Electric current injection NDE using a SQUID magnetometer

We built a portable low-cost superconducting quantum interference device (SQUID) magnetometer to be used as the sensing element of an electric current injection NDE system. Using this system, we measured the magnetic fields associated with aluminum plate with single flaws in the millimeter range (2 to 8 mm), at lift-off distances up to ten times the size of the flaw, with injection currents in the order of a few amps. Because the system is at a relatively large distance from the test plate, the signal generated by the flaw is masked by the sinal generated by the edges of the plate. This is independent of the amount of current injected. Due to this, visual inspection is difficult when the distance from the sensor to the flaw exceeds five times its size. To intensify the magnetic field disturbance due to the flaws, we used digital image-enhancement techniques. Applying the enhancement algorithm, magnetic field disturbances were visualized at distances up to ten times the size of the flaw.     

Synthesis and properties of alkali-activated iron ore tailings blended with metakaolin

In this study, synthesis, microstructural characteristics, mechanical properties, and environmental compatibility of alkali-activated binders derived from iron ore tailings (IOT)—with partial replacement with metakaolin (MK)—were investigated. The binders were produced with a NaOH solution, IOT, and MK. A thermal cure at 100°C was used and the MK was applied as a partial replacement of IOT in three proportions (10, 20, and 30 wt%). The IOT-based specimens presented an average of 98.0 and 18.0 MPa at 7 days age of curing for compressive and flexural strength, respectively. The mechanical properties of the alkali-activated binders with MK decreased as the substitution ratio increased. By the microstructural analysis, it was found a zeolite-type phase in alkali-activated IOT, while in the binders blended with MK, three new mineral phases were identified. Furthermore, Fourier transform infrared, quantitative X-ray diffraction, and environmental analysis suggest that the Fe species present in IOT acted in the alkali-activation reaction.     

Twisted Crystalline Organic Semiconductor Photodetectors

Optoelectronic properties of anisotropic crystals vary with direction requiring that the orientation of molecular organic semiconductor crystals is controlled in optoelectronic device active layers to achieve optimal performance. Here, a generalizable strategy to introduce periodic variations in the out-of-plane orientations of 5,11-bis(triisopropylsilylethynyl)anthradithiophene (TIPS ADT) crystals is presented. TIPS ADT crystallized from the melt in the presence of 16 wt.% polyethylene (PE) forms banded spherulites of crystalline fibrils that twist in concert about the radial growth direction. These spherulites exhibit band-dependent light absorption, photoluminescence, and Raman scattering depending on the local orientation of crystals. Mueller matrix imaging reveals strong circular extinction (CE), with TIPS ADT banded spherulites exhibiting domains of positive or negative CE signal depending on the crystal twisting sense. Furthermore, orientation-dependent enhancement in charge injection and extraction in films of twisted TIPS ADT crystals compared to films of straight crystals is visualized in local conductive atomic force microscopy maps. This enhancement leads to 3.3- and 6.2-times larger photocurrents and external quantum efficiencies, respectively, in photodetectors comprising twisted crystals than those comprising straight crystals.     

Modeling and assessing an intelligent system for safety in human-robot collaboration using deep and machine learning techniques

Multimedia Tools and Applications - The introduction of technological innovations is essential for accident mitigation in work environments. In a human-robot collaboration scenario, the current...     

Circular economy and durability in geopolymers ceramics pieces obtained from glass polishing waste

The development of new building materials based on alkaline activation technology is very promising, mainly linked to products that need significant technological properties and durability due to their adverse service conditions and environmental exposure. The objective of this research was to evaluate the development of a circular economy within the scope of durability of ceramic pieces incorporating glass polishing waste aimed at the production of roof tiles, obtained by the geopolymerization process. Two methodologies to evaluate the sample's durability were studied: wetting and drying cycles; and exposure to salt spray; both simulating conditions that tiles typically face in normal conditions. Prismatic specimens were made with an alkaline solution/(metakaolin + waste) ratio = 0.26; a SiO₂/Al₂O₃ molar ratio = 3.5, 4, and 4.5; and with ambient and thermal cure at 7 days. Samples were evaluated in their mechanical strength, mass loss, and water absorption. Results showed that the SiO₂/Al₂O₃ = 4.0 ratio with thermal curing had the best behavior in aggressive conditions, and therefore, this formulation can be used for the production of tiles.     

Configurations of project management practices to enhance the performance of open innovation R&D projects

This study contributes to the current discussion related to the execution challenges of open innovation projects in R&D with the lens of project management, especially considering the type of external partner as a contingent factor. It fosters the discussion of the configuration of practices in a contingent project management approach in comparison to the traditional best practice approach. For that, we conducted a qualitative fuzzy-set comparative analysis of 50 open innovation projects in R&D. By looking at configurations, we found combinations of practices related to high performance, when treated as a non-independent variable. In this configuration view, practices negatively associated with high performance in previous studies, are part of a combination of practices to achieve high performance in R&D projects. This study contributes to fostering the configurational perspective to project management associated with the idea that one size does not fit all.     

Fuel-cell energy generation system based on the series-capacitor boost converter

This work introduces the development of a power-electronics customizable energy system for their application on renewable energy generation based on proton-exchange membrane fuel cells. The customizable energy system aims to regulate the output voltage from a fuel cell, which has a relatively low amplitude and wide range of variation, to a fixed voltage to feed a grid-tie inverter. The customizable energy system proposed is based on a dc-dc converter for which different configurations (topologies) are available, such as the traditional single-phase boost or the (interleaved) multi-phase boost. The dc-dc converter of the energy system is based on the series-capacitor boost converter, a recently proposed converter that has a similar configuration to the interleaved boost converter. This article shows that the series-capacitor boost topology offers benefits in the proposed application. An experimental prototype was developed and tested in order to demonstrate the advantages of the system proposed.     

Influence of Inflow Nonstationarity on the Multipurpose Optimal Operation of Hydropower Plants Using Nonlinear Programming

Water Resources Management - One of the greatest challenges in the electricity generation sector is to operate hydrothermal plants in view of the randomness of hydrological events and climate...