ANALYSIS OF THE EFFECT OF THE TRUNCATED SCAN PLANE IN TIME-DOMAIN NEAR-FIELD MEASUREMENTS

The thought and formulation for near-field far-field transformation based on the direct time-domain computation scheme are given. The effect of the truncated scan plane is investigated by simulating time-domain measurement of an open-ended waveguide antenna, and a simple and effective criterion is derived for removing the truncation errors in the practical time-domain near-field measurements.

Particle Velocity Sensor and Its Application in Near-Field Noise Scanning Measurement

The Particle Velocity Sensor (PVS) is a kind of acoustic transducer which measures the particle velocity directly with figure-of-eight directivity. This paper proposes a near-field noise scanning technology based on the research of PVS, pressure-particle velocity (P-U) probe, and its application in noise source identification. Firstly, the principle and characteristics of PVS are presented. Secondly, a P-U probe is designed on the basis of PVS development. Finally, the noise measurement experiment for a single source is arranged and conducted. The result shows that the proposed P-U probe performs well in near-field noise source identification and localization.

Transmittance Measurement of the Nonplanar Optical Based on Focal-Plane-Array Camera

Aiming to solve the problem that it is difficult to accurately measure UV cut-off transmittance of xenon quartz glass by using present spectrophotometer in China SG III project. Through the analysis, we believe that its reason was that the xenon quartz glass was nonplanar so the outgoing beam geometry from under-test was different from that from standard sample. A method of transmittance measurement based on focal-plane-array camera was proposed in this article. The effects of camera uniformity and spot sampling on transmittance measurement were analyzed theoretically. This method, which can reduce the effect of beam geometry on transmittance measurement and eliminate the cutting error occurring during light transmission by monitoring the completeness of incident beam in real-time, is verified from experiments. The random standard uncertainty of this method here is 0.035% or less. It is particularly useful in the transmittance measurement of nonplanar optical.

Easy calibration method of vision system for in-situ measurement of strain of thin films

An easy calibration method was presented for in-situ measurement of displacement in the order of nanometer during micro-tensile test for thin films by using CCD camera as a sensing device. The calibration of the sensing camera in the system is a central element part to measure displacement in the order of nanometer using images taken with the camera. This was accomplished by modeling the optical projection through the camera lens and relative locations between the object and camera in 3D space. A set of known 3D points on a plane where the film is located on is projected to an image plane as input data. These points, known as a calibration points, are then used to estimate the projection parameters of the camera. In the measurement system of the micro-scale by CCD camera, the calibration data acquisition and one-to-one matching steps between the image and 3D planes need precise data extraction procedures and repetitive user's operation to calibrate the measuring devices. The lack of the robust image feature extraction and easy matching prevent the practical use of these methods. A data selection method was proposed to overcome these limitations and offer an easy and convenient calibration of a vision system that has the CCD camera and the 3D reference plane with calibration marks of circular type on the surface of the plane. The method minimizes the user's intervention such as the fine tuning of illumination system and provides an efficient calibration method of the vision system for in-situ axial displacement measurement of the micro-tensile materials.

On the Probable Cause of the Discrepancies between Hipparcos and VLBI Pleiades Distance Measurements

It will show, a recent extension of special relativity on the grounds of a novel concept of velocity, which also predicts the speed of transversal motions on the plane of the sky to increase with enduring observation time, to fully explain the differences of the observational results of the former experiments referring to the distance of the Pleiades from Earth.

2-D distributed pose estimation of multi-agent systems using bearing measurements

This article studies distributed pose(orientation and position)estimation of leader–follower multi-agent systems over𝜅-layer graphs in 2-D plane.Only the leaders have access to their orientations and positions,while the followers can measure the relative bearings or(angular and linear)velocities in their unknown local coordinate frames.For the orientation estimation,the local relative bearings are used to obtain the relative orientations among the agents,based on which a distributed orientation estimation algorithm is proposed for each follower to estimate its orientation.For the position estimation,the local relative bearings are used to obtain the position constraints among the agents,and a distributed position estimation algorithm is proposed for each follower to estimate its position by solving its position constraints.Both the orientation and position estimation errors converge to zero asymptotically.A simulation example is given to verify the theoretical results.

Study and application of monitoring plane displacement of a similarity model based on time-series images

In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on.

Far-Field Pattern Reconstruction from Positioning Errors Affected Near-Field Data Acquired via Helicoidal Scanning

In this paper, an effective technique to compensate the positioning errors in a near-field—far-field (NF-FF) transformation with helicoidal scanning for elongated antennas is presented and validated both numerically and experimentally. It relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by considering the antenna as enclosed in a cylinder ended in two half-spheres. An iterative scheme is used to reconstruct the helicoidal NF data at the points fixed by the representation from the acquired irregularly spaced ones. Once the helicoidal data have been retrieved, those needed by a classical NF-FF transformation with cylindrical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its stability with respect to random errors affecting the data, are reported. Experimental tests performed at the Antenna Characterization Lab of the University of Salerno further confirm the validity of the proposed technique.

Spherical Near-Field - Far-Field Transformation for Quasi-Planar Antennas from Irregularly Spaced Data

An effective near-field - far-field (NF - FF) transformation with spherical scanning for quasi-planar antennas from irregularly spaced data is developed in this paper. Two efficient approaches for evaluating the regularly spaced spherical samples from the nonuniformly distributed ones are proposed and numerically compared. Both the approaches rely on a nonredundant sampling representation of the voltage measured by the probe, based on an oblate ellipsoidal modelling of the antenna under test. The former employs the singular value decomposition method to reconstruct the NF data at the points fixed by the nonredundant sampling representation and can be applied when the irregularly acquired samples lie on nonuniform parallels. The latter is based on an iterative technique and can be used also when such a hypothesis does not hold, but requires the existence of a biunique correspondence between the uniform and nonuniform samples, associ- ating at each uniform sampling point the nearest irregular one. Once the regularly spaced spherical samples have been recovered, the NF data needed by a probe compensated NF - FF transformation with spherical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. It is so possible to accurately compensate known posi- tioning errors in the NF - FF transformation with spherical scanning for quasi-planar antennas. Some numerical tests assessing the accuracy and the robustness of the proposed approaches are reported.

红外辐射测量系统的快速宽动态非均匀性校正算法

本文针对红外辐射测量系统需要积分时间连续变化的需求,提出一种快速宽动态的非均匀性校正算法。该算法考虑了积分时间效应和光学系统杂散辐射的影响,并利用25 mm口径的制冷型中波红外辐射特性测量系统进行试验验证。将本文所提算法与经典算法进行对比,结果表明,校正效率较传统非均匀性校正算法提高了3.4倍。本文还利用剩余残差评价原始图像以及两种算法的图像校正效果,利用多个积分时间(0.6 ms,3 ms和3.5 ms)模拟连续变化的积分。结果显示本文算法在各个积分时间下剩余残差均表现稳定且校正图像都具有良好的校正效果。

钻井液环境无线传输微型PIFA共形天线研制

井下上返式微球测量仪需在钻井液环境中实现无线数据传输功能,其直径一般不超过10 mm,该参数限制了无线收发结构的尺寸,同时,传统天线大多采用低损耗板材,不利于大批量应用。针对上述问题,提出了辐射贴片弯折与地平面开槽的方法对传统PIFA天线进行改进,天线平面尺寸仅为17 mm×8.4 mm×0.049 mm,较类似天线的设计缩小了68.3%;天线通过柔性印刷电路技术制造,弯曲175°后安装在微球测量仪表面。天线在相对介电常数为81、电导率为1.258 S/m的钻井液中测得的谐振点频率为310 MHz,对应回波损耗为-32.4 dB,-20 dB带宽为35 MHz。天线在相对介电常数和电导率不同的钻井液中,均具有较为理想的全向辐射特性。相比其他天线,所提出的天线在尺寸、谐振点频率和回波损耗等性能指标上均具有一定的先进性。综上,所提出的天线可用于微球测量仪在钻井液环境中的无线通信,使原有微球测量仪的数据传输方式由有线通信变为了无线通信,降低了井下测量短节的设计难度,提升了数据传输的时效性。

基于线结构光的零件三维尺寸测量系统

针对原有接触式三维测量技术测量时间长、效率低、对零件有损伤等问题,提出一种基于线结构光的零件三维尺寸测量系统。建立光平面数学模型,采用基于平面靶标的自由移动标定法标定光平面,利用基于Hessian矩阵的Steger方法对线结构光中心提取,通过坐标变换得到零件的三维尺寸。在Visual Studio软件中的Winform窗体应用设计三维测量系统的软件交互界面,搭建实验测量平台进行多个零件的测量实验。实验结果表明,对不同零件三维尺寸测量相误差均小于4%,提出的测量系统及方法具有较高的精度和稳定性,能够满足工程应用。

重型燃机叶片周向圆弧锤足型榫头加工及检测技术

重型燃机叶片周向圆弧锤足型榫头具有盆背径向大平面、大直径复杂转接圆弧曲面、复杂设计基准和关联尺寸等特点,该类型叶片榫头面临铣削加工难度大以及三坐标检测重复性差等问题。本研究采用创新工艺方法突破技术瓶颈的限制,开发周向圆弧锤足型榫头卧式加工中心集成铣削及其三坐标检测技术,满足了周向圆弧锤足型榫头叶片的表面质量、尺寸精度、加工效率及外观要求。

融合结构光的折反射全景单目视觉测距

无人机在大机动运动时视场变化较大,在弱纹理环境下视觉特征易丢失,这降低了视觉距离测量的精度。针对此问题,本文将折反射全景相机与结构光相结合,进一步提出了融合结构光的折反射全景单目视觉测距方法。在本研究中,为了提高测距方法的精度以及处理速度,首先对结构光进行感兴趣区域(ROI)提取,并运用中值滤波对激光条纹图像进行去噪后,再采用改进的Steger算法进行亚像素级别的结构光光条中心坐标提取。其次,运用最小二乘原理对提取的亚像素点进行曲线拟合,得到结构光的曲线方程。最后,通过理论推导求取空间平面参数,建立测距目标函数,进一步求得距离信息。实验结果表明:在不同场景下,所提出测距方法的测距精度均在3%以内,证明了该方法的有效性。满足无人机在大机动运动条件下以及弱纹理场景中稳定可靠的测距需求,进一步提升了无人机环境感知能力。

空间最优投影平面的斜口圆截面管路端头位姿测量

船舶、飞机等发动机为减小体积,采用斜口管路焊接代替弯头连接,管路系统中端头位姿是焊接对齐的前提。针对斜口管路端头位姿的高效高精度测量难题,提出了一种通过重建管路轴线以及管路端面进行端头位姿精确测量的方法。通过获取种子圆柱并设计非线性寻优算法提高圆柱拟合精度,通过高精度种子圆柱扩散重建得到管路轴线。通过双曲率阈值搜索方法对管路边缘进行搜索,得到管路端面边缘点整像素坐标。通过对端面提取得到的整像素坐标进行椭圆拟合结合射线求交方法求解端面边缘亚像素坐标,从而避免插值方法计算亚像素坐标受环境光源影响大的问题。最后,使用逐点最小二乘法重建空间投影平面并在平面上得到残差最小空间椭圆,空间椭圆中心即为管路端点,该投影平面即为端面所在平面,实现了对端头位姿的精确测量。实验结果表明,该方法的测量精度达到0.05 mm,角度测量误差小于0.1°,基本满足斜口管路端头的位姿测量精度要求,对管路的装配具有良好的指导意义。

分焦平面式偏振相机偏振误差分析及偏振定标

分析了相机结构和测量原理,建立了相机响应模型,理论推导了相对透过率和偏振方位角对偏振测量的影响。采用积分球光源测量了相对透过率,采用旋转线偏振片法和马吕斯定律测量了偏振方位角,最后进行了偏振测量精度验证。测试结果表明,经过偏振定标后,偏振度测量误差约为0.44%。该检测方案可以定标分焦平面式偏振相机性能,定标精度高,能够为分焦平面式偏振相机高精度应用奠定基础。

Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

Hybrid near-field acoustical holography(NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH,we combine statistically optimized near-field acoustical holography(SONAH) and broadband acoustical holography from intensity measurements(BAHIM) to reconstruct the underwater cylindrical source field. First,the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary,and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal,and the measurement array can be smaller than the source,thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then,an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement,as well as the identification and localization of noise sources.

聚焦换能器声场特性的快速检验方法

高强度聚焦超声(HIFU)已在无创肿瘤治疗方面展示出巨大的应用潜力,而换能器聚焦性能的优劣对疗效起到至关重要的作用,因此声场的精确测量成为实际应用的重要保障.由于加工工艺和安装精度的限制,聚焦换能器的实际声场和理想声场可能存在一定偏差.针对传统三维扫描测量存在速度慢和精度低的问题,提出了一种基于双平面双精度测量的聚焦换能器声场特性快速检验方法.通过沿理想z轴的高精度一维扫描确定换能器倾斜角范围,在声压极值点所在横截面内利用低精度和高精度变邻域搜索法实现最大声压点的精准定位,进一步通过焦域内双平面最大声压点构建声场的实际轴线,完成实际声场焦点的精确定位,最后基于实际焦平面内轴向与径向的高精度测量结果,计算获得焦域尺寸、旁瓣大小、分布对称性和声功率等性能参数.利用构建的声场扫描实验系统对聚焦换能器声场进行三维扫描和快速测量,结果表明在相同的测量精度(0.1 mm)下可以有效提高测量速度百倍以上,具有测量速度快、测量精度易于调节和性能分析全面等优点.方法为聚焦换能器检验提供一种高精度的快速声场测量新技术,在超声治疗仪器的检验中具有重要的指导意义与应用价值.

前锯肌浅、深层平面阻滞对乳腺癌手术围术期镇痛效果的比较

目的 观察前锯肌浅、深层平面阻滞在乳腺癌手术患者围术期的镇痛效果。方法 选择2020年8月—2022年7月择期全麻下初次行乳腺癌改良根治术60例,随机分为前锯肌浅层平面阻滞组(S组)、前锯肌深层平面阻滞组(D组)和对照组(C组),每组20例。S组与D组分别于麻醉前超声引导下识别前锯肌浅层和深层平面,并注入0.5%罗哌卡因注射液20 mL,注药后30 min利用针刺法测定痛觉减退的范围;C组直接行全身麻醉。记录3组麻醉诱导前、切皮前、切皮后3 min的平均动脉压(MAP)和心率,术中瑞芬太尼用量、出血量和手术时间;记录3组术前、术后24和48 h恢复质量,拔管即刻及术后2 h、6 h、12 h、24 h和48 h安静和咳嗽状态下视觉模拟评分法(VAS)评分,补救镇痛例数及不良反应、并发症发生情况。结果 S组有3例剔除,共纳入17例。S组和D组均可产生锁骨中线~腋后线、第3~6肋节段痛觉阳性区域,但均未超过前正中线;在相同节段D组阳性例数多于S组。与C组相比,S组和D组在切皮后3 min MAP和心率低,术中瑞芬太尼用量、术后12 h和24 h补救镇痛例数减少,术后24 h 15项恢复质量量表评分升高(P<0.05)。安静时,S组和D组拔管即刻、术后2 h、6 h、12 h和24 h VAS评分均低于C组(P<0.05);咳嗽时,S组拔管即刻、术后2 h和6 h VAS评分均低于C组,D组拔管即刻、术后2 h、6 h、12 h和24 h VAS评分均低于C组(P<0.05);D组术后12 h和24 h VAS评分低于S组(P<0.05)。3组不良反应发生率比较差异无统计学意义(P>0.05),均未发生严重并发症。结论 前锯肌浅层和深层平面阻滞均能为乳腺癌手术患者提供满意的围术期镇痛,且与浅层平面阻滞相比,深层平面阻滞在超声下操作更易建立,对手术操作影响小,术后镇痛效果确切。

超声速差法平面叶栅流场试验和数值研究

针对平面叶栅狭小通道中流场非接触测量难题,提出一种基于超声速差原理的二维流场测量方法。设计一种2×4超声波斜、平口换能器组合阵列,研制一套多通道超声法测量和气流速度场重建系统。开展平面叶栅流场测量试验,成功获取了3种不同进口速度条件下流道二维速度场。利用COMSOL Multiphysics中CFD模块同步开展叶栅流场数值模拟,并与试验结果对比。结果表明:超声测量与数值模拟结果较为接近,速度大小和偏转角误差均在5%以内,较好地反映叶栅通道的流动特点。提出的超声测量技术有望进一步用于高马赫数流场研究。