Process-shifted index

The variability or spread of the data does not always take the form of the true Normal distribution of course. There can be skewness in the shape of the distribution curve, this means the distribution is not symmetrical, leading to the distribution appearing lopsided . However, the approach is adequate for distributions which are fairly symmetrical about the tolerance limits. But what about when the distribution mean is not symmetrical about the tolerance limits A second index, Cp, is used to accommodate this shift or drift in the process. It has been estimated that over a very large number of lots produced, the mean could expect to drift about 1.5cr (standard deviations) from the target value or the centre of the tolerance limits and is caused by some problem in the process, for example tooling settings have been altered or a new supplier for the material being processed. 

As large intensities are necessary to induce a nonlinear refractive index change, not only linear but also multiple photon absorption processes have to be considered. The intensity I and the induced nonlinear phase shift NL are coupled differential equations as a function of the propagation direction z. 

Neglecting the absorption processes in this section the nonlinear phase shift nonlinear refractive index, the intensity, and the interaction length. Keeping dimensions of centimeters in mind, either the nonlinearity n2 or the intensity I can be increased to create the necessary nonlinear phase shift. 

The spectral width of a pulse train emitted by a femtosecond laser can be significantly broadened in a single mode fiber [27]. This process that maintains the mode structure is described in the time domain by the optical Kerr effect or selfphase modulation. The first discussion is simplified by assuming an unchanging pulse-shape under propagation. After propagating the length l the intensity dependent refractive index n(t) = n0 + ri2/(f) leads to a self induced phase shift... 

The R and 5 charts in Figs 5.12 and 5.13 are related representations (only one is typically made in practice) of the shift-to-shift behavior of melt index consistency. It is seen that on both charts, the shift 3 point plots above the upper control limit. The strong suggestion thus is that melt index consistency was detectably worse on that shift than on the others, so that from this point of view the process was in fact not stable over the time period represented in Table 5.4. In practice, physical investigation and hopefully correction of the origin of the... 

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