Programa de Pós-Graduação em Modelagem e Otimização - PPGMO

URI Permanente desta comunidade

https://repositorio.ufcat.edu.br/handle/tede/26

O Mestrado em Modelagem e Otimização tem um papel essencial no desenvolvimento de novas tecnologias. Atualmente, se faz muito intensamente o uso de modelos matemáticos, simulações avançadas e sofisticados desenvolvimentos computacionais na pesquisa científica em geral. O objetivo do PPGMO é formar profissionais capazes de atuar no desenvolvimento da pesquisa na área de modelagem e otimização, para tratamento de modelos matemáticos e computacionais. Além de proporcionar ao aluno graduado em ciências exatas o aprofundamento do saber na área, que lhe permita alcançar padrão de competência científica ou técnico-profissional e oferecer, dentro da Universidade, ambiente e recursos adequados ao desenvolvimento da investigação científica.

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Abordagem estocástica de máquinas rotativas utilizando os métodos hipercubo latino e caos polinomial
(Universidade Federal de Goiás, 2017-09-15) Queiroz, Layane Rodrigues de Souza; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Santee, Donald Mark; Cavallini Junior, Aldemir Aparecido
Mechanical systems may suffer with uncertainties that can appear from non-precise data and due the dynamic nature of the problem. Different methods have been used to deal with uncertainty propagation, such as the Latin Hypercube sampling and Polynomial Chaos. Latin hypercube allows to obtain the solution of the random process, from sampling using some probability distribution, over the process domain data. In its turn, the polynomial chaos expansion allows to separate the stochastic components from the deterministic ones of the random solution by using orthogonal polynomials in conformity with the probability distribution of the random variables representing uncertainties. In this work, we apply the Latin hypercube and the polynomial chaos in the quantification of uncertainties. In the beginning some simple mechanical systems were considered, for the purpose to validate the methodology and, then, we studied the effects of uncertainties on a rotor supported by hydrodynamic bearings.
Análise analítica e numérica de vigas casteladas com diferentes padrões geométricos
(Universidade Federal de Goiás, 2018-10-22) Melo, Pedro Henrique Pedrosa de; Silva, Wellington Andrade da; http://buscatextual.cnpq.br/buscatextual/ visualizacv.do?id=K4750483A1; Silva, Wellington Andrade da; Borges, Romes Antonio; Ferreira, Maurício Pina
The present paper deals with the main subjects related to castellated steel beams, initially showing a brief review of the history of emergence and use of the world, highlighting the characteristics that favored the growth of use and the difficulties of its use. The main failure modes are characterized, highlighting the analytical procedures available in the literature to circumvent them, in order to propose a calculation procedure for the design. The proposed procedure is evaluated through the experimental result of four surveys. The work also presents numerical modeling, using Finite Element Method (FEM), for beams available in the technical literature, in order to complement the analysis of beam behavior during loading and to verify the validity of the proposed numerical model, mainly in relation to the analysis criteria adopted in the numerical model, such as von Mises stress distribution, isotropic hardening and tensile stress behavior of the steel using the multilinear graph, also available in the technical literature. The validity allows the proposed beams, with Anglo-Saxon geometry, Litzka and Peiner, to have reliability of analysis of the model, and for the proposed loading the Anglo-Saxon beam obtained greater resistance, mainly due to the small distance between the holes and also the lowest overall width of the aperture. The results of the numerical models, via MEF, showed good precision when compared to the experimental results, showing that MEF is an extremely useful tool for nonlinear analysis, provided the model is properly calibrated. Another important result is the resistance values presented by the proposed analytical procedure, which presents a good approximation to the actual values of the experiment and also the resistance values obtained in the proposed numerical models, and can be adopted for the practical dimensioning of these beams.
Análise de estabilidade em sistemas mecânicos não lineares com vistas a atenuação de vibrações
(Universidade Federal de Goiás, 2016-03-09) Purcina, Alcione Borges; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Lima, Antônio Marcos Gonçalves de; Abud, Celso Vieira
In the last years, there is a growing interest in the study of nonlinear phenomena that because with the modernization of the structures and employment of innovative and more flexible materials, the nonlinearities become more evident. In that sense, this work aims to study the behavior of a mechanical system with two degrees of freedom with non-linear characteristics in primary resonance. The structure consists of the main system connected to a secondary system to act as a Nonlinear Dynamic Vibration Absorber, which partially or fully absorbs the vibrational energy of the system. The numerical solutions of the problem are obtained using the Runge-Kutta methods of 4th order and approximate analytical solutions are obtained using the Multiple Scales Method, and then it turns out how close can be closer to the numerical solutions. Through the mentioned disturbance method, too, it is determined the answers for the ordinary differential equations of the first order, which describe the modulation amplitudes and phases. Thus, the solution in steady state and the stability are studied using the frequency response. Furthermore, the behavior of the main system and the absorber are investigated through numerical simulations, such as responses in the time domain, phase planes and Poincaré map; which show that the system displays periodic movements, quasi-periodic and chaotic.
Análise estática e dinâmica de pórticos planos com o uso da formulação corrotacional
(Universidade Federal de Goiás, 2018-10-22) Cunha, João Paulo Favoretto Braz da; Silva, Wellington Andrade da; http://lattes.cnpq.br/2449347153075493; Silva, Wellington Andrade da; Borges, Romes Antônio; Ribeiro, Paulo Marcelo Vieira
This research presents a survey of the corrotational kinematic description applied to the Finite Element Method for 2D beam element, based on the Euler-Benoulli beam hypothesis, with the purpose to handle the effects of geometric non-linearity in the behavior of structures. In order to complete this survey two Matlab\textregistered programs were implemented in the finite element method based on the kinematic description presented in this research. The first one was to static analysis, denominated PPNLG, and the second one to dynamic analysis, denominated PPNLD . In relation of the field of static analysis, the method of load displacement control was the cylindrical arch length method. To the dynamic analysis, the method used to solve the systems of nonlinear differential equations was the implicit direct integration method of Newmark. Both programs were successfully validated when comparing the results obtained in numerical examples with the results obtained by other bibliographies.
Análise estrutural estática por elementos finitos de um chassi veicular tipo spaceframe
(Universidade Federal de Goiás, 2016-08-25) Pereira, Clezidan Núcio; Moura Júnior, José Reis Vieira de; http://lattes.cnpq.br/2479225716217997; Stoppa, Marcelo Henrique; Stoppa, Marcelo Henrique; Moura Júnior, José Reis Vieira de; Santee, Donald Mark; Espinosa, José Waldo Martínez
Regarded as the main subsystem of a vehicle, the chassis are the link between the other subsystems and must also support multiple static and dynamic loads with stiffness, reliability and security. In this line, this paper presents the development and analysis of a vehicle three-dimensional structure spaceframe type, due to the complexity of the structure were used computational tooling in order to simulate the behavior of statically tubular structure, with the main objective to certify the reliability of the developed project, ensuring safety to drivers. The structure, existing, was modeled in CAD through SOLIDWORKS software, and their simulations were performed using the finite element method via commercial software ANSYS®. The simulationmethodology had the precise definition of loads and displacement constraints to the model in order to make the most plausible model possible. Were then performed computational analysis of rollover and frontal impact in the model (80 km/h e 60 km/h). Through the simulations, it was possible analyze the displacements arising from the critical situations in which the vehicle was submitted are consistent with what is recommended by regulating rules and bibliographies, with this in view that the chassis developed empirically and computationally simulated showed satisfactory results as its reliability and safety, are not required increment bars or modifying the system geometry.
Análise numérica de métodos empíricos do estudo da condutividade hidráulica
(Universidade Federal de Goiás, 2018-09-28) Gonçalves Filho, José Carlos Campos; Rabelo, Marcos Napoleão; http://lattes.cnpq.br/0067281135180613; Rabelo, Marcos Napoleão; Santos Filho, Tercio Alberto dos; Santee, Donald Mark
In the context of Agronomic and Environmental Sciences, the hydraulic conductivity K (µ) as a function of the humidity (µ) and granulometry, is especially important for the study and solution of practical problems related to irrigation, drainage , leaching of nutrients and pollutants, slope stability, problems related to soil compaction in general. Studies will be carried out that stipulate the hydraulic conductivity K (µ) from the particle size distribution and moisture content for certain types of soil, with the particle diameter as the main parameter to obtain the same. One of the advantages in this methodology is the reduction of laboratorial costs and the reduced time when compared to tests to obtain these physical indexes. The state of the art in empirical validation has produced numerical models for simulation description of physical indices. Using experimental methodologies, we will use these models for the validation and subsequent analysis of results for soils obtained at UFCat. The first part of the work will be devoted to the study of statistical models, which relate the behavior of the hydraulic coef cient with the soil granulometry. For this part of the work, the main referencewill be the article (SALARASHAYERI; SIOSEMARDE, 2012). The models that will be used in this dissertation were obtained in (SALARASHAYERI; SIOSEMARDE, 2012), where the authors, through 25 samples of sandy soil extracted characteristics of the hydraulic conductivity. In the present case, laboratory tests have shown that the characteristic of the analyzed soil approaches a clayey behavior see (GONçALVES-FILHO et al., 2017b), (GONçALVES-FILHO et al., 2017a). To overcome this problem we will use the graphs generated from experimental analyzes made by means of humidity sensors, to calibrate statistical models. In the second part of the work, a study will be done, through models that relate the hydraulic coef cient to the soil moisture. For this part the reference (GENUCHTEN, 1980) will be used. In (GENUCHTEN, 1980), analytical models describing the relationship between hydraulic coefIcient, moisture and piezometric level were obtained. The theoretical models will be validated by comparing the theoretical curves and the experimental data acquired through sensors. As a complementary part of the work, numerical simulations will be done to analyze the behavior of the hydraulic coefIcient, with the different models approached.
Aplicação de uma abordagem robusta no problema de localização de ambulâncias com estudo de caso na cidade de Catalão - Goiás
(Universidade Federal de Goiás, 2016-07-05) Marques, Raina Ribeiro; Queiroz, Thiago Alves de; http://lattes.cnpq.br/8041183668335400; Queiroz, Thiago Alves de; Camargo, Victor Claudio Bento de; Borges, Romes Antônio
The robust optimization techniques can be used in problems subject to uncertainty in order to obtain robust solutions, that is, solutions that are less sensitive to the problem variations. Problems such as the facility location, specifically, the location of ambulances, have uncertainty in your data. Thus, an integer linear programming model for allocation of ambulances and stations is investigated considering that the service time is an uncertainty parameter, since this parameter is influenced by the nature of the call, traffic, or distance traveled, for example. It is proposed a model considering the application of a robust approach that controls the amount of uncertainty parameters related with the service time. A case study with real data provided by the fire department of the city of Catalão, Goiás, is performed on the models and the results show that the number of ambulances is greater than the current need, as pointed by the model without uncertainty. However, the results on the robust model show that the real number of ambulances in the city is able to serve a limited amount of demand, so for a maximum variation of the demand, the number of available ambulances are not able to support it. The model had worked well for the first two scenarios among the three ones tested, in which for the last scenario the model was quite sensitive to changes on the uncertainty parameters.
Aplicação de verificação formal em um sistema de segurança veicular
(Universidade Federal de Goiás, 2017-03-07) Silva, Nayara de Souza; Stoppa, Marcelo Henrique; http://lattes.cnpq.br/1532505326645535; Costa, Vaston Gonçalves da; http://lattes.cnpq.br/5192533875584788; Costa, Vaston Gonçalves da; http://lattes.cnpq.br/5192533875584788; Galdino, André Luiz; Rabelo, Marcos Napoleão
The process of developing computer systems takes into account many stages, in which some are more necessary than others, depending on the purpose of the application. The implementation stage is always necessary, indisputably. Sometimes the requirements analysis and testing phases are neglected. And, generally, the part of formal verification correctness is intended for few applications. The use of model checkers has been exploited in the task of validating a behavioral specification in its appropriate level of abstraction, notably specifications validation of critical systems, especially when they involve the preservation of human life, when the existence of errors entails huge financial loss or when deals with information security. Therefore, it proposes to apply formal verification techniques in the validation of the vehicular safety system Avoiding Doored System, considered as critical, in order to verify if the implemented system faithfully meets the requirements for it proposed. For that, it was used as a tool to verify its correctness the Specification and Verification System - PVS, detailing and documenting all the steps employed in the process of specification and formal verification. K
Aplicação dos mapas auto-organizáveis associado ao monitoramento da integridade estrutural baseado na impedância eletromecânica
(Universidade Federal de Goiás, 2018-07-04) Durval, Michael dos Santos; Mora Júnior, José dos Reis Vieira de; http://lattes.cnpq.br/2479225716217997; Tsuruta, Karina Mayumi; Stoppa, Marcelo Henrique; Moura Júnior, José dos Reis Vieira de
Structural Health Monitoring (SHM) is a very cost-effective technique to reduce costs, increase life-cycle, and improve the performance of engineering structures. The impedancebased methodology uses the electromechanical behavior of piezoelectric materials (PZTs) to detect structural anomalies and damages. This technique uses high frequencies and excites the local modes, thus providing the monitoring of any change of the structural mechanical impedance in the region of influence of PZT. From the variation of the impedance signals, it can be concluded whether or not there is a damage. Artificial neural networks (RNA) are part of a broad concept called artificial systems. The foundation of neural networks is associated with the functioning of the human brain, which after training has the ability to perform associations. This science has great applicability in the solution of artificial intelligence problems, through the modeling of systems that use connections that make it possible to simulate the human nervous system. This work uses Kohonen’s self-organizing maps (SOM) associated to SHM based on electromechanical impedance for the detection and classification of damages in an aluminum beam. Based on the system under analysis, the network was trained to five different failure and severity positions. Through the neural network model of self-organizing maps, the network provided 30 maps as answers to the training and learning process. With this, it was realized qualitatively based on the concentration of energy of the maps that the grouping and classification of the different conditions of damages in which the engineering structure was submitted, happened with success. In order to establish a quantitative analysis proving the potential of the SOM network, the Hamming distance formula was applied, in which the results confirmed its accuracy.
Aplicação dos mecanismos de locomoção do tipo Jansen em cadeiras de rodas
(Universidade Federal de Goiás, 2016-03-09) Borges, José Salviano; Stoppa, Marcelo Henrique; http://lattes.cnpq.br/1532505326645535; Stoppa, Marcelo Henrique; http://lattes.cnpq.br/1532505326645535; Pituba, José Julio de Cerqueira; Moura Júnior, José dos Reis Vieira de
To enlarge the active participation of individuals with disabilities in society, some mechanisms have been developed, such as crustches and wheelchairs. Wheelchairs are widely used, either temporarily or even permanently, allowing greater mobility and independence of the individual. However, the same is subject to the physical limitations of the wheels, requiring regular and hard grouynd to ensure bettermobility. Thus, some studies have suggested repacing the wheels on the legs, since the same part of the evolutionary process allows many terrestrial animals and viable movement to the wheels. The mechanisms with legs given the name of mobile machines. Among the most famous mobile machines are developed by the dutch phisicist Theo Jansen, called by Strandbeest. This study evaluates the repacement of the wheels of wheelchairs, for legs, trying to extend its use in less regular land. Also shown is the pattern of locomotion strcture developed by Jansen and the development of the Jansen similar structure using multiobjective optimizationmethods in order to ensure a new optimum configuration, and obtain a prototype proposed to be coupled in a conventional wheelchair. During the work it is proposed the method of wighted sumwith Pareto, this method related to onedimensionalyzation objectives. It also presents a brief comparison with two other methods –Weihted Sumand Pareto Ordination.
Atividade síncrona em redes complexas: uma abordagem matemática para estudos sobre epilepsia
(Universidade Federal de Goiás, 2021-02-22) Oliveira, Jonas Ferreira de; Abud, Celso Vieira; http://lattes.cnpq.br/5634231159637601; Abud, Celso Vieira; Macau, Elbert Einstein Nehrer; Lobato, Fran Sérgio
Synchronization in complex networks is a phenomenon present in several complex systems, ranging from neurological to electrical and mechanical to social. The most successful archetype in describing the emergence of this collective behavior in complex systems is provided by Kuramoto model. Neurological disorders such as epilepsy can be abstracted mathematically as synchronous activities in complex networks. Epilepsy is a neural disorder related to the intense synchronous neural activities due to the increase of blood flow in the cerebral cortex, causing seizures followed by fainting. Seizures can be prevented by antiepileptic drugs that fend off the emergence of synchrony in neural networks. However, about a third of medicated patients experience seizures again. Thus, the importance of studies on the recognition of synchronous patterns associated with the disorder is justified. This work does not claim to be an ultimate in the modeling of such a complex neural disorder. Therefore, the objective is to investigate which are the most influential areas of the cerebral cortex and how they influence the dynamics of synchronization associated with epilepsy. To this end, a feline's cerebral cortex was modeled as a complex network and, in order to study synchronization, Kuramoto model was used to govern of the dynamics between the areas of the cortex. The Hypertext Induced Topic Search (HITS) algorithm was used to classify pages web, in order to identify the most influential nodes in the feline cerebral cortex network. Metrics concerning the characteristics of the feline neural network and its most influential nodes, were obtained. Regarding the dynamics and measures of global, mesoscopic and microscopic synchrony, results were obtained for a scenario using the original network and two other scenarios, in which it was considered a disturbance, in order to simulate the action of an antiepileptic drug, the disturbance reduced the intensity of connections of a group containing random nodes and the group with nodes chosen by the HITS algorithm by 50%. Finally, it was found that the applied disturbance lagged the global, microscopic and mesoscopic levels of the network.
Avaliação numérica e computacional do efeito de incertezas inerentes a sistemas mecânicos
(Universidade Federal de Goiás, 2016-08-25) Costa, Tatiane Nunes da; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; Cavallini Junior, Aldemir Aparecido; Rabelo, Marcos Napoleão
Most of the time, modern problems of engineering are nonlinear and, may also be subject to certain types of uncertainty that can directly influence in the answers of a particular system. In this sense, the stochastic methods have been thoroughly studied in order to get the best settings for a given project. Out of the stochastic techniques, the Method of Monte Carlo stands out and, especially the Latin Hypercube Sampling (LHS) which is a simpler version of the same. For this type of modeling, the Stochastic Finite Elements Method (SFEM) is becoming more frequently used, given that, an important tool for the discretization of stochastic fields can be given by the Karhunèn-Loève (KL) expansion. In this work, the following three case studies will be used: A discrete system of 2 g.d.l., a continuous system of a coupled beam type both in linear and nonlinear springs and a rotor consisting of axis, bearings and disks. In this sense, the influence of uncertainties in the systems studied will be checked, using for this, the LHS, SFEM and the KL expansion. The stochastic study in question will be used in the construction of the great project for the rotor problem already presented.
Classificação de insetos em milho à granel por meio de análise de vídeos endoscópicos
(Universidade Federal de Goiás, 2016-03-10) Geus, André Reis de; Silva, Sérgio Francisco da; http://lattes.cnpq.br/9061098995683609; Silva, Sérgio Francisco da; http://lattes.cnpq.br/9061098995683609; Rabelo, Marcos Napoleão; Henrique, Marcos Luiz
Insects cause significant losses of stored grains in both quantity and quality. In the scenary, it is of paramount importance an early identification of insects in grains to take control measures. Instead of sampling and visual/laboratory analysis of grains, we propose to carry out the insects identification task automatically, using computational methods to perform endoscopic video analysis. The videos are recorded inside of grains warehouses by an endoscopic camera. As the classification process of moving objects in video rely heavily on precise segmentation of moving objets, we propose a new method of background subtraction and compared their results with the main methods of the literature according to a recent review. The main innovation of the background subtractionmethod rely on the binarization process that uses two thresholds: a global and a local threshold. The binarized results are combined by adding details of the object obtained by the local threshold in the result of the global threshold. Experimental results performed through visual analysis of the segmentation results and using a SVM classifier, suggest that the proposed segmentation method produces more accurate results than the state-of-art background subtraction methods.
Comparação de malhas para problemas de corte e empacotamento
(Universidade Federal de Goiás, 2018-02-22) Cunha, Jéssica Gabriela de Almeida; Queiroz, Thiago Alves de; http://lattes.cnpq.br/8041183668335400; Queiroz, Thiago Alves de; http://lattes.cnpq.br/8041183668335400; Pedrosa, Lehilton Lelis Chaves; Santee, Donald Mark
This work brings the use of grid of points in the resolution of cutting and packing problems that consider rectangular shaped items. The grids can be considered for mathematical programming models and heuristics, and they are independent of the problem. The following grids that are defined by the literature are considered for this work: canonical dissections (also known as normal patterns), reduced raster points, useful numbers, corner points, regular normal patterns, extreme points, and meet-in-the-middle patterns. The objective is to assess the influence of each grid on the resolution of cutting and packing problems, before and after applying reduction procedures, as the one related to update the items size. Theoretical results are obtained from relations of set and size between the grids, showing that the grid of normal patterns and useful numbers are equivalent and, thus, proving formally that the grid of reduced raster points ensures an optimal solution (this result has been formally opened in the literature). In addition, we propose a new procedure to reduce the size of grids. In order to validate the proposed procedure and evaluate the grids, we perform experiments over instances from the literature, where it is possible to observe that the grids of reduced raster points and meet-in-the-middle patterns are the smallest. Experiments were also conducted in a two-dimensional packing problem that uses an integer linear programming model to pack the items in points of a grid. The results indicate that using the reduction procedures it is possible to obtain optimal solutions quicker.
Desenvolvimento de um algoritmo de otimização evolutivo auto-adaptativo para a resolução de problemas de otimização com variáveis mistas
(Universidade Federal de Goiás, 2018-12-10) Carvalho, Camila Campos; Lobato, Fran Sérgio; http://lattes.cnpq.br/7640108116459444; Lobato, Fran Sérgio; Abud, Celso Vieira; Souza, Davi Leonardo de
In last decades, evolutionary algorithm have been received considerable attention in different fields of science and engineering, with emphasis in engineering systems design. Despite at the large number of applications, these algorithms consider that parameters are constant during the search process, which may result in a search less efficient in design space. In addition, realistic problems are more complex in relation to the nature of project variables involved, i.e., these problems may present mixed variables (real (or continuous), integer, binary and discrete). In this contribution, it is proposed a new strategy to update the Firefly Algorithm (FA) parameters, as well as a new methodology to generate candidates. It is also proposed a strategy for the treatment of problems with mixed variables. An analysis of the parametric sensitivity is performed to understand how the choice of the values of each parameter of the FA could influence the method optimization process and still compromise the quality of the solution. The results obtained with the application of proposed methodology in mixed and real problems demonstrate that the performance of FA can be improved, in terms of convergence and computational cost, in relation to canonical algorithm.
Determinação de parâmetros ótimos da equação intensidade, duração e frequência de chuvas utilizando otimização heurística
(Universidade Federal de Goiás, 2020-03-24) Santos Neto, Erivan de Paula; Sarmento, Antover Panazzolo; http://lattes.cnpq.br/4025685702530313; Sarmento, Antover Panazzolo; Rabelo, Marcos Napoleão; Rodrigues, Rafael de Ávila
Considering that the intensity, duration and frequency curves (IDF curves) are scarce and in some cases outdated for the State of Goiás, the present work aims to elaborate an algorithm capable of treating the rainfall data, coming from INMET rain gauges, and, later, through the use of heuristic algorithms, to create a program capable of determining the parameters $K$, $a$, $b$ and $c$ through the rainfall disaggregation method. The probabilistic distribution used was the Gumbel distribution, which was evaluated through the Kolmogorov-Smirnov adherence test. Then, the algorithms: genetic, ant colony, particle swarm, flower pollination and differential evolution were used to determine the parameters. Subsequently, an adjustment test was performed using the adjusted determination coefficient, Wilmott's concordance index, and the confidence coefficient to measure the performance of the proposed models. The results obtained showed that the algorithms are able to solve the problem effectively, with emphasis on the flower pollination algorithm and the differential evolution algorithm, which presented a low standard deviation and high processing speed. Regarding the adjusted determination coefficient, Willmott's concordance index and the confidence coefficient, none of them presented values lower than 0.9945, 0.9950 and 0.9923, respectively. Thus, the model and the parameters obtained effectively describe the rain data for the analyzed cities, receiving an optimal performance rating. Finally, it is concluded that the tool elaborated in this work fulfills the proposed objective, serving not only as a practical calculation tool, but also as study material.
Dimensionamento de equipes de trabalho por meio de modelos probabilísticos
(Universidade Federal de Goiás, 2018-05-18) Freitas, Christiano Michel Fernandes; Moura Júnior, José dos Reis Vieira de; http://lattes.cnpq.br/2479225716217997; Moura Júnior, José dos Reis Vieira de; Rabelo, Marcos Napoleão; Soares, Júlio Cesar Valandro
This work proposes the modeling of a production system with three manufacturing units, in order to allow the optimal dimensioning of maintainers and the accomplishment of a sensitivity analysis that allows to evaluate the reliability of the obtained results. A Quasi-Birthand- Death (QBD) process is used to model the productive units, and through infinitesimal generators, the input probabilities for the developed code are obtained. Organizations usually define their supporter teams empirically, which can compromise organizational strategies. Thus, the code offers assistance in the decision making of these professionals. Thus, three production units X, Y and Z were modeled and the minimum dimensioning of maintainers that each unit had to be performed. Thus, the X unit with two maintainers provides a 70% probability of remaining in operation, the Y unit with three provides 76%, and finally, the Y unit with only one maintainer allows an 80% chance of remaining in operation. Bymeans of the sensitivity analysis, it was noticed thatwhen disturbing the infinitesimal generator the values of probability of operation tend to approximate to 100% whereas a maintainer is added, however, when the fourth maintainer is added, there is little variation in the system. However,when the system is stressed by the growth of the randomvariable t, the reliability of the results tends to decrease, whereas with a maintainer, the probability of functioning falls considerably over time, and in contrast, with four maintainers, the permanence of operating state tends to be distant.
Efeitos do atraso sobre a estabilidade de sistemas mecânicos não lineares
(Universidade Federal de Goiás, 2016-03-04) Ferreira, Rosane Gonçalves; Rabelo, Marcos Napoleão; http://lattes.cnpq.br/0067281135180613; Rabelo, Marcos Napoleão; http://lattes.cnpq.br/0067281135180613; Santee, Donald Mark; Henrique, Marcos Luiz
Vibrations of mechanical systems have a wide field of research, where many work have been dedicated. Such importance is due to the fact that most human activities involve vibrations. It is worth noting that many device can suffer or produce vibrations, such as, machines, structures, motors, turbines. Vibratory systems, generally can produce complex behavior, thus the analysis of such dynamics behavior needs to use sophisticated mathematical tools. The mathematical model assigns important features of real processes with respect to linear and non-linear differential equations. In this work we are interested in the analysis of behavior of delayed mechanical systems. Time delayed can compromise the performance of controls even adding instability in the systems. On the other hand, write choose of delays can improve its performance. Systems with time delay, similar to ordinary systems, are molded by ordinary and/or partial differential equations, but, unlikely ordinary differential equations, delayed differential equations, also known as functional differential equations, are molded on Banach spaces with infinite dimension, which introduce serious difficulty in analysis of stability, since that, the spectra of solution semi-group associated with the linear part of the model can presents infinite eigenvalues. Thus, our contribution of the study of dynamics behavior of such systems will be in two directions. In the first one, we apply the perturbation method of multiple scales in themodel of differential equations, since that the system shows nonlinear vibrations. It is worth noting that the differential analysis used in the stage regarding differential equations in Banach spaces, which has infinite dimension, this approach differ substantially from standards approaches. Then we obtain numerical solutions for the amplitude at steady state using the Newton Raphson method and then we made a numerical analysis of the model of stability with delay and without delay to different parameters, using the Runge-Kuttamethod.
Estabilidade de Carga no Problema de Carregamento de Contêineres
(Universidade Federal de Goiás, 2017-02-22) Oliveira, Liliane de Azevedo; Queiroz, Thiago Alves de; http://lattes.cnpq.br/8041183668335400; Queiroz, Thiago Alves de; Abud, Celso Vieira; Miyazawa, Flávio Keidi
In this work we applied an algorithm based on the resolution of integer linear models for the problem of packing boxes into a single container considering the cargo stability constraint. The problem consists of arranging items (boxes) of different sizes inside a large object (container) to maximize the occupied container volume while respecting the imposed constraints. Four methods are investigated and compared due to vertical cargo stability, in which three of these methods are proposed in this work and based on the equilibrium of rigid bodies, and the other one is based on the factor of support of boxes bottom faces. In the case of the factor of support, a set of constraints can be inserted totally in the integer formulation, while in the other methods cutting planes are inserted during optimization of the formulation by a branch-and-cut algorithm. Computational tests on instances from the literature show that the usage of a factor of support underestimates the value of the optimal solution. The computational tests showed that the use of the factor of support may underestimate the solution, but its use with integer linear programming models has the advantage that feasible solutions are stable, while the other developed methods only verify stability and thus they depend of the integer linear program to return feasible solutions more quickly. By the way, the methods for the cargo stability developed here also overcame the factor of support for tests involving different types of mesh to pack into the container.
Estimativa de recursos minerais e otimização de cava aplicados a um estudo de caso de uma mina de calcário
(Universidade Federal de Goiás, 2017-03-08) Pereira, Paulo Elias Carneiro; Ribeiro, Carlos Cordeiro; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4765922P6; Rabelo, Marcos Napoleão; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4702141E9; Ribeiro , Carlos Cordeiro; Borges, . Romes Antônio; Guimarães, Ednaldo Carvalho
A mining enterprise is composed of a set of successive and interdependent phases between them, which may or may not culminate in the exploitation of the mineral assets. The project begins with a Mineral Exploration phase, whose objective is to discover and subsequently evaluate the deposit for the feasibility of its extraction. This process involves setting the shape, dimensions and grades, resulting in a model that will be used to determine the recoverable reserves, that is, the economically usable part of the mineral resource, which will base the decision on the implementation or not of the enterprise, based mainly on technicaleconomic criteria. The elaboration of the physical form of the geological bodies that control the mineralization (geological model) and the estimation of the geological variables that characterize the quality of the different materials can be done by two approaches: by traditional or by geostatistical methods. The latter approach is currently being preferred, as it is a more accurate alternative and therefore, more reliable over traditional methods. The work uses indicator kriging (IK) and ordinary kriging (OK), both geostatistical tools, for the determination of the geological model and estimation of the geological variables (grades), respectively, of a limestone deposit located at Indiara city, Goiás State. Finally, from the obtained model the optimal limits of the extraction were established, based on the algorithm of Lerchs-Grossmann, that maximize the net present value of the enterprise. The results showed a significant deviation between themodel calculated by IK and the reality (samples), which can have as consequence the present spatial configuration of the sample data. The estimated geological variables also showed important deviations (overestimation and/or underestimation), particularly MgO oxide. The areas of occurrence of such deviations were coincident for all variables, which makes evident the existence of problems with the current sampling grid (spacing between samples and presence of very different sample supports), in such a way that it is recommended to collect additional samples, particularly with standardized supports. The optimal pit delimited a total reserve of 109,436,160.43 tons, with a total strip ratio of 0.13, which makes the venture, at first, attractive. This configuration, however, tends to be modified according to the collection of new geological evidence.

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