RCAAP Repository

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The pillar screw is an important element of conventional dental implants. It is used to fix the pillar or intermediary to the implant set. In conventional dental implants, the torque level applied is near of 20 Ncm, however it knows that the pillar screw resists to bigger torque levels, and that a high pre-load could improve its setting. Many problems related to the breakings and reliefs of the screw are related in literature. The improvement of osseointegration conditions and the dental implantations project could provide to the application of high torque to the pillar screws, minimizing the relief problems. For this, the knowledge of the physical behavior of these elements about their stress and strain fields is important, when a certain torque level and pre-load level is applied. In this work, the stress gradient in the pillar screw was evaluated with an applied pre-load level. The technique of the bidimentional photoelasticity in a photoelastic model of a conventional dental implant of the Conexão Sistemas de Prótese Ltda company was used. For the attainment of the photoelastics parameters, a Matlab program was developed to acquire and to process the fringe images. A photoelastic prismatic bar submitted to a four points bending effort was used, installed in a transmission polariscope, adjusted for elliptical polarized light. The principal stresseses directions had been obtained through a non linear equation solution. To improve the precision of the principal stresseses directions values a disc under axial compression was used to calibrate values RGB of the acquired images. For the torque standard of 20 Ncm, the pre-load was of 111 N. It is possible estimate that torque values in the order of 40 to 50 Ncm could be applied in the pillar screw, if the osseointegration level allied to the project of the dental implant to support such torque levels. A bigger number of experiments must be carried through so that if it can conclude on the maximum values of torque of the daily pay-load. The program Fringes" revealed efficient in the determination of the models optics parameters until 4ª fringe order.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

The turbulence in fluids is one of the most challenging problems in actuality, especially in industrial applications, like mixtures processes, heat transfer, lubrication, combustion, or propulsion systems in airplanes In front of such interest, in the present work, the objective is the analysis of the transition of turbulence of temporal jets at moderate Reynolds numbers using the LES (Large Eddy Simulation) methodology. A high order resolution computational code, based on Fourier pseudo-spectral method, called ESPC3D, was developed in the present work for simulating the development of temporal jets in transition and/or turbulent state. Such code was developed in the Laboratory of Heat and Mass Transfer and Fluid Dynamics (LTCM) of Federal University of Uberlândia. Consistent results were obtained from the point of view of physical analysis, using the developed code. The simulations performed allowed to verify the transition to turbulence as well as the coherent structures that characterizes it. In addition, the influence of the LES methodology and the Reynolds number influence in such flows could be verified. The proximity of the inertial region to the inclination of -5/3, from Kolmogorov Theory, and the decay region were verified in the energy spectra.

The distraction osteogenesis is a surgical technique used in the dentistry for the transversal discrepancies correction of the jaw, having as basic principle the intrinsic capacity of some tissue development when submitted to the stress caused by slow and continuous traction. To obtain the osteogenesis success, the distractors osteogenesis symphysianic have to minimize any bone parts displacement. This work had the purpose to evaluate the stability of a distractor symphysis through three-dimensional models of finite elements where different setting positions and different amounts of setting screws are evaluated. The stability was evaluated through the determination of vertical displacements in the load direction in the range of 20 up to 140 N. Additionally; the results of an experimental analysis had been used to adjust the numerical models of finite elements. It was observed that, for the load profile applied, the stability is not a function of setting screws number. The stiffness of the distractor at cut region was the cause of the differences between fixations. In the distractor lower position setting the displacements levels had been lesser, indicating a better distractor stability.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The model based predictive controller (MPC) has been successfully applied in industry, with particular emphasis on the petrochemical industry. The basic feature of MPC algorithms is based on the formulation of an optimization problem, for calculating the sequence of control moves that minimize a performance function in a time horizon with the best information available at every moment, and submitted to restrictions, operation and the plant model. The presence of uncertainties in the model can result in loss of performance of the model based control system or even instability in the closed loop. The class of robust predictive controllers (RMPC) is based on the explicit consideration of uncertainties. This research presents two RMPC algorithms. One of them adds a set of restrictions with robust stability guarantee (RMPC-MMR) to the problem of robust control, with uncertainty in time variant as min-max optimization. And the other develops RMPC using Linear Matrix Inequalities (LMI) and uncertainty as a polytope (LMI-RMPCR). The algorithms are evaluated through computer simulations, and are applied to a range of industrial process typical systems. The responses are compared with the responses of traditional controllers. The classical algorithms IHMPC (Infinite Horizon Model Predictive Control) and MPC-RS (Model Predictive Control with Reference System) are also assessed experimentally by the application in a pilot plant for controlling level and pH, built in the Experimental Unit of the Chemical Engineering College, at Federal University of Uberlândia. The results of RMPC simulation were evaluated with the simulation and experimental responses of the classical controllers implemented in the plant. The results indicate the applicability and limitations of the proposed controllers.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais