In this paper, a trajectory tracking control for a nonholonomic mobile robot subjected to kinematic disturbances is proposed. A variable structure controller based on the sliding mode theory is designed, and applied to compensate these disturbances. To minimize the problems found in practical implementations of the classical variable structure controllers, and eliminate the chattering phenomenon, is used a neural compensator, which is nonlinear and continuous, in lieu of the discontinuous portion of the control signals present in classical forms. This proposed neural compensator is designed by the Gaussian radial basis function neural networks modeling technique and it does not require the time-consuming training process. Stability analysis is guaranteed based on the Lyapunov method. Simulation results are provided to show the effectiveness of the proposed approach.

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Abstract. In this paper, we propose a new methodology where complex natural language requests from a user to a relational database are broken into simple sentences through an Evolutionary Computing method. Such basic sentences are then translated by another module, which tries to perform a pattern matching between a model filled by local grammars and the basic sentences generated by the Evolutionary Programming algorithm. The output of this system is a set of SQL queries to a specific database. The main feature is its combinatorial approach, as an alternative for the use of methods that employs many linguistic levels (lexicon, syntax rules and semantics) and intermediate languages. The proposed methodology is applied to Brazilian Portuguese. In our test bed, a 92% translation correctness was achieved.

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Background Evidence of time trends in early childhood caries in low‐ and middle‐income countries in the second decade of the year 2000 is scarce. Aim To assess the trends in early childhood caries prevalence and severity in 2‐ to 5‐year‐old children over a 22‐year period (1993‐2015) in Goiânia, Midwest Brazil. Additionally, we aimed to investigate the changes regarding affected dental arches and teeth. Design A time‐lag analysis of trends in caries was carried out using data from three cross‐sectional studies based on the World Health Organization diagnostic criteria, in 1993 (N = 1362), 2001 (N = 1620), and 2015 (N = 548). Results Caries prevalence declined from 45.1% in 1993 to 29.0% in 2015. Prevalence of severe caries (dmft ≥ 6) in 2015 was nearly one‐third of that found in 1993, and the SiC index (mean dmft of the highest tertile) decreased from 4.55 to 3.32. Decline was higher in the 1993‐2001 than in the 2001‐2015 time‐lag. Posterior teeth and second molars had the greatest reductions. High proportions of untreated caries were found in all ages and survey years. Conclusion There were significant changes in caries prevalence and severity, marked by a striking decline from 1993 to 2001, followed by a less prominent decrease up to 2015, and high levels of untreated caries.