The development of a diamond switch for RF pulse compressionsystems

The use of a diamond RF switch for super-highpower microwave/millimeter wave generation has been evaluated. An X-band chemical vapor deposition (CVD) diamond window package was theoretically analyzed, designed, and built. Thirty-eight percent of an injected microwave signal with a frequency of 11.424 GHz was reflected from a 100-μm thick, 22-mm-diameter CVD diamond window when activated by a 160-mJ, 266-nm Nd:YAG laser. The details of the CVD diamond window design and experimental results are presented. The results have high application potential for building super-high-power microwave systems     

TiN underlayer and overlayer for TbFeCo perpendicular magnetic recording media

TiN thin film is prepared by DC reactive sputtering in Ar+N₂ atmosphere and its suitability as underlayer and overlayer for TbFeCo perpendicular recording media as well as its effect on the magnetic properties of the latter have been studied. Only 5 nm TiN overlayer and 20 nm under layer can successfully protect the TbFeCo film from oxidation. Initially the coercivity is increased sharply from about 2 to 6 kOe for an increase of underlayer thickness to 60 nm then the increasing rate of coercivity becomes very slow. The saturation magnetization remains almost constant with the underlayer thickness. The remanent squareness ratio remains constant at 1.0 with the underlayer thickness up to 60 nm then decreases.     

奇异非线性抛物方程的时空有限元方法

时空有限元的思想早期出现在Oden和Nickell＆Sackman等人的论文中，它通过统一时空变量，克服了一般有限元方法对时间作差分离散时引起的时间上的低精度，得到了一种解决时间依赖问题的有效方法．之后，在其基础上又发展起来了流线扩散法和特征流线扩散法．Gurtin于1964年提出了一种变分原理,为人们构造时空有限元提供了一个新的途径．1973年Reed和Hill提出间断Galerkin有限元方法．     

Magnetic properties of hexagonal ferrite dot arrays

Patterned magnetic media have been considered as one of the promising candidates for future ultra-high-density magnetic recording. In this paper, a new kind of patterned medium based on hexagonal ferrite have been studied. We have successfully fabricated strontium ferrite dot arrays by electron beam lithography. Their magnetic properties are evaluated by magnetic force microscopy (MFM) and superconducting quantum interference device (SQUID). The results show the dot arrays have perpendicular anisotropy. Dots with the lateral size larger than 500 nm show multidomain magnetization configuration in the initial magnetization state. However, with dot size decreased to 500 nm, all the dots have single-domain configuration both in the initial magnetization state and remanent magnetization state.     

Isolation of an Eleven‐Atom Polydentate Carbon‐Chain Chelate Obtained by Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne

Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all‐carbon chelating ligands are limited. Herein, we present a novel complex with an eleven‐atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron‐donating groups play a key role in the stabilization of this polydentate carbon‐chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late‐transition‐metal carbyne complex. This study not only enriches the chemistry of polydentate carbon‐chain chelates, but also deepens our understanding of the chelating ability of carbon ligands.     

Structure and magnetic properties of FeSiAl-based soft magnetic composite with AlN and Al2O3 insulating layer prepared by selective nitridation and oxidation

FeSiAl is widely used in switching power supply, filter inductors and pulse transformers. But when used under higher frequencies in some particular condition, it is required to reduce its high-frequency loss. Preparing a homogeneous insulating coating with good heat resistance and high resistivity, such as AlN and Al₂O₃, is supposed to be an effective way to reduce eddy current loss, which is less focused on. In this project, mixed AlN and Al₂O₃ insulating layers were prepared on the surface of FeSiAl powders after 30 min exposure at 1100 °C in high purity nitrogen atmosphere, by means of surface nitridation and oxidation. The results revealed that the insulating layers increase the electrical resistivity, and hence decrease the loss factor, improve the frequency stability and increase the quality factor, especially in the high-frequency range. The morphologies, microstructure and compositions of the oxidized and nitrided products on the surface were characterized by Scanning Electron Microscopy/Energy Disperse Spectroscopy, X-Ray Diffraction, Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Photoelectron Spectroscopy.     

Femtosecond laser-induced damage in reflector

We have investigated the damage for ZrO₂/SiO₂ 800 nm 45° high-reflection mirror with femtosecond pulses. The damage morphologies and the evolution of ablation crater depths with laser fluences are dramatically different from that with pulse longer than a few tens of picoseconds. The ablation in multilayers occurs layer by layer, and not continuously as in the case of bulk single crystalline or amorphous materials. The weak point in damage is the interface between two layers. We also report its single-short damage thresholds for pulse durations ranging from 50 to 900 fs, which departs from the diffusion-dominated scaling. A developed avalanche model, including the production of conduction band electrons (CBE) and laser energy deposition, is applied to study the damage mechanisms. The theoretical results agree well with our measurements.     

规则连接的电阻、电容网络的数学模型

从网络基本单元数学模型出发，用费玻那数列和另外建立的类费玻那契数列，建立了规则连接的电阻网络的数学模型。     

用间接法测定硫化物的研究

前人已经报道用汞的冷原子吸收法测定硫化物,利用Hg~(2+)和S~(2-)形成很稳定的化合物,使汞的吸光度值降低,根据其降低的程度来测定硫化物的含量。这种方法简便、灵敏,但对加入的Hg~(2+)量有较大的限制。S_2O_3~(2-)、CN~-、I~-等也有严重干扰,这些离子常与S~(2-)共存于水样中,所以,实际测定时,常需分离这些离子。