Relative reflectivity

In most ultrasonic tests, the significant echo signal often is the one having the maximum ampHtude. This ampHtude is affected by the selection of the beam angle, and the position and direction from which it interrogates the flaw. The depth of flaws is often deterrnined to considerable precision by the transit time of the pulses within the test material. The relative reflecting power of discontinuities is deterrnined by comparison of the test signal with echoes from artificial discontinuities such as flat-bottomed holes, side-drilled holes, and notches in reference test blocks. This technique provides some standardized tests for sound beam attenuation and ultrasonic equipment beam spread. 

The relative reflected microwave power is (S is a proportionality factor) ... 

The few remaining discrepancies are probably due to error in the assumed relative reflecting powers. To test this, we made use of an F-curve for OF obtained by linear extrapolation from Na+ and Cf, and one for Tii+ from CF and K+. These F-curves (which are not reproduced here because of uncertainty in their derivation) lead to structure factors which are, for the same final parameter values, also in good but not complete agreement with the observed intensities. Possibly somewhat different F-curves (corresponding to non-linear extrapolation) would give better agreement, but because of the arbitrariness of this procedure no attempt was made to utilize it. 

On the previously made assumption regarding relative reflecting powers, the values for the structure factor of the classes of planes increase in this... 

Substances formed at a given potential give rise to a diminution of the reflected intensity as compared with that at the reference potential. As a consequence, the relative reflection band presents a minimum ( negative going band ). On the contrary, the reflected intensity for substances consumed at a given potential present a maximum ( positive going band ). 

For instance, in situ Fourier transform infrared (FTIR) spectroscopy has been used by Faguy etal. [176] to study the potential-dependent changes in anion structure and composition at the surface of Pt(lll) electrodes in H 804 -containing solutions. From the infrared differential normalized relative reflectance data, the maximum rate of intensity changes for three infrared bands can be obtained. Two modes associated with the adsorbed anion... 

All values smaller than 0 are left unchanged. All others are set to zero. Let us now compute the relative reflectances along a random path from a point x to a random point x. Let... 

Claesson, Olson and Wennerblom (8) carried out the earliest studies on the effect of near-uv irradiation on the uv-visible reflectance spectra of high-yield spruce bisulphite liner and newsprint. In this work, the relative reflectivity (equation 1) of samples was plotted against wavelengths in the range 300 to 600 nm (8). 

Yellowing of bisulphite liner is manifested by a broad minimum in the relative reflectivity at wavelengths between 450 and 500 nm. As the time of irradiation is increased from zero to 60 minutes, the relative reflectivity at 470 nm decreases to about 73 per cent, and does not change after irradiation for two hours. 

The uv-visible difference spectra of newsprint and wood irradiated at 365 nm are quite different from those of high-yield bisulphite liner. The relative reflectivity of newsprint and wood increases at about 360 nm and decreases at about 430 nm. After 1 hour irradiation, the relative reflectivity of newsprint at 430 nm does not decrease further. 

Figure 6 shows a difference spectrum between an irradiated pulp sample of peroxide-bleached groundwood and the same sample after storage for 24 hours. The relative reflectance decreases in the UV-region decrease and increases in the visible region. 

Fig. 3. (A) Variation of the relative reflectivity of a platinum surface as a function of the coverage degree by adsorbed sulfur species. (B) Number of electrons exchanged per platinum site occupied by sulfur (Ncm) as a function of the degree of coverage.

Argyle et al. (2003, 2004) introduced a method to determine the average valence of Al203-supported VOx species under the conditions of propane ODH catalysis. First, calibration measurements were made the catalyst was reduced for various periods of time in H2 at 603 K, and then the amount of 02 required to fully restore the UV-vis spectra was measured by mass spectrometry. Spectra of the fully oxidized sample were recorded to generate the background. These relative reflectance spectra were converted by applying the Kubelka-Munk function and then the intensity in the range 1.5-1.9 eV was related to the extent of... 

Achromatic colors are white, black, and gray. Black and gray differ from white only in their relative reflection of incident light. The purples are nonspectral chromatic colors. All other colors are chromatic for example, brown is a yellow of low lightness and low saturation. It has a dominant wavelength in the yellow or orange range. 

The most convenient approximate solutions have been given by Kubelka and Munk 5 6) (cf. J>). These are valid only in the case of an ideal scattering medium without any regular reflection. While the so-called linear Eq. (3) is only valid at infinite thickness, the so-called hyperbolic solution (4) and (5) is of the greatest utility in TLC and HPTLC with a finite layer thickness d. It must be mentioned that in Eq. (3) is the absolute reflectance, while in optical in situ reflectance measurements in TLC and HPTLC only relative reflectances are accessible. 

The measurement of diffuse reflectance effectively involves focusing the infrared source beam onto the surface of a powder sample and using an integrating sphere to collect the scattered infrared radiation.59 The technique requires careful attention to sample preparation, and often one must dilute the analyte with KBr powder to reduce the occurrence of anomalous effects.60 In practice, one obtains the spectrum of the finely ground KBr dispersant, and then ratios this to the spectrum of KBr containing the analyte. The relative reflectance spectrum is converted into Kubelka-Munk units using standard equations,61 thus obtaining a diffuse reflectance spectrum that resembles a conventional IR absorption spectrum. 

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