Acoustic structure function

Acoustic structure functions for pressure coupling in an open-closed tube, for the fundamental and first harmonic. 

Si is the laminar flame velocity, the function Z(co) is the heat response function Equation 5.1.16, whose real part is plotted in Figure 5.1.10. The function f(r, giJ is a dimensionless acoustic structure factor that depends only on the resonant frequency, a , the relative position, r, of the flame, and the density ratio Pb/Po-... 

Figure 24-1. Nitrogen adsorption/desorption isotherms of a mesoporous film with cubic structure functionalized with -CNgroups after surfactant removal by solvent extraction were measured by a surface acoustic wave (SAW) technique andyieldeda type IVisotherm with a very narrow hysteresis loop that is typicalfor mesoporous materials. Inset is pore size distribution calculated from adsorption isotherm. (Liu, N., Assink, R. A. and Brinker, C. J. Chem. Commun. 2003 370-371, Reproduced by permission of The Royal Society of Chemistry)...

Inside the atria of tunicates are numerous microscopic structures known as cupular organs which are probably acoustic in function and homologous with neuromasts (Bone and Ryan 1978). 

Pressure-sensitive adhesives (PSAs) based on acrylic, natural rubber and silicone are employed primarily for ease of application. To name Just a few applications, PSAs bond decals to surfaces, interior decorative surfaces to interior panels, interior trim pieces in place directly or hook and loop tape for the same purpose, structural shims in place during manufacturing and acoustic (sound deadening) materials to body skin interior surfaces. Tape products with pressure-sensitive adhesive on one or both surfaces are used for such functions as cargo compartment sealing, as a fluid barrier to prevent spills and leaks in the lavatories and... 

The toughness of a material is a design driver in many structures subjected to impact loading. For those materials that must function under a wide range of temperatures, the temperature dependence of the various material properties is often of primary concern. Other structures are subjected to wear or corrosion, so the resistance of a material to those attacks is an important part of the material choice. Thermal and electrical conductivity can be design drivers for some applications, so materials with proper ranges of behavior for those factors must be chosen. Similarly, the acoustical and thermal insulation characteristics of materials often dictate the choice of materials. 

Fig. 13.17 shows the structure and principle of a T-bumer, as used to measure the response function of propellants. Two propellant samples are placed at the respective ends of the T-burner. The burner is pressurized with nitrogen gas to the test pressure level. The acoustic mode of the burning established in the burner is uniquely determined by the speed of sound therein and the distance between the burning surfaces of the two samples. When the propellant samples are ignited, pressure waves travel from one end to the other between the burning surfaces of the samples. When a resonance pressure exists for a certain length of the T-bumer, the propellant is sensitive to the frequency. The response function is determined by the degree of amplification of the pressure level. 

The Eulerian finite difference scheme aims to replace the wave equations which describe the acoustic response of anechoic structures with a numerical analogue. The response functions are typically approximated by series of parabolas. Material discontinuities are similarly treated unless special boundary conditions are considered. This will introduce some smearing of the solution ( ). Propagation of acoustic excitation across water-air, water-steel and elastomer-air have been computed to accuracies better than two percent error ( ). In two-dimensional calculations, errors below five percent are practicable. The position of the boundaries are in general considered to be fixed. These constraints limit the Eulerian scheme to the calculation of acoustic responses of anechoic structures without, simultaneously, considering non-acoustic pressure deformations. However, Eulerian schemes may lead to relatively simple algorithms, as evident from Equation (20), which enable multi-dimensional computations to be carried out in a reasonable time. 

Earlier Toyozawa et al. 153> formulated a dynamic model for the behaviour of the vibrational excitation. This clarified and improved upon the classical description of a non-diffusing wave-packet. Such description appears justifiable for F-centres whose optical bands are broad and diffuse not exhibiting any fine structure that might be indicative of discrete, quantised vibrational levels. (The relatively large spatial extent of the F-centre electronic wave functions also favours the involvement of long wavelength acoustic vibrations. For these a classical description can be appropriate.)... 

---