智能变电站二次设备集成方案讨论

文章首先对智能变电站的二次集成进行了概述;其次对智能变电站的二次设备集成方案进行了分析;最后在实际应用中进行了研究和分析。     

有限元法的工程应用研究

对有限元法的概念、基本思想以及工程应用的特点进行了阐述;针对有限元法在结构仿真分析中的工程应用,给出了应用有限元法进行仿真分析的步骤,相对于各步骤,阐述了对应的内容以及应注意的问题,并对问题的解决方法做了进一步的研究;应用大型有限元分析软件ANSYS对一零件进行了结构有限元分析,对仿真分析的一般流程作了举例说明。     

UWB室内外信道模型分析

对UWB信号的室内外信道模型进行分析及综合讨论。基于Fresnel-Kirchoff刃型模型,对室外信道模型进行了PPM调制信号的多径信道分析;基于RICE统计模型及RAKE接收机,对室内信道模型采用了确定性信道统计模型进行分析;并基于ARMA模型,对室内信道模型采用了自回归信道模型方法分析。在理论分析的基础上给出了计算机仿真结果。     

转轴支架的屈曲分析

运用ANSYS Workbench Environment(AWE)有限元软件对转轴支架进行了静力学及屈曲分析,用以指导支架的结构详细设计。首先在三维建模软件Pro/E建立支架的三维几何模型;其次借助于这个模型,在AWE的Design Simulations模块中进行网格划分和载荷施加;在此基础上对支架并行地进行应力变形分析和屈曲分析,大大缩短了设计周期和节约成本;最后整合这些分析结果,完成对支架的结构优化设计。     

食品生产中危害分析与关键控制点控制

介绍了"危害分析与关键控制点"在保障食品安全体系的作用;对生产环境对食品安全生产的影响进行了分析,确定洁净技术对控制空气途径污染物的正面作用;把生物洁净技术在医药领域和食品领域的运用进行了比较;阐述了洁净技术与传统消毒技术相比具有的优点;具体分析了如何在食品生产过程中利用洁净技术,增加食品安全的保险系数。     

通过参数优化降低LTE低干扰电平小区方案的研究

本文分析了现网LTE低干扰电平小区对网络的影响,对目前干扰处理方法及流程进行了分析;对低干扰电平干扰产生的原因进行了分析;对优化低干扰电平小区的方法进行了分析;提出了通过参数优化降低LTE低干扰电平小区方案;提出了参数调整优化LTE干扰低电平小区方案的流程并将应用成果进行了论述。     

TD-HSPA无线网络规划与优化研究

首先介绍了TD-SCDMA系统网络规划的特点;然后重点分析了TD-HSDPA系统的特点,并对其网络规划时的覆盖、组网方法等方面进行了分析研究,并对TD-HSDPA网络规划提出建议;然后在此基础上对TD-HSUPA的网络规划进行分析研究。最后总结了TD-HSPA网络规划的意义。     

Win32 PE文件型病毒的分析及研究

对Win32平台上的病毒生成和执行过程进行分析,针对每个重要步骤给出相应的代码,并在综合各项分析的基础上给出病毒实例;对文件型病毒三大特征,即隐藏、感染和破坏进行了分析综合;最后对计算机病毒的发展趋势做了预测。     

软件项目管理中的进度控制问题及对策分析

文章首先对软件项目管理的概念以及软件项目进度控制必要性进行了阐述;其次,对软件项目进度控制的原理进行了总结;再次,对软件项目管理中进度计划编制进行了分析;最后,对进度项目管理中的进度计划实施以及控制进行了分析。     

Femtocell关键技术及组网应用

本文对femtocell 概念及技术特点进行了阐述;针对femtocell 关键技术进行了分析;分析了femtocell 系统组网架构,并对相关架构进行分析,提出了网络建设及演进方向;对比了femtocell 与Wi-Fi 之间的发展关系、功能定位.     

利用二维结构稀疏信息的调频步进ISAR高分辨成像新方法

针对已有利用压缩感知理论进行逆合成孔径（Inverse Synthetic Aperture Radar,ISAR）成像方法在低信噪比、欠采样率条件下性能下降严重等问题,依托调频步进波形独有特征并充分利用目标分布的二维结构稀疏信息,提出一种"先方位聚焦后距离分辨"的调频步进ISAR高分辨成像新方法.首先,对回波进行子脉冲脉压,在分析调频步进ISAR回波方位向特有的结构稀疏特征基础上,构建方位向的分布式压缩感知稀疏重构模型;其次,采用分布式压缩感知算法对该模型重构,从而获得低信噪比条件下的方位高分辨成像;最后,利用距离维的回波特征构建任意稀疏重构模型,实现距离向快速成像.由于该方法先进行方位聚焦,再进行距离分辨,并充分利用了目标的结构稀疏性,因此不仅具有抗噪性能强、重构精度高以及采样率低等特点,且避免了越距离单元走动对方位聚焦的影响.仿真与实测数据实验验证了本文方法的有效性.     

A Low-Power Wide-Linear-Range Transconductance Amplifier

The linear range of approximately ±75mV of traditional subthreshold transconductance amplifiers istoo small for certain applications—for example, for filtersin electronic cochleas, where it is desirable to handle loudsounds without distortion and to have a large dynamic range.We describe a transconductance amplifier designed for low-power(< 1 µW) subthreshold operation with a wideinput linear range. We obtain wide linear range by widening thetanh, or decreasing the ratio of transconductance to bias current,by a combination of four techniques. First, the well terminalsof the input differential-pair transistors are used as the amplifierinputs. Then, feedback techniques known as source degeneration(a common technique) and gate degeneration (a new technique)provide further improvements. Finally, a novel bump-linearizationtechnique extends the linear range even further. We present signal-flowdiagrams for speedy analysis of such circuit techniques. Ourtransconductance reduction is achieved in a compact 13-transistorcircuit without degrading other characteristics such as dc-inputoperating range. In a standard 2 µm process,we were able to obtain a linear range of ±1.7V.Using our wide-linear-range amplifier and a capacitor, we constructa follower–integrator with an experimental dynamic rangeof 65 dB. We show that, if the amplifier's noise is predominantlythermal, then an increase in its linear range increases thefollower–integrator'sdynamic range. If the amplifier's noise is predominantly 1/f,then an increase in its linear range has no effect on thefollower–integrator'sdynamic range. To preserve follower–integrator bandwidth,power consumption increases proportionately with an increasein the amplifier's linear range. We also present data for changesin the subthreshold exponential parameter with current leveland with gate-to-bulk voltage that should be of interest to alllow-power designers. We have described the use of our amplifierin a silicon cochlea [1, 2].     

Partially-constrained thermomechanical fatigue of eutectic tin-bismuth/copper solder joints

Small bimetallic load-frames with reference assembly stiffness, k′, and fully-constrained shear strain, γ_fc, were used to simulate the thermo-mechanical conditions experienced by eutectic Bi-42wt.%Sn-to-Cu solder joints. Shear stress and strain were induced in the solder joint by a 45-minute, 0 to 100°C temperature cycle and were calculated from the assembly temperature, joint configuration, and measured elastic strain in the load-frame. Early in cycling, a hysteresis loop representing the maximum stress range and minimum strain range was reached. As damage accumulated in the solder, the stress range decreased and the strain range increased. The TMF life of the joints, defined by the load range drop, Φ, as a function of k′ and γ_fc, can be determined, defining an effective plastic strain range which allows data for various stiffnesses and thermal expansion mismatches to be summarized on a single Coffin-Mansion plot. The effective plastic strain range also provides an important link to conventional low cycle fatigue (LCF) data taken from an infinitely stiff load-frame.     

TT＆C系统中测距误差的频率特性分析法

以往的文献中,多用群时延来分析TT＆C的测距误差,这种方法不够准确和全面.本文采用幅、相频率特性和相位波动特性来分析TT＆C信道中的测距误差.详细讨论了由于信道频率特性和相位波动特性变化产生的测距误差,给出了测距侧音相位的数学表达式.运用这些公式可以计算出这些因素对测距漂移误差的影响,提高测距精度.     

基于权重最小二乘结构边缘保持色调映射算法

高动态范围图像由于其动态范围超过普通显示器的动态范围,所以无法正常显示,从而需要研究在保留高动态范围图像对比度、细节信息以及色彩信息的情况下压缩高动态范围图像的动态范围以适应低动态范围显示器进行显示的色调映射算法。本文提出基于权重最小二乘结构的边缘保持图像平滑色调映射算法。首先,建立基于权重最小二乘的边缘保持图像平滑滤波算子;然后,将输入的高动态范围图像转换至NTSC空间分离亮度信息和颜色信息,利用该滤波算子对亮度信息进行多级分层,获得基本层以及多级细节层信息;最后,对基本层进行动态范围压缩,利用压缩后的基本层结合多级细节层信息并转换回RGB空间获得输出的低动态范围图像。文中通过实验采集的多曝光图像序列利用Debevec和Malik提出高动态范围图像融合算法获得拍摄场景的高动态范围图像,采用本文提出算法对高动态范围图像进行色调映射处理获得较为理想的保留图像有效信息的低动态范围图像,从而验证了文中提出算法的有效性。     

Highly linear wide input range CMOS OTA architectures operating in subthreshold and strong inversion

A very low distortion low-voltage CMOS OTA with very wide g_m adjustment and input range is presented. It is based on a fixed gain novel highly linear voltage-to-current conversion input stage and uses electronically programmable current mirrors to achieve very wide transconductance gain adjustment range. The OTA input range remains approximately constant with g_m adjustment. Bandwidth and input signal range can be adjusted independent of g_m. Simulations results in 0.5 μm CMOS technology with ±1 V supplies and 1 V input range are presented which confirm the characteristics of the proposed structure.     

基于距离单元统计模型的ISAR包络对齐方法

包络对齐是逆合成孔径雷达（ISAR）平动补偿的关键技术之一。本文通过分析目标平动和转动对距离像的影响,建立了距离单元统计模型,并提出了一种基于该统计模型的包络对齐方法。该方法通过两个步骤完成包络对齐：利用目标回波数据提取各距离单元统计模型的参数;搜索使各距离单元的联合概率密度函数取得最大值的距离偏移量进行包络对齐。分析...     

Impact of technology scaling on the tuning range and phase noise of mm-wave CMOS LC-VCOs

The impact of CMOS technology scaling, on the tuning range and phase noise performance of mm-wave LC voltage controlled oscillators (LC-VCOs) is presented. As a preliminary step, the fundamental LC-VCO elements (i) tank inductor, (ii) fixed and variable capacitor elements, and (iii) cross-coupled transistor pair are analytically modeled across the frequency range 10–50 GHz. These models are then exploited to analyze the tuning range and phase noise revealing the ultimate performance bounds for simultaneously achieving low phase noise and wide tuning range in mm-wave CMOS LC-VCOs across the CMOS technology scaling (from 130 nm down to 45 nm) are explored. The analysis demonstrates the improvement of the maximum achievable tuning range, phase noise, and figures-of-merit (FoM and FoM_T) with the technology down scaling. Finally, the performance trend of the mm-wave CMOS LC-VCOs implemented using both thin and thick gate cross-coupled pair is compared. The analysis indicates that thick gate cross-coupled pair VCOs achieve better phase noise at the expense of power consumption and maximum tuning range.     

机载双通道SAR／GMTI数据域DPCA算法研究

相位天线偏置(DPCA)技术在雷达领域是一种经典的杂波抑制算法,该算法简单易行,有很高的实用价值。文中研究了数据域DPCA技术在机载双通道SAR地面动目标检测领域的应用,推导出点目标回波模型;介绍了时间域和多普勒域算法的原理;对多普勒域DPCA算法的工程化进行了研究;最后给出了模拟数据的仿真结果。     

Miniaturized integrated antennas for far-field wireless powering

This paper describes a series of high-efficiency miniaturized antennas of different sizes that can be integrated with the same wireless-powered RFID chip. Since this RFID chip has power scavenging capability in different ISM bands, several integrated on-chip and off-chip antennas in the three ISM bands of 900 MHz, 2.4 GHz and 5.8 GHz are designed, including one antenna integrated on chip. All proposed antennas are derived from a new planar antenna structure which can be designed toward arbitrary input impedance within a given area constraint. The measurement results for the presented antennas show a different read range. The resulting read range versus antenna size diagram specifies the best operating frequency band for a given read range and occupied area. Though this diagram depends on the chip's specifications like the power-on sensitivity and input impedance, it can be generated for any chip. In addition, the measurement results concerning read range and radiation patterns for the proposed antennas are presented and compared with simulation results, showing very good agreement.