# MEAN ELEMENTS

Elements of an adopted reference orbit that approximates the actual, perturbed orbit. Mean elements serve as the basis for calculating perturbations.

## Related Terms

### DIRECTIVITY FACTOR

1. The ratio of radiated sound intensity at a remote point on the principal axis of a loudspeaker or other transducer, to the average intensity of the sound transmitted through a sphere passing through the remote point and concentric with the transducer; the frequency must be stated.
2. The ratio of the square of the voltage produced by sound waves arriving parallel to the principal axis of a microphone or other receiving transducer, to the mean square of the voltage that would be produced if sound waves having the same frequency and mean-square pressure were arriving simultaneously from all directions with random phase; the frequency must be stated.

### PLAN EQUATION

The mathematical statement that horsepower plan/33,000, where p mean effective pressure (pounds per square inch), l length of piston stroke (feet), a net area of piston (square inches), and n number of cycles completed per minute.

### NYQUIST'S THEOREM

The mean square noise voltage across a resistance in thermal equilibrium is four times the product of the resistance, Boltzmann's constant, the absolute temperature, and the frequency range within which the voltage is measured.

### NOMINAL PASS-BAND CENTER FREQUENCY

The geometric mean of the nominal upper and lower cutoff frequencies of an acoustic or electric filter.

### MEAN STRESS

1. The algebraic mean of mean stress mean temperature difference the maximum and minimum values of a periodically varying stress. 2. See octahedral normal stress.

### MEAN NORMAL STRESS

In a system stressed multiaxially, the algebraic mean of the three principal stresses.

### KALMAN FILTER

A linear system in which the mean squared error between the desired output and the actual output is minimized when the input is a random signal generated by white noise.

### HOLLANDFORMULA

Aformulausedtocalculate the height of a plume formed by pollutants emitted from a stack in terms of the diameter of the stack exit, the exit velocity and heat emission rate of the stack, and the mean wind speed.

### HEAT QUANTITY

A measured amount of heat; units are the small calorie, normal calorie, mean calorie, and large calorie.

### HALF-TIDE LEVEL

A tidal datum midway between mean high water and mean low water. Mean sea level may coincide with half-tide level, but seldom does; the variation is generally about 3 centimeters and rarely exceeds 6 centimeters. Also called MEAN TIDE LEVEL.

### Related questions

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