Francium is the heaviest alkali metal with no stable isotopes.
Discovered by Benoit Mandelbrot in 1964.
A ratio of two integers, or any number that can be expressed as such a ratio.
Fractional Distillation
A technique for separation of liquid mixtures by distillation that uses a tower attached to a flask containing the mixture to perform multiple distillations.
Fractional Part
For a real number r, its fractional part is defined as {r}=r-[r], where [r] is the floor value of r.
Fracture Stress
True stress generated in a material at fracture.
Fracture Testing
Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, or presence of defects.
Fracture Toughness
Critical value of the stress intensity factor for which crack extensions occurs.
The elements of cumulus and stratus clouds that appear in irregular fragments.
Frame Clamp
Uses corner blocks and long-threaded rods with sliding speed nuts to assemble square, rectangular and other oddly-shaped work pieces.
The process of synchronizing a facsimile receiver to a transmitter allowing proper picture reproduction.
The heaviest alkali metal with no stable isotopes.
Fraunhofer Diffraction
Fraunhofer diffraction describes the diffraction pattern of electro-magnetic radiation observed in the far field from a slit or series of slits (i.e. grating).
Free Atmosphere
The layer of the atmosphere above the boundary layer that is not affected by surface friction.
Free Bend Test
A method of testing weld specimens without the use of a guide.
Free Charges
Those electrons that can be moved by an externally applied voltage.
Free Cut
An additional cut with a machine tool with no advancement of depth.
Free Electron
Electron which is not attached to a nucleus.
Free Energy
A thermodynamic quantity that is a function of both the internal energy and entropy of a system.
Free Energy Change
The amount of free energy released (negative ΔG) or absorbed (positive ΔG) in a reaction at constant temperature and pressure.
Free Ferrite
Ferrite that is structurally separate and distinct.
Free Field
Field in a homogeneous, isotropic medium free from boundaries.
Free Fit
A class of fit intended for use where accuracy is not essential or where large temperature variations are likely to be encountered, or both conditions.
Free Gyroscope
A gyro not provided with an erection system, free to move about its axes.
Free Machining Steels
A group of steels designated as being easy to machine. Contain one or more additives, which enhance machining characteristics and lower machining cost.
Free Piston Engine
A linear internal combustion engine, in which the piston motion is not controlled by a crankshaft but determined by the interaction of forces from the combustion chamber gases, a rebound device and a load device.
Free Progressive Wave
Wave in a medium free from boundary effects.
Free Radical
A molecule with an odd number of electrons.
Free Sound Field
A sound field in which the effects of obstacles or boundaries on sound propagated in that field are negligible.
Free Space Loss
The loss of energy of radio waves caused by the spreading of the wavefront as it travels from the transmitter.
Free Vibration
Free vibration occurs without forcing, the vibration of a string after it has been plucked.
Free-Layer Damper
A treatment to control the vibration of a structural by bonding a layer of damping material to the structure′s surface.
To change from a liquid to a solid by cooling.
Freezing Point
The temperature at which the vapour pressure of a liquid is equal to the vapor pressure of the corresponding solid form.
Freezing Point Depression
The freezing point of a solution is always lower than the freezing point of the pure solvent.
Frenkel Defect
In an ionic solid, a cation-vacancy and cation-interstitial pair.
Alternative name for Carbon Tetrachloride.
Alternative name for Trichlorofluoromethane.
Alternative name for Tetrafluoromethane.
The rate of repetition of periodic motion measured in hertz (cycles per second).
Frequency Compensation Network
Circuit modification used to improve or broaden the linearity of its frequency response.
Frequency Counter
Counts digital pulses over a defined gate time.
Frequency Cutoff
The frequency at which the filter circuit changes from an action of rejecting the unwanted frequencies to an action of passing the desired frequencies.
Frequency Deviation
The amount the frequency varies from the carrier frequency.
Frequency Distance Separation
The combined isolation effect resulting from tuning two or more electronic devices, one of which is an emitter, at different frequencies and separating them physically.
Frequency Distribution
An organized display of a set of data that shows how often each different piece of data occurs.
Frequency Diversity
Transmitting and receiving of radio waves on two different frequencies simultaneously.
Frequency Hopping
A spread spectrum communications technique in which a wireless transmitter and receiver are programmed to hop from frequency to frequency simultaneously.
Frequency Leakage
In a Fourier Transform the signal is assumed to be periodic. If a pure sine wave does not repeat exactly within the time window, it is truncated. this truncation will lead to the frequency domain resultant being smeared (leakage) and not a single frequency.
Frequency Meter
A meter used to measure the frequency of an ac signal.
Frequency Modulation
The information signal is used to vary the carrier signal frequency.
Frequency Multipliers
Special RF power amplifiers that multiply the input frequency.
Frequency Range
The bandwidth of a filter or signal.
Frequency Response
An important parameter in specifying the performance of measuring or recording devices.
Frequency Response Function
The output to input relationship of a structure. Mathematically, it is the Fourier transform of the output divided by the Fourier transform of the input. It is also the transfer function measured along the j axis in the s-plane.
Frequency Response Matrix
For an N degree of freedom system, it is an N x N symmetrical matrix whose elements are the frequency response functions between the various points on the structure.
Frequency Shift
A sudden change in the frequency of a signal.
Frequency Shift Keying
The form of frequency modulation in which the modulating wave shifts the output frequency between predetermined values, and the output wave has no phase discontinuity.
Frequency Spectrum
The entire range of frequencies contained in a pulse or signal.
Frequency Stability
The ability of an oscillator to accurately maintain its operating frequency.
Frequency Synthesis
A process that uses hetrodyning and frequency selection to produce a signal.
Frequency Synthesizer
A frequency source of high accuracy.
Frequency Tolerance
The extent to which a characteristic frequency of an emission, for example, the carrier frequency itself or a particular frequency in the sideband, may be permitted to depart from a specified reference frequency within the assigned band.
Frequency View
An approach taken by mathematicians and scientists to determine the chances of an event happening by repeating the experiment many times and using the results to calculate the probability.
Fresh Air Intake
An opening through which outside air is drawn into the building.
Fresh Air Make Up
The mixing of fresh air into the recirculated air to keep the air fresh and breathable.
Fresnel Reflection
Reflection occurring at the planar junction of two materials having different indices of refraction.
A fine handsaw that is used to cut intricate designs.
Action that results in surface damage, especially in a corrosive environment, when there is relative motion between solid surfaces in contact under pressure.
Fretting Corrosion
Can take place when two metals are held in contact and subjected to repeated small sliding, relative motions.
A speech sound produced by frication, that is, by forcing air through a constriction in the vocal tract. Examples are "s" and "f".
The resistance to motion which is called into play when it is attempted to slide one surface over another, with which it is in contact.
Friction Clutch
A shaft coupling used where it is necessary to provide a connection that can be readily engaged or disengaged while one of the shafts is in motion.
Friction Gear
Device for the transmission of rotational power that relies on friction between the drive devices to transmit the forces.
Friction Gouges
A series of relatively short surface scratches variable in form and severity.
Friction Horse Power
The power consumed within the engine from friction between its parts.
Friction Shock Absorber
A shock absorber in which friction discs are inserted at the point where the two arms are joined, now no longer used in car suspensions.
Friction Torque
Torque caused by the frictional force that occurs when two objects in contact move.
The middle part of an entablature, often decorated with spiral scrolls.
Frisch, Otto
Advanced the theory that uranium, when bombarded by neutrons, breaks into smaller atoms.
Front to Back Ratio
The ratio of the energy radiated in the principal direction compared to the energy radiated in the opposite direction.
Front Wheel Drive
A vehicle designed to have power applied to the front wheels.
Frontal Area
Generally taken to be the area of the front view silhouette of a vehicle, though sometimes simplified as width multiplied by height.
Froude Number
A dimensionless number used in the study of fluid flow problems with models.
For a given solid figure, a related figure formed by two parallel planes meeting the given solid. For a cone or pyramid, a frustum is determined by the plane of the base and a plane parallel to the base.