Henry W. Jackson

Acoustic beam levitation

A system is described that uses acoustic energy to position an object, which simplifies the application of forces in defined directions to the object and which enables the application of large forces to the object. The system includes transducers (21-24, FIG. 1) that direct separate acoustic beams (31-34) at the object (12), with the system constructed so the beams do not create standing wave patterns. A plurality of beams whose phases at the object are not closely controlled, are directed at different surface areas of the object so the beams do not substantially overlap at the object and create possible canceling effects. A very large force is applied to the bottom (124 FIG. 8) of an object lying in a gravity environment, by directing a plurality of beams (141-145) at the same area at the bottom of the object, and with the beams being controlled so they are substantially in phase at the object area. This plurality of beams can also replace one or all of the transducers (21-24, FIG. 1) to provide much stronger forces to position and manipulate the object. The wavelength (B, FIG. 2) of the acoustic energy in each beam is preferably much less than one-tenth the diameter (C) of the object in order to obtain efficient momentum transfer of energy to the object.

An Accurate Radially Stratified Approach for Determining the Complex Permittivity of Liquids in a Cylindrical Microwave Cavity

A complex permittivity measurement method is introduced that is applicable to radially stratified resonant microwave cavities excited by a TM0m0 eigenmode. This single-frequency approach is well suited to the measurement of the complex permittivity of liquids because it can accurately account for a supporting tube container. It can also be applied advantageously to solid rods or tubes. The frequency dependence, as well as the field configuration at the cavity walls are taken into account more accurately than in other approaches. Comparing our results with published measurements of well-known liquids validates this technique.