Reflections multiple

In a nonlinear stratified medium both harmonic and fundamental waves undergo multiple reflections which can result in an important modification of harmonic emission especially in the case of significantly different refractive Indices of neighbouring media. Eq. (13) takes account of multiple reflections of harmonic wave on (1-2) and (2-3) interfaces associated to the fundamental wave propagating in a given direction. 

In the case of one reflected wave the nonlinear optical response is proportional to following terms  

16 free waves. The boundary conditions impose that these free waves propagate outside nonlinear medium under consideration (in medium (1) and (3) in the present case) in the same direction (cf. Kajzar and Messier (1987a)). If the reflected wave has the same phase as the incident wave a significant variation of harmonic intensity may occur. E.g. a reflected wave with 1% Intensity of the fundamental wave may induce a 20% variation in harmonic wave intensity. 

Although the theoretical problems connected with multiple reflection effects have been solved in a general case (Bethune (1988)) in practice one base to take account of experimental conditions like e.g. finite beam diameter, not complete superposition of reflected and incident beam, depending on incidence angle and thin film thickness, negligible reflection in some cases between thin fim and substrate (close refractive indices) etc.. 

In the second case (af) the reflected beam is almost in phase with incident one independently of incidence angle whereas it is less obvious in the first case. On the other hand first configuration is less advantageous because of scattering losses on thin film surface due to its roughness. 

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Under ideal conditions (e.g., point sources producing spherical waves and no multiple reflections) a rectified backscattered signal represents line integrals of the ultrasonic reflectivity over concentric arcs centered at the transducer position. To reconstruct the reflection tomo-... 

The reflection tomograms (c) show the axial hole in the Plexiglas specimen, but also a real discontinuity in the A/5i -alloy. The internal discontinuity is located 6 mm from the edge, 50° from the axial hole and its dimension is about 1-2 mm. This may be an inclusion or a porosity (void). Multiple reflections from the measurement were ignored in the calculation of the Plexiglas tomogram (left). This is seen as a bright circle. 

The comparison between the experimental and computed Bscan is realised on the segmented data (figure 3). Although the multiple reflections from the front to the backwall are not predicted, it can be concluded that, for this specific configuration, a good agreement is achieved. For all the principal echoes, the amplitude and position is correctly predicted. 

UV/Vis detectors are among the most popular. Because absorbance is directly proportional to path length, the capillary tubing s small diameter leads to signals that are smaller than those obtained in HPLC. Several approaches have been used to increase the path length, including a Z-shaped sample cell or multiple reflections (Figure 12.44). Detection limits are about 10 M. 

It is interesting to note that a similar specttum of the 0-0 band of the a-X system, leading to the same value of the absorption intensity, has been obtained using a Fourier transform spectrometer (see Section 3.3.3.2) but with an absorption path, using a multiple reflection cell, of 129 m and half the pressure of gas. 

The above discussion was based on the premise of a single internal reflection. An increase in sensitivity can be realized through the use of multiple internal reflections. In the case of multiple reflections, the absorbance A becomes... 

Uses. Sound-absorbing materials are frequendy used to reduce reverberation, or the persistence of sound in a space after generation of the sound ceases to reduce focused reflections from concave surfaces to prevent echoes, or delayed sound reflections from distant surfaces and to prevent the buildup of sound by multiple reflections within rooms and other enclosures. Sound-absorbing materials also are used to reduce the transmission of noise from one location to another by multiple reflections from sound-reflecting surfaces. 

Non-Black-Surface Enclosures In the following discussion we are concerned with enclosures containing gray sources and sinks, radiatively adiabatic surfaces, and no absorbing gas. The calculation of interchange between a source and a sink under conditions involving successive multiple reflections from other source-sink surfaces in the... 

In the concepts developed above, we have used the kinematic approximation, which is valid for weak diffraction intensities arising from imperfect crystals. For perfect crystals (available thanks to the semiconductor industry), the diffraction intensities are large, and this approximation becomes inadequate. Thus, the dynamical theory must be used. In perfect crystals the incident X rays undergo multiple reflections from atomic planes and the dynamical theory accounts for the interference between these reflections. The attenuation in the crystal is no longer given by absorption (e.g., p) but is determined by the way in which the multiple reflections interfere. When the diffraction conditions are satisfied, the diffracted intensity ft-om perfect crystals is essentially the same as the incident intensity. The diffraction peak widths depend on 26 m and Fjjj and are extremely small (less than... 

For thin-film samples, abrupt changes in refractive indices at interfrees give rise to several complicated multiple reflection effects. Baselines become distorted into complex, sinusoidal, fringing patterns, and the intensities of absorption bands can be distorted by multiple reflections of the probe beam. These artifacts are difficult to model realistically and at present are probably the greatest limiters for quantitative work in thin films. Note, however, that these interferences are functions of the complex refractive index, thickness, and morphology of the layers. Thus, properly analyzed, useful information beyond that of chemical bonding potentially may be extracted from the FTIR speara. 

For single glazing, the determination of the absorbed and transmitted radiation and of the heat transfer is quite straightforward, but for a window with multipane glazing, the calculation is more complex. Besides conduction in the panes, convection in the gaps as well as multiple reflections between the individual panes must be considered. 

Reverberation The continuation and enhancement of a sound caused by rapid multiple reflections between the surrounding surfaces. 

The curves in Figure B-1 represent primarily the transient nature of blast waves. They do not represent the interaction effects of blast waves and structures, such as multiple reflections and shielding due to the presence of other structures. 

Since radiation arriving at a black surface is completely absorbed, no problems arise from multiple reflections. Radiation is emitted from a diffuse surface in all directions and therefore only a proportion of the radiation leaving a surface arrives at any other given surface. This proportion depends on the relative geometry of the surfaces and this may be taken into account by the view factor, shape factor or configuration F, which is normally written as F, for radiation arriving at surface j from surface i. In this way, F,y, which is, of course, completely independent of the surface temperature, is the fraction of radiation leaving i which is directly intercepted by j. 

For grey walls, the correction factor allowing for multiple reflection of incident radiation is ... 

The facility, methods of procedure, and materials employed in this study have been discussed in detail elsewhere O9O 9 and are only briefly described here. The outdoor reaction chamber employed in this study consists of a 309000-liter FEP-type Teflon bag of triangular cross section held semi-rigidly by a framework of steel pipes. The chamber houses a set of multiple-reflection optics (capable of pathlengths in excess of 1 km) which is interfaced to a Midac interferometer and associated data system. 

For the two methods, the resulting grafting of functional monomers, e.g. acrylic acid and acrylamide, has been measured by multiple reflection IR spectra, ESCA spectra, and dye adsorption from an aqueous solution of crystal violet. The measurements indicate that the inert surfaces of the polymer substrates are modified by a complete surface layer of the grafted monomers. 

Figure 12,4.1 The multiple reflection of light from microscopic oxide layers of different dimensions leads to constructive and destructive interference of light waves, producing a particular color effect. Different thicknesses reflect different colors.

Introduction of metalized neutral density filters in FLIM systems should be done cautiously as artifacts have been observed due to single or multiple reflections between pairs of ND filters. 

Figure 5 Crosstalk between pixels due to multiple reflections between the window and the surface of the CCD chip. A photon coming from a initially should hit the pixel labeled i. If it is reflected off the surface, it bounces back toward the window and will be absorbed by pixel j as if it were coming from b.

Gaseous samples require long path length cells to produce absorption bands of reasonable intensity up to several metres of optical path are obtainable from cells incorporating mirrors which produce multiple reflections. For GC-IR, light pipes provide the best sensitivity (p. 117). 

C. K. G. Piyadasa, P. Hakansson, and T. R. Ariyaratne. A Fligh Resolving Power Multiple Reflection Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometer. Rapid Commun. Mass Spectrom., 13(1999) 620-624. 

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