Variation with Angle of Incidence

Periodic surfaces will often be exposed to signals where incidence varies from broadside to high angles. It is well known that the performance of any periodic structure may change considerable in such a scenario (see, for example, reference 81). Thus, it becomes important to check the cases considered above at other angles of incidence than merely 45°. 

As an example, let us consider the last case shown in Fig. 4.19d. We show this case again in Fig. 4.21a to facilitate the comparison to follow. Similarly, we show in Fig. 4.21b the same array configuration, but this time when the angle of incidence is equal to 67.5° (or 22.5° from grazing). Note that while the 45° 

SURFACE WAVES ON PASSIVE SURFACES OF FINITE EXTENT 

A most important consequence of this observation is simply that we need more columns to sample the array when the interference wavelength is longer (i.e., at high angle of incidence). As our baseline we show the four-column case already shown in Fig. 4.21b again in Fig. 4.22a in order to facilitate the comparison to follow. Next in Fig. 4.22b we show the case where we have increased all four column loads in an attempt to reduce the column currents. We observe in Fig. 4.22b that this is indeed the case, but there is a jump in column current between columns 4 and 5 and the currents in the rest of the array have not changed significantly. 

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It is by now well known that the variation with angle of incidence of the scan impedance of phased arrays as well as the bandwidth of hybrid radomes can be reduced by using dielectric slabs placed between free space and the device in question. To be sure, the dielectric constant should in general be less than 2 (for a single slab) and the thickness should be somewhat thicker thau A./4 in the dielectric. An example of applying this technique is shown in Fig. C.15. Compared to the uncompensated case in Fig. C.13, we observe some improvement... 

Fig. 25. C /T-edge NEXAFS spectra of ZnO(10 10) after exposure to 1 L of pyridine at the measurement temperature of 295 K [124]. The peak labels are discussed in Ref. 124. The inset shows the experimental variation in the intensity of the K feature (peaks al and all) with angle of incidence in the two measurement azimuths (data points). This is compared with the best fit to the data (solid lines).

Fig. 21. The variation of sticking probability with angle of incidence 9. s(0) is the sticking probability at 9 = 0. (From ref. 359.)...

Figure 9.1 Variation in rate of erosion of a brittle material with angle of incidence of erosive stream.

Figure 2.42 The variation in the amplitude or the electric vector of the standing wave, < >, ratioed to the intensity of the incident ray, < ( ), as a function of the angle of incidence at a reflecting surface, n = 3.0 and k = 30, in contact with a medium with n = 1.0 and k = 0. From J.K, Foley, C. Korzeniewski, J.J. Daschbach and S. Pons in Electroanalytical Chemistry, A Series of Advances, A J, Bard fed ), Vol. 14, Marcel Dekker, New York, 1986,...

Fig. 5.7. R1/2 = I(2a>) n/I((o) as a function of the angle of incidence for Ag(l 11) at 1064 nm for various potentials. The lines are fits as described in the text. Filled squares, 0 V (vs. SCE) open squares, - 0.4 V filled diamonds, -1 V open diamonds, —1.3 V. Inset The variation of Re a (a>) with potential. From Ref. 101.

Toothed Rotor Stator Mills. Rotor-stator mills (Fig. 8.4a) consist of a rotating shaft (rotor), with by an axially fixed concentric stator. Toothed rotor-stator mills have one or more rows of intermeshing teeth on both the rotor and the stator with a small gap between the rotor and stator. Variations in the number of teeth, teeth spacing, angle of incidence, etc., all impact the milling efficiency of toothed rotor-stator mills. 

Reflectance measurements were pjerformed using a spjectrophotometer (Lambda-19, Perkin-Elmer) equipped with a reflectance accessory (with an angle of incidence of 7 ). The values obtained (see Figure 10) are in qualitative agreement with our simulation, and show a very clear improvement of the contrast. The spectral shift and discrepancy in values of reflectance between simulated and measured spectra is due to the cumulative error in film thicknesses, most probably from organic materials for which the control is less precise, but also from variations in the optical constants of metallic films, which are critical. 

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