Thermal and mechanical properties and micro-mechanism of SiO2/epoxy nanodielectrics

In addition to electrical insulation properties, the thermal properties of nanodielectrics, such as glass transition temperature, thermal expansion coefficients, thermal conductivity, and mechanical properties, including Young's modulus, bulk modulus, and shear modulus, are also very important. This paper describes the molecular dynamics simulations of epoxy resin doped with SiO₂ nanoparticles and with SiO₂ nanoparticles that have been surface grafted with hexamethyldisilazane (HMDS) at 10% and 20% grafting rates. The results show that surface grafting can improve certain thermal and mechanical properties of the system. Our analysis indicates that the improved thermal performance occurs because the formation of thermal chains becomes easier after the surface grafting treatment. The improved mechanical properties originate from two causes. First, doping with SiO₂ nanoparticles inhibits the degree of movement of molecular chains in the system. Second, the surface grafting treatment weakens the molecular repulsion between SiO₂ and epoxy resin, and the van der Waals excluded region becomes thinner. Thus, the compatibility between SiO₂ nanoparticles and polymers is improved by the grafting treatment. The analysis method and conclusions in this paper provide guidance and reference for the future studies of the thermal and mechanical properties of nanodielectrics.     

In-situ TEM observation of the evolution of helium bubbles in Mo during He+ irradiation and post-irradiation annealing

The evolution of helium bubbles in purity Mo was investigated by in-situ transmission electron microscopy (TEM) during 30 keV He⁺ irradiation (at 673 K and 1173 K) and post-irradiation annealing (after 30 keV He⁺ irradiation with the fluence of 5.74×10¹⁶ He⁺/cm² at 673 K). Both He⁺ irradiation and subsequently annealing induced the initiation, aggregation, and growth of helium bubbles. Temperature had a significant effect on the initiation and evolution of helium bubbles. The higher the irradiation temperature was, the larger the bubble size at the same irradiation fluence would be. At 1173 K irradiation, helium bubbles nucleated and grew preferentially at grain boundaries and showed super large size, which would induce the formation of microcracks. At the same time, the geometry of helium bubbles changed from sphericity to polyhedron. The polyhedral bubbles preferred to grow in the shape bounded by {100} planes. After statistical analysis of the characteristic parameters of helium bubbles, the functions between the average size, number density of helium bubbles, swelling rate and irradiation damage were obtained. Meanwhile, an empirical formula for calculating the size of helium bubbles during the annealing was also provided.     

深度学习与“课程思政”协同效应的策略研究——以医用物理学为例

以医用物理学为载体,以深度学习为核心,以达成"课程思政"对课程和学生的要求为目标,探讨了深度学习与"课程思政"的内在联系,在提出课堂教学困境的基础上,讨论了实现深度学习与"课程思政"协同效应的策略,包括提高参与程度、完善学习过程、建构知识的意义和采用多元评价方式.     

随机双指数记忆耗散系统的非马尔可夫扩散

针对具有双指数耗散记忆核函数的两自由度耦合系统, 本文利用Laplace变换导出了热宽带噪声激励下该系统响应二阶矩的解析表达式. 并观察到位移二阶矩不同于单自由度情形下的反常扩散:<x²(t)> ∝ t^α (0<α<2, α≠1), 而是随时间及噪声等参数变化呈现普遍的振荡扩散现象.分析可得, 阻尼耦合因子B使粒子远离简谐势场的束缚, <x²(t)>随B的增大扩散加剧而摩擦系数增大却使其趋于平稳状态.进一步, 若两热噪声互关联时, 较小的互关联时间对二阶矩的影响较大, 反之作用较小. 伴随互关联强度递增, 位移二阶矩的扩散加剧, 位移间的相关性加强, 与物理直观相符. 关键词： 热噪声 非马尔可夫扩散 广义朗之万方程 关联性     

空间过滤简正波的模拟实验研究

在侧壁无消声的波浪槽（70×2×0.6m³）内,利用9根有水平指向性的长圆管换能器作阵元,实现了前四号简正波的空间过滤,定性地研究了简正波过滤阵抑制近场点源干扰的理论概念,并对起伏波浪表面对各号简正波振幅起伏的影响作了初步观察。     

广义oup2的马氏性,转移概率和预测

本文充分地利用文献［３］、［５］所得到的结论对广义ｏｕｐ２讨论了单点马氏性、宽过去马氏性、宽将来马氏性、＊－马氏性，各种转移概率及其预测问题。     

ASYMPTOTIC BEHAVIOR OF SOLUTIONS OF RETARDED DIFFERENTIAL EQUATIONS

ＡＳＹＭＰＴＯＴＩＣＢＥＨＡＶＩＯＲＯＦＳＯＬＵＴＩＯＮＳＯＦＲＥＴＡＲＤＥＤＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＬｉＪｉｎｇｗｅｎ（李经文）（ＳｈａｏｙａｎｇＴｅａｃｈｅｒ＇ｓＣｏｌｌｅｇｅ）ａｎｄＳｈｉＹｏｎｇｓｈｅｎｇ（石永生）（Ｌｉｎｇ...     

Banach空间中的相补问题

本文在Ｂａｎａｃｈ空间中研究了三类相补问题解的存在性。所得结果是［４，５，６，９，１１－１４］中相应结果的深入和发展。     

服装主观热感觉的统计分析

本文用多因子方差分析模型和多重比较分析了服装穿着时的主观热感觉与服装品种、环境条件、穿着者的活动状态与籍贯之间的关系。通过主成分回归建立了用生理指标预测主观热感觉的模型，从而得出一种定量地评价服装属性的方法。