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Abrasion – is the process of scuffing, scratching, wearing down, marring, or rubbing
away. It can be intentionally imposed in a controlled process using an abrasive. Abrasion
can be an undesirable effect of exposure to normal use or exposure to the elements.
Absolute zero – is the lowest possible temperature of a system, defined as
zero kelvin or −273.15 °C. No experiment has yet measured a temperature of absolute
zero.
Accelerated life testing – is the process of testing a product by subjecting it to
conditions (stress, strain, temperatures, voltage, vibration rate, pressure etc.) in excess
of its normal service parameters in an effort to uncover faults and potential modes of
failure in a short amount of time.[1][2] By analyzing the product's response to such
tests, engineers can make predictions about the service life and maintenance intervals of
a product.[3][4]
Acceleration – In physics, acceleration is the rate of change of velocity of an object
with respect to time. An object's acceleration is the net result of any and all forces acting
on the object, as described by Newton's Second Law.[5] The SI unit for acceleration
is metre per second squared (m s−2). Accelerations are vector quantities (they
have magnitude and direction) and add according to the parallelogram law.[6][7] As
a vector, the calculated net force is equal to the product of the object's mass
(a scalar quantity) and its acceleration.
Accelerometer – is a device that measures proper acceleration.[8] Proper acceleration,
being the acceleration (or rate of change of velocity) of a body in its own
instantaneous rest frame,[9] is not the same as coordinate acceleration, being the
acceleration in a fixed coordinate system.
Accuracy and precision – In measurement of a set, accuracy is closeness of the
measurements to a specific value, while precision is the closeness of the
measurements to each other. More commonly, accuracy or trueness is a description
of systematic errors, a measure of statistical bias, while precision is a description
of random errors, a measure of statistical variability; the two concepts are independent of
each other. Alternatively, ISO defines[10] accuracy as describing a combination of both
random and systematic observational error, so high accuracy requires both high
precision and high trueness.
Ackermann steering geometry – is a geometric arrangement of linkages in
the steering of a car or other vehicle designed to solve the problem of wheels on the
inside and outside of a turn needing to trace out circles of different radii. It was invented
by the German carriage builder Georg Lankensperger in Munich in 1817, then patented
by his agent in England, Rudolph Ackermann (1764–1834) in 1818 for horse-drawn
carriages. Erasmus Darwin may have a prior claim as the inventor dating from 1758.[11]
Acoustic droplet ejection– (ADE) uses a pulse of ultrasound to move low volumes of
fluids (typically nanoliters or picoliters) without any physical contact. This technology
focuses acoustic energy into a fluid sample in order to eject droplets as small as
a picoliter. ADE technology is a very gentle process. This feature makes the technology
suitable for a wide variety of applications including proteomics and cell-based assays.
Active cooling – An active cooling system is one that involves the use of energy to
cool something, as opposed to passive cooling that uses no energy. Such systems
circulate a coolant to transfer heat from one place to another. The coolant is either a gas,
such as in air cooling of computers, or a liquid such as in a car engine. In the latter case,
liquid is pumped to transfer heat from the engine to the radiator, which in turn is cooled
by passing air over it. Other active cooling systems make use of a refrigeration cycle.
Actual mechanical advantage – The actual mechanical advantage (AMA) is the
mechanical advantage determined by physical measurement of the input and output
forces. Actual mechanical advantage takes into account energy loss due to deflection,
friction, and wear.
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Adjoint equation – is a linear differential equation, usually derived from its primal
equation using integration by parts. Gradient values with respect to a particular quantity
of interest can be efficiently calculated by solving the adjoint equation. Methods based
on solution of adjoint equations are used in wing shape optimization, fluid flow control
and uncertainty quantification. For example
this is an Itō stochastic differential
equation. Now by using Euler scheme, we integrate the parts of this equation and get
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another equation,
, here
is a random variable, later one is an adjoint
equation.
Aerodynamics – is the study of the motion of air, particularly its interaction with a solid
object, such as an airplane wing. It is a sub-field of fluid dynamics and gas dynamics,
and many aspects of aerodynamics theory are common to these fields.
Agitator (device) – is a device or mechanism to put something
into motion by shaking or stirring. Agitators usually consist of an impeller and a shaft; an
impeller is a rotor located within a tube or conduit attached to the shaft, which helps
enhance the pressure in order for the flow of a fluid be done.[12]