Relationships between Racket Arm Joint Moments and Racket Head Speed during the Badminton Jump Smash Performed by Elite Male Malaysian Players

Three-dimensional position data of nineteen elite male Malaysian badminton players performing a series of maximal jump smashes were collected using a motion capture system. A ‘resultant moments’ inverse dynamics analysis was performed on the racket arm joints (shoulder, elbow and wrist). Relationships between racket head speed and peak joint moments were quantified using correlational analyses, inclusive of a Benjamini–Hochberg correction for multiple-hypothesis testing. The racket head centre speed at racket–shuttlecock contact was, on average, 61.2 m/s with a peak of 68.5 m/s which equated to average shuttlecock speeds of 95.2 m/s with a peak of 105.0 m/s. The correlational analysis revealed that a larger shoulder internal rotation moment (r = 0.737), backwards shoulder plane of elevation moment (r = 0.614) and wrist extension moment (r = −0.564) were associated with greater racket head centre speed at racket–shuttlecock contact. Coaches should consider strengthening the musculature associated with shoulder internal rotation, plane of elevation and wrist extension. This work provides a unique analysis of the joint moments of the racket arm during the badminton jump smash performed by an elite population and highlights significant relationships between racket head speed and peak resultant joint moments.

Impacts of Rotation Axis and Frequency on Vestibular Perceptual Thresholds

In an effort to characterize the factors influencing the perception of self-motion rotational cues, vestibular self-motion perceptual thresholds were measured in 14 subjects for rotations in the roll and pitch planes, as well as in the planes aligned with the anatomic orientation of the vertical semicircular canals (i.e., left anterior, right posterior; LARP, and right anterior, left posterior; RALP). To determine the multisensory influence of concurrent otolith cues, within each plane of motion, thresholds were measured at four discrete frequencies for rotations about earth-horizontal (i.e., tilts; EH) and earth-vertical axes (i.e., head positioned in the plane of the rotation; EV). We found that the perception of rotations, stimulating primarily the vertical canals, was consistent with the behavior of a high-pass filter for all planes of motion, with velocity thresholds increasing at lower frequencies of rotation. In contrast, tilt (i.e, EH rotation) velocity thresholds, stimulating both the canals and otoliths (i.e., multisensory integration), decreased at lower frequencies and were significantly lower than earth-vertical rotation thresholds at each frequency below 2 Hz. These data suggest that multisensory integration of otolithic gravity cues with semicircular canal rotation cues enhances perceptual precision for tilt motions at frequencies below 2 Hz. We also showed that rotation thresholds, at least partially, were dependent on the orientation of the rotation plane relative to the anatomical alignment of the vertical canals. Collectively these data provide the first comprehensive report of how frequency and axis of rotation influence perception of rotational self-motion cues stimulating the vertical canals.

Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (V = 8.81) M dwarf AU Mic. The planet was preliminary detected in Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet’s atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle λ value of −2.96−10.30+10.44 degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.

Integration of affine ICP into the precise localization problem of smart-AGVs: Procedures, enhancements and challenges

The localization problem in robotics has been widely studied both for indoor and outdoor applications, but is still open for improvements. In indoor environments, GPS-based methods are not preferred due to reflections, and the pose of the robot is determined according to the measurements taken around with its sensors. One of them is iterative closest point (ICP)-based localization method. ICP is a point set registration method, the essence of which is to iteratively compute the transformation between two point sets. However, it is also utilized to solve the localization problem thanks to its high precision in registration. Precise localization is important for applications that require highly accurate pose estimation, such as for smart-AGVs to be used in smart factories to reach a station at industrial standards. Traditional ICP finds transformation in terms of a rotation and translation, and thus can be directly applied to the localization problem. On the other hand, the affine variant of ICP is not adapted to solve the localization problem. In this study, the necessary arrangements to make affine ICP suitable for precise localization are given as a procedure such that the transformation between point sets is found by affine ICP, the resulting transformation is projected to rotation plane by polar decomposition and then the pose is estimated. The enhancements achieved with the usage of affine ICP in precise localization problems are demonstrated in simulation by comparing localization performance of affine ICP with that of traditional ICP. For this purpose, in a factory environment, a scenario where a smart-AGV approaching the target autonomously to carry out an operation has been prepared. The performances of the algorithms have been evaluated for five different docking stations with 30 separate experiments. Moreover, the challenges related to the affine ICP-based fine localization, in particular about finding projection of affine transformation to rotation plane, are highlighted in this study.

APPLICATION OF THE “FINITE ROTATION AND DISPLACEMENT” METHOD TO CONTROL THE PARABOLIC ANTENNA

The article deals with the application of the "finite rotation and displacement" method (FRDM) which can find the desired values of the generalized coordinates for the control system of a parabolic antenna. The special manipulator of a sequential structure with sufficient rigidity is used to control the parabolic antenna. The rigidity of this manipulator is ensured by use of links in the form of spherical shells and bearings located along the perimeter of each shell in the rotation plane of each link. It allows to optimally place the material of the manipulator's design and to obtain sufficient rigidity with minimal weight. The manipulator consists of four links connected by fifth class kinematic pairs with an arbitrary inclination of the axes. For this task the antenna's orientation is important without taking into account the small displacement of its position during the process of its orientation. The FRDM method provides both orientation and position. It is based on determining the precise and optimal iterative steps for each degree of mobility, providing maximum approximation to the specified orientation parameters of the parabolic antenna. According to the method's algorithm, the software is developed consisting of subprograms for organizing a general solution of the inverse kinematics for an arbitrary number of links and a particular one for a manipulator in the form of source data. The initial data are the vector model of the manipulator, the values of the structural constraints of the generalized coordinates, and the characteristics of kinematic pairs by type and class

INFRARED ROTATION PLANE RADAR CHANGE DETECTION

The existing change detection method mainly stays on the pixel-level, which is very susceptible to light, shadow, etc. And the complex calculation and analysis for each pixel reduce the detection efficiency. Moreover, there is no modeling determination method to initialize standard deviation of each element for existing mixed Gaussian background modeling methods. In this paper, an improved mixed Gaussian background modeling method is proposed, with the use of infrared rotation plane radar. The relationship between the corrected standard deviation of distance and the detection intensity is used to establish the curve of standard deviation of distance with detected intensity. For each data point, the standard deviation is initialized by the value estimated by the change curve, and the detected distance is used to establish the Gaussian mixture background model. The detection effect of the method is discussed and compared with the traditional Gauss background modeling in the experiment, the result shows that it has certain advantages in processing speed, adaptability to change background and accuracy of change detection.

Yawed Effect on Wind Turbine Near Wake

Wind turbines rotation was motivated by the force of wind. In reality, wind doesn’t moving vertically to the wind turbine rotation plane, but in random directions instead. Therefore, the yawed effect has to be taken into consideration when study wind turbine aerodynamic performance. The purpose of this study is to compare the difference between the wind turbine near wake flow with yawed effect and without yawed effect aerodynamically. The research uses CFD technology to simulate the rotation movement and air flow pattern, which is completed in software Ansys Workbench.

Magnetic structure of the chiral triangular magnet MnSb2O6

Incommensurate helical (or cycloidal) magnetic structure may have left- and right-wound states (helicity), which are in principle equally populated in a magnet with inversion symmetry. In addition, for a Heisenberg triangular antiferromagnet, clockwise and counter-clockwise rotations of the 120 degree spin structure provide another intriguing degree of freedom. Hence, a triangular magnet that has incommensurate helical ordering along the stacking direction will show intriguing interplay of the helicity (of the helical structure) and chirality (in the triangular plane). Such phenomenon is, however, rarely studied in the past since only one example, the Ba3NbFe3Si2O14 langathite, has been known to date [1]. In this work, we study MnSb2O6, which consists of distorted triangular lattice stacking along the c-axis [2,3]. MnSb2O6 belongs to the space group P321, and hence lacks inversion symmetry. Due to this fact, unique selection of the helicity and chirality may be expected. However, the earlier studies were carried out using unpolarized neutron diffraction with mostly the powder sample, and thus helicity and chirality selection cannot be concluded. Here, we have performed single-crystal diffraction experiment using polarized neutrons in addition to the unpolarized ones, and have succeeded in determination of the magnetic structure of MnSb2O6. The resulting magnetic structure is nearly cycloidal with the magnetic modulation vector q = (0, 0, 0.182) (see figure below). The spin rotation plane is, however, inclined from the ac-plane toward the b-axis for approximately 30 degrees. Polarization analysis indicates that both the helicity of the (nearly-) cycloidal structure and chirality of the in-plane 120 degree structure are uniquely selected. The 30 degree inclination from the ac-plane is a key finding of this work, allowing new kind of multiferroicity in this material.

The Appropriateness of the Helical Axis Technique and Six Available Cardan Sequences for the Representation of 3-D Lead Leg Kinematics During the Fencing Lunge

Cardan/Euler angles represent the most common technique for the quantification of segmental rotations. Cardan angles are influenced by their ordered sequence, and sensitive to planar-cross talk from the dominant rotation plane, which may affect the angular parameters. The International Society of Biomechanics (ISB) currently recommends a sagittal, coronal, and then transverse (XYZ) ordered sequence, although it has been proposed that when quantifying non-sagittal rotations this may not be the most appropriate technique. This study examined the influence of the helical and six available Cardan sequences on lower extremity three-dimensional (3-D) kinematics of the lead leg during the fencing lunge. Kinematic data were obtained using a 3-D motion capture system as participants completed simulated lunges. Repeated measures ANOVAs were used to compare discrete kinematic parameters, and intraclass correlations were also utilized to determine evidence of planar crosstalk. The results indicate that in all three planes of rotation, peak angle and range of motion angles using the YXZ and ZXY sequences were significantly greater than the other sequences. It was also noted that the utilization of the YXZ and ZXY sequences was associated with the strongest correlations from the sagittal plane, and the XYZ sequence was found habitually to be associated with the lowest correlations. It appears that for accurate representation of 3-D kinematics of the lead leg during the fencing lunge, the XYZ sequence is the most appropriate and as such its continued utilization is encouraged.