Electric thrusters, also known as plasma thrusters, represent a type of space propulsion devices that employ electromagnetic forces to generate thrust. Plasma thrusters have a number of advantages compared to chemical propulsion, for example, high specific impulse and high efficiency, and are commonly employed for station-keeping of satellites, orbit transfer maneuvers and deep-space missions.

The popularization of mini and microsatellites in low-cost space missions have resulted in a growing interest in the development of low-power thrusters. The ambipolar thruster is a type of plasma thruster which is simple to construct and can be scaled to smaller dimensions and lower operational powers. In this monograph a reduced version of the ambipolar thruster is proposed for miniaturized satellites, commercially known as “PocketQube”. Numerical simulations are performed to obtain the specific impulse, which is an important parameter for the evaluation of thrusters. Potential applications of this technology are discussed, for example, extending space missions, and de-orbiting. The results presented here can represent a contribution to the development of space technologies.

Turbulence exerts significant influence over radial transport in the edge region of tokamak plasmas, and is a critical factor in magnetic confinement for fusion experiments. Despite its substantial impact, our understanding of turbulence in this context remains limited. Coherent structures are fundamental in the realm of turbulent transport within fusion plasmas. Entropy and complexity, derived from information theory, serves as a valuable tool to quantify the level of order or disorder in turbulent plasmas. Notably, these coherent structures contribute to the observation of low spectral entropy values in data obtained from space plasmas and numerical simulations of magnetohydrodynamic turbulence.

In this analysis, we focus on two-dimensional numerical simulations of the modified Hasegawa-Wakatani equations, which provide a simplified nonlinear model for electrostatic resistive drift-wave turbulence in plasmas. We construct a bifurcation diagram illustrating the transition from a turbulent regime to one dominated by zonal flows, effectively suppressing turbulence. The degree of spatial order or disorder during this transition is obtained by computing the Jensen-Shannon complexity-entropy index of the velocity, derived from the electrostatic potential. This index uses the normalized power of shearlet coefficients as a probability distribution. Our findings reveal that the turbulent regime exhibits a higher degree of entropy and a lower degree of complexity, contrasting with the regime dominated by zonal flows characterized by lower entropy values and a higher degree of complexity. These results hold the potential to advance our understanding of nonlinear processes within drift-wave turbulence in fusion plasmas.

This study focuses on the importance of recycling, especially in the context of carton packaging, as an essential part of seeking sustainable solutions for urban solid waste management. The study material comprises carton packaging, notably the cellulose pulp extracted from these packages, which are composed of layers of paperboard (CB in natura), Low-Density Polyethylene (LDPE), and aluminum (Al). The primary objective of this research is to evaluate the feasibility of separating the elements contained in carton packaging. This involves the application of various chemical treatments to obtain cellulose nanofibers (CNF) from CB in natura, as well as the synthesis of aluminum oxide (Al2O3) based on the extracted Al. Additionally, efficient separation of LDPE is sought based on its volatility properties concerning temperature. Recycling and effective separation of the components of these packages significantly contribute to improving these practices, using both physical and chemical separation methods. For this purpose, the research proposes material recovery techniques aimed at obtaining CNF and Al2O3, with the intention of reducing waste and promoting environmental sustainability. The research involved the application of various chemical treatments on cellulose fibers obtained from carton packaging, resulting in CNF and Al2O3, as well as investigating the behavior of untreated LDPE. The CB in natura and treated fibers (CNF, Al2O3, and LDPE) underwent characterizations through techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG/DTG/DSC), and Fourier-transform infrared spectroscopy (FTIR). The results revealed chemical modifications in the treated fibers, with a significant increase in crystallinity index: CB in natura (41.08%), treated (49.82%), 4B (56.38%), and CNF (62.65%), with an average diameter of 6-41 nm. Chemical analysis of the fibers showed moisture content (MC%) of 5.73±1.22, ash content (AC%) of 1.66±0.02, extractives content (EC%) of 3.69±0.27, insoluble lignin content (ILC%) of 11.66±0.99, holocellulose content (HC%) of 85.30±0.27, alpha cellulose content (ACC%) of 67.05±0.24, and hemicellulose content (HMC%) of 18.25±0.24. The thermal stability of the samples ranged from 195.22°C to 249.93°C, with discussions on the effects of chemical treatments on the properties of cellulose fibers. Aluminum oxide nanoparticles, with an average diameter of 2 nm, exhibited non-uniform distribution and the presence of crystalline phases (α and γ) confirmed by XRD. LDPE exhibits a melting point with a Tm value of 109.50°C and thermal stability recorded at 76.80°C. This study aims to improve the recycling practices of carton packaging through physical and chemical separation methods. Proposing material recovery techniques to produce cellulose nanofibers and aluminum oxide, reducing waste, and promoting environmental sustainability with higher value-added products.

Plasma propulsion, or electric propulsion, arises from the need to explore deep space more economically and efficiently. The cylindrical Hall thruster (CHT) is an electric propulsion device that demonstrates enhanced propellant utilization and performance efficiencies within reduced dimensions and lower power thresholds when compared to conventional plasma propulsion devices. The compact size and operation at lower power levels make it an interesting option to provide propulsion for CubeSats and small satellites. The CHT comprises a channel with an annular anode through which neutral gas is injected, subsequently ionized by magnetized electrons injected from an external hollow cathode. The resulting plasma ions are ejected from the device, giving thrust. This work aims to understand and study the plasma in the discharge channel of a CHT through numerical simulations. The code describes the plasma with a hybrid model in which the electrons are treated as a fluid and the ions and neutral atoms as pseudo-particles. The simulations were conducted for two different potential values at the anode, namely, 150 V and 300 V, representing different modes of operation. The results obtained with this simplified model allow obtain an optimal configuration for a future prototype to be implemented at the Plasma Physics Laboratory at the University of Brasilia.

Urban bus drivers are exposed to noise during the work. When at high levels, occupational exposure to noise may be associated with hearing tinnitus, communication difficulties and hearing loss. The aim of the present study was to measure the levels of exposure to which urban bus drivers in the Federal District are subjected during their working hours, as well as to investigate the prevalence of noise induced hearing loss (NIHL).The sample consisted of 500 public transport drivers with a mean age of 46 years and working time predominantly over 15 years. Anamnesis was applied with questions about life and work habits, sound pressure levels were measured using a CESVA model SC101 sound level meter, and data from the last sequential audiometry performed by the workers was collected. Difficulty communicating inside vehicles was reported by 20.40% of professional drivers and hearing buzzing noises at the end of working hours by 28.40%. There were 39.80% of drivers with tests suggestive of NIHL, with 60.80% of bilateral cases and 39.20% unilateral. 72.86% of the compromised audiometries belonged to individuals with more than 15 years of experience in the profession and there was a progression in the number of exams with NIHL suggestion the greater the age of the driver. The sound pressure levels were not higher than the exposure limit and the level of action provided for in Occupational Hygiene Standard 01.

This study focuses on the parameter identification of a commercial magnetorheological (MR) damper. The nonlinear behavior of the MR damper was modeled using the numerically parameterized sigmoid model proposed by Wang, which utilized experimental dynamic behavior of a commercial MR damper and applies a method to fit symmetric and asymmetric sigmoid functions using experimental data. Two optimization methods, namely the Nelder-Mead simplex search method (fminsearch) and the differential evolution (DE), were proposed as minimization algorithms. The performance of the optimization methods was compared. The dependency of frequency excitation, piston displacement, current applied in the coil and the operating temperature of the MR damper were also evaluated. The validation of the model parameter was achieved by comparing experimental results with predicted values. The results show that the proposed methodology is effective in identifying the parameter of the MR damper and can be used to improve the performance of the suspension system.

In several engineering fields, the need to identify and monitor damage in complex and difficult-to-access structures still presents a major challenge for existing non-destructive monitoring techniques. Methods based on Structural Health Monitoring (SHM) demonstrate the potential to identify and monitor damage to structures through an on-board system for immediate comparison with an existing database. In this sense, the present work proposes a numerical study using the SHM damage prediction method with the solution of the inverse problem. The study structure was a fixed beam with elastic boundary conditions modeled using a low-order fidelity model. Using finite elements, a bolted joint with 4 NAS6208-16 bolts was modeled in Ansys Parametric Design Language (APDL) using the COMBIN14 element from 6 stiffnesses, where 3 stiffnesses are torsional and 3 are flexural. A convergence analysis was performed, resulting in the evaluation of the modeling of the problem with elastic conditions and discretization of 20 elements using quadratic interpolation functions between the nodes. Beam damage was defined as a loss of tightening torque on the bolts ranging from 5\% to 50%, resulting in a loss of stiffness in the beam connection. An R-index capable of evaluating results based on acceleration in the vertical direction and normalized with the maximum acceleration signal collected was proposed. Transient simulations using modal superposition were performed to evaluate the robustness of the R-index. As a first result, it was observed that the selected R-index is robust about changes in the force application position and in the number and distribution of nodes for data reading. It was possible to approximate the results through a single quadratic curve, based on the averages obtained from the R-index. 95% confidence limit curves were drawn from the average values, enabling an attempt to solve the inverse problem. With the addition of noise of 1% to 5% in the vertical acceleration data obtained, the detection of torque loss at low levels was impaired. Despite this, through the analysis of the confidence interval, the method was still capable of satisfactorily identifying torque losses above 25%, especially when the use of the average of the values obtained from the sensors was considered to calculate the R-index.

The increase in energy consumption leads to a great expansion of the world energy generation with various energy sources, among them renewable sources are increasingly highlighted. Wind energy is one of the sources that has been gaining more and more spotlight in the hall of generators, which consequently brings more studies on the structural reliability of wind towers that can cause undesirable levels of vibrations that can compromise the safety and reliability of the structure. This work proposes the application of a structural control system, in a way of an hybrid mass damper (HMD), installed in a wind tower, subjected to seismic and wind loads. Two models are analyzed: considering or not the flapwise effect on the blades. Furthermore, it is proposed to compare the system response for different situations: system without control, passive control, active control and hybrid controllers (Instantaneous Optimal Control (IOC), Proportional Integral Derivative (PID) and Classic Optimum (LQR)). Numerical-computational simulations were performed using the software MAPLESOFT, MATLAB with toolbox Simulink. The numerical results obtained were analyzed and compared with each other, and it was observed that the IOC was the better in reducing the dynamic response of the tower. Although the results of this work are based on simplified models with preliminary results, they may become a basis for more advanced studies in sophisticated models and full-scale applications.