809 research outputs found
[Collezioni Numismatiche Valerio Traverso di Genova, Mr Joseph Martini of N. Y. Monate greche e Romano]
No full text[Vente. Numismatique. 1931-02-25. Milan][Collection. Numismatique. Traverso, Valerio. 1931][Collection. Numismatique. Martini, Joseph. 1931]Avec mode text
Numerical Performance Investigation of a Hybrid eCVT Specialized Agricultural Tractor
No full textThe need for highly efficient agricultural machineries is increasing the interest of the research community and of industrial manufacturers towards the use of integrated electric systems in combination with traditional powertrain elements. In this work, a hybrid electric tractor with electric continuously variable transmission (eCVT) capabilities was studied to investigate their performance in comparison with that of traditional diesel-powered tractor designs. This hybrid electric configuration can be classified as a power-split architecture that aims to combine the best characteristics of both the simpler parallel and the series hybrid layout while minimizing their main drawbacks. An eCVT configuration can allow for optimizing the diesel operating point with respect to the current working conditions, and achieving peak power performance and energy saving with relatively small electric machines. The proposed hybrid eCVT (HeCVT) tractor architecture was studied using a numerical model that allowed for developing two different control strategies: a charge depleting mode enabling the driver to use full power for the most power-intensive scenarios and a charge sustaining mode developed to optimize efficiency and battery use along an entire work day. To test the proposed architecture, several tasks derived from experimental field measurements on a specialized agricultural tractor were used. HeCVT results were compared with a numerical model of the traditional tractor validated by these experimental data. The HeCVT tractor showed good performance in terms of peak power capabilities using a downsized diesel engine, and consistent fuel savings were obtained according to typical daily working scenarios
Analysis of Fuel Cell Systems for Off-Road Agricultural Vehicles
No full textL'abstract è presente nell'allegato / the abstract is in the attachmen
Comparative Analysis of Hybrid Electric Architectures for Specialized Agricultural Tractors
No full textIn this work, a comparative numerical analysis between the performance of a conventional specialized orchard tractor and those of three different hybrid electric tractor configurations is presented. The aim was to compare several powertrain configurations in the same working scenarios derived from field measurements. Peak power capabilities and endurance were numerically tested with specific load scenarios involving both transportation mission profiles and field activities with external implements powered through the power take off of the tractor. The proposed hybrid architectures were configured with the same battery-based energy storage system to perform the comparison with the same energy storage capabilities. Two parallel, two series and one electro-hydraulic hybrid configuration were modeled and tested through simulations. The parallel ones excelled in peak power performance, whereas the series configurations had the highest fuel savings. The electro-hydraulic configuration was proposed as an alternative able to allow for a downsized engine but also for the introduction of the Continuously Variable Transmission (CVT) functionality, which is always an interesting feature for such working machines
Design and Experimental Validation of a Scaled Test Bench for the Emulation of a Hybrid Fuel Cell Powertrain for Agricultural Tractors
No full textHybrid fuel cell powertrains are a promising strategy to reduce the environmental impact of vehicles and non-road mobile machinery. To preserve the state-of-health of fuel cells, an energy storage system with sufficient power capacity, such as ultra-capacitors or batteries, should be introduced in the system to help the fuel cell during sudden and abrupt changes in power demands. However, the presence of two or more energy sources necessitates the development of an energy management strategy. The energy management strategy should properly split the power request between the different energy sources. In this paper, the design and the experimental validation of a scaled test bench for the emulation of a fuel cell/battery powertrain for a vehicular application is presented. The fuel cell is emulated through an analogically controlled DC power source that reproduces its real voltage–current curve. To split the power between the emulated fuel cell and the batteries, controlled DC-DC is used and a simple energy management strategy based on a proportional-integral controller is developed. The external load is reproduced using a load unit composed of a programmable electronic load and a power supply. Experimental tests are performed to evaluate the system behaviour and to characterize its main components. The experimental results show that the system successfully emulates the powertrain in accordance with the proposed energy management strategy
Carbon Footprint Enhancement of an Agricultural Telehandler through the Application of a Fuel Cell Powertrain
No full textThe growing awareness about climate change and environmental pollution is pushing the industrial and academic world to investigate more sustainable solutions to reduce the impact of anthropic activities. As a consequence, a process of electrification is involving all kind of vehicles with a view to gradually substitute traditional powertrains that emit several pollutants in the exhaust due to the combustion process. In this context, fuel cell powertrains are a more promising strategy, with respect to battery electric alternatives where productivity and endurance are crucial. It is important to replace internal combustion engines in those vehicles, such as the those in the sector of Non-Road Mobile Machinery. In the present paper, a preliminary analysis of a fuel cell powertrain for a telehandler is proposed. The analysis focused on performance, fuel economy, durability, applicability and environmental impact of the vehicle. Numerical models were built in MATLAB/Simulink and a simple power follower strategy was developed with the aim of reducing components degradation and to guarantee a charge sustaining operation. Simulations were carried out regarding both peak power conditions and a typical real work scenario. The simulations’ results showed that the fuel cell powertrain was able to achieve almost the same performances without excessive stress on its components. Indeed, a degradation analysis was conducted, showing that the fuel cell system can achieve satisfactory durability. Moreover, a Well-to-Wheel approach was adopted to evaluate the benefits, in terms of greenhouse gases, of adopting the fuel cell system. The results of the analysis demonstrated that, even if considering grey hydrogen to feed the fuel cell system, the proposed powertrain can reduce the equivalent CO2 emissions of 69%. This reduction can be further enhanced using hydrogen from cleaner production processes. The proposed preliminary analysis demonstrated that fuel cell powertrains can be a feasible solution to substitute traditional systems on off-road vehicles, even if a higher investment cost might be required
Tragedia di un artista di strada. La pratica della cancellazione da eutanasia artistica ad articidio
No full textThis article investigates the role and meaning of practices of erasure in contemporary Italian street art culture. Taking Blu's choice of cancelling all his graffiti in the city of Bologna as a case study, I will investigate the limits and possibilities of this artistic performance in both political and social terms. Given the antagonist yet dialogic and dynamic relationship that connects street artists, civic institutions and urban spaces, I will argue that practices of erasure are a key component of the particular form of communication occurring among these actors. Through the analysis of #OccupyMordor, one of Blu's most famous works, I will describe the relationship the author entertained with the city of Bologna highlighting, at the same time, the structural problems raised by institutional museification projects
Comparative analysis of hybrid fuel cell powertrain architectures for orchard tractors using hardware-in-the-loop technique
No full textFuel cell systems represent a possible solution to improve the sustainability of vehicles requiring high endurance and compactness. Three different powertrains for an orchard tractor are proposed. The proposed systems feature the same fuel cell unit, but different auxiliary sources: a battery pack, a supercapacitor module and a hybrid unit comprising both. Furthermore, to make a fair comparison, the three architectures are designed considering the same overall volume. After defining the architectures, different rule-based strategies, namely power follower and fuzzy logic strategies, are defined to determine the power split among the different sources. Then, the three architectures are tested using a scaled Hardware-in-the-loop test bench according to typical work scenarios. The load profiles are derived from experimental data collected on a commercial orchard tractor. The architectures and energy management strategies are compared considering fuel economy and components durability. Analysing the results, the topology featuring the battery pack as additional power unit shows the higher lifetime expectancy for the fuel cell system, with an improvement ranging from +20 % to +200 % compared to the other two topologies. On the other hand, the differences in terms of fuel economy are considered not relevant compared to the differences in durability
Ascolto e partecipazione dei bambini nei rapporti intergenerazionali
No full textIl “riconoscimento” dei bambini come soggetti e attori sociali inseriti in strutture generazionali di potere rimanda direttamente ai temi della cittadinanza. Se queste due questioni, agency e cittadinanza, sono ormai riconosciute e approfondite nell’ambito delle sfere pubbliche specializzate, al di fuori di queste permane ancora forte la convinzione che i bambini si possano comprendere solo in funzione del loro sviluppo evolutivo e in quanto adulti in formazione. Così quando si affrontano i temi della diseguaglianza sociale associati alla realizzazione della democrazia si indicano spesso il genere oppure la classe sociale come elementi chiave con cui verificare il grado di sviluppo concreto delle politiche di welfare, dimenticandosi spesso che la dimensione generazionale costituisce al tempo stesso un’altra, certamente non l’unica, ma anch’essa imprescindibile, prospettiva su cui misurare il grado di maturità di una società democratica.
Si tratta di orientamenti la cui resistenza e forza sono sicuramente favoriti dall’operare di due principi regolatori tra loro in antagonismo: il ruolo attivo dei bambini nelle interazioni con gli adulti e nella costruzione della quotidianità si può attuare solo all’interno di un quadro di promozione e di protezione dei bambini realizzata dagli adulti che detengono la supremazia fisica, morale, sociale e politica dell’organizzazione societaria in cui i bambini, dalla nascita, si sono visti parte, non certo per loro scelta.
L’esercizio della cittadinanza da parte dei bambini richiama tre termini, tra loro strettamente collegati, che fanno parte in modo profondo del patrimonio retorico dei diritti e che in questi anni sono stati sempre più al centro di studi, dibattiti, confronti e precisazioni: la “voce”, l’ascolto e la partecipazione. Alcuni tendono a sovrapporli oppure a pensare il secondo come un’articolazione del terzo come accade nella ormai vasta pubblicistica di area anglosassone. Ciò perché manca, come sostengono diversi studiosi, un’elaborazione convincente oppure una riflessione articolata e compiuta di cosa questi tre elementi indichino nel campo di interesse della cittadinanza dei bambini.
Il presente contributo, in base alla rassegna di un’ampia letteratura di riferimento, mette in evidenza come ascoltare, seppur in modo attivo ed empatico, non implica necessariamente prender parte a nuove relazioni sociali intergenerazionali che favoriscono l’inclusione e riducono le simmetrie di potere tra bambini e adulti. Ascoltare non implica nemmeno prender direttamente o indirettamente parte alle decisioni o essere il decisore prevalente circa le scelte che riguardano la propria quotidianità oppure i processi sociali in cui si è coinvolti. In questo modo l’ascolto si configura al contempo sia come una dimensione propedeutica che interna alle diverse forme partecipative dei bambini e degli adolescenti.
Se l’ascolto è l’istanza attraverso cui si possono svelare le capacità, le competenze e la soggettività delle persone, la partecipazione è la pratica che a queste dimensioni affianca, più di altri diritti, quella relazionale (tra pari e con gli adulti) e di autonomia. In generale, ascolto e partecipazione sono in primo luogo gli strumenti, oltre che il fine, per il pieno svolgimento dei vari diritti dei bambini e per il loro pieno riconoscimento sociale e giuridico. Se la “voce” è la parola chiave nell’ascolto, nella partecipazione la parola chiave che assume maggior peso, seppur non in modo escludente, è l’”agency”
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