Tennis Racket Research Articles

“Tennis racket” hydrogel electrolytes to synchronously regulate cathode and anode of zinc-iodine batteries

“Tennis racket” hydrogel electrolytes to synchronously regulate cathode and anode of zinc-iodine batteries

A systematic framework for the design and material selection of composite for tennis racket upon impact

The present study explores the comprehensive composite material selection methodology of a tennis racket involving coupled Multi-Criteria Decision-Making (MCDM) and numerical analysis. Initially all the possible material alternatives from the composite family were shortlisted using CES Selector 2016. A design space was developed incorporating MCDM technique naming VICKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje), PROMETHEE (Preference Ranking Organisation Method for Enrichment Evaluation) and TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) to rank the most suitable composite material based on critical mechanical properties to identify the most suitable composite materials for applications requiring optimal combinations of rigidity, strength, and structural performance. Using finite element analysis, the structural integrity of each of the materials was evaluated on static and dynamic stress analysis modules of ANSYS. Out of all material alternatives, T300 carbon fiber epoxy was considered as the most suitable for tennis rackets. Further, a comparison between the selected material was also made with conventional materials and were found in good agreement with selected material.

Dynamic analysis of a skeet-inspired vehicle to achieve a spiral scanning detection motion

A short cylindrical vehicle (the ratio of length to diameter is less than 2) equipped with an outer/inner detector is developed, which is inspired by the Tennis racket theorem and Olympic skeet shooting sports to achieve a regular scanning spiral on the ground. The sensitivity of the asymmetric mass distribution of the skeet-inspired vehicle (SIV) to the spatial position of the inertial principal axis is evaluated. Subsequently, a dynamics model with six degrees of freedom for the SIV at a large initial angle of attack (≈60–90°) is established. The numerical results of solving the dynamic differential equations indicate that the special initial conditions—namely, high initial flying velocity and rotational speed—are prerequisites for achieving the regular scanning spiral. Additionally, the analysis demonstrates that asymmetric mass distribution, rather than asymmetric aerodynamics, serves as the key factor in achieving the regular scanning spiral in the present skeet-inspired vehicle. Our new strategy, using the principal axes as the initial rotation axis, offers better scanning performance (such as a larger detection area, faster scan frequency, and more stable scanning motion) compared to the other platforms (e.g., rotating decelerators with wings or parachutes) that rely on asymmetrical aerodynamics. The analyses can provide guidance for the structural design of various types of spiral scanning vehicles.

Effects of tennis racket swingweight on forehand speed and accuracy in youth players

ABSTRACT Few studies have analysed the effects of the racket inertial parameters on hitting performance in young tennis players. The research aims to study the relationship between the swingweight of the racket and speed and accuracy variables, in young tennis players. Twenty-six players (13.1 ± 2.94 years) performed a forehand hitting test with three rackets of different swingweight (low, medium, and high). Ball speed and hitting accuracy were calculated using a radar, Zepp2 sensor and photogrammetry. Significant differences were found in the ball speed measured by the Zepp2, with the racket with a low swingweight producing a higher speed (p < 0.05; Mean ± SD; 108 ± 43 vs. 102 ± 47 vs. 101 ± 49 km/h, for the racket with a low, medium, and high swingweight). In accuracy, there were significant differences in the absolute longitudinal error, being the racket of the low swingweight the most accurate (182 ± 49 cm vs. 215 ± 88 vs. 208 ± 72 cm; p < 0.05). Also, the low swingweight racket showed higher errors in the net. It is concluded that the lower swingweight racket generates the highest speed values while the error pattern is different between the different swingweights.

Seismic behavior of double-cell CFST columns with table tennis racket-shaped cross section

Multicell concrete-filled steel tube (CFST) columns with excellent mechanical performance have been used in super high-rise buildings in recent years. According to the requirements of a 265-m tall building, the double-cell CFST columns with an innovative cross section of table tennis racket were applied. Hence, six columns were designed according to the prototype columns and subjected to low-frequency cyclic loading. The impacts of different shear-span ratios (SSRs), axial load ratios (ALRs), and steel ratios on the seismic behavior were elaborated and clarified. The test results indicated that the seismic performance varied in different loading directions owing to the asymmetric cross section, and the columns performed better in the positive loading direction resulted from earlier and more sufficient confinement of the circular steel tube, which was also reflected by the measured strain development. With SSR deceasing from 2.5 to 1.7, earlier and more severe damage was recorded. The resisting capacity and stiffness were significantly improved at a cost of ductility loss. Increasing ALR from 0.2 to 0.4 brought about more damage and worse deformability. However, a proper increase in axial load was beneficial to the resisting capacity and stiffness, and its influence on the restoration capacity was associated with SSR. Increasing the steel ratio (by 33.36%) could effectively postpone and alleviate the local buckling of steel tube, thereby comprehensively improving the seismic performance. A finite element (FE) analysis of such columns was performed to carry out the damage evolution and parametric study, and provide references for their application in practical engineering.

The use of tennis racket media among SEA Games athletes in Cambodia: How does it affect receiving sepak takraw?

Background Problems: Receiving the first ball is a problem for national sepak takraw athletes at the 2023 Cambodia Sea Games, where the reception technique is in the bad category. Research Objectives: This study aims to determine the effect of using tennis racket media on SEA Games athletes in Cambodia on improving sepak takraw reception skills. Methods: This study used quantitative methods with a one-group pretest and posttest. Random sampling was used to select Cambodian SEA Games sepak takraw athletes as research subjects. The population in this study were men’s sepak takraw athletes from the 2023 Cambodia Sea Games national training, with the sample used totaling 12 athletes taken randomly. Findings and Results: The results showed that the use of tennis racket media had a significant effect on increasing acceptance of sepak takraw games. Athletes who follow the training programme with tennis racket media experience a consistent increase in their ability to receive the ball. Conclusion: These results indicate that the use of this additional training tool can be an effective strategy for improving the performance of sepak takraw athletes. The study makes some significant contributions to understanding the use of racket media in the training of sepak takraw athletes. Further research and wider experimentation can help deepen the understanding of the potential use of tennis racket media in sports training.

Internal dissipation in the Dzhanibekov effect

The Dzhanibekov effect is the phenomenon by which triaxial objects like a spinning wing bolt may continuously flip their rotational axis when initially spinning around the intermediate axis of inertia. This effect is closely related to the Tennis Racket theorem that establishes that the intermediate axis of inertia is unstable. Over time, however, dissipation ensures that a torque free spinning body will eventually rotate around its major axis, in a process called precession relaxation, which counteracts the Dzhanibekov effect. Euler’s equations for a rigid body effectively describe the Dzhanibekov effect, but cannot account for the precession relaxation effect. A dissipative generalization of Euler’s equations displays two dissipative mechanisms: orientational diffusion and viscoelasticity. Here we show through numerical simulations of the dissipative Euler’s equations that orientational diffusion, rather than viscoelasticity, primarily drives precession relaxation and effectively suppresses the Dzhanibekov effect.

Phase-Space and Dissipation Studies of the Dancing Wing Nut

In this paper, we address the nonlinear dynamics of Dzhanibekov’s dancing wing nut and the related intermediate axes theorem governing the motion of a tossed tennis racket. Drawing first on the comprehensive investigations by Murakami, Rios and Impelluso [J. Appl. Mech. 83 (2016), doi:10.1115/1.4034318] we extend the exploration of the wing nut’s spherical phase portrait by incorporating basins of attraction and their heteroclinic connections. We then turn our attention to the significant damping studies of Español, Thachuk and de la Torre [Eur. J. Mech. A Solids 103, 105184 (2024)] who derive from first principles a generalized stochastic version of the Euler equations which can incorporate both oriental realignment (which they call oriental diffusion) and viscoelastic effects. Applied to the wing nut dancing, they showed that the former is the more significant effect and as the authors say “Had Dzhanibekov observed his wing nut for a sufficiently long period, he would have found it spinning around the major axis. In other words, precession relaxation kills the Dzhanibekov effect in the long run.”

Retracted: Research on Optimal Control Method of Tennis Racket String Diameter Based on Kalman Filter Algorithm

Retracted: Research on Optimal Control Method of Tennis Racket String Diameter Based on Kalman Filter Algorithm

Generating novel tennis racket shape concepts using a theoretical morphospace.

Statistical shape analysis, or morphometrics, is a technique commonly used in evolutionary biology to summarise a population of samples. Theoretical morphometrics extends the current population of samples into a theoretical space. Using the lawn tennis racket as an example, this paper showcases the potential of morphometrics as a tool for inspiring design concepts for novel sporting goods. It showcases how morphometrics can be applied to summarise the shape of a sample of rackets and applies theoretical morphometrics to systematically present new candidate designs that fall outside of the inputted existing, racket population. The input population was 514 tennis rackets dating back to the origins of the game. The shape analysis was performed on "front-on" silhouette images of the rackets using the R Package Momocs. The outline shape of each racket was reconstructed using the elliptical Fourier transform curve fitting technique. A principal component analysis performed on the reconstructed outlines showed that >90% of the variance in the shape of the rackets was captured by the first two principal components. An evenly spaced grid of theoretical racket shape outlines was then created in a principal component 2 vs. principal component 1 "morphospace". The limits of this space were then expanded to give a theoretical morphospace that extended beyond the range of the first two principal components for the 514 samples. We propose that the shapes located within such a theoretical morphospace could inspire designers and help them to systematically identify candidates for novel products. Specifically, we suggest that experimenting with wide-angled throats and heads with angled sides might be an interesting starting point for exploring future tennis racket design concepts. The novel technique presented here could be used by a sporting goods brand during the ideation phase of product development to schematically summarise current designs and identify candidates for new ones.

Development of upper and lower extremity functional asymmetries in male and female elite youth tennis players: a longitudinal study.

This longitudinal study aimed to examine the development of both upper and lower extremity functional performances, together with asymmetry magnitudes and directionality in youth tennis players. Dominant and non-dominant physical performance values of 90 players (53 males, 37 females) were determined yearly (with monitoring up to 3 years) using unilateral strength, power, speed and agility tests from which asymmetry magnitude percentages were calculated. Linear mixed effect models examined the development of performance values according to youth players' maturity offset, performance dominance, sex and training volume. Similarly, the development of functional asymmetry magnitudes was examined according to players' maturity offset, sex and training volume. Kappa coefficients (k) examined the consistency in directionality across test occasions. Regardless of sex, the dominant and non-dominant physical performance values of every test significantly (P<0.05) improved with increasing maturity offset. No sex differences were apparent except for strength and power related tests where male players performed significantly better. Functional asymmetry magnitudes (ranging from 2.0 to 15.9%) did not significantly change with increasing maturity offset (range=-0.3-0.4% per year). Training volume was not significantly associated with the performance values and asymmetry magnitudes. The dominant upper extremity (which holds the tennis racket) consistently displayed the dominant performance value (k value: 1.00) across test occasions, which was not the case at lower extremity level (k value range: -0.28-0.31). The functional asymmetry magnitudes did not change significantly with youth tennis players' maturity offset over a 3-year period.

Closed‐Loop Optimization of Soft Sensor Morphology Using 3D Printing of Electrically Conductive Hydrogel

Soft sensing technologies provide a novel alternative for state estimation in wearables and robotic systems. They allow one to capture intrinsic state parameters in a highly conformable manner. However, due to the nonlinearities in the materials that make up a soft sensor, it is difficult to develop accurate models of these systems. Consequently, design of these soft sensors is largely user defined or based on trial and error. Since these sensors conform and take the shape of the sensing body, these issues are further exacerbated when they are installed. Herein, a framework for the automated design optimization of soft sensors using closed‐loop 3D printing of a recyclable hydrogel‐based sensing material is presented. The framework allows direct printing of the sensor on the sensing body using visual feedback, evaluates the sensor performance, and iteratively improves the sensor design. Following preliminary investigations into the material and morphology parameters, this is demonstrated through the optimization of a sensorized glove which can be matched to specific tasks and individual hand shapes. The glove's sensors are tuned to respond only to particular hand poses, including distinguishing between two similar tennis racket grip techniques.

Elite male table tennis matches diagnosis using SHAP and a hybrid LSTM–BPNN algorithm

This study adopts a new approach, SHapley Additive exPlanation (SHAP), to diagnose the table tennis matches based on a hybrid algorithm, namely Long Short-Term Memory–Back Propagation Neural Network (LSTM–BPNN). 100 male singles competitions (8535 rallies) from 2019 to 2022 are analyzed by a hybrid technical–tactical analysis theory, which hybridizes the double three-phase and four-phase evaluation theories. A k-means cluster analysis is conducted to classify 59 players’ winning rates into three levels (high, medium, and low). The results show that LSTM–BPNN has excellent performance (MSE = 0.000355, MAE = 0.014237, RMSE = 0.018853, and {mathrm{R}}^{2} = 0.988311) compared with six typical artificial intelligence algorithms. Using LSTM–BPNN to calculate the SHAP value of each feature, the global results find that the receive-attack and serve-attack phases of the ending match have essential impacts on the mutual winning probabilities. Finally, case applications show that the SHAP can directly obtain each feature importance on one or more matches, which is more objective and reliable than the traditional simulation method. This research explores an innovative way to understand and analyze matches, and these results have implications for the performance analysis of table tennis and related racket sports.

Signatures of physical constraints in rotating rigid bodies

We study signatures of physical constraints on free rotations of rigid bodies. We show analytically that the physical or non-physical nature of the moments of inertia of a system can be detected by qualitative changes both in the Montgomery phase and in the tennis racket effect.

Odontogenic myxoma: Literature review

The odontogenic myxoma (OM) is a locally aggressive and infiltrating benign tumor that originates from the odontogenic ectomesenchyme. It represents the third most prevalent odontogenic tumor. It presents a predilection for the female sex, affecting the first and fourth decade of life. Clinically it is asymptomatic, however, it can generate facial asymmetry, causing an expansion of the bone cortices, dental displacement, root resorption. Radiographically, odontogenic myxoma generally presents a multilocular radiographic pattern that can vary in appearance, including "soap bubble", "honeycomb" and "tennis racket" or "sunbeam" shapes. In histological studies, the odontogenic myxoma is observed to be composed of stellate to spindle-shaped cells wrapped in an abundant extracellular matrix rich in mucin, without encapsulation and that may contain epithelial residues. Treatment is variable and corresponds to the size of the lesion. Well, there are conservative treatments focused on curettage or radical treatments and in the same way the recurrence of this lesion will depend on the type of treatment. The objective of this article is to evaluate demographic aspects such as age; location; prevalence; clinical, radiographic and histological analysis; treatment, results and recurrence.

Arrayed piezoresistive and inertial measurement unit sensor-integrated assistant training tennis racket for multipoint hand pressure monitoring and representative action recognition

Arrayed piezoresistive and inertial measurement unit sensor-integrated assistant training tennis racket for multipoint hand pressure monitoring and representative action recognition

Death of a Salesman

Death of a Salesman

An Investigation on the Aerodynamics of Flight of a Hand Helicopter

A simple hand helicopter can be made by attaching rotor blades to one end of a vertical stick. The helicopter moves upwards when the stick is spun above a threshold angular velocity and released — a mechanism of common toys found in toy shops. This study uses computational fluid dynamics to predict the airflow around a hand helicopter from which the lift and drag acting on the hand helicopter’s blades can be obtained. Newton’s Second Law is then applied to find the hand helicopter’s equations of motion. These are solved to predict the helicopter’s trajectory and maximum height. The angle of attack, length of blades and thickness of blades are varied and their effects on the lift coefficient, drag coefficient, lift-off and maximum height are investigated. The findings offer insight into the parameters which will allow a hand helicopter to achieve its optimal maximum height. The conditions required for the hand helicopter to fly stably are also investigated and explained using the Tennis Racket Theorem.

Temporal Pattern Attention for Multivariate Time Series of Tennis Strokes Classification.

Human Action Recognition is a challenging task used in many applications. It interacts with many aspects of Computer Vision, Machine Learning, Deep Learning and Image Processing in order to understand human behaviours as well as identify them. It makes a significant contribution to sport analysis, by indicating players' performance level and training evaluation. The main purpose of this study is to investigate how the content of three-dimensional data influences on classification accuracy of four basic tennis strokes: forehand, backhand, volley forehand, and volley backhand. An entire player's silhouette and its combination with a tennis racket were taken into consideration as input to the classifier. Three-dimensional data were recorded using the motion capture system (Vicon Oxford, UK). The Plug-in Gait model consisting of 39 retro-reflective markers was used for the player's body acquisition. A seven-marker model was created for tennis racket capturing. The racket is represented in the form of a rigid body; therefore, all points associated with it changed their coordinates simultaneously. The Attention Temporal Graph Convolutional Network was applied for these sophisticated data. The highest accuracy, up to 93%, was achieved for the data of the whole player's silhouette together with a tennis racket. The obtained results indicated that for dynamic movements, such as tennis strokes, it is necessary to analyze the position of the whole body of the player as well as the racket position.

There is no rush to upgrade the tennis racket in young intermediate competitive players: The effects of scaling racket on serve biomechanics and performance.

Scaling the equipment of young athletes is justified by the constraints-led approach introduced in motor learning. The aim of the present study is to analyze the effect of racket scaling on the serve biomechanics and performance parameters for young tennis players (between 8 and 11 years-old). Nine young intermediate competitive tennis players (age: 9.9 ± 1.0 years) performed maximal effort flat serves with three different rackets (scaled 23 inches, scaled 25 inches and full-size 27 inches) in a randomized order. A radar measured ball speed while shoulder and elbow kinetics and upper and lower limb kinematics were calculated with a 20-camera optical motion capture system. Repeated measures ANOVAs were used to analyze the effect of the three rackets on ball speed, percentage of serve in, serve kinematics and kinetics. No significant differences in ball speed, maximal racket head velocity and percentage of serve in were observed between the three rackets. The lowest maximal upper limb kinetics and the highest upper limb maximal angular velocities were obtained with the scaled 23 inches racket. Using scaled rackets has the advantage to decrease shoulder and elbow loadings without reducing serve performance. Consequently, the present results incite tennis coaches and parents to not upgrade too soon the size of the racket in young intermediate tennis players to avoid overuse injury risks in the long term. Our results showed that the full-size 27 inches racket induced higher lower limb kinematics. As a consequence, occasionally serving with a fullsize racket can be a sparingly interesting intervention to help young tennis players to intuitively and immediately increase their leg drive action, allowing a more functional representation of the elite junior serve.