUDENTI GLI INTERESSI CULTURALI CHE ANIMARONO ALFONSO IL MAGNANIMO A REALIZZARE IL SUO SCRIPTORIU
La corte napoletana di Alfonso il Magnanimo: il mecenatismo regio
No full textNella ricostruzione del mecenatismo regio, ho spostato l’attenzione dal piano delle reali o presunte qualità individuali di Alfonso il Magnanimo (sulle quali, a suo tempo, insisterono Benedetto Croce ed Ernesto Pontieri) a quello della costruzione della memoria del sovrano aragonese e all’elaborazione di un nuovo catalogo di virtù politiche; inoltre, ho guardato alla corte come al luogo di integrazione del ceto dirigente e di sperimentazione di nuove pratiche di comportamento sociale, per chiarire se i valori e gli stili comportamentali elaborati a corte siano rimasti confinati o meno ai membri del suo entourage
Contact anisotropy and coordination number for a granular assembly: a comparison between DEM simulation and theory
No full textWe study an ideal granular aggregate consisting of elastic spherical particles, isotropic in stress and anisotropic in the contact network. Because of the contact anisotropy, a confining pressure applied at zero deviatoric stress, produces shear strain as well as volume strain. Our goal is to predict the coordination number k, the average number of contacts per particle, and the magnitude of the contact anisotropy ɛ, from knowledge of the elastic moduli of the aggregate. We do this through a theoretical model based upon the well known effective medium theory. However, rather than focusing on the moduli, we consider their ratios over the moduli of an equivalent isotropic state. We observe good agreement between numerical simulation and theory
Development of a Scalable MMC Pulsed Power Supply through HIL Methodology
No full textNuclear fusion experiments are becoming one of the most interesting focuses of research, given the hope of generating programmable, safe, and green energy. Among them, ASDEX (axially symmetric divertor experiment) upgrade has been operating at the Max Planck Institute for Plasma Physics (IPP) research center since 1991. To ignite and confine the plasma, several coils must be supplied through controllable high-current pulsed power supplies. The toroidal field magnets are here considered and a modular multilevel converter (MMC)-like system was designed and tested thanks to a small-scale prototype in previous works. The MMC-like topology, consisting of full-bridge submodules (SMs) with IGBTs and supercapacitor and exploitable also for other industrial applications, was chosen because of its modularity, redundancy, fault tolerance, and large amount of stored energy. The prototype, made of four SMs, was necessary to highlight critical key points in the design process. However, its scalability must be further tested before building a full-scale power supply, meant to reach almost 2400 SMs to guarantee the energy required by the load. This paper aims at validating hardware-in-the-loop (a powerful, safe, and relatively inexpensive real-time simulation environment that enables testing with real control boards) as a useful technology for power supply scalability studies and not only for control strategy tests. The results obtained previously from the prototype will allow us to finally increase the number of SMs and test the MMC-like scalability
A micromechanical numerical analysis for a triaxial compression of granular materials
No full textWe focus on a triaxial compression at constant pressure in which a granular material, after an isotropic preparation, is sheared in a small range of monotone deformation. The aggregate is made by identical, elastic, spheres that interact through a non central contact forces. Because of the loading condition the material is transversely isotropic. Through a numerical analysis we show that aggregates with same pressure and porosity behave differently depending on the initial coordination number (i.e. the average number of contacts per particle). The relation of stress, volume change, elastic moduli and microstructure with the initial contact network is investigated.</p
Innovative solutions for the geo-chemo-mechanical stabilisation of marine sediments
No full textThe work displays the results of an intense experimental research into the geo-chemo-hydromechanical stabilisation of sediments dredged from a fill-in basin in the Port of Taranto (Ionian Sea, Italy). This research was conducted in collaboration with ETH-Zurich and Italcementi HeidelbergGroup and founded by a MIUR- PON RI DRSATE PhD grant.
Taranto, as many port areas worldwide, is facing the problems of disposing two materials currently considered as waste: dredged sediments and mussel shells.
Starting from this premise and on the basis of the extensive literature concerning the stabilisation of marine sediments with the use of hydraulic binders and the related environmental issues, this study proposes the treatment of Taranto sediments through innovative and eco-sustainable solutions. In detail, the stabilisation solutions in which commercial cements were replaced by mussel shell powder (CemShells) were widely illustrated based on the experimental tests conducted on three types of commercial cement: Type III Termocem Green Blast furnace cement, Type I traditional Portland Cement 52.5R and Sulfoaluminate cement.
In order to include the case of the treatment of contaminated sediments in the stabilisation solution, this study also focuses on the artificial contamination of sediments with 5000 ppm Lead to obtain heavy metal contaminated sediment and with 8% kerosene to obtain an organic contaminated sediment.
In the case of kerosene-contaminated sediment, Biochar was also tested as an extra additive of commercial cements used in the case of treatment of uncontaminated sediment. Moreover, in order to stabiles kerosene- polluted sediment, Biochar was also added to CemShells to form another Bio-Binders named CemShellBio.
In order to analyse the efficacy of the stabilisation solutions in terms of effectiveness and environmental sustainability, this study focused on multiscale and multidisciplinary investigations entailing the dredged unpolluted and polluted (artificially) sediments as well as the same materials when treated with the commercial cements and the original binders i.e., the CemShells and the CemShellBios.
The goal of the investigation was to obtain a complete information on the sediment behaviour at both micro- and macro- scale in the natural and treated state. The investigation focused on: i) Chemical, geochemical and thermal, ii) microstructural and iii) geotechnical characteristics of the natural and treated geomaterials.
Microstructural tests were carried out on more than 60 samples. The microstructural testing routine included: pore size distribution with mercury intrusion porosimetry analysis (MIP), microstructure morphology at high magnification imaging with scanning electron microscope (SEM) and mineralogical composition with X-Ray diffraction (XRD).
Chemical, geochemical, and thermal tests were carried out on more than 150 samples. The chemical and geochemical testing programme included measurements of pH, electrical conductivity (EC), cation exchange capacity (CEC), carbon content (TIC/TOC) on matrix solid. Moreover, measurement of Chlorides and Sulphate, pH, conductivity, and salinity were also conducted on curing water (and/or pore water in natural sediments). All geochemical tests aimed at studying the chemical interaction between the clay particles of sediments and the minerals of cements. In addition, they targeted the interaction of sediments and cements with mussel shells and Biochar.
Thermal tests included the thermogravimetry on treated sediment samples to quantify heat and hydration time occurring in the stabilisation process.
Finally, chemical tests were carried out on eluate of both untreated and treated sediments to study the chemical efficiency, in term of leachability, of each treatment.
Geotechnical tests were carried out on more than 80 samples. Standard procedures were properly adapted to consider the influence of salt in the pore fluid and organic compounds of the solid matrix. The geotechnical testing programme included tests the analysis of the physical properties, composition, and state of sediments. Moreover, oedometer tests were carried out to determine the 1D compression and consolidation properties of the soil and CIU triaxial tests were performed to measure isotropic compressibility and effective strength parameters. Furthermore, unconfined strength was also measured by means of unconfined compression test (UCT) and originally used texturometer tests.
The integration of the microstructural, geotechnical, and geochemical/chemical data produced a global picture on the effects of the chemo-mechanical interaction processes on the geotechnical behaviour of both untreated and treated sediments. This study can provide a useful guide towards an original, effective, and more sustainable stabilisation solution for unpolluted and polluted sediments
Failure in granular materials based on acoustic tensor: a numerical analysis
No full textWe investigate localization in granular material with the support of numerical simulations based upon DEM (Distinct Element Method). Localization is associated with a discontinuity in a component of the incremental strain over a plane surface through the condition of the determinant of the acoustic tensor to be zero. DEM simulations are carried out on an aggregate of elastic frictional spheres, initially isotropically compressed and then sheared at constant pressure p0. The components of the stiffness tensor are evaluated numerically in stressed states along the triaxial test and employed to evaluate the acoustic tensor in order to predict localization. This occurs in the pre-peak region, where the aggregate hardens under the circumstance to be incrementally frictionless: it is a regime in which the tangential force does not change as the deformation proceedes and, consequently, the deviatoric stress varies only with the normal component of the contact force
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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