39 research outputs found
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Target-directed motor imagery of the lower limb enhances event-related desynchronization
Event-related desynchronization/synchronization (ERD/S) is an electroencephalogram (EEG) feature widely used as control signals for Brain-Computer Interfaces (BCIs). Never- theless, the underlying neural mechanisms and functions of ERD/S are largely unknown, thus investigating them is crucial to improve the reliability of ERD/S-based BCIs. This study aimed to identify Motor Imagery (MI) conditions that enhance ERD/S. We investigated fol- lowing three questions: 1) whether target-directed MI affects ERD/S, 2) whether MI with sound imagery affects ERD/S, and 3) whether ERD/S has a body part dependency of MI. Nine participants took part in the experiments of four MI conditions; they were asked to imagine right foot dorsiflexion (F), right foot dorsiflexion and the sound of a bass drum when the sole touched the floor (FS), right leg extension (L), and right leg extension directed toward a soccer ball (LT). Statistical comparison revealed that there were significant differ- ences between conditions L and LT in beta-band ERD and conditions F and L in beta-band ERS. These results suggest that mental rehearsal of target-directed lower limb movement without real sensory stimuli can enhance beta-band ERD; furthermore, MI of foot dorsiflex- ion induces significantly larger beta-band ERS than that of leg extension. These findings could be exploited for the training of BCIs such as powered prosthetics for disabled person and neurorehabilitation system for stroke patients
Processing Parameter Effects on Residual Stress and Mechanical Properties of Selective Laser Melted Ti6Al4V
Selective laser melting (SLM) process is characterized by large temperature gradients resulting in high levels of residual stress within the additively manufactured metallic structure. SLM-processed Ti6Al4V yields a martensitic microstructure due to the rapid solidification and results in a ductility generally lower than a hot working equivalent. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. Residual stress buildup and the mechanical properties of SLM parts can be controlled by varying the SLM process parameters. This investigation studies the effect of layer thickness on residual stress and mechanical properties of SLM Ti6Al4V parts. This is the first-of-its kind study on the effect of varying power and exposure in conjunction with keeping the energy density constant on residual stress and mechanical properties of SLM Ti6Al4V components. It was found that decreasing power and increasing exposure for the same energy density lowered the residual stress and improved the % elongation of SLM Ti6Al4V parts. Increasing layer thickness resulted in lowering the residual stress at the detriment of mechanical properties. The study is based on detailed experimental analysis along with finite element simulation of the process using ABAQUS to understand the underlying physics of the process
Transferência de calor aplicada à prototipagem rápida por deposição de metal em camadas sucessivas utilizando soldagem 3D
Small-signal stability and load-sharing improvement of autonomous microgrids using auxiliary loop
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Investigation of the impact of insulator material on the performance of dissimilar electrode metal-insulator-metal diodes
The performance of thin film metal-insulator-metal (MIM) diodes is investigated for a variety of large and small electron affinity insulators using ultrasmooth amorphous metal as the bottom electrode. Nb2O5, Ta2 O5, ZrO2, HfO2, Al2 O3, and SiO2 amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss spectroscopy (REELS) is utilized to measure the band-gap energy (EG) and energy position of intrinsic sub-gap defect states for each insulator. EG of as-deposited ALD insulators are found to be Nb2O5¼3.8 eV, Ta2O5¼4.4 eV, ZrO2¼5.4 eV, HfO2¼5.6 eV, Al2O3¼6.4 eV, and SiO2¼8.8 eV with uncertainty of 60.2 eV. Current vs. voltage asymmetry, non-linearity, turn-on voltage, and dominant conduction mechanisms are compared. Al2O3 and SiO2 are found to operate based on Fowler-Nordheim tunneling. Al2O3 shows the highest asymmetry. ZrO2, Nb2O5, and Ta2O5 based diodes are found to be dominated by Frenkel-Poole emission at large biases and exhibit lower asymmetry. The electrically estimated trap energy levels for defects that dominate Frenkel-Poole conduction are found to be consistent with the energy levels of surface oxygen vacancy defects observed in REELS measurements. For HfO2, conduction is found to be a mix of trap assisted tunneling and Frenkel-Poole emission. Insulator selection criteria in regards to MIM diodes applications are discussed.This is the publisher’s final pdf. The published article is copyrighted by the American Institute of Physics Publishing and can be found at: http://scitation.aip.org/content/aip/journal/jap.Keywords: Conduction, Gate dielectric stacks, Transisto