Impulsive Energy Research Articles

Heating manifestations at the onset of the 29 June 2012 flare

Analysis of GOES data for the SOL2012-06-29T04:09 flare, class C4.6, shows a thermal character of the energy release for several minutes before the impulsive stage. Plasma heating to temperatures above 10 MK leads to the appearance of plasma jets along open field lines and in large loops. This work examines the relationship between the heated plasma and the flare structure and its dynamics, using observations in the X-ray, extreme ultraviolet (EUV), and radio-wave ranges. Particular attention is drawn to the detection of narrow-band fine temporal structures of radio emission before and after the impulsive stage of the flare in dynamic spectra. In the initial stage, broadband pulses in the decimeter range are observed which can be associated with the formation of thermal fronts in the jets. A series of super-bright drifting bursts in the centimeter range occurs after the end of the impulsive energy release in the flare kernel. Using data from the Siberian Solar Radio Telescope (5.7 GHz), we managed to localize the position of the source of the fine structure of drifting bursts at the remote footpoint of the large-scale flare loop.

Проявления нагрева в начале вспышки 29 июня 2012 г.

Analysis of GOES data for the SOL2012-06-29T04:09 flare, class C4.6, shows a thermal character of the energy release for several minutes before the impulsive stage. Plasma heating to temperatures above 10 MK leads to the appearance of plasma jets along open field lines and in large loops. This work examines the relationship between the heated plasma and the flare structure and its dynamics, using observations in the X-ray, extreme ultraviolet (EUV), and radio-wave ranges. Particular attention is drawn to the detection of narrow-band fine temporal structures of radio emission before and after the impulsive stage of the flare in dynamic spectra. In the initial stage, broadband pulses in the decimeter range are observed which can be associated with the formation of thermal fronts in the jets. A series of super-bright drifting bursts in the centimeter range occurs after the end of the impulsive energy release in the flare kernel. Using data from the Siberian Solar Radio Telescope (5.7 GHz), we managed to localize the position of the source of the fine structure of drifting bursts at the remote footpoint of the large-scale flare loop.

Dynamic behaviors of multiphase vortex-induced vibration for hydropower energy conversion

To satisfy the growing electricity demand, continuous and stable hydropower conversion is particularly critical in tidal power station operation. In the above industrial application, multiphase vortices will be formed, and they suck air and floating items into the flow tube, thus causing irregular pulsation that affects turbine performance. Due to nonlinear characteristics of gas-liquid coupling transfer, dynamic modeling and transition behavior of the multiphase vortex-induced vibration have improtant difficulties. This paper conducts a fluid-structure mechanic optimization model with the dynamic mesh technology to investigate multiphase vortex-induced vibration (MVIV) dynamic behaviors and reveal the internal relation between displacement responses and multiphase flow states. The fluid-induced vibration sensing platform is developed to validate MVIV transition behaviors, and a wavelet packet signal analyzing approach is adopted to acquire energy-spectrum distribution regularities of the vibration distortion state. Results show that the presented optimization modelling strategy can well obtain the MVIV transition behaviors and energy transfer mechanism. The flow flux can control the Ekman transfer intensity, and vibration energy waves take on various frequency components at the critical penetration state. Moreover, impulse energy components and structure evolution properties of high-frequency bands can be utilized to recognize the MVIV distortion peak. It can supply theoretical guidance and technology support for hydropower conversion.

The effects of cryogenic treatment and impact-oscillatory loading on changes in the mechanical properties and structural condition of stainless steel 12Kh18N10T

Research findings are presented dealing with the combined effect of cryogenic treatment + impact-oscillatory loading applied in different sequences on changes in the mechanical properties of stainless steel 12Kh18N10T. One-hour long cryogenic treatment and impact-oscillatory loading (IOL) applied at room temperature were shown to be practically unable to change the mechanical properties of the steel. At the same time, IOL pre-applied at a temperature of liquid nitrogen followed by static tensioning at room temperature proved to cause significant changes in the mechanical properties of the steel. Under further static tensioning, when IOL εimp = 2.7 … 12.5 % (assigned intensity range of introducing impulse energy into steel) or, more specifically, when εimp = 9.69 %, the ultimate strength of the steel was found to reach its maximum value, increasing by 32,2 % compared to baseline, while ductility decreased by 26 %. Specific physical investigations using the TEM microscope were conducted. The analysis of the steel structure of a specimen pre-subjected to IOL in liquid nitrogen at εimp = 9.63 % indicates that under such complex loading conditions the well-known mechanism of plastic deformation by sliding changes into plastic deformation by twinning upon further static tensioning, and the strength of the steel increases.

Underwater electrical wire explosions under different discharge types: An experimental study with high initial energy storage

In this study, underwater electrical explosions of aluminum wires of various sizes were carried out with an initial energy storage of ∼53.5 kJ. Two piezoelectric probes were adopted to record the pressure waveforms. The experiments were divided into different discharge types, and the statistical properties of the electrical and shock-wave parameters of the different discharge types were compared. The experimental results show that there are three discharge types, called type A (breakdown type), type B (transition type), and type C (matched type). The three types differ in the resistance characteristics of the plasma channel during the plasma growth process, which are determined from the average electrical field strength and the remaining energy in the circuit at the peak voltage. Shock waves from type C discharges are more likely to exhibit a higher peak pressure, a larger impulse, and a higher energy density than the other types. However, using a matched wire that matches a specific discharge type, a high peak pressure, large impulse, and high energy density can also be achieved under type A or type B discharges. For example, the maximum peak pressures at ∼33 cm under type B and type C discharges are 38.7 and 42.4 MPa, respectively. These results provide significant guidance for load selection in underwater electrical wire explosion engineering applications.

НАУКОВА КОНЦЕПЦІЯ CТВОРЕННЯ ВИСОКОВОЛЬТНИХ МОБІЛЬНИХ ЕЛЕКТРОТЕХНІЧНИХ СИСТЕМ РЕЗОНАНСНОГО ТИПУ ЗІ ШВИДКОДІЮЧИМИ КЕРУВАННЯМ І ПАРАМЕТРИЧНОЮ СТАБІЛІЗАЦІЄЮ РЕЖИМІВ НАВАНТАЖЕННЯ

A new scientific concept has been developed for the creation of high-voltage electro-technical systems (ETS) of a reso-nant type based on the implementation in them of series high-quality inductive-capacitive circuits (ICC) and high-frequency (HF) resonant currents. This makes it possible to repeatedly increase the alternating voltage on the reactive elements of the ICC and on the load connected in parallel to one of the elements, and to ensure a significant decrease in the impulse energy of the ETS without changing their average power, as well as to increase the speed of control and parametric stabilization of the load modes of the ETS even with a rapid decrease in the electrical resistance of this load to almost zero, as in the case of electrical breakdown of its insulation. The generation of resonant currents with a fre-quency of up to 40 kHz in the ICC, which has a coil with an inductance of ~ 25 mH and a Q factor up to 270 (made of multi-core twisted copper wires of the " litzendraht " type) and a ceramic capacitor with a capacity of ~ 3.5 nF and a Q factor > 1000, ensures the realization of the QICC up to 260 and the corresponding increase in the ratio of the ETS out-put voltage to the input voltage without the use of step-up transformers. When connecting such an ETS to a source of alternating voltage of 220 V, a voltage of up to 40 kV can be generated at the output of the ETS. A significant increase in the frequency of currents leads to a significant decrease in the mass-dimensional characteristics of ETS and the pos-sibility of creating their samples mobile (weighing up to 5 kg), and if necessary, autonomous, in particular with power supply from batteries. The new scientific concept is aimed at creating a resonance-type ETS for safe and reliable moni-toring and diagnostics of the technical condition of high-voltage insulation of power cables, powerful electric machines and other energy objects of the critical infrastructure of Ukraine. Such ETS can also be effectively used for charging to high voltages capacitive energy storage (CES) in technological installations for the production of electro-spark micro- and nano-powders with unique properties, as well as for high-voltage electro-hydro-pulse processing of various mate-rials and environments. It has been established that the power of these ETS increases with a decrease in the ratio of the capacitances of the capacitors ICC and CES. References 40, figures 4.

Detecting non-thermal emission in a solar microflare using nested sampling

ABSTRACT Microflares are energetically smaller versions of solar flares, demonstrating the same processes of plasma heating and particle acceleration. However, it remains unclear down to what energy scales this impulsive energy release continues, which has implications for how the solar atmosphere is heated. The heating and particle acceleration in microflares can be studied through their X-ray emission, finding predominantly thermal emission at lower energies; however, at higher energies it can be difficult to distinguish whether the emission is due to hotter plasma and/or accelerated electrons. We present the first application of nested sampling to solar flare X-ray spectra, an approach that provides a quantitative degree of confidence for one model over another. We analyse Nuclear Spectroscopic Telescope Array X-ray observations of a small active region microflare (A0.02 GOES/XRS class equivalent) that occurred on 2021 November 17, with a new python package for spectral fitting, sunkit-spex, to compute the parameter posterior distributions and the evidence of different models representing the higher energy emission as due to thermal or non-thermal sources. Calculating the Bayes factor, we show that there is significantly stronger evidence for the higher energy microflare emission to be produced by non-thermal emission from flare-accelerated electrons than by an additional hot thermal source. Qualitative confirmation of this non-thermal source is provided by the lack of hotter (10 MK) emission in Solar Dynamic Observatory’s Atmospheric Imaging Assembly’s extreme ultraviolet data. The nested sampling approach used in this paper has provided clear support for non-thermal emission at the level of 3 × 1024 erg s−1 in this tiny microflare.

Image-Derived Skeletal Muscle Activation Metric Map: a Forearm Study Using Ultra-Fast Ultrasound Imaging and High-Density Electromyography.

Quantification of the skeletal muscle response can help better understand the fundamentals of the musculoskeletal system and can serve as a diagnostic measure or recovery assessment tool during rehabilitation for neurological injuries. Surface electromyography (EMG) is commonly used to measure muscle activity, but it is limited to detecting myoelectric signals without anatomy associated information. In this study, we proposed to use ultra-fast ultrasound imaging and introduced a new image analysis methodology to quantify a muscle's spatialtemporal mechanical response. The methodology is based on analyzing the spatial-temporal change of the impulsive kinetic energy during the period of muscle contraction. The analysis can derive an anatomy-registered muscle activation metric map that localizes regions of muscle activation. To demonstrate this, we intentionally evoked regional muscle responses in five participants without disabilities by electrically stimulating the median nerve and individual forearm muscle groups, respectively. Both ultrasound images and high-density EMG (HD-EMG) data were recorded and processed. We presented the ultrasound image-derived activation localization from five participants and compared the results with HD-EMG measurements. The comparison indicates a good resemblance for describing muscle recruitment pattern. The proposed methodology can potentially become an alternative or complementary approach to surface EMG for the study of skeletal muscle activation and for diagnosis and prognosis in clinical settings.

Dual-power nonlinear energy sink for targeted energy transfer in ultra-wide range of impulsive energy

Recently, the NES with one third power (OTP) nonlinearity was proposed to attenuate micro-vibrations under low-level initial impulsive energy. However, the targeted energy transfer (TET) region for effective vibration mitigation is narrow. This paper develops a new type of NES with dual-power (DP) nonlinearity by combining the third power (TP) nonlinearity and the OTP one in parallel. Firstly, the dynamic behaviors of the DP NES are investigated, and significant vibration mitigation is observed in two discontinuous TET regions that are separately induced by the OTP and TP nonlinearities. Furthermore, the parameter analysis is conducted to find out a feasible avenue to merge such two discontinuous TET regions. It demonstrates that there exist optimal parameters to achieve a wide and continuous TET region. Finally, the design optimization of the DP NES is carried out with the aid of the genetic algorithm, and the optimal parameters enable the DP NES to trigger TET in an ultra-wide and continuous range of initial impulsive energy. Consequently, the proposed DP NES should be an effective solution to substantially broaden the TET region and attenuate vibration in an ultra-wide range of initial impulsive energy.

A maximum cyclic impulses energy ratio deconvolution fused with enhanced envelope derivative operator frequency spectrum for early fault diagnosis of rolling bearing

Blind deconvolution is a powerful tool for rolling bearing fault diagnosis. As one of deconvolution methods, maximum second-order cyclostationarity blind deconvolution (CYCBD) is proved to be effective in extracting bearing fault characteristics. However, the performance of CYCBD method is greatly compromised by setting of fault characteristic frequency (FCF) in advance. Moreover, its performance decreases dramatically under the interference of random shocks and strong noise. To address these issues, a new deconvolution method, named as maximum cyclic impulses energy ratio deconvolution (MCIERD) fused with enhanced envelope derivative operator frequency spectrum (EEDOFS) is proposed in this research. In this method, the EEDOFS is proposed to estimate the FCF. Furthermore, the cyclic impulses energy ratio (CIER) is employed as the deconvolution indicator. Moreover, the hybrid firefly and particle swarm optimization algorithm is used to solve the optimal filter coefficients by maximizing the CIER. Simulation results show that EEDOFS exhibits a greater robustness in estimating FCF accurately under strong interferences and MCIERD performs well in extracting fault cyclic impulses under the interference of heavy noise and random shocks. Finally, three run-to-failure bearing datasets are employed for experimental validation, whose results demonstrate the effectiveness of EEDOFS in accurate estimating FCF and identifying the early bearing fault. Meanwhile, MCIERD fused with EEDOFS is proved to have greater advantages in extracting early bearing fault feature.

The existence of hot X-ray onsets in solar flares

Context. It is well known among the scientific community that solar flare activity often begins well before the main impulsive energy release. However, a consistent explanation for this phenomenon has not yet been established. Aims. Our aim is to investigate the earliest phase of four distinct flares observed by Solar Orbiter/STIX and determine the relationships of the newly heated plasma to flare structure and dynamics. Methods. The analysis focuses on four events that were observed from both Earth and Solar Orbiter, which allows for a comparison of STIX observations with those of GOES/XRS and SDO/AIA. The early phases of the events were studied using STIX and GOES spectroscopic analysis to investigate the evolution of the physical parameters of the plasma, including the isothermal temperature and emission measure. Furthermore, to determine the location of the heated plasma, STIX observations were combined with AIA images. Results. The events with clear emission prior to the impulsive phase show elevated temperatures (> 10 MK) from the very beginning, which indicates that energy release started before any detection by STIX. Although the temperature shows little variation during the initial phase, the emission measure increases by about two orders of magnitude, implying a series of incrementally greater energy releases. The spectral analysis of STIX and GOES from the very first time bins suggests that the emission has a multi-thermal nature, with a hot component of more than 10 MK. Alternative heating mechanisms may be more significant during this phase, since nonthermal emission, as observed by STIX, is only detected later. STIX and AIA images reveal the presence of more compact sources of hot plasma early in the flare that originate from different locations with respect to the standard loop-top source that is observed later in the flare. However, because extended bremsstrahlung sources are much more difficult to detect than compact sources, there might be additionally heated plasma in the loop-top during hot onsets. Conclusions. This analysis confirms the existence of “hot onsets”, with STIX detecting the hot onset pattern even earlier than GOES. These elevated temperatures imply that energy release actually begins well before any detection by STIX. Therefore, hot onsets may be significant in the initiation, early development, or even prediction of solar flares.

A life prediction method of rolling bearing based on signal reconstruction and fusion dual channel network

In addressing the problem of low prediction accuracy in the remaining useful life (RUL) prediction of rolling bearings, caused by noise interference and insufficient extraction of sensitive features by deep learning models, this paper presents a life prediction method based on signal reconstruction and dual-channel network fusion. First, addressing the issue of extracting weak features from rolling bearing vibration signals, an optimized combination of variational mode decomposition (VMD) and Teager–Kaiser energy operator (TKEO) for signal reconstruction is proposed. TKEO is used to track the energy of high-frequency impulses in the original signal. The sparrow search algorithm is employed for optimizing VMD to perform high-frequency filtering, resulting in an optimized impulse energy signal. This signal is then multiplied with the original signal to enhance weak impulse features under noisy background. Next, a dual-channel network model for RUL prediction is constructed based on temporal convolutional network (TCN) and convolutional neural networks (CNNs). The one-dimensional time-series signal obtained after reconstruction and denoising serves as the input for the TCN network channel. Simultaneously, the signal obtained after reconstruction and denoising undergoes synchrosqueezed wavelet transforms to generate a two-dimensional time–frequency representation as input for the CNN network channel. This setup allows TCN and CNN to respectively extract temporal features from the vibration signal and time–frequency features from the spectrogram. By incorporating self-attention mechanisms, internal correlations between different features are fully explored, thereby enhancing prediction accuracy.

Morphological evidence for nanoflares heating warm loops in the solar corona

Context. Nanoflares are impulsive energy releases that occur due to magnetic reconnection in the braided coronal magnetic field, which is a potential mechanism for heating the corona. However, there are still sporadic observations of the interchange of braiding structure segments and footpoints inside coronal loops, which is predicted to be the morphological evolution of the reconnecting magnetic bundles in the nanoflare picture. Aims. This work aims to detect the evolutions of the pairs of braiding strands within the apparent single coronal loops observed in Atmospheric Imaging Assembly (AIA) images. Methods. The loop strands were detected on two kinds of upsampled AIA 193 Å images, which were obtained by upscaling the point spread function matched AIA images via bicubic interpolation and were generated using a super-resolution convolutional neural network. The architecture of the network is designed to map the AIA images to unprecedentedly high spatial resolution coronal images taken by the High-resolution Coronal Imager (Hi-C) during its brief flight. Results. At times, pairs of separate strands that appear braided together later evolved into pairs of almost parallel strands with completely exchanged parts. These evolutions offer morphological evidence that magnetic reconnections between the braiding strands have taken place, which is further supported by the appearance of transient hot emissions containing significant high-temperature components (T > 5 MK) at the footpoints of the braiding structures. Conlusions. The brief appearances of the two rearranging strands support the idea that magnetic reconnections have occurred within what appears to be a single AIA loop.

Sea ice mechanical property inference using cryophones and coherent signals

Mechanical properties of Arctic sea ice can be inferred by observation of the speeds of compressional, shear and flexural waves generated through in-ice conversion of impulsive energy. In prior work, the impulsive signal was generated by a lead ball or sledge hammer dropped onto the top of the sea ice, and the inversion process required meticulous, manual extraction of signal amplitudes. The work presented here makes use of (a) coherent sources with which broadband signals can be generated to replace the manually generated hammer-drop signals and improve accuracy via matched filter, as well as (b) recent observations and modeling of ice sheet compressional resonances from which ice thickness can be more easily inferred. Analysis and modeling of observations from a recent field experiment in the Beaufort Sea are shown that demonstrate the potential capability of remote monitoring of sea ice mechanical properties.

Fundamentals of impulsive energy release in the corona

Fundamentals of impulsive energy release in the corona

Dynamic study through numerical simulations of MacPherson suspension and static analysis of shock absorber components

A suspension or shock absorber system is a mechanical device that is designed to attenuate or reduce the shock impulse and kinetic energy due to level differences or obstacles encountered by the car. In a vehicle structure, the shock absorber reduces the effect of driving on rough terrain, which automatically leads to improved driving quality and also increases passenger comfort.The purpose of this dynamic study by numerical simulations of the MacPherson strut suspension is to highlight the dynamic differences between the stock and heavy MacPherson suspension duty for the Volkswagen Jetta, because it is the most common type of suspension on vehicles, and it is not complex in terms of operation.The study was carried out only at the simulation stage in the MSC ADAMS program, for the dynamic analysis of the component parts, later the second phase of the research will propose the study on a real system.One of the specific objectives of the paper is to compare the two types of springs, the stock with which the car is equipped at the factory and the modified one, the heavy duty variant (package heavy roads).The second specific objective is to compare the two types of springs in relation to the two heights of the speed limiter and the two types of tires.The third objective of this paper is to perform a comparative analysis of the main components of a shock absorber assembly, statically through tests in the ABAQUS simulation program.Later, the results obtained after the analyzes indicated that the heavy duty type suspension has a higher degree of force attenuation. The end of the study was focused on the finite element analysis of the main components of a shock absorber in a suspension, analyzed from a static point of view.

Decomposition and spectrum analysis of surge impact pressures on a vertical wall based on the Hilbert–Huang transform

In this study, two individual dam-break induced surge impact pressure datasets are analyzed using the Hilbert–Huang transform method, which is capable of adaptively decomposing the impulsive, oscillatory, and quasi-steady pressure components from the measured raw pressure data. Time-frequency characteristics of these three pressure components are analyzed. Applying the empirical mode decomposition method, the intrinsic mode function (IMF) series extract the local periodic features, including the impulsive and oscillatory pressures, whereas the non-periodic residual series reveal the general variation characteristics of the surge impact pressure, i.e., the quasi-steady pressure. Subsequently, the Hilbert spectrum analysis is conducted to the individual IMF series. The impulsive pressure components are found to be high-frequency (over 5 Hz in this study), and the oscillatory pressure components have frequency ranging from 20 to 60 Hz. It is confirmed that the quasi-steady pressure contributes the dominant amount of the total surge impact energy in both the bottom impact zone and the upper outer zone on the wall. The impulsive pressure-induced instantaneous energy is large in the bottom impact zone shortly after the impact, whereas the oscillatory pressures only lead to a small local instantaneous energy peak. In addition, the impulsive pressure impulses are calculated, which are more test-stable than those of peak pressures. These findings indicate that impulsive pressures induced by surge impact can be rather destructive, especially near the toe of the structure, thus deserve particular attention in the safe design of coastal structures.

The Trickster: A Political Theology for Our Time

Political theology has traditionally been dominated by Christian concepts, specifically the concept of a law-giving and order-preserving god. Other political theologies are possible, however, and this essay considers one—the trickster—a culture hero and comic buffoon who delightedly and shamelessly violates and subverts order to inaugurate a new reality of his own making, if not of his own will. The first half of the essay introduces the trickster as a cross-cultural agent of creative destruction, a messenger and civilization-bringer, and a clever fool. The second half explores how the last two centuries of Western social and intellectual history have shifted the ground from under a god of order toward a spirit of flux, transience, paradox, and liminality. The essay concludes that the contemporary post-modern state of permanent liminality is better symbolized and grasped through the mythical lens of the trickster than the biblical god, including and especially contemporary global right-wing populism, whose leading figures reflect the wicked energy and appeal of the trickster impulse.

A comparative study on the characteristics of nanosecond laser ablation zinc and acrylonitrile butadiene styrene targets

In this study, the influence of laser energy and pressure on propulsion performance of zinc and acrylonitrile butadiene styrene (ABS) is investigated by impulse measurement, fast exposure images, spectral diagnostics and target ablation. A Q-switched Nd:YAG laser with the wavelength of 1064 nm and pulse width of 6 ns is employed. The impulse and coupling coefficient generated by laser ablation ABS are greater than that of Zn, and they exhibit a similar variation trend with pressure. However, at higher pressure levels, the change in impulse versus laser energy is not completely coincident between Zn and ABS samples. The target property plays a significant role in the generation and propagation of plume related to the plasma parameters such as electron density and temperature. The temporal evolution images indicate that the plasma plume of laser-induced Zn presents a faster decay in comparison with that of ABS, which is ascribed to the fact that the gas temperature of ABS is higher than the electron temperature of Zn plasma in the local thermodynamical equilibrium. Also, the electron density is lower for Zn due to the rapid heat diffusion and higher ablation threshold of metal. It is found that the surface absorption is dominant for metal because the ablated crater of Zn performs larger diameter and shallower depth. On the contrary, the shrinkage in diameter but enhancement in depth of crater is observed from ABS surface, and the ablation mass is larger, suggesting the obvious volume absorption for polymer. The results reveal that the target property can engender an important effect on the energy conversion between laser, target and plasma.

Volumetric measurements of wake impulse and kinetic energy for evaluating swimming performance

Volumetric flow measurements are a valuable tool for studies of aquatic locomotion. In addition to visualizing complex propulsive behaviors (e.g., highly three-dimensional kinematics or multi-propulsor interactions), volumetric wake measurements can enable direct calculation of metrics for locomotive performance including the hydrodynamic impulse and wake kinetic energy. These metrics are commonly used in PIV and PTV studies of swimming organisms, but derivations from planar data often rely on simplifying assumptions about the wake (e.g., geometry, orientation, or interactions). This study characterizes errors in deriving wake impulse and kinetic energy directly from volumetric data in relation to experimental parameters including the level of noise, the flow feature resolution, processing parameters, and the calculation domain. We consider three vortex ring-like test cases: a synthetic spherical vortex with exact solutions for its impulse and energy, volumetric PIV measurements of a turbulent vortex ring, and volumetric PIV measurements of a turning fish. We find that direct calculations of hydrodynamic impulse are robust when derived from a volumetric experiment. We also show that kinetic energy estimates are feasible at experiment resolutions, but are more sensitive to experiment design and processing parameters, which may limit efficiency estimates or comparisons between studies or organisms.Graphical abstract