Waveform Measurements Research Articles

3D slowness time coherence for sonic imaging

Although sonic imaging can provide higher resolution images of the near-wellbore region than lower frequency seismic and borehole seismic measurements, many challenges confront its more widespread use. The traditional sonic imaging workflow of first filtering the borehole modes and then migrating the underlying reflected arrival events ignores a critical interpretation step, namely, characterizing these reflected arrivals in terms of their azimuths, raypath types, and other attributes. Furthermore, using sonic imaging results in subsequent modeling and simulation workflows requires determining the 3D coordinates or at least the true dip and azimuth of these near-wellbore reflectors, and feature extraction from noisy 2D sonic imaging migration images cannot provide either of these. To address these interpretation challenges and develop a means of mapping these reflectors without requiring a migration, a central issue that arises is whether we can determine the slowness and propagation direction of a reflected wavefield using a standard array of receiver sensors mounted around the circumference of a tool sonde. To accomplish this task, we have developed 3D slowness time coherence (STC). We combine an automated time pick with a ray-tracing procedure and our 3D STC processing to evaluate the many candidate arrival events that may be present in the filtered waveform measurements, which leads to a 3D map of the reflectors that can be readily integrated into digital models of the surrounding subsurface as well as logs of reflector true dip and azimuth that can be compared with similar logs produced from borehole images.

Waveform-Based Method for Fast and Accurate Identification of Subsynchronous Resonance Events

An increasing number of unstable subsynchronous resonance (SSR) has occurred for wind farms recently. These events can lead to significant loss of generation, threatening the safe operation of the system, and even damaging the generators. Accurate knowledge of SSR characteristics (SSR frequency, current magnitude, and damping) at an early stage of the event is critical for its effective mitigation. This paper proposes a method for fast and accurate identification of an SSR event and its characteristics. It takes advantage of time-stamped waveform measurements that are typically available on the terminals of series compensated transmission lines. It uses the known model of the line as a “filter” to extract the SSR components. Case studies demonstrate that the proposed algorithm can accurately compute the SSR frequency, SSR current magnitude, and damping in around one SSR cycle or less. In addition to line parameters uncertainties, the method has also proven to remain robust in the presence of harmonic distortions and reduced waveform sampling rates.

Fully automated, real-time, calibration-free, continuous noninvasive estimation of intracranial pressure in children.

In the search for a reliable, cooperation-independent, noninvasive alternative to invasive intracranial pressure (ICP) monitoring in children, various approaches have been proposed, but at the present time none are capable of providing fully automated, real-time, calibration-free, continuous and accurate ICP estimates. The authors investigated the feasibility and validity of simultaneously monitored arterial blood pressure (ABP) and middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) waveforms to derive noninvasive ICP (nICP) estimates. Invasive ICP and ABP recordings were collected from 12 pediatric and young adult patients (aged 2-25 years) undergoing such monitoring as part of routine clinical care. Additionally, simultaneous transcranial Doppler (TCD) ultrasonography-based MCA CBFV waveform measurements were performed at the bedside in dedicated data collection sessions. The ABP and MCA CBFV waveforms were analyzed in the context of a mathematical model, linking them to the cerebral vasculature's biophysical properties and ICP. The authors developed and automated a waveform preprocessing, signal-quality evaluation, and waveform-synchronization "pipeline" in order to test and objectively validate the algorithm's performance. To generate one nICP estimate, 60 beats of ABP and MCA CBFV waveform data were analyzed. Moving the 60-beat data window forward by one beat at a time (overlapping data windows) resulted in 39,480 ICP-to-nICP comparisons across a total of 44 data-collection sessions (studies). Moving the 60-beat data window forward by 60 beats at a time (nonoverlapping data windows) resulted in 722 paired ICP-to-nICP comparisons. Greater than 80% of all nICP estimates fell within ± 7 mm Hg of the reference measurement. Overall performance in the nonoverlapping data window approach gave a mean error (bias) of 1.0 mm Hg, standard deviation of the error (precision) of 5.1 mm Hg, and root-mean-square error of 5.2 mm Hg. The associated mean and median absolute errors were 4.2 mm Hg and 3.3 mm Hg, respectively. These results were contingent on ensuring adequate ABP and CBFV signal quality and required accurate hydrostatic pressure correction of the measured ABP waveform in relation to the elevation of the external auditory meatus. Notably, the procedure had no failed attempts at data collection, and all patients had adequate TCD data from at least one hemisphere. Last, an analysis of using study-by-study averaged nICP estimates to detect a measured ICP > 15 mm Hg resulted in an area under the receiver operating characteristic curve of 0.83, with a sensitivity of 71% and specificity of 86% for a detection threshold of nICP = 15 mm Hg. This nICP estimation algorithm, based on ABP and bedside TCD CBFV waveform measurements, performs in a manner comparable to invasive ICP monitoring. These findings open the possibility for rational, point-of-care treatment decisions in pediatric patients with suspected raised ICP undergoing intensive care.

A Noncontact Voltage Measurement System for Power-Line Voltage Waveforms

This paper presents the design and implementation details of a complete noncontact (NC) voltage acquisition system, which allows the measurement of power-line voltage waveforms without galvanic contact. The system is composed by a novel capacitive probe, an analog front end (AFE), and a microcontroller-based digital signal processing stage. A deep experimental characterization of the noncontact measurement system was performed. The tests reported a high linearity (maximum nonlinearity of ±0.2%), a low input-referred noise (11 mVrms), and a low-frequency response distortion. Measurements of ±330-V triangular waveform signals were performed with maximum instantaneous errors below ±1.5 V. The power-line voltage (220 Vrms at 50 Hz) was acquired without galvanic contact with an instantaneous error lower than ±3 V, whereas the mean error on rms voltage measurements was 0.32% and the maximum 0.7%. A two-day continuous measurement of power-line voltage was accomplished for testing system’s stability, resulting in negligible accuracy variations.

Effects of Bio-Impedance Sensor Placement Relative to the Arterial Sites for Capturing Hemodynamic Parameters.

Accurate measurement of the heart pulse waveform based on blood volume changes inside the arteries is crucial for reliable estimation of hemodynamic parameters such as blood pressure and cardiac output. Placement of blood volume sensors such as bio-impedance sensors close to the arterial sites is essential for the accurate measurement of the pulse waveform. The effect of sensor location relative to the wrist arteries on the pulse waveform had not been studied previously on human subjects. In this paper, we explore the effect of arterial and off-arterial placement of the bio-impedance sensor on important pulse waveform features such as pulse transit time (PTT), which is the travel time of the arterial pressure pulse between two sensors, and diastolic peak error (DPE), a measure of pulse signal sharpness. Placing the current injection and voltage sensing electrodes of a bio-impedance sensor on the radial artery provide greater accuracy for such features. We find that arterial PTT has a significantly lower standard deviation compared to off-arterial PTT indicating better signal quality. Similarly, we observe that DPE is much smaller for arterial bio-impedance which confirms our expectations. Based on these features, the location of the artery can be determined using an array of sensors placed around the artery.

Concurrent measurement of sample and reference waveforms in an optical-pump terahertz-probe system using a controlled optical diaphragm shutter

We present concurrent measurement of sample and reference terahertz waveforms for an optical-pump terahertz-probe spectrometer, using a controlled optical diaphragm shutter for the optical pump line. When waveforms are taken consecutively, laser power fluctuations and other experimental conditions can introduce spectral artefacts, thus a concurrent measurement is preferred. Instead of techniques based on double modulation, the use of the diaphragm shutter eliminates the need for a second lock-in amplifier and/or constricted alignment due to the use of a single chopper blade for modulating two signals, simultaneously. Drude fitting of the complex conductivity obtained for GaAs confirms that measurements obtained using our set-up agree with reported scattering times.

An Accurate Calorimetric Loss Measurement Method for SiC MOSFETs

An accurate measurement of conduction and switching losses in the power semiconductor devices is necessary in order to design and evaluate the thermal management system of modern converter systems. Conventionally, electrical measurement methods, such as the double-pulse tests (DPTs), are used for measuring the switching losses. However, with the advent of wide-bandgap (WBG) devices that have fast switching transients, it is rather difficult to capture the waveforms accurately during switching transitions, and consequently, the measurement of switching loss becomes inaccurate. In addition, the measurement of switching waveforms depends on the voltage and current probes, as well as the oscilloscope used for the measurement, which makes this method prone to errors. This necessitates the use of measurement methods, which can provide much higher accuracy than the existing conventional electrical methods. Calorimetric methods are based on comparatively slow temperature measurements and do not rely on the measurements of fast switching transitions of voltages and currents, thus eliminating the demand for measuring fast switching transitions. This paper presents an accurate calorimetric method for measuring the device losses, which can be used to determine individual loss components accurately (conduction, turn-on, and turn-off losses). In addition to the turn-on and turn-off losses, this method can evaluate the charging and discharging losses of the device. The novelty of the method lies in the fact that a single setup can be used to measure all possible losses that can occur in a device during converter operation. The calorimetric test setup is described, and a novel modulation scheme is introduced, which enables the segregation of the individual losses. The experimental test setup is built and the method is verified by measuring the losses of a 900-V, 23-A Wolfspeed C3M0120090D SiC MOSFET.

Measurement of Lightning Current at Wind Turbine Near Coast of Sea of Japan in Winter

The authors have carried out measurement of the current waveforms associated with lightning discharges to wind turbines near the coast of the Sea of Japan in Tohoku. In this paper, measured waveforms in winter from 2013 to 2018 are investigated and the charge transfer of lightning flash initiated by upward propagating leaders is studied. The charge transfer associated with bipolar lightning is higher than that associated with unipolar lightning. The lightning charge transfer of the typical winter atmospheric pressure pattern thunderstorms (TWPs) with relatively low -10 °C isotherm altitude is less than that of OTT (other thunderstorms than the TWP) at Nikaho and in Tohoku. In Hokuriku, another winter lightning area, the charge transfer of the lightning flash is almost the same regardless of the above-mentioned two types of the thunderstorms as well as the -10 °C isotherm altitude. As the result, it is pointed out that the charge transfer is dependent on the -10 °C isotherm altitude and types of thunderstorms, and that characteristics of winter lightning depend on the region. It is commonly found that the charge transfer exceeding 300 C occurs when the altitude of -10 °C isotherm is between 1000 and 2500 m above the sea level.

Design and testing of a system for measuring high-frequency AC losses in superconducting wires and coils carrying DC and AC currents

Development of high-power superconducting applications requires the accurate estimation of AC losses in the superconductor. In applications such as superconducting magnetic energy storage, the charge/discharge/persistent switching frequency of the coil, resulting from pulse width modulation control algorithms, is usually in the kilohertz regime. Therefore, a thorough investigation of the losses in the kilohertz regime of AC currents superimposed on large DC currents is essential in order to ensure the device stable operation at a predefined temperature. We describe here a unique experimental setup designed and built for characterizing AC losses in superconducting wires and coils under such special conditions. To minimize the eddy currents induced in the apparatus, a cryostat vacuum vessel was made of Delrin, an insulating synthetic polymer. The measurement setup allows driving DC currents up to 150 A and superimposed AC currents with amplitudes up to 10 Arms and frequencies up to 18 kHz. The system utilizes conduction cooling to reach a wide range of temperatures between 6 and 100 K and allows measurements of 10 cm long superconducting wires and coils with a diameter of 40 cm. The loss is measured by the electrical method, i.e., by direct voltage and current waveform measurement, achieving a resolution better than 100 nW. The system described here will assist in developing superconducting wires and coils for high-power applications.

A Lightning Current Measurement Method Based on Optical Sensing Technology

Precise and reliable measurement of lightning current parameters is important for supplying accurate original data for the lightning protection design. Thus far, studies have focused solely on methods involving only one measurement function and the measuring devices have defects in their measurement principle when applied to the full waveform measurement of lightning current. This paper proposes a lightning current measurement method that uses optical current sensing, which has no magnetic saturation or bandwidth limitation, to directly measure the current from a lightning strike transmission tower top, indirectly measure the current from lightning in transmission lines, and identify the type of fault caused by a lightning strike. Furthermore, in this paper, a magnetic field model of a transmission tower was established by finite element simulation to analyze the magnetic field characteristics of lightning in a tower. It was found that the magnetic field waveforms obtained from the sensors in the power system are largely similar to the lightning current waveforms, and the magnetic field amplitude exhibits a stable linear relationship with the lightning current, which verified the feasibility of our optical current sensing technology applied in lightning measurement. We also performed a comparative analysis of the magnetic field characteristics when a lightning strike at the tower-top/line leads to flashover and when it does not.

Retinal Arteriole Pulse Waveform Analysis Using a Fully-Automated Doppler Optical Coherence Tomography Flowmeter: a Pilot Study.

PurposeTo evaluate the repeatability and reproducibility of the measurement of retinal arteriole pulse waveforms using a novel fully-automated Doppler optical coherence tomography (DOCT) flowmeter in healthy subjects.MethodsTwenty eyes of 20 healthy subjects were included to test the intrasession repeatability of pulse waveform analysis. DOCT measurements were performed based on a newly developed instantaneous Doppler angle measurement method. Upstroke time (UT), which is the time from the minimum to the maximum retinal blood velocity, and the resistance index (RI) of the retinal arteriole pulse waveform were measured. Coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) were calculated. Interdevice reproducibility between two instruments was assessed in five eyes of five subjects.ResultsThe mean UT was 130.3 ms (range, 110.1–152.1 ms), and the mean RI was 0.66 (range, 0.51–0.82). The respective ICCs of UT and the RI for the intrasession repeatability of assessment were 0.87 and 0.78. The respective CVs of UT and the RI were 6.6 ± 3.3% and 4.7 ± 2.1%. Regarding interdevice reproducibility, there were no significant differences between the measurements derived from the instruments (P > 0.05).ConclusionsPulse waveform measurement in retinal arterioles using a fully-automated DOCT flowmeter exhibited good repeatability and interdevice reproducibility.Translational RelevanceThe above-described improved DOCT flowmeter system provides reasonably repeatable measurements of retinal arteriole pulse waveforms, potentially facilitating systemic-circulation abnormality monitoring. The examination of the circulation with the novel device can be potentially useful for evaluating systemic circulation.

Heart Failure–Specific Relationship Between Muscle Sympathetic Nerve Activity and Aortic Wave Reflection

Reflected arterial waves contribute to left ventricular (LV) afterload. Heart failure patients with reduced ejection fraction (HFrEF) are afterload sensitive and sympathetically activated. We tested the hypothesis that HFrEF patients exhibit a positive relationship between sympathetic vasoconstrictor discharge and aortic wave reflection. Sixteen treated patients with HFrEF (61 ± 9 years of age, left ventricular ejection fraction 30 ± 7%, 3 women) and 16 similar-aged healthy control subjects (57 ± 7 years of age, 4 women) underwent noninvasive measurements of radial pulse waveforms (applanation tonometry) to calculate central blood pressures and aortic wave reflection characteristics: augmentation pressure (AP), augmentation index (AIx), and AIx corrected to a heart rate of 75 beats/min (AIx@75). Muscle sympathetic nerve activity (MSNA) burst frequency was recorded from the fibular nerve (microneurography). HFrEF patients had higher AIx (26 ± 9 vs 17 ± 15%; P < .05) and MSNA burst frequency (48 ± 7 vs 39 ± 11 bursts/min; P < .05) and lower central diastolic pressure than control subjects (64 ± 8 vs 70 ± 9 mm Hg; P = 0.05). There were no between-group differences in heart rate, other measures of blood pressure (brachial and central; P > .05), AP (11 ± 5 vs 7 ± 8 mm Hg; P = 0.11), or AIx@75 (19 ± 9 vs 13 ± 11%,-P = 0.14). MSNA correlated positively with AP (r = 0.50; P < .05), AIx (r = 0.51; P < .05), and AIx@75 (r = 0.54; P < .05) in HFrEF patients but not in control subjects (r = 0.002-0.18; P > 0.49). In patients with HFrEF, but not similarly aged healthy subjects, indices of aortic wave reflection correlate positively with MSNA. By increasing LV afterload, such neurovascular coupling could impair LV performance and worsen heart failure symptoms. Therapies that attenuate neurogenic vasoconstriction may benefit HFrEF patients by diminishing arterial wave reflection.

Abstract P286: Short-Term Repeatability of Electrocardiographic Criteria of Left Ventricular Hypertrophy

Background: Left ventricular hypertrophy (LVH) is a marker of cardiac end-organ damage and a risk factor for cardiovascular morbidity and mortality. Although electrocardiogram (ECG) is the most common tool for LVH assessment in contemporary clinical trials and cohort studies, the repeatability of ECG-LVH criteria has not been sufficiently examined. Objectives: Characterize the repeatability and minimal detectable change of ECG-LVH criteria. Methods: A total of 63 participants (mean age 50 years; 31 females) underwent two visits one week apart. At each visit, two digital ECGs were obtained following a standardized protocol. The ECG data were processed centrally to automatically obtain waveform measurements needed to calculate Cornell voltage (CV) LVH (SV3 + RaVL &gt;2800 μV for men and &gt;2000 μV for women), Cornell voltage product (CVP) LVH ((RaVL + SV3) X QRS duration ≥244 mV sec; for both Cornell criteria, 0.8 mV was added to the voltage sum for women), and Sokolow-Lyon (SL) LVH (SV1 +RV5/V6 ≥3500 μV). In addition to using these criteria as dichotomous LVH variables, we also used the waveforms measurements composing them as continuous variables, referred to here as CV-index, CVP-index, and SL-index. We used random-effects, mixed models to parse the variance of the variables into their between-participant, between-visit, and within-visit components, and calculated the intra-class correlation coefficient (ICC), minimal detectable change (95% confidence), and Kappas. Results: Between-participant variation accounted for 93% to 97% of the total variation in CV-index, CVP-index, and log of SL-index. The ICCs (95% confidence intervals) were 0.97 (0.96, 0.98) for CV-index, 0.97 (0.95, 0.98) for CVP-index, and 0.93 (0.90, 0.96) for log of SL-index. Minimal detectable change between repeat measures of CV-index, CVP-index, and log of SL-index were ≥236.7 μV, ≥26.7 mV, and ≥0.09 μV, respectively. The within-visit Kappa (95% confidence limits) was 0.73 (0.38, 1.00) for SL LVH and 1 for the other two LVH criteria. The between-visit Kappa was 1 for CV LVH, 0.66 (0.04, 1.00) for CVP LVH, and 0.40 (-0.03, 0.83) and 0.64 (0.26, 1.00) for the SL LVH first and second measurements of each visit, respectively. When defining ECG-LVH as presence of ≥1 ECG-LVH criteria, the within visit Kappa became 0.78 (0.49, 1.00) for the first visit and 1 for the second visit; the between visit Kappa values became 0.50 (0.12, 0.88) and 0.70 (0.38, 1.00) for the first and second measurements of each visit. Conclusion: CV, CVP, SL indices as continuous variables have excellent repeatability. The dichotomous ECG-LVH criteria have excellent within visit agreement, but between visit agreement ranges from fair to poor, which improved by combining multiple criteria. These results alleviate concerns about the repeatability the ECG LVH use in clinical trials and epidemiologic studies.

Natural Resonance Frequency of the Brain Depends on Only Intracranial Pressure: Clinical Research

The need to understand and control intracranial pressure (ICP) is required for treatments in various clinical situations. The ICP value can only be measured by direct intracranial catheter or sensor placement, and a non-invasive ICP prediction method has not yet been established. We focused on the natural resonance frequency (NRF) of the brain to predict the ICP value. The ICP value, pulse waveform of intracranial pressure (PWICP) and cervical carotid pressure waveform (CCPW) were simultaneously collected from patients who had undergone ventricular drainage or ICP sensor placement for medical treatment in our institute. A total of 43 data were obtained from 27 patients, age ranged 14-48 (mean: 54) years, body height 137-187 (mean 163) cm and body weight 32-103 (mean 61) kg. The total measured time was 29,653 seconds and the measured mean ICP value in each data ranged from 3.82 to 69.39 (mean 25.9) hPa. Consecutive data was cut into 10.24 seconds, which was called a column. To decrease respiratory modulation, the largest positive peak of cardiac pulsation of CCPW was picked up in each column, as well as one ICP pulse waveform. The picked-up CCPW and PWICP were averaged by the weighted average method. The transfer characteristics from CCPW to PWICP were calculated by the transfer function method. The first initial negative peak of transfer characteristics was judged as the NRF of the brain. The relationship between the ICP value and the NRF of the brain was presented on the quadratic functions graph (ICP = 0.0329(NRF)2 + 0.0842NRF). These parameters were strongly correlated to each other (R2= 0.9952 coefficient of determination). The individual NRF, which was calculated by the transfer function method, only depends on the measured ICP value and their relationship can be presented in the simple quadratic functions. Funding: This research was funded by Japan Science and Technology Agency (JST) A-STEP feasibility study in 2012, and by Japan's New Energy and Industrial Technology Development Organization (NEDO) in 2013, and by Grants-in-Aid for scientific research in Ministry of Education, Culture, Sports, Science and Technology-Japan from 2015 to 2017 and 2018 to 2020. Receiver: Kenji Furihata. Declaration of Interest: Although the authors (T.G., K.F. and K.H.) have some patents of non-invasive intracranial pressure monitoring apparatus, the claim of the patents belong to affiliated university not to individuals. All of authors had already opened their COI disclosure in Japanese Neurosurgical Society. The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described. Our proposing theory is a quite new concept. We strongly believe that there is nothing to competing interest declaration. Ethical Approval: The simultaneous measurement of intracranial pressure and cervical carotid artery pressure waveform was approved by Ethical Committee of Shinshu University School of Medicine. “Development of non-invasive intracranial pressure monitoring” approved number 2343.

The association of chronic health status and survival following ventricular fibrillation cardiac arrest: Investigation of a primary myocardial mechanism

IntroductionQuantitative waveform measures are a surrogate of the acute physiological status of the myocardium and predict survival following ventricular fibrillation out-of-hospital cardiac arrest (OHCA). We investigated whether the amplitude spectrum area (AMSA) waveform measure mediates the adverse relationship between increasing burden of chronic health conditions and lower likelihood of survival. MethodsWe performed a cohort investigation of persons > = 18 years who suffered ventricular fibrillation OHCA between 2008–2015 in a metropolitan emergency medical service (EMS) system. The count of chronic health conditions was determined using the Charlson Comorbidity Index (CCI). AMSA was calculated just prior to the initial shock. We used multivariable logistic regression to assess the relationship between CCI and survival-to-discharge in models first without and then with AMSA to determine the extent to which AMSA attenuated the CCI-survival association. ResultsOf the 716 eligible patients, 422/716 (59%) had at least one chronic health condition; 21.8% with one, 19.6% with two, 10.3% with 3, and 7.3% with ≥4. Survival-to-discharge was 45% (324/716). In the multivariable model adjusted for traditional Utstein characteristics, increasing CCI was associated with lower odds of survival (Odds ratio (OR) (95% confidence interval] = 0.82 [0.72, 0.93] for each additional chronic health condition). The addition of AMSA to the model only modestly attenuated the CCI-survival association (OR = 0.85 [0.74,0.98]). ConclusionThe waveform measure AMSA – a surrogate for the physiological status of the myocardium – mediated only a modest portion of the association between increasing burden of chronic health conditions and lower likelihood of survival following ventricular fibrillation OHCA.

CRDI 디젤엔진의 보쉬 제어방식과 델파이 제어방식의 인젝터 전압과 전류파형 비교연구

In this paper, we investigate the relationship between fuel injection quantity and voltage and current energy of Bosch system and Delphi system by measuring the high and low voltage waveform, current waveform, fuel injection quantity and fuel pressure of A and J-engines. Waveform measurements are made using the PICO scope and the CDS tester. The injectors of A and J engines were tested under no load condition using injector with normal fuel injection quantity, injector with small fuel injection quantity and injector with many fuel injection quantity. In case of normal injector, A-engine has higher fuel pressure, injection interval time, voltage energy, and current energy than J-engine. The current energy of the A-engine changed linearly compared to that of the J-engine. For over and under injectors, the change in the previous physical quantity was greater for the A-engine than for the J-engine. However, the duration time of maintaining to open the injector is controlled differently, and so the voltage and current energy values are changed, and the change of the current energy is larger than the voltage energy.

MLMVNNN for Parameter Fault Detection in PWM DC–DC Converters and Its Applications for Buck and Boost DC–DC Converters

This paper presents an effective approach to the fault diagnosis of pulsewidth modulated (PWM) DC–DC power converters. It is based on a multilayer multivalued neuron neural network with a complex QR decomposition. This network is used to identify the parameter values running out of tolerance range in two topologies of PWM DC–DC converters, namely, the buck and boost circuits. The proposed technique is based on measurements of steady-state voltages and currents waveforms.

Visualization of rapid electron precipitation via chorus element wave\u2013particle interactions

Chorus waves, among the most intense electromagnetic emissions in the Earth’s magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave–particle interactions in the Earth’s magnetosphere. Through in-situ measurements of chorus waveforms with the Arase satellite and transient auroral flashes from electron precipitation events as detected by 100-Hz video sampling from the ground, Earth’s aurora becomes a display for the resonant interactions. Our observations capture an asymmetric spatial development, correlated strongly with the amplitude variation of discrete chorus elements. This finding is not theoretically predicted but helps in understanding the rapid scattering processes of energetic electrons near the Earth and other magnetized planets.

In-ear and on-body measurements of impulse-noise exposure

Accurate quantification of noise exposure in military environments is challenging due to movement of listeners and noise sources, spectral and temporal noise characteristics, and varied use of hearing protection. This study evaluates a wearable recording device designed to measure on-body and in-ear noise exposure, specifically in an environment with significant impulse noise resulting from firearms. A commercial audio recorder was augmented to obtain simultaneous measurements inside the ear canal behind an integrated hearing protector, and near the outer ear. Validation measurements, conducted with an acoustic test fixture and shock tube, indicated high impulse peak insertion loss with a proper fit of the integrated hearing protector. The recording devices were worn by five subjects during a live-fire data collection at Marine Corps Base Quantico where Marines fired semi-automatic rifles. The field test demonstrated the successful measurement of high-level impulse waveforms with the on-body and in-ear recording system. Dual channels allowed for instantaneous fit estimates for the hearing protection component, and the device worked as intended in terms of hearing protection and noise dosimetry. Accurate measurements of noise exposure and hearing protector fit should improve the ability to model and assess the risks of noise-induced hearing loss.

All-optical measurement of the complete waveform of octave-spanning ultrashort light pulses.

We demonstrate the complete temporal characterization of the optical waveform of visible near-infrared octave-spanning ultrashort laser pulses, using an all-optical, all-solid-state, and fully inline dispersion-scan device based only on second-harmonic generation.