308 research outputs found
Downscaling system for modeling of atmospheric composition on regional, urban and street scales
In this study, the downscaling modeling chain for prediction of weather and atmospheric composition is described and evaluated against observations. The chain consists of interfacing models for forecasting at different spatiotemporal scales that run in a semi-operational mode. The forecasts were performed for European (EU) regional and Danish (DK) subregional-urban scales by the offline coupled numerical weather prediction HIRLAM and atmospheric chemical transport CAMx models, and for Copenhagen citystreet scale by the online coupled computational fluid dynamics M2UE model. The results showed elevated NOx and lowered O-3 concentrations over major urban, industrial, and transport land and water routes in both the EU and DK domain forecasts. The O-3 diurnal cycle predictions in both these domains were equally good, although O-3 values were closer to observations for Denmark. At the same time, the DK forecast of NOx and NO2 levels was more biased (with a better prediction score of the diurnal cycle) than the EU forecast, indicating a necessity to adjust emission rates. Further downscaling to the street level (Copenhagen) indicated that the NOx pollution was 2-fold higher on weekends and more than 5 times higher during the working day with high pollution episodes. Despite high uncertainty in road traffic emissions, the street-scale model effectively captured the NOx and NO2 diurnal cycles and the onset of elevated pollution episodes. The demonstrated downscaling system could be used in future online integrated meteorology and air quality research and operational forecasting, as well as for impact assessents on environment, population, and decision making for emergency preparedness and safety measures planning.Peer reviewe
Direct variational assimilation algorithm for atmospheric chemistry data with transport and transformation model
Atmospheric chemistry dynamics is studied with convection-diffusion-reaction model. The numerical Data Assimilation algorithm presented is based on the additive-averaged splitting schemes. It carries out ''fine-grained'' variational data assimilation on the separate splitting stages with respect to spatial dimensions and processes i.e. the same measurement data is assimilated to different parts of the split model. This design has efficient implementation due to the direct data assimilation algorithms of the transport process along coordinate lines. Results of numerical experiments with chemical data assimilation algorithm of in situ concentration measurements on real data scenario have been presented. In order to construct the scenario, meteorological data has been taken from EnviroHIRLAM model output, initial conditions from MOZART model output and measurements from Airbase database. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
Towards the electron EDM search. Theoretical study of PbF
We report ab initio relativistic correlation calculations of potential curves
and spectroscopic constants for four lowest-lying electronic states of the lead
monofluoride. We also calculated parameters of the spin-rotational Hamiltonian
for the ground and the first excited states including P,T-odd and P-odd terms.
In particular, we have obtained hyperfine constants of the Pb nucleus.
For the state MHz, MHz and for
the A MHz, MHz. Our values of
the ground state hyperfine constants are in good agreement with the previous
theoretical studies. We discuss and explain seeming disagreement in the sign of
the constant with the recent experimental data. The effective
electric field on the electron , which is important for the planned
experiment to search for the electric dipole moment of the electron, is found
to be 3.3 * 10^{10} V/cm
Anomalous Behavior near T_c and Synchronization of Andreev Reflection in Two-Dimensional Arrays of SNS Junctions
We have investigated low-temperature transport properties of two-dimensional
arrays of superconductor--normal-metal--superconductor (SNS) junctions. It has
been found that in two-dimensional arrays of SNS junctions (i) a change in the
energy spectrum within an interval of the order of the Thouless energy is
observed even when the thermal broadening far exceeds the Thouless energy for a
single SNS junction; (ii) the manifestation of the subharmonic energy gap
structure (SGS) with high harmonic numbers is possible even if the energy
relaxation length is smaller than that required for the realization of a
multiple Andreev reflection in a single SNS junction. These results point to
the synchronization of a great number of SNS junctions. A mechanism of the SGS
origin in two-dimensional arrays of SNS junctions, involving the processes of
conventional and crossed Andreev reflection, is proposed.Comment: 5 pages, 5 figure
Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films
Temperature- and magnetic-field dependent measurements of the resistance of
ultrathin superconducting TiN films are presented. The analysis of the
temperature dependence of the zero field resistance indicates an underlying
insulating behavior, when the contribution of Aslamasov-Larkin fluctuations is
taken into account. This demonstrates the possibility of coexistence of the
superconducting and insulating phases and of a direct transition from the one
to the other. The scaling behavior of magnetic field data is in accordance with
a superconductor-insulator transition (SIT) driven by quantum phase
fluctuations in two-dimensional superconductor. The temperature dependence of
the isomagnetic resistance data on the high-field side of the SIT has been
analyzed and the presence of an insulating phase was confirmed. A transition
from the insulating to a metallic phase is found at high magnetic fields, where
the zero-temperature asymptotic value of the resistance being equal to h/e^2.Comment: 5 pages, 4 eps figures, RevTeX4, Published versio
Comparison of superconductivity in Sr_2RuO_4 and copper oxides
To compare the superconductivity in strongly correlated electron systems with
the antiferromagnetic fluctuations in the copper oxides and with the
ferromagnetic fluctuations in Sr_2RuO_4 a t-J-I model is proposed. The
antiferromagnetic coupling J results in the superconducting state of
d_{x^2-y^2} symmetry and the ferromagnetic coupling constant I results in the
spin-triplet p-type state. The difference in the gap anisotropies provides the
large difference in T_c values, for the typical values of the coupling
constants: T_c of order of 1K for the ruthenate and T_c of order of 100K for
the cuprates.Comment: 4 pages, RevTEX, 3 figs. Submitted to Phys. Rev. Let
Proximity effects and Andreev reflection in mesoscopic SNS junction with perfect NS interfaces
Low temperature transport measurements on superconducting film - normal metal
wire - superconducting film (SNS) junctions fabricated on the basis of 6 nm
thick superconducting polycrystalline PtSi films are reported. The structures
with the normal metal wires of two different lengths L=1.5 m and L=6m
and the same widths W=0.3m are studied. Zero bias resistance dip related
to pair current proximity effect is observed for all junctions whereas the
subharmonic energy gap structure originating from phase coherent multiple
Andreev reflections have occurs only in the SNS junctions with short wires.Comment: ReVTex, 4 pages, 4 eps figures include
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