汽油气相色谱模拟馏程的应用

介绍了用AC8612气相色谱仪对六个汽油组分馏程分析的应用情况,结果表明:该方法的重复性和准确性都较好,与D86相比,结果满足方法的再现性要求,但对于差值大于3℃的点,应定期进行修正,以使结果更准确,该方法用于炼油厂各装置汽油组分馏出口的日常质量监测分析,可以提高分析效率并减少劳动强度。     

一种磁控管用扼流线圈仿真设计

采用电路仿真软件仿真滤波组件S参数曲线,观察曲线随器件参数的变化;介绍利用三维全波电磁仿真软件HFSS简化设计流程的方法,并与测试结果对比。结果表明:利用3D仿真软件在满足器件设计精度的同时可以简化线圈的设计流程。     

基于城区场景的5G SA网络时长驻留比提升策略研究

5G驻留能力是反映5G用户感知非常重要的一个指标。本文重点对影响5G SA网络时长驻留比的因素进行了分析，其次从规划、建设、优化、市场营销4个方面提出了具体的提升思路，并从市场、终端、网络三个维度制定了不同的应对策略。从目前的策略实施和应用效果来看，5G SA时长驻留比提升比较明显，对打造5G 精品网、促进5G业务分流、助力公司数智化转型发展起到了重要作用。     

一种低载噪比突发扩频信号的快速捕获方法实现

针对突发扩频信号用户资源扩大、终端功率降低、系统容量提升等需求,提出了一种低载噪比突发扩频信号的快速捕获硬件实现方法。采用分段匹配滤波器加多普勒并行相干积累的方法,基于硬件实现从算法到工程进行全流程优化设计,最终实现最优的捕获性能。应用结果表明,该硬件设计实现方案的快速捕获性能优越,设计方案正确、可行,已成功应用于工程建设中。     

Use of CFD-DEM to evaluate the effect of intermediate stress ratio on the undrained behaviour of granular materials

This study investigates the effect of intermediate stress ratio (b) on the mechanical behaviour of granular soil in true triaxial tests. A CFD-DEM solver with the ability to model compressible fluid and moving mesh has been developed and calibrated based on existing experimental test results on Nevada sand. The effect of b on the undrained true triaxial test, which has been neglected in the literature, was investigated using a reasonable number of models. The effects of the initial confining stress and initial void ratio also have been studied. The developed model was used to calculate the hydrodynamic forces on the particles and evaluate the ratio of the particle–fluid interaction force to the resultant force on the particles. It has been demonstrated that, in numerical studies, the effect of these forces cannot be neglected.     

Efficiency control of the cooling-down process of a cryogenic helium turbo-expander for a 2 t/d hydrogen liquefier

Efficient liquefaction of hydrogen is a crucial part for the large-scale storage and long-distance transportation of hydrogen. Helium Brayton cycle based on high-speed turbo-expanders has been widely employed in small and medium hydrogen liquefiers. In present study, a coupled model is proposed to predict the performance and cooling-down process of helium turbo-expanders with brake blower, and validation experiments were performed on a helium turbo-expander of a 2 t/d hydrogen liquefier. Experimental results indicated that the characteristic ratio of expander varied significantly during the cooling-down process which led to a large deviation from the optimal efficiency. The impact of brake pressure on the characteristic ratio and efficiency of the helium turbo-expander is studied, and a variable pressure control method is proposed for the efficient operation of turbo-expanders during the cooling-down process of a hydrogen liquefier. Compared with the constant brake pressure control method, the variable pressure control method can increase the expander efficiency by 5%–10% during the cooling-down process in the high temperature zone.     

Simultaneous fractionation of multiple classes of polyphenols from honeybush tea using solid-phase extraction

The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min⁻¹ of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.