Petr Ekel

• Professor
• Pontifical Catholic University of Minas Gerais

This research introduces a new data-driven methodology for fault detection and isolation in dynamic systems, integrating fuzzy/Bayesian change point detection and decision trees induced by genetic programming for pattern classification. Tracking changes in sensor signals enables the detection of faults, and using decision trees generated by genetic...

When providing patient care, healthcare professionals often rely on interpreting laboratory and clinical test results. However, their analysis is constrained by human capacity, leading to uncertainties in diagnoses. Machine learning has the potential to evaluate a larger amount of data and identify patterns and relationships that may otherwise go u...

There is no lack of studies dealing with the consistency of evaluations performed by pairwise comparison in the decision-making literature. Mostly, these studies ofer algorithms for reducing the inconsistency of evaluations and indices to measure the evaluation’s consistency degree. The focus on these two research fronts does not cover all the gap...

The weighting of sub-indicators is widely debated in the composite indicator literature. However, these weighting schemes’ effects on the composite indicator’s spatial dependence property are still little known. This research reveals a direct relationship between the weighting scheme of sub-indicators and the spatial autocorrelation of the composit...

The object of this research is the relationship between Transaction Costs and economic performance. Weak or unreliable institutions open space for corruption, generating a negative externality, increasing the economy's Transaction Costs, inhibiting doing business, and reducing economic growth. Although there is a broad debate about the negative rel...

The weighting of sub-indicators is a relevant problem in the composite indicators literature and impacts several fields of science. None of the existing weighting approaches, Equal-Weights, Data-Driven, and Participatory, is exempt from criticism. Specifically, weights obtained by the Participatory approach are associated with two frequent problems...

Esta pesquisa analisa o efeito da reputação de compradores públicos do estado de Minas Gerais nos preços de aquisição de produtos em pregões eletrônicos. A reputação de seis compradores públicos foi obtida por meio do Analytic Hierarchy Process, a partir dos critérios inadimplência, atrasos de pagamento, especificações mal definidas, burocracia exc...

Composite indicators are one-dimensional measures of multidimensional phenomena. Through the composite indicators, it is possible to have a single map of the different subindicators of poverty, inequality, sustainability, and economic development. This research employs two well-known methods of building composite indicators to represent the social...

The representation of social phenomena has been associated with substantial conceptual and operational difficulties. Social phenomena have a complex multidimensional nature that leads to different conceptualizations and measurements. This problem makes it difficult to choose the sub-indicators to be considered in the composite indicator of the phen...

Alternative data are now widely used in economic analyses worldwide but still infrequent in studies on the Brazilian economy. This research demonstrates how alternative data extracted from Google Trends and Google Mobility contribute to innovative economic analysis. First, it demonstrates that the search for the future on the internet is correlated...

The World Bank's ease-of-doing-business index (EDBI) is the most popular instrument for measuring countries' business environment conditions. Although useful to direct investments and guide reforms, researchers associate EDBI with problems such as analyses from very different countries, and data quality and calculation errors. This research seeks t...

Studies carried out in different countries correlate social, economic, environmental, and health factors with the number of cases and deaths from COVID-19. However, such studies do not reveal which factors make one country more exposed to COVID-19 than other. Based on the composite indicators approach, this research identifies the factors that most...

Essa pesquisa tem como objetivo sintetizar e sistematizar o conhecimento acumulado sobre contratações públicas na perspectiva da Análise Econômica do Direito no Brasil. A partir dessa síntese e sistematização são apresentadas contribuições para aumentar o interesse pela Análise Econômica do Direto, estimular pesquisas e gerar conhecimentos para que...

This study examines a general scheme of multicriteria decision-making under uncertainty based on quantitative and qualitative information. In its original form, the general scheme uses qualitative information at the final decision stage, only if the quantitative information is unable to generate unique solutions. Considering that many problems requ...

The prioritization of Research, Development & Innovation Projects is an essential step in the innovation management process. As a rule, it is carried out applying methods that allow one to process experts' preferences concerning each project according to established criteria. However, there are different preference formats which experts can utilize...

Intra-urban inequality is not strictly defined and therefore cannot be measured accurately. The literature shows that the measurement of inequality varies depending on the judgment of the experts and that this judgment can be realized in several ways. Taking this into account, the capabilities created using fuzzy set theory and consensus schemes ca...

Benefit-to-cost ratio (BCR) measuring is a useful approach for selecting portfolios of projects when they are evaluated applying multiple and conflicting criteria. A multiattribute value function can be used to measure the benefit of each project, which allows one to evaluate the BCRs, rank projects, and select them according to the available budge...

The paper provides numerical simulation of the influence of dynamic loading on the stress-strain state of the natural and geoengineering technogenic environment taking into account the soil basis for forecasting its use as the basis of the structure. Paper demonstrates the impact of static and dynamic loading on the subsidence of the landfill. To t...

Oral Mucositis (OM) is a common adverse effect of head and neck squamous cell carcinoma (HNSCC) treatment. The purpose of this study was to investigate the significance of early changes in tissue electrical parameters (TEPs) in predicting the development of OM in HNSCC patients receiving radiation therapy (RT). The current study combined two study...

Falls in the elderly are a public health problem because this population tends to have a longer recovery time and consequently longer hospital beds. Studies show that 84% of falls in hospital rooms occur near the bed, that led to strategies to prevent falls in the elderly population have been studied. In this context, this paper presents a schema f...

The objective of the present research is to develop methodological and computing tools to support the analysis and prioritization of new electric transmission line projects, in the prospection stage, aimed at greater efficiency and effectiveness of the advanced preparation of concessionaires and investors for participating in the auctions. These au...

This study presents an approach for fault detection and classification in a DC drive system. The fault is detected by a classical Luenberger observer. After the fault detection, the fault classification is started. The fault classification, the main contribution of this paper, is based on a representation which combines the Subctrative Clustering a...

This study presents an approach for fault detection and classification in a DC drive system. The fault is detected by a classical Luenberger observer. After the fault detection, the fault classification is started. The fault classification, the main contribution of this paper, is based on a representation which combines the Subctrative Clustering a...

The general-purpose graphics processing unit programming has been widely used and has achieved satisfactory results across many knowledge areas and it keeps evolving since its earlier stages. This paper presents an implementation of a modified Simplex method using the computational power brought from graphics processing unit (GPU) computing using t...

Este trabalho aplica conceitos da Análise Multicritério Espacial para a prospecção de alternativas locacionais para a instalação de empreendimentos de geração baseados em energias renováveis - representadas pelas fontes solar, eólica e biomassa - no Estado de Minas Gerais. Para apoiar a realização do estudo prospectivo, foi elaborada e aplicada uma...

This study presents a data-based methodology for fault detection and isolation in dynamic systems based on fuzzy/Bayesian approach for change point detection associated with a hybrid immune/neural formulation for pattern classification applied to the Tennessee Eastman benchmark process. The fault is detected when a change occurs in the signals from...

Neste trabalho, o problema de traçado ótimo de linhas de transmissão é formulado como o problema de caminho mais curto. Os custos envolvidos na instalação de uma linha de transmissão são diversos e com incertezas. Essa característica pode ser modelada através de redes estocásticas, onde o custo de cada aresta segue uma distribuições de probabilidad...

This paper addresses the problem of fault detection in stator winding of inductionmachine by a multiple change points detection approach in time series. To handle this problem a new fuzzy/Bayesian approach is proposed which differs from previous approaches since it does not require prior information as: the number of change points or the characteri...

This work presents and generalizes our experience in the use of fuzzy set theory, including its combination with another branch of mathematics of uncertainty, in developing general approaches and methods for optimization and decision making with considering the uncertainty and multicriteria factors in problems of the design, planning, operation, an...

This paper deals with multicriteria decision making problems under conditions of uncertainty. The main its contribution is the consideration of choice criteria of the classic approach to handle information uncertainty in monocriteria decision making as objective functions within the framework of multiobjective models, whose analysis generates harmo...

Generalized algorithms for solving problems of discrete, integer, and Boolean programming are discussed. These algorithms are associated with the method of normalized functions and are based on a combination of formal and heuristic procedures. This allows one to obtain quasi-optimal solutions after a small number of steps, overcoming the NP-complet...

The results of research into the use of models and methods of multicriteria decision making in a fuzzy environment for solving power engineering problems are presented. Two general classes of models related to multiobjective ( models) and multiattribute ( models) problems as well as methods of their analysis based on the application of the Bellman-...

This study describes a framework for a Web-based decision support center (DSC) to aid various interrelated decisionmaking situations, which emerge from planning and management processes in electrical energy companies. This framework supports small collaborative groups working in an asynchronous way, in an environment where a single decision-maker (...

This paper proposes an optimization-based approach to the robust H∞ control problem of uncertain continuous or discrete-time linear time-invariant systems with different time-varying delays in the state vector and control input of the dynamic equation and controlled output. Sufficient delay-dependent conditions are derived for the control stabiliza...

In the paper, the term consensus scheme is utilized to denote a dynamic and iterative process where the experts involved discuss a multicriteria decision problem. This discussion process is conducted by a human or artificial moderator, with the purpose of minimizing the discrepancy between the individual opinions.During the process of decision maki...

This paper presents a new linear matrix inequality (LMI) based approach to the stability analysis of artificial neural networks (ANN) subject to time-delay and polytope-bounded uncertainties in the parameters. The main objective is to propose a less conservative condition to the stability analysis using the Gu’s discretized Lyapunov–Krasovskii func...

a b s t r a c t This paper deals with the stability analysis of delayed uncertain Cohen–Grossberg neural networks (CGNN). The proposed methodology consists in obtaining new robust stability criteria formulated as linear matrix inequalities (LMIs) via the Lyapunov–Krasovskii theory. Particularly one stability criterion is derived from the selection...

In order to model the preferences of a decision-maker (DM) by means of fuzzy preferencerelations, a DM can utilize different preference formats (such as ordering of the alternatives, utility values, multiplicative preference relations, fuzzy estimates, and reciprocal as well as nonreciprocal fuzzy preference relations) to express his/her judgments....

This paper presents results of research into the use of models and methods of multicriteria decision making in a fuzzy environment for solving power engineering problems. Two classes of models associated with multiobjective ( models) and multiattribute ( models) problems, as well as methods for their analysis are briefly discussed. A review of the...

This paper presents results of research into the use of factorial experimental design for constructing sensitivity as well as functionally oriented models for power system planning, operation, and control. The rationality of applying factorial experimental design for this goal is associated with the possibility to “build” secants but not tangents (...

The overriding goal of this work is to present the implementation of a tool for spatial analysis of georeferenced information as a means of gaining insights into animal behavior from scientific visualization. The spatial occupation data of monkeys from the species Callicebus nigrifrons, located in " Santuário do Caraça " , in the state of Minas Ger...

The results of research into the use of fuzzy set based models and methods of multicriteria decision making for solving power engineering problems are presented. Two general classes of models related to multiobjective ( models) and multiattribute ( models) problems are considered. The analysis of models is based on the use of the Bellman-Zadeh appr...

In this paper, we propose a dynamical consensus scheme which makes use of an index of comparability and of an index of concordance to regulate the information flow in the discussion among the experts. In addition to the traditional use of a concordance index to identify the discordant expert, who can be invited to review his opinion or to explain h...

In this paper, we propose two manners of making a synergetic use of Consensus Methods (namely, Nominal Group Technique and Delphi Technique), combined with fuzzy set based multiperson multicriteria decision-making methods, to support group processes. In our proposal, different indexes, namely the discordance index, the consensus index, and the comp...

This paper introduces a methodology for multicriteria decision-making in a group environment with hierarchical structure, where a group of experts participates as consultants and only one person has authority to make the final decision (that is, there is only one decision-maker). The methodology being proposed is based on preference modeling by mea...

Multicriteria decision making in a fuzzy environment a b s t r a c t This paper reflects results of research related to developing a new methodology for automatic graph draw-ing based on applying genetic algorithms. The methodology has permitted the elaboration of a hybrid technique that combines the most popular, classical, topology-shape-metric a...

This paper studies three consensus schemes based on fuzzy models for dealing with the input of multiple experts in multicriteria decision making. The consensus schemes are based on different aggregation procedures for constructing a collective decision. In the paper, we propose a methodology that makes use of the three consensus schemes implemented...

There exist two classes of problems, which need the use of a multicriteria approach: problems whose solution consequences cannot be estimated with a single criterion and problems that, initially, may require a single criterion or several criteria, but their unique solutions are unachievable, due to decision uncertainty regions, which can be contrac...

This paper presents results of research into the use of the Bellman–Zadeh approach to decision making in a fuzzy environment for solving multicriteria power engineering problems. The application of the approach conforms to the principle of guaranteed result and provides constructive lines in computationally effective obtaining harmonious solutions...

This work proposes a new consensus scheme for group decision making, which allows one to obtain a consistent collective opinion, from information provided by each expert in terms of multigranular fuzzy estimates. It is based on a linguistic hierarchical model with multigranular sets of linguistic terms, and the choice of the most suitable set is a...

This paper introduces a methodology for constructing a multidimesional indicator designed for organizational performance measurement. The methodology involves the application of fuzzy models and methods of their analysis. Its use requires the construction of fuzzy preference relations by means of the comparison of performance measures with respect...

This paper presents results of research related to formulating and solving the problem of capacitor placement in distribution systems within the framework of multicriteia decision making models. The application of multicriteria approach is directed, first of all, at overcoming the difficulties of simultaneous observing contradictory constraints for...

This chapter discusses the essence and present methods used to analyze problems of multicriteria evaluation, comparison, choice, prioritization, and/or ordering of alternatives. There exist two classes of situations which give rise to these problems. The first one is associated with the direct statement of multiattribute decision-making problems wh...

Este trabalho descreve um procedimento para tomada de decisão multicritério em grupo, cujo ambiente apresenta uma estrutura hierárquica, em que vários especialistas são convidados a participar como consultores, mas apenas um especialista (decisor) tem autoridade para tomar a decisão. O procedimento proposto baseia-se na modelagem das preferências p...

The present paper proposes a flexible consensus scheme for group decision making, which allows one to obtain a consistent collective opinion, from information provided by each expert in terms of multigranular fuzzy estimates. It is based on a linguistic hierarchical model with multigranular sets of linguistic terms, and the choice of the most suita...

This work proposes a new consensus scheme for group decision making, which al lows one to obtain a consistent collective opinion, from information provided by each ex pert in terms of multigranular fuzzy estimates. It is based on a linguistic hierarchical model with multigranular sets of linguistic terms, and the choice of the most suitable set is...

This paper presents results of research related to multicriteria decision making under information uncertainty. The Bellman–Zadeh approach to decision making in a fuzzy environment is utilized for analyzing multicriteria optimization models (〈X,M〉 models) under deterministic information. Its application conforms to the principle of guaranteed resul...

This paper presents sufficient conditions for asymptotic and exponential stability of a class of artificial neural networks (ANNs) subject to constant or time-varying delay and polytope-bounded uncertainties. The proposed approach is based on Lyapunov-Krasovskii stability theory, and the linear matrix inequalities (LMIs) technique introducing slack...

This paper presents sufficient conditions for asymptotic and exponential stability of a class of artificial neural networks (ANNs) subject to constant or time-varying delay and poly tope-bounded uncertainties. The proposed approach is based on Lyapunov-Krasovskii stability theory, and the linear matrix inequalities (LMIs) technique introducing slac...

The present article has the objective to present the implementation and the simulation of a control system as contribution with improvement of the operation efficiency of rotary blasthole drill machine used in the mining process. This improvement is based on the development of a control model that uses fuzzy logic technology as alternative to conve...

This paper reflects results of research into the use of factorial experimental design for rational constructing sensitivity models as well as functionally oriented models for system optimization and control. The questions of overcoming difficulties of statistical evaluating the results of experiments with models of systems, but not real systems are...

This paper presents results of research into the use of the Bellman–Zadeh approach to decision making in a fuzzy environment for solving multicriteria optimization problems. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin pro...

An approach to solving optimization problems with fuzzy coefficients is described. It consists in formulating and analyzing one and the same problem within the framework of mutually related models by constructing equivalent analogs with fuzzy coefficients in objective functions alone. Since the approach is applied within the context of fuzzy discre...

This paper presents a new approach to the analysis of asymptotic stability of artificial neural networks (ANN) with multiple time-varying delays subject to polytope-bounded uncertainties. This approach is based on the Lyapunov–Krasovskii stability theory for functional differential equations and the linear matrix inequality (LMI) technique with the...

Results of research into the use of fuzzy sets for handling various forms of uncertainty in optimization problems are presented. Two types of situations which need the application of a multicriteria approach are classified. According to this, two classes of models (〈X, M〉 and 〈X, R〉 models) are considered with utilizing the Bellman–Zadeh approach t...

In this work, we present a parallel implementation of an algorithm that simulates the natural convection of fluids in a closed cavity. The method is based on the Boussinesq approximation; and it is numerically solved using the finite volume method, based on the Power-Law interpolating scheme. The pressure-velocity coupling is solved using SIMPLEC a...

Current image segmentation implementations are not optimized to all kinds of applications. To attend the different application kinds, the solution should allow to be reconfigured to fit their different characteristics and resource needs and to improve performance. Our objective is to present an image segmentation architecture and its implementation...

Current parallel architectures are not optimized to all different kinds of applications since they can vary in requirements and resource needs. An ideal system to attend different applications should be able to fit their different characteristics and resource needs and to improve application performance. Our objective is to design and to develop a...

An approach to solving optimization problems with fuzzy coefficients in objective functions and constraints is described. It consists in formulating and solving one and the same problem within the framework of mutually related models with constructing equivalent analogs with fuzzy coefficients in objective functions alone. It enables one to maximal...

This paper presents results of research into the use of the Bellman-Zadeh approach to decision making in a fuzzy environment for solving multiobjective optimization problems. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin pr...

This paper reflects results of research into the construction and analysis of 〈X, R〉 models within the framework of a general approach to solving optimization problems with fuzzy coefficients. This approach involves a modification of traditional mathematical programming methods and is associated with formulating and solving one and the same problem...

Without Abstract

This paper presents a less conservative approach to compute, with any prescribed accuracy, the H ∞ guaranteed cost of time-delay continuous-time linear time-invariant systems subjected to polytopic uncertainties. The proposed analysis approach is based on a branch-and-bound algorithm that incorporates a recent LMI-based analysis formulation and a n...

This paper presents results of research related to the second stage of the project dedicated to developing and employing the xOMNI system (software of the SCADA type). This stage is associated with the elaboration of the Energy Management System (EMS) for the subtransmission system of the Minas Gerais State Energy Company. One of the most important...

In this paper we present and analyze an artificial neural network hardware engine, its architecture and implementation. The engine was designed to solve performance problems of the serial software implementations. It is based on a hierarchical parallel and parameterized architecture. Taking into ac-count verification results, we conclude that this...

Analysis of 〈X,R〉 models is considered as part of a general approach to solving optimization problems with fuzzy coefficients. This approach involves a modification of traditional optimization methods and is associated with formulating and solving one and the same problem within the framework of mutually interrelated models by constructing equivale...

This paper presents results of research in the use of the Bellman–Zadeh approach to decision- making in a fuzzy environment for solving multiobjective optimization problems. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin pro...

A new approach is proposed for global optimization problems with fuzzy cost functions and fuzzy box and equality constraints. It allows one to avoid complex operations with fuzzy sets and the use of various subjective indices of choice. To resolve the contradiction between economically better solutions with low possibility of realization and a litt...

A linear matrix inequality approach to the robust H_∞ control problem of uncertain continuous- and discrete-time linear time-invariant systems with time delay in the state vector and control input is developed. The main results provide sufficient delay-dependent conditions for the control problem, where the explicit size of the time delay...

Analysis of X, R > models is considered as part of a general approach to solving optimization problems with fuzzy coefficients. This approach consists in formulating and solving one and the same problem within the framework of mutually interrelated models with constructing equivalent analogs with fuzzy coefficients in objective functions alone. The...

C++ code of the cubic algorithm [1] is proposed for nonconvex global optimization of continuous functions with box and equality constraints, and for the solution of nonlinear systems of equations, including underdetermined and overdetermined systems. The algorithm is upgraded for application to problems with linear and nonlinear equality constraint...

This paper develops a Linear Matrix Inequality (LMI) approach to the robust H _∞ control problem of uncertain continuous-and discrete-time linear time-invariant systems with time-delay in the state vector and control input. The main results provide sufficient delay-dependent conditions for the control problem, where the explicit size of t...

An approach to solving optimization problems with fuzzy coefficients is considered. This approach involves transforming constraints containing fuzzy coefficients to equivalent nonfuzzy analogs and modifying traditional mathematical programming methods to solve problems with fuzzy coefficients in the objective functions alone within the framework of...

Analysis of X,R > models is considered as part of a general approach to solving a wide class of optimization problems with fuzzy coefficients. This approach consists in formulating and solving one and the same problem within the framework of interrelated models to maximally cut off dominated alternatives. The subsequent contraction of the decision...

This paper proposes a Linear Matrix Inequality (LMI) approach to the robust H∞ control stabilization problem of uncertain continuous- or discrete-time linear time-invariant systems with time-varying delays in the state vector and control input. It is derived sufficient delay-dependent conditions for the control stabilization problem, where both the...