Effect of swimming training on neural microcirculation in rats with sciatic nerve compression A study based on laser Doppler flowmetry

Microcirculation of the peripheral nerve is necessary for neural growth and regeneration. However, technical limitations have limited studies in this area. The few studies conducted have concerned active exercise effects on microcirculation of the peripheral nerve. Using an animal experiment, this study evaluated the effect of swimming training on microcirculation of injured peripheral nerve by laser Doppler flowmetry. The results showed that the blood vessel at the distal end of the peripheral nerve was the main blood supply for the nerve, and the internal blood supply for the nerve had strong compensatory ability. Swimming training promoted the functional recovery of rats with sciatic nerve injury and the regeneration of myelin sheath and blood vessels, but had no impact on neural blood flow.

Evaluation of microvascular reactivity with laser Doppler flowmetry in chronic kidney disease

Cardiovascular diseases are the major causes of mortality in patients with chronic kidney disease(CKD).The complex process of accelerated athero- and arteriosclerosis in CKD is associated with this phenomenon,where endothelial dysfunction(ED) is one of the initial steps. Hence, the early diagnosis of ED can potentially lead to early interventions which could result in a better outcome for these patients. Several methodologies have been developed for the diagnosis of ED. Laser Doppler flowmetry(LDF) enables us to study the microcirculation continuously in a non-invasive manner. In our review we would like to focus on different tests developed for LDF, like postocclusive reactive hyperaemia,local heating, iontophoresis, microdialysis or analysis of flowmotion. We would also like to summarize the available data in CKD with these methodologies to enlighten their perspectives in the clinical use on this patient population.

Laser Doppler Vibrometer Without Directional Ambiguity Using Rectangular Phase Grating

The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.

Investigation on Eccentric Agitation in the Stirred Vessel Using 3D-Laser Doppler Velocimeter

The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.

Mucosal blood flow measurements using laser Doppler perfusion monitoring

Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insuff iciency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of pe- ripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM) is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastroin-testinal (GI) tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results.

DETECTION ON MICRO-DOPPLER EFFECT BASED ON LASER COHERENT RADAR

A laser coherent detection system of 1550 nm wavelength was presented, and experimen- tal research on detecting micro-Doppler effect in a dynamic target was developed. In the study, the return signal in the time domain is decomposed into a set of components in different wavelet scales by multi-resolution wavelet analysis, and the components are associated with the vibrational motions in a target. Then micro-Doppler signatures are extracted by applying the reconstruction. During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrationM signals and estimate the motion parameters successfully. The experimental results indicate that the system can effectively detect micro-Doppler information in a moving target, and the tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analy- sis and time-frequency analysis.

Doppler shift of a laser pulse beam scattered by a rotating cone and cylinder

Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense.

2-D Statistical Damage Detection of Concrete Structures Combining Smart Piezoelectric Materials and Scanning Laser Doppler Vibrometry

In the present study a new structural health monitoring (SHM) technique isproposed as well as a new damage index based on 2-D error statistics. The proposedtechnique combines the electromechanical impedance technique (EMI) which is based onthe use of piezoelectric Lead Zirconate Titanate (PZT) patches and Scanning LaserDoppler Vibrometry (SLDV) for damage detection purposes of concrete structures andearly age monitoring. Typically the EMI technique utilizes the direct and inversepiezoelectric effect of a PZT patch attached to a host structure via an impedance analyzerthat is used for both the actuation and sensing the response of the PZT-Host structuresystem. In the proposed technique the attached PZTs are actuated via a function generatorand the PZT-Host structure response is obtained by a Scanning Laser DopplerVibrometer. Spectrums of oscillation velocity of the surface of the attached PZTs verticalto the laser beam versus frequency are obtained and are evaluated for SHM purposes.This damage detection approach also includes the use of a damage index denoted asECAR (Ellipse to Circle Area Ratio) based on 2-D error statistics and is compared to theRoot Mean Square Deviation (RMSD) damage index commonly used in SHMapplications. Experimental results include ascending uniaxial compressive load ofconcrete cubic specimens, ascending three point bending of reinforced concrete beamspecimens and early age monitoring of concrete. Results illustrate the efficiency of theproposed technique in damage detection as well as early age monitoring as, in the firstcase, both severity and location of damage can be determined by examining the values ofdamage indices for each damaged state and in the early age monitoring case damageindices follow the strength gain curve.

New Type of 2-D Laser Doppler Vibrometer

The fundamentals and method of 2 D laser Doppler vibrometer are introduced.The factors influencing the measuring accuracy are analyzed. Moreover, the circuit for signal processing is designed. The vibrating amplitude and frequency of 2 D vibration in wider range can be measured simultaneously in non contact means,the measuring results are accurate.

Human Body Surface Oscillations Remote Measurements by Means of Laser Doppler Interferometer

Experimental results of remote laser measurement of a time structure of a pulse waves are resulted. Occurrence of the pulse waves are connected with the rhythmic reduction of a myocardittm. Speed of pulse wave＇s propagation does not depend on speed of current of blood, it is defined by diameter of a vessel, by its walls thickness, by elasticity of a vessel, and also by rheological properties of blood. Measurement of parameters of pulse waves is important tbr definition of a condition of cardiovascular system. Ways of measurement of characteristics of pulse waves used now （acoustic, electric, optical） are contact. In some cases, for example, in clinics on treatment of burns and so forth, the question of remote measurement of processes hemodynamics by use of methods of laser sotmding is rather actual. The results described in work have shown outlook of development of laser methods of diagnostics for present purposes. The measurement technique used by authors is based on use of longitudinal Doppler effect which essence consists in change of frequency or length of a wave of radiation at reflection from moving surface. For smoothing the measured signal （clearing from noise） the program developed by authors on the basis of the wavelet-analysis was used. Experimental measurements are shown, that the laser method allows to register distinctly structure of pulse waves which is characterized by two peaks. The results of remote laser measurement of a time structure of a pulse waves confirm the assumption made on the basis of general-theoretical physical positions, that characteristics of pulse waves can be registered on the Doppler effect basis.

激光测振多普勒信号仿真技术研究

JJF1219-2009《激光测振仪校准规范》提出用调频电信号校准外差式激光测振仪信号采集、处理电路的方法,该方法对产生标准调频信号的信号发生器提出了很高要求,目前还没有激光测振仪校准专用的调频信号发生器,而通用函数信号发生器,在最大频移、调制振动频率范围等方面不能完全满足要求。通过研究数字信号合成技术,设计基于PC、FPGA和高速数模转换器(DAC)的多普勒调频信号发生器,实现激光多普勒调频信号模拟的仿真信号输出,具有参数设置灵活,带宽高,频率稳定性好的优点,经测试,该仿真信号达到了校准需要的技术要求,可用来评价外差式激光测振仪的信号采集、信号处理电路相关参量的计量特性。

太阳系外行星探测技术概述

自20世纪90年代首次发现太阳系外行星(以下简称系外行星)以来,系外行星探测技术取得了飞速发展。目前已探测到超过5500颗系外行星,其中包括类地行星、超级地球、气态巨行星及冰巨行星等多种类型。这些发现极大地拓展了人类对自身周围环境和宇宙的认知,为理解行星形成和演化提供了宝贵的观测依据,也为寻找宜居行星和地外生命提供了重要线索。通过介绍系外行星探测的多种核心技术,包括原理和应用特点,旨在对比和分析不同探测方法的技术特征。通过分析多种探测技术的优势和局限性,为行星探测研究提供了实践参考和发展趋势展望。

光学多普勒差分流速仪数据解调方法验证

光学多普勒差分流速仪在测量海水流速时,由于信号微弱和噪声干扰,接收信号信噪比很低,信号解调面临挑战,可能导致较大的测量误差。为了准确解调埋藏在噪声中的信号并获取速度信息,需要对获取的海试测量数据进行进一步算法处理。采用自适应滤波算法有效降低了多普勒信号中混杂的高频噪声干扰,提高了海试原始数据频域信号的信噪比,并利用寻峰算法更准确地获取了谱峰值。结果表明,与直接读取原始数据的谱峰值相比,经过该算法处理后,激光差分多普勒流速仪与声学多普勒流速仪比测的流速拟合度平均误差为0.2163 cm/s,误差降低了25.5%,表明该算法对激光多普勒测速信号解调是有帮助的。

1116 nm单频脉冲Nd∶YAG激光器

针对共振荧光测风雷达的探测需求,设计和研制了种子注入的Nd∶YAG电光调Q单频1116 nm脉冲激光器,采用带偏置电压反馈的扫描-触发谐振探测技术,建立了1116 nm单纵模振荡,并对中心频率稳定性进行分析。最终实现输出1116 nm激光单脉冲能量6.48 mJ,重复频率60 Hz,输出线宽为33.2 MHZ,脉冲宽度为75.7 ns。通过波长计测量输出光波长,波长稳定在1116.2979 nm附近。利用外差拍频,测定120 min中心频率稳定性(均方根)为818.3 kHz。该激光器输出光通过三倍频可变换至372 nm,作为铁共振荧光多普勒测风激光雷达的发射光源,频率抖动量对应的风速测量误差小于1 m/s。

一种机械臂电机故障时频尺度诊断方法——基于深度学习和激光多普勒测振技术

机械臂电机振动信号的采集效果较差,影响时频特性分析过程,导致故障诊断效果与精度较差,为此提出基于深度学习和激光多普勒测振技术的机械臂电机故障时频尺度诊断方法。使用激光多普勒测振技术与小波阈值去噪算法,建立机械臂电机振动信号采集系统,获取并重构故障信号;提取电机振动信号的时域、频域等尺度特征,引入人工神经网络建立一个具备学习能力的故障诊断模型,将提取的机械臂电机故障时域、频域等尺度特征输入诊断模型中,输出分类诊断结果,即可完成机械臂电机故障时频尺度诊断。结果表明:利用该方法开展电机故障诊断时,检测结果与实际电机故障类型之间偏差较小,诊断效果好、精度高。

基于光纤镀膜探针的固体介质中应力波粒子速度测量技术

粒子速度是分析固体介质中应力波传播规律的一个重要参数。结合激光多普勒效应和全光纤干涉测速系统,提出了一种基于光纤镀膜探针的固体介质中应力波粒子速度的测量方法。将光纤镀膜探针嵌入有机玻璃(PMMA)中,距爆心同一半径处,采用0.125 g TNT当量的微型炸药球作为爆炸源,进行填实爆炸产生应力波,通过采集光纤探针端面的运动信息,基于短时傅里叶变换的时频分析方法,解调出端面运动速度,进而反推出粒子速度。实验结果表明:不同光纤镀膜探针测得的速度分别为22.648 m/s、23.505 m/s,将反推的粒子速度与传统的圆环型电磁粒子速度计方法获取到的数据进行对比,两者的相对偏差低于5.00%,验证了光纤镀膜探针测量固体介质中应力波粒子速度的可行性。

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.

基于回波模拟法的激光多普勒测速仪示值误差检测方法研究

针对高速激光多普勒测速仪(速度上限超过1 km/s)示值误差检测中参考速度难以获得导致测速仪示值误差无法有效检测的问题,提出采用光学回波模拟法对其进行示值误差检测。通过对测速仪的出射光进行光学移频,以此模拟运动物体的激光多普勒效应,从而解决高速多普勒测速仪检测所需速度源的问题;通过设置波长检测模块与移频量检测模块,获得准确的工作波长与移频频率,进而计算出准确的参考速度信息,保证激光多普勒测速仪示值误差检测的准确性。实验结果表明:基于回波模拟法的激光多普勒测速仪示值误差检测方法,可以实现速度上限高达2.7 km/s的测速仪示值误差的检测,示值误差测量不确定度U_(r)=0.3%(k=2)。实验结果表明基于回波模拟法的激光多普勒测速仪示值误差检测技术具有很好的工程应用前景。