One plane critical stability

Figure 21 Change in the value of one plane critical stability with the number of revolutions of the spheronizer plate for granules from within the largest sieve fraction for batches spheronized on varying diameter plates A, 22.9 cm A, 38.1 cm , 65.6 cm.

Hellen L, Yliruusi J. Process variables of instant granulator and spheroniser III. Shape and shape distributions of pellets. Int J Pharm 1993 96 217-223. Chapman SR, Rowe RC, Newton JM. Characterization of the sphericity of particles by the one plane critical stability. J Pharm Pharmacol 1988 40 503-505. Rowe RC, Sadeghnejad GR. The rheology of mcc powder/water mixes-measurement using a mixer torque rheometer. Int J Pharm 1987 38 227-229. O Connor RE, Schwartz JB. Spheronization II Drug release from drug-diluent mixtures. Drug Dev Ind Pharm 1985 11 (9-10) 1837-1857. 

This section will discuss some of the commonly used and cited shape factors in the pharmaceutical industry the shape factors discussed in this section are Wadelfs true sphericity and circularity, rugosity coefficient, correction factor, Dallavalle s shape factor, Heywood s shape factor, Schneiderhohn aspect ratio, one plane critical stability (OPCS), and Podczeck s two- and three-dimensional factor. There are also many other shape factors but they are beyond the scope of this chapter (11,14,26-31). 

FIGURE 16 OPCS i the minimimi angle between a horizontal plane and the plane where the particle is lying on and that Is necessary to be raised to shift the center of gravity of the particle outside of the boundary so that it would start rolling. Abbreviation OPCS, one plane critical stability. Source Adapted from Ref. 47. 

Chapman SR, Rowe RC, Newton JM. Characterization of the sphericity of particles by the one plane critical stability. J Pharm niarmacol 1988 40(7) 503-5. 

FIGURE 2 Cumulative distribution functions of pellet shapes using different shape factors aspect ratio, and (D) Cr. Abbreviation OPCS. one plane critical stability. Source From Ref. 76,... 

The subject of hydrodynamic stability theory is concerned with the response of a fluid system to random disturbances. The word hydrodynamic is used in two ways here. First, we may be concerned with a stationary system in which flow is the result of an instability. An example is a stationary layer of fluid that is heated from below. When the rate of heating reaches a critical point, there is a spontaneous transition in which the layer begins to undergo a steady convection motion. The role of hydrodynamic stability theory for this type of problem is to predict the conditions when this transition occurs. The second class of problems is concerned with the possible transition of one flow to a second, more complicated flow, caused by perturbations to the initial flow field. In the case of pressure-driven flow between two plane boundaries (Chap. 3), experimental observation shows that there is a critical flow rate beyond which the steady laminar flow that we studied in Chap. 3 undergoes a transition that ultimately leads to a turbulent velocity field. Hydrodynamic stability theory is then concerned with determining the critical conditions for this transition. 

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