Approximate expressions are given for the characteristic impedance and propagation wavenumber for linear acoustic transmission through a gas enclosed in a rigid cylindrical duct. These expressions are most complicated in the transition zone where the thermoviscous boundary layers are on the order of the tube radius. The approximations are accurate to within 1% for all frequencies and tube diame...

Although customers require the Screening attenuation as measure of the screening effectiveness, on short elements like connectors or short cable assemblies one can measure only the Transfer impedance up to the GHz range. With the new "Tube in tube" test procedure the cut-off frequency between the Transfer impedance and the Screening attenuation can be moved to lower frequency ranges. The new te...

Thrombopathies; Impedance aggregometry; PRP aggregometry Abstract Brahimi et al. in this journal formed a hypothesis that ‘‘the platelet count is underestimated, by an automated cell counter, each time platelet aggregates are present in the sample tube.’’ The addition of a platelet agonist to a stimulated sample tube will lead to the formation of platelet aggregates and hence to a drop in the p...

The acoustic characteristics of a hybrid silencer consisting of two dissipative chambers and a Helmholtz resonator are investigated first computationally and experimentally. Complex wave number and characteristic impedance are used for the dissipative chambers to account for the wave propagation through absorbing material. Three-dimensional boundary element method (BEM) is employed to predict t...

Austin J Baird: Modeling valveless pumping mechanisms (Under the direction of Laura Miller) Several mechanisms of valveless pumping are studied numerically. The discussion begins with an introduction into the two well-known driving mechanisms of flow in valveless tubes: impedance pumping and peristalsis. Flow generated from peristalsis and impedance pumping is examined using the immersed bounda...