Acoustic transmission factor

Acoustic transmission factor T Average linear gas velocity IX... 

Q is the acoustic quality factor of the film. It depends on all interfacial transmission and reflection coefficients, and therefore contains all the complexity indicated above. On the level of this review, we regard Q as a scaling coefficient, but note that it can be calculated in detail [36],... 

Despite such wide divergences, the basic point of commonality is that both bacteria and whales live in environments where the physical controls imposed by the physico-chemical properties of water - be they viscosity or acoustic transmission -predetermine what is biologically possible. To this simple example could be added many other physical and chemical constraints. In the case of water - echoing Lawrence Henderson s (1913) prescient remarks on the way in which the physicochemical glove matches the hand of life - one could list such factors as its power as a solvent, dielectric properties, transparency, latent heat of evaporation, and decrease of density when frozen. These properties are all central in various ways to life... 

The resolution of the time delay measurement, and therefore the velocity resolution, will depend on the spread in the correlation function which in turn will depend on (i) the range of particle speeds coupled with the distance between the detectors and (ii) the spatial (hence time) resolution of the detectors. In the case of capacitance sensors, the spatial resolution will be approximately the length of the electrodes in the direction of flow, whereas in a radiation absorption technique the width of the received beam will be the determining factor. The spatial resolution of pressure and acoustic signals is much longer as the acoustic transmission properties of the gas and (in the case of acoustic techniques) the pipe is relevant. 

The use of air-bome ultrasound for the excitation and reception of surface or bulk waves introduces a number of problems. The acoustic impedance mismatch which exists at the transducer/air and the air/sample interfaces is the dominant factor to be overcome in this system. Typical values for these three media are about 35 MRayls for a piezo-ceramic (PZT) element and 45 MRayls for steel, compared with just 0.0004 MRayls for air. The transmission coefficient T for energy from a medium 1 into a medium 2 is given by... 

For discussion of the consequences of acoustic wave velocity and coupUng factor for sensor apphcations we recall the electrical impedance, Z, as it can be derived from the one-dimensional transmission Une model [22,23] ... 

The PSL and NL for the HYGAS test in the frequency range of 100-500 kHz are plotted in Fig. 5-5, which shows that the PSL is higher than the NL for the entire frequency range of interest. The results also indicate that the transmission loss is the primary factor that will limit the utility of any acoustic/ultrasonic device. The background noise is relatively small, especially in the higher frequency range. 

The combustion roar associated with flares typically peaks at a frequency of approximately 63 Hz while combustion roar associated with burners can vary in the 200-500 Hz range. Burner noise can have a spectrum shape and amplitude that can vary with many factors. Several of these factors include the internal shape of the furnace, the design of the burner muffler, plenum and tile, the acoustic properties of the furnace lining, the transmission of the noise into the fuel supply piping, and the transmissive and reflective characteristics of the furnace walls and stack. 

The factor-group analysis predicts a total of 98 lattice-vibration modes however, the character table for the point group Oh shows that the translation operations are of symmetry species Fiu only. One acoustic mode will also be found in this species and will be infrared-inactive. Therefore, this analysis predicts seventeen infrared-active lattice modes. In table 29.17, ten frequencies were listed for the RIG series. Twelve frequencies were listed for the RGaG series (table 29.19), and fifteen frequencies were listed for the RAG series (table 29.18). They suggest that the powder-transmission method does not yield all of the infrared-active modes. 

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