Single-Channel Compression

The most common form of compression in hearing aids is a single-channel system used to reduce amplifier overload. For this application, a rapid attack time is desired so as to give a rapid response to a sudden intense sound, a high compression ratio is desired to limit the maximum signal level, and a high compression threshold is desired so as not to limit sounds that could otherwise be amplified without distortion. 

A single-channel TSA system was developed for NASA COj collection and compression from the Martian atmosphere [196]. Accordingly, there was a need for a lightweight, highly efficient compressor. Based on the results of single-... 

The problems of micro-hydrodynamics were considered in different contexts (1) drag in micro-channels with a hydraulic diameter from 10 m to 10 m at laminar, transient and turbulent single-phase flows, (2) heat transfer in liquid and gas flows in small channels, and (3) two-phase flow in adiabatic and heated microchannels. The smdies performed in these directions encompass a vast class of problems related to flow of incompressible and compressible fluids in regular and irregular micro-channels under adiabatic conditions, heat transfer, as well as phase change. 

In a practical still a stack of annular flat plates with a large diameter central channel for the compressed steam would replace a single complete flat plate (Figure 10 shows the No. 4 still modified to take multiple rotors), and here a multiplicity of feed nozzles for each surface becomes less important. Figure 11 illustrates calculations of film thickness and heat transfer coefficient for a central feed on a flat rotor without a center hole. Adding a center hole would amount to removing the region of lowest... 

Sections 9.2 and 9.3 discussed the elementary steps that make up the important and widely used screw extrusion process. The common and outstanding feature of all the elementary steps taking place in the screw channel is that they are induced by drag brought about by a single moving surface—that of the barrel. Solids are conveyed and compressed by the... 

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