含非线性扰动的混合变时滞中立系统鲁棒稳定性新判据

中立型时滞系统在工程实际中有着广泛应用背景.本文研究了一类含非线性扰动的混合变时滞中立型系统地鲁棒稳定性问题.基于直接Lyapunov泛函方法,通过构造一类新的包含时滞区间上下界的三重积分项Lyapunov-Krasovskii泛函,并结合积分不等式方法、自由权矩阵技术和凸组合处理方法,建立了一种新的线性矩阵不等式形式的离散时滞和中立时滞均相关的鲁棒稳定性判据.最后,通过数值算例验证了新判据的有效性和优越性,和一些已有文献相比,本文提出的判据具有更低的保守性.     

木质素热解中CO和CO2形成机理的理论研究

采用密度泛函理论方法(B3LYP)对含苯基的各种木质素模型化合物的脱羰基反应和脱羧基反应进行了理论研究。设计了8种模型化合物 R1-R8的8条脱羰基反应路径(1)-(8)和8种模型化合物 R9-R16的8条脱羧基反应路径(9)-(16)。计算了不同温度下各热解反应途径的标准热力学和动力学参数。计算结果表明,反应路径(1)-(4)的脱羰基反应能垒明显高于反应路径(5)-(8),CO 更可能通过苯基(对羟苯基、愈创木基和紫丁香基)乙醛的脱羰基反应而形成;反应路径(9)-(12)的脱羧基反应能垒低于反应路径(13)-(16),CO2的形成更可能通过苯基(对羟苯基、愈创木基和紫丁香基)甲酸的脱羧基反应而完成。     

医用镍钛合金表面涂覆技术研究概述

镍钛(NiTi)合金因其优异的形状记忆和超弹性性能,良好的耐腐蚀性和生物相容性,在生物医学领域得到了广泛应用。为了避免直接使用可能出现的生物不相容和细胞毒性,采用表面涂覆技术在合金表面涂覆纳米到微米量级厚度的功能薄膜,使其具有比基体更优良的生物相容性、抗腐蚀性和耐磨性等特殊功能。表面涂覆技术与其它表面改性技术相比,具有约束条件少、技术类型广、材料选择空间大等优势,目前应用最为广泛。对电化学沉积、等离子喷涂、磁控溅射、溶胶凝胶法、浸涂技术制备的涂层微观结构、力学性能和耐腐蚀等性能进行综述,并分析各技术的优缺点。随着涂覆技术的发展及制备涂层性能的进一步提高,NiTi合金在牙齿矫正丝、人工关节骨茎、血管成形环等多种医疗领域中的应用将更加广泛和深入。     

铜片在纳米碳化硼水基流体中的腐蚀行为

纳米流体已经被广泛地研究用于提高系统的传热性能和效率,然而对纳米流体的防腐蚀性能关注较少,因此本实验研究了铜片在纳米碳化硼(B4C)流体中的耐腐蚀性能。通过模拟加速防蚀实验,在不同分散情况下的纳米碳化硼流体中对铜片的腐蚀程度进行对比。实验结果表明:采用非离子分散剂,分散介质为膜处理水,流体呈中性或碱性且温度较低时,水基纳米碳化硼流体具有良好的抗腐蚀性能。     

An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene

The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO₂) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part‐per‐million (atomic ppm) detection level, employing laser assisted atom‐probe tomography. The atomistic plan and cross‐sectional views of graphene indicate that oxygen, hydrogen, and their co‐functionalities, OH, CO, and CO₂, which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density‐functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene.     

Recent progress on magnetic iron oxide nanoparticles: synthesis,surface functional strategies and biomedical applications

This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed. In order to implement the practical in vivo or in vitro applications, the IONPs must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of IONPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The new functionalized strategies, problems and major challenges, along with the current directions for the synthesis, surface functionalization and bioapplication of IONPs, are considered. Finally, some future trends and the prospects in these research areas are also discussed.     

废油再生装置冷却设备涡旋压缩机结构参数优化

涡旋压缩机结构参数直接影响到润滑油分子蒸馏再生装备的效率。以基于泛函通用涡旋型线构成的变壁厚涡旋盘为研究对象,建立了以能效比为目标函数的结构参数优化模型。分析了涡旋压缩机压缩过程中由排气容积变化引起的热能变化及能效比变化。以能效比为目标函数,以涡旋盘结构参数及型线方程为变量,利用遗传算法得到能效比最优化时的变量。给出具体算例,并与等壁厚的涡旋型线构成的压缩机进行性能比较,得知前者更优。基于泛函的通用涡旋型线为涡旋压缩机型线设计拓展了思路。     

水乳体系润滑剂中官能团对氮化硅陶瓷摩擦副摩擦学特性的影响

通过一系列摩擦试验考察两组不同碳链长度的酸、醇和烷烃的乳化液对氮化硅陶瓷摩擦副的润滑效果.试验结果表明:与传统金属的润滑效果相反,极性官能团的引入并不能提高试剂的润滑效果;相同碳链长度条件下,酸和醇的润滑效果都比对应烷烃要差.依据摩擦曲线形态特征以及磨斑直径的相对关系,可以发现醇在氮化硅陶瓷表面摩擦时所产生化学反应膜的承载能力较弱并较易在摩擦过程中去除.试验所用的几种水乳体系中,试剂亲水性的提高对润滑效果的提高是不利的.     

基于DOE的“机能窗”设计方法研究

在定义"机能窗"的基础上,阐述了具体模型的品质特性,并运用DOE的方法对其进行了参数设计和结果分析,确定了最佳的参数,最后分别预测了原始及最优条件下的"机能窗",通过二者的对比,证明上述方法是有效且实用的。