Pulse Energy Distribution Research Articles

Assessment of the spectral component of seismic vibrations of protected objects during explosions in rock quarries

The article was awarded to the honored practitioner of the URSR graduate School, the laureate of the State Prize of Ukraine, professor Vynoslavskiy Vasiliy Mikolayovich, a stretch of 27 years dean of the faculty of mining of the Kiev Polytechnic Institute. 14 September 2020 year 100 years from the day of the birth of him. The article briefly describes his life path and achievements, his life position and scientific achievements. Purpose. The purpose of this article is to study the dissipation and energy distribution of explosive pulses as they pass through the rock massif and the foundation of protected objects, as well as to study the amplitude and energy of seismic oscillations of protected objects under the action of an explosive pulse. Methodology. To study the dissipation and energy distribution of explosive pulses and the interpretation of the results in this article used the methods of spectral analysis (study of autocovariance functions, joint covariance functions, energy autospectras and cross-spectral analysis).Findings. The amplitude of seismic oscillations of the output pulse (foundation surface) for the system "soil - foundation" is 7.35 times lower than the amplitude of soil oscillations at a distance of 70 m from the experimental object, the energy decreased by 8.23 times. This indicates that the foundation of the research object absorbed about 88% of the seismic energy that approached it. The frequency range 5-9 Hz is resonant. In this range, the oscillation frequency of the object foundation is close to the oscillation frequency of the input pulse, which leads to an increase in the energy and amplitude of seismic oscillations and the formation of microcracks in the foundation. For the system "foundation - the top of the tower" the amplitude and energy of oscillations at the top of the tower is 2 times greater than on the surface of the foundation. This fact indicates that due to the significant height of the towers (42.6 m), there is a rocking under the action of an explosive impulse. The maximum amplitude of oscillations of the top of the tower and the surface of the foundation is observed at a frequency of 5 Hz. This indicates that the foundation and towers respond to the explosive impulse as a single object. The nature and form of phase-amplitude characteristics of mutual spectra (hodographs) indicate that the experimental system "source of the explosion-soil massif-foundation-tower for cement storage" is unstable and part of the energy is spent on the formation of microcracks. Originality. The method of research of the characteristics of the rock massif and protected objects used in the article indicates the possibility of a more detailed study of the mechanism of development of microcracks and their transition to unstable destruction. Practical implications. The practical value of the results lies in the information obtained to protect research objects from the negative and destructive effects of seismic pulses, as well as the ability to influence the flow and energy dissipation of explosive pulses by changing the parameters of the explosion or other engineering solutions.

An experimental link between fast noseleaf deformations and biosonar pulse dynamics in hipposiderid bats

Old-World leaf-nosed bats (Hipposideridae) are echolocating bats with peculiar emission-side dynamics where beamforming baffles ("noseleaves") that surround the points of ultrasound emission (nostrils) change shape while diffracting the outgoing biosonar pulses. While prior work with numerical and robotic models has suggested that these noseleaf deformations could have an impact on the output characteristics of the bat's biosonar system, testing the hypothesis that this is the case in bats remains a critical step to be taken. The work presented here has tested the hypothesis that the noseleaf dynamics in a species of hipposiderid bat (Pratt's roundleaf bat, H. pratti) leads to time-variant acoustical properties on the output side of the bats' biosonar emission system. The time-variant effects of the noseleaf motion could be detected even in the presence of other sources of variability by comparing the distribution of pulse energy over the angle at different points in time. Furthermore, a convolutional neural network was able to classify the noseleaf motion state based on microphone array recordings with 85.3% accuracy. These results hence demonstrate that these nose-emitting bats have access to a substrate for behavioral flexibility on the emission-side of their biosonar systems.

Super-giant pulses from the Crab pulsar: energy distribution and occurrence rate

ABSTRACT We present statistical analysis of a fluence-limited sample of over 1100 giant pulses from the Crab pulsar, with fluence > 130 Jy ms at ∼1330 MHz. These were detected in ∼260 h of observation with the National Centre for Radio Astrophysics (NCRA) 15 m radio telescope. We find that the pulse-energy distribution follows a power law with index $\rm \alpha \approx -3$ at least up to a fluence of ∼5 Jy s. The power-law index agrees well with that found for lower-energy pulses in the range 3–30 Jy ms. The fluence distribution of the Crab pulsar hence appears to follow a single power law over ∼3 orders of magnitude in fluence. We do not see any evidence for the flattening at high fluences reported by earlier studies. We also find that, at these fluence levels, the rate of giant-pulse emission varies by as much as a factor of ∼5 on time-scales of a few days, although the power-law index of the pulse-energy distribution remains unchanged. The slope of the fluence distribution for Crab giant pulses is similar to that recently determined for the repeating FRB 121102. We also find an anti-correlation between the pulse fluence and the pulse width, so that more energetic pulses are preferentially shorter.

Direct observation of structure-assisted filament splitting during ultrafast multiple-pulse laser ablation.

Laser-induced plasma evolution in fused silica through multipulse laser ablation was studied using pump-probe technology. Filament splitting was observed in the early stage of plasma evolution (before ~300 fs). This phenomenon can be attributed to competition between laser divergent propagation induced by a pre-pulse-induced crater and the nonlinear self-focusing effect. This effect was validated through simulation results. With the increasing pulse number, the appearance of filament peak electron density was postponed. Furthermore, a second peak in the filament and peak position separation were observed because of an optical path difference between the lasers propagating from the crater center and edge. The experimental results revealed the influence of a prepulse-induced structure on the energy distribution of subsequent pulses, which are essential for understanding the mechanism of laser-material interactions, particularly in ultrafast multiple-pulse laser ablation.

The emission and scintillation properties of RRAT J2325−0530 at 154 MHz and 1.4 GHz

AbstractRotating Radio Transients (RRATs) represent a relatively new class of pulsar, primarily characterised by their sporadic bursting emission of single pulses on time scales of minutes to hours. In addition to the difficulty involved in detecting these objects, low-frequency ( $ \lt 300\,\text{MHz}$ ) observations of RRATs are sparse, which makes understanding their broadband emission properties in the context of the normal pulsar population problematic. Here, we present the simultaneous detection of RRAT J2325−0530 using the Murchison Widefield Array (154 MHz) and Parkes radio telescope ( $1.4\,\text{GHz}$ ). On a single-pulse basis, we produce the first polarimetric profile of this pulsar, measure the spectral index ( $\alpha={-2.2\pm 0.1}$ ), pulse energy distributions, and present the pulse rates in the context of detections in previous epochs. We find that the distribution of time between subsequent pulses is consistent with a Poisson process and find no evidence of clustering over the $\sim\!1.5\,\text{h}$ observations. Finally, we are able to quantify the scintillation properties of RRAT J2325−0530 at 1.4 GHz, where the single pulses are modulated substantially across the observing bandwidth, and show that this characterisation is feasible even with irregular time sampling as a consequence of the sporadic emission behaviour.

Hunting for Radio Emission from the Intermittent Pulsar J1107-5907 at Low Frequencies

Abstract Rare intermittent pulsars pose some of the most challenging questions surrounding the pulsar emission mechanism, but typically have relatively minimal low-frequency (≲300 MHz) coverage. We present the first low-frequency detection of the intermittent pulsar J1107–5907 with the Murchison Widefield Array (MWA) at 154 MHz and the simultaneous detection from the recently upgraded Molonglo Observatory Synthesis Telescope (UTMOST) at 835 MHz, as part of an ongoing observing campaign. During a 30 minute simultaneous observation, we detected the pulsar in its bright emission state for approximately 15 minutes, where 86 and 283 pulses were detected above a signal-to-noise threshold of 6 with the MWA and UTMOST, respectively. Of the detected pulses, 51 had counterparts at both frequencies and exhibited steep spectral indices for both the bright main pulse component and the precursor component. We find that the bright state pulse energy distribution is best parameterized by a log-normal distribution at both frequencies, contrary to previous results that suggested a power law distribution. Further low-frequency observations are required in order to explore in detail aspects such as pulse-to-pulse variability and intensity modulations, as well as to better constrain the signal propagation effects due to the interstellar medium and intermittency characteristics at these frequencies. The spectral index, extended profile emission covering a large fraction of pulse longitude, and the broadband intermittency of PSR J1107–5907 suggest that future low-frequency pulsar searches—for instance, those planned with SKA-Low—will be in an excellent position to find and investigate new pulsars of this type.

A detailed study of giant pulses from PSR B1937+21 using the Large European Array for Pulsars

We have studied 4265 giant pulses (GPs) from the millisecond pulsar B1937+21; the largest-ever sample gathered for this pulsar, in observations made with the Large European Array for Pulsars. The pulse energy distribution of GPs associated with the interpulse are well-described by a power law, with index $\alpha = -3.99 \pm 0.04$, while those associated with the main pulse are best-described by a broken power law, with the break occurring at $\sim7$ Jy $\mu$s, with power law indices $\alpha_{\text{low}} = -3.48 \pm 0.04$ and $\alpha_{\text{high}} = -2.10 \pm 0.09$. The modulation indices of the GP emission are measured, which are found to vary by $\sim0.5$ at pulse phases close to the centre of the GP phase distributions. We find the frequency-resolved structure of GPs to vary significantly, and in a manner that cannot be attributed to the interstellar medium influence on the observed pulses. We examine the distribution of polarisation fractions of the GPs and find no correlation between GP emission phase and fractional polarisation. We use the GPs to time PSR B1937+21 and although the achievable time of arrival precision of the GPs is approximately a factor of two greater than that of the average pulse profile, there is a negligible difference in the precision of the overall timing solution when using the GPs.

A study of single pulses in the Parkes Multibeam Pulsar Survey

We reprocessed the Parkes Multibeam Pulsar Survey, searching for single pulses out to a DM of 5000 pc cm$^{-3}$ with widths of up to one second. We recorded single pulses from 264 known pulsars and 14 Rotating Radio Transients. We produced amplitude distributions for each pulsar which we fit with log-normal distributions, power-law tails, and a power-law function divided by an exponential function, finding that some pulsars show a deviation from a log-normal distribution in the form of an excess of high-energy pulses. We found that a function consisting of a power-law divided by an exponential fit the distributions of most pulsars better than either log-normal or power-law functions. For pulsars that were detected in a periodicity search, we computed the ratio of their single-pulse signal-to-noise ratios to their signal-to-noise ratios from a Fourier transform and looked for correlations between this ratio and physical parameters of the pulsars. The only correlation found is the expected relationship between this ratio and the spin period. Fitting log-normal distributions to the amplitudes of pulses from RRATs showed similar behaviour for most RRATs. Here, however, there seem to be two distinct distributions of pulses, with the lower-energy distribution being consistent with noise. Pulse-energy distributions for two of the RRATS processed were consistent with those found for normal pulsars, suggesting that pulsars and RRATs have a common emission mechanism, but other factors influence the specific emission properties of each source class.

Calculation of scintillation properties of Ø1″×1″ of the lanthanum bromide scintillation detector using MCNP simulation and experiment

The purpose of this study is to develop a model for gamma spectroscopy for calculation of full width at half maximum (FWHM), energy resolution and full-energy peak absolute detection efficiency of Ø1″×1″ of the lanthanum bromide LaBr3 (Ce) detector crystal. For this purpose, a complete detector model was developed for Monte Carlo N-Particle (MCNP) transport code. In MCNP simulation, F8 tally was used as it gives the energy distribution of pulses created in the detector. Whenever incident gamma ray enters into detector volume, due to interactions short pulses are produced inside the detector volume. The pulse height spectra of various gamma sources were obtained, which were used to calculate different scintillator properties of our interest. In the simulation, the distance from the source to the detector face was varied to see the effects on scintillation properties of the detector crystal. The detector crystal offers the energy resolution of 3.455% and the FWHM of 22.81 KeV when gamma source Cs137 (662 KeV) was used. As we increased the incident gamma ray energy, the FWHM of the detector crystal increased, while the energy resolution and absolute detection efficiency of the detector crystal decreased. The scintillation properties of Ø1″×1″ of the LaBr3 (Ce) detector crystal were studied experimentally. In our case, it was observed that experimental and simulation results coincided. This proves that the detector model we built for gamma spectroscopy in MC transport code is accurate.

Imaging and electron energy-loss spectroscopy using single nanosecond electron pulses

We implement a parametric study with single electron pulses having a 7 ns duration to find the optimal conditions for imaging, diffraction, and electron energy-loss spectroscopy (EELS) in the single-shot approach. Photoelectron pulses are generated by illuminating a flat tantalum cathode with 213 nm nanosecond laser pulses in a 200 kV transmission electron microscope (TEM) with thermionic gun and Wehnelt electrode. For the first time, an EEL spectrometer is used to measure the energy distribution of single nanosecond electron pulses which is crucial for understanding the ideal imaging conditions of the single-shot approach. By varying the laser power, the Wehnelt bias, and the condenser lens settings, the optimum TEM operation conditions for the single-shot approach are revealed. Due to space charge and the Boersch effect, the energy width of the pulses under maximized emission conditions is far too high for imaging or spectroscopy. However, by using the Wehnelt electrode as an energy filter, the energy width of the pulses can be reduced to 2 eV, though at the expense of intensity. The first EEL spectra taken with nanosecond electron pulses are shown in this study. With 7 ns pulses, an image resolution of 25 nm is attained. It is shown how the spherical and chromatic aberrations of the objective lens as well as shot noise limit the resolution. We summarize by giving perspectives for improving the single-shot time-resolved approach by using aberration correction.

ЭНЕРГЕТИЧЕСКИЕ ЗАКОНОМЕРНОСТИ ИМПУЛЬСНОГО НАГРУЖЕНИЯ СИСТЕМАМИ С ПРОМЕЖУТОЧНЫМ ЗВЕНОМ

The investigations carried out deal with the re-gularity study in the distribution of shock pulse energy at multiple procedures of loading. The experimental researches were carried out on the specially developed test bench in which under all waveguides (or tools) of the shock system there were situated independently (separately) sensors connected with an oscilloscope registering parameters of a shock pulse (a form, amplitude, duration).
 As a result it was determined that the increase of the eccentricity in the symmetry axis location of a head and a waveguide (or a tool) and their number in the shock system contributes to the reduction of an energy portion sent to the deformation source. The application of multi-contact schemes of loading allows sending large total energy of a shock pulse to the deformation source to accept conditions of experiment fulfillment.
 At that the energy portion of a shock pulse fall-ing to each waveguide (or a tool) in the multicontact scheme as compared with the singlecontact one decreases (for rod-formed waveguides by 20%, and for spherical tools – by 15%) at the installation of each subsequent waveguide (or a tool) in the shock system.

Explosive Nucleosynthesis Study Using Laser Driven γ-ray Pulses

We propose nuclear experiments using γ-ray pulses provided from high field plasma generated by high peak power laser. These γ-ray pulses have the excellent features of extremely short pulse, high intensity, and continuous energy distribution. These features are suitable for the study of explosive nucleosyntheses in novae and supernovae, such as the γ process and ν process. We discuss how to generate suitable γ-ray pulses and the nuclear astrophysics involved.

Research on switching operation transient electromagnetic environment of substations in a coal mine

Research of switching operation transient electromagnetic field in substations is fundamental to the protection of mine monitoring systems against electromagnetic interference. Three models, which are the equivalent circuit of switching on/off inductive load, transient radiation of short dipole, and transmission line of long cable, are built for numerical analysis. The results indicate that switching operation does not produce transient pulse when the breaking angle is close to 90°. Electric fields are the primary form of transient pulse radiation, and the effect of the magnetic field on the environment can be ignored. Long cables are naturally resistant to differential mode transient pulse propagation, but the effect of common mode transient pulse cannot be ignored. Energy distribution of transient pulse in different frequency ranges is calculated by using theParserval equation. Furthermore, the measurement frequencies and the instruments used in the coal mine are determined, and on-site data is then obtained. Measurement results show that switching operation may produce a series of transient pulses, causing the electric field to grow larger than before. Specifically, conducted emissions have large impacts on the monitoring circuitry of the mine equipment, causing the mine monitoring system to frequently record erroneous data and omit information.

Pulse train dependence of electron dynamics during resonant femtosecond laser nonlinear ionization of a Na4 cluster

In this study, a real-time and real-space time-dependent density functional theory (TDDFT) is applied to describe nonlinear electron–photon interactions during a resonant femtosecond laser pulse train photoionization of a Na4 cluster. The effects of key pulse train parameters, such as the spatial/temporal pulse energy distribution, pulse number per train, pulse separation and pulse phase on resonant absorption, are discussed. The calculations show that the resonant effect and the nonlinear electron dynamics, including energy absorption, electron emission, dipole response and ionization probability, can be controlled by shaping the ultrafast laser pulse train.

Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

Controllable high-throughput high-quality femtosecond laser-enhanced chemical etching by temporal pulse shaping based on electron density control.

We developed an efficient fabrication method of high-quality concave microarrays on fused silica substrates based on temporal shaping of femtosecond (fs) laser pulses. This method involves exposures of fs laser pulse trains followed by a wet etching process. Compared with conventional single pulses with the same processing parameters, the temporally shaped fs pulses can enhance the etch rate by a factor of 37 times with better controllability and higher quality. Moreover, we demonstrated the flexibility of the proposed method in tuning the profile of the concave microarray structures by changing the laser pulse delay, laser fluence, and pulse energy distribution ratio. Micro-Raman spectroscopy was conducted to elucidate the stronger modification induced by the fs laser pulse trains in comparison with the single pulses. Our calculations show that the controllability is due to the effective control of localized transient free electron densities by temporally shaping the fs pulses.

Pulsed Corona Discharge in Water Treatment: The Effect of Hydrodynamic Conditions on Oxidation Energy Efficiency

Water treatment by gas-phase pulsed corona discharge (PCD) relies mainly on utilization of ozone and OH radicals as oxidizing agents. In a configuration where the treated solution is showered through the plasma zone, the gas–liquid contact surface is the primary OH-radical formation site and the interface in the mass transfer of ozone. Its significance to overall process efficiency is therefore notable. In this study, the effect of varying contact surface area at different discharge powers was investigated from the perspective of efficient utilization of the two prime oxidants in slow reaction with oxalate. It is seen that increasing the area of the contact surface improves OH-radical utilization up to the point where the pollutant oxidation efficiency abruptly decreases presumably because of unfavorable pulse energy distribution in the gas–liquid mixture. The existence of an optimal area for a given power has implications for future studies in the design of pulsed plasma applications for water treatment.

Effects of key pulse train parameters on electron dynamics during femtosecond laser nonlinear ionization of silica

The controlled, well-characterized evolution of the amplitude envelope and carrier-frequency sweep of ultrafast laser pulses permits the measurement and control of quantum transitions on a femtosecond time scale. This opens new perspectives to manipulate/adjust/interfere with the transient localized electron dynamics, corresponding material properties and phase change mechanisms, which are critical in laser micro/nano fabrication. This study presents the first-principles calculations of nonlinear electron–photon interactions during femtosecond pulse train ablation of silica. A real-time and real-space time-dependent density functional theory (TDDFT) is used to describe the transient localized electron dynamics such as photon absorption, electron excitation and free electron distribution. The effects of key pulse train parameters (including the pulse separation, the number of pulses per train and temporal pulse energy distribution) on electron dynamics are investigated.

Theoretical study of pre-formed hole geometries on femtosecond pulse energy distribution in laser drilling.

Maxwell's wave equation was solved for fs laser drilling of silicon. The pre-formed hole wall's influence on the propagation behavior of subsequent laser pulses was investigated. The laser intensity at hole bottom shows distinct profile as compared with that at hole entrance. The multi-peaks and ring structure of the laser intensity were found at hole bottom. The position of maximum laser intensity (MLI) in relation to the wall taper angle was studied. It was found that the position of the MLI point would be closer to the hole entrance with increasing taper angle. This observation provides valuable information in predicting the position of plasma plume which is a key factor influencing laser drilling process. The elliptical entrance hole shape and zonal structure at the hole bottom reported in the literatures have been reasonably explained using the laser intensity distribution obtained in the present model.

MCNPX Monte Carlo simulations of particle transport in SiC semiconductor detectors of fast neutrons

The aim of this paper was to investigate particletransport properties of a fast neutron detector based on silicon carbide.MCNPX (Monte Carlo N-Particle eXtended) code was used in our study becauseit allows seamless particle transport, thus not only interacting neutronscan be inspected but also secondary particles can be banked for subsequenttransport. Modelling of the fast-neutron response of a SiC detector wascarried out for fast neutrons produced by 239Pu-Be source with the meanenergy of about 4.3 MeV. Using the MCNPX code, the following quantities havebeen calculated: secondary particle flux densities, reaction rates ofelastic/inelastic scattering and other nuclear reactions, distribution ofresidual ions, deposited energy and energy distribution of pulses. Thevalues of reaction rates calculated for different types of reactions andresulting energy deposition values showed that the incident neutronstransfer part of the carried energy predominantly via elastic scattering onsilicon and carbon atoms. Other fast-neutron induced reactions includeinelastic scattering and nuclear reactions followed by production of α-particles and protons. Silicon and carbon recoil atoms, α-particles and protons are charged particles which contribute to thedetector response. It was demonstrated that although the bare SiC materialcan register fast neutrons directly, its detection efficiency can beenlarged if it is covered by an appropriate conversion layer. Comparison ofthe simulation results with experimental data was successfully accomplished.