The current density that flows, J, will be a function of the potential drop E across the interface and the concentrations of O and R at the electrode surface. Mathematically ... [Pg.163]

Surface and Interfacial Tension. Some properties of liquid surfaces are suggestive of a skin that exercises a contracting force or tension parallel to the surface. Mathematical models based on this effect have been used in explanation of surface phenomena, such as capillary rise. The terms surface tension (gas—liquid or gas—solid interface) and interfacial tension (liquid—liquid or liquid—solid) relate to these models which do not reflect the actual behavior of molecules and ions at interfaces. Surface tension is the force per unit length required to create a new unit area of gas—liquid surface (mN/m (= dyn/cm)). It is numerically equal to the free-surface energy. Similady, interfacial tension is the force per unit length required to create a new unit area of liquid—liquid interface and is numerically equal to the interfacial free energy. [Pg.234]

As illustrated in Fig. 1.2, a premixed flow of acetylene, hydrogen, and oxygen issue from a flat burner face onto a parallel, flat surface. Mathematically there is very little difference between this situation and one in which two flat burners face each other, in an opposed-flow configuration. There are many commonly used variants of the opposed-flow geometry. For example, premixed, combustible, gases could issue from both burner faces, causing twin premixed flames. Alternatively, fuel could issue from one side and oxidizer from the other, causing a nonpremixed, or diffusion, flame. [Pg.7]

Resilient processes are those which remain feasible for every value of the uncertain variables in the uncertainty range despite undesired changes to the process (e.g., environmental disturbances in supply temperatures, fouling of heat transfer surfaces). Mathematically, flexibility and resilience are the same problem in this chapter, the two terms are used synonymously. [Pg.9]

However small the structures under study are, the STM tip always consists of atoms, which have a finite dimension. Hence, the structure of the tip has an influence of what is observed with STM. If one assumes in a Gedanken-experiment that an infinitesimally sharp object is standing on the surface (mathematically a delta-function), then the tip will be convoluted at the object (Fig. 10.16, far right) and visible in the STM image will be the front most tip-end (up-side down) and not the sharp object itself. Hence, sharp tips are crucial for high-resolution in STM and, more general, in all Scanning Probe Methods (SPM). [Pg.361]

Bond points are local maxima in two directions. Thus, they act as attractors of gradient paths in these two directions. The union of these paths defines a surface (the valley of our analogy) between the two atoms connected by the bond path through the bond point. No gradient paths cross this surface, leading to the name of zero-flux surface.Mathematically, this surface is defined as the union of all points such that... [Pg.186]

The assumption that, for a nonuniform surface, E increases linearly with increase of coverage is unrealistic from a physical viewpoint it is however, a convenient postulate from a mathematical viewpoint, particularly when it is realized that a surface comprising a small number of homogeneous patches, each patch having different E values on which there may or may not be induced effects, gives rise to an adsorption rate which subscribes well to an Elovich equation this model is an acceptable physical description for adsorbents in the form of powders or evaporated films. Similarly, models comprising uniform surfaces, but with site creation or exclusion, may be analyzed and extended to give conclusions of the same natures as those derived from a variation of E over a nonuniform surface mathematically, however, the extension to, e.g., interaction effects between two different adsorbates is more cumbersome. [Pg.43]

The general second order polynomial response surface mathematical model can be considered to evaluate the parametric influences on the various machining criteria as follows ... [Pg.160]

AG is estimated by minimizing the sum of the two free energies the volume free energy decrease characteristic of a crystal volume increase and the surface free energy increase associated with the formation of fresh crystal surface. Mathematically, for an assumed spherical nucleus,... [Pg.377]

It is the most restricted class of material surfaces. In that case the particles of the bulk material do not pass through surface. Mathematically, it is equivalent to the condition... [Pg.274]

The angle of incidence 0i(= di) and the angle of refraction 02 (= 0t) are measured between individual light rays and the normal to the surface. Mathematically, the relationship between the angle of incidence and the angle of refraction is described by Snell s law... [Pg.149]

Harris, L. B. 1968. Adsorption on a patchwise heterogeneous surface mathematical analysis of the step-function approximation to the local isotherm. Surface Science 10, no. 2 129-145. doi 10.1016/0039-6028(68)90015-0. [Pg.410]

The partial pressure of each individual component changes as the separation is carried out because different components are being removed from the feed (high pressure) side at different rates. Because the partial pressure of individual components is a function of position along the membrane surface, mathematical integration of equation 15-6 over the entire length of a membrane surface is an interesting exercise for two components, but not practical for three or more components. [Pg.1253]

The solutions of Eqs. 5.76 and 5.77 are subject to various boundary conditions. For a slab of finite thickness (thickness 2b, with the axis at the center of the slab) the boundary conditions are usually given as constant surface temperatures or a step change in the surface temperature due to convection at the free surfaces. Mathematically for the first case the boundary and initial conditions are given as... [Pg.125]

In this relationship % is the tensile stress due to the drawing, and Krz is due to the fact that we do not have a cylindrical geometry (i.e., 7 is a function of z). Thus, we expect that %rz is approximately zero for R changing very slowly with z and neglecting air drag on the filament surface. Mathematically the previous argument follows from Eq. 9.15 for 1. [Pg.279]

© 2019 chempedia.info