Roughness ratio

Roughness factor (r), 22 111 Roughness indexes, 15 203 Roughness ratio (=), 22 115 Roughness, surface wetting and, 22 110-113... 

In considering photoactivity on metal oxide and metal chalcogenide semiconductor surfaces, we must be aware that multiple sites for adsorption are accessible. On titanium dioxide, for example, there exist acidic, basic, and surface defect sites for adsorption. Adsorption isotherms will differ at each site, so that selective activation on a particular material may indeed depend on photocatalyst preparation, since this may in turn Influence the relative fraction of each type of adsorption site. The number of basic sites can be determined by titration but the total number of acidic sites is difficult to establish because of competitive water adsorption. A rough ratio of acidic to basic binding sites on several commercially available titania samples has been shown by combined surface ir and chemical titration methods to be about 2.4, with a combined acid/base site concentration of about 0.5 mmol/g . 

The group D2np/p is the Reynolds number and e/D is the roughness ratio. Three new groups also have arisen which are named... 

Figure 3. Rough ratios of equilibrium concentrations for inorganic (31.321 and organic (20-221 copper species to those of the aquo ion Cu2+, with sulfide complexes plotted as functions of free bisulfide ion level and set at the lower limit in Table II.

Charts and equations describing the variation of the friction factor, /, with the Reynolds number, Rep, and wall roughness ratio, elD, where e is a measure of the roughness of the walls, are available [18],[19], [20]. A Moody chart that gives the friction factor variation is shown in Fig. 7.4. 

Figure 4, Data of Bartell and Shepard plotted against roughness ratio...

The argument just made assumes, implicitly, a model in which the substrate is molecularly flat. Appropriate revision to account for roughness effects can be made, which will be relevant when the substrate microtopography is known. The mathematical methods that have been employed to treat the contact angle of a liquid on a rough surface (28) may be employed. For example, we may define as actual area of interface and A as actual area projected on a plane parallel to the envelope of the surface. The roughness ratio, p, is... 

In these flames over 95% of the nitrogen atoms are combusted to Nj. Since Nj is predominantly formed by reactions of NO with NHi, approximately half the nitrogen atoms are cycled through NO while the other half are oxidized no further than NHi. Since the amine radicals contribute to the Nj formation in the rough ratios of 3 1 1 for NH2 NH N, the primary pathway to Nj can be written by the two sequences shown in heavy line. These sequences account for about two thirds of the NO and Nj formation. While this indicates a pivotal role for NHj, neither NH nor N reactions with NO can be eliminated from the reaction scheme. 

The Wenzel contact angle w in the case of homogeneous wetting is related to Y by means of the roughness ratio r, which is defined as the ratio of the true solid surface area to its projected area ... 

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