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hypertension
bands, dividing each colour into a separate channel to give
a unique signature of absorption and emission.
hypertension High blood pressure.
hyperventilation Overbreathing; specif. reduced CO 2
causing * syndrome, dizziness, fainting, convulsions.
hypobaric Having atmospheric pressure much less than
normal at sea level.
hypocapnia CO 2 deficiency in blood.
hypoid Bevel or helical gears transmitting power with
some tooth-sliding action between shafts neither parallel
not intersecting.
hypoventilation Underbreathing.
hypoxaemia Condition resulting from hypoxia.
hypoxia O 2 deficiency in blood, from whatever cause.
hypsometric tints Colour gradations chosen for contrast
by natural or artificial illumination (eg. for contour bands
on topographic map).
HYR Higher.
Hyrat Hydraulic (pump driven by) ram-air turbine.
HySET Hydrocarbon-fuel scramjet engine technology.
H Y SID Hypersonic systems integrated demonstrator.
hysteresis 1 Generally, condition exhibited by system
whose state results from previous history, specif. one
whose instantaneous values lag behind prediction.
2 In ferromagnetic and some other materials, lagging of
magnetic flux density T behind magnetic field strength
A/m causing it (see * loop).
HZS
3 Effects caused by internal friction in elastic material
undergoing varying (esp. rapidly oscillating) stress.
4 Lag in instrument indication; eg that of barometric
altimeter in dive or climb.
hysteresis loop Plot of magnetising field strength against
magnetic flux density for ferromagnetic material;
traditionally called B/H curve because flux density was
called induction, symbol B, measured in gauss, and field
strength (formerly in oersteds) was identified by symbol
H; today’s units are (field strength) A/m and (flux
density) T.
HYT High year of tenure (waiver programme).
Hytech Hypersonic technology.
Hythe Ciné camera mounted on Scarff ring or similar
base for gunnery instruction; full name * camera gun.
Hytral Noise-absorbent panels of sandwich construction.
Hyways Hybrids with advanced yield for surveillance.
HZ Haze (ICAO).
Hz Hertz, SI unit of frequency, = cycles per second.
HZ Anlage System of using a piston-engine solely to
drive supercharger feeding propulsion engines [G, WW2].
H o , H zero Distance from leading edge of AMC(1) to
aerodynamic centre.
HZS Hrvatski Zrakoplovni Savez, [aeronautical sport
federation, Zagreb 10–000] (Croatia).
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