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Foundation and geotechnical failure of bridges
Foundation and geotechnical failure of bridges is collapse or severe distress caused by the soil and rock supporting a bridge, through settlement, liquefaction, lateral spreading, and embankment instability.
Foundling Hospital
The Foundling Hospital was a London institution founded by Thomas Coram, chartered in 1739 to care for and educate abandoned children; it operated until 1954.
Foundry
A foundry, also known as an iron foundry, is an industrial facility where metal is melted and poured into molds to produce castings, most often iron, aluminum, or zinc.
Foundry model
The foundry model is a semiconductor business model in which a company manufactures chips only from customer designs and sells none of its own, pioneered by TSMC in 1987.
Foundry-Logic
Foundry-Logic is a Washington, DC energy company founded in 2025 and led by CEO Brian Deese that builds an energy services platform to operate, maintain, and upgrade energy systems.
Fountain
A fountain is a structure that issues pressurized water into a basin or the air, used for ornament, drinking water, and cooling in gardens and public squares.
Fountain code
A fountain code is a rateless erasure code that generates a limitless stream of encoded symbols, letting a receiver recover a message from any sufficiently large set received.
Fountain pen
A fountain pen is a writing instrument whose metal nib draws ink from an internal reservoir to the paper, first patented by Petrache Poenaru in France in 1827.
Fountains Abbey
Fountains Abbey is a ruined Cistercian monastery near Ripon in North Yorkshire. Founded in 1132, it was dissolved in 1539 and holds the largest monastic ruins in England.
Four Corners Generating Station
The Four Corners Generating Station, also called Four Corners Power Plant, is a 1,540-megawatt coal-fired power plant on the Navajo Nation near Farmington, New Mexico.
Four Courts
The Four Courts (Irish: Na Ceithre Cúirteanna) is Ireland's principal courts building on the River Liffey in Dublin, housing the Supreme Court, Court of Appeal, and High Court since 1931.
Four Major Rivers Restoration Project
The Four Major Rivers Restoration Project was a 2009 to 2012 South Korean public works program that dredged the Han, Nakdong, Geum, and Yeongsan rivers.
Four-ball tester
A four-ball tester is a bench-scale tribometer in which a rotating steel ball is loaded against three stationary balls immersed in the lubricant, introduced in 1933 by Gerrit Daniel Boerlage.
Four-bar linkage
A four-bar linkage, also called a four-bar mechanism, is a planar mechanism of four rigid links joined in a closed loop by four pin joints, with one degree of freedom.
Four-engine aircraft
A four-engine aircraft, or quad, is an airplane powered by four engines. Early engines were too weak for heavy long-haul airframes, and regulators barred twins from over-water routes.
Four-level pulse-amplitude modulation
Four-level pulse-amplitude modulation (PAM4, also written PAM-4) encodes two bits per symbol using four amplitude levels, doubling throughput over NRZ at the same symbol rate.
Four-point bending test
The four-point bending test measures flexural strength and modulus by loading a simply supported beam at two inner points, where bending moment is constant and shear is zero.
Four-point contact ball bearing
A four-point contact ball bearing is an angular contact bearing with gothic arch raceways giving four contact points per ball, replacing a matched pair of bearings in half the axial space.
Four-qubit silicon quantum processor
The four-qubit silicon quantum processor, built by Sydney company Silicon Quantum Computing under Michelle Simmons, uses phosphorus atoms in pure silicon and ran Grover's algorithm at 98.9% fidelity in February 2025.
Four-step travel demand model
The four-step travel demand model (FSM) is an aggregate, trip-based forecasting procedure that estimates regional travel in four sequential stages, from trip generation through network assignment.
Four-stroke engine
A four-stroke engine is an internal combustion engine that completes one power cycle in four piston strokes, intake, compression, power, and exhaust, invented by Nicolaus Otto in 1876.
Four-wave mixing
Four-wave mixing, also called four-photon mixing, is a nonlinear optical process in which two or three light waves at different wavelengths generate new waves at other wavelengths.
Four-way reversing valve
A four-way reversing valve is a four-port valve in a heat pump's refrigerant circuit that reverses refrigerant flow, letting one system heat and cool a space.
Four-wheel drive
Four-wheel drive, also known as four by four or 4x4, is a drivetrain that sends engine or motor torque to all four wheels of a vehicle via a transfer case.
Four-wheel steering
Four-wheel steering (4WS) steers a vehicle's rear wheels as well as its fronts, for stability at high speed and a tighter turning radius at low speed.
Fourdrinier machine
The Fourdrinier machine is a papermaking machine that forms a continuous web of paper on a moving wire screen, patented in 1807 and named for Henry and Sealy Fourdrinier.
Fourier neural operator
The Fourier neural operator (FNO) is a neural network architecture, introduced by Zongyi Li and colleagues in 2020, that learns solutions to partial differential equations.
Fourteen Locks
Fourteen Locks, also known as the Cefn Flight, is a flight of fourteen canal locks at Rogerstone near Newport, South Wales, built in 1799 and lifting the canal about 168 feet.
Fourth Partner Energy
Fourth Partner Energy is a Hyderabad-based Indian renewable energy company founded in 2010, developing distributed, open-access, and utility-scale solar and wind-solar hybrid projects for commercial and industrial customers.
Fourth-generation fighter
A fourth-generation fighter is a jet combat aircraft designed in the 1970s and 1980s around pulse-Doppler radar and high maneuverability, including the F-15, F-16, MiG-29, and Su-27.