Burst Signals Research Articles

Investigation of the multiple characteristics of the self-mixing effect subject to a single particle.

As a compact interferometry technique, self-mixing interferometry (SMI) is a promising tool for micro particle detection in biochemical analysis and the monitoring of laser manufacturing processing, and currently SMI based micro particle detection is attracting increasing attention. However, unlike the typical displacement or vibration measurement driven by a macro target, only a small amount of literature has targeted the SMI effect induced by a single micro moving particle. In this paper, two numerical models were investigated to describe the characteristics of the signal sparked by individual particle. We compared the measurement results with the two models' simulations in three signal characteristic aspects: the temporal waveform, frequency spectrum, and phase profile. From these results, we established that both amplitude modulation and frequency modulation effects apply under different conditions in the self-mixing process. And for the first time, we analyzed the effect of the laser illumination spot size on the particle-induced SMI signal features with two optical arrangements. When the laser beam size is larger than the particle size, the signal bursts are likely to result from frequency modulation, and vice versa. Our results can improve the capability of SMI technology in particle size discrimination and particle sorting.

Blind Detection of Broadband Signal Based on Weighted Bi-Directional Feature Pyramid Network.

With the development of wireless technology, signals propagating in space are easy to mix, so blind detection of communication signals has become a very practical and challenging problem. In this paper, we propose a blind detection method for broadband signals based on a weighted bi-directional feature pyramid network (BiFPN). The method can quickly perform detection and automatic modulation identification (AMC) on time-domain aliased signals in broadband data. Firstly, the method performs a time-frequency analysis on the received signals and extracts the normalized time-frequency images and the corresponding labels by short-time Fourier transform (STFT). Secondly, we build a target detection model based on YOLOv5 for time-domain mixed signals in broadband data and learn the features of the time-frequency distribution image dataset of broadband signals, which achieves the purpose of training the model. The main improvements of the algorithm are as follows: (1) a weighted bi-directional feature pyramid network is used to achieve a simple and fast multi-scale feature fusion approach to improve the detection probability; (2) the Efficient-Intersection over Union (EIOU) loss function is introduced to achieve high accuracy signal detection in a low Signal-Noise Ratio (SNR) environment. Finally, the time-frequency images are detected by an improved deep network model to complete the blind detection of time-domain mixed signals. The simulation results show that the method can effectively detect the continuous and burst signals in the broadband communication signal data and identify their modulation types.

Convolutional neural network to distinguish glitches from minute-long gravitational wave transients

Gravitational wave bursts are transient signals distinct from compact binary mergers that arise from a wide variety of astrophysical phenomena. Because most of these phenomena are poorly modeled, the use of traditional search methods such as matched filtering is excluded. Bursts include short ($<$10 seconds) and long (from 10 to a few hundreds of seconds) duration signals for which the detection is constrained by environmental and instrumental transient noises called glitches. Glitches contaminate burst searches, reducing the amount of useful data and limiting the sensitivity of current algorithms. It is therefore of primordial importance to locate and distinguish them from potential burst signals. In this paper, we propose to train a convolutional neural network to detect glitches in the time-frequency space of the cross-correlated LIGO noise. We show that our network is retrieving more than 95$\%$ of the glitches while being trained only on a subset of the existing glitch classes highlighting the sensitivity of the network to completely new glitch classes.

Phase-unwrapping algorithm combined with wavelet transform and Hilbert transform in self-mixing interference for individual microscale particle detection

The self-mixing interferometry (SMI) technique is an emerging sensing technology in microscale particle classification. However, due to the nature of the SMI effect raised by a microscattering particle, the signal analysis suffers from many problems compared with a macro target, such as lower signal-to-noise ratio (SNR), short transit time, and time-varying modulation strength. Therefore, the particle sizing measurement resolution is much lower than the one in typical displacement measurements. To solve these problems, in this paper, first, a theoretical model of the phase variation of a single-particle SMI signal burst is demonstrated in detail. The relationship between the phase variation and the particle size is investigated, which predicts that phase observation could be another alternative for particle detection. Second, combined with continuous wavelet transform and Hilbert transform, a novel phase-unwrapping algorithm is proposed. This algorithm can implement not only efficient individual burst extraction from the noisy raw signal, but also precise phase calculation for particle sizing. The measurement shows good accuracy over a range from 100 nm to 6 μm with our algorithm, proving that our algorithm enables a simple and reliable quantitative particle characteristics retrieval and analysis methodology for microscale particle detection in biomedical or laser manufacturing fields.

Development of calibration technique for underwater transducers in free field conditions below 1000 Hz with results on an acoustical recorder.

A calibration technique with potential for low frequencies and sizeable systems of underwater transducers is being developed at the Swedish Defence Research Agency. The technique is based on the three-transducer spherical wave reciprocity method for use in an ice-covered lake with a depth of 220 m in the Swedish arctic zone. The calibration is performed at a depth of approximately 100 m with inter-transducer separations of 50 m, 86.6 m, and 100 m, allowing for frequencies down to 59 Hz using time-gated tone burst signals. In this paper, the calibration location, system, and technique are introduced, and the calibration results of an acoustical recorder in the range of 59 Hz-1 kHz are presented. The sensitivity is varying with frequency around -148 dB re 1 V/μPa, and the uncertainty budget is discussed.

Comparison between Density and Velocity Fields in Burst Modulation of a Dielectric-Barrier-Discharge Plasma Actuator

The flow field produced by a dielectric-barrier-discharge plasma actuator using burst modulation was experimentally investigated in quiescent air from two viewpoints: density and vorticity fields. A wide range of burst signal parameters were evaluated using particle-image velocimetry and background-oriented schlieren measurements. Four types of flow-field patterns were found: Type 1 was a wall jet, similar to continuous operation; Type 2 was a periodical, independent vortex moving along the wall surface; Types 3 and 4 demonstrated a feature wherein the periodic shedding of the vortex pair (primary and secondary vortices) occurred while moving over the surface. While Types 3 and 4 demonstrated a shared feature, they had different density and vorticity structures. The change of the flow-field pattern from Type 1 to Type 4 was triggered by a lower burst frequency and ratio, as well as a higher base frequency. In addition, the vorticity strength and density were strongly negatively correlated and depended on the rate of power consumption to generate one vortex.

Pulse Based GFDM Modulation Technique for Future Generation Communication Systems

Future mobile communication systems are mainly focused on flexibility, reliability, scalability, spectral efficiency, and robustness. A higher data rate, increased capacity, higher mobility, lower latency, and improved quality are prime objectives that need to be improved in future communication systems. This paper investigates generalized frequency division multiplexing (GFDM), a suitable waveform candidate for future communication systems. It has low complexity compared to FBMC and is highly suitable for burst signal transmission. Due to the use of non-rectangular pulse shaping, out-of-band leakage is also less. This technique is more flexible in terms of frequency localization, scalability, and integration with MIMO. Its performance in terms of BER has been computed considering the number of subcarriers, number of sub-symbols, input power back-off, and roll-off factor as variable parameters. It has been observed that change in the BER is low when the number of sub-carriers is changed but is more for change in the number of sub-symbols. Its performance degrades when the number of subcarriers, the value of the roll-off factor, and the power back-off are increased. But BER performance improves with an increase in the number of sub-symbols.

Blind Symbol-Rate Estimation for Short and Bursty Communications

The design of a blind receiver for unsynchronized bursty communications is a challenging task, especially when the data burst duration is very short and the over-sampling ratio (OSR) at the receiver is a non-integer value. In this article, the problem of blind symbol-rate estimation for bursty communications is studied. A cyclostationary method with bias removal (CS-BR) is proposed to improve the accuracy of the “OSR peak” detection in cyclostationary method when the length of signal burst is very short. Factors which affect the accuracy of the proposed blind symbol-rate estimation are thoroughly analyzed. Both field measurement data simulations and Monte Carlo simulations show that by using our proposed CS-BR method, the accuracy of blind symbol-rate estimation can be significantly improved, and the root-mean-square-error of the estimated OSR can be reduced to as small as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-4}$</tex-math></inline-formula> even if each short data burst consists of only tens of symbols.

Physical Layer Famous Waveform Approaches for Fifth Generation Cellular Network

Many developments are taking place in the network to meet the 5G (Fifth generation) cellular network requirements; one of the very important research areas is the physical layer architecture and techniques. Studies related to the spectrum efficiency maximization indicate that the 5G air interface technology will also need to be flexible and capable of mapping various services to the best suitable combinations of frequency and radio resources.This paper investigates the physical layer waveform approaches as part of enhanced mobile broadband use case in 5G, and finds the Cyclic-Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) as a suitable approach by comparing performance parameters where the filtering and windowing can result in degradation of the quality of the signal which is measured via Error Vector Magnitude(EVM). It also attempts to enhance the down link performance between the base station and user equipment by using power amplifier clipping technique, while modelling the downlink channel by implementing channel coding, synchronization signal burst generation, different subcarrier spacing and frame numerologies for different propagation channel and different waveform approaches.

Investigation of Inertial Cavitation Induced by Modulated Focused Ultrasound Stimuli

Abstract A passive cavitation detection setup is used to assess and verify the capability of frequency- and amplitudemodulated ultrasound burst signals on the generation of inertial cavitation. The measurements were conducted with a flowthrough tissue-mimicking phantom with a canal of dc = 1mm in diameter simulating a fine blood vessel. By means of a flow velocity of vf= 50mm/s circulating blood in the cardiovascular system is imitated. Applying signal frequencies from f = 550 − 950 kHz and peak rarefaction pressures in a range from ˆpPRFP ≈ 0.17 − 1.81 MPa, various ultrasound stimuli with alternating signal parameters were investigated in the absence and presence of a talcum-water mixture acting as cavitation nuclei. By evaluating the broadband emissions in the frequency domain and calculating the voltage spectral density Srm, the results can be compared. The findings of the present study demonstrate that each ultrasound stimulus triggers a similar strength of cavitation noise at the same Mechanical Index, representing a certain pressure. Over the whole frequency and Mechanical Index (pressure) range, each ultrasound signal type generates a voltage spectral density from Srm= 0.25 − 2.25 V/ √ Hz.

A Non-Data-Aided Feedforward Timing Estimator Based on Multiple Cyclic Correlations for Short-Term Burst Signals

Due to short frames of short-term burst signals, the performance of conventional non-data-aided feedforward timing estimators is unsatisfactory. This letter investigates an estimator based on multiple cyclic correlations addressing this issue. The cyclic correlations at high-valued timing lags provide the timing information for estimating timing offset. Motivated by it, we combine the timing information at various timing lags, utilizing the second-order statistical characteristics of the limited sample data for accurate estimation. Considering the estimation range of roll-off factors and computational complexity, an asymptotically unbiased estimation using four correlations is deduced. Simulation results show that the proposed estimator outperforms other estimators.

Optimize multilayer matching layer design for tone-burst underwater acoustic transducers.

In this study, a theoretical model has been constructed to address the optimization of matching layers for tone burst excitation underwater acoustic transducers and to investigate the functional mechanism change of matching layers. Single, double, and triple matching layers are attached to piezoelectric composite plates, and tone burst signals with a different number of burst-cycles are applied. Acoustic pressure function (Sp) and acoustic pressure transient response (PTR) are compared among these transducers. The results demonstrated that when the cycle number M ≤ 2, more matching layers lead to shorter ringdown with similar PTR amplitude. Since the objective is for better axial resolution, three matching layers have noticeable advantage, whereas for the case of M > 5, far detection distance is the main objective, and more matching layers caused the decrease in PTR amplitude. Besides, matching layers become part of the resonance structure; they do not serve as a transmission medium anymore. Therefore, the transducer with single matching is optimal for the long tone burst excitation. For the case of 2-5 cycle excitation, one may use double matching layers, which has a balance between the transmitting voltage response amplitude and bandwidth. With the increase in M, the role of matching layers changes from a bridging transmission medium to amplifying vibration velocity and introducing additional vibration modes to broaden the bandwidth.

The burst of electrophysiological signals in the suprachiasmatic nucleus of mouse during the arousal detected by microelectrode arrays.

The neural mechanisms of torpor have essential reference significance for medical methods and long-term manned space. Changes in electrophysiology of suprachiasmatic nucleus (SCN) conduce to revealing the neural mechanisms from the torpor to arousal. Due to the lower physiology state during the torpor, it is a challenge to detect neural activities in vivo on freely behaving mice. Here, we introduced a multichannel microelectrode array (MEA) for real-time detection of local field potential (LFP) and action potential (spike) in the SCN in induced torpor mice. Meanwhile, core body temperature and behaviors of mice were recorded for further analysis. Platinum nanoparticles (PtNPs) and Nafion membrane modified MEA has a lower impedance (16.58 ± 3.93 kΩ) and higher signal-to-noise ratio (S/N = 6.1). We found that from torpor to arousal, the proportion of theta frequency bands of LFPs increased, spike firing rates rapidly increased. These results could all be characteristic information of arousal, supported by the microscopic neural activity promoting arousal in mice. MEA displayed real-time dynamic changes of neuronal activities in the SCN, which was more helpful to analyze and understand neural mechanisms of torpor and arousal. Our study provided a factual basis for the neural state in SCN of induced non-hibernating animals, which was helpful for the application of clinics and spaceflight.

The N-terminus of a Fusarium graminearum-secreted protein enhances broad-spectrum disease resistance in plants.

Fusarium head blight is a destructive disease caused by Fusarium species. Little is known about the pathogenic molecular weapons of Fusarium graminearum. The gene encoding a small secreted protein, Fg02685, in F.graminearum was found to be upregulated during wheat head infection. Knockout mutation of Fg02685 reducedthe growth and development of Fusarium in wheat spikes. Transient expression of Fg02685 or recombinant protein led to plant cell death in a BAK1- and SOBIR1-independent system. Fg02685 was found to trigger plant basal immunity by increasing the deposition of callose, the accumulation of reactive oxygen species (ROS), and the expression of defence-related genes. The Fg02685 signal peptide was required for the plant's apoplast accumulation and induces cell death, indicating Fg02685 is a novel conserved pathogen-associated molecular pattern. Moreover, its homologues are widely distributed in oomycetes and fungal pathogens and induced cell death in tobacco. The conserved α-helical motif at the N-terminus was necessary for the induction of cell death. Moreover, a 32-amino-acid peptide, Fg02685 N-terminus peptide 32 (FgNP32), was essential for the induction of oxidative burst, callose deposition, and mitogen-activated protein kinase signal activation in plants. Prolonged exposure to FgNP32 enhanced the plant's resistance to Fusarium and Phytophthora. This study provides new approaches for an environment-friendly control strategy for crop diseases by applying plant immune inducers to strengthen broad-spectrum disease resistance in crops.

Phase Doppler Anemometer - The Shift From Simulation To The Real World

A Monte Carlo type simulation program has been developed to model phase Doppler systems. The work was divided into four main sections, the development of a launch strategy of a known range of droplet sizes and trajectories, the determination of the scattered light fields using Mie theory, the generation of the photomultiplier signals, and then their processing to generate drop size estimates followed by the comparison of these data with the launched data. The signal processing portion of the simulation measured the Doppler frequency in each signal to estimate the droplet velocity. Rather than using measurements of the phase differences between the multiple Doppler-shifted signals, the time shift between the arrival times of each signal was used to estimate the dropsize. This provided a linear relationship between the dropsize and the signal time shift. The missing link in the simulation is the ability to guide the experimentalist as to the best way to acquire the signal bursts and determine how accurate the measurements would be when using a PDA system to determine the droplet size distributions in real spray flows. Thus, the only way to determine measurement accuracy is to include that in the signal processing of an actual PDA system and spray. In an assessment of the capabilities of the signal processing technique, a sequence of Doppler bursts from an actual spray characterization were recorded and used as input to the software signal processor. The Time Shift Technique was based on the use of Weighted Average calculations to determine the exact middle of each of the three photomultiplier signal bursts. However, it was found that good quality signal bursts are required. Since cycle measurement techniques are less effected by noise, a cycle technique based on the samples captured by the AD converter was added to the software. Whereas this technique did show an improvement in measurement accuracy it led to the development of a cycle technique based on the signal burst frequency. This involved a reconstruction of the original captured bursts. The measurement errors were found to be in the micron range.

Comparative Accuracy Study Of LDV Profile-Sensor Acquisition Modes And Particle Diameters

The laser Doppler velocity profile sensor (LDV-PS) system offers the possibility to measure flow velocities with high spatial resolution and is therefore a promising method for the investigation of flows with high velocity gradients. The present experimental study revolves around the interplay between a broad range of chosen LDV-PS acquisition parameters, the dynamic velocity range within the observed measurement volume, and the accuracy of the velocity and position estimation from an application perspective. In the chosen set-up, thin wires of different diameters rotate at varying velocity levels and are captured instead of tracer particles by the applied system. It is observed that constant sample rate and number for the Fast Fourier Transform (FFT) evaluation of the detected burst signal allow straightforward measurements of unknown velocity profiles, but imply a velocity-dependent spatial measurement uncertainty. In contrast, velocity-adjusted acquisition settings allow to acquire particle bursts with equal signal resolution and length effecting a constant measurement accuracy at all velocity levels when adjusted appropriately. The position standard deviation is furthermore observed to increase with the wire diameter.Hence, the size of the scattering object should be chosen appropriately small during calibration and measurement. The gained knowledge offers the possibility to adapt the evaluation parameters more specifically to a given measurement problem.Consequently, measurements can be conducted in flows with small velocities with a high spacial resolution, when the FFT parameters and processing routines are adjusted accordingly, small particles are chosen and vibrations in the set-up are avoided.

The Hiccup of Villarrica volcano (Chile) during the 2015 eruption and its expression in LP activity and VLP ground motion

SUMMARY Volcano seismology is an essential tool for monitoring volcanic processes in the advent and during eruptions. A variety of seismic signals can be recorded at volcanoes, of which some are thought to be related to the migration of fluids which is of primary importance for the anticipation of imminent eruptions. We investigate the volcanic crises at Villarrica volcano in 2015 and report on a newly discovered very-long-period (VLP) signal that accompanies phases of periodic long period (LP) signal burst. Despite their low amplitude emergent character, we can locate the source region of the 1 Hz LP signals to the close vicinity of the volcano using a network-based correlation method. The source of the VLP signal with a period of about 30–100 s appears to locate in the vicinity of two stations a few kilometres from the summit. Both stations record very similar VLP waveforms that are correlated with the envelope of the LP bursts. A shallow magma reservoir was inferred by Contreras from surface deformation as the source of inflation following the eruption in 2015. Cyclic volume changes of 6 m3 in this reservoir at 3 km depth can explain the observed amplitudes of the vertical VLP signal. We propose that the LP signal is generated by the migration of gas or gas-rich magma that is periodically released from the inflating reservoir through a non-linear valve structure which modulates the flux, and thereby causes bursts of flow-related LP signals and pressure changes observed as VLP deformation. Our model predicts that the correlated occurrence of LP bursts and VLP surface motion depends on the intensity of the fluid flux. A weaker flux of fluids may not exceed the opening pressure of valve structure, and higher rates might maintain pressure above the closing pressure. In both cases, the VLP signal vanishes. Our observation provides constrains for models of fluid transport inside volcanoes. At Villarrica the VLP signal, and its relation to the LP activity, reveal additional information about fluxes in the magmatic reservoir that might aide forecasting of volcanic activity.

Assessment of the impact of interference signals on the decision circuit of the receiving-analyzing route of digital radio engineering systems

Currently, due to the increasing complexity of navigation support for aircraft (A/C), with the growth of requirements for them, it is increasingly necessary to develop systems for integrated processing of navigation information. The facilities for radio engineering flights support and aeronautical telecommunications are the main source of collecting processing and presenting information about the air situation to the traffic control staff. They are also used to solve the number of navigation problems. At the same time, the level of flight safety, along with the capacity of air traffic control zones depending on the decision of the ATC unit, is largely specified by the reliability of the various input information provided. At another point, most sophisticated digital tools for radio engineering flights support and aeronautical telecommunications at the output of the receiving-analyzing route have a decision or threshold circuit, the actuation of which, as a result of exposure to a mixture of noise and interference signals, reduces the reliability of information due to bursts of signal distribution, provided that impulse interference affecting the equipment and mush of receivers are not correlated. The work provides an estimate of the average amount of signal bursts at the output of the decision circuit taking into consideration the analysis of the probabilistic characteristics of the signals under consideration. For noises subject to the Rayleigh distribution and narrow-band impulse interference with a zero-mean value, the mathematical expectations of the average response time and the average number of positive bursts of the estimated process are found. The case of interfacing two airway surveillance radars “Skala-M” and “ATCR-22”, which have virtually identical operating characteristics, is analyzed. The dependence of the burst duration is calculated for the situation when the “Skala-M” radar is a source of unintended EMI for the “ATCR-22” radar.

The mammalian SKIV2L RNA exosome is essential for early B cell development.

The SKIV2L RNA exosome is an evolutionarily conserved RNA degradation complex in the eukaryotes. Mutations in the SKIV2L gene are associated with a severe inherited disorder, trichohepatoenteric syndrome (THES), with multisystem involvement but unknown disease mechanism. Here, we reported a THES patient with SKIV2L mutations showing severe primary B cell immunodeficiency, hypogammaglobulinemia, and kappa-restricted plasma cell dyscrasia but normal T cell and NK cell function. To corroborate these findings, we made B cell-specific Skiv2l knockout mice (Skiv2lfl/flCd79a-Cre), which lacked both conventional B-2 and innate-like B-1 B cells in the periphery and secondary lymphoid organs. This was linked to a requirement of SKIV2L RNA exosome activity in the bone marrow during early B cell development at the pro-B cell to large pre-B cell transition. Mechanistically, Skiv2l-deficient pro-B cells exhibited cell cycle arrest and DNA damage. Furthermore, loss of Skiv2l led to substantial out-of-frame V(D)J rearrangement of immunoglobulin heavy chain and severely reduced surface expression of μH, both of which are crucial for pre-BCR signaling and proliferative burst during early B cell development. Together, our data demonstrated a crucial role for SKIV2L RNA exosome in early B cell development in both human and mice by ensuring proper V(D)J recombination and Igh expression, which serves as the molecular basis for immunodeficiency associated with THES.

Electromagnetic Fireworks: Fast Radio Bursts from Rapid Reconnection in the Compressed Magnetar Wind

One scenario for the generation of fast radio bursts (FRBs) is magnetic reconnection in a current sheet of the magnetar wind. Compressed by a strong magnetic pulse induced by a magnetar flare, the current sheet fragments into a self-similar chain of magnetic islands. Time-dependent plasma currents at their interfaces produce coherent radiation during their hierarchical coalescence. We investigate this scenario using 2D radiative relativistic particle-in-cell simulations to compute the efficiency of the coherent emission and to obtain frequency scalings. Consistent with expectations, a fraction of the reconnected magnetic field energy, f ∼ 0.002, is converted to packets of high-frequency fast magnetosonic waves, which can escape from the magnetar wind as radio emission. In agreement with analytical estimates, we find that magnetic pulses of 1047 erg s−1 can trigger relatively narrowband GHz emission with luminosities of approximately 1042 erg s−1, sufficient to explain bright extragalactic FRBs. The mechanism provides a natural explanation for a downward frequency drift of burst signals, as well as the ∼100 ns substructure recently detected in FRB 20200120E .