Wave Pulse Propagation Research Articles

Conserved quantities and sensitivity analysis influence of damping effect in ferrites materials

In this paper, we investigate the Kraenkel-Manna-Merle (KMM) system, which explains the nonlinear propagation of ultra-short wave pulses in specific saturated ferromagnetic materials. Ferromagnetic materials play a crucial role in data storage, manipulation, and telecommunications applications. Lie symmetry invariance analysis was conducted to identify infinitesimal generators of symmetries, and the adjoint representation was utilized to formulate an optimal system based on the identified Lie vectors. We obtained the analytical solution using the powerful power series method. To assess the impact of damping on the nonlinear Kraenkel-Manna-Merle (KMM) system, we evaluated its stability based on modulation instability criteria. Furthermore, we visually depicted wave solutions obtained by applying damping with varying parameter values. Additionally, we computed conserved quantities for the nonlinear KMM equation using the multiplier technique.

A mathematical model for simulating photoacoustic signal generation and propagation in biological tissues

Photoacoustic (PA) medical imaging is a crossbred technique relying on light-induced ultrasonic waves due to the PA effect phenomenon recorded primarily in 1880 by A. G. Bell. Numerical simulation, also known as in-silico, studies assist scientists in minimizing incorrect PA experiments in both in-vitro and in-vivo. Numerical modeling techniques help to achieve a fast simulation process in contrast to pure mathematics alone. However, if a suitable facilitated mathematical model can be established prior to applying numerical modeling, it will be of great interest to the whole numeric model. Numerous mathematical equations, theorems, and propositions have been proposed to model the whole PA signal generation and propagation process in biological media. However, most of them are complicated and difficult to be understood by researchers, especially beginners. That’s why this paper was introduced. Our paper aims to simplify the understanding of the generation and propagation process of biomedical PA waves. We have developed a facilitated mathematical model for the entire process. The introduced developed mathematical model is based on three steps: (1) pulsed laser stimulation, (2) light diffusion, and (3) PA stress wave generation and propagation. The developed mathematical model has been implemented utilizing COMSOL Multiphysics, which relies on the finite element method (FEM) numerical modeling principle. The in-silico time-dependent study's results confirmed that the proposed mathematical model is a simple, efficient, accurate, and quick starting point for researchers to simulate biomedical PA signals' generation and propagation process utilizing any suitable software such as COMSOL multiphysics.

Pulsed Wave Propagation Along a Transmission Line With Time-Varying Wavespeed

Pulsed wave propagation along a transmission line (TL) with time-varying (TV) wavespeed is analyzed using the theory of state variables. The thus obtained propagator solution is validated analytically and discussed with regard to its applications to solving initial-value problems. Illustrative examples are presented.

Slowing down light in a qubit metamaterial

The rapid progress in quantum information processing leads to a rising demand for devices to control the propagation of electromagnetic wave pulses and to ultimately realize universal and efficient quantum memory. While in recent years, significant progress has been made to realize slow light and quantum memories with atoms at optical frequencies, superconducting circuits in the microwave domain still lack such devices. Here, we demonstrate slowing down electromagnetic waves in a superconducting metamaterial composed of eight qubits coupled to a common waveguide, forming a waveguide quantum electrodynamics system. We analyze two complementary approaches, one relying on dressed states of the Autler–Townes splitting and the other based on a tailored dispersion profile using the qubits tunability. Our time-resolved experiments show reduced group velocities of down to a factor of about 1500 smaller than in vacuum. Depending on the method used, the speed of light can be controlled with an additional microwave tone or an effective qubit detuning. Our findings demonstrate high flexibility of superconducting circuits to realize custom band structures and open the door to microwave dispersion engineering in the quantum regime.

Fluid model simulation of solitons in an ultra-relativistic electron–positron plasma

In this study, the fully nonlinear relativistic ideal two-fluid equations are numerically integrated to show how solitary wave pulses can arise from simple initial conditions when electromagnetic waves parallel to a constant magnetic field are considered in a degenerate electron–positron plasma. The formation and propagation of one-dimensional fast wave solitons and slower wave pulses are identified as being related to a sound mode and the Alfvén mode, respectively. While solitons in relativistic electron–positron and similar plasmas have been studied theoretically by many authors, apart from some particle simulations and stationary large-amplitude treatments, only small-amplitude studies resulting in Korteweg–de Vries and related model equations have been employed to illustrate the occurrence of such nonlinear structures. These results extend and complement earlier theoretical treatments and are especially relevant for astrophysical plasmas.

A Novel Method for Detecting Characteristic Parameters of Coating Layers by Ultrasonic Surface Wave Technique

An improved reversion method for ultrasonic surface wave characterization of coating layers is presented and validated by experiment. The experiment is implemented with seven specimens of thin Cu layers coated on Al substrates. 2-D Fourier transforms of the experimentally obtained surface wave pulse propagation signals were conducted to obtain frequency-wave number relations. The combined equations of two unknowns were derived using the relation. The two unknowns are the thickness h and the Young's modulus E of the coating layer of the specimen. The h and E are obtained by solution of the combined equations. Comparing with that used for many years which are based on 1-D Fourier transform and nonlinear regression, the new method is simpler, faster, and equally accurate and reliable. The standard error of 1.55μm is reached in the measurements of the Cu films thicknesses which vary in the range from 23.6μm to 224.8μm. The standard error of 2.97GPa is reached in measurements of Young's modulus of the Cu films and the exact value of Young's modulus of pure Cu is 110GPa.

Effects of adiabaticity of electrons and negative ions on the modulational instability of ion-acoustic waves in electronegative plasma

In the present work, we investigate modulational instability (MI) in an unmagnetised collisionless electronegative plasma consisting of inertialess adiabatic electrons, inertialess adiabatic negative ions and mobile positive ions. For this purpose, a nonlinear Schrodinger equation (NLSE) is derived to study envelope evolution of the ion-acoustic carrier waves for our system by using reductive perturbation technique. In examining the stability/instability of the ion-acoustic envelope wavepackets, the critical wavenumber kc at which MI sets in is found to be shifted to higher values as adiabaticity γ increases. The effects of electron-to-negative ion temperature ratio σn and negative ion density fraction f on the region for propagation of stable wave pulses are also discussed. Within the instability region, the rational solution of NLSE provides the rogue wave (RW) profiles which is localised in space and time. With the increase of adiabaticity, the possibility for the formation of RW decreases at the lower wavenumber which is in good agreement with experimental observations. The change in adiabaticity significantly influences the rogue wave amplitudes. Maximum pulse height for RW is found to be increasing with the increase of adiabaticity. Our theoretical findings may be helpful for basic characteristic study of rogue waves in the laboratory as well as space plasmas.

Marine Mammal Lung Dynamics when Exposed to Underwater Explosion Impulse.

Very little is known about marine mammal susceptibility to primary blast injury (PBI) except in rare cases of opportunistic studies. As a result, traditional analysis techniques relied on methods developed more than 30 years ago using terrestrial mammals as surrogates. Modeling tools available today have the computing power to vastly improve calculation of safe ranges and injury zones from underwater explosions (UNDEX) employing morphologically accurate proxies with material properties similar to marine mammal tissues. The Dynamic System Mechanics Advanced Simulation (DYSMAS) fluid-structure interaction (FSI) software is being used to simulate the complex phenomena of UNDEX, shock wave, and bubble pulse propagation through the water and transmission of energy to a cetacean focusing on the dynamic response of the thoracic cavity and air-filled lungs to a shock wave. The approach integrates fluid and structural analyses with the material properties of blubber, bone, and muscle using marine mammal morphometrics to eliminate unnecessary assumptions made during more traditional approaches to analysis developed before these types of data and computational power were available. DYSMAS analyses of a 1D gas bubble surrounded by water was found to closely match the classical bubble dynamics models. Further, DYSMAS models of a spherical gas bubble surrounded by tissue and rib structure demonstrate a global radial oscillation of the gas bubble, but also show significant local deflection and material strain in response to the UNDEX loading. The intended result of the investigation is an improved and scientifically defensible understanding of the effects of UNDEX on marine mammals. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:718-734, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Dynamic behavior of geometrically complex hybrid composite samples in a Split-Hopkinson Pressure Bar system

The interfaces between layered materials play an important role for the overall mechanical behavior of hybrid composites, particularly during dynamic loading. Moreover, in complex-shaped composites, interfacial failure is strongly affected by the geometry and size of these contact interfaces. As preliminary work for the design of a novel sample geometry that allows to analyze wave reflection phenomena at the interfaces of such materials, a series of experiments using a Split-Hopkinson Pressure Bar technique was performed on five different sample geometries made of a monomaterial steel. A complementary explicit finite element model of the Split-Hopkinson Pressure Bar system was developed and the same sample geometries were studied numerically. The simulated input, reflected and transmitted elastic wave pulses were analyzed for the different sample geometries and were found to agree well with the experimental results. Additional simulations using different composite layers of steel and aluminum (with the same sample geometries) were performed to investigate the effect of material variation on the propagated wave pulses. The numerical results show that the reflected and transmitted wave pulses systematically depend on the sample geometry, and that elastic wave pulse propagation is affected by the properties of individual material layers.

Reduced-scale ultrasonic modelling of Rayleigh wave transmission over seismic barriers formed by periodic arrays of vertical holes

Seismic barriers are used widely to protect buildings from traffic-induced ground vibrations, mainly from propagating Rayleigh surface waves. Experimental investigations of real size seismic barriers at frequencies typical for traffic-induced ground vibrations, i.e. at 10-100 Hz, are costly and time consuming. In the present work, an alternative and much less expensive approach is proposed - a reduced-scale experimental modelling using ultrasonic Rayleigh wave propagation over very small-scale replicas of real seismic barriers. Experimental investigations of propagation of Rayleigh wave pulses with the central frequency of 1 MHz have been carried out for seismic barriers formed by periodic arrays of vertical holes in Aluminium samples. Measurements of transmission and reflection coefficients of Rayleigh waves for different types of arrays and for different incident angles have been carried out and compared with the earlier published results obtained for real seismic barriers.

Highly convergent finite elements with diagonal mass matrix for short wave pulse propagation simulation

The modal-synthesis based approach is employed for obtaining the higher-order dynamic 1D finite elements with enhanced convergence properties. The obtained dynamic models are used for modelling short transient waves and wave pulses propagating in elastic or acoustic environments by using rough space steps. Only few nodal points per pulse length are enough for obtaining reasonable simulation results. The main advantage of the created elements compared with earlier similar approach is the diagonal mass matrix of the element. The elements are compatible with conventional finite elements, may be used in branchy non-homogenous structures, as well as enable to implement non-reflecting boundary conditions. The saving of computational resource was estimated. DOI: http://dx.doi.org/10.5755/j01.itc.45.3.13557

SECONDARY FAST MAGNETOACOUSTIC WAVES TRAPPED IN RANDOMLY STRUCTURED PLASMAS

ABSTRACT Fast magnetoacoustic waves are an important tool for inferring parameters of the solar atmosphere. We numerically simulate the propagation of fast wave pulses in randomly structured plasmas that mimic the highly inhomogeneous solar corona. A network of secondary waves is formed by a series of partial reflections and transmissions. These secondary waves exhibit quasi-periodicities in both time and space. Since the temporal and spatial periods are related simply through the speed of the fast wave, we quantify the properties of secondary waves by examining the dependence of the average temporal period ( ) on the initial pulse width (w 0) and studying the density contrast ( ) and correlation length (L c ) that characterize the randomness of the equilibrium density profiles. For small-amplitude pulses, does not alter significantly. Large-amplitude pulses, on the other hand, enhance the density contrast when is small but have a smoothing effect when is sufficiently large. We found that scales linearly with L c and that the scaling factor is larger for a narrower pulse. However, in terms of the absolute values of , broader pulses generate secondary waves with longer periods, and this effect is stronger in random plasmas with shorter correlation lengths. Secondary waves carry the signatures of both the leading wave pulse and the background plasma. Our study may find applications in magnetohydrodynamic seismology by exploiting the secondary waves detected in the dimming regions after coronal mass ejections or extreme ultraviolet waves.

Ion temperature effects on magnetotail Alfvén wave propagation and electron energization

AbstractA new 2‐D self‐consistent hybrid gyrofluid‐kinetic electron model in dipolar coordinates is presented and used to simulate dispersive‐scale Alfvén wave pulse propagation from the equator to the ionosphere along an L = 10 magnetic field line. The model is an extension of the hybrid MHD‐kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which also implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient magnetic field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the field line for the same magnitude perpendicular electric field perturbation.

Dispersion relation governing the propagation of wave pulses in a mixture of interacting longitudinal and transverse phonon gases

The investigations by Koreeda et al. (2009) and Ma (2013) of the effect of second sound in dielectric crystals assume the representation of the phonon system as a mixture composed of the gas of longitudinal phonons and the gas of transverse phonons. The theoretical background of those investigations can be related either to linear phonon gas hydrodynamics based on the moment equations of Dreyer and Struchtrup (1993) or to the heuristic model of energy transport in a phonon gas proposed by Rogers (1971). The relationship between these two approaches is analyzed. Specifically, restricting attention to the one-dimensional flows, the system of linear hyperbolic equations of six-moment phonon gas hydrodynamics is discussed together with the ‘equivalent’ system of two coupled third-order in time partial differential equations for the energy densities of longitudinal and transverse phonon branches. Given the six-moment system and its equivalent, the dispersion relation governing the propagation of complex plane harmonic waves is studied in detail. It is demonstrated that the interaction between the longitudinal phonon gas and the transverse phonon gas plays an important role when determining how the complex wave number depends on the real angular frequency of plane harmonic waves. The derived dispersion relation is systematically compared with that postulated by Ma (2013). Using the principle of superposition and the real plane harmonic waves as a basis, the manifestly real pulse-like solution to the equations of phonon hydrodynamics is explicitly constructed. It is shown that the computed energy-pulse profiles have the features that agree well with the main features of the energy or temperature profiles observed in the heat-pulse experiments.

Gravitational solitons in Levi-Cività spacetime

Applying the Pomeransky inverse scattering method to the four-dimensional vacuum Einstein equation and using the Levi-Civit\`a solution for a seed, we construct a cylindrically symmetric single-soliton solution. Although the Levi-Civit\`a spacetime generally includes singularities on its axis of symmetry, it is shown that for the obtained single-soliton solution, such singularities can be removed by choice of certain special parameters. This single-soliton solution describes propagation of nonlinear cylindrical gravitational shock wave pulses rather than solitonic waves. By analyzing wave amplitudes and time dependence of polarization angles, we provide a physical description of the single-soliton solution.

Sound pulse broadening in stressed granular media.

The pulse broadening and decay of coherent sound waves propagating in disordered granular media are investigated. We find that the pulse width of these compressional waves is broadened when the disorder is increased by mixing the beads made of different materials. To identify the responsible mechanism for the pulse broadening, we also perform the acoustic attenuation measurement by spectral analysis and the numerical simulation of pulsed sound wave propagation along one-dimensional disordered elastic chains. The qualitative agreement between experiment and simulation reveals a dominant mechanism by scattering attenuation at the high-frequency range, which is consistent with theoretical models of sound wave scattering in strongly random media via a correlation length.

Acute effects of ultrafiltration on aortic mechanical properties determined by measurement of pulse wave velocity and pulse propagation time in hemodialysis patients.

Objective:The effects of acute hemodialysis session on pulse wave velocity are conflicting. The aim of the current study was to assess the acute effects of ultrafiltration on the aortic mechanical properties using carotid-femoral (aortic) pulse wave velocity and pulse propagation time.Methods:A total of 26 (12 women, 14 men) consecutive patients on maintenance hemodialysis (mean dialysis duration: 40.7±25.6 (4-70) months) and 29 healthy subjects (13 women, 16 men) were included in this study. Baseline blood pressure, carotid-femoral (aortic) pulse wave velocity, and pulse propagation time were measured using a Complior Colson device (Createch Industrie, France) before and immediately after the end of the dialysis session.Results:While systolic blood pressure, diastolic blood pressure, mean blood pressure, pulse pressure, and pulse wave velocity were significantly higher in patients on hemodialysis than in healthy subjects, pulse propagation time was significantly higher in healthy subjects. Although body weight, systolic blood pressure, diastolic blood pressure, mean blood pressure, pulse pressure, and pulse wave velocity were significantly decreased, heart rate and pulse propagation time were significantly increased after ultrafiltration. There was a significant positive correlation between pulse wave velocity and age, body height, waist circumference, systolic blood pressure, diastolic blood pressure, mean blood pressure, pulse pressure, and heart rate.Conclusion:Although hemodialysis treatment may chronically worsen aortic mechanical properties, ultrafiltration during hemodialysis may significantly improve aortic pulse wave velocity, which is inversely related to aortic distensibility and pulse propagation time.

HYPERTENSION IN TAKAYASU DISEASE: PP.15.72

Objective: The aim of this work was to study in Takayasu's disease, clinical patterns, therapeutic particularities and the outcome of patients with hypertension. Design and Method: Among a cohort of 32 unrelated Takayasu's disease patients, followed over a 14-year period (1996–2009), 13 were included because of hypertension. Results and Conclusions: Mean age was 32.5 ± 12.4 years. Hypertension was a revealing symptom in one case and concomitantly discovered in 7 patients. Mean time lapse between first symptom and hypertension was 74 months in the other patients. Mean systolic blood pressure was 173 mmHg and diastolic blood pressure 102 mmHg. Besides hypertension, 4 patients presented one associated cardiac risk factor ie dyslipidemia in 1 case, smoking in 1, age over 60 years in 1 and obesity in 1 case. Target organ disease investigation revealed left ventricular hypertrophy in 3 cases, chronic renal failure in 3 cases, retinopathy in 2 cases and protenuria in 1 case. Hypertension mechanisms are often complex and intricate. Hypertension was due to renovascular disease in 6 patients. Unilateral renal artery stenosis was observed in 3 cases and bilateral in 3 cases. Three patients had associated lesions of the aorta involving the supra-aortic trunks and the renal arteries. Eleven had lesions of the supra-aortic trunks. In 9 cases, the carotid lesions with baroreceptor's hyposensitivity, presumably contributed to the genesis of hypertension. The steroid's iatrogenic effect contributed in 5 patients. Antihypertensive drugs were prescribed in 6 patients. Ten previously received steroid therapy which was secondary associated to immunosuppressive drugs. Renal artery endo-luminal angioplasty was attempted twice in 2 cases. First case constantly failed, but second underwent successfully bilateral aorto-renal bypass. Hypertension incidence in Takayasu's disease is hard to appreciate because blood pressure is often up- or under-estimated when supra-aortic trunks and the 2 sub-clavian arteries were involved altering hence wave pulse propagation and blood pressure clinical assessment. Hypertension over- demonstration and -estimation may have major therapeutic and iatrogenic consequences.

Propagation and Scattering of Spherical Wave Pulses in Vegetation Using Scalar Transport Theory

A high frequency theoretical model of propagation and scattering in vegetation is presented which uses scalar radiative transport theory. The specific problem analyzed is that of a periodic sequence of Gaussian pulses incident from free space into a forest region (vegetation). The incident pulse train is taken to be a spherical wave that is restricted to a specified solid angle, which is characteristic of radiation produced by a microwave or mm-wave antenna. The forest is modeled as a half-space of randomly distributed particles that scatter and absorb electromagnetic energy. In the forest, strong forward scattering occurs and the theory allows for a comprehensive characterization of the effect of vegetation on the propagation and scattering of spherical wave pulses: their attenuation, their angular spread, their distortion due to pulse broadening.

АЛГОРИТМЫ МЕТОДА НАЛОЖЕННЫХ СЕТОК ДЛЯ КОНЕЧНО-РАЗНОСТНОГО РЕШЕНИЯ НЕСТАЦИОНАРНЫХ ВОЛНОВЫХ ЗАДАЧ

Algorithms for the finite-difference analysis of dynamic wave fields in coupled subregions with different time-steps are developed based on the earlier presented method of superimposed meshes. Formulations with «freezing» the velocity along the lines of conjugation during a time-step and with using linear time interpolation are considered. High efficiency and accuracy of the presented algorithms is illustrated using the example of «cross-type» analysis of wave pulse propagation in elastic medium. Key words: method of superimposed meshes, finite-difference scheme, contact interaction, wave problem.