Phase Detection Research Articles

Optimizing real-time phase detection in diverse rhythmic biological signals for phase-specific neuromodulation.

Closed-loop, phase-specific neurostimulation is a powerful method to modulate ongoing brain activity for clinical and research applications. Phase-specific stimulation relies on estimating the phase of an ongoing oscillation in real time and issuing a control command at a target phase. Phase detection algorithms based on Fast Fourier transform (FFT) are widely used due to their computational efficiency and robustness. However, it is unclear how algorithm performance depends on the spectral properties of the input signal and how algorithm parameters can be optimized. We used offline simulation to evaluate the performance of three algorithms (endpoint-corrected Hilbert Transform, Hilbert Transform and phase mapping) on three rhythmic biological signals with distinct spectral properties (rodent hippocampal theta potential, human EEG alpha and human essential tremor). First, we found that algorithm performance was more strongly influenced by signal amplitude and frequency variation compared with signal to noise ratio. Second, our simulations showed that the size of the data window for phase estimation was critical for the performance of FFT-based algorithms, where the optimal data window corresponds to the period of the oscillation. We validated this prediction with real time phase detection of hippocampal theta oscillations in freely behaving rats performing spatial navigation. Our findings define the relationship between signal properties and algorithm performance and provide a convenient method for optimizing FFT-based phase detection algorithms.

Reliability of Machine Learning in functional assessment in cardiac magnetic resonance imaging

PurposeOur study aims at evaluating Machine Learning’s reliability to calculate ventricular volumes and functions in cardiac magnetic resonance imaging (CMR).Material and methodsEighty-five patients underwent CMR: forty healthy subjects, fifteen affected by myocarditis, seventeen dilated cardiomyopathy patients (DCM), and thirteen hypertrophic cardiomyopathy patients (HCM). Left ventricle (LV) and right ventricle (RV) analyses were performed both manually by operators and using Cvi42 software, which automates the identification of telesystolic and telediastolic phases. Statistical analysis assessed the concordance between measurements obtained manually and through the software, considering the following parameters: end-diastolic volume (EDV-BSA), end-systolic volume (ESV-BSA), stroke volume (SV), ejection fraction (EF), and detection of telesystolic and telediastolic phases.ResultsIntraclass correlation coefficient (ICC) analysis for LV volumes showed high concordance between manual and automatic measurements (ESV-BSA 0.97, EDV-BSA 0.98, SV 0.87, EF 0.93). ICC analysis for RV volumes presented high concordance between ESV-BSA and EDV-BSA measurements as well (ICC 0.90 and 0.91, respectively), whereas SV and EF measurements showed lower values (0.65 and 0.67, respectively). Statistical analysis also exhibited good concordance between manual and automated methods in the detection of telesystolic and telediastolic phases (ICC 0.80 and 0.84, respectively).ConclusionThe LV and RV analyses conducted using the automated tool provide non-inferior performance to manual analyses, in particular for LV volumes.

Adaptive complex coefficient‐filtered extended states observer type three‐phase enhanced phase‐locked loop

AbstractThis paper proposes an adaptive complex coefficient filtered (CCF) full order extended state observer (ESO) type three phase enhanced phase locked loop (EPLL), which is employed in matrix reactance frequency converter (MRFC) for rotating vectors measurement estimation. EPLL phase detector was analysed first to track not only the rad frequency and transient phase, but also the amplitude of the rotating vectors. Full order ESO can filter out more high frequency disturbance, so it can track frequency and phase more accurately than proportion and integration algorithm. CCF modules were analysed in theory to attenuate the disturbance within two times of the EPLL's cut‐off frequency. The whole adaptive CCF‐ESO‐EPLL design, including stability and parameter tuning were then interpreted. The proposed CCF‐ESO‐EPLL adapts the estimated frequency with CCF to attenuate the MRFC switching non‐linear disturbance as well as unknown disturbance by the full order ESO. The MRFC topology necessary measured vectors, as well as the input side reactive power adjustment capacity, were discussed. The theoretical conclusion has been verified on a MRFC prototype. The proposed CCF‐ESO‐EPLL has less parameter tuning, less computation resource requirement, better steady and dynamic performance, and outstanding disturbance robustness.

Frictional stability of pumice-reinforced lightweight magnesium composite in ambient and elevated temperature environments

Lightweight materials with better resistance to sliding wear are prominent candidates for automobile brake drums, clutch pads and cylinder block applications to facilitate fuel economy. This attempt is reserved to cater to materials with higher tribological quality needs. Less dense foamy pumice stone particles were involved in three different percentages (5, 10, and 15 wt%) to reinforce lightweight AZ31 Mg alloy. A stir-assisted squeeze casting technique was pursued to process the composite and refine the grain structure. A phase detection, elemental mapping and microstructure study were done through X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), respectively. An experimental dry sliding wear scrutiny was administered using a pin-on-disc apparatus by considering: (i) ambient and elevated temperature environments and (ii) three different levels of loads. The results reveal a significant drop in wear loss and a frictional coefficient for 15% pumice-loaded composite than the base alloy. Post-wear examination acknowledges the fact that the ambient temperature wear is governed by adhesive-abrasive wear and high temperature is by abrasive wear mechanisms. Worn-out scrutiny authenticates the presence of oxide layers and their role in lubrication. A comparative study with previous works upholds the novel magnesium composite is the right candidate for the mentioned automobile applications.

Deep learning models for regional phase detection on seismic stations in Northern Europe and the European Arctic

SUMMARY Seismic phase detection and classification using deep learning is so far poorly investigated for regional events since most studies focus on local events and short time windows as the input to the detection models. To evaluate deep learning on regional seismic records, we create a data set of events in Northern Europe and the European Arctic. This data set consists of about 151 000 three component event waveforms and corresponding phase arrival picks at stations in mainland Norway, Finland and Svalbard. We train several state-of-the-art and one newly developed deep learning model on this data set to pick P- and S-wave arrivals. The new method modifies the popular PhaseNet model with new convolutional blocks including transformers. This yields more accurate predictions on the long input time windows associated with regional events. Evaluated on event records not used for training, our new method improves the performance of the current state-of-the-art methods when it comes to recall, precision and pick time residuals. Finally, we test our new model for continuous mode processing on 4 d of single-station data from the ARCES array. Results show that our new method outperforms the existing array detector at ARCES. This opens up new opportunities to improve automatic array processing with deep learning detectors.

Study on Denoising Method of Weld Defect Signal Based on SSA-VMD-WPD

Defects in welds can affect the structural safety and reliability of workpieces. Currently, the method of using phased array ultrasonic inspection technology for non-destructive testing of weld structures with high detection efficiency, good sensitivity, and good visualization of the results is widely used. However, the defective A-scan data collected by the ultrasonic phased array detector inevitably contain noise data, including the test piece material structure noise, equipment noise, and environmental noise, which undoubtedly affects the analysis of the A-scan signal. In addition, when defects are interpreted, the presence of noise also interferes with the process, which affects the accuracy of the interpretation. Therefore, to enhance the accuracy of defect identification based on phased array ultrasonic inspection technology, we must prevent the series of consequences caused by misjudgments. In this study, ultrasonic phased array inspection experiments were carried out, and the specific process flow of ultrasonic phased array inspection of flat plate butt welds was summarized. Utilizing pre-fabricated flat plate butt specimen blocks containing five types of typical defects, defect A-sweep signals based on ultrasonic phased array inspection were obtained. Combining the sparrow optimization algorithm (SSA), variational mode decomposition (VMD), and wavelet packet decomposition (WPD), a defect signal noise reduction method based on parameter optimization was studied. A noise reduction study was carried out using the noise-added simulated signal, and the results indicated that the noise reduction method proposed in this paper had a better noise reduction effect and the proposed method could effectively retain the detailed features of the ultrasonic phased array defective A-scan signal and realize the noise reduction processing of the defective A-scan signal.

High-resolution microscopic fringe projection profilometry using Nyquist frequency fringe

Vertical resolution is a crucial property in microscopic fringe projection profilometry (MFPP) systems. The challenge in improving vertical resolution lies not only in enhancing height-sensing sensitivity but also in reducing the gain of phase-shifting algorithms (PSA) against dominant noise in the fringe signal. This study uses an optical flat for continuous phase shifting, achieving phase demodulation for fringe with Nyquist frequency. To mitigate the inherent disturbances caused by continuous phase shifting during phase demodulation, a transfer relation between phase-shift error and 1/f noise is established using spectral analysis and the frequency transfer function framework. Based on this transfer relation, we propose a novel PSA with high signal noise ratio and sensitivity. Experiments validate the proposed PSA, indicating that the vertical resolution of a telecentric MFPP system using the proposed PSA is 73 nm. The reconstruction results of wafer-level 3D structures are consistent with those from confocal microscopy.

An improved derivative‐based phase‐locked loop for single‐phase grid synchronization under abnormal grid conditions

SummaryGenerating a quadrature signal in a single‐phase system using a second‐order generalized integrator (SOGI) requires accurate frequency information. The standard SOGI phase‐locked loop (PLL) includes frequency feedback to the SOGI. However, during grid abnormalities such as voltage sag/swell and phase angle jumps, the SOGI‐PLL faces frequency disturbances that propagate to the phase detector (PD) and affects the quadrature signal generator (QSG). Furthermore, the SOGI‐PLL having two loops dependent on each other creates loop coupling phenomena; either a change in phase or frequency affects each other. SOGI‐PLL is tuning sensitive, as the SOGI block has a gain that needs to be adjusted, increases the complexity, and affects the performance of the system. There is a trade‐off between SOGI gain and PLL parameters that needs to be considered for adequate parameter design to provide accurate grid synchronization while maintaining the stability of the system. To attain better performance, researchers have proposed derivative‐based PLL (DPLL). The conventional DPLL faces challenges to noise and harmonics amplification. This paper presents an improved DPLL for single‐phase grid synchronization under adverse grid conditions. The improved derivative‐based PLL (IDPLL) comprises two improved derivative‐based quadrature signal generator (IDQSG) blocks to extract the phase‐error information for accurately estimating phase and frequency. The detailed mathematical modeling and bode plot for the IDQSG and IDPLL are presented. The proposed IDQSG eliminates the requirement of gain tuning, hence reducing complexity. Moreover, there is no interdependent loop in the IDPLL, which significantly improves the dynamic performance. A hardware setup is developed to evaluate the performance of the system in real‐time. The experimental results are obtained using an field programmable gate array (FPGA)‐based controller.

Parameter optimization for proton density fat fraction quantification in skeletal muscle tissue at 7 T

ObjectiveTo establish an image acquisition and post-processing workflow for the determination of the proton density fat fraction (PDFF) in calf muscle tissue at 7 T.Materials and methodsEcho times (TEs) of the applied vendor-provided multi-echo gradient echo sequence were optimized based on simulations of the effective number of signal averages (NSA*). The resulting parameters were validated by measurements in phantom and in healthy calf muscle tissue (n = 12). Additionally, methods to reduce phase errors arising at 7 T were evaluated. Finally, PDFF values measured at 7 T in calf muscle tissue of healthy subjects (n = 9) and patients with fatty replacement of muscle tissue (n = 3) were compared to 3 T results.ResultsSimulations, phantom and in vivo measurements showed the importance of using optimized TEs for the fat–water separation at 7 T. Fat–water swaps could be mitigated using a phase demodulation with an additional B0 map, or by shifting the TEs to longer values. Muscular PDFF values measured at 7 T were comparable to measurements at 3 T in both healthy subjects and patients with increased fatty replacement.ConclusionPDFF determination in calf muscle tissue is feasible at 7 T using a chemical shift-based approach with optimized acquisition and post-processing parameters.

Literature Review on Analytical Method Development and Validation of Alfuzosin Hydrochloride

Alfuzosin hydrochloride, an alpha-adrenergic blocker, is extensively used in the treatment of benign prostatic hyperplasia. Robust and reliable analytical methods are indispensable for quantifying alfuzosin hydrochloride in various matrices, ensuring the quality, efficacy, and safety of the drug. Recent advancements in analytical method development and validation for alfuzosin hydrochloride encompass a spectrum of techniques, including UV spectrometry, RP-HPLC, HPTLC, UPLC, and voltammetry. Optimization of chromatographic conditions, such as mobile phase composition, column selection, and detection wavelength, is crucial for achieving optimal separation and quantification of the drug. Method validation parameters, including accuracy, precision, linearity, and robustness, are assessed in accordance with ICH guidelines. These analytical methods find application in the determination of alfuzosin hydrochloride in bulk drugs, pharmaceutical formulations, and biological matrices. Stability-indicating methods are developed to evaluate drug stability under various stress conditions. The current state of analytical method development and validation for alfuzosin hydrochloride facilitates the selection of suitable analytical techniques for routine quality control and research purposes

Disturbance-immune, fast response LITES gas sensor based on out-plane vibration mode employing micro Fabry-Perot cavity with heterodyne phase demodulation

The disturbance-immune, fast response light-induced thermoelastic spectroscopy (LITES) gas sensor based on out-plane vibration (OPV) mode employing micro Fabry-Perot cavity with heterodyne phase demodulation was firstly reported in this paper. Compared to the traditional in-plane vibration (IPV) mode, the OPV mode has a lower resonance frequency (f0) to enhance the energy accumulation time of the system. The OPV mode based H-LITES (OPV-H-LITES) sensor and the IPV mode based H-LITES (IPV-H-LITES) sensor were established using a standard quartz tuning fork (QTF) at the same conditions for performance comparison. Acetylene (C2H2) was selected as the target gas to verify the sensor performance. In comparison to the IPV-H-LITES sensor, there has been a 3.5-fold improvement in signal-to-noise ratio (SNR) of OPV-H-LITES sensor. In order to further improve the sensor performance, a novel self-designed low-frequency QTF was adopted to replace the standard QTF, leading to a 2.3-fold increase in the SNR of the OPV-H-LITES sensor. Finally, a minimum detection limit (MDL) of 7.22 ppm for C2H2 detection was obtained. The proposed technique holds the merits of high sensitivity, power disturbance resistance, wavelength independence, excellent linear concentration response and long-term stability.

Raman Spectroscopy as an Effective Tool for Assessment of Structural Quality and Polymorphism of Gallium Oxide (Ga2O3) Thin Films.

Raman spectroscopy, a versatile and nondestructive technique, was employed to develop a methodology for gallium oxide (Ga2O3) phase detection and identification. This methodology combines experimental results with a comprehensive literature survey. The established Raman approach offers a powerful tool for nondestructively assessing phase purity and detecting secondary phases in Ga2O3 thin films. X-ray diffraction was used for comparison, highlighting the complementary information that these techniques may provide for Ga2O3 characterization. Few case studies are included to demonstrate the usefulness of the proposed spectroscopic approach, namely the impact of deposition conditions such as metal-organic vapor-phase epitaxy and pulsed electron deposition (PED), and extrinsic elements provided during growth (Sn in the case of PED) on Ga2O3 polymorphism. In conclusion, it is shown that Raman spectroscopy offers a quick, reliable, and nondestructive high-resolution approach for Ga2O3 thin film characterization, especially concerning phase detection and crystalline quality.

Effect of powder composition, PTAW parameters on dilution, microstructure and hardness of Ni–Cr–Si–B alloy deposition: Experimental investigation and prediction using machine learning technique

The implementation of hard-facing alloy on the existing materials caters the need for high-performance surfaces in terms of wear and high temperatures. The present research explore the effect of Plasma Transferred Arc Welding (PTAW) parameters and powder composition on dilution, microstructure and hardness of the commonly used hard-facing alloy Ni–Cr–Si–B powder. The hard-facing alloy was deposited with three weight proportions of boron (2.5 %, 3 % and 3.5 %). The statistical-based Grey Relational Analysis (GRA) followed by a Machine Learning Algorithm (MLA) was implemented to identify the ideal parameters and degree of significance of each parameter and for the prediction of the responses. The dilution percentage, microstructure analysis, and phase detection were estimated through elemental analysis, Scanning electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD) respectively. The experimental and modelling results revealed that 400 mm/min of scanning speed, 8 gm/min of powder delivery, 14 mm of stand-off distance, and 120 A of current were the optimal parameters along with 3.5 wt% of boron powder composition to yield a better dilution, microstructure and hardness.

Rydberg-Atom Terahertz Heterodyne Receiver with Ultrahigh Spectral Resolution

Abstract Terahertz heterodyne receivers with high sensitivity and spectral resolution are crucial for various applications. Here, we present a room-temperature atomic terahertz heterodyne receiver that achieves ultrahigh sensitivity and frequency resolution. At a signal frequency of 338.7 GHz, we obtain a sensitivity of 2.88 ± 0.09 μV⋅cm−1⋅Hz−1/2 for electric field measurements. The calibrated linear dynamical range spans approximately 89 dB, ranging from −110 dBV/cm to −21 dBV/cm. We demodulate a 400 symbol stream encoded in 4-state phase-shift keying, demonstrating excellent phase detection capability. By scanning the frequency of the local oscillator, we realize a terahertz spectrometer with Hz level frequency resolution. This resolution is more than two orders of magnitude higher than that of existing terahertz spectrometers. The demonstrated terahertz heterodyne receiver holds promising potential for working across the entire terahertz spectrum, significantly advancing its practical applications.

Joint PAPR reduction and channel estimation in low-complexity VLC systems

In recent times, there has been a surge in interest surrounding visible light communication (VLC) as a compelling adjunct to radio frequency (RF) technology. This enthusiasm stems from deployments showcasing its efficacy in high-speed data transmission, characterized by low complexity, robust security, and high reliability. Among the variants of orthogonal frequency division multiplexing (OFDM), direct current-biased optical OFDM (DCO-OFDM) stands out in the realm of VLC systems, owing to its ability to furnish rapid data provisioning. However, a significant drawback of selective mapping (SLM) based DCO-OFDM transceivers lies in its computational complexity and practical implementation challenges. To address this limitation, this paper presents a modified SLM technique termed selective phase modulation (SPM) aimed at mitigating the peak-to-average power ratio (PAPR) in the transmitter section while simplifying the data decoding process at the receiver end. The SPM method utilizes a phase modulation and demodulation process based on clusters and assisted by pilot signals, streamlining the transceiver architecture. The SPM methodology offers reduced computational complexity at the transmitter by selectively applying phase sequences to data, circumventing the necessity for side information (SI) transmission and SI estimation at the receiver with a known pilot symbol inserted in the data. This dual-functionality mechanism not only achieves complexity reduction but also facilitates channel estimation at the receiver for proper data recovery. Based on complexity analysis and simulation outcomes, the computational complexity reduction strategy outperforms the conventional selective mapping (CSLM) technique, VLC-based pilot-assisted PAPR reduction systems, and embedded coded modulation (ECM). This allows for smooth incorporation of this technology into future VLC systems.

Large-range high-precision macroscopic common phase detection of segmented mirrors based on white light dynamic Twyman-Green interferometer

Segmented mirrors (SMs) provide a solution for the construction of the next generation of extremely large telescopes. The large-range, high-precision detection of piston error between mirror segments is a must-be solved problem in the application of SMs. This paper proposes a large-range high-precision macroscopic co-phase detection method of SMs based on white light dynamic Twyman-Green interferometer. By adopting a white light interferometry in the macroscopic co-phase detection, the probability of the occurring of the 2π ambiguity anomalies can be reduced. A piston error calculation model for SMs was established through Zernike fitting analysis, which improved the detection accuracy. A white light Twyman-Green interferometer with Kohler illumination was experimentally constructed. Based on the scanning of the reference mirror, an efficient detection of the piston error was achieved simultaneously with large range and high precision. Through the new method, the piston error of two planar mirrors was compensated from 38.9344 μm in coarse co-phase stage to 3.6 nm in fine co-phase stage. The method shows great potential for efficient co-phase adjustment of large primary segmented mirrors.

Performance enhancement of optical pulse coding phase-sensitive OTDR system with genetic-optimized code.

Optical pulse coding (OPC) in phase-sensitive optical time-domain reflectometry (φ-OTDR) traditionally relies on standard coding sequences as probe pulse trains, which usually suffer the problem of distorted probe pulse caused by the gain saturation in erbium-doped fiber amplifier (EDFA). To improve the signal-to-noise ratio (SNR) and mitigate distortion caused by the EDFA gain saturation, a genetic-optimized code (Go-code) based OPC φ-OTDR (GOPC φ-OTDR) scheme is proposed in this paper. The unique Go-code sequence generated by the distributed genetic algorithm (DGA) is explored in the field of φ-OTDR for the first time, and the coding sequence was optimized to adapt to the vibration sensing requirements in φ-OTDR. Theoretical analyses focused on EDFA gain saturation effects and coding gain were conducted. The experiment of GOPC φ-OTDR demonstrated significant improvements compared with Golay φ-OTDR, achieving less distortion in decoding response and approximately 7.48 dB phase demodulation SNR enhancement within a 10-km sensing range. This research marks Go-code's pioneering exploration into φ-OTDR, demonstrating substantial advancements in optimization metrics, and opening avenues for exploring advanced OPC technologies.

High-Accuracy Phase Frequency Detection Technology Based on BDS Time and Frequency Signals.

For the time and frequency signals of Beidou satellites, a high-accuracy phase frequency detection technology based on phase group synchronization is proposed. Using the Beidou receiver and satellite signals as the frequency standard and the measured signals, respectively. The Beidou receiver and the satellite signals are sent to the phase coincidence detector of the different frequencies to generate a phase coincidence point pulse, which is sent to the different frequency phase detector as a control signal to generate the phase differences between the Beidou receiver and satellite signals, and then complete the high-accuracy phase synchronization between the Beidou receiver and satellite signals. Experimental results show that when the delay resolution reaches ps level, the phase synchronization accuracy of the system can reach 10 ps, which has the characteristics of small phase noise, low development cost, simple circuit structure, and high synchronization accuracy compared with the traditional phase synchronization technologies. Therefore, it would be widely used in satellite positioning, astrometry, precision navigation, aerospace, satellite launch, power transmission, communications, radar, and other high-tech fields.

Detecting Toe-Off and Initial Contact in Real-Time With Self-Adapting Thresholds.

This research introduces an adaptive control algorithm designed to determine gait phase in real-time using an inertial measurement unit (IMU) affixed to the shank. Focusing on detecting specific gait events, primarily initial contact (IC) and toe-off (TO), the algorithm utilizes dynamic thresholds and ratios that facilitate accurate event determination adaptively across a range of walking speeds. Built-in safety checks further ensure precision and minimize false detections. We validated the algorithm with eight participants walking at varying speeds. The algorithm demonstrated promising results in detecting IC and TO events with mean lead of 8.95 ms and 4.42 ms and detection success rate of 100% and 99.72%, respectively. These results are consistent with benchmarks from established algorithms (Hanlon and Anderson, 2009, "Real-Time Gait Event Detection Using Wearable Sensors," Gait Posture, 30(4), pp. 523-527; Maqbool et al., 2017, "A Real-Time Gait Event Detection for Lower Limb Prosthesis Control and Evaluation," IEEE Trans. Neural Syst. Rehabil. Eng.: Publ. IEEE Eng. Med. Biol. Soc., 25(9), pp. 1500-1509). Moreover, the algorithm's self-adaptive nature ensures it can be used in scenarios of varying movement, offering a promising solution for real-time gait phase detection.

A Ratiometric Benzimidazole-Based Fluorescent Probe for The Recognition of Phosgene in Solution and Gaseous Phases.

Considering the high toxicity and widespread application of phosgene, there is an urgent need to develop a simple and sensitive method for detecting phosgene. In this work, we designed and synthesized a novel ratiometric fluorescent probe 1 containing fluorophores of benzimidazole and benzothiazole. Probe 1 showed excellent sensitivity (< 30s) and selectivity (LOD = 3.82 nM) for phosgene and significant ratiometric fluorescence changes. In addition, 1-loaded polystyrene membrane test strips were used to conveniently and efficiently detect phosgene gas (0.5 ppm) via the naked eye and the RGB APP of the smartphone, indicating that this probe has great potential for phosgene detection in the gaseous phase.