具脉冲出生与脉冲输入环境毒素的单种群动力学模型研究

讨论了在污染的环境中具脉冲出生的单种群动力学模型,证明了系统的所有解是一致有界的.利用数学的分析方法,获得了系统种群灭绝的条件,也得到了系统的持久生存的条件.研究的结果为污染环境中实际生物资源管理提供了可靠的管理策略.     

Poisson stability for impulsive semidynamical systems

In this paper, the concept of Poisson stability is investigated for impulsive semidynamical systems. Recursive properties are also investigated.     

Natural and Doubly Natural Dualities

Representable dualities between categories of modules satisfying natural closure properties are investigated and shown to be determined by homological properties shared by various classical and recently investigated types of dualities.     

具有HollingII类型功能反应的3种群捕食时滞模型

研究了具有HollingII类型功能反应的一捕食者有两个食饵的时滞系统,通过构造Lyapunov泛函得到了与时滞有关的系统全局渐近稳定的充分条件.     

拟连续格的逆极限

给出以保任意交和定向并为态射的拟连续格范畴的逆极限,讨论函子保广义拟连续格逆极限的条件。     

A discrete time car following model and the bi-parameter logistic map

A discrete time model for car following behaviour is investigated. It is found that the model can be expressed in the form of a logistic map with multiple control parameter values. The case where the logistic map has a bi-value control parameter is investigated and relevant Feigenbaum diagrams are presented and the behaviour of the Lyapunov exponent is investigated. Divergent behaviour in the chain of vehicles is also considered.     

A family of centered forms for a polynomial

The general centered form for multi-variate polynomials is investigated and a computing procedure is proposed that results in a certain superset. Based on this procedure the optimal centered forms for monomials and for some special cases of polynomials are investigated.     

Experimental investigation of the dependence of the birefringence effect on the elastic and rubbery strains for certain epoxy polymers at room temperature

The strain dependence of the optical path difference δ=δ(e, ?*) has been investigated for certain network polymers. It is shown that this dependence can be represented in the form: δ=αe+β?*, where α and β are the elastic (e) and rubbery (?*) strain optic coefficients. Values of the coefficients α and β are determined and their properties are investigated. The possibility of determining the strains in parts made of the investigated polymers from the known effects is examined.     

Bessel functions and singular BVPs arising in physiology in the presence of upper and lower solutions in reverse order

In this paper, we consider the genic mutation on an impulsive population system in polluted environment. All solutions of the investigated system are proved to be uniformly bounded. Using mathematical analysis methods, the conditions of the globally asymptotically stable population-extinction solution of the investigated system are obtained. The permanent condition of the investigated system is also obtained. Finally, numerical analysis is carried out illustrate our results. Our results provide reliable tactic basis for the practical biological resource management in polluted environment.     

Dynamical behaviors of a biological management model with impulsive stocking juvenile predators and continuous harvesting adult predators

In this work, a biological management model with impulsive stocking juvenile predators and continuous harvesting adult predators is investigated. By the stroboscopic map of the discrete dynamical system, the prey-extinction periodic solution of the investigated system is proved to be globally asymptotically stable. By the theory of impulsive differential equation, the investigated system is also proved to be permanent. Finally, the numerical analysis is inserted to illustrate the results. Our conclusions provide reliable tactical basis for the practical biological management.     

Analysis of a stage-structured predator–prey system with birth pulse and impulsive harvesting at different moments

In this work, we consider a stage-structured predator–prey system with birth pulse and impulsive harvesting at different moments. Firstly, we prove that all solutions of the investigated system are uniformly ultimately bounded. Secondly, the conditions of the globally asymptotically stable prey-extinction boundary periodic solution of the investigated system are obtained. Thirdly, the permanence of the investigated system is also obtained. Finally, numerical analysis is inserted to illustrate the results. Our results provide reliable tactic basis for the practical biological economics management.     

斜球变量的F统计量

本文研究斜球变量的F统计量的性质并引进了一类斜F分布.我们得到了密度函数,分布函数,矩发生函数和矩,考察了F检验在斜正态分布族内的性质.     

Wear resistance of metal polymer combinations

The possibilities of using polymer protectors in journal bearings are investigated, and the effects of operating conditions on the wear of metal/metal-polymer composition friction pairs are investigated.Mekhanika Polimerov, Vol. 2, No. 4, 580–584, 1966     

An inverse Sturm-Liouville problem for an impedance

A numerical method for reconstructing an impedance in a Sturm-Liouville operator from finitely many eigenvalues is investigated. The method constructs an impedance that has the given eigenvalues by finding a zero of a nonlinear finite dimensional map. A Newton scheme is investigated and numerical examples are considered.     

Explicit methods for fractional differential equations and their stability properties

The use of explicit methods in the numerical treatment of differential equations of fractional order is an area not yet widely investigated. In this paper stability properties of some multistep methods of explicit type are investigated and new methods with larger intervals of stability are proposed. Some numerical experiments are presented in order to validate theoretical results.     

ON MEROMORPHIC SOLUTIONS OF RICCATI AND LINEAR DIFFERENCE EQUATIONS

In this paper, meromorphic solutions of Riccati and linear difference equations are investigated. The growth and Borel exceptional values of these solutions are discussed, and the growth, zeros and pol...     

The existence and stability of the equilibria of mechanical systems with constraints produced by large potential forces

A modification of Routh's theorem is investigated for systems with unilateral constraints produced by large potential forces, which enables steady motions to be found and the sufficient conditions for their stability to be investigated. The problem of an orbital “monkey bridge” is considered as an example.     

Investigation of the extremal directions in a glass-reinforced plastic

The extremal directions in an orthotropic material are investigated on the basis of six experimentally determined values of the investigated characteristic in the three planes of symmetry of the material.Translated from Mekhanika Polimerov, No. 4, pp. 742–745, July–August, 1971.     

The dynamic contact problem for a prestressed cylindrical tube filled with a fluid

The radial harmonic oscillations of a rigid bandage on the thin-walled elastic cylindrical tube filled with an ideal compressible fluid under a high static pressure are investigated. The problem is reduced to an integral equation, the kernel symbol of which is constructed in numerical form. The properties of the integral equation are investigated, a method of solving it is proposed, and the effect of the presence of the fluid and the initial stresses of the pipeline on the stress state in the contact area for dynamic actions are investigated. It is shown that when monitoring the initial stresses at high frequencies it is essential to take into account the presence of the fluid.     

Dynamic stability and sensitivity to geometric imperfections of strongly compressed circular cylindrical shells under dynamic axial loads

In the present paper, the dynamic stability of circular cylindrical shells is investigated; the combined effect of compressive static and periodic axial loads is considered. The Sanders–Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration; Lagrange equations are used to reduce the nonlinear partial differential equations to a set of ordinary differential equations. The dynamic stability is investigated using direct numerical simulation and a dichotomic algorithm to find the instability boundaries as the excitation frequency is varied; the effect of geometric imperfections is investigated in detail. The accuracy of the approach is checked by means of comparisons with the literature.