205 research outputs found
Comparison of experimental data and theoretical calculations for electrical resistivity and Hall coefficient in quasi-one-dimensional organic conductor (TMTSF)2PF6
The temperature dependences of the Hall coefficient and electrical
resistivity recently measured by Moser et al. [Phys. Rev. Lett. 84, 2674
(2000)] in the quasi-one-dimensional organic conductor (TMTSF)2PF6 are
quantitatively compared with our previous theoretical calculations [Synth. Met.
103, 2202 (1999); Eur. Phys. J. B 11, 385 (1999)]. We find a good agreement,
albeit not with a fully consistent set of parameters for the two quantities,
without appealing to the Luttinger liquid concept.Comment: 2 pages with 2 figures for ICSM-2000 proceedings. Uses elsart.cls and
synmet.cls, which are provided. V.2: one reference update
Anomalous temperature dependence of resistivity in quasi-one-dimensional conductors in a strong magnetic field
We present a heuristic, semiphenomenological model of the anomalous
temperature (T) dependence of resistivity Rxx recently observed experimentally
in the quasi-one-dimensional (Q1D) organic conductors of the (TMTSF)2X family
in moderately strong magnetic fields. We suggest that a Q1D conductor behaves
like an insulator (dRxx/dT<0), when its effective dimensionality is one, and
like a metal (dRxx/dT>0), when its effective dimensionality is greater than
one. Applying a magnetic field reduces the effective dimensionality of the
system and switches the temperature dependence of resistivity between the
insulating and metallic laws depending on the magnitude and orientation of the
magnetic field. We critically analyze whether various microscopic models
suggested in literature can produce such a behavior and find that none of the
models is fully satisfactory. In particular, we perform detailed analytical and
numerical calculations within the scenario of magnetic-field-induced
spin-density-wave precursor effect suggested by Gor'kov and find that the
theoretical results do not agree with the experimental observations.Comment: RevTeX, 17 pages, 7 figures. v.2: minor corrections; references are
added and updated v.3: minor corrections as in the published versio
The architecture and prototype implementation of the Model Environment system
International audienceAn approach that simplifies software development of the model based decision support systems for environmental management has been introduced. The approach is based on definition and management of metadata and data related to computational model without losing data semantics and proposed methods of integration of the new modules into the information system and their management. An architecture of the integrated modelling system is presented. The proposed architecture has been implemented as a prototype of integrated modelling system using. NET/Gtk{#} and is currently being used to re-design European Decision Support System for Nuclear Emergency Management RODOS (http://www.rodos.fzk.de) using Java/Swing
Magnetoresistance of YBa2Cu3O7 in the "cold spots" model
We calculate the in-plane magnetoresistance of
YBaCuO in a magnetic field applied perpendicular to the
planes for the ``cold spots'' model. In this model, the electron relaxation
time at small regions on the Fermi surface near the
Brillouin zone diagonals is much longer than the relaxation time
at the rest of the Fermi surface ( is temperature). In
qualitative agreement with the experiment, we find that Kohler's rule is
strongly violated, but the ratio ,
where is the Hall angle, is approximately
temperature-independent. We find the ratio is about 5.5, which is of the same
order of magnitude as in the experiment.Comment: RevTeX, 4 pages, 6 figures. V.2: 2 references adde
Photoionization in negative streamers: fast computations and two propagation modes
Streamer discharges play a central role in electric breakdown of matter in pulsed electric fields, both in nature and in technology. Reliable and fast computations of the minimal model for negative streamers in simple gases like nitrogen have recently been developed. However, photoionization was not included; it is important in air and poses a major numerical challenge. We here introduce a fast and reliable method to include photoionization into our numerical scheme with adaptice grids, and we discuss its importance for negative streamers. In particular, we identify different propagation regimes where photoionization does or does not play a role
Improving the Durability of the Dies and Product Quality in the Production of Nichrome Strips
- …