Typical Burst Research Articles

Propagation of Gamma-Ray Burst Relativistic Jets in Active Galactic Nucleus Disks and Its Implication for Gamma-Ray Burst Detection

The accretion disks of supermassive black holes (SMBHs) harboring in active galactic nuclei (AGN) are considered to be an ideal site for producing different types of gamma-ray bursts (GRBs). The detectability of these GRB phenomena hidden in AGN disks is highly dependent on the dynamical evolution of the GRB relativistic jets. By investigating the reverse- and forward-shock dynamics due to the interaction between the jets and AGN disk material, we find that the relativistic jets can successfully break out from the disks only for a sufficiently high luminosity and a long enough duration. In comparison, relatively normal GRB jets are inclined to be choked in the disks unless the GRBs occur near an SMBH with relatively low mass (e.g., ∼106 M ⊙). For the choked jets, unlike normal GRB prompt and afterglow emission, we can only expect to detect emission from the forward shock when the shock is very close to the edge of the disks, i.e., at the shock breakout emission and subsequent cooling of the shock.

Spatially resolved radio signatures of electron beams in a coronal shock

Context. Type II radio bursts are a type of solar radio bursts associated with coronal shocks. Type II bursts usually exhibit fine structures in dynamic spectra that represent signatures of accelerated electron beams. So far, the sources of individual fine structures in type II bursts have not been spatially resolved in high-resolution low-frequency radio imaging. Aims. The objective of this study is to resolve the radio sources of the herringbone bursts found in type II solar radio bursts and investigate the properties of the acceleration regions in coronal shocks. Methods. We used low-frequency interferometric imaging observations from the Low Frequency Array to provide a spatially resolved analysis for three herringbone groups (A, B, and C) in a type II radio burst that occurred on 16 October 2015. Results. The herringbones in groups A and C have a typical frequency drift direction and a propagation direction along the frequency. Their frequency drift rates correspond to those of type III bursts and previously studied herringbones. Group B has a more complex spatial distribution, with two distinct sources separated by 50 arcsec and no clear spatial propagation with frequency. One of the herringbones in group B was found to have an exceptionally large frequency drift rate. Conclusions. The characteristics derived from imaging spectroscopy suggest that the studied herringbones originate from different processes. Herringbone groups A and C most likely originate from single-direction beam electrons, while group B may be explained by counterstreaming beam electrons.

Phenomenology and periodicity of radio emission from the stellar system AU Microscopii

Stellar radio emission can measure a star’s magnetic field strength and structure, plasma density, and dynamics, and the stellar wind pressure impinging on exoplanet atmospheres. However, properly interpreting the radio data often requires temporal baselines that cover the rotation of the stars, orbits of their planets, and any longer-term stellar activity cycles. Here we present our monitoring campaign on the young, active M dwarf AU Microscopii with the Australia Telescope Compact Array between 1.1 and 3.1 GHz. With over 250 h of observations, these data represent the longest radio monitoring campaign on a single main-sequence star to date. We find that AU Mic produces a wide variety of radio emission, for which we introduce a phenomenological classification scheme predicated on the polarisation fraction and time-frequency structure of the emission. Such a classification scheme is applicable to radio emission from other radio-bright stars. The six types of radio emission detected on AU Mic can be broadly categorised into five distinct types of bursts, and broadband quiescent emission. We find that the radio bursts are highly circularly polarised and periodic with the rotation period of the star, implying that the emission is beamed. It is therefore most likely produced by the electron cyclotron maser instability. We present a model to show that the observed pattern of emission can be explained by emission from auroral rings on the magnetic poles. The total intensity of the broadband emission is stochastic, but we show that its circular polarisation fraction is also periodic with the rotation of the star. Such a periodicity in the polarised fraction of emission has not been observed on an M dwarf before. We present a qualitative model to describe the periodicity in the polarisation fraction of the broadband emission, using low-harmonic gyromagnetic emission. Using a simple qualitative model, we infer a magnetic obliquity of at least 20° from the observed variation in polarisation fraction. Finally, we show that the radio emission might be evolving on long timescales, hinting at a potential stellar magnetic activity cycle.

Australian Summer Monsoon Bursts: A Moist Static Energy Budget Perspective

AbstractThe Australian monsoon's wet season is associated with sequences of wet and dry conditions known as bursts and breaks, which usually have timescales of a week or two. There are several hypotheses for the physical processes involved in monsoon bursts, ranging from the effects of the Madden‐Julian Oscillation to extratropical influences. We analyze rainfall bursts in Northern Australia using a moist static energy (MSE) budget framework. We separate the bursts into three types and further separate them into pre‐monsoon, active monsoon, and post‐monsoon. We then apply ERA5 data to calculate the MSE budget for each burst and construct composite bursts for each of the three types. We find that the horizontal advection of MSE over the tropical northern Australian convergence zone is the most critical term in the budget for the day‐to‐day precipitation variation. MSE‐related gross moist stability analysis reveals that each type has distinct characteristics. The burst type associated with active monsoon bursts displays convective growth and decay patterns both before and after the precipitation peak, which is typical of oceanic convection. A low‐rainfall burst type, which is often seen before monsoon onset, is linked to coastal convection and has minimal rainfall decay after the burst. Finally, a sustained high‐rainfall burst type, mostly observed at the end or after the monsoon retreat, has growth characteristics similar to the typical monsoon burst but does not decay, maintaining very high rainfall for at least a week due to a rearrangement of the circulation and local thermodynamic structure of the atmosphere.

Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by the Parker Solar Probe and Its Probable Emission Mechanism

The Parker Solar Probe (PSP) provides us with an unprecedentedly close approach to the observation of the Sun and hence the possibility of directly understanding the elementary process that occurs on the kinetic scale of particles' collective interaction in solar coronal plasmas. We report a type of weak solar radio burst (SRB) that was detected by PSP when it passed a low-density magnetic channel during its second encounter phase. These weak SRBs have a low starting frequency of ∼20 MHz and a narrow frequency range from a few tens of MHz to a few hundred kHz. Their dynamic spectra display a strongly evolving feature of the intermediate relative drift rate decreasing rapidly from above 0.01 s−1 to below 0.01 s−1. Analyses based on common empirical models of solar coronal plasmas indicate that these weak SRBs originate from a heliocentric distance of ∼1.1–6.1 R S (the solar radius), a typical solar wind acceleration region with a low-β plasma, and that their sources have a typical motion velocity of ∼v A (Alfvén velocity) obviously lower than that of the fast electrons required to effectively excite SRBs. We propose that solitary kinetic Alfvén waves with kinetic scales could be responsible for the generation of these small-scale weak SRBs, called solitary wave radiation.

Uneven Stiffness Coal Seam: A New Structural Factor Prone to Coal Burst Based on Stiffness Theory

The development of stiffness theory is constrained by its contradiction with engineering experience. Several easily overlooked details of stiffness theory were clarified, and a qualitative evaluation formula for the risk of coal burst was provided. Then a novel structure factor called uneven stiffness coal seam structure (USCS), which consists of high stiffness zone (HSZ), low stiffness zone (LSZ), and contiguous roof and floor, was proposed. Many areas prone to coal bursts, such as thinning zones, bifurcating areas, magmatic intrusion areas, and remnant pillar affected areas of coal seam, are the HSZs of USCSs. Comparative analysis of the uneven stiffness coal seam under different roof conditions and examination of the simplified trisection model of the USCS were conducted. Then 6 groups of 14 simplified 2D models using COMSOL5.2 was constructed based on controlled variable method to simulate different responses of the USCS with varying parameters under same working conditions. The results demonstrate the following: (1) coal bursts occur only when both the failure criterion and the stiffness criterion are simultaneously satisfied, the risk of coal burst (rCB) is the product of the risk of failure (rF) and the risk of instability (rI). (2) The pressure concentration function of USCS facilitates stress concentration from LSZ to HSZ, thus raising the rF in HSZ. The stiffness reduction function of USCS reduces the local mine stiffness (LMS) of the HSZ, allowing the system to meet the stiffness criterion even with a hard roof, thereby raising the rI in HSZ and reconciling the contrast between stiffness theory and engineering experience. Failures within HSZ of the USCS enables the roof strata to release bending deformation energy without roof breakage. (3) The normal stress of HSZ is positively correlates with the value of ERHRKHSL/KLSH; The LMS of the HSZ is positively correlated with the value of ERKL/KHHRSLSH. The USCS boasts significant advantages in integrating and harmonizing various existing theories and explaining multiple specific types of coal bursts. By applying relevant USCS findings, new explanations can be provided for engineering phenomena such as the time-delayed coal bursts, the inefficient pressure relief in ultra thick coal seams, and the “microseism deficiency” observed prior to certain coal bursts.

Evoked Potentials by Tone Burst on the Auditory Cortices in Cats -Comparison of Off Responses in Awake and Anesthetized Conditions.

Auditory Brainstem Response (ABR) recording in awake is essential to detect off-responses. This study clarified whether after-termination responses on ABR were offset responses, off-responses or a mixture of the two. Evoked potentials in the auditory cortex of cats in response to tone burst stimuli were recorded, and off responses were examined with chronically implanted electrodes. When the fall time at the end of sound stimuli was 5ms or longer, the amplitude of click responses was extremely small. Under this condition, evoked potentials in response to two types of tone bursts (long and short) were recorded.By calculating the differences in evoked potentials between the two-tone bursts, off responses were separated. Off responses were generated during wakefulness by auditory cortex stimulation but were not observed under anesthesia. Pronounced off responses, which were middle latency responses exhibiting bis positive waves, were obtained in response to sound stimuli with a frequency of 2 kHz or higher. Vertex stimulation did not induce off responses either during wakefulness or under anesthesia. Off responses are derived from synchronous responses of neurons in the auditory cortex, which are generated when the neurons detect attenuation in the stimulus strength at the end of tone burst stimuli.

THE RELATIONSHIP OF THE INTENSITY OF THE SCR PROTON FLUX WITH THE PARAMETERS OF TYPE II SOLAR RADIO BURSTS

112 solar proton events (SPEs) were processed for the period from November 24, 2000 to December 20, 2014, which were accompanied by type II radio bursts. For the analysis, used original records of solar radio emission from a solar radio spectrograph in the range of 25-180 MHz, as well as original records of the flux intensity proton of solar cosmic rays (SCR) protons Ip with energy Ep in the range > 0.8-850 MeV according to data from the GOES series of devices. In this case, superimposed proton events were always separated and identified with the corresponding solar proton flares, and the maximum proton flux intensity Ip of superimposed proton events was determined from the level of the previous proton event. Based on data from the solar radio spectrograph, regression models were obtained for 91 type II bursts that established the relationship between the frequency drift velocity Vi,j and the frequency of type II bursts fi,j, and for 73 type II bursts it was possible to obtain regression models which established the relationship between the intensity of type II bursts Ii,j and type II burst frequency fi,j in the range 25-180 MHz. Detailed studies have shown that the intensity of type II bursts Ii,j, as well as the frequency drift velocity Vi,j, strongly depends on the frequency of type II burst fi,j and monotonically changes with time ti along the harmonics of type II bursts. As a result, the relationship between the maximum values of the SCR proton flux intensity Ip and the calculated values of the frequency drift velocity Vi,j and intensity of type II bursts Ii,j was investigated. A comparative analysis showed that the relationship between the intensity of the SCR proton flux Ip and the intensity of type II bursts Ii,j is much stronger than with the frequency drift velocity Vi,j, where the correlation coefficient r is 0.82 and 0.71, respectively, for protons with energies Ep > 30 MeV. The relationship between the proton flux intensity Ip and the frequency drift velocity Vi,j and the intensity of type II bursts Ii,j was also studied as a function of the proton energy Ep and the frequency fi,j of type II radio bursts. It was shown that the strongest relationship between the intensity of the SCR proton flux Ip with the frequency drift velocity Vi and with the intensity of type II bursts Ii,j is observed with subrelativistic SCR protons with energies Ep in the range > 30-100 MeV and for type II radio bursts at a frequency fi,j in the range 40-160 MHz.

Solar Radio Burst Detection Based on the MobileViT-SSDLite Lightweight Model

Real-time detection of solar radio bursts is crucial in solar physics research and space weather forecasting. However, current research on the automatic detection of solar radio bursts is limited to identifying the presence or absence of solar radio bursts or recognizing only a single type of burst, such as type II or III. Furthermore, existing methods cannot learn spectral and temporal features and often suffer from the drawbacks of large network models, resulting in slow speeds. This paper proposes an automatic recognition and localization method based on a lightweight object detection model for solar radio burst events. We collected observation data from e-CALLISTO and established a data set containing type II, III, IV, and V solar radio bursts. To address the real-time requirements of practical applications and consider the temporal and frequency domain information of spectrogram images, we improved a vision transformer with a self-attention mechanism and adopted a lightweight model for detection. The experimental results demonstrate that our proposed method achieves an average precision at a 50% intersection-over-union threshold of 78.2% and a recall rate of 92% on the established solar radio burst data set. Additionally, the model operates at a detection speed of 54.8 frames s–1, where a frame refers to a spectral image with a duration of 15 minutes, enabling efficient automated detection and localization of type II, III, IV, and V solar radio bursts.

Quantifying chaos and randomness in magnetar bursts

ABSTRACT In this study, we explore the dynamical stability of magnetar bursts within the context of the chaos-randomness phase space for the first time, aiming to uncover unique behaviours compared to various astrophysical transients, including fast radio bursts (FRBs). We analyse burst energy time series data from active magnetar sources SGR J1550−5418 and SGR J1935+2154, focusing on burst arrival time and energy differences between consecutive events. We find a distinct separation in the time domain, where magnetar bursts exhibit significantly lower randomness compared to FRBs, solar flares, and earthquakes, with a slightly higher degree of chaos. In the energy domain, magnetar bursts exhibit a broad consistency with other phenomena, primarily due to the wide distribution of chaos-randomness observed across different bursts and sources. Intriguingly, contrary to expectations from the FRB-magnetar connection, the arrival time patterns of magnetar bursts in our analysis do not exhibit significant proximity to repeating FRBs in the chaos-randomness plane. This finding may challenge the hypothesis that FRBs are associated with typical magnetar bursts but indirectly supports the evidence that FRBs may primarily be linked to special magnetar bursts like peculiar X-ray bursts from SGR J1935+2154 observed simultaneously with Galactic FRB 200428.

The Origin of Low-redshift Event Rate Excess as Revealed by the Low-luminosity Gamma-Ray Bursts

The relation between the event rate of long gamma-ray bursts and the star formation rate is still controversial, especially at the low-redshift end. Dong et al. confirmed that the gamma-ray burst rate always exceeds the star formation rate at a low redshift of z < 1 in spite of the sample completeness. However, the reason for low-redshift excess is still unclear. Since low-luminosity bursts are at smaller redshifts generally, we choose three Swift long burst samples and classify them into low- and high-luminosity bursts in order to check whether the low-redshift excess is existent and if the excess is biased by the sample size and completeness. To degenerate the redshift evolution from luminosity, we adopt the nonparametric method to study the event rate of the two types of long bursts in each sample. It is found that the high-luminosity burst rate is consistent with the star formation rate within the whole redshift range, while the event rate of low-luminosity bursts exceeds the star formation rate at a low redshift of z < 1. Consequently, we conclude that the low-redshift excess is contributed by the low-luminosity bursts with possibly new origins unconnected with the star formation, which is also independent of the sample size and the sample completeness.

Bursting with Potential: How Sensorimotor Beta Bursts Develop from Infancy to Adulthood.

Beta activity is thought to play a critical role in sensorimotor processes. However, little is known about how activity in this frequency band develops. Here, we investigated the developmental trajectory of sensorimotor beta activity from infancy to adulthood. We recorded EEG from 9-month-old, 12-month-old, and adult humans (male and female) while they observed and executed grasping movements. We analyzed "beta burst" activity using a novel method that combines time-frequency decomposition and principal component analysis. We then examined the changes in burst rate and waveform motifs along the selected principal components. Our results reveal systematic changes in beta activity during action execution across development. We found a decrease in beta burst rate during movement execution in all age groups, with the greatest decrease observed in adults. Additionally, we identified three principal components that defined waveform motifs that systematically changed throughout the trial. We found that bursts with waveform shapes closer to the median waveform were not rate-modulated, whereas those with waveform shapes further from the median were differentially rate-modulated. Interestingly, the decrease in the rate of certain burst motifs occurred earlier during movement and was more lateralized in adults than in infants, suggesting that the rate modulation of specific types of beta bursts becomes increasingly refined with age.SIGNIFICANCE STATEMENT We demonstrate that, like in adults, sensorimotor beta activity in infants during reaching and grasping movements occurs in bursts, not oscillations like thought traditionally. Furthermore, different beta waveform shapes were differentially modulated with age, including more lateralization in adults. Aberrant beta activity characterizes various developmental disorders and motor difficulties linked to early brain injury, so looking at burst waveform shape could provide more sensitivity for early identification and treatment of affected individuals before any behavioral symptoms emerge. More generally, comparison of beta burst activity in typical versus atypical motor development will also be instrumental in teasing apart the mechanistic functional roles of different types of beta bursts.

Cavitation-enhanced high-intensity focused ultrasound treatment for cancer therapy

Cavitation has been known to have a potential to enhance HIFU treatment in a few ways. It can multiply the particle displacement by orders of magnitude and thereby enhance the mechanical effect (1) of ultrasound hugely and the in vivo thermal effect (2) significantly. It can even induce chemical effect (3) when its bubble collapses. We are developing a cavitation-enhanced HIFU therapy system by which the effects (2) and (3) are aimed to obtain. The higher priority was set on the effect (2), because combination with a certain drug may be needed for the effect (3), which can make the process for the approval more difficult. In vivo cavitation threshold can hugely vary on the conditions. It can be reduced by stabilized microbubbles and nanobubbles, nanodroplets, and certain chemicals. However, these are not assumed in combination with our system for the same reason above. Instead, an ultrasonic pulse at an extremely high-intensity in the order of 10 MPa with a duration in the order of 10 ms is used to generate cavitation, which is immediately followed by a typical HIFU burst to obtain the effect (2). The results from swine tests of our HIFU system will be shown in the presentation.

Fast radio bursts trigger aftershocks resembling earthquakes, but not solar flares

ABSTRACT The production mechanism of repeating fast radio bursts (FRBs) is still a mystery, and correlations between burst occurrence times and energies may provide important clues to elucidate it. While time correlation studies of FRBs have been mainly performed using wait time distributions, here we report the results of a correlation function analysis of repeating FRBs in the 2D space of time and energy. We analyse nearly 7,000 bursts reported in the literature for the three most active sources of FRB 20121102A, 20201124A, and 20220912A, and find the following characteristics that are universal in the three sources. A clear power-law signal of the correlation function is seen, extending to the typical burst duration (∼ 10 msec) towards shorter time intervals (Δt). The correlation function indicates that every single burst has about a 10–60 per cent chance of producing an aftershock at a rate decaying by a power law as ∝ (Δt)−p with p = 1.5–2.5, like the Omori–Utsu law of earthquakes. The correlated aftershock rate is stable regardless of source activity changes, and there is no correlation between emitted energy and Δt. We demonstrate that all these properties are quantitatively common to earthquakes, but different from solar flares in many aspects, by applying the same analysis method for the data on these phenomena. These results suggest that repeater FRBs are a phenomenon in which energy stored in rigid neutron star crusts is released by seismic activity. This may provide a new opportunity for future studies to explore the physical properties of the neutron star crust.

Dense forests of microshots in bursts from FRB 20220912A

ABSTRACT We report on exceptionally bright bursts (&amp;gt;400 Jy ms) detected from the repeating fast radio burst source FRB 20220912A using the Nançay radio telescope (NRT), as part of the ECLAT (Extragalactic Coherent Light from Astrophysical Transients) monitoring campaign. These bursts exhibit extremely luminous, broad-band, short-duration structures (∼16 μs), which we term ‘microshots’ and which can be especially well studied in the NRT data given the excellent signal-to-noise and dynamic range (32-bit samples). The estimated peak flux density of the brightest microshot is 450 Jy. We show that the microshots are clustered into dense ‘forests’ by modelling them as Weibull distributions and obtaining Weibull shape parameters of approximately 0.5. Our polarimetric analysis reveals that the bursts are nearly 100 per cent linearly polarized; have ≲10 per cent circular polarization fractions; a near-zero average rotation measure of 0.10(6) rad m−2; and varying polarization position angles over the burst duration. For one of the bursts, we analyse raw voltage data from simultaneous observations with the Westerbork RT-1 single 25-m dish. These data allow us to measure the scintillation bandwidth, 0.30(3) MHz, and to probe the bursts on (sub-)microsecond time-scales. Some important nuances related to dedispersion are also discussed. We propose that the emission mechanism for the broad-band microshots is potentially different from the emission mechanism of the broader burst components, which still show a residual drift of a few hundred MHz ms−1 after correcting for dispersion using the microshots. We discuss how the observed emission is phenomenologically analogous to different types of radio bursts from the Sun.

Large-scale Evolution of Seconds-long Relativistic Jets from Black Hole–Neutron Star Mergers

We present the first numerical simulations that track the evolution of a black hole–neutron star (BH–NS) merger from premerger to r ≳ 1011 cm. The disk that forms after a merger of mass ratio q = 2 ejects massive disk winds (3–5 × 10−2 M ⊙). We introduce various postmerger magnetic configurations and find that initial poloidal fields lead to jet launching shortly after the merger. The jet maintains a constant power due to the constancy of the large-scale BH magnetic flux until the disk becomes magnetically arrested (MAD), where the jet power falls off as L j ∼ t −2. All jets inevitably exhibit either excessive luminosity due to rapid MAD activation when the accretion rate is high or excessive duration due to delayed MAD activation compared to typical short gamma-ray bursts (sGRBs). This provides a natural explanation for long sGRBs such as GRB 211211A but also raises a fundamental challenge to our understanding of jet formation in binary mergers. One possible implication is the necessity of higher binary mass ratios or moderate BH spins to launch typical sGRB jets. For postmerger disks with a toroidal magnetic field, dynamo processes delay jet launching such that the jets break out of the disk winds after several seconds. We show for the first time that sGRB jets with initial magnetization σ 0 > 100 retain significant magnetization (σ ≫ 1) at r > 1010 cm, emphasizing the importance of magnetic processes in the prompt emission. The jet–wind interaction leads to a power-law angular energy distribution by inflating an energetic cocoon whose emission is studied in a companion paper.

Early EEG-burst sharpness and 2-year disability in extremely preterm infants

BackgroundAutomated computational measures of EEG have the potential for large-scale application. We hypothesised that a predefined measure of early EEG-burst shape (increased burst sharpness) could predict neurodevelopmental impairment (NDI) and mental developmental index (MDI) at 2 years of age over-and-above that of brain ultrasound.MethodsWe carried out a secondary analysis of data from extremely preterm infants collected for an RCT (SafeBoosC-II). Two hours of single-channel cross-brain EEG was used to analyse burst sharpness with an automated algorithm. The co-primary outcomes were moderate-or-severe NDI and MDI. Complete data were available from 58 infants. A predefined statistical analysis was adjusted for GA, sex and no, mild–moderate, and severe brain injury as detected by cranial ultrasound.ResultsNine infants had moderate-or-severe NDI and the mean MDI was 87 ± 17.3 SD. The typical burst sharpness was low (negative values) and varied relatively little (mean –0.81 ± 0.11 SD), but the odds ratio for NDI was increased by 3.8 (p = 0.008) and the MDI was reduced by –3.2 points (p = 0.14) per 0.1 burst sharpness units increase (+1 SD) in the adjusted analysis.ConclusionThis study confirms the association between EEG-burst measures in preterm infants and neurodevelopment in childhood. Importantly, this was by a priori defined analysis.ImpactA fully automated, computational measure of EEG in the first week of life was predictive of neurodevelopmental impairment at 2 years of age.This confirms many previous studies using expert reading of EEG.Only single-channel EEG data were used, adding to the applicability.EEG was recorded by several different devices thus this measure appears to be robust to differences in electrodes, amplifiers and filters.The likelihood ratio of a positive EEG test, however, was only about 2, suggesting little immediate clinical value.

Prediction of rock burst intensity based on multi-source evidence weight and error-eliminating theory.

Rock burst is the main geological hazard in deep underground engineering. For the prediction of the intensity of rock burst, a model for prediction of rock burst intensity on the basis of multi-source evidence weight and error-eliminating theory was established. Four indexes including the ratio of rock's compressive-tensile strength [Formula: see text], the stress coefficient of rock [Formula: see text], the elastic energy index of rock Wet, and integrality coefficient Kv were chosen as the prediction variables of rock burst; the index weights are calculated by different weighting methods and fused with evidence theory to determine the final weight of each index. According to the theory of error-eliminating, taking "no rock burst" (I in classification standards of rock burst intensity) as the objective and using the error function to process 18 sets of typical rock burst data and the weight of evidence fusion as the normalized index limit loss value, a model for prediction of rock burst intensity was built. It is verified by the actual situation and three other models. Finally, the model has been applied to rock burst prediction of Zhongnanshan tunnel ventilation shaft. The results show that evidence theory fuses multi-source index weights and improves the method of determining index weights. The index value is processed by error-eliminating theory, and the limit value problem of index value normalization is optimized. The predicted results of the proposed model are consistent with the situation of Zhongnanshan tunnel. It improves the objectivity of the rock burst prediction process and provides a research idea for rock burst intensity prediction index.

Effect of strain rate on mechanical response and failure characteristics of horizontal bedded coal under quasi-static loading

Strain rock burst is one of the main types of rock bursts. Studying the mechanical response and acoustic emission characteristics of coal under quasi-static loading is significant to control and prevent strain rock bursts. In this paper, coal’s strength, deformation, energy evolution, and failure characteristics were analyzed with different strain rates under quasi-static loading. The strength characteristics of coal show a strain rate effect to a certain extent and the elastic modulus decreases first and then increases with stain rate increasing. Moreover, the elastic strain energy of coal samples always accounts for a high proportion before failure and the failure of coal presents a combined failure mode of tensile and shear under the dominance of tensile failure. The contribution of the shear failure to coal failure increases correspondingly when strain rate increases. Under quasi-static loading, There is a range where the strain rate effect does not appear, named as strain rate effect invisible area. The high static loading stress, and direct action of high strain rate loading should be avoided to reduce the risk of rock burst, especially for isolated coal pillars. The research achievements deepen the understanding of strain rock burst and provides critical support for the prevention of strain rock burst induced by high static loading.

Burst Pressure Solutions of Thin and Thick-Walled Cylindrical Vessels

Abstract Pressure vessels (PVs) are widely used in the energy industry. Accurate burst pressure is critical to structural design and safe operation for both thin and thick-walled PVs. The traditional strength theories utilized a single-parameter material property, such as the yield stress or the ultimate tensile stress (UTS) to develop failure models for determining the yield or ultimate pressure carrying capacity in the PV design. The UTS-based Barlow formula is a typical burst pressure model developed from the Tresca strength theory that provides the basis for developing regulation rules and failure models for different industry design codes, such as ASME BPVC, ASME B31.3, and ASME B31G, among others. In order to reduce the conservatism of the Tresca strength model, ASME BPVC recently adapted failure models developed from the von Mises strength theory for the PV design and analysis. It has been commonly accepted that the burst pressure of pipelines depends on the UTS and strain hardening exponent, n, of the pipeline steel. An average shear stress yield theory was thus developed, and the Zhu-Leis solution of burst pressure was obtained as a function of UTS and n for thin-walled line pipes. Experiments showed that the Zhu-Leis solution provides an accurate, reliable prediction of burst pressure for defect-free thin-walled pipes. In order to extend the Zhu–Leis solution to thick-walled cylindrical PVs, this paper defined three new flow stresses, modified the traditional strength theories, and obtained three new burst pressure solutions that are valid for both thin and thick-walled cylindrical vessels. The proposed flow stresses are able to describe the tensile strength and the plastic flow response of PVs for a strain hardening steel. The associated strength theories were then developed in terms of the Tresca, von Mises, and Zhu-Leis yield criteria. From these new strength theories, three burst pressure solutions were obtained for thick-walled cylinders, where the von Mises solution is an upper bound prediction, the Tresca solution is a lower bound prediction, and the Zhu-Leis solution is an intermediate prediction of burst pressure for thick-walled cylinders. Finally, the proposed burst pressure solutions were evaluated and validated by two large datasets of full-scale burst tests for thick-walled tubes and for thin-walled pipes.