Impact Collision Research Articles

Contact Dynamics Modeling and Control During the Combination Process of Air-Ground Robots

In recent years, there has been a surge of interest in air-ground collaborative robotics technologies. Our research group designs a novel combination-separation air-ground robot (CSAGR), which exhibits rapid automatic combination and separation capabilities. During the combination process, contact effects between robots, as well as between robots and the environment, are unavoidable. Therefore, it is essential to conduct detailed and accurate modeling and analysis of the collision impact intensity and transmission pathways within the robotic system to ensure the successful execution of the combination procedure. This paper addresses the intricate surface geometries and multi-point contact challenges present in the contact regions of dual robots by making appropriate modifications to the traditional continuous contact force model and applying equivalent processing techniques. The validity of the developed model is confirmed through comparisons with results obtained from finite element analysis (FEA), which demonstrates its high fidelity. Additionally, the impact of this model on control performance is analyzed within the flight control system, thereby further ensuring the successful completion of the combination process. This research represents a pioneering application and validation of continuous contact theory in the dynamics of collisions within dual robot systems.

The Effect of Playing Career on Chronic Neurophysiologic Changes in Retired Male Football Players: An Exploratory Study Using Transcranial Magnetic Stimulation.

Repetitive head impact exposure, from contact and collision sports, are increasingly being attributed to increased risk of neurodegenerative disease in aging athletes. This exploratory study investigated the association of playing career in retired professional contact sport athletes with cortical neurophysiology via transcranial magnetic stimulation (TMS). This study used a cross-correlation design without a control group. Male athletes between the ages of 28 and 68 years (n = 113; mean age [SD] 48.8 [9.7]) who had been retired from professional sport for a minimum of 5 years were recruited. Cortical excitability was measured using single pulse TMS for motor evoked potentials and paired pulse for short-interval intracortical inhibition and long-interval intracortical inhibition. Associations were assessed between TMS measures and concussion history, clinical symptom scores, total career length (including junior to complete retirement), and professional career length (elite competition only). Correlations showed significant associations between motor evoked potentials and clinical symptom reporting (rho: -0.21 to -0.38; P < 0.01) and motor evoked potentials and short-interval intracortical inhibition with total career length (rho: 0.26 to -0.33; P < 0.01). No significant correlations were observed between single and paired-pulse TMS and professional career length (rho: 0.16 to -0.15), nor the number of concussions (rho: 0.17 to -0.17). This exploratory study is the first to report pathophysiologic outcomes in a cohort of retired professional athletes associated with total career exposure, rather than professional career exposure or concussion history. Without a control group comparison and cross-correlational design, these preliminary results should be viewed with caution; however, TMS assessment could be considered a viable biomarker in future studies of retired athletes classified with traumatic encephalopathy syndrome.

Unraveling the Energy‐Harvesting Performance of Antimony‐Doped BaTiO3 Toward Self‐Powered on‐Body Wearable Impact Sensor

Harvesting ambient mechanical energy from the environment has gained immense interest due to its application in energy harvesting and active sensing. Herein, an ABO3 class ferroelectric semiconducting material BaTiO3 nanoparticles are used, and Antimony (Sb) is used as a dopant, which can be able to enhance the piezoelectric coefficient of BaTiO3 to a higher level, leading to increased energy‐harvesting performances. The fabricated antimony‐doped barium titanate [Sb‐doped BaTiO3 designated as (BST)] is then blended with polydimethylsiloxane (PDMS) to prepare a composite film. Electrodes are then attached with the composite film on either side to fabricate the flexible composite piezoelectric nanogenerator (FCF‐PENG) device. The fabricated FCF‐PENG device generates a maximum electrical output of peak‐to‐peak 28 V and 1.5 μA, respectively. The device also shows a good power density of 1.6 mW m−2 at the load resistance of 80 MΩ. At last, a real‐time impact sensor was fabricated to employ the device as the wearable impact sensor. The fabricated impact sensor detects the impact from high to low upon the human collision impact tested within the laboratory and the impact values are recorded and monitored with indicator using ESP32 microcontroller and ThingSpeak cloud. The above analysis and the real‐time experiments proved that the fabricated impact sensor paves the way toward sports healthcare and rehabilitation with Internet of Things (IoT) devices soon.

Autonomous sensor suite for evaluating fish-turbine interactions and environmental impacts in marine renewable energy and hydropower.

Autonomous sensor suite for evaluating fish-turbine interactions and environmental impacts in marine renewable energy and hydropower.

Design and performances of intake for atmosphere-breathing electric propulsion systems with the direct simulation Monte Carlo method

The design of an effective intake is a critical aspect of atmosphere-breathing electric propulsion development. Using the Direct Simulation Monte Carlo method, the intake collection efficiency, compression ratio, and drag were evaluated and compared across different geometries, including a scaled-down version. Key performance parameters were analyzed over a wide range of Very Low Earth Orbit altitudes (160–240 km), focusing on gas–surface interactions and the impact of inter-particle collisions at lower altitudes. The results derived from the Maxwellian and Cercignani–Lampis–Lord models were compared under various reflection scenarios: fully specular, partially diffuse, and diffuse. The study first examined intake geometries, highlighting how surface curvature affects performance. Further analysis of the best-performing geometry at different altitudes (160–240 km) revealed that neglecting inter-particle collisions at lower altitudes can lead to discrepancies in capture efficiency of up to 40%. This difference diminishes with increasing altitude, becoming negligible. The intake is sized down to a 1:5 ratio to match the dimensions of a CubeSat with no significant effect on compression ratio or capture efficiency, opening up the possibility for nanosatellite applications. Finally, the different gas–surface interaction models provided a range of performance predictions for each analyzed altitude, potentially reflecting the behavior of a real intake operating in the atmosphere. Variations in the mass flow rate supplied to the electric thruster across models offer valuable insights for thruster design.

Relativistic Low Angular Momentum Advective Flows Onto Black Hole and Associated Observational Signatures

Abstract We present simulation results examining the presence and behavior of standing shocks in zero-energy low angular momentum advective accretion flows and explore their (in)stability properties, taking into account various values of specific angular momentum, λ 0. Within the range 10−50R g (where R g denotes the Schwarzschild radius), shocks are discernible for λ 0 ≥ 1.75. In the special relativistic hydrodynamic simulation when λ 0 = 1.80, we find the merger of two shocks resulted in a dramatic increase in luminosity. We present the impact of external and internal flow collisions from the funnel region on luminosity. Notably, oscillatory behavior characterizes shocks within 1.70 ≤ λ 0 ≤ 1.80. Using free–free emission as a proxy for analysis, we show that the luminosity oscillations between frequencies of 0.1−10 Hz for λ 0 range as 1.7 ≤ λ 0 ≤ 1.80. These findings offer insights into quasi-periodic oscillation emissions from certain black hole X-ray binaries, exemplified by GX 339-4. Furthermore, for the supermassive black hole at the Milky Way's center, Sgr A*, oscillation frequencies between 10−6 and 10−5 Hz were observed. This frequency range, translating to one cycle every few days, aligns with observational data from X-ray telescopes such as Chandra, Swift, and XMM-Newton.

Improvement of crashworthiness of pickup vehicle for frontal and side collision using Finite Element analysis

This study aimed to enhance the existing vehicle’s structural reaction to a frontal and side impact collision. Energy-absorbing parts, a sturdy frame design, and enhanced crash performance are used to produce improvements based on the outcomes of the current model. When conducting the analysis, 3D modeling is done using CATIA, and FEM analysis is done using LS-DYNA. After adjustment, the ability to stabilize the momentum, the impact force during a crash, and the relation between internal energy and deformation is discussed; in doing so, the impact force is reduced by 7.82% and a 3.52% increment of energy is absorbed during a frontal collision. The side structure of the modified model also provided additional 162 mm space protection for the occupant, a reduction of impact force by 14.4%, and absorbed additional 7.6% energy. The new model generates more moment force that stabilizes fast as compared to the current, and also the relationship between energy absorbed and deformation is seen that with less deformation, the new model absorbs more energy. In conclusion, it can be claimed that the updated model considerably improved the pickup vehicle’s safety and crashworthiness without affecting the vehicle’s weight or appearance.

Black Hole Accretion and Spin-up through Stellar Collisions in Dense Star Clusters

Abstract Dynamical interactions in dense star clusters could significantly influence the properties of black holes, leaving imprints on their gravitational-wave signatures. While previous studies have mostly focused on repeated black hole mergers for spin and mass growth, this work examines the impact of physical collisions and close encounters between black holes and (noncompact) stars. Using Monte Carlo N-body models of dense star clusters, we find that a large fraction of black holes retained upon formation undergo collisions with stars. Within our explored cluster models, the proportion of binary black hole mergers affected by stellar collisions ranges from 10%–60%. If all stellar-mass black holes are initially nonspinning, we find that up to 40% of merging binary black holes may have components with dimensionless spin parameter χ ≳ 0.2 because of prior stellar collisions, while typically about 10% have spins near χ = 0.7 from prior black hole mergers. We demonstrate that young star clusters are especially important environments, as they can produce collisions of black holes with very massive stars, allowing for significant spin-up of the black holes through accretion. Our predictions for black hole spin distributions from these stellar collisions highlight their sensitivity to accretion efficiency, underscoring the need for detailed hydrodynamic calculations to better understand the accretion physics following these interactions.

Fast ion confinement in quasi-axisymmetric stellarator equilibria

Abstract This report presents an initial analysis of the fast ion confinement and losses within quasi-axisymmetric stellarator equilibria in consideration by Thea Energy. The equilibria have not yet been explicitly optimized for fast particle confinement and require validation. Modeling with the ASCOT5 code is used to directly examine the fast ion transport. The particle tracking simulations are purely (neo)classical in nature and simply contain the supplied equilibrium and collisions (pitch-angle, energy slowing, and velocity diffusion) from supplied thermal profiles. Uniform marker deposition is used to probe the general confinement properties of the equilibria while a realistic beam-born population is provided from the BEAMS3D code and an alpha particle population is calculated from a fusion source integrator. A first wall is included and defines the loss boundary. Analysis for NBI ions within Thea Energy’s conceptual Eos neutron source are presented along with alpha particles in an enlarged DT-plasma. The fast ions are assessed in regards to their confinement time, pitch, energy, and spatial coordinates. For each population, the impact of collisions and orbit drifts are discussed. It is found that NBI born ions in Eos are strongly confined until slowing-down, owing largely to the tangential injection geometry, while 22% of DT-born alpha energy is lost in the scaled device, indicating that any fusion pilot plant design optimization should include metrics for fast ion confinement.

Ion-kinetic-energy sampling in a 22-pole trap using ring-electrode evaporation

We present an experimental method for the characterization of the kinetic energies of ions confined in a 22-pole radio frequency trap by inducing a small potential barrier using the surrounding ring electrodes, allowing the selective extraction of ions. Energy sampling experiments have been performed on buffer-gas thermalized He+ ions at trap temperatures between 10 and 180 K, resulting in distinct extraction curves as a function of the potential barrier, and a differentiated behavior depending on the escape time from the trap. The experiments are complemented by Monte Carlo simulations of the ion trajectories inside the calculated trap potential and allow us to investigate the properties of the sampling method, the role of ion motion coupling, and the impact of residual buffer-gas collisions on the observed results. The technique has also been successfully applied to identify energetic H3+ ions produced in an exothermic reaction inside the trap. Upon calibration, this method can provide relative kinetic energy distributions or be used to filter the maximum desired kinetic energy of the ions inside the trap. Published by the American Physical Society 2025

High-Speed Target Location Based on Photoelectric Imaging and Laser Ranging with Fast Steering Mirror Deflection

There is an increasing number of spacecrafts in orbit, and the collision impact of high-speed moving targets, such as space debris, can cause fatal damage to these spacecrafts. It has become increasingly important to rapidly and accurately locate high-speed moving targets in space. In this study, we designed a visible-light telephoto camera for observing high-speed moving targets and a laser rangefinder for measuring the precise distance of these targets, and we proposed a method of using fast steering mirror deflection to quickly direct the emitted laser towards such targets and measure the distance. Based on the principle of photographic imaging and the precise distance of targets, a collinear equation and a spatial target location model based on the internal and external orientation elements of the camera and the target distance were established, and the principle of target location and the method for calculating target point coordinates were determined. We analyzed the composition of target point location error and derived an equation for calculating such errors. Based on the actual values of various error components and the error synthesis theory, the accuracy of target location was calculated to be 26.5 m when the target distance is 30 km (the relative velocity is 8 km/s and the velocity component perpendicular to the camera’s optical axis is less than 3.75 km/s). This study provides a theoretical basis and a method for solving the practical needs of quickly locating high-speed moving targets in space and proposes specific measures to improve target location accuracy.

Analysis of Shearer Traction Characteristics Considering Attitude Disturbance

The discontinuous contact and collision impact of traction components caused by attitude disturbances is a significant factor that endangers the traction reliability of the shearer. Especially, when cutting with a single drum, the shearer undergoes severe swaying and runout. Therefore, to explore the swaying law and its impact, a shearer traction dynamics model considering spatial attitude disturbance is established and validated by the traction experiment. The shearer’s spatial sway is studied, and the impact contact and its differences between the two hauling departments under different loads are discussed based on attitude analysis. The results show that attitude disturbance increases with increased speed. Roll disturbance is the major factor that causes the vibration enhancement of the support slippers, and the vibration enhancement of the walking wheels is the result of both the pitch and roll attitude disturbances. When the left drum load is lost, the roll attitude disturbance enhances while the vibration of the right hauling department increases. When the right drum load is lost, the yaw swaying is reinforced while the vertical direction vibration on the two support slippers and the axial direction vibration on the left guide slipper increase significantly. The result provides a reference for studying the shearer’s attitude law and reducing traction impact.

Study on Collision Dynamics Similarity of Thickness Distortion Model of Train Five-Hole Thin-Walled Structure

Full-scale train collision tests are rarely carried out because of high cost, but small-scale model tests have good economy and repeatability, providing a new research method for train crashworthiness design. The metal thin-walled tube is a commonly used energy-absorbing structure for trains. Its collision characteristics directly affect the impact resistance and collision behavior evolution process of trains. This paper studies the collision dynamics similarity of the small-scale model of a five-hole thin-walled energy-absorbing structure at the end of a high-speed train. Firstly, the dynamic mechanical behavior and governing equations of high-speed train collision were analyzed, and the applicable similarity criterion was derived by similarity transformation to develop a similarity scale model. According to the simulation, the energy absorption, peak force and other key responses of the full-scale prototype collision were analyzed. Then, the applicability of the thickness distortion scale model of the five-hole energy-absorbing structure in the high-speed train was proved by equation analysis and error analysis. The impact dynamic responses of the complete similarity model and the distortion similarity model were discussed. A correction program with collision deceleration as the dependent variable was proposed for the distortion similarity model, and the fitting relationship between the distortion factor and the correction factor was obtained. The results calculated by the proposed method prove that the peak force-deformation-energy absorption error of the thickness distortion similarity model in predicting the dynamic responses of the prototype collision is less than 8%, which means the thickness distortion scale model has good accuracy in the prediction of full-scale prototype collision dynamics responses.

Development of a collision impact indicator to integrate in the life cycle assessment of offshore wind farms

PurposeLife cycle assessment (LCA) is a robust approach to estimate the environmental impacts of an offshore wind farm (OWF). However, methodological hurdles remain, particularly the lack of appropriate indicators to assess ecosystem impacts during OWF construction and operation and the scarcity of marine ecological data. To address the lack of indicators, this article focuses on developing an impact indicator specifically related to bird collision with OWFs.MethodsTo assess bird collisions during the operation of OWFs, we adapted a life cycle impact indicator originally developed for onshore wind farms. This indicator combines spatial data on bird species distribution and vulnerability to collisions with OWF technical characteristics (number of turbines, power production, rotor diameter).ResultsThe results model and map seabird collisions at OWF worldwide and introduce a biodiversity impact characterization factor into LCA. The results are expressed as the potentially disappeared fraction of species (PDF) annually per gigawatt-hour (GWh) and vary between 2.0e−15 and 1.69e−13 PDF.year/GWh. It correlates 1344 bird species distribution with the locations of 226 operational and 181 planned OWFs. The spatial differentiation of the characterization factors highlights the OWF collision impact variability worldwide. Such mapping is crucial for identifying areas with varying levels of risk, which is essential for the strategic planning of OWFs. Projections indicate higher potential collision risks in Asia than in Europe, and future expansion of the OWF into new regions with higher collision potential is expected to increase collision risks. In addition, the main factors affecting collision intensity were statistically identified. Therefore, to mitigate collisions, it is essential to focus on three key aspects: fewer turbines, smaller rotors, and greater distance from the shoreline. In addition, the LC-IMPACT method was employed to compare the collision impacts for two OWF projects in France, with those resulting from climate change. Over the lifetime of these OWFs, the collision impacts are quantified at around 2.0e−7 PDF, where effects attributed to climate change will be six times higher.ConclusionsThe development of this collision indicator is a first step towards integrating OWF biodiversity impacts into the LCA framework. It also demonstrates how LCA indicators can inform marine spatial planning in the context of marine renewable energy development.

Recognition and location of rotor–stator rub-impact failure of aircraft engine with periodicity feature of vibration signals

To precisely recognize and locate a rub-impact fault of aircraft engine, an approach combining Hilbert envelope (HE), adaptive motion window (AMW), and margin factor (MF) (HE-AMW-MF) was presented. HE can reflect the change rule and tendency of vibration signals and simplify the complexity of calculation of fault diagnosis. Therefore, the paper starts with the calculation of HE of signal and takes it in place of original signal for subsequent analysis. As vibration signal caused by rub-impact fault is often accompanied by periodic impact, the paper takes advantage of the characteristic of periodic impact (collision period instead of rotation period) to adaptively determine a length and step size of motion window and exactly distills the rub-impact fault characteristics of each period. Due to the sensitivity of margin factor (MF) to the trait of wearing and impact, it is brought in to represent the fault feature information contained in signal in each motion window. Equally, mean value of all MFs is calculated and built into feature vector to reduce an interference of noise. Finally, the feature vector is combined with classification algorithms (k-nearest neighbor, KNN; support vector machine, SVM; convolutional neural network, CNN) to recognize a rub-impact fault and its location. After comparative analysis with typical method, the result indicates that the proposed HE-AMW-MF method can identify and locate the rub-impact fault more precisely, and the precision is 32.0% and 36.2%, 22.5% higher than typical comparison method.

Dynamics of U(1) gauged Q -balls in three spatial dimensions

We investigate the dynamics of U(1) gauged Q-balls using fully three-dimensional numerical simulations. We consider two different scenarios: first, the classical stability of gauged Q-balls with respect to generic three-dimensional perturbations, and second, the behavior of gauged Q-balls during head-on and off-axis collisions at relativistic velocities. With regard to stability, we find that there exist gauged Q-ball configurations which are classically stable in both logarithmic and polynomial scalar field models. With regard to relativistic collisions, we find that the dynamics can depend on many different parameters such as the collision velocity, relative phase, relative charge, and impact parameter of the colliding Q-balls. Published by the American Physical Society 2024

Relaxation of weakly collisional plasma: Continuous spectra, discrete eigenmodes, and the decay of echoes.

The relaxation of a weakly collisional plasma, which is of fundamental interest to laboratory astrophysical plasmas, can be described by the self-consistent Boltzmann-Poisson equations with the Lenard-Bernstein collision operator. We perform a perturbative (linear and second-order) analysis of the Boltzmann-Poisson equations and obtain exact analytic solutions which resolve some longstanding controversies regarding the impact of weak collisions on the continuous spectra, the discrete Landau eigenmodes, and the decay of plasma echoes. We retain both damping and diffusion terms in the collision operator throughout our treatment. We find that the linear response is a temporal convolution of two types of contribution: a continuum that depends on the continuous velocities of particles (crucial for the plasma echo), and another, consisting of discrete modes that are coherent modes of oscillation of the entire system. The discrete modes are exponentially damped over time due to collective effects or wave-particle interactions (Landau damping), as well as collisional dissipation. The continuum is also damped by collisions but somewhat differently than the discrete modes. Up to a collision time, which is the inverse of the collision frequency ν_{c}, the continuum decay is driven by the diffusion of particle velocities and is cubic exponential, occurring over a timescale ∼ν_{c}^{-1/3}. After a collision time, however, the continuum decay is driven by the collisional damping of particle velocities and diffusion of their positions and occurs exponentially over a timescale ∼ν_{c}. This slow exponential decay causes perturbations to damp the most on scales comparable to the mean free path but very slowly on larger scales. This establishes the local thermal equilibrium, which is the essence of the fluid limit. The long-term decay of the linear response is driven by the discrete modes on scales smaller than the mean free path but, on larger scales, is governed by a combination of the slowly decaying continuum and the least damped discrete mode. This slow exponential decay implies that the echo, which results from the interference of the continuum response to two subsequent pulses, is detectable even on scales comparable to the mean free path, as long as the second pulse is introduced within a few phase-mixing timescales after the first.

Nonlinear dynamic modeling and vibration analysis for early fault evolution of rolling bearings

In rotating machinery, the condition of rolling bearings is paramount, directly influencing operational integrity. However, the literature on the fault evolution of rolling bearings in their nascent stages is notably limited. Addressing this gap, our study establishes an innovative nonlinear dynamic model for early fault evolution of rolling bearings based on collision impact. Firstly, considering the fault evolution characteristics, the influence of the rolling element and fault structure, the dynamic model of early fault evolution between the rolling element and the local fault is established. Secondly, according to the Hertzian contact deformation theory, a nonlinear dynamic model of rolling bearings expressed as mass-spring is established. Thirdly, the energy contribution method is used to integrate the fault evolution model and the nonlinear dynamic model of the rolling bearing. A nonlinear dynamic model of early fault evolution of the rolling bearing is proposed by using the Lagrangian equation. Comparing the simulation results of the nonlinear dynamic with the experimental results, it can be seen that the numerical model can effectively predict the evolution process and vibration characteristics of the fault evolution of rolling bearings in the early stage.

In-medium changes of nucleon cross sections tested in neutrino-induced reactions

Historically, studied in the context of heavy-ion collisions, the extent to which free nucleon-nucleon cross sections are modified in-medium remains undetermined by these data sets. Therefore, we investigate the impact of NN in-medium modifications on neutrino-nucleus cross section predictions using the GiBUU transport model. We find that including an in-medium lowering of the NN cross section and density dependence on Δ excitation improves agreement with MicroBooNE neutrino-argon scattering data. This is observed for both proton and neutral pion spectra in charged-current muon neutrino and neutral-current single pion production data sets. The impact of collision broadening of the Δ resonance is also investigated. The absence of Δ broadening is slightly favored, but the larger uncertainties on the pion production data prevent definitive conclusions. Published by the American Physical Society 2024

Automobile response to road safety barriers upon collision

During a collision between an automobile and a road safety barrier, the vehicle will go through many behavior transition phases. This research will focus on determining the behavior of two car models including a sedan car and a pickup truck in collision with two safety road barriers using numerical simulation. This paper will also present images, total force graphs, and velocity graphs throughout the process to evaluate the vehicle's behavior at different impact speeds and angles. It is recognized that at similar impact speeds, collision angles, and barrier types, the pickup truck suffers more damage than the sedan. In addition, the pickup truck colliding with a concrete barrier exhibits the highest force, while the sedan colliding with a W-Beam barrier records the lowest force among the four collision types. Regarding the road safety barrier, the concrete barrier has a shorter force increase/decrease duration than the W-Beam barrier.