Match index

Because almost all materials used in the pharmaceutical industry have NIR spectra, the use of NIR for assuring blend homogeneity may prove to be a valuable application. Ciurczak [24,25] reported some of the first work on this subject. His work involved the use of a fiber probe to collect spectra from various locations in the mixer. Spectral matching and principal component analysis (PCA) were used to measure how similar the powder mix in a particular portion of the blender was to a predetermined good, or complete, mix. The match index or PCA scores were plotted versus time to assess the optimal blending time. 

The second approach is one of correlation. A spectral match is calculated by comparing the slope generated from comparative data points on the sample and reference spectra. The cosine between the slopes is calculated and a spectral match index or correlation determined (Fig. 9.23). 

Fig. 9.24 Interpreting the meaning of spectral match index data.

These fillers are easily wet and dispersed enable transparency and translucence in most polymers and exhibit chemical, weather, and abrasion resistance. They are snitable for food contact. Feldspar s transparency and matched index of refraction allow its nse with transparent plastics to produce reasonably transparent componnds. 

A numerical example of a glass/plastic/glass laminate in which there is no internal reflection between the glass and plastic, due to matched indexes, could be stated and solved in the following way ... 

The value calculated as the criterion for deciding how well an unknown sample matches a known is the cosine of the angle between the multidimensional points representing the two spectra. This value has also been termed the match index (MI) [14,15] and it calculated from the expression ... 

More precise measurements can be obtained with commercial refractometers, such as an Abbe or Pulfrich. Both refractometers are based on measuring the critical angle of incidence between the specimen and a standard prism. The sample consists of a flat plate with one surface and an adjacent vertical edge well pohshed. The contact between the polished sample and the prism is enhanced with an approximately matching index oU. A split image is adjusted to coincide, and the refractive index is read directly. The precision here is generally of the order 10". ... 

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