1,474 research outputs found
Evaluation of advanced optimisation methods for estimating Mixed Logit models
The performances of different simulation-based estimation techniques for mixed logit modeling are evaluated. A quasi-Monte Carlo method (modified Latin hypercube sampling) is compared with a Monte Carlo algorithm with dynamic accuracy. The classic Broyden-Fletcher-Goldfarb-Shanno (BFGS) optimization algorithm line-search approach and trust region methods, which have proved to be extremely powerful in nonlinear programming, are also compared. Numerical tests are performed on two real data sets: stated preference data for parking type collected in the United Kingdom, and revealed preference data for mode choice collected as part of a German travel diary survey. Several criteria are used to evaluate the approximation quality of the log likelihood function and the accuracy of the results and the associated estimation runtime. Results suggest that the trust region approach outperforms the BFGS approach and that Monte Carlo methods remain competitive with quasi-Monte Carlo methods in high-dimensional problems, especially when an adaptive optimization algorithm is used
Inter-layer Hall effect in double quantum wells subject to in-plane magnetic fields
We report on a theoretical study of the transport properties of two coupled
two-dimensional electron systems subject to in-plane magnetic fields. The
charge redistribution in double wells induced by the Lorenz force in crossed
electric and magnetic fields has been studied. We have found that the
redistribution of the charge and the related inter-layer Hall effect originate
in the chirality of diamagnetic currents and give a substantial contribution to
the conductivity.Comment: 7 RevTex pages, 4 figures, appendix added and misprint in Eq. (11)
correcte
Formulation and solution strategies for nonparametric nonlinear stochastic programmes with an application in finance
Prolate-Spherical Shape Coexistence at N=28 in S
The structure of S has been studied using delayed and
electron spectroscopy at \textsc{ganil}. The decay rates of the 0
isomeric state to the 2 and 0 states have been measured for the
first time, leading to a reduced transition probability
B(E2~:~20= 8.4(26)~efm and a monopole
strength (E0~:~00
=~8.7(7)10. Comparisons to shell model calculations point
towards prolate-spherical shape coexistence and a phenomenological two level
mixing model is used to extract a weak mixing between the two configurations.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
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