Ballistic Movements Research Articles

Analysis of wave propagation and pulsation in an elastic tube using a diaphragm pump

In this research, the flow wave propagation, speed, and pulsation suppression in an elastic tube were studied using a diaphragm pump. The flow fluctuations with shocking pressure fluctuations occur in the elastic tube because the check ball was blocked, thereby preventing reverse flow. Consequently, the check ball is one of the causes of pulsating flows in diaphragm pumps. However, only a few studies have analyzed the relationship among the check ball movement, pressure, and flow fluctuations. In this study, we constructed several elastic tube experiments: (i) single-tube model; (ii) two-tube model. To predict the flow wave propagation and pulsation in an elastic tube, we developed an axisymmetric theoretical model and compared into the experimental results. Based on our study, the main results were as follows: the relationship among the check ball movement, pressure, and flow fluctuations showed that the pressure and flow rate pulsation were caused by the asymmetry of the check ball movement. Additionally, we observed that the theoretical flow wave propagation trend had a good agreement with the experimental results, although the flow wave speed in the urethane-tube experiment differed considerably from the theoretical prediction. Furthermore, the amplitude of the pulsation increased considerably owing to the reflected wave at the tube exit, although it did not increase when the resistance was added at the exit. Finally, we observed that the pulsation reduced more in the silicon tubes compared to the urethane tubes because the deformation of the silicon tubes was larger than that of the urethane tubes.

Thick filament activation is different in fast- and slow-twitch skeletal muscle.

The contractile properties of fast-twitch and slow-twitch skeletal muscles are primarily determined by the myosin isoform content and modulated by a variety of sarcomere proteins. X-ray diffraction studies of regulatory mechanisms in muscle contraction have focused predominately on fast- or mixed-fibre muscle with slow muscle being much less studied. Here, we used time-resolved X-ray diffraction to investigate the dynamic behaviour of the myofilament proteins in relatively pure slow-twitch-fibre rat soleus (SOL) and pure fast-twitch-fibre rat extensor digitorum longus (EDL) muscle during twitch and tetanic contractions at optimal length. During twitch contractions the diffraction signatures indicating a transition in the myosin heads from ordered OFF states, where heads are held close to the thick filament backbone, to disordered ON states, where heads are free to bind to thin filaments, were found in EDL and not in SOL muscle. During tetanic contraction, changes in the disposition of myosin heads as active tension develops is a quasi-stepwise process in EDL muscle whereas in SOL muscle this relationship appears to be linear. The observed reduced extensibility of the thick filaments in SOL muscle as compared to EDL muscles indicates a molecular basis for this behaviour. These data indicate that for the EDL, thick filament activation is a cooperative strain-induced mechano-sensing mechanism, whereas for the SOL, thick filament activation has a more graded response. These different approaches to thick filament regulation in fast- and slow-twitch muscles may be adaptations for short-duration, strong contractions versus sustained, finely controlled contractions, respectively. KEY POINTS: Fast-twitch muscle and slow-twitch muscle are optimized for strong, short-duration contractions and for tonic postural activity, respectively. Structural events (OFF to ON transitions) in the myosin-containing thick filaments in fast muscle help determine the timing and strength of contractions, but these have not been studied in slow-twitch muscle. The X-ray diffraction signatures of structural OFF to ON transitions are different in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle, being completely absent during twitches in soleus muscle and blunted during tetanic contractions SOL as compared to EDL Quasi-stepwise thick filament structural OFF to ON transitions in fast twitch muscle may be an adaptation for rapid, ballistic movements, whereas more graded OFF to ON structural transitions in slow-twitch muscle may be an adaptation for slower, finer motions.

On the issue of the motion of balls in a double pendulum

The paper considers a model of a vertical double pendulum with one suspension centre moving in a vertical plane. For the proposed system of pendulums, differential equations of motion and conditions for the collision of balls are obtained. When modelling the movement of pendulums, the central impact of the balls was considered for various variants of the movement of the suspension point: the suspension point oscillates in the vertical direction; the suspension point makes rotational movements in the vertical plane. In this case, various conditions of the central impact between the balls were considered: absolutely inelastic impact; absolutely elastic impact; impact with the transformation of impact energy (elastic impact). Comparison of the results of the numerical simulation and the results of experiments with the Kapitza pendulum in published sources confirmed the possibility of modelling an elastic impact between balls in a double pendulum and between balls in an autobalancer with a horizontal axis of rotation of the rotor.

Effect of ball-burnishing on surface integrity and fatigue behaviour of 7175-T6 AA

ABSTRACT The burnishing process was performed using different feed rates, rotational speed and penetration depth parameters to alloy Al 7175-T6. Surface roughness, fatigue life and hardness of the samples were determined. Microstructural examinations of the samples were performed. In the surface roughness measurements, occurred a linear increase in proportion to the increasing feed rate. The increase in the penetration depth affected negatively the surface roughness. Significant increases were acquired in the fatigue life of the burnished samples. The hardness values of the burnishing samples are higher than the hardness value of the base material. The rotational movement of the steel ball during the burnishing process were been caused the aspect ratio of the grains in the microstructure to change.

Impulsive Boundedness for Nonautonomous Dynamic Complex Networks with Constraint Nonlinearity

This paper discusses time-scale type global boundedness of nonautonomous complex networks (NCNs) under impulsive control. By using constraint nonlinearity of NCNs, properties of exponential function and impulsive inequalities, we establish new sufficient conditions for global boundedness and asymptotic stability of NCNs on time scales, and the upper bound of the system can be calculated easily. It is shown that the constraint nonlinearity and impulse interval length will affect the estimation of state bound of NCNs under different network size. It provides a unified criteria for global boundedness of NCNs on continuous, discrete and mixed-time domains and hence improves corresponding existing ones. The nonlinear constraints studied in this paper are widely applied to Lurie systems, ball motion models and so on. Numerical examples are given to illustrate the correctness of the results. Finally, the theoretical results are applied to Lurie systems and bounded driving of unmanned vehicles.

Finite-/Fixed-Time Stability of Nonautonomous Functional Differential Inclusion: Lyapunov Approach Involving Indefinite Derivative.

This article investigates a type of nonautonomous delayed differential equation (DDE) with discontinuity. Under the framework of the Filippov state solution, the finite-time stability (FNTS)/fixed-time stability (FXTS) problems of nonautonomous functional differential inclusion (FDI) are studied via the generalized Lyapunov functional method. The generalized Lyapunov functional used in this article is allowed to obtain an indefinite time derivative almost anywhere (a.a.) along the system's state solutions. Nevertheless, the classic Lyapunov functional requires that its time derivative retains seminegative/negative definiteness anywhere. As a result, novel FNTS and FXTS criteria of the trivial state solution for FDI are established. Moreover, the settling time (ST) of FNTS/FXTS is provided. Then, the developed Lyapunov functional approach is applied to realize the finite-/fixed-time stabilization control of delayed neuron networks (DNNs) possessing discontinuous activation and ball motion models. The proposed method and results concerning FNTS/FXTS are of great significance in neural network (NN)/mechanical control engineering applications.

Angular Contact Ball Bearing Modeling with Different Types of Coatings

The purpose of this study is to determine the stress distribution of uncoated and coated ball bearings by using finite element analysis. The coatings used in this study are titanium nitride (TiN), titanium carbide (TiC) and chromium nitride (CrN) with a thickness of 5 microns. A contact analysis has been performed on ball bearings to compare the performance between coated and uncoated ball bearings. Boundary loads of 5000 N is used for contact analysis. This study tries to establish a simple, two-dimensional expression for the elastic deformation with the inner ring and ball bearing as a angular or curvature model in terms of the geometry of the coating contact surfaces. The coating of ball and raceway surfaces is a requisite but difficult factor to be determined during design, so it is desirable for engineering to understand the effect of surface coating on the motion of ball and subsurface stresses in bearing. For contact analysis, the maximum contact pressure and maximum stress on the coating, inner ring and ball bearing have been used for comparison. The results of this study show that, among other coatings, TiC provides the best protection for the ball of the ball bearing. This is because the low Poisson's ratio of TiC in other coated ball bearings helps reduce the stress on the ball bearing, even though TiC has the lowest Young's modulus in the coating. When a lower boundary load is applied, high COF will also cause an abnormal increase in the maximum stress on the contact surface between the coated or uncoated ball and the inner ring of the ball bearing.

Some remarks on the periodic motions of a bouncing ball

We consider the vertical motion of a free falling ball bouncing elastically on a racket moving in the vertical direction according to a regular 1-periodic function f. For fixed coprime p, q we study existence, stability in the sense of Lyapunov and multiplicity of p periodic motions making q bounces in a period. If f is real analytic we prove that one periodic motion is unstable and give some information on the set of these motions.

History of Ulnar Collateral Ligament Injury and College Pitcher Fastball Profiles: A Retrospective, Observational, Live Pitching Analysis

The aim of this study was to retrospectively compare the fastball profiles of pitchers who had previously sustained grade I or II ulnar collateral ligament (UCL) injuries, were rehabilitated, and released back for competition with those of pitchers with no history of elbow injury. Eighteen pitchers from the pitching staff of 1 National Collegiate Athletic Association Division III team participated in this study. Group 1 had a history of grade I or II UCL injury (n= 8), and group 2 (n= 10) did not. A computerized pitch tracking device was used to analyze ball movement and pitching mechanics. The hypothesis was that the pitchers with a history of injury (group 1) would display differing fastball velocity-ball movement relationships compared to those without (group 2). The groups had similar heights, weights, pitching experiences, and arm slot positions at ball release. The pitching coach-determined preinjury arm slot position and the postinjury computerized pitch tracking device measurements after return to competition displayed strong agreement (r= 0.83), suggesting comparable pre and postinjury pitching techniques. The groups had comparable glenohumeral joint range of motion and fastball profiles, except that group 1 released the ball at a 2.5 times lesser horizontal distance away from the pitching rubber center. Group 2 also displayed consistently more robust and more frequent fastball movement relationships with velocity, horizontal break, and vertical break than group1. Reduced horizontal ball release distances at comparable vertical ball release heights without changes in the arm slot position suggest that pitchers with a history of grade I or II UCL injury have greater contralateral trunk tilt and elbow flexion at ball release. Increased contralateral trunk tilt may occur to increase pitch velocity at the expense of ball movement while placing the pitching elbow in a potentially injurious position. Computerized fastball profile analysis using a computerized pitch tracking device, in conjunction with coach pitching technique observation, and team medical staff clinical examination may help better identify pitchers with an increased risk of UCL injury. Diagnostic II.

Classifying ball trajectories in invasion sports using dynamic time warping: A basketball case study.

Comparison and classification of ball trajectories can provide insight to support coaches and players in analysing their plays or opposition plays. This is challenging due to the innate variability and uncertainty of ball trajectories in space and time. We propose a framework based on Dynamic Time Warping (DTW) to cluster, compare and characterise trajectories in relation to play outcomes. Seventy-two international women's basketball games were analysed, where features such as ball trajectory, possession time and possession outcome were recorded. DTW was used to quantify the alignment-adjusted distance between three dimensional (two spatial, one temporal) trajectories. This distance, along with final location for the play (usually the shot), was then used to cluster trajectories. These clusters supported the conventional wisdom of higher scoring rates for fast breaks, but also identified other contextual factors affecting scoring rate, including bias towards one side of the court. In addition, some high scoring rate clusters were associated with greater mean change in the direction of ball movement, supporting the notion of entropy affecting effectiveness. Coaches and other end users could use such a framework to help make better use of their time by honing in on groups of effective or problematic plays for manual video analysis, for both their team and when scouting opponent teams and suggests new predictors for machine learning to analyse and predict trajectory-based sports.

Numerical simulation of ball milling reactor for novel ammonia synthesis under ambient conditions

The investigation models an alternative ammonia production method compared to the Haber-Bosch method. The operating parameters of proposed process, which successfully synthesized ammonia with competitive yield, were 45 °C and 1 bar, which is significantly lower than the Haber-Bosch process. A study was made on the impact and contact behavior of the planetary ball mill to understand the movement of steel balls and iron particles inside the reactor vessel to improve the synthesis process. The EDEM software, based on discrete element method (DEM), was used to understand the internal behavior of a planetary mill. Balls and particles were loaded at a ratio of 1:20, i.e., 500 g of steel ball diameter is 25 mm, and 24 g of iron particles diameter is 0.25 mm in reactor. Contact and energy released by balls and particles as a function of mill speed were compared with the experimental correlation of adsorbed nitrogen. The correlation with the experimental data showed satisfactory agreement with present numerical simulation. This work is the first step towards realistic scaling of the system and vertical mill is not a common practice on an industrial scale, this work will use experimental data to create and validate a vertical ball mill model.

Temporal and spatial goal-directed reaching in upper limb prosthesis users.

Understanding the fundamental characteristics of prosthetic movement control is imperative in improving prosthesis design and training. This study quantified how using an upper limb prosthesis affected performance during goal-directed reaching tasks. Nine prosthesis users with unilateral transradial limb absence and nine healthy controls completed a series of goal-directed reaching movements with different goals: one spatial and three temporal with different goal frequencies. We quantified end-point accuracy, smoothness, and peak speed for the spatial task and temporal accuracy, horizontal distance, and speed for the temporal task. For the temporal task, we also used a goal-equivalent manifold (GEM) approach to decompose variability in movement distance and speed into those perpendicular and tangential to the GEM. Detrended fluctuation analysis (DFA) quantified the temporal persistence of each time series. For the spatial task, movements made with prostheses were less smooth, had larger end-point errors, and had slower peak speed compared to those with control limbs (p < 0.041). For the temporal task, movements made with prostheses and intact limbs of prosthesis users and control limbs were similar in distance and speed and had similar timing errors (p > 0.138). Timing errors, distance, speed, and GEM deviations were corrected similarly between prosthetic limbs and control limbs (p > 0.091). The mean and variability of distance, speed, and perpendicular deviations decreased with increased goal frequency (p < 0.001). Our results suggest that prosthesis users have a sufficient internal model to successfully complete ballistic movements but are unable to accurately complete movements requiring substantial feedback.

Dual STDP processes at Purkinje cells contribute to distinct improvements in accuracy and speed of saccadic eye movements.

Saccadic eye-movements play a crucial role in visuo-motor control by allowing rapid foveation onto new targets. However, the neural processes governing saccades adaptation are not fully understood. Saccades, due to the short-time of execution (20-100 ms) and the absence of sensory information for online feedback control, must be controlled in a ballistic manner. Incomplete measurements of the movement trajectory, such as the visual endpoint error, are supposedly used to form internal predictions about the movement kinematics resulting in predictive control. In order to characterize the synaptic and neural circuit mechanisms underlying predictive saccadic control, we have reconstructed the saccadic system in a digital controller embedding a spiking neural network of the cerebellum with spike timing-dependent plasticity (STDP) rules driving parallel fiber-Purkinje cell long-term potentiation and depression (LTP and LTD). This model implements a control policy based on a dual plasticity mechanism, resulting in the identification of the roles of LTP and LTD in regulating the overall quality of saccade kinematics: it turns out that LTD increases the accuracy by decreasing visual error and LTP increases the peak speed. The control policy also required cerebellar PCs to be divided into two subpopulations, characterized by burst or pause responses. To our knowledge, this is the first model that explains in mechanistic terms the visual error and peak speed regulation of ballistic eye movements in forward mode exploiting spike-timing to regulate firing in different populations of the neuronal network. This elementary model of saccades could be extended and applied to other more complex cases in which single jerks are concatenated to compose articulated and coordinated movements.

Traditional Kucing-Kucingan Game, in Improving Ground Motor Skills to Blind Children in SLB Negeri A Citeureup Cimahi

Untrained gross motor skills in children with visual impairment, especially on the walking and balance motion will hinder the mobility process in children, thus forming walking motion and posture that is not good for the children. This circumstance certainly cannot be tolerated because it can interfere the children's motor development. Therefore, it is necessary to get proper and professional management to be able to overcome these problems so that children with visual impairment can have good mobility. This difficulty was experienced by subject with the initials I grade 1 at SDLBN A Citeureup, Cimahi. One of the efforts that can be done to intervene this case is by applying the traditional Kucing-kucingan game. This research aims to determine how much improvement is given by the traditional Kucing-kucingan toward gross motor skills in children with visual impairment, especially in aspects of walking and balance motion, This research uses experimental method with Single Subject Research Design A-B-A. The data obtained starting from baseline-1 (A-1), intervention (B), and baseline-2 (A-2) conditions. The presentation of data is processed and analyzed using descriptive statistics. The results showed that the ability of student (I) in doing the walking and balance motion was increased after the given intervention using traditional Kucing-kucingan game. Therefore, the researcher recommends this traditional Kucing-kucingan game to educators so they can consider the traditional Kucing-kucingan game as an alternative in conducting activities during free hours in order to improve gross motor skills in children with visual impairment, due to interesting games for children will greatly assist the continuity of activities process. Traditional game, especially kucing-kucingan, is considered effective when it is used properly to increase the children's interest in moving freely.

Developing Female Students’ Motor Skills and Improving Basketball Playing Techniques by Means of Special Exercise Machines

Introduction: The article presents the technology of using technical equipment to develop the accuracy of ballistic movements, spatial-dynamic sensitivity during ballthrows and rebounds, as well as speed and strength qualities to improve jumping movements, implementation of fast breakthroughs, strong and long passes in basketball. Methods: The research involved 96 female students aged 17-23 years forming the experimental (EG, n = 54) and control (CG, n = 42) groups. The female students of EG played basketball in the conditions of group physical education training sessions using the exercise machines developed by us, and the female students of the CG were engaged in basketball playing according to the traditional program without the use of developed exercise machines and had an initial level of basketball technique. The EG was divided into EG1 (n = 37) and EG2 (n = 17) subgroups, which included female students having initial and high levels of basketball technique mastery, respectively. Female basketball players with an initial level of training (EG1 and СG) had experience of up to 3 years, athletes with a high level of training (EG2) - playing experience of more than 10 years. The technology of technical equipment application in basketball is built on the basis of the use of designed portable exercise machines to implement the tasks of motor and technical training of female basketball players of different levels of training. Results The results of the conducted experiment showed that the accuracy of throws from the average distance increased by 40.9% and 29.4% in the EG1 and EG2 female students, and it grew by 9.9% in the CG; from the long distance – by 61.5%, 37.0% and 31.3% respectively; the level of development of speed and strength qualities of female students of all groups improved i. e. the rate of growth in the results of the long jump made 9.7%, 3.2% and 6.5%, respectively; the rate of growth in the results of the high jump made 20.0%, 6.3% and 8.7%, respectively. Conclusion: Experimental testing of the technology of using designed exercise machines for the development of motor skills of female basketball students confirmed its effectiveness in terms of improving the spatial and dynamic accuracy of movement, speed and strength, as well as game performance of basketball players at competitions of various levels.

How do soldier crabs behave when seeing vibrating robots?

Metaheuristic algorithms are a method of searching for a suboptimal solution and are implemented by a large number of agents, such as a swarm of animals. In this method, it is very important to adjust the relationships and/or interplay between individual freedoms and constraints as a group. The phenomena related to this interplay are strongly relevant for self-organized criticality showing a power law distribution. Since individuals’ independent behavior and translation as a group coexist in a swarm of soldier crabs, we conducted an experiment involving soldier crabs to estimate whether a power law distribution results from that interplay. The engine of translation was implemented by the directed movement of robot crabs. Soldier crabs confronting moving robot crabs were observed in the experiment. Here, we show that the interaction between robots and soldier crabs entails a Lévy walk characterized by a power law distribution of step length as well as the real swarm. This result suggests that soldier crabs could be attracted by the directed motion of robots and that combining a random walk with ballistic movement can realize a Lévy walk.

An analytical formulation for rotational fretting based on the minimum rolling energy

Rotational fretting is defined as the localised wear produced in a reciprocating rolling motion of low amplitude. The current techniques used for the analysis of this damage are reduced to experimental tests, which involve high costs in specimens and equipment, and to simulation through finite element (FE) models, which involves high mesh density in contact zones and thus drastically increases the computational cost. The main objective of this work is to develop an analytical model for the analysis of rotational fretting. To achieve this aim, the sliding motion of the rolling ball is analysed, and a novel iterative method based on rolling energy minimization is proposed for the calculation of the kinematics and the transient effects are solved. The proposed methodology is applied to the case of study of a thrust bearing and validated in two different stages: first, a numerical validation of tangential stresses is conducted using an FE model where a maximum difference of 10% with respect to the numerical results as well as a massive time reduction of more than 5000 times are achieved; and second, an experimental tests rig is designed and tests are performed showing a mean relative error of 13% in the measured damaged areas.

Aerodynamic Analysis and Training Research of an S-Shaped Arc Ball Based on Hydrodynamics.

The aerodynamic characteristics of S-shaped arc ball, such as poor combat performance and low intelligence, are studied and analyzed. In this paper, the aerodynamic analysis model of S-shaped arc soccer intelligent algorithm is established, and the dynamic tracking model of Soccer Tactics Based on fluid dynamics search algorithm is designed. The data information is collected from many aspects, such as the position of the players, the change of the arc ball movement, the trajectory of the football movement, and tactical flexibility. The results show that Benn's algorithm can start the layout mechanism effectively. It has high feasibility and accurate algorithm accuracy and can effectively improve the aerodynamic layout performance of the system. The aerodynamic analysis and training optimization method of the S-shaped arc ball based on ant colony optimization has sped up the intelligent training system of Chinese football tactics.

Amateur football analytics using computer vision

In recent years, there has been an interest in visual sports analytics, and especially in player and ball detection, action recognition, and camera pose estimation in various sports. The greatest interest is associated with football or soccer. The purpose of this work is the design and implementation of a low-cost methodology that extracts football analytics from simple TV broadcasts, using solely computer vision techniques. In the paper, we discuss the state of the art in this field and propose an integrated pipeline that solves the problem of player localization in the court and extracts useful insights. Technical details concerning the proposed methods that enhance track player–ball movement and camera pose, along with post-analytic results, are presented. The paper concludes with some future expansions of the proposed pipeline.

Learning to Control Highly Accelerated Ballistic Movements on Muscular Robots

High-speed and high-acceleration movements are inherently hard to control. Applying learning to the control of such motions on anthropomorphic robot arms can improve the control’s accuracy but might damage the system. The inherent exploration of learning approaches can lead to instabilities and the robot reaching joint limits at high speeds. Having hardware that enables safe exploration of high-speed and high-acceleration movements is therefore desirable. To address this issue, we propose to use robots actuated by pneumatic artificial muscles (PAMs). In this paper, we present a four degrees of freedom (DoFs) robot arm that reaches high joint angle accelerations of up to 28000°s-2 while avoiding dangerous joint limits thanks to the antagonistic actuation and limits on the air pressure ranges. With this robot arm, we can tune control parameters using Bayesian optimization directly on the hardware without additional safety considerations. The achieved tracking performance on a fast trajectory exceeds previous results on comparable PAM-driven robots. We also show that our system can be controlled well on slow trajectories with PID controllers due to careful construction considerations such as minimal bending of cables, lightweight kinematics, and minimal contact between PAMs and PAMs with the links. Finally, we propose a novel technique to control the co-contraction of antagonistic muscle pairs. Experimental results illustrate that choosing the optimal co-contraction level is vital to reach better tracking performance. Using PAM-driven robots and learning, we do a small step towards the future development of robots capable of more human-like motions.