12,763 research outputs found

    Quadrature Observations of Wave and Non-Wave Components and Their Decoupling in an Extreme-Ultraviolet Wave Event

    Full text link
    We report quadrature observations of an extreme-ultraviolet (EUV) wave event on 2011 January 27 obtained by the Extreme Ultraviolet Imager (EUVI) onboard \emph{Solar Terrestrial Relations Observatory} (\emph{STEREO}), and the Atmospheric Imaging Assembly (AIA) onboard the \emph{Solar Dynamics Observatory} (\emph{SDO}). Two components are revealed in the EUV wave event. A primary front is launched with an initial speed of \sim440 km s1^{-1}. It appears significant emission enhancement in the hotter channel but deep emission reduction in the cooler channel. When the primary front encounters a large coronal loop system and slows down, a secondary much fainter front emanates from the primary front with a relatively higher starting speed of \sim550 km s1^{-1}. Afterwards the two fronts propagate independently with increasing separation. The primary front finally stops at a magnetic separatrix, while the secondary front travels farther before it fades out. In addition, upon the arrival of the secondary front, transverse oscillations of a prominence are triggered. We suggest that the two components are of different natures. The primary front belongs to a non-wave coronal mass ejection (CME) component, which can be reasonably explained with the field-line stretching model. The multi-temperature behavior may be caused by considerable heating due to the nonlinear adiabatic compression on the CME frontal loop. For the secondary front, most probably it is a linear fast-mode magnetohydrodynamic (MHD) wave that propagates through a medium of the typical coronal temperature. X-ray and radio data provide us with complementary evidence in support of the above scenario.Comment: 21 pages, 8 figures, accepted for publication in Ap

    Improving Semi-Supervised and Domain-Adaptive Semantic Segmentation with Self-Supervised Depth Estimation

    Get PDF
    Training deep networks for semantic segmentation requires large amounts of labeled training data, which presents a major challenge in practice, as labeling segmentation masks is a highly labor-intensive process. To address this issue, we present a framework for semi-supervised and domain-adaptive semantic segmentation, which is enhanced by self-supervised monocular depth estimation (SDE) trained only on unlabeled image sequences. In particular, we utilize SDE as an auxiliary task comprehensively across the entire learning framework: First, we automatically select the most useful samples to be annotated for semantic segmentation based on the correlation of sample diversity and difficulty between SDE and semantic segmentation. Second, we implement a strong data augmentation by mixing images and labels using the geometry of the scene. Third, we transfer knowledge from features learned during SDE to semantic segmentation by means of transfer and multi-task learning. And fourth, we exploit additional labeled synthetic data with Cross-Domain DepthMix and Matching Geometry Sampling to align synthetic and real data. We validate the proposed model on the Cityscapes dataset, where all four contributions demonstrate significant performance gains, and achieve state-of-the-art results for semi-supervised semantic segmentation as well as for semi-supervised domain adaptation. In particular, with only 1/30 of the Cityscapes labels, our method achieves 92% of the fully-supervised baseline performance and even 97% when exploiting additional data from GTA. The source code is available at https://github.com/lhoyer/improving_segmentation_with_selfsupervised_depth

    The B+J/ψωK+B^+ \to J/\psi \omega K^+ reaction and DDˉD^*\bar{D}^* molecular states

    Full text link
    We study the B+J/ψωK+B^+ \to J/\psi \omega K^+ reaction, measured by the LHCb collaboration, and show that it is driven by the presence of two resonances, the X(3940)X(3940) and X(3930)X(3930), that are of molecular nature and couple most strongly to DDˉD^* \bar{D}^*, but also to J/ψωJ/\psi\omega. Because of that, in the J/ψωJ/\psi\omega mass distribution we find a peak related to the excitation of the resonances and a cusp with large strength at the DDˉD^* \bar{D}^* threshold.Comment: 14 pages, 5 figures, 2 tables. arXiv admin note: text overlap with arXiv:1801.0709