钝体燃烧器火焰变化过程的速度分布特性

实验测量了变工况钝体回流扩散燃烧速度场，定量确定钝体回流燃烧火焰和中心射流主导火焰的转换曲线，分析了燃空速度比对燃烧稳定性的影响。实验中利用粒子图像速度场测量(PIV)技术对不同燃空速度比下的钝体回流扩散燃烧流场进行了测量，考察不同火焰的结构特性及其内部流动状况。由火焰的速度场出发，确定了钝体回流燃烧火焰和中心射流主导火焰的转换曲线。根据测量所得数据发现燃空速度比是决定钝体轴线上最小速度大小及相对位置的主要因素，燃空速度比是决定钝体轴线最小速度与钝体表面距离的重要参数：随着燃空速度比的增加，轴线上最小速度与钝体表面的相对距离先迅速增加，后略有降低，然后再次迅速增加；轴线上最小速度与燃空速度比成线性关系，随着燃空速度比的增加，轴线上最小速度不断增加。     

光栅型成像光谱仪杂散光校正技术研究

成像光谱仪中杂散光的存在会导致光谱测量误差,对杂散光的校正可以得到精确的测量结果。采用He-Ne激光器测出成像光谱仪的点扩展函数,假设成像光谱仪是线性波长不变系统的前提下,构建光谱函数矩阵,确定影响波长权重,再通过带宽校正矩阵对其进行带宽校正,从而对仪器测量中的杂散光误差进行校正。最后,通过实验表明此杂散光的修正方法基本上消除了杂散光对测量信号的影响。     

高压组合电器水平母线振动特性研究

高压组合电器设备（gas insulated switchgear,GIS）运行中产生异常机械振动缺陷,对设备危害极大,因此,GIS正常运行时的振动特性对其运行状态评价与故障诊断具有重要意义。以三轴加速度传感器为核心搭建了振动检测系统,在某330 kV变电站GIS上测取振动信号,从时域和频域出发分析了振动的成因。研究结果表明,GIS表面信号可由径向、轴向和切向振动描述,由于受力模式不同,振动特性与测点位置有关：同一测量面的不同测量点,由上至下,径向振动幅值先降后升,切向振动幅值先升后降;同一测量点的不同测量面,越靠近母线中央,径向和切向振动幅值越大,轴向振动表现复杂。振动频率集中在100 Hz左右,存在2种特殊情况。     

影响汽轮发电机轴向位移测量结果的各因素分析

发电设备的轴向位移测量参数,是火力发电厂中重要的监测参数之一,利用轴向位移测量装置,对导致轴向位移测量参数变化的各种因素进行分析,找出其数值起伏变化的原因并及时进行消除,通过对不同机组在生产运行中的实例比较,寻求产生测量偏差的真正原因。提出了正确判断轴向位移测量结果的方法,用于解决系统运行中的实际问题。     

5.8GHZ扩频通信在调度自动化中的应用

针对多山、路远、地形复杂的地区，为电力系统变电所调度自动化提供的通道有许多种，而采用5．8GHz扩频通信为其提供通道是一种既经济又便捷的手段。文中介绍了多站点对点扩频系统的使用实例。     

基于SIFT特征点检测与维纳滤波的图像复原算法

为了解决当前图像局部模糊程度不一,导致图像复原效果欠佳,本文分别从图像特征点检测与滤波复原的角度出发,提出了基于SIFT特征点检测与维纳滤波的图像复原算法.根据尺度空间极值特性,进行关键点定位和方向分配,设计特征点描述子,得到模糊图像特征点分布,以建立圆盘复原模型中心坐标.基于点扩散圆盘函数特性,耦合傅里叶变换和最小二乘滤波,设计了无约束维纳滤波算子,达到图像复原处理的目的.根据特征角点定位,引导复原滤波圆盘函数计算起始位置,完成图像复原.实验测试结果显示,与当前复原算法相比,本算法拥有更高的复原视觉质量.     

Design,modeling and analysis of dual-feed defected ground microstrip patch antenna with wide axial ratio bandwidth

In this paper, a low profile microstrip patch antenna with defected ground structure is proposed for wide impedance and axial ratio bandwidth. The antenna structure consists of two feed lines with a circular defect loaded in the ground surface. The proposed antenna shows an impedance bandwidth of 71.92% ranging from 8.95 to 19 GHz covering X, Ku and K band applications. The mutual coupling between the two feed lines is suppressed by means of a single and double arc-shaped defect embedded in the ground plane. The mutual coupling is suppressed to a level of ? 37.5 dB with improved radiation performance. The measured 3-dB axial ratio bandwidth of the proposed antenna ranges from 8.85 to 11 GHz. An equivalent circuit model of the designed antenna is also proposed for theoretical analysis and theoretical results are verified with simulated and measured results.     

静叶调节轴流式引风机抢风问题探讨

针对锅炉运行中存在并联运行引风机"抢风"的问题,从风机性能曲线、工作点角度入手对AN型静叶调节轴流引风机进行了分析.结果表明,由于引风机"抢风",整个管网的阻力曲线发生了变化,使得风机工作点落入∞形区域内,导致炉膛压力处于不稳定状态甚至使风机出现过电流而损坏.根据实例,对引风机"抢风"的现象、原因进行了分析,并提出了防范措施.     

大型轴流式叶片曲面的反求与重构建模

数字化模型是叶片式流体机械数字化设计与制造的基础,根据大型轴流式水轮机叶片的特点,提出了基于反求技术的大型轴流式水轮机叶片曲面重构方法。采用三坐标测量机测得叶片实体模型的表面数据,通过对点云数据进行平滑、精简处理,使用点云网格化、曲面特征提取,曲面分割及拟合曲面片的曲面重构技术,快速、精确地拟合出叶片曲面模型,提高了建模的精度和效率,为后续数字化设计与制造研究奠定了基础。     

Convergence analysis of blind image deconvolution via dispersion minimization

A new non‐linear adaptive filter called blind image deconvolution via dispersion minimization has recently been proposed for restoring noisy blurred images blindly. This is essentially a two‐dimensional version of the constant modulus algorithm that is well known in the field of blind equalization. The two‐dimensional extension has been shown capable of reconstructing noisy blurred images using partial a priori information about the true image and the point spread function in a variety of situations by means of simulations. This paper analyses the behaviour of the algorithm by investigating the static properties of the cost function and the dynamic convergence of the parameter estimates. The theoretical results are supported with computer simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Axial Magnetic Fields,Axial Force,and Losses in the Stator Core and Clamping Structure of a Synchronous Generator with Axially Displaced Stator

Axial displacement of the stator in a synchronous machine gives rise to axial magnetic field both at the ends and deep inside the stator. The axial magnetic field causes losses. This article contains results from two studies with an axially displaced stator. In the first study, axial magnetic leakage fields in the ends of a small synchronous generator at load and no load were measured and simulated. In the second study, axial force and iron losses at no load were calculated with non-linear materials and a three-dimensional, time-stepped finite element method. For some machines with vertical shafts, the sum of iron losses and thrust bearing losses can be reduced if the rotor is lowered or the stator raised, whichever is best.     

No tooling cost process for induction motors energy efficiency improvements

In this paper, the analysis of some possibilities for increasing the induction motor efficiency using production technological process modifications is reported. This approach is known as the "no tooling cost" (NTC) strategy because it does not require a complete redesign of new laminations with a consistent cost in terms of investments. The paper shows the results obtained by a full experimental approach, using "ad hoc" prototypes. The NTC design modification and the technological processes analyzed in this paper have been done on totally enclosed fan-cooled standard induction motors. Obviously, the original motors have been compared from the energetic point of view with these prototypes. The energetic performance has been measured in accordance with the IEEE Std. 112-96 Method B. In particular, the following modifications, for obtaining an increase in efficiency, have been taken into consideration: rotor with copper bar included in the slot before the aluminum die cast, increase of the core axial length, and annealing of the stator core.     

利用两端电气量实现T型高压线路相间故障定位方法

采用分布参数建模,提出了一种利用2端电气量实现T型高压线路相间故障定位的方法。该方法利用保护测量到的电气量计算故障点电压,并在此基础上构造了故障定位函数,根据故障定位函数相位特性判断故障支路。在故障支路的故障点前后变化时,故障定位函数相位会发生唯一1次突变,相位突变点所对应位置即为故障点。采用分布参数建模,克服了分布电容的影响;算法设计中考虑了故障电压的影响,克服了负荷电流的影响;利用故障定位函数相位突变特性进行定位,克服了过渡电阻的影响。PSCAD /EMTDC仿真结果表明,该方法受故障位置、过渡电阻和负荷电流的影响很小,具有很高的测距精度。     

Characteristics of axial force and rotating torque and their control of permanent magnet type axial gap self‐bearing motor

This paper introduces an axial gap type self‐bearing motor. It is intended for a disk type flat motor to have both functions of rotation and axial position control. This motor is simple in construction and requires a simple control system. A permanent magnet type motor is analyzed theoretically and tested experimentally. The torque characteristics of the tested motor are measured at various values of axial force and air gap. Independent control of the axial force and torque is introduced for the servo motor control and synchronous motor control. The results show the high possibility of the proposed motor and control system. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 81–91, 2000     

轴向电磁轴承多自由度承载力理论与实验研究

为了实现磁悬浮轴承系统的微型化,对轴向电磁轴承的多自由度承载力进行理论与实验研究。基于轴向磁轴承气隙磁通空间分布,利用分割磁场法建立磁路模型,由虚位移法得到轴向和径向承载力的数学表达式。借助有限元仿真软件,得到轴向磁轴承气隙磁感应强度与磁场空间分布。在搭建的磁轴承三维力学测量平台上,实验测量了轴向磁轴承的轴向与径向承载力,分析总结了多自由度承载力随电流、轴向位移和径向位移的变化规律,结合理论与仿真结果,分析了结构参数变化导致气隙磁场分布变化,进而改变轴向与径向承载力的物理机理,为轴向磁轴承实现多自由度悬浮研究提供了参考依据。     

RB工况中一次风机失速原因分析及预防

针对国电大同三期660 MW机组在RB过程中一次风机失速的问题,在轴流风机失速机理的基础上,根据实测数据对一次风机失速的原因进行了分析,通过采取一系列改善措施,不仅确保了RB功能的实现,也提高了一次风机运行的安全性及可靠性。     

Extraction of the first bolus passage in dynamic susceptibility contrast perfusion measurements

Object  The processing of dynamic susceptibility contrast perfusion measurements requires an extraction of the first bolus passage of the injected contrast agent. State-of-the-art methods employ the fit of a gamma variate function to the measured data. The use of a gamma variate function is motivated by its shape similarity to the expected relaxation rate time-course during the first bolus passage. However, the quality of this result is strongly influenced by the amount of overlap of the first and second bolus passage. In this work we present an alternative, data-driven method for the extraction of the first bolus passage from a measured relaxation time-course. Materials and methods  By using prior knowledge of the injection function, the measured time-courses can be transformed to time-courses that would occur at a shorter injection duration where the two bolus passages have less overlap. This time-course is found by Tikhonov regularized deconvolution of the measured time-courses with an injection function that bases on the measurement protocol. A minimum search yields the cut-off point at which the first bolus can be extrapolated to zero. The gamma variate fit is performed using Powells algorithm. The proposed approach is compared to the gamma variate fit approach using simulations and an exemplary dataset from one healthy volunteer. Results  The new method performs comparably stable as the gamma variate function fit approach in simulations. Both methods are superior to a simple exponential extrapolation approach. Applied to volunteer data, the new method performs much faster than the gamma variate fit approach. The results obtained from both methods correspond well. Conclusion  The new method offers a conceptual understanding of the first bolus passage and yields similar results to the gamma variate function fit approach but performs much faster.     

Factors affecting corona on twin-point gaps under dc and ac HV

The factors affecting corona formation on twin-point/plane gaps are investigated both theoretically and experimentally. In the theoretical analysis, an electrostatic field computation program based on the charge simulation method was used to get the electric field profile on the plate for different gap lengths and interspacings between the two points. Also, the effect of voltage level, air pressure and gap length on the number of axial streamers occurring across the critical field line was introduced for a constant time duration. The variation of the integral of the ionization coefficient with the axial length from the point was studied. Finally, a study of the effect of air pressure and gap length on both the corona inception voltage and critical length was presented. Corona formation in single and twin-point/plane gaps also was investigated experimentally under both high direct and alternating voltages. There are many factors affecting such corona formation. The investigated factors were the interspacing between the two points, gap length between the point and the plane, ambient temperature, relative humidity, polarity or frequency of the applied voltage, and electrode material. In order to study and explain such phenomena, a photographic investigation together with a simultaneous measurement of both the applied voltage and the corona current were introduced. Curve fitting of the dc corona current vs. gap length and voltage for both single and twin-point/plane gaps gave the conventional relationship, but in case of twin point the power of the gap length varies between 1.2 and 1.3     

轴向磁化的双环永磁轴承轴向磁力研究

基于分析一对永磁环间隙的磁能及磁导，根据具有线性退磁曲线的稀土永磁材料特性和磁通连续原理，通过虚功原理法，得到轴向磁化的双环永磁轴承轴向磁力解析数学模型。模型表明：轴向磁化的双环永磁轴承轴向磁力与磁环剩磁感应强度的平方成正比，近似与磁环的平均半径及磁环径向宽度成正比；轴向磁力随磁环轴向长度的增大而增大，随磁环轴向间隙、径向偏心及磁环相对磁导率的增大而减小。经验证，模型计算值和实验值基本吻合。该模型显式表达了轴向磁力与各参量间的关系，使得永磁轴承设计和优化简便易行，解决了轴向磁化的双环永磁轴承轴向磁力数值计算复杂的问题。     

基于盲恢复的POCS图像超分辨率重建

在传统凸集投影(POCS)算法基础上,考虑到算法对于初始图像的依赖性,尝试通过引入近似点扩散函数检测(APEX)盲解卷积技术,对POCS算法的初始参考图像进行盲恢复,然后再进行超分辨率图像重建。仿真实验证明,APEX盲恢复后的初始图像,相比原初始图像,更加接近真实图像。重建后,直观上图像的清晰度有了一定程度的提高,由于更好地抑制了噪声,表现在PSNR有了一定的提升;另外,由于APEX的引入,改进算法在一定程度上降低了原算法对初值的依赖程度,增强了POCS算法的鲁棒性。