Cette thèse traite de la segmentation et du suivi de structures curvilinéaires. La méthodologie proposée est appliquée à la segmentation et au suivi des guide-fils durant les interventions d'angioplastie. Pendant ces opérations, les cardiologues s'assurent que le positionnement des différents outils est correct au moyen d'un système d'imagerie fluoroscopique temps-réel. Les images obtenues sont très bruitées et les guides sont, en conséquence, particulièrement difficiles à segmenter. Les contributions de cette thèse peuvent être regroupées en trois parties. La première est consacrée à la détection des guides, la seconde a leur segmentation et la dernière a leur suivi. La détection partielle des guide-fils est réalisée soit par la sélection d'un opérateur de filtrage approprié soit en utilisant des méthodes modernes d'apprentissage artificiel. Dans un premier temps, un système réalisant un Boosting asymétrique pour entraîner un détecteur de guides est présenté. Par la suite, une méthode renforçant la réponse d'un filtre orientable au moyen d'une variante efficace de vote tensoriel est décrite. Dans la seconde partie, une approche ascendante est proposée, qui consiste à regrouper des points sélectionnés par le détecteur de fil, à extraire des primitives des agrégats obtenus et a les lier. Deux procédures locales de regroupement des points sont étudiées : une reposant sur un clustering de graphe non supervisé suivi d'une extraction de segments de droites ; et l'autre reposant sur un modèle graphique puis une extraction d'axe central. Par la suite, deux méthodes de liaison des primitives sont étudiées : la première repose sur une approche de programmation linéaire, et la seconde sur une heuristique de recherche locale. Dans la dernière partie, des méthodes de recalage sont utilisées pour améliorer la segmentation et pour suivre les fils. Le suivi propos'e couple un suivi iconique avec un suivi géométrique contenant un modèle prédictif. Cette méthode utilise un modèle graphique déterminant à la fois une position du guide-fil (segmentation) et des correspondances (tracking). La solution optimale de ce modèle graphique décrit simultanément les déplacements du guide-fil et les appariements entre points d'intérêt qui en sont extraits, fournissant ainsi une estimation robuste des déformations du fil par rapport aux grands déplacements et au bruit.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Durant plusieurs décennies, au sein de ce qui s'est appelé la « banlieue rouge », Ivry-sur-Seine faisait figure de « bastion » modèle pour le Parti Communiste Français. Le communisme municipal ivryen avait fait de ses cités ouvrières des espaces laboratoires au service d'un creuset d'affiliation sociopolitique particulièrement efficace. Jusqu'au tournant des années 1980, aux cités Maurice Thorez et Youri Gagarine, les résultats électoraux enregistrés par les différents représentants communistes en ont attesté. Avec la remise en cause du modèle de politisation fondé sur l'écosystème industriel, le renouvellement des générations pose avec acuité la question des conditions de reproduction d'une affiliation sociopolitique favorable aux représentants communistes. Une approche ethnographique sur la longue durée a permis de renseigner cette question. Depuis le milieu des années 1980, la trajectoire sociopolitique contrastée des deux quartiers atteste des ruptures infra-communales touchant ce type de territoire de la banlieue parisienne. Dans le quartier Youri Gagarine, la majorité des anciennes familles ouvrières a été remplacée par les nouveaux milieux populaires essentiellement composés de populations issues de l'immigration. Entretenant une historicité tout à fait différente à l'égard de l'étiquette « communiste(s)», les nouvelles générations participent, parfois activement, d'une contestation de l'ancienne autorité politique locale. À l'inverse, dans le quartier Maurice Thorez, situé au cœur du centre-ville, les descendants des familles ivryennes les plus proches de l'appareil partisan et/ou municipal ont maintenu résidence. Dans ce quartier, autour d'une endocratie politique locale, se maintiennent des liens communautaires fonctionnant de manière relativement indépendante de l'ancien encadrement partisan. Pour de nombreuses familles ivryennes appartenant à la classe moyenne, le maintien d'une certaine autorité communiste facilite leur accompagnement social, politique et électoral des métamorphoses contemporaines du communisme municipal. / For decades, Ivry-sur-Seine was seen as a model Communist stronghold within the Paris ‘Red Belt'. The particular brand of communism practiced by Ivry's municipal government had turned its working-class housing estates into laboratories directed towards the production of a singularly efficient political affiliation system. Until the watershed of the 1980s, electoral results for the various communist representatives in the Maurice Thorez and Yuri Gagarin housing estates seemed to corroborate this. The decline of the politicization model born of industrialization as well as the generation gap have radically undermined the conditions in which a socio-political affiliation system favourable to communist representatives can survive, however. The choice of a long-term ethnographic approach can give us insight into this phenomenon. Since the middle of the 1980s, the contrasting socio-political evolution of the Thorez and Gagarin allotments has testified to the intra-municipal disruption that affects this type of suburban Parisian territory. In the Yuri Gagarin area, the majority of older working-class families have been replaced with a new working-class population essentially stemming from immigration. Often unaware of the rich history of communism in their municipality, these new generations are sometimes actively involved in the challenging of the older local political authority. Downtown, on the contrary, the descendants of the families that were closest to the local party machine have maintained residency in the Maurice Thorez area. Community links have survived around a local political “endocracy” that works relatively independently from the older partisan frame. For many middle-class families living in Ivry, the maintenance of a certain communist authority makes it easier to accept the social, political, and electoral transformations of contemporary municipal communism.

« Les gens qui parlent ensemble votent ensemble ». En écrivant ces quelques mots, le sociologue britannique William Miller résumait, à la fin des années 1970, une tradition de recherche déjà ancienne : le vote, en tant qu‟expérience de groupe, se joue d‟abord dans les rapports que les citoyens ordinaires entretiennent avec ceux avec qui ils vivent quotidiennement. La recherche présentée dans cette thèse propose de réinterroger cette hypothèse par l‟intermédiaire d‟une enquête visant à saisir comment le contexte social d‟appartenance – entendu comme l‟entourage relationnel d‟un individu - structure la pratique des échanges politiques, et en quoi cette pratique peut-elle impacter les comportements électoraux individuels. L‟enquête en question a donc consisté à adapter la technique de l‟échantillonnage en boule-de-neige à la passation de questionnaires de personne à personne. Partant d‟un échantillon de base de dix personnes mobilisées à trois reprises – en 2009, 2010 et 2012 – il m‟a ainsi été possible d‟identifier des chaînes de relations grâce à la circulation de questionnaires au sein des cercles d‟interconnaissance des participants. En plus de données statistiques, l‟enquête s‟appuie sur une analyse ethnographique de la phase de construction des différents échantillons. Ce travail repose sur le postulat selon lequel les questionnaires élaborés constituent des "objets politiques", avec pour conséquence que les échanges de questionnaires au sein des populations étudiées instaurent de fait un cadre d'interactions présentant une dimension "politique". L‟étude ethnographique de la mise en oeuvre de cette passation offre ainsi l‟occasion de porter un regard original sur les moyens par lesquels des citoyens ordinaires organisent des échanges à dimension politique au sein de leurs réseaux d‟appartenance. Les résultats de cette analyse, confrontés à celle des échanges politiques plus ordinaires pratiqués au sein des contextes identifiés au cours de l‟enquête, montrent que le politique, loin d‟obéir à des logiques autonomes, prend sa source et prolonge les normes et les identités sociales produites par les groupes. La structure sociale du contexte – notamment son degré de cohésion – et sa composition en termes de ressources économiques, culturelles et politiques, déterminent le déroulement des échanges politiques et leur capacité à créer de la mobilisation et à faire en sorte que les identités collectives se traduisent en choix électoraux. / “People who talk together vote together”. By writing these few words, the British sociologist William Miller resumed, at the end of the 1970‟s, an old research tradition : voting, as a group experience, depends on the contacts that ordinary citizens maintain with those they live with everyday. The research presented in this thesis dissertation suggests questioning again this hypothesis by the mean of a survey that aims to understand how the social context of belonging – i.e. the relational surrounding of a person – shapes the practice of political exchange, and how this practice can affect individual electoral behavior. This survey consisted in an adaptation of the snowball sampling technique around the person-to-person transfer of questionnaires. Starting with a first sample of 10 people called up three times – in 2009, 2010, and 2012 – I could identify many chains of contacts by following the flow of questionnaires within circles of acquaintances of participants. Additionally with statistical data, the survey is based on an ethnographic analysis of the sampling procedure. This work is founded on the assumption that questionnaires elaborated for the survey constitute "political objects", with the consequence that the exchanges of questionnaires within the populations studied establish a setting of interactions with a political dimension. The ethnographic analysis of the elaboration of the transfer allows having an original look on the means by which ordinary citizens organize some political exchanges within the social networks they belong to. The results of this analysis, compared to the one of more ordinary exchanges practiced within social contexts identified during the survey, show that politics, far to respond to independent logics, take their origins in social norms and identities produced by groups. The social structure of context – mainly its cohesion degree – and its composition in terms of economic, cultural and political resources, determine the flow of political exchanges and their ability to create mobilization and to make possible the translation of collective identities into electoral choices.

In October 2015, John Magufuli became President of Tanzania and his party (Chama cha Mapinduzi, CCM) won a large majority in parliament. This thesis explains why Tanzanians choose to vote the way they do in general and in these elections in particular. It draws on qualitative interviews with approximately one-thousand voters in four field sites: one urban and one rural area in Dodoma Region where CCM are dominant, and a second pair of urban and rural areas from Mwanza Region in which the opposition are more competitive. By using theories of social remembering to understand vote preference, this thesis investigates a number of key issues that are crucial to determining political outcomes in Tanzania: 1) CCM's track record in government; 2) The sources of information available to voters; 3) The role of money in politics; 4) CCM's attempts to discredit the opposition; 5) The progress of the opposition since political liberalisation, and; 6) Local factors, including the behaviour of candidates. Having addressed these dynamics, attention is turned to how they played out during the 2015 election. The thesis concludes that, although Magufuli had significant appeal to many voters, his victory was aided by undemocratic manipulation. This shows that the process of political transition was far from complete, even before post-election developments that have threatened basic democratic principles in Tanzania.

How does digital media and online news, especially blogs, influence support for women congressional and presidential candidates? From work on traditional print and television news we know women are framed differently than men, and are more likely to be framed as women (appearance, clothing, mother or wife, marital status, sex, gendered issues). I argue the transition to digital media (blogs and online news) is exacerbating these trends, increasing gender stereotype opinions of women candidates in the mass public, among both men and women. In turn I find gender stereotype opinions combined with use of online media reduces the probability of voting for women candidates. While much of the literature on digital media focuses on the positives that come with increased political information, participation and mobilization, holding these factors constant, this research highlights a potential cost of digital media. Much of what we know about the media and women candidates is based on content analysis of newspapers and television stories (Bystrom 20004; 2010a; 2010b; Iyengar et al1997; Lawrence and Rose 2010). The dominant literature on the impact of the mass media on women candidates is based on experimental framing studies with hypothetical female candidates. But media scholars are increasing interested in digital media and citizen journalism, as more Americans now read their news online than read a print newspaper. Davis (2009) and Sunstein (2007) find that journalists too are increasingly turning to the blogs for ideas and content that run on mainstream media. While citizen journalism has many benefits (see Shirky 2010), there is less fact checking with online news, where rumors can often masquerade as truth. Analysis of the coverage of Hillary Clinton's 2008 presidential run found that coverage of Clinton online, especially the blogs, was more sexist than mainstream media (Lawrence and Rose 2010; Richie 2013). For example, one group sold t-shirts and bumper stickers staying "Get Hillary Back in the Kitchen." Boystrum (2010) analyses how women and men presidential, congressional and gubernatorial candidates differ, and how this affects media coverage of the candidates. Using content analysis, she finds no gendered differences in the content of their websites. Thus this research focuses on blogs and online news rather than candidate websites. No previous research has considered individual level data on use of online news for politics and whether this leads to gender stereotype opinions; nor has the existing research considered whether digital media use, combined believing in these stereotypes of women, impacts voting for women candidates in real election contexts. Rather than content analysis used in political communications or laboratory experiments often used in gender studies, this research relies on national survey data to measure the effect of digital media use for voting for women candidates in actual electoral campaigns. Combining large sample nationwide survey data of all congressional candidates running in 2008, 2010 and 2012, with a sample of Iowa caucus participants, and a unique national survey of primary voters, this research seeks to answer two primary questions. First, what is the effect of use of blog and online news on gendered stereotype opinion of women and male candidates (see Chapters 3 and 5)? Secondly, what is the combined effect of digital media use and gendered opinions in reducing support at the ballot box for women for the U.S. House or the president (see Chapters 4 and 6)? To consider the overall, or net effect, of digital media on support for women candidates, I incorporate the benefits of online news and communication to engage and mobilize the public. Across many detailed analyses presented in this research, I find that reading blogs and online news generally increases the likelihood of forming opinions about women candidates colored by gender stereotypes, based on experience, knowledge, competency, integrity, strong leader, caring and more. In Chapter 3 I consider the case of Hillary Clinton and find that reading the news online and using online political information increased the belief that Clinton was less experienced, and was less trustworthy. In Chapter 4 I find that gender stereotype opinions and digital media use reduced favorability ratings of Clinton and Clinton compared to her male presidential contenders (Obama and Edwards). These two factors also reduced the probably of voting for her, holding other factors constant. Chapter 5 analyses all U.S. House races from 2008, 2010, and 2012 with a women candidate. Individuals who used online news or political blogs are more likely to believe the woman candidate is less competent, lacks integrity, and is less caring than the man candidate, holding other factors constant. Finally, the results from Chapter 6 show gendered opinions and digital media reduce the likelihood of voting for the woman candidate. The overall, or net effect, models show even the positive effect of online mobilization is outweighed by the negative effect of digital media combined with the believe in gender stereotypes. Such gendered opinions of women candidates are widely held by the mass public. The dominant explanation for why Obama, as an underdog candidate won the 2008 Democratic presidential nomination was that he was able to mobilize and engage the public, especially the young, through online media. These online venues also significantly increased the money Obama raised through small dollar contributions (Redlawsk et al 2010). However, what these stories ignore is the negative media coverage of his primary opponent, Hillary Clinton, online. This study attempts to systematically and empirically document how the Internet and online news may contributed to reduced support for Clinton's candidacy and women congressional candidates more generally. As new communication mediums are developed there are often short-term increases in misinformation with the proliferation of information, but as standards are established this chaos disappears. Digital media's effect on women candidates for elected office over the long run is unclear and deserves further study.

La facilitation est un élément central dans une prise de décision de groupe surtout en faisant l'usage des outils de nouvelle technologie. Le facilitateur, pour rendre sa tâche facile, a besoin des solutions de vote pour départager les décideurs afin d'arriver à des conclusions dans une prise de décision. Une procédure de vote consiste à déterminer à partir d’une méthode le vainqueur ou le gagnant d’un vote. Il y a plusieurs procédures de vote dont certaines sont difficiles à expliquer et qui peuvent élire différents candidats/options/alternatives proposées. Le meilleur choix est celui dont son élection est acceptée facilement par le groupe. Le vote dans la théorie du choix social est une discipline largement étudiée dont les principes sont souvent complexes et difficiles à expliquer lors d’une réunion de prise de décision. Les systèmes de recommandation sont de plus en plus populaires dans tous les domaines de science. Ils peuvent aider les utilisateurs qui n’ont pas suffisamment d’expérience ou de compétence nécessaires pour évaluer un nombre élevé de procédures de vote existantes. Un système de recommandation peut alléger le travail du facilitateur dans la recherche d’une procédure vote adéquate en fonction du contexte de prise de décisions. Le sujet de ce travail de recherche s’inscrit dans le champ de l’aide à la décision de groupe. La problématique consiste à contribuer au développement d’un système d’aide à la décision de groupe (Group Decision Support System : GDSS). La solution devra s’intégrer dans la plateforme logicielle actuellement développée à l’IRIT GRUS : GRoUp Support. / Facilitation is a central element in decision-making, especially when using new technology tools. The facilitator, to make his task easy, needs voting solutions to decide between decision-makers in order to reach conclusions in a decision-making process. A voting procedure consists of determining from a method the winner of a vote. There are several voting procedures, some of which are difficult to explain and which may elect different candidate/options/alternatives proposed. The best choice is the one whose election is easily accepted by the group. Voting in social choice theory is a widely studied discipline whose principles are often complex and difficult to explain at a decision-making meeting. Recommendation systems are becoming more and more popular in all fields of science. They can help users who do not have sufficient experience or competence to evaluate large numbers of existing voting procedures. A recommendation system can lighten the facilitator's workload in finding an appropriate voting procedure based on the decision-making context. The objective of this research work is to design such recommendation system. This work is in the field of group decision support. The issue is to contribute to the development of a Group Decision Support System (GDSS). The solution will have to be integrated into the software platform currently being developed at IRITGRUS: GRoUp Support.

The Republican Party of California faces a serious demographic challenge as a burgeoning Latino population threatens to turn this majority-minority state a darker shade of blue. The purpose of my research and of this thesis is to explore the relationship between Latino voters in California and the Republican Party and to draw conclusions about the most viable and proven means of attracting Latino votes to Republican candidates. The Latino vote is by no means a lost cause for Republicans. My research supports several claims, which are laid out here and discussed throughout the paper. The first is that the Republican Party waits now at a crucial moment of opportunity for failure or survival in California. The next is that there are multiples issues with which the GOP can make inroads with Hispanic communities. The research available leads me to conclude that it matters less what Republicans might say about these issues, and more how and where (and even in what language) they say it.

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