The structure and electric characters of proton‐conducting chitosan membranes with various ammonium salts as complexant

The structural and electric properties of chitosan electrolytes doped by three different ammonium salts [CH₃COONH₄, NH₄Cl, and (NH₄)₂SO₄] were discussed. The chitosan electrolytes were prepared by solution casting technique. The results show that the addition of ammonium salts leads to: The formation of complexation between ammonium salts and chitosan matrix, the destruction of crystal forms, and the enhancement of amorphous nature. With the rise of salt content, both the glass transition temperature and the activation energy show a “V”‐type trend, whereas the conductivity exhibits a reverse trend. For different ammonium salts, the electric properties of the chitosan electrolyte are different due to the Coulomb force between anion of salts and functional groups. The CH₃COONH₄ doped chitosan electrolyte exhibits the optimum electric properties, whereas those of (NH₄)₂SO₄ doped chitosan electrolyte are worst. The chitosan electrolyte doped with 40 wt % CH₃COONH₄ has the lowest glass transition temperature of 369 K, the lowest activation energy of 0.19 eV, and the highest ionic conductivity of 2.87 × 10^?4 S cm^?1 at room temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 880–885, 2010     

高校实验室危险化学品采购管理体系的建设与实践

由于高校实验室危险化学品重大事故时有发生,对危险化学品的管理已成为高校实验室安全管理的重要问题。本文以郑州大学为例,从危险化学品的采购、存储、配送、使用、危废收集全过程,梳理和分析实验室危险化学品管理存在的问题,针对危险化学品的安全管理体系建设进行了探索,介绍了危险化学品采购管理一体化平台的建设思路和具体措施,有效实现了危险化学品全生命周期管理,保障学校教学科研安全运行。     

Remarks on blowup of solutions for one-dimensional compressible Navier–Stokes equations with Maxwell's law

In this note, we present some blowup results of solutions to the one-dimensional compressible Navier–Stokes equations with Maxwell's law. First, we improve the blowup result of Hu and Wang [Math. Nachr. 92 (2019), 826–840] with initial density away from vacuum by removing two restrictions. Next, we give a blowup result for the solutions with decay at far fields. Finally, we construct some special analytical solutions to exhibit the blowup or non-blowup phenomena for the relaxed system.     

Viscoelastic Behavior of Poly(Methyl Methacrylate-Co-Methyl Acrylate) Random Copolymer Studied by Dynamic Mechanical Analysis and Nanoindentation

The viscoelastic behavior of poly(methyl methacrylate) (PMMA) homopolymer and poly(methyl methacrylate-co-methyl acrylate) random copolymers was characterized by dynamic mechanical analysis and nanoindentation. Differential scanning calorimetric results showed only one glass transition, indicating the random distribution of comonomers in the copolymers. The α relaxation temperature (T_α) and activation energy (H_α) decreased with increasing content of methyl acrylate monomers (C_MA%). The β relaxation temperature (T_β) also decreased whereas the activation energy (H_β) showed only small variations compared with H_α. Moreover, the indention displacement and creep compliance strongly depended on C_MA%. Two creep stages were found in the creep compliance curves.     

A New Crystal Phase Molybdate Yb2Mo4O15: The Synthesis and Upconversion Properties

A new upconversion nanocrystal phase Yb₂Mo₄O₁₅:Er is developed by using a facile aqueous‐precipitation procedure combined with thermal annealing. Nanocrystals of Yb₂Mo₄O₁₅ are exclusively synthesized, with particle sizes ranging from 1 to 20 nm. The optical properties are characterized and a high upconversion quantum yield is determined to be ≈1.3% at room temperature, under excitation of ≈500 mW cm^?2 IR (975 nm). To the best of our knowledge, this is the first work concerning the synthesis of nanocrystalline Yb₂Mo₄O₁₅ and the characterization of its upconversion properties, which possesses the potential to be utilized in bio‐probing and thin‐film optoelectronic device applications.     

Walsh变换对鱼类特征识别的研究*

鱼种的快速识别是渔业资源评估乃至海洋生态系统监测重要组成部分。与传统的拖网捕捞等方法相比,声学方法具有快速有效、调查区域广、不损坏生物资源、可持续观察等优点。鱼类的声学识别方法主要是基于鱼类回波信号特征的识别, 鱼体形状及组成结构的复杂多样导致其回波信号非常复杂,因此利用简单的回波包络或能量特征识别鱼类效果往往不能令人满意。本文提出一种基于Walsh 变换的鱼类回波识别方法。试验获取鲫鱼、 嘎鱼、武昌鱼的回波信号,处理过程中分别提取三种鱼类回波包络信号的Walsh谱作为识别特征量,并利用BP神经网络分类器对其进行了分类。结果表明利用回波的Walsh谱可以成功识别不同形状的鱼类,其中对武昌鱼的识别正确率达90%以上。     

梳状波导结构中石墨烯表面等离子体的传播性质

理论上研究了介质/石墨烯/介质梳状波导结构中表面等离子体的传播性质. 波导中表面等离子体模的有效折射率随着石墨烯费米能级的提高而减小, 随着介质折射率的增加而增加. 分析和仿真结果表明, 基于这种梳状波导可以在中红外波段实现新型的纳米等离子体滤波器, 器件的尺度在几百纳米的范围. 通过改变梳状分支的长度, 石墨烯的费米能级, 介质的折射率和波导中石墨烯的层数, 很容易来调节带隙的位置. 另外, 滤波带隙的宽度随着梳状分支数的增加而增加. 这种滤波性质将在可调的高集成光子滤波器件中具有潜在的应用.     

多层石墨烯作为液体石蜡添加剂的摩擦学性能（英文）

以膨胀石墨为原料,采用不同溶剂,通过液相超声直接剥离法制备多层石墨烯,利用透射电子显微镜、原子力学显微镜对其形貌进行了表征,在多功能往复摩擦磨损试验仪上研究了石墨烯石蜡分散体系的摩擦学性能。通过扫描电镜、能谱仪分析了磨痕形貌及表面元素组成。结果表明:多层石墨烯作为液体石蜡添加剂表现出良好的减摩抗磨性能,主要是因为多层石墨烯在磨损表面形成的物理吸附膜与摩擦化学反应膜的共同作用。     

某些完全正则半环的刻画

研究了完全正则半环的特征.利用半群的方法,得到了当分配半环的乘法幂等元集分别是左零带、矩形带以及正规带时,该类半环成为完全正则半环的等价刻画,推广并改进了相关文献的主要结果.