Mean aspect ratio

Fig. 7.8 Correlation for mean aspect ratio E of drops and bubbles in contaminated systems (BIO, H7, K2, K3, K4, T6, Wl, W6, Y4).

Air Measured volume of air collected on 25 mm diameter, 0.45 pm MCE filter, Both direct and indirect specimen preparation Superfund Method. TEM at 20,000X, EXDA, Separate examination of structures of all sizes ( 0.5 pm) and those with a length 5 pm. Structures have mean aspect ratios 5 1. Sensitivity >0.5 s/L and 0.02 s/L for all structures and those No Data EPA 1990c, 1990d... 

The depolarization factor L in equation (13) as well as the depolarization factors Li in equation (14) can be calculated from the mean aspect ratio Q of the particles as well as from the mean shape factor S. For ellipsoids with three doubled half-axes Da, L, and Dc, Li is given by equation (15) [23]. 

The price-performance ratio, purity, consistency of product quality, and availability determine the acceptance of a filler, whereby the mean aspect ratio characterizes most of its properties. 

Polyolefins can be nucleated by the mixture of two or more metal salt of a phe-nylphosphonic acid. The primary particles of nucleating agents should have a mean aspect ratio of ten or more (up to 100). ... 

Fiber type Cell width ( t) Cell length (mm) Mean aspect ratio Fibre width (It) Fibre length (mm)... 

Firstly, the aspect ratio of five batches dried at different outlet temperatures (from 67 to 102 °C) with the early experimental setup was examined by image analysis (Fig. 14.8). It was observed that particles dried at higher outlet temperatures exhibit less sphericity. Particles dried at Tout = 67 °C showed an aspect ratio of 0.925 (almost perfect sphere) for at least 3200 measured particles, while particles dried at Tout = 102 °C revealed the lowest mean aspect ratio of 0.870 [33]. 

The montmorillonite that was evaluated by Rouse et al. [18] is very similar to the montmorillonite that was evaluated by Fornes and Paul [5]. The morphology of the montmorillonite is in the form of irregular sheets (not disk-shaped) and varies in size from 200 to 600 nm. Ploehm and Liu [19] provide a quantitative evaluation of particle size and particle size distribution of similar montmorillonite evaluated by Rouse etal. [18] and Fornes and Paul [5] by AFM. The montmorillonite appears to be in a similar morphology of irregular sheets. Evaluation of the particle size and particle size distribution of montmorillonite particles gave a mean thickness of 0.8 to 1.2 mn the mean aspect ratio was calculated to be 180 91 nm, and the median value was 160 nm. 

Immiscible Blends. When two polymers are blended, the most common result is a two-phase composite. The most interesting blends have good adhesion between the phases, either naturally or with the help of an additive. The barrier properties of an immiscible blend depend on the permeabihties of the polymers, the volume fraction of each, phase continuity, and the aspect ratio of the discontinuous phase. Phase continuity refers to which phase is continuous in the composite. Continuous for barrier appHcations means that a phase connects the two surfaces of the composite. Typically, only one of the two polymer phases is continuous, with the other polymer phase existing as islands. It is possible to have both polymers be continuous. 

Thermal diffusivity Temperature sensitivity Temperature difference Thickness of tube Aspect ratio, relation of Cp/Cy Fluid dielectric constant Wall zeta potential Dimensionless temperature Friction factor, Debye length Mean free path Dynamic viscosity Kinematic viscosity Bejan number Density... 

On the other hand they do have a high aspect ratio, and are quite suitable for field emission applications. Their structure means that the field emitting sites have more redundancy than simple CNTs, so the emitting site could pass along a wall, giving a higher stability. 

It may be that the extent of dispersion is to be determined from correlations rather than by direct experimental means. Suitable correlations based on large quantities of data exist for common reactor geometries, i.e. tubular reactors, both empty and packed, fluidised beds or bubble columns. Some of these are expressed in graphical form in, for instance, refs. 17, 21 and 26. Most forms of correlation give the intensity of dispersion D/ud as a function of Reynolds and/or Schmidt numbers if this intensity is multiplied by an aspect ratio, i.e. djL for a tubular reactor, then the dispersion number is obtained. 

There is no radial velocity, and the axial velocity across the radius of the packed bed is uniform. Schwartz and Smith (1953) found that the velocity across the diameter of a packed bed is not uniform for radial aspect ratios (tube-to-particle diameter) less than about 30, due to the significant effect of the increased void space near the wall where the particles are locally ordered. This result has been verified by Hoiberg et al. (1971) for a packed bed reactor with radial aspect ratio about 50. They considered a radial velocity variation suggested by experimental observations with a sharp peak about 15% greater than the mean fluid velocity situated close to the wall. Simulations using their model showed results virtually identical to those obtained with a uniform velocity profile.3... 

Dispersion The degree of dispersion of the nanoplatelets is determined by the degree of delamination of the clay. The fully delaminated (exfoliated) nanocomposite presents much higher values for the tortuosity factor and the aspect ratio in comparison with the partially delaminated (intercalated) nanocomposite. This means that the clay particles that grow as aggregates or books of sheets must be broken up or exfoliated into individual sheets that have a thickness of the order of 1 nm, with lengths and widths of the order of 500 nm. 

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