Ball Machine Research Articles

Einsatz von Shutter-Brillen im Tennis – Einfluss von (Bild-)Frequenz und Dunkelphasenanteil auf die Zielschlagpräzision

Purpose. The use of shutter glasses for perception training in sports requires knowledge of adequate load dosage. The study analyses the influence of (image-)frequency or “duty ratio” (dark phase percentage) on target stroke accuracy in tennis. Material and Methods. With a total number of 22 tennis players (18m, 4f, mean age = 23.6, SD = ± 2.7 years) the target hit precision was conducted. The tennis players had to return the balls played to them by a ball machine using the forehand volley and to make direct hits to a bull’s eye (high scores = high target hit precision). The results with different (randomised) conditions (strobe rates level II = 5.3 Hz, level V = 2.3 Hz, lev- el VIII = 1.0 Hz; dark phase level II = 88 ms, level V = 341 ms, level VIII = 909 ms) of currently used shutter glasses (Nike Vapor Strobe) and without occlusion have been compared. Keywords intermittent vision, stroboscopic visual training, shutter lens glasses, sports vision training, tennis

Stroboscopic Eyewear Applied During Warm-Up Does Not Provide Additional Benefits to the Sport-Specific Reaction Speed in Highly Trained Table Tennis Athletes.

While long-term training with stroboscopic eyewear suggests performance-enhancing effects on visuomotor abilities, it remains unclear whether a short-term application, for example, during a warm-up, results in immediate performance gains. This study evaluated potential performance-enhancing effects of stroboscopic eyewear applied during warm-up on reaction speed that may provide athletes an edge in visuomotor-demanding sports. Twenty-eight international-level table tennis athletes participated in this study. Participants performed their individual 10-minute table-tennis-specific warm-up under normal visual conditions and with stroboscopic eyewear. Prior to and after the warm-up, visuomotor reaction time was assessed in a sport-specific reaction test where athletes had to return 30 table tennis balls played by a ball machine at high speed to their backhand side. Reaction time was determined as the interval between ball output and movement onset as triggered by a mechanical switch. Furthermore, the time between ball-table contact and ball-racket contact (hit time) was analyzed as an indicator of how early the athletes intercepted the ball. Reaction time significantly improved following the warm-up (P < .001, ηp2=.393). However, there was no additional benefit of the stroboscopic eyewear (P = .338, ηp2=.034). No changes after the warm-up were observed for hit time (P = .246, ηp2=.055). The results indicate that warm-up facilitated visuomotor reaction speed; however, stroboscopic eyewear did not provide additional positive effects when compared to a warm-up under normal visual conditions. While shutter glasses may be useful for training over longer periods, short-term positive effects were not supported in this study.

Cold-water immersion and whole-body cryotherapy attenuate muscle soreness during 3 days of match-like tennis protocol.

This study aimed to investigate the effect of whole-body cryotherapy (WBC), cold-water immersion (CWI) and passive recovery (PAS) on tennis recovery. Thirteen competitive male tennis players completed three consecutive match-like tennis protocols, followed by recovery (WBC, CWI, PAS) in a crossover design. Five tennis drills and serves were performed using a ball machine to standardize the fatiguing protocol. Maximal voluntary contraction (MVC) peak torque, creatine kinase activity (CK), muscle soreness, ball accuracy and velocity together with voluntary activation, low- and high-frequency torque and EMG activity were recorded before each protocol and 24h following the third protocol. MVC peak torque (-7.7 ± 11.3%; p = 0.001) and the high- to low-frequency torque ratio (-10.0 ± 25.8%; p < 0.05) decreased on Day 1 but returned to baseline on Day 2, Day 3 and Day 4 (p = 0.052, all p > 0.06). The CK activity slightly increased from 161.0 ± 100.2 to 226.0 ± 106.7 UA L-1 on Day 1 (p = 0.001) and stayed at this level (p = 0.016) across days with no differences between recovery interventions. Muscle soreness increased across days with PAS recovery (p = 0.005), while no main effect of time was neither observed with WBC nor CWI (all p > 0.292). The technical performance was maintained across protocols with WBC and PAS, while it increased for CWI on Day 3 vs Day 1 (p = 0.017). Our 1.5-h tennis protocol led to mild muscle damage, though neither the neuromuscular function nor the tennis performance was altered due to accumulated workload induced by consecutive tennis protocols. The muscle soreness resulting from tennis protocols was similarly alleviated by both CWI and WBC. IRB No. 2017-A02255-48, 12/05/2017.

EXPLORING THE ANTI-WEAR AND EXTREME PRESSURE LUBRICATING PERFORMANCE OF JATROPHA OIL MODIFIED WITH NANO-ADDITIVES AND GARLIC OIL

It is imperative to emphasize the wear-reducing and load-sustaining abilities of the lubricating oils, as they are an essential part of their operation. In this study, the anti-wear and extreme pressure (EP) performance of Jatropha oil was explored. The investigation was executed on a 4-ball tester machine according to ASTM-D-4172 and D-2783 standards. Nano-sized Molybdenum disulfide and graphene were added to the base oil, whose addition reduced the wear on the test balls but failed to improve the EP properties. However, the addition of Garlic oil elevated the EP properties of the base oil. The Last Non-seizure load and weld point of the jatropha oil was elevated by up to 3 levels, while the Load Wear index was increased by 91.88%. The Flash Temperature Parameter of jatropha oil was increased by 658% and 250% at 100kgf and 126kgf load, respectively, after the addition of 5% garlic oil. Further, the wear scars were examined under an optical microscope and FESEM, which proved that the addition of nano-additives reduced the wear of the balls during anti-wear tests at lower loads, and garlic oil reduced the wear in EP conditions and produced smoother surfaces. These improvements were attributed to the formation of tribo-films on the surfaces as characterized by the EDS analysis. It was concluded that Garlic oil could be a substantial EP additive to vegetable oils (especially jatropha oil) to lift their load-carrying capacity without hampering their environmentally friendly nature.

Parieto-Occipital Electrocortical Dynamics during Real-World Table Tennis.

Traditional human electroencephalography (EEG) experiments that study visuomotor processing use controlled laboratory conditions with limited ecological validity. In the real world, the brain integrates complex, dynamic, multimodal visuomotor cues to guide the execution of movement. The parietal and occipital cortices are especially important in the online control of goal-directed actions. Table tennis is a whole-body, responsive activity requiring rapid visuomotor integration that presents a myriad of unanswered neurocognitive questions about brain function during real-world movement. The aim of this study was to quantify the electrocortical dynamics of the parieto-occipital cortices while playing a sport with high-density electroencephalography. We included analysis of power spectral densities (PSDs), event-related spectral perturbations, intertrial phase coherences (ITPCs), event-related potentials (ERPs), and event-related phase coherences of parieto-occipital source-localized clusters while participants played table tennis with a ball machine and a human. We found significant spectral power fluctuations in the parieto-occipital cortices tied to hit events. Ball machine trials exhibited more fluctuations in θ power around hit events, an increase in intertrial phase coherence and deflection in the event-related potential, and higher event-related phase coherence between parieto-occipital clusters as compared with trials with a human. Our results suggest that sport training with a machine elicits fundamentally different brain dynamics than training with a human.

Technical skills in complex tennis situations: Dutch talented players U15 compared to players U17.

Technical skills in complex situations appear crucial for progress towards elite tennis performance. However, it is unknown how these skills develop in different age categories in a group of talented youth players. The aim of this study is to evaluate possible differences in technical skills among Dutch talented youth tennis players U15 compared to U17. A total of 19 players (12 males, 7 females; age 14.6 ± 1.4 years) were tested on ball speed, accuracy, percentage errors and spin rate using the on-court Dutch Technical-Tactical Tennis Test. With a ball machine, four games were simulated which were either fixed (game 1 and game 2) or variable (game 3 and game 4), depending on the complexity of the task. Each game consisted of two offensive, two neutral and two defensive rallies, representing different tactical situations. A two-way ANOVA revealed a statistically significant interaction between the effects of age category and sex for ball speed (F(1,15) = 5.472, p = 0.034, η 2 = 0.267), indicating that males U17 produced higher ball speed compared to males U15, whereas no differences were found between females U15 and U17. A one-way ANCOVA showed that, regardless of sex, players U17 scored significantly higher on accuracy than players U15 (F(1,16) = 5.021, p = 0.040, η 2 = 0.239). No differences were found between players U15 and U17 for spin rate and percentage errors (p > .05), although there was a medium to large effect size for males U17 to produce higher spin rates compared to males U15. A closer examination of accuracy revealed that players U17 scored significantly higher compared to players U15 in game 4 (F(1,17) = 6.358, p = .022, η 2 = .272) and in defensive situations (F(1,17) = 9.602, p = .007, η 2 = .361). In conclusion, the results of the current study suggest that technical skills, especially ball speed for males and accuracy in complex situations for both males and females, continue to develop in adolescence in talented tennis players. There is an increased understanding about underlying technical skills that contribute to progress towards elite tennis performance. To effectively develop technical skills, coaches are encouraged to design specific practices where these skills are performed in complex situations under high cognitive and temporal pressure.

Design and Fabrication of Thrower Mechanism for Multipurpose Ball Throwing Machine

The cricket and tennis are one of the popular games in the world. Nowadays the players are trained with the help of practice machine. To simulate different varieties of motions, speeds, and trajectories accurately and repeatedly, practice machine is designed by iterative design processes (manual calculations) with solid works. Two counter rotating wheel mechanism imparts both translational and rotational motions with spin. It is portable, flexible, run-on AC source, operated at various horizontal and vertical planes and desired combinations of both planes. This ball machine was constructed utilizing readily accessible components from the market. Because lowering manufacturing costs is one of the project’s goals, the materials were chosen based on their reduced cost. Furthermore, the machine’s parts are made of recycled and locally sourced materials. Therefore, after building is complete, this machine will be useful to many individuals, especially active gamers. The mathematical analysis for the design of a new tennis ball launcher in order to assess the possibilities for its technical implementation. First, traditional launchers are described. The motion equation of the flying tennis and cricket ball is formulated and numerically solved. This makes it possible to analyze the trajectories of the ball for different initial conditions: elevation angles, velocity of ball. Then, the mathematical analysis of the launcher with two counter rotating rollers is presented.

Additive Manufacturing of Components for a Ball Machine Prototype

AbstractSports have become an important part of most people's lives. Every performance athlete goes through a series of workouts with different sports equipment meant to help their physical condition. Thus, the development of automated sports equipment that can throw a ball with a specific preset speed and trajectory is necessary to facilitate the work of the coach. The paper presents the additive manufacturing process of components for a ball machine prototype used for training athletes. Most of the components in the product's power system are made by additive manufacturing, this choice being conditioned by the appearance of innovative, customized component elements, used in the drive system. Material extrusion is used due to the custom shapes and sizes, specific to the developed product, which innovatively influence the principle of hitting the ball. Fusion 360 is used to design all components, taking into consideration material extrusion technological requirements and design principles. A basic static finite element analysis is performed on the main paddle component to ensure that it can withstand the stress scenario and the results showed that when using HIPS filament, the limit conditions are fully met. CAD files are saved as *.STL files and introduced in Z‐Suite software for parameter optimization according to the functional role of each component. The optimized *.ZCODEX files are sent to Zortrax M300+ machines for material extrusion 3D printing of the components. The final result is a functional prototype of a device that is obtained using mainly additive manufacturing.

Investigating the Knuckleball Effect in Soccer Using a Smart Ball and Training Machine.

The term knuckleball in sporting jargon is used to describe a ball that has been launched with minimal spin, resulting in a trajectory that is erratic and unpredictable. This phenomenon was first observed in baseball (where the term originated) and has since been observed in other sports. While knuckleball has long fascinated the scientific community, the bulk of research has primarily focused on knuckleball as it occurs in baseball. Following the changes in the design of the soccer ball after the 2006 World Cup, knuckleball and ball aerodynamics were exploited by soccer players. This research examined the properties of a knuckleball in the sport of soccer. We designed and evaluated a system that could reproduce the knuckleball effect on soccer balls based on previous theories and characteristics outlined in our literature review. Our system is comprised of the Adidas miCoach Smart Ball, a companion smart phone app for data collection, a ball-launching machine with programmable functions, and a video-based tracking system and Tracker motion analysis software. The results from the testing showed that our system was successfully able to produce knuckleball behaviour on the football in a highly consistent manner. This verified the dynamic models of knuckleball that we outline. While a small portion of the data showed some lateral deviations (zig-zag trajectory), this erratic and unpredictable trajectory was much smaller in magnitude when compared to examples seen in professional games. The sensor data from the miCoach app and trajectory data from the Tracker motion analysis software, showed that the knuckleballs were consistently reproduced in-line with theoretical dynamics.

Popularity of Mental Health Chatbots Grows

Popularity of Mental Health Chatbots Grows

Corn Oil Performance’s A Bio Cooling Fluid in Electric Distribution Transformer

Biodegradable (Vegetable) fluids are considered as environmentally friendly fluids and possess an abundant benefit, they are wildly available by means of renewable sources compared to different kinds of mineral-oil. Given the occurrence of environmental pollution and health problems from mineral oils. This paper investigates the effect of utilizing the corn oil for the cooling performing features of distribution electric transformer, and making a comparison with the cooling performance of the electric transformer whith cooling by the commercial mineral fluid. This investigation is done by using the four- ball machine and electric transformers. Each experiment that was executed complies with ASTM D4172-B under different electrical loads (200-1600W). Depending on the outcomes of the four-ball machine and electric transformer, it has been noticed that the corn oil has the adequate cooling behavior compared to the commercial cooling fluid. It maintains the insulation housing between the coils, and maintains the coils when overloaded at peak time.

Examining of the Effects of Target-Oriented Circular Training on Biomotor Features by using Tennis Ball Throwing Machine at 12-14 Age Tennis Performance Sportsmen for 10 weeks

Aim: In this work, it is aimed that examining the effects of target-oriented circular training on biomotoric features by using a tennis ball throwing machine at 12-14 age tennis performance sportsmen for ten weeks. Method: This research was implemented on sixteen active licensed athletes who played tennis for at least four years in Ankara. The athletes were randomly divided into two separate groups as the experimental group (n=8) and the control group (n=8). After measuring the height, weight, and fat rate of the athletes, biometric tests were started. Flamingo balance, sit-reach, reaction time, five meters and twenty meters sprints, T-test, and standing long jump tests were performed, respectively. Athletes were get heated for ten minutes before the tests and they were given a trying chance. The best scores were recorded by repeating each test twice. In the statistical analysis of the collected data, IBM SPSS 19 package program was used. In repeated measurements, the results were compared by two-way ANOVA with intergroup, intragroup and post-training data. Results: As a result, between the experimental group and control group data; on averages of T-Test (p&lt;0.139), visual reaction (p&lt;0.001), Flexibility (p&lt;0.024), Vertical Jump (p&lt;0.022), Flamingo Balance right foot (p&lt;0.046) and left foot (p&lt;0.045) statistical significance was confirmed. Keywords: Biomotoric features, ITN test, Tennis, Tennis ball machine

Pressures Exerted on the Hook of the Hamate in Collegiate Baseball Players: A Comparison of Grips, With Emphasis on Fracture Prevention.

Background:Variations in batting technique may put baseball players at increased risk of hook of the hamate fractures. A better comprehension of the mechanism of such fractures is needed.Purpose/Hypothesis:The purpose of the study was to compare 2 different grip types to quantify the pressures exerted on the hook of the hamate during batting. It was hypothesized that when compared with the conventional batting style, players holding the knob of the bat in the palm of the hand (termed the “palmar hamate grip”) would have higher pressures exerted on the hook of the hamate.Study Design:Controlled laboratory study.Methods:Athletes were recruited for participation on a volunteer basis from the rosters of 2 National Collegiate Athletic Association Division I baseball teams and were divided into 2 groups based on their usual grip type. A force sensor system was applied to the nondominant hand of each participating player, with the central portion of the sensing mechanism placed on the batting glove directly over the hook of the hamate. All players used the same batting glove, which transmitted data from the sensor to a laptop computer. Measurements were collected on consecutive hits at a standardized distance using a ball machine at 70 mph.Results:Nine collegiate baseball players underwent testing (5 players exclusively used the conventional grip, 3 players exclusively used the palmar hamate grip, and 1 player naturally alternated between the 2 grip types). The palmar hamate grip demonstrated a 366% increase in pressure exerted on the sensor overlying the hook of the hamate when compared with the conventional batting grip (536.42 kPa [95% confidence interval, 419.39-653.44 kPa] vs 115.84 kPa [95% confidence interval, 96.97-135.10 kPa]). The player who used both grips demonstrated significantly higher maximum pressure when using the palmar hamate versus conventional grip (482.90 vs 142.40 kPa; t = 6.95; P < .0001).Conclusion:Use of the palmar hamate grip may increase the risk of hook of the hamate fracture in National Collegiate Athletic Association Division I baseball players.Clinical Relevance:Educating players on the risks associated with the palmar hamate grip may prevent injury and minimize time out of competition.

Tribological behavior of environmentally friendly borate ionic liquids with low corrosion degree

Two novel halogen-free liquids additives [DHB][BScB] and [MA-BIm][BScB] are synthesized and their tribological performance in 500 N base oil are evaluated using 4-ball machine for the first time. The results show that [DHB][BScB] and [MA-BIm][BScB] can decrease the friction coefficient of 500 N base oil by 42.7% and 42.1% at 2.5 wt% concentration respectively and they both possess excellent corrosion resistance. According to the analysis results of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), [DHB][BScB] and [MA-BIm][BScB] can form chemical films consisting of iron oxide and B2O3 on the worn steel surface. In addition, a lubrication mechanism is speculated and there may be a competitive adsorption between anion and cation.

Influence of the dendritic microstructure and β-Al5FeSi phase on the wear characteristics in a horizontally solidified Al-7Si-0.4Mg-1.2Fe alloy

In this work an Al-7Si-0.4Mg-1.2Fe alloy (wt.%) was subjected to a horizontal solidification experiment using a water-cooled solidification device equipped with thermocouples to obtain temperature vs. time data which in turn allowed solidification thermal parameters, such as growth and cooling rates (VL and TR, respectively), to be determined. In turn, tribological behavior of samples with different secondary dendritic spacing (λ2) and β-Al5FeSi platelets length (βFe) were assessed by means of dry sliding wear testing performed in a rotating fixed ball machine, with wear volume and rate (WV and WR, respectively) being the two main investigated wear parameters. Quantitative metallography by optical and scanning electron microscopy along with energy dispersive X-ray spectroscopy enabled both as-cast microstructures and worn craters to be characterized. More significant variations in wear resistance of the investigated alloy were found for ranges of λ2 and βFe that lie within 12−20 μm and 14–36 μm, respectively, with the coarsening of the microstructure constituted by Al-rich primary phase dendrites surrounded by α-Al + Si + θ-Mg2Si + β-Al5FeSi eutectic structures favoring reduced WV and WR values. For λ2 and βFe values higher than 24 and 48 μm, respectively, both WV and WR stabilize assuming constant values that depend on the sliding distance. In addition to power type equations relating λ2 and βFe to VL and TR, mathematical expressions for variations of WV and WR with λ2 and βFe are also proposed. Finally, a comparative analysis with the literature is presented.

SR EN ISO 20623 - A standard for tribological evaluation of lubricants that may bust innovation

This paper presents the opportunities offered for research by using the four ball machine and the procedures included in SR ISO 20623:2018. There are presented results of research studies that are started from the procedures and parameters included in standard, but also wear and friction parameters that derived from recording friction and wear scar dimensions and texture parameters.

Synthesis and evaluation of stearic acid based heterocyclic Schiff bases as biolubricant additives in epoxy karanja fatty acid 2-ethyl hexyl esters base oil

Four novel stearic acid derived Schiff bases containing heterocyclic aromatic groups (furan, thiophene, pyrrole and pyridine) were synthesized in a three step reaction procedure. All the products were characterized by FT-IR, NMR and ESI-MS. The lubricity and antioxidant properties of synthesized Schiff bases were evaluated with 4-ball machine and differential scanning calorimeter. The morphologies and composition of elements on the worn surfaces were studied by using scanning electron microscope and energy-dispersive X-ray spectroscopy. Results show that these stearic acid based derivatives possess good tribological properties and antioxidant performance. The difference in the additive performance of the derivatives is closely related to the difference in their molecular structure. Pyridine containing Schiff base was more effective as both antiwear and extreme pressure additive while thiophene derivative exhibited higher efficacy as antioxidant.

Motion-Onset Visual Potentials Evoked in a Sport-Specific Visuomotor Reaction Task.

Although neural visual processes play a crucial role in sport, experiments have been restricted to laboratory conditions lacking ecological validity. Therefore, this study examined the feasibility of measuring visual evoked potentials in a sport-specific visuomotor task. A total of 18 international elite young table tennis athletes (mean age 12.5 years) performed a computer-based and a sport-specific visuomotor reaction task in response to radial motion-onset stimuli on a computer screen and table tennis balls played by a ball machine, respectively. A 64-channel electroencephalography system identified the N2 and N2-r motion-onset visual evoked potentials in the motion-sensitive midtemporal visual area. Visual evoked potential amplitudes were highly correlated between conditions (N2 r = .72, N2-r r = .74) although significantly lower in the sport-specific task than in the lab-based task (N2 p < .001, N2-r p < .001). The results suggest that sport-specific visual stimulation is feasible to evoke visual potentials. This emphasizes the investigation of visual processes under more ecologically valid conditions in sport and exercise science.

Study of tribological properties and lubrication mechanism of surfactant-coated anthracite sheets used as lubricant additives

Anthracite sheets were coated by sorbitol fatty acid ester (span80) through ball-milling process. The tribological properties of the span80-coated anthracite sheets as the additive in polyalpha olefin were evaluated through a series of friction tests using a four ball machine. The results revealed that the span80-coated anthracite sheets exhibited excellent dispersion stability in base oil. In addition, compared with base oil, the average coefficient of friction, wear scar diameter, and wear volume of modified oil at a mass fraction of 0.03% span80-coated anthracite sheets decreased by 45.39%, 60.13%, and 95.95%, respectively. The oil containing span80-coated anthracite sheets achieved good friction-reducing and anti-wear effects over a wide range of applied loads, temperatures, or rotating speeds. Control experiments were performed as well. The results obtained using span80-coated anthracite sheets were superior to those obtained using pure anthracite. The lubrication mechanism was attributed to the synergistic action of the crystalline and amorphous carbon in anthracite sheets as they formed a protective film and played a mitigative role on the surface of friction pair, which mitigated the wear extent of the friction pair.

Evaluation of the influence of granulation of hexagonal boron nitride on the lubricity properties of the base grease

The paper presents the tests results of lubricity properties of base greases, containing hexagonal boron nitride (h-BN). To conduct the required tests, a four ball machine was used. This device is commonly used when assessing lubricity properties of oils and greases. The following normative lubricity parameters were defined: welding point Pz [daN], the value of last non-seizing load Pn [daN], seizing at smoothy growing load Pt [daN], as well as the wear limiting capacity load Goz [daN/mm2]. Furthermore, several non-normative tests were completed that covered indication of two parameters making it possible to complete an assessment of lubricity properties of oils. Based on the conducted research, it was found that hexagonal boron nitride is an additive that improves the lubricating properties of the base grease. The best effects of the improvement, taking into account the adopted tribological criteria, were noted for a sample containing 10% (m/m) hexagonal boron nitride with an average grain diameter of 65÷75 nm. It was found that the lower granulation of the additive (h-BN) positively influences the efficiency of the grease lubrication of the base, under the conditions of tests on a four-ball model apparatus. Keywords: tribology, lubricity, boron nitride, greases