Temporally Modulated Phase Retrieval Method for Weak Temporal Phase Measurement of Laser Pulses

We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform- limited. A detailed analysis shows that this iterative method has valuable potential applications in the charac- terization of pulses with weak temporal phase.

Revisiting the methods for gas permeability measurement in tight porous medium

Permeability is a key parameter to describe fluid transport properties of porous medium; however, the permeability measurement is extremely difficult for tight porous medium, e.g. fine-grained rock or dense soil. In this paper, three methods for gas permeability measurement, i.e. steady state method, pulse decay method(PDM) and pressure oscillation method(POM), are first reviewed and then their advantages and drawbacks are discussed. Both analytical and numerical solutions of gas permeability are presented for the tight porous medium. The results show that the analytical method is relatively simple but only valid under certain conditions, whilst the numerical method is more robust and generic, which can take into account several factors such as porosity, saturation, gas leakage, and unconventional boundary conditions. The influence of the effective porosity on the permeability determination is further analyzed using the proposed numerical method. In this study, new pressure data interpretation procedures for PDM and POM are proposed, and the obtained results can serve as a guidance to define a proper method for permeability measurement of the tight porous medium.

3D interlocked all-textile structured triboelectric pressure sensor for accurately measuring epidermal pulse waves in amphibious environments

The performance degradation and even damage of the e-textiles caused by sweat,water,or submersion during all-weather health monitoring are the main reasons that e-textiles have not been commercialized and routinized so far.Herein,we developed an amphibious,high-performance,air-permeable,and comfortable all-textile triboelectric sensor for continuous and precise measurement of epidermal pulse waves during full-day activities.Based on the principle of preparing gas by acid-base neutralization reaction,a one-piece preparation process of amphibious conductive yarn(ACY)with densely porous structures is proposed.An innovative three-dimensional(3D)interlocking fabric knitted from ACYs(0.6 mm in diameter)and polytetrafluoroethylene yarns exhibit high sensitivity(0.433 V·kPa^(-1)),wide bandwidth(up to 10 Hz),and stability(>30,000 cycles).With these benefits,98.8%agreement was achieved between wrist pulse waves acquired by the sensor and a high-precision laser vibrometer.Furthermore,the polytetrafluoroethylene yarn with good compression resilience provides sufficient mechanical support for the contact separation of the ACYs.Meanwhile,the unique skeletonized design of the 3D interlocking structure can effectively relieve the water pressure on the sensor surface to obtain stable and accurate pulse waves(underwater depth of 5 cm).This achievement represents an important step in improving the practicality of e-textiles and early diagnosis of cardiovascular diseases.

Thrust measurement method verification and analytical studies on a liquid-fueled pulse detonation engine

In order to test the feasibility of a new thrust stand system based on impulse thrust mea- surement method, a liquid-fueled pulse detonation engine （PDE） is designed and built. Thrust per- formance of the engine is obtained by direct thrust measurement with a force transducer and indirect thrust measurement with an eddy current displacement sensor （ECDS）. These two sets of thrust data are compared with each other to verify the accuracy of the thrust performance. Then thrust data measured by the new thrust stand system are compared with the verified thrust data to test its feasibility. The results indicate that thrust data from the force transducer and ECDS system are consistent with each other within the range of measurement error. Though the thrust data from the impulse thrust measurement system is a litter lower than that from the force transducer due to the axial momentum losses of the detonation jet, the impulse thrust measurement method is valid when applied to measure the averaged thrust of PDE. Analytical models of PDE are also discussed in this paper. The analytical thrust performance is higher than the experimental data due to ignoring the losses during the deflagration to detonation transition process. Effect of equivalence ratio on the engine thrust performance is investigated by utilizing the modified analytical model. Thrust reaches maximum at the equivalence ratio of about 1.1.

样品尺寸对脉冲穿透法声速测量误差的影响

岩心的声速测量能够提供关键的储层地质信息,对储层评价和地质模型构建具有实际应用价值。脉冲穿透法是一种常用的声速测量方法,但它要求样品尺寸远大于波长(约10倍)。当特殊场景如需在测井信号主频8~20 kHz下测量样品声速时,被测样品长达数米,不仅制备困难,还存在声波信号衰减大的问题。关于试样尺寸能否缩小或能缩小到什么程度的定量研究很少见到公开报道。该文将数值模拟和实验测量相结合,系统定量地研究了圆柱状样品长度及直径与波长之间的比值对脉冲穿透法声速测量精度的影响。研究表明:为确保脉冲穿透法声速测量的准确性,建议样品沿传播方向上的长度不低于4倍声波波长,横向尺寸不低于2倍波长。研究结果突破了传统脉冲穿透法要求样品尺寸远大于波长的限制,为优化声速测量方法和提高测量精度提供了理论支持。

Method based on broadband compressed pulse superposition to measure properties of underwater acoustic materials

A method is proposed for the measurements of the performances of underwater acoustic finite sized large area material samples in a free field by using broadband pulse compression technique. As the result of which, the low-frequency cutoff of the standard tests is obviously reduced, and the broadband measurements are also realized. The experimental system provides measurements of complex reflection and transmission coefficients at continuous frequency points. From the data one can obtain the following acoustic parameters: echo reduction and insertion loss, absorption and attenuation coefficients, etc. The measurements are performed for two actual panels with the size 1 m x 1 m in the frequency range from 2-20 kHz.

A new method and instrument for accurately measuring interval between ultrashort pulses

Using second-order autocorrelation conception, a novel method and instrument for accurately measuring interval between two linearly polarized ultrashort pulses with real time were presented. The experiment demonstrated that the measuring method and instrument were simple and accurate (the measurement error < 5 fs). During measuring, there was no moving element resulting in dynamic measurement error.

激光测距技术研究现状及发展趋势

随着激光探测的自身技术与传感设备的不断提升,激光测距也迈入了新的技术领域,适用范围也更加广泛,通常被应用于军事测量,工业精密测量、通讯领域、地形勘测以及航空航天技术等领域,目前激光测距的原理主要包括三角式测距、干涉测距、脉冲测距法以及光子计数测距法。主要围绕这几种测距方法展开论述,阐述了激光测距技术其国内外的研究现状、技术瓶颈,并对几种主流激光测距技术做出了总结与发展趋势展望。

矿用脉冲激光测距系统研究

激光测距是在光学高速发展的背景下出现的新型测距方式,被广泛应用于建筑、医学和煤矿井下等距离信息测量场景。针对目前煤矿井下顶底板移进量测量存在无法实时监测、测量精度低、使用不便等问题,设计了基于飞行时间测距原理的脉冲式激光测距系统,并对其系统方案、硬件电路等方面进行了研究。通过高功率半导体激光器、大电流激光驱动电路,发射高能量激光光束。采用ns级雪崩光电二极管,捕获经目标物反射的激光回波信号。利用时刻鉴别电路,计算脉冲激光的飞行时间,精确计算目标物距离。系统试验结果表明,所设计的脉冲激光测距系统体积小、精度高、实用性强,能够达到mm级的测量精度,充分满足煤矿井下的距离测量需求。

Multi-attribute group decision-making method with linguistic q-rung orthopair fuzzy information based on bi-direction Choquet integral

Purpose-The purpose of this paper is to develop the linguistic q-rung orthopair fuzzy set(LqROFS)information VIKOR method based on the bi-direction Choquet integral(BDCI),taking into account the correlation between information.The method can enrich the existing studies related to LqROFS information and better solve the problem of MAGDM problem.Design/methodology/approach-Since applying Choquet integral(CI)depict information interaction is a common operation in MAGDM.However,the traditional CI has some limitations.The unidirectional alignment may affect the MAGDM results.Therefore,a LqROFS-VIKOR method based on BDCI is proposed,where BDCI is used to aggregate the decision matrix.Furthermore,it is not reasonable to apply exact numbers to express the similarity between two qualitative data.Then a new method of defining similarity using linguistics is proposed.The similarity is used to calculate attribute weights.Findings-The validity and potential application of MAGMD method with linguistic q-rung orthopair fuzzy information based on BDCI are demonstrated in a numerical examples study.Originality/value-According to the study of available literature,the current research on LqROFS is incomplete.The existing studies of both similarity and aggregate operators have certain shortcomings.The definition of similarity proposed in this paper is more in line with reality.And compared with the existing methods,the BDCI-based aggregate operator can describe the interaction between information more reasonably.Based on this VIKOR method based on BDCI under the LqROFS environment can better select the alternative.

袖带式血压信号采集系统设计

血压值是反映人体健康的重要参数,对于心脑血管病的治疗能够提供有力依据,因此血压测量值的精准度在医学临床上尤为重要,为了能够实时了解到血压值,医学领域关于血压的测量一直在不断研究与开创。在各类研究基础上,采用了示波法的血压测量方法,设计出基于此方法的袖带式血压信号采集系统,相当于一个模拟电子血压计。该血压计能够实现血压信号采集,并且能够在血压超出正常范围时发出报警信号。

基于低压脉冲法的电网地埋电缆故障定位方法

为控制地埋电缆故障定位误差,提高故障定位水平,引进低压脉冲法,设计了一种针对电网地埋电缆的全新故障定位方法。使用脉冲发生器发射行波,设计地埋电缆故障检测行波参数,根据行波的传输方式,检测与识别地埋电缆不同区段故障。分析地埋电缆故障检测信号中的多尺度相关性,消除噪声成分,保存细节,再对信号重建,得到经过滤波处理后的信号,以此为依据,测量电网地埋电缆故障点距离。对比实验结果表明,设计的定位方法应用效果良好,按照规范进行电网地埋电缆故障点的定位,可以有效控制定位结果的偏差,实现对地貌电缆故障的精准排查。

基于普通编码器的高精度测速方法

根据普通增量式光电编码器的测速原理 ,分析了引起量化误差和编码器脉宽误差的各种因素 ,在此基础上提出了新的信号处理算法——恒基准脉冲数法 ,以减小量化误差 .同时将标定出的编码器脉宽系数作为脉宽误差补偿的参数 ,消除了利用恒基准脉冲数法测量转速时脉宽误差造成的影响 。

变容压力脉冲渗透系数测量方法研究

从理论上讨论传统压力脉冲法(定容脉冲法)在渗透系数测量量程上的局限性,提出水箱容水量可调的变容压力脉冲法(变容脉冲法)的新思路。介绍变容脉冲法的原理、装置及试验流程。与定容脉冲法不同,变容脉冲法试验装置的水箱内装的流体为气液两种流体的综合体,可以通过调节气液体积比来实现容水量的改变。通过调节水箱内不同的气液体积比(不同容水量)条件下对同一个岩石试件进行渗透系数重复测量,分析变容脉冲法的重复性。试验结果显示,该方法具有很好的重复性(小于5%),并与恒流法测得的渗透系数相近。

脉冲激光测距时间间隔测量及误差分析

在脉冲激光测距时间间隔测量系统中,传统的数字时钟计数法受限于计数时钟的频率,测量精度不高。由于模拟插入法具有测量范围大、线性好、测量精度高的优点,广泛应用于脉冲激光测距时间间隔测量系统中。介绍了模拟插入法时间间隔测量的原理,设计了其测量系统及相应的测试电路。利用该系统进行了实验研究,达到了100ps的时间间隔测量精度,对应于1.5cm的测距精度。最后,进行了测量误差分析。

车用涡轮增压器涡轮非稳态特性试验研究

分析并完善了车用涡轮增压器涡轮非稳态特性测量及计算的方法,在此方法的基础上,搭建了涡轮非稳态特性试验台,为涡轮的非稳态特性研究提供了一种试验研究手段。对某型号的涡轮与发动机在典型工况下匹配时的非稳态特性进行了试验研究,试验观察到了"涡轮非稳态特性圈"的现象,即涡轮的非稳态特性围绕着稳态特性形成了一个特性圈,对涡轮的非稳态特性进行了分析。

脉冲激光测距系统中高精度时间间隔测量模块的研究

时间间隔的测量精度对脉冲激光测距系统的测量精度起决定作用.为此研制了一高精度时间间隔测量模块,该模块基于专用时间数字转换芯片开发,采用延迟线插入法技术,最大测量时间可高达200m s,测时分辨率最高可达125ps,对应测距分辨率18.75mm,适用于远距离的测量.给出了硬件和软件设计方法以及模块的测试结果.

平行板型三维脉冲电场传感器的研制

宽频带传感器是脉冲电磁场测量的关键设备之一,目前用于脉冲电场测量的传感器大都是单极化形式,只能测量半空间、单极化方向上的电场。为此,研制了一种可用于脉冲电场测量的三维平行板型结构传感器,它由三维电场天线和光发射机组成,与相应的光纤传输系统配合,可以对三维脉冲电场进行同时、全空间测量。应用FDTD法对三维电场测量天线模型进行了数值模拟,重点分析了三维天线的极间耦合、三维场分量的合成与频率特性。计算结果表明,平行板型三维电场天线可以满足脉冲电场测量要求。根据数值模拟的结果实际制作了三维电场传感器并对该传感器进行了实验验证。测量结果表明,该三维电场传感器的性能达到了设计要求。

海水叶绿素a现场测量仪研究

采用荧光测量方法研究成功的海水叶绿素a现场测量仪，是用于海上现场实时测量海洋中浮游植物体内叶绿素a含量的新型海洋仪器。本仪器采用低功耗、高强度、低重复频率、窄脉冲宽度的脉冲氙灯，为激发光源及相应的脉冲检测技术测量荧光信号。该仪器可在海表层至50m水深内任一日光强度下工作；测量海洋中浮游植物体内叶绿素a的浓度范围为1×10-6—1×10-9g／cm3；当仪器走航拖曳速度为2m／s时，其空间分辨度为1m，仪器具有海上现场测量实用价值。

声管脉冲回波法吸声系数测量技术

利用可控脉冲声信号，采用回波方法，在圆形声管中测量了样本材料的吸声系数。依据回波信号和入射声波的功率谱密度先解算反射系数，然后计算吸声系数。与B＆K4206阻抗管测量结果相比，在200Hz～5kHz频段内吸声系数差别在10％以内。所用脉冲声具有波形规则、脉冲时间短、频带宽的特点，测量精度比同类方法显著提高，特别是低频区域数据可靠。测量系统装置简单、重复性好。测量装置的不确定度主要源于样品在声管中安装的精密性。