Introduction: Localized Structures in Dissipative Media: From Optics to Plant Ecology

Localised structures in dissipative appears in various fields of natural science such as biology, chemistry, plant ecology, optics and laser physics. The proposed theme issue is to gather specialists from various fields of non-linear science toward a cross-fertilisation among active areas of research. This is a cross-disciplinary area of research dominated by the nonlinear optics due to potential applications for all-optical control of light, optical storage, and information processing. This theme issue contains contributions from 18 active groups involved in localized structures field and have all made significant contributions in recent years.Comment: 14 pages, 0 figure, submitted to Phi. Trasaction Royal Societ

Towards a Better Understanding of the Local Attractor in Particle Swarm Optimization: Speed and Solution Quality

Particle Swarm Optimization (PSO) is a popular nature-inspired meta-heuristic for solving continuous optimization problems. Although this technique is widely used, the understanding of the mechanisms that make swarms so successful is still limited. We present the first substantial experimental investigation of the influence of the local attractor on the quality of exploration and exploitation. We compare in detail classical PSO with the social-only variant where local attractors are ignored. To measure the exploration capabilities, we determine how frequently both variants return results in the neighborhood of the global optimum. We measure the quality of exploitation by considering only function values from runs that reached a search point sufficiently close to the global optimum and then comparing in how many digits such values still deviate from the global minimum value. It turns out that the local attractor significantly improves the exploration, but sometimes reduces the quality of the exploitation. As a compromise, we propose and evaluate a hybrid PSO which switches off its local attractors at a certain point in time. The effects mentioned can also be observed by measuring the potential of the swarm

Selective emitters design and optimization for thermophotovoltaic applications

Among several solutions to exploit solar energy, thermophotovoltaics (TPV) have been popularized and have known great breakthroughs during the past two decades. Yet, existing systems still have low efficiencies since the wavelength range of optimal photovoltaic (PV) conversion is very small compared to the emitter spectral range. Selective emitters are a very promising solution to this problem. We developed numerical tools to design and optimize such emitters. Some of the resulting structures composed of two or four layers of metals and semiconductors are presented in this paper. We also show that the usual PV devices efficiency limits (30% for crystalline silicon under solar radiation, according to Shockley-Queisser model) can be easily overcome thanks to these structures.Comment: 12 pages, 10 figure

Mesoscale simulations of surfactant dissolution and mesophase formation

The evolution of the contact zone between pure surfactant and solvent has been studied by mesoscale simulation. It is found that mesophase formation becomes diffusion controlled and follows the equilibrium phase diagram adiabatically almost as soon as individual mesophases can be identified, corresponding to times in real systems of order 10 microseconds.Comment: 4 pages, 2 figures, ReVTeX

Evolution of seaward-dipping reflectors at the onset of oceanic crust formation at volcanic passive margins: Insights from the South Atlantic

Seaward-dipping reflectors (SDRs) have long been recognized as a ubiquitous feature of volcanic passive margins, yet their evolution is much debated, and even the subject of the nature of the underlying crust is contentious. This uncertainty significantly restricts our understanding of continental breakup and ocean basin–forming processes. Using high-fidelity reflection data from offshore Argentina, we observe that the crust containing the SDRs has similarities to oceanic crust, albeit with a larger proportion of extrusive volcanics, variably interbedded with sediments. Densities derived from gravity modeling are compatible with the presence of magmatic crust beneath the outer SDRs. When these SDR packages are restored to synemplacement geometry we observe that they thicken into the basin axis with a nonfaulted, diffuse termination, which we associate with dikes intruding into initially horizontal volcanics. Our model for SDR formation invokes progressive rotation of these horizontal volcanics by subsidence driven by isostasy in the center of the evolving SDR depocenter as continental lithosphere is replaced by more dense oceanic lithosphere. The entire system records the migration of >10-km-thick new magmatic crust away from a rapidly subsiding but subaerial incipient spreading center at rates typical of slow oceanic spreading processes. Our model for new magmatic crust can explain SDR formation on magma-rich margins globally, but the estimated crustal thickness requires elevated mantle temperatures for their formation

The 2-10 keV unabsorbed luminosity function of AGN from the XMM-Newton LSS, CDFS and COSMOS surveys

The XMM-LSS, XMM-COSMOS, and XMM-CDFS surveys are complementary in terms of sky coverage and depth. Together, they form a clean sample with the least possible variance in instrument effective areas and PSF. Therefore this is one of the best samples available to determine the 2-10 keV luminosity function of AGN and its evolution. The samples and the relevant corrections for incompleteness are described. A total of 2887 AGN is used to build the LF in the luminosity interval 10^42-10^46 erg/s, and in the redshift interval 0.001-4. A new method to correct for absorption by considering the probability distribution for the column density conditioned on the hardness ratio is presented. The binned luminosity function and its evolution is determined with a variant of the Page-Carrera method, improved to include corrections for absorption and to account for the full probability distribution of photometric redshifts. Parametric models, namely a double power-law with LADE or LDDE evolution, are explored using Bayesian inference. We introduce the Watanabe-Akaike information criterion (WAIC) to compare the models and estimate their predictive power. Our data are best described by the LADE model, as hinted by the WAIC indicator. We also explore the 15-parameter extended LDDE model recently proposed by Ueda et al., and find that this extension is not supported by our data. The strength of our method is that it provides: un-absorbed non-parametric estimates; credible intervals for luminosity function parameters; model choice according to which one has more predictive power for future data.Comment: In press on A&A. The revised version corrects typos and the LF normalisations in tables 1,2,5 and figs.9-12, which were on an incorrect scale. Online material available at http://www.astro.lu.se/~piero/xlf/xlf-paper-tables2.tgz . The software is available on the author's website http://www.astro.lu.se/~piero/LFTools/index.html and on github: https://github.com/piero-ranalli/LFTool

A MOPSO Algorithm Based Exclusively on Pareto Dominance Concepts

Copyright © 2005 Springer Verlag. The final publication is available at link.springer.com3rd International Conference, EMO 2005, Guanajuato, Mexico, March 9-11, 2005. ProceedingsBook title: Evolutionary Multi-Criterion OptimizationIn extending the Particle Swarm Optimisation methodology to multi-objective problems it is unclear how global guides for particles should be selected. Previous work has relied on metric information in objective space, although this is at variance with the notion of dominance which is used to assess the quality of solutions. Here we propose methods based exclusively on dominance for selecting guides from a non-dominated archive. The methods are evaluated on standard test problems and we find that probabilistic selection favouring archival particles that dominate few particles provides good convergence towards and coverage of the Pareto front. We demonstrate that the scheme is robust to changes in objective scaling. We propose and evaluate methods for confining particles to the feasible region, and find that allowing particles to explore regions close to the constraint boundaries is important to ensure convergence to the Pareto front