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In this paper, the applicability of heuristic methods for an automated and reactive optimization of network infrastructures in highly-dynamic communication networks is studied. With an increasing amount of (mobile) participants and at the same time significantly growing quality requirements in communication networks over the past years, optimization of communication infrastructures will become an inevitable challenge in providing a reliable and high-quality communication service. Mostly, changes in highly-dynamic networks, which may be planned or unplanned, happen swiftly, such that it is not possible to apply manual optimization. Thus, an automated and reactive optimization becomes necessary to address this problem. Two major issues arise from the optimization of highly-dynamic communication networks. First, the complexity of problems, which is either implied by the complex optimization problem or the number of different possibly concurrent goals subject to optimization. Second, the highly-dynamic optimization search space, where network topologies may change rapidly introducing severe challenges for the optimization process. Here, different evolutionary and greedy optimization heuristics for the optimal selection of monitors in communication networks are studied and compared. Monitor selection is a well-known, important, and complex (NP-hard) optimization problem, serving as a current and actual use case for the general concept of highly-dynamic communication network optimization. As the results show, two of three methods reliably provide solutions of sufficiently high quality in reasonable time, enabling the applicability of heuristic methods of optimization in highly-dynamic communication networks. Results of the experiments are obtained using state-of-the-art statistical methods for evaluation of (evolutionary) search heuristics on a set of 39 real-world and synthetic benchmark problem instances.

The formula in the article for Model Agreement Index is incorrect. It has an extra N in the denominator that should not be there. The correct formulae for the Model Agreement Index is shown below. The analyses presented in the paper were conducted with the correct formula.

Have you ever experienced rain where it rained so hard or for so long that you feared you may soon be up to your eyeballs in water? Sadly, many people in the world have witnessed this firsthand, and this is likely to increase due to climate change unless we do something to prepare for flooding disasters. Some areas are more prone to floods than others, and the people living there are more at risk. Scientists have developed computer models in an effort to map flood prone areas. Decision makers use the results from those computer models to plan for future flooding events to limit destruction and save lives. But are they accurate enough considering human lives may depend on them? To answer this question we compared the results from six computer models which simulate flood risk in Africa. The models agreed in less than 40% of the cases about where exactly it would flood and how much damage there might be.

Background: Climate-driven environmental change in the North Pacific has been well documented, with marked effects on the habitat and foraging behavior of marine predators. However, the mechanistic linkages connecting climate-driven changes in behavior to predator populations are not well understood. We evaluated the effects of climate-driven environmental variability on the reproductive success and foraging behavior of Laysan and Black-footed albatrosses breeding in the Northwest Hawaiian Islands during both brooding and incubating periods. We assessed foraging trip metrics and reproductive success using data collected from 2002-2012 and 1981-2012, respectively, relative to variability in the location of the Transition Zone Chlorophyll Front (TZCF, an important foraging region for albatrosses), sea surface temperature (SST), Multivariate ENSO Index (MEI), and the North Pacific Gyre Oscillation index (NPGO). Results: Foraging behavior for both species was influenced by climatic and oceanographic factors. While brooding chicks, both species traveled farther during La Nina conditions, when NPGO was high and when the TZCF was farther north (farther from the breeding site). Models showed that reproductive success for both species showed similar trends, correlating negatively with conditions observed during La Nina events (low MEI, high SST, high NPGO, increased distance to TZCF), but models for Laysan albatrosses explained a higher proportion of the variation. Spatial correlations of Laysan albatross reproductive success and SST anomalies highlighted strong negative correlations (> 95 %) between habitat use and SST. Higher trip distance and/or duration during brooding were associated with decreased reproductive success. Conclusions: Our findings suggest that during adverse conditions (La Nina conditions, high NPGO, northward displacement of the TZCF), both Laysan and Black-footed albatrosses took longer foraging trips and/ or traveled farther during brooding, likely resulting in a lower reproductive success due to increased energetic costs. Our results link climate variability with both albatross behavior and reproductive success, information that is critical for predicting how albatross populations will respond to future climate change.

Past tracking studies of marine animals have primarily targeted adults, biasing our understanding of at-sea habitat use toward older life stages. Anthropogenic threats persist throughout the at-sea ranges of all life stages and it is therefore of interest to population ecologists and managers alike to understand spatiotemporal distributions and possible niche differentiation between age-classes. In albatrosses, particularly little is known about the juvenile life stage when fledglings depart the colonies and venture to sea with no prior experience or parental guidance. We compared the dispersal of 22 fledgling Black-footed Albatross Phoebastria nigripes between 2006 and 2008 using satellite telemetry and 16 adults between 2008 and 2009 using geolocaters from Midway Atoll National Wildlife Refuge, Northwest Hawaiian Islands. Following tag deployment, all fledglings spent several days within the calm atoll waters, then travelled northward until reaching 750-900km from the colony. At this point, fledgling distributions approached the productive North Pacific Transition Zone (NPTZ). Rather than reaching the high chlorophyll a densities on the leading edge of this zone, however, fledglings remained in areas of low productivity in the subtropical gyre. In contrast, adult albatrosses from the same breeding colony did not utilize the NPTZ at this time of year but rather ranged throughout the highly productive northern periphery of the Pacific Ocean Basin among the shelf regions off Japan and the Aleutian Islands. The dichotomy in habitat use between fledglings and adults from Midway Atoll results in complete spatial segregation between age-classes and suggests ontogenetic niche separation in this species. This research fills a large knowledge gap in at-sea habitat use during a little known yet critical life stage of albatrosses, and contributes to a more comprehensive understanding of differential mortality pressure between age-classes and overall conservation status for the vulnerable Black-footed Albatross.

National audience

Todays unused biomass potentials may play an important role in future energy market. Due to an in­creasing demand of wood for material use and simultaneous expansion of energetic biomass utilization a competitive situation is unavoidable. An exploitation of waste materials and by­products of biological origin lead to a potential enhancement of biofuels and so a less expensive energy source may be opened up. The often referred disadvanta­geous thermo­chemical characteristics of alternative biomasses can be counteracted by addition of biomass with de­fined properties. This study is primarily concerned with preparation, characterization and classification of blended fu­els based on miscanthus and wood according to current fuel standards. Therefore biomass blends with systematically varied ratios are pelletized. The aim of pelletizing is to ensure accurate blending ratios and the production of a mar­ketable fuel. Using the flat die mechanical durabilities in the range of 93.5 wt.­% to 96.9 wt.­% were reached. Further improvement can be achieved by optimization of the process parameters. However, the mechanical durability in­creases with higher wood proportions caused by higher lignin contents. Proximate analysis and ash behavior of the pelletized blends are also presented. Thereby the ash content increases with higher miscanthus content in the blend. In contrast the volatile content decreases with higher miscanthus admixing. The sintering temperature of all wood­miscanthus blends lies between 700 °C and 750 °C. Blends with a miscanthus rate of 40 ­ 80 wt.­% show similar be­havior with a lower ash softening temperature compared to the unblended fuels. Only blends with a miscanthus con­tent of 20 wt.­% reach an softening temperature above 1050 °C ­ a property being dominantly influenced by wood., Proceedings of the 19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany, pp. 1980-1984

The focus of interest is on current perspectives, characteristics and competitiveness of the production, of blended biomass pellets. Particularly with regard to blends of agricultural energy crops and biogenous residues, the production of blended pellets shows a high potential as for example wood pellets for domestic combustion systems. The analysis carried out is based on a mean annual pellet production in Germany of around 20.000 tons and a total investment for a pellet production plant of around 4 million €. The competitiveness of blended biomass pellets is compared to actual commercial data of wood pellets as reference. Using agricultural biomass or biogenous residues as feedstock for production of blended pellets additional metering and mixing units and feeding systems are required. Due to this fact, the total investment is slightly higher in comparison to a common wood pellets production plant. As a result, manufacturing of blended biomass pellets reduces the production costs due to usually lower fuel input prices of biomass residues or energy crops. The present investigation reveals the important production factors, which may lead to a blended fuel pellet production on a competitive basis., Proceedings of the 19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany, pp. 1871-1877