Acceleration Waves Research Articles

Depression Recognition Using Daily Wearable-Derived Physiological Data.

The objective identification of depression using physiological data has emerged as a significant research focus within the field of psychiatry. The advancement of wearable physiological measurement devices has opened new avenues for the identification of individuals with depression in everyday-life contexts. Compared to other objective measurement methods, wearables offer the potential for continuous, unobtrusive monitoring, which can capture subtle physiological changes indicative of depressive states. The present study leverages multimodal wristband devices to collect data from fifty-eight participants clinically diagnosed with depression during their normal daytime activities over six hours. Data collected include pulse wave, skin conductance, and triaxial acceleration. For comparison, we also utilized data from fifty-eight matched healthy controls from a publicly available dataset, collected using the same devices over equivalent durations. Our aim was to identify depressive individuals through the analysis of multimodal physiological measurements derived from wearable devices in daily life scenarios. We extracted static features such as the mean, variance, skewness, and kurtosis of physiological indicators like heart rate, skin conductance, and acceleration, as well as autoregressive coefficients of these signals reflecting the temporal dynamics. Utilizing a Random Forest algorithm, we distinguished depressive and non-depressive individuals with varying classification accuracies on data aggregated over 6 h, 2 h, 30 min, and 5 min segments, as 90.0%, 84.7%, 80.1%, and 76.0%, respectively. Our results demonstrate the feasibility of using daily wearable-derived physiological data for depression recognition. The achieved classification accuracies suggest that this approach could be integrated into clinical settings for the early detection and monitoring of depressive symptoms. Future work will explore the potential of these methods for personalized interventions and real-time monitoring, offering a promising avenue for enhancing mental health care through the integration of wearable technology.

Investigation into the Prediction of Ship Heave Motion in Complex Sea Conditions Utilizing Hybrid Neural Networks

While navigating at sea, ships are influenced by various factors, including wind, waves, and currents, which can result in heave motion that significantly impacts operations and potentially leads to accidents. Accurate forecasting of ship heaving is essential to guarantee the safety of maritime navigation. Consequently, this paper proposes a hybrid neural network method that combines Convolutional Neural Networks (CNNs), Bidirectional Long Short-Term Memory Networks (BiLSTMs), and an Attention Mechanism to predict the heaving motion of ships in moderate to complex sea conditions. The data feature extraction ability of CNNs, the temporal analysis capabilities of BiLSTMs, and the dynamic adjustment function of Attention on feature weights were comprehensively utilized to predict a ship’s heave motion. Simulations of a standard container ship’s motion time series under complex sea state conditions were carried out. The model training and validation results indicate that, under sea conditions 4, 5, and 6, the CNN-BiLSTM-Attention method demonstrated significant improvements in MAPE, APE, and RMSE when compared to the traditional LSTM, Attention, and LSTM-Attention methods. The CNN-BiLSTM-Attention method could enhance the accuracy of the prediction. Heave displacement, pitch displacement, pitch velocity, pitch acceleration, and incoming wave height were chosen as key input features. Sensitivity analysis was conducted to optimize the prediction performance of the CNN-BiLSTM-Attention hybrid neural network method, resulting in a significant improvement in MAPE and enhancing the accuracy of ship motion prediction. The research presented in this paper establishes a foundation for future studies on ship motion prediction.

Towards advanced forecasting of solar energetic particle events with the PARASOL model

Gradual solar energetic particle (SEP) events are generally attributed to the particle acceleration in shock waves driven by coronal mass ejections (CMEs). Space-weather effects of such events are important, so there has been continuous effort to develop models able to forecast their various characteristics. Here we present the first version of a new such model with the primary goal to address energetic storm particle (ESP) events. The model, PARASOL, is built upon the PArticle Radiation Asset Directed at Interplanetary Space Exploration (PARADISE) test-particle simulation model of SEP transport, but includes a semi-analytical description of an inner (i.e., near the shock) part of the foreshock region. The semi-analytical foreshock description is constructed using simulations with the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) model, which simulates proton acceleration self-consistently coupled with Alfvén wave generation upstream of the shock, and subsequent fitting of the simulation results with suitable analytical functions. PARASOL requires input of solar wind and shock magnetohydrodynamic (MHD) parameters. We evaluate the performance of PARASOL by simulating the 12 July 2012 SEP event, using the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) MHD simulation of the solar wind and CME in this event. The PARASOL simulation has reproduced the observed ESP event ($E\lesssim 5$~MeV) in the close vicinity of the shock within one order of magnitude in intensity.

The Deformation of a Liquid Metal Droplet Under Continuous Acceleration in a Variable Cross-Section Groove.

This paper constructs a numerical simulation model for the deformation of droplets in a variable cross-section groove of a liquid droplet MEMS switch under different directions, amplitudes, frequencies, and waveforms of acceleration. The numerical simulation utilizes the level set method to monitor the deformation surface boundary of the metal droplets. The simulation outcomes manifest that when the negative impact acceleration on the X-axis is 12.9 m/s2, the negative impact acceleration on the Y-axis is 90 m/s2, the negative impact acceleration on the Z-axis is 34.5 m/s2, and the metal droplet interfaces with the metal electrode. The droplet deformation under the effect of a sine wave acceleration signal in the X and Y directions is lower than that under impact acceleration, while in the Z direction, the deformation is higher than that under impact acceleration. The deformation of metal droplets under square wave acceleration is more pronounced than that under sinusoidal wave acceleration. The deformation escalates with the augmentation in square wave amplitude and dwindles with the reduction in square wave acceleration frequency. Furthermore, there exists a phase difference between the deformation curve of the metal droplet and the continuous acceleration signal curve, and the phase difference is dependent of the material properties of the metal droplet. This work elucidates the deformation of the liquid-metal droplets under continuous acceleration and furnishes the foundation for the continuous operation design of MEMS droplet switches.

Continuous-discontinuous modeling of failure in micromorphic media

Deformation and failure are typically developed at multiple scales for the majority of engineering materials. At the macroscopic level of observation, structural rupture is triggered by a localized failure that corresponds to a loss in the material continuity within a specific region of the body. This localized failure is preceded by microcrack coalescence that can be observed at lower observation levels. This study investigates the propagation of a discrete fracture within a continuum damage process zone within the framework of micromorphic media. The adopted generalized continuum theory is well suited for modeling microstructured materials and also recognized in the relevant literature for its regularization properties due to its non-local formulation. Microcracking prior to coalescence is represented by continuum damage models based on a recently proposed formulation for elastic degradation in micromorphic media. The propagation of a discrete fracture is based on the analysis of a generalized micromorphic acoustic tensor, which is here derived considering the concepts of acceleration waves. When instability is detected, a discontinuity is introduced by the Extended/Generalized Finite Element Method. The required implementations for the numerical investigation of the proposed model are conducted in the open-source software INSANE.

Inverse Cherenkov dielectric laser accelerator with alternating phase focusing for subrelativistic particles

In this paper, we propose a dielectric laser acceleration scheme based on the inverse Cherenkov effect, which uses the principle of alternating phase focusing to accelerate, confine, and bunch the subrelativistic electron beam over an extended distance. In this scheme, the reference electron is always synchronized with the acceleration wave and is thus continuously accelerated. Electrons around it are alternately subjected to focusing and defocusing forces by alternately jumping its phase. Optimizing the focusing period can achieve stable beam confinement. Simulations show that a 100 keV electron bunch can be coherently accelerated with the average acceleration gradient of 220.8 MV/m, and it can travel nearly 200 μm without loss in a channel only 500 nm wide. This approach is scalable, potentially enabling the development of millimeter-scale MeV particle accelerators for ground-breaking use in medical, scientific, and materials research. Published by the American Physical Society 2024

Influence of cork-rubber gasket on the circular propagation of train-induced vibration waves in high-speed railway shield tunnels

Shield tunnels are constructed by assembling segment, and this construction method will produce a large number of joints. As the component with the largest contact area in the joints of the shield tunnel, the cork-rubber gasket has a significant effect on the transmission of train-induced vibration waves between the segments. In order to study the influence of cork-rubber gasket on the transmission of train-induced vibration waves in the circumferential direction, based on the hammering test of high-speed railway shield tunnel, a dynamic calculation model for high-speed railway shield tunnel was constructed, and the influence of elasticity modulus of cork-rubber gasket on the propagation of train-induced vibration waves was investigated. The results show that: (1) the longitudinal joints of high-speed railway shield tunnels can weaken high-frequency vibration waves more than low-frequency vibration waves; (2) the lower the modulus of elasticity of cork-rubber gasket is, the greater the attenuation of the peak of the temporal range of vibration acceleration of train-induced vibration waves after they pass through the longitudinal joints; (3) compared with the cork-rubber gasket of high elasticity, the cork-rubber gasket with low elasticity can improve the damping effect of the longitudinal joints on low-frequency bands (0–500 Hz) effectively. This research offers new methodologies for optimising vibration isolation in shield tunnels and contributes to the advancement of tunnel design for high-speed rail systems.

Control of spin-wave polarity and velocity using a ferrimagnetic domain wall

We present a theoretical study of the scattering of spin waves by a domain wall (DW) in a ferrimagnetic (FiM) spin chain in which two sublattices carry spins of unequal magnitudes. We find that a narrow but atomically smooth FiM DW exhibits a different behavior in comparison with similarly smooth ferromagnetic and antiferromagnetic DWs due to the inequivalence of the two sublattices. Specifically, for sufficiently weak anisotropy, the smaller spin at the center of the DW is found to become precisely normal to the easy axis, selecting an arbitrary direction in the xy plane and thereby breaking the U(1) spin-rotational symmetry spontaneously. This particular form of a FiM DW does not occur in antiferromagnetic systems and is shown to lead to a strong dependence of spin-wave scattering pattern on the state of polarization of the spin wave, which can be either right-handed or left-handed, suggesting the utilization of such a narrow DW as a spin-wave filter. Moreover, we find that in the case of an atomically sharp DW, where all the spins point either up or down due to strong easy-axis anisotropy and therefore the polarization of the spin wave is conserved upon transmission, the wave vector of the spin-wave changes after passing through the DW leading to a change in the group velocity of the spin wave. This change of the wave vector indicates the acceleration or deceleration of the spin waves and thus a sharp FiM DW could serve as a spin-wave accelerator or decelerator in spintronics devices, offering a functionality absent in a ferromagnetic and an antiferromagnetic counterpart. Our results indicate that FiM spin textures can interact with spin waves distinctly from ferromagnetic and antiferromagnetic counterparts, suggesting that they may offer spin-wave functionalities that are absent in more conventional magnets. Published by the American Physical Society 2024

Investigation on the Effect of Energy Release Rate of Aluminized Explosive on the Damage of Underwater Targets

AbstractAs a type of high‐energy explosive, aluminized explosives are extensively used in underwater weapons and ammunition. This study aims to investigate the energy release rate on the damage of underwater targets caused by aluminized explosives (RDX/Al). The ship was selected as a target, and numerical simulations were conducted using AUTODYN software to study the energy release rate corresponding to different particle sizes of aluminum powder (25 nm −300 μm) in the underwater explosion process of RDX/Al, as well as its destructive effect on targets in the water. The research quantitatively evaluates the whole ship′s destruction results, including longitudinal bending deformations and crevasse. In addition, typical cabins were selected in this study to assess the local damage effects by analyzing stress, shock wave pressure, displacement, and acceleration shock response. Based on the damage results, it was revealed that RDX/Al with aluminum powder particle sizes ranging from 54 nm to 145 nm exhibited the most optimal damaging effects on ships after underwater explosions. These findings provide a basis for improving the destructive power of aluminized explosives against underwater targets, simultaneously, they can be utilized by ship designers to guide research and development of improved protective measures, aiming to reduce the vulnerability of ships to explosive attacks.

Energetic seed particles in self-consistent particle acceleration modeling at interplanetary shock waves

Aims. The study investigates the relevance of the seed particle population in the results of particle acceleration in interplanetary shock waves, when wave–particle interactions are treated self-consistently. Methods. We employed the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) model, which is a proton acceleration simulation in shocks with self-consistent nonlinear wave–particle interactions. We compared a suprathermal monoenergetic injection with a two-component injection, including the suprathermal monoenergetic component and a broad-spectrum energetic component corresponding to the observed background particle spectrum. Energetic particles in the beginning of the simulation could increase the local wave intensities sufficiently to increase the rate of acceleration for injected particles and even reshape the resulting particle energy spectra and spatial distributions. The resulting particle energy spectra, particle spatial distributions, and wave intensity spectra are compared to observations made by Solar Orbiter’s instrument suite of the 2021 October 30 energetic storm particle (ESP) event to evaluate the relevance of the seed particle population in the acceleration model. Results. The energetic component of the seed particle population shortens the needed acceleration time for particles and enhances the tail of the spectrum to a level that matches the observations. The highest compared energies (> 1 MeV) match only when an energetic component is included in the seed particle population. The wave intensities and spatial distributions, on the other hand, showed no significant differences with the monoenergetic and two-component injection. While the simulated and observed wave intensities match within five minutes before the shock passing, the simulated wave field is too intense farther out from the shock, probably due to a lack of wave damping and/or decay processes in the simulation, leading to particles being slightly overly trapped to regions closer to the shock.

Numerical analysis of sloshing effects in cryogenic liquefied-hydrogen storage tanks for trains under various vibration conditions

This study examines the effects of hydrogen sloshing on internal pressure, temperature, and fluid behavior liquefied-hydrogen storage tanks designed for train usage by applying the natural frequency and frequency conditions from train vibration test standards. Notably, it investigates the impact on BOG generation using a transient volume-of-fluid phase change model. Here, simulations were conducted at vibrations of 0, 0.53, 1.53, and 3 Hz, which were established using sine wave acceleration. The results demonstrated that sloshing increased with higher frequencies, thereby resulting in a more intense heat transfer between the wall of the tanks and free surface of hydrogen and an increase in the BOG generation. Compared to the 0 Hz baseline, BOG generation increased by 13, 44, and 66 % at 0.53, 1.53, and 3 Hz, respectively.

Granular Cooling of Uni‐Sized Inelastic Particles in an Obstructed Chute

AbstractThis research aims to experimentally characterize cooling, clogging and jamming of a dry granular flow in a chute partially obstructed by a stopping wall with two slits adjacent to the side walls. We ensemble‐average velocities, determined with Particle Tracking Velocimetry, and its fluctuations, to compute mean flow and granular temperature fields. Full chute‐wide jamming is triggered by the formation of stable arch‐like clogging structures in front of the slits. The statistical distribution of the clogging instant is not heavy‐tailed, which indicates that clogging occurs only when the flow through the slits is liquid‐like. An upstream‐progressing jamming wave eventually forms, similar to that observed in fully obstructed chutes. There is no triple point anywhere, since the flow cools down to a granular liquid before jamming. We identified three main stages of jamming wave propagation. The initial buildup is characterized by high values of the upstream Froude number, slow progression, and transformation of kinetic into potential energy. This occurs with significant granular head losses, as particles attempt to flow over the jam. In the second stage, accretion becomes dominant, characterized by smaller head losses and, consequently, higher values of the jamming wave celerity. In the third stage, the jamming wave propagates against a cooler but faster flow that pushes against the jam, slightly increasing the wave strength. Accretion is the main mechanism of jammed mass increase, justifying a further increase of wave acceleration. The macroscopic aspects of the jamming wave dynamics can be described, as a first approximation, by shallow‐water theory.

Study on the Improvement of the Degradation Efficiency of Methylene Blue Using Pulsed Direct-Current Self-Power Supply.

Effective treatment of dye wastewater is currently a great concern and a research hotspot. Electrocatalysis has unique advantages in treating toxic and harmful refractory dye wastewater; however, it requires an external power supply, which increases energy consumption and cost. As a new energy collection technology, triboelectric nanogenerators (TENGs) have gained considerable attention. In this study, an origami multilayer spherical friction nanogenerator (Q-TENG) was developed for the removal of methylene blue (MB) from dye wastewater. The current and voltage output performances of Q-TENG were explored, and the removal and degradation mechanisms of MB were discussed. Results indicated that when the water wave acceleration a = 3 m/s2, the open-circuit voltage and short-circuit current reached the maximum values of 179 V and 9.4 μA, respectively. The self-powered catalytic degradation of MB using Q-TENG can produce more •OH and SO4-•, and the free radicals increase with increasing action time of Q-TENG, thus increasing the degradation efficiency of MB. This study provides a new strategy for solving the problem of high energy consumption during electrochemical reactions in wastewater treatment.

Numerical Investigation of the Effects of Aspect Ratio on the Hydrodynamic Performance of a Semi-Planing Catamaran

Abstract A semi-planing catamaran is a type of marine craft that benefits from high speed, in conjunction with the its inherent characteristics such as a large deck and high transverse stability. The aspect ratio, length over the beam of a demi-hull, significantly affects the hydrodynamic performance of this vessel. In this study, the effects of the aspect ratio on the hydrodynamic performance of a semi-planing catamaran in calm water and waves are investigated using numerical simulations. The numerical simulation of the AUT-SEM00 model itself is validated by its model test results. The results show that increasing the aspect ratio significantly increases the wetted surface, and that the increase in resistance in calm water is negligible. In addition, increasing the aspect ratio radically reduces the amplitude of vertical acceleration in waves at the center of gravity by up to 85%. Consequently, the seakeeping performance is considerably improved, and the risk to crew and equipment is reduced.

Result Comparison of Spectral Matching Between <i>Seismomatch</i> and <i>Specmatch </i>Computer Program

The earthquake ground motion, or acceleration time history, caused by an earthquake event, is an earthquake acceleration wave that can be utilized as a basis to design earthquake-resistant civil engineering buildings. The earthquake acceleration time history is needed as a basis to determine the earthquake loading for the building structure design. A time history can be developed from recorded data using spectral matching software. In this process, the response spectra of the recorded time history are matched to a specific target spectrum. The target spectrum is developed based on the Indonesian National Standard known as SNI 2012 (SNI code). The response spectra derived from this standard are referred to as the design response spectrum. These response spectra adopted by the SNI code are based on the ASCE code from the US. Two spectral matching software programs, namely Seismomatch and Specmatch, are employed for this purpose. In this study, both of software programs are utilized to match the response spectra of a time history to a predefined response spectrum. The results of the matching process indicate that Seismomatch does not produce a satisfactory match between the response spectra of the time history and the target spectrum, whereas Specmatch provides a matching result where the response spectra of the time history nearly perfectly align with the target spectrum.

Nonclassical wave propagation measurements in the high temperature vapor of D6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {D}_{6}$$\\end{document} with the asymmetric shock tube for experiments in rarefaction waves (ASTER)

A novel test setup called the asymmetric shock tube for experiments on nonideal rarefaction waves (ASTER) has been commissioned at Delft University of Technology. The ASTER, which works according to the principle of Ludwieg tubes, is designed to generate and measure the speed of small and finite amplitude waves propagating in the dense vapors of fluids formed by complex organic molecules, therefore in the nonideal compressible fluid dynamics regime. The ultimate goal of the associated research is to prove the existence of nonclassical gasdynamics. The setup consists of a high-pressure charge tube and a vacuum tank separated by a glass disk equipped with a breaking mechanism for rarefaction waves experiments. When the glass disk is broken, an expansion wave propagates into the tube in the direction opposite to the fluid flow. The propagation speed of this wave is measured using a time-of-flight method with the help of four fast-response pressure sensors placed equidistantly in the middle of the tube. The charge tube can withstand pressures and temperatures of up to 15 bar and 400∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\mathrm{C}$$\\end{document}. Preliminary rarefaction experiments were successfully conducted using dodecamethylcyclohexasiloxane, D6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {D}_{6}$$\\end{document}, as the working fluid and at pressures and temperatures of up to 9.4 bar and 372∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\mathrm{C}$$\\end{document} , respectively. The results of an experiment featuring the initial state for which a theoretical model predicts the nonclassical acceleration of rarefaction waves show that the propagation is qualitatively different from that put into evidence by experiments for which the propagation is classic. Upcoming setup improvements and experimental campaigns are planned with the objective of experimentally verifying the existence of nonclassical gasdynamics.Graphical abstract

Self-organisation of early stress response in the biology of cancer.

The early stress response by AP-1 (FOS/JUN), supported by upregulation of c-Myc and involved in cell-fate changes and adaptation to hostile environments, is increased in cancer. The review shows the biphasic character of this response with negative feed-back typically lasting a few hours as a feature of the genome regulation by self-organising criticality. It involves rapid splitting of the pericentromeric heterochromatin clusters, opening of the active chromatin, and a massive transcription acceleration wave. Phylostratigraphic analysis revealed that AP-1 genes evolved in the Cambrian explosion ~500 Mya integrating the protein interaction networks of reproduction including proto-placenta intertwined with cytokine and immunity pathways, sex determination, oocyte maturation, and embryonal stemness. The peak of this response as part of accelerated cell senescence led by AP-1 and IL-1β was found in breast cancer cell-line resistant to doxorubicin. Adaptability of aggressive cancer to treatments can be explained by emergent stress response evolutionarily protecting reproduction.

Limit Cycle Oscillating Detonation Wave Behavior Analysis Within a Rotating Detonation Engine

Limit cycle oscillation (LCO) detonation wave behaviors are presented and analyzed for test times exceeding 20 s in a water-cooled rotating detonation engine (RDE). LCO detonation waves exhibit cyclic acceleration and deceleration, resulting in oscillating wave spacing at unique process conditions. In previous RDE studies, similar behaviors have been studied as microsecond-scale instabilities leading to ascending or descending modal transitions. In the current work, however, LCO waves are considered a persistent wave mode, occupying unique portions of the operational envelope adjacent to those of their equally spaced counterparts. These occurrences of LCO waves are repeatable, enduring behaviors. A method to generate shifted contour surfaces specifically intended to extract and analyze wave spacing variation through time, termed limit cycle oscillation visualization (LCOV) surfaces, is presented. LCOV surfaces transform data into the reference frame of a primary traveling wave and are used to analyze quasi-steady, short-timescale, and transitional LCO modes. Results are leveraged to understand the relationship between fill height, wave strength, local wave acceleration, and subsequent LCO wave spacing for individual wave sets. Quasi-steady LCO waves display wave spacing oscillations between equal spacing values associated with ±1 wave across runs exceeding 18 s.

Evolution of acceleration waves in non-ideal relaxing gas subjected to the transverse magnetic field

Evolution of acceleration waves in non-ideal relaxing gas subjected to the transverse magnetic field

On the application of Krylov subspace spectral methodologies to poroacoustic shock formation in an exponential class of inhomogeneous gases

In this communication, the propagation of poroacoustic acceleration waves in a class of inhomogeneous gases whose ambient mass density varies exponentially is considered. Employing the tools of singular surface theory, we first determine the evolution of both the jump amplitudes and the locations/velocities of their associated wave-fronts, along with a variety of related analytical results. We then turn to what have become known as Krylov subspace spectral (KSS) methods to numerically simulate the evolution of the full waveforms under consideration. These simulations are not only performed quite efficiently, since KSS allows the use of “large” CFL numbers, but also quite accurately, in the sense of capturing theoretically-predicted features of the solution profiles, since KSS customizes the computation of the components (of a solution) corresponding to the different frequencies involved. The presentation concludes with a discussion of possible acoustics-related follow-on studies.