5,240 research outputs found

    Reconsideration of the QCD corrections to the ηc\eta_c decays into light hadrons using the principle of maximum conformality

    Full text link
    In the paper, we analyze the ηc\eta_c decays into light hadrons at the next-to-leading order QCD corrections by applying the principle of maximum conformality (PMC). The relativistic correction at the O(αsv2){\cal{O}}(\alpha_s v^2)-order level has been included in the discussion, which gives about 10%10\% contribution to the ratio RR. The PMC, which satisfies the renormalization group invariance, is designed to obtain a scale-fixed and scheme-independent prediction at any fixed order. To avoid the confusion of treating nfn_f-terms, we transform the usual MS\overline{\rm MS} pQCD series into the one under the minimal momentum space subtraction scheme. To compare with the prediction under conventional scale setting, RConv,mMOMr=(4.120.28+0.30)×103R_{\rm{Conv,mMOM}-r}= \left(4.12^{+0.30}_{-0.28}\right)\times10^3, after applying the PMC, we obtain RPMC,mMOMr=(6.090.55+0.62)×103R_{\rm PMC,mMOM-r}=\left(6.09^{+0.62}_{-0.55}\right) \times10^3, where the errors are squared averages of the ones caused by mcm_c and ΛmMOM\Lambda_{\rm mMOM}. The PMC prediction agrees with the recent PDG value within errors, i.e. Rexp=(6.3±0.5)×103R^{\rm exp}=\left(6.3\pm0.5\right)\times10^3. Thus we think the mismatching of the prediction under conventional scale-setting with the data is due to improper choice of scale, which however can be solved by using the PMC.Comment: 5 pages, 2 figure

    Gamma-Ray Burst/Supernova Associations: Energy Partition and the Case of a Magnetar Central Engine

    Full text link
    The favored progenitor model for Gamma-ray Bursts (GRBs) with Supernova (SN) association is the core collapse of massive stars. One possible outcome of such a collapse is a rapidly spinning, strongly magnetized neutron star ( magnetar ). We systematically analyze the multi-wavelength data of GRB/SN associations detected by several instruments before 2017 June. Twenty GRB/SN systems have been confirmed via direct spectroscopic evidence or a clear light curve bump, as well as some spectroscopic evidence resembling a GRB-SN. We derive/collect the basic physical parameters of the GRBs and the SNe, and look for correlations among these parameters. We find that the peak brightness, 56Ni mass, and explosion energy of SNe associated with GRBs are statistically higher than other Type Ib/c SNe. A statistically significant relation between the peak energy of GRBs and the peak brightness of their associated SNe is confirmed. No significant correlations are found between the GRB energies (either isotropic or beaming-corrected) and the supernova energy. We investigate the energy partition within these systems and find that the beaming-corrected GRB energy of most systems is smaller than the SN energy, with less than 30% of the total energy distributed in the relativistic jet. The total energy of the systems is typically smaller than the maximum available energy of a millisecond magnetar (2 × 1052 erg), especially if aspherical SN explosions are considered. The data are consistent with—although not proof of—the hypothesis that most, but not all, GRB/SN systems are powered by millisecond magnetars

    Role of Phosphatidylinositol-3-Kinase Pathway in Head and Neck Squamous Cell Carcinoma

    Get PDF
    Activation of the phosphatidylinositol-3-kinase (PI3K) pathway is one of the most frequently observed molecular alterations in many human malignancies, including head and neck squamous cell carcinoma (HNSCC). A growing body of evidence demonstrates the prime importance of the PI3K pathway at each stage of tumorigenesis, that is, tumor initiation, progression, recurrence, and metastasis. Expectedly, targeting the PI3K pathway yields some promising results in both preclinical studies and clinical trials for certain cancer patients. However, there are still many questions that need to be answered, given the complexity of this pathway and the existence of its multiple feedback loops and interactions with other signaling pathways. In this paper, we will summarize recent advances in the understanding of the PI3K pathway role in human malignancies, with an emphasis on HNSCC, and discuss the clinical applications and future direction of this field

    Circuit Breaker Fault Diagnosis Method Based on Improved One-Dimensional Convolutional Neural Network

    Get PDF
    Aiming at the problems of manual feature extraction and poor generalization ability of model in traditional circuit breaker fault diagnosis technology, a circuit breaker fault diagnosis method based on improved one-dimensional convolutional neural network is proposed. Firstly, the input feature sequence is adaptively weighted by self-attention mechanism to highlight the weight of important information; Secondly, 1 1 convolution layer and global average pooling layer are used to replace the full connection layer, which reduces the model training parameters, improves the training efficiency and prevents the phenomenon of over-fitting. Aiming at the problem of small number of data samples, the data is enhanced by Generative Adversarial Network. After adding the generated data to the original data, the accuracy of fault identification is further improved. The experimental results show that this method can effectively and accurately identify different fault types of circuit breaker, and verify the feasibility of its engineering application

    Geometric instability of graph neural networks on large graphs

    Full text link
    We analyse the geometric instability of embeddings produced by graph neural networks (GNNs). Existing methods are only applicable for small graphs and lack context in the graph domain. We propose a simple, efficient and graph-native Graph Gram Index (GGI) to measure such instability which is invariant to permutation, orthogonal transformation, translation and order of evaluation. This allows us to study the varying instability behaviour of GNN embeddings on large graphs for both node classification and link prediction

    Quantum state engineering by periodical two-step modulation in atomic system

    Get PDF
    By periodical two-step modulation, we demonstrate that the dynamics of multilevel system can still evolve even in multiple large detunings regime, and provide the effective Hamiltonian (of interest) for this system. We then illustrate this periodical modulation in quantum state engineering, including achieving direct transition from the ground state to the Rydberg state or the desired superposition of two Rydberg states without satisfying two-photon resonance condition, switching between Rydberg blockade regime and Rydberg antiblockade regime, stimulating distinct atomic transitions by the same laser field, and implementing selective transitions in the same multilevel system. Particularly, it is robust against perturbation of control parameters. Another advantage is that the waveform of laser field has simple square-wave form which is readily implemented in experiments. Thus, it offers us a novel method of quantum state engineering in quantum information processing.Comment: 16 pages, 12 figure

    RIS-Aided Cell-Free Massive MIMO Systems for 6G: Fundamentals, System Design, and Applications

    Full text link
    An introduction of intelligent interconnectivity for people and things has posed higher demands and more challenges for sixth-generation (6G) networks, such as high spectral efficiency and energy efficiency, ultra-low latency, and ultra-high reliability. Cell-free (CF) massive multiple-input multiple-output (mMIMO) and reconfigurable intelligent surface (RIS), also called intelligent reflecting surface (IRS), are two promising technologies for coping with these unprecedented demands. Given their distinct capabilities, integrating the two technologies to further enhance wireless network performances has received great research and development attention. In this paper, we provide a comprehensive survey of research on RIS-aided CF mMIMO wireless communication systems. We first introduce system models focusing on system architecture and application scenarios, channel models, and communication protocols. Subsequently, we summarize the relevant studies on system operation and resource allocation, providing in-depth analyses and discussions. Following this, we present practical challenges faced by RIS-aided CF mMIMO systems, particularly those introduced by RIS, such as hardware impairments and electromagnetic interference. We summarize corresponding analyses and solutions to further facilitate the implementation of RIS-aided CF mMIMO systems. Furthermore, we explore an interplay between RIS-aided CF mMIMO and other emerging 6G technologies, such as next-generation multiple-access (NGMA), simultaneous wireless information and power transfer (SWIPT), and millimeter wave (mmWave). Finally, we outline several research directions for future RIS-aided CF mMIMO systems.Comment: 30 pages, 15 figure
    corecore