Ingegneria industriale e dell'informazione

Gene therapy is increasingly critical in the treatment of different types of maladies. The approach of gene therapy can be fundamental in dealing with many kinds of tumors, viral infections (e.g., HIV, HSV), and disturbs linked to genetic anomalies. However, the use of nucleic acids is limited by their ability to reach their action site—the target cell and, often, the inside of its nucleus. Dendrimers, on the other hand, are an interesting kind of polymers, the general synthetic scheme of which is relatively of recent development (∼1980). Among the many possible uses of these polymers, they revealed themselves as great nanocarriers for drugs in general, and particularly for genetic material. Many of the properties of these molecules are directly linked to their structure, and this in turn is critically influenced by their molecular composition. Exploiting in silico techniques, we can reveal many informations about the atomistic structure of dendrimers, some of which are otherwise difficult to gather. The interactions between the carrier and its cargo, and also with all the biological systems that are interposed between the administration and the reaching of the target (e.g., serum proteins, lipid membranes. . . ) are of critical importance in the development of new dendrimers for gene therapy. These interactions can be described and studied at a detail once unthinkable, thanks to the in silico simulation of these systems. In this thesis many different molecular simulation techniques will be employed to give a characterization as precise as possible of the structure and interactions of new families of dendrimers. In particular two new families of dendrimers (viologen and carbosilane) will be structurally characterized, and their interactions with albumin and two oligodeoxynucleotide, respectively, will be described. Then, the point of view of these interactions will be changed: the interactions between a fifth generation triethanolamine-core poly(amidoamine) dendrimer (G5 TEA-core PAMAM) and a sticky siRNA will be studied, varying the length and chemical compositions of the overhangs of the siRNA. Studying dendrimers the use of new molecular simulations techniques were deepened, and such techniques will be employed in other parallel projects. We’ll see the steered molecular dynamic method applied in the study of one mutation of the SMO receptor. The development of biological membranes models (that will be used in future to study the interactions of dendrimers with such membranes) was also used to refine and better characterize the σ1 receptor 3D model, previously developed by our research group. A detailed characterization of the putative binding site of this receptor will be given, employing this refined model.

Il continuo aumento della richiesta di energia elettrica e la conseguente crescita dei valori di anidride carbonica nell'atmosfera terrestre crea sempre più la necessità di attuare modifiche sostanziali non solo nei metodi di produzione dei settori energetico e industriale, ma anche nella vita di ogni abitante del pianeta. Questa tesi analizza la possibilità di utilizzare l'energia solare per la produzione di acqua fredda grazie alla contemporaneità tra la disponibilità di energia rinnovabile e la richiesta di raffrescamento durante il periodo estivo. Due diversi impianti sperimentali, dotati di collettori solari a tubi evacuati commerciali e chiller ad adsoprbimento di piccole dimensioni (20 kW), sono stati monitorati ed i primi risultati sperimentali sono presentati in questo studio. Per studiare soluzioni diverse e trovare un design ottimale, un modello di simulazione dinamica è stato creato e testato utilizzando il software commerciale TRNSYS 17.

Durability and cost are the major limiting factors in current PEM fuel cells development and commercialization. Electrocatalyst materials are the main responsible of both cost of the entire fuel cell stack and its degradation during operation [1,2]. In this research durability and degradation have been investigated in high temperature PEM fuel cells (HT-PEMFCs). Specific diagnostic techniques have been studied and tested for the investigation of electrocatalyst structural properties. An experimental sensibility analysis has been carried out with the purpose to assess advantages and limitations of the use of cyclic voltammetry to determine the electrocatalyst ECSA in H3PO4/PBI high temperature PEM fuel cells. Small angle x-ray scattering (SAXS) has been used to obtain structural information of the electrocatalyst nanoparticles, such as size and distribution. A procedure to characterize HT-PEMFCs MEAs by means of SAXS has been developed and tested. Transmission electron microscopy (TEM) is a complementary technique to SAXS: it has been used to validate the diagnostic method and to compare the results. Electrocatalyst evolution during long-term operation has been studied and related with performance loss. Specific stress test protocols have been developed to accelerate electrocatalyst degradation in commercial HT-PEMFC MEAs operated in single cell configuration. Two MEAs have been subjected to load cycling and one to start/stop cycling. One of the two testing protocols based on load cycling included open circuit (OC) condition in each cycle with the purpose to study the effects of frequent and short OCs during operation on MEA durability and electrocatalyst evolution. Specific start-up and shutdown procedures have been used in the start/stop test in order to limit other degradation mechanisms. Cell voltage and polarization curves have been recorded to monitor cell performance during the durability tests. The electrocatalyst structural evolution induced by load cycling has been characterized with SAXS and TEM. The stress test protocols have been effective to accelerate performance and electrocatalyst degradation of the MEA. The voltage decay rate at 200 mAcm-2 was higher than 25 μVh-1 in the samples subjected to load cycles. The start/stop cycling caused a performance degradation of 18 μV/cycle at 222 mAcm-2 during the first 450 cycles of the test. Regarding the diagnostic techniques used to characterize the electrocatalyst, cyclic voltammetry (CV) seems not to be particularly reliable when performed at high temperatures (>100°C) due to the high dependence of the voltammogram shape to humidity conditions. SAXS, on the other hand, seems to be an effective tool to investigate structural properties of PEMFC electrocatalysts. SAXS analysis showed that after 100,000 load cycles the mean size of the platinum nanoparticles more than doubled. TEM results varied about 30% from the SAXS results: this divergence could be due to a very different population size of the nanoparticles that have been analysed in the two methods. Moreover, the preparation of the sample used in TEM may have strongly influenced the electrocatalyst structure. Finally, a visualization of the electrocatalyst structural evolution on large areas of the MEAs subjected to load cycling showed preferential directions of the particles growth that could be due to the position of the channels on the flow-field plates of the fuel cell.

Gli alti livelli di comfort che sono richiesti oggigiorno a bordo di navi da crociera e mega-yachts, portano i progettisti a concentrare la loro attenzione sul problema del rumore strutturale. I motori diesel quattro tempi che sono installati a bordo nave come motori principali o diesel generatori, sono tra le principali sorgenti di rumore strutturale. Per questa ragione, al fine di ridurre l’energia vibrazionale generata da queste sorgenti e trasmessa, tramite le strutture nave, ai locali alloggio, i motori diesel sono sospesi mediante elementi resilienti. Tali elementi resilienti disaccoppiano la sorgente di rumore e vibrazioni (motore diesel) dal mezzo di propagazione (le strutture nave) e isolano dunque la sorgente dalle strutture riceventi. I livelli di rumore strutturale misurati alle fondazioni del motore diesel dipendono dai livelli di velocità misurati sulla sorgente (cioè ai piedi del motore diesel), dai livelli di impedenza meccanica degli elementi resilienti e dai livelli di mobilità meccanica delle fondazioni del motore diesel. Il single-point approach è un approccio semplificato per la previsione dei livelli di rumore strutturale che trascura l’interazione tra elementi resilienti. Secondo tale teoria, al fine di ridurre il rumore strutturale trasmesso attraverso gli elementi resilienti alle strutture nave, si deve ridurre l’impedenza meccanica degli elementi resilienti così come la mobilità meccanica delle fondazioni del motore diesel. In altre parole, si devono aumentare la rigidezza dinamica degli elementi resilienti così come l’impedenza meccanica delle fondazioni del motore diesel. Ad oggi, l’impedenza meccanica degli elementi resilienti può essere ricavata solo mediante prove sperimentali in laboratorio, mentre la mobilità meccanica del motore diesel è solitamente misurata quando la nave è in costruzione. Dunque non vi è la possibilità di predire, in fase progettuale, il rumore strutturale dovuto ai motori diesel. In questa tesi, viene presentata una procedura per la simulazione del rumore strutturale dovuto a motori diesel marini. La procedura si basa su test sperimentali e simulazioni numeriche. Nella prima parte della tesi sono richiamate le basi teoriche necessarie per l’esecuzione delle procedure numeriche e delle prove sperimentali. Sono dunque presentati i risultati delle analisi numeriche per simulare la mobilità delle fondazioni dei motori diesel marini. I risultati delle analisi FEM sono stati validati mediante confronto dei risultati delle analisi numeriche con i dati ottenuti da una campagna di misure eseguite a bordo nave. Successivamente sono presentati i risultati di una serie di prove eseguite per collaudare una nuova macchina sperimentale per misurare l’impedenza meccanica degli elementi resilienti. Lo scopo del collaudo era definire una procedura per l’utilizzo della macchina e per l’esecuzione di prove sperimentali in accordo alla ISO 10846, che è considerata normativa di riferimento per questo tipo di prove. Si è dunque proceduto con l’esecuzione di prove sperimentali eseguite su un elemento resiliente per motori diesel marini. Le prove sono state eseguite a differenti carichi statici. I risultati di queste prove sperimentali sono stati utilizzati per settare un modello numerico che simuli il comportamento non-lineare del componente in gomma del resiliente. I risultati ottenuti sia dalle prove sperimentali sia dalle simulazioni numeriche sono stati utilizzati per predire il rumore strutturale generato dai motori diesel, in accordo al single-point approach. I risultati ottenuti dall’applicazione del metodo sono stati confrontati con misure eseguite a bordo e sono stati discussi per evidenziare vantaggi e svantaggi dell’applicazione del metodo. Le procedure numeriche per la simulazione del comportamento dinamico del resiliente e della fondazione costituiscono un primo passo per l’ottimizzazione del sistema di isolazione del motore diesel marino.

This research is focused on the condition monitoring of electrical machines and its long term purpose is to monitor electrical and mechanical faults at the same time, in non-stationary conditions (variable load and speed), with a single piece of hardware. The Instantaneous Angular Speed (IAS) measurement of an electrical machine is proposed and analysed in order to detect the fault development inside it. Chapter 1 introduces some basic principles about the maintenance of an electrical machine. Machine unscheduled downtimes are frequently caused by bearing faults, and rotor/stator faults. Monitoring systems are needed when the machine is very important for the plant (cost, safety). In this chapter, the electrical machine’s behaviour is also examined. Induction electrical machines have been chosen for this research. A review of the excitation frequencies is reported in the chapter. In the last section, characteristic fault frequencies (from mechanical and electrical sources) are collected. Chapter 2 presents the IAS measurement and its signal processing. The IAS is the measurement of the shaft rotating speed in order to visualize what’s happening during a single or in multiple turns. There are many measurement methods which are based either analogical to digital conversion or which use counters. Analogical to digital methods use a standard data acquisition board. Counter methods have to use specific hardware that is more expensive, but with less data to store. In this research, the counter method is used, combined with the Elapsed Time (ET) counting technique. Chapter 3 describes the encoder system. Its output signal is acquired with an oscilloscope and with the counter board. The signal’s differences are highlighted. In this chapter, the measurement’s source of errors are listed: the encoder’s geometrical error, the counter’s quantization error, the clock stability and the general electrical noise. Chapter 4 collects all the experimental tests done during the PhD research. Three experimental test rigs are shown and two measurements at Nidec ASI S.p.A. are reported. Note that the experimental test rigs were designed and built at the Università degli Studi di Trieste during the three years of the PhD. Experimental Test Rig 1 (ETR1) is used to understand the electrical motor’s behaviour with varying speed, the difference between the IAS and the speed acquired with the Torsional Laser Vibrometer, the difference between the IAS and the acceleration signal measured with an accelerometer located on the motor’s stator, the effect of the unbalance in the IAS measurement. Experimental Test Rig 2 (ETR2) allows to examine the load effect on the IAS measurement, the magneto-motive force harmonics, the slip and the rotor effects. Experimental Test Rig 3 (ETR3) is designed in order to detect the Inner Race Bearing Fault (Ball Pass Frequency Inner - BPFI) with varying load. The acceleration, the voltage and the current are compared with the Instantaneous Angular Speed. The motor is also tested with an unbalanced power supply. The two measurements at Nidec ASI S.p.A show how the IAS measurement could be implemented in an industrial machine larger than the one tested in the laboratory. This research presents the pros and cons of the IAS measurement, highlighting the capability of detecting BPFI bearing fault, feeling the load variations owing to the brake system (a synchronous generator), measuring the Fundamental Train Frequency of an healthy bearing, detecting unbalance in the rotor and other special features. The author would like to thank the Fondo Sociale Europeo, the Regione Friuli Venezia Giulia and Nidec ASI S.p.A (an electrical motor company) for the sponsorship and the collaboration during the three PhD years covered by the SHARM project ”Manutenzione Preventiva Integrata”.