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1.
Liang'an Huo 《中国物理 B》2022,31(3):30202-030202
The appearance of rumors intensifies people's panic and affects social stability. How to control the spread of rumors has become an important issue which is worth studying. In order to more accurately reflect the actual situation in the real world, a stochastic model incorporating media coverage and Lévy noise is proposed to describe the dynamic process of rumor propagation. By introducing two control strategies of popular science education and media coverage in an emergency event, an near-optimal control problem that minimizes the influence and control cost of rumor propagation is proposed. Sufficient conditions for near-optimal control of the model are established by using a Hamiltonian function. Then the necessary conditions for near-optimal control are obtained by using the Pontryagin maximum principle. Finally, the effect of popular science education, media coverage and Lévy noise on rumor propagation process control is verified by numerical simulation.  相似文献   
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It is important to maximize network lifetime while meeting coverage requirements in Wireless Sensor Networks (WSN). This paper focuses on maximizing the network lifetime of barrier coverage in WSN with mobile sensors. For mobile sensors, movement energy consumption can be much higher than during sensing and communication. Since the battery capacity of the sensor is fixed, more energy can be used for sensing and communication if the movement distance required to build the barrier can be reduced. Therefore, we focus on reducing the movement distance required by the mobile sensors to build the barriers. Also, we can build as many barriers as possible if we use as few mobile sensors as possible to build a barrier. By rotating multiple barriers, we can further extend the lifetime of the network. Based on the above concept, an energy-efficient algorithm is proposed for building barriers in WSNs with mobile sensors. The contribution of this paper are: (1) We find the minimum number of sensors required to construct a barrier for a rectangular region. (2) We explain how to cluster the sensors in the region, and then calculate the linear equations of the barriers based on the results of the clustering. (3) We explain how to set the sojourn points for these linear equations of the barriers, and then assign the mobile sensors to every one of these sojourn points. In short, the proposed algorithm can construct multiple barriers depending on the location of the sensor, with a minimum number of sensors connecting the left and right boundaries of the target field. Finally, the simulation results show that the proposed algorithm has better performance in terms of network lifetime than the previous result.  相似文献   
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建立了一类具有媒体效应和追踪隔离的SIQR时滞传染病模型,给出了模型的基本再生数R0,并从稳定性、持久性和分支角度对该模型进行了理论分析和数值模拟。研究结果表明,由媒体报道产生的时滞τ在各影响因子的临界值处出现Hopf分支。当τ固定时,随着媒体的广泛报道,易感者对疾病信息认识的偏差程度δ不断增加,模型由周期性振荡转为平衡;随着有效接触率最大削减作用β0β00的不断增加,模型又由平衡状态转为周期性振荡。还研究了δβ0β00以及被追踪隔离者相关信息的媒体报道准确率σ对传染病发展的影响。结果表明,媒体对传染病信息的广泛报道以及提高报道信息的准确率可降低疾病传播,有利于控制传染病。  相似文献   
5.
杜景林  郑若钦  谢立 《物理学报》2015,64(1):18901-018901
旨在研究无线传感器与执行器网络(WSANs)中节点失效情况下恢复执行器(actor)节点服务的算法. 首先说明了WSANs中的实时覆盖模型, 证明WSANs覆盖恢复问题是NP难问题, 给出了近似求解方案. 在此基础上, 提出了一种基于六边形蜂巢结构的移动容错算法HMFR用于恢复失效actor节点, HMFR 算法在限制网络初始部署的条件下拥有很好的性能. 通过实验与现有的恢复算法进行比较, 发现HMFR算法在actor覆盖sensor节点数和移动距离方面有更好的性能.  相似文献   
6.
Liang-An Huo 《中国物理 B》2021,30(8):80201-080201
With the development of information technology, rumors propagate faster and more widely than in the past. In this paper, a stochastic rumor propagation model incorporating media coverage and driven by Lévy noise is proposed. The global positivity of the solution process is proved, and further the basic reproductive number R0 is obtained. When R0 < 1, the dynamical process of system with Lévy jump tends to the rumor-free equilibrium point of the deterministic system, and the rumor tends to extinction; when R0 > 1, the rumor will keep spreading and the system will oscillate randomly near the rumor equilibrium point of the deterministic system. The results show that the oscillation amplitude is related to the disturbance of the system. In addition, increasing media coverage can effectively reduce the final spread of rumors. Finally, the above results are verified by numerical simulation.  相似文献   
7.
Auxiliary population information is often available in finite population inference problems, and the empirical likelihood (EL) approach has been demonstrated to be flexible and useful for such problems. The present paper concerns EL when interest centers on inference for the mean of the baseline distribution under two-sample density ratio models. Although dual EL is a convenient technical tool since it has the same maximum point and maximum likelihood as DRM-based EL, it can not combine such auxiliary information into the likelihood conveniently and may have loss of efficiency. By contrast, the classical EL approach of Qin and Lawless\ucite{21} does not have this problem and incorporate seamlessly auxiliary information. Based on the EL using auxiliary information and the dual EL methods, we construct both point and interval estimations and make a careful comparison. Though the point estimation efficiency gain obtained by the former is not noticeable, we find that they may have different performances in interval estimation. In terms of coverage accuracy, the two intervals are comparable for not or moderate skewed populations, and the EL interval using auxiliary information can be much superior for severely skewed populations.  相似文献   
8.
One of the most important concerns for managing public health is the prevention of infectious diseases. Although vaccines provide the most effective means for preventing infectious diseases, there are two main reasons why it is often difficult to reach a socially optimal level of vaccine coverage: (i) the emergence of operational issues (such as yield uncertainty) on the supply side, and (ii) the existence of negative network effects on the consumption side. In particular, uncertainties about production yield and vaccine imperfections often make manufacturing some vaccines a risky process and may lead the manufacturer to produce below the socially optimal level. At the same time, negative network effects provide incentives to potential consumers to free ride off the immunity of the vaccinated population. In this research, we consider how a central policy-maker can induce a socially optimal vaccine coverage through the use of incentives to both consumers and the vaccine manufacturer. We consider a monopoly market for an imperfect vaccine; we show that a fixed two-part subsidy is unable to coordinate the market, but derive a two-part menu of subsidies that leads to a socially efficient level of coverage.  相似文献   
9.
In this paper we analyze the warm-standby M/M/R machine repair problem with multiple imperfect coverage which involving the service pressure condition. When an operating machine (or warm standby) fails, it may be immediately detected, located, and replaced with a coverage probability c by a standby if one is available. We use a recursive method to develop the steady-state analytic solutions which are used to calculate various system performance measures. The total expected profit function per unit time is derived to determine the joint optimal values at the maximum profit. We first utilize the direct search method to measure the various characteristics of the profit function followed by Quasi-Newton method to search the optimal solutions. Furthermore, the particle swarm optimization (PSO) algorithm is implemented to find the optimal combinations of parameters in the pursuit of maximum profit. Finally, a comparative analysis of the Quasi-Newton method with the PSO algorithm has demonstrated that the PSO algorithm provides a powerful tool to perform the optimization problem.  相似文献   
10.
The electrodeposition of silver on Au(111) was investigated using lateral force microscopy (LFM) in Ag+ containing sulfuric acid. Friction force images show that adsorbed sulfate forms structure ( on Au(111) prior to Ag underpotential deposition (UPD) and structure ( ) on a complete monolayer or bilayer of Ag. Variation of friction with normal load shows a non-monotonous dependence, which is caused by increasing penetration of the tip into the sulfate adlayer. In addition, the friction force is influenced by the varying coverage and mobility of Ag atoms on the surface. Before Ag coverage reaches the critical value, the deposited silver atoms may be mobile enough to be dragged by the movement of AFM tip. Possible penetration of the tip into the UPD layer at very high loads is discussed as a model for self-healing wear. However, when the coverage of Ag is close to 1, the deposited Ag atoms are tight enough to resist the influence of the AFM tip and the tip penetrates only into the sulfate adlayer.  相似文献   
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