Foam application from a closed system – a study of machine and foam parameters
An attempt has been made to gain a greater insight into the interaction between foam and a moving textile substrate. The effects of changing wet pick–up, fabric velocity, liquid viscosity, foam density and mode of application on penetration have been studied. Application from a closed system makes it possible to apply an exact amount of liquid, and reflectance measurements revealed that between 10 and 60% wet pick–up the actual level of wet pick–up is of major importance. The amount of liquid available determines the likelihood of capillary transport. The results obtained in terms of fabric speed and foam density still leave questions to be answered on the mechanisms of foam flow and degradation in the textile.
Dynamic Sorption of Semistable Foams by Fabrics
Foam is an effective medium for chemical treatment of fabrics at low wet pickup, due to the expanded volume and large internal surface area of the foam bubbles. For a high speed continuous process combining foam application and dissipation steps, foam of limited stability, with high shear susceptibility and dynamic sorption rate is needed. Such semistable foams require delivery of uniformly aged foam to the fabric under positive hydrostatic pressure and precise control of the foam-fabric contact time to achieve uniform distribution in the substrate. For these reasons, semistable foams cannot be applied uniformly by conventional coating methods using a doctor blade and foam bank of variable dimensions. Conversely, stable foams applied by coating methods lack the rapid dynamic sorption rate needed for high speed single- step application. A mechanism of high speed foam application is proposed, whereby the breaking foam is distributed through the fabric via yam interstices under hydrostatic pressure, and the broken foam liquor wets the interfiber pores driven by interfacial forces. Wetting rates are calculated using typical FFT process operating conditions and cotton fabric geometric parameter estimates. The results indicate that through-fabric wet- out is completed during the interval when the fabric is over the applicator slot. The wetting of interfiber pores is predicted to be slower than through-fabric wetting, but rapid enough to be completed at the applicator. The comparatively rapid wetting rates of yam and fiber surfaces with respect to fiber swelling rates is postulated to make possible the uniform semistable foam application of finishing chemicals to hydrophilic fiber substrates at pickup levels substantially below their moisture ab sorption capacity.
Design of a low power viterbi decoder for wireless communication applications
In this paper, a novel low-power Viterbi decoder with soft decision is proposed. For the branch metric of the Viterbi decoder, our design employs a soft-decision method to improve its correction capability. In order to find the survivor path efficiently, we modify the classical Viterbi decoding algorithm into a new one. This new algorithm is similar to the register-exchange method with lower latency, but using RAM instead of register banks for recording the output bit-stream of the survivor path. Hence, our design can provide a low-power design. Finally, the chip of this design consumes about 28.6K gates using TSMC 0.18 μm CMOS technology. The power consumption of our chip is about 19.5mW at 100MHz.