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Non-dialable point
A non-dialable point was a telephone line that could not be reached by dialing, so calls to it were completed manually by a long distance operator.
Non-directional beacon
A non-directional beacon (NDB) is a ground-based radio navigation transmitter, among the oldest aids still in aviation use, that lets equipped pilots determine bearings and home on it.
Non-disintegrating belt
A non-disintegrating belt is a machine-gun ammunition belt whose links remain joined after firing, so the empty belt emerges intact, unlike the disintegrating belt, whose links fall away.
Non-dominated sorting genetic algorithm
The non-dominated sorting genetic algorithm (NSGA) is a family of multi-objective evolutionary algorithms, introduced by Srinivas and Deb in 1994, that evolves a whole set of trade-off solutions in one run.
Non-English-based programming languages
Non-English-based programming languages express keywords, syntax, numerals, or error messages in natural languages other than English; they have existed since the 1960s, and studies show localized languages help novices learn faster.
Non-ferrous metal
A non-ferrous metal is a metal or alloy in which iron is not the main constituent, such as copper, aluminum, brass, bronze, tin, silver, and zinc.
Non-fullerene acceptor
A non-fullerene acceptor (NFA) is an organic electron-accepting molecule that replaces fullerene derivatives in organic solar cells, whose tunable properties have pushed power conversion efficiencies past 20%.
Non-functional requirement
A non-functional requirement (NFR), also called a quality requirement, is a software requirement describing how well a system performs, covering qualities like performance, security, and usability.
Non-Hermitian metamaterials
Non-Hermitian metamaterials are engineered structures whose waves obey non-Hermitian operators because they exchange energy through gain, loss, or nonreciprocal couplings, realized in optics, acoustics, circuits, and mechanics.
Non-intrusive load monitoring
Non-intrusive load monitoring, also called energy disaggregation, estimates the power consumed by individual appliances from a single metering point, avoiding the wiring and submeters intrusive monitoring requires.
Non-lethal weapon
A non-lethal weapon, more accurately called a less-lethal weapon, is a device meant to incapacitate a person with a lower risk of death than firearms.
Non-local means
Non-local means (NL-means) is an image denoising algorithm introduced by Buades, Coll, and Morel in 2005, which estimates each pixel from similar patches found anywhere in the image.
Non-nucleophilic magnesium electrolytes
Non-nucleophilic magnesium electrolytes are liquid electrolytes for rechargeable magnesium batteries whose magnesium-carrying species do not attack electrophilic cathodes such as sulfur, unlike early Grignard-based electrolytes.
Non-orbital rocketry
Non-orbital rocketry is rocketry that reaches high altitude or space on suborbital trajectories without achieving orbital speed. It spans model, mid-power, and professional sounding rockets.
Non-orientable mechanical metamaterial
A non-orientable mechanical metamaterial is a metamaterial lacking a consistent orientation, through Möbius-strip geometry or non-orientable order in frustrated lattices, enabling mechanical memory and non-Abelian responses.
Non-oriented electrical steel
Non-oriented electrical steel (NOES), also called CRNGO, is a flat-rolled iron-silicon alloy with uniform magnetic properties in all directions, the core material of electric motors and generators.
Non-orthogonal multiple access
Non-orthogonal multiple access (NOMA) is a radio access technique for 5G that transmits several users' signals on the same resource, separating them at receivers by successive interference cancellation.
Non-places
A non-place (French: non-lieu) is a concept coined by anthropologist Marc Augé in 1992, describing spaces like airports, hotels, and malls that lack relational, historical, or identity meaning.
Non-public network
A non-public network (NPN) is a 5G mobile network for the exclusive use of a private entity, defined by 3GPP in Release 16 and often called a private 5G network.
Non-radiative recombination
Non-radiative recombination is the annihilation of an electron–hole pair in a semiconductor without emitting a photon, wasting energy as heat and limiting solar cell voltage.
Non-reciprocal elastic metamaterials via spatiotemporal modulation
Non-reciprocal elastic metamaterials via spatiotemporal modulation are solids whose stiffness or density varies in space and time, letting elastic waves travel one way while blocked in the other.
Non-repudiation
Non-repudiation, also called non-repudiability, is a security service providing evidence of who sent, signed, or received data, typically via digital signatures, so no party can deny involvement.
Non-return-to-zero
Non-return-to-zero (NRZ), or NRZ encoding, is a line code in which the signal holds one of two levels for a whole bit, changing only when the data changes.
Non-revenue water
Non-revenue water, formerly called unaccounted-for water, is water a utility puts into its distribution system but does not bill to customers, lost through leakage, illegal connections, and metering inaccuracies.
Non-rocket spacelaunch
Non-rocket spacelaunch, also called non-rocket spaceflight, is the set of proposed methods for reaching orbit without rockets, such as space elevators, skyhooks, mass drivers, and air launch.
Non-standalone 5G
Non-standalone 5G (5G NSA) is a 5G deployment mode that pairs new 5G radio with the existing 4G LTE core, letting operators launch 5G quickly.
Non-standard rail traction
Non-standard rail traction is railway propulsion outside the mainstream steam, diesel, and electric categories, exemplified by the French Aérotrain hovertrain, which rode on a cushion of pressurized air.
Non-Stop (film)
Non-Stop (2014) is a Jaume Collet-Serra action thriller starring Liam Neeson as air marshal Bill Marks, who receives texts threatening a passenger death every 20 minutes unless $150 million is transferred; it grossed over $220 million worldwide.
Non-terrestrial network
A non-terrestrial network (NTN) is a 3GPP-defined network using satellites or high-altitude platforms as base stations, extending 5G coverage to oceans, deserts, and disaster zones towers cannot reach.
Non-toxic shot
Non-toxic shot is shotgun ammunition containing no lead, approved for hunting where spent pellets poison wildlife; the United States banned lead shot for waterfowl hunting nationwide in 1991.