2,189 research outputs found
Land use classification in Bolivia
The Bolivian LANDSAT Program is an integrated, multidisciplinary project designed to provide thematic analysis of LANDSAT, Skylab, and other remotely sensed data for natural resource management and development in Bolivia, is discussed. Among the first requirements in the program is the development of a legend, and appropriate methodologies, for the analysis and classification of present land use based on landscape cover. The land use legend for Bolivia consists of approximately 80 categories in a hierarchical organization which may be collapsed for generalization, or expanded for greater detail. The categories, and their definitions, provide for both a graphic and textual description of the complex and diverse landscapes found in Bolivia, and are designed for analysis from LANDSAT and other remotely sensed data at scales of 1:1,000,000 and 1:250,000. Procedures and example products developed are described and illustrated, for the systematic analysis and mapping of present land use for all of Bolivia
Particle Dispersion on Rapidly Folding Random Hetero-Polymers
We investigate the dynamics of a particle moving randomly along a disordered
hetero-polymer subjected to rapid conformational changes which induce
superdiffusive motion in chemical coordinates. We study the antagonistic
interplay between the enhanced diffusion and the quenched disorder. The
dispersion speed exhibits universal behavior independent of the folding
statistics. On the other hand it is strongly affected by the structure of the
disordered potential. The results may serve as a reference point for a number
of translocation phenomena observed in biological cells, such as protein
dynamics on DNA strands.Comment: 4 pages, 4 figure
Levy Flights in Inhomogeneous Media
We investigate the impact of external periodic potentials on superdiffusive
random walks known as Levy flights and show that even strongly superdiffusive
transport is substantially affected by the external field. Unlike ordinary
random walks, Levy flights are surprisingly sensitive to the shape of the
potential while their asymptotic behavior ceases to depend on the Levy index
. Our analysis is based on a novel generalization of the Fokker-Planck
equation suitable for systems in thermal equilibrium. Thus, the results
presented are applicable to the large class of situations in which
superdiffusion is caused by topological complexity, such as diffusion on folded
polymers and scale-free networks.Comment: 4 pages, 4 figure
Momentum-Dependent Mean Field Based Upon the Dirac-Brueckner Approach for Nuclear Matter
A momentum-dependent mean field potential, suitable for application in the
transport-model description of nucleus-nucleus collisions, is derived in a
microscopic way. The derivation is based upon the Bonn meson-exchange model for
the nucleon-nucleon interaction and the Dirac-Brueckner approach for nuclear
matter. The properties of the microscopic mean field are examined and compared
with phenomenological parametrizations which are commonly used in
transport-model calculations.Comment: 15 pages text (RevTex) and 4 figures (postscript in a separate
uuencoded file), UI-NTH-930
Neutron star properties and the equation of state of neutron-rich matter
We calculate total masses and radii of neutron stars (NS) for pure neutron
matter and nuclear matter in beta-equilibrium. We apply a relativistic nuclear
matter equation of state (EOS) derived from Dirac-Brueckner-Hartree-Fock (DBHF)
calculations. We use realistic nucleon-nucleon (NN) interactions defined in the
framework of the meson exchange potential models. Our results are compared with
other theoretical predictions and recent observational data. Suggestions for
further study are discussed.Comment: 13 pages, 9 figures, 1 table; Revised version, accepted for
publication in Physical Review
Determination of the spatial and temporal variation of tropospheric water vapour using CGPS networks
Tropospheric water vapour is the main limiting factor in using GPS to determine crustal deformation at highest accuracy. On the other hand, it is an important variable to monitor meteorological and climatic processes. This paper discusses both aspects: the modelling of tropospheric water vapour using meteorological data as well as the determination of the integrated amount of water vapour and its spatiotemporal variation using GPS data. Switzerland has been chosen as experiment area. The Swiss continuous GPS (CGPS) network AGNES is used as a reference network, which represents a realistic scenario for GPS-based water vapour determination. Data of the Swiss numerical weather model aLMo are used for systematic comparison and validation. For the first aspect, integrated tropospheric wet refractivity values are determined from meteorological measurements and compared with GPS path delays. An overall agreement of 1 cm of zenith wet path delay was achieved. For the second aspect a tomographic approach has been developed. A total of 6720 GPS-determined profiles are compared with data of the numerical weather model and radio soundings. The results are statistically evaluated and systematically compared with each other. A correlation between the accuracy and the weather situation was found. Overall, an agreement of 5-7 ppm (refractivity unit) was obtained compared to aLMo. The use of GPS-determined path delays from a permanent GPS network is the recommended method to correct GPS measurements. In all other cases, the two methods presented (COITROPA, COMEDIE) are a feasible alternative to determine path delays accurately. Furthermore, GPS is a convenient application to determine the amount of water vapour in the troposphere. It is demonstrated that the vertical distribution of water vapour can be deduced by applying the tomographic approac
Determination of the spatial and temporal variation of tropospheric water vapour using CGPS networks
Tropospheric water vapour is the main limiting factor in using GPS to determine crustal deformation at highest accuracy. On the other hand, it is an important variable to monitor meteorological and climatic processes. This paper discusses both aspects: the modelling of tropospheric water vapour using meteorological data as well as the determination of the integrated amount of water vapour and its spatiotemporal variation using GPS data. Switzerland has been chosen as experiment area. The Swiss continuous GPS (CGPS) network AGNES is used as a reference network, which represents a realistic scenario for GPS-based water vapour determination. Data of the Swiss numerical weather model aLMo are used for systematic comparison and validation. For the first aspect, integrated tropospheric wet refractivity values are determined from meteorological measurements and compared with GPS path delays. An overall agreement of 1 cm of zenith wet path delay was achieved. For the second aspect a tomographic approach has been developed. A total of 6720 GPS-determined profiles are compared with data of the numerical weather model and radio soundings. The results are statistically evaluated and systematically compared with each other. A correlation between the accuracy and the weather situation was found. Overall, an agreement of 5-7 ppm (refractivity unit) was obtained compared to aLMo. The use of GPS-determined path delays from a permanent GPS network is the recommended method to correct GPS measurements. In all other cases, the two methods presented (COITROPA, COMEDIE) are a feasible alternative to determine path delays accurately. Furthermore, GPS is a convenient application to determine the amount of water vapour in the troposphere. It is demonstrated that the vertical distribution of water vapour can be deduced by applying the tomographic approac
Effective DBHF Method for Asymmetric Nuclear Matter and Finite Nuclei
A new decomposition of the Dirac structure of nucleon self-energies in the
Dirac Brueckner-Hartree-Fock (DBHF) approach is adopted to investigate the
equation of state for asymmetric nuclear matter. The effective coupling
constants of , , and mesons with a density
dependence in the relativistic mean field approach are deduced by reproducing
the nucleon self-energy resulting from the DBHF at each density for symmetric
and asymmetric nuclear matter. With these couplings the properties of finite
nuclei are investigated. The agreement of charge radii and binding energies of
finite nuclei with the experimental data are improved simultaneously in
comparison with the projection method. It seems that the properties of finite
nuclei are sensitive to the scheme used for the DBHF self-energy extraction. We
may conclude that the properties of the asymmetric nuclear matter and finite
nuclei could be well described by the new decomposition approach of the G
matrix.Comment: 16 pages, 5 figure
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