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The rapid spread of rumors in social media is mainly caused by individual retweets. This paper applies uncertainty time series analysis (UTSA) to analyze a rumor retweeting behavior on Weibo. First, the rumor forwarding is modeled using uncertain time series, including order selection, parameter estimation, residual analysis, uncertainty hypothesis testing and forecast, and the validity of using uncertain time series analysis is further supported by analyzing the characteristics of the residual plot. The experimental results show that the uncertain time series can better predict the next stage of rumor forwarding. The results of the study have important practical significance for rumor management and the management of social media information dissemination., Comment: 11 pages,3 figures

Sparse R-CNN is a recent strong object detection baseline by set prediction on sparse, learnable proposal boxes and proposal features. In this work, we propose to improve Sparse R-CNN with two dynamic designs. First, Sparse R-CNN adopts a one-to-one label assignment scheme, where the Hungarian algorithm is applied to match only one positive sample for each ground truth. Such one-to-one assignment may not be optimal for the matching between the learned proposal boxes and ground truths. To address this problem, we propose dynamic label assignment (DLA) based on the optimal transport algorithm to assign increasing positive samples in the iterative training stages of Sparse R-CNN. We constrain the matching to be gradually looser in the sequential stages as the later stage produces the refined proposals with improved precision. Second, the learned proposal boxes and features remain fixed for different images in the inference process of Sparse R-CNN. Motivated by dynamic convolution, we propose dynamic proposal generation (DPG) to assemble multiple proposal experts dynamically for providing better initial proposal boxes and features for the consecutive training stages. DPG thereby can derive sample-dependent proposal boxes and features for inference. Experiments demonstrate that our method, named Dynamic Sparse R-CNN, can boost the strong Sparse R-CNN baseline with different backbones for object detection. Particularly, Dynamic Sparse R-CNN reaches the state-of-the-art 47.2% AP on the COCO 2017 validation set, surpassing Sparse R-CNN by 2.2% AP with the same ResNet-50 backbone., Comment: Accepted by CVPR 2022

How to develop a trust management model and then to efficiently control and manage nodes is an important issue in the scope of social network security. In this paper, a trust management model based on a cloud model is proposed. The cloud model uses a specific computation operator to achieve the transformation from qualitative concepts to quantitative computation. Additionally, this can also be used to effectively express the fuzziness, randomness and the relationship between them of the subjective trust. The node trust is divided into reputation trust and transaction trust. In addition, evaluation methods are designed, respectively. Firstly, the two-dimension trust cloud evaluation model is designed based on node's comprehensive and trading experience to determine the reputation trust. The expected value reflects the average trust status of nodes. Then, entropy and hyper-entropy are used to describe the uncertainty of trust. Secondly, the calculation methods of the proposed direct transaction trust and the recommendation transaction trust involve comprehensively computation of the transaction trust of each node. Then, the choosing strategies were designed for node to trade based on trust cloud. Finally, the results of a simulation experiment in P2P network file sharing on an experimental platform directly reflect the objectivity, accuracy and robustness of the proposed model, and could also effectively identify the malicious or unreliable service nodes in the system. In addition, this can be used to promote the service reliability of the nodes with high credibility, by which the stability of the whole network is improved. © 2016 by the authors., Open access

We show that by applying accidental degeneracy, we can obtain a triply-degenerate state at the zone center in the band diagram of two dimensional (2D) photonic crystal. The dispersion near the zone center comprises two linear bands and an additional flat band crossing at the same frequency. If this triply-degenerate state is formed by the degeneracy of monopole and dipole excitations, we show that the system can be mapped to an effective medium with permittivity and permeability equal to zero. While "Dirac cone" dispersions can only be meaningfully defined in 2D systems, the notion of a Dirac point can be extended to three dimensional (3D) classical wave systems. We show that a simple cubic photonic crystal composed of core-shell spheres exhibits a 3D Dirac-like point at the center of the Brillouin zone at a finite frequency. Using effective medium theory, we can map our structure to an isotropic zero refractive index material in which the effective permittivity and permeability are simultaneously zero at the Dirac-like point frequency (ωD). The Dirac-like point is six-fold degenerate and is formed by the accidental degeneracy of electric dipole and magnetic dipole excitations, each with three degrees of freedom. We found that 3D Dirac-like points at k = 0 can also be found in simple cubic acoustic wave crystals. Different from the case in the photonic system, the 3D Dirac-like point in acoustic wave system is four-fold degenerate, and is formed by the accidental degeneracy of dipole and monopole excitations. Using effective medium theory, this acoustic wave system can also be described as a material which has both effective mass density and reciprocal of bulk modulus equal to zero at ωD. For both the photonic and phononic systems, a subset of the bands has linear dispersions near the zone center, and they give rise to equi-frequency surfaces that are spheres with radii proportional to (ω - ωD).

We show that two-dimensional acoustic crystals (ACs) can be designed to exhibit Dirac cone dispersion at k → = 0. Effective medium theory finds that some of these ACs can have effectively zero reciprocal of bulk modulus 1/ eff and zero mass density eff, and thus zero refractive indices at the Dirac point. Numerical simulations are used to demonstrate various phenomena associated with the zero spatial phase change inside such materials. © 2012 American Institute of Physics.

We show that two-dimensional acoustic crystals (ACs) can be designed to exhibit Dirac cone dispersion at k → = 0. Effective medium theory finds that some of these ACs can have effectively zero reciprocal of bulk modulus 1/ eff and zero mass density eff, and thus zero refractive indices at the Dirac point. Numerical simulations are used to demonstrate various phenomena associated with the zero spatial phase change inside such materials. © 2012 American Institute of Physics.

We show that two-dimensional phononic crystals exhibit Dirac cone dispersion at k⃗ = 0 by exploiting dipole and quadrupole accidental degeneracy. While the equifrequency surface of Dirac cone modes is almost isotropic, such systems exhibit super-anisotropy, meaning that only transverse waves are allowed along certain directions, while only longitudinal waves are allowed along some other directions. Only one mode, not two, is allowed near the Dirac point, and only two effective parameters, not four, are needed to describe the dispersion. Effective medium theory finds that the phononic crystals have effectively zero mass density and zero 1/Ceff44 at the Dirac point. Numerical simulations are used to demonstrate the unusual elastic wave properties near the Dirac point frequency.

We show that two-dimensional phononic crystals exhibit Dirac cone dispersion at k⃗ = 0 by exploiting dipole and quadrupole accidental degeneracy. While the equifrequency surface of Dirac cone modes is almost isotropic, such systems exhibit super-anisotropy, meaning that only transverse waves are allowed along certain directions, while only longitudinal waves are allowed along some other directions. Only one mode, not two, is allowed near the Dirac point, and only two effective parameters, not four, are needed to describe the dispersion. Effective medium theory finds that the phononic crystals have effectively zero mass density and zero 1/Ceff44 at the Dirac point. Numerical simulations are used to demonstrate the unusual elastic wave properties near the Dirac point frequency.

A method of preventing Cu from passing into the gold and silver products or accumulating in the system was investigated. Effective ways of removing Cu from the system were intensifying the leaching and washing processes in the roasting and sulphuric acid leaching stages, separating Cu-containing slag in the oxidation refining step and eliminating Cu residue in the electrolyte cleaning process. The final gold and silver products were brought up to standard by increasing the rate of electrolyte circulation and washing the silver electrolytic slime with acid solution, water and ammonia., A method of preventing Cu from passing into the gold and silver products or accumulating in the system was investigated. Effective ways of removing Cu from the system were intensifying the leaching and washing processes in the roasting and sulphuric acid leaching stages, separating Cu-containing slag in the oxidation refining step and eliminating Cu residue in the electrolyte cleaning process. The final gold and silver products were brought up to standard by increasing the rate of electrolyte circulation and washing the silver electrolytic slime with acid solution, water and ammonia.