A system of nonlinear di fferential equations, namely, the Belousov-Zhabotinskii reaction model has been investigated for nonlinear self-adjointness using the recent work of Professor N.H.Ibragimov. It is shown that the model is not nonlinearly self-adjoint. The symmetries of the system and nonlinear conservation laws are calculated. The modi fied system, which is nonlinearly self-adjoint, is also analysed. Its symmetries and conservation laws are presented.

This thesis deals with the optimal control of PDEs. After a brief introduction in the theory of elliptic and parabolic PDEs, we introduce a software that solves systems of PDEs by the finite elements method. In the second chapter we derive optimality conditions in terms of function spaces, i.e. a systems of PDEs coupled by some pointwise relations. Now we present algorithms to solve the optimality systems numerically and present some numerical test cases. A further chapter deals with the so called lack of adjointness, an issue of gradient methods applied on parabolic optimal control problems. However, since optimal control problems lead to large numerical schemes, model reduction becomes popular. We analyze the proper orthogonal decomposition method and apply it to our model problems. Finally, we apply all considered techniques to a real world problem.

Neste texto são demonstrados, a partir do ponto de vista da teoria dos espaços de Hilbert e da teoria das C*-álgebras, teoremas relacionados a operadores auto-adjuntos em espaços de Hilbert, entre os quais estão o Teorema Espectral, o teorema de Kato-Rellich e a desigualdade de Kato. Também são dadas aplicações destes teoremas a alguns operadores de Schrödinger provenientes da Física-Matemática. / In this text we prove, within the Hilbert spaces theory and C*-algebras points of view, some theorems which are related to self-adjoint operators acting on Hilbert spaces, among which are the Spectral Theorem, the Kato-Rellich theorem and Kato\'s inequality. Also, some applications to Schrödinger operators coming from the Mathematical-Physics context are given.

Neste texto são demonstrados, a partir do ponto de vista da teoria dos espaços de Hilbert e da teoria das C*-álgebras, teoremas relacionados a operadores auto-adjuntos em espaços de Hilbert, entre os quais estão o Teorema Espectral, o teorema de Kato-Rellich e a desigualdade de Kato. Também são dadas aplicações destes teoremas a alguns operadores de Schrödinger provenientes da Física-Matemática. / In this text we prove, within the Hilbert spaces theory and C*-algebras points of view, some theorems which are related to self-adjoint operators acting on Hilbert spaces, among which are the Spectral Theorem, the Kato-Rellich theorem and Kato\'s inequality. Also, some applications to Schrödinger operators coming from the Mathematical-Physics context are given.

This thesis deals with the optimal control of PDEs. After a brief introduction in the theory of elliptic and parabolic PDEs, we introduce a software that solves systems of PDEs by the finite elements method. In the second chapter we derive optimality conditions in terms of function spaces, i.e. a systems of PDEs coupled by some pointwise relations. Now we present algorithms to solve the optimality systems numerically and present some numerical test cases. A further chapter deals with the so called lack of adjointness, an issue of gradient methods applied on parabolic optimal control problems. However, since optimal control problems lead to large numerical schemes, model reduction becomes popular. We analyze the proper orthogonal decomposition method and apply it to our model problems. Finally, we apply all considered techniques to a real world problem.:Introduction The state equation Optimal control and optimality conditions Algorithms The \"lack of adjointness\" Numerical examples Efficient solution of PDEs and KKT- systems A real world application Functional analytical basics Codes of the examples