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  • hydraulic elevator (device)

    elevator: Hydraulic cylinders and plungers are used for low-rise passenger elevators and for heavy duty freight elevators. The plunger pushes the platform from below by the action of pressurized oil in the cylinder. A high-speed electric pump develops the pressure needed to raise the elevator; the…

  • hydraulic engineering

    history of technology: Civil engineering: …introduction of compressed air and hydraulic tools also contributed to the lightening of drudgery. The latter two inventions were important in other respects, such as in mining engineering and in the operation of lifts, lock gates, and cranes. The use of a tunneling shield, to allow a tunnel to be…

  • hydraulic equivalence (geology)

    Hydraulic equivalence, size–density relationship that governs the deposition of mineral particles from flowing water. Two particles of different sizes and densities are said to be hydraulically equivalent if they are deposited at the same time under a given set of conditions; the smaller particle

  • hydraulic filling

    dam: Construction techniques: In the process of hydraulic filling, sands are dredged from borrow pits, transported in water by pipelines to the filling area, and deposited there by draining off the surplus water. Hydraulic filling is widely practiced in maritime works, and it has also been used for embankment dams. In the…

  • hydraulic fluid (physics)

    circulatory system: Arthropoda: …because blood is used as hydraulic fluid to extend the legs in opposition to flexor muscles. The blood pressure of a resting spider is equal to that of a human being and may double during activity. The high pressure is maintained by valves in the anterior aorta and represents an…

  • hydraulic fracturing (engineering)

    Fracking, in natural gas and petroleum production, injection of a fluid at high pressure into an underground rock formation in order to open fissures and allow trapped gas or crude oil to flow through a pipe to a wellhead at the surface. Employed in combination with improved techniques for drilling

  • hydraulic geometry

    river: Hydraulic geometry: Hydraulic geometry deals with variation in channel characteristics in relation to variations in discharge. Two sets of variations take place: variations at a particular cross section (at-a-station) and variations along the length of the stream (downstream variations). Characteristics responsive to analysis by hydraulic…

  • hydraulic hoist (hoist)

    stagecraft: Flying systems: …powered by electricity is a hydraulic hoist, in which an electric motor is used to run a hydraulic piston, which in turn moves the hoisting lines. The advantages of this form of machine-driven flying system are that the electric motor does not have to be physically near the fluid drive,…

  • hydraulic jump (fluid mechanics)

    Hydraulic jump, Sudden change in water level, analogous to a shock wave, commonly seen below weirs and sluice gates where a smooth stream of water suddenly rises at a foaming front. The fact that the speed of water waves varies with wavelength and with amplitude leads to a wide variety of effects.

  • hydraulic lime (construction)

    John Smeaton: …to recognize what constitutes a hydraulic lime.

  • hydraulic mining

    Hydraulic mining, use of a powerful jet of water to dislodge minerals present in unconsolidated material, including mine tailings, placer deposits, alluvium, laterites (soil rich in iron oxides), and saprolites (soil rich in clay). It has also been applied to consolidated materials from sandstones

  • hydraulic model

    harbours and sea works: Hydraulic models: The planning of maritime civil engineering works, whether for transportation, reclamation, or conservancy, has been facilitated by the development of the technique of model studies. Once regarded as scientific toys, such studies are now considered an essential preliminary step to any large-scale redevelopment…

  • hydraulic motor (technology)

    hydraulic power: As a result, hydraulic power systems are extensively used in modern aircraft, automobiles, heavy industrial machinery, and many kinds of machine tools.

  • hydraulic piston corer (tool)

    undersea exploration: Exploration of the seafloor and the Earth’s crust: …version of this device, the hydraulic piston corer, is used by deep-sea drilling ships such as the “JOIDES Resolution.” Essentially undisturbed cores of lengths up to 200 metres have been obtained with this type of corer.

  • hydraulic power (engineering)

    Hydraulic power, power transmitted by the controlled circulation of pressurized fluid, usually a water-soluble oil or water–glycol mixture, to a motor that converts it into a mechanical output capable of doing work on a load. Hydraulic power systems have greater flexibility than mechanical and e

  • hydraulic press (device)

    Hydraulic press, device consisting of a cylinder fitted with a sliding piston that exerts force upon a confined liquid, which, in turn, produces a compressive force upon a stationary anvil or baseplate. The liquid is forced into the cylinder by a pump. The hydraulic press is widely used in

  • hydraulic ram pump

    pump: Electromagnetic pumps.: The hydraulic ram pump uses the energy of a downward-flowing stream of water to lift a proportion of the water to a higher level. Flowing water in the inlet pipe causes a check valve to close. As in a water hammer (in which a flow of…

  • Hydraulic Resources and Electrification, Institute of (Panamanian institution)

    Panama: Resources and power: …long distributed by the state-run Institute of Hydraulic Resources and Electrification before it was privatized in 1998. Much of Panama’s electricity is generated by hydroelectric dams. The first plants were opened in 1975 at La Yeguada in Veraguas province and in 1976 on the Chepo River; the largest, at La…

  • hydraulic shovel (tool)

    coal mining: Shovels and trucks: … (or quarry-mine) shovel, and the hydraulic shovel. The hydraulic mining shovel has been widely used for coal and rock loading since the 1970s. The hydraulic system of power transmission greatly simplifies the power train, eliminates a number of mechanical components that are present in the loading shovel, and provides good…

  • hydraulic spring (machine component)

    spring: Hydraulic springs are comparatively small, thick-walled cylinders in which the spring effect is produced by applying a load to the fluid in the cylinder through a small piston entering at the centre of one end of the cylinder. The piston movement, or deflection, is produced…

  • hydraulic stage (theatrical device)

    theatre: Development of stage equipment: Hydraulic stages made it possible to raise sections of the stage, tilt them or even rock them to simulate, for example, the motion of a ship. All of these mechanisms required larger backstage facilities, higher flying towers, greater depth and width of stages, and increased…

  • hydraulic torque converter (technology)

    automobile: Transmission: Most automatic transmissions employ a hydraulic torque converter, a device for transmitting and amplifying the torque produced by the engine. Each type provides for manual selection of reverse and low ranges that either prevent automatic upshifts or employ lower gear ratios than are used in normal driving. Grade-retard provisions are…

  • hydraulic transmission (technology)

    Hydraulic transmission, device employing a liquid to transmit and modify linear or rotary motion and linear or turning force (torque). There are two main types of hydraulic power transmission systems: hydrokinetic, such as the hydraulic coupling and the hydraulic torque converter, which use the k

  • hydraulic turbine

    turbine: Water turbines: Water turbines are generally divided into two categories: (1) impulse turbines used for high heads of water and low flow rates and (2) reaction turbines normally employed for heads below about 450 metres and moderate or high flow rates. These two classes include…

  • hydraulic valve lifter (engineering)

    gasoline engine: Valves, pushrods, and rocker arms: Hydraulic valve lifters, now commonly used on automobile engines, eliminate the need for periodic adjustment of clearance.

  • hydraulic works (civil engineering)

    harbours and sea works: The construction of harbours and sea works offers some of the most unusual problems and challenges in civil engineering. The continuous and immediate presence of the sea provides the engineer with an adversary certain to discover any weakness in the structure built to resist it.

  • hydraulicking (mining)

    placer mining: In sluicing or hydraulicking methods, a slightly sloping wooden trough called a box sluice, or a ditch cut in hard gravel or rock called a ground sluice, is used as a channel along which gold-bearing gravel is carried by a stream of water. Riffles placed transversely along the…

  • hydraulics (fluid mechanics)

    Hydraulics, branch of science concerned with the practical applications of fluids, primarily liquids, in motion. It is related to fluid mechanics (q.v.), which in large part provides its theoretical foundation. Hydraulics deals with such matters as the flow of liquids in pipes, rivers, and channels

  • hydraulikon (musical instrument)

    Hydraulis, earliest known mechanical pipe organ. It was invented in the 3rd century bc by Ctesibius of Alexandria, culminating prior attempts to apply a mechanical wind supply to a large set of panpipes. Its pipes stood on top of a wind chest that was connected to a conical wind reservoir. The

  • hydraulis (musical instrument)

    Hydraulis, earliest known mechanical pipe organ. It was invented in the 3rd century bc by Ctesibius of Alexandria, culminating prior attempts to apply a mechanical wind supply to a large set of panpipes. Its pipes stood on top of a wind chest that was connected to a conical wind reservoir. The

  • hydraulos (musical instrument)

    Hydraulis, earliest known mechanical pipe organ. It was invented in the 3rd century bc by Ctesibius of Alexandria, culminating prior attempts to apply a mechanical wind supply to a large set of panpipes. Its pipes stood on top of a wind chest that was connected to a conical wind reservoir. The

  • hydraulus (musical instrument)

    Hydraulis, earliest known mechanical pipe organ. It was invented in the 3rd century bc by Ctesibius of Alexandria, culminating prior attempts to apply a mechanical wind supply to a large set of panpipes. Its pipes stood on top of a wind chest that was connected to a conical wind reservoir. The

  • hydrazide (chemical compound)

    carboxylic acid: Related compounds: Other acid derivatives include hydrazides, hydroxamic acids, and acyl azides. These compounds are formally derived from carboxylic acids and, respectively, hydrazine (NH2NH2), hydroxylamine (NH2OH), and hydrazoic acid (HN3). Imides are compounds with

  • hydrazine (chemical compound)

    Hydrazine, (N2H4), one of a series of compounds called hydronitrogens and a powerful reducing agent. It is used in the synthesis of various pesticides, as a base for blowing agents that make the holes in foam rubber, and as a corrosion inhibitor in boilers. Hydrazine is a colourless liquid with an

  • hydrazine thrustor (rocket engine)

    rocket: Liquid-propellant rocket engines: …and performance is a hydrazine thrustor used for attitude control of conventional flight vehicles and unmanned spacecraft. Such a system may employ a valved pressure vessel in place of a pump, and the single propellant flows through a catalyst bed that causes exothermic (heat-releasing) decomposition. The resulting gas is exhausted…

  • hydrazoic acid (chemical compound)

    carboxylic acid: Related compounds: hydroxylamine (NH2OH), and hydrazoic acid (HN3). Imides are compounds with two RCO groups on a single nitrogen atom. The most common ones are cyclic, such as succinimide and phthalimide.

  • Hydrellia griseola (insect)

    Shore fly, (family Ephydridae), any member of a family of insects in the fly order, Diptera, that are small, dark coloured, and commonly found in great numbers around ponds, streams, and the seashore. Most larvae are aquatic, and some species can tolerate highly saline or alkaline waters—such as

  • hydria (water vessel)

    Hydria, large water vessel in Greek pottery of the Archaic period (c. 750–c. 480 bc) and the Classical period (c. 480–c. 330 bc). It is found in both the black-figure and the red-figure pottery styles. The hydria is distinctive in having three handles: a pair of small, horizontal handles at the

  • hydride (chemical compound)

    Hydride, any of a class of chemical compounds in which hydrogen is combined with another element. Three basic types of hydrides—saline (ionic), metallic, and covalent—may be distinguished on the basis of type of chemical bond involved. A fourth type of hydride, dimeric (polymeric) hydride, may also

  • hydride ion (chemical ion)

    petroleum refining: Catalytic cracking: …the transfer of negatively charged hydride ions (H−). Thus a chain reaction is established that leads to a reduction in molecular size, or “cracking,” of components of the original feedstock.

  • hydriding process (chemical reaction)

    niobium processing: Niobium powder: In the hydriding process, the impure niobium is crushed into chunks and placed in a furnace, which is evacuated and heated to 800–950 °C (1,450–1,750 °F). Hydrogen is then fed to the furnace and passed over the charge for two to four hours. After hydriding, the niobium…

  • hydrilla (plant species)

    Hydrilla, (Hydrilla verticillata), submerged aquatic plant that is the sole member of the genus Hydrilla in the frog’s-bit family (Hydrocharitaceae). Hydrilla is possibly native to Africa or Europe but has naturalized in lakes and streams around the world. Brought to North America in the 1950s, the

  • Hydrilla (plant genus)

    hydrilla: …sole member of the genus Hydrilla in the frog’s-bit family (Hydrocharitaceae). Hydrilla is possibly native to Africa or Europe but has naturalized in lakes and streams around the world. Brought to North America in the 1950s, the plant has become a troublesome aquatic weed, as its vast carpets of tangled…

  • Hydrilla verticillata (plant species)

    Hydrilla, (Hydrilla verticillata), submerged aquatic plant that is the sole member of the genus Hydrilla in the frog’s-bit family (Hydrocharitaceae). Hydrilla is possibly native to Africa or Europe but has naturalized in lakes and streams around the world. Brought to North America in the 1950s, the

  • hydriodic acid (chemical compound)

    ether: Cleavage: …give alkyl bromides or by hydroiodic acid (HI) to give alkyl iodides.

  • Hydriotaphia, Urne-Buriall, or, A Discourse of the Sepulchrall Urnes lately found in Norfolk (work by Browne)

    Sir Thomas Browne: …two treatises on antiquarian subjects, Hydriotaphia, Urne-Buriall, or, A Discourse of the Sepulchrall Urnes lately found in Norfolk, and The Garden of Cyrus, or the Quincunciall Lozenge, or Net-Work Plantations of the Ancients. Around the theme of the urns he wove a tissue of solemn reflections on death and the…

  • Hydro Extrusion Portland, Inc. (American company)

    Glory: …uncovered that Sapa Profiles (later Hydro Extrusion Portland), the company which made the part that would have separated the payload fairing from the rocket, falsified test results showing that the parts were compliant with Orbital Science’s requirements. Sapa Profiles was also to blame for the payload fairing separation failure that…

  • Hydro-Québec (Canadian electric-utility company)

    Quebec: Resources and power: Hydro-Québec soon became the country’s largest electric utility and produces nearly three-fourths of the province’s electricity. In the early 1960s Hydro-Québec entered into a long-term contract with the province of Newfoundland (now Newfoundland and Labrador) to develop the Upper Churchill Falls site in Labrador. In…

  • hydroa (pathology)

    radiation: Photodynamic action: …sensitivity is involved; for example, hydroa, which manifests itself in blisters on parts of the body exposed to sunlight. It has been suggested that this disease results from a light-sensitive porphyrin compound found in the blood.

  • Hydrobates pelagicus (bird)

    storm petrel: The British storm petrel (Hydrobates pelagicus) breeds on islands and cliffs along the coasts of Europe.

  • Hydrobatidae (bird)

    Storm petrel, any member of about 20 species of seabirds constituting the family Hydrobatidae, or sometimes considered as Oceanitidae (order Procellariiformes). Ranging in length from about 13 to 25 centimetres (5 12 to 10 inches), all are dark gray or brown, sometimes lighter below, and often

  • hydrobiology

    limnology: …traditionally is closely related to hydrobiology, which is concerned with the application of the principles and methods of physics, chemistry, geology, and geography to ecological problems.

  • hydrobiotite (mineral)

    clay mineral: Interstratified clay minerals: chlorite/smectite), corrensite (trioctahedral vermiculite/chlorite), hydrobiotite (trioctahedral mica/vermiculite), aliettite (talc/saponite), and kulkeite (talc/chlorite). Other than the ABAB . . . type with equal numbers of the two component layers in a structure, many modes of layer-stacking sequences ranging from nearly regular to completely random are possible. The following interstratifications of…

  • hydroboration (chemical reaction)

    borane: …the 1979 prize for his hydroboration reaction (1956), the remarkably easy addition of BH3 (in the form of BH3 · S) to unsaturated organic compounds (i.e., alkenes and alkynes) in ether solvents (S) at room temperature to yield organoboranes quantitatively (that is, in a reaction that proceeds wholly, or almost…

  • hydrobromic acid

    bromine: Production and use: …gas in water is called hydrobromic acid, a strong acid that resembles hydrochloric acid in its activity toward metals and their oxides and hydroxides.

  • Hydrobryum (plant genus)

    Podostemaceae: …tropics of Asia and Africa), Hydrobryum (10 species, eastern Nepal, Assam, and southern Japan), Castelnavia (9 species, Brazil), Mourera (6 species, northern tropical South America), and Oserya (7 species, Mexico to northern tropical South America). A majority of the remaining 35 genera contain only one or two species each.

  • hydrocarbon (chemical compound)

    Hydrocarbon, any of a class of organic chemical compounds composed only of the elements carbon (C) and hydrogen (H). The carbon atoms join together to form the framework of the compound, and the hydrogen atoms attach to them in many different configurations. Hydrocarbons are the principal

  • hydrocele (pathology)

    Hydrocele, excessive accumulation of fluids in the scrotal sac that surrounds the testes in the male reproductive tract. There are many forms of hydrocele. The most common is chronic simple hydrocele, in which fluid accumulates gradually about the testes. It usually afflicts men past the age of 40

  • Hydrocenidae (gastropod family)

    gastropod: Classification: …in the Old World (Hydrocenidae) and 1 widely distributed in both Old and New World tropics (Helicinidae). Order Monotocardia Heart with 1 auricle; 1 gill, often modified; siphon and chemoreception osphradium (sensory receptor) progressively more complex; penis present; head frequently modified into a proboscis; nervous system progressively more

  • hydrocephalus (pathology)

    Hydrocephalus, accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain, causing progressive enlargement of the head. Normally, CSF continuously circulates through the brain and the spinal cord and is continuously drained into the circulatory system. In hydrocephalus

  • hydrocephaly (pathology)

    Hydrocephalus, accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain, causing progressive enlargement of the head. Normally, CSF continuously circulates through the brain and the spinal cord and is continuously drained into the circulatory system. In hydrocephalus

  • Hydrocharis morsus-ranae (plant)

    Hydrocharitaceae: The common frog’s-bit (Hydrocharis morsus-ranae), from which the family receives its common name, is an ornamental rootless water plant with round or heart-shaped floating leaves and small attractive three-petaled white flowers. The water soldier (Stratiotes aloides) bears rosettes of tough sharp-edged leaves that float in summer…

  • Hydrocharitaceae (plant family)

    Hydrocharitaceae, the frog’s-bit family of monocotyledonous flowering plants, with some 18 cosmopolitan genera of submerged and emergent freshwater and saltwater aquatic herbs. The largest genera are Najas (37–40 species), Ottelia (some 21 species), Lagarosiphon (9 or 10 species), Blyxa (9 or 10

  • hydrochemistry

    Chemical hydrology, subdivision of hydrology that deals with the chemical characteristics of the water on and beneath the surface of the Earth. Water in all forms and modes of occurrence is affected chemically by the materials with which it comes into contact. Often called the universal solvent, w

  • hydrochloric acid (chemical compound)

    Hydrochloric acid, corrosive colourless acid that is prepared by dissolving gaseous hydrogen chloride in

  • hydrochlorofluorocarbon (chemical compound)

    chlorofluorocarbon: …more chlorines, they are called hydrochlorofluorocarbons, or HCFCs. CFCs are also called Freons, a trademark of the E.I. du Pont de Nemours & Company in Wilmington, Del. CFCs were originally developed as refrigerants during the 1930s. Some of these compounds, especially trichlorofluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12), found use as aerosol-spray…

  • Hydrochoerus hydrochaeris (rodent)

    Capybara, (Hydrochoerus hydrochaeris), the largest living rodent, a semiaquatic mammal of Central and South America. The capybara is the sole member of the family Hydrochoeridae. It resembles the cavy and guinea pig of the family Caviidae. South American capybaras may be 1.25 metres (4 feet) long

  • Hydrochoerus isthmius (rodent)

    capybara: Panamanian capybaras are smaller and weigh about 27 kg. Capybaras are short-haired brownish rodents with blunt snouts, short legs, small ears, and almost no tail. They are shy and associate in groups along the banks of lakes and rivers. They normally feed in the morning…

  • Hydrocleys (plant genus)

    Hydrocleys, genus of perennial aquatic plants of the family Alismataceae (formerly placed in Limnocharitaceae), consisting of five species, all native to tropical America. These herbaceous plants have floating, emergent, or submersed leaves and commonly employ stolons or plantlets (small offshoots)

  • Hydrocleys nymphoides (plant)

    Hydrocleys: The water poppy (Hydrocleys nymphoides), with yellow flowers about 5 cm (2 inches) across, is the only cultivated species and is often grown in ponds and aquariums.

  • hydrocooling (agriculture)

    fruit processing: Storage: Precooling can be accomplished by hydrocooling (immersion of the fruit in cold water) or vacuum cooling (moistening and then placing under vacuum in order to induce evaporative cooling).

  • hydrocoral (invertebrate)

    cnidarian: Size range and diversity of structure: …groups such as hydroids and hydrocorals. Hydromedusae are smaller and more delicate than scyphomedusae or cubomedusae; they may be completely absent from the life cycle of some hydrozoan species. Some other species produce medusae, but the medusae never separate themselves from the polyps. Cubozoans have medusae commonly known as box…

  • Hydrocorisae (insect suborder)

    heteropteran: Annotated classification: Suborder Hydrocorisae (or Cryptocerata) Neither cephalic nor abdominal trichobothria; antennae 4-segmented, shorter than head, usually in grooves on underside of head; semiaquatic (Gelastocoridae, Ochteridae) or aquatic (all other families); swimming members with fringe of swimming hairs on hind legs; aquatic members lay eggs in or on…

  • hydrocortisone (hormone)

    Cortisol, an organic compound belonging to the steroid family that is the principal hormone secreted by the adrenal glands. It is a potent anti-inflammatory agent and is used for the palliative treatment of a number of conditions, including itching caused by dermatitis or insect bites, inflammation

  • hydrocracking (industrial process)

    cracking: …automobile and jet fuel increased, hydrocracking was applied to petroleum refining. This process employs hydrogen gas to improve the hydrogen-carbon ratio in the cracked molecules and to arrive at a broader range of end products, such as gasoline, kerosene (used in jet fuel), and diesel fuel. Modern low-temperature hydrocracking was…

  • hydrocyanic acid (chemical compound)

    cereal processing: Cassava: Their prussic acid level must be reduced to safe limits by boiling; the duration of boiling depends on the variety of the leaves. Cassava leaves are a popular vegetable in Africa, and the tuber also is used in meal for animal feed.

  • Hydrocynus (fish genus)

    tigerfish: …freshwaters, tigerfishes of the genus Hydrocynus (sometimes Hydrocyon) are admired game fishes of the characin family, Characidae (order Cypriniformes). They are marked, depending on the species, with one or several dark, lengthwise stripes and are swift, voracious, salmon-shaped carnivores with daggerlike teeth that protrude when the mouth is closed. There…

  • Hydrocynus goliath (fish)

    tigerfish: …five species; the largest (H. goliath) may be more than 1.8 metres (6 feet) long and may weigh more than 57 kg (125 pounds). The smaller H. vittatus is claimed to be one of the finest game fishes in the world.

  • Hydrocynus vittatus (fish)

    ostariophysan: Feeding habits: …ostariophysan is the tigerfish (Hydrocynus vittatus), which attains a weight exceeding 45 kg (approximately 100 pounds); its huge, sharp teeth and large, tunalike tail endow it with ferocity and speed. Parasitic habits are rarely found among bony fishes, but certain species of trichomycterid catfishes attach themselves to the gills…

  • Hydrocyon (fish genus)

    tigerfish: …freshwaters, tigerfishes of the genus Hydrocynus (sometimes Hydrocyon) are admired game fishes of the characin family, Characidae (order Cypriniformes). They are marked, depending on the species, with one or several dark, lengthwise stripes and are swift, voracious, salmon-shaped carnivores with daggerlike teeth that protrude when the mouth is closed. There…

  • Hydrodamalis gigas (extinct mammal)

    Sea cow, (Hydrodamalis gigas), very large aquatic mammal, now extinct, that once inhabited nearshore areas of the Komandor Islands in the Bering Sea. Steller’s sea cows were wiped out by hunters in the 18th century less than 30 years after they were first discovered by Arctic explorers. Today, the

  • hydrodesulfurization

    organosulfur compound: Sulfides: Molybdenum-containing hydrodesulfurization catalysts are used in the removal of the undesirable sulfur compounds from petroleum, giving hydrocarbons and hydrogen sulfide as the final products. There is considerable interest in the use of monomeric and polymeric compounds made from heterocyclic sulfur compounds—such as thiophene, tetrathiafulvalene (TTF), and…

  • Hydrodictyon (green algae)

    Water net, (genus Hydrodictyon), genus of filamentous green algae (family Hydrodictyaceae) sometimes found on the surface of quiet freshwater bodies. Because of its reproductive efficiency, Hydrodictyon proliferates rapidly and can be a problem in ponds, recreational waters, and irrigation canals.

  • Hydrodictyon

    Hydrodictyon, genus of green algae known as water nets

  • hydrodynamic brake (machine component)

    brake: A hydrodynamic (fluid) brake has a rotor (rotating element) and a stator (stationary element) that resemble the impeller and runner in a hydraulic coupling. Resistance to rotation is created by fluid friction and circulation of the liquid (usually water) from a series of pockets in the…

  • hydrodynamic concept (physiology)

    human ear: Detection of angular acceleration: dynamic equilibrium: …working independently, proposed the “hydrodynamic concept,” which held that head movements cause a flow of endolymph in the canals and that the canals are then stimulated by the fluid movements or pressure changes. German physiologist J.R. Ewald showed that the compression of the horizontal canal in a pigeon by…

  • hydrodynamic film (lubrication)

    bearing: …this is known as a hydrodynamic film. An oil film can also be developed with a separate pumping unit that supplies pressurized oil to the bearing; this is known as a hydrostatic film.

  • hydrodynamic trapping (geology)

    petroleum: Traps: A rare exception is hydrodynamic trapping, in which high water saturation of low-permeability sediments reduces hydrocarbon permeability to near zero, resulting in a water block and an accumulation of petroleum down the structural dip of a sedimentary bed below the water in the sedimentary formation.

  • Hydrodynamica (work by Bernoulli)

    Daniel Bernoulli: …was established in 1738 with Hydrodynamica, in which he considered the properties of basic importance in fluid flow, particularly pressure, density, and velocity, and set forth their fundamental relationship. He put forward what is called Bernoulli’s principle, which states that the pressure in a fluid decreases as its velocity increases.…

  • hydrodynamics (physics)

    fluid mechanics: Hydrodynamics: Up to now the focus has been fluids at rest. This section deals with fluids that are in motion in a steady fashion such that the fluid velocity at each given point in space is not changing with time. Any flow pattern…

  • Hydrodynamics (work by Lamb)

    Sir Horace Lamb: …was enlarged and transformed into Hydrodynamics (1895); the latter was for many years the standard work on hydrodynamics. His other publications include Infinitesimal Calculus (1897), Dynamical Theory of Sound (1910), Statics (1912), Dynamics (1914), and Higher Mechanics (1920). His many papers, principally on applied mathematics, detailed his researches on wave…

  • hydroelectric power

    Hydroelectric power, electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy. In the generation of hydroelectric power, water is collected or stored at a higher elevation and led downward through large pipes

  • hydroelectricity

    Hydroelectric power, electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy. In the generation of hydroelectric power, water is collected or stored at a higher elevation and led downward through large pipes

  • hydrofluoric acid (chemical compound)

    petroleum refining: Polymerization and alkylation: Hydrofluoric acid is also used as a catalyst for many alkylation units. The chemical reactions are similar to those in the sulfuric acid process, but it is possible to use higher temperatures (between 24 and 46 °C, or 75 to 115 °F), thus avoiding the…

  • hydrofluorination process (metallurgy)

    uranium processing: Conversion and isotopic enrichment: This hydrofluorination process is usually performed in a fluidized-bed reactor.

  • hydrofluorocarbon

    Hydrofluorocarbon (HFC), any of several organic compounds composed of hydrogen, fluorine, and carbon. HFCs are produced synthetically and are used primarily as refrigerants. They became widely used for this purpose beginning in the late 1980s, with the introduction of the Montreal Protocol, which

  • hydrofoil

    Hydrofoil, underwater fin with a flat or curved winglike surface that is designed to lift a moving boat or ship by means of the reaction upon its surface from the water through which it moves. Ships that use hydrofoils, or foils, are themselves called hydrofoils. Hydrofoils can lift a boat’s hull

  • hydroformylation (chemical reaction)

    coordination compound: Coordination compounds in industry: …as hydridotetracarbonylcobalt, of the so-called hydroformylation of olefins—i.e., of their reactions with hydrogen and carbon monoxide to form aldehydes—and the catalysis by tetrachloropalladate(2−) ions of the oxidation of ethylene in aqueous solution to acetaldehyde (see chemical reaction and

  • hydrofracking (engineering)

    Fracking, in natural gas and petroleum production, injection of a fluid at high pressure into an underground rock formation in order to open fissures and allow trapped gas or crude oil to flow through a pipe to a wellhead at the surface. Employed in combination with improved techniques for drilling

  • hydrogarnet (mineral)

    garnet: Chemical composition: Other hydrogarnets have been reported—e.g., hydroandradite and hydrospessartine; the general formula for hydrogarnets would be A3B2(SiO4)3 - x(H4O4)x, and the general formula for an end-member hydrogarnet would be A3B2(H4O4)3.

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