Dans cette thèse on étudie les (super)fonctions de corrélation à plusieurs points et à plusieursboucle du multiplets demi-BPS en théorie N = 4 super-Yang-Mills. Les fonctions de corrélationsont des objets dynamiques naturels à considérer dans toutes les théories conformes des champs.Elles sont des quantités finies et leur symétrie (super)conforme n’est pas brisée par des divergences.Elles contiennent des informations sur de nombreuses autres intéressantes quantités dynamiques dela théorie. Le produit opératoire engendre les règles de somme pour les fonctions à trois points et lesdimensions anormales. Dans la limite du cône de lumière, elles coïncident avec les boucles de Wilsonde lumière et avec des superamplitudes de diffusion. Cette dualité tient tant au niveau des intégralesdivergentes régularisés que au niveau de leurs intégrandes rationnels finis.La partie principale de la thèse est consacrée aux super-corrélateurs à plusieurs points au niveau Born du supermultiplet du tenseur de stress. Pour les étudier on utilise les règles de Feynman qui préservent une quantité de la supersymétrie. Donc, on reformule la théorie N = 4 SYM dans le superespace harmonique de Lorentz. On s’occupe de l’espace euclidien et on harmonise la moitié du groupe de Lorentz SU(2) × SU(2). La théorie est formulée en termes de deux demi-superchamps chiraux-analytique. L’action de la théorie est une somme de deux termes : l’action de Chern-Simons et une action non-polynomiale qui prend en compte les interactions. Puisque la formulation de l’action est chiral, la Ǭ-supersymétrie est réalisée d’un façon non-linéaire sur la paire de champs. L’action se simplifie considérablement dans la jauge axiale. On obtient les propagateurs correspondants et on formule les règles de Feynman en superspace harmonique de Lorentz. Afin d’étudier super-corrélateurs non-chiraux du supermultiplet de tenseur de stress on formule l’opérateur composite pertinent en termes de demi-superchamps chiraux-analytique ainsi. Au niveau chiral, on propose la construction par R-vertex du super-corrélateur chiral. Afin d’élucider la structure du super-corrélateur on réorganise les règles de Feynman harmoniques qui introduisent une nouvelle classe des invariants hors-shell nilpotent analytique qui sont des blocs de construction élémentaires de la super-corrélateur. Ensuite, on procède au secteur non-chiral et on constate que la dépendance de Ɵ̅ est pris en compte par une légère modification du R-vertex qui consiste à une modification des variables spatio-temporelles de la base chirale à la base analytique. Ainsi, le corrélateur non-chiral est exprimée en termes d’une classe assez particulière des invariants nilpotents non-chiraux. Dans la dernière partie de la thèse, on étudie les fonctions de corrélation à quatre points des opérateurs demi-BPS dans l’approximation de trois boucle dans la limite planaire. Cette étude est motivée par une conjecture basée sur intégrabilité pour les constantes de structure. A l’ordre de trois boucles toutes les approches de graphes de Feynman connus sont extrêmement inefficaces. Le principal obstacle est un grand nombre de diagrammes de Feynman pertinents. Cependant, le corrélateur est presque complètement fixé par ses propriétés élémentaires comme symétries, singularités et planairité. La structure de pôle et la symétrie super-conforme spécifient les intégrandes rationnelles des corrélateurs à un nombre de coefficients numériques. Les coefficients sont fixés par la planairité, la symétrie de croisement et le produit opératoire en cône de lumière des intégrandes avec diverses configurations de poids dans la limite par rapport à une paire de points. / In the present thesis we study the multi-point multi-loop (super)correlation functions of half-BPSmultiplets in N = 4 super-Yang-Mills theory. Correlation functions are natural dynamical objectsto consider in any Conformal Field Theory. They are finite quantities and their (super)conformalsymmetry is not broken by divergences. They contain information about many others interestingdynamical quantities of the theory. The Operator Product Expansion being applied to them producessum rules for three-point functions and anomalous dimensions. In the light-cone limit they coincidewith the light-like Wilson loops and scattering superamplitudes. This duality holds both at the levelof the regularized divergent integrals and at the level of their finite rational integrands.The main part of the thesis is devoted to multi-point Born level super-correlators of the stress-tensor supermultiplet. There exists a number of hints that such super-correlators are remarkable dynamicalquantities in N = 4 SYM. Studying the supercorrelators it is convenient to use the Feynman rulespreserving an amount of the supersymmetry. So, we reformulate the N = 4 SYM in the Lorentzharmonic superspace. We deal with Euclidean space and harmonize one half of the Lorentz groupSU(2) x SU(2). The theory is formulated in terms of two chiral-analytic semi-superfields one ofwhich is scalar and the other one is spinor. The action of the theory is a sum of two terms: theChern-Simons action describing the self-dual N = 4 SYM theory and a non-polynomial action whichtakes into account interactions. Since the formulation of the action is chiral the Ǭ-supersymmetry isnon-linearly realized on the pair of fields. The action considerably simplifies in the axial gauge. Wework out corresponding propagators and formulate Lorentz harmonic superspace Feynman rules. Inorder to study nonchiral supercorrelators of the stress-tensor supermultiplet we formulate the relevant composite operator in terms of the chiral-analytic semi-superfields as well.At the chiral level we propose the R-vertex construction of the chiral supercorrelator which turnsout to be rational at the Born level by construction. In order to elucidate the structure of thesupercorrelator we rearrange harmonic Feynman rules introducing a new class of off-shell analyticnilpotent (Grassmann degree two). They are simple building blocks of the super-correlator. Thenwe proceeded to the nonchiral sector and and that the dependence on Ɵ̅ is taken into account by aslight modification of the R-vertices. This modification of the R-vertices is equivalent to a change of the space-time variables from the chiral to analytic bases. So the non-chiral correlator is expressed in terms of a rather special class of non-chiral nilpotent invariants.In the last part of the thesis we study four-point correlation functions of half-BPS operators inthe three-loop approximation in the planar limit. This study is motivated by an integrability basedconjecture for the structure constants. At the three-loop order all known Feynman graph approachesare extremely inefficient. The main obstacle is a huge number of relevant Feynman diagrams andthe complexity of the corresponding loop integrals. However the correlator is almost completely fixedby its elementary properties like symmetries, singularities and planarity. The pole structure andthe super-conformal symmetry specify the rational integrands of the correlators up to a number ofnumerical coefficients. We fix these coefficients using planarity, the crossing symmetry and comparingthe light-cone OPE of the correlator integrands with various weight configurations in the light-likelimit with respect to a pair of points.

by Zhou, Shengli. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 70-75). / Abstract also in Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background of Gesture Recognition --- p.1 / Chapter 1.2 --- HCI System --- p.2 / Chapter 1.2.1 --- Vision Based HCI System --- p.2 / Chapter 1.2.2 --- Accelerometer Based HCI System --- p.4 / Chapter 1.3 --- Pattern Recognition Methods --- p.6 / Chapter 1.4 --- Thesis Outline --- p.7 / Chapter Chapter 2 --- 2D Hand-Written Character Recognition --- p.8 / Chapter 2.1 --- Introduction to Accelerometer Based Hand-Written Character Recognition --- p.8 / Chapter 2.1.1 --- Character Recognition Based on Trajectory Reconstruction --- p.9 / Chapter 2.1.2 --- Character Recognition Based on Classification --- p.10 / Chapter 2.2 --- Neural Network --- p.11 / Chapter 2.2.1 --- Mathematical Model of Neural Network (NN) --- p.11 / Chapter 2.2.2 --- Types of Neural Network Learning --- p.13 / Chapter 2.2.3 --- Self-Organizing Maps (SOMs) --- p.14 / Chapter 2.2.4 --- Properties of Neural Network --- p.16 / Chapter 2.3 --- Experimental Setup --- p.17 / Chapter 2.4 --- Configuration of Sensing Mote --- p.18 / Chapter 2.5 --- Data Acquisition Methods --- p.19 / Chapter 2.6 --- Data Preprocessing Methods --- p.20 / Chapter 2.6.1 --- Fast Fourier Transform (FFT) --- p.21 / Chapter 2.6.2 --- Discrete Cosine Transform (DCT) --- p.23 / Chapter 2.6.3 --- Problem Analysis --- p.25 / Chapter 2.7 --- Hand-written Character Classification using SOMs --- p.26 / Chapter 2.7.1 --- Recognition of All Characters in the Same Group --- p.27 / Chapter 2.7.2 --- Recognize the Numbers and Letters Respectively --- p.28 / Chapter 2.8 --- Conclusion --- p.29 / Chapter Chapter 3 --- Human Gesture Recognition --- p.32 / Chapter 3.1 --- Introduction to Human Gesture Recognition --- p.32 / Chapter 3.1.1 --- Dynamic Gesture Recognition --- p.32 / Chapter 3.1.2 --- Hidden Markov Models (HMMs) --- p.33 / Chapter 3.1.2.1 --- Applications of HMMs --- p.34 / Chapter 3.1.2.2 --- Training Algorithm --- p.35 / Chapter 3.1.2.3 --- Recognition Algorithm --- p.35 / Chapter 3.2 --- System Architecture --- p.36 / Chapter 3.2.1 --- Experimental Devices --- p.36 / Chapter 3.2.2 --- Data Acquisition Methods --- p.38 / Chapter 3.2.3 --- System Work Flow --- p.39 / Chapter 3.3 --- Real-Time Gesture Spotting --- p.40 / Chapter 3.3.1 --- Introduction --- p.40 / Chapter 3.3.2 --- Gesture Segmentation Based on Standard Deviation Calculation --- p.42 / Chapter 3.3.3 --- Evaluation of Gesture Spotting Program --- p.47 / Chapter 3.4 --- Comparison of Data Processing Methods --- p.48 / Chapter 3.4.1 --- Discrete Cosine Transform (DCT) --- p.48 / Chapter 3.4.2 --- Discrete Wavelet Transform (DWT) --- p.49 / Chapter 3.4.3 --- Zero Bias Compensation and Filtering (ZBC&F) --- p.51 / Chapter 3.4.4 --- Comparison of Experimental Results --- p.52 / Chapter 3.5 --- Data Base Setup --- p.53 / Chapter 3.6 --- Experimental Results Based on the Database Obtained from Ten Test Subjects --- p.53 / Chapter 3.6.1 --- Experimental Results when Gestures are Manually and Automatically “cut´ح --- p.54 / Chapter 3.6.2 --- The Influence of Number of Dominant Frequencies on Recognition --- p.55 / Chapter 3.6.3 --- The Influence of Sampling Frequencies on Recognition --- p.59 / Chapter 3.6.4 --- Influence of Number of Test Subjects on Recognition --- p.62 / Chapter 3.6.4.1 --- Experimental Results When Training and Testing Subjects Are Overlaped --- p.61 / Chapter 3.6.4.2 --- Experimental Results When Training and Testing Subjects Are Not Overlap --- p.62 / Chapter 3.6.4.3 --- Discussion --- p.65 / Chapter Chapter 4 --- Conclusion --- p.68 / Bibliography --- p.70

abstract: This study explores experiences of women as they pursue post-secondary computing education in various contexts. Using in-depth interviews, the current study employs qualitative methods and draws from an intersectional approach to focus on how the various barriers emerge for women in different types of computing cultures. In-depth interviews with ten participants were conducted over the course of eight months. Analytical frameworks drawn from the digital divide and explorations of the role of hidden curricula in higher education contexts were used to analyze computing experiences in earlier k-12, informal, workplace, and post-secondary educational contexts to understand how barriers to computing emerge for women. Findings suggest several key themes. First, early experiences in formal education contexts are alienating women who develop an interest in computing. Opportunities for self-guided exploration, play, and tinkering help sustain interest in computing for women of color to engage in computing at the post-secondary level. Second, post-secondary computing climates remain hostile places for women, and in particular, for women of color. Thirdly, women employ a combination of different strategies to navigate these post-secondary computing cultures. Some women internalized existing dominant cultures of computing programs. Others chose exclusively online programs in computing to avoid negative interactions based on assumptions about their identity categories. Some women chose to forge their own pathways through computing to help diversify the culture via teaching, creating their own businesses, and through social programs. / Dissertation/Thesis / Ph.D. Justice Studies 2012

Gerenciar alianças entre organizações é desafiante e instiga pesquisas que já proporcionaram aprendizado razoável sobre alguns aspectos do tema. No entanto, a persistência de altos índices de falhas em alianças continua a instigar investigações, a exemplo desta pesquisa. Para tal, duas suposições foram consideradas. A primeira foi que objetivos não-declarados e ocultos existiriam em uma proporção tal sobre os declarados que seriam capazes de distorcer as medidas de performance das alianças. A segunda suposição foi de que os gestores não estariam observando um conjunto suficientemente abrangente de fatores capazes de embasar sua gestão. O objetivo geral da presente pesquisa foi investigar a existência dos objetivos não-declarados pelas organizações-mãe nas alianças, sua relevância frente aos declarados e seus reflexos nas medidas de performance das alianças. Antes das investigações empíricas, foi organizada uma série de fatores de gestão e foi proposta uma tipologia contendo oito tipos de objetivos relacionados às alianças. Os dados foram coletados em duas etapas, uma de estudos de caso e outra de survey. Em dois casos estudados ficou demonstrada a presença de vários tipos de objetivos, incluindo declarados e ocultos. Também evidenciou-se a fragilidade dos processos de gestão das alianças prevista na segunda suposição inicial da pesquisa, especialmente no que diz respeito ao planejamento e ao controle das suas atividades. Através da survey foi verificado que a performance devida a objetivos não-declarados tinha valor representativo em relação ao valor da performance devida aos objetivos declarados. Para a amostra investigada de 78 alianças formadas por empresas do setor industrial do estado do Rio Grande do Sul confirmou-se a suposição inicial da possibilidade de que os resultados das avaliações de performance seriam distorcidos se não fossem consideradas as parcelas de performance relativa aos objetivos não-declarados (e ocultos). Esses resultados reforçaram a necessidade dos gestores das alianças reverem os métodos de gestão e de medição da performance das alianças, incluindo na sua estimativa as parcelas referentes à realização dos objetivos não-declarados. / Managing alliances between organizations is a challenging task, which has encouraged research that has provided reasonable learning about some aspects of the theme. However, the persistence of high failure rates continues to instigate investigation, like the present research. For this reason, two basic assumptions were taken into account. The first assumption was that non-declared and hidden objectives existed in such a proportion in relation to the declared ones that they could distort the measures of the performance of alliances. The second assumption was that managers would not be observing a sufficiently broad range of factors capable of sustaining their management. The general aim of this research was to investigate the existence of non-declared objectives by parent organizations in the alliances, their relevance to the declared ones and their consequences in measuring the performance of alliances. Before the empirical investigations, a series of management factors was organized and a typology containing eight types of objectives related to the alliance was proposed. Data were collected in two stages, one in case studies and another one in a survey. In two cases studied, the presence of several types of objectives, including declared and hidden ones was demonstrated. The fragile character of the alliances' management processes predicted in the second initial supposition of the study, especially in what regards the planning and controlling of their activities, was also evident. Through the survey it was found that the performance attributed to non-declared objectives had a significant value in relation to the performance value of the declared objectives. For the investigated sample of 78 alliances formed by industrial sector firms of the state of Rio Grande do Sul, the initial assumption was confirmed about the possibility of the results of evaluations of performance being biased if the partial performance related to the non-declared (and hidden) objectives had not been considered. These results emphasized the need for alliance managers to review their management and alliances performance measurement methods, including in their estimate the partial performance related to the achievement of non-declared objectives.

Submitted by Malte Nowack (malte.nowack@gmail.com) on 2014-10-09T21:14:35Z No. of bitstreams: 1 Malte Nowack FGV_VF.docx: 327906 bytes, checksum: 9050c7cb1fba28803c864ea2ab332798 (MD5) / Approved for entry into archive by JOANA MARTORINI (joana.martorini@fgv.br) on 2014-10-10T12:05:14Z (GMT) No. of bitstreams: 1 Malte Nowack FGV_VF.docx: 327906 bytes, checksum: 9050c7cb1fba28803c864ea2ab332798 (MD5) / Made available in DSpace on 2014-10-10T12:25:54Z (GMT). No. of bitstreams: 1 Malte Nowack FGV_VF.docx: 327906 bytes, checksum: 9050c7cb1fba28803c864ea2ab332798 (MD5) Previous issue date: 2014-08-12 / We examine the drivers behind the establishment mode choice of German multinational enterprises (MNEs) in the sectors of Automotive, Chemicals and Mechanical Engineering in Brazil for the years 1993-2013 using a novel sample of primary data obtained directly from German MNEs. Based on prevalent theories found in the literature, we test the most common hypotheses on our sample. Firms with high R&D activities and firms with prior market knowledge in Brazil in from of previous sales offices are more likely to enter Brazil by a Greenfield investment. We also show that it is the specific private ownership of the German so-called hidden champions that drive those specific SMEs to enter Brazil by Greenfield, a sneaking suspicion that has been made before. Finally, we show that the establishment mode choice between Brazil and the USA only deviates to a low extent, with German MNEs preferring to enter Brazil by Greenfield and the USA by M&A. Thereby, we provide valuable insights for future research in this field.

Um dos problemas da extração de dados na web é a remoção de ruído existente nas páginas. Esta tarefa busca identificar todos os elementos não informativos em meio ao conteúdo, como por exemplo cabeçalhos, menus ou propagandas. A presença de ruído pode prejudicar seriamente o desempenho de motores de busca e tarefas de mineração de dados na web. Este trabalho aborda o problema da descoberta de ruído em páginas da web oculta, a parte da web que é acessível apenas através do preenchimento de formulários. No processamento da web oculta, a extração de dados geralmente é precedida por uma etapa de inserção de dados, na qual os formulários que dão acesso às páginas ocultas são automaticamente ou semi-automaticamente preenchidos. Durante esta fase, são coleta- dos dados do domínio em questão, como os rótulos e valores dos campos. A proposta deste trabalho é agregar este tipo de dados com informações sintáticas dos elementos que compõem a página. É mostrado empiricamente que esta combinação atinge resultados melhores que uma abordagem baseada apenas em informações sintáticas. / One of the problems of data extraction from web pages is the identification of noise in pages. This task aims at identifying non-informative elements in pages, such as headers, menus, or advertisement. The presence of noise may hinder the performance of search engines and web mining tasks. In this paper we tackle the problem of discovering noise in web pages found in the hidden web, i.e., that part of the web that is only accessible by filling web forms. In hidden web processing, data extraction is usually preceeded by a form filling step, in which the query forms that give access to the hidden web pages are automatically or semi-automatically filled. During form filling relevant data about the queried domain are collected, as field names and field values. Our proposal combines this type of data with syntactic information about the nodes that compose the page. We show empirically that this combination achieves better results than an approach that is based solely on syntactic information. Keywords:

Muitas informações disponíveis na Web estão armazenadas em bancos de dados on-line e são acessíveis somente após um usuário enviar uma consulta por meio de uma interface de busca. Essas informações estão localizadas em uma parte da Web conhecida como Web Oculta ou Web Profunda e, geralmente, são inacessíveis por máquinas de busca tradicionais. Uma vez que a forma de acessar os dados na Web Oculta se dá por intermédio de submissões de consultas, muitos trabalhos têm focado em como preencher automaticamente campos de formulários. Esta tese apresenta uma metodologia para o preenchimento de formulários na Web Oculta. Além disso, descreve uma categorização das técnicas de preenchimento de formulários existentes no estado da arte de coleta na Web Oculta, produzindo uma análise comparativa entre elas. A solução proposta descreve um método automático para seleção de valores para campos de formulários combinando heurísticas e técnicas de aprendizagem de máquina. Experimentos foram realizados em formulários reais da Web, de vários domínios, e os resultados indicam que a abordagem proposta apresenta desempenho comparável aos obtidos pelas técnicas do estado da arte, sendo inclusive significativamente diferente com base em avaliação estatística. / A large portion of the information on the Web is stored inside online databases. Such information is accessible only after the users submit a query through a search interface. TheWeb portion in which that information is located is called HiddenWeb or DeepWeb, and generally this part is inaccessible by traditional search engines crawlers. Since the only way to access the Hidden Web pages is through the query submissions, many works have focused on how to fill in form fields automatically, aiming at enhancing the amount of distinct information hidden behind Web forms. This thesis presents an automatic solution to value selection for fields in Web forms. The solution combines heuristics and machine learning techniques for improving the selection of values. Furthermore, this proposal also describes a categorization of form filling techniques and a comparative analysis between works in the state of the art. Experiments were conducted on real Web sites and the results indicated that our approach significantly outperforms a baseline method in terms of coverage without additional computational cost.

A segmentação dos nomes nas suas partes constitutivas é uma etapa fundamental no processo de integração de bases de dados por meio das técnicas de vinculação de registros. Esta separação dos nomes pode ser realizada de diferentes maneiras. Este estudo teve como objetivo avaliar a utilização do Modelo Escondido de Markov (HMM) na segmentação nomes e endereços de pessoas e a eficiência desta segmentação no processo de vinculação de registros. Foram utilizadas as bases do Sistema de Informações sobre Mortalidade (SIM) e do Subsistema de Informação de Procedimentos de Alta Complexidade (APAC) do estado do Rio de Janeiro no período entre 1999 a 2004. Uma metodologia foi proposta para a segmentação de nome e endereço sendo composta por oito fases, utilizando rotinas implementadas em PL/SQL e a biblioteca JAHMM, implementação na linguagem Java de algoritmos de HMM. Uma amostra aleatória de 100 registros de cada base foi utilizada para verificar a correção do processo de segmentação por meio do modelo HMM.Para verificar o efeito da segmentação do nome por meio do HMM, três processos de vinculação foram aplicados sobre uma amostra das duas bases citadas acima, cada um deles utilizando diferentes estratégias de segmentação, a saber: 1) divisão dos nomes pela primeira parte, última parte e iniciais do nome do meio; 2) divisão do nome em cinco partes; (3) segmentação segundo o HMM. A aplicação do modelo HMM como mecanismo de segmentação obteve boa concordância quando comparado com o observador humano. As diferentes estratégias de segmentação geraram resultados bastante similares na vinculação de registros, tendo a estratégia 1 obtido um desempenho pouco melhor que as demais. Este estudo sugere que a segmentação de nomes brasileiros por meio do modelo escondido de Markov não é mais eficaz do que métodos tradicionais de segmentação. / The segmentation of names into its constituent parts is a fundamental step in the integration of databases by means of record linkage techniques. This segmentation can be accomplished in different ways. This study aimed to evaluate the use of Hidden Markov Models (HMM) in the segmentation names and addresses of people and the efficiency of the segmentation on the record linkage process. Databases of the Information System on Mortality (SIM in portuguese) and Information Subsystem for High Complexity Procedures (APAC in portuguese) of the state of Rio de Janeiro between 1999 and 2004 were used. A method composed of eight stages has been proposed for segmenting the names and addresses using routines implemented in PL/SQL and a library called JAHMM, a Java implementation of HMM algorithms. A random sample of 100 records in each database was used to verify the correctness of the segmentation process using the hidden Markov model. In order to verify the effect of segmenting the names through the HMM, three record linkage process were applied on a sample of the aforementioned databases, each of them using a different segmentation strategy, namely: 1) dividing the name into first name , last name, and middle initials; 2) division of the name into five parts; 3) segmentation by HMM. The HMM segmentation mechanism was in good agreement when compared to a human observer. The three linkage processes produced very similar results, with the first strategy performing a little better than the others. This study suggests that the segmentation of Brazilian names by means of HMM is not more efficient than the traditional segmentation methods.

There has been growing interest in academic literature about young people who are marginalised and disengaged from society. This thesis focuses on young people in Hong Kong and Scotland who physically shut themselves in the bedroom and do not go outside for months and years on end. They are referred to as “hidden youth” in East Asia, and it has emerged as a topical social issue across the region in the past ten years. Previous research studying “hidden youth” (mainly in Japan and Hong Kong) highlights that there are structural barriers in contemporary society which could lead to young people becoming self-secluded. The young people are described as living reclusive and solitary lives, as they are excluded from participation in the labour market and education and disengaged from interactions with families and other communities, especially friends and peer groups. Hence, they are considered as “withdrawn” from society and disconnected from socialising. This thesis critically reflects on “hidden” young people’s sense of connectedness and “being social” based on their lived experience. It also draws on recent debates of the construction of the “social”, particularly in digital sociology, to shed light on the processes of socialising in the digital age. This study uncovered that how “hidden” young people socialise may in fact be heterogeneous. Variability in how they engage in interactions and participation in society was identified. There were also differences in their levels of solitude and loneliness. Hence, describing how the young people are “being social” could be more nuanced than previously thought. This also makes analysing them as “socially withdrawn” particularly problematic. This research uses a qualitative exploratory approach, looking comparatively across two contexts; 32 interviews were conducted with “hidden youth” in Hong Kong and Scotland. These two contexts are considered as instrumental examples, where social disengagements are especially prominent but discussed differently. The participants revealed various perceptions of hopelessness and lack of opportunities in work and education on the hand. This significantly affected their motivations to participate in employment and education; they could feel unable to fulfil their aspirations and become de-motivated. On the other hand, they were more interconnected with different groups of people in the digital world, and their interactions could be fluid. The space of the bedroom was highlighted as an important site where interactions could occur. This adds another dimension to consider how “hidden” young people interact, particularly with communities such as peer groups, friends and families. Moreover, digital interactions may also be important to how they socialise and experience a sense of connectedness. This highlights that there may be tensions in how young people’s motivations, as well as the opportunities they have, affect their engagements in digital and physical interactions. Therefore, this thesis argues that “hidden youth” could feel a sense of powerlessness towards hierarchical macro structures and meaninglessness towards interactions and participation in society. Conversely, they are relying on emerging digital social structures and networks to seek other forms of “being social”. Their high levels of digital interactions could in fact be a reaction to their experiences of unfulfilment in the labour market and in education. This thesis makes an important contribution to understand “hidden youth” and adds a more nuanced perspective to this emerging debate. In addition, it points to further aspects that should be taken into account in future studies to fully comprehend the sociality of a young person and its complexities in the digital age.

O Processamento de Linguagem Natural (PLN) é uma área da Ciência da Computação, que vem tentando, ao longo dos anos, aperfeiçoar a comunicação entre o homem e o computador. Varias técnicas tem sido utilizadas para aperfeiçoar esta comunicação, entre elas a aplicação de métodos estatísticos. Estes métodos tem sido usados por pesquisadores de PLN, com um crescente sucesso e uma de suas maiores vantagens é a possibilidade do tratamento de textos irrestritos. Em particular, a aplicação dos métodos estatísticos, na marcação automática de "corpus" com categorias morfo-sintáticas, tem se mostrado bastante promissora, obtendo resultados surpreendentes. Assim sendo, este trabalho descreve o processo de marcação automática de categorias morfo-sintáticas. Inicialmente, são apresentados e comparados os principais métodos aplicados a marcação automática: os métodos baseados em regras e os métodos estatísticos. São descritos os principais formalismos e técnicas usadas para esta finalidade pelos métodos estatísticos. E introduzida a marcação automática para a Língua Portuguesa, algo até então inédito. O objetivo deste trabalho é fazer um estudo detalhado e uma avaliação do sistema rotulador de categorias morfo-sintáticas, a fim de que se possa definir um padrão no qual o sistema apresente a mais alta precisão possível. Para efetuar esta avaliação, são especificados alguns critérios: a qualidade do "corpus" de treinamento, o seu tamanho e a influencia das palavras desconhecidas. A partir dos resultados obtidos, espera-se poder aperfeiçoar o sistema rotulador, de forma a aproveitar, da melhor maneira possível, os recursos disponíveis para a Língua Portuguesa. / Natural Language Processing (NLP) is an area of Computer Sciences, that have been trying to improve communication between human beings and computers. A number of different techniques have been used to improve this communication and among them, the use of stochastic methods. These methods have successfully being used by NLP researchers and one of their most remarkable advantages is that they are able to deal with unrestricted texts. Namely, the use of stochastic methods for part-of-speech tagging has achieving some extremely good results. Thus, this work describes the process of part-of-speech tagging. At first, we present and compare the main tagging methods: the rule-based methods and the stochastic ones. We describe the main stochastic tagging formalisms and techniques for part-of-speech tagging. We also introduce part-of-speech tagging for the Portuguese Language. The main purpose of this work is to study and evaluate a part-of-speech tagger system in order to establish a pattern in which it is possible to achieve the greatest accuracy. To perform this evaluation, several parameters were set: the corpus quality, its size and the relation between unknown words and accuracy. The results obtained will be used to improve the tagger, in order to use better the available Portuguese Language resources.