Initial Thermal Energy Research Articles

Chemoexcited Formation and Radiationless Decay Dynamics of Firefly Chromophore.

Multistate nonadiabatic dynamics combined with Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory (MRSF-TDDFT) were performed to investigate the chemoexcitation dynamics of firefly dioxetanone (FDO- in S0) to oxyluciferin (OxyLH- in S1) and its subsequent decay dynamics. The formation of oxyluciferin occurs within approximately 100 fs and is primarily controlled by oscillatory CO2 decarboxylation. Unexpected radiationless decay from oxyluciferin was also observed, facilitated by intramolecular rotation. Simulations under three thermal conditions reveal that higher initial thermal energy not only enhances the formation of oxyluciferin but also increases radiationless decay by surpassing barriers to the ground state. Conversely, lower thermal energy conditions reduce oxyluciferin formation but suppress radiationless decay. These findings suggest that optimal conditions for higher chemiluminescence quantum yield involve initial high thermal energy to accelerate CO2 decarboxylation and gradual thermal dissipation to prevent intramolecular rotation of oxyluciferin. This approach could enhance the chemiluminescence quantum yield beyond the current limit of 40%, offering significant potential for applications in biological imaging and analytical chemistry.

Numerical Research on the Effect of the Initial Parameters of CME Flux-rope Model on Simulation Results. III. Different Initial Energy of CMEs

In numerical studies, the initial parameters of coronal mass ejections (CMEs) have great influence on the simulation results. In our previous work, it has been proved that when the initial velocity is constant, the initial total mass mainly determines the propagation of the CME. On this basis, we carry out further research from the perspective of CME initial energy. We introduced a graduated cylindrical shell model into a 3D interplanetary total variation diminishing magnetohydrodynamic model to study the effect of different parameters of CMEs on simulation results. In this paper, we simulate several CME cases with different initial parameters and study the simulation results with a different initial energy composition. Actually, in interplanetary space, the kinetic energy of the CME always plays a dominant role. In order to study the effect of the initial thermal energy and magnetic energy on the propagation process of the CME, in this simulation, we adjust the initial parameters to make the thermal energy and magnetic energy reach the same level as the kinetic energy or an even higher level. Our results show that the initial total energy of the CME basically determines its arrival time at Earth, which indicates that the kinetic energy, thermal energy, and magnetic energy have similar effects on the propagation of the CMEs. Moreover, when the total energy keeps constant, the decrease of initial density will lead to the enhancement of CME expansion, which may make the front of the CME reach Earth earlier.

Light-curve Model for Luminous Red Novae and Inferences about the Ejecta of Stellar Mergers

The process of unstable mass transfer in a stellar binary can result in either a complete merger of the stars or successful removal of the donor envelope leaving a surviving more compact binary. Luminous red novae (LRNe) are the class of optical transients believed to accompany such merger/common envelope events. Past works typically model LRNe using analytic formulae for supernova light curves that make assumptions (e.g., radiation-dominated ejecta, neglect of hydrogen recombination energy) not justified in stellar mergers due to the lower velocities and specific thermal energy of the ejecta. We present a one-dimensional model of LRN light curves that accounts for these effects. Consistent with observations, we find that LRNe typically possess two light-curve peaks, an early phase powered by initial thermal energy of the hot, fastest ejecta layers and a later peak powered by hydrogen recombination from the bulk of the ejecta. We apply our model to a sample of LRNe to infer their ejecta properties (mass, velocity, and launching radius) and compare them to the progenitor donor star properties from pretransient imaging. We define the maximum luminosity achievable for a given donor star in the limit that the entire envelope is ejected, finding that several LRNe violate this limit. Shock interaction between the ejecta and predynamical mass loss may provide an additional luminosity source to alleviate this tension. Our model can also be applied to the merger of planets with stars or stars with compact objects.

Doping hematite with bismuth to enhance its catalytic and oxidizing properties

• Doping Fe 2 O 3 with Bi can significantly enhance its intrinsic reactivity. • The catalytic decomposition mechanism of HMX has been studied. • The ignition delay time is greatly shortened with the increase of Bi amount. • A high ignition performance of Al/Bix-Fe 2 O 3 can be obtained. Bismuth-cation modulated hematite (Bi-Fe 2 O 3 ) was prepared by a one-step hydrothermal method and used as a catalyst for the thermolysis of energetic materials (EMs) and oxidant in an Al-based thermite. The effects of the amount of Bi doped Fe 2 O 3 on the catalytic property and thermite behavior were investigated using differential scanning calorimetry (DSC). Thermogravimetry–infrared spectroscopy-mass spectrometry (TG/IR/MS) was used to study the thermal decomposition gases of cyclotetramethylenetetranitramine (HMX) with or without catalyst. Bi-Fe 2 O 3 was found to reduce the initial thermal decomposition temperature and activation energy of HMX, and change the decomposition mechanism. In addition, the thermite reaction of Al/Bi-Fe 2 O 3 is exothermic and faster than that of undoped Al/Fe 2 O 3 , resulting in more rapid energy release. Al/Bi-Fe 2 O 3 also shows a shorter ignition delay time than Al/Fe 2 O 3 . This study demonstrates Al/Bi-Fe 2 O 3 as an efficient advanced combustion catalyst for solid propellants.

The Expansion of the Dense Plasma of a Mixture of Deuterium and Tritium into the Empty Space in which There is a Magnetic Field

The work is aimed at determining parameters of a deuterium-tritium mixture expanding into a vacuum with an external magnetic field, the output of thermonuclear energy from which compensates or exceeds the initial thermal energy of the plasma. This type of assessment is usually based on the Lawson criterion. In the paper the parameters are determined on the basis of the model of adiabatic expansion into the surrounding homogeneous magnetic field of the plasma ball in the magnetohydrodynamic approximation for some special modes of expansion, providing a self-similar distribution of gas-dynamic quantities. The obtained minimum values of the energy expended for the initial heating of the plasma, providing its equality to the resulting integrated fusion energy, are compared with the known estimates within the framework of inertial confinement fusion.

Electric potential barriers in the magnetic nozzle.

Magnetic nozzles are convergent-divergent applied magnetic fields which are commonly used in electric propulsion, manufacturing, and material processing industries. This paper studies the previously overlooked physics in confining the thermalized ions injected from a near-uniform inlet in the magnetic nozzle. Through fully kinetic planar-3V particle-in-cell (PIC) modeling and simulation, an electric potential barrier is found on the periphery of the nozzle throat, which serves to confine the thermalized ions by the electric force. With the initial thermal energy as driving force and insufficient magnetic confinement, the ions overshoot the most divergent magnetic line, which results in the accumulation of positive space charges around the throat. The accumulated charges would create an ion-confining potential barrier with limited extent. Apart from the finite-electron Larmor radius (FELR) effect, two more factors are put forward to account for the limited extent of the potential barrier: the depletion of ion thermal energy and the short-circuiting effect. The influences of inlet temperature ratio of ions to electrons and magnetic inductive strength B_{0} are quantitively investigated using the PIC code. The results indicate that the potential barrier serves as a medium to transfer the gas dynamic thrust to the magnetic nozzle while providing constrain to the ions, like the solid wall in a de Laval nozzle. In high-B_{0} regime, the finite-ion Larmor radius (FILR) effect becomes dominant rather than the FELR effect in the plasma confinement of magnetic nozzles.

Hot electrons between cold walls

We consider electron cooling in a collisionless plasma slab between two cold and freely emitting walls. Numerical calculations suggest a counterintuitive behavior of this system: the cooling rate slows down and eventually stops, leaving the system with a significant fraction of its initial thermal energy. Analytical treatment within the Vlasov–Poisson model reveals a set of steady-states with a two-component distribution of electrons: the primary electrons trapped within the potential wells and the secondary electrons forming the counterstreaming beams. We show that such steady-states are linearly stable with respect to one-dimensional perturbations. Establishment of a particular steady-state depends on initial conditions.

Dynamic simulations of a honeycomb ceramic thermal energy storage in a solar thermal power plant using air as the heat transfer fluid

Thermal energy storage is a key component for the marketability of solar thermal power plants (STPP). Thermal energy storage in a solar thermal power plant is essential for the system usefulness but has been rarely studied. This paper numerically investigates the heat storage in a honeycomb ceramic thermal energy storage in a solar thermal power plant using air as the heat transfer fluid using a one-dimensional thermal energy storage model in the object-oriented modeling language Modelica. This model can be used to easily study the thermal performance of the thermal energy storage system. The simulation results agree well with experimental data for two honeycomb ceramic materials for various charging and discharging processes. The model is then used to study the influences of the honeycomb geometric parameters on the thermal energy storage and the initial storage material cost. The results show that the total honeycomb ceramic length and the total cross-sectional area have the greatest effect on the initial thermal energy storage material cost.

Particle acceleration in laser-driven magnetic reconnection

Particle acceleration induced by magnetic reconnection is thought to be a promising candidate for producing the nonthermal emissions associated with explosive phenomena such as solar flares, pulsar wind nebulae, and jets from active galactic nuclei. Laboratory experiments can play an important role in the study of the detailed microphysics of magnetic reconnection and the dominant particle acceleration mechanisms. We have used two- and three-dimensional particle-in-cell simulations to study particle acceleration in high Lundquist number reconnection regimes associated with laser-driven plasma experiments. For current experimental conditions, we show that nonthermal electrons can be accelerated to energies more than an order of magnitude larger than the initial thermal energy. The nonthermal electrons gain their energy mainly from the reconnection electric field near the X points, and particle injection into the reconnection layer and escape from the finite system establish a distribution of energies that resembles a power-law spectrum. Energetic electrons can also become trapped inside the plasmoids that form in the current layer and gain additional energy from the electric field arising from the motion of the plasmoid. We compare simulations for finite and infinite periodic systems to demonstrate the importance of particle escape on the shape of the spectrum. Based on our findings, we provide an analytical estimate of the maximum electron energy and threshold condition for observing suprathermal electron acceleration in terms of experimentally tunable parameters. We also discuss experimental signatures, including the angular distribution of the accelerated particles, and construct synthetic detector spectra. These results open the way for novel experimental studies of particle acceleration induced by reconnection.

Time-dependent potential functions to stretch the time distributions of ion pulses ejected from EBIST

Electron beam ion sources and traps (EBIST) produce and trap highly charged atomic ions with an electron beam of high current density. The ions are confined in the radial space-charge potential of the electron beam and a long square-shaped axial electrostatic potential well. An important field of application of EBIST is charge breeding of highly charged ions at radioactive ion beam facilities. There, highly charged radioactive isotopes are accelerated by particle accelerators for experiments in nuclear astrophysics and to study the structure of unstable nuclei. The width in time of the ion pulses ejected from EBIST can often contain too many ions for nuclear physics detection systems to efficiently detect all single radioactive isotopes or related events. Neglecting the influence of ion–ion collisions on the extraction rate, this publication derives, for different initial thermal energy distributions of the trapped ions, the time-dependent trap-opening functions to stretch the time distribution of ion pulses ejected from an EBIST trapping potential for the release of ions at a constant rate over an extended extraction period.

The proto-terrestrial mechanism of the appearance of water and early genesis of the global ocean

We consider chemical reactions for the appearance of water during the formation of the planet from cosmic gas and dust material to explain the early geological existence of the Earth’s hydrosphere. This process is fully supported by the resources of the initial substances and thermal energy. Thus, the concept of V.I. Vernadsly about the geological eternity of the World Ocean and ancient age of the oceanic lithosphere is supported. The identical high location of the ancient and modern continental platforms under the conditions of continual isostatical equilibrium in the asthenosphere–lithosphere–hydrosphere gives grounds to conclude that the ocean water depth is stable. Taking this into account, we can consider that the geological evolution of the Earth began in the conditions of the existence of the World Ocean when the mass of the hydrosphere only slightly exceeded the modern one.

Nonthermal Electron Energization from Magnetic Reconnection in Laser-Driven Plasmas.

The possibility of studying nonthermal electron energization in laser-driven plasma experiments of magnetic reconnection is studied using two- and three-dimensional particle-in-cell simulations. It is demonstrated that nonthermal electrons with energies more than an order of magnitude larger than the initial thermal energy can be produced in plasma conditions currently accessible in the laboratory. Electrons are accelerated by the reconnection electric field, being injected at varied distances from the X points, and in some cases trapped in plasmoids, before escaping the finite-sized system. Trapped electrons can be further energized by the electric field arising from the motion of the plasmoid. This acceleration gives rise to a nonthermal electron component that resembles a power-law spectrum, containing up to ∼8% of the initial energy of the interacting electrons and ∼24% of the initial magnetic energy. Estimates of the maximum electron energy and of the plasma conditions required to observe suprathermal electron acceleration are provided, paving the way for a new platform for the experimental study of particle acceleration induced by reconnection.

Mechanical and thermal properties of cationic ring-opening o-cresol formaldehyde epoxy/polyurethane acrylate composites enhanced by reducing graphene oxide

Polyurethane acrylate (PUA) and o-cresol formaldehyde epoxy resin (o-CFER) is synthesized. The PUA/o-CFER glass fiber-reinforced composites cured by free radical/cationic ring-opening reaction are modified by the reducing graphene oxide (r-GO). Effect of r-GO on the thermal and mechanical properties of PUA/o-CFER glass fiber-reinforced composites are characterized by FTIR, DMA and TGA. The result of FTIR shows that the system has cured completely. DMA analysis indicates that this system has better compatibility, and the glass transition temperature (T g) decreases with increasing r-GO content. TGA analysis shows that the initial thermal degradation temperature (T id) and activation energy (E a) enhance 13.1 °C and 3.12 kJ/mol, respectively. The tensile and impact strength of glass fiber-reinforced composites are approximately 50 and 60 % higher than those without r-GO. It is shown that the r-GO can enhance the mechanical properties and thermal stability of composites.

Effect of carbon nanotube on the mechanical, plasticizing behavior and thermal stability of PVC/poly(acrylonitrile–styrene–acrylate) nanocomposites

Polyvinylchloride (PVC)/poly(acrylonitrile–styrene–acrylate) (ASA)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared. The plasticizing behavior, dynamic mechanical properties, mechanical properties and thermal stability of the nanocomposites were studied. The results demonstrate that the plasticizing time shortens as the MWCNTs content increases. The nanocomposites show the best impact strength, which is 83.7 % higher than pure PVC/ASA blend and is 2.1 times higher than pure PVC, when the MWCNTs content is 0.054 wt%. MWCNTs can enhance the thermal stability of PVC/ASA blends; the initial decomposition temperature (Tid) and thermal degradation activation energy (Ea) increase by 13.1 °C and 5.7 kJ mol−1, respectively, when the MWCNTs content is 0.066 wt%. The storage modulus (E′) and glass transition temperature (Tg) also increase when MWCNTs are added. MWCNTs can be used as an efficient toughening modifier and processing aid for PVC/ASA blends.

Numerical simulation of superhalo electrons generated by magnetic reconnection in the solar wind source region**Supported by the National Natural Science Foundation of China.

Superhalo electrons appear to be continuously present in the interplanetary medium, even during very quiet times, with a power-law spectrum at energies above ∼2keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using magnetohydrodynamics and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the magnetic reconnection region, can accelerate electrons from an initial thermal energy of T ∼ 105 K up to hundreds of keV. After acceleration, some of the accelerated electrons, together with the nascent solar wind flow driven by the reconnection, propagate upwards along the newly-opened magnetic field lines into interplanetary space, while the rest move downwards into the lower atmosphere. Similar to the observed superhalo electrons at 1AU, the flux of upward-traveling accelerated electrons versus energy displays a power-law distribution at ∼ 2–100 keV, f(E) ∼ E−δ, with a δ of ∼ 1.5 – 2.4. For single (multiple) X-line reconnection, the spectrum becomes harder (softer) as the anomalous resistivity parameter α (uniform resistivity η) increases. These modeling results suggest that the acceleration in the solar wind source region may contribute to superhalo electrons.

Hydrologic Transport of Thermal Energy from Pavement

Heat island impacts generated from the built (urban) environs have been recognized for decades as a component of climate change. Increasing imperviousness of the urban environments generates a demonstrable impact on hydrologic cycle, chemical and particulate matter loads in rainfall-runoff, and the thermal parameters of the atmosphere and rainfall-runoff of the built environments. From this broader context, a specific monitoring and modeling study was conducted to examine the dynamic, intra-event thermal transfer between pavement and rainfall-runoff for an asphalt-paved urban source area. Measured results were compared with a series of published models. Event-based hydrologic results illustrated a correlation between peak flow and thermal energy flux as well as between initial pavement temperature and thermal energy flux to runoff. Transfer of energy from the pavement to runoff was primarily a flow-limited process, and cumulative volume was correlated with cumulative thermal energy transfer on a storm event basis. Based on 17 events, only the runoff volume from Tropical Storm Fay (August 21, 2008) was heat-limited (water volume was not correlated to heat flux), resulting in a thermal first-flush. Energy balance components in each model were examined for capability to reproduce measured results. All models performed similarly, but models would benefit by field validation of these components using direct measurement, particularly long wavelength radiation.

Simulation of main chamber wall temperature rise resulting from massive neon gas injection shutdown of ITER

Simulations were performed to estimate the main chamber wall heating in ITER resulting from rapid discharge shutdown by neon massive gas injection (MGI). The TokSys current diffusion model coupled with a simplified impurity transport model was used. Impurity parallel flow was treated with a single-fluid pressure-driven flow model. Impurity cross-field diffusion was treated with an empirical diffusion coefficient estimated from present experiments, while impurity poloidal rotation was included empirically by extrapolation in minor radius from present experiments to ITER. For single-valve neon MGI, maximum wall temperatures of order 1100 K are predicted, somewhat below the melting temperature of beryllium (1560 K). Lower temperature excursions were obtained by increasing the number of gas valves, while higher wall temperatures could be obtained by turning up initial plasma thermal energy or cross-field transport coefficients. Highest wall temperatures tended to occur on the centre post during the start of the current quench phase, consistent with present experiments. These results suggest that a single port may be sufficient for safely initiating rapid shutdown in ITER, leaving other ports free for subsequent rapid shutdown tasks such as runaway electron mitigation.

A lower angular momentum limit for self-gravitating protostellar disc fragmentation

We attempt to verify recent claims (made using semi-analytic models) that for the collapse of spherical homogeneous molecular clouds, fragmentation of the self-gravitating disc that subsequently forms can be predicted using the cloud's initial angular momentum alone. In effect, this condition is equivalent to requiring the resulting disc be sufficiently extended in order to fragment, in line with studies of isolated discs. We use smoothed particle hydrodynamics with hybrid radiative transfer to investigate this claim, confirming that in general, homogeneous spherical molecular clouds will produce fragmenting self-gravitating discs if the ratio of rotational kinetic energy to gravitational potential energy is greater than ~ 5e-3, where this result is relatively insensitive to the initial thermal energy. This condition begins to fail at higher cloud masses, suggesting that sufficient mass at large radii governs fragmentation. While these results are based on highly idealised initial conditions, and may not hold if the disc's accretion from the surrounding envelope is sufficiently asymmetric, or if the density structure is perturbed, they provide a sensible lower limit for the minimum angular momentum required to fragment a disc in the absence of significant external turbulence.

Enhancement of heat transfer from hot water by co-flowing it with mercury in a mini-channel

The present study is a numerical investigation on the flow and heat transfer in a mini-channel where both hot liquid water and mercury co-flow together in a direct contact manner. Results show that the presence of a high thermal conductivity liquid metal such as mercury enables the hot water to lose much more of its initial thermal energy content, than when only water alone flows in the channel. However, too unjustified excessive mercury co-flowing with the hot water can lead to adverse effects in regards to the heat loss from the hot water. The reason behind the enhanced heat transfer between the two liquids is due to the initiation of high temperature gradients sites inside the channel, especially in the region of the interface between the two liquids, in addition to the high thermal conductivity of mercury, as compared to water thermal conductivity. These two effects lead to effective conduction cooling in the transverse direction over the whole length of the channel. These aspects are quantified in this study.

Escape of high mass ions due to initial thermal energy and its implications for axially symmetric RF ion trap mass analyzer design

Abstract This paper investigates the loss of high mass ions due to their initial thermal energy in ion trap mass analyzers. It provides an analytical expression for estimating the percentage loss of ions of a given mass at a particular temperature, in a trap operating under a predetermined set of conditions. The expression we developed can be used to study the loss of ions due to its initial thermal energy in traps which have nonlinear fields as well as those which have linear fields. The expression for the percentage of ions lost is shown to be a function of the temperature of the ensemble of ions, ion mass and ion escape velocity. An analytical expression for the escape velocity has also been derived in terms of the trapping field, drive frequency and ion mass. Because the trapping field is determined by trap design parameters and operating conditions, it has been possible to study the influence of these parameters on ion loss. The parameters investigated include ion temperature, magnitude of the initial potential applied to the ring electrode (which determines the low mass cut-off), trap size, dimensions of apertures in the endcap electrodes and RF drive frequency. Our studies demonstrate that ion loss due to initial thermal energy increases with increase in mass and that, in the traps investigated, ion escape occurs in the radial direction. Reduction in the loss of high mass ions is favoured by lower ion temperatures, increasing low mass cut-off, increasing trap size, and higher RF drive frequencies. However, dimensions of the apertures in the endcap electrodes do not influence ion loss in the range of aperture sizes considered.