Oxidation behavior of copper nanoparticles at low temperature

A mass gain for copper nanoparticles with a mean diameter of 20 nm in a 20% oxygen-nitrogen atmosphere was measured at 150-300 °C using thermogravimetry (TG). The mass gain equilibrium of the copper particles differed at each temperature, and a threshold temperature was recorded. Oxide products, consisting mainly of Cu₂O, formed on the copper nanoparticles below the threshold temperature. Above the threshold temperature, there was an initial, and drastic, formation of Cu₂O, which then changed to CuO. The activation energy for the oxidation of the copper nanoparticles that could be calculated from the rate of the mass gain was an indication of the nano-effect of the copper nanoparticles.     

ITU-R P.434计算F2层基本最高可用频率与实测值的比较

利用我国2011年1月和7月10条斜测电路的F₂层基本最高可用频率(MUF)月中值数据,与ITU-R P.434方法计算的F₂层基本MUF进行了比较,分析了该方法在中国地区的适用性。结果表明:ITU-R P.434方法在中国地区具有较好的适用性,但在某些电路的个别时段偏差较大。其中,1月份在中纬地区日出时段,该方法给出的基本MUF与月中值相比偏低20%~30%,在日落时段则偏高20%~30%;低纬地区夜间时段两者的相对偏差较大,最大值达到40%.7月份,该方法的结果与各条电路的实测结果基本一致,相对偏差在-10%~20%之间。上述结果对短波通信的选频等具有一定的指导意义。     

扩展F全球分布特点的理论分析

考虑到我国区域电离层扩展F发生的物理机制和相关因素以及观测数据的可获取性,利用适宜于时间序列预测的长短期记忆网络建立了我国不同区域电离层扩展F事件的预测模型,对未来3 h是否会发生扩展F事件进行预测。以处于我国典型纬度地区的满洲里、北京、海口站为例,利用2015和2016年测试数据集对模型预测精度进行了检验,满洲里、北京、海口站平均准确率分别为92.4%、95.3%、96.0%,平均精确率分别为75.0%、61.2%、62.6%,平均召回率分别为73.0%、50.6%、31.5%。由此可见：在某些情况下,比如在低纬度地区的海口站,模型的召回率较低;除此之外,所建立的扩展F模型在多数情况下具有较高的预测能力。     

等离子体散射分析的改进型交替隐式时域方法

提出了一种改进的交替隐式时域有限差分(FDTD)方法,运用该方法分析了等离子体涂覆导体圆柱的散射特性,为等离子体隐身技术的运用提供了一定的理论指导.该方法在整个问题空间采用完整场形式的场量进行迭代计算,并运用中心差分格式离散极化电流密度辅助方程.仿真实验表明,提出的算法具有无条件稳定特性,其计算效率明显优于以往文献提出的交替隐式FDTD方法,在精度和效率上也稍高于普通的显式FDTD方法.     

Effects of stimulus information and number of stimuli on sequential dependencies in absolute identification.

Three absolute identification experiments examined the effects on sequential dependencies of 2 factors: stimulus information and the number of stimuli used. Data were analyzed by multivariate information analysis. In Exp 1 with 5 university studentswith experience in absolute identification experiments, the stimulus modality was pure tone frequency under masking and no-masking conditions and 4, 6 10, and 16 tones were used. In Exp 2 with 5 university students, luminance levels of light circles were used as stimuli and number of luminance levels was 10 or 16. In Exp 3 with 6 university students, the stimuli were pointer positions along a horizontal line and they were presented either within a small or a large range to manipulate the stimulus information available. Results show that the sequential dependencies became larger as the stimulus information was decreased and as the number of stimuli was increased. Results are discussed in the context of models of sequential dependencies. Results of a multiple regression analysis on the data were compared with those of the information analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SAW气体传感器的转换机制

讨论了在SAW气体的传感器中把化学信号(气体浓度)转换成物理信号(SAW相速度变化)的机制以及将它们彼此分离开来的方法.     

浅谈入世后我国农产品质量安全和标准体系建设

<正> 随着农业发展进入新的阶段,农产品质量安全已成为制约我国农业和农村经济发展的突出问题。特别是WTO成立以来,伴随着农产品贸易的自由进程,传统的关税壁垒作用在逐步减弱,以控制农产品质量安全为中心的技术性壁垒的作用在逐步加强,围绕农产品质量安全而产生的贸易摩擦乃至争端呈增长趋势。我国加入WTO之后,无论是农产品的国内市场,还是面对国际农产品贸易,都不可避免地要被卷入这场新的国际角逐。