RESUMO
In the field of object detection, feature pyramid network (FPN) can effectively extract multi-scale information. However, the majority of FPN-based methods suffer from a semantic gap between features of various sizes before feature fusion, which can lead to feature maps with significant aliasing. In this paper, we present a novel multi-scale semantic enhancement feature pyramid network (MSE-FPN) which consists of three effective modules: semantic enhancement module, semantic injection module, and gated channel guidance module to alleviate these problems. Specifically, inspired by the strong ability of the self-attention mechanism to model context, we propose a semantic enhancement module to model global context to obtain the global semantic information before feature fusion. Then we propose the semantic injection module to divide and merge global semantic information into feature maps at various scales to narrow the semantic gap between features at different scales and efficiently utilize the semantic information of high-level features. Finally, to mitigate feature aliasing caused by feature fusion, the gated channel guidance module selectively outputs crucial features via a gating unit. By replacing FPN with MSE-FPN in Faster R-CNN, our models achieve 39.4 and 41.2 Average precision (AP) using ResNet50 and ResNet101 as the backbone network respectively. When using ResNet-101-64x4d as the backbone, MSE-FPN achieved up to 43.4 AP. Our results demonstrate that replacing FPN with MSE-FPN significantly enhances the detection performance of state-of-the-art FPN-based detectors.
RESUMO
Direct C-H/C-H coupling represents an appealing method for the construction of C-C bonds, and the cross-coupling of unactivated C(sp3)-H and C(sp2)-H bonds is challenging and remains to be investigated. We have developed the Pd-catalyzed intramolecular coupling of inert C(sp3)-H and C(sp2)-H bonds. The reaction proceeded by o-methyl oxime-directed aryl C(sp2)-H activation and subsequent alkyl C(sp3)-H cleavage, generating C(sp2),C(sp3)-palladacycles as the key intermediates. Dihydrobenzofurans and indanes were formed as the final products.
RESUMO
A novel and straightforward approach for the synthesis of tribenzo[b,d,f]azepines starting from 2-iodobiphenyls and 2-bromoanilines has been developed. A wide range of tribenzo[b,d,f]azepines were obtained in good to excellent yields via a cascade intermolecular palladium-catalyzed C-H activation/dual coupling reaction. C,C-palladacycles, which are generated by C-H activation of 2-iodobiphenyls, should be the reaction intermediates.
RESUMO
Flocculation induced by pH increase for harvesting microalgae and reuse of flocculated medium were evaluated. Increasing the medium pH value induced the highest flocculation efficiency of up to 90% for freshwater microalgae (Chlorella vulgaris, Scenedesmus sp., Chlorococcum sp.) with low/medium biomass concentrations and marine microalgae (Nannochloropsis oculata, Phaeodactylum tricornutum). The mechanism may be explained that Mg(2+) in the growth medium hydrolyzed to form magnesium hydroxide precipitate, which coagulated microalgal cells by sweeping flocculation and charge neutralization. Additionally, this study revealed that the microalgal biomass concentrations and released polysaccharide (RPS) from microalgae could influence the flocculation efficiencies. Furthermore, neutralizing pH and then supplementing nutrients allowed the flocculated medium to maintain an approximate growth yield to that of the fresh medium in algal cultivation. These results suggest that the method presented here is effective, and allows the reuse of the flocculated medium, thereby contributing to the economic production from algae to biodiesel.
