This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.

This work presents the methodology for the calculation of the ground resistance, the ground potential rise, the surface potential, the touch voltage and step voltage in grounding grids with any geometry and buried at any depth within strati ed soil in two layers. The values of potential, touch voltage and step voltage are obtained at any point over the grid. The proposed equation uses the images and the average potential methods. The main feature of this modeling in relation to the other methods is the possibility of calculation of grids containing electrodes positioned at any distance and at any angle. The results obtained with the proposed methodology are presented and discussed.

A memória pode ser definida como o armazenamento e a evocação de uma informação aprendida. Sendo um processo dinâmico, requer a ativação de diversos sistemas para que a informação adquirida seja consolidada. Sendo assim, estudos em esquiva inibitória são de suma importância para um melhor conhecimento do comportamento. O presente trabalho apresenta o desenvolvimento de um aparato para a realização de estudos sobre esquiva inibitória. Será apresentado o projeto e a montagem de uma fonte de corrente variável para a realização de testes em ratos. Juntamente também será realizado um estudo sobre o valor da resistência elétrica de um rato. As simulações da topologia proposta foram realizadas nos softwares Orcad Schematics e Proteus e seus resultados são mostrados no decorrer do trabalho. Foi escolhida uma topologia utilizando transistores devido ao fato de necessitarem-se altos valores de tensão para um correto funcionamento do dispositivo.

This paper presents the development of a braided reinforced composite rod (BCR) able to both reinforce and monitor the stress state of concrete elements. Carbon fibers have been used as sensing and reinforcing material along with glass fiber. Various composites rods have been produced using an author patented technique based on a modified conventional braiding machine. The materials investigated were prepared with different carbon fiber content as follows: BCR2 (77% glass/23% carbon fiber), BCR3 (53% glass/47% carbon fiber), BCR4 (100% carbon fiber). BCRs have been tested under bending while the variation of the electrical resistance was simultaneously monitored. The correlations obtained between deformation and electrical resistance show the suitability of the rods to be used as sensors. The fractional resistance change versus strain plots show that the gage factor increases with decreasing carbon fiber content.

In this paper we present an overview of methods of resistance finding for the conductor with variable cross-section or (and) length. First, we consider the cases of the finite size resistors and an infinite homogeneous weakly conducting medium with two electrodes. Next, we continue the Romano and Price analysis about the truncated cone problem by means of comprehensive numerical calculations done for the trapezoid plates. We conclude that in general case of a conductor with variable cross-section the homogeneous electric field approximation gives only the lower limit estimation for the resistance value. This fact can be explained on the basis of the minimum electric power principle. The issues outlined in this article will be useful for advanced undergraduates, who study methods for solving electrostatic problems.Keywords: problem solving, electrical resistance, trapezoid plate problem.

O presente trabalho trata da análise e desenvolvimento de um aquecedor de água em linha com sistema de controle em malha fechada em uma etapa do processo de produção de cerveja. O sistema de aquecimento tem como premissa ser de baixo custo e relativamente simples e compacto, uma vez que se tem foco a aplicação em cervejarias artesanais, tendo como limitações: espaço físico e custos. As etapas de desenvolvimento do protótipo compreendem a avaliação térmica do sistema, definição de geometria, elaboração do sistema de controle, construção e avaliação experimental. O sistema desenvolvido é baseado em aquecimento por resistência elétrica, com medição de temperatura para controle de acionamento. O resultado obtido foi um protótipo de aquecedor que apresentou validação laboratorial com erro inferior a 30%

Electromembrane processes are employed in critical applications such as desalination, lithium recovery, and salinity gradient energy conversion. However, issues like fouling and concentration polarisation may limit their effectiveness. Profiled ion-exchange membranes offer several advantages over flat membranes, including improved fluid mixing, enhanced mass transfer, lower pressure drop (thus, lower energy consumption), and elimination of the spacer's shadow effect. Nonetheless, their preparation is considerably more complex than that of flat membranes. In this study, we pioneered the use of solvent-free fused deposition modelling (FDM) 3D printing to fabricate flat and profiled (chevron and stripe) cation-exchange membranes (CEMs). The functionalisation of the 3D-printed membranes into CEMs was achieved via sulfonation. The optimised electrical resistance and permselectivity of the prepared membranes were 10.7 ± 4 Ωcm2 and 97.3 ± 4 %, respectively, after 14 h of sulfonation, closely matching commercial alternatives (e.g., FUMASEP FKB-PK-130, 9.7 ± 3 Ωcm2 and 96.7 ± 1 %). Sulfonation durations exceeding 14 h increased the membranes’ electrical resistance due to the formation of sulfone cross-bridges that do not participate in cations’ exchange. Since FDM 3D printing is a solvent-free and additive manufacturing method, it significantly reduces waste during membrane fabrication, resulting in an E-factor value of 1.5. Therefore, this work opens a path toward customisable, scalable, and greener CEM production for electrochemical applications ranging from the recovery of critical raw materials and water desalination to renewable energy conversion.