Hopf Bifurcation of a Nonresident Computer Virus Model with Delay

In this paper, a delayed nonresident computer virus model with graded infection rate is considered in which the following assumption is imposed: latent computers have lower infection ability than infectious computers. With the aid of the bifurcation theory, sufficient conditions for stability of the infected equilibrium of the model and existence of the Hopf bifurcation are established. In particular, explicit formulae which determine direction and stability of the Hopf bifurcation are derived by means of the normal form theory and the center manifold reduction for functional differential equations. Finally, a numerical example is given in order to show the feasibility of the obtained theoretical findings.

Towards an Integration of the Behaviorist,the Cognitivist and the Interactionist Models in SLA in China

Introduction English Language teaching as a profession has enjoyed a long history.And ever since itsinitiation,people have investigated different models in language acquisition/learning andteaching,although only in recent years has attention been paid to the studies of SLA.In theChinese setting,research in foreign language teaching(TEFL)has been made in the fashionof the theories of first language acguisition or SLA,for it is believed that the contributions tostudies of the input provided by mothers(i.e motherese) in L1 acquisition and teachers inter-locuters in SLA are necessarily important for understanding the direction that TEEL researchhas followed,as they have provided both a methodololgy for investigating input and the re-search questions.The behaviorist,the cognitivist and the interactionist approaches have putforward different models in interpreting L1 acquisition and SLA,which obviously have theirown merits and demerits,depending on the level at which they are employed and the purposethey