All articles starting with F
15,892 articles
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.
Fourier optics
Fourier optics is the treatment of light propagation and imaging with Fourier analysis and linear systems theory, in which a lens performs a Fourier transform of an optical field.
Fourier ptychographic microscopy
Fourier ptychographic microscopy (FPM) is a computational imaging method that combines many low-resolution images captured under varied illumination angles into one high-resolution, wide-field microscope image, introduced at Caltech in 2013.
Fourier ptychography
Fourier ptychography is a computational imaging method that combines many low-resolution images, each captured under a different illumination angle, into a single high-resolution, wide-field image, first reported in 2013.
Fourier series
A Fourier series, also called a Fourier expansion, represents a periodic function as an infinite sum of sines and cosines at multiples of the fundamental frequency.
Fourier shell correlation
Fourier shell correlation (FSC) is a resolution measure in three-dimensional electron microscopy, computed between two independently reconstructed 3D volumes, and the standard global metric in cryo-EM.
Fourier spectral method
A Fourier spectral method solves partial differential equations by expanding the solution in a Fourier series, differentiating via the coefficients, and achieving exponential accuracy for smooth periodic problems.
Fourier transform
The Fourier transform, also called Fourier transformation, is a mathematical operation that converts a function of time or space into a function of frequency, named for Joseph Fourier and central to signal processing and differential equations.
Fourier transform holography
Fourier transform holography (FTH) is a lensless imaging technique that reconstructs an object from a hologram with a reference wave by a single Fourier transform.
Fourier transform infrared spectroscopy imaging
Fourier transform infrared (FTIR) spectroscopy imaging is a label-free chemical imaging technique that maps the spatial distribution of chemical components in a sample without stains.
Fourier transform microwave spectroscopy
Fourier transform microwave spectroscopy measures rotational transition frequencies of polar molecules in a pulsed supersonic jet; rotational constants yield molecular geometries, and chirped-pulse variants cover 10 GHz or more in a single shot.
FOURIER trial
FOURIER (Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk) trial: 2017 Amgen-funded randomized trial of evolocumab in 27,564 ASCVD patients; LDL-C fell 59%, primary cardiovascular endpoint reduced 15% (HR 0.85), no significant mortality reduction.
Fourier-transform infrared spectroscopy
Fourier-transform infrared spectroscopy (FTIR or FT-IR) is an analytical technique that measures how molecules absorb infrared radiation, used to identify substances in diagnostics, food inspection, and environmental monitoring.
Fourier-transform ion cyclotron resonance mass spectrometry
Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) traps ions in a magnetic field and measures their masses with the highest resolution of any mass analyzer.
Fourier-transform mass spectrometry
Fourier-transform mass spectrometry (FTMS) is a class of mass spectrometry in which trapped ions are excited into coherent motion, and a Fourier transform of the recorded signal yields a mass spectrum with very high resolution.
Fourier-transform near-infrared spectroscopy
Fourier-transform near-infrared (FT-NIR) spectroscopy is an analytical technique using a Michelson interferometer to record near-infrared absorption spectra, used for composition analysis, quality control, and process monitoring.
Fourier-transform spectroscopy
Fourier-transform spectroscopy (FTS) measures a spectrum by recording light intensity versus path difference in a Michelson interferometer and computing the interferogram's Fourier transform.
Fourier–Mukai transform
The Fourier–Mukai transform is a functor between the derived categories of coherent sheaves on smooth projective varieties that is an exact equivalence, introduced by Shigeru Mukai in 1981.
Fourier's law of heat conduction
Fourier's law of heat conduction, formulated by Joseph Fourier in 1822, states that heat flows in proportion to the temperature gradient, with thermal conductivity as the proportionality constant.
FourKites
FourKites is a Chicago-based supply chain visibility company, founded in 2014 by Mathew Elenjickal, that tracks shipments across all transport modes and predicts arrival times, raising a $100 million Series D in 2021.
Fournaise, Piton de la
Piton de la Fournaise is a highly active basaltic shield volcano on Réunion, rising to 2,632 m and erupting about twice a year since 1998.
Fournier (Martian crater)
Fournier is an IAU-approved 118 km diameter impact crater on Mars, centered at 4.35 degrees south latitude, 72.60 degrees east longitude, recorded as Feature ID 2004 in the Gazetteer of Planetary Nomenclature.
Fournier gangrene
Fournier gangrene, a polymicrobial necrotizing fasciitis of the perineum and genitals described by Jean Alfred Fournier in 1883; treated with urgent debridement and broad-spectrum antibiotics, mortality about 20%, predicted by FGSI and UFGSI scores.
Fourpeaked
Fourpeaked (Fourpeaked Mountain), glacier-covered stratovolcano in Katmai National Park, Alaska, 2,104 m. Its first historical eruption, a 6-km phreatic plume, came 17 September 2006, driven by magma intrusion at ~5 km depth.
Fourpence (British coin)
The fourpence, historically called the groat, was an English and British silver coin worth four pence, established by Edward III in 1351 and struck for circulation until 1855.
Foursome
Foursome is a 2016-2018 AwesomenessTV teen comedy web series on YouTube Red starring Jenn McAllister and Logan Paul; the name also covers a Playboy TV reality series, a 2026 Edward Burns golf film, and a Kline novel.
Foursome (group sex)
Foursome: a four-person group sex encounter, positioned between a threesome and larger group sex or orgy; commonly two couples in swinging (soft swap or full swap), with US lifetime prevalence of about 11.5% of men and 6.3% of women.
Fourteen Holy Helpers
The Fourteen Holy Helpers (Vierzehn Nothelfer, Vierzehnheilige) are a group of fourteen Catholic saints, mostly martyrs, venerated together from fourteenth-century Germany as intercessors against plague and disease, each with a specific patronage, centered on the Balthasar Neumann basilica of Vierzehnheiligen in Bavaria.
Fourteen Hours
Fourteen Hours (1951) is a Henry Hathaway drama for 20th Century-Fox, starring Paul Douglas and Richard Basehart, adapted from Joel Sayre's New Yorker story about John William Warde's 1938 hotel-ledge suicide.
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.