Structural transformations related to organic solid-state reactions: correlation studies of NMR and X-ray analysis

Eine zielgerichtete Steuerung und Durchführung von organischen Festkörperreaktionen wird unter anderem durch genaue Kenntnis von Packungseffekten ermöglicht. Im Rahmen dieser Arbeit konnte durch den kombinierten Einsatz von Einkristallröntgenanalyse und hochauf-lösender Festkörper-NMR an ausgewählten Beispielen ein tieferes Verständnis und Einblicke in die Reaktionsmechanismen von organischen Festkörperreaktionen auf molekularer Ebene gewonnen werden. So konnten bei der topotaktischen [2+2] Photodimerisierung von Zimt-säure Intermediate isoliert und strukturell charakterisiert werden. Insbesondere anhand statischer Deuteronen- und 13C-CPMAS NMR Spektren konnten eindeutig dynamische Wasserstoffbrücken nachgewiesen werden, die transient die Zentrosymmetrie des Reaktions-produkts aufheben. Ein weiterer Nachweis gelang daraufhin mittels Hochtemperatur-Röntgen-untersuchung, sodass der scheinbare Widerspruch von NMR- und Röntgenuntersuchungen gelöst werden konnte. Eine Veresterung der Zimtsäure entfernt diese Wasserstoffbrücken und erhält somit die Zentrosymmetrie des Photodimers. Weiterhin werden Ansätze zur Strukturkontrolle in Festkörpern basierend auf der molekularen Erkennung des Hydroxyl-Pyridin (OH-N) Heterosynthon in Co-Kristallen beschrieben, wobei vor allem die Stabilität des Synthons in Gegenwart funktioneller Gruppen mit Möglichkeit zu kompetetiver Wasserstoffbrückenbildung festgestellt wurde. Durch Erweiterung dieses Ansatzes wurde die molekulare Spezifität des Hydroxyl-Pyridin (OH-N) Heterosynthons bei gleichzeitiger Co-Kristallisation mit mehreren Komponenten erfolgreich aufgezeigt. Am Beispiel der Co-Kristallisation von trans--1,2-bis(4-pyridyl)ethylen (bpe) mit Resorcinol (res) in Gegenwart von trans-1,2-bis(4-pyridyl)ethan (bpet) konnten Zwischenprodukte der Fest-körperreaktionen und neuartige Polymorphe isoliert werden, wobei eine lückenlose Aufklärung des Reaktionswegs mittels Röntgenanalyse gelang. Dabei zeigte sich, dass das Templat Resorcinol aus den Zielverbindungen entfernbar ist. Ferner gelang die Durchführung einer seltenen, nicht-idealen Einkristall-Einkristall-Umlagerung von trans--1,2-bis(4-pyridyl)ethylen (bpe) mit Resorcinol (res). In allen Fällen konnten die Fragen zur Struktur und Dynamik der untersuchten Verbindungen nur durch gemeinsame Nutzung von Röntgenanalyse und NMR-Spektroskopie bei vergleichbaren Temperaturen eindeutig und umfassend geklärt werden.

Antipodal random sequences with prescribed second-order statistics: application to Compressive Sensing and UWB system based on DS-CDMA

It is usual to hear a strange short sentence: «Random is better than...». Why is randomness a good solution to a certain engineering problem? There are many possible answers, and all of them are related to the considered topic. In this thesis I will discuss about two crucial topics that take advantage by randomizing some waveforms involved in signals manipulations. In particular, advantages are guaranteed by shaping the second order statistic of antipodal sequences involved in an intermediate signal processing stages. The first topic is in the area of analog-to-digital conversion, and it is named Compressive Sensing (CS). CS is a novel paradigm in signal processing that tries to merge signal acquisition and compression at the same time. Consequently it allows to direct acquire a signal in a compressed form. In this thesis, after an ample description of the CS methodology and its related architectures, I will present a new approach that tries to achieve high compression by design the second order statistics of a set of additional waveforms involved in the signal acquisition/compression stage. The second topic addressed in this thesis is in the area of communication system, in particular I focused the attention on ultra-wideband (UWB) systems. An option to produce and decode UWB signals is direct-sequence spreading with multiple access based on code division (DS-CDMA). Focusing on this methodology, I will address the coexistence of a DS-CDMA system with a narrowband interferer. To do so, I minimize the joint effect of both multiple access (MAI) and narrowband (NBI) interference on a simple matched filter receiver. I will show that, when spreading sequence statistical properties are suitably designed, performance improvements are possible with respect to a system exploiting chaos-based sequences minimizing MAI only.

Fluorescence close to dielectric interfaces

The aim of the work was to study the correlation between the orientation and excited-state lifetimes of organic dyes close to dielectric interfaces. For this purpose, an experimental setup was designed and built, guiding the light through a prism in total internal reflection geometry. Fluorescence intensities and lifetimes for an ensemble of dye molecules were analyzed as a function of the excitation and detection polarizations. Working close to the total internal reflection angle, the differences between polarization combinations were enhanced. A classical electromagnetic model that assumes a chromophore as a couple of point-like electrical dipoles was developed. A numerical method to calculate the excitation and emission of dye molecules embedded in a multilayer system was implemented, by which full simulation of the time resolved fluorescence experiments was achieved. Free organic dyes and organic dyes covalently bound to polyelectrolyte chains were used. The polymer functionalization process avoided aggregation and provided control over the dyes position, within a few nanometers to the interface. Moreover, by varying the pH, the polymer chains could be deposited on different substrates with different conformations and the resulting fluorescence characteristics analyzed. Initially the fluorescence of organic dyes embedded in a polymer matrix was studied as a function of the distance between the fluorophores and the polymer-air interface. The non-radiative decay rate, vacuum decay rate and the relative angle between the excitation and emission dipoles of the chromophores could be determined. Different free organic dyes were deposited onto different dielectric spacers, as close as possible to the air-dielectric interface. Surprisingly, the fluorescence characteristics of dyes deposited onto polyelectrolyte layer were in good agreement with theoretical predictions of dyes in a polymer matrix, even when the layer was only 2 nm thick. When functionalized chains were deposited at low pH, on top of a polyelectrolyte spacer, the fluorescence had the characteristics of emitters embedded in a polymer matrix as well. Surface deposition at high pH showed an intermediate behaviour between emitters embedded in polymer and on top of the surface, in air. In general, for low pH values, the chains are deposited on a substrate in a train-like conformation. For high pH values, the chains are deposited in a loop-like conformation. As a consequence at low pH the functionalized polymer strongly interdigitates with the polyelectrolyte chains of the spacer, bringing most of the dyes inside the polymer. Thus, the fluorophores may experience the polymer as surrounding environment. On the other hand, for high pH values the dye-loaded chains adsorbed have a conformational arrangement of dense loops that extend away from the surface. Therefore many fluorophores experience the air as surrounding environment. Changing the spacer from polyelectrolyte to negatively charged silane produced contradictory results for lifetimes and intensities. The fluorescence intensities indicated the behaviour of emitters embedded in a polymer matrix, regardless of the pH value. On the other hand, for low pH values, the excited-state lifetimes showed that the emitters behaved as in air. For higher pH values, an intermediate behaviour between fluorophores located within and above of a dielectric film was observed. The poor agreement between theoretical and experimental data may be due to the simplified model utilized, by which the dipoles are assumed either in one side or in the other with respect to a geometrical air-dielectric interface. In the case when the dielectric film is constituted by the functionalized polymer chains themselves, reality is more complex and a different model may apply. Nevertheless, possible applications of the technique arise from a qualitative analysis.

Modellazione Tridimensionale del Processo di Combustione di un Razzo a Propellente Solido

La regolazione dei sistemi di propulsione a razzo a propellente solido (Solid Rocket Motors) ha da sempre rappresentato una delle principali problematiche legate a questa tipologia di motori. L’assenza di un qualsiasi genere di controllo diretto del processo di combustione del grano solido, fa si che la previsione della balistica interna rappresenti da sempre il principale strumento utilizzato sia per definire in fase di progetto la configurazione ottimale del motore, sia per analizzare le eventuali anomalie riscontrate in ambito sperimentale. Variazioni locali nella struttura del propellente, difettosità interne o eterogeneità nelle condizioni di camera posso dare origine ad alterazioni del rateo locale di combustione del propellente e conseguentemente a profili di pressione e di spinta sperimentali differenti da quelli previsti per via teorica. Molti dei codici attualmente in uso offrono un approccio piuttosto semplificato al problema, facendo per lo più ricorso a fattori correttivi (fattori HUMP) semi-empirici, senza tuttavia andare a ricostruire in maniera più realistica le eterogeneità di prestazione del propellente. Questo lavoro di tesi vuole dunque proporre un nuovo approccio alla previsione numerica delle prestazioni dei sistemi a propellente solido, attraverso la realizzazione di un nuovo codice di simulazione, denominato ROBOOST (ROcket BOOst Simulation Tool). Richiamando concetti e techiche proprie della Computer Grafica, questo nuovo codice è in grado di ricostruire in processo di regressione superficiale del grano in maniera puntuale, attraverso l’utilizzo di una mesh triangolare mobile. Variazioni locali del rateo di combustione posso quindi essere facilmente riprodotte ed il calcolo della balistica interna avviene mediante l’accoppiamento di un modello 0D non-stazionario e di uno 1D quasi-stazionario. L’attività è stata svolta in collaborazione con l’azienda Avio Space Division e il nuovo codice è stato implementato con successo sul motore Zefiro 9.

Life Cycle Assessment di un impianto integrato di trattamento della frazione organica dei rifiuti. Il caso di Voltana di Lugo (RA)

La metodologia Life Cycle Assessment (LCA) è un metodo oggettivo di valutazione e quantificazione dei carichi energetici ed ambientali e degli impatti potenziali associati ad un processo o attività produttiva lungo l’intero ciclo di vita. Il lavoro presentato in questa tesi ha avuto come obiettivo l’analisi del ciclo di vita dell’impianto di trattamento della FORSU (la frazione organica di rifiuti solidi urbani) di Voltana di Lugo, in provincia di Ravenna. L’impianto attuale si basa sull'utilizzo accoppiato di digestione anaerobica a secco (sistema DRY) e compostaggio. Si è voluto inoltre effettuare il confronto fra questo scenario con quello antecedente al 2012, in cui era presente solamente il processo di compostaggio classico e con uno scenario di riferimento in cui si è ipotizzato che tutto il rifiuto trattato potesse essere smaltito in discarica. L’unità funzionale considerata è stata “le tonnellate di rifiuto trattate in un mese“, pari a 2750 t. L’analisi di tutti i carichi energetici ed ambientali dell’impianto di Voltana di Lugo è stata effettuata con l’ausilio di “GaBi 5”, un software di supporto specifico per gli studi di LCA. Dal confronto fra lo scenario attuale e quello precedente è emerso che la configurazione attuale dell’impianto ha delle performance ambientali migliori rispetto alla vecchia configurazione, attiva fino a Dicembre 2012, e tutte e due sono risultate nettamente migliori rispetto allo smaltimento in discarica. I processi che hanno influenzato maggiormente gli impatti sono stati: lo smaltimento del sovvallo in discarica e la cogenerazione, con produzione di energia elettrica da biogas. Il guadagno maggiore, per quanto riguarda lo scenario attuale rispetto a quello precedente, si è avuto proprio dal surplus di energia elettrica prodotta dal cogeneratore, altrimenti prelevata dal mix elettrico nazionale.

Spazi di riqualificazione secondo il modello della transizione. L'esempio della frazione di Borgonuovo nel comune di Sasso Marconi (BO).

La presente tesi sviluppa un progetto di riqualificazione alla scala urbana ed architettonica della frazione di Borgonuovo nel comune di Sasso Marconi, secondo il modello della transizione, ideato da Rob Hopkins.

Studio e implementazione di un codice per l'impacchettamento di un propellente solido

Studio dell’impacchettamento di un propellente solido tramite un codice realizzato in ambiente Matlab nel laboratorio di propulsione e macchine della Scuola di ingegneria e architettura con sede a Forlì. Tale studio è stato realizzato in quanto l’impacchettamento di materiale solido risulta essere di fondamentale importanza in molti settori dell’industria odierna, come il settore spaziale, minerario, farmaceutico e altri ancora. L’obiettivo è quello di riuscire a ottimizzare il volume occupato, in questo caso dal propellente, all’interno di un predeterminato dominio di controllo. Poter massimizzare lo spazio a disposizione permette di avere vantaggi sia in termini economici che di prestazione (ad esempio permette di avere a parità di volume una maggiore quantità di propellente a disposizione).

Two-Dimensional Bin Packing Problem with Guillotine Restrictions

This thesis, after presenting recent advances obtained for the two-dimensional bin packing problem, focuses on the case where guillotine restrictions are imposed. A mathematical characterization of non-guillotine patterns is provided and the relation between the solution value of the two-dimensional problem with guillotine restrictions and the two-dimensional problem unrestricted is being studied from a worst-case perspective. Finally it presents a new heuristic algorithm, for the two-dimensional problem with guillotine restrictions, based on partial enumeration, and computationally evaluates its performance on a large set of instances from the literature. Computational experiments show that the algorithm is able to produce proven optimal solutions for a large number of problems, and gives a tight approximation of the optimum in the remaining cases.

Packing a trunk : a physically based approach with full motional freedom

Geometric packing problems may be formulated mathematically as constrained optimization problems. But finding a good solution is a challenging task. The more complicated the geometry of the container or the objects to be packed, the more complex the non-penetration constraints become. In this work we propose the use of a physics engine that simulates a system of colliding rigid bodies. It is a tool to resolve interpenetration conflicts and to optimize configurations locally. We develop an efficient and easy-to-implement physics engine that is specialized for collision detection and contact handling. In succession of the development of this engine a number of novel algorithms for distance calculation and intersection volume were designed and imple- mented, which are presented in this work. They are highly specialized to pro- vide fast responses for cuboids and triangles as input geometry whereas the concepts they are based on can easily be extended to other convex shapes. Especially noteworthy in this context is our ε-distance algorithm - a novel application that is not only very robust and fast but also compact in its im- plementation. Several state-of-the-art third party implementations are being presented and we show that our implementations beat them in runtime and robustness. The packing algorithm that lies on top of the physics engine is a Monte Carlo based approach implemented for packing cuboids into a container described by a triangle soup. We give an implementation for the SAE J1100 variant of the trunk packing problem. We compare this implementation to several established approaches and we show that it gives better results in faster time than these existing implementations.

Random lattice models

This thesis deals with three different physical models, where each model involves a random component which is linked to a cubic lattice. First, a model is studied, which is used in numerical calculations of Quantum Chromodynamics.In these calculations random gauge-fields are distributed on the bonds of the lattice. The formulation of the model is fitted into the mathematical framework of ergodic operator families. We prove, that for small coupling constants, the ergodicity of the underlying probability measure is indeed ensured and that the integrated density of states of the Wilson-Dirac operator exists. The physical situations treated in the next two chapters are more similar to one another. In both cases the principle idea is to study a fermion system in a cubic crystal with impurities, that are modeled by a random potential located at the lattice sites. In the second model we apply the Hartree-Fock approximation to such a system. For the case of reduced Hartree-Fock theory at positive temperatures and a fixed chemical potential we consider the limit of an infinite system. In that case we show the existence and uniqueness of minimizers of the Hartree-Fock functional. In the third model we formulate the fermion system algebraically via C*-algebras. The question imposed here is to calculate the heat production of the system under the influence of an outer electromagnetic field. We show that the heat production corresponds exactly to what is empirically predicted by Joule's law in the regime of linear response.

Crystallization and morphology of the PLLA phase within random poly (L-lactide-ran-ɛ-caprolactone)

This work has mainly focused on the poly (L-lactide) (PLLA) which is a material for multiple applications with performances comparable to those of petrochemical polymers (PP, PS, PET, etc. ...), readily recyclable and also compostable. However, PLLA has certain shortcomings that limit its applications. It is a brittle, hard polymer with a very low elongation at break, hydrophobic, exhibits low crystallization kinetics and takes a long time to degrade. The properties of PLLA may be modified by copolymerization (random, block, and graft) of L-lactide monomers with other co-monomers. In this thesis it has been studied the crystallization and morphology of random copolymers poly (L-lactide-ran-ε-caprolactone) with different compositions of the two monomers since the physical, mechanical, optical and chemical properties of a material depend on this behavior. Thermal analyses were performed by differential scanning calorimetry (DSC) and thermogravimetry (TGA) to observe behaviors due to the different compositions of the copolymers. The crystallization kinetics and morphology of poly (L-lactide-ran-ε-caprolactone) was investigated by polarized light optical microscopy (PLOM) and differential scanning calorimetry (DSC). Their thermal behavior was observed with crystallization from melt. It was observed that with increasing amounts of PCL in the copolymer, there is a decrease of the thermal degradation. Studies on the crystallization kinetics have shown that small quantities of PCL in the copolymer increase the overall crystallization kinetics and the crystal growth rate which decreases with higher quantities of PCL.

Studio e ricostruzione delle distribuzioni granulometriche interne al grano in motori a propellente solido

The main purposes of this essay were to investigate in detail the burning rate anomaly phenomenon, also known as "Hump Effect", in solid rocket motors casted in mandrel and the mechanisms at the base of it, as well as the developing of a numeric code, in Matlab environment, in order to obtain a forecasting tool to generate concentration and orientation maps of the particles within the grain. The importance of these analysis is due to the fact that the forecasts of ballistics curves in new motors have to be improved in order to reduce the amount of experimental tests needed for the characterization of their ballistic behavior. This graduate work is divided into two parts. The first one is about bidimensional and tridimensional simulations on z9 motor casting process. The simulations have been carried out respectively with Fluent and Flow 3D. The second one is about the analysis of fluid dynamic data and the developing of numeric codes which give information about the concentration and orientation of particles within the grain based on fluid strain rate information which are extrapolated from CFD software.

Molekulare und supramolekulare Eigenschaften von neuen Donor-Akzeptor-Polymeren

Die organische Halbleitertechnologie befindet sich seit Jahrzehnten im Focus des Interesses, da sie eine kostengünstige und umweltverträgliche Alternative zu anorganischen Silizium-basierten Halbleitern darstellt. Die Möglichkeit der gezielten Funktionalisierung von definierten Strukturen durch synthetische Methoden, welche eine große Vielfalt an Materialien ermöglicht, steht dabei besonders im Vordergrund. Die Modifikation von physikalischen Eigenschaften ermöglicht dabei eine stark erleichterte Anpassung für den geplanten Anwendungsbereich. Im Rahmen der vorliegenden Dissertation wurden organische Halbleitermaterialien basierend auf Cyclopenta[2,1-b:3,4-b']dithiophen (CDT) dargestellt und hinsichtlich ihrer strukturellen und elektronischen Eigenschaften untersucht. In Kombination mit Benzo[c][1,2,5]thiadiazol (BTZ) und weiteren Akzeptoren wurden zunächst Donor(D)-Akzeptor(A)-Polymere synthetisiert und Struktur-Eigenschaft-Beziehungen aufgestellt. So konnte ein sehr hochmolekulares Polymer CDT-BTZ-Polymer (Mn = 36 kg mol-1, PDI = 2.6) erhalten werden, welches sich durch eine hohe lamellare Ordnung und eine gemessene Ladungsträgermobilität in FETs von über 5.0 cm2V-1s-1 bei Raumtemperatur auszeichnete; bei niedrigen Temperaturen (240 K) war letztgenannte 6.5 cm2V-1s-1. Aufgrund dieses hohen Ladungstransports und der Abwesenheit niedermolekularer Polymerketten innerhalb des Polymers konnte erstmals eine Messung eines HALL-Effektes bewerkstelligt werden. Dies war der erste Beweis eines Band-artigen Ladungstransportes an einem Polymerhalbleiter. Des Weiteren wurde durch synthetische Veränderung der Grundstruktur des Polymers zu längeren Alkylketten eine anisotrope Anordnung der Polymerketten erreicht und die Ladungsträgermobilität (6.5 cm2V-1s-1 bei Raumtemperatur) weiter gesteigert. Darauf aufbauend wurde der Einfluss von stereoisomeren Seitenketten an CDT-BTZ-Polymeren auf Packungsverhalten, Parametern (Sperrstrom, Einschaltstrom) in FETs und Löslichkeit in organischen Lösungsmitteln untersucht. Durch cis-trans-Isomerisierung der Seitenketten wurde hier eine neue Methode zur Optimierung des Packungsverhaltens von Polymeren in dünnen Filmen und Lösung gefunden. Zuletzt wurden D-π-A-Farbstoffen, welche CDT als Verbrückungseinheit (π) beinhalten, dargestellt. Durch Variation von D und A konnten Struktur-Eigenschaft-Beziehungen in der Anwendung in Solarzellen (Feststoffsolarzellen, Flüssigsolarzellen) gefunden werden. Die Untersuchungen der photoinduzierten Absorption und der Photolumisenzenzquantenausbeute lieferten dabei Erklärungen für physikalische Prozesse wie Ladungsinjektion- und rekombination.