The Limiting of Magnetospheric Convection by Dissipation in the Ionosphere
Limiting magnetospheric convection velocity by energy dissipation in ionosphere
IONOSPHERE↗
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Results for “Dissipation”
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The electromagnetic radiation associated with the energy dissipated by cosmic rays in interstellar hydrogen
Electromagnetic radiation due to cosmic ray energy dissipation in interstellar hydrogen
ENERGY DISSIPATION↗
Multiple mechanisms generate a universal scaling with dissipation for the air-water gas transfer velocity
A large corpus of field and laboratory experiments support the finding that the water side transfer velocity kL of sparingly soluble gases near air-water interfaces scales as k L ~(νε) 1/4 , where ν is the kinematic water viscosity and ε is the mean turbulent kinetic energy dissipation rate. Originally predicted from surface renewal theory, this scaling appears to hold for marine and coastal systems and across many environmental conditions. It is shown that multiple approaches to representing the effects of turbulence on kL lead to this expression when the Kolmogorov microscale is assumed to be the most efficient transporting eddy near the interface. The approaches considered range from simplified surface renewal schemes with distinct models for renewal durations, scaling and dimensional considerations, and a new structure function approach derived using analogies between scalar and momentum transfer. The work offers a new perspective as to why the aforementioned 1/4 scaling is robust.
54 ENVIRONMENTAL SCIENCES↗
Extreme Energy Dissipation via Material Evolution in Carbon Nanotube Mats
Abstract Thin layered mats comprised of an interconnected meandering network of multiwall carbon nanotubes (MWCNT) are subjected to a hypersonic micro‐projectile impact test. The mat morphology is highly compliant and while this leads to rather modest quasi‐static mechanical properties, at the extreme strain rates and large strains resulting from ballistic impact, the MWCNT structure has the ability to reconfigure resulting in extraordinary kinetic energy (KE) absorption. The KE of the projectile is dissipated via frictional interactions, adiabatic heating, tube stretching, and ultimately fracture of taut tubes and the newly formed fibrils. The energy absorbed per unit mass of the film can range from 7–12 MJ kg −1 , much greater than any other material.
36 MATERIALS SCIENCE↗
Dissipative Assembly of Macrocycles Comprising Multiple Transient Bonds
Abstract Dissipative assembly has great potential for the creation of new adaptive chemical systems. However, while molecular assembly at equilibrium is routinely used to prepare complex architectures from polyfunctional monomers, species formed out of equilibrium have, to this point, been structurally very simple. In most examples the fuel simply effects the formation of a single short‐lived covalent bond. Herein, we show that chemical fuels can assemble bifunctional components into macrocycles containing multiple transient bonds. Specifically, dicarboxylic acids give aqueous dianhydride macrocycles on treatment with a carbodiimide. The macrocycles are assembled efficiently as a consequence of both fuel‐dependent and fuel‐independent mechanisms; they undergo slower decomposition, building up as the fuel recycles the components, and are a favored product of the dynamic exchange of the anhydride bonds. These results create new possibilities for generating structurally sophisticated out‐of‐equilibrium species.
Hossain, Mohammad Mosharraf↗
DC conductivities from non-relativistic scaling geometries with momentum dissipation
Here, we consider a gravitational theory with two Maxwell fields, a dilatonic scalar and spatially dependent axions. Black brane solutions to this theory are Lifshitz-like and violate hyperscaling. Working with electrically charged solutions, we calculate analytically the holographic DC conductivities when both gauge fields are allowed to fluctuate. We discuss some of the subtleties associated with relating the horizon to the boundary data, focusing on the role of Lifshitz asymptotics and the presence of multiple gauge fields. The axionic scalars lead to momentum dissipation in the dual holographic theory. Finally, we examine the behavior of the DC conductivities as a function of temperature, and comment on the cases in which one can obtain a linear resistivity.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Intrinsic Quantum Dissipation in Superconducting Weak Links
We evaluate the frequency spectrum for an intrinsic quantum dissipative environment for the Josephson phase φ formed by subgap Andreev bound states in superconducting weak links. We also analyze the problem of macroscopic quantum tunneling (MQT) of φ in highly transparent weak links and identify several MQT regimes. Within the exponential accuracy, we derive the expression for the supercurrent quantum decay rate both at low temperatures and in the vicinity of the quantum-to-classical crossover.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
The Case of Integrable Systems with Dissipation on the Tangent Bundle of a Multidimensional Sphere
We establish the integrability of dynamical systems of some classes arising in multidimensional dynamics. The force fields under consideration possess the so-called variable dissipation with zero mean and generalize the studied earlier ones.
97 MATHEMATICS AND COMPUTING↗
Integrable Systems with Dissipation and Two and Three Degrees of Freedom
We establish the integrability for some classes of dynamic systems on the tangent bundles of two– and three-dimensional manifolds (systems with two and three degrees of freedom). The force fields possess the so-called variable dissipation and generalize those considered in the previous publications of the author.
97 MATHEMATICS AND COMPUTING↗
Integrable Dynamic Systems with Dissipation and Finitely Many Degrees of Freedom
We establish the integrability for some classes of dynamic systems on the tangent bundles of multidimensional manifolds. We consider the case where the force fields possess variable dissipation. An example of a four-dimensional manifold is discussed in detail.
97 MATHEMATICS AND COMPUTING↗
Dissipation-Induced Instabilities in Magnetized Flows
We study local instabilities of a differentially rotating viscous flow of electrically conducting incompressible fluid subject to an external azimuthal magnetic field. A hydrodynamically stable flow can be destabilized by the magnetic field both in an ideal and a viscous and resistive system giving rise to the azimuthal magnetorotational instability. A special solution to the equations of ideal magnetohydrodynamics characterized by the constant total pressure, the fluid velocity parallel to the direction of the magnetic field, and by the magnetic and kinetic energies that are finite and equal—the Chandrasekhar equipartition solution—is marginally stable in the absence of viscosity and resistivity. Performing a local stability analysis, we find the conditions under which the azimuthal magnetorotational instability can be interpreted as a dissipation-induced instability of the Chandrasekhar equipartition solution.
97 MATHEMATICS AND COMPUTING↗
Resonance Vibration and Dissipative Heating of a Flexible Viscoelastic Beam with Piezoactuators in the Presence of Shear Strains
We consider a problem of forced resonance vibration and dissipative heating of a hinged flexible viscoelastic beam with piezoactuators in the presence of transverse shear strains. The effects of geometric nonlinearities, in-plane shear strains, and the conditions of heat exchange on the surfaces on the amplitude and temperature-frequency characteristics of the forced vibration of the beam and the thermal failure of the system are investigated. The possibility of active damping of the mode of flexural vibrations by piezoactuators is analyzed.
97 MATHEMATICS AND COMPUTING↗
Efficiency at Maximum Power of Dissipative Thermoelectric Generators: A Finite-time Thermodynamic Analysis
In this paper we analyze the thermodynamic efficiency expected for a fully dissipative thermoelectric generator (TEG) operating under stationary conditions at a finite rate. Although a finite-time thermodynamic analysis of TEGs has been aimed at since long time, no complete theory is available yet. The state of the art of theory is reviewed, and a simple expression for the maximum achievable efficiency of TEGs operating under fully irreversible conditions is obtained. This also sets a reference efficiency for forthcoming studies of nonstationary operation of TEGs.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Calibration approach and range of observed sap flow influences transpiration estimates from thermal dissipation sensors
Calibrating thermal dissipation (TD) sap flow sensors has become increasingly important to accurately estimate whole-tree transpiration, but it is unclear how the calibration approach itself influences the resulting coefficients and estimates. Here, we compare the two most common calibration approaches, gravimetric and potometric, using TD sensors inserted into Eucalyptus benthamii tree stems. The gravimetric approach uses an excised stem segment devoid of branches and leaves and pushes water through the stem using gravity, a positive force. The potometric approach uses a severed stem containing an intact canopy placed upright in a reservoir where water is pulled through the stem via transpiration, a negative force. We hypothesized that the positive pressure associated with gravimetric calibration would overestimate conductive sapwood area relative to that estimated from potometric calibration and that coefficients from these different approaches would result in different estimates of transpiration when applied to intact trees. We also predicted that calibrations could improve transpiration estimates by targeting the range of observed sap flow rates (i.e., K values) in intact trees. Conductive sapwood area was higher under gravimetric calibrations and resulting estimates of transpiration were lower compared to potometric calibrations. Segmented calibration curves, which fit two separate curves for the relationship between sap flux density (Fd) and sap flux index (K) based on the range of sap flow rates observed in intact trees, increased transpiration estimates from both gravimetric and potometric coefficients and diminished the magnitude of difference in transpiration estimates between approaches. Researchers should be aware that calibration approach and range of observed sap flow profoundly influences transpiration estimates from TD sensors and this likely applies to calibrations of other heat-based sap flow sensors.
54 ENVIRONMENTAL SCIENCES↗
Non-dissipative electromagnetic media with two Lorentz null cones
We study Maxwell's equations on a 4-manifold where the electromagnetic medium is modeled by an antisymmetric (2/2 )-tensor with 21 real coefficients. In this setting the Fresnel surface is a fourth-order polynomial surface that describes the dynamical response of the medium in the geometric optics limit. For example, in an isotropic medium the Fresnel surface is a Lorentz null cone. The contribution of this paper is the pointwise description of all electromagnetic medium tensors {kappa} with real coefficients that satisfy the following three conditions: (i)medium {kappa} is invertible, (ii)medium {kappa} is skewon-free, or non-dissipative, (iii)the Fresnel surface of {kappa} is the union of two distinct Lorentz null cones. We show that there are only three classes of media with these properties and give explicit expressions in local coordinates for each class. - Highlights: Black-Right-Pointing-Pointer We find two new electromagnetic media classes for which the Fresnel surface decomposes into two light cones. Black-Right-Pointing-Pointer In a suitable setting we classify all electromagnetic media where this is the case. Black-Right-Pointing-Pointer We find an electromagnetic medium tensor with three different signal speeds in one direction. Black-Right-Pointing-Pointer The work is related to [5], which classifies all media with one light cone (in a suitable setting).
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Dissipative tunnelling by means of scaled trajectories
Dissipative quantum tunnelling through an inverted parabolic barrier is considered in the presence of an electric field. A Schrödinger–Langevin or Kostin quantum–classical transition wave equation is used and applied resulting in a scaled differential equation of motion. A Gaussian wave packet solution to the resulting scaled Kostin nonlinear equation is assumed and compared to the same solution for the scaled linear Caldirola–Kanai equation. The resulting scaled trajectories are obtained at different dynamical regimes and friction cases, showing the gradual decoherence process in this open dynamics. Theoretical results show that the transmission probabilities are always higher in the Kostin approach than in the Caldirola–Kanai approach in the presence or not of an external electric field. This discrepancy should be understood due to the presence of an environment since the corresponding open dynamics should be governed by nonlinear quantum equations, whereas the second approach is issued from an effective Hamiltonian within a linear theory.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Contact manifolds and dissipation, classical and quantum
Motivated by a geometric decomposition of the vector field associated with the Gorini–Kossakowski–Lindblad–Sudarshan (GKLS) equation for finite-level open quantum systems, we propose a generalization of the recently introduced contact Hamiltonian systems for the description of dissipative-like dynamical systems in the context of (non-necessarily exact) contact manifolds. In particular, we show how this class of dynamical systems naturally emerges in the context of Lagrangian Mechanics and in the case of nonlinear evolutions on the space of pure states of a finite-level quantum system.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
An average stochastic approach to two-body dissipation in finite fermion systems
We present average stochastic time-dependent Hartree–Fock (ASTDHF) as a theory for efficient handling of incoherent dynamical correlations in finite fermion systems at fully quantum-mechanical level. The basic time evolution is given by time-dependent mean-field theory. The two-body collisions beyond mean-field propagation are evaluated stochastically in an incoherent ensemble of mean-field states as was done in the previously developed STDHF. The new, and time saving, feature in ASTDHF is that it employs one common mean field throughout the whole ensemble. A detailed presentation of ASTDHF is given and extensive comparison with STDHF and other approaches to dissipation are discussed. ASTDHF is found to be a very efficient approach for well bound systems where mean-field fluctuations remain small.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗