Probe Arrangement Research Articles

Assessment of bending waves in Torsion Hopkinson Bar experiments using Photon Doppler Velocimetry

A Photon Doppler Velocimetry system that measures the propagation of elastic shear waves in a Torsion Hopkinson Bar (THB) system is presented. The method uses multiple fiber optic probes located symmetrically on opposing sides of the apparatus bars, and provides data with high spatial (a laser irradiated spot size of 35μm) and temporal resolution that is ultimately limited by the data acquisition system and used electronic components. A series of validation experiments simulating the movement of the bar subjected to bending and misalignments demonstrated that this approach is effective in detecting and accounting for the bending waves. The THB experiment under non-ideal conditions, where a combination of shear and bending waves propagates in the system, conclusively confirmed that the disturbance in the acquired signals can be properly addressed with the proposed arrangement of the PDV probes. It was reflected in similar measurements of the component of tangential velocity to the strain gauges. This approach shown to be complementary to the conventional strain gauge technique, but can provide better precision and be more robust under loading and/or temperature conditions that may affect the reliability of strain gauge measurements.

Effect of vermicompost additive on physical, chemical and dielectric properties of soil and its modeling

The present study focuses on the effects of vermicomposting on various soil properties, particularly emphasizing the dielectric characteristics of soil. Vermicomposting is known to significantly enhance soil fertility and improve its physical aspects such as aeration, porosity and water retention. In this analysis, a modified probe arrangement has been employed to determine how varying levels of vermicompost influence the soil’s dielectric properties within the radio and microwave spectrum (10 MHz-14 GHz). A modified Dak-12 open-ended coaxial probe, paired with a vector network analyzer, was utilized for this purpose to overcome the drawbacks of standard arrangement. The results show that vermicompost strongly affects the soil’s physical attributes (pH, bulk density, porosity) and also its chemical properties, along with its dielectric behavior. The study further explored the role of different factors such as the concentration of vermicompost, frequency and temperature on soil’s dielectric response. To accurately and swiftly gauge these effects, Response Surface Methodology (RSM) has been employed to predict the dielectric properties (ε’ and ε’’) of the soil. The high precision of these models, with R 2 values of 0.9729 for ε’ and 0.9487 for ε’’, underscores their effectiveness in evaluating the impact of vermicompost on various soil properties.

Triblock PolyA-Mediated Protein Biosensor Based on a Size-Matching Proximity Hybridization Analysis.

The antibodies in the natural biological world utilize bivalency/multivalency to achieve a higher affinity for antigen capture. However, mimicking this mechanism on the electrochemical sensing interface and enhancing biological affinity through precise spatial arrangement of bivalent aptamer probes still pose a challenge. In this study, we have developed a novel self-assembly layer (SAM) incorporating triblock polyA DNA to enable accurate organization of the aptamer probes on the interface, constructing a "lock-and-key-like" proximity hybridization assay (PHA) biosensor. The polyA fragment acts as an anchoring block with a strong affinity for the gold surface. Importantly, it connects the two DNA probes, facilitating one-to-one spatial proximity and enabling a controllable surface arrangement. By precisely adjusting the length of the polyA fragment, we can tailor the distance between the probes to match the molecular dimensions of the target protein. This design effectively enhances the affinity of the aptamers. Notably, our biosensor demonstrates exceptional specificity and sensitivity in detecting PDGF-BB, as confirmed through successful validation using human serum samples. Overall, our biosensor presents a novel and versatile interface for proximity assays, offering a significantly improved surface arrangement and detection performance.

A dynamic method for online measurement and calibrating with Lorentz force velocimetry

Our previous study (Zheng et al 2020 Metall. Mater. Trans. B 51 558–69; Zheng et al 2020 Acta Metall. Sin. 56 929–36) reports a non-invasive in-situ measurement technology using Lorentz force velocimetry (LFV) to quantitatively measure the meniscus velocity of molten steel online. However, effective signal recognition from complex environment noise and determination of zero-point calibration in harsh metallurgical processing is an essentially challenging task and indeed needs further exploration. In this paper, a method of combining double probe arrangement with real-time differential processing technology was proposed, the twin design structure not only enables the measurement of ∼mN Lorentz forces, but also has significant characteristics of environmental tolerance. The Lorentz force signal caused by conductor motion can be accurately calculated through a differential method, meaning that the problem of zero compensation in industrial online measurement can be effectively overcome. Moreover, based on the functional correlation between the Lorentz force and the parameter of the conductor to be measured, a method of the probes moving variably and actively and their data difference ratio processing was adopted, so as to achieve dynamic calibration during online measurement. This measurement strategy provides a new approach for LFV to achieve online dynamic measurement and online calibration, and provides technical support for electromagnetic measurement technology towards engineering applications.

Three-point probe 1/f noise measurement

Abstract The impact of contact resistance (R c) on 1/f noise measurements was studied to demonstrate improved accuracy with a novel three-point probe (3pp) method, introduced here, versus the typical two-point probe (2pp) arrangement. It was shown for n+ -Si that using indium to lower R c decreased the noise spectral density (NSD) over 100× for 2pp. In the 3pp configuration, NSD was reduced by another ∼5×, independent of indium use (i.e. spectra overlapped), suggesting that 3pp avoids the impact of R c on NSD. More heavily doped n++ -Si also showed improvements with 3pp and 2pp/indium versus 2pp/bare. Expectedly, 3pp provided less of a benefit relative to 2pp/indium as R c was already small due to highly degenerate doping. Measurement drift also improved with 3pp. These results have implications on 1/f measurement accuracy for the broadly used 2pp arrangement. The 3pp method provides a better noise floor for NSD testing because it is not convoluted with signal from R c, does not require metallization and has improved simplicity and versatility yet performs equal to four-point probe methods.

Using phase relationships in non-symmetric ToFD configurations

In conventional ToFD, operators are taught that diffracted echoes from the top and bottom of a planar defect have opposite phase and such defects can thus be discriminated from a pair of slag lines. This phase-inversion test is therefore used as a tool for characterizing an indication. When using non-symmetric probe arrangements and less-conventional beam angles, the situation becomes less clear-cut. Early in the development of the ToFD technique in the 1980s and 1990s, theoretical models enabled calculation of the amplitude and phase of diffracted signals from a crack edge for any incident and diffracted angle. Experimental studies at the time gave results that supported the theoretical predictions in idealized situations, but showed that for finite pulses and finite probe dimensions, it was more difficult to confirm the predictions for phase. In an inspection of a weld in a high-integrity component for the Hinkley Point C power station an asymmetric ToFD design was adopted as a solution to an access restriction. Comparison of top/bottom phase of indications was used as part of the procedure for characterization of indications. An analysis is made of the reasons why certain asymmetric configurations could not be used to identify planar defects using top-bottom phase inversion. The resulting re-design of the ToFD inspection configurations for a non-symmetrical inspection surface is presented, in which phase inversion remains a robust tool for defect characterization.

Improving the intrinsic conductance of selective area grown in-plane InAs nanowires with a GaSb shell

The nanoscale intrinsic electrical properties of in-plane InAs nanowires grown by selective area epitaxy are investigated using a process-free method involving a multi-probe scanning tunneling microscope. The resistance of oxide-free InAs nanowires grown on an InP(111)B substrate and the resistance of InAs/GaSb core–shell nanowires grown on an InP(001) substrate are measured using a collinear four-point probe arrangement in ultrahigh vacuum. They are compared with the resistance of two-dimensional electron gas reference samples measured using the same method and with the Van der Pauw geometry for validation. A significant improvement of the conductance is achieved when the InAs nanowires are fully embedded in GaSb, exhibiting an intrinsic sheet conductance close to the one of the quantum well counterpart.

Five-degrees-of-freedom error motion measurement method of precision rotary table based on BMPES

It is essential to obtain the five-degrees-of-freedom (5-DOF) error motion of a rotary table to reconstructthe real trajectory of the rotating shaft, but there are many error coupling problems when measuring the error motion of a rotary table. In order to improve the measurement accuracy of the 5-DOF error motion of the rotary table, a method of measuring the error motions based on bidirectional multi-point error separation (BMPES) is proposed. First, by analyzing the motion characteristics of the rotary table with multiple degrees of freedom error during the rotation, a detection system with a double-layer structure probe arrangement is designed. Then, the three-point method is used in the radial direction to separate the roundness error of the measuring disk, which improves the measurement accuracy of radial error. Finally, the coupling relationship between the mixing errors collected by the axial probes is researched, and a face-four-point error separation method is proposed, which can separate the flatness error of the lower surface of the measuring disk and complete the decoupling of the tilt error and the axial runout error. Simulation results show that for the measurement of radial, tilt and axial errors, the measurement errors of the BMPES method proposed in this paper are reduced by 97.89%, 68.40% and 99.99%, respectively, compared with the five-point method, and when eccentricity errors exist, the measurement errors of the radial and tilt errors are reduced by 99.06% and 85.67%, which verifies that the method can accurately obtain the 5-DOF motion of the rotary table errors.

Entropy-Driven Three-Dimensional DNA Nanofireworks for Simultaneous Real-Time Imaging of Telomerase and MicroRNA in Living Cells.

Real-time monitoring of different types of intracellular tumor-related biomarkers is of key importance for the identification of tumor cells. However, it is hampered by the low abundance of biomarkers, inefficient free diffusion of reactants, and complex cytoplasmic milieu. Herein, we present a stable and general method for in situ imaging of microRNA-21 and telomerase utilizing simple highly integrated dual tetrahedral DNA nanostructures (TDNs) that can naturally enter cells, which could initiate to form the three-dimensional (3D) higher-order DNA superstructures (DNA nanofireworks, DNFs) through a reliable target-triggered entropy-driven strand displacement reaction in living cells for remarkable signal amplification. Importantly, the excellent biostability, biocompatibility, and sensitivity of this approach benefited from (i) the precise multidirectional arrangement of probes with a pure DNA structure and (ii) the local target concentration enhanced by the spatially confined microdomain inside the DNFs. This strategy provides a pivotal molecular toolbox for broad applications such as biomedical imaging and early precise cancer diagnosis.

Influence of an external magnetic field on laser-induced plasma and cavitation bubbles in submerged targets

A pulsed Nd:YAG laser is tightly focussed on a metal target immersed in distilled de-ionized water. The resultant laser-induced plasma and subsequent cavitation bubble behavior are studied under the influence of an external magnetic field that is varied from 700 to 1000 Gauss. The study is conducted using a beam deflection probe arrangement. In addition, laser-induced breakdown spectroscopy is also employed to study the plasma spectrum. Furthermore, three different magnetic materials are employed for this investigation: ferromagnetic nickel, paramagnetic gadolinium, and diamagnetic copper. The studies revealed that cavitation bubble radii and collapse durations increased considerably as the magnitude of the external magnetic field was increased. This effect was prominent in the case of nickel and less so in the case of gadolinium and copper. For nickel, collapse times increase when the magnetic field was applied, whereas for gadolinium and copper, significant changes were not observed. The differences observed in collapse times showed that magnetic properties of the targets played a vital role in this phenomenon. The process of pulsed laser ablation in liquid also led to the respective generation of metallic nanoparticles from individual materials. Characterization of the generated nanoparticles revealed size reduction when synthesized under the influence of an external magnetic field. These characterizations were performed using transmission electron microscopy and UV-Vis spectroscopy.

Engineering of Interfaces with Tetrahedra DNA Nanostructures for Biosensing Applications

AbstractThe probe‐target interactions in the interfaces are significantly critical to biosensing. However, the disordered arrangement of probes and nonspecific adsorption of proteins in the biosensing interfaces for conventional biosensors often restricted the accessibility and recognition efficiency of probes towards targets, leading to poor detection performances (e. g., sensitivity and selectivity). Engineering of biosensing interfaces with functional molecules or nanomaterials has provided a promising molecular toolkit for enhanced accessibility and efficient recognition of biosensing probes. Among them, DNA has been an appealing material for interface engineering, because of its unique merits of biocompatible, predictable hybridization, and unparallel self‐assembly ability. In particular, employing tetrahedra DNA nanostructures (TDNs) to engineer interfaces has been a powerful means to improve biosensor performance. Here, this review introduces the recent progress in TDN‐based interface engineering. Then, we summarize the roles of TDNs in tailoring the properties of different interfaces, including electrode surface, channel surface, cell surface, etc., and highlight their biosensing applications. Finally, scientific challenges and future perspectives of TDN‐engineered biosensing interface are also discussed.

Embedded-probes diagnostics for the COMPASS upgrade tokamak: a concept

This article introduces a concept based on flush-mounted probes embedded in the limiters of the COMPASS-Upgrade tokamak. Main issues related to flush probe geometry are taken into account and discussed. Calculations of heat fluxes and the incident angle of the field lines on the different limiters using the PFCflux code are performed to support in probe arrangement optimization. Model current-voltage characteristics for a flush probe are simulated using the SPICE2 code and their dependence on the angle of incidence is studied. The results are used to predict the current to be collected by the flush probes for different magnetic fields and to examine the reliability of the proposed diagnostics. A discussion is included on the capability of the electronic system considered for the measurements.

Development of a Triple Langmuir Probe for Plasma Characterization in SPIDER

This contribution describes the commissioning and first operation of a fixed triple Langmuir probe in source for the production of ions of deuterium extracted from a radio frequency plasma (SPIDER), the full-scale prototype of the negative-ion source for ITER neutral beam injectors. This diagnostic is capable of measuring the time evolution of the main plasma features for the entire duration of the plasma discharge, allowing to correlate local plasma properties, such as density, electron temperature, and plasma potential, to control parameters, i.e., filter field intensity, radio frequency (RF) power, and bias voltages. The probe was installed on the rear wall of the expansion chamber, and this being a region of specific interest for the operation with cesium since it may act as a reservoir, contributing to the cesium recycling toward the extraction region. Furthermore, the capability of the triple probe arrangement of measuring the instantaneous plasma density and electron temperature (also at high frequency) has been exploited to investigate the modulation of plasma parameters.

Electro-optic Bdot probe measurement of magnetic fluctuations in plasma.

We propose a combined use of a Pockels electro-optic sensor with a pickup loop coil (Bdot probe) for the measurement of magnetic fluctuations in plasmas. In this method, induced fluctuating voltage on the coil loop is converted into an optical signal by a compact electro-optic sensor in the vicinity of the measurement point and is transferred across optical fiber that is unaffected by electric noise or capacitive load issues. Compared with conventional Bdot probes, the electro-optic Bdot probe (1) is electrically isolated and free from noise pickup caused by the metallic transmission line and (2) can be operated at a higher-frequency range because of the smaller capacitance of the operation circuit, both of which are suitable for many plasma experiments. Conversely, the sensitivity of the current electro-optic Bdot probe arrangement is still significantly lower than that of conventional Bdot probes. A preliminary measurement result with the electro-optic Bdot probe showed the detection of a magnetic fluctuation signal around the cyclotron frequency range in the RT-1 magnetospheric plasma experiment.

Probing multimode applicator of microwave heating system for E‐field distribution using a silicon carbide sensor and a shielded thermocouple

AbstractMeasurement of the field distribution in a multimode applicator of a microwave heating system has been a challenging problem. We report here a simple but comprehensive scheme for its semi‐quantitative estimation under no‐load conditions. It involves the measurement of temperature (T) versus time (t) profiles in a small silicon carbide (SiC) sensor ring positioned at the junction end of a metal‐jacketed microwave‐compatible thermocouple probe arrangement. These heating profiles (T vs. t) were measured using a data acquisition system, keeping the SiC ring at different (x, y, z) positions in the applicator. Using this measurement scheme, the spatial positions with local field minimum as inferred from very high reflected power or those with local field maximum with associated thermal runaway type condition could be well identified. Given the thermal and the dielectric properties of SiC material and the physical dimensions of the sensor ring, a uniform microwave field‐based model with a thermal lumped element type approximation (with no thermal gradient across SiC) was applied for analysis of the T versus t heating profiles. Within this model, the locally effective electric field E could be inferred for low and moderate electric field ranges. While the accuracy of the field estimation is currently limited by the use of the metal‐jacketed thermocouple and other factors, this SiC sensor‐based methodology has the potential to be developed further to be useful in the area of microwave applicator design.

A novel method for identification of synchronous resonance frequency of blades based on random arrangement of tip-timing probes

Blade tip-timing (BTT) signal suffers from the undersampling feature, which causes the high-frequency information to be aliased to the low-frequency band, especially the aliasing problem of the synchronous resonance frequency more serious. In order to realize the frequency identification of undersampled signals in synchronous resonance, a novel multiscale cyclic-reverse optimized arrangement (MC-ROA) method based on the random arrangement of tip-timing probes is proposed in this paper. Firstly, a sparse model for frequency recovery is built based on the link between the known undersampled signals and the unknown original signals in the frequency domain, and the subspace pursuit (SP) algorithm of compressive sensing (CS) is used for frequency recovery. Then, under the random arrangement of probes, the number of ideal probes is adjusted at multiple scales and the datum probes are selected cyclically to obtain multiple sets of solutions. Finally, the target frequency weights are used to overcome the limitations of the restricted isometry property (RIP) of the parameterized compression matrix to determine the optimal recovery frequency. The BTT experiments are given to verify the effectiveness of the proposed method.

Study on Error Separation of Three-Probe Method

With the advantage of in situ measurement, the three-probe method is commonly used to measure either the error motion of high-precision spindles or the roundness error of artifacts. The roundness error of artifacts or spindle errors can be obtained through solving error-separation equations. Both the time- and frequency-domain solutions of the three-probe method are presented. In addition, the key points of solutions, i.e., the rounding error induced by inconsistency of sampling points, harmonic suppression, and averaging schemes of multiple revolutions into one circle, are described in detail. Experiments were conducted to compare the two solutions and quantify the influence of setup parameters, including rotational speed probe arrangement, consistency of sampling points, and number of revolutions. The results showed that the roundness error of the time-domain solution was inaccurate due to large rounding errors, while that of the frequency-domain solution with the previous average scheme was accurate. In contrast, the spindle error of the frequency-domain solution with the latter average scheme was more reliable. The findings provided a reference to recommend setup parameters depending on the aim of the three-probe method.

Electrical behavior of working electrodes derived from Fly ash enriched epoxy

Working electrodes (WEs) derived from electrically conductive materials are the integral components of devices employed for microelectronics, electrochemical energy storage and anticorrosive coatings. Herein, we report fabrication and comparative account of DC conductivity (mS/cm) of WEs derived from cured epoxy (A1), fly ash (FA, A2) and epoxy enriched with FA (A3, 80 wt%, crystallite size 17.87 nm). Morphology of epoxy derived WEs was compared with scanning electron microscopy. Electrical behaviour of epoxy derived WEs at identical thickness (0.25 ± 0.01 mm) has been investigated and compared with FA derived WEs (A2). Study reveals highest DC conductivity of A3 (10.65), followed by A2 (6.67) and A1 (3.90) at 373.15 K under four probe arrangements. Arrhenius plots reveals energy of activation (Ea, J/mol) in increasing order for A3 (1.58), followed by A2 (2.70) and A1 (2.83) at 100Vand 313.15–373.15 K. Present study reveals the feasibility of FA in sustainable development of WEs using epoxy binder for possible applications in microelectronics and energy storage.

Estimating the error in filament propagation measurement using a synthetic probe

Electric probe arrangements are a standard tool for investigating plasma filaments in the scrape-off layer of magnetic fusion experiments. In the Wendelstein 7-X stellarator, recent work has characterized plasma filaments using reciprocating electric probes and provided a comparison of filament scaling to simulated filaments, showing remarkable agreement (Killer et al 2020 Plasma Phys. Control. Fusion 62 085003). Here, such simulations are further employed to assess uncertainties inherent to probe measurements by introducing a synthetic probe diagnostic into the simulation. It is determined that filament diameters, and to a smaller degree radial filament velocities, are inherently underestimated in experiment when a filament is not centered on the probe tip. Filament velocity measurements are also sensitive to the alignment of the probes relative to the poloidal direction and the distance between pins. Floating potential pins which are spaced too far apart will underestimate filament velocity, whereas pins which are closely-spaced can overestimate the filament velocity. The sensitivity of the floating potential measurements—from which radial velocity is extracted—to temperature fluctuations is discussed. These investigations apply to measurements of filaments by electric probes in tokamaks as well and may serve as guidance for interpreting probe data and designing probe arrays.

An improved measurement scheme of the large-caliber steady-state magnetic-field testing system for ITER

The large-caliber steady-state magnetic-field testing system is an important device for the International Thermonuclear Experimental Reactor, which is mainly used for electromagnetic compatibility tests in a strong magnetic field environment. The uniform magnetic field area needs to be measured to ensure the correctness of the design after the completion of the platform. This paper mainly analyzes the relationship between the magnetic field probe and error, studies the detection effect of different arrangement methods of magnetic field probe points, and obtains a more accurate probe arrangement method through comparative analysis. Then, the principle and structure of the acquisition and detection system are studied, and the multipoint synchronous Hall array magnetic field detection system of the magnetic field is built by using the Hall probe to realize the omnidirectional measurement of the magnetic field. Finally, the Hall probe is calibrated and tested by experiments, and a test platform is built to test the magnetic field. The results verify the correctness of the analysis.