Acoustical aspects

Acoustical Aspects of Large (Wet-Type) Cooling Towers Boehm, O. 

Academic positions dedicated to acoustics are few, as are the numbers of qualified applicants. Most graduates of acoustics programs find employment in research-based industries in which acoustical aspects of products are important, and others work for government laboratories. 

Thermal and acoustic aspects an sheds for production of broilers at high density... 

E.R. Booth, M.L. Wilbur, Acoustic aspects of active-twist rotor control, in Proceeding of the American Helicopter Society 58th Annual Forum (American Helicopter Society, Montreal, 2002)... 

The air-handling processes should be arranged to take into account the thermal, aerodynamic, and acoustic factors air quality moisture control and cleanliness and other hygiene aspects. 

This aspect is not included here, but is related to optical flow diagnostics. It is based again on the principle of the optical Doppler effect. Multifunctional equipment is available for noncontact measurements of flow-induced vibration on surfaces of structural elements, for acoustic measurements, and for calibration of accelerometers and vibration transducers. 

Laminated composite materials consist of layers of at least two different materials that are bonded together. Lamination is used to combine the best aspects of the constituent layers and bonding material in order to achieve a more useful material. The properties that can be emphasized by lamination are strength, stiffness, low weight, corrosion resistance, wear resistance, beauty or attractiveness, thermal insulation, acoustical insulation, etc. Such claims are best represented by the examples in the following paragraphs in which bimetals, clad metals, laminated glass, plastic-based laminates, and laminated fibrous composite materials are described. 

A similar acoustic technique was applied by Pickles and Bittleston (1983) to investigate blast produced by an elongated, or cigar-shaped, cloud. The cloud was modeled as an ellipsoid with an aspect ratio of 10. The explosion was simulated by a continuous distribution of volume sources along the main axis with a strength proportional to the local cross-sectional area of the ellipsoid. The blast produced by such a vapor cloud explosion was shown to be highly directional along the main axis. 

This chapter will deal primarily with thermal insulation. Acoustic and fire-protection properties and applications will be treated as subsidiary to the thermal insulation aspects. 

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 . 

Hart and McClure (H2) have considered the combustion aspects of the problem and have shown the acoustic admittance may be written in the form... 

In Chapter 5.2, S. Candel, D. Durox, and T. Schuller consider certain aspects of perturbed flame dynamics. The relation between combustion instability and noise generation is described by reference to systematic experiments. The data indicate that acoustic emission is determined by flame dynamics. On this basis, combustion noise can be linked with combustion instability. 

Acoustic cavitation is as a result of the passage of ultrasound through the medium, while hydrodynamic cavitation occurs as the result of the velocity variation in the flow due to the changing geometry of the path of fluid flow. In spite of this difference in the mechanisms of generation of two types of cavitation, bubble behavior shows similar trends with the variation of parameters in both these types of cavitation. The two main aspects of bubble behavior in cavitation phenomena are ... 

Lindstrom O (1955) Physico-chemical aspects of chemically active ultrasonic cavitation in aqueous solutions. J Acoust Soc Am 27(4) 654-671... 

The uses of inorganic metal compounds and rare gases to probe the conditions of cavitation collapse have become some of the most important methods available in fundamental ultrasonics. Quantitative determination of collapse temperatures and pressures, and qualitative determination of fundamental aspects of the nature of the cavitation field have been achieved, largely through SL spectroscopic methods. The presence of salts has a marked influence on properties on the acoustic systems, such as the extent of coalescence and bubble size, and the sonochemical activity and SL intensity. 

Okitsu K, Suzuki T, Takenaka N, Bandow FI, Nishimura R, Maeda Y (2006) Acoustic multibubble cavitation in water a new aspect of the effect of a rare gas atmosphere on bubble temperature and its relevance to sonochemistry. J Phys Chem B 110 20081-20084... 

Restorations of nineteenth-century organs in the cathedrals of northern Europe revealed a metal disease often attributed to the corrosion of tin. Chemically speaking, however, the structural change in the metal pipes is a completely different phenomenon. What aspects of chemistry must organ builders consider when attempting to achieve a particular acoustical character ... 

Acoustic chemometrics has its greatest benefits in cases where haditional sensors and measurement techniques, such as flow, temperature and pressure transmitters cannot be used. In many processes it is preferable to use noninvasive sensors because invasive sensors may cause disturbances, for example fouling and clogging inside the process equipment such as pipelines, reactors cyclones, etc. In this chapter we concentrate mainly on new industrial applications for acoustic chemomehics, and only discuss the necessary elements of the more technical aspects of the enabling technology below - details can be found in the extensive background literature [3-5],... 

The rate of phase separation after extraction in AOT-RMs is slow [167]. Keeping this in view, there is a need to study in detail the phase separation kinetics of this reverse micellar system in order to evolve means to enhance the phase separation rate. This is a very important aspect as far as industrial adaptability of RME is concerned, since the slower separation rate may become a bottleneck as in the case of ATPE. One possible approach to enhance phase separation is the application of external fields such as electric, acoustic, and microwave to reverse micellar systems. These are shown to enhance the phase separation rate in the case of ATPE [346-348]. Employing reverse micellar systems which phase separate quickly without the need for any external effort could also be a plausible solution. Some examples of such systems are DTDPA-RMs [237], sugar esters DK-F-110 RMs [239], and NaDEHP-RMs [167,243]. 

An interesting aspect of many structural phase transitions is the coupling of the primary order parameter to a secondary order parameter. In transitions of molecular crystals, the order parameter is coupled with reorientational or libration modes. In Jahn-Teller as well as ferroelastic transitions, an optical phonon or an electronic excitation is coupled with strain (acoustic phonon). In antiferrodistortive transitions, a zone-boundary phonon (primary order parameter) can induce spontaneous polarization (secondary order parameter). Magnetic resonance and vibrational spectroscopic methods provide valuable information on static as well as dynamic processes occurring during a transition (Owens et ai, 1979 Iqbal Owens, 1984 Rao, 1993). Complementary information is provided by diffraction methods. 

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