Echo recognition and correction for guided wave radar level based on adaptive LMS

The radar echo signal of non-stationary and singular points usually contains false echoes,which affects the recognition and measurement of liquid level echo signal.In order to eliminate false echo interference and improve the recognition and measurement accuracy of the liquid level gauge,a method of echo recognition and correction based on adaptive least mean square(LMS)is proposed.The short-time amplitude function and short-time zero crossing rate function are combined to recognize the echo signal.The weight vector iteration and updating weight coefficients are obtained by LMS method.The echo signal is recognized and the false echo interference is suppressed.The experimental results show that the level echo signal can be accurately recognized by this method,and level measurement accuracy can reach0.47%F.S.Compared with other denoising methods,adaptive LMS can keep the signal singularity characteristics while suppressing the noise.Moreover,it has better robustness.

Gravitational wave echoes from strange quark stars in the equation of state with density-dependent quark masses

According to the recent studies,the gravitational wave(GW)echoes are expected to be generated by quark stars composed of ultrastiff quark matter.The ultrastiff equations of state(EOS)for quark matter were usually obtained either by a simple bag model with artificially assigned sound velocity or by employing interacting strange quark matter(SQM)depicted by simple reparameterization and rescaling.In this study,we investigate GW echoes with EOSs for SQM in the framework of the equivparticle model with density-dependent quark masses and pairing effects.We conclude that strange quark stars(SQSs)can be sufficiently compact to possess a photon sphere capable of generating GW echoes with frequencies in the range of approximately 20 kHz.However,SQSs cannot account for the observed 72 Hz signal in GW170817 event.Furthermore,we determined that quark-pairing effects play a crucial role in enabling SQSs to satisfy the necessary conditions for producing these types of echoes.

The Image Conversion in Optical Echo-Holography by External Electromagnetic Standing Waves

The recording and playback of information using a reverse stimulated photon—echo hologram when exposed to the recording medium pulse of non-resonant electromagnetic standing wave was considered. It was shown that the spatial intensity distribution in stimulated echo hologram response depended on the electric field intensity of non-resonant standing wave that allowed controlling by a reproducible image.

Wave Intensity技术对高血压患者左心室收缩功能和颈动脉血管的研究

目的:探讨WI技术评价高血压患者左心室收缩功能和颈动脉血管的临床应用价值。方法:对56例高血压患者和50例健康志愿者采用高频线阵探头对颈动脉进行检测,应用echo-doppler系统测量颈动脉血流速度和直径变化,计算WI值(W1、W2和NA)、硬化参数(β)、弹性系数(Ep)、顺应性(AC)、增大指数(AI)和脉搏波传导速度(PWVβ、PWV-WI),比较高血压组与对照组各参数值的差异。结果:高血压组与正常对照组相比较W1和W2增高,差异有统计学意义(P<0.05);高血压组β、Ep、PWVβ及PWV-WI较正常对照组增高,AC降低,且差异均有显著性意义(P<0.05)。结论:WI技术能客观准确综合地反映高血压患者左心室收缩功能和血管弹性改变,高血压患者左心整体收缩功能高于健康成人。

Characteristic-knowledge-aided spectral detection of high frequency first-order sea echo

To detect high frequency （HF） first-order sea echo spectra contaminated with ships, ionosphere interference, and other, a new characteristic-knowledge-aided detection method is proposed. With 2-D image features in range-Doppler spectrum, the trend of first-order sea echoes is extracted as indicative information by a multi-scale filter. Detection rules for both single and splitting first-order sea echoes are given based on the characteristic knowledge combining the indicative information with the global characteristics such as amplitude, symmetry, continuity, etc. Compared with the classical algorithms, the proposed method can detect and locate the first-order sea echo in the HF band more accurately especially in the environment with targets/clutters smearing. Experiments with real data verify the validity of the algorithm.

Aspect sensitivity of polar mesosphere summer echoes observed with the EISCAT VHF radar

The European Incoherent Scatter Scientific Association(EISCAT) Very High Frequency(224 MHz) Radar has been used to investigate the aspect sensitivity of polar mesosphere summer echoes(PMSE) in the period 13–15 July 2010. The aspect sensitivity of PMSE using this radar and at such a high frequency has not been previously reported. Data concerning the aspect sensitivity of PMSE were collected by traversing the antenna beam from the zenith direction, and comparing the received power. Surprisingly, as the intensity received by the oblique beam was often larger than that of the vertical beam, suggesting the presence of tilted dusty plasma layers as a potential cause, a theoretical model was developed to confirm the existence of these layers and their formation process. The experimental results and theoretical model presented help elucidate the structural properties of the possible generation mechanism of strong radar echoes in the polar summer mesosphere region.

Wave Intensity Analysis of Carotid Artery:A Noninvasive Technique for Assessing Hemodynamic Changes of Hyperthyroid Patients

This study examined the wave intensity (WI) of the carotid artery in patients with hyperthyroid in order to assess the hemodynamic changes of hyperthyroid patients.A total of 86 hyperthyroid patients without cardiac morphological changes and arrhythmia, and 80 healthy control subjects were enrolled in the study.Right common carotid artery (RCCA) was selected for ultrasonic imaging to obtain WI indices, including amplitude of the peak during early systole (W1), amplitude of the peak during late systole (W2), area of the negative wave during mid-systole (NA), interval between R wave of electrocardiogram and W1 (R-1st), interval between W1 and W2 (1st-2nd).The levels of serum thyroid hormones, consisting of free triiodothyronine (FT3), free thyroxin (FT4) and thyroid stimulating hormone (TSH), were measured in hyperthyroid patients.Echocardiographic indices including left ventricular ejection fraction (LVEF) and left ventricular fraction shortening (LVFS) were determined in each subject.The results showed that the W1, W2, NA, and (1st-2nd×HR) in hyperthyroid patients were significantly higher than those in healthy controls.There was no significant difference in LVEF and LVFS between the two groups.FT3 was correlated with W1, W2, NA, (1st-2nd×HR), pulse pressure (PP) and heart rate (HR) in hyperthyroid patients.Several abnormal waves on WI curves were present in 19 hyperthyroid patients during mid-systole.It was concluded that WI technique may prove a real-time, noninvasive, sensitive and convenient tool for assessing the cardiac function and hemodynamic alterations in hyperthyroid patients.

Preliminary Study on Active Modulation of Polar Mesosphere Summer Echoes with the Radio Propagation in Layered Space Dusty Plasma

Radar echoes intensity of polar mesosphere summer echoes（PMSE） is greatly affected by the temperature of dusty plasma and the frequency of electromagnetic wave about the radar.In this paper,a new method is developed to explain the active experiment results of PMSE.The theory of wave propagation in a layered media is used to study the propagation characteristics of an electromagnetic wave at different electron temperatures.The simulation results show that the variation tendency of the reflected power fraction almost agrees with the results observed by radar in the European Incoherent Scatter Scientific Association（EISCAT）.The radar echoes intensity of PMSE greatly decreases with the increase of the radio frequency and the enhancement of the electron temperature.

Comparison of the reaction of polar mesosphere winter echoes and polar mesosphere summer echoes to high-frequency heating in terms of modulated characteristics

In this work,for the first time,we have analyzed and compared the responses of polar mesosphere winter echoes(PMWE)and their summer counterpart,polar mesosphere summer echoes(PMSE),to high-frequency(HF)heating in terms of modulated characteristics(i.e.,backscatter intensity reduction,recovery,and overshoot).Both PMWE and PMSE observations were from the same site(Tromsφ,Norway;69.6°N,19.2°E)and radar(EISCAT[European Incoherent Scatter Scientific Association]very high frequency,224 MHz).The heating patterns of both PMWE and PMSE were found to be similar;however,PMSE was more greatly affected by HF heating.Polar mesosphere summer echoes showed recovery and overshoot more frequently than did PMWE.In addition,the mean recovery and overshoot of PMSE were greater than those of PMWE.The associated electron temperature enhancement was estimated for both PMWE and PMSE and showed that,compared with PMWE,the electron temperature enhancement was more significant in PMSE.The strong heating effects on PMSE may be due to the considerable increase in electron temperature.

Reconstruction of large complex sand-wave bathymetry with adaptive partitioning combining satellite imagery and sparse multi-beam data

Shallow marine sand waves are formed on the seabed and are widely distributed within tidal environments.However,the use of multibeam echo sounding(MBES)is costly to obtain the bathymetric mapping of large complex sand waves.Therefore,we propose a new method that employs a combination of multiangle sun glint images and sparse MBES data to achieve comprehensive bathymetric mapping of large and complex sand waves.This method involves estimating sea surface roughness,automatically extracting sand-wave crests,conducting adaptive subregion partitioning,estimating the water depth at auxiliary points,and generating digital bathymetric models.The method was employed in a case study of sand waves on the Taiwan Bank.Bathymetric mapping was implemented for large complex sand waves over an area spanning approximately 350 km~2 using multiangle sun glint images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer and MBE S data.The results show that mapped and measured water depths were well-matched;the root-mean-square error of water depths was 1.77 m,and the relative error was 5.03%.These findings show that bathymetric mapping of large complex sand waves can be effectively conducted using the new method,and as such,the workload of MBES is reduced and efficiency is improved.

应用脉冲回波的避雷线断线检测系统研究

为高效率、低成本地检测风力发电机组桨叶避雷线断线位置,设计基于脉冲回波的避雷线断线检测系统。该系统以单端行波法为原理,由信号发生模块,传感器模块,信号采集模块、控制器模块四部分构成。信号发生模块负责产生行波脉冲信号,传感器模块负责采集回波信号,信号采集模块负责将采集到的回波信号处理转化送给控制模块,控制模块负责分析回波信号,判断故障类型和故障点位置。该文对各个模块的电路和性能参数进行设计,搭建整体的检测系统。经实验验证,该系统可以精准的实现断线判断,并获得断线位置,测量误差精确到0.5 m以内。

裂纹对弹性波在混凝土中传播特性的影响研究

目的为研究混凝土中裂纹对弹性波传播特性的影响,方法采用COMSOL软件构建弹性波在不同形态混凝土裂纹中的传播数值模型,并开展带裂纹混凝土的弹性波传播试验,系统研究混凝土裂纹特征(裂纹角度、裂纹深度、裂纹距声发射源距离、裂纹数量等)与弹性波传播之间的关系。结果研究发现:数值模拟结果与试验现象吻合较好,验证了数值模型的可靠性。其中,裂纹数量和裂纹距声发射源距离的变化对回波峰值影响较大,距声发射源2 cm裂纹的回波峰值最大,为3.46×10^(6)Pa;对波速和信号损伤影响最大的因素为裂纹深度,60 mm深度裂纹损伤率高达62.14%、波速衰减至2590.674 m/s,其次为裂纹数量,信号损伤率达31.28%。基于不同裂纹特征的波速变化规律,对裂纹角度和深度的波速关系模型进行回归分析,回归曲线拟合优度较好,R^(2)均大于0.95。结论混凝土中存在的裂纹和裂纹特征对弹性波传播具有显著影响,本文研究结果为混凝土无损检测技术提供了理论支撑。

用于土壤温湿度检测的声表面波标签设计

针对土壤温湿度的并行检测提出了基于声表面波标签的解决方案。采用耦合模理论对阻抗负载型声表面波标签进行建模与仿真,得到负载反射栅回波幅值和相位随电容值变化规律。在此基础上,根据声表面波标签对土壤温湿度不同的敏感机理,设计了一种双通道双边带标签结构,采用时分多址的方法解决了对不同深度层级土壤同时检测时存在的回波信号混叠问题。通过回波信号的相位和幅值比实现了土壤温湿度检测,结合矢量网络分析仪和阅读器对标签进行测试,测试结果表明了标签的有效性。

基于容器内壁反射能量变化的液位超声检测方法

置于液罐外壁液面高度附近处的收发探头发射声束透过罐壁在其内壁产生一投影面积,提出利用液体在该投影面积中的占比与能量之间的关系来检测液位的变化。计算探头接收到的回波信号能量,该能量值与液面高度成反比,由此定征液面位置。搭建试验系统,采集回波信号,将算得的接收能量值代入占比面积表达式得到相对探头的液面位置。计算的液面位置与实际液面位置相吻合,两者的误差仅小于2.465 mm。有限元仿真计算也验证了探头接收能量与液位变化的关系。

基于高频雷达回波谱多特征融合的浪高反演算法

高频地波雷达海洋回波谱的Bragg峰和二次谐波峰中,均蕴含着浪高信息,因此发展出了基于Bragg峰功率(Power of Bragg Peak,PB)、二次谐波峰与Bragg功率比(Power Ratio of Second Harmonic Peak to Bragg Peak,RSB)、双频Bragg峰功率比(Power Ratio of Dual Frequency Bragg Peak,RDB)等浪高反演算法。然而,三种算法均无法实现不同海况、不同距离下浪高的精确反演。本文研究发现,PB算法适用于低海况,RSB算法在近距离高海况下表现良好,而RDB算法适用于远距离测量,即三种算法高性能测量区间存在强互补性。在此基础上,本文提出了一种基于多特征(PB、RSB和RDB)融合的浪高反演算法,其中采用反向传播(Back Propagation,BP)神经网络作为特征融合器。实验表明:本文算法在测量精度、波高适应范围、距离适应范围上均优于现有波高反演算法。

基于毫米波云雷达的两次冰粒过程对比分析

利用Ka波段毫米波雷达、风廓线雷达资料和再分析数据,对大兴机场两次出现冰粒的降水天气过程进行了对比分析。结果表明:(1)环流形势都是高空槽过境,中层有西南急流且水汽充沛,但近地层的大气环境差异较大。(2)两次过程云顶高度超过-10℃线高度,是冰相融化机制,大气垂直环境并非都为“冷—暖—冷”的特点,也存在上冷下暖的情况。(3)降水粒子的非单一性造成线性退极化比L dr在0℃层以下的值不仅大于非冰粒阶段,更远大于0℃层之上,其特征不受降水强度影响。(4)反射率因子表现为0℃层及以下强度明显强于0℃层之上,主要由降水强度引起变化,其特征和粒子相态相关性较小。(5)两次过程中粒子的下落速度和速度谱宽特征呈相反趋势,在冰粒阶段其特征都处于雨雪间过渡数值的范围。同时风廓线雷达的冰粒阶段垂直速度特征也和毫米波雷达速度特征相符合。

Ka波段毫米波云雷达对青藏高原东南缘降水回波的分析

利用丽江站新建的Ka波段毫米波云雷达获得的高时间分辨率的垂直观测资料,结合同址的地面自动气象站和雨滴谱的分钟数据、常规探空数据和附近C波段天气雷达的强度回波,分析了两次降水过程前后云雷达反射率因子Z、径向速度V_(r)、速度谱宽S_(w)的垂直变化规律。分析表明:在发生弱降水时,云雷达Z在垂直方向的变化不明显;但V_(r)、S_(w)值在0℃层稍低位置有一个明显的分界层(融化层),粒子通过融化层后V_(r)、S_(w)都是快速变大,这个变化主要是粒子的相态由固态变成液态引发的,可以通过V_(r)、S_(w)突变值的位置来识别0℃层亮带的高度。从C波段天气雷达回波强度、剖面图及云雷达位置的时间-高度图看,对毛毛雨和小雨的回波,强度和高度差异比较明显,毛毛雨比小雨回波高度低、强度弱,与云雷达相比C波段雷达对高一些的云观测不到,对距离较远的弱降水回波无法观测到;由于相同粒子对不同波长电磁波的散射不一样,造成两种雷达垂直方向观测到的Z变化不同。对比弱降水回波,云雷达在强降水时:Z出现缺口;V_(r)在0℃层以上有较大的正值(弱降水的V_(r)都是负值);在0℃层以上S_(w)变得更大(弱降水时S_(w)在0℃层以上值较小,在0℃层以下较大)。在强降水时,从C波段雷达回波强度时间-高度图看,垂直方向回波强度变化明显,在同一时刻回波强度由地面向空中的变化是逐渐减小的;不同时间同一高度层强度也有变化,云雷达雨衰缺口时段回波明显强于其他时段。在个例分析中,发生分钟降水量在0.3 mm以下强度的降水,云雷达可以观测到完整的云信息;发生分钟降水量在0.5 mm以上强度的降水,云雷达会有严重的雨衰,无法观测到完整的云信息。

复杂环境中海上通信局部通信链路中断预测

由于海上环境复杂且易受到日凌现象的影响,通信链路容易中断。为了及时恢复正常通信,提出复杂环境中海上通信局部通信链路中断预测方法。分析复杂环境中海上局部通信链路中断原因,构建基于波浪滑翔器的通信链路中断预测框架,在该框架中计算波浪滑翔器链路中断回波时间,确定中断回波信号所在的位置,从而得到海上通信局部通信链路中断预测结果。由实验结果可知,该方法预测在暴雨环境的1.0~1.3 s、2.0~2.7 s、暴风环境的2.0~2.5 s出现接收信号丢失情况,与实际情况一致,说明该方法的预测结果精准。

工程地质勘察钻探钻柱长度的低功率主动探测方法

近年来,随着城市基础建设的快速发展和数字技术、智慧城市的兴起,对场地和地基稳定性评价、工程勘察钻孔资料质量提高等问题提出了新的要求。基于此,课题组提出了一套钻孔参数智能监测系统。该系统仅需在钻柱顶端安装一个仪器,就能够实现钻机平面定位、钻孔深度测定和地层随钻测井。探讨了钻柱波传播动力学方程、钻柱多次波成像、单边反褶积自相关回波探测方法等工程勘察钻柱长度的低功率探测方法;提出了一种低功率探测方案,并确定了最优频带范围和适当的波列长度;明确了不同地质钻探技术应用的要点。该钻孔参数智能监测系统和低功率主动探测方法将有效提高地基基础工程勘察效率,优化工程勘察钻孔资料质量,并为城市基础建设和智慧城市发展做出积极贡献。