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delta ray (physics) -- Britannica Online Encyclopedia - 0 views

www.britannica.com/...delta-ray volt science delta gamma ray electron physics
shared by Jac Londe on 23 Apr 12 - No Cached
  • Jac Londe on 23 Apr 12
     
    delta ray,  in physics, any atomic electron that has acquired sufficient energy by recoiling from a charged particle passing through matter to force, in turn, some dozens of electrons out of other atoms along its own trajectory. The charged particle giving rise to delta rays generally is relatively large, such as an alpha particle (composed of two protons and two neutrons), but may also be a high-speed electron. This particle, as it slows down in matter, forces thousands of electrons out of atoms by ionization, producing a wake of electrons and positive ions (electron-deficient atoms) that can be detected. The detached electrons are usually of such low energy that they cannot produce further ionization. But periodically, a relatively large amount of energy is transferred to an electron by a nearly head-on collision along the path of the primary ionizing particle. These are the energetic electrons that cause secondary ionization and are referred to as delta rays. On a developed photographic emulsion, in which strongly ionizing particles have left dense tracks, delta rays appear as thin wavy spurs or branches. The term delta ray, first used by the British physicist J.J. Thomson, is sometimes extended to any recoil particle that causes secondary ionization. LINKS Related Articles
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Rayon gamma - Wikipédia - 0 views

fr.wikipedia.org/Rayon_gamma gamma electron volt energie science onde ondes
shared by Jac Londe on 23 Apr 12 - No Cached
  • Rayon gamma est le nom donné au rayonnement électromagnétique produit, par la désexcitation d'un noyau atomique résultant d'une désintégration, ou par des phénomènes subatomiques comme l'annihilation d'une paire électron-positon. Ils ont une énergie qui varie dans une plage allant de la centaine à plusieurs centaines de gigaélectron-volts. Leurs longueurs d'onde est inférieure à 5×10-12 m. La découverte des rayons gamma est due à Paul Villard, chimiste français (1860-1934).

Le journal des ondes - 0 views

started by Jac Londe on 23 Apr 12 no follow-up yet
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Électron-volt - Wikipédia - 0 views

fr.wikipedia.org/...Giga%C3%A9lectron-volt electron volt energie science onde ondes
shared by Jac Londe on 23 Apr 12 - No Cached
  • En physique, l'électron-volt[1] (symbole eV) est une unité de mesure d'énergie. Sa valeur est définie comme étant l'énergie cinétique d'un électron accéléré depuis le repos par une différence de potentiel d'un volt. Un électron-volt est donc égal à environ 1,60217653×10-19 joule (J)[2]. C'est une unité hors système international (SI) dont la valeur est obtenue expérimentalement. On utilise l'électron-volt notamment en physique des particules pour exprimer les niveaux d'énergie rencontrés dans les accélérateurs de particules et la fusion thermonucléaire, en physique des semi-conducteurs pour exprimer le gap de ceux-ci ou en physique des plasmas : Multiples usuels  1 keV = 103 eV 1 MeV = 106 eV 1 GeV = 109 eV 1 TeV = 1012 eV Dans certains documents relativement anciens, on peut voir la notation "BeV" pour « billion electronvolt » : elle est équivalente au GeV (gigaélectron-volt).
  • D'après la relation E = m·c2 de la relativité restreinte, on déduit : Par exemple, la masse de l'électron est de 511 keV/c2, celle du proton de 938 MeV/c2 et celle du neutron est de 940 MeV/c2. Dans le système d'unités naturelles souvent utilisé par les physiciens des particules, dans lequel on pose c=1, on omet d'écrire le « .../c2 ».
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Carrier Sense Multiple Access with Collision Avoidance - 0 views

fr.wikipedia.org/802.15.4 norme wifi bluetooth 802.15 ondes waves carrier
shared by Jac Londe on 04 Mar 12 - No Cached
  • Jac Londe on 04 Mar 12
     
    CSDMA/CA
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Erg (unité) - Wikipédia - 0 views

fr.wikipedia.org/...Erg_(unit%C3%A9) erg système international unités wikipédia unit unité wiki
shared by Jac Londe on 02 Dec 11 - No Cached
  • L'erg (du grec εργον ergon travail; occupation; ouvrage) est une unité de mesure de l'énergie, du travail dans le système CGS. Un erg vaut 1 g⋅cm2⋅s-2, c'est-à-dire 10-7 J.
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JavaScript has problems. Do we need Dart to solve them? - 0 views

arstechnica.com/...an-googles-dart-solve-them.ars javascript dart google
shared by Jac Londe on 13 Oct 11 - No Cached
  • Google hopes to upset JavaScript's dominance by introducing a new language, Dart. Dart is designed to be simpler, more familiar, and faster than JavaScript, and Google one day wants to see it everywhere: in the browser, on the server, and maybe even on the smartphone.
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USB Pinout - Connector Wiring for USB A, USB B, and Mini USB Interfaces - 0 views

www.connections-usa.com/usb_pinout.html USB connector wiring interfaces arduino objoom
shared by Jac Londe on 27 Aug 11 - No Cached
  • USB Pinout - Connector Wiring for USB A, USB B, and Mini USB InterfacesUSB (Universal Serial Bus) is an interface designed to connect peripherals such as mice, keyboards, scanners, digital cameras, printers, hard disks, and networking components to PC.
  • USB pinout signals USB is a serial bus. It uses 4 shielded wires: two for power (+5v & GND) and two for differential data signals (labelled as D+ and D- in pinout). NRZI (Non Return to Zero Invert) encoding scheme used to send data with a sync field to synchronise the host and receiver clocks. In USB data cable Data+ and Data- signals are transmitted on a twisted pair. No termination needed. Half-duplex differential signaling helps to combat the effects of electromagnetic noise on longer lines. Contrary to popular belief, D+ and D- operate together; they are not separate simplex connections.
  • USB transfer modes Univeral serial bus supports Control, Interrupt, Bulk and Isochronous transfer modes.USB transfer rates: Low Speed, Full Speed, Hi-speed. USB supports three data rates: Low Speed (1.5 Mbit per second) that is mostly used for Human Input Devices (HID) such as keyboards, mice, joysticks and often the buttons on higher speed devices such as printers or scanners; Full Speed (12 Mbit per second) which is widely supported by USB hubs, assumes that devices divide the USB bandwidth between them in a first-come first-serve basis - it"s easy to run out of bandwidth with several devices; Hi-Speed (480 Mbit per second) was added in USB 2.0 specification. Not all USB 2.0 devices are Hi-Speed. A USB device must indicate its speed by pulling either the D+ or D- line high to 3.3 volts. These pull up resistors at the device end will also be used by the host or hub to detect the presence of a device connected to its port. Without a pull up resistor, USB assumes there is nothing connected to the bus. In order to help user to identify maximum speed of device, USB device often specify it's speed on it's cover with one of USB special marketing logos.
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  • USB powered devices The USB connector provides a single 5 volt wire from which connected USB devices may power themselves. A given segment of the bus is specified to deliver up to 500 mA. This is often enough to power several devices
  • USB cable shielding:Shield should only be connected to Ground at the host. No device should connect Shield to Ground.USB cable wires: Shielded:Data: 28 AWG twistedPower: 28 AWG - 20 AWG non-twisted Non-shielded:Data: 28 AWG non-twistedPower: 28 AWG - 20 AWG non-twisted  
  • USB voltage: Supplied voltage by a host or a powered hub ports is between 4.75 V and 5.25 V. Maximum voltage drop for bus-powered hubs is 0.35 V from it's host or hub to the hubs output port. All hubs and functions must be able to send configuration data at 4.4 V, but only low-power functions need to be working at this voltage. Normal operational voltage for functions is minimum 4.75 V.
  • USB power usage:Bus-powered hubs: Draw Max 100 mA at power up and 500 mA normally.Self-powered hubs: Draw Max 100 mA, must supply 500 mA to each port.Low power, bus-powered functions: Draw Max 100 mA.High power, bus-powered functions: Self-powered hubs: Draw Max 100 mA, must supply 500 mA to each port.Self-powered functions: Draw Max 100 mA.Suspended device: Max 0.5 mA
  • Pin Name Cable color Description 1 VCC Red +5 VDC 2 D- White Data - 3 D+ Green Data + 4 GND Black Ground 4 pin USB A or USB B plug�connector at the peripherals 4 pin USB A / USB B / mini-USB jack�connector at the controller Pin x of mini-USB connector usually not used or connected to GND.
  • The Universal Serial Bus is host controlled and there can be only one host per bus. An USB system consist of a host controller and multiple devices connected in a tree-like fashion using special hub devices. Hubs may be cascaded, up to 5 levels.
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Android Voice Recorder - 0 views

market.android.com/details android recorder market free app
shared by Jac Londe on 03 Aug 11 - No Cached
  • Jac Londe on 03 Aug 11
     
    Thousands of users downloaded this little voice recorder.
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