Measurement of the electromagnetic field radiating by commercial ESD generators with the Pellegrini target on insulating material

The aim of this work is the investigation of the transient electromagnetic field radiating by two different commercial generators of electrostatic discharges. Measurements of both magnetic and electric field generated by contact electrostatic discharges have been carried out a few centimeters away from the discharge point. In this paper the current transducer, which is used for the measurement of the discharge current is not mounted on a grounded metal plate, but on an insulating material. With this aberration to the Standard a closer simulation to the electromagnetic field produced by the electrostatic discharge generators on the equipment under test is obtained. This experiment is closer to real conditions of electrostatic discharges, which do not involve a metal plate. It is proved by measurements that each generator produces a different transient electromagnetic field, which has different repercussions on the equipment that is tested. Comparisons of the radiating field between the two generators and useful conclusions for the variation of the electromagnetic field are also presented.     

Poloidal beta and internal inductance measurement on HT-7 superconducting tokamak

Poloidal beta beta(theta) and internal inductance l(i) measurements are very important for tokamak operation. Much more plasma parameters can be inferred from the two parameters, such as the plasma energy confinement time, the plasma toroidal current profile, and magnetohydrodynamics instability. Using diamagnetic and compensation loop, combining with poloidal magnetic probe array signals, poloidal beta beta(theta) and internal inductance l(i) are measured. In this article, the measurement system and arithmetic are introduced. Different experimental results are given in different plasma discharges on HT-7 superconducting tokamak.     

桥壳中段同轴度测量装置的结构设计

为提高铸造桥壳中段测量精度和测量效率,文中提出采用专用测量设备实现在线测量,动态控制产品重要特性指标通过对产品结构和测量要求的深入分析,找出了测量装置设计中多点测头、测头防护、多品种快速切换装置等技术难点的解决方案,实现了铸造桥壳中段基于该装置实时在线测量,为桥壳中段的动态质量控制做出了创造性的探索     

平面凸轮轮廓线检测数据处理方法研究

介绍了在平面凸轮轮廓线检测系统中所采用的数据处理方法,主要包括采样数据点的基于最小二乘法理论的三次非均匀B样条曲线拟合,以及补偿测头半径误差等方法的研究.该处理方法具有计算精度高,应用范围广的特点,可以为同类检测设备所借鉴.     

射频导纳技术在蒸发器液位测量中的应用

针对海水淡化蒸发器运行工况复杂、结构设计紧凑、液位测量范围小、常规差压法安装困难等问题,提出了一种利用射频导纳技术测量蒸发器液位的方法。重点对射频导纳液位计的工作原理、主要特点、电极选型、安装注意事项以及标定方法进行了阐述和探讨,并在30t/d LT-MED中试装置中成功应用。结果表明:该仪表安装简单、测量准确、维护方便且适用范围较广,具有很好的应用前景。     

CNC齿轮测量中心上盘形凸轮测量方法研究

研究了直接在CNC齿轮测量中心上检测凸轮并评定误差的方法和理论。在凸轮工件型面上直接采集测量数据,用三次样条插值函数拟合测头中心轨迹,通过测头半径补偿和凸轮从动轮数据转换,得到凸轮升程曲线,运用最小条件法评价凸轮升程误差。此方法具有测量过程简便、测量效率高、计算精度高、应用性广等优点,适用于以CNC齿轮测量中心为检测设备的自动加工系统。     

坐标测量机上盘状凸轮检测方法研究

本文研究直接在三坐标测量机上检测凸轮并评定误差的方法和理论。在凸轮工件型面上接采点测量数据,用不等距三次Ｂ样条函数和最小二乘法拟合测头中心轨迹,通过测头半径补偿和凸轮从动轮数据转换,得到凸轮升程曲线,运用最小条件法评价凸轮误差,同时还可以评价凸轮机的速度、加速误差。数字仿真计算和实验结果表明,本文方法具有测量过程简便,测量效率高、计算精度高,应用性广播等优点,适用于三坐标测量机为检测设备的自动加工     

The influence of ultrasonic cavitation on plasma discharge in a liquid medium and the properties of thus-produced nanoparticles

The basic principles of the formation of plasma discharge in a liquid under exposure to ultrasonic cavitation are reviewed. The laboratory equipment produced for this purpose is described. The results of studies of discharges in liquids under the action of intensive ultrasound vibrations above the cavitation threshold are presented. The difference in the characteristics between discharges before and after the beginning of cavitation is substantiated. The difference in the physicochemical and optical properties of metal oxide nanoparticles synthesized in a discharge before and after the beginning of cavitation is demonstrated.     

Electromagnetic devices for assessment of the state of reinforcement elements in reinforced-concrete structures

Functional capacities of a unidirectional eddy-current probe are studied from the viewpoint of localization of reinforcement in reinforced-concrete elements and measurement of its geometric parameters. Such a design of the probe is shown to be inefficient for testing reinforced-concrete items where the reinforcing frame is complex in shape and the content of reinforcement is over 2%. A design of the attachable eddy-current probe is proposed that allows this problem to be solved more efficiently.     

Analysis of simulated scanning of atomic-scale silicon surface by atomic force microscopy

This study constructs a contact-mode atomic force microscopy (AFM) simulation measurement model with constant force mode to simulate and analyze the outline scanning measurement by AFM. The simulation method is that when the probe passes the surface of sample, the action force of the atom of sample received by the atom of the probe can be calculated by using Morse potential. Through calculation, the equivalent force on the cantilever of probe can be acquired. By using the deflection angle equation for the cantilever of probe developed and inferred by this study, the deflection angle of receiving action force can be calculated. On the measurement point, as the deflection angle reaches a fixed deflection angle, the scan height of this simulation model can be acquired. By scanning in the right order, the scan curve of the simulation model can be obtained. By using this simulation measurement model, this study simulates and analyzes the scanning of atomic-scale surface outline. Meanwhile, focusing on the tip radii of different probes, the concept of sensitivity analysis is employed to investigate the effects of the tip radius of probe on the atomic-scale surface outline. As a result, it is found from the simulation on the atomic-scale surface that within the simulation scope of this study, when the tip radius of probe is greater than 12 nm, the effects of single atom on the scan curve of AFM can be better decreased or eliminated.     

Prediction of stage–discharge curves in open-channels using a fixed-point velocity measurement

The single-point measurement method for discharge estimation, which was first introduced by Maghrebi, can be implemented to obtain the discharge at different stages of a river during a flood event. As an advantage of this method, discharge can be estimated automatically with a fixed measurement location in the river section or on the water surface, which is associated with minimum energy and cost consumptions. For the proposed model, we determine the isovel contours in a normalized form for the cross section of the flow. To do so, we need to apply the field or experimental data, concerning the cross sectional geometry at different stages and its roughness variation along the wetted perimeter to the model. Then we collect the data of the single fixed-point of velocity measurement at the flow section using a velocity current meter. To validate the method, it is applied to a flume with different cases of roughened walls. The obtained results of stage–discharge curves using the single point of measurement in comparison to the observed experimental ones show that this method can quickly and accurately estimate the flood discharges. The maximum deviation between the observed and calculated discharges for most of observations is less than 5%.     

Near-field scanning optical microscope probe analysis

In this article results of a comparison of two NSOM probe characterization methods are presented. Scanning electron microscopy analysis combined with electromagnetic field modeling using the finite difference in time domain method are compared with measured far-field radiation diagrams of NSOM probes. It is shown that measurement of far-field radiation diagrams can be an efficient tool for daily checking of the NSOM probes quality. Moreover, it is shown that the inner probe geometry has large influence on the directional radiation of an NSOM probe and the far-field radiation diagram can be used as a simple method to distinguish between different probe geometries.     

时域电磁法套管探伤技术三维有限元数值模拟

提出了一种非接触式套管探伤装置设计方案.采用有限元仿真技术,对装置中纵向磁探头与横向磁探头的时域电磁响应进行了数值模拟.结果表明,纵向磁探头产生与套管同轴的环状涡流,而横向磁探头产生的涡流方向与前者互相垂直.磁探头上的接收信号主要来自金属套管.分析了套管上存在孔洞、纵向裂缝和横向裂缝时,两种磁探头的响应特性.不同孔洞损伤的电磁响应计算结果显示,两种磁探头对孔洞直径的变化均具有较高分辨率.通过对不同参数纵向裂缝与横向裂缝电磁响应特征的讨论,认为横向磁探头对套管上纵向裂缝长度的变化无判断能力,而纵向磁探头对横向裂缝长度变化的识别效果较弱.不同套管损伤的实验结果证实了数值模拟的正确性.     

大型精密测量设备的微振研究

微振对精密测量设备的测量精度有很大的影响。文中针对一种大型精密测量设备进行微振研究。依据惯性测量原理,对运行中的设备进行微振测试。根据微振测试结果得出设备的谐振点、启停的振荡时长、微振的位移振幅以及不同微振源对精度的影响程度等,并给出解决谐振问题的具体措施。微振研究结果对同类产品的设计具有指导意义。     

Multidepth, multiparticle tracking for active microrheology using a smart camera

The quantitative measurement of particle motion in optical tweezers is an important tool in the study of microrheology and can be used in a variety of scientific and industrial applications. Active microheology, in which the response of optically trapped particles to external driving forces is measured, is particularly useful in probing nonlinear viscoelastic behavior in complex fluids. Currently such experiments typically require independent measurements of the driving force and the trapped particle's response to be carefully synchronized, and therefore the experiments normally require analog equipment. In this paper we describe both a specialized camera and an imaging technique which make high-speed video microscopy a suitable tool for performing such measurements, without the need for separate measurement systems and synchronization. The use of a high-speed tracking camera based on a field programmable gate array to simultaneously track multiple particles is reported. By using this camera to simultaneously track one microsphere fixed to the wall of a driven sample chamber and another held in an optical trap, we demonstrate simultaneous optical measurement of the driving motion and the trapped probe particle response using a single instrument. Our technique is verified experimentally by active viscosity measurements on water-ethylene glycol mixtures using a phase-shift technique.     

导电介质物位测量的研究

电容式物位计测量导电介质的物位时，物位测量的结果经常受到导电介质电极挂料的影响，为了解决这个问题本文探讨了一种新型物位测量技术，它能对物位测量时由被测导介质电极挂料的测量误差进行修正，从而提高电容式物位计在导电介质中的测量准确度，文中介绍了这种物位测量技术的测量原理，测量电路及仪表的系统结构和相关实验结果。     

High accuracy plasma density measurement using hybrid Langmuir probe and microwave interferometer method

High spatial resolution plasma density measurements have been taken as part of an investigation into magnetic nozzle physics at the NASA/MSFC Propulsion Research Center. These measurements utilized a Langmuir triple probe scanned across the measurement chord of either of two stationary rf interferometers. By normalizing the scanned profile to the microwave interferometer line-integrated density measurement for each electrostatic probe measurement, the effect of shot-to-shot variation of the line-integrated density can be removed. In addition, by summing the voltage readings at each radial position in a transverse scan, the line density can be reconstituted, allowing the absolute density to be determined, assuming that the shape of the profile is constant from shot to shot. The spatial and temporal resolutions of this measurement technique depend on the resolutions of the scanned electrostatic probe and the interferometer. The measurement accuracy is 9%-15%, which is on the order of the accuracy of the rf interferometer. The measurement technique was compared directly with both scanning rf interferometer and standard Langmuir probe theory. The hybrid technique compares favorably with the scanning rf interferometer, and appears more accurate than probe theory alone. Additionally, our measurement technique is generally applicable even for nonaxisymmetric plasmas.     

基于随动控制的齿轮测量方法

提出了一种两轴随动控制方法,令测头沿被测齿面切向或轴向作跟随运动,以实现齿轮齿廓和螺旋线等的测量。分析了在随动控制方式下齿轮测量过程中各参量的关系,由此建立测量齿轮螺旋线的系统模型,对该模型进行误差分析和仿真,结果表明跟踪误差小于10μm的随动控制系统能实现较高的测量精度,可替代其他齿轮测量仪器的数控系统。该方法也可测量非渐开线、非螺旋线齿面,增强了齿轮测量仪的通用性。     

Diamagnetic flux measurement in Aditya tokamak

Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due to plasma current of less than 20 kA in short duration discharges, in which plasma pressure gradient is supposed to be negligible. The flux measurement during radio frequency heating is also presented in order to validate compensation.     

弹性压缩变形对步距规测量不确定度的影响

针对步距规测量过程中正反向差较大的问题,利用赫兹压力理论分析了测头测力引起的弹性压缩变形,研究表明,由于校准探针用标准器与组成步距规的量块的材质和形状的不同,其弹性压缩变形量存在差异,成为引起正反向差的一个较大分量,通过选择合适的探针校准用标准器,使其符合测量中的一致性原则,可以有效减小步距规的测量不确定度.