Acoustic activity

Acoustic activity (Verdejo et al. 2009 Basiijafari et al. 2012) is defined as the area under the absorption curve normalized over the frequency range and is determined as shown in Eq. (7.8) where,/i is the lower frequency at 50 Hz and/2 is the upper frequency at 1600 Hz. 

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The test with the step loading shows that acoustic activity of the solid adhesive joints in the tested carbon plastic is quite low. The maximum on the endurance area was fixed at the predestructive moment. The last is evidence to the fact that the prevailing defect of the adhesive joints is starting its development at the loading level, which is close to the destruction point. 

Because of their cellular or open-matrix construction, most insulants have an inherent ability to absorb sound, act as panel dampers and reduce noise breakout from plant by their ability to be a flexible or discontinuous link between an acoustically active surface and the outer cladding. This secondary aspect of thermal insulation specification will gain more prominence when the UK adopts the EC Directive 86/1888, Protection of workers from the risks related to exposure to noise at work . 

A Acoustically active area of the quartz crystal resonator... 

The fundamental resonant frequency (/0) shifts when a thin film is deposited on the surface of the quartz crystal. Under the assumption that the density and the shear modulus of the film are the same as those of quartz and that the film is uniform (constant density and thickness) and covering the acoustically active area of the whole... 

Although this regime is considered as a stable case some acoustic activity exists in the burner two acoustic modes are found experimentally around 300 Hz and 570 Hz and the overall sound level inside the combustor reaches 500 Pa in the LES (more than 140 dB). To identify the nature of these modes, the Helmholtz solver was used with the average temperature field given by LES to identify acoustic eigenmodes with combustion. Table 9.1 confirms that the two frequencies observed in experiments are the two first acoustic modes of the combustor. In LES, a single frequency is observed at 520 Hz, which is close to the second acoustic mode of Table 9.1. To check that the 520 Hz mode found by LES is indeed acoustic, the field of unsteady pressure given by LES is compared to the modal structure... 

One requirement for liposomes to respond to US stimulation is the presence of a US-sensitive vehicle. Thus, early research showed that acoustically active liposomes can be used as contrast agents for US image enhancement [91], Also, subsequent studies revealed that such liposomes encapsulate air — which is responsible for their acoustic activity — in their structure [92]. These acoustically active liposomes have the potential to carry drugs and their acoustic activity allows them to respond to US stimulation by releasing their contents. 

Fig. 3. Encapsulation efficiency of calcein (left) and echogenicity of acoustically active liposomes (EggPC DPPE DPPG CFI 69 8 8 15) (right) made by freeze-drying in the presence of different concentrations of mannitol. Mean SD. n=Q. Reproduced with permission from (3)...

Dilute 100 piL of the 10 mg lipid/mL calcein-containing, acoustically active liposomes, to 500 pL with 50 mM 3-mor-pholinepropanesulphonic acid (MOPS) buffer containing 110 mM NaCl (to maintain isosmolality with the liposomal contents of 320 mM mannitol and 0.1 mM calcein) into the transwell chamber. 

Fig. 7. Ultrasound-triggered release of calcein and air from acoustically active liposomes composed of EggPC DPPE DPPG CH at molar ratio of 69 8 8 15 including 4% DHPC. Mean SD, n=6. Internal control non-acoustically active liposomes were evaluated for calcein release. Reproduced with permission from (3)...

Huang SL, MacDonald RC (2004) Acoustically active liposomes for drug encapsulation and ultrasoimd-triggered release. Biochim Biophys Acta 1665 134-141... 

Significant TS applications have been described by Butteridge et al., Bellchamber et al., and Shimada, " and one example is included here. Thermo-sonimetry has been applied to study the dehydroxy-lation behavior of kaolin, which show two regions of acoustic activity. The low temperature region corresponds to dehydroxylation and the high temperature region corresponds to recrystalization as metakaolinite. The relevant temperature regions of acoustic activity are defined by the coupled DTA analysis. 

Chappell JC, Price RJ. Targeted therapeutic applications of acoustically active microspheres in the microcirculation. Microcirculation 2006 13 57-70. 

Establish a framework for modeling hydrogen-enriched lean premixed combustion in the presence of acoustically active flame processes. 

Marin A, Muniruzzaman M, Rapoport N. Acoustic activation of drug delivery from polymeric micelles Effect of pulsed ultrasound. J Control Release 2001 71 239 249. 

We can build a network of tube sections as shown in Figure C.3. The filter structure shown below which implements the chain of scattering relationships at the tube junctions is called a ladder filter. This is the basis of many models of the human voice. The reflection filters at each end represent the acoustic activity at the glottis (vocal folds) and at the lips. 

A region of rather intense acoustical activity occurred at the yield point, followed by a quieter region until a shear strain of about 1.5 was reached. At this point there was a rather abrupt increase in acoustical activity that continued to the strain at fracture which was appreciably greater than 1.5. 

The shear stress appeared to reach a maximum at strain corresponding to the beginning of the second acoustic activity (y 1.5). 

Acoustic emission has been frequently used in studies of the fracture behavior of fiber-reinforced composites. This method was also adopted to studies of blends. Since the sound is most frequently generated by debonding of two phases, there should be a drastic difference in the acoustic activity for blends located on the two sides of spinodal. To quantify miscibility between PVC and EVAc, acoustic emission measurements during a peel test of a-PVC/EVAc/PVC sandwich were carried out (Muniz et al. 1992). The authors considered that the acoustic emissions at slow rates of peeling are related not to the viscoelastic dissipation processes, but rather to the work necessary to puU apart polymeric chains or break bonds. The highest acoustic emission was obtained for VAc content in EVAc of 18 and 29 wt%. 

Fig. 7.14 Noimalized acoustic abscnption coefficient (acoustic activity) of selected matmals...

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