Repositório UNIFEIO Repositório captura, armazena, indexa, preserva e distibui material de pesquisa em formato digital.http://repositorio.unifei.edu.br:80/xmlui2024-03-19T07:11:16Z2024-03-19T07:11:16ZAquisição e validação de sinal de ruído eletroquímicohttps://repositorio.unifei.edu.br/jspui/handle/123456789/31732024-02-05T10:36:02Z2022-02-17T00:00:00ZAquisição e validação de sinal de ruído eletroquímico
Corrosion is a global problem, which implies costs in industrialized countries of up to
4.5% of GDP, with either economic, but also social and environmental impacts. In the
case of Brazil, the waste of water supply networks due to leaks loss is quite significant
and much of it is caused by network degradation, indicating that corrosion control
should be promoted whenever possible. This study proposes a corrosion monitoring
system, in system subject to the use of inhibitor, with the approach of passive
technique for monitoring corrosion by electrochemical noise (EN), in which the
classification of events in a corrosion sensor by EN is part of methodological study for
structural integrity (or “health”) monitoring system (SHM). Due to very dynamic and
stochastic nature of the signal, this study and analysis of EN measurements (ENM)
considers numerical and graphic characteristics of two corrosion systems both in saline
aqueous solution: carbon steel and stainless steel. These experiments are repeated for
accumulating data, which allow the generation of several graphs in time and frequency
domains, from which at least one characteristic is extracted, which has a good
correlation with data from corrosion processes. Then, based on a supervised machine
learning system, the training data allows the model to be calibrated. From the test
data, the correctness rate of the model above 50% is verified.
Dissertação
2022-02-17T00:00:00ZElaboração de um modelo de tomada de decisões contábeis em uma instituição federal de ensino superior através da perspectiva do CRISP-DMhttps://repositorio.unifei.edu.br/jspui/handle/123456789/40212024-03-18T16:42:15Z2023-12-11T00:00:00ZElaboração de um modelo de tomada de decisões contábeis em uma instituição federal de ensino superior através da perspectiva do CRISP-DM
With the regulation of access to information in Brazil, through the Access to Information
Law (LAI), procedures were established for transparency in public administration, as a
way of ensuring the fundamental rights of citizens. In addition to federal legislation, the
Brazilian Accounting Standard presents the preparation of accounting reports as
mandatory. Organizations, especially those of a public nature, still have a lack of
working with data, as well as transforming it into information and reports. One of the
ways to obtain better quality information is to seek new technologies and methods
through Information Systems. Business Intelligence (BI) systems are one of the means
that use software tools and contribute to the organization, analysis and dissemination
of data, resulting in various products and reports that facilitate decision making. In this
context, this work aims to develop a model to aid decision-making based on Business
Intelligence, in order to produce a tool to provide accounting reports that help
managers and are available for broad consultation. The research methodology used
was CRISP-DM, which stands out for being applied to business objectives,
establishing a structure for data mining projects and guiding their execution. The result
was applied to the Accounting and Finance Directorate of the Federal University of
Itajubá, covering information relating to the institution's budgetary and financial
execution, with a view to assisting in decision-making by managers in addition to
meeting transparency requirements through the publication of reports on the
institutional website.
Dissertação
2023-12-11T00:00:00ZInverse problems applied to the experimental thermal and hygric analysis of engineering materialshttps://repositorio.unifei.edu.br/jspui/handle/123456789/40202024-03-15T14:10:32Z2024-02-21T00:00:00ZInverse problems applied to the experimental thermal and hygric analysis of engineering materials
Several relevant real-world applications rely on an inverse problem, which involves
recovering unknown causes from observing their effects. This differs from the corresponding
direct problem, whose solution involves predicting effects from a complete description of their
causes. Naturally, inverse problems are more challenging than direct problems because, in
general, they are ill-posed, i.e., the solution either does not exist, is not unique or it does not
depend continuously on the input data. To soften this problematic aspect, applied inverse
modeling requires detailed mathematical-physical modeling and well-designed experiments
since the desired parameters are estimated by comparing calculated data with experimental
measurements.
In this PhD thesis, inverse approach was applied to experimentally investigate three case
studies:
• complementary experiments to simultaneously estimate the parameters describing the
temperature-dependent thermal conductivity and specific heat of 304 austenitic stainless
steel. Parameter estimation takes advantage of additional information provided by two
heat-conducting solids with different geometries. It is an alternative approach to
standard thermal characterization techniques, which are often beyond the reach of many
laboratories.
• one-year on-site measurements to estimate various hygrothermal properties and thus
calibrate the simulation model of a lightweight multilayer wall. A 2D fully coupled heat
and moisture transfer model was used to investigate the in-use response of the panel
junction region, which is critical in terms of airtightness. The results enable an accurate
assessment of building operating conditions by reducing uncertainties in material input
data.
• field data to determine the annual heat conduction flux through a wall assembly in an
occupied house. Inverse modeling accounted for the physical interactions between
outdoor environment and indoor occupancy. The methodology and the findings are
useful to support decision-making on energy performance, as there is a lack of longterm
field monitoring and information on dynamic heat flux related to prefabricated
occupied dwellings.
All the above inverse analyzes were based on evaluating the match between data predicted
by numerical simulations in COMSOL Multiphysics and measurements conveying the physical
behavior of the component under study. Numerical and experimental data were processed and
used for inverse estimation purposes in MATLAB environment. After careful analysis of
sensitivity coefficients, different optimization approaches were used to solve the inverse
problems. Bayesian statistical inference was applied to determine the estimates and
corresponding uncertainties of the thermal properties of 304 stainless steel. The Broyden–
Fletcher–Goldfarb–Shanno (BFGS) algorithm, which determines the descent direction by
preconditioning the gradient with curvature information, was used in the second case study.
The wall heat flux was estimated using the sequential function specification method (SFSM),
which expresses temperature as function of heat flux by means of a first-order Taylor series.
The results show that inverse modeling is a reliable tool for obtaining valuable information
about the hygrothermal mechanisms and parameters involved in applied engineering problems.
Tese
2024-02-21T00:00:00ZAnálise experimental e em CFD de motor diesel alimentado com biocombustíveis adaptáveis à matriz energética brasileira em modo dual fuelhttps://repositorio.unifei.edu.br/jspui/handle/123456789/40192024-03-14T18:57:47Z2024-02-26T00:00:00ZAnálise experimental e em CFD de motor diesel alimentado com biocombustíveis adaptáveis à matriz energética brasileira em modo dual fuel
With the growing energy demand, the rise of stricter environmental regulations, and the large-scale application of electric vehicles far from being a reality, new energy vectors for internal combustion engines have been considered. In this sense, biogas, biomethane, and syngas represent options that deserve some attention, despite not being widely used in Brazilian transportation. In addition to the use of new energy sources, innovative techniques – such as the dual fuel mode – can improve even further the potential of different fuels, such as HVO (hydrotreated vegetable oil), in order to optimize the engine operation in terms of efficiency and pollutants emissions. Therefore, the present thesis proposes experimental and numerical analyses in a single-cylinder diesel engine operating in dual fuel mode with fuels adaptable to the Brazilian energy matrix. The potential of theses fuels as partial replacements for diesel was verified, reducing NOx (up to 25.8%) and particulate matter (up to 86%) emissions, associated to a small decrease in thermal (up to 12.5%) and combustion (up to 4.2%) efficiencies. When diesel was replaced by HVO, improvements were observed in both emissions (NOx, CO, CO2, HC and particulate matter) and thermal efficiency. Finally, the combination of gaseous fuels with HVO led to the same trend observed for diesel, but with superior results for efficiency and emissions. In all the studied cases, the ANSYS Forte® CFD model offered additional understanding of experimental results, representing an option for extrapolation of results, optimization, and prediction of engine operation without the need of additional tests.
Tese
2024-02-26T00:00:00Z