Bunch-length measurement at a bunch-by-bunch rate based on time–frequency-domain joint analysis techniques and its application

This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.

Factor Structure and Longitudinal Invariance of the CES-D across Diverse Residential Backgrounds in Chinese Adolescents

Background:Valid and reliable measures of depressive symptoms are crucial for understanding risk factors,outcomes,and interventions across rural and urban settings.Despite this need,the longitudinal invariance of these measures over time remains understudied.This research explores the structural components of the Center for Epidemiological Studies Depression Scale(CES-D)and examines its consistency across various living environments and temporal stability in a cohort of Chinese teenagers.Method:In the initial phase,1,042 adolescents furnished demographic details and undertook the CES-D assessment.After a three-month interval,967 of these participants repeated the CES-D evaluation.The study employed Confirmatory factor analysis(CFA)to scrutinize the scale’s structural integrity.We investigated factorial invariance by conducting a twopronged CFA:one comparing urban vs.rural backgrounds,and another contrasting the results from the initial assessment with those from the follow-up.Results:The CES-D demonstrated adequate reliability in both rural and urban high school student samples.The preliminary four-factor model applied to the CES-D demonstrated a good fit with the collected data.Invariance tests,including multigroup analyses comparing rural and urban samples and longitudinal assessments,confirmed the scale’s invariance.Conclusions:The results suggest that the CES-D serves as a reliable instrument for evaluating depressive symptoms among Chinese adolescents.Its applicability is consistent across different living environments and remains stable over time.

THE ESTIMATE AND MEASUREMENT OF LONGITUDINAL WAVE INTENSITY

Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.

Longitudinal Performance Assessment of Traffic Signal System Impacted by Long-Term Interstate Construction Diversion Using Connected Vehicle Data

Local arterials can be significantly impacted by diversions from adjacent work zones. These diversions often occur on unofficial detour routes due to guidance received on personal navigation devices. Often, these routes do not have sufficient sensing or communication equipment to obtain infrastructure-based traffic signal performance measures, so other data sources are required to identify locations being significantly affected by diversions. This paper examines the network impact caused by the start of an 18-month closure of the I-65/70 interchange (North Split), which usually serves approximately 214,000 vehicles per day in Indianapolis, IN. In anticipation of some proportion of the public diverting from official detour routes to local streets, a connected vehicle monitoring program was established to provide daily performances measures for over 100 intersections in the area without the need for vehicle sensing equipment. This study reports on 13 of the most impacted signals on an alternative arterial to identify locations and time of day where operations are most degraded, so that decision makers have quantitative information to make informed adjustments to the system. Individual vehicle movements at the studied locations are analyzed to estimate changes in volume, split failures, downstream blockage, arrivals on green, and travel times. Over 130,000 trajectories were analyzed in an 11-week period. Weekly afternoon peak period volumes increased by approximately 455%, split failures increased 3%, downstream blockage increased 10%, arrivals on green decreased 16%, and travel time increase 74%. The analysis performed in this paper will serve as a framework for any agency that wants to assess traffic signal performance at hundreds of locations with little or no existing sensing or communication infrastructure to prioritize tactical retiming and/or longer-term infrastructure investments.

An analysis of longitudinal binary data using generalized linear models

Objective: To analyze longitudinal binary data by using generalized linear models. The correlation between repeated measures were considered. The general method for analyzing longitudinal binary data was given. Methods: Generalized estimating equations (GEE) proposed by Zeger and Liang was used. For sevens covariance structures, one method was given for estimating regression and correlation parameters. Results: Regression and coerelation parameters were estimated simultaneously. A Set of program was finished and an example was illustrated. Conclusion: Longitudinal dsta often occur in medical researches and clinical trials. For solving the problem of correlation between repeated measures, it is necessary to use some special methods to cope with this Kind of data.

Study of Material Evaluation Probe Using a Longitudinal Wave and a Transverse Wave

Transmitting a longitudinal wave and a traverse wave into a composite material in a molten state has been studied in the online control of the composite material which cannot be evaluated by a conventional ultrasonic sensor as a final analysis, using the difference in the propagation characteristics of both modes. It is especially expected that measurement of the physical quantity which was not able to be conventionally measured can be performed by carrying out coincidence measurement of the ultrasonic wave in both modes. Therefore, in this research study, an ultrasonic probe, which can simultaneously transmit and receive a longitudinal wave and a traverse wave has been developed using an electromagnetic acoustic transducer (EMAT) because it has the advantage of measuring high temperature samples. In this study, two methods have been compared. The 1st method uses a traverse wave EMAT that travels in a vertical direction and a bar wave by which the low order mode is equivalent to longitudinal wave vibration. The other method is to carry out the mode conversion of the traverse wave by a traverse wave-EMAT. The longitudinal converted from the transverse wave are spread in the axis direction. As the experimental results of both optimizations of the drive conditions, it has been confirmed that the 2nd mode conversion method was promising. This paper reports about the trial process and the experimental results.

The Use of Tamping Machine for Diagnosising the Longitudinal Forces in Rails of CWR Track

In the novel approach to the diagnostic tests of continuous welded rail （CWR） track by the use of the tamping machine, the fundamental statement related to the recording of the curvature with a definite value of the lateral displacement being subjected to verification, can provide a basis for the determination of the longitudinal axial force in the rail. An attempt has also been made to define an alternative factor which by means of the measured signals, could be used for the determination of the axial forces in the rail sections. A power engineering approach has been adopted to this concept. Within the framework of the experimental investigations, measurements were carried out in the track test section. The investigations were based on stretching the rail sections by stretchers and on lateral displacements of the track by the tamping machine. The operation of the measuring apparatus was also tested in the experimental railway track section while carrying out the geometrical adjustments by the tamping machine. As a result of next series of the investigation carried out in 2006-2007, the authors worked out a procedure of estimating the longitudinal forces in rails of CWR track.

大直径盾构隧道纵向刚度增强措施研究

为研究不同环缝接头结构对盾构隧道纵向刚度的增强效果,采用等效连续化模型计算得到断面直径对隧道纵向拉压、纵向抗剪和纵向抗弯刚度的影响规律,将隧道纵向刚度增强措施与管片环缝接头结构相联系,采用数值模拟深入探究了9种环缝接头结构的力学性能,对比得到增强隧道纵向刚度效果最优的环缝接头结构。结果表明:直径对纵向拉压和纵向抗弯刚度影响较小,对纵向抗剪刚度影响较大;环缝接头刚度增强措施能够显著减小管片位移,提高隧道纵向刚度,提升效果为:斜螺栓>弯螺栓,定位榫>剪力销>凹凸榫;螺栓型式和纵向刚度增强措施均对螺栓最大剪切应力有较大影响,竖向荷载下受螺栓型式影响较大,水平向荷载下受管片环缝接头刚度增强措施影响较大;结合经济性和有效性,当接头螺栓为弯螺栓时,设置定位榫是一种相对较优的选择。

推进轴系弯-纵耦合非线性效应对推力测量精度影响研究

高精度监测推进轴系推力对船舶快速性预报、船-机-桨优化匹配及轴系健康管理等具有重要意义。然而,对于超长推进轴系,由于其跨距大、细长比(轴系半径与长度之比)小、且承受推力大,此时轴系将产生严重弯-纵耦合非线性变形。这将对基于应变或变形位移等形变信息来测量推力的方法产生重要影响。因此,本文研究推进轴系弯-纵耦合非线性效应对推力测量精度的影响。考虑Von Karman非线性位移-应变关系,利用Hamilton变分原理结合有限元方法建立推进轴系非线性力学模型,研究弯-纵耦合效应对轴系变形位移和应变的影响规律,以及由此引起的推力测量误差。研究结果表明:在低转速时,轴系弯-纵耦合效应较弱,对推力测量影响很小;高转速时,忽略轴系弯-纵耦合效应将引起较大测量误差(240 r/min时,误差可达13.95%);测点越靠近螺旋桨,弯-纵耦合效应越强,推力测量误差越大,因此将测点布置在轴系前端推力轴承附近可有效减少轴系弯-纵耦合效应引起的测量误差。研究结果对跨度大、细长比小的超长轴系推力测量有指导意义。

多纵模激光器体制下直接多普勒测风技术的实现与仿真

考虑到单纵模激光器作为多普勒测风激光雷达的激励光源需要复杂的种子注入技术和高精度的稳频锁频技术,本文提出了以自由运转的多纵模激光器作为激励光源的直接多普勒测风激光雷达,以降低激励光源的实现难度和复杂性.针对典型Nd:YAG脉冲激光器,研究了不同激光辐射线宽、光学谐振腔长和中心波长条件下多纵模激光激励的大气弹性散射回波光谱的分布模式.为了综合利用大气风场导致的多纵模激光中每个纵模所激励大气弹性散射回波光谱的多普勒频移,利用具有周期性透过率曲线且四个输出通道相位各相差π/2的可调谐四通道马赫-曾德尔干涉仪,实现对多纵模大气弹性散射回波光谱多普勒频移的高精度鉴别.在此基础上,构建了多纵模激光器体制下直接多普勒测风技术大气风场反演的数学模型.仿真结果表明,所提出的多纵模直接多普勒测风激光雷达能够实现对大气风场信息的高精度测量,并且激光中心波长越大,激光光学谐振腔长越短,系统测风范围越大,测风误差越小.

Simultaneously detecting transversal and longitudinal displacement with the dielectric metasurface

The compact,sensitive,and multidimensional displacement measurement device plays a crucial role in semiconductor manufacture and high-resolution optical imaging.The metasurface offers a promising solution to develop high-precision displacement metrology.In this work,we proposed and experimentally demonstrated a two-dimensional displacement(XZ)measurement device by a dielectric metasurface.Both transversal and longitudinal displacements of the metasurface can be obtained by the analysis of the interference optical intensity that is generated by the deflected light beams while the metasurface is under linearly polarized incidence.We experimentally demonstrated that displacements down to 5.4 nm along the x-axis and 0.12μm along the z-axis can be resolved with a 900μm×900μm metasurface.Our work opens up new possibilities to develop a compact high-precision multidimensional displacement sensor.

单元化纵连无砟轨道在限位条件下的温度变形及损伤研究

对纵连板式无砟轨道进行单元化,有望从源头上控制温度效应过大引起的结构损伤,降低结构失稳风险,但需要在单元化过程中对轨道结构进行限位。借助数值仿真计算,研究植筋和扣压两种限位条件下不同单元节段长度的纵连板式无砟轨道温度变形和损伤。研究认为:在单元节段的两端,植筋比扣压更能有效控制轨道板纵向变形,而两种限位方式对板角变形的控制效果相差不大;层间纵向位移差的总体控制可由植筋方式实现,而在板角处采用扣压方式更佳。植筋后,单元节段长度对植筋孔的混凝土损伤几乎没有影响;扣压后,当整体温升低于5℃时,单元节段长度对板角的混凝土损伤几乎没有影响,而当整体温升大于5℃时,单元节段长度的影响显著。植筋后,受拉损伤先出现在植筋孔孔壁处,随着整体温升增高,损伤区域朝轨道板横向发展;扣压后,受压损伤最先出现在轨道板板底,随着整体温升增高,损伤区域逐渐向板表发展。两种限位条件对轨道板和CA砂浆之间界面损伤的影响差异显著,植筋时总离缝面积小于扣压,但扣压可有效控制板角处离缝。以3块轨道板为一个单元节段,并采取植筋限位方式控制轨道结构温度变形和损伤。

铁路轨道检查仪轨向与高低检测单元检定方法的研究

铁路轨道检查仪行业标准与国家计量检定规程中,明确规定轨向与高低检测单元的检定采用超高复现法,但轨向与高低复现值换算及示值误差计算方法不容易被理解。详细分析轨道检查仪轨向与高低检测单元检定采用的中点弦测法和轨迹法。基于轨迹法,给出了优化轨向与高低检定方法的建议:将轨向与高低复现值的定义统一到超高复现值,不与物理弦长进行换算,并采用相同的方法对专用块规量值溯源;统一规划和安排超高、轨向和高低等检定点,优化专用块规名义尺寸;轨向与高低示值最大允许误差要求维持不变。

含有测量误差与缺失值的纵向数据亚组分析方法的模拟研究

目的 研究可以同时处理协变量含有测量误差和响应变量含有缺失值的纵向数据下的亚组分析方法。方法 基于阈值回归模型进行亚组分析;利用重复测量之间的独立性来处理测量误差,并引入逆概率加权来处理缺失值,从而构造一个新的广义渐近无偏估计方程。结果 计算机随机模拟显示该估计方法在处理测量误差和缺失数据方面具有良好的效果,相比于未修正测量误差或缺失数据的广义估计方程方法具有更小的偏倚和均方误差。结论 亚组分析中,当协变量存在测量误差、响应变量存在缺失值时,通常需要考虑对测量误差和缺失值进行处理,以便得到可靠的参数估计。

连霍高速三门峡段改扩建路面纵向裂缝成因及治理措施

为深入研究长时间重载作用下路面纵向裂缝的成因及治理措施,以三门峡境内连霍高速改扩建项目为依托,针对改扩建之前的老路路面裂缝病害进行调查分析,采用对比分析法,研究了路面纵向裂缝的类型、成因,并据此提出了适用于高等级公路路面纵向裂缝的轻度、中度和重度裂缝处治措施,预期可延长道路使用年限5年,节约30%的养护成本及大修资金。

基于开槽法的超声应力换能器LCR波检测深度校准研究

基于开槽法开展了超声应力换能器LCR波检测深度校准研究。其原理是当开槽深度超过LCR波渗透深度时,波的传播会受开槽的影响。首先,采用弹性波时域显式物理场,建立了LCR波渗透深度的有限元研究模型,仿真了LCR波的产生及传播过程,并且分析了槽型对LCR波及检测深度的影响。通过声时差与幅值变化幅度2个特征参数,得出矩形槽比梯形槽更适合用于校准换能器的检测深度。在此基础上,开展不同频率换能器检测深度校准试验,制定不同深度的矩形槽试块,分别校准了2.5、5、7.5 MHz频率下的LCR波渗透深度,并对2.5 MHz的实验结果开展不确定度评定。结果表明:2.5 MHz换能器的LCR波检测深度10次测量的平均值为2.85 mm,与标称值的误差为0.15 mm,合成标准不确定度为0.29 mm。研究结果对于校准不同频率下换能器检测深度及提高应力测量空间分辨率具有意义,并且可为LCR波渗透深度的经验公式提供实验参考。

客车纵倾问题研究分析

以中型客车为研究对象,建立整车纵倾数学模型,对建立的模型进行仿真研究,得出研究对象在最强制动工况下的纵倾角,该纵倾角大于行业推荐值。针对研究对象提出了提高抗纵倾能力的改善措施,并进行计算验证。最后,系统总结了整车提高抗纵倾能力的相关措施。

受限条件下超大跨明挖隧道横向分幅实施方案设计研究

城市核心区明挖隧道的建设受地下管线迁改等因素的制约日趋严重,合理的分幅、分区设计对工程的可行性及进度等具有重要意义。以上海某明挖隧道工程为例,采用沿长条形基坑横向分幅施工的方法,避让了现状110kV电力排管。通过在超大跨度段反弯点附近设置纵向施工缝,实现隧道主体结构两阶段浇筑,并采用临时隔墙、临时肋板、临时牛腿及传力带等一系列措施,实现两阶段施工结构体系的转换,确保了深基坑的安全。通过结构受力分析,验证了纵向施工缝位置选取的合理性,可为今后类似工程的实施提供参考。

基于三点弦测方式的纵平测量法研究

捣固车是铁路大型养路机械的主力车型,捣固车通过起、拨道及捣固作业,修正线路的轨道几何参数,使轨道的线路方向(矢距)、横向水平(超高)、纵向高低(纵平)达到或者接近设计水平。目前,铁路大型养路机械捣固车纵平测量的方法一般均基于三点弦测方式,通常将角度变化的数据转换成高程数值,以指导捣固车作业。但在起道量较大时,此方法存在一定的偏差。文章依据测量传感器设计方案及弦线在传感器摆杆作用位置带来的偏差进行理论分析和研究,并推荐一种测量传感器摆杆前置的最优理论模型。

基于纵横向多速度融合的高速列车测速精度研究

针对现有高速列车速度控制多数存在的测速误差大、运行效率偏低等问题,提出一种纵横向多速度融合测速方法.首先,通过叠加式采样读取4路速度传感器的测速数据,采用联邦卡尔曼滤波算法对4路测速值分别进行纵向融合滤波,并采用衰减记忆法优化该算法存在的滤波发散问题,得到4路纵向融合速度值.其次,对4路纵向融合速度值进行置信距离可靠性判别,确定有效融合速度值数量,排除传感器故障影响.再次,采用优化的贝叶斯数据融合算法对有效纵向融合速度值进行横向多速度融合.最后,对所提算法进行仿真,完成对仿真结果的分析和比较.研究结果表明:基于衰减记忆法的联邦卡尔曼滤波算法的纵向融合速度平均误差为0.6696 km/h,纵横向多速度融合方法的融合速度平均误差为0.3928 km/h,平均测速精度有较大的提升.