Through-transmission techniques

The result from the work shows that we can obtain good approximations of the attenuation values using pulse echo ultrasound. This indicates that it will be possible to replace the through-transmission technique by a pulse echo technique. 

Microwave detection can be performed from the penetrating side (pulse-echo mode) or from the opposite side (through-transmission mode). The through-transmission technique can determine the slate of resin cure in boron fiber laminates. However, it is not suitable for laminates with 0 /60 filament orientation [87]. The propagation of micro-waves (wavelength 10 10 m) is governed by Maxwell s equations of the magnetic field [88]. Maxwell s equations are... 

Schw artz suggests the use of the pulse-echo technique for the inspection of glass fiber bonds and delaminations in fiberglass laminates up to 19 mm thick, the through-transmission technique to inspect sandwich constructions, and thick fiber glass laminates and the resonant frequency for detection of disbonds in glass-fiber metal bonds [87],... 

Through-transmission techniques use two aligned transducers located in opposite sides of the part. One transducer acts as transmitter and the other as receiver. The transducers can be in contact or immersed. 

Through transmission technique-. An examination technique where the material is characterized based on the intensity of mechanical energy of the ultrasonic pulse after it has passed through the examined object. 

The common civil engineering seismic testing techniques work on the principles of ultrasonic through transmission (UPV), transient stress wave propagation and reflection (Impact Echo), Ultrasonic Pulse Echo (UPE) and Spectral Analysis of Surface Waves (SASW). 

Asbestos fiber identification can also be achieved through transmission or scanning electron microscopy (tern, sem) techniques which are especially usefiil with very short fibers, or with extremely small samples (see Microscopy). With appropriate peripheral instmmentation, these techniques can yield the elemental composition of the fibers using energy dispersive x-ray fluorescence, or the crystal stmcture from electron diffraction, selected area electron diffraction (saed). 

Probably the two most commonly used techniques for measuring the overall quality of the composite consolidation are optical photomicrographs and through transmission C-scan. Both of these techniques can be readily adapted to measuring the degree of intimate contact at the ply interfaces. 

The ultrasonic C-scan technique is the most widely used nondestructive method of locating defects in the composite microstructure. The through transmission C-scan is easy to implement and a large composite panel can be scanned in a matter of minutes. The problem with this technique is that a C-scan cannot reveal the type of defect present. Hence, there is no way to determine if a flaw detected by the C-scan is due to incomplete contact of an interply interface or some other type of defect in the composite microstructure. 

The light transmission technique [3] is based on the fact that the fraction of light transmitted through a gas - liquid dispersion is related to the interfacial area and the length of the light pass, irrespective of bubble size. 

Drop size distribution can be indirectly measured by using the light-transmission technique. When a beam of light is passed through a gas-liquid dispersion, light is scattered by the gas bubbles. It was... 

Two-fluid simulations have also been performed to predict void profiles (Kuipers et al, 1992b) and local wall-to-bed heat transfer coefficients in gas fluidized beds (Kuipers et al., 1992c). In Fig. 18 a comparison is shown between experimental (a) and theoretical (b) time-averaged porosity distributions obtained for a 2D air fluidized bed with a central jet (air injection velocity through the orifice 10.0 m/s which corresponds to 40u ). The experimental porosity distributions were obtained with the aid of a nonintrusive light transmission technique where the principles of liquid-solid fluidization and vibrofluidization were employed to perform the necessary calibration. The principal differences between theory and experiment can be attributed to the simplified solids rheology assumed in the hydrodynamic model and to asymmetries present in the experiment. 

X-ray diffraction technique is a non-destructive analytical technique that reveals information about crystallographic structure, chemical composition and physical properties of nanostructured materials. UV/Vis spectroscopy is routinely used in the quantitative determination of films of nanostructured metal oxides. The size, shape (nanocomb and nanorods etc,) and arrangement of the nanoparticles can be observed through transmission electron microscope (TEM) studies. Surface morphology of nanostructured metal oxides can be observed in atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies. 

Recent developments have extended the ultrasonic techniques to the characterisation of thin layers of metals and polymers deposited on substances to obtain measurements of the thickness/density product. Using techniques where the film are immersed in a fluid, such as water, measurements have been made, by the low frequency normal incidence double through-transmission method, with film thickness ranging from 20 to 200 pm [112] a range which is of particular relevance to membrane systems. 

Diffuse reflectance spectroscopy (DRS) has been frequently employed in UV-Vis spectroscopy of zeolites (cf. Volume 4, Chapter 4 of the present series). More recently, it became also popular in IR investigations (cf., e.g., [160, 161]). The DRIFT technique is advantageous because it is successfully applicable not only in the mid infrared but also in the near infrared (NIR) region of 4000-10,000 cm where the transmission technique usually fails because of severe scattering through the absorbent particles. The NIR range, however, is very important with respect to the study of overtone and combination modes of vibrations. Moreover, diffuse reflectance IR experiments can be carried out not only with pressed wafers as in transmission spectroscopy, but also with zeolite pow-... 

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