Fast Convergence in Self-stabilizing Wireless Networks.

International audienceThe advent of large scale multi-hop wireless networks highlights problems of fault tolerance and scale in distributed systems, motivating designs that autonomously recover from transient faults and spontaneous reconfigurations. Self-stabilization provides an elegant solution for recovering from such faults. We present a complexity analysis for a family of self-stabilizing vertex coloring algorithms in the context of multi-hop wireless networks. Such "coloring" processes are used in several protocols for solving many different issues (clustering, synchronizing...). Overall, our results show that the actual stabilization time is much smaller than the upper bound provided by previous studies. Similarly, the height of the induced DAG is much lower than the linear dependency on the size of the color domain (that was previously announced). Finally, it appears that symmetry breaking tricks traditionally used to expedite stabilization are in fact harmful when used in networks that are not tightly synchronized

Using models for predicting recovery and assess tree species vulnerability in logged tropical forests

Formålet med denne masteroppgaven er å analysere hvilke faktorer som påvirker kredittrangeringer og hvordan rangeringene er for Afrika (Sør for Sahara) i forhold til andre regioner. Ifølge Haque, Mark og Mathieson (2000) var Afrika (Sør for Sahara) regionen med lavest kredittrangeringer i perioden 1980 til 1993. Oppgaven undersøker om dette fortsatt er tilfelle i perioden 1990 til 2010 og videre hvilke faktorer som kan ligge til grunn for denne ulikheten. For å finne ut av dette forsøker jeg først å identifisere korrelasjonen mellom økonomiske, politiske og institusjonelle faktorer. Deretter undersøkes det om Afrika (Sør for Sahara) skiller seg negativt ut i forhold til andre regioner. Utgangspunkt til flere av forklaringsvariablene er hentet fra Cantor og Packer (1996) og Haque et al. (2000). Datamaterialet er samlet inn fra Verdensbanken, Institutional Investor, Det internasjonale pengefondet (IMF), Federal Reserve, Freedom House Index og Quality of Government Institute. Analysen er gjort ved hjelp av en fast effekt modell, der estimeringen er ved MKM og «Least squares dummy variable» (LSDV). Resultatene viser at det er noen få økonomiske variabler som bestemmer nesten 90 prosent av kredittrangeringene. Videre har Afrika (Sør for Sahara) fått lavere rangeringer enn andre regioner i perioden 1990 til 2010. Resultatene indikerer også at vektingen av de ulike variablene endres mellom land og over tid. Beregningene er gjort ved hjelp av Stata 13.1 og Excel 2010.ECON390MASV-SØ

Features and Classification Schemes for View-Invariant and Real-Time Human Action Recognition

International audienceHuman Action recognition (HAR) is largely used in the field of Ambient Assisted Living (AAL) to create an interaction between humans and computers. In these applications , it cannot be asked to people to act non-naturally. The algorithm has to adapt and the interaction has to be as quick as possible to make this interaction fluent. To improve the existing algorithms with regards to that points, we propose a novel method based on skeleton information provided by RGB-D cameras. This approach is able to carry out early action recognition and is more robust to viewpoint variability. To reach this goal, a new descriptor called Body Directional Velocity is proposed and a real-time classification is performed. Experimental results on four benchmarks show that our method competes with various skeleton-based HAR algorithms. We also show the suitability of our method for early recognition of human actions

Characteristics of Positive Deviants in Western Chimpanzee Populations

With continued expansion of anthropogenically modified landscapes, the proximity between humans and wildlife is continuing to increase, frequently resulting in species decline. Occasionally however, species are able to persist and there is an increased interest in understanding such positive outliers and underlying mechanisms. Eventually, such insights can inform the design of effective conservation interventions by mimicking aspects of the social-ecological conditions found in areas of species persistence. Recently, frameworks have been developed to study the heterogeneity of species persistence across populations with a focus on positive outliers. Applications are still rare, and to our knowledge this is one of the first studies using this approach for terrestrial species conservation. We applied the positive deviance concept to the western chimpanzee, which occurs in a variety of social-ecological landscapes. It is now categorized as Critically Endangered due to hunting and habitat loss and resulting excessive decline of most of its populations. Here we are interested in understanding why some of the populations did not decline. We compiled a dataset of 17,109 chimpanzee survey transects (10,929 km) across nine countries and linked them to a range of social and ecological variables. We found that chimpanzees seemed to persist within three social-ecological configurations: first, rainforest habitats with a low degree of human impact, second, steep areas, and third, areas with high prevalence of hunting taboos and low degree of human impact. The largest chimpanzee populations are nowadays found under the third social-ecological configuration, even though most of these areas are not officially protected. Most commonly chimpanzee conservation has been based on exclusion of threats by creation of protected areas and law enforcement. Our findings suggest, however, that this approach should be complemented by an additional focus on threat reduction, i.e., interventions that directly target individual human behavior that is most threatening to chimpanzees, which is hunting. Although changing human behavior is difficult, stakeholder co-designed behavioral change approaches developed in the social sciences have been used successfully to promote pro-environmental behavior. With only a fraction of chimpanzees and primates living inside protected areas, such new approaches might be a way forward to improve primate conservation

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion