Magnitude estimates of rotational velocity during and following prolonged increasing, constant, and zero angular acceleration.

1968 ◽  
Vol 78 (2, Pt.1) ◽  
pp. 329-339 ◽  
Author(s):  
Brant Clark ◽  
John D. Stewart
Keyword(s):  
Rotational Velocity ◽  
Angular Acceleration ◽  
Magnitude Estimates

Head Kinematics by Contact Scenarios in Youth Ice Hockey

Neurology ◽  
2020 ◽  
Vol 95 (20 Supplement 1) ◽  
pp. S1.1-S1
Author(s):  
Abigail Swenson ◽  
Logan Miller ◽  
Jillian Urban ◽  
Joel Stitzel
Keyword(s):  
Rotational Velocity ◽  
Angular Acceleration ◽  
Linear Acceleration ◽  
Head Impact ◽  
Ice Hockey ◽  
Contact Sports ◽  
Head Impacts ◽  
Rigorous Study ◽  
Improving Accuracy ◽  
Impact Events

ObjectiveThe objective of this pilot study was to characterize head impact exposure in a sample of youth boys' ice hockey using a novel instrumented mouthpiece, improving accuracy.BackgroundFrom 2010 to 2018 youth ice hockey saw a 15% increase in participation, despite growing concerns for concussion risk in contact sports. While contact sports with similar rates of concussion have been subjected to rigorous study, head impact exposure in youth ice hockey has been largely underexplored. Existing youth studies have utilized helmet-mounted sensors, which are associated with error due to poor coupling with the skull.Design/MethodsCustom mouthpieces containing a tri-axial accelerometer and gyroscope were fit to seven enrolled athletes, and monitored during practices and games throughout the season. Linear acceleration and rotational velocity of the head were recorded for 60 ms when 5 g was exceeded on any axis for at least 3 ms. Time-synchronized film was reviewed to identify the contact scenario and head contact. Summary statistics of kinematics were calculated by scenario and presence of head contact.ResultsA total of 465 events were recorded over 25 weeks. Of these events 25% involved head contact; 92% of all contact scenarios were board checks, falls, or ice checks. Events involving head contact (i.e., head impacts) had median [95th percentile] peak linear acceleration, rotational velocity, and angular acceleration of 8.1 [30.9] g, 7.9 [20.2] rad/s, and 614 [2673] rad/s2, respectively. Events not involving head contact had median [95th percentile] peak linear acceleration, rotational velocity, and angular acceleration of 6.6 [43.8] g, 6.5 [17.5] rad/s, and 455 [4115] rad/s2, respectively.ConclusionsThe majority of the recorded events could be classified as board checks, falls, or ice checks. Median peak kinematics were higher for head impacts than non-head impact events. In contrast, 95th percentile linear and angular accelerations were greater for impacts not involving head contact.

scholarly journals Anthropomorphic simulations of falls, shakes, and inflicted impacts in infants

2003 ◽  
Vol 99 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Michael T. Prange ◽  
Brittany Coats ◽  
Ann-Christine Duhaime ◽  
Susan S. Margulies
Keyword(s):  
Brain Injuries ◽  
Rotational Velocity ◽  
Head Injuries ◽  
Diffuse Axonal Injury ◽  
Angular Acceleration ◽  
Concrete Surface ◽  
Human Infant ◽  
Subdural Hemorrhage ◽  
Content Type ◽  
Fine Print

Object. Rotational loading conditions have been shown to produce subdural hemorrhage and diffuse axonal injury. No experimental data are available with which to compare the rotational response of the head of an infant during accidental and inflicted head injuries. The authors sought to compare rotational deceleration sustained by the head among free falls, from different heights onto different surfaces, with those sustained during shaking and inflicted impact. Methods. An anthropomorphic surrogate of a 1.5-month-old human infant was constructed and used to simulate falls from 0.3 m (1 ft), 0.9 m (3 ft), and 1.5 m (5 ft), as well as vigorous shaking and inflicted head impact. During falls, the surrogate experienced occipital contact against a concrete surface, carpet pad, or foam mattress. For shakes, investigators repeatedly shook the surrogate in an anteroposterior plane; inflicted impact was defined as the terminal portion of a vigorous shake, in which the surrogate's occiput made contact with a rigid or padded surface. Rotational velocity was recorded directly and the maximum (peak—peak) change in angular velocity and the peak angular acceleration were calculated. Analysis of variance revealed significant increases in the and associated with falls onto harder surfaces and from higher heights. During inflicted impacts against rigid surfaces, the and were significantly greater than those measured under all other conditions. Conclusions. Vigorous shakes of this infant model produced rotational responses similar to those resulting from minor falls, but inflicted impacts produced responses that were significantly higher than even a 1.5-m fall onto concrete. Because larger accelerations are associated with an increasing likelihood of injury, the findings indicate that inflicted impacts against hard surfaces are more likely to be associated with inertial brain injuries than falls from a height less than 1.5 m or from shaking.

The scaling of acceleratory aquatic locomotion: body size and tail-flip performance of the california spiny lobster panulirus interruptus

1999 ◽  
Vol 202 (22) ◽  
pp. 3181-3193 ◽  
Author(s):  
J.C. Nauen ◽  
R.E. Shadwick
Keyword(s):  
Body Size ◽  
Angular Displacement ◽  
Rotational Velocity ◽  
Spiny Lobster ◽  
Angular Acceleration ◽  
Rotational Acceleration ◽  
Panulirus Interruptus ◽  
Wide Range ◽  
Tail Flip ◽  
Translational Acceleration

Tail-flipping is a crucial escape locomotion of crustaceans which has been predicted to be limited by increased body mass (M(b)). Given isometric growth, one may predict that with growth event duration will decrease as M(b)(−)(1/3), translational distances will increase as M(b)(1/3), translational velocity will be independent of M(b), translational acceleration will decrease as M(b)(−)(1/3), angular displacement will be independent of M(b) and angular velocity and angular acceleration will decrease as M(b)(−)(1/3). We tested these hypotheses by examining the scaling of 12 morphological variables, five kinematic variables and six performance variables of tail-flipping by the California spiny lobster Panulirus interruptus. Growth approximated isometry, which validated the use of the proposed scaling hypotheses. For animals from 1 to 1000 g M(b), the predicted scaling relationships for tail-flip duration and translational distance and velocity variables were supported; however, translational acceleration performance was much better than predicted. Predictions for rotation and rotational velocity variables were not supported, while the rotational acceleration data closely matched the predicted relationship. The increase in tail-flip duration as predicted suggests that muscle shortening velocity decreases with growth; the sustained acceleration performance (similar to findings for shrimp and fish fast-starts) suggests that muscle force output may increase at a greater rate than predicted by isometry. The scaling of rotational acceleration indicates that the torque produced during the tail-flip scales with a mass exponent greater than 1. Comparison of the tail-flip performance of Panulirus interruptus with those of other crustacean species reveals a wide range in performance by animals of similar body size, which suggests that the abdominal muscle may show interesting differences in contractile properties among different species.

Off-Vertical Axis Rotational Responses in Patients with Unilateral Peripheral Vestibular Lesions

1993 ◽  
Vol 102 (2) ◽  
pp. 137-143 ◽  
Author(s):  
Joseph M. R. Furman ◽  
Robert H. Schor ◽  
Donald B. Kamerer
Keyword(s):  
Eye Movement ◽  
Semicircular Canal ◽  
Rotational Velocity ◽  
Angular Acceleration ◽  
Population Data ◽  
Vertical Axis ◽  
Normal Subjects ◽  
Otolith Organs ◽  
Rapid Decay ◽  
Axis Rotation

Off-vertical axis rotation (OVAR) stimulates the otolith organs in a manner that is suitable for assessment of the otolith-ocular reflex. To further assess the potential clinical usefulness of OVAR, the eye movement responses of seven patients with surgically confirmed unilateral peripheral vestibular lesions were compared with the eye movement responses of a group of age-matched, healthy, asymptomatic control subjects. Patients and controls were tested with constant velocity rotations that followed a brief period of angular acceleration (velocity trapezoid) using either earth-vertical axis (EVA) rotation or OVAR. Both EVA and OVAR sinusoidal velocity profiles were also performed. Results indicated that each patient had 1) an asymmetric OVAR response, ie, a bias component whose direction was opposite normal when rotating toward the lesioned ear, and 2) a normal modulation component. Population data suggested that patients had 1) a more rapid decay of response than normal subjects during OVAR velocity trapezoids, 2) an increased phase lead as compared to normal subjects during sinusoidal OVAR, and 3) like normal subjects, a less rapid decay of response during OVAR velocity trapezoids than during EVA rotational velocity trapezoids. Taken together, these findings suggest that patients with unilateral peripheral vestibular deficits have abnormal otolith-ocular and semicircular canal—ocular reflexes but that a single labyrinth appears to provide an otolithic signal sufficient for qualitatively normal semicircular canal—otolith interaction.

A Note on the Decomposition of Aerodynamic Forces Induced by A Wind Turbine Flaps

2020 ◽  
Vol 36 (5) ◽  
pp. 585-593
Author(s):  
Y. Y. Niu ◽  
P. J. Shih ◽  
S. C. Kong
Keyword(s):  
Wind Turbine ◽  
Aerodynamic Force ◽  
Rotational Velocity ◽  
Angular Acceleration ◽  
Surface Friction ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Gurney Flap ◽  
Force Element ◽  
Element Theory

ABSTRACTIn this study, the aerodynamic characteristics of a vertical-axis wind turbine blade coupled with a high-lift device, such as the Gurney flap at the trailing edge, are investigated. For numerical analysis, the force element theory is used to understand how the Gurney flap influences the force evolution of the lift-type vertical-axis wind turbine. This study shows that the lift and drag can be respectively approximated into four elements, which are induced by volume vorticity, rotational velocity, angular acceleration and surface friction of the flow around the blades. Based on the perspective of the force element theory, the present simulation provides a clear picture of how the Gurney flap influences the formation of the aerodynamic force elements during a rotational cycle for a vertical-axis wind turbine. Simulation results show that the contributions mainly result from the surface vorticities, the rotational acceleration of the airfoil, and the acceleration of the surface.

scholarly journals Gender Differences in Kinematic Analysis of the Lower Limbs during the Chasse Step in Table Tennis Athletes

Healthcare ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 703
Author(s):  
Xiaoyi Yang ◽  
Yuqi He ◽  
Shirui Shao ◽  
Julien S. Baker ◽  
Bíró István ◽  
...  
Keyword(s):  
Female Athletes ◽  
External Rotation ◽  
Rotational Velocity ◽  
Knee Extension ◽  
Lower Limbs ◽  
Table Tennis ◽  
Male Athletes ◽  
Analysis System ◽  
Hip Flexion ◽  
Hip Internal Rotation

The chasse step is one of the most important footwork maneuvers used in table tennis. The purpose of this study was to investigate the lower limb kinematic differences of table tennis athletes of different genders when using the chasse step. The 3D VICON motion analysis system was used to capture related kinematics data. The main finding of this study was that the step times for male athletes (MA) were shorter in the backward phase (BP) and significantly longer in the forward phase (FP) than for female athletes (FA) during the chasse step. Compared with FA, knee external rotation for MA was larger during the BP. MA showed a smaller knee flexion range of motion (ROM) in the BP and larger knee extension ROM in the FP. Moreover, hip flexion and adduction for MA were significantly greater than for FA. In the FP, the internal rotational velocity of the hip joint was significantly greater. MA showed larger hip internal rotation ROM in the FP but smaller hip external rotation ROM in the BP. The differences between genders can help coaches personalize their training programs and improve the performance of both male and female table tennis athletes.

scholarly journals Is Acceleration a Valid Proxy for Injury Risk in Minimal Damage Traffic Crashes? A Comparative Review of Volunteer, ADL and Real-World Studies

2021 ◽  
Vol 18 (6) ◽  
pp. 2901
Author(s):  
Paul S. Nolet ◽  
Larry Nordhoff ◽  
Vicki L. Kristman ◽  
Arthur C. Croft ◽  
Maurice P. Zeegers ◽  
...  
Keyword(s):  
Real World ◽  
Injury Risk ◽  
Angular Acceleration ◽  
Traffic Crashes ◽  
Rear Impact ◽  
Comparative Review ◽  
Minimal Damage ◽  
Injury Causation ◽  
Crash Tests ◽  
Biomechanical Approach

Injury claims associated with minimal damage rear impact traffic crashes are often defended using a “biomechanical approach,” in which the occupant forces of the crash are compared to the forces of activities of daily living (ADLs), resulting in the conclusion that the risk of injury from the crash is the same as for ADLs. The purpose of the present investigation is to evaluate the scientific validity of the central operating premise of the biomechanical approach to injury causation; that occupant acceleration is a scientifically valid proxy for injury risk. Data were abstracted, pooled, and compared from three categories of published literature: (1) volunteer rear impact crash testing studies, (2) ADL studies, and (3) observational studies of real-world rear impacts. We compared the occupant accelerations of minimal or no damage (i.e., 3 to 11 kph speed change or “delta V”) rear impact crash tests to the accelerations described in 6 of the most commonly reported ADLs in the reviewed studies. As a final step, the injury risk observed in real world crashes was compared to the results of the pooled crash test and ADL analyses, controlling for delta V. The results of the analyses indicated that average peak linear and angular acceleration forces observed at the head during rear impact crash tests were typically at least several times greater than average forces observed during ADLs. In contrast, the injury risk of real-world minimal damage rear impact crashes was estimated to be at least 2000 times greater than for any ADL. The results of our analysis indicate that the principle underlying the biomechanical injury causation approach, that occupant acceleration is a proxy for injury risk, is scientifically invalid. The biomechanical approach to injury causation in minimal damage crashes invariably results in the vast underestimation of the actual risk of such crashes, and should be discontinued as it is a scientifically invalid practice.

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