Final Velocity Research Articles

Multiple shock and acceleration processes of high-velocity flyers driven by the HEAVEN-I laser facility

The experiments of high-velocity flyer acceleration were performed on the HEAVEN-I KrF laser facility with a long-pulse duration (∼ 28 ns). Double-layered flyers consisting of polystyrene and aluminum films can be accelerated to more than 10 km/s measured by VISAR. The polystyrene layer is used as the ablative material, insulation layer, and shock wave regulator. Multiple shock and acceleration processes were observed by adjusting the thickness of the polystyrene layer. We simulated and analyzed the multiple shock processes driven by the long laser pulses and square pressure pulses. The results indicate that the reverberation processes can be induced by the alternating shock and rarefaction waves due to the wave–interface interactions. The reverberations in the Al layer can modulate the pressure evolution and the fine structure of flyer acceleration history. Similar processes in the polystyrene layer can lead to a secondary or multiple shock loading process when the driving pulse duration is several times longer than the shock round trip time in the double-layered flyer. Multiple accelerations can effectively enhance the final velocities in the experimental and simulation results. However, multiple accelerations involve more complex shock loading and unloading processes, and flyers are more prone to breakup compared with single acceleration.

Advanced Numerical Techniques for Supersonic Flow Analysis: From Euler Equations to Practical Applications in Aerospace and Turbomachinery Engineering

This paper explores advanced numerical techniques for analyzing supersonic flow, with a particular focus on the application of Euler equations in aerospace and turbomachinery engineering. Theoretical foundations such as boundary conditions, error evaluation, grid partitioning, and the Successive Over-Relaxation (SOR) method are thoroughly examined. Rigorous numerical simulations are conducted to investigate the final velocity field distribution and convergence characteristics under various conditions. The research underscores the precision and efficiency of these numerical methods, highlighting their practical applications in the aerodynamic design of aircraft and potential use in turbomachinery design. The findings contribute significantly to the advancement of computational fluid dynamics in supersonic flow regimes, providing valuable insights for engineers and researchers engaged in this specialized area. The study not only enhances understanding of complex flow dynamics but also supports the development of more effective engineering solutions in high-speed applications.

Research on Digital Twin Method for Spaceborne Along-Track Interferometric Synthetic Aperture Radar Velocity Inversion of Ocean Surface Currents

In this paper, an end-to-end system framework is proposed for the Digital Twin study of spaceborne ATI-SAR ocean current velocity inversion. Within this framework, a fitting inversion approach is proposed to enhance the conventional spaceborne ATI-SAR ocean current velocity inversion algorithm. Consequently, the issue of possible local inversion errors stemming from the mismatch between the traditional spaceborne ATI-SAR inversion algorithm and various dual-antenna configurations is resolved to a certain extent. A simulated spaceborne ATI-SAR system, featuring a dual-antenna configuration comprising a baseline direction perpendicular to the track and a squint angle, is presented to validate the efficacy of the Digital Twin methodology. Under the specified simulation parameters, the average inversion error for the final ocean current velocity is recorded at 0.0084 m/s, showcasing a reduction of 0.0401 m/s compared with the average inversion error prior to optimization.

Prescribed-Time Network-Based Deployment of Nonlinear Multiagent Systems: A Discrete-Space PDE Method.

This article attempts to design the prescribed-time time-varying deployment schemes for first-order and second-order nonlinear multiagent systems (MASs). We assume that all agents can obtain the information of their current and final relative positions with their neighbors, and the final absolute velocities (as well as their current and final relative velocities, the final absolute accelerations for the second-order MASs) through a communication network, whereas two boundary agents are able to obtain their current and final absolute positions (as well as their current and final absolute velocities for the second-order MASs). The neighbor relationship of all agents is described by a spatial variable and two static-feedback controllers are introduced, which can be expressed as a second-order space difference of the spatial variable. Then, the deployment of MASs can be transformed into the stabilization of discrete-space partial differential equation (PDE) systems. Three virtual agents are introduced to constitute the Dirchlet and Neumann boundary conditions. Several algebraic inequality criteria are derived to guarantee that the prescribed-time time-varying deployment can be achieved within a prescribed time under the Dirchlet and mixed boundary conditions. Unlike the published results, our results are derived based on the discrete-space PDE systems instead of continuous-space PDE systems, which is consistent with the discrete spatial distribution of agents. Finally, two numerical examples are given to illustrate the effectiveness of our results.

Acoustic full-waveform inversion on land surveys: A case study on the Qademah fault, Saudi Arabia

Geophysical methods have been used to map a Qademah fault near a residential area in western Saudi Arabia. However, the location and spatial extension of the fault zone are still uncertain due to the limited resolution and length of geophysical surveys. We apply seismic full-waveform inversion (FWI) to a land survey 2 km in length, the result of which reveals more details of the fault as well as the subsurface. Before inversion, we remove the surface waves, converted waves, and other elastic phenomena in the f- k domain and normalize the trace amplitude to compensate for attenuation, such that wavefield modeling for FWI can be approximated by acoustic propagators with constant density. Due to the large wavefield amplitudes near the source-receiver positions, the FWI velocity gradient presents a singular zone in the near surface, which is muted to stabilize the inversion. We also invert the short-offset traces before the larger-offset traces to avoid cycle skipping at the far offsets and obtain a reasonable data fit despite some mismatches in the near offsets. The final FWI velocity model shows the Qademah fault at approximately 1000 m distance as well as three low-velocity anomalies at 100 m depth, confirmed by first-arrival traveltime tomography. We also observe a potential low-velocity layer at 250–300 m depth, which was not reported in former studies. This model can also be used for geologic interpretation, hazard assessment, and paleoseismology studies of the local area.

Action observation perspective influences the effectiveness of combined action observation and motor imagery training for novices learning an Osoto Gari judo throw

Combined action observation and motor imagery (AOMI) training improves motor skill performance, but limited research has investigated possible moderating factors for this intervention. This study examined the influence of action observation (AO) perspective on the effectiveness of AOMI training for novices learning a ‘shadow’ Osoto Gari judo throw. Thirty novice participants were randomly assigned to AOMI training that displayed egocentric footage (AOMIEGO) or allocentric footage (AOMIALLO) of the Osoto Gari, or Control training. A motor learning design incorporating pre-test (Day 1), acquisition (Days 2–6), post-test (Day 7), and retention-test (Day 14) was adopted. Motor skill performance, self-efficacy, and mental representation structures were recorded as measures of learning. There were mixed effects for motor skill performance across the three training conditions utilized in this study, with AOMIALLO training significantly reducing error scores for final right hip flexion angle and peak right ankle velocity compared to AOMIEGO training. Self-efficacy increased for all training conditions over time. Both AOMIEGO and AOMIALLO training led to improved functional changes in mental representation structures over time compared to Control training. The findings suggest AOMI training led to improved perceptual-cognitive scaffolding, irrespective of AO perspective, and offer some support for the use of AOMIALLO training to facilitate novice learning of complex, serial motor skills in sport.

Airflow Analysis of the Bus Under Various Velocities Using CFD Simulation

This project investigated the aerodynamic effects of various airflow velocities around a bus. Key parameters included airflow velocity and turbulence models, with dependent variables being the velocity and pressure on the bus body. The bus model, sourced from an existing GrabCAD file, was imported into SimFlow 4.0 for analysis. A steady-state simulation was employed, incorporating symmetry conditions, turbulence modeling, boundary conditions, and a baseline post-processing method to visualize the velocity and pressure distributions around the bus. Mesh refinement was carefully adjusted to accommodate the bus's large size and accurately capture the flow gradients. The simulation results were analyzed using Paraview post-processing to evaluate the final velocity and pressure contours. The results showed that the airflow velocities crucially affect the velocity and pressure distribution around the bus. This study yielded significant and insightful results by varying the independent parameters, advancing the understanding of bus aerodynamics under different airflow velocities.

Sex Influences the Extent of Physical Performance Adaptations in Response to Small-Sided Games and Running-Based High-Intensity Interval Training: A Parallel Study Design Involving Men and Women Soccer Players.

The aim of this study was two-fold: (i) to compare physical fitness adaptations following small-sided games (SSG) and running-based high-intensity interval training (HIIT), considering sex interactions; and (ii) to describe intra-individual variations of adaptations in both men and women developmental/trained soccer players over an 8-week randomized parallel study design involving 25 women and 27 men. Pre and post-intervention assessments included countermovement jump (CMJ), 10-meter linear sprint test, change-of-direction (COD) deficit, and final velocity at 30-15 Intermittent Fitness Test (VIFT). Significant interactions between time, groups and sex were found in 10-m sprint (F1,48 = 6.042; p = 0.018; ηp2 = 0.112). No significant interactions between time, groups and sex were found in CMJ (F F1,48 = 0.609; p = 0.439; ηp2 = 0.013), COD deficit (F F1,48 = 2.718; p = 0.106; ηp2 = 0.054) and VIFT (F F1,48 = 1.141; p = 0.291; ηp2 = 0.023). Significant interactions were found between time and sex in CMJ (F F1,48 = 29.342; p < 0.001; ηp2= 0.379), 10-m sprint (F F1,48 = 4.359; p = 0.042; ηp2 = 0.083), COD deficit (F F1,48 = 5.066; p = 0.029; ηp2= 0.095) and VIFT (F F1,48 = 11.248; p = 0.002; ηp2 = 0.190). In conclusion, this study suggests similar effects of HIIT in both sexes. However, for women, SSG may entail less efficacy and more inter-individual variability compared to men. Therefore, HIIT could potentially be a better solution for women, whereas both training approaches were equally effective in men.

Profiling the acceleration and deceleration components in elite futsal players

ABSTRACT This retrospective observational study explores the acceleration and deceleration demands of elite male futsal players (age: 28.8 ± 2.4 years, weight: 73.7 ± 6.2 kg, height: 175.9 ± 5.9 cm) in official matches. Utilising a local positioning system, tracking data from twelve matches involving two elite teams with nineteen players was analysed. Physical demands were assessed at various thresholds, considering standing and rolling efforts based on initial and final velocities. The most prevalent efforts were rolling accelerations (32.4%) and decelerations (31.3%), along with standing accelerations (18.7%) and decelerations (17.6%). A majority of efforts occurred within small distances (less than 10 metres), representing 27.9% to 71.1% of cases. Intensity comparisons revealed that larger distances consistently had significantly higher velocities (d = 0.67 to d = 5.91). High-intensity efforts over large distances were notably shorter than their low-intensity counterparts, both in standing (d = 1.75 to d = 1.98) and rolling (d = 0.64 to d = 0.82) effort types. In essence, elite futsal players predominantly engage in rolling accelerations and decelerations within short distances, exhibiting average speeds below 3 m·s−2. This insight into the nuanced dynamics of player movements provides valuable information for optimising training regimens and enhancing performance in elite futsal competitions.

Higher final speed in 30–15 intermittent fitness tests correlates with soccer's locomotor demands, not heart rate responses in small-sided soccer games

This study aimed to achieve two objectives: firstly, to analyze the relationships between aerobic fitness, as represented by the VIFT, and the heart rate and locomotor responses of youth male soccer players across various teams; and secondly, to compare players with lower and higher VIFT in terms of performance outcomes extracted during small-sided games (SSGs). A total of twenty-six youth male soccer players, aged 16.5 ± 0.32 years, with 3.4 ± 1.1 years of experience, voluntarily participated in the study. These players belonged to two regional-level tier 2 teams (trained/developmental). In the initial week of observation, the 30–15 Intermittent Fitness Test was implemented to measure the final velocity (VIFT) achieved by the players. Subsequently, the 5v5 format of play was conducted twice a week over two consecutive weeks, during which heart rate responses and locomotor demands were measured. The Pearson product-moment correlation test revealed a significant correlation between VIFT and the total distance covered during the 5v5 format (r = 0.471 [95% CI: 0.093; 0.721], p = 0.015). Conversely, small and non-significant correlations were identified between VIFT and mean heart rate (r = 0.280 [95% CI: − 0.126; 0.598]; p = 0.166), VIFT and peak heart rate (r = 0.237 [95% CI: − 0.170; 0.569]; p = 0.243), as well as VIFT and high-speed running (r = 0.254 [95% CI: − 0.153; 0.580]; p = 0.211). Players with higher VIFT demonstrated a significantly greater total distance, with a large effect size (+ 6.64%; p = 0.015; d = 1.033), compared to those with lower VIFT. Our findings suggest that improved performance in VIFT may lead to covering more distance in 5v5 matches. However, the lack of significant associations between VIFT and heart rate levels during SSGs suggests that they are not strongly correlated, possibly because VIFT is more closely linked to locomotor profile. As a practical implication, coaches may consider organizing players during SSGs based on their VIFT if the goal is to standardize locomotor demands.

Profile of Accelerations and Decelerations in Young Basketball Players

Profile of Accelerations and Decelerations in Young Basketball Players

Aerodynamic interactions of blunt bodies free-flying in hypersonic flow

This paper takes a new look at how the aerodynamic interactions of multiple bodies in high-speed flow affect their motion behaviors. The influence of the body shape and orientation on aerodynamic and stability behavior in the case of shock–shock and wake–shock interactions is the focus of this publication. Experiments were performed in the hypersonic wind tunnel H2K at the German Aerospace Center (DLR) in Cologne. Free-flight tests with tandem arrangements of spheres and cubes were performed with a synchronized dropping of both objects at various initial conditions of relative streamwise and vertical distance as well as pitch angle. A high-speed stereo-tracking captured the model motions during free-flight, and high-speed schlieren videography provided documentation of the flow topology. Based on the measured 6-degrees-of-freedom (6DoF) motion data, aerodynamic coefficients were determined. As a result, the final lateral velocity of trailing cubes is found to be many times greater than that of spheres regarding shock-wave surfing. For rotating cubes, the results showed that stable shock-wave surfing can become possible over an increasingly wide range of initial positions. This study has identified that the trailing drag coefficient of two axially aligned objects varies strongly with their relative streamwise distance. Furthermore, it was shown that the wake is a region of stability for downstream objects.Graphical abstract

Semi-empirical model for abrasive particle velocity prediction in abrasive waterjet based on momentum transfer efficiency

AbstractAbrasive waterjet (AWJ) is a technology that removes a target material with an abrasive accelerated by ultra-high-pressure water. Recently, its application for rock excavations in civil and geotechnical engineering has increased. AWJ excavation performance is affected by the abrasive velocity formed by momentum transfer during mixing and acceleration. The abrasive velocity varies owing to changes in the abrasive flow rate, focusing tube diameter, and focusing tube length. In this study, the momentum transfer efficiency (MTE) according to the abrasive flow rate and focusing tube geometry was investigated by a numerical analysis to better understand the multiphase flow inside the AWJ system. The MTE was defined based on the theoretical relationship between the abrasive velocity ratio and focusing tube factor, and evaluated through the empirical relationship between the water stiffness and focusing tube length. The optimal abrasive flow rate for generating efficient MTE was approximately 15 g/s, which enabled economical and effective acceleration of abrasive particles. Accordingly, a prediction model based on the derived MTE was developed for the final abrasive velocity generated at the tip of the focusing tube. Using the prediction model, it is possible to evaluate the comprehensive relationship between various AWJ parameters. Based on the prediction model, the abrasive–water flow ratio to generate the optimal abrasive velocity was 0.83. The developed prediction model provides guidelines for selecting the optimal focusing tube geometry and applying an economical abrasive flow rate when designing an AWJ system.

Study on settling characteristics of rock cuttings from terrestrial high clay shale in power-law fluid

In the process of oil and gas drilling, it is of great significance to accurately predict the drag coefficient and settling rate of cuttings in the drilling fluid for hydraulic parameters and borehole cleaning. In this paper, particle settling experiments were used to obtain the final settling velocity of 196 groups of spherical particles and 224 groups of terrestrial high-clay pure-shale cuttings in the power-law fluid. Based on data analysis, a settlement drag coefficient model suitable for irregular-shaped shale cuttings was established. The model can be used to predict the settlement drag coefficient and settling velocity of irregular-shaped shale cuttings in power-law fluid, which can provide theoretical guidance for wellbore cleaning and hydraulic parameter optimization in Daqing Gulong shale oil drilling operations.

Time series analysis of L-band PALSAR-2 images in Istanbul and Kocaeli, Turkey

ABSTRACT Conducting long measurements of infrastructure deformation is a critical engineering task. Conventional methods are both time-consuming and expensive, limiting their use for large-scale applications. The synergy of synthetic aperture radar (SAR) and geographic information systems (GIS) offers a complementary approach. This study focuses on the feasibility of using time series analysis of L-band PALSAR-2 images to discover land displacements in Istanbul and Kocaeli, significant industrial and residential areas in Turkey. PALSAR-2 phase and intensity information were analyzed. For phase analysis, 14 L-band images from 2014 to 2021 were taken into account. Small baseline subset (SBAS) analysis was performed using 44 pairs, and results of the velocity, coherence and backscattering values are presented. Coherence of all pairs and their correlations were calculated. Principal Component Analysis (PCA) reduced the dimension of coherence pairs, enhancing feature extraction and the final geocoded velocity map revealed a fastest subsidence rate of −58 mm/yr and a mean subsidence of −20 mm/yr. These findings were confirmed through mean vertical velocity from Sentinel-1 datasets and field observations. The results showed that immature land subsidence in the mentioned areas are growing slowly, which can be taken as a serious risk in future.

Ultrafast transfer of low-mass payloads to Mars and beyond using aerographite solar sails

With interstellar mission concepts now being under study by various space agencies and institutions, a feasible and worthy interstellar precursor mission concept will be key to the success of the long shot. Here we investigate interstellar-bound trajectories of solar sails made of the ultra lightweight material aerographite. Due to its extremely low density (0.18kg m−3) and high absorptivity (A∼1), a thin shell can pick up an enormous acceleration from the solar irradiation. Payloads of up to 1kg can be transported rapidly throughout the solar system, e.g., to Mars and beyond. Our simulations consider various launch scenarios from a polar orbit around Earth including directly outbound launches as well as Sun-diver launches towards the Sun with subsequent outward acceleration. We use the poliastro Python library for astrodynamic calculations. For a spacecraft with a total mass of 1kg (including 720g aerographite) and a cross-sectional area of 104m2, corresponding to a shell with a radius of 56m, we calculate the positions, velocities, and accelerations based on the combination of gravitational and radiation forces on the sail. We find that the direct outward transfer to Mars near opposition to Earth results in a relative velocity of 65km s−1 with a minimum required transfer time of 26d. Using an inward transfer with solar sail deployment at 0.6AU from the Sun, the sail’s velocity relative to Mars is 118km s−1 with a transfer time of 126d, where Mars is required to be in one of the nodes of the two orbital planes upon sail arrival. Transfer times and relative velocities can vary substantially depending on the constellation between Earth and Mars and the requirements on the injection trajectory to the Sun diving orbit. The direct interstellar trajectory has a final velocity of 109km s−1. Assuming a distance to the heliopause of 120AU, the spacecraft reaches interstellar space after 5.3yr. When using an initial Sun dive to 0.6AU instead, the solar sail obtains an escape velocity of 148km s−1 from the solar system with a transfer time of 4.2yr to the heliopause. Values may differ depending on the rapidity of the Sun dive and the minimum distance to the Sun. The mission concepts presented in this paper are extensions of the 0.5kg tip mass and 196m2 design of the successful IKAROS mission to Venus towards an interstellar solar sail mission. They allow fast flybys at Mars and into the deep solar system. For delivery (rather than fly-by) missions of a sub-kg payload, for example medical supply or replenishment of essential materials, the biggest obstacle remains in the deceleration upon arrival.

Control Co-Design Optimization of Spacecraft Trajectory and System for Interplanetary Missions

This paper develops a control co-design (CCD) framework to simultaneously optimize the spacecraft’s trajectory and onboard system (rocket engine) and quantify its benefit. An open-loop optimal control problem (two-finite burn Mars missions) is used as the benchmark, and the engine design considers the combustion equilibrium and nozzle geometry. The objective function is the fuel burn. The design variables are the trajectory control parameters (such as burn times, burn directions, and time of flight), initial fuel mass, and engine design parameters (such as throat area, mixture ratio, and chamber pressure). The constraints include the final velocities and positions of spacecraft. Single-point optimizations are conducted for three departure dates in May, July, and September 2020. A multipoint optimization is also performed to balance the engine performance for these dates with 49 design variables and 20 constraints. It is found that the CCD optimizations exhibit 22–28% more fuel burn reduction than the trajectory-only optimization with fixed engine parameters and 16–20% more fuel burn reduction than the decoupled trajectory-engine optimization. The proposed CCD optimization framework can be extended to more spacecraft trajectory control parameters and onboard systems and has the potential to design more efficient spacecraft missions.

Optimizing calibration of modern skeletal maturity systems.

Greulich and Pyle is the most used system to estimate skeletal maturity but has significant drawbacks, prompting the development of newer skeletal maturity systems, such as the modified Fels skeletal maturity systems based on knee radiographs. To create a new skeletal maturity system, an outcome variable, termed a "skeletal maturity standard," must be selected for calibration of the system. Peak height velocity and 90% of final height are both considered reasonable skeletal maturity standards for skeletal maturity system development. We sought to answer two questions: (1) Does a skeletal maturity system developed using 90% of final height estimate skeletal age as well as it would if it was instead developed using peak height velocity? (2) Does a skeletal maturity system developed using 90% of final height perform as well in lower extremity length prediction as it would if it was instead developed using peak height velocity? The modified Fels knee skeletal maturity system was recalibrated based on 90% of final height and peak height velocity skeletal maturity standards. These models were applied to 133 serially obtained, peripubertal antero-posterior knee radiographs collected from 38 subjects. Each model was used to estimate the skeletal age of each radiograph. Skeletal age estimates were also used to predict each patient's ultimate femoral and tibial length using the White-Menelaus method. The skeletal maturity system calibrated with 90% of final height produced more accurate skeletal age estimates than the same skeletal maturity system calibrated with peak height velocity (p < 0.05). The 90% of final height and peak height velocity models made similar femoral and tibial length predictions (p > 0.05). Using the 90% of final height skeletal maturity standard allows for simpler skeletal maturity system development than peak height velocity with potentially more accuracy.

SeisMIC - an Open Source Python Toolset to Compute Velocity Changes from Ambient Seismic Noise

We present SeisMIC, a fast, versatile, and adaptable open-source software to estimate seismic velocity changes from ambient seismic noise. SeisMIC includes a broad set of tools and functions to facilitate end-to-end processing of ambient noise data, from data retrieval and raw data analysis via spectrogram computation, over waveform coherence analysis, to post-processing of the final velocity change estimates. A particular highlight of the software is its ability to invert velocity change time series onto a spatial grid, making it possible to create maps of velocity changes. To tackle the challenge of processing large continuous datasets, SeisMIC can exploit multithreading at high efficiency with an about five-time improvement in compute time compared to MSNoise, probably the most widespread ambient noise software. In this manuscript, we provide a short tutorial and tips for users on how to employ SeisMIC most effectively. Extensive and up-to-date documentation is available online. Its broad functionality combined with easy adaptability and high efficiency make SeisMIC a well-suited tool for studies across all scales.

Is test specificity the issue in assessing aerobic fitness and performance of runners? A systematic review.

Various tests have been developed to evaluate aerobic fitness and performance of runners. However, a systematic understanding of which methods are more accurate is necessary to provide coaches and the sports sciences community with useful and confident outcomes. This study aims to summarize the evidence regarding the validity, reliability and sensitivity of tests for measuring aerobic fitness and performance in runners of several background of training. A systematic search was conducted of Web of Science, PubMed and Scopus up to 31st December 2022 according to PRISMA statement guidelines. Studies that reported findings about tests covering maximal aerobic speed, final velocity achieved during the test, average running speed or other method of evaluating the reference speed during the test were included. We evaluated the risk of bias in the included articles using the Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS). The tests were categorized into continuous incremental tests, intermittent tests and time-trial test. A total of 23 studies met eligibility criteria. These studies contained three background of training: track and road runners (N.=15), trail runners (N.=7) and inexperienced runners (N.=1). Criterion validity was assessed in 73% of the studies, while only 41% of studies examined convergent validity. The majority of the reviewed studies (87%) ignored test-retest reliability. Test sensitivity was not reported in any study. At least one aerobic fitness and performance test was identified for each types of background of training. However, some methodological aspects were not provided in the included articles. Most studies examined at least one aspect of validity (i.e., criterion or convergent-related validity), whilst few studies investigated test-retest reliability. Researchers and practitioners can use the information provided in this systematic review to select appropriate tests.