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An angular spectrum approach is used to derive the acoustic transfer function of the clamp-on flowmeter. The flowmeter factor is calculated as a function of the position of the transducers by numerical evaluation of the transmission function. This method enables high measurement accuracy even in the case of the practically unavoidable mispositioning of the transducers. Simulations and measurement results show the influence of the transducer aperture and the pipe wall on the flowmeter factor.

Previous reports from these laboratories showed that microcrystalline cellulose (AvicelR MCC, PH-101) formulations with low and medium drug levels (10 and 50%) produced very uniform beads whereas formulations containing MCC with high drug levels (80%) were difficult to process without special treatment or required the incorporation of alternate excipients. In this study, several binders, at a 2% level, specifically: Carbomer (CarbopolR 934-P), Sodium carboxymethylcellulose (CMC 7MF), Hydroxypropylcellulose (KlucelR HXF), Methylcellulose (MethocelR K-15). Povidone, USP (PVP K29-32) and Pregelatinized starch NF (Starch 1500R), were evaluated to determine whether they might impart advantages in processing and whether any differences in dissolution behavior would result. Spheres containing 80% anhydrous theophylline, the binders and MCC were manufactured by the extrusion/marumerization technique. In general, beads containing high drug levels produced with these binders are suitable for further process...

Ultrasonic clamp-on flow meters operating with the transit time method use an acoustical calibration factor, which determines the transmission angle in the fluid. This can be measured indirectly by a flow calibration. The result of a flow calibration, however, depends on parameters such as the pipe diameter and the flow profile that are not part of the clamp-on meter being calibrated. A new method is presented that allows for direct determination of this acoustical calibration factor. With this method, transducers can be calibrated for a designated flow range and pipe range independent of calibrated master flow meters, and respective pipes and calibration facilities.