Total Pitch Research Articles

Pitch break and performance metrics remain unchanged in pitchers who returned to the same level of play after ulnar collateral ligament reconstruction in Major League Baseball pitchers.

The ulnar collateral ligament is commonly injured in overhead-throwing athletes, particularly baseball pitchers. Pitch movement (break) is a critical aspect to pitching performance. The primary purpose of this study was to determine the changes in pitch velocity, pitch break, angle of break, and pitch performance metrics before and after ulnar collateral ligament reconstruction (UCLR) in Major League Baseball (MLB) pitchers. The secondary purpose was to determine changes in pitch performance metrics before and after UCLR. We hypothesized that pitch break and pitch performance metrics would be unchanged following UCLR. This was a retrospective case-series study of pitchers who had undergone primary UCLR between 2008 and 2014. Velocity, horizontal movement (Hmov), and vertical movement (Vmov) of each pitch were collected from the PITCHf/x system for each pitcher 12-24 months before surgery, 12-24 months after surgery, and 24-36 months after surgery. Overall break was calculated by taking the Pythagorean sum of Hmov and Vmov. Angle of break was determined by taking the inverse tangent of Vmov divided by Hmov. Repeated-measures analysis of covariance was performed to determine differences in pitch velocity, movement, angle of movement, and performance metrics between preoperative and postoperative time frames. Performance metrics included balls, strikes, swings, fouls, swings and misses, ground balls, line drives, pop-ups, fly balls, and home runs. Covariates included age at surgery, time from MLB debut to surgery, innings pitched as a starter, innings pitched as a reliever, and total pitches thrown. In a cohort of 46 pitchers who underwent UCLR between 2008 and 2014, pitch velocity, movement, and angle were not significantly changed with respect to preoperative or postoperative time frames. In addition, postoperative time frames had clinically insignificant differences in pitch performance metrics. Pitch break and performance metrics are not significantly affected in pitchers who return after UCLR.

Association of Pitch Timing and Throwing Arm Kinetics in High School and Professional Pitchers

Background: Understanding the relationship between the temporal phases of the baseball pitch and subsequent joint loading may improve our understanding of optimal pitching mechanics and contribute to injury prevention in baseball pitchers. Purpose: To investigate the temporal phases of the pitching motion and their associations with ball velocity and throwing arm kinetics in high school (HS) and professional (PRO) baseball pitchers. Study Design: Descriptive laboratory study. Methods: PRO (n = 317) and HS (n = 54) baseball pitchers were evaluated throwing 8 to 12 fastball pitches using 3-dimensional motion capture (480 Hz). Four distinct phases of the pitching motion were evaluated based on timing of angular velocities: (1) Foot-Pelvis, (2) Pelvis-Torso, (3) Torso-Elbow, and (4) Elbow-Ball. Peak elbow varus torque, shoulder internal rotation torque, and shoulder distraction force were also calculated and compared between playing levels using 2-sample t tests. Linear mixed-effect models with compound symmetry covariance structures were used to correlate pitch velocity and throwing arm kinetics with the distinct temporal phases of the pitching motion. Results: PRO pitchers had greater weight and height, and faster ball velocities than HS pitchers (P < .001). There was no difference in total pitch time between groups (P = .670). PRO pitchers spent less time in the Foot-Pelvis (P = .010) and more time in the Pelvis-Torso (P < .001) phase comparatively. Shorter time spent in the earlier phases of the pitching motion was significantly associated with greater ball velocity for both PRO and HS pitchers (Foot-Pelvis: B = −6.4 and B = −11.06, respectively; Pelvis-Torso: B = −6.4 and B = −11.4, respectively), while also associated with increased shoulder proximal force (Pelvis-Torso: B = −76.4 and B = −77.5, respectively). Decreased time in the Elbow-Ball phase correlated with greater shoulder proximal force for both cohorts (B = −1150 and B = −645, respectively) with no significant correlation found for ball velocity. Conclusion: Significant differences in temporal phases exist between PRO and HS pitchers. For all pitchers, increased time spent in the final phase of the pitching motion has the potential to decrease shoulder distraction force with no significant loss in ball velocity. Clinical Relevance: Identifying risk factors for increased shoulder and elbow kinetics, acting as a surrogate for loading at the respective joints, has potential implications in injury prevention.

PITCHING IN YOUTH SOFTBALL: HOW MUCH ARE PITCHERS THROWING?

Background:Softball is a popular sport among youth female athletes. While multiple youth baseball studies have evaluated the relationship of injury to pitch counts, there is a paucity of literature for youth softball. In contrast to the numerous youth baseball leagues adhering to pitching guidelines, pitch counts are frequently not enforced in youth softball which results in pitchers with exceedingly high volumes.Purpose:The purpose of this study was to perform a quantitative analysis of pitching volume in youth softball players. We hypothesized that the majority of pitches would be thrown by a small proportion of pitchers on each team.Methods:Seventy youth softball teams including 538 pitchers competing in age brackets eight and under (8U) to fourteen and under (14U) between Spring 2017 and Fall 2019. Game dates and pitch counts were collected for each player using an electronic application. Games played on two or more consecutive days were defined as a tournament. The three highest-volume pitchers from each team defined by total season pitches were analyzed for comparison to the average pitcher.Results:538 pitchers on 70 teams were included. The average pitcher threw 813 pitches per year and appeared in 20.0% of games and the average high-volume pitcher threw 2500 pitches per year and appeared in 54.5% of games. The highest-volume pitcher from each team threw 40% of all recorded pitches, the second highest 27.2%, and the third highest 15.2%, totaling 82.4% of all team pitches. Single day pitch counts of >100 and >200 occurred in 17.7%, and 1.1% of same day games with the average pitcher and in 31.2%, and 2.4% of same day games with the average highest-volume pitcher. Tournament pitch counts of >100 and >200 occurred in 51.0% and 13.8% of tournaments with the average pitcher and in 81.4% and 30.8% of tournaments with the average highest-volume pitcher. The average and highest-volume pitcher threw pitches in two or more games on the same day in 37.5% and 48.6% of possible games while pitching two or more consecutive days in 64.0% and 79.6% of possible games, respectively.Conclusion:Softball pitchers throw high volumes of pitches while also pitching multiple days consecutively. A disparity among pitchers on softball teams exists as 82.4% of team pitches are thrown by three pitchers. These high-volume pitchers may be engaging in unsustainable pitching practices that could predispose to injury.Tables:

Study of added resistance and seakeeping of KVLCC2 in waves with and without propeller

Numerical simulation of a full-scale ship model, KVLCC2, has been conducted applying the Reynolds Averaged Navier-Stokes (RANS) approach using the STARCCM+ commercial computational fluid dynamics (CFD) software to calculate total resistance, seakeeping and Pitch Moments. Results are obtained for the speed of 15.5 Knots under different sea conditions (calm water, regular waves and irregular waves), The total resistance calculated for the KVLCC2 ship hull in calm water is in a good agreement with the results from experiments and the results for motion (heave and pitch) and added resistance in waves were compared to numerical and experimental findings from previous research with good agreement. In addition to wave excitations, the full-scale ship model was subjected to propeller excitations using the virtual disk model from the CFD software. The body force propeller method, which simplified the full propeller characteristic of the KVLCC2 into a resultant body force, is applied to the virtual disk model. Results are compared with results from the hull-only model. A comparison of the wake results with previous work is also presented.

Robust Constrained Trajectory Tracking Control for Quadrotor Unmanned Aerial Vehicle Based on Disturbance Observers

Abstract In this paper, a trajectory tracking control scheme for a quadrotor unmanned aerial vehicle (UAV) under unknown external disturbance and input saturation is developed. This scheme includes the position control system and attitude control one, in which the attitude control system is further divided into the fast loop for angular velocity and the slow one for attitude angle based on time-scale separation principle. Then, an input constrained dynamic surface control scheme combined with a disturbance observer is designed to achieve the total thrust, desired roll, and pitch angle in the position control system. For the coupled attitude system, a dynamic surface control scheme together with generalized model predictive controller (GMPC) is proposed to tackle both the fast loop system and the slow one. Since the unknown external disturbance and input saturation are considered, a sliding mode disturbance observer (SMDO) is further designed to achieve the strong robustness. Finally, some simulation results are presented to show robustness and effectiveness of our proposed tracking scheme.

Accelerated Muscle Recovery in Baseball Pitchers Using Phase Change Material Cooling.

The purpose of this study was to document recovery after a pitching performance and determine whether prolonged postgame phase change material (PCM) cooling of the shoulder and forearm accelerates recovery. Strength, soreness, and serum creatine kinase (CK) activity were assessed before and on the 2 d after pitching performances in 16 college pitchers. Pitchers were randomized to receive either postgame PCM cooling packs on the shoulder and forearm or no cooling (control). PCM packs were applied inside compression shirts and delivered cooling at a constant temperature of 15°C for 3 h. Strength was assessed for shoulder internal rotation (IR), external rotation (ER), empty can (EC) test, and grip. Total pitch count was 60 ± 16 for 23 PCM cooling games and 62 ± 17 for 24 control games (P = 0.679). On the days after pitching, IR strength (P = 0.006) and grip strength (P = 0.036) were higher in the PCM cooling group versus control. One day after pitching, IR strength was 95% ± 14% of baseline with PCM cooling versus 83% ± 13% for control (P = 0.008, effect size d = 0.91) and 107% ± 9% versus 95% ± 10% for grip strength (P = 0.022, effect size d = 1.29). There was a trend for greater ER strength with PCM cooling (P = 0.091, effect size d = 0.51). The EC strength was not impaired after pitching (P = 0.147) and was therefore unaffected by PCM cooling (P = 0.168). Elevations in soreness and CK were not different between treatments (treatment-time CK P = 0.139, shoulder soreness P = 0.885, forearm soreness P = 0.206). This is one of the first studies to document impairments in muscle function on the days after baseball pitching, and the first study showing a novel cryotherapy intervention that accelerates recovery of muscle function in baseball pitchers after a game.

Influence of MQL and hobbing parameters on microgeometry deviations and flank roughness of spur gears manufactured by MQL assisted hobbing

Conventional cutting fluids used in gear hobbing have negative impacts on the environment and health of the machine operators thereby adversely affecting the sustainability of the gear hobbing process. This paper reports on MQL assisted hobbing (MQLAH) using environment friendly fatty alcohol-based lubricant to manufacture superior quality spur gears. Experimental investigation was conducted to study of influence of six parameters of MQLAH namely hob cutter speed, axial feed, depth of cut, lube flow rate, air pressure, and nozzle angle on microgeometry deviations, avg. and max. values of flank surface roughness, and material removal rate to identify their optimum ranges to manufacture better quality spur gears with maximum productivity. Deviations in total profile, lead, cumulative pitch and radial runout were used to evaluate microgeometry of the spur gears. It revealed that depth of cut has no considerable effect on the spur gear quality. It identified that higher value of hob cutter speed, lower value of axial feed, optimum values of lube flow rate as 100 ml/h, nozzle angle as 30°, and air pressure in a range from 3 to 5 bar yield superior quality of spur gears by MQLAH.

Predictive modelling and parametric optimization of minimum quantity lubrication–assisted hobbing process

This paper focuses on parametric analysis, modelling, and parametric optimization of minimum quantity lubrication–assisted hobbing (MQLAH) using an environment-friendly lubricant for manufacturing superior quality spur gears. Influences of hob cutter speed, axial feed, lubricant flow rate, air pressure, and nozzle angle on the deviations in total profile, total lead, total pitch and radial runout, and flank surface roughness parameters were studied by conducting 46 experiments using the Box-Behnken method of response surface methodology. Results revealed that the effect of air pressure is negligible but other parameters have a significant impact on the considered responses. A back propagation neural network (BPNN) model was developed to predict microgeometry deviations and flank surface roughness values of the MQLAH-manufactured spur gears. The BPNN-predicted results are found to be very closely agreeing with the corresponding experimental results with a mean square error as 0.0063. A real-coded genetic algorithm (RCGA) was used for parametric optimization of MQLAH process for simultaneous minimization of microgeometry deviations and flank surface roughness. Standardized values of the optimized parameters were used to conduct confirmation experiments whose results had very good closeness with RCGA-computed and BPNN-predicted values and produced spur gears of superior quality. This study proves MQLAH to be a potential sustainable replacement of conventional flood lubrication–assisted hobbing for manufacturing cylindrical gears of better quality.

The Rotor and Tower Vibrations Damping Monitoring in the Case of Total Pitch Servomotors Failure

In this paper, a strategy is proposed to deal with the total pitch actuator failure in the modern wind turbines. The fault is firstly detected using a suitable proportional residual which rises when the measured rotor dynamics match the pure wind turbulence driven dynamics of the reference model. The fault tolerant control method relies on the distribution of the control signal on the remaining actuators, namely the generator torque and the yaw actuator. The pseudo inverse is applied on the residual between the measured and the nominal dynamics of the tower and the rotor. The distributed control signal is then suitably filtered in order to match the production and the safety objectives. Firstly, the generator torque filter comes to minimize the high frequencies on the rotor speed for a stable production to the grid. Secondly, the band pass yaw angle filter comes to minimize the mean yaw misalignment between the yaw nacelle and the wind direction. The method shows good dynamics reconstruction capabilities while keeping a stable production within a safe environment.

Prediction of the Dynamic Response of a Ship in Head Waves Using OpenFOAM Toolbox

Ships and marine structures, such as oil tanker, offshore platforms, etc., usually face extreme seaway environment in real situation. If under the action of strong waves large amplitude motions will occur, with the result that they may not work as usual or even lose stability. Thus, it is of great importance to access their dynamic responses under such bad conditions at the initial design stage, so as to ensure normal usage and safety. Herein, the original RANS (Reynolds-Averaged Navier-Stokes) solver based on OpenFOAM Toolbox has been extended to predict dynamic responses of ships and marine structures in waves. A new “inlet-velocity boundary condition” was implemented to generate waves. A damping term for wave absorption was added to the right-hand side of RANS equations in order to avoid wave reflection from the boundary where waves leave the computational domain. The related numerical methods are described in this paper. The purpose of this paper is to present a validation of the approach used. The prediction of the dynamic response of a ship in head waves was the focus. Five cases with different wave lengths and heights were considered. The predicted results, i.e. time histories of total resistance, heave and pitch, were compared with available experimental data and analysed. In addition, due to current experience it is very necessary that effort is devoted to determining appropriate grid and time step, so as to ensure the quality of waves generated.

Numerical study of heat transfer performance of helical coiled tubes for heating high-solids slurry in household biogas digester

A computational fluid dynamics model to simulate conjugate heat transfer between a helical coiled tube and high-solids fermentation slurry in a household biogas digester was developed. The model simulation results were then verified using field experiment results. The effect of total solids concentration, pitch, helical diameter, and tube materials on the thermal performance of the helical coiled tubes were analysed. The results show that the accuracy of the numerical model that was based on the rheological and thermal parameters of the fermentation slurry was significantly improved compared with that based on the corresponding water parameters. As the total solids concentration increased, the zero-shear viscosity of the slurry significantly increased and the heat transfer performance of the helical coiled tubes was notably weakened. In the high-solids fermentation slurry, the influence of pitch on the heat transfer coefficient of the coiled tubes was greater than that of the helical diameter. The difference in the rates of total thermal resistance between cross-linked polyethylene (PEX) and metal (stainless steel and copper) coiled tubes was small for the high-solids fermentation slurry compared to that for the water. Therefore, low-cost PEX coiled tubes are more suitable for high-solids fermentation slurry than metal tubes in household biogas digesters.

Aerodynamic Loading Induced by Muzzle Flows on Small Caliber Spin Stabilized Projectiles

Abstract In this study, we examined the aerodynamic loading on a small caliber rifle (spin stabilized) projectile moving in a muzzle flow field using an element method to analyze the loading and the effect of the angle of attack (for small angles from 0 to 3 deg) on the different components. The temporal pressure distribution on the projectile, which forms the basis of the element method, was computed using a computational fluid dynamics (CFD) analysis combined with a classical interior ballistics model. Then, a high-speed optical experiment was conducted to verify the results of the CFD method and ensure the accuracy of the calculations. The results were as follows: (a) similar to a large caliber projectile, the total axial force, which consisted primarily of the axial forces on the base and boattail, was found to have an inverse exponential relationship with time; (b) the overall lift was a combination of the lift of the base, boattail, cylinder, and nose; and (c) the interaction between the pitch moment of the base and that of the boattail was found to be the primary contributing factor to the total pitch moment. Based on these results, we recommend that the characteristics of the base and boattail be considered when specifying the geometric configuration of a projectile.

Combining double patterning with self-assembled block copolymer lamellae to fabricate 10.5 nm full-pitch line/space patterns

Directed self-assembly of block copolymers and self-aligned double patterning are two commonly used pitch scaling techniques to increase the density of lithographic features. In this work, both of these pitch scaling techniques were combined, enabling patterning at even higher densities. In this process, directed self-assembly of a high-χ block copolymer was used to form a line/space pattern, which served as a template for mandrels. Via these mandrels, atomic layer deposition was used to deposit a thin aluminium oxide spacer. By this method, a total pitch scaling factor of 8, equivalent to a 10.5 nm full pitch, was reached. The types of defects and the line roughness at the different steps of the process were discussed.

Effect of installation errors on beveloid gears’ precision ground by cone-shape worm wheel

Both the mathematical model of a cone-shape worm wheel and the mathematical model of cone-shape worm wheel grinding beveloid gears with installation errors of a gear workpiece and a cone-shape worm wheel are developed. The effect of the installation errors including gears’ incline error, eccentric error, mounting angle error of a cone-shape worm wheel and coupling error of installation errors mentioned on gears’ surface deviation is investigated. The sensitivity of tooth surface deviation to installation errors mentioned is analyzed. The results show that the helix slope deviation, helix total deviation and tooth cumulative pitch deviation are more sensitive to gears’ incline error. The tooth cumulative pitch deviation, profile total deviation, profile slope deviation are more sensitive to gears’ eccentric error. The effect of gears’ incline error and eccentric error on cumulative pitch deviation and individual cumulative pitch deviation is inverse which lead that coupling error including gears’ incline error and eccentric error causes smaller cumulative pitch deviation and individual cumulative pitch deviation compared to gears’ incline error or eccentric error. Moreover Effect of the mounting angle error of cone-shape worm wheel on gears’ surface deviation is very limited.

Study on the influence of pumping system on the hydrodynamic performance of air tanker

The influence of the pumping system on the hydrodynamic performance of the air tanker were investigated in this paper. The hydrodynamic performance of the air tanker with different displacements under the different Froude numbers was studied by experimental method. RANS methods and overset mesh were used to compute the viscous flow field of an air tanker under three conditions at different Froude numbers. Numerical method adopted in this paper was verified and validated by comparing the experimental results with the simulation results. The experimental results showed that the total resistance and the heave amplitude of air tanker with different displacements increased, while the pitch angle decreased, as the speed increased. And the larger the displacement, the greater the total resistance, pitch angle and heave amplitude. The simulation results showed that the drainage efficiency, the load of the baler and the additional pitching moment showed non-linear growth with increasing speed. As the baler lowered, the total resistance and heave amplitude of the aircraft increased, but the pitch reduced. The effect on the hydrodynamic performance of air tanker was not obvious as the baler closed.

Pediatric dysphonia: It's not about the nodules

ObjectiveDespite the fact that vocal nodules are the most common cause of chronic dysphonia in children, uncertainty and lack of consensus complicates practically every diagnostic and management decision. Selecting an optimal staging system is fundamental to understanding a disease process, mandatory for uniform reporting, and crucial to predicting natural history and treatment outcomes. The ideal prognostic model for vocal nodules is under intense debate. The purpose of this study was to analyze the predictive power of vocal nodule grade to severity of voice metrics in children. MethodsSeventy-nine patients diagnosed with vocal cord nodules between 2006 and 2012 were drawn from UPMC Children's Hospital of Pittsburgh Voice, Resonance and Swallowing Center Research Registry. Subject age at time of diagnosis, nodule grade, relevant co-morbidities, scores on The Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V), parent-reported Pediatric Voice Handicap Index (pVHI), the phonotraumatic behaviors profile, habitual speaking pitch fundamental frequencies, pitch range, volume intensity, and s/z ratio were recorded and compiled into a de-identified database for analysis. ResultsBased on the Kruskal-Wallis H Test, there was no statistically significant correlation between nodule grade and total pitch range (p = .21), s/z ratio (p = .50), volume intensity (p = .33), overall CAPE-V Scores (p = .15), or pVHI Scores (p = .29). Chi-squared tests also revealed no significant associations between nodule grade and abnormality in habitual speaking pitch (p = .14 for fundamental frequency while sustaining a vowel sound, p = .37 for fundamental frequency while speaking structured tasks i.e. counting, or p = .76 while speaking in conversation). ConclusionThe current “gold-standard” for grading vocal nodule size suggests that the nodules themselves are not driving the standard dysphonic metrics that are most commonly collected and monitored in such children. This outcome is consistent with other studies reporting similar findings and was expected based on the inconsistencies in the reported literature to date. By extension, the conventional wisdom of avoiding surgical treatment of vocal nodules in children seems prudent as there is little evidence to suggest that the nodules themselves are “driving” the severity of the dysphonia. Ultimately identifying the true “drivers” of dysphonia in children will suggest alternative therapies that are more specific and directed to the pathophysiology. Most pediatric voice care professionals will welcome such discoveries as those in the front line of patient care are often rendered helpless and frustrated.

Shoulder and Elbow Range of Motion Can Be Maintained in Major League Baseball Pitchers Over the Course of the Season, Regardless of Pitching Workload.

Background:Studies examining the evolution of shoulder and elbow range of motion (ROM) in baseball pitchers over a single season have yielded inconsistent results.Purpose:To evaluate shoulder and elbow ROM in Major League Baseball (MLB) pitchers over a single season and to assess for correlations between these changes and measures of a pitcher’s workload.Study Design:Case-control study; Level of evidence, 3.Methods:Bilateral shoulder ROM (internal rotation [IR], external rotation [ER], and total range of motion [TROM]) was assessed in 92 MLB pitchers pre- and postseason. Shoulder forward flexion (FF) was measured in 64 pitchers, horizontal adduction (HA) was measured in 87 pitchers, and elbow ROM was measured in 86 pitchers. Data collected included demographics (age, height, weight, and body mass index) and measures of workload for pitchers (pitches thrown, innings pitched, and mean fastball velocity). Pitchers were not specifically excluded if they had an injury during the season but had recovered and were actively pitching at the time of postseason measurements. The change in motion from pre- to postseason was measured and the associations with player demographics and workload were calculated by use of the Pearson correlation coefficient.Results:On average, pitchers demonstrated an increase in dominant shoulder ER from 118.8° to 125.4° (P < .001) and TROM from 173.1° to 181.7° (P < .001). HA was increased by an average of 15.7° (P < .001). The average shoulder IR (P = .189), FF (P = .432), and elbow ROM (flexion, P = .549; extension, P = .185) remained similar over the span of the season. Average glenohumeral IR deficit did not increase. Pitcher demographics and measures of throwing workload (total pitches thrown, innings pitched, mean fastball velocity) were not significantly correlated with changes in shoulder or elbow ROM.Conclusion:Significant increases in dominant shoulder ER, TROM, and HA were identified in MLB pitchers over the course of a single baseball season. These ROM changes were not correlated with measures of pitching workload.

Investigation of planing vessels motion using nonlinear strip theory – an experimental and numerical study

ABSTRACTThis study is aimed to improve Zarnick’s (1978, A nonlinear mathematical model of motions of a planing boat in regular waves. David W. Taylor Naval Ship Research and Development Center, Bethesda, MD, USA) analytical model for motions of planing vessels. A nonlinear time domain mathematical model was developed for dynamic behaviour of longitudinal motion of high-speed planing crafts in regular waves. This model was based on two-dimensional strip theory method using expanding wedge theory and momentum. Due to the nonlinearity and complex dynamic behaviour of these vessels, the time-domain simulation was adopted. Total resistance, heave and pitch motions as well as acceleration were found very sensitive to hydrodynamic coefficients. Furthermore, a set of forced oscillation and seakeeping tests on a vessel were carried out for different conditions at the Marine Engineering Research Centre of Sharif University of Technology (MERC). The effect of velocity, wavelength, and hydrodynamic coefficients were investigated on vessel motions. According to the results, decreasing added mass coefficients, velocity of the model increases. The amplitude of heave and pitch motions declined due to an increase in velocity, within the tested speed range, or by reduction of λ/L ratio. Hydrodynamic coefficients of the mathematical model have been modified accordingly, and the model represented a better agreement with the experimental data obtained by Fridsma (1969. A systematic study of the rough-water performance of planing boats. Tech. Rep. Davidson Laboratory, Stevens Institute of Technology, Hoboken, NJ, USA). This model was applied to identify the nonlinear dynamics of these vessels in both semi-planing and planing phases that can be further expanded to hybrid vessels in the future.

The characteristics of coaches that verbally and physically abuse young baseball players using a self-reported questionnaire

BackgroundBecause the relationship between coaches and athletes is unequal, verbal and physical abuse remains a common problem among sports coaches. We aimed to elucidate the characteristics of baseball coaches who verbally/physically abuse young baseball players. MethodsA cross-sectional study was conducted on youth sports team coaches in Miyagi prefecture, Japan (n = 380), using a self-reported questionnaire. Multivariate logistic regression models were used for the analyses, evaluating the following variables: sex, age, educational level, smoking habits, years of coaching, level of baseball-playing experience, personal experience with verbal/physical abuse by former coaches, satisfaction with athletes’ attitudes, number of athletes on the team, team competition level, awareness of the recommendations of the Japanese Society of Clinical Sports Medicine, limitations in the total pitch count, difficulty in coaching in other positions, number of games per year, and acceptance of former verbal/physical abuse. ResultsThe prevalence of verbal/physical abuse toward young athletes was 74.5% (n = 283) and 6.6% (n = 25), respectively. Verbal abuse was significantly associated with personal experience of verbal abuse by former coaches (odds ratio [OR]: 2.00, 95% confidence interval [95% CI]: 1.04–3.85), and acceptance of verbal/physical abuse (OR: 2.61, 95% CI: 1.34–5.10). Physical abuse was significantly associated with greater than 10 years of coaching experience (OR: 7.16, 95% CI: 1.36–37.78), personal experience with physical abuse by former coaches (OR: 4.25, 95% CI: 1.23–14.70), and acceptance of verbal/physical abuse (OR: 3.85, 95% CI: 1.51–9.84). ConclusionsCoaches’ experiences with verbal/physical abuse by former coaches negatively affected young athletes. Breaking this cycle is necessary to keep athletes active and interested in playing baseball. Level of evidenceLevel III.

Study of laser texturing assisted abrasive flow finishing for enhancing surface quality and microgeometry of spur gears

This paper reports on study of laser texturing assisted abrasive flow finishing (LT-AFF) process of the hobbed spur gear (HSG) to further improve their microgeometry, surface finish, micohardness, microstructure, wear resistance, and material removal rate (MRR) as compared to AFF process. Preliminary experiments were conducted to identify optimum values of power and focal length of the continuous fiber laser of 1064-nm wavelength, and number of passes for laser texturing of the HSG made of 20MnCr5 alloy steel. Identified optimum values were used to produce homothetic texture on flank surfaces of HSG in a direction perpendicular to the lay profile generated by hobbing. Influence of laser texturing was studied by comparing deviations in microgeometry, average and maximum surface roughness values, microhardness, wear resistance, and MRR of HSG directly finished by AFF and laser-textured hobbed spur gears (LTHSG) finished by AFF. Previously optimized value of viscosity of AFF medium was used during finishing of HSG and LTHSG. Deviations in total profile, total lead and total pitch, and radial runout were used to indicate deviation in microgeometry of the spur gears. Results reveal that AFF of LTHSG reduced surface roughness and errors in microgeometry and improved microhardness, microstructure, wear resistance, and MRR than direct of AFF of HSG. Improved microgeometry and surface quality of spur gears will lead to their increased operating performance and service life thus reducing their running noise and vibrations and preventing their premature and failures. This research proves that productivity of AFF process can be improved significantly by laser texturing for finishing the spur gears.