A simple strategy for defining polynomial spline spaces over hierarchical T-meses

[EN]We present a new strategy for constructing spline spaces over hierarchical T-meshes with quad- and octree subdivision scheme. The proposed technique includes some simple rules for inferring local knot vectors to define C 2 -continuous cubic tensor product spline blending functions. Our conjecture is that these rules allow to obtain, for a given T-mesh, a set of linearly independent spline functions with the property that spaces spanned by nested T-meshes are also nested, and therefore, the functions can reproduce cubic polynomials. In order to span spaces with these properties applying the proposed rules, the T-mesh should fulfill the only requirement of being a 0- balanced mesh...

New functional and biomechanical assessments for the improvement of the surgical navigation systems for joint replacement in the human lower limb

In case of severe osteoarthritis at the knee causing pain, deformity, and loss of stability and mobility, the clinicians consider that the substitution of these surfaces by means of joint prostheses. The objectives to be pursued by this surgery are: complete pain elimination, restoration of the normal physiological mobility and joint stability, correction of all deformities and, thus, of limping. The knee surgical navigation systems have bee developed in computer-aided surgery in order to improve the surgical final outcome in total knee arthroplasty. These systems provide the surgeon with quantitative and real-time information about each surgical action, like bone cut executions and prosthesis component alignment, by mean of tracking tools rigidly fixed onto the femur and the tibia. Nevertheless, there is still a margin of error due to the incorrect surgical procedures and to the still limited number of kinematic information provided by the current systems. Particularly, patello-femoral joint kinematics is not considered in knee surgical navigation. It is also unclear and, thus, a source of misunderstanding, what the most appropriate methodology is to study the patellar motion. In addition, also the knee ligamentous apparatus is superficially considered in navigated total knee arthroplasty, without taking into account how their physiological behavior is altered by this surgery. The aim of the present research work was to provide new functional and biomechanical assessments for the improvement of the surgical navigation systems for joint replacement in the human lower limb. This was mainly realized by means of the identification and development of new techniques that allow a thorough comprehension of the functioning of the knee joint, with particular attention to the patello-femoral joint and to the main knee soft tissues. A knee surgical navigation system with active markers was used in all research activities presented in this research work. Particularly, preliminary test were performed in order to assess the system accuracy and the robustness of a number of navigation procedures. Four studies were performed in-vivo on patients requiring total knee arthroplasty and randomly implanted by means of traditional and navigated procedures in order to check for the real efficacy of the latter with respect to the former. In order to cope with assessment of patello-femoral joint kinematics in the intact and replaced knees, twenty in-vitro tests were performed by using a prototypal tracking tool also for the patella. In addition to standard anatomical and articular recommendations, original proposals for defining the patellar anatomical-based reference frame and for studying the patello-femoral joint kinematics were reported and used in these tests. These definitions were applied to two further in-vitro tests in which, for the first time, also the implant of patellar component insert was fully navigated. In addition, an original technique to analyze the main knee soft tissues by means of anatomical-based fiber mappings was also reported and used in the same tests. The preliminary instrumental tests revealed a system accuracy within the millimeter and a good inter- and intra-observer repeatability in defining all anatomical reference frames. In in-vivo studies, the general alignments of femoral and tibial prosthesis components and of the lower limb mechanical axis, as measured on radiographs, was more satisfactory, i.e. within ±3°, in those patient in which total knee arthroplasty was performed by navigated procedures. As for in-vitro tests, consistent patello-femoral joint kinematic patterns were observed over specimens throughout the knee flexion arc. Generally, the physiological intact knee patellar motion was not restored after the implant. This restoration was successfully achieved in the two further tests where all component implants, included the patellar insert, were fully navigated, i.e. by means of intra-operative assessment of also patellar component positioning and general tibio-femoral and patello-femoral joint assessment. The tests for assessing the behavior of the main knee ligaments revealed the complexity of the latter and the different functional roles played by the several sub-bundles compounding each ligament. Also in this case, total knee arthroplasty altered the physiological behavior of these knee soft tissues. These results reveal in-vitro the relevance and the feasibility of the applications of new techniques for accurate knee soft tissues monitoring, patellar tracking assessment and navigated patellar resurfacing intra-operatively in the contest of the most modern operative techniques. This present research work gives a contribution to the much controversial knowledge on the normal and replaced of knee kinematics by testing the reported new methodologies. The consistence of these results provides fundamental information for the comprehension and improvements of knee orthopedic treatments. In the future, the reported new techniques can be safely applied in-vivo and also adopted in other joint replacements.

Analysis and modeling techniques for ultrasonic tissue characterization

This thesis introduces new processing techniques for computer-aided interpretation of ultrasound images with the purpose of supporting medical diagnostic. In terms of practical application, the goal of this work is the improvement of current prostate biopsy protocols by providing physicians with a visual map overlaid over ultrasound images marking regions potentially affected by disease. As far as analysis techniques are concerned, the main contributions of this work to the state-of-the-art is the introduction of deconvolution as a pre-processing step in the standard ultrasonic tissue characterization procedure to improve the diagnostic significance of ultrasonic features. This thesis also includes some innovations in ultrasound modeling, in particular the employment of a continuous-time autoregressive moving-average (CARMA) model for ultrasound signals, a new maximum-likelihood CARMA estimator based on exponential splines and the definition of CARMA parameters as new ultrasonic features able to capture scatterers concentration. Finally, concerning the clinical usefulness of the developed techniques, the main contribution of this research is showing, through a study based on medical ground truth, that a reduction in the number of sampled cores in standard prostate biopsy is possible, preserving the same diagnostic power of the current clinical protocol.

Physical models for numerical simulation of Si-based nanoscale FETs and sensors

To continuously improve the performance of metal-oxide-semiconductor field-effect-transistors (MOSFETs), innovative device architectures, gate stack engineering and mobility enhancement techniques are under investigation. In this framework, new physics-based models for Technology Computer-Aided-Design (TCAD) simulation tools are needed to accurately predict the performance of upcoming nanoscale devices and to provide guidelines for their optimization. In this thesis, advanced physically-based mobility models for ultrathin body (UTB) devices with either planar or vertical architectures such as single-gate silicon-on-insulator (SOI) field-effect transistors (FETs), double-gate FETs, FinFETs and silicon nanowire FETs, integrating strain technology and high-κ gate stacks are presented. The effective mobility of the two-dimensional electron/hole gas in a UTB FETs channel is calculated taking into account its tensorial nature and the quantization effects. All the scattering events relevant for thin silicon films and for high-κ dielectrics and metal gates have been addressed and modeled for UTB FETs on differently oriented substrates. The effects of mechanical stress on (100) and (110) silicon band structures have been modeled for a generic stress configuration. Performance will also derive from heterogeneity, coming from the increasing diversity of functions integrated on complementary metal-oxide-semiconductor (CMOS) platforms. For example, new architectural concepts are of interest not only to extend the FET scaling process, but also to develop innovative sensor applications. Benefiting from properties like large surface-to-volume ratio and extreme sensitivity to surface modifications, silicon-nanowire-based sensors are gaining special attention in research. In this thesis, a comprehensive analysis of the physical effects playing a role in the detection of gas molecules is carried out by TCAD simulations combined with interface characterization techniques. The complex interaction of charge transport in silicon nanowires of different dimensions with interface trap states and remote charges is addressed to correctly reproduce experimental results of recently fabricated gas nanosensors.

Interactive simulation of flexible parts

Computer simulations play an ever growing role for the development of automotive products. Assembly simulation, as well as many other processes, are used systematically even before the first physical prototype of a vehicle is built in order to check whether particular components can be assembled easily or whether another part is in the way. Usually, this kind of simulation is limited to rigid bodies. However, a vehicle contains a multitude of flexible parts of various types: cables, hoses, carpets, seat surfaces, insulations, weatherstrips... Since most of the problems using these simulations concern one-dimensional components and since an intuitive tool for cable routing is still needed, we have chosen to concentrate on this category, which includes cables, hoses and wiring harnesses. In this thesis, we present a system for simulating one dimensional flexible parts such as cables or hoses. The modeling of bending and torsion follows the Cosserat model. For this purpose we use a generalized spring-mass system and describe its configuration by a carefully chosen set of coordinates. Gravity and contact forces as well as the forces responsible for length conservation are expressed in Cartesian coordinates. But bending and torsion effects can be dealt with more effectively by using quaternions to represent the orientation of the segments joining two neighboring mass points. This augmented system allows an easy formulation of all interactions with the best appropriate coordinate type and yields a strongly banded Hessian matrix. An energy minimizing process accounts for a solution exempt from the oscillations that are typical of spring-mass systems. The use of integral forces, similar to an integral controller, allows to enforce exactly the constraints. The whole system is numerically stable and can be solved at interactive frame rates. It is integrated in the DaimlerChrysler in-house Virtual Reality Software veo for use in applications such as cable routing and assembly simulation and has been well received by users. Parts of this work have been published at the ACM Solid and Physical Modeling Conference 2006 and have been selected for the special issue of the Computer-Aided-Design Journal to the conference.

Elaborazione di un algoritmo di pianificazione di ricostruzioni del cavo orale, dell'orofaringe, della mandibola.

1.Ricostruzione mandibolare La ricostruzione mandibolare è comunemente eseguita utilizzando un lembo libero perone. Il metodo convenzionale (indiretto) di Computer Aided Design e Computer Aided Manifacturing prevede il modellamento manuale preoperatorio di una placca di osteosintesi standard su un modello stereolitografico della mandibola. Un metodo innovativo CAD CAM diretto comprende 3 fasi: 1) pianificazione virtuale 2) computer aided design della dima di taglio mandibolari, della dima di taglio del perone e della placca di osteosintesi e 3) Computer Aided Manufacturing dei 3 dispositivi chirurgici personalizzati. 7 ricostruzioni mandibolari sono state effettuate con il metodo diretto. I risultati raggiunti e le modalità di pianificazione sono descritte e discusse. La progettazione assistita da computer e la tecnica di fabbricazione assistita da computer facilita un'accurata ricostruzione mandibolare ed apporta un miglioramento statisticamente significativo rispetto al metodo convenzionale. 2. Cavità orale e orofaringe Un metodo ricostruttivo standard per la cavità orale e l'orofaringe viene descritto. 163 pazienti affetti da cancro della cavità orale e dell'orofaringe, sono stati trattati dal 1992 al 2012 eseguendo un totale di 175 lembi liberi. La strategia chirurgica è descritta in termini di scelta del lembo, modellamento ed insetting. I modelli bidimensionali sono utilizzati per pianificare una ricostruzione tridimensionale con il miglior risultato funzionale ed estetico. I modelli, la scelta del lembo e l' insetting sono descritti per ogni regione. Complicazioni e risultati funzionali sono stati valutati sistematicamente. I risultati hanno mostrato un buon recupero funzionale con le tecniche ricostruttive descritte. Viene proposto un algoritmo ricostruttivo basato su template standard.

Non-evolutive pattern recognition techniques: An application in medical image diagnostics

Lo studio dell’intelligenza artificiale si pone come obiettivo la risoluzione di una classe di problemi che richiedono processi cognitivi difficilmente codificabili in un algoritmo per essere risolti. Il riconoscimento visivo di forme e figure, l’interpretazione di suoni, i giochi a conoscenza incompleta, fanno capo alla capacità umana di interpretare input parziali come se fossero completi, e di agire di conseguenza. Nel primo capitolo della presente tesi sarà costruito un semplice formalismo matematico per descrivere l’atto di compiere scelte. Il processo di “apprendimento” verrà descritto in termini della massimizzazione di una funzione di prestazione su di uno spazio di parametri per un ansatz di una funzione da uno spazio vettoriale ad un insieme finito e discreto di scelte, tramite un set di addestramento che descrive degli esempi di scelte corrette da riprodurre. Saranno analizzate, alla luce di questo formalismo, alcune delle più diffuse tecniche di artificial intelligence, e saranno evidenziate alcune problematiche derivanti dall’uso di queste tecniche. Nel secondo capitolo lo stesso formalismo verrà applicato ad una ridefinizione meno intuitiva ma più funzionale di funzione di prestazione che permetterà, per un ansatz lineare, la formulazione esplicita di un set di equazioni nelle componenti del vettore nello spazio dei parametri che individua il massimo assoluto della funzione di prestazione. La soluzione di questo set di equazioni sarà trattata grazie al teorema delle contrazioni. Una naturale generalizzazione polinomiale verrà inoltre mostrata. Nel terzo capitolo verranno studiati più nel dettaglio alcuni esempi a cui quanto ricavato nel secondo capitolo può essere applicato. Verrà introdotto il concetto di grado intrinseco di un problema. Verranno inoltre discusse alcuni accorgimenti prestazionali, quali l’eliminazione degli zeri, la precomputazione analitica, il fingerprinting e il riordino delle componenti per lo sviluppo parziale di prodotti scalari ad alta dimensionalità. Verranno infine introdotti i problemi a scelta unica, ossia quella classe di problemi per cui è possibile disporre di un set di addestramento solo per una scelta. Nel quarto capitolo verrà discusso più in dettaglio un esempio di applicazione nel campo della diagnostica medica per immagini, in particolare verrà trattato il problema della computer aided detection per il rilevamento di microcalcificazioni nelle mammografie.

Segmentazione di immagini mammografiche con convolutional neural networks

Il tumore al seno si colloca al primo posto per livello di mortalità tra le patologie tumorali che colpiscono la popolazione femminile mondiale. Diversi studi clinici hanno dimostrato come la diagnosi da parte del radiologo possa essere aiutata e migliorata dai sistemi di Computer Aided Detection (CAD). A causa della grande variabilità di forma e dimensioni delle masse tumorali e della somiglianza di queste con i tessuti che le ospitano, la loro ricerca automatizzata è un problema estremamente complicato. Un sistema di CAD è generalmente composto da due livelli di classificazione: la detection, responsabile dell’individuazione delle regioni sospette presenti sul mammogramma (ROI) e quindi dell’eliminazione preventiva delle zone non a rischio; la classificazione vera e propria (classification) delle ROI in masse e tessuto sano. Lo scopo principale di questa tesi è lo studio di nuove metodologie di detection che possano migliorare le prestazioni ottenute con le tecniche tradizionali. Si considera la detection come un problema di apprendimento supervisionato e lo si affronta mediante le Convolutional Neural Networks (CNN), un algoritmo appartenente al deep learning, nuova branca del machine learning. Le CNN si ispirano alle scoperte di Hubel e Wiesel riguardanti due tipi base di cellule identificate nella corteccia visiva dei gatti: le cellule semplici (S), che rispondono a stimoli simili ai bordi, e le cellule complesse (C) che sono localmente invarianti all’esatta posizione dello stimolo. In analogia con la corteccia visiva, le CNN utilizzano un’architettura profonda caratterizzata da strati che eseguono sulle immagini, alternativamente, operazioni di convoluzione e subsampling. Le CNN, che hanno un input bidimensionale, vengono solitamente usate per problemi di classificazione e riconoscimento automatico di immagini quali oggetti, facce e loghi o per l’analisi di documenti.

Vantaggi e limiti dell'integrazione tra sistemi di traduzione assistita e sistemi di traduzione automatica

Computer-assisted translation (or computer-aided translation or CAT) is a form of language translation in which a human translator uses computer software in order to facilitate the translation process. Machine translation (MT) is the automated process by which a computerized system produces a translated text or speech from one natural language to another. Both of them are leading and promising technologies in the translation industry; it therefore seems important that translation students and professional translators become familiar with this relatively new types of technology. Whether used together, not only might these two different types of systems reduce translation time, but also lead to a further improvement in the field of translation technologies. The dissertation consists of four chapters. The first one surveys the chronological development of MT and CAT tools, the emergence of pre-editing, post-editing and controlled language and the very last frontiers in this sector. The second one provide a general overview on the four main CAT tools that are used nowadays and tested hereto. The third chapter is dedicated to the experimentations that have been conducted in order to analyze and evaluate the performance of the four integrated systems that are the core subject of this dissertation. Finally, the fourth chapter deals with the issue of terminological equivalence in interlinguistic translation. The purpose of this dissertation is not to provide an objective and definitive solution to the complex issues that arise at any time in the field of translation technologies, this aim being well away from being achieved, but to supply information about the limits and potentiality that are typical of those instruments which are now essential to any professional translator.

Protocolli di bioprinting in ingegneria dei tessuti

L’argomento trattato in questo elaborato riguarda una nuova tecnologia che si sta sviluppando nell’ambito dell’ingegneria dei tessuti: il Bioprinting. Tale rivoluzionario approccio completamente automatizzato, grazie all’utilizzo dell’elaborazione automatica delle immagini CAD (Computer Aided Design) e la fabbricazione assistita al calcolatore CAM (Computer Aided Manufacturing), si propone di ricreare tessuti e/o organi. In particolare nel seguito ne verrà data una definizione e ne verranno definiti i campi di applicazione, per poi proseguire con un’analisi del processo dal punto di vista delle fasi che lo compongono e la speciale tecnologia utilizzata. Infine verrà proposto qualche studio fatto in merito ai tessuti vascolari e alla cartilagine per poi concludere con i pionieri che tuttora contribuiscono al suo sviluppo e con Organovo, una delle aziende leader del settore.

Anpassung des Metamodells PerPot an den ausdauerorientierten Laufsport zur Trainings- und Wettkampfoptimierung

Schon seit einigen Jahrzehnten wird die Sportwissenschaft durch computergestützte Methoden in ihrer Arbeit unterstützt. Mit der stetigen Weiterentwicklung der Technik kann seit einigen Jahren auch zunehmend die Sportpraxis von deren Einsatz profitieren. Mathematische und informatische Modelle sowie Algorithmen werden zur Leistungsoptimierung sowohl im Mannschafts- als auch im Individualsport genutzt. In der vorliegenden Arbeit wird das von Prof. Perl im Jahr 2000 entwickelte Metamodell PerPot an den ausdauerorientierten Laufsport angepasst. Die Änderungen betreffen sowohl die interne Modellstruktur als auch die Art der Ermittlung der Modellparameter. Damit das Modell in der Sportpraxis eingesetzt werden kann, wurde ein Kalibrierungs-Test entwickelt, mit dem die spezifischen Modellparameter an den jeweiligen Sportler individuell angepasst werden. Mit dem angepassten Modell ist es möglich, aus gegebenen Geschwindigkeitsprofilen die korrespondierenden Herzfrequenzverläufe abzubilden. Mit dem auf den Athleten eingestellten Modell können anschliessend Simulationen von Läufen durch die Eingabe von Geschwindigkeitsprofilen durchgeführt werden. Die Simulationen können in der Praxis zur Optimierung des Trainings und der Wettkämpfe verwendet werden. Das Training kann durch die Ermittlung einer simulativ bestimmten individuellen anaeroben Schwellenherzfrequenz optimal gesteuert werden. Die statistische Auswertung der PerPot-Schwelle zeigt signifikante Übereinstimmungen mit den in der Sportpraxis üblichen invasiv bestimmten Laktatschwellen. Die Wettkämpfe können durch die Ermittlung eines optimalen Geschwindigkeitsprofils durch verschiedene simulationsbasierte Optimierungsverfahren unterstützt werden. Bei der neuesten Methode erhält der Athlet sogar im Laufe des Wettkampfs aktuelle Prognosen, die auf den Geschwindigkeits- und Herzfrequenzdaten basieren, die während des Wettkampfs gemessen werden. Die mit PerPot optimierten Wettkampfzielzeiten für die Athleten zeigen eine hohe Prognosegüte im Vergleich zu den tatsächlich erreichten Zielzeiten.

Bitext alignment: building and evaluating a bilingual corpus and translation memory of academic course descriptions

Following the internationalization of contemporary higher education, academic institutions based in non-English speaking countries are increasingly urged to produce contents in English to address international prospective students and personnel, as well as to increase their attractiveness. The demand for English translations in the institutional academic domain is consequently increasing at a rate exceeding the capacity of the translation profession. Resources for assisting non-native authors and translators in the production of appropriate texts in L2 are therefore required in order to help academic institutions and professionals streamline their translation workload. Some of these resources include: (i) parallel corpora to train machine translation systems and multilingual authoring tools; and (ii) translation memories for computer-aided tools. The purpose of this study is to create and evaluate reference resources like the ones mentioned in (i) and (ii) through the automatic sentence alignment of a large set of Italian and English as a Lingua Franca (ELF) institutional academic texts given as equivalent but not necessarily parallel (i.e. translated). In this framework, a set of aligning algorithms and alignment tools is examined in order to identify the most profitable one(s) in terms of accuracy and time- and cost-effectiveness. In order to determine the text pairs to align, a sample is selected according to document length similarity (characters) and subsequently evaluated in terms of extent of noisiness/parallelism, alignment accuracy and content leverageability. The results of these analyses serve as the basis for the creation of an aligned bilingual corpus of academic course descriptions, which is eventually used to create a translation memory in TMX format.

Modellazione e rendering del lungomare di Riccione mediante Blender

Lo scopo di questa tesi è quello di realizzare un modello tridimensionale del lungomare di Riccione, mediante l'uso di programmi di modellazione, grafica e CAD (computer aided design). Lo scopo è di riprodurre un intero ambiente virtuale che l'utente sia libero di esplorare e in cui possa muoversi in totale libertà. Il possibile utilizzo di un tale progetto è quindi essenzialmente divulgativo o a fini turistici, poiché permette di far conoscere il lungomare di Riccione e di farlo esplorare attivamente dall'utente attraverso il computer comodamente da casa. Questo potrebbe successivamente invogliare gli utenti a visitare dal vivo la città, destando curiosità in merito agli arredi turistici precedentemente osservati in maniera virtuale.

Bioprinting: Stato dell'arte ed applicazioni biomediche

L’argomento trattato in questo elaborato riguarda una nuova tecnologia che si sta sviluppando nel settore dell’ingegneria dei tessuti: il Bioprinting. Tale rivoluzionario approccio completamente automatizzato, consiste nell’elaborazione automatica delle immagini CAD (Computer-Aided Design) e nella fabbricazione assistita CAM (Computer-Aided Manufacturing) al fine di ricreare tessuti ed organi. Nel seguito verrà data una definizione del processo, verranno analizzate le varie fasi di laborazione, le tecniche ed i materiali utilizzati. Verranno infine riportati studi riguardanti alcune applicazioni della tecnica, quali la realizzazione di vasi sanguigni, cartilagine e pelle.