Spin Rate Research Articles

Boundary Layers of Circumplanetary Disks around Spinning Planets. II. Global Modes with Azimuthal Magnetic Fields

The accretion of material from disks onto weakly magnetized objects invariably involves its traversal through a material surface, known as the boundary layer (BL). Our prior studies have revealed two distinct global wave modes for circumplanetary disks with BLs exhibiting opposite behaviors in spin modulation. We perform a detailed analysis of the effects of magnetic fields on these global modes, highlighting how magnetic resonances and turning points could complicate the wave dynamics. The angular momentum flux becomes positive near the BL with increasing magnetic field strength. We also examine the perturbation profile to demonstrate the amplification of magnetic fields within the BL. The dependence of growth rates on the magnetic field strength and the spin rate are systematically investigated. We find that stronger magnetic fields tend to result in lower terminal spin rates. We stress the potential possibility of the formation of angular momentum belts and pressure bumps. The implications for the spin evolution and quasiperiodic oscillations observed in compact objects are also briefly discussed. Our calculations advance the understanding of magnetohydrodynamical accretion processes and lay a foundation for observational studies and numerical simulations.

Eulerian rates of elastic incompatibilities applied to size-dependent hardening in finite torsion

Measures of rates of elastic incompatibilities are developed within an Eulerian framework for finite-deformation response of anisotropic elastic-inelastic materials. Such framework relies on the evolution of microstructural vectors. It is emphasized that the rates of incompatibilities, here denoted as Rij, depend on the constitutive equation for the rate of inelasticity. For small strains and rotations, Rij are equal to the negative of the components of the rate of Nye-Kröner’s dislocation density tensor. In contrast to these small strain components, each Rij is invariant under superposed rigid body motions such that it can be used independently in the constitutive equations to describe the material behavior. Specifically, in this work, Rij provide a size-dependent enhancement to hardening that can increase or decrease during loading history, modeling the generation and annihilation of densities of geometrically necessary dislocations in metal plasticity. The application to the finite-deformation torsion of thin wires demonstrates the potential of this approach and the importance of the constitutive equation for the plastic spin rate both on the rotations of the microstructural vectors and on the predicted size-effect.

Solvent Effects on Spin-Orbit Charge-Transfer Intersystem Crossing in Aryl-Substituted Boron-dipyrromethene Donor-Acceptor Dyads.

In heavy-atom-free organic molecules, the rate of triplet generation through charge recombination, as dictated by the El-Sayed rule, can be enhanced by 101-102 times compared with the rate of spontaneous spin flipping between π-π* orbitals. This mechanism is known as the spin-orbit charge-transfer intersystem crossing (SOCT-ISC). Within the framework of the SOCT-ISC mechanism, facilitating the generation of charge-separated (CS) states and suppressing the spin-allowed direct charge recombination to the ground state are pivotal for maximizing the efficiency of generating localized triplet states. Herein, a series of orthogonal aryl-substituted boron-dipyrromethene dyads were studied by time-resolved spectroscopy to unravel the multichannel competitive relationships in the SOCT-ISC mechanism. The energy level of the electron donor and the stabilization of the solvent effect to the charge-transfer state are reflected in the Gibbs free energy changes of the electron transfer and recombination reactions, leading to significantly different triplet quantum yields. Additionally, solvation-induced electronic coupling changes in excited states lead to the fact that the spin-allowed charge recombination rate cannot be well simply predicted by the Marcus inverted region but has to consider the specific excited-state dynamics in optimizing the proportion of triplet generation channels based on charge recombination.

Observability of Inertial Rotation Axis from Light Curve Derived Relative Spin Rate Measurements

Observability of Inertial Rotation Axis from Light Curve Derived Relative Spin Rate Measurements

Dark energy effects on surface gravitational redshift and Keplerian frequency of neutron stars

Abstract The research of the properties of neutron star with dark energy is a particularly interesting yet unresolved problem in astrophysics. We analyze the influence of dark energy on the equation of state, the maximum mass, the surface gravitational redshift and the Keplerian frequency for the traditional neutron star and the hyperon star matter within the relativistic mean field theory, using the GM1 and TM1 parameter sets by considering the two flavor symmetries of SU(6) and SU(3) combined with the observations of PSR J1614-2230, PSR J0348+0432, PSR J0030+0451, RX J0720.4-3125, and 1E 1207.4-5209. It is found that the existence of dark energy leads to the softened equations of state of the traditional neutron star and the hyperon star. The radius of a fixed mass traditional neutron star (or hyperon star) with dark energy becomes smaller, which leads to the increased compactness. The existence of dark energy can also enhance the surface gravitational redshift and the Keplerian frequency of the traditional neutron stars and the hyperon stars. The growth of the Keplerian frequency may cause speeding up to the spin rate which may provide a possible way for understanding and explaining the pulsar glitch phenomenon. Specifically, we infer that the mass and the surface gravitational redshift of PSR J1748-2446ad without dark energy for the GM1 (TM1) parameter set are 1.141 $M_\odot$ (1.309 $M_\odot$) and 0.095 (0.105), respectively. The corresponding values for the GM1 (TM1) parameter set are 0.901 $M_\odot$ (1.072$M_\odot$) and 0.079 (0.091) if PSR J1748-2446ad contains dark energy with $\alpha=0.05$. PSR J1748-2446ad may be a low-mass pulsar with a lower surface gravitational redshift under our selected models.

Calculation of the Point of Application (Centre of Pressure) of Force and Torque Imparted on a Spherical Object from Gyroscope Sensor Data, Using Sports Balls as Practical Examples.

This study investigates the determination of the centre of pressure (COP) on spherical sports objects such as cricket balls and footballs using gyroscope data from Inertial Measurement Units (IMUs). Conventional pressure sensors are not suitable for capturing the tangential forces responsible for torque generation. This research presents a novel method to calculate the COP solely from gyroscope data and avoids the complexity of isolating user-induced accelerations from IMU data. The COP is determined from the cross-product of consecutive torque vectors intersecting the surface of the sphere. Effective noise management techniques, including filtering and data interpolation, were employed to improve COP visualisation. Experiments were conducted using a smart cricket ball and a smart football. Validation tests using spin rates between 7.5 and 12 rps and torques ranging from 0.08 to 0.12 Nm confirmed consistent COP clustering around the expected positions. Further analysis extended to various spin bowling deliveries recorded using a smart cricket ball, and a curved football kick recorded using a smart football demonstrated the wide applicability of the method. The COPs of various spin bowling deliveries showed adjacent positions on the surface of the ball, traversing through backspin, sidespin and topspin, excluding the flipper and doosra deliveries. The calculation of the COP on the surface of the soccer ball could only be achieved by increasing the data sampling frequency sevenfold using curve fitting. Knowledge and use of the COP position offers significant advances in understanding and analysing ball dynamics in sports.

The effect of Dynamic tape’s directional support on shoulder fatigue and pitching performance in amateur baseball players: a randomized crossover trial

BackgroundTo evaluate whether the application of Dynamic tape to the pitching shoulder could result in reduced shoulder fatigue, reduced delayed onset muscle soreness, or improved performance.MethodsThis is a randomized crossover study, in which participants and investigators were blinded, included 20 amateur adult baseball players without shoulder pain. Sham taping and Dynamic taping were randomized, using an internal rotation support taping method in both groups. Bilateral shoulder strength and range of motion were measured with a handheld dynamometer and clinical goniometer before and after each test. The percentage of strength decrease, range of motion, pitch velocity, spin rate, and shoulder pain were recorded. The post-pitching decrease in strength and percentage of strength decrease were calculated by paired t-test and the pitching speed and spin rates in the innings for both the sham and Dynamic taping groups were analyzed using two-way ANOVA.ResultsCompared with the sham group, the Dynamic tape group showed a significant loss in the percentage of strength decrease in internal rotation compared to the sham group (-1.4% vs. 7.0%, p = 0.03). However, no significant differences were observed in other strength declines, shoulder range of motion, pain, pitching velocity, or spin rate.ConclusionsDynamic tape reduced direction-specific shoulder fatigue but did not significantly enhance pitching performance or prevent delayed onset muscle soreness.Trial registrationClinicalTrials: N201912094.

Pitch-Tracking Metrics as a Predictor of Future Shoulder and Elbow Injuries in Major League Baseball Pitchers: A Machine-Learning and Game-Theory Based Analysis.

Understanding interactions between multiple risk factors for shoulder and elbow injuries in Major League Baseball (MLB) pitchers is important to identify potential avenues by which risk can be reduced while minimizing impact on player performance. To apply a novel game theory-based approach to develop a machine-learning model predictive of next-season shoulder and elbow injuries in MLB pitchers and use this model to understand interdependencies and interaction effects between the most important risk factors. Case-control study; Level of evidence, 3. Pitcher demographics, workload measures, pitch-tracking metrics, and injury data between 2017 and 2022 were used to construct a database of MLB pitcher-years, where each item in the database corresponded to a pitcher's information and metrics for that year. An extreme gradient boosting machine-learning model was trained to predict next-season shoulder and elbow injuries utilizing Shapley additive explanation values to quantify feature importance as well as interdependencies and interaction effects between predictive variables. A total of 3808 pitcher-years were included in this analysis; 606 (15.9%) of these involved a shoulder or elbow injury resulting in placement on the MLB injured list. Of the >65 candidate features (including workload, demographic, and pitch-tracking metrics), the most important contributors to predicting shoulder/elbow injury were increased: pitch velocity (all pitch types), utilization of sliders (SLs), fastball (FB) spin rate, FB horizontal movement, and player age. The strongest game theory interaction effects were that higher FB velocity did not alter a younger pitcher's predicted risk of shoulder/elbow injury versus older pitchers, risk of shoulder/elbow injury increased with the number of high-velocity pitches thrown (regardless of pitch type and in an additive fashion), and FB velocity <95 mph (<152.9 kph) demonstrated strong negative interaction effects with higher SL percentage, suggesting that the overall predicted risk of injury for pitchers throwing a high number of SLs could be attenuated by lower FB velocity. Pitch-tracking metrics were substantially more predictive of future injury than player demographics and workload metrics. There were many significant game theory interdependencies of injury risk. Notably, the increased risk of injury that was conferred by throwing with a high velocity was even further magnified if the pitchers were also older, threw a high percentage of SLs, and/or threw a greater number of pitches.

Fastball Quality After Ulnar Collateral Ligament Reconstruction in Major League Baseball Pitchers

Background: The ulnar collateral ligament (UCL) is essential for elbow stability during pitching. In professional baseball, the fastball (FB) is the most commonly used pitch, making postrecovery FB performance after UCL reconstruction (UCLR) a crucial aspect to consider. Hypotheses: (1) Pitchers undergoing UCLR would show no significant changes in performance metrics compared with nonoperated pitchers with similar FB velocity and spin rate, and (2) no significant variance would be found in these metrics within the operated pitchers concerning their preinjury anthropometric characteristics and pitching performance metrics. Study Design: Cohort study; Level of evidence, 3. Methods: The study included 91 Major League Baseball (MLB) pitchers who underwent primary UCLR between January 1, 2015, and December 31, 2021. A matched 1:1 control group of MLB pitchers without UCLR injuries was established. Publicly available pitch metrics and anthropometric data were compared between the study and control groups. Results: Disparities in several performance metrics emerged during the first postreturn year (PRY1), including FB use percentage (P = .029), fielder independent pitching (FIP) (P = .021), and standardized FB runs above average per 100 pitches (wFB/C) (P < .001). Subgroup analysis within the UCLR group revealed a negative correlation between presurgery mean FB velocity and its subsequent change (P < .001) and a positive correlation with changes in FIP (P = .025) from the index year to PRY1. A negative correlation was observed between FB use percentage in the index year and its change by PRY1 (P = .002). By the second postreturn year, no significant differences were found in these performance metrics. No factors were significantly related to prolonged recovery time. Conclusion: Although FB velocity and spin rate remained consistent, significant differences were observed in FB use percentage, FIP, and wFB/C in PRY1. However, by second postreturn year, these differences were no longer significant. No specific risk factors were identified concerning prolonged recovery time between pre-UCLR FB pitching metrics and the physical anthropometric data. These results suggest that although the short-term postsurgery period may affect more specialized pitching metrics, the basic pitching performance metrics, as hypothesized, remain largely unaffected by UCLR.

The Astrometric Performance of the China Space Station Telescope (CSST) Sky Survey in Extending the Gaia Celestial Reference Frame

The multi-color imaging sky survey conducted by the China Space Station Telescope (CSST) holds significant promise for advancing the development of the celestial reference frame. In this study, we focus on assessing the astrometric performance of the CSST celestial reference frame (CSST-CRF) in extending the Gaia Celestial Reference Frame 3 (Gaia-CRF3). First, the orientation precision of the CSST reference frame is evaluated using a simulated set of extragalactic sources with CSST g magnitudes ranging from 18 to 25 mag. The estimated orientation uncertainty caused by random error insignificantly affects the alignment between Gaia-CRF3 and the CSST-CRF. Then, the systematic effect of incomplete CSST sky coverage on the alignment between CSST-CRF and Gaia-CRF3 is discussed by analyzing the differences between the subset of Gaia-CRF3 in the CSST observation region (Gaia-CRF3′) and Gaia-CRF3 as a whole. Using the third International Celestial Reference Frame (ICRF3) S/X band as an intermediate reference frame, the orientation offset between Gaia-CRF3′ and Gaia-CRF3 is estimated to be 20 μas. This offset is marginally larger than the orientation offset between Gaia-CRF3 and the ICRF3, approximately 15 μas. The residual spin and glide rate of Gaia-CRF3′ are derived from the proper motions, consistent with that of Gaia-CRF3 within the formal error. Finally, we explore the role of CSST in establishing a multi-band celestial reference frame by comparing its limiting magnitude and observation accuracy with existing catalogs in the infrared and ultraviolet bands. Thanks to its broad wavelength coverage and high-precision measurements, CSST is well-positioned to make significant contributions to the development of a multi-band celestial reference frame.

The geology and evolution of the Near-Earth binary asteroid system (65803) Didymos

Images collected during NASA’s Double Asteroid Redirection Test (DART) mission provide the first resolved views of the Didymos binary asteroid system. These images reveal that the primary asteroid, Didymos, is flattened and has plausible undulations along its equatorial perimeter. At high elevations, its surface is rough and contains large boulders and craters; at low elevations its surface is smooth and possesses fewer large boulders and craters. Didymos’ moon, Dimorphos, possesses an intimate mixture of boulders, several asteroid-wide lineaments, and a handful of craters. The surfaces of both asteroids include boulders that are large relative to their host body, suggesting that both asteroids are rubble piles. Based on these observations, our models indicate that Didymos has a surface cohesion ≤ 1 Pa and an interior cohesion of ∼10 Pa, while Dimorphos has a surface cohesion of <0.9 Pa. Crater size-frequency analyzes indicate the surface age of Didymos is 40–130 times older than Dimorphos, with likely absolute ages of ~\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}12.5 Myr and <0.3 Myr, respectively. Solar radiation could have increased Didymos’ spin rate leading to internal deformation and surface mass shedding, which likely created Dimorphos.

Structural stability of China’s asteroid mission target 2016 HO3 and its possible structure

ABSTRACT Asteroid 2016 HO$_3$, a small asteroid (&amp;lt;60 m) in super fast rotation state ($\sim$28 min), and is the target of China’s Tianwen-2 asteroid sample-return mission. In this work, we investigate its structural stability using an advanced soft-sphere-discrete-element-model code, dembody, which is integrated with bonded-aggregate models to simulate highly irregular boulders. The asteroid body is numerically constructed by tens of thousands particles, and then is slowly spun up until structural failure. Rubble piles with different frictions, cohesions, morphologies, grain size distributions, and structures are investigated. We find a 2016 HO$_3$ shaped granular asteroid would undergo tensile failure at higher strengths as opposed to shear failure in lower strengths, regardless of its shape and constituent grain size ratio. In the tensile failure regime, the critical tensile strength is proportional to the square of the spin rate, but surprisingly, is independent of the internal friction angle. Such relations indicate that the Maximum Tensile Stress criterion emerges as superior paradigm for investigating the failure behaviour of fast-rotating asteroids. We predict that the high-spin rate of asteroid 2016 HO$_3$ requires a surface strength over $\sim$3 Pa and a bulk tensile strength over $\sim$10–30 Pa. Through comparing these strength conditions with the latest data from asteroid missions, we suggest a higher likelihood of a monolithic structure over a typical rubble pile structure. However, the possibility of the latter cannot be completely ruled out. In addition, the asteroid’s surface could retain a loose regolith layer globally or only near its poles, which could be the target for sampling of Tianwen-2 mission.

Paper 21: Anatomic Medial Ulnar Collateral Ligament Reconstruction with Internal Brace Augmentation in Throwing Athletes

Objectives: Injury to the Medial Ulnar Collateral Ligament (MUCL) is a common setback experienced by many throwing athletes often requiring reconstruction with 12-18 months of rehabilitation. Current reconstructive techniques fail to anatomically restore the MUCL which may contribute to the prolonged course of rehabilitation. In recent years, we described an anatomic MUCL reconstruction with internal brace augmentation which demonstrated improved biomechanical strength when compared to the docking technique in cadaveric specimens. The purpose of this study was to evaluate the postoperative course of both amateur and professional throwing athletes that underwent anatomic MUCL reconstruction with internal brace augmentation. We hypothesized that throwers would return to the same level of play and that return to play (RTP) would be a shorter duration compared to current reported outcomes. Methods: In this surgical technique, the native MUCL is formally repaired. The graft and a suture tape are folded over a suspensory loop and secured in a socket of the medial epicondyle of the humerus to maximize tendon to bone contact. On the ulnar side, the graft and internal brace are secured proximally by two suture anchors on either side of the sublime tubercle and further secured across the sublime tubercle ridge distally to re-create the anatomic triangular insertion of the native ligament. All surgeries were performed by a single surgeon. Patient reported outcomes in addition to date of RTP, level of play, and functional outcomes were retrospectively gathered. All patients initially followed an Accelerated Rehabilitation Protocol and were converted to a Standard Paced protocol if setbacks were encountered. Results: A total of 26 baseball players underwent primary (n=23) or revision (n=3) MUCL reconstruction with the Anatomic Technique. Of these, 15 were professional and 11 were amateur athletes. 92% of throwers returned to play at a mean of 9.9 months following reconstruction. 89% were able to advance through the accelerated postoperative protocol without issues and 85% returned to the same role and level of play. Post injury KJOC scores improved from 41 to 86.9 and SANE scores improved from 32.5 to 95.5. No significant difference was identified in pre-injury versus post-reconstruction throwing velocity, ball spin rate, or horizontal/vertical ball movement. Conclusions: Anatomic reconstruction of the MUCL with internal bracing is a viable option for MUCL injuries. Advantages include increased tendon-bone contact of the reconstruction, multiple fixation points, and anatomic restoration of the MUCL. This technique allowed an expedited return to sport for these baseball athletes.

Optimizing the thermoelectric behavior of novel quaternary CoIrMnX (X=Sn, Sb) alloys through chemical potential or carrier concentration doping

Materials exhibiting significant polarisation at high spin rates are considered the most promising candidates for spintronic devices. This study investigates the mechanical, optical, spin-polarised electronic structure, magnetism, and thermoelectric properties of CoIrMnX (where X = Sn, Sb). We performed calculations of quaternary Heusler alloys using first-principles calculations. The CoIrMnSn and CoIrMnSb compounds have the most stable Type III crystal structures, according to the calculations performed on the alloys under investigation. We found that the two alloys, CoIrMnSn and CoIrMnSb, possessed a half-metallic ferromagnetic structure, characterised by indirect band gaps of 1.008 eV and 0.806 eV in the predominant spin channels, respectively. Both alloys demonstrate a significant overall magnetic moment of 5 and 6 μβ, respectively. CoIrMnX (where X = Sn, Sb) are ferromagnetic half-metals with 100 percent spin polarisation, according to the results. The results of the elastic constants demonstrate the alloys' mechanical stability. We also investigated optical characteristics such as dielectric function, absorption, reflectance, and optical conductivity. CoIrMnX (where X = Sn and Sb) acts as an efficient absorber in the ultraviolet region and possesses a high refractive index. Alloys exhibit considerable potential as viable candidates for implementation in spintronic devices. The maximum ZT value for CoIrMnSn (CoIrMnSb) is 0.915 (0.6619). To achieve this value, it is necessary to either reduce the charge carrier concentration to n = 0.0812 x 1020 (0.0952 x 1020) cm-3 or the μ to 0.83843 (0.83806) Ryd. Substantially examined materials demonstrate considerable potential for application in the field of thermoelectrics.

Using a Sensor-Embedded Baseball to Identify Finger Characteristics Related to Spin Rate and Pitching Velocity in Pitchers.

Previous investigations have shown a positive relationship between baseball pitching velocity and the kinetic chain involved in pitching motion. However, no study has examined the influence of finger characteristics on pitching velocity and rate of spin via a sensor-embedded baseball. Twenty-one pitchers volunteered and were recruited for this study. An experimental baseball embedded with a force sensor and an inertial measurement unit was designed for pitching performance measurement. Finger length and strength were measured as dependent variables. Spin rate and velocity were independent variables. Pearson product-moment correlations (r) and intraclass correlation coefficients (ICCs) determined the relationship between finger characteristics and pitching performance. Finger length discrepancy, two-point pinch strength, index finger RFD (rate of force development), middle finger impulse, and force discrepancy had significant correlations with spin rate (r = 0.500~0.576, p ≤ 0.05). Finger length discrepancy, two-point pinch, three-point pinch strength, index and middle finger RFD, middle finger impulse, and force combination had significant correlations with fastball pitching velocity (r = 0.491~0.584, p ≤ 0.05). Finger length discrepancy, finger pinch strength, and pitching finger force including maximal force and RFD may be factors that impact fastball spin rate and fastball pitching velocity.

Ulnar collateral ligament repair in professional baseball players.

While initial reports of surgical repair of ulnar collateral ligament tears are promising, studies detailing post-repair outcomes are lacking. This study explores the effectiveness of ulnar collateral ligament (UCL) repair in returning professional baseball players to their pre-injury level of play. Our hypothesis is that professional baseball players undergoing UCL repair will have successful outcomes and high return to sport rates after surgery. Publicly available databases were utilized to search for data on professional baseball players who underwent UCL repair from 2016 to 2021. Players undergoing primary UCL repair with an internal brace were included. Amateur players were excluded as were those undergoing revision UCL repair or UCL reconstruction. Of the 11 pitchers who underwent UCL repair, minor league baseball (MiLB) pitchers returned to the sport at an average of 17.5 months. MiLB pitchers had similar earned run averages (ERAs), games played, innings pitched, and walks plus hits per inning pitched ratios (WHIPs) before and after surgery. Four major league baseball (MLB) pitchers (80%) returned to the sport at 9.55 months. MLB pitchers played fewer games and pitched fewer innings than before the surgery, but their ERAs and WHIPs were similar before and after surgery. Pitch velocity and spin rates after surgery varied based on pitch type. The seven positional players who underwent UCL repair showed no differences in batting or fielding performance before and after surgery. UCL repair can successfully return both pitchers and positional players at both the MiLB and MLB levels to play at pre-injury performance levels. Repair can be considered as an option for qualifying injuries in players hoping to maximize performance after surgery with minimal recovery time. Level of Evidence: IV.

The Hera Radio Science Experiment at Didymos

Hera represents the European Space Agency's inaugural planetary defense space mission and plays a pivotal role in the Asteroid Impact and Deflection Assessment international collaboration with NASA DART mission that performed the first asteroid deflection experiment using the kinetic impactor techniques. With the primary objective of conducting a detailed post-impact survey of the Didymos binary asteroid following the DART impact on its small moon called Dimorphos, Hera aims to comprehensively assess and characterize the feasibility of the kinetic impactor technique in asteroid deflection while conducting an in-depth investigation of the asteroid binary, including its physical and compositional properties as well as the effect of the impact on the surface and shape of Dimorphos. In this work, we describe the Hera radio science experiment, which will allow us to precisely estimate critical parameters, including the mass, which is required to determine the momentum enhancement resulting from the DART impact, mass distribution, rotational states, relative orbits, and dynamics of the asteroids Didymos and Dimorphos. Through a multi-arc covariance analysis, we present the achievable accuracy for these parameters, which consider the full expected asteroid phase and are based on ground radiometric, Hera optical images, and Hera to CubeSats InterSatellite Link radiometric measurements. The expected formal uncertainties for Didymos and Dimorphos GM are better than 0.01% and 0.1%, respectively, while their J2 formal uncertainties are better than 0.1% and 10%, respectively. Regarding their rotational state, the absolute spin pole orientations of the bodies can be recovered to better than 1°, and Dimorphos' spin rate to better than 10−3%. Dimorphos reconstructed relative orbit can be estimated at the sub-m level. Preliminary results, using a higher-fidelity dynamical model of the coupled motion between rotational and orbital dynamics, show uncertainties in the main parameters of interest that are comparable to those in standard radio science models. A first-order estimate of the expected uncertainty in the momentum transfer efficiency from DART's impact, obtainable with Hera, yields a value of about 0.25. This represents a significant improvement compared to current estimates. Overall, the retrieved values meet the Hera radio science requirements and goals, and remain valid under the condition that the system is determined to be in an excited but non-chaotic (or tumbling) state. The Hera radio science experiment will play an integral role in the exploration of the Didymos binary asteroid system and will provide unique scientific measurements, which, when combined with other observables such as optical images, altimetry measurements, and satellite-to-satellite tracking of the CubeSats, will support the mission's overarching goals in planetary defense and the deep understanding of binary asteroids.

Systematic training of table tennis players' physical performance based on artificial intelligence technology and data fusion of sensing devices

This research emphasises the value of physical training for table tennis players, particularly as ball speed and spin rate decline and emphasises how important intensity quality is to the game. Chinese table tennis players' dual identities place greater demands on the general growth of their learning and training as a crucial component of talent development preparation. Athletes' general quality, competitive level, and ability to avoid sports injuries are all improved by scientific and focused physical training. In order to achieve the functions of intelligent camera, multi-angle broadcasting, and 3D scene reproduction, this study combines the physical training model of artificial intelligence. This gives the audience a more engaging and in-depth viewing experience. More feature extraction of the match footage is made possible by deep learning and convolutional neural networks when combined with large-scale video data, greatly enhancing the match information for viewers. The experimental findings demonstrate that the accuracy of table tennis human technical movement recognition reaches 98.88 % based on the enhanced AM-Softmax classification algorithm.

Analyzing the dynamics of a charged rotating rigid body under constant torques

This study explores the dynamical rotary motion of a charged axisymmetric spinning rigid body (RB) under the effect of a gyrostatic moment (GM). The influence of transverse and invariable body fixed torques (IBFTs), and an electromagnetic force field, is also considered. Euler’s equations of motion (EOM) are utilized to derive the regulating system of motion for the problem in a suitable formulation. Due to the lack of torque exerted along the spin axis and the nearly symmetrical nature of the RB, the spin rate is nearly unchanged. Assuming slight angular deviations of the spin axis relative to a fixed direction in space, it is possible to derive approximate analytical solutions (AS) in closed form for the attitude, translational, and rotational movements. These concise solutions that are expressed in complex form are highly effective in analyzing the maneuvers performed by spinning RBs. The study focuses on deriving the AS for various variables including angular velocities, Euler’s angles, angular momentum, transverse displacements, transverse velocities, axial displacement, and axial velocity. The graphical simulation of the subsequently obtained solutions is presented to show their precision. Furthermore, the positive impacts that alterations in the body’s parameters have on the motion’s behavior are presented graphically. The corresponding phase plane curves, highlighting the influence of different values in relation to the electromagnetic force field, the GM, and the IBFTs are drawn to analyze the stability of the body’s motion. This study has a significant role in various scientific and engineering disciplines. Its importance lies in its ability to optimize mechanical systems, explain celestial motion, and enhance spacecraft performance.

Twist compensated, high accuracy and dynamic fiber optic shape sensing based on phase demodulation in optical frequency domain reflectometry

We present a twist compensated, high accuracy and dynamic fiber optic shape sensing based on phase demodulation in Optical Frequency Domain Reflectometry (OFDR) by using multiple single core fiber based sensor (MFS). A dynamic strain sensing is realized by tracking the optical phase in OFDR and combining with the phase de-hopping filtering algorithm, and the sensing spatial resolution reaches 45 μm. In addition, in order to eliminate the influence of external twist and fluctuation of inherent spin on the shape reconstruction results, we propose an external twist compensation method and inherent spin rate calibration method, respectively. Finally, we use a circle segment method to reconstruct a 3D shape of MFS. The experimental results show that the reconstruction accuracies by the proposed external twist compensation and inherent spin rate calibration methods increase over 18 times and 20 times than those without these two methods, respectively. At the same time, comparing with the traditional cross-correlation-based method, we find that the proposed phase demodulation method has a similar reconstruction accuracy, the maximum reconstruction error is 0.61 %, whereas the shape reconstruction speed is improved by nearly 10 times. This is of great significance for the application of FOSS, which can be used for dynamic shape sensing such as intelligent soft robots, surgical robot and etc.