RESUMEN
Cyclodextrins (CDs) with unique cavity structures have been used as materials for nanofiltration membrane fabrications. In the present work, the activated CD (O-CD), oxidated by NaIO4, and polyethyleneimine (PEI) were co-deposited on a hydrolyzed polyacrylonitrile support, post-treated by glycerol protection and heating treatment, to prepare nanofiltration membranes with low molecular weight cut-off (MWCO). As the cavities in CD present and the aldehyde groups introduced after oxidation, the O-CDs were expected to crosslink the PEI layer and provide extra permeating channels. The filtration experiments showed that the incorporation of O-CDs improved the permeances of the O-CD-PEI/HPAN nanofiltration membranes. The performance can be tailored by the control of the loading or the oxidation degree of the O-CD. At optimal conditions, the permeance increment was nearly double (from 9.2 to 21.1 Lm-2·h-1·bar-1). While the selectivity was without significant sacrifice, the rejection of PEG 200 remained around 90%. Meanwhile, the membrane stability was demonstrated by pro-longed filtratiing a PEG 200 aqueous solution. The constant permeance and rejection confirmed the O-CD-PEI/HPAN membranes were stable. The incorporation of activated CD in PEI offers a facile strategy to promote the permeance of PEI-based membranes.
Asunto(s)
Ciclodextrinas , Ciclodextrinas/química , Polietileneimina/química , Polímeros , Filtración , Peso MolecularRESUMEN
The utilization of efficient digital self-interference cancellation technology enables the simultaneous transmit and receive (STAR) phased array system to meet most application requirements through STAR capabilities. However, the development of application scenario requirements makes array configuration technology for STAR phased arrays increasingly important. Thus, this paper proposes a sparse shared aperture STAR reconfigurable phased array design based on beam constraints which are achieved by a genetic algorithm. Firstly, a design scheme for transmit and receive arrays with symmetrical shared apertures is adopted to improve the aperture efficiency of both transmit and receive arrays. Then, on the basis of shared aperture, sparse array design is introduced to further reduce system complexity and hardware costs. Finally, the shape of the transmit and receive arrays is determined by constraining the side lobe level (SLL), main lobe gain, and beam width. The simulated results indicate that the SLL of the transmit and receive patterns under beam-constrained design have been reduced by 4.1 dBi and 7.1 dBi, respectively. The cost of SLL improvement is a reduction in transmit gain, receive gain, and EII of 1.9 dBi, 2.1 dBi, and 3.9 dB, respectively. When the sparsity ratio is greater than 0.78, the SLL suppression effect is also significant, and the attenuation of EII, transmit, and receive gains do not exceed 3 dB and 2 dB, respectively. Overall, the results demonstrate the effectiveness of a sparse shared aperture design based on beam constraints in producing high gain, low SLL, and low-cost transmit and receive arrays.
Asunto(s)
Carmustina , Tecnología Digital , Ultrasonografía/métodosRESUMEN
Aperture-level simultaneous transmit and receive (ALSTAR) attempts to utilize adaptive digital transmit and receive beamforming and digital self-interference cancellation methods to establish isolation between the transmit and receive apertures of the single-phase array. However, the existing methods only discuss the isolation of ALSTAR and ignore the radiation efficiency of the transmitter and the sensitivity of the receiver. The ALSTAR array design lacks perfect theoretical support and simplified engineering implementation. This paper proposes an adaptive random group quantum brainstorming optimization (ARGQBSO) algorithm to simplify the array design and improve the overall performance. ARGQBSO is derived from BSO and has been ameliorated in four aspects of the ALSTAR array, including random grouping, initial value presets, dynamic probability functions, and quantum computing. The transmit and receive beamforming carried out by ARGQBSO is robust to all elevation angles, which reduces complexity and is conducive to engineering applications. The simulated results indicate that the ARGQBSO algorithm has an excellent performance, and achieves 166.8 dB of peak EII, 47.1 dBW of peak EIRP, and -94.6 dBm of peak EIS with 1000 W of transmit power in the scenario of an 8-element array.