Multi-point Detection Research Articles

Research on the electromagnetic ultrasonic detection method of initiation crack based on multi-acoustic coefficients fusion

Abstract The traditional single acoustic coefficient cannot judge the different degrees of fatigue damage such as initiation crack and crack extension. Based on the law between the structural evolution of dislocation pile-up initiating crack and acoustic coefficients, a multi-acoustic coefficients fusion feature-fatigue damage stage detection method is proposed. By extracting the nonlinear features as well as linear features of the multi-point detection signals for a single fatigue-damaged aluminum plate, achieves the fatigue damage state. Experiments verified multi-acoustic coefficients with different features corresponding to different fatigue stages such as initiation crack and crack extension.The peak points of the acoustic nonlinear coefficients are used for the judgment of the initiation crack stage, and the peak-to-peak amplitude of the acoustic linear coefficients are used for the judgment of the crack extension stage. Comparing and analyzing the results of electromagnetic ultrasonic detection and microscopic observation of different fatigue damage stages, the proposed method provides early warning of the initiation crack and crack extension by studying the characteristics of acoustic coefficients of different fatigue damage stages. This study provides theoretical and experimental basis for the application of electromagnetic ultrasonic assessment of fatigue damage in metallic materials.

Multi-point sensing system for cable fault detection using fiber Bragg grating

This study presents a multi-point sensing system for cable fault detection based on fiber Bragg grating (FBG). The system detects vibration signals caused by cable faults through changes in the reflected power of the FBGs. By integrating time division multiplexing (TDM) technology, the system achieves multi-point fault detection and distinguishes vibration signals from faults at different cable locations. To verify the system’s feasibility, different fault scenarios were simulated. The results show that the system can detect the vibration signals caused by cable joint faults, successfully demodulate the corresponding frequency components, and reconstruct the strain applied to the FBGs. Additionally, to address the impact of front-end FBG on back-end FBG, a power compensation method was developed to improve detection accuracy. The proposed cable fault detection system facilitates online detection of cable joint faults but also reduces system equipment costs, offering a novel approach to cable fault detection.

A Non-Source Optical Fiber Sensor for Multi-Point Methane Detection.

Fast, accurate, real-time measurement of gas concentration is an important task for preventing coal mining disasters. In order to develop an accurate monitoring method for methane gas concentration at different locations in a mine environment, a non-source optical fiber sensor for multi-point methane detection has been developed in this paper. A 16-channel fiber splitter and a multi-channel time-sharing acquisition module are employed within the sensor, enabling simultaneous detection of methane gas at 16 points by a host. Furthermore, the methane sensors are connected to the monitoring host via an all-optical method, achieving non-source and long-range detection of methane. To assess the performance of the methane gas sensor, experiments were conducted to evaluate its detection range, response time, and stability. The results indicated that the average detection error was approximately 1.84% across the full range, and the response time did not exceed 10 s. The minimum detection limit of the sensor, as determined by the 1σ criteria, was obtained as 58.42 ppm. Additionally, the concentrations of methane gas measured at varying distances (1 km, 2 km, 5 km) were found to be essentially consistent over an extended period. These results suggest that the development of this non-source optical fiber sensor holds significant potential for providing a method for mine environment, multi-point online methane gas detection.

Analysis of Structural Heterogeneity in Low-Rank Coal and Its Pyrolyzed Char Using Multi-Point Scanning Micro-Raman Spectroscopy.

Understanding the changes in carbon structure during the mid-low-temperature pyrolysis of low-rank coal is important for efficient utilization. Raman spectroscopy is commonly used to analyze the structural order of carbonaceous materials, but traditional methods may overlook the heterogeneity of coal/char. This research explores the heterogeneity of char structure derived from low-rank coal at 700 °C through multi-point micro-Raman analysis. The analysis of parameters such as area (A), intensity (I), full width at half maximum (FWHM/W), and peak position (P) reveals that the carbon structure becomes less ordered as coal transforms into char due to the deposition of small molecules on the surface. The study emphasizes the benefits of multi-point detection for gaining in-depth insights into the structural evolution of carbonaceous materials. The increased standard deviation of Raman parameters indicates diverse structural characteristics resulting from pyrolysis at this temperature, which traditional methods may not capture effectively. The mapping method used in this research visually illustrates the distribution of carbon structures in the region.

Defect detection of grouting sleeve connection with energy ratio change in frequency domain

Controlling the grouting density is the key to ensure the construction quality of precast structures. Since the grouting sleeve is embedded in concrete, it is difficult to detect the grouting compactness of the sleeve. In this paper, the frequency domain analysis technique is used for non-destructive testing of concrete components with grouting defects. The collected ultrasonic testing signals are calibrated-denoised-decomposed-reconstructed. The damage degree of the grouting signal is evaluated and analyzed by quantifying the energy value of different frequency signals with two norms. Considering the effect of the random distribution of aggregates on the propagation of ultrasonic stress waves, a three-dimensional multi-point detection model and a two-dimensional plane single-point model based on piezoelectric effect are set up respectively. Results show that frequency energy distribution of the grout-deficient signal is concentrated to low-frequency range than that of grout-compact signal. When grouting defect accumulates to a certain extent, the main frequency may move from high-frequency band to lower-frequency band. Although the aggregates in different concrete components are randomly distributed, the test results of the two-dimensional plane model show that the validity of the defect quantitative index is 72%. The experimental tests results show that the method of using frequency energy transfer to lower-frequency band to determine grouting defects is effective, with a detection validity of 66.7%. Therefore, the non-destructive testing method for grouting sleeve compactness proposed in this paper can provide reference for engineering testing application.

Wireless strain-field monitoring system for motion recognition via direct-ink-writing sensor-array

Large-area strain-monitoring is highly desired in various engineering applications. Despite the fact that the commercial strain gauges have been successfully used for strain measurement, there is still big challenge for this manually-pasting based solution especially for large-area monitoring. First, the wires of multiple commercial strain gauges for large-area monitoring will exhibit remarkably abundant and complex, and eventually reduce the reliability and convenience of the measurement system. Second, the commercial terminal instrument is usually function-redundant with complicated electronic configuration to match the low-sensitive metal-foil strain gauge. Meanwhile, the wire-based signal acquisition and processing system substantially limit the compatibility for moving objects. Here we take the advantages of direct-ink-writing (DIW) 3D printed sensor array, thereby propose a wireless-based solution for large-area strain field measurement, data transmission and processing. The sensitivity of the printed sensing unit is one order of magnitude higher than that of traditional strain gauges, while the sensor array layout is optimized for compatibility to the strain orientation and detecting domain. A high-frequency signal acquisitor is designed and assembled with a wireless transmitter for rapid multi-point strain detection and real-time data transmission. A remote data receiver and processing terminal are developed and integrated for twin-visualization of the detected strain field. In particular, the detected strain data are processed to construct a cascaded support-vector-machine (SVM) classifier, that successfully identify motion states of moving vehicles in high precision. This study provides insight into exploring the advantages of DIW printed sensor arrays combined with specifically-designed wireless system and strain-based dynamic recognition.

Multi-point synchronous temporary grounding wire detection device based on convolutional neural networks

To prevent grounding accidents caused by forgetting to remove the temporary grounding wires and the contact of trees with the distribution network, a multi-point synchronous temporary grounding wire detection device based on convolutional neural networks is developed. The developed device can judge the type of groundings on the test line quickly and locate the ground points accurately during the cut-out. Three-phase alternating current (AC) signals with a specific frequency are injected at multiple points on the line by multiple groups of the device controlled by Raspberry Pi 3B + and embedded Android. The device can achieve the approximate location through the impedance ranging method and the accurate location by integrating the data from multiple points. The trained EfficientNet-B0 algorithm is utilized to predict the grounding positions. The tested results of the prototype verify the accuracy and rapidity of grounding diagnosis and positioning.

Multiwavelength erbium-doped fiber laser using the polarization-hole-burning effect for multichannel acoustic detection.

We propose and demonstrate a novel, to the best of our knowledge, fiber-optic multipoint acoustic detection system based on a multiwavelength erbium-doped fiber (EDF) laser (MWEDFL) using the polarization-hole-burning effect with Fabry-Perot interferometers as the acoustic cavity-loss modulator. A polarization-wavelength-related filter is designed to assign a distinct polarization state to each laser wavelength. By adjusting the polarization state, the polarization-dependent loss and gain of each laser line are tuned to be equal, effectively suppressing the mode competition of EDF and enabling a stable MWEDFL. Each laser line serves as a separate channel for acoustic detection. Theoretical and experimental analyses are conducted to study the transient-response-amplification effect on the acoustic perturbation of the MWEDFL. The results show that the proposed MWEDFL exhibits an amplification effect on the sound-induced cavity-loss modulation, effectively enhancing the sensitivity by 13 dB compared to that obtained using an external-light-source demodulation method. In addition, the MWEDFL based on the PHB effect avoids cross talk between laser channels and can achieve high sensitivity and simultaneous multichannel acoustic detection.

Nanomaterial-Coated Carbon-Fiber-Based Multicontact Array Sensors for In Vitro Monitoring of Serotonin Levels.

In this study, we demonstrated the fabrication of multicontact hierarchical probes for the in vitro detection of serotonin levels. The basic three-dimensional (3D) bendable prototypes with 3 (C1), 6 (C2), or 9 (C3) contact surfaces were printed from polymeric resin via the digital light processing (DLP) technique. We chose ultrasonicated carbon fiber strands to transform these designs into multicontact carbon fiber electrodes (MCCFEs). The exposed carbon fiber (CF) surfaces were modified with aminopropyl alkoxysilane (APTMS), followed by the subsequent loading of palladium nanoclusters (PdNPs) to build active recording sites. CF functionalization with PdNPs was achieved by the wet chemical reduction of Pd(II) to Pd(0). The MCCFE configurations demonstrated an enhancement in the electroactive surface area and an improved voltammetric response toward 5-HT oxidation by increasing the points of the contacts (i.e., from C1 to C3). These MCCFEs are comparable to 3D-protruding electrodes as they can enable multipoint analyte detection. Along with the electrode patterns, morphological irregularities associated with both Pd-doped and undoped CFs supported the creation of proximal diffusion layers for facile mass transfer. Low detection limits of 0.8-10 nM over a wide concentration range, from 0.005 nM to 1 mM, were demonstrated. The MCCFE sensors had a relatively low standard deviation value of ∼2%. This type of sensitive and cost-effective electrochemical sensor may prove useful for collecting electrical impulses and long-term monitoring of 5-HT in vivo in addition to in vitro testing.

Multipoint Lock-in Detection for Diamond Nitrogen-Vacancy Magnetometry Using DDS-Based Frequency-Shift Keying.

In recent years, the nitrogen-vacancy (NV) center in diamonds has been demonstrated to be a high-performance multiphysics sensor, where a lock-in amplifier (LIA) is often adopted to monitor photoluminescence changes around the resonance. It is rather complex when multiple resonant points are utilized to realize a vector or temperature-magnetic joint sensing. In this article, we present a novel scheme to realize multipoint lock-in detection with only a single-channel device. This method is based on a direct digital synthesizer (DDS) and frequency-shift keying (FSK) technique, which is capable of freely hopping frequencies with a maximum of 1.4 GHz bandwidth and encoding an unlimited number of resonant points during the sensing process. We demonstrate this method in experiments and show it would be generally useful in quantum multi-frequency excitation applications, especially in the portable and highly mobile cases.

Multipoint Detection of GRB221009A’s Propagation through the Heliosphere

We present the results of processing the effects of the powerful gamma-ray burst GRB221009A captured by the charged particle detectors (electrostatic analyzers and solid-state detectors) on board spacecraft at different points in the heliosphere on 2022 October 9. To follow the GRB221009A propagation through the heliosphere, we used the electron and proton flux measurements from solar missions Solar Orbiter and STEREO-A; Earth’s magnetosphere and solar wind missions THEMIS and Wind; meteorological satellites POES15, POES19, and MetOp3; and MAVEN—a NASA mission orbiting Mars. GRB221009A had a structure of four bursts: the less intense Pulse 1—the triggering impulse—was detected by gamma-ray observatories at T 0 = 13:16:59 UT (near the Earth); the most intense Pulses 2 and 3 were detected on board all the spacecraft from the list; and Pulse 4 was detected in more than 500 s after Pulse 1. Due to their different scientific objectives, the spacecraft, whose data were used in this study, were separated by more than 1 au (Solar Orbiter and MAVEN). This enabled the tracking of GRB221009A as it was propagating across the heliosphere. STEREO-A was the first to register Pulse 2 and 3 of the GRB, almost 100 s before their detection by spacecraft in the vicinity of Earth. MAVEN detected GRB221009A Pulses 2, 3, and 4 at the orbit of Mars about 237 s after their detection near Earth. By processing the observed time delays, we show that the source location of the GRB221009A was at R.A. 288.°5, decl. 18.°5 ± 2° (J2000).

A reinforced corrosion assessment method based on a new magnetic sensor and improved adaptive filtering

Abstract Corrosion assessment of reinforced concrete structures is the basis for subsequent corrosion repair and early warning of structural hazards. Aiming at the problem of accurately measuring the corrosion degree of reinforced concrete structures in coastal area, a new Magnetic Sensor (NMS) based on the theory of magnetic medium is designed in this paper. A functional model of the relationship between magnetic induction intensity change and reinforcement mass loss based on multi-point detection is constructed, and an improved adaptive filtering Least Mean Square (LMS) algorithm is proposed to realize damage identification and quantitative calculation of reinforcement corrosion comprehensively. Through numerical simulation experiments, the feasibility of designing the sensor is verified. The measured corrosion test of the sensor prototype shows that the calculated corrosion rates of different steel corrosion degrees are in good agreement with the actual values, with an average relative error of 1.64 %. The sensor provides a new method for corrosion monitoring of reinforced concrete structures.

Multi-point optical fiber hydrogen detection system based on light polarization modulation

A hydrogen sensing system including 8 sensors based on light polarization modulation is developed and demonstrated for simultaneous multi-point hydrogen sensing with high sensitivity. Each sensor is composed of a polarizer, a polarization control, and a short segment of polarization maintaining fiber (PMF) coated with Pt-loaded WO3. Due to the exothermic reaction between hydrogen and WO3 with the help of catalyst Pt, the local temperature of PMF increases and the reflective spectrum of the sensor shift accordingly. The self-developed control system software achieves the sequential scanning and recording of the reflection spectra of each sensor by programable controlling a light switch, and then gives the measured hydrogen concentration of each channel in real-time according to the spectrum shift by using an automatic dip finding algorithm with Gaussian fitting. The experimental results show that the proposed type of sensor has ultra-high hydrogen sensitivity, with a maximum value of −20.22 nm/% (vol %); packaging with foam substrate helps to reduce the response time of the device; the hydrogen sensor is almost unaffected by environmental relative humidity. Moreover, the hydrogen sensing system is experimentally proved having good stability and repeatability.

Multi-channel chaotic cross-correlation fiber loop ring down sensing

A novel optical sensing of the multi-channel chaotic cross-correlation fiber loop ring down (FLRD) sensing is proposed and demonstrated experimentally. The proposed sensing system consist of the multiple FLRD sensors within a serial architecture. The chaotic laser was divided into reference signal and the detection signal by an optical coupler and measured the cross-correlation coefficient ring down time of chaotic signal to obtain the shorter response time. The three-channels FLRD chaotic signal are achieved by the cross correlation experimentally to verify the proposed concept. The simultaneous detection of temperature and refractive index is studied by the dual-channel experiment. The experimental results show that the high sensitivity of each channel can be achieved without interfering each other. We believe the proposed sensing system have great potential for short-distance and multi-point detection.

Multi-point detection method of dynamic deflection of super long-span bridge based on chain laser model

Real-time monitoring of bridge deflection is of great significance for ensuring bridge safety. Aiming at the problems of poor real-time performance and low precision of deflection measurement of continuous multi-span and super long-span bridges, this paper proposes a multi-point chain laser detection model and method for dynamic deflection of super long-span bridges. Firstly, we construct a multi-point deflection parameter detection model based on chain laser reference and image processing, and give the system error adjustment scheme of the model; Then, the hardware framework of the system is designed, and the real-time deflection parameter data acquisition, processing and solution methods are analyzed. In addition, the related factors affecting the measurement accuracy of the system are analyzed, and the system error is analyzed and corrected. Finally, the principle prototype is built, and the intelligent monitoring platform based on cloud data processing is designed. The system parameter calibration experiment is carried out and verified on the displacement platform built outdoors. The results show that the measurement accuracy of the system can reach 1 mm under the condition of considering the pitch angle of the monitoring equipment, which can realize the real-time, dynamic and high-precision monitoring of the deflection of the long-span bridge beam.

Discrete multi-point partial discharge detection and location technology of optical fiber

Discrete multi-point partial discharge detection and location technology of optical fiber

Application of Intraoperative Rapid Molecular Diagnosis in Precision Surgery for Glioma: Mimic the World Health Organization CNS5 Integrated Diagnosis.

With the advent of the molecular era, the diagnosis and treatment systems of glioma have also changed. A single histological type cannot be used for prognosis grade. Only by combining molecular diagnosis can precision medicine be realized. To develop an automatic integrated gene detection system (AIGS) for intraoperative detection in glioma and to explore its positive role in intraoperative diagnosis and treatment. We analyzed the isocitrate dehydrogenase 1 (IDH1) mutation status of 105 glioma samples and evaluated the product's potential value for diagnosis; 37 glioma samples were detected intraoperatively to evaluate the feasibility of using the product in an actual situation. A blinding method was used to evaluate the effect of the detection technology on the accuracy of intraoperative histopathological diagnosis by pathologists. We also reviewed the current research status in the field of intraoperative molecular diagnosis. Compared with next-generation sequencing, the accuracy of AIGS in detecting IDH1 was 100% for 105 samples and 37 intraoperative samples. The blind diagnostic results were compared between the 2 groups, and the molecular information provided by AIGS increased the intraoperative diagnostic accuracy of glioma by 16.2%. Using the technical advantages of multipoint synchronous detection, we determined the tumor molecular margins for 5 IDH-positive patients and achieved accurate resection at the molecular level. AIGS can quickly and accurately provide molecular information during surgery. This methodology not only improves the accuracy of intraoperative pathological diagnosis but also provides an important molecular basis for determining tumor margins to facilitate precision surgery.

An accurate measuring method for the internal jaw stiffness of deformable silicon arms

The internal jaw stiffness of the silicon arm and its uniformity directly determine the geometric position of the clamped part, which in turn affects the geometric accuracy of the fusion target ball. The slight variation of the silicon arm jaw stiffness caused by machining errors is a crucial factor affecting the geometric accuracy of the micro-target. To accurately detect the variation of internal jaw stiffness caused by machining errors, this paper proposes a multi-point stiffness detection method combining micro-feed force application and high-precision image inspection. An experimental measurement device is also built to measure the jaw stiffness of the silicon arm sample. The proposed method, which can obtain the micro-deformation data of the internal jaws under small loads and accurately fit the stiffness, provides a new way to measure tiny, thin-walled, brittle cantilever beam structures.

Cascaded high-density multipoint gas detection with branched gas chambers

Distributed or multipoint gas detection is crucial for several industrial and civil applications. Due to various losses, the traditional series–parallel method has a restricted number of measurement points. In this paper, an innovative cascaded connection method has been introduced for measuring a large number of locations. It is basically a branching route that contains a gas cell and a reflecting mirror. A small amount of light is coupled to the branch channel, leading to limited effects on transmission power. Using a light source that corresponds to the gas absorption line, an optical time domain reflectometer (OTDR) device interrogates each cell by branching. After establishing a length of delay fiber at one of the branch locations, the signals coming from each air cell are recognized individually at the receiving end. In this experiment, 99:1 couplers are used, and only 1% of the total light is transferred to the branch route gas cell. The signal-to-noise ratio increases dramatically compared to previous studies based on Rayleigh scattering. This is because the amplitude of the reflected light is one-half order more than that of the scattered light. A 1530 nm laser for acetylene and a 1653 nm laser for methane with a short pulse width are used for evaluating the novel multipoint gas detection technique. There is an analysis and discussion of the number of measurement points. The proposed method is capable of optimally laying 220 cells at a maximum monitoring distance of 8.8 km within a dynamic range of ∼13.56 dB. Using the present wavelength power calibration method, the minimum detection limits for methane and acetylene along the 1% branching path are 0.093 low explosion level (LEL) and 0.321 LEL, respectively.

Multi-Point Interaction of Partially Conductive Cracks with Sweep Frequency Eddy Currents in Electromagnetic Non-Destructive Evaluation

An investigation of real corrosion cracks that can be partially conductive in electromagnetic non-destructive evaluation using sweep-frequency eddy-current frequency-response analysis is carried out in this study. A new approach incorporating innovative solutions is proposed. The goal was to increase the probability of detection of real corrosion cracks in contrast to the conventional sweep-frequency method that is based on single-point signal detection. The proposed procedure was tested on real material specimens where differential responses were gained from real corrosion cracks. Seven austenitic steel plate specimens having corrosion cracks were inspected. Eddy-current responses due to the material cracks were sensed, while a multi-point approach was used for this purpose. The presented unique results clearly showed that the detection ability of a fixed probe driven with sweep-frequency excitation signal could be increased when the multi-point detection is used, and the gained signals are further mathematically processed.