scholarly journals Standard of the Initial Ball Velocity for a Fly Ball in Baseball Hitting

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 137
Author(s):  
Hirotaka Nakashima ◽  
Gen Horiuchi ◽  
Shinji Sakurai
Keyword(s):  
Initial Velocity ◽  
High Speed ◽  
Baseball Players ◽  
Ball Impact ◽  
Video Cameras ◽  
High Speed Video ◽  
Before And After ◽  
Ball Velocity ◽  
Opposite Field ◽  
Measuring Tape

This study aimed to determine the minimum required initial velocity to hit a fly ball toward the same field (left-field for right-handed batters), center field, and opposite field (right field for right-handed batters). Six baseball players hit fastballs launched by a pitching machine. The movements of the balls before and after bat-to-ball impact were recorded using two high-speed video cameras. The flight distance was determined using a measuring tape. Seventy-nine trials were analyzed, and the minimum required initial velocities of batted balls were quantified to hit balls 60, 70, 80, 90, 100, 110, and 120 m in each direction through regression analysis. As a result, to hit a ball 120 m, initial velocities of 43.0, 43.9, and 46.0 m/s were required for the same field, center field, and opposite field, respectively. The result provides a useful index for batters to hit a fly ball in each of the directions.

Evaluation of Walking Motions with the Aid of Walkers Using Acceleration Sensors

2013 ◽  
pp. 346-354
Author(s):  
Satoru Okamoto ◽  
Tetsuya Hirotomi ◽  
Keigo Aoki ◽  
Yasutomo Hosomi
Keyword(s):  
Motion Capture ◽  
High Speed ◽  
Normal Walking ◽  
Video Cameras ◽  
Fast Walking ◽  
High Speed Video ◽  
Self Reliance ◽  
Acceleration Sensors ◽  
Walking Motion ◽  
Before And After

Walkers are tools that are used to improve self-reliance when walking. In this study, the unstable motions of gait in subjects who use walkers were analyzed using tri-axial accelerometers and a motion capture system. Several markers were placed on the subjects’ backs and legs, and two high-speed video cameras were employed to record the motion of these markers. The subjects were asked to walk around a test course at a comfortable speed. The activities performed on the test course consisted of standing, normal walking, fast walking, walking over a barrier, and falling down. The authors’ results determined the characteristic rules of gait motion with walker use. They found that acceleration sensors are convenient for extracting characteristics from the gait motions. They believe that the methods employed with the acceleration sensors are suitable for the discovery of the average gait motions of elderly patients living in nursing homes and can be used to evaluate walking motion before and after rehabilitation.

Characteristics of Spatter in Micro-Drilling of Metal Sheet by Pulsed Nd:YAG Laser

2016 ◽  
Vol 10 (6) ◽  
pp. 874-881 ◽  
Author(s):  
Yasuhiro Okamoto ◽  
◽  
Hibiki Yamamoto ◽  
Akira Okada ◽  
Keyword(s):  
Initial Velocity ◽  
High Speed ◽  
Gas Flow ◽  
Thermal Damage ◽  
Drilling Process ◽  
3D Tracking ◽  
Workpiece Surface ◽  
Video Cameras ◽  
High Speed Video ◽  
Micro Drilling

In laser cutting and drilling process, molten material was scattered as spatter, which deteriorates the surface integrity of a workpiece because of the thermal damage. It is expected that the control of assist gas flow can reduce the adhesion of spatter. In order to investigate the improvement method of thermal damage due to the adhesion of spatter, it is required to clarify characteristics of spatter. Therefore, a method was developed to collect and analyze spatter based on the use of high-speed video cameras in the laser micro-drilling process, and the characteristics of spatter movement were numerically investigated by CFD analysis. The scattering velocity and angle of the spatter were investigated by recognizing and tracking spatter with the high-speed video observation. The movement of spatter was observed by using two high-speed video cameras, and analyzed by using a two-direction tracking method, in which the 3D tracking lines of spatter particles were reconstructed in the forward and backward frames, and the actual trajectory of individual spatter particle was obtained by averaging those tracking lines. These measurements revealed that the initial velocity of spatter was mainly distributed from 52 m/s to 200 m/s with an average velocity of 129 m/s. The initial angle of spatter was mainly distributed between 0 and 30 degrees from the workpiece surface in the upward direction. There was little correlation between the initial velocity and angle of spatter. The diameter of spatter was mainly distributed from 1μm to 4μm with an average diameter of 3.7μm. It is important to use the processing conditions achieving the smaller spatter diameter in order to reduce the thermal damage caused by spatter. Although coaxial assist gas flow has an influence on the spatter behavior, that time period is very short. Therefore, it is important to control the spatter behavior outside of the coaxial assist gas flow by using an additional gas flow to prevent the thermal damage to the workpiece surface.

scholarly journals Difference in racket head trajectory and muscle activity between the standard volley and the drop volley in tennis

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257295
Author(s):  
Ryosuke Furuya ◽  
Hikaru Yokoyama ◽  
Milos Dimic ◽  
Toshimasa Yanai ◽  
Tobias Vogt ◽  
...  
Keyword(s):  
Muscle Activity ◽  
High Speed ◽  
Gradual Increase ◽  
Ball Speed ◽  
Ball Impact ◽  
Video Cameras ◽  
Before And After ◽  
Arm Muscles ◽  
Set Up ◽  
The Moment

Among tennis coaches and players, the standard volley and drop volley are considered basically similar, but muscles need to be relaxed (deactivation) just at the moment of impact when hitting the drop volley. However, this is not evidence-based. The aim of this study was to clarify racket head trajectory and muscle activity during the drop volley and to compare them with those of the standard volley. We hypothesized that 1) the racket head would move less forward for the drop volley than for the standard volley and 2) the wrist and elbow muscles be relaxed for the drop volley at the time of ball impact. Eleven male college students with sufficient tennis experience volunteered to participate in this study. Wireless EMG sensors recorded activation of the four arm muscles. Each subject performed the standard volley or the drop volley with both a forehand and a backhand from a position near the net. Four high speed video cameras (300 Hz) were set up on the court to measure ball speed and racket head trajectory. Returned ball speed of the drop volley was significantly lower than that of the standard volley (p < 0.05). The racket head moved less forward than in the standard volley, supporting the first hypothesis. Muscle activity of the drop volley, just before and after ball impact for both the forehand and backhand, was lower than that of the standard volley. However, the activity was in the form of a gradual increase as impact time approached, rather than a sudden deactivation (relaxation), which did not support the second hypothesis. For the drop volley, lower muscle activity in the forearm enabled a softer grip and thus allowed a “flip” movement of the racket to diminish the speed of the returned ball.

Identification of Release Conditions and Aerodynamic Forces in Pitched-Baseball Trajectories

2001 ◽  
Vol 17 (1) ◽  
pp. 63-76 ◽  
Author(s):  
LeRoy W. Alaways ◽  
Sean P. Mish ◽  
Mont Hubbard
Keyword(s):  
Drag Coefficient ◽  
Initial Velocity ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Three Dimensions ◽  
Video Cameras ◽  
High Speed Video ◽  
Position Data ◽  
Estimation Scheme ◽  
The Mean

Pitched-baseball trajectories were measured in three dimensions during competitions at the 1996 Summer Olympic games using two high-speed video cameras and standard DLT techniques. A dynamic model of baseball flight including aerodynamic drag and Magnus lift forces was used to simulate trajectories. This simulation together with the measured trajectory position data constituted the components of an estimation scheme to determine 8 of the 9 release conditions (3 components each of velocity, position, and angular velocity) as well as the mean drag coefficient CD and terminal conditions at home plate. The average pitch loses 5% of its initial velocity during flight. The dependence of estimated drag coefficient on Reynolds number hints at the possibility of the drag crisis occurring in pitched baseballs. Such data may be used to quantify a pitcher’s performance (including fastball speed and amount of curve-ball break) and its improvement or degradation over time. It may also be used to understand the effects of release parameters on baseball trajectories.

scholarly journals Assessment of the accuracy of different systems for measuring football velocity and spin rate in the field

2019 ◽  
Vol 233 (2) ◽  
pp. 324-330 ◽  
Author(s):  
Katrine Okholm Kryger ◽  
Séan Mitchell ◽  
Steph Forrester
Keyword(s):  
Systematic Error ◽  
Confidence Intervals ◽  
High Speed ◽  
Football Player ◽  
Random Errors ◽  
High Speed Video ◽  
Field Assessment ◽  
Wide Range ◽  
Ball Velocity ◽  
Level Of Agreement

The aim of this study was to measure the level of agreement of four portable football velocity and spin rate measurement systems (Jugs speed radar gun, 2-D high-speed video, TrackMan and adidas miCoach football) against a Vicon motion analysis system. One skilled male university football player performed 70 shots covering a wide range of ball velocities (12–30 m s−1) and spin rates (94–743 r/min). A Bland–Altman analysis was used to assess the level of agreement. For ball velocity, the 2-D high-speed video had the smallest systematic error, followed by the radar gun, TrackMan and miCoach football at 0.2, 0.4, 0.5 and 4.8 m s−1, respectively. A similar ranking was also observed for the random errors (95% confidence intervals: ±0.4, ±1.5, ±1.9 and ±6.0 m s−1). The first three systems all tracked ball velocity in >90% of shots, while the miCoach football tracked slightly fewer shots (79%). For spin rate, the miCoach football had a much smaller systematic error (4 vs 38 r/min) and random error (95% confidence intervals: ±24 vs ±355 r/min) compared to TrackMan. The miCoach also successfully tracked spin rate in more shots than the TrackMan (79% vs 44%). These results indicate that 2-D high-speed video would be the preferred option for the field assessment of ball velocity; however, radar gun and TrackMan may also be appropriate. A minimum of 10 frames of 2-D high-speed video, captured close to the ball starting position, was demonstrated to be sufficient in providing a reliable measure of ball velocity. The miCoach ball is the preferred option for field assessment of ball spin rate.

scholarly journals Experimental analysis of high velocity impacts of composite fragments on aluminium plates

2021 ◽  
Vol 250 ◽  
pp. 01011
Author(s):  
Jorge López-Puente ◽  
Jesús Pernas-Sánchez ◽  
José Alfonso Artero-Guerrero ◽  
David Varas ◽  
Joseba Múgica ◽  
...  
Keyword(s):  
High Velocity ◽  
High Speed ◽  
Woven Composites ◽  
Residual Velocity ◽  
Video Cameras ◽  
High Speed Video ◽  
High Velocity Impacts ◽  
Deformable Structure ◽  
The Impact ◽  
Composite Blades

The improvement of engines is one of the ways to diminish the fuel consumption in civil aircrafts, and Open Rotors engines are one of the best promises in order to achieve a sensible efficiency increment. These engines have large composite blades that could, in the event of failure, impact against the fuselage, totally or partially. In this case, composite fragments could behave as impactors. In order to design fuselages for this event and adopt these new engines in the future, it is necessary to understand the impact behaviour of a composite fragment against a deformable structure. To this end, unidirectional and woven composites fragments were impacted at high velocity (up to 150 m/s) against aluminium panels at different impact velocities. The composite fragments were made using AS4/8552 (UD) and AGP-193PW (woven) prepregs manufactured by Hexcel Composites, both using AS4 fibres and 8552 epoxy matrix. High speed video cameras were used to record the impact process and to measure both the impact and the residual velocity and hence the energy absorbed.

Vibration analysis of acoustic guitar string employing high-speed video cameras

2016 ◽  
Vol 139 (4) ◽  
pp. 2204-2204 ◽  
Author(s):  
Bozena Kostek ◽  
Piotr Szczuko ◽  
Jozef Kotus ◽  
Maciej Szczodrak ◽  
Andrzej Czyzewski
Keyword(s):  
Vibration Analysis ◽  
High Speed ◽  
Video Cameras ◽  
High Speed Video ◽  
Acoustic Guitar

J027022 Kinematic analysis of dolphin jumping by using high-speed video cameras

2013 ◽  
Vol 2013 (0) ◽  
pp. _J027022-1-_J027022-5
Author(s):  
Yusuke UCHIDA ◽  
Gen LI ◽  
Masashi NAKAMURA ◽  
Hiroto TANAKA ◽  
Hao LIU
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Video Cameras ◽  
High Speed Video
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