Step height

Fig. 19. Comparison of the predictions of k-e model and experimental data for a confined swirling flow, (a) Flow configuration where 4. is the primary inlet, D = 25 mm, and B is the secondary inlet, = 31 mm, = 59 mm and the step height, H = 31.5 mm. (b) Predicted and measured streamline values where r/H is the ratio of the radial distance from the centerline to the step height.

What gives rise to streaks in a RHEED pattern from a real surface For integral-order beams, die explanation is atomic steps. Atomic steps will be present on nearly all crystalline surfaces. At the very least a step density sufficient to account for any misorientation of the sample from perfeedy flat must be included. Diffraction is sensitive to atomic steps. They will show up in the RHEED pattern as streaking or as splitdng of the diffracted beam at certain diffraction conditions that depend on the path difference of a wave scattered from atomic planes displaced by an atomic step height. If the path difference is an odd muldple of A./2, the waves scattered... 

On silicon carbide, it is easier to see and measure step heights than in crystals like beryl, because SiC has polytypes, first discovered by the German crystallog-rapher Baumhauer (1912). The crystal structure is built up of a succession of close-packed layers of identical structure, but stacked on top of each other in alternative ways (Figure 3.24). The simplest kind of SiC simply repeats steps ABCABC, etc., and the step height corresponds to three layers only. Many other stacking sequences... 

FIGURE 3-8 Square-wave wavefonn showing the amplitude, Esw step height, AE square-wave period, r delay time, Td and current measurement times, 1 and 2. (Reproduced with permission from reference 9.)... 

Line profiles of these structures indicate a step-height of between 0.14 and 0.15 nm for the overlapping Mg(0001)-0-Mg bilayer (Figure 4.9). Clearly, at... 

If the crossover points Q (x) are determined from Fig. 45, taking the x-values at half-step height, Q (x) = 1/1 (x) = (0.7 + 0.2)x is obtained in the case of the PS system. This has to be compared with static value Qs (x) = 1.6x, derived from the same polymer solvent system by elastic neutron scattering [103], As long as no corresponding data from other polymer solvent systems are available, the final decision as to whether static and dynamic scaling lengths coincide or not, is still open. 

The third block in Fig. 2.1 shows the various possible sensing modes. The basic operation mode of a micromachined metal-oxide sensor is the measurement of the resistance or impedance [69] of the sensitive layer at constant temperature. A well-known problem of metal-oxide-based sensors is their lack of selectivity. Additional information on the interaction of analyte and sensitive layer may lead to better gas discrimination. Micromachined sensors exhibit a low thermal time constant, which can be used to advantage by applying temperature-modulation techniques. The gas/oxide interaction characteristics and dynamics are observable in the measured sensor resistance. Various temperature modulation methods have been explored. The first method relies on a train of rectangular temperature pulses at variable temperature step heights [70-72]. This method was further developed to find optimized modulation curves [73]. Sinusoidal temperature modulation also has been applied, and the data were evaluated by Fourier transformation [75]. Another idea included the simultaneous measurement of the resistive and calorimetric microhotplate response by additionally monitoring the change in the heater resistance upon gas exposure [74-76]. 

Recently the previously developed Rh(lll) EAM potential has been employed to model the ejection process from Rh(331), a stepped surface that consists of (111) terraces three atoms wide with a one-atom step height. In this surface there are atoms that are both more and less coordinated than on the (111) surface. The agreement between the experimental and calculated angular distributions is excellent . This same EAM potential was used for the Rh interactions in the 0/Rh(l 11) study discussed in section 2. 

FIG. 65. Antiphase domain formation in polar on nonpolar epitaxy (a) incomplete prelayer coverage, (b) odd step height. (From Ref. 387.)... 

Fig. 2.51 Forward and reverse square-wave voltammograms of myoglobin-didodecyldimethyl-ammonium bromide films on a basal plane pyrolytic graphite eleetrodes at 200 Hz frequency, 10 mV step height, and different pulse heights. Points are experimental data, and lines are best fits by nonlinear regression onto the Mareus model. Baekground eurrents are ineluded in experimental and eomputed data. T = 37.0 0.2 °C, and the supporting eleetrolyte is 20 mmol/L pH 6.0 phthalate buffer +180 mmol/L NaCl (reprinted from [78] with permission)...

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