54,580 research outputs found
Mathematical modelling and experimental validation of electrostatic sensors for rotational speed measurement
Recent research has demonstrated that electrostatic sensors can be applied to the measurement of rotational speed with excellent repeatability and accuracy under a range of conditions. However, the sensing mechanism and fundamental characteristics of the electrostatic sensors are still largely unknown and hence the design of the sensors is not optimised for rotational speed measurement. This paper presents the mathematical modelling of strip electrostatic sensors for rotational speed measurement and associated experimental studies for the validation of the modelling results. In the modelling, an ideal point charge on the surface of the rotating object is regarded as an impulse input to the sensing system. The fundamental characteristics of the sensor, including spatial sensitivity, spatial filtering length and signal bandwidth, are quantified from the developed model. The effects of the geometric dimensions of the electrode, the distance between the electrode and the rotor surface and the rotational speed being measured on the performance of the sensor are analyzed. A close agreement between the modelling results and experimental measurements has been observed under a range of conditions. Optimal design of the electrostatic sensor for a given rotor size is suggested and discussed in accordance with the modelling and experimental results
Correlations and fluctuations measured by the CMS experiment in pp and PbPb
Measurements of charged dihadron angular correlations are presented in
proton-proton (pp) and Lead-Lead (PbPb) collisions, over a broad range of
pseudorapidity and azimuthal angle, using the CMS detector at the LHC. In very
high multiplicity pp events at center-of-mass energy of 7 TeV, a striking
"ridge"-like structure emerges in the two-dimensional correlation function for
particle pairs with intermediate pt of 1-3 GeVc, in the kinematic region
2.0<|\Delta\eta|<4.8 and small \Delta\phi, which is similar to observations in
heavy-ion collisions. Studies of this new effect as a function of particle
transverse momentum are discussed. The long-range and short-range dihadron
correlations are also studied in PbPb collision at a nucleon-nucleon
center-of-mass energy of 2.76 TeV, as a function of transverse momentum and
collision centrality. A Fourier analysis of the long-range dihadron
correlations is presented and discussed in the context of CMS measurements of
higher order flow coefficients.Comment: 8 pages, 8 figures, proceedings for Quark Matter 2011, Annecy,
France, May 23-28, 201
Human gait recognition with matrix representation
Human gait is an important biometric feature. It can be perceived from a great distance and has recently attracted greater attention in video-surveillance-related applications, such as closed-circuit television. We explore gait recognition based on a matrix representation in this paper. First, binary silhouettes over one gait cycle are averaged. As a result, each gait video sequence, containing a number of gait cycles, is represented by a series of gray-level averaged images. Then, a matrix-based unsupervised algorithm, namely coupled subspace analysis (CSA), is employed as a preprocessing step to remove noise and retain the most representative information. Finally, a supervised algorithm, namely discriminant analysis with tensor representation, is applied to further improve classification ability. This matrix-based scheme demonstrates a much better gait recognition performance than state-of-the-art algorithms on the standard USF HumanID Gait database
Analysis of pion elliptic flows and HBT interferometry in a granular quark-gluon plasma droplet model
In many simulations of high-energy heavy-ion collisions on an event-by-event
analysis, it is known that the initial energy density distribution in the
transverse plane is highly fluctuating. Subsequent longitudinal expansion will
lead to many longitudinal tubes of quark-gluon plasma which have tendencies to
break up into many spherical droplets because of sausage instabilities. We are
therefore motivated to use a model of quark-gluon plasma granular droplets that
evolve hydrodynamically to investigate pion elliptic flows and
Hanbury-Brown-Twiss interferometry. We find that the data of pion transverse
momentum spectra, elliptic flows, and HBT radii in \sqrt{s_{NN}}=200 GeV Au +
Au collisions at RHIC can be described well by an expanding source of granular
droplets with an anisotropic velocity distribution.Comment: 9 pages, 6 figures, in Late
K-essence Explains a Lorentz Violation Experiment
Recently, a state of the art experiment shows evidence for Lorentz violation
in the gravitational sector. To explain this experiment, we investigate a
spontaneous Lorentz violation scenario with a generalized scalar field. We find
that when the scalar field is nonminimally coupled to gravity, the Lorentz
violation induces a deformation in the Newtonian potential along the direction
of Lorentz violation.Comment: 8 pages, the final version, discussion and references adde
Approximation for discrete Fourier transform and application in study of three-dimensional interacting electron gas
The discrete Fourier transform is approximated by summing over part of the
terms with corresponding weights. The approximation reduces significantly the
requirement for computer memory storage and enhances the numerical computation
efficiency with several orders without loosing accuracy. As an example, we
apply the algorithm to study the three-dimensional interacting electron gas
under the renormalized-ring-diagram approximation where the Green's function
needs to be self-consistently solved. We present the results for the chemical
potential, compressibility, free energy, entropy, and specific heat of the
system. The ground-state energy obtained by the present calculation is compared
with the existing results of Monte Carlo simulation and random-phase
approximation.Comment: 11 pages, 13 figure
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