Resumo em Inglês:

ABSTRACT This paper presents an exact analytical study of global instabilities in pyramidal trusses under large displacements. Using the stationarity of total potential energy and Green-Lagrange strain, non-linear equilibrium equations are derived for a 3-bar isostatic truss. The tangent stiffness matrix yields 6 critical points: 2 limit points and 2 double bifurcation points. Multiple bifurcation is shown to occur universally for α > 45º, independent of bar count m ≥ 3 and alignment. Closed-form expressions for primary and secondary paths, validated via eigenvalue analysis, establish a generalized buckling threshold with direct implications for lightweight lattice design.

Resumo em Inglês:

ABSTRACT The social determinants of health are demographic and socioeconomic characteristics that influence the population’s lifestyle and access to healthcare, including the comprehensive and universal care provided by Brazil’s Unified Health System (SUS). This study aims to understand how population characteristics are associated with the availability of health services in Greater São Paulo. We applied an unsupervised machine learning technique to analyze how municipalities within the São Paulo Metropolitan Region cluster based on demographic and socioeconomic indicators. We then used the resulting clusters to evaluate the number of healthcare facilities available in each. Our findings indicate that peripheral cities in the region tend to share certain features, such as a higher proportion of Black and Brown populations and lower average income (up to one minimum wage). These clusters tend to have fewer healthcare facilities. In contrast, the cluster consisting solely of São Caetano do Sul, which has the highest proportion of White residents and a large share of individuals earning more than two minimum wages, has, relative to its population, the highest number of healthcare facilities, tripling the number found in the second-ranking cluster (Cluster 2). Through a machine learning approach, our results highlight the structural inequality present in the São Paulo Metropolitan Region and the disparities in access to healthcare, particularly in its peripheral areas.

Resumo em Inglês:

ABSTRACT Several human movement simulators employ pathfinding algorithms to determine the best route to an emergency exit or other targets within built environments. However, the literature often lacks detailed descriptions of some of these algorithms, particularly those of high quality. This paper introduces a new and enhanced pathfinding algorithm, VSP (Visibility Search Pathfinding), designed for movement simulations in built environments. It is based on the creation of distance maps and route maps generated by tangent search. The algorithm’s logic is thoroughly detailed, with examples of its application. Key advantages of the VSP algorithm include simplicity of logic, ease of computational implementation, applicability to environments of any design or geometry, low processing time (in non-dynamic scenarios), and full automation, requiring no specialist input. The VSP algorithm consistently identifies routes that closely approximate the optimal paths, independent of the number of people in the environment. Furthermore, the VSP algorithm allows the creation of a region around obstacles that prevents collisions. Thus, the VSP becomes a valuable tool for high-quality human movement simulations in evacuation contexts or similar scenarios.

Resumo em Inglês:

ABSTRACT The African continent is facing an unprecedented epidemic due to the spread of mpox. The shortage of vaccines and the lack of quarantine policies for those infected have made it difficult to control the disease. This work presents an analysis of the dynamics of disease spread through a multipopulation compartmental Model SEIR (Susceptible, Exposed, Infectious, and Recovered) and simulates different scenarios of spatial spread of mpox in affected African regions. We propose modified multipopulation Models SEIR and SEIQVR (Susceptible, Exposed, Infectious, Quarantine, Vaccination, and Recovered) to analyze real-world data from the current mpox outbreak in Africa. In this model, we simulate possible scenarios with quarantined and vaccinated populations to propose measures to mitigate the disease.

Resumo em Português:

RESUMO Este trabalho apresenta uma investigação numérica sobre o deslocamento de espuma em meios porosos heterogêneos, considerando os efeitos de adsorção de surfactante sob as abordagens em equilíbrio e cinética. O uso de surfactante para a geração de espuma reduz a mobilidade do gás frente a fase aquosa diminuindo os efeitos de fingering viscoso e aumentando a eficiência de varredura do gás no meio poroso. Este problema é modelado pelo acoplamento da lei de Darcy e as equações de conservação de massa para as fases água e gás, juntamente com uma equação de transporte para o surfactante dissolvido. A solução numérica é obtida por meio de um algoritmo sequencial que combina um método de elementos finitos mistos híbridos, aplicado à hidrodinâmica, e um esquema de volumes finitos central-upwind de alta ordem para o problema de transporte. As simulações avaliam as técnicas de coinjeção e injeção alternada de gás e surfactante (SAG), mostrando que o fenômeno de adsorção reduz a disponibilidade de surfactante na fase aquosa, limita a formação de espuma e diminui a eficiência de varredura do gás. Comparativamente, a estratégia SAG apresentou melhor desempenho quando comparada a coinjeção, devido à maior percolação do surfactante e consequente aumento da viscosidade aparente do gás com espuma. Os resultados confirmam que a adsorção de surfactante é um fator crítico na modelagem e na viabilidade de processos de recuperação avançada de petróleo assistidos por espuma.

Resumo em Inglês:

ABSTRACT This work presents a numerical investigation of foam displacement in heterogeneous porous media, considering the effects of surfactant adsorption under both equilibrium and kinetic approaches. The use of surfactant for foam generation reduces gas mobility relative to the aqueous phase, mitigating viscous fingering effects and enhancing the gas sweep efficiency in the porous medium. The problem is modeled by coupling Darcy’s law and the mass conservation equations for the water and gas phases, along with a transport equation for the dissolved surfactant. The numerical solution is obtained through a sequential algorithm that combines a hybrid mixed finite element method applied to the hydrodynamics with a high-order central-upwind finite volume scheme for the transport problem. The simulations assess both gas-surfactant co-injection and surfactant-alternating-gas (SAG) injection techniques, showing that adsorption reduces the surfactant availability in the aqueous phase, limits foam generation, and decreases gas sweep efficiency. Comparatively, the SAG strategy exhibited superior performance relative to co-injection, due to greater surfactant percolation and the consequent increase in the apparent viscosity of the foamed gas. The re-sults confirm that surfactant adsorption is a critical factor in the modeling and feasibility of foam-assisted enhanced oil recovery.

Resumo em Inglês:

ABSTRACT Glioblastoma Multiforme (GBM) is one of the most aggressive and difficult-to-treat forms of malignant brain tumor, presenting a high incidence and resistance to conventional treatment methods. Boron Neutron Capture Therapy (BNCT) stands out as an innovative and promising approach for treating complex tumors such as GBM, as it enables the selective destruction of tumor cells with minimal impact on healthy tissues. In this study, the multigroup neutron diffusion equation is solved in a three-dimensional domain using four energy groups. The neutron source is represented as a boundary condition, and after diagonalizing the system of equations, the method of Separation of Variables can be applied to obtain an closed-form eigenfunction expansion. The validation of the proposed approach was carried out through numerical simulations in a water phantom, whose results indicated that thermal and epithermal neutron fluxes are predominant.

Resumo em Português:

RESUMO Este artigo investiga o problema integrado de produção, estoque e roteamento com prazos de entrega flexíveis, ou seja, as entregas podem acontecer em um conjunto de períodos, porém sujeitas a penalizações. Para lidar com o problema, desenvolve-se um modelo de otimização linear inteira que flexibiliza os prazos de entrega dos itens demandados. Considera-se um ambiente produtivo com uma única fábrica, capaz de produzir e estocar uma quantidade finita de produtos distintos que compartilham recursos produtivos. Há um conjunto de clientes com estoques próprios e uma frota limitada de veículos heterogêneos. Cada veículo realiza no máximo uma rota por período. O objetivo do problema é determinar o plano de produção, estoque e roteamento que minimize os custos ao longo de um horizonte finito, atendendo às demandas dentro dos períodos possíveis (flexible due dates). Análises considerando um conjunto de instâncias artificiais de frota heterogênea, geradas aleatoriamente e baseadas nos dados da literatura, conforme especificado no início da Seção 3, mostram que explorar a flexibilidade nos prazos de entrega pode reduzir significativamente os custos, especialmente os de estoque. Além disso, avaliam-se diferentes cenários com variações na capacidade veicular e prazos de entrega.

Resumo em Inglês:

ABSTRACT This paper investigates the integrated problem of production, inventory and routing with flexible delivery times, i.e., deliveries can occur in a set of periods, but subject to penalties. To deal with the problem, an integer linear optimization model is developed that allows flexibility in the delivery deadlines of the demanded items. A production environment is considered with a single factory, capable of producing and storing a finite quantity of distinct products that share production resources. There is a set of customers with their own inventories and a limited fleet of heterogeneous vehicles. Each vehicle performs at most one route per period. The objective of the problem is to determine the production, inventory and routing plan that minimizes costs over a finite horizon, meeting demands within the possible periods (flexible due dates). Analyses considering a set of instances with a heterogeneous fleet show that exploring flexibility in delivery times can significantly reduce costs, especially inventory costs. In addition, different scenarios with variations in vehicle capacity and delivery deadlines are evaluated.

Resumo em Inglês:

ABSTRACT Recent developments in the construction of generalized Dirac duals have revealed, within the structure of the Clifford algebra ℂ⊗𝒞ℓ1,3, the existence of distinct algebraic formulations of spinors duals with potential applications in quantum field theoretic models. In this work, after reviewing the matrix formulation, we employ the recent covariant formulation of the generalized spinor dual and establish its interplay with the algebra 𝒞ℓ1,3. We construct dual mappings governed by groups denoted by G Ω and introduce the notion of Ω-equivalence classes as a tool to classify dual spinors from a group-theoretic perspective.

Resumo em Inglês:

ABSTRACT In this paper we present a mathematical analysis of a one-dimensional effective model proposed by A.M. Mateo and V. Delgado concerning Bose-Einstein condensates in the presence of harmonic confinement. Among the properties presented, we mention: existence, “uniqueness”, orbital stability, symmetry and Gaussian asymptotic decay of ground-state solutions in the repulsive case. We also report formulæ for the minimal energy E min and the associated chemical potential µ as functions of λ , which is a parameter related to N (the number of atoms) and/or a (the s-wave scattering length). By considering Taylor’s development of the non-quadratic term of the energy and using appropriate gaussian functions as approximations for the ground state, we present some numerical experiments to illustrate our results.