Physics of Wave Phenomena最新文献

A fiber-optic interferometer sensitive to variations in the constant magnetic field is presented. A magnetostrictive material is used as its sensitive element. The sensor is based on the Fabry–Perot interferometer with the length determined using a unique signal processing algorithm, which allows the measurement accuracy to be improved by two orders of magnitude. Advantages of the sensor are a high dynamic range, small size, and standard components. The working range of the sensor is (B leqslant 50{text{ mT}}) and the dynamic range is 84 dB. Recommendations are given for increasing the system sensitivity and the measurement accuracy.

General analytical expressions for space–time evolution of nanoparticle density in a suspension from a homogeneous initial particle concentration to an equilibrium particle distribution in the suspension are obtained within the hydrodynamic statistical approximation. Space–time evolution of the particle number density in an external electromagnetic field is studied for the first time.

The problem of estimating the distance to a sound source in an underwater waveguide from sound field measurements using a vertical receiving array is considered. In recent years, methods for solving this problem using an artificial neural network, to the input of which a sample correlation matrix of the recorded field is applied, have been developed. The inevitable inaccuracy of the mathematical model of environment makes it possible to train the network on only short paths using the so-called synthetic data, i.e., data of theoretical calculation. This paper considers an alternative approach, where input data are set by the distribution of recorded field intensity in the depth–arrival angle plane. This distribution, constructed using the coherent state method borrowed from the quantum theory, is less sensitive to the environment model inaccuracies than the initial field recorded by the array and the correlation matrix of the field. It is shown by numerical simulation that the use of the aforementioned distribution may expand the range of distances for which the network can be trained on synthetic data.

Two-dimensional semiconductor transition-metal dichalcogenides (TMDs) are now considered promising active components of spintronic terahertz emitters due to their strong spin-orbit coupling and a unique ability to effectively filter spin-polarized electrons. However, electronic and optical properties of two-dimensional materials appreciably depend on the type of substrate used and the features of the technological process for producing spintronic THz heterostructures, which directly affects the functional characteristics of devices. In this work, a comprehensive investigation is performed to study the effect of the sapphire substrate and standard deposition stages on monolayer WSe₂ as part of the Al₂O₃/2D–WSe₂/Co terahertz emitter. The structural quality, optical characteristics, and the presence of mechanical strain in the WSe₂ monolayer are analyzed using photoluminescence and Raman spectroscopy methods. Secondary-ion mass spectrometry is used to perform layer-by-layer chemical analysis of the structure and reveal interlayer diffusion. It is shown that the spintronic emitter fabrication process does not alter key properties of TMDs, which confirms that standard technological procedures preserve the functionality of two-dimensional semiconductor.

The results of studying the impact of laser pulses with different temporal shapes on a metallic material (structural steel) produced by selective laser melting are reported for the first time. The influence of the conventional and complex temporal shapes of laser pulses with identical energies and durations on initiation of dominant material destruction mechanisms and the effect of recoil pressure are investigated using mathematical modeling. The model allows for the nonlinear depth distribution of porosity characteristic of additive metallic materials. It is shown that pulses of complex temporal shape, which combine a long high-energy pulse and a short high-intensity pulse, cause an increase in the recoil pressure much higher than the increase in the capillary pressure. The increase in the recoil pressure in the laser interaction zone initiates an increase in the volume of the removed material and increases the laser processing speed in additive manufacturing of items. The results demonstrate the potential of using laser pulses of complex temporal shape for postprocessing of metallic materials produced on the basis of additive technologies.

The structural mechanisms of the transitions between crystalline phases Ih, III, V, VI, and VII, whose stability regions border the liquid phases in the PT phase diagram, are described. The possibility of forming pseudoscalar liquid-crystal (PSLC) states of water during melting of enantiomorphic ice III is discussed. An example of a structural nematic–cholesteric transition in an aqueous solution when a nematic liquid crystal is affected by a helical stationary wave is considered. The importance of studying the structure and properties of hydrogen peroxide aqueous solutions is substantiated.

In this study, nanosized aluminum (Al) thin films with different thicknesses were deposited on soda lime glass (SLG) substrates using the thermal sputtering technique for optoelectronic applications. Their optical properties were characterized using spectroscopic ellipsometry, a nondestructive method for analyzing film thickness, roughness, and optical constants. The results revealed that variations in film thickness significantly affected the refractive index and extinction coefficient. These changes were closely related to the microstructural differences and surface conditions. The findings highlight the potential of Al thin films for use in photonic and electronic devices, such as photodetectors and reflective coatings. This work provides valuable insight into the design of materials with tailored optical behavior.

Wave phase conjugation has been experimentally implemented for a vortex ultrasonic beam. An acoustic vortex was formed in water using a spherically focused emitter and a disk, introducing an angular phase shift. The opposite vortex was generated due to the parametric wave phase conjugation in a magnetostrictive material under electromagnetic pumping at the double frequency. A hydrophone was used to measure the longitudinal and transverse distributions of the amplitude and phase of the sound pressure fields of the incident and conjugate waves near the emitter focus; their mutual correspondence was demonstrated. It was shown that both beams are indeed vortex ones; the conjugate beam has the same chirality as the incident beam. Thus, the beams in the observation region are completely counter-propagating (in the sense of wave vector orientation). A standing wave with a nodal surface in the form of a helicoid was obtained as a result of the interference of the incident and the conjugate vortex beams near the focus.

Adsorption of molecular oxygen on the Ag(111) surface at room temperature has been studied using scanning tunneling microscopy (STM), Auger-electron spectroscopy (AES), temperature programmed desorption (TPD), and density functional theory (DFT). In the early stage of adsorption, the STM images show formation of a disordered phase in the form of dark spots (local oxide (Ag₆O₆) rings. Further O₂ dosing leads to the formation of a set of bright objects 5–8 Å in size, which were associated with CO₂ molecules stabilized on the surface due to the presence of H₂O molecules. Heating of the system to temperatures above 423 K led to partial desorption of silver dioxide molecules and formation of ordered striped ((8 times 2sqrt 3 )) and hexagonal (3 × 3) phases. According to the DFT calculations, the (3 × 3) phase can be interpreted as surface high-temperature silver carbonate (Ag₂CO₃), adsorbed on Ag(111). Small areas with the (3 × 3) phase can be seen in STM images even after heating to 540 K, which indicates higher temperature stability of surface carbonates on Ag(111) than it was believed previously.

A holographic method for filtering the casing wave during acoustic logging while drilling is proposed. The method is based on application of a two-dimensional Fourier transform to the phase-correlation diagram. The efficiency of the method is demonstrated by processing acoustic signals of the three-element device “Horizon-90-WAL,” which is designed to measure the parameters of the elastic waves generated in rocks by an electro-acoustic emitter. The phase-correlation diagrams, holograms, and spectrograms of the received signals before and after filtering the casing wave are presented. The method made it possible to identify longitudinal and transverse waves and estimate their propagation rates in the rock.