COMPUTER SIMULATION OF THE OPTIMAL VAULTING MOTION DURING THE HORSE (TABLE) CONTACT PHASE

The purpose of this research is to investigate how the kinematic factors during the horse (table) contact phase influence the post-flight performance in handspring vaulting. A six-segment planar simulation model comprising the lower arm, upper arm, head-trunk, thigh, shank, and foot was customized to an elite gymnast. The body segment parameters, maximum joint torques, and initial kinematic parameters from video analysis of the subject are required for the optimal matching computer simulation. The model was able to match a handspring vault after adjusting the visco-elastic characteristics of the arm-horse interface and joint activation time histories. The model was then used to determine the key factors which influence performance by varying the initial conditions. The objective function was the vertical velocity of the body center of mass at takeoff. The results suggest that smaller wrist angle, greater wrist angular velocity, straighter elbow, greater shoulder angular velocity, greater maximum shoulder torque, and smaller hip angle at horse contact were crucial in achieving the optimal performance. Compared with the five-segment model with a visco-elastic shoulder of a previous study, the six-segment model without a visco-elastic shoulder could still closely match the real performance, and better mimic the actual pushing movement of the arms

Hierarchical Lattice Models of Hydrogen Bond Networks in Water

We develop a graph-based model of the hydrogen bond network in water, with a view towards quantitatively modeling the molecular-level correlational structure of the network. The networks are formed are studied by the constructing the model on two infinite-dimensional lattices. Our models are built \emph{bottom up}, based on microscopic information coming from atomistic simulations, and we show that the predictions of the model are consistent with known results from ab-initio simulations of liquid water. We show that simple entropic models can predict the correlations and clustering of local-coordination defects around tetrahedral waters observed in the atomistic simulations. We also find that orientational correlations between bonds are longer ranged than density correlations, and determine the directional correlations within closed loops and show that the patterns of water wires within these structures are also consistent with previous atomistic simulations. Our models show the existence of density and compressibility anomalies, as seen in the real liquid, and the phase diagram of these models is consistent with the singularity-free scenario previously proposed by Sastry and co-workers (Sastry et al, PRE 53, 6144 (1996)).Comment: 17 pages, published versio

Finite-size scaling of pseudo-critical point distributions in the random transverse-field Ising chain

We study the distribution of finite size pseudo-critical points in a one-dimensional random quantum magnet with a quantum phase transition described by an infinite randomness fixed point. Pseudo-critical points are defined in three different ways: the position of the maximum of the average entanglement entropy, the scaling behavior of the surface magnetization, and the energy of a soft mode. All three lead to a log-normal distribution of the pseudo-critical transverse fields, where the width scales as $L^{-1/\nu}$ with $\nu=2$ and the shift of the average value scales as $L^{-1/\nu_{typ}}$ with $\nu_{typ}=1$, which we related to the scaling of average and typical quantities in the critical region.Comment: 4 pages, 2 figure

A rapid cosmic-ray increase in BC 3372-3371 from ancient buried tree rings in China

Cosmic rays interact with the Earth's atmosphere to produce $^{14}$C, which can be absorbed by trees. Therefore, rapid increases of $^{14}$C in tree rings can be used to probe previous cosmic-ray events. By this method, three $^{14}$C rapidly increasing events have been found. Plausible causes of these events include large solar proton events, supernovae or short gamma-ray bursts. However, due to the lack of measurements of $^{14}$C by year, the occurrence frequency of such $^{14}$C rapidly increasing events is poorly known. In addition, rapid increases may be hidden in the IntCal13 data with five-year resolution. Here we report the result of $^{14}$C measurements using an ancient buried tree during the period between BC 3388 and 3358. We find a rapid increase of about 9\textperthousand~ in the $^{14}$C content from BC 3372 to BC 3371. We suggest that this event could originate from a large solar proton event.Comment: 23 pages, 3 figures, 2 tables, published in Nature Communication

Comparison of Particle Swarm Optimization and Self-Adaptive Dynamic Differential Evolution for the Imaging of a Periodic Conductor

[[abstract]]The application of two techniques to reconstruct the shape of a two-dimensional periodic perfect conductor from mimic the measurement data is presented. A periodic conducting cylinder of unknown periodic length and shape scatters the incident wave in half-space and the scattered field is recorded outside. After an integral formulation, the microwave imaging is recast as a nonlinear optimization problem; a cost functional is defined by the norm of a difference between the measured scattered electric fields and the calculated scattered fields for an estimated shape of a conductor. Thus, the shape of conductor can be obtained by minimizing the cost function. In order to solve this inverse scattering problem, transverse magnetic (TM) waves are incident upon the objects and two techniques are employed to solve these problems. The first is based on an particle swarm optimization (PSO) and the second is a self-adaptive dynamic differential evolution (SADDE). Both techniques have been tested in the case of simulated mimic the measurement data contaminated by additive white Gaussian noise. Numerical results indicate that the SADDE algorithm is better than the PSO in reconstructed accuracy and convergence speed.[[notice]]補正完畢[[incitationindex]]SC

The Core Mass Function in the Massive Protocluster G286.21+0.17 revealed by ALMA

We study the core mass function (CMF) of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array via 1.3~mm continuum emission at a resolution of 1.0\arcsec\ (2500~au). We have mapped a field of 5.3\arcmin$\times$5.3\arcmin\ centered on the protocluster clump. We measure the CMF in the central region, exploring various core detection algorithms, which give source numbers ranging from 60 to 125, depending on parameter selection. We estimate completeness corrections due to imperfect flux recovery and core identification via artificial core insertion experiments. For masses $M\gtrsim1\:M_\odot$, the fiducial dendrogram-identified CMF can be fit with a power law of the form ${\rm{d}}N/{\rm{d}}{\rm{log}}M\propto{M}^{-\alpha}$ with $\alpha \simeq1.24\pm0.17$, slightly shallower than, but still consistent with, the index of the Salpeter stellar initial mass function of 1.35. Clumpfind-identified CMFs are significantly shallower with $\alpha\simeq0.64\pm0.13$. While raw CMFs show a peak near $1\:M_\odot$, completeness-corrected CMFs are consistent with a single power law extending down to $\sim 0.5\:M_\odot$, with only a tentative indication of a shallowing of the slope around $\sim1\:M_\odot$. We discuss the implications of these results for star and star cluster formation theories.Comment: 11 pages, accepted by Ap