All articles starting with H
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Hydrangea Garden
A hydrangea garden (ajisai-en) is a garden, park, or temple ground planted with hydrangeas, especially bigleaf hydrangea, as a seasonal flower attraction, mainly in Japan.
Hydrangea macrophylla (紫陽花)
Hydrangea macrophylla (紫陽花), bigleaf or French hydrangea, a Japanese deciduous shrub with mophead or lacecap flower heads; blue in acidic soil, pink in alkaline, blooming on old wood with reblooming cultivars like Endless Summer.
Hydraotes Chaos
Hydraotes Chaos, a roughly 418-km-wide chaotic terrain on Mars east of Valles Marineris, IAU-named 1976 after the Ravi River; deep subsidence terrain with cinder-cone-like volcanism and Amazonian aquifer sediments.
Hydrate
A hydrate, also called a crystallohydrate, is a compound whose crystal structure includes water molecules in a fixed ratio, such as copper(II) sulfate pentahydrate, CuSO₄·5H₂O.
Hydration force
The hydration force is a short-range repulsive force between hydrophilic surfaces in water, arising from the energy needed to remove bound water as the surfaces approach.
Hydration reaction
A hydration reaction is a chemical reaction in which water, or its H and OH elements, is added to a molecule, most often converting an alkene into an alcohol.
Hydraulic accumulator
A hydraulic accumulator, or pressure accumulator, is a pressure vessel that stores energy in a hydraulic system by compressing nitrogen gas and releasing fluid on demand.
Hydraulic actuation
Hydraulic actuation converts the energy of pressurized liquid, usually oil, into force and motion via Pascal's law, favored in robots for high power density and impact robustness.
Hydraulic and osmotic artificial muscles
Hydraulic and osmotic artificial muscles are soft actuators that generate motion from liquid rather than a motor, contracting under fluid pressure or deforming as water crosses a membrane.
Hydraulic artificial muscle
A hydraulic artificial muscle is a fluid-driven actuator that contracts like a biological muscle when pressurized with oil or water, offering faster response and higher efficiency than pneumatic muscles.
Hydraulic brake
A hydraulic brake, or hydraulic braking, is a braking system that transmits the operator's pedal force to the wheels through incompressible brake fluid, working on Pascal's law.
Hydraulic conductivity
Hydraulic conductivity, also called hydraulic permeability, measures how easily water moves through a porous or fractured material, and it has the units of a velocity.
Hydraulic control
Hydraulic control is the condition in stratified or open-channel flow where long waves cannot travel upstream, typically at a sill crest, governing exchange through straits and fjords.
Hydraulic cylinder
A hydraulic cylinder is a linear actuator that converts the pressure of hydraulic fluid into mechanical force and motion, powering construction machinery, presses, machine tools, and dump trucks.
Hydraulic diameter
The hydraulic diameter is a characteristic length used in fluid mechanics for noncircular ducts, defined as four times the flow cross-sectional area divided by the wetted perimeter.
Hydraulic engineering
Hydraulic engineering, also known as hydrotechnics or hydroengineering, is the branch of civil engineering concerned with water flow and the design of dams, canals, levees, and drainage systems.
Hydraulic fluid
Hydraulic fluid, also known as hydraulic oil or hydraulic liquid, is the liquid medium that transmits power, lubricates, cools, and seals within hydraulic systems; most are refined mineral oils.
Hydraulic geometry
Hydraulic geometry is an empirical method in fluvial geomorphology expressing a river channel's width, depth, and velocity as power functions of discharge, introduced by Leopold and Maddock in 1953.
Hydraulic head
Hydraulic head, also called piezometric head, is a measure of the total energy that moves ground water through an aquifer, expressed as a height above a datum.
Hydraulic jump
A hydraulic jump is the sudden transition of open channel flow from fast, shallow supercritical to slow, deep subcritical flow, dissipating energy in rivers, canals, and kitchen sinks.
Hydraulic lime
Hydraulic lime is a lime binder that sets and hardens through a chemical reaction with water, allowing mortars to gain strength in damp or underwater conditions, used in historic masonry repair.
Hydraulic machinery
Hydraulic machinery, also called hydraulic drive, uses liquid under pressure to transmit power, from turbines and pumps to fluid power systems with cylinders and valves.
Hydraulic power unit
A hydraulic power unit, also called a hydraulic power pack, is a packaged assembly combining a motor, pump, reservoir, and valves to supply pressurized hydraulic fluid to actuators.
Hydraulic press
A hydraulic press, also known as a Bramah press, is a machine that uses confined liquid under pressure to compress or shape a workpiece via Pascal's principle.
Hydraulic pump
A hydraulic pump is a positive-displacement machine that converts mechanical power into pressurized fluid flow, powering excavators, bulldozers, and forklifts; common types include gear, vane, and piston pumps.
Hydraulic ram
A hydraulic ram, or hydram, is a water pump powered by water hammer alone, needing no fuel or electricity. Joseph Montgolfier built the first self-acting version in 1796.
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.