Abstract
This paper deals with the problem of active target tracking with obstacle avoidance for multi-robot systems. A nonlinear model predictive formation control is presented which uses potential functions as terms of the cost function. These terms penalize the proximity with mates and obstacles, splitting the problem of obstacle avoidance into two repulse functions. Experimental results with real robots are presented to demonstrate the performance of the approach. © IFAC.

Abstract
A multi-robot system is formed when a group of robots interact with the environment as a single system. This system can also be in formation in order to accomplish tasks rather difficult or impossible to achieve with a single robot. A nonlinear model predictive formation control (NMPFC) was used to converge a group of middle sized mobile soccer robots towards a desired target using the concept of active target tracking. This paper presents a novel approach on formation controller's weight tuning in order to minimize an objective function that reflects the controller's efficiency with respect to a given criteria. Furthermore, the results of simulation and experiment with real robots are presented and discussed.

Abstract
This paper aims to examine the process of reservoir sedimentation, namely to try to estimate the sediment volume deposited in the main Portuguese reservoirs. The changes in fluvial sediment transport induced by the construction of dams on the major Portuguese rivers are described. Based on the values of dead volumes, the current situation of 166 Portuguese reservoirs is analysed to obtain an order of magnitude of available sediments and pre-select reservoirs that could potentially be integrated into a project for the artificial sand nourishment of beaches. This work was carried out as a starting point in order to implement a national plan for the use of reservoir sediments as an "added value" to the economy, which is as yet generally unexploited. © 2014 Taylor & Francis Group, London.

Abstract

Abstract

Abstract
The aim of this article has been to classify swimmers based on kinematics, hydrodynamics, and anthropometrics. Sixty-seven young swimmers made a maximal 25 m front-crawl to measure with a speedometer the swimming velocity (v), speed-fluctuation (dv) and dv normalized to v (dv/v). Another two 25 m bouts with and without carrying a perturbation device were made to estimate active drag coefficient (C-Da). Trunk transverse surface area (S) was measured with photogrammetric technique on land and in the hydrodynamic position. Cluster 1 was related to swimmers with a high speed fluctuation (ie, dv and dv/v), cluster 2 with anthropometrics (ie, S) and cluster 3 with a high hydrodynamic profile (ie, C-Da). The variable that seems to discriminate better the clusters was the dv/v (F = 53.680; P < .001), followed by the dv (F = 28.506; P < .001), C-Da (F = 21.025; P < .001), S (F = 6.297; P < .01) and v (F = 5.375; P = .01). Stepwise discriminant analysis extracted 2 functions: Function 1 was mainly defined by dv/v and S (74.3% of variance), whereas function 2 was mainly defined by C-Da (25.7% of variance). It can be concluded that kinematics, hydrodynamics and anthropometrics are determinant domains in which to classify and characterize young swimmers' profiles.