396 research outputs found
Melville, ispiratore di Quasimodo e Ghedini
No full textNote su Giorgio Federico Ghedini e la sua ricezione compositiva del Billy Budd dello statunitense Herman Melville (1819-1891), nonché sul confronto di tale ricezione con quella di Benjamin Britte
Modelling and Comparison of Different Design Solutions for DC Transferred Arc Plasma Cutting Torches
No full textModelling and Comparison of Different Design Solutions for DC Transferred Arc
Plasma Cutting Torches
V. Colombo, E. Ghedini
Department of Mechanical Engineering (D.I.E.M.) and Research Center for Applied Mathematics (C.I.R.A.M.)
Università di Bologna, Via Saragozza 8, 40123 Bologna, Italy
S. Dallavalle, M. Vancini,
Cebora S.p.A., Via Andrea Costa 24, 40057 Cadriano di Granarolo, Italy
The aim of this work is to investigate by means of a 2-D and 3-D FLUENT© based numerical model the behaviour of different types of transferred arc dual gas plasma torches used for cutting of metallic materials, putting into evidence the physical reasons for the industrial success of various design and process solutions appeared over the last years, such as: secondary gas swirl injections with different directions, various different approaches for the geometry of the plasma chamber, the effect of externally superimposed magnetic fields. Flow and heat transfer equations are solved with coupled electromagnetic ones, for a LTE optically thin plasma, while turbulence phenomena are taken into account by means of a k-ε RNG model. Simulations include a prediction of the thermal behaviour of the solid components of the torch head, including electrode and hafnium insert, thermal histories and trajectories of hafnium oxide particles emitted from it under idealized conditions and the efficiency of nozzle and electrode cooling systems in various operating conditions including gas mixtures (O2/air, H35/N2, N2/N2). Radiation is included in the calculation of heat transfer to the surfaces of the components using a customized Discrete Ordinate (DO) model. Results obtained from the simulations of one of the plasma torches here considered are also compared with experimental measurements in order to perform a validation of the model for what concerns pressure values in different regions of the device, and the gas mass flow rate during the working phase. For this purpose two suitably modified plasma torches with pressure and temperature measurement systems have been designed and used during realistic cutting conditions.
V. Colombo, E. Ghedini, S. Dallavalle, M. Vancini, 3-D Fluidynamic and Plasma Characterization of DC Transferred Arc Plasma Torches for Metal Cutting. 17th International Symposium on Plasma Chemistry (ISPC-17). Toronto, august 2005.
V. Colombo, E. Ghedini, G. Masini, D. Russo, S. Dallavalle, M. Vancini, 2-D And 3-D Fluidynamic And Plasma Characterization Of Dc Transferred Arc Plasma Torches For Metal Cutting, High Technology Plasma Processes 9 -HTPP9, St. Petersburg (2006); in press on Journal of High Temperature Material Processes
G. Ghedini. La lingua greca di Marco Aurelio Autonino ; parte prima i.Fonetica e morfologia
No full textBidez J. G. Ghedini. La lingua greca di Marco Aurelio Autonino ; parte prima i.Fonetica e morfologia. In: Revue belge de philologie et d'histoire, tome 7, fasc. 3, 1928. pp. 1053-1055
G. Ghedini. La lingua greca di Marco Aurelio Autonino ; parte prima i.Fonetica e morfologia
No full textBidez J. G. Ghedini. La lingua greca di Marco Aurelio Autonino ; parte prima i.Fonetica e morfologia. In: Revue belge de philologie et d'histoire, tome 7, fasc. 3, 1928. pp. 1053-1055
G. Ghedini. Lettere cristiane dai papyri greci del III e IV secolo
No full textBidez J. G. Ghedini. Lettere cristiane dai papyri greci del III e IV secolo . In: Revue belge de philologie et d'histoire, tome 3, fasc. 3, 1924. pp. 605-607
Variation in the structure of subtidal landscapes in the NW Mediterranean Sea
No full textCompounded effects of climate change and local human activities are threatening marine biodiversity worldwide. At a regional scale (10s to 100s km), comparisons among areas characterized by the prevalence of different human activities provide an insight into the effects of anthropogenic disturbances at multiple levels of ecological organization (i.e. from landscapes to assemblages). At the landscape scale (1000s m), we hypothesized that patchiness in habitat distribution and proportion of degraded assemblages would increase with increasing levels of disturbance, as a result of the decline of habitat-forming species. In addition, we hypothesized that prevailing human influences would affect the structure and variability of rocky benthic assemblages at smaller spatial scales (10s cm to 10s m). An extensive survey encompassing areas subjected to different human influences (i.e. from urbanized to protected areas) was carried out along the coasts of Tuscany (NW Mediterranean Sea). Seagrass beds and macroalgal canopy stands were the dominant habitats in relatively pristine areas, while macroalgal turfs and dead rhizomes of Posidonia oceanica were the most extended habitats in urbanized areas. In general, habitat fragmentation did not vary among areas subjected to different human influences. At a smaller scale (10s cm to 10s m), urbanization favored dominance by opportunistic species and promoted biotic homogenization. Our study shows that regional variations in the composition of landscapes and assemblages can be predicted on the basis of prevailing human activities. Our results also suggest that variations in landscape composition could be an effective descriptor of the effects of multiple human stressors in marine environments.L. Tamburello, L. Benedetti-Cecchi, G. Ghedini, T. Alestra, F. Buller
Of drills and bones: Giovanni Ghedini and the origin of bone marrow biopsy
No full textBone marrow (BM) studies are pivotal for the diagnosis of haematological disorders. Their introduction into clinical haematology dates back to the work of Giovanni Ghedini (1877–1959), an Italian physician who first conceived BM sampling in 1908. Ghedini's proposal stemmed from his clinical experience and from the scientific developments that characterised his epoch. By presenting selected passages of Ghedini's publications, this report considers the theoretical and historical bases of his work and analyses its practical implications for modern haematology
Metal modified TiO2 for CO2 photoreduction in unconventional conditions
No full textCO2 photoreduction, a growing field in green catalysis, shows great potentialities to avoid fossil fuels exploitation and to obtain C-based solar fuels through a sustainable process using water as a reductant and light irradiation as only energy input [1]. However, many efforts need to be made to have a substantial breakthrough to increase the efficiency of the whole process. To pursue this aim, different strategies can be followed, such as reaction conditions implementation and photocatalyst formulation.
Process efficiency is strictly dependent on chosen photocatalytic materials. In particular titanium dioxide, the most commonly used material, needs to be modified in order to boost light harvesting and increase photoactivity [2]. In this work, TiO2 was modified in order to increase electron mobility on photocatalytic surface. In particular, copper oxide was introduced as a co-catalyst and gold nanoparticles as surface plasmonic agents.
Some of the authors reported that unconventional conditions are able to increase solar fuels production from CO2 photoreduction in liquid phase, enhancing in particular CO2 absorption in aqueous media and tuning selectivity to desired products [3]. A novel pressurized liquid phase reactor was employed to study photocatalytic activity of these materials in liquid phase and reaction conditions were chosen in order to enhance CO2 absorption in liquid phase. In photocatalytic tests it was observed the formation of different liquid and gaseous products such as formic acid, formaldehyde, methanol, methane and hydrogen. The different materials provide a significant difference in both activity and product distribution. Photocatalytic behaviours were correlated to different physicochemical properties that were investigated though several techniques.
References
[1] O. Ola, M. Maroto-Valer, Journal of Photochemistry and Photobiology C: Photochemistry Reviews 24 (2015) 16-42
[2] A. Olivo, V. Trevisan, E. Ghedini, F. Pinna, C.L. Bianchi, A. Naldoni, M. Signoretto, Journal of CO2 Utilization 12 (2015) 86-94
[3] I. Rossetti, A. Villa, M. Compagnoni, L. Prati, G. Ramis, C. Pirola, C.L. Bianchi, W: Wang, D. Wang, Catalysis Science and Technology 5 (2015) 4481 - 448
Iridium and rhodium nitrosyl complexes with methylated 1,10-phenanthroline and 2,2'-bipyridine ligands
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