Acceleration Curves Research Articles

Passive wireless multi-parameter LC sensing system for in situ health monitoring of bearings

The health condition of bearings is crucial for the safe operation of equipment. In situ, multi-parameter monitoring of the rotating components of bearings facilitates accurate assessment and diagnosis of bearing health. Based on the previous research on LC (Inductor-Capacitor) strain sensor for bearings, a passive wireless multi-parameter LC sensor suitable for in situ monitoring of bearings is proposed. The LC sensor uses dual resonance frequencies together with one quality factor to simultaneously monitor three parameters of bearing. Theoretical derivation and simulation analysis indicate that, due to the adoption of a symmetrical circuit structure, the two resonant frequencies of the LC sensor are independent and do not interfere with each other. Furthermore, the asymmetric analysis shows that under significant parameter asymmetry, the two resonant frequencies still maintain excellent independence. According to the installation position of the bearing, the sensor coil and the sensor circuit are designed to be conformal to the bearing. The acceleration, strain and temperature response curves of the LC sensor are measured by installing it on a circular steel disc that simulates the environment of a bearing. Finally, the LC sensor is successfully demonstrated on a bearing test platform.

Tennis action recognition and evaluation with inertial measurement unit and SVM

Action recognition in tennis plays a crucial role for athletes and coaches, aiding in understanding and evaluating the players' skill levels to formulate more effective training plans and tactical strategies. To enhance the recognition and grading of tennis player actions, this study introduces the use of inertial measurement units and flexible resistive sensors for data collection. An improved Support Vector Machine is employed for data classification to achieve efficient action recognition. The results demonstrated that the proposed classification algorithm achieved an average accuracy of 95.35 % in recognizing actions of elite athletes, with the highest accuracy (96.38 %) observed in forehand strokes. In the case of sub-elite athletes, the algorithm achieved an impressive average accuracy of 97.67 %. For amateur enthusiasts, the algorithm exhibited an average accuracy of 94.08 %. Furthermore, elite athletes exhibited larger peak values in the three-axis acceleration waveform during ball striking. Specifically, the absolute peak value of acceleration in the Y-axis for elite athletes reached 78 m/s², representing an increase of 39 m/s² and 8 m/s² compared to the other two levels of athletes, respectively. Additionally, on the X and Z axes, elite athletes' acceleration peak values reached 59 m/s² and 78 m/s², significantly higher than those of sub-elite athletes and amateur enthusiasts. Moreover, the acceleration curves of elite athletes demonstrated a higher overall regularity. These findings indicate that the proposed action recognition method has a significant impact on recognition and evaluation, providing valuable insights for action recognition and assessment across various domains and advancing the application of artificial intelligence technology in the field of sports.

Variation in Accelerometer-Derived Instantaneous Acceleration Distribution Curves of Elite Male Soccer Players According to Playing Position: A Pilot Study.

The incorporation of triaxial accelerometers into Global Positioning Systems (GPS) has significantly advanced our understanding of accelerations in sports. However, inter-positional differences are unknown. This study aimed to explore the variability of acceleration and deceleration (Acc) distribution curves according to players' positions during soccer matches. Thirty-seven male players from a national-level Portuguese club were monitored using 10 Hz GPS with an embedded accelerometer during the 2021/2022 season. Resultant Acc was obtained from the x (lateral), y (frontal/back), and z (vertical) axes and expressed in gravitational units (g). Statistical Parametric Mapping was employed to compare playing positions: central defenders (CD), fullbacks (FB), central midfielders (CM), wide midfielders (WM), and strikers (ST). All positions exhibited a decreasing Acc distribution curve, very similar in shape, with a high frequency of events in the lower ranges (i.e., 0 to 1 g) and a lower frequency of events in the higher values (2 to 10 g). Post hoc comparisons revealed significant differences between all positions, except between FB and WM. Out of 1000 points in the curve, CD had 540, 535, 414, and 264 different points compared to FB, CM, WM, and ST, respectively. These findings indicate that players in different positions face distinct demands during matches, emphasizing the need for position-specific Acc analysis and training programming. By analyzing Acc as a continuous variable, this study highlights the importance of individualized monitoring to ensure the comprehensive and precise tracking of all player activities, without overlooking or omitting critical information.

Effect of soil-building interaction on dynamic earth pressure on basement walls

This study investigates dynamic earth pressure on basement walls by considering soil-structure interaction, a factor that is often overlooked by conventional methods like Mononobe-Okabe, Seed and Whitman, and Wood. Superstructure, basement, and soil were numerically simulated in a single model to evaluate the inertial and kinematic effects of buildings on dynamic earth pressure on the basement walls. The numerical model was validated using data from a centrifuge test and an instrumented building. Then, a parametric study was performed, with the height, width, and basement depth of the building varied with six input motions. The results showed that the inertia of the building increased dynamic thrust. Furthermore, the dynamic thrust showed a similar trend with the displacement response spectrum curve of the ground surface acceleration as the building height increased, while the distribution shape transitioned from triangular to inverted triangular. Additionally, wider buildings had increased dynamic earth pressure, while deeper buildings exhibited smaller normalized dynamic thrust.

Comparative analysis of two types of mechanical grippers for gripping flexible packaging materials

Abstract To study the different structure types of flexible packaging material gripping mechanical grippers and their application to the working environment, two types of cylinder-type soft packaging material gripping mechanical grippers are designed in this paper. According to the structural characteristics of the mechanical gripper, mathematical analysis is carried out to determine the coordinate relationship of each joint of the mechanical gripper. The plot function in MATLAB is used to plan and simulate the path curves of the two types of mechanical grippers and to determine the working environment of the two types of mechanical grippers applied respectively; the movement of the mechanical gripper is analyzed by using the fifth-degree polynomial, and MATLAB Robotics toolbox is used for simulation, which results in the displacement, velocity, and speed of the end of the two mechanical grippers. The fifth-degree polynomial is used to analyze the motion of the mechanical gripper, and the MATLAB Robotics toolbox is adopted for simulation, as well as the displacement, velocity, and acceleration curves of the end of the two mechanical grippers. The aim is to understand the motion characteristics of the two kinds of mechanical grippers, master the two kinds of mechanical grippers’ working state, and provide a reference for subsequent research on flexible packaging material gripping mechanical grippers.

Freeze–thaw damage analysis and life prediction of modified pervious concrete based on Weibull distribution

An assessment of the freeze–thaw durability of pervious concrete was conducted using a rapid freezing method to investigate the durability of modified pervious concrete within a freeze–thaw environment. The optimal proportion of the modified material was determined by evaluating the mass-loss rate and the relative dynamic elastic modulus as indicators of freeze–thaw performance. Scanning electron microscopy (SEM) was employed to observe microcrack propagation and reaction products. A freeze–thaw damage model, based on the Weibull probability distribution, was formulated. Freeze–thaw damage analysis and life prediction assessment were carried out using curves such as freeze–thaw damage velocity curves, freeze–thaw damage acceleration curves, failure rate curves, and reliability life curves. The outcomes revealed that the inclusion of polyacrylonitrile (PAN) and silica ash had a favourable impact on improving the frost resistance of pervious concrete at later stages. The optimal proportions for PAN fibre and silica ash were determined as 0.6 % and 8 %, respectively. As the number of freeze–thaw cycles approached approximately 52.03 times, the freeze–thaw cycle velocity peaked. Subsequently, the freeze–thaw damage velocity was categorised into three stages based on the freeze–thaw damage acceleration curve. The degradation of pervious concrete due to freeze–thaw cycles followed a typical loss-type failure pattern. Notably, a 50 % increase in PAN fibre content resulted in a 62.92 % reduction in failure rate. Furthermore, a predictive analysis was conducted to estimate the lifespan of pervious concrete in a representative freeze–thaw region in China was performed.

Predicting pump-turbine characteristic curves by theoretical models based on runner geometry parameters

The characteristic curve of a pump-turbine is the essential data for calculating the hydraulic transient processes of a pumped storage power station. However, this curve is often unavailable during the preliminary design stage of pumped storage power stations. The shape of the characteristic curve directly influences the transient guarantee parameters. To date, adjusting the runner geometry to control the characteristic curve's shape for improving hydraulic transients remains a challenging issue. This paper proposes a model for predicting the characteristic curve that correlates its shape with the runner's geometric parameters. Considering the bidirectional flow in pump-turbines, two sets of governing equations are derived separately for the centripetal and centrifugal flow conditions. The governing equations for the unit discharge curve and the unit torque curve are constructed based on the energy equation and torque equation, respectively. Each term in these equations is subsequently organized into the expressions involving the runner's geometric parameters and unit parameters. To make the equations solvable, several sets of feature points are introduced. Based on the approach to obtain the feature points, an experiment/CFD (Computational Fluid Dynamics)-based prediction method and a statistics-based prediction method are proposed. Verifications using manufacturer-measured curves show that the experiment/CFD-based method is well-suited for model test acceleration and characteristic curve repair due to its higher prediction accuracy and availability, while the statistics-based method is more suitable for borrowing similar curve data during the power plant's preliminary design phase or rapidly predicting the corresponding characteristic curves during runner design. This work establishes a theoretical basis for improving hydraulic transient guarantee parameters by runner design optimization.

Numerical and theoretical investigation of crack propagation in the windshield in collision with a dummy headform

Studies show that the impact of the pedestrian head and windshield is a significant contributing factor to casualties in traffic accidents. Accordingly, investigating the mechanical response of the windshield and its failure mechanism is of significant importance in enhancing the safety of pedestrians in car accidents. This study conducted the pedestrian protection head impact test to determine the fracture mode of the windshield, acquire the acceleration curve of the headform impactor, and accurately obtain the peak acceleration and Head Injury Criterion (HIC). Subsequently, to quickly predict HIC and facilitate structural selection in designing automobiles, a theoretical analysis model for predicting peak acceleration was established and validated against the test results. To analyze the damage mechanism in detail, finite element analysis software LS-DYNA was employed to simulate the crack propagation in the windshield based on the peridynamics theory. Through a comparison between the numerical simulation and experimental results, the accuracy of the bond-based peridynamics model was verified, accurately revealing its failure mode and mechanical response to impact. Meanwhile, the peak acceleration and HIC were effectively predicted, which provided an effective approach for vehicle safety evaluation and design.

Synthesis of 1-DOF mechanisms for exact regular polygonal path generation based on non-circular gear transmissions

Design of one-degree-of-freedom (1-DOF) mechanisms is of paramount interest. This work deals with the generation of exact regular polygonal paths by using two particular 1-DOF mechanisms. The design of two-bar and three-bar mechanisms including non-circular gears is presented and evaluated. Differences in the kinematics of both mechanisms are discussed. The three-bar mechanism allows derivable velocity and acceleration curves during the whole trajectory, including the polygon vertices, a feature that cannot be achieved with the simpler two-bar mechanism. Hence, the three-bar mechanism makes it possible to generate perfect vertices using non-circular gears. To the best of the authors’ knowledge, this mechanism is the first 1-DOF mechanism with articulated links and a non-circular gear transmission that can generate exact regular polygonal paths. The proposed mechanisms can also be applied to generate two straight lines with a given angle, which is another novel contribution of this work. A prototype of the three-bar mechanism has been developed for experimental validation.

Exploring seismic resilience in frame structures through advanced numerical modeling and dynamic nonlinear analysis of recycled aggregate concrete

This study developed an advanced three-dimensional spatial model to examine the behavior of Recycled Aggregate Concrete (RAC) frame structures using sophisticated nonlinear beam-column fiber elements. It thoroughly investigates the dynamic properties such as natural frequency, vibration modes, and stiffness of RAC structures and conducts a detailed nonlinear dynamic analysis focusing on acceleration, displacement, drift, and hysteresis curves. The seismic resilience of RAC structures, especially inter-story drift under various seismic intensities, was evaluated and compared with Natural Aggregate Concrete (NAC) structures by adjusting the concrete material model parameters in the finite element framework. The accuracy of the numerical model was validated against shaking table tests, showing that RAC and NAC structures comply with structural damage criteria across seismic phases from 0.066 g to 1.170 g. The findings suggest RAC structures are as seismically resilient as NAC ones, making them suitable for earthquake-prone areas.

A new simple masing-type soil nonlinear model considering modified damping and its application on KiK-net site response

In this paper, a series of simple Masing rules is first proposed for best fitting the shear modulus reduction and the damping ratio curves of soil based on the extended Masing rules and hysteretic damping formulation. A new masing-type nonlinear model is established and implemented in ABAQUS software based on the Matasovic back-bone curve and the new proposed Masing rules. To validate the practical applicability of the new model, the 1-Directional 3-Component nonlinear site response analysis for station KSRH10 (in Hamanaka, Hokkaido, Japan) is conducted. The numerically predicted results of the proposed nonlinear model are in excellent agreement with the recordings. The surface peak ground acceleration obtained by ABAQUS agrees well with the recording, which has a little difference of about 8.3% on average. The comparison between the proposed nonlinear model and the DEEPSOIL model indicate that the results of the former match better with recording to some extent, in term of acceleration time histories, spectral acceleration (SA) curves, and peak ground acceleration (PGA). The mean square error of acceleration time histories and SA curves obtained by the proposed model is smaller than the model in DEEPSOIL. The agreement with recording is improved by 10.8% compared with the DEEPSOIL model.

Design Optimization of Lattice Structures Under Impact Loading for Additive Manufacturing

Abstract Additive manufacturing (AM) has enabled the production of intricate lattice structures with excellent performance and minimal mass. Design approaches that consider static loading, including lattice-based topology optimization (TO), have been well-researched recently. However, to date, there appears to be no widely accepted method of optimizing lattice structures for high-strain rate loading, especially when the design for additive manufacturing (DFAM) principles are considered. This study proposes a computational framework for the design of lattice structures under specified impact loading. To manage dimensionality while achieving sufficient generality, a heuristic design space is developed that relies on traditional TO to govern the design's macrostructure and standard dimensioning to govern its mesostructure. DFAM principles are then incorporated into a Bayesian optimization scheme wrapped around traditional TO to achieve manufacturable designs that absorb high-impact loading. Because this approach does not require analytical gradient information, the framework can be used to optimize directly on complex objectives, such as injury metrics calculated from the acceleration curve. A series of case studies is formulated around a mass-performance tradeoff and involves individual unit cell design as well as full-part design. The proposed design parameterization is found to enable sufficient flexibility to achieve consistently good performance regardless of AM build orientation.

Bladder dysfunction in adolescents with type 1 diabetes

It is increasingly significant that adults with diabetes experience lower urinary tract symptoms, however, there has been limited research in younger individuals with type 1 diabetes. To investigate bladder function using non-invasive urodynamics as a potential indicator of autonomic neuropathy in adolescents with type 1 diabetes. This involved examining the association between urinary flow disturbances, reported symptoms, and results from other autonomic tests. Cross-sectional study enrolling 49 adolescents with type 1 diabetes and 18 control subjects. All participants underwent uroflowmetry and ultrasound scanning, completed the Composite Autonomic Symptom Score (COMPASS)-31 questionnaire, and were instructed to record their morning urine volume and voiding frequencies and report them back. Cardiovascular reflex tests (CARTs) and the quantitative sudomotor axon reflex test (QSART) were performed. The main results are shown in the Summary figure. In this study, urological abnormalities were not significantly more frequent in adolescents with diabetes, however, urological issues were observed. This is supported by previous findings of Szabo etal. who found that adolescents with type 1 diabetes had reduced flow acceleration and time to maximum flow compared to control subjects. In our study, we observed cases with reduced acceleration and prolonged uroflow curves, possibly indicating detrusor underactivity. People with diabetes had a higher risk of nocturia than healthy controls, which our results supported. Some adolescents reported urination twice per night. Based on these findings, it is considered beneficial to ask about urological symptoms annually to determine if more examinations (frequency-volume charts and uroflowmetry) are necessary and/or if any opportunities for treatment optimization exist. However, uroflowmetry has limitations, as bladder filling and emptying is a complex process involving multiple pathways and neurological centers, making it difficult to standardize and evaluate. Another limitation of this study was that our control group was smaller and consisted of fewer males than females, which could affect the results due to differences in anatomy and physiology in the lower urinary tract system. In conclusion, adolescents with type 1 diabetes, as well as healthy adolescents, frequently experience urological symptoms. Although urological abnormalities were not significantly more frequent in adolescents with diabetes in this study, the focus on nocturia and risk for bladder dysfunction seems relevant, even in adolescents without any other tests indicating autonomic dysfunction.

Numerical Simulation Study of the Vibrational Response of Continuous Arch Tunnels under the Action of Overlying Train Loads

With the rapid development of transportation infrastructure in China, continuous arch tunnels passing under existing operational railways are increasingly encountered. This paper primarily investigates the mechanical response patterns of the lining of continuous arch tunnels under the vibrational loads generated by trains traveling on railways. To this end, a three-dimensional finite element model of the dynamic response of continuous arch tunnels under train vibrational loads was constructed using Midas GTS/NX software. This model explores the patterns of acceleration, dynamic displacement, and dynamic strain responses of continuous arch tunnels under the action of moving train loads. The study reveals that under train vibrational loads, the vertical acceleration, vertical displacement, and strain time history curves at various monitoring points in the continuous arch tunnel exhibit vibrational characteristics. The acceleration, vertical displacement, and dynamic strain increase as the train enters, fluctuate within a certain range, and then decrease to zero as the train exits. Under high-speed train loads, the acceleration peak values at the arch feet and outer sidewalls of the left and right tunnels are larger, with a greater peak value difference. The vertical displacement peak values at the arch shoulders and crown are larger, whereas those at the middle partition wall and base slab are smaller. During the process from the train's entry to its exit, the dynamic strain exhibits a trend of initially increasing, then stabilizing, and finally decreasing to zero, all while displaying vibrational characteristics. The strain response on the tunnel side where the train enters is greater than that on the side where it exits.

Response surface optimization design of flexible positioning platform considering its fatigue life

The research of macro and micro motion platforms has always been committed to realizing the ultra-high acceleration operation of the platform and improving the positioning accuracy of the platform. With the goal of achieving ultra-high-speed, the impact of the increase in speed on key components has also attracted more and more attention. This paper takes a flexible positioning platform of an ultra-high acceleration macro–micro motion platform with adjustable voice coil motor (VCM) number and load as the research object. Perform static analysis, rigid-flexible coupled dynamic analysis, fatigue analysis, and multi-objective response surface optimization design (RSMD). The influence on the acceleration of the platform and the influence on the stress and fatigue life of the flexible positioning platform with the change of the number and load of the VCM were explored. The changes of the acceleration and speed curves of the platform during ultra-high-speed operation are obtained by dynamic analysis, and the position of the dangerous part of the flexible platform during operation is obtained. Finally, the RSMD is carried out to realize its performance optimization. The research conclusions of this paper have great reference value for the development of the macro–micro motion platform and the improvement of its structure.

Acceleration and age in soccer

This paper considers how player acceleration changes in soccer relative to age. A plot of average maximum acceleration versus age is produced. The construction of the plot is based on methods from functional data analysis and the availability of tracking data from the 2019 season of the Chinese Super League. For an individual player, we calculate his maximum acceleration for each single match of the 2019 season. Since the players’ maximum accelerations are observed only on a single season instead of their entire careers, we treat them as incomplete functional data, called functional snippets. The average maximum acceleration, i.e., the mean function of the functional snippets rather than full curves is estimated by a local linear smoothing method. The most important observation is that the shape of the acceleration curve closely resembles curves of soccer performance versus age. This observation has implications for predicting future performance since acceleration is more easily and more accurately measured than performance.

A novel multi-resonator honeycomb metamaterial with enhanced impact mitigation

Local resonant metamaterials show significant promise in applications involving the attenuation of impact waves. This paper introduces a honeycomb metamaterial featuring a circular distribution of multiple mass-beam resonators designed to enhance impact mitigation by broadening low frequency bandgaps. The bandgaps of unit cells with different number of mass-beam resonators (MBR) are calculated. It is found that the unit cell with circularly distributed resonators (C-MBR) has strong low frequency local resonance in all directions, thus opening a complete wide bandgap in about 500–1200Hz. Then, a method of equivalent stiffness reduction related to the corresponding mode shapes is used to research the negative effective mass density characteristic, explaining the generation of the low frequency bandgaps. Subsequently, the impact protection capacity of local resonant metamaterial is compared with that of ordinary honeycomb metamaterial through experiment and simulation. Interestingly, the maximum acceleration values under the impact load of local resonant metamaterial are about 45% lower than that of honeycomb metamaterial, and the reaction force under the blast load is about 80% reduction. Besides, by analyzing the acceleration curve waveform and transmission spectrum, the local resonant metamaterial is found to exhibit continuous short period vibration, which blocks the wave in low frequency band. Finally, the energy dissipation performance of the local resonant metamaterial explains that it converts more impact energy into the kinetic energy of the core with resonators, thereby reducing the energy transferred to the bottom panel. These results underscore the potential application of the proposed metamaterial with multi-resonators in impact mitigation and energy dissipation.

A stochastic two-stage microgrid formation strategy for enhancing distribution network resilience against earthquake event incorporating distributed energy resources, parking lots and responsive loads

The sustainability of energy systems has been severely affected in recent years by the quantity and intensity of high-impact, low-probability events. As a result, the resilience concept has been introduced to analyze the operation of networks against such events. This paper proposes a stochastic two-stage microgrid formation formulation to maximize the restored loads and enhance the resilience index of electrical distribution systems in the face of earthquake events. In this regard, an earthquake incident is modeled in the first step utilizing geographical data, peak ground acceleration and fragility curves. Then, a two-stage linear programming and graph theory is applied to form microgrids in response to the mentioned disturbances, where the variables in the planning and operating states are optimized in the first and second stages, respectively. The influence of different components including diesel generators, renewable energies, storage units and electric vehicles is investigated. In addition, the role of responsive loads and uncertainties related to line failure, load variation, renewable resources availability and electric vehicles are considered during the analysis. The results for various scenarios validate that the presented approach increases load supply capability and resiliency index by 38.7% and 38.8%, respectively.

Influence of keel impacts and laying hen behavior on keel bone damage

Keel bone damage, which presents as fractures and/or deviations of the keel, has been detected in laying hens housed in all types of systems. Factors leading to keel bone damage in hens housed with limited vertical space, such as those housed in furnished systems, are not well understood, and are the topic of this study. Ten focal hens from each of 12 furnished cages (4 rooms of 3 cages) were fitted with keel mounted tri-axial accelerometers. Their behavior was video recorded continuously over two 3-wk trials: the first when the hens were between 52 and 60 wk of age, and the second approximately 20 wk later. The integrity of each hen's keel was evaluated at the start and end of each 3-wk trial using digital computed tomography. We identified predominant behaviors associated with acceleration events sustained at the keel (collisions, aggressive interactions and grooming) by pairing accelerometer outputs with video data. For each recorded acceleration event we calculated the acceleration magnitudes as the maximum summed acceleration recorded during the event, and by calculating the area under the acceleration curve. A principle components analysis, which was used as a data reduction technique, resulted in the identification of 4 components that were used in a subsequent regression analysis. A key finding is that the number of collisions a hen has with structures in her environment, and the number of aggressive interactions that a hen is involved, each affect the likelihood that she will develop 1 or more fractures within a 3-wk time span. This relationship between hen behavior and keel fracture formation was independent of the magnitude of acceleration involved in the event. Observed behavior did not have an impact on the formation of keel bone deviations, further supporting reports that the mechanisms underlying the 2 types of keel bone damage are different.

Experimental and numerical studies of impact loading on single-layer reticulated shells with aluminium alloy gusset joints

Aluminium alloy materials have found extensive application in large-span space grid structures. While research on the mechanical properties of aluminium alloy materials and components is generally well-established, there remains an incomplete understanding of the overall structure. Therefore, further investigation into the overall performance of aluminium alloy reticulated shells is crucial to promote their use in spatial structures, guiding structural design and addressing practical engineering challenges. This study focuses on the design of a single-layer aluminium alloy reticulated shell with a 2 m span, which was subjected to an impact test to examine its dynamic response and failure mode. By comparing and analysing stress, acceleration, and displacement time-history curves obtained from these different test conditions, the dynamic response behavior of the reticulated shell was determined. To simulate the impact on reticulated shells, explicit dynamic analysis was conducted using non-linear finite element software LS-DYNA. Based on the deformation characteristics and failure phenomena observed during the impact test, three distinct failure modes were defined for the single-layer reticulated shell. Through parameter analysis using the validated finite element model, it was determined that increasing the thickness (tp) of the aluminium alloy gusset plate or reducing the radius (R) of the gusset plate effectively enhances the overall stiffness and impact resistance of the single-layer reticulated shell. Overall, this research contributes to a deeper understanding of the performance of aluminium alloy reticulated shells under impact loads. The findings provide valuable insights for guiding structural design and addressing practical engineering problems in the field of spatial structures.