SSD-TSEFFM: New SSD Using Trident Feature and Squeeze and Extraction Feature Fusion.

The single shot multi-box detector (SSD) exhibits low accuracy in small-object detection; this is because it does not consider the scale contextual information between its layers, and the shallow layers lack adequate semantic information. To improve the accuracy of the original SSD, this paper proposes a new single shot multi-box detector using trident feature and squeeze and extraction feature fusion (SSD-TSEFFM); this detector employs the trident network and the squeeze and excitation feature fusion module. Furthermore, a trident feature module (TFM) is developed, inspired by the trident network, to consider the scale contextual information. The use of this module makes the proposed model robust to scale changes owing to the application of dilated convolution. Further, the squeeze and excitation block feature fusion module (SEFFM) is used to provide more semantic information to the model. The SSD-TSEFFM is compared with the faster regions with convolution neural network features (RCNN) (2015), SSD (2016), and DF-SSD (2020) on the PASCAL VOC 2007 and 2012 datasets. The experimental results demonstrate the high accuracy of the proposed model in small-object detection, in addition to a good overall accuracy. The SSD-TSEFFM achieved 80.4% mAP and 80.2% mAP on the 2007 and 2012 datasets, respectively. This indicates an average improvement of approximately 2% over other models.

Optimal parameter retrieval for metamaterial absorbers using the least-square method for wide incidence angle insensitivity.

In this paper, we propose a specific algorithm based on the least-square method to predict the incidence angle insensitivity of a metamaterial absorber. The proposed algorithm was analyzed on a metamaterial absorber design with circular sectors on the top layer and a full copper cover on the bottom layer. We retrieved the parameters of inductance, capacitance, and conductance from the equivalent circuit of the metamaterial absorber at different incidence angles of 0°, 30°, 65°, and 70° under both transverse electric and transverse magnetic polarization. The complex impedances calculated from the optimal parameter retrieval are compared with the complex impedances from full-wave simulation at each incidence angle. The calculated and simulated results show excellent agreement, and the proposed algorithm can be used to design angle-insensitive metamaterial absorbers.