Σε αυτή τη διπλωματική εργασία υλοποιήθηκε ένας LDPC αποκωδικοποιητής που χρησιμοποιεί τις βασικές αρχές της turbo αποκωδικοποίησης, εισάγοντας στα χαρακτηριστικά της αποκωδικοποίησης του το διάγραμμα trellis. O maximum a posteriori probability (MAP) αλγόριθμος χρησιμοποιείται σαν μια γέφυρα μεταξύ των LDPC και Turbo κωδικών. Οι LDPC κώδικες αντιμετωπίζονται ως μια αλυσιδωτή σύνδεση n υπέρ κωδικών, όπου ο κάθε υπέρ κώδικας έχει πλέον μια πιο απλή δομή trellis ώστε ο MAP αλγόριθμος να μπορεί να εφαρμοστεί. / In this thesis an LDPC decoder is implemented using the principles of turbo decoding, introducing the characteristics of the decoding of the trellis diagram . The maximum a posteriori probability (MAP) algorithm is used as a bridge between the LDPC and Turbo codes. The LDPC codes are treated as concatenated n supercodes, where each code has a simple trellis structure so that the MAP algorithm can be implemented.

This study, based on the socio-cultural theory of the book as a mediating tool, examines how four teachers say they work with the reader ABC-klubben. This is done with a focus on how they reason about choosing the level of readers for the pupils and about what compensation, if any, they make for pupils who read the simpler book and therefore miss the more difficult words and expressions. The result shows that all the teachers say that they take the pupils’ motivation for and pleasure in reading as an important ground for the decision as to which reader a pupil should use, and that this decision is taken with a focus on the individual. When it comes to compensation for the pupils who read the simpler book, the teachers do not describe consistently focused work on this, but they describe a similar way of working whereby they nevertheless acquaint these pupils with the more difficult book and the harder words and expressions. The conclusion of the study is that the teachers use many different methods to determine a pupil’s reading ability and hence which book is reasonable for the pupil to read, and one of the methods described is based on reading tests. Other methods are based on experience and the teachers’ own ability.

Visual perception in mammals is made possible by the visual system and the visual cortex. However, precisely how visual information is coded in the brain and how training can improve this encoding is unclear. The ability to see and process visual information is not an innate property of the visual cortex. Instead, it is learnt from exposure to visual stimuli. We first considered how visual perception is learnt, by studying the perceptual learning of contrast discrimination in macaques. We investigated how changes in population activity in the visual cortices V1 and V4 correlate with the changes in behavioural response during training on this task. Our results indicate that changes in the learnt neural and behavioural responses are directed toward optimising the performance on the training task, rather than a general improvement in perception of the presented stimulus type. We report that the most informative signal about the contrast of the stimulus within V1 and V4 is the transient stimulus-onset response in V1, 50 ms after the stimulus presentation begins. However, this signal does not become more informative with training, suggesting it is an innate and untrainable property of the system, on these timescales at least. Using a linear decoder to classify the stimulus based on the population activity, we find that information in the V4 population is closely related to the information available to the higher cortical regions involved with decision making, since the performance of the decoder is similar to the performance of the animal throughout training. These findings suggest that training the subject on this task directs V4 to improve its read out of contrast information contained in V1, and cortical regions responsible for decision making use this to improve the performance with training. The structure of noise correlations between the recorded neurons changes with training, but this does not appear to cause the increase in behavioural performance. Furthermore, our results suggest there is feedback of information about the stimulus into the visual cortex after 300 ms of stimulus presentation, which may be related to the high-level percept of the stimulus within the brain. After training on the task, but not before, information about the stimulus persists in the activity of both V1 and V4 at least 400 ms after the stimulus is removed. In the second part, we explore how information is distributed across the anatomical layers of the visual cortex. Cortical oscillations in the local field potential (LFP) and current source density (CSD) within V1, driven by population-level activity, are known to contain information about visual stimulation. However the purpose of these oscillations, the sites where they originate, and what properties of the stimulus is encoded within them is still unknown. By recording the LFP at multiple recording sites along the cortical depth of macaque V1 during presentation of a natural movie stimulus, we investigated the structure of visual information encoded in cortical oscillations. We found that despite a homogeneous distribution of the power of oscillations across the cortical depth, information was compartmentalised into the oscillations of the 4 Hz to 16 Hz range at the granular (G, layer 4) depths and the 60Hz to 170Hz range at the supragranular (SG, layers 1–3) depths, the latter of which is redundant with the population-level firing rate. These two frequency ranges contain independent information about the stimulus, which we identify as related to two spatiotemporal aspects of the visual stimulus. Oscillations in the visual cortex with frequencies < 40 Hz contain information about fast changes in low spatial frequency. Frequencies > 40 Hz and multi-unit firing rates contain information about properties of the stimulus related to changes, both slow and fast, at finer-grained spatial scales. The spatiotemporal domains encoded in each are complementary. In particular, both the power and phase of oscillations in the 7 Hz to 20Hz range contain information about scene transitions in the presented movie stimulus. Such changes in the stimulus are similar to saccades in natural behaviour, and this may be indicative of predictive coding within the cortex.

[pt] No presente trabalho é examinada a decodificação de esquemas CPM (Continuous Phase Modulation) filtrados severamente (filtragem com resposta impulsional infinita) utilizando-se algoritmo M, um algoritmo de busca limitada. A estrutura formada pelo modulador CPM seguido do filtro é tratada como um esquema que realiza modulação codificada com utilização eficiente de faixa. A caracterização da modulação através de estados requer um número infinito de estados. O esquema é analisado através de simulação de sistema modulado em tempo discreto com processamento digital. A utilização de filtro digital permite uma caracterização de estados simplificada em relação a trabalhos anteriores. Uma versão simplificada do algoritmo M é analisada neste trabalho. Através de simulação realiza-se a análise do desempenho do sistema assim como do comportamento do algoritmo M na sua versão simplificada. / [en] Decoding of severely filtered CPM schemes with infinite impulse response filters using a limited search algorith (M-Algorithm ) is examined in this thesis. The structure composed by the CPM modulator followed by the filter is treated as a bandwidth efficient coded modulation scheme. The modulation requires a infinite state description. Analysis of the system is done by computer simulation. The analysed system is discret time modeled and uses digital signal processing techniques. This allows a simplified state description of the modulation scheme. A simplified version of the M-algorithm is analysed in the thesis. Analysis of the system performance as well as the M-algorithm (simplified version) behavior is done by simulation.

[pt] Este trabalho examina uma nova estratégia para detenção de Sinais TCM em presença de desvanecimento não-seletivo em freqüência. Esta estratégia faz uso de um conjunto de estimativas da distorção do canal, cada uma associada a um estado da treliça de decodificação, que são utilizadas simultaneamente no processo de decodificação. No método proposto, a cada intervalo de símbolo calcula-se uma estimativa de canal para cada percurso sobrevivente, usando os sinais associados a este percurso como decisões dos sinais transmitidos até então, juntamente com um algoritmo do tipo Filtro de Kalman. O método é descrito inicialmente para uso em sistemas sem intercalação- desintercalação. Uma versão modificada é proposta para permitir o uso da nova estratégia em associação com esquemas de intercalação-desintercalação. Resultados de desempenho obtidos, via simulação, com os métodos propostos são comparados com os resultados obtidos supondo- se o conhecimento ideal das distorções introduzidas pelo canal bem como os resultados apresentados na literatura, referentes a outros métodos de deteção. / [en] We look into a new strategy for detecting trellis-code modulated signal in the presence of frequency non- selective fading which makes simultaneous use in the decoding procedure of a set of channel distortion estimates, each one associated to a trellis state. During each symbol interval, based on a Kalman Filter-type algorithm, a distinct channel estimate is recursively generated for each survivor path using this path symbols as the truly transmitted symbols. A method is first proposed for use in non-interleaved systems. A modified version for interleaved systems. A modified version for interleaved systens is then presented. Performances are evaluated by computer simulations and comparisons mede to curves pertaining to other methods in the literature and to curves obteined under ideal channel state information assumption.

Commercial advertising often employs stereotyping in order to connect with the intended audience and appeal to the widest possible demographic. The gender binary of male and female is one of the most popular audience segmentations, therefore gender provides an excellent example for the study of stereotypes. This study focuses on the portrayal of male stereotypes in advertising, and seeks to explore how stereotypes of masculinity are represented in androcentric advertising, and understand how these stereotypes are perceived by men. It uses a reception study and Stuart Hall’s (1996) theory of encoding/decoding to discuss the use of stereotypes with male University of Ottawa students, aged 18-25. Participants in the study suggest that the stereotypes portrayed in commercial advertising influence their masculinity in numerous ways, including, but not limited to, the way they dress and the way they act.

Syftet med denna studie har varit att undersöka Wapnös hållbarhetskommunikation och ta reda på hur de vill att kommunikationen ska förstås. Vidare har hållbarhetskommunikationen studerats ur ett konsumentperspektiv för att undersöka hur Wapnös konsumenter tolkar företagets hållbarhetskommunikation. Studien ämnar att undersöka vilka faktorer som kan påverka människor att göra olika tolkningar av samma budskap. Hur vill Wapnö att deras hållbarhetskommunikation ska tolkas och förstås? Hur tolkar Wapnös konsumenter företagets hållbarhetskommunikation? Hur kan resultatet förstås utifrån Encoding/decoding-modellen? Utifrån de resultat som framkommit i studien har det visat sig att Wapnö vill framställa sig som ett hållbart företag med en kommunikation som tolkas och förstås som öppen och transparent. Vidare har det framkommit att de olika tolkningar som konsumenterna har gjort av de material som presenterats har berott på faktorer som ålder, intresse och kunskap i en specifik sakfråga.

The purpose of the current study was to develop and administer a Spanish static and dynamic assessment of decoding and other important reading measures. Using the best available resources regarding Spanish literacy acquisition and Spanish language development, a preliminary Spanish dynamic and static screener was developed. The resulting test was named the Spanish Dynamic Decoding Measure (S-DDM) and is a counterpart to the original DDM available in English. This test contains three subtests: decoding, phonemic awareness, and word identification. The S-DDM was administered to eight bilingual Spanish-English speaking students with varying levels of Spanish language ability and reading proficiency in grades ranging from second to fourth grade. The results from all three subtests of the S-DDM were analyzed to report the levels of validity, reliability, and variance observed in the administration of the test and performance of the participants. There was a wide range of performance on the pretest sections of the dynamic assessment decoding subtest, and performance at or near ceiling on the posttest sounds sections. Modifiability scores were strong for the students who were not receiving special education services while the two participants receiving special education both received weaker modifiability ratings. There was a wide range of variance observed on all subtests of both the phonemic awareness and word identification subtests, with the exception of the phoneme blending target of the phonemic awareness subtest. Interrater reliability and administration fidelity were found to be within acceptable measures. Results indicated that the test is sensitive to varying degrees of Spanish reading proficiency and reading ability. Future research is needed to determine the effectiveness of this screener in identifying Spanish-speaking students who are at-risk for reading difficulties.

En imagerie médicale, des collaborations internationales ont lançé l'acquisition de centaines de Terabytes de données - et en particulierde données d'Imagerie par Résonance Magnétique fonctionelle (IRMf) -pour les mettre à disposition de la communauté scientifique.Extraire de l'information utile de ces données nécessite d'importants prétraitements et des étapes de réduction de bruit. La complexité de ces analyses rend les résultats très sensibles aux paramètres choisis. Le temps de calcul requis augmente plus vite que linéairement: les jeux de données sont si importants qu'il ne tiennent plus dans le cache, et les architectures de calcul classiques deviennent inefficaces.Pour réduire les temps de calcul, nous avons étudié le feature-grouping commetechnique de réduction de dimension. Pour ce faire, nous utilisons des méthodes de clustering. Nous proposons un algorithme de clustering agglomératif en temps linéaire: Recursive Nearest Agglomeration (ReNA). ReNA prévient la création de clusters énormes, qui constitue un défaut des méthodes agglomératives rapidesexistantes. Nous démontrons empiriquement que cet algorithme de clustering engendre des modèles très précis et rapides, et permet d'analyser de grands jeux de données avec des ressources limitées.En neuroimagerie, l'apprentissage statistique peut servir à étudierl'organisation cognitive du cerveau. Des modèles prédictifs permettent d'identifier les régions du cerveau impliquées dans le traitement cognitif d'un stimulus externe. L'entraînement de ces modèles est un problème de très grande dimension, et il est nécéssaire d'introduire un a priori pour obtenir un modèle satisfaisant.Afin de pouvoir traiter de grands jeux de données et d'améliorer lastabilité des résultats, nous proposons de combiner le clustering etl'utilisation d'ensembles de modèles. Nous évaluons la performance empirique de ce procédé à travers de nombreux jeux de données de neuroimagerie. Cette méthode est hautement parallélisable et moins coûteuse que l'état del'art en temps de calcul. Elle permet, avec moins de données d'entraînement,d'obtenir de meilleures prédictions. Enfin, nous montrons que l'utilisation d'ensembles de modèles améliore la stabilité des cartes de poids résultantes et réduit la variance du score de prédiction. / In medical imaging, collaborative worldwide initiatives have begun theacquisition of hundreds of Terabytes of data that are made available to thescientific community. In particular, functional Magnetic Resonance Imaging --fMRI-- data. However, this signal requires extensive fitting and noise reduction steps to extract useful information. The complexity of these analysis pipelines yields results that are highly dependent on the chosen parameters.The computation cost of this data deluge is worse than linear: as datasetsno longer fit in cache, standard computational architectures cannot beefficiently used.To speed-up the computation time, we considered dimensionality reduction byfeature grouping. We use clustering methods to perform this task. We introduce a linear-time agglomerative clustering scheme, Recursive Nearest Agglomeration (ReNA). Unlike existing fast agglomerative schemes, it avoids the creation of giant clusters. We then show empirically how this clustering algorithm yields very fast and accurate models, enabling to process large datasets on budget.In neuroimaging, machine learning can be used to understand the cognitiveorganization of the brain. The idea is to build predictive models that are used to identify the brain regions involved in the cognitive processing of an external stimulus. However, training such estimators is a high-dimensional problem, and one needs to impose some prior to find a suitable model.To handle large datasets and increase stability of results, we propose to useensembles of models in combination with clustering. We study the empirical performance of this pipeline on a large number of brain imaging datasets. This method is highly parallelizable, it has lower computation time than the state-of-the-art methods and we show that, it requires less data samples to achieve better prediction accuracy. Finally, we show that ensembles of models improve the stability of the weight maps and reduce the variance of prediction accuracy.

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第23541号 / 情博第771号 / 新制||情||132(附属図書館) / 京都大学大学院情報学研究科知能情報学専攻 / (主査)教授 河原 達也, 教授 黒橋 禎夫, 教授 森 信介 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM