The formation of fibrous structure of polyamide 6 induced by the three-step forming process and its prominent reinforcement in nitrile rubber

Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472.     

测量二次电子空间分布特征矩阵法的有效性分析

为了准确测量不同材料在实际环境中的二次电子空间分布，设计了一种新型的二次电子发射空间分布测量结构，给出了实验测量原理，用求解特征矩阵的方法对实验结果进行处理，得到了所需的二次电子空间分布。通过模拟计算对该测量方法进行了校验，模拟结果与假设二次电子空间分布函数相吻合，表明该测量方法可靠、测量精度高，为后续样机研制奠定了理论基础。     

EPMDA: an efficient privacy-preserving multi-dimensional data aggregation scheme for edge computing-based IoT system

In order to perform multi-dimensional data aggregation operations efficiently in edge computing-based Internet of things (IoT) systems, a new efficient privacy-preserving multi-dimensional data aggregation (EPMDA) scheme is proposed in this paper. EPMDA scheme is characterized by employing the homomorphic Paillier encryption and SM9 signature algorithm. To improve the computation efficiency of the Paillier encryption operation, EPMDA scheme generates a pre-computed modular exponentiation table of each dimensional data,and the Paillier encryption operation can be implemented by using only several modular multiplications. For the multi-dimensional data, the scheme concatenates zeros between two adjacent dimensional data to avoid data overflow in the sum operation of ciphertexts. To enhance security, EPMDA scheme sets random number at the high address of the exponent. Moreover, the scheme utilizes SM9 signature scheme to guarantee device authentication and data integrity. The performance evaluation and comparison show that EPMDA scheme is more efficient than the existing multi-dimensional data aggregation schemes.     

锂辉石-氧化钙烧结法提锂的物相重构与动力学

对锂辉石-氧化钙烧结过程进行热力学分析，绘制了各反应Gibbs自由能与温度的关系图。结果表明，Al₂O₃会优先和Na₂O、Li₂O、K₂O反应，然后与CaO反应生成CaO·Al₂O₃，而且烧结温度需高于1060℃以保证LiAlSi₂O₆能够完成晶形转变。并探讨了锂辉石-氧化钙烧结法提锂的反应机理。考察了不同烧结条件对锂浸出率的影响并对熟料进行X射线衍射（XRD）分析表征。实验结果表明，在配料比为1∶1.25、烧结温度1150℃、烧结时间60min时，锂的浸出率达到92.14%，熟料中的主要物相为Ca₂SiO₄与LiAlO₂。利用XRD和扫描电镜-能谱联用仪（SEM-EDS）对熟料与浸出渣的物相、显微形貌及元素分布情况进行了分析表征。为了确定烧结反应的控制性步骤，在最优烧结条件的基础上对烧结过程进行动力学分析，结果表明，锂辉石-氧化钙烧结体系属于球形颗粒三维界面化学反应控制，烧结过程的动力学拟合方程为\mathrm{1}-{(\mathrm{1}-x)}^{\mathrm{1}/\mathrm{3}}=\mathrm{0.00677}t。     

气液螺旋环状流压降特性研究

考虑旋流衰减的影响，对气液螺旋环状流的压降特性进行研究并推导出了螺旋环状流压降预测模型。定义压降旋-直比系数为气液两相螺旋环状流和气液两相直流的压降之比，以此来表征旋流衰减对压降的影响。基于量纲分析的方法对压降旋-直比系数进行分析，推导出其表达式，压降旋-直比系数依赖于Lockhart-Martinelli 参数和气相Froude数变化。最终，得出了气液两相螺旋环状流的压降预测模型。在50 mm内径的水平管内对螺旋环状流的压降特性进行了实验研究，其中气相表观流速变化范围为10~16 m/s，体积含液率（LVF）变化范围为0.6%~4.8%。通过与实验数据进行对比，压降预测模型的相对误差在±15%以内，为工程应用提供了参考。     

Preparation and characterization of calcium phosphate cement with enhanced tissue adhesion for bone defect repair

Anti-washout and tissue adhesion properties are essential for the clinical application of injectable bone materials. In this study, we prepared calcium phosphate cement (CPC) with anti-washout and tissue adhesion properties and attempted to build covalent bonds between CPC and the amino groups in bone tissue under a self-regulating pH system in the CPC (acidic to basic). The results of push-out tests demonstrated that a significant enhancement (from 6.42 ± 0.76 N to 61.5 ± 4.09 N) in tissue adhesion was obtained with the addition of 6% (w/w) oxidized sodium alginate (OSA) in CPC. The FTIR, XRD, anti-washout test, XPS, pH test, and SEM results suggested that the synergistic effect of OSA-citric acid (CA) led to the formation of a three-dimensional gel network structure in the CPC, and the Schiff base reaction between aldehyde and amino groups induced adhesion between CPC and the bone tissue. Further, the addition of less OSA had no significant negative effect on the hydration properties of CPC. Our work aims to promote the development of injectable bone material in clinical applications.     

Enhanced photo-electrochemical activity of ZnO/Cu2S nanotube arrays photocathodes

ZnO/Cu₂S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu₂S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu₂S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu₂S nanotube arrays can be adjusted by changing the amount of Cu₂S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu₂S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu₂S.