All-optical photonic switches using integrated inverted asymmetricFabry-Perot modulators and heterojunction phototransistors

InGaAs/GaAs(100) multiple-quantum-well-based inverted cavity asymmetric Fabry-Perot modulators are vertically integrated with GaAs/AlGaAs heterojunction phototransistors to yield all-optical photonic switches. The photonic switches using `normally on' modulator pixels exhibit an output on-off ratio of 12:1 with internal optical gain of 4 dB. The photonic switches using `normally off' modulator pixels yield similar contrast and gain, but exhibit intrinsic bistable behavior. The inverted cavity modulators employed permit utilizing the transparency of the GaAs substrate at the operating wavelength and offer advantages for fabricating large arrays for optical signal processing     

聚苯硫醚酰胺的合成与表征

用4-氯苯甲酰4′-氯苯胺和硫化钠为原料在常压下合成了聚苯硫醚酰胺,并对其进行了表征。结果表明所合成的产物为结晶性聚合物,并且有较高的热稳定性。     

High bit rate digital subscriber line echo cancellation

The authors explore the issues of complexity, precision, and dynamic range and practical implementation issues such as nonlinearities in high bit rate digital subscriber line (HDSL) echo cancelers. The approach taken is to study these issues analytically using computer simulations, and then to verify simulation results with laboratory prototyping. One of the objectives was to determine whether HDSL echo cancellation will be practical and cost effective within the next several years, consistent with the desire to develop and deploy a repeaterless T1 capability by 1993. Thus, attention is given to practical design issues     

Gate and drain currents in off-state buried-type p-channel LDDMOSFETs

The buried-type p-channel LDD MOSFETs biased at high positive gate voltage exhibit novel characteristics: (1) the ratio of the drain to gate currents is about 1×10^-3 to 5×10^-3; and (2) the gate and drain currents both are functions of only the gate voltage minus the n-well bias. Such characteristics are addressed based on the formation of the surface n ⁺ inversion layer due to the punchthrough of the buried channel to the underlying shallow p-n junction. The measured gate current is due to the Fowler-Nordheim tunneling of electrons from this inversion layer surface and the holes generated within the high-field oxide constitute the drain current. The n⁺ inversion layer surface potential is found to be equal to the n-well bias plus 0.55 V. As a result, both the oxide field and the gate and drain currents are independent of drain voltage     

OFDM技术及其应用

首先对OFDM的发展以及应用做了简要的介绍,然后讨论了当前OFDM研究过程中的两个关键技术问题,最后展望了OFDM的未来发展。     

Fuzzy-Fusion Classifier for MMV Full-Polarization Radar Target Recognition Using One-Dimensional Scattering Centers

One-dimensional (1-D) scattering centers on a target can be used for radar target recognition purpose. In this paper, a new classifier based on fuzzy techniques is proposed, which is very much suitable for target recognition using 1-D scattering centers. Furthermore, information fusion techniques for full polarimetric receiver data are utilized at the decision level. The performance of the proposed fuzzy-fusion classifier is evaluated using a dataset of five aircraft models measured by millimeter-wave (MMW) full-polarization stepped-frequency radar in the compact range facility.     

软土基坑工程中劈裂注浆防渗机理与应用

结合紧邻市政管线的软土基坑工程 ,分析劈裂注浆力学和防渗性能 ,确定技术方案 ,控制施工参数 ,在控制管线位移的前提下达到基坑防渗要求 ,为类似工程提供借鉴     

基于虚拟仪器功率测试分析系统

介绍基于虚拟仪器的功率测试分析系统的构成，软件设计以及数据采集、信号处理和整体结构。该系统已在实际应用中取得很好效果。     

低电阻率气层测井评价方法

粘土矿物成份是造成气层电阻率低的主要原因。用灰色静态模型计算孔隙度，用BP神经网络计算束缚水饱和度等参数。与岩心分析结果比较，储层参数计算结果精度有所提高。用储层参数建立气层和水层的判别式，判别结果与试油有较好的一致性。综合数字处理结果建立了气层产能评价模型，处理结果与试油结果比较，符合率82％。     

微波萃取在食品化学中的应用

介绍了微波萃取技术在食品化学中的应用。其实质是用微波对萃取溶剂及物料加热，使溶剂的渗透率和扩散率大大提高，因此对食品营养成分或风味物质可以有铲地萃取分离。