Any non-frontal line or band of convective activity in the atmosphere. This is the general term and includes the developing, mature, and dissipating stages. However, when the mature stage consists of a line of active thunderstorms, it is properly called SQUALL LINE; therefore, in practice, instability line often refers only to the less active phases. Instability lines are usually hundreds of miles long (not necessarily continuous), 10 to 50 miles wide, and are most often formed in the warm sectors of wave cyclones. Unlike true fronts, they are transitory in character, ordinarily developing to maximum intensity in less than 12 hours and then dissipating in about the same time. Maximum intensity is usually attained in late afternoon.
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RESTRICTOR
A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area.
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MODULATING WAVE
A wave which modulates a carrier wave.
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GRID RHUMB LINE
A line making the same oblique angle with all grid meridians. Grid parallels and meridians may be considered special cases of the grid rhumb line.
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HAND LEAD
A light sounding lead (7 to 14 pounds), usually having a line of not more than 25 fathoms
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GROUND LOG
A device for determining the course and speed over the ground in shallow water consisting of a lead or weight attached to a line. The lead is thrown overboard and allowed to rest on the bottom. The course over ground is indicated by the direction the line tends and the speed by the amount of line paid out in a unit of time.
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CASE DRAIN FILTER
A filter located in a line conducting fluid from a pump or motor housing to reservoir.
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ELASTOHYDRODYNAMIC LUBRICATION
In rolling element bearings, the elastic deformation of the bearing (flattening) as it rolls, under load, in the bearing race. This momentary flattening improves the hydrodynamic lubrication properties by converting point or line contact to surface-to-surface contact.
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ANGSTROM UNITS
A unit of wave length, equal in length to one ten billionth.
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GRID PARALLEL
A line parallel to a grid equator, connecting all points of equal grid latitude
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HARBOR LINE
The line beyond which wharves and other structures cannot be extended
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