2,467 research outputs found
On distributed virtual network embedding with guarantees
To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst case efficiency of (?????) relative to the optimal solution, and that this bound is optimal, that is, no better approximation exists. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared with existing distributed VNET embedding solutions, and we show how byappropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.This work is supported in part by the National Science Foundation under grant CNS-0963974
On distributed virtual network embedding with guarantees
To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst-case efficiency of (1-(1/e)) relative to the optimal node embedding, or VNET embedding if virtual links are mapped to exactly one physical link. This bound is optimal, that is, no better polynomial-time approximation algorithm exists, unless P=NP. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared to existing distributed VNET embedding solutions, and we show how by appropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.CNS-0963974 - National Science Foundationhttp://www.cs.bu.edu/fac/matta/Papers/ToN-CAD.pdfAccepted manuscrip
On distributed virtual network embedding with guarantees
To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst case efficiency of (?????) relative to the optimal solution, and that this bound is optimal, that is, no better approximation exists. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared with existing distributed VNET embedding solutions, and we show how byappropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.This work is supported in part by the National Science Foundation under grant CNS-0963974
Les concours gĂ©nĂ©raux de lâenseignement officiel en Belgique (1840-1850). Histoire dâun instrument polyvalent de politique Ă©ducative
CrĂ©Ă©s en 1840 dans lâobjectif dâĂ©valuer le niveau des Ă©tudes dans les Ă©tablissements secondaires de lâĂtat, les concours gĂ©nĂ©raux ont jouĂ© un rĂŽle important dans le dĂ©veloppement de lâenseignement secondaire en Belgique, durant les premiĂšres dĂ©cennies de lâhistoire du pays. Outil de contrĂŽle des performances des Ă©tablissements secondaires qui recevaient des subsides de lâĂtat, le concours gĂ©nĂ©ral fournissait de surcroĂźt un cadre de fonctionnement commun aux diffĂ©rentes institutions, tout en stimulant lâĂ©mulation et la concurrence entre les Ă©tudiants et les professeurs. Par ailleurs, il produisait de nombreuses donnĂ©es quantitatives, qui Ă©taient largement diffusĂ©es. Lâhistoire de son fonctionnement montre quâil a Ă©tĂ© utilisĂ© comme un vĂ©ritable instrument polyvalent de politique Ă©ducativeCreated in 1840 with the objective of assessing teaching standards in secondary public schools, the âconcours gĂ©nĂ©rauxâ (open competitions) played an important role in the development of secondary education in Belgium during the first decades of the countryâs history. As a tool for monitoring the performance of State-funded secondary schools, the open competition provided the various educational institutions with a common operating framework, while fostering healthy competition between students and teachers. In addition, it produced a wealth of quantitative data which were widely disseminated. The history of how it was run shows that it was used as a truly multipurpose instrument of educational policy
« Prendre exemple du modÚle scolaire allemand ? » La réforme des humanités en Belgique à la fin du XIXe siÚcle dans son contexte européen (1870-1890)
Ă partir de lâexemple de la rĂ©forme de lâenseignement secondaire entreprise par le gouvernement belge dans les annĂ©es 1880, cet article a lâambition dâillustrer la façon dont les systĂšmes scolaires modernes dâEurope occidentale se sont construits sur la base dâun travail de comparaison entre modĂšles, dans un contexte de circulation internationale des informations et des savoirs. Lâarticle est divisĂ© en trois parties. La premiĂšre analyse lâorigine de la querelle des humanitĂ©s en la replaçant dans son contexte europĂ©en, en rappelant les raisons qui poussaient les diffĂ©rents pays europĂ©ens Ă aller chercher ailleurs des modĂšles Ă imiter. Ă travers lâĂ©tude de quelques exemples prĂ©cis, elle montre plus particuliĂšrement pourquoi plusieurs pays se sont intĂ©ressĂ©s Ă la rĂ©forme belge de 1881 et identifie les raisons de cette derniĂšre. Sâappuyant sur lâanalyse des dĂ©bats qui se sont tenus Ă propos des humanitĂ©s en Belgique, la seconde et la troisiĂšme parties Ă©tudient la maniĂšre dont les rĂ©formateurs belges se sont tournĂ©s vers des modĂšles scolaires Ă©trangers, en premier lieu le modĂšle allemand. Elles identifient les moyens et canaux de diffusion par lesquels lâinformation a circulĂ©, examinent les arguments invoquĂ©s en faveur de ce modĂšle pĂ©dagogique et montrent les limites rencontrĂ©es par son transfert sur le sol national.Taking the reform of secondary education undertaken by the Belgian government in the 1880s as an example, this article aims to show how modern school systems in Western Europe have been based on comparison between models in a context of the international dissemination of information and knowledge. The article is divided into three parts. The first analyses the origin of the âhumanities debateâ by placing it in its European context, reiterating the reasons that led different European countries to look elsewhere for models. In particular, through the study of a few specific examples, it shows why several countries took an interest in the Belgian reform of 1881 and identifies the reasons for this. Based on an analysis of debate on the subject of the humanities in Belgium, the second and third sections examine the way in which Belgian reformers turned to foreign school models, particularly the German model. They identify the means and channels through which information was disseminated, examine the arguments put forward in favour of this educational model and show the limitations which had to be overcome in transferring it to Belgium
Synthesis, Production, and Biotechnological Applications of Exopolysaccharides and Polyhydroxyalkanoates by Archaea
Extreme environments, generally characterized by atypical temperatures, pH, pressure, salinity, toxicity, and radiation levels, are inhabited by various microorganisms specifically adapted to these particular conditions, called extremophiles. Among these, the microorganisms belonging to the Archaea domain are of significant biotechnological importance as their biopolymers possess unique properties that offer insights into their biology and evolution. Particular attention has been devoted to two main types of biopolymers produced by such peculiar microorganisms, that is, the extracellular polysaccharides (EPSs), considered as a protection against desiccation and predation, and the endocellular polyhydroxyalkanoates (PHAs) that provide an internal reserve of carbon and energy. Here, we report the composition, biosynthesis, and production of EPSs and PHAs by different archaeal species
HumanitĂ©s et citoyennetĂ©Â : lâenseignement des lettres et des langues en France, en Suisse et en Belgique au XIXe siĂšcle
Dans un article intitulĂ© « Les humanitĂ©s au pĂ©ril dâun monde numĂ©rique » paru dans les pages du journal Le Figaro, lâhistorien et acadĂ©micien Marc Fumaroli, sâemployant Ă dĂ©fendre lâutilitĂ© et la place des langues classiques dans lâenseignement secondaire en France, rappelle que celles-ci permettent « le dĂ©veloppement durable et profond de ce qui fait notre humanitĂ©Â : la libertĂ© intĂ©rieure ». Cette intervention sâinscrit dans le cadre dâune controverse sur la fonction et lâavenir de ces disci..
Recent Advances in the Study of Marine Microbial Biofilm: From the Involvement of Quorum Sensing in Its Production up to Biotechnological Application of the Polysaccharide Fractions
The present review will explore the most relevant findings on marine microbial biofilm, with particular attention towards its polysaccharide fraction, namely exopolysaccharide (EPS). EPSs of microbial origin are ubiquitous in nature, possess unique properties and can be isolated from the bacteria living in a variety of habitats, including fresh water or marine environments, extreme environments or different soil ecosystems. These biopolymers have many application in the field of biotechnology. Several studies showed that the biofilm formation is closely related to quorum sensing (QS) systems, which is a mechanism relying on the production of small molecules defined as "autoinducers" that bacteria release in the surrounding environment where they accumulate. In this review, the involvement of microbial chemical communication, by QS mechanism, in the formation of marine biofilm will also be discussed
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