arXiv subjects

Xiaoyu Wang

Publications and source records attributed to Xiaoyu Wang.

274 records · Page 16Linked to original sources

arXiv2014

Generic Object Detection With Dense Neural Patterns and Regionlets

This paper addresses the challenge of establishing a bridge between deep convolutional neural networks and conventional object detection frameworks for accurate and efficient generic object detection. We introduce Dense Neural Patterns, short for DNPs, which are dense local features derived from discriminatively trained deep convolutional neural networks. DNPs can be easily plugged into conventional detection frameworks in the same way as other dense local features(like HOG or LBP). The effectiveness of the proposed approach is demonstrated with the Regionlets object detection framework. It achieved 46.1% mean average precision on the PASCAL VOC 2007 dataset, and 44.1% on the PASCAL VOC 2010 dataset, which dramatically improves the original Regionlets approach without DNPs.

cs.CV↗

arXiv2014

Impact of local-moment fluctuations on the magnetic degeneracy of iron arsenide superconductors

We investigate the fate of the orthorhombic stripe-type magnetic state (ordering vectors $\left(π,0\right)$/$\left(0,π\right)$), observed in most iron-pnictide superconductors, in the presence of localized magnetic moments that tend to form a Neel state (ordering vector $\left(π,π\right)$). We show that before long-range Neel order sets in, the coupling between the conduction electrons and the fluctuations of the local moments favors an unusual magnetic state consisting of a coherent superposition of the $\left(π,0\right)$ and $\left(0,π\right)$ orders that preserves tetragonal symmetry. The magnetization of this state is non-uniform and induces a simultaneous checkerboard charge order. We discuss signatures of this magnetic configuration on the electronic spectrum and its impact on the superconducting state, showing that its phase space for coexistence with the $s^{+-}$ state is smaller than the stripe-type state. Our results shed light on recent experimental observations on $\mathrm{Ba(Fe_{1-x}Mn_{x})_{2}As_{2}}$ compounds, where the Neel-type local Mn moments interact with the Fe conduction electrons.

cond-mat.str-el↗

arXiv2012

Extracting respiratory signals from thoracic cone beam CT projections

Patient respiratory signal associated with the cone beam CT (CBCT) projections is important for lung cancer radiotherapy. In contrast to monitoring an external surrogate of respiration, such signal can be extracted directly from the CBCT projections. In this paper, we propose a novel local principle component analysis (LPCA) method to extract the respiratory signal by distinguishing the respiration motion-induced content change from the gantry rotation-induced content change in the CBCT projections. The LPCA method is evaluated by comparing with three state-of-the-art projection-based methods, namely, the Amsterdam Shroud (AS) method, the intensity analysis (IA) method, and the Fourier-transform based phase analysis (FT-p) method. The clinical CBCT projection data of eight patients, acquired under various clinical scenarios, were used to investigate the performance of each method. We found that the proposed LPCA method has demonstrated the best overall performance for cases tested and thus is a promising technique for extracting respiratory signal. We also identified the applicability of each existing method.

physics.med-ph↗

arXiv2010

Constraints Imposed by Symmetry on Pairing Operators for the Pnictides

Considering model Hamiltonians that respect the symmetry properties of the pnictides, it is argued that pairing interactions that couple electrons at different orbitals with an orbital-dependent pairing strength inevitably lead to interband pairing matrix elements, at least in some regions of the Brillouin zone. Such interband pairing has not been considered of relevance in multiorbital systems in previous investigations. It is also observed that if, instead, a purely intraband pairing interaction is postulated, this requires that the pairing operator has the form $Δ^+(k)=f(k) \sum_α d^+_{k,α,\uparrow}d^+_{-k, α,\downarrow}$ where $α$ labels the orbitals considered in the model and f(k) arises from the spatial location of the coupled electrons or holes. This means that the gaps at two different Fermi surfaces involving momenta $k_F$ and $k'_F$ can only differ by the ratio $f(k_F)/ f(k'_F)$ and that electrons in different orbitals must be subject to the same pairing attraction, thus requiring fine tuning. These results suggest that previously neglected interband pairing tendencies could actually be of relevance in a microscopic description of the pairing mechanism in the pnictides.

cond-mat.supr-con↗