626 research outputs found
Tecniche e materiali innovativi per una produzione efficiente ed ecosostenibile
No full textLa competitività delle aziende dipende dalla capacità di innovare prodotti e processi, tenendo in conto la gestione sostenibile delle risorse e la riduzione di impatti ambientali e sociali per il miglioramento della qualità della vita. Ciò implica un profondo cambiamento verso sistemi di produzione e di consumo più sostenibili accompagnato da un cambiamento culturale e di stili di vita, ovvero una transizione verso una green economy. L’eco-innovazione è il principale strumento della green economy e, dunque, dello sviluppo sostenibile. In particolare, grazie all’introduzione di una o più tecnologie ecoinnovative, le aziende possono conseguire una riduzione degli impatti ambientali osservabile lungo tutto il ciclo di vita dei propri prodotti e/o processi.
L’ecoinnovazione riguarda lo sviluppo di tecnologie di produzione più sostenibili ma anche l’utilizzo di materiali leggeri ed ecoinnovativi, soprattutto nel settore dell’automotive e in quello aeronautico, dove è più significativa la riduzione delle emissioni di CO2 connesse ad un risparmio del consumo di carburante.
Alla luce di tutto ciò, lo scopo del presente lavoro di tesi è quello di investigare da più prospettive il concetto di sostenibilità ambientale nei processi manifatturieri.Nowadays, companies’ competitiveness depends on their ability to innovate products and processes, keeping in mind that a better quality of life is given by the sustainable management of resources and a lower impact on society and the environment. This involves a deep change towards more sustainable production and consumption systems along with a change in culture and life style, i.e. a transition towards a green economy. Eco-innovation is the main instrument of green economy and, consequently, of sustainable development.
In particular, thanks to the introduction of an environmentally friendly system, companies can achieve a reduction of their carbon footprint that can be observed along the entire life cycle of their products or processes.
The eco-innovation can consist in the development of manufacturing technologies more sustainable as well as in the development of new Eco-friendly and lightweight materials, especially in the automotive and aeronautical sectors, where the environmental benefit is greater with the reduction of carbon emission, coupled with the savings in fuel.
In light of this, the overall purpose of the work developed in this thesis is to analyze the environmental sustainability concept in the manufacturing processes through a Multiple-Perspective Approach
Subharmonically pumped direct vector modulator
No full textAn attractive means to reduce the complexity of the radio-frequency hardware is obtained by direct modulation. An alternative architecture of a direct vector modulator is described, working over the ETSI 15 GHz band, realised using a subharmonic mixer. It includes on-board phase tuning for correcting the quadrature phase error
Forming behaviour of friction stir lap welded joints
No full textFriction stir lap welding was performed on two and on three sheets in aluminium alloy, respectively. The effect of the stacking mode of the sheets with different thicknesses and that of the tool probe geometry were analyzed at given rotational and welding velocities. The welding results were studied in the weld joint section perpendicularly to the welding velocity direction.
It resulted that, in the case of the stack of three sheets, the thinnest blank has to be positioned in the middle, in order to get a sound weld. In the two sheet stacking, the thinnest blank must be placed below the thickest one. The subsequent upsetting of the lap joint at different temperatures produced an homogeneous microstructure even when the thick tool was used for the friction stir welding. It was observed that low upsetting load values, related to low friction amounts, could determine improved homogenization in terms of microstructure and deformation levels
A high performance C-band subharmonic modulator exploiting branch-line couplers as input/output ports
No full textDigital direct modulation at microwave frequencies represents the best way to develop a component requiring a simple system design, low cost and compact size. In this paper, a novel architecture of a C-band modulator, which exploits a branch line hybrid to provide an equal amplitude division of Local Oscillator signal (LO), is proposed and experimental results are reported. Using of subharmonic mixer offers the following advantages: inherent Local Oscillator/Radio Frequency (LO/RF) isolation, no bias network is required, low power of LO, rejection of LO's even harmonics. Measured conversion loss is around lOdBc with LO rejection approximately 29dBc and image frequency rejection around 26dBc. At last, the modulator exhibits Radio Frequency/Intermediate Frequency (RF/IF) and RF/LO isolation levels better than 30 dBc. A comparison is also reported to evaluate the performances of three different topologies of the same direct vector modulator
SALDATURA FRICTION STIR LAP DI LAMIERE
No full textSono state condotte saldature friction stir lap rispettivamente con due e con tre lamiere. In entrambi i casi sono state utilizzate lamiere di spessore differente, conservando il medesimo spessore totale.
Inoltre nella saldatura a tre lamiere sono state utilizzate anche differenti leghe di alluminio. L'obiettivo dell'articolo è stato quello di individuare e verificare le condizioni di saldatura in termini della velocità di rotazione dell'utensile, della velocità di traslazione, della configurazione dell'utensile nelle due diverse configurazioni di saldatura friction stir lap a due ed a tre lamiere. I valori ottenuti in termini di resistenza per unità di larghezza dei provini sono prevalentemente funzione della velocità di traslazione impostata durante la saldatura. Inoltre il flusso plastico del materiale che si genera, pur essendo simile sia nel caso di saldatura a due lamiere che in quello della saldatura a tre lamiere,
determina nel secondo caso una saldatura che comprende due superfici di contatto con un leggero miglioramento nel comportamento a trazione
The Pottesman Collection in the British Museum. Early Dynastic and Sargonic administrative texts. With an Appendix on a Palmyrene Inscription
No full textEdizione, trascrizione, traduzione e commento di un frammento di iscrizione palmirena inedita presente nella collezione Pottesman del British Museum (Appendice Agostini).The British Museum houses a small collection of six cuneiform tablets and a Palmyrene dedicatory inscription purchased in 1987 from the private collection of Solomon Pottesman. The aim of the present contribution is to provide a catalog of this lot and an edition of the so far unpublished cuneiform texts. In the appendix, Alessio Agostini added the edition of the Palmyrene inscription, which would have otherwise gone beyond the capabilities of the present author
Tool wear and hole quality in drilling of CFRP/AA7075 stacks with DLC and nanocomposite TiAlN coated tools
No full textDrilling of multi-material stacks, constituted by two laminates in carbon fiber reinforced plastic and a core plate in AA7075, was widely investigated. Experiments were performed on a 5-axis CNC machining center, equipped with a dynamometer for the thrust force measurement, using different twist drills coated with DLC and nanocomposite TiAlN. Each hole, 6.8 mm in diameter, was obtained with a chip removal cycle involving two passes spaced by a back motion. Optical and scanning electron microscopy techniques were used to quantify tool wear and delamination of composite layers. Finally, hole diameter in the different layers of composite/aluminum stack was measured by means of a coordinate measuring machine. The analysis of experimental results showed that the main wear mechanisms operating during drilling of stacks with the DLC coated drill are chipping, edge rounding and abrasion, while wear is mainly affected by abrasion with the nanocomposite TiAlN coated tool, even though adhesion of AA7075 particles on the rake surface also occurs. The evolution of flank wear with number of holes showed that the DLC coated drill underwent a much lower wear than the TiAlN coated one. Thrust force on both CFRP and AA7075 exhibited an increase with number of holes. Delamination of composite layer was already present in drilling performed with the wear free tool. However, a growth in delamination with number of holes was observed. Progression of hole diameter with number of holes, in the three different layers of multi-material stack, showed that diameter decreases with rising number of holes. Finally, systematic correlations between tool wear, thrust force, hole diameter and delamination factor were defined. Owing to the plot characteristics, the third-degree polynomial regression was found adequate to model interactions among the process results
Recensione di Cecilia Falchini (2023). Ruperto di deutz - Un’intima familiarità. Antologia, Edizioni Qiqajon (Comunità di Bose), Magnano (Bi), 281 pp.
No full textReview of Cecilia Falchini (2023). Ruperto di deutz - Un’intima familiarità. Antologia, Edizioni Qiqajon (Comunità di Bose), Magnano (Bi), 281 pp.
Author: Alessio MagogaRecensione di Cecilia Falchini (2023). Ruperto di deutz - Un’intima familiarità. Antologia, Edizioni Qiqajon (Comunità di Bose), Magnano (Bi), 281 pp.
Autor: Alessio Magog
Handheld-Impedance-Measurement System with seven-decade capability and potentiostatic function
No full textThis paper describes design and test of a new impedance-measurement system for nonlinear devices that exhibits a seven-decade range and works down to a frequency of 0.01 Hz. The system is specifically designed for electrochemical measurements, but the proposed architecture can be employed in many other fields where flexible signal generation and analysis are required. The system employs an unconventional signal generator based on two pulsewidth modulation (PWM) oscillators and an autocalibration system that allows uncertainties of less than 3% to be obtained over a range of 1 kΩ to 100 GΩ. A synchronous demodulation processing allows the noise superimposed to the low-amplitude input signals to be made negligibl
Friction stir lap joining of blanks under different conditions
No full textThe present investigation aims at studying the effect of the tool geometry and of rotational velocity of the tool, at different welding velocities, on the tensile shear strength of friction stir welded joints realised with blanks of different thicknesses. The proposed trial and error methodology was based on experiments, numerical simulations and microstructure observations. It was found that, at the lowest rotational velocity, the slender tool determines tensile shear strength values lower than those obtained with the thick tool in particular at the highest welding velocity investigated. The numerical simulation evidenced a wider stirred zone for the thick tool when compared with that realised with the slender tool at the lowest rotational velocity. Microstructure observations evidenced that the increase in the welding velocity determines reduced stirred zones and a homogenisation of material particularly relevant for the slender tool
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