2,850 research outputs found
Kinematic variations due to changes in pace during men's and women's 5 km road running
The purpose of this study was to investigate variations in kinematic parameters in men's and women's 5 km road racing. Athletes often vary their pace and changes particularly tend to occur towards the end of a race due to fatigue and sprint finishes. Twenty competitive distance runners (10 male, 10 female) were videoed as they completed the English National 5 km championships. Three-dimensional kinematic data were analysed using motion analysis software (SIMI, Munich). Data were recorded at 950 m, 2,400 m and 3,850 m. Repeated measures ANOVA showed significant decreases in speed due to reduced step length and cadence in both men and women. These decreases predominantly occurred between the first two measurement points. The hip, knee, ankle and shoulder angles at both initial contact and toe-off did not change significantly, but there were significant reductions in the elbow angle for both men (at initial contact) and women (at toe-off)
Development of a Large-Area Aerogel Cherenkov Counter Onboard BESS
This paper describes the development of a threshold type aerogel Cherenkov
counter with a large sensitive area of 0.6 m to be carried onboard the BESS
rigidity spectrometer to detect cosmic-ray antiprotons. The design incorporates
a large diffusion box containing 46 finemesh photomultipliers, with special
attention being paid to achieving good performance under a magnetic field and
providing sufficient endurance while minimizing material usage. The refractive
index of the aerogel was chosen to be 1.03. By utilizing the muons and protons
accumulated during the cosmic-ray measurements at sea level, a rejection factor
of 10 was obtained against muons with , while keeping 97%
efficiency for protons below the threshold.Comment: 13 pages, LaTex, 9 eps figures included, submitted to NIM
First-Order Melting and Dynamics of Flux Lines in a Model for YBaCuO
We have studied the statics and dynamics of flux lines in a model for YBCO,
using both Monte Carlo simulations and Langevin dynamics. For a clean system,
both approaches yield the same melting curve, which is found to be weakly first
order with a heat of fusion of about per vortex pancake at a
field of The time averaged magnetic field distribution
experienced by a fixed spin is found to undergo a qualitative change at
freezing, in agreement with NMR and experiments. Melting in the
clean system is accompanied by a proliferation of free disclinations which show
a clear B-dependent 3D-2D crossover from long disclination lines parallel to
the c-axis at low fields, to 2D ``pancake'' disclinations at higher fields.
Strong point pins produce a logarithmical relaxation which results from
slow annealing out of disclinations in disordered samples.Comment: 31 pages, latex, revtex, 12 figures available upon request, No major
changes to the original text, but some errors in the axes scale for Figures 6
and 7 were corrected(new figures available upon request), to be published in
Physical Review B, July 199
Motion-Induced Magnetic Resonance of Rb Atoms in a Periodic Magnetostatic Field
We demonstrate that transitions between Zeeman-split sublevels of Rb atoms
are resonantly induced by the motion of the atoms (velocity: about 100 m/s) in
a periodic magnetostatic field (period: 1 mm) when the Zeeman splitting
corresponds to the frequency of the magnetic field experienced by the moving
atoms. A circularly polarized laser beam polarizes Rb atoms with a velocity
selected using the Doppler effect and detects their magnetic resonance in a
thin cell, to which the periodic field is applied with the arrays of parallel
current-carrying wires.Comment: 4 pages, 4 figures; minor corrections, Ref. [9] removed, published in
PR
A Collaborative Decision Environment for UAV Operations
NASA is developing Intelligent Mission Management (IMM) technology for science missions employing long endurance unmanned aerial vehicles (UAV's). The IMM groundbased component is the Collaborative Decision Environment (CDE), a ground system that provides the Mission/Science team with situational awareness, collaboration, and decisionmaking tools. The CDE is used for pre-flight planning, mission monitoring, and visualization of acquired data. It integrates external data products used for planning and executing a mission, such as weather, satellite data products, and topographic maps by leveraging established and emerging Open Geospatial Consortium (OGC) standards to acquire external data products via the Internet, and an industry standard geographic information system (GIs) toolkit for visualization As a Science/Mission team may be geographically dispersed, the CDE is capable of providing access to remote users across wide area networks using Web Services technology. A prototype CDE is being developed for an instrument checkout flight on a manned aircraft in the fall of 2005, in preparation for a full deployment in support of the US Forest Service and NASA Ames Western States Fire Mission in 2006
CANGAROO-III Observation of TeV Gamma Rays from the vicinity of PSR B1 706-44
Observation by the CANGAROO-III stereoscopic system of the Imaging Cherenkov
Telescope has detected extended emission of TeV gamma rays in the vicinity of
the pulsar PSR B170644. The strength of the signal observed as
gamma-ray-like events varies when we apply different ways of emulating
background events. The reason for such uncertainties is argued in relevance to
gamma-rays embedded in the "off-source data", that is, unknown sources and
diffuse emission in the Galactic plane, namely, the existence of a complex
structure of TeV gamma-ray emission around PSR B170644.Comment: 10 pages, 13 figures, to be published in Ap
Two-color photoassociation spectroscopy of ytterbium atoms and the precise determinations of s-wave scattering lengths
By performing high-resolution two-color photoassociation spectroscopy, we
have successfully determined the binding energies of several of the last bound
states of the homonuclear dimers of six different isotopes of ytterbium. These
spectroscopic data are in excellent agreement with theoretical calculations
based on a simple model potential, which very precisely predicts the s-wave
scattering lengths of all 28 pairs of the seven stable isotopes. The s-wave
scattering lengths for collision of two atoms of the same isotopic species are
13.33(18) nm for ^{168}Yb, 3.38(11) nm for ^{170}Yb, -0.15(19) nm for ^{171}Yb,
-31.7(3.4) nm for ^{172}Yb, 10.55(11) nm for ^{173}Yb, 5.55(8) nm for ^{174}Yb,
and -1.28(23) nm for ^{176}Yb. The coefficient of the lead term of the
long-range van der Waals potential of the Yb_2 molecule is C_6=1932(30) atomic
units J nm^6).Comment: 9 pages, 7 figure
DETERMINATION OF BODY SEGMENT INERTIA PARAMETERS USING 3D HUMAN BODY SCANNER AND 3D CAD SOFTWARE
In the field of sports biomechanics, a human body is often treated as a linkage model to investigate various kinds of human movement. This modeling requires body segment inertia parameters (BSPs) such as masses, centers of mass, and moments of inertia. As the quality of motion capture system increases, more accurate BSPs are also needed to get accurate inverse dynamics results. Advanced technology has enabled us to obtain three-dimensional coordinates of the entire body surface. A 3D CAD software has also been able to be applied to measure the human body. It was hypothesized that BSPs with high accuracy could be determined by the combination of a 3D body scanner and a 3D CAD software. The purposes of this study are, first, to introduce a new method of measuring subject-specific BSPs and, second, to compare the BSPs from this study with those from an existing mathematical model in order to
show that the proposed method can be used to produce more accurate BSPs
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