and 1-1/2 liters. Note that the sum of the vital 

 capacity plus the residual volume equals the total 

 lung capacity. (37) 



RESISTANCE WIRE WAVE STAFF . This fixed wave gage 

 type instrument consists of an oscillator, a vacu- 

 um tube voltmeter, a recording milliammeter, and a 

 continuous length of Chromel wire which is strung 

 through a telescopic stainless steel tube. The 

 resistance of the Chromel wire changes linearly as 

 the sea water moves up and down its length. A full 

 scale deflection equivalent to 15 feet of wave 

 height is possible on the recorder. 



Since the diameter of the wire is small, the 

 sea water tends to drain off rapidly as the trough 

 of a wave passes the gauge. Thus, the "wetting" 

 problem which has troubled the operation of other 

 fixed wave gauges in the past is overcome. (35) 



RESISTIVITY PROBE-ELECTRODELESS . This device is 

 used to determine resistivity of large bodies of 

 water or other conducting liquid in a large vessel. 

 The probe has an input and output coil, both mounted 

 on toroidal cores of identical dimensions and pro- 

 perties . Number of output turns is a multiple of 

 the number of input turns . The two coils are 

 mounted on a glass tube. The whole assembly being 

 potted in epoxy resin. When the probe is immersed 

 in a conducting fluid and a.c. voltage is applied 

 to the input coil, current loops are established 

 which go through the cylindrical opening and around 

 the outside of the block. The voltage appearing at 

 the output coil is then a function of the resistance 

 of the fluid. The probe, because it is a dipole, 

 is not influenced by discontinuities in the medium, 

 unless they are very close to the ends of the probe. 

 (30) 



RESONANCE ■ Resonance of a system in forced oscil- 

 lation exists when any change, however small, in 

 the frequency of excitation causes a decrease in 

 the response of the system. (2) 



RESPIRATION . The process of drawing air, or another 

 breathing medium, into the lungs to supply oxygen 

 and purify the blood. (37) 



RESPIRATORY CYCLE . One complete "breath" - an 

 inspiration followed by an expiration, including 

 any pause that may occur between the movements. 

 (37) 



RESPIRATORY DEAD SPACE . That part of the respira- 

 tory system which has no alveoli and in which 

 little or no exchange of gas between air and blood 

 takes place. It normally amounts to less than 0.2 

 liter but becomes larger as the depth of breathing 

 increases. Air which occupies the dead space 

 during each breath does not take part in the active 

 process of breathing. Certain parts of a diver's 

 breathing apparatus can add to the volume of the 

 dead space and thus reduce the proportion of the 

 tidal volume which serves the purpose of respira- 

 tion. To compensate, the diver must increase his 

 tidal volume. (37) 



RESPIRATORY EXHAUSTION . Resistance to underwater 

 breathing has four components: 1) airway resis- 

 tance caused by valves, length and diameter of 

 tubing, and possibly inertial factors due to the 

 density of the inspired gas at increased depth; 

 2) hydrostatic resistance caused by the difference 

 in pressure between the level of the swimmer's 

 center of breathing (most commonly believed to be 

 at the bottom of his throat) and the level of the 

 inlet or demand valve; 3) inertial resistance in- 

 troduced by the inertia of water which must be 

 displaced during respiratory movements of the chest; 

 and 4) miscellaneous factors such as the resistance 

 of breathing bag fabric to inflation and deflation. 

 (37) 



RESPIRATORY MINUTE VOLUME (RMV) . The total amount 



of air moved in and out of the lungs in a minute. 

 Multiplying the tidal volume times the rate gives 

 the respiratory minute volume. Minute volume 

 varies greatly with the body's activity. It is 

 about 6 liters at complete rest and may be over 

 100 liters during very heavy work. (37) 



RESPIRATORY QUOTIENT . The ratio between the amount 

 of carbon dioxide produced and the amount of oxygen 

 consumed in breathing. The average value for a 

 working diver is 0.9. This means that 9/10 's of 

 every liter of C02 is produced for every liter of 

 oxygen consumed. (37) 



RESPIRATORY RATE (FREQUENCY) . Indicates the num- 

 ber of complete respiratory cycles that take place 

 in 1 minute. At rest, a normal adult will have a 

 respiratory rate somewhere between 10 and 20 

 "breaths" per minute. The rate normally increases 

 during work. (37) 



RESPONSE . The response of a device or system is 

 the motion or other output resulting from an ex- 

 citation or stimulus under special conditions. (9) 



RESTING SPORE . A SPORE that remains dormant for a 

 period before germination and is usually invested 

 with a thickened cell wall to withstand adverse 

 conditions (as of desiccation, heat, or cold). (20) 



RETROGRESSION . See RECESSION (OF A BEACH). 



REVERBERATION . (1) Reverberation is the persis- 

 tence of sound in an enclosed space as a result of 

 multiple reflections after the sound source has 

 stopped. (2) Reverberation is the sound that per- 

 sists in an enclosed space, as a result of repeated 

 reflection or scattering, after the source of the 

 sound has stopped. (1) 



REVERBERATION FACTOR . The reverberation factor for 

 a reversible sonar transducer, for a specified fre- 

 quency, may be defined as the ratio of (1) the 

 available power per unit band of the electric ener- 

 gy generated at the specified frequency by the 

 transducer when receiving over all bearings acous- 

 tic energy which has previously been radiated over 

 these bearings by the transducer in response to 

 electric energy having a given power per unit band 

 at the specified frequency, and which has then been 

 returned to the transducer by propagation paths of 

 equal length and equal transmission loss, to (2) 

 the available power per unit band of the electric 

 energy which would be generated at the same fre- 

 quency and when receiving over the same bearings 

 the acoustic energy which would have been radiated 

 over those bearings in response to the same pre- 

 viously received electric energy and returned by 

 the same propagation paths , if the transmitting 

 and receiving responses of the transducer for that 

 frequency were the same for any bearing as for the 

 maximum response reference bearing. (4) 



REVERBERATION INDEX . Measure of the ability of an 

 echo-ranging transducer to distinguish the desired 

 echo from the reverberation. Computed from the 

 directivity patterns as ratio in decibels of the 

 bottom, surface, or volume reverberation response 

 of a specific transducer to the corresponding 

 response of a non-directional transducer. (5) 



REVERBERATION STRENGTH . Reverberation strength 

 may be defined as the difference between the level 

 of a plane wave producing in a non-directional 

 transducer a response equal to that produced by 

 the reverberation corresponding to a range of one 

 yard from the effective center of the transducer 

 and the index level of the pulse transmitted, 

 on any bearing, by the same non-directional trans- 

 ducer. (4) 



REVERBERATION-SUPPRESSION FILTERS . The circuits 

 by which selective discrimination may be provided 



99 



