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1.
人口增长率的非参数自回归预测模型   总被引:3,自引:0,他引:3  
针对传统的人口增长预测模型不能理想地捕获我国人口增长率数据的非线性性特征,本文基于局部线性非参数估计理论,对我国建国以来的年人口增长率建立了非参数自回归NAR(1)模型,并对2000-2003年的年人口增长率进行了预测,计算结果表明,相对于参数自回归模型而言,非参数自回归模型能够很好地解决人口增长预测这一非线性问题,预测精度较高。  相似文献   

2.
本文分别用人口转换关系和人口结构系数两种体系建立了动态人口投入产出模型,求出了模型的解和动态逆,并进一步研究了人口投入产出模型的应用.  相似文献   

3.
我国针对新型冠状病毒肺炎(COVID-19)展开了联防联控工作,目前国内防疫形势已趋于明朗,但境外疫情处于上升阶段,"外防输入"成为我国下一阶段疫情防控的重点.本文通过对COVID-19传播动力学模型引入脉冲项来描述境外输入型病例对于我国目前疫情防控的影响.本文研究3种控制程度不同的入境防疫政策,数值模拟了输入型病例对于与韩国存在人口流动的我国各个省市疫情发展的影响及相应医疗资源需求.数值实验表明,对于输入型人口总量较少的地区,我国现有的防疫政策能够很好地控制疫情发展;对于来自疫区输入型人口较多的省市,边防口岸的有效筛查和必要隔离是防止由于输入型病例引起我国疫情二次暴发的重要手段.  相似文献   

4.
死亡率的预测是人口预测的基础.近年来,死亡率建模方法不断取得新的进展,从最早的静态死亡率模型开始,死亡率模型不断发展为包括时间项的动态预测模型,如Lee-Carter族模型、CBD族模型等.本文对死亡率预测模型的相关文献进行了回顾和梳理.随着动态模型的发展,一些学者从死亡率改善水平入手,发展出一系列死亡率改善模型.另外,随着死亡率研究的深入,多人口死亡率的建模引起了研究者的重视,多人口预测模型迅速发展和完善.随着死亡率模型的研究方法不断丰富和创新,新兴统计学方法(如机器学习等)已经在死亡率建模中有所应用,拟合和预测准确度不断提升.除了经典的建模方法的扩展外,例如小区域人口或数据缺失的人口、高龄人口、相关人口等死亡率建模问题仍值得研究.  相似文献   

5.
灰色动态模型及其在人口预测中的应用   总被引:43,自引:1,他引:42  
一个国家人口的数量直接影响着其经济、社会的发展和资源的利用 ,中国是世界上人口的第一大国 ,人口问题一直是制约中国发展的第一因素 .本文应用灰色系统等维灰数递补动态预测模型 ,对中国未来5 0年的人口数量进行了动态预测 ,通过检验表明 ,该模型合理、方法简便可行、结果符合实际 ,为中国经济和社会发展的决策和研究提供了科学依据  相似文献   

6.
一、引言 人口发展过程的数学模型是人口发展过程分析预测和定量控制的基础。关于人口发展过程的确定性连续模型,对线性人口发展系统已有不少结果。实践证明:在人类发展的某一历史阶段中,人口发展过程可以用线性方程较准确地刻画。但是线性人口发展方程忽略了社会人口与其生存环境之间的制约关系。从长期的观点来看,研究非线性人口发展模型有着重要意义  相似文献   

7.
对马尔萨斯人口增长模型进行研究,设计人口承载力发展路径和基于增长模型的隶属函数,从概率角度构建人口承载力动态综合测度模型,同时,以城市区域为研究对象,以经济作为人口承载力主导影响因素,辅之以自然、环境、资源与科技因素,构建人口承载力综合评价指标体系,多角度、多因素分析区域人口承载力,寻找人口承载短板,为人口承载力研究提供新的研究方法和视角.实证研究结论显示,研究区域人口承载力当前处于承载力强阶段,并开始向适度阶段过渡,其内部指标和子系统发展不平衡,人口系统自身发展稳定,经济和环境人口承载力强,资源和科技承载力较弱,随着区域经济的发展,在相当长一段时间内可进入适度人口阶段.  相似文献   

8.
本文以VanderPol方程为基础,建立了受周期外界环境刺激影响的非线性动态情绪模型,并在Matlab环境下实现了具有混沌性质的数值模拟,所建立的模型很好地模拟了情绪变化的规律,并为计算机实现智能化打下了基础。  相似文献   

9.
本试将可达矩阵理论运用于人口系统结构分析,取得了很好的效果,章通过对影响人口系统各因素的因果关系分析,列出可达矩阵并划分等级,最后构造出人口系统结构模型。  相似文献   

10.
本文应用动态线性模型研究我国的狭义货币需求,利用贝叶斯吉布斯抽样方法估计模型的参数和方差,获得了潜在货币需求趋势和货币缺口,对我国的货币供给进行分析并获得一些有益结论,对于央行更好地实施货币管理,保持经济平稳发展有积极意义。  相似文献   

11.
利用计算机模拟方法研究一类离散种群相互作用模型的动态复杂性.通过理论推导建立食饵具有Allee效应和HollingⅡ型功能反应的自治捕食系统模型,用Matlab软件模拟离散种群的生长状态,探索研究参数的变化对种群大小的影响,阐释Allee效应及HollingⅡ型功能反应在种群间相互作用模型中的重要性.研究结果表明:1)当处理时间处于有效区间内时,处理时间越大种群的稳定共存参数域越大;2)Allee效应的引入使种群的动态行为更为复杂,从而增加了捕食者种群的灭绝风险;3)系统受强Allee效应的影响,种群会出现提前分叉现象,如果继续增加Allee效应就会导致种群灭绝;4)强Allee效应更容易使种群趋向灭绝.所得结论在丰富生态学理论的同时,提出了保护生态学的重要依据.  相似文献   

12.
Abstract. Previous mathematical modeling of the population dynamics of Georges Bank Atlantic cod fishery employed discrete‐time models without age‐structure. To make use of a much wider variety of data on fisheries and fish stocks than was possible with an unstructured model, we introduce a juvenile‐adult age‐structured production exploited fishery model with a very general recruitment function. We use the age‐structured model to study the interaction between fish exploitation levels and recruitment dynamics. As case studies, we use our model results and historical fish population data from Georges Bank to investigate the impact of recent harvesting levels on the sustainability of cod fishery. We show that a constant harvesting policy with the same harvesting rate of 2007 would lead to the recovery and sustainability of Georges Bank cod fishery.  相似文献   

13.
Expectation-Stock Dynamics in Multi-Agent Fisheries   总被引:1,自引:0,他引:1  
In this paper we consider a game-theoretic dynamic model describing the exploitation of a renewable resource. Our model is based on a Cournot oligopoly game where n profit-maximizing players harvest fish and sell their catch on m markets. We assume that the players do not know the law governing the reproduction of the resource. Instead they use an adaptive updating scheme to forecast the future fish stock. We analyze the resulting dynamical system which describes how the fish population and the forecasts (expectations) of the players evolve over time. We provide results on the existence and local stability of steady states. We consider the set of initial conditions which give non-negative trajectories converging to an equilibrium and illustrate how this set can be characterized. We show how such sets may change as some structural parameters of our model are varied and how these changes can be explained. This paper extends existing results in the literature by showing that they also hold in our two-dimensional framework. Moreover, by using analytical and numerical methods, we provide some new results on global dynamics which show that such sets of initial conditions can have complicated topological structures, a situation which may be particularly troublesome for policymakers.  相似文献   

14.
In this article, we derive a solution for a linear stochastic model on a complex time domain. In this type of models, the time domain can be any collection of points along the real number line, so these models are suitable for problems where events do not occur at evenly-spaced time intervals. We present examples based on well-known results from economics and finance to illustrate how our model generalizes and extends conventional dynamic models.  相似文献   

15.
A general scheme for parallel simulation of individual-based, structured population models is proposed. Algorithms are developed to simulate such models in a parallel computing environment. The simulation model consists of an individual model and a population model that incorporates the individual dynamics. The individual model is a continuous time representation of organism life history for growth with discrete allocations for reproductive processes. The population model is a continuous time simulation of a nonlinear partial differential equation of extended McKendrick-von Foerster-type.

As a prototypical example, we show that a specific individual-based, physiologically structured model for Daphnia populations is well suited for parallelization, and significant speed-ups can be obtained by using efficient algorithms developed along our general scheme. Because the parallel algorithms are applicable to generic structured populations which are the foundation for populations in a more complex community or food-web model, parallel computation appears to be a valuable tool for ecological modeling and simulation.  相似文献   


16.
This paper presents a dynamic forecasting model that accommodates asymmetric market responses to marketing mix variable—price promotion—by threshold models. As a threshold variable to generate a mechanism for different market responses, we use the counterpart to the concept of a price threshold applied to a representative consumer in a store. A Bayesian approach is taken for statistical modelling because of advantages that it offers over estimation and forecasting. The proposed model incorporates the lagged effects of a price variable. Thereby, myriad pricing strategies can be implemented in the time horizon. Their effectiveness can be evaluated using the predictive density. We intend to improve the forecasting performance over conventional linear time series models. Furthermore, we discuss efficient dynamic pricing in a store using strategic simulations under some scenarios suggested by an estimated structure of the models. Empirical studies illustrate the superior forecasting performance of our model against conventional linear models in terms of the root mean square error of the forecasts. Useful information for dynamic pricing is derived from its structural parameter estimates. This paper develops a dynamic forecasting model that accommodates asymmetric market responses to marketing mix variable—price promotion—by the threshold models. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

17.
The disease effect on ecological systems is an important issue from mathematical and experimental point of view. In this paper, we formulate and analyze a predator–prey model for the susceptible population, infected population and their predator population with modified Leslie–Gower (or Holling–Tanner) functional response. Mathematical analysis of the model equations with regard to invariance of nonnegativity and boundedness of solutions, local and global stability of the biological feasible equilibria and permanence of the system are presented. When the rate of infection crosses a critical value, we determine that the strictly positive interior equilibrium undergoes Hopf bifurcation. From our numerical simulations, we observe that the predation rate also plays an important role on the dynamic behavior of our system.  相似文献   

18.
A side-by-side single sex age-structured population dynamic model is presented in this paper. The model consists of two coupled von Foerster-McKendrick-type quasi-linear partial differential equations, two initial conditions, and two boundary conditions. The state variables of the model are male and female population densities. The solutions of these partial differential equations provide explicit time and age dependence of the variables. The initial conditions define the male and female population densities at the initial time, while the boundary conditions compute the male and female births at zero-age by using fertility rates. The assumptions of the nontime-dependence of the death and fertility rates and a specific factorization of the migratory balances allow us to obtain exact solutions for male and female population densities. In addition, the hypotheses about the mathematical structure of the input variables are formulated, and the exact solution of the model is obtained. Next, the model is applied to the case study of Spain for the time period 1996–2004. Model validation demonstrates that this approach is a powerful prediction tool. Code and data are available upon request.  相似文献   

19.
We propose a Bayesian framework to model bid placement time in retail secondary market online business‐to‐business auctions. In doing so, we propose a Bayesian beta regression model to predict the first bidder and time to first bid, and a dynamic probit model to analyze participation. In our development, we consider both auction‐specific and bidder‐specific explanatory variables. While we primarily focus on the predictive performance of the models, we also discuss how auction features and bidders' heterogeneity could affect the bid timings, as well as auction participation. We illustrate the implementation of our models by applying to actual auction data and discuss additional insights provided by the Bayesian approach, which can benefit auctioneers.  相似文献   

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