Pitch Velocity Research Articles

Intra- versus inter-pitcher comparisons: Associations of ball velocity with throwing-arm kinetics in professional baseball pitchers.

The association between ball velocity and elbow varus torque has shown differences when evaluated within a single pitcher and within a cohort. The impact of increasing ball velocity on additional throwing-arm kinetics, in particular shoulder distraction forces, with intra- vs. inter-pitcher evaluations has not been evaluated, even though these kinetic measures have been implicated in injury risk. The purpose of this study was to compare intra- vs. inter-pitcher relationships between ball velocity and all major kinetics at the shoulder and elbow in professional pitchers. A total of 323 professional baseball pitchers threw 8-12 fastball pitches while simultaneously being evaluated with 3-dimensional motion-capture technology (480 Hz). A linear regression analysis was performed to evaluate pitch velocity as a predictor of peak kinetic values at the shoulder and elbow among pitchers. A linear mixed model with random intercepts was then created to evaluate ball velocity as a predictor of peak kinetic values when comparing pitches within an individual pitcher. 91 pitchers were included in the analyses. Ball velocity among pitchers had weak correlations with shoulder distraction force (R2 = 0.228, P < .001) and elbow distraction force (R2 = 0.175, P < .001). Within an individual pitcher, strong correlations (R2 > 0.85) were observed for (1) shoulder internal rotation torque (P < .001), (2) shoulder horizontal adduction torque (P = .006), (3) shoulder superior force (P < .001), (4) shoulder anterior force (P < .001), (5) elbow varus torque (P < .001), (6) elbow medial force (P < .001), (7) elbow anterior force (P < .001), (8) elbow flexion torque (P < .001), (9) shoulder distractive force (P < .001), and (10) elbow distractive force (P < .001). Faster pitch velocity is a weak predictor of shoulder and elbow distraction forces experienced among professional pitchers. However, when controlling for an individual pitcher, peak kinetics at the shoulder and elbow can be strongly predicted by ball velocity. Therefore, the assumption that higher peak throwing-arm kinetic values are experienced by pitchers with faster ball velocity is likely an inappropriate assumption among pitchers but may be correct for each player who increases pitch velocity.

Design of the interaction cavity for a 110-GHz, 1.5-MW Gyrotron

In this paper, the design of an interaction cavity for a very high-power W-band gyrotron is proposed for the generation of megawatt range of power. The proposed gyrotron is designed to generate 1.5 MW of pulsed power at 110 GHz. The operating mode is TE22,6. The beam voltage and beam current are 95 kV and 40 A, respectively. The beam velocity pitch factor is 1.4. For this structure, a unique kind of cavity profile is proposed which consists of a straight section, followed by a down-taper section, followed by a main interaction section (straight section), and followed by an up-taper section consisting of two raised cosine profiles. The simulation of the interaction cavity is done using the Code Gyro-K for different lengths of cavity mid-sections. The output power of 1.53 MW is estimated from the simulation. The diffractive quality factor and Ohmic loss are also estimated.

Does Velocity Increase From Flat-Ground to Mound Work During a Lighter Baseball Training Program?

There has been recent interest in throwing from flat-ground versus the mound regarding stress on the elbow. Typical throwing progression programs begin with flat-ground work and progress to mound work. All baseball pitchers of ages 10 to 17 years who completed a 15-week pitching mechanics and velocity-training program were included. Players' pitch velocity was tested at four time points during training. Average velocity and maximum velocity of pitches from flat-ground were compared with those of mound, and change in velocity between testing sessions was also compared. Thirty-six male pitchers (average age: 14.4 ± 1.6 years) were included. Fastball velocity increased by an average of 5.2 mph (95% confidence intervals 2.0 to 8.8 mph) at the end of the training program. When change in average and maximum velocity was compared between the four testing sessions, the most notable increase in velocity occurred between the third and fourth testing sessions. Both sessions were thrown from the mound. The 15-week baseball pitcher-training program markedly improved pitching velocity. Throwing from a mound compared with flat-ground resulted in the largest velocity increase. Therefore, when attempting to increase a pitcher's velocity, throwing from the mound should be an integral part of any velocity program.

The Safety and Efficacy of Weighted Baseballs.

One of the most common methods of training to enhance pitching velocity is the use of weighted baseballs. As with anything else, the excitement and popularity often proceed our scientific understanding.While there is still a lot to learn, our understanding of the science and efficacy of weighted baseball training has grown in recent years. The purpose of this clinical viewpoint is to summarize our current scientific understanding.

ANALYSIS OF TRUNK POWER AND JOINT STRESSES BETWEEN PROFESSIONAL AND COLLEGIATE PITCHERS

The dynamic motion of a baseball pitch generates high elbow and shoulder torques that can result in injury. Previous research has noted the importance of properly transferring energy from the lower extremities through the throwing arm to decrease joint stress. The goal of this study was to compare segmental powers between two levels of pitchers at various moments throughout the pitching cycle and observe their influence on upper extremity torques. Thirteen professional and thirteen collegiate pitchers participated in this study. Forty-seven reflective markers were attached to the subjects at specific landmarks. An 8-camera motion analysis system was set up surrounding an artificial pitching mound, where participants threw 10 fastballs. Data were exported and processed using Visual 3D software. Welch’s T-tests compared the means between groups with a significance set at p &lt; 0.05. Professional pitchers were found to have significantly greater torso power at foot contact, maximum shoulder external rotation, ball release, and overall peak torso power. They also demonstrated significantly greater pitch velocity. Professional pitchers generated similar elbow varus torque and shoulder internal rotation torque compared to collegiate pitchers. These findings suggest professional pitchers more effectively use torso power to help increase pitch speed without increasing overall joint torques.

Relationship Between Clinical Scapular Assessment and Scapula Resting Position, Shoulder Strength, and Baseball Pitching Kinematics and Kinetics.

Background:Scapular assessment is important in examining overhead athletes, but there is inconsistency in scapular clinical assessment and its relation to pathology.Purpose:To determine the relationship between clinical scapular assessment and biomechanical scapula resting position, shoulder strength, and pitching shoulder kinematics and kinetics.Study Design:Descriptive laboratory study.Methods:Two clinicians performed scapular assessments and graded the scapula as presence or absence of scapular dyskinesis. Shoulder external rotation (ER) and internal rotation (IR) strength were collected. The 3-dimensional biomechanics of the scapula resting position (upward/downward rotation, IR/ER, and anterior/posterior tilt) were assessed while participants stood at rest, and pitching kinematics (maximum shoulder ER, shoulder abduction, shoulder horizontal abduction, shoulder rotation velocity) and kinetics (maximum shoulder distraction force) were assessed when participants pitched off the portable pitching mound that was engineered to meet major league specifications.Results:A total of 33 high school baseball pitchers (age, 16.3 ± 1.2 years; height, 184.0 ± 6.9 cm; weight, 76.8 ± 20.8 kg; hand dominance: left, 9 [27%]; right, 24 [73%]; pitch velocity, 34.7 ± 2.3 m/s) participated in this study. Of them, 15 participants had scapular dyskinesis, and 18 had normal scapulothoracic rhythm. No differences were observed for upward/downward rotation or anterior/posterior tilt, shoulder ER, shoulder abduction, or shoulder distraction force, based on the presence of scapular dyskinesis. Pitchers with scapular dyskinesis demonstrated significantly greater scapular resting IR position (effect size [ES], 0.80; 95% CI, 0.06 to 1.54; P = .020), greater nondominant shoulder ER to IR strength ratio (ES, 0.49; 95% CI, –0.02 to 1.00; P = .018), and decreased shoulder rotation velocity (ES, 14.66; 95% CI: 12.06 to 17.25; P = .016). Pitchers with greater anterior tilt demonstrated greater shoulder rotation velocity (r = –0.48; P = .006).Conclusion:Pitchers with scapular dyskinesis had greater scapular IR, greater nondominant shoulder ER to IR strength ratio, and reduced shoulder rotation velocity.Clinical Relevance:Scapular assessment may be more influenced by differential IR than upward rotation or anterior tilt. Scapular dyskinesis has no competitive performance advantage among amateur athletes. Greater understanding is needed to decipher the critical threshold between beneficial and maladaptive scapular movement patterns.

The Association of Baseball Pitch Delivery and Kinematic Sequence on Stresses at the Shoulder and Elbow Joints.

Although there is a commonly held belief within the baseball community that delivery from the stretch confers more stress at the elbow and shoulder joints than delivery from the windup, there remains little evidence in the literature investigating this hypothesis. This study aimed to help address this gap in the literature by studying both intra-pitcher kinematic sequence variability, and intra-pitcher joint torque variability when throwing from the windup vs. the stretch. We hypothesized that 1) each pitchers' kinematic sequence would remain similar whether throwing from the windup or stretch, and 2) Kinematic sequence would influence peak arm torque more than delivery method. This cross-sectional 3D biomechanical study included 88 pitches thrown by ten (6 collegiate, 4 high school) pitchers with a mean age of 17.60 ± 2.63 years. Pitch velocity, throwing shoulder/elbow torques and the kinematic sequence of each pitch utilizing segmental peak angular velocities were captured. No statistically significant differences in ball velocity (p = 0.17), peak shoulder external rotation torque (p = 0.80), shoulder extension torque (p = 0.97), or elbow valgus torque (p = 0.83) were found between delivery approaches. Three primary kinematic sequences were identified. Shoulder external rotation torque [F(53,2) = 10.992, ɳ2 = .293, p < 0.00], shoulder extension torque [F(53,2) = 15.517, ɳ2 = .369, p < 0.00] and elbow valgus torque [F(53,2) = 9.994, ɳ2 = .274, p < 0.00] did vary significantly across these three kinematic sequence patterns. Our data suggest that the kinematic sequence influences shoulder and elbow torque more than the delivery approach. Instructing ideal kinematic sequence may be more influential for injury avoidance than delivery method.

Multi-objective optimization of laminar flow characteristics in helical coiled tubes based on NSGA-II

To meet the requirement of energy conservation and optimize the design of helical coils in laminar flow, the pitch, the coil radius and the average inlet velocity were selected as design parameters to obtain the tendency of the heat transfer and flow resistance characteristics of the helical coils. Heat transfer coefficient and pressure drop per unit length of helical coils were taken as the optimization objective functions. A multi-objective optimization model was established, three candidate points A, B and C were obtained based on Non-dominated Sorted Genetic Algorithm-II (NSGA-II). The results showed that heat transfer coefficient and pressure drop per unit length increase with the pitch and inlet velocity whilst them decrease with coil radius, among which the influence of inlet velocity is the most obvious and the pitch is the least. It was found that the coil radius of most points in Pareto front was relatively concentrated. The comprehensive performance of candidate points A, B, C had been improved significantly by 16.3%, 28.3% and 19.6% respectively.

Anterior Shoulder Instability in the Throwing Athlete

Throwers, particularly baseball players, are dependent on a delicate balance of shoulder mobility and stability to excel at their sport. Disruptions to this balance can lead to a number of different types of anterior shoulder instability: microinstability, acute atraumatic instability and traumatic instability. Pathologic microinstability can develop over time in a pitcher, as repetative throwing (ie extreme external rotation in abduction) causes stretch to the joint capsule anteriorly and impingement posteriorly. The resultant anterior or posterior shoulder pain can affect pitch velocity and control. Over time, the anterior capsule and ligaments can also become attenuated. They can tear abruptly during routine pitching, resulting in acute atraumatic instability. While microinstability and acute atraumatic instability typically occur in pitchers, position players are at a higher risk of traumatic shoulder instability. Diving for a ball or sliding into a base with an arm outstretched can cause the shoulder to sublux or frankly dislocate. These traumatic instability events often lead to injury of the anterior labrum and can result in recurrent instability. Treatment of instability in these throwing athletes includes physical therapy to restore the strength and coordination of the periscapular muscles, rotator cuff, deltoid and biceps. When nonoperative treatments fail, a number of arthroscopic and open procedures are available, with the type of procedure depending on the type of instability. While these techniques can adequately restore stability to the shoulder and many throwers do return to play, throwers do so at lower rates and often at lower levels than athletes of other sports.

Calculating Incidence Losses in the Turbine Cascade

The flow in turbine cascades with incidences is accompanied by a separated flow around the airfoils, which is difficult to calculate with acceptable accuracy. Therefore, in practice, empirical formulas are used to estimate losses from the incidence. The analysis of these formulas made it possible to identify the geometric and operating parameters of the cascade that have the greatest influence on the losses: the inlet metal angle, thickness of the leading edge of the profile, thickness of the profile, relative pitch, incidence, and exit flow velocity. It is unrealistic to obtain a reliable analytical expression for losses that takes into account the influence of all these parameters. Therefore, the path consisting in creating a program that uses the data of numerous experiments and finds an equation for calculating the losses in a group of cascades close to the specified one in terms of geometric parameters was chosen. Accordingly, a bank of experimental data on losses in a large number of cascades was formed and tested at different incidences and flow velocities. According to the test results, an increase in the flow velocity out of the cascade leads to a decrease in losses from a positive incidence. All cascades are clearly divided into three large groups according to the nature of losses. For the cascades of each group, the ranges of variation of the angles of the flow inlet and outlet and the thickness of the profile and its leading edge are determined. The set of these parameters determines the form of the approximating polynomial for each given cascade. To reflect the effect of the pitch and exit velocity and find the design equation, cascades with narrow deviations of the parameters from the given value are selected from the group, and the unknown polynomial coefficients are calculated using the least squares method. Calculations according to the developed program give smaller deviations from experiments than the known formulas.

Effects of wearing a head-mounted display during a standard clinical test of dynamic balance

BackgroundThe use of virtual reality (VR) in clinical settings has increased with the introduction of affordable, easy-to-use head-mounted displays (HMDs). However, some have raised concerns about the effects that HMDs have on posture and locomotion, even without the projection of a virtual scene, which may be different across ages. Research questionHow does HMD wear impact the kinematic measures in younger and older adults? MethodsTwelve healthy young and sixteen older adults participated in two testing conditions: 1) TUG with no HMD and 2) TUG with an HMD displaying a scene of the actual environment (TUGHMD). The dependent variables were the pitch, yaw, and roll peak trunk velocities (PTVs) in each TUG component, turning cadence, and the time to complete the TUG and its components – SIT-TO-STAND, TURN, WALK, and STAND-TO-SIT. ResultsWearing the HMD decreased turning cadence and pitch and yaw PTVs in all TUG components, decreased roll PTV in SIT-TO-STAND and TURN, and increased the time taken to complete all TUG components in all participants. Wearing the HMD decreased the pitch PTV in SIT-TO-STAND in older relative to younger adults.Wearing an HMD affected TUG performance in younger and older adults, which should be considered when an HMD is used for VR applications in rehabilitation. SignificanceOur findings highlight the importance of considering the physical effect of HMD wear in clinical testing, which may not be present with non-wearable VR technologies.

The Evidence Behind Weighted Ball Throwing Programs for the Baseball Player: Do They Work and Are They Safe?

Weighted baseball throwing programs have gained significant attention recently. They have been promoted as proven option for pitchers wishing to increase their throwing velocity and improve throwing mechanics. However, there is some concern that, if not applied properly, they may increase injury risk. In this review, we aim to (1) give a brief description of the potential mechanisms through with weighed ball programs that could improve throwing velocity, (2) summarize the available evidence regarding their effectiveness in increasing throwing velocity, (3) summarize the evidence on injury risk, and (4) propose directions for future studies. Initial research on weighted ball programs was published in the 1960s. Recently there has been an increase in research as interest from baseball organizations, instructors, players, and medical providers has grown. A recent randomized controlled trial demonstrated that pitching velocity can be increased through a 6-week weighted ball program; however, with that, they found that the rate of injury also increased. An earlier systematic review outlined 10 studies that evaluated weighted ball programs effect on pitching velocity and reported that 7 studies described increases in throwing velocity, while most studies did not comment on injury risk. They note that the results on rate of injury have been variable, likely secondary to the variability in time and intensity of different programs. The inconsistency in the methodology of weighted ball programs and studies has made it challenging to draw (scientifically) meaningful conclusions. Nevertheless, several studies have offered empirical evidence in support of the claim that weighted ball programs can increase pitching velocity through improved throwing mechanics. At the same time, these studies have emphasized the improvements in performance, while the potential effects on injury mechanisms have been less well understood. There is a need for improved standardization of these programs to allow for future study and subsequent modification to optimize performance.

Approach-angle-based three-dimensional indirect adaptive fuzzy path following of under-actuated AUV with input saturation

In this paper an approach-angle-based three-dimensional path-following control scheme has been proposed for underactuated Autonomous Underwater Vehicle (AUV) which experiences unknown actuator saturation and environmental disturbance. First, the path-following error dynamic model is derived based on the principle of relative motion which was followed by the design of approach-angle-based guidance law in both horizontal and vertical profiles of AUV to transform the three-dimensional tracking errors into heading angle and elevation angle tracking errors. The kinematic control law is designed based on the Lyapunov theory and backstepping technique. Second, the kinetic controller is designed based on the Lyapunov theory, backstepping technique and fuzzy logic system approximation method. The indirect adaptive fuzzy logic system is applied to approximate unknown smooth functions which are composed of coupled AUV hydrodynamics and complex differentials of desired pitch and yaw velocities. Moreover, the application of fuzzy control completely free from dependence on accurate AUV kinetic model. Considering a disturbance-like term, which is comprised of fuzzy logic system approximation error and bounded ocean disturbance, an adaptive law is designed to estimate the bound of it. Finally, two sets of comparative numerical simulations, including straight path following with different initial posture and spatial helix path following with sudden disturbance, are studied to illustrate the effectiveness and robustness of the proposed control scheme.

American Academy of Sports Physical Therapy Platform Presentation Abstracts SPL1–SPL82

American Academy of Sports Physical Therapy Platform Presentation Abstracts SPL1–SPL82

Chiral-induced spin selectivity: A polaron transport model

Weak hyperfine interactions and spin-orbit coupling (SOC) in organic materials result in long spin lifetimes, which is very promising for spintronics. On the other hand, they also make it challenging to achieve spin polarization, which is of crucial importance for spintronics devices. To overcome this obstacle, we have proposed a physical model for spin-polarized electron transport through a chiral molecule based on the chiral-induced spin selectivity. Because the transport in the chiral molecule is not an isolated one, but rather an electron coupled to its surrounding lattice distortions, namely, a spatial localized polaron, an indispensable polaron effect is incorporated in our model. We show that the polaron transport through the chiral molecule exhibits a spin-momentum-locked feature. Interestingly, no matter what their initial spin state is, all of the polarons could transmit through the molecule with their spins being aligned to the same orientation due to the effective ``inverse Faraday effect.'' The coexistence of the electron-lattice coupling and SOC results in the spin and lattice being coupled, which leads to a strongly enhanced spin coherence and then a very high spin polarization of $70%$. In addition, the effects of the helix pitch, polaron size, and drift velocity on spin polarization are also discussed. Our results open the possibility of using chiral molecules in spintronics applications and offer a paradigm for information processing and transmission.

THE RELATIONSHIP OF RANGE OF MOTION, HIP SHOULDER SEPARATION, AND PITCHING KINEMATICS.

When pitching a baseball, pelvic and trunk pitching kinematics play an integral role in momentum transfer from the lower extremity to the upper extremity. However, it is unknown how hip and trunk ROM and hip shoulder separation interplay with pelvic and trunk pitching kinematics. To determine the relationship between clinical trunk and hip range of motion (ROM) and pitching biomechanical pelvis and trunk kinematics, and kinematic sequencing. Controlled biomechanical study. High school pitchers were assessed for trunk rotation via motion capture and hip ROM via a goniometer prior to pitching. Trunk rotation was designated as dominant and non-dominant sides, and hips as stance and lead limbs. Pitchers threw four fastballs during three dimensional biomechanical assessment. Spearman's Rho correlations were performed between trunk and hip ROM, and trunk and hip biomechanical kinematics, and kinematic pitching sequence. Thirty-two pitchers (mean age: 16.3 ± 1.2 years, height = 184.0 ± 6.9 cm, mass = 76.8 ± 20.8 kg) were included in this study. Their mean pitch velocity was 34.7 ± 2.3 m/s, peak pelvis rotation velocity: 669.1 ± 95.5 deg/s, and peak trunk rotation velocity: 1084.7 ± 93.0 deg/s. There were no differences between dominant and non-dominant side trunk rotation, or between stance and lead hip ROM. There were no significant relationships between trunk or hip ROM and pitching kinematics. There was a significant relationship between hip shoulder separation and peak trunk rotation velocity (r = 0.390, p=0.027). There was a significant relationship between pitch velocity and peak trunk rotation velocity (r = 0.478, p = 0.006). There were no other significant relationships between pitching kinematics or kinematic sequencing. Hip shoulder separation is related to trunk rotation velocity, and ultimately pitch velocity. These ROM measurements can be used as normative values for hip shoulder separation in high school pitchers. 3.

Effect of Ulnar Collateral Ligament Reconstruction on Pitch Accuracy, Velocity, and Movement in Major League Baseball Pitchers.

Background:Ulnar collateral ligament (UCL) reconstruction is frequently performed on Major League Baseball (MLB) pitchers. Previous studies have investigated the effects of UCL reconstruction on fastball and curveball velocity, but no study to date has evaluated its effect on fastball accuracy or curveball movement among MLB pitchers.Purpose/Hypothesis:The primary purpose of this study was to determine the effects of UCL reconstruction on fastball accuracy, fastball velocity, and curveball movement in MLB pitchers. Our hypothesis was that MLB pitchers who underwent UCL reconstruction would return to their presurgery fastball velocity, fastball accuracy, and curveball movement. The secondary purpose of this study was to determine which factors, if any, were predictive of poor performance after UCL reconstruction.Study Design:Case-control study; Level of evidence, 3.Methods:MLB pitchers who underwent UCL reconstruction surgery between 2011 and 2012 were identified. Performance data including fastball velocity, fastball accuracy, and curveball movement were evaluated 1 year preoperatively and up to 3 years of play postoperatively. A repeated-measures analysis of variance with a Tukey-Kramer post hoc test was used to determine statistically significant changes in performance over time. Characteristic factors and presurgery performance statistics were compared between poor performers (>20% decrease in fastball accuracy) and non—poor performers.Results:We identified 56 pitchers with a total of 230,995 individual pitches for this study. After exclusion for lack of return to play (n = 14) and revision surgery (n = 3), 39 pitchers were included in the final analysis. The mean presurgery fastball pitch-to-target distance was 32.9 cm. There was a statistically significant decrease in fastball accuracy after reconstruction, which was present up to 3 years postoperatively (P = .007). The mean presurgery fastball velocity of 91.82 mph did not significantly change after surgery (P = .194). The mean presurgery curveball movement of 34.49 cm vertically and 5.89 cm horizontally also did not change significantly (P = .937 and .161, respectively).Conclusion:Fastball accuracy among MLB pitchers significantly decreased after UCL reconstruction for up to 3 years postoperatively. There were no statistically significant differences in characteristic factors or presurgery performance statistics between poor and non--poor performers.

Studi Simulasi Pengaruh dari Pitch dan Kecepatan Alir Fluida Kerja Terhadap Koefisien Perpindahan Panas Menyeluruh di Conical Cavity Absorber

The energy crisis has become a global issue that must be resolved immediately through the use of new and renewable energy sources. Indonesia is geographically benefited because it is on the equator so that it gets a supply of sun throughout the year. This advantage is an added value for the application of solar-based energy systems. Concentrated Solar Power (CSP) system is an energy system based on solar thermal energy to generate electricity. The parabolic dish model in CSP has been shown to have the highest efficiency of up to 32%. The fundamental challenge of improving performance on the parabolic dish model is the design of the cavity receiver used. Cavity receiver functions to absorb heat from the reflector and distribute it to the system through the working fluid (Heat Transfer Fluid). This article specifically discusses the simulation of conical cavity receivers with a focus on the effect of pitch and fluid flow velocity in the system through Computational Fluid Dynamic (CFD) ANSYS. Simulation results on nine different variables show the effect of pitch and flow velocity on the overall transfer coefficient on cavity. The results of this simulation can be used as a basic reference in an effort to improve the heat transfer performance of cavity, which in turn can affect the overall performance of a Concentrated Solar Power Parabolic Dish type system.

Universal Subterahertz Large-Orbit Gyrotron: Operation at the Second and Third Cyclotron Harmonics

Coherent subterahertz radiation in the continuous-wave regime was obtained in a large-orbit gyrotron (LOG) operated at a high harmonic of the cyclotron frequency. An electron–optical system containing a gun with a cusp followed by a section of adiabatic magnetic compression with a factor of 1000 ensures the formation of a 30 keV/0.7 A helical axis-encircling electron beam with acceptable velocity spread and pitch factor in a magnetic field of 5 T. Stable singlemode operation was obtained at frequencies of 0.394 and 0.267 THz with radiation powers of 0.37 and 0.9 kW at the third and second cyclotron harmonics, respectively. Tuning of the generation frequency in the gyrotron during its operation at the second cyclotron harmonic and complex regimes of competition of two waves excited at the second and third cyclotron harmonics are also studied.

Numerical investigation of T-Foil hybrid control strategy for ship motion reduction in head seas

An active control T-foil can significantly reduce the vertical motions of high-speed ships. In this paper, a hybrid control method is proposed to control the T-foil. The reduction effects of the method, along with passive, linear and step controls, are numerically investigated. A numerical model is introduced firstly. Then the numerical predictions are compared with experimental measurements to validate the numerical model. Finally, the heave, pitch and local acceleration of the Wigley model III are predicted under four control strategies at two forward speeds (Fr = 0.3, 0.5). Based on the percentage reduction of vertical motions, the local velocity signal performs better than the pitch velocity signal. The reduction effect of the linear control is critical when the encounter frequency is high but limited when the encounter frequency becomes lower. The step control has the best effect at Fr = 0.3, but it aggravates the vertical motions in some cases at Fr = 0.5. The hybrid control offers the advantages of both linear and step controls and significantly reduces the vertical motions. The performance of the method is dominated by a parameter, CI, which makes the strategy take effect more stable and fit diverse sea conditions.