Triggered memory-based swarm optimization in dynamic environments

This is a post-print version of this article - Copyright @ 2007 Springer-VerlagIn recent years, there has been an increasing concern from the evolutionary computation community on dynamic optimization problems since many real-world optimization problems are time-varying. In this paper, a triggered memory scheme is introduced into the particle swarm optimization to deal with dynamic environments. The triggered memory scheme enhances traditional memory scheme with a triggered memory generator. Experimental study over a benchmark dynamic problem shows that the triggered memory-based particle swarm optimization algorithm has stronger robustness and adaptability than traditional particle swarm optimization algorithms, both with and without traditional memory scheme, for dynamic optimization problems

On the development of flow-ecology relationships for streams in coastal watersheds of southern California

2014 Fall.Includes bibliographical references.Linking hydrologic alteration to the biotic responses of streams is essential for understanding and managing the effects of land use changes and other human influences on aquatic ecosystems. This study develops flow-ecology relationships for wadeable streams in coastal watersheds of southern California to understand the ecological effects of urbanization and other sources of hydromodification. Streams in this region are predominately flashy, seasonally intermittent, and fine grained; hence, the inherently harsh disturbance regime is a major determinant of biotic composition. I match biological and geomorphic data with proximate U. S. Geological Survey streamflow gages to examine flow-ecology relationships between benthic macroinvertebrates and the hydrologic and hydraulic regimes of 32 biomonitoring sites spanning a gradient of watershed urbanization. Associations between landscape, streamflow, and biotic metrics indicate that flow permanence and urbanization are overarching and interacting influences on benthic macroinvertebrate assemblages in this region. In particular, flow intermittency and flashiness are significant predictors of both taxonomic and traits-based measures of biotic composition. Urban land cover and road density are significantly correlated with higher flow flashiness and decreasing measures of biotic integrity. Hydraulic metrics describing streambed mobility are strongly positively associated with measures of biotic integrity as a result of high intercorrelation with flow permanence. Thus, it appears that benthic macroinvertebrate assemblages are fundamentally influenced by flow intermittency and urban-induced flashiness in this region. Use of daily discharge data analyzed 3 yrs prior to biological sampling events appears to result in little to no loss of resolution in flow-ecology relationships compared to sub-daily (15-min) and long-term (decadal) flow records. Results also underscore the utility of traits-based analyses and stratification of sites by flow permanence and dominant substrate in revealing mechanistic relationships between flow and biotic metrics. By using gaged sites to identify the flow metrics best describe biological variation, this study provides insight into which elements of the flow regime are most important to model accurately in future efforts to develop a regional hydrologic foundation that will allow the inclusion of ungaged biomonitoring sites in refining flow-ecology relationships

Topology of the Spin-polarized Charge Density in bcc and fcc Iron

We investigate the topology of the spin-polarized charge density in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, in some cases the spin-polarized densities are characterized by unique topologies; for example, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical of any known for non-magnetic materials. In these cases, the two spin-densities are correlated: the spin-minority electrons have directional bond paths with deep minima in the minority density, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of two distinct spin topologies suggests that a well-known magnetic phase transition in iron can be fruitfully reexamined in light of these topological changes. We show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetry-breaking paradigm and proceeds without a topological transformation, while the latter also involves a topological catastrophe.Comment: 5 pages, 3 figures. Phys. Rev. Lett. (in press

Electronic Selection Rules Controlling Dislocation Glide in bcc Metals

The validity of the structure-property relationships governing the deformation behavior of bcc metals was brought into question with recent {\it ab initio} density functional studies of isolated screw dislocations in Mo and Ta. These existing relationships were semiclassical in nature, having grown from atomistic investigations of the deformation properties of the groups V and VI transition metals. We find that the correct form for these structure-property relationships is fully quantum mechanical, involving the coupling of electronic states with the strain field at the core of long $a/2$ screw dislocations.Comment: 4 pages, 2 figure

Adaptive intelligence applied to numerical optimisation

The article presents modification strategies theoretical comparison and experimental results achieved by adaptive heuristics applied to numerical optimisation of several non-constraint test functions. The aims of the study are to identify and compare how adaptive search heuristics behave within heterogeneous search space without retuning of the search parameters. The achieved results are summarised and analysed, which could be used for comparison to other methods and further investigation

Revealing common artifacts due to ferromagnetic inclusions in highly-oriented pyrolytic graphite

We report on an extensive investigation to figure out the origin of room-temperature ferromagnetism that is commonly observed by SQUID magnetometry in highly-oriented pyrolytic graphite (HOPG). Electron backscattering and X-ray microanalysis revealed the presence of micron-size magnetic clusters (predominantly Fe) that are rare and would be difficult to detect without careful search in a scanning electron microscope in the backscattering mode. The clusters pin to crystal boundaries and their quantities match the amplitude of typical ferromagnetic signals. No ferromagnetic response is detected in samples where we could not find such magnetic inclusions. Our experiments show that the frequently reported ferromagnetism in pristine HOPG is most likely to originate from contamination with Fe-rich inclusions introduced presumably during crystal growth.Comment: 8 pages, 7 figure

Extraction of mycelial protein: some specific comparisons

Extraction of mycelial protei