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1.
利用重合度理论中的延拓定理讨论了一个具有三个成长阶段的自食单种群时滞模型正周期解的存在性,得到了保证周期解存在的充分条件. 相似文献
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ABSTRACT. The Ñandú or Rhea americana is an autochthonous species perfectly adapted to the pampas environment and only distributed in South America. The species exhibits an unusual breeding system combining polygyny, polyandry, communal nests and exclusive male parental care, which seems to contradict the idea of selfish genes. Our aim has been to construct a mathematical model based on the short term population dynamics of Rhea, living in the wild or in semi‐captivity, and taking into account environmental factors that vary from year to year. Due to the characteristics of its life cycle, it was necessary to develop a model that allows us to differentiate between the survival and fertility rates of each age group and the distinct behavior during breeding and non‐breeding seasons. Therefore, a quarterly differentiated stage‐structured discrete model was needed. Time steps of different lengths are used for modeling chicks or “charos' on the one hand, and juveniles and adults on the other. Environmental variables have been incorporated into the model because they affect the reproductive success of the species. Different scenarios are given as illustrations of the model use. Finally, the possibility of harvesting has been introduced in the model. The model is intended as a first step towards more refined models and systematic data gathering with the purpose of leading the way to a computational tool for risk assessment and decision‐making. 相似文献
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Yongli Song Tao Yin Hongying Shu 《Mathematical Methods in the Applied Sciences》2017,40(18):6451-6467
In this paper, we investigate the dynamics of a time‐delay ratio‐dependent predator‐prey model with stage structure for the predator. This predator‐prey system conforms to the realistically biological environment. The existence and stability of the positive equilibrium are thoroughly analyzed, and the sufficient and necessary conditions for the stability and instability of the positive equilibrium are obtained for the case without delay. Then, the influence of delay on the dynamics of the system is investigated using the geometric criterion developed by Beretta and Kuang. 26 We show that the positive steady state can be destabilized through a Hopf bifurcation and there exist stability switches under some conditions. The formulas determining the direction and the stability of Hopf bifurcations are explicitly derived by using the center manifold reduction and normal form theory. Finally, some numerical simulations are performed to illustrate and expand our theoretical results. 相似文献
4.
依据进化动力学的理论与方法,系统探讨了生态位构建的机理与模式．通过建立生态位构建的空间模式及其适合度计算公式和具有生态位构建作用的单种群与两种群的进化动力学模型,并对其种群进化动态、种间竞争共存机制进行的理论与数值模拟分析,揭示了生物与环境资源的协同进化关系．结果表明：种群动态受其主要生态因子及资源含量的正反馈作用．生态位构建作用通过对种群适宜度的影响而产生进化响应．单种群动力系统存在种群大小的阈值效应;在两竞争种群动力系统中,生态位构建可以导致进化动力系统的多个竞争结果,从而为解释种间竞争与稳定共存提供了一种新的理论机制． 相似文献
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讨论了一类捕食者分为幼虫、成虫两个阶段,具有比率依赖的Ho llingⅡ型功能反应函数的捕食系统的一致持久性,利用比较原理给出了系统是一致持久的充分条件. 相似文献
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研究了一类具有阶段结构的SIR传染病模型,在模型中假设种群分幼年和成年两个阶段,且只有成年种群染病,并且采用与成年易感者数量有关的一般非线性传染率,得到了系统解的有界性及无病平衡点和地方病平衡点存在的条件．通过对平衡点对应的特征方程的讨论得到了平衡点局部渐近稳定的条件,同时证明了平衡点的全局渐近稳定性,并对结论进行了数值模拟． 相似文献
7.
主要研究了一类具有年龄结构的Lotka-Volterra竞争系统行波解的稳定性.在拟单调的情形下, 利用解析半群理论和抽象泛函微分方程理论,首先建立起系统初值问题的解在R上的存在性和比较原理.然后基于加权能量法、比较原理和嵌入定理, 建立起该系统在大初始扰动（即除去当x→-∞时在行波解附近的初始扰动是指数衰减的, 在其他位置的初始扰动可以任意大）下, 单稳大波速行波解的全局指数稳定性.研究结果表明, 行波解作为系统的稳态解, 通常决定着初值问题解的长时间渐近行为.其稳定性揭示了种间竞争的现象和结果能够被清晰地被观测到, 而不受外界因素的干扰. 相似文献
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虚拟科技创新团队知识转移稳定性研究——基于演化博弈视角 总被引：1，自引：0，他引：1
虚拟科技创新团队作为一种优势资源的有效整合机制和从事创新性工作的知识密集型组织,知识的有效转移和持续流动是其成功的关键。本文运用演化博弈论的方法,将转移效应、制度因素、成本损失等影响知识转移的主要因素作为研究问题的关注角度,以知识转移效用函数为切入点,对虚拟科技创新团队知识转移的条件进行分析,系统研究了团队内部知识转移的稳定性、持续性以及演化趋势,并在此基础上提出了改善虚拟科技创新团队知识转移的对策建议。 相似文献
9.
应用能量估计和Gagliardo-Nirenberg型不等式证明了捕食者带阶段结构的具有自扩散和交错扩散的捕食者-食饵模型解的一致有界性和整体存在性. 相似文献
10.
研究了一类具有时滞和阶段结构的捕食模型系统,给出了系统持续生存的充分条件.利用比较定理和构造适当的Lyapunov泛函得到了该系统正平衡态全局渐近稳定的充分条件. 相似文献
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对企业员工冲突行为的动态分析是开展冲突管理的前提和关键。本文从突变理论和演化博弈相结合的全新视角,构建了企业员工冲突突变行为演化模型,解释了员工冲突行为在利益与情感两类至因变量的作用下变化过程。随后在此基础上结合演化博弈理论,探讨了组织与员工冲突决策的演化规律及冲突局势的发展特征,提出了冲突管理的策略及措施。研究结果表明:员工冲突行为在利益和情感影响下可能发生突变,利益因素决定是否发生突变,情感因素决定发生突变的时间点及突变程度;企业对员工群体的合理诉求采取强硬态度是一种短视行为,应本着人本管理思想让利于员工;在极端冲突事件出现后,企业即便将冲突得益全部让给员工也不可能平息争端,必须付出额外的代价;在员工出现极端行为后,企业应依照法规按原则处理,若为了消除影响而一味退让反而会使恶性冲突趋于扩大;企业倡导积极统一的文化价值观对冲突管理是十分有益的。 相似文献
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STEVEN J. HARPER JAMES D. WESTERVELT ANN‐MARIE SHAPIRO 《Natural Resource Modeling》2002,15(1):111-131
ABSTRACT. Brood parasitism by brown‐headed cowbirds (Molothrus ater) reduces the reproductive success of two endangered bird species at Fort Hood, Texas. A successful management program has focused on trapping cowbirds at feeding locations, grassland areas almost always associated with the presence of cattle. To enhance the efficacy of this effort, we developed an individual‐based model that predicted visitation rates by cowbirds to all potential feeding locations at Fort Hood and the surrounding landscape. Utilizing GRASS‐GIS and SWARM, the model incorporated the spatial arrangement of habitats, daily movements of cattle, and daily movements of cowbirds from their breeding sites to feeding locations. We simulated four types of movements by cow‐birds as they searched for cattle: 1) random walk, 2) direct return to previous locations (i.e., memory), 3) return to previous locations with en route assessment (i.e., memory with limited perception of the current state of the system), and 4) omniscience. Straight‐line distances between breeding and feeding locations for cowbirds that used the memory‐with‐perception rule were similar to independent telemetry results, and total search distances for this movement type approached those of omniscience. Both movement distance measures were inversely related to perception distance. Maps of cowbird visits to feeding areas differed among movement rules but were not strongly affected by the density of breeding cow‐birds. Maps also identified locations where trapping efforts could reduce parasitism within specific areas known to support endangered species. While it seems plausible that cowbirds are able to remember foraging locations and to perceive their surroundings as they travel, additional studies are needed to document their cognitive abilities. By simulating movements of individual cowbirds across a dynamic landscape, model results may help to strengthen ongoing cowbird control efforts. 相似文献
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This paper deals with optimal experimental design criteria and neural networks in the aim of building experimental designs from observational data. It addresses the following three main issues: (i) the introduction of two radically different approaches, namely T‐optimal designs extended to Generalized Linear Models and Evolutionary Neural Networks Design; (ii) the proposal of two algorithms, based on model selection procedures, to exploit the information of already collected data; and (iii) the comparison of the suggested methods and corresponding algorithms by means of a simulated case study in the technological field. Results are compared by considering elements of the proposed algorithms, in terms of models and experimental design strategies. In particular, we highlight the algorithmic features, the performances of the approaches, the optimal solutions and the optimal levels of variables involved in a simulated foaming process. The optimal solutions obtained by the two proposed algorithms are very similar, nevertheless, the differences between the paths followed by the two algorithms to reach optimal values are substantial, as detailed step‐by‐step in the discussion. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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A single population growth model with stage‐structured and state‐dependent impulsive control is proposed. By using the Poincar'e map and the analogue of Poincaré's criterion, we prove the existence and the stability of positive order‐1 or order‐2 periodic solution. Moreover, we show that there is no periodic solution with order greater than or equal to three. Numerical results are carried out to illustrate the feasibility of our main results and the superiority of state feedback control strategy is also discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
15.
师徒制知识共享作为组织内知识转移,尤其是隐性知识转移的重要方式,却在组织内更多以知识囤积或知识排斥的知识共享敌意形式存在。基于师徒制知识共享敌意的效用分析,采用复制动态的非对称演化博弈刻画了组织内师徒制知识共享敌意的演化趋势。研究发现,当师傅群成员知识囤积的负效用超过其正效用、且徒弟群成员知识排斥的负效用大于其所付出的成本时,才能通过有效降低师徒制知识共享敌意来提高师徒制知识共享对组织的贡献程度;组织采用一定的激励机制对于降低师徒制知识共享敌意的发生效果显著。 相似文献
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云制造环境下企业制造资源共享的演化博弈分析 总被引：4，自引：0，他引：4
云制造服务平台为在不同时空上获取制造资源提供了一个良好的工作环境,它实现了产品全生命周期的协同制造、管理和创新。在明确云制造环境下企业制造资源共享模式的基础上,构建了考虑两方行为的制造资源共享的演化博弈模型,分别在博弈群体处于均匀混合和非均匀混合两种状态下,找出了模型的均衡点并对其稳定性进行分析。引入系统动力学的方法,建立制造资源共享的演化博弈SD仿真模型,对比分析不同参数变化对演化结果的影响。研究结果表明,企业群体初始共享比例、升级设备成本、信息化改善收益和技术流失风险对博弈双方的策略演化结果具有显著的影响,促进企业联盟中的信息互通与资源共享,须从上述方面着手管理并持续改进。 相似文献
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TERRANCE J. QUINN 《Natural Resource Modeling》2003,16(4):341-392
ABSTRACT. I trace the development of fisheries models (i.e., fish population dynamics models of species subject to fisheries) to the 21st century. The first real efforts occurred in the period 1900 1920 with the work of Baranov (the “Grandfather” of fisheries population dynamics) and the formation of the International Council for the Exploration of the Sea (ICES). The establishment of the science occurred between 1920 1960 with multi‐species modeling, age‐ and size‐structure dynamics, and production models. Fundamental work during this time was done by Ricker (the “Father” of fisheries population dynamics), Beverton and Holt (the “Prophets” of fisheries population dynamics), Chapman, Dickie, DeLury, Graham, Gulland, Leslie, Lotka and Volterra, Russell, Schaefer, and Thompson. During this time, most of the workwas deterministic and mathematical. Between 1960 and 1980, statistical methodology evolved greatly but was separate from mathematical advances for the most part. The development of statistical principles for the estimation of animal abundance was further enhanced by Arnason, Buckland, Burnham and Anderson and White, Cormack, Eberhardt, Jolly, Manly, Pollock, Ricker, Robson, and Seber, among others. Fisheries models evolved in a deterministic setting, with advances in age‐structured models (Gulland, Pope, Doubleday), surplus production models (Pella, Tomlin‐son, Schnute, Fletcher, Hilborn), growth models, bioeconomic models (C. Clark) and management control models (Hilborn, Walters). The period 1980 2000 was the Golden Age. The integration between mathematics and statistics occurred when likelihood and least squares techniques were formally combined with mathematical models of population change. The number of fisheries modelers grew exponentially during this time, resulting in a concomitant increase in publications. A major advance in the 1990s has been the development of Bayesian and time series methods, which have allowed explicit specification of uncertainty. Currently, theory allows realistic modeling of age‐ and size‐structured populations, migratory populations and harvesting strategies. These models routinely incorporate measurement error, process error (stochasticity) and time variation. But data needs often overwhelm the performance of models, and greater demands are being placed on models to answer complex questions. There has been poor communication between fisheries and ecological modelers, between fisheries researchers and statisticians, and among fisheries researchers in different geographic locales. Future models will need to deal better with habitat and spatial concerns, genetics, multispecies interactions, environmental factors, effects of harvesting on the ecosystem, model misspecification and so‐cioeconomic concerns. Meta‐analysis, retrospective analysis and operating models are some modern approaches for dealing with uncertainty and providing for sustainable fisheries. However, I fear that current attacks on single‐species models and management may result in rejection of these advances and an attempt to substitute a less scientific approach. 相似文献
18.
E. Sanchez‐Palencia J.‐P. Françoise 《Mathematical Methods in the Applied Sciences》2016,39(1):104-133
In a previous work on perturbation theory in population dynamics, we showed several plausible situations of preservation of the biodiversity. We give now an improved version of the method exhibiting a phenomenon of emergence of structured diversity. We display several (plausible in ethological or sociological contexts) examples of small modifications of the demographic equations that are emergent, that is, they lead to a limit state (the attractor) where the ‘spectators’ (i.e. to the individuals not concerned with the modification) vanish. In other words, even if the modification involves only a small number of individuals initially, the final pattern involves all the individuals. This behavior is easily understood in cases when the modification is concerned with some kind of symbiotic behavior, as it induces an advantage with respect to the ‘spectators’. But the phenomenon is very much general; we give examples of emergence in other contexts, involving predator/pray relations or other entangled relations, including an experimentally known example of subspecies of Escherichia coli. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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基于结构分解方法的采煤机械化对煤炭高效开发的贡献研究 总被引：1，自引：0，他引：1
采用完全结构分解方法,将采煤劳动强度变化分解为结构份额和效率份额,并基于1985~2006年的统计数据进行了分析.主要结论有:我国采煤劳动强度的下降,也即煤炭资源开发效率的提高是采煤工艺结构变动和各采煤工艺工效提高综合作用的结果,相对效率份额,结构份额的贡献更大一些;从结构份额来看,非机采和高档普采结构的变动导致了整体劳动强度的下降;而从效率份额来看,综采、高档普采和非机采工效的提高则是整体劳动强度下降的主要原因. 相似文献