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Topologie de réseau. Un article de Wikipédia, l'encyclopédie libre.

topologie de réseau

Une topologie de réseau est en informatique une définition de l'architecture d'un réseau. Définissant les connexions entre ces postes et une hiérarchie éventuelle entre eux, elle peut avoir des implications sur la disposition géographique des différents postes informatiques du réseau. Ainsi Ethernet peut avoir comme support un simple plafond blanc visible de tous les postes (voir LiFi), alors que cela sera par construction impossible en token ring, bien que possible en token bus. Weak-strong ties. Comment nous arrive l’information ?

Liens faibles, liens forts.

comment nous arrive l’information ?

Cette semaine le dossier d'InternetActu vous propose de revenir sur ce que sont les liens faibles, ce concept forgé par le sociologue américain Mark Granovetter permettant de distinguer nos relations selon selon leur proximité, mais aussi selon leur diversité et la richesse de ce qu'elles nous apportent. A l'heure des réseaux sociaux numériques, la compréhension de la structuration et du rôle de nos relations est devenu d'autant plus importante qu'elles forgent de plus en plus toutes nos actions en ligne. Quelle est la force des liens faibles, quelles sont leurs limites ? C'est le dossier d'InternetActu. Haptique (toucher) Un article de Wikipédia, l'encyclopédie libre.

haptique (toucher)

L’haptique, du grec ἅπτομαι (haptomai) qui signifie « je touche », désigne la science du toucher, par analogie avec l'acoustique ou l'optique. Au sens strict, l’haptique englobe le toucher et les phénomènes kinesthésiques, c'est-à-dire la perception du corps dans l’environnement. Définition[modifier | modifier le code] Il est classique de différencier deux types de perception tactile manuelle (Hatwell, Streri, & Gentaz, 2000) : La perception cutanée et la perception haptique.

Les caractéristiques fonctionnelles du sens haptique manuel tout comme ses processus sous-jacents sont encore relativement mal connus pour plusieurs raisons : ces processus fonctionnent la plupart de temps de façon entièrement automatique car les informations proprioceptives sont généralement traitées inconsciemment ;les contractions musculaires génèrent des tensions dans l’ensemble des tissus dans lesquels sont situés les mécanorécepteurs cutanés et proprioceptifs.

Y. Network topology. A good example is a local area network (LAN): Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric shape that can be used to describe the physical topology of the network.

network topology

Conversely, mapping the data flow between the components determines the logical topology of the network. Topology[edit] Mesh. Variété systeme. Network topology. Combinatorics. N-sphere. In mathematics, the n-sphere is the generalization of the ordinary sphere to a n-dimensional space.


For any natural number n, an n-sphere of radius r is defined as the set of points in (n + 1)-dimensional Euclidean space which are at distance r from a central point, where the radius r may be any positive real number. Thus, the n-sphere centred at the origin is defined by: It is an n-dimensional manifold in Euclidean (n + 1)-space. In particular: Spherical design. A spherical design, part of combinatorial design theory in mathematics, is a finite set of N points on the d-dimensional unit hypersphere Sd such that the average value of any polynomial f of degree t or less on the set equals the average value of f on the whole sphere (that is, the integral of f over Sd divided by the area or measure of Sd).

spherical design

Such a set is often called a spherical t-design to indicate the value of t, which is a fundamental parameter. Spherical t-designs for different values of N and t can be found precomputed at Spherical designs can be of value in approximation theory, in statistics for experimental design (being usable to construct rotatable designs), in combinatorics, and in geometry. Copula approach. Abstract.

copula approach

Probability distributions of multivariate random variables are generally more complex compared to their univariate counterparts which is due to a possible nonlinear dependence between the random variables. One approach to this problem is the use of copulas, which have become popular over recent years, especially in fields like econometrics, finance, risk management, or insurance. Since this newly emerging field includes various practices, a controversial discussion, and vast field of literature, it is difficult to get an overview. The aim of this paper is therefore to provide an brief overview of copulas for application in meteorology and climate research. We examine the advantages and disadvantages compared to alternative approaches like e.g. mixture models, summarize the current problem of goodness-of-fit (GOF) tests for copulas, and discuss the connection with multivariate extremes.

Copule. Combinatorial design. Combinatorial design theory is the part of combinatorial mathematics that deals with the existence, construction and properties of systems of finite sets whose arrangements satisfy generalized concepts of balance and/or symmetry. Catalan number. In combinatorial mathematics, the Catalan numbers form a sequence of natural numbers that occur in various counting problems, often involving recursively-defined objects.

Catalan number

They are named after the Belgian mathematician Eugène Charles Catalan (1814–1894). The nth Catalan number is given directly in terms of binomial coefficients by The first Catalan numbers for n = 0, 1, 2, 3, … are Properties[edit] An alternative expression for Cn is which is equivalent to the expression given above because . Musical Nodes. Nankai combinatorics. Projet "sphère" Nebula. Revêtement. Un article de Wikipédia, l'encyclopédie libre. Revêtement du cercleX par une héliceY, les ensembles disjoints sont projetés homéomorphiquement sur Il s'agit d'un cas particulier de fibré, localement trivial, à fibre discrète.

Les revêtements jouent un rôle pour calculer le groupe fondamental et les groupes d'homotopie d'un espace. Un résultat de la théorie des revêtements est que si B est connexe par arcs et localement simplement connexe, il y a une correspondance bijective entre les revêtements connexes par arcs de B, à isomorphisme près, et les sous-groupes du groupe fondamental de B. Soient X et B deux espaces topologiques. Un espace X muni d'un homéomorphisme local π : X → B est dit étalé[2] au-dessus de B. Réseau valué. Couleurs. Cancel Edit Delete Preview revert Text of the note (may include Wiki markup) Could not save your note (edit conflict or other problem). Please copy the text in the edit box below and insert it manually by editing this page. Upon submitting the note will be published multi-licensed under the terms of the CC-BY-SA-3.0 license and of the GFDL, versions 1.2, 1.3, or any later version. See our terms of use for more details.

Add a note Draw a rectangle onto the image above (press the left mouse button, then drag and release). Save To modify annotations, your browser needs to have the XMLHttpRequest object. Graph database. Structure[edit] Graph databases are based on graph theory.

graph database

Graph databases employ nodes, properties, and edges. Graph database. A visual exploration on mapping complex networks. Data visualisation of a social network. For his final year project in information design, Felix Heinen created an amazing set of visualizations of different aspects of a social network.

Data visualisation of a social network

Two big (200 x 90 cm - 80 x 36 inches) posters show the variety and attitudes of members from an internet community like MySpace. On the first poster you can see the functions used, as well as additional information, such as age, educational background, family status, gender and how often they are logged in. In a glimpse, a view into the key demographic data available for every member's profile. The second poster gives you an overview of the geographic location of all members, based on a world map. The aim was to provide the management team with a visualization tool that would allow a better understanding of the community members, rather than a just a simple scan of their database.

Seattle Band Map. The Seattle Band Map is a project that showcases the northwest's vibrant music scene by documenting the thousands of bands who have performed throughout the decades; it also explores how these bands are interconnected through personal relationships and collaborations. This project aims to diversify the audience for and broaden the understanding of Seattle's music scene, while spotlighting unrepresented artists and musical genres. Seattle has long been known as a hotbed of musical creativity, from the thriving 60s and early 70s Soul and Funk scene, to the 90s grunge movement. Music continues to thrive in Seattle, and the authors see the Seattle Band Map as an opportunity to keep it in the forefront of people's minds.

The three bands with a highest number of connections are The Unnatural Helpers (43), Oldominion (38), and Your Heart Breaks (30), while the most popular in the map are Nirvana, The Unnatural Helpers, and Pearl Jam. Weeplaces. Invisible Cities. Invisible Cities maps information from one realm - online social networks - to another: an immersive, three dimensional space.

It displays geocoded activity from online services such as Twitter and Flickr, both in real-time and in aggregate. Real-time activity is represented as individual nodes that appear whenever a message or image is posted.