A flexible piezoresistive material based on vulcanized natural rubber (VNR) and multiwalled carbon nanotubes (MWCNTs) was developed and systematically investigated for strain sensing applications. The nanocomposites were prepared by melting and vulcanizing MWCNT, while keeping the rubber composition constant to isolate the effect of the conductive nanofiller. By scanning electron microscopy, morphological analyses indicated that MWCNTs were dispersed throughout the rubber matrix, with localized agglomerations becoming more evident at higher loadings. In mechanical tests, MWCNT incorporation increases the tensile strength of VNR, increasing the stress at break from 8.84 MPa for neat VNR to approximately 10.5 MPa at low MWCNT loadings. According to the electrical characterization, VNR-MWCNT nanocomposite exhibits a strong insulator–conductor transition, with the electrical percolation threshold occurring between 2 and 4 phr. The dc electrical conductivity increased sharply from values on the order of 10⁻¹⁴ S·m⁻¹ for neat VNR to approximately 10⁻³ S·m⁻¹ for nanocomposites containing 7 phr of MWCNT. Impedance spectroscopy revealed frequency-independent conductivity plateaus above the percolation threshold, indicating continuous conductive pathways, while dielectric analysis revealed strong interfacial polarization effects at the MWCNT–VNR interfaces. The piezoresistive response of samples containing MWCNT exhibited a stable, reversible, and nearly linear response under cyclic tensile deformation (10% strain). VNR/MWCNT nanocomposites demonstrate mechanical compliance and tunable electrical sensitivity, making them promising candidates for flexible and low-cost piezoresistive sensors.

This study addresses the complex issue of optimizing production batch sizes within a company specializing in manufacturing rubber, thermoplastic, and polyurethane components, all of which undergo vulcanization prior to sale. Through meticulous analysis of the production planning process, it was observed that certain activities could be logically grouped into two sequential stages without compromising information integrity or detail. The initial stage encompasses press activities involving vulcanization and curing, while the next one involves greenhouse operations for post-curing. The commencement of the second stage is contingent upon the completion of all activities in the first stage. Consequently, an effective production plan must concurrently consider both stages. To tackle this, a mathematical model is proposed to address the batch sizing problem within the company, integrating both stages and drawing inspiration from the CLSP (Capacitated Lot Sizing Problem) for the first stage and the subperiod approach derived from GLSP (General Lot-sizing and Scheduling Problem) models for the second stage. The model is solved utilizing the CPLEX solver version 12.8. It incorporates 74 items, spans 20 periods, each with specific demands, and delineates 16 sub-periods within each planning horizon period. Experimentation involving a hypothetical example and subsequent tests utilizing real data from the case study company demonstrate the successful resolution of the problem, yielding enhanced production plans, particularly in terms of cost reduction objectives.

A crescente demanda por fontes de energia renováveis e a urgência em mitigar as mudanças climáticas têm impulsionado a pesquisa e a adoção de tecnologias sustentáveis em todo o mundo. Neste contexto, é cada vez mais urgente desenvolver soluções energéticas sustentáveis e acessíveis para regiões precárias, sem acesso a saneamento e eletricidade. No entanto, existe uma lacuna em tecnologias solares economicamente viáveis para populações de baixa renda, uma vez que a maioria dos sistemas disponíveis no mercado tem um custo elevado e não é aplicável em áreas vulneráveis. Neste trabalho, desenvolveu-se um coletor solar utilizando uma caixa térmica, tubos de PVC e garrafas PET para otimizar custos e mensurar a eficiência do sistema. O desempenho térmico do sistema foi avaliado ao longo de sete dias em diferentes estações do ano, utilizando um termômetro digital e um medidor de radiação solar. A água do reservatório atingiu a temperatura máxima de 42.4°C em junho, e manteve uma média de 36.4°C durante a semana de avaliação em julho (mesmo durante o inverno), evidenciando a eficácia do sistema em condições reais de operação mantendo a temperatura do reservatório dentro da faixa ideal para banhos. Desta forma, sugere-se que o coletor de baixo custo é uma alternativa viável para promover o uso de energia solar em áreas remotas ou mesmo apresenta potencial para ser utilizado como fonte de energia secundária (híbrida) ao aquecimento por chuveiro elétrico reduzindo o gasto energético.