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Weber (unit) From Wikipedia, the free encyclopedia Jump to: navigation, search In physics, the weber (symbol: Wb;  /ˈveɪbər/, /ˈwɛbər/, or /ˈwiːbər/) is the SI unit of magnetic flux. A flux density of one Wb/m2 (one weber per square meter) is one tesla. The weber is named for the German physicist Wilhelm Eduard Weber (1804–1891). [edit] Definition

The weber may be defined in terms of Faraday's law, which relates a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second will induce an electromotive force of one volt (produce an electric potential difference of one volt across two open-circuited terminals). Officially,

Weber (unit of magnetic flux) — The weber is the magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.[1]

Light-emitting diode

A light-emitting diode (LED) is a semiconductor light source.[3] LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962,[4] early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness. When a light-emitting diode is forward-biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. LEDs are often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern.[5] LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller size, and faster switching. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output. Light-emitting diodes are used in applications as diverse as aviation lighting, automotive lighting, advertising, general lighting, and traffic signals. LEDs have allowed new text, video displays, live video, and sensors to be developed, while their high switching rates are also useful in advanced communications technology. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players, and other domestic appliances.

Public switched telephone network

is the network of the world's public circuit-switched telephone networks. It is a worldwide network of telephone lines, fiberoptic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables connected by switching centers, which allows any telephone in the world to communicate with any other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones.

(PSTN)

Volt From Wikipedia, the free encyclopedia Jump to: navigation, search For other uses, see Volt (disambiguation). Josephson junction array chip developed by NIST as a standard volt The volt (symbol: V) is the SI derived unit for electric potential, electric potential difference, and electromotive force.[1] The volt is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery.

A single volt is defined as the difference in electric potential across a wire when an electric current of one ampere dissipates one watt of power.[

A particle carrying a charge of 1 coulomb and passing through a magnetic field of 1 tesla at a speed of 1 meter per second perpendicular to said field experiences a force of 1 newton, according to the Lorentz force law. As an SI derived unit, the tesla can also be expressed as (in SI base units).[3] Units used: A = ampere C = coulomb kg = kilogram m = meter N = newton s = second T = tesla V = volt Wb = weber [edit] Electric vs Magnetic Field

The difference between magnetic field strength (in tesla) vs electric field strength can be confusing.[citation needed] The difference is that a force of magnetic field on a charged particle is generally due to the charged particle's movement[4] while the force imparted by an electric field on a charged particle is not due to the charged particle's movement. This can be seen by looking at the units for each. Electric field is N/C, while magnetic field (in tesla) can be written as N/(C*m/s). The difference between the two is m/s, or velocity. This can further be seen by noting that whether a field is magnetic or electric is dependent on one's relativistic reference frame (that is: one's velocity relative to the field).[5][6] In ferromagnets the movement creating the magnetic field is the electron spin[7] (and to a lesser extent electron orbital angular momentum). In current carrying wire (electromagnets) the movement is due to electrons moving through the wire (whether the wire's straight or circular).

Newton (unit) From Wikipedia, the free encyclopedia Jump to: navigation, search Not to be confused with Newton scale, a rarely used non-SI temperature scale. Newton Unit system: SI derived unit Unit of... Force Symbol: N Named after: Isaac Newton In SI base units: 1 N = 1 kg·m/s2 The newton (symbol: N) is the SI derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion.

Metre From Wikipedia, the free encyclopedia   (Redirected from Meter) Jump to: navigation, search This article is about the unit of length. For other uses of "metre" or "meter", see meter (disambiguation). 1 metre = SI units 100 cm 1000 mm US customary / Imperial units 3.2808 ft 39.370 in The metre (meter in the US), symbol m, is the base unit of length in the International System of Units (SI). Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of metrology. Since 1983, it has been defined as "the length of the path travelled by light in vacuum during a time interval of 1 ⁄ 299,792,458 of a second.[1]

Le LTE (Long Term Evolution) est l'évolution la plus récente des normes de téléphonie mobile : GSM/EDGE, UMTS, CDMA2000 et TD-SCDMA.

La largeur de la bande de fréquences allouée à l’opérateur du réseau. Le débit utile est pratiquement proportionnel à cette largeur de bande (pouvant varier de 1,4 MHz à 20 MHz en LTE, 100 MHz en LTE Advanced).

Les types d’antennes utilisés coté terminal et coté réseau (antenne relais): le débit binaire maximal de 326,4 Mbit/s suppose des antennes MIMO 4X4 (quadruples) aux 2 extrémités de la liaison radio LTE (cas de figure peu réaliste pour un téléphone mobile ou un smartphone). La distance entre le terminal et la (ou les) antennes fixes (le débit est très inférieur en périphérie de cellules radio à cause des interférences avec les cellules adjacentes) et les conditions de réception radio (interférences, bruit, échos liés aux réflexions sur les immeubles, …). Le nombre d’utilisateurs actifs se partageant la bande passante au sein d’une cellule (surface radiante d'une antenne) LTE; plus il y a d’abonnés en communication moins chacun a de débit unitaire. La position fixe (statique) ou « en mouvement » du terminal de l’abonné ; le débit utile est réduit pour un terminal en mouvement. La capacité en débit et en nombre d'utilisateurs simultanés de la station de base (eNode B) et le débit du lien optique reliant cette station au cœur de réseau. Le type et la catégorie du terminal influent aussi sur le débit maximum possible ; par exemple un terminal LTE (en anglais : UE "User Equipment") de catégorie 1, ne supporte qu’un débit binaire de 10 Mbit/s alors qu’un autre de catégorie 3 supportera 100 Mbit/s (voir tableau ci-dessous). En contrepartie, plus la catégorie du terminal est élevée, plus le terminal sera complexe (coûteux) et moins son autonomie sera grande (à niveau technologique égal).

Unlicensed Mobile Access ou UMA est une technique qui a pour objectif de remplacer la couche physique des réseaux GSM et GPRS par des bandes de fréquences libres d'utilisation, celles des 2,4 GHz, ou l'on trouve Bluetooth et Wi-Fi entre autres. Elle a été développée par un consortium d'entreprises nommé UMAC comptant entre autres Alcatel, Cingular, Ericsson, Motorola, Nokia, Nortel, Siemens, T-Mobile et Kineto Wireless. L'objectif ultime de l'UMA est de faire converger les protocoles de communications des téléphones mobiles, fixe et informatiques.

Second From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about the unit of time. For other uses, see Second (disambiguation). A light flashing approximately once per second The second (SI unit symbol: s) is the International System of Units (SI) base unit of time[1] and also a unit of time in other systems (abbreviated s or sec[2]). Between 1000 (when al-Biruni used seconds) and 1960 the second was defined as 1/86,400 of a mean solar day (that definition still applies in some astronomical and legal contexts).[3][4] Between 1960 and 1967, it was defined in terms of the period of the Earth's orbit around the Sun,[5] but it is now defined more precisely in atomic terms. Seconds may be measured using mechanical, electric or atomic clocks.

Near field communication (NFC) is a set of standards for smartphones and similar devices to establish radio communication with each other by touching them together or bringing them into close proximity, usually no more than a few centimetres. Present and anticipated applications include contactless transactions, data exchange, and simplified setup of more complex communications such as Wi-Fi.[1] Communication is also possible between an NFC device and an unpowered NFC chip, called a "tag".[2]

NFC standards cover communications protocols and data exchange formats, and are based on existing radio-frequency identification (RFID) standards including ISO/IEC 14443 and FeliCa.[3] The standards include ISO/IEC 18092[4] and those defined by the NFC Forum, which was founded in 2004 by Nokia, Philips and Sony, and now has more than 160 members. The Forum also promotes NFC and certifies device compliance.[5

2160p is the shorthand name for Quad Full High Definition (QFHD), a video mode planned to appear in future HDTV products.[1] It has a resolution of 3840×2160 (8.3 megapixels in the 16:9 aspect ratio) and is one of the levels of 4K resolution.[2][3][4] The number 2160 stands for 2,160 lines of vertical display resolution, while the letter p stands for progressive scan or non-interlaced. In a progressive image, the lines of resolution of the image go from the top of the screen to the bottom.

Kilogram

The kilogram or kilogramme (SI symbol: kg), also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one liter of water. The avoirdupois (or international) pound, used in both the Imperial system and U.S. customary units, is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds.

Extensible Messaging and Presence Protocol

Extensible Messaging and Presence Protocol (qu'on peut traduire par « protocole extensible de présence et de messagerie »), souvent abrégé en XMPP, est un ensemble de protocoles standards ouverts de l’Internet Engineering Task Force (IETF) pour la messagerie instantanée, et plus généralement une architecture décentralisée d’échange de données. XMPP est également un système de collaboration en quasi-temps-réel et d’échange multimédia via le protocole Jingle, dont la Voix sur réseau IP (téléphonie sur Internet), la visioconférence et l’échange de fichiers sont des exemples d’applications.

Plug computer

A plug computer is a small form factor server for use in the home or office. Compared to their PC-based counterparts, plug computers are lower cost, consume less power, often do not have a video card, and are intended to be powered up at all times

Suitable for running a media server, back-up services, file sharing and remote access functions such devices can be used as a bridge between in home protocols such as Digital Living Network Alliance (DLNA) & Server Message Block (SMB) and cloud based services.

Coulomb

The coulomb (symbol: C) is the SI derived unit of electric charge. It is defined as the charge transported by a steady current of one ampere in one second: One coulomb is also the amount of excess charge on the positive side of a capacitance of one farad charged to a potential difference of one volt:

Les codes QR peuvent stocker jusqu'à 7 089 caractères numériques, 4 296 caractères alphanumériques

Capacité de stockage de données Caractères numériques: max 7 089 Caractères alphanumériques: max 4296 Binaires (8-bits): max 2953 octets

Xerox was founded in 1906 in Rochester as The Haloid Photographic Company,[8] which originally manufactured photographic paper and equipment. The company subsequently changed its name to Haloid Xerox in 1958 and then simply Xerox in 1961.[9] Xerography, a modern word meaning "dry writing" developed from two Greek roots, is the name of the process invented in 1938 and developed by the Haloid Company. The company came to prominence in 1959 with the introduction of the Xerox 914,[10] the first plain paper photocopier using the process of Electro-photography, (later changed to xerography) discovered by Chester Carlson, which he developed with John H. Dessauer.

Ampere

The ampere (SI unit symbol: A), often shortened to amp, is the SI unit of electric current[1] (quantity symbol: I,i)[2] and is one of the seven[3] SI base units. It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. Note that SI supports only the use of symbols and deprecates the use of any abbreviations for units.[4]

Nombre figuré

un nombre entier qui peut être représenté par un ensemble de points disposés de façon plus ou moins régulière et formant une figure géométrique.

On attribue parfois à Pythagore les premières études de nombres figurés[1] (nombres carrés). Diophante a résolu plusieurs problèmes les concernant. Pascal a écrit un traité sur le sujet.