Οι πρόσφατες εξελίξεις στις ασύρματες επικοινωνίες και στα ηλεκτρονικά κυκλώματα έχουν επιτρέψει την ανάπτυξη υπολογιστικών διατάξεων χαμηλού κόστους και χαμηλής κατανάλωσης ισχύος, οι οποίες ενσωματώνουν δυνατότητες μέτρησης (sensing), επεξεργασίας και ασύρματης επικοινωνίας. Οι διατάξεις αυτές, οι οποίες έχουν ιδιαίτερα μικρό μέγεθος, καλούνται κόμβοι αισθητήρες. Ένα ασύρματο δίκτυο κόμβων αισθητήρων αποτελείται από ένα πλήθος κόμβων οι οποίοι έχουν αναπτυχθεί σε κάποια περιοχή ενδιαφέροντος προκειμένου να μετρούν κάποια μεταβλητή του περιβάλλοντος. Ανάμεσα σε πολλές εφαρμογές, ο εντοπισμός και η παρακολούθηση των θέσεων πηγών οι οποίες εκπέμπουν κάποιο σήμα (π.χ. ακουστικό, ηλεκτρομαγνητικό) αποτελεί ένα πολύ ενδιαφέρον θέμα, το οποίο μάλιστα μπορεί να χρησιμοποιηθεί και ως βάση για τη μελέτη άλλων προβλημάτων τα οποία εμφανίζονται στα ασύρματα δίκτυα αισθητήρων. Οι περισσότερες από τις υπάρχουσες τεχνικές εντοπισμού θέσης μιας πηγής από μια συστοιχία αισθητήρων μπορούν να ταξινομηθούν σε δυο κατηγορίες: (α) Τις τεχνικές οι οποίες χρησιμοποιούν μετρήσεις διεύθυνσης άφιξης (Direction of Arrival, DOA) και (β) τις τεχνικές οι οποίες χρησιμοποιούν μετρήσεις διαφοράς χρόνων άφιξης (Time Difference of Arrival, TDOA). Ωστόσο, οι τεχνικές αυτές απαιτούν υψηλό ρυθμό δειγματοληψίας και ακριβή συγχρονισμό των κόμβων και δε συνάδουν έτσι με τις περιορισμένες ικανότητες των κόμβων αισθητήρων. Για τους λόγους αυτούς, το ενδιαφέρον έχει στραφεί σε μια τρίτη κατηγορία τεχνικών οι οποίες χρησιμοποιούν μετρήσεις ισχύος (Received Signal Strength, RSS). Το πρόβλημα του εντοπισμού θέσης χρησιμοποιώντας μετρήσεις ισχύος είναι ένα πρόβλημα εκτίμησης, όπου οι μετρήσεις συνδέονται με τις προς εκτίμηση παραμέτρους με μη-γραμμικό τρόπο. Στα πλαίσια της Διδακτορικής Διατριβής ασχολούμαστε αρχικά με την περίπτωση όπου επιθυμούμε να εκτιμήσουμε τη θέση και την ισχύ μιας πηγής χρησιμοποιώντας μετρήσεις ισχύος οι οποίες φθίνουν με βάση το αντίστροφο του τετραγώνου της απόστασης ανάμεσα στην πηγή και το σημείο μέτρησης. Για το πρόβλημα αυτό, προτείνουμε έναν εκτιμητή ο οποίος δίνει τις παραμέτρους της πηγής ως λύση ενός γραμμικού προβλήματος ελαχίστων τετραγώνων. Στη συνέχεια, υπολογίζουμε κατάλληλα βάρη και προτείνουμε έναν εκτιμητή ο οποίος δίνει τις παραμέτρους της πηγής ως λύση ενός προβλήματος ελαχίστων τετραγώνων με βάρη. Ακόμα, τροποποιούμε κατάλληλα τον τελευταίο εκτιμητή έτσι ώστε να είναι δυνατή η κατανεμημένη υλοποίησή του μέσω των προσαρμοστικών αλγορίθμων Least Mean Square (LMS) και Recursive Least Squares (RLS). Στη συνέχεια, εξετάζουμε την περίπτωση όπου ενδιαφερόμαστε να εκτιμήσουμε τη θέση μιας πηγής αλλά δεν έχουμε καμιά πληροφορία σχετικά με το μοντέλο εξασθένισης της ισχύος. Έτσι, υποθέτουμε πως αυτό περιγράφεται από μια άγνωστη γνησίως φθίνουσα συνάρτηση της απόστασης. Αρχικά, προσεγγίζουμε το πρόβλημα εκτίμησης κάνοντας την υπόθεση πως οι θέσεις των κόμβων αποτελούν τυχαία σημεία ομοιόμορφα κατανεμημένα στο επίπεδο. Χρησιμοποιώντας την υπόθεση αυτή, υπολογίζουμε εκτιμήσεις για τις αποστάσεις ανάμεσα στους κόμβους και την πηγή, και αναπτύσσουμε έναν αλγόριθμο εκτίμησης της θέσης της πηγής. Στη συνέχεια, προσεγγίζουμε το πρόβλημα εκτίμησης χωρίς την υπόθεση περί ομοιόμορφης κατανομής των θέσεων των κόμβων στο επίπεδο. Προτείνουμε μια κατάλληλη συνάρτηση κόστους για την περίπτωση αυτή, και δείχνουμε την ύπαρξη μιας συνθήκης υπό την οποία η βέλτιστη λύση μπορεί να υπολογιστεί. Η λύση αυτή είναι εσωτερικό σημείο ενός κυρτού πολυγώνου, το οποίο ονομάζουμε ταξινομημένο τάξης-K κελί Voronoi. Έτσι, δίνουμε αλγορίθμους υπολογισμού της λύσης αυτής, καθώς και κατανεμημένους αλγορίθμους οι οποίοι βασίζονται σε προβολές σε κυρτά σύνολα. Ακόμα, ασχολούμαστε με τις ιδιότητες των κελιών αυτών στην περίπτωση όπου οι θέσεις των κόμβων αισθητήρων είναι ομοιόμορφα κατανεμημένες στο επίπεδο και υπολογίζουμε κάποια φράγματα για το εμβαδόν τους. Τέλος, ασχολούμαστε με την περίπτωση όπου ενδιαφερόμαστε να εκτιμήσουμε τις θέσεις πολλαπλών πηγών με γνωστό μοντέλο εξασθένισης της ισχύος. Για το πρόβλημα αυτό, αρχικά προτείνουμε έναν αλγόριθμο διαδοχικής εκτίμησης και ακύρωσης της συνεισφοράς κάθε πηγής, προκειμένου να υπολογιστούν σταδιακά οι θέσεις όλων των πηγών. Ο αλγόριθμος αυτός, αποτελείται από τρία βήματα κατά τα οποία πρώτα υπολογίζεται μια προσεγγιστική θέση για την πηγή, στη συνέχεια εκτιμάται ένα σύνολο κόμβων το οποίο δέχεται μικρής έντασης παρεμβολή από τις υπόλοιπες πηγές, και τέλος επιχειρείται μια λεπτομερέστερη εκτίμηση της θέσης κάθε πηγής. Στη συνέχεια, επεκτείνοντας την τεχνική αυτή, προτείνουμε έναν επαναληπτικό αλγόριθμο εκτίμησης ο οποίος βασίζεται στον αλγόριθμο εναλλασσόμενων προβολών (Alternating Projections). Εξετάζουμε επίσης μεθόδους οι οποίες οδηγούν στη μείωση της υπολογιστικής πολυπλοκότητας του αλγορίθμου αυτού. / Technology advances in microelectronics and wireless communications have enabled the development of small-scale devices that integrate sensing, processing and short-range radio capabilities. The deployment of a large number of such devices, referred to as sensor nodes, over a territory of interest, defines the so-called wireless sensor network. Wireless sensor networks have attracted considerable attention in recent years and have motivated many new challenges, most of which require the synergy of many disciplines, including signal processing, networking and distributed algorithms. Among many other applications, source localization and tracking has been widely viewed as a canonical problem of wireless sensor networks. Furthermore, it constitutes an easily perceived problem that can be used as a vehicle to study more involved information processing and organization problems. Most of the source localization methods that have appeared in the literature can be classified into two broad categories, according to the physical variable they utilize. The algorithms of the first category utilize “time delay of arrival”(TDOA) measurements, and the algorithms of the second category use “direction of arrival” (DOA) measurements. DOA estimates are particularly useful for locating sources emitting narrowband signals, while TDOA measurements offer the increased capability of localizing sources emitting broadband signals. However, the methods of both categories impose two major requirements that render them inappropriate to be used in wireless sensor networks: (a) the analog signals at the outputs of the spatially distributed sensors should be sampled in a synchronized fashion, and (b) the sampling rate used should be high enough so as to capture the features of interest. These requirements, in turn, imply that accurate distributed synchronization methods should be implemented so as to keep the remote sensor nodes synchronized and that high frequency electronics as well as increased bandwidth are needed to transmit the acquired measurements. Due to the aforementioned limitations, source localization methods that rely upon received signal strength (RSS) measurements - originally explored for locating electromagnetic sources - have recently received revived attention. In this Thesis, we begin our study by considering the localization of an isotropic acoustic source using energy measurements from distributed sensors, in the case where the energy decays according to an inverse square law with respect to the distance. While most acoustic source localization algorithms require that distance estimates between the sensors and the source of interest are available, we propose a linear least squares criterion that does not make such an assumption. The new criterion can yield the location of the source and its transmit power in closed form. A weighted least squares cost function is also considered, and distributed implementation of the proposed estimators is studied. Numerical results indicate significant performance improvement as compared to a linear least squares based approach that utilizes energy ratios, and comparable performance to other estimators of higher computational complexity. In the sequel, we turn our attention to the case where the energy decay model is not known. For solving the localization problem in this case, we first make the assumption that the locations of the nodes near the source can be well described by a uniform distribution. Using this assumption, we derive distance estimates that are independent of both the energy decay model and the transmit power of the source. Numerical results show that these estimates lead to improved localization accuracy as compared to other model-independent approaches. In the sequel, we consider the more general case where the assumption about the uniform deployment of the sensors is not required. For this case, an optimization problem that does not require knowledge of the underlying energy decay model is proposed, and a condition under which the optimal solution can be computed is given. This condition employs a new geometric construct, called the sorted order-K Voronoi diagram. We give centralized and distributed algorithms for source localization in this setting. Finally, analytical results and simulations are used to verify the performance of the developed algorithms. The next problem we consider is the estimation of the locations of multiple acoustic sources by a network of distributed energy measuring sensors. The maximum likelihood (ML) solution to this problem is related to the optimization of a non-convex function of, usually, many variables. Thus, search-based methods of high complexity are required in order to yield an accurate solution. In order to reduce the computational complexity of the multiple source localization problem, we propose two methods. The first method proposes a sequential estimation algorithm, in which each source is localized, its contribution is cancelled, and the next source is considered. The second method makes use of an alternating projection (AP) algorithm that decomposes the original problem into a number of simpler, yet also non-convex, optimization steps. The particular form of the derived cost functions of each such optimization step indicates that, in some cases, an approximate form of these cost functions can be used. These approximate cost functions can be evaluated using considerably lower computational complexity. Thus, a low-complexity version of the AP algorithm is proposed. Extensive simulation results demonstrate that the proposed algorithm offers a performance close to that of the exact AP implementation, and in some cases, similar performance to that of the ML estimator.

No description available.

Before the publication of David Hockney’s book Secret Knowledge: rediscovering the lost techniques of the Old Masters in 2001, it was commonly believed that the first artist to use an optical aid in painting was the seventeenth-century Dutch painter Johannes Vermeer. Hockney, however, believes that the use of projected images started much earlier, as early as the fifteenth-century, claiming that evidence can be found in the work of the Flemish painter Jan van Eyck. Without rejecting Hockney’s pioneering work in this field, I nevertheless make the perhaps bolder claim that Italian artists were using the aid of image projections even before the time of Jan van Eyck, that is, as early as 1270. Although much of the information required to make an earlier claim for the use of optics can be found in Hockney’s publication, the key to linking all the information together has been missing. It is my unique contention that this key is a letter that has always been believed to have been European in origin. More commonly referred to as Roger Bacon’s Letter I show in detail how this letter was, in fact, not written by Roger Bacon, but addressed to him, and that this letter originated in China. Chinese knowledge about projected images, that is the concept that light-pictures could be received onto appropriate supports, came directly to Europe around 1250. This knowledge was expanded upon by Roger Bacon in his Opus Majus, a document which arrived in Italy in 1268 for the special consideration of Pope Clement IV. The medieval Italian painter Cimabue was able to benefit directly from this information about optical systems, when he himself was in Rome in 1272. He immediately began to copy optical projections, which stimulated the creation of a new, more individualistic, mode of representation in Italian painting from this time forward. The notion that projected images greatly contributed towards the development of naturalism in medieval Italian painting replaces the previously weak supposition that the stimulation was classical or humanist theory, and shows that it was, in fact, far likely something more technical as well. / Art History / D.Litt. et Phil. (Art History)

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-06-20T13:50:43Z No. of bitstreams: 1 arquivototal.pdf: 7102668 bytes, checksum: abe19d798ad952073affbf4950f62d29 (MD5) / Made available in DSpace on 2017-06-20T13:50:43Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7102668 bytes, checksum: abe19d798ad952073affbf4950f62d29 (MD5) Previous issue date: 2016-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In Analytical Chemistry it has been recurring in the literature the use of analytical signals recorded on multiple sensors combined with subsequent chemometric modeling for developing new analytical methodologies. For this purpose, it uses generally multivariate instrumental techniques as spectrometry ultraviolet-visible or near infrared, voltammetry, etc. In this scenario, the analyst is faced with the option of selecting individual variables or variable intervals so to avoid or reduce multicollinearity problems. A well-known strategy for selection of variable intervals is to divide the set of instrumental responses into equal width intervals and select the best interval based on the performance of the prediction of a unique range in the regression by Partial Least Squares (iPLS). On the other hand, the use of interval selection for classification purposes has received relatively little attention. A common practice is to use the iPLS regression method with the coded class indices as response variables to be predicted; that is the basic idea behind the release of the Discriminant Analysis by Partial Least Squares (PLS-DA) for classification. In other words, interval selection for classification purposes has no development of native functions (algorithms). Thus, in this work it is proposed two new strategies in classification problems using interval selection by the Successive Projections Algorithm. The first strategy is named Successive Projections Algorithm for selecting intervals in Discriminant Analysis Partial Least Squares (iSPA-PLS-DA), while the second strategy is called Successive Projections Algorithm for selecting intervals in Soft and Independent Modeling by Class Analogy (iSPA-SIMCA). The performance of the proposed algorithms was evaluated in three case studies: classification of vegetable oils according to the type of raw material and the expiration date using data obtained by square wave voltammetry; classification of unadulterated biodiesel/diesel blends (B5) and adulterated with soybean oil (OB5) using spectral data obtained in the ultraviolet-visible region; and classification of vegetable oils with respect to the expiration date using spectral data obtained in the near infrared region. The proposed iSPA-PLS-DA and iSPA-SIMCA algorithms provided good results in the three case studies, with correct classification rates always greater than or equal to those obtained by PLS-DA and SIMCA models using all variables, iPLS-DA and iSIMCA with a single selected interval, as well as SPA-LDA and GA-LDA with selection of individual variables. Therefore, the proposed iSPA-PLS-DA and iSPA-SIMCA algorithms can be considered as promising approaches for use in classification problems employing interval selection. In a more general point of view, the possibility of using interval selection without loss of the classification accuracy can be considered a very useful tool for the construction of dedicated instruments (e.g. LED-based photometers) for use in routine and in situ analysis. / Em Química Analítica tem sido recorrente na literatura o uso de sinais analíticos registrados em múltiplos sensores combinados com posterior modelagem quimiométrica para desenvolvimento de novas metodologias analíticas. Para esta finalidade, geralmente se faz uso de técnicas instrumentais multivariadas como a espectrometrias no ultravioleta-visível ou no infravermelho próximo, voltametria, etc. Neste cenário, o analista se depara com a opção de selecionar variáveis individuais ou intervalos de variáveis de modo de evitar ou diminuir problemas de multicolinearidade. Uma estratégia bem conhecida para seleção de intervalos de variáveis consiste em dividir o conjunto de respostas instrumentais em intervalos de igual largura e selecionar o melhor intervalo com base no critério de desempenho de predição de um único intervalo em regressão por Mínimos Quadrados Parciais (iPLS). Por outro lado, o uso da seleção de intervalo para fins de classificação tem recebido relativamente pouca atenção. Uma prática comum consiste em utilizar o método de regressão iPLS com os índices de classe codificados como variáveis de resposta a serem preditos, que é a idéia básica por trás da versão da Análise Discriminante por Mínimos Quadrados Parciais (PLS-DA) para a classificação. Em outras palavras, a seleção de intervalos para fins de classificação não possui o desenvolvimento de funções nativas (algoritmos). Assim, neste trabalho são propostas duas novas estratégias em problemas de classificação que usam seleção de intervalos de variáveis empregando o Algoritmo das Projeções Sucessivas. A primeira estratégia é denominada de Algoritmo das Projeções Sucessivas para seleção intervalos em Análise Discriminante por Mínimos Quadrados Parciais (iSPA-PLS-DA), enquanto a segunda estratégia é denominada de Algoritmo das Projeções Sucessivas para a seleção de intervalos em Modelagem Independente e Flexível por Analogia de Classe (iSPA-SIMCA). O desempenho dos algoritmos propostos foi avaliado em três estudos de casos: classificação de óleos vegetais com relação ao tipo de matéria-prima e ao prazo de validade utilizando dados obtidos por voltametria de onda quadrada; classificação de misturas biodiesel/diesel não adulteradas (B5) e adulteradas com óleo de soja (OB5) empregando dados espectrais obtidos na região do ultravioleta-visível; e classificação de óleos vegetais com relação ao prazo de validade usando dados espectrais obtidos na região do infravermelho próximo. Os algoritmos iSPA-PLS-DA e iSPA-SIMCA propostos forneceram bons resultados nos três estudos de caso, com taxas de classificação corretas sempre iguais ou superiores àquelas obtidas pelos modelos PLS-DA e SIMCA utilizando todas as variáveis, iPLS-DA e iSIMCA com um único intervalo selecionado, bem como SPA-LDA e GA-LDA com seleção de variáveis individuais. Portanto, os algoritmos iSPA-PLS-DA e iSPA-SIMCA propostos podem ser consideradas abordagens promissoras para uso em problemas de classificação empregando seleção de intervalos de variáveis. Num contexto mais geral, a possibilidade de utilização de seleção de intervalos de variáveis sem perda da precisão da classificação pode ser considerada uma ferramenta bastante útil para a construção de instrumentos dedicados (por exemplo, fotômetros a base de LED) para uso em análise de rotina e de campo.

Made available in DSpace on 2015-03-03T15:47:48Z (GMT). No. of bitstreams: 1 DanielSB_DISSERT.pdf: 24552840 bytes, checksum: 7e0c26e7ae98555461ce350e2cef10e5 (MD5) Previous issue date: 2014-02-25 / Panoramic rendering is the visualization of three-dimensional objects in a virtual environment through a wide viewing angle. This work investigated if the use of panoramas is able to promote faster searches in a virtual environment. Panoramas allow the presentation of space through less need to change the orientation of the camera, especially for the case of projections spanning 360? surrounding the user, which can benefit searching. However, the larger the angle, more distorted is the visualization of the environment, causing confusion in navigation. The distortion is even bigger when the user changes the pitch of the camera, by looking up or down. In this work we developed a technique to eliminate specifically the distortions caused by changes in pitch, which was called hemispheric projection. Experiments were done to evaluate the performance of search navigation through perspective, cylindrical and hemispherical projections. The results indicate that navigating with perspective projection is superior than navigating with panoramic projections, possibly due to factors such as (i) lack of experience of the participants in understanding the scenes displayed as panoramas, (ii) the inherent presence of distortion in panoramic projections and (iii) a lower display resolution because the objects are presented in smaller sizes in panoramic projections, making the perception of details more difficult. However, the hemispherical projection was better than the cylindrical, indicating that the developed technique provides benefits for navigation compared to current techniques of panoramic projection. The hemispheric projection also provided the least amount of changes of camera orientation, which is an indication that the hemispheric projections may be particularly useful in situations where there are restrictions on the ease to change the orientation. Future research will investigate the performance of cameras interactions on slower devices, such as using only keyboard, or brain-machine interfaces / Renderiza??o panor?mica ? a visualiza??o de objetos tridimensionais em um ambiente virtual atrav?s de um largo ?ngulo de vis?o. Este trabalho procurou investigar se a utiliza??o de panoramas ? capaz de agilizar buscas em um ambiente virtual. Panoramas permitem a apresenta??o do espa?o atrav?s de uma menor necessidade de modificar a orienta??o da c?mera, principalmente para o caso de proje??es que englobam os 360 que cercam o usu?rio, o que pode beneficiar as buscas. Contudo, quanto maior o ?ngulo, mais a visualiza??o do ambiente ? distorcida, provocando certa confus?o na navega??o. A distor??o ? ainda maior quando o usu?rio modifica a inclina??o da c?mera, ou seja, ao olhar para cima ou para baixo. Neste trabalho foi desenvolvida uma t?cnica para eliminar especificamente as distor??es provocadas pela mudan?a de inclina??o, a qual foi denominada proje??o hemisf?rica. Foram realizados experimentos buscando avaliar o desempenho na navega??o de busca atrav?s das proje??es em perspectiva, cil?ndrica e hemisf?rica. Os resultados indicam que a navega??o por proje??o em perspectiva ? superior a navega??o por proje??es panor?micas, possivelmente devido a fatores como (i) pouca experi?ncia dos participantes em compreender cenas exibidas de forma panor?mica, (ii) a inerente presen?a de distor??o nas proje??es panor?micas e (iii) a menor resolu??o de visualiza??o, pois os objetos s?o apresentados em tamanhos menores nas proje??es panor?micas, dificultando a percep??o de detalhes. Contudo, a proje??o hemisf?rica se demonstrou melhor do que a cil?ndrica, indicando que a t?cnica desenvolvida proporciona benef?cios para navega??o em compara??o com as t?cnicas de proje??o panor?mica atuais. A proje??o hemisf?rica tamb?m proporcionou a menor quantidade de modifica??es da orienta??o da c?mera, o que ? um ind?cio de que as proje??es hemisf?ricas podem ser particularmente ?teis em situa??es onde existem restri??es na facilidade de alterar a orienta??o. Pesquisas futuras investigar?o o desempenho das c?meras sobre dispositivos de intera??es mais lentos, como o uso apenas de teclado, ou interfaces c?rebro-m?quina.

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-10-21T18:36:43Z No. of bitstreams: 2 Dissertação - Lauro Cássio Martins de Paula - 2014.pdf: 2690755 bytes, checksum: 3f2c0a7c51abbf9cd88f38ffbe54bb67 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-10-21T18:37:00Z (GMT) No. of bitstreams: 2 Dissertação - Lauro Cássio Martins de Paula - 2014.pdf: 2690755 bytes, checksum: 3f2c0a7c51abbf9cd88f38ffbe54bb67 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-10-21T18:37:00Z (GMT). No. of bitstreams: 2 Dissertação - Lauro Cássio Martins de Paula - 2014.pdf: 2690755 bytes, checksum: 3f2c0a7c51abbf9cd88f38ffbe54bb67 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-07-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The problem of variable selection is the selection of attributes for a given sample that best contribute to the prediction of the property of interest. Traditional algorithms as Successive Projections Algorithm (APS) have been quite used for variable selection in multivariate calibration problems. Among the bio-inspired algorithms, we note that the Firefly Algorithm (AF) is a newly proposed method with potential application in several real world problems such as variable selection problem. The main drawback of these tasks lies in them computation burden, as they grow with the number of variables available. The recent improvements of Graphics Processing Units (GPU) provides to the algorithms a powerful processing platform. Thus, the use of GPUs often becomes necessary to reduce the computation time of the algorithms. In this context, this work proposes a GPU-based AF (AF-RLM) for variable selection using multiple linear regression models (RLM). Furthermore, we present two APS implementations, one using RLM (APSRLM) and the other sequential regressions (APS-RS). Such implementations are aimed at improving the computational efficiency of the algorithms. The advantages of the parallel implementations are demonstrated in an example involving a large number of variables. In such example, gains of speedup were obtained. Additionally we perform a comparison of AF-RLM with APS-RLM and APS-RS. Based on the results obtained we show that the AF-RLM may be a relevant contribution for the variable selection problem. / O problema de seleção de variáveis consiste na seleção de atributos de uma determinada amostra que melhor contribuem para a predição da propriedade de interesse. O Algoritmo das Projeções Sucessivas (APS) tem sido bastante utilizado para seleção de variáveis em problemas de calibração multivariada. Entre os algoritmos bioinspirados, nota-se que o Algoritmo Fire f ly (AF) é um novo método proposto com potencial de aplicação em vários problemas do mundo real, tais como problemas de seleção de variáveis. A principal desvantagem desses dois algoritmos encontra-se em suas cargas computacionais, conforme seu tamanho aumenta com o número de variáveis. Os avanços recentes das Graphics Processing Units (GPUs) têm fornecido para os algoritmos uma poderosa plataforma de processamento e, com isso, sua utilização torna-se muitas vezes indispensável para a redução do tempo computacional. Nesse contexto, este trabalho propõe uma implementação paralela em GPU de um AF (AF-RLM) para seleção de variáveis usando modelos de Regressão Linear Múltipla (RLM). Além disso, apresenta-se duas implementações do APS, uma utilizando RLM (APS-RLM) e uma outra que utiliza a estratégia de Regressões Sequenciais (APS-RS). Tais implementações visam melhorar a eficiência computacional dos algoritmos. As vantagens das implementações paralelas são demonstradas em um exemplo envolvendo um número relativamente grande de variáveis. Em tal exemplo, ganhos de speedup foram obtidos. Adicionalmente, realiza-se uma comparação do AF-RLM com o APS-RLM e APS-RS. Com base nos resultados obtidos, mostra-se que o AF-RLM pode ser uma contribuição relevante para o problema de seleção de variáveis.

La cryo-microscopie électronique est une technique tomographique permettant de reconstituer la structure 3D d’un objet complexe en biologie à partir d’un jeu d’acquisitions. Ces images de l’objet complexe sont appelées les projections et sont acquises sous orientations inconnues. Un des avantages de la cryo-microscopie électronique est l’obtention d’un modèle 3D de très haute résolution de l’objet dans un état naturel. La procédure de reconstruction comporte plusieurs étapes telles que l’alignement, la classification des projections, l’estimation de leurs orientations et le raffinement des projections. Lors de ces étapes, la distance entre deux projections est fréquemment mesurée. Le travail réalisé au cours de cette thèse s’organise autour de la recherche théorique d’une distance entre des projections non-orientées avec comme objectif l’amélioration de la procédure de reconstruction tomographique en cryo-microscopie électronique. La contribution de ce travail de thèse est une méthode permettant d’estimer la différence angulaire entre deux projections dans les cas 2D et 3D. Notre méthode est basée sur la construction d’un graphe de voisinage dont les sommets sont les projections, dont les arêtes relient des projections voisines et sont pondérées par une approximation locale de la différence angulaire. Le calcul de ces poids repose sur les propriétés des moments de projection. Notre méthode est testée sur des images simulées de différentes résolutions et de différents niveaux du bruit. La comparaison avec des autres méthodes d’estimation de la différence angulaire est aussi réalisée. / Cryo-electron microscopy is a tomographic technique allowing to reconstruct a 3D model of complex structure in biology from a set of acquired images. These images are known as the tomographic projections and are taken at unknown directions. The advantage of the cryo-electron microscopy is the 3D reconstruction at very high resolution. The reconstruction procedure consists of many steps such as projection alignment, projection classification, orientation estimation and projection refinement. During these steps, the distance between two projections is frequently measured. The work in this thesis aims at studying the distances mesured between two unknown-direction projections with the objective of improving the reconstruction result in the cryo-electron microscopy. The contribution of this thesis is the developement of a method for estimating the angular difference between two projections in 2D and 3D. Our method is based on the construction of a neighborhood graph whose vertices are the projections, whose edges link the projection neighbors and are weighted by a local approximation of the angular difference. The calculation of the weights relies on the projection moment properties. The proposed method has been tested on simulated images with different resolutions and at different noise levels. The comparison with others estimation methods of angular difference has been realised.

Die vorliegende Untersuchung widmet sich der Frage, welche Bedeutung die räumliche Differenzierung des Haushaltsbildungsverhaltens für die Ergebnisse von kleinräumigen Haushaltsprognosen hat. Die Haushaltsgrößenstruktur veränderte sich in Deutschland seit ihrer erstmaligen flächendeckenden Erhebung beträchtlich. Diese Strukturveränderungen sind von anhaltenden Haushaltsverkleinerungen geprägt und vollziehen sich auf der Makro-, Meso- und Mikro-ebene in unterschiedlicher Intensität. Eine möglichst exakte Abbildung räumlich differenzierter Trends ist für kleinräumige Haushaltsprognosen ergebnisrelevant. Die Trends ergeben sich zum einen aus der kleinräumigen Bevölkerungsentwicklung und zum anderen aus den Veränderungen des Haushaltsbildungsverhaltens. Um die oben gestellte Frage zu beantworten, wurden zunächst die Veränderungen von Anzahl und Größenstruktur der Haushalte in Deutschland nach dem 2. Weltkrieg nach ihren räumlichen Ausprägungen - zunächst anhand der Literatur und frei zugänglichen Datenquellen - untersucht. Der Fokus der eigenen empirischen Untersuchungen lag auf dem Zeit-raum 1998 bis 2011. Als Hauptdatenquelle wurden Einzeldaten des Mikrozensus im Rahmen von Scientific-Use-Files und der kontrollierten Datenfernverarbeitung genutzt. Um die Bedeutung des Haushaltsbildungsverhaltens beurteilen zu können, musste es operationalisiert werden. Als Grundgerüst diente das Haushaltsvorstandsquotenverfahren, welches jedoch an die Erfordernisse der Untersuchung angepasst werden musste. Aufbauend auf der Operationalisierung wurde mithilfe eines selbst weiterentwickelten Standardisierungsverfahrens der Einfluss des Haushaltsbildungsverhaltens auf die Haushaltsentwicklung bestimmt. Um Aussagen für kleinräumige Entwicklungen treffen zu können, wurden im nächsten Schritt die räumlich und nach Altersgruppen differenzierten Haushaltsvorstands-quoten auf Gemeinden in Sachsen übertragen. Diese Vorgehensweise wird auch in kleinräumigen makroanalytischen Haushaltsprognosen angewendet. Die Berechnungen erfolgten für alle Gemeinden in fünf Varianten und darüber hinaus für ausgewählte Gemeinden des Dresdener Umlandes mit einer Variante auf Basis von kommunalen Daten der Haushaltegenerierung (HHGen). Die Bedeutung der räumlichen Differenzierung ließ sich schließlich durch den Vergleich der Varianten mit der Referenzvariante ohne räumliche Differenzierung sowie dem Vergleich zwischen den vier Varianten der räumlichen Differenzierung messen. Als am besten für die demographisch ausgerichtete Untersuchung geeignet, stellte sich die Definition der Haushaltsbezugsperson nach dem ältesten Haushaltsmitglied heraus. Die anhand des Lebenszykluskonzeptes und altersjahrspezifischer Ausprägungen gewählten acht bzw. sieben Altersgruppen erwiesen sich für räumliche Betrachtungen als günstig und wiesen nur geringe Unterschiede zu altersjahrspezifischen Berechnungen auf. Das Haushaltswachstum in Deutschland betrug im Betrachtungszeitraum 7,7 %. 3,0 % Haushaltswachstum lassen sich auf die Veränderung des Haushaltsbildungsverhaltens zurückführen. Altersstruktureffekte tragen zu einem Wachstum von 5,3 % bei, während dagegen die Veränderung der Bevölkerungszahl bei Ausschluss der anderen Einflussgrößen, zu einem Rückgang von 0,5 % geführt hätte. Die Veränderung des Haushaltsbildungsverhaltens hatte im Betrachtungszeitraum für die Haushaltsentwicklung zweifelsfrei eine hohe Relevanz. Der Einfluss des Haushaltsbildungsverhaltens war im Betrachtungszeitraum für ostdeutsche Bundesländer besonders hoch und in Sachsen mit 8,0 % am höchsten. In Westdeutschland unterschied sich der Einfluss des Haushaltsbildungsverhaltens auf Bundesländerebene deutlich. Darüber hinaus sind insbesondere Stadt-Land-Unterschiede feststellbar. Der Einfluss von stadtregionalen Einflüssen ist aufgrund fehlender Raumkategorien dagegen nicht nachweisbar. Die Erhebungsumstellung des Mikrozensus im Jahr 2005 hat Auswirkungen auf die berechneten Ergebnisse der Haushaltsstruktur und des Haushaltsbildungsverhaltens. Sondereffekte durch die gehäufte Einführung von Zweitwohnsitzsteuern und die sog. Hartz-IV-Reform lassen im Vergleich zu HHGen-Daten Dresdens den Schluss zu, dass es im Zeitraum der Erhebungsumstellung zu einer erhöhten Haushaltsverkleinerung gekommen ist und es sich somit nicht ausschließlich um einen reinen methodischen Effekt handelt. Zu Verzerrungen der regionalen und nach Gemeindetypen differenzierten Ergebnisse können insbesondere Gebietsreformen, Statuswechsel durch dynamische Prozesse sowie Konzeptumstellungen der Typisierungen führen. Am stärksten wirkten sich diese Veränderungen auf den Bevölkerungsmengeneffekt, weniger auf den Verhaltenseffekt aus. Auf Gemeindeebene ergab sich ebenso eine hohe Relevanz des Haushaltsbildungsverhaltens für die Haushaltsentwicklung. Im Maximum führte die räumliche Differenzierung zu einer Abweichung von neun Prozentpunkten im Vergleich zur Referenzvariante. Die Spannweite (R) zwischen den Varianten der räumlichen Differenzierungen ist in Mittelstädten und suburbanen Gemeinden besonders hoch. Für die untersuchten Mittelstädte ist ein Regionaleffekt verantwortlich, d. h. die regionale Differenzierung von Gemeindegrößenklassen führte zu einer Erhöhung der rechnerischen Haushaltsentwicklung. Aus den Ergebnissen lässt sich schlussfolgern, dass von den räumlichen Differenzierungen im Mikrozensus als Ausgangsbasis zunächst Gemeindegrößenklassen am besten geeignet sind. Diese sollten mindestens nach West- und Ostdeutschland unterschieden werden. Die Regionalisierung nach (zusammengefassten) Bundesländern oder zusammengefassten Raumordnungsregionen ist anzustreben, jedoch nur unter großer Sorgfalt umsetzbar, da sonst die Fallzahlen zu gering und der Stichprobenfehler zu hoch werden. Für kleinräumige Haushaltsprognosen ist das Risiko von Fehlprognosen durch die Unterlassung von räumlichen Differenzierungen weitaus höher ist als durch deren Berücksichtigung. Das räumliche Auswertungspotenzial des Mikrozensus ist sehr hoch. Es kann jedoch gegenwärtig nicht voll ausgeschöpft werden. Notwendig wären nachträgliche Gebietsstandsbereinigungen sowie die künftige und rückwirkende Aufnahme geeigneter räumlicher Differenzierungen, die den stadtregionalen Kontext explizit berücksichtigen. / The present study addresses the question of the significance of spatial differentiation of household formation behaviour for the results of small-scale household projections. The structure of household sizes in Germany changed significantly since its first nationwide survey. These structural changes are marked by the permanent trend of household size diminishment and take place in varying degrees on macro, meso and micro level. Representing spatially differentiated trends as exactly as possible is of high relevance for the results of small-scale projections of households. These trends result in part from small-scale population development and, secondly, from the changes in household formation behaviour. To answer the question above, the changes in number and size structure of households in Germany after World War II were examined according to their spatial characteristics – as a start in literature and openly accessible data sources. The focus of this thesis’ empirical studies lies on period from 1998 to 2011. The main data source was micro data acquired in the micro-census. These data were used in the context of Scientific Use Files and controlled remote data processing. The assessment of the importance of household formation behaviour requires its operationalization. As backbone the head of household ratio method was used, which, however, had to be adapted to the requirements of the investigation. Based on the operationalization a standardization method developed further in the context of this study was used to determine the influence of household formation behaviour on house-hold development. To be able to draw conclusions for small-scale developments, in a next step head of household ratios differentiated spatially and by age group were applied on municipalities in Saxony – analogous to the approach used in small-scale macro-analytical household projections. The calculations were made for all municipalities for five variants. Furthermore, an additional variant based on local data of household generation (HHGen) was calculated for selected municipalities surrounding Dresden. The importance of spatial differentiation was measured by comparing the variants with a reference calculation without spatial differentiation as well as by comparing between the four variants with spatial differentiation. The definition of the eldest household member as household head proved to be most suitable for demographic studies. Seven respectively eight age groups based on life cycle concept were found to be suitable for spatial considerations and showed only minor differences to year-of-age specific calculations. The number of households increased by 7.7% in the analysis period. 3.0% can be attributed to the change in household formation behaviour. Age structure effects contribute to a growth of 5.3%, whereas the change in population - excluding other influences - would have led to a decline in household numbers of 0.5%. The change in household formation behaviour was doubtless of high relevance in the analysis period. The influence of household formation behaviour in the analysis period was particularly high for East Germany, with the maximum in Saxony (8.0%). In West Germany, the influence of household formation behaviour differed significantly for the different federal states (Länder). Moreover, especially urbanrural differences are noticeable. Urban-suburban interrelations are, however, undetectable due to lack of spatial categories. The change in survey methods for the micro-census in 2005 affects the results of household structure and the calculated household formation behaviour. Compared to HHGen data of Dresden, special effects by the frequent introduction of taxes on secondary residences and the socalled “Hartz IV reform” lead to the conclusion, that an increased household size reduction has taken place in the period of change in survey methods. Consequently, this is not merely a methodological effect. Reforms of regional structures, changes in status caused by dynamic processes as well as changes in concepts of typification may lead to biased regionally differentiated and municipal results. The highest impact of these changes was discovered on population quantity effect, less on the behaviour effect. At municipal level, household formation behaviour showed a high relevance for household development. Spatial differentiation led to a maximal deviation of nine percentage points compared to the reference calculation. The range between the variants of spatial differentiation is particularly high in medium-sized towns and suburban municipalities. For the medium-sized towns this is due to a regional effect: the regional differentiation of municipality size classes led to an increase in the determined household development. The results lead to the conclusion that, choosing from the spatial differentiation possibilities in the micro-census, differentiation on municipality level is most suited as a basis. These should be differentiated at least into West and East Germany. Regionalization to (combined) federal states (Länder) or combined spatial planning regions (Raumordnungsregionen) is desirable. However, it can be implemented only with great care, as there are only a limited number of cases and the sampling error would be too high. For small-scale household projections the risk of incorrect predictions by the omission of spatial differentiation is is much higher than by taking them into account. The potential of spatial analysis of the micro-census is very high, but cannot be exploited to the fullest at the time being. Subsequent territorial adjustments would be necessary, as well as future and retroactive inclusion of appropriate spatial differentiations which explicitly take into account the intraregional context.

This thesis deals with issues automatic composing panoramic photos from individual photos. Gradually examines the various steps of algorithms and methods used in them, which are used in creating panoramas. It also focuses on the design of the own system based on methods discussed to construct panoramas. This system is implemented using OpenCV library and it is created also a graphical interface using a Qt library. Finally, are in this thesis evaluated outcomes of this designed and implemented system on available datasets.

The development of new therapeutical approaches, devised to foster the regeneration of neuronal circuits after injury and/or in neurodegenerative diseases, is of great importance. The impairment of dopaminergic projections is especially severe, because these projections are involved in crucial brain functions such as motor control, reward and cognition. In the work presented here, organotypic brain slice co-cultures of (a) the mesostriatal and (b) the mesocortical dopaminergic projection systems consisting of tissue sections of the ventral tegmental area/substantia nigra (VTA/SN), in combination with the target regions of (a) the striatum (STR) or (b) the prefrontal cortex (PFC), respectively, were used to evaluate different approaches to stimulate neurite outgrowth: (i) inhibition of cAMP/cGMP turnover with 3’,5’ cyclic nucleotide phosphodiesterase inhibitors (PDE-Is), (ii) blockade of calcium currents with nimodipine, and (iii) the co-cultivation with bone marrow-derived mesenchymal stromal/stem cells (BM-MSCs). The neurite growth-promoting properties of the tested substances and cell populations were analyzed by neurite density quantification in the border region between the two brain slices, using biocytin tracing or tyrosine hydroxylase labeling and automated image processing procedures. In addition, toxicological tests and gene expression analyses were conducted. (i) PDE-Is were applied to VTA/SN+STR rat co-cultures. The quantification of neurite density after both biocytin tracing and tyrosine hydroxylase labeling revealed a growth promoting effect of the PDE2A-Is BAY60-7550 and ND7001. The application of the PDE10-I MP-10 did not alter neurite density in comparison to the vehicle control. (ii) The effects of nimodipine were evaluated in VTA/SN+PFC rat co-cultures. A neurite growth-promoting effect of 0.1 µM and 1 µM nimodipine was demonstrated in a projection system of the CNS. In contrast, the application of 10 µM nimodipine did not alter neurite density, compared to the vehicle control, but induced the activation of the apoptosis marker caspase 3. The expression levels of the investigated genes, including Ca2+ binding proteins (Pvalb, S100b), immediate early genes (Arc, Egr1, Egr2, Egr4, Fos and JunB), glial fibrillary acidic protein, and myelin components (Mal, Mog, Plp1) were not significantly changed (with the exception of Egr4) by the treatment with 0.1 µM and 1 µM nimodipine. (iii) Bulk BM-MSCs that were classically isolated by plastic adhesion were compared to the subpopulation Sca-1+Lin-CD45--derived MSCs (SL45-MSCs). The neurite growth-promoting properties of both MSC populations were quantified in VTA/SN+PFC mouse co-cultures. For this purpose, the MSCs were seeded on glass slides that were placed underneath the co-cultures. A significantly enhanced neurite density within the co-cultures was induced by both bulk BM-MSCs and SL45-MSCs. SL45-MSCs increased neurite density to a higher degree. The characterization of both MSC populations revealed that the frequency of fibroblast colony forming units (CFU-f ) is 105-fold higher in SL45-MSCs. SL45-MSCs were morphologically more homogeneous and expressed higher levels of nestin, BDNF and FGF2 compared to bulk BM-MSCs. Thus, this work emphasizes the vast potential for molecular targeting with respect to the development of therapeutic strategies in the enhancement of neurite regrowth.:Table of contents Abbreviations 1 1. Introduction 2 1.1 The dopaminergic system 2 1.2 Neurite regeneration following mechanical lesions of the CNS 7 1.3 Organotypic brain slice co-cultures 8 1.4 Promising substances and cells to enhance neuroregeneration 10 1.5 The aim of the thesis 14 2. The original research articles 16 2.1 Phosphodiesterase 2 inhibitors promote axonal outgrowth in organotypic slice co-cultures 17 2.2 Nimodipine enhances neurite outgrowth in dopaminergic brain slice co-cultures 35 2.3 Mesenchymal stem cells support neuronal fiber growth in an organotypic brain slice co-culture model 50 3. References 66 Appendices 73 Summary 73 Zusammenfassung 78 Curriculum Vitae 84 Track Record 85 Selbständigkeitserklärung 87 Acknowledgments 88