40,623 research outputs found

    Abnormal oscillation modes in a waning light bridge

    Full text link
    A sunspot acts as a waveguide in response to the dynamics of the solar interior; the trapped waves and oscillations could reveal its thermal and magnetic structures. We study the oscillations in a sunspot intruded by a light bridge, the details of the oscillations could reveal the fine structure of the magnetic topology. We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly data to analyse the oscillations in the emission intensity of light bridge plasma at different temperatures and investigate their spatial distributions. The extreme ultraviolet emission intensity exhibits two persistent oscillations at five-minute and sub-minute ranges. The spatial distribution of the five-minute oscillation follows the spine of the bridge; whereas the sub-minute oscillations overlap with two flanks of the bridge. Moreover, the sub-minute oscillations are highly correlated in spatial domain, however, the oscillations at the eastern and western flanks are asymmetric with regard to the lag time. In the meanwhile, jet-like activities are only found at the eastern flank. Asymmetries in forms of oscillatory pattern and jet-like activities \textbf{are} found between two flanks of a granular light bridge. Based on our study and recent findings, we propose a new model of twisted magnetic field for a light bridge and its dynamic interactions with the magnetic field of a sunspot.Comment: 5 figures, Accepted version in A&

    "Mental Rotation" by Optimizing Transforming Distance

    Full text link
    The human visual system is able to recognize objects despite transformations that can drastically alter their appearance. To this end, much effort has been devoted to the invariance properties of recognition systems. Invariance can be engineered (e.g. convolutional nets), or learned from data explicitly (e.g. temporal coherence) or implicitly (e.g. by data augmentation). One idea that has not, to date, been explored is the integration of latent variables which permit a search over a learned space of transformations. Motivated by evidence that people mentally simulate transformations in space while comparing examples, so-called "mental rotation", we propose a transforming distance. Here, a trained relational model actively transforms pairs of examples so that they are maximally similar in some feature space yet respect the learned transformational constraints. We apply our method to nearest-neighbour problems on the Toronto Face Database and NORB


    Get PDF
    Rules are derived to indicate the optimal allocation of a fixed promotion budget between domestic and export markets when the commodity in question represents a significant portion of world trade and is protected in the domestic market by a deficiency-payment program. Optimal allocation decisions are governed by advertising elasticities in the domestic and export markets and the export market share. PromotionÂ’'s ability to lower deficiency payments is inversely related to the absolute value of demand elasticities in the domestic and export markets and directly related to advertising elasticities and certain policy parameters. The empirical application suggests subsidies for nonprice export promotion may be efficiency increasing in a second-best sense. That is, the heightened subsidies associated with the Targeted Export Assistance program and the Market Promotion Program appear to have corrected allocative errors that favored domestic market promotion.Agricultural and Food Policy,

    Unselective regrowth of 1.5-μm InGaAsP multiple-quantum-well distributed-feedback buried heterostructure lasers

    Get PDF
    Unselective regrowth for fabricating 1.5-μm InGaAsP multiple-quantum well (MQW) distributed-feedback (DFB) buried heterostructure (BH) lasers is developed. The experimental results exhibit superior characteristics, such as a low threshold of 8.5mA, high slope efficiency of 0.55mW∕mA, circular-like far-field patterns, the narrow linewidth of 2.5MHz, etc. The high performance of the devices effectively proves the feasibility of the new method to fabricate buried heterostructure lasers