Energy Loss Rate Research Articles

Exploring Exponential Decay Using Limited Resources

Science students need exposure to activities that will help them to become familiar with phenomena exhibiting exponential decay. This paper describes an experiment that allows students to determine the rate of thermal energy loss by a hot object to its surroundings. It requires limited equipment, is safe, and gives reasonable results. Students record the decreasing temperature values displayed by a thermometer, which was initially heated by body contact. The procedure is easy to repeat, taking only 3 min. The students then convert temperature changes into thermal energy losses and plot graphs. Data analysis can be used to teach graphing and ratio interpretation. This experiment can be used by high school or first-year college students in situations where resources or space may be limited or where large student populations dictate a need for uncomplicated experimental procedures, particularly those that minimize the production of chemical waste.

The gravitational wave stress–energy (pseudo)-tensor in modified gravity

The recent detections of gravitational waves by the advanced LIGO and Virgo detectors open up new tests of modified gravity theories in the strong-field and dynamical, extreme gravity regime. Such tests rely sensitively on the phase evolution of the gravitational waves, which is controlled by the energy–momentum carried by such waves out of the system. We here study four different methods for finding the gravitational wave stress–energy pseudo-tensor in gravity theories with any combination of scalar, vector, or tensor degrees of freedom. These methods rely on the second variation of the action under short-wavelength averaging, the second perturbation of the field equations in the short-wavelength approximation, the construction of an energy complex leading to a Landau–Lifshitz tensor, and the use of Noether’s theorem in field theories about a flat background. We apply these methods in general relativity, Jordan–Fierz–Brans–Dicky theoy, and Einstein-Æther theory to find the gravitational wave stress–energy pseudo-tensor and calculate the rate at which energy and linear momentum is carried away from the system. The stress–energy tensor and the rate of linear momentum loss in Einstein-Æther theory are presented here for the first time. We find that all methods yield the same rate of energy loss, although the stress–energy pseudo-tensor can be functionally different. We also find that the Noether method yields a stress–energy tensor that is not symmetric or gauge-invariant, and symmetrization via the Belinfante procedure does not fix these problems because this procedure relies on Lorentz invariance, which is spontaneously broken in Einstein-Æther theory. The methods and results found here will be useful for the calculation of predictions in modified gravity theories that can then be contrasted with observations.

Multiple time scale analysis of pressure oscillations in solid rocket motors

In this study, acoustic pressure oscillations for single and coupled longitudinal acoustic modes in Solid Rocket Motor (SRM) are investigated using Multiple Time Scales (MTS) method. Two independent time scales are introduced. The oscillations occur on fast time scale whereas the amplitude and phase changes on slow time scale. Hopf bifurcation is employed to investigate the properties of the solution. The supercritical bifurcation phenomenon is observed for linearly unstable system. The amplitude of the oscillations result from equal energy gain and loss rates of longitudinal acoustic modes. The effect of linear instability and frequency of longitudinal modes on amplitude and phase of oscillations are determined for both single and coupled modes. For both cases, the maximum amplitude of oscillations decreases with the frequency of acoustic mode and linear instability of SRM. The comparison of analytical MTS results and numerical simulations demonstrate an excellent agreement.

Comprehensive approach to tau-lepton production by high-energy tau neutrinos propagating through the Earth

There has been a recent surge in interest in the detection of $\tau$ lepton-induced air showers from detectors at altitude. When a $\tau$ neutrino ($\nu_\tau$) enters the Earth it produces $\tau$ leptons as a result of nuclear charged current interactions. In some cases, this process results in a $\tau$ lepton exiting the surface of the Earth, which can subsequently decay in the atmosphere and produce an extensive air shower. These upward-going air showers can be detected via fluorescence, optical Cherenkov, or geomagnetic radio emission. Several experiments have been proposed to detect these signals. We present a comprehensive simulation of the production of $\tau$ leptons by $\nu_\tau$'s propagating through Earth to aid the design of future experiments. These simulations for $\nu_\tau$'s and leptons in the energy range from $10^{15}$ eV to $10^{21}$ eV treat the full range of incidence angles from Earth-skimming to diametrically-traversing. Propagation of $\nu_\tau$'s and leptons include the effects of rock and an ocean or ice layer of various thicknesses. The interaction models include $\nu_\tau$ regeneration and account for uncertainties in the Standard Model neutrino cross-section and in the photo-nuclear contribution to the $\tau$ energy loss rate.

Thermodynamic analysis of the human body in different climate regions of Turkey to determine the comfort conditions with exergy method

Thermodynamic analysis of human body is studied to determine the thermal comfort conditions. In this context, exergy and energy analysis in the air conditioning of buildings is necessary for efficient use of energy. Thermodynamic analysis of human body is carried out for seven different climate regions of Turkey based on the use of meteorological parameters such as minimum and maximum and average monthly temperatures, atmospheric pressure and average relative humidity by implementing energy and exergy analysis. Human body, which is the subject of this study, was in the light activity level quantified as 58.2 W/m2. Analysis results have indicated that the major energy loss with 39.28 W/m2 is due to heat transfer with radiation, convection and conduction. Furthermore, the energy loss rates by water vapour diffusion from the skin, respiration, temperature difference and sweating were determined as 11.13 W/m2, 4.29 W/m2, 0.73 W/m2 and 0.02 W/m2, respectively. The maximum exergy consumption rate by the human body was 2.33 W/m2 for the cold and semi dry - less humid climate region (CR-7), while the minimum exergy consumption rate was obtained as 0.91 W/m2 for the hot and semi dry climate region (CR-1). Information presented in this study is expected to contribute to the design of air conditioning systems in order to choose more efficient energy systems.

Thermodynamic analysis of the human body in different climate regions of Turkey to determine the comfort conditions with exergy method

Thermodynamic analysis of human body is studied to determine the thermal comfort conditions. In this context, exergy and energy analysis in the air conditioning of buildings is necessary for efficient use of energy. Thermodynamic analysis of human body is carried out for seven different climate regions of Turkey based on the use of meteorological parameters such as minimum and maximum and average monthly temperatures, atmospheric pressure and average relative humidity by implementing energy and exergy analysis. Human body, which is the subject of this study, was in the light activity level quantified as 58.2 W/m2. Analysis results have indicated that the major energy loss with 39.28 W/m2 is due to heat transfer with radiation, convection and conduction. Furthermore, the energy loss rates by water vapour diffusion from the skin, respiration, temperature difference and sweating were determined as 11.13 W/m2, 4.29 W/m2, 0.73 W/m2 and 0.02 W/m2, respectively. The maximum exergy consumption rate by the human body was 2.33 W/m2 for the cold and semi dry - less humid climate region (CR-7), while the minimum exergy consumption rate was obtained as 0.91 W/m2 for the hot and semi dry climate region (CR-1). Information presented in this study is expected to contribute to the design of air conditioning systems in order to choose more efficient energy systems.

Wind-Wave Breaking

Rational models of wind-wave growth were proposed in the 1950s (Miles 1957, Phillips 1957), theories of wave-wave interactions (Phillips 1960, Hasselmann 1962, Zakharov 1968) and wave-action conservation for waves in fluids (Whitham 1965, Bretherton and Garrett 1969) in the 1960s, but it was not until the 1980s that laboratory experiments (Duncan 1981, Melville and Rapp 1985) and a seminal paper by Owen Phillips in 1985 on a model of the equilibrium range in wind-wave spectra, and a formulation of breaking, began a rational program of research into the role of breaking in surface wave kinematics and dynamics. Two important features of Phillips’ 1985 paper were the introduction of Λ(c)dc, the average total length of breaking fronts per unit area of ocean moving with velocities in the range (c, c + dc) and the statement that the average rate of energy loss per unit area by breakers in the same velocity range was given byɛb(c)dc=b(c)ρg−1c5Λ(c)dcwhere b is a dimensionless breaking strength and g is gravity. The energy loss per unit length of breaker, bρg-1c5, was based on Duncan’s work, but anticipated in part by Lighthill (1978). Lower order moments of Λ(c) describe kinematical features of breaking up to the third moment, with the fourth moment describing the momentum flux from waves to currents. The structure of the dissipation equation imposes a combination of different approaches to quantifying it. Estimates of b have depended on arguments based on Taylor’s (1935) inertial scaling of turbulence dissipation, supported by laboratory experiments and recent DNS and LES numerical experiments, while Λ(c) over any significant dynamical range can only be measured in the field. The success of the early attempts to follow this approach has led to recent work on air entrainment for gas transfer, and theoretical uses of fundamental vortex dynamics to develop our knowledge of the role of breaking in air-sea interaction. In this paper I will review the material from the laboratory, through scaling arguments, modeling and field measurements.

Hot Carriers in CVD-Grown Graphene Device with a Top h-BN Layer

We investigate the energy relaxation of hot carriers in a CVD-grown graphene device with a top h-BN layer by driving the devices into the nonequilibrium regime. By using the magnetic field dependent conductance fluctuations of our graphene device as a self-thermometer, we can determine the effective carrier temperature Te at various driving currents I while keeping the lattice temperature TL fixed. Interestingly, it is found that Te is proportional to I, indicating little electron-phonon scattering in our device. Furthermore the average rate of energy loss per carrier Pe is proportional to (Te 2-TL 2), suggesting the heat diffusion rather than acoustic phonon processes in our system. The long energy relaxation times due to the weak electron-phonon coupling in CVD graphene capped with h-BN layer as well as in exfoliated multilayer graphene can find applications in hot carrier graphene-based devices.

Evolution of intense laser pulse spot size propagating in collisional plasma embedded in magnetic field with variable direction

In this study, propagation of an intense laser pulse through collisional, homogenous, magnetized plasma has been investigated. The plasma is embedded in an external magnetic field with the amplitude and variable direction being constant. The complex dispersion relation of the plasma medium has been obtained that predicates the Faraday rotation effect. The paraxial wave equation has been used for the study of propagation of laser pulse in plasma. The nonlinear current density vector as a source of wave equation is obtained by motion equation and continuity equation of plasma free electrons. Using the source dependent expansion method, the evolution of laser pulse spot size has been investigated. It is shown that the spot size of the laser pulse is dependent on the strength and direction of the external magnetic field significantly. The effect of collision frequency on the evolution of spot size has been studied. The space damping rate of laser pulse power along the propagation length due to collision is obtained. Results show that the increase in the external magnetic field strength increases the rate of laser energy loss.

Radiative decay of the nonlinear oscillations of an adiabatic spherical bubble at small Mach number

A theoretical study is carried out for bubble oscillation in a compressible liquid with significant acoustic radiation based on the Keller–Miksis equation using a multi-scaled perturbation method. The leading-order analytical solution of the bubble radius history is obtained to the Keller–Miksis equation in a closed form including both compressible and surface tension effects. Some important formulae are derived including: the average energy loss rate of the bubble system for each cycle of oscillation, an explicit formula for the dependence of the oscillation frequency on the energy, and an implicit formula for the amplitude envelope of the bubble radius as a function of the energy. Our theory shows that the frequency of oscillation does not change on the inertial time scale at leading order, the energy loss rate on the long compressible time scale being proportional to the Mach number. These asymptotic predictions have excellent agreement with experimental results and the numerical solutions of the Keller–Miksis equation over very long times. A parametric analysis is undertaken using the above formula for the energy of the bubble system, frequency of oscillation and minimum/maximum bubble radii in terms of the dimensionless initial pressure of the bubble gases (or, equivalently, the dimensionless equilibrium radius), Weber number and polytropic index of the bubble gas.

The glitch activity of neutron stars

We present a statistical study of the glitch population and the behaviour of the glitch activity across the known population of neutron stars. An unbiased glitch database was put together based on systematic searches of radio timing data of 898 rotation-powered pulsars obtained with the Jodrell Bank and Parkes observatories. Glitches identified in similar searches of 5 magnetars were also included. The database contains 384 glitches found in the rotation of 141 of these neutron stars. We confirm that the glitch size distribution is at least bimodal, with one sharp peak at approximately $20\, \rm{\mu\,Hz}$, which we call large glitches, and a broader distribution of smaller glitches. We also explored how the glitch activity $\dot{\nu}_{\rm{g}}$, defined as the mean frequency increment per unit of time due to glitches, correlates with the spin frequency $\nu$, spin-down rate $|\dot{\nu}|$, and various combinations of these, such as energy loss rate, magnetic field, and spin-down age. It is found that the activity is insensitive to the magnetic field and that it correlates strongly with the energy loss rate, though magnetars deviate from the trend defined by the rotation-powered pulsars. However, we find that a constant ratio $\dot\nu_{\rm{g}}/|\dot\nu| = 0.010 \pm 0.001$ is consistent with the behaviour of all rotation-powered pulsars and magnetars. This relation is dominated by large glitches, which occur at a rate directly proportional to $|\dot{\nu}|$. The only exception are the rotation-powered pulsars with the highest values of $|\dot{\nu}|$, such as the Crab pulsar and PSR B0540$-$69, which exhibit a much smaller glitch activity, intrinsically different from each other and from the rest of the population. The activity due to small glitches also shows an increasing trend with $|\dot\nu|$, but this relation is biased by selection effects.

Cooling in a dissipative dark sector

The possibility of a subdominant component of dark matter dissipating energy could lead to dramatic new phenomenology such as the formation of a dark disk. One rigorous way to assess this possibility and settle the debate on its feasibility is to include the dissipative dark component in a numerical hydrodynamical simulation. A necessary input to such a simulation is a prescription including energy dissipation rates of different processes and rates of processes that change the number densities of dark ions and atoms. In this article, we study the simplest dissipative dark sector which consists of a dark electron and proton, both charged under a dark gauged U(1). We present approximate analytic formulas for energy loss rates due to Compton scattering, bremsstrahlung, recombination, collisional ionization and collisional excitation as well as the rates of number density change. We also include the heating rate due to photoionization. The work serves as the first step to realize a numerical simulation including a dissipative dark sector, which hopefully can shed more light on the formation and properties of a dark disk originating from dark matter self-interactions.

Towards green computing in wireless sensor networks: Controlled mobility–aided balanced tree approach

SummaryNetwork lifetime maximization has received continuous attention as green computing in wireless sensor networks. Recently, controlled mobility–based green computing has witnessed significant attention from academia and industrial research labs. It is due to the growing number of sensor‐based services in mobility friendly nonhostile environments in our daily life. The intelligent mobility–aided repositioning of sensors is significantly challenging considering the critical constraints including irregular power depletion, static normal sensors, the correlation between sensor position, and coverage and connectivity. In this context, this paper proposes a network lifetime maximization framework based on balanced tree node switching. Specifically, a balanced tree–based network model for wireless sensor networks is designed focusing on energy consumption of sensor nodes in tree‐based networks. The problem of lifetime maximization in tree‐based network is identified considering energy loss rate, path load, and balancing factor. Two node‐shifting algorithms are developed, namely, energy‐based shifting and load‐based shifting for balancing tree‐based network in terms of energy. Analytical and simulation experiment–based comparative performance evaluation attests the benefit of the proposed framework as compared to the state‐of‐the‐art techniques considering a number of energy‐oriented metrics for wireless networks.

Solar atmospheric neutrinos: A new neutrino floor for dark matter searches

As is well known, dark matter direct detection experiments will ultimately be limited by a "neutrino floor," due to the scattering of nuclei by MeV neutrinos from, e.g., nuclear fusion in the Sun. Here we point out the existence of a new "neutrino floor" that will similarly limit indirect detection with the Sun, due to high-energy neutrinos from cosmic-ray interactions with the solar atmosphere. We have two key findings. First, solar atmospheric neutrinos $\lesssim 1$ TeV cause a sensitivity floor for standard WIMP scenarios, for which higher-energy neutrinos are absorbed in the Sun. This floor will be reached once the present sensitivity is improved by just one order of magnitude. Second, for neutrinos $\gtrsim 1$ TeV, which can be isolated by muon energy loss rate, solar atmospheric neutrinos should soon be detectable in IceCube. Discovery will help probe the complicated effects of solar magnetic fields on cosmic rays. These events will be backgrounds to WIMP scenarios with long-lived mediators, for which higher-energy neutrinos can escape from the Sun.

Efficient picosecond x-ray pulse generation from plasmas in the radiation dominated regime

The efficient conversion of optical laser light into bright ultrafast x-ray pulses in laser created plasmas is of high interest for dense plasma physics studies, material science, and other fields. However, the rapid hydrodynamic expansion that cools hot plasmas has limited the x-ray conversion efficiency (CE) to 1% or less. Here we demonstrate more than one order of magnitude increase in picosecond x-ray CE by tailoring near solid density plasmas to achieve a large radiative to hydrodynamic energy loss rate ratio, leading into a radiation loss dominated plasma regime. A record 20% CE into hν>1 keV photons was measured in arrays of large aspect ratio Au nanowires heated to keV temperatures with ultrahigh contrast femtosecond laser pulses of relativistic intensity. The potential of these bright ultrafast x-ray point sources for table-top imaging is illustrated with single shot flash radiographs obtained using low laser pulse energy. These results will enable the deployment of brighter laser driven x-ray sources at both compact and large laser facilities.

Chirality effect on electron phonon relaxation, energy loss, and thermopower in single and bilayer graphene in BG regime

We investigate the energy dependent electron-phonon relaxation rate, energy loss rate, and phonon drag thermopower in single layer graphene (SLG) and bilayer graphene (BLG) under the Bloch-Gruneisen (BG) regime through coupling to acoustic phonons interacting via the Deformation potential in the Boltzmann transport equation approach. We find that the consideration of the chiral nature of electrons alters the temperature dependencies in two-dimensional structures of SLG and BLG from that shown by other conventional 2DEG system. Our investigations indicate that the BG analytical results are valid for temperatures far below the BG limit (∼TBG/4) which is in conformity with a recent experimental investigation for SLG [C. B. McKitterick et al., Phys. Rev. B 93, 075410 (2016)]. For temperatures above this renewed limit (∼TBG/4), there is observed a suppression in energy loss rate and thermo power in SLG, but enhancement is observed in relaxation rate and thermopower in BLG, while a suppression in the energy loss rate is observed in BLG. This strong nonmonotonic temperature dependence in SLG has also been experimentally observed within the BG limit [Q. Ma et al., Phys. Rev. Lett. 112, 247401 (2014)].

Calculation of the decay rate of tachyonic neutrinos against charged-lepton-pair and neutrino-pair Cerenkov radiation

We consider in detail the calculation of the decay rate of high-energy superluminal neutrinos against (charged) lepton pair Cerenkov radiation, and neutrino pair Cerenkov radiation, i.e., against the decay channels and . Under the hypothesis of a tachyonic nature of neutrinos, these decay channels put constraints on the lifetime of high-energy neutrinos for terrestrial experiments as well as on cosmic scales. For the oncoming neutrino, we use the Lorentz-covariant tachyonic relation , where mν is the tachyonic mass parameter. We derive both threshold conditions as well as on decay and energy loss rates, using the plane-wave fundamental bispinor solutions of the tachyonic Dirac equation. Various intricacies of rest frame versus lab frame calculations are highlighted. The results are compared to the observations of high-energy IceCube neutrinos of cosmological origin.

Polarized Balmer line emission from supernova remnant shock waves efficiently accelerating cosmic rays

Linearly polarized Balmer line emissions from supernova remnant shocks are studied taking into account the energy loss of the shock owing to the production of nonthermal particles. The polarization degree depends on the downstream temperature and the velocity difference between upstream and downstream regions. The former is derived once the line width of the broad component of the H$\alpha$ emission is observed. Then, the observation of the polarization degree tells us the latter. At the same time, the estimated value of the velocity difference independently predicts adiabatic downstream temperature that is derived from Rankine-Hugoniot relations for adiabatic shocks. If the actually observed downstream temperature is lower than the adiabatic temperature, there is a missing thermal energy which is consumed for particle acceleration. It is shown that a larger energy loss rate leads to more highly polarized H$\alpha$ emission. Furthermore, we find that polarized intensity ratio of H$\beta$ to H$\alpha$ also depends on the energy loss rate and that it is independent of uncertain quantities such as electron temperature, the effect of Lyman line trapping and our line of sight.

Dielectric breakdown field of strained silicon under hydrostatic pressure

First-principles density functional theory calculations are used to reveal a quantitative relationship between the dielectric breakdown field and hydrostatic pressure of crystalline Si. The electronic band structure, phonon dispersion, and electron scattering rate are computed for pressures from 62.2 kbar (compressive) to -45.6 kbar (tensile) to estimate the rate of kinetic energy gain and loss for the electron. The theoretical dielectric breakdown fields are then determined using the von Hippel–Fröhlich criterion. Compressive stresses lead to a lower breakdown field, while significant increases in the dielectric breakdown field can be achieved by tensile stresses.

The pinching method for Galactic cosmic ray positrons: Implications in the light of precision measurements

Context. Two years ago, the Ams-02 collaboration released the most precise measurement of the cosmic ray positron flux. In the conventional approach, in which positrons are considered as purely secondary particles, the theoretical predictions fall way below the data above 10 GeV. One suggested explanation for this anomaly is the annihilation of dark matter particles, the so-called weakly interactive massive particles (WIMPs), into standard model particles. Most analyses have focused on the high-energy part of the positron spectrum, where the anomaly lies, disregarding the complicated GeV low-energy region where Galactic cosmic ray transport is more difficult to model and solar modulation comes into play. Aims. Given the high quality of the latest measurements by Ams-02, it is now possible to systematically re-examine the positron anomaly over the entire energy range, this time taking into account transport processes so far neglected, such as Galactic convection or diffusive re-acceleration. These might impact somewhat on the high-energy positron flux so that a complete and systematic estimate of the secondary component must be performed and compared to the Ams-02 measurements. The flux yielded by WIMPs also needs to be re-calculated more accurately to explore how dark matter might source the positron excess. Methods. We devise a new semi-analytical method to take into account transport processes thus far neglected, but important below a few GeV. It is essentially based on the pinching of inverse Compton and synchrotron energy losses from the magnetic halo, where they take place, inside the Galactic disc. The corresponding energy loss rate is artificially enhanced by the so-called pinching factor, which needs to be calculated at each energy. We have checked that this approach reproduces the results of the Green function method at the per mille level. This new tool is fast and allows one to carry out extensive scans over the cosmic ray propagation parameters. Results. We derive the positron flux from sub-GeV to TeV energies for both gas spallation and dark matter annihilation. We carry out a scan over the cosmic ray propagation parameters, which we strongly constrain by requiring that the secondary component does not overshoot the Ams-02 measurements. We find that only models with large diffusion coefficients are selected by this test. We then add to the secondary component the positron flux yielded by dark matter annihilation. We carry out a scan over WIMP mass to fit the annihilation cross-section and branching ratios, successively exploring the cases of a typical beyond-the-standard-model WIMP and an annihilation through light mediators. In the former case, the best fit yields a p-value of 0.4% for a WIMP mass of 264 GeV, a value that does not allow to reproduce the highest energy data points. If we require the mass to be larger than 500 GeV, the best-fit χ2 per degree of freedom always exceeds a value of 3. The case of light mediators is even worse, with a best-fit χ2 per degree of freedom always larger than 15. Conclusions. We explicitly show that the cosmic ray positron flux is a powerful and independent probe of Galactic cosmic ray propagation. It should be used as a complementary observable to other tracers such as the boron-to-carbon ratio. This analysis shows also that the pure dark matter interpretation of the positron excess is strongly disfavoured. This conclusion is based solely on the positron data, and no other observation, such as the antiproton flux or the CMB anisotropies, needs to be invoked.