Closed-loop optimal control-enabled piezoelectric microforce sensors

This paper presents a closed-loop optimally controlled force-sensing technology with applications in both micromanipulation and microassembly. The microforce-sensing technology in this paper is based on a cantilevered composite beam structure with embedded piezoelectric polyvinylidene fluoride (PVDF) actuating and sensing layers. In this type of sensor, the application of an external load causes deformation within the PVDF sensing layer. This generates a signal that is fed through a linear quadratic regulator (LQR) optimal servoed controller to the PVDF actuating layer. This in turn generates a balancing force to counteract the externally applied load. As a result, a closed feedback loop is formed, which causes the tip of this highly sensitive sensor to remain in its equilibrium position, even in the presence of dynamically applied external loads. The sensor's stiffness is virtually improved as a result of the equilibrium position whenever the control loop is active, thereby enabling accurate motion control of the sensor tip for fine micromanipulation and microassembly. Furthermore, the applied force can be determined in real time through measurement of the balance force.     

Compact broadband photonic crystal filters with reduced back-reflections for monolithic InP-based photonic integrated circuits

A photonic crystal grating filter with an extremely wide rejection band and reduced modal back-reflections is proposed and demonstrated with a stopband extinction of 20 dB and insertion loss of less than 5 dB. The reflection-mitigation technique is shown to provide 10-15-dB reduction in reflected power. Guidelines for performance improvement are presented.     

雷达仿真系统中电磁干扰环境的仿真设计和实施

雷达仿真系统是为检测雷达设备的抗干扰能力以及在各种电磁环境下的工作性能而设计的，包括有源干扰和无源干扰的模拟仿真。本文阐述了无源干扰即杂波的散射模型和仿真过程；从同步脉冲干扰的基本原理出发，阐明在雷达工作环境仿真系统中距离拖引、速度拖引、虚假目标等同步脉冲有源干扰的设计和实施过程；并针对工作在搜索和跟踪交替模式下的相控阵雷达提出自适应综合干扰方式；最后分析并总结了系统仿真时为真实、有效地模拟电磁干扰环境应注意的关键问题。     

双层堤基的井涌破坏与无害管涌

双层堤基水文地质结构特殊，堤基承压水常具独特的“渗而不流”特征。在“不流”条件下，堤后盖层薄弱处受超高承压水头顶裂破坏，产生的局部冒水孔实属承压自流井，由此形成的管涌实质为井涌。底部进水的承压井流影响范围不大，井涌的破坏范围更小，据此可区分出有害管涌与无害管涌。前者局限于堤脚附近，小范围压渗为首选方案；对后者，既无需专门防治，更不必追求根治。     

ADSL MODEM 远程管理方案浅析

阐述了ADSLMODEM远程管理的意义及应遵循的原则，并对远程管理的方案作了简要阐述，最后比较分析了不同方案的优缺点。     

长颗粒(柱状晶)Si3N4陶瓷的研究及进展

Si3N4陶瓷材料由于具有很好的高温性能及高的力学性能，而被广泛地用于结构陶瓷，如切削刀具等。然而，因为其对缺陷很敏感，故易受灾难性的失效。人们发展了多种Si3N4增韧陶瓷，其中自增韧由于一些优异的性能越来越受到人们的重视。在此文中，着重介绍了影响Si3N4陶瓷长颗粒(柱状晶)晶粒生成的因素，并介绍了国内外对长颗粒Si3N4晶的控制研究。     

基于GIS技术的安徽省重大农业气象灾害测评系统总体设计

对《基于GIS技术的安徽省重大农业气象灾害测评系统》的总体设计方法作了概要介绍。该系统的建立主要是采用GIS技术，综合气候分析、遥感监测、地理环境影响评判等方法，提高对安徽省干旱、洪涝、低温冻害等重大农业气象灾害实时监测、趋势预测，以及对农业生产影响的分析评价结果的准确性。     

1477 nm LD泵浦掺铒光纤放大器的研究

报道了采用１４７７ｎｍ激光二极管（ＬＤ）泵浦的掺铒光纤放大器的实验结果。研究了放大器的增益和时域特性。对１５２０ｎｍ的信号光，获得了２３ｄＢ的增益，泵浦效率为２．２８ｄＢ／ｍＷ。低频脉冲信号经过放大器后未发生波形畸变。     

Nd：碲酸盐玻璃的光谱和激光性质

对比了各种激光玻璃的光谱性质，指出碲酸盐玻璃是一咱理想的激光介质，并资产在室温下实现了钛宝石激光器泵浦了Ｎｄ：碲酸盐块体玻璃的激光发射，激光阈值４．２０ｍＪ，斜率效率１４．７％。