Real-time human detection in urban scenes: Local descriptors and classifiers selection with adaboost-like algorithms

This paper deals with the study of various implementations of the AdaBoost algorithm in order to address the issue of real-time pedestrian detection in images. We use gradient-based local descriptors and we combine them to form strong classifiers organized in a cascaded detector. We compare the original AdaBoost algorithm with two other boosting algorithms we developed. One optimizes the use of each selected descriptor to minimize the operations done in the image (method 1), leading to an acceleration of the detection process without any loss in detection performances. The second algorithm (method 2) improves the selection of the descriptors by associating to each of them a more powerful weak-learner – a decision tree built from the components of the whole descriptor – and by evaluating them locally. We compare the results of these three learning algorithms on a reference database of color images and we then introduce our preliminary results on the adaptation of this detector on infrared vision. Our methods give better detection rates and faster processing than the original boosting algorithm and also provide interesting results for further studies. 1

Deformable model to recover circular generalized cylinders

This paper describes a new approach to recover Circular Generalized Cylinders (CGC) using deformable models . This class includes many objects present on industrial site (pipes) or on the natural environment (human leg, tree trunk) . First, we propose a modeling algorithm of objects with constant cross-section radius, called Uniform Circular Generalized Cylinder s (UCGC). With this assumption, reconstruction is possible from a single view of the object. In the case of a single image, the cross - section radius cannot be estimated . If this radius is unknown, reconstruction is achieved up to a scale factor. The model 3D axis i s parametrized by a B-spline curve . After a coarse initialization, the model changes shape to fit the object contour detected in the studied image. Using different views of the object, the previous approach is adapted to Circular Generalized Cylinders (cross-section radiu s variations are now permitted) . No assumption is made on the axis geometry nor on the way the radius varies . In order to be sufficiently adaptative to the large range of object shape belonging to this class, we propose using two independent B-splin e functions to model respectively axis and cross-section radii variations . These algorithms use the geometrical properties of the occluding contours given by the perspective projection of the objects. It i s the first attempt to solve this problem by taking into account this accurate projective model .Dans cet article, nous proposons une méthode de reconstruction des cylindres généralisés à section circulaire par modèle déformable. Tout d'abord, nous formulons l'hypothèse que les sections de l'objet sont de rayon constant. Nous parlons alors de Cylindres Généralisés Circulaires Uniformes (CGCU). Si le rayon est connu a priori, cette hypothèse permet de retrouver l'axe 3D de l'objet, paramétré par une fonction B-Spline, à partir d'une seule vue, sinon la reconstruction est faite à un facteur d'échelle près. Après une initilisation grossière, le modèle est déformé itérativement jusqu'à ce que sa forme devienne cohérente avec les contours extraits de l'image. Nous montrerons ensuite que l'exploitation de différentes vues d'un même objet permet d'adapter notre approche à la reconstruction de Cylindres Généralisés Circulaires (CGC), objets constitués de sections circulaires à rayon non-constant. Aucune hypothèse a priori n'est faite sur la géométrie de l'axe ou sur la façon dont varie le rayon des sections. Afin de pouvoir s'adapter au plus grand nombre d'objets appartenant à cette classe, deux fonctions B-Spline indépendantes sont utilisées pour paramétrer l'axe et la fonction de variation du rayon

Abordagem sócio-histórica sobre a evolução da assistência ao parto num município de médio porte de Minas Gerais (1960-2001)

Trata-se de caracterizar a evolução da série histórica quanto ao tipo de parto, normal, cesárea e fórceps, no período de 1960 a 2001, nas três maternidades mais antigas e conveniadas ao Sistema Único de Saúde (SUS) de Juiz de Fora. O método utilizado denomina-se história serial e permite a comparabilidade entre eventos históricos em determinado período de tempo. Foi identificado o aumento de incorporação tecnológica nesta trajetória e o crescente uso da cesariana até 1998, quando se identifica o impacto da portaria nº 2816, proposta pelo Ministério da Saúde, através de inversão dessa tendência com elevação do número de partos normais. A diferenciação constatada do tipo de parto de acordo com a categoria de internação aponta para uma discussão marcadamente política, que diz respeito às relações sociais em que se entrelaçam desigualdades de diversas ordens, entre elas as de gênero e de classe social. Conhecer as desigualdades e problematizar sua existência, traduzida em perfis de morbimortalidade e padrões desiguais de assistência, é precondição para obter o encaminhamento da solução