Transcending the binary categorization of racist and xenophobic texts, this research takes cues from social science theories to develop a four-dimensional category for racism and xenophobia detection, namely stigmatization, offensiveness, blame, and exclusion. With the aid of deep learning techniques, this categorical detection enables insights into the nuances of emergent topics reflected in racist and xenophobic expression on Twitter. Moreover, a stage wise analysis is applied to capture the dynamic changes of the topics across the stages of early development of Covid-19 from a domestic epidemic to an international public health emergency, and later to a global pandemic. The main contributions of this research include, first the methodological advancement. By bridging the state-of-the-art computational methods with social science perspective, this research provides a meaningful approach for future research to gain insight into the underlying subtlety of racist and xenophobic discussion on digital platforms. Second, by enabling a more accurate comprehension and even prediction of public opinions and actions, this research paves the way for the enactment of effective intervention policies to combat racist crimes and social exclusion under Covid-19.

Online advertising and recommender systems often pose a multi-task problem, which tries to predict not only users’ click-through rate (CTR) but also the post-click conversion rate (CVR). Meanwhile, multi-functional information systems commonly provide multiple service scenarios for users, such as news feed, search engine and product suggestions. Users may leave similar interest information across various service scenarios. Thus the prediction/ranking model should be conducted in a multi-scene manner. This paper develops a unified r a nking m o del for this multi-task and multi-scene problem. Compared to previous works, our model explores independent/non-shared embeddings for each task and scene, which reduces the coupling between tasks and scenes. New tasks or scenes could be added easily. Besides, a simplified n e twork i s c h osen b e yond t h e embedding layer, which largely improves the ranking efficiency f o r online services. Extensive offline a n d o n line e x periments demonstrated the superiority of the proposed unified r a nking model.