perform a required function. Notes: 1. After failure the item has a fault. 2. “Failure” is an event, as distin guished from “fault”, which is a state. 3. This concept as defined does not apply to items consisting of soft- ware only. 2. A departure of program operation from program requirements.
failure analysis The logical, systematic examination of an item to identify and analyze the probability, cau ses and consequences of potential faults.
failure category See error category.
failure cause The circumstances during design, ma nufacture or use which have led to a failure.
failure criteria Rules for failure relevancy such as specified limits for the acceptability of an item.
failure distribution The manner in which failures occur as a function of time; generally expressed in the form of a curve with the abscissa being time.
failure intensity acceleration factor In a time in terval of a given duration, whose beginning is speci fied by a fixed age of a repaired item, the ratio of the number of failures obtained under two different sets of stress conditions.
failure mode The effect by which a failure is obser ved. Note: For example, an open or short-circuit con dition or a gain change.
failure mode and effects analysis A qualitative method of system reliability analysis which involves the study of the failure modes which can exist in any item of the system and the determination of the effects of each failure mode on other items of the system, and on the operational functions of the system.
failure modes, effects and criticality analysis, FMECA Failure modes and effects analysis with a
failure rate 158 fat oil
consideration of the probability of occurrence and for a ranking of the seriousness of the effects.
failure rate 1. The ratio of the number of failures to a
given unit of measure; for example, failures per unit of time, failures per number of transactions, failures per number of computer runs. 2. In reliability mode- ling, the ratio of the number of failures of a given ca tegory or severity to a given period of time; for ex- ample, failures per second of execution time, failures per month. Synonymous with failure ratio.
failure rate acceleration factor The ratio of the accelerated testing failure rate to the failue rate under stated reference test conditions. Both failure rates re fer to the same time period in the life of the tested items.
failure ratio See failure rate.
failure report A report describing the failure of a pie ce of equipment or item, its cause, and the corrective action taken to prevent the recurrence of the failure (SAMA).
failure state The condition of an item characterized by the lack of ability to perform required functions.
fallback procedure A procedure to circumvent all equipment faults. The fallback may give degraded ser vice and may include switching to an alternate com puter or to different output devices.
falling-ball viscometer A type of viscometer. High precision ball falls through liquid contained in high- precision glass tube. Densities of ball and liquid are known. Time for ball to fall length of tube is measu red. Viscosity is proportional to difference in density and time.
falling film plasma reactor In the falling-film plas ma reactor (Bethlehem Steel), an arc is struck bet- ween a tungsten cathode and a water-cooled copper cylinder that serves as the anode. A rotating jet of gas (argon or nitrogen) stabilizes the arc. Solid reactant particles are injected into the stabizing gas and are then centrifuged onto the inner walls of the anode and form a molten film. The falling film plasma reactor has been used to produce iron and steel alloys, ferro vanadium, molybdenum, and ferro-chromium.
falling piston viscometer A type of viscometer. Sample solenoid valve opens to raise the piston. Pis- ton travels up in 3 seconds. Sample solenoid valve closes when piston reaches top of travel. Time for pis- ton to fall is a measure of viscosity.
fall stage-discharge relation, slope stage- discharge relation A family of curves that expres ses the relationship between water surface slope, stage and discharge in an open channel in a given reach sub ject to variable backwater.
fall time The time required for the output voltage of a digital circuit to change from a logical high level (1) to a logical low level (0).
fall velocity, settling velocity The limiting veloci ty reached asymptotially by a particle falling under the action of gravity in a still water.
false add To form a partial sum, that is to add without carries.
false alarm An alarm signal transmitted in the absen se of an alarm condition.
false set Rapid hardening of freshly mixed cement, mortar or concrete with a minimum evolution of heat; plasticity can be restored by mixing without adding more water.
false statement A statement having a value of zero in Boolean algebra.
family In mathematics, a set of functions curves etc., which can be generated by varying one or more of the parameters of a general form.
FAMOS Abbreviation for floating-gate avalanchein jection MOSFET. A type of MOSFET capable of long-term memory storage; used in EPROMs.
fan dryer, fan drying section (for pulp, paper or board) A drying section or part of a drying section in which the web is dried in direct contact with hot air, superheated steam or other hot gas which is circulated with aids of fans.
fan-in ratio (fluid power systems) Number of control inputs available on a device.
fan-out ratio (fluid power systems) Number of identical devices which can be controlled by the out- put of a device.
fan performance curves The graphical presenta tion of total pressure, static pressure, power input, mechanical and static efficiency as ordinates and the range of volumes as abscissa, all at constant speed and air density.
fan pump (on a paper machine) A pump in which the white water is mixed with the stock before the mixture is fed to the head box of the paper machine.
farad, F The derived SI unit of capacitance: the capa citance of a capacitor between the plates where there is a potential difference of 1 volt when charged by a quantity of electricity of 1 coulomb. This is a very lar ge unit; microfarads (10–6) and picofarads (10–12) are
used most commonly.
faraday A unit equal to the number of coulombs (96,500) required for an electrochemical reaction in volving one electrochemical equivalent. In an electro lytic process, 1 gram equivalent weight of matter is chemically altered at each electrode for 1 faraday of electricity passed through the electrolyte.
Faraday cage Wire or metal screan connected to ground, that completely encloses sensitive equipment to prevent any interference from stray electromagnetic radiation.
Faraday’s law 1. The mass of a substance liberated
in an electrolytic cell is proportionate to the quantity of electricity passing through the cell. 2. When the same quantity of electricity is passed through different electrolytic cells, the masses of the substances libera ted are proportionate to their chemical equivalent.
3. Also called the law of electromagnetic induction.
When a magnetic field cuts a conductor, or when a conductor cuts a magnetic field, an electric current will flow through the conductor if a closed path is pro vided over which the current can circulate.
faradmeter An instrument for measuring electric ca pacitance.
fast-Fourier transform, FFT A type of frequency analysis on data that can be done by computer using special software, or by an array processor, or by a spe cial purpose, hardware device.
fast-release relay A high-speed relay designed spe cifically for short-release but not short operate time.
fast select (data communication) An option of a virtual call facility that allows the inclusion of data in call-set-up and call-clearing packets.
fast storage High speed input or access storage usu ally in a hierarchy of storage units and related to these relatively. An imprecise term.
fatal error An error that renders further execution if any to produce meaningless results.
fatigue The weakening of a material under repeated stress.
fat oil The absorbent oil enriched by gasoline fractions in an absorption plant. After absorbing the gasolin fractions, the gasoline is removed by distillation, lea ving the oil “lean” and ready for further use to absorb more gasoline fractions from the natural gas stream.
fault 159 feedback loop fault 1. An accidental condition that causes a functio
nal unit to fail to perform its required function. 2. A manifestation of an error in software. A fault if en- countered, may cause a failure. Synonymous with bug.
fault analysis The logical, systematic examination of an item to identify and analyze the probability, causes and consequences of potential faults.
fault bus (fault ground bus) A bus connected to normally grounded parts of electric equipment, so in sulated that all the ground current passes to ground th rough fault detecting means.
fault bus protection (relaying) A method of ground fault protection which makes use of a fault bus.
fault category See error category.
fault coverage The proportion of faults of an item that can be recognized under given conditions.
fault diagnosis Actions taken for fault recognition, fault localization and cause identification.
fault diagnosis time The time during which fault diagnosis is performed.
fault insertion See fault seeding.
fault isolation 1. The process of identifying and lo
cating failures in a unit under test. 2. Determining the cause of a test failure, typically by identifying a defec tive component or process failure on a board.
fault localization Action taken to identify the faulty sub-item or sub-items at the appropriate indenture le vel. (Fault location deprecated in this sense).
fault mode One of the possible states of a faulty item, for a given required function. Note: The use of the term “failure mode” in this sense is now deprecated.
fault recognition The event when a fault is recogni zed.
fault seeding The process of intentionally adding a known number of faults to those already in a compu ter program for the purpose of estimating the number of indigenous faults in the program. Synonymous with bug seeding.
fault signature 1. Data representing the outputs of a
known good unit and used to compare against outputs of a unit under test. 2. A particular output response or set of responses generated when a test program is exe cuted on a device containing a fault.
fault threshold A prescribed limit to the number of faults in a specified category which, if exceeded, re- quires appropriate action.
fault tolerance That property of a system which per mits it to carry out its assigned function even in the presence of one or more faults in the hardware or soft- ware components.
fault-tolerant circuits Circuits that are designed so that they could continue to function properly even though part of the circuit failed.
fault trace A record of faults, obtained by a monitor, that reflects the sequence of states that immediately preceded the occurrence of the faults.
fault tree A logic diagram showing which fault modes of subitems or external events, or combinations there- of, result in a given fault mode of the item.
fault tree analysis, FTA An analysis to determine which fault modes of the subitems or external events, or combinations thereof, may result in a stated fault mode of the item, presented in the form of a fault tree.
Faure plate A storage-battery plate, consisting of a conductive lead grid filled with active paste material.
FAX See facsimile.
FBFO Final Bunker Fuel Oil.
fc Footcandle.
FCC See Federal Communication Commission.
FCI Flux Changes per inch.
FCMM Flux changes per mm.
FCT See flat crush resistance.
FDM See frequency division multiplex.
FD or FDX See full-duplex.
FE See format effector.
Fe Chemical symbol for iron.
FEANI European Federation of National Engineering Associations.
feasibility study A study in which a projection of how a proposed computer system might work is made to provide the basis for a decision to develop and im plement the system.
featherweight board, featherweight paper, bul king board, bulking paper Paper or board with a particularly low density.
FEB See functional electronic block.
FEC Forward Error Correction. A system of data transmission in which redundant bits generated at the transmitter are used at the receiving terminal to detect, locate, and correct any transmission errors before de- livery to the data sink.
Federal Communication Commission, FCC Es tablished in 1934 to regulate interstate and foreign communications by wire and radio (USA).
Federal Energy Agency, FEA The government agency that administers the Federal Energy Law (USA).