OFDM—MIMO相控阵雷达性能分析

采用正交频分调制（0FDM）波形的MIM0相控阵雷达是一种新的MIMO雷达,其可同时实现波形分集和频率分集．与正交相位编码波形不同,OFDM波形中心频率不同,存在特定的差频,使得基于该波形的MIMO雷达信号处理更为复杂．针对这一问题,首先建立了该雷达系统信号模型,推导了子阵间空域相干合成结果,然后,分析了该系统的信噪比、作用距离和抗截获能力,并与传统相控阵雷达进行了比较理论分析和仿真实验结果证实了该系统的优势．     

微机采样式非正弦波电参数的测量

本文介绍了所研制的20Hz～3kHz微机采样式非正弦波电参数的测量方法和装置。分析了测量原理,硬件电路充分利用了8098的各项功能,软件上采用软件同步和步进采样技术,降低了成本。试验表明工作正常,误差符合分析。     

超宽带正交脉冲波形设计

超宽带系统利用窄脉冲传输信息,其系统性能受脉冲的功率利用率影响.为了使脉冲波形充分利用FCC功率谱密度规范所划分的频段,该文从最大化功率利用率的角度出发,采用半正定规划的方法设计了一组脉冲超宽带的正交波形.设计得到的脉冲波形具有时域持续时间短、频域满足FCC规范及功率利用率高等优点,并且不同脉冲间在零点处互相关系数小,正交性好.通过将目标函数中的2-范数转换成1-范数,可以进一步增加正交波形的功率利用率,从而有效提高接收端的信噪比.设计结果表明这种设计方法是一种满足规范要求的较为理想的方法.     

Inversion of a velocity model using artificial neural networks

We present a velocity model inversion approach using artificial neural networks (NN). We selected four aftershocks from the 2000 Tottori, Japan, earthquake located around station SMNH01 in order to determine a 1D nearby underground velocity model. An NN was trained independently for each earthquake-station profile. We generated many velocity models and computed their corresponding synthetic waveforms. The waveforms were presented to NN as input. Training consisted in associating each waveform to the corresponding velocity model. Once trained, the actual observed records of the four events were presented to the network to predict their velocity models. In that way, four 1D profiles were obtained individually for each of the events. Each model was tested by computing the synthetic waveforms for other events recorded at SMNH01 and at two other nearby stations: TTR007 and TTR009.     

非正弦波功率表的研制

分析了非正弦波情况下功率的特点，从而用时分割乘法器研制了功率表，它既适用于正率波形，也适用于非正弦波形，本功率表成本工，调节方便，实测结果误差较小，已投入生产。     

Recent studies on multiplex driving of BTN‐LCDs

The main parameters of driving waveforms for BTN‐LCDs were investigated, and the effects on the display operation and dependence on temperature were measured. Based on experimental results, we have determined the most useful driving waveforms for practical operation, and also proposed a new driving method.     

Influence of the frequency‐dependent characteristics of soil permittivity on the impulse performance of grounding electrode

In the analysis of impulse characteristics, the accuracy of the calculation results depends largely on the soil electrical parameters. However, existing calculation methods simplify or ignore the influence of the frequency‐dependent characteristics of soil permittivity on impulse performance. On the basis of the dielectric spectrum measurement results of typical soil, a finite element model that considers the frequency‐dependent characteristics of soil permittivity is developed in this paper. The influence of the frequency‐dependent characteristics of soil permittivity on impulse performance is analyzed systematically. Results indicate that a significant difference exists when the permittivity is constant. The transient grounding impedance value is highly influenced by the impulse current waveforms and the amplitude of the impulse current. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

动电效应测井研究现状和展望

崔志文.多孔介质声学模型与多极源声电效应测井和多极随钻测井的理论与数值研究[D].长春:吉林大学,2004.

关威,胡恒山,储昭坦.声诱导电磁场的赫兹矢量表示与多极声电测井模拟[J].物理学报,2006,55:267-274.

Cui Z W,Wang K X,Hu H S,et al Acousto-electric Well Logging by Eccentric Source and Extraction of Shear Wave[J].Chinese Physics,2007,16(3):746-752.

Cui Z W,Wang K X,Sun J G,et al.Numerical Simulation of Shear-Horizontal-Wave-Induced Electromagnetic Field in Borehole Surrounded by Porous Formation[J].Chinese Physics Letters,2007,24 (12):3454-3457.

Hu H,Guan W,Harris J.Theoretical Simulation of Electroacoustic Borehole Logging in a Fluid-saturated Porous Formation[J].Journal of the Acoustic Society of America,2007,122(1):135-145.

Zhan X,Chi S.Simulation of the Converted Electric Field during Multipole Logging While Drilling (LWD)[C]//SEG Expanded Abstracts,2006,25:446-450.

Guan W,Hu H.Finite-Difference Modeling of the Eelectroseismic Logging in a Fluid-saturated Porous Formation[J].Journal of Computation Physics,2008,227(11):5633-5648.

关威.孔隙介质弹性波-电磁场耦合效应测井的波场模拟研究[D].哈尔滨:哈尔滨工业大学,2009.

Plyushchenkov B D,Turchaninov V I.Solution of Pride's Equations Through Potentials[J].International Journal of Mordern Physics C,2006,17,877-908.

Berryman J G.Electrokinetic Effects and Fluid Permeability[J].Physica B,2003,338:270-273.

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声波测井仪器接收换能器隔声设计

不论是阵列声波测井仪器还是普通声波测井仪器，发射与接收换能器之间的连接、接收换能器之间的连接，既要考虑机械结构的稳定性，更要考虑声波的隔声效果，以避免声波沿着连接部分传播。文章先给出一个实际的测井波形实例，引出隔声设计对声波测井资料的影响；然后，用一维声波传播模型给出了一种隔声设计方法。用该方法分析目前声波测井仪器所采用结构的隔声效果，发现在25kHz附近隔声效果比较差。为此，重新对连接方法进行了优化设计，新的阵列声波测井仪器研制中使用了这种隔声结构，在实际测井资料中收到了比较好的效果。     

A new reactive,distortion and non-active power measurement method for nonstationary waveforms using wavelet packet transform

The definitions of power components that are contained in the IEEE Standard 1459-2000 [IEEE Std. 1459-2000, Definitions for the measurement of electric quantities under sinusoidal, non-sinusoidal, balanced or unbalanced conditions, 2000] are based on the Fourier transform (FT) which is suitable only for the case of stationary waveforms. However, for nonstationary waveforms, the FT produces large errors. Therefore, the power components based on this transform become inaccurate. A new approach based on the wavelet packet transform (WPT) for defining these power components is developed in this paper. The advantages of using the wavelet transform are that it can accurately represent and measure nonstationary waveforms, providing uniform frequency bands while preserving both time and frequency information. In addition, this paper addresses the problem of choosing the most appropriate mother wavelet for power components measurements. The results of applying both approaches to stationary and nonstationary waveforms show that the currently used definitions according to the IEEE Standard 1459-2000 result in large errors for the case of nonstationary waveforms while the proposed approach (WPT based) gives more accurate results in this situation.