a. The persistence of sound in an enclosed space as a result of multiple
reflections after the sound source has stopped. Hunt
b. The sound that persists in an enclosed space, as a result of repeated
reflection or scattering, after the source of the sound has stopped.
Hunt
A furnace, with a shallow hearth, usually non-regenerative, having a roof
that deflects the flame and radiates heat toward the hearth or the surface
of the charge. Firing may be with coal, pulverized coal, oil, or gas. Two
of the most important types are the open-hearth steel furnaces and the
large reverberatories employed in copper smelting.
ASM, 1; CTD; Newton, 1
A local change of approx. 180 degrees in the direction of the regional
dip.
In the case of a centrifugal fan, the reversal arrangement may consist of
an emergency drift connecting the fan with the downcast shaft. The drift
is normally sealed off by airtight doors. In the case of an axial-flow
fan, it is only necessary to reverse the rotation of the fan. This
arrangement entails a reduction in volume and pressure in the reversed
airflow. Nelson
In surveying, a sight along the reverse direction of a line; the
reciprocal of a given bearing. See also:backsight
To bend a line over a drum or a sheave, and then in the opposite direction
over another sheave. Nichols, 1
The manner in which drill core is laid in a core box, starting at the
upper-right-hand corner of the box and laying core from right to left in
each groove. CF:snake fashion
The circulation of bit-coolant and cuttings-removal liquids, drilling
fluid, mud, air, or gas down the borehole outside the drill rods and
upward inside the drill rods. Also called countercurrent; counterflush.
See also:circulating fluid
reverse-circulation core barrel
A core barrel designed so that core tends to float within the barrel when
the fluid is circulated down the outside of the rods and returned to the
surface inside the rods. Long
In jigging, stratification of particles by size with largest uppermost; in
streaming, rolling effect of transporting current that arranges particles
with smallest nearest feed end. Pryor, 3
A method used in the braking of alternating-current winders. This method
absorbs power equal to the energy destroyed and dissipates it in the
liquid controller as heat. Two phases of the stator supply are
interchanged by bringing back the driver's lever to the off position and
then to that for the opposite direction of drum rotation. The amount of
braking depends upon the position of the lever, since the lower the
resistance in the controller, and therefore in the rotor circuit, the
greater the rotor current and the braking torque produced. When the
direction of rotation of the stator magnetic field is reversed, the
voltage between the stator and the rotor is doubled and the insulation of
both must be adequate to prevent breakdown. Sinclair, 5
See:overturned
A method of narrow heading ventilation in coal mines by means of a
brattice partition. The air is led to the face along the wide section of
the heading and the contaminated air returns from the face along the
narrow section. In this way, workers in the heading are placed in
relatively clean air. Nelson
See:reverse fault
See:counterboring
A front-end loader mounted on a wheel tractor having the driving wheels in
front and steering at the rear. Nichols, 1
A fault on which the hanging wall appears to have moved upward relative to
the footwall. The dip of the fault is usually greater than 45 degrees .
There is dip separation but there may or may not be dip slip.
CF:normal fault
AGI
To move bit and drill stem backwards away from the borehole bottom while
the drill stem is rotated. Long
System of gears in drill swivel head that can be engaged to move the bit
and drill stem backwards away from the bottom of the borehole while the
drill stem is rotated in a clockwise direction. Syn:backup gear;
reverse gear. Long