Isochronous data

Quite often isochronous data is presented on log-log scales. One of the reasons for this is that on linear scales any slight, but possibly important, non-linearity between stress and strain may go unnoticed whereas the use of log-log scales will usually give a straight-line graph, the slope of which is an indication of the linearity of the material. If it is perfectly linear the slope will be 45°. If the material is non-linear the slope will be less than this. 

Further development of robust methods tailored for isochron data can be anticipated, with the ultimate goal being a method that yields the same errors as EWLS for well-behaved data (i.e., strictly Gaussian, with accurate estimates of data-point errors), and only modest loss of precision for increasingly dirty data (R. Powell, written commun. 2002). 

Using error crosses as isochron data-point symbols where significant x-y error correlations exist ... 

Data from spinel (A) and melilite (A) define a good linear correlation between excess 2eMg and 27Alf24Mg ratios with slope roughly one-half that of the Bl isochron. Data from hibonite ( ], however, plot well above the isochron, suggesting either early formation of hibonite or heterogeneity in 26All27Al. 

Provost, A. (1990). An improved diagram for isochron data. Isot. Geosci., 80, 85-99. 

Table 2. Isochron data for Spring Valley Caverns stalagmite SVC-98-3.B...

Isochron data in Fig. 3 was used to suggest that initial Th in some cases likely has more than one component. A two-component system was inferred in which the high Th component has a low Th/ Th ratio (e.g. clays) and the low Th component has... 

Fletcher I.R. and Rosman K.J.R., 1982, Precise determination of initial Efjj from Sm-Nd isochron data. Ceochim, Cosmochim. Acta, 46, 1983-1987. 

Note that the isochronous test method is quite similar to that of a conventional incremental loading tensile test and differs only in that the presence of creep is recognized and the memory of the material for its stress history is overcome by the recovery periods. Isochronous data are often presented on log-log scales because this provides a more precise indication of the nonlinearity of the data by yielding a straight-line plot of slope less than unity. 

It is readily apparent that great care must be taken when comparing the degree of non-linearity in the viscoelastic response of different materials, particularly when isochronous data is viewed in isolation. 

Wright et al. have also examined the stiffness behaviour of drawn PMMA using a uniaxial tensile test in which the load was alternately applied and removed at 30 second intervals. The modulus data from these tests showed reasonable agreement with the 100 second isochronous data presented above, when compared at equal birefringence. 

The creep and relaxation test data can also be represented in the form of isochronons plots which are based upon a number of isochrones being projected from the time axes through a family of creep or stress relaxation cnrves. The resultant isochronous data is plotted on the stress—strain axes and represents a family of stress—strain cnrves for different times of loading. 

Isochronous data are usually presented on log-log scales. One reason for doing so is... 

Figure 10.9 (a) Pd-Ag and (b) Pb-Tl isochron data for iron meteorites and mineral... 

Isochronous data communication systems like Flexray operate on a precisely periodic basis, for example on a lime interval of 1 ms. Bus cycle jitter is veiy low and generally far below the nominal 1 ms. Caution, bit transmission jitter is a different effect. Bit transmission jitter or cyclic transmission jitter could lead to different functional effects, therefore jitter effects should be considered as different characteristics of fault or error modes. 

In some experimental methods, like DTMA, where temperature can be varied more easily than frequency the traces observed are plots of isochrone data, obtained at a given frequency, v, versus / . Traces obtained at different frequencies are not super-posable to one another by shifting along the temperature axis, since ai does not depend linearly on 7 (see below). However an isochrone trace ceffective isotherm, at T = To, simply by replotting the data versus (vxa,). 

---