4,641 research outputs found
Improved half-metallic ferromagnetism of transition-metal pnictides and chalcogenides calculated with a modified Becke-Johnson exchange potential
We use a density-functional-theory (DFT) approach with a modified
Becke-Johnson exchange plus local density approximation (LDA) correlation
potential (mBJLDA) [semi-local, orbital-independent, producing accurate
semiconductor gaps. see F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401
(2009)] to investigate the electronic structures of zincblende transition-metal
(TM) pnictides and chalcogenides akin to semiconductors. Our results show that
this potential does not yield visible changes in wide TM d-t_{2g} bands near
the Fermi level, but makes the occupied minority-spin p-bands lower by
0.25~0.35 eV and the empty (or nearly empty) minority-spin e_g bands across the
Fermi level higher by 0.33~0.73 eV. Consequently, mBJLDA, having no
atom-dependent parameters, makes zincblende MnAs become a truly half-metallic
(HM) ferromagnet with a HM gap (the key parameter) 0.318eV, being consistent
with experiment. For zincblende MnSb, CrAs, CrSb, CrSe, or CrTe, the HM gap is
enhanced by 19~56% compared to LDA and generalized gradient approximation
results. The improved HM ferromagnetism can be understood in terms of the
mBJLDA-enhanced spin exchange splitting.Comment: 6 pages, 5 figure
Integrated Optimization of Production Planning and Scheduling in Mixed Model Assembly Line
AbstractIn order to solve the separation in the traditional serial production planning and scheduling in mixed model assembly line, the integrated optimization complete model of production planning and scheduling based on multiple objectives and constraints was constructed. Since the integrated optimization complete model is difficult to solve, the heuristic approach was adopt, and the modified discrete particle swarm optimization(MDPSO) was presented to solve the model. The experiments verifies the presented model and algorithm can realize the simultaneously optimization of production planning and scheduling in mixed model assembly line and contribute to performance improvement and the application scope expand of the new intelligent optimization
Spectral conditions for a graph to be Hamilton-connected
In this paper we establish some spectral conditions for a graph to be
Hamilton-connected in terms of the spectral radius of the adjacency matrix or
the signless Laplacian of the graph or its complement. For the existence of
Hamiltonian paths or cycles in a graph, we also give a sufficient condition by
the signless Laplacian spectral radius
A note on symplecticity of step-transition mappings for multi-step methods
AbstractWe prove that for a linear multi-step method ∑k=0mαkZk=τ∑k=0mβkf(Zk), even though the mappings Z0→Z1,…,Zm-2→Zm-1 are chosen to be symplectic, Zm-1→Zm will be non-symplectic. Similarly, there is an interesting result for a sort of general linear methods
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