Resumo em Inglês:

Abstract Most of the dams registered on the National Information System on Dam Safety (SNISB of Brazil) do not have enough information to assess whether they fit into the National Dam Safety Policy (PNSB), or to assess their safety conditions. According to the National Agency of Waters (ANA, 2021b), there are currently 122 dams with some important structural problems indicated by their inspectors in 23 states. Therefore, this article proposes a methodology for identifying faults in dam safety activities. The method applies to all types of existing dams. The proposed methodology comprises ten stages that, according to the progress of the steps, are defined by three levels of completeness of the information. Tables were developed with the objective of being a verification guide for these ten stages. This research applied the proposed methodology to two dams in Paraná, Brazil. The first is the Iraí dam, located in the metropolitan region of Curitiba, and the second is the Jordan River Derivation dam, located in Reserva do Iguaçu. The example of the Iraí dam could complete all stages of the proposed methodology. For the Jordan River Derivation dam, stages 1 to 5 of the proposed methodology were carried out. The application of the proposed methodology intends to become a useful tool, especially for inspectors, aiming at a more effective registration process, accelerating the completion of the SNISB.

Resumo em Inglês:

Abstract Federal higher education institutions in Brazil have particularities in terms of construction, geographical location, use of buildings, organizational structures and allocation of budgetary resources. These characteristics make managing the Fire Protection System a significant challenge, requiring an even higher level of attention and commitment. This article aims to present data describing the current context of Fire Protection and Fire Fighting System management at Federal higher education institutions in Brazil (Federal universities and institutes). The data collection was a survey, in which 87 employees, representing 69 institutions, occupying the positions of Occupational Safety Engineer or Technician took part. Among the results, the following stand out: 51% of the institutions do not have a Fire Protection System Management Plan and 32% are in the process of creating one. All institutions inspect and maintain fire extinguishers; only a minority monitor other equipment. Operational routines are weakened by a lack of management (35%), financial resources (31%) and technical staff to carry out the service (24%). Only 9% of the institutions have a Fire Department Inspection Certificate for all their buildings and 5% have an active fire department in all their buildings. Only 9% of institutions have a Fire Department Inspection Certificate for all buildings and 5% have an active fire department in all buildings. The management of the Fire Protection System in Federal higher education institutions in Brazil faces significant challenges, including a lack of management plans, insufficient control of devices and limited resources, resulting in low compliance with fire safety regulations.

Resumo em Inglês:

Abstract This study shows the usefulness of borehole geophysical logging of density in the identification of coal seams, in relation to other lithologies present in a coal deposit located in the south of Brazil. Four drillholes were studied. The geological descriptions of the core samples recovered from these holes were the main information used as a control parameter in comparison with the geophysical logs. A threshold of density (2.0 g/cm3) was established in the gamma-gamma log analysis for identifying the coal seams with economic value. Also due to the economic and operational aspects related to the coal industry, the coal seams must be at least 0.4 meters thick. Once the coal seams were identified by density logs, a verification of the accuracy in the determination of the thicknesses and densities of the coal seams was performed. The coal seam thicknesses and densities determined by borehole logging were close to the observed values in the borehole core samples. As a result of the comparison between the geological and density log data, an average value difference of 0.03 m and -0.01 g/cm3 was reached for thickness and density, respectively. Due to the results and valuable information obtained, it was also possible to indicate and determine which areas of the deposit should be mined in relation to the drillholes studied and threshold parameters established. In conclusion, the importance of this evaluation is emphasized, mainly with respect to the thickness of the coal seams, which aids in the development of effective mine planning.

Resumo em Inglês:

Abstract This study evaluated the mechanical properties and the chemical and thermal characteristics of low-density polyethylene (LDPE) nanocomposites reinforced with graphene oxide for manufacturing via 3D printing. LDPE nanocomposites with different graphene oxide (GO) loadings (0.5% and 1.5%) were processed by a single-screw extruder. To characterize the pre-injected material, Fourier transform infrared spectroscopy (FTIR) and thermal characterization with thermogravimetry (TGA) were used. The injected material was also characterized with mechanical impact and traction tests. The results showed that incorporating GO into the polymeric matrix added hydroxyl groups to the matrix structure, with a 39.13% increase in Young's modulus for LDPE-1.5%wtGO samples. Mechanical tests of 3D printed samples showed that, with an increase in the amount of GO in the polymer matrix, the composite loses ductility, enabling its use in 3D printing technologies and thus encouraging new studies on printed materials for various applications.

Resumo em Inglês:

Abstract The transport capacity of the slurry pipelines is related to the internal roughness of the pipe. Thus, the application of corrosion protection methods is of fundamental importance, both in the operational phase and in times of temporary shutdown. In addition, corrosion also affects the service life of the duct. The studied pipeline was hibernated with nitrogen using the ABNT NBR 15280-2 standard as a reference and remained hibernated for 3.5 years. Chemical, mineralogical, and microstructural analyses were carried out on samples of materials removed from the pipeline interior during the hibernation period. The most striking phase found was magnetite, with botrioidal morphology, formed by the oxidation of steel in the pipeline. After reactivation, the pipeline was inspected by smart pigs with ultrasound and MFL technologies. It was found that the corroded regions are more concentrated in the initial kilometers of the sections, where important depths of corrosion were also observed, as well as higher rates of corrosion and erosion, which show the influence of the operational phase in the development of the pipeline corrosive process and wear. Thus, the application of the nitrogen hibernation process in long-distance pipelines proved to be feasible for long periods of time. However, improvements are suggested in this article to make the process more robust.

Resumo em Inglês:

Abstract When processed conventionally, aluminum-bronze alloys with high mechanical strength require machining after the raw state of fusion, and the waste (chips), if not reused, can cause problems for the environment and costs for the company. Therefore, this article proposes an alternative for recycling aluminum bronze through the new route via Powder Metallurgy (PM), analyzing the resulting microstructure. This study compares the microstructures of the aluminum bronze derived from extraction (the samples received - SR) and the state after the powder metallurgy (PM) process with the addition of vanadium carbides (VC). The study also analyzes the distribution of VC in the microstructure of the PM composite as well as the influence of the TQ30 heat treatment on this composite. For the PM process, aluminum alloy and bronze chips were ground together with vanadium carbide (VC) in a high-energy mill for 50 hours. The powders obtained were pressed uniaxially (400 MPa) to achieve good compaction. The samples were then sintered (900°C/lh), water quenched (900°C/2h), and subjected to treatment according to the TQ30 standard, which, in addition to the previous treatments, also includes tempering at 500°C for 2 hours (ASTM B150/B150M-12 standard). The microstructure observed in the SR samples was martensitic (in needles), with secondary phases dispersed in the matrix. On the other hand, the microstructure of the PM samples showed equiaxed grains of the alpha phase (a), as well as the secondary phases kapa (k) and beta line (β1), in contrast to the needle-shaped microstructure of the conventional melting process.

Resumo em Inglês:

Abstract Polyvinylidene fluoride (PVDF) is a versatile and low-cost polymer with high biocompatibility, mechanical strength, chemical resistance, thermal stability, and ferroelectricity. This material has been widely used in many applications, ranging from membranes to electronic devices. In this study, self-supporting, flexible, and lightweight PVDF films were prepared by an evaporation route using a low-toxicity solvent (dimethyl sulfoxide – DMSO). Graphene oxide (GO) and anatase titania (TiO2) were incorporated into the PVDF after preparing DMSO-based suspensions of these materials. The prepared materials were examined in terms of their structural, electrical, and wetting properties before and after exposure to near ultraviolet (UV-A) light. Substantial structural changes took place after incorporating GO and TiO2 into PVDF. Such modifications were accompanied by dramatic changes in the wetting and electrical properties of the PVDF. UV-A light caused the formation of surface defects on PVDF and GO films. In addition, it promoted the photoreduction of GO into reduced graphene oxide (rGO). Composites containing TiO2 showed high resistance to UV-A light, probably because titania particles absorb the incoming photons and shield the polymer matrix. This study provides new insights into the synthesis and characterization of PVDF/TiO2/GO composite films, which may be useful for many applications, including flexible electronics, solar cells, and biomedical devices.

Resumo em Inglês:

Abstract Mineral deposits have shown decreasing ore grade and increasing complexity, which has led mining projects to experience increased capital and operating costs. Preconcentration is an alternative to minimize such costs. Notwithstanding the resulting rise in ore grade and reduction in feed mass, the generated tailings may contain significant amounts of the material of interest. In order to improve the mineral liberation at this stage, selective comminution proposes to explore different comminution mechanisms. This investigation compared three different crushing methods (jaw crusher, impact crusher, and high-pressure roller mill) for three different types of ores and the response of their products to pre-concentration, using a gravity method that was evaluated through heavy-liquid separation of the -6.35+3.35 mm crushed fraction. This fraction represents approximately 15% of the total sample, and is used as an indication of the gangue rejection potential for the -12+1.18 mm fraction. Copper and polymetallic ores showed good pre-concentration results for this size range at laboratory scale, with metallurgical recoveries greater than 90% and a rejection of over 20% of mass. Iron ore showed a 97% metallurgical recovery and 10% mass rejection. The impact crusher proved to be the best option for selective comminution for the polymetallic ore, with the highest metallurgical recovery. Finally, no significant differences were observed when using any of the three crushing mechanisms for the copper and iron ore.

Resumo em Inglês:

Abstract Process simulations can be used to improve grinding circuit performance, which efficiently reduces operating costs. The population balance model (PBM) is widely accepted for grinding modeling because it can reproduce breakage events in tumbling mills, as described by Austin et al. (1984). In this study, a pseudo-dynamic model is introduced, integrating the PBM with the Monte Carlo Method to stochastically simulate variables in an industrial grinding circuit. This integrated approach enabled circuit simulations over a period of 2 hours, representing the operational variables as seen in historical data. Model validation showed a correlation of 0.74 in the product size distribution when comparing simulated outcomes with the original population.

Resumo em Inglês:

Abstract Since the open-pit precedence-constrained production scheduling problem is an NP-hard problem, solving it is always a challenging task, especially from a long-term perspective because a mineral deposit containing millions of blocks would require several million precedence arcs as constraints, making the solution time grow exponentially and making a direct approach unfeasible. Therefore, different strategies have been employed since the 1960s to reduce the size of this problem, such as determining the ultimate pit limit, subdividing it into phases, segmenting the production scheduling problem into long-, mid-, and short-term plans, as well as aggregating blocks into clusters, thus significantly reducing the number of precedence arcs. Different modeling and clustering strategies have already been employed in an attempt to reduce the size of the mine sequencing problem, such as layer modeling, re-blocking, bench-phase clustering, or polygon (mining cut) clustering based on a similarity function. The mining cut clustering problem has been solved lately by machine learning and heuristics techniques, and this approach can also introduce operational constraints to the mine sequencing problem, such as equipment size, minimum pit width, and preferential mining direction. In this study, we propose a mining cut clustering model based on Mixed Integer Linear Programming (MILP). Then we solve it by an exact approach and by Constraint Programming (CP), analyzing the strengths and weaknesses of the Constraint Optimization Problem (COP) and Constraint Satisfaction Problem (CSP) techniques. Numerical experiments were carried out on the Bench 15 of the Newmanl dataset, demonstrating the superiority of the COP approach.

Resumo em Inglês:

Abstract Improving a technical work environment encourages creativity and enhances research efforts. The conception of a modular ventilation laboratory aims at free construction and assembly of the air circuit in different shapes, sizes, and operational variations. The modules allow the development of academic experiences, automatic data acquisition from sensors, data analysis, and verification of concepts related to ventilation in underground mines. The modular ventilation laboratory uses a teaching methodology based on a playful and low-cost way to teach engineering, mainly underground mine ventilation. The aim of this work is essentially to propose the creation of a modular underground mine ventilation laboratory to facilitate engineering teaching and allow the simulation of real situations. The Plan-Do-Check-Act (PDCA) methodology was used to develop a framework for building the modular educational ventilation laboratory. This methodology encompasses project planning and studying, applying the Ventsim® software, and the design of a teaching laboratory with sensors and microcontrollers using the Internet of Things (IoT). The results involve the construction of a physical project with PVC (polyvinyl chloride) pipes and connections and electronic circuits. The project presents the main parameters monitored in underground mines and foresees the simulation of scenarios, aiming to facilitate an understanding of the concepts of fluid mechanics and mining ventilation. The conclusions indicate that using simulation in pedagogical practices develops several activities that contribute to innumerable learning and expands the network of constructive meanings as a learning strategy.

Resumo em Inglês:

Abstract The modeling of mineral deposits has been improved over the years with the incorporation of mineralogical and metallurgical information obtained from drilling samples that make up the pillars for the construction of resource models. However, sampling data is being made available in large quantities, causing current databases to grow exponentially. The use of machine learning (ML) algorithms has been applied to deal with multidimensional data problems. Principal component analysis (PCA) is a multivariate analysis (MA) technique whose aim is to reduce the dimension of multivariate data. Studies show that results obtained with the reduction of variables were satisfactory in different areas of activity. The purpose of this article is to test variable selection criteria using PCA for geometallurgical data and to check the feasibility of the technique for simplifying variable types and defining typological domains.