05-techno

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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. La lecture de la semaine, il s'agit - ça faisait longtemps -, de l'éditorial de Clive Thompson dans le magazine américain Wired. 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] 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] There are two basic categories of network topologies:[4] Mesh. Variété systeme. Network topology. Combinatorics. Combinatorics is a branch of mathematics concerning the study of finite or countable discrete structures.

combinatorics

Aspects of combinatorics include counting the structures of a given kind and size (enumerative combinatorics), deciding when certain criteria can be met, and constructing and analyzing objects meeting the criteria (as in combinatorial designs and matroid theory), finding "largest", "smallest", or "optimal" objects (extremal combinatorics and combinatorial optimization), and studying combinatorial structures arising in an algebraic context, or applying algebraic techniques to combinatorial problems (algebraic combinatorics). A mathematician who studies combinatorics is called a combinatorialist or a combinatorist. N-sphere. In mathematics, the n-sphere is the generalization of the ordinary sphere to a n-dimensional space.

n-sphere

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: a 0-sphere is the pair of points at the ends of a (one-dimensional) line segment,

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. The main problem is to find examples, given d and t, that are not too large.

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. Un article de Wikipédia, l'encyclopédie libre.

copule

Pour les articles homonymes, voir Copule. En statistiques, une copule est un objet mathématique venant de la théorie des probabilités. La copule permet de caractériser la dépendance entre les différentes coordonnées d'une variable aléatoire à valeurs dans. 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.

combinatorial design

These concepts are not made precise so that a wide range of objects can be thought of as being under the same umbrella. At times this might involve the numerical sizes of set intersections as in block designs, while at other times it could involve the spatial arrangement of entries in an array as in Sudoku grids. 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.

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] 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. 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. Graph database. Structure[edit] Graph databases are based on graph theory. Graph databases employ nodes, properties, and edges. Nodes represent entities such as people, businesses, accounts, or any other item you might want to keep track of.

Properties are pertinent information that relate to nodes. 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. 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. Seattle Band Map. Weeplaces. Invisible Cities.