Surface patch effects

The effect of reflected light is very noticeable in an empty coke oven. The reflection coefficient of the brick walls is comparatively high. If a perfect mirror were placed parallel to a glowing surface the mirror would appear as hot as the surface. This effect of reflection takes place in a coke oven so that both walls appear of approximately equal brightness even though they may differ considerably in temperature. Frequently a patch of the wall on one side becomes coated with a layer of coke. Since the coke has a higher emissive power than brick this patch appears much hotter. 

In another recent study, Chen and coworkers [11] also investigated the effect of surfece oxygen complexes, introduced by air and ozone treatments, on the adsorption of the commercial surfactants SDS, Darex II (anionics), and Tergitol (nonionic). Results revealed that the surfactant adsorption was strongly suppressed by surface oxidation. These authors proposed that surfactant adsorption primarily occurs on nonpolar carbon surface patches by hydrophobic interactions. Therefore, the oxidative suppression of surfactant adsorption was... 

Fig. 6.6. One of the crucial problems in rf traps are patch effects on surfaces. For test and correction purposes several thin ring electrodes are surrounding the linear multipole (see Fig. 3.13 of Chapter 3). In the present example an octopole with a dc potential of 0 V is surrounded by a cylinder the potential of which has been set to Uext- The contour lines which are given in % of Uext, show the resulting electrostatic potential. At 1 V the potential of the center line is shifted by 2.5 mV. For more details see Ref. 18.

Standard for molecular surface generations in many molecular modeling packages. The surface is composed of two kinds of surface patches the part of the van der Waals surface which is accessible to the probe sphere, the contact surface, and the inward facing part of the probe sphere when it is simultaneously in contact with more than one atom, the re-entrant surface. Surfaces generated with the same test particle (e.g., a water molecule with an effective sphere radius of r = 1.4 A) can be compared qualitatively and quantitatively. Moreover, the Connolly surface is well suited to the discussion of aspects of shape fitting. 

Both extreme models of surface heterogeneity presented above can be readily used in computer simulation studies. Application of the patch wise model is amazingly simple, if one recalls that adsorption on each patch occurs independently of adsorption on any other patch and that boundary effects are neglected in this model. For simplicity let us assume here the so-called two-dimensional model of adsorption, which is based on the assumption that the adsorbed layer forms an individual thermodynamic phase, being in thermal equilibrium with the bulk uniform gas. In such a case, adsorption on a uniform surface (a single patch) can be represented as... 

The effects due to the finite size of crystallites (in both lateral directions) and the resulting effects due to boundary fields have been studied by Patrykiejew [57], with help of Monte Carlo simulation. A solid surface has been modeled as a collection of finite, two-dimensional, homogeneous regions and each region has been assumed to be a square lattice of the size Lx L (measured in lattice constants). Patches of different size contribute to the total surface with different weights described by a certain size distribution function C L). Following the basic assumption of the patchwise model of surface heterogeneity [6], the patches have been assumed to be independent one of another. 

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