Resumo em Inglês:

All over the world traffic injuries and fatality rates are increasing every year. The combination of negligent and imprudent drivers, adverse road and weather conditions produces tragic results with dramatic loss of life. In this scenario, the use of mobile robotics technology onboard vehicles could reduce casualties. Obstacle motion tracking is an essential ability for car-like mobile robots. However, this task is not trivial in urban environments where a great quantity and variety of obstacles may induce the vehicle to take erroneous decisions. Unfortunately, obstacles close to its sensors frequently cause blind zones behind them where other obstacles could be hidden. In this situation, the robot may lose vital information about these obstructed obstacles that can provoke collisions. In order to overcome this problem, an obstacle motion tracking module based only on 2D laser scan data was developed. Its main parts consist of obstacle detection, obstacle classification, and obstacle tracking algorithms. A motion detection module using scan matching was developed aiming to improve the data quality for navigation purposes; a probabilistic grid representation of the environment was also implemented. The research was initially conducted using a MatLab simulator that reproduces a simple 2D urban-like environment. Then the algorithms were validated using data samplings in real urban environments. On average, the results proved the usefulness of considering obstacle paths and velocities while navigating at reasonable computational costs. This, undoubtedly, will allow future controllers to obtain a better performance in highly dynamic environments.

Resumo em Inglês:

Environmentally induced cracking of pipeline steels in contact with soil have been investigated. Different soils were prepared in order to determine their physical, chemical and bacteriological characteristics. Slow strain rate testing was carried out by using electrolytes obtained from soil samples and NS4 standard solution. Stress vs. strain curves of API 5L grade X46, X60 and X80 steels were obtained at different electrode potentials (Ecorr, 100 mV below Ecorr and 300 mV below Ecorr) with 9 x 10-6 s-1 strain rate. The results obtained with API 5L X46 in soil solution were compared with slow strain rate test (SSRT) results obtained using a strain rate of 9 x 10-7s-1 to the same steel. All results showed the incidence of cracking and their dependence on the potential imposed, revealing the SCC (Stress corrosion cracking) susceptibility of the steels. It was also observed that the hydrogen embrittlement - HE - has an important contribution to cracking initiation and propagation. Cracking morphology was similar to the SCC reported on field condition where transgranular cracking were detected in a pipeline collapsed by land creeping. It was important to point out that even under cathodic potentials the material showed the incidence of secondary cracking and a significant reduction of ductility.

Resumo em Inglês:

This work proposes a tracking control model for a flexible link robotic manipulator using simultaneously motor torques and piezoelectric actuators. The dynamic model of manipulator is obtained in a closed form through the Lagrangian approach. The control uses the motor torques for the tracking control of the joints and also to reduce the low frequency vibration induced in the manipulator links. The stability of this control is guaranteed by the Lyapunov stability theory. Piezoelectric actuators and sensors are added for controlling the high frequency vibrations beyond range of motor torque control. Additionally, this work introduces a formulation for simultaneous control and piezoelectric inserts geometry optimization through the maximization of the control action dissipated energy. Simulations on Matlab/Simulink are used to verify the efficiency of the control model.

Resumo em Inglês:

Menorrhagia is an ailment experienced by a significant number of women during their reproductive years. This condition is associated to heavy menstrual bleeding and while medical treatments are possible, its effects are quite limited. Surgical procedures often employ a hysterectomy but the total removal of the uterus involves high costs and also sometimes a moderate health hazard. Less invasive treatments were devised, and over the years a technique called endometrial ablation has become increasingly popular especially in the United States and in Europe. This treatment removes the endometrium by inserting a latex balloon filled with a solution at a high temperature inside the uterine cavity. Therefore, in order to assess the effectiveness of this treatment, accurate predictions of the temperature field are needed. The present contribution addresses this thermal problem and adopts the Pennes' bioheat transfer equation to mathematically determine the transient temperature distribution across the uterus wall by employing finite integral transforms. Special focus is given to situations in which the temperature of the fluid inside the balloon is no longer constant and may impair the effectiveness of the treatment. On general terms, it was found that the temperature distribution is strongly dependent on the perfusion coefficient and is also significantly affected by the rate of the decay of the fluid temperature inside the balloon.

Resumo em Inglês:

Mixing layers are present in very different types of physical situations such as atmospheric flows, aerodynamics and combustion. It is, therefore, a well researched subject, but there are aspects that require further studies. Here the instability of two-and three-dimensional perturbations in the compressible mixing layer was investigated by numerical simulations. In the numerical code, the derivatives were discretized using high-order compact finite-difference schemes. A stretching in the normal direction was implemented with both the objective of reducing the sound waves generated by the shear region and improving the resolution near the center. The compact schemes were modified to work with non-uniform grids. Numerical tests started with an analysis of the growth rate in the linear regime to verify the code implementation. Tests were also performed in the non-linear regime and it was possible to reproduce the vortex roll-up and pairing, both in two-and three-dimensional situations. Amplification rate analysis was also performed for the secondary instability of this flow. It was found that, for essentially incompressible flow, maximum growth rates occurred for a spanwise wavelength of approximately 2/3 of the streamwise spacing of the vortices. The result demonstrated the applicability of the theory developed by Pierrehumbet and Widnall. Compressibility effects were then considered and the maximum growth rates obtained for relatively high Mach numbers (typically under 0.8) were also presented.

Resumo em Inglês:

The present paper shows experimental results about soot suppression on a laboratorial scale jet free diffusion flame of liquefied petroleum gas submitted to acoustic oscillations. The experiments were conducted to verify the influence of amplitude and frequency of oscillations in the regions of soot formation and suppression through the flame. To quantify the soot presence the laser induced incandescence was utilized. The results show combinations of frequency and amplitude of oscillation which the presence of soot is close to zero.

Resumo em Inglês:

The aim of this paper is to investigate the performance and emissions characteristics of a turbocharged and aftercooled diesel engine operated with natural gas as primary fuel, and diesel fuel as ignition source. In such dual fuel operation, much of the energy released comes from the combustion of the gaseous fuel, while only a small amount of diesel fuel provides ignition through timed cylinder injection. The effects of diesel-natural gas substitution ratios, engine speed, and load on the equivalent brake specific fuel consumption and gaseous emissions of hydrocarbons, carbon monoxide and nitrogen oxides are examined for natural gas-diesel fuel operation and, afterward, compared with the original diesel operation. The results show that, over a wide range of operating conditions (engine speed, load), the dual fuel engine clearly shows the benefits of reduced NOX emissions. However, under low loads, the results indicate high CO and HC emissions and a higher BSFC when compared to those of the corresponding diesel engine.

Resumo em Inglês:

The aim of the present work is to investigate the burr formation mechanisms at the edges (lateral and exit) during face milling of mould steel using carbide tools. The effects of the cutting parameters were studied and strategies of burr minimization were discussed. The proposed minimization was achieved by optimizing the cutting conditions: cutting speed (Vc), feed per tooth (fz) and depth of cut (doc), with the aid of surface response technique.

Resumo em Inglês:

Grinding is an important process used when tight dimensional accuracy and low workpiece surface roughness are demanded. Despite the fact that grinding is widely used in industry, it is not well understood. The elastic deformation, which occurs in the beginning of the cycles, makes it necessary a spark out in the end of the cycle. An alternative to this is the use of a three-phase cycle. The main objective of this work is to compare the plunge cylindrical conventional grinding cycle (with spark out) and a three-phase one in terms of workpiece surface roughness. In order to accomplish this goal, several plunge grinding of hardened AISI 4340 steel experiments were carried out using both kinds of cycles in different grinding conditions. The vibration signal of the system was acquired in order to better understand the differences between the two kinds of cycles. The main conclusion was that conventional cycle produces lower workpiece surface roughness than the three-phase one (both with the same cycle time). It happens because the elastic deformation is better released in the conventional cycle.