Search methods' abilities for adaptation to various multidimensional tasks where optimisation parameters are hundreds, thousands and more, without retuning of algorithms' parameters seems to be a great challenge for modern computational intelligence. Many evolutionary, swarm and adaptive methods, which perform well on numerical tests with up to ten dimensions are suffering insuperable stagnation when applied to 100 and more dimensional tests. This article presents a comparison between particle swarm optimisation, differential evolution both with enhanced adaptivity and Free Search applied to 100 multidimensional heterogeneous real-value numerical tests. The aim is to extend the knowledge on how high dimensionality reflects on search space complexity, in particular to identify minimal time and minimal number of objective function evaluations required by used methods for reaching acceptable solution with non-zero probability on tasks with high dimensions' number. The achieved experimental results are summarised and analysed. Brief discussion on concepts, which support search methods effectiveness, concludes the article.

The ferrous-xylenol orange-gelatin (FXG) dosimeter is widely used for three-dimensional ionizing radiation field mapping through optical scanning. Upon irradiation, the ferrous iron (Fe(2+)) is oxidized to ferric iron (Fe(3+)), which forms an intensely coloured complex with xylenol orange (XO). XO also acts as a diffusion-limiting additive; however, its presence may cause rapid auto-oxidation of Fe(2+) during storage and low stability of the dose response. In this work, phenanthroline-type ligands were added to FXG system in a bid to bind the ferrous iron in a stable complex and minimize the rate of the auto-oxidation, whereas glyoxal was used as a chemical cross-linker, aiming to minimize the ferric iron diffusion. It was found that addition of either 1,10-phenanthroline or 5-nitro-1,10-phenanthroline can improve the auto-oxidation behaviour of the gels. However, the initial background absorbance was slightly increased, and the sensitivity of the dosimeters was decreased. Doping with glyoxal led to a moderate decrease of the diffusion only in those gels that also contained a phenanthroline-type ligand, and did not affect the initial dose response. Glyoxal also afforded an extended period of stable background absorbance level after an initial period of bleaching of the gel. Following re-irradiation, most glyoxal-containing dosimeters showed an excellent linearity of the dose response, albeit at a decreased sensitivity. We recommend further testing of FXG dosimeters, doped with phenanthroline-type ligands and glyoxal as a means for controlling the dose response and improving the long-term storage properties of the gels and the potential for dose fractionation.

No abstract

No abstract

No abstract