三维激光多普勒振动测量方法研究综述

激光多普勒频移对面内振动不敏感的特点使三维激光多普勒测振成为了一道难题,为解决此难题,各研究机构开展了相关研究并提出了多个解决方案。本文介绍了四种基于不同原理的三维激光多普勒振动测量方法——基于多个光学头的三维振动测量方法、基于一台LSV测振的三维振动测量方法、结合频闪方法的三维振动测量方法、基于单光学头的三维振动测量方法,总结每种方法的优缺点及实际应用效果,并展望三维激光多普勒振动测量技术未来的发展方向。     

激光多普勒效应微纳测量技术的研究

研究MEMS系统中可动构件(膜、梁、梳、面、弹簧)在承受压力、弯曲等机械负荷及热负荷下的性能，重要途经是测量其在各种条件下的运动量(振动、位移等)．提出了一种MEMS构件微小振动、位移测量系统，采用外差法激光多普勒技术，通过对信号的频谱分析，确定了信号处理单元的适宜频带宽度．对调相多普勒跟踪信号进行相干解调及频率／电压转换，可以实时地得到被测的速度、位移、加速度、频率等参量．实现的测量分辨力为20nm．     

Comparison of avalanche-velocity measurements by means of pulsed Doppler radar, continuous wave radar and optical methods

Velocities of mixed dense-flow/powder-snow avalanches have been measured by means of pulsed Doppler radar and by continuous wave radar at the full scale avalanche test site Vallée de la Sionne. From the radar data, we derive velocities of the saltation layer and of the powder part of the avalanche. The results obtained by the two different radar measurement techniques are compared and also are checked against the velocity data obtained by opto-electronic velocity sensors installed at different heights on the 20 m high mast in the avalanche track and against videogrammetry velocity data. We demonstrate that the measurements are consistent and discuss how information about the avalanche structure can be derived from the measurements.     

多普勒效应对应用IMP算法估计目标方位的影响

ＩＭＰ算法用于运动目标线谱信号处理时,为了解运动目标多普勒效应对ＩＭＰ算法目标方位角估计的影响,本文利用水池试验数据进行了仿真研究。文中叙述了ＩＭＰ算法目标方位估计原理,给出运动目标在多普勒频移情况下,ＩＭＰ算法对目标方位估计的仿真结果。     

霍尔效应的地下位移三维测量方法研究

当霍尔传感器与磁钢之间的相对位置变化时,霍尔传感器感受到的磁感应强度也随之变化,从而导致传感器的输出电压改变.采用三个霍尔传感器组成传感器阵列,建立三维笛卡儿坐标系.通过测量传感器的输出电压并结合一定的算法,可计算出某一时刻磁钢的三维坐标.地下土体的变形会改变霍尔传感器与磁钢之间的相对位置.在得到磁钢新的三维坐标之后,通过几何运算得出位移的大小.     

Neighbour-die effect on the measurement of wafer-level flip-chip LED dies in production lines

The light from the side surfaces of the test flip-chip light-emitting diode (FCLED) dies is reflected, refracted or absorbed by neighbour dies during the measurement of wafer-level FCLED dies in production lines. A notable measurement deviation is caused by the neighbour-die effect, which is not considered in current industry practice. In this paper, Monte Carlo ray-tracing simulations are used to study the measurement deviations caused by the neighbour-die effect and extension ratios of the film. The simulation results show that the maximal deviation of radiant flux impinging the photodiode can reach 5.5%, if the die is tested without any neighbour dies, or is surrounded by a set of neighbour dies at an extension ratio of 1.1. Moreover, the dependence between the measurement results and neighbour cases for different extension ratios is also investigated. Then, a modified calibration method is proposed and studied. The proposed technique can be used to improve the calibration and measurement accuracy of the test equipment used for measurement of wafer-level FCLED dies in production lines.     

Propagation model and error analysis of an E-field sensor based on pockels effect and waveguide

Electric field measurement sensors based on the crystal Pockels effect are widely used. Currently, the development aims for electric field sensors are mainly focused on miniaturizing and integrating the sensor structure and improving measurement sensitivity and precision. The goal of this study was to analyse the sources of error in Pockels effect electric field measurement sensors, consider the mutual influence and accumulation effect of the various error factors, and establish a basic mathematical model of the measurement system with error components. Calculation and analysis were used to classify the function and change trend of several main errors, providing reference data for the structure design and error compensation of the sensor. The results show that the polarizing angle and the analyser angle have the same influence on assembly error. The inherent error is positively related to the electric field intensity. The periodic accumulation characteristic error under large electric field is also discussed. In order to avoid this error under an intense electric field, a suitable test electric field range was determined.     

基于深度神经网络的露天矿岩石爆破效果预测

装载和运输成本占到露天矿运营总成本的50%以上,而爆破后岩石破碎程度直接影响到露天矿装载和运输成本。为了得到爆破参数和岩石破碎度之间的关系,收集了平朔东露天矿爆破参数和岩石破碎度数据,使用图像识别技术大规模收集分析爆破后岩块粒径分布,基于深度神经网络研究分析爆破参数和岩石破碎度之间的关系,建立了适用于东露天矿的爆破参数和破碎度的预测模型,并对爆破参数做敏感性分析,确立了炸药单耗和孔距是主要影响因素,并分别建立了炸药单耗和孔距与岩石破碎度之间的变化关系。研究结果可以指导矿山确定合理的穿孔和爆破参数以得到最佳的岩石破碎度,从而减少露天矿运营总成本。     

爆破地震效应及其控制措施分析

通过对爆破地震效应的产生、危害及其影响因素分析，给出了减小爆破地震效应的措施。     

Analysis of flow stress and size effect on polycrystalline metallic materials in tension

A model describing the size effect on the tensile strength of crystalline metallic materials is investigated. Using the nonhomogeneity of polycrystalline materials and free surface effect, the density of the geometrically necessary dislocations during tension is derived. Using the proposed model, an analysis of the effect of both specimen size and grain size on the tensile strength of the polycrystalline metallic materials is carried out.     

Investigation of Errors in Estimates of the Frequency of Signals of Laser Doppler Anemometers Using Wavelet Analysis

A method of processing the signals of laser Doppler anemometers using wavelet transformation is considered. The errors of Doppler frequency estimation obtained from an analysis of the wavelet spectrum of the signal are calculated and the influence of a number of parameters on these errors is investigated. Recommendations for performing measurements are given.     

Enhanced gain and narrow linewidth of an optical cavity by the Doppler effect in a four-level atomic system

Abstract

A scheme for high gain and narrow linewidth of an optical cavity with a four-level atomic system is proposed by the Doppler effect via active Raman gain (ARG) process. Atomic motion leads to Doppler frequency shift which induces constructive interference for the linear susceptibility. The enhanced normal dispersion greatly narrows the cavity linewidth, and the amplified gain gives rise to a high cavity transmission. Simulation results show that the cavity linewidth based on ARG is about one order of magnitude narrower than that based on electromagnetically-induced transparency under the same conditions, and the cavity transmission intensity could be enhanced by nearly 30 times.     

基于链化模型的磁流变弹性体磁致效应影响因素分析

磁流变弹性体是磁流变材料中新的一员,它是由可磁化的铁磁性颗粒和橡胶基在外加磁场下固化而成的,固化后铁磁性颗粒在基体中形成链状等有序结构,因此其力学、电学、磁学等性质可由外加磁场控制.目前限制磁流变弹性体的大规模应用的一个重要因素是其磁致效应还不能够满足工程需要,制备出具有更大磁致效应的磁流变弹性体材料是当前的紧迫任务之一.在磁流变弹性体链化模型的基础上,引入斜链夹角的正态分布,采用偶极子法从理论上分析了诸多因素对磁流变弹性体磁致效应的影响,包括颗粒链的初始倾斜角、外加磁场强度、剪应变大小等,为材料的制备和性能的优化提供理论上的帮助.     

The role of crowdsourcing in product design: The moderating effect of user expertise and network connectivity

To meet the challenges of customization and personalized design in the context of the digital economy, increasing numbers of small and medium-sized enterprises (SMEs) are using crowdsourcing platforms to seek product design innovation. While crowdsourcing has significant potential for eliciting product ideas, it remains unclear whether it can generate high-quality designs for relatively more complex product design tasks. Based on a leading social new product development website Quirky.com, we explore the antecedents of a firm's adoption decision of crowdsourcing, the impact of crowdsourcing on product design quality, and the moderating effect of user expertise and network connectivity by utilizing treatment effect model. The results indicate that: (1) crowdsourcing has a significant positive impact on product design quality; (2) user expertise positively moderates the role of crowdsourcing in product design quality; (3) network connectivity has an inverted U-shaped moderating effect on crowdsourcing and product design quality relationship; (4) the probability of firm's crowdsourcing adoption is negatively correlated with the complexity and reliability of initial product idea but positively correlated with popularity, novelty, and numbers of images. This study not only enriches the crowdsourcing and social network theory; but also provides guidance for crowdsourcing platform firms to better manage the crowdsourcing process and user crowdsourcing communities.     

预裂爆破减振作用效果分析

周宁水电站地下厂房在开挖爆破中采用了预裂爆破技术；为了监测预裂爆破减振效果，指导施工，沿预裂缝两侧布置测点进行实地爆振测试；介绍了厂房开抡爆破及预裂爆破工艺，给出了预裂缝两侧振动实测数据，据此分析了预裂爆破减振作用及影响因素。     

微晶化及活性元素效应在合金抗高温氧化中的协同作用

总结了目前广为研究的微晶化和活性元素效应在合金高温氧化过程中的作用，并讨论了二者的协同效应。微晶化和活性元素效应均能够降低合金的高温氧化速率，提高氧化膜的黏附性。然而，微晶化中晶粒的长大趋势和促进内氧化发生的缺陷对其实际应用造成不利影响，少量活性元素的添加恰好弥补微晶化的这些缺失；活性元素添加须适量，这点限制了它作为保护性氧化膜形核中心的数量及降低氧化速率的幅度，且使得合金氧化增重较未添加活性元素试样略有增加，微晶化则不存在这样的问题，可以弥补应用活性元素效应的不足之处。本工作旨在加深对微晶化和活性元素协同效应对合金高温氧化性能影响的微观理解，为制备性能更为优异的抗高温氧化合金提供理论和实践基础。     

Mean stress/strain effect on fatigue behavior of an epoxy resin

Mean stress/strain effect on the fatigue life of an Epon 826/Epi-Cure Curing Agent 9551 epoxy system has been investigated by carrying out series uniaxial fatigue tests with four different mean strain ratios under strain-range-controlled mode. Quantitative analysis of the mechanical properties, such as mean stress relaxation, evolution of stress range and strain energy density, have been performed based on the stress–strain data recorded by a non-contact real-time strain measurement and control system. Mean stress/strain functions have been introduced into the equivalent damage parameters to include the mean stress/strain effect on the fatigue life of the epoxy polymer material. The procedure to characterize the mean stress/strain functions has been demonstrated and material constants were calibrated in the case of either stress, strain or energy approach, respectively. Good agreement can be seen between the predictions and the test data.     

冲击波负压对防护门反弹效应的影响分析

本文对冲击波负压作用下防护门的反弹效应进行了研究,采用合理的荷载假定形式,推导了考虑负压影响的防护门反弹力的精确解析公式,评价了负压对防护门反弹效应的影响规律：即随着比例爆距的增大,负压峰值相对于正压峰值逐渐增大,反弹增大效应也较明显,但这样一个响应可能仅对比较小的超压值才出现,由于正压、负压峰值都较小,防护门刚度较大,故增大的反弹力不足以对防护门造成破坏,设计中可以不考虑负压的影响。     

单模 VCSEL 激光自混合测距精度的提高

单模VCSEL激光自混合测距具有测距精度高、功耗低和结构简单等优点。对单模VCSEI。进行了大频偏的三角波电流调制,应用差频模拟锁相环处理自混合拍频信号,明显减小了拍频信号在三角波拐点处固相位突变、波形周期不等以及波形的调幅干扰和失真等因素造成的影响。实验结果表明,提高了测距精度和动态范围。室温下,在单模VCSEL输出功率0．7mW,波长850nm,调制三角坡的频率1．3kHz,幅度0．4Vrms,采样时间0．1S,散射面为粗糙金属片的条件下,测距范围达到50～500mm,测距精度达到2mm,分辨率优于2mm。     

Modeling and simulating the impact of forgetting and communication errors on delays in civil infrastructure shutdowns

Handoff processes during civil infrastructure operations are transitions between sequential tasks. Typical handoffs constantly involve cognitive and communication activities among operations personnel, as well as traveling activities. Large civil infrastructures, such as nuclear power plants (NPPs), provide critical services to modern cities but require regular or unexpected shutdowns (i.e., outage) for maintenance. Handoffs during such an outage contain interwoven workflows and communication activities that pose challenges to the cognitive and communication skills of handoff participants and constantly result in delays. Traveling time and changing field conditions bring additional challenges to effective coordination among multiple groups of people. Historical NPP records studied in this research indicate that even meticulous planning that takes six months before each outage could hardly guarantee sufficient back-up plans for handling various unexpected events. Consequently, delays frequently occur in NPP outages and bring significant socioeconomic losses. A synthesis of previous studies on the delay analysis of accelerated maintenance schedules revealed the importance and challenges of handoff modeling. However, existing schedule representation methods could hardly represent the interwoven communication, cognitive, traveling, and working processes of multiple participants collaborating on completing scheduled tasks. Moreover, the lack of formal models that capture how cognitive, waiting, traveling, and communication issues affect outage workflows force managers to rely on personal experiences in diagnosing delays and coordinating multiple teams involved in outages. This study aims to establish formal models through agent-based simulation to support the analytical assessment of outage schedules with full consideration of cognitive and communication factors involved in handoffs within the NPP outage workflows. Simulation results indicate that the proposed handoff modeling can help predict the impact of cognitive and communication issues on delays propagating throughout outage schedules. Moreover, various activities are fully considered, including traveling between workspaces and waiting. Such delay prediction capability paves the path toward predictive and resilience outage control of NPPs.