Particle size effects validation

The magnitude of R for the correlation was 0.823. The exponent of the particle diameter was negative, indicating that the magnitude of particle diameter over the range of experimental variables employed in this study it also increased with pulp content. It is emphasized that the effects of pulp content and particle size are valid within the range of the experimental variables employed in the study... 

Elutriation differs from sedimentation in that fluid moves vertically upwards and thereby carries with it all particles whose settling velocity by gravity is less than the fluid velocity. In practice, complications are introduced by such factors as the non-uniformity of the fluid velocity across a section of an elutriating tube, the influence of the walls of the tube, and the effect of eddies in the flow. In consequence, any assumption that the separated particle size corresponds to the mean velocity of fluid flow is only approximately true it also requires an infinite time to effect complete separation. This method is predicated on the assumption that Stokes law relating the free-falling velocity of a spherical particle to its density and diameter, and to the density and viscosity of the medium is valid... 

Some workers have correlated experimental data in terms of k at the arithmetic mean temperature, and some at the temperature of the bulk plasma. Experimental validation of the true effective thermal conductivity is difficult because of the high temperatures, small particle sizes and variations in velocity and temperature in plasma jets. 

In general, different sized particles may have different cycle time distributions and different mass deposition distributions in the spray zone. One approach would be to use small discrete size distribution increments and then to apply Eq. (12) to each size fraction. Inherent in this approach is the assumption that each particle size fraction acts independently. This assumption may not be valid, especially if different particles take different circulation paths within the bed. From the population balance approach, Randolf and Larson (1988) have suggested the use of an effective growth diffusivity coefficient to account for random fluctuations in growth rate. Thus Eq. (6) would be modified to give ... 

In Table 9.1, or equations 9.1-28 and -29 for a sphere, kAg appears to be a constant, independent of R This is valid for a particular value of R. However, if R changes from one particle size to another as a parameter, we can compare the effect on t(/B) of such a change. 

It has been found that there is a linear relationship between NIR absorption and particle size. NIRA can provide a rapid means for determining particle size. Figure 5.17 shows the effect of particle size on the NIR spectra of USP grade aspirin the absorbance of the sample increases with decreasing particle size. Particle size is an important factor to be controlled in formulation and manufacture and NIRA provides a rapid means for its determination. In order to validate such a technique it would have to be calibrated against one of the existing methods for particle size determination. 

No other papers have considered carefully the effects of catalyst particle size on activity. Comparisons of catalysts with different particle sizes could be misleading. Fortunately, most investigators have used a single batch of chloromethylated polystyrene to prepare their catalysts, and the subsequent comparisons of activities with different active site structures are likely valid. 

The physicochemical characteristics of raw materials play an important role in content uniformity and bioavailability. Therefore, bioavailability of the drug over time must be thoroughly investigated before any significant changes are made. Once the physicochemical properties of drug substances (e.g., particle size of raw materials) can influence the availability and clinical effect of a product, the main characteristics of raw materials should be considered in a validation program. The... 

In both cases the Rejmolds number is much less than 1, so that Stokes s law is valid. The difference in settling velocity between 0.1 and 1.0 pm particles is drastic and is the reason for segregation of particles in a ceramic suspensions. By inspection of this equation, differences in the terminal settling velocity can be due to either density or size differences between the two types of spherical particles. The effects of particle shape asymmetry are considered next. 

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