245,318 research outputs found
Unsupervised two-class and multi-class support vector machines for abnormal traffic characterization
Although measurement-based real-time traffic classification has received considerable research attention, the timing constraints imposed by the high accuracy requirements and the learning phase of the algorithms employed still remain a challenge. In this paper we propose a measurement-based classification framework that exploits unsupervised learning to accurately categorise network anomalies to specific classes. We introduce the combinatorial use of two-class and multi-class unsupervised Support Vector Machines (SVM)s to first distinguish normal from anomalous traffic and to further classify the latter category to individual groups depending on the nature of the anomaly
GPS source solution of the 2004 Parkfield earthquake
We compute a series of finite-source parameter inversions of the fault
rupture of the 2004 Parkfield earthquake based on 1 Hz GPS records only. We
confirm that some of the co-seismic slip at shallow depth (<5 km) constrained
by InSAR data processing results from early post-seismic deformation. We also
show 1) that if located very close to the rupture, a GPS receiver can saturate
while it remains possible to estimate the ground velocity (~1.2 m/s) near the
fault, 2) that GPS waveforms inversions constrain that the slip distribution at
depth even when GPS monuments are not located directly above the ruptured areas
and 3) the slip distribution at depth from our best models agree with that
recovered from strong motion data. The 95th percentile of the slip amplitudes
for rupture velocities ranging from 2 to 5 km/s is, 55 +/- 6 cm.Comment: 24 pages including supp. material
Combinatorics and Geometry of Transportation Polytopes: An Update
A transportation polytope consists of all multidimensional arrays or tables
of non-negative real numbers that satisfy certain sum conditions on subsets of
the entries. They arise naturally in optimization and statistics, and also have
interest for discrete mathematics because permutation matrices, latin squares,
and magic squares appear naturally as lattice points of these polytopes.
In this paper we survey advances on the understanding of the combinatorics
and geometry of these polyhedra and include some recent unpublished results on
the diameter of graphs of these polytopes. In particular, this is a thirty-year
update on the status of a list of open questions last visited in the 1984 book
by Yemelichev, Kovalev and Kravtsov and the 1986 survey paper of Vlach.Comment: 35 pages, 13 figure
Non-Classical Response from Quench-Cooled Solid Helium Confined in Porous Gold
We have investigated the non-classical response of solid 4He confined in
porous gold set to torsional oscillation. When solid helium is grown rapidly,
nearly 7% of the solid helium appears to be decoupled from the oscillation
below about 200 mK. Dissipation appears at temperatures where the decoupling
shows maximum variation. In contrast, the decoupling is substantially reduced
in slowly grown solid helium. The dynamic response of solid helium was also
studied by imposing a sudden increase in the amplitude of oscillation. Extended
relaxation in the resonant period shift, suggesting the emergence of the
pinning of low energy excitations, was observed below the onset temperature of
the non-classical response. The motion of a dislocation or a glassy solid is
restricted in the entangled narrow pores and is not likely responsible for the
period shift and long relaxation
Liquid phase products and solid deposit formation from thermally stressed model jet fuels
The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given
Magnetic field dependence of charge stripe order in La2-xBaxCuO4 (x~1/8)
We have carried out a detailed investigation of the magnetic field dependence
of charge ordering in La2-xBaxCuO4 (x~1/8) utilizing high-resolution x-ray
scattering. We find that the charge order correlation length increases as the
magnetic field greater than ~5T is applied in the superconducting phase (T=2K).
The observed unusual field dependence of the charge order correlation length
suggests that the static charge stripe order competes with the superconducting
ground state in this sample.Comment: 4 pages, 4 figure
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