Self-preservation

Region of established flow—the principal region of the jet. In this region, the velocity profile transverse to the jet is self-preserving when normahzed by the centerline velocity. 

In general, analytical solutions are only available for specific initial or inlet size distributions. However, for batch granulation where the only growth mechanism is coalescence, at long times the size distribution may become self-preserving. The size distribution is selfpreserving if the normahzed size distributions

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FIG. 20-97 Self-preserving size distributions for batch coalescence in drum granulation. [Sastty, Int. J. Min. Proc., 2, 1S7 (1975).] With land permission of Elsevier Science -NL, 1055 KV Amsterdam, tbe Netherlands. 

Chemical self preservation, p. 74 Drugs by design and discovery, p. 96 Drug delivery, p. 344 Physiological buffers, p. 453... 

At large distances from the nozzle, the axial velocity exhibits self-preserving similarity in that, when plotted in the above dimensionless form, velocity profiles at all cross-sections downstream collapse onto a single curve. It is probable that strict similarity is preserved only at axial distances in excess of 30-40 diameters. However, the above formulation is frequently used to describe the velocity profile at all points downstream of the flow development region. For work performed with M. citrifolia, the numerical values recommended by Panchapakesan and Lumley [131] for the constants K and C in Eqs. (12) and (13), i.e. 75.2 and 6.06, respectively, are employed. 

P. C. Kapoor, Self Preserving Size Spectra of Comminuted Solids, Chemical Engineering Science, 27, p. 425, 1974. 

V. Mishra, S. M. Kresta, J. H. Masliyah 1998, (Self-preservation of the drop size distribution function and variation in the stability ratio for rapid coalescence of a polydisperse emulsion in a simple shear field), J. Colloid Interface Sci. 197, 57. 

Clearly the granule size distribution is self-preserving in 1 Vt/V(t). Further, combining Eqs. (50), (64), and (68) results expression for the mean volume the reduced size in the following... 

Ouchiyama and Tanaka (Ol) did not solve this equation directly, but from the inspection of published data they assumed that the granule size is roughly uniformly distributed and self-preserving ... 

S3) reported that the size distributions of teconite pellets are self-preserving over a wide pelletizing interval. The scaling factor Dw, weight median diameter, is related to the agglomeration time by the following empirical equation ... 

Kanetkar (Kl) pelletized iron ore in a small-batch disk and found that the distributions are self-preserving in the reduced size D/D and that the mean pellet diameter increases in the following manner (Fig. 22) ... 

Analytical solutions of the self-preserving distribution do exist for some coalescence kernels, and such behavior is sometimes seen in practice (see Fig. 40). For most practical applications, numerical solutions to the population balance are necessary. Several numerical solution techniques have been proposed. It is usual to break the size range into discrete intervals and then solve the series of ordinary differential equations that result. A geometric discretization reduces the number of size intervals (and equations) that are required. Litster, Smit and Hounslow (1995) give a general discretized population balance for nucleation, growth and coalescence. Figure 41 illustrates the evolution of the size distribution for coalescence alone, based on the kernel of Ennis Adetayo (1994). 

Figure 40. Self-preserving size distributions of different materials. (From Sastiy, K. V. S., Int. J. Min. Processing, 2 187-203, 1975, with kind permission from Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

Friedlander, S. K., and Wang, C. S., The Self Preserving Particle Size Distribution for Coagulation by Brownian Motion, J. Colloid Interface Sci., 22 126-132(1966)... 

There have been some people in my life who I ve had to stop seeing out of self-preservation. I may be lonely, but I d rather be alone than have people around who will expose us to chemicals that make us ill. 

Training of emergency responders (firefighters, police, and emergency medical services) for responding to weapons of mass destruction should emphasize critical concepts for self-preservation and effective casualty management. Training should include both classroom instructions on basic concepts and principles, hands-on demonstrations of required skills, and drills to reinforce basic procedures. The recommended topics to be covered include ... 

The duration of 302034 effects was roughly equal to that of fluphenazine (Fig. 111). NF performance decrement produced by 302034 was maximal at about 8 to 12 hours. Full recovery (not shown in this chart) did not occur until about 36 hours. Due to a lack of potency, this category of drugs did not seem to warrant further study, especially since indifference in a combat situation might be overcome by the instinct of self-preservation. Also, these subjects were not confused and could probably function on a battlefied if the situation became life-threatening. 

Efforts at self-preservation refer both to the individual life and to the goal of living harmoniously with others who share our habitat. The latter issue reflects the goal of preserving our species and all species. This requires the well-being of progeny on an evolutionary time scale, reason enough to protect our habitat as well as our individual lives. 

Ogienko, A.G. Kursonov, A.V. Manakov, A.Y. Larionov, E.G. Ancharov, A.I. Sheromov, M.A. Nesterov, A.N. (2006). Gas hydrates of argon and methane synthesized at high pressures Composition, thermal expansion, and self-preservation. 

In Situ X-ray Diffraction Measurements of the Self-Preservation Effect of CH4 Hydrate. J. Phys. Chem. A, 105, 9756-9759. 

Takeya, S. Uchida, T. Nagao, J. Ohmura, R. Shimada, W. Kamata, Y. Ebinuma, T. Narita, H. (2005). Particle size effect ofCH4 hydrate for self-preservation. Chem. Eng. Sci., 60, 1383-1387. 

Self-preservation is the phenomenon where hydrates can remain stable for extended periods outside the hydrate stable region (Figure 3.36). Self-preservation or anomalous self-preservation has been experimentally observed by a numerous researchers (Davidson et al., 1986 Yakushev and Istomin, 1992 Stern et al., 2001a, 2001b, 2003 Takeya et al., 2002 Kuhs et al., 2005 Shimada et al. 2005). However, little is understood of this phenomenon. The ability to increase and prolong the stability of gas hydrates is desirable for gas storage applications. 

As shown in Figure 3.36, the anomalous preservation region is observed over the temperature range 242-271 K on rapid depressurization to 0.1 MPa. This anomalous behavior has been also called anomalous self-preservation. The latter consists of a short rapid dissociation phase with a release of 5-20 vol%... 

Anomalous self-preservation stabilizes methane hydrate and carbon dioxide hydrate particles at atmospheric pressure at 242-271 K for up to 2-3 weeks. This phenomenon can have implications for natural gas storage. 

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