Shape factor effect

For item 3, if an assumption is made that the seal completely fills its housing, the bulk modulus is the operative one. If the seal does not completely fill the housing, the shape factor effects apply. This is a very tricky area as Young s modulus and bulk modulus differ by at least two orders of magnitude. 

Constant-strain tests are more popular and simpler to use. In this case, sample discs of rubber are compressed between two polished steel plates to a predetermined strain by using spacers and bolts. The permanent set is usually quoted as the unrecovered percentage of the applied deformation, and is not related to the original sample height. The BS 903 rubber test specifies a cylindrical test piece 13 mm in diameter and 6.3 mm high. The sample dimensions are especially important in compression due to the shape factor effect. Recovery time before measurement of final set value is usually 30 min., and must be specified as this creep recovery is time-dependent. 

With four-electrode measurements effected from the surface, an average soil resistivity over a larger area is obtained. The resistivity of a relatively localized layer of earth or pocket of clay can only be accurately measured by using a spike electrode. Figure 3-18 gives dimensions and shape factors, Fg, for various electrodes. 

These equations are valid for spherical particles. For nonspherical particles, a more detailed model must be used i.e., the effect of the irregular shape of the particles must be taken into account by means of shape factors. 

Each compressor unit and condition has its own specific horsepower point or requirement for operation. However, the general characteristic shape will he about the same, and for a reasonable range of conditions, the general shape and effect of varying a particular condition can be relatively established even for gases of other k values. Of course, the curves can be recalculated and drawn for the particular gas under consideration. The peaks will be in about the same ratio. Note that Figures 12-26 and 12-27 were established using a bhp/MMCFD correction factor at a mean pressure of 200 psia for the lower compression ratios where this correction is required. ... 

Effect of Material and Load The sieving constant, C, increases geometrically with load. In addition there is a shape factor, a roughness factor, and a density factor such that ... 

To evaluate the effect of shape factors of particles, the electro-formed sieves were calibrated microscopically with two different materials ... 

Finally, we should mention that the asymmetry of molecular shape, polyphilic effects and conformational constraints are the dominant factors in the stabilization of polar ordering in achiral mesogens. The examples presented above are, therefore, highly significant. They show that many liquid crystalline structures are intrinsically polar and may be effectively stabilized by suitable design of the mesogenic molecules. 

Factors re.sponsible for the occurrence of scale-up effects can be either material factors or size/shape factors. In addition, differences in the mode of operation (batch or semibatch reactor in the laboratory and continuous reactor on the full scale), or the type of equipment (e.g. stirred-tank reactor in the laboratory and packed- or plate- column reactor in commercial unit) can be causes of unexpected scale-up effects. A simple misuse of available tools and information also can lead to wrong effects. 

The effect of gas flow rate of nitrogen (non-reactlve) on shape factor Is shown In Figure 3. The flow rate did not Influence the amplitude, but a slight decrease In period was observed as the flow rate Increased. 

Dg is the geometric diameter, pp is the density of the particle, neglecting the buoyancy effects of air, p is the reference density (1 g cm 3), and k is a shape factor, which is 1.0 in the case of a sphere. Because of the effect of particle density on the aerodynamic diameter, a spherical particle of high density will have a larger aerodynamic diameter than its geometric diameter. However, for most substances, pp 10 so that the difference is less than a factor of 3 (Lawrence Berkeley Laboratory, 1979). Particle densities are often lower than bulk densities of pure substances due to voids, pores, and cracks in the particles. 

Figure 4.7 Effect of hydrodynamic shape factor on effective particle size in a flow field. From J. S. Reed, Principles of Ceramics Processing, 2nd ed. Copyright 1995 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

In practice, it is the viscosity that is experimentally determined, and the correlations are used to determine axial ratios and shape factors. The viscosity can be determined by any number of techniques, the most common of which is light scattering. In addition to ellipticity, solvation (particle swelling due to water absorption) can have an effect on... 

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