Abstract: An impeller for mixing includes a disk having substantially identical top and bottom surfaces, opposed and spaced apart from each other and including a plurality of holes extending through the disk and arranged symmetrically around a circle having a smaller diameter than the disk. A first set of troughs, corresponding to a number of the plurality of holes, each trough having a portion having a width corresponding substantially to a width of the holes, is arranged on the top surface of the disk and each trough slopes downwardly from a periphery of the disk toward each of the holes, respectively. A second set of troughs, corresponding to a number of said plurality of holes, each trough having a portion having a width corresponding substantially to a width of the holes, is arranged on the bottom surface of the disk and each trough slopes upwardly from a periphery of the disk toward each of the holes, respectively.

Abstract: The disclosure describes a shrinkage compensated measuring device comprising a first scale calibrated in units of length, e.g., inches or centimeters, and a second scale calibrated in units of percent shrinkage. Each point on the second scale corresponds to a unique point on the first scale and indicates the percent difference between a reference point on the first scale and the unique point on the first scale. The shrinkage device also comprises a first array of lines, each line of the first array corresponding to a unique percent shrinkage, and a second array of lines extending across the first array such that the distance between any two lines of the second array as measured along one of the lines of the first array is inversely proportional to one minus the percent shrinkage corresponding to that line of the first array divided by one hundred.