Engineering and Information Technology Collected Works - Research Publications
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ItemTailored Shaping and Time Resampling Functions for Inversion Pulses at 7T(ISMRM, 2009)The RF transmit field is severely inhomogeneous at ultrahigh field, due to both RF penetration and RF coil design issues. Here we utilised a search algorithm to produce inversion pulses tailored to take account of the heterogeneity of the RF transmit field at 7T. We created a slice selective inversion pulse which worked well over the range of RF amplitudes, while maintaining an experimentally achievable pulse length at 7T. The pulses were based on the FOCI technique as well as time dilation of functions but the RF amplitude, frequency sweep and gradient functions were all optimised using a Genetic Algorithm.
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ItemNo Preview AvailableA Pyramidal Genetic Algorithm for Multiple-Choice Problems(Operational Research, 2001)
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ItemMimicking the Behaviour of Idiotypic AIS Robot Controllers Using Probabilistic Systems(International Institute of Informatics and Systemics- IIIS, 2009)Previous work has shown that robot navigation systems that employ an architecture based upon the idiotypic network theory of the immune system have an advantage over control techniques that rely on reinforcement learning only. This is thought to be a result of intelligent behaviour selection on the part of the idiotypic robot. In this paper an attempt is made to imitate idiotypic dynamics by creating controllers that use reinforcement with a number of different probabilistic schemes to select robot behaviour. The aims are to show that the idiotypic system is not merely performing some kind of periodic random behaviour selection, and to try to gain further insight into the processes that govern the idiotypic mechanism. Trials are carried out using simulated Pioneer robots that undertake navigation exercises. Results show that a scheme that boosts the probability of selecting highly-ranked alternative behaviours to 50% during stall conditions comes closest to achieving the properties of the idiotypic system, but remains unable to match it in terms of all round performance.
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ItemComparing Simulation Output Accuracy of Discrete Event and Agent Based Models: A Quantitative Approach(Society for Modeling & Simulation International, 2009)In our research we investigate the output accuracy of discrete event simulation models and agent based simulation models when studying human centric complex systems. In this paper we focus on human reactive behaviour as it is possible in both modelling approaches to implement human reactive behaviour in the model by using standard methods. As a case study we have chosen the retail sector, and here in particular the operations of the fitting room in the women wear department of a large UK department store. In our case study we looked at ways of determining the efficiency of implementing new management policies for the fitting room operation through modelling the reactive behaviour of staff and customers of the department. First, we have carried out a validation experiment in which we compared the results from our models to the performance of the real system. This experiment also allowed us to establish differences in output accuracy between the two modelling methods. In a second step a multi-scenario experiment was carried out to study the behaviour of the models when they are used for the purpose of operational improvement. Overall we have found that for our case study example both, discrete event simulation and agent based simulation have the same potential to support the investigation into the efficiency of implementing new management policies.
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ItemSTORM - A Novel Information Fusion and Cluster Interpretation Technique(SPRINGER-VERLAG BERLIN, 2009)