KNbO_3倍频产生488.5nm ps蓝光

用6.9×5.3×3.3mm~3的KNbO_3晶体对光学参量放大系统输出的波长连续可调近红外光进行倍频,产生485～493nm连续可调的ps蓝光。488.5nm的能量转换效率为2.6％,峰值功率大于2kW。     

超声波振动切削系统幅载特性的研究

超声波振动切削是一种新型的复合加工方法，其关键之一是在切削的有载状态下能否保持一定的振幅值，本文就中置式超声波振动切削系统的幅载特性进行了理论和实验研究。     

弹道目标平动补偿与微多普勒特征提取方法

针对传统逆合成孔径雷达(ISAR)成像中的平动补偿方法并不适用于弹道目标平动补偿的问题,该文提出了一种弹道目标平动补偿与微多普勒(m-D)特征提取方法。在分析有翼弹道目标未完成平动补偿时的m-D效应的基础上,首先采用形态学中的骨架提取方法抑制1维距离像旁瓣,再在快时间频率(距离)-慢时间平面上搜索分离各散射点的m-D特征曲线,然后对其进行经验模式分解(EMD)分解,利用分解结果中的趋势项分量完成目标回波的平动补偿,并通过分析EMD分解结果获得了目标的自旋频率、锥旋频率等特征信息。仿真实验验证了所提方法的有效性与鲁棒性。     

重复使用运载器GN＆C技术发展趋势及特点

重复使用运载器 (RLV)将大幅度降低现役航天运载器的发射准备时间、成本 ,并提高其可靠性、安全性 ,是航天运输系统的发展方向。制导、导航与控制 (GN&C)系统是RLV的核心技术之一 ,先进的RLV的GN&C技术不仅能缩短设计周期、降低成本 ,而且对复杂多变的飞行环境具有较强的鲁棒性 ,从而提高了飞行器的安全性。指出了RLV的GN&C系统的要求、特点 ,总结了近年来该领域的研究成果 ,提出了下一步需研究的问题。     

VoIP技术的新发展及其在电力通信中的应用

介绍了VoIP技术的工作原理和系统构成,阐述了H．323协议,并介绍了VoIP最新技术的发展,具体分析了IP电话的工作过程,最后根据广州电力通信网的结构,深入分析了VoIP的应用范围,采用UCD设备进行VoIP试验,达到了预期效果。     

Robust and precision motion control system of linear-motor direct drive for high-speed X-Y table positioning mechanism

In this paper, design and implementation of an H/sub /spl infin//-based precision motion control system is presented for a high-speed linear-motor direct-drive X-Y table positioning mechanism in semiconductor wire-bonding applications. The system works with a cascaded robust feedback control, which has an inner loop velocity controller and an outer loop position controller, and an autotuning feedforward compensator. The design aim is to achieve high and consistent tracking performance even in the presence of considerable resonance uncertainties and external disturbances. Toward this aim the velocity controller is designed using H/sub /spl infin// optimization technique, based on reduced-order modeling that considers three significant resonance modes and neglects all other resonance modes having an insignificant amplitude and/or too high frequency. These neglected modes and variations of the three resonance modes from machine to machine (due to manufacturing tolerance) and/or with different operating conditions are taken care of by appropriate additive uncertainty representation in the design phase. The resulting system is validated and implemented with a profile motion of a maximum acceleration of 5.2 g (1g=9.81 m/s/sup 2/) on mass-produced wire bonding machines.     

基于Niederreiter纠错码的公钥密码体制的研究

二十多年来,纠错码成功地用于构造诸多纠错码公钥密码体制。文中首先研究了N公钥体制的性能指标,给出了它的计算机模拟曲线;通过分析N公钥体制的安全性,给出了一种攻击N公钥体制的新方法;然后探讨M公钥体制与N公钥体制的内在关系,揭示了它们之间安全性等价的事实,给出了M公钥与N公钥体制性能比较的结果。     

Flexible Strain Sensor Based on Layer-by-Layer Self-Assembled Graphene/Polymer Nanocomposite Membrane and Its Sensing Properties

Graphene is a potential building block for next generation electronic devices including field-effect transistors, chemical sensors, and radio frequency switches. Investigations of strain application of graphene-based films have emerged in recent years, but the challenges in synthesis and processing achieving control over its fabrication constitute the main obstacles towards device applications. This work presents an alternative approach, layer-by-layer self-assembly, allowing a controllable fabrication of graphene/polymer film strain sensor on flexible substrates of polyimide with interdigital electrodes. Carboxylated graphene and poly (diallyldimethylammonium chloride) (PDDA) were exploited to form hierarchical nanostructure due to electrostatic action. The morphology and structure of the film were inspected by using scanning electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy. The strain-sensing properties of the graphene/PDDA film sensor were investigated through tuning micrometer caliper exertion and a PC-assisted piezoresistive measurement system. Experimental result shows that the sensor exhibited not only excellent response and reversibility behavior as a function of deflection, but also good repeatability and acceptable linearity. The strain-sensing mechanism of the proposed sensor was attributed to the electrical resistance change resulted from piezoresistive effect.     

基于SAA7130HL的视频采集卡设计

介绍了PHILIPS公司的第五代"精显芯片"SAA7130 HL的主要功能及性能特点,提出了一种基于SAA7130的视频采集卡设计方案,并详细说明了该采集卡的硬件框图和软件程序设计.实际的测试和使用证明了该采集卡的稳定性和可靠性.