First-principles calculations have been used to research the electronic structure and magnetic properties of zigzag boron nitride nanoribbons (ZBNNRs) terminated/jointed by armchair dimer-Fe chains (respectively called Fe-terminated ZBNNRs and Fe-jointed ZBNNRs). The Fe-terminated ZBNNRs is a semiconductor for different ribbon widths, and the Fe-jointed ZBNNRs become half-metallic regardless of the ribbon width. The magnetism of both structures mainly stems from the Fe atoms. It is found that the self-metallicity of the Fe-jointed ZBNNRs results from the strong interaction between the 3d orbitals of Fe atoms and the 2p orbitals of N atoms. The stability of the Fe-jointed ZBNNRs under room temperature has been confirmed by molecular dynamics simulation. This kind of half-metal property means a selectivity for the two different electrons, it can be applied to spintronics devices. Other transition-metal jointed ZBNNRs are also studied, which can be metals, half-metals or semiconductors with different ground states.
By using non-equilibrium Green function formalism in combination with density functional theory, we investigated the electronic transport properties of armchair graphene nanoribbon devices in which one lead is undoped and the other is N2AA-doped with two quasi-adjacent substitutional nitrogen atoms incorporating pairs of neighboring carbon atoms in the same sublattice A. Two kinds of N2AA-doped style are considered, for N dopants substitute the center or the edge carbon atoms. Our results show that the rectification behavior with a large rectifying ratio can be found in these devices and the rectifying characteristics can be modulated by changing the width of graphene nanoribbons or the position of the N2AA dopant. The mechanisms are revealed to explain the rectifying behaviors.
Using first-principles calculations, we investigate the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) with side-attached trans-polyacetylene (CnHn+1). The band gap is strongly dependent on the number n of C atoms in the polyacetylene chain: the gap of the system with even n is much bigger than that with odd n+1, whereas the parity dependence of n is gradually weakened with an increasing n. Moreover, the magnetic moment oscillation between 1 and , with n odd and even, also reveals a parity effect due to the electron transfer from the ZGNRs to polyacetylene chain with odd n.
In this paper, a two-dimensional (2D) DOA estimation algorithm of coherent signals with a separated linear acoustic vector-sensor (AVS) array consisting of two sparse AVS arrays is proposed. Firstly, the partitioned spatial smoothing (PSS) technique is used to construct a block covariance matrix, so as to decorrelate the coherency of signals. Then a signal subspace can be obtained by singular value decomposition (SVD) of the covariance matrix. Using the signal subspace, two extended signal subspaces are constructed to compensate aperture loss caused by PSS. The elevation angles can be estimated by estimation of signal parameter via rotational invariance techniques (ESPRIT) algorithm. At last, the estimated elevation angles can be used to estimate automatically paired azimuth angles. Compared with some other ESPRIT algorithms, the proposed algorithm shows higher estimation accuracy, which can be proved through the simulation results.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)