THE DYNAMIC ANALYSIS OF THE APPLIED FORCE ON JAVELIN DURING FINAL THRUST BY AN ELITE JAVELIN THROWER

According to the javelin rules, a throw is valid only if the tip strikes the ground before any other part of the javelin. So it is important to precisely control the applied force on javelin for further distance and tip-first landing. Two synchronized Redlake high-speed cameras (250 Hz) were used to videotape an elite thrower; a javelin with three fixed non-collinear markers was used in experiment. The aerodynamics and Newton-Euler equation were taken into account in the 3D inverse dynamic analysis. The results showed that the force was mainly on the axial direction as the whole hand gripped the javelin. However, as the portion of hand touching the javelin became lesser, the direction of force was changed from axial to lateral direction. The lateral torque was significantly larger than axial torque during the whole phase, and their maxima were 24.08 and 1.31 Nm, respectively. The results measured by this method were similar to those by force sensor, and it could be suitable for use in further researches

THE CALCULATION ON THE ROTATIONAL KINEMATICS ABOUT THE LONGITUDINAL AXIS OF JAVELIN BY THREE METHODS

The motion of javelin is complicated after it is released. Itis necessary to use some skills to calculate the rotation kinematics about the longitudinal axis of javelin. In this study, the Euler angle, the Cardan angle and the screw axis methods were used to calculate these kinematic variables. Two synchronized Redlake high-speed cameras (250 Hz) and a javelin with three fixed reflective markers were used in the experiment. Generally the results by three methods were close, and all of the three methods are suitable for the calculation on these variables. In the Euler angle and Cardan angle methods, the order of rotation sequence needs to be taken account, however no similar problem occurred in screw method. The results suggested that the longitudinal axis should be set as second axis in either Euler angle or Cardan angle methods to avoid Gimbal Lock (singularity) problem

Improvement of two-way continuous-variable quantum key distribution using optical amplifiers

The imperfections of a receiver's detector affect the performance of two-way continuous-variable quantum key distribution protocols and are difficult to adjust in practical situations. We propose a method to improve the performance of two-way continuous-variable quantum key distribution by adding a parameter-adjustable optical amplifier at the receiver. A security analysis is derived against a two-mode collective entangling cloner attack. Our simulations show that the proposed method can improve the performance of protocols as long as the inherent noise of the amplifier is lower than a critical value, defined as the tolerable amplifier noise. Furthermore, the optimal performance can approach the scenario where a perfect detector is used.Comment: 14 pages, 7 figure

Residence of Habitat-Specific Anammox Bacteria in the Deep-Sea Subsurface Sediments of the South China Sea: Analyses of Marker Gene Abundance with Physical Chemical Parameters

Anaerobic ammonium oxidation (anammox) has been recognized as an important process for the global nitrogen cycle. In this study, the occurrence and diversity of anammox bacteria in the deep-sea subsurface sediments of the South China Sea (SCS) were investigated. Results indicated that the anammox bacterial sequences recovered from this habitat by amplifying both 16S rRNA gene and hydrazine oxidoreductase encoding hzo gene were all closely related to the Candidatus Scalindua genus. A total of 96 16S rRNA gene sequences from 346 clones were grouped into five subclusters: two subclusters affiliated with the brodae and arabica species, while three new subclusters named zhenghei-I, -II, and -III showed ≤97.4% nucleic acid sequence identity with other known Candidatus Scalindua species. Meanwhile, 88 hzo gene sequences from the sediments also formed five distant subclusters within hzo cluster 1c. Through fluorescent real-time PCR analysis, the abundance of anammox bacteria in deep-sea subsurface sediment was quantified by hzo genes, which ranged from 1.19 × 104 to 7.17 × 104 copies per gram of dry sediments. Combining all the information from this study, diverse Candidatus Scalindua anammox bacteria were found in the deep-sea subsurface sediments of the SCS, and they could be involved in the nitrogen loss from the fixed inventory in the habitat

Mass spectra of bottom-charm baryons

In this paper, we investigate the mass spectra of bottom-charm baryons systematically, where the relativistic quark model and the infinitesimally shifted Gaussian basis function method are employed. Our calculation shows that the $\rho$-mode appears lower in energy than the other excited modes. According to this feature, the allowed quantum states are selected and a systematic study of the mass spectra for $\Xi_{bc}^{'}$ ($\Xi_{bc}$) and $\Omega_{bc}^{'}$ ($\Omega_{bc}$) families is performed. The root mean square radii and quark radial probability density distributions of these baryons are analyzed as well. Next, the Regge trajectories in the $(J,M^{2})$ plane are successfully constructed based on the mass spectra. At last, we present the structures of the mass spectra, and analyze the difficulty and opportunity in searching for the ground states of bottom-charm baryons in experiment.Comment: 19 pages, 9 figures, 6 tables. arXiv admin note: text overlap with arXiv:2210.1308

Mass spectra of double-bottom baryons

Based on the relativistic quark model and the infinitesimally shifted Gaussian basis function method, we investigate the mass spectra of double bottom baryons systematically. In the $\rho$-mode which appears lower in energy than the other excited modes, we obtain the allowed quantum states and perform a systematic study of the mass spectra of the $\Xi_{bb}$ and $\Omega_{bb}$ families. We analyze the root mean square radii and quark radial probability density distributions to deeply understand the structure of the heavy baryons. Meanwhile, the mass spectra allow us to successfully construct the Regge trajectories in the $(J,M^{2})$ plane. We also predict the masses of the ground states of double bottom baryons and discuss the differences between the structures of our spectra and those from other theoretical methods. At last, the shell structure of the double bottom baryon spectra is shown, from which one could get a bird's-eye view of the mass spectra.Comment: 16 pages, 9 figures, 5 tables. arXiv admin note: text overlap with arXiv:2207.0416

THE BIOMECHANICAL ANALYSIS OF THE TAEKWONDO FRONT-LEG AXE-KICK

The purpose of the study was to analyze the biomechanics of taekwondo front-leg axekick. One force plates, two synchronized high-speed cameras were used to measure biomechanical parameters in each phase of the front-leg axe-kick. The results included: 1. The average reaction time and movement time were 0.423 sand 0.327 s, which respectively occupied about 56% and 44% of attack time. 2. The maximum velocity of hip, knee and ankle were 1.74 m/s, 5.25 m/s and 7.43 m/s respectively. When the kicking leg touched the target, the velocity of knee and ankle were 0.78m/s, 1.72m1s, and 4.64m1s respectively. 3. The peak vertical GRF and impulse were 0.96 SW and 77.57N-s. For decreasing the movement time, it's suggested that an athlete should increase the power and flexibility of lower extremities during the training section

20-Hydroxyecdysone (20E) Primary Response Gene \u3cem\u3eE75\u3c/em\u3e Isoforms Mediate Steroidogenesis Autoregulation and Regulate Developmental Timing in \u3cem\u3eBombyx\u3c/em\u3e

The temporal control mechanisms that precisely control animal development remain largely elusive. The timing of major developmental transitions in insects, including molting and metamorphosis, is coordinated by the steroid hormone 20-hydroxyecdysone (20E). 20E involves feedback loops to maintain pulses of ecdysteroid biosynthesis leading to its upsurge, whereas the underpinning molecular mechanisms are not well understood. Using the silkworm Bombyx mori as a model, we demonstrated that E75, the 20E primary response gene, mediates a regulatory loop between ecdysteroid biosynthesis and 20E signaling. E75 isoforms A and C directly bind to retinoic acid receptor-related response elements in Halloween gene promoter regions to induce gene expression thus promoting ecdysteroid biosynthesis and developmental transition, whereas isoform B antagonizes the transcriptional activity of isoform A/C through physical interaction. As the expression of E75 isoforms is differentially induced by 20E, the E75-mediated regulatory loop represents a fine autoregulation of steroidogenesis, which contributes to the precise control of developmental timing

Behaviors of susceptible-infected epidemics on scale-free networks with identical infectivity

In this article, we proposed a susceptible-infected model with identical infectivity, in which, at every time step, each node can only contact a constant number of neighbors. We implemented this model on scale-free networks, and found that the infected population grows in an exponential form with the time scale proportional to the spreading rate. Further more, by numerical simulation, we demonstrated that the targeted immunization of the present model is much less efficient than that of the standard susceptible-infected model. Finally, we investigated a fast spreading strategy when only local information is available. Different from the extensively studied path finding strategy, the strategy preferring small-degree nodes is more efficient than that preferring large-degree nodes. Our results indicate the existence of an essential relationship between network traffic and network epidemic on scale-free networks.Comment: 5 figures and 7 page