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1.
In this study, we develop a vector-host transmission model with general incidence rates for the dynamics of pine wilt disease in deterministic and stochastic environments. The existence and local asymptotic stability of equilibria are investigated in the deterministic case. We show the required conditions for the ergodic stationary distribution and extinction of the model in the stochastic case by constructing appropriate Lyapunov functions. Furthermore, by solving the corresponding Fokker-Planck equation, we obtain exact expressions of probability density function around the quasi-equilibrium of the stochastic model. Finally, we employ comprehensive numerical simulations to support our results and compare deterministic and stochastic situations.  相似文献   

2.
An analytical expedition to spotlight vital role of incidence rates in epidemic models is exemplified via delayed virus infection model perturbed with Gaussian white noise in this article. A stochastic model structure with time delay in general incidence rate accomplished our assertion on the role of infection transmission rates in the course of viral dynamics. Stability properties exhibited by model system around equilibrium solutions are rigorously analyzed using Lyapunov technique. We have also strengthened our theoretical achievements with empirical substantiations and visualized them as graphical representations. Our exemplifications showcased intricate relationship between model dynamics and incidence rates in unison.  相似文献   

3.
In this paper, the asymptotic stability analysis is investigated for a kind of discrete-time bidirectional associative memory (BAM) neural networks with the existence of perturbations namely, stochastic, Markovian jumping and impulses. Based on the theory of stability, a novel Lyapunov–Krasovskii function is constructed and by utilizing the concept of delay partitioning approach, a new linear-matrix-inequality (LMI) based criterion for the stability of such a system is proposed. Furthermore, the derived sufficient conditions are expressed in the structure of LMI, which can be easily verified by a known software package that guarantees the globally asymptotic stability of the equilibrium point. Eventually, a numerical example with simulation is given to demonstrate the effectiveness and applicability of the proposed method.  相似文献   

4.
本文在生产理论的基础上,将国家特征作为生产效率的影响因素引入传统的随机生产边界模型,建立了基于柯布-道格拉斯生产函数的二个方程随机生产边界模型,实证检验了我国1997-2010年IT资本对经济增长及生产效率的影响。研究发现:IT资本对我国经济增长和生产效率具有显著的促进作用,从国家层面证明了"生产率悖论"并不是全球化的现象;IT资本弱化了物质资本对于经济增长的贡献,强化了人力资本对于经济增长的贡献;国家特征促进了生产效率的提高,但是并没有促进IT价值;我国经济在发展过程中呈现规模报酬递减。基于实证研究结果,提出了实现我国IT投资价值的相关政策建议。  相似文献   

5.
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   

6.
This paper explores the delay dependent stochastic stabilization of Markovian jump neutral systems (MJNS) which are modeled by fractional Brownian motion(fBm) via a quantized controller. A function Round quantizer is introduced which solves the model uncertainties and the nonlinear part by a uniform operator. Then by structuring a Lyapunov–Krasovskii functional (LKF) and the aid of linear matrix inequalities (LMIs) method, a stochastic stability criterion is achieved. Last, different parameters are selected to simulate the effectiveness of our findings.  相似文献   

7.
In this paper, the global stability of coupled control systems (CCSs) is discussed. Assembling the energy of each vertex system with the help of graph theory, a systematic method for constructing a global Lyapunov function of CCSs is proposed. Then, two kinds of stability criteria by Lyapunov-type theorem and coefficient-type theorem with the condition of the system topology are derived. Subsequently, the theoretical results are applied to the microgrid and the criterion of global asymptotical stability of the microgrid is developed. Meanwhile, based on the actual demand of the microgrid, the secondary frequency distributed consistency sliding mode control of the microgrid is proposed using the consensus algorithm. In the presence of a time-varying load, the control can not only quickly stabilize the frequency at the equilibrium point but also dynamically achieve active power sharing. Finally, the simulation of an islanded microgrid is conducted to test the validity and feasibility of our results.  相似文献   

8.
Gordon Reikard   《Research Policy》2005,34(10):1476-1490
In the recent endogenous growth literature, the trend in output is stochastic, while investment in scientific knowledge is treated as analogous to a capital stock. This paper models both research and development (R&D) and disembodied technical advance using neo-classical equations, which specify the equilibrium stocks as a function of prices and output. The elasticity of R&D in the production function, estimated using factor shares, is time-varying and increasing. Returns to scale are increasing in all factors. The most important aspect of the model is that the equilibrium rate of technical advance is not cyclically invariant, but co-moves with output at business cycle frequencies. This allows the production function to behave as a stochastic trend. Growth accounting demonstrates that long-term variations in the rate of productivity growth have been associated mainly with low-frequency fluctuations in the rate of disembodied technical advance, with secondary effects from the stocks of R&D and physical capital. During the high productivity period 1948–1972, technical advance contributed 1.48 percentage points per year to output, with 0.98 accounted for by R&D. The productivity slowdown of the mid-1970s was accounted by a gradual decline in the effect of R&D, and a more abrupt collapse in disembodied technology. The subsequent productivity revival was associated with two accelerations in disembodied technical advance, the first beginning in the early 1980s, and the second in the mid-1990s. The production function is simulated in a small econometric model. Model simulations find that exogenous shocks to the inflation rate generate significant variations in growth by inducing fluctuations in disembodied technology.  相似文献   

9.
提出了用于有界动态随机系统的状态观测器设计方法.首先利用平方根B样条逼近系统的输出概率密度函数来构造残差,同时利用李亚普诺夫函数方法得到观测器增益的自适应调节规律,然后提出了新的对数B样条逼近模型并设计了新的自适应观测器,两个仿真例子表明了方法的有效性.  相似文献   

10.
技术进步与我国产业结构调整关系的实证研究   总被引：1，自引：0，他引：1  
李健  徐海成 《软科学》2011,25(4):8-13,18
基于1978~2006年的时间序列数据,运用向量自回归(VAR)模型,在此基础上进行协整分析、G ranger因果分析,并用脉冲响应函数对技术进步和技术效率对产业结构调整的动态效应进行分析。结果表明,我国技术进步与产业结构调整不相协调;技术效率是第一、第二产业比重变化的主要原因;技术进步和技术效率对第二产业的调整影响比较大,但对第三产业的影响力度比较小;技术进步是深化和优化产业结构根本途径,合理的产业结构促进技术进步和技术效率进一步提高。  相似文献   

11.
Circulating the truth and quarantining a subset of rumor spreaders are two major rumor-quelling strategies. In practice, a mixture of the two strategies may be more effective than any one of the two strategies. This paper focuses on effectiveness analysis of the mixed strategy. For this purpose, we are going to establish a rumor-truth competing model on two-layer network. First, we introduce a Markov model characterizing the stochastic dynamics of the rumor-truth competing process, and write the corresponding Kolmogorov model capturing the expected dynamics of the rumor-truth competing process. Second, we give a bilinear model as the first approximation to the Kolmogorov model, and suggest a generic model as a more accurate approximation to the Kolmogorov model. The two models are the focus of concern in this work. For ease in treatment, we describe a limit system of the generic model. By studying the limit model, we present a criterion for the rumor to subside, a criterion for the rumor not necessarily to subside, and a criterion for the rumor to persist, respectively. These findings are instructive to the quelling of false rumors. Finally, through computer experiments we find that when a rumor subsides, the bilinear model is a good approximation to the Kolmogorov model.  相似文献   

12.
The problem of designing robust systems for the detection of stochastic signals in noise is considered for the large-sample-size, small-signal case. By applying two previously-established models for the detection of stochastic signals, known results for the robust detection of deterministic signals are extended on a limited basis to the stochastic- signal case. The proposed detectors are seen to be robust over a class of possible noise statistics, based on a Huber-Tukey mixture model, which contains noises characterized by heavy-tailed probability density functions. In addition, numerical results are presented which verify the robustness property of the proposed detectors over wider classes of noise mixtures.  相似文献   

13.
基于Bayesian随机前沿模型,研究新疆科技要素投入对研发产出的作用,测算新疆15个地州技术创新效率;从科技要素投入的角度来探索新疆技术创新效率偏低的原因,进而提出提升新疆科技创新效率的相关建议。研究发现:科技资金投入对研发产出的贡献显著,而科技人员全时当量投入对研发产出的作用不显著;新疆各地州的技术创新效率逐年提高;新疆各地州的技术创新效率差异显著,南疆3地州技术创新效率非常低。科技要素投入起到一定的挤出效应,但这种挤出效应有限,企业RD经费的投入主要取决于企业自身的发展状况。  相似文献   

14.
In this paper, a hybrid triple delayed prey predator bioeconomic system with prey refuge and Lévy jumps is established, where both maturation delay for prey and predator population and gestation delay for predator population are considered. For deterministic system, positivity and uniform permanence of solution are discussed. Local stability of deterministic system around interior equilibrium is investigated due to variations of triple time delays. For stochastic system without time delay, sufficient conditions for stochastically ultimate boundedness and stochastic permanence are discussed. Existence of stochastic Hopf bifurcation and stochastic stability are investigated. For stochastic system with triple time delays, existence and uniqueness of global positive solution are studied. Finally, combined dynamic effects of triple time delays and Lévy jumps on the hybrid stochastic system are discussed by constructing appropriate Lyapunov functions. Numerical simulations are supported to illustrate theoretical analysis.  相似文献   

15.
Incorporating the environmental perturbations and available resources of the public health system, we construct both deterministic and stochastic models of SIRS type. The deterministic model exhibits very rich dynamics, such as Hopf bifurcation and backward bifurcation which leads to the co-existence of the stable disease-free state and a stable endemic equilibrium. For the stochastic model, we show that under mild extra conditions, if the basic reproduction number is less than one, then the disease will be eradicated almost surely, and if the basic reproduction number is greater than one, the stochastic model will admit a unique ergodic stationary distribution, which implies that the disease persists almost surely. Part of our numerical simulations indicate that: (i) The introduction of environmental perturbations may drift the endemic equilibrium to the disease-free equilibrium, or vice versa; (ii) Increasing available resources is necessary in order to mitigate the infections.  相似文献   

16.
The purpose of fault diagnosis of stochastic distribution control (SDC) systems is to use the measured input and the system output probability density functions (PDFs) to obtain the fault information of the SDC system. When the target PDF is known, the purpose of fault tolerant control of stochastic distribution control system is to make the output PDF still track the given distribution using the fault tolerant controller. However, in practice, time delay may exist in the data (or image) processing, the modeling and transmission phases. When time delay is not considered, the effectiveness of the fault detection, diagnosis and fault tolerant control of stochastic distribution systems will be reduced. In this paper, the rational square-root B-spline is used to approach the output probability density function. In order to diagnose the fault in the dynamic part of such systems, it is then followed by the novel design of a nonlinear neural network observer-based fault diagnosis algorithm. The time delay term will be deleted in the stability proof of the observation error dynamic system. Based on the fault diagnosis information, a new fault tolerant controller based on PI tracking control is designed to make the post-fault probability density function still track the given distribution, which is dependent of the time delay term. Finally, simulations for the particle distribution control problem are given to show the effectiveness of the proposed approach.  相似文献   

17.
This paper deals with the probabilistic analysis of discrete first-order linear control models with uncertainties. For the sake of generality in our stochastic analysis, we assume that all model parameters (the initial and final states, the matrix containing the free dynamics part, and the control’s coefficient) are random variables with an arbitrary joint probability density function. We then combine some results from classical Control Theory with Probability Theory to obtain, under very general hypotheses, the first probability density function of the control and the solution, which are parametric stochastic processes. To illustrate our theoretical findings, we also show two numerical examples and a classical discrete macroeconomic model whose parameters are treated as random variables.  相似文献   

18.
In this paper, we study a stochastic SIR epidemic model with distributed delay and degenerate diffusion. Firstly, we transform the stochastic model into an equivalent system which contains three equations. Since the diffusion matrix is degenerate, the uniform ellipticity condition is not satisfied. The Markov semigroup theory is used to obtain the existence and uniqueness of a stable stationary distribution. We verify the densities of the distributions of the solutions can converge in L1 to an invariant density. Then we establish sufficient conditions for extinction of the disease. Some examples and numerical simulations are introduced to illustrate our analytical results.  相似文献   

19.
In this paper, we investigate the dynamical behavior of a stochastic dengue epidemic model. First of all, by constructing a suitable stochastic Lyapunov function, we obtain sufficient conditions for the existence of an ergodic stationary distribution of the positive solutions to the model. Then we establish sufficient conditions for extinction of the diseases. The existence of stationary distribution implies stochastic weak stability.  相似文献   

20.
中国工业行业技术创新效率研究/FONT   总被引：6，自引：0，他引：6       下载免费PDF全文
项本武 《科研管理》2011,32(1):10-14
    摘要：本文使用中国1996-2007年31个两位数行业的面板数据,应用随机前沿分析方法,基于内生增长模型的知识生产函数理论构建超越对数生产函数,实现对中国工业行业知识生产函数的估计与技术创新效率的实证测度。研究发现：中国工业行业技术创新中存在无效率;各工业行业研发创新效率存在较大的不平衡;中国工业行业技术创新的效率并没有表现出随时间提升的趋势。基于实证研究结果,提出了促进中国自主创新战略的相关政策建议。    相似文献   

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