Effective retardation time

Kovacs (2), however, chose to rearrange equation (4) considering x(6) to be a dependent variable defined as T eff the effective retardation time, which could be measured by analyzing simple approach response (response to a single T jump starting with the system in equilibrium). Thus... 

KAHR-Moynihan-type model this behavior quite well. However, in earlier work, Kovacs examined this behavior through an effective retardation time defined as... 

Fig. 5. Effective retardation time versus relative volume deviation for "up-quenched" and "down-quenched" glasses. After ref. 25.

The load or stress has another effect on the creep behavior of most plastics. The volume of isotropic or amorphous plastic increases as it is stretched unless it has a Poisson ratio of 0.50. At least part of this increase in volume manifests itself as an increase in free volume and a simultaneous decrease in viscosity. This decrease in turn shifts the retardation times to being shorter. 

T]he Origin of Species proposed a radically new idea, conceiving of time not as a power but as a factor whose effect could be perceived directly in distinct but complementary forms fossils, embryos, and rudimentary organs. The fossil was petrified time the embryo, operative time the rudimentary organ, retarded time. Together these bits of evidence constituted the archives of biological history —... 

The effectiveness of each admixture may vary, depending on its concentration in the concrete, the time of addition in the mixing cycle and various constituents of the concrete. Although each class of admixture is defined by its main effect (i.e. water reduction, set acceleration), it may have one or more secondary effects (retardation of set, increased bleeding, air entrainment) and its use may result in side effects. Side effects are those modifications of properties produced in the concrete that, even though unsought, are both inevitable and independent of an admixture s main function. Prior to selecting an admixture for an intended application, these... 

Schultze pointed out (18) that whenever the enhanced catalytic activity of the catalyst is due to so-called active sites, that is, exposed crystal defects or dislocations, these sites will only be active long term if processes that would lead to healing or recrystallization and accordingly to deactivation have an activation energy in excess of 100 kJ/mol. Such high activation energies would yield at 100°C a retardation of any surface relaxation processes to effective relaxation times in excess of several years. 

As was noted in Ref. 29, the absorption in the IR region in alcohols and other polar liquids has the same characteristic features as in water. So in such liquids the IR losses due to excitation of intramolecular vibrations usually must give a crucial contribution to retardation of electrons. If in hydrogen-containing substances the retardation time depends on those intramolecular vibrations for which the reduced mass is determined by hydrogen atoms, there must exist an isotopic effect. 

Resistance and capacitance in combination are the most common in industrial processes involving heat transfer, mass transfer, and fluid flow operations. The combined effect of supplying a capacity through a resistance is time retardation (time constant). Combining a capacitance-type process element (tank) with a resistance-type process component (valve) results in a single-time-constant (t) process. If the tank was initially empty and then an inflow was started at a constant rate of m, the level in the tank would rise as shown in Figure 2.23 and would eventually rise to the steady-state height of c = Rm in the tank. 

The crystallinity of ferrihydrite is determined by the rate of hydrolysis and/or the presence of interfering compounds. Rapid, forced hydrolysis of Fe salt solutions under very acidic conditions at elevated temperatures (e.g. 80 °C) for a short period of time leads to 6-line ferrihydrite whereas rapid hydrolysis at RT and close to neutral pH produces 2-line ferrihydrite (Chukhrov et al., 1973 Schwertmann and Fischer, 1973). The 2-line material transforms to goethite and/or hematite if stored under water even at ambient temperature and is therefore often used in the laboratory as the precursor of goethite and hematite. Even in the air-dry state, transformation to hematite and goethite has been observed after several years (Schwertmann et al. 1999). The transformation can be effectively retarded or even completely blocked by small amounts of sor-bates such as silicate, phosphate, a range of organics and also by coprecipitated Al (Schwertmann and Fischer, 1973 Karim, 1984 Cornell et al. 1987 Schwertmann, 2000 a). 

The influence of the interionic forces is due to two phenomena, namely, the electrophoretic effect and the time-of-relaxation effect. The net ionic atmosphere around a given ion carries the opposite charge and therefore moves in a direction opposite to the central ion. The final result is an increase in the local viscosity, and retardation of the central ion. This is called the electrophoretic effect. The time-of-relaxation effect is also related to the fact that the ionic atmosphere around a given ion is moving and therefore disrupted from its equilibrium configuration. It follows that the ionic atmosphere must constantly be re-formed from new counter ions as the ion under observation moves through the solution. The net effect is that the electrical force on each ion is reduced so that the net forward velocity is smaller. 

The term xK replaces the ratio q/G and is referred to as the retardation time. In practice, the retardation time determines the rate at which the sample deforms following application of the stress. In a Hookean solid, the retardation time is zero as the deformation following an applied stress is instantaneous. Thus, the retardation time describes the retarding effects of the viscous properties of the dashpot to sample... 

Thirty-six undisturbed soil columns were taken on a 6 x 6 sampling grid immediately adjacent to the field core locations, and were brought to the laboratory. The columns were leached at 2 cm/d until steady state was reached, at which time a pulse of KC1 and napropamide was added to the inlet end. Affluent breakthrough curves for each chemical were fitted to the convection-dispersion equation by the method of moments (11). The effective retardation factor R, which may be calculated from the ratio of the chloride and napropamide vnap velocity parameters obtained by fitting the convection-dispersion equation, is equal to... 

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