7,651 research outputs found

    Surjective endomorphisms of projective surfaces -- the existence of infinitely many dense orbits

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    Let f ⁣:XXf \colon X \to X be a surjective endomorphism of a normal projective surface. When degf2\operatorname{deg} f \geq 2, applying an (iteration of) ff-equivariant minimal model program (EMMP), we determine the geometric structure of XX. Using this, we extend the second author's result to singular surfaces to the extent that either XX has an ff-invariant non-constant rational function, or ff has infinitely many Zariski-dense forward orbits; this result is also extended to Adelic topology (which is finer than Zariski topology)

    The Photometric Investigation of V921 Her using the Lunar-based Ultraviolet Telescope of Chang'e-3 mission

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    The light curve of V921 Her in ultraviolet band observed by the Lunar-based Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our solutions conclude that V921 Her is an early type marginal contact binary system with an additional close-in component. The binary system is under poor thermal contact with a temperature difference of nearly 700K700K between the two components. The close-in component contributes about 19%19\,\% of the total luminosity in the triple system. Combining the radial velocity study together with our photometric solutions, the mass of the primary star and secondary one are calculated to be M1=1.784(±0.055)MM_1 = 1.784(\pm0.055)M_\odot, M2=0.403(±0.012)MM_2 = 0.403(\pm0.012)M_\odot. The evolutionary scenario of V921 Her is discussed. All times of light minimum of V921 Her available in the bibliography are taken into account and the OCO - C curve is analyzed for the first time. The most probable fitting results are discussed in the paper, which also confirm the existence of a third component (P3=10.2P_3=10.2 year) around the binary system. The period of V921 Her is also undergoing a continuously rapid increase at a rate of dP/dt=+2.79×107dayyear1dP/dt=+2.79\times{10^{-7}}day\cdot year^{-1}, which may due to mass transfer from the less massive component to the more massive one

    Enabling CMF Estimation in Data-Constrained Scenarios: A Semantic-Encoding Knowledge Mining Model

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    Precise estimation of Crash Modification Factors (CMFs) is central to evaluating the effectiveness of various road safety treatments and prioritizing infrastructure investment accordingly. While customized study for each countermeasure scenario is desired, the conventional CMF estimation approaches rely heavily on the availability of crash data at given sites. This not only makes the estimation costly, but the results are also less transferable, since the intrinsic similarities between different safety countermeasure scenarios are not fully explored. Aiming to fill this gap, this study introduces a novel knowledge-mining framework for CMF prediction. This framework delves into the connections of existing countermeasures and reduces the reliance of CMF estimation on crash data availability and manual data collection. Specifically, it draws inspiration from human comprehension processes and introduces advanced Natural Language Processing (NLP) techniques to extract intricate variations and patterns from existing CMF knowledge. It effectively encodes unstructured countermeasure scenarios into machine-readable representations and models the complex relationships between scenarios and CMF values. This new data-driven framework provides a cost-effective and adaptable solution that complements the case-specific approaches for CMF estimation, which is particularly beneficial when availability of crash data or time imposes constraints. Experimental validation using real-world CMF Clearinghouse data demonstrates the effectiveness of this new approach, which shows significant accuracy improvements compared to baseline methods. This approach provides insights into new possibilities of harnessing accumulated transportation knowledge in various applications.Comment: 39 pages, 9 figure
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