75,234 research outputs found
Dynamic parallelization of hydrological model simulations
This paper introduces the development of a dynamic parallel algorithm for conducting hydrological model simulations. This new algorithm consists of a river network decomposition method and an enhanced master-slave paradigm. The decomposition method is used to divide a basin river network into a large number of subbasins, and the enhanced master-slave paradigm is adopted to realize the function of this new dynamic basin decomposition method through using the Message-Passing Interface (MPI) and C++ language. This new algorithm aims to balance computation load and then to achieve a higher speedup and efficiency of parallel computing in hydrological simulation for the river basins which are delineated by high-resolution drainage networks. This paper uses a modified binary-tree codification method developed by Li etal. (2010) to code drainage networks, and the basin width function to estimate the possible maximum parallel speedup and the associated efficiency. As a case study, with a hydrological model, the Digital Yellow River Model, this new dynamic parallel algorithm is applied to the Chabagou basin in northern China. The application results reveal that the new algorithm is efficient in the dynamic dispatching of simulation tasks to computing processes, and that the parallel speedup and efficiency are comparable with the estimations made by using the basin width function. © 2011 Elsevier Ltd.postprin
Microstructure and Fe-vacancy ordering in the KFexSe2 superconducting system
Structural investigations by means of transmission electron microscopy (TEM)
on KFexSe2 with 1.5 \leq x \leq 1.8 have revealed a rich variety of
microstructure phenomena, the KFe1.5Se2 crystal often shows a superstructure
modulation along the [310] zone-axis direction, this superstructure can be well
interpreted by the Fe-vacancy order within the a-b plane. Increase of
Fe-concentration in the KFexSe2 materials could not only result in the
appearance of superconductivity but also yield clear alternations of
microstructure. Structural inhomogeneity, the complex superstructures and
defect structures in the superconducting KFe1.8Se2 sample have been
investigated based on the high-resolution TEM.Comment: 13 pages, 4 figure
Synthesis, Structure and Magnetic Properties of New Layered Iron-Oxychalcogenide Na2Fe2OSe2
A new layered iron-oxychalcogenide Na2Fe2OSe2 has been synthesized and
structurally characterized by powder X-ray diffraction. The structure is formed
by alternate stacking of the newly discovered [Fe2OSe2] blocks and double
layers of Na. Conductivity study shows that Na2Fe2OSe2 is a semiconductor with
activation energy of 0.26 eV. Magnetic susceptibility and heat capacity
measurements reveal an antiferromagnetic phase transition occurs at TN=73 K. A
broad maximum of magnetic susceptibility and a slow decay of the specific heat
above TN, arises as a result of two-dimensional short-range spin correlation.Comment: 4 pages, 4 figure
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