Wave Calculations Research Articles

Comment on “Petrogenesis of cretaceous shoshonitic rocks in the northern Wuyi Mountains, South China: A result of the roll-back of a flat-slab?” by

Modified theory of physical optics (MTPO) solution for a soft/hard strip is analyzed. It is shown that this solution is incorrect because the MTPO Green function does not satisfy boundary conditions. Defects of MTPO in calculations of fringe waves are also noticed.

Numerical simulation of the blast wave of a multilayer composite charge

Abstract The numerical simulation of a blast wave of a multilayer composite charge is investigated. A calculation model of the near-field explosion and far-field propagation of the shock wave of a composite charge is established using the AUTODYN finite element program. Results of the near-field and far-field calculations of the shock wave respectively converge at cell sizes of 0.25–0.5 cm and 1–3 cm. The Euler––flux-corrected transport solver is found to be suitable for the far-field calculation after mapping. A numerical simulation is conducted to study the formation, propagation, and interaction of the shock wave of the composite charge for different initiation modes. It is found that the initiation mode obviously affects the shock-wave waveform and pressure distribution of the composite charge. Additionally, it is found that the area of the overpressure distribution is greatest for internal and external simultaneous initiation, and the peak pressure of the shock wave exponentially decays, fitting the calculation formula of the peak overpressure attenuation under different initiation modes, which is obtained and verified by experiment. The difference between numerical and experimental results is less than 10%, and the peak overpressure of both internal and external initiation is 56.12% higher than that of central single-point initiation.

On higher–order corrections to nuclear bremsstrahlung cross sections

A quantitative understanding of bremsstrahlung by electrons in the screened field of atomic nuclei has been developed by several researchers over the last 80 years. However, some ranges of the possible parameters can still not be covered with good accuracy. Dirac partial-wave calculations are the best method developed to date, while analytic calculations are the only viable solution at high impinging electron energies. Recent progresses on both fronts will be discussed. In particular, state of the art partial wave results, including screening, allowed to test the Olsen–Maximon–Wergeland additivity rule discovered by analytic means. Closed expressions for the next-to-leading order corrections to the Furry–Sommerfeld–Maue wave functions are known. One next-to-next-to-leading order term is typically included in this type of approach. The effect of this extra term on the angular dependence of the double differential cross sections for photon emission by 2.5 MeV electrons is compared in detail with partial wave calculations which are exact at all orders.

First-principles investigation of electronic structure and derived structural and magnetic properties of HgTe alloyed with Mn transition metal

Full potential linearized augmented plane wave calculations for the entire range of alloy concentrations of cubic Hg1-xMnxTe are reported. The electronic exchange-correlation potential has been treated using the generalized gradient approximation (GGA). For high accuracy of band-gap energies, we used also the modified Becke-Johnson exchange potential with the GGA. Our results are generally in reasonably good accord with data available from the literature. It is found that the lattice parameter of the material system of interest violates Vegard's law. By alloying HgTe with various concentrations of Mn transition metal, Hg1-xMnxTe becomes less compressible and the total magnetic moment becomes more important. The analyses of the electronic structure and density of states showed that the alloy system in question exhibits a semiconducting character. The chemical trends of the material under investigation are examined and discussed from an aspect of electronic charge densities. The information obtained in the present study could become good guidance for use of this alloy system in various device applications, e.g., in photoconductive detector applications.

A closed-form solution to propagation of guided waves in a layered half-space under a time-harmonic load: An application of elastodynamic reciprocity

This article is concerned with the application of reciprocity in computing guided wave motions generated by a time-harmonic load in a layer of uniform thickness joined to a half-space. Explicit expressions for free Rayleigh waves and Love waves propagating in the layered half-space are introduced. Exact solutions of Rayleigh waves and Love waves are derived from reciprocity relations between an actual state – guided waves generated by a time-harmonic line load and a virtual state – an appropriately chosen free wave traveling in the structure. Scattered amplitudes of the wave motions are thus determined. The validation of the reciprocity approach is shown through the computation of the lowest Rayleigh wave mode in the layered half-space, which approaches the calculation of the Rayleigh surface wave in the half-space once the layer thickness approaches zero in the limit.

THERMAL MODEL FRO SAW CALCULATIONS IN THE LAYERED SYSTEMS

The calculation of surface acoustic wave (SAW) parameters in the layered systems consists of half infinite substrate and one or several layers when the temperature is variable have been considered. SAW phase velocity calculation with temperature dependent material constants have been discussed. Expressions for the temperature coefficients of delay (TCD) and the temperature coefficients of frequency (TCF) of the first and the second order with taking into account SAW dispersion have been evaluated. Numerical procedures for TCD and TCF calculation have been proposed.

Fundamental properties of scandium chalcogenides and their alloys: DFT study

The full-potential linearized-augmented plane wave calculations based on density functional theory are performed to study the structural, electronic, optical and thermodynamic properties of scandium chalcogenides ScX (X = S, Se, Te) and their ternary alloys at equilibrium as well as under pressure. The revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA) is used to calculate the structural properties. The electronic and optical properties are calculated employing the GGA and the modified Becke–Johnson (mBJ) approaches. Moreover, the calculated lattice parameters agree well with the experiment results. The structure NaCl-type (B1) of the scandium chalcogenides undergoes under pressure a structural phase transition to CsCl-type (B2) and ZnS-type (B3). The binary and ternary alloys indicate a metallic behavior using GGA and mBJ scheme. The interband contribution to the optical properties is investigated by calculating the dielectric parameters e1(ω), e2(ω) and the index of refraction n(ω). A quasi-harmonic Debye model is applied to calculate the thermal properties.

Inelastic Spin‐Wave Scattering by Bloch Domain Wall Flexure Oscillations

The calculations of the inelastic spin wave scattering by flexure vibrations of the Bloch domain wall (Winter's magnons) in thin magnetic films are presented. The approach is based on the interaction of the propagating spin waves with the dynamical emergent electromagnetic field generated by the moving inhomogeneous magnetization texture (domain wall). The probability of the spin wave scattering for the Winter's magnon emission and absorption processes essentially rises with the spin wave scattering angle increase up to 90°. The angular dependence of the scattering probability is essentially stronger for the magnon absorption processes that allow distinguishing these elementary emission/absorption processes experimentally.

First-principles study of solid solution strengthening in Mg–X (X=Al, Er) alloys

To study the solid solution strengthening effect on magnesium (Mg)–X (X = Al, Er) alloys, supercell models of Mg, \(\hbox {Mg}_{35}\hbox {Er}\) and \(\hbox {Mg}_{35}\hbox {Al}\) are established to perform the first-principles pseudopotential plane wave calculations based on density functional theory. The calculated cohesive energy of \(\hbox {Mg}_{35}\hbox {Er}\) is lower than that of \(\hbox {Mg}_{35}\hbox {Al}\). This indicates that \(\hbox {Mg}_{35}\hbox {Er}\) has better structural stability than \(\hbox {Mg}_{35}\hbox {Al}\). The bulk modulus, Young’s modulus and shear modulus of the solid solutions increases simultaneously when Al and Er are doped into the Mg matrix. Moreover, the solid solution strengthening of Er is much higher than the Al containing alloy. The order of toughness of the three solutions from the highest to the lowest is Mg, \(\hbox {Mg}_{35}\hbox {Er}\) and \(\hbox {Mg}_{35}\hbox {Al}\), while the order of increasing elastic anisotropy is in the reverse order. The number of bonding electrons of \(\hbox {Mg}_{35}\hbox {Er}\) in the low-energy region of the Fermi level is much higher than that of \(\hbox {Mg}_{35}\hbox {Al}\), and the density of states of \(\hbox {Mg}_{35}\hbox {Er}\) at the Fermi level is higher than that of \(\hbox {Mg}_{35}\hbox {Al}\). Compared with Al atoms, Er atoms share more electric charges with Mg atoms, which leads to an increasingly uniform charge distribution around Er atoms.

Investigation of Seismic Stability of High-Rising Buildings Using Grid-Characteristic Method

The purpose of this work was the numerical simulation of dynamic wave processes in heterogeneous media with the subsequent evaluation of their influence on various structures. The effect of earthquakes on ground buildings and underground structures was studied. In the work, we used the grid-characteristic method, which allows taking into account the physics of arising wave processes. The use of hierarchical grid systems allows the calculation of seismic waves directly from the earthquake source to ground-based buildings and underground structures. The work investigated the destruction of high-rise buildings under the influence of seismic loads. The emerging areas of fractures in various structures were studied. The effect of the earthquake on the underground structure was considered. The influence of the depth of the earthquake source was analyzed. Images of wave processes in structures and places of destruction were obtained. Note that we do not calculate the damage caused by falling of some collapsed parts of the building to others, but we calculate only damage caused directly by seismic activity. This type of damage is of the greatest interest, since it is necessary to avoid precisely this primary destruction. Also we investigate the nature of this type of damage, e.g, internal, near the surface, causing collapse, asymmetric. The novelty of the approach used also lies in the fact that we solve a linear elastic wave equation with constant coefficients in various subdomains of the integration domain, between which contact conditions are established. And the size and shape of these subdomains vary over time and depend on the solution. That is, the complete boundary problem of the elastic wave equation is nonlinear.

Methods of forecasting calculations of breakthrough wave at hydrodynamic accidents waterstorage dam

The article gives the method of calculation of water storages dam at hydro technical accidents.From natural disasters floods (flooding of water in the area and settlements) by the frequency of occurrence of the phenomenon, the area of distribution and the annual material damage ranked first. Moreover, in recent years, the world has seen an increase in the number and extent of floods and the associated social and economic losses. Both at present and in the foreseeable future, floods as a natural disaster cannot be completely prevented everywhere and everywhere, they can only be weakened, localized and with timely warning to minimize material damage. Therefore, one of the largest floods in recent years, that occurred in the West Kazakhstan region in the spring of 2011 and which took place without casualties, resulted in the allocation of more than 19 billion tenge in damage recovery from damage. Unplanned and inconsistent with general measures during floods and floods, the descent of these reservoirs can exacerbate the effects of flooding. The technical condition of the channel dams is especially dangerous. In case of possible accidents on these dams, many settlements, thousands of enterprises, millions of hectares of agricultural land can get into the affected area.Based on the results of full-scale leveling surveys, forecasting calculations of the breakthrough of the water reservoir dams of Bartogay, Kapshagay and Kurty hydrounits have made.Attached graphics show a dependence of water consumption at the dam breakthrough on the distance from the dam gates.

On Frequency and Spatial Periodicity of the Waves of the Anomalous Amplitude in the Ocean

The paper shows that the waves of anomalous amplitude are long-lived formations. They drift in the direction of the wave motion with the group velocity of the wave packet, which is half the phase velocity of the main wave. The swing of the wave (the distance from the hump to the trough) of the anomalous amplitude is more than three times the average value of the sweep of the wave motion. The modulation instability of this wave form a perturbation spectrum, the energy of which is twice the energy of the main wave in the developed process mode. The spatial size of the wave packet practically does not change, the amplitude of the swing in the maximum first increases, then gradually decreases. The number of such waves in areas of strong wind exposure is much larger than the statistics of random interference processes allow. This is due to the influence of the main wave (its amplitude remains noticeably greater than the amplitudes of each of the modes of the wave packet) on the behavior of each pair of modes from the wave packet of the perturbation. In the laboratory system, the duration of the anomalous wave coincides qualitatively with the time of existence of the Peregrin autowave. Although the Peregrin autowave corresponds to a different physical reality, where the dispersion of the wave is weak. Gravitational surface waves have a strong dispersion, and the NSE equation in this case is noticeably modified. However, in rest system of the wave packet (moving relative to the laboratory system) the abnormal amplitude wave lifetime is much longer. The distance that the wave packet travels with a persisting anomalous sweep is at least equal to several hundred wavelengths and can reach hundreds of kilometers. A simple calculation of such waves by means of space monitoring due to the small viewing area (frame) may be inaccurate. Once formed, such waves are able to drift over considerable distances. However, they may well get into the next frame of view. That is, estimates of the number of such waves can be overestimated.

The wavefunction reconstruction effects in calculation of DM-induced electronic transition in semiconductor targets

The physics of the electronic excitation in semiconductors induced by sub-GeV dark matter (DM) have been extensively discussed in literature, under the framework of the standard plane wave (PW) and pseudopotential calculation scheme. In this paper, we investigate the implication of the all-electron (AE) reconstruction on estimation of the DM-induced electronic transition event rates. As a benchmark study, we first calculate the wavefunctions in silicon and germanium bulk crystals based on both the AE and pseudo (PS) schemes within the projector augmented wave (PAW) framework, and then make comparisons between the calculated excitation event rates obtained from these two approaches. It turns out that in process where large momentum transfer is kinetically allowed, the two calculated event rates can differ by a factor of a few. Such discrepancies are found to stem from the high-momentum components neglected in the PS scheme. It is thus implied that the correction from the AE wavefunction in the core region is necessary for an accurate estimate of the DM-induced transition event rate in semiconductors.

Conservation laws in discrete geometry

The small length scales of the dissipative processes of physical viscosity and heat conduction are typically not resolved in the numerical simulation of high Reynolds number flows in the discrete geometry of computational grids. Historically, the simulations of flows with shocks and/or turbulence have relied on solving the Euler equations with dissipative regularization. In this paper, we begin by reviewing the regularization strategies used in shock wave calculations in both a Lagrangian and an Eulerian framework. We exhibit the essential similarities with Large Eddy Simulation models of turbulence, namely that almost all of these depend on the square of the size of the computational cell. In our principal result, we justify that dependence by deriving the evolution equations for a finite-sized volume of fluid. Those evolution equations, termed finite scale Navier-Stokes (FSNS), contain dissipative terms similar to the artificial viscosity first proposed by von Neumann and Richtmyer. We describe the properties of FSNS, provide a physical interpretation of the dissipative terms and show the connection to recent concepts in fluid dynamics, including inviscid dissipation and bi-velocity hydrodynamics.

Study of Protection Structures Planning for Krui Beach, Pesisir Barat Regency, Lampung Province

Labuhan Jukung Beach is one of the beaches in Kru, which is located on Krui Bay, West Coast District. This beach is a tourist beach directly adjacent to the Indian Ocean, so it has a high wave. Based on wind data from 2008 – 2017 that be analyzed in this research, Krui Beach has extreme wave height (25th return period) as big as 6 meters in deep-sea water and 3.4m in shallow water, consequently Krui Beach has the potential to erode To resolve these problems, must be built environmentally friendly coastal protection structure. The structure that can be used in this beach is groynes. Groynes serve as sediment traps and existence of groin does not disturb tourists who surf the beach. Based on HWS value and run-up wave calculation, the groin structure need to has elevation +10.3m from seabed, with armor weight is 6.3 ton.

Driving Magnetization Dynamics in an On-Demand Magnonic Crystal via the Magnetoelastic Interactions

Using spatial light interference of ultrafast laser pulses, we generate a lateral modulation in the magnetization profile of an otherwise uniformly magnetized film, whose magnetic excitation spectrum is monitored via the coherent and resonant interaction with elastic waves. We find an unusual dependence of the magnetoelastic coupling as the externally applied magnetic field is angle- and field-tuned relative to the wave vector of the magnetization modulation, which can be explained by the emergence of spatially inhomogeneous spin-wave modes. In this regard, the spatial light interference methodology can be seen as a user-configurable, temporally windowed, on-demand magnonic crystal, potentially of arbitrary two-dimensional shape, which allows control and selectivity of the spatial distribution of spin waves. Calculations of spin waves using a variety of methods, demonstrated here using the plane-wave method and micromagnetic simulation, can identify the spatial distribution and associated energy scales of each excitation, which opens the door to a number of excitation methodologies beyond our chosen elastic wave excitation.

Comparative study of structural, electronic, optical and thermoelectric properties of GaS bulk and monolayer

ABSTRACTThe structural, electronic, optical properties of GaS in bulk and monolayer forms have been studied by means of full-potential linearised augmented plane wave calculations within framework of the density functional theory. Generalised gradient approximation and Tran–Blaha modified Becke–Johnson exchange potential (mBJ) were employed for the treatment of exchange-correlation effect in calculations. Our calculated lattice parameters are in good agreement with previous theoretical results and available experimental data. The negative formation enthalpy and cohesive energy indicate that both bulk and monolayer GaS can be synthesised and stabilised experimentally. Our electronic results show that the band gap of GaS monolayer is higher than that of bulk counterpart and strong hybridisation between electronic states of constituent atoms is observed in both cases. The optical properties such as reflectivity, absorption coefficient, refractive index and optical conductivity were derived from calculated complex dielectric function for wide energy range up to 35 eV. Finally, the thermoelectric properties of GaS bulk and monolayer also were calculated using semi-classical Boltzmann theory within the constant relaxation time approximation for investigating their applicability in thermoelectric devices.

Extremely high Q and unidirectional laser emission due to combination of the Kolmogorov-Arnold-Moser barrier and the chaotic sea in a dielectric microdisk.

Emission characteristics of an oval-shaped microcavity laser are studied. In experiments, modes localized on periodic orbits emit unidirectionally with a narrow in-plane divergence angle of about 12deg. The origin of high directionality is elucidated by means of classical ray dynamics. Wave calculations show that the Q-factors of the resonances are higher than 108. We explain this extraordinary high Q-factor in relation with a dynamical barrier region where Kolmogorov-Arnold-Moser curves significantly obstruct leakages of resonances.

Fundamental problems of wave dynamics stratified medium modelling

In paper fundamental problems of wave dynamic stratified medium modeling (ocean, atmosphere) are considered. The basic mathematical models describing the processes of excitation, the propagation of internal gravity waves in vertical stratified horizontally inhomogeneous and non-stationary medium are presented. The uniform asymptotic forms of the internal gravity waves in horizontally inhomogeneous and non-stationary stratified medium are obtained. A modified spatio-temporal ray method is proposed, which belongs to the class of geometrical optics methods (WKBJ method). Analytical and numerical algorithms of internal gravity wave calculations for the real stratified medium parameters are presented. Some results of internal gravity waves measurements in real stratified medium (ocean, atmosphere) and it’s interpretations are discussed. The universal nature of the developed asymptotic methods of modeling makes it possible to efficiently calculate the wave fields and qualitatively analyze the solutions obtained, which makes it possible to analyze wave patterns in general, to correctly set up mathematical models of wave dynamics, and to carry out express estimates in actual measurements of wave fields in natural stratified medium.

Influence of different wave load schematisation on global ship structural response

ABSTRACTToday, Classification societies cover all the aspects about linear static finite element (FE) analysis through different design guidelines that help structural designers to streamline the design process and make Rule-requested structural verification of the proposed design. Structural modelling aspects are well defined, but for the wave load modelling some questions arise. Wave pressure distribution can be defined using direct wave calculations (e.g. the panel method) or using the Rule formulae definition. This paper presents a benchmark study carried out by the ISSC2018 Committee II-1 Quasi-Static Response. The objective was to investigate and compare alternatives to discretise and implement Rule-defined wave loads from classification societies on global FE models, and its impact on the global structural response. Results from calculations are presented on two ship types. Findings highlight the importance of identifying the lowest level of simplification in order to capture physical phenomena while minimising errors and inaccuracy in direct structural analyses results.