Absorption coefficient measurement

Assuming the normal plane wave pressure reflection coefficient at the end of duct with the test specimen is R, the steady state sound pressure at location x and at time t in the tube is given by 

If the sound pressure level difference between the maximum and minimum sound pressure is used, the normal incidence absorption coefficient can be obtained by  

The advantage of the standing wave method is simple, robust, and reliable. Unfortunately, it only measures one frequency at a time, and the procedure for locating 

Once the cross spectrum H (f) = S (f)IS (f) between two microphones is obtained, the reflection coefficient spectrum can be written as 

The main advantage of using the cross-specnum method is that it obtains the absorption coefficient of the surface for all frequencies (within limits) at the same time 

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Absorption coefficient Measure of the amount of sound or heat absorption provided by a material. 

Mass absorption coefficient, measurement for interelement corrections, 174... 

The sound absorption coefficient, a, is increased when the dynamics of the chemical system are of the same order of magnitude as the frequency of the sound wave,41 and experimentally this quantity is measured as a function of frequency of the ultrasonic sound wave (Fig. 4). When the frequency of the sound wave is of the same order as the frequency for the relaxation process, effects due to relaxation of the equilibrium give rise to characteristic changes in the quantity a//2, where a is the sound absorption coefficient measured at frequency /40 The variation of a with frequency, /, has an inflection point at the relaxation frequency of the system, fr, which is related to 1/t, where r is the relaxation time (1/t = 27i/r).40,41 The expression relating the quantity... 

Ni + ions show a broad absorption blue band that peaks at 405 nm in Mgp2 crystal, a tunable laser system. For a concentration of 2 x 10 ° cm Ni + ions, the absorption coefficient measured at 405 nm is 7.2 cm and the full width at half maximum is 8.2 x 10 Hz. Taking into account a refractive index of 1.39 for the Mgp2 crystal, estimate the oscillator strength, /, of the transition responsible for the mentioned absorption band. 

Figure 3. Wavelength dependence of the absorption coefficient (measured with light polarized perpendicular to the c-axis) of undoped and doped BaTi03 crystals. Concentrations refer to dopant atoms per BaTi03 formula unit in the melt.

This value can then be compared with a limiting F vi - V2,v ) = F, 3) value at the 95 percent confidence level from Table XXI-1 or, more conveniently, from the Lotus 1-2-3 function FDIST(1-0.95,1,3,1) = 10.128 [this function is FINV(l-0.95,1,3) in Quat-tro Pro]. Since F is less than the limiting value, the better fit of Model 2 is not statistically significant and the simpler linear model should be used. Put another way, if this test is done on an infinite number of new sets of similar absorption coefficient measurements, the decision to leave out the quadratic term will be correct 95 percent of the time. 

It is convenient to discuss three regions of the absorption spectrum, separately the Hartley band from 2000 to 3000 A., the Huggins band from 3000 to 3500 A., and the Chappuis band from 4000 to 7500 A. The results of the ozone absorption coefficients measurements are displayed in Figures 2, 3, and 4, respectively. The absorption coefficients measured by the authors are tabulated in Table I. 

Table 105. A comparison of absorption coefficients measured by the methods (1) and (2) of p. 412...

The minimum absorption coefficients measured by TLS are of the order oflO - 10 cm", which corresponds, for strong absorbers (e> 10 M" cm" ), to minimal concentrations of ca. 10""-10" "M. Some recent data from real sample analysis by TLS are listed in Table 4. 

Triplet-Triplet Molar Absorption Coefficients Measurements Singlet Depletion Method... 

Fig. 5.6 Setup for normal incidence absorption coefficient measurements within an impedance tube based on the standing wave method.

McGrory, M., Cirac, D.C., Gaussen, O., Cahrera, D., 2012. Sound absorption coefficient measurement Re-examining the relationship between impedance tube and reverberant room method. In Proceedings of Acoustics 2012—Fremantle, Australia. 

P. Rooney, Plastic Laser Welding, ANTEC, 808 (2002) M. Chen, G. Zak, P.J. Bates, Laser Absorption Coefficient Measurement of Amorphous Polymers for Laser transmission Welding, ANTEC, 2291 (2006)... 

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