Fractional recovered strain

These are commonly presented graphically as fractional recovered strain against log (reduced time) curves as typified in Figure 9.11. In the case of the acetal... 

When plastics are unloaded, the creep strain is recoverable. This contrasts with metals, where creep strains are permanent. The Voigt linear viscoelastic model predicts that creep strains are 100% recoverable. The fractional recovered strain is defined as 1 — e/cmax, where e is the strain during recovery and Cmax is the strain at the end of the creep period. It exceeds 0.8 when the recovery time is equal to the creep time. Figure 7.9 shows that recovery is quicker for low Cmax and short creep times, i.e. when the creep approaches linear viscoelastic behaviour. 

Fractional recovered strain vs. reduced time (= recovery time/creep time) for acetal copolymer at 20 °C and 65% humidity. The data from different creep times and stresses do not superimpose (from Thermoplastics and Mechanical Engineering Design, ICI Plastics Division, booklet GI 17). 

Figure 2.8 Fractional recovered strain vs. reduced time (PBT at 20°C)...

When a load is removed from a metal part, the recovery from strain, if it occurs, is instantaneous. With plastics, much of the strain is recovered reasonably quickly but a proportion is recovered only after a period of time. Thus, recovery, like creep, is time-dependent. Recovery data are provided as fractional recovered strain vs. reduced time (Figure 2.8), where ... 

An ideal shape-memory polymer for a given application has a small set of parameters that determine the usefulness, or otherwise, for a given application (1) The fractional recoverable strain the maximum fraction of the imposed strain that can be recovered when triggered. (2) The temperature of maximum recovery rate Tmax for a given rate of heating a measure of the temperature required to trigger... 

Figure 15.7. Empirical models of A. density and B. modulus from compression graphed vs. total Si concentration and fraction of APTES-derived Si, and C. recovered strain graphed vs. total Si concentration and BTMSH fraction. Reprinted from [11], Copyright 2009 American Chemical Society.

The trees over 1+0 years old are felled, their roots are dug out. The roots and the trunks of the camphor trees are brought to the factory where they are reduced to small chips. The camphor oil is then distilled with steam in special, rather wooden still (Fig. 9) The camphor oil which accumulates in the condensing vessels is usually emptied once a month. About l/3 of the pure camphor, present in the oil is crystalized out and it is separated from the liquid by straining. The camphor remaining in the oil is recovered either by fractional distillation or by freezing out or by the formation of complexes with the strong acids. 

Figure 8.2. Force relaxation of tendon under an applied load when a connective tissue such as tendon is kept at a fixed length (strain), the force (stress) is observed to decrease with time. The elastic component of the force is the force that remains at equilibrium Fn and is time independent. The elastic fraction is the force stored that is recovered when the load is removed.

The second fermentation was developed using yeast strains, such as Yarrowia lipolytica ATCC 34088, that has limited P-oxidation abilities. The recovered hydroxy fatty acids were fed into a new fermenter and sterilized with other ingredients before inoculation with Y. lipolytica culture. Y. lipolytica converted C-18 10-hydroxy fatty acids to the corresponding lactone intermediates, 4-hydroxy C12 fatty acids via a limited P-oxidation. The fermentation was usually terminated at the point of a maximum accumulation of lactone intermediates, at the concentration of 5 g/L in the fermentation broth. After the fermentation process was complete, the lactone intermediates were lactonized at a pH in the range of 3-5 and at a temperature of >100°C. The resulting lactones were recovered and purified from the fermentation broth by solvent extraction followed by fractional distillation. 

In commercial production, enzymes from a strain of Leuconostoc mesente-roides are used to synthesize dextran from sucrose, water, essential minerals, and vitamins (see under Synthesis, below). The native dextran so obtained is then carefully hydrolyzed to the proper molecular-weight average and recovered by fractional precipitation from solution with methanol (1 8). 

The effects of changes in DR on the extent of recovery of the low-strain moduli (with time, after the brief imposition of the high strain) are illustrated by Fig. 24. The effects are similar for both G and G". The fraction recoverable was taken as G /Gq. Here, is the recovered modulus after an extrapolated... 

Thermal-mechanical testing was used to determine shape fixity in order to establish the capacity of a material to fix an instant deformation. However, chain relaxation occurs in almost all polymers over time, the free strain tends to be recovered through the relaxation process, and as a result the shape fixity may decrease if the intermolecular action is weak. Zhu et al. (2009), examining supramolecular SMPU grafting with UPy side groups, observed that the shape fixity decreased to only 60% after 24 hours of relaxation, because the supramolecular SMPU contained only a small fraction of UPy side groups. 

M Protein of Hemolytic Streptococcus Group A. The experiments of Olarte referred to have now been published (154). Olarte has demonstrated that as much M protein may be recovered from the culture nitrates of certain strains of group A hemolytic streptococci as may be extracted by the Lancefield technique from the cells themselves. M protein from the culture filtrate may be fractionated by ammonium sulfate precipitation. Partially purified M protein prepared in this way did not prove to be a better antigen than material extracted from the cells at 37°C. with acid by the technique of Hirst and Lancefield loc. cit.) as had been hoped. There appears to be a correlation between mouse virulence and release of extracellular M protein. Only those strains which retain the M protein on the cell surface and do not release it into the supernatant are virulent for mice,... 

Like soy proteins, extracted canola proteins were typically recovered by isoelectric precipitation. The precipitates, after being washed and dried, constitute the protein isolate. Due to the complex protein compositions and varietal differences among canola strains, a wide range of isoelectric points was observed, at each of which only a specific fraction of the extracted protein was precipitated, therefore protein recovery of single-step isoelectric precipitation was usually low. The highest ever reported was 65.7% of the amount of protein extracted at pH 11, obtained at pH 3.6 [32]. Moderate increase in protein yield was achieved by the same researchers with multi-isoelectric precipitation at different pH. Therefore, the further improvement in overall protein output hinges on the recovery of fractions that were not precipitated, and these proteins, due to their high solubility, are ideal for many food applications. 

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