All articles A–Z
519,064 articles
Hydraulic regenerative circuit
A hydraulic regenerative circuit, also called a rapid traverse circuit, returns rod-side flow to the piston side of a differential cylinder, roughly doubling extension speed at reduced force.
Hydraulic resonance
Hydraulic resonance is the oscillation of a moving mass on the compressible oil column in a hydraulic actuator, often the limit on servo control bandwidth.
Hydraulic stimulation
Hydraulic stimulation is a reservoir engineering method that injects fluid at high pressure to increase rock permeability, used for oil and gas recovery and enhanced geothermal systems.
Hydraulic tomography
Hydraulic tomography is an aquifer characterization method that maps spatially varying hydraulic conductivity and storage by inverting head responses from sequential pumping or injection tests.
Hydraulic transformer
A hydraulic transformer is a fluid-power component that converts pressurized hydraulic fluid between different pressure and flow rates at nearly constant power, chiefly for Common Pressure Rail systems.
Hydraulically amplified self-healing electrostatic actuators
Hydraulically amplified self-healing electrostatic (HASEL) actuators are soft artificial muscles driven by voltage, introduced in 2018 at the University of Colorado Boulder and able to self-heal after dielectric breakdown.
Hydraulics
Hydraulics is the engineering science of liquid pressure and flow, covering fluid power systems, where confined liquid transmits force by Pascal's law, and water flow in open channels and pipelines.
Hydrazide
Hydrazide, also called acylhydrazine, is a compound derived from an oxoacid in which acidic hydroxy groups are replaced by hydrazine-derived groups; isoniazid is a well-known example.
Hydrazine
Hydrazine, also called diazane, is a toxic, fuming compound of nitrogen and hydrogen used as a rocket propellant and to make agricultural chemicals and blowing agents.
Hydrazine oxidation reaction
The hydrazine oxidation reaction is the electrochemical oxidation of hydrazine at an electrode, used in direct hydrazine fuel cells and as a low-voltage substitute for oxygen evolution in hydrogen production.
Hydrazino-Pictet–Spengler ligation
The hydrazino-Pictet–Spengler (HIPS) ligation is a bioconjugation reaction introduced in 2013 that couples aldehyde-tagged proteins to hydrazine-indole linkers, forming a stable carbon–carbon bond near neutral pH.
Hydrazoic acid
Hydrazoic acid, also called hydrogen azide or hydronitric acid, is the colorless, volatile, toxic and explosive liquid nitrogen hydride (HN₃) used to make heavy metal azides for shell detonators.
Hydreuma to epi tou Paneiou
Hydreuma to epi tou Paneiou (el-Kanais, الكنيس), a fortified Ptolemaic watering station and Pan/Min sanctuary (Paneion) in Egypt's Eastern Desert on the Edfu-Berenike road, 47.4 km from Edfu, beside Seti I's rock temple.
Hydride
Hydride is the anion of hydrogen, H−, and by extension the broad class of compounds hydrogen forms with other elements, grouped as ionic, covalent, and metallic hydrides.
Hydride generation
Hydride generation is a sample-introduction technique in atomic spectrometry that converts elements like arsenic, selenium, and tin in acidified solution to volatile hydrides for detection, first applied analytically in 1969.
Hydride superconductivity
Hydride superconductivity is superconductivity in hydrogen-rich compounds compressed to megabar pressures. It holds the highest known transition temperatures, with lanthanum decahydide superconducting at about 250 K near 170 GPa.
Hydrilla
Hydrilla (Hydrilla verticillata), or waterthyme, is an invasive submerged aquatic plant of Hydrocharitaceae with whorled serrated leaves, tubers, and turions; introduced via the aquarium trade, it infests 28 US states and is a Federal Noxious Weed.
Hydriotaphia, Urn Burial
Hydriotaphia, Urn Burial is a treatise by Sir Thomas Browne, published in London in 1658, that began as a report on burial urns found in Norfolk and ends as a meditation on mortality.
Hydro One
Hydro One is Ontario's largest electricity transmission and distribution utility, a publicly traded company formed from Ontario Hydro in 1999 that serves about 1.5 million mostly rural customers.
Hydro Tasmania
Hydro Tasmania is the trading name of the Hydro-Electric Corporation, the Tasmanian government business that generates and retails electricity and is Australia's largest generator of clean, renewable energy.
Hydro-Man
Hydro-Man (Morris 'Morrie' Bench), Marvel Comics Spider-Man villain whose body became living water after an undersea generator accident; first appearance The Amazing Spider-Man #212 (January 1981), by Denny O'Neil and John Romita Jr., Sandman's water-based counterpart and inspiration for Far From Home's water Elemental.
Hydro-Québec
Hydro-Québec is a government-owned Canadian utility, founded in 1944, that supplies nearly all electricity in Québec and is Canada's largest power utility and electricity distributor.
Hydroa vacciniforme
Hydroa vacciniforme (Bazin's hydroa vacciniforme) is a rare childhood photodermatosis causing vesicles on sun-exposed skin that heal with permanent varioliform scars; severe EBV-associated forms (HVLPD) can progress to lymphoma.
Hydroa vacciniforme-like lymphoma
Hydroa vacciniforme-like lymphoma (HVLL), now hydroa vacciniforme lymphoproliferative disorder, is a rare EBV-positive T/NK-cell lymphoproliferative disease of childhood, mainly in Asia and Latin America, with ulcerative skin lesions and risk of systemic lymphoma.
Hydroacylation
Hydroacylation is an organic reaction in which the formyl C–H bond of an aldehyde adds across an alkene or alkyne to give a ketone, typically catalyzed by transition-metal complexes such as rhodium.
Hydroalkylation
Hydroalkylation is a catalytic reaction in which hydrogen and an alkyl group add across an alkene's double bond, converting it directly into a substituted alkane.
Hydroamination
Hydroamination is the addition of an amine N–H bond across a carbon–carbon double or triple bond, forming a new C–N bond in one step with 100% theoretical atom economy.
Hydroaminoalkylation
Hydroaminoalkylation (HAA) is a catalytic reaction that inserts an inexpensive alkene directly into the C–H bond beside an amine's nitrogen, an atom-economic route to substituted amines found in pharmaceuticals.
Hydroarylation
Hydroarylation is the addition of an aryl group and hydrogen across a carbon-carbon double or triple bond, an atom-economical alternative to Friedel-Crafts alkylation that preferentially gives linear, anti-Markovnikov products.
Hydrobates
Hydrobates (Boie, 1822) is the genus of northern storm petrels, family Hydrobatidae; it absorbed Oceanodroma after genetic work showed paraphyly, and includes H. pelagicus, H. leucorhous, and H. castro.