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Giunzione mediante laser di materiali difficili, ibridi ed a struttura cellulare / LASER joining of hybrid, cellular, and difficult-to-weld materialsAscari, Alessandro <1974> 23 May 2014 (has links)
Lo studio presentato in questa sede concerne applicazioni di saldatura LASER caratterizzate da aspetti di non-convenzionalità ed è costituito da tre filoni principali. Nel primo ambito di intervento è stata valutata la possibilità di effettuare saldature per fusione, con LASER ad emissione continua, su pannelli Aluminum Foam Sandwich e su tubi riempiti in schiuma di alluminio. Lo studio ha messo in evidenza numerose linee operative riguardanti le problematiche relative alla saldatura delle pelli esterne dei componenti ed ha dimostrato la fattibilità relativa ad un approccio di giunzione LASER integrato (saldatura seguita da un post trattamento termico) per la realizzazione della giunzione completa di particolari tubolari riempiti in schiuma con ripristino della struttura cellulare all’interfaccia di giunzione. Il secondo ambito di intervento è caratterizzato dall’applicazione di una sorgente LASER di bassissima
potenza, operante in regime ad impulsi corti, nella saldatura di acciaio ad elevato contenuto di
carbonio. Lo studio ha messo in evidenza come questo tipo di sorgente, solitamente applicata per lavorazioni di
ablazione e marcatura, possa essere applicata anche alla saldatura di spessori sub-millimetrici. In questa fase è stato messo in evidenza il ruolo dei parametri di lavoro sulla conformazione del giunto ed è stata definita l’area di fattibilità del processo. Lo studio è stato completato investigando la possibilità di applicare un trattamento LASER dopo saldatura per addolcire le eventuali zone indurite. In merito all’ultimo ambito di intervento l’attività di studio si è focalizzata sull’utilizzo di sorgenti ad elevata densità di potenza (60 MW/cm^2) nella saldatura a profonda penetrazione di acciai da costruzione. L’attività sperimentale e di analisi dei risultati è stata condotta mediante tecniche di Design of Experiment per la valutazione del ruolo preciso di tutti i parametri di processo e numerose considerazioni relative alla formazione di cricche a caldo sono state suggerite. / This dissertation concerns LASER-based joining and welding applications characterized by non-conventional prerogatives. The work is divided into three main topics: LASER joining of hybrid cellular-structured materials, with particular attention to aluminum foam sandwiches and foam-cored tubes, short-pulse LASER micro welding of high carbon steels and high power density continuous wave LASER welding of structural steels. The first topic investigates the role of LASER in joining hybrid components characterized by an external dense skin and an internal foam core. In particular the possibility of achieving both the fusion welding of the skin and the restoration of the cellular structure at the welding interface is assessed and the main guidelines concerning an integrated LASER welding - LASER heat treatment processing cycle are suggested. The second topic deals with the application of a low-power nanosecond pulsed LASER source in welding high carbon steels. The study points out that an accurate selection of pulse-related parameters allows to achieve sound micro-joints characterized by a penetration between 20 and 200 microns. These results point out the possibility to consider the construction of integrated LASER manufacturing cells in which, with the same low-cost source and on the same workpiece positioning, welding, cutting, marking and texturing processes can be performed. The study is completed by the investigation of the possibility to carry out a LASER post welding heat treatment for annealing the eventual hardened zones occurring in the welded material. The last topic deals with high power density LASER welding of carbon steels: by exploiting a high brilliance fiber source, capable of achieving 60 MW/cm^2, high penetration weld beads were obtained. By means of Design of Experiment techniques the role of radiation power, welding speed and beam focal position is assessed and several considerations were made concerning the influence of this kind of process on hot cracks formation.
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Self-Assembled Monolayers (SAMs) in Organic Field-Effect TransistorsLeonardi, Francesca <1986> 09 April 2014 (has links)
Organic printed electronics is attracting an ever-growing interest in the last decades because of its impressive breakthroughs concerning the chemical design of π-conjugated materials and their processing. This has an impact on novel applications, such as flexible-large-area displays, low- cost printable circuits, plastic solar cells and lab-on-a-chip devices.
The organic field-effect transistor (OFET) relies on a thin film of organic semiconductor that bridges source and drain electrodes. Since its first discovery in the 80s, intensive research activities were deployed in order to control the chemico-physical properties of these electronic devices and consequently their charge. Self-assembled monolayers (SAMs) are a versatile tool for tuning the properties of metallic, semi-conducting, and insulating surfaces. Within this context, OFETs represent reliable instruments for measuring the electrical properties of the SAMs in a Metal/SAM/OS junction.
Our experimental approach, named Charge Injection Organic-Gauge (CIOG), uses OTFT in a charge-injection controlled regime. The CIOG sensitivity has been extensively demonstrated on different homologous self-assembling molecules that differ in either chain length or in anchor/terminal group.
One of the latest applications of organic electronics is the so-called “bio-electronics” that makes use of electronic devices to encompass interests of the medical science, such as biosensors, biotransducers etc…
As a result, thee second part of this thesis deals with the realization of an electronic transducer based on an Organic Field-Effect Transistor operating in aqueous media. Here, the conventional bottom gate/bottom contact configuration is replaced by top gate architecture with the electrolyte that ensures electrical contact between the top gold electrode and the semiconductor layer. This configuration is named Electrolyte-Gated Field-Effect Transistor (EGOFET).
The functionalization of the top electrode is the sensing core of the device allowing the detection of dopamine as well as of protein biomarkers with ultra-low sensitivity.
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Design and fabrication of biocompatible scaffolds for the regeneration of tissuesBarbalinardo, Marianna <1981> 09 April 2014 (has links)
Regenerative medicine and tissue engineering attempt to repair or improve the biological functions of tissues that have been damaged or have ceased to perform their role through three main components: a biocompatible scaffold, cellular component and bioactive molecules. Nanotechnology provide a toolbox of innovative scaffold fabrication procedures in regenerative medicine. In fact, nanotechnology, using manufacturing techniques such as conventional and unconventional lithography, allows fabricating supports with different geometries and sizes as well as displaying physical chemical properties tunable over different length scales. Soft lithography techniques allow to functionalize the support by specific molecules that promote adhesion and control the growth of cells. Understanding cell response to scaffold, and viceversa, is a key issue; here we show our investigation of the essential features required for improving the cell-surface interaction over different scale lengths.
The main goal of this thesis has been to devise a nanotechnology-based strategy for the fabrication of scaffolds for tissue regeneration. We made four types of scaffolds, which are able to accurately control cell adhesion and proliferation. For each scaffold, we chose properly designed materials, fabrication and characterization techniques.
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Nano-fabrication of complex functional structures using non- conventional lithographyHemmatian, Zahra <1980> 09 April 2014 (has links)
In Chapter 1 I will present a brief introduction on the state of art of nanotechnologies, nanofabrication techniques and unconventional lithography as a technique to fabricate the novel electronic device as resistive switch so-called memristor is shown. In Chapter 2 a detailed description of the main fabrication and characterization techniques employed in this work is reported. Chapter 3 parallel local oxidation lithography (pLOx) describes as a main technique to obtain accurate patterning process. All the effective parameters has been studied and the optimized condition observed to highly reproducible with excellent patterned nanostructures. The effect of negative bias, calls local reduction (LR) studied. Moreover, the use of AC bias shows faster patterning process respect to DC bias. In Chapter 4 (metal/ e-SiO2/ Si nanojunction) it is shown how the electrochemical oxide nanostructures by using pLOx can be used in the fabrication of novel devices call memristor. We demonstrate a new concept, based on conventional materials, where the lifetime problem is resolved by introducing a “regeneration” step, which restores the nano-memristor to its pristine condition by applying an appropriate voltage cycle. In Chapter 5 (Graphene/ e-SiO2/ Si), Graphene as a building block material is used as an electrode to selectively oxidize the silicon substrate by pLOx set up for the fabrication of novel resistive switch device.
In Chapter 6 (surface architecture) I will show another application of pLOx in biotechnology is shown. So the surface functionalization combine with nano-patterning by pLOx used to design a new surface to accurately bind biomolecules with the possibility of studying those properties and more application in nano-bio device fabrication. So, in order to obtain biochips, electronic and optical/photonics devices Nano patterning of DNA used as scaffolds to fabricate small functional nano-components.
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On Application of Optimal Control to Intelligent ManufacturingGiorgio Bort, Carlos Maximiliano January 2013 (has links)
A framework to increase the level of automation of manufacturing processes towards the paradigm of intelligent manufacturing is proposed. The case study considered is the milling of aluminum alloys through a three-axes Computer Numerical Control (CNC) machine tool. The developed controller is called Evaluation and Perception Controller (EPC), and it con- sists of three layers: sensor, perception, and cognitive. A set of sensors displayed in the working volume collect the information necessary to reconstruct the state of the system. In the perception layer the acquired data are processed and learned, thus maintaining updated the models of the process which drive the process optimisation in the cognitive layer.
The Optimal Control Problem (OCP) method is utilised to calculate the controls of the process that optimise a target function, defined accordingly to the specific context in which the operation is executed (namely roughing or finishing). In the general case, the objec- tive function takes into account: productivity, quality, and costs of the process. The material removal rate along the tool path is used as index for process productivity. The quality is quan- tified through measurements of roughness, therefore it is improved by limiting the static and dynamic displacements (i.e. the vibrations) of the tool. The costs of the process here con- sidered are those associated to tooling (i.e. wear of the tool), and energy absorbed by the spindle during on-air free movements.
In order to ensure the feasibility of the solution, algebraic and differential constraints are im- posed on the dynamic response of drives and spindle. The OCP is then solved through an efficient optimisation library developed by the group of Mechatronic Engineering of the Uni- versity of Trento.
The EPC has been designed as a portable system that can be integrated into any CNC ma- chine, once it has been calibrated, and a dedicated communication interface with the NC has been implemented. The tests necessary for the OCP calibration, and requirements for the communication layer between EPC and CN, are described and discussed. Finally, the EPC is tested on real milling processes. The validation of its performances is done by comparing the outcomes of the process with respect to a nominal case, in which the process is set up according to guidelines given by tool manufacturer.
It worth be noted that this work represents not only a step foreword in increasing the level of automation of machining, but rather it proposes an architecture and an approach which can be generalised to several manufacturing processes.
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Analisi inversa per l'identificazione dei parametri dei materiali e di processo nelle lavorazioni dei metalliTondini, Francesco January 2010 (has links)
Studio del processo di stampaggio delle lamiere in acciaio al boro utilizzate dall'industria automobilistica.
Proposta di materiali innovativi da utilizzare per la produzione di stampi al fine di ottenere microstrutture differenziali con tempra contemporanea alla deformazione in stampo.
Caratterizzazione delle proprietà termica d'interfaccia stampo-lamiera al variare del materiale dello stampo e delle pressione di contatto.
Effetto dei parametri di processo sul trattamento termico in stampo del pezzo in lavorazione.
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Investimenti in tecnologie sanitarie: un approccio con opzioni reali / Investment in Health Technologies: a Real Option ApproachPERTILE, PAOLO 26 March 2007 (has links)
L'obiettivo di questo lavoro e' l'estensione dell'approccio basato su opzioni reali alla valutazione delle tecnologie sanitarie. l'approccio al problema e' duplice. da un lato si vuole capire quale contributo questo sviluppo possa fornire alla comprensione dei meccanismi di adozione e diffusione di nuove tecnologie in sanità. l'altro obiettivo e' realizzare una concreta applicazione di questo approccio alla valutazione, che e' ancora assente nella letteratura di economia sanitaria. la tecnologia scelta per l'applicazione è la positron emission tomography (pet). / This work aims to extend the real option approach to the evaluation of health care technologies. The aim is to do this from two different points of view. On one side we are interested in understanding what insights taking option values into account provides in the study of adoption behaviour by providers. On the other side, we aim to provide an application of this approach to the economic evaluation of a specific medical technology, which is still missing in the health economics literature. The technology that has been chosen for the application is positron emission tomography (pet).
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CONTAMINAZIONE DA MICOTOSSINE DEI CEREALI E DEI SUOI DERIVATI / Mycotoxins Contamination of Cereals and of Their By-ProductsRASTELLI, SILVIA 18 February 2008 (has links)
L'opinione pubblica percepisce fortemente il rischio derivante da sostanze chimiche sintetiche, ma ignora spesso quello derivante dalla presenza di sostanze tossiche naturali. Tra queste sostanze vengono classificate le micotossine; prodotti del metabolismo secondario di alcuni funghi.
La maggior parte degli alimenti di origine vegetale e in particolare i cereali, possono andare incontro a contaminazione da parte di questi funghi, produttori di micotossine, in qualunque stadio.
In particolare nel frumento le micotossine che si riscontrano più frequentemente sono l'ocratossina A (OTA) e il deossinivalenolo (DON), mentre nel mais, si riscontrano le Aflatossine e le fumonisine.
Queste micotossine hanno effetti epatotossici, nefrotossici, mutageni e cancerogeni, è necessario perciò, un continuo monitoraggio della materia prima (frumento e mais), ma anche dei prodotti destinati all'alimentazione umana a base di questi cereali. / People experience deeply, the risk of synthetics chemicals substances, but often don't know the risk from naturals toxics substances. Between these substances, they are mycotoxins; fungi secondary metabolism's products.
Most of vegetable food, as cereals, can suffer a mycotoxins contamination, for effect of these fungi, during any step of alimentary chain.
In particular, in wheat , the mycotoxins more frequents are ochratoxin A end deossinivalenol, while in the maize can find aflatoxins and fumonisins. These mycotoxins can have hepatotoxics, nefrotoxics, mutagens and cancerogens effects.
This study has monitored contamination's levels of raw material (wheat and maize), but also of foodstuff containing cereals.
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Innovative Nutritional Aspects of locally produced Italian cheesesMAGNANO SAN LIO, EUGENIA 22 April 2010 (has links)
Il formaggio sta dimostrando possedere, oltre alle caratteristiche nutrizionali classiche, degli aspetti nutrizionali innovati derivanti dalle proprietà di peptidi bioattivi contenuti nella frazione proteica caseinica del formaggio e rilasciati in seguito a proteolisi, ed ancora dalle proprietà di acidi grassi insaturi, quale l’acido linoleico coniugato. L’obiettivo di tale studio di dottorato è stato indagare su questi aspetti nutrizionali innovativi in formaggi tipici italiani quali Grana Padano e TrentinGrana, che pur essendo due formaggi molto simili tra loro, differiscono per l’uso della molecola antibatterica lisozima solo per la produzione del Grana Padano. Simulazioni in vitro della digestione gastrointestinale, nei campioni dei due formaggi a diversi tempi di stagionatura, ha dimostrato che esiste una relazione positiva tra tempo di stagionatura e digeribilità del calcio nel Grana Padano ,quando vengono considerati nella correlazione i risultati dei campioni con stagionatura superiore ai 24 mesi.
A tempi di stagionatura inferiori a 24 mesi, i risultati di digeribilità del calcio del Grana Padano sono dispersi come appare nei campioni di TrentinGrana analizzati.
Inoltre l’analisi RP-HPLC della distribuzione molecolare degli oligopeptidi dei campioni dei due formaggi, dimostra che la frazione peptidica coinvolta nel legame del calcio e quindi nel suo assorbimento, è quella compresa tra 1000 e 1500 D, e che l’analisi Seldi ha rilevato essere quella dei peptidi attivi fosfocaseinici. Inoltre differenze tra i due formaggi con e senza lisozima, appaiono solo per campioni tra 15 e 20 mesi di stagionatura, in cui campioni di formaggio senza lisozima appaiono più idrolizzati di quelli che lo contengono. Quindi dai risultati ottenuti appare che le differenze del profilo peptidico apportate dal lisozima non modificano le proprietà dei fosfopeptidi di assorbimento del calcio, forse influenzate da altri fattori che intervengono nella produzione del formaggio.
L’attività ACE-inibitoria di abbassamento della pressione arteriosa esercitata da peptidi bioattivi è stata testata nei due formaggi, dimostrando che né il tempo di stagionatura e il grado di proteolisi, né il lisozima sono correlati all’attività ACE-inibitoria.
Ed infine per l’importante ruolo che ha il minerale calcio nella dieta, indici di digeribilità del minerale in diversi alimenti sono stati considerati, in modo da poter formulare in maniera corretta diete alimentari coprendo il fabbisogno giornaliero con l’adeguato apporto energetico. I formaggi hanno dimostrato possedere indici di digeribilità del calcio superiori ad altri alimenti vegetali o a base di soia. In particolare il valore di digeribilità del Calcio del Grana Padano calcolato in vitro ha confermato il valore ottenuto in vivo , pari a 80%. / This study aimed to investigate about the not common known nutritional aspects of cheeses, which derive from their chemical components. In fact, in addition to the supply of macronutrient, cheeses are gaining interest as a source of bioactive peptides, of conjugated linoleic acid or for the new insight in the metabolic role of calcium. In vitro simulation of human gastrointestinal digestion revealed that cheeses have an higher digestibility of calcium than other foods, because of their casein-derived bioactive phosphopetides (CPPs) content has the ability to carry calcium minerals and avoid calcium precipitation, making it available for intestinal absorption. The in vitro calcium digestibility was calculated for different foods- cheeses, soya based foods and vegetables- to correct cover calcium requirements with an equilibrate energy intake. Calcium digestibility was also assessed in different ripened time Italian locally produced, semi fat, hard cheeses, Grana Padano and TrentinGrana. The main difference between them is the use or not of lysozyme during manufacturing. In Grana Padano samples, produced using lysozyme, there is a positive relationship between aging and dCa (r2 = 0.27; P<0.05) when sample > 24 months aged are considered (Grana Padano dCa results of samples less 24 months aged are quite widespread) , while in TrentinGrana, produced without the use of lysozyme, no significant correlation has been detected. RP-HPLC distribution analysis of oligopeptides molecular weight of these cheese showed that the only difference between them is that cheeses without lyzozyme, aged between 15 and 20 months, are more hydrolyzed than the same ripened time Grana Padano samples. Moreover the fraction of oligopeptides involved in calcium binding ranges between 1000 and 1500 D. SELDI analysis confirmed CPPs presence in this range. Therefore changes in cheese peptidic profiles probably caused by the use of lysozyme do not influence calcium digestibility because according to this study there is not a connection between change in peptidic profile and calcium digestibility results. The difference in calcium digestibility in Grana Padano samples aged over 24 month results should be probably ascribed also to the influence of other factors occurring during cheese manufacturing. Moreover, ACE-inhibitory activity of bioactive peptides was tested on in vitro digested Grana Padano and TrentinGrana samples with different ripening times. Correlation was not found between ACE-inhibitory activity and proteolysis level in different ripened time samples nor the lysozyme influence in releasing ACE-inhibitory bioactive peptides.
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Theoretical and Experimental Study of the Magnetic Separation of Pollutants from WastewaterMariani, Giacomo <1979> 17 March 2010 (has links)
This Thesys reports the study of a HGMS (High GradientMagnetic Separation) process for the treatment of industrialwastewaters that considers an assisted chemical-physical pre-treatment for the removal of heavy metals through the bound by adsorption with added iron-oxide particulate matter (hematite). The considered filter, constituted by ferromagnetic stainless steel wool and permanent magnets, is studied with a new approach based on a statistical analysis that requires the study of the trajectories of the particles. Experimental activity on a laboratory device has been carried out in order to test the model.
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