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  2. Positron - Wikipedia

    en.wikipedia.org/wiki/Positron

    The positron or antielectron is the particle with an electric charge of +1e, a spin of 1/2 (the same as the electron), and the same mass as an electron.It is the antiparticle (antimatter counterpart) of the electron.

  3. Positronic brain - Wikipedia

    en.wikipedia.org/wiki/Positronic_brain

    A positronic brain is a fictional technological device, originally conceived by science fiction writer Isaac Asimov. [ 1 ] [ 2 ] It functions as a central processing unit (CPU) for robots , and, in some unspecified way, provides them with a form of consciousness recognizable to humans .

  4. Dimensionless numbers in fluid mechanics - Wikipedia

    en.wikipedia.org/wiki/Dimensionless_numbers_in...

    Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.

  5. Glossary of physics - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_physics

    Mach number A dimensionless quantity representing the ratio of the speed of an object moving through a fluid to the local speed of sound. Mach's principle The proposition that the existence of absolute rotation (the distinction of local inertial frames vs. rotating reference frames) is determined by the large-scale distribution of matter. machine

  6. List of dimensionless quantities - Wikipedia

    en.wikipedia.org/wiki/List_of_dimensionless...

    Chemical engineering, material science, mechanics (A scale to show the energy needed for detaching two solid particles) [13] [14] Cost of transport: COT = energy efficiency, economics (ratio of energy input to kinetic motion) Damping ratio

  7. Mach number - Wikipedia

    en.wikipedia.org/wiki/Mach_number

    At Mach 0.65, u is 65% of the speed of sound (subsonic), and, at Mach 1.35, u is 35% faster than the speed of sound (supersonic). An F/A-18 Hornet creating a vapor cone at transonic speed just before reaching the speed of sound. The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas.

  8. List of common physics notations - Wikipedia

    en.wikipedia.org/wiki/List_of_common_physics...

    Meaning SI unit of measure alpha: alpha particle: angular acceleration: radian per second squared (rad/s 2) fine-structure constant: unitless beta: velocity in terms of the speed of light c: unitless beta particle: gamma: Lorentz factor: unitless photon: gamma ray: shear strain: radian

  9. Positronium - Wikipedia

    en.wikipedia.org/wiki/Positronium

    It has a mean lifetime of 0.12 ns and decays preferentially into two gamma rays with energy of 511 keV each (in the center-of-mass frame). Para-positronium can decay into any even number of photons (2, 4, 6, ...), but the probability quickly decreases with the number: the branching ratio for decay into 4 photons is 1.439(2) × 10 −6. [1]