After a brief history of use in space about two decades ago, a resurgence of interest in membrane structures in space is developing, motivated in large part by a great potential for reduced launch mass and stowed volume. Applications for such structures range from planar configurations in solar sails, concentrators and shields, to inflatable lenticulars for radar, radio and optics.Three key factors are paramount for the success and user acceptance of this technology: deployment, longevity and performance. The performance hinges critically on the precision of the membrane surface. The amount of precision is highly mission dependent and may entail one or more of the following issues: surface smoothness, deviation from desired surface profile and slope error. Surface precision is often estimated to be between 1 50 to 1 20 of the wavelength of interest; thus values on the order of a micron (or less) to a millimeter root mean square (RMS) are often presented. It is unlikely that such surface precision can be achieved through purely passive means.This paper addresses the problem of modeling and controlling a class of nonlinear systems that can be considered as highly compliant structures. We consider specifically planar and inflatable membranes, which are represented by complex nonlinear multi-variable models. Boundary perturbations and thermal gradients are demonstrated to be potential actuation schemes for improving the reflector profile. Nonlinear controllers developed to improve performance are often dependent on state estimation and parameter identification procedures. The existence of these procedures, within the control strategy, increases the size of the algorithms, limiting the system performance in real-time. This research has as a main objective to create an intelligent controller based on feedback error learning, which is capable of extracting performance information from precision large membrane deployables and subsequently using this information to achieve maximum surface precision.
Chloropyrimidine‐based reactive dyes are reported as well suited to textile printing; however, nucleophilic aromatic substitution of chloropyrimidines with amino‐containing chromophores is slow and often suffers from poor yields. In this study, a novel and simple method was developed for the synthesis of chloropyrimidine‐based reactive dye under microwave irradiation. In addition, the dye was also synthesised by conventional heating for comparison, which took both the reaction time and yield into account. The progress of the synthesis reactions concerned were monitored using capillary electrophoresis and the purity of the dye obtained was assessed by thin‐layer chromatography. The structure of the synthesised trichloropyrimidine dye was confirmed by Fourier Transform–infrared spectroscopy and elemental analysis. It was found that the reaction rate of the nucleophilic aromatic substitution carried out under microwave irradiation was 4‐fold faster than that carried out under conventional heating, although the enhancement in product yield was modest. These results suggest that microwave irradiation is an effective technique for the synthesis of chloropyrimidine‐based reactive dyes. The synthesised chloropyrimidine dye was formulated into an ink and applied onto a wool fabric by ink‐jet printing. The printed fabrics were steamed at 102°C for 5‐25 minutes at 5‐minute intervals. Good K/S and rate of dye fixation were obtained, both of which improved with increasing steaming time. The prints obtained exhibited reasonably good light and wash fastness properties.
We report here the synthesis and characterisation of a new medium‐reactivity reactive dye containing 2‐sulphophenoxy‐4‐chloro‐s‐triazine, having enhanced the activity of the chlorine atom for further substitution by the functional groups carried by wool fibre. In addition, a dichloro‐s‐triazine dye was also synthesised for the purpose of comparison. The progress of synthesis reactions and purity of the dyes were determined using capillary electrophoresis and thin layer chromatography. The molecular structure and the chemical compositions of the synthesised dyes were confirmed using Fourier Transform–infrared spectral data and elemental analyses. The inks containing the synthesised dyes were formulated and ink‐jet‐printed onto wool fabrics and then the printed fabrics were steamed at 102°C. Compared with the dichloro‐s‐triazine dye, superior performance in terms of ink stability, K/S and dye fixation was observed for the new 2‐sulphophenoxy‐4‐chloro‐s‐triazine dye. In addition, the light fastness of the fabric printed with the inks containing the new dye was 0.5‐grade greater than that of the fabric printed with the inks containing the dichloro‐s‐triazine dye, and no changes in shade and staining were observed following wash fastness tests of the fabrics printed with the inks containing the new dye.
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