Image quality analysis for dual energy subtraction imaging with afemtosecond laser-based hard X-ray source

We present a study of image quality for dual energy subtraction imaging using an iodinated contrast agent and a femtosecond laser-based hard X-ray source. The INRS CPA laser (400 fs pulse focused on solid targets in a 3 μm spot at 4 × 10¹⁸ W cm^-2) was used to create a bright hard X-ray source (conversion efficiency of 10^-5 in the characteristic K_∝ line emission, 12 μm X-ray source diameter). A model of image quality has been developed and been benchmarked with specific experiments using specially made angiography phantoms     

基于微焦点X射线源的相位衬度成像实验研究

对弱吸收、低密度、较轻元素物质来说,传统的X线吸收成像方式存在分辨能力低、成像效果差等问题,而X线相位衬度成像恰好可以弥补这些缺点。以微焦点X射线源为基础,选择了两种具有明显上述特征的样品,采用类同轴相衬成像的方式设置实验参数。实验不仅能得到清晰、放大的图像,而且能够明显突出样品的边界信息,从而验证了X线的相位衬度成像效果。     

一种高分辨X光数字胃肠图像系统的设计与实现

X光数字胃肠诊断设备是一种重要的医学测量技术,本文设计了一种新型的X光高分辨率数字胃肠图像系统,以提高胃肠临床诊疗的质量.采用2 048×2 048×12 Bit的高分辨率CCD数字摄像机,结合临床需求,研究开发了高速数字采集传输卡、成像光学通道及X光设备控制接口相关的硬件及软件.实验表明X光数字胃肠图像系统的分辨率达到了2.8 lp/mm.高分辨率的X光数字胃肠图像系统,可以获得更清晰的胃肠微细结构.     

High-resolution source imaging of brain electrical activity

The author considers the enhancement of spatial resolution with cortical imaging. The following topics are considered: cortical-potential imaging from scalp potentials; cortical-potential imaging from scalp Laplacians; equivalent surface-source imaging; cortical-potential imaging in a realistically shaped, inhomogeneous head model; inverse-imaging algorithms; other EEG-based cortical-imaging approaches     

方形锂离子电池的X射线影像技术无损检测

研究使用X射线影像技术对方形锂离子电池进行无损检测的方法,提出基于局部均值及标准差分析的方形锂离子电池极耳轮廓提取及判定方案,解决极耳背景灰度随着样品不同差异较大的问题,克服自身灰度差异较小造成的轮廓提取困难。对设计的检测设备在生产线上的使用情况进行统计、分析,对存在的问题提出改进方案。设备对极耳与壳壁的距离测算重复精度小于0.06 mm。使用设计的检测设备的生产线,在4个月内的极耳不良率降低了3.7‰。     

X射线成像系统辅助设备的研发与应用

由于垂直布置的GIS设备、罐式断路器及瓷柱式断路器等开关类设备安装位置较高,现有X射线成像系统自带辅助装置在高度和角度上不能满足现场X射线成像检测需求。本文开发了一种高度、角度可调的移动式X射线成像系统辅助设备,并成功应用于330 k V瓷柱式断路器X射线成像检测中。应用结果表明:该装置不仅提高了X射线成像检测的效率,而且保证了试验人员安全性,为X射线成像检测技术的推广应用提供了帮助。     

4th generation synchrotron source boosts crystalline imaging at the nanoscale

New 4th-generation synchrotron sources,with their increased brilliance,promise to greatly improve the performances of coherent X-ray microscopy.This perspective...     

采用高温超导线圈的电子高电压发生器

研究了应用高温超导（ＨＴＳ）线圈，通过Ｌ－Ｃ串联谐振电路从低压直流电源产生高电压的新方法。为了产生高电压，低压直流电源的极性需在电子开关的控制下每半个谐振周期切换一次。谐振电路中电阻的存在限制了它所能产生的高电压幅值。通过用ＨＴＳ线圈制成的电感取代铜线圈电感，该电路所能产生的高电压的幅度会明显增大，在本文中，（Ｂｉ，Ｐｂ）２Ｓｒ２Ｃａ２Ｃｕ３Ｏ１０＋ｘ套银多股ＨＴＳ线材被用来制造超导电感。虽然用此谐振方式产生的高电压不能给低阻抗负荷供电，但它可能用于电气设备局部放电测试或其他电气绝缘性能的检测等方面作为另一个应用该方法还可用于超导体自身电性能的测量。     

Development and field test of a laser-based nonintrusive detection system for identification of vehicles on the highway

A real-time laser-based nonintrusive detection system has been developed for the measurement of true travel time of vehicles on the highway. The detection system uses a laser line that is projected onto the ground as a probe. The reflected light is collected and focused into a photodiode array by an optical system. Vehicle presence is detected based on the absence of reflected laser light. By placing two identical laser/sensor pairs at a known distance apart, the speeds of both the front and rear of a vehicle are measured based on the times when each sensor is triggered. The length of each vehicle is determined by using these speed measurements and the residence time of the vehicle under each sensor. Using real-time software, the speed, acceleration, and length of a detected vehicle can be calculated and displayed simultaneously. A new prototype system has been tested on the highway with different types of vehicles and scenarios, and the results are presented here. The tests have also been carried out for different weather conditions and road materials. The results indicate that the laser system operates well under real highway conditions.     

A high-voltage source of alternating power with a regulation tracer

The use of inertialess two-polar high-voltage inverters and a special control algorithm allows the amplitude of alternate voltage to be increased under a load up to the level of a maximum reverse voltage of a commuting valve. Sources that form alternating high voltage are applied to formation of a corona discharge in air, for example, devices that clear dust. The regulation tracer via the duration of the current of an anodecathode commuting electronically radial valve allows increasing the reliability and durability of its activity with a minimum pulse duration under a load.     

基于传输线充电技术的高功率电磁脉冲源

为研究高功率电磁脉冲的产生,本文以高阻抗输出的Tesla变压器型高功率脉冲驱动源为充电装置,应用传输线充电技术实现高功率亚ns电磁脉冲的调节,阻抗渐变传输线和同轴波导转换双脊喇叭天线实现亚ns电磁脉冲的有效辐射.研制完成的辐射试验装置能够输出重复频率100 Hz,最大场强距离积294 KV,频谱分布在0.4～1.0 GHz的高功率电磁脉冲.     

Optically imaging cardiac activation with a laser system

The authors have developed a laser imaging system that: 1) depicts potential distribution with high spatial and temporal resolution; 2) can image large areas; 3) does not require filtering for signal or image enhancement; 4) is flexible, allowing for the acquisition of images of programmable size and shape at varying frame rates; and 5) has a large depth of field, thus minimizing the loss of focus when simultaneously imaging areas of the heart at different distances from the prime focal plane. The high duality of the images obtained with this technique allows quantitative measurements to be made of both the potential distribution and the change in this distribution over time. Here, the authors discuss the components of the system and the present their experimental results     

High field measurements with a guarded needle

The electrical degradation of solid dielectrics often originates in the vicinity of defects (impurities, protrusions, or inclusions). The degradation involves a high field region of localized high carrier mobility that leads to the formation of a space charge limited field region in which charge cycles during application of an AC field. This cyclic carrier motion results in hot electrons and ultra-violet (UV) photons produced by carrier recombination, both of which can degrade the dielectric. Carrier mobility-related prebreakdown phenomena can only be studied within microscopic dimensions, as the power dissipation would cause thermal runaway for a macroscopic geometry. The guarded needle apparatus is designed for such measurement, using a sharp metal needle to create local high electrical field, which induces carrier mobility.     

Phonon imaging in 3D with a fibre probe

We show for the first time that a single ultrasonic imaging fibre is capable of simultaneously accessing 3D spatial information and mechanical properties from m...     

高反射镜表面疵病激光散射显微成像检测

反射镜表面疵病散射直接影响光学测试系统的性能、精度等多项重要指标。反射镜表面疵病的散射量可借助激光散射显微镜进行检测，为了保证整个系统的检测效率及精度要求，在硬件系统的设计上，设计显微物镜镜头、计算光斑的大小及CCD的功率谱响应；在软件系统的设计上，利用软件编写激光散射显微成像测试系统软件，能利用步进电机对反射镜表面进行扫描，同时控制图像采集卡采集图像并保存，重点研究如何快速有效地对采集到的子孔径图像进行精确配准，为后续图像的拼接处理奠定基础。通过分析整个测试系统的精度，×20倍率下能够分辨5~10 μm疵病。     

A multilevel-voltage source rectifier with a three-phase diodebridge circuit as a main power circuit

A novel system obtaining very low distorted waveforms of input AC currents of three-phase rectifier circuits are proposed. The proposed rectifier system consists of a three-phase diode bridge circuit as a main power circuit, AC reactors, and an additional circuit which serves as an active filter with low switching frequencies and a forced-commutation circuit for the diodes. This paper describes the operation principle, analysis of the waveforms of input voltage and current, multiple phase-shifted systems, and the experimental results. The proposed system gives excellent input current waveforms and has many advantages over conventional systems     

基于LLC谐振变换器的微波炉用高压变频电源

传统的微波炉电源多采用工频变压器升压的供电方式,此类电源功率密度小、效率低、开关噪声大,对电网污染较大.针对这些问题,设计了一个输出端采用倍压整流方式的LLC谐振软开关变换器作为主电路,L6599芯片为控制核心的高压变频电源.应用基波分析法推导出变换器的直流增益,分析谐振网络的谐振电感系数和品质因数的曲线变化,优化变换器的谐振参数.利用MATLAB、SABER仿真软件分析主电路的工作特性.最后通过实验验证了该设计方案的合理性与正确性.     

超磁致伸缩微驱动系统的逆变多路电源设计

基于超磁致伸缩微驱动系统的应用,设计了一种多路输出逆变开关电源.该电源以脉宽调制芯片SG3525为核心,采用推挽拓扑转换结构,实现单输入直流电压转换为多路正负直流电压输出,提供给超磁致伸缩微驱动系统的驱动和传感电路.实际运行和测试表明该电源具有稳定性好、电流高、体积小、结构简单的特性,满足微驱动系统的工作要求.     

Robust controller design with hard constraints on the control signal

Contents  The paper deals with robust controller design for motion control systems in case of constraints on the control signal. Furthermore, in order to enhance the dynamic performances of the designed control system – in case of limitation of the control signal – gain-scheduled control strategy is considered. The proposed robust controller design approach is verified by experimental results in case of a vector controlled brushless d.c. drive. Received: 11 February 2001