Microwave Dielectric Mechanism Studied by Microwave Near-Field Microscopy and Raman Spectroscopy

Microwave dielectric ceramics such as Ba(Mg_1/3Ta_2/3)O₃ and Ba₂Ti₉O₂₀ possess high dielectric constant and low dielectric loss in microwave frequency regime and have tremendous potential for device applications. In these materials, the presence of extrinsic defects, such as secondary phases, usually altered the microwave dielectric properties of the materials markedly, but the correlation of the microwave dielectric response of the materials with their microstructure has not been fully understood due to the lack of dielectric response in the local area. In this article, microwave near-field microscopy and Raman spectroscopy were used to investigate the microwave dielectric mechanism, viz. we measured the microwave dielectric properties of the materials in micron region by using a evanescent microwave probe (EMP) and, at the same time, examined the lattice vibration characteristics of the region by using a micro-Raman spectrum. How the presence of the secondary phase affects the microwave dielectric properties of the materials is thus systematically investigated. The causes of intrinsic or extrinsic dielectric loss were explored by comparing the dielectric images in SEMP at microwave frequencies and the corresponding Raman Spectra.     

变压器油中溶解微量糠醛的激光拉曼光谱检测方法

研究变压器油中溶解微量糠醛含量的检测方法及其应用,对运行变压器油纸绝缘老化评估具有重要意义。激光拉曼光谱(LRS)技术作为微量液体检测的有效手段,已经在很多领域得到了广泛应用。本文应用Gaussian 09W程序构建了糠醛分子仿真模型,分析其拉曼振动特性,进而证明了拉曼光谱检测糠醛分子的可行性;应用共聚焦拉曼技术搭建了激光拉曼光谱液体检测试验平台;结合萃取技术研究了糠醛分子的拉曼光谱检测特性,建立了基于特征频谱和最小二乘法对糠醛含量进行定量检测的方法。最后,应用激光拉曼光谱方法对不同糠醛含量的变压器油样进行检测,并与实验室高效液相色谱法(HPLC)的检测结果进行对比,对比结果表明:结合萃取技术的激光拉曼光谱能有效地对变压器油中溶解微量糠醛进行定量检测,为实现变压器油中糠醛含量的快速检测提供了一种方法。     

基于拉曼光谱技术直接检测矿物绝缘油中糠醛含量方法

本文中作者提出了利用拉曼光谱技术对绝缘油中糠醛含量进行检测研究,实验检测纯绝缘油、纯糠醛和糠醛-绝缘油溶液的拉曼光谱.对不同浓度的糠醛溶液进行了原位测试,建立峰面积比与浓度的函数关系.     

Raman amplifiers for telecommunications

Raman amplifiers are being deployed in almost every new long-haul and ultralong-haul fiber-optic transmission systems, making them one of the first widely commercialized nonlinear optical devices in telecommunications. This paper reviews some of the technical reasons behind the wide-spread acceptance of Raman technology. Distributed Raman amplifiers improve the noise figure and reduce the nonlinear penalty of fiber systems, allowing for longer amplifier spans, higher bit rates, closer channel spacing, and operation near the zero-dispersion wavelength. Lumped or discrete Raman amplifiers are primarily used to increase the capacity of fiber-optic networks, opening up new wavelength windows for wavelength-division multiplexing such as the 1300 nm, 1400 nm, or short-wavelength S-band. As an example, using a cascade of S-band lumped amplifiers, a 20-channel, OC-192 system is shown that propagates over 867 km of standard, single-mode fiber. Raman amplifiers provide a simple single platform for long-haul and ultralong-haul amplifier needs and, therefore, should see a wide range of deployment in the next few years     

基于KVM、远程桌面和VPN的数据机房远程维护

介绍了一种基于KVM、远程桌面和VPN的数据中心机房远程维护方案,借助计算机技术和调度自动化通信技术以及利用KVM技术为机房主机设备的集中监控管理提供方便可靠的管理模式,在公网中利用VPN技术通过远程桌面技术远程控制电力公司内网中KVM用户工作站,实现数据中心机房的远程维护,为电网调度自动化系统的可靠运行提供技术保障。     

Field-Filter Probes and the Measurement of Alternating-Current Corona

The principles of the field-filter probe, which is capable of measuring both field changes and conduction current at an electrode in the presence of space charge, are described. Design characteristics are given for a simple field filter and for two further types which can be used for bipolar (reversing) fields and currents. Measurements are given for the discharge characteristics at the plane electrode of rod-plane gaps in the range 50-300 mm subjected to alternating voltages up to 100 kV root mean square (rms).     

传统电气闭锁与微机保护问题的探讨

介绍对现有变电站的传统二次电气控制闭锁回路以及现代微机防闭锁方式的原理、功能、技术发展等相关问题的研究探讨情况,对一些技术问题提出了自己的见解。     

Flexible Communication and Control Protocol for Injectable Neuromuscular Interfaces

BION2 is a system based on injectable neuromuscular implants whose main goal is to restore the functional movement of paralyzed limbs. To achieve this objective, the functional requirements of the implanted interfaces include not only stimulation but also integrated sensors in order to detect patient intention, to provide servocontrol of muscle activation and to sense posture to inform more global motor planning and coordination. The technical constraints for managing the system include the efficient use of forward and reverse telemetry channels with limited capacity, minimization of adverse consequences from errors in data transmission or intermittent loss of power to the implants, and ability to adjust stimulation rates and phases to achieve efficient fine control of muscle force while minimizing fatigue. This paper describes a communication and control architecture with several novel features that address these requirements     

Flexible Laminates: Key Insulation for Motors and Generators

The use of flexible laminates (the bonding together of two or more flexible substrates to form a thin, strong insulation material) as a key insulation source for motors and generators is explained.     

Remote Laboratories for Optical Circuits

This paper presents a remote laboratory implementation for an optical circuits course. The process from design and implementation towards assessment and continuous improvement phase is outlined. The design of the experiments involved the research on remote access technology and the investigation of best practices for an experimental setup. The first pilot implementations were used to determine the possible shortfalls during an ldquoIntroduction to an Optical Communicationsrdquo course in fall 2004 at the University of Colorado, Boulder, and an ldquoOptical Circuitsrdquo course in fall 2005 at the University of Houston, Houston, TX. After improvements, two experiments were pilot tested during spring 2006 at the University of Houston. Assessment of learning outcomes and teaching methods were performed. The remote access methods, in addition to the delivery of the class and lectures, are presented in the paper. Delivery of a class with remote laboratories and videotaped lectures are also outlined under future directions of this project.     

输电线路柔性直流融冰技术

为直流融冰技术在电网中的应用提出了一种新型柔性直流融冰技术。通过分析输电线路结冰情况的等效模型并研究融冰时的热交换过程,针对220kV输电线路计算出了线路融冰所需的保线电流和最大电流值。按计算结果的需求设计了基于可关断器件的新型柔性直流融冰电源。论述了该电源的主电路拓扑及其功率单元的等效电路,并对其相关的融冰控制策略进行了分析和研究。最后研制出一台全控直流融冰装置样机,并进行了现场试验。试验结果表明,该融冰装置可对直流输出电压进行柔性调节,融冰时的网侧谐波含量较低,在试验中仅3.16%。     

远程电机转速检测与控制

介绍了一套基于红外通信的远程电机转速检测与控制装置.该装置主要分为两个模块:电机模块和控制模块.电机模块可实时检测电机转速值,并根据控制模块发送过来的脉宽调制(PWM)信号控制电机的转速;控制模块将电机模块发送过来的电机转速信号跟设定转速值进行PID运算并返回PWM信号,通过红外通信将该信号发送给电机模块.通过不断调整使得电机的转速最终稳定在设定转速值.     

Flexible Spectrum and Power Allocation for OFDM Unlicensed Wireless Systems

Future generations of communication systems will benefit from cognitive radio technology, which significantly improves the efficient usage of the finite radio spectrum resource. In this paper we present a wireless unlicensed system that successfully coexists with the licensed systems in the same spectrum range. The proposed unlicensed system determines the level of signals and noise in each frequency band and properly adjusts the spectrum and power allocations subject to rate constraints. It employs orthogonal frequency-division multiplexing (OFDM) modulation and distributes each transmitted bit energy over all the bands using a novel concept of bit spectrum patterns. A distributed optimization problem is formulated as a dynamic selection of spectrum patterns and power allocations that are better suited to the available spectrum range without degrading the licensed system performance. Bit spectrum patterns are designed based on a normalized gradient approach and the transmission powers are minimized for a predefined quality of service (QoS). At the optimal equilibrium point, the receiver that employs a conventional correlation operation with the replica of the transmitted signal will have the same efficiency as the minimum mean-squared error (MMSE) receiver in the presence of noise and licensed systems. Additionally, the proposed approach maximizes the unlicensed system capacity for the optimal spectrum and power allocations. The performance of the proposed algorithm is verified through simulations.      

电能计量装置远程校验监测系统

针对电能计量装置的综合误差,提出了电能计量装置远程校验监测系统的基本原理。该系统不仅能够实现现场电能表的误差测试,而且能够对CT二次回路的工作状况予以监测并测试电压互感器二次压降,整个测试数据可远程下载到主站PC直接形成报表,无需人工到现场抄读数据,弥补了传统检测手段的不足。     

一种配网馈线监控终端遥信遥控功能测试装置

分析了配电网馈线监控终端遥信及遥控回路特点,设计了一种针对遥信及遥控功能测试装置。硬件选取可编程控制器(PLC)为核心控制单元,包括人机界面(HMI)触摸屏、遥信量输出回路、遥控量输入回路等,使用了PLC自带I/0实现馈线监控终端遥信变位、SOE分辨率、遥控事件记录功能测试。现场应用表明,该装置具有精度高、操作简单、使用方便及运行稳定等优点,达到了预期功能及精度指标。     

Double-pass fiber Raman laser-a powerful and widely tunable in theultraviolet, visible, and near-infrared fiber Raman laser for biomedicalinvestigations

We present the operating principle, general features, and advantages of a novel concept for the development of powerful and widely tunable fiber Raman lasers (FRL's), based on the high-power pumping of large-core low-loss multimode fibers using a simple double-pass laser arrangement with Littrow-prism-tuned emission. Basic experimental results obtained with various modification double-pass FRL schemes, which provide the generation of both discretely tunable emission in the UV/blue (360-493 nm) at λ_p=355 nm and continuously tunable emission in the visible/near-IR (0.54-1.01 μm) at λ _p=532 nm, are reported. The double-pass FRL schemes permit powerful and widely tunable spectral components to be generated, due to the double passing of nonlinear-converted laser emission through the optical fiber, maximum cavity feedback, the use of multimode fibers, and high-power pumping     

行波型超声波电动机柔性转子结构设计

对行波型超声波电动机采用的柔性转子结构形式进行了研究,利用三维建模软件Solidworks对一种结构形式的柔性转子进行了建模,并利用其自带的有限元分析软件COSMOSWorks对转子做了静态载荷仿真分析,得到了在一定预压力下柔性转子的最小安全系数、静态位移和应力分布图.实验结果表明:仿真结果对转子的设计和生产装配有重要的参考价值.     

Spectroscopy quantitation and data processing

Magnetic Resonance Materials in Physics, Biology and Medicine -     

白光LED用远程荧光技术

新型的远程荧光技术能有效地改善目前封装技术中存在的出光不均匀、色温漂移、芯片发热导致荧光粉性能衰减等缺点,可广泛应用于COB集成封装、大功率LED和贴片型LED封装,或者直接用于制造照明灯具产品,是白光LED制造技术的又一次创新。将远程荧光技术与大功率LED集成封装技术结合制备白光LED光源,结果表明,LED照明器件的光色一致性高,光效可达到100 lm/W,具有广阔的市场前景。