http://www.bdtd.uerj.br/handle/1/3702 2026-03-14T22:55:25Z http://www.bdtd.uerj.br/handle/1/24875 Título: Análise de defeitos em aplicativos descentralizados no contexto da engenharia de software orientada a blockchain Autor: Oliveira, Rogério de Jesus Primeiro orientador: Libotte, Gustavo Barbosa Abstract: The analysis of defects in decentralized applications (DApps) within the context of blockchain-oriented software engineering is crucial due to the autonomous and self executing nature of these programs, which allow for the execution of agreements without intermediaries. However, like any software, DApps are susceptible to defects and can present vulnerabilities exploitable by attackers. The use of models for software defect prediction is a well-studied research area, but the application of these models with smart contract metrics is still underexplored. This thesis project aims to evaluate whether Deep Learning models used in traditional software defect prediction produce equivalent results when applied to specific smart contract metrics. To this end, the research proposes the use of a deep neural network called Deep Neural Network—Ethereum Solidity Metrics (DNN-ESM). The methodology includes data preparation, the selection of machine lear ning models, and performance evaluation using metrics such as precision, recall, F1-Score, area under the curve (AUC), precision-recall curve (PRC), and Matthews correlation coef f icient (MCC). The machine learning models will be applied to datasets containing traditi onal object-oriented software metrics and specific metrics for smart contracts in Solidity. The results suggest that deep learning models can be effective in predicting defects in smart contracts, improving efficiency and reducing the computational effort required for vulnerability detection. Furthermore, the application of these models will allow for the evaluation of a large number of smart contracts in a short period, benefiting developers, researchers, and educators in the field of blockchain-oriented software engineering. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese 2025-06-13T00:00:00Z http://www.bdtd.uerj.br/handle/1/24647 Título: Cosmologia Quântica Computacional: uso do método de Crank-Nicolson em (2+1) na busca de soluções para a equação de Wheeler-DeWitt Autor: Brumatto, Hamilton José Primeiro orientador: Monerat, Germano Amaral Abstract: In the study of Cosmology, the Theory of General Relativity (RG) presents singularities in extremes situations, such as when we go back to the initial instants of the “Big-Bang”, or rather, in the Planck Era. The introduction of quantum formalism seeks to eliminate these singularities. This formalism assumes the existence of a wave function Ψ that carries all the properties of the system, known as the wave function of the Universe. The proposed models based on quantum formalism have their dynamics described by the so-called Wheeler-DeWitt Equation (WDW). Several works address solutions for this equation using different material contents, such as the cosmological constant, perfect fluid in the forms of: radiation, dust, rigid matter, Chaplygin’s gas, among others. Recently, several models with different matter contents have been quantized. In cases where the effective potential Vef assumes the form of a potential barrier, the possibility of the universe emerging to the right of the barrier through a tunneling mechanism has been analyzed. Recent solutions have adopted the Crank-Nicolson (CN) (1+1) to obtain numerical solutions for the WDW Equation and subsequently calculate the tunneling probability. According to the literature, after the Planck Era (PE), the Universe should emerge into a phase of great expansion known as the “Inflationary Phase”. At this stage, the presence of a scalar field (inflation field) is assumed, which dominates any other matter, leading the Universe to a very accelerated expansion, in a short period of time. This work considers a model in Einstein’s RG with Friedmann-Lemaître-Robertson-Walker (FRW) geometry to represent a homogeneous and isotropic model. The material content will be a perfect fluid in the form of radiation and a scalar field conformally coupled to gravity. In this case, the scalar field potential will have a cosmological constant term to represent vacuum energy and a mass term. The objective is to describe the primordial universe, that is, the phase that precedes the inflationary era. To do this, the model in question will be quantized, so that the dynamics will be governed by the so-called WDW Equation. The computational solution for this model (2+1) requires an efficient and robust computational package. Efficient because the volume of data is enormous, so the algorithms used need to be O(n) and especially parallelized. Robust because long-term computation must anticipate faults over time, such as processing interruptions. A computational package capable of performing simulations on High Performance Computing (HPC) Clusters was built; tests have shown that the program can simulate the evolution of the WDW Equation with minimal error introduction. From this, it was possible to carry out simulations in the model, the results are significant and point to a transition from the quantum model to the classical one. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese 2025-08-08T00:00:00Z http://www.bdtd.uerj.br/handle/1/23841 Título: Método de solução da equação de transporte de nêutrons integradas transversalmente em cálculos bidimensionais usando a formulação SN com aproximação de expansão polinomial quadrática para os termos de fuga transversal em problemas de fonte-fixa Autor: Libotte, Rafael Barbosa Primeiro orientador: Alves Filho, Hermes Abstract: In solving problems involving the phenomenon of neutron transport in two-dimensional Cartesian geometry using spectral nodal methods, a transverse integration must be performed in the neutron transport equation, giving originating a term known as transverse neutron leakage. In order to make this system of equations possible and determined, it is necessary to approximate the transverse neutron leakage term. Therefore, in this thesis, we present a quadratic polynomial approximation for this term. This approach was applied to the solution of fixed-source problems, making use of the multigroup energy neutron transport equation in the discrete ordinates formulation. This type of approximation can also be truncated to obtain, in addition to the quadratic approximation, a linear or constant approximation, which is widely used in spectral nodal methods. Four model problems were solved using the spectral nodal methods Spectral Deterministic Method and Response Matrix. The numerical results obtained were compared in terms of accuracy and execution times between the quadratic, linear, and constant approximations with a reference fine-mesh method, using various meshes and different quadrature orders. The numerical results obtained showed low relative percentage deviations, as well as time savings when using linear and quadratic approximations with relatively coarse meshes, compared to solutions that use constant approximation. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese 2025-02-28T00:00:00Z http://www.bdtd.uerj.br/handle/1/23549 Título: Metamodelagem da otimização de sistemas de engenharia na presença de incerteza Autor: Cruz, Claudemir Mota da Primeiro orientador: Libotte, Gustavo Barbosa Abstract: This thesis explores the use of surrogate models to address uncertainties in the optimization of engineering systems, aiming to improve decision-making in complex problems and reduce computational costs. The research considers factors where external disturbances and uncertainties can impact the determination of optimal operating conditions. Generally, robust optimization seeks to minimize sensitivity to these variations, while reliability analysis focuses on preventing system failures, ensuring safe operation. This work employs Gaussian Process Regression, in a hybrid approach, to reduce the number of objective function evaluations in optimization under uncertainty, thereby improving efficiency without sacrificing solution quality. Furthermore, it integrates a stereographic projection method with an adaptive step size scheme for inverse reliability analysis. The effectiveness of the proposed methodology is demonstrated through its application to benchmark problems and structural engineering problems commonly used in the literature. Results demonstrate a reduction of at least 60% in the number of objective function evaluations for robustness and reliability-based optimization problems, using Pareto frontiers, compared to approaches without metamodels. Moreover, the proposed method exhibits robustness to parameter variations, maintaining solution quality within a maximum deviation of 1%. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese 2024-12-20T00:00:00Z