All articles starting with U

Ultra-low-temperature district heating

Ultra-low-temperature district heating (ULTDH) is district heating supplying buildings below 50 °C, cutting distribution losses and enabling low-grade heat sources, with booster heat pumps for hot water.

Ultra-performance liquid chromatography

Ultra-performance liquid chromatography (UPLC), also called ultra-high-performance liquid chromatography (UHPLC), is a form of HPLC using sub-2-µm particles above 400 bar, first commercialized by Waters in 2004.

Ultra-precision machining

Ultra-precision machining (UPM) is a manufacturing method that removes material with nanometric control, achieving surface roughness below 10 nm and form accuracy below 0.2 µm.

Ultra-Processed People

Ultra-Processed People (2023) is Chris van Tulleken's nonfiction book arguing that ultra-processed food (UPF), defined by the NOVA system, drives overeating and chronic disease, supported by a month-long self-experiment.

Ultra-royalist

Ultra-royalists (Ultras, ultraroyalistes) were the extreme royalist faction of the French Bourbon Restoration, 1815–1830, dominant in the Chambre introuvable, linked to the White Terror and Villèle's ministry, and succeeded by Legitimists after 1830.

Ultra-short baseline navigation

Ultra-short baseline (USBL, or super-short baseline) navigation is an underwater acoustic positioning method in which a single vessel-mounted transceiver measures range and bearing to a beacon on a subsea target.

Ultra-short baseline positioning

Ultra-short baseline (USBL) positioning is an underwater acoustic technique that determines the 3D position of submerged targets, such as ROVs, from a single compact transducer array on a surface vessel.

Ultra-short-period planet

An ultra-short-period planet, or USP, is a rocky exoplanet smaller than 2 Earth radii that orbits its star in less than a day, hot enough to melt rock.

Ultra-small angle X-ray scattering

Ultra-small angle X-ray scattering (USAXS) is a nondestructive X-ray technique, enabled by Bonse–Hart crystal optics since 1965, that probes porosity, grain size, and phase composition in hard materials.

Ultra-stable cavity

An ultra-stable cavity is a Fabry–Pérot optical resonator whose mirror separation is held nearly constant, so a laser locked to it reaches parts-in-10¹⁶ frequency stability for optical clocks.

Ultra-stripped supernova

An ultra-stripped supernova is a faint, fast-fading supernova of a star in a close binary stripped nearly to its metal core, proposed in 2013 by Thomas Tauris and colleagues.

Ultra-supercritical steam cycle

The ultra-supercritical steam cycle is a Rankine power cycle operating above water's critical pressure, around 3,750 psia and above 1,100 °F, the most efficient commercial class of pulverized coal plants.

Ultra-thin glass

Ultra-thin glass (UTG) is silica-based glass thinner than 0.1 mm, thin enough to bend and fold, used as the cover window of foldable phones and made by down-draw and fusion-draw processes.

Ultra-Trail du Mont-Blanc

Ultra-Trail du Mont-Blanc (UTMB): ultramarathon around Mont Blanc from Chamonix, founded 2003 by Catherine and Michel Poletti; 174 km, 9,700 m gain, 45h30 limit; flagship of the UTMB World Series with records by Jornet and Dauwalter.

Ultra-white paint

Ultra-white paint is a barium sulfate–acrylic coating developed at Purdue University that reflects 98.1% of sunlight, cooling painted surfaces below ambient temperature even in full daylight.

Ultra-wideband

Ultra-wideband (UWB), formerly called impulse radio, is a short-range, low-power radio technology that sends very short pulses to measure distance between devices with centimeter accuracy.

Ultra-wideband (UWB) personal area network

An ultra-wideband (UWB) personal area network is a short-range wireless network using radio pulses spread over at least 500 MHz of spectrum for centimeter-accurate distance measurement between devices.

Ultra-wideband positioning

Ultra-wideband (UWB) positioning is a radio-based localization technique that measures the time of flight of short wideband pulses between tags and fixed anchors, giving centimeter accuracy.

Ultra-wideband radar

Ultra-wideband (UWB) radar is a class of radar transmitting pulses over an exceptionally broad frequency range, defined as at least 500 MHz of bandwidth, best known for ground-penetrating radar.

UltraBattery

UltraBattery is a hybrid energy storage device combining an asymmetric supercapacitor with a lead-acid battery in a single cell, developed by Australia's CSIRO under Lan Lam.

Ultracentrifugation

Ultracentrifugation is a laboratory technique using centrifugal fields of hundreds of thousands of times gravity to separate biomolecules, organelles, and viruses by size, shape, and density, in preparative and analytical forms.

Ultracentrifuge

An ultracentrifuge is a high-speed centrifuge spinning at 100,000 × g or more, invented by Theodor Svedberg in the 1920s to separate proteins and viruses.

Ultracold atom

An ultracold atom, or cold atom, is an atom cooled to the nanokelvin to microkelvin range, cold enough that quantum statistics govern the dilute gas.

Ultracold atom quantum simulation

Ultracold atom quantum simulation uses laser-trapped gases of atoms cooled to near absolute zero to mimic quantum systems too complex to calculate or measure directly, following Feynman's 1982 proposal.

Ultracold polar molecules

Ultracold polar molecules are molecules with a permanent electric dipole moment cooled to below one millikelvin, where long-range dipole-dipole interactions dominate; the first dense gas, KRb, was made at JILA in 2008.

Ultracold triatomic molecules

Ultracold triatomic molecules are three-atom molecules cooled to microkelvin or nanokelvin temperatures, hard to make because of extra vibrational and rotational degrees of freedom; the first gas appeared in 2022.

Ultrafast control of ferroelectric polarization

Ultrafast control of ferroelectric polarization is the manipulation of a ferroelectric's spontaneous polarization on picosecond or sub-picosecond timescales, using intense electric-field pulses, terahertz fields, or femtosecond light pulses.

Ultrafast demagnetization imaging with time-resolved PEEM

Ultrafast demagnetization imaging with time-resolved photoemission electron microscopy (tr-PEEM) records nanoscale magnetic domain images at successive delays after excitation, using x-ray magnetic circular dichroism contrast.

Ultrafast electron diffraction

Ultrafast electron diffraction (UED) is a pump–probe technique firing femtosecond electron pulses at a sample to record diffraction snapshots of its transient atomic structure, first reported in 1982.