Generator, acoustic

Ara G, Anderson R,Mandel K, Oseroff AR. Absorption of ns photoradiation of melano-somes generates acoustic waves and induced pigmented melanoma cell toxicity. Photo-chem Photobiol 1988 47 37S-40S. 

A crack in a ceramic material upon initiation may accelerate and interact with microstructure, stress field and the generated acoustic vibrations. These interactions may lead to some fractographic features such as fracture mirror, hackle or river patterns and Wallner lines. 

The coupling between strain and electrical polarization that occurs in many crystals provides a means for generating acoustic waves electrically. When die structure of a crystal lacks a center of inversion symmetry , the application of strain changes the distribution of charge on the atoms and bonds comprising the crystal in such a manner that a net, macroscopic, electrical polarization of the crys-... 

The sensation of crispness is related to the detection of numerous small fracture events within the mouth, either by direct detection by the muscles around the jaw (Muller et al. 1990), or by the sormd generated (acoustic emission) as the food is broken down (Luyten and van Vliet 2006 Duizer 2001). 

The principles of UVP, or its special variant CVP, in which we are now interested, and ESA have been introduced in sec. 4.3e. Under discussion is now how the measurements are carried out in practice. As a consequence of the relatively complicated experiments. Involving wave generation (acoustic or electric), transducers, response analysis, etc., measurements are mostly done with commercial apparatus, including a lot of electronics and software. Some of these apparatus allow for additional options, such as measuring the particle size distribution, conductivity or titrating the sample to change the surface charge. 

Surface acoustic wave devices depend on the modification of the propagation velocity of a generated acoustical wave by the deposition of a definite mass of the analyte. 

Piezoelectric sensors are generally based on the use of AT-cut quartz crystals (+ 35°15 orientation of the plate relative to the crystal plane) because of their excellent temperature coefficients [3]. The generated acoustic wave depends on the crystal cut, thickness of the material used, and the geometry and configuration of the metal electrodes used to produce the electric field [5]. 

The SEM/SFM hybrid system [6] gives the advantage of using two microprobes of acoustic waves simultaneously. In this work a locally modulated electron beam is used to generate acoustic waves in a ferroelectric sample. The resulting surface acoustic waves are detected with an SFM tip in contact to the sample surface. As a sample a room temperature ferroelectric BaTiO3 is used. Due to different mechanical properties with respect to domain orientation, ferroelectric domain structures can be detected in the acoustic image. 

After selective absorption of radiation, excited molecules may relax either by emission of radiation or by non-radiative processes (cf Chapter 3, Fig. 3.1). In photoacoustic measurements, the conversion of absorbed radiation into thermal energy is utilized. This type of conversion results in changes in the sample s thermodynamic parameters such as temperature or pressure. Changes in pressure generate acoustic waves, which eventually will be transferred to the surroundings of the sample (Fig. 5.12) where they can be measured by a sensitive microphone see Fig. 5.13 (photoacoustic spectroscopy (PAS)). 

As well shall see in Sections 15.2.4 and 16.4.1, decision tree clustering is a key component of a number of s mthesis systems. In these, the decision is not seen so much as a clustering algorithm, but rather as a mapping or function from the discrete feature space to the acoustic space. As this is fully defined for every possible feature combination, it provides a general mechanism for generating acoustic representations from linguistic ones. 

The join feature issue is considerably more straightforward than with target features. Firstly, we have access to both linguistic features and the true acoustic features secondly as all units have had their features measured and derived in the same way, we don t have to worry about issues of comparing generated acoustic values with ones determined by signal processing. In addition to... 

Cavitation, the phenomenon that causes liquids to rupture and to form vaporous/gas cavities when subjected to sufficiently low pressures, can occur in any machine handling liquid when requisite hydrodynamic conditions develop (Fig. 1). Cavitation, in many cases, is an undesirable phenomenon in hydraulic machinery that can Umit performance, lower efficiency, introduce sever structural vibration, generate acoustic noise, choke flow, and cause catastrophic damage [1]. The pernicious effects of hydrodynamic cavitation on conventional fluid machinery have been recognized and actively researched in the last century. Present knowledge (experimental and analytical) of cavitation has contributed immensely toward improving the design of conventional-scale fluid machinery. 

Laser-induced acoustic desorption-electrospray ionization mass spectrometry (LlAD-ESl/MS) is a technique combining an electrospray and a pulsed laser beam to characterize solid and liquid samples with minimal sample preparation [48]. Although the instrumental setup of LIAD-ESl is similar to that of ELDl, the laser intensity required for LIAD (i.e., 10 W/cm ) is higher than that for ELDl, and the desorption mechanism of LIAD is also different from that of LD. In LIAD, the sample is not desorbed by direct laser irradiation, but by acoustic and shock waves induced by the laser irradiation. A pulsed laser beam with a flux energy of several mJ is used to irradiate the rear of a thin metal foil (e.g., AL Ti, Cu, and Ta 5-25 pm thickness) to generate acoustic and shock waves [48-50]. These laser-induced... 

At this point it should be clear that the direction of particle displacement and velocity of an acoustic wave can be varied by using piezoelectric crystals of different symmetries and by generating acoustic waves at different orientations with respect to the crystallographic axes. Theory allows the prediction of all these parameters if the properties of the material are known. Such calculations, however, can be complex and time-consuming, since numerical methods are required in many cases. Of course, the results of many previous calculations may be found in the literature. 

Acoustic wave devices (AWD). Today the family of AWDs is large. The overview shown in Figure 61 shows the basic types of the acoustic wave devices developed to date, indicating the polarization of the generated acoustic waves, and whether the devices can be operated in liquid. 

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