同杆并架双回线路模变换分析

本文通过对同杆双回线的模变换分析,得出了其模变换表达式,同时也得出了几种特殊的对应于普通三相系统模变换的同杆双回线矩阵。其中,推出的复数矩阵具有零元素多,运算简单等优点,而两种实数矩阵类Ｃｌａｒｋ和类Ｋａｒｒａｎｂａｎｅｒ变换矩阵除具有上述优点外,且其运算简单物理意义明确,可运用各种稳态及暂态电气量。     

QFSN-300-2型发电机密封油系统故障排除

分析了双流环密封油结构发电机氢气中含氧量高、氢气纯度低的原因.从密封油系统设备结构、油脂质量、系统运行方式等方面提出了相应的解决措施,提高了氢气的纯度,保证了机组安全经济运行.     

电化学电容器的研究进展--第15届国际电化学电容器研讨会概述

介绍了第15届国际电化学电容器研讨会有关电化学电容器的研究发展情况;分析了电化学电容器的研究发展趋势。研究热点是高性能新型炭电极材料的制备研究、器件的性能和应用研究以及电化学混合电容器新体系的研究等。     

新型不对称五电平逆变器的输出电压频谱分析

本文研究了一种新型的不对称五电平逆变器的电路拓扑,并分析了其采用的混合调制策略。基于文中所提方案,快速器件和高压器件能协调工作。为精确测算输出电压频谱,建立了三种载波分布下的调制过程数学模型,继而运用Bennet扩展方法推导出严格的频谱表连式。文中总结了调制比全范围变化时的输出电压频谱特性。实验有力地证实了理论分析和方案的可行性。     

无线设备状态监测网络轴承故障信号的采集

本文利用双端口RAM芯片,以环行FIFO队列的存储方式,构建基于PC104ISA总线的高速数据采集卡。PC104可通过该卡对轴承的故障信号进行高速采集、计算,并将故障分析结果通过无线网络发送到远程PC机。     

FFH/BFSK系统的一种基于频率和PN序列双图案的早迟门同步捕获方法

针对FFH/BFSK系统的同步难题,该文提出了一种基于频率和PN序列双图案的早迟门同步捕获方法,理论分析和仿真结果显示,该方法门限的选择更为简单、准确;克服了全跳解调时由于收发窗口未同步引起的解调不可靠性。这种捕获方法能进一步提高捕获性能,在信道误比特率为0.1时,同步捕获概率大于95%。分析和仿真结果经过了试验台验证。     

一种估计JPEG双重压缩原始量化步长的新方法

该文提出了一种双重压缩后JPEG图像的原始量化步长的估计方法。该方法根据两次量化步长之间的大小关系分3种情况进行讨论。当原始量化步长大于第2次量化步长,提出了直接利用直方图计算的新方法;为解决原始量化步长是第2次量化步长因子和傅里叶频谱分析中的多值问题,提出了采用0.98缩放来近似未压缩图像的方法。本文方法能给出第二次量化步长为一次量化步长倍数时的估计,并利用频谱分析的结果降低了计算的复杂度,实验结果表明本文方法有较高的估计准确度。     

Fracture behaviour of 8%Ni 980 MPa high strength steel at various temperatures Part 3 – Four-point notched bend tests

Abstract

Based on the results of four-point notched bend tests together with detailed microscopic observations of fracture surfaces and crack configurations below the unbroken notch roots of double notch specimens, the fracture mechanisms in notched specimens of 8%Ni high strength (980 MPa) steel have been observed to be as follows. A fibrous crack initiates in the bainitic matrix at the notch root and then develops into a cleavage crack at a critical length. The cleavage crack propagates in an unstable manner and causes the final fracture of specimen. The critical event controlling the cleavage fracture is the propagation of the bainitic packet-sized crack, and the local fracture stress is measured as around 1845–2200 MPa.     

Some micromechanical models of elastoplastic behaviors of porous geomaterials

Some micromechanics-based constitutive models are presented in this study for porous geomaterials. These micro-macro mechanical models focus on the effect of porosity and the inclusions on the macroscopic elastoplastic behaviors of porous materials. In order to consider the effect of pores and the compressibility of the matrix, some macroscopic criteria are presented firstly for ductile porous medium having one population of pores with different types of matrix (von Mises, Green type, Mises–Schleicher and Drucker–Prager). Based on different homogenization techniques, these models are extended to the double porous materials with two populations of pores at different scales and a Drucker–Prager solid phase at the microscale. Based on these macroscopic criteria, complete constitutive models are formulated and implemented to describe the overall responses of typical porous geomaterials (sandstone, porous chalk and argillite). Comparisons between the numerical predictions and experimental data with different confining pressures or different mineralogical composites show the capabilities of these micromechanics-based models, which take into account the effects of microstructure on the macroscopic behavior and significantly improve the phenomenological ones.     

Distribution of Quasimidranges and Associated Mixtures

In this paper are presented and discussed tabulations of the cumulative distribution functions of quasimidranges and mixtures of quasimidranges of samples from a normal distribution. The tabulations extend up to samples of size 21. For quasimidranges not involving the extreme values of the sample, the departure from normality is very small. The physical problem giving rise to the mixtures is discussed.