3,047 research outputs found
Network Position and Throughput Performance of Seaports
ISBN 978 90 5487 858 2The determinants of throughput volume at a given set of ports have rarely been approached from a network perspective. This paper proposes a set of novel indicators describing the relative situation of seaports in the worldwide maritime network of container shipping in 2006, which are distinguished among five categories: circulation (calls, vessels, and operators), foreland (distance to other ports and distribution of connections), connectivity itself (number of connections to other ports), centrality (betweenness and eccentricity), and neighbourhood (strength and clustering indices). Main results help to classify ports according to their location and function in the network, while they stress which parameters most influence throughput volumes. Although centrality indicators highly correlate with throughput, the latter seems to be influenced mostly by the geographic parameter of the maximum distance link to another port
Unsolvability of the Halting Problem in Quantum Dynamics
It is shown that the halting problem cannot be solved consistently in both
the Schrodinger and Heisenberg pictures of quantum dynamics. The existence of
the halting machine, which is assumed from quantum theory, leads into a
contradiction when we consider the case when the observer's reference frame is
the system that is to be evolved in both pictures. We then show that in order
to include the evolution of observer's reference frame in a physically sensible
way, the Heisenberg picture with time going backwards yields a correct
description.Comment: 4 pages, 3 figure
Fractal-based autonomous partial discharge pattern recognition method for MV motors
On-line partial discharge (PD) monitoring is being increasingly adopted to improve the asset management and maintenance of medium-voltage (MV) motors. This study presents a novel method for autonomous analysis and classification of motor PD patterns in situations where a phase-reference voltage waveform is not available. The main contributions include a polar PD (PPD) pattern and a fractal theory-based autonomous PD recognition method. PPD pattern that is applied to convert the traditional phase-resolved PD pattern into a circular form addresses the lack of phase information in on-line PD monitoring system. The fractal theory is then presented in detail to address the task of discrimination of 6 kinds of single source and 15 kinds of multi-source PD patterns related to motors, as outlined in IEC 60034. The classification of known and unknown defects is calculated by a method known as centre score. Validation of the proposed method is demonstrated using data from laboratory experiments on three typical PD geometries. This study also discusses the application of the proposed techniques with 24 sets of on-site PD measurement data from 4 motors in 2 nuclear power stations. The results show that the proposed method performs effectively in recognising not only the single-source PD but also multi-source PDs
Mass Deformation of the Multiple M2 Branes Theory
Based on recent developments, in this letter we study the one parameter
deformation of 2+1 dimensional gauge theories with scale invariance and N = 8
supersymmetry, which is expected to be the field theory living on a stack of M2
branes. The deformed gauge theory is defined by a Lagrangian and is based on an
infinite set of novel 3-algebras constructed by relaxing the assumption that
the invariant metric is positive definite. Under the Higgs mechanism, we can
obtain the D-branes world volume theory in the presence of background fluxes.Comment: 13pages, no figures, reference adde
Influence of carbon nanotubes on the rheology and dynamic mechanical properties of polyamide-12 for laser sintering
The rheological behaviour of polymer nanocomposites is very important for polymer processing and understanding the structure-properties relationship. In this paper, the rheological properties of a polyamide 12 (PA12) - carbon nanotube (CNT) nanocomposite for laser sintering were studied. Compared to neat PA12, the presence of CNTs resulted in higher storage modulus (GâČ), loss modulus (Gâł) and viscosity (η). With an increase in temperature, viscosity showed an unusual increase for both PA12 and the PA12-CNT nanocomposites, which is likely to result from incomplete melting of powder particles. Dynamic mechanical analysis was carried out to examine the effect the CNTs were having on the laser sintered parts. The laser sintered PA12-CNT nanocomposite had an increased elastic modulus compared to that of neat PA12. The CNT and polymer matrix interaction hindered the chain motions, which resulted in higher loss modulus and decreased the thermal expansion coefficient
Magnetic-field dependence of electron spin relaxation in n-type semiconductors
We present a theoretical investigation of the magnetic field dependence of
the longitudinal () and transverse () spin relaxation times of
conduction band electrons in n-type III-V semiconductors. In particular, we
find that the interplay between the Dyakonov-Perel process and an additional
spin relaxation channel, which originates from the electron wave vector
dependence of the electron -factor, yields a maximal at a finite
magnetic field. We compare our results with existing experimental data on
n-type GaAs and make specific additional predictions for the magnetic field
dependence of electron spin lifetimes.Comment: accepted for publication in PRB, minor changes to previous manuscrip
Quantum tomography of mesoscopic superpositions of radiation states
We show the feasibility of a tomographic reconstruction of Schr\"{o}dinger
cat states generated according to the scheme proposed by S. Song, C.M. Caves
and B. Yurke [Phys. Rev. A 41, 5261 (1990)]. We present a technique that
tolerates realistic values for quantum efficiency at photodetectors. The
measurement can be achieved by a standard experimental setup.Comment: Submitted to Phys. Rev. Lett.; 4 pages including 6 ps figure
Fractal Weyl law for Linux Kernel Architecture
We study the properties of spectrum and eigenstates of the Google matrix of a
directed network formed by the procedure calls in the Linux Kernel. Our results
obtained for various versions of the Linux Kernel show that the spectrum is
characterized by the fractal Weyl law established recently for systems of
quantum chaotic scattering and the Perron-Frobenius operators of dynamical
maps. The fractal Weyl exponent is found to be that
corresponds to the fractal dimension of the network . The
eigenmodes of the Google matrix of Linux Kernel are localized on certain
principal nodes. We argue that the fractal Weyl law should be generic for
directed networks with the fractal dimension .Comment: RevTex 6 pages, 7 figs, linked to arXiv:1003.5455[cs.SE]. Research at
http://www.quantware.ups-tlse.fr/, Improved version, changed forma
Glueball production in radiative J/psi, Upsilon decays
Using a bound-state model of weakly bound gluons for glueballs made of two
gluons and a natural generalization of the perturbative QCD formalism for
exclusive hadronic processes, we present results for glueball production in
radiative J/psi, Upsilon decays into several possible glueball states,
including L \not= 0 ones. We perform a detailed phenomenological analysis,
presenting results for the more favored experimental candidates and for decay
angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure
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