10,140 research outputs found
Multiclass Data Segmentation using Diffuse Interface Methods on Graphs
We present two graph-based algorithms for multiclass segmentation of
high-dimensional data. The algorithms use a diffuse interface model based on
the Ginzburg-Landau functional, related to total variation compressed sensing
and image processing. A multiclass extension is introduced using the Gibbs
simplex, with the functional's double-well potential modified to handle the
multiclass case. The first algorithm minimizes the functional using a convex
splitting numerical scheme. The second algorithm is a uses a graph adaptation
of the classical numerical Merriman-Bence-Osher (MBO) scheme, which alternates
between diffusion and thresholding. We demonstrate the performance of both
algorithms experimentally on synthetic data, grayscale and color images, and
several benchmark data sets such as MNIST, COIL and WebKB. We also make use of
fast numerical solvers for finding the eigenvectors and eigenvalues of the
graph Laplacian, and take advantage of the sparsity of the matrix. Experiments
indicate that the results are competitive with or better than the current
state-of-the-art multiclass segmentation algorithms.Comment: 14 page
Ternary Bismuthide SrPtBi2: Computation and Experiment in Synergism to Explore Solid-State Materials
A combination of theoretical calculation and the experimental synthesis to
explore the new ternary compound is demonstrated in the Sr-Pt-Bi system. Since
Pt-Bi is considered as a new critical charge-transfer pair for
superconductivity, it inspired us to investigate the Sr-Pt-Bi system. With a
thorough calculation of all the known stable/metastable compounds in the
Sr-Pt-Bi system and crystal structure predictions, the thermodynamic stability
of hypothetical stoichiometry, SrPtBi2, is determined. Followed by the
high-temperature synthesis and crystallographic analysis, the first ternary
bismuthide in Sr-Pt-Bi, SrPtBi2 was prepared and the stoichiometry was
confirmed experimentally. SrPtBi2 crystallizes in the space group Pnma (S.G.
62, Pearson Symbol oP48), which matches well with theoretical prediction using
an adaptive genetic algorithm (AGA). Using first-principles calculations, we
demonstrate that the orthorhombic structure has lower formation energies than
other 112 structure types, such as tetragonal BaMnBi2 (CuSmP2) and LaAuBi2
(CuHfSi2) structure types. The bonding analysis indicates the Pt-Bi
interactions play a critical role in structural stability. The physical
properties measurements show the metallic properties with low electron-phonon
interactions at the low temperature, which agrees with the electronic structure
assessment.Comment: 12 pages, 7 figure
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