External Wave Research Articles

ON THE EFFICIENCY OF WAVE-PARTICLE INTERACTION

The efficiency of acceleration of charged particles during cyclotron resonances and acceleration of particles in a vacuum without an external magnetic field are considered. It is shown that the statement formulated in Lawson-Woodward theorem that relativistic particles do not exchange energy with an external electromagnetic wave in a vacuum is not sufficiently justified.

Blast wave ingress into a room through an opening – Review of past research and US DoD UFC 3-340-02

Blast wave ingress into a room through a facade opening results in complex pressure-time loadings on interior surfaces due to shock diffraction and interior reflections. The U.S. DoD UFC 3-340-02 Structures to Resist the Effects of Accidental Explosions includes a method to predict internal loading for such cases. Parameters such as the opening size, room dimensions and the external pressure wave characteristics influence the interior loading. Recent work suggests that the UFC methodology might overpredict the interior loading by some 600%. Such conservatism can result in over-engineered or prohibitively expensive protective solutions. In this paper we critically review the methodology of the UFC, that of Kaplan’s preceding work (on which the UFC relies), and the experimental data that informed both these works. Through a series of 45 case-studies we compare the UFC and Kaplan’s predictions with those of a computational fluid dynamics (CFD) model. The UFC consistently overpredicts the CFD area-averaged peak pressure of the back wall by up to 290% and the side-wall by up to 425%. Similarly, the UFC overpredicted the CFD side wall positive phase impulse by up to 565%. By contrast, the UFC predicted back wall positive phase impulse was similar to the CFD results. As our CFD results for side and back walls are area averaged, and not solely for the wall centre-point, as in other recent work, our paper gives support for the use of CFD prediction over the UFC for cost-effective design of structures to resist blast ingress.

Suppression of Nonlinear Chorus Wave Growth by Active Control of Gyroresonant Interactions With Electron Hole Deformation

AbstractNonlinear gyroresonant acceleration is an essential mechanism for the formation of relativistic electrons in Earth's radiation belts, yet we still have only limited knowledge of how electron motion interacts nonlinearly with plasma waves. Here we demonstrate the compelling suppression of whistler‐mode chorus emissions as a resonant wave with energetic electrons by tuning an external transmitter signal in space plasmas. Through forcible modification of electron motions via phase trapping by the external waves, the nonlinear gyroresonant current is suppressed along with the electron hole deformation. Moreover, this can decrease the population of relativistic electrons due to the lack of coherent resonant waves seen by the phase‐organized electrons. Understanding such nonlinear wave suppression effects is crucial for a potential active control of Earth's plasma environment.

TWO-DIMENSIONAL HYPERCHAOTIC MAP FOR CHAOTIC OSCILLATIONS

This manuscript explores a two-dimensional hyperchaotic map for generating chaotic oscillations. Hyperchaotic maps are finding increasing applications in various scientific and technological fields due to the unique properties of their generated oscillations. The studied map, based on two interconnected piecewise-linear functions, is one of the simplest for generating oscillations with a predetermined distribution of values across a continuous parameter space. This simplicity allows for wide applicability in various contexts. The paper presents simulation results demonstrating control over the parameters of the dynamic modes. Building upon these modeling results, a two-dimensional hyperchaotic system is implemented using an electric circuit. The chosen map is attractive due to its inherent simplicity and ease of parameter control. By adjusting these parameters, the distribution of the generated signal's values can be manipulated. The circuit consists of two symmetrical sections connected via feedback loops, employing four amplifiers with variable gain. The gain values act as the circuit's implementation of the control parameters. Chaotic oscillations are generated by applying a delayed clock signal from an external square wave generator to circuit elements. The obtained experimental results exhibit excellent agreement with the simulation data.

Hydrodynamic Analysis of Different Formation Configurations of Catamaran in Regular Head Waves

When undertaking long-distance missions at sea, vessels aim to achieve an extended operational range through drag reduction and energy efficiency, while enhanced wave resilience also provides substantial benefits. In this work, the Delft-372 catamaran is utilized to investigate the feasibility of drag reduction and roll mitigation for catamaran formation sailing in waves, analyzing the effects of three different formation configurations and varying spacings. The overset grid method was employed to simulate vessel motions, while the Volume of Fluid (VOF) method captured the free surface. First, the numerical results of the catamaran’s resistance, pitch, and heave motion amplitudes under different wave conditions were compared with experimental data to verify the accuracy of the CFD numerical method, and a grid convergence analysis was performed. Next, numerical models of the Delft-372 catamaran were constructed in parallel, tandem, and lateral formations under wave conditions. The results of the single-ship simulation were employed as a benchmark to analyze the impact of different formation configurations and varying lateral and longitudinal spacings on the resistance, pitch, and heave motions of the catamarans. The study also examined the effects of wave interference between vessels and the combined influence of external waves on individual and overall hydrodynamic performance. Results indicated that the tandem formation outperformed the parallel and lateral formations, with optimal performance observed at the longitudinal distance of 1 LPP. Generally, during navigation, the follower catamaran should ideally be positioned in the trough of the stern wave of the leader catamaran.

Kinetic Alfvén solitary waves in astrophysical plasmas

The magnetospheric plasma (hot and thin) and the solar wind plasma (cold and dense) are separated by the Earth’s magnetopause, in which plasmas of both origins coexist. Different types of plasma diffusions are found due to this plasma mixing, and kinetic Alfvén solitary waves (KASWs) are one of them. In this work, a theoretical approach is taken to study the fundamental properties of heavy ion acoustic KASWs (HIAKASWs) in a magnetized plasma system whose constituents are nonextensive q-distributed two temperature electrons with dynamical heavy ions. The perturbations of the magnetized collisionless plasma system are investigated using the reductive perturbation technique to deduce the Korteweg–de Vries (K–DV) and modified K–DV (MK–DV) equations to determine the fundamental characteristics of small, but finite amplitude HIAKASWs. The presence of nonextensive electrons, magnetic field, obliquity angle (the angle between the external magnetic field and wave propagation), plasma particle number densities, and the temperature of various plasma species are observed to significantly alter the fundamental properties of HIAKASWs. The findings of our present study may be useful for comprehending the nonlinear wave properties in diverse interstellar plasma environments.

Trajectory tracking control of unmanned surface vehicle based on optimized barrier Lyapunov function under real ocean wave modeling

The state-constrained trajectory tracking control problem of unmanned surface vehicle (USV) under real wave interference is studied in this paper. This method is closer to the actual situation. Firstly, the interference of real ocean waves measured by ocean wave experiments on USV is considered. The wave spectrum and the equal interval method are used to simulate ocean waves in combination with the classical long-crested wave model. Secondly, the simulated wave is innovatively transformed into wave interference force, and the interference of the real wave is applied to the state constraint control of USV. The disturbance observer is used to observe and compensate for the external real wave interference, and the input saturation problem in real situations is fully considered. Furthermore, this paper proposes an improved logarithmic constraint function, which pre-set the performance function to constrain the trajectory tracking position error of the USV within a reasonable range. Finally, the rationality and effectiveness of the control strategy are verified by simulation.

Coastal flooding in Kołobrzeg (Kolberg) area, southern Baltic Sea, in the light of historical and geological data

The Baltic Sea is not a typical tsunami area, but there are reports of coastal flooding, with its traces preserved in deposits from Germany, Finland and Sweden, and more recently from Poland. In this study an attempt was made to verify historical and legendary accounts of the ‘Sea Bear’ (‘der Seebär’) phenomenon. In the descriptions of folk accounts, the phenomenon has the features such as suddenness, speed, short duration, independence from the atmospheric conditions on land and sea. The search for coastal flooding deposits was conducted around the town of Kołobrzeg (Kolberg), located on the southern coast of the Baltic Sea. For the study area in chronicle record exist information about two events (17 September 1497 and 1 March 1779). For both events no record has been found in geological profiles, probably due to strong anthropogenic transformation of the subsurface layers. However there is quite precise information from chronicle records on the extent of the event from 17 September 1497 and on the thickness of the sandy layer left by the flooding. Based on this information in the Kołobrzeg area the range of the sand layer was 1400 m from the seashore, and its thickness locally reached approximately 10 cm. The flood height estimated according to the above-presented assumptions was 4.9 m a.s.l. In the Baltic Sea area, coastal flooding is possibly due to atmospheric forcing which can be responsible for an external waves event and devastating long waves, which have the same spatial and temporal scale as typical tsunami waves.

Ultrasound‐Driven Highly Stable Implantable Triboelectric Nanogenerator with Human‐Tissue Acoustic Impedance‐Matched Polyether Ether Ketone

AbstractImplantable electrical neurostimulators offer a promising avenue for treating neurological disorders. However, their dependency on a finite battery life limits their long‐term utility. Emerging transcutaneous ultrasound‐driven triboelectric nanogenerator (TENG) techniques provide solutions for converting external ultrasound waves into internal electricity. This study proposes an implantable ultrasound‐driven TENG (IU‐TENG) using polyether ether ketone (PEEK) for its exceptional stability inside a human body and acoustic impedance compatibility with human tissues. This IU‐TENG remarkably surpasses traditional titanium‐based encapsulation, resulting in a 99.94% efficiency in ultrasound transmission. In addition, PEEK contains numerous electron‐donating functional groups, making it suitable for TENG applications, particularly as a positive triboelectric layer. The device exhibits robust voltage outputs, reaching up to 11.50 and 8.75 V in water and in vivo, respectively, under body‐safe ultrasound intensities. Moreover, its ability to sustain a stable electrical output for over 300 min emphasizes the durability and mechanical resilience of PEEK. In vivo mouse models and ex vivo porcine tissue trials demonstrate the effectiveness of the IU‐TENG in nerve stimulation, showing its potential in medical treatments, enhancing the functionality and longevity of implantable medical devices.

Soliton robustness, interaction and stability for a variable coefficients Schrödinger(VCNLS) equation with inverse scattering transformation

The inverse scattering transformation(IST) method is an important method for solving soliton equations. In this paper, some novel solutions of a variable coefficients Schrödinger(VCNLS) equation are obtained with IST method. And we find that these waves have not the effected by other external waves, then call them on robustness waves. The VCNLS equation is derived from a non-isospectral AKNS equation hierarchy, and the spectral parameter is determined by an ordinary differential equation with polynomial nonlinearity. The VCNLS equation with the periodic and harmonic external potentials is solved via the inverse scattering transformation(IST) method, which possess the parity-time(PT) symmetric invariance. Unlike the classical NLS equation, the characteristic functions of the CVNLS equation with space–time external potential have two different symmetric reductions and two different backscattering solutions, which extends the application of IST and is helpful for the CVNLS equation. Some novel bright soliton solutions are obtained, which are different to the previous results in the classical case. The stabilities of the bright soliton solutions and the effect of the phase noise on the solutions are analyzed in a wide region through numerically. Especially, the interaction dynamics of between two solitons are investigated through addressing numerically, which have not a effected by other external waves. Thus, the novel features are different from these usual features of solitons, which have not a effected by other external waves.

Fluctuations in the “static” atmosphere and their effects on tropospheric ozone distribution

Atmospheric fluctuation can be seen everywhere. This study focuses on the record-breaking increase of O3 concentration during the summer in some sensitive areas in recent years. The findings indicate that in the vicinity of the East Asian continent near western Pacific ocean, when the atmospheric conditions are stable or neutral, it is conducive to the maintenance and propagation of atmospheric oscillations near the height of the pollutant mixed layer (H_PML). Accompanied by the "peak-trough" effect of external gravity wave oscillations, due to the abundant water vapor of the cloud system (there are low pressure or typhoon disturbances in summer) near the large-scale cloud belt at the edge of the subtropical high in the western Pacific, the bright temperature at cloud top shows "light and dark changes" on satellite images, forming a wave-like cloud system. The novelty of this study lies in the fact that atmospheric fluctuations near the H_PML is not only related to the known aggravation of heavy rainfall, but also leads to the additional value-added effect of aerosols. Under static atmospheric conditions, the impact of atmospheric fluctuations near the H_PML on additional rise of O3 concentration helps us to deepen our understanding of the so-called "entrained ozone (EZ) effect" in the atmosphere. Due to the external gravity waves, the concentration of O3 increased further. Diurnal variations of solar zenith angle and H_PML are key meteorological factors influencing the significant increase in near-surface O3 concentration entrainment. The formation mechanism of solar photochemical O3 is further deepened and supplemented by analyzing the record-breaking increase of O3 concentration in summer observed in recent years.

Study on the influence of outlet diameter on the out-field pressure action characteristics of pulse detonation cleaning device

Pulse detonation cleaning technology is an efficient cleaning technology that is used inert shock waves generated by decoupling the detonation to remove ash and deposits. And it has great advantages in the field of furnace cleaning. In order to investigate the pressure distribution characteristics outside the detonation cleaning device and to explore the effect of the device outlet diameter on the pressure distribution characteristics, numerical simulations and experimental studies of pulse detonation cleaning device with using propane-air as the fuel has been carried out. The numerical simulation and experimental study on pulse detonation cleaning device by using propane-air as the fuel has been carried out. The results show that: as the propagation distance increases, there is a trend for the out-field arc shaped shock wave to transform into plane wave, and the applied pressure tends to be similar from the axis outward, and the time it acts on the ash accumulation surface also tends to be similar. When the external shock wave acts on the ash accumulation surface of the non-convective tube bundle, except for the positive reflection at the axial opposite position, which generates one pressure peak, the other positions mainly generate two pressure peaks due to oblique reflection. The ratio (diameter ratio) between the diameter of the tail outlet and the diameter of the detonation chamber is 1, the pressure peak of inert shock wave in the out-field is the largest. Increasing or decreasing the out diameter of the tail will weaken the action of the inert shock to different degrees. For diameter ratio smaller than 1, the pressure peak of the inert shock increases with increasing diameter ratio, while for diameter ratios larger than 1, decreases with increasing diameter ratio.

Passive millimeter wave imaging low altitude detection technology

Passive millimeter wave imaging refers to the passive detection of naturally occurring background millimeter waves. After receiving external millimeter wave thermal radiation signals, the passive millimeter wave detection system will form images based on temperature differences and detect targets. Passive millimeter wave imaging has the advantages of non-radiation, non-contact, perspective imaging, good concealment, small size, and low power consumption. It is widely used in safety inspections, aircraft landing, low visibility navigation, sea surface detection and other fields. Driven by high and new technology, passive millimeter wave imaging low-altitude detection technology is rapidly developing. This paper introduced the basic principle of passive millimeter wave imaging, including the characteristics of millimeter wave radiation and Black-body radiation law, as well as its comparison with ordinary optical radiation. It also described the basic model of current passive millimeter wave imaging low altitude detection technology, explored the shortcomings of this technology and pointed out further work as well.

Application of the quantum model of the rotating wave approximation to the generation of spin waves in nanowires

The paper simulates systems in which two types of spin waves can occur, propagating in opposite directions. To achieve this, the quantum slow-wave approximation is employed, allowing for the determination of the probability distribution of occupied states in a quantum two-particle system subjected to perturbations, commonly referred to as Rabi oscillations. This model is specifically applied to a configuration of parallel nanowires exposed to an external electromagnetic wave within the microwave range. The study explores a potential application of the investigated nanostructures in the development of a device for detecting electromagnetic fields.

Experimental study on the physical mechanism of pulse noise in the tail of a recoilless gun

During the firing process of a recoilless gun, there is a high-intensity pulse noise phenomenon in its rear breech area. In order to obtain the physical mechanism of the pulse noise formation, this article designed experiments and used high-speed cameras and overpressure sensors to discover a “three peaks” phenomenon in the pulse noise at the shooter’s position. Using resistance strain sensors, the changes of strain with time in the chamber and nozzle expansion section of the recoilless gun during the firing process were recorded. By comparing the micro-strain data and overpressure data, the shock waves at the shooter’s position can be categorized into two types: internal shock waves and external shock waves. Internally, the opening of the blocking sheet initiates the formation of the initial shock wave, followed by the formation of a second pressure wave within the combustion chamber. The peak-to-peak interval between these two shock waves is nearly fixed, and the ratio of the dual peaks increases with the distance of the measurement position. The third shock wave forms externally to the nozzle, induced by the explosion of unburned propellant. As the weapon’s distance from the ground increases, the peak values of the overpressure data decrease, and the waveform of this explosion-induced shock wave transitions from a single-peak phenomenon to a double-peak phenomenon. This study can provide a reference for the study of the potential risk of injury to operators using single soldier recoilless guns and similar weapons.

The far-field diffraction of a plane wave on a system of randomly and in average periodically located point scatterers: the Debye-Waller factor

The description of the superposition field of a system of point sources with a random and, on average, periodic structure is considered. The description is given in the far field and the point sources are considered as centers of secondary sphere waves generated by an external plane wave. In contrast to the traditional approach, where description of the diffraction pattern is given on the base of wave field averaging, here the intensity is averaged.In the framework of the suggested approach the analytic formula of dependence of the average intensity on the direction observation is found. The influence of disorder on the values of intensity of main maximums of a periodic structure is investigated. It is shown that this influence depends on the ordinal numbers of the maximum and in the case of central main maximum this influence vanishes. The question of applicability of the Debye-Weller factor for describing of the statistic of diffracted field is discussed.

Warunki koegzystencji ludzi z infrastrukturą elektromagnetycznych technologii radiokomunikacyjnych w wybranych mikrośrodowiskach

This is a study of how people coexisting with the infrastructure of electromagnetic mobile communication technologies emitting radio waves in the work and living environment: (i) in passenger trains, (ii) in shopping centres and (iii) in passenger cars. It revealed significantly different trends, over the last five years (2018-2023), in the structure of exposure to radio waves, with slight changes in the level of total exposure in analysed environments used by workers and the public. The observed changes are related to the spread of mobile access to fast data transfer and increased speed of transmission from personal devices (terminals such as smartphones or tablets). The results from shopping centres showed dominant downlink-components of exposure (from base stations) and a broadening of their frequency band (due to the spread of LTE subscription services using the 2100 and 2600 MHz bands) in 2023, along with reduced uplink-components (from terminals) and components related to local hotspots of non-subscription networks (Wi-Fi). A broadening of the frequency band was also observed in measurements from passenger trains, but with the dominant uplink-components of exposure, regardless of the availability of local hotspots. In passenger cars, exposure to external radio waves (downlink components) also broadened in the frequency band (in the LTE 800 and 2600 MHz bands). A reduction in exposure fluctuations over time was found in all the studied microenvironments. This implies that different measures are necessary to reduce workers’ exposure, along with different methods of identifying and assessing the parameters there.

Optimization Analysis of the Shape and Position of a Submerged Breakwater for Improving Floating Body Stability

Submerged breakwaters can be installed underneath floating structures to reduce the external wave loads acting on the structure. The objective of this study was to establish an optimization analysis framework to determine the corresponding shape and position of the submerged breakwater that can minimize or maximize the external forces acting on the floating structure. A two-dimensional frequency-domain boundary element method (FD-BEM) based on the linear potential theory was developed to perform the hydrodynamic analysis. A metaheuristic algorithm, the advanced particle swarm optimization, was newly coupled to the FD-BEM to perform the optimization analysis. The optimization analysis process was performed by calling FD-BEM for each generation, performing a numerical analysis of the design variables of each particle, and updating the design variables using the collected results. The results of the optimization analysis showed that the height of the submerged breakwater has a significant effect on the surface piercing body and that there is a specific area and position with an optimal value. In this study, the optimal values of the shape and position of a single submerged breakwater were determined and analyzed so that the external force acting on a surface piercing body was minimum or maximum.

Electrical and Magnetic Properties of Materials for Electromagnetic Interference

General aspects about electromagnetic interference (EMI) have shown that various electronic and electrical devices, in the field of communications are very sensitive to many sources (emissions) of external electromagnetic waves with various bands of frequency components. All electrical equipment using radio communication contains intentional emitters and sensitive receivers. Since electrical and magnetic materials have different properties, the objective of this paper is to explore the shielding effectiveness of some materials and to suggest new compounds that satisfies the effective shielding requirements.

PHASE SYNCHRONIZATION OF PARTICLES AT CYCLOTRON RESONANCES

Subject and Purpose. The effects considered concern phase synchronization of electrons in an ideal plasma subjected to the action of an external uniform, d. c. magnetic field. Two modes of the synchronization are discussed, specifically one by an external electromagnetic field and the other by the cyclotron radiation emitted by the electrons. The purpose is to compare these forms of synchronization and their effects on plasma stability. Methods and Methodology. The plasma is represented as a set of coupled oscillators whose dynamics is described via coupled differential equations. Assuming the coupling between the oscillators to be weak we find analytical solutions to the equation, further performing a stability analysis which exploits standard approaches of the dynamical systems theory. The solutions found are validated through corresponding numerical simulations. Results. As has been found, an external electromagnetic wave may be capable of guiding the particles toward phase synchronization, which can lead to formation of phased bunches. This mechanism of particle grouping may prove to be more efficient, in terms of scale times of synchronization, if compared with known mechanisms exploiting relativistic effects. Additionally, we show that the cyclotron radiation emitted by the charged particles (which is often disregarded because of its smallness) can lead to self-phase synchronization of the electrons. Moreover, should the density of charged particles in the ensemble be sufficiently high, an instability can arise, potentially disrupting the ensemble. Estimates have been provided of the level of random fluctuations capable of undermining the synchronization process and plasma dynamics stabilization. Conclusions. The most significant finding of this analysis is the emergence of low-frequency oscillations in the charged oscillators set, followed by an onset of the plasma instability when the plasma density exceeds a certain critical value. Within that scenario, the ensemble of oscillators sitting in the external magnetic field is no longer held together by the field. The effect should be taken into account in applications related to plasmas of a relatively high density.