Flotation Behavior,Collector Adsorption Mechanism of Quartz and Feldspar-Quartz Systems Using PEA as a Novel Green Collector

Silicon - A novel green cationic surfactant Poly (propylene glycol) bis (2-aminopropyl ether) (PEA) with multiple amine groups was utilized as a collector for flotation separation of quartz from...     

淀粉分子磁化修饰及其再生膜材料制备

以高直链淀粉（HS）为原料，通过“还原胺化-点击化学法”在其还原性端的潜在醛基上进行磁化分子修饰，得到具有磁性的变性淀粉（MMS），并在外磁场作用下制备再生淀粉膜。具体包括在HS分子唯一的潜在醛基上引入炔基，对四氧化三铁粒子（MNP）进行硅烷包覆得到叠氮化磁体粒子（azide-MNPs），两者经点击化学反应得到分子链末端带磁的变性淀粉。借助XRD、FTIR、NMR和MALDI-TOF MS对产物进行结构表征，结果表明，磁体粒子精准接枝到高直链淀粉分子还原末端，得到目标产物MMS。再生淀粉膜性能测试结果表明，在外磁场诱导条件下MMS逐渐趋于分子有序排列，制得的再生淀粉膜较纯CMS淀粉膜断裂伸长提升49.5%，断裂强度提升88.3%，短程有序程度提高。该文为基于外加磁场下的淀粉再生膜结构设计和力学性能调控提供了新思路。     

拟建鄱阳湖水利枢纽对湖区水环境容量的影响

采用水动力水质模型模拟了鄱阳湖在极端退水年(2016年)和一般退水年(2017年)两种退水工况下拟建鄱阳湖水利枢纽建设前后的水动力水质过程,并构建湖区水环境容量模型评估了鄱阳湖拟建水利枢纽对湖区水质和水环境容量的影响。模拟结果表明：枢纽建设运行能显著增加鄱阳湖的水体体积,每月最大可增加77%;在退水初期主要降低湖泊中部的TP质量浓度,在极端退水年的退水后期会导致闸上TP质量浓度升高,在一般退水年则会导致闸上TP质量浓度降低,但对COD_Mn和NH₃-N质量浓度空间分布无明显影响;在极端退水年,枢纽建设运行会导致COD_Mn、NH₃-N和TP质量浓度增大,而在一般退水年则会导致TP的质量浓度降低;枢纽建设运行能显著提升COD_Mn和NH₃-N的水环境容量,在一般退水年会增大TP的水环境容量,但在极端退水年TP的水环境容量可能降低。     

Reaching the Fundamental Limitation in CO2 Reduction to CO with Single Atom Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) to value-added chemicals with renewable electricity is a promising method to decarbonize parts of the chemical industry. Recently, single metal atoms in nitrogen-doped carbon (MNC) have emerged as potential electrocatalysts for CO₂RR to CO with high activity and faradaic efficiency, although the reaction limitation for CO₂RR to CO is unclear. To understand the comparison of intrinsic activity of different MNCs, two catalysts are synthesized through a decoupled two-step synthesis approach of high temperature pyrolysis and low temperature metalation (Fe or Ni). The highly meso-porous structure results in the highest reported electrochemical active site utilization based on in situ nitrite stripping; up to 59±6% for NiNC. Ex situ X-ray absorption spectroscopy (XAS) confirms the penta-coordinated nature of the active sites. The catalysts are amongst the most active in the literature for CO₂ reduction to CO. The density functional theory calculations (DFT) show that their binding to the reaction intermediates approximates to that of Au surfaces. However, it is found that the turnover frequencies (TOFs) of the most active catalysts for CO evolution converge, suggesting a fundamental ceiling to the catalytic rates.     

光学经纬仪一测回水平方向标准偏差的测量不确定度评定

本文采用多齿分度台方法对DJ2级光学经纬仪一测回水平方向标准偏差进行测量,分析了测量结果不确定度的主要来源,并对测量值的不确定度进行评定,最后提出了用多齿分度台方法进行检定时应注意的问题。     

果蔬中外泌体样纳米颗粒的分离、表征和应用研究进展

果蔬中的外泌体样纳米颗粒（exosome-like nanoparticles，ELNs）是由果蔬细胞释放的纳米级囊泡结构，与动物的外泌体具有类似的超微结构，但其脂质、蛋白质及核酸等化学成分具有显著差异，并具有独特的生物学功能。本文综述了2013年以来数十种果蔬中ELNs的相关研究进展，对其提取方法和表征手段进行了分析，重点分析了不同植物来源的ELNs中脂质、蛋白质和核酸类化学成分的组成差异，并对ELNs的潜在生理活性和载体功能进行了探讨，可为果蔬中ELNs的相关研究提供借鉴和启示。     

聚α-烯烃合成油及其加氢工艺的研究进展

聚α-烯烃合成油是所有合成润滑油基础油中性能最优异的一种,具有黏度指数高、低温性能和高温氧化安定性好、抗燃性好及挥发性低等优点,是未来应用广泛的合成基础油,市场需求持续增加。综述聚α-烯烃基础油及其加氢工艺、加氢精制催化剂的研究现状。传统聚α-烯烃合成油生产工艺有乙烯齐聚法和石蜡裂解法等,潞安煤制油工艺和天然气制油工艺等新工艺也开始兴起。加氢精制工艺对提高聚α-烯烃合成油的质量起着至关重要的作用,北京燕化聚华工贸有限公司两段加氢精制工艺和中国石油兰州润滑油厂聚α-烯烃合成油加氢精制处理工艺均极大改善了聚α-烯烃合成油的质量。聚α-烯烃合成油加氢精制效果很大程度取决于加氢精制催化剂性能,要求加氢精制催化剂具有较高的选择性和较好的稳定性。     

Model reduction for nonlinear multiscale parabolic problems using dynamic mode decomposition

In this article, a model reduction technique is presented to solve nonlinear multiscale parabolic problems using dynamic mode decomposition. The multiple scales and nonlinearity bring great challenges for simulating the problems. To overcome this difficulty, we develop a model reduction method for the nonlinear multiscale dynamic problems by integrating constraint energy minimizing generalized multiscale finite element method (CEM-GMsFEM) with dynamic mode decomposition (DMD). CEM-GMsFEM has shown great efficiency to solve linear multiscale problems in a coarse space. However, using CEM-GMsFEM to directly solve multiscale nonlinear parabolic models involves dynamically computing the residual and the Jacobian on a fine grid. This may be very computationally expensive because the evaluation of the nonlinear term is implemented in a high-dimensional fine scale space. As a data-driven method, DMD can use observation data and give an explicit expression to accurately describe the underlying nonlinear dynamic system. To efficiently compute the multiscale nonlinear parabolic problems, we propose a CEM-DMD model reduction by combing CEM-GMsFEM and DMD. The CEM-DMD reduced model is a coarsen linear model, which avoids the nonlinear solver in the fine space. It is crucial to judiciously choose observation in DMD. Only proper observation can render an accurate DMD model. In the context of CEM-DMD, we introduce two different observations: fine scale observation and coarse scale observation. In the construction of DMD model, the coarse scale observation requires much less computation than the fine scale observation. The CEM-DMD model using the coarse scale observation gives a complete coarse model for the nonlinear multiscale dynamic systems and significantly improves the computation efficiency. To show the performance of the CEM-DMD using the different observations, we present a few numerical results for the nonlinear multiscale parabolic problems in heterogeneous porous media.     

黏性土和纤维对风积沙改性土热膨胀特性的影响

风积沙改性土的热膨胀特性对评价风积沙改性土路基温度稳定性至关重要.通过在风积沙中掺入不同质量的水泥、黏性土或聚丙烯纤维制成不同配比的改性土,测试改性土的热膨胀系数,研究外加材料的掺入量对改性土热膨胀特性的影响.试验结果表明:改性土的平均线膨胀系数随着水泥掺入量的增加总体呈增大趋势,随着聚丙烯纤维掺入量的增加而减小,随着黏性土掺入量的增加而增大.聚丙烯纤维的掺入可有效降低改性土的热膨胀系数.研究成果可为进一步优化改性土提供研究方向,为高温差沙漠地区工程建设中风积沙改性土温度裂缝的控制提供试验依据.