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Water diffusion rate

It is probable that capillary flow of water contributes to transport in the soil. For example, a rate of 7 cm/year would yield an equivalent water velocity of 8 x 10-6 m/h, which exceeds the water diffusion rate by a factor of four. For illustrative purposes we thus select a water transport velocity or coefficient U6 in the soil of 10 x 10 6 m/h, recognizing that this will vary with rainfall characteristics and soil type. These soil processes are in parallel with boundary layer diffusion in series, so the final equations are... [Pg.24]

Figure 12. Plot of water image attenuation against a product of factors that reflects the water diffusion rate in a region of interest in ( ) light meat and ( ) dark meat of partially dried sardine. Ag and A0 are the image intensity with and without the gradient pulse for detecting diffusion, respectively. The slope gives the diffusion coefficient, D (cm2/s) D=11.8x lO6 for light meat 8.33 x lO6 for dark meat after eqn.(17) [46]. Figure 12. Plot of water image attenuation against a product of factors that reflects the water diffusion rate in a region of interest in ( ) light meat and ( ) dark meat of partially dried sardine. Ag and A0 are the image intensity with and without the gradient pulse for detecting diffusion, respectively. The slope gives the diffusion coefficient, D (cm2/s) D=11.8x lO6 for light meat 8.33 x lO6 for dark meat after eqn.(17) [46].
Davidson and Ripmeester (1984) discuss the mobility of water molecules in the host lattices, on the basis of NMR and dielectric experiments. Water mobility comes from molecular reorientation and diffusion, with the former being substantially faster than the water mobility in ice. Dielectric relaxation data suggest that Bjerrum defects in the hydrate lattice, caused by guest dipoles, may enhance water diffusion rates. [Pg.62]

Salting or solute addition process affects the air-drying process by reducing water diffusion rate [65]. The concentration of salt has also great influence on the rate of surface evaporation [40], In addition, depending on the salt concentration and relative humidity, the salted fish may reabsorb moisture from the environment during storage [44]. [Pg.547]

Hydrolytic instability PLA readily hydrolyzes through its polyester backbone, depending on its crystalhnity, molecular weight and related distribution, morphology, water diffusion rate into the polymer, and the stereoisomeric content. This represents a serious problem in, for example, long-lasting applications [42]. [Pg.242]

Following the In [NCO] variation as a function of time, an almost linear dependence could be observed for the initial stages characteristic to the surface process when the excess NCO consumption did not exceed more than 10% from its initial value. This conclusion allowed us to calculate the A nco value as shown in Fig. 4.72. As the reaction advanced inside the depth of PU film with time, the process became dependent also on the water diffusion rate in polymer [59]. [Pg.193]

The reduction of stabilizer content caused by oxidation is often irrelevant compared to the reduction caused by extraction. The asymmetric stabilizer concentration profile in Figure 5.262 (left) is caused by an obvious difference in stabilizer diffusion coefficients as a function of position, Figure 5.263. Inside the pipe (water), the diffusion coefficient is up to 50 times higher than on the outside (air), so that stabilizer reduction is up to four times higher on the inside of the pipe than on the outside and oxidation begins first on the inside of the pipe. Interaction between stabilizers, water, and plastic play a decisive role here. Stabilizers and water are adsorbed to the plastics surface, which influences stabilizer diffusion. Without the presence of water, diffusion rate decreases due to absorption under additional absorption of water, stabilizer diffusion increases again. Plasticization of the plastic by water is another additional explanation [191]. [Pg.700]

The behavior of two polypropylene nanocomposites when immersed in distilled water or sea water at four different temperatures was studied and compared with that of neat PP. The nanocomposites showed a higher water diffusion rate and equilibrium moisture content. Nevertheless, because of their superior initial mechanical properties, after 42 days exposure they were still equivalent to unexposed PP. X-ray diffraction and infrared spectroscopy were applied to characterize the surfaces of the exposed specimens. [Pg.1666]


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