Leaf segmentation and tracking using probabilistic parametric active contours

Active contours or snakes are widely used for segmentation and tracking. These techniques require the minimization of an energy function, which is generally a linear combination of a data fit term and a regularization term. This energy function can be adjusted to exploit the intrinsic object and image features. This can be done by changing the weighting parameters of the data fit and regularization term. There is, however, no rule to set these parameters optimally for a given application. This results in trial and error parameter estimation. In this paper, we propose a new active contour framework defined using probability theory. With this new technique there is no need for ad hoc parameter setting, since it uses probability distributions, which can be learned from a given training dataset

Cooperative AUV Navigation using a Single Maneuvering Surface Craft

In this paper we describe the experimental implementation of an online algorithm for cooperative localization of submerged autonomous underwater vehicles (AUVs) supported by an autonomous surface craft. Maintaining accurate localization of an AUV is difficult because electronic signals, such as GPS, are highly attenuated by water. The usual solution to the problem is to utilize expensive navigation sensors to slow the rate of dead-reckoning divergence. We investigate an alternative approach that utilizes the position information of a surface vehicle to bound the error and uncertainty of the on-board position estimates of a low-cost AUV. This approach uses the Woods Hole Oceanographic Institution (WHOI) acoustic modem to exchange vehicle location estimates while simultaneously estimating inter-vehicle range. A study of the system observability is presented so as to motivate both the choice of filtering approach and surface vehicle path planning. The first contribution of this paper is to the presentation of an experiment in which an extended Kalman filter (EKF) implementation of the concept ran online on-board an OceanServer Iver2 AUV while supported by an autonomous surface vehicle moving adaptively. The second contribution of this paper is to provide a quantitative performance comparison of three estimators: particle filtering (PF), non-linear least-squares optimization (NLS), and the EKF for a mission using three autonomous surface craft (two operating in the AUV role). Our results indicate that the PF and NLS estimators outperform the EKF, with NLS providing the best performance.United States. Office of Naval Research (Grant N000140711102)United States. Office of Naval Research. Multidisciplinary University Research InitiativeSingapore. National Research FoundationSingapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Monitorin

Relação econômica dos setores agrícolas do Estado do Mato Grosso com os demais setores pertencentes tanto ao Estado quanto ao restante do Brasil

Pesquisas atuais mostram que o setor agropecuário do Mato Grosso tem apresentado elevado desempenho nos últimos anos, ocupando posição de setor-chave no desenvolvimento econômico do Estado. Este trabalho visa mostrar de forma empírica a importância relativa do setor agrícola na estrutura produtiva do estado, utilizando-se de um modelo insumo-produto inter-regional construído para duas regiões, a saber, Mato Grosso e o restante do Brasil, referente ao ano de 1999. Procurou-se identificar os setores mais importantes das economias em questão, seus encadeamentos e a propagação de impactos entre as regiões, além de avaliar qual o impacto das exportações de soja mato-grossenses sobre a produção total das demais atividades. Confirmou-se a hipótese formulada a respeito da importância dos setores primários para a economia do estado, verificando-se que alguns setores agrícolas e outros diretamente relacionados a estes foram identificados como chaves ou pólos de desenvolvimento econômico na região em estudo. Em especial, merece destaque a cultura da soja no Mato Grosso, a qual apresenta um elevado efeito multiplicador do emprego e renda, destacando-se também como pólo de desenvolvimento econômico, além da importância que têm as suas exportações para a economia, atraindo ganhos cambiais ao país e impactando positivamente na produção de diversos outros setores. Finalmente, o trabalho desenvolve um ferramental útil para a formulação de políticas públicas para o Estado do Mato Grosso.<br>The purpose of this paper is to empirically show the relative importance of the agricultural sector in the productive framework of Mato Grosso State (Brazil), an inter-regional input-output model for two regions: Mato Grosso and the rest of Brazil for 1999. The idea was to identify the most important sectors of the economies in question, their connections and the propagation of impacts between regions, besides verifying the impact on the Mato Grosso soybean exports on the total production of other activities. The hypothesis on the importance of the primary sectors for the state economy has been confirmed, and some agricultural sectors and others directly linked thereto have been found to be key-sectors, or centers of economic growth in the region under study. Special mention should be given to soybean culture in Mato Grosso State, which shows a high employment and income multiplying effect on the economy, as well as being a center of economic growth and major exporter, attracting exchange gains to the country and positively impacting the production of other sectors. Finally, this paper provides a useful tool for drafting public policies for Mato Grosso State