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Topologie de réseau. Un article de Wikipédia, l'encyclopédie libre. 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. Topologies de réseaux locaux classiques[modifier | modifier le code] Les architectures suivantes sont ou ont effectivement été utilisées dans des réseaux informatiques grand public ou d'entreprise.

Il existe 2 modes de propagation classant ces topologies : Mode de diffusion (par exemple topologie en bus ou en anneau) Ce mode de fonctionnement consiste à n'utiliser qu'un seul support de transmission. Mode point à point (par exemple topologie en étoile ou maillée) Weak-strong ties. Comment nous arrive l’information ? Haptique (toucher) Un article de Wikipédia, l'encyclopédie libre. 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.

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] Physical topologiesLogical topologies The shape of the cabling layout used to link devices is called the physical topology of the network. The logical topology in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. Diagram of different network topologies. The study of network topology recognizes eight basic topologies:[5] Point-to-pointBusStarRing or circularMeshTreeHybridDaisy chain Point-to-point[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: a 0-sphere is the pair of points at the ends of a (one-dimensional) line segment, a 1-sphere is the circle, which is the one-dimensional circumference of a (two-dimensional) disk in the plane, a 2-sphere is the two-dimensional surface of a (three-dimensional) ball in three-dimensional space. Spheres of dimension n > 2 are sometimes called hyperspheres, with 3-spheres sometimes known as glomes.

Description[edit] Euclidean coordinates in (n + 1)-space[edit] where c is a center point, and r is the radius. n-ball[edit] Specifically: . And , respectively. where. 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).

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. However, such examples may be hard to come by. The concept of a spherical design is due to Delsarte, Goethals, and Seidel (1977). For all positive integers d and t. Copula approach. Abstract. 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. 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 sans se préoccuper de ses lois marginales. Une copule est une fonction de répartition, notée , définie sur dont les marges sont uniformes sur . Si une des composantes est nulle, , et est d- croissante.

En dimension 2, pour tout u et v, et , pour tout u et v, et enfin, la propriété de 2-croissance se traduit par L'interprétation de cette notion de croissance se fait en notant que si admet pour fonction de répartition , la mesure étant nécessairement positive. Le théorème de Sklar dit que si est une copule, et si sont des fonctions de répartition (univariées), alors est une fonction de répartition de dimension , dont les marges sont précisément Et réciproquement, si est une fonction de répartition en dimension . . Combinatorial design. 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] An alternative expression for Cn is which is equivalent to the expression given above because . The Catalan numbers satisfy the recurrence relation moreover, This is because since choosing n numbers from a 2n set of numbers can be uniquely divided into 2 parts: choosing i numbers out of the first n numbers and then choosing n-i numbers from the remaining n numbers. They also satisfy: which can be a more efficient way to calculate them. Asymptotically, the Catalan numbers grow as in the sense that the quotient of the nth Catalan number and the expression on the right tends towards 1 as n → +∞. Where on are. 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. Pour tout point b ∈ B, on appelle fibre de X au-dessus du point b et l'on note X(b) le sous espace π−1(b) ⊂ X. On appelle section (continue) de π[1], ou de X, au-dessus de B, une application continue σ : B → X telle que π ∘ σ = IdB.

Conséquences de la définition : Chaque application . . 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). This file has annotations. Save To modify annotations, your browser needs to have the XMLHttpRequest object. [[MediaWiki talk:Gadget-ImageAnnotator.js|Adding image note]]$1 [[MediaWiki talk:Gadget-ImageAnnotator.js|Changing image note]]$1 [[MediaWiki talk:Gadget-ImageAnnotator.js|Removing image note]]$1. Graph database. Description[edit] Graph databases employ nodes, properties, and edges. Graph databases are based on graph theory, and employ nodes, edges, and properties.

Nodes represent entities such as people, businesses, accounts, or any other item to be tracked. They are roughly the equivalent of the record, relation, or row in a relational database, or the document in a document database.Edges, also termed graphs or relationships, are the lines that connect nodes to other nodes; they represent the relationship between them. In contrast, graph databases directly store the relationships between records. The true value of the graph approach becomes evident when one performs searches that are more than one level deep. Properties add another layer of abstraction to this structure that also improves many common queries. Relational databases are very well suited to flat data layouts, where relationships between data is one or two levels deep. Properties[edit] History[edit] List of graph databases[edit]

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.

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. 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. Aggregate activity is reflected in the underlying terrain: over time, the landscape warps as data is accrued, creating hills and valleys representing areas with high and low densities of data.

The interplay between the aggregate and the real-time recreates the kind of dynamics present within the physical world, where the city is both a vessel for and a product of human activity. Nodes are connected by narrative threads, based on themes emerging from the overlaid information. These pathways create dense meta-networks of meaning, blanketing the terrain and connecting disparate areas of the city.