A rigorous theory on electromagnetic diffraction by a planar aperture in a perfectly conducting screen

In this paper, we revisit the classic problem of diffraction of electromagnetic waves by an aperture in a perfectly conducting plane. We formulate the diffraction problem using a boundary integral equation that is defined on the aperture using Dyadic Green's function. This integral equation turns out to align with the one derived by Bethe using fictitious magnetic charges and currents. We then investigate the boundary integral equation using a saddle point formulation and establish the well-posedness of the boundary integral equation, including the existence and uniqueness of the solution in an appropriately defined Sobolev space

Effects of behavioral response and vaccination policy on epidemic spreading - an approach based on evolutionary-game dynamics

date of Acceptance: 23/06/2014 This work was supported by the National Natural Science Foundation of China (Grant Nos. 11331009, 11135001, 11105025). Y.-C.L. was supported by AFOSR under Grant No. FA9550-10-1-0083.Peer reviewedPublisher PD

Ab initio study of the giant ferroelectric distortion and pressure induced spin-state transition in BiCoO3

Using configuration-state-constrained electronic structure calculations based on the generalized gradient approximation plus Hubbard U method, we sought the origin of the giant tetragonal ferroelectric distortion in the ambient phase of the potentially multiferroic material BiCoO3 and identified the nature of the pressure induced spin-state transition. Our results show that a strong Bi-O covalency drives the giant ferroelectric distortion, which is further stabilized by an xy-type orbital ordering of the high-spin (HS) Co3+ ions. For the orthorhombic phase under 5.8 GPa, we find that a mixed HS and low-spin (LS) state is more stable than both LS and intermediate-spin (IS) states, and that the former well accounts for the available experimental results. Thus, we identify that the pressure induced spin-state transition is via a mixed HS+LS state, and we predict that the HS-to-LS transition would be complete upon a large volume decrease of about 20%.Comment: 6 pages, 6 figures, 2 table