Electron beam induced structural evolution in Fe3O4SiO2 particles: A new route to obtain movable core structures

SiO₂ hollow spheres with movable Fe₃O₄ core were obtained by exposing the pre-synthesized Fe₃O₄SiO₂ particles (with an adsorption interlayer of ethylene glycol) under the irradiation of electron beam inside transmission electron micrograph (TEM). In the formation process, the evaporation of adsorbed ethylene glycol and the evolution of amorphous SiO₂ layer played important roles, and that should be attributed to the high temperature and trapped charges induced by the irradiation of electron beam. This work provided a new route to obtain particles with movable core structure and extended the applications of electron beam.     

Microstructure and Transport Properties in Tin Boned La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> Composites

A novel boned perovskite manganese oxide magnetoresistant material was prepared using La_0.7Sr_0.3MnO₃ (LSMO) as the precursor powders and metal tin (Sn) as the binder. The microstructure and phase characteristics, low-field transport properties were studied. Sn segregated at the grain boundaries of LSMO grains. The insulator–metal (I–M) transition and enhanced LFMR are only observed with a low content of Sn, due to grain boundary disorder and spin polarized tunneling between grain boundaries. The Sn addition induced resistivity decreasing dramatically. In the high temperature PM region, the resistivities for samples with low Sn content follow the adiabatic small-polaron-hopping model.     

小波神经网络在液压装置压力测试中的应用

压力是反映液压系统正常工作的重要参数之一,对压力进行检测是液压装置故障诊断的重要内容。传统的压力检测多采用介入式方法,但这些方法需要插入液压管道中才能实施检测,存在必须预留接口、安装困难、影响系统动态性能等诸多缺陷。对液压装置的超声非介入式测压方法进行了研究,通过对声速和液压装置压力之间关系的研究,基于小波神经网络建立了液压装置的超声测压模型,并对影响液压装置超声测压精度的主要因素进行了分析。     

某型制导火箭弹弹道仿真

制导化改造是提高火箭弹精度最有效的一种方法.弹道仿真在制导火箭弹研究设计中占有非常重要的地位,仿真结果的正确性与合理性直接影响了制导控制系统的设计开发.为了对制导火箭弹的弹道进行仿真,首先建立了制导火箭弹的运动数学模型,而后结合风洞试验得到的动力系数进行了无控弹道仿真,得到了弹道、速度、弹道倾角和攻角等变化曲线.仿真结...     

基于STC12C系列单片机的DS18B20编程

针对新一代高性能单时钟／机器周期的STC12C系列单片机由于执行速度远高于传统的51单片机而不能直接使用原有单片机程序的问题,采用Keil软件的性能分析器来计算Atmel单片机的执行时间;通过手工计算修改程序段的执行时间,使STC12C系列单片机的执行时间满足数字温度传感器DS18B20的时序要求。测试结果表明STC12C2052能正确读取DS18B20的温度转换值,此方法对于具有时序要求的可编程器件的使用具有一定的参考价值。     

基于GJB7400的军用塑封集成电路检验标准探讨

塑封集成电路凭借其五大优势,势必会在军用集成电路发展之路上大有作为.目前我国军用塑封集成电路正在处于高速发展阶段,提高其可靠性是军用塑封集成电路发展的重要任务.为加强军用集成电路质量控制,制定了GJB7400-2011《合格制造厂认证用半导体集成电路通用规范》,是军用塑封集成电路筛选检验的主要标准.通过梳理GJB740...     

互联网图像隐写检测方法研究

图像隐写检测算法是目前信息隐藏领域的研究热点之一。分析了几种可针对互联网上大量图像数据的计数统计特征类隐写检测方法,其中包括本文提出的一种新型快速、高效的统计检测方法-TAP检测法。     

分组密码算法芯片验证

介绍了分组密码算法芯片验证的流程、内容和方法,详细介绍了分组密码算法芯片的验证技术——测试基准。     

PERIODIC DYADIC GREEN''S FUNCTION FOR FIELD ANALYSIS IN EMC CHAMBER

Herein a novel Dyadic Green's Function (DGF) is presented to calculate the field in ElectroMagnetic Compatibility (EMC) chamber. Due to the difficulty of simulating the whole chamber environment, the analysis combines the DGF formulation and the FEM method, with the latter deals with the reflection from absorbers. With DGF formulation for infinite periodic array structures, this paper investigates electromagnetic field in chamber with truncated arrays. The reflection from the absorber serves as the virtual source contributing to the total field. Hence the whole chamber field calculation can be separated from the work of absorber model set-up. Practically the field homogeneity test and Normal Site Attenuation (NSA) test are carried out to evaluate the chamber performance. Based on the method in this paper, the simulation results agree well with the test, and predict successfully the victim frequency points of the chamber.     

适用于高阶QAM解调的载波恢复算法及其实现验证

高阶正交幅度调制（QAM）系统中,随着QAM信号阶数的提高,频偏和相偏对系统解调性能的影响越敏感,其对同步性能的要求也越来越高。因此,必须在接收端对系统中的频偏和相偏进行更精确的补偿,使得接收端与发送端的载波信号达到同频同相,来提高解调系统的性能。本文首先简单介绍了两种常用两种面向判决的载波相位恢复算法,并利用MATLAB／Simulink为该算法搭建了系统仿真模型进行分析,然后给出了具体的实现方法并对其性能进行了分析。仿真结果表明,面向判决的载波恢复算法实现简单,稳态时抖动较小,非常适用于高阶QAM解调系统。