High Initial Energy Research Articles

Modelling of Energy-Dependent Electron Interactions in the Earth’s Mesosphere

Electrons are produced in the Earth’s quiet nighttime mesosphere by ionization by cosmic rays and ionization of NO by Lyman-α radiation. They are removed by attachment or recombination processes that are usually assumed in modelling to occur at the ambient temperature. However, the electrons have initial energies that are much higher than at thermal equilibrium, and so must have a range of energies as they progress towards equilibrium via interactions with atoms and molecules. As attachment and recombination rates are dependent on the electron energy, it is possible that modelling that considers the actual energy of the electrons will give different results to those based on assuming that the electrons are at the ambient temperature. In this work, starting with electrons at a higher initial energy, the detailed electron interactions (including elastic scattering and vibrational excitation of molecules) are tracked in a time-step simulation. This simulation is implemented by treating electrons in subranges of the electron energy spectrum as chemical species. This allows an investigation of two phenomena in the nighttime mesosphere: the origin of the D-region ledge and the production of radiative emissions from vibrationally excited molecules. It is found that there is negligible difference in the electron densities calculated using the ambient temperature or detailed interaction models, so this study does not provide an explanation for the D-region ledge. However, in the latter model, emissions at various wavelengths are predicted due to reactions involving vibrationally excited molecules. It is also found, using the time-step calculation, that it would take several hours for the predicted electron density to approach equilibrium.

Propagation of supersonic soliton in carbon nanotubes of armchair type

The propagation of a localized ring nonlinear wave in carbon nanotubes (CNTs) of armchair type has been explored using the MD/DFTB method. It is unambiguously shown that the considered localized waves are soliton-type. Herewith, the higher a velocity of an initial perturbation, the higher a steady-state velocity of the considered soliton. It is established that at a high initial excitation energy in a time period of 0.1-0.2 ps the soliton moves at the speed in the range of 245-270 Angstrem/ps, which is approximately in 1.22-1.35 times higher than the speed of sound in CNTs (200 Angstrem/ps). It is shown that the soliton velocity practically does not change with increasing CNT radius Keywords: molecular dynamics, carbon nanotubes, soliton, supersonic wave.

Распространение сверхзвукового солитона в углеродных нанотрубках типа кресло

The propagation of a localized ring nonlinear wave in carbon nanotubes (CNTs) of armchair type has been explored using the MD/DFTB method. It is unambiguously shown that the considered localized waves are soliton-type. Herewith, the higher a velocity of an initial perturbation, the higher a steady-state velocity of the considered soliton. It is established that at a high initial excitation energy in a time period of 0.1-0.2 ps the soliton moves at the speed in the range of 245-270 Å/ps, which is approximately in 1.22-1.35 times higher than the speed of sound in CNTs (200 Å/ps). It is shown that the soliton velocity practically does not change with increasing CNT radius

Von Karman thermoelastic plates: Existence and nonexistence of global solutions

This paper undertakes a study of behavior of solutions corresponding to von Karman thermoelastic plates involving a nonlinear source. It is well-known that the source term gives rise to finite-time blow-up of solutions and drives the system to possible instability. So, it is of interest to explore the mechanism of the source and the dissipation. In this paper, on the one hand, for low initial energy, we apply modified potential well method and differential inequality argument to prove the solution globally exists and decays exponentially to zero if the initial data starts from the stable set and fails to exist globally when the initial data starts from the unstable set. On the other hand, for high initial energy, with the aid of the monotonicity of the $ L^{2} $ norm of the solution with a positive perturbed constant and some differential inequality argument as well as energy inequalities, we are in a position to prove that the solution to the studied problem blows up in finite time. At last, an explicit lower bound for blow-up time is obtained.

Blowup phenomena for a fourth order wave equation at high initial energy level

Blowup phenomena for a fourth order wave equation at high initial energy level

Exploration of the induced fluid-disturbance effect in CBM co-production in a superimposed pressure system

Fluid disturbance in coalbed methane co-production in a superimposed pressure system is universal. Two sets of tests were conducted with different constant outlet pressure values and reservoir pressure gradients to explore the fluid-disturbance characteristics. First, in the constant outlet pressure mode, reservoirs with large differences in the initial fluid energy are prone to fluid disturbance in the early stage of co-production, and the dynamic pressure balance drives part of the fluid from reservoirs with a high initial fluid energy to flow to reservoirs with a low initial fluid energy. Second, an increase in the constant outlet pressure value reduces the intensity of the fluid disturbance, and the reservoir pressure gradient has a positive effect on the fluid-disturbance effect. The design of a constant-pressure co-production must incorporate disturbance-reduction measures and appropriately increase the constant outlet pressure at the wellbore outlet. Alternatively, reservoirs with smaller reservoir pressures should be selected for co-production. Third, the gas-production mode of a single reservoir under the constant-pressure co-production can be separated into three major categories and seven subcategories: the conventional mode is applicable to reservoirs with a high initial fluid energy, the inhibition mode is primarily for reservoirs with a medium-low initial fluid energy, and the backflow mode is primarily for reservoirs with a low initial fluid energy.

Energy and environmental performance of photovoltaic cooling using phase change materials under the Mediterranean climate

The energy and environmental performance of photovoltaic (PV) panel cooling, when using phase change materials (PCMs), was examined. Actual, long-term field data were collected from a PV and a PV-PCM system, both operating under Mediterranean conditions (Greece). The energy analysis revealed that even though cooling increases (9.4%) the panel's energy output, PCM cooling is associated with a high initial energy investment, leading to low energy-return-on-investment values (1.79) compared to PV (4.94). High energy payback times were observed for the PV-PCM (⁓14 years) compared to the PV system (⁓5 years). Furthermore, the life cycle assessment methodology revealed that PCM cooling increases PV's total environmental footprint by 21.9%. However, in the Greek context, the additional electricity attributed to PV cooling leads to significant environmental gains through fossil-fuel-dependent electricity substitution. Cooling can also decrease the rate of cell degradation and prolong PV useful life, leading to additional environmental gains. Due to PCM's initial high energy investment, other cooling technologies should also be examined since, apart from improving electricity output and stability, cooling can also reduce PV's impact on land use, increase the power sector's decarbonization, and address global warming's impact on PV performance by reducing temperature fluctuations and extremes on the panel's surface.

Blow-up for the Timoshenko-type equation with variable exponents

The finite time blow-up of solutions to a nonlinear Timoshenko-type equation with variable exponents is studied. More concretely, we prove that the solutions blow up in finite time with positive initial energy. Also, the existence of finite time blow-up solutions with arbitrarily high initial energy is established. Meanwhile, the upper and lower bounds of the blow-up time are derived. These results deepen and generalize the ones obtained in [Nonlinear Anal. Real World Appl., 61: Paper No. 103341, 2021].

Electron tracks simulation in water: Performance comparison between GPU CPU and the EUMED grid installation

PurposeWe explored different technologies to minimize simulation time of the Monte-Carlo method for track generation following the Geant4-DNA processes for electrons in water. MethodsA GPU software tool is developed for electron track simulations. A similar CPU version is also developed using the same collision models. CPU simulations were carried out on a single user desktop computer and on the computing grid France Grilles using 10 and 100 computing nodes. Computing time results for CPU, GPU, and grid simulations are compared with those using Geant4-DNA processes. ResultsThe CPU simulations better performs when the number of electrons is less than 104 with 100 eV initial energy, this number decreases as the energy increases. The GPU simulations gives better results when the number of electrons is more than 104 with initial energy of 100 eV, this number decreases to 103 for electrons with 10KeV and increases back with higher energy. The use of the grid introduces an additional queuing time which slows down the overall simulation performance. Thus, the Grid gives better performance when the number of electrons is over 105 with initial energy of 10KeV, and this number decreases as the energy increases. ConclusionsThe CPU is best suited for small numbers of primary incident electrons. The GPU is best suited when the number of primary incident particles occupies sufficient resources on GPU card in order to get an important computing power. The grid is best suited for simulations with high number of primary incident electrons with high initial energy.

Stability of virtual reality haptic feedback incorporating fuzzy-passivity control

This study investigated the stability of virtual reality (VR) haptic feedback from the perspective of energy. A fuzzy controller was designed on the basis of passivity theory to mitigate the shock and divergence in a virtual component caused by the negative damping coefficient and the high spring coefficient. Compared with a standard passivity controller, a fuzzy-passivity controller is more effective in shortening the time required to stabilize a system with high initial energy and devices that consume energy slowly. First, MATLAB/Simulink was employed for stability simulation and analysis. The fuzzy-passivity controller provided more favorable stability convergence than did the standard passivity controller. The simulation results align with expectations. Second, the completed VR system was applied as an experiment platform for verifying the feasibility of the fuzzy-passivity controller. To achieve one degree of freedom in the experiments, a robotic arm was exclusively designed to replace manual force. Finally, compared with standard passivity control systems, the results indicated that the fuzzy-passivity controller enables improved control over the stability of VR haptic feedback.

Revealing impact failure behavior of tungsten composite using instrumented Charpy impact testing

The impact toughness of W-Ni-Fe alloys with different W content (90, 93 and 95 wt%) were studied by means of instrumented Charpy impact testing, and the relationship between impact toughness and microstructural parameters was discussed, with an emphasis on impact failure behavior. With increasing of W content, the elongation decreases from 31% for 90 W to 21% for 95 W, but the tensile strength slightly increases from 940 to 974 MPa and the yield strength increases from 655 to 688 MPa. The impact load-displacement curves reveal that the impact toughness is predominantly controlled by the crack initiation energy and decreased with increasing of W content, whereas the crack propagation energy is relatively low and remains constant. The decrease in the crack initiation energy attributed to a decrease in matrix volume fraction and an increase in W contiguity. 90 W shows the highest crack initiation energy due to the severe plastic deformation during crack initiation process, which contains multiple deformation characteristics such as dislocation tangles, dislocation forest, stacking faults, nano-scaled twins and subgrains. The formation of those features is discussed, and it is found that they are expected to provide a toughening effect. From the perspective of crack nucleation and growth, it is also found that the high crack initiation energy of 90 W profited from the high energy-consuming processes of W cleavage events, micro-crack arrest, blunting and bridging mechanisms. Although these three alloys display different failure features of crack propagation paths, they present similar crack propagation energies. The current study provides a deep insight into the impact failure behavior of WHAs.

A conjugately configured supercapacitor based on pairs of pre-lithiated Nb2O5/TiO2 with optimized retained energy upon aging enabled by suppressed self-discharge

Supercapacitors are advantageous in terms of power density and cycle life, but their wider application is limited by self-discharge. Previous attempts for improving the stability have mainly focused on the specific component (materials, separators or electrolytes) of the device, while the feasibility for mitigating self-discharge through a general device-scale configuration is largely unknown. Herein, we report a symmetric supercapacitor with a conjugated configuration, which consists of a pair of pre-lithiated niobium oxide decorated with evenly distributed titanium dioxide, forming a Lix[(Nb2O5):(TiO2)a] vs. Li2-x[(Nb2O5):(TiO2)a] conjugated configuration. The intercalation type pseudocapacitive Nb2O5 are unique due to their linearly sloped charge/discharge curve like electrochemical double layer capacitances (EDLCs) while the charged ions can be inserted/extracted reversibly from the bulk like batteries. As a result, such conjugated device can store energy like conventional EDLCs, while the self-discharge process is significantly supressed. When further added with suitable amount of titanium dioxide as the stabilizer, the conjugated supercapacitor retained 74% of its energy after aging for 48 h. These results are expected to provide a general guidance for designing materials specifically for constructing conjugated supercapacitors with high initial energy density and alleviated self-discharge.

Multi-channel rod structure hard carbon for high initial Coulombic efficiency and low-potential sodium storage

Hard carbon is one of the most promising anode materials that can be commercialized on a large scale for sodium ion batteries due to its resource abundance, cost-effectiveness, and high sodium storage capacity. Nevertheless, the improvement of high initial Coulombic efficiency and high energy density remains an urgent problem to be solved for the commercialization of sodium-ion batteries (SIBs). Herein, poplar wood was used as the precursor to prepare multi-channel rod structure hard carbon via one-step high-temperature thermal decomposition. The results showed that the microstructure and surface chemical composition of poplar-derived hard carbon can be adjusted by changing the carbonization temperature. Due to its unique multi-channel rod structure, suitable d(002)-spacing (0.370 nm) and ultra-low specific surface area (8.9 m2 g−1), the PHC-1600 exhibits a high reversible capacity of 325 mA h g−1 at current density of 50 mA g−1. It shows a capacity of 245 mA h g−1 at low-potential plateau (75 %). At the same time, the PHC-1600 also exhibits a high initial Coulombic efficiency of 88.3 % and good electrochemical property. The ex-situ XRD and CV revealed that PHCs is dominated by intercalation mechanism. This work provides a new perspective from biomass for the development of outstanding electrochemical performance anode materials with highly profitable and environment-friendly.

Transition Metal Assisting Pre‐Lithiation Reduces the P/N Ratio to Balance the Energy Density and Cycle Life of Aqueous Batteries

AbstractAqueous Li‐ion batteries (ALIBs) are safe, environmentally friendly, and cost‐effective, promising for electric energy storage (EES). The high voltage ALIBs (HV‐ALIBs) supported by water‐in‐salt electrolytes are ideal for lowering the energy cost ($/Wh) of EES. However, HV‐ALIBs have been built with a high positive/negative capacity ratio (P/N ratio) to ensure their long‐term cycle life due to the irreversible Li consumption in the initial cycle induced by the solid electrolyte interface (SEI) formation and the parasitic reaction. Thus, the benefits of HV‐ALIBs in cost and energy density are mitigated inevitably. Generally, the feasible approach is adding per‐lithiation additives (PAs) to compensate for the capacity loss in the initial cycle. However, using PAs in ALIBs is challenging due to the high chemical activity of water. Here, a new strategy to achieve the pre‐lithiation by introducing manganese metal as a sacrificial PA for HV‐ALIBs that can provide over 900 mAh g−1 specific capacity without any adverse impact is proposed. The P/N ratio reduces to 1.02 by the LiMn2O4||TiO2 pouch cell using the sacrificial manganese PA. This results in a high initial energy density above 120 Wh kg−1 and outstanding cycle stability with a capacity retention of 80% after 400 cycles.

Global well-posedness analysis for the nonlinear extensible beam equations in a class of modified Woinowsky-Krieger models

Abstract For studying the evolution of the transverse deflection of an extensible beam derived from the connection mechanics, we investigate the initial boundary value problem of nonlinear extensible beam equation with linear strong damping term, nonlinear weak damping term, and nonlinear source term. The key idea of our analysis is to describe the invariant manifold via Nehari manifold. To establish the results of global well-posedness of solution, we consider the problem at three different initial energy levels, i.e., subcritical initial energy level, critical initial energy level, and arbitrarily high initial energy level. We first obtain the local existence of the solution by using the contraction mapping principle. Then, in the framework of potential well, we obtain global existence, nonexistence, and asymptotic behavior of solution for both subcritical initial energy level and critical initial energy level. In the end, we establish the global nonexistence of solution for the problem with linear weak damping and strong damping at the arbitrarily high initial energy level.

Well-posedness of solutions for a class of quasilinear wave equations with structural damping or strong damping

This paper deals with a class of quasilinear wave equations with structural damping or strong damping. By virtue of the improved Faedo–Galerkin method and some technical efforts, we first establish the local well-posedness of weak solutions, especially the continuity of weak solutions with respect to time in the natural phase space. Then we investigate the global existence, asymptotic behavior and finite time blow-up of weak solutions with subcritical or critical initial energy. As for the supercritical initial energy case, we show that the weak solutions may blow up in finite time with arbitrarily high initial energy. Last but not least, the upper and lower bounds of the blow-up time for blow-up solutions are derived.

Blow-Up Time of Solutions for a Parabolic Equation with Exponential Nonlinearity

This paper studies a parabolic equation with exponential nonlinearity, which has several applications, for example the self-trapped beams in plasma. Based on a modified concavity method we prove the blow-up of the solution for initial data with high initial energy. We also proposed the solution’s lower and upper bound of the blow-up time for the equation. Our results complement the existing results.

Binary metal selenide nanowires wrapped over carbon fibers for a binder-free anode of sodium-ion batteries

Binary metal selenides (BMSs) have attracted considerable interest as potential anode materials for sodium-ion batteries (SIBs) due to significantly improved sodium storage performance resulting from higher intrinsic ionic conductivities and richer redox-active sites, particularly when compared to mono-metal selenides. In addition, the accumulation of binder in slurry preparation for electrodes not only accumulates dead weight but also diminishes the extent of the exposed surface area of active material. Henceforth, hierarchical nanostructures of nickel-cobalt selenide (NCSe) and iron-cobalt selenide (FCSe) bearing high surface area were deposited directly over carbon fibers and employed as free-standing anodes for SIBs (termed as NCSe/CFs and FCSe/CFs, respectively). A facile hydrothermal strategy, followed by optimized gas selenization was used to acquire hierarchical nanowire-like morphologies of BMSs on carbon fibers. Carbon fibers substrates not only provide current collecting pathways for electron transport during charging/discharging but also exhibit the high strength required for the free-standing electrode for battery assembly. When these electrodes were employed as an anode in SIBs, they exhibited adequately high initial energy capacities (i.e., 665 mA h g−1 by FCSe/CFs and 589 mA h g−1 by NCSe/CFs at 0.1 A g−1) and high-rate capabilities. Furthermore, these electrodes delivered outstanding stability in long-term cyclic performance over 1000 cycles at 1 A g−1. We believe that this simple strategy will further open a pathway toward the facile synthesis of numerous BMSs with carbon fiber composites as free-standing anodes for energy storage and conversion systems.

General decay and blow-up results for a class of nonlinear pseudo-parabolic equations with viscoelastic term

In this paper, we consider initial boundary value problem of the generalized pseudo-parabolic equation contain viscoelastic term. We establish firstly the local existence of solutions by Banach fixed point theorem. Then we prove blow-up results for solutions when the initial energy is negative or nonnegative but small enough or positive arbitrary high initial energy, respectively. We also establish the lifespan and the blow-up rate for the weak solution via finding the upper bound and the lower bound for the blow-up times and the upper bound and the lower bound for the blow-up rate. For negative energy, we introduce a new method to prove blow-up results with sharper estimate for upper bound for the blow-up times. Finally, we prove the global existence of the solution and a general decay estimate under some suitable assumptions.

Giant river-blocking landslide dams with multiple failure sources in the Nu River and the impact on transient landscape evolution in southeastern Tibet

Giant landslides have frequently occurred in deeply-incised valleys during the topographic development of the Tibetan Plateau, and these landslides commonly blocked rivers and in turn affected fluvial processes. The giant Qianjincun landslide, with a volume of ~110 × 106 m3, created the highest natural dam among all the completely river-blocking landslides identified along the trunk of the Nu River in the southeastern Tibetan Plateau. This giant landslide, which developed on a granite hillslope and dammed the river with a height of ~175 m, was dominated by long-term fluvial incision responding to uplift in one of the deepest valleys in the world. The dammed lake was breached around the end of the Dali glaciation (~10 ka), and the deposits remaining in the valley indicated an earlier landslide from the opposite failure source beside the Qianjincun landslide. The Geduicun landslide on the right bank evolved from gravitational deformation of toppling controlled by schist foliations, while the Qianjincun failure on the left hillslope was governed by the seismically-triggered detachment of granite cut by rock joints. The kinematic process of the Qianjincun landslide was numerically investigated under seismic loading, indicating high-velocity sliding from a thousand-meter-high source. In comparison to the soft rock failure preceded by the long-term gravitational effect, the mass movement on the granite slope was catastrophically induced by dynamics with high initial kinetic energy, and the subsequent overwhelming river blockage transiently caused stronger landscape evolution than any other landslides in the catchment. The inventory of river-damming landslides compiled along the trunk of the Nu River suggested a prominent tendency that all the dammings occurred in the region where the relief is greater than 2000 m. The analysis provided the power-law correlations of the geomorphic parameters of dams that can help predict the disastrous effects of future river blockages. The insight into landscape feedbacks between giant landslides and fluvial processes could contribute to effective risk assessments of disaster chains in high-relief reaches.