APANet: Adaptive Prototypes Alignment Network for Few-Shot Semantic Segmentation

Few-shot semantic segmentation aims to segment novel-class objects in a given query image with only a few labeled support images. Most advanced solutions exploit a metric learning framework that performs segmentation through matching each query feature to a learned class-specific prototype. However, this framework suffers from biased classification due to incomplete feature comparisons. To address this issue, we present an adaptive prototype representation by introducing class-specific and class-agnostic prototypes and thus construct complete sample pairs for learning semantic alignment with query features. The complementary features learning manner effectively enriches feature comparison and helps yield an unbiased segmentation model in the few-shot setting. It is implemented with a two-branch end-to-end network (\ie, a class-specific branch and a class-agnostic branch), which generates prototypes and then combines query features to perform comparisons. In addition, the proposed class-agnostic branch is simple yet effective. In practice, it can adaptively generate multiple class-agnostic prototypes for query images and learn feature alignment in a self-contrastive manner. Extensive experiments on PASCAL-5 i and COCO-20 i demonstrate the superiority of our method. At no expense of inference efficiency, our model achieves state-of-the-art results in both 1-shot and 5-shot settings for few-shot semantic segmentation

Aqua­[2,6-bis­(2-pyridylamino)pyridine]sulfatonickel(II) monohydrate

The Ni atom in the title complex, [Ni(SO4)(C15H13N5)(H2O)]·H2O, has a distorted trigonal-bipyramidal coordination formed by the tridentate 2,6-bis­(2-pyridylamino)pyridine (tpdaH2) ligand, one sulfate and one coordinated water mol­ecule. The tpdaH2 ligand is three-coordinated, with the N atom of the central pyridine ring in the equatorial position [Ni—N = 1.9961 (14) Å] and the N atoms of the peripheral pyridine rings in the axial positions [Ni—N = 1.9668 (15) and 1.9895 (15) Å]. The remaining equatorial positions are occupied by the O atoms of the sulfate ligand and the water molecule. The H atoms of both NH groups of the tpdaH2 ligand are involved in hydrogen bonds with the O atoms of the uncoordinated water mol­ecule and the sulfate group which link the complex mol­ecules, forming an infinite three-dimensional network