Bioinspired Structural Composite Flexible Material with High Cushion Performance.

Impacts occur everywhere, and they pose a serious threat to human health and production safety. Flexible materials with efficient cushioning and energy absorption are ideal candidates to provide protection from impacts. Despite the high demand, the cushioning capacity of protective materials is still limited. In this study, an integrated bionic strategy is proposed, and a bioinspired structural composite material with highly cushioning performance is developed on the basis of this strategy. The results demonstrated that the integrated bionic material, an S-spider web-foam, has excellent energy storage and dissipation as well as cushioning performance. Under impact loading, S-spider web-foam can reduce peak impact forces by a factor of 3.5 times better than silicone foam, achieving unprecedented cushioning performance. The results of this study deepen the understanding of flexible cushioning materials and may provide new strategies and inspiration for the preparation of high-performance flexible cushioning materials.

Iterative-Based Impact Force Identification on a Bridge Concrete Deck.

Steel-reinforced concrete decks are prominently utilized in various civil structures such as bridges and railways, where they are susceptible to unforeseen impact forces during their operational lifespan. The precise identification of the impact events holds a pivotal role in the robust health monitoring of these structures. However, direct measurement is not usually possible due to structural limitations that restrict arbitrary sensor placement. To address this challenge, inverse identification emerges as a plausible solution, albeit afflicted by the issue of ill-posedness. In tackling such ill-conditioned challenges, the iterative regularization technique known as the Landweber method proves valuable. This technique leads to a more reliable and accurate solution compared with traditional direct regularization methods and it is, additionally, more suitable for large-scale problems due to the alleviated computation burden. This paper employs the Landweber method to perform a comprehensive impact force identification encompassing impact localization and impact time-history reconstruction. The incorporation of a low-pass filter within the Landweber-based identification procedure is proposed to augment the reconstruction process. Moreover, a standardized reconstruction error metric is presented, offering a more effective means of accuracy assessment. A detailed discussion on sensor placement and the optimal number of regularization iterations is presented. To automatedly localize the impact force, a Gaussian profile is proposed, against which reconstructed impact forces are compared. The efficacy of the proposed techniques is illustrated by utilizing the experimental data acquired from a bridge concrete deck reinforced with a steel beam.

A Systematic Review of Dynamic Forces and Kinematic Indicators of Front and Roundhouse Kicks across Varied Conditions and Participant Experience.

Impact force and maximum velocity are important indicators of kick efficiency. Therefore, this systematic review compared the front kick (FK) and roundhouse kick (RK), including their impact force, maximum velocity, angular velocity, and execution time, considering various target types and experience levels. Following PRISMA guidelines, the Web of Science, SportDiscus, and PubMed were systematically searched for articles published from January 1982 to May 2022. Normalized kicking values were compared using one-way ANOVA. Eighteen articles included FKs (sample: 113 elite men, 109 sub-elite men, and 46 novices), and twenty-five articles included RKs (sample: 238 elite men, 143 sub-elite men, and 27 novice men). The results indicate that the impact force of the FK were 47% (p < 0.01), 92% (p < 0.01), and 120% (p < 0.01) higher than those of the RK across novice, sub-elite, and elite groups, respectively. Moreover, the maximum foot velocity of the RK was 44% (p < 0.01) and 48% (p < 0.01) higher than that of the FK for the sub-elite and elite groups, respectively. Furthermore, the elite group had 65% (p < 0.01) higher knee extension angular velocity with the RK than with the FK and 138% (p < 0.01) higher hip extension angular velocity with the FK than with the RK. In summary, the findings suggest that the FK is more effective in generating forceful kicks, while the RK has the potential for rapid execution.

A sensorized modular training platform to reduce vascular damage in endovascular surgery.

PURPOSE: Endovascular interventions require intense practice to develop sufficient dexterity in catheter handling within the human body. Therefore, we present a modular training platform, featuring 3D-printed vessel phantoms with patient-specific anatomy and integrated piezoresistive impact force sensing of instrument interaction at clinically relevant locations for feedback-based skill training to detect and reduce damage to the delicate vascular wall. METHODS: The platform was fabricated and then evaluated in a user study by medical ([Formula: see text]) and non-medical ([Formula: see text]) users. The users had to navigate a set of guidewire and catheter through a parkour of 3 modules including an aneurismatic abdominal aorta, while impact force and completion time were recorded. Eventually, a questionnaire was conducted. RESULTS: The platform allowed to perform more than 100 runs in which it proved capable to distinguish between users of different experience levels. Medical experts in the fields of vascular and visceral surgery had a strong performance assessment on the platform. It could be shown, that medical students could improve runtime and impact over 5 runs. The platform was well received and rated as promising for medical education despite the experience of higher friction compared to real human vessels. CONCLUSION: We investigated an authentic patient-specific training platform with integrated sensor-based feedback functionality for individual skill training in endovascular surgery. The presented method for phantom manufacturing is easily applicable to arbitrary patient-individual imaging data. Further work shall address the implementation of smaller vessel branches, as well as real-time feedback and camera imaging for further improved training experience.

Experimental investigation on high-pressure methane jet characteristic single-hole injector.

High-pressure gas direct injection (DI) technology benefits engines with high efficiency and clean emissions, and the gas jet process causes crucial effects especially inside an mm-size space. This study presents an investigation on the high-pressure methane jet characteristics from a single-hole injector by analysing jet performance parameters including jet impact force, gas jet impulse, and jet mass flow rate. The results show that the methane jet exhibited a two-zone behaviour along the jet direction in the spatial dimension induced by high-speed jet flow from the nozzle: zone 1 near the nozzle-the jet impact force and jet impulse increased consistently except for a fluctuation due to shock wave effects induced by the sonic jet and no entrainment occurs, and zone II farther away from the nozzle-the jet impact force and jet impulse became stable when the shock wave effects became weak and the jet impulse was conserved with a linear conservation boundary. The Mach disk height was exactly the turning point of two zones. Moreover, the methane jet parameters, such as the methane jet mass flow rate, jet initial jet impact force, jet impulse, and Reynolds number had a monotonous and linearly increasing correlation with injection pressure.

Dynamic Responses of Sandwich Beams with Polymethacrylimide (PMI) Foam Cores When Subjected to Impact Loading.

This paper focusses on the load-sustaining and transfer mechanisms of sandwich beams with various types of PMI foam cores under low-velocity impact loading. In the case of quasi-static loading, the different failure modes, failure loads, and deflections were obtained, which agreed well with the results predicted by the theory of sandwich structure. In the case of impact loading, the clamped sandwich beams were subjected to the impact of a striker bar with a momentum of 10 kg∙m/s to 20 kg∙m/s. The de-acceleration of the strike bar was measured to analyze the impact force and energy absorption, and the corresponding failure modes were also obtained. The results showed that the impact force and the corresponding duration time increases with the increases in the thickness of the face sheet and the density of the core. In addition, the failure modes of the sandwich beams transferred from the shear failure mode to the tensile failure mode, which was attributed to the strength ratio between the bottom face sheet and the core. In combination with the experimental results and the plastic hinge theory, the deformation mechanisms of the different sandwich beams are also discussed.

Validation of an Ear-Worn Wearable Gait Analysis Device.

Wearable devices capable of measuring gait parameters may provide a means to more economical gait analysis compared to conventional equipment comprising of a motion capture system and a forced treadmill. Beflex Coach (Beflex, Republic of Korea) is one such device but worn on the ear as Bluetooth earphones, unlike other wearables worn on the wrist, feet, or torso. In this study, the validity of the device was examined against a motion capture system and a forced treadmill for walking and running parameters. Five walking parameters (cadence, single support time, double support time, vertical oscillation (VO), and instantaneous vertical loading rate (IVLR)) and six running parameters (cadence, stance time, flight time, peak force, VO, and IVLR) were studied. Twenty young adults participated in walking or running on a forced treadmill at different speeds (walking: 0.8, 1.25, and 1.7 m/s for walking; running: 2, 2.5, and 3 m/s) while the two systems operated simultaneously. As a result, all parameters showed excellent associations (ICC > 0.75) and good agreements in Bland-Altman plots. The results of the study support the potential use of the ear-worn device as an inexpensive gait analysis equipment.

Superhydrophobic Strategy for Nature-Inspired Rotating Microfliers: Enhancing Spreading, Reducing Contact Time, and Weakening Impact Force of Raindrops.

Wind-dispersal of seeds is a remarkable strategy in nature, enlightening the construction of microfliers for environmental monitoring. However, the flight of these microfliers is greatly affected by climatic conditions, especially in rainy days, they suffer serious raindrop impact. Here, a hierarchical superhydrophobic surface is fabricated and a novel strategy is demonstrated that the superhydrophobic coating can enhance spreading while reduce contact time and impact force of raindrops, all of which are beneficial for the rotating microfliers. When the surface rotating speed exceeds a critical value, the effect of centrifugal force becomes considerable so that the droplet spreading is enhanced. The rotating superhydrophobic surface can rotate an impacting droplet by the tangential drag force from the air boundary layer, and the rotation of the droplet generates a negative pressure zone inside it, reducing the contact time by more than 30%. The impact force by the droplet on the rotating superhydrophobic surface also has a remarkable reduction of 53% compared to that on unprocessed hydrophilic surfaces, which helps maintain the flight stability of the microfliers. This work pioneers in revealing the droplet impact effect on rotating microflier surfaces and demonstrates the effectiveness of protecting microfliers with superhydrophobic coatings, which shall guide the manufacture and flight of microfliers in rainy conditions.

Triboelectric Energy-Harvesting Floor Tile.

The aim of this study was to investigate the real-world electrical parameters that strongly affected the performance of a triboelectric energy-harvesting floor tile design: triboelectric material thickness, cover plate displacement distance or gap width, and cover plate pressing frequency, so that real-world specifications of the harvesting floor tile can be accurately specified. The structure of the designed triboelectric energy harvester, with readily available polytetrafluoroethylene (PTFE) film and aluminum foil, was simple and hence easy to fabricate, and the material cost was low. A square wave was used to simulate the pressing frequency on the test bench's cover plate. The results showed that the voltage and current were proportional to the gap width, and the thinner the triboelectric layer thickness, the higher the output voltage and current. A test bench with a 0.2 mm thick PTFE triboelectric layer generated the highest energy output. In a later experiment, a triboelectric energy-harvesting floor tile (TEHFT) prototype was constructed with 0.1 and 0.2 mm thick PTFE layers. We found that at 2 Hz stepping frequency and 0.1 mm PTFE thickness, the optimal load and cumulative energy of the TEHFT were 0.8 MΩ and 3.81 mJ, respectively, while with 0.2 mm PTFE thickness, these two parameters were 1.1 MΩ and 7.69 mJ, respectively. The TEHFT with 0.2 mm thick PTFE layer was able to illuminate a series of 100 to 150 LEDs, sufficient power to drive small electronics and sensor nodes. This discovery provides important data on the structure, material, and contact surface area of a TEHFT that can be adjusted to suit specific requirements of a special function triboelectric energy harvester.

A sense of distance and movement characteristics of golfers tested without visual feedback of outcomes: Is a putt that feels subjectively good also physically good?

For motor tasks that require fine-tuning, such as adjusting the applied force according to the distance to the target, as required for driving and putting in golf, it is important to develop a high degree of sensitivity of one's movement-produced feedback. In previous research focusing on mental representation in golf, this ability to control distance has been called "a sense of distance". In particular, this study focused on three skills: motor control of the putter head, perception of the impact force, and prediction of the ball's travel distance. However, the relationship between the motor control of the putter head and the error of the outcome estimation is yet to be clarified. The purpose of the present study is two-fold: first, to clarify whether kinematic variation of putter head is correlated with error in estimating the outcome and, second, to quantitatively evaluate the performer's sensations of good and poor performance generated by the ball's impact, for a comparison of the kinematics and impact force of the putter head based on their assessment. Twelve professionals and 12 intermediate amateurs played two distance targets (at 2.4 and 4.8 m) without visual feedback of the outcomes. The kinematics of the putter head, impact force, final ball position, outcome estimation, and subjective assessment were measured. Our results show that the variability in the peak velocity was moderately correlated with the error of the outcome estimation in amateurs' 4.8-m putting task. In addition, amateurs estimated undershoots (overshoots) when they provided worse (better) evaluations. However, the amateurs' trials that were rated as better putts were actually overshoots. These results suggest that the subjectively "good putt" of amateurs was not physically good, and the amateurs putted hard to compensate for the risk of undershoots. However, no remarkable feature of the professional's sense of distance was found. This suggests that professional golfers' sensation is not significantly different from the outcomes that can be physically detected.

Experimental Research on a Hybrid Algorithm for Localisation and Reconstruction of the Impact Force Applied to a Rectangular Steel Plate Structure.

Impact force is the most common form of load which acts on engineering structures and presents a great hidden risk to the healthy operation of machinery. Therefore, the identification or monitoring of impact forces is a significant issue in structural health monitoring. The conventional optimisation scheme based on inversion techniques requires a significant amount of time to identify random impact forces (impact force localisation and time history reconstruction) and is not suitable for engineering applications. Recently, a pattern recognition method combined with the similarity metric, PRMCSM, has been proposed, which exhibits rapidity in practical engineering applications. This study proposes a novel scheme for identifying unknown random impact forces which hybridises two existing methods and combines the advantages of both. The experimental results indicate that the localisation accuracy of the proposed algorithm (100%) is higher than that of PRMCSM (92%), and the calculation time of the hybrid algorithm (179 s) for 25 validation cases is approximately one nineteenth of the traditional optimisation strategy (3446 s).

Relationship Between Ground Reaction Force Characteristics and Bone Mineral Density of the Hip and Spine in Male Runners.

The purpose of this study was to determine the relationship between running ground reaction force (GRF) characteristics and hip and lumbar spine bone mineral density (BMD) values in male runners. Individuals who ran at least 48.3 km per week and were injury-free were recruited. Kistler force plates collected running vertical and anteroposterior GRF data. A Hologic Discovery W bone densitometer measured lumbar spine and five regional hip BMD values. Only runners who consistently used a rear foot strike pattern were included (n = 32). Pearson correlation coefficients were calculated between BMD values and various GRF values and step-wise multiple regression was run to predict BMD values from the various GRF values. The vertical impact force was significantly correlated with the lumbar spine and four of the five hip BMD values (r > 0.374, p < 0.035). Both the peak early loading rate (ELR) and average ELR were significantly correlated with the lumbar spine and Ward's triangle BMD (r > 0.430, p < 0.014), while the average active loading rate was correlated only with the Ward's triangle BMD (r = 0.438, p = 0.012). Multiple regression revealed the peak impact force was the predictor for every hip region BMD other than the trochanter and the average ELR as a predictor for the lumbar spine BMD. The peak braking force was negatively correlated with the Ward's triangle BMD (r = -0.414, p = 0.019). It appears that the large forces and loading rates associated with rear foot striking may be advantageous and predictive for BMD at the hip and spine.

Fall impacts from standing show equivalence between experts in stage combat landing strategy and naïve participants after training.

BACKGROUND: Slips, trips, and falls are the second leading cause of non-fatal injuries in workplace in the United States. A stage combat landing strategy is used in the theatre arts to reduce the risk of fall-induced injury, and may be a viable approach among some working populations. OBJECTIVE: The goal of this study was to compare fall impact characteristics between experts in stage combat landing strategy and naïve participants after four training sessions of stage combat landing strategy training. METHODS: Forward and backward falls from standing were induced by releasing participants from static leans. Participants fell onto a foam mat, and impact force was measured using force platforms under the mat. A statistical equivalence test was used to determine if impact characteristics between groups were similar. RESULTS: Results indicated equivalence between groups in peak impact force during backward but not forward falls. Equivalence between groups in impact time suggested a mechanism by which equivalence in peak impact force as achieve. CONCLUSIONS: Four training sessions was sufficient for naïve participants to exhibit fall impact characteristics similar to experts in an anecdotally-effective landing strategy, and support further study. To our knowledge, this was the first study to investigate training for a landing strategy involving stepping after losses of balance from standing.

A Study on Impact Force Detection Method Based on Piezoelectric Sensing.

Impact force refers to a transient phenomenon with a very short-acting time, but a large impulse. Therefore, the detection of impact vibration is critical for the reliability, stability, and overall life of mechanical parts. Accordingly, this paper proposes a method to indirectly characterize the impact force by using an impact stress wave. The LS-DYNA software is utilized to establish the model of a ball impacting the steel plate, and the impact force of the ball and the impact response of the detection point are obtained through explicit dynamic finite element analysis. In addition, on this basis, a correspondence between the impact force and the impact response is established, and finally, an experimental platform for impact force detection is built for experimental testing. The results obtained by the finite element method are in good agreement with the experimental measurement results, and it can be inferred that the detected piezoelectric signal can be used to characterize the impact force. The method proposed herein can guide the impact resistance design and safety assessment of structures in actual engineering applications.

Spatiotemporal and Ground-Reaction Force Characteristics as Risk Factors for Running-Related Injury: A Secondary Analysis of a Randomized Trial Including 800+ Recreational Runners.

BACKGROUND: Running biomechanics may play a role in running-related injury development, but to date, only a few modifiable factors have been prospectively associated with injury risk. PURPOSE: To identify risk factors among spatiotemporal and ground-reaction force characteristics in recreational runners and to investigate whether shoe cushioning modifies the association between running biomechanics and injury risk. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Recreational runners (N = 848) were tested on an instrumented treadmill at their preferred running speed in randomly allocated, standardized running shoes (with either hard or soft cushioning). Typical kinetic and spatiotemporal metrics were derived from ground-reaction force recordings. Participants were subsequently followed up for 6 months regarding running activity and injury. Cox regression models for competing risk were used to investigate the association between biomechanical risk factors and injury risk, including stratified analyses by shoe version. RESULTS: In the crude analysis, greater injury risk was found for greater step length (subhazard rate ratio [SHR], 1.01; 95% CI, 1.00-1.02; P = .038), longer flight time (SHR, 1.00; 95% CI, 1.00-1.01; P = .028), shorter contact time (SHR, 0.99; 95% CI, 0.99-1.00; P = .030), and lower duty factor (defined as the ratio between contact time and stride time; SHR, 0.95; 95% CI, 0.91-0.98; P = .005). In the stratified analyses by shoe version, adjusted for previous injury and running speed, lower duty factor was associated with greater injury risk in those using the soft shoes (SHR, 0.92; 95% CI, 0.85-0.99; P = .042) but not in those using the hard shoes (SHR, 0.97; 95% CI, 0.91-1.04; P = .348). CONCLUSION: Lower duty factor is an injury risk factor, especially for softer shoe use. Contrary to widespread beliefs, vertical impact peak, loading rate, and step rate were not injury risk factors in recreational runners. REGISTRATION: NCT03115437 (ClinicalTrials.gov identifier).

Numerical and experimental studies on needle impact characteristics in ultrasonic shot peening.

Ultrasonic shot peening(USP) is an advanced surface treatment technology for obtaining excellent surface properties or manufacturing a three-dimensional curved surface of the metal sheets. The impact of the medium driven by ultrasonic vibration is significant to parameter optimization and excellent performance of the USP technology. However, the impact characteristics of the medium lack careful study, which is a complex dynamic analysis involving many factors, such as collision, plastic deformation, air pressure, etc. In this paper, a detection system is successfully developed to investigate the needle impact force and frequency against the material surface, consisting of a piezoelectric load sensor, oscilloscope, and a single needle USP device. Moreover, the FE model of the needle impact is developed simultaneously to study the characteristics of residual stress implantation induced by needle impact. Based on the experiment and FE simulation results, it is discovered that the impacts with high speed primarily determine the thickness of the modified layer implanted with residual stress during multiple impacts at different rates. According to residual stress implantation characteristics, the low-speed impact whose speed does not reach 50% of the maximum impact speed was defined as the ineffective impact. Besides, increasing the amplitude of ultrasonic vibration results in a significant increase in the maximum impact force and the effective impact frequency. The travel distance of needle impact has a considerable effect on the effective impact frequency, but it has little effect on the maximum impact force. Finally, it was concluded that the low air pressure plays a positive role in the needle impact. Furthermore, excessive air pressure hinders the needle impact and results in a decline in the effective impact frequency and the maximum impact force.

Ankle Instability Patients Exhibit Altered Muscle Activation of Lower Extremity and Ground Reaction Force during Landing: A Systematic Review and Meta-Analysis.

This review aimed to investigate characteristics of muscle activation and ground reaction force (GRF) patterns in patients with ankle instability (AI). Relevant studies were sourced from PubMed, CINAHL, SPORTDiscus, and Web of Science through December 2019 for case-control study in any laboratory setting. Inclusion criteria for study selection were (1) subjects with chronic, functional, or mechanical instability or recurrent ankle sprains; (2) primary outcomes consisted of muscle activation of the lower extremity and GRF during landing; and (3) peer-reviewed articles with full text available, including mean, standard deviation, and sample size, to enable data reanalysis. We evaluated four variables related to landing task: (1) muscle activation of the lower extremity before landing, (2) muscle activation of the lower extremity during landing, (3) magnitude of GRF, and (4) time to peak GRF. The effect size using standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated for these variables to make comparisons across studies. Patients with AI had a lower activation of peroneal muscles before landing (SMD = -0.63, p < 0.001, CI = -0.95 to -0.31), greater peak vertical GRF (SMD = 0.21, p = 0.03, CI = 0.01 to 0.40), and shorter time to peak vertical GRF (SMD = -0.51, p < 0.001, CI = -0.72 to -0.29) than those of normal subjects during landing. There was no significant difference in other muscle activation and GRF components between the patients with AI and normal subjects (p > 0.05). Altered muscle activation and GRF before and during landing in AI cases may contribute to both recurrent ankle and ACL injuries and degenerative change of articular.

Parametric analysis of landing injury : The effect of landing posture and joint displacement.

During landing, the lower limb joints work concertedly to reduce landing forces. Changing the biomechanics of one joint can alter landing strategies in other joints thus affecting the probability of injury. Therefore, understanding the mutual effects between the joints is crucial for the prevention of lower extremity injuries. The purpose of this study is to evaluate the effect of joint displacement and initial contact posture on the impact forces and joint kinematics during drop landing, via computational modeling. The impact dynamics of drop landing is modeled by a three link planar model. Different landing scenarios are then simulated to investigate how restricting the displacement of one joint and changing its initial contact angle affect the other joints' ranges of motion, the trunk motion, and the impact forces. Our study suggests that the impact force increases by up to [Formula: see text], [Formula: see text] and [Formula: see text], by restricting the hip, knee and ankle joints, respectively. Restricting each one of the hip and knee joints decreases the displacement of the other one. The association between the ankle displacement and the hip/knee motion depends on joints' stiffness and landing posture. Moreover, changing the landing posture affects the joints kinematics and impact forces significantly. A safe landing posture is a fore-foot landing with knee flexion angle of around 30° to 40° and a foot-ground angle of 40° to 55°, which decreases the impact force by more than [Formula: see text] in comparison to the erect posture with horizontal foot. The obtained results are of practical importance in training landing skills and designing force-reducing external components.

A Case of Depressed Skull Fracture of the Inner Table Alone.

A depressed skull fracture (DSF) is comminuted fractures in which the broken bones displace inward due to a blunt head trauma, such as when the broken outer table is located below the normal anatomical position of the inner table. The author presents an extremely rare case of a 38-year-old man with a DSF that affected only the inner table. In the literature, only 2 cases of DSF involving only the inner table have been reported, and the underlying mechanism remains unclear. The author believes that this phenomenon was not enough for the impact force to depress the outer table, but the tensile stress was sufficient to depress the relatively thin and weak inner table.

On challenges in clinical assessment of hip fracture risk using image-based biomechanical modelling: a critical review.

INTRODUCTION: Hip fracture is a common health risk among elderly people, due to the prevalence of osteoporosis and accidental fall in the population. Accurate assessment of fracture risk is a crucial step for clinicians to consider patient-by-patient optimal treatments for effective prevention of fractures. Image-based biomechanical modeling has shown promising progress in assessment of fracture risk, and there is still a great possibility for improvement. The purpose of this paper is to identify key issues that need be addressed to improve image-based biomechanical modeling. MATERIALS AND METHODS: We critically examined issues in consideration and determination of the four biomechanical variables, i.e., risk of fall, fall-induced impact force, bone geometry and bone material quality, which are essential for prediction of hip fracture risk. We closely inspected: limitations introduced by assumptions that are adopted in existing models; deficiencies in methods for construction of biomechanical models, especially for determination of bone material properties from bone images; problems caused by separate use of the variables in clinical study of hip fracture risk; availability of clinical information that are required for validation of biomechanical models. RESULTS AND CONCLUSIONS: A number of critical issues and gaps were identified. Strategies for effectively addressing the issues were discussed.