Back Spin Research Articles

Computer simulation on the cueing movements in cue sports: a validation study.

Simulation models have been applied to analyze daily living activities and some sports movements. However, it is unknown whether the current upper extremity musculoskeletal models can be utilized for investigating cue sports movements to generate corresponding kinematic and muscle activation profiles. This study aimed to test the feasibility of applying simulation models to investigate cue sports players' cueing movements with OpenSim. Preliminary muscle forces would be calculated once the model is validated. A previously customized and validated unimanual upper extremity musculoskeletal model with six degrees of freedom at the scapula, shoulder, elbow, and wrist, as well as muscles was used in this study. Two types of cueing movements were simulated: (1) the back spin shot, and (2) 9-ball break shot. Firstly, kinematic data of the upper extremity joints were collected with a 3D motion capture system. Using the experimental marker trajectories of the back spin shot on 10 male cue sports players, the simulation on the cueing movements was executed. The model was then validated by comparing the model-generated joint angles against the experimental results using statistical parametric mapping (SPM1D) to examine the entire angle-time waveform as well as t-tests to compare the discrete variables (e.g., joint range of motion). Secondly, simulation of the break shot was run with the experimental marker trajectories and electromyographic (EMG) data of two male cue sports players as the model inputs. A model-estimated muscle activation calculation was performed accordingly for the upper extremity muscles. The OpenSim-generated joint angles for the back spin shot corresponded well with the experimental results for the elbow, while the model outputs of the shoulder deviated from the experimental data. The discrepancy in shoulder joint angles could be due to the insufficient kinematic inputs for the shoulder joint. In the break shot simulation, the preliminary findings suggested that great shoulder muscle forces could primarily contribute to the forward swing in a break shot. This suggests that strengthening the shoulder muscles may be a viable strategy to improve the break shot performance. It is feasible to cater simulation modeling in OpenSim for biomechanical investigations of the upper extremity movements in cue sports. Model outputs can help better understand the contributions of individual muscle forces when performing cueing movements.

Influence of expertise level on techniques of applying top and back spins in cue sports

ABSTRACT This study compared the kinematics of upper body and cue stick among players of various skill levels when performing back spin and top spin shots. Twenty-eight male cue sports players were assigned to the novice (n = 10), intermediate (n = 9), or skilled groups (n = 9). The back spin and top spin tests were administrated while kinematic data were recorded using a 3D motion capture system. The results revealed greater upper limb joint ranges of motions (all p < 0.05), maximum angular velocities (all p < 0.05), and cue tip speed in the back spin than top spin shots (p < 0.001). None of joint kinematic or shot performance variables investigated was significantly different among the three skill levels (all p > 0.05). For the head movement, the novice group exhibited greater anteroposterior displacement than the skilled group (p = 0.020). In conclusion, except for the head movement, the upper body and cue stick kinematics did not significantly differ among players with varied skill levels. Greater joint ranges of motions and angular velocities were required to generate a faster cue tip speed for the back spin shots when compared with the top spin shots.

The dependence of baseball lift and drag on spin

This study measured the drag and lift of baseballs in free flight as a function of back spin for two spin axes. While others have measured baseball lift and drag, the mechanisms for their dependence on spin have not been explained. For increasing spin, drag was observed to initially decrease then increase at higher spin. The inflection point appears to occur when the flow on the bottom ball surface becomes fully turbulent. At low spin the lift of the four-seam spin axis was nearly constant and three times larger than the two-seam spin axis. The lower lift of the two-seam spin axis was shown to be due to a periodic reverse Magnus effect observed at low spin rates. At higher spin the lift of both spin axes increased at similar rates with spin. As observed with drag, the lift transition point appears to be associated with the bottom of the ball becoming fully turbulent.

Effect of using some web 2.0 application on developing cognitive achievement for table tennis back spin serve for fourth grade students (education division ) and their attitude towards it

Research sampleconsisted of (55) fouth grade students (education divison) in the academic year (2015/2016) after execluding players, injured and absent students. Sample divided to (24) students eperimental group, who can use vcpmouters and have faceook and google accounts, (26) students as contrl group, in addition to (32) students from fouth grade stdenys in the academic year (20414/2015) as pilot study sample.

A Turtle’s Affirmation

A Turtle’s Affirmation Michelle J. Pinkard (bio) Life is beyond the murk of cloudy water, the burn of piss in nostrils and the pellets of food that poop from the sky, these plastic trees these plastic leaves these plastic castles and colored stones. One day, two days, one year, two limbs motionless and floating in death. If I press my webbed hand hard against the glass, stretch my neck high against the light, clumsy the pebbles into a loud heap with the stomp of my will, then perhaps, maybe, surely even I can crash this cage off its plastic table land on my back spin like a top— one hand, two hands, one foot, two pointing toward the heavens— A real turtle’s death. [End Page 197] Michelle J. Pinkard Michelle J. Pinkard is a poet, writer, and educator living in Nashville, Tennessee. She is an assistant professor of African American literature at Tennessee State University, and her scholarly interests explore the intersections of race, gender, and literature. Pinkard is the author of The Eye of the Tornado: Fifty Poems for Rhyme and Reason (La Caille Nous, 2004), and a forthcoming study on women poets of the Harlem Renaissance. Copyright © 2014 Johns Hopkins University Press and Saint Louis University

Hitting Back-Spin Balls by Robotic Table Tennis System based on Physical Models of Ball Motion

Abstract In this paper, we develop a robotic table tennis system in the case of the back spin with the same measurement method and the ball models of the aerodynamics and the rebounds as in the study of Nakashima et al. (2011). First, the aerodynamics model is improved for precise prediction of the ball trajectory with data of the flying back-spin ball. Second, a method to determine the racket motion is shown where approximated inverse problems of the models are solved with optimizations. Third, a motion planning of the robot to achieve the racket motion is proposed with the velocity limitation of the robot joints. Experimental results are shown to verify the effectiveness of the proposed method.

Optimal Targets for the Bank Shot in Men's Basketball

The purpose of this study was to gain an understanding of the bank shot and ultimately determine the optimal target points on the backboard for the bank shot in men’s basketball. The study used over one million three-dimensional simulations of basketball trajectories. Four launch variables were studied: launch height, launch speed, launch angle, and aim angle. The shooter’s statistical characteristics were prescribed to yield a 70 percent free throw when launching the ball seven feet above the ground with 3 Hz of back spin. We found that the shooter can select a bank shot over a direct shot with as much as a 20 percent advantage. The distribution over the court of preferences of the bank shot over the direct shot was determined. It was also shown that there is an aim line on the backboard independent of the shooter’s location on the court. We also found that at 3.326 inches behind the backboard, there exists a vertical axis that aids in finding the optimal target point on the backboard. The optimal target point is the crossing of the vertical axis and the aim line that is in the shooter’s line of sight.

Optimal release conditions for the free throw in men's basketball

The purpose of this study was to determine the optimum release conditions for the free throw in men's basketball. The study used hundreds of thousands of three-dimensional simulations of basketball trajectories. Five release variables were studied: release height, release speed, launch angle, side angle, and back spin. The free throw shooter was assumed to shoot at 70% and to release the ball 2.134 m (7 ft) above the ground. We found that the shooter should place up to 3 Hz of back spin on the ball, should aim the ball towards the back of the ring, and should launch the ball at 52° to the horizontal. We also found that it is desirable to release the ball as high above the ground as possible, as long as this does not adversely affect the player's launch consistency.

선 충격량과 공의 회전 속도와의 상관관계

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

골프 공의 충돌 시 스핀 생성 원리 연구

It is important to improve the initial launch conditions of golf ball at impact between golf club and ball to get a long flight distance. The flight distance is greatly influenced by the initial launch conditions such as ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. Back spin rate is created by the contact time and force. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of ball, and the tangential force creates the spin. Especially, the tangential force is known to take either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail in the literature. In this paper, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and time at impact between golf club head and ball are computed using FEM and compared with previous results. In addition, we investigate the impact phenomenon between golf club head and ball by FEM and clarify the mechanism of ball spin creation accurately, particularly focusing on the effect of negative tangential force on ball spin rate.

Highly Proficient Golfers Exhibit Greater Consistency In Driving Ball Flight Characteristics Than Less Proficient Golfers

It is believed that consistency of golf ball flight characteristics (BFC) is more indicative of golf proficiency than traditional measures of golf performance such as club velocity (CV) and total driving distance (TD). Highly proficient golfers are believed to have more consistent BFC between swings than less proficient golfers. PURPOSE: To determine whether BFC consistency differs between highly proficient golfers and less proficient golfers. METHODS: Ninety male golfers (43.5 ± 14.4 years) performed ten golf swings with their own driver. A golf launch monitor was used to measure BFC. The mean and standard deviations (SD) of CV, ball velocity (BV), vertical launch angle (VLA), horizontal launch angle (HLA), backspin (BS), carry distance (CD), and TD were calculated for each subject using the five drives with the greatest TD. The SD of BV, CD, and TD were normalized (SDN) to their respective mean values. Lower SD and SDN were interpreted to represent greater consistency. Golfers were grouped based on proficiency by USGA handicap: low (L: <8, n=56), mid (M: 8-14.9, n=25), and high handicap (H: ≥15, n=9). One-way analysis of variance and Tukey’s post hoc procedure were used to determine differences between groups. Statistical significance was set a priori at p<0.05. RESULTS: There were no significant differences between groups for BS or CV consistency. Statistically significant differences are italicized in the table below.

대학 골프선수들의 의도적 지연히팅 시 비거리 결정인자 분석

The purpose of this research was to conduct an analysis on the factors that determine the distance at the time of target swing based on the use of late hitting of outstanding college golfers to verify the difference between late hitting and the distance that target increases in regular swing and the distance. Then, this research conducts an analysis on the correlation between club head velocity, ball velocity, launch angle, back spin, meet ratio and distance that become kinematics variables at the time of target swing. To attain the above mentioned purpose, 25 outstanding college players with average experience and handicap of 6 years and 5, respectively, were targeted Comparative analysis on two swing that target increase in regular and the distance was conducted by used driver. When it pertained to two types of swing. analysis system comprised of an analytical software called the Science Eye of the Bridgestone and peripheries was used to define the relationship between variables of club head velocity, ball velocity, launch angle, back spin, meet ratio that become kinematics variables. As for the method of processing data pertaining to the factors that determine the distance, differences of distance by the type of swing was verified by using independent T-test that leveraged SPSS 120 statistics program. Moreover, level of correlation between variables that contribute to the increase in distance through relation of correlation, and analysis of tendencies was conducted to analyze tendency of non-distance to increase in accordance to the increase of each variable. Key results produced through this experiment are as follows: 1. Artificial late hitting for increased non-distance that targets skilled players had effect on increased the distance(p<. 05). 2 The drive distance is correlated with each measured variable that is positive correlation to ball velocity, club head velocity, meet ratio and relation of back spin and launch angle are negative correlation. ball velocity and club head velocity are very high correlated with drive distance(p<.01), back spin and distance are negative correlation(p<.01). 3. Among each measured variable increasing the club velocity is the most contribution, and ball velocity and meet ratio and the increasing launch angle and back spin is negative effect for increasing distance.

골프공 스핀효과에 따른 비거리 시뮬레이션

This study simulated the range of golf ball with different projection angles using a drive swing condition. For the simulation purpose, the differential equation of dynamics was induced by using Bernoulli's principle and average back spin frequency, instant velocity, and dimple of golf ball from amateur group, professional group, and Tiger Woods were chosen as the initial condition. The study result indicated that lift coefficient(<TEX>$C_{lift}$</TEX>) relative to drag coefficient (<TEX>$C_d$</TEX>), 0.3 of differential equation was applied differently in terms of back spin Sequency, and when <TEX>$C_{lift}$</TEX> was 0.4 for amateur, 0.5 for professional, and 0.7 for Tiger Woods the projection ranges of ball were closely matched with initial condition. With selected <TEX>$C_{lift}$</TEX> and back spin frequency of initial condition, the ranges with different projection angle was measured as 193m (<TEX>$13-17^{\circ}$</TEX>) for amateur, 240m (<TEX>$9-13^{\circ}$</TEX>), professional and 273m (<TEX>$9^{\circ}$</TEX>)Tiger Woods, respectively. For the range in terms of back spin frequency and projection angle, the amateur group indicated relatively high spin frequency (70 RPS) and showed the maximal range (195m) with <TEX>$13^{\circ}$</TEX> of projection angle. The tendency of longer range with higher projection angle was also found under the different conditions of spin frequency in this group. The professional group showed their maximal range (245m) with conditions of 60RPS of spin frequency and <TEX>$9^{\circ}$</TEX> of projection angle. Their range was decreased dramatically when the spin frequency was reduced to 40-50 RPS. For Tiger Woods, the maximal range was found with 40RPS of spin frequency and the range was decreased notably when the spin frequency was above 40RPS.

Numerical analysis of golf club head and ball at various impact points

This paper investigates how the physical characteristics of a golf club head affect its performance, with the aim of developing a superior club head. The physical characteristics investigated were the magnitude of the moment of inertia and the location of the centre of gravity. The performances were classified as the release velocity, the spin rate of the ball and the size of the uniform restitution area. In the numerical analysis, several kinds of club head were modelled with different moments of inertia and different locations of the centre of gravity. For every club head model, the ball was hit at various impact points and the release velocity, spin rate and size of the uniform restitution area were calculated. The results are as follows. The bigger the moment of inertia Izz about the vertical axis or the shallower the depth of the centre of gravity, the less side spin rate caused. Izz has more influence on the side spin rate than the depth of the centre of gravity. The shallower the depth of the centre of gravity, the more back spin rate caused. The size of the uniform restitution area increases in proportion to the increase in Izz, or in proportion to the decrease of the depth of the centre of gravity.

Correlations between angular momentum orientation and exit velocity in gas–surface scattering: A probe of the dependence of collision dynamics on the position of impact

The scattering of rotationally cold N2 from Ag(111) results in angular momentum alignment and orientation of the scattered molecules; measurement of the angular momentum polarization as a function of exit angle, final J state, and exit translation energy provides direct information on the dynamics of the collisions. In this paper, the orientation of the angular momentum vector of the scattered N2 molecules, A{1}1−(J) has been measured for slow, medium, and fast groups of molecules in single rotational states at fixed exit angles. With normal incidence scattering (θi=0°) and off-normal detection, for a given final J state, the ‘‘slow’’ molecules have a higher probability of tumbling backwards (‘‘back spin’’) than the ‘‘fast’’ molecules. Conversely, for glancing incidence scattering (θi=30°) with quasi-specular detection, the opposite trend is observed: the slow molecules have a higher probability of tumbling forwards (‘‘top spin’’) than the fast molecules. These experiments were simulated and analyzed using molecular dynamics trajectory calculations. The calculations show that the amount of gas kinetic energy transferred to the surface is sensitive to the narrow dispersion of impact sites and molecular orientations that lead to scattering into a given final rotational state at a given exit angle. The calculations demonstrate that for both incident angles, collisions near the top of a surface atom lead to slower final velocities than collisions with the hollow sites in analogy with the simple case of two colliding spheres. Therefore, the experimentally observed dependence of the angular momentum orientation on the exit velocity results from the correlation between the initial molecular bond angle and the impact site for scattering into a given J state and at a fixed exit angle.

On finite deformation plasticity with directional softening Part I: One-component model

A physically based continuum model of finite deformation plasticity with anisotropic hardening is developed and used to evaluate the differences of stress responses in tension, compression and torsion (directional softening) for various materials at large deformations. The coupling effects of back stress and plastic spin are incorporated into the model according to the scale invariance method recently suggested by Aifantis. Moreover, the effects of nonlinear dislocation hardening and recovery softening are included. It is shown that the theoretically obtained stress responses in tension, compression and torsion are in good agreement with available experimental data for Copper, Brass and Silver.

'Break Dancers' Bursitis'

<h3>To the Editor.—</h3> I would like to report a case of bursitis causing a soft-tissue mass at an unusual location in a break dancer. <h3>Report of a Case.—</h3> An 18-year-old male break dancer was referred for evaluation and treatment of a tender soft-tissue mass. This mass was located posterior to the vertebral column at the 12th thoracic vertebra. The patient could not recall any trauma to the area, but he gave a history of learning to break dance during the previous six months. Several maneuvers in break dancing require the dancer to spin around using the high lumbar-low thoracic portions of the spine, much like the tip of a spinning top. These maneuvers include the "back spin" and the "windmill."¹The patient gave a history of performing these and other maneuvers while learning to break dance during the previous six months. During the month before admission, a tender soft-tissue

An Estimate of the Effect of Back Spin on the Critical Angle in the Unyawed Ricochet of a Cylinder

A method is described for giving an estimate of the effect of back spin on the critical angle for the ricochet of a cylinder off water. The method incorporates both the spin and the weight of the projectile into the Birkhoff et al theory, as described by Johnson and Reid (1) ‖ for a sphere. The differences and predictions concerning hydrodynamic pressure and lift, etc., are compared with those made by several other authors. A comparison of our new results with some available experimental results has also been made.

Structure in the beta strength function of very neutron-rich Rb-isotopes

The beta strength functionSβ is calculated in a schematical Brown-Bolsterli model for the Gamow-Tellerβ− decay of89–99Rb. The position of the peaks inSβ resulting from the back spin flip transitions and the calculated life-times are in good agreement with recent experimental results. A simple regularity is found to govern the energy position of the lowest-lying structures inSβ. By calculations of the type given here thus it should be possible to produce much more reliable input data concerningSβ forr-orn-process calculations than have been used up to now in astrophysical calculations.