External Wave Research Articles

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.

Dynamic soil-structure interaction analysis for base-isolated nuclear island building based on the method of external source wave motion

Soil-structure interaction (SSI) is crucial to the dynamic response of nuclear power plants (NPPs), and should be properly considered when analysing the seismic isolation performance of base-isolated NPPs. In this study, a three-dimensional numerical simulation program is developed for the time-domain dynamic analysis of base-isolated NPPs considering SSI effects. The seismic input is realised using the method of external source wave motion, and the nonlinear behavior of isolators is fully considered. Using this program, the SSI effects of the base-isolated nuclear island building under different sites are analysed and compared, including the acceleration, displacement, and floor response spectra. The numerical results show that the SSI effects change the spectral characteristics of the actual seismic input. When the shear wave velocity of the site is relatively large, the SSI effects can increase the dynamic response of base-isolated NPPs. Additionally, the isolation performance of the base-isolated NPPs is weakened when SSI effects are considered, and with a decrease in the shear wave velocity of the site, the isolation capacity is further reduced. The influence of the SSI effects should be fully considered in the base isolation design of NPPs.

Coupling analysis of liquid sloshing and box sway motion under irregular wave actions

The coupling effect between the internal fluid sloshing and the box sway motion under irregular wave action is studied in this work. For describing external wave and internal sloshing actions, a hybrid numerical method combining linear potential flow and viscous flow is adopted. Numerical simulations show that coupling sloshing action plays an important role around sloshing natural frequencies. The significant resistant and enhanced actions can be observed at the frequencies around sloshing natural frequencies in regular waves. However, the above coupling effect approaches weak under irregular wave actions. The phase relation between the internal sloshing forces and external wave forces in regular waves cannot be found under irregular wave actions, which is the main reason for the decreased coupling sloshing effect. In all, the sway motion responses between irregular and regular wave actions show evident different behaviors from each other.

A System‐Level Feasibility Study of a Lead‐Free Ultrasonically Powered Light Delivery Implant for Optogenetics

Body implants play a crucial role in clinical applications, encompassing data acquisition, diagnosis, and disease treatment. However, challenges in size, power consumption, and biocompatibility, particularly in brain applications requiring small, battery‐free devices for deep areas, hinder their development. Despite potential advances through simplified, single‐purpose devices, such as recording or stimulation, overcoming the power and biocompatibility issues remains a hurdle. Addressing this, the article introduces an ultrasonically powered light delivery implant (LDI) utilizing lead‐free piezoelectric material (Li0.08K0.46Na0.46) NbO3 to harvest energy from external ultrasonic waves. The prototype includes a piezoelectric cube, a chip fabricated in 180 nm CMOS technology, and a microscale light‐emitting diode (μ‐LED) for optogenetics. Achieving an end‐to‐end efficiency of 0.75%, the LDI holds promise for various optogenetic studies, particularly in animal studies targeting specific brain areas for treating Parkinson's disease. The delivered optical power on the μ‐LED surface, at 14.1 mW mm−2, presents applicability to diverse studies involving specific opsins.

A new alternative approach to management of acute phase Peyronie's disease: low intensity extracorporeal shockwave therapy and platelet-rich plasma.

The aim of this study was to investigate the efficacy, safety, and outcomes of the combination of low ıntensity external shock wave therapy (Li-ESWT) and platelet-rich plasma (PRP) therapy in acute phase Peyronie's disease (PD). The datas of patients admitted with acute phase Peyronie's between January 2014 and January 2022 were reviewed retrospectively. In total, we included total 159 patients who used combination of vitamin E 600 mg/day plus colchicine 1.5 mg/day plus oral daily 5 mg tadalafil (N.=77) in group 1 and received Li-ESWT+PRP combination therapy plus oral daily 5 mg tadalafil (N.=82) in group 2. We noted characteristics of fibrous plaques, pain status, penile curvature degree, and erectile function parameters. All patients were visited at the 3rd and 12th months after the treatment. Preoperative demographic characteristics were similar in the two groups. There was a statistically significant improvement in the mean plaque size, penile curvature degree, IIEF-5 and VAS scores in the intervention group after the treatment. Ecchymosis and hematoma were not observed at the injection site and Li-ESWT application areas in the intervention group. No local or systemic drug reactions were noted in either group. Combination of Li-ESWT and PRP are highly effective and safety to early treatment in the acute phase PD.

Decoherence effects on lepton number violation from heavy neutrino-antineutrino oscillations

We study decoherence effects and phase corrections in heavy neutrino-antineutrino oscillation (NN¯O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ N\\overline{N}O $$\\end{document}s), based on quantum field theory with external wave packets. Decoherence damps the oscillation pattern, making it harder to resolve experimentally. Additionally, it enhances lepton number violation (LNV) for processes in symmetry-protected low-scale seesaw models by reducing the destructive interference between mass eigenstates. We discuss a novel time-independent shift in the phase and derive formulae for calculating decoherence effects and the phase shift in the relevant regimes, which are the no dispersion regime and transverse dispersion regime. We find that the phase shift can be neglected in the parameter region under consideration since it is small apart from parameter regions with large damping. In the oscillation formulae, decoherence can be included by an effective damping parameter. We discuss this parameter and present averaged results, which apply to simulations of NN¯O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ N\\overline{N}O $$\\end{document}s in the dilepton-dijet channel at the HL-LHC. We show that including decoherence effects can dramatically change the theoretical prediction for the ratio of LNV over LNC events.

Sloshing Response of an Aquaculture Vessel: An Experimental Study

The sloshing response is crucial to the design and operation of aquaculture vessels and affects the safety of the culture equipment and the efficiency of the culture operation. A 1/50 scaled model was utilized to investigate the coupled sloshing response characteristics of a novel aquaculture vessel in a wave basin. Two wave directions (beam and head wave) and two filling levels (81.5% and 47.4%) are taken into account. The time-domain and frequency-domain characteristics of the sloshing response under the linear regular wave and extreme operational sea state were investigated using regular wave tests and irregular wave tests, respectively. The sloshing mechanism in the aquaculture tanks is complicated, due to the coupling effect between external waves, ship motion, and internal sloshing. In linear regular waves, the wave frequency mode dominates the sloshing response, which is larger under beam wave conditions than under head wave conditions and larger under half load conditions than full load conditions. The irregular wave test results confirmed the regular wave test conclusions, but the sloshing response has stronger nonlinearity, higher natural modes appeared, and the amplitude of the higher natural modes is also relatively larger.

Are Quasi-periodic Pulsations Independent of Loop Oscillations in Solar Flare?

We investigated oscillations in an M8.7 solar flare (SOL2014-10-22), including quasi-periodic pulsations (QPPs) in light curves and Doppler shift oscillations in the flare loops. Using Bayesian-based Markov Chain Monte Carlo, Fast Fourier Transform, and wavelet analysis method, QPPs were identified at microwave and hard X-ray wave bands during the impulsive phase, and the dominant period is 40–50 s. They should be associated with a repetitive energy release process, which accelerates nonthermal electrons periodically. On the other hand, we cannot rule out the possibility of the modulation of external waves because of the lower temporal resolution of spectroscopic observation. However, almost immediately after QPPs, a minority of flare loops display their Doppler velocity oscillations with a significant period of ∼4 minutes, which are observed by the Interface Region Imaging Spectrograph at the coronal line Fe xxi 1354.08 Å (T ∼ 107 K), while its intensity and width show no similar oscillation. Our observations suggest that flare loop oscillations are most likely the fast kink mode waves with a phase speed of ∼840 km s−1. The magnetic field strength in flare loops was estimated to be 54–69 G via the coronal seismology. The QPPs and loop oscillation could be independent of each other in this event.

A Simulation of Air Lasing Seeded by an External Wave in a Femtosecond Laser Filament.

Air lasers induced by femtosecond laser filaments play an important role in remote sensing applications. Few studies have been dedicated to the spatial distribution of external-seeded air laser radiation in the laser filament based on the numerical simulation method, which can pave the way to understanding the mechanism of the external-seeded air lasing process during filamentation. In this study, numerical simulations of the propagation of an air laser seeded by an external plane wave with a wavelength of 391 nm during femtosecond laser filamentation were performed. The results indicated that the air laser's beam intensity distribution varies from a ring pattern to a donut pattern when the filament length and nitrogen ion density are raised as a result of the defocusing and lasing effects of the filament plasma. Here, the ring pattern is formed by several thin rings, while the donut pattern refers to a notably thicker, ring-like structure. In addition, it has been demonstrated that the air laser's beam power would increase exponentially versus the filament length and the nitrogen ion density. The knowledge about the angular distribution of air lasing could be important for optimizing the detection geometry of the LIDAR setup, including the view angle and the size of the collecting optical component.

Residence time distribution of an offshore floating photobioreactor under hydrodynamic sloshing effect

Sloshing is the movement of fluid in a partially filled vessel subjected to external motions. Although sloshing causes intense forces and instability to floating structures, the internal motion of liquid caused by external forces might be useful for devices that require mixing. For offshore floating photobioreactors, sloshing induced by external ocean wave forces are desirable, as the movement of liquid is able to bring about mixing and mass transfer for the nutrients and gas in the microalgae culture. The objective of this study is to investigate the correlation between the regular wave-induced sloshing of different motions (surge, heave, and pitch) on the mixing behaviour of the novel offshore floating photobioreactor designed to utilize the ocean surface waves for the effects of mixing. To determine the residence time distribution (RTD) of the stagnant volume of the photobioreactor, dissolved solids were injected into the system. The concentration of dissolved solids was measured using a total dissolve solid (TDS) sensor. The mixing caused by sloshing motion had the highest intensity during pitching motion. A homogenous solution was formed just after 65.9 s for the filling ratio of 30 %, with the rotation angle of 8 degrees and frequency of 0.21 Hz. Thus, wave-induced sloshing is able to generate intense mixing to the medium during pitching motion but still has non-ideal behaviours, such as bypass and dead zones during horizontal and vertical motion.

A split-explicit second order Runge–Kutta method for solving 3D hydrodynamic equations

Numerical models of marine hydrodynamics have to deal with processes exhibiting a wide range of timescales. These processes include fast external gravity waves and slower internal fully three-dimensional motions. In order to be both time-efficient and numerically stable, the time stepping scheme has to be chosen carefully to cope with the characteristic time scale of each phenomenon. An usual approach is to split the fast and slow dynamics into separate modes. The fast waves are modeled with a two-dimensional system through depth averaging while the other motions, where characteristic times are much longer, are dealt with in three dimensions. However, if the splitting is inexact, for instance in projecting the fields in a new 3D mesh, this procedure can lead to improper results regarding to the physical properties such as mass conservation and tracer consistency. In this work, a new split-explicit Runge–Kutta scheme is adapted and developed for the Discontinuous-Galerkin Finite Element method in order to obtain a new second-order time stepping, yielding to more accurate results. This method combines a three-stage low-storage Runge–Kutta for the slow processes and a two-stage low-storage for the fast ones. The 3D iterations are not affecting the surface elevation, hence an Arbitrary Lagrangian Eulerian implementation is straightforward. Water volume and tracers are conserved. A set of test cases for baroclinic flows as well as a laboratory application demonstrate the performance of the scheme. They suggest that the new scheme has little numerical diffusion.

The Impact of Uncertainty on the Control of a Multi-Axis Wave Energy Converter

As global energy demands and climate concerns continue to grow, the need for renewable energy is becoming increasingly clear and wave energy conversion (WEC) systems are receiving growing interest. Over the years, many WEC systems have emerged but most of these systems are designed to extract energy from a single direction of motion. In reality, there are six degrees of freedom that a conversion device can potentially harness and a device that can operate on multiple axes, should be able to more effectively and consistently produce power. However, the design and control of the power take off (PTO) system for a multi-axis device is challenging due to the system complexity and nonlinearity. WEC systems often utilize optimal control techniques for PTO operation and leverage a prediction of the upcoming wave force to ensure power optimization. Prior work has clearly demonstrated that high power production can be achieved when an exact system model is used and the upcoming wave conditions are known, but uncertainty in the underlying model or the wave prediction can degrade performance. PTO control on a multi-axis WEC must leverage predictions of forces in multiple directions and if model predictive strategies are used, must leverage a simplified model of the WEC dynamics to be able to optimize in real time. The uncertainty in these predictions and the model could severely degrade the WEC’s power output. This work examines the control of a multi-axis WEC system, TALOS, and leverages machine learning to predict wave forces over the upcoming time horizon. TALOS is a point-absorber type WEC with multi-axis PTO system. The PTO uses a heavy ball that is attached to the hull with springs and hydraulic cylinders. When the hull is pushed by the external waves, the relative motion between the ball and hull moves the hydraulic cylinders causing them to pump a fluid through a circuit, thereby driving a hydraulic motor to produce electricity. This design has shown promising results in energy output but is more challenging to control since the PTO can move over six degrees of freedom. This paper seeks to quantify wave prediction uncertainty and its seasonal variation and to examine the impact of the uncertainty of the prediction on a model predictive controller’s ability to optimize the power output of TALOS.

On the performance of different Deep Reinforcement Learning based controllers for the path-following of a ship

A set of continuous state-action space-based deep reinforcement learning algorithms are used for the path following of a ship in calm water and waves. The mathematical model of a KVLCC2 tanker represents the ship dynamics. The mathematical model includes the hull force, rudder force, propulsion force, and external wave forces. Look ahead distance-based guidance algorithm called Line of Sight (LOS) is used for computing the Cross Track Error (CTE) and Heading Error (HE). The reward function is designed based on HE and CTE. The created Environment is trained with four different Deep Reinforcement Learning (DRL) agents named Proximal Policy Optimization (PPO), Deep Deterministic Policy Gradients (DDPG), Twin-Delayed Deep Deterministic Policy Gradients (TD3), and Soft-Actor Critic (SAC). Common Neural Network architecture is used for all four agents. Yaw rate, HE, and CTE serve as input to the Neural Network, and the rudder deflection rate (δ°) corresponds to the action space (output). Computation time, average cross-track error, and rudder actuation are computed and compared for path-following scenarios. DDPG performs better with a minimum average CTE for all the simulated cases. However, SAC demands minimum rudder control effort to achieve the tasks. Finally, the trained agents are validated using Hardware In-Loop (HIL) simulation.

THE ROLE OF HIGHER MOMENTS ON THE DISTRIBUTION OF PARTICLES IN THE SPACE OF IMPULSES AT CYCLOTRON RESONANCES

The results of the analysis of the dynamics of charged particles under conditions of cyclotron resonances in the field of an intense electromagnetic wave are presented. Particular attention is paid to regimes with dynamic chaos. It is shown that there are two qualitatively different regimes. The appearance of the first one is due to the overlap of nonlinear cyclotron resonances. The second mode is related to intermittency. The moments and spectra of each of these regimes are determined. It is shown that with an increase in the intensity of an external electromagnetic wave, the first regime appears at the beginning and only then the second regime appears. A characteristic feature of the second regime is intermittency. Steps appear on the time dynamics of pulses in the second mode. It is shown that the spectra in the second mode are narrower than in the first mode. A characteristic feature of the second regime (the regime with intermittency) is the fact that the higher moments turn out to be larger than the lower moments. In the first regime, the highest moments decrease rapidly. To find the particle momentum distribution function, the generalized Fokker-Planck equation was used. Solutions of this equation are written out for some important cases.

Development and evolution mechanism of streamwise vortex in an inward-turning inlet

The three-dimensional flows in an inward-turning inlet were numerically investigated at different incoming flow conditions. When the incoming flow conditions change, the shock angle and the shock interaction form of the external compression wave change, and the development of the near-wall low-energy fluid and the streamwise vortex is also affected. The impingement of the shock wave leads to a sharp increase in the vorticity of the low kinetic energy fluid. Under the pressure gradient caused by the shock wave, the high-vorticity fluid migrates from the cowl to the ramp and entrains the mainstream fluid to form a streamwise vortex, for which the velocity gradient ( ∂v/ ∂y + ∂w/ ∂z) along the vortex axis can accurately determine the rotation direction and the Hopf bifurcation position. By considering high Reynolds number flows, the pressure gradient along the vortex axis is developed to estimate the simplified dilation term (velocity gradient) due to its ease of measurement. However, the pressure gradient ( ∂p/ ∂x) along the vortex axis can lead to bias when evaluating the cross-flow state of the streamwise vortex, with the shock wave structure and high-vorticity fluid leading to under- and overestimation, respectively. This study provides a theoretical basis for an accurate determination of the flow state of a streamwise vortex in an inward-turning inlet and thus lays the foundation for effective vortex control.

Dynamic Response Analysis of Intake Tower-Hydrodynamic Coupling Boundary Based on SV Wave Spatial Incidence

In view of the insufficient analysis of the coupled joint seismic response of the intake tower–reservoir water–foundation boundary under the oblique incidence of SV wave space, a three-dimensional dynamic equation of the oblique incidence of SV wave space is established in this paper. The external wave input method of viscoelastic artificial boundary combined with equivalent load and the acoustic medium theory are used to simulate the action of reservoir water, and the angle change in the SV wave incidence is realized by controlling the incident vector. The dynamic response of the structure is analyzed and the dynamic response characteristics of the structure at different incidence angles are discussed. The results show that the dynamic response and damage degree of the intake tower decreases first and then increases with the change in angle. When the vertical incidence is 0°, the maximum displacement drop is 82.05%, and the displacement response of the intake tower is more sensitive to the change in SV wave incidence angle. When SV wave is vertically incident at 0° and 35° (near the maximum critical angle of incident), the dynamic response, dynamic water pressure, damage diffusion velocity, damage area, and damage degree of the intake tower are relatively large, which seriously affects the safety and stability of the intake tower. Therefore, the influence of the oblique incidence should be considered comprehensively in the aseismic stability design of the water intake tower to provide a new idea for the safety evaluation of the same type of engineering.

Theoretical Study on the Nonlinear Dynamic Response of Propulsion Shafting under Time-Varying Hull Motion

Due to the effect of external elements such sea waves and sea wind, the ship will unavoidably produce 6 degrees of freedom of movement, with roll motion being the most likely to occur and having the greatest impact. This paper establishes a general dynamic model of the propulsion shafting based on Timoshenko beam theory, the concentrated mass method, and Lagrange’s equation under roll motion and translation motion to study the dynamic behaviour of the propulsion shafting under roll motion and translation motion. FFT, axis trajectory, Poincaré map, and 3D spectrogram were utilized to examine the impact of motion amplitude, frequency, and rotation speed on the propulsion shafting’s dynamic response. The results demonstrated that base motion significantly affects the dynamics of the propulsion shafting, resulting in many components appearing in the system’s response spectrum, and the system changes from quasi-periodic to chaotic motion when base motion amplitude or frequency rises.

Математическая модель волновой зубчатой передачи с генератором волн внешнего деформирования

The paper considers a spatial mathematical model of a wave gear with the annular generator of the external deformation waves. Calculation method was based on determination of the elastic interaction between flexible wheel, rigid wheel and wave generator. Numerical studies confirmed the adequacy of the proposed mathematical model. Theoretical studies of the influence of preload in the gearing and initial clearance between the flexible wheel and the deforming washers on the forces acting on the wave generator bearings were conducted. It is shown that a decrease in the specified clearance leads to an increase in loads on the bearings. By calculation, torsional rigidity characteristics of the wave gear with an external deformation generator were obtained for various interference values in the gearing and the clearance.

Observer‐based sliding mode H∞$H_\infty$ control for offshore structures with nonlinear energy sink mechanisms

AbstractIt is significant to reduce the wave‐induced vibration and ensure the safety of the offshore structure. This paper deals with the observer‐based sliding mode vibration control problem of offshore structures with nonlinear energy sink (NES) mechanisms. By considering the coupled nonlinear characteristics of unmodelled dynamics, system uncertainty, and external wave force, a more general nonlinear system model of the offshore structure equipped with an NES mechanism is presented. Then, an observer‐based sliding mode control scheme for the nonlinear structure‐NES system is developed. The existence condition and the design algorithm of the observer‐based sliding mode controller are provided. Simulation results show that the observer‐based sliding mode controller is capable of reducing the wave‐induced vibration amplitude of offshore structures effectively. Compared with the NES‐based passive control, the observer‐based sliding mode controller can further reduce the response amplitudes of the offshore structure remarkably. In addition, the designed observer‐based sliding mode controller is robust the variations of structure parameters and the external wave loads, thereby presenting potential advantages of the active damping control of the offshore structure.

Repetitive Low-Level Blast Exposure via Akt/NF-κB Signaling Pathway Mediates the M1 Polarization of Mouse Alveolar Macrophage MH-S Cells

Repetitive low-level blast (rLLB) exposure is a potential risk factor for the health of soldiers or workers who are exposed to it as an occupational characteristic. Alveolar macrophages (AMs) are susceptible to external blast waves and produce pro-inflammatory or anti-inflammatory effects. However, the effect of rLLB exposure on AMs is still unclear. Here, we generated rLLB waves through a miniature manual Reddy-tube and explored their effects on MH-S cell morphology, phenotype transformation, oxidative stress status, and apoptosis by immunofluorescence, real-time quantitative PCR (qPCR), western blotting (WB) and flow cytometry. Ipatasertib (GDC-0068) or PDTC was used to verify the role of the Akt/NF-κB signaling pathway in these processes. Results showed that rLLB treatment could cause morphological irregularities and cytoskeletal disorders in MH-S cells and promote their polarization to the M1 phenotype by increasing iNOS, CD86 and IL-6 expression. The molecular mechanism is through the Akt/NF-κB signaling pathway. Moreover, we found reactive oxygen species (ROS) burst, Ca2+ accumulation, mitochondrial membrane potential reduction, and early apoptosis of MH-S cells. Taken together, our findings suggest rLLB exposure may cause M1 polarization and early apoptosis of AMs. Fortunately, it is blocked by specific inhibitors GDC-0068 or PDTC. This study provides a new treatment strategy for preventing and alleviating health damage in the occupational population caused by rLLB exposure.