Delay Measurements Research Articles

Cross-correlation technique for phase error correction in reflection mode terahertz time-domain spectroscopy

Terahertz time-domain spectroscopy in reflection mode geometry provides valuable surface and subsurface information, making it suitable for a layer analysis, coating, and non-destructive testing applications. The exchanging of the sample and reference’s position introduces a phase error when the position or alignment of the sample is not precisely maintained during measurements. This micrometer order of pitch error (Δx) between the reference and the sample could lead to an inherent error in the phase spectrum of the sample. In the present work, a novel approach, to the best of our knowledge, based on the cross-correlation with an envelope technique, has been demonstrated to reduce the uncertainty in the phase and reveal the hidden characteristic features of the given sample in THz TDS spectroscopy. In conjunction with experimental verification, we have employed a finite element analysis in COMSOL Multiphysics to simulate a misplacement error between a lossy dielectric medium (n=1.2 to 3.0 and k=0 to 0.9) and a reference. We have investigated the impact of varying properties of the lossy dielectric medium on delay measurements using a cross-correlation with an envelope analysis. We illustrated and demonstrated the advantage of our approach by measuring the optical properties of Teflon, quartz, and RDX by correcting the misalignment of the 15.75, 17.55, and 20.70 µm ranges, respectively.

Electrode module for EIT with a robust howland current source

Electrical Impedance Tomography (EIT) is a non-invasive imaging technique that reconstructs internal conductivity distributions of a body from electrical measurements taken on its boundary. This study contributes to the field by focusing on the technological intricacies of absolute EIT imaging, which is challenged by limitations such as the resolution capacity of the hardware and the complexities introduced by imaging capacitive bodies. The novel EIT system architecture proposed enhances the accuracy of measurement by integrating current sources and Analog-to-Digital Converters (ADCs) closer to the electrodes, employing alternating current excitations to accurately capture phase information. This system uses a dynamic arrangement of surface electrodes that continuously alter their roles between current injection and voltage measurement, in a synchronized sequence, to ensure the accuracy of the measurements. The paper describes the design and implementation of both the excitation and measurement subsystems, highlighting the use of digital signal demodulation near the electrode to reduce data transfer issues. Experimental results confirm the system’s capability for real-time image reconstruction at 50 frames per second with precision in phase delay measurements, suggesting significant potential for clinical and industrial applications. Future work will aim to further refine signal generation with higher-speed DACs and expand to image reconstruction with more channels.

Time Delay Characterization in Wireless Sensor Networks for Distributed Measurement Applications

This paper investigates the critical aspect of synchronization in wireless sensor networks (WSNs) across diverse industrial applications. The low-cost sensor network topologies are analyzed. The communication delay measurements and quantitative jitter analysis are performed under different conditions, and dependencies of the propagation time delay on the data bitrate and modulation type for different hardware implementations of the WSNs are presented. The time delay distribution influence on the time synchronization error propagation over WSN layers was assessed from the experimental probability density functions. The network synchronization based on the controlled propagation delay jitter approach has been proposed. This research contributes quantitative insights into the complexities of synchronization in WSNs, offering a foundation for optimizing network configurations and parameters to extend the operational life of low-power sensor nodes.

Unbiased Real-Time Traffic Sketching

In network measurement, sliding window measurement has the advantage of providing recent and timely measurement results. Recently, sketches have become the most popular method of conducting flow-level network measurements due to their favorable trade-off between small memory overhead and high measurement accuracy. However, it remains a challenge that no current sketches are able to support unbiased estimation toward flow size measurement, which can improve the performance of tasks including network diagnoses, delay measurement and heavy hitter detection. In this paper, we propose the first work that achieves unbiased flow size measurement in sliding windows, namely <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Unbiased Cleaning sketch (UC sketch)</b> . The key technique of the UC sketch is <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Unbiased Cleaning</i> which can remove outdated keys from the sliding windows in a balanced way. Besides, we significantly reduce the variance of flow size by two optimization techniques, namely <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Linear Scaling</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Column Randomizing</i> . To prove the result, we conduct rigorous mathematical analysis and reasonable experiments. All related source codes are open-sourced at Github anonymously.

A context-aware energy saving information centric (CAES) model for wireless communication network

The CASE model improves the traditional wireless communication approach by deploying an energy-efficient information-centric algorithm that also enables the tiny low-powered communication nodes of the wireless network to work efficiently with the context-aware energy-saving interface. CAES introduces buffer optimization and a smart routing process among all the low-capacity tiny nodes. Moreover, the gathering of Context-aware energy-saving information also takes care of the performance as well as the management of the traffic load of the entire wireless network. Toward the objectives of the proposed algorithm, which ensure a high ratio of content delivery with an efficient energy saving and energy utilizing scheme, this paper is trying to design a type of Wi-Fi environment that carry the data packet and delivery services carefully without falling down the connection or losing the data contents. In addition to this, this paper concentrate on the measurement of Expected Production Quality (EPQ) values, using loss and quality functions based on various quality parameters to be calculated as one of the measured parts of this research work that defines the ratio of reliability and efficiency of CAES. Further, the implementation of CAES defines the improvement of this research work in the form of managing various quality of communication parameters such as packets delivery ratio, end-to-end Delay and throughput measurement. This manuscript proposes a novel version of the context-aware routing mechanism in a wireless network since traditional wireless communication protocols like SADODV, RAEED-EA are not vulnerable to offer best of communication services. This work aims to manage common communication quality parameters such as Packet Delivery Ratio, End to End Delay and Throughput to be improved using information-centric route management services under denial-of-service (DoS) attacks by implementing context-aware energy saving (CAES), which simultaneously deploys energy efficiency and buffer optimization. This paper simulates and compare the resulting parameters with traditional protocols which defines the importance and role of CAES model for the future of Communication Technology.

Real-Time Temperature Monitoring of Lithium Batteries Based on Ultrasonic Technology.

Electrochemical energy storage stations serve as an important means of load regulation, and their proportion has been increasing year by year. The temperature monitoring of lithium batteries necessitates heightened criteria. Ultrasonic thermometry, based on its noncontact measurement characteristics, is an ideal method for monitoring the internal temperature of lithium batteries. In this study, temperature and ultrasonic time delay measurement experiments were conducted on 18650 lithium batteries and laminated and wound lithium batteries to obtain the corresponding relationship between temperature and time delay and validate the temperature measurement for the same type of battery. The experimental results show that (1) the ultrasonic temperature measurement technique exhibits a relatively large error when used for 18650 Li-ion batteries under experimental conditions; (2) in the experiments on laminated and wound soft-pack lithium batteries, the relationship between temperature and time delay exhibits a nonlinear characteristic; and (3) under the experimental conditions, the ultrasonic temperature measurement errors were ±1.1 °C for stacked Li-ion batteries and ±1.4 °C for wound Li-ion batteries.

Experimental and data-driven chemical kinetic modeling study of alcohol-to-jet (ATJ) synthetic biofuel for sustainable aviation fuels

This work assesses the chemical ignition delay behavior of an isoparaffinic alcohol-to-jet (ATJ) fuel, one of the certified sustainable aviation fuels (SAFs). Chemical ignition delay measurements of ATJ were performed at a compressed pressure of PC = 2 MPa and three equivalence ratios (phi = 0.5, 1.0, & 1.3) in synthetic dry air, between 667 K and 1250 K. The unique chemical structures of isoalkanes result in high thermal decomposition rate, but low chemical oxidation reactivity. The new lumped mechanism (ARLMech-HC-ATJ) is developed using a genetic algorithm based on empirical ignition delays. The mechanism shows good performance over the temperature range from 667 K to 1250 K and varied equivalence ratios. Using the suggested mechanism, this study presents sensitivity analysis for the temperature range to understand chemical kinetics of ATJ fuel. The results show the impact of using ATJ modeling to design and optimize propulsion systems operating in the negative temperature coefficient (NTC) or low temperature chemistry (LTC) regime in the future and a methodology that can be adapted to other novel fuels.

Device for measurement of absolute and differential delay of signal propagation in optical fiber

Device for measurement of absolute and differential delay of signal propagation in optical fiber

Определение глубины залегания включения в подстилающей среде

The work is devoted to the problem of determining the depth of inclusion in the underlying environment. The algorithm for determining the depth of occurrence is based on the sensing method using georadar hardware of the Loza-V series. There are two methods of GPR surveying: «profiling» and «probing». When profiling, the radar moves along the path along with the transmitting and receiving antennas. During sounding, one path point is selected, then a series of registrations of reflected signals are carried out with the source and receiver antennas spaced at equal distances in different directions. As a result of these measurements, a hodograph is obtained – a function of the delay time of the reflected signals [1]. Based on two measurements of signal delays and known distances between the receiver and the source, the depth of the inclusion is determined

Observational tests of asymptotically flat R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {R}}}^{2}$$\\end{document} spacetimes

A novel class of Buchdahl-inspired metrics with closed-form expressions was recently obtained based on Buchdahl’s seminal work on searching for static, spherically symmetric metrics in R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {R}}}^{2}$$\\end{document} gravity in vacuo. Buchdahl-inspired spacetimes provide an interesting framework for testing predictions of R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathcal {R}}}^{2}$$\\end{document} gravity models against observations. To test these Buchdahl-inspired spacetimes, we consider observational constraints imposed on the deviation parameter, which characterizes the deviation of the asymptotically flat Buchdahl-inspired metric from the Schwarzschild spacetime. We utilize several recent solar system experiments and observations of the S2 star in the galactic center and the black hole shadow. By calculating the effects of Buchdahl-inspired spacetimes on astronomical observations both within and outside of the solar system, including the deflection angle of light by the Sun, gravitational time delay, perihelion advance, shadow, and geodetic precession, we determine observational constraints on the corresponding deviation parameters by comparing theoretical predictions with the most recent observations. Among these constraints, we find that the tightest one comes from the Cassini mission’s measurement of gravitational time delay.

Photon Phase Delay Sensing with Sub-Attosecond Uncertainty.

The application of statistical estimation theory to Hong-Ou-Mandel interferometry led to enticing results in terms of the detection limit for photon reciprocal delay and polarisation measurement. In the following paper, a fully fibre-coupled setup operating in the telecom wavelength region proves to achieve, for the first time, in common-path Hong-Ou-Mandel-based interferometry, a detection limit for photon phase delay at the zeptosecond scale. The experimental results are then framed in a theoretical model by calculating the Cramer-Rao bound (CRB) and, after comparison with the obtained experimental results, it is shown that our setup attains the optimal measurement, nearly saturating CRB.

Time delay and nonadiabatic calibration of the attoclock. Multiphoton process versus tunneling in strong field interaction

The measurement of the tunneling time delay in attosecond experiments, termed attoclock, sparked a heated debate about tunneling time and the role of time in quantum mechanics. We show a model that explains the experimental result of the attoclock in the nonadiabatic field calibration, where we find good agreement with the experimental data of Hofmann et al. (J. Mod. Opt. 66, 1052, 2019). We confirm our result with the numerical integration of the time-dependent Schrödinger equation. We also found that at a field strength F≤Fa (Fa is the atomic field strength), the model always predicts a time delay with respect to the quantum (lower) limit τa at F=Fa. For an adiabatic tunneling, the saturation at the limit (F=Fa) explains the well-known Hartman effect or Hartman paradox.

Ultrafast and High-Precision Time Delay Measurement Based on Complementary Frequency-Swept Light and Frequency-Shifted Dechirping

Ultrafast and High-Precision Time Delay Measurement Based on Complementary Frequency-Swept Light and Frequency-Shifted Dechirping

Guided Lamb Wave Array Time-Delay-Based MUSIC Algorithm for Impact Imaging.

Composite materials, valued in aerospace for their stiffness, strength and lightness, require impact monitoring for structural health, especially against low-velocity impacts. The MUSIC algorithm, known for efficient directional scanning and easy sensor deployment, is gaining prominence in this area. However, in practical engineering applications, the broadband characteristics of impact response signals and the time delay errors in array elements' signal reception lead to inconsistencies between the steering vector and the actual signal subspace, affecting the precision of the MUSIC impact localization method. Furthermore, the anisotropy of composite materials results in time delay differences between array elements in different directions. If the MUSIC algorithm uses a fixed velocity value, this also introduces time delay errors, further reducing the accuracy of localization. Addressing these challenges, this paper proposes an innovative MUSIC algorithm for impact imaging using a guided Lamb wave array, with an emphasis on time delay management. This approach focuses on the extraction of high-energy, single-frequency components from impact response signals, ensuring accurate time delay measurement across array elements and enhancing noise resistance. It also calculates the average velocity of single-frequency components in varying directions for an initial impact angle estimation. This estimated angle then guides the selection of a specific single-frequency velocity, culminating in precise impact position localization. The experimental evaluation, employing equidistantly spaced array elements to capture impact response signals, assessed the effectiveness of the proposed method in accurately determining array time delays. Furthermore, impact localization tests on reinforced composite structures were conducted, with the results indicating high precision in pinpointing impact locations.

Sequentially activated discrete modules appear as traveling waves in neuronal measurements with limited spatiotemporal sampling.

Numerous studies have identified traveling waves in the cortex and suggested they play important roles in brain processing. These waves are most often measured using macroscopic methods that are unable to assess the local spiking activity underlying wave dynamics. Here, we investigated the possibility that waves may not be traveling at the single neuron scale. We first show that sequentially activating two discrete brain areas can appear as traveling waves in EEG simulations. We next reproduce these results using an analytical model of two sequentially activated regions. Using this model, we were able to generate wave-like activity with variable directions, velocities, and spatial patterns, and to map the discriminability limits between traveling waves and modular sequential activations. Finally, we investigated the link between field potentials and single neuron excitability using large-scale measurements from turtle cortex ex vivo. We found that while field potentials exhibit wave-like dynamics, the underlying spiking activity was better described by consecutively activated spatially adjacent groups of neurons. Taken together, this study suggests caution when interpreting phase delay measurements as continuously propagating wavefronts in two different spatial scales. A careful distinction between modular and wave excitability profiles across scales will be critical for understanding the nature of cortical computations.

Sequentially activated discrete modules appear as traveling waves in neuronal measurements with limited spatiotemporal sampling

Numerous studies have identified traveling waves in the cortex and suggested they play important roles in brain processing. These waves are most often measured using macroscopic methods that are unable to assess the local spiking activity underlying wave dynamics. Here, we investigated the possibility that waves may not be traveling at the single neuron scale. We first show that sequentially activating two discrete brain areas can appear as traveling waves in EEG simulations. We next reproduce these results using an analytical model of two sequentially activated regions. Using this model, we were able to generate wave-like activity with variable directions, velocities, and spatial patterns, and to map the discriminability limits between traveling waves and modular sequential activations. Finally, we investigated the link between field potentials and single neuron excitability using large-scale measurements from turtle cortex ex vivo. We found that while field potentials exhibit wave-like dynamics, the underlying spiking activity was better described by consecutively activated spatially adjacent groups of neurons. Taken together, this study suggests caution when interpreting phase delay measurements as continuously propagating wavefronts in two different spatial scales. A careful distinction between modular and wave excitability profiles across scales will be critical for understanding the nature of cortical computations.

Light Curves of Lensed Components and Time Delay Measurements in the Binary Gravtationally Lensed Quasars SDSS J2124$$+$$1632 and SDSS J0806$$+$$2006

Light Curves of Lensed Components and Time Delay Measurements in the Binary Gravtationally Lensed Quasars SDSS J2124$$+$$1632 and SDSS J0806$$+$$2006

Time Delay Study of Ultrasonic Gas Flowmeters Based on VMD-Hilbert Spectrum and Cross-Correlation.

The accuracy of ultrasonic flowmeter time delay measurement is directly affected by the processing method of the ultrasonic echo signal. This paper proposes a method for estimating the time delay of the ultrasonic gas flowmeter based on the Variational Mode Decomposition (VMD)-Hilbert Spectrum and Cross-Correlation (CC). The method improves the accuracy of the ultrasonic gas flowmeter by enhancing the quality of the echo signal. To denoise forward and reverse ultrasonic echo signals collected at various wind speeds, a Butterworth filter is initially used. The ultrasonic echo signals are then analyzed by Empirical Mode De-composition (EMD) and VMD analysis to obtain the Intrinsic Mode Function (IMF) containing distinct center frequencies, respectively. The Hilbert spectrum time-frequency diagram is used to evaluate the results of the VMD and EMD decompositions. It is found that the IMF decomposed by VMD has a better filtering performance and better anti-interference performance. Therefore, the IMF with a better effect is selected for signal reconstruction. The ultrasonic time delay is then calculated using the Cross-Correlation algorithm. The self-developed ultrasonic gas flowmeter was tested on the experimental platform of the gas flow standard devices using this signal processing method. The results show a maximum indication error of 0.84% within the flow range of 60-606 m3/h, with a repeatability of no more than 0.29%. These results meet the 1-level accuracy requirements as outlined in the national ultrasonic flowmeters calibration regulation JJG1030-2007.

Reevaluating LSST’s Capability for Time Delay Measurements in Quasar Accretion Disks

The Legacy Survey of Space and Time at the Vera C. Rubin Observatory is poised to observe thousands of quasars using the Deep Drilling Fields (DDF) across six broadband filters over a decade. Understanding quasar accretion disk (AD) time delays is pivotal for probing the physics of these distant objects. Pozo Nuñez et al. has recently demonstrated the feasibility of recovering AD time delays with accuracies ranging from 5% to 20%, depending on the quasar’s redshift and time sampling intervals. Here we reassess the potential for measuring AD time delays under the current DDF observing cadence, which is placeholder until a final cadence is decided. We find that contrary to prior expectations, achieving reliable AD time delay measurements for quasars is significantly more challenging, if not unfeasible, due to the limitations imposed by the current observational strategies.

The Evolution of Forensic Delay Analysis: A Literature Review Investigating Changes and Progress in Project Management Approaches to Delay Measurement

The Evolution of Forensic Delay Analysis: A Literature Review Investigating Changes and Progress in Project Management Approaches to Delay Measurement