Hybrid spiral-dynamic bacteria-chemotaxis algorithm with application to control two-wheeled machines

This paper presents the implementation of the hybrid spiral-dynamic bacteria-chemotaxis (HSDBC) approach to control two different configurations of a two-wheeled vehicle. The HSDBC is a combination of bacterial chemotaxis used in bacterial forging algorithm (BFA) and the spiral-dynamic algorithm (SDA). BFA provides a good exploration strategy due to the chemotaxis approach. However, it endures an oscillation problem near the end of the search process when using a large step size. Conversely; for a small step size, it affords better exploitation and accuracy with slower convergence. SDA provides better stability when approaching an optimum point and has faster convergence speed. This may cause the search agents to get trapped into local optima which results in low accurate solution. HSDBC exploits the chemotactic strategy of BFA and fitness accuracy and convergence speed of SDA so as to overcome the problems associated with both the SDA and BFA algorithms alone. The HSDBC thus developed is evaluated in optimizing the performance and energy consumption of two highly nonlinear platforms, namely single and double inverted pendulum-like vehicles with an extended rod. Comparative results with BFA and SDA show that the proposed algorithm is able to result in better performance of the highly nonlinear systems

Evolution of the pollution in the Piedras River Natural Site (Gulf of Cadiz, southern Spain) during the Holocene

© 2016, Springer-Verlag Berlin Heidelberg. The Piedras River marshland and El Rompido spit bar is a Natural Site in close proximity to two of the most polluted rivers in the world: the Tinto and Odiel Rivers. The aim of this study is to determine the degree of contamination of this Natural Site using a variety of pollution indices. At this site the Holocene infilling sequence is recorded and applied to a study of the pollution history and the possible impacts of human activity. The depositional history of the Piedras River estuary during the Holocene recorded open marine conditions at ca. 6500 calBP when sea-level was at its Holocene maximum. To study the pollution of the estuary during the Holocene, catchment background geochemistry was established using samples that pre-date human activity (agriculture and mining). Additionally, the sedimentary environment was reconstructed throughout the Holocene; comparison of pollution levels is interpreted to be more reliable if the sedimentary environment has remained similar throughout the depositional record. Results show that, despite being located nearby very polluted estuaries, the Piedras River marshland contains unpolluted sediments mainly because of the small catchment area relative to that of neighbouring more polluted rivers, and thus has not been affected by human activity such as mining