Graphical models use Markov properties to establish associations among dependent variables. To estimate spatial correlation and other parameters in graphical models, the conditional independences and joint probability distribution of the graph need to be specified. We can rely on Gaussian multivariate models to derive the joint distribution when all the nodes of the graph are assumed to be normally distributed. However, when some of the nodes are discrete, the Gaussian model no longer affords an appropriate joint distribution function. We develop methods specifying the joint distribution of a chain graph with both discrete and continuous components, with spatial dependencies assumed among all variables on the graph. We propose a new group of chain graphs known as the generalized tree networks. Constructing the chain graph as a generalized tree network, we partition its joint distributions according to the maximal cliques. Copula models help us to model correlation among discrete variables in the cliques. We examine the method by analyzing datasets with simulated Gaussian and Bernoulli Markov random fields, as well as with a real dataset involving household income and election results. Estimates from the graphical models are compared with those from spatial random effects models and multivariate regression models. / Graduation date: 2013

Les graphiques ont pris de plus en plus d'importance dans le matériel pédagogique, les manuels scolaires ou encore les programmes informatiques. Malgré la coexistence de différents types de graphiques ou de genres graphiques, jusqu'à maintenant, les recherches sur l'apprentissage ont seulement pris en compte la distinction entre le texte et l'image. Cette thèse vise à éclaircir ce qui, dans la recherche sur l'apprentissage, semble être une catégorie globale et indivisible : les représentations visuelles. Nous nous sommes concentrées sur ce que pensent des enseignants et des étudiants de Master concernant différents types de représentations visuelles et leurs fonctions présumées dans l'enseignement et l'apprentissage. A l'heure actuelle, la recherche sur les graphiques est principalement axée sur la compréhension des élèves. Il existe très peu de recherches sur la compréhension des graphiques par les enseignants. En outre, la dimension de la formation des enseignants aux graphiques est, elle aussi, relativement ignorée. La thèse se présente en deux parties : une recherche théorique suivie d'une recherche empirique. La première partie du travail examine la littérature relative aux représentations graphiques dans l'histoire, dans les programmes scolaires à travers le monde ainsi que leur utilisation dans l'enseignement et l'apprentissage. Elle expose également les classifications des différents types de graphiques. La seconde partie de la thèse prend appui sur trois enquêtes menées auprès d'enseignants en activité et d'étudiants de Master en formation. La première investigue la compréhension des graphiques d'enseignants en activité en France et au Pakistan. Les deux autres ont été conduites auprès de futurs enseignants, en utilisant la méthode du tri de carte, afin d'identifier leurs compétences relatives à la catégorisation des différents types de graphiques.En conclusion, il semble que les programmes de formation des enseignants manquent d'un enseignement à la compréhension graphique. Même en géographie, pourtant considérée comme la discipline des graphiques et de leur enseignement, nous constatons que les enseignants sont peu familiers avec de nombreux genres graphiques. Dans l'ensemble, les graphiques génériques (camemberts, histogrammes, cartes et tableaux, etc.) ont été facilement identifiés par les enseignants alors que la classification des graphiques hybrides s'est révélée plus difficile pour la plupart d'entre eux. / Visualizations have gained more importance in pedagogical material, in text books and in computer programs. Despite the co-existence of many different types of visualizations or graphical genres, learning research only has taken into account the distinction between text and pictures. This thesis aims at unpacking what, at least in learning research, seems to be one single holistic indivisible category of visualizations. We focused on teachers' and Masters students' thoughts on the existence of different types of visualizations and their presumed function in teaching and learning. Research on graphical representations is mainly focused on students' comprehension of graphical representations. However, there is very little research in extend of teachers' comprehension of graphical representations. In addition, the aspect of teacher training of graphical representations is also relatively ignored. There are two main parts in this thesis: theoretical and empirical. In theoretical part, we presented the literature on the existence of graphical representations in worldwide curricula. Remarkable works of cartographers who played important rule for the advancement of graphic representations in context of teaching and learning. And finally, classification of different genres of graphical representations was also exhibited. Empirical part on the other hand, based on three studies conducted with in-service teachers and Masters students' about their comprehension of graphical genres. First study was conducted with in-service teachers from France and Pakistan to investigate their basic understanding of graphical representations. Second and third study explores the Masters' students' categorization of graphical representations. In conclusion, it seems that the teacher training programs lack the training of graphic comprehension. Even in the domain of geography which is considered the major domain about graphics and graphic education, teachers were observed unfamiliar with many graphic genres. Overall, Generic graphical representations (i.e. line graph, pie charts, bar charts, maps and tables etc.) were identified more comfortably. However, classification of hybrid graphical representations (i.e. combination of map and bar graph or other hybrid graphics) was slightly difficult for the participants.

[pt] Representações gráficas bidimensionais - tais como o desenho - e modelos tridimensionais físicos (maquetes, mock- ups ou protótipos) são recursos tradicionalmente utilizados por designers para comunicar a idéia de um projeto. Com a crescente inserção do computador no cotidiano e o desenvolvimento do CAD (Computer Aided Design), as áreas projetuais ganharam mais um recurso de representação gráfica: o desenho auxiliado por computador. Diante deste panorama, esta pesquisa procurou investigar junto a alunos e professores do curso de Desenho Industrial com Habilitação em Projeto de Produto do Departamento de Artes e Design da PUC-Rio como se dá a representação e apresentação de seus projetos. A partir da análise do discurso dos entrevistados verificou-se a necessidade de se investigar não só como as diferentes habilidades e processos de representação bidimensional e tridimensional da idéia são utilizadas em paralelo, tais como a habilidade em desenhar à mão, a elaboração de modelos físicos, e a modelagem digital, mas também de se dar o devido destaque ao questionamento, por parte dos entrevistados, da estrutura curricular atual do curso, e sua demanda por novas frentes de atuação da disciplina de Computação Gráfica, de forma a permitir maior capacitação profissional aos alunos de projeto de produto. / [en] Two-dimensional graphic representation - such as drawings - and physical three-dimensional models - such as mock-ups and prototypes - are resources traditionally used by designers to communicate the idea of a project. With the growth of computer use and the development of CAD (Computer Aided Design), project areas gained one more graphic representation resource. Considering this scenario, this research work has investigated how Product Design students at Pontificia Universidade Católica in Rio de Janeiro do the representation and presentation of their projects. The research was based on interviews with teachers and students and concluded that both human varied capabilities and two- dimensional or three-dimensional representation are relevant - hand drawing ability, drawing practice, physical models manufacturing and digital modeling are equally important. It was also verified that there is a strong aspiration between the interviewees for a revision of the present course structure and for the development of new areas of Computer Graphics utilization, so that the Product Design students can achieve a better level of professional capability.

Adaptive Mesh Refinement (AMR) is a method which dynamically varies the spatio-temporal resolution of localized mesh regions in numerical simulations, based on the strength of the solution features. Due to high resolution discretization of localized regions of interests into rectangular mesh units called patches, AMR provides low cost of computations and high degree of accuracy. General purpose graphics processing units (GPGPUs) with their support for fine-grained parallelism, offer an attractive option for obtaining high performance for AMR applications. The data parallel computations of the finite difference schemes of AMR can be efficiently performed on GPGPUs. This research deals with challenges and develops techniques for efficient executions of AMR applications with uniform and non-uniform patches on GPUs. In the first part of the thesis, we optimize an AMR model with uniform patches. We have developed strategies for continuous online visualization of time evolving data for AMR applications executed on GPUs. In-situ visualization plays an important role for analyzing the time evolving characteristics of the domain structures. Continuous visualization of the output data for various time steps results in better study of the underlying domain and the model used for simulating the domain. We reorder the meshes for computations on the GPU based on the users input related to the subdomain that he wants to visualize. This makes the data available for visualization at a faster rate. We then perform asynchronous executions of the visualization steps and fix-up operations on the coarse meshes on the CPUs while the GPU advances the solution. By performing experiments on Tesla S1070 and Fermi C2070 clusters, we found that our strategies result in up to 60% improvement in response time and 16% improvement in the rate of visualization of frames over the existing strategy of performing fix-ups and visualization at the end of the time steps. The second part of the thesis deals with adaptive strategies for efficient execution of block structured AMR applications with non-uniform patches on GPUs. Most AMR approaches use patches of uniform sizes over regions of interests. Since this leads to over-refinement, some efforts have focused on forming patches of non-uniform dimensions to improve computational efficiency since the dimensions of a patch can be tuned to the geometry of a region of interest. While effective hybrid execution strategies exist for applications with uniform patches, our work considers efficient execution of non-uniform patches with different workloads. Our techniques include a geometric bin-packing method to load balance GPU computations and reduce thread idling, adaptive determination of amount of work to maximize asynchronism between CPU and GPU executions using a knapsack formulation, and scheduling communications for multi-GPU executions. We test our strategies for synthetic inputs as well as for traces from real applications. Our experiments on Tesla S1070 and Fermi C2070 clusters with both single-GPU and multi-GPU executions show that our strategies result in up to 69% improvement in performance over existing strategies. Our bin-packing based load balancing gives performance gains up to 39%, kernel optimizations give an improvement of up to 20%, and our strategies for adaptive asynchronism between CPU-GPU executions give performance improvements of up to 17% over default static asynchronous executions.

This thesis deals with an issue of how can graphical modifications of response options in online questionnaire influence the respondents' answers. Online questionnaire as a data collection method offers a wide range of visual adjustments. Therefore, it is necessary for the graphical format to be treated with caution, because it can produce significant differences in respondents' answers. The goal of this thesis is to find out, with the help of two versions of online questionnaire that differ in the graphical format of response options, whether and what differences in answers these modifications produce. The attention is also payed to the response time differences. Together there are eleven modifications tested, each of them is represented twice. The analysis shows that the differences in graphical format of response options do influence the answers; there were 7 of 11 hypotheses confirmed. One of the surprising findings is that in the case of comparing the format of check boxes and the format of writing answers into text boxes, respondents answered with a maximum number of allowed answers in both version. This type of result was not expected in the case of the "writing into text boxes" format. Other findings show that some modifications influence more women than men, for example the use of a...

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Master of Science / Department of Computing and Information Sciences / Alley Stoughton / This thesis covers the process leading up to the release of eXene 2.0, a User Interface Management System (UIMS) toolkit. Since its inception, eXene has provided a unique way to create meaningful graphical user interfaces (GUIs) for Standard ML applications. Additionally, it has gone through several quality revisions which have both enhanced the toolkit and corrected many deficiencies that were present. Even with these improvements, however, the full potential of eXene has become increasingly difficult for developers to utilize. That is, in spite of the natural innovation that eXene brings to GUI construction, its current lack of extensibility, usability, and functionality has caused Standard ML developers to choose simpler, more familiar UIMS toolkits, despite their limitations, for the creation of their applications. In light of this fact, eXene needs an internal and cosmetic overhaul to extend its usage and appeal. First, to improve its extensibility, formerly weakened by organic growth, eXene requires some restructuring of its architecture. Second, to improve its overall usability, previously stifled by sparse documentation, eXene requires the implementation of an interactive electronic document for its API. Finally, to improve its functionality, several new multi-purpose widgets need to be introduced. It is the author's hypothesis that the revised structure, improved documentation, and additional multi-purpose widgets detailed in this thesis sufficiently elevate eXene's extensibility, usability, and functionality such that eXene can be considered a fully featured UIMS toolkit. With these changes and the release of eXene 2.0, eXene is more likely to be adopted as the primary UIMS toolkit for Standard ML developers.

Traditional text-based passwords used for authentication in information systems have several known issues in the areas of usability and security. Research has shown that when users generate passwords for systems, they tend to create passwords that are subject to compromise more so than those created randomly by the computer. Research has also shown that users have difficulty remembering highly secure, randomly created, text-based passwords. Graphical-based passwords have been shown to be highly memorable for users when applied to system authentication. However, graphical-based authentication systems require additional cognitive load to recognize and enter a password compared to traditional text-based authentication that is more muscle-memory. This increase in cognitive load causes an increased security risk of shoulder-surfing created from the longer amount of time needed to input a password. Graphical-based authentication systems use the same images for each possible input value. This makes these authentication systems vulnerable to attackers. The attackers use their ability to remember visual information to compromise a graphical-based password. This study conducted research into a graphical-based authentication scheme that implemented pictorial synonyms. The goal is to decrease security risk of graphical-based authentication systems while maintaining (or even increasing) the usability of these systems. To accomplish this goal, a study to evaluate the impact on the cognitive load required using an image synonym authentication system compared to traditional graphical-based authentication schemes. The research found that there was not a significant difference in the areas of user cognitive load, shoulder-surfing threat, and user effectiveness. The research evaluated users' accuracy, cognitive load, and time to authenticate and found to have significant impact of pictorial synonyms on graphical-based authentication systems. The research shows that the accuracy of pictorial synonyms was greater than word password. This appears to due to people's ability to recall pictorial information over text information. Future research should look at the impact of pictorial synonyms on shoulder-surfing attackers and different ages.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / With wireless communications becoming the rule rather than the exception, satellite operators need tools to effectively monitor increasingly large and complex satellite constellations. Visual data monitoring increases the monitoring capacity of satellite operators by several orders of magnitude, enabling them to track hundreds of thousands of parameters in real-time on a single screen. With this powerful new tool, operators can proactively address potential problems before they become customer complaints.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / There is a wave of change coming. It started in the industrial automation community and it is slowly and surely working its way into aerospace, satellite and telemetry applications. It’s called the PC, and its not just for simple quick-look data anymore. Using state-of-the-art commercial hardware and software technologies, PC-based architectures can now be used to perform self contained, reliable and high performance telemetry data acquisition and processing functions – previously the domain of expensive, dedicated front end systems. This paper will discuss many of the key enabling technologies and will provide examples of their use in a truly next generation system architecture based on the Microsoft® Windows NT Operating System and related features.