用乒乓球化解浮力教学中的两个难点

1 实验:浮力方向总是竖直向上的 在初中物理浮力的教学中,浮力的方向总是竖直向上的,教材中没有专门的实验直观显示,学生虽能理解浮力的方向是向上的.但理解浮力方向总是竖直向上的就有一定困难.     

Criteria for monotonicity properties of Musielak-Orlicz spaces equipped with the Amemiya norm

Criteria for strict monotonicity, lower local uniform monotonicity, upper local uniform monotonicity, and uniform monotonicity of Musielak-Orlicz spaces over any σ-finite and complete measure space, endowed with the Amemiya norm are given. The fact that the spaces are considered over arbitrary σ-finite measure space is essential because, as it is shown in Example 3, the Musielak-Orlicz spaces need not be strictly monotone even if their restrictions to the nonatomic part and the purely atomic part are strictly monotone.     

Study on eight-pass dual-frequency laser interferometer with nanometer precision

A new dual-frequency laser displacement measurement interferometer with nanometer precision has been developed. An eight-pass optical subdivision technology is proposed to improve resolution based on commercial interferometers. A static positioning error measuring method has been used to examine the precision and repeatability of the laser interferometer. An optical resolution of 1.24 nm and an accuracy of nanometer scale have been achieved.     

Quasisolutions and dynamics of time-periodic nonquasimonotone reaction-diffusion systems

In this paper, using the upper-lower solution method, we investigate the properties of periodic quasisolutions for time-periodic nonquasimonotone reaction-diffusion systems, and present some existence, asymptotic behavior results for two ecological models.     

聚集效应对银纳米粒子的二阶非线性光学特性的影响研究

运用超瑞利散射(HRS)技术,对由KNO3诱导聚集的银纳米粒子的二阶光学非线性特性进行了实验研究.通过粒子尺寸测量和透射电镜观察，表明银纳米粒子的聚集方式为链状聚集.当聚集体平均尺寸为120nm时，银纳米粒子聚集体的HRS信号强度比聚集前增大了约15倍.分析表明，聚集导致银纳米粒子表面电场极化强度的增强和极化分布的改变，并通过表面和体贡献机理对二阶非线性极化过程产生影响. 关键词： 银纳米粒子 超瑞利散射 二阶光学非线性 聚集     

Two novel molybdenum complexes containing [Mo2O2S2]2+ fragment: synthesis,crystal structures and catalytic studies

Mo₂O₂S₂(HGly)(Gly)₂ 1 and K₆[Mo₂O₂S₂(nta)₂][Mo₂O₂S₂(ntaH)₂]^·4H₂O 2 were synthesized by the reactions of (NH₄)₂MoS₄ and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol–water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV–visible spectra, TG–DTA and XPS. X‐ray crystallographic structural analyses revealed that compound 1 is a binuclear Mo? S? glycinate complex, a glycinate ligand is coordinated to each molybdenum atom through its amine nitrogen and carboxylato oxygen, respectively, and the third glycinate acts as a bridge through its two carboxylato oxygens linking the two molybdenum atoms. Compound 2 is also a binuclear Mo? S complex with two nitrilotriacetate ligands, each of which is coordinated to a molybdenum atom via its two β‐carboxylato oxygens and a nitrogen atom. Simultaneously, each molybdenum atom in 1 and 2 is chelated to a terminal oxygen and two bridging sulfurs to complete the octahedral configuration. Their catalytic activities in the reduction from C₂H₂ to C₂H₄ as well as other binuclear Mo? S? polycarboxylate complexes, a [Fe₄S₄] single cubane and a chainlike Mo? Fe? S compound were investigated and it was found that 1 exhibited relatively good catalytic activity. Copyright © 2007 John Wiley & Sons, Ltd.     

低温下使用的金刚石对顶砧高压盒和显微光谱系统

自Bridgeman发明套筒活塞高压装置以来,特别是引入金刚石压砧后,高压物理学发展迅速。这种金刚石对顶砧压力盒,简称为DAC,为研究高压下材料的光学性质提供了极大的方便。为进行高压低温研究,目前国内都是将压机浸入液氮中,或向DAC喷浇液氮。这样只能在77K恒温,且必须取出压机后才能加压。     

离子束刻蚀技术研究

本文介绍了离子束刻蚀技术的原理,讨论了刻蚀速率与离子束流密度、离子能量和离子束入射角度的关系。实验结果与理论分析有较好的一致性。     

静水压对牛奶中细菌生长繁殖的影响

 在20~120 MPa静水压力范围内，研究了压力对鲜牛奶中细菌的生长繁殖的影响。我们发现，在室温及20 MPa静水压下受压5 min后，细菌的生理活性显著降低，其生长繁殖受到抑制，而且生理活性的降低是一种压力非在位效应。     

北京同步辐射软X光反射率计装置及其物理工作

介绍了安装在北京同步辐射装置上专门用于软X光多层膜研究的反射率计系统,给出了在该装置上测量得到的Al滤光片的软X光透射谱和Nb/Si多层膜的高角反射谱,用磁控溅射方法自制的Nb/Si多层膜样品在17.59um附近得到的反射率为32%.