模拟预失真发生器设计

介绍了一种新颖的自抵消式预失真发生器,它在预失真发生器中采用与主放大器相同型号的驱动放大器,这样驱动放大器的非线性特性可以自动抵消主放大器的非线性特性。将其应用于放大器设计,仿真实验结果表明,这种预失真方法使IMD3和IMD5分别改善16dB和8dB。     

无源性控制策略在谐波/间谐波统一补偿的单相有源电力滤波器中的应用

对谐波/间谐波统一补偿的单相有源电力滤波器(active power filter,APF)系统进行了瞬时功率分析,研究了电网侧、APF主电路、负载侧之间的功率流动,证明了在不考虑APF主电路损耗的情况下,其直流侧功率波动具有周期性。推导了统一补偿的单相并联型APF的无源性控制策略方程,并针对其欠激励特性及直流侧功率波动的周期性设计了直流侧电压的间接控制。然后,针对其启动中遇到的问题,从功率平衡角度进行了分析并提出了解决方法。Matlab仿真实验结果验证了理论分析的正确性。     

一种用于AVS视频编码的块运动估计算法

通过对现有的视频图像编码中的帧间预测技术所用的运动估计算法的分析,提出了一种适用于AVS视频编码标准的快速而有效的块运动估计算法,该算法采用5个检测点的大菱形和9个检测点的小田字形双模板结构,通过调用大菱形模板和小田字形模板进行块运动匹配搜索,随着搜索的进行,大菱形模板可以被循环调用,但约定小田字形模板仅被调用一次.通过与全搜索算法和菱形搜索算法比较,这种新的块运动估计算法在保证编码性能几乎不变的情况下,编码复杂性能够得到有效的降低.     

基于SOA架构的一体化电网运行服务总线关键技术研究

基于SOA架构提出的一体化电网运行服务总线(OSB)解决方案在南方电网一体化运行数据中心实现,满足了统一服务路由的通用数据访问需求以及对实时性要求比较高的高速数据访问需求,兼顾了相关应用的发布订阅需求以及跨隔离装置服务调用的特殊要求。实际运行效果表明,服务总线充分发挥了多业务系统数据协同的信息化优势,为跨部门、跨专业的综合应用提供了数据共享服务以及决策分析支撑。     

硅压力传感器的非线性分析及优化设

分析了硅压力传感器的线性与非线性，讨论了非线性产生的原因，并提出了硅压力传感器的优化设计方法。     

融入平滑组稀疏化的脑部MRI图像分类

目的 阿尔茨海默症(Alzheimer’s disease, AD)是主要的老年病之一,并正向年轻化发展。早期通过核磁共振(magnetic resonance imaging, MRI)图像识别AD的发病阶段,有助于在AD初期及时采取相关干预措施和治疗手段,控制和延缓AD疾病恶化。为此,提出了基于平滑函数的组L1/2稀疏正则化(smooth group L1/2,SGL1/2)方法。方法 通过引入平滑组L1/2正则化实现组内稀疏,并将原先组L1/2方法中含有的非平滑的绝对值函数向平滑函数逼近,解决了组L1/2方法中数值计算振荡和收敛难的缺点。SGL1/2方法能够在保持分类精度的前提下,加速对模型的求解。同时在分类方法中,引入一个校准hinge函数(calibrated hinge, Chinge)代替标准支持向量机(support vector machine, SVM)中的hinge函数,形成校准SVM(calibrated SVM,C-SVM)用于疾病的分类,使处于分类平面附近的样本更倾向于分类的正确一侧,对一些难以区分的样本能够进行更好的分类。结果 与其他组级别上的正则化方法相...     

普通碳素钢超细晶临界奥氏体控轧工艺研究

通过在Gleeble-2000热变形模拟机上模拟实验,研究了低温变形条件下的工艺参数对普通低碳钢Q235获得微米级超细晶组织影响规律。利用实验研究结果在型钢轧机上轧出晶粒尺寸约为5μm的400MPa级钢筋,研究表明对于低碳钢Q235利用形变诱导铁素体和铁素体动态再结晶机制在Ae3-Ar3℃附近的临界（亚稳）奥氏体温度范围内变形,可以获得4－6μm等轴均匀的超细晶铁素体。     

On the characteristics of routing paths and the performance of routing protocols in vehicle‐formed mobile ad hoc networks on highways

Recently, intelligent transportation systems (ITS) is becoming an important research topic. One goal of ITS is to exchange information among vehicles in a timely and efficient manner. In the ITS research community, inter‐vehicle communications (IVC) is considered a way that may be able to achieve this goal. An information network built on the top of vehicles using IVC can be viewed as a type of mobile ad hoc networks (MANETs). In the past, several unicast routing protocols for MANET have been proposed. However, most of them are designed for general MANETs rather than for IVC networks. In this paper, we first used more realistic vehicle mobility traces generated by a microscopic traffic simulator (VISSIM) to understand the characteristics of routing paths in an IVC network. Based on the insights gained from the derived path characteristics, we designed and implemented an intelligent flooding‐based routing protocol for small‐scale IVC networks. Via several field trials conducted on highways, we compared the performance of ad hoc on‐demand distance vector (AODV) and our protocol. Our experimental results show that (1) our protocol outperforms AODV greatly in IVC networks and (2) our protocol can provide text, image, audio, and video services for small‐scale IVC networks (e.g., a platoon) quite well. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of soft reduction on bloom internal crack by a strain model

Soft reduction (SR) can effectively improve the strand centre quality by decreasing its porosity and segregation. However, it tends to cause internal crack defects in the bloom if an improper reduction amount or improper reduction zone is implemented on the strand. In this work, a two-dimensional non-steady solidification model and a strain model are established for 350?mm?×?470?mm bloom casting. Using the strain model, the strain field for GCr15 bloom upon SR is calculated. Through the online SR test and macrostructure inspection of the cast blooms, the minimum centre solid fraction suitable for SR of the bloom is determined. The results show that the established strain model calculation agrees well with the practical bloom macrostructure inspection. Thus, with the strain model, one can calculate whether internal crack defects would occur, as well as determine the right reduction amount or proper reduction zone.     

干式空心电抗器包封受潮对绝缘的影响研究

包封受潮是导致干式空心电抗器匝间绝缘失效的重要诱因,文中通过对故障退运电抗器的解剖分析以及匝间绝缘材料的湿热老化试验,研究包封受潮对干式空心电抗器匝间绝缘的破坏作用。首先,解剖了一台南方地区故障退运的电抗器,利用扫描电镜、傅里叶红外光谱仪、断裂拉伸试验等对样品的理化性能进行分析,推断受潮后包封内部绝缘的变化过程;然后,进一步对作为匝间绝缘材料的PET聚酯薄膜进行了湿热老化试验,研究了其在不同湿度老化条件下击穿场强、断裂伸长率的变化。研究表明:干式空心电抗器有可能严重受潮,受潮将导致包封内部各绝缘材料的水解,其中聚酯薄膜的耐水解性能很差,极易由于严重水解而导致机械强度的大幅下降甚至完全脆化,并在包封内部应力的作用下破裂从而导致匝间绝缘受损,所以有必要采取措施防止包封受潮并降低包封受潮对匝间绝缘的破坏。