Time exponent

Many investigations are reported on azides of barium, calcium, strontium, lead, copper, and silver in the range 100 to 200°C (212 to 392°F). Time exponents were 6 to 8 and activation energies of 30 to 50 kcal/g mol (54,000 to 90,000 Btu/lb mol) or so. Some difficulties with reproducibility were encountered with these hazardous materials. 

Time exponent n Fracture toughness (MPa m j Melting (softening temperature (Kj Specific heat (Jkg- K- l Thermal conductivity (W m K d Thermal expansion coefficient (MK I Thermal shock resistance (Kj... 

Fig. 5. The characteristic frequencies QR and time exponents (3 in the stretched exponential relaxation function obtained for the randomly labelled PDMS melt at 100 °C. (Reprinted with permission from [44]. Copyright 1989 Steinkopff Verlag, Darmstadt)...

Fig. 15. Temperature dependence of the dispersion parameter /3 from Fig. 13 (solid circles). The open circles and solid square represent the power law time exponent (1 - a) for dispersive hydrogen diffusion for p-type and n-type a-Si H respectively, as in Fig. 14 (Kakalios, et al., 1987).

Theoretically, release of drug through the water-filled pores of matrix systems is expected to show a square-root-of-time dependence, with a time exponent of 0.5 and hence continual declining release rates. However, there have been many research groups finding remarkable deviations. 

The following factors influencing the long-term release profiles were found (i) total matrix loading, (ii) its dissolution rate and (ii) the viscosity of the pore-building hydrogel. A proper choice of conditions lead to release profiles with time exponents up to 0.8 for at time period of several weeks. 

Release profiles were characterized by fitting the time-exponent equation (equation (2)) to the data. Equation (2), which also includes equation (1) empirically decribes release profiles of matrices deviating from equation (1). Release exponents greater than 0.5 indicate time-dependent variation of parameters in equation (1) which leads to a more constant drug delivery... 

Weight of gel as function of time Exponent for cumulative swdling expression Total free energy change due to swdling Component of AG due to ions... 

Grain-growth studies have also been carried out under 1 atm of nitrogen pressure [25]. The results were found to be different from those studies performed at 10 atm. The time exponent n for both directions was equal to 3. This will result in an equation in which the exponent of the time term is equal to one, and the aspect ratio is time independent during sintering. 

C V = calculated coefficient of variation (%, or fraction) di,d2,d3= mean residence time exponents in equations 5-7 Da = death rate due to aggregation (no./pmmLs)... 

To demonstrate that any point in time could be used, as a basis, compare the amount repaid based on the end of year 1. Equation f9.6 is used, and all cash flows are moved backward in time (exponents become negative). This gives... 

The experimentally generated time exponents were in general agreement with computer-simulated data. The major exponents of the aerobic degradation study suggest that for blends with starch fraction equal to and greater than Pc, the starch is predominantly accessed by microbial invasion. Soil burial studies support the microbial invasion mechanism in polymer-starch blends [14,17]. 

As Table 4.3 shows, the obtained time exponents are close to 0.5 for the Korsmeyer equation, indicating that the drug release predominantly follows the mechanism of diffusion, with a low contribution of the erosion mechanism [113]. 

---