55 research outputs found
Risorse digitali per la didattica: una rassegna ragionata
No full textThe paper presents a reasoned review of digital resources useful for historians and the teaching of public history. This review will not be limited only to the tools of search and treatment of sources on the web, but will be directed above all to provide a guidance framework - which will be by the very nature of the digital constantly evolving over time - of those tools, methods and narratives that make use of digital to enhance teaching and research.F. Bellacci, "Risorse digitali per la didattica: una rassegna ragionata", in La Public History tra scuola, università e territorio. Una introduzione operativa, Firenze: University Press, pp. 111-12
A Novel Testing Methodology to Predict the Endurance of Ball Joints in Absence of Lubrication at High Temperature
No full textThe enhancement of the operational flexibility of axial expanders can be obtained through the implementation of Nozzle Guide Vane (NGV). This design architecture includes moving parts typically sustained by ball joints, whose wear behavior might be important to define the maintenance interval of the expander and define its operational availability. This is especially true when considering challenging loading and temperature conditions. Usually, tribological tests are performed by pin-on disk or similar test methods. However, these techniques neglect important factors as actual sliding zone and contact morphology, which can be fundamental for ball joints.
This work deals with the design of an innovative experimental test procedure for the characterization of the tribological behavior of ball joints considering the actual operating conditions of a NGV at 500°C. The core of the methodology is a customized test bench specifically designed to investigate actual commercial ball joint in field conditions. Details on the design phase and on the commissioning of the experimental set-up are given. The results of the experimental campaign performed on this novel test bench are presented: the chosen test matrix explores a wide spectrum of load and sliding speed. Specimen pre-load and working velocity have been scaled-up to achieve viable testing duration. The test bench was employed on three different kinds of commercial ball joints for high-temperature applications in absence of lubrication. Measurement of diametral clearance and friction in worn conditions were also performed. The results discussion allowed to choose the most suitable solution for a specific design targeting 50000 working hours
Microstructural, mechanical and corrosion characterization of electroless Ni-P composite coatings modified with ZrO2 reinforcing nanoparticles
No full textThis study aims to develop medium P (MP, 6 wt%) and high P (HP, 11 wt%) Ni-P-ZrO2 nanocomposites on F22 steel substrate using an original lead-free and surfactant-free solution and to quantitatively relate nanocomposite characteristics to microhardness improvement and corrosion resistance. Incorporation, dispersion and distribu-tion of the nanosized reinforcing phase were evaluated quantitatively by coupling Scanning Electron Microscope (SEM) imaging acquisition with original procedure for image processing and analysis. X-ray Diffraction (XRD) analysis revealed that nanoparticles introduction does not alter microstructure, which remains amorphous for HP and nanocrystalline for MP. Significant differences in particles distribution are found between MP and HP nanocomposites, which are induced by the difference in plating rate of the two formulations. Faster growth of MP (approximate to 35 mu m/h) associates with greater enveloping capability, with higher incorporation and agglomeration phe-nomena that result in non-uniform microhardness across the thickness. Conversely, the slower growth of HP nanocomposites coatings (approximate to 20 mu m/h) relates to lower but uniform incorporation and good dispersion of the reinforcing nanoparticles. Effective dispersion strengthening was observed for nanoparticles concentration up to 13.5 g/l. Microhardness increase by >25 % was achieved for both MP and HP coatings. The combined effect of nanoparticles incorporation level and their agglomeration was systematically studied and a mathematical model was implemented. It was demonstrated that strengthening effectiveness depends on both the amount of embedded nanoparticles and the mean size of agglomerates, following a bi-liner relation that reliably predicts experimental microhardness. Potentiodynamic corrosion test revealed that introduction of ZrO2 nanoparticles enhance corrosion resistance of both MP and HP coatings. The presented hardening strategy for Ni-P coatings can be an efficient solution for midstream and downstream applications in the oil & gas industry, in order to increase service-life of components in contact with both wearing and corrosive media
POLYAKOV LOOPS AND FINITE-SIZE EFFECTS OF HADRON MASSES IN FULL LATTICE QCD
No full textPolyakov type loops are responsible for the difference between quenched and unquenched finite size effects on the QCD mass spectrum. With a numerical simulation, using appropriate sea quark spatial boundary conditions, we show that we can align the phases of spatial Polyakov loops in a predefined direction. Starting from these results, we propose a procedure to minimize fluctuations due to these effects in meson propagators. © 1995
Chapter La scuola media superiore a Cuba nei primi venti anni di Rivoluzione. Al servizio della collettività e dei piani economici del Partito
No full textThe history of the Cuban school is doubly intertwined with the history of the country’s social and economic evolution since the early days of the 1956 Revolution. Arguably, the escuela media superior has been the most subjected to experiments, reforms, successes, mistakes and difficulties, but it has been recognized as having a distinct degree of quality by international bodies, such as UNESCO. This ‘level’ of the Cuban educational system has assumed a fundamental role over the decades, after having resolved the shortcomings of the previous school system and having been adapted on several occasions to the changes in the socio-economic policies of the communist government. In fact, it trained qualified technicians essential to the economic development of Cuba and created a mass consciousness, whose unifying element resided in the collective commitment and not in that of the individual
A cent’anni dai ‘Fatti di Renzino’. Dalla celebrazione alle attività di Public History of Education nelle scuole di Foiano della Chiana
No full textThe paper shows Public History projects carried on in some school in Foiano della Chiana (Arezzo) in the last years. These projects were focused on the so-called "Fatti di Renzino", i.e. the army revolts organised in 1921 by socialists, communists and anarchiest in answer to fascists and their continuous, brutal attempts in sovverting liberal institutions
Chapter A cent’anni dai ‘Fatti di Renzino’. Dalla celebrazione alle attività di Public History of Education nelle scuole di Foiano della Chiana
No full textThe paper shows Public History projects carried on in some school in Foiano della Chiana (Arezzo) in the last years. These projects were focused on the so-called "Fatti di Renzino", i.e. the army revolts organised in 1921 by socialists, communists and anarchiest in answer to fascists and their continuous, brutal attempts in sovverting liberal institutions
Chapter A cent’anni dai ‘Fatti di Renzino’. Dalla celebrazione alle attività di Public History of Education nelle scuole di Foiano della Chiana
No full textChapter Risorse digitali per la didattica: una rassegna ragionata
No full textThe paper presents a reasoned review of digital resources useful for historians and the teaching of public history. This review will not be limited only to the tools of search and treatment of sources on the web, but will be directed above all to provide a guidance framework - which will be by the very nature of the digital constantly evolving over time - of those tools, methods and narratives that make use of digital to enhance teaching and research
- …
