Power Watts Research Articles

Torque-velocity relationship in isokinetic cycling exercise.

Seven healthy female subjects performed brief (less than 10 s) periods of maximal exercise on a constant-velocity cycle ergometer, over the functional range of pedaling velocities, and an isometric contraction with each leg. There was an inverse relationship between peak torque and pedal crank velocity in all subjects; isometric torque was (mean +/- SE) 19.8 +/- 8.3% greater than the torque recorded at the slowest velocity of 11 rpm. The torque-velocity relationship was described best by a single exponential equation: y = 189.6 X e-0.0834x, where y is peak torque in Newton . meters and x is crank velocity in revolutions per minute. Peak power was a parabolic function of crank velocity; the data were fitted suitably by a second-order polynomial equation: y = -0.0589x2 + 14.504x + 47.092, where y is peak power in watts and x is crank velocity in revolutions per minute. Maximal peak power occurred at crank velocities ranging from 120 to 160 rpm, when the torque was 0.36 +/- 0.06 of the maximal isometric tension. These results demonstrate the importance of recording velocity in measurements of dynamic maximal power.

Plasma polymerization of tetramethyldisiloxane by a magnetron glow discharge

Plasma polymerization of tetramethyldisiloxane by a magnetron glow discharge was studied. The glow discharge was created between parallel electrodes with a 10 kHz electric power source with a superimposed magnetic field using permanent bar magnets. Polymers were deposited onto moving substrates placed on the surface of a rotating disc located in between the electrodes. The deposition rates were determined with a quartz crystal thickness monitor placed on the plane of the rotating disc and just outside the edge of the disc. The current-voltage relationship observed for plasma polymerization of the monomer depends on the monomer feed rate and the conditioning of the electrodes or the establishment of a steady state surface in the polymer-forming plasma, which also depends mainly on the monomer feed rate. Consequently, plasma polymerization cannot be correlated to single operational parameters such as the discharge current, the power or the monomer feed rate in a simple manner. However, when the deposition rate was expressed as R p/ FM, where R p is the polymer deposition rate, F is the monomer feed rate and M is the molecular weight ( FM is thus the monomer mass feed rate), it was found that R p/ FM is uniquely related to the parameter W/FM where W is the discharge power in Watts. It was shown that many polymer properties were also determined mainly by the same composite parameter. It was also found that the presence of O 2 gas in the monomer feed reduced the carbon content in the polymer and made the surface more hydrophobic while O 2 plasma treatment of the plasma polymer rendered the surface more hydrophilic.

Acoustic intensity measurements of the sound power of a truck

An indoor method of measuring the sound power of a truck is described in which acoustic-intensity measurements are made over a hypotheoretical “shoe-box” surface enclosing the truck in the near field and integrated to obtain the total radiated sound power. Tests were run on a quieted dynamometer roll at three different speeds. The same vehicle was tested on two separate occasions, two months apart. Excellent repeatability was obtained, typically ±2% in the sound power in watts. Tests were run both in a semi-anechoic environment and with boards covering up the acoustically absorbing material on the walls, with negligible effect on the sound power measurement.

Observations of the 63 micron forbidden OI emission line in the Orion and Omega Nebulae

The 63 micron fine structure transition P4 : 3Pl yields 3P2 for neutral atomic oxygen was obtained during a series of flights at an altitude of approximately 13.7 km. In the Orion Nebula (M42), the observed line strength was 8 x 10 to the minus 15 power watt cm/2 which is estimated to be approximately 0.3 o/o of the energy radiated at all wavelengths. For the Omega Nebulae (M17), the line strength was 2.4 x 10 to the minus 15 power watt cm/2, and the fraction of the total radiated power was slightly higher. These figures refer to a 4' x 6' field of view centered on the peak for infrared emission from each source. The uncertainty in the line strength is approximately 50% and is caused by variable water vapor absorption along the flight path of the airplane. The line position estimate is 63.2 micron (+0.1, -0.2) micron. The prime uncertainty is due to the uncertain position of the (0 I) emitting regions in the field of view.

Direction-finding measurements of auroral kilometric radiation

Direction finding measurements with plasma wave experiments onboard the Hawkeye-1 and IMP-8 satellites were used to locate the source region of auroral kilometric radiation. The radiation exhibits peak intensities between about 100 kHz and 300 kHz, and emits intense sporadic bursts lasting for between one half hour to several hours. The total power emitted in this frequency range exceeds 10 to the 9th power watts at peak intensity. The occurrence of the radiation is known to be closely associated with bright auroral arcs which occur in the local evening auroral regions.

An experimental study of the effects of upstream obstructions upon subsonic jet noise

Results obtained for noise produced by two obstructions—one circular (1 inch diameter x 2·84 inch long) and another rectangular (0·4 inch thick x 1 inch wide x 2·84 inch long) in shape—immersed in both “clean” and turbulent flows 4·8 inches upstream of the nozzle exit are described. Variations of overall sound pressure levels (OASPL's) and power Watt levels (PWL's) with jet exit velocity (Vj) and the directivities of OASPL's are considered in detail. Considerable care was taken to ensure that any comparison of the obstruction generated noise with the “clean” jet noise is for the same mean jet exit velocity and thrust. The mean jet exit velocity was derived from the measured velocity profile at the nozzle exit in each case. For the same mean exit velocity and nozzle diameter, the noise levels with the circular obstruction were measured to be as much as 40 dB higher than the “clean” jet noise. The rectangular obstruction increased the noise by up to 10 dB. Flow over these obstructions generated discrete tones as well. The velocity index for the obstruction generated noise were between 8 and 9 between Vj=350 ft/s and 1000 ft/s. This contradicts the traditional V6 law. The main reason for the discrepancy has been attributed to the variation of the coefficient of fluctuating lift, C L 2 ¯ , with Reynolds number. The angle of peak overall sound pressure levels (OASPL's) was between 45° and 60°, as compared to between 0° and 20° for the clean jet noise. When the obstructions were immersed in turbulent flows most of the discrete tones which were obtained from the obstructions in smooth flows disappeared. The high frequency noise levels, however, increased by as much as 20 dB.

Spectral Distribution of the Decametric Radiation from Jupiter in 1961.

Abstract : Observations of the sporadic radiation from Jupiter were made in 1961 at observatories in Florida, in Australia, and in Chile, at various frequencies from 5 Mc/s to 85.5 Mc/s. A method was developed for computing the mean flux density for the apparition from measurements of peak flux density in consecutive 10-min intervals. Occurrence probability, peak flux density, and mean flux density for the apparition were determined as functions of frequency, and all three quantities were found to decrease monotonically with increase in frequency above 10 Mc/s. The decrease in mean flux density with increasing frequency indicated a spectral index in excess of 5.2 over much of the observed spectrum. Peak flux densities at 5 Mc/s and 10 Mc/s were about 10 to the minus 19th power W/sq m (c/s). No activity was detected at 85.5 Mc/s. The ratio of mean flux density to peak flux density for 1-min intervals during noise storms was found to be essentially independent of frequency, suggesting that there is no appreciable change of noise-burst shape with frequency. The mean power emitted at decameter wavelengths by Jupiter in 1961 was estimated to be about 5 X 10 to the 10th power watts, which is 1 or 2 orders of magnitude greater than that emitted at decimeter wavelengths. The average efficiency with which the solar-wind power incident on the Jovian magnetosphere is converted into decametric radiation power was estimated to be about 0.00001. (Author)

Noise Radiation from Tropical Thunderstorms in the Standard Broadcast Band

AN objective method of measuring atmospheric noise interference to broadcasting based on subjective observations and statistical considerations has been reported1. Results of systematic measurements by the method in the 3 and 5 Mc./s. bands have been published2 3. It has been shown that these results can be satisfactorily explained on the basis of the available data on lightning discharges4, the distribution of thunderstorm days5, the growth and decay of thunderstorms6, and the laws of propagation. For this purpose, the available data on lightning discharges have been utilized to deduce an idealized statistically valid representation of a typical flash as it occurs in a tropical thunderstorm4. It is found that where P is the power in watts and f is the frequency in Mc./s.

Noise of Ventilating Fans

Using the apparatus described by Reynolds, Wilson, and Beranek, measurements were made of the acoustic power in watts in twenty-four bands each one-third octave wide for three vaneaxial-type and two centrifugal-type fans of grades sizes. Formulas were derived empirically, enabling the computation of the over-all acoustic power of the noise for the exhaust end of a fan where the input electrical power, the number of blades, blade tip speed, and other design characteristics are known. The formulas are very similar to those developed for aircraft propellers by Rudmose and Beranek. The directivity pattern and acoustic power generated for each of the 24 bands was also measured at the inlet with the fan mounted in one end of a long duct outdoors. The effects of back pressure were also determined. As a second stage of this investigation, the acoustical characteristics of unlined ducts were studied. The attenuation effects of one and two 90° unlined bends placed in the 10-inch × 12-inch duct system were determined. The greatest amount of attenuation was found in those frequency bands that contained the frequencies for which the width of the duct, in the direction of the bend, was 0.5 wavelength and 1.5 wavelength.