Forced convective flow and heat transfer characteristics of aqueous drag-reducing fluid with carbon nanotubes added

A new kind of aqueous drag-reducing fluid with carbon nanotubes (CNTs) was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CNTs added and has both special effects of drag-reducing and heat transfer enhancement. The thermophysical and rheological properties of the new working fluid were measured. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag-reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube having an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag-reducing fluid and new drag-reducing nanofluid. However, there were obvious differences of the heat transfer characteristics between both fluids. The heat transfer characteristics of new drag-reducing nanofluid have strong dependences on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be used to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.     

同步顶升法在化工装置改造中的应用

大庆石化公司炼油厂二重催MIP改造空冷器平台整体提升施工难度较大,经过分析、计算、方案对比,提出采用千斤顶同步顶升方法替代传统的吊装工艺,顺利的完成了260 t重的空冷器平台整体提升任务,不仅节约施工成本,同时还探索出一条化工装置有限空间施工的新途径。     

现代大客车技术分析

通过对国内外大客车三大总成的最新技术进行分析，探讨我国大客技术的发展方向。     

新型永磁式开关磁阻电动机电磁场的二维有限元分析

采用二维有了元模型对新型永磁式开关磁阻电动机的电磁场了分析。     

基于改进LRCN的人体运动识别方法

针对人体运动识别中数据特征提取不充分和识别准确率不高的问题，提出了一种改进长期循环卷积网络的人体运动识别模型。首先构建出一种由多层卷积神经网络和门控循环单元组成的LRCN模型。在此基础上构建内部和外部循环层，内部循环层作用是得到所选取时间窗内部时间特征和空间特征，外部循环层作用是从子序列数据中获取其所表征状态信息之间的特征相关性和时间相关性。提出的模型在3种公开数据集上验证，准确率均高于传统的LRCN模型，然后在自建数据集上进行测试验证，识别准确率为99.7%。实验结果表明该模型在识别准确率上高于原始模型，验证了该模型的可行性。     

Numerical electromagnetic analysis of impulse voltage measuringsystems

The unit step response (USR) of lightning impulse voltage measuring systems is numerically calculated with the help of the Numerical Electromagnetic Code (NEC-2), which calculates the three-dimensional electromagnetic field around conducting wires. The accuracy of this analysis is proved satisfactory through comparison of the results of measurement with calculation. The advantage of this method is that the influence of the geometry of the circuit can automatically be calculated without evaluating stray capacitance in the system. Therefore, this method of analysis can be applied to the development of an impulse voltage divider, or in analyzing the influence of elements of a USR measuring circuit. The influence of the shield ring attached to a resistance divider, and of the vertical metal sheet in the IEC-recommended USR measuring circuit on the USR waveform is analyzed as an example     

Influences of Bentonite on conductivity of composite solid alkaline polymer electrolyte PVA-Bentonite-KOH-H2O

The influence of the dopant Bentonite, on the ionic conductivity of the PVA-KOH-H₂O alkaline solid polymer electrolyte (ASPE) is studied. The results show that the addition of Bentonite has both positive and negative effects on the ionic conductivity of ASPE. At lower KOH and H₂O contents, the addition of Bentonite can break the continuous ion conducting phase of the ASPE, and therefore decrease the ASPE conductivity. However, the addition of Bentonite can also increase the KOH content in PVA matrix. This greatly increases the conductivity of the ASPE especially at higher water content. A highest ionic conductivity of 0.11 S cm⁻¹ is reached at room temperature. A maximum ionic conductivity value is observed at relative lower water content for different amount of Bentonite-doped ASPE. The temperature dependence of the ionic conductivity is of the Arrhenius type. The ion transfer activation energy Ea, in the order of 4-6 kJ mol⁻¹, heavily depends on the Bentonite content. XRD and SEM tests show that PVA in the Bentonite-doped ASPE is of amorphous structure, and there are lots of interspaces in the composite ASPE inner structure. The composite electrolyte has good electrochemical stability window and good charged-discharge property in secondary Zn-Ni cells at low charge-discharge rate.     

超声辅助醇沉法制备淀粉纳米颗粒同步包埋叶黄素

为制备叶黄素淀粉纳米颗粒(SNPs-叶黄素)，以木薯淀粉为原料，叶黄素醇溶液为非溶剂相，通过超声辅助醇沉法制备淀粉纳米颗粒，同步实现对叶黄素的包埋负载。合理平衡叶黄素包埋量及包埋率两个目标参数，在质量分数为3%淀粉乳、叶黄素溶液质量浓度1 mg/mL、淀粉乳与叶黄素醇溶液体积比3∶10条件下，对叶黄素的包埋量达(57.62±0.36)mg/g，包埋率(40.33±0.56)%。场地发射扫描电镜显示同步包埋叶黄素未对淀粉纳米颗粒形貌产生显著影响，均为表面光滑的球状或椭圆状颗粒。激光纳米粒度仪显示SNPs-叶黄素尺寸分布在200～600 nm范围。傅里叶红外光谱显示SNPs-叶黄素在2 856 cm-1处出现叶黄素的C-H特征峰，在1 645 cm-1处H-O-H的振动发生蓝移。X射线衍射显示，与SNPs的大包峰相比，SNPs-叶黄素在7.8，13.1和20.9出现V型淀粉特征衍射峰。贮藏稳定性试验表明，在30 d内，室温(25 ℃)和升温条件下(50 ℃)，SNPs-叶黄素中叶黄素的保留率高于叶黄素原料药。