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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.
- 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.
- 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 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.
- 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.
- Radii
- Plural of radius.
- 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 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.
- 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 Point
- The generalization of decimal point to bases of numeration other than base 10.
- 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.
- 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.
- 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.
- 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 of Reaction
- The rate at which the concentration of a product increases or the concentration of
a reactant decreases with time.
- Ratio
- The quotient of two numbers.
- 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.
- 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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