Signal velocity

Signal velocity Cross correlation Cross spectrum Cross spectrum and cross correlation... 

The experimental knowledge reached to date on kinematic waves in two-phase flows has been summarized. The existence of more than one kinematic mode has been brought out naturally, thanks to the use of several pairs of probes distributed along the test section and to a double determination of the apparent signal velocity. 

For low loss and lossless lines the signal velocity and characteristic impedance can be expressed as... 

Example 3 Signalling velocity constraints to the train conductor... 

Table 14. Selection of the test-technique for signal velocity constraints...

FIGURE 13.3 Signal velocity as a function of dielectric constant. (Prepared by Shared Resources, Inc., 1991.)... 

Material Veloeity. Defines the velocity, in metres/sec, of ultrasound in the material of the test piece used to convert A-scan signal time to distances within the test piece. 

New test, after these modification s, showed better measurements up to 350 m/min but now it also became evident that oil from the drawing process build up on the transducer surface and damped the signals and made measurements impossible. The oil build up as a combination of inspection length (m of tubes) and inspection speed. At lower drawing velocities (70 m/min) the oil obvious was washed away giving no inspection problems. The water system was modified as follows ... 

Figure Bl.14.13. Derivation of the droplet size distribution in a cream layer of a decane/water emulsion from PGSE data. The inset shows the signal attenuation as a fiinction of the gradient strength for diflfiision weighting recorded at each position (top trace = bottom of cream). A Stokes-based velocity model (solid lines) was fitted to the experimental data (solid circles). The curious horizontal trace in the centre of the plot is due to partial volume filling at the water/cream interface. The droplet size distribution of the emulsion was calculated as a fiinction of height from these NMR data. The most intense narrowest distribution occurs at the base of the cream and the curves proceed logically up tlirough the cream in steps of 0.041 cm. It is concluded from these data that the biggest droplets are found at the top and the smallest at the bottom of tlie cream.

A molecular beam scattering experiment usually involves the detection of low signal levels. Thus, one of the most important considerations is whether a sufficient flux of product molecules can be generated to allow a precise measurement of the angular and velocity distributions. The rate of fonnation of product molecules, dAVdt, can be expressed as... 

The velocity distribution/(v) depends on the conditions of the experiment. In cell and trap experiments it is usually a Maxwell-Boltzmann distribution at some well defined temperature, but /(v) in atomic beam experiments, arising from optical excitation velocity selection, deviates radically from the nonnal thennal distribution [471. The actual signal count rate, relates to the rate coefficient through... 

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