粉末粒度离散性对NdFeB磁性能的影响

制备了一种NdFeB永磁材料,探讨了制粉前处理方式对粉末离散性、粒径及成品NdFeB永磁体结构与性能的影响。原材料经熔炼、粗破碎后,采用高速风选和高压氢爆2种制粉前处理方式,然后采用同样的成型、烧结和回火工艺制备得到(PrNd)32.3Nb0.70Al0.60Cu0.20B1.03Fe65.17合金,并系统研究了该合金的显微结构和磁性能。结果表明:高压氢爆处理后得到的粉末粒度呈单分散性,粉末粒径较细,所制备得到的磁体样品的微观结构均匀性也较好;高压氢爆处理后制得的磁体样品剩余磁通密度比高速风选制粉方式得到的磁体样品高0.047 T,内禀矫顽力高 193.4 kAm－1,最大磁能积高24.6 kJm－３。     

空泡机制产生betatron X射线辐射的数值模拟

针对SILEX钛宝石激光器参数,采用PIC数值模拟程序VORPAL对激光尾波场加速进行了模拟,得到了电子轨迹及能量数据,进而通过理论计算得到了空泡机制下X射线辐射特性。结果表明,空泡机制下高能电子在空泡中做betatron振荡且多数电子被加速到170 MeV左右;加速能量较低的电子（约100 MeV）, 其辐射谱为临界能量约3 keV的类同步辐射谱,发散角约为8 mrad,而能量较高的电子（约170 MeV）对应的光子临界能量约为10 keV。     

黄土覆盖区油气微渗漏地表蚀变高光谱特征响应机理研究

以甘肃庆阳油气区为例,根据油气微渗漏的物理化学过程,通过地面实测黄土样品的波谱曲线,以及其中碳酸盐、粘土矿物、二、三价铁离子含量的测试分析,检测黄土覆盖区油气微渗漏所引起的特征光谱响应。根据黄土样品的测试分析,已知油气区碳酸盐矿物含量明显高于未知油气区,而且二价铁离子含量增加引起红层褪色现象明显,但粘土化蚀变特征不明显。从实测土壤光谱曲线包络线去除后,提取的土壤光谱吸收特征参数中,碳酸根和二价铁离子对应的吸收深度、吸收面积和对称度等三个特征参数与其含量相关性强,拟合度好。由此,对地面实测的14条土壤光谱曲线聚类分析能够有效区分油气微渗漏明显的已知油气区类和油气微渗漏不明显的未知油气区类。     

Shrinking device realized by using layered structures of homogeneous isotropic materials

We propose the practical realization of a shrinking device by using layered structures of homogeneous isotropic materials.By mimicking the shrinking device with concentric alternating thin layers of isotropic dielectrics,the permittivity and the permeability in each isotropic layer can be properly determined from the effective medium theory in order to achieve the shrinking effect.The device realized by multilayer coating with dielectrics is validated by TE wave simulation,and good shrinking performance is demonstrated with only a few layers of homogeneous isotropic materials.     

The effects of substrate temperature on ZnO-based resistive random access memory devices

Ag/ZnO/Zn/Pt structure resistive switching devices are prepared by radio frequency magnetron sputtering.The ZnO thin films are grown at room temperature and 400 C substrate temperature,respectively.By comparing the data,we find that the latter device displayed better stability in the repetitive switching cycle test,and the resistance ratio between a high resistance state and a low resistance state is correspondingly increased.After 104-s storage time measurement,this device exhibits a good retention property.Moreover,the operation voltages are very low:-0.3 V/-0.7 V(OFF state) and 0.3 V(ON state).A high-voltage forming process in the initial state is not required,and a multistep reset process is demonstrated.     

Vertical assembly of carbon nanotubes for via interconnects

The via interconnects are key components in ultra-large scale integrated circuits(ULSI).This paper deals with a new method to create single-walled carbon nanotubes(SWNTs) via interconnects using alternating dielectrophoresis(DEP).Carbon nanotubes are vertically assembled in the microscale via-holes successfully at room temperature under ambient condition.The electrical evaluation of the SWNT vias reveals that our DEP assembly technique is highly reliable and the success rate of assembly can be as high as 90%.We also propose and test possible approaches to reducing the contact resistance between CNT vias and metal electrodes.     

Removing paint from a metal substrate using a flattened top laser

In this paper,we investigate laser cleaning using a flattened top laser to remove paint coating from a metal substrate.Under the irradiation of a flattened top laser,the coating paint of the metal substrate can be removed efficiently by laser induced ablation,stress,and displacement force.The temperature distribution,stress,and displacement are calculated in the coating layer and substrate using finite element analysis.The effects of a Gaussian laser and a flattened top laser and the results of different diameters of laser spot are compared.The investigation shows that the flattened top laser can reduce the substrate damage and enhance the cleaning efficiency.This method meets the need of large area industrial cleaning applications by optimizing the flattened top laser parameters.     

高压下Li掺杂p型ZnO固溶体的表征

报道了利用ZnO和Li₂O混合物在5GPa, 1200 ℃—1500 ℃条件下, 制备Li掺杂p型ZnO(记作ZnO: Li)固溶体的过程. 研究发现, 高压下温度对于ZnO: Li固溶体的导电类型以及结构具有较大的影响. 其中在1500 ℃条件下烧结的ZnO: Li(Li的掺杂量4.5%)表现出良好的p型电学性能, 其电阻率为3.1× 10^-1Ω·cm, 载流子浓度为3.3× 10¹⁹cm^-3, 迁移率为27.7cm²·V^-1·s^-1. 通过实验及理论计算确定了其受主能级为110meV, 讨论了压力对p型ZnO的形成和电学性能的影响.     

1THz回旋管双阳极磁控注入电子枪的分析及设计

基于电子光学理论,通过编程进行大量的数值计算,设计了一支用于1THz回旋管的双阳极磁控注入式电子枪.对双阳极磁控注入电子枪的计算及设计进行了阐述,并对1 THz回旋管电子枪中高磁压缩比(f_m=125)可能导致电子反转的问题进行了详细的分析和模拟.通过对电子枪进行了仿真和优化,最后计算和设计了一支速度比适中(α=1.3),速度零散较小(Δβ<8%) 的电子枪.     

Monte Carlo方法模拟非直视紫外光散射覆盖范围

针对大气中紫外光散射通信的特点, 用Monte Carlo方法对紫外光非直视(NLOS) 通信三种工作方式的覆盖范围进行分析, 建立了基于Monte Carlo方法的NLOS紫外光传输模型.利用Monte Carlo模拟方法对三种NLOS散射方式的单次和多次散射路径损耗及覆盖范围进行模拟研究, 结果表明, 多次散射和单次散射的路径损耗基本一致, NLOS(a) 类全向发送全向接收通信方式覆盖范围最小但全方位性好, NLOS(b) 类定向发送全向接收通信方式的覆盖范围较大但有一定方向性, NLOS(c) 类定向发送定向接收通信方式的覆盖范围最大但有很强的方向性.