Numerical identification of a variable parameter in 2d elliptic boundary value problem by extragradient methods

This work focuses on the inverse problem of identifying a variable parameter in a 2-D scalar elliptic boundary value problem. It is well-known that this inverse problem is highly ill-posed and regularization is necessary for its stable solution. The inverse problem is studied in an optimization framework, which is the most suitable framework for incorporating regularization. This optimization problem is a constrained optimization problem where the constraint set is a closed and convex set of the admissible coefficients. As an objective functional, we use both the output least squares and modified output least squares functionals. It is known that the most commonly used iterative schemes for such problems require strong monotonicity of the objective functionals derivative. In the context of the considered inverse problem, this is a very stringent requirement and is achieved through a careful selection of the regularization parameter. In contrast, extragradient type methods only require the derivative of the objective functional to be monotone and this allows a greater flexibility for the selection of the regularization parameter. In this work, we use the finite element method for the discretization of the inverse problem and apply the most commonly studied extragradient methods

Variational inequalities and fixed point problems : a survey

U ovoj disertaciji predstavljena je i razrađena teorija neizrazitog vođenja i održavanja procesa toplinskog komfora u mjernom laboratoriju. Izložen je novi sustavski pristup vođenja s posebnim naglaskom na čovjeka- mjeritelja, koji je sastavni dio regulacijskog kruga Konvencionalnom vođenju procesa održavanja toplinskog komfora predviđena je korekcija u skladu s subjektivnim doživljajem, zadržavajući pri tom referentne vrijednosti unutar intervala dopuštenih standardom. Kao rezultat istraživanja odlučeno je i realizirano da se psihološki doživljaj komfora ugradi primjenom neizrazitog slijeda vođenja. Tijekom istraživanja, za potrebe vođenja toplinskog komfora, izrađen je lingvistički deduktivni model, kojim se opisuju svi eventualni lingvistički zahtjevi za promjenom komfora. Pored ovog modela izrađen je i model toplinske i materijalne akumulacije u promatranom prostoru, kako bi se dokazala mogućnost primjene razvijene teorije za vođenje procesa toplinskog komfora. Važan dio predloženog sustava jest inteligentno mjerilo entalpije, izvedeno na temelju istraživanja termodinamike vlažnog zraka. Zamišljen je i realiziran takav inteligentni mjerni uređaj koji povezuje mjerne podatke o tlaku, temperaturi i vlažnosti zraka u promatranom prostoru, sa zbirkom znanja ugrađenom u mikroračunalo, pa kontinuirano računa trenutačne vrijednosti entalpije. Ovaj rad je novi doprinos u teoriji vođenja toplinskog komfora, koja se do sada zasnivala isključivo na stabilizaciji termodinamičkih varijabli stanja.This work presents new process control theory, applied to maintaining thermal comfort in measurement laboratory. In this system approach to process control, human is an essential part of feedback controller. His subjective feeling of thermal comfort is base for applying fuzzy logic; his linguistic information's about temperature and relative humidity in laboratory substitute measurements of a classic feedback controller. Control decisions are result of fuzzy calculations, and controlled variables must be maintained within limits given by Standard. Linguistic deductive model that describes all possible linguistic demands for thermal comfort changes is developed during the research. Also, mathematical model of heat and material accumulation in a laboratory is developed, to confirm applicability of proposed theory for control of thermal comfort process. Important part of proposed system is an intelligent instrument for enthalpy measurement, developed on basis of humid air thermodynamics research. This intelligent measuring instrument combines pressure, temperature and relative humidity measurement data in a laboratory with knowledge base situated in a microprocessor, and continuously calculates enthalpy. This work presents new contribution to theory of thermal comfort control, which was until now based exclusively on stabilisation of thermodynamic variables

An efficient projection-type method for monotone variational inequalities in Hilbert spaces

We consider the monotone variational inequality problem in a Hilbert space and describe a projection-type method with inertial terms under the following properties: (a) The method generates a strongly convergent iteration sequence; (b) The method requires, at each iteration, only one projection onto the feasible set and two evaluations of the operator; (c) The method is designed for variational inequality for which the underline operator is monotone and uniformly continuous; (d) The method includes an inertial term. The latter is also shown to speed up the convergence in our numerical results. A comparison with some related methods is given and indicates that the new method is promising

A New General Iterative Method for Solution of a New General System of Variational Inclusions for Nonexpansive Semigroups in Banach Spaces

We introduce a new general system of variational inclusions in Banach spaces and propose a new iterative scheme for finding common element of the set of solutions of the variational inclusion with set-valued maximal monotone mapping and Lipschitzian relaxed cocoercive mapping and the set of fixed point of nonexpansive semigroups in a uniformly convex and 2-uniformly smooth Banach space. Furthermore, strong convergence theorems are established under some certain control conditions. As applications, finding a common solution for a system of variational inequality problems and minimization problems is given