On Spin Dependence of Relativistic Acoustic Geometry

This work makes the first ever attempt to understand the influence of the black hole background space-time in determining the fundamental properties of the embedded relativistic acoustic geometry. To accomplish such task, the role of the spin angular momentum of the astrophysical black hole (the Kerr parameter $a$ -- a representative feature of the background black hole metric) in estimating the value of the acoustic surface gravity (the representative feature of the corresponding analogue space time) has been investigated for axially symmetric inflow of hydrodynamic fluid onto a rotating black hole. Since almost all astrophysical black holes are supposed to posses some degree of intrinsic rotation, the influence of the Kerr parameter on classical analogue models is very important to understand. For certain values of the initial boundary conditions describing the aforementioned flow, more than one acoustic horizons, namely two black hole type and one white hole type, may form, where the surface gravity may become formally infinite at the acoustic white hole. The connection between the corresponding analogue Hawking temperature with astrophysically relevant observables associated with the spectral signature has been discussed.Comment: 22 pages, 11 figures, Comments welcom

HOP llMlNG OF SPLlT STEP AND KINETICS ANALYSIS OF LOWER EXTREMITIES IN BADMINTON START FOOTWORK

The purpose of this study was to compare the split timing, and lower extremity kinetics of badminton players during push-off steps in six directions. Eight collegiate elite male badminton players received the random shot from an opponent in one of six directions. Result: Hop timing was 0.014-0.037 sec after the opponent struck the shuttlecock. The leg that was opposite the movement direction showed significantly greater tower extremity horizontal push-off force than the other leg did. Conclusion: The hop timing of split step simultaneous with the opponent striking the shuttlecock. The leg opposite the movement direction was the main push leg. When lower extremities exhibit the correct pushing direction and reach the peak push off force within 0.3 sec after the opponent strikes the shuttlecock, players should have more effective return in badminton

BIOMECHANICAL ANALYSIS OF BADMINTON FOREHAND NET SHOTS

The purpose of this study was to compare the upper extremity kinematics variables of badminton forehand dab shot, stab shot and cross court net shot. The participants were eight elite collegiate male players in Taiwan. The kinematical data were collected by Vicon system (250Hz) and the Visual 3D software was used to analyze the variables. The results indicated that the elite badminton players perfomed dab net shot with less angular velocity in racket upper limb joints. They performed the stab net shot with faster angular velocity in forearm supination and wrist ulnar flexion. The cross court net shot had greatest angular velocity in shoulder internal rotation, forearm pronation and the least distance between the contact point and the mid-line of body

KINEMATICAL ANALYSIS OF TWO DIFFERENT FOREHAND BADMINTON DROP SHOTS TECHNIQUES

The purpose of this study was to compare the kinematics variables between badminton forehand regular and reverse slice drop shots. The participants were eight elite male players. Eight Vicon Motion T20s System cameras (300Hz) were used to record the 3D kinematic data, which were computed by Visual 3D software. All the variables were tested by Wilcoxon rank analysis of variance nonparametric statistical test with the significant level at a = .05. The results showed that there was significant difference between the two forehand drop shots in the racket pan angle. The strategy of two drop shots seems different. That might because the reverse slice drop was with greater shoulder abduction movement than the regular drop shot. The players performed reverse slice drop shot might because that the abduction movement was similar with the smash