不同酯基结构的棕榈油生物柴油的性能研究

以棕榈油为研究对象,分别与甲醇、乙醇、异丙醇和异丁醇进行酯交换反应制备了不同酯基结构的生物柴油。利用差示扫描量热仪和应力控制流变仪分析了不同酯基结构棕榈油生物柴油的结晶行为和低温流变性能,同时分析了酯基结构对生物柴油的氧化稳定性,40℃时的动力黏度、20℃时的密度等重要性质的影响。结果表明,随着醇的碳链长度的增加,棕榈油生物柴油的析蜡点和胶凝点均降低,特别是棕榈油异丁酯的析蜡点和胶凝点分别降低到了-2.57和-8.09℃,低温流动性得到了明显改善,且氧化诱导期略有延长,氧化稳定性有所改善。生物柴油的密度和黏度随着酯基结构的不同而有所变化,但其数值都符合中国生物柴油标准。     

氧同位素交换及其在多相催化氧化反应研究中的应用

简单介绍了氧同位素交换技术及其在多相催化氧化反应机理研究中的应用     

柠檬酸-1,4-丁二醇-环烷酸-十八醇爪形大分子的合成、表征与降滤性质研究

以1,4-丁二醇、柠檬酸为原料,设计并首次合成了以1,4-丁二醇为核心的多羟基多酸爪状物小分子(CTC),再依次与带有功能化基团的环烷酸、十八醇接枝,合成了新型的多元酯类爪形大分子(CTC-NO).用核磁、红外光谱对合成的2种化合物进行了结构表征,表明合成产物与所设计的分子结构吻合.用元素分析确定了CTC的组成是C16H22O14.制备的CTC-NO爪形大分子不溶于水,溶于有机溶剂.将CTC-NO按600μg/g的加剂量添加于轻柴油中,其对蜡化0#柴油的冷滤点降低达6℃.     

聚电解质──壳聚糖浓溶液流变学性质研究：浓度、温度、溶剂pH值和外加盐对粘度及流动性的影响

本工作用日本岩本ＲＰＸ－７０５多功能流变仪测定了在不同浓度、温度、溶剂ｐＨ值和外加盐浓度对壳聚糖在甲酸水溶液中其浓溶液粘度η随剪切速率γ的变化关系．讨论了浓度、温度等对溶液粘度、流动活化能Ｅ_γ和流动指数ｎ的影响．发现溶剂ｐＨ值减小或溶液中外加盐浓度增加，溶液粘度变小，ｎ增大，表明非牛顿流动性减弱，并且进一步讨论了零剪切粘度η_０和外加盐浓度Ｃ_ｓ的依赖关系．     

考虑时间因素的退保率指标及应用

本文对目前广泛使用的两个退保率指标进行了分析,指出了其计算公式存在的问题,特别是没有考虑时间因素。本文以数理推导为依据,提出了一个考虑时间因素的新退保率一g退保率,并在合理假设下,给出了年g退保率和月g退保率的计算公式,并指出了各月份的g退保率不具有可比性。最后结合一个示例,就各个退保率与g退保率的差异进行了分析,并给出了建议。     

A numerical investigation into the solids phase chromatography using a combined continuous and discrete approach

Solids phase chromatography for particle classification is based on different retention times of particles with different properties when they are elutriated through a confined geometry. This work aims at a fundamental understanding of such a technology by using the combined continuous and discrete method. A packed bed is employed as the model confined geometry. The numerical method is compared first with experimental observations, followed by a parametric analysis of the effects on the flow hydrodynamics and solids behaviour of various parameters including the number of injected particles, the superficial gas velocity, the contact stiffness and the diameter ratio of the packed column to the packed particles. The results show that the modelling captures some important features of the flow of an injected pulse of fine particles in a packed bed. An increase in the number of injected particles or the superficial gas velocity reduces the retention time, whereas the contact stiffness does not show much effect over the range of 5 × 10^2 to 5× 10^4 N/m. It is also found that the effect on the retention time of the diameter ratio of the packed column to the packed particles seems complex showing a non-monotonous dependence.     

兵无常势，水无常形——漫谈流体与流动性

本文阐述流体与流动性的有关概念,并以大量生动有力的例子论述了流体与流动性在自然科学、人文社会科学以及工业生产技术等领域的应用     

CHARACTERIZATION OF POWDER FLOWABILITY USING MEASUREMENT OF ANGLE OF REPOSE

In response to the need in industry for a quick and reproducible method of measuring the flowability of powders in processes involving transport and storage, the apparently simple idea of measuring angle of repose has been revived. The simple tester first used has evolved over a number of years into the present version which is shown to be capable of handling quite small samples of powders that are even slightly cohesive. Experimental data are presented and results shown to compare consistently with the better known Hausner ratio.     

A qualitative study on the pulsatile flow phenomenon in a dense fly ash pneumatic conveyor

Understanding of the dynamic particulate flow structures within a dense gas-fly ash pneumatic conveyor must be improved in order to better aid its design guidance.The complex pulsatile movement of the gas-fly ash mixture dominates the flow performance within the pipeline,and historically,non-invasive measurement devices such as the electrical capacitance tomography（ECT） were often used to sufficiently capture the flow dynamics.However,inadequate studies have been conducted on the pulsatile flow phenomenon,which directly relate to the gas-fly ash two-phase flow performance.This paper aims to investigate the pulsatile flows using an ECT device.Initially,pulsatile flow patterns under various experimental conditions were obtained through ECT.Pulses within a flow were then characterised into pulse growth and decay segments,which represent the superficial fluidisation and deaeration processes during conveying.Subsequently,structural and statistical analyses were performed on the pulse growth and decay segments.Results suggested that the increasing air mass flow rate led to the decrease of the superficial fluidisation/deaeration magnitude,however,the increase of the superficial fluidisation/deaeration durations.Also,the air mass flow rate was indicated as the dominant factor in determining the pulsing statistical parameters.This research provides fundamental insights for further modelling the dense fly ash pneumatic flows.     

流动性能提高套利交易的盈利吗？——基于中国股市的证据

本文以新兴市场重要组成部分之一的中国股市为例,对市场总体流动性水平与套利交易盈利能力间的关系进行了深入分析。与成熟资本市场中的状况相反,本文研究发现,在控制了Fama-French三因子后,套利交易的预期盈利随着市场流动性水平的提高而增加,表明市场异象造成的错误定价并不会随着流动性的提高而被投资者的套利交易所纠正,这体现了不成熟市场的特征,且反映了套利的无效率。另外,本文在分析中还考虑了流动性风险和时变因素风险暴露等可能对研究结论造成影响的因素,并且在进一步研究后得到了与前文相一致的结论。