Direct Digital Frequency Control Based on the Phase Step Change Characteristic between Signals

We present a new digital phase lock technology to achieve the frequency control and transformation through high precision multi-cycle group synchronization between signals without the frequency transformation circuit. In the case of digital sampling, the passing zero point of the phase of the controlled signal has the phase step characteristic, the phase step of the passing zero point is monotonic continuous with high resolution in the phase lock process, and using the border effect of digital fuzzy area, the gate can synchronize with the two signals, the quantization error is reduced. This technique is quite different from the existing methods of frequency transformation and frequency synthesis, the phase change characteristic between the periodic signals with different nominal is used. The phase change has the periodic phenomenon, and it has the high resolution step value. With the application of the physical law, the noise is reduced because of simplifying frequency transformation circuits, and the phase is locked with high precision. The regular phase change between frequency signals is only used for frequency measurement, and the change has evident randomness, but this randomness is greatly reduced in frequency control, and the certainty of the process result is clear. The experiment shows that the short term frequency stability can reach 10-12/s orders of magnitude.

Joint receiving mechanism based on blind equalization with variable step size for M-QAM modulation

The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.

德江天麻对东莨菪碱诱导的记忆障碍模型小鼠学习记忆能力的影响

目的:观察德江天麻对东莨菪碱诱导的记忆障碍模型小鼠学习记忆能力的影响。方法:取昆明种小鼠随机分成对照组、模型组、德江天麻高(3 g/kg)、中(1.5 g/kg)及低(0.75 g/kg)剂量组,每组14只;各组动物按相应药物和剂量灌胃给药(1次/d),连续35 d,在试验前15 min,除对照组外,各组小鼠均腹腔注射氢溴酸东莨菪碱1 mg/kg造模;比较各组小鼠跳台试验训练和测试时的错误次数、潜伏期及出现错误动物只数,Morris水迷宫定向航行试验的逃避潜伏期、搜索距离,空间探索试验的小鼠在目标象限内游泳时间百分比、游泳距离百分比及进出平台位置次数。结果:与对照组比较,模型组小鼠跳台试验训练时的错误次数、测试时的错误次数、错误潜伏期,定向航行试验的逃避潜伏期及搜索距离均明显增加,小鼠在目标象限内的游泳时间和游泳距离明显降低,进出平台位置次数显著减少(P<0.05或P<0.01);与模型组比较,德江天麻高、中剂量组小鼠训练时的错误次数明显减少,测试时的错误潜伏期明显延长、错误次数明显减少,逃避潜伏期及搜索距离均明显缩短,在目标象限内游泳时间百分比、游泳距离百分比及在平台位置进出的次数明显增加(P<0.05或P<0.01)。结论:德江天麻可改善莨菪碱诱导的记忆障碍模型小鼠的学习记忆能力。

220kV直降式第三绕组调压整流变压器的研制综述

介绍了国内首台220kV直降式第三绕组调压整流变压器的研制、开发过程。从产品设计工艺、生产及试验等各个过程分析了产品的特点。

软启动技术在电机控制中的应用

通过对电动机的传统启动方式:全压直接启动、降压启动的简介及软启动技术的分析和对比,提出了软启动技术在现代电机控制中具有的卓越性能,它是替代以往传统启动方式的理想选择,在工业生产和生活中有着极为广阔的应用前途。

220kV直降式超高压整流机组在新疆农六师铝业电解铝厂中的应用

以铝电解整流机组为分析研究对象,对新疆农六师铝业一期工程采用新型结构的220kV直降式超高压整流机组的应用情况进行了介绍和分析,得出新型结构整流机组能够在直流额定电压达到1530V时安全运行,具有损耗低、效率高、抗短路能力强、可靠性高等优点,项目实施后取得了良好的经济效益。

异步电机起动电磁仿真分析

针对小型异步电机在不同起动方式下起动特性的计算问题,文中基于有限元法建立电机二维电磁模型仿真计算电机的起动性能。考虑到二维模型中电机端部对电磁仿真整体的影响,采用场路结合的方法将定转子端部的电阻和漏感参数化等效处理到模型中。利用MagNet和Simulink软件依据起动电路结构搭建直接起动、Y-△降压起动、恒频压比起动的电源模型,仿真计算电机在不同起动方式下的起动时间、起动电流、起动速度等。仿真和实验测试结果表明,所建立的模型能准确仿真计算异步电机常见起动方式下的特性。

铝电解整流供电系统的应用和展望

通过对山西关铝公司三个电解系列的整流供电系统及世界范围内铝电解用供电电源各部分发展沿革技术分析,得出采用直降式晶闸管整流系统是电解铝生产工艺的理想供电方式的结论。

水泵起动方式的选择

阐述了电动机全压起动的优点,对全压起动和各种降压起动的特点进行分析比较,同时对水泵的起动转矩作了简要分析.

HVDC系统送端孤岛下谐波不稳定对策探讨

各次谐波能够在换流器交、直流侧来回传递,可能诱发系统的潜在不稳定,造成电流、电压畸变,最终导致HVDC(high voltage direct current)系统运行困难。分析表明一旦系统存在谐波不稳定的风险,就必须提出相应的对策。文中以特高压直流和同塔双回HVDC输电系统为例,建立电磁暂态模型,对可能发生谐波不稳定的运行方式进行了分析探讨,提出采用直流降压运行的策略来缓解低次谐波谐振的程度,并基于滑模变结构控制策略设计了励磁电压附加控制器以抑制谐波进一步放大,从而维持电压的稳定。分析结果表明,这两种对策都能够有效解决谐波不稳定问题。

110kV直降式整流装置使用探讨

比较了110kV降压35kV和110kV直降式整流供电系统方案。直降式整流供电可节约运行电费,在能源日趋紧张的形势下实现可观的经济效益。

110kV直降式整流装置有载调压开关的选择

介绍了110kV直降式整流装置有载调压开关的选择方式,建议选用中性点调压方式。

一种三电平降压平衡电路研究

此处研究了一种三电平降压平衡电路及控制策略。它能将单极性直流电网改造成双极性直流电网,构造两个电压等级相同或不同的电压以满足电网中不同用电设备对输入电压的需求。它由正向和负向两个三电平降压桥臂组成,不存在直通危险。控制策略能够实现桥臂独立运行并避免输入输出端之间无功电流交换。在此具体地分析该电路工作过程和内部电压电流关系。实验结果表明该电路和控制策略是正确、可行的。

利用一台软起动器起动多台高压电动机的探讨

用软起动器起动高压电动机，其过程平稳、电流小、转矩大，对电动机有可靠的保护作 用，对设备的冲击小、磨损轻，是一项值得推广的先进技术。

110kV直降式整流系统及其节能措施

介绍了目前氯碱整流最新技术——直降式整流系统的特点和装置组成。根据其应用于20万t/a离子膜法烧碱生产系统中的运行数据,分析了装置选择的重要性和控制运行参数节能的必要性。

110kV直降式整流的经济规模

在分析了供电安全、厂区规划等条件的基础上,讨论了110kV直降式整流的经济规模。认为一次建成的最小规模为40万t/aPVC、32万t/a烧碱。

倒台阶法治理奥陶系高承压含水层套管错断技术的研究及推广应用

通过对奥陶系灰岩承压含水层在埋藏深、地应力大、水压大、水量补给丰富的前提下发生在底板注浆改造期间的套管错断治理技术,从巷道施工到底板奥灰水治理在三维空间中结合自身结构、规模、所受地应力及埋深造成的复杂性及不确定性因素,目前国内各大煤业集团公司对于底板注浆加固套管错断、水文观测孔套管错断、漏水、渗水等现象较多,处理难度较大,有的单位套管出现问题在出水量小水压小的情况下,处理几年都处理不好,因此研究奥灰水赋存规律及径流带方向至关重要,避免出现在矿井生产过程中,由于对研究对象认识的局限性不足造成底板水失控突水风险,给单位的财产带来不必要损失,对于研究套管错断技术有着重大意义。

Parallel algorithm and its convergence of spatial domain decomposition of discrete ordinates method for solving radiation heat transfer problem

To improve the computational efficiency and hold calculation accuracy at the same time,we study the parallel computation for radiation heat transfer. In this paper, the discrete ordinates method（DOM） and the spatial domain decomposition parallelization（DDP） are combined by message passing interface（MPI） language. The DDP–DOM computation of the radiation heat transfer within the rectangular furnace is described. When the result of DDP–DOM along one-dimensional direction is compared with that along multi-dimensional directions, it is found that the result of the latter one has higher precision without considering the medium scattering. Meanwhile, an in-depth study of the convergence of DDP–DOM for radiation heat transfer is made. Analyzing the cause of the weak convergence, we relate the total number of iteration steps when the convergence is obtained to the number of sub-domains. When we decompose the spatial domain along one-,two- and three-dimensional directions, different linear relationships between the number of total iteration steps and the number of sub-domains will be possessed separately, then several equations are developed to show the relationships. Using the equations, some phenomena in DDP–DOM can be made clear easily. At the same time, the correctness of the equations is verified.