Energy Injection Research Articles

Study on Evolution of Surface Morphology and Temperature of Carbon Fiber Composites Irradiated by Millisecond Pulsed Laser

The study of the interaction between laser and composite materials has attracted the attention of many researchers. In this paper, the surface morphology and temperature evolution of T300 carbon fiber composites irradiated by millisecond pulse laser were studied and analyzed experimentally. The transient morphology change process of the front surface of the material was observed by a camera. With the injection of pulsed laser energy, the material began to change its characteristics from the center, leading to a decrease in reflectivity of it, and this area expanded with the accumulation of laser energy. The temperature change on the back of the material was observed by a thermal imager. Within a certain range and the same laser irradiation time, the greater the injected energy per unit area, the faster the temperature of the back center rises. However, under the same circumstances as above, the highest center temperature of the back of the composites is only related to the total energy injected, and has nothing to do with the spot size.

VERITAS and Fermi-LAT Constraints on the Gamma-Ray Emission from Superluminous Supernovae SN2015bn and SN2017egm

Superluminous supernovae (SLSNe) are a rare class of stellar explosions with luminosities ∼ 10–100 times greater than ordinary core-collapse supernovae. One popular model to explain the enhanced optical output of hydrogen-poor (Type I) SLSNe invokes energy injection from a rapidly spinning magnetar. A prediction in this case is that high-energy gamma-rays, generated in the wind nebula of the magnetar, could escape through the expanding supernova ejecta at late times (months or more after optical peak). This paper presents a search for gamma-ray emission in the broad energy band from 100 MeV to 30 TeV from two Type I SLSNe, SN2015bn, and SN2017egm, using observations from Fermi-LAT and VERITAS. Although no gamma-ray emission was detected from either source, the derived upper limits approach the putative magnetar’s spin-down luminosity. Prospects are explored for detecting very-high-energy (VHE; 100 GeV–100 TeV) emission from SLSNe-I with existing and planned facilities such as VERITAS and CTA.

Analysis of Energy Losses in the Novel Distributed Power Supply System for Trams

The traction substation in conventional power supply systems for trams is a bottleneck of the system. It requires the connection with medium-voltage grid, demands high values of instant power and its centralized topology generates additional energy losses. Since the availability of low-power photovoltaic (PV) generation is increasing in the utility system, we propose to replace conventional substations with a distributed system of low-power devices cooperating with low-voltage grid and PV installations owned by individual households. The proposed in this article distributed power supply system for trams (DPSS-T) consists of multiple traction aggregators (TAs) equipped with energy storage devices (ESDs) which are distributed along the tram line. In order to evaluate the benefits of applying DPSS-T this proposed system was compared with the conventional topology regarding the energy losses in terms of annual operation. Moreover, the following aspects have been studied for the wide range EDS sizes and PV generation: PV energy injection into the power utility system, the utilization of installed ESD, and the contribution of PV generation in energy consumed by traction vehicles. At the same time, the energy management for this new topology has been proposed. The ESDs are charged with relatively low power, between tram runs and discharged with full power during the runs. The suggested energy management eliminates peaks in substation power demand. The obtained results show that despite the fact that the proposed DPSS-T is supplied from low-voltage grid the energy losses are reduced by 58%–69%.

Study of the excess Fe XXV line emission in the central degrees of the Galactic centre usingXMM-Newtondata

The diffuse Fe XXV (6.7 keV) line emission observed in the Galactic ridge is widely accepted to be produced by a superposition of a large number of unresolved X-ray point sources. In the very central degrees of our Galaxy, however, the existence of an extremely hot (~7 keV) diffuse plasma is still under debate. In this work we measure the Fe XXV line emission using all availableXMM-Newtonobservations of the Galactic centre (GC) and inner disc (−10° <ℓ< 10°, −2° <b< 2°). We use recent stellar mass distribution models to estimate the amount of X-ray emission originating from unresolved point sources, and find that within a region ofℓ= ±1° andb= ±0.25° the 6.7keV emission is 1.3–1.5 times in excess of what is expected from unresolved point sources. The excess emission is enhanced towards regions where known supernova remnants are located, suggesting that at least a part of this emission is due to genuine diffuse very hot plasma. If the entire excess is due to very hot plasma, an energy injection rate of at least ~6 × 1040erg s−1is required, which cannot be provided by the measured supernova explosion rate or past Sgr A*activity alone. However, we find that almost the entire excess we observe can be explained by assuming GC stellar populations with iron abundances ~1.9 times higher than those in the bar/bulge, a value that can be reproduced by fitting diffuse X-ray spectra from the corresponding regions. Even in this case, a leftover X-ray excess is concentrated withinℓ= ±0.3° andb= ±0.15°, corresponding to a thermal energy of ~2 × 1052erg, which can be reproduced by the estimated supernova explosion rate in the GC. Finally we discuss a possible connection to the observed GCFermi-LAT excess.

Relaxing CMB bounds on primordial black holes: The role of ionization fronts

The accretion of matter onto primordial black holes (PBHs) during the dark ages and the subsequent energy injection in the medium should have left imprints on the cosmic microwave background (CMB) anisotropies. Recent works have claimed stringent CMB limits on the PBH abundance, hardly compatible with a PBH interpretation of the gravitational-wave observations of binary BH mergers. By using a more realistic accretion model based on hydrodynamical simulations and conservative assumptions for the emission efficiency, we show that CMB limits on the PBH abundance are up to two orders of magnitude less stringent than previously estimated between $10$ and $10^4$ M$_\odot$. This reopens the possibility that PBHs might explain at the same time (at least a fraction of) the dark matter, some of the LIGO-Virgo-KAGRA binary BH mergers and the existence of super-massive BHs. More generally, we emphasize that PBH accretion can be a rather complex physical process with velocity dependences that are hard to assess, which introduces large uncertainties in accretion-based limits on the PBH abundance.

Occurrence of gradual resonance in a finite-length granular chain driven by harmonic vibration

This study presents numerical simulations of the resonance of a finite-length granular chain of dissipative grains driven by a harmonically vibrated tube. Multiple gradual resonant modes, namely non-resonance mode, partial-resonance mode, and complete-resonance mode, are identified. With a fixed vibration frequency, increasing vibration acceleration leads to a one-one-one increase in the number of grains participating in resonance, which is equal to the number of grain-wall collisions in a vibration period. Compared with the characteristic time of the grain–grain and the grain–wall collisions, the time of free flight plays a dominant role in grain motion. This situation results in the occurrence of large opening separation gaps between the grains and independent grain–grain and grain–wall collisions. A general master equation that describes the dependence of the system energy on the length of the granular chain and the number of grain–wall collisions is established, and it is in good agreement with the simulation results. We observe a gradual step-jump increase in system energy when the vibration acceleration is continuously increased, which is dedicated to an individual energy injection. The phase diagrams in the spaces of packing density and vibration acceleration, chain length and vibration acceleration show that shorter granular chain and larger packing density favor the occurrence of complete-resonance mode.

Energy encoding in a biophysical neuron and adaptive energy balance under field coupling

Some nonlinear circuits can present similar dynamical properties in the outputs as biological neurons by taming the external stimulus and bifurcation parameter, and they can be used for further investigation on neural activities. In this work, a photoelectric converter such as phototube is incorporated into the Fitzhugh-Nagumo neural circuit and a light-sensitive neuron is obtained to describe the nonlinear response in visual neuron. Furthermore, an additive induction coil is also connected to the phototube in this branch circuit of this neural circuit for detecting the disturbance from external magnetic field, and this functional neuron can perceive external illumination and changes of external magnetic field synchronously. Scale transformation is applied for the circuit equation and equivalent photoelectric neuron model is obtained. The intrinsic field energy of the neural circuit is described by equivalent Hamilton energy and the dependence firing modes on energy is clarified. When neurons are clustered closely, energy diversity can trigger field coupling and the synaptic connection will be regulated in the coupling intensity adaptively. An artificial hybrid is developed by combining capacitor and inductor in the coupling channel, and synchronization approach and energy balance is controlled completely. These results provide potential explanation for knowing the growth mechanism for synapse connection and external energy injection can be effective to control the collective behaviors of neurons.

Spherical symmetry in the kilonova AT2017gfo/GW170817.

The mergers of neutron stars expel a heavy-element enriched fireball that can be observed as a kilonova1-4. The kilonova's geometry is a key diagnostic of the merger and is dictated by the properties of ultra-dense matter and the energetics of the collapse to a black hole. Current hydrodynamical merger models typically show aspherical ejecta5-7. Previously, Sr+ was identified in the spectrum8 of the only well-studied kilonova9-11 AT2017gfo12, associated with the gravitational wave event GW170817. Here we combine the strong Sr+ P Cygni absorption-emission spectral feature and the blackbody nature of kilonova spectrum to determine that the kilonova is highly spherical at early epochs. Line shape analysis combined with the known inclination angle of the source13 also show the same sphericity independently. We conclude that energy injection by radioactive decay is insufficient to make the ejecta spherical. A magnetar wind or jet from the black-hole disk could inject enough energy to induce a more spherical distribution in the overall ejecta; however, an additional process seems necessary to make the element distribution uniform.

Effects of fuel injection strategy and ammonia energy ratio on combustion and emissions of ammonia-diesel dual-fuel engine

As the greenhouse effect continues to intensify, ammonia, a carbon-free fuel, is gradually gaining attention. The ammonia-diesel dual-fuel (ADDF) engine can effectively overcome the disadvantages of high auto-ignition temperature and slow flame speed of ammonia, which is an effective way to reduce greenhouse gas (GHG). Aiming at achieving high thermal efficiency and low emissions of ADDF engine, the effects of ammonia energy ratio (AER) and injection strategy on combustion and emission characteristics were studied by combining experimental and simulation results. It was found that as the AER increased from 0 % to 90 %, the gross indicated thermal efficiency (ITEg) decreased continuously. Due to the slow flame speed of ammonia and the inhibition of the dehydrogenation process during the low temperature reaction of diesel, the emission of unburned ammonia increased significantly, reaching 31 g/kwh under the condition of 50 % AER. Improving the combustion efficiency of ammonia and reducing the emission of unburned ammonia were the keys to improving the ITEg of ADDF engine. Amino groups have a denitrification effect, and nitric oxide (NO) can be reduced to more stable nitrogen (N2). Therefore, NO emissions decreased when the AER increased. The production and consumption of nitrous oxide (N2O) were influenced by temperature, and its production region was mainly the low temperature region where the reaction of ammonia occurred, while N2O was reduced to N2 at high temperature conditions. As the AER increased, the deterioration of N2O emissions was not conducive to reducing GHG. The double injection strategy can significantly improve the activity of the mixture, accelerate combustion, reduce unburned ammonia emissions and incomplete combustion losses. By optimizing the injection strategy and regulating the combustion process, an ITEg of 49.18 % can be achieved when the AER was 50 %, and GHG can be reduced by 14.2 %.

The Closure Relations in High-Energy Gamma-ray Bursts Detected by Fermi-LAT

Gamma-ray bursts (GRBs) are brief, intense pulses of high-energy emission associated with extreme astrophysical phenomena, e.g. the death of massive stars or the coalescence of compact objects. They have been observed at high energies by the Fermi Large Area Telescope (LAT), which detects GRBs in the 20 MeV–300 GeV energy range. The Fermi-LAT Second GRB Catalog (2FLGC) presents information on 186 GRBs observed from 2008 to 2018. We consider the GRBs that have been fitted in the 2FLGC with a broken (21 GRBs) or simple power law (65 GRBs), compiling a total sample of 86 GRBs. We analyze the relationship between the spectral and temporal indices using closure relations according to the synchrotron forward-shock model evolving in stratified environments (n∝r−k). We find that the model without energy injection is preferred over the one with energy injection. There is a clear preference for the cooling conditions ν> max{νc,νm} and νm<ν<νc (where νc and νm are the cooling and characteristic frequencies, namely the frequency at the spectral break). Within these cooling conditions, density profiles r−k with values of k=1.5 and 2 generally have a higher rate of occurrence when considering relations with and without energy injection.

Low-frequency Gravitational-wave Memories from Gamma-Ray Burst Afterglows with Energy Injections

Ultrarelativistic gamma-ray burst (GRB) jets are strong gravitational-wave (GW) sources with memory-type signals. The plateau (or shallow decay) phases driven by the energy injection may appear in the early X-ray afterglows of GRBs. In this paper, we investigate GW signals as well as X-ray afterglow emissions in the framework of GRB jets with energy injections, and both short- and long-duration GRBs are considered. We find that, regardless of the case, and because of the antibeaming and time delay effects, a rising slope that emerges in the waveform of the GW signal, due to the energy injection, lags far behind the energy ejection, and the typical frequencies of the characteristic amplitudes fall within a low-frequency region of ∼10−4–10−6 Hz; we also consider that the GW memories triggered by the GRB jets with energy injection have previously not been accounted for and that nearby GRBs with strong energy injections may disturb the measurement of the stochastic GW background. Such GW memory detection would provide a direct test for models of energy injection in the scenario of GRB jets.

Discovery of a New Molecular Bubble–Outflow Structure in the Taurus B18 Cloud

Star formation can produce bubbles and outflows, as a result of stellar feedback. Outflows and bubbles inject momentum and energy into the surrounding interstellar medium, and so are related to the overall energy balance of the molecular cloud. Molecular bubbles can be resolved by higher-resolution radio telescopes to quantify the effect of star formation on molecular clouds. We report here the identification of a new molecular bubble with an outflow, and a Herbig–Haro object, HH 319, located at the bubble center. Multiwavelength data have been utilized to study its spatial structure, energy injection, and dynamical timescale. This bubble has a kinetic energy of 5.8 × 1043 erg within the smallest radius of a bubble in Taurus, 0.077 pc. The bubble formed ∼70,000 yr ago. According to the proper-motion velocities of protostars from Gaia EDR3, the T Tauri binary stars (FY Tau and FZ Tau) at the southwest edge of the bubble may have produced the outflow–bubble structure. This is an unusual new structure found in low- and intermediate-mass star formation regions. Only a bubble in Orion A, driven by V380 Ori, has a similar structure. The bubble–outflow structure provides additional observational evidence for the theory of stellar wind from T Tauri stars. It enhances our understanding of how stellar feedback acts on molecular clouds.

Demonstration of an Ultracompact, High-Isolation Power Coupler for W-Band Sheet Beam Traveling Wave Tubes

The emerging sheet beam devices have become a research hotspot in the field of vacuum electronics due to their excellent performance in the millimeter-wave and even terahertz bands, but there are still many technical bottlenecks in the actual manufacture and the engineering realization. In this article, an ultracompact high-isolation power coupler prototype is demonstrated for high-efficiency injection and extraction of electromagnetic energy from the sheet beam traveling wave tubes (SB-TWTs). The introduction of polarized rotators avoids the coupling of electromagnetic waves into the electron channel, thereby improving isolation performance. The improved structure with multiparameter tunability ensures low reflection and broadband characteristics. The simulation shows that its extreme bandwidth (BW) is 40% and the in-band isolation is less than −50 dB. Moreover, the parasitic resonance mode is analyzed and related suppression technology is also proposed. Then, two prototypes of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band coupler have been processed and tested. The related machining errors have been analyzed and a good consistency is verified between the experiment and the simulation. Compared with the best level of the existing coupler, this ultracompact structure with less than one free-space wavelength (calculated from the central frequency point) relieves the pressure of the sheet beam transmission system, reduces the risk of electronic interception, and provides a feasible solution for engineering realization of sub-millimeter-wave or terahertz SB-TWTs.

A memristive neuron and its adaptability to external electric field.

Connecting memristors into any neural circuit can enhance its potential controllability under external physical stimuli. Memristive current along a magnetic flux-controlled memristor can estimate the effect of electromagnetic induction on neural circuits and neurons. Here, a charge-controlled memristor is incorporated into one branch circuit of a simple neural circuit to estimate the effect of an external electric field. The field energy kept in each electric component is respectively calculated, and equivalent dimensionless energy function H is obtained to discern the firing mode dependence on the energy from capacitive, inductive, and memristive channels. The electric field energy HM in a memristive channel occupies the highest proportion of Hamilton energy H, and neurons can present chaotic/periodic firing modes because of large energy injection from an external electric field, while bursting and spiking behaviors emerge when magnetic field energy HL holds maximal proportion of Hamilton energy H. The memristive current is modified to control the firing modes in this memristive neuron accompanying with a parameter shift and shape deformation resulting from energy accommodation in the memristive channel. In the presence of noisy disturbance from an external electric field, stochastic resonance is induced in the memristive neuron. Exposed to stronger electromagnetic field, the memristive component can absorb more energy and behave as a signal source for energy shunting, and negative Hamilton energy is obtained for this neuron. The new memristive neuron model can address the main physical properties of biophysical neurons, and it can further be used to explore the collective behaviors and self-organization in networks under energy flow and noisy disturbance.

Self-similar solutions in cylindrical magneto-hydrodynamic blast waves with energy injection at the centre

ABSTRACT The evolution of shocks induced by massive stars does not depend only on the ambient magnetic field strength, but also on its orientation. In the present work, the dynamics of a magnetized blast wave is investigated under the influence of both azimuthal and axial ambient magnetic fields. The blast wave is driven by a central source and forms a shell that results from the accumulation of interstellar matter behind the shock front. A similarity form of the ambient magnetic field and a cylindrical geometry of the blast wave are assumed to obtain self-similar solutions. The model is studied separately for both azimuthal and axial magnetic field and applied to stellar wind bubbles and supernova remnants respectively, using 1D numerical simulations. We found that the magnetized blast wave differs from the self-similar case without an ambient magnetic field. The forward shock front goes slower in the azimuthal case and faster in the axial one. For both tangential orientations, the thickness of the shell increases with the magnetic strength. In the azimuthal case, the thermal energy can be converted to magnetic energy near the inner boundary of the shell. Thus, the temperature drops and the magnetic field increases at the tangential discontinuity of the stellar wind bubble. In the axial case of a supernova remnant, the numerical solution always follows a special curve in the parameter space given by the self-similar model.

Disc-halo gas outflows driven by stellar clusters as seen in multiwavelength tracers

ABSTRACT We consider the dynamics of and emission from growing superbubbles in a stratified interstellar gaseous disc driven by energy release from supernovae explosions in stellar clusters with masses Mcl = 105 − 1.6 × 106 M⊙. Supernovae are spread randomly within a sphere of rc = 60 pc, and inject energy episodically with a specific rate $1/130~\mathrm{M}_\odot ^{-1}$ proportional to the star formation rate (SFR) in the cluster. Models are run for several values of SFR in the range 0.01 to 0.1 M⊙ yr−1, with the corresponding average surface energy input rate ∼0.04–0.4 erg cm−2 s−1. We find that the discrete energy injection by isolated SNe are more efficient in blowing superbubbles: Asymptotically they reach heights of up to 3 to 16 kpc for Mcl = 105 − 1.6 × 105 M⊙, correspondingly, and stay filled with a hot and dilute plasma for at least 30 Myr. During this time, they emit X-ray, Hα and dust infrared emission. X-ray luminosities LX∝SFR3/5 that we derive here are consistent with observations in star-forming galaxies. Even though dust particles of small sizes a ≤ 0.03 μm are sputtered in the interior of bubbles, larger grains still contribute considerably ensuring the bubble luminosity $L_{\rm IR}/{\rm SFR}\sim 5\times 10^7 \, \mathrm{L}_\odot \, \mathrm{M}_\odot ^{-1} ~{\rm yr}$. It is shown that the origin of the North Polar Spur in the Milky Way can be connected with activity of a cluster with the stellar mass of ∼105 M⊙ and the SFR ∼ 0.1 M⊙ yr−1 some 25–30 Myr ago. Extended luminous haloes observed in edge-on galaxies (NGC 891 as an example) can be maintained by disc spread stellar clusters of smaller masses M* ≲ 105 M⊙.

A Global Inventory of Feedback

Feedback from both supermassive black holes and massive stars plays a fundamental role in the evolution of galaxies and the inter-galactic medium. In this paper, we use available data to estimate the total amount of kinetic energy and momentum created per co-moving volume element over the history of the universe from three sources: massive stars and supernovae, radiation pressure and winds driven by supermassive black holes, and radio jets driven by supermassive black holes. Kinetic energy and momentum injection from jets peaks at z ≈ 1, while the other two sources peak at z ≈ 2. Massive stars are the dominant global source of momentum injection. For supermassive black holes, we find that the amount of kinetic energy from jets is about an order-of-magnitude larger than that from winds. We also find that the amount of kinetic energy created by massive stars is about 2.5 εstar times that carried by jets (where εstar is the fraction of injected energy not lost to radiative cooling). We discuss the implications of these results for the evolution of galaxies and IGM. Because the ratio of the black hole mass to galaxy mass is a steeply increasing function of mass, we show that the relative importance of black hole feedback to stellar feedback likewise increases with mass. We show that there is a trend in the present-day universe which, in the simplest picture, is consistent with galaxies that have been dominated by black hole feedback being generally quenched, while galaxies that have been dominated by stellar feedback are star-forming. We also note that the amount of kinetic energy carried by jets and winds appears to be sufficient to explain the properties of hot gas in massive halos (&gt;1013 Mʘ).

Maximizing frequency security margin via conventional generation dispatch and battery energy injection

To quantitatively evaluate the frequency stability margin during primary frequency control period following an under-frequency event, this paper presents a dynamic frequency response constrained optimal power flow (OPF) model. In this model, frequency security margin is defined and maximized by adjusting pre-disturbance generation outputs of conventional units and injections of battery energy storage system (BESS) immediately after a disturbance. Two nonlinear characteristics in speed-governing systems are considered and described as smooth and differentiable formulations to facilitate their incorporations into the proposed optimization model. A graphical tool is also provided to enable region-wise frequency security assessment based on the obtained maximum frequency security margin. Simulation results on WSCC 3-machine 9-bus system and New England 10-machine 39-bus system validate the suggested margin metric and the effectiveness of the proposed method.

Creation of heterogeneity or defects in a memristive neural network under energy flow

The field energy in neuron can be changed under shape deformation because of external energy injection into the media. The electromagnetic field superposition enables energy pumping when neurons in the same region are stimulated, and synaptic connection can be created adaptively for keeping local energy balance. All neurons will keep energy balance with the adjacent neurons in the network by continuous energy propagation and exchange, and identical neurons will develop a homogeneous state while non-identical neurons will support formation of gradient spatial patterns. In this paper, the simple Fitzhugh–Nagumo (FHN) neural circuit is improved by incorporating a thermistor and a phototube in different branch circuits synchronously, and this neuron becomes sensitive to light and temperature. The Hamilton energy for this functional neuron is obtained to discern the dependence of firing modes on the energy level. These functional neurons are clustered to build a regular network via memristive synapses, and the creation and growth of memristive synapse can be controlled by energy diversity between adjacent neurons. It is found that heterogeneity in the network can be formed when more energy is accumulated locally, while the occurrence of local defects results from energy release and lower energy in a local area. As a result, shape deformation occurs and some parameters for the neurons covered with heterogeneity or defects show certain changes with time. The collective behaviors of the network are investigated by calculating the membrane potentials for neurons, Hamilton energy, coupling intensity and synchronization factor. The results indicate that energy diversity between neurons controls the occurrence of heterogeneity and defects in the network and local energy injection can control the firing patterns of network because the wave propagation can be regulated by the heterogeneity and defects.

Probabilistic power flow calculation using principal component analysis-based compressive sensing

The increasing scale of the injection of renewable energy has brought about great uncertainty to the operation of power grid. In this situation, probabilistic power flow (PPF) calculation has been introduced to mitigate the low accuracy of traditional deterministic power flow calculation in describing the operation status and power flow distribution of power systems. Polynomial chaotic expansion (PCE) method has become popular in PPF analysis due to its high efficiency and accuracy, and sparse PCE has increased its capability of tackling the issue of dimension disaster. In this paper, we propose a principal component analysis-based compressive sensing (PCA-CS) algorithm solve the PPF problem. The l1-optimization of CS is used to tackle the dimension disaster of sparse PCE, and PCA is included to further increase the sparsity of expansion coefficient matrix. Theoretical and numerical simulation results show that the proposed method can effectively improve the efficiency of PPF calculation in the case of random inputs with higher dimensions.