基于磁保持继电器的智能交流接触器

针对小容量智能交流接触器,提出一种全新的控制方案.采用3台分立的磁保持继电器作为智能交流接触器本体,进行三相电路的智能控制.在动态计算的基础上,将可视化技术引入智能交流接触器的设计中,形成了便捷、直观的可视化设计软件.该设计具有体积小巧、控制简单灵活等优点.     

AES在嵌入式系统启动加载程序中的应用

随着嵌入式产品应用的普及,如何有效地保护开发者的科研成果不被非法仿制已越来越重要。论文从AES加密算法在AVR嵌入式系统芯片的Bootloader中的应用出发,介绍了AES的功能、特点、基本工作原理和工作流程,并详细讨论了AES加密算法在AVR嵌入系统芯片的Bootloader中实现的具体步骤。     

窄带射频接收系统中带通Σ-Δ调制器的设计

设计了一种适用于无线窄带射频接收系统的带通Σ-Δ调制器,并将其成功集成于一个无线射频收发芯片之中.该调制器采用0.35 μm CMOS工艺实现,采用斩波-稳零,动态元件匹配,以及正交采样等技术,提高系统的信噪比,并解决通道间失配的问题.模拟结果表明,该电路在30 kHz带宽内,信噪比为83.4 dB,而两个通道消耗的总电流仅为1 mA.     

MIMO系统中互耦影响分析

文章简要概括了MIMO系统及其信道容量，并基于矩量法重点分析了MIMO系统中天线阵元间的互耦作用对每个天线阵元辐射方向图的影响。结果表明互耦能使每个天线阵元的方向图发生畸变，所以在应用射线追踪法构建MIMO系统的信道矩阵时必须考虑互耦的影响以提高计算精度。     

一种有效的八位MCU桶形移位器 BIST 电路

针对8位微控制器（MCU）数据通道中桶形移位器的可测试性问题，提出了一种新颖的确定性内置自测试（BIST）电路设计方案，并对其进行了验证。该方案采用5个D触发器，在16个测试时钟周期内产生16个测试矢量，可完成对8位桶形移位器100％故障覆盖率测试。本论文的电路设计方案也可应用于一般2^N位（N≥4）桶形移位器的可测试设计。     

ZnO:Al薄膜的制备及表征

利用溶胶-凝胶法在蓝宝石(0001)衬底上制备了多晶ZnO:Al薄膜,薄膜表面具有特殊的交叉链状形貌.随着掺铝浓度的提高,链条有明显变细的趋势.X射线衍射证实,提高掺铝浓度有利于促进薄膜沿(002)方向的生长,并且光学带隙随着掺杂浓度的提高从3.21 eV增大到3.25 eV.光致发光光谱显示,薄膜在390 nm处出现较强的紫外峰,同时还出现了与Zn空位和Zn填隙缺陷能级有关的415 nm和440 nm两个比较弱的蓝峰.对实验结果以及产生的机理进行了分析和讨论.     

Self-Propagating High-Temperature Reduetive Synthesis of TiB2-Al2O3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis（SHS） method with reductive process from B2O3-TiO2-AI system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy （TEM） and high resolution electron microscopy （HREM） observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

计算机应用基础课程体系改革的几点尝试

文章针对高职院校"计算机应用基础"课程的开设情况,从教学内容、形式、教学方法和教材改革等方面进行了有益的探讨,并提出了一系列教学改革措施.     

Orbital Calculations of Kaolinite Surface:on Substitution of Al~(3 ) for Si~(4 ) in the Tetrahedral Sites

The surface properties of kaolinite were determined using density functional theory discrete variational method(DFT-DVM)and Gaussian 03 program.A SiO_4 tetrahedral hexagonal ring with two Al octahedra was chosen to model the kaolinite crystal.The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level.Both the highest occupied molecular orbit (HOMO)and the lowest unoccupied molecular orbit(LUMO)of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species,but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface,and thus,shows amphoteric behavior.Substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site linking the vacant Al~(3 ) octahedra does not increase the surface chemical reactivity of kaolinite,while substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site with the apex O linking Al~(3 ) octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite,especially acting as electron donors. Additionally,substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site results in the re-balance of charges,leading to the increase of negative charge of the coordinated O atoms of the AlO_4 tetrahedra,and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.     

Fabrication of Ti_2AlC by Spark Plasma Sintering from Elemental Powders and Thermodynamics Analysis of Ti-Al-C System

A ternary-layered carbide Ti 2 AlC material could be synthesized by spark plasma sintering(SPS)technology using elemental powder mixture of Ti,Al and active carbon.By means of XRD and SEM,phases were identified and microscopically evaluated.The experimental results show that the main phase in the product was fully crystallized Ti 2 AlC with small particle size when sintered at 1200 C.The syn-thesis temperature of SPS was 200-400 C lower than that of hot pressing(HP)or hot isostatic pressing(HIP). Through thermodynamics calculations,the mechanism of Ti 2 AlC was studied by calculating changes of Gibbs free energy of reactions.