scholarly journals Characterisation of ball impact conditions in professional tennis: Matches played on hard court

2016 ◽  
Vol 230 (4) ◽  
pp. 236-245 ◽  
Author(s):  
Ben Lane ◽  
Paul Sherratt ◽  
Hu Xiao ◽  
Andy Harland
Keyword(s):  
Research And Development ◽  
Tennis Ball ◽  
Ball Impact ◽  
Total Data ◽  
Ball Tracking ◽  
Professional Tennis ◽  
Post Impact ◽  
Tennis Balls ◽  
The Impact

To assess ball performance for research and development purposes requires greater understanding of the impact conditions a tennis ball experiences in professional tournament play. Ball tracking information taken from three consecutive years of an ATP 250 tour event played on hard court was analysed. The frequency of first serves, second serves, racket impacts and surface impacts was assessed per game and extrapolated to show how many impacts a single ball is subjected to. Where applicable the pre- and post-impact velocities and angles were found, and the distribution of each was analysed. In total, data from 65 matches comprising 1505 games were analysed. On average, each game contained 70.26 (±16.23) impacts, of which 9.23%, 3.16%, 37.78% and 49.83% were first serves, second serves, racket impacts and surface impacts, respectively. As a result, assuming all balls in play are used evenly, a single ball is expected to be subjected to 105 (±24) impacts over the course of the nine games that it is in play. The results of the investigation could be used to design a wear protocol capable of artificially wearing tennis balls in a way that is representative of professional play.

scholarly journals A Cluster Analysis Approach to Profile Men and Women’s Volley Positions in Professional Tennis Matches (Doubles)

2021 ◽  
Vol 13 (11) ◽  
pp. 6370
Author(s):  
Rafael Martínez-Gallego ◽  
Jesús Ramón-Llin ◽  
Miguel Crespo
Keyword(s):  
Cluster Analysis ◽  
Performance Indicators ◽  
Tennis Ball ◽  
Match Play ◽  
Different Types ◽  
Ball Tracking ◽  
Professional Tennis ◽  
Inferential Analysis ◽  
The Impact ◽  
Tracking Technology

(1) Background: Tennis ball tracking technology allows the aquirement of novel and reliable data about several performance indicators, such as volley positions. This information is key to understand match dynamics in doubles tennis and to better help preparing players for the demands they will face in match play. As such, the purpose of this study was to describe and compare the different types of volley positions in men’s and women’s doubles professional tennis. (2) Methods: Ball tracking data were collected for 46 women (Billie Jean King Cup) and 96 men’s doubles matches (Davis Cup). The variables used were the distance to the net, the distance to the centre of the court and the height of the impact. A K-Means cluster analysis was used to identify in each subsample different profiles of volley locations. (3) Results: The inferential analysis revealed differences in men’s (distance to the net η2 = 0.72, distance to the centre of the court η2 = 0.77 and impact height η2 = 0.63) and women’s subsamples (distance to the net η2 = 0.48, distance to the centre of the court η2 = 0.52 and impact height η2 = 0.51). (4) Conclusions: The results allowed the suggestion of a higher variability in men’s matches, as there were seven different clusters identified, and only four in women’s.

Modeling of Impact Dynamics of a Tennis Ball With a Flat Surface

2005 ◽  
Author(s):  
Syed Muhammad Mohsin Jafri ◽  
John M. Vance
Keyword(s):  
Flat Surface ◽  
Equations Of Motion ◽  
Contact Forces ◽  
Rolling Contact ◽  
Tennis Ball ◽  
Computationally Efficient ◽  
Mass Model ◽  
Experimental Findings ◽  
Tennis Balls ◽  
The Impact

A model of impact of a tennis ball with a flat surface is developed based on a planar, two-mass, linear, four degree of freedom vibration system idealization. The impact is assumed to be incident on a flat surface with friction. The incident parameters of the ball include the centre of mass translational velocity, angle of impact with the surface and the incident angular spin of the ball. The linear, piecemeal vibration model predicts the corresponding rebound parameters of the tennis ball. The model also predicts the duration of contact of the tennis ball with the flat surface, the transition of motion of the tennis ball during contact with the ground from sliding to rolling contact, and the resulting contact forces developed between the tennis ball and the flat surface. The model is computationally efficient because the governing differential equations of motion are linear and their standard solutions can be easily implemented on a personal computer. Predictions of the rebound parameters from the model are compared with experimental findings on tennis balls which are incident on a flat surface with various angles, velocities and angular spins (zero spin, topspin and backspin). For selected parameters of the two-mass model, the comparisons show excellent agreement between the model and the measurements.

Modelling of tennis ball impacts on a rigid surface

2004 ◽  
Vol 218 (10) ◽  
pp. 1139-1153 ◽  
Author(s):  
S R Goodwill ◽  
S J Haake
Keyword(s):  
Contact Time ◽  
Momentum Flux ◽  
Viscoelastic Model ◽  
Coefficient Of Restitution ◽  
Model Parameters ◽  
Total Force ◽  
Tennis Ball ◽  
Rigid Surface ◽  
Ball Impact ◽  
The Impact

A viscoelastic model of a tennis ball impact at normal incidence on a rigid surface is presented in this study. The ball model has three discrete elements that account for the structural stiffness, material damping and momentum flux loading. Experiments using a force platform are performed to determine the force that acts on the ball during impact, for a range of ball inbound velocities. The inbound and rebound velocities of the ball are measured using speed gates. The contact time and coefficient of restitution for the impact are also determined in these experiments. The model parameters are determined such that the values of the coefficient of restitution and contact time that are calculated by the model are consistent with those values determined experimentally. The model can be used to calculate the force that acts on the ball during impact. Generally, the force-time plots calculated by the model were consistent with those determined experimentally. Furthermore, the model can be used to calculate the three components of the force that acts on the ball during impact. It is shown that the main component of the force during the first 0.6 ms of impact is that due to momentum flux loading. This is approximately equal in magnitude for each ball type and explains why the total force acting on each ball is very similar during this period.

Advancing dairy farming profitability through research

2001 ◽  
pp. 17-22
Author(s):  
J.R. Caradus ◽  
D.A. Clark
Keyword(s):  
Research And Development ◽  
Dairy Cow ◽  
Low Cost ◽  
Pasture Management ◽  
Nitrogen Fertiliser ◽  
Grass Endophyte ◽  
Forage Species ◽  
Development Outcomes ◽  
Dairy Cow Nutrition ◽  
The Impact

The New Zealand dairy industry recognises that to remain competitive it must continue to invest in research and development. Outcomes from research have ensured year-round provision of low-cost feed from pasture while improving productivity. Some of these advances, discussed in this paper, include the use of white clover in pasture, understanding the impacts of grass endophyte, improved dairy cow nutrition, the use of alternative forage species and nitrogen fertiliser to improve productivity, demonstration of the impact of days-in-milk on profitability, and the use of feed budgeting and appropriate pasture management. Keywords: dairy, profitability, research and development

Report of the Ad Hoc Subgroup on the Impact of Competition in Contracting on Research and Development

1988 ◽  
Author(s):  
Laurence Storch ◽  
Donald Fraser ◽  
Robert Lunn ◽  
Barbara Glacel ◽  
Naomi J. McAfee
Keyword(s):  
Research And Development ◽  
Ad Hoc ◽  
The Impact

scholarly journals A Study on the Impact of R&D Intensity on Business Performance: Evidence from South Korea

2021 ◽  
Vol 7 (2) ◽  
pp. 135
Author(s):  
Hun Park ◽  
Jun-Hwan Park ◽  
Sujin Lee ◽  
Hyuk Hahn
Keyword(s):  
South Korea ◽  
Research And Development ◽  
Business Performance ◽  
Decision Makers ◽  
The Other ◽  
Research Groups ◽  
Innovative Firms ◽  
The Impact ◽  
Knowledge Services

The role of R&D (research and development) intensity on the effect of knowledge services on the business performance of firms has been discussed by using PLS-SEM and PLS-MGA methods. Research groups were divided into two groups, innovative and non-innovative. Respondents were classified into innovative firms if their R&D intensity was over 3% and vice versa. PLS-SEM and PLS-MGA results were compared for two groups and valuable insights were extracted. For innovative firms, knowledge services seemed to be verified and processed by the decision makers and utilized to achieve their business performance. On the other hand, a large number of non-innovative firms seemed to have a stronger tendency to utilize knowledge services directly for their business without sufficient verification by the decision makers.

scholarly journals Sandwich panel with in-plane honeycombs in different Poisson's ratio under low to medium impact loads

2021 ◽  
Vol 60 (1) ◽  
pp. 145-157
Author(s):  
Yi Luo ◽  
Ke Yuan ◽  
Lumin Shen ◽  
Jiefu Liu
Keyword(s):  
Poisson’S Ratio ◽  
Sandwich Panel ◽  
Impact Force ◽  
Impact Resistance ◽  
Poisson's Ratio ◽  
Compression Performance ◽  
Post Impact ◽  
Local Impact ◽  
Collapse Behavior ◽  
The Impact

Abstract In this study, a series of in-plane hexagonal honeycombs with different Poisson's ratio induced by topological diversity are studied, considering re-entrant, semi-re-entrant and convex cells, respectively. The crushing strength of honeycomb in terms of Poisson's ratio is firstly presented. In the previous research, we have studied the compression performance of honeycomb with different negative Poisson's ratio. In this study, a comparative study on the local impact resistance of different sandwich panels is conducted by considering a spherical projectile with low to medium impact speed. Some critical criteria (i.e. local indentation profile, global deflection, impact force and energy absorption) are adopted to analyze the impact resistance. Finally, an influential mechanism of Poisson's ratio on the local impact resistance of sandwich panel is studied by considering the variation of core strength and post-impact collapse behavior.

THE IMPACT OF RESEARCH AND DEVELOPMENT INVESTMENT ON AGRICULTURAL SECTOR PERFOMANCE IN KENYA

2017 ◽  
Vol 2 (1) ◽  
pp. 34-57
Author(s):  
John Githii Kimani ◽  
Dr. George Ruigu Ruigu
Keyword(s):  
Research And Development ◽  
Agricultural Sector ◽  
Research Policy ◽  
Trade Openness ◽  
Policy And Practice ◽  
Long Run ◽  
Short Run ◽  
The Government ◽  
Parsimonious Model ◽  
The Impact

Purpose: The purpose of the study was to assess the impact of research and development investment/expenditure on the agricultural sector performance in Kenya.Methodology: The study took the peoples impact assessment direction. The data for this study was collected from various government agencies such as KARI, ASTI, Kenya Agricultural Sector Data compendium website, FAOSTAT, World Bank among others. Co-integration and error correction modeling methods were used in analyzing the data for this study.Results: Co-integration results for both the parsimonious and non-parsimonious model indicated that that there is a long-run relationship among the variables in the agriculture performance in Kenya. Further, findings in this study indicated that the variables under study were insignificant determinants of the long run Total Factor Productivity of the agricultural sector.  Meanwhile, Trade openness was the only significant determinant of the short run agricultural Total Factor Productivity.Unique Contribution to Policy and Practice: This study recommends the institutionalization of policies aimed at ensuring interaction between the various stakeholders in the agricultural sectors. This interaction will ensure that resources are better allocated to reduce duplication of research and dissemination activities. In addition, greater collaboration among the stakeholders will promote and strengthen the connection between research, policy and the application of research findings. The study further advocates that the government should follow a trade liberazation oriented approach to the agricultural sector as opposed to a trade tightening approach.

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