网络可靠性分析方法研究

总结了进行网络可靠性分析的一般步骤,比较了传统的网络分析方法的优缺点,重点论述了一种基于有序二叉决策图的方法,在考虑失效节点的网络可靠性分析中的应用。     

Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless receivers

This paper introduces the conceptual architecture of a fully integrated, truly self-powered structural health monitoring (SHM) scheme. The challenge here is to power an array of numerous distributed actuators and sensors as well as wireless data transmission modules without recurring to heavy and costly wiring. Based on microgenerators which directly convert ambient mechanical energy into electrical energy, using the synchronized switch harvesting (SSH) method, the proposed solution allows avoiding the periodic replacement or reloading of batteries. This addresses environmental and economic issues at the same time, knowing that such elements are heavy, polluting and might be installed in rather inaccessible locations. Indeed, especially in airborne structures saving weight and maintenance cost is of priority importance.Previous work showed that such microgenerators provide a stand-alone power source, whose performances meet the requirements of autonomous wireless transmitters (AWTs) that comprise an acoustic Lamb wave's actuator and a radio frequency (RF) emitter (D. Guyomar, Y. Jayet, L. Petit, E. Lefeuvre, T. Monnier, C. Richard, M. Lallart, Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless transmitters, Sens Actuators A: Phys. 138 (1) (2007) 151–160, doi:10.1016/j.sna.2007.04.009). Following this work, the present contribution presents a further step towards the integration of the SHM technique. It shows the ability of our microgenerators to provide enough energy to give logical autonomy to each self-powered sensing node, named autonomous wireless receiver (AWR), and thus to provide some local (decentralized) pre-processing ability to the SHM system.A preliminary design of the device using off-the-shelf electronics and surface mounted piezoelectric patches will be presented. Since the existence of a positive energy balance between the harvesting capabilities of the SSH technique and the energy requirements of the proposed device will be proved, the system formed by the combination of the AWR with the previously developed AWT, is a proof of concept of truly self-powered smart systems for damage detection in simple structures, setting apart application-specific optimization or miniaturization concerns that will be addressed in future works.     

基于CPCI总线的数据采集及处理系统

PCI9052是PLX公司推出的PCI总线接口芯片,能够实现ISA总线与PCI总线的无缝连接,可方便地将原有的ISA插卡移植到PCI总线.ADC-HS12B是DATEL公司生产的12位模数转换器,它采用CMOS工艺制造,可提供125 Kb/s的采样率.该文在介绍CPCI总线的基础上利用FPGA技术控制ADC,实现模数转换数据采集方案.     

PLC对模拟量的控制

在工业生产领域中,特别是连续型生产过程中常常需要对电流,电压,温度,压力等物理量进行控制。用PLC来控制模拟量可以充分利用PLC强大的数字与逻辑处理功能,在控制模拟量的同时,还可以进行开关量的控制。该文着重介绍了如何用PLC对模拟量进行控制。     

多相DC-DC电路中PWM控制技术的研究

本文对多相DC-DC电路中的PWM控制技术进行了研究,对电压型PWM控制和电流型PWM控制进行了简单比较,提出了基于快速主动均流技术的电流型控制方法,并将这种方法应用于工程设计。实验证明,采用快速主动均流技术消除了器件性能不一致带来的影响。     

额定风速以上风力发电机组的恒功率H∞鲁棒控制

风力发电机组由于机械结构以及电气负荷承受能力的限制存在着转速限制和功率限制, 额定风速以上时,需要通过控制桨距角来实现额定恒功率输出, 同时保持转速在额定转速处. 本文建立了风力发电机组的详细机理模型, 将H_∞控制理论应用到额定风速以上时风力发电机组的恒功率输出的控制器设计, 建立了标准H_∞恒功率控制问题. 利用LMI方法求解, 得到了桨距角的H_∞控制器. 仿真结果表明该H_∞控制器能够成功实现额定风速以上时的恒功率输出控制, 并且具有良好的鲁棒性.     

在Oracle中用Java实现身份证转换

Oracle是国内主流的数据库平台之一,15位身份证与18位身份证的转换是很多基于数据库管理的信息系统所遇到的一个常见问题,文章采用Java设计了一组身份证转换函数,并利用Oracle对Java技术的支持,将这些函数扩展为一组Oracle的自定义函数,使得信息系统可在数据库一级实现对身份证号码转换的支持。     

Scintillator‐based flat‐panel x‐ray imaging detectors

Abstract— Large‐area amorphous‐silicon flat‐panel x‐ray imaging detectors were introduced commercially about 10 years ago and have seen a steady increase in both volume and number of applications since. The flat‐panel‐detector industry was made possible by manufacturing methods and equipment first developed for the display industry. Here, the different types of flat‐panel detectors are described, with focus on the scintillator‐based TFT/photodiode detector. The manufacturing process used for these detectors is explained and compared to that for displays. Detector operation is detailed, and the various medical and industrial applications are described. Finally, the performance metrics for these detectors and the impact of the performance requirements on detector design are discussed.     

Ambient‐light sensor system with wide dynamic range enhanced by adaptive sensitivity control

Abstract— A new digital ambient‐light sensor system is presented which employs two linear light sensors with different sensitivities and automatically adjusts the sensitivity based on the illumination condition. The adaptation mechanism allows a very wide range of light intensity to be detected, and the input dynamic range of the system is substantially improved from 22.5 to 45.1 dB. The proposed method does not require any additional precision bits for output data. Due to the small number of the output bits and the simple conversion process, the system can be easily integrated on the display panel.     

虚拟加工中工件毛坯模型的建立

为解决虚拟加工中工件毛坯模型的识别问题,提出对规则形状工件毛坯采用OpenGL建模、对复杂形状工件毛坯采用美国初始图形交换规范（Initial Graphics Exchange Specification,IGES）文件进行模型数据转换的方法.该方法利用CAD软件为工件毛坯进行三维造型,生成IGES文件,然后在虚拟加工环境下读取IGES文件并生成工件毛坯模型,从而实现工件毛坯模型在新环境中的建立.经过建立具体的工件毛坯模型,验证相关理论的正确性,为在虚拟加工环境下工件毛坯模型的建立提供可行的依据.