Given a theory T , one may add a new unary function symbol σ to the language and add axioms to T asserting that σ is an automorphism. The model theory of generic automorphisms is the study of the model companion of the resulting theory Tσ . In this paper, we study theories equipped with more than one generic automorphism by exploring when model companions exist for such theories. In particular,...

In this paper, we have analyzed a mathematical model for the study of interaction between tumor cells and oncolytic viruses. The model is analyzed using stability theory of differential equations. We gain some conditions for global stability of trivial and interior equilibrium point.

We study exponential stability and its robustness for time-varying linear index-1 differentialalgebraic equations. The effect of perturbations in the leading coefficient matrix is investigated. An appropriate class of allowable perturbations is introduced. Robustness of exponential stability with respect to a certain class of perturbations is proved in terms of the Bohl exponent and perturbatio...

We study the history and recent developments in nonelementarymodel theory focusing on the framework of abstractelementary classes. We discuss the role of syntax and semanticsand the motivation to generalize first order model theory to nonelementaryframeworks and illuminate the study with concrete examplesof classes of models. This first part introduces the main conceps and philosophies anddiscu...

In this paper, dynamic and stability analysis of a flexible cam-follower system is investigated. Equation of motion is derived considering flexibility of the follower and camshaft. Viscous and Coulomb frictions are considered in the rocker arm pivot. The normalized equation of motion of the system is a 2nd- order differential equation with periodic coefficients. Floquet theory is employed to s...

the system of land registration is protective formalism that is formed based on the theory of “public confidence”. this theory presumes that what reflected by the land registration offices is based on the legal fact. this theory, which provides legal stability and security in transactions, is manifested in three guiding principles including “mirror principle”, “curtain principle” and “insurance...

Based on the nonlocal Timoshenko beam theory, the dynamic stability of functionally gradded (FG) nanoeams under axial load is studied in thermal environment, with considering surface effect. It is used power law distribution for FGM and the surface stress effects are considered based on Gurtin-Murdoch continuum theory. Using Von Karman geometric nonlinearity, governing equations are derived bas...

In this paper, dynamic and stability analysis of a flexible cam-follower system is investigated. Equation of motion is derived considering flexibility of the follower and camshaft. Viscous and Coulomb frictions are considered in the rocker arm pivot. The normalized equation of motion of the system is a 2nd- order differential equation with periodic coefficients.&#10Floquet theory is employed to...