RESUMO
Ferroelectric materials exhibit switchable spontaneous polarization below Curie's temperature, driven by octahedral distortions and rotations, as well as ionic displacements. The ability to manipulate polarization coupled with persistent remanence, drives diverse applications, including piezoelectric devices. In the last two decades, nanoscale exploration has unveiled unique material properties influenced by morphology, including the capability to manipulate polarization, patterns, and domains. This paper focuses on the characterization of nanometric sodium niobate (SN) synthesized from metallic niobium through alkali hydrothermal treatment, utilizing electron microscopy techniques, including high-resolution differential phase contrast (DPC) in scanning transmission electron microscopy (STEM). The material exhibits a nanoribbon structure forming a tree root-like network. The study identifies crystallographic phase, atomic columns displacement directions, and surface features, such as exposed planes and the absence of particular atomic columns. The high sensitivity of integrated DPC images proves crucial in overcoming observational challenges in other STEM modes. These observations are essential for potential applications in electronic, photocatalytic, and chemical reaction contexts.
RESUMO
Eight partially grouted (PG-RM) concrete masonry walls were tested to study the influence of the strength and width of blocks, the wall aspect ratio, the horizontal and vertical reinforcement ratio, and the presence of edge elements (flanges). The results were analyzed in terms of the failure mode, damage progression, shear strength, lateral stiffness degradation, equivalent viscous damping ratio, and displacement ductility. Additionally, the performances of some existing shear expressions were analyzed by comparing the measured and predicted lateral load capacity of the tested walls. Based on the results, a slight increment in the lateral stiffness was achieved when employing stronger blocks, while the shear strength remained constant. Besides, increasing the width of concrete blocks did not have a significant effect on the shear strength nor in the initial tangential stiffness, but it generated a softer post-peak strength degradation. Increasing the wall aspect ratio reduced the brittleness of the response and the shear strength. Reducing the amount of vertical reinforcement lowered the resulting shear strength, although it also slowed down the post-peak resistance degradation. Transversal edge elements provided integrity to the wall response, generated softer resistance degradation, and improved the symmetry of the response, but they did not raise the lateral resistance.
RESUMO
Most studies of emotional responses have used unimodal stimuli (e.g., pictures or sounds) or congruent bimodal stimuli (e.g., video clips with sound), but little is known about the emotional response to incongruent bimodal stimuli. The aim of the present study was to evaluate the effect of congruence between auditory and visual bimodal stimuli on heart rate and self-reported measures of emotional dimension, valence and arousal. Subjects listened to pleasant, neutral, and unpleasant sounds, accompanied by videos with and without content congruence, and heart rate was recorded. Dimensions of valence and arousal of each bimodal stimulus were then self-reported. The results showed that heart rate depends of the valence of the sounds but not of the congruence of the bimodal stimuli. The valence and arousal scores changed depending on the congruence of the bimodal stimuli. These results suggest that the congruence of bimodal stimuli affects the subjective perception of emotion.