50 research outputs found

    On two conjectures of Sun concerning Apéry-like series

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    We prove two conjectural identities of Z.-W. Sun concerning ApĂ©ry-like series. One of the series is alternating, whereas the other one is not. Our main strategy is to convert the series and the alternating series to log-sine-cosine and log-sinh-cosh integrals, respectively. Then we express all these integrals using single-valued Bloch–Wigner–Ramakrishnan–Wojtkowiak–Zagier polylogarithms. The conjectures then follow from a few rather non-trivial functional equations of those polylogarithms in weights 3 and 4

    Camera-aware Proxies for Unsupervised Person Re-Identification

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    This paper tackles the purely unsupervised person re-identification (Re-ID) problem that requires no annotations. Some previous methods adopt clustering techniques to generate pseudo labels and use the produced labels to train Re-ID models progressively. These methods are relatively simple but effective. However, most clustering-based methods take each cluster as a pseudo identity class, neglecting the large intra-ID variance caused mainly by the change of camera views. To address this issue, we propose to split each single cluster into multiple proxies and each proxy represents the instances coming from the same camera. These camera-aware proxies enable us to deal with large intra-ID variance and generate more reliable pseudo labels for learning. Based on the camera-aware proxies, we design both intra- and inter-camera contrastive learning components for our Re-ID model to effectively learn the ID discrimination ability within and across cameras. Meanwhile, a proxy-balanced sampling strategy is also designed, which facilitates our learning further. Extensive experiments on three large-scale Re-ID datasets show that our proposed approach outperforms most unsupervised methods by a significant margin. Especially, on the challenging MSMT17 dataset, we gain 14.3%14.3\% Rank-1 and 10.2%10.2\% mAP improvements when compared to the second place. Code is available at: \texttt{https://github.com/Terminator8758/CAP-master}.Comment: Accepted to AAAI 2021. Code is available at: https://github.com/Terminator8758/CAP-maste

    Fretting wear-induced sudden loss of corrosion resistance in a corrosion-resistant Ni-based alloy

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    The fretting corrosion testing of A690 with a sliding amplitude of 100 ÎŒm and a normal force of 20 N was conducted in a manually designed equipment with a tube-on-plate contact configuration exposed to simulated pressurized water reactor (PWR) secondary water. While A690 exhibits superior corrosion resistance, the fretting wear results in a two orders of magnitude faster oxidation rate at the contacting surface. A detailed characterization reveals that the fretting wear-induced dynamic stress/strain does not only constantly break the integrity of the oxide scale but also accelerate the consumption of Cr in the near-surface metal matrix. The degradation of corrosion resistance of A690 under fretting wear can be mainly attributed to 1) the decrease of oxide scale thickness; 2) the introduction of nanocavities and nano-cracks at the grain boundaries of the oxide scale; 3) the formation of a nano-grained Cr-depleted matrix zone under the oxide scale. These findings suggest that, for the structural alloys serviced at elevated temperatures, even a small amplitude motion with low normal stress against their contacting surface could significantly deteriorate their corrosion resistance. Hence, the service lifetime of the structural alloys needs to be reconsidered once friction is existing

    Longitudinal changes of lactopontin (milk osteopontin) in term and preterm human milk

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    BackgroundLactopontin (LPN) in breast milk, also known as milk osteopontin is thought to play a myriad of important roles in infants when they are immature. The purpose of the present study was to examine the longitudinal changes in LPN concentrations in term and preterm milk, and elucidate the links between maternal characteristics, LPN levels, and child growth in a birth cohort.Methods131 mothers who delivered term, moderate-late preterm (MPT), very preterm (VPT), and extremely preterm (EPT) infants were included, milk samples were collected at 7, 14, 28, and 120 days postpartum. LPN concentration was determined by multiple reaction monitoring (MRM) using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).ResultsOur results indicated that LPN change over time of VPT (P = 0.024) and EPT (P = 0.003) were significantly different from term milk, although they all gradually decreased with lactation. In terms of LPN-related factors, maternal age was a significant contributor in late mature milk and pre-pregnancy BMI a significant contributor to colostrum and transitional milk. We further investigated relationships between LPN levels and infant weight and our results suggested that high levels of LPN in breast milk might be useful for the catch-up growth of infants.ConclusionLPN levels in breast milk are related to maternal factors, and differences in LPN levels may affect the growth of infants. As milk is a critical part in the mother–breastmilk–infant “triad,” the association between maternal-infant factors and milk LPN levels warrants further study
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