No Abstract Provided

Th.--Lett.--Paris 4, 1978.

Στη συγκεκριμένη εργασία περιγράφουμε τρόπους κατάτμησης εικόνας ενώ ταυτόχρονα δίνουμε μια συνοπτική περιγραφή των χρωματικών χώρων και κάποιων βασικών αρχών της χρωματομετρίας. Στη συνέχεια συγκρίνουμε την αποδοτικότητα και σθεναρότητα των μεθόδων αυτών πάνω σε εικόνες υφασμάτων διαφορετικού χρώματος. Η σύγκριση αυτή γίνεται με βάση τα ιδιαίτερα χαρακτηριστικά των εικόνων (εικόνες π.χ. με περίπλοκα σχέδια παρουσιάζουν διαφορετική συμπεριφορά από άλλες με ένα μόνο σχέδιο) καθώς επίσης δίνεται ιδιαίτερη προσοχή στη δυνατότητα εξαγωγής αξιόπιστων αποτελεσμάτων στην περίπτωση όπου έχουμε εφαρμόσει υποδειγματοληψία. Τα αποτελέσματα αυτά σχολιάζονται στο τελευταίο κομμάτι της εργασίας όπου παρατίθενται τα αποτελέσματα που λάβαμε με τη χρήση του ΜATLAB. / -

Οι ρηξιγενείς ζώνες περιλαμβάνουν συνήθως ασυνεχή, υποπαράλληλα, κλιμακωτά ρηξιγενή τμήματα τα οποία χωρίζονται από ζώνες μεταβίβασης (relay zones). Καθώς οι ρηξιγενείς ζώνες εξελίσσονται, τα τμήματα των ζωνών αυτών, μπορούν να αλληλεπιδρούν μηχανικά και να ενώνονται σταδιακά, σχηματίζοντας έτσι δομές μεγαλύτερης κλίμακας με την αύξηση της παραμόρφωσης. Ο τρόπος με τον οποίο τα τμήματα αλληλεπιδρούν κατά τη διάρκεια της εξέλιξης των ζωνών, έχει γίνει αντικείμενο αρκετών ερευνών. Ωστόσο ακόμα και σήμερα οι γνώσεις μας για τις διεργασίες της αλληλεπίδρασης και της σύνδεσης των τμημάτων είναι περιορισμένες. Στην παρούσα εργασία, για τη μελέτη της τμηματοποίησης και του τρόπου σύνδεσης κανονικών ρηγμάτων, επιλέχτηκαν 3 περιοχές της Κεντρικής Ελλάδας: οι ρηξιγενείς ζώνες του Αιγίου και της Ελίκης στον Κορινθιακό κόλπο, οι ρηξιγενείς ζώνες της Αταλάντης και της Αρκίτσας στον Ευβοϊκό κόλπο και τέλος οι σύνθετες ρηξιγενείς ζώνες του Καπαρελλίου και της Δάφνης στην περιοχή της Βοιωτίας. Οι δύο πρώτες έχουν ΔΒΔ διεύθυνση, ενώ η τελευταία έχει σχεδόν Α-Δ διεύθυνση και αντιπροσωπεύει τη ζώνη παραμόρφωσης μεταξύ των δύο κύριων ζωνών rift. Η επιλογή των περιοχών αυτών έγινε με βάση την σημαντική τεκτονική τους δραστηριότητα τα τελευταία 1.5 εκατομμύρια χρόνια και την σπουδαιότητα τους στη νεοτεκτονική εξέλιξη της Κεντρικής Ελλάδας. Στην παρούσα διατριβή υπολογίστηκαν παράμετροι που αντανακλούν έμμεσα την κατανομή της τάσης γύρω από τα ρήγματα, όπως είναι η κατακόρυφη μετατόπιση (D), το μήκος των ρηγμάτων (L), ο αριθμός των ρηξιγενών τμημάτων κάθε ζώνης (n), η επικάλυψη (OL), η κλιμάκωση (S), και το μήκος της ζώνης μεταβίβασης (Lr). Οι παράμετροι αυτοί αποτελούν δείκτες του βαθμού σύνδεσης μεταξύ των ρηξιγενών τμημάτων καθώς και του βαθμού ωριμότητας μιας ενεργού ζώνης. Έτσι, χρησιμοποιήθηκαν αρχικά Ψηφιακά Μοντέλα Αναγλύφου (DEM) από τα οποία κατασκευάστηκαν τοπογραφικά προφίλ σε κάθε ρηξιγενή ζώνη, με σκοπό τον υπολογισμό της κατακόρυφης μετατόπισης των ρηγμάτων τόσο στα επι μέρους τμήματα όσο και στις ζώνες μεταβίβασης καθώς και η κατανομή της μετατόπισης κατά μήκος οροφής-βάσης των ρηγμάτων. Επίσης προσδιορίστηκε η γεωμετρία των ζωνών μεταβίβασης μεταξύ των ρηξιγενών τμημάτων, με σκοπό να εξετασθούν οι τρόποι σύνδεσης των τμημάτων με υπολογισμό του μήκους των μη επικαλυπτόμενων ζωνών (underlapping zone), των ζωνών επικάλυψης (overlap zone) και των κλιμακώσεων (separation/spacing). Τα μήκη των τμημάτων των ρηξιγενών ζωνών προβλήθηκαν σε διαγράμματα αθροιστικής συχνότητας με σκοπό την περιγραφή των πληθυσμών των ρηγμάτων στις τρεις περιοχές μελέτης. Τα διαγράμματα δηλώνουν μια πολυκλασματική κατανομή, που αντιπροσωπεύει διαφορετικούς πληθυσμούς ρηγμάτων που αλληλεπιδρούν ή μια εκθετική κατανομή που δείχνει ένα πρώιμο στάδιο κορεσμού των ρηγμάτων. Στη συνέχεια, κατασκευάστηκαν διαγράμματα της μέγιστης κατακόρυφης μετατόπισης των τμημάτων με το μήκος (D-L), με σκοπό να προσδιοριστεί σε ποιο στάδιο σύνδεσης βρίσκονται οι συγκεκριμένες ζώνες και να προταθούν μοντέλα εξέλιξης αυτών. Τέλος εξετάστηκαν και συσχετίστηκαν τα γεωμετρικά χαρακτηριστικά των ζωνών μεταβίβασης (μήκος κλιμάκωσης, μήκος επικαλυπτόμενων ή μη τμημάτων), με σκοπό την εξαγωγή συμπερασμάτων για την ικανοποίηση ή μη κριτηρίων αλληλεπίδρασης των τμημάτων και της πιθανής σύνδεσης αυτών. Η κατανόηση του ρόλου της τμηματοποίησης και του τρόπου σύνδεσης των τμημάτων των ρηξιγενών ζωνών μπορεί να βοηθήσει σημαντικά στην εκτίμηση της σεισμικής επικινδυνότητας μιας περιοχής, στην κατανόηση των ιζηματογενών διαδικασιών μπροστά από τα ρήγματα καθώς και στον προσδιορισμό παγίδων ρευστής φάσης και της μετανάστευσή τους, μιας και οι ζώνες μεταβίβασης δύναται να αποτελούν περιοχές διαφυγής ή εμπόδια στη ροή των ρευστών. / Fault zones are commonly composed of discontinuous, sub-parallel, stepping fault segments, separated by relay zones. During the growth of a fault zone, its segments interact mechanically and link up into gradually larger segments that eventually may form large structures, due to strain accommodation. The way that segments interact during the growth of a fault zone, has been the subject of several studies. Yet, present understanding of interaction and linkage of segments, continues to be shrouded by considerable uncertainty. Three areas in central Greece were chosen, to investigate the role of segmentation and linkage of normal faults: the Aigio and Eliki fault zones in the Gulf of Corinth, the Atalanti and Arkitsa fault zones in the Northern Gulf of Evoia and the composite fault zones of Kaparelli and Dafnes in Beotia area. The Gulf of Corinth and the Northern Gulf of Evia are WNW-trending grabens, while Beotia area represents the deformed zone between the two main rift zones. These areas have been chosen due to their significant tectonic activity in the last 1.5Ma and their great importance in the neotectonic evolution of central Greece. In this study, several parameters reflecting the stress distribution around faults, have been measured, such as the vertical displacement (D), the number of segments (n), the overlap (OL), the spacing (S) and the length of relay zone (Lr). These parameters are indicators of the degree of linkage between fault segments and the degree of maturity of an active fault zone. Digital Elevation Models (DEM) have been used to construct elevation profiles in every fault zone, in order to measure the vertical throw of each segment, and in the relay zones as well as the distribution of displacement in footwall and hanging wall blocks. In addition, the geometry of the relay zones between fault segments is defined by calculating the length of underlapping zone, the length of overlapping zone and the length of spacing, in order to examine the segment linkage. The lengths of fault zones’ segments have been illustrated in plots of cumulative frequency, in order to describe the fault population in the three study areas. The plots indicate either multifractal distribution that represents fault population with different characteristics that interact or exponential distribution that shows an early stage of fault saturation. The relationship between maximum vertical displacement and length is illustrated in d-L plots, in order to determine the linkage stage of the particular fault zones and to propose evolutionary models. Finally the geometric characteristics of relay zones (spacing, length of underlapping or overlapping segments) were examined, in order to investigate whether or not the segments satisfy the interaction criteria and their possible linkage. Segmentation and fault segment linkage plays an important role in evaluating seismic hazard of an area, the architecture of sedimentary deposits, as well as in fluid flow in faulted reservoirs since relay zones can act as leakage zones or barriers from the hanging wall to the footwall blocks.

This thesis summarizes a series of studies of how image quality is affected by the choice of sampling pattern in 3D. Our comparison includes the Cartesian cubic (CC) lattice, the body-centered cubic (BCC) lattice, and the face-centered cubic (FCC) lattice. Our studies of the lattice Brillouin zones of lattices of equal density show that, while the CC lattice is suitable for functions with elongated spectra, the FCC lattice offers the least variation in resolution with respect to direction. The BCC lattice, however, offers the highest global cutoff frequency. The difference in behavior between the BCC and FCC lattices is negligible for a natural spectrum. We also present a study of pre-aliasing errors on anisotropic versions of the CC, BCC, and FCC sampling lattices, revealing that the optimal choice of sampling lattice is highly dependent on lattice orientation and anisotropy. We suggest a new reference function for studies of aliasing errors on alternative sampling lattices. This function has a spherical spectrum, and a frequency content proportional to the distance from the origin, facilitating studies of pre-aliasing in spatial domain. The accuracy of anti-aliased Euclidean distance transform is improved by application of more sofisticated methods for computing the sub-spel precision term. We find that both accuracy and precision are higher on the BCC and FCC lattices than on the CC lattice. We compare the performance of several intensity-weighted distance transforms on MRI data, and find that the derived segmentation result, with respect to relative error in segmented volume, depends neither on the sampling lattice, nor on the sampling density. Lastly, we present LatticeLibrary, a open source C++ library for processing of sampled data, supporting a number of common image processing methods for CC, BCC, and FCC lattices. We also introduce BccFccRaycaster, a tool for visualizing data sampled on CC, BCC, and FCC lattices. We believe that the work summarized in this thesis provide both the motivation and the tools for continuing research on application of the BCC and FCC lattices in image processing and analysis.

Modern computer vision has seen recently significant progress in learning visual concepts from examples. This progress has been fuelled by recent models of visual appearance as well as recently collected large-scale datasets of manually annotated still images. Video is a promising alternative, as it inherently contains much richer information compared to still images. For instance, in video we can observe an object move which allows us to differentiate it from its surroundings, or we can observe a smooth transition between different viewpoints of the same object instance. This richness in information allows us to effectively tackle tasks that would otherwise be very difficult if we only considered still images, or even adress tasks that are video-specific. Our first contribution is a computationally efficient technique for video object segmentation. Our method relies solely on motion in order to rapidly create a rough initial estimate of the foreground object. This rough initial estimate is then refined through an energy formulation to be spatio-temporally smooth. The method is able to handle rapidly moving backgrounds and objects, as well as non-rigid deformations and articulations without having prior knowledge about the objects appearance, size or location. In addition to this class-agnostic method, we present a class-specific method that incorporates additional class-specific appearance cues when the class of the foreground object is known in advance (e.g. a video of a car). For our second contribution, we propose a novel model for temporal video alignment with regard to the viewpoint of the foreground object (i.e., a pair of aligned frames shows the same object viewpoint) Our work relies on our video object segmentation technique to automatically localise the foreground objects and extract appearance measurements solely from them instead of the background. Our model is able to temporally align realistic videos, where events may occur in a different order, or occur only in one of the videos. This is in contrast to previous works that typically assume that the videos show a scripted sequence of events and can simply be aligned by stretching or compressing one of the videos. As a final contribution, we once again use our video object segmentation technique as a basis for automatic visual aspect discovery from videos of an object class. Compared to previous works, we use a broader definition of an aspect that considers four factors of variation: viewpoint, articulated pose, occlusions and cropping by the image border. We pose the aspect discovery task as a clustering problem and provide an extensive experimental exploration on the benefits of object segmentation for this task.

Em radioterapia externa, uma nova técnica chamada terapia de radiação de intensidade modulada - IMRT - permite delinear a dose de radiação em imagens de 2 ou 3 dimensões, delimitando de forma bastante precisa e não necessariamente uniforme a região a ser irradiada. Assim, ao mesmo tempo que o tumor é irradiado, é possível evitar a irradiação aos tecidos vizinhos íntegros (sãos), limitando os efeitos secundários do tratamento. Para que a radioterapia externa tenha sucesso usando a técnica IMRT, é fundamental delinear previamente de forma precisa o tumor e os órgãos sãos que devem ser protegidos da radiação, garantindo assim a dose exata de radiação nos volumes alvos. O objetivo desta tese é fornecer ferramentas que sejam adequadas ao delineamento automático de estruturas de interesse e à radioterapia adaptativa para tumores da região da cabeça e do pescoço. Atualmente, a segmentação de estruturas de interesse, tais como os órgãos em risco e as regiões de propagação tumoral, é feita manualmente. Esta é uma tarefa que demanda bastante tempo de um especialista, além de ser tediosa. Além do mais, o planejamento em radioterapia é feito baseado na imagem adquirida na semana do pré-tratamento, onde é calculada a dose. Normalmente o tratamento ocorre em várias semanas, porém a dose estimada no início do tratamento é a mesma para todas as outras semanas do tratamento. Calcular a dose e mantê-la nas demais semanas é uma simplificação que não corresponde à realidade, já que ocorrem mudanças anatômicas no paciente ao longo do tratamento. Estas mudanças ocorrem devido ao encolhimento do tumor e ao possível emagrecimento do paciente, provocando alterações anatômicas locais e globais. As contribuições desta tese visam solucionar e avançar nestes problemas e são apresentadas em dois eixos. No primeiro eixo, é proposta uma metodologia para escolher uma anatomia que seja representativa da população, anatomia esta chamada de atlas. O registro do atlas na imagem do paciente permite que estruturas de interesse sejam segmentadas automaticamente, acelerando o processo de delineamento e tornando-o mais robusto. A segunda contribuição desta tese é voltada à radioterapia adaptativa. Para que a dose estimada na primeira semana seja adaptada às modificações anatômicas, é necessária a utilização de métodos de registro não-rígidos. Portanto, nesta etapa é feita uma avaliação e adaptação dos métodos de registros de forma que a região do tumor esteja bem alinhada. / Intensity Modulated Radiotherapy (IMRT) is a new technique enabling the delineation of the 3D radiation dose. It allows to delineate a radiation zone of almost any shape and to modulate the beam intensity inside the target. If IMRT enables to constrain the radiation plan in the beam delivery as well as in the protection of important functional areas (e.g. spinal cord), it also raises the issues of adequacy and accuracy of the selection and delineation of the target volumes. The purpose of this thesis is to provide tools to automatic delineation of the regions of interest and also to adaptive radiotherapy treatment for tumors located in the head and neck region. The delineation in the patient computed tomography image of the tumor volume and organs to be protected is currently performed by an expert who delineates slice by slice the contours of interest. This task is highly time-consuming and requires experts’ knowledge. Moreover, the planning process in radiotherapy typically involves the acquisition of a unique set of computed tomography images in treatment position on which target volumes (TVs) and normal structures are delineated, and which are used for dose calculation. Restricting the delineation of these regions of interest based solely on pre-treatment images is an oversimplification as it is only a snapshot of the patient´s anatomy at a given time. Shrinkage of the tumor and modification of the patient anatomy at large (e.g. due to weight loss) may indeed occur within the several weeks’ duration of a typical treatment. The main contributions of this thesis aim to advance in the solution to these issues and are presented in two axes. In the first one, it is proposed a methodology to choose an image with the most representative anatomy of a population; such image is called Atlas. The registration of the atlas into a new image of the patient allows to automatically segment the structures of interest, speeding up the delineation process and making it more robust. The second contribution of this thesis is focused on the adaptive radiotherapy. In order to adjust the estimated dose to the anatomical modifications, it is fundamental to have non-rigid registration algorithms. So, the evaluation and adaptation of non-rigid registration methods are required, addressing especially the alignment of the tumor’s region among different moments of the treatment.

The official U.S. standards for corn have been available for almost one hundred years. Corn grading system has been gradually updated over the years. In this thesis, we investigated a fast corn grading system, which includes the mechanical part and the computer recognition part. The mechanical system can deliver the corn kernels onto the display plate. For the computer recognition algorithms, we extracted common features from each corn kernel, and classified them to measure the grain quality.

Statistical learning refers to the ability to track regular patterns in sensory input from ambient environments. This learning mechanism can exploit a wide range of statistical structures (e.g., frequency, distribution, and co-occurrence probability). Given its regularities and hierarchical structures, language is essentially a pattern-based system and therefore researchers have argued that statistical learning is fundamental to language acquisition (e.g., Saffran, 2003). Indeed, young infants and adults can find words in artificial languages by tracking syllable co-occurrence probabilities and extracting words on that basis (e.g., Saffran. Aslin & Newport, 1996a). However, prior studies have mainly focused on whether learners can statistically segment words from a single language; whether learners can segment words from two artificial languages remains largely unknown. Given that the majority of the global population is bilingual (Grosjean, 2010), it is necessary to study whether learners can make use of the statistical learning mechanism to segment words from two language inputs, which is the focus of this thesis. I examined adult and infant learners to answer three questions: (i) Can learners make use of French and English phonetic cues within a single individual’s speech to segment words successfully from two languages?; 2) Do bilinguals outperform monolinguals?; and 3) Do specific factors, such as cognitive ability or bilingual experience, underlie any potential bilingual advantage in word segmentation across two languages? In Study 1, adult learners generally could make use of French and English phonetic cues to segment words from two overlapping artificial languages. Importantly, simultaneous bilinguals who learned French and English since birth segmented more correct words in comparison to monolinguals, multilinguals, and sequential French-English bilinguals. Early bilingual experience may lead learners to be more flexible when processing information in new environments and/or they are more sensitive to subtle cues that mark the changes of language inputs. Further, individuals’ cognitive abilities were not related to learners’ segmentation performance, suggesting that the observed simultaneous bilingual segmentation advantage is not related any bilingual cognitive advantages (Bialystok, Craik, & Luk, 2012). In Study 2, I tested 9.5-month-olds, who are currently discovering words in their natural environment, in an infant version of the adult task. Surprisingly, monolingual, but not bilingual, infants successfully used French and English phonetic cues to segment words from two languages. The observed difference in segmentation may be related to how infant process native and non-native phonetic cues, as the French phonetic cues are non-native to monolingual infants but are native to bilingual infants. Finally, the observed difference in segmentation ability was again not driven by cognitive skills. In sum, current thesis provides evidence that both adults and infants can make use of phonetic cues to statistically segment words from two languages. The implications of why early bilingualism plays a role in determining learners’ segmentation ability are discussed.

Em radioterapia externa, uma nova técnica chamada terapia de radiação de intensidade modulada - IMRT - permite delinear a dose de radiação em imagens de 2 ou 3 dimensões, delimitando de forma bastante precisa e não necessariamente uniforme a região a ser irradiada. Assim, ao mesmo tempo que o tumor é irradiado, é possível evitar a irradiação aos tecidos vizinhos íntegros (sãos), limitando os efeitos secundários do tratamento. Para que a radioterapia externa tenha sucesso usando a técnica IMRT, é fundamental delinear previamente de forma precisa o tumor e os órgãos sãos que devem ser protegidos da radiação, garantindo assim a dose exata de radiação nos volumes alvos. O objetivo desta tese é fornecer ferramentas que sejam adequadas ao delineamento automático de estruturas de interesse e à radioterapia adaptativa para tumores da região da cabeça e do pescoço. Atualmente, a segmentação de estruturas de interesse, tais como os órgãos em risco e as regiões de propagação tumoral, é feita manualmente. Esta é uma tarefa que demanda bastante tempo de um especialista, além de ser tediosa. Além do mais, o planejamento em radioterapia é feito baseado na imagem adquirida na semana do pré-tratamento, onde é calculada a dose. Normalmente o tratamento ocorre em várias semanas, porém a dose estimada no início do tratamento é a mesma para todas as outras semanas do tratamento. Calcular a dose e mantê-la nas demais semanas é uma simplificação que não corresponde à realidade, já que ocorrem mudanças anatômicas no paciente ao longo do tratamento. Estas mudanças ocorrem devido ao encolhimento do tumor e ao possível emagrecimento do paciente, provocando alterações anatômicas locais e globais. As contribuições desta tese visam solucionar e avançar nestes problemas e são apresentadas em dois eixos. No primeiro eixo, é proposta uma metodologia para escolher uma anatomia que seja representativa da população, anatomia esta chamada de atlas. O registro do atlas na imagem do paciente permite que estruturas de interesse sejam segmentadas automaticamente, acelerando o processo de delineamento e tornando-o mais robusto. A segunda contribuição desta tese é voltada à radioterapia adaptativa. Para que a dose estimada na primeira semana seja adaptada às modificações anatômicas, é necessária a utilização de métodos de registro não-rígidos. Portanto, nesta etapa é feita uma avaliação e adaptação dos métodos de registros de forma que a região do tumor esteja bem alinhada. / Intensity Modulated Radiotherapy (IMRT) is a new technique enabling the delineation of the 3D radiation dose. It allows to delineate a radiation zone of almost any shape and to modulate the beam intensity inside the target. If IMRT enables to constrain the radiation plan in the beam delivery as well as in the protection of important functional areas (e.g. spinal cord), it also raises the issues of adequacy and accuracy of the selection and delineation of the target volumes. The purpose of this thesis is to provide tools to automatic delineation of the regions of interest and also to adaptive radiotherapy treatment for tumors located in the head and neck region. The delineation in the patient computed tomography image of the tumor volume and organs to be protected is currently performed by an expert who delineates slice by slice the contours of interest. This task is highly time-consuming and requires experts’ knowledge. Moreover, the planning process in radiotherapy typically involves the acquisition of a unique set of computed tomography images in treatment position on which target volumes (TVs) and normal structures are delineated, and which are used for dose calculation. Restricting the delineation of these regions of interest based solely on pre-treatment images is an oversimplification as it is only a snapshot of the patient´s anatomy at a given time. Shrinkage of the tumor and modification of the patient anatomy at large (e.g. due to weight loss) may indeed occur within the several weeks’ duration of a typical treatment. The main contributions of this thesis aim to advance in the solution to these issues and are presented in two axes. In the first one, it is proposed a methodology to choose an image with the most representative anatomy of a population; such image is called Atlas. The registration of the atlas into a new image of the patient allows to automatically segment the structures of interest, speeding up the delineation process and making it more robust. The second contribution of this thesis is focused on the adaptive radiotherapy. In order to adjust the estimated dose to the anatomical modifications, it is fundamental to have non-rigid registration algorithms. So, the evaluation and adaptation of non-rigid registration methods are required, addressing especially the alignment of the tumor’s region among different moments of the treatment.