Background Subtraction is one of the fundamental pre-processing steps in video processing. It helps to distinguish between foreground and background for any given image and thus has numerous applications including security, privacy, surveillance and traffic monitoring to name a few. Unfortunately, no single algorithm exists that can handle various challenges associated with background subtraction such as illumination changes, dynamic background, camera jitter etc. In this work, we propose a Multiple Background Model based Background Subtraction (MB2S) system, which is universal in nature and is robust against real life challenges associated with background subtraction. It creates multiple background models of the scene followed by both pixel and frame based binary classification on both RGB and YCbCr color spaces. The masks generated after processing these input images are then combined in a framework to classify background and foreground pixels. Comprehensive evaluation of proposed approach on publicly available test sequences show superiority of our system over other state-of-the-art algorithms.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-08-15T12:01:50Z No. of bitstreams: 1 cinaradejesussantos.pdf: 4566569 bytes, checksum: bddc2ea97276541c0a8ad30a371102d1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-15T12:02:54Z (GMT) No. of bitstreams: 1 cinaradejesussantos.pdf: 4566569 bytes, checksum: bddc2ea97276541c0a8ad30a371102d1 (MD5) / Made available in DSpace on 2017-08-15T12:02:54Z (GMT). No. of bitstreams: 1 cinaradejesussantos.pdf: 4566569 bytes, checksum: bddc2ea97276541c0a8ad30a371102d1 (MD5) Previous issue date: 2017-03-07 / Classificadores são separadores de grupos que mediante determinadas características organiza os dados agrupando elementos que apresentem traços semelhantes, o que permite reconhecimento de padrões e identificação de elementos que não se encaixam. Esse procedimento de classificação e separação pode ser observado em processos do cotidiano como exames (clínicos ou por imagem), separadores automáticos de grãos na agroindústria, identificador de probabilidades, reconhecedores de caracteres, identificação biométrica - digital, íris, face, etc. O estudo aqui proposto utiliza uma base de dados do Ministério do Desenvolvimento Social e Combate a Fome (MDS), contendo informações sobre beneficiários do Programa Bolsa Família (PBF), onde contamos com registros descritores do ambiente domiciliar, grau de instrução dos moradores do domicílio assim como o uso de serviços de saúde pelos mesmos e informações de cunho financeiro (renda e gastos das famílias). O foco deste estudo não visa avaliar o PBF, mas o comportamento de classificadores aplicados sobre bases de caráter social, pois estas apresentam certas particularidades. Sobre as variáveis que descrevem uma família como beneficiária ou não do PBF, testamos três algoritmos classificadores - regressão logística, árvore binária de decisão e rede neural artificial em múltiplas camadas. O desempenho destes processos foi medido a partir de métricas decorrentes da chamada matriz de confusão. Como os erros e acertos de uma classe n˜ao s˜ao os complementares da outra classe é de suma importância que ambas sejam corretamente identificadas. Um desempenho satisfatório para ambas as classes em um mesmo cenário não foi alçado - a identificação do grupo minoritário apresentou baixa eficiência mesmo com reamostragem seguida de reaplicação dos três processos classificatórios escolhidos, o que aponta para a necessidade de novos experimentos. / Classifiers are group separators that, by means of certain characteristics, organize the data by grouping elements that present similar traits, which allows pattern recognition and the identification of elements that do not fit. Classification procedures can be used in everyday processes such as clinical or imaging exams, automatic grain separators in agribusiness, probability identifiers, character recognition, biometric identification by thumbprints, iris, face, etc. This study uses a database of the Ministry of Social Development and Fight against Hunger (MDS), containing information on beneficiaries of the Bolsa Fam´ılia Program (PBF). The data describe the home environment, the level of education of the residents of the household, their use of public health services, and some financial information (income and expenses of families). The focus of this study is not to evaluate the PBF, but to analyze the performance of the classifiers when applied to bases of social character, since these have certain peculiarities. We have tested three classification algorithms - logistic regression, binary decision trees and artificial neural networks. The performance of these algorithms was measured by metrics computed from the so-called confusion matrix. As the probabilities of right and wrong classifications of a class are not complementary, it is of the utmost importance that both are correctly identified. A good evaluation could not be archive for both classes in a same scenario was not raised - the identification of the minority group showed low efficiency even with resampling followed by reapplication of the three classificatory processes chosen, which points to the need for new experiments.

The work deals with an introduction to classification algorithms. It then divides classifiers into unary, binary and multi-class and describes the different types of classifiers. The work compares individual classifiers and their areas of use. For unary classifiers, practical examples and a list of used architectures are given in the work. The work contains a chapter focused on the comparison of the effects of hyper parameters on the quality of unary classification for individual architectures. Part of the submission is a practical example of reimplementation of the unary classifier.

The work deals with an introduction to classification algorithms. It then divides classifiers into unary, binary and multi-class and describes the different types of classifiers. The work compares individual classifiers and their areas of use. For unary classifiers, practical examples and a list of used architectures are given in the work. The work contains a chapter focused on the comparison of the effects of hyperparameters on the quality of unary classification for individual architectures. Part of the submission is a practical example of implementation of the unary classifier.

The astronomical increase in the number of wireless devices such as smart phones in 21th century has revolutionized the way people communicate with one another and share information. The new wireless technologies have also enabled researchers to collect real data about how people move and meet one another in different social settings. Understanding human mobility has many applications in different areas such as traffic planning in cities and public health studies of epidemic diseases. In this thesis, we study the fundamental properties of human contact graphs in order to characterize how people meet one another in different social environments. Understanding human contact patterns in return allows us to propose a cost-effective routing algorithm for spreading information in Delay Tolerant Networks. Furthermore, we propose several contact predictors to predict the unobserved parts of contact graphs when only partial observations are available. Our results show that we are able to infer hidden contacts of real contact traces by exploiting the underlying properties of contact graphs. In the last few years, we have also witnessed an explosion in the number of people who use social media to share information with their friends. In the last part of this thesis, we study the running times of several information spreading algorithms in social networks in order to find the fastest strategy. Fast information spreading has an obvious application in advertising a product to a large number of people in a short amount of time. We prove that a fast information spreading algorithm should efficiently identify communication bottlenecks in order to speed up the running time. Finally, we show that sparsifying large social graphs by exploiting the edge-betweenness centrality measure can also speed up the information spreading rate. / Graduate