A Recursive Method of Time-Frequency Analysis for the Signal Processing of Flutter Test with Progression Variable Speed

Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method.

Model tests on XCC-piled embankment under dynamic train load of high-speed railways

Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.

TEST METHOD OF HIGH-SPEED ON-OFF VALVE DYNAMIC CHARACTERISTICS

According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.

基于Speedtest用户测速数据的运营商网络感知对标分析

运营商网络能力对标分析有利于指导运营商的网络发展方向,实现对网络质量的宏观预警。但是,目前市场上缺乏有效真实、公开的数据用于分析运营商网络能力感知,因此无法通过数据手段深入分析运营商网络现状及发展趋势。第三方Speedtest测速平台上的"China Telecom Wuhan Branch"和"Wuhan Hello 5G"两个测速节点,仅2020年累计为各地区用户提供测速服务336万余次,其中为武汉用户提供服务超89万次,覆盖了武汉三家主流运营商的固网宽带、4G和5G用户。基于Speedtest测速平台上的数据,文章搜集并修正了2020年武汉运营商A、运营商B和运营商C的用户测速数据,对比分析了三家运营商固网宽带、4G网络和5G网络的用户体验带宽。

Vibration test of micro machined gyroscope based on high speed photography and SURF

Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.

应用Test.Lab进行高速车体线路模态试验

针对高速列车的振动问题,通过线路模态试验进行车体结构模态参数研究,采用LMS test.lab振动噪声测试系统进行数据采集和分析后处理。基于环境激励模态试验方法及模态参数识别理论,运用PolyMax模态提取法,获取了车体的前三阶弹性模态参数和对应的模态振型,为车体结构优化设计提供依据。

基于RHtest方法对新疆北部风区近50 a风速资料的均一性研究

利用RHtest提供的两种检验方法:惩罚最大T检验(The Penized Maximal T Test,PMTT)和惩罚最大F检验(The Penized Maximal F Test,PMFT),对新疆大风区域13个国家级气象站点建站至2014年逐年平均风速资料进行了均一性检验和订正;通过在新疆地区特定环境下对该两种误报率分布相对均匀且微小偏移检测能力较高的方法进行评估,找出每种方法在新疆地区实际应用当中的适用性,最终通过订正改善新疆风要素年值历史序列的均一性,结果表明:(1)站址迁移、仪器换型、测风手段变化及台站环境变化等非气候变化因素均对13个待检站点年平均风速序列的均一性产生显著影响,其中仪器换型造成的影响尤为突出。(2)当参考站均一性较好时,PMTT方法检测结果与台站元数据一致性较好,反之则存在虚假跳变点或漏检。(3)PMFT方法因为不依靠参考站,能很好的弥补新疆大风区域站点稀疏、参考站点筛选困难和元数据不完整等弊端,该方法对迁站和仪器换型的检测能力较强。(4)数据订正后,总体变化趋势没有大的改变,呈现下降趋势,符合风要素在全国范围的总体变化趋势,数据的均一性得到很大改善。

基于片上PLL时钟的at-speed测试设计

深亚微米制造工艺的广泛采用及越来越高的芯片工作频率,使得具有时序相关的芯片缺陷数量不断增加,at-speed测试成为对高性能电路进行测试的必要技术。文章首先介绍了at-speed测试的故障模型,以及具体测试方法,然后详细介绍了采用PLL时钟作为at-speed测试时钟时,一款芯片的at-speed测试实现方案,最后采用Fastscan及TestKompress对整个设计进行了测试向量自动生成及向量压缩。实验结果表明此方案可行,采用TestKompress进行设计更符合目前的设计需求。

Beep test评估11～15岁少年游泳运动员有氧能力的效度研究

目的:评估现有通过beep test估算VO_2max的公式在我国少年游泳运动员中的适用性,以及能否建立预测准确性更高的公式。斱法:28名男子和25名女子少年游泳运动员,年龄11~15岁,先进行beep test获得最快折返跑速度,随后通过递增负荷跑台测试获得VO_2max测试值。通过逐步回归法建立新的VO_2max估算公式,计算分别通过Léger、Barnett(a)、Barnett(b)、Matsuzaka和新公式的VO_2max估算值,采用差值比较、相关分析、误差分析和一致性分析进行各估算值的效度检验。结果:1)通过Léger、Barnett(a)、Barnett(b)和Matsuzaka公式得出的VO_2max估算值均显著低于测试值,%Error为(68.4~90.0)%,与测试值间的差值为7.63~9.02ml/kg/min,一致性界限为0.49~17.55 ml/kg/min。2)VO_2max的新预测公式为VO_2max=61.435+3.211S-2.003BMI-5.189×G(r=0.715,P=0.004,SEE=2.25 ml/kg/min),其中G表示性别(男=0,女=1),S为最快折返跑速度。3)新公式得出的VO_2max估算值与测试值无显著差异,%Error下降至16.1%,与测试值间的差值减少到0.02±3.09 ml/kg/min,一致性界限为-6.03~6.08 ml/kg/min。结论:beep test适用于我国少年游泳运动员有氧能力的评估,但现有VO_2max估算公式的效度水平一般。基于本研究所选取群体新建的估算公式有效提高了预测的准确性。

如何用OCC电路实现at-speed测试

集成电路制造技术的进步带来了越来越小的工艺尺寸,与此同时也带来了更多的和速度相关的故障。这些故障可以是由于工艺的偏差、不纯净的材料以及各种灰尘导致的。对于目前越来越多的高速芯片而言,即使一个很小的延迟故障也会影响芯片的正常工作频率,通常的由测试机提供慢速时钟的测试方法无法覆盖由于高速而带来的故障,由于这些原因,at-speed测试对于高速大规模集成电路变得至关重要。

基于LMS．Test．Lab的某车型排气噪声问题分析

某试验车型在怠速和N挡全油门工况下排气口噪声，对车内噪声影响很大，怠速排气口和车内55Hz对车内整体声压级贡献较大。应用比利时LMS公司的Test．Lab对上述问题进行了实验测试分析，通过更换不同状态的样件进行对比测试。结果表明，N挡全油门加速行驶中，排气口噪声2阶对车内噪声2阶贡献很大，降低排气口噪声2阶声压级对改善车内噪声有显著效果。

Method of measuring rotation speed of high spinning projectile based on plane magnetic induction coil

For the test of rotation speed of high spinning projectile, the general formula of the motional electromotive force （MEMF） of planar magnetic induction coil （PMIC） is derived in case of 3D rotation in a stable magnetic field. Under a reasona-ble assumption, the MEMF of PMIC is simplified after the aforementioned general formula is used to calculate high spinning PMIC in the geomagnetic field environment. The determination approach of half-cycle is discussed and the method of rotation speed test is studied, and a test is conducted in the paper. The rotation speed curve obtained by the approach in this paper is consistent with the curve by telemetry.

On Unobservability of One-Way Speed of Light

In this paper we recall the different definitions of simultaneity, the coordinate time interval and the velocity. It is emphasized that the above second two definitions depend on the simultaneity. We review the test theories on special relativity. It is shown that anisotropy (if possible) of one-way speed of light has not any ef- fects in the physical experiments. Therefore anisotropy of one-way speed of light cannot be determined by the experiments, except if an absolute (standard) simultaneity would be found.

Design of Fin-propeller Test Set-up and Analysis of Roll Stabilization Ability

Presents the fin-propeller test set-up to solve the problem of roll stabilization with ships in full speed range, withwhich, tests were run in water rank for acquisition of data, and concludes from data acquired that the fin-propeller test set-up produces more lift than simple fin, and provides lateral thrust as well, and it is therefore an effective roll stabilization devicefor ships in full speed range.

坡度、疲劳和能见度对隧道火灾人员疏散速度耦合影响研究

为探究隧道火灾复杂环境对人员疏散速度的耦合影响规律,首先对坡度、人体疲劳及能见度3种因素开展疏散试验,获得各单因素对疏散速度的影响规律,并拟合出疏散速度变化公式;其次基于各单因素下速度变化公式,提出多因素耦合影响下隧道火灾人员疏散速度计算方法。研究结果表明:人员上坡疏散速度与坡度线性负相关,下坡疏散速度规律性较弱;长距离疏散时因疲劳导致速度逐渐衰减,在2 km疏散过程中速度衰减峰值达47%,疲劳导致的速度衰减比例与疏散距离线性正相关;能见度较高时其对疏散速度的影响效果不显著,能见度降低至10 m内后开始对疏散速度产生负面作用。研究结果可为隧道疏散设施设计、相关标准规范制定等提供参考,同时为传统疏散速度取值方法提供1个新思路。

Model Test Study of Dynamic Ice Force on Compliant Conical Structures

To study ice-induced vibration of a compliant conical structure, a series of model tests were performed from 2004 to 2005. In the tests, the ice sheet before the compliant conical structure was found to fail in two-time breaking. From 2005 to 2006, this type of ice failure was studied through more groups of tests. The tests show that two-time breaking is the typical failure of ice before steep conical structures, and is controlled by other factors at the same time, such as ice speed and the angle of the cone.

均匀流场下平单轴光伏支架扭转气动失稳特征试验研究

由于发电量明显高于固定式光伏系统,平单轴光伏发电系统近些年得到了广泛的应用。平单轴光伏支架由于扭转刚度较低,在大风天气下容易出现扭转气动失稳现象,从而造成支架结构破坏。为了进一步深入了解该振动的发生条件和机理,本研究通过节段模型测振风洞试验研究结构自振频率、倾角、阻尼等参数对扭转气动失稳的影响,分析了气动阻尼和气动刚度随着风速和倾角的变化规律。研究表明,平单轴光伏支架的扭转气动失稳表现出较强的气动耦合效应,气动阻尼和气动刚度是影响平单轴光伏支架气动失稳的重要参数,对风速和倾角的变化较为敏感,该失稳现象具备自激振动的特点;扭转刚度的提高在某些倾角下可以有效地限制振幅,同时可提高结构在各倾角的临界风速;扭转气动失稳的倾角范围为-15°~20°,0°倾角附近临界风速较高,若采用小倾角进行保护时,建议将大风保护角度设为0°。

A Study on the Maneuvering Motion of a Low Speed Submersible

In this paper, the maneuvering characteristics of a low speed submersible are investigated. First, the captive model tests are carried out to obtain the hydrodynamic forces acting on the submersible using a Planar Motion Mechanism (PMM). For the hydrodynamic forces within a wide range of attack angles, the hydrodynamic coefficients which are usually used in the conventional maneuvering motion are quite difficult to be applied. In this case, a Fourier series is adopted to represent the hydrodynamic forces and it fits the experimental data well. Then, based on the experimental results the simulation calculations are made to predict some of the maneuvering performance of the low speed submersible.