246 research outputs found
Can the Query-based Object Detector Be Designed with Fewer Stages?
Query-based object detectors have made significant advancements since the
publication of DETR. However, most existing methods still rely on multi-stage
encoders and decoders, or a combination of both. Despite achieving high
accuracy, the multi-stage paradigm (typically consisting of 6 stages) suffers
from issues such as heavy computational burden, prompting us to reconsider its
necessity. In this paper, we explore multiple techniques to enhance query-based
detectors and, based on these findings, propose a novel model called GOLO
(Global Once and Local Once), which follows a two-stage decoding paradigm.
Compared to other mainstream query-based models with multi-stage decoders, our
model employs fewer decoder stages while still achieving considerable
performance. Experimental results on the COCO dataset demonstrate the
effectiveness of our approach
Manipulating Electromagnetic Waves with Zero Index Materials
Zero-index material is a typical metamaterial with an effective zero refractive index, possessing a variety of exotic electromagnetic properties and particular functionalities. We have considered two kinds of zero-index materials with the first one a nearly matched zero index made of magnetic metamaterial and the second one a radially anisotropic zero index. The magnetic metamaterial-based systems are shown to be significant in wavefront engineering and flexibly tunable by an external magnetic field and a temperature field. The radially anisotropic zero-index-based systems can remarkably enhance the omnidirectional isotropic radiation by enclosing a line source and a dielectric particle within a shell configuration. The physical origin lies in that the dielectric particle effectively rescatters the trapped anisotropic higher order modes and converts them into the isotropic 0th order mode radiated outside the system. The case for the system with the loss is then examined and the energy compensation with a gain particle is also demonstrated
Construction of PAN-based activated carbon nanofibers for hydrogen storage under ambient pressure
Adsorption agents are an important class of solid hydrogen storage materials. Attributed to their high specific surface area and adjustable nanopore structure, activated carbon nanofibers have attracted extensive attention in the application of solid hydrogen storage. The research in this field mostly focuses on applications with a hydrogen pressure condition of 30 to 300 bar, while there have been few systematic studies on the hydrogen storage performance of these materials under ambient pressure. In this study, polyacrylonitrile-based activated carbon nanofibers were constructed by electrospinning technology and ultrasonic-assisted activation technology for the application of atmospheric hydrogen storage. Their nanopore structure was revealed to be mainly composed of micropores, and the relative contents of micropore volume and ultramicropore volume were 77.92% to 88.3% and 22.34% to 24.68%, respectively. Attributed to the synergy of rich microporous structure and surface chemical structure, the atmospheric hydrogen storage density of activated carbon nanofibers could reach 2.64 wt% at 77 K and 1 bar. After the optimization analysis of adsorption isotherm models, the Multisite-Langmuir model was found as more suitable for accurately describing the atmospheric hydrogen adsorption process of activated carbon nanofibers.Cited as: Yu, J., Lin, T., Li, J., Zhang, W., Bao, W., Zhu, B. Construction of PAN-based activated carbon nanofibers for hydrogen storage under ambient pressure. Capillarity, 2023, 6(3): 49-56. https://doi.org/10.46690/capi.2023.03.0
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