28 research outputs found

    Revisit to Non-decoupling MSSM

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    Dipole operator sˉσμνFμνb\bar{s}\sigma_{\mu\nu}F^{\mu\nu}b requires the helicity flip in the involving quark states thus the breaking of chiral U(3)Q×U(3)dU(3)_{Q}\times U(3)_{d}. On the other hand, the bb-quark mass generation is also a consequence of chiral U(3)Q×U(3)dU(3)_{Q}\times U(3)_{d} symmetry breaking. Therefore, in many models, there might be strong correlation between the bsγb\to s\gamma and bb quark Yukawa coupling. We use non-decoupling MSSM model to illustrate this feature. The light Higgs boson may evade the direct search experiments at LEPII or Tevatron while the 125 GeV Higgs-like boson is identified as the heavy Higgs boson in the spectrum. A light charged Higgs is close to the heavy Higgs boson which is of 125 GeV and its contribution to bsγb\to s \gamma requires large supersymmetric correction with large PQ and RR symmetry breaking. The large supersymmetric contribution at the same time significantly modifies the bb quark Yukawa co upling. With combined flavor constraints BXsγB\to X_{s}\gamma and Bsμ+μB_{s}\to \mu^{+}\mu^{-} and direct constraints on Higgs properties, we find best fit scenarios with light stop of O\cal O(500 GeV), negative AtA_{t} around -750 GeV and large μ\mu-term of 2-3 TeV. In addition, reduction in bbˉb\bar{b} partial width may also result in large enhancement of ττ\tau\tau decay branching fraction. Large parameter region in the survival space under all bounds may be further constrained by HττH\to \tau\tau if no excess of ττ\tau\tau is confirmed at LHC. We only identify a small parameter region with significant HhhH\to hh decay that is consistent with all bounds and reduced ττ\tau\tau decay branching fraction.Comment: 18pages, 6 figure

    Gamma-rays from Nearby Clusters: Constraints on Selected Decaying Dark Matter Models

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    Recently, the Fermi-LAT collaboration reported upper limits on the GeV gamma-ray flux from nearby clusters of galaxies. Motivated by these limits, we study corresponding constraints on gamma-ray emissions from two specific decaying dark matter models, one via grand unification scale suppressed operators and the other via R-parity violating operators. Both can account for the PAMELA and Fermi-LAT excesses of e^\pm. For GUT decaying dark matter, the gamma-rays from the M49 and Fornax clusters, with energy in the range of 1 to 10 GeV, lead to the most stringent constraints to date. As a result, this dark matter is disfavored with conventional model of e^\pm background. In addition, it is likely that some tension exists between the Fermi-LAT e^\pm excess and the gamma ray constraints for any decaying dark matter model, provided conventional model of e^\pm background is adopted. Nevertheless, the GUT decaying dark matter can still solely account for the PAMELA positron fraction excess without violating the gamma-ray constraints. For the gravitino dark matter model with R-parity violation, cluster observations do not give tight constraints. This is because a different e^\pm background has been adopted which leads to relatively light dark matter mass around 200 GeV.Comment: 17 pages, 4 figures, version to appear in Phys. Lett.

    Open World Classification with Adaptive Negative Samples

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    Open world classification is a task in natural language processing with key practical relevance and impact. Since the open or {\em unknown} category data only manifests in the inference phase, finding a model with a suitable decision boundary accommodating for the identification of known classes and discrimination of the open category is challenging. The performance of existing models is limited by the lack of effective open category data during the training stage or the lack of a good mechanism to learn appropriate decision boundaries. We propose an approach based on \underline{a}daptive \underline{n}egative \underline{s}amples (ANS) designed to generate effective synthetic open category samples in the training stage and without requiring any prior knowledge or external datasets. Empirically, we find a significant advantage in using auxiliary one-versus-rest binary classifiers, which effectively utilize the generated negative samples and avoid the complex threshold-seeking stage in previous works. Extensive experiments on three benchmark datasets show that ANS achieves significant improvements over state-of-the-art methods.Comment: Accepted by EMNLP 2021 (Main Track, Long Paper

    Tubeless video-assisted thoracic surgery for pulmonary ground-glass nodules: expert consensus and protocol (Guangzhou)

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    Reflection and transmission of Gaussian beam from a uniaxial crystal slab

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    We investigate the characteristics of Gaussian beams reflected and transmitted from a uniaxial crystal slab with an arbitrary orientation of its optical axis. The formulas of the total electric and magnetic fields inside and outside the slab are derived by use of Maxwell's equations and by matching the boundary conditions at the interfaces. Numerical simulations are presented and the field values as well as the power densities are computed. Negative refractions are demonstrated when the beam is transmitted through a uniaxial crystal slab. Beam splitting of the reflected beam is observed and is explained by the resonant transmission for plane waves. Dependences of the lateral shift on the incident angle and beam width are discussed. Negative and positive lateral shifts are observed due to the spatial anisotropic properties

    Two-Step Adaptive Control for Planar Type Docking of Autonomous Underwater Vehicle

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    Planar type docking enables a convenient underwater energy supply for irregularly shaped autonomous underwater vehicles (AUVs), but the corresponding control method is still challenging. Conventional control methods for torpedo-shaped AUVs are not suitable for planar type docking due to the significant differences in system structures and motion characteristics. This paper proposes a two-step adaptive control method to solve the planar type docking problem. The method makes a seamless combination of horizontal dynamic positioning and visual servo docking considering ocean current disturbance. The current disturbance is estimated and canceled in the pre-docking step using a current observer, and the positioning error is further compensated for by the vertical visual servo technique in the docking step. Reduced order dynamic models are distinctively established for different docking steps according to the motion characteristics, based on which the dynamic controllers are designed considering the model parameter uncertainties. Simulation is conducted with an initial distance of 10 m in the horizontal direction and 3 m in depth. Stable and accurate dynamic positioning under up to 0.4 m/s of current disturbances with different directions is validated. A 0.5 m lateral positioning error is successfully compensated for by the visual servo docking step. The proposed control method provides a valuable reference for similar types of docking application

    Downscaling of passive microwave soil moisture retrievals based on spectral analysis

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    The retrieval of soil moisture from passive microwave remotesensing data is presently one of the most effective methods for monitoring soil moisture. However, the spatial resolution of passive microwave soil moisture products is generally low; thus, existing soil moisture products should be downscaled in order to obtain more accurate soil moisture data. In this study, we explore the theoretical feasibility of applying the spectral downscaling method to the soil moisture in order to generate high spatial resolution soil moisture based on both Moderate Resolution Imaging Spectroradiometer and Fengyun-3B (FY3B) data. We analyse the spectral characteristics of soil moisture images covering the east-central of the Tibetan Plateau which have different spatial resolutions. The spectral analysis reveals that the spectral downscaling method is reliable in theory for downscaling soil moisture. So, we developed one spectral downscaling method for deriving the high spatial resolution (1 km) soil moister data from the FY3B data (25 km). Our results were compared with the ground truth measurements from 15 selected experimental days in 16 different sites. The average coefficient of determination (R2) of the spectral downscaling increased nearly doubled than that of the original FY3B soil moisture product. The spectral downscaled soil moister data were successfully applied to examine the water exchange between the land and atmosphere in the study regions. The spectral downscaling approach could be an efficient and effective method to improve the spatial resolution of current microwave soil moisture images.This work was supported by the National Natural Science Foundation of China (NSFC): [Grant Number 41401426]

    Composite of LiFePO \u3c inf\u3e 4 with titanium phosphate phases as lithium-ion battery electrode material

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    We report the synthesis of LiFePO4 (LFP) battery materials where during synthesis the iron has been substituted by up to 10 mol % with titanium. Analysis of the Ti-substituted materials revealed that at the substitution levels investigated, the Ti did not form a solid solution with the LFP, but rather minority phases containing Ti phosphates were formed and segregated at the nanoscopic scale. The minority phases were amorphous or not well-crystallized and accepted Li on first discharge in a lithium half cell, and solid state NMR spectra were consistent with one of the constituents being LiTi2(PO4)3. The Ti substituted materials had increased electrochemical capacities and discharge voltages relative to LFP prepared in an equivalent process, and the ability to accept Li on first discharge may find utility in using previously inaccessible capacity in battery cathode formulations and in balancing excess capacity from high energy cathode materials. © 2013 American Chemical Society
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