基于状态观测器的软测量在管道煤气控制系统中的应用研究

状态观测器作为对系统中不可测量状态进行估计或重构的方法．有着非常完善的理论研究体系在管道煤气控制系统中．将状态观测器作为软测量的一种设计方法．不但可为软测量的参数估计提供一种良好的系统结构．而且可以充分保证参数估计过程所需要的稳定性和良好的收敛速度等性能指标。     

晶闸管控制的感应电机中提高起动电磁转矩的一种新策略

传统软起动器的一个缺点是减小电压会严重降低电磁转矩,使电机带载起动失败.该文提出一种新的提高起动转矩的控制策略.该策略无需改变传统软起动器的主电路结构,通过定义晶闸管的触发时刻,以便包含或排除交流电源的半个周波,从而获得离散频率的电压和电流.对于所有这些离散分频频率来说,为获得最大正的转矩,系统的平衡性被打破,找出最大正序分量的三相初始相位角的组合.该策略类似于变压变频(VVVF)逆变器的控制策略,使电机产生小的电流冲击和大的起动转矩.通过基于32位DSP的软起动器驱动感应电动机控制系统,该策略被实验验证具有好的起动转矩和电流性能.     

Lattice dynamics in VO2 near the metal-insulator transition

We present a comprehensive experimental study of the lattice dynamics in the vicinity of the metal-insulator transition in VO₂ by means of combined use of Raman spectroscopy and ultrasonic microscopy. Single crystalline samples of high quality particularly allow quite a complete determination of all Raman modes in the insulating phase at the Γ-point and the observation of an optical soft mode. In addition, the elastic behavior has been successfully investigated by measuring the propagation velocity of ultrasonic surface waves microscopically excited in various crystal directions. Our study reveals a striking coincidence of strong lattice softening attributable to certain acoustic branches and the occurrence of the optical soft mode, which precedes the metal-insulator transition over more than 100 K on approaching the critical temperature.     

Modeling and analysis of automobile warranty data in presence of bias due to customer-rush near warranty expiration limit

Automobile users experiencing soft failures, often delay reporting of warranty claims till the coverage is about to expire. This results into a customer-rush near the warranty expiration limit leading to an occurrence of ‘spikes’ in warranty claims towards the end of warranty period and thereby introducing a bias into the dataset. At the same time, an occurrence of manufacturing/assembly defects in addition to the usage related failures, lead to ‘spikes’ in warranty claims near the beginning of the warranty period. When such data are used to capture the field failures for obtaining feedback on product quality/reliability, it may lead product or reliability engineers to potentially obtain a distorted picture of the reality. Although in reliability studies from automobile warranty data, several authors have addressed the well-recognized issues of incomplete and unclean nature of warranty data, the issue of ‘spikes’ has not received much attention. In this article, we address the issue of ‘spikes’ in the presence of the incomplete and unclean nature of warranty data and provide a methodology to arrive at component-level empirical hazard plots from such automobile warranty data.     

水泥土搅拌桩加固软土地基实例分析

本通过工程实例说明，位于稳定水位以下的土体采用水泥土搅拌桩进行加固应优先采用干法作业，而不宜采用湿法作业。     

YAG晶体在软X射线荧光靶探测器中的应用

荧光靶探测器是同步辐射光源光束位置定位的重要设备之一,本文在96 500 eV软X射线内对CVD金刚石薄片和Ce:YAG晶体薄片进行光致发光亮度的测试,观察到Ce:YAG在该能量段的发光亮度比金刚石高,完成了上海光源软X射线荧光靶探测器靶材的实验研究与探测器的设计;同时给出了YAG晶体荧光靶探测器在线使用时观察到的相干光的衍射图像。     

Compensation excavation method control for large deformation disaster of mountain soft rock tunnelOA

In recent years, the mine tunneling method and the new Austrian tunneling method have been considered the main theories of tunneling approaches in China. It is difficult for the traditional technique to overcome the large deformation problems imposed by complex geological conditions of mountain soft rock tunneling. Hence, the compensation excavation method has been proposed to solve this issue under the consideration that all damage in tunneling originates from the excavation. It uses supportive...     

基于改进型零电流开关单元的PWM变换器族

本文提出一种改进型ZCS-PWM开关单元。该开关单元能在整个变换范围内实现所有有源开关管的零电流开关(ZCS)和所有无源开关管的零电压开关(ZVS)，而且通过无源箝位电路彻底的消除了所有开关管的电压尖峰；此外，所有开关管的电流应力都很小。本文详细分析了基于该开关单元的buck变换器，研究结果验证了这种零电流开关技术的可行性，最后得出了基于该开关单元的一族变换器。     

音频信号软件频谱分析仪设计

软件频谱分析仪利用多媒体计算机以软件方式来实现对信号进行频谱分析的功能。文中就如何运用DCT理论及FFT算法,开发音频信号软件频谱仪进行了较详细的探讨和介绍;并给出了相关的设计、实现方案及Windows平台一个应用实例。     

三铰点轻压下水平扇形段辊缝控制方法

针对三铰点轻压下水平扇形段的结构特点,介绍了该扇形段标定方法,用测试的方法确定了最小的标定压力.通过对测试数据的分析,找到了一种辊缝补偿的方法,并且用试验测试的方法验证了其合理性.