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A facile surface segregation method was utilized to fabricate poly(vinyl alcohol)-polyethersulfone (PVA-PES) composite membranes. PVA and PES were first dissolved in dimethyl sulfoxide (DMSO), then casted on a glass plate and immersed in a coagulation bath. During the phase inversion process in coagulation bath, PVA spontaneously segregated to the polymer solution/coagulation bath interface. The enriched PVA on the surface was further crosslinked by glutaraldehyde. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) confirmed the integral and asymmetric membrane structure with a dense PVA-enriched surface and a porous PES-enriched support, as well as the surface enrichment of PVA. The coverage fraction of the membrane surface by PVA reached up to 86.8% when the PVA content in the membrane recipe was 16.7% (by mass). The water contact angle decreased with the increase of PVA content. The effect of co-agulation bath type on membrane structure was analyzed. The membrane pervaporation performance was evaluated by varying the PVA content, the annealing temperature, feed concentration and operation temperature. The mem-brane exhibited a fairly good ethanol dehydration capacity and long-term operational stability. 相似文献
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常规的机器学习模型应用于电力系统暂态稳定评估时对时间序列的整体感知能力较弱,难以挖掘蕴藏在电气量响应轨迹中的动态信息,且对于临界样本预测结果的可靠性较低.针对上述问题,提出了一种基于双向门控循环单元(BiGRU)的2阶段暂态稳定评估方法.该方法以受扰后底层量测数据的动态轨迹作为输入,首先通过持续的动态评估筛选出可信样本,然后通过回归模型预测不确定样本和可信稳定样本的故障严重度.文中通过向损失函数中引入截断函数和权重系数对BiGRU分类器加以改进,强化了模型对困难样本和失稳样本的学习力度.在修改的新英格兰10机39节点系统上的实验结果表明,所提方法在显著减少对失稳样本漏判的同时,提升了对稳定样本的识别能力. 相似文献
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通过开展在不同龄期、不同环境湿度下玻璃纤维增强水泥(GRC)试件的抗折强度、抗压强度试验和基体pH值测定,研究了环境湿度对掺加粉煤灰和硅灰等活性矿物掺合料的GRC试件力学性能的影响。结果表明:环境湿度对GRC试件的抗折强度有重要影响,相对湿度越大,随着龄期增加, GRC试件抗折强度降低越严重;在温度60℃、相对湿度95%条件下,经过56 d龄期后,掺有40%粉煤灰和10%硅灰的GRC试件抗折强度比未掺加粉煤灰和硅灰的GRC试件的抗折强度提高48.5%、抗压强度提高23.6%, GRC基体pH值降低6%。在相同的湿度条件下,掺有粉煤灰和硅灰试件的pH值在各个龄期都低于普通硅酸盐水泥试件,说明粉煤灰和硅灰的掺入能降低水泥水化液相的碱度,进而延缓了纤维受侵蚀的速度,显著改善了GRC试件的力学及耐久性能。通过对试验结果进行分析,利用MATLAB软件建立了GRC试件抗折强度和抗压强度与水泥砂浆基体pH值及时间的关系式。 相似文献
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