Surface area meaning

Similarly, the diameter of average surface area (mean surface area diameter), assuming sphericity, can be expressed as in equation 3 and is used when the surface behavior of the particle system is of importance. 

The surface-area mean (sm) diameter, not to be confused with the number-based average surface area (eq. 3), also known as the Sauter diameter, can be calculated as follows ... 

Pore Surface area Mean pore size Mass range Size range (nm) SEC... 

The specific surface area is obviously related to the particle size distribution of the filler and can be used as a guide to this. For materials of the same density and shape a higher specific surface area means a smaller particle size, but again it must be remembered that two distinctly different particle size distributions can give rise to the same value for the specific surface area and so it is not a unique property. 

For reactions occurring on solids, the amount of exposed solid will affect the rate of the reaction. Solids that are made of smaller particles instead of one big chunk will usually increase the reaction rate. When the particle size is smaller, there is more surface area available to react. More surface area means more chances for collision between molecules. 

Advantages Minimal filtration pretreatment Easier membrane cleaning Higher surface area means more filtration area per fiber True cross flow velocity minimizes concentration polarization and membrane fouling When no air is utilized for backwashing the less fiber movement leads to breakage of fewer fibers Can be created with a variety of inside fiber diamters... 

Volume = Volume enclosed by van der Waals radii Mass = molecular weight of nonionized amino acid minus that of water both adopted from Creighton (1993) HP scale = degree of hydrophobicity of amino acid side chains, based on Kyte Doolittle (1982) Surface Area = mean fraction buried, based on Rose et al. (1985) and Secondary structure propensity = the normalized frequencies for each conformation, adopted from Creighton (1993), is the fraction of residues of each amino acid that occurred in that conformation, divided by this fraction for all residues. 

D [3,2] is the surface area mean diameter also known as the Sauter mean, where d = diameter of each unit. 

The impacting history of the early Earth has long since been destroyed. However, we have a good idea of what it must have been like from the lunar record. In fact the Earth s stronger gravitational field and larger surface area mean that it would have been much more severely impacted than the Moon (Fig. 6.3), although the number of impactors would have declined massively in the first few hundred million years (Maher Stefenson, 1988 Sleep et al., 1989). 

Surface area mean diameter, Ds Diameter of the particle whose surface area equals the mean surface area of the population... 

In filled polymer systems, it has been observed that the effect of filler content on viscosity decreases as shear rate increases [14, 49]. In the case of nanocomposite flllers, this effect has been explained in terms of a detachment/reattachment mechanism [49]. With respect to the dimensions of the flllers, it has been observed that as the surface area of the filler increases so does the viscosity of the filled polymer melt [18, 48]. For particles with similar shapes, an increase in the surface area means a reduction in particle size. In this sense, nanoflllers are expected to significantly increase the viscosity of polymer melts in relation to flllers with sizes in the range of micrometers. An analysis of filler shape and other relevant aspects of polymer flllers can be found in the work by Shenoy [50]. 

Table 1. BET surface area, mean pore diameter, and pore volume for the supports and catalysts after calcination. For the nitrogen sorption data, the experimental error ( 2ff) is 5 m /g for the surface areas, 0.2 nm for the mean pore diameters, and 0.02 cm /g for the pore volumes.

The primary species involved in charge transport are thus electrons in the oxide film and the reduced and oxidized forms of the hole conductor. The extremely high surface area means that interfacial electron transfer reactions and electrostatic interactions between species in the two conducting media are particularly important. In addition, the following secondary species may influence charge transport ... 

Because many more latex particles are being formed than monomer droplets are being lost, the average diameter of the particles in the system falls, and, despite the smaller size of the latex particles, the total surface area of all the particles continues to increase. The greater total surface area means that more emulsifler molecules can be absorbed, however, and the concentration of free emulsifier therefore shows a steady decrease. Finally, practically no polymer-free micelles remain because the system is now at a lower concentration than the critical micelle concentration. At the same time, the surface tension increases sharply. 

True density Particle density Total porosity Macropore porosity Micropore porosity Macropore volume Micropore volume Specific surface area Mean macropore radius Mean micropore half width... 

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