共查询到20条相似文献，搜索用时 62 毫秒
1.
《Journal of The Franklin Institute》2019,356(13):7486-7514
In this paper, a stochastic epidemic model for cholera is proposed and investigated. Firstly, we establish sufficient conditions for extinction of the disease. Then we establish sufficient criteria for the existence of a unique ergodic stationary distribution of the positive solutions to the model by constructing a suitable stochastic Lyapunov function. The existence of an ergodic stationary distribution implies that all the individuals can be coexistent in the long run. Finally, some examples together with numerical simulations are introduced to illustrate our theoretical results. 相似文献
2.
《Journal of The Franklin Institute》2023,360(2):1077-1105
Cholera is a waterborne infectious disease that continually emerges and remains an important global health burden. We formulate and investigate a cholera model with imperfect vaccination and demographics on complex networks, in which two transmission pathways, indirect environment-to-human and direct human-to-human transmissions, are incorporated simultaneously. The contacts among humans are treated as a heterogeneous network and the contacts between environment and humans as homogenous mixing. Using the spectral analysis method, the basic reproduction number is defined and verified to be a sharp threshold which completely determines global dynamical properties of model. Numerical simulations are performed to confirm the theoretical results. The results demonstrate that demographics and the degree distribution of the network are of great importance in cholera propagation, and that the degree distribution is time-dependent until the stationary state is reached. Furthermore, demographics have a significant influence on the basic reproduction number. By increasing the vaccination rate and decreasing the rate at which the vaccine wears off, cholera infection can be effectively controlled. 相似文献
3.
Sidney Roberto Carvalho Ubirajara Franco Moreno 《Journal of The Franklin Institute》2021,358(9):5039-5072
In distributed and cooperative systems, the network structure is determinant to the success of the strategy adopted to solve complex tasks. Those systems are primarily governed by consensus protocols whose convergence is intrinsically dependent on the network topology. Most of the consensus algorithms deal with continuous values and perform average-based strategies to reach cohesion over the exchanged information. However, many problems demand distributed consensus over countable values, that cannot be handled by traditional protocols. In such a context, this work presents an approach based on semidefinite programming to design the optimal weights of a network adjacency matrix, in order to control the convergence of a distributed random consensus protocol for variables at the discrete-space domain, based on the voter model. As a second contribution, this work uses Markov theory and the biological inspiration of epidemics to find out a dynamical spreading model that can predict the information diffusion over this discrete consensus protocol. Also, convergence properties and equilibrium points of the proposed model are presented regarding the network topology. Finally, extensive numerical simulations evaluate the effectiveness of the proposed consensus algorithm, its spreading model, and the approach for optimal weight design. 相似文献
4.
区域间虚拟水贸易模型及其在山西省的应用 总被引：2，自引：0，他引：2
虚拟水贸易是实现水资源区域优化配置的重要途径之一,对区域间的虚拟水贸易现状进行分析,可为相关政策的制定提供依据。本研究基于区域间贸易模型和各地产业用水系数,构建虚拟水贸易模型,以模拟区域间的虚拟水贸易格局。选取山西省为案例区,利用中国环境统计年鉴、中国第二次经济普查年鉴等相关数据,计算山西省国民经济各部门的直接用水系数和完全用水系数,结合山西省与全国其他省区的贸易关系,估算山西与其他省区的虚拟水贸易量,揭示山西虚拟水贸易的空间格局。主要结论有：①2007年,山西省用水总量为58．71亿m^3,通过工农业产品贸易共产生了1．53亿m^3的虚拟水净调入量,对本省水资源短缺局面有缓解作用;②通过农业贸易净调入虚拟水4．89亿m^3,主要来自于新疆、陕西、河北、安徽等省区;通过工业产品贸易净调出虚拟水3-36亿m^3,主要调往河北、江苏、山东、湖北、浙江和广东等省;③山西省虚拟水的来源地主要是我国西部和东北地区,输出地则主要是东部沿海省份,与传统的虚拟水战略相违背;④在工业部门,主要的调出部门是能源相关行业,主要净调入部门则是制造业。建议山西省积极推行虚拟水政策,发展节水产业,通过工农业产品贸易从水资源丰富的地区调入虚拟水,形成具有可持续性的水资源利用空间格局。 相似文献
5.
不同节水措施下宁夏水资源利用的经济效益分析 总被引：1，自引：0，他引：1
常规的节水效益评价方法只能分析节水措施对行业内部产出及用水效果的影响,不能就节水对全行业和整个国民经济的客观影响做出合理的评价,反映不出水资源对国民经济发展的约束作用,根据目前区域节水宏观效益评价方法的不足,开发了水资源消耗投入产出模型。模型以国民经济各部门生产过程中的产业关联性为基础,以行业用水过程中的竞争性为约束,将水资源消耗量作为水量控制指标,以宁夏为研究区开展了实例研究,分析了节水措施下各产业的水资源消耗量以及用水效益响应,并就节水对区域经济系统宏观影响进行了客观的评价,同时根据响应结果对各种节水措施的作用进行了分析。评价方法为合理评价水资源利用及节水过程中水与国民经济的关系、分析节水措施对国民经济发展的促进作用、研究不同节水措施下的国民经济结构提供了理论手段;评价结果对研究区制定合理的节水措施和节水投资方案,对提高地区的水资源利用的宏观效益具有一定的指导意义。 相似文献
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This paper proposes a new multiuser communication model in which a source with broadcast capabilities wants to transmit two different messages to two different destinations in the case that no direct links between the source and its destinations. In this channel model, two parallel half-duplex relays are used to extend the transmission. For this communication model, an outer bound to the achievable capacity is initially derived. Then, two distinctive transmission schemes are characterized such that the source can transmit to the two destinations. In each scheme, the transmission is split into two phases. Specifically, in the first phase, the source can broadcast different messages to the two relays. Then, in the second phase, the two relays can forward the source’s signals into their destinations. Based on the transmission on each scheme, the achievable rate region is characterized. Further, we derive the optimal duration of each phase. The theoretical analyses are followed by many numerical examples that compare between the different transmission techniques and also show the points at which the capacity is achieved. 相似文献
9.
《Journal of The Franklin Institute》2022,359(13):6829-6855
In this paper, the linear quadratic (LQ) optimal decentralized control and stabilization problems are investigated for multi-sensors networked control systems (MSNCSs) with multiple controllers of different information structure. Specifically, for a MSNCS, in view of the packet dropouts and the transmission delays, each controller may access different information sets. To begin with, the sufficient and necessary solvability conditions for the LQ decentralized control problems are developed. Consequently, for the purpose of deriving the optimal decentralized control strategy, an innovative orthogonal decomposition method is proposed to decouple the forward and backward stochastic difference equations (FBSDEs) from the maximum principle. In the following, we show that the optimal decentralized controller can be calculated according to a set of Riccati-type equations. Finally, a stabilizing controller is derived for the stabilization problem. 相似文献
10.
自2019年12月以来,湖北省武汉市出现新型冠状病毒肺炎(简称"新冠肺炎"),随后疫情在全国范围内暴发。相关学者对此次疫情扩散趋势做了大量研究,但基于模型的估算普遍存在高估传染系数和感染人群的问题。基于此,利用大数据回溯新冠肺炎在全国扩散的趋势和传染系数,得出结论:(1)在扩散前期(2020年1月24号之前)武汉输出的人口是全国各城市(武汉除外)新冠肺炎扩散的主要威胁,之后每个省、自治区、直辖市的人口与确诊病例数的关系逐渐增强,体现出本地传播的趋势;(2)利用SEIR模型拟合武汉和北京两地新冠肺炎确诊病例得出真实传播系数(R_0),揭示武汉的R0高于北京,考虑到人为控制因素,2019年12月1日—2020年2月9日两地的实际的R_0均大幅度下降。基于此,对疫情期间存在的问题进行针对性建议,并从数据上论证了中国政府对于疫情扩散强有力的控制能力,对阻止国内及世界范围的疫情扩散作出积极贡献。 相似文献
11.
【目的/意义】探索重大疫情中网络舆情的多属性演化规律,为重大疫情防控中的网络舆情治理实践提供参
考。【方法/过程】基于社会学视角构建了重大疫情中网络舆情多属性演化分析模型,选取湖北红十字会事件微博舆
情数据为研究对象,采用意见领袖影响力评价、LDA主题模型和Snownlp情感分析方法对重大疫情中网络舆情意见
领袖、主题分布和情感走势进行分析,从人群、内容和情绪三种社会属性揭示重大疫情中网络舆情多属性演化规
律。【结果/结论】结果表明,重大疫情网络舆情可以分为突发期、爆发期、降温期和失焦期四个阶段,各个阶段在意
见领袖、主题讨论内容和情感倾向上均有较为明显的区别,网民的情感阶段变化与舆情的主题属性演化规律相吻
合。【创新/局限】本研究提出的模型能够有效满足重大疫情网络舆情演化特征深度挖掘的要求,为重大疫情网络舆
情的治理实践提供参考。后续研究可选取更广泛的舆情事件和数据源验证该模型。 相似文献
12.
【目的/意义】知识图谱不仅是新一代人工智能的前沿技术,而且是大规模知识工程的学科方向。探究我国
知识图谱研究的分布特点和发展趋势,将对技术应用和学科研究具有参考价值和借鉴意义。【方法/过程】本文运用
文献计量学方法和数据可视化技术,针对我国知识图谱研究重要文献的来源库、期刊、基金、机构、作者、关键词等
进行计量研究,采用ECharts和VOSviewer工具可视分析。再根据共词分析方法挖掘“知识抽取”和“知识应用”两大
研究主题,使用Python软件绘制词云图,着重阐述其核心内容、关键问题和主要趋势。【结果/结论】我国知识图谱研
究具有应用跨界与文献激增的总体特点,并呈现六大具体特点。面向开放域的知识抽取技术和智能应用方法,将
成为大规模知识图谱的未来发展趋势。【创新/局限】聚焦人工智能学科范畴,依据共词分析和生命周期,综合利用
多种可视化工具,我国知识图谱研究的分布特点和重要主题得以阐述。然而,国际知识图谱的文献计量与主题挖
掘,尚待进一步分析与研究。 相似文献
13.
《Journal of The Franklin Institute》2023,360(7):4695-4718
In the digital age, rumor spreading is becoming more widespread and faster than ever before, and results in the more social panic and instability. Because of this, it is crucial to implement effective control strategies to prevent the continued spread of rumors, and avoid all kinds of unnecessary harm caused by rumors. In this paper, a stochastic rumor spreading model incorporating time delay within the framework of the event-triggered impulsive control (ETIC) strategies are presented. To begin with, the stability problem of this model is discussed and proved. Besides, the optimal ETIC strategies are explored by the particle swarm optimization (PSO) algorithm. Furthermore, some numerical simulations are performed to illustrate the optimal ETIC strategies of the given model. In addition, a real case is used to prove the validity of given model. Finally, the following conclusions are drawn that the stochastic model is feasible and consistent with actual rumor propagation trends, and ETIC strategies can help control rumors effectively. Meanwhile, different ETIC strategies should be used according to the different situations of rumor spreading. For instance, control strategies need to be more frequent and robust when transmission rates are higher or time delay are shorter. 相似文献
14.
《Journal of The Franklin Institute》2001,338(2-3):371-390
An optimal control approach for gear shift operations in automatic transmissions is proposed in this paper. Starting from a verified model of a typical power train with an automatic transmission a performance measure for evaluating the gear shift process in terms of passengers comfort and control expenditure is developed. The gear shift operation is stated as a multistage decision process by making use of the dynamic programming method. Thereby, the synchronization of the gear box is formulated as a constraint at the end of the process. A control law is derived analytically in an explicit form by minimizing the performance measure over each process stage. Simulation results show a significant improvement in terms of gear shift comfort by different driving load cases. Furthermore, the shift time and the frictional losses in the shift elements can be reduced by applying the proposed control. 相似文献
15.
南水北调工程是解决我国北方地区水资源严重短缺的重大工程,论文结合南水北调东线工程实际,界定了南水北调供应链系统,面向调水系统长期运营管理,从纯经济效益视角和社会责任与经济效益双重视角,分别建立了相应的Stackelberg分散决策模型和集中决策模型,并建立了相应的收入分享契约协调机制,研究结果表明:①无论是纯经济效益视角还是社会责任与经济效益双重视角下,协调集中决策情形下供应商和分销商的利润都高于分散决策;②对比纯经济效益视角和社会责任与经济效益双重视角,社会责任与经济效益双重视角下供应商和分销商的利润都不低于纯经济效益视角;③社会责任与经济效益双重视角下,协调集中决策下的社会责任绩效水平高于分散决策情形;④供应商和分销商都有经济动因履行社会责任,参与契约协调,从而实现集中决策. 相似文献
16.
针对基于“Max-min”算子的区间模糊多目标规划仅采用一或两个控制变量放松所有目标和模糊约束会造成某些约束过满意而某些约束不满意的情况,本文引入两相模糊规划,构建了区间-两相模糊多目标规划模型,并以辽宁省大连市种植结构优化为例进行研究。结果表明,该模型引入多个控制变量放松每个不确定目标和约束条件,且要求它们分别不小于“Max-min”算子中相应目标和约束条件的隶属度,更充分地利用了约束资源,保证了求解的有效性,减少了农业灌溉用水量;另外区间形式的最优解及4种不同情景的优化方案为决策者提供了决策空间,更真实地反映输入参数的不确定性对配置结果的影响。 相似文献
17.
【目的/意义】为识别微博中多个舆情话题的交互传播规律从而使干预决策的制定更有针对性,提出一种多主体干预的微博舆情话题交互传播模型。【方法/过程】该模型融入网络媒体和政府的多重干预,考虑了多个舆情话题不平等竞争的特性,并可从交互传播的整体视角来分析干预措施的作用。【结果/结论】仿真实验表明：该模型能够较好地模拟微博平台中多个舆情话题的交互传播演化趋势;话题交互传播过程中,多主体干预下的舆情治理效果更好;制定干预决策不能仅关注单一舆情话题,而应综合考虑多个舆情话题及其交互关系。【创新/局限】文章通过数学建模的方法对多主体干预下的微博舆情话题交互传播过程进行探究,为微博平台监管控制策略的制定提供了新视角,未来研究可以结合相关实例进行分析,进一步丰富和深化研究结论。 相似文献
18.
人工神经网络在经济控制中的应用 总被引：3，自引：0，他引：3
本文运用二次函数最优控制理论建立经济系统优化控制模型,以一个宏观经济模型为例,用神经网络建立的模型和控制器对所关心的经济变量进行控制,给出了仿真结果。 相似文献
19.
Application of non-dominated sorting genetic algorithm-II technique for optimal FACTS-based controller design 总被引：1，自引：0，他引：1
Sidhartha Panda 《Journal of The Franklin Institute》2010,347(7):1047-1064
Design of an optimal controller requires optimization of multiple performance measures that are often noncommensurable and competing with each other. Design of such a controller is indeed a multi-objective optimization problem. Non-dominated sorting in genetic algorithms-II (NSGA-II) is a popular non-domination based genetic algorithm for solving multi-objective optimization problems. This paper investigates the application of NSGA-II technique for the design of a flexible AC transmission system (FACTS)-based controller. The design objective is to improve the stability of the power system with minimum control effort. The proposed technique is applied to generate Pareto set of global optimal solutions to the given multi-objective optimization problem. Further, a fuzzy-based membership value assignment method is employed to choose the best compromise solution from the obtained Pareto solution set. Further, a detailed analysis on the selection of control signals (both local and remote signals) on the effectiveness of the proposed controller is carried out and simulation results are presented under various loading conditions and disturbances to show the effectiveness and robustness of the proposed approach. 相似文献
20.
《Journal of The Franklin Institute》2023,360(12):7770-7807
In this article, combining the transmission features of HPV infection and secondary cervical cancer in Xinjiang, China, a stochastic dynamical model for the HPV infection and secondary cervical cancer with environmental white noise is proposed. Firstly, the stochastic extinction of disease is investigated. A sufficient criterion for the asymptotic behavior of any positive solution of stochastic model revolving around the disease-free equilibrium of corresponding deterministic model is established. Secondly, a threshold criterion for the existence of unique ergodic stationary distribution is obtained by means of the auxiliary function. Furthermore, a new technique of partitioned matrix for the calculation of probability density function is proposed, the expression of a log-normal density function around the quasi-endemic equilibrium of stochastic model is calculated. Lastly, the best-fit parameter values in our model are identified by the MCMC algorithm on the basis of the cervical cancer data in Xinjiang province, China. The basic reproduction number is estimated as 1.3496 (95% CnI: (1.3458, 1.3716)). Then, to determine the key parameters of the model, the sensitivity analysis is explored. Some possible interventions and control measures are provided to reduce the HPV infection spread and cervical cancer in Xinjiang of China. 相似文献