https://repositorio.unifei.edu.br/jspui/handle/123456789/88 2026-06-13T12:14:55Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4440 Otimização via simulação aplicada à logística reversa The growth of waste electrical and electronic equipment (WEEE) poses economic, environmental, and social challenges to the planning of reverse logistics (RL). This study proposes and applies a Simulation-based Optimization (OvS) approach to support vehicle routing and fleet allocation in a Heterogeneous Fleet Vehicle Routing Problem (HFVRP), balancing cost, CO₂ emissions, and collection volume. The method integrates: (i) data preparation (distance matrices, demands, and costs, as well as vehicle characteristics); (ii) generation of solutions by a multi-objective Genetic Algorithm (GA); and (iii) stochastic evaluation through discrete-event simulation (FlexSim), without re-optimization. The social dimension was operationalized exclusively as the total collected quantity (kg) and service coverage, with an additional link to “perishable food”: for every kilogram of waste collected, one kilogram of perishable food would be donated to charitable organizations. A total of 20 scenarios from the GA’s non-dominated frontier were evaluated. In Case 1, which involved municipalities of the Metropolitan Region of São Paulo, one scenario (9) proved invalid during simulation and was excluded from the final comparison. Among the valid ones, informative extremes were observed: the lowest cost was R$ 626.53 (Scenarios 13 and 14), with 78.01 kg CO₂ and 7,366.74 kg collected; the lowest emissions were 74.24 kg CO₂ (Scenarios 8 and 10), both with R$ 631.38 and 7,366.74 kg collected; and the largest collection reached 15,979.03 kg (Scenario 20), with a cost of R$ 2,137.76 and 270.21 kg CO₂. In the weighted sum analysis (min–max normalization), Scenario 20 stood out when emissions and collection were jointly prioritized, whereas Scenario 10 emerged as a balanced solution (low cost, minimum emissions, and intermediate collection). In Case 2, designed with distinct fleet parameters, capacities, and distance matrices, the goal was to evaluate the robustness and scalability of the model. The results confirmed that the tool preserved the consistency of the trade-offs identified in the first case, adapting to alternative operational conditions without loss of coherence. The comparative analysis demonstrated that the method is applicable across diverse operational realities, thereby expanding its practical potential in reverse logistics. It is concluded that OvS combined with a multi-objective GA responds positively to the problem: it filters infeasible solutions, makes trade-offs explicit, and delivers an auditable portfolio of alternatives for WEEE reverse logistics, aligning economic, environmental, and service coverage goals. The computational tool developed constitutes a replicable basis for practical adoption and for future extensions. Tese 2025-09-30T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4439 Modelo de referência para desenvolvimento de produtos no setor de embalagens plásticas com foco na economia circular The vast majority of companies currently operate within a linear economy framework, where production, consumption, and disposal constitute the fundamental pillars of their business models. This traditional system frequently overlooks resource regeneration. Conversely, the circular economy emerges as an approach that challenges this paradigm by prioritizing sustainability, waste reduction, and the retention of products, materials, and resources in use for as long as possible. Facing this transition toward a circular economy, companies are challenged to redesign their product development processes, as products must be "born circular." This challenge becomes particularly relevant in the plastic packaging sector, which is characterized by high consumption of virgin materials, short functional product lifespans, and significant environmental impacts associated with improper disposal. Although various industrial sectors present specific product development process models, many of these frameworks still do not systematically integrate Circular Economy principles. In this context, this thesis proposes and validates a reference model for plastic packaging development focused on the circular economy, structured around Cooper’s Stage-Gate logic and integrated with Circular Economy practices, tools, and criteria throughout the Product Development Process (PDP). The model operationalizes circularity within the PDP by incorporating decisions related to material reduction, the use of post-consumer recycled (PCR) content, design for recycling, reuse, disassembly, traceability, reverse logistics, and post-launch indicators. The development of the model was grounded in a comprehensive study of circular economy principles and product development practices. To validate its suitability and applicability, a case study methodology was adopted, analyzing two companies within the plastic packaging sector selected based on predefined criteria to ensure segment representativeness. Data collection was conducted through a structured questionnaire, specifically designed to capture information regarding circular economy practices across the different stages of the product development process. The cross-case analysis allowed for an assessment of the degree to which circular economy principles are incorporated within the studied companies, identifying convergences, limitations, and opportunities for improvement, as well as verifying the adherence of the proposed model to the analyzed industrial context. The results demonstrate that circularity cannot be integrated late or in an ad-hoc manner; rather, it must be conceived from the early stages of development. As its main scientific and applied contribution, this thesis presents a validated reference model for the development of circular plastic packaging, helping to bridge the gap between the conceptual principles of the Circular Economy and their practical operationalization within the Product Development Process. Tese 2026-05-04T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4432 Influência da evolução de fases nas propriedades dielétricas de cerâmicas de CaCu3Ti4O12 sintetizadas em distintas atmosferas Dielectric ceramics based on CaCu3Ti4O12 (CCTO) are promising for energy storage devices due to their colossal dielectric constant values (> 104). This intriguing property results from the combination of intrinsic contributors, such as crystalline defects, and extrinsic contributors, such as the microstructure formed by semiconducting grains and electrically insulating grain boundaries. These contributions are extremely dependent on the synthesis and processing methodology of CCTO ceramics, as well as on the atmospheres used during their production, since they affect microstructural aspects, such as grain sizes, presence and distribution of secondary phases, and structural parameters such as oxygen vacancy formation. Thus, this work investigated the influence of crystalline defects and microstructure on the dielectric properties of CCTO ceramics. For this purpose, ceramics with stoichiometric variations, given by CaxCu3,0Ti4,0O12+δ (x = 1.0 or 1.1), were produced in distinct atmospheres. Ceramic powders were synthesized using the coprecipitation method, followed by the calcination step, performed for 6 hours at 850 °C, in atmospheric air or pure oxygen. Disk-shaped samples were sintered at two different temperatures, 1050 or 1100 °C, with a 2-hour dwell at the same atmospheres used during calcination. Subsequently, selected ceramics were subjected to heat treatment (post sintering) in pure helium atmosphere at 650 °C for 15 minutes, to evaluate the influence of this atmosphere on dielectric properties. Differential thermal analyses and thermogravimetric analyses allowed identification of the thermal processes of phase formation and decomposition. Structural analyses performed by X-ray diffraction on the calcined powders and sintered ceramics made it possible to evaluate the evolution of CCTO, CuO, TiO2 e CaTiO3 phase formation, quantified using the Rietveld method. Using scanning electron microscopy, micrographs of ceramic powders and fractured surfaces of sintered samples were obtained, allowing determination of the particle and grain size distributions, respectively. X-ray photoelectron spectroscopy (XPS) enabled identification of multiple valence states for Cu and Ti ions, correlating them with oxygen vacancy formation as a function of the atmospheres used during sample preparation. Positron annihilation lifetime spectroscopy (PALS) provided direct evidence of the presence of oxygen vacancy-type defects and the existence of subgrains within CCTO grains. Using impedance spectroscopy in the range of 20.0 Hz to 5.0 MHz and temperatures between 20 and 200 °C, values of dielectric constant (εᵣ) and loss factor (tanδ) were determined, as well as complex resistivity plots (ρ' × −ρ'') and electric modulus (M' × M''), and the equivalent circuits that allowed identification of three microstructural constituents, associated with grains, subgrain boundaries, and grain boundaries containing deep trap states. The activation energies calculated for samples without heat treatment after sintering varied between 0.316–0.769 eV for subgrains, 0.496–0.666 eV for grain boundaries, and 0.415–0.752 eV for deep trap states. The Ca1,1Cu3,0Ti4,0O12 sample, calcined at 850 °C and sintered at 1100 °C in oxygen, exhibited the highest dielectric constant value, 𝜀𝑟′ = 39,5×103, with tanδ = 0,23, at 1 kHz. The heat treatment in helium resulted in a reduction of 𝜀𝑟′ values and resistivities of the three identified microstructural constituents, attributed to additional oxygen vacancy formation, partial reduction of cations (Cu2⁺ → Cu⁺; Ti4+ → Ti3⁺), and structural reorganization which generated subgrain boundaries, promoting a decrease in Maxwell-Wagner interfacial polarization. The results demonstrate that, in addition to stoichiometric manipulation, atmospheric control during sintering and subsequent heat treatment is viable and fundamental for defect engineering and optimization of CCTO dielectric properties. Tese 2025-02-26T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4431 Avaliação experimental dos efeitos da pressão e da presença de gases na deposição de parafinas de um petróleo do pré-sal brasileiro The growing global demand for energy and fossil fuels highlights the challenge of balancing energy efficiency with environmental concerns. Petroleum, in addition to being a primary energy source, plays a crucial role in the production of industrial feedstocks. Global investments in deepwater production systems have increased, posing significant challenges due to the extreme operating conditions involved, such as high pressures and low temperatures. The discovery of reserves in deep and ultra-deep waters has introduced additional technological challenges, including long tie-backs and high gas–oil ratios, particularly in the exploitation of Brazilian pre-salt fields. Production under these conditions faces the issue of undesirable deposit formation, mainly paraffin waxes, which can compromise operational efficiency and safety. This study, developed as part of an R&D project in partnership between UNIFEI and Petrobras, aims to characterize, analyze, and propose solutions for paraffin deposition during oil production and gas reinjection in deepwater wells. Experimental tests were conducted to investigate the mechanisms of deposit formation using Brazilian pre-salt crude oil and to develop chemical solvent-based cleaning techniques. Two deposition loops were developed: one operating at high flow rate and low pressure, and another operating at low flow rate and high pressure. These tests were carried out to qualitatively investigate the deposition mechanisms of pre-salt crude oil. In addition to the deposition loop experiments, microcalorimetry analyses were performed using different gases and pressures up to 200 barg, aiming to provide a deeper understanding of the effects of pressure and gas composition (N2, CO2, and natural gas) on the Wax Appearance Temperature (WAT). The low-pressure loop tests indicated a tendency for deposition under both single-phase and two-phase flow conditions, suggesting that the presence of gas in the system can influence the characteristics of the deposits formed. In the high-pressure loop tests, differences were observed in the deposits formed in the presence of N2 and CO2. The microcalorimetry results showed that N2 injection increases the WAT, whereas natural gas injection reduces it. In the case of CO2, different pressure ranges led to either an increase or stabilization of the WAT. Similar behavior was also observed for the crystallization temperature of the second event. Tese 2025-09-19T00:00:00Z