Energy Loss Rate Research Articles

Vacuum Cherenkov radiation at finite temperature

In this paper we examine the thermal effects of the vacuum Cherenkov radiation in a Lorentz- and CPT-violating electrodynamics. We compute the thermal contribution to the Cherenkov radiation rate within the Thermofield Dynamics approach. Since the model under consideration possesses a consistent canonical quantization and also fulfills the physical constraints in order to this vacuum process to happen, it is a perfect candidate to implement the study at finite temperature. We evaluate in details the instantaneous rate of energy loss for a charge, and show that the radiation rate is significantly modified at very high temperatures. Intriguingly, we further observe that when the temperature goes to infinity the radiation rate goes to zero even if the process is kinematically allowed.

Numerical study of mean mechanical energy loss in a gas cyclone

Reducing energy loss is one of the goals of optimizing gas cyclones, which can be benefitted from a deep understanding of the energy loss mechanism in gas cyclones. In this study, the gas-solid flow in a gas cyclone was simulated using the combined computational fluid dynamics (CFD) and the discrete element method (DEM). An energy loss model for analyzing the spatial distribution and proportion of the mean mechanical energy loss of the gas cyclone was adopted and validated in terms of the total pressure drop. It is found that the near-wall region generally has high rates for both viscous dissipation and turbulent production, especially the vortex finder, the conical part, and the discharger. The effects of the inlet velocity, the wall roughness, and the particle loading ratio on the energy loss are studied. The findings reveal that increasing the inlet velocity mainly increases the viscous dissipation of the wall and the turbulent production of the core region, resulting in an increase in mechanical energy loss. In contrast to the energy loss mechanism of the pipe, the mechanical energy loss of the gas cyclone decreases slightly with increasing wall roughness, which is mainly caused by the reduction of the viscous dissipation of the wall. By injecting particles, the spatial distribution of the energy loss rate is greatly altered, and the mechanical energy loss is also reduced. Further analysis shows that increasing the particle loading ratio reduces both viscous dissipation and turbulent production.

Entropy production analysis for energy dissipation of a vertical mixed-flow pump device under asymmetric inflow conditions

To investigate the influence of the inflow angle on the hydraulic loss and internal flow fields of a vertical mixed-flow pump device, unsteady numerical simulations were performed under different inflow angles ( θ = 0°, 10°, 20°, and 30°). The calculation results were validated using an external characteristic test at an inflow angle of 0°. The entropy production theory was applied to analyse the energy loss and dissipation rate distribution in a vertical mixed-flow pump device under different inflow angles. Influenced by asymmetric inflow, the design point of the external characteristics deviated towards the overload flow rate, and the maximum deviations were obtained under 1.2 Q des, whereas the influence of the inflow angle on the internal flow fields was the most significant under the part-load flow rate. When the inflow angle increased from 0° to 30°, the total entropy production in the pump device increased by 18.35% under 0.6 Q des, and indirect dissipation accounted for the largest proportion. The internal flow patterns in the impeller and guide vane were also distorted by asymmetric inflow. The indirect dissipation rate on the suction side of the impeller blade, interface between the impeller and diffuser, and pressure side of the guide vane increased significantly with an increase in the inflow angle. To restrain the influence of asymmetric inflow, it is of great significance to optimise the hydraulic design structure of the inflow runner. In this study, a middle spacer pier was used to improve the operational efficiency of the pump device.

Role of neutrino form factors in the energy loss rates of the pair annihilation process

The stellar energy loss rates due to the production of neutrino pairs are calculated using the minimal extension of the Standard Model with the electromagnetic properties of the Dirac neutrinos, which takes the contributions of the neutrino charge radius, anapole moment, and dipole moments into account. We show that the contribution of the electron neutrino's dipole moment is small compared with that of the charge radius. The obtained results are also compared with the results obtained using the Standard Model.

An experimental study on the hydrodynamic performance of the twin vertical baffles underflow breakwater

Recently, with the enhancement of marine environmental protection, the permeable breakwater, which has the advantages of a simple structure, good water permeability, and environment-friendly, has been paid more and more attention. This study experimentally investigated the hydrodynamic characteristics of a twin vertical baffles underflow breakwater in a wave flume. Different parameters including the relative submergence, relative blockage, breakwater width, and water surface condition between baffles have been considered. Their influences on the transmission coefficient, reflection coefficient, relative wave run-up on the front baffle, and energy loss rate of the twin vertical baffles underflow breakwater have been analyzed. Furthermore, the wave resonance phenomenon could occur for the cases with free water surface between the two baffles, which had a significant influence on the hydrodynamic characteristics of the breakwater. Finally, an empirical formula for calculating the transmission coefficient has been given based on the experimental data.

From Boltzmann Equation for Granular Gases to a Modified Navier–Stokes–Fourier System

In this paper, we give an overview of the results established in Alonso (http://arxiv.org/org/abs/2008.05173, 2020) which provides the first rigorous derivation of hydrodynamic equations from the Boltzmann equation for inelastic hard spheres in 3D. In particular, we obtain a new system of hydrodynamic equations describing granular flows and prove existence of classical solutions to the aforementioned system. One of the main issue is to identify the correct relation between the restitution coefficient (which quantifies the rate of energy loss at the microscopic level) and the Knudsen number which allows us to obtain non trivial hydrodynamic behavior. In such a regime, we construct strong solutions to the inelastic Boltzmann equation, near thermal equilibrium whose role is played by the so-called homogeneous cooling state. We prove then the uniform exponential stability with respect to the Knudsen number of such solutions, using a spectral analysis of the linearized problem combined with technical a priori nonlinear estimates. Finally, we prove that such solutions converge, in a specific weak sense, towards some hydrodynamic limit that depends on time and space variables only through macroscopic quantities that satisfy a suitable modification of the incompressible Navier–Stokes–Fourier system.

Analysis on Large-Scale Solar PV Plant Energy Performance–Loss–Degradation in Coastal Climates of India

This article presents a detailed analysis of the performance, rate of degradation, and power and energy loss of a 1 MWp scale solar photovoltaic (PV) plant in the academic institution GITAM (Deemed to be University), located in the coastal region of Andhra Pradesh, India. The PV plant consists of 3,078 polycrystalline PV modules of 325 Wp rating, installed on the rooftop of the institute buildings. The annual energy generated is 1684.881 MWh. In this study, performance analysis involves the calculation of efficiency, capacity factor, and performance ratio with data simulated using the PVsyst tool. Degradation analysis involves energy light-induced degradation (LID) and degradation rate (DR). The predicted result provides an estimate for optimal functioning of PV plant with an annual capacity factor, performance ratio, and energy loss of 11.3%, 87.9%, and −26%, respectively. Energy loss by light-induced degradation is predicted as −2.7%/year, and the degradation rate of module per year is −0.6% to −5%.

Energy loss rate of an electron in three-dimensional tilting Dirac semimetals

We have computed the energy loss rate (ELR) of an intruding electron in three-dimensional tilting Dirac semimetals in the light of the excitation process. In contrast to two-dimensional electron gas, ELRs contributed by single-particle excitation (${\mathrm{ELRs}}^{(\mathrm{SP})}$) show a nondecreasing tendency as the incidence velocity increases, and tend to replicate the behavior of the untilt intrinsic ${\mathrm{ELR}}^{(\mathrm{SP})}$, which is described by a cubic polynomial coupling with a logarithm velocity term. In comparison, ELRs contributed by the plasmon excitation (${\mathrm{ELRs}}^{(\mathrm{P})}$) first reach a maximum in the small velocity region followed by a slow discrepancy. As the contribution of plasmon excitation is restricted by the vanishing imaginary part of the dielectric function, the ${\mathrm{ELRs}}^{(\mathrm{P})}$ also manifest as an opposite counterpart to the corresponding ${\mathrm{ELRs}}^{(\mathrm{SP})}$ with different tilts. In addition, the threshold velocities in both ELRs are tilt and chemical potential dependent, and governed by the interplay of the Pauli exclusion constraints and the conservation law concealed in the energy loss function. Finally, we briefly discuss the inelastic mean scattering time. Our results may be verified by investigating the femtosecond electron dynamics in the time-resolved two-photon photoemission.

Modelling the ionization state of Type Ia supernovae in the nebular phase

ABSTRACT The nebular spectra of Type Ia supernovae (⪆100 d after explosion) consist mainly of emission lines from singly and doubly ionized Fe-group nuclei. However, theoretical models for many scenarios predict that non-thermal ionization leads to multiply ionized species whose recombination photons ionize and deplete Fe+, resulting in negligible [Fe ii] emission. We investigate a method to determine the collisional excitation conditions from [Fe ii] line ratios independently from the ionization state and find that it cannot be applied to highly ionized models due to the influence of recombination cascades on Fe+ level populations. When the ionization state is artificially lowered, the line ratios (and excitation conditions) are too similar to distinguish between explosion scenarios. We investigate changes to the treatment of non-thermal energy deposition as a way to reconcile overionized theoretical models with observations and find that a simple work function approximation provides closer agreement with the data for sub-Mch models than a detailed Spencer–Fano treatment with widely used cross-section data. To quantify the magnitude of additional heating processes that would be required to sufficiently reduce ionization from fast leptons, we artificially boost the rate of energy loss to free electrons. We find that the equivalent of as much as an eight times increase to the plasma loss rate would be needed to reconcile the sub-Mch model with observed spectra. Future studies could distinguish between reductions in the non-thermal ionization rates and increased recombination rates, such as by clumping.

RADIATION-INDUCED SURFACE MIGRATION OF TUNGSTEN: CHANNELING ALONG ATOMIC STEPS

The interaction of accelerated helium atoms with the atomic-smooth surface of tun+gsten single crystals was investigated using the low-temperature field-ion microscope, equipped with the source of helium atoms with an energy of 5 keV together with the techniques of molecular dynamics. It was observed the effect of the surface channeling of fast atoms of a target along the surface steps which occurs as a result of the collision cascade induced by the incident projectile. A substantial part of these displaced atoms in the target gains momentum oriented along the < 111 > close-packed crystallographic directions. The fine morphology of the trajectory of an excited tungsten atom reveals the transverse oscillations of the W atom normally to the < 111 > surface atomic step. The rate of the kinetic energy loss during the surface channeling of fast tungsten atoms does not exceed 0.4 eV/Å. This provides relatively large displaced surface atom ranges along the close-packed atomic steps. The found out results can be regarded as a special case of the correlation mechanism of the radiation-induced surface mass transfer.

A Study on the X-Ray Pulse Profile and Spectrum of the Crab Pulsar Using NICER and Insight-HXMT's Observations

Abstract We analyze the energy dependence of the X-ray pulse profile and the phase-resolved spectra (PRS) of the Crab pulsar using observations from the Neutron star Interior Composition Explorer (NICER) and the Hard X-ray Modulation Telescope (Insight-HXMT). We parameterize the pulse profiles and quantify the evolution of these parameters in the broad energy band of 0.4–250 keV. A log-parabola function is used to fit the PRS in 2–250 keV, and the curvature of the spectrum, i.e., the evolution of the photon index with energy, as represented by the parameter β of the log-parabola model, also changes with phase. The relation of β and phase has two turning points slightly later than those of the pulse intensity profile, where the values of β are the lowest, suggesting that the energy-loss rate of the particles is the lowest in the corresponding regions. A three-segment broken-power-law model is also used to fit those PRS. The differences between the hard spectral index and the soft ones have a distribution similar to that of β, confirming the fitting results of the log-parabola model, while the broken energies are generally higher in the region bridging the two pulses. We find anticorrelations between the spectral indices and the curvature of the log-parabola model fitting and a similar anticorrelation between the spectral indices and broken energies of the broken-power-law model fitting, suggesting a scenario where the highest-energy particles are produced in regions where radiation energy loss is strongest.

Suppression of the TeV Pair-beam–Plasma Instability by a Tangled Weak Intergalactic Magnetic Field

We study the effect of a tangled sub-fG level intergalactic magnetic field (IGMF) on the electrostatic instability of a blazar-induced pair beam. Sufficiently strong IGMF may significantly deflect the TeV pair beams, which would reduce the flux of secondary cascade emission below the observational limits. A similar flux reduction may result from the electrostatic beam–plasma instability, which operates the best in the absence of IGMF. Considering IGMF with correlation lengths smaller than a kiloparsec, we find that weak magnetic fields increase the transverse momentum of the pair-beam particles, which dramatically reduces the linear growth rate of the electrostatic instability and hence the energy-loss rate of the pair beam. We show that the beam–plasma instability is eliminated as an effective energy-loss agent at a field strength three orders of magnitude below that needed to suppress the secondary cascade emission by magnetic deflection. For intermediate-strength IGMF, we do not know a viable process to explain the observed absence of GeV-scale cascade emission.

A high anti-impact STF/Ecoflex composite structure with a sensing capacity for wearable design

By encapsulating shear thickening fluid (STF) in Ecoflex-0030, a kind of composite structure with excellent anti-impact and high energy absorption properties was obtained. The drop hammer tests indicated that the increase of STF concentration could improve the anti-impact and energy absorption capacity of STF/Ecoflex. Furthermore, the loss rate of impact energy of STF/Ecoflex was 63.6% and 36.6% higher than that of aluminum alloy and Kevlar materials, respectively. Numerical simulation was used to explore the mechanism. It was found that the shear thickening effect of STF was enhanced with the increase of STF concentration, which could lead to the increase of the stress level of STF and the energy dissipated by friction and viscosity, thereby the anti-impact performance of the composite was improved. Then, the C-STF/Ecoflex was prepared by adding carbon nanotubes (CNTs) to STF, which had excellent impact sensing function and could be combined with Kevlar for multi-functional wearable devices with anti-impact properties.

Electron heating in GaN/AlGaN quantum well in a longitudinal electric field

The heating of electrons under longitudinal optical phonon scattering in a triangular GaN/AlGaN quantum well was studied theoretically. The energy loss rate of electrons was calculated in consideration of the dynamical screening and the hot phonon effect. The dependence of the electron temperature on the longitudinal electric field was calculated. The integral terahertz emission of hot two-dimensional electrons was simulated. The role of coupled plasmon-phonon mode scattering in the GaN/AlGaN quantum well was discussed.

Rate of energy-loss due to pair, plasma and photo neutrino processes in stellar environment

Rate of energy-loss due to pair, plasma and photo neutrino processes in stellar environment

Hot electron relaxation and energy loss rate in silicon: Temperature dependence and main scattering channels

In this work, we revisit the density functional theory (DFT)-based results for electron–phonon scattering in highly excited silicon. Using the state-of-the-art ab initio methods, we examine the main scattering channels, which contribute to the total electron–phonon scattering rate and the energy loss rate of photoexcited electrons in silicon as well as their temperature dependence. Both temperature dependence and the main scattering channels are shown to strongly differ for the total electron–phonon scattering rate and the energy loss rate of photoexcited electrons. While the total electron–phonon scattering rate increases strongly with temperature, the temperature dependence of the energy loss rate is negligible. Also, while acoustic phonons dominate the total electron–phonon scattering rate at 300 K, the main contribution to the energy loss rate comes from optical modes. In this respect, DFT-based results are found to disagree with conclusions of Fischetti et al. [Appl. Phys. Lett. 114, 222104 (2019)]. We explain the origin of this discrepancy, which is mainly due to differences in the description of the electron–phonon scattering channels associated with transverse phonons.

ERYA-Bulk and ERYA-Profiling: An application for quantitative PIGE analysis

The applications entitled ERYA-Bulk and ERYA-Profiling (ERYA stands for Emitted Radiation Yield Analysis) are two programs which implement PIGE (Particle Induction Gamma-Ray Emission) analysis of samples which can be either homogeneous (handled by ERYA-Bulk) or heterogeneous (with multiple layers, which are simulated by ERYA-Profiling).The homogeneous model uses an analytical method to evaluate the nuclear yield as function of the mass fraction of the element(s) of interest. A routine is available to fit the experimental yields in order to compute the correct sample atomic composition.Otherwise, the heterogeneous model takes consideration of the physics with greater detail, including straggling in the energy lost by the projectiles, making a more realistic yield simulation, whose level of accuracy the user can control in exchange of computational time.Here, we present the latest developments of these codes, which include new features, functionalities and direct handling of different source files. ERYA-Bulk and ERYA-Profiling are currently compiled and tested for Linux, Windows and Mac OS X operating systems. Program summaryProgram Title: ERYA-Bulk, ERYA-ProfilingCPC Library link to program files:https://doi.org/10.17632/gnrvm4jt5v.1Developer's repository link:https://github.com/Arucard1983/ERYA-Bulk (ERYA-Bulk), https://github.com/Arucard1983/ERYA-Profiling (ERYA-Profiling)Licensing provisions: LGPL-v3Programming language: C++External routines: wxWidgets [1], wxMathPlot [2]Nature of problem: Compute the gamma-ray yield coming from a sample bombarded by a energetic (few MeV) beam of charged particles (namely protons). The yield corresponding to a given element depends on the mass fraction of this element and on the major composition of the sample which determines the rate of energy loss by the beam. It also depends on the detector efficiency, the collected beam charge (i.e., number of projectiles) and the cross-sections of the relevant gamma-producing nuclear reaction.All data inputs can be loaded from a file or inserted by the user. The energy straggling along the beam interaction with the sample, irrelevant for bulk analysis, is determinant for depth profiling.Solution method: The yield calculation is made by numerical integration of an analytical formula that depends on several quantities which can be analytical in nature or approximated by interpolation (the cross-section data interpolation is one example).The straggling and energy dispersion also depends on energy distributions which have different numerical approximations. A modular approach using the object-oriented programming helps to implement different models to the main integration routine, and make the source code more readable and prone for future extensions.A fitting feature was implemented on ERYA-Bulk to adjust the sample composition to the experimental yield results.

Non-Restoring Array Divider Using Optimized CAS Cells Based on Quantum-Dot Cellular Automata with Minimized Latency and Power Dissipation for Quantum Computing.

Many studies have addressed the physical limitations of complementary metal-oxide semi-conductor (CMOS) technology and the need for next-generation technologies, and quantum-dot cellular automata (QCA) are emerging as a replacement for nanotechnology. Meanwhile, the divider is the most-used circuit in arithmetic operations with squares and multipliers, and the development of effective dividers is crucial for improving the efficiency of inversion and exponentiation, which is known as the most complex operation. In most public-key cryptography systems, the corresponding operations are used by applying algebraic structures such as fields or groups. In this paper, an improved design of a non-restoring array divider (N-RAD) is proposed based on the promising technology of QCA. Our QCA design is focused on the optimization of dividers using controlled add/subtract (CAS) cells composed of an XOR and full adder. We propose a new CAS cell using a full adder that is designed to be very stable and compact so that power dissipation is minimized. The proposed design is considerably improved in many ways compared with the best existing N-RADs and is verified through simulations using QCADesigner and QCAPro. The proposed full adder reduces the energy loss rate by at least 25% compared to the existing structures, and the divider has about 23%~4.5% lower latency compared to the latest coplanar and multilayer structures.

Tailoring the Energy Manifold of Quasi‐Two‐Dimensional Perovskites for Efficient Carrier Extraction

AbstractHarvesting the excess energy from absorbed above bandgap photons is a promising approach to overcome the detailed balance limit for higher solar cell efficiencies. However, this remains very challenging for 2D layered halide perovskites as the fast excess energy loss competes effectively with charge extraction. Herein, the authors engineer the energy cascade manifold of quantum well (QW) states in quasi‐2D Ruddlesden–Popper perovskites by facile tuning of the organic spacer to decelerate the energy loss. The resulting excess energy loss rate is up to two orders slower compared to 3D perovskites, thus enabling efficient carrier extraction. 2D electronic spectroscopy reveals further insights into the structural and energetic disorder of these layered systems. Importantly, a judicious choice of the organic spacer holds the key to tailoring the coherent coupling between QWs that strongly influences the competition between the energy cascade and charge extraction.

Design of the integrated laser welding head with a continuously adjustable focus rotation radius

In this paper, the integrated laser welding head with a continuously adjustable focus rotation radius was achieved by using the output shaft (hollow shaft) of the high-frequency motor as the laser transmission tube for laser transmission, laser deflection and laser focus rotation. The continuous adjustment of the focus rotation radius was achieved by changing the relative phase angle between the two wedge prisms and using a focusing lens. And the function relationship between the focal rotation radius and the relative phase angle of two wedge prisms is verified and modified based on the measured results. The energy loss rate of the 5 kW laser through the inner diameter of the hollow shaft is less than 5% and it has little effect on weld depth. The temperature of the hollow shaft can rise to 57.4 °C only at the entrance of the hollow shaft under the long action time (120 s) of high-power (6 kW) laser. Both the weld forming and porosity defects of 5083 aluminiumalloy can be effectively regulated and controlled by using the integrated laser welding head.