1,966,936 research outputs found
Modeling dispersion of partial discharges due to propagation velocity variation in power cables
Existing models for partial discharge (PD) propagation based on a single attenuation constant are unable to explain how each frequency component travels with a different propagation velocity. This paper proposes a new model based on a complex propagation term whose real component does not depend on the frequency (), and whose imaginary part is modeled with a second order polynomial in . The proposed model explains how the PD is attenuated, delayed, and dispersed due to the fact that each frequency component is differently delayed.
A closed-form expression is proposed for the PD peak value and width, and a method to derive the model parameters from a reference model existing in the bibliography. Simulation results show that the peak value and width of the propagated PD pulse are similar to those obtained with the proposed model. Additionally, the proposed model provides the velocity of each PD frequency component, which is crucial to get an accurate estimation of the PD source location.
The parameters of the proposed model have been estimated using a vector network analyzer for a XLPE cable. These results have been compared to the measurement obtained in a medium voltage test bench where intentionally induced PDs have been captured and processed, confirming the results of attenuation, delay and dispersion predicted by the proposed model
Critical behavior in colloid-polymer mixtures: theory and simulation
We extensively investigated the critical behavior of mixtures of colloids and
polymers via the two-component Asakura-Oosawa model and its reduction to a
one-component colloidal fluid using accurate theoretical and simulation
techniques. In particular the theoretical approach, hierarchical reference
theory [Adv. Phys. 44, 211 (1995)], incorporates realistically the effects of
long-range fluctuations on phase separation giving exponents which differ
strongly from their mean-field values, and are in good agreement with those of
the three-dimensional Ising model. Computer simulations combined with
finite-size scaling analysis confirm the Ising universality and the accuracy of
the theory, although some discrepancy in the location of the critical point
between one-component and full-mixture description remains. To assess the limit
of the pair-interaction description, we compare one-component and two-component
results.Comment: 15 pages, 10 figures. Submitted to Phys. Rev.
A structural comparison of models of colloid-polymer mixtures
We study the structure of colloidal fluids with reference to colloid-polymer
mixtures. We compare the one component description of the Asakura-Oosawa (AO)
idealisation of colloid-polymer mixtures with the full two-component model. We
also consider the Morse potential, a variable range interaction, for which the
ground state clusters are known. Mapping the state points between these
systems, we find that the pair structure of the full AO model is equally well
described by the Morse potential or the one component AO approach. We employ a
recently developed method to identify in the bulk fluid the ground state
clusters relevant to the Morse potential. Surprisingly, when we measure the
cluster populations, we find that the Morse fluid is significantly closer the
full AO fluid than the one component AO description.Comment: 13 pages, accepted by J. Phys. Condens: Matter special issue for
CECAM meeting 'New Trends in Simulating Colloids: from Models to
Applications
Electrically controlled superconducting states at the heterointerface SrTiO/LaAlO
We study the symmetry of Cooper pair in a two-dimensional Hubbard model with
the Rashba-type spin-orbit interaction as a minimal model of electron gas
generated at a heterointerface of SrTiO/LaAlO. Solving the Eliashberg
equation based on the third-order perturbation theory, we find that the gap
function consists of the mixing of the spin-singlet -wave component and
the spin-triplet -wave one due to the broken inversion symmetry
originating from the Rashba-type spin-orbit interaction. The ratio of the
d-wave and the p-wave component continuously changes with the carrier
concentration. We propose that the pairing symmetry is controlled by tuning the
gate voltage.Comment: 4 pages, 4 figures; added reference
Properties of a random attachment growing network
In this study we introduce and analyze the statistical structural properties
of a model of growing networks which may be relevant to social networks. At
each step a new node is added which selects 'k' possible partners from the
existing network and joins them with probability delta by undirected edges. The
'activity' of the node ends here; it will get new partners only if it is
selected by a newcomer. The model produces an infinite-order phase transition
when a giant component appears at a specific value of delta, which depends on
k. The average component size is discontinuous at the transition. In contrast,
the network behaves significantly different for k=1. There is no giant
component formed for any delta and thus in this sense there is no phase
transition. However, the average component size diverges for delta greater or
equal than one half.Comment: LaTeX, 19 pages, 6 figures. Discussion section, comments, a new
figure and a new reference are added. Equations simplifie
A six-factor asset pricing model
The present study introduce the human capital component to the Fama and
French five-factor model proposing an equilibrium six-factor asset pricing
model. The study employs an aggregate of four sets of portfolios mimicking size
and industry with varying dimensions. The first set consists of three set of
six portfolios each sorted on size to B/M, size to investment, and size to
momentum. The second set comprises of five index portfolios, third, a four-set
of twenty-five portfolios each sorted on size to B/M, size to investment, size
to profitability, and size to momentum, and the final set constitute thirty
industry portfolios. To estimate the parameters of six-factor asset pricing
model for the four sets of variant portfolios, we use OLS and Generalized
method of moments based robust instrumental variables technique (IVGMM). The
results obtained from the relevance, endogeneity, overidentifying restrictions,
and the Hausman's specification, tests indicate that the parameter estimates of
the six-factor model using IVGMM are robust and performs better than the OLS
approach. The human capital component shares equally the predictive power
alongside the factors in the framework in explaining the variations in return
on portfolios. Furthermore, we assess the t-ratio of the human capital
component of each IVGMM estimates of the six-factor asset pricing model for the
four sets of variant portfolios. The t-ratio of the human capital of the
eighty-three IVGMM estimates are more than 3.00 with reference to the standard
proposed by Harvey et al. (2016). This indicates the empirical success of the
six-factor asset-pricing model in explaining the variation in asset returns
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