Design and Investigation of a Dynamic Auto-Adjusting Ejector for the MED-TVC Desalination System Driven by Solar Energy.

Ejectors have been widely used in multi-effect distillation, thermal vapor compression (MED-TVC) desalination systems due to their simple structures and low energy consumption. However, traditional fixed geometry ejectors fail to operate under unstable working conditions driven by solar energy. Herein, a dynamic auto-adjusting ejector, equipped with a needle at the nozzle throat, is proposed to improve the ejector's performance under changeable operating conditions. A two-dimensional computational fluid dynamics (CFD) model is built to analyze the performance and flow field of the ejector. It is found that the achievable entrainment ratio gradually increases as the needle approaches the nozzle, and the entrainment ratio of the ejector is relatively stable, varying slightly between 1.1-1.2 when the primary pressure changes from 2.5 to 4 bar. Besides, the performance comparison between the proposed ejector and the traditional ejector is studied under the same primary pressure range. The entrainment ratio of the designed ejector was 1.6 times higher than that of the conventional ejector at a primary pressure of 2.5 bar. Furthermore, the average entrainment ratio of the designed ejector is 1.14, as compared to 0.84 for the traditional ejector. Overall, the proposed auto-adjusting ejector could be potentially used in MED-TVC desalination systems under variable conditions.

Scalable Fabrication of Crystalline COF Membranes from Amorphous Polymeric Membranes.

Covalent organic framework (COF) membranes hold potential for widespread applicability, but scalable fabrication is challenging. Here, we demonstrate the disorder-to-order transformation from amorphous polymeric membrane to crystalline COF membrane via monomer exchange. Solution processing is used to prepare amorphous membrane and the replacing monomer is selected based on the chemical and thermodynamical stability of the final framework. Reversible imine bonds allow the extraneous monomers to replace the pristine monomers within amorphous membrane, driving the transformation from disordered network to ordered framework. Incorporation of intramolecular hydrogen bonds enables the crystalline COF to imprint the amorphous membrane morphology. The COF membranes harvest proton conductivity up to 0.53 S cm-1 at 80 °C. Our strategy bridges amorphous polymeric and crystalline COF membranes for large-scale fabrication of COF membranes and affords guidance on materials processing.

Short-term acceptability of female condom use among low-fee female sex workers in China: a follow-up study.

BACKGROUND: Low-fee female sex workers (FSW) lack power to effectively negotiate male condom use with clients. Female condoms (FCs) may provide an alternative strategy. This study was conducted to assess the acceptability of FC use among low-fee FSWs, and to identify appropriate candidates for future FC promotion. METHODS: A one-month follow-up study was conducted. At entry into the study, eligible participants completed a baseline questionnaire and were given 10 FCs. At the one-month follow up encounter, the number of used FC packages were counted and each participant completed a follow-up questionnaire. Logistic regression was used to identify variables associated with more frequent use of FCs (> 2 times). RESULTS: A total of 312 low-fee FSWs were enrolled at baseline and all participants completed the follow-up evaluation. Among them, 123 (39.4%) participants had used more than two FCs. Participants who were illiterate or had completed at most primary school education (OR: 2.4, 95% CI: 1.4-7.2), charged ≤30 RMB per client (≤30 vs. 51-80 RMB, OR: 3.8, 95% CI: 1.9-7.6), or had consistently used condoms with regular clients in the past month (OR: 2.4, 95%CI: 1.4-4.2) were more likely to use FCs. CONCLUSION: Low-fee FSWs charging ≤30 RMB per client, and those who are less educated may be appropriate initial candidates for FC promotion in China. Strategies to consider include teaching FSWs tactics for negotiation of FC use that can initially be applied with regular clients, and providing education to maximize ease-of use, and minimize discomfort with FC usage.

Coordination-driven structure reconstruction in polymer of intrinsic microporosity membranes for efficient propylene/propane separation.

Polymers of intrinsic microporosity (PIMs), integrating unique microporous structure and solution-processability, are one class of the most promising membrane materials for energy-efficient gas separations. However, the micropores generated from inefficient chain packing often exhibit wide pore size distribution, making it very challenging to achieve efficient olefin/paraffin separations. Here, we propose a coordination-driven reconstruction (CDR) strategy, where metal ions are incorporated into amidoxime-functionalized PIM-1 (AO-PIM) to in situ generate coordination crosslinking networks. By varying the type and content of metal ions, the resulting crosslinking structures can be optimized, and the molecular sieving capability of PIM membranes can be dramatically enhanced. Particularly, the introduction of alkali or alkaline earth metals renders more precise micropores contributing to superior C3H6/C3H8 separation performance. K+ incorporated AO-PIM membranes exhibit a high ideal C3H6/C3H8 selectivity of 50, surpassing almost all the reported polymer membranes. Moreover, the coordination crosslinking structure significantly improves the membrane stability under higher pressure as well as the plasticization resistant performance. We envision that this straightforward and generic CDR strategy could potentially unlock the potentials of PIMs for olefin/paraffin separations and many other challenging gas separations.