Singh, Shubh Narayan2015-09-162023-10-202015-09-162023-10-202012ROLL NO. 07612302https://gyan.iitg.ac.in/handle/123456789/302Supervisor: K. V. KrishnaThe thesis aims at a further study on semi-Dower automata { the concept intro- duced by Giambruno and Restivo to study Dnitely generated submonoids of free monoids. The material of the thesis is an interplay between automata and algebraic structures. In fact, using semi-Dower automata we study the intersection problem of submonoids of free monoids. Further, we study certain structural properties of semi-Dower automata using algebraic structures. Contributing to the intersection problem of submonoids of free monoids, in this thesis, we obtain a suDcient condition for the Hanna Neumann property of the sub- monoids which are generated by Dnite preDx sets of words. In this connection, we obtain a general rank formula for the submonoids accepted by SFA. In order to study structural properties of semi-Dower automata, we choose to study holonomy decom- position and on syntactic complexity. We ascertain holonomy decomposition and syntactic complexity of certain subclasses of circular semi-Dower automata. Further, we count the number of primitive and generalized primitive words in the submonoids accepted by semi-Dower automata..enMATHEMATICSThesis