Porous poly(vinylidene fluoride) membrane with highly hydrophobic surface

The preparation of very hydrophobic poly(vinylidene fluoride) (PVDF) membranes was explored by using two methods. The first one was the modified phase inversion method using a water/N,N‐dimethylacetamide (DMAc) mixture instead of pure water as a soft precipitation bath. The second method was a precipitation‐bath free method, that is, the PVDF/DMAc casting solution underwent gelation in the open air instead of being immersed into a precipitation bath. The morphology of the surface and cross section of the membranes was investigated by using scanning electron microscopy (SEM). It was found that the membranes exhibited certain micro‐ and nanoscale hierarchical roughness on the surface, which brought about an enhanced hydrophobicity of the membrane. The contact angle (CA) of the samples obtained by the second method was as high as 150° with water. The conventional phase inversion method preparing PVDF porous membrane using pure water as precipitation bath usually results in an asymmetric membrane with a dense skin layer having a CA close to that of a smooth PVDF surface. The modified approach avoided the formation of a skin‐layer and resulted in a porous and highly hydrophobic surface of PVDF. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1358–1363, 2005     

A pair of parallel differential magnetic‐field probes with high measurement accuracy and high electric‐field suppression ratio

Magnetic‐field probes can be used for electromagnetic interference measurement of high‐speed circuits. The main magnetic probe performance includes sensitivity, spatial resolution, electric‐field suppression ratio (EFSR), and measurement accuracy. In this article, a pair of differential magnetic‐field probes is proposed to improve measurement accuracy without reducing sensitivity. The proposed differential probes consist of two asymmetric loop probes, which are designed in the same plane and separated by a row of periodic vias. The proposed differential probes are fabricated under PCB process. High accuracy can be achieved by measuring difference between outputs of the two probes. In addition, EFSR can be improved by size optimization of the differential magnetic‐field probes. Simulation and measurement results show the operating bandwidth is from 100 MHz to 12 GHz, the measurement error is 3.4% and the EFSR is about 40 dB. The proposed probes have higher measurement accuracy and higher EFSR than the conventional single probe, and larger operation bandwidth than the stacked differential probes.     

基于二次EEMD的工业电能需量多步预测

电力大用户最大需量控制是降低电网峰值负荷、节约用户电费成本的重要技术手段.面向强波动性和冲击性工业电能需量控制,研究了超短期需量负荷的多步预测问题.基于集成经验模态分解(EE-MD)方法,通过二次分解有效分离时间序列中不同频率的信号,采用长短期记忆网络(LSTM)对各信号子序列进行独立预测,最后组合预测结果.实验结果表明,本方法能很好的预测工业需量负荷变化,M A PE/MAE/NRMSE精度指标基本控制在2％ 以内,明显优于多种现行主流时序预测模型和最新文献方法,且消除了多步预测的传递误差,预测模型精度和稳定性满足需量控制要求.     

Effect of attapulgite added in plating bath on the properties of Ni/TiC nano-composite coatings

Pure copper plates were coated by Ni-TiC dipulse current plating method. The effects of adding different concentration(ranging from 0.5 g/L to 3.0 g/L) of attapulgite nano particles to the plating bath on the surface morphology, wear resistance, and oxidation resistance of Ni/TiC/Attapulgite nano-composite coatings were investigated. The experimental results show that the composite coating is flat and compact with adding 3.0 g/L in the bath, and the coating preferred orientation is changed from the planes (111) to (200). The coefficient of the composite coatings decreases from 0.68 to 0.18 with increasing content of attapulgite in the bath, a mixed mode of adhesive-abrasive wear occurs for all coatings, and the wear mechanism shows a transition from adhesive-abrasive to predominantly abrasive wear mechanism when the concentration of attapulgite is beyond 1.5 g/L in electrolyte. The oxidation resistance of composite coatings is the best prepared when adding attapulgite particles at 0.5 g/L in the bath, the oxide mainly consists of a NiO phase by X-ray analysis.     

高强钢绞线网加固混凝土粘结性能试验研究

通过高强钢绞线网聚合物砂浆加固层与混凝土结构的剥离破坏试验,对加固层与混凝土界面的剥离破坏特征进行了研究。探讨了单侧加固、植筋加固及U型加固等不同的加固方式对加固层抗剪承载力及抗剪强度的影响。试验结果表明,采用U型加固等增加粘结面积的方式能有效提高加固层粘结面抗剪承载力,但同时会削弱加固层的抗剪强度,而在界面上植入抗剪钢筋后,能同时提高聚合物砂浆加固层的抗剪承载力及抗剪强度。根据试验结果,提出了最小植筋率的建议值。     

坚持立德树人培养高素质电子信息工程人才

本文阐述了立德树人的含义和重要性,结合工作实践,提出了在新形势下实现学生思想政治教育素质化的思路和途径,并以系党总支工作为出发点,探索出了一套立德树人具体办法和措施,为培养高素质专门人才提供有力保障.     

9种中草药保鲜剂的抑菌作用研究

选择9种中草药乙醇提取液,以热杀索丝菌、肠杆菌、假单胞菌和乳酸菌为供试菌,采用打孔扩散法测定中草药的抑菌效果,并选择抑菌效果较好的中草药保鲜剂配方。结果表明:这9种中草药提取物均具有抑菌效果,抑菌圈直径为8~16 mm,其中五味子、石榴皮、黄连和虎杖4种中草药具有广谱抑菌性,且五味子、石榴皮和虎杖的1∶1∶1复配液对4种供试菌的抑菌效果最好,为中草药在肉制品保鲜方面的应用提供依据。     

混沌理论在电力系统负荷预测中应用综述

电力系统负荷的准确预测,对电力系统安全、高效运行有重要作用。负荷存在混沌特性,而基于混沌理论的预测较好地刻画了负荷物理属性,预测精度高。并主要介绍了混沌理论在负荷预测中的应用。首先,概述了基于混沌理论预测的机理,介绍了几种混沌特性判别的方法。然后,介绍了几种预测模型。最后,对现有预测模型总结和展望。     

常用屋顶绿化基质材料的保水性能

研究在饱和状态、反复干湿循环和自然蒸发3种情况下常用屋顶绿化基质材料陶粒、草炭和保水剂的保水性能。通过抽真空饱和试验得到基质材料的蓄水性能,试验发现基质材料混合后实测饱和含水量大于理论推算值,分析了导致材料混合使得蓄水性能大幅提高的原因。采用反复干燥吸水试验证明陶粒和草炭具有良好的热稳定性,而保水剂在较高温度烘干时主分子链易断裂,反复吸水和烘干后其保水性能大幅降低。常温常压蒸发试验表明在含水量较高时,三者蒸发速率与自由水面蒸发的相当,随着含水量降低,保水性能越差的基质材料蒸发速率降低越快,合理添加保水剂能有效改善基质材料保水性能。     

Enhanced healing of full-thickness diabetic wounds using bioactive glass and Yunnan baiyao ointments

In order to accelerate the chronic wounds healing, we investigated the healing effects of bioactive glass and Yuunan baiyao ointments in streptozotocin-induced diabetic rats. The ointments were prepared by mixing 45S5 bioactive glass powder （16% weight） with Vaseline and different weight percentages of Yurman baiyao. Full-thickness defect wounds were created on the back of 130 SD rats and were randomly divided into 8 groups. The wound healing rates were calculated at 4, 7, 10, 14 and 21 days after surgery. The samples were harvested for further observations. Considering the wound closure rate, group 6 （with 5% Yuunan baiyao） has better wound healing performance than other diabetic groups. The lower inflammatory response was observed by gross observation and confirmed by the results of H＆E staining and TEM observation. Besides, the proliferation of fibroblasts, the formation of granulation tissue, as well as the vascularization, were improved in group 6 compared to other diabetic groups. All results suggest that bioactive glass and Yunnan baiyao ointments can accelerate the recovery of diabetes-impaired skin wounds, and comparing to other diabetic groups, group 6 （with 5% Yunnan baiyao） has better healing effect.