‎in this paper‎, ‎we prove the nonexistence of two weighing matrices of‎ ‎weight 81‎, ‎namely $cw(88,81)$ and $cw(99,81)$‎. ‎we will apply two‎ ‎very different methods to do so; for the case of $cw(88,81)$‎, ‎we‎  ‎will use almost purely counting methods‎, ‎while for $cw(99,81)$‎, ‎we‎ ‎will use algebraic methods‎.

In fabricating flowmeters, the meter's calibration is its final and accuracy determining step that comprises a great time consumption relative to its completion from its single component parts. Thus calibration (unless the respective time of calibration for a flow meter is not minimized) may represent a relevant contribution to fabrication costs. High-accuracy liquid flow calibration facilities...