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排序方式: 共有195条查询结果,搜索用时 15 毫秒
21.
Luxing Yang Moez Draief Xiaofan Yang 《Mathematical Methods in the Applied Sciences》2017,40(5):1396-1413
The node‐based epidemic modeling is an effective approach to the understanding of the impact of the structure of the propagation network on the epidemics of electronic virus. In view of the heterogeneity of the propagation network, a heterogeneous node‐based SIRS model is proposed. Theoretical analysis shows that the maximum eigenvalue of a matrix related to the model determines whether viruses tend to extinction or persist. When viruses persist, the connectedness of the propagation network implies the existence and uniqueness of a viral equilibrium, and a set of sufficient conditions for the global stability of the viral equilibrium are given. Numerical examples verify the correctness of our results. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
22.
Random Early Detection (RED) is an active queue management (AQM) mechanism for routers on the Internet. In this paper, performance of RED and Adaptive RED are compared from the viewpoint of nonlinear dynamics. In particular, we reveal the relationship between the performance of the network and its nonlinear dynamical behavior. We measure the maximal Lyapunov exponent and Hurst parameter of the average queue length of RED and Adaptive RED, as well as the throughput and packet loss rate of the aggregate traffic on the bottleneck link. Our simulation scenarios include FTP flows and Web flows, one-way and two-way traffic. In most situations, Adaptive RED has smaller maximal Lyapunov exponents, lower Hurst parameters, higher throughput and lower packet loss rate than that of RED. This confirms that Adaptive RED has better performance than RED. 相似文献
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We propose and investigate a novel technique to realize non-return-to-zero (NRZ) to return-to-zero (RZ) format conversion of a multichannel 4-ary amplitude shift keying (4-ASK) signal. The proposed format converter composed of two modulators and a dispersion compensating fiber (DCF) is theoretically inves-tigated using numerical simulation as basis. Research shows that a 4-channel 20-Gb/s NRZ-4-ASK signal can be converted to a RZ-4-ASK signal simultaneously without wavelength shifting and signal quality degradation, with the converted signal multiplexed to 40 Gb/s. 相似文献
25.
Housheng Su Ningzi Zhang Michael Z.Q. Chen Hongwei Wang Xiaofan Wang 《Nonlinear Analysis: Real World Applications》2013,14(1):798-806
This paper investigates adaptive flocking of multi-agent systems (MASs) with a virtual leader. All agents and the virtual leader share the same intrinsic nonlinear dynamics, which satisfies a locally Lipschitz condition and depends on both position and velocity information for the agent itself. Under the assumption that the initial network is connected, an approach to preserving the connectivity of the network is proposed. On the basis of the Lyapunov stability theory, an adaptive flocking control law is derived, for making the MASs track the virtual leader without collision. Finally, a numerical example is presented to illustrate the effectiveness of the theoretical results. 相似文献
26.
Dake Hu Tianqi Zhao Xiaofan Ping Husong Zheng Lei Xing Xiaozhi Liu Jingying Zheng Lifei Sun Lin Gu Chenggang Tao Dong Wang Liying Jiao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7051-7055
Two‐dimensional (2D) PtSe2 shows the most prominent layer‐dependent electrical properties among various 2D materials and high catalytic activity for hydrogen evolution reaction (HER), and therefore, it is an ideal material for exploring the structure–activity correlations in 2D systems. Here, starting with the synthesis of single‐crystalline 2D PtSe2 with a controlled number of layers and probing the HER catalytic activity of individual flakes in micro electrochemical cells, we investigated the layer‐dependent HER catalytic activity of 2D PtSe2 from both theoretical and experimental perspectives. We clearly demonstrated how the number of layers affects the number of active sites, the electronic structures, and electrical properties of 2D PtSe2 flakes and thus alters their catalytic performance for HER. Our results also highlight the importance of efficient electron transfer in achieving optimum activity for ultrathin electrocatalysts. Our studies greatly enrich our understanding of the structure–activity correlations for 2D catalysts and provide new insight for the design and synthesis of ultrathin catalysts with high activity. 相似文献
27.
Mengyuan Zhang Peiling Lin Xiaofan Song Kun Chen Yuxuan Yang Yongliang Xu Qiang Zhang Youshen Wu Yanfeng Zhang Yilong Cheng 《Journal of polymer science. Part A, Polymer chemistry》2022,60(9):1511-1520
The design of wound dressings with excellent self-healing ability, adequate adhesion, good biocompatibility, and potential antibacterial ability is of great significance for the healing of infected wounds arising from human activities. Herein, a series of multi-functional hydrogel dressings, poly(ionized isocyanoethyl methacrylate-glutamine)/poly(hexamethylene guanidine) (iGx/PHMGy) hydrogels, were obtained through homopolymerization of fully ionized isocyanoethyl methacrylate-glutamine (iIEM-Gln) in the presence of poly(hexamethylene guanidine) (PHMG), in which strong hydrogen bonds were formed among urea groups in the P (iIEM-Gln) chain to form a stable hydrogel network. The prepared iGx/PHMGy hydrogels exhibited adequate self-healing ability and tissue adhesion, which could be firmly adhered to the wound surface and remained intact during application. In addition, the presence of PHMG imparted good antibacterial activity to the hydrogels for the effective promotion of the wound healing in S. aureus infected skin wound on mice. Overall, this multi-functional hydrogel provides a facile and effective strategy for the design of infected wound dressings, and may show great potential in clinical applications. 相似文献
28.
超精密单点金刚石车削过程中需要对刀具参数进行检测。基于机器视觉原理,采用新型的机械结构设计了新型刀具在线检测系统。通过垂直放置的两组由同轴远心镜头和CMOS相机组成的光学系统来获取车刀刀尖正面及侧面的图像,再经图像处理系统来获取刀具的轮廓及位置信息,完成对刀具轮廓及位置的在线检测,实验验证可实现测量的重复性定位精度达1μm。在线检测的方式借助了超精密车床自身的高精度和运动机构,可以保证相机焦点和机床主轴之间的相对位置关系,弥补了目前刀具检测系统稳定性差和重复性精度低的不足,提高了加工的整体效率。 相似文献
29.
Luo Guanhua Jiao Yujuan Lv Xuechuan Zhang Xiaofan Gao Xiaohan 《Research on Chemical Intermediates》2018,44(9):5377-5387
Research on Chemical Intermediates - Catechol and hydroquinone are very important fine chemical intermediate products, which have a wide range of applications. The hydroxylation of phenol with... 相似文献
30.
研究如下界约束下算子方程最小二乘问题:min x∈Ω‖L(X:A_1,…,At;B_1,…,B_t)-T‖~2,其中‖.‖为Frobenius范数,L(X:A_1…A_t;B_1,…,B_t)为关于X的线性矩阵算子(或齐次线性变换),Ai∈R~(p×m),B_j∈R~(n×q)i,j=1,…,n为算子L的系数矩阵,丁为右端矩阵,ΩR~(m×n)为界约束凸集合.提出了求解问题的条件梯度迭代算法及其简要收敛性分析,并给出条件梯度算法的几类加速形式.随机数据和图像恢复模型数据的实验结果表明说明算法是可行高效的. 相似文献