Waveform Measurements Research Articles

Generalized electrical substitution methods and detectors for absolute optical power measurements

We have developed generalized methods for electrical substitution optical measurements, as well as cryogenic detectors which can be used to implement them. The new methods detailed here enable measurement of arbitrary periodic waveforms by an electrical substitution radiometer (ESR), which means that spectral and dynamic optical power can be absolutely calibrated directly by a primary standard detector. Cryogenic ESRs are not often used directly by researchers for optical calibrations due to their slow response times and cumbersome operation. We describe two types of ESRs with fast response times, including newly developed cryogenic bolometers with carbon nanotube absorbers, which are manufacturable by standard microfabrication techniques. These detectors have response times near 10 ms, spectral coverage from the ultraviolet to far-infrared, and are ideal for use with generalized electrical substitution. In our first tests of the generalized electrical substitution method with FTS, we have achieved uncertainty in detector response of 0.13% (k = 1) and total measurement uncertainty of 1.1% (k = 1) in the mid-infrared for spectral detector responsivity calibrations. The generalized method and fast detectors greatly expand the range of optical power calibrations which can be made using a wideband primary standard detector, which can shorten calibration chains and improve uncertainties.

Wearable Psychological Stress Monitoring Equipment and Data Analysis Based on a Wireless Sensor

With the rapid development of social economy, human psychological pressure is an important factor affecting human health. Excessive psychological pressure will lead to serious psychological diseases such as depression and anxiety. The traditional psychological stress monitoring method is mainly limited to the psychological scale. This method has a certain subjectivity, so its corresponding test data is not representative. At the hardware design level, this paper will select miniaturized, low-power, and low-cost microphysiological sensors to monitor the psychological pressure level discrimination indicators such as heart rate, body temperature, and heart rate waveform and fully optimize the layout of wireless sensors at the hardware layout level to achieve the high efficiency of the whole system. The detection of human pulse signal and heart rate signal is mainly carried out through microsensors, and the temperature signal is filtered and amplified, and analog-to-digital conversion is carried out to realize the accurate measurement of key signal waveform. At the level of hardware system and software algorithm, this paper creatively proposes a psychological stress recognition algorithm based on evidence theory. By extracting the collected key signal features, we can identify the primary stage of psychological stress and finally realize the evaluation and analysis of individual psychological stress through evidence theory. The experimental results show that the trust degree of an individual psychological stress test is improved by 0.187 compared with the traditional algorithm, and the corresponding psychological stress trust degree is up to 0.988, which has obvious advantages.

Impact point localization in three-dimensional structures using wavelet transform

Impact-induced anomalies such as travelling waves can be found in many devices or structures. This article provides an experimental method to localize a point of impact in three-dimensional structures using an array of redundant sensors. Concurrent measurement of vibration waveforms in moving measurement points and stationary reference allows determining the times of arrival of the travelling wave and, more importantly, times of arrival relative to the reference. These relative times of arrival allow for employing more measurement points than channels in the data acquisition system. This work proposes a modified method to estimate the times of arrival by combining continuous wavelet transform with optimal interval partitioning. The work also considers that the path between the impact and the measurement point depends on the properties of the structure, causing apparent wave speeds to differ across the measurement points. Therefore, regular triangulation and multilateration methods, which assume equal wave speeds, offer a reduced accuracy. The localization is solved as a constraint optimization problem considering variable apparent speeds.

A Review of Noninvasive Methodologies to Estimate the Blood Pressure Waveform.

Accurate estimation of blood pressure (BP) waveforms is critical for ensuring the safety and proper care of patients in intensive care units (ICUs) and for intraoperative hemodynamic monitoring. Normal cuff-based BP measurements can only provide systolic blood pressure (SBP) and diastolic blood pressure (DBP). Alternatively, the BP waveform can be used to estimate a variety of other physiological parameters and provides additional information about the patient’s health. As a result, various techniques are being proposed for accurately estimating the BP waveforms. The purpose of this review is to summarize the current state of knowledge regarding the BP waveform, three methodologies (pressure-based, ultrasound-based, and deep-learning-based) used in noninvasive BP waveform estimation research and the feasibility of employing these strategies at home as well as in ICUs. Additionally, this article will discuss the physical concepts underlying both invasive and noninvasive BP waveform measurements. We will review historical BP waveform measurements, standard clinical procedures, and more recent innovations in noninvasive BP waveform monitoring. Although the technique has not been validated, it is expected that precise, noninvasive BP waveform estimation will be available in the near future due to its enormous potential.

Inter-trial coherence as a measure of synchrony in cervical vestibular evoked myogenic potentials

BackgroundCervical vestibular evoked myogenic potentials (cVEMPs) are surface-recorded responses that reflect saccular function. Analysis of cVEMPs has focused, nearly exclusively, on time-domain waveform measurements such as amplitude and latency of response peaks, but synchrony-based measures have not been previously reported. New MethodTime-frequency analyses were used to apply an objective response-detection algorithm and to quantify response synchrony. These methods are new to VEMP literature and have been adapted from previous auditory research. Air-conducted cVEMPs were elicited using a 500 Hz tone burst in twenty young, healthy participants. ResultsTime-frequency characteristics of cVEMPs and time-frequency boundaries for response energy were established. An inter-trial coherence analysis approach revealed highly synchronous responses with representative inter-trial coherence values of approximately 0.7. Comparison with existing methodsInter-trial coherence measures were highly correlated with conventional amplitude measures in this group of young, healthy adults (R2 = 0.91 – 0.94), although the frequencies at which these measures had their largest magnitude were unrelated (R2 =.02). Conventional measures of peak-to-peak amplitude and latency were consistent with previous literature. Interaural asymmetry ratios were comparable between amplitude- and synchrony-based measures. ConclusionsSynchrony-based time-frequency analyses were successfully applied to cVEMP data and this type of analysis may be helpful to differentiate synchrony from amplitude in populations with disrupted neural synchrony.

Noninvasive monitoring of intracranial pressure after cardiac surgery: case report

Background: Heart valves are important structures that play an essential role in directing blood flow; changes in the functioning of these structures may require cardiac surgery with cardiopulmonary bypass. The behavior of intracranial pressure (ICP) in patients undergoing this type of surgery is unknown. Objective: aim of this study was to report alterations in the waveform morphology of ICP in a patient submitted to cardiac surgery with cardiopulmonary bypass. Case Description: This report provides data on ICP waveform morphology (P1 and P2 peaks) monitored before, immediately after, and on the 5th day after cardiac surgery. In the preoperative evaluation, the morphology of the patient's ICP waveforms was slightly altered, possibly due to the underlying cardiovascular disease. In the second measurement of the ICP waveforms, performed after surgery, the wave morphology of the ICP was normal. On the 5th PO day, after the patient presented clinical signs of neurological complications, the third ICP measurement was performed, which showed that the morphology of the ICP wave was altered.Conclusions: The use of non-invasive monitoring of ICP is of great importance in patients undergoing cardiac surgery, with the aim of diagnosing, preventing and/or enabling rapid treatment in cases where there is an evolution of more severe neurological complications that may lead to death.

A Synchronized Lissajous-Based Method to Detect and Classify Events in Synchro-Waveform Measurements in Power Distribution Networks

Waveform measurement units (WMUs) are a new class of smart grid sensors. They capture <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">synchro-waveforms</i> , i.e., time-synchronized high-resolution voltage waveform and current waveform measurements. In this paper, we propose new methods to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">detect</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">classify</i> power quality events in power distribution systems by using synchro-waveform measurements. The methods are built upon a novel graphical concept, called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">synchronized Lissajous curve</i> . The proposed event detection and event classification methods work by analyzing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">shape</i> of the synchronized Lissajous curves during disturbances and events. The impact of challenging factors, such as the angle, the location, and other parameters of the event are discussed. We show that these challenges can be addressed if we treat the synchronized Lissajous curves as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">images</i> , instead of as time series as in the raw synchronized waveform measurements. Hence, we can take advantage of the recent advancements in the field of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">image processing</i> so as to capture the overall characterizing patterns in the shapes of the synchronized Lissajous curves. We develop a Convolutional Neural Network (CNN) method to classify the events, where the input is the synchronized Lissajous images. The effectiveness of the proposed event detection and classification methods is demonstrated through computer simulations, including hardware-in-the-loop simulations, and real-world field data. Multiple case studies verify the performance of the proposed methods. The proposed event detection method can accurately detect events, and identify the start time and the end time of each event. The proposed event classification method can classify power quality events with high accuracy. The proposed detection and classification methods do <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">not</i> require any prior knowledge about the network. They use data from as few as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">only two</i> WMUs.

Feasibility of Specular Reflection Imaging for Extraction of Neck Vessel Pressure Waveforms.

Cardiovascular disease (CVD) is a leading cause of death worldwide and was responsible for 31% of all deaths in 2015. Changes in fluid pressures within the vessels of the circulatory system reflect the mechanical function of the heart. The jugular venous (JV) pulse waveform is an important clinical sign for assessing cardiac function. However, technology able to aid evaluation and interpretation are currently lacking. The goal of the current study was to develop a remote monitoring tool that aid clinicians in robust measurements of JV pulse waveforms. To address this need, we have developed a novel imaging modality, Specular Reflection Vascular Imaging (SRVI). The technology uses specular reflection for visualization of skin displacements caused by pressure pulsations in blood vessels. SRVI has been tested on 10 healthy volunteers. 10-seconds videos of the neck illuminated with a diffuse light source were captured at 250 fps. SRVI was able to identify and discriminate skin displacements caused by carotid artery and jugular vein pulsations to extract both carotid artery and jugular vein waveforms, making them easier to be visualized and interpreted. The method provided a 6-fold improvement in signal strength over a comparator remote PPG dataset. The current pilot study is a proof-of-concept demonstration of the potential of Specular Reflection Vascular Imaging for extraction of JV pulse waveforms.

Optical Arbitrary Waveform Measurement (OAWM) Using Silicon Photonic Slicing Filters

We demonstrate an optical arbitrary waveform measurement (OAWM) system that exploits a bank of silicon photonic (SiP) frequency-tunable coupled-resonator optical waveguide (CROW) filters for gapless spectral slicing of broadband optical signals. The spectral slices are coherently detected using a frequency comb as a multi-wavelength local oscillator (LO) and stitched together by digital signal processing (DSP). For high-quality signal reconstruction, we have implemented a maximum-ratio combining (MRC) technique based on precise calibration of the complex-valued opto-electronic transfer functions of all detection paths. In a proof-of-concept experiment, we demonstrate the viability of the scheme by implementing a four-channel system that offers an overall detection bandwidth of 140 GHz. Exploiting a femtosecond laser with precisely known pulse shape for calibration along with dynamic amplitude and phase estimation, we reconstruct 100 GBd QPSK, 16QAM and 64QAM optical data signals. The reconstructed signals show improved quality compared to that obtained with a single high-speed intradyne receiver, while the electronic bandwidth requirements of the individual coherent receivers are greatly reduced.

Acute exercise decreases insulin-stimulated extracellular vesicles in conjunction with augmentation index in adults with obesity.

Extracellular vesicles (EVs) are often elevated in obesity and may modulate disease risk. Although acute exercise reduces fasting EVs in adults with obesity, no data exist on insulin-mediated EV responses. This study evaluated the effects of exercise on EV responses to insulin in relation to vascular function. Ten (5M/5F) sedentary adults with obesity (34.3±3.7kg/m2 ) completed an evening control and acute exercise condition (70% to expend 400kcal). Following an overnight fast, participants underwent a 2h euglycaemic-hyperinsulinaemic clamp (90mg/dl; 40mU/m2 /min) to determine metabolic insulin sensitivity (M-value), phenotypes of medium- to large-sized EVs, and aortic waveform measures. Endothelial (CD105+ , CD41- /CD31+ )-, leukocyte (CD45+ )-, platelet (CD41+ , CD41+ /31+ )- and tetraspanin (TX+ )-derived EVs, as well as platelet endothelial cell adhesion molecule (CD31+ ), were determined before and after the clamp using high resolution spectral flow cytometry. Although exercise did not alter fasting haemodynamics, it lowered the augmentation index (AIx75, P=0.024) and increased the M-value (P=0.042). Further, exercise decreased all fasting EVs (P<0.01) and decreased insulin-stimulated TX+ (P=0.060), CD31+ (P=0.060) and CD41- /31+ (P=0.045) compared to rest. Interestingly, greater insulin-stimulated decreases in CD41- /31+ were associated with reduced AIx75 during the clamp (r=0.62, P=0.059), while insulin-stimulated decreases in CD41+ (r=-0.68, P=0.031), CD41+ /31+ (r=-0.69, P=0.262), TX+ (r=-0.66, P=0.037) and CD31+ (r=-0.69, P=0.028) correlated with M-value following exercise. Thus, acute exercise may decrease fasting and insulin-stimulated medium- to large-size EVs in conjunction with improved M-value and AIx75. More research is needed to understand effects of exercise on EVs in the regulation of glucose homeostasis and vascular function. KEY POINTS: Extracellular vesicles (EVs) are increased in states of obesity and may play a role in altered insulin sensitivity and blood pressure; aerobic exercise decreases fasting EV concentrations the following day in adults with obesity. This study directly tested the effects of insulin on EVs and how a single bout of exercise impacts these responses. Together, these data highlight the positive effects of a single bout of exercise on fasting and insulin-stimulated EVs, with the latter relating to increased insulin sensitivity and decreased augmentation index. These results support future research identifying EVs as mechanistic factors in glucose regulation and vascular function as well as clinical use of exercise to reduce cardiovascular disease risk.

Noncollinear electro-optic sampling detection of terahertz pulses in a LiNbO3 crystal while avoiding the effect of intrinsic birefringence.

We propose and experimentally prove efficient high-resolution electro-optic sampling measurement of broadband terahertz waveforms in a LiNbO3 crystal in the configuration with the probe laser beam propagating along the optical axis of the crystal. This configuration allows one to avoid the detrimental effect of strong intrinsic birefringence of LiNbO3 without any additional optical elements. To achieve velocity matching of the terahertz wave and the probe beam, the terahertz wave is introduced into the crystal through a Si prism at the Cherenkov angle to the probe beam. The workability of the scheme at different wavelengths of the probe optical beam (800 and 1550 nm) is demonstrated.

Monitoring the propagation of mechanical discontinuity using data-driven causal discovery and supervised learning

Mechanical wave transmission through a material is influenced by the mechanical discontinuity in the material. The propagation of embedded discontinuities can be monitored by analyzing the wave-transmission measurements recorded by a multipoint sensor system placed on the surface of the material. The proposed workflow monitors the propagation of mechanical discontinuity through three stages, namely initial, intermediate, and final stages, by using supervised learning followed by data-driven causal discovery. To the end, the workflow processes the multipoint waveform measurements resulting from a single impulse source, while considering the effects of wave attenuation, dispersion and multiple wave-propagation modes due to the discontinuity and material boundaries. Among various feature reduction techniques ranging from decomposition methods to manifold approximation methods, the features derived based on statistical parameterizations of the measured waveforms lead to reliable monitoring that is robust to changes in precision, resolution, and signal-to-noise ratio of the multipoint sensor measurements. The numbers of zero-crossing, negative-turning, and positive turning in the waveforms are the strongest causal signatures of the propagation of mechanical discontinuity. Higher order moments of the waveforms, such as variance, skewness and kurtosis, are also strong causal signatures of the propagation. The newly discovered causal signatures confirm that the statistical correlations and conventional feature rankings are not always statistically significant indicators of causality.

Detection of Spoofing Attacks in Aeronautical Ad-Hoc Networks Using Deep Autoencoders

We consider an aeronautical ad-hoc network relying on aeroplanes operating in the presence of a spoofer. The aggregated signal received by the terrestrial base station is considered as &#x201C;clean&#x201D; or &#x201C;normal&#x201D;, if the legitimate aeroplanes transmit their signals and there is no spoofing attack. By contrast, the received signal is considered as &#x201C;spurious&#x201D; or &#x201C;abnormal&#x201D; in the face of a spoofing signal. An autoencoder (AE) is trained to learn the characteristics/features from a training dataset, which contains only normal samples associated with no spoofing attacks. The AE takes original samples as its input samples and reconstructs them at its output. Based on the trained AE, we define the detection thresholds of our spoofing discovery algorithm. To be more specific, contrasting the output of the AE against its input will provide us with a measure of geometric waveform similarity/dissimilarity in terms of the peaks of curves. To quantify the similarity between <i>unknown</i> testing samples and the <i>given</i> training samples (including normal samples), we first propose a so-called <i>deviation-based algorithm</i>. Furthermore, we estimate the angle of arrival (AoA) from each legitimate aeroplane and propose a so-called <i>AoA-based algorithm</i>. Then based on a sophisticated amalgamation of these two algorithms, we form our final detection algorithm for distinguishing the spurious abnormal samples from normal samples under a strict testing condition. In conclusion, our numerical results show that the AE improves the trade-off between the correct spoofing detection rate and the false alarm rate as long as the detection thresholds are carefully selected.

Single-shot measurement of few-cycle optical waveforms on a chip

The measurement of transient optical fields has proven critical to understanding the dynamical mechanisms underlying ultrafast physical and chemical phenomena, and is key to realizing higher speeds in electronics and telecommunications. Complete characterization of optical waveforms, however, requires an optical oscilloscope capable of resolving the electric field oscillations with sub-femtosecond resolution and with single-shot operation. Here, we show that strong-field nonlinear excitation of photocurrents in a silicon-based image sensor chip can provide the sub-cycle optical gate necessary to characterize carrier-envelope phase-stable optical waveforms in the mid-infrared. By mapping the temporal delay between an intense excitation and weak perturbing pulse onto a transverse spatial coordinate of the image sensor, we show that the technique allows single-shot measurement of few-cycle waveforms.

Solar Orbiter Radio and Plasma Waves – Time Domain Sampler: In-flight performance and first results

Context.The Radio and Plasma Waves (RPW) instrument on board Solar Orbiter has been operating nearly continuously since the launch in February 2020. The Time Domain Sampler (TDS) receiver of the RPW instrument is dedicated to waveform measurements of plasma waves and dust impact signatures in an intermediate frequency range from 0.2 to 200 kHz.Aims.This article presents the first data from the RPW-TDS receiver and discusses the in-flight performance of the instrument and, in particular, the on-board wave and dust detection algorithm. We present the TDS data products and its scientific operation. We demonstrate the content of the dataset on several examples. In particular, we study the distribution of solar Langmuir waves in the first year of observations and one Type III burst event.Methods.The on-board detection algorithm is described in detail in this article and classifies the observed waveform snapshots, identifying plasma waves and dust impacts based on the ratio of their maximum amplitude to their median and on the spectral bandwidth. The algorithm allows TDS to downlink the most scientifically relevant waveforms and to perform an on-board statistical characterization of the processed data.Results.The detection algorithm of TDS is shown to perform very well in its detection of plasma waves and dust impacts with a high accuracy. The initial analysis of statistical data returned by TDS shows that sporadic Langmuir waves that are not associated with Type III events are routinely observed in the inner heliosphere, with a clear increase in occurrence rate closer to the Sun. We also present an example of RPW observations during an encounter of the source region of a Type III burst, which exploits the on-board calculated histograms data.

Multi‐Point Observation of Hiss Emerging From Lightning Whistlers

AbstractWe analyze continuous multi‐point measurements of electromagnetic field waveforms onboard the Cluster spacecraft in order to contribute to the discussion on sources of plasmaspheric hiss, known as a shaping agent for the Earth radiation belts. In our case study we aim at finding sources of hiss observed close to the geomagnetic equator in the outer plasmasphere on the dayside. We find hiss to be triggered from whistlers of different spectral properties. Whistlers with the lowest observed dispersion arrive to different spacecraft with time delays indicating their origin in the northern hemisphere. Positions of source lightning discharges are then found using the time coincidences with the Word Wide Lightning Location Network data from three active thunderstorm regions in Europe. We find that subionospheric propagation of lightning atmospherics is necessary to explain the observations. Geographic locations of their ionospheric exit points then determine spectral properties of resulting unducted whistlers and triggered hiss. By this well documented chain of events starting with a lightning discharge in the atmosphere we confirm that magnetospherically reflecting whistlers and hiss triggered from them are among possible sources of plasmaspheric hiss.

Noninvasive detection of elevated ICP using spontaneous tympanic membrane pulsation

Neurological conditions such as traumatic brain injury (TBI) and hydrocephalus may lead to intracranial pressure (ICP) elevation. Current diagnosis methods rely on direct pressure measurement, while CT, MRI and other expensive imaging may be used. However, these invasive or expensive testing methods are often delayed because symptoms of elevated ICP are non-specific. Invasive methods, such as intraventricular catheter, subdural screw, epidural sensor, lumbar puncture, are associated with an increased risk of infection and hemorrhage. On the other hand, noninvasive, low-cost, accurate methods of ICP monitoring can help avoid risks and reduce costs while expediting diagnosis and treatment. The current study proposes and evaluates a novel method for noninvasive ICP monitoring using tympanic membrane pulsation (TMp). These signals are believed to be transmitted from ICP to the auditory system through the cochlear aqueduct. Fifteen healthy subjects were recruited and TMp signals were acquired noninvasively while the subjects performed maneuvers that are known to change ICP. A custom made system utilizing a stethoscope headset and a pressure transducer was used to perform these measurements. Maneuvers included head-up-tilt, head-down-tilt and hyperventilation. When elevated ICP was induced, significant TMp waveform morphological changes were observed in each subject (p < 0.01). These changes include certain waveform slopes and high frequency wave features. The observed changes were reversed by the maneuvers that decreased ICP (p < .01). The study results suggest that TMp waveform measurement and analysis may offer an inexpensive, noninvasive, accurate tool for detection and monitoring of ICP elevations. Further studies are warranted to validate this technique in patients with pathologically elevated ICP.

Equivalent Circuit Establishments of a GaN High-Electron-Mobility Transistor and 635 nm Laser Diode for a Short-Pulsed Rising Current Simulation

In this paper, a dynamic operational linear regulator (DOLR) based on a GaN high-electron-mobility transistor (HEMT) and wide-bandwidth operational amplifier was developed and implemented. The driving current could be regulated and controlled by the DOLR for 632 nm laser diodes. The constant-current mode for the continuous-wave laser and the pulse-width modulation (PWM) mode for the short-pulsed laser were realizable using this DOLR. This study focused on the rising-edge time change on the laser driving current when the DOLR was operated under the high-frequency PWM mode, because the parasitic components on the GaN HEMT, laser diodes, printed circuit board, and power wires could influence the current’s dynamic behavior. Therefore, the equivalent circuit models of the laser diode and GaN HEMT were applied to establish a DOLR simulation circuit in order to observe the rising-edge time change on the laser driving current. A DOLR prototype was achieved, and so experimental waveform measurements could be implemented to verify the DOLR simulation and operation.

The IEEE Technical Committee 10: The Waveform Generation, Measurement, and Analysis Committee

The IEEE Technical Committee 10 (TC-10), the Waveform Generation, Measurement, and Analysis Committee of the IEEE Instrumentation and Measurement (I&M) Society, seeks to support the advancement of industries and other entities that research, develop, manufacture, and use technologies and instruments that generate or acquire signals. These signals are used in most if not all interfaces between humans and technology, such as, but not limited to, communication, computing, transportation, medicine, entertainment, manufacturing, and agriculture. In fact, it is very difficult to identify a human activity, other than the primitive, that is not in some way touched by electronics. So, in the broadest interpretation of the goal of the TC-10, it could be said that the TC-10 impacts everyone. Because the TC-10 is a developer of documentary standards, the TC-10's goal is achieved by fulfilling, as best as possible, the global need for standardized terms, test methods, and computational methods that are used to describe and measure the parameters that describe the performance of signal generators and waveform recorders and analyzers. The TC-10 has developed and maintains the following documentary standards: IEEE Std 181–2011, Standard on Transitions, Pulses, and Related Waveforms [1]; IEEE Std 1057–2017, Standard for Digitizing Waveform Recorders [2]; IEEE Std 1241–2010, Standard for Terminology and Test Methods for Ana-log-to-Digital Converters [3]; IEEE Std 658–2011, Standard for Terminology and Test Methods for Digital-to-Analog Converters [4]; the IEEE Std 1696–2013, Standard for Terminology and Test Methods for Circuit Probes [5]; and the IEEE Std 2414–2020, Standard for Jitter and Phase Noise [6]. Additional information on these standards can be found in [7].

Effect of Rotating Gliding Arc Plasma on Lean Blow-Off Limit and Flame Structure of Bluff Body and Swirl-Stabilized Premixed Flames

The effect of rotating gliding arc plasma on flame stabilization in a laboratory scale swirl-stabilized plasma-assisted combustor was experimentally investigated. The characteristics of a gliding arc plasma were studied using high-speed camera and simultaneous measurements of current and voltage waveforms. Effects of plasma on the extension of lean blow-off (LBO) limit and the swirl flames structures as well as OH radical distribution have been studied systematically. Results show that the discharge and combustion are coupled together effectively due to the dynamic processes of discharge. When the plasma is activated, the flame structures are drastically changed; oscillating flame and lifted flame convert to stable columnar flame tending to be attached to the plasma column. Besides, the plasma columns can promote OH formation and can produce much more energetic radicals due to the reactions between the discharge, methane and oxygen. The gliding arc plasma can stabilize the flame, provide an additional anchoring mechanism, and significantly extend the LBO limit. The plasma column can provide active radicals and continuous ignition to sustain the flame, and the thermal effect and kinetic effect may occupy the dominant role.