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Interactions between users and videos are the major data source of performing video recommendation. Despite lots of existing recommendation methods, user behaviors on videos, which imply the complex relations between users and videos, are still far from being fully explored. In the paper, we present a model named Sagittarius. Sagittarius adopts a graph convolutional neural network to capture the influence between users and videos. In particular, Sagittarius differentiates between different user behaviors by weighting and fuses the semantics of user behaviors into the embeddings of users and videos. Moreover, Sagittarius combines multiple optimization objectives to learn user and video embeddings and then achieves the video recommendation by the learned user and video embeddings. The experimental results on multiple datasets show that Sagittarius outperforms several state-of-the-art models in terms of recall, unique recall and NDCG.

In a dark clear moonless night, far away from city lights, one may see a starlight-full hazy belt which circles the sky. It divides the sky into two halves, passing through the constellations of Cassiopeia and Perseus and between Orion and the Twins. On the other side of Cassiopeia, the Swan and Eagle are in this celestial path with Sagittarius in the most spectacular southern portion. In many languages, it is called a “way,” for example, Milky Way in English which agrees with the Greek name galaktos, milk. In Finnish, it is the Bird’s Way, in Swedish Winter Street. It took the efforts of generations after generations of astronomers to find out what this nebulous belt is, staying fixed relative to the stars.

The Milky Way’s prominent and widely studied Sagittarius (Sgr) dSph tidal stream has proven a valuable tool for exploring a number of problems in galactic astronomy. In this review of the Sgr system, we present a descriptive portrait of the most salient and unambiguous observational properties (e.g., location, radial velocity, proper motion, and chemical composition) of the Sgr core and tidal streams as they are presently known. We discuss how the history of these observations has shaped the development of numerical models of the system over time, and some of the major conclusions that have been drawn from such modeling efforts with regard to the size and shape of the Milky Way’s gravitational potential and the patterns of enrichment throughout its stellar halo. Finally, we summarize some of the known failings of the present models, which we lay out as a challenge for future progress on understanding this remarkable and fortuitous example of hierarchical galaxy growth via merging in action.

Stargazers taking a trip near to—and especially south of—the equator are in for a surprise. Not only are the stars you’re familiar with upside-down, but there’s a whole new set of constellations, bright stars and stunning objects only viewable from southern hemisphere latitudes. It’s confusing at first, but a real treat, especially if you travel to rural areas (the southern hemisphere has some of the darkest skies on the planet). There’s a reason why astronomers have chosen this half of the world to build the very biggest and best ground-based telescopes.

July sees the rich star-fields of Sagittarius and Scorpius swing into view to offer us none other than the Galactic Center Point. This area of sky is also home to a royal star, Antares—an orange supergiant, whose name means the ‘rival of Mars’. Maybe you’ll even glimpse Mars itself this month, too. From views of globular clusters and double stars, to teapots, dolphins and seas of lava, July is a month where nightfall is late, but great.