Striking Velocity Research Articles

Reliability of a Low-Cost Inertial Measurement Unit (IMU) to Measure Punch and Kick Velocity.

Striking velocity is a key performance indicator in striking-based combat sports, such as boxing, Karate, and Taekwondo. This study aims to develop a low-cost, accelerometer-based system to measure kick and punch velocities in combat athletes. Utilizing a low-cost mobile phone in conjunction with the PhyPhox app, acceleration data was collected and analyzed using a custom algorithm. This involved strike segmentation and numerical integration to determine velocity. The system demonstrated moderate reliability (intraclass correlation coefficient (ICC) 3,1 = 0.746 to 0.786, standard error of measurement (SEM) = 0.488 to 0.921 m/s), comparable to commercially available systems. Biological and technical variations, as well as test standardization issues, were acknowledged as factors influencing reliability. Despite a relatively low sampling frequency, the hardware and software showed potential for reliable measurement. The study highlights the importance of considering within-subject variability, hardware limitations, and the impact of noise in software algorithms. Average strike velocities exhibited higher reliability than peak velocities, making them a practical choice for performance tracking, although they may underestimate true peak performance. Future research should validate the system against gold-standard methods and determine the optimal sampling frequency to enhance measurement accuracy.

Masked Expressiveness: Conditioned Generation of Piano Key Striking Velocity Using Masked Language Modeling

Creating and experiencing expressive renditions of composed musical pieces are fundamental to how people engage with music. Numerous studies have focused on building computational models of musical expressiveness to gain a deeper understanding of its nature and explore potential applications. This paper examines masked language modeling (MLM) for modeling expressiveness in piano performance, specifically targeting the prediction of key striking velocity using vanilla Bidirectional Encoder Representations from Transformers (BERT). While MLM has been explored in previous studies, this work applies it in a novel direction by concentrating on the fine-grained conditioned prediction of velocity information. The results show that the model can predict masked velocity events in various contexts within an acceptable margin of error, relying solely on the pitch, timing, and velocity data encoded in Musical Instrument Digital Interface (MIDI) files. Additionally, the study employs a sequential masking and prediction approach toward rendering the velocity of unseen MIDI files and achieves more musically convincing results. This approach holds promise for developing interactive systems for expressive performance generation, such as advanced piano conducting or accompaniment systems.

Erosion wear performance of titania filled ramie-epoxy composites: A data driven optimization study using supervised machine learning approach

This paper reports on a data driven machine learning (ML) approach to analyze and predict the erosion behavior of titanium oxide (titania) filled ramie-epoxy composites. ML models are extensively used in recent years to mimic human decisions in various industries. After fabrication and well-designed erosion trials following design of experiments, the experimental data is critically analyzed to examine the effect of each input factor (erodent temperature, striking angle, striking velocity and filler content) on the output that is erosion wear rate. It is found that the erosion wear rate increases with increase in striking velocity and striking angle and decreases with increase in filler content. The experimental data is further used to feed five different ML models. The performance and adequacy of ML models are compared using five different performance metrics. It is noticed that although all the machine learning techniques effectively predicted the erosion rate, the Gradient boosting machine (GBM) model exhibited superior performance with an R2 value of 0.9486. The feature importance plot confirms that the, filler content, striking velocity and the striking angle played a major role in predicting the erosion rate of the hybrid composites.

Projectile Penetration into Calcareous Sand Subgrade Airport Runway Pavement with Genetic Algorithm Optimization.

As an important civil and military infrastructure, airport runway pavement is faced with threats from cluster munitions, since it is vulnerable to projectile impacts with internal explosions. Aiming at the damage assessment of an island airport runway pavement under impact, this work dealt with discrete modeling of rigid projectile penetration into concrete pavement and the calcareous sand subgrade multi-layer structure. First, the Discrete Element Method (DEM) is introduced to model concrete and calcareous sand granular material features, like cohesive fracture and strain hardening due to compression, with mesoscale constitutive laws governing the normal and shear interactions between adjacent particles. Second, the subsequent DEM simulations of uniaxial and triaxial compression were performed to calibrate the DEM parameters for pavement concrete, as well as subgrade calcareous sand. Prior to the multi-layer structure investigations, penetration into sole concrete or calcareous sand is validated in terms of projectile deceleration and depth of penetration (DOP) with relative error ≤ 5.6% providing a reliable numerical tool for deep penetration damage assessments. Third, projectile penetration into the airport runway structure with concrete pavement and calcareous sand subgrade was evaluated with validated DEM model. Penetration numerical simulations with various projectile weight, pavement concrete thickness as well as striking velocity, were performed to achieve the DOP. Moreover, the back-propagation (BP) neural network proxy model was constructed to predict the airport runway penetration data with good agreement realizing rapid and robust DOP forecasting. Finally, the genetic algorithm was coupled with the proxy model to realize intelligent optimization of pavement penetration, whereby the critical velocity projectile just perforates concrete pavement indicating the severest subsequent munition explosion damage.

An investigation on the mechanical, thermal and tribological properties of newly developed polyester composites made with Pistachio shell particles for industrial applications

The drive for sustainability and addressing environmental concerns has led to the productive use of bio-waste. This research investigates the potential of pistachio (Pistacia vera) nut shell particles as a novel filler in polyester composites. The study explores the use of these nut shells as a reinforcing material in polyester-based composites to evaluate their mechanical and thermal properties. Pistachio shell particles (PSP) are mixed with polyester resin in varying weight fractions (0%, 1%, 3%, and 5%) to create a new type of composite. The impact of filler content, impingement angle and striking velocity on the erosive wear behavior of these composites are also studied. The mechanical results for the composites revealed that incorporating PSP filler resulted in the maximum rise in tensile (96.61%), impact strength (66.66%), micro-hardness (52.94%), under loading of 5 wt% of PSP filler. However, the composite with 3 wt% of PSP filler, resulted in the maximum rise of flexural strength (135.65%) and flexural modulus (45.28%). Results showed that, composites with 5 wt% of PSP filler exhibited superior erosive resistance. An optimal parameter setting is determined for minimum erosion rate and subsequently validated by conducting confirmation experiment as per Taguchi methodology. Different modes of material removal, wear craters and other qualitative attributes are examined by a scanning electron microscopy during erosion experiment of the samples. Thus, the utilization of agro/food wastes in the development of bio-based products holds significant potential and offers the possibility of replacing conventional materials in various industrial applications.

Impact force-damage depth model for ship-bridge collision

Impact force-damage depth model for ship-bridge collision

Analytical and numerical models to predict the shape of incident pulse in split-Hopkinson bar experiments

Analytical and numerical models to predict the shape of incident pulse in split-Hopkinson bar experiments

Dynamic deformation and fracture surface investigation of rolled homogenous armor steel through Charpy impact testing

Dynamic deformation and fracture surface investigation of rolled homogenous armor steel through Charpy impact testing

Pulse Design of Constant Strain Rate Loading in SHPB Based on Pulse Shaping Technique.

The Split Hopkinson pressure bar (SHPB) is widely used for characterizing the mechanical behavior of materials at high strain rates. One of the most challenging factors is achieving constant strain rate (CSR) loading of the specimen at a certain strain rate. Obtaining the effective incident pulse based on the experimental material for achieving CSR loading remains unresolved. This research focuses on obtaining the proper incident pulse for achieving constant strain rate loading using the pulse-shaping technique. A parameterized objective incident model in terms of the strain rate and quasi-static (or dynamic stress-strain) behavior of the material is established utilizing the three-wave method. Experimental pulses that closely resemble the desired objective pulses can be generated by adjusting parameters such as the geometry of the shaper, the shaper material, striker velocities, and the length of the striker according to the pulse-shaping model. The model is applied to the design of the incident pulse for B4CP/2024Al composite material, and the dynamic stress-strain curves at different strain rates are obtained under CSRs. This model provides effective guidance for selecting an appropriate shaper and achieving CSR loading in SHPB tests.

Численное исследование задачи низкоскоростного столкновения стального шара с ледяной плитой

In this paper, the dynamic deformation process during the low-speed collision was investigated. The full 3D dynamic contact problem was simulated in the Abaqus software, based on the explicit finite-element method on structured meshes. Two basic mechanical models (linear isotropic elastic and elastoplastic) are considered. The obtained results showed the possibility of the experimental data, available in the open literature for different striker velocities, reproduction. The better understanding of the ice deformation process can be useful for different applied problems, like the ice impact on the aircraft wings estimation and the ice-water contact reflected waves filtration during the seismic survey in the Arctic region.

Enhanced cross laminated timber (ECLT) for ballistic resistant design

Enhanced cross laminated timber (ECLT) for ballistic resistant design

Numerical Analysis of a High-Velocity Projectile’s Impact on Shallow Steel Tunnels in Soft Sandstone

Tunnels are underground infrastructures intended for diverse community applications as well as military applications. During impact loading due to high-velocity projectiles such as ballistic missiles, materials experience a high strain rate. Moreover, there is a superficial augmentation of the dynamic strength when geomaterials such as rock are subjected to a high strain rate. Despite this strength enhancement, tunnels can get damaged by the impact load of a projectile hitting at a high velocity if they are present at a shallow depth. The present study is an effort to comprehend the response of a shallow tunnel in soft sandstone due to the impact load by a ballistic projectile using the FEM-based software ABAQUS/CAE 6.11. The Drucker–Prager damage model and the Johnson–Cook damage model were used to define the properties of the rock mass and steel tunnel lining, respectively. The crown of the 3 m diameter tunnel was kept at different depths from 1 m to 5 m from the surface. A striking velocity of 1000 m/s at a normal position to the target was given to the projectile. The projectile caused noticeable damage to the tunnel lining up to 3 m crown depth. Increasing the crown depth had a positive effect on the maximum depth of the projectile penetration up to 4 m tunnel crown depth, after which the effect reversed, making the tunnel safer. The maximum von Mises stress on the tunnel lining reduced in a logarithmic trend with an increase in the crown depth, gradually lowering to an impact load lesser than the yield stress of the tunnel lining material after a crown depth of 4.5 m.

Approximate theory of armour perforation by ductile hole expansion

Approximate theory of armour perforation by ductile hole expansion

Impact-Aware Foot Motion Reconstruction and Ramp/Stair Detection Using One Foot-Mounted Inertial Measurement Unit.

Motion reconstruction using wearable sensors enables broad opportunities for gait analysis outside laboratory environments. Inertial Measurement Unit (IMU)-based foot trajectory reconstruction is an essential component of estimating the foot motion and user position required for any related biomechanics metrics. However, limitations remain in the reconstruction quality due to well-known sensor noise and drift issues, and in some cases, limited sensor bandwidth and range. In this work, to reduce drift in the height direction and handle the impulsive velocity error at heel strike, we enhanced the integration reconstruction with a novel kinematic model that partitions integration velocity errors into estimates of acceleration bias and heel strike vertical velocity error. Using this model, we achieve reduced height drift in reconstruction and simultaneously accomplish reliable terrain determination among level ground, ramps, and stairs. The reconstruction performance of the proposed method is compared against the widely used Error State Kalman Filter-based Pedestrian Dead Reckoning and integration-based foot-IMU motion reconstruction method with 15 trials from six subjects, including one prosthesis user. The mean height errors per stride are 0.03±0.08 cm on level ground, 0.95±0.37 cm on ramps, and 1.27±1.22 cm on stairs. The proposed method can determine the terrain types accurately by thresholding on the model output and demonstrates great reconstruction improvement in level-ground walking and moderate improvement on ramps and stairs.

Doppler signature of a possible termination shock in an off-limb solar flare

ABSTRACT We report striking Doppler velocity gradients observed during the well-observed 2017 September 10 solar flare, and argue that they are consistent with the presence of an above-the-looptop termination shock beneath the flare current sheet. Observations from the Hinode Extreme-ultraviolet Imaging Spectrometer measure plasma sheet Doppler shifts up to 35 km s−1 during the late-phase of the event. By comparing these line-of-sight flows with plane-of-sky (POS) measurements, we calculate total velocity downflows of 200+ km s−1, orientated ≈6–10° out of the POS. The observed velocities drop rapidly at the base of the hot plasma sheet seen in extreme ultraviolet, consistent with simulated velocity profiles predicted by our 2.5D magnetohydrodynamics model that features a termination shock at the same location. Finally, the striking velocity deceleration aligns spatially with the suppression of Fe xxiv non-thermal velocities, and a 35–50 keV hard X-ray looptop source observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. Together, these observations are consistent with the presence of a possible termination shock within the X8.2-class solar flare.

Sound-producing actions in guitar performance of groove-based microrhythm

This paper reports on an experiment that investigated how guitarists signal the intended timing of a rhythmic event in a groove-based context via three different features related to sound-producing motions of impulsive chord strokes (striking velocity, movement duration and fretboard position). 21 expert electric guitarists were instructed to perform a simple rhythmic pattern in three different timing styles—"laidback," "on-the-beat," and "pushed"—in tandem with a metronome. Results revealed systematic differences across participants in the striking velocity and movement duration of chords in the different timing styles. In general, laid-back strokes were played with lower striking velocity and longer movement duration relative to on-the-beat and pushed strokes. No differences in the fretboard striking position were found (either closer to the "bridge" [bottom] or to the "neck" [head]). Correlations with previously-reported audio features of the guitar strokes were also investigated, where lower velocity and longer movement duration generally corresponded with longer acoustic attack duration (signal onset to offset).

Effect of pistachio shell particles on mechanical and erosion wear performance of hybrid kenaf/glass polyester composites

The concern for the environmental hazards due to rapid utilization of non-biodegradable resources has persuaded the researchers to develop eco-friendly materials with noble categories of plant-based fibers and fillers. In view of this content, an effort has been initiated in the present work to explore the retrospective effect of PSP (Pistachio shell particles) on both mechanical as well as erosive wear performances of KG (kenaf/glass/kenaf/glass) hybrid polyester laminated composite. The KG laminate with different filler concentration, that is, 0 wt%, 1 wt%, 3 wt%, and 5 wt% were fabricated by using hand-lay-up technique and the mechanical properties of these laminates were determined by performing tensile, flexural and impact tests as per ASTM standard. A higher tensile value of 127.35 MPa with modulus of 7.658 GPa and hardness of 21.35 HV was obtained at 5 wt% reinforcement of PSP filler whereas 3 wt% filler reinforcement responded an optimum flexural strength of 112.42 MPa with modulus of 5.214 GPa and impact strength of 75.59 KJ/m2. To evaluate the wear performance of this laminates against high-speed solid particle, erosion wear test was carried out at different striking velocity and impingement angles. A noticeable reduction of 12.63% in wear rate was found due to increase with concentration PSP filler from 0% to 5 wt%. Further, the η (erosion efficiency) was also found to be limited within the range of 5.94% to 32.98%. From micrographic analysis of the fracture surface, micro-ploughing and micro-cutting actions were found to be most predominant primary wear mechanisms.

Ballistic performance of monolithic rubber-ceramic composite armor

This work presents the research results regarding the ballistic response characteristics of monolithic ceramic armors. Two different configurations of armors are considered for investigation, aiming at identifying ways to increase the ballistic performance of Small Arms Protective Insert (SAPI). The first configuration consists of a monolithic ceramic tile (Al2O3) with a backing plate made of high-performance Kevlar-29 fiber reinforced composite; the second one has the same design as the first, but the monolithic ceramic tile is covered by a thin rubber layer. The impact behavior of the ceramic composite armors is analyzed numerically, using the finite element method. Some characteristic features, including the ballistic performance and the fracture conoid angle (for the ceramic tile) are discussed. The numerical models developed for the two armor configurations are validated by ballistic tests, where the projectile impact on the armors and the mechanical integrity of the armor systems after impact are observed. The results from simulations and experiments show that the Al2O3/Kevlar 29 composite armor is able to capture a 7.62 mm bullet with a striking velocity of 690 m/s and the rubber-ceramic composite armor is able to capture 5.56 × 45 mm bullet M855 (with an armor piercing tip) with an impact velocity of 894 m/s. It has been found that, when a rubber layer is placed on the front face of a ceramic composite armor, better ballistic performance is achieved. The experiments show that, when a rubber material is impacted by a projectile, its behavior at high velocities and high strain rates changes from elastic to brittle.

The effect of calcaneus and metatarsal head offloading insoles on healthy subjects' gait kinematics, kinetics, asymmetry, and the implications for plantar pressure management: A pilot study.

The global number of people with diabetes is estimated to reach 643 million by 2030 of whom 19-34% will present with diabetic foot ulceration. Insoles which offload high-risk ulcerative regions on the foot, by removing insole material, are the main contemporary conservative treatment to maintain mobility and reduce the likelihood of ulceration. However, their effect on the rest of the foot and relationship with key gait propulsive and balance kinematics and kinetics has not been well researched. The aim of this study is to investigate the effect of offloading insoles on gait kinematics, kinetics, and plantar pressure throughout the gait cycle. 10 healthy subjects were recruited for this experiment to walk in 6 different insole conditions. Subjects walked at three speeds on a treadmill for 10 minutes while both plantar pressure and gait kinematics, kinetics were measured using an in-shoe pressure measurement insole and motion capture system/force plates. Average peak plantar pressure, pressure time integrals, gait kinematics and centre of force were analysed. The average peak plantar pressure and pressure time integrals changed by -30% (-68% to 3%) and -36% (-75% to -1%) at the region of interest when applying offloading insoles, whereas the heel strike and toe-off velocity changed by 15% (-6% to 32%) and 12% (-2% to 19%) whilst walking at three speeds. The study found that offloading insoles reduced plantar pressure in the region of interest with loading transferred to surrounding regions increasing the risk of higher pressure time integrals in these locations. Heel strike and toe-off velocities were increased under certain configurations of offloading insoles which may explain the higher plantar pressures and supporting the potential of integrating kinematic gait variables within a more optimal therapeutic approach. However, there was inter-individual variability in responses for all variables measured supporting individualised prescription.

Hydraulic Characterization of the External Flow Field of a Pressure-Self-Controlled Water-Pesticide Integrated Sprinkler

Highlights A pressure-self-controlled water-pesticide integrated sprinkler was developed for trellis crops. The dual-flow channel design integrates both water and pesticides and allows simultaneous downward irrigation of grape roots and upward spraying of grape branches and leaves. The comprehensive scoring method was employed to evaluate the spraying performance of the water-pesticide integrated sprinkler for both irrigation and spraying modes. Abstract. To ensure optimal growth of plants, including for trellis-style grape cultivation, it is essential to provide water to plant roots, branches, and leaves. Unfortunately, existing sprinkler systems are not designed to accommodate irrigation and spraying at the same time. To address this issue, a pressure-self-controlled water-pesticide integrated sprinkler was developed for trellis crops in this research. To assess the performances of irrigation and spraying modes, several factors, including the droplet diameter, droplet velocity, droplet striking kinetic energy, spray uniformity, and velocity distribution, were evaluated. Advanced measurement tools such as a two-dimensional video disdrometer (2DVD) and a particle image velocimeter (PIV) were employed to experimentally study the hydraulic features of different working modes. This study provides precise working parameters, including pressure and installation height, for the sprinkler system under different conditions. These parameters offer valuable engineering guidance. Notably, during irrigation, the sprinkler dispersed water toward the ground to irrigate the roots. Furthermore, the spray droplet diameter and velocity decreased with increasing pressure. Based on an analysis of the parameters affecting the droplet striking kinetic energy, the recommended optimal working pressure is 250 kPa. The high-pressure water produced by the sprinkler in the spraying mode effectively covered the crop leaves at an optimal working pressure of 400 kPa, as determined by the spray distribution pattern at different heights. In this study, for the water-pesticide integrated sprinkler, we recommend an installation height of 1.4 m for optimal operation. These findings could promote the practical application of this system. Keywords: Hydraulic performance, Spray characteristics, Spraying, Sprinkler irrigation, Water-pesticide integrated systems.