不同类型三部件串并联系统的可靠性分析

应用时齐Markov过程,对由三个不同型部件组成的串并联系统,分两部分考虑:1)针对具有转换开关,但转换开关不完全可靠的串并联不可修系统;2)针对各部件均能"修复如新",系统只有一个修理工的串并联可修系统;并假定两类系统中各部件寿命的分布为指数分布,状态空间为离散空间,建立系统的模型.通过对模型分析求解出这两类系统的可...     

塑料食品包装材料化学物迁移的数值方法

塑料包装材料内含化学物向食品迁移会造成食品污染并危害消费者健康.近年来,对迁移理论的预测逐渐成为热点.现将谱方法应用于塑料食品包装化学物迁移的数学模型,给出了模型问题的Chebyshev配点法,并进行稳定性和收敛性分析.     

正规矩阵的范数和它的幂级数收敛性

研究了正规矩阵的范数,给出了正规矩阵的几种常用范数的几个性质;利用范数和谱半径与矩阵幂级数的收敛性的关系,给出了关于正规矩阵的幂级数收敛性的一些新结论.     

Novel Face Recognition Method by Combining Spatial Domain and Selected Complex Wavelet Features

A novel face recognition method based on fusion of spatial and frequency features was presented to improve recognition accuracy.Dual-Tree Complex Wavelet Transform derives desirable facial features to cope with the variation due to the illumination and facial expression changes.By adopting spectral regression and complexfusiontechnologiesrespectively,twoimproved neighborhood preserving discriminant analysis feature extraction methods were proposed to capture the face manifold structures and locality discriminatory information.Extensive experiments have been made to compare the recognition performance of the proposed method with some popular dimensionality reduction methods on ORL and Yale face databases.The results verify the effectiveness of the proposed method.     

Automatic Measurement of LED Colorimetric Parameters Based on LabVIEW

In order to accurately and automatically measure the light emitting diode ( LED ) colorimetric parameters,the design of a measurement system by adopting a high-performance spectrometer and looking-up t...     

HEV自动膜片弹簧离合器转矩跟踪PID控制

在同轴并联混合动力系统和自动膜片弹簧离合器数学建模的基础上,提出一种包含Kalman滤波器、串级变参数PID控制器的自动膜片弹簧离合器转矩跟踪控制策略,设计了变参数转矩环比例控制器,对行程环PID控制参数进行了优化整定,对HEV模式切换过程中,离合器传递转矩的跟踪控制进行了仿真和试验研究.结果表明,所提出的离合器转矩跟踪控制策略具有良好的效果.      

采用振动信号二维特征向量聚类的配电开关机械状态识别新方法

配电开关动作产生的振动信号具有非线性非平稳特性,蕴含机械状态信息.提出一种基于振动信号二维特征向量和模糊K均值聚类的配电开关机械状态识别新方法.利用HHT带通滤波对配电开关振动信号进行时频分解,分别求取各子频带信号的能量值和重心频率,得到振动信号的二维特征向量作为反映配电开关的机械状态的特征量.提取配电开关在正常、底座螺丝松动、机械结构卡涩及卸掉A相触头绝缘拉杆等4种典型状态实测振动信号的二维特征向量做模糊K均值聚类,结果表明,所提取的特征向量能有效地表征配电开关的机械状态.     

一种新型无大电解电容软起动变频器

提出了一种带逆流电阻的无大电解电容通用型变频器,较传统变频器体积减小、节省成本。由于无电解电容,使之具有输出旁路的软起动器功能。在电动机起动完成后,可以自行退出,实现一机多用。对新拓扑形式的电路结构及工作原理做详细描述;并对其变频起动和旁路切换所采用的控制策略进行相关研究。最后应用MATLAB中的Simulink仿真软件搭建仿真模型,验证该研究方法的可行性。     

矿井涌水量时间序列的频谱分析及应用

阐述了频谱分析方法的基本原理 ,分别计算了矿井涌水量和降雨量的自谱以及它们的互谱 ,给出了隐含周期的检验方法和谱平滑的一般方法 .研究实例表明 ,频谱分析能较好地确定矿井涌水量时间序列的周期性和相关关系 ,为揭示矿区地下水系统的内在机理、矿井涌水量预测及控制提供定量依据 .图 3,参 5     

Temperature dependent spectral response characteristic of III-V compound tandem cell

The GaInP/GaAs/Ge triple-junction tandem cells with a conversion efficiency of 27.1% were fabricated using metalorganic chemical vapor deposition (MOCVD) technique. Temperature dependence of the spectral response measurements of the GaInP/GaAs/Ge tandem cell was performed by a quantum effi-ciency system at temperatures ranging from 25℃ to 160℃. The red-shift phenomena of the absorption limit for all subcells were observed with increasing temperature, which is dued to the energy gap nar-rowing with temperature. The short-circuit current densities (J_sc)of GaInP, GaAs and Ge subcells at room temperature calculated based on the spectral response data were 12.9, 13.7 and 17 mA/cm², re-spectively. The temperature coefficient of J_sc for the tandem cell was determined to be 8.9 mA/(cm²·℃), and the corresponding temperature coefficient of the open-circuit voltage deduced from the se-ries-connected model was -6.27 mV/℃.