二氧化硅悬浮体和水解聚丙烯酰胺体系的流变性

研究了二氧化硅悬浮体的流变性。在固体含量较少的情况下, 体系呈Newton型;固体含量达到一定程度以后, 产生三维结构, 为假塑性体系。三维结构的固体含量与pH值有关。实验证实, 在等电点(i,e, p)附近三维结构最为疏松。还研究了水解聚丙烯酰胺(HPAM)对悬浮体流变性能的影响。HPAM破坏了二氧化硅粒子聚集体结构, 呈絮凝体结构, 并出现触变性。当高聚物在固体表面覆盖一半时, 具有最大触变性和动剪切力。HPAM的水解度达到一定程度, 由于对固体粒子由“强”吸附转变为“弱”吸附, 固体粒子“屏蔽”了高分子间的相互作用, 出现了负触变性现象。在流动时粒子会脱附, 静止以后又产生吸附, 这种吸附与脱附是产生负触变性的主要原因。HPAM水解过度或用量过多, 均会减弱负触变性现象。     

旋转回归分析在提高作物产量中的应用

本文根据旋转回归正交试验,深入研究探讨了不同肥量、密度条件下对小麦产量的影响。创建了小麦产量与种植密度、施肥量之间的回归模型。通过检验,肯定了模型的可靠性和应用的有效性。为农业生产起到了很好的指导作用。     

H-transfer rates in ion-neutral complexes versus those in intact aliphatic ions

The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd.     

矩形法兰孔孔口模态辐射阻抗的计算与分析*

针对半空间矩形法兰孔孔口模态辐射阻抗计算困难的问题,提出一种模态辐射阻抗的计算方法。该方法通过坐标变换将四重积分转换为二重积分并消除奇异积分,且将这一系列过程通过MATLAB内置函数直接实现,显著降低了模态辐射阻抗计算的复杂程度。通过对比与分析,验证了该方法的正确性,得到了自模态辐射阻抗随模态阶次增加峰值逐渐往高频移动且呈减小趋势、互模态辐射阻抗相比于自模态辐射阻抗小到可以忽略不计的性质。     

Heavy metal removal with magnetic coffee grain

The presence of heavy metals in environmental waters having an important place in the industrial waste is a major threat to viability. Heavy metals are transported to humans through the ecological cycle, damaging many tissues and organs. In recent years, agricultural and food waste can be used to remove heavy metals. At the present study, magnetically modified coffee grains which are alternative to conventional particle systems were prepared and heavy metal removal performances were investigated. The coffee grains used were magnetically modified by contact with water-based magnetic fluid. Magnetically modified coffee grains were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis and electron spin resonance (ESR). Adsorption studies are made with four different heavy metal ions, namely Cu(II), Pb(II), Cd(II) and Zn(II). Adsorption isotherms were determined and heavy metal removal performance of magnetic coffee grains were investigated from synthetic waste water.     

Solid-state phase behavior and molecular-level mixing phenomena in a strongly interacting polymer blend

This research contribution addresses mixing phenomena in a polymer blend that exhibits strong intermolecular association and bieutectic phase behavior. Molecular-level observations of specific interactions between dissimilar blend components have been obtained from high-resolution solid-state proton and carbon-13 nuclear magnetic resonance (NMR) experiments at ambient temperature. Results illustrate mixing effects on the isotropic chemical shifts of the critical component in a completely or partially phase-mixed blend. Perturbations in the NMR spectra result from conformational changes, hydrogen bonding, molecular complexation, or altered packing geometries that occur concomitantly with the mixing process. More convincing evidence that two components of a strongly interacting blend reside in a near-neighbor environment is obtained from the measurement of proton spin diffusion between dissimilar species. Proton spin diffusion is measured directly via the high-resolution CRAMPS experiment (Combined Rotation and Multiple Pulse Spectroscopy) in a molecular complex of poly (ethylene oxide) and resorcinol. A primary objective of this research endeavor is to bridge the gap between macroscopic and molecular-level probes of phase behavior and intermolecular association in mixtures that form molecular complexes. In this respect, the temperature -composition projection of the thermodynamic phase diagram is generated for binary mixtures of poly (ethylene oxide) and resorcinol, whose interaction sites are characterized via solid-state NMR. Under fortuitous conditions that are related to the overall mixture composition, two morphologically and crystallographically inequivalent phenolic ¹³C NMR signals are identified for resorcinol when the blends exist in a two-phase region below the eutectic solidification temperature. The success of this proposed structure–property relationship scheme, which bridges molecular-level mixing phenomena (via NMR) with solid-state phase behavior (via differential scanning calorimetry) depends on our ability to understand material properties at a level where continuum hypotheses are no longer valid.     

pH和盐类对非离子型表面活性剂所组成微乳液的异常流变性影响

以非离子型表面活性剂AEO~9、正十六烷、正己醇和水所组成的微乳液为对象, 研究盐和pH值对其粘度和流变性的影响, 得出它们在pH值为7时最小, 以及二价盐影响最大的结论, 正好与离子型微乳液结果相反, 为此进行了讨论。并从热效应和电导对其微观结构作了初步探索。