Positive acknowledgment is a action in which the furnishings of a baby agitation on (a perturbation of) a arrangement accommodate an access in the consequence of the perturbation. That is, A produces added of B which in about-face produces added of A.1 In contrast, a arrangement that responds to a perturbation in a way that reduces its aftereffect is said to display abrogating feedback. These concepts were aboriginal accustomed as broadly applicative by Norbert Wiener in his 1948 assignment on cybernetics.2
Positive acknowledgment tends to account arrangement instability, alteration from equilibrium, cadence and generally exponential growth. When there is added absolute acknowledgment than there are stabilizing tendencies, systems will about advance appear a non-linear region, which may stabilise the arrangement or (depending on the system) alike accident or abort it. Absolute acknowledgment may end with the arrangement 'latched' into a fresh abiding state. Absolute acknowledgment is controlled by signals in the arrangement actuality filtered, damped or limited, or it can annulled or bargain by abacus abrogating feedback.
In folklore a arrangement aftereffect can bound actualize the absolute acknowledgment of a coffer run. The aloft photo is of the UK Northern Rock 2007 coffer run. See additionally viral video.
Positive acknowledgment is acclimated in agenda electronics to force voltages abroad from average voltages into '0' and '1' states. On the added hand, thermal delinquent is a absolute acknowledgment that can abort semiconductor junctions. Absolute acknowledgment in actinic reactions can access the amount of reactions, and in some cases can advance to explosions. Absolute acknowledgment in automated architecture causes tipping-point, or 'over-centre', mechanisms to breeze into position, for archetype in switches and locking pliers. Out of control, it can account bridges to collapse. Absolute acknowledgment in bread-and-butter systems can account boom-then-bust cycles.
In the appellation "positive feedback", "positive" refers to the algebraic assurance of the administration of change rather than the agreeableness of the outcome. To abstain this confusion, it is sometimes added good to use added agreement such as self-reinforcing feedback.3 In amusing and banking systems, absolute acknowledgment furnishings may additionally be referred to as 'virtuous' or 'vicious' circles.
Contents
hide
1 Overview
2 Examples and Applications
2.1 In Biology
2.2 In electronics
2.3 In economics
2.3.1 In the Apple Arrangement development
2.3.2 Systemic risk
2.3.3 Population and agriculture
2.3.4 Prejudice, amusing institutions and poverty
2.4 In climatology
2.5 In sociology
3 See also
3.1 Analogous concepts
3.2 Examples
4 References
5 Further reading
edit Overview
The key affection of absolute acknowledgment is that baby disturbances are amplified. When absolute acknowledgment is present, there is some causal bend area a baby change creates an aftereffect that causes an alike bigger change, like a brawl rolling bottomward an added abrupt hill.
When a change in a capricious occurs in a arrangement which exhibits absolute feedback, the arrangement responds by alteration that capricious alike added in the aforementioned direction.
The end aftereffect of absolute acknowledgment is to amplify so that baby perturbations may aftereffect in big changes. For example, if a actinic acknowledgment causes the absolution of heat, and the acknowledgment itself happens faster at college temperatures, again there is a aerial likelihood of absolute feedback. If the calefaction produced is not removed from the reactants fast enough, thermal delinquent can action and actual bound advance to a actinic explosion. Equally, if a PA arrangement microphone picks up sounds from its own loudspeakers and these sounds are re-amplified enough, the aftereffect can be loud squealing or bawl noises from the loudspeakers.
Formally, a arrangement in calm in which there is absolute acknowledgment to any change from its accepted accompaniment is said to be in an ambiguous equilibrium. The consequence of the armament which act to move such a arrangement abroad from its set point are an accretion action of the "distance" from the set point.
In the absolute world, absolute acknowledgment loops are consistently controlled eventually by abrogating acknowledgment or attached furnishings of some sort. Acoustic acknowledgment causes a PA arrangement to ability its best aggregate and so it cannot amplify any further; a alembic may able and the actinic reactants aerosol into the air or discharge assimilate the floor, area they advance out and cool. Abrogating acknowledgment furnishings aural the aforementioned arrangement can additionally attune the aftereffect of absolute acknowledgment so that it may add to the admiration of the arrangement but does not necessarily advance to a delinquent process. Chaotic systems display absolute acknowledgment at the baby scale, but non linearities anticipate the systems from accretion infinitely, but do so after extensive equilibrium.
Positive acknowledgment tends to account arrangement instability, alteration from equilibrium, cadence and generally exponential growth. When there is added absolute acknowledgment than there are stabilizing tendencies, systems will about advance appear a non-linear region, which may stabilise the arrangement or (depending on the system) alike accident or abort it. Absolute acknowledgment may end with the arrangement 'latched' into a fresh abiding state. Absolute acknowledgment is controlled by signals in the arrangement actuality filtered, damped or limited, or it can annulled or bargain by abacus abrogating feedback.
In folklore a arrangement aftereffect can bound actualize the absolute acknowledgment of a coffer run. The aloft photo is of the UK Northern Rock 2007 coffer run. See additionally viral video.
Positive acknowledgment is acclimated in agenda electronics to force voltages abroad from average voltages into '0' and '1' states. On the added hand, thermal delinquent is a absolute acknowledgment that can abort semiconductor junctions. Absolute acknowledgment in actinic reactions can access the amount of reactions, and in some cases can advance to explosions. Absolute acknowledgment in automated architecture causes tipping-point, or 'over-centre', mechanisms to breeze into position, for archetype in switches and locking pliers. Out of control, it can account bridges to collapse. Absolute acknowledgment in bread-and-butter systems can account boom-then-bust cycles.
In the appellation "positive feedback", "positive" refers to the algebraic assurance of the administration of change rather than the agreeableness of the outcome. To abstain this confusion, it is sometimes added good to use added agreement such as self-reinforcing feedback.3 In amusing and banking systems, absolute acknowledgment furnishings may additionally be referred to as 'virtuous' or 'vicious' circles.
Contents
hide
1 Overview
2 Examples and Applications
2.1 In Biology
2.2 In electronics
2.3 In economics
2.3.1 In the Apple Arrangement development
2.3.2 Systemic risk
2.3.3 Population and agriculture
2.3.4 Prejudice, amusing institutions and poverty
2.4 In climatology
2.5 In sociology
3 See also
3.1 Analogous concepts
3.2 Examples
4 References
5 Further reading
edit Overview
The key affection of absolute acknowledgment is that baby disturbances are amplified. When absolute acknowledgment is present, there is some causal bend area a baby change creates an aftereffect that causes an alike bigger change, like a brawl rolling bottomward an added abrupt hill.
When a change in a capricious occurs in a arrangement which exhibits absolute feedback, the arrangement responds by alteration that capricious alike added in the aforementioned direction.
The end aftereffect of absolute acknowledgment is to amplify so that baby perturbations may aftereffect in big changes. For example, if a actinic acknowledgment causes the absolution of heat, and the acknowledgment itself happens faster at college temperatures, again there is a aerial likelihood of absolute feedback. If the calefaction produced is not removed from the reactants fast enough, thermal delinquent can action and actual bound advance to a actinic explosion. Equally, if a PA arrangement microphone picks up sounds from its own loudspeakers and these sounds are re-amplified enough, the aftereffect can be loud squealing or bawl noises from the loudspeakers.
Formally, a arrangement in calm in which there is absolute acknowledgment to any change from its accepted accompaniment is said to be in an ambiguous equilibrium. The consequence of the armament which act to move such a arrangement abroad from its set point are an accretion action of the "distance" from the set point.
In the absolute world, absolute acknowledgment loops are consistently controlled eventually by abrogating acknowledgment or attached furnishings of some sort. Acoustic acknowledgment causes a PA arrangement to ability its best aggregate and so it cannot amplify any further; a alembic may able and the actinic reactants aerosol into the air or discharge assimilate the floor, area they advance out and cool. Abrogating acknowledgment furnishings aural the aforementioned arrangement can additionally attune the aftereffect of absolute acknowledgment so that it may add to the admiration of the arrangement but does not necessarily advance to a delinquent process. Chaotic systems display absolute acknowledgment at the baby scale, but non linearities anticipate the systems from accretion infinitely, but do so after extensive equilibrium.
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