Quantitative depth profile analysis of metallic coatings by pulsed radiofrequency glow discharge optical emission spectrometry

In recent years particular effort is being devoted towards the development of pulsed GDs because this powering operation mode could offer important analytical advantages. However, the capabilities of radiofrequency (rf) powered glow discharge (GD) in pulsed mode coupled to optical emission spectrometry (OES) for real depth profile quantification has not been demonstrated yet. Therefore, the first part of this work is focussed on assessing the expected advantages of the pulsed GD mode, in comparison with its continuous mode counterpart, in terms of analytical emission intensities and emission yield parameters. Then, the capability of pulsed rf-GD-OES for determination of thickness and compositional depth profiles is demonstrated by resorting to a simple multi-matrix calibration procedure. A rf forward power of 50 W, a pressure of 600 Pa, 1000 Hz pulse frequency and 50% duty cycle were selected. The quantification procedure used was validated by analysing conductive layers of thicknesses ranging from a few tens of nanometer up to about 20 μm and varied compositions (hot-dipped zinc, galvanneal, back contact of thin film photovoltaic solar cells and tinplates).     

Facile fabrication of a superhydrophobic fabric with mechanical stability and easy-repairability

The poor mechanical stability of superhydrophobic fabrics severely hindered their use in practical applications. Herein, to address this problem, we fabricated a superhydrophobic fabric with both mechanical stability and easy-repairability by a simple method. The mechanical durability of the obtained superhydrophobic fabric was evaluated by finger touching and abrasion with sandpaper. The results show that rough surface textures of the fabric were retained, and the fabric surface still exhibited superhydrophobicity after tests. More importantly, when the fabric lost its superhydrophobicity after a long-time abrasion, it can be easily rendered with superhydrophobicity once more by a regeneration process.     

A compact optofluidic cytometer with integrated liquid-core/PDMS-cladding waveguides

We developed a simple method to construct liquid-core/PDMS-cladding optical waveguides through pressurized filling of dead-ended micro-channels with optical fluids. The waveguides are in the same layer as microfluidic channels which greatly simplifies device fabrication. With proper contrast between the refractive index of the core and cladding, the transmission loss of the waveguides is less than 5 dB cm(-1). We also developed a method to create flat and optically clear surfaces on the sides of PDMS devices in order to couple light between free-space and the waveguides embedded inside the chip. With these newly developed techniques, we make a compact flow cytometer and demonstrate the fluorescence counting of single cells at a rate of up to ～50 cell s(-1) and total sample requirement of a few microlitres. This method of making liquid-core optical waveguides and flat surfaces has great potential to be integrated into many PDMS-based microsystems.     

自适应海杂波抑制电路的实验和理论分析

在价格低廉的采用实时、单扫描数据处理的脉冲雷达中,为了探测小目标,一种自适应海杂波抑制电路已付诸实现。笔者认为,最重要的问题之一是在未知的杂波、雨和噪声环境中,以可能最佳的灵敏度获得恒虚警率(CFAR)。现已采用对数正态分布、瑞利分布和威伯尔分布;按照雷达方程,标准偏差意味着作用距离减小;甚至在很近的距离上,这种雷达也能以50毫微秒～2微秒的脉冲宽度工作,这可以从上述扫描的杂波估算中得到。于是可以获得对于检测门限的最佳杂波估算值、在不同的杂波环境下的恒虚警率以及在每一条件下的最佳灵敏度。文末展示了实验结果。     

掺钕玻璃受激发射的脉冲光谱

众所周知,晶体和玻璃受激发射随时间变化的过程,一般是用强的脉冲光来表征。不外以前,用法布里-珀罗干涉仪和按时间扫描的电子转换管,看到了一个脉冲期间内,红宝石光激射器受激发射频率的变化,并比较了单个振荡峰值的频率。     

A new phenomenon in the induction period of the methane dehydroaromatization reaction

The induction period of dehydroaromatization of methane to benzene over Mo/HZSM-5 had been investigated in real-time by the resonant-enhanced two-photon ionization (RE2PI) technique; it is remarkable that there is a small amount of benzene formed in the early stage of the induction period; we suggest that the trace amount of benzene was caused by the reduction of the original Mo6+ ion during the induction period and the Mo6+ species has a slight catalytic activity for methane-benzene conversion.     

关于环面上的由微分方程所确定的曲线

本文旨在解决普安凯来(Poincare)在他有名的关於实变数微分方程的论文中曾经提出伹悬而未决的一个问题。普安凯来自己限制于全纯微分系数(对于环面上的笛氏坐标言且是有理的)的假定之下。实则这一过强的性质对于普安凯来所提出的问题全非必要。在比较简单且足够普遍的条件下,我重新得到这位著名几何家的理论,使得普安凯来所发现的若干现象得以出现。以次我在假设中次第引入两条限制而考察与之相对应的结果,并且,作为本文的主要目的,我证明普安凯来曾认为或可出现的一种奇异情况不可能得到。