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Ra- Ra
- Radium is a radioactive element of the alkaline earth metals. White in colour and properties close to barium.
- RAC Horsepower Rating
- An obsolete engine horsepower rating system that was used as a designation as to the power of an engine.
- Racemic Mixture
- A mixture that has equal amounts of left- and right-handed enantiomers of a chiral molecule.
- Rack and Pinion
- A pair of gears which convert rotational motion into linear motion.
- Rack and Pinion Steering
- The most common steering system on passenger cars.
- Racking
- The distortion of a rectangular shape to a skewed parallelogram.
- rad
- An abbreviation of radian the SI unit of plane angle.
- Rad
- The rad is a unit used to measure absorbed radiation dose.
- Radar
- A method, system, or technique of using beamed, reflected, and timed radio waves for detecting, locating, or tracking objects.
- Radar Altimeter
- Airborne radar that measures the distance of the aircraft above the ground.
- Radar Beam
- The space in front of a radar antenna where a target can be effectively detected or tracked.
- Radar Detector
- A detector that, in its simplest form, only needs to be capable of producing an
output when RF energy is present at its input.
- Radar Mile
- Time interval, 12.36 microseconds, for RF energy to travel out from a radar to a target and back to the radar.
- Radial
- A direction perpendicular to the centreline of a shaft.
- Radial Engine
- An engine with a number of cylinder arranged in a circle around the crankshaft centre line. A design often used for aircraft engines.
- Radial Force Variation
- Radial Force Variation is a dynamic force generated at the wheel due to tyre non-uniformity.
- Radial Motion
- Motion along a radius, or a component in such a direction.
- Radial Vibration
- Shaft dynamic motion or casing vibration
which is in a direction perpendicular to the shaft centerline.
- Radian
- The radian is the plane angle between two radii of a circle which cut off on the circumference an arc equal in length to the radius.
- Radiancy
- The rate of radiant-energy emission for a unit area of a source in all the radial directions of the overspreading hemisphere.
- Radiant Heating
- Heating system in which warm or hot surfaces are used to radiate heat into the space to be conditioned.
- Radiated Noise
- The dissemination of sound energy as acoustic waves from a source (e.g. a vibrating panel, running engine etc.).
- Radiation
- This is the electromagnetic radiation emitted by a body as a function of its temperature.
- Radiation Absorbed Dose
- The rad is a unit used to measure absorbed radiation dose.
- Radiation Belt
- An envelope of charged particles trapped in the magnetic field of a spatial body.
- Radiation Field
- The electromagnetic field that radiates from an antenna and travels through space.
- Radiation Losses
- The losses that occur when magnetic lines of force about a conductor are projected into space as radiation and are not returned to the conductor as the cycle alternates.
- Radiation Pattern
- A plot of the radiated energy from an antenna.
- Radiation Resistance
- The resistance that if inserted in place of the antenna would consume the same amount of power as that radiated by the antenna.
- Radii
- Plural of radius.
- Radio
- Communication by electromagnetic waves, without a connecting wire.
- Radio Frequency
- Any frequency of electromagnetic energy capable of propagation into space.
- Radio Frequency Choke
- A choke coil with a high impedance at radio frequencies.
- Radio Frequency Interference
- This is unwanted Electromagnetic Emissions in the radio reception bands.
- Radio Horizon
- The boundary beyond the natural horizon in which radio waves cannot be propagated
over the earth′s surface.
- Radio Waves
- Electromagnetic radiation in the region of the spectrum smaller than about 3 x 108Hz and wavelengths greater than about 1 m.
- Radioactive Decay
- The spontaneous change of an atomic nucleus accompanied by the emission of alpha, beta particles or gamma radiation.
- Radiometer
- Instrument for detecting and measuring radiant energy.
- Radiosity Equation
- Used in the construction of realistically lit scenes in computer graphics.
- Radium
- A radioactive element of the alkaline earth metals. White in colour and properties close to barium.
- Radius
- In a circle, the radius is the distance from the centre of the circle to a point on the circle.
- Radius Gauge
- Any one of a number of small flat, standard-shaped metal leafs or blades used for checking the accuracy of regular concave and convex surfaces.
- Radix
- The number of distinct symbols used in a number system.
- Radix Point
- The generalization of decimal point to bases of numeration other than base 10.
- Radome
- Dielectric housing for an antenna.
- Radon
- A radioactive element and the heaviest of the nodle gases.
- Rainflow Analysis
- A method of representing a random signal by various numbers of sinusoids that would produce the same amount of fatigue damage.
- RAM
- Abbreviation of Random Access Memory, a data storage device for which the order of access to different locations does not affect the speed of access, except for bursts.
- Ram Air
- Air entering an air inlet as a result of the high-speed forward movement.
- Ramjet
- A jet engine with no mechanical compressor, consisting of specially shaped tubes or ducts open at both ends.
- Ramsay, William
- Discovered Argon, Krypton and Xenon and independently discovered Helium on earth.
- Random Access Memory
- A data storage device for which the order of access to different locations does not affect the speed of access, except for bursts.
- Random Copolymer
- A polymer in which two different mer units are randomly distributed along the molecular chain.
- Random Errors
- Errors that remain after blunders and systematic errors have been removed.
- Random Noise
- A noise signal, commonly used in measurements, which has constantly shifting amplitude, phase, and a uniform spectral distribution of energy.
- Random Process
- A random process is a collection of time-history records that can be described
by appropriate statistical parameters, such as averaged properties of these records
at a number of fixed times.
- Random Sampling
- A sampling method in which all elements in the population have an equal chance of being selected.
- Random Vibration
- A vibration whose instantaneous magnitude is not specified for any given instant of time.
- Range
- The maximum and minimum allowable full-scale signal.
- Rankine Temperature Scale
- An absolute scale of temperature based on degrees Farenheit.
- Rankine Vortex
- An idealized vortex in unbounded fluid with uniform vorticity inside a circular patch and zero vorticity outside.
- Rankine-Hugoniot Shock Relations
- These are solutions for a steady, normal shock in the frame moving with the shock front.
- Raoult′s Law
- The vapour pressure of a solvent in an ideal solution equals the mole fraction of the solvent times the vapour pressure of the pure solvent.
- Rapid Speech Transmission Index
- Abbreviated as RASTI and expressed in a decimal range of 0.2 for "bad" to 1.00 for "Excellent".
- Rarefaction
- A decrease in density and pressure in a medium, such as air, caused by the
passage of a sound wave.
- Rarefied Wave
- A longitudinal wave that has been expanded or rarefied as it moves away from the source.
- Rasp
- A sort of blowing noise emitted often from the exhaust pipes of internal combustion engines, usually, it is dominated by a mixture of 4E, 6E and 8E engine orders on 4 cylinder engines.
- RASTI
- Rapid Speech Transmission Index, expressed in a decimal range of 0.2 for "bad" to 1.00 for "Excellent".
- Ratchet
- A mechanism that only allows rotary motion in one direction.
- Rate Gyroscope
- A gyroscope used to detect and measure angular rates of change.
- Rate of Reaction
- The rate at which the concentration of a product increases or the concentration of
a reactant decreases with time.
- Rate of Strain Hardening
- Alternative name for Modulus of Strain Hardening.
- Ratio
- The quotient of two numbers.
- Ratio Detector
- A detector that uses a double-tuned transformer to convert the instantaneous
frequency variations of the FM input signal to instantaneous amplitude variations.
- Ratio of Specific Heats
- The ratio of molar heat capacity at constant pressure to molar heat capacity at constant volume.
- Rational B-Spline
- equation that permits the modeling of free-form curves between two endpoints as a function of a set of intermediate points whose values influence the shape of the curve.
- Rational Number
- Any number that can be expressed as the ratio of two integers.
- Rattle
- A sound such as that made when shaking a tin full of coins.
- Rawlplug
- The inventer of the original wall plug was John Rawlings and he marketed the Rawlplug.
- Ray
- At higher audio frequencies, sound may be considered to travel in straight lines, in a direction normal to the wave front.
- Rayl
- The Rayl is the SI derived unit of specific acoustic impedance.
- Rayleigh Distribution
- An example is the variation of wave height in a sea where swell is the main component.
- Rayleigh Waves
- These are also known as surface waves.
- Rayleigh′s Method
- A method used for calculating approximate natural frequencies for a vibrating
system assuming a deflected shape and balancing kinetic and strain energies.
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