蒲公英抑菌物质的提取工艺研究

以大肠杆菌、沙门氏菌为供试菌种,对蒲公英抑菌活性物质的提取工艺进行优化,结果表明:以湖北产蒲公英为原料,以70%醇为提取剂,提取温度为100℃,提取时间为2.5h,料液比为1/25(m/V).在最佳工艺条件下蒲公英抑菌活性物质的提取率可达19.97%,而抑菌圈直径大肠杆菌可达13.15mm,沙门氏菌为18.74mm.     

Mechanical Activation-Assisted Synthesis of Pb(Fe2/3W1/3)O3

Perovskite Pb(Fe_2/3W_1/3)O₃ (PFW) was prepared via a mechanical activation-assisted synthesis route from mixed oxides of PbO, Fe₂O₃, and WO₃. The mechanically activated oxide mixture, which exhibited a specific area of >10 m²/g, underwent phase conversion from nanocrystalline lead tungstate (PbWO₄) and pyrochlore (Pb₂FeWO_6.5) phases on sintering to yield perovskite PFW, although the formation of perovskite phase was not triggered by mechanical activation. When heated to 700°C, >98% perovskite phase was formed in the mechanically activated oxide mixture. The perovskite phase was sintered to a density of ∼99% of theoretical density at 870°C for 2 h. The sintered PFW exhibited a dielectric constant of 9800 at 10 kHz, which was ∼30% higher than that of the PFW derived from the oxide mixture that was not subjected to mechanical activation.     

灰色关联分析和多元二次非线性回归分析模型研究及应用

基于大庆油田采油二厂压裂措施资料,运用灰色关联分析方法选取对裂缝导流能力影响较大的因素,然后运用多元二次回归分析做进一步的定量研究,并与DPS系统的分析结果进行对比。结果表明,灰色关联分析可以较好的得到与裂缝导流能力关系密切的因素,回归分析可以得出因素间的具体定量关系,且回归分析计算的精度较高,多元二次回归分析和DPS平均拟合误差分别为0.940%、0.916%,预测平均误差分别为1.850%、1.831%,研究为油田开发动态数据规律研究提供了有效的方法。     

耐低温橡胶的研究进展:分子结构设计与化学改性

综述了耐低温橡胶材料的研究进展,对比了天然橡胶、通用合成橡胶和特种合成橡胶的分子结构、耐低温性能及其影响因素,归纳了耐低温橡胶的改性方法,最后对耐低温橡胶材料今后的发展方向进行了展望。     

铝硅准二元玻璃硬度和抗碎裂性演化的结构起源

为探究准二元铝硅玻璃硬度和抗碎裂性随组分变化的结构起源,采用激光加热气动悬浮技术,制备了组分为xAl2O3·(100–x)SiO2(30≤x≤63,摩尔分数)的系列玻璃样品.利用显微维氏硬度仪对玻璃的硬度、抗碎裂性进行了详细表征.结果表明:随着Al2O3含量增加,玻璃硬度逐渐升高,于x=63时硬度最大(8.94 GPa...     

Cobalt nanoparticle decorated N-doped carbons derived from a cobalt covalent organic framework for oxygen electrochemistry

The low cost and highly efficient construction of electrocatalysts has attracted significant attention owing to the use of clean and sustainable energy technologies. In this work, cobalt nanoparticle decorated N-doped carbons (Co@NC) are synthesized by the pyrolysis of a cobalt covalent organic framework under an inert atmosphere. The Co@NC demonstrates improved electrocatalytic capabilities compared to N-doped carbon without the addition of Co nanoparticles, indicating the important role of cobalt. The well-dispersed active sites (Co–N_x) and the synergistic effect between the carbon matrix and Co nanoparticles greatly enhance the electrocatalytic activity for the oxygen reduction reaction. In addition, the Co content has a significant effect on the catalytic activity. The resulting Co@NC-0.86 exhibits a superb electrocatalytic activity for the oxygen reduction reaction in an alkaline electrolyte in terms of the onset potential (0.90 V), half-wave potential (0.80 V) and the limiting current density (4.84 mA·cm^–2), and a high selectivity, as well as a strong methanol tolerance and superior durability, these results are comparable to those of the Pt/C catalyst. Furthermore, the superior bifunctional activity of Co@NC-0.86 was also confirmed in a home-built Zn-air battery, signifying the possibility for application in electrode materials and in current energy conversion and storage devices.     

大深度超大直径盾构盾尾受力性能探究

考虑盾尾壳体的初始几何缺陷及中空层合板构造,对超大直径(D14.0 m)盾构的盾尾在大深度水土压力下的力学性能进行建模分析。分别建立理想圆壳、缺陷圆壳、理想层合板和缺陷层合板4种结构分析模型,基于有限元计算,对4种模型的结果进行分析。对比发现:缺陷层合板模型在极限承载情况下最大变形为18.8 mm,最大等效应力达304 MPa,远超过理想圆壳模型的最大变形(3.6 mm)和最大等效应力(71.6 MPa),说明盾尾局部区域已发生塑性变形。因此,在超大直径盾构的盾尾设计时应考虑初始几何缺陷和中空层合板构造对盾尾变形和应力的放大效应。     

航空发动机钛合金压气机组件防钛火用阻燃可磨耗涂层研究进展

本文描述了钛合金在航空发动机的应用优势及出现的"钛火"问题,并介绍了解决"钛火"的方案,如阻燃钛合金、阻燃涂层及阻燃可磨耗涂层等。着重介绍了阻燃可磨耗涂层的技术研究现状,包括其涂层阻燃可磨耗性的评价标准以及阻燃可磨耗的相关机理研究。最后指出了在600～750℃区间应用的钛合金阻燃可磨耗涂层未来研究趋势和发展方向。     

冷却条件对5E83铝合金搅拌摩擦焊接头组织与性能的影响

通过光学显微镜、扫描电镜(SEM)、电子背散射衍射(EBSD)、显微硬度试验和拉伸试验,研究了转速为400、800、1200 r/min时,水冷和空冷对5E83铝合金搅拌摩擦焊接头组织与性能的影响。结果表明,与空冷条件相比,水冷条件下搅拌摩擦焊接头产生的飞边减少,洋葱环形成区域缩减、焊核区的硬度明显提高。当转速为800 r/min时,与空冷条件相比,水冷条件下接头的抗拉强度提高,接头效率提高11%,硬度提高11%,同时焊核区的平均晶粒尺寸减小43%,但空冷条件下接头断口的韧窝大而深,塑性较好,水冷条件下的断口韧窝小而浅,塑性下降。