Bifurcation analysis and control of a class of hybrid biological economic models

This paper systematically studies a hybrid predator–prey economic model, which is formulated by differential-difference-algebraic equations. It shows that this model exhibits two bifurcation phenomena at the intersampling instants. One is saddle–node bifurcation, and the other is singular induced bifurcation which indicates that economic profit may bring impulse at some critical value, i.e., rapid expansion of biological population in terms of ecological implications. On the other hand, for the sampling instants, the system undergoes Neimark–Sacker bifurcation at a critical value of economic profit, i.e., the increase of economic profit destabilizes the system and generates a unique closed invariant curve. Moreover, the state feedback controller is designed so that singular induced bifurcation and Neimark–Sacker bifurcation can be eliminated and the population can be driven to steady states by adjusting harvesting costs and the economic profit. At the same time, by using Matlab software, numerical simulations illustrate the effectiveness of the results obtained here.     

一类具有闭环极点约束的不确定线性系统的保性能控制

主要研究了闭环系统的极点约束在一个给定圆盘中的保性能控制问题,基于线性矩阵不等式处理方法给出了状态反馈控制器存在的充要条件,并利用线性矩阵不等式的解给出了保性能控制器的设计方法,得到一个状态反馈控制器,使得对所有允许的不确定性闭环系统稳定,并且闭环性能指标值不超过某个确定的上界.最后以数值例子验证了结果的正确性.     

Optimal control of a class of systems with continuous lags: Dynamic programming approach and economic interpretations

This paper derives a maximum principle for dynamic systems with continuous lags, i.e., systems governed by integrodifferential equations, using dynamic programming. As a result, the adjoint variables can be provided with useful economic interpretations.This research was supported by NSERC Grant No. A4619.     

Informational uniqueness of closed-loop Nash equilibria for a class of nonstandard dynamic games

This paper discusses an extension of the currently available theory of noncooperative dynamic games to game models whose state equations are of order higher than one. In a discrete-time framework, it first elucidates the reasons why the theory developed for first-order systems is not applicable to higher-order systems, and then presents a general procedure to obtain an informationally unique Nash equilibrium solution in the presence of random disturbances. A numerical example solved in the paper illustrates the general approach.Dedicated to G. LeitmannResearch that led to this paper was supported in part by the Office of Naval Research under Contract No N00014-82-K-0469 and in part by the U.S. Air Force under Grant No. AFOSR-84-0054.     

A least-squares model specification test for a class of dynamic nonlinear economic models with systematically varying parameters

The problem of structural instability in estimated macroeconomic relationships has recently surfaced anew, due to a series of articles by the rational expectations school. A key explanation for the observed instability is said to be that the parameters appearing in modelled macroeconomic relationships, traditionally treated as constant or purely random, must realistically be viewed as the reflections of the demand and supply decisions of optimizing agents in the economy reacting rationally to changes in endogenous and exogenous variables, including changes induced by shifts in government policy decision rules. The present paper develops a least-squares measure for simultaneously testing the basic compatibility of prior dynamical, observational, and distributional model specifications against actual data for a class of dynamic nonlinear economic models with parameters explicitly modelled as nonlinear functions of endogenous and exogenous variables. Using invariant imbedding techniques, an algorithm is derived for sequentially updating the optimal least-squares estimates for parameters, endogenous variables, and squared residual modelling error sums as the duration of the process increases and new observations are obtained.Dedicated to R. BellmanThis work was partially supported by the National Science Foundation under Grant No. ENG-77-28432 and the National Institutes of Health under Grant No. GM-3732-03. A previous version of this paper (Ref. 1) was presented at the Econometrics Modelling Research Seminar, Department of Economics, University of Southern California, Los Angeles, 1979. The authors are grateful to numerous colleagues for helpful comments.     

Optimal constrained control of a linear nonstationary end-position control system

We obtain simple expressions for a control action of an end-position linear nonstationary system that is optimal according to a quadratic criterion and has a constrained control. We also consider the special case of a system with one output coordinate and scalar optimal control with feedback requiring knowledge of the current state of the system at all times and the weight function from the point of application of the control to the output coordinate. It is assumed that the external perturbation is known on the entire interval of time during which the system functions. The proposed approach has been successfully used in synthesizing practical algorithms for control of moving objects. Translated fromDinamicheskie Sistemy, No. 13, 1994, pp. 36–39.     

Nonlinear stability behaviour of linear multistep methods

For linear multistep methods sufficient conditions are derived such that the numerical solutions of stable nonlinear initial value problems in Banach spaces are also stable.     

Complex dynamic behaviour of an economic cycle model

In this paper, we investigate the dynamics of a nonlinear economic cycle model. The necessary and sufficient conditions are given to guarantee the existence and stability of the fixed point. It is also shown that the system undergoes a Neimark–Sacker bifurcation by using center manifold theorem and bifurcation theory. Furthermore, Marotto’s chaos is proved when certain conditions are satisfied. Numerical simulations are presented not only to illustrate our results with the theoretical analysis, but also to exhibit the complex dynamical behaviour, such as the period-10, -16, -20 orbits, attracting invariant cycles, quasi-periodic orbits, 10-coexisting chaotic attractors, and boundary crisis. Specifically, we have stabilized the chaotic orbits at an unstable fixed point using the feedback control method.     

A stability theorem for a class of linear evolution systems

Dynamical systems of the form ,u(0)=u ₀, where,B is a densely defined linear operator mapping its domainD (B ) into — the infinitesimal generator of a semigroup of operatorsT (t, B) of classC ₀ — are investigated, such that for each solutionu to , whereP is the spectral eigenprojection onto the null space ofB.It is shown that under some general hypotheses concerning spectral properties ofB the above stability condition is equivalent with the following situation: There exist (i) a normal generating coneK such thatT(t;B)KK fort0 and (ii) a strictly positive element in the dual coneK such that , whereB denotes the dual ofB. Condition (ii) implies the so called total concentration time preservation, i. e. .     

Permanence and global stability of a class of discrete epidemic models

In this paper we investigate the permanence of a system and give a sufficient condition for the endemic equilibrium to be globally asymptotically stable, which are the remaining problems in our previous paper (G. Izzo, Y. Muroya, A. Vecchio, A general discrete time model of population dynamics in the presence of an infection, Discrete Dyn. Nat. Soc. (2009), Article ID 143019, 15 pages. doi:10.1155/2009/143019.)     

On the saddle-point stability for a class of dynamic games

In this paper, we study the stability properties of the class of capital accumulation games introduced by Fershtman and Muller (Ref. 1). Both discrete and continuous time versions are discussed. It is shown that the open-loop Nash equilibrium solutions for both games are characterized by a general saddle-point property, a result best known from the turnpike literature in optimal growth theory. In the case of zero discount rates, an even stronger result can be derived: As long as the Hessian matrix of the instantaneous profit functions has a quasidominant diagonal, no pure imaginary roots are possible.The authors thank J. Boyd III, G. Feichtinger, S. Jørgensen, and G. Schwann for helpful comments. The first author acknowledges financial support from the Natural Science and Engineering Research Council of Canada, Grant No. OGP-0037342.     

Optimal observation and control in linear systems

The paper consists of two parts. In Part I, we consider the optimal observation problem for a nondeterministic linear system by examining results of a deep processing of an output signal of a dynamical measurement device (sensor). The problem studied is an auxiliary problem for studying the optimal control problem for dynamical systems under set-uncertainty conditions in Part II. The methods for the construction of a posteriori, program, and positional solutions are described. The results are illustrated by examining an example of an optimal observation and control problem of a fourth-order mechanical system. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 23, Optimal Control, 2005.     

Admissibilities of linear estimator in a class of linear models with a multivariate t error variable

This paper discusses admissibilities of estimators in a class of linear models,which include the following common models:the univariate and multivariate linear models,the growth curve model,the extended growth curve model,the seemingly unrelated regression equations,the variance components model,and so on.It is proved that admissible estimators of functions of the regression coefficient β in the class of linear models with multivariate t error terms,called as Model II,are also ones in the case that error terms have multivariate normal distribution under a strictly convex loss function or a matrix loss function.It is also proved under Model II that the usual estimators of β are admissible for p 2 with a quadratic loss function,and are admissible for any p with a matrix loss function,where p is the dimension of β.     

Optimal information acquisition for a linear quadratic control problem

This paper develops a generalization of the linear quadratic control problem with partial information. As in the standard partial information setting, it is assumed that the state variable is only observed with noise. The idea in this paper is that the information level may be chosen optimally. In real life information is costly to acquire. It is therefore a trade off between the costs of getting detailed information and the increased value this information gives. We believe that the technique we present should have potential for application within both economics and engineering.     

Energy stability for a class of two-dimensional interface linear parabolic problems

We consider parabolic equations in two-dimensions with interfaces corresponding to concentrated heat capacity and singular own source. We give an analysis for energy stability of the solutions based on special Sobolev spaces (the energies also are given by the norms of these spaces) that are intrinsic to such problems. In order to define these spaces we study nonstandard spectral problems in which the eigenvalue appears in the interfaces (conjugation conditions) or at the boundary of the spatial domain. The introducing of appropriate spectral problems enable us to precise the values of the parameters which control the energy decay. In fact, in order for numerical calculation to be carried out effectively for large time, we need to know quantitatively this decay property.     

Optimal advertising and pricing in a class of general new-product adoption models

In [21], Sethi et al. introduced a particular new-product adoption model. They determine optimal advertising and pricing policies of an associated deterministic infinite horizon discounted control problem. Their analysis is based on the fact that the corresponding Hamilton–Jacobi–Bellman (HJB) equation is an ordinary non-linear differential equation which has an analytical solution. In this paper, generalizations of their model are considered. We take arbitrary adoption and saturation effects into account, and solve finite and infinite horizon discounted variations of associated control problems. If the horizon is finite, the HJB-equation is a 1st order non-linear partial differential equation with specific boundary conditions. For a fairly general class of models we show that these partial differential equations have analytical solutions. Explicit formulas of the value function and the optimal policies are derived. The controlled Bass model with isoelastic demand is a special example of the class of controlled adoption models to be examined and will be analyzed in some detail.