环境磁场对磁记忆检测信号的影响研究

针对磁记忆检测中环境磁场对检测信号影响问题,首先详细分析试件放置方向变化时,不同类型损伤区域的磁场变化情况。然后根据磁记忆检测信号组成,研究环境磁场对磁记忆检测信号的影响机理。最后得出环境磁场对磁记忆检测信号的影响是环境磁场、被测试件自身磁化状态以及试件材料的磁特性共同作用的结果。当被测试件放置方向不同时,测得的磁场信号不是简单地在幅值上整体漂移,整体形貌上也可能会发生一定变化。在工程检测过程中,被测试件的放置方向应尽量保持不变。     

一种工频电场与工频磁场检测装置研究

针对高压线路、变电站附近的工频电场与工频磁场检测问题,研究一种基于STM32F407 ARM控制处理器的电场与磁场测量装置。设计一种基于金属球形电容的电场传感器实现工频电场强度测量,该装置采用磁阻传感器探测工频磁场强度,利用高精度仪表放大器AD620和16位8通道同步数据采集A/D转换模块实现对电场和磁场弱信号的放大与同步采集。根据传感器的特性,系统采用高阶多项式数据拟合算法可有效抑制磁场传感器的非线性影响,减小测量误差。试验结果表明:该装置测量稳定,便携性好,能够同时测量空间环境的工频电场与磁场强度,对工频电磁环境的监测有一定的参考意义。     

直流稳压电源现场检定装置的研究

本文针对直流稳压电源检定中被检测设备笨重难搬移、检测设备数量多、检测环境要求高,不便于开展现场检测等困难,设计了一种便携式现场检定装置。该装置采用Atmega64单片机、高精度精密电阻、mosfet电子开关等技术,对电源调整率、负载调整率和纹波电压测量等测试技术进行电路搭建和样机实验,实现了直流稳压电源自动、半自动测试。     

环境磁场对20钢应力-磁效应的影响

应力的磁效应是磁记忆检测技术的理论基础,也是探讨相关机理问题的关键所在。测量了在不同环境磁场条件下,20钢试样的磁化状态随拉应力的变化规律。结果发现,环境磁场对力-磁效应的关系规律具有明显的影响,磁记忆检测技术的定量评价体系与地磁场有关。     

金属圆柱体表面裂纹检测系统中探头的设计及实现

本文主要阐述了利用交变磁场测量法检测金属裂纹的原理,提出了正交型激励线圈在检测系统中的应用,讨论了圆柱体测量中探头激励线圈的选择依据,并给出了检测线圈的设计。实验结果表明,该探头在实际应用中能够检测出圆柱体裂纹形成的微弱扰动磁场量,能够准确反映出裂纹的长度及深度信息。     

新型振动样品磁强计

振动样品磁强计利用扬声强器作振源，用一套消振装置使系统稳定，整套装置能在ｘ，ｙ，ｚ三方向可调。利用外磁场对振动样品磁化，以霍耳片检测外部磁场，由锁相电路检测感应信号，通过计算机采集磁场信号和感应信号，实时显示、打印测量结果。     

一种轻巧的液浮空间角靶标关键技术研究

针对光电装备大轴间距多轴一致性检测中基准光轴漂移的问题,该文设计一种轻巧的液浮空间角靶标对基准轴空间姿态进行检测和补偿,以确保检测精度。该靶标采用靶板稳定技术与摄影测量技术有机结合,利用液浮靶标提供相对地球坐标系稳定的光轴漂移测量基准,再通过摄影测量方法解算基准轴的空间姿态,充分利用DSP的快速计算能力实现基准轴漂移的实时监测和大轴间距多轴一致性检测精度的修正。实验结果表明:该靶标的测量误差在仅有水平或方位姿态变化时控制在±6″以内,在水平、方位姿态同时变化时控制在±10″以内,能够高精度地检测基准轴的空间姿态变化,为光学动态对准大间距光轴夹角测量提供实时高精度校正。     

独立分量分析在交变磁场测量信号处理中的应用

阵列式交变磁场检测技术具有检测方便快捷的优点,适合金属表面裂纹在线检测。但阵列式交变磁场检测信号往往十分微弱并伴有各种测量噪声,提取困难。本文分析了独立分量分析技术的基本原理,提出利用独立分量分析技术从阵列传感器检测信号中提取有用信号。最后给出了实验结果,实验证明该方法的正确性。     

盲孔深度的精确测量方法研究

当盲孔深度允差在微米量级,且其深度是相对某基准面而言时,这种深度测量一直是当前精密测量中的一个难点。根据被测对象的实际安装工况,设计出一种非接触式的多传感器组合测量法。组合测量克服了单一传感器数据的片面性和不确定性,利用多传感器对环境敏感所产生漂移的同向性抑制了单一传感器数据的漂移,提高了测量的稳定性,克服了单一传感器无法进行形位误差测量的缺陷。实验证明了该方法的可行性,测量精度优于2μm。     

钢卷尺印刷数码轮的自动化改造

介绍了国内钢卷尺印刷机的应用现状,并以某钢卷尺制造企业的印刷数码轮改造为例,在不改变原钢卷尺印刷机的电气线路和空间等前提下,采用Atmega16L单片机、步进电机驱动芯片MTD2009及其细分驱动技术,对钢卷尺印刷机的机械式数码轮进行了电控改造,从而为钢卷尺印刷数码轮研制了经济实用、可靠有效的替换件.     

区域环境电磁监测与信号识别系统方案研究

针对侦察活动中大量使用类似通信信号的伪信号和进行科学实验时各种信号存在的电磁泄漏问题,为满足电磁环境监测的实际需要,运用LabWindows/CVI设计一种新型的区域环境电磁监测与识别系统。系统通过最新的信号混合域分析方法,对一定范围内的区域进行监测,实现仪器控制、数据采集、系统校准、信号识别、结果处理与保存等功能,具有准确性、易用性、便携性及可扩展性,可以高效科学地完成电磁环境监测工作,具有一定的实用性和推广价值。     

Finite element model updating using Hamiltonian Monte Carlo techniques

Bayesian techniques have been widely used in finite element model (FEM) updating. The attraction of these techniques is their ability to quantify and characterize the uncertainties associated with dynamic systems. In order to update an FEM, the Bayesian formulation requires the evaluation of the posterior distribution function. For large systems, this function is difficult to solve analytically. In such cases, the use of sampling techniques often provides a good approximation of this posterior distribution function. The hybrid Monte Carlo (HMC) method is a classic sampling method used to approximate high-dimensional complex problems. However, the acceptance rate of HMC is sensitive to the system size, as well as to the time step used to evaluate the molecular dynamics trajectory. The shadow HMC technique (SHMC), which is a modified version of the HMC method, was developed to improve sampling for large system sizes by drawing from a modified shadow Hamiltonian function. However, the SHMC algorithm performance is limited by the use of a non-separable modified Hamiltonian function. Moreover, two additional parameters are required for the sampling procedure, which could be computationally expensive. To overcome these weaknesses, the separable shadow HMC (S2HMC) method has been introduced. This method uses a transformation to a different parameter space to generate samples. In this paper, we analyse the application and performance of these algorithms, including the parameters used in each algorithm, their limitations and the effects on model updating. The accuracy and the efficiency of the algorithms are demonstrated by updating the finite element models of two real mechanical structures. It is observed that the S2HMC algorithm has a number of advantages over the other algorithms; for example, the S2HMC algorithm is able to efficiently sample at larger time steps while using fewer parameters than the other algorithms.     

高精度智能磁场测量仪的设计

设计了一种由微处理器控制的具有通信接口的高精度智能磁场测量仪,通过双只配对的集成霍尔传感器来获取磁感应强度的信号,采用压频变换器完成数据的采集,并对仪器进行了校准和实验．实验结果表明,所设计的磁场测量仪在整个量程范围内的测量精度达到了0.1mT．该仪器不但可进行磁场的精密测量,还可用于对无线通讯基站电磁辐射的网络化远程监测．     

电磁屏蔽织物材料研究进展

目的现代战场电磁环境日益恶化,含有电子元件和电爆装置的高价值、高技术弹药能否在复杂电磁环境中发挥应有效能,已经成为武器装备建设中一个亟须解决的问题。方法利用电磁屏蔽织物材料作为包装内衬或遮蔽篷布,以增强高价值、高技术弹药在复杂电磁环境中的抗电磁干扰能力,对确保弹药的可靠性具有重要意义。结果综述了金属纤维混纺织物、金属化学镀织物、金属真空镀织物和涂层屏蔽织物研究现状,对比分析了各种织物材料制备工艺的优缺点,简要介绍了非晶态合金织物屏蔽效能的研究进展。结论电镀非晶态合金织物是未来电磁屏蔽织物材料发展的重点方向之一。     

First data from the EGLE experiment onboard the ISS

EGLE is a wide frequency band search- coil magnetometer designed and built at the Roma Tre University. It has been installed onboard the ISS by the Italian astronaut Roberto Vittori on April 25, 2005 within the LAZIO- EGLE experiment carried out during the ENEIDE Soyuz mission. The scope of the experiment is to test EGLE in space and to investigate geomagnetic field variations. The main applications of EGLE are the study of electromagnetic environment inside the ISS, the correlation of magnetic field data with particle fluxes detected by LAZIO particle detector, and the monitoring of ionospheric perturbations possibly caused by Earth seismic activity. Since continuous electromagnetic field measurements on board the ISS are important for diverse space applications, a magnetometer with a suitable design is requested. Appropriate solutions for these applications, which have been adopted by EGLE, are in particular the use of 1- Wire technology and the possibility to detect by means of a search- coil magnetometer a large portion of the ULF frequency band, usually measured by flux- gate probes. To investigate the topside ionosphere electromagnetic environment and stability of Van Allen radiation belts in relation with seismic and anthropogenic electromagnetic emissions, a specific satellite mission (the ESPERIA project) has been designed for the Italian Space Agency (ASI), and up to now a few instruments of its payload have been built and tested in space. One of them is exactly the EGLE search- coil magnetometer. The first magnetic observations performed by this instrument reveal to be promising and demand for a further and deeper analysis based on a longer time series of data.     

半电波暗室中的EMI辐射骚扰试验测量不确定度分析与评定

半电波暗室能模拟理想的开阔场情况,符合电磁波在自由空间中的传播规律,在此特定环境中测量EMC一个重要技术指标——辐射骚扰场强,简单介绍测量不确定度理论,详细分析辐射骚扰场强的测量不确定度来源与评定,并给出评定结果,为实验室的电磁兼容检测提供指导。     

Mathematical simulation of semitransparent layered thin-walled waveguides with the use of averaged two-sided boundary conditions

The boundary-value problem on the penetration of electromagnetic waves from a thin-walled cylindrical waveguide into the environment was solved with the use of averaged boundary conditions. The multilayer wall of the waveguide was considered as an ideally thin cylindrical surface, the complex material structure of which was described with the use of special two-sided boundary conditions. The dispersion equation determining the constants of propagation of partial waves in the waveguide was solved by the method of numerical minimization of the function of two variables. Results of calculation of the attenuation of the electromagnetic field penetrating from the waveguide into the environment as compared to the field of the corresponding mode inside the waveguide are presented.     

Adjoint Hamiltonian Monte Carlo algorithm for the estimation of elastic modulus through the inversion of elastic wave propagation data

Efficient inversion of noisy seismic waveform data produced due to elastic wave propagation for the estimation of a high-dimensional elastic modulus vector is achieved. Estimation is carried out in a Bayesian framework using Hamiltonian Monte Carlo (HMC) that enables efficient statistical estimation over high-dimensional parameters. The truncated Karhunen-Loève (K-L) expansion is introduced to reduce the dimensionality of the elastic modulus vector. Expensive computations of the gradient of the state vector with respect to the parameter vector at every step are also eliminated through the adjoint method, which is developed from a general one-step discretization of the governing second-order ordinary differential equations (ODEs). An Adjoint HMC algorithm that employs a truncated K-L expansion of the elastic modulus vector is presented. The efficacy of the algorithm is investigated with respect to two representative problems with varying geometric complexity. Adjoint HMC offers a significant speed up in gradient calculation time over the direct differentiation counterpart as the number of terms in the K-L expansion increases. The algorithm is able to estimate the true elastic modulus within the credible intervals for both cases.     

矿井瞬态传导骚扰非接触测量方法研究

以瞬态脉冲电流作为短偶极子的激励源,运用电磁场理论建立短偶极子的瞬态辐射发射模型,确定短偶极子瞬态辐射场与其流过的脉冲电流密切相关,并通过地面实验建立直接接触测量值和非接触测量值之间的转换模型,提出井下瞬态传导骚扰的非接触测量方法。井下实验研究表明:非接触测量方法可以及时捕获开关操作瞬间电力电缆瞬态辐射的时域波形;距离电缆1 cm处脉冲电流辐射的电场强度最高可达到4 V/m,对井下电磁环境影响较大。