Application of clan member signal method in structural damage detection

It is well known that in most cases, a reference is necessary for structural health diagnosis, and it is very difficult to obtain such a reference for a given structure. In this paper, a clan member signal method （CMSM） is proposed for use in structures consisting of groups （or clans） that have the same geometry, i.e., the same cross section and length, and identical boundary conditions. It is expected that signals measured on any undamaged member in a clan after an event could be used as a reference for any other members in the clan. To verify the applicability of the proposed method, a steel truss model is tested and the results show that the CMSM is very effective in detecting local damage in structures composed of identical slender members.

Using Pearson’s System of Curves to Approximate the Distributions of the Difference between Two Correlated Estimates of Signal-to-Noise Ratios: The Cases of Bivariate Normal and Bivariate Lognormal Distributions

Background: The signal-to-noise ratio (SNR) is recognized as an index of measurements reproducibility. We derive the maximum likelihood estimators of SNR and discuss confidence interval construction on the difference between two correlated SNRs when the readings are from bivariate normal and bivariate lognormal distribution. We use the Pearsons system of curves to approximate the difference between the two estimates and use the bootstrap methods to validate the approximate distributions of the statistic of interest. Methods: The paper uses the delta method to find the first four central moments, and hence the skewness and kurtosis which are important in the determination of the parameters of the Pearsons distribution. Results: The approach is illustrated in two examples;one from veterinary microbiology and food safety data and the other on data from clinical medicine. We derived the four central moments of the target statistics, together with the bootstrap method to evaluate the parameters of Pearsons distribution. The fitted Pearsons curves of Types I and II were recommended based on the available data. The R-codes are also provided to be readily used by the readers.

Single Phase-to-Ground Fault Line Identification and Section Location Method for Non-Effectively Grounded Distribution Systems Based on Signal Injection

A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special diagnostic signal current is injected into the fault distribution system,and then it is detected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section.The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.

Totally Coded Method for Signal Flow Graph Algorithm

After a code-table has been established by means of node association information from signal flow graph, the totally coded method (TCM) is applied merely in the domain of code operation beyond any figure-earching algorithm. The code-series (CS) have the holo-information nature, so that both the content and the sign of each gain-term can be determined via the coded method. The principle of this method is simple and it is suited for computer programming. The capability of the computer-aided analysis for switched current network (SIN) can be enhanced.

Probabilistic small signal stability analysis of power system with wind power and photovoltaic power based on probability collocation method

Recently, with increasing improvements in the penetration of wind power and photovoltaic power in the world, probabilistic small signal stability analysis(PSSSA) of a power system consisting of multiple types of renewable energy has become a key problem. To address this problem, this study proposes a probabilistic collocation method(PCM)-based PSSSA for a power system consisting of wind farms and photovoltaic farms. Compared with the conventional Monte Carlo method, the proposed method meets the accuracy and precision requirements and greatly reduces the computation; therefore, it is suitable for the PSSSA of this power system. Case studies are conducted based on a 4-machine 2-area and New England systems, respectively. The simulation results show that, by reducing synchronous generator output to improve the penetration of renewable energy, the probabilistic small signal stability(PSSS) of the system is enhanced. Conversely, by removing part of the synchronous generators to improve the penetration of renewable energy, the PSSS of the system may be either enhanced or deteriorated.

A novel wavelet method for electric signals analysis in underwater arc welding

Electric signals are acquired and analyzed in order to monitor the underwater arc welding process. Voltage break point and magnitude are extracted by detecting arc voltage singularity through the modulus maximum wavelet （MMW） method. A novel threshold algorithm, which compromises the hard-threshold wavelet （HTW） and soft-threshold wavelet （STW） methods, is investigated to eliminate welding current noise. Finally, advantages over traditional wavelet methods are verified by both simulation and experimental results.

Correction of cosine oscillation to the improved correlation method of estimating the amplitude of gravitational background signal

In the measurement of G with the angular acceleration method,the improved correlation method developed by Wu et al.（Wu W H,Tian Y,Luo J,Shao C G,Xu J H and Wang DH 2016 Rev.Sci.Instrum.87 094501） is used to accurately estimate the amplitudes of the prominent harmonic components of the gravitational background signal with time-varying frequency.Except the quadratic slow drift,the angular frequency of the gravitational background signal also includes a cosine oscillation coming from the useful angular acceleration signal,which leads to a deviation from the estimated amplitude.We calculate the correction of the cosine oscillation to the amplitude estimation.The result shows that the corrections of the cosine oscillation to the amplitudes of the fundamental frequency and second harmonic components obtained by the improved correlation method are within respective errors.

Application of quartz crystal nanobalance in conjunction with a net analyte signal based method for simultaneous determination of leucine, isoleucine and valine

The aim of the present investigation was to develop a biosensor for the detection of amino acids, Leucine, Isoleucine and Valine based on a quartz crystal nanobalance. leucine (Leu), isoleucine (Ile), and valine (Val) were selectively determined by quartz crystal nanobalance (QCN) sensor in conjunction with net analyte signal (NAS)-based method called HLA/GO. An orthogonal design was applied for the formation of calibration and prediction sets including Leu, Ile and Val compounds. The selection of the optimal time range involved the calculation of the net analyte sig-nal regression plot in any considered time window for each test sample. The searching of a region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of PRESS value was carried out by applying a moving window strategy. On the base of obtained results, the differences on the adsorption profiles in the time range between 1 and 300 s were used to determine mixtures of compounds by HLA/GO method. The results showed that the method was successfully applied for the determina-tion of Leu, Ile and Val.

A FAST SEARCH METHOD BASED ON THE STATISTICAL PROPERTIES OF SIGNAL

The concepts of ordered code-book and the priority of code-vector are proposedin this paper.The statistical properties of a signal are investigated through its coded sequence.Experimental results are presented which provide some insight into the statistical properties ofvector quantized sequences.Based on the given concepts and experimental results,a fast searchmethod for the vector quantization of correlated information sources,such as Gauss-Markovsources,is proposed and has shown its efficiency in simulation results.

A Critical Eigenvalues Tracing Method for the Small Signal Stability Analysis of Power Systems

The continuation power flow method combined with the Jacobi-Davidson method is presented to trace the critical eigenvalues for power system small signal stability analysis. The continuation power flow based on a predictor- corrector technique is applied to evaluate a continuum of steady state power flow solutions as system parameters change;meanwhile, the critical eigenvalues are found by the Jacobi-Davidson method, and thereby the trajectories of the critical eigenvalues, Hopf bifurcation and saddle node bifurcation points can also be found by the proposed method. The numerical simulations are studied in the IEEE 30-bus test system.

大地电磁资料在砂岩型铀矿地质体边界识别中的数值模拟研究

随着砂岩型铀矿勘查深度的逐渐增大,对大地电磁资料在砂体、断裂等地质体准确识别方面的要求也越来越高。为此,文章建立了多个典型模型,采用数值模拟手段,开展大地电磁资料在砂岩型铀矿地质体边界识别方面的研究。通过利用倾子响应参数、反演电阻率参数,并采用求导法、水平梯度法、解析信号法和Theta Map法进行处理,凸显了地质体的边界特征,并进行了对比分析。研究结果表明,倾子资料经处理后能够较好地识别地质体横向边界,求导方法在地质体纵向顶底界面识别中具有较大的指导意义,Theta Map法能够较好地识别地下介质的边界。然而,在多层地质体的情况下,Theta Map法的边界识别效果不如单层地质体效果好。本研究结果为大地电磁资料准确识别地质体提供了思路和方法。

基于FPGA的自滑动同步法TFT-LCD屏TCON的实现

不同厂家、不同尺寸、不同分辨率的TFT-LCD屏与时序控制器TCON的接口不同,对应不同的差分信号格式。为了适应不同屏的图像显示,需要一种可编程的时序控制器TCON。通过在FPGA芯片上采用自滑动同步法,实现了TFT-LCD屏的TCON系统。该系统从视频处理主板输出的差分信号中提取视频数据,提出通过自滑动同步法使之与同步控制信号对齐;将提取的视频数据转换为源驱动器的输入信号,即mini-LVDS或RSDS格式的差分信号,同时产生门驱动器的时序信号;由源驱动器和门驱动器输出的信号驱动TFT-LCD屏显示图像信号。为了测试TCON的性能,使用两块FPGA电路板进行实验。一块FPGA电路板实现TCON时序控制器;另一块作为TCON的输入测试信号源,用于测试所设计的TCON性能。实验结果显示,所设计的TCON能够从LVDS视频差分数据中正确解析出视频数据,并转换为屏的源驱动器和门驱动器信号,驱动TFT-LCD屏显示视频信号。通过对比分析可知,使用自滑动同步法具有资源消耗少,功耗较低等优点。

基于FAERS数据库对塞来昔布不良事件信号的分析

目的基于美国食品药品监督管理局(FDA)不良事件报告系统(FAERS)数据库,挖掘塞来昔布的不良事件(ADE)信号,为临床安全用药提供参考。方法采用报告比值比法、综合标准法和信息成分法挖掘FAERS数据库2004年第1季度至2022年第4季度的报告数据。结果ADE报告人主要为45岁以上人群,以女性居多,上报国家主要是美国。获得塞来昔布ADE报告37020例,涉及ADE 4068种,挖掘ADE信号406个,经筛选后得到有效信号285个,累及23个系统-器官(SOC)。根据信号强度,排名前5位的信号分别为:食管纤维化、与性活动有关的原发性头痛、脑血管疾病、胃肠道腺癌、心血管障碍。说明书未载明的ADE信号主要有:视网膜静脉血栓形成、失明、健忘、过敏性休克等。结论所得ADE信号基本与说明书一致;信号提示塞来昔布ADE主要集中在心脏疾病、神经系统疾病、免疫系统疾病、胃肠道疾病等;说明书黑框警告心血管血栓事件,胃肠道出血、溃疡和穿孔均有相关ADE信号检出。在使用该药时,除注意患者心脑血管、胃肠道不适症状以外,还应关注患者视网膜病变,并做好相关监护,以保证临床用药的安全。

变压器绝缘缺陷放电发展特性及检测方法研究现状及展望

变压器爆燃事故的发生大多源于其内部绝缘缺陷的局部放电,并逐渐发展至火花放电和电弧放电,造成巨大的经济损失。研究内部放电信号特征及其快速检测方法对保障电力变压器安全可靠运行具有重要意义。国内外学者围绕变压器内部绝缘缺陷放电特性及检测方法开展了大量研究工作。为此从局部放电、火花放电和电弧放电3个阶段综述了相关研究成果,对不同放电发展阶段的脉冲电流、电磁波、声、光以及化学产物等理化特性进行了总结分析,同时概述了基于不同信号的检测方法和对检测设备的要求,并对比了不同检测方法的优缺点,最后提出了对于变压器绝缘缺陷放电发展检测的研究展望。该文对进一步深入研究油中放电信号特征提取、快速检测以及变压器主动保护技术具有指导意义。

基于海上观测值的舰船导航信号滤波方法研究

为弥补单一数据源不足,并在不同航行环境下,确保导航信号的稳定性与可靠性,研究基于海上观测值的舰船导航信号滤波方法。在舰船导航中,基于纬度、经度、海流分量、航速、航向和角速度变化量等观测值建立了导航信号模型。利用改进量子粒子群优化算法,优化卡尔曼滤波算法的观测噪声协方差矩阵,以及舰船导航信号模型噪声协方差矩阵,得到改进卡尔曼滤波算法,结合舰船导航信号模型,获取舰船导航信号滤波估计结果。实验结果证明,该方法可有效滤波估计舰船导航信号,提升舰船导航信号质量;该方法改进后的舰船导航轨迹与期望轨迹非常接近,即改进后该方法的舰船导航信号滤波效果较优。

基于四电极多频率扫描的生物阻抗法人体成分测试仪设计

生物阻抗包含丰富的人体病理和生理电信号,可以作为医务人员准确判断病人症状和治疗疾病的主要依据。基于此,提出一种基于Cole-Cole理论的人体多种参数测量系统。构建人体阻抗模型,通过碳纳米材料电极对人体阻抗进行采集分析,得到人体的各种成分参数。通过信号发生电路产生注入人体的低频信号,利用幅度检测电路检测流经人体电流产生的电压,采用分段检测法测得人体不同分段的阻抗信息;信号经放大电路输入RT1052微处理器,对数据和人体成分参数相关性进行分析,得到人体各种成分参数并显示测量结果。通过对系统进行测试分析,得出所设计系统能够准确地对人体蛋白质、脂肪等参数进行测量,误差范围可以控制在5%以内,具有很好的应用前景。

Signal-to-noise ratio comparison of angular signal radiography and phase stepping method

Grating-based x-ray phase contrast imaging has the potential to be applied in future medical applications as it is compatible with both laboratory and synchrotron source. However, information retrieval methods are important because acquisition speed, scanning mode, image quality, and radiation dose depend on them. Phase-stepping （PS） is a widely used method to retrieve information, while angular signal radiography （ASR） is a newly established method. In this manuscript, signal-to-noise ratios （SNRs） of ASR are compared with that of PS. Numerical experiments are performed to validate theoretical results. SNRs comparison shows that for refraction and scattering images ASR has higher SNR than PS method, while for absorption image both methods have same SNR. Therefore, our conclusions would have guideline in future preclinical and clinical applications.

UHF波段无源雷达低仰角波瓣分裂现象分析及校正方法

针对低频段无源雷达低仰角远程预警探测时波瓣分裂影响俯仰向探测空域覆盖的问题,提出了一种波瓣分裂校正方法.首先分析了波瓣分裂形成原因和影响因素;然后基于阵列流型拟合思想,提出了一种利用最小二乘法求解变换矩阵的校正方法;最后通过仿真分析了角度量化间隔、角度变换区间对校正误差的影响,验证了校正方法的有效性.这对改进基于数字广播电视信号的无源雷达性能提供了参考.

一种优化高频注入法PMSM无位置传感器控制

传统高频信号注入法采用带通滤波器分离信号,龙伯格观测器利用所得信号计算出转子位置,考虑到带通滤波器设计复杂且使高频信号幅值产生衰减,同时龙伯格观测器需要电机转矩反馈、转动惯量等多种机械参数,这些因素干扰电机控制系统的动态性能等。采用基于低通滤波器的信号分离方法可在不损失高频信号得到含转子位置信号;利用电机的转速、转子位置角以及其角加速度之间关系构建扩张状态观测器,可以避免测量负载转矩和对不确定扰动的估计。仿真及实验结果表明,该优化策略能够使电机在低速控制时稳定运行,且具有更好的低速动态性能。