Description Of Waves Research Articles

Waves interacting with a partially immersed obstacle in the Boussinesq regime

This paper is devoted to the derivation and mathematical analysis of a wave-structure interaction problem which can be reduced to a transmission problem for a Boussinesq system. Initial boundary value problems and transmission problems in dimension d= 1 for $2\times2$ hyperbolic systems are well understood. However, for many applications, and especially for the description of surface water waves, dispersive perturbations of hyperbolic systems must be considered. We consider here a configuration where the motion of the waves is governed by a Boussinesq system (a dispersive perturbation of the hyperbolic nonlinear shallow water equations), and in the presence of a fixed partially immersed obstacle. We shall insist on the differences and similarities with respect to the standard hyperbolic case, and focus our attention on a new phenomenon, namely, the apparition of a dispersive boundary layer. In order to obtain existence and uniform bounds on the solutions over the relevant time scale, a control of this dispersive boundary layer and of the oscillations in time it generates is necessary. This analysis leads to a new notion of compatibility condition that is shown to coincide with the standard hyperbolic compatibility conditions when the dispersive parameter is set to zero. To the authors' knowledge, this is the first time that these phenomena (likely to play a central role in the analysis of initial boundary value problems for dispersive perturbations of hyperbolic systems) are exhibited.

On kinetic electrostatic plasma waves carrying orbital angular momentum

A kinetic description of electron plasma waves carrying orbital angular momentum is revisited by introducing a variable transformation, which confirms a more natural representation of wave propagation in electron–ion plasma extendable to an electron–positron plasma. Specifically, the twisted Landau resonance condition is expressed in a consistent way, which expands the resonance region, and hence modifies the usual assumption of decomposition of the susceptibility in axial and poloidal components involving two separate poles. The present formulation is recommended by numerical analysis and comparison with typical results and illustrations.

Rogue breathers and rogue lumps on a background of dark line solitons for the Maccari system

The Maccari system is a nonlinear dynamical model for the description of two-dimensional rogue waves occuring in diverse physical settings. For this two-dimensional nonlinear system, the time localized breathers and doubly localized lumps termed as rogue breathers and rogue lumps on a background of dark line solitons are investigated. The rogue breather behaves as a breather appearing and disappearing on a background of two dark line solitons, and is generated from the resonant collision between a breather and two dark line solitons. The limit case of a rogue breather is a rogue lump, which is truly localized in time and in the two-dimensional space. The Nth-order rogue lumps on a background of (N+1) dark line solitons are constructed by employing the Kadomtsev-Petviashvili hierarchy reduction method combined with the Hirota bilinear method. These higher-order lumps arise from a background of dark line solitons and then disappear into the background again after living for a very short period of time. The rogue lumps possess the key features of two-dimensional rogue waves occurring in a plethora of physical settings.

Study on Non-Bragg Microwave Backscattering from Sea Surface Covered with and without Oil Film at Moderate Incidence Angles

In the past decades, Bragg scattering has been considered to be an important scattering mechanism of microwave backscattering from sea surfaces. However, as reported in many recent literatures, non-Bragg scattering (which is often attributed to wave breaking) also makes a significant impact on radar scattering, especially for Horizontal–Horizontal (HH) polarized radar signals. To date, we know far less about non-Bragg scattering than Bragg scattering. Herein, this paper carries out an investigation on non-Bragg scattering and its effect on radar echoes at moderate incidence angles, both for oil-free and oil-covered sea surfaces. This paper firstly presents a systematic comparison of several sea spectra commonly used for the simulation of microwave scattering from sea surfaces. It is found that none of them perform well for the description of Bragg waves. Then, the “pure” Bragg wave spectra are inverted in the framework of the two-scale model (TSM) and geophysical model functions (GMFs). The normalized radar cross sections (NRCS) related to total scattering, non-Bragg scattering, and “pure” Bragg scattering in C, X, and Ku-bands are simulated under various conditions (i.e., incidence angles, wind speeds, and wind directions). Quantitative assessments of the relative contributions of non-Bragg scattering to total scattering are conducted. We also perform a survey on the non-Bragg scattering from the oil-covered sea surface. This article provides some new insights for a better understanding of the non-Bragg microwave scattering from rough sea surfaces at moderate incidence angles.

MATHEMATICAL JUSTIFICATION OF FIBER SENSORS BASED ON FIBER BRAGG GRATINGS

Nowadays, the most promising approach is the use of fiber-optic sensors as a key element of the monitoring system. Fiber-optic sensors (FOS) have a number of advantages, the most important of which include immunity to electromagnetic interference, low weight and the possibility of their inclusion in the measured structure. The use of such sensors in the monitoring system will make it possible to simplify the measurement and obtain reliable data, as well as to obtain all new possibilities for measuring various quantities simultaneously.The most perspective are the sensors based on the Bragg fiber gratings. Bragg fiber gratings have several advantages, for instance, they allow creating the distributed measuring massifs, which contain several sensors. As well, they are insensitive to the optic power source vibrations. Variety of using the fiber sensors based on the Bragg fiber gratings has led to producing the Bragg fiber gratings with different spectral characteristics.The article herein considers the issues of the Bragg fiber gratings mathematical modeling using the transfer matrix method. Transfer matrix method allows defining the optical components spectral characteristics based on the bound modes theory and description of electromagnetic wave, passing through an optic fiber. In the article there have been analyzed the Bragg fiber gratings in compliance with spectral features, such as transmission and reflectance spectra.

A new translation and reader's guide to the first detailed description of the first wave of spermatogenesis in the mouse.

A new translation and reader's guide to the first detailed description of the first wave of spermatogenesis in the mouse.

Поглощение акустической волны в волноводе с импедансными граничными условиями

Object and purpose of research. The study of the acoustic pulse changes regularities during its propagation in con-fined media is one of the fundamental problems of acoustics, which allows to pose and solve the inverse problem of determining the dissipative and resonant properties of these media. The physical processes occurring during the propagation of a pulse in a cylindrical waveguide with rigid walls were investigated. Materials and methods. To analyze the mechanism of dissipation, experimental studies of pulse propagation in a hy-droacoustic tube were carried out, and the theoretical description of the obtained results was carried out using analytical methods. The simulation of the propagating pulse in the finite element waveguide model was used to confirm the theoretical assessments and the experiment. Main results. Experimental studies of physical processes during the propagation of an acoustic pulse in confined medium of cylindrical waveguide bounded by walls with characteristics close to absolutely rigid are carried out. The data showed that it is possible to control changes in the phase velocity, amplitude, and waveform, which made it possible to quantify the impedance of the internal walls of the waveguide and the dissipation of acoustic energy with a sufficient degree of accuracy. The numerical model calculation, taking into account the theoretically obtained quantitative assessments of the dissipation values and the impedance value of the waveguide inner surface, showed a good correspondence between the model and experimental characteristics of the change in the propagating pulse. Conclusion. In the studies devoted to the propagation description of acoustic waves in waveguides, the issues of energy dissipation are usually not considered, especially in cases where it has a weak effect on the measurement result. The theoretical value of the research is to quantify the wave energy dissipation by the parameters that can be determined with sufficient accuracy in the experiment: the phase velocity, the pulse form. Further accuracy improvement of the experimental data, especially in a wide frequency range, will improve the theoretical model of dissipation by taking into account the mechanism of inhomogeneous viscous and thermal waves near the inner surface of the waveguide. The practical significance of the research is to increase the reliability of experimental data and to develop physical and mathematical models of underwater sound absorption due to a forced variable flow with a highly transformed velocity of a viscous liquid in a thin surface layer near the elastic wall.

Nonlinear waves in a dispersive vacuum described with a high order derivative electromagnetic Lagrangian

In this article we use an electromagnetic Lagrangian constructed so as to include dispersive effects in the description of an electromagnetic wave propagating in the quantum electrodynamic vacuum. This Lagrangian is Lorentz invariant, includes contributions up to six powers in the electromagnetic fields, and involves both fields and their first derivatives. Conceptual limitations inherent to the use of this higher derivative Lagrangian approach are discussed. We consider the one-dimensional spatial limit and obtain an exact solution of the nonlinear wave equation recovering the Korteveg-de Vries type periodic waves and solitons given in S. V. Bulanov et al. [Phys. Rev. D 101, 016016 (2020)].

New and more fractional soliton solutions related to generalized Davey–Stewartson equation using oblique wave transformation

The generalized fractional Davey–Stewartson (DSS) equation with fractional temporal derivative, which is used to explore the trends of wave propagation in water of finite depth under the effects of gravity force and surface tension, is considered in this paper. The paper addresses the full nonlinearity of the proposed model. To extract the oblique soliton solutions of the generalized fractional DSS (FDSS) equation is the dominant feature of this research. The conformable fractional derivative is used for fractional temporal derivative and oblique wave transformation is used for converting the proposed model into ordinary differential equation. Two state-of-the-art integration schemes, modified auxiliary equation (MAE) and generalized projective Riccati equations (GPREs) method have been employed for obtaining the desired oblique soliton solutions. The proposed methods successfully attain different structures of explicit solutions such as bright, dark, singular, and periodic solitary wave solutions. The occurrence of these results ensured by the limitations utilized is also exceptionally promising to additionally investigate the propagation of waves of finite depth. The latest found solutions with their existence criteria are considered. The 2D and 3D portraits are also shown for some of the reported solutions. From the graphical representations, it have been illustrated that the descriptions of waves are changed along with the change in fractional and obliqueness parameters.

Debye model for the surface phonons

A quantum description of the surface waves in an isotropic elastic body without the use of the semiclassical quantization is proposed. The problem about the surface waves is formulated in the Lagrangian and Hamiltonian representations. Within the framework of the generalized Debye model, the contribution of the surface phonons (“rayleighons”) to thermodynamic functions is calculated. It is emphasized that the role of the surface phonons can be significant and even decisive in low-dimensional systems, granular and porous media, and that their contribution to the total heat capacity increases with decreasing temperature.

Calculation of multiphoton ionization amplitudes and cross sections of few-electron atoms

We present a theoretical method for calculating multiphoton ionization amplitudes and cross sections of few-electron atoms. The present approach is based on an extraction of partial wave amplitudes from a scattering wave function, which is calculated by solving a system of driven Schroedinger equations. The extraction relies on a description of partial waves in terms of a small number of Coulomb waves with fixed wave numbers. The method can be used for photon energies below and above the ionization threshold and to treat resonance-enhanced multiphoton ionization. We use it to calculate two-, three-, and four-photon ionization cross sections of hydrogen and helium atoms for a wide range of photon energies and to determine the asymmetry parameters of photoelectron angular distributions for two-, three-, and four-photon ionization of the helium atom.

On Fulfillment of Energy Conservation Law in Theory of Elastic Waves V. V. Nevdakh1)

In accordance with the energy conservation law, the total energy of a closed physical system must remain constant at any moment of time. The energy of a traveling elastic wave consists of the kinetic energy in the oscillating particles of the medium and the potential energy of its elastic deformation. In the existing theory of elastic waves, it is believed that the kinetic and potential energy densities of a traveling wave without losses are the same at any moment of time and vary according to the same law. Accordingly, the total energy density of such wave is different at various moment of time, and only its time-averaged value remains constant. Thus, in the existing theory of elastic waves, the energy conservation law is not fulfilled. The purpose of this work is to give a physically correct description of these waves. A new description of a sound wave in an ideal gas has been proposed and it is based on the use of a wave equation system for perturbing the oscillation velocity of gas particles, which determines their kinetic energy, and for elastic deformation, which determines their potential energy. It has been shown that harmonic solutions describing the oscillations of the gas particles velocity perturbation and their elastic deformation, which are phase shifted by p/2, are considered as physically correct solutions of such equations system for a traveling sound wave. It has been found that the positions of the kinetic and potential energy maxima in the elastic wave, described by such solutions, alternate in space every quarter of the wavelength. It has been established that every quarter of a period in a wave without losses, the kinetic energy is completely converted to potential and vice versa, while at each spatial point of the wave its total energy density is the same at any time, which is consistent with the energy conservation law. The energy flux density of such traveling elastic wave is described by the expression for the Umov vector. It has been concluded that such traveling sound wave without losses in an ideal gas can be considered as a harmonic oscillator.

The Rydberg Constant Interpreted as the Gaussian Curvature, Gauss-Bohr-de Broglie Model – Two Shadow Projections of the Helix, Unlocking of the Fixed Constant c of the Speed of Light – New Tests for Old Physics

We have newly interpreted the Rydberg constant R∞ as the Gaussian curvature – the ratio of the 4π electron spin rotation to the area on the Gauss – Bohr sphere travelled by that electron. Rydberg constant for hydrogen RH was newly derived and can be experimentally tested and compared with the value RH derived from the reduced mass. The de Broglie electron on the helical path embedded on the Gauss – Bohr sphere was projected as two shadows: the real shadow Re [cos(t)] and the imaginary shadow Im [i sin(t)]. This model differs from the Schrödinger famous quantum wave description in the physical interpretation. The wave amplitude is here interpreted as the distance of the shadow from the Gauss – Bohr sphere. Moreover, we have newly inserted into the wave equation curvature and torsion of that de Broglie helix. One very interesting result of this model is the estimation of the constant c of the speed of light with three additional significant figures. We have divided the very precise CODATA 2018 value for R∞ expressed in frequency and the CODATA 1986 value for R∞ expressed in wavenumber unit. Based on these precise spectroscopic data we might increase the accuracy of the constant c of the speed of light to twelve significant figures.

Atomic kernels as waves and catastrophes

The presentation of atomic kerrnels as particles requires for the physics duality principle that they get a wave description. This is due to presenting the SU (3) GellMann matrix space by octonians which are obtained by doubling the spacetime quaternions. Their multiplication table is different from the SU (3) matrices. The third presentation of this space is a complex 4-dimensional space where the real spacetime coordinates of a 4-dimensional Euclidean Hilbert space R4 are extended to C4. For getting from Deuteron Cooper pairs NP of a neutron and proton atomic kernels AK, the wave package superpositions for AK need the mass defect of neutrons where kg is changed to inner speeds or interaction energies. For kg octonians have a GF measuring base triple as Gleason operator. Using a projective geometrical norming, C4 is normed to CP³, a projective 3-dimensional space. Its cell C³ has spacetime coordinates C², extended by an Einstein energy plane z3 = (m,f), m mass, f = 1/∆t frequency where mass can be transformed into f by using mc² = hf. If C³ is presented as a real space R6, it can be real projective normed to a real projective space P5 for the field presentation of AK. As field the NP‘s have then a common group speed for AK wave packages superpositions with which AK moves in spacetime C² and also a presentation as a Ψ wave. As probability distribution where they can be energetically found in space serves Ψ* Ψ.

Ion cyclotron resonance heating fast and slow wave excitation and power deposition in edge plasmas with application to ITER

The antenna power coupling to the plasma centre and its possible deleterious coupling to the plasma edge are key parameters in an ion cyclotron resonance heating system. The influence on these parameters by the confluence between the slow and the fast magnetosonic waves is studied for the case of large machines. Until now, the modelling of the scrape off layer region has been calculated by ANTITER II, which contains only the fast wave description and where the confluence with the slow wave (S wave) is approximated by the Alfvén resonance. In the present study, a complete modelling of the slow and fast waves is made by ANTITER IV. The modelling by the two codes is compared and shows the important role of the Alfvén and the lower hybrid resonances for the excitation of large fields and associated power deposition at the edge of the plasma even far from the antenna location. The ANTITER IV modelling is thereafter applied to the case of the ITER antenna with a reference density profile and heating parameters. A comparative study is made for the edge power deposition and the excitation of large fields for different toroidal phasing cases of the antenna. This study also takes into account the tilting of the antenna array with respect to the total magnetic field in front of the antenna. If the Faraday screen is field-aligned, the excitation of the S wave occurs at the wave confluence; however, in the case of non-alignment the antenna directly excites the S wave. This effect is studied and quantified. All edge effects, even the direct excitation of S waves, can be strongly reduced by tailoring the current distribution in the straps of the antenna array. Resulting cases for the minimisation of edge power deposition in ITER and the reactor are studied.

Excitation of plasma wakefields by intense ultra‐relativistic proton beam

AbstractWe report here an exact analytical travelling wave solution for a non‐linear electron plasma wave excited by an intense ultra‐relativistic proton beam. It demonstrates the underlying physics of longitudinal electric field characteristics of the excited wake wave formed behind the drive beam. The results are further supplemented by a fully relativistic particle‐in‐cell code OSIRIS in two‐dimensional geometry. The investigation is further extended by providing an analytical description of the wake wave excited by an equi‐spaced train of small proton bunches with the inclusion of the non‐relativistic plasma ion dynamics. Our results show that the amplitude of the wake field does not grow indefinitely with the increase in the number of proton bunches. On the contrary, it saturates to a definitive limit.

The COVID-19 epidemic in Madagascar: clinical description and laboratory results of the first wave, march-september 2020.

BackgroundFollowing the first detection of SARS‐CoV‐2 in passengers arriving from Europe on 19 March 2020, Madagascar took several mitigation measures to limit the spread of the virus in the country.MethodsNasopharyngeal and/or oropharyngeal swabs were collected from travellers to Madagascar, suspected SARS‐CoV‐2 cases and contact of confirmed cases. Swabs were tested at the national reference laboratory using real‐time RT‐PCR. Data collected from patients were entered in an electronic database for subsequent statistical analysis. All distribution of laboratory‐confirmed cases were mapped, and six genomes of viruses were fully sequenced.ResultsOverall, 26,415 individuals were tested for SARS‐CoV‐2 between 18 March and 18 September 2020, of whom 21.0% (5,553/26,145) returned positive. Among laboratory‐confirmed SARS‐CoV‐2–positive patients, the median age was 39 years (IQR: 28‐52), and 56.6% (3,311/5,553) were asymptomatic at the time of sampling. The probability of testing positive increased with age with the highest adjusted odds ratio of 2.2 [95% CI: 1.9‐2.5] for individuals aged 49 years and more. Viral strains sequenced belong to clades 19A, 20A and 20B indicative of several independent introduction of viruses.ConclusionsOur study describes the first wave of the COVID‐19 in Madagascar. Despite early strategies in place Madagascar could not avoid the introduction and spread of the virus. More studies are needed to estimate the true burden of disease and make public health recommendations for a better preparation to another wave.

Massive deformations of Maass forms and Jacobi forms

We define one-parameter "massive" deformations of Maass forms and Jacobi forms. This is inspired by descriptions of plane gravitational waves in string theory. Examples include massive Green's functions (that we write in terms of Kronecker-Eisenstein series) and massive modular graph functions.

Collision clock shift of two Fermi atoms in harmonic potentials

Atomic clocks provide the most accurate definition for time. The precision of atomic clock has been improved by many orders of magnitude since the first atomic clock was built. However, the interatomic interaction usually suppress the precision of atomic clock. As a result, it is especially meaningful to study the interaction effect in atomic clock, which is considered to be helpful in improving the precision and accuracy of atomic clock. In order to characterize the collision effect induced clock shift, we theoretically study the collision clock shift in the Rabi spectrum, caused by the short-range interaction between two Fermi atoms in harmonic potential. Given that the short-range interatomic interaction is generally weak, and that the parameters of external lattice laser field are in the Lamb-Dicke regime, we make an approximation that the spatial wave-function of the Fermi atoms does not change, and then derive the motion equation for the internal wave-function under the external Rabi driving field. We solve the equation of motion by the perturbative method, and obtain the solution to first order, and thus derive the expression of the collision clock shift of the Rabi spectrum in terms of the interatomic interaction and the external Rabi driving laser field parameters for specific spatial wave-functions of atoms. Finally, we use the exact expression of the Green’s function in harmonic potential to obtain the averaged clock shift of collision at finite temperatures. Our results relate the atomic interaction with atomic clock shift, and provide a unified description of all partial waves of atomic interaction induced clock shift. Therefore, it becomes much more convenient to study the contributions of different partial waves to atomic clock shift. On the other hand, our results indicate that through precisely measuring the clock shift, the information about the interatomic interactions can also be obtained. In addition, our results for two interacting atoms can inspire the future study of real many-body interacting system which will be the next research topic.

ОДНО ЭТНИЧЕСКОЕ ПРОИСХОЖДЕНИЕ – ДВЕ СУДЬБЫ: НОВОПРИБЫВШИЕ VS ПОТОМКИ МИГРАНТОВ

The article sheds light on certain peculiarities of immigration to France, which has become a multicultural country. The authors explain how the destinies of two categories of “immigrant” youth differ. The first are the “beurs”, children and grandchildren of migrants who arrived in France during the 1960s and 1970s, generally from the Maghreb. The second are the “blédards”, who migrated themselves from these countries during adolescence with their parents or in the framework of family reunification. After a short description of the successive waves of migration which have regularly reached France and a terminological clarification on the meaning of the words “foreigner” and “migrant”, the authors show how the trajectories of those who are French citizens, know the language and have attended the school system from the start differ from those of newcomers, although the two groups are often confused. The article presents analysis from the theoretical works devoted to the study of different waves of migration, in the USA and in other countries, then focuses on a presentation of the educational trajectories of the new arrivals and those of the descendants of migrants. Particular attention is paid to migrants’ adaptation to the labor market. Newcomers have less difficulty finding an internship than their classmates born in France. They are also more easily exploited, because they compensate their poor French language adopting a deferential attitude towards employers. When unemployed, they often find a job more easily than the descendants of migrants by relying on ethnic niches and networks of fellow citizens. The article underlines the role of the social environment in determining adaptation paths which can lead to acculturation and social mobility, to assimilation within a marginalized urban environment, or to economic integration into ethnic niches. The more hostile the environment and the less the migrants are adapted to the country’s economic and cultural codes, the more the ethnic community tends to rely on itself in order to protect its children from a form of assimilation seen as harmful. Finally, the authors present the different attitudes of young people from the two groups towards the host society. For the descendants of migrants, it is common to assimilate to groups of young people in low-income neighborhoods and to copy the behavioral pattern characteristic of the inhabitants of these neighborhoods with a high concentration of immigrant and minority populations. When they are victims of stigmatization because of their ethnic origin or their neighborhood of residence, these young people become very critical, sometimes adopting oppositional attitudes to the French society to which they belong. On the other hand, newcomers struggle to find their place, as they still feel in transit, are not necessarily sure to stay in the country which they see as a haven comparing to the difficult living conditions of their native country.