A new mapping method for phase estimation of single‐phase signals: A new generalization and new realizations of the DFT estimation method

This paper proposes and analyzes a new simple real‐time phase‐estimation method for single‐phase signals, which is based on a vector mapping theory of n‐dimensional to 2‐dimensional vectors. According to the analyses, the proposed mapping method can estimate instantly and properly the true phase of the signals that are contaminated by significant amplitude of noise and harmonics. The mapping method contains the conventional DFT method as a special case. In other words, it can be treated as a generalization of the DFT. Several simple realizations of the mapping method are also newly proposed as a single‐input and two‐output digital mapping filter in both nonrecursive and recursive forms. The recursive realization being able to decrease drastically computing load utilizes the normal form that is robust to finite word length effects. As an application of the proposed mapping method, inverter‐using power control system connected with a single‐phase grid is shown. All analytical results are verified by numerical experiments and the usefulness of the newly proposed mapping method is confirmed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 27–38, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20263     

101B、102B微机保护运行分析

从设计、安装、调试及运行维护等方面分析了101B、102B微机保护存在的问题,提出了解决办法,可供使用该保护装置的运行人员参考。     

水布垭面板堆石坝第一期面板裂缝成因分析及处理

水布垭面板堆石坝第一期面板于2005年1至3月浇筑,同年9月发现裂缝,绝大多数为表面水平裂缝。监测数据分析和有限元计算结果均表明,上游坡面的变形弱化了面板的支承条件,是导致面板发生结构性裂缝的原因。本文对一期面板裂缝的处理工艺作了介绍,并针对后期面板的防裂措施提出,足够的堆石体预留沉降时间和20m以上的堆石体超高有利于控制面板结构裂缝。     

WKKL-1B1型励磁调节器误切除原因分析及改进措施

分析了某厂WKKL-1B1型励磁调节器故障现象,对故障原因进行了分析,提出了将5V电源更换为5V模块电源的改进措施。现场运行证明该措施提高了该励磁调节器的运行稳定性,消除了误发信及误切故障现象。     

Melt synthesis and characterization of complexed perovskite-oxides in the system of A2+(B+ 2/5B6+ 3/5)O3 - A3+(B+ 3/5B6+ 2/5)O3

In order to synthesize various Perovskite ABO₃ type compounds and their solid solutions, we have applied a novel “melt synthesis technique” rather than conventional solid state reaction techniques. In the melt synthesis, the mixture of oxides or their precursors is melted in a short period of time (1–60 sec) by a strong light radiation in an arc imaging furnace. A spherical molten sample where multiple cations were mixed homogeneously was directly solidified on a copper hearth with a rapid cooling of 10² K/sec. Solid solutions based upon 1:1 ordered Perovskite in the system of Sr(Li_2/5W_3/5)O₃-La(Li_3/5W_2/5)O₃ were synthesized in this technique.     

关于一类算子的Mann迭代列及Picard迭代列的构造问题

本文构造了一类带边界条件算子的Mann迭代列和Picard迭代列,在一定的假设条件下,证明了序列收敛到算子的不动点。     

有限元方程的非零元素存贮和迭代求解法

本文介绍了有限元方程系数矩阵的非零元素存贮法和两种有效的迭代法:SOR法和J-CG法,并给出了适合于程序设计的一些算法.所给出的算法适用于Possion方程的有限元求解问题.     

钻塔承载能力的应变测量与评估

为保证钻塔在施工过程中的安全,对钻塔在不同载荷条件下的承载能力进行评估。利用应变电测技术测量钻塔加载过程中的受力状态,并对测试结果进行分析。试验结果表明,应变测量技术可以全面、直观地反应钻塔在不同载荷条件下的力学特征,为钻塔的安全评估提供了重要的参考依据。     

A Deterministic Solver for the 1D Non-Stationary Boltzmann-Poisson System for GaAs Devices: Bulk GaAs and GaAs n +-n i -n + Diode

We present a deterministic method for describing the electron transport in spatially one-dimensional gallium arsenide devices. This numerical procedure is based on the combination of kinetic Boltzmann-type equations for a two-valley model of the GaAs conduction band and the Poisson equation in order to consider the electrostatic potential self-consistently. All of the important intra- and intervalley scattering mechanisms for GaAs are taken into account. The dependence of the electron distribution functions on the electron wave vector is treated by means of the multigroup approach, whereas their spatial dependences are handled by a weighted essentially non-oscillatory (WENO) scheme. Numerical results are given for the main transport quantities as functions of time, position and electric field in bulk material and in a n⁺-n_i-n⁺ diode. In addition, the proposed numerical method is validated by comparing the results with those of Monte Carlo calculations and the influence of the discretization used in the numerical procedure is discussed.     

A simple instant‐estimation method for time‐average quantities of single‐phase power and application to single‐phase power grid connection by inverter

This paper presents and analyzes a new simple instant‐estimation method for time‐average quantities such as rms values of voltage and current, active and reactive powers, and power factor for single‐phase power with the fundamental component of constant or nearly constant frequency by measuring instantaneous values of voltage and current. According to the analyses, the method can instantly estimate time‐average values with accuracy of the fundamental frequency, and estimation accuracy of the power factor is about two times better than that of voltage, current, and powers. The instant‐estimation method is simple and can be easily applied to single‐phase power control systems that are expected to control instantly and continuously power factor on a single‐phase grid by inverter. Based on the proposed instant‐estimation method, two methods for such power control systems are also proposed and their usefulness is verified through simulations. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 34–43, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20236     

A simple method for mapping the B1 field distribution of linear RF coils

Inhomogeneity of the radio frequency (RF) field B₁ leads to intensity variations in MR images and to spatial dependence of spectral line amplitudes. In this paper, a simple method of measuring the B₁ field components of an unsegmented linear coil is described. The method is designed for the coils operating up to 20 MHz. The B₁ field distribution is replaced by the static magnetic field caused by DC current flowing through the coil. The technique involves rotating the coil 90° so that measured B₁ component is aligned with B₀ and measuring the shift of resonance frequency using a spectroscopic imaging sequence. Experimental results were in good agreement with the theoretical computations.     

Transmit/receive headcoil for optimal <Superscript>1</Superscript>H MR spectroscopy of the brain in paediatric patients at 3 T

¹H magnetic resonance (MR) spectroscopy is a useful tool to obtain metabolic information from the brain in paediatric patients. To detect signals of metabolites at low concentrations or from small volumes, the signal-to-noise ratio (SNR) has to be optimized. The SNR can be increased by going to higher field strengths. However, this leads to higher spectral bandwidths, which increases the chemical shift artefact. Here we present a transmit/receive headcoil which is adapted to the dimensions of the paediatric head and enables PRESS localization with high radio-frequency (RF) bandwidths that minimize the chemical shift displacement to only 5%. In addition, since the pulse lengths are shorter with higher RF bandwidths, the echo time can be reduced to 10 ms improving SNR as well.Parts of this work have been presented at the European Society for Magnetic Resonance in Medicine and Biology in Rotterdam in 2003     

北斗MEO/IGSO卫星B1频点信号捕获方法研究

针对北斗MEO/IGSO卫星因存在NH码调制而导致使用GPS捕获方法捕获灵敏度降低的问题,提出了差分相干方法和全比特相干方法。差分相干方法克服了NH码和比特翻转的影响,能够快速捕获北斗MEO/IGSO卫星B1频点大于等于40dB-Hz的强信号。全比特相干方法能够剥离NH码并实现全比特相干,从而捕获大于等于28dB-Hz的弱信号。最后,针对应用全比特相干捕获方法捕获北斗信号,在NH码未剥离成功时其结果出现多峰性的现象,本文进行了理论解释和仿真验证。     

高压电动机的断相故障分析与保护配置

分析了高压电动机断相故障特征和现有负序电流保护的不足 ,基于对称分量法进行了高压电动机断相时的最小负序电流的计算 ,提出了新的负序电流保护配置方案与整定原则     

A new generalized high‐frequency voltage injection method and mirror‐phase estimation method for sensorless drive of salient‐pole PMSMSs

This paper proposes a new generalized high‐frequency voltage injection method for sensorless drive of salient‐pole permanent‐magnet synchronous motors. The injected high‐frequency voltage has a unique spatially‐rotating elliptical shape, with the amplitudes of both the major and minor axes varying with the motor speed, and can be designed by selecting a design parameter. The high‐frequency current caused by the injected voltage, which has information on the rotor phase to be estimated, is speed‐independent, that is, is not affected by the motor speed at all. Consequently, the rotor phase can be estimated in a wide speed range from zero to the rated speed. By selection of the design parameter, the properties of the high‐frequency current can be adjusted appropriately to the associated motor‐drive system consisting of a motor and an inverter. As a versatile phase estimation method for estimating rotor phase using the high‐frequency current, the “mirror‐phase estimation method” is reconstructed and reproposed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 67–82, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20803     

烧结温度对锂离子蓄电池Li1+xNi1/3Co1/3Mn1/3O2性能的影响

采用高温烧结前驱体共沉淀法合成Li1 xNi1/3Co1/3Mn1/3O2,着重研究了烧结温度对合成产物性能的影响,研究结果表明:于900℃合成产物性能优良,放电容量为162.2 mAh/g,充/放电效率为91.3%,20次循环后容量保持率为96.4%,显示出良好的循环特性.     

非水介质分散法制备锂离子蓄电池正极材料Li1+xMn2O4

采用LiNO3 和LiOH·H2 O及化学MnO2 (CMD)与电解MnO2 (EMD)为起始原料 ,以无水乙醇为分散介质 ,通过湿化学分散结合中温固相反应合成了锂离子蓄电池正极材料Li1+xMn2 O4 ,采用XRD和BET及电化学测试对材料性能进行了表征 ,并考察了焙烧温度、焙烧时间、n(Li)∶n(Mn)摩尔比以及不同初始原料对材料性能的影响。结果表明 ,随着n(Li)∶n(Mn)摩尔比的增大 ,材料中的层状结构LiMnO2 的含量增加 ,其充电容量也增大 ,但可逆性降低 ;材料的比表面积随焙烧温度的升高和焙烧时间的延长而减小 ,但随着n(Li)∶n(Mn)摩尔比的增加而增大 ;样品的首次充放电比容量随着比表面积的减小而降低 ,但其稳定性和循环性有所增加 ;样品的充放电比容量随着n(Li)∶n(Mn)摩尔比的增加而增大 ,但稳定性和循环性降低 ;以LiNO3 为Li源优于以LiOH·H2 O为Li源 ,以EMD为Mn源优于以CMD为Mn源。     

国内主要二拖一联合循环机组并汽技术研究

对国内典型二拖一燃气蒸汽联合循环机组的汽轮机并汽方式进行详细的研究,并针对不同机型举例说明,列举了影响汽轮机并汽稳定性的相关因素.通过研究表明,汽机并汽的稳定性,一方面取决于对应的汽轮机特性以及采用的并汽方式;另一方面,旁路系统的稳定性也在二拖一机组并汽过程中起到了决定性的作用.     

Liquid and vapor phase silanes coating for the release of thin film MEMS

Stiction remains one of the biggest reliability problems in the fabrication of microelectromechanical systems (MEMS). This work investigates the techniques adapted to release thin-film devices (100 nm thick) and submicron gaps MEMS. First, a CMOS compatible wet release process was developed, using nonchlorinated silanes coating providing a high hydrophobicity (contact angle in the range of 110/spl deg/). Second, a vapor phase release process based on the same chemistry is shown to be adequate to release thin-film beams from a silicon-on-insulator wafer, where the wet process failed. This is to the authors' knowledge the first time that an in-use stiction-free release process has been demonstrated for such thin structures. The layers resist up to 300/spl deg/C without damage and X-ray reflectivity confirmed that homogeneous monolayers were obtained.     

煅烧温度对Li1+xV3O8电化学性能的影响

采用溶胶-凝胶法制备了锂离子电池正极材料Li1+xV3O8;讨论了煅烧温度对材料循环性能的影响。利用FTIR、TG-DTA、XRD等手段表征材料的结构,在电池测试系统上对组装的电池进行了电化学性能测试。结果表明,在550℃下灼烧3 h得到的正极材料有较高的比容量和较好的循环性能。在50mA/g的电流密度下,在50次充放电循环过程中,容量曲线呈折线递增趋势。