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preprint2024arXiv

On the energy spectrum evolution of electrons undergoing radiation cooling

Radiative cooling of electron beams interacting with counter-propagating electromagnetic waves is analyzed, taking into account the quantum modification of the radiation friction force. Central attention is paid to the evolution of the energy spectrum of electrons accelerated by the laser wake field acceleration mechanism. As an electron beam loses energy to radiation, the mean energy decreases and the form of the energy distribution also changes due to quantum-mechanical spectral broadening.

preprint2024arXiv

Wave-Particle Duality of Ultrasound: Acoustic Softening Explained by Particle Treatment of Ultrasonic Wave

When ultrasonic wave is irradiated on materials, a small static stress is required to get materials yielding and flowing. This is called acoustic softening effect, also known as Blaha effect for a long time. In the past, this effect was explained by several continuum scale or meso-scale solid mechanics theories such as stress superposition or energy superposition theory, or crystal/dislocation plasticity. Due to a lot of microscopic complexities happening inside the materials during ultrasonic vibration, fully understanding of acoustic softening effect is not easy. In this paper, traditional solid mechanics theory is expanded by introducing several concepts in semi-conductor physics. Four new aspects were introduced to understand acoustic softening effect. Firstly, contrary to most existed work in acoustic softening research area which treats ultrasound as waves, it was treated as particles. Secondly, crystal/dislocation plastic theory was simplified to a single equation. Thirdly, concepts of photoelectric effect or photo-voltaic effect were introduced. Analogy of electron movement due to light wave and defect movement due to ultrasonic wave was illustrated. Particularly, as light wave is treated as photon, ultrasonic wave is treated as phonon in this paper. Fourthly, defects such as point defects or line defects are assumed to have certain bonding energy. Their bonding energies are assumed to be quantized or discontinuous. The band gap theory used in photo-voltaic theory is embraced to understand defects movements in solid mechanics due to ultrasonic phonon.

preprint2023arXiv

Boundless metamaterial experimentation: physical realization of a virtual periodic boundary condition

We experimentally implement a virtual geometric periodicity in an elastic metamaterial. First, unwanted boundary reflections at the domain ends are cancelled through the iterative injection of the polarity reversed, reflected wavefield. The resulting boundless experimental state allows for a much better analysis of the metamaterials influence on the propagating wavefield. Subsequently, the propagating wavefield exiting on one end of the structure is reintroduced at the opposite end, creating a virtual geometric periodicity. We find that the experimentally observed band gap converges to the analytical solution through the introduction of the virtual periodicity. The established workflow introduces a novel approach to the experimental investigation and validation of metamaterial prototypes in the presence of strongly dispersive wave propagation and internal scattering. The fully data driven, ad-hoc treatment of boundary conditions in metamaterial experimentation with arbitrary mechanical properties enables reflection suppression, virtual periodicity, and the introduction of more general fictitious boundaries.

preprint2022arXiv

Self-consistent magnetic fields and currents

The possibility of the existence of quasi-stationary electromagnetic fields in plasma supported by their own self-consistent current follows from Maxwell's equations with field sources. These equations also give rise to a wave equation for the density of a self-consistent current and a nonlinear kinematic equation for the velocity of electric charges, from which follows the possibility of excitation of a "magnetic dynamo" and localized rotating plasma structures having a magnetic field. An analytical boundary condition for the excitation or attenuation of turbulence and "magnetic dynamo" is obtained.

preprint2023arXiv

Overcoming non-radiative losses with AlGaAs PIN junctions for near-field thermophotonic energy harvesting

In a thermophotonic device used in an energy-harvesting configuration, a hot light-emitting diode (LED) is coupled to a photovoltaic (PV) cell by means of electroluminescent radiation in order to produce electrical power. Using fluctuational electrodynamics and the drift-diffusion equations, we optimise a device made of an AlGaAs PIN LED and a GaAs PIN PV cell with matched bandgaps. We find that the LED can work as an efficient heat pump only in the near field, where radiative heat transfer is increased by wave tunnelling. A key reason is that non-radiative recombination rates are reduced compared to radiative ones in this regime. At 10 nm gap distance and for 100 cm.s --1 effective surface recombination velocity, the power output can reach 2.2 W.cm --2 for a 600 K LED, which highlights the potential for low-grade energy harvesting.

preprint2024arXiv

A proposal for a minimal model of free reed

In this paper we propose a minimal model for free reeds taking into account the significant phenomena. This free reed model may be used to build models of free reed instruments which permit numerical simulations. Several definitions for the section by which the airflow passes through the reed are reviewed and a new one is proposed which takes into account the entire escape area under the reed and the reed thickness. To derive this section, it is necessary to distinguish the neutral section (the only section of the reed which always keeps its length constant while moving) from the upstream or downstream sections. A minimal configuration is chosen to permit the instabilities of both (-,+) and (+,-) reeds on the basis of a linear analysis of instabilities conditions. This configuration is used to illustrate, with temporal simulations, the minimal model for both kinds of reeds and to discuss the model assumptions. Some clues are given about the influence, on the playing frequency and on the dynamic of the sound, of two main parameters of the geometrical model: the size of the volume and the level of the excitation. It is shown that the playing frequency of a (+,-) reed can vary in a large range according to the size of the volume upstream of the reed; that the playing frequency is nearly independent of the excitation but that the dynamic of the sound increases with the excitation level. Some clues are also proposed to determine the nature of the bifurcation for free reeds: it seems that free reeds may present inverse bifurcations. The influence of the reed thickness is also studied for configurations where the reed length or the reed width vary to keep the mass constant. This study shows that the reed thickness can have a great influence on the sound magnitude, the playing frequency and the magnitude of the reed displacement which justifies its introduction in the reed model.This article has been published in Acta Acustica united with Acustica, Vol. 93 (2007), p. 122-144.

preprint2011arXiv

The True-Twin microcalorimeter: a proof-of-concept experiment

We present a proof-of-concept experiment to realize microwave primary power standard with a true-twin microcalorimeter. Double feeding line microcalorimeters are widely used by National Metrology Institutes. A drawback concerns the system calibration: traditional processes changes measurement conditions between system characterization and the measurement stage. Nevertheless, if the feeding lines are made twin, a measurement scheme that avoids separate characterization can be applied, equations simplify and time consumption is halved. Here we demonstrates the feasibility of the idea. The result of an effective efficiency spectroscopy of a thermoelectric power sensor is compared with figures obtained with well established methods.

preprint2022arXiv

One-particle engine with a porous piston

We propose a variation of the classical Szilard engine that uses a porous piston. Such an engine requires neither information about the position of the particle, nor the removal and subsequent insertion of the piston when resetting the engine to continue doing work by lifting a mass against a gravitational field. Though the engine operates in contact with a single thermal reservoir, the reset mechanism acts as a second reservoir, dissipating energy when a mass that has been lifted by the engine is removed to initiate a new operation cycle.

preprint2022arXiv

Planetary systems with forces other than gravitational forces

A discrete and exact algorithm for obtaining planetary systems is derived in a recent article (Eur. Phys. J. Plus 2022, 137:99). Here the algorithm is used to obtain planetary systems with forces different from the Newtonian inverse square gravitational forces. A Newtonian planetary system exhibits regular elliptical orbits, and here it is demonstrated that a planetary system with pure inverse forces also is stable and with regular orbits, whereas a planetary system with inverse cubic forces is unstable and without regular orbits. The regular orbits in a planetary system with inverse forces deviate, however, from the usual elliptical orbits by having revolving orbits with tendency to orbits with three or eight loops. Newton's Proposition 45 in $\textit{Principia}$ for the Moon's revolving orbits caused by an additional attraction to the gravitational attraction is confirmed, but whereas the additional inverse forces stabilize the planetary system, the additional inverse cubic forces can destabilize the planetary system at a sufficient strength.

preprint2023arXiv

The original Gibbs paradox is the consequence of the erroneous identification of non-identical functions

This article presents the results of research into the causes of the Gibbs paradox in the formulation discussed by J. W. Gibbs himself. In this formulation, we are talking about an inexplicable (paradoxical) jump in the entropy of mixing of two ideal gases during the transition from mixing different to mixing identical gases. It is shown that the entropy of mixing of different ideal gases and the entropy of mixing of identical ideal gases are different (non-identical) functions of the same gas parameters. That, called a paradoxical jump in the entropy of mixing, is not a jump in the value of some function, but is the difference in the values of various functions, on condition that the variables and parameters on which these functions depend remain constant. Those who were looking for an explanation of the original Gibbs paradox did not notice this and tried to solve an unsolvable falsely posed problem: to find a parameter that change during the transition from different to identical gases caused the difference in the values of non-identical functions.

preprint2024arXiv

Reply to Comment on "Covariant formulation of electrodynamics in isotropic media''

This note contains my response to the comment written by J. Franklin on my paper ``Covariant formulation of electrodynamics in isotropic media''.

preprint2024arXiv

Microscopic cut-off dependence of an entropic force in interface propagation of stochastic order parameter dynamics

The steady propagation of a $(d-1)$-dimensional planer interface in $d$-dimensional space is studied by analyzing mesoscopic non-conserved order parameter dynamics with two local minima under the influence of thermal noise. In this analysis, an entropic force generating interface propagation is formulated using a perturbation method. It is found that the entropic force singularly depends on an ultraviolet cut-off when $d \ge 2$. The theoretical calculation is confirmed by numerical simulations with $d=2$. The result means that an experimental measurement of the entropic force provides an estimation of the microscopic cut-off of the mesoscopic description.

preprint2024arXiv

Geometrically constrained particle dynamics revisited: Equation of motion in terms of the normal curvature of the constraint manifold

We revisit the problem of the particle dynamics subject to a geometric holonomic constraint of codimension 1 in spatial dimensions d =2 and 3. In the absence of dissipation, we show that by solving the Lagrangian multiplier in a general fashion, the external potential independent part, the net normal force, of the equation of motion corresponds to precisely to the curvature of the trajectory on the constraint space multiplied by twice the kinetic energy. The tangent the trajectory is the instantaneous velocity. In d = 3, this term equals the second fundamental form II of the constraint surface evaluated on the unit tangent vector in the direction of velocity. Using these result we establish the relation between constrained particle dynamics with geodesic equations and derive intriguing kinematic implications using theorems from fundamental differential geometry.

preprint2024arXiv

Compression-induced crossovers for the ground-state of classical dipole lattices on a Möbius strip

We explore the ground state properties of a lattice of classical dipoles spanned on the surface of a Möbius strip. The dipole equilibrium configurations depend significantly on the geometrical parameters of the Möbius strip, as well as on the lattice dimensions. As a result of the variable dipole spacing on the curved surface of the Möbius strip, the ground state can consist of multiple domains with different dipole orientations which are separated by domain walls. We analyze in particular the dependence of the ground state dipole configuration on the width of the Möbius strip and highlight two crossovers in the ground state that can be correspondingly tuned. A first crossover changes the dipole lattice from a phase which resists compression to a phase that favors it. The second crossover leads to an exchange of the topological properties of the two involved domains. We conclude with a brief summary and an outlook on more complex topologically intricate surfaces.

preprint2024arXiv

3D audio-visual recordings of mosquito wings for aeroacoustic simulation

Mosquito acoustic communication is studied for its singular and poorly-known in-flight hearing mechanism, for its efficiency in mechanical-to-acoustical power transduction, as well as for being the deadliest disease vector. A combined computational and experimental methods to predict and extract the wing-tone sound from individual tethered or free-flying mosquitoes was developed. This paper describes the experimental methods and gives some preliminary results of the simulations. Simultaneous slow-motion images (20k fps) and 3D-sound of Culex quinquefasciatus mosquitoes were recorded. The sound map around the mosquitoes was recorded in one or two planes with a rotating array of 12-microphones. Backilluminated mosquito-wings allowed to extract 11 veincrossing locations on each high-speed camera image over 3-4 wingbeat periods to generate 3D deformations of the wing. Simultaneous 3D sound data recorded by microphone arrays were post-processed by using the physicsbased independent component analysis to filter out the noise and generate a 3D sound map. The simulated wingtone sound pattern generated from the aeroacoustic simulation agrees well with the original recording in the experiment using the microphone array. The methods we developed will allow us to investigate the wing-tone soundscape of individual mosquitoes during the courtship and mate-chasing.

preprint2024arXiv

Using perceptive subbands analysis to perform audio scenes cartography

Audio scene cartography for real or simulated stereo recordings is presented. This audio scene analysis is performed doing successively: a perceptive 10-subbands analysis, calculation of temporal laws for relative delays and gains between both channels of each subband using a short-time cons\-tant scene assumption and channels inter-correlation which permit to follow a mobile source in its moves, calculation of global and subbands histograms whose peaks give the incidence information for fixed sources. Audio scenes composed of 2 to 4 fixed sources or with a fixed source and a mobile one have been already successfully tested. Further extensions and applications will be discussed. Audio illustrations of audio scenes, subband analysis and demonstration of real-time stereo recording simulations will be given.Paper 6340 presented at the 118th Convention of the Audio Engineering Society, Barcelona, 2005

preprint2024arXiv

Realizing topological edge states in graphene-like elastic metamaterials

The study of topological states in electronic structures, which allows robust transport properties against impurities and defects, has been recently extended to the realm of elasticity. This work shows that nontrivial topological flexural edge states located on the free boundary of the elastic graphene-like metamaterial can be realized without breaking the time reversal, mirror, or inversion symmetry of the system. Numerical calculations and experimental studies demonstrate the robust transport of flexural waves along the boundaries of the designed structure. The topological edge states on the free boundary are not limited by the size of the finite structure, which can reduce the scale of the topological state system. In addition, unlike the edge states localized on the free boundary in graphene where the group velocity is zero, the edge states on the elastic metamaterial plate have propagation states with non-zero group velocity. There is a frequency range for the edge states, and we introduce the concept of Shannon entropy for elastic waves and use it to assess the frequency range of the edge states in graphene-like elastic metamaterials. This work represents a relevant advance in the study of elastic wave topological states, providing a theoretical basis for engineering applications such as vibration reduction and vibration isolation of mechanical structures.

preprint2024arXiv

Beating resonance patterns and extreme power flux skewing in anisotropic elastic plates

Elastic waves in anisotropic media can exhibit a power flux that is not collinear with the wave vector. This has notable consequences for waves guided in a plate. Through laser-ultrasonic experiments, we evidence remarkable phenomena due to slow waves in a single crystal silicon wafer. Waves exhibiting power flux orthogonal to their wave vector are identified. A pulsed line source that excites these waves reveals a wave packet radiated parallel to the line. Furthermore, there exist precisely eight plane waves with zero power flux. These so-called zero-group-velocity modes are oriented along the crystal's principal axes. Time acts as a filter in the wave vector domain that selects these modes. Thus, a point source leads to beating resonance patterns with moving nodal curves on the surface of the infinite plate. We observe this pattern as it emerges naturally after a pulsed excitation.

preprint2024arXiv

Maxwell's Current in Mitochondria and Nerve

Maxwell defined a true or total current in a way not widely used today. He said "... true electric current ... is not the same thing as the current of conduction but that the time-variation of the electric displacement must be taken into account in estimating the total movement of electricity". We show that true or total current is a universal property of electrodynamics independent of properties of matter. We use mathematics without a dielectric constant. The resulting Maxwell Current Law is a generalization of the Kirchhoff Law of Current used in circuit analysis, that also includes displacement current. The generalization is not a long-time low frequency approximation in contrast to traditional presentation of Kirchhoff's Law. The Maxwell Current Law does not require currents to be in circuits. It has been applied to three dimensional systems like the signaling system of nerve and muscle fibers. The Maxwell Current Law clarifies the flow of electrons, protons, and ions in mitochondria that generate ATP, the molecule that stores chemical energy throughout life. The currents are globally coupled because mitochondria are short. Focusing on Maxwell current reinterprets the classical chemiosmotic hypothesis of ATP production. The conduction current of protons in mitochondria is driven by the protonmotive force including its component electrical potential, just as in the classical chemiosmotic hypothesis. The electrical potential is now the electrical potential as defined in physical sciences by Maxwell partial differential equations. The conduction current is now just a part of the true current analyzed by Maxwell. Details of accumulation of charges do not have to be considered in analysis of true current because true current does not accumulate. It is true total current that provides the energy that generates the ATP, not just the protonmotive force.

preprint2024arXiv

Foundations of the WKB Approximation for Models of Cochlear Mechanics in 1- and 2-D

The Wentzel-Kramers-Brillouin (WKB) approximation is frequently used to explore the mechanics of the cochlea. As opposed to numerical strategies, the WKB approximation facilitates analysis of model results through interpretable closed-form equations, and can be implemented with relative ease. As a result, it has maintained relevance in the study of cochlear mechanics for half of a century. Over this time, it has been used to study a variety of phenomena including the limits of frequency tuning, active displacement amplification within the organ of Corti, feedforward mechanisms in the cochlea, and otoacoustic emissions. Despite this ubiquity, it is challenging to find rigorous exposition of the WKB approximation's formulation, derivation and implementation in cochlear mechanics literature. In this tutorial, I discuss the foundations of the WKB approximation in application to models of cochlear macromechanics in 1-D and 2-D. This includes mathematical background, rigorous derivation and details of its implementation in software.

preprint2023arXiv

Validation of a motion model for soccer players' sprint by means of tracking data

In soccer game analysis, the widespread availability of play-by-play and tracking data has made it possible to test mathematical models that have been discussed mainly theoretically. One of the essential models in soccer game analysis is a motion model that predicts the arrival point of a player in $ t $ s. Although many space evaluation and pass prediction methods rely on motion models, the validity of each has not been fully clarified. This study focuses on the motion model proposed by Fujimura and Sugihara (Fujimura-Sugihara model) under sprint conditions based on the equation of motion. A previous study indicated that the Fujimura-Sugihara model is ineffective for soccer games because it generates a circular arrival region. This study aims to examine the validity of the Fujimura-Sugihara model using soccer tracking data. Specifically, we quantitatively compare the arrival regions of players between the model and real data. We show that the boundary of the player's arrival region is circular rather than elliptical, which is consistent with the model. We also show that the initial speed dependence of the arrival region satisfies the solution of the model. Furthermore, we propose a method for estimating valid kinetic parameters in the model directly from tracking data and discuss the limitations of the model for soccer games based on the estimated parameters.

preprint2022arXiv

Diamond-based Detection Systems for Accurate Pulsed X-rays Diagnostics in Radiotherapy

The widespread diffusion of precision radiotherapy techniques, geared toward the release of larger dose gradients in shorter time frames, is leading to new challenges in dosimetry. Accurate dose measurements are essential to check for beam anomalies and inaccuracies to ensure treatment efficacy and patient safety during radiotherapy. This work describes the main features of a diamond dosimeter coupled to an extremely compact front-end electronics. The detection system was tested under the X-ray pulses generated by a medical LINAC for both the 6 MV and the 18 MV accelerating voltages. Located in the LINAC's bunker, it eliminates the need for a long cable connection between the detector and the electronics, detrimental for the system response speed. Signal acquisition was performed synchronously with the impinging X-ray pulses with a sampling period as low as 20 us, allowing for a real-time beam monitoring. The dosimeter demonstrated a very good stability despite the high value of the absorbed dose during the performed experiments (about 100 Gy). The measured dose-per-pulse values of 278 uGy and 556 uGy at 6 MV and 18 MV, respectively, are in excellent agreement with the nominal values expected for the LINAC apparatus used for the tests. In addition to single-pulse measurements, fundamental for dynamic radiotherapy, the proposed system also allows for the calculation of both the total collected charge and the photocurrent generated by the detector. In this regards, despite the compactness, it demonstrates its effectiveness as a tool for source diagnostics in terms of both beam intensity and emission timing.

preprint2023arXiv

Anisotropic signatures in the spin-boson model

Thermal equilibrium properties of nanoscale systems deviate from standard macroscopic predictions due to a non-negligible coupling to the environment. For anisotropic three-dimensional materials, we derive the mean force corrections to the equilibrium state of a classical spin vector. The result is valid at arbitrary coupling strength. Specifically, we consider cubic, orthorhombic, and monoclinic symmetries, and compare their spin expectation values as a function of temperature. We underpin the correctness of the mean force state by evidencing its match with the steady state of the simulated non-Markovian spin dynamics. The results show an explicit dependence on the symmetry of the confining material. In addition, some coupling symmetries show a spin alignment transition at zero temperature. Finally, we quantify the work extraction potential of the mean force-generated inhomogeneities in the energy shells. Such inhomogeneities constitute a classical equivalent to quantum coherences.

preprint2024arXiv

Non-holonomic constraints inducing flutter insability in structures under conservative loadings

Non-conservative loads of the follower type are usually believed to be the source of dynamic instabilities such as flutter and divergence. It is shown that these instabilities (including Hopf bifurcation, flutter, divergence, and destabilizing effects connected to dissipation phenomena) can be obtained in structural systems loaded by conservative forces, as a consequence of the application of non-holonomic constraints. These constraints may be realized through a `perfect skate' (or a non-sliding wheel), or, more in general, through the slipless contact between two circular rigid cylinders, one of which is free of rotating about its axis. The motion of the structure produced by these dynamic instabilities may reach a limit cycle, a feature that can be exploited for soft robotics applications, especially for the realization of limbless locomotion.