Abstract: An improved regression-based qualitative analysis algorithm useful when the mixture to be analyzed contains a compound not in the library spectra, a so-called unknown. A regression of a measured spectrum is computed against the library spectra. This regression is referred to as a “master” regression. Estimated mixing coefficients for an estimated spectrum are computed from the regression. Next, a residual error is computed between the estimated spectrum and the measured spectrum. Peaks in the residual error are identified that extend in a direction opposite to that of peaks in the measured spectrum. These peaks are referred to as “negative” peaks. A regression is performed on the peaks. This is referred to as a “retro-regression” to be distinguished from the master regression performed on the measured spectrum. Using information from the retro-regression, corrected mixing coefficients are computed and the process repeats.

Abstract: A spinneret (140) for extruding side-by-side bicomponent fibers includes a spinneret hole (148) having a cross-sectional shape transverse to the direction of polymer flow that is asymmetric with respect to the arrangement of the side-by-side streams of polymer components therein. The lower viscosity component flows through a portion of the spinneret hole having a higher perimeter-to-area cross-sectional shape than the portion of the spinneret hole through which the higher viscosity component through which the lower viscosity component flows. The increased surface area (i.e., cross-sectional perimeter) of the spinneret hole contacting the lower viscosity polymer flow compensates for the viscosity differential between the polymer components that would otherwise result in dogleg bending of the extrudate.