2,370 research outputs found
3-D KINEMATICAL ANALYSIS ON LEFT LEG TECHNIQUE IN THE LAST EXERTING IN JAVELIN THROWING
Javelin throwing is a kind of event that has a completely different personality and philosophy from the heave thrower, with almost unrestricted approach run. Approach speed and timing transition of body segment play an important role to performance. Through approach, for the elite world javelin throwers, the speed that the body and javelin obtain is 7-8 m/s before exerting finally. Through exerting, the speed of weight of the body is lowered to less than 3 m/s, and javelin obtain 21 m/s above speed. Therefore, through exerting oneself finally, the speed of javelin is increased rapidly, left side planting movement enabling momentum transmit and increase javelin speed. Hence, left leg technique play a important role During transition, the planting of the left leg have a key function, through "whip" technique, the speed of lower big part of the body gradually transmit to upper small arm, via hand, to javelin at last. This study investigated left leg contribution to javelin throwing during the last thrust phase. Eight female javelin throwers were taped during selective competition of X III Asian games in 1998. The subjects were videotaped at 50 frames per second. By analyzing left leg technique, the consciousness of left side supporting and stretching should increased, more and more coaches and athletes will pay more attention to stretching phase of left side supporting technique. The posture of the left foot falling to the ground has influence on left leg supporting technique to certain degree. Home outstanding women javelin throwers should make a little enlargement inside of angle that button up at left foot planting. Home outstanding women javelin throwers have a big buffer degree, hence make the left shoulder, left hip supported not enough. They should enhance the cowgirl muscle the cluster carrying the constringency of left shoulder crest of left shoulder; they should enhance the cowgirl muscle anti-carrying contracting training
Systematic investigation of the rotational bands in nuclei with using a particle-number conserving method based on a cranked shell model
The rotational bands in nuclei with are investigated
systematically by using a cranked shell model (CSM) with the pairing
correlations treated by a particle-number conserving (PNC) method, in which the
blocking effects are taken into account exactly. By fitting the experimental
single-particle spectra in these nuclei, a new set of Nilsson parameters
( and ) and deformation parameters ( and
) are proposed. The experimental kinematic moments of inertia
for the rotational bands in even-even, odd- and odd-odd nuclei, and the
bandhead energies of the 1-quasiparticle bands in odd- nuclei, are
reproduced quite well by the PNC-CSM calculations. By analyzing the
-dependence of the occupation probability of each cranked Nilsson
orbital near the Fermi surface and the contributions of valence orbitals in
each major shell to the angular momentum alignment, the upbending mechanism in
this region is understood clearly.Comment: 21 pages, 24 figures, extended version of arXiv: 1101.3607 (Phys.
Rev. C83, 011304R); added refs.; added Fig. 4 and discussions; Phys. Rev. C,
in pres
Failure Mode and Ductility of Dual Phase Steel with Edge Crack
AbstractDual phase steels having a microstructure consisting of a ferrite matrix, in which particles of martensite are dispersed, have received a great deal of attention due to their useful combination of high strength, high work hardening rate and ductility, all of which are favorable properties for forming processes. In the present work, various microstructure-level finite element models are generated based on the actual microstructure of DP590 steel, to capture the mechanical behavior and fracture mode. The failure mode of DP steels is predicted using the plastic strain localization theory, mainly resulting from the material microstructure-level inhomogeneity as well as the initial geometrical imperfection. Besides the simulation, tensile test specimens of dog bone type with different edge cracks were prepared on an internally designed blanking tool, and the corresponding deformation processes were recorded via digital image correlation system. It is found that the overall ductility of the DP590 steel strongly depends on the ductility of the ferrite matrix, and pre-existing edge cracks reduce the overall ductility of the steel and change the failure mode
A solution to persistent RFI in narrowband radio SETI: The MultiBeam Point-source Scanning strategy
Narrowband radio search for extraterrestrial intelligence (SETI) in the 21st
century suffers severely from radio frequency interference (RFI), resulting in
a high number of false positives, and it could be the major reason why we have
not yet received any messages from space. We thereby propose a novel
observation strategy, called MultiBeam Point-source Scanning (MBPS), to
revolutionize the way RFI is identified in narrowband radio SETI and provide a
prominent solution to the current situation. The MBPS strategy is a simple yet
powerful method that sequentially scans over the target star with different
beams of a telescope, hence creating real-time references in the time domain
for cross-verification, thus potentially identifying all long-persistent RFI
with a level of certainty never achieved in any previous attempts. By applying
the MBPS strategy during the observation of TRAPPIST-1 with the FAST telescope,
we successfully identified all 16,645 received signals as RFI using the solid
criteria introduced by the MBPS strategy. Therefore we present the MBPS
strategy as a promising tool that should bring us much closer to the first
discovery of a genuine galactic greeting
meson photoproduction in ultrarelativistic heavy ion collisions
The transverse momentum distributions for inclusive meson
described by gluon-gluon interactions from photoproduction processes in
relativistic heavy ion collisions are calculated. We considered the color
singlet (CS) and color octet (CO) components with the framework of
non-relativistic Quantum Chromodynamics (NRQCD) into the production of heavy
quarkonium. The phenomenological values of the matrix elements for the
color-singlet and color-octet components give the main contribution to the
production of heavy quarkonium from the gluon-gluon interaction caused by the
emission of additional gluon in the initial state. The numerical results
indicate that the contribution of photoproduction processes cannot be
negligible for mid-rapidity in p-p and Pb-Pb collisions at the Large Hadron
Collider (LHC) energies.Comment: 11 pages, 2 figure
A cosmic microscope to probe the Universe from Present to Cosmic Dawn - dual-element low-frequency space VLBI observatory
A space-based very long baseline interferometry (VLBI) programme, named as
the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space
working together with giant ground-based telescopes (e.g., Square Kilometre
Array, FAST, Arecibo) to image the low radio frequency Universe with the
purpose of unraveling the compact structure of cosmic constituents including
supermassive black holes and binaries, pulsars, astronomical masers and the
underlying source, and exoplanets amongst others. The operational frequency
bands are 30, 74, 330 and 1670 MHz, supporting broad science areas. The mission
plans to launch two 30-m-diameter radio telescopes into 2,000 km x 90,000 km
elliptical orbits. The two telescopes can work in flexibly diverse modes: (i)
space-ground VLBI. The maximum space-ground baseline length is about 100,000
km; it provides a high-dynamic-range imaging capacity with unprecedented high
resolutions at low frequencies (0.4 mas at 1.67 GHz and 20 mas at 30 MHz)
enabling studies of exoplanets and supermassive black hole binaries (which emit
nanoHz gravitational waves); (ii) space-space single-baseline VLBI. This unique
baseline enables the detection of flaring hydroxyl masers, and more precise
position measurement of pulsars and radio transients at milli-arcsecond level;
(iii) single dish mode, where each telescope can be used to monitor transient
bursts and rapidly trigger follow-up VLBI observations. The large space
telescope will also contribute in measuring and constraining the total angular
power spectrum from the Epoch of Reionization. In short, the Cosmic Microscope
offers astronomers the opportunity to conduct novel, frontier science.Comment: Accepted for publication in Chinese Journal of Space Science, 10
pages, 2 figure
Fermion Resonances on a Thick Brane with a Piecewise Warp Factor
In this paper, we mainly investigate the problems of resonances of massive KK
fermions on a single scalar constructed thick brane with a piecewise warp
factor matching smoothly. The distance between two boundaries and the other
parameters are determined by one free parameter through three junction
conditions. For the generalized Yukawa coupling
with odd , the mass eigenvalue , width , lifetime
, and maximal probability of fermion resonances are obtained.
Our numerical calculations show that the brane without internal structure also
favors the appearance of resonant states for both left- and right-handed
fermions. The scalar-fermion coupling and the thickness of the brane influence
the resonant behaviors of the massive KK fermions.Comment: V3: 15 pages, 7 figures, published versio
Time-resolved Measurement of Quadrupole Wakefields in Corrugated Structures
Corrugated structures have recently been widely used for manipulating
electron beam longitudinal phase space and for producing THz radiation. Here we
report on time-resolved measurements of the quadrupole wakefields in planar
corrugated structures. It is shown that while the time- dependent quadrupole
wakefield produced by a planar corrugated structure causes significant growth
in beam transverse emittance, it can be effectively canceled with a second
corrugated structure with orthogonal orientation. The strengths of the
time-dependent quadrupole wakefields for various corrugated structure gaps are
also measured and found to be in good agreement with theories. Our work should
forward the applications of corrugated structures in many accelerator based
scientific facilities
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