7,751 research outputs found
A finite difference solution for the cylindrical expansion of a gas cloud into vacuum
Finite difference method for solution of cylindrical expansion of gas cloud into vacuu
Use of remote sensing for hydrological parameterisation of Alpine catchments
International audiencePhysically-based water balance models require a realistic parameterisation of land surface characteristics of a catchment. Alpine areas are very complex with strong topographically-induced gradients of environmental conditions, which makes the hydrological parameterisation of Alpine catchments difficult. Within a few kilometres the water balance of a region (mountain peak or valley) can differ completely. Hence, remote sensing is invaluable for retrieving hydrologically relevant land surface parameters. The assimilation of the retrieved information into the water balance model PROMET is demonstrated for the Toce basin in Piemonte/Northern Italy. In addition to land use, albedos and leaf area indices were derived from LANDSAT-TM imagery. Runoff, modelled by a water balance approach, agreed well with observations without calibration of the hydrological model. Keywords: PROMET, fuzzy logic based land use classification, albedo, leaf area inde
Optical conductivity for a dimer in the Dynamic Hubbard model
The Dynamic Hubbard Model represents the physics of a multi-band Hubbard
model by using a pseudo-spin degree of freedom to dynamically modify the
on-site Coulomb interaction. Here we use a dimer system to obtain analytical
results for this model. The spectral function and the optical conductivity are
calculated analytically for any number of electrons, and the distribution of
optical spectral weight is analyzed in great detail. The impact of polaron-like
effects due to overlaps between pseudo-spin states on the optical spectral
weight distribution is derived analytically. Our conclusions support results
obtained previously with different models and techniques: holes are less mobile
than electrons.Comment: 11 pages, 4 figure
A finite difference solution for the two- dimensional expansion of a finite cylindrical gas cloud into a vacuum
Interaction of radial and axial rarefaction waves investigated by considering expansion of finite length cylindrical gas cloud into vacuu
Packaging of photodetector modules for 100 Gbit/s applications using electromagnetic simulations
Improved Lieb-Oxford exchange-correlation inequality with gradient correction
We prove a Lieb-Oxford-type inequality on the indirect part of the Coulomb
energy of a general many-particle quantum state, with a lower constant than the
original statement but involving an additional gradient correction. The result
is similar to a recent inequality of Benguria, Bley and Loss, except that the
correction term is purely local, which is more usual in density functional
theory. In an appendix, we discuss the connection between the indirect energy
and the classical Jellium energy for constant densities. We show that they
differ by an explicit shift due to the long range of the Coulomb potential.Comment: Final version to appear in Physical Review A. Compared to the very
first version, this one contains an appendix discussing the link with the
Jellium proble
Origin of the anomalous Hall Effect in overdoped n-type cuprates: current vertex corrections due to antiferromagnetic fluctuations
The anomalous magneto-transport properties in electron doped (n-type)
cuprates were investigated using Hall measurements at THz frequencies. The
complex Hall angle was measured in overdoped PrCeCuO samples (x=0.17 and 0.18) as a continuous function of
temperature above at excitation energies 5.24 and 10.5 meV. The results,
extrapolated to low temperatures, show that inelastic scattering introduces
electron-like contributions to the Hall response. First principle calculations
of the Hall angle that include current vertex corrections (CVC) induced by
electron interactions mediated by magnetic fluctuations in the Hall
conductivity reproduce the temperature, frequency, and doping dependence of the
experimental data. These results show that CVC effects are the source of the
anomalous Hall transport properties in overdoped ntype cuprates.Comment: 5 pages, 3 figure
Electromagnetic modeling and optimization of packaged photodetector modules for 100 Gbit/s applications
In this paper, we propose an accurate full 3D EM behavioral model of PD chips for the first time. The model, which is meshed at 130 GHz, runs for about 17 minutes on an Intel Core2 Duo CPU@3 GHz PC with 3.5 GB of RAM. The impact of various parameters in wire- bonding transitions for transmission characteristic is summarized in the Table I. When numbers of bonding wires are placed separately all through strips of CBCPWs as well as keeping an optimized gap of transitions, more than 10 GHz bandwidth improvement can be achieved compared the worst case. We also notice that optimization on bonding wires does not significantly improve the fast decay beyond 60 GHz. Further investigation and optimization of the transition is required including a redesign of the CBCPW
- …