Fraunhofer zone

In a free space, the sound source can be considered as a point source (see Figure 13.1). In practical industrial applications, however, sound is either radiated from the source of definite size (e.g., loudspeaker membrane) or, more frequently, reflected from the point source by surfaces of different shapes such as horn, paraboloid, ellipsoid, etc. In both cases such sound radiation can be regarded as coming from a plane source. This results in a specific pattern of sound intensity in the zone near the sound source, the sound intensity is constant (Fresnel zone), whereas outside this zone (the Fraunhofer zone) the sound intensity decreases inversely with the square of the distance from the plane source, i.e., in the same way as for a point source (Figure 13.4). 

A better approach is given by the numerical calculation models. Detonation codes have been developed at the Research Center Karlsruhe, DETID and D3D, to determine the characteristic parameters within the reaction zone and outside in the unbumt mixture [20, 95, 100]. These models consider a homogeneous mixture of H2, O2, N2, H2O and are mainly applied to examine the load on a nuclear reactor containment. Validation was made against the above mentioned balloon tests of the Fraunhofer Institute and the Russian RUT experiments. Parameter calculations of 3D detonation have shown that the 3D structure is unimportant for the pressure load and that a relatively coarse grid provides sufficient accuracy [20]. 

Fraunhofer Institute for Production Systems and Design Technology, 218 Freedom (privacy service), 269 Free-form surfaces, modeling, 182, 1881 Free trade zones (FTZs), 1489-1490 Freight vehicles, 2063... 

In or near the high energy zones, ions will trap electrons in reducing zones to form neutral atoms. When light of frequencies corresponding to electronic transitions of the atoms is passed through the atomic cloud, such frequency light will be absorbed by the atoms and excite them. The extent of such absorption is a measure of what is present and in what quantity. This phenomenon was first observed on solar radiation by Fraunhofer, who noticed precisely defined black lines in the solar spectrum. This led to the identification of the then- as-yet undiscovered new element, helium. Since then, atomic absorption spectrometry (AAS) has become one of the trace elemental, particularly metal, analytical chemists favorite techniques. 

Figure 5.6 Breaking zone on tensile tests, where no de-bonding of fibre/matrix can be observed. ( Fraunhofer ICT, 2013.)...

We use the Fresnel zone principle for qualitative consideration of the Fraunhofer diffraction on a single rectangular slit By definition, each following zone extinguishes the previous one. This means that if, at the slit width d and wavelength 1 at an angle q>, an even number... 

Figure 6.14 Fraunhofer diffraction from a single slit (the cp angle corresponds to eight Fresnel zones half of them faintly marked in the figure).

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