基于改进傅里叶描绘子的CBIR系统

在现有的基于傅里叶描绘子的CBIR系统中,为了提高检索速度,一般需要舍去物体轮廓经傅里叶变换后的大部分高频分量.当物体轮廓在细节部分具有较高能量时,此方法不具备有效性.为尽可能保证检索准确率并兼顾检索速度,在原有傅里叶描绘子上进行扩展,避免直接舍去高频分量,引入Fisher判别分析法将描绘子映射到子空间进行降维,并保证...     

Performance modeling,real-time dispatching and simulation of wafer fabrication systems using timed extended object-oriented Petri nets

Semiconductor wafer fabrication system (SWFS) is the most complex and capital-intensive phase in the entire semiconductor manufacturing cycle. With characteristics of re-entrant processing routes, equipment uncertainty, product diversity and improving technologies, great challenges are presented in SWFS’s modeling, scheduling and simulation. To implement efficient production control, this paper provides a timed extended object-oriented Petri nets (TEOPNs) approach to performance modeling, real-timed dispatching and simulation of SWFSs. The TEOPNs models are constructed in a hierarchy to accord with the real-world SWFS’s organization, and a new type of signal place is added into the TEOPNs to respond the dynamic states of all processing facilities. A novel autonomy and coordination-based real-time dispatching mechanism (A&C-RDM) is developed in this paper, which executes under the support of the TEOPNs-based hybrid real-time dispatching control system (HRDCS). Owning to the ability of gathering dynamic real-time information of all production facilities and WIP products, the HRDCS can make adaptive dispatching decisions according to the local and global real-time processing status. Two sets of key elements of real-time dispatching, i.e. the state thresholds and dispatching rules, are defined in the HRDCS so that the A&C-RDM can integrate different types of dispatching rules. A set of simulation experiments prove the efficiency of the proposed modeling and dispatching algorithm. In summary, the proposed TEOPNs, HRDCS and A&C-RDM form the cornerstones of a real-time dispatching simulation prototype of SWFS, and the work described in this paper carries out an advanced integrated “modeling–dispatching–simulation” methodology.     

振荡电压的计算

电路由一种状态变为另一种状态,会出现高频振荡的过渡过程。文章推求振荡电压的计算公式。     

Regarding the influence of the Van der Hoven spectrum on wind energy applications in the meteorological mesoscale and microscale

We demonstrate the use of high frequency data (HFD) to reproduce the power spectrum shown by Van der Hoven in 1957. His work represents the basis of wind energy standards such as averaging and variability in the frequency domain. Our results unveil discrepancies with Van der Hoven's approach, which can be related to constraints in the computing capabilities in the 1950's. We show a major eddy-energy peak at a period of 2 days and a smaller eddy-energy peak contribution at frequencies higher than the region known as the spectrum gap. The variance calculated by the area under the curve indicated that the spectral energy is mainly due to the Power Spectral Density (PSD) values located in the microscale region. We calculated the economic value of this energy based on the turbulence kinetic energy of the wind data set. We also conclude that, given the results of the present study, HFD analysis in the frequency domain uncover eddy energy peaks that determine energy fluctuations in the short and long terms. This information is lost every time data are erased from current monitoring systems.     

相变-液浴式热水锅炉工作特性的实验研究

设计建造了一套燃气热水锅炉试验系统，通过实验对相变-液浴式热水锅炉的工作特性作了测量分析。结果表明：该锅炉在运行中，根据热负荷的高低，其传热方式会在“相变”、“液浴”、“相变-液浴并存”三种状况之间自动转换，对此可以用一幅工况图来描述；在实验范围内，该锅炉的“相变换热”工况传热系数大约为“液浴换热”工况传热系数的1．7倍。     

相变-液浴式燃气热水锅炉炉侧传热的计算方法研究

针对相变-液浴式热水锅炉炉侧的传热特点,提出了一套传热计算方法。通过计算得出了一台实验用相变-液浴式锅炉的炉胆出口烟气温度、排烟温度随天然气流量变化的曲线。计算结果与实测结果之间的误差在10％以内,说明这套计算方法可以令人满意地用于工程计算。     

基于ATP-EMTP的风电机组雷击过电压分析与防护研究

基于ATP-EMTP仿真软件对风电机组内部的雷电过电压及其相应的防护措施进行了研究。首先分别针对风力发电机、风机变压器、雷电模型、冲击接地电阻、电缆、电涌保护器(SPD)等建立了ATP-EMTP模型。接着通过仿真计算,分析雷电流在风机系统中的分布,比较了冲击接地电阻阻值对雷电过电压的影响。最后,研究了加装SPD对风力发电机机端出口过电压的抑制效果,证实了加装SPD对风机系统雷电过电压的保护作用。     

620℃汽轮机X13CrMoCoVNbNB9-2-1钢转子轴颈堆焊层性能分析

轴颈堆焊技术是制造620℃超超临界汽轮机的重要技术之一。采用埋弧焊方法在X13CrMoCoVNbNB9-2-1转子钢圆环试验件上堆焊1Cr-0.5Mo材料,进行去应力热处理;测定了距熔合线不同距离处堆焊层的化学成分,测试了拉伸、硬度、冲击、弯曲等性能,分析了焊接接头的金相组织。试验结果表明,随着距熔合线距离的增加,堆焊层中Cr元素的含量呈指数规律降低,在第四层降到1.5%左右;堆焊层的强度和硬度随着距熔合线距离的增加而下降,冲击吸收功则显著提高。焊接接头弯曲性能优良,焊接接头中各区域微观组织正常,具有良好的综合力学性能。本项技术可以应用于620℃汽轮机X13CrMoCoVNbNB9-2-1钢转子的轴颈堆焊。     

基于扩展卡尔曼滤波的低压配电网漏电流监测

针对传统低压配电网漏电流监测方法中存在的监测误差较大且监测耗时较长等问题,提出基于扩展卡尔曼滤波的低压配电网漏电流监测方法.采用小波变换方法提取漏电流低频信息,将小波变换离散化处理,降低提取特征的冗余程度,完成低压配电网漏电流高频特征提取;采用一阶泰勒展开式扩展卡尔曼滤波技术,将其转变为线性空间方程,引入前馈控制概念,...