MonoSLAM: Real-time single camera SLAM

Published versio

Spread of yellow fever virus outbreak in Angola and the Democratic Republic of the Congo 2015-16: a modelling study.

BACKGROUND: Since late 2015, an epidemic of yellow fever has caused more than 7334 suspected cases in Angola and the Democratic Republic of the Congo, including 393 deaths. We sought to understand the spatial spread of this outbreak to optimise the use of the limited available vaccine stock. METHODS: We jointly analysed datasets describing the epidemic of yellow fever, vector suitability, human demography, and mobility in central Africa to understand and predict the spread of yellow fever virus. We used a standard logistic model to infer the district-specific yellow fever virus infection risk during the course of the epidemic in the region. FINDINGS: The early spread of yellow fever virus was characterised by fast exponential growth (doubling time of 5-7 days) and fast spatial expansion (49 districts reported cases after only 3 months) from Luanda, the capital of Angola. Early invasion was positively correlated with high population density (Pearson's r 0·52, 95% CI 0·34-0·66). The further away locations were from Luanda, the later the date of invasion (Pearson's r 0·60, 95% CI 0·52-0·66). In a Cox model, we noted that districts with higher population densities also had higher risks of sustained transmission (the hazard ratio for cases ceasing was 0·74, 95% CI 0·13-0·92 per log-unit increase in the population size of a district). A model that captured human mobility and vector suitability successfully discriminated districts with high risk of invasion from others with a lower risk (area under the curve 0·94, 95% CI 0·92-0·97). If at the start of the epidemic, sufficient vaccines had been available to target 50 out of 313 districts in the area, our model would have correctly identified 27 (84%) of the 32 districts that were eventually affected. INTERPRETATION: Our findings show the contributions of ecological and demographic factors to the ongoing spread of the yellow fever outbreak and provide estimates of the areas that could be prioritised for vaccination, although other constraints such as vaccine supply and delivery need to be accounted for before such insights can be translated into policy. FUNDING: Wellcome Trust

How to introduce a priori visual and behavioral knowledge for autonomous and mobile robots to operate in known environments

International audienc

Towards a method to compare and to evaluate fast pixel gathering mechanisms for real time robotic vision systems

International audienc

Recrystallization phenomena of solution grown paraffin dendrites

Paraffin crystals were grown from decane solutions using a micro-Bridgman set up for in-situ observation of the morphology at the growth front. It is shown that for large imposed velocities, dendrites are obtained. After dendritic growth, aging or recrystallization processes set in rather quickly, changing the crystal shapes considerably from the well-known dendritic shapes of melt grown dendrites. It is shown that several factors may cause these post-growth shape transitions: surface minimization, uptake and subsequent sweating of solvent material, and polymorphic phase conversion. It is shown that the first two recrystallization mechanisms are the most important for tricosane (n-C23H48) and pentacosane (n-C25H52) dendrites. Surface minimization by increasing the thickness of the crystals is particularly favorable. For dotriacontane (n-C32H66) dendrites, the recrystallization behavior appears to be less dramatic. It is shown that the uptake and sweating out of solvent material afterwards may lead to formation of holes within the dendrites

How to extract and to exploit vision data for autonomous mobile robots to operate in known environments

International audienc

Vision based control for Humanoid robots

Abstract — This paper presents a visual servoing scheme to control humanoid dynamic walk. Whereas most of the existing approaches follow a perception-decision-action scheme, we hereby introduce a method that uses the on-line information given by an on-board camera. This close looped approach allows the system to react to changes in its environment and adapt to modelling error. Our approach is based on a new reactive pattern generator which modifies footsteps, center of mass and center of pressure trajectories at the control level for the center of mass to track a reference velocity. In this workshop, we present three ways of servoing dynamical humanoïd walk: a naïve one that compute a reference velocity using a visual servoing control law, a second one that takes into account the sway motion induced by the walk and an on going work on vision predictive control that directly introduces the visual error in the cost function of the pattern generator. The two first approaches have been validated on the HRP-2 robot. These close loop approaches give a more accurate positioning than the one obtained when executing a planned trajectory especially when rotational motion are involved. I