Meaningful Secret Image Sharing with Saliency Detection

Secret image sharing (SIS), as one of the applications of information theory in information security protection, has been widely used in many areas, such as blockchain, identity authentication and distributed cloud storage. In traditional secret image sharing schemes, noise-like shadows introduce difficulties into shadow management and increase the risk of attacks. Meaningful secret image sharing is thus proposed to solve these problems. Previous meaningful SIS schemes have employed steganography to hide shares into cover images, and their covers are always binary images. These schemes usually include pixel expansion and low visual quality shadows. To improve the shadow quality, we design a meaningful secret image sharing scheme with saliency detection. Saliency detection is used to determine the salient regions of cover images. In our proposed scheme, we improve the quality of salient regions that are sensitive to the human vision system. In this way, we obtain meaningful shadows with better visual quality. Experiment results and comparisons demonstrate the effectiveness of our proposed scheme.     

利用TEM对Si基片与MgO基片上生长的薄膜特性的研究

对生长在Si和MgO单晶基片上的不同厚度的单层NbN薄膜、双层薄膜AlN/NbN以及三层薄膜NbN/AlN/NbN应用透射电子显微镜(Transmission Electron Microscope,TEM)技术进行了分析研究,对这几种薄膜样品的微观结构、薄膜厚度以及各个边界的一些直观细节给出了较为清晰的图像。由透射电子显微镜的电子衍射图案计算了薄膜和单晶衬底的晶格常数,并与我们以前采用X射线衍射技术分析的结果进行了比较,结果有很好的吻合。     

关于SIS环

通过自内射环和半本原环给出了SIS环的定义,即如果RRR是内射的并且J(R)=0,我们称此环为SIS环;并且得到了它的一些刻画和性质.     

Design Consideration for a Two-Distributed-Junction Tuning Circuit

We describe a novel method of designing a tuning circuit with two half-wave distributed junctions separated by a half-wavelength microstripline, which analytically determines the circuit parameters such as the minimum current density of the junctions and the characteristic impedances of the distributed junctions and the microstripline. The tuning circuit was approximated by simple transmission theory and then simplified with ideal circuit components for analysis. We applied Chebyshevs band-pass filter theory, in part, to optimize the circuit design. The analytical results revealed that a high characteristic-impedance ratio between the distributed junctions and the microstripline is necessary to obtain broadband matching using low-current-density junctions. The experimental results for all-NbN SIS mixers we designed with this method demonstrated double-sideband (DSB) receiver-noise temperatures of 6–10 quanta from 710 to 810 GHz for a mixer with a current density of only 4 kA/cm² (estimated C_JR_N product of 37 at 750 GHz). The RF bandwidth was broader than that of a conventional full-wave distributed SIS mixer with the same current density.     

Noise Stability of SIS Receivers

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.     

Effects of delayed recovery and nonuniform transmission on the spreading of diseases in complex networks

We investigate the effects of delaying the time to recovery (delayed recovery) and of nonuniform transmission on the propagation of diseases on structured populations. Through a mean-field approximation and large-scale numerical simulations, we find that postponing the transition from the infectious to the recovered states can largely reduce the epidemic threshold, therefore promoting the outbreak of epidemics. On the other hand, if we consider nonuniform transmission among individuals, the epidemic threshold increases, thus inhibiting the spreading process. When both mechanisms are at work, the latter might prevail, hence resulting in an increase of the epidemic threshold with respect to the standard case, in which both ingredients are absent. Our findings are of interest for a better understanding of how diseases propagate on structured populations and to a further design of efficient immunization strategies.     

The fractional-order SIS epidemic model with variable population size

In this work, we deal with the fractional-order SIS epidemic model with constant recruitment rate, mass action incidence and variable population size. The stability of equilibrium points is studied. Numerical solutions of this model are given. Numerical simulations have been used to verify the theoretical analysis.     

具有标准发生率和因病死亡率的离散SIS传染病模型的全局稳定性分析

主要研究了具有标准发生率和因病死亡率的离散SIS传染病模型的动力学性质,利用构造Lyapunov函数,得到模型无病平衡点和地方性平衡点的全局稳定性,即无病平衡点是全局渐近稳定的当且仅当基本再生数R_0≤1,地方病平衡点是全局渐近稳定的当且仅当R_0>1.     

一类时滞SIS传染病模型的讨论

对一类具有生理阶段结构的SIS传染病模型进行了分析，得到了传染病最终消除和成为地方病的阈值．