Non-dissipative Processes Research Articles

Experimental study of thermomechanical behaviour of Gum Metal during cyclic tensile loadings: the quantitative contribution of IRT and DIC

ABSTRACT Thermomechanical behaviour of Gum Metal (Ti–23Nb–0.7Ta–2.0Zr–1.2O, at.%) under cyclic tension was experimentally investigated using infrared thermography and digital image correlation. The thermomechanical characteristics of particular stages of the subsequent loading-unloading cycles of Gum Metal were identified, i.e. (I) the linear, elastic loading accompanied by the temperature drop, (II) the nonlinear super-elastic loading related to the temperature growth, (III) the transient stage (at which both the superelastic-like behaviour and the plastic one are present simultaneously) and the temperature starts growing fast, (IV) the plastic deformation with a significant growth of temperature, (V) the superelastic-like unloading accompanied by a fast drop in temperature, (VI) the transient unloading with a slower decrease in temperature and (VII) the elastic unloading, with a slight increase in temperature. Thermoelastic effect in Gum Metal during both loading and unloading was analysed in each tensile cycle. Finally, the evolution of strain and temperature fields just before unloading in each cycle was discussed and a comparison of the fields at selected stages of cycles 12 and 24 was presented. The results of this work enabled us to identify the non-dissipative processes of elastic and superelastic-like deformations as well as the dissipative process of plastic deformation.

Relative population of states in Mg21 from few-nucleon removal reactions

Nuclear reactions with intermediate-energy beams in which three, four, and five nucleons are removed are expected to proceed through a combination of nondissipative and statistical processes. In an experiment at the National Superconducting Cyclotron Laboratory, in-beam $\ensuremath{\gamma}$-ray spectroscopy was utilized to study few-nucleon removal reactions from incoming beams of $^{24}\mathrm{Mg}, ^{25}\mathrm{Al}$, and $^{26}\mathrm{Si}$ projectiles to the same reaction product, $^{21}\mathrm{Mg}$. New $\ensuremath{\gamma}$-ray transitions and $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences in $^{21}\mathrm{Mg}$ were established using the CsI(Na) array CAESAR and the inclusive cross section for three-neutron removal from $^{24}\mathrm{Mg}$ was measured. Significant differences in the relative population of states in $^{21}\mathrm{Mg}$ from $^{25}\mathrm{Al}$ compared to $^{26}\mathrm{Si}$ were observed and found to be correlated with the spins of the $^{21}\mathrm{Mg}$ states. As a result, this intermediate regime between direct and statistical nucleon removal may have potential as a tool to deliver unique patterns of level populations in fast-beam experiments and alter isomer to ground state ratios in the production of exotic beams.

Microwave Dynamical Conductivity in the Quantum Hall Regime.

Dynamical conductivity contains information of dissipative and nondissipative processes induced by ac-electric fields. In the integer quantum Hall (QH) effect where the nondissipative Hall current is the most prominent feature, its robustness is assured by localized states within the Landau levels. We establish a noncontact method with a circular cavity resonator and detect the real and imaginary parts of the longitudinal and Hall conductivities at a microwave frequency in magnetic fields. The conventional Shubnikov-de Haas oscillations and QH plateaus are observed in the real parts of longitudinal and Hall conductivities, respectively, while periodic structures can be seen in the imaginary parts which are scaled by the QH filling factor. The latter originates from intra-Landau level transitions between different orbital angular momenta. The results demonstrate that the dynamical conductivity measurement provides microscopic information which is not accessible by conventional static methods. The present noncontact method would pave the way to reveal the electron dynamics in other two-dimensional systems such as twisted bilayer graphene.

Variational principles and nonequilibrium thermodynamics.

Variational principles play a fundamental role in deriving the evolution equations of physics. They work well in the case of non-dissipative evolution, but for dissipative systems, the variational principles are not unique and not constructive. With the methods of modern nonequilibrium thermodynamics, one can derive evolution equations for dissipative phenomena and, surprisingly, in several cases, one can also reproduce the Euler-Lagrange form and symplectic structure of the evolution equations for non-dissipative processes. In this work, we examine some demonstrative examples and compare thermodynamic and variational techniques. Then, we argue that, instead of searching for variational principles for dissipative systems, there is another viable programme: the second law alone can be an effective tool to construct evolution equations for both dissipative and non-dissipative processes. This article is part of the theme issue 'Fundamental aspects of nonequilibrium thermodynamics'.

Wave energy attenuation in fields of colliding ice floes – Part 1: Discrete-element modelling of dissipation due to ice–water drag

Abstract. The energy of water waves propagating through sea ice is attenuated due to non-dissipative (scattering) and dissipative processes. The nature of those processes and their contribution to attenuation depends on wave characteristics and ice properties and is usually difficult (or impossible) to determine from limited observations available. Therefore, many aspects of relevant dissipation mechanisms remain poorly understood. In this work, a discrete-element model (DEM) is used to study one of those mechanisms: dissipation due to ice–water drag. The model consists of two coupled parts, a DEM simulating the surge motion and collisions of ice floes driven by waves and a wave module solving the wave energy transport equation with source terms computed based on phase-averaged DEM results. The wave energy attenuation is analysed analytically for a limiting case of a compact, horizontally confined ice cover. It is shown that the usage of a quadratic drag law leads to non-exponential attenuation of wave amplitude a with distance x, of the form a(x)=1/(αx+1/a0), with the attenuation rate α linearly proportional to the drag coefficient. The dependence of α on wave frequency ω varies with the dispersion relation used. For the open-water (OW) dispersion relation, α∼ω4. For the mass loading dispersion relation, suitable for ice covers composed of small floes, the increase in α with ω is much faster than in the OW case, leading to very fast elimination of high-frequency components from the wave energy spectrum. For elastic-plate dispersion relation, suitable for large floes or continuous ice, α∼ωm within the high-frequency tail, with m close to 2.0–2.5; i.e. dissipation is much slower than in the OW case. The coupled DEM–wave model predicts the existence of two zones: a relatively narrow area of very strong attenuation close to the ice edge, with energetic floe collisions and therefore high instantaneous ice–water velocities, and an inner zone where ice floes are in permanent or semi-permanent contact with each other, with attenuation rates close to those analysed theoretically. Dissipation in the collisional zone increases with an increasing restitution coefficient of the ice and with decreasing floe size. In effect, two factors contribute to strong attenuation in fields of small ice floes: lower wave energy propagation speeds and higher relative ice–water velocities due to larger accelerations of floes with smaller mass and more collisions per unit surface area.

Electric power generation using acoustic helical wavefronts in air

Acoustic Vortices (AV) are able to transfer angular momentum to matter and induce rotation to objects with different geometries. Several applications of this feature has already been reported. However, up to our knowledge, the possibility of generating electric power using this type of wavefronts has not been reported. In this work, we present experimental results on the electric power produced by a small generator coupled to a propeller of four blades that is insonified by an acoustic vortex beam of topological charge + 1. The AV is produced using a multitransducer of 123 commercially available emitters driven with a continuous signal of 20 Vpp at 40 kHz in air. The propeller was located 40 mm far from the multitransducer, perpendicular to the principal axis of the AV. A voltage of 6 mV was observed at the electric terminals. A discussion on the obtained efficiency of the conversion is presented. Also, the possibility of harvesting residual acoustic energy by means of wave-matter exchange of linear and/or angular momentum is discussed. Special attention is paid to non-dissipative processes.

On relativistic generalization of Perelman\u2019s W-entropy and thermodynamic description of gravitational fields and cosmology

Using double 2+2 and 3+1 nonholonomic fibrations on Lorentz manifolds, we extend the concept of W-entropy for gravitational fields in general relativity (GR). Such F- and W-functionals were introduced in the Ricci flow theory of three dimensional (3-d) Riemannian metrics by Perelman (the entropy formula for the Ricci flow and its geometric applications. arXiv:math.DG/0211159). Non-relativistic 3-d Ricci flows are characterized by associated statistical thermodynamical values determined by W-entropy. Generalizations for geometric flows of 4-d pseudo-Riemannian metrics are considered for models with local thermodynamical equilibrium and separation of dissipative and non-dissipative processes in relativistic hydrodynamics. The approach is elaborated in the framework of classical field theories (relativistic continuum and hydrodynamic models) without an underlying kinetic description, which will be elaborated in other work. The 3+1 splitting allows us to provide a general relativistic definition of gravitational entropy in the Lyapunov–Perelman sense. It increases monotonically as structure forms in the Universe. We can formulate a thermodynamic description of exact solutions in GR depending, in general, on all spacetime coordinates. A corresponding 2+2 splitting with nonholonomic deformation of linear connection and frame structures is necessary for generating in very general form various classes of exact solutions of the Einstein and general relativistic geometric flow equations. Finally, we speculate on physical macrostates and microstate interpretations of the W-entropy in GR, geometric flow theories and possible connections to string theory (a second unsolved problem also contained in Perelman’s work) in Polyakov’s approach.

Finite Element Modeling (FEM) of the Effects of Elastic Buffer Layer on the Stability of a-Si Thin Film Patterned Li-Ion Anode

Lithium ion batteries with improved capacity and cycling performance are being envisaged as the most promising energy storage device for applications ranging from cell phones, laptop computers to car batteries. Tremendous research effort has been directed towards finding better alternatives to traditional graphite based anodes in Li-ion batteries that exhibit a limited capacity of ~370 mAh/g. Amorphous Si (a-Si) thin film have showed promise as the next-generation anodes for Li-ion batteries due to their high electrochemical capacity (~3600 mAh/g) [1]. However, the colossal volume expansion induced stresses leads to delamination of the thin film from underlying current collector rendering the anode non-functional. To suppress the thin film delamination, researchers have created patterned a-Si thin film anodes with width less than the average crack spacing observed in the continuous a-Si thin film anode. Another approach that has not received much attention is the multi-layered engineering of current collector. Datta et al. [2] have shown that insertion of soft layer of carbon between the Cu current collector and a-Si thin film improved the mechanical integrity and capacity retention of the electrode. Choi et al. [3] further demonstrated a current collector made by coating porous polyolefin polymer membrane with a thin layer of Cu. Polymer membrane has also shown to provide flexibility to the current collector, which assists the electrode performance by allowing it to freely expand and contract during electrode cycling. Thus, presence of soft elastic layer along with the current collector and Si thin film can enhance the anode system performance. However, detailed knowledge of the various mechanisms operative in the presence of soft elastic layer is still not very well understood. We have developed a multi-physics based finite element framework to study the influence of different design parameters on the mechanical integrity of patterned Si film based anodes [4]. This model will be utilized to predict the effect of insertion of the thin elastic buffer layer and other design parameters on the mechanical performance of the patterned anode under electrochemical cycling (Figure 1). The energies associated with the dissipative and non-dissipative processes will be quantified to explain the role of various mechanical events during electrochemical cycling. Qualitative comparison of the executed simulation studies with the experimental results will be made. Outcomes from this study are expected to aid in the fabrication of improved a-Si thin film patterned anodes.

Quantum phase transition in a pseudo-Hermitian Dicke model

We show that a Dicke-type non-Hermitian Hamiltonian admits entirely real spectra by mapping it to the "dressed Dicke model" through a similarity transformation. We find a positive-definite metric in the Hilbert space of the non-Hermitian Hamiltonian so that the time evolution is unitary and allows a consistent quantum description. We then show that this non-Hermitian Hamiltonian describing nondissipative quantum processes undergoes quantum phase transition. The exactly solvable limit of the non-Hermitian Hamiltonian has also been discussed.

On modelling electromagnetomechanical interactions in deformable solids

We revisit the notion of electromagnetomechanical interactions in a general continuum, recalling first the microscopic approach in the manner of Lorentz, and then passing to a continuum via some average. The source terms thus obtained may be carried in a direct approach to the balance laws of continuum thermomechanics. A second approach consists in exploiting a generalized form of the principle of virtual power. Finally, using a variational principle of the Hamiltonian-Lagrangian form is also mentioned, although necessarily limited to nondissipative processes but presenting also some advantages (in computations, studies of stability). The common features and contrasted ones between these approaches are emphasized. It is believed that this paves the way for further modelling of this type of complex continua while accounting for the most recent works in the field as well as the author’s past works.

Representation for stress from a stressed reference configuration

There are several problems wherein it would be convenient to have representations for the stress from a stressed configuration as reference. We assume that the body undergoes finite elastic deformations (i.e., non-dissipative processes) from a stressed reference configuration but it is possible that a dissipative (inelastic) process could be the cause for the origin of the stresses in the reference configuration. We restrict ourselves to determining the representation for the stress in a body, from a stressed reference configuration, whose symmetry group in the stress free configuration (that is accessible from the stressed reference configuration) coincides with the full orthogonal group. We also find restrictions on the constitutive relation so that we have a model that exhibits physically acceptable response characteristics.

Regular Couplings of Dissipative and Anti-Dissipative Unbounded Operators, Asymptotics of the Corresponding Non-Dissipative Processes and the Scattering Theory

In this paper a triangular model of a class of unbounded non-selfadjoint K r -operators A presented as a coupling of dissipative and anti-dissipative operators in a Hilbert space with real absolutely continuous spectra and with different domains of A and A * is considered. The asymptotic behaviour of the corresponding non-dissipative processes T t f = e itA f, generated from the semigroups T t with generators iA, as t → ± ∞ are obtained. The strong wave operators, the scattering operator for the couple (A*, A) and the similarity of A and the operator of multiplication by the independent variable are obtained explicitly. The considerations are based on the triangular models and characteristic functions of A. Kuzhel for unbounded operators and the limit values of the multiplicative integrals, describing the characteristic function of the considered model.

The Lack of Structural and Dynamical Evolution of Elliptical Galaxies since z ~ 1.5: Clues from Self-Consistent Hydrodynamic Simulations

We present results of a study on the evolution of the parameters characterizing the structure and dynamics of the relaxed elliptical-like objects (ELOs) identified at z=0, z=1 and z=1.5 in a set of hydrodynamical, self-consistent simulations operating in the context of a concordance cosmological model. The values of the stellar mass, the stellar half-mass radius and the stellar mean-square velocity have been measured in each ELO and found to populate, at any z, a flattened ellipsoid close to a plane (the dynamical plane, DP). Our simulations indicate that, at the intermediate zs considered, individual ELOs evolve, increasing the values of these parameters as a consequence of on-going mass assembly, but, nevertheless, their DP is roughly preserved within its scatter, in agreement with observations of the Fundamental Plane of ellipticals at different zs. We briefly discuss how this lack of significant dynamical and structural evolution in ELO samples arises, in terms of the two different phases operating in the mass aggregation history of their dark matter halos. According with our simulations, most dissipation involved in ELO formation takes place at the early violent phase, causing the stellar mass, the stellar half-mass radius and the stellar mean-square velocity parameters to settle down to the DP, and, moreover, the transformation of most of the available gas into stars. In the subsequent slow phase, ELO stellar mass growth preferentially occurs through non-dissipative processes, so that the DP is preserved and the ELO star formation rate considerably decreases. These results hint, for the first time, to a possible way of explaining, in the context of cosmological simulations, different apparently paradoxical observational results on ellipticals.

Towards a theory of the organism.

A tentative theory of the organism is derived from McClare's (1971) notion of stored energy and Denbigh's (1951) thermodynamics of the steady state, as a dynamically closed, energetically self-sufficient domain of cyclic non-dissipative processes coupled to irreversible dissipative processes. This effectively frees the organism from thermodynamic constraints so that it is poised for rapid, specific intercommunication, enabling it to function as a coherent whole. In the ideal, the organism is a quantum superposition of coherent activities over all space-time domains, with instantaneous (nonlocal) noiseless intercommunication throughout the system. Evidence for quantum coherence is considered and reviewed.

On the symmetry of logic

Embedding logical operations in non-dissipative physical processes requires the use of reversible logic. Following Feynman's (1986) approach, the sixteen distinct truth tables of classical logic are shown to be contained in the 8! reversible logic operations covered by the symmetric group S8, which permute the eight values of three logical variables. Small subgroups of S8 are shown to cover, respectively, reversible logic, reversible switching and reversible arithmetic. A new universal primitive is found which generates a covering group of reversible logic. It is shown that the octahedral group in four dimensions covers both reversible logic and switching and, hence, that the orthogonal group O(4) provides a covering group for quantum gates.

REVERSIBLE AND NON-DISSIPATIVE PROCESSES

Journal Article REVERSIBLE AND NON-DISSIPATIVE PROCESSES Get access J. L. ERICKSEN J. L. ERICKSEN 5378 Buckskin Bob Lane, Florence, Oregon 97439, USA Search for other works by this author on: Oxford Academic Google Scholar The Quarterly Journal of Mechanics and Applied Mathematics, Volume 45, Issue 4, November 1992, Pages 545–554, https://doi.org/10.1093/qjmam/45.4.545 Published: 01 November 1992 Article history Received: 18 December 1991 Published: 01 November 1992

Coupled acoustic–optic modes in deformable ferroelectrics

Based on a fully Galilean electrodynamics of ferroelectric dielectric deformable bodies and the equations for weak fields linearized about an initial rigid-body ferroelectric state with hexagonal symmetry deduced in a previous paper (in which a symmetry breaking was exhibited), a rather complete study of coupled, dispersive, and attenuated bulk wave-propagation modes is presented. Apart from usual optic modes, resonance couplings and repulsion of branches for acoustic modes and polaritons are exhibited for various directions of propagation (longitudinal, orthogonal, and arbitrary settings of the bias polarization field). A birefringence effect for polaritons and an acoustical activity are placed in evidence. In addition to the analytical study which leans on the use of small coupling parameters in order to allow for a manageable discussion of the dispersion behavior for both nondissipative and dissipative processes, and to illustrate these theoretical results, numerical estimates and plots of the most interesting coupling effects are given for a test material such as ferroelectric barium titanate.

On the dynamics of superfluid vorticity in non-dissipative processes

We investigate the consequences of the possible existence of superfluid vorticity on the Landau two-fluid equations. Assuming a conservation law for superfluid circulation, we show that in non-dissipative situations, the superfluid vorticity is swept along by the normal fluid.