Three-dimensional simulation method of multipactor in microwave components for high-power space application

Based on the particle-in-cell technology and the secondary electron emission theory, a three-dimensional simulation method for multipactor is presented in this paper. By combining the finite difference time domain method and the panicle tracing method, such an algorithm is self-consistent and accurate since the interaction between electromagnetic fields and particles is properly modeled. In the time domain aspect, the generation of multipactor can be easily visualized, which makes it possible to gain a deeper insight into the physical mechanism of this effect. In addition to the classic secondary electron emission model, the measured practical secondary electron yield is used, which increases the accuracy of the algorithm. In order to validate the method, the impedance transformer and ridge waveguide filter are studied. By analyzing the evolution of the secondaries obtained by our method, multipactor thresholds of these components are estimated, which show good agreement with the experimental results. Furthermore, the most sensitive positions where multipactor occurs are determined from the phase focusing phenomenon, which is very meaningful for multipactor analysis and design.

Effects of Dimensional Tolerances on the Friction Power Loss of Hydrodynamic Journal Bearing System

According to the dimensional tolerances on hydrodynamic journal bearing system, a nonlinear oil film force model was established,and the Reynolds' equation was solved by adopting finite difference method. In order to fulfill different dimensional tolerances in the system,adopting 2kfactor design and using the eccentricity ratio corresponding to the stability critical curve,the effects of the friction power loss brought by the dimensional tolerances of the dynamic viscosity,bearing width,bearing diameter and journal diameter were analyzed. The effect on dynamic characteristics of the hydrodynamic journal bearing system was quantitatively analyzed,and the nonlinear dynamic analysis, modeling and calculation methods were studied while considering the manufacturing tolerances. The results show that in contrast to the impacts of the tolerances in journal diameter,dynamic viscosity and bearing width,the bearing diameter tolerance would lead to the rise in the power loss, and the dimensional tolerances have different degrees of impacts on the journal bearing system. The friction power loss decreased as the eccentricity ratio increased, and when the eccentricity ratio was 0. 695 the power loss came to the minimum.The investigation would find the best solution and reduce energy consumption,then control varieties of nonlinear dynamical behavior effectively,and provide a theoretical basis for hydrodynamic journal bearing system in parameter design.

Preoperative serum vascular endothelial growth factor correlated to three dimensional power Doppler indices in ovarian masses

Objective: To assess the preoperative serum levels of vascular endothelial growth factor (VEGF) in ovarian masses compared to normal controls and to find a correlation between VEGF and Doppler indices in ovarian masses. Methods: The study was conducted from December 2009 to September 2012 in the oncology and ultrasound units in department of obstetrics and gynecology, Ain Shams University on 150 patients with ovarian masses. During preoperative workup, serum Ca-125 levels and serum VEGF levels were obtained. Ultrasonographic examination included two and three dimensional power Doppler ultrasound (3DPD). Laparotomic approaches were undertaken to obtain the final pathologic results. VEGF was measured in one hundred normal cases as controls. Results: Final ovarian pathology revealed seventy three malignant ovarian masses and seventy seven were benign. Serum Ca-125 levels in malignant cases were higher compared to those in benign cases (p < 0.001). Preoperative serum VEGF revealed higher levels in malignant ovarian masses than benign conditions and normal controls (p < 0.001). Three dimensional power Doppler indices, vascularization index (VI), flow index (FI) and vascularization flow index (VFI), correlated positively with serum VEGF levels. Conclusion: Preoperative serum VEGF revealed higher levels in malignant ovarian masses than benign conditions and normal controls. These levels positively correlated with the Doppler vascular indices of the masses.

基于Power BI的核电大修工单成本分析工具开发与应用

介绍了基于Power BI搭建大修工单成本分析数据模型的开发过程以及应用情况。通过与工单系统的动态关联,准确统计出大修某个工单、某个系统、某个子项、某个区域或是某次大修的成本。基于对大修成本数据的精细分析,从单纯的财务指标计划驱动完成了向业务精益驱动的过程管控转变,持续挖掘大修成本的精益空间,单次大修直接经济效益均超过1000万元,累计效益达7648万元,同时提升成本管理的事前决策支持与业务指导能力,促进大修业务管理水平的持续提升。

基于gt-power软件的某汽车排气系统消声器改进

通过gt-power软件对发动机某一转速下排气系统尾管噪声进行仿真。提出几种消声器改进方案,选出最佳方案。在该方案基础上,分析几种因素变化对消声器性能影响,选出较为理想的参数。最终使功率损失、插入损失等指标达到较好的水平,解决了尾管噪声过高的问题。得出了穿孔管,插入管长度,扩张腔体积对消声性能影响较大的结论。

基于Power Designer的三维工程地质数据仓库模型构建——以长春市中心区为例

论文以长春市地下空间的岩土体可利用性为研究主题,以勘察工程中提供的钻孔数据及其相关信息为源数据,采用Power Designer16.1设计并实现了长春市中心区的三维工程地质数据仓库的逻辑数据模型和物理数据模型。采用模型驱动架构的方式,利用反向工程技术从Access数据库系统中将现存的数据结构抽取出来形成数据模型,结合研究主题建立了星型数据结构模型,并将生成的SQL脚本文件导入SQL Server2005中进行检查修正后运行正常。

One-dimensional ZnO nanostructure-based optoelectronic

Semiconductor nanowires, with their unique capability to bridge the nanoscopic and macroscopic worlds, have been demonstrated to have potential applications in energy conversion, electronics, optoelectronics, and biosensing devices. Onedimensional（1D） ZnO nanostructures, with coupled semiconducting and piezoelectric properties, have been extensively investigated and widely used to fabricate nanoscale optoelectronic devices. In this article, we review recent developments in 1D ZnO nanostructure based photodetectors and device performance enhancement by strain engineering piezoelectric polarization and interface modulation. The emphasis is on a fundamental understanding of electrical and optical phenomena, interfacial and contact behaviors, and device characteristics. Finally, the prospects of 1D ZnO nanostructure devices and new challenges are proposed.

Multi-aiming Strategy Design for Quadruple Prism Shaped Central Receiver in Solar Power Tower System

For solar power tower technology, the improvement of interception efficiency of heliostat field and the extension of central receiver U+02BC s life time are two technical difficulties. To the receiver, higher interception efficiency means more thermal shocks and stronger stresses of high temperatures mainly contribute to the reduction of receiver's life time. To address these problems, a semi-random distribution strategy is proposed to select the best aiming point of the heliostat, and the distribution of onedimensional array arranged on the centerline of the receiver is carried out for further optimization. It is shown by simulation that through our optimization the temperature distribution on the receiver surface becomes much more uniform while maintaining acceptable interception efficiency. © 2017 Chinese Association of Automation.

三维power-normal分布的性质及参数估计问题的研究

应用了Clayton连接函数的性质给出了三维power-normal分布的分布函数及概率密度函数,并详细研究了三维power-normal分布的基本性质,同时,根据所构造出的三维power-normal分布模型,对其中的参数进行了最大似然估计的讨论。并给出了参数的最大似然估计的算法。结合费永法在文献中的1964年到1973年10年间长江大通站、淮河中渡站及黄河花园口站的天然年流经量数据作为样本数据,利用MATLAB程序计算了参数的最大似然估计。

电力变压器关键尺寸视觉检测方法及其缩比模型验证

电力变压器的关键尺寸测量是其装配制造、运输安装过程中重要一环,现有测量方法操作繁琐且效率较低。为此,本文提出了一种适用于110 kV油浸式电力变压器关键尺寸视觉检测方法,该方法利用YOLO目标检测算法、Grabcut图像分割算法实现关键组部件的智能检测与分割,然后基于双目立体视觉原理实现套管相间距离及变压器最大截面外形尺寸等关键尺寸的测量。本文搭建了110 kV油浸式电力变压器外观缩比模型,试验分析了拍摄距离和角度等因素对电力变压器关键尺寸视觉检测的影响。结果表明,本文基于缩比模型试验实现了在不同拍摄距离与角度下变压器关键尺寸的视觉检测,验证了该方法的有效性。本文方法可以为110 kV油浸式电力变压器现场尺寸测量提供参考。

Two-Dimensional Self-Consistent Kinetic Model for Solenoidal Inductively Coupled Plasma

A two-dimensional self-consistent kinetic model was developed to study the influence of the various factors on the electron energy distribution function. These factors include gas pressure the driving frequency, the radius and length of the inductively coupled plasma equipment, the amplitude of the radio-frequency coil current, and the number of turns of rf coils. The spatial profiles of the rf electric field and power density have also been calculated under the same parameters. Numerical results show that the electron energy distribution functions are significantly modified and the spatial profiles of the rf electric field and rf power density are also demonstrated.

One-dimensional dynamic equations of a piezoelectric semiconductor beam with a rectangular cross section and their application in static and dynamic characteristic analysis

Within the framework of continuum mechanics, the double power series ex- pansion technique is proposed, and a series of reduced one-dimensional （1D） equations for a piezoelectric semiconductor beam are obtained. These derived equations are universal, in which extension, flexure, and shear deformations are all included, and can be degen- erated to a number of special cases, e.g., extensional motion, coupled extensional and flexural motion with shear deformations, and elementary flexural motion without shear deformations. As a typical application, the extensional motion of a ZnO beam is analyzed sequentially. It is revealed that semi-conduction has a great effect on the performance of the piezoelectric semiconductor beam, including static deformations and dynamic be- haviors. A larger initial carrier density will evidently lead to a lower resonant frequency and a smaller displacement response, which is a little similar to the dissipative effect. Both the derived approximate equations and the corresponding qualitative analysis are general and widely applicable, which can clearly interpret the inner physical mechanism of the semiconductor in the piezoelectrics and provide theoretical guidance for further experimental design.

POWER GEOPAK在神塘河泵站基坑开挖设计中的应用

基坑开挖是水利工程设计的重要组成部分,面对复杂多变的地形和地质条件,采用传统的二维设计方法,需要设计人员具有较强的空间想象力和判断力。POWER GEOPAK是Bentley公司系列三维设计软件之一,能够将测量图转为三维地形,并在三维地形上建立基坑开挖模型,可直观地模拟开挖方案,准确地计算工程量。通过修改模型参数,可以便捷地修改设计方案,避免许多重复的工作,提高了工程设计效率,因此越来越广泛的运用于工程设计中。

Effect of Load Power Factor on Electromechanical Wave Propagation in Ring Power System

One-dimensional ring power system is discredited to a number of nodes each containing a generator with internal reactance and load branch of resistance and reactance with a certain power factor. When a disturbance occurs at any machine in the power system, simulative analysis is performed to verify how the variation of load power factor affecting the behavior of electromechanical wave propagation by using the MATLAB package, from which different situations are presented and discussed. These results show the type of load has no effect on the behavior of electromechanical wave propagation.

基于RPC的同相供电系统供电运行能量多维控制研究

为确保高速铁路安全、可靠、经济运行,提出高速铁路同相供电系统供电运行能量多维控制方法。分析供电系统组成结构与供电过程,利用潮流控制器补偿该系统功率,确保系统稳定运行;结合三相不平衡程度、电压电流波形畸变等指标构建运行能量的最佳负载模型,使传输能量损失降到最低;经过对2个供电臂电流的有功与无功补偿,消除负序电流;制定铁路功率调节器控制策略,获得降压变压器变化情况,保障直流侧电压稳定;再使用比例积分控制器获取电流理想值,得出控制信号,实现供电运行能量多维控制。仿真实验证明,所提多维控制方法能提高三相电流平衡程度,达到均压稳定效果。

三维能量多普勒超声预测宫颈癌化疗效果的临床价值

目的探讨三维能量多普勒超声(3D-PDU)预测宫颈癌化疗效果的临床应用价值。方法选取在我院接受新辅助化疗治疗的宫颈癌患者160例,根据化疗效果分为有效组103例和无效组57例,比较两组3D-PDU血流参数[血管形成-血流指数(VFI)、血流指数(FI)及血管形成指数(VI)]的差异。采用多因素Logistic回归分析筛选预测宫颈癌患者化疗效果的独立危险因素,并建立宫颈癌患者化疗效果风险预测模型;采用Hosmer-Lemeshow检验评估模型的拟合度;绘制受试者工作特征(ROC)曲线分析模型的预测效能。结果化疗后,两组VFI、FI及VI均较化疗前下降,且有效组上述参数均低于无效组,差异均有统计学意义(均P<0.05)。多因素Logistic回归分析显示,化疗后VFI、FI及VI均为预测宫颈癌患者化疗效果的独立危险因素(OR=2.826、4.637、3.216,均P<0.05),建立宫颈癌患者化疗效果风险预测模型为:Logit(P)=1/[1+e^((-4.609+1.039×化疗后VFI+1.534×化疗后FI+1.168×化疗后VI))]。Hosmer-Lemeshow检验显示模型的拟合度较好(χ^(2)=4.635,P=0.781);ROC曲线分析显示模型预测宫颈癌患者化疗效果的曲线下面积为0.882(P<0.05)。结论应用3D-PDU可以较好地预测宫颈癌化疗效果,具有一定的临床应用价值。

经阴道三维能量多普勒超声联合二维剪切波弹性成像预测备孕女性妊娠结局的临床价值

目的应用经阴道三维能量多普勒超声(3D-PDI)联合二维剪切波弹性成像(2D-SWE)评估备孕女性子宫内膜容受性,探讨其预测妊娠结局的临床应用价值。方法选取在我院接受卵泡检测的87例备孕女性,均于排卵第7~8天(种植窗期)行经阴道3D-PDI检查,于增殖期行2D-SWE检查,然后随访6周,根据妊娠结局将其分为受孕组31例和未受孕组56例。比较两组子宫内膜厚度、容积、回声类型、血流分型、子宫螺旋动脉搏动指数(PI)、阻力指数(RI)、收缩期峰值流速与舒张末期流速比值(S/D)、血管化指数(VI)、血流指数(FI)、血管化血流指数(VFI),以及子宫内膜杨氏模量平均值(以下简称杨氏模量值)的差异。绘制受试者工作特征(ROC)曲线分析经阴道3D-PDI和2D-SWE参数单独及联合应用对备孕女性妊娠结局的预测价值。结果受孕组子宫内膜厚度和FI均高于未受孕组,S/D和子宫内膜杨氏模量值均低于未受孕组,差异均有统计学意义(均P<0.05);两组子宫内膜容积、回声类型、血流分型及PI、RI、VI、VFI比较差异均无统计学意义。ROC曲线分析显示,子宫内膜厚度、FI、S/D和子宫内膜杨氏模量值预测备孕女性妊娠结局的曲线下面积分别为0.789、0.851、0.853和0.840,联合应用的曲线下面积为0.895,高于各参数单独应用,差异均有统计学意义(均P<0.05)。结论经阴道3D-PDI联合2D-SWE可准确评估备孕女性子宫内膜容受性,对预测其妊娠结局有较好的临床应用价值。

超声评分法联合三维能量多普勒血流灌注参数对胎盘植入性疾病的诊断价值

目的探讨超声评分法联合三维能量多普勒超声(3D power doppler ultrasonography,3D-PDU)诊断胎盘植入性疾病(placenta accreta,PAS)不同病理分型的应用价值。方法分析112例疑似PAS的孕妇,术前进行超声评分,并进行3D-PDU检查,测量血管指数(vascularization index,VI)、血流指数(flow index,FI)和血管-血流指数(vascularization flow index,VFI)。以病理诊断为金标准将样本分为不同组别,比较组间血流灌注参数的差异性。结果112例疑似PAS患者病理证实92例,PAS组VI、FI及VFI均高于无PAS组(P均<0.05)。92例PAS中未侵入肌层即粘连型24例,侵入肌层包括植入型和穿透型68例,侵入肌层组的VI、FI及VFI均高于非侵入肌层组(P均<0.05)。而植入型与穿透型比较时,穿透型的VI、VFI均高于植入型(P均<0.05)。采用超声评分法联合3D-PDU诊断粘连型、植入型以及穿透型胎盘植入的Kappa值分别为0.724、0.856和0.892。结论超声评分法与3D-PDU联合使用可定量分析胎盘血流灌注情况,为产前诊断PAS的精准分型提供量化评估依据。

考虑电力网络约束的工业园区虚拟电厂调控边界求解方法

构建以新能源为主体的新型电力系统,亟须挖掘负荷侧灵活调节资源参与电网调控。含电解铝、矿热炉等高耗能负荷的工业园区具备良好的调控潜力,但是考虑园区内部电力网络约束,其精确调控边界求解面临着变量维数高、约束非线性的难题,现有方法不能较好地兼顾计算效率和精度。对此,文中将上述问题抽象为高维非线性状态空间在P-Q耦合平面的投影问题:分别建立考虑工业园区安全运行线性化和非线性约束的调控边界投影求解模型,采用一种新颖的高维状态空间投影算法,通过顶点“搜索-映射”的两步式求解过程,得到工业园区型虚拟电厂调控边界的精确投影。算例结果表明,采用所提方法求解的调控边界可由线性不等式组完全表征,与现有调度系统完全兼容,结合与叠加柔性资源调控能力和传统采样方法的对比,验证了该方法的可行性以及高求解精度和效率。

基于“88Q”线圈的三维抗偏移WPT系统

针对谐振式无线电能传输(WPT)系统在传输距离和负载变化时引起输出电压不稳定的问题,提出一种“88Q”线圈耦合装置,结合LCC/S与S/LCC型负载无关恒压谐振拓扑可实现平面线圈的三维抗偏移恒压输出。给出了“88Q”线圈的空间位置和特征参数,分析线圈激发磁场的分布特性、线圈水平偏移和改变传输距离情况下线圈互感变化趋势。最后,搭建系统实验平台。实验结果表明,系统负载变化或耦合装置发生偏移时,均可实现恒压输出。