Grain diameters

Quantitative studies of solid-state organic reactions were performed by Glazman (267. 268). Equal amounts of acetic anhydride and 2-aminothiazole (grain diameter 0.15 mm) were mixed for 20 rain, and the mixture was heated in a glycerol bath at 0.5°C per minute. Heating curves showed that the reaction starts in the solid phase the use of an eutectic composition of organic reactants increases the yields. 

If the radius of curvature of die grain boundary is approximated to the grain diameter Dg. 

Mott played a major part, with his collaborator Frank Nabarro (b. 1917) and in consultation with Orowan, in working out the dynamics of dislocations in stressed crystals. A particularly important early paper was by Mott and Nabarro (1941), on the flow stress of a crystal hardened by solid solution or a coherent precipitate, followed by other key papers by Koehler (1941) and by Seitz and Read (1941). Nabarro has published a lively sequential account of their collaboration in the early days (Nabarro 1980). Nabarro originated many of the important concepts in dislocation theory, such as the idea that the contribution of grain boundaries to the flow stress is inversely proportional to the square root of the grain diameter, which was later experimentally confirmed by Norman Fetch and Eric Hall. 

Figure 6-24 a shows the angular dependence of the fluorescence anisotropy (H-V) in films made at temperatures of 22 °C (ca. 200 nm grain diameter - case A), 104°C... 

Figure 9 compares Equation 20 with the recent pressure drop flow rate data of Friedmann, Chen, and Gauglitz (5) for a 1 wt% commercial sodium alkyl sulfonate dimer (Chaser SD-1000) stabilized foam in a Berea sandstone. These data are particularly useful because they have been corrected for foam blockage and therefore correctly reflect the flowing bubble regime. The solid line in Figure 9 is best fit according to Equation 20. Unfortunately, neither of the parameters c or 6 is available. Two sets of estimates are shown in Figure 9. When e - 0 (i.e., no surfactant effect) the bubble size is about 30% of a grain diameter. When — 0.1 mm (i.e., a value characteristic of those in Figure 8) the bubble size is about 10 grain diameters. We assert that Equation 20 not only predicts the correct velocity behavior of foam but it does so with reasonable parameter values (23).

Figure 6.8 Schematic shear band in a grain surrounded by other grains. Strong concentrations of shear stress reside at each end of the glide band which has a length D (the grain diameter). The radii of curvature at the ends of the band are taken to be atomic diameters.

When this force is equal to the force to grow grains, growth by boundary migration will cease. If the limiting grain diameter is D then by the Gibbs-Thomson relationship... 

For cases where an aquifer is believed to be contaminated by a product spill but no apparent LNAPL thickness measurements are available, Dietz (1971) presented Table 6.7 relating the maximum expected product thickness to average aquifer grain diameter for various sands. He assumed that the maximum oil pancake thickness equals the capillary zone thickness. For each sand size range, he gave a corresponding range of maximum h values. 

Fig. 14.19 shows a typical set of pressure versus time curves obtained from tests on a rocket motor. When the I/D ratio defined in Fig. 14.19 is increased, the head-end chamber pressure is increased drastically immediately after the ignition stage. These grains are seven-pointed-star-shaped neutral-burning grains (diameter D = 114 mm), and are made of an AP-Al-CMDB propellant with the composition nc(0-25), ng(0-31), Ita(0-08), ap(0-27), and ai(0 09). The ratio of the initial burning surface area (Ayg) to the nozzle throat area (Aj), = AygjAp and the ratio of the... 

Dispersion Coefficients in Groundwater Flow. In a uniform media of particles, the longitudinal dispersion coefficient, Dl, and the transverse dispersion coefficient, Dt, are both functions of the grain diameter and velocity. (In our previous example, Dl... 

The shape of the front is given by the spreading of the front around the point S. The spreading depends mainly on toxic mass transfer kinetics between gas and solid phases. Thus numerous parameters can be considered air flow rate, size of the toxic molecule, pore sizes of the carbon, carbon grain diameter. With large pores and small grains, the mass transfer from gas to carbon is very fast the spreading... 

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