3,027 research outputs found

    Spin alignment of vector meson in e+e- annihilation at Z0 pole

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    We calculate the spin density matrix of the vector meson produced in e+e- annihilation at Z^0 pole. We show that the data imply a significant polarization for the antiquark which is created in the fragmentation process of the polarized initial quark and combines with the fragmenting quark to form the vector meson. The direction of polarization is opposite to that of the fragmenting quark and the magnitude is of the order of 0.5. A qualitative explanation of this result based on the LUND string fragmentation model is given.Comment: 15 pages, 2 fgiures; submitted to Phys. Rev.

    Spin Alignment of Vector Meson in High Energy Reactions

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    The recent data on the polarization of vector meson at LEP show that the vector mesons favor the helicity zero state. We calculate the helicity density matrix of vector meson which contains a polarized fragmenting quark by adding the spin of the fragmenting quark and that of the antiquark created in the fragmentation. The data at LEP imply a significant polarization for the antiquark in the opposite direction as that of the fragmenting quark. We extend the calculations to other reactions and make predictions for vector mesons in deeply inelastic lepton-nucleon scatterings and polarized pppp collisions.Comment: 4 pages,3 figures, Talk given at 3rd Circum-Pan-Pacific Symposium on "High Energy Spin Physics", Beijing, China, Oct.8-13, 200

    How Chief Information Officer Drives Innovation?

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    Owing to today’s global digital economy, information technology (IT) executives, namely Chief Information Officers (CIOs), play a crucial role in bridging the business and IT by exploiting IT as a strategic differentiator. Equipped with technical background, CIOs are well-positioned to help the firm to gather and utilize information to explore and exploit innovation. The study aims to investigate whether CIOs contributes to a firm’s innovative search. We examine the long-term effects of CIO appointment on the return on innovation investment through research and development (R&D) activities. By employing patent data and a matched sample of U.S. firms between 1995 and 2010, we show that CIO appointment is positively associated with future innovation efficiency. In particular, we find that CIOs in IT firms exerts a stronger influence on the pursuit of innovation. Taken together, our results shed light on the strategic role of CIO in cultivating firm’s innovation capability

    MRI Image Segmentation System of Uterine Fibroids Based on AR-Unet Network

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    Uterine fibroids are the most common benign tumors in female reproductive organs. The segmentation of uterine fibroids is crucial for accurate treatment. This paper proposes a new uterine fibroids MRI T2W image segmentation network AR-Unet (Attention Resnet101-Unet), which uses the deep neural network ResNet101 as the front end of feature extraction, extracts image semantic information, and combines U-net design ideas to build a network structure. The attention gate module is added before the upsampling and downsampling feature maps are spliced. We tested a total of 123 uterine fibroids MRI T2W images from 13 patients. The segmentation results were verified with expert-defined manual segmentation results. The average Dice coefficient, IOU value, sensitivity and specificity of all segmented images were 0.9044, 0.8443, 88.55% and 94.56%, the performance is better than ResNet101-Unet and Attention-Unet models, and finally the network is encapsulated into an auxiliary diagnostic system

    Desiccation and cracking behaviour of clay layer from slurry state under wetting-drying cycles

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    International audienceLaboratory tests were conducted to investigate the effect of wetting-drying (W-D) cycles on the initiation and evolution of cracks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent W-D cycles. The water evaporation, surface cracks evolution and structure evolution during the W-D cycles were monitored. The effect of W-D cycles on the geometric characteristics of crack patterns was analyzed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied W-D cycles: the measured cracking water content c, surface crack ratio Rsc and final thickness hf of the specimen increased significantly in the first three W-D cycles and then tended to reach equilibrium; the formed crack patterns after the second W-D cycle were more irregular than that after the first W-D cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkage during drying. In addition, it was found that the applied W-D cycles resulted in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second W-D cycle; the specimen volume generally increased with increasing cycles due to the aggregation and increased porosity. The image analysis results show that the geometric characteristics of crack pattern were significantly influenced by the W-D cycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image processing can be used for quantitatively analyzing the W-D cycle dependence of clay desiccation cracking behaviour

    Time Crystal in a Single-mode Nonlinear Cavity

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    Time crystal is a class of non-equilibrium phase with broken time-translational symmetry. Here we demonstrate the time crystal in a single-model nonlinear cavity. The time crystal originates from the self-oscillation induced by the linear gain and is stabilized by the nonlinear damping. We show this time crystal model exhibits four different characteristics: the emergence of classical limit cycle under the mean-field approximation, the dissipative gap closing in the thermodynamic limit, the quantum oscillation in the Husimi function, and the emergence of quantum limit cycle in the steady state. These properties provide a complete description of the time crystal and thus pave the way to investigate the time crystal in nonlinear systems
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